An exotic terrane in the Sulu UHP region, China

NASA Astrophysics Data System (ADS)

Chu, W.; Zhang, R.; Tsujimori, T.; Liou, J. G.

2004-12-01

The Haiyangsuo region of about 15 km2 along the coast in the NE part of the Triassic Sulu UHP terrane occurs three major rock types: amphibolitized metagabbro, gneiss and granitic dikes. Three different gneisses were observed in the field: A) Light color felsic gneiss is the dominant country rock and contains Qtz, Pl, Ms and Bi. B) Dark color plagioclase-amphibole gneiss occurs as thin layers within country rock; C) Granulite facies rock occurs as discontinuous lens. The amphibolitized metagabbros intrude into the gneisses as massive bodies (several m to hundreds of m in size) and thin dikes. Both metamorphic intrusives and gneisses are cross-cut by granitic dikes. The amphibolitized metagabbro was divided into three types: coronal metagabbro, transitional rock and garnet amphibolite: 1) Coronal metagabbro preserves gabbroic texture and primary assemblage of Opx+Cpx+Pl+Amp+Ilm. Most pyroxene grains are partially rimmed by thin corona of Amp+Ab+Qtz. Garnet occurs as fine-grained coronas at interface between plagioclase, pyroxene or ilmenite. 2) Transitional rocks contain similar assemblage and texture but most orthopyroxenes were partially or totally replaced by Amp+Qtz; garnet increases in content and size. Some gabbroic textures are preserved, but calcic plagioclase was replaced by zoisite, albite and muscovite. 3) Garnet amphibolite occurs at the margins of intrusive bodies and boudins where only minor relict clinopyroxenes preserve. Garnet coronal chains are not clear any more. Granitic dikes show pronounced deformation with mylonitic texture and contain 40-50% quartz porphyroclasts. Zircon separates from 2 metagabbros, 4 gneisses and 1 granitic rock were dated by using Stanford SHRIMP-RG. Metagabbroic zircons are angular and fractured shapes. The upper-intercept ages of gneisses rang from 1730 to about 2400 Ma, indicating variable protoith age. The 2 garnet amphibolites have upper-intercept ages 1734±5Ma and 1735±21Ma respectively. They are much older than the protolith ages (680-850 Ma) of the Sulu eclogite and country rock. At least two possible metamorphic events are indicated by the lower-intercept ages. One metagabbroic rock has a lower-intercept age of 842±37 Ma; this records a garnet amphibolite metamorphic event. One gneiss and one metagabbroic rock yield lower-intercept ages of about 340±25 Ma, suggesting a second metamorphic event. The granitic dike has upper-intercept age 749±43 Ma and lower-intercept age 150±17 Ma. All these petrological and geochronological results indicate that the Haiyangsuo region is not part of the Triassic Sulu UHP terrane.

Petrologic and chemical changes in ductile shear zones as a function of depth in the continental crust

NASA Astrophysics Data System (ADS)

Yang, Xin-Yue

Petrologic and geochemical changes in ductile shear zones are important for understanding deformational and geochemical processes of the continental crust. This study examines three shear zones that formed under conditions varying from lower greenschist facies to upper amphibolite facies in order to document the petrologic and geochemical changes of deformed rocks at various metamorphic grades. The studied shear zones include two greenschist facies shear zones in the southern Appalachians and an upper amphibolite facies shear zone in southern Ontario. The mylonitic gneisses and mylonites in the Roses Mill shear zone of central Virginia are derived from a ferrodiorite protolith and characterized by a lower greenschist facies mineral assemblage. Both pressure solution and recrystallization were operative deformation mechanisms during mylonitization in this shear zone. Strain-driven dissolution and solution transfer played an important role in the mobilization of felsic components (Si, Al, K, Na, and Ca). During mylonitization, 17% to 32% bulk rock volume losses of mylonites are mainly attributed to removal of these mobile felsic components by a fluid phase. Mafic components (Fe, Mg, Ti, Mn and P) and trace elements, REE, Y, V and Sc, were immobile. At Rosman, North Carolina, the Brevard shear zone (BSZ) shows a deformational transition from the coarse-grained Henderson augen gneiss (HAG) to proto-mylonite, mylonite and ultra-mylonite. The mylonites contain a retrograde mineral assemblage as a product of fluid-assisted chemical breakdown of K-feldspar and biotite at higher greenschist facies conditions. Recrystallization and intra-crystalline plastic deformation are major deformation mechanisms in the BSZ. Fluid-assisted mylonitization in the BSZ led to 6% to 23% bulk volume losses in mylonites. During mylonitization, both major felsic and mafic elements and trace elements, Rb, Sr, Zr, V, Sc, and LREE were mobile; however, the HREEs were likely immobile. A shear zone in the Parry Sound domain, Ontario, formed at upper amphibolite facies conditions. The deformation process of the shear zone involves fully plastic deformation and high-temperature dynamic recrystallization and annealing recovery of both quartz and plagioclase. Geochemical evidence indicates that the chemical changes in the deformed rocks resulted from mixing of mafic and felsic layers together with fluid-assisted mass transfer within the shear zone. A geochemical model that incorporates closed-system two-component mixing with open-system mass transfer can well explain the observed major and trace element data.

Early Cretaceous wedge extrusion in the Indo-Burma Range accretionary complex: implications for the Mesozoic subduction of Neotethys in SE Asia

NASA Astrophysics Data System (ADS)

Zhang, Ji'en; Xiao, Wenjiao; Windley, Brian F.; Cai, Fulong; Sein, Kyaing; Naing, Soe

2017-06-01

The Indo-Burma Range (IBR) of Myanmar, the eastern extension of the Yarlung-Tsangpo Neotethyan belt of Tibet in China, contains mélanges with serpentinite, greenschist facies basalt, chert, sericite schist, silty slate and unmetamorphosed Triassic sandstone, mudstone and siltstone interbedded with chert in the east, and farther north high-pressure blueschist and eclogite blocks in the Naga Hills mélange. Our detailed mapping of the Mindat and Magwe sections in the middle IBR revealed a major 18 km antiformal isocline in a mélange in which greenschist facies rocks in the core decrease in grade eastwards and westwards symmetrically `outwards' to lower grade sericite schist and silty slate, and at the margins to unmetamorphosed sediments, and these metamorphic rocks are structurally repeated in small-scale imbricated thrust stacks. In the Mindat section the lower western boundary of the isoclinal mélange is a thrust on which the metamorphic rocks have been transported over unmetamorphosed sediments of the Triassic Pane Chaung Group, and the upper eastern boundary is a normal fault. These relations demonstrate that the IBR metamorphic rocks were exhumed by wedge extrusion in a subduction-generated accretionary complex. Along strike to the north in the Naga Hills is a comparable isoclinal mélange in which central eclogite lenses are succeeded `outwards' by layers of glaucophane schist and glaucophanite, and to lower grade greenschist facies sericite schist and slate towards the margins. In the Natchaung area (from west to east) unmetamorphosed Triassic sediments overlie quartzites, sericite schists, actinolite schists and meta-volcanic amphibolites derived from MORB-type basalt, which are in fault contact with peridotite. Olivine in the peridotite has undulatory extinction suggesting deformation at 600-700 °C, similar to the peak temperature of the amphibolite; these relations suggest generation in a metamorphic sole. The amphibolites have U/Pb zircon ages of 119 ± 3 Ma and 115 Ma, which are close to the zircon ages of nearby calc-alkaline granite and diorite, which belong to an active continental margin arc that extends along the western side of the Shan-Thai block. The IBR accretionary complex and the active continental margin arc were generated during Early Cretaceous (115-128 Ma) subduction of the Neotethys Ocean.

Unraveling the polymetamorphic history of garnet-bearing metabasites: Insights from the North Motagua Mélange (Guatemala Suture Zone)

NASA Astrophysics Data System (ADS)

Bonnet, G.; Flores, K. E.; Martin, C.; Harlow, G. E.

2014-12-01

The Guatemala Suture Zone is the fault-bound region in central Guatemala that contains the present North American-Caribbean plate boundary. This major composite geotectonic unit contains a variety of ophiolites, serpentinite mélanges, and metavolcano-sedimentary sequences along with high-grade schists, gneisses, low-grade metasediments and metagranites thrusted north and south of the active Motagua fault system (MFS). The North Motagua Mélange (NMM) outcrops north of the MFS and testifies the emplacement of exhumed subduction assemblages along a collisional tectonic setting. The NMM is composed of a serpentinite-matrix mélange that contains blocks of metabasites (subgreenschist facies metabasalt, grt-blueschist, eclogite, grt-amphibolite), vein-related rocks (jadeitite, omphacitite, albitite, mica-rock), and metatrondhjemites. Our new detailed petrographic and thermobarometric study on the garnet-bearing metabasites reveals a complex polymetamorphic history with multiple tectonic events. Eclogites show a classical clockwise PT path composed of (a) prograde blueschist/eclogite facies within garnet cores, (b) eclogite facies metamorphic peak at ~1.7 GPa and 620°C, (c) post-peak blueschist facies, (d) amphibolite facies overprint, and (e) late stage greenschist facies. Two types of garnet amphibolite blocks can be found, the first consist of (a) a relict eclogite facies peak at ~1.3 GPa and 550°C only preserved within anhedral garnet cores, and (b) surrounded by a post-peak amphibolite facies. In contrast, the second type displays a prograde amphibolite facies at 0.6-1.1 GPa and 400-650°C. The eclogites metamorphic peak suggests formation in a normal subduction zone at ~60 km depth, a subsequent exhumation to the middle section of the subduction channel (~35 km), and a later metamorphic reworking at lower P and higher T before its final exhumation. The first type of garnet amphibolite shows a similar trajectory as the eclogites but at warmer conditions. In contrast, the second type of garnet amphibolite recorded a single prograde evolution along a hotter thermal gradient. These different PT paths suggest multiple metamorphic events that may be related to subduction initiation, partial exhumation and storage of HP-LT rocks, subduction of buoyant crust, final exhumation and obduction.

STRUCTURAL GEOMETRY OF AN EXHUMED UHP TERRANE IN THE EASTERN SULU OROGEN, CHINA: IMPLICATIONS FOR CONTINENTAL COLLISIONAL PROCESSES

NASA Astrophysics Data System (ADS)

Wang, L.; Kusky, T.

2009-12-01

High-precision 1:1,000 mapping of Yangkou Bay, eastern Sulu orogen, defines the structural geometry and history of the world’s most significant UHP (Ultrahigh Pressure) rock exposures. Four stages of folds are recognized in the UHP rocks and associated quartzo-feldspathic gneiss. Eclogite facies rootless F1 and isoclinal F2 folds are preserved locally in coesite-eclogite. Mylonitic to ultramylonitic cosesit-eclogite shear zones separate 5-10-meter-thick nappes of ultramafic-mafic UHP rocks from banded quartzo-feldspathic gneiss. These shear zones are folded, and progressively overprinted by amphibolite and greenschist facies shear zones that become wider with lower grade. The deformation sequences is explained by deep subduction of offscraped thrust slices of oceanic or lower continental crust, caught between the colliding North and South China cratons in the Mesozoic. After these slices were structurally isolated along the plate interface, they were rolled like ball-bearings, in the subduction channel during their exhumation, forming several generations of folds, sequentially lower-grade foliations and lineations, and intruded by several generations of in situ and exotically derived melts. The shear zones formed during different generations of deformation are wider with lower grades, suggesting that deep-crustal/upper mantle deformation operates efficiently (perhaps with more active crystallographic slip systems) than deformation at mid to upper crustal levels.

Relationship between high- and low-grade Archean terranes: Implications for early Earth paleogeography

NASA Technical Reports Server (NTRS)

Eriksson, K. A.

1986-01-01

The Western Gneiss Terrain (WGT) of the Yilgarn Block, Western Australia was studied. The WGT forms an arcuate belt of Archean gneisses that flank the western margin of the Yilgarn Block. In general the WGT is composed of high-grade orthogneisses and paragneisses which contain supracrustal belts composed largely of siliciclastic metasediments and subordinate iron formation. The platformal nature of the metasedimentary belts and lack of obvious metavolcanic lithologies contrasts with the composition of typical Yilgarn greenstones to the east. Radiometric data from WGT rocks indicates that these rocks are significantly older than Yilgarn rocks to the east (less than 3.3 Ga) and this has led to the suggestion that the WGT represents sialic basement to Yilgarn granite-greenstone belts. The Mount Narryer region exposes the northernmost occurrence of high-grade metasediments within the WGT and consists of quartz-rich clastic metasediments at upper amphibolite to granulite grade. Most occurrences of supracrustal rocks in this region comprise isolated lenses within the gneissic basement. However, at Mount Narryer a unique sequence of metaclastics with preserved bedding provide an unusual window into the parentage of similar supracrustal bodies in this region.

Metaultramafic schists and dismembered ophiolites of the Ashe Metamorphic Suite of northwestern North Carolina, USA

USGS Publications Warehouse

Raymond, Loren A.; Merschat, Arthur J.; Vance, R. Kelly

2016-01-01

Metaultramafic rocks (MUR) in the Ashe Metamorphic Suite (AMS) of northwestern North Carolina include quartz ± feldspar-bearing QF-amphibolites and quartz-deficient, locally talc-, chlorite-, and/or Mg-amphibole-bearing TC-amphibolites. Some workers divide TC-amphibolites into Todd and Edmonds types, based on mineral and geochemical differences, and we provisionally add a third type – olivine ± pyroxene-rich, Rich Mountain-type rocks. Regionally, MUR bodies range from equant, Rich Mountain- to highly elongate, Todd-TC-amphibolite-type bodies. The MURs exhibit three to five mineral associations containing assemblages with olivine, anthophyllitic amphibole, Mg-hornblende, Mg-actinolite, cummingtonite, and serpentine representing decreasing eclogite to greenschist facies grades of metamorphism over time. MUR protoliths are difficult to determine. Southwestern MUR bodies have remnant olivine ± pyroxene-rich assemblages representing ultrabasic-basic, dunite-peridotite-pyroxenite protoliths. Northeastern TC-amphibolite MURs contain hornblende and actinolitic amphiboles plus chlorites – aluminous and calcic assemblages suggesting to some that metasomatism of basic, QF-amphibolites yields all TC-amphibolites. Yet MgO-CaO-Al2O3 and trace element chemistries of many TC-amphibolites resemble compositions of plagioclase peridotites. We show that a few AMS TC-amphibolites had basaltic/gabbroic protoliths, while presenting arguments opposing application of the metasomatic hypothesis to all TC-amphibolites. We establish that MUR bodies are petrologically heterolithic and that TC-amphibolites are in contact with many rock types; that those with high Cr, Ni, and Mg have olivine- or pyroxene-dominated protoliths; that most exhibit three or more metamorphic mineral associations; and that contacts thought to be metasomatic are structural. Clearly, different MUR bodies have different chemistries representing various protoliths, and have different mineral assemblages, reflecting both chemical composition and metamorphic history. Spot sampling of heterolithic MUR bodies does not reveal MUR body character or history or allow ‘type’ designations. We recommend that the subdivision of MUR bodies into ‘types’ be abandoned and that the metasomatic hypothesis be carefully applied. AMS MURs and associated metamafic rocks likely represent fragments of dismembered ophiolites from various ophiolite types.

Multiple Generations of Boudinage in a P-T Path: Insights from 3D Analysis of Amphibolite Boudins in Marble on Naxos, Greece

NASA Astrophysics Data System (ADS)

von Hagke, C.; Virgo, S.; Urai, J. L.

2016-12-01

Boudins are periodic structures in mechanically layered rocks deformed by layer parallel extension. At first sight, 2D sections of boudinaged layers are similar although 3D boudin patterns can be dramatically different. We aim to develop criteria to infer 3D strain from 2D outcrop observation of boudins. In marble quarries in the high grade complex on Naxos, Greece, we studied spectacular outcrops of amphibolite and pegmatite boudins, in combination with serial slicing of quarried blocks to reconstruct the 3D boudin structures. We identified multiple boudin generations, with early, high grade pinch and swell boudins followed by two generations of brittle shearband and torn boudins formed along the retrograde path under greenschist facies conditions. This shows how the rheological contract between marble and amphibolite changes from amphibolite to greenschist facies and suggests E-W shortening and N-S stretching in the footwall of the Naxos detachment. The later phases of boudinage interact with existing boudin geometries, producing complex structures in 3D. In 2D section the complexity is not directly apparent and reveals itself only in statistical analysis of long continuous sections. Our findings highlight the importance of 3D characterization of boudinage structures for boudin classification. The insights we gain from the analysis of multiphase boudinage structures on Naxos are the basis for quantitative boudin analysis to infer rheology, effective stress, vorticity and strain and establish a mechanics-based boudin classification scheme.

Partial melting of amphibolites in the Eastern Segment of the Sveconorwegian orogen, southern Sweden.

NASA Astrophysics Data System (ADS)

Brophy, E.; Hansen, E. C.; Möller, C.; Huffman, M.

2017-12-01

Mafic migmatites with amphibolitic melanosome and tonalitic leucosome are a common feature in continental collision orogenic zones. However, the anatexis of mafic rocks has received much less attention than anatexis in felsic, intermediate or pelitic compositions. We examined mafic migmatites along a traverse within the Eastern Segment of the 1.14-0.9 Ga Sveconorwegian orogen, between Forsheda and Fegen southern Sweden. This traverse occurs in the center of a >150 km metamorphic transition from sub-greenschist facies in the east to high-pressure granulite and eclogite facies in the west (Möller and Andersson, unpublished metamorphic map). The Eastern Segment is a parautochthonous belt made up of rocks of the Fennoscandian shield that were deformed and metamorphosed during the Sveconorwegian orogeny. Within the traverse amphibolite bodies occur within migmatitic felsic to intermediate orthogneisses. The first appearance of tonalitic leucosome in amphibolite was observed towards the eastern edge of the traverse and continued to occur sporadically westward ranging in abundance (by outcrop area) from 0 to 25 %. The mineral assemblage in amphibolite is hbl + plag ( An30) + qtz + bt ± grt ± ilm ± ttn ± py ± SO2-rich scp. No examples of peritectic pyroxene associated with leucosome were found. The lack of peritectic pyroxene suggests that a water-rich phase was present at the onset of anatexis. The highly variable amount of leucosome further suggests that the amount of melt generated was determined by the amount of water available. Together these suggest that partial was driven by the local influx of a water-rich fluid. In the higher grade portions further west migmatitic amphibolite with tonalitic leucosome occurs in two varieties: one with peritectic pyroxene and relatively small amounts of leucosome, interpreted as forming by water-undersaturated dehydration melting, and another without peritectic pyroxene and with larger amounts of leucosome which is interpreted as having formed from water-fluxed melting (Hansen et al., Lithos, 2015). Thus, water-undersaturated melting in mafic rocks appears to have been limited to the higher-grade portions of the orogen. The variable amounts of leucosome produced by partial melting indicate that the presence of water-rich fluids was localized rather than penetrative.

P- T- t constraints on the development of the Doi Inthanon metamorphic core complex domain and implications for the evolution of the western gneiss belt, northern Thailand

NASA Astrophysics Data System (ADS)

Macdonald, A. S.; Barr, S. M.; Miller, B. V.; Reynolds, P. H.; Rhodes, B. P.; Yokart, B.

2010-01-01

The western gneiss belt in northern Thailand is exposed within two overlapping Cenozoic structural domains: the extensional Doi Inthanon metamorphic core complex domain located west of the Chiang Mai basin, and the Mae Ping strike-slip fault domain located west of the Tak batholith. New P- T estimates and U-Pb and 40Ar/ 39Ar age determinations from the Doi Inthanon domain show that the gneiss there records a complex multi-stage history that can be represented by a clockwise P- T- t path. U-Pb zircon and titanite dating of mylonitic calc-silicate gneiss from the Mae Wang area of the complex indicates that the paragneissic sequence experienced high-grade, medium-pressure metamorphism (M1) in the Late Triassic - Early Jurassic (ca. 210 Ma), in good agreement with previously determined zircon ages from the underlying core orthogneiss exposed on Doi Inthanon. Late Cretaceous monazite ages of 84 and 72 Ma reported previously from the core orthogneiss are attributed to a thermal overprint (M2) to upper-amphibolite facies in the sillimanite field. U-Pb zircon and monazite dating of granitic mylonite from the Doi Suthep area of the complex provides an upper age limit of 40 Ma (Late Eocene) for the early stage(s) of development of the actual core complex, by initially ductile, low-angle extensional shearing under lower amphibolite-facies conditions (M3), accompanied by near-isothermal diapiric rise and decompression melting. 40Ar/ 39Ar laserprobe dating of muscovite from both Doi Suthep and Doi Inthanon provided Miocene ages of ca. 26-15 Ma, representing cooling through the ca. 350 °C isotherm and marking late-stage development of the core complex by detachment faulting of the cover rocks and isostatic uplift of the sheared core zone and mantling gneisses in the footwall. Similarities in the thermochronology of high-grade gneisses exposed in the core complex and shear zone domains in the western gneiss belt of northern Thailand (and also in northern Vietnam, Laos, Yunnan, and central Myanmar) suggest a complex regional response to indentation of Southeast Asia by India.

Microstructural evidence for northeastward movement on the Chocolate Mountains fault zone, southeastern California

DOE Office of Scientific and Technical Information (OSTI.GOV)

Simpson, C.

1990-01-10

Microstructural analysis of rocks from the Chocolate Mountains fault zone, Gavilan Hills area, southeastern California, show unequivocal evidence for northeast directed transport of the upper plate gneisses over lower plate Orocopia schists. Samples were taken from transects through the fault zone. Prefaulting fabrics in upper plate gneisses show a strong component of northeast directed rotational deformation under lower amphibolite facies conditions. In contrast, prefaulting lower plate Orocopia schists show strongly coaxial fabrics (minimum stretch value of 2.2) formed at greenschist grade. Mylonitic fabrics associated with the Chocolate Mountains fault are predominantly northeast directed shear bands that are unidirectional (northeastward) inmore » the gneisses but bi-directional in the schists, suggesting a significant component of nonrotational deformation occurred in the Orocopia schists during and after emplacement of the upper plate. The kinematic findings are in agreement with Dillon et al. (1989), who found that the vergence of asymmetrical folds within the fault zone indicates overthrusting to the northeast, toward the craton, in this region. The available evidence favors a single protracted northeastward movement on the Chocolate Mountains fault zone with temperatures waning as deformation proceeded.« less

Pluton emplacement within an extensional transfer zone during dextral strike-slip faulting: an example from the late Archaean Abitibi Greenstone Belt

NASA Astrophysics Data System (ADS)

Lacroix, S.; Sawyer, E. W.; Chown, E. H.

1998-01-01

The Lake Abitibi area within the late Archaean Abitibi Greenstone Belt exhibits an interlinked plutonic, structural and metamorphic evolution that may characterize segmented strike-slip faults at upper-to-mid-crustal levels. Along the major, southeastward propagating Macamic D2 dextral strike-slip fault, Theological and preexisting D1 structural heterogeneities induced the development of NNW-trending dextral-oblique splays which evolved into an extensional trailing fan and created an extensional, NNW-dipping stepover. Magma flowing upwards from deeper parts of the Macamic Fault spread towards the southeast at upper crustal levels along both the oblique-slip and extensional D2 splays, and built several plutons in a pull-apart domain between 2696 and 2690 Ma. Different emplacement and material transfer mechanisms operated simultaneously in different parts of the system, including fault dilation and wedging, lateral expansion, wall-rock ductile flow and stoping. Transfer of movement between D2 splays occurred under ductile conditions during syn-emplacement, amphibolite-grade metamorphism (500-700 °C). During cooling (< 2690 Ma), narrower brittle-ductile zones of greenschist-grade shearing were concentrated along the pluton-wall rock contacts, but the extensional stepover locked since both normal and reverse movements occurred along NNW-dipping faults. Pluton emplacement, contact metamorphism and propagation of D2 faults appear to have been closely linked during the Superior Province-wide late transpressional event.

Carbonic fluid inclusions in amphibolite-facies pelitic schists from Bodonch area, western Mongolian Altai

NASA Astrophysics Data System (ADS)

Zorigtkhuu, Oyun-Erdene; Tsunogae, Toshiaki; Dash, Batulzii

We report first fluid inclusion data on amphibolite-facies pelitic schists from Bodonch area of western Mongolian Altai in the Central Asian Orogenic Belt. Three categories of fluid inclusions have been observed in quartz: dominant primary and secondary inclusions, and least dominant pseudosecondary inclusions. The melting temperatures of all the categories of inclusions lie in the narrow range of -57.5 °C to -56.6 °C, close to the triple point of pure CO2. Homogenization of fluids occurs into liquid phase at temperature between -33.3 °C to +19.4 °C, which convert into densities in the range of 0.78 g/cm3 to 1.09 g/cm3. The estimated CO2 isochores for primary and pseudosecondary high-density inclusions is broadly consistent with the peak metamorphic condition of the studied area (6.3-7.3 kbar at 655 °C). The results of this study, together with the primary and pseudosecondary nature of the inclusions, indicate CO2 was the dominant fluid component during the peak amphibolite-facies metamorphism of the study area. The examined quartz grains are texturally associated with biotite, kyanite and staurolite, which are regarded as high-grade minerals formed during prograde to peak metamorphism. Therefore quartz probably formed by high-grade metamorphism and the primary fluid inclusions trapped in the minerals probably preserve fluids at around peak metamorphism.

Bedrock Geologic Map of the Headwaters Region of the Cullasaja River, Macon and Jackson Counties, North Carolina

USGS Publications Warehouse

Burton, William C.

2007-01-01

The headwaters region of the Cullasaja River is underlain by metasedimentary and meta-igneous rocks of the Neoproterozoic Ashe Metamorphic Suite, including gneiss, schist, and amphibolite, that were intruded during Ordovician time by elongate bodies of trondhjemite, a felsic plutonic rock. Deformation, metamorphism, and intrusion occurred roughly simultaneously during the Taconic orogeny, about 470 million years ago, under upper-amphibolite-facies metamorphic conditions. Two generations of foliation and three major phases of folds are recognized. The second- and third-generation folds trend northeast and exert the most control on regional foliation trends. Since the orogeny, the region has undergone uplift, fracturing, and erosion. Resistance to erosion by the plutonic rock may be the primary reason for the relatively gentle relief of the high-elevation basin, compared to surrounding areas. Amphibolite is the most highly fractured lithology, followed by trondhjemite; the latter may have the best ground-water potential of the mapped lithologies by virtue of its high fracture density and high proportion of subhorizontal fractures.

Structural development of high-temperature mylonites in the Archean Wyoming province, northwestern Madison Range, Montana

USGS Publications Warehouse

Kellogg, Karl S.; Mogk, David W.

2009-01-01

The Crooked Creek mylonite, in the northwestern Madison Range, southwestern Montana, is defined by several curved lenses of high non-coaxial strain exposed over a 7-km-wide, northeast-trending strip. The country rocks, part of the Archean Wyoming province, are dominantly trondhjemitic to granitic orthogneiss with subordinate amphibolite, quartzite, aluminous gneiss, and sills of metabasite (mafic granulite). Data presented here support an interpretation that the mylonite formed during a period of rapid, heterogeneous strain at near-peak metamorphic conditions during an early deformational event (D1) caused by northwest–southeast-directed transpression. The mylonite has a well-developed L-S tectonite fabric and a fine-grained, recrystallized (granoblastic) texture. The strong linear fabric, interpreted as the stretching direction, is defined by elongate compositional “fish,” fold axes, aligned elongate minerals, and mullion axes. The margins of the mylonitic zones are concordant with and grade into regions of unmylonitized gneiss. A second deformational event (D2) has folded the mylonite surface to produce meter- to kilometer-scale, tight-to-isoclinal, gently plunging folds in both the mylonite and country rock, and represents a northwest–southeast shortening event. Planar or linear fabrics associated with D2 are remarkably absent. A third regional deformational event (D3) produced open, kilometer-scale folds generally with gently north-plunging fold axes. Thermobarometric measurements presented here indicate that metamorphic conditions during D1 were the same in both the mylonite and the country gneiss, reaching upper amphibolite- to lower granulite-facies conditions: 700 ± 50° C and 8.5 ± 0.5 kb. Previous geochronological studies of mylonitic and cross-cutting rocks in the Jerome Rock Lake area, east of the Crooked Creek mylonite, bracket the timing of this high-grade metamorphism and mylonitization between 2.78 and 2.56 Ga, nearly a billion years before the 1.78-Ga Big Sky orogeny, which overprinted the basement rocks exposed in adjacent ranges of the Wyoming province.

Northward extension of Carolina slate belt stratigraphy and structure, South-Central Virginia: Results from geologic mapping

USGS Publications Warehouse

Hackley, P.C.; Peper, J.D.; Burton, W.C.; Horton, J. Wright

2007-01-01

Geologic mapping in south-central Virginia demonstrates that the stratigraphy and structure of the Carolina slate belt extend northward across a steep thermal gradient into upper amphibolite-facies correlative gneiss and schist. The Neoproterozoic greenschist-facies Hyco, Aaron, and Virgilina Formations were traced northward from their type localities near Virgilina, Virginia, along a simple, upright, northeast-trending isoclinal syncline. This syncline is called the Dryburg syncline and is a northern extension of the more complex Virgilina synclinorium. Progressively higher-grade equivalents of the Hyco and Aaron Formations were mapped northward along the axial trace of the refolded and westwardly-overturned Dryburg syncline through the Keysville and Green Bay 7.5-minute quadrangles, and across the northern end of the Carolina slate belt as interpreted on previous geologic maps. Hyco rocks, including felsic metatuff, metawacke, and amphibolite, become gneisses upgrade with areas of local anatexis and the segregation of granitic melt into leucosomes with biotite selvages. Phyllite of the Aaron Formation becomes garnet-bearing mica schist. Aaron Formation rocks disconformably overlie the primarily felsic volcanic and volcaniclastic rocks of the Hyco Formation as evidenced by repeated truncation of internal contacts within the Hyco on both limbs of the Dryburg syncline at the Aaron-Hyco contact. East-northeast-trending isograds, defined successively by the first appearance of garnet, then kyanite ?? staurolite in sufficiently aluminous rocks, are superposed on the stratigraphic units and synclinal structure at moderate to high angles to strike. The textural distinction between gneisses and identifiable sedimentary structures occurs near the kyanite ?? staurolite-in isograd. Development of the steep thermal gradient and regional penetrative fabric is interpreted to result from emplacement of the Goochland terrane adjacent to the northern end of the slate belt during Alleghanian orogenesis. This mapping study indicates that the Carolina slate belt does not terminate on the north against through-going faults or rest on higher-grade basement as previously suggested.

Reconnaissance geology of the Jabal Bitran quadrangle, Kingdom of Saudi Arabia

USGS Publications Warehouse

Kahr, Viktor P.; Overstreet, W.C.; Whitlow, J.W.; Ankary, A.O.

1972-01-01

The Jabal Bitten quadrangle covers an area of 2833 sq km in the eastern part of the Precambrian Shield in Saudi Arabia. The rocks in the quadrangle are divided geographically alone arcuate north-trending lines into an eastern area of granite intruded by a swarm of dikes of rhyolite and andesite, and a western area of dominantly pelitic chlorite-sericite schist, separated by the narrow central complex of the Idsas Range. This complex is composed of pyroclastic rocks, lava, conglomerate, marble, and plutonic mafic rocks that have been intricately modified by episodes of metamorphism, igneous intrusion, and faulting. The Idsas Range contains ancient gold and copper mines, and deposits of magnetite, copper, asbestos, and chromite. The rocks in the Jabal Bitten quadrangle are here interpreted to consist of three major sedimentary and volcanic groups, the lowermost of which was deposited unconformably on hornblende-biotite granite gneiss, and all of which are intruded by granite dikes and plutons. From oldest to youngest the layered rocks are called Halaban Group, Bi'r Khountina Group, and Murdama Group, A biotite-hornblende granite is older than uppermost Bi'r Khountina, and peralkalic granite is younger than Murdama. The layered rocks of these groups are generally metamorphosed to the greenschist facies. The metamorphic grade rises abruptly at the Idsas Range to the albite-epidote-amphibolite facies and lower subfacies of the amphibolite facies in parts of the Halaban Group; some skarn east of the range may be in the upper part of the amphibolite facies. Characteristically, the Halaban Group has the highest grade and the greatest range in metamorphic grade, and the Murdama Group has the lowest but most uniformly developed metamorphic grade. The metamorphism of the rocks was caused by three successive pulses of regional dynamothermal metamorphism plus contact metamorphism around the younger bodies of plutonic igneous rocks. Four major structural elements of the quadrangle are reflected in the geography and geologic units. These are a mantled gneiss dome on the east separated from a north-plunging synclinorium in rocks of the Murdama and Bi?r Khountina Groups on the west by a narrow dejective zone of the Halaban and lower Bi?r Khountina. The dejective zone is much modified by impricate overthrusts and accompanying tear faults. These major faults have pushed elements of the Halaban and Bi?r Khountina westward over Bi?r Khountina and Murdama, with the result that very complex fault patterns have evolved. Open geochemical reconnaissance of the area disclosed one positive anomaly for nickel and 40 threshold indications of several elements, principally nickel, chromium, copper, and tungsten. Heavy-mineral and radiometric reconnaissance showed 18 areas containing scheelite and/or powellite and four areas of anomalous radioactivity. Most of these features are in the dejective zone, as are five of the nine ancient workings, the massive and disseminated magnetite, most of the secondary copper minerals, and the traces of asbestos, magnesite, and chromite known in the quadrangle. The mantled gneiss dome and a complex of gabbro and amphibolite on its southwestern flank are the next most mineralized areas. Scant evidence of mineralization is present in the Murdama Group west of the dejective zone. Magnetite deposits at Jabal Idsas have the greatest potential of the mineral deposits in the Jabal Bitran quadrangle. Further study of gold at Fawara and Selib mines is recommended, as is investigation of a positive nickel anomaly that shows threshold cobalt and above background radioactivity. The garnetiferous skarn in the east-central part of the quadrangle should be examined for composition and abrasive character of the garnet and for the remote possibility of tungsten in scheelite and beryllium in helvite.

Genesis of base-metal sulfide deposits, Alabama Piedmont: Final report for the 1985-1986 SOMED (School of Mines and Energy Development) project year

DOE Office of Scientific and Technical Information (OSTI.GOV)

Lesher, C.M.

1987-03-18

The best characterized massive sulfide deposit in the Northern Alabama Piedmont is the Stone Hill deposit, one of several small Fe-Cu-Zn deposits and prospects associated with metasedimentary and metavolcanic rocks of the Ashland Supergroup. The Fe-Cu-Zn sulfide mineralization in the Stone Hill district is hosted by thin felsic schist horizons within the Ketchepedrakee amphibolite, along the contact between metasediments of the Mad Indian and Poe Bridge Mountain Groups. Associated lithologies include garnetites, tremolite-chlorite rocks, and oxide facies iron-formations. The mineralized felsic schists and garnetites are of very limited stratigraphic extent, generally occur within the interpreted upper part of the amphibolite,more » and normally exhibit gradational contacts with enclosing amphibolites. The mineralized felsic schists contain enigmatic grains and polycrystalline aggregates of quartz +- feldspar +- amphibole +- mica that probably represent boudinaged quartz-feldspar segregations, but it is impossible to completely preclude an origin as recrystallized clastic sedimentary particles, recrystallized and deformed igneous phenocrysts, or cataclastic particles. Multivariate statistical analyses and mass balance calculations suggest that the mineralized felsic schists and garnetites are hydrothermally-altered, metamorphosed equivalents of the amphibolites, consistent with the field relationships. Interpretation of the Ketchepedrakee amphibolite as an ocean floor basalt, the mineralized felsic schists and garnetites as hydrothermally-altered variants, and the enclosing graphitic and garnetiferous schists as flysch-type sediments suggests that the rocks of the Stone Hill district were deposited along a rifted continental margin. The close association of mineralization and hydrothermal alteration indicates that a proximal volcanogenic model is most appropriate for the massive sulfide deposits in this area.« less

[sup 40]Ar/[sup 39]Ar mineral ages from southwestern Penobscot Bay, Maine: Evidence for Silurian metamorphism

DOE Office of Scientific and Technical Information (OSTI.GOV)

West, D.P. Jr.; Guidotti, C.V.; Lux, D.R.

1992-01-01

The nature and timing of metamorphic events in the Coastal Lithotectonic Block of Maine remain poorly understood. Immediately west and southwest of Penobscot Bay the rocks are polymetamorphic showing evidence for at least two episodes of amphibolite facies metamorphism and later, perhaps regionally extensive, retrograde events. Hornblende mineral separates from two amphibolites din the Port Clyde area have identical Ar-40/Ar-39 plateau ages of 414.0 [+-] 3.3 and 414.0 [+-] 3.9 Ma. These ages are interpreted to reflect the time of cooling following the last significant thermal event in this area. Biotite from an amphibolite in the Port Clyde area givesmore » a total gas age of 346.5 [+-] 3.2 Ma. Hornblende from an amphibolite 7 km to the west near Friendship gives a nearly concordant release spectrum with a plateau age of 369.0 [+-] 3.7 Ma. Coexisting biotite from this amphibolite gives a total gas age of 289.2 [+-] 2.7 Ma. Muscovite from the Waldoboro pluton has a nearly concordant release spectrum with a plateau age of 306.3 [+-] 2.2 Ma. Biotite from this sample gives a total gas age of 288.9 [+-] 2.2 Ma. The 414.0 Ma hornblende cooling ages from the Port Clyde area reflect cooling following a significant high grade Silurian thermal event. This Silurian metamorphism is the same age as tectonothermal events in the Nashoba Terrane in eastern Massachusetts, the Kingston Complex in southern New Brunswick, the Aspy Terrane in Cape Breton island, Nova Scotia, and the Hermitage Flexure in southern Newfoundland.d Thus a distinctive Silurian tectonothermal province located along the western edge of the Avalon Zone appears to extend discontinuously from Massachusetts to Newfoundland.« less

Microstructures of the Kirsehir Complex, Central Turkey

NASA Astrophysics Data System (ADS)

ISIK, V.; Caglayan, A.; Uysal, T.; Bolhar, R.

2011-12-01

Turkey is positioned on the boundary between the Eurasian and African/Arabian plates, providing an ideal natural laboratory for learning passive and active earth processes such as deformation, metamorphism, earthquakes and volcanism. Central Turkey historically has played an important role in evolution of the Alpine orogeny. The Kirsehir Complex is one of three Mesozoic-Early Tertiary metamorphic and plutonic mid-crustal basement units exposed in central Turkey. The most common lithology of the metamorphites are the banded gneisses, which are intercalated with layers of schists, amphibolites and quartzite, and marbles representing the structurally the highest metamorphites of the study area. The metamorphites are characterized by multiple folding episodes and overprinting faults (thrust, normal and strike-slip). These metamorphites reached peak metamorphic conditions of upper amphibolite facies, as indicated by local presence of clinopyroxene, sillimanite, hornblende, andalusite and garnet. Later, retrograde greenschist facies conditions were attained characterized by the alteration of feldspar and mafic minerals to muscovite and chlorite/actinolite, respectively. The microstructures of selected minerals can be used to bracket the metamorphic grade during which microstructure formed. Quartz displays undulose extinction, deformation bands, subgrains and deformation lamellae, and recrystallisation. The presence of lobate grain boundaries of quartz indicates that GBM recrystallisation occurred. Undulose extinction and recrystallisation are common in micas. Recrystallisation, core-mantle structures in feldspar, myrmekites in K-feldspars within the gneisses suggest that deformation occurred within the amphibolite facies. Garnet occurs as slightly elliptical porphroclats. Sillimanite is present as fibrolite growing near biotite and microboudinaged. Andalusite porphyroblast/porphroclats are elongate and microboudinaged. Kinematic indicators (asymmetric mantled grains, S-C fabrics and mineral fish) suggest top-to-the-southwest shear sense. Our preliminary field observations and microstructure studies suggest the following deformation history in the study area: (1) S-directed thrusting, folding of bedding and forming of S1 foliation, (2) the forming of S2 foliation/mineral stretching lineation/kinematic indicators, emplacement of plutons and exhumation of metamorphites during regional extension, (3) folding of metamorphites, plutons and Paleogene sedimentary units, NNE-directed thrusting and local S3 foliation.

Structural evolution of the Sarandí del Yí Shear Zone, Uruguay: kinematics, deformation conditions and tectonic significance

NASA Astrophysics Data System (ADS)

Oriolo, S.; Oyhantçabal, P.; Heidelbach, F.; Wemmer, K.; Siegesmund, S.

2015-10-01

The Sarandí del Yí Shear Zone is a crustal-scale shear zone that separates the Piedra Alta Terrane from the Nico Pérez Terrane and the Dom Feliciano Belt in southern Uruguay. It represents the eastern margin of the Río de la Plata Craton and, consequently, one of the main structural features of the Precambrian basement of Western Gondwana. This shear zone first underwent dextral shearing under upper to middle amphibolite facies conditions, giving rise to the reactivation of pre-existing crustal fabrics in the easternmost Piedra Alta Terrane. Afterwards, pure-shear-dominated sinistral shearing with contemporaneous magmatism took place under lower amphibolite to upper greenschist facies conditions. The mylonites resulting from this event were then locally reactivated by a cataclastic deformation. This evolution points to strain localization under progressively retrograde conditions with time, indicating that the Sarandí del Yí Shear Zone represents an example of a thinning shear zone related to the collisional to post-collisional evolution of the Dom Feliciano Belt that occurred between the Meso- to Neoproterozoic (>600 Ma) and late Ediacaran-lower Cambrian times.

Strain softening along the MCT zone from the Sikkim Himalaya: Relative roles of Quartz and Micas

NASA Astrophysics Data System (ADS)

Bhattacharyya, Kathakali; Mitra, Gautam

2011-06-01

In the Darjeeling - Sikkim Himalaya, two distinct faults form the Main Central thrust (MCT), the structurally higher MCT1 and the lower MCT2; each has accommodated translation greater than 100 km. The lower MCT2 places Greater Himalayan amphibolite grade Paro-Lingtse gneiss over Lesser Himalayan greenschist grade Daling metapelites. The MCT2 is folded by the underlying Lesser Himalayan duplex and is exposed at different structural positions of the fold. At Pelling, the MCT2 zone is exposed as a ˜373 m thick NW dipping fault zone that exposes ˜19 m of hanging wall mylonitized Lingtse gneiss. The Lingtse protolith shows evidence of amphibolite grade plastic deformation features in quartz and feldspar. Within the hanging wall mylonite zone (HWMZ), quartz and feldspar have undergone grain-size reduction by different deformation mechanisms and feldspars are sericitized suggesting the presence of fluids during deformation. We estimate a temperature of ˜300 °C within the fault zone during fluid-assisted retrogression and deformation. Reaction softening of feldspars produced a large proportion of intrinsically weak matrix. This, in combination with development of a strong foliation defined by parallel mica grains, resulted in strain softening along the MCT2 zone, and concentrated the deformation along a thin zone or zones.

ISOTOPIC COMPOSITIONS OF SULFATE ASSOCIATED WITH THE OXIDATION OF ARSENIAN SULFIDE MINERALOGY IN THE GOOSE RIVER GROUNDWATERSHED, MAINE

EPA Science Inventory

Geogenic arsenic occurs in groundwater within the polymethamorphic amphibolite-grade Waldoboro Pluton Complex in mid-coastal Maine. A few As water samples exceeded 10 ug l(-1). Part of the fractured hydrogeologic "aquifer" is exposed in the Goose River groundwatershed (33 km(2))....

Deformation of the Songshugou ophiolite in the Qinling orogen

NASA Astrophysics Data System (ADS)

Sun, Shengsi; Dong, Yunpeng

2017-04-01

The Qinling orogen, middle part of the China Central Orogenic Belt, is well documented that was constructed by multiple convergences and subsequent collisions between the North China and South China Blocks mainly based on geochemistry and geochronology of ophiolites, magmatic rocks as well as sedimentary reconstruction. However, this model is lack of constraints from deformation of subduction/collision. The Songshugou ophiolite outcropped to the north of the Shangdan suture zone represents fragments of oceanic crust and upper mantle. Previous works have revealed that the ophiolite was formed at an ocean ridge and then emplaced in the northern Qinling belt. Hence, deformation of the ophiolite would provide constraints for the rifting and subduction processes. The ophiolite consists chiefly of metamorphosed mafic and ultramafic rocks. The ultramafic rocks contain coarse dunite, dunitic mylonite and harzburgite, with minor diopsidite veins. The mafic rocks are mainly amphibolite, garnet amphibolite and amphibole schist, which are considered to be eclogite facies and retrograde metamorphosed oceanic crust. Amphibole grains in the mafic rocks exhibit a strong shape-preferred orientation parallel to the foliation, which is also parallel to the lithologic contacts between mafic and ultramafic rocks. Electron backscattered diffraction (EBSD) analyses show strong olivine crystallographic preferred orientations (CPO) in dunite including A-, B-, and C-types formed by (010)[100], (010)[001] and (100)[001] dislocation slip systems, respectively. A-type CPO suggests high temperature plastic deformation in the upper mantle. In comparison, B-type may be restricted to regions with significantly high water content and high differential stress, and C-type may also be formed in wet condition with lower differential stress. Additionally, the dunite evolved into amphibolite facies metamorphism with mineral assemblages of olivine + talc + anthophyllite. Assuming a pressure of 1.5 GPa, which corresponds to equilibration in the spinel stability field, application of the olivine-spinel thermometer (Ballhaus et al., 1991) suggests temperature of 622 ± 22 °C. Amphibole schists display well-developed amphibole CPO with [100], [010] and [001] axes concentrate parallel to Z-, Y- and X-directions, respectively. The strong CPO of amphiboles could be interpreted as anisotropic growth and passive rigid-body rotation under various different stresses rather than results of dislocation creep. The Hbl + Pl thermometer (Holland and Blundy, 1994) constrains the equilibrium temperature to be 640 ± 34 °C for the amphibolite facies metamorphism. Zircons in light-color from the amphibolite with Th/U<0.1 and depletion of HREE yield a U-Pb age of 504 ± 10 Ma, representing the metamorphic age of eclogite. In comparison, the zircons in dark-color from amphibolite showing flat HREE patterns and negative abnormal of Eu give a U-Pb age of 489 ± 5.2 Ma, constraining the time of retrograde metamorphism of eclogite. Together with field investigation and regional geology, our new data propose that the A-type olivine CPO was formed in oceanic upper mantle with the spreading of Shangdan ocean before ca. 514 Ma. At ca. 504 Ma, the deep subduction of oceanic lithosphere endured eclogite facies metamorphism and induced B-type olivine CPO. Up to ca. 489 Ma, obduction of the fragments of metamorphosed oceanic lithosphere resulted in the C-type olivine CPO in dunite and amphibole CPO in the retrograded metamorphic eclogite.

The Hardwood Gneiss: Evidence for high P-T Archean metamorphism in the southern province of the Lake Superior region

DOE Office of Scientific and Technical Information (OSTI.GOV)

Peterson, J.W.; Geiger, C.A.

1990-03-01

The Hardwood Gneiss is an areally small unit of Precambrian granulite-grade rocks exposed in the Archean gneiss terrane of the southern Lake Superior region. The rocks are located in the southwestern portion of the Upper Peninsula of Michigan and consist of a structurally conformable package of quartzitic, metapelitic, amphibolitic, and metabasic units. Three texturally distinct garnet types are present in the metabasites and are interpreted to represent two metamorphic events. Geothermobarometry indicates conditions of {approximately}8.2-11.6 kbar and {approximately}770C for M1, and conditions of {approximately}6.0-10.1 kbar and {approximately}610-740C for M2. It is proposed that M1 was Archean and contemporaneous with amore » high-grade metamorphic event recorded in the Minnesota River Valley. The M2 event was probably Early Proterozoic and pre-Penokean, with metamorphic conditions more intense than those generally ascribed to the Penokean Orogeny in Michigan, but similar to the conditions reported for the Kapuskasing zone of Ontario. The high paleopressures and temperatures of the M1 event make the Hardwood Gneiss distinct from any rocks previously described in the southern Lake Superior region, and suggest intense tectonic activity during the Archean.« less

The mafic-ultramafic complex of Aniyapuram, Cauvery Suture Zone, southern India: Petrological and geochemical constraints for Neoarchean suprasubduction zone tectonics

NASA Astrophysics Data System (ADS)

Yellappa, T.; Venkatasivappa, V.; Koizumi, T.; Chetty, T. R. K.; Santosh, M.; Tsunogae, T.

2014-12-01

Several Precambrian mafic-ultramafic complexes occur along the Cauvery Suture Zone (CSZ) in Southern Granulite Terrain, India. Their origin, magmatic evolution and relationship with the associated high-grade rocks have not been resolved. The Aniyapuram Mafic-Ultramafic Complex (AMUC), the focus of the present study in southern part of the CSZ, is dominantly composed of peridotites, pyroxenites, gabbros, metagabbros/mafic granulites, hornblendites, amphibolites, plagiogranites, felsic granulites and ferruginous cherts. The rock types in the AMUC are structurally emplaced within hornblende gneiss (TTG) basement rocks and are highly deformed. The geochemical signature of the amphibolites indicates tholeiitic affinity for the protolith with magma generation in island arc-setting. N-MORB normalized pattern of the amphibolites show depletion in HFS-elements (P, Zr, Sm, Ti, and Y) and enrichment of LIL-elements (Rb, Ba, Th, Sr) with negative Nb anomalies suggesting involvement of subduction component in the depleted mantle source and formation in a supra-subduction zone tectonic setting. Our new results when correlated with the available age data suggest that the lithological association of AMUC represent the remnants of the Neoarchean oceanic lithosphere.

The behaviour of monazite from greenschist facies phyllites to anatectic gneisses: An example from the Chugach Metamorphic Complex, southern Alaska

PubMed Central

Gasser, Deta; Bruand, Emilie; Rubatto, Daniela; Stüwe, Kurt

2012-01-01

Monazite is a common accessory mineral in various metamorphic and magmatic rocks, and is widely used for U–Pb geochronology. However, linking monazite U–Pb ages with the PT evolution of the rock is not always straightforward. We investigated the behaviour of monazite in a metasedimentary sequence ranging from greenschist facies phyllites into upper amphibolites facies anatectic gneisses, which is exposed in the Eocene Chugach Metamorphic Complex of southern Alaska. We investigated textures, chemical compositions and U–Pb dates of monazite grains in samples of differing bulk rock composition and metamorphic grade, with particular focus on the relationship between monazite and other REE-bearing minerals such as allanite and xenotime. In the greenschist facies phyllites, detrital and metamorphic allanite is present, whereas monazite is absent. In lower amphibolites facies schists (~ 550–650 °C and ≥ 3.4 kbar), small, medium-Y monazite is wide-spread (Mnz1), indicating monazite growth prior and/or simultaneous with growth of garnet and andalusite. In anatectic gneisses, new low-Y, high-Th monazite (Mnz2) crystallised from partial melts, and a third, high-Y, low-Th monazite generation (Mnz3) formed during initial cooling and garnet resorption. U–Pb SHRIMP analysis of the second and third monazite generations yields ages of ~ 55–50 Ma. Monazite became unstable and was overgrown by allanite and/or allanite/epidote/apatite coronas within retrograde muscovite- and/or chlorite-bearing shear zones. This study documents polyphase, complex monazite growth and dissolution during a single, relatively short-lived metamorphic cycle. PMID:26525358

Building the Pamir-Tibet Plateau: Eo-Oligocene Crustal Stacking and Orogen Parallel Evasion of Upper and Middle Crustal Material in the Pamir

NASA Astrophysics Data System (ADS)

Rutte, D.; Ratschbacher, L.; Stübner, K.; Schneider, S.

2015-12-01

The gneisses of the Central Pamir Domes and their cover document crustal stacking of a ~10 km thick Ediacaran-Paleogene succession to a thickness of >35 km and their exhumation along bi-vergent, top-to-N and top-to S, normal-sense shear zones. The giant South Pamir Shakhdara-Alichur gneiss-dome system formed similarly by N-S extension along bivergent detachments. Prograde amphibolite-facies metamorphism in the domes and low-grade metamorphism in their hanging wall is dated at ~40 Ma (Lu-Hf garnet, U-Pb titanite) [Smit et al., 2014; Stearns et al., 2015] and ~33 Ma (K/Ar sericite). Retrograde metamorphism―driven by crustal extension―started at ~21 Ma (multi-method thermochronology; Stearns et al.[2013]). These Gneiss Domes offer a unique window into the Eocene-Miocene state of the Asian middle crust of the Pamir-Tibet Plateau. Top-to-N thrust stacking accommodated thickening in the upper crust, with displacements of single thrust sheets of > 30 and > 19 km. At depth, ductile flow formed km-scale recumbent fold nappes. We reconstruct their geometry by structural mapping and U-Pb zircon dating, documenting repetition of metatuffite, and paragneiss layers. In the interior of the domes, amphibolite-facies deformation fabrics with prograde kyanite define an E-W stretching lineation. Associated microstructures indicate top-to-E and top-to-W shear senses. Chocolate tablet boudinage indicate vertical flattening during bulk crustal thickening. We suggest that prograde E-W stretching relates to an early orogen-parallel flow component in the middle crust, contemporaneous with crustal stacking during bulk top-to-N convergence prior to ~21 Ma. Material likely evaded laterally out of the Pamir, contributing to >60 km thick crust in the Hindu Kush, west of the India-Asia frontal collision. In the Neogene crust extruded laterally from the Pamir Plateau to the west by dextral wrenching and E-W extension; this component of deformation is accommodated by E-W shortening in the Afghan-Tajik Depression.

Sm-Nd dating of multiple garnet growth events in an arc-continent collision zone, northwestern U.S. Cordillera

NASA Astrophysics Data System (ADS)

Getty, Stephen R.; Selverstone, Jane; Wernicke, Brian P.; Jacobsen, Stein B.; Aliberti, Elaine; Lux, Daniel R.

1993-03-01

Integrated petrologic and Sm-Nd isotopic studies in garnet amphibolites along the Salmon River suture zone, western Idaho, delineate two periods of amphibolite grade metamorphism separated by at least 16 million years. In one amphibolite, P-T studies indicate a single stage of metamorphism with final equilibration at ˜600°C and 8 9 kbar. The Sm-Nd isotopic compositions of plagioclase, apatite, hornblende, and garnet define a precise, 8-point isochron of 128±3 Ma (MSWD=1.2) interpreted as mineral growth at the metamorphic peak. A40Ar/39Ar age for this hornblende indicates cooling through ˜525°C at 119±2 Ma. In a nearby amphibolite, garnets with a two-stage growth history consist of inclusion-rich cores surrounded by discontinuous, inclusion-free overgrowths. Temporal constraints for core and overgrowth development were derived from Sm-Nd garnet — whole rock pairs in which the garnet fractions consist of varying proportions of inclusion-free to inclusion-bearing fragments. Three garnet fractions with apparent “ages” of 144, 141, and 136 Ma are thought to represent mixtures between late Jurassic (pre-144 Ma) inherited radiogenic components preserved within garnet cores and early Cretaceous (˜128 Ma) garnet overgrowths. These observations confirm the resilience of garnet to diffusive exchange of trace elements during polymetamorphism at amphibolite facies conditions. Our geochronologic results show that metamorphism of arc-derived rocks in western Idaho was episodic and significantly older than in arc rocks along the eastern margin of the Wrangellian Superterrane in British Columbia and Alaska. The pre-144 Ma event may be an expression of the late Jurassic amalgamation of marginal oceanic arc-related terranes (e.g., Olds Ferry, Baker, Wallowa) during the initial phases of their collision with North American rocks. Peak metamorphism at ˜128 Ma reflects tectonic burial along the leading edge of the Wallowa arc terrane during its final penetration and suturing to cratonic North America.

Zircon ion microprobe dating of high-grade rocks in Sri Lanka

DOE Office of Scientific and Technical Information (OSTI.GOV)

Kroener, A.; Williams, I.S.; Compston, W.

1987-11-01

The high-grade gneisses of Sri Lanka display spectacular in-situ granulitization phenomena similar to those observed in southern India and of current interest for evolutionary models of the lower continental crust. The absolute ages of these rocks are poorly constrained and so, using the SHRIMP ion microprobe, the authors have analyzed small spots on zircons from upper amphibolite to granulite grade quartzitic and pelitic metasediments. Detrital grains from a metaquartzite of the Highland Group preserve premetamorphic U-Pb ages of between 3.17 and 2.4 Ga and indicate derivation of the sediment from an unidentified Archean source terrain. The Pb-loss patterns of thesemore » zircons and the other samples suggest severe disturbance at ca 1100 Ma ago, which the authors attribute to high-grade regional metamorphism. Two pelitic gneisses contain detrital zircons with ages up to 2.04 Ga and also record an approx. = 1100 Ma event that is also apparent from metamorphic rims around old cores and new zircon growth. A granite intrusive into the Highland Group granulites records an emplacement age of 1000-1100 Ma as well as metamorphic disturbance some 550 Ma ago but also contains older, crustally derived xenocrysts. Zircons from a metaquartzite xenolith within the granitoid Vijayan Complex are not older than approx. 1100 Ma; therefore the Vijayan is neither Archean in age nor acted as basement to the Highland Group, as previously proposed. The authors suggest that the Vijayan Complex formed significantly later than the Highland Group and that the two units were brought into contact through post-1.1 Ga thrusting. Although the granulitization phenomena in India and Sri Lanka are similar, the granulite event in Sri Lanka is not Archean in age but took place in the late Proterozoic.« less

Ammonium loss and nitrogen isotopic fractionation in biotite as a function of metamorphic grade in metapelites from western Maine, USA

NASA Astrophysics Data System (ADS)

Plessen, Birgit; Harlov, Daniel E.; Henry, Darrell; Guidotti, Charles V.

2010-08-01

Ammonium fixed in micas of metamorphic rocks is a sensitive indicator both of organic-inorganic interactions during diagenesis as well as of the devolatilization history and fluid/rock interaction during metamorphism. In this study, a collection of geochemically well-characterized biotite separates from a series of graphite-bearing Paleozoic greenschist- to upper amphibolite-facies metapelites, western Maine, USA, were analyzed for ammonium nitrogen ( NH4+-N) contents and isotopic composition (δ 15N NH4) using the HF-digestion distillation technique followed by the EA-IRMS technique. Biotite separates, sampled from 9 individual metamorphic zones, contain 3000 to 100 ppm NH4+-N with a wide range in δ 15N from +1.6‰ to +9.1‰. Average NH4+-N contents in biotite show a distinct decrease from about 2750 ppm for the lowest metamorphic grade (˜500 °C) down to 218 ppm for the highest metamorphic grade (˜685 °C). Decreasing abundances in NH4+ are inversely correlated in a linear fashion with increasing K + in biotite as a function of metamorphic grade and are interpreted as a devolatilization effect. Despite expected increasing δ 15N NH4 values in biotite with nitrogen loss, a significant decrease from the Garnet Zones to the Staurolite Zones was found, followed by an increase to the Sillimanite Zones. This pattern for δ 15N NH4 values in biotite inversely correlates with Mg/(Mg + Fe) ratios in biotite and is discussed in the framework of isotopic fractionation due to different exchange processes between NH4+-NH or NH4+-N, reflecting devolatilization history and redox conditions during metamorphism.

New evidence for an old idea: Geochronological constraints for a paired metamorphic belt in the central European Variscides

NASA Astrophysics Data System (ADS)

Will, T. M.; Schmädicke, E.; Ling, X.-X.; Li, X.-H.; Li, Q.-L.

2018-03-01

New geochronological data reveal a prolonged tectonothermal evolution of the Variscan Odenwald-Spessart basement, being part of the Mid-German Crystalline Zone in central Europe. We report the results from (i) secondary ion mass spectrometry (SIMS) U-Pb dating of zircon, rutile and monazite, (ii) SIMS zircon oxygen isotope analyses, (iii) laser ablation-multicollector-inductively coupled plasma mass spectrometry (LA-MC-ICPMS) zircon Lu-Hf isotope analyses and, (iv) LA-ICPMS zircon and rutile trace element data for a suite of metamorphic rocks (five amphibolite- and eclogite-facies mafic meta-igneous rocks and one granulite-facies paragneiss). The protoliths of the mafic rocks formed from juvenile as well as depleted mantle sources in distinct tectonic environments at different times. Magmatism took place at a divergent oceanic margin (possibly in a back-arc setting) at 460 Ma, in an intraoceanic basin at ca. 445 Ma and at a continental margin at 329 Ma. Regardless of lithology, zircon in eclogite, amphibolite and high-temperature paragneiss provide almost identical Carboniferous ages of 333.7 ± 4.1 Ma (eclogite), 329.1 ± 1.8 to 328.4 ± 8.9 Ma (amphibolite), and 334.0 ± 2.0 Ma (paragneiss), respectively. Rutile yielded ages of 328.6 ± 4.7 and 321.4 ± 7.0 Ma in eclogite and amphibolite, and monazite in high-temperature paragneiss grew at 330.1 ± 2.4 Ma (all ages are quoted at the 2σ level). The data constrain coeval high-pressure eclogite- and high-temperature granulite-facies metamorphism of the Odenwald-Spessart basement at ca. 330 Ma. Amphibolite-facies conditions were attained shortly afterwards. The lower plate eclogite formed in a fossil subduction zone and the upper plate high-temperature, low-pressure rocks are the remains of an eroded Carboniferous magmatic arc. The close proximity of tectonically juxtaposed units of such radically different metamorphic conditions and thermal gradients is characteristic for a paired metamorphic belt sensu Miyashiro (1961). Thus, the Odenwald-Spessart basement represents the first recognised paired metamorphic belt in the European Variscides.

Geological evolution of the late Proterozoic ``Mozambique Belt'' of Kenya

NASA Astrophysics Data System (ADS)

Mosley, P. N.

1993-05-01

Within the "Mozambique Belt" of Kenya at least four distinct tectonothermal episodes are recognised on Rb-Sr isotopics. The dates are in broad agreement with those from surrounding countries; principal ages/age ranges being 830 - 800, ~ 760, 630 - 580 and 560 - 520 Ma. All except the last attained at least upper amphibolite/granulite grade (with local melts). The first event was responsible for the primary transformation of an essentially sedimentary sequence to paragneisses with an initial near-horizontal fabric parallel to the compositional layering. Associated with the later part of the first phase, and linked to the second, is the emplacement of allochthonous ophiolitic and volcanosedimentary "packages", coupled with thrusting and imbrication of the paragneiss groups. The subsequent phases record progressive shortening across the orogenic belt during collision between two major continental fragments (east and west Gondwana), involving extensive structural reorganisation and isotopic resetting. During the progressive 630 - 580 Ma event, regional N-S- to NNW-SSE-trending ductile shear zones (generally sinistral) were produced giving the dominant regional fabric (including a regional N-S-stretching lineation), and controlling the present gross distribution of gneiss groups. Cooling and uplift post a ~ 560 Ma thermal event has exposed high-grade gneisses with a distinct structural and metamorphic asymmetry across the orogen. The western part of the orogen shows clockwise P- T- t paths and involves overthrusting of, and imbrication with, the Tanzanian craton which probably obscures older (1900 and 1100 Ma) tectonothermal episodes. In contrast, the eastern part has anti-clockwise P- T- t paths, is characterised by extensive crustal melts, and retains the isotopic imprint of earlier Proterozoic events. The present level of uplift exposes tectonised high-grade gneisses of more than one age. Current evidence supports the suggestion that low-grade ophiolitic/volcanosedimentary sequences are allochthonous and structurally emplaced over the higher-grade gneisses.

Mineral texture based seismic properties of meta-sedimentary and meta-igneous rocks in the orogenic wedge of the Central Scandinavian Caledonides

NASA Astrophysics Data System (ADS)

Almqvist, B. S. G.; Czaplinska, D.; Piazolo, S.

2015-12-01

Progress in seismic methods offers the possibility to visualize in ever greater detail the structure and composition of middle to lower continental crust. Ideally, the seismic parameters, including compressional (Vp) and shear (Vs) wave velocities, anisotropy and Vp/Vs-ratio, allow the inference of detailed and quantitative information on the deformation conditions, chemical composition, temperature and the amount and geometry of fluids and melts in the crust. However, such inferences regarding the crust should be calibrated with known mineral and rock physical properties. Seismic properties calculated from the crystallographic preferred orientation (CPO) and laboratory measurements on representative core material allow us to quantify the interpretations from seismic data. The challenge of such calibrations lies in the non-unique interpretation of seismic data. A large catalogue of physical rock properties is therefore useful, with as many constraining geophysical parameters as possible (including anisotropy and Vp/Vs ratio). We present new CPO data and modelled seismic properties for amphibolite and greenschist grade rocks representing the orogenic wedge in the Central Scandinavian Caledonides. Samples were collected from outcrops in the field and from a 2.5 km long drill core, which penetrated an amphibolite-grade allochthonous unit composed of meta-sedimentary and meta-igneous rocks, as well as mica and chlorite-rich mylonites. The textural data was acquired using large area electron backscatter diffraction (EBSD) maps, and the chemical composition of minerals obtained by energy dispersive x-ray (EDS). Based on the texture data, we compare and evaluate some of the existing methods to calculate texture-based seismic properties of rocks. The suite of samples consists of weakly anisotropic rocks such as felsic gneiss and calc-silicates, and more anisotropic amphibolite, metagabbro, mica-schist. The newly acquired dataset provides a range of seismic properties that improves compositional and structural characterization of deformed middle and lower crust.

The Younger Age Limit of Metasedimentary Protolith Formation of the Lower Part of the Udokan Group Rocks (Aldan Shield)

NASA Astrophysics Data System (ADS)

Kotov, A. B.; Salnikova, E. B.; Kovach, V. P.; Velikoslavinskii, S. D.; Sklyarov, E. V.; Gladkochub, D. P.; Larin, A. M.; Tolmacheva, E. V.; Fedoseenko, A. M.; Plotkina, Yu. V.

2018-04-01

Biotite plagiogranite intruding sediments of the Kodar Sub-Group of the Udokan Group that have both undergone amphibolite grade alterations has been dated by the U-Pb ID TIMS technique using zircon to 2105 ± 6 Ma. This age estimate to a first approximation corresponds to the younger age limit of deposition of the siliciclastics in the lower section of the Udokan Group.

Late Mesoproterozoic to Early Paleozoic history of metamorphic basement from the southeastern Chiapas Massif Complex, Mexico, and implications for the evolution of NW Gondwana

NASA Astrophysics Data System (ADS)

Weber, Bodo; González-Guzmán, Reneé; Manjarrez-Juárez, Román; Cisneros de León, Alejandro; Martens, Uwe; Solari, Luigi; Hecht, Lutz; Valencia, Victor

2018-02-01

In this paper, U-Pb zircon geochronology, Lu-Hf and Sm-Nd isotope systematics, geochemistry and geothermobarometry of metaigneous basement rocks exposed in the southeastern Chiapas Massif Complex are presented. Geologic mapping of the newly defined "El Triunfo Complex" located at the southeastern edge of the Chiapas Massif reveals (1) partial melting of a metamorphic basement mainly constituted by mafic metaigneous rocks (Candelaria unit), (2) an Ediacaran metasedimentary sequence (Jocote unit), and (3) occurrence of massif-type anorthosite. All these units are intruded by undeformed Ordovician plutonic rocks of the Motozintla suite. Pressure and temperature estimates using Ca-amphiboles, plagioclase and phengite revealed prograde metamorphism that reached peak conditions at 650 °C and 6 kbar, sufficient for partial melting under water saturated conditions. Relict rutile in titanite and clinopyroxene in amphibolite further indicate a previous metamorphic event at higher P-T conditions. U-Pb zircon ages from felsic orthogneiss boudins hosted in deformed amphibolite and migmatite yield crystallization ages of 1.0 Ga, indicating that dry granitic protoliths represent remnants of Rodinia-type basement. Additionally, a mid-Tonian ( 920 Ma) metamorphic overprint is suggested by recrystallized zircon from a banded gneiss. Zircon from folded amphibolite samples yield mainly Ordovician ages ranging from 457 to 444 Ma that are indistinguishable from the age of the undeformed Motozintla plutonic suite. Similar ages between igneous- and metamorphic- zircon suggest a coeval formation during a high-grade metamorphic event, in which textural discrepancies are explained in terms of differing zircon formation mechanisms such as sub-solidus recrystallization and precipitation from anatectic melts. In addition, some amphibolite samples contain inherited zircon yielding Stenian-Tonian ages around 1.0 Ga. Lu-Hf and Sm-Nd isotopes and geochemical data indicate that the protoliths of the amphibolite have E-MORB characteristics and were derived from a depleted mantle source younger than the Rodinia-type basement. Inasmuch as similar amphibolites also occur in the Ediacaran metasedimentary rocks as dykes or lenses, Late Neoproterozoic magmatism in a rift setting is suggested. Hence, the geologic record of the El Triunfo Complex includes evidences for Rodinia assemblage, Tonian circum-Rodinia subduction, and breakup during the Late Neoproterozoic. Metamorphism, and partial melting are interpreted in terms of a convergent margin setting during the Ordovician. The results place the southern Chiapas Massif along with Oaxaquia and similar Northern Andes terranes on the NW margin of Gondwana interpreted as the extension of the Famatinian orogen that evolved during the closure of the Iapetus Ocean.

Paleostress analysis of the upper-plate rocks of Anafi Island (Cyclades, Greece)

NASA Astrophysics Data System (ADS)

Soukis, Konstantinos; Lozios, Stylianos

2017-04-01

The Attic Cycladic complex (Aegean Sea, Greece) is an area where profound extension, as a result of the Hellenic trench retreat due to slab-rollback, has exhumed mid-crustal rocks to the surface. The remnants of the upper plate are observed in the form of clippen scattered throughout the complex, occupying a very small percentage of the area. Anafi Island, located at the southeastern rim of the Attic-Cycladic complex, represents one of the few areas where a significant part of the upper plate units can be observed and studied. The complex tectonostratigraphy of Anafi Island is characterized by inverted metamorphism and includes a series of medium to high-grade metamorphic rocks that are thrusted onto a non-metamorphosed Paleogene flysch. The uppermost amphibolitic-facies thrust sheets were intruded in the late Cretaceous by intermediate to felsic magmatic rocks. The nappe pile was later destroyed in the late Miocene - Pliocene through successive stages of normal faulting that included both low- and high-angle normal faults. During that stage, supra-detachment syn-extensional sedimentation has taken place thus giving the opportunity to put some age constraints on the fault activity. Paleostress analysis with the separation and stress inversion method TRM revealed two stress tensors that can explain the fault-slip data-set of Anafi Island related to NE-SW and N-S extension, respectively. The older NE-SW trend is related to the late Miocene stress field whereas the N-S is likely related to the present day stress field. These results show that there was a gradual rotation to the trend of least principal stress axis (σ3), that could be associated with regional events such as the escape of Anatolia towards the Aegean and fastest retreat of the Hellenic subduction zone.

13C 12C exchange between calcite and graphite: A possible thermometer in Grenville marbles

USGS Publications Warehouse

Valley, J.W.; O'Neil, J.R.

1981-01-01

The fractionation of 13C between calcite and graphite, ??(Cc-Gr). is consistently small (2.6-4.8 permil) in 34 assemblages from upper amphibolite- and granulite-facies marbles of the Grenville Province. In 25 samples from the Adirondack Mountains, New York, it decreases regularly with increasing metamorphic temperature. The fractionations are independent of absolute ??13C values of calcite (-2.9 to +5.0). For T = 600-800??C, the Adirondack data are described by ??(Cc-Gr) = -0.00748T (??C) + 8.68. This good correlation between ?? and T suggests that carbon isotope equilibrium was attained in these high-grade marbles and that the theoretical calculations of this fractionation by Bottinga are approximately 2 permil too large in this temperature range. Because of the relatively high temperature sensitivity suggested by these results and by Bottinga's calculations, and the pressure independence of isotope fractionation, ??(Cc-Gr) may provide a very good thermometer for high-grade marbles. Comparison of this field calibration for ??(Cc-Gr) vs temperature with results from other terranes supports the utility of ??(Cc-Gr) for geothermometry and suggests that graphite is much more sluggish to exchange than calcite, that exchange between calcite and graphite occurs at temperatures as low as 300??C, and that equilibrium may normally be attained only when peak metamorphic temperatures are greater than 500-600??C. Because 13C exchange is an unavoidable metamorphic process at temperatures above 300??C, high values of ??13C(Gr) in moderate- to high-grade carbonate-bearing rocks do not provide a sufficient criterion to infer an abiogenic origin for the graphite. ?? 1981.

New U-Pb zircon age data on polyphase plutono-metamorphic complex in western Enderby Land (East Antarctica) and its implications for Neoproterozoic amalgamation of the Gondwanaland

NASA Astrophysics Data System (ADS)

Mikhalskii, Evgenii; Krylov, Dmitriy; Rodionov, Nikolay

2017-04-01

Western Enderby Land occupies a key position on Gondwanaland reconstructions near India - Sri Lanka - Antarctica junction and eastwards the Lützow-Holm Bay metamorphic complex commonly identified as a Cambrian suture zone. We present U-Pb zircon isotopic age determinations with SHRIMP II obtained on tonalite- to granite-gneiss samples from the Thala Hills and the Polkanova Hills. In the Thala Hills three high-temperature tectonomagmatic episodes may be distinguished at ca 980-970 Ma, ca 780-720 Ma, and ca 545-530 Ma. All of them included sin-kinematic granitic orthogneiss protolith emplacements and high-grade metamorphism. In the Polkanova Hills tonalitic to granodioritic orthogneisses, intercalated with prevailing amphibolites, were emplaced during ca 980-950 Ma episode (or at both of these ages) and subsequently metamorphosed under amphibolite facies accompanied by migmatization at ca 600-530 Ma. The ca 980-950 Ma event corresponds to the Rayner Structural Episode which affected much of East Antarctica, including Sør Rondane Mountains to the west and Kemp Land to the east of study area. The Polkanova Hills area is underlain by basic amphibolites and tonalitic to granodioritic orthogneisses characterized by LILE enrichment and Nb-Ta troughs in a primitive mantle normalized spiderdiagram suggestive of derivation in arc-related convergent palaeotectonic environments. Co-eval orthogneisses in the Thala Hills are characterized by granitic compositions and occur in intercalation with paragneisses, which points out to more in-land palaeotectonic environments. The ca 780-720 Ma episode included two events at ca 780 Ma (high-grade anatexis) and 720 Ma (sin-tectonic granitoid emplacement) and was roughly co-eval with magmatic and/or metamorphic events in Dronning Maud Land of East Antarctica as well as in other Gondwanaland regions, like Madagascar, Sri Lanka and eastern Africa. The ca 780-720 Ma episode (Thala Episode) may be correlated with the East African Orogeny. Our new data provide a correlation of both ca 980-950 Ma and ca 800-700 Ma events between western Enderby Land and (partly) Dronning Maud Land, thus indicating their conjugate positions in the early Neoproterozoic, which in turn argues against a late Neoproterozoic-Cambrian suture running between them (i.e., the Lützow-Holm Bay Complex). We suggest that these terrains were juxtaposed prior to final amalgamation of the Gondwanaland. The Polkanova Hills basic to intermediate protoliths may represent a Rayner-aged active continental margin. The Late Neoproterozoic - Cambrian (ca 600-530 Ma) episode was manifested by high-grade anatexis (under granulite facies in the Thala Hills and amphibolite facies in the Polkanova Hills) co-eval with the Lützow-Holm Bay metamorphic complex. However, the nature of this metamorphism yet seems to have not been understood well and we believe it was of within-plate rather than continent collision origin. This study was supported by the RFBR grant #15-05-02761 to EVM.

Geology of the Sierra de Fiambala, northwestern Argentina: implications for Early Palaeozoic Andean tectonics

USGS Publications Warehouse

Grissom, G.C.; DeBari, S.M.; Snee, L.W.

1998-01-01

This paper is included in the Special Publication entitled 'The proto- Andean margin of Gondwana', edited by R.J. Pankhurst and C.W. Rapela. Field mapping in conjunction with structural, metamorphic, and geochronological data document the tectono-thermal history of exhumed deep crustal rocks in the Sierra de Fiambala, NW Argentina. The range consists of two structural blocks distinguished by different metasedimentary sequences and different grades of metamorphism. Orthogneiss and paragneiss in the northern structural block may have a Precambrian history. Greenschist- to amphibolite-facies metamorphism, intrusion, and injection magmatization affected all rocks at 540-550 Ma. A subsequent event in the Late Cambrian to Ordovician (c.515 to 470 Ma) involved amphibolite- to granulite-facies metamorphism, mafic intrusion, and deformation, followed by cooling through mid-Palaeozoic time. The emplacement of Carboniferous (325-350 Ma) post-tectonic granites caused reheating and retrogression that was strongest toward the northeast part of the range. The Cambrian, Ordovician, and Carboniferous events in the Sierra de Fiambala were of regional extent as indicated by temporal correlations with events reported for other deep crustal rocks of the northern Sierras Pampeanas. Correlations between periods of intrusion and high-grade metamorphism in the northern Sierras Pampeanas and volcanic-sedimentary events in the adjacent supracrustal exposures confirm that rocks in the northern Sierras Pampeanas formed at deep (10-25 km) structural levels in the early Palaeozoic continental margin of Gondwana.

Precambrian tholeiitic-dacitic rock-suites and Cambrian ultramafic rocks in the Pennine nappe system of the Alps: Evidence from Sm-Nd isotopes and rare earth elements

USGS Publications Warehouse

Stille, P.; Tatsumoto, M.

1985-01-01

Major element, trace element and Sm-Nd isotope analyses were made of polymetamorphic hornblendefelses, plagioclase amphibolites and banded amphibolites from the Berisal complex in the Simplon area (Italy, Switzerland) to determine their age, origin and genetic relationships. In light of major and rare earth element data, the hornblendefelses are inferred to have originally been pyroxene-rich cumulates, the plagioclase amphibolites and the dark layers of the banded amphibolites to have been tholeiitic basalts and the light layers dacites. The Sm-Nd isotope data yield isochron ages of 475??81 Ma for the hornblendefelses, 1,018??59 Ma for the plagioclase amphibolites and 1,071??43 Ma for the banded amphibolites. The 1 Ga magmatic event is the oldest one ever found in the crystalline basement of the Pennine nappes. The Sm -Nd isotope data support the consanguinity of the tholeiitic dark layers and the dacitic light layers of the banded amphibolites with the tholeiitic plagioclase amphibolites and the ultramafic hornblendefelses. The initial e{open}Nd values indicate that all three rock types originated from sources depleted in light rare earth elements. We suggest that plagioclase and banded amphibolites were a Proterozoic tholeiite-dacite sequence that was strongly deformed and flattened during subsequent folding. The hornblendefelses are thought to be Cambrian intrusions of pyroxene-rich material. ?? 1985 Springer-Verlag.

Precambrian tholeiitic-dacitic rock-suites and Cambrian ultramafic rocks in the Pennine nappe system of the Alps: Evidence from Sm-Nd isotopes and rare earth elements

NASA Astrophysics Data System (ADS)

Stille, P.; Tatsumoto, M.

1985-04-01

Major element, trace element and Sm-Nd isotope analyses were made of polymetamorphic hornblendefelses, plagioclase amphibolites and banded amphibolites from the Berisal complex in the Simplon area (Italy, Switzerland) to determine their age, origin and genetic relationships. In light of major and rare earth element data, the hornblendefelses are inferred to have originally been pyroxene-rich cumulates, the plagioclase amphibolites and the dark layers of the banded amphibolites to have been tholeiitic basalts and the light layers dacites. The Sm-Nd isotope data yield isochron ages of 475±81 Ma for the hornblendefelses, 1,018±59 Ma for the plagioclase amphibolites and 1,071±43 Ma for the banded amphibolites. The 1 Ga magmatic event is the oldest one ever found in the crystalline basement of the Pennine nappes. The Sm -Nd isotope data support the consanguinity of the tholeiitic dark layers and the dacitic light layers of the banded amphibolites with the tholeiitic plagioclase amphibolites and the ultramafic hornblendefelses. The initial ɛ Nd values indicate that all three rock types originated from sources depleted in light rare earth elements. We suggest that plagioclase and banded amphibolites were a Proterozoic tholeiite-dacite sequence that was strongly deformed and flattened during subsequent folding. The hornblendefelses are thought to be Cambrian intrusions of pyroxene-rich material.

Regional metamorphism in the Condrey Mountain Quadrangle, north-central Klamath Mountains, California

USGS Publications Warehouse

Hotz, Preston Enslow

1979-01-01

A subcircular area of about 650 km 2 in northern California and southwestern Oregon is occupied by rocks of the greenschist metamorphic facies called the Condrey Mountain Schist. This greenschist terrane is bordered on the east and west by rocks belonging to the amphibolite metamorphic facies that structurally overlie and are thrust over the Condrey Mountain Schist. The amphibolite facies is succeeded upward by metavolcanic and metasedimentary rocks belonging to the greenschist metamorphic facies. The Condrey Mountain Schist is composed predominantly of quartz-muscovite schist and lesser amounts of actinolite-chlorite schist formed by the metamorphism of graywacke and spilitic volcanic rocks that may have belonged to the Galice Formation of Late Jurassic age. Potassium-argon age determinations of 141?4 m.y. and 155?5 m.y. obtained on these metamorphic rocks seem to be incompatible with the Late Jurassic age usually assigned the Galice. The rocks that border the amphibolite facies are part of an extensive terrane of metavolcanic and metasedimentary rocks belonging to the western Paleozoic and Triassic belt. The metavolcanic rocks include some unmetamorphosed spilite but are mostly of the greenschist metamorphic facies composed of oligoclase (An15-20) and actinolite with subordinate amounts of chlorite and clinozoisiteepidote. The interbedded sedimentary rocks are predominantly argillite and slaty argillite, less commonly siliceous argillite and chert, and a few lenticular beds of marble. On the south, high-angle faults and a tabular granitic pluton separate the greenschist metavolcanic terrane from the amphibolite facies rocks; on the east, nonfoliated amphibolite is succeeded upward, apparently conformably, by metasedimentary rocks belonging to the greenschist metavolcanic terrane. In the southern part of Condrey Mountain quadrangle, an outlier of a thrust plate composed of the Stuart Fork Formation overlies the metavolcanic and metasedimentary rocks. The Stuart Fork in this region is composed of siliceous phyllite and phyllitic quartzite and is believed to be the metamorphosed equivalent of rocks over which it is thrust. In the Yreka-Fort Jones area, potassium-argon determinations on mica from the blueschist facies in the Stuart Fork gave ages of approximately 220 m.y. (Late Triassic) for the age of metamorphism. Rocks of the amphibolite facies structurally overlie the Condrey Mountain Schist along a moderate to steeply dipping thrust fault. The amphibolite terrane is composed of amphibolite and metasedimentary rocks in approximately equal amounts accompanied by many bodies of serpentinite and a number of gabbro and dioritic plutons. Most of the amphibolite is foliated, but some is nonfoliated; the nonfoliated amphibolite has an amphibolite mineralogy and commonly a relict volcanic rock texture. The nonfoliated amphibolite occurs on the southern and eastern borders of the amphibolite terrane between the areas offoliated amphibolite and the overly ing metavolcanic and metasedimentary rocks. Hornblende and plagioclase (An30-35) are the characteristic minerals, indicating that the rocks are of the almandine-amphibolite metamorphic facies. The metasedimentary rocks interbedded with the amphibolites include siliceous schist and phyllite, minor quartzite, and subordinate amounts of marble. Potassium-argon age dates obtained on hornblende from foliated amphibolite yield ages of 146?4 and 148? 4 m.y., suggesting a Late Jurassic metamorphic episode. Mafic and ultramafic rocks are widespread in the amphibolite terrane but are almost entirely absent from the area of greenschist facies metavolcanic and metasedimentary rocks. The ultramafic rocks, predominantly serpentinite, occur as a few large bodies and many small tabular concordant bodies interleaved with the foliated rocks. The ultramafic rocks include harzburgite and d1lIlite and their serpentinized equivalents. In the Condrey Mountain quadrangle, probably more t

Extended history of a 3.5 Ga trondhjemitic gneiss, Wyoming Province, USA: Evidence from U-Pb systematics in zircon

USGS Publications Warehouse

Mueller, P.A.; Wooden, J.L.; Mogk, D.W.; Nutman, A.P.; Williams, I.S.

1996-01-01

The Beartooth-Bighorn magmatic zone (BBMZ) and the Montana metasedimentary province (MMP) are two major subprovinces of the Archean Wyoming province. In the northwestern Beartooth Mountains, these subprovinces are separated by a structurally, lithologically and metamorphically complex assemblage of lithotectonic units that include: (1) a strongly deformed complex of trondhjemitic gneiss and interlayered amphibolites; and (2) an amphibolite facies mafic unit that occurs in a nappe that structurally overlies the gneiss complex. Zircons from a trondhjemitic blastomylonite in the gneiss complex yield concordant U-Pb ages of 3.5 Ga, establishing it as the oldest rock yet documented in the Wyoming province. Two younger events are also recorded by zircons in this rock: (1) an apparently protracted period of high-grade metamorphism and/or intrusion of additional magmas at ??? 3.25 Ga; and (2) growth of hydrothermal zircon at ??? 2.55 Ga, apparently associated with ductile deformation that immediately preceded structural emplacement of the gneiss. Although this latter event appears confined to areas along the BBMZ-MMP boundary, evidence of ??? 3.25 Ga igneous activity is found in the overlying amphibolite (3.24 Ga) and throughout the MMP. These data suggest that this boundary first developed as a major intracratonic zone of displacement at or before 3.25 Ga. The limited occurrences of 2.8 Ga magmatic activity in the MMP suggest that it had a controlling influence on late Archean magmatism as well.

Metamorphic reactions in ruby corundum amphibolite from the Chunky Gal Mountain mafic-ultramafic complex, Clay County, North Carolina

DOE Office of Scientific and Technical Information (OSTI.GOV)

Ranson, W.A.; Garihan, J.M.; Ulmer, K.E.

1992-01-01

Amphibolite outcrops of unusual mineralogy within the Chunky Gal Mountain mafic-ultramafic complex display cm-scale rhythmic layers with moderate-steep dips. Layers are troctolitic, gabbroic, and anorthositic in composition, locally in contact with dunite of the Buck Creek ultramafic body. Meta-gabbroic layers contain striking bladed, emerald green amphibole as the chief mafic phase and relict bronzite with reacted margins. An additional major phase is plagioclase, [approximately]An 95 based on microprobe analysis. Ruby corundum is a minor (> 5%) constituent, which in some of the gabbroic rocks is mantled by a reaction rim of fibrolite. The clinoamphibole has optical properties resembling magnesio-cummingtonite: colorlessmore » to pale green in plane light with (+) sign and 2V = 60--70[degree]. However, microprobe analysis of the clinoamphibole indicates alumino-magnesio-hornblende. Although the texture of the bronzite shows that it is breaking down, it is clear that the clinoamphibole and corundum could not be the reaction products without the addition of Al, Ca, and Si in an aqueous fluid. Associated meta-troctolitic layers contain plagioclase and coarse, anhedral olivines displaying an inner corona of bladed orthopyroxene, rimmed by symplectite. The granulite facies reactions is: plagioclase + olivine = clinopyroxene + garnet. The mesoscopic-scale proximity of troctolitic and gabbroic rhythmic layers indicates both underwent granulite facies metamorphism. Retrogression to amphibolite grade is apparent only in the gabbroic layers, resulting in assemblages distinguished locally by abundant emerald green clinoamphibole and corundum porphyroblasts rimmed by fibrolite.« less

Zircon and monazite petrochronologic record of prolonged amphibolite to granulite facies metamorphism in the Ivrea-Verbano and Strona-Ceneri Zones, NW Italy

NASA Astrophysics Data System (ADS)

Guergouz, Celia; Martin, Laure; Vanderhaeghe, Olivier; Thébaud, Nicolas; Fiorentini, Marco

2018-05-01

In order to improve the understanding of thermal-tectonic evolution of high-grade terranes, we conducted a systematic study of textures, REE content and U-Pb ages of zircon and monazite grains extracted from migmatitic metapelites across the amphibolite to granulite facies metamorphic gradient exposed in the Ivrea-Verbano and Strona-Ceneri Zones (Italy). This study documents the behaviour of these accessory minerals in the presence of melt. The absence of relict monazite grains in the metasediments and the gradual decrease in the size of inherited zircon grains from amphibolite to granulite facies cores indicate partial to total dissolution of accessory minerals during the prograde path and partial melting. The retrograde path is marked by (i) growth of new zircon rims (R1 and R2) around inherited cores in the mesosome, (ii) crystallisation of stubby zircon grains in the leucosome, especially at granulite facies, and (iii) crystallisation of new monazite in the mesosome. Stubby zircon grains have a distinctive fir-tree zoning and a constant Th/U ratio of 0.20. Together, these features reflect growth in the melt; conversely, the new zircon grains with R1 rims have dark prismatic habits and Th/U ratios < 0.1, pointing to growth in solid residues. U-Pb ages obtained on both types are similar, indicating contemporaneous growth of stubby zircon and rims around unresorbed zircon grains, reflecting the heterogeneous distribution of the melt at the grain scale. In the Ivrea-Verbano Zone the interquartile range (IQR) of U-Pb ages on zircon and monazite are interpreted to represent the length of zircon and monazite crystallisation in the presence of melt. Accordingly, they provide an indication on the minimum duration for high-temperature metamorphism and partial melting of the lower crust: 20 Ma and 30 Ma in amphibolite and granulite facies, respectively. In amphibolite facies, zircon crystallisation between 310 and 294 Ma (IQR) is interpreted to reflect metamorphic peak condition and earlier retrograde history; conversely, monazite crystallisation between 297 and 271 Ma (IQR) reflects cooling under 750 °C to a temperature close to the solidus. In granulite facies, zircon crystallisation between 295 and 265 Ma (IQR) is interpreted to reflect high-temperature conditions, which were attained after peak of metamorphism during isothermal decompression and subsequent cooling under 850-950 °C. The observed decrease of U-Pb ages in metamorphic zircon and monazite from amphibolite to granulite facies (i.e. from the middle to the lower crust) is interpreted to record slow cooling and crystallisation of the Variscan orogenic root at the transition from orogenic collapse to opening of the Tethys Ocean.

Geochemistry of amphibolites from the Kolar Schist Belt

NASA Technical Reports Server (NTRS)

Balakrishnan, S.; Hanson, G. N.; Rajamani, V.

1988-01-01

How the Nd isotope data suggest that the amphibolites from the schist belt were derived from long-term depleted mantle sources at about 2.7 Ga is described. Trace element and Pb isotope data from the amphibolites also suggest that the sources for the amphibolites on the western and eastern sides of the narrow schist belt were derived from different sources. The Pb data from one outcrop of the central tholeiitic amphibolites lies on a 2.7 Ga isochron with a low model. The other amphibolites (W komatiitic, E komatiitic, and E tholeiitic) do not define isochrons, but suggest that they were derived from sources with distinct histories of U/Pb. There is some suggestion that the E komatiitic amphibolites may have been contaminated by fluids carrying Pb from a long-term, high U/Pb source, such as the old granitic crust on the west side of the schist belt. This is consistent with published galena Pb isotope data from the ore lodes within the belt, which also show a history of long-term U/Pb enrichment.

Mesozoic units in SE Rhodope (Bulgaria): new structural and petrologic data and geodynamic implications for the Early Jurassic to Mid-Cretaceous evolution of the Vardar ocean basin

NASA Astrophysics Data System (ADS)

Bonev, N.; Stampfli, G.

2003-04-01

In the southeastern Rhodope, both in southern Bulgaria and northern Greece, Mesozoic low-grade to non-metamorphic units, together with similar units in the eastern Vardar zone, were designated as the Circum-Rhodope Belt (CRB) that fringes the Rhodope high-grade metamorphic complex. In the Bulgarian southeastern Rhodope, Mesozoic units show a complicated tectono-stratigraphy underlaid by amphibolite-facies basement units. The basement sequence includes a lower orthogneiss unit with eclogite and meta-ophiolite lenses overlain by an upper marble-schist unit, presumably along a SSW-directed detachment fault as indicated by shear sense indicators. The Mesozoic sequence starts with greenschist units at the base, overlaying the basement along the tectonic contact. Mineral assemblages such as actinolite-chlorite-white mica ± garnet in schists and phyllites indicate medium greenschist facies metamorphism. Kinematic indicators in the same unit demonstrate a top-to-the NNW and NNE shear deformation coeval with metamorphism, subparallel to NW-SE to NE-SW trending mineral elongation lineation and axis of NW vergent small-scale folds. The greenschist unit is overlain by tectonic or depositional contact of melange-like unit that consists of diabases with Lower Jurassic radiolarian chert interlayers, Upper Permian siliciclastics and Middle-Upper Triassic limestones found as blocks in olistostromic member, embedded in Jurassic-Lower Cretaceous turbiditic matrix. The uppermost sedimentary-volcanogenic unit is represented by andesito-basalt lavas and gabbro-diorites, interbedded with terrigeneous-marl and tufaceous sediments that yield Upper Cretaceous (Campanian) fossils, related to the Late Cretaceous back-arc magmatic activity to the north in Sredna Gora zone. Petrologic and geochemical data indicates sub-alkaline and tholeiitic character of the greenschists and ophiolitic basaltic lavas, and the latter are classified as low-K and very low-Ti basalts with some boninitic affinity. Immobile trace element discrimination of both rock types constrains the volcanic (oceanic)-arc origin. They generally show low total REE concentrations (LREE>HREE) with enrichment of LIL elements relative to the HFS elements, and also very low Nb and relatively high Ce content consistent with an island-arc tectonic setting. We consider that the Meliata-Maliac ocean northern passive margin could be the source provenance for the Upper Permian clastics and Middle-Upper Triassic limestone blocks within the olistostromic melange-like unit, whereas turbidites and magmatic blocks may originate in an island arc-accretionary complex that relates to the southward subduction of the Maliac ocean under the supra-subduction back-arc Vardar ocean/island arc system. These new structural and petrologic data allow to precise the tectonic setting of the Mesozoic units and their geodynamic context in the frame of the Early Jurassic to Late Cretaceous evolution of the Vardar ocean.

Petrography, mineralogy, and geochemistry of deep gravelly sands in the Eyreville B core, Chesapeake Bay impact structure

USGS Publications Warehouse

Bartosova, Katerina; Gier, Susanne; Horton, J. Wright; Koeberl, Christian; Mader, Dieter; Dypvik, Henning

2010-01-01

The ICDP–USGS Eyreville drill cores in the Chesapeake Bay impact structure reached a total depth of 1766 m and comprise (from the bottom upwards) basement-derived schists and granites/pegmatites, impact breccias, mostly poorly lithified gravelly sand and crystalline blocks, a granitic slab, sedimentary breccias, and postimpact sediments. The gravelly sand and crystalline block section forms an approximately 26 m thick interval that includes an amphibolite block and boulders of cataclastic gneiss and suevite. Three gravelly sands (basal, middle, and upper) are distinguished within this interval. The gravelly sands are poorly sorted, clast supported, and generally massive, but crude size-sorting and subtle, discontinuous layers occur locally. Quartz and K-feldspar are the main sand-size minerals and smectite and kaolinite are the principal clay minerals. Other mineral grains occur only in accessory amounts and lithic clasts are sparse (only a few vol%). The gravelly sands are silica rich (~80 wt% SiO2). Trends with depth include a slight decrease in SiO2 and slight increase in Fe2O3. The basal gravelly sand (below the cataclasite boulder) has a lower SiO2 content, less K-feldspar, and more mica than the higher sands, and it contains more lithic clasts and melt particles that are probably reworked from the underlying suevite. The middle gravelly sand (below the amphibolite block) is finer-grained, contains more abundant clay minerals, and displays more variable chemical compositions than upper gravelly sand (above the block). Our mineralogical and geochemical results suggest that the gravelly sands are avalanche deposits derived probably from the nonmarine Potomac Formation in the lower part of the target sediment layer, in contrast to polymict diamictons higher in the core that have been interpreted as ocean-resurge debris flows, which is in agreement with previous interpretations. The mineralogy and geochemistry of the gravelly sands are typical for a passive continental margin source. There is no discernible mixing with marine sediments (no glauconite or Paleogene marine microfossils noted) during the impact remobilization and redeposition. The unshocked amphibolite block and cataclasite boulder might have originated from the outer parts of the transient crater.

50 Myr. in a serpentinite subduction channel: Insights into slow eclogite exhumation

NASA Astrophysics Data System (ADS)

Flores, K. E.; Bonnet, G.; Cai, Y.; Martin, C.; Hemming, S. R.; Brueckner, H. K.; Harlow, G. E.

2017-12-01

Modern petrochronology shows that the exhumation of metamorphosed oceanic rocks in subduction zones is commonly a brief process (<10-20 Ma) characterized by rates of 2-5 km/Ma. This rapid exhumation is essential to avoid complete retrogression of high grade assemblages during ascension. However, our multi-approach P-T-t results on retrograde eclogites from the Northern Motagua Mélange (NMM) in Guatemala challenges those previous findings because they record remarkably slower exhumation rates ( 1 km/Ma). The retrograde eclogites occur as cm to tens of m sized blocks within a serpentinite matrix mélange that also contains blocks of subgreenschist to amphibolite and blueschist facies metabasites, jadeitites, omphacitites, albitites, mica-rocks, metatrondhjemites, and minor low grade metasediments. The studied samples range from almost unaltered eclogites to retrograde blueschist and ep-amphibolite facies metabasites containing eclogite relicts. The successive assemblages define classical clockwise P-T paths: comprised of (a) prograde blueschist/eclogite facies metamorphism within garnet cores, (b) eclogite facies peak recrystallization at 2.1 GPa and 500°C, (c) post-peak blueschist facies recrystallization, (d) amphibolite facies overprinting, and (e) late stage greenschist facies retrogression. This complex polymetamorphic history defines an exhumation path with a metamorphic peak at 136-125 Ma (Sm-Nd mineral isochrons) at 70 km depth, an ascent to the middle section of a subduction channel ( 40 km) at 99-92 Ma (Ar-Ar in Ph), and exhumation to 25-20 km at 80-75 Ma (Ar-Ar in Mhb). Synchronous jadeitite and mica-rocks yielded crystallization and exhumation ages of 95 Ma (U-Pb in Zrn) and 77-53 Ma (Ar-Ar in Ph), respectively. In contrast, an associated eclogite-bearing sheet of continental crust shows a younger eclogite metamorphic peak of 77-75 Ma at 80 km depth, but similar exhumation ages of 76-66 Ma and near surface regional exposure at 30 Ma (AFT). These new data argues for significantly low exhumation rate of 1 km/Ma, which satisfactorily explains the highly retrograde nature of most eclogites and the well documented rock-fluids interactions inside a serpentinite subduction channel. However, it contradicts most current buoyancy- low viscosity driven exhumation models.

Fluid heterogeneity during granulite facies metamorphism in the Adirondacks: stable isotope evidence

USGS Publications Warehouse

Valley, J.W.; O'Neil, J.R.

1984-01-01

The preservation of premetamorphic, whole-rock oxygen isotope ratios in Adirondack metasediments shows that neither these rocks nor adjacent anorthosites and gneisses have been penetrated by large amounts of externally derived, hot CO2-H2O fluids during granulite facies metamorphism. This conclusion is supported by calculations of the effect of fluid volatilization and exchange and is also independently supported by petrologic and phase equilibria considerations. The data suggest that these rocks were not an open system during metamorphism; that fluid/rock ratios were in many instances between 0.0 and 0.1; that externally derived fluids, as well as fluids derived by metamorphic volatilization, rose along localized channels and were not pervasive; and thus that no single generalization can be applied to metamorphic fluid conditions in the Adirondacks. Analyses of 3 to 4 coexisting minerals from Adirondack marbles show that isotopic equilibrium was attained at the peak of granulite and upper amphibolite facies metamorphism. Thus the isotopic compositions of metamorphic fluids can be inferred from analyses of carbonates and fluid budgets can be constructed. Carbonates from the granulite facies are on average, isotopically similar to those from lower grade or unmetamorphosed limestones of the same age showing that no large isotopic shifts accompanied high grade metamorphism. Equilibrium calculations indicate that small decreases in ??18O, averaging 1 permil, result from volatilization reactions for Adirondack rock compositions. Additional small differences between amphibolite and granulite facies marbles are due to systematic lithologie differences. The range of Adirondack carbonate ??18O values (12.3 to 27.2) can be explained by the highly variable isotopic compositions of unmetamorphosed limestones in conjunction with minor 18O and 13C depletions caused by metamorphic volatilization suggesting that many (and possibly most) marbles have closely preserved their premetamorphic isotopic compositions. Such preservation is particularly evident in instances of high ??18O calcites (25.0 to 27.2), low ??18O wollastonites (-1.3 to 3.5), and sharp gradients in ??18O (18 permil/15m between marble and anorthosite, 8 permil/25 m in metasediments, and 6 permil/1 m in skarn). Isotopic exchange is seen across marble-anorthosite and marble-granite contacts only at the scale of a few meters. Small (<5 m) marble xenoliths are in approximate exchange equilibrium with their hosts, but for larger xenoliths and layers of marble there is no evidence of exchange at distances greater than 10 m from meta-igneous contacts. ?? 1984 Springer-Verlag.

Structures, microfabrics, fractal analysis and temperature-pressure estimation of the Mesozoic Xingcheng-Taili ductile shear zone in the North China craton

NASA Astrophysics Data System (ADS)

Liang, Chenyue; Neubauer, Franz; Liu, Yongjiang; Jin, Wei; Zeng, Zuoxun; Bernroider, Manfred; Li, Weimin; Wen, Quanbo; Han, Guoqing; Zhao, Yingli

2014-05-01

The ductile shear zone in Xingcheng-Taili area (western Liaoning Province in China) is tectonically located in the eastern section of the northern margin of the North China craton, and dominantly comprises deformed granitic rocks of Neoarchean and Triassic to Late Jurassic age, which were affected by shearing within middle- to low-grade metamorphic conditions. Because a high-temperature metamorphic overprint is lacking, microstructures attesting to low-temperature ductile deformation are well preserved. However, the rocks and its structures have not been previously analyzed in detail except by U-Pb zircon dating and some geochemistry. Here, we describe the deformation characteristics and tectonic evolution of the Xingcheng-Taili ductile shear zone, in order to understand the mode of lithosphericscale reactivation, extension and thinning of the North China craton. The ductile deformation history comprises four successive deformation phases: (1) In the Neoarchean granitic rocks, a steep gneissosity and banded structures trend nearly E-W (D1). (2) A NE-striking sinistral structure of Upper Triassic rocks may indicate a deformation event (D2) in Late Triassic times, which ductile deformation structures superimposed on Neoarchean granitic rocks. (3) A gneissose structure with S-C fabrics as well as an ENE-trending sinistral strike-slip characteristic (D3) developed in Upper Jurassic biotite adamellite and show the deformation characteristics of a shallow crustal level and generated mylonitic fabrics superimposed on previous structures. (4) Late granitic dykes show different deformational behavior, and shortening with D4 folds. The attitude of the foliation S and mineral stretching lineation of three main types of rocks shows remarkable differences in orientation. The shapes of recrystallized quartz grains from three main types of granitic rocks with their jagged and indented boundaries were natural records of deformation conditions (D1to D3). Crystal preferred orientation of quartz determined by electron back scatter diffraction (EBSD) suggest sinistral strike-slip displacement within a temperature at about 400 to 500° C. Quartz mainly shows low-temperature fabrics with dominant {0001}-slip system. As the deformed rocks show obvious deformation overprint, we have estimated flow stresses from dynamically recrystallized grain sizes of quartz separately. But coincident fractal analysis showed that the boundaries of recrystallized grains had statistically self similarities with the numbers of fractal dimension from 1.153 to 1.196 with the range of deformation temperatures from 500 to 600° C, which is corresponding to upper greenschist to lower amphibolite facies conditions. Together with published flow laws to estimated deformation rates between the region of 10-11 - 10-13 S-1depending on the temperature 500 ° C, and the paleo-stress was calculated with grain size of recrystallized quartz to be at 5.0 to 32.3 MPa. Even though the deformation history and kinematics are different, progressive microstructures and texture analysis indicate an overprint by the low-temperature deformation (D3). Typical regional-dynamic metamorphic conditions ere deduced by mineral pair hornblende-plagioclase and phengite barometry identified within the ductile shear zone. The hornblende-plagioclase pair of porphyritic granitic gneiss gives metamorphic conditions of T =450-500 ° C and p=0.39 GPa, which indicate a metamorphic grade of lower-amphibolite facies conditions and a depth of around 13 km estimated following a normal lithostatic pressure. All of the structural characteristics indicate that the Xingcheng-Taili ductile shear zone represents a mainly ENE-striking sinistral ductile strike-slip zone, which formed after intrusion of the Upper Jurassic biotite adamellite and transformed and superimposed previous deformation structures. This deformation event might have occurred in Early Cretaceous times and was related to the lithospheric thinning and extension, due to roll-back of the Pacific plate beneath the eastern North China craton.

Partial melting of amphibolite to trondhjemite near Ykutat, Alaska

NASA Technical Reports Server (NTRS)

Barker, F.

1986-01-01

At Nunatak Fiord, 55 km NE of Yakutat, Alaska, a uniform layer of Cretaceous metabasalt approximately 3 km thick was metamorphosed to amphibolite facies and locally partially melted to trondhjemite pegmatite. Results of the rare earth element analysis performed on the amphibolite and the trondhjemite pegmatite are discussed.

1.45 Ga granulites in the southwestern Grenville province: Geologic setting, P-T conditions, and U-Pb geochronology

NASA Astrophysics Data System (ADS)

Ketchum, J. W. F.; Jamieson, R. A.; Heaman, L. M.; Culshaw, N. G.; Krogh, T. E.

1994-03-01

In the southwestern Grenville province, the parautochthonous Britt domain includes a variety of pre-Grenvillian metamorphic and plutonic rocks that were reworked at upper amphibolite facies during the Grenvillian orogeny. Near Pointe-au-Baril, Ontario, a crustal block containing pre-Grenvillian granulite facies mineral assemblages and pre-Grenvillian to early Grenvillian tectonic fabrics has been identified. The block is bounded on the northwest and southeast by extensional shear zones that may have isolated it from regional late Gren- villian deformation. Multiequilibria pressure-temperature (P-T) calculations for orthopyroxene-bearing mafic rocks suggest conditions of 625-700 °C and 7.2-8.4 kbar for the pre-Grenvillian metamorphism. The granulite facies assemblages were locally overprinted during higher pressure Grenvillian metamorphism, which peaked at 720-775 °C and 10.8-11.5 kbar. U-Pb zircon data from migmatitic, mafic supracrustal gneiss indicate metamorphism and leucosome development at ca. 1450-1430 Ma, in agreement with other pre-Grenvillian metamorphic ages for the Central gneiss belt and Grenville Front tectonic zone. An expanding data base on pre-Grenvillian events in the southwestern Grenville province indicates that high-grade metamorphism at ca. 1450-1430 Ma affected a large region of crust and was coeval with widespread felsic to intermediate plutonism.

Grain-scale Sr isotope heterogeneity in amphibolite (retrograded UHP eclogite, Dabie terrane): Implications for the origin and flow behavior of retrograde fluids during slab exhumation

NASA Astrophysics Data System (ADS)

Guo, Shun; Yang, Yueheng; Chen, Yi; Su, Bin; Gao, Yijie; Zhang, Lingmin; Liu, Jingbo; Mao, Qian

2016-12-01

To constrain the origin and flow behavior of amphibolite-facies retrograde fluids during slab exhumation, we investigate the textures, trace element contents, and in situ strontium (Sr) isotopic compositions (using LA-MC-ICP-MS) of multiple types of epidote and apatite in the UHP eclogite and amphibolites from the Hualiangting area (Dabie terrane, China). The UHP epidote porphyroblasts in the eclogite (Ep-E), which formed at 28-30 kbar and 660-720 °C, contain high amounts of Sr, Pb, Th, Ba, and light rare earth elements (LREEs) and have a narrow range of initial 87Sr/86Sr ratios (0.70431 ± 0.00012 to 0.70454 ± 0.00010). Two types of amphibolite-facies epidote were recognized in the amphibolites. The first type of epidote (Ep-AI) developed in all the amphibolites and has slightly lower trace element contents than Ep-E. The Ep-AI has a same initial 87Sr/86Sr ratio range as the Ep-E and represents the primary amphibolite-facies retrograde product that is associated with an internally buffered fluid at 8.0-10.3 kbar and 646-674 °C. The other type of epidote (Ep-AII) occurs as irregular fragments, veins/veinlets, or reaction rims on the Ep-AI in certain amphibolites. Elemental X-ray maps reveal the presence of Ep-AI relics in the Ep-AII domains (appearing as a patchy texture), which indicates that Ep-AII most likely formed by the partial replacement of the Ep-AI in the presence of an infiltrating fluid. The distinctly lower trace element contents of Ep-AII are ascribed to element scavenging by a mechanism of dissolution-transport-precipitation during replacement. The Ep-AII in an individual amphibolite exhibits large intra- and inter-grain variations in the initial 87Sr/86Sr ratios (0.70493 ± 0.00030 to 0.70907 ± 0.00022), which are between those of the Ep-AI and granitic gneisses (wall rock of the amphibolites, 0.7097-0.7108). These results verify that the infiltrating fluid was externally derived from granitic gneisses. The matrix apatite in the amphibolites has the same initial 87Sr/86Sr ratio range as the Ep-AI, indicating that the amphibolite-facies fluid involved in the apatite crystallization was also internally derived. We propose that at least two separate stages of fluids were accounted for the amphibolite-facies retrogression of the Hualiangting eclogite. The fluid responsible for the growth of most of the amphibolite minerals was locally derived and behaved in a pervasive manner, whereas the influx of gneiss-derived fluid was transient, episodic, and highly channelized with a longer transport distance (> 60 m). The disparate origins and flow behavior of these fluids significantly influence the water budget and element transfer in exhumed HP-UHP slabs. This study also indicates that examining grain-scale Sr isotopic variations provides key information regarding the isotopic (dis)equilibrium, fluid origins, and fluid-flow regimes in metamorphic or metasomatic rocks that form in subduction-zone environments.

Uplifted ophiolitic rocks on Isla Gordon, southernmost Chile: implications for the closure history of the Rocas Verdes marginal basin and the tectonic evolution of the Beagle Channel region

NASA Astrophysics Data System (ADS)

Cunningham, W. D.

1994-04-01

A succession of mafic rocks that includes gabbro, sheeted dikes and deformed pillow basalts has been mapped in detail on Isla Gordon, southernmost Chile and is identified as an upper ophiolitic complex representing the uplifted floor of the Late Jurassic-Early Cretaceous Rocas Verdes marginal basin. The complex was uplifted, deformed, and regionally metamorphosed prior to the intrusion of an undeformed 90 Ma granodiorite that cuts the complex. The complex appears para-autochthonous, is gently tilted to the northeast and is internally sheared by near-vertical foliation zones. No evidence for obduction was observed although the base of the complex is not exposed. The ophiolitic rocks have been regionally metamorphosed to mid-upper greenschist levels. Isla Gordon is bounded by the northwest and southwest arms of the Beagle Channel, two important structural boundaries in the southernmost Andes that are interpreted to have accommodated north-side-up and left-lateral displacements. Directly north of Isla Gordon is the Cordillera Darwin metamorphic complex that exposes the highest grade metamorphic rocks in the Andes south of Peru. On the north coast of Isla Gordon a volcaniclastic turbidite sequence that is interpreted to have been deposited above the mafic floor is metamorphosed to lower greenschist levels in strong metamorphic contrast to amphibolite-grade othogneisses exposed in Cordillera Darwin only 2 km away across the northwest arm of the Beagle Channel. The profound metamorphic break across the northwest arm of the Beagle Channel and the regional northeast tilt of the ophiolitic complex are consistent with the previously proposed hypothesis that Isla Gordon represents the upper plate to an extensional fault that accommodated tectonic unroofing of Cordillera Darwin. However, limited structural evidence for extension was identified in this study to support the model and further work is needed to determine the relative importance of contractional, extensional and strike-slip displacements during the closure of the Rocas Verdes marginal basin and uplift of Cordillera Darwin. The Isla Gordon ophiolitic complex is correlative with other regional occurrences of ophiolitic rocks including the previously studied Tortuga, Sarmiento and Larsen Harbour complexes. The existence of the Isla Gordon ophiolitic complex helps link the known occurrences of the marginal basin floor into a semi-continuous belt that sheds light on the original continuity of the basin.

High-pressure granulite-facies metamorphism in central Dronning Maud Land (East Antarctica): Implications for Gondwana assembly

NASA Astrophysics Data System (ADS)

Palmeri, Rosaria; Godard, Gaston; Di Vincenzo, Gianfranco; Sandroni, Sonia; Talarico, Franco M.

2018-02-01

Central Dronning Maud Land (DML; East Antarctica) is located in a key region of the Gondwana supercontinent. The Conradgebirge area (central DML) consists of orthogneisses, derived from both volcanic and plutonic protoliths, and minor metasedimentary rocks, intruded by Cambrian syn- to post-metamorphic plutons and dykes. Mafic-ultramafic boudins in the metavolcanic and metaplutonic gneisses from Conradgebirge consist of amphibolites and high-grade garnet-bearing pyroxene- and amphibole-rich granofels. They occur either as discontinuous levels or as pods boudinaged within highly-strained and strongly-migmatized gneisses. Bulk-rock major and trace-element compositions, together with geochemical discriminant diagrams (e.g., Th/Yb versus Ta/Yb and V versus Ti), suggest derivation from enriched mantle source for the mafic rocks boudinaged in metaplutonic gneisses, whereas a calc-alkaline signature is common for the mafic boudins in metavolcanic rocks. The microstructural study and P-T modelling of an ultramafic metagabbroic rock reveal a prograde metamorphic evolution from amphibolite-facies (ca. 0.5 GPa; 500 °C) up to high-P granulite-facies conditions (ca. 1.5-1.7 GPa; 960-970 °C). Partial melting is testified by "nanogranitoid" inclusions enclosed in garnet. An almost isothermal decompression down to ca. 0.4 GPa and 750-850 °C produced well-developed An + Opx-bearing symplectites around garnet. A final isobaric cooling at nearly 0.4 GPa is testified by Grt coronas around high-T symplectites. The above reconstruction traces a clockwise loading-heating P-T evolution with a peak metamorphism at high-P granulite-facies conditions suggesting crustal thickening at nearly 570 Ma, followed by a tectonically assisted rapid exhumation, and then, by an isobaric cooling. 40Ar-39Ar dating of amphibole and biotite at 505-480 Ma testify mineral re-equilibration at upper crustal level (T < 650 °C) during the isobaric cooling. This tectono-metamorphic scenario seems representative of the evolution resulting from the Neoproterozoic/Early Palaeozoic (600-500 Ma) collision between parts of East- and West-Gondwana blocks that led to the final assembly of Gondwana.

Metamorphic records for subduction erosion and subsequent underplating processes revealed by garnet-staurolite-muscovite schists in central Qiangtang, Tibet

NASA Astrophysics Data System (ADS)

Zhang, Xiu-Zheng; Dong, Yong-Sheng; Wang, Qiang; Dan, Wei; Zhang, Chunfu; Xu, Wang; Huang, Ming-Liang

2017-01-01

Subduction erosion is confirmed as a crucial geodynamic process of crustal recycling based on geological, geochemical, and geophysical observations at modern convergent plate margins. So far, not a single metamorphic record has been used for constraining a general tectonic evolution for subduction erosion. Here we first revealed metamorphic records for a subduction erosion process based on our study of the Late Paleozoic garnet-staurolite-muscovite schists in the central Qiangtang block, Tibet. Provenance analyses suggest that the protoliths of garnet-staurolite-muscovite schists have the Northern Qiangtang-affinity and were deposited in an active continental margin setting. Mineral inclusion data show that the early metamorphic stage (M1) recorded blueschist facies pressure-temperature (P-T) conditions of 0.8-1.1 GPa and 402-441°C, indicating that a part of the material from the overriding plate had been abraded into the subduction channel and undergone high-pressure/low-temperature metamorphism. The peak metamorphic stage (M2) recorded amphibolite facies P-T conditions of 0.3-0.5 GPa and 470-520°C. The 40Ar/39Ar cooling ages (263-259 Ma) yielded from muscovite suggest the amphibolite facies metamorphism (>263 Ma) occurred at oceanic subduction stage. The distinctly staged metamorphism defines a clockwise and warming decompression P-T-t path which reveals an underplating process following the early subduction erosion. During the tectonic process, the eroded low-density material escaped from the cold subduction channel and rise upward into the warm middle-lower crust of the upper plate, undergoing amphibolite facies metamorphism. Our new results revealed a complete evolutional process from the early subduction erosion to the subsequent underplating during the northward subduction of the Paleo-Tethys Ocean.

Partial melting of amphibolite to trondhjemite at Nunatak Fiord, St. Elias Mountains, Alaska

DOE Office of Scientific and Technical Information (OSTI.GOV)

Barker, F.; McLellan, E.L.; Plafker, G.

1985-01-01

At Nunatak Fiord, 55km NE of Yakutat, Alaska, a uniform layer of Cretaceous basalt ca. 3km thick was metamorphosed ca. 67 million years ago to amphibolite and locally partially melted to pegmatitic trondhjemite. Segregations of plagioclase-quartz+/-biotite rock, leucosomes in amphibolite matrix, range from stringers 5-10mm thick to blunt pods as thick as 6m. They tend to be parallel to foliation of the amphibolite, but crosscutting is common. The assemblage aluminous hornblende-plagioclase-epidote-sphene-quartz gave a hydrous melt that crystallized to plagioclase-quartz+/-biotite pegmatitic trondhjemite. 5-10% of the rock melted. Eu at 2x chondrites is positively anomalous. REE partitioning in melt/residum was controlled largelymore » by hornblende and sphene. Though the mineralogical variability precludes quantitative modeling, partial melting of garnet-free amphibolite to heavy-REE-depleted trondhjemitic melt is a viable process.« less

Hematite-coated microfossils: primary ecological fingerprint or taphonomic oddity of the Paleoproterozoic?

PubMed

Shapiro, R S; Konhauser, K O

2015-05-01

Microfossils belonging to the 1.88-billion-year-old 'Gunflint-biota' are preserved as carbonaceous and hematitic filaments and spheres that are believed to represent ancient chemolithoautotrophic Fe(II) oxidizing bacteria that grew above a chemocline where ferruginous seawater upwelled into shallow, oxygenated waters. This 'biological' model posits that hematite formed during burial from dewatering of the precursor ferric oxyhydroxides that encrusted Fe(II)-oxidizing bacteria. Here, we present an alternate 'taphonomic' model in which iron-rich groundwaters discharged into buried stromatolites; thus, the mineralization reactions are more informative of diagenetic processes than they are for primary marine conditions. We sampled centimeter-scale columnar stromatolites from both the lower and upper stromatolite horizons of the Biwabik and Gunflint formations, across a range of metamorphic gradients including unaltered to prehnite-pumpellyite taconite, supergene altered ore, and amphibolite-pyroxene grade contact-metamorphic zones. Fossils are rare to very rare and comprise curved filaments that exist in clusters with similar orientations. The filaments from throughout the Biwabik are similar to well-preserved carbonaceous Gunflintia from Ontario. Spheres of Huroniospora are also found in both formations. Microfossils from the least altered sections are preserved as carbon. Prehnite-pumpellyite samples are composed of either carbon or hematite (Fe2 O3 ). Within the contact aureole, filaments are densely coated by magnetite (Fe3 O4 ); the highest grade samples are secondarily oxidized to martite. The consistency in stromatolite microstructure and lithofacies throughout the metamorphic grades suggests they formed under similar environmental conditions. Post-depositional alteration led to replacement of the carbon by iron oxide. The facies association, filament distribution, and lack of branching and attached spherical cells argue against Gunflintia being a direct analogue to common marine, chemolithoautotrophic Fe(II)-oxidizing bacteria. Instead, we propose that the presence of hematite-coated microfossils is a reflection of taphonomic processes and does not necessarily reflect the byproduct of an original microbial ecosystem. © 2015 John Wiley & Sons Ltd.

Archaean and Palaeoproterozoic gneisses reworked during a Neoproterozoic (Pan-African) high-grade event in the Mozambique belt of East Africa: Structural relationships and zircon ages from the Kidatu area, central Tanzania

NASA Astrophysics Data System (ADS)

Vogt, M.; Kröner, A.; Poller, U.; Sommer, H.; Muhongo, S.; Wingate, M. T. D.

2006-06-01

This study presents new zircon ages and Sm-Nd whole-rock isotopic compositions for high-grade gneisses from the Udzungwa Mountain area in the central part of the Mozambique belt, Tanzania. The study area comprises a succession of layered granulite-facies para- and orthogneisses, mostly retrograded to amphibolite-facies. The original intrusive contacts became obscured or severely modified during non-coaxial ductile deformation, and extensive shearing occurred during retrogression. Structures reflecting the early deformational history were mostly obscured when the rocks were transported into the lower crust as documented by severe flattening. Only the fragmented gneisses in the eastern part of the area testify to a brittle regime. Structures in narrow low strain zones that predate the currently observed layering are preserved in rootless isoclinal folds and boudins. Magmatic and detrital zircons from tonalitic to felsic orthogneisses and a metapelite sample were dated using the U-Pb and Pb-Pb evaporation methods and SHRIMP II. Cathodoluminiscence images reveal ubiquitous xenocrystic cores, rimmed by clear, unzoned overgrowth due to high-grade metamorphism. Discordant U-Pb data therefore reflect core-rim relationships, and it was not always possible to obtain precise crystallisation ages. The analyses reveal Neoarchaean, Palaeoproterozoic and Neoproterozoic protolith ages. Nd isotopic systematics yielded strongly negative ɛNd( t) -values and Neoarchaean to Palaeoproterozoic model ages, even for gneisses emplaced in the Neoproterozoic. The trace element distribution suggests upper crustal derivation of the gneisses. Therefore, our study provides evidence that recycling of older crust played a major role during the evolution of the Kidatu area. Neoarchaean rocks are interpreted to represent fragments of the Tanzania craton. Our results, together with those of earlier workers, lead to the conclusion that the central part of the Mozambique belt mainly consists of ancient crustal remnants that were reworked during the Neoproterozoic Pan-African orogeny.

Thermobaric structure of the Himalayan Metamorphic Belt in Kaghan Valley, Pakistan

NASA Astrophysics Data System (ADS)

Rehman, Hafiz Ur; Yamamoto, Hiroshi; Kaneko, Yoshiyuki; Kausar, Allah Bakhsh; Murata, Mamoru; Ozawa, Hiroaki

2007-02-01

The thermobaric structure of the Himalayan Metamorphic Belt (HMB) has been constructed along the Kaghan Valley transect, Pakistan. The HMB in this valley represents mainly the Lesser Himalayan Sequence (LHS) and Higher Himalayan Crystallines (HHC). Mineral parageneses of 474 samples, from an approximately, 80-km traverse from southwest to northeast, were examined. Microprobe analyses were carried out to quantify the mineral composition. To determine the pressure-temperature (P-T) conditions, 65 thin sections (7 pelites from LHS and 25 pelites, 9 mafic rocks/amphibolites and 19 eclogites from HHC) were selected. Based on field observations and mineral paragenesis, low-grade to high-grade metapelites, show Barrovian-type progressive metamorphic sequence, with chlorite, biotite, garnet and staurolite zones in LHS and staurolite, kyanite and sillimanite zones in HHC. By using well-calibrated geothermobarometers, P-T conditions for pelitic and mafic rocks are estimated. P-T estimates for pelitic rocks from the garnet zone indicate a condition of 534 ± 17 °C at 7.6 ± 1.2 kbar. P-T estimates for rocks from the staurolite and kyanite zones indicate average conditions of 526 ± 17 °C at 9.4 ± 1.2 kbar and 657 ± 54 °C at 10 ± 1.6 kbar, respectively. P-T conditions for mafic rocks (amphibolites) and eclogites from HHC are estimated as 645 ± 54 °C at 10.3 ± 2 kbar and 746 ± 59 °C at 15.5 ± 2.1 kbar, respectively. The coesite-bearing ultrahigh-pressure (UHP) eclogites record a peak P-T condition of 757-786 °C at 28.6 ± 0.4 kbar and retrograde P-T conditions of 825 ± 59 °C at 18.1 ± 1.7 kbar. These results suggest that HMB show a gradual increase in metamorphic grade from southwest to northeast. The P-T conditions from Pelitic and adjacent mafic rocks having identical peak conditions in the same metamorphic zone, while the structural middle in HHC reached the highest P-T condition upto the UHP grade.

Metamorphic conditions and CHIME monazite ages of Late Eocene to Late Oligocene high-temperature Mogok metamorphic rocks in central Myanmar

NASA Astrophysics Data System (ADS)

Maw Maw Win; Enami, Masaki; Kato, Takenori

2016-03-01

The high temperature (T)/pressure (P) regional Mogok metamorphic belt is situated in central Myanmar, and is mainly composed of pelitic gneisses, amphibolites, marbles, and calc-silicate rocks. The garnet-biotite-plagioclase-sillimanite-quartz assemblage and its partial system suggest equilibrium P/T conditions of 0.6-1.0 GPa/780-850 °C for the peak metamorphic stage, and 0.3-0.5 GPa/600-680 °C for the exhumation and hydration stage. Monazite grains show complex compositional zoning consisting of three segments-I, II, and III. Taking into consideration the monazite zoning and relative misfit curves, the calculated chemical Th-U-total Pb isochron method (CHIME) monazite age data (284 spot analyses) indicated four age components: 49.3 ± 2.6-49.9 ± 7.9, 37.8 ± 1.0-38.1 ± 1.7, 28.0 ± 0.8-28.8 ± 1.6, and 23.7 ± 1.3 Ma (2σ level). The ages of the Late Eocene and Late Oligocene epochs were interpreted as the peak metamorphic stage of upper-amphibolite and/or granulite facies and the postdated hydration stage, respectively.

Ultrastructural and geochemical characterization of Archean-Paleoproterozoic graphite particles: implications for recognizing traces of life in highly metamorphosed rocks.

PubMed

Schiffbauer, James D; Yin, Leiming; Bodnar, Robert J; Kaufman, Alan J; Meng, Fanwei; Hu, Jie; Shen, Bing; Yuan, Xunlai; Bao, Huiming; Xiao, Shuhai

2007-08-01

Abundant graphite particles occur in amphibolite-grade quartzite of the Archean-Paleoproterozoic Wutai Metamorphic Complex in the Wutaishan area of North China. Petrographic thin section observations suggest that the graphite particles occur within and between quartzite clasts and are heterogeneous in origin. Using HF maceration techniques, the Wutai graphite particles were extracted for further investigation. Laser Raman spectroscopic analysis of a population of extracted graphite discs indicated that they experienced a maximum metamorphic temperature of 513 +/- 50 degrees C, which is consistent with the metamorphic grade of the host rock and supports their indigenicity. Scanning and transmission electron microscopy revealed that the particles bear morphological features (such as hexagonal sheets of graphite crystals) related to metamorphism and crystal growth, but a small fraction of them (graphite discs) are characterized by a circular morphology, distinct marginal concentric folds, surficial wrinkles, and complex nanostructures. Ion microprobe analysis of individual graphite discs showed that their carbon isotope compositions range from -7.4 per thousand to -35.9 per thousand V-PDB (Vienna Pee Dee Belemnite), with an average of -20.3 per thousand, which is comparable to bulk analysis of extracted carbonaceous material. The range of their size, ultrastructures, and isotopic signatures suggests that the morphology and geochemistry of the Wutai graphite discs were overprinted by metamorphism and their ultimate carbon source probably had diverse origins that included abiotic processes. We considered both biotic and abiotic origins of the carbon source and graphite disc morphologies and cannot falsify the possibility that some circular graphite discs characterized by marginal folds and surficial wrinkles represent deflated, compressed, and subsequently graphitized organic-walled vesicles. Together with reports by other authors of acanthomorphic acritarchs from greenschist-amphibolite-grade metamorphic rocks, this study suggests that it is worthwhile to examine carbonaceous materials preserved in highly metamorphosed rocks for possible evidence of ancient life.

Geologic Map of the Upper Wolf Island Creek Watershed, Reidsville Area, Rockingham County, North Carolina

USGS Publications Warehouse

Horton, J. Wright; Geddes, Donald J.

2006-01-01

This geologic map provides a foundation for hydrogeologic investigations in the Reidsville area of Rockingham County, north-central North Carolina. The 16-mi2 area within the Southeast Eden and Reidsville 7.5-min quadrangles includes the watershed of Wolf Island Creek and its tributary, Carroll Creek, upstream of their confluence. Layered metamorphic rocks in this area of the Milton terrane, here informally named the Chinqua-Penn metamorphic suite, include a heterogeneous mica gneiss and schist unit that contains interlayers and lenses of white-mica schist, felsic gneiss, amphibolite, and ultramafic rock; a felsic gneiss that contains interlayers of amphibolite, white-mica schist, and minor ultramafic lenses; and a migmatitic biotite gneiss. Crushed stone is produced from an active quarry in the felsic gneiss. Igneous intrusive rocks include a mafic-ultramafic assemblage that may have originated as mafic intrusive bodies containing ultramafic cumulates, a foliated two-mica granite informally named the granite of Reidsville, and unmetamorphosed Jurassic diabase dikes. The newly recognized Carroll Creek shear zone strikes roughly east-west and separates heterogeneous mica gneiss and schist to the north from structurally overlying felsic gneiss to the south. Regional amphibolite-facies metamorphism accompanied polyphase ductile deformation in the metamorphic rocks. Two phases of isoclinal to tight folding and related penetrative deformation, described as D1 and D2, were followed by phases of high-strain mylonitic deformation in shear zones and late gentle to open folding. Later brittle deformation produced minor faults, steep joints, foliation-parallel parting, and sheeting joints. The metamorphic and igneous rocks are mantled by saprolite and residual soil derived from weathering of the underlying bedrock, and unconsolidated Quaternary alluvium occupies the flood plains of Wolf Island Creek and its tributaries. The geologic map delineates lithologic and structural features that may act as barriers or conduits for ground-water flow. It provides a hydrogeologic framework for the upper Wolf Island Creek drainage basin, including coreholes and ground-water monitoring wells along two transects. Collaborative hydrogeologic investigations by the North Carolina Department of Environment and Natural Resources and the U.S. Geological Survey are in progress to increase understanding of the influence of geological features on ground-water quality, availability, and transport in an area representative of large areas in the west-central Piedmont.

Isotopic mapping of age provinces in Precambrian high-grade terrains: Sri Lanka

DOE Office of Scientific and Technical Information (OSTI.GOV)

Milisenda, C.C.; Liew, T.C.; Hofmann, A.W.

1988-09-01

Nd model ages of amphibolite- and granulite-grade rocks in Sri Lanka form a simple region pattern that broadly correlates with mappable geological units, and is in effect an isotopic map of the island's basement. The granulite-grade units of the Highland Group and Southwest Group have model ages of 2.2-3.0 Ga indicating derivation mainly from late Archean sources. They are bounded to the east and west by late Proterozoic gneisses of the Vijayan Complex with model ages of 1.1-2.0 Ga. The isotopic data identify three distinct crustal provinces and are not consistent with earlier suggestions that the Vijayan gneisses are retrogrademore » equivalents of the Highland granulites. Sri Lanka is not a direct continuation of the Archean Dharwar Craton of southern India. Identification of Vijayan-type juvenile crustal terrains in other Gondwana fragments may play a key role in determining the precise attachment of southern India-Sri Lanka in eastern Gondwana.« less

A field trip guidebook to the type localities of Marland Billings' 1935 Paleozoic bedrock stratigraphy near Littleton, New Hampshire

USGS Publications Warehouse

Rankin, Douglas W.; Rankin, Mary B.

2014-01-01

Marland Billings' classic paper published in 1937 in the Geological Society of America Bulletin established a succession of six stratigraphic units in rocks of low metamorphic grade near Littleton, New Hampshire. The two youngest units are fossiliferous in the area, with ages established at the time as “middle” Silurian and Early Devonian. Billings and students mapped the same stratigraphic section in adjacent areas of progressively higher regional metamorphic grade. This work laid the foundation upon which a major part of subsequent work in New England has been directly or indirectly built. This guidebook was written for a field trip held in March 2013 to visit roadcuts that are as close as possible in March to the type localities or areas of Billings’ six-fold stratigraphic succession. Ten stops are in rocks of chlorite grade of Acadian(?) metamorphism; the final stop visits amphibolite of the Ammonoosuc Volcanics. Fieldwork by the authors over the past 20 years confirms Billings’ broad conclusions.

Textural and Rb-Sr isotopic evidence for late Paleozoic mylonitization within the Honey Hill fault zone southeastern Connecticut

DOE Office of Scientific and Technical Information (OSTI.GOV)

O'Hara, K.D.; Gromet, L.P.

A petrographic and Rb-Sr isotopic study of rocks within and near the Honey Hill fault zone places important constraints on its history of movement. Rb-Sr apparent ages for micas and plagioclase from these rocks have been reset and range from Permian to Triassic, considerably younger than the minimum stratigraphic age (Ordovician) of the rocks studied or of Acadian (Devonian) regional metamorphism. Permian Rb-Sr ages of dynamically recrystallized muscovite date the development of mylonite fabric. An older age is precluded by the excellent preservation of unrecovered quartz, which indicates that these rocks did not experience temperatures high enough to anneal quartzmore » or thermally reset Rb-Sr isotopic systems in muscovite since the time of mylonitization. Metamorphic mineral assemblages and mineral apparent ages in rocks north of the fault zone indicate recrystallization under similar upper greenschist-lower amphibolite grade conditions during Permian to Triassic time. Collectively these results indicate that the Honey Hill fault zone was active during the Late Paleozoic and that ductile deformation and metamorphism associated with the Alleghanian orogeny extend well into southern Connecticut. An Alleghanian age for mylonitization within the Honey Hill fault zone suggests it should be considered as a possible site for the major Late Paleozoic strike-slip displacements inferred from paleomagnetic studies for parts of coastal New England and maritime Canada.« less

Amphibolite boudins in marble on Naxos, Greece: 3D analysis of multiphase deformation on a retrograde P-T path

NASA Astrophysics Data System (ADS)

Virgo, Simon; von Hagke, Christoph; Urai, Janos L.

2017-04-01

Boudins are periodic structures that form by layer parallel extension in mechanically layered rocks. The characteristics of boudins such as orientation and geometry provide constraints on the paleo stress field as well as the rheology of the rocks during deformation. However, most characterizations of boudinage are based on 2D observations and do not consider the 3-dimensional complexity and potentially non-coaxial polyphase genesis of boudinage structures. In marble quarries in the high grade complex on Naxos, Greece, we studied spectacular outcrops of amphibolite and pegmatite boudins, in combination with serial slicing of quarried blocks to reconstruct the 3D boudin structures. We identified five boudin generations with two distinct generations of early, high grade pinch-and-swell followed by two generations of brittle shearband and torn boudins formed along the retrograde path under greenschist facies conditions. The five generations of boudinage indicate that E-W compression is the main mode of deformation in the marbles. The axis of extension changes from subvertical during pinch-and swell deformation to subhorizontal N-S extension at later stages of deformation. Later phases of boudinage are influenced by existing boudin geometries, producing complex structures in 3D. In 2D section the complexity is not directly apparent and reveals itself only after statistical analysis of long continuous sections. Apart from implications for the regional geology, our findings highlight the importance of 3D characterization of boudinage structures for boudin classification. The insights we gain from the analysis of multiphase boudinage structures on Naxos are the basis for quantitative boudin analysis to infer rheology, effective stress, vorticity and strain, and establish a boudin classification scheme with appeal to a complete mechanics.

Tectonic slicing and mixing processes along the subduction interface: The Sistan example (Eastern Iran)

NASA Astrophysics Data System (ADS)

Bonnet, G.; Agard, P.; Angiboust, S.; Monié, P.; Jentzer, M.; Omrani, J.; Whitechurch, H.; Fournier, M.

2018-06-01

Suture zones preserve metamorphosed relicts of subducted ocean floor later exhumed along the plate interface that can provide critical insights on subduction zone processes. Mélange-like units are exceptionally well-exposed in the Sistan suture (Eastern Iran), which results from the closure of a branch of the Neotethys between the Lut and Afghan continental blocks. High pressure rocks found in the inner part of the suture zone (i.e., Ratuk complex) around Gazik are herein compared to previously studied outcrops along the belt. Detailed field investigations and mapping allow the distinction of two kinds of subduction-related block-in-matrix units: a siliciclastic-matrix complex and a serpentinite-matrix complex. The siliciclastic-matrix complex includes barely metamorphosed blocks of serpentinized peridotite, radiolarite and basalt of maximum greenschist-facies grade (i.e., maximum temperature of 340 °C). The serpentinite-matrix complex includes blocks of various grades and lithologies: mafic eclogites, amphibolitized blueschists, blue-amphibole-bearing metacherts and aegirine-augite-albite rocks. Eclogites reached peak pressure conditions around 530 °C and 2.3 GPa and isothermal retrogression down to 530 °C and 0.9 GPa. Estimation of peak PT conditions for the other rocks are less-well constrained but suggest equilibration at P < 1 GPa. Strikingly similar Ar-Ar ages of 86 ± 3 Ma, along 70 km, are obtained for phengite and amphibole from fourteen eclogite and amphibolitized blueschist blocks. Ages in Gazik are usually younger than further south (e.g., Sulabest), but there is little age difference between the various kinds of rocks. These results (radiometric ages, observed structures and rock types) support a tectonic origin of the serpentinite-matrix mélange and shed light on subduction zone dynamics, particularly on coeval detachment and exhumation mechanisms of slab-derived rocks.

Direct dating of left-lateral deformation along the Red River shear zone, China and Vietnam

NASA Astrophysics Data System (ADS)

Gilley, Lisa D.; Harrison, T. Mark; Leloup, P. H.; Ryerson, F. J.; Lovera, Oscar M.; Wang, Jiang-Hai

2003-02-01

Exposures of high-grade, midcrustal rocks within the Red River shear zone (RRSZ), which separates the Indochina and South China blocks, exhibit clear evidence of left-lateral, ductile deformation. Assuming that the South China Sea represents a pull-apart basin formed at the southeastern termination of the RRSZ, it has been argued that seafloor magnetic anomalies constrain the timing of sinistral slip accommodated by the RRSZ between ˜32 and 17 Ma at a rate of ˜4 cm/yr. While 40Ar/39Ar thermochronometry indicates that left-lateral slip occurred along the RRSZ between 25 and 17 Ma, the timing of earlier high-temperature deformation has not been directly constrained. In situ Th-Pb ion microprobe dating of monazite inclusions in garnets allows direct assessment of the timing of amphibolite-grade metamorphism and synchronous left-lateral shearing. Results from northern segments of the RRSZ in Yunnan, China, indicate that synkinematic garnet growth occurred between 34 and 21 Ma and are the first to document late Oligocene metamorphism and left-lateral shearing. Data from the southern RRSZ within Vietnam are complicated by Tertiary overprinting of rocks that experienced amphibolite facies metamorphism during the Indosinian orogeny (˜220 Ma). The period during which sinistral deformation is now constrained to have occurred along the RRSZ (i.e., 34-17 Ma) is essentially coincident with spreading of the South China seafloor (32-17 Ma). This temporal and kinematic link between left-lateral shearing along the RRSZ and opening of the South China Sea supports the view that Indochina was extruded from Asia as a block along lithospheric-scale strike-slip faults.

The connection between crustal reworking and petrological diversity in the deep crust: clues from migmatites

NASA Astrophysics Data System (ADS)

Carvalho, Bruna B.; Sawyer, Edward W.; de Assis Janasi, Valdecir

2016-04-01

The deep levels of the continental crust have been extensively reworked as result of crustal differentiation. Migmatites are widespread in these high-grade metamorphic terrains, and provide valuable information on how processes such as partial melting, segregation of the melt from the residue and subsequent chemical exchanges lead to the petrological diversity found in the deep crust. This study investigates processes that transformed a largely uniform, metagranodiorite protolith into a very complex migmatite that contains three varieties of diatexites (grey, schlieren and homogenous diatexites) and several types of leucosomes. The Kinawa Migmatite is part of the Archean TTG crust in the São Francisco Craton (Brazil), which has been reworked in a shear zone environment at upper amphibolite facies conditions (<730°C and 5-6 kbar); thus it may be typical of crustal reworking in the interior of old cratons [1]. Grey diatexites are residual rocks formed by the extraction of a water-fluxed melt created via the reaction Pl + Kfs + Qz + H2O = melt. Diversity within the grey diatexites arises from different degrees of melt segregation (maximum ~40% melt). Schlieren diatexites are very heterogeneous rocks in which residuum-rich domains alternate with leucocratic quartzo-feldspathic domains where melt accumulated. Homogeneous diatexites are coarse-grained leucocratic rocks and represent larger bodies of anatectic melt with minor amounts (<20%) of entrained residuum. Leucosomes display a wide range of compositions from tonalitic to alkali-feldspar granite. Leucosomes, homogeneous diatexites and the quartzo-feldspathic domains in the schlieren diatexites all show a sequence of microstructural stages from plagioclase-dominated to K-feldspar-dominated frameworks many of which show evidence for tectonic compaction. Thus, further segregation of melt from solids occurred during crystallization. Minor amphibolite dykes in the metagranodiorite did not melt. They occur as angular to rounded fragments (schollen or rafts) in the diatexites and show strong evidence for mechanical and chemical interaction with their melt rich hosts. Typically, the diatexites and the leucosomes around the schollen contain higher proportion of amphibole and/or biotite than that farther away; a number of features suggest that this is due to disaggregation that contaminated the melt rich rocks. Our data indicates that in the deep levels of the crust petrological diversity is produced by melt segregation, both during partial melting and crystallization, and by interaction of the anatectic melt with unmelted material in the source. During melting, segregation produced residuum plus anatectic melt and all intermediate stages, whereas during crystallization it resulted in crystal fractionation and generated diverse plagioclase-rich rocks and fractionated melts. Finally, crystals disaggregated from the amphibolites entrained and interact with anatectic melt producing leucosomes and diatexites with the compositional signature of contamination. [1] Carvalho, B.B; Sawyer, E.W.; Janasi, V.A. (2016). Crustal reworking in a shear zone: transformation of metagranite to migmatite. Journal of Metamorphic Geology DOI: 10.1111/jmg.12180

Geochemistry of Archean Mafic Amphibolites from the Amsaga Area, West African Craton, Mauritania: What Is the Message?

NASA Astrophysics Data System (ADS)

El Atrassi, F.; Debaille, V.; Mattielli, N. D. C.; Berger, J.

2014-12-01

While Archean terrains are mainly composed of a TTG (Tonalite-trondhjemite-granodiorite) suite, more mafic lithologies such as amphibolites are also a typical component of those ancient terrains. Although mafic rocks represent only ~10% of the Archean cratons, they may provide key evidence of the role and nature of basaltic magmatism in the formation of the Archean crust as well as the evolution of the Archean mantle. This study focuses on the Archean crust from the West African Craton in Mauritania (Amsaga area). The Amsaga Archean Crust mainly consists of TTG and thrust-imbricated slices of mafic volcanic rocks, which have been affected by polymetamorphic events from the amphibolite to granulite facies. Our main objectives aim to the identification of the mafic lithology origin and a better understanding of their role in the continental crust emplacement. Our petrological observations show that these amphibolites have fine to medium granoblastic and nematoblastic textures. The amphibolites are dominated by amphibolite-facies mineral assemblages (mainly amphibole and plagioclase), but garnet and clinopyroxene occur in a few samples. Two groups are distinct in their geochemical characteristics (major and trace elements), although both have tholeiitic basalt composition. The first group show LREE-enriched patterns and negative Nb-Ta anomalies. The second group is characterized by near-flat LREE patterns and flat HREE patterns. This second group clearly shows no Nb-Ta anomalies. The first group could be related to arc-like basalts, as it is many similarities with some Archean amphibolites probably formed in a supra-subduction zone, for instance the volcanic rocks from the southern edge of the Isua Supracrustal Belt. On the contrary, the second group has a MORB-like signature which is more unusual during the Archean. Different scenarios will be discussed regards to the Archean geodynamics.

Lead isotope evolution across the Neoproterozoic boundary between craton and juvenile crust, Bayuda Desert, Sudan

NASA Astrophysics Data System (ADS)

Evuk, David; Lucassen, Friedrich; Franz, Gerhard

2017-11-01

Metaigneous mafic and ultramafic rocks from the juvenile Neoproterozoic Arabian Nubian Shield (ANS) and the Proterozoic, reworked Saharan Metacraton (SMC) have been analysed for major- and trace elements and Sr, Nd, and Pb isotopes. Most of the rocks are amphibolites metamorphosed at amphibolite facies conditions, some with relicts of a granulite facies stage. The other rocks are metapyroxenites, metagabbros, and some ultramafic rocks. Trace element compositions of the metabasaltic (dominantly tholeiitic) rocks resemble the patterns of island arcs and primitive lavas from continental arcs. Variable Sr and Nd isotope ratios indicate depleted mantle dominance for most of the samples. 207Pb/204Pb signatures distinguish between the influence of high 207Pb/204Pb old SMC crust and depleted mantle signatures of the juvenile ANS crust. The Pb isotope signatures for most metabasaltic rocks, metapyroxenites and metagabbros from SMC indicate an autochthonous formation. The interpretation of the new data together with published evidence from mafic xenoliths on SMC and ophiolite from ANS allows an extrapolation of mantle evolution in time. There are two lines of evolution in the regional mantle, one, which incorporates potential upper crust material during Neoproterozoic, and a second one with a depleted mantle signature since pre-Neoproterozoic that still is present in the Red Sea and Gulf of Aden spreading centres.

Extensional Late Paleozoic deformation on the western margin of Pangea, Patlanoaya area, Acatlán Complex, southern Mexico

NASA Astrophysics Data System (ADS)

Ramos-Arias, M. A.; Keppie, J. D.; Ortega-Rivera, A.; Lee, J. W. K.

2008-02-01

New mapping in the northern part of the Paleozoic Acatlán Complex (Patlanoaya area) records several ductile shear zones and brittle faults with normal kinematics (previously thought to be thrusts). These movement zones separate a variety of units that pass structurally upwards from: (i) blueschist-eclogitic metamorphic rocks (Piaxtla Suite) and mylonitic megacrystic granites (Columpio del Diablo granite ≡ Ordovician granites elsewhere in the complex); (ii) a gently E-dipping, listric, normal shear zone with top to the east kinematic indicators that formed under upper greenschist to lower amphibolite conditions; (iii) the Middle-Late Ordovician Las Minas quartzite (upper greenschist facies psammites with minor interbedded pelites intruded by mafic dikes and a leucogranite dike from the Columpio del Diablo granite) unconformably overlain by the Otate meta-arenite (lower greenschist facies psammites and pelites): roughly temporal equivalents are the Middle-Late Ordovician Mal Paso and Ojo de Agua units (interbedded metasandstone and slate, and metapelite and mafic minor intrusions, respectively) — some of these units are intruded by the massive, 461 ± 2 Ma, Palo Liso megacrystic granite: decussate, contact metamorphic muscovite yielded a 40Ar/ 39Ar plateau age of 440 ± 4 Ma; (iv) a steeply-moderately, E-dipping normal fault; (v) latest Devonian-Middle Permian sedimentary rocks (Patlanoaya Group: here elevated from formation status). The upward decrease in metamorphic grade is paralleled by a decrease in the number of penetrative fabrics, which varies from (i) three in the Piaxtla Suite, through (ii) two in the Las Minas unit (E-trending sheath folds deformed by NE-trending, subhorizontal folds with top to the southeast asymmetry, both associated with a solution cleavage), (iii) one in the Otate, Mal Paso, and Ojo de Agua units (steeply SE-dipping, NE-SW plunging, open-close folds), to (iv) none in the Patlanoaya Group. 40Ar/ 39Ar analyses of muscovite from the earliest cleavage in the Las Minas unit yielded a plateau age of 347 ± 3 Ma and show low temperature ages of ˜ 260 Ma. Post-dating all of these structures and the Patlanoaya Group are NE-plunging, subvertical folds and kink bands. An E-W, vertical normal fault juxtaposes the low-grade rocks against the Anacahuite amphibolite that is cut by megacrystic granite sheets, both of which were deformed by two penetrative fabrics. Amphibole from this unit has yielded a 40Ar/ 39Ar plateau age of 299 ± 6 Ma, which records cooling through ˜ 490 °C and is probably related to a Permo-Carboniferous reheating event during exhumation. The extensional deformation is inferred to have started in the latest Devonian (˜ 360 Ma) during deposition of the basal Patlanoaya Group, lasting through the rapid exhumation of the Piaxtla Suite at ˜ 350-340 Ma synchronous with cleavage development in the Las Minas unit, deposition of the Patlanoaya Group with active fault-related exhumation suggested by Mississippian and Early Permian conglomerates (˜ 340 and 300 Ma, respectively), and continuing at least into the Middle Permian (≡ 260 Ma muscovite ages). The continuity of Mid-Continent Mississippian fauna from the USA to southern Mexico suggests that this extensional deformation occurred on the western margin of Pangea after closure of the Rheic Ocean.

Prolonged episodic Paleoproterozoic metamorphism in the Thelon Tectonic Zone, Canada: an in-situ SHRIMP/EPMA monazite geochronology study

NASA Astrophysics Data System (ADS)

Mitchell, Rhea; William, Davis; Robert, Berman; Sharon, Carr; Michael, Jercinovic

2017-04-01

The Thelon Tectonic zone (TTZ), Nunavut, Canada, is a >500km long geophysically, lithologically and structurally distinct N-NNE striking Paleoproterozoic boundary zone between the Slave and Rae Archean provinces. The TTZ has been interpreted as a ca. 2.0 Ga continental arc on the western edge of the Rae craton, that was deformed during collision with the Slave craton ca. 1.97 Ga. Alternatively, the Slave-Rae collision is interpreted as occurring during the 2.35 Ga Arrowsmith orogeny while the 1.9-2.0 Ga TTZ represents an intra-continental orogenic belt formed in previously thinned continental crust, postdating the Slave-Rae collision. The central part of the TTZ comprises three >100 km long, 10-20 km wide belts of ca. 2.0 Ga, mainly charnockitic plutonic rocks, and a ca. 1910 Ma garnet-leucogranite belt. Metamorphism throughout these domains is upper-amphibolite to granulite-facies, with metasedimentary rocks occurring as volumetrically minor enclaves and strands of migmatites. The Ellice River domain occurs between the western and central plutonic belts. It contains ca. 1950 Ma ultramafic to dacitic volcanic rocks and foliated Paleoproterozoic psammitic metasedimentary rocks at relatively lower grade with lower to middle amphibolite-facies metamorphic assemblages. In-situ U-Pb analyses of monazite using a combination of Sensitive High-Resolution Ion Microprobe (SHRIMP) and Electron Probe Microanalyzer (EPMA) were carried out on high-grade metasedimentary rocks from seventeen samples representing the eastern margin of the Slave Province and all major lithological domains of the TTZ. 207Pb/206Pb monazite ages from SHRIMP analysis form the foundation of this dataset, while EPMA ages are supplementary. The smaller <6µm spot size of EPMA allowed for further constraint on ages of micro-scale intra-crystalline domains in some samples. Monazite ages define four distinct Paleoproterozoic metamorphic events and one Archean metamorphic event at ca. 2580 Ma. The latter is recorded exclusively along the eastern margin of the Slave Province. Metamorphism ca. 1996 Ma, recorded in one high-grade gneiss from the central plutonic belt appears to reflect a regional contact metamorphism associated with intrusion of 2000 Ma plutons. Throughout the TTZ, a selection of monazite grains included in garnet porphyroblasts define a metamorphic event ca. 1962 Ma. One sample from the eastern margin of the Slave Province similarly records metamorphism at 1961 Ma in monazite grains in the matrix. This sample interestingly does not record the ca. 2580 Ma metamorphism typical of the Slave Province. The longest lived and most wide spread metamorphic event in the TTZ occurred ca. 1922 to 1883 Ma. This event is interpreted as the main compressional/collisional and anatectic event, with partial melting forming the extensive ca. 1910 Ma garnet-leucogranite belts. Three samples, located in the eastern margin of the Slave province, the Ellice River domain and the eastern plutonic belt, record younger metamorphism at ca. 1814 Ma. These events may represent post-collisional transpression coeval with movement along nearby regional-scale faults.

Tectonic Evolution of the Careón Ophiolite (Northwest Spain): A Remnant of Oceanic Lithosphere in the Variscan Belt.

PubMed

Díaz García F; Arenas; Martínez Catalán JR; González del Tánago J; Dunning

1999-09-01

Analysis of the Careón Unit in the Ordenes Complex (northwest Iberian Massif) has supplied relevant data concerning the existence of a Paleozoic oceanic lithosphere, probably related to the Rheic realm, and the early subduction-related events that were obscured along much of the Variscan belt by subsequent collision tectonics. The ophiolite consists of serpentinized harzburgite and dunite in the lower section and a crustal section made up of coarse-grained and pegmatitic gabbros. An Early Devonian zircon age (395+/-2 Ma, U-Pb) was obtained in a leucocratic gabbro. The whole section was intruded by numerous diabasic gabbro dikes. Convergence processes took place shortly afterward, giving rise to a mantle-rooted synthetic thrust system, with some coeval igneous activity. Garnet amphibolite, developed in metamorphic soles, was found discontinuously attached to the thrust fault. The soles graded downward to epidote-amphibolite facies metabasite and were partially retrogressed to greenschist facies conditions. Thermobarometric estimations carried out at a metamorphic sole (T approximately 650 degrees C; P approximately 11.5 kbar) suggested that imbrications developed in a subduction setting, and regional geology places this subduction in the context of an early Variscan accretionary wedge. Subduction and imbrication of oceanic lithosphere was followed by underthrusting of the Gondwana continental margin.

Geochemistry of Archean Mafic Amphibolites from the Amsaga Area, West African Craton, Mauritania: Occurrence of Archean oceanic plateau

NASA Astrophysics Data System (ADS)

El Atrassi, Fatima; Debaille, Vinciane; Mattielli, Nadine; Berger, Julien

2015-04-01

While Archean terrains are mainly composed of a TTG (Tonalite-trondhjemite-granodiorite) suite, more mafic lithologies such as amphibolites are also a typical component of those ancient terrains. Although mafic rocks represent only ~10% of the Archean cratons, they may provide key evidence of the role and nature of basaltic magmatism in the formation of the Archean crust as well as the evolution of the Archean mantle. This study focuses on the Archean crust from the West African craton in Mauritania (Amsaga area). The Amsaga Archean crust mainly consists of TTG and thrust-imbricated slices of mafic volcanic rocks, which have been affected by polymetamorphic events from the amphibolite to granulite facies. We report the results of a combined petrologic, Sm-Nd isotopic, major element and rare earth element (REE) study of the Archean amphibolites in the West African craton. This study was conducted in order to characterize these rocks, to constrain the time of their formation and to evaluate their tectonic setting and their possible mantle source. Our petrological observations show that these amphibolites have fine to medium granoblastic and nematoblastic textures. They are dominated by amphibolite-facies mineral assemblages (mainly amphibole and plagioclase), but garnet and clinopyroxene occur in a few samples. These amphibolites have tholeiitic basalt composition. On a primitive mantle-normalized diagram, they display fairly flat patterns without negative anomalies for either Eu or Nb-Ta. We have shown using Sm-Nd whole rock isotopic data that these amphibolites formed at 3.3 ±0.075 Ga. They have positive ɛNdi values (+5.2 ± 1.6). These samples show isotopically juvenile features, which rule out the possibility of significant contamination of the protolith magmas by ancient continental crust. Based on these geochemical data we propose that the tholeiitic basalts were formed in an oceanic plateau tectonic setting from a mantle plume source and that they have a depleted mantle source. It is the first time that such a signature is observed in the Archean part of the West African craton, and would suggest a widespread bimodal distribution of trace elements signature in all Archean basalts.

Palaeoproterozoic tectonic evolution of the Alto Tererê Group, southernmost Amazonian Craton, based on field mapping, zircon dating and rock geochemistry

NASA Astrophysics Data System (ADS)

Lacerda Filho, J. V.; Fuck, R. A.; Ruiz, A. S.; Dantas, E. L.; Scandolara, J. E.; Rodrigues, J. B.; Nascimento, N. D. C.

2016-01-01

New geochemical and geochronological U-Pb and Sm-Nd data from amphibolites of the Alto Tererê Group, which are of Palaeoproterozoic age, are presented. The amphibolites are exposed in the central-eastern portion of the Rio Apa Block, southern Amazonian Craton, Mato Grosso do Sul, Brazil, and are composed of hornblende, plagioclase, quartz, biotite, cummingtonite and epidote. The amphibolites are subdivided into three lithofacies: (i) thinly banded amphibolites (metabasalts), (ii) coarse- and medium-grained amphibolites with relic subophitic texture (metagabbros), and (iii) amphibolites with relic cumulate texture (metapyroxenites). Chemical data also suggest the subdivision of the amphibolites into three different types. These rocks yield a U-Pb zircon age of 1768 ± 6 Ma and are therefore older than rocks of part of the Rio Apa Complex. Their Sm-Nd model ages range between 2.89 and 1.88 Ga, and their εNd (T) values range between -3.40 and + 3.74. Chemical analyses of these rocks indicate SiO2 concentrations between 45.23 and 50.65 wt.%, MgO concentrations between 4.34 and 8.01 wt.%, TiO2 concentrations between 0.91 and 1.74 wt.%, weakly fractionated rare-earth element (REE) patterns with mild depletion in heavy REEs, enrichment in large-ion lithophile elements (LILEs) and high-field-strength element (HFSEs), negative Nb, Ta and Co anomalies, positive Ba and Pb anomalies, low Ce concentrations, high Rb/Y ratios and low Th/La and Hf/Sm ratios. These features reflect metasomatism of the mantle wedge produced by sediments from the subducted plate. Various degrees of melting mark the evolution of the parent basic magmas, although subordinate crustal contamination may also have occurred. The geochemical signature of the amphibolites corresponds to that of tholeiitic basalts generated in an extensional back-arc-basin environment. The deposition in the basin apparently ceased during the first episode of compression and deformation at approximately 1.68 Ga, and the main deformation was most likely related to the San Ignácio Orogeny, which dates to approximately 1.3 Ga.

Review of metamorphic and kinematic data from Internal Crystalline Massifs (Western Alps): PTt paths and exhumation history

NASA Astrophysics Data System (ADS)

Gasco, Ivano; Gattiglio, Marco; Borghi, Alessandro

2013-01-01

Detailed geological mapping combined with micro-structural and petrological investigation allowed to clarify the tectono-metamorphic relationships between continental and oceanic units transition in the Penninic domain of the Western Alps. The three study areas (Gressoney, Orco and Susa sections) take into consideration the same structural level across the axial metamorphic belt of the Western Italian Alps, i.e., a geological section across the Internal Crystalline Massifs vs Piedmont Zone boundary. The units outcropping in these areas can be grouped into two Tectonic Elements according to their tectono-metamorphic evolution. The Lower Tectonic Element (LTE) consists of the Internal Crystalline Massifs and the Lower Piedmont Zone (Zermatt-Saas like units), both showing well preserved eclogite facies relics. Instead, the Upper Tectonic Element (UTE) consists of the Upper Piedmont Zone (Combin like units) lacking evidence of eclogite facies relics. In the Lower Tectonic Element two main Alpine tectono-metamorphic stages were identified: M1/D1 developed under eclogite facies conditions and M2/D2 is related to the development of the regional foliation under greenschist to epidote-albite amphibolite facies conditions. In the Upper Tectonic Element the metamorphic stage M1/D1 developed under bluschist to greenschist facies conditions and M2/D2 stage under greenschist facies conditions. These two Tectonic Elements are separated by a tectonic contact of regional importance generally developed along the boundary between the Lower and the Upper Piedmont zone under greenschist facies conditions. PT data compared to geochronology indicate that the first exhumation of ICM can be explained by buoyancy forces acting along the subduction channel that occurred during the tectonic coupling between the continental and oceanic eclogite units. These buoyancy forces vanished at the base of the crust where the density difference between the subducted crustal units and the surroundings rocks is too low. A stage where compression prevails on the previous exhumation followed, which leads to the development of the regional foliation under greenschist to amphibolite facies metamorphic conditions. Further exhumation occurred after the M2/D2 stage at shallower crustal levels along conjugated shear zones leading to the development of a composite axial dome consisting of eclogite-bearing continental-oceanic units (ICM and Zermatt-Saas Zones) beneath greenschist ones (Combin Zone).

SHRIMP U-Pb dating, trace elements and the Lu-Hf isotope system of coesite-bearing zircon from amphibolite in the SW Sulu UHP terrane, eastern China

NASA Astrophysics Data System (ADS)

Liu, Fulai; Gerdes, Axel; Zeng, Lingsen; Xue, Huaimin

2008-06-01

In this study, we link mineral inclusion data, trace element analyses, U-Pb age and Hf isotope composition obtained from distinct zircon domains of complex zircon to unravel the origin and multi-stage metamorphic evolution of amphibolites from the Sulu ultrahigh-pressure (UHP) terrane, eastern China. Zircon grains separated from amphibolites from the CCSD-MH drill hole (G12) and Niushan outcrop (G13) were subdivided into two main types based on cathodoluminescence (CL) and Laser Raman spectroscopy: big dusty zircons with inherited cores and UHP metamorphic rims and small clear zircons. Weakly zoned, grey-white luminescent inherited cores preserve mineral inclusions of Cpx + Pl + Ap ± Qtz indicative of a mafic igneous protolith. Dark grey luminescent overgrowth rims contain the coesite eclogite-facies mineral inclusion assemblage Coe + Grt + Omp + Phe + Ap, and formed at T = 732-839 °C and P = 3.0-4.0 GPa. In contrast, white luminescent small clear zircons preserve mineral inclusions formed during retrograde HP quartz eclogite to LP amphibolite-facies metamorphism (T = 612-698 °C and P = 0.70-1.05 GPa). Inherited zircons from both samples yield SHRIMP 206Pb/238U ages of 695-520 Ma with an upper intercept age of 800 ± 31 Ma. The UHP rims yield consistent Triassic ages around 236-225 and 239-225 Ma for G12 and G13 with weighted means of 229 ± 3 and 231 ± 3 Ma, respectively. Small clear zircons from both samples give 206Pb/238U ages around 219-210 Ma with a weighted mean of 214 ± 3 Ma, interpreted as the age of retrograde quartz eclogite-facies metamorphism. Matrix amphibole from both samples indicate Ar-Ar ages of 209 ± 0.7 and 207 ± 0.7 Ma, respectively, probably dating late amphibolite-facies retrogression. The data suggest subduction of Neoproterozoic mafic igneous rocks to UHP conditions in Middle Triassic (∼230 Ma) times and subsequent exhumation to an early HP (∼214 Ma) and a late LP stage (∼208 Ma) over a period of ∼16 and 6 Myr, respectively. Thus, early exhumation from a mantle depth of 120-100 km to about 60 km occurred at an average rate of 0.3 cm/y, while subsequent exhumation to a middle crustal level took place at approximately 0.54 cm/y. These exhumation rates are considerably slower than those obtained for UHP rocks in the Dora Maira and Kokchetav massifs (2-3 cm/y). Based on similar P-T estimates and trace element and Hf isotope compositions, Sulu amphibolites can be identified as retrograde UHP eclogites. The εHf(800) of +8 implies a significant input from the depleted mantle to the Sulu-Dabie terrane during the middle Neoproterozoic. Overgrown rims are characterized by a distinct trace element composition with low Lu/Hf and Th/U and significantly higher 176Hf/177Hf ratios than inherited cores, consistent with formation during/after garnet (re-)crystallization and fractionation of the Lu-Hf system during UHP metamorphism. The combined dataset suggests homogenization of the 176Hf/177Hf ratio within the metamorphic mineral assemblage and during protolith formation. Observed variations are explained by mixing of material from both domains during laser ablation, e.g., due to partial recrystallization of inherited cores.

Geochemical recognition of a captured back-arc basin metabasaltic complex, southwestern Oregon

USGS Publications Warehouse

Donato, M.M.

1991-01-01

An extensive fault-bounded amphibolite terrane of Late Jurassic (145 ?? 2 Ma) metamorphic age occurring in the northeastern Klamath Mountains of southern Oregon has been recognized as the remnants of an ancient back-arc basin. In spite of thorough metamorphic recrystallization under amphibolite-facies conditions, the amphibolite locally displays relict igneous textures which suggest that the protoliths included basaltic dikes or sills, shallow diabase intrusions, and gabbros. The geochemical data, together with the present-day geologic context, indicate that the tectonic setting of eruption/intrusion was probably within a back-arc basin that existed inboard (east) of a pre-Nevadan volcanic arc. The basalt (now amphibolite) and the overlying sediments (now the May Creek Schist) were metamorphosed and deformed during accretion to North America during the Late Jurassic Nevadan orogeny. -from Author

Late Paleozoic onset of subduction and exhumation at the western margin of Gondwana (Chilenia Terrane): Counterclockwise P-T paths and timing of metamorphism of deep-seated garnet-mica schist and amphibolite of Punta Sirena, Coastal Accretionary Complex, central Chile (34° S)

NASA Astrophysics Data System (ADS)

Hyppolito, T.; García-Casco, A.; Juliani, C.; Meira, V. T.; Hall, C.

2014-10-01

In this study, the Paleozoic albite-epidote-amphibolite occurring as meter-sized intercalations within garnet-mica schist at Punta Sirena beach (Pichilemu region, central Chile) is characterized for the first time. These rocks constitute an unusual exposure of subduction-related rocks within the Paleozoic Coastal Accretionary Complex of central Chile. Whereas high pressure (HP) greenschist and cofacial metasediments are the predominant rocks forming the regional metamorphic basement, the garnet-mica schist and amphibolite yield higher P-T conditions (albite-epidote amphibolite facies) and an older metamorphic age. Combining detailed mineral chemistry and textural information, P-T calculations and Ar-Ar ages, including previously published material from the Paleozoic Accretionary Complex of central Chile, we show that the garnet-mica schist and associated amphibolite (locally retrograded to greenschist) are vestiges of the earliest subducted material now forming exotic bodies within the younger HP units of the paleo-accretionary wedge. These rocks are interpreted as having been formed during the onset of subduction at the southwestern margin of Gondwana. However, we show that the garnet-mica schist formed at a slightly greater depth (ca. 40 km) than the amphibolite (ca. 30 km) along the same hot-subduction gradient developed during the onset of subduction. Both lithotypes reached their peak-P conditions at ca. 335-330 Ma and underwent near-isobaric cooling followed by cooling and decompression (i.e., counterclockwise P-T paths). The forced return flow of the garnet-mica schist from the subduction channel started at ca. 320 Ma and triggered the exhumation of fragments of shallower accreted oceanic crust (amphibolite). Cores of phengite (garnet-mica schist) and amphibole (amphibolite) grains have similar chemical compositions in both the S1 and S2 domains, indicating rotation of these grains during the transposition of the burial-related (prograde peak-T) foliation S1 by the non-coaxial exhumation-related foliation S2. During exhumation and retrograde D2 deformation, the garnet-mica schist and amphibolite were tectonically mingled at a depth of ca. 30 km at ca. 315 Ma. We propose that the Punta Sirena unit comprises a “pseudo”-coherent sequence formed by heterogeneous lithologies that followed non-chaotic exhumation mingling, now representing the remnants of the fossil subduction channel developed at the onset of the Late Paleozoic subduction at central Chile.

Magnetic Petrology of Variably Retrogressed Eclogites: a Case Study From the Hercynian Basement of Northern Sardinia (Italy)

NASA Astrophysics Data System (ADS)

Strada, E.; Talarico, F.; Florindo, F.

2005-12-01

The silicate parageneses of variably retrogressed eclogite facies metabasites are extensively used by metamorphic petrologists to reconstruct the tectono-metamorphic evolution which ophiolites-bearing units and high-pressure continental tectonic slices experienced in orogenic belts from initial burial to exhumation. On the other hand the opaque mineralogy of these rocks is generally not studied in detail although its characterization has a great potential to better understand the processes controlling the formation and stability of magnetic minerals (mainly magnetite and pyrrhotite) in collisional orogens and to improve geological interpretation of magnetic survey data. To define the relationships between metamorphic evolution and magnetic properties of eclogite and amphibolite facies metabasites we conducted a series of minero-petrographical analyses and mineral magnetic measurements in several outcrops of the Hercynian basement of Northern Sardinia. Magnetic susceptibility measurements with a hand-kappameter have been recorded for each outcrop together with structural features. The carriers of magnetization and their distribution within selected samples are described using a set of rock magnetic analyses (low-field magnetic susceptibility, natural and artificial remanences, thermomagnetic analyses, coercivity of remanence, hysteresis loops), and the petrological characterization of opaque minerals. Investigated samples include eclogites and amphibolites hosted in both kyanite-zone medium grade schists (MG) and high grade migmatitic gneisses (HG). Consistently with petromagnetic results and their variable magnetic susceptibilities (12.38-1047.7 10-8 m3/kg), HG metabasites contain variable contents of monoclinic pyrrhotite (intergrown with rutile) and titanomagnetite (occurring as inclusions in garnet), abundant ilmenite (associated to secondary hornblende and with sphene +/- low-Ti magnetite rims), rutile both as inclusions in ilmenite and as discrete grains. In MG metabasites (28.71- 97.98 10-8m3/kg) pyrrhotite is restricted to amphibolites as rare inclusions in garnet whereas ilmenite, rutile and sphene show the same microstructural features described in HG rocks. Microstructural evidence and geothermobarometric data indicate that: 1- pyrrhotite and titanomagnetite likely formed prior to and remained stable during the eclogite facies metamorphic peak (680-720°C, >1.5 GPa); 2 - the growth of ilmenite and sphene can be attributed to the amphibolite facies retrogression (500-650°C, 0.3-0.6 GPa), mainly due to model reactions such as garnet + omphacite+ rutile+ H2O --> hornblende + plagioclase+ ilmenite and amphibole+ ilmenite+ O2 --> sphene+ magnetite + quartz + H2O. These preliminary interpretations are the first contribution of an ongoing broader magnetic petrology investigation in the Hercynian basement in Sardinia. Particularly, these results point to a renewed interest for a further research effort i) to verify primary and secondary oxide contributions to the overall magnetization, ii)to link the stability/instability of magnetic assemblages to specific metamorphic or late magmatic processes, and iii) to provide a regional scale perspective on the level of magnetization in the different rock units. These data, integrated with geological information, will also be used to discuss the bearing of the highly-magnetic metabasites on the geological interpretation of regional anomalies revealed by aeromagnetic surveys in the region.

The Chunky Gal Mountain fault-detachment-normal fault providing evidence for Early-to-Middle Paleozoic extensional unroofing of the eastern Blue Ridge, or folded thrust

DOE Office of Scientific and Technical Information (OSTI.GOV)

Hatcher, R.D. Jr.

1993-03-01

The Chunky Gal Mountain fault (CGMF), located in the western Blue Ridge of southern NC and northern GA, contains unequivocal evidence for hanging wall-down-to-the-west movement. The 50 m-thick fault zone here consists of a series of shear zones in the footwall in a mass of mylonitized garnet-rich biotite gneiss. The main contact with the hanging wall reveals both a contrast in rock type and truncation of fabrics. Above the fault are amphibolite, ultramafic rocks, and minor metasandstone and pelitic schist of the Buck Creek mafic-ultramafic complex, while the footwall contains complexly folded metasandstone, pelitic schist, and calcsilicate pods of themore » Coleman River Formation. In the present orientation, the mylonitic foliation in the footwall rocks of the GGMF is subvertical; foliation in the hanging wall is subhorizontal at road level. These rocks were metamorphosed to upper amphibolite facies assemblages, and, after emplacement of the CGMF, were cut by brittle faults and trondhjemite dikes that contain no obvious tectonic fabric. Movement on the CGMF occurred near the thermal peak because enough heat remained in the rocks after movement to statically anneal the mylonite microfabric, but mesoscopic rotated porphyroclasts, rotated (dragged) earlier foliation, and some S-C fabrics clearly indicate the shear sense and vergence of this structure. Shear zones related to the CGMF transposed earlier fabrics, although some relicts preserving earlier structures remain in the shear zones. These rotated but untransposed relicts of amphibolite and garnet-rich biotite gneiss mylonite may indicate locally higher strain rates in subsidiary shear zones. The thermal/mechanical properties of the CGMF make it difficult to connect to the Shope Fork or Soque River thrusts farther south and east. Thus the hanging-wall-down configuration provides an alternative hypothesis that the CGMF may be a detachment-normal fault related to Taconian extensional unroofing of the Appalachians.« less

Constraining Crustal Anisotropy by Receiver Functions at the Deep Continental Drilling Site KTB in Southern Germany

NASA Astrophysics Data System (ADS)

Bianchi, Irene; Qorbani, Ehsan; Bokelmann, Götz

2016-04-01

As one of the rare observational tools for studying deformation and stress within the Earth, seismic anisotropy has been one of the focuses of geophysical studies over the last decade. In order to unravel the anisotropic properties of the crust, the teleseismic receiver functions (RF) methodology has started to be widely applied recently. Such effects of anisotropy on RF were illustrated in theoretical studies, showing the strong backazimuthal dependence of RF on the 3D characteristics of the media sampled by the waves. The use of teleseismic RF has the advantage of not being affected by a heterogeneous depth distribution of local earthquakes, since teleseismic rays sample the entire crust beneath the stations. The application of this technique however, needs to be critically assessed using a suitable field test. To test the technique, we need a crustal block where the underground structure is reasonably well-known, e.g., where there is extensive knowledge from local seismic experiments and drilling. A field experiment has thus been carried out around the KTB (Kontinental Tiefbohrung) site in the Oberpfalz area in Southeastern Germany, in order to compare with previous results from deep drilling, and high-frequency seismic experiments around the drill site. The investigated region has been studied extensively by local geophysical experiments, and geological studies. The deep borehole was placed into gneiss rocks of the Zone Erbendorf-Vohenstrauss. The drilling activity lasted from 1987 to 1994, and descended down to a depth of 9101 meters, sampling an alternating sequence of paragneiss and amphibolite, with metamorphism of upper amphibolite facies conditions, and ductile deformation produced a strong foliation of the rocks. The application of the RFs reveals strong seismic anisotropy in the upper crust related to the so-called Erbendorf body. The SKS shear-wave splitting method has been applied as well, revealing coherent results for the whole region with exception of the southernmost station, for which the seismic waves show larger delays. We use the RF observations to test the effect of crustal anisotropy on the SKS records, which sample entire crust and upper mantle.

Geology of quadrangles H-12, H-13, and parts of I-12 and I-13, (zone III) in northeastern Santander Department, Colombia

USGS Publications Warehouse

Ward, Dwight Edward; Goldsmith, Richard; Cruz, Jaime B.; Restrepo, Hernan A.

1974-01-01

A program of geologic mapping and mineral investigation in Colombia was undertaken cooperatively by the Colombian Instituto Nacional de Investigaciones Geologico-Mineras (formerly known as the Inventario Minero Nacional), and the U. S. Geological Survey; by the Government of Colombia and the Agency for International Development, U. S. Department of State. The purpose was to study, and evaluate mineral resources (excluding of petroleum, coal, emeralds, and alluvial gold) of four selected areas, designated Zones I to IV, that total about 70,000 km2. The work in Zone III, in the Cordillera Oriental, was done from 1965 to 1968. The northeast trend of the Cordillera Oriental of Colombia swings abruptly to north-northwest in the area of this report, and divides around the southern end of the Maracaibo Basin. This section of the Cordillera Oriental is referred to as the Santander Massif. Radiometric age determinations indicate that the oldest rocks of the Santander massif are Precambrian and include high-grade gneiss, schist, and migmatite of the Bucaramanga Formation. These rocks were probably part of the Precambrian Guayana Shield. Low- to medium-grade metamorphic rocks of late Precambrian to Ordovician age .include phyllite, schist, metasiltstone, metasandstone, and marble of the Silgara Formation, a geosynclinal series of considerable extent in the Cordillera Oriental and possibly the Cordillera de Merida of Venezuela. Orthogneiss ranging from granite to tonalite is widely distributed in the high- and medium-grade metamorphic rocks of the central core of the massif and probably represents rocks of two ages, Precambrian and Ordovician to Early Devonian. Younger orthogneiss and the Silgara are overlain by Middle Devonian beds of the Floresta Formation which show a generally low but varying degree of metamorphism. Phyllite and argillite are common, and infrequent marble and other calcareous beds are fossiliferous. Except for recrystallization in limestones of !the Permian-Carboniferous Diamante Formation, sedimentary rocks younger than Devonian are unmetamorphosed. The effects of Precambrian regional dynamothermal metamorphism and plutonism on Precambrian geosynclinal deposits reached the upper amphibolite facies in the Bucaramanga Gneiss. The geosynclinal Silgara Formation was subjected to similar conditions in Late Ordovician and Early Silurian time but reached only the greenschist or lower amphibolite facies. Orthogneisses generally show a concordance of foliation and lineation with the neighboring Silgara Formation and the Bucaramanga Gneiss as well as similarities in grade of metamorphism. Regional dynamothermal metamorphism in Late Permian and Triassic time reached, low grade in the Floresta Formation and caused recrystallization of limestone of the Diamante Formation. The Bucaramanga and Silgara metamorphic rocks show evidence of metrogressive metamorphism accompanied by high activity or potassium and water, but whether this occurred at the time the Floresta was metamorphosed or later is not clear. Batholiths, plutons, and stocks of igneous rocks in the Santander massif range from diorite to granite. Radioactive age data indicate that most belong to a single plutonic interval. These are referred to as the Santander Plutoniq Group and are Jurassic and Jurassic-Triassic- Two suites of this group are pink granite and quartz monzonite, and gray quartz monzonite and granodiorite. Contact relations indicate that the pink and more granitic rocks are younger than the gray and more mafic rocks, but radioactive age data are in conflict with this. Undated plutonic rocks that are not clearly related to the group are assigned to relatively older or younger age positions. West of the Bucanamanga fault rhyolite makes up a small body at one locality and forms an intrusive sheet with granophyre and intrusive breccias in Triassic sedimentary rocks at another locality. Its age is unknown, but it probably is younger than the

Petrography and character of the bedrock surface beneath western Cape Cod, Massachusetts

USGS Publications Warehouse

Hallett, B.W.; Poppe, L.J.; Brand, S.G.

2004-01-01

Cores collected during recent drilling in western Cape Cod, Massachusetts provide insight into the topography and petrology of the underlying bedrock. 62 drill sites spread over a ???140 km2 study area produced cores of granitoids (31), orthogneisses (20), basalts/diabases (4), amphibolites (3), felsic mylonites (2), and dolomitic rock (2). Granitoid cores range in composition from granite to tonalite to quartz diorite, but are dominated by single-mica granites. Alteration is common in nearly all cores examined in this study, and is evidenced by the secondary growth of chlorite and epidote. The granitoids resemble rocks of the Dedham and Fall River terranes (Wones and Goldsmith 1991). Gneisses from the study area generally contain the mineral assemblage hornblende+plagioclase+quartz+biotite+epidote??chlorite?? sphene??K-feldspar??sericite+oxides. Based on mineral assemblages, we estimate peak metamorphic grade to be of lower amphibolite facies. X-ray powder diffraction of unmetamorphosed dolomitic cores shows presence of layered silicates (clays), plagioclase, and possible magnesite. Contours of the bedrock surface show locally irregular topography suggesting erosion by glacial scour. The distribution of lithologies suggests a possible continuation of the New Bedford gneissic terrane that outcrops 25 km to the west. Dolomitic rocks may represent a lithified fault gouge material at the eastern edge of the gneissic zone. Basalts/diabases are interpreted to be post-metamorphic dikes of Late Paleozoic age, or possibly associated with Mesozoic rifting.

Petrology and tectonic history of the Green Bay Schist, Portmore, St. Catherine Parish, Jamaica

USGS Publications Warehouse

Abbott, Richard N.; West, David P.; Bandy, Betsy R.; McAleer, Ryan J.

2016-01-01

There are three occurrences of medium- to high-grade metamorphic rocks in Jamaica: amphibolite facies Westphalia Schist, blueschist/greenschist facies Mt. Hibernia Schist, and the hitherto poorly characterized amphibolite facies Green Bay Schist. New trace element data and thermodynamic calculations show that Green Bay Schist is closely related to Westphalia Schist. The protoliths for both are very similiar (basalt-andesitic basalt, C-MORB), consistent with a subducted ocean-ridge tectonic environment, hence arc-related. The protolith for Mt. Hibernia Schist is quite different (basalt, P-MORB), related to the Caribbean Large Igneous Province. Whereas the P-T-t paths for Green Bay Schist and Westphalia Schist prior to the middle Campanian (>78 Ma) are inferred to be similar, the late Campanian, Maastrichtian and Cenozoic P-T-t paths are very different. New 40Ar/39Ar age determinations show the following: (1) While the difference in the late Campanian and Maastrichtian remains problematic, (2) the difference in the Cenozoic clearly reflects the location relative to the NW-trending, NE-dipping Wagwater Fault: Westphalia Schist to the NE (hanging wall); Green Bay Schist to the SW (foot wall). The Cenozoic P-T-t paths are complementary, and consistent with the behavior of the Wagwater Fault: 65-50 Ma, normal motion (transtension); 50-10 Ma, inactive (quiescent); 10 Ma-present, reverse motion (transpression).

Geologic map of the Ennis 30' x 60' quadrangle, Madison and Gallatin Counties, Montana

USGS Publications Warehouse

Kellogg, Karl S.; Williams, Van S.

1998-01-01

The Ennis 1:100,000 quadrangle lies within both the Laramide (Late Cretaceous to early Tertiary) foreland province of southwestern Montana and the northeastern margin of the middle to late Tertiary Basin and Range province. The oldest rocks in the quadrangle are Archean high-grade gneiss, and granitic to ultramafic intrusive rocks that are as old as about 3.0 Ga. The gneiss includes a supracrustal assemblage of quartz-feldspar gneiss, amphibolite, quartzite, and biotite schist and gneiss. The basement rocks are overlain by a platform sequence of sedimentary rocks as old as Cambrian Flathead Quartzite and as young as Upper Cretaceous Livingston Group sandstones, shales, and volcanic rocks. The Archean crystalline rocks crop out in the cores of large basement uplifts, most notably the 'Madison-Gravelly arch' that includes parts of the present Tobacco Root Mountains and the Gravelly, Madison, and Gallatin Ranges. These basement uplifts or blocks were thrust westward during the Laramide orogeny over rocks as young as Upper Cretaceous. The thrusts are now exposed in the quadrangle along the western flanks of the Gravelly and Madison Ranges (the Greenhorn thrust and the Hilgard fault system, respectively). Simultaneous with the west-directed thrusting, northwest-striking, northeast-side-up reverse faults formed a parallel set across southwestern Montana; the largest of these is the Spanish Peaks fault, which cuts prominently across the Ennis quadrangle. Beginning in late Eocene time, extensive volcanism of the Absorka Volcanic Supergroup covered large parts of the area; large remnants of the volcanic field remain in the eastern part of the quadrangle. The volcanism was concurrent with, and followed by, middle Tertiary extension. During this time, the axial zone of the 'Madison-Gravelly arch,' a large Laramide uplift, collapsed, forming the Madison Valley, structurally a complex down-to-the-east half graben. Basin deposits as thick as 4,500 m filled the graben. Pleistocene glaciers sculpted the high peaks of the mountain ranges and formed the present rugged topography.

Geologic map of the Ennis 30' x 60' quadrangle, Madison and Gallatin Counties, Montana, and Park County, Wyoming

USGS Publications Warehouse

Kellogg, Karl S.; Williams, Van S.

2000-01-01

The Ennis 1:100,000 quadrangle lies within both the Laramide (Late Cretaceous to early Tertiary) foreland province of southwestern Montana and the northeastern margin of the middle to late Tertiary Basin and Range province. The oldest rocks in the quadrangle are Archean high-grade gneiss, and granitic to ultramafic intrusive rocks that are as old as about 3.0 Ga. The gneiss includes a supracrustal assemblage of quartz-feldspar gneiss, amphibolite, quartzite, and biotite schist and gneiss. The basement rocks are overlain by a platform sequence of sedimentary rocks as old as Cambrian Flathead Quartzite and as young as Upper Cretaceous Livingston Group sandstones, shales, and volcanic rocks. The Archean crystalline rocks crop out in the cores of large basement uplifts, most notably the 'Madison-Gravelly arch' that includes parts of the present Tobacco Root Mountains and the Gravelly, Madison, and Gallatin Ranges. These basement uplifts or blocks were thrust westward during the Laramide orogeny over rocks as young as Upper Cretaceous. The thrusts are now exposed in the quadrangle along the western flanks of the Gravelly and Madison Ranges (the Greenhorn thrust and the Hilgard fault system, respectively). Simultaneous with the west-directed thrusting, northwest-striking, northeast-side-up reverse faults formed a parallel set across southwestern Montana; the largest of these is the Spanish Peaks fault, which cuts prominently across the Ennis quadrangle. Beginning in late Eocene time, extensive volcanism of the Absorka Volcanic Supergroup covered large parts of the area; large remnants of the volcanic field remain in the eastern part of the quadrangle. The volcanism was concurrent with, and followed by, middle Tertiary extension. During this time, the axial zone of the 'Madison-Gravelly arch,' a large Laramide uplift, collapsed, forming the Madison Valley, structurally a complex down-to-the-east half graben. Basin deposits as thick as 4,500 m filled the graben. Pleistocene glaciers sculpted the high peaks of the mountain ranges and formed the present rugged topography.

A probabilistic model for the persistence of early planar fabrics in polydeformed pelitic schists

USGS Publications Warehouse

Ferguson, C.C.

1984-01-01

Although early planar fabrics are commonly preserved within microlithons in low-grade pelites, in higher-grade (amphibolite facies) pelitic schists fabric regeneration often appears complete. Evidence for early fabrics may be preserved within porphyroblasts but, within the matrix, later deformation often appears to totally obliterate or reorient earlier fabrics. However, examination of several hundred Dalradian pelites from Connemara, western Ireland, reveals that preservation of early fabrics is by no means uncommon; relict matrix domains, although volumetrically insignificant, are remarkably persistent even when inferred later strains are very large and fabric regeneration appears, at first sight, complete. Deterministic plasticity theories are ill-suited to the analysis of such an inhomogeneous material response, and a probabilistic model is proposed instead. It assumes that ductile polycrystal deformation is controlled by elementary flow units which can be activated once their associated stress barrier is overcome. Bulk flow propensity is related to the proportion of simultaneous activations, and a measure of this is derived from the probabilistic interaction between a stress-barrier spectrum and an internal stress spectrum (the latter determined by the external loading and the details of internal stress transfer). The spectra are modelled as Gaussian distributions although the treatment is very general and could be adapted for other distributions. Using the time rate of change of activation probability it is predicted that, initially, fabric development will be rapid but will then slow down dramatically even though stress increases at a constant rate. This highly non-linear response suggests that early fabrics persist because they comprise unfavourable distributions of stress-barriers which remain unregenerated at the time bulk stress is stabilized by steady-state flow. Relict domains will, however, bear the highest stress and are potential upper-bound palaeostress estimators. Some factors relevant to the micromechanical explanation of relict matrix domains are discussed. ?? 1984.

The Limits of Extrusion in the Western Himalaya

NASA Astrophysics Data System (ADS)

Zhang, K.; Webb, A. G.; Donaldson, D.; Johnson, S.; Elorriaga, T.

2014-12-01

Himalayan orogenesis is commonly explained by 1) extrusion models, involving expulsion of high-grade rocks southwards from beneath Tibet and up towards the High Himalayan orographic front, and/or 2) duplexing models, involving accretion of thrust horses from the downgoing Indian plate to the over-riding orogenic wedge. Most extrusion models predict exhumation and erosion of upper-amphibolite facies metamorphic rocks between the Main Central thrust (MCT) and a structurally higher normal fault, and therefore can be tested by determining if such high grade rocks occur between the MCT and the Indus-Yalu suture to the north. Prior qualitative studies suggest that such rocks are missing across the east Ladakh / Chamba and Kashmir regions of the western Himalaya. Here we present new quantitative and semi-quantitative results that document low peak metamorphic temperatures along a northeast-trending transect across the east Ladakh / Chamba Himalaya. We performed illite crystallinity (IC) and quartz grain boundary analyses to determine metamorphic and deformation temperatures, respectively. Calibrated IC values of structurally high samples range from 0.25 to 0.54, indicating temperatures of ~100 ˚C to ~300 ˚C. In structurally lower, muscovite +/- biotite-bearing meta-pelitic and meta-psammitic rocks, quartz grain boundaries show bulging recrystallization fabrics, corresponding to deformation temperatures of <~450 ˚C. Local exceptions occur along the southeast margin of the study region near a dome, where quartz sub-grain rotation fabrics indicate deformation temperatures between ~450 ˚C and ~550 ˚C. Our results, combined with similar IC values to the north from Girard et al. [2001, Clay Minerals v. 36, p. 237-247], demonstrate that a continuous strip of <~450 ˚C rocks extends from the MCT to the Indus-Yalu suture here. Therefore the predictions of extrusion models are not met in this portion of the Himalaya; we present alternative duplexing models.

Interplay between deformation, fluid release and migration across a nascent subduction interface: evidence from Oman-UAE and implications for warm subduction zones

NASA Astrophysics Data System (ADS)

Agard, Philippe; Prigent, Cécile; Soret, Mathieu; Guillot, Stéphane; Dubacq, Benoît

2017-04-01

Frozen-in subduction plate interfaces preserving the first 1-2 My of the subduction history are found beneath ophiolites. These contacts are a key target to study the inception of mantle wedge metasomatism and the mechanical coupling between the upper plate and the top part of the sinking slab shortly after subduction initiation. Combining structural field and EBSD data, detailed petrology, thermodynamic modelling and geochemistry on both sides, i.e. the base of the mantle wedge (Oman-UAE basal peridotites) and the underlying accreted crustal fragments from the subducting slab (metamorphic soles), this study documents the continuous evolution of the plate contact from 1 GPa 900-750°C to 0.6 GPa 750-600°C, with emphasis on strain localization and feedbacks between deformation and fluid migration. In the mantle wedge, the (de)formation of proto-ultramylonitic peridotites is coeval with mantle metasomatism by focused hydrous fluid migration. Peridotite metasomatism results in the precipitation of new minerals (clinopyroxene, amphibole and spinel ± olivine and orthopyroxene) and their enrichment in FMEs (particularly B, Li and Cs, with concentrations up to 40 times that of the PM). Boron concentrations and isotopes (δ11B of metasomatized peridotites up to +25‰) suggest that these fluids with a "subduction signature" are probably sourced from the dehydrating amphibolitic metamorphic sole. Concomitantly, deformation in the lower plate results in the stepwise formation, detachment and accretion to the mylonitic s.l. mantle of successive slices of HT metabasalts from the downgoing slab, equilibrated at amphibolite/granulite conditions (900-750°C). Two major stages may be outlined: - between 900 and 750°C, the garnet-clinopyroxene-amphibole bearing sinking crust (with melting < 6 vol%) gets juxtaposed and mechanically coupled to the mantle, leading to the transfer of subduction fluids and metasomatism (possibly into the arc zone ultimately). Deformation is distributed on the km scale, typically 200-500 m thick in the mantle and 100-200 m thick in the slab crust. Dislocation creep is the dominant mechanism in the mantle wedge while, in the lower plate crust, deformation is accomodated by cataclasis and reorientation of amphibole grains and dislocation creep of clinopyroxene. Amphibole LPO suggests that granulite to amphibolite deformation was accommodated by thinning of the crustal fragments accreted to the upper plate (by up to a factor of 5-10). - between 750-600°C, the plate contact is further deformed (and partially exhumed) with considerable increase in strain localization on both sides, and fluid channelization in the mantle through (milli)metric ultramylonitic shear bands. Strain is accommodated by a change from olivine dislocation to grain size sensitive creep in mantle ultramylonites, and in the footwall by dislocation creep of amphibole and plagioclase (with progressive increase of rigid body rotation). This example sheds light on the behaviour of warm subductions (e.g., Cascadia, Nankai) where slab material gets amphibolitized at depths of 40 km, on how fluids are fluxed into the mantle wedge and how mechanical coupling resumes at depth (i.e., beyond those where serpentine is stable). Documented deformation patterns also suggest that, where serpentine is stable in the mantle wedge, deformation should be very localized.

P-T evolution of metasedimentary rocks of the Santa Filomena Complex, Riacho do Pontal Orogen, Borborema Province (NE Brazil): Geothermobarometry and metamorphic modelling

NASA Astrophysics Data System (ADS)

Santos, Felipe H.; Amaral, Wagner S.; Luvizotto, George L.; Martins de Sousa, Daniel F.

2018-03-01

We present in this paper petrologic data and discuss the pressure-temperature (P-T) metamorphic history of the neoproterozoic metasedimentary rocks of the Santa Filomena Complex, Riacho do Pontal Orogen, which is inserted in the southern portion of the Borborema Province (Northeast Brazil). Therefore, the data provide constraints on metamorphic evolution during Neoproterozoic Brasiliano Orogeny in Northeast Brazil. The rocks studied are aluminous schists and paragneisses. Silver-gray and red pelitic schists are intensely deformed, biotite-muscovite rich, contain centimeter-sized garnet, staurolite and kyanite porphyroblasts, and subordinately plagioclase and quartz. Paragneisses are from light gray to dark gray colored, medium to coarse-grained and display a well-spaced foliated matrix of biotite, and kyanite and garnet porphyroblasts. Locally, the schists and paragneisses are migmatized. Pressure-temperature modelling based on thermobarometric calculations indicate that metamorphism reached 643 °C with pressures estimated in 12 kbar. Pre-peak and post-peak metamorphic conditions are constrained by mineralogical and textural relationships: garnet inclusion-rich and inclusion-free (possible of higher T) are documented and the inclusion-rich core probably indicates a Sn-1 foliation that was transposed by Sn. The pre-peak stage most probably occurred close to 500 °C and 8 kbar, in upper greenschist to lower amphibolite facies metamorphism along kyanite stability field. We also propose that post-peak stage was associated with isothermal decompression along a possible path of tectonic exhumation in conditions of 600 °C and 7 kbar. To further evaluate the equilibrium condition, pressure-temperature pseudosections were calculated for the metasedimentary rocks. Thus, the estimated metamorphic peak took place in the upper amphibolite facies. A suggested clockwise pressure-temperature path is compatible with the regional tectonic setting of continent-continent collision which occurred in the Late Neoproterozoic of Borborema Province, during the Brasiliano Orogeny.

Plate tectonics 2.5 billion years ago: evidence at kolar, South India.

PubMed

Krogstad, E J; Balakrishnan, S; Mukhopadhyay, D K; Rajamani, V; Hanson, G N

1989-03-10

The Archean Kolar Schist Belt, south India, is a suture zone where two gneiss terranes and at least two amphibolite terranes with distinct histories were accrted. Amphibolites from the eastern and western sides of the schist belt have distinct incompatible element and isotopic characteristics sugesting that their volcanic protoliths were derived from dint mantle sources. The amphibolite and gneiss terranes were juxtaposed by horizontal compression and shearing between 2530 and 2420 million years ago (Ma) along a zone marked by the Kolar Schist Belt. This history of accretion of discrete crustal terranes resembles those of Phanerozoic convergent margins and thus suggests that plate tectonics operated on Earth by 2500 Ma.

Plate tectonics 2.5 billion years ago - Evidence at Kolar, south India

NASA Technical Reports Server (NTRS)

Krogstad, E. J.; Hanson, G. N.; Balakrishnan, S.; Rajamani, V.; Mukhopadhyay, D. K.

1989-01-01

The Archean Kolar Schist Belt, south India, is a suture zone where two gneiss terranes and at least two amphibolite terranes with distinct histories were accreted. Amphibolites from the eastern and western sides of the schist belt have distinct incompatible element and isotopic characteristics suggesting that their volcanic protoliths were derived from different mantle sources. The amphibolite and gneiss terranes were juxtaposed by horizontal compression and shearing between 2530 and 2420 million years ago (Ma) along a zone marked by the Kolar Schist Belt. This history of accretion of discrete crustal terranes resembles those of Phanerozoic convergent margins and thus suggests that plate tectonics operated on earth by 2500 Ma.

A preliminary synthesis of structural, stratigraphic, and magnetic data from part of the northwest Adirondacks, New York

USGS Publications Warehouse

Foose, M.P.; Brown, C. Ervin

1976-01-01

Synthesis of recent work in the NW Adirondacks, New York allows the development of a coherent geologic picture. Mapping of the Precambrian rock units enables the recognition of four major units which are, from bottom to top, 1) Granitic Gneiss (alaskite), 2) Lower Marble, 3) Major Gneiss, and 4) Upper Marble. Additionally, lenses of amphibolite and granite occur as intrusives within this succession. These rock units have been complexly deformed by three major folding episodes, and by two distinctly different styles of faulting. The result has been to produce large northeast-southwest trending dome and basin structures. Patterns of magnetic intensity closely parallel distribution of rock units and provide additional information for a structural and stratigraphic synthesis-.

Ediacaran ( 620 Ma) high grade regional metamorphism in the northern Arabian Nubian Shield: U/Th-Pb monazite ages of the Elat schist

NASA Astrophysics Data System (ADS)

Elisha, Bar; Katzir, Yaron; Kylander-Clark, Andrew

2017-04-01

Ediacaran times witnessed a hemisphere-scale orogenesis forming the extensive Pan-African mountain ranges and resulting in the final assembly of Gondwana supercontinent. The Elat metamorphic basement (S Israel) located at the northernmost tip of a major Pan-African orogenic suture, the Arabian Nubian Shield (ANS), comprises amphibolite facies schists and gneisses and was most likely shaped by this major continental collision. However the timing, number and duration of metamorphic events in Elat and elsewhere in the ANS are non-conclusive and a major emphasis was given to pre-Ediacaran island-arc related tectonics. This is mostly because U-Pb dating of zircon, widely used in Elat and elsewhere, is very successful in constraining the ages of the igneous and sedimentary protoliths, but is 'blind' to metamorphism at grades lower than granulite. Here U/Th-Pb dating of monazite, a precise chronometer of metamorphic mineral growth, is systematically applied to the Elat schist and unveils the tectono-metamorphic evolution of the Elat basement. Previous U-Pb dating of detrital zircon has shown that the sedimentary protoliths of the Elat schist are the oldest basement components (≥800 Ma), and detailed structural observations of the schists portrayed a complex deformation history including four successive phases (Shimron, 1972). The earliest three phases were defined as ductile and penetrative, but some of the available geochronological data apparently contradict field relations. In-situ analysis of metamorphic monazites by LASS (Laser Ablation Split Stream) involves simultaneous measurement of U/Th-Pb isotope ratios and REE contents in a single 10 μm sized grain or domain, thus allowing determining the age of specific texture and metamorphic assemblage. Monazite dating of the Elat schist yielded two concordant age clusters at 712±6 and 613±5 Ma. The corresponding REE patterns of the dated monazite grains indicate that porphyroblast growth, either garnet or staurolite, took place only during the younger event (M2). Likewise the regional south dipping penetrative foliation, common to the Elat schist and to all of the rocks of the Elat association, formed during the Ediacaran event (M2). This profound event started at 630 Ma and reached peak conditions of mid amphibolite facies at 620 Ma. Retrogression and stress relaxation shortly followed, involving overprint of staurolite schists by a cordierite-bearing assemblage at 613 Ma (M3), and was contemporaneous with the intrusion of andesitic dykes that were immediately metamorphosed to low-amphibolite. This metamorphic P-T-t path corresponds to the collision of East- and West-Gondwana as constrained by large goechronological database of post collision batholiths from all around the Arabian-Nubian Shield.

The talc, soapstone, and asbestos deposits of Massachusetts

USGS Publications Warehouse

Chute, Newton Earl

1969-01-01

Several talc and soapstone deposits were worked in Massachusetts from about 1810 to 1922. Most of these deposits are in the Chester Amphibolite, or in serpentine lenses in or adjacent to the amphibolite along a belt that extends north-south across the State from Rowe to West Granville; it appears to be a continuation of the Vermont talc belt. The only deposits outside of this belt that have been worked are a talc and soapstone deposit in the north-west corner of Hinsdale and soapstone deposits on the east side of Soapstone Hill in the western part of Petersham. Very little asbestos has been produced in Massachusetts. A small amount of anthophyllite asbestos was obtained from the deposit in Hinsdale, and from a deposit in southwestern Pelham. The talc and soapstone deposits of Massachusetts were formed from serpentine and possibly from amphibolite, schist, and dolomitic limestone. Those fromed from serpentine are mainly at the ends of the serpentine bodies, and those that appear to have been formed from amphibolite or schist are on the faults and folds.

The basal part of the Oman ophiolitic mantle: a fossil Mantle Wedge?

NASA Astrophysics Data System (ADS)

Prigent, Cécile; Guillot, Stéphane; Agard, Philippe; Godard, Marguerite; Chauvet, Alain; Dubacq, Benoit; Monié, Patrick; Yamato, Philippe

2014-05-01

Although the Oman ophiolite is classically regarded as being the direct analog of oceanic lithosphere created at fast spreading ridges, the geodynamic context of its formation is still highly debated. The other alternative end-member model suggests that this ophiolite entirely formed in a supra-subduction zone setting. Fluids involved in the hydration of the oceanic lithosphere and in the presence of a secondary boninitic and andesitic volcanism may provide a way to discriminate between these two interpretations: are they descending near-axis hydrothermal fluxes (first model) or ascending from a subducting slab (second model)? We herein focus on the base of the ophiolitic mantle in order to characterize the origin of fluids and decipher hydration processes. Samples were taken along hecto- to kilometre-long sections across the basal banded unit directly overlying the amphibolitic/granulitic metamorphic sole. We carried out a petrological, structural and geochemical study on these rocks and their constitutive minerals. Our results show that, unlike the generally refractory character of Oman harzburgites, all the basal mantle rocks display secondary crystallization of clinopyroxene and amphibole through metasomatic processes. The microstructures and the chronology of these secondary mineralizations (clinopyroxene, pargasitic amphibole, antigorite and then lizardite/chrysotile) suggest that these basal rocks have been affected by cooling from mantle temperatures (<1200°C) to low-T serpentinisation (<300°C). Furthermore, major elements required to crystallize these minerals and the observed fluid-mobile elements (FMEs) enrichments in the clinopyroxenes and in the amphiboles (B, Pb, Sr), as well as in the serpentines (B, Sr, Rb, Ba, As), are consistent with amphibolite-derived fluids (Ishikawa et al., 2005) and cannot be easily explained by other sources. Based on these observations, we propose a geodynamic model in which intense and continuous metasomatism of the cooling base of the ophiolitic mantle is due to the release of fluids coming from the progressive dehydration of underlying amphibolitic rocks. This process is compatible with the progressive subduction of the Arabian margin during the Upper Cretaceous (e.g., HP-LT units history, and tectonic structures observed on top of it). The basal part of the Oman ophiolite would thus represent a fossil incipient mantle wedge.

Geochemistry and structure of the Hawley Formation: Northwestern Massachusetts

DOE Office of Scientific and Technical Information (OSTI.GOV)

Kim, J.; Jacobi, R.

1993-03-01

The Hawley Formation in northwestern Massachusetts is composed of mafic and felsic, (trondhjemitic) igneous units and black sulfidic schists and quartzites. The dominant lithology is a thinly foliated hbd-plag.-chi-qtz.-Fe carbonate schist with or without hornblende fasicules. Locally, this schist has alternating folia of chl/hbd and plag. and probably has a volcaniclastic protolith. Distinct pillows and tuffs are observed locally. In general, these schists have flat REE patterns at 10X chondrite and plot as IABs on discrimination diagrams. In the eastern part of the Hawley, some amphibolites show concave upward REE patterns, plot in the IAT or boninite field on discriminationmore » diagrams, and appear to have boninitic affinities. The felsic lithologies are trondhjemitic and are intrusive into the IAT/boninite amphibolites. The intrusive nature is based on the presence of mafic xenoliths and intruded rafts of country rock in the trondhjemite as well as the occurrence of thin tabular trondhjemite bodies in sharp contact with the surrounding amphibolite. The trondhjemite varies from coarse-grained weakly foliated qtz-plag.-biotite gneiss with probable relict igneous zoned plagioclases to finer-grained well foliated qtz-plag.-garnet-hbd gneiss. REE patterns for the trondhjemites are weakly U-shaped with moderate to pronounced negative Eu anomalies. The trondhjemites, surrounding amphibolites, and black sulfidic schists and quartzites of the eastern part of the Hawley are intruded by massive, granular, medium grained, plagioclase phenocryst amphibolites with chilled margins. These intrusive sills predate or are coeval with the dominant foliation in the Hawley. Both sills and country rock contain a contact-parallel foliation as well as a later foliation at a low angle to the earlier foliation. The sill amphibolites are high TiO2 high Zr varieties that plot as MORBs to WPBs on discrimination diagrams and exhibit slightly LREE enriched MORB-like to T-MORB REE patterns.« less

Trace-element geochemistry of metabasaltic rocks from the Yukon-Tanana Upland and implications for the origin of tectonic assemblages in east-central Alaska

USGS Publications Warehouse

Dusel-Bacon, C.; Cooper, K.M.

1999-01-01

We present major- and trace- element geochemical data for 27 amphibolites and six greenstones from three structural packages in the Yukon-Tanana Upland of east-central Alaska: the Lake George assemblage (LG) of Devono-Mississippian augen gneiss, quartz-mica schist, quartzite, and amphibolite; the Taylor Mountain assemblage (TM) of mafic schist and gneiss, marble, quartzite, and metachert; and the Seventymile terrane of greenstone, serpentinized peridotite, and Mississippian to Late Triassic metasedimentary rocks. Most LG amphibolites have relatively high Nb, TiO2, Zr, and light rare earth element contents, indicative of an alkalic to tholeiitic, within-plate basalt origin. The within-plate affinities of the LG amphibolites suggest that their basaltic parent magmas developed in an extensional setting and support a correlation of these metamorphosed continental-margin rocks with less metamorphosed counterparts across the Tintina fault in the Selwyn Basin of the Canadian Cordillera. TM amphibolites have a tholeiitic or calc-alkalic composition, low normalized abundances of Nb and Ta relative to Th and La, and Ti/V values of <20, all indicative of a volcanic-arc origin. Limited results from Seventymile greenstones indicate a tholeiitic or calc-alkalic composition and intermediate to high Ti/V values (27-48), consistent with either a within-plate or an ocean-floor basalt origin. Y-La-Nb proportions in both TM and Seventymile metabasalts indicate the proximity of the arc and marginal basin to continental crust. The arc geochemistry of TM amphibolites is consistent with a model in which the TM assemblage includes arc rocks generated above a west-dipping subduction zone outboard of the North American continental margin in mid-Paleozoic through Triassic time. The ocean-floor or within-plate basalt geochemistry of the Seventymile greenstones supports the correlation of the Seventymile terrane with the Slide Mountain terrane in Canada and the hypothesis that these oceanic rocks originated in a basin between the continental margin and an arc to the west.

Restoration of Late Neoarchean-Early Cambrian tectonics in the Rengali orogen and its environs (eastern India): The Antarctic connection

NASA Astrophysics Data System (ADS)

Bhattacharya, A.; Das, H. H.; Bell, Elizabeth; Bhattacharya, Atreyee; Chatterjee, N.; Saha, L.; Dutt, A.

2016-10-01

Geological mapping and P-T path reconstructions are combined with monazite chemical age and Secondary Ion Mass Spectrometric (SIMS) U-Pb zircon age determinations to identify crustal domains with distinctive evolutionary histories in the Rengali orogen sandwiched between two Grenvillian-age metamorphic belts, i.e. the Eastern Ghats Granulite Belt (EGGB) in the south, and the amphibolite facies Gangpur Schist Belt (GSB) in the north, which in turn forms a collar along the NW/W margins of the Paleo/Mesoarchean Singhbhum Craton (SC) north of the Rengali orogen. Anatectic gneisses in the orogen core exhibit multi-phase Neoarchean/Paleoproterozoic deformation, metamorphic P-T histories and juvenile magma emplacement events. The high-grade belt is inferred to be a septum of the Bastar Craton (BC). The flanking supracrustal belt in the orogen - dominated by quartz-muscovite schists (± staurolite, kyanite, garnet pyrophyllite), inter-bedded with poorly-sorted and polymict meta-conglomerate, and meta-ultramafic/amphibolite bands - evolved along P-T paths characterized by sub-greenschist to amphibolite facies peak P-T conditions in closely-spaced samples. The supracrustal rocks and the anatectic gneisses of contrasting metamorphic P-T histories experienced D1, D2 and D3 fabric-forming events, but the high-angle obliquity between the steeply-plunging D3 folds in the anatectic gneisses and the gently-plunging D3 folds in the supracrustal unit suggests the two lithodemic units were tectonically accreted post-S2. The supracrustal belt is inferred to be a tectonic mélange formed in an accretionary wedge at the tri-junction of the Bastar Craton, the Eastern Ghats Granulite Belt and the Singhbhum Craton; the basin closure synchronous with the assembly of EGGB and the Singhbhum Craton-Gangpur Schist belt composite occurred between 510 and 610 Ma. Based on the available evidence across the facing coastlines of the Greater India landmass and the Australo-Antarctic blocks at 500 Ma, it is suggested that the EGGB welded with the Greater India landmass during the Pan African along an accretion zone, of which the Rengali orogen is a part, synchronous with the final assembly of the Gondwanaland.

Geochronology of pervasive top-to-the-SE directed deformation in the Caledonian nappe stack, Jämtland, Sweden

NASA Astrophysics Data System (ADS)

Bender, Hagen; Glodny, Johannes; Ring, Uwe; Almqvist, Bjarne S. G.; Grasemann, Bernhard; Stephens, Michael B.

2017-04-01

The Caledonian orogen of Scandinavia is thought to be a Himalaya-style head-on collisional orogen. However, in contrast to the Himalayas, the Caledonides are characterized by various ultrahigh-pressure belts of different ages, which make them a unique orogen on Earth. The Seve Nappe Complex (SNC) in Jämtland (Sweden) holds the key to better understanding the multi-stage tectonometamorphic evolution of a well-studied ultrahigh-pressure belt in the central Scandinavian Caledonides. Leucogranites and migmatic gneisses record an ultrahigh-pressure event at 460 Ma (Brueckner and Van Roermund, 2007; Grimmer et al., 2015), followed by migmatization at 440 Ma (Ladenberger at al. 2014). How those high-grade metamorphic events relate to the nappe structure remains elusive. We use a combined structural and geochronological approach to show that amphibolite- and greenschist-facies foreland-directed, top-to-the-ESE shearing formed the nappe pile consisting of the Köli Nappe overlying the SNC, the various nappes of the SNC, and the underlying units. Furthermore, we present new Rb-Sr internal multi-mineral isochron ages from two east-west transects in central and northern Jämtland. Most isotopic ages, complemented by a dense network of kinematic field data, range between 431 and 427 Ma. These ages are interpreted to reflect the timing of amphibolite-facies top-to-the-ESE-directed nappe stacking. Blackwall formation, i.e., in-situ chemical interaction between ultramafic rocks and felsic gneiss, at the Seve-Köli boundary occurred at 423 Ma, an age interpreted to postdate nappe emplacement. Biotite in top-to-the-ESE greenschist-facies shear bands in the Middle Köli nappe formed at 416 Ma. These new geochronological data show that the nappe assembly postdates deep subduction and subsequent decompression melting. Top-to-the-foreland directed thrusting occurred at 430 Ma and continued for several million years, while amphibolite-facies shear criteria yield older ages than retrograde structures. References: Brueckner and Van Roermund, 2007, J. Geol. Soc. 164, 117-128. Grimmer et al., 2015, Geology 43 (4), 347-350. Ladenberger et al., 2014, Geol. Soc. Spec. Publ. 390, 337-368.

Pre-Alpine contrasting tectono-metamorphic evolutions within the Southern Steep Belt, Central Alps

NASA Astrophysics Data System (ADS)

Roda, Manuel; Zucali, Michele; Li, Zheng-Xiang; Spalla, Maria Iole; Yao, Weihua

2018-06-01

In the Southern Steep Belt, Italian Central Alps, relicts of the pre-Alpine continental crust are preserved. Between Valtellina and Val Camonica, a poly-metamorphic rock association occurs, which belongs to the Austroalpine units and includes two classically subdivided units: the Languard-Campo nappe (LCN) and the Tonale Series (TS). The outcropping rocks are low to medium grade muscovite, biotite and minor staurolite-bearing gneisses and micaschists, which include interlayered garnet- and biotite-bearing amphibolites, marbles, quartzites and pegmatites, as well as sillimanite-bearing gneisses and micaschists. Permian intrusives (granitoids, diorites and minor gabbros) emplaced in the metamorphic rocks. We performed a detailed structural, petrological and geochronological analysis focusing on the two main lithotypes, namely, staurolite-bearing micaschists and sillimanite-bearing paragneisses, to reconstruct the Variscan and Permian-Triassic history of this crustal section. The reconstruction of the tectono-metamorphic evolution allows for the distinction between two different tectono-metamorphic units during the early pre-Alpine evolution (D1) and predates the Permian intrusives, which comprise rocks from both TS and LCN. In the staurolite-bearing micaschists, D1 developed under amphibolite facies conditions (P = 0.7-1.1 GPa, T = 580-660 °C), while in the sillimanite-bearing paragneisses formed under granulite facies conditions (P = 0.6-1.0 GPa, T> 780 °C). The two tectono-metamorphic units coupled together during the second pre-Alpine stage (D2) under granulite-amphibolite facies conditions at a lower pressure (P = 0.4-0.6 GPa, T = 620-750 °C) forming a single tectono-metamorphic unit (Languard-Tonale Tectono-Metamorphic Unit), which comprised the previously distinguished LCN and TS. Geochronological analyses on zircon rims indicate ages ranging between 250 and 275 Ma for D2, contemporaneous with the emplacement of Permian intrusives. This event developed under a high thermal state, which is compatible with an extensional tectonic setting that occurred during the exhumation of the Languard-Tonale Tectono-Metamorphic Unit. The extensional regime is interpreted as being responsible for the thinning of the Adriatic continental lithosphere during the Permian, which may be related to an early rifting phase of Pangea.

Elastic properties and seismic anisotropy of the Seve Nappe Complex - Laboratory core measurements from the International Continental Drilling Project COSC-1 well, Åre, Sweden

NASA Astrophysics Data System (ADS)

Wenning, Q. C.; Almqvist, B. S. G.; Zappone, A. S.

2015-12-01

The COSC-1 scientific borehole was drilled in the summer of 2014 to ~2.5 km depth to study the structure and composition of the Middle Allochthon of the Central Scandinavian Caledonides. It crosscuts the amphibolite-grade lower part of the Seve nappe and intersects a mylonite zone in the lower 800 m of the borehole. We selected six core samples representing the primary lithologies in the COSC-1 borehole for laboratory investigation of elastic properties. The cores consisted of two amphibolites with differing grain sizes, a calc-silicate gneiss, a felsic gneiss, a coarse grained amphibole bearing gneiss, and a garnet bearing mylonitic schist from the basal shear zone. Both P- and S-waves were measured at ultrasonic frequency (1 MHz), and room temperature hydrostatic pressure conditions up to 260 MPa. Measurements were made along three mutually perpendicular directions, one perpendicular to foliation and two parallel to the foliation with one aligned with mineral lineation. Vp and Vs, anisotropy, and elastic properties are reported as an extrapolation of the high-pressure portion of the ultrasonic measurements back to the intersection with the zero pressure axis. The Vp and Vs in the direction perpendicular to foliation ranges from 5.51-6.67 km/s and 3.18-4.13 km/s, respectively. In the direction parallel to foliation the Vp and Vs ranges from 6.31-7.25 km/s and 3.52-4.35 km/s, respectively. Vp anisotropy ranges from 3% in the calc-silicate gneiss to 18% in mylonitic schist. Acoustic impedance estimations at lithostatic pressure conditions at base of the borehole (70 MPa) show that acoustic impedance contrast generating reflection coefficients between the basal shear zone and overlying units are significant enough to cause seismic reflections. Above the mylonite zone/shear zone, the reflectivity within the lower Seve nappe is due to the impedance contrast between the felsic gneiss and the amphibolite. This result fits with 3D seismic reflection imaging in the area of the borehole. Layered anisotropic mica-schists of metasedimentary origin are suitable candidates for reflections in the middle crust of orogens.

Metamorphism in the Potomac composite terrane, Virginia-Maryland

DOE Office of Scientific and Technical Information (OSTI.GOV)

Drake, A.A. Jr.

1985-01-01

Metamorphic rocks in the Potomac Valley occur in three allochthon-precursory melange pairs unconformably overlain by the Popes Head Formation which is at greenschist facies of metamorphism. The highest motif, the Piney Branch Complex and Yorkshire Formation are also in the greenschist facies. The middle motif, consists of the Peters Creek Schist and the Sykesville Formation. Quartzose schists and metagraywacke of the Peters Creek contain serpentinite debris and have had a complex metamorphic history: Barrovian prograde to amphibolite facies (with sillimanite), a localized retrograde event producing chlorite phyllonite, and a later greenschist prograde event. The Sykeville is at biotite +/- garnetmore » grade and contains deformed olistoliths of Peters Creek, including phyllonite, at various grades. The lower motif consists of the Annandale Group (pelitic schists and metasandstone) and Indian Run Formation. The Annandale has experienced two greenschist metamorphisms. The Indian Run is at biotite +/- garnet grade and contains previously metamorphosed and deformed olistoliths of Annandale. The allochthons have had different histories, but after stacking they were metamorphosed with their melanges and the Popes Head to biotite grade. The Popes Head has experienced three phases of folding, the earliest synkinematic with Occoquan emplacement. These fold phases are superposed on earlier structures in the older rocks and are probably of Late Cambrian age (Penobscotian). Earlier deformation is probably of Late Proterozoic age (Cadomian). Neither of these deformations is recognized in North American rocks.« less

Mental health problems in the 10th grade and non-completion of upper secondary school: the mediating role of grades in a population-based longitudinal study

PubMed Central

2014-01-01

Background School drop-out is a problem all over the world with adverse life-course consequences. The aim of this paper is to study how internalising and externalising problems in the 10th grade are associated with non-completion of upper secondary school, and to examine the mediating role of grade points in the 10th grade across general academic and vocational tracks in upper secondary school. We also study the impact of health behaviour. Methods Population-based health surveys were linked with Norwegian registries on education and sociodemographic factors (n = 10 931). Mental health was assessed by the self-report Strengths and Difficulties Questionnaire. Logistic regression was used to analyse the relations between mental health and health behaviour in 10th grade and non-completion of upper secondary school. The mediating effect of grade points was studied by causal mediation analysis. Results Adolescents not completing upper secondary school reported more externalising problems and girls more internalising problems in the 10th grade, after adjustments. Smoking and physical inactivity increased the odds of non-completion of upper secondary school. Causal mediation analyses showed that a reduction in externalising problems of 10 percentage points led to lower rates of non-completion of 4–5 percentage points, and about three-quarters of this total effect was mediated by grades. For internalising problems the total effect was significant only for girls (1 percentage point), and the mediated effect of grades was about 30%. The effect of mental health problems on school dropout was mainly the same in both vocational and general tracks. Conclusions Assuming a causal relationship from mental health problems to school performance, this study suggests that externalising problems impair educational attainment. A reduction of such problems may improve school performance, reduce school drop-out and reduce the adverse life-course consequences. PMID:24406098

Oxygen isotope evidence for submarine hydrothermal alteration of the Del Puerto ophiolite, California

USGS Publications Warehouse

Schiffman, P.; Williams, A.E.; Evarts, R.C.

1984-01-01

The oxygen isotope compositions and metamorphic mineral assemblages of hydrothermally altered rocks from the Del Puerto ophiolite and overlying volcaniclastic sedimentary rocks at the base of the Great Valley sequence indicate that their alteration occurred in a submarine hydrothermal system. Whole rock ??18O compositions decrease progressively down section (with increasing metamorphic grade): +22.4??? (SMOW) to +13.8 for zeolite-bearing volcaniclastic sedimentary rocks overlying the ophiolite; +19.6 to +11.6 for pumpellyite-bearing metavolcanic rocks in the upper part of the ophiolite's volcanic member; +12.3 to +8.1 for epidote-bearing metavolcanic rocks in the lower part of the volcanic member; +8.5 to +5.7 for greenschist facies rocks from the ophiolite's plutonic member; +7.6 to +5.8 for amphibolite facies or unmetamorphosed rocks from the plutonic member. Modelling of fluid-rock interaction in the Del Puerto ophiolite indicates that the observed pattern of upward enrichment in whole rock ??18O can be best explained by isotopic exchange with discharging 18O-shifted seawater at fluid/rock mass ratios near 2 and temperatures below 500??C. 18O-depleted plutonic rocks necessarily produced during hydrothermal circulation were later removed as a result of tectonism. Submarine weathering and later burial metamorphism at the base of the Great Valley sequence cannot by itself have produced the zonation of hydrothermal minerals and the corresponding variations in oxygen isotope compositions. The pervasive zeolite and prehnite-pumpellyite facies mineral assemblages found in the Del Puerto ophiolite may reflect its origin near an island arc rather than deep ocean spreading center. ?? 1984.

Lithological architecture and petrography of the Mako Birimian greenstone belt, Kédougou-Kéniéba Inlier, eastern Senegal

NASA Astrophysics Data System (ADS)

Dabo, Moussa; Aïfa, Tahar; Gning, Ibrahima; Faye, Malick; Ba, Mamadou Fallou; Ngom, Papa Malick

2017-07-01

The new lithological and petrographic data obtained in the Mako sector are analyzed in the light of the geochemical data available in the literature. It consists of ultramaic, mafic rocks of tholeiitic affinities associated with intermediate and felsic rocks of calc-alkaline affinities and with intercalations of sedimentary rocks. The whole unit is intruded by Eburnean granitoids and affected by a greenschist to amphibolite facies metamorphism related to a high grade hydrothermalism. It consists of: (i) ultramafic rocks composed of a fractional crystallization succession of lherzolites, wehrlites and pyroxenites with mafic rock inclusions; (ii) layered, isotropic and pegmatitic metagabbros which gradually pass to metabasalts occur at the top; (iii) massive and in pillow metabasalts with locally tapered vesicles, completely or partially filled with quartzo-feldspathic minerals; (iv) quarzites locally overlying the mafic rocks and thus forming the top of the lower unit. This ultramafic-mafic lower unit presents a tholeiitic affinity near to the OIB or N-MORB. It represents the Mako Ophiolitic Complex (MOC), a lithospheric fragment of Birimian lithospheric crust. The upper unit is a mixed volcanic complex arranged in the tectonic corridors. From bottom to top it comprises the following: (i) andesitic, and (ii) rhyodacitic and rhyolitic lava flows and tuffs, respectively. They present a calc-alkaline affinity of the active margins. Three generations of Eburnean granitoids are recognized: (i) early (2215-2160 Ma); (ii) syn-tectonics (2150-2100 Ma) and post-tectonics (2090-2040 Ma). The lithological succession, geochemical and metamorphic characteristics of these units point to an ophiolitic supra-subduction zone.

Kinematic and rheological model of exhumation of high pressure granulites in the Variscan orogenic root: example of the Blanský les granulite, Bohemian Massif, Czech Republic

NASA Astrophysics Data System (ADS)

Franěk, J.; Schulmann, K.; Lexa, O.

2006-03-01

A large-scale relict domain of granulite facies deformation fabrics has been identified within the Blanský les granulite body. The granulite facies mylonitic fabric is discordant to the dominant amphibolite facies structures of the surrounding retrograde granulite. The complex geometry of retrograde amphibolite facies fabric indicates a large-scale fold-like structure, which is interpreted to be a result of either crustal-scale buckling of an already exhumed granulite sheet or active rotation of a rigid granulite facies ellipsoidal domain in kinematic continuity with the regional amphibolite facies deformation. We argue that both concepts allow similar restoration of the original granulite facies fabrics prior to the amphibolite facies deformation and “folding”. The geometry of the granulite facies foliations coincides with the earliest fabrics in the nearby mid-crustal units suggesting complete mechanical coupling between the deep lower crust and the mid-crustal levels during the vertical movements of crustal materials. Microstructures indicate grain-size sensitive flow enhanced by the presence of silicate melts at deep crustal levels and a beginning of an exhumation process of low viscosity granulites through a vertical channel. The amphibolite facies fabrics developed at middle crustal levels and their microstructures indicate significant hardening of feldspar-made rigid skeleton of the retrograde granulite. Increase in the strength of the granulite allowed an active buckling or a rigid body rotation of the granulite sheet, which acted as a strong layer inside the weaker metasediments.

Constructivist-Centered Professional Development in Vocabulary Instruction for Upper Grade Elementary Teachers

ERIC Educational Resources Information Center

Samson, Beatrice

2012-01-01

This research study was designed to investigate the impact of constructivist-centered professional development in vocabulary instruction for 14 upper-grade elementary school teachers. The researcher facilitated 10 training sessions held in small groups, during grade level meetings at an urban public school, to develop individual and collective…

Mathematical tasks, study approaches, and course grades in undergraduate mathematics: a year-by-year analysis

NASA Astrophysics Data System (ADS)

Maciejewski, Wes; Merchant, Sandra

2016-04-01

Students approach learning in different ways, depending on the experienced learning situation. A deep approach is geared toward long-term retention and conceptual change while a surface approach focuses on quickly acquiring knowledge for immediate use. These approaches ultimately affect the students' academic outcomes. This study takes a cross-sectional look at the approaches to learning used by students from courses across all four years of undergraduate mathematics and analyses how these relate to the students' grades. We find that deep learning correlates with grade in the first year and not in the upper years. Surficial learning has no correlation with grades in the first year and a strong negative correlation with grades in the upper years. Using Bloom's taxonomy, we argue that the nature of the tasks given to students is fundamentally different in lower and upper year courses. We find that first-year courses emphasize tasks that require only low-level cognitive processes. Upper year courses require higher level processes but, surprisingly, have a simultaneous greater emphasis on recall and understanding. These observations explain the differences in correlations between approaches to learning and course grades. We conclude with some concerns about the disconnect between first year and upper year mathematics courses and the effect this may have on students.

Significance of the Nestos Shearzone in the southern Rhodopes (Northern Greece/Southern Bulgaria)

NASA Astrophysics Data System (ADS)

Nagel, T. J.; Schmidt, S.; Froitzheim, N.; Jahn-Awe, S.; Georgiev, N.

2009-04-01

The Nestos Shearzone can be traced over 100 kilometers and separates the two main units of the Rhodopes, the Upper Complex in the hangingwall from the Pangaion-Pirin Unit in the footwall. The Upper Complex consists of mingled continental and oceanic basement rocks, intruded by granitic bodies of Cretaceous and Tertiary age. It underwent at least amphibolite facies conditions during the Alpine orogenic cycle and several localities with preserved high-pressure and/or ultrahigh-pressure rocks have been found. The age of orogenesis and metamorphism is ambiguous and several Mesozoic and Tertiary cycles may be recorded in that unit. The lowermost level immediately on top of the Nestos Shearzone (Sidironero subunit) mainly consists of rocks derived from a Jurassic arc and appears to show the youngest reported (i.e. Eocene) high-grade metamorphism (including ultra-high-pressure conditions and a subsequent migmatic stage). The underlying Pangaion-Pirin Unit beneath the Nestos Shearzone is build of marbles and Variscan gneisses of disputed Mesozoic paleogeographic position. It is intruded by Oligocene granitoids, which also crosscut the Nestos shearzone. The Pangaion-Pirin Unit experienced only blueschist facies and subsequent upper greenschist facies conditions during the Alpine cycle. The Nestos Shearzone is defined by top-to-the-southwest-directed mylonites formed under upper greenschist facies conditions. So far, it has been viewed as a thrust. We present structural and petrological data suggesting that the Nestos Shearzone is instead a major mid-crustal detachment related to late Eo-Oligocene backarc extension. Mylonitisation along the shear zone occurred under greenschist facies conditions and postdates the blueschist facies stage. The shear zone formed between about 40 Ma and 34 Ma as indicated by the age of high temperature conditions in the hangingwall and the age of Oligocene granitoids crosscutting the mylonites. During this time, pronounced extension and basin formation took place in the hangingwall of the Nestos Shearzone. We propose that the brittle Mesta detachment, which bounds the Mesta Graben to the East, roots into the Nestos Shearzone. The metamorphic history of the Pangaion-Pirin Unit as well as the proposed young age of the Nestos Shearzone is in conflict with studies proposing that this unit represents an independent microcontinent (Drama) accreted to the future Rhodopes in late Jurassic or early Cretaceous times. Instead, we hypothesize that the Pangaion-Pirin Unit could be derived from the Apulian plate, which would have far reaching consequences for the structural architecture of the Aegean Sea area.

Petrology and chemistry of Jebel Tanumah complex, Khamis Mushayt, Southern Arabian shield, Saudi Arabia

NASA Astrophysics Data System (ADS)

Nassief, M. O.; Ali, H. M.; Zakir, F. A.

The mafic intrusive complex at Jebel Tanumah is located 15 km north-west of Khamis Mushayt in the southern Arabian Shield and includes olivine-bearing gabbro as well as amphibole-diopside-hornblende gabbro cumulates. These rocks have been generally metamorphosed to upper greeenschist-lower amphibolite facies. Fourteen white rock silicate analyses indicate that the majority of the rocks are calc-alkaline to tholeiitic in composition. The two major structural units in the Khamis Mushayt region identified by Coleman consist of the basement complex of Asir Mountains and the younger metamorphic rocks. Syntectonic granitic rocks intruded the antiforms characterizing the younger rocks whereas the lower parts of the synforms are intruded by post-tectonic intrusions of layered gabbros such as the one studied at Jebel Tanumah.

The Pikwitonei granulite domain: A lower crustal level along the Churchill-Superior boundary in central Manitoba

NASA Technical Reports Server (NTRS)

Weber, W.

1983-01-01

The greenschist to amphibolite facies tonalite-greenstone terrain of the Gods Lake subprovince grades - in a northwesterly direction - into the granulite facies Pikwitonei domain at the western margins of the Superior Province. The transition is the result of prograde metamorphism and takes place over 50 - 100 km without any structural or lithological breaks. Locally the orthopyroxene isograd is oblique to the structural grain and transects greenstone belts, e.g., the Cross Lake belt. The greenstone belts in the granulite facies and adjacent lower grade domain consist mainly of mafic and (minor) ultramafic metavolcanics, and clastic and chemical metasedimentary rocks. Typical for the greenstone belts crossed by the orthopyroxene isograd are anorthositic gabbros and anorthosites, and plagiophyric mafic flows. The Pikwitonei granulite domain has been interpreted as to represent a lower crustal level which was uplifted to the present level of erosion. On the basis of gravimetric data this uplift has been modelled as an obduction onto the Churchill Province during the Hudsonian orogeny, similar to the Ivrea Zone. The fault between the Churchill and Superior Province is described.

Sm-Nd isotopic data from Archean metavolcanic rocks at Holenarsipur, South India

DOE Office of Scientific and Technical Information (OSTI.GOV)

Drury, S.A.; Van Calsteren, P.C.; Reeves-Smith, G.J.

1987-11-01

Results of a Sm-Nd isotopic analysis of Archean metavolcanics in the Holenarsipur greenstone belt, Karnataka, South India, give a whole-rock isochron age of 2.62 Ga for lightly deformed metabasaltic amphibolites in the northern part of the belt. This is within error of the age of high-grade metamorphism and crustal thickening which affected areas further to the south during the late Archean. Together with the geochemical affinities of these and other metavolcanics in Karnataka, and results of regional structural analysis, this unexpected age supports a model relating volcanism and crustal thickening to northward subduction and crustal accretion during the late Archean.more » Data from basic and ultrabasic metavolcanics from the more strongly deformed and higher-grade southern arm of the Holenarsipur belt do not permit an age greater than 3.0 Ga. Previously, these rocks were regarded as part of an older supracrustal sequence that predated the local 3.0 to 3.3 Ga gneissic complex. The new dates therefore considerably simplify attempts at accounting for greenstone evolution in South India.« less

Emerald mineralization and metasomatism of amphibolite, khaltaro granitic pegmatite - Hydrothermal vein system, Haramosh Mountains, Northern Pakistan

USGS Publications Warehouse

Laurs, B.M.; Dilles, J.H.; Snee, L.W.

1996-01-01

Emerald mineralization is found within 0.1- to 1-m-thick hydrothermal veins and granitic pegmatites cutting amphibolite within the Nanga Parbat - Haramosh massif, in northern Pakistan. The amphibolite forms a sill-like body within garnet-mica schist, and both are part of a regional layered gneiss unit of Proterozoic (?) age. The 40Ar/39Ar data for muscovite from a pegmatite yield a plateau age of 9.13 ?? 0.04 Ma. Muscovite from mica schist and hornblende from amphibolite yield disturbed spectra with interpreted ages of 9 to 10 Ma and more than 225 Ma, respectively, which indicate that peak Tertiary metamorphism reached 325 to 550??C prior to 10 Ma. Pegmatites were emplaced after peak metamorphism during this interval and are older than pegmatites farther south in the massif. At Khaltaro, simply zoned albite-rich miarolitic pegmatites and hydrothermal veins containing various proportions of quartz, albite, tourmaline, muscovite, and beryl are associated with a 1- to 3-m-thick heterogeneous leucogranite sill, that is locally albitized. The pegmatites likely crystallized at 650 to 600??C at pressures of less than 2 kbar. Crystals of emerald form within thin (0.20, 0.54-0.89 wt%), to pale blue beryl (<0.07, 0.10-0.63%), to colorless beryl (<0.07, 0.07-0.28%). The amphibolite is metasomatized in less than 20-cm-wide selvages that are symmetrically zoned around veins or pegmatites. A sporadic inner zone containing F-rich biotite, tourmaline, and fluorite, with local albite, muscovite, quartz, and rare beryl, gives way to an intermediate zone containing biotite and fluorite with local plagioclase and quartz, and to an outer zone of amphibolite containing sparse biotite and local quartz. The inner and intermediate zones experienced gains of K, H, F, B, Li, Rb, Cs, Be, Ta, Nb, As, Y and Sr, and losses of Si, Mg, Ca, Fe, Cr, V and Sc. The outer alteration zone has gained F, Li, Rb, Cs, and As. Oxygen isotope analyses of igneous and hydrothermal minerals indicate that a single fluid of magmatic origin with ??18OH2O = 8??? produced the pegmatite-vein system and hydrothermal alteration at temperatures between 550 and 400??C. The formation of emerald results from introduction of HF-rich magmatic-hydrothermal fluids into the amphibolite, which caused hydrogen ion metasomatism and released Cr and Fe into the pegmatite-vein system.

Neoarchean Subduction Recorded in the Northern Margin of the Yangtze Craton, South China

NASA Astrophysics Data System (ADS)

Zhang, S. B.; Zheng, Y. F.

2016-12-01

The Neoarchean is an important era during which plate tectonics began to operate widely on the earth and the continental crust compositions changed dramatically. However, reliable record of plate subduction has never been reported yet in the Yangtze Craton. Here we report geochemical studies on gneissic tonalite, trondhjemite and amphibolite in the Yudongzi Complex in the northern margin of the Yangtze Craton, which suggests that there is a plate subduction recorded in this area at about 2.7 Ga.The rocks in the Yudongzi Complex are gneissic granite, gneissic tonalite, amphibolite gneiss and magnetite quartzite. Most rocks are enriched in sodic. The gneissic granites show positive Eu anomalies, high (La/Yb)cn and Sr/Y ratios, low Ybcn and Y, resembling typical TTG. The amphibolite and tonalite gneiss show less fractionated REE patterns. SHRIMP zircon U-Pb dating on one gneissic trondhjemite, one amphibolite and one tonalite gave crystallization ages of 2667±21 Ma, 2701±10 Ma and 2697±9 Ma, respectively. They all recorded a metamorphic event at about 2.48 Ga. The SHRIMP zircon oxygen isotope analysis for a trondhjemite and an amphibolite gave δ18O values of 6.2±0.3‰ and 6.3±0.4‰, respectively. The oxygen isotope ratios higher than normal mantle values suggest a source experienced low temperature alteration. The laser fluoration analysis of bulk minerals gave δ18O values of 6.4-8.8‰ for zircon and 12.5-15.2‰ for quartz. The zircon Lu-Hf isotope analysis on the trondhjemite and amphibolite gave similar ɛHf(t) values of 0.08±0.48 and 0.07±0.63, respectively. Whole-rock ɛNd(t) values range from -1.5 to +1.0. These trondhjemite and tonalite can be interpreted as derivation from partial melting of subducted oceanic slab with a garnet-amphibolite residue.Considering the 2.67 Ga A-type granitic rocks at Huji in the interior of the craton, plate subduction took place in the northern edge of the Yangtze Craton. The Yudongzi trondhjemite and tonalite were formed in an active continental margin and the A-type granites formed as a response to the back-arc extension. The identification of 2.65-2.7 Ga subduction provides a possible link of the Yangtze Craton with the other cratons worldwide. This is also a new clue to reconstruct the Neoarchean supercontinent Kenorland.

Formative Assessment and Increased Student Involvement Increase Grades in an Upper Secondary School Biology Course

ERIC Educational Resources Information Center

Granbom, Martin

2016-01-01

This study shows that formative methods and increased student participation has a positive influence on learning measured as grades. The study was conducted during the course Biology A in a Swedish Upper Secondary School. The students constructed grade criteria and defined working methods and type of examination within a given topic, Gene…

Preliminary Geologic Map of the Hemet 7.5' Quadrangle, Riverside County, California

USGS Publications Warehouse

Morton, Douglas M.; Matti, Jon C.

2005-01-01

The Hemet 7.5' quadrangle is located near the eastern edge of the Perris block of the Peninsular Ranges batholith. The northeastern corner of the quadrangle extends across the San Jacinto Fault Zone onto the edge of the San Jacinto Mountains block. The Perris block is a relatively stable area located between the Elsinore Fault Zone on the west and the San Jacinto Fault Zone on the east. Both of the fault zones are active; the San Jacinto being the seismically most active in southern California. The fault zone is obscured by very young alluvial deposits. The concealed location of the San Jacinto Fault Zone shown on this quadrangle is after Sharp, 1967. The geology of the quadrangle is dominated by Cretaceous tonalite formerly included in the Coahuila Valley pluton of Sharp (1967). The northern part of Sharp's Coahuila Valley pluton is separated out as the Hemet pluton. Tonalite of the Hemet pluton is more heterogeneous than the tonalite of the Coahuila Valley pluton and has a different sturctural pattern. The Coahuila Valley pluton consists of relatively homogeneous hornblende-biotite tonalite, commonly with readily visible large euhedral honey-colored sphene crystals. Only the tip of the adjacent Tucalota Valley pluton, another large tonalite pluton, extends into the quadrangle. Tonalite of the Tucalota Valley pluton is very similar to the tonalite of the Coahuila Valley pluton except it generally lacks readily visible sphene. In the western part of the quadrangle a variety of amphibolite grade metasedimentary rocks are informally referred to as the rocks of Menifee Valley; named for exposures around Menifee Valley west of the Hemet quadrangle. In the southwestern corner of the quadrangle a mixture of schist and gneiss marks a suture that separated low metamorphic grade metasedimentary rocks to the west from high metamorphic grade rocks to the east. The age of these rocks is interpreted to be Triassic and the age of the suturing is about 100 Ma, essentially the same age as the adjacent Coahuila Valley pluton. Rocks within the suture zone consist of a mixture of lithologies from both sides of the suture. Gneiss, schist, and anatectic gneiss are the predominate lithologies within the rocks on the east side of the suture. Lesser amounts of metalithic greywacke and lenticular masses of black amphibolite are subordinate rock types. Biotite, biotite-sillimanite and lesser amounts of garnet-biotite-sillimanite schist and metaquartzite-metalithic greywacke lithologies occur west of the suture. Pleistocene continental beds, termed the Bautista beds occur east of the San Jacinto Fault Zone in the northeast corner of the quadrangle. Most of the Bautista beds were derived from the San Jacinto pluton that is located just to the east of the sedimentary rocks. Along the northern part of the quadrangle is the southern part of a large Holocene-late Pleistocene fan emanating from Baustista Canyon. Sediments in the Bautista fan are characterized by their content of detritus derived from amphibolite grade metasedimentary rocks located in the Bautista Canyon drainage. Between the Holocene-late Pleistocene Bautista fan and the Santa Rosa Hills is the remnant of a much older Bautista Canyon alluvial fan. A pronounced Holocene-late Pleistocene channel was developed along the south fringe of the very old alluvial fan and the Santa Rosa Hill. A now dissected late to middle Pleistocene alluvial complex was produced by the coalesced fans of Goodhart, St. Johns, and Avery canyons, and Cactus Valley. Pleistocene continental beds, termed the Bautista beds occur east of the San Jacinto Fault Zone in the northeast corner of the quadrangle. Most of the Bautista beds were derived from the San Jacinto pluton that is located just to the east of the sedimentary rocks. Along the northern part of the quadrangle is the southern part of a large Holocene-late Pleistocene fan emanating from Baustista Canyon. Sediments in the Bautista fan are characterized by

A Five-Year Follow-Up on the Role of Educational Support in Preventing Dropout From Upper Secondary Education in Finland.

PubMed

Hakkarainen, Airi M; Holopainen, Leena K; Savolainen, Hannu K

2015-01-01

In this longitudinal study, we investigated the role of word reading and mathematical difficulties measured in 9th grade as factors for receiving educational support for learning in upper secondary education in Grades 10 to 12 (from ages 16 to 19) and furthermore as predictors of dropout from upper secondary education within 5 years after compulsory education. In addition, we studied the role of school achievement in Grades 9 and 11 in this prediction. The participants of this study were members of one age group of 16-year-old ninth graders (N = 595, females 302, males 293) in a midsized Finnish city, who were followed for 5 years after completing compulsory education. The path model results, where the effects of gender, educational track, and SES were controlled, showed, first, that students with academic learning difficulties received educational support for learning particularly in the 11th grade. Second, academic learning difficulties directly affected school achievement in the 9th grade, but no longer in the 11th grade. Third, mathematical difficulties directly predicted dropout from upper secondary education, and difficulties in both word reading and mathematics had an indirect effect through school achievement in Grades 9 and 11 on dropout. © Hammill Institute on Disabilities 2013.

Early paleozoic gabbro-amphibolites in the structure of the Bureya Terrane (eastern part of the Central Asian Fold Belt): First geochronological data and tectonic position

NASA Astrophysics Data System (ADS)

Smirnov, Yu. V.; Sorokin, A. A.; Kudryashov, N. M.

2012-07-01

Resulting from U-Pb geochronological study, it has been found that the gabbro-amphibolites composing the Bureya (Turan) Terrane in the eastern part of the Central Asian Fold Belt are Early Paleozoic (Early Ordovician; 455 ± 1.5 Ma) in age rather than Late Proterozoic as was believed earlier. The gabbro-amphibolites and associated metabasalts are close to tholeiites of the intraoceanic island arcs in terms of the geochemical properties. It is suggested that the tectonic block composed of these rocks was initially a seafloor fragment that divided the Bureya and Argun terranes in the Early Paleozoic and was later tectonically incorporated into the modern structure of the Bureya Terrane as a result of Late Paleozoic and Mesozoic events.

The effect of rock fabric on P-wave velocity distribution in amphibolites

NASA Astrophysics Data System (ADS)

Vajdová, V.; Přikryl, R.; Pros, Z.; Klíma, K.

1999-07-01

This study presents contribution to the laboratory investigation of elastic properties and rock fabric of amphibolites. P-wave velocity was determined on four spherical samples prepared from a shallow borehole core. The measurement was conducted in 132 directions under various conditions of hydrostatic pressure (up to 400 MPa). The rock fabric was investigated by image analysis of thin sections that enabled precise determination of grain size, modal composition and shape parameters of rock-forming minerals. Laboratory measurement of P-waves revealed pseudoorthorhombic symmetry of rock fabric in amphibolites studied. This symmetry reflects rocks' macro- and microfabric. Maximum P-wave velocity corresponds to the macroscopically visible stretching lineation. Minimum P-wave velocity is oriented perpendicular to the foliation plane. The average grain size is the main microstructural factor controlling mean P-wave velocity.

Petrogenesis of the ∼500 Ma Fushui mafic intrusion and Early Paleozoic tectonic evolution of the Northern Qinling Belt, Central China

NASA Astrophysics Data System (ADS)

Shi, Yu; Pei, Xiaoli; Castillo, Paterno R.; Liu, Xijun; Ding, Haihong; Guo, Zhichao

2017-06-01

The Fushui mafic intrusion in the Qinling orogenic belt (QOB) is composed of meta-gabbro, meta-gabbro-diorite, diorite, and syenite. Most of these rocks are metamorphosed under the upper greenschist facies to lower amphibolite facies metamorphism. Zircon separates from eight samples have LA-ICP-MS U-Pb ages of 497-501 Ma which are taken to be the emplacement age of magmas that formed the Fushui intrusion. Most of the zircon grains exhibit negative εHf values, correspond to TDM2 model ages of late Paleoproterozoic-early Mesoproterozoic or Neoproterozoic and suggest that the mafic rocks were most probably derived from mafic melts produced by partial melting of a previously metasomatized lithospheric mantle. The intrusion is not extensively contaminated by crustal materials and most chemical compositions of rocks are not modified during the greenschist to amphibolite-facies metamorhism. Rocks from the intrusion have primitive mantle-normalized trace element patterns with significant enrichment in light-REE and large ion lithophile elements (LILE) and depletion in high field-strength elements (HFSE). On the basis of the trace element contents, the Fushui intrusion was derived from parental magmas generated by <10% partial melting of both phlogopite-lherzolite and garnet-lherzolite mantle sources. These sources are best interpreted to be in a subduction-related arc environment and have been modified by fluids released from a subducting slab. The formation of the Fushui intrusion was related to the subduction of the Paleotethyan Shangdan oceanic lithosphere at ∼500 Ma.

Polymetamorphic evolution of the granulite-facies Paleoproterozoic basement of the Kabul Block, Afghanistan

NASA Astrophysics Data System (ADS)

Collett, Stephen; Faryad, Shah Wali; Mosazai, Amir Mohammad

2015-08-01

The Kabul Block is an elongate crustal fragment which cuts across the Afghan Central Blocks, adjoining the Indian and Eurasian continents. Bounded by major strike slip faults and ophiolitic material thrust onto either side, the block contains a strongly metamorphosed basement consisting of some of the only quantifiably Proterozoic rocks south of the Herat-Panjshir Suture Zone. The basement rocks crop-out extensively in the vicinity of Kabul City and consist predominantly of migmatites, gneisses, schists and small amounts of higher-grade granulite-facies rocks. Granulite-facies assemblages were identified in felsic and mafic siliceous rocks as well as impure carbonates. Granulite-facies conditions are recorded by the presence of orthopyroxene overgrowing biotite in felsic rocks; by orthopyroxene overgrowing amphibole in mafic rocks and by the presence of olivine and clinohumite in the marbles. The granulite-facies assemblages are overprinted by a younger amphibolite-facies event that is characterized by the growth of garnet at the expense of the granulite-facies phases. Pressure-temperature (P-T) conditions for the granulite-facies event of around 850 °C and up to 7 kbar were calculated through conventional thermobarometry and phase equilibria modeling. The younger, amphibolite-facies event shows moderately higher pressures of up to 8.5 kbar at around 600 °C. This metamorphism likely corresponds to the dominant metamorphic event within the basement of the Kabul Block. The results of this work are combined with the litho-stratigraphic relations and recent geochronological dating to analyze envisaged Paleoproterozoic and Neoproterozoic metamorphic events in the Kabul Block.

What is an Oceanic Core Complex?

NASA Astrophysics Data System (ADS)

Schroeder, T.; Cheadle, M. J.

2007-12-01

The Mid-Atlantic Ridge (MAR) 75km north and south of the 15-20 Fracture Zone (FZ) has produced upper oceanic lithosphere composed dominantly of mantle peridotite with gabbro intrusions. In the absence of diapirism, mantle peridotite can only be exposed on the seafloor by extensional faulting, thus the sea floor geology and bathymetry provide widespread evidence for extensive low-angle faulting. However, only 3% of the seafloor in this region has the domal morphology characteristic of features that have been termed oceanic core complexes; suggesting that other processes, in addition to low-angle faulting, are responsible for the generation of domal core complexes. Most low-angle faults near the 15-20 FZ form gently dipping (10-15°), 10-15km-wide dip slopes on the flanks of 2000m relief bathymetric ridges that are up to 15-40km long (parallel to the MAR). Core recovered from ODP Leg 209 drill holes in these ridges is dominantly peridotite with small (<50m thick) gabbro intrusions. The peridotite is cut by a very high density of brittle faults dipping at both steep and gentle angles. Several holes also contain long-lived shear zones/faults in their upper reaches in which strain was localized at granulite facies, indicated by mylonitic olivine and cpx, and remained active during cooling to sub-greenschist grade, indicated by cross-cutting of progressively lower-grade syn-deformation mineral assemblages. These observations suggest that seafloor spreading is largely accommodated here by slip on low-angle faults, and that these faults are correctly termed detachment faults. Holes drilled into a domal oceanic core complex north of the 15-20 FZ during Leg 209 (ODP Site 1275) recovered dominantly gabbro and not mantle peridotite. This hole is cut by significantly fewer brittle and ductile faults than the peridotite drilled at the non-core-complex detachment fault sites. The detachment fault in the upper reaches (50m) of Site 1275 was localized at temperatures near feldspar's ductile-to-brittle transition, indicated by cataclasis with minor crystal plastic flow in plagioclase, and a lack of pervasive pure-ductile deformation. Amphibole-plagioclase thermometry in the fault yields equilibrium temperatures from 600-650°C, compared to equilibrium temperatures of 750-850°C for the gabbro outside the fault. The presence of talc- chlorite schists and cataclasites cutting the higher-temperature deformation textures indicate fault activity down- temperature from amphibolite through greenschist facies. This core-complex-bounding fault contrasts with the fault that bounds the Atlantis Bank Core Complex on the Southwest Indian Ridge (SWIR). There, the fault is 100m thick and strain was initially localized at granulite grade (>800°C) (Mehl & Hirth, 2007); significantly hotter than the Site 1275 fault. Therefore, the formation of core-complex morphology does not seem to depend on the initial faulting conditions. Both oceanic core complexes that have been drilled besides Site 1275, Atlantis Massif at 30°N (IODP Hole 1309D) on the MAR and Atlantis Bank on the SWIR (ODP Hole 735B), are also comprised dominantly of gabbro. This suggests that magma supply may be an essential requirement for core complex formation and raises the question whether all domal oceanic core complexes are cored by gabbro? We also ask whether the term 'oceanic core complex' should be restricted to these domal features and not applied to detachment-bound, non- domal, peridotite-cored ridges; or if these should be considered two sub-classes of oceanic core complexes.

The metamorphic basement of the southern Sierra de Aconquija, Eastern Sierras Pampeanas: Provenance and tectonic setting of a Neoproterozoic back-arc basin

NASA Astrophysics Data System (ADS)

Cisterna, Clara Eugenia; Altenberger, Uwe; Mon, Ricardo; Günter, Christina; Gutiérrez, Antonio

2018-03-01

The Eastern Sierras Pampeanas are mainly composed of Neoproterozoic-early Palaeozoic metamorphic complexes whose protoliths were sedimentary sequences deposited along the western margin of Gondwana. South of the Sierra de Aconquija, Eastern Sierras Pampeanas, a voluminous metamorphic complex crops out. It is mainly composed of schists, gneisses, marbles, calk-silicate schists, thin layers of amphibolites intercalated with the marbles and granitic veins. The new data correlate the Sierra de Aconquija with others metamorphic units that crop out to the south, at the middle portion of the Sierra de Ancasti. Bulk rock composition reflects originally shales, iron rich shales, wackes, minor litharenites and impure limestones as its protoliths. Moreover, comparisons with the northern Sierra de Aconquija and from La Majada (Sierra de Ancasti) show similar composition. Amphibolites have a basaltic precursor, like those from the La Majada (Sierra de Ancasti) ones. The analyzed metamorphic sequence reflects low to moderate weathering conditions in the sediments source environment and their chemical composition would be mainly controlled by the tectonic setting of the sedimentary basin rather than by the secondary sorting and reworking of older deposits. The sediments composition reveal relatively low maturity, nevertheless the Fe - shale and the litharenite show a tendency of minor maturity among them. The source is related to an acid one for the litharenite protolith and a more basic to intermediate for the other rocks, suggesting a main derivation from intermediate to felsic orogen. The source of the Fe-shales may be related to and admixture of the sediments with basic components. Overall the composition point to an upper continental crust as the dominant sediment source for most of the metasedimentary rocks. The protolith of the amphibolites have basic precursors, related to an evolving back-arc basin. The chemical data in combination with the specific sediment association (wackes, shales, Fe-shales and minor litharenites) are characteristic for turbidity currents deposits along tectonically active region. They are also commonly associated with calcareous clays (marbles), commonly observed in the evolution of basins with slope and shelf derived carbonate turbidites. The amphibolites members are probably derived from lava-flows synchronous with the sedimentation during the basin evolution. The basin was controlled by a continental island arc possible evolving to a back-arc setting, as indicated for the mixed nature of the inferred source. The metasedimentary sequence from the Cuesta de La Chilca have petrographic, structural and strong chemical similarities, building a north-south striking belt from the north of the Sierra de Aconquija and to the south along the Sierra de Ancasti (La Majada area). The observed similarities allow to present this portion of the Eastern Sierras Pampeanas as a crustal block that records the sedimentary sequences developed along the geodynamic context of the southwestern margin of Gondwana during the Neoproterozoic and Early Palaeozoic.

The Role of Brines in the Fluid Induced Dehydration of the Mafic Lower Crust from Amphibolite to Granulite Grade: Nature and Experiment

NASA Astrophysics Data System (ADS)

Harlov, D. E.

2016-12-01

Natural evidence for the role of low H2O activity fluids (CO2 or concentrated brines) in the dehydration of H2O-rich, mafic amphibolite-facies rocks to H2O-poor, Opx-bearing granulite-facies rocks (700-900 °C and 500-1000 MPa) for both highly localised dehydration zones (CO2; cm's) (Harlov et al. 2006, J Petrol, 47, 3) as well as regional terranes (NaCl-KCl brines; km's) (Harlov and Förster 2002, J Petrol, 43, 769; Hansen and Harlov 2007, 48, 1641) include the presence of Kfs micro-veins along Qtz-Plg grain boundaries; Plg grains metasomatised in a K-rich fluid; Mnz and/or Xn inclusions in the FAp grains; Bt enriched in Ti, F, and Cl; and FAp enriched in Cl and F. These features are not seen in the "source" amphibolite facies terrane along the same traverse. When log(fHF/fH2O) for either Bt or FAp is plotted as a function of the distance from the fluid/heat source, a uniform decrease in log(fHF/fH2O) is observed across the granulite to amphibolite facies traverse suggesting the presence of a uniform low H2O activity uniform fluid front. Dehydration experiments (900 °C; 1000 MPa; 3 weeks; Au capsule; quenched) involving a cylinder of natural tonalitic Bt gneiss (Plg, Qtz, Bt) (220 mg) and a concentrated KCl brine (20-30 % H2O; 70-80 % KCl) (8 mg) placed at the base of the cylinder have been conducted in the piston cylinder apparatus (CaF2 setup). Micro-veins primarily of Kfs, with some evidence of partial melting, formed along Qtz/Plg grain boundaries though only where Bt and Qtz were in contact. Here the Bt reacted with Qtz to form numerous small Opx and Cpx grains as well as minor Ilm from the 2-3 wt % of TiO2 present in the Bt. The two principle reactions responsible for both the formation of the Kfs micro-veins as well as the pyroxenes include: (1) An (in Plg) + Qtz + KCl (in fluid) = Kfs + CaCl2 (in fluid) and (2) Bt + Qtz = Opx + Kfs + H2O. The same experiment performed under the same P-T conditions involving either a concentrated NaCl brine (20-30 % H2O; 70-80 % NaCl) or a CO2-rich fluid (80 % CO2, 20 % H2O) or a fluid absent dry melt resulted in micro-veins approximating a granitic composition along Qtz/Plg grain boundaries with numerous small Opx grains minor Ilm forming along biotite grain boundaries, again only when the Bt and Qtz were in contact. Due to an absence of KCl in these three cases, only reaction (2) was relevant.

Bedrock Geology and Asbestos Deposits of the Upper Missisquoi Valley and Vicinity, Vermont

USGS Publications Warehouse

Cady, Wallace Martin; Albee, Arden Leroy; Chidester, A.H.

1963-01-01

The upper Missisquoi Valley and vicinity as described in this report covers an area of about 250 square miles at the headwaters of the Missisquoi River in north-central Vermont. About 90 percent of the area is forested and the remainder is chiefly farm land. The topography reflects the geologic structure and varied resistance of the bedrock to erosion. Most of the area is on the east limb of the Green Mountain anticlinorium, which is the principal structural feature of Vermont. The bedrock is predominantly sedimentary and volcanic rock that has been regionally metamorphosed. It was intruded before metamorphism by mafic and ultramafic igneous rocks, and after metamorphism by felsic and mafic igneous rocks. The metamorphosed sedimentary and volcanic rocks range in age from Cambrian(?) to Middle Silurian, the intrusive igneous rocks from probably Late Ordovician to probably late Permian. Metamorphism and principal folding in the region occurred in Middle Devonian time. The metamorphosed sedimentary and volcanic rocks make up a section at least 25,000 feet thick and can be divided into nine formations. The Hazens Notch formation of Cambrian(?) and Early Cambrian age is characterized by carbonaceous schist. It is succeeded in western parts of the area by the Jay Peak formation of Early Cambrian age, which is chiefly a schist that is distinguished by the general absence of carbonaceous zones; in central parts of the area the Hazens Notch formation is followed by the Belvidere Mountain amphibolite, probably the youngest of the formations of Early Cambrian age. The Ottauquechee formation, composed of carbonaceous phyllite and quartzite, and phyllitic graywacke, is of Middle Cambrian age. The Stowe formation of Late Cambrian(?) and Early(?) Ordovician age overlies the Ottauquechee and is predominantly noncarbonaceous schist, though it also contains greenstone and carbonaceous schist and phyllite. The Umbrella Hill formation of Middle Ordovician age is characteristically a conglomerate in which the mineral chloritoid is common. The overlying Moretown formation, also of Middle Ordovician age, contains granulite and slate, also greenstone and amphibolite of the Coburn Hill volcanic member. The Shaw Mountain formation, made up of conglomerate, phyllite, and limestone, is the oldest Silurian unit. The Shaw Mountain formation is succeeded by the Northfield slate of Middle Silurian age. The igneous rocks of the region include various ultramafic plutonic rocks, such as dunite, peridotite, and serpentinite, probably of Late Ordovician age; sills and nearly concordant dikes of metagabbro of Late Ordovician age; biotite granite plutons or Middle or Late Devonian age, most notably on Eltey Mountain; and hypabyssallamprophyre, probably of late Permian age. Metamorphic zoning is shown by the distribution of rocks of the epidote-amphibolite facies and the greenschist facies in and near the Green Mountains, and near Coburn Hill and Eltey Mountain. Metasomatism related to regional metamorphism has produced porphyroblasts and quartz segregations in the sedimentary and volcanic rocks, and steatitization and carbonatization of serpentinite. Contact metamorphism has formed rocks of the epidote-amphibolite facies near granite plutons, and probably calc-silicate rock at the contacts of ultramafic plutons. The axial anticline of the Green Mountain anticlinorium and other anticlines and synclines to the east are the major longitudinal structural features of the area. These structures are complicated by transverse folds, particularly a syncline in the vicinity of Tillotson Peak. Early minor cross folds that are best developed in the Hazens Notch formation are believed to be genetically related to the transverse folds. The axial planes of the cross folds are folded about the axes of the later longitudinal folds of the Green Mountain anticlinorium. The longitudinal and transverse fold systems probably formed in the same episode of defor

Minimum age of the Neoproterozoic Seven Hundred Acre Island Formation and the tectonic setting of the Islesboro Formation, Islesboro block, Maine

USGS Publications Warehouse

Stewart, D.B.; Tucker, R.D.; Ayuso, R.A.; Lux, D.R.

2001-01-01

Two platformal stratigraphic sequences occur on Islesboro, Penobscot Bay, Maine. The older Seven Hundred Acre Island Formation is at least 200 m thick, its base is not exposed, and it makes up fault-bounded blocks of siliceous colour-banded dolomitic marble, muscovite-rich quartzite, coarse-grained splendent muscovite-garnet-staurolite-andalusite schist, and calcareous metapelite, with minor garnet amphibolite and amphibolite. It was initially metamorphosed to lower amphibolite facies and was later to lower greenschist facies. The lower amphibolite facies metamorphism is Neoproterozoic (670 to 650 Ma) as inferred from the 40Ar/39Ar high temperature release spectra of hornblende separates. A U-Pb zircon age of 646.7 ?? 2.7 Ma obtained for a pegmatite that intruded deformed rocks is taken to be the minimum age of the Formation. The platformal Islesboro Formation probably unconformably overlies the Seven Hundred Acre Island Formation. It is primarily turbiditic pelite with many beds of quartzite, impure dolomitic marble, some conglomerate, and a few feldsparrich volcaniclastic beds and is thought to be either Neoproterozoic or Cambrian. It was metamorphosed only to lower greenschist facies, possibly in the same event that retrograded the Seven Hundred Acre Island Formation. Geochemical interpretations of minor and trace element analyses of six amphibolite and four schist samples from the Seven Hundred Acre Island Formation show that the protoliths of the amphibolite samples were intermediate between tholeiitic and within-plate type basaltic flows or dikes that intruded attenuated continental crust, or were eroded from these basalts. Four amphibolite and three schist samples analyzed for Pb isotopes were found to be enriched in radiogenic Pb. The Pb isotopic compositions are similar to those in peri-Gondwanan basement rocks from Atlantic Canada. The peri-Gondwanan Islesboro block was placed against the peri-Gondwanan Middle and Late Cambrian Ellsworth terrane on the east by significant Late Silurian strike-slip faulting. The Late Silurian or Early Devonian Turtle Head dextral strike-slip fault separates the Islesboro block from the peri-Gondwanan St. Croix terrane to the west. The timing and nature of the movements of these faults are given from offsets of the isograds around the zircon-dated Late Silurian Sedgwick Granite (419.5 ?? 1.4 Ma) and South Penobscot Intrusive Suite (419.2 ?? 2.2 Ma). These terranes and others like them in Atlantic Canada make up a composite terrane that is different from the composite Avalonian terranes sensu stricto of southeastern New England and Atlantic Canada. The composite peri-Gondwanan terrane that included the Islesboro block was amalgamated with the margin of ancestral North America in the Silurian.

Pressure Solution Creep and Textural Softening in Greenschist Facies Phyllonites

NASA Astrophysics Data System (ADS)

Wintsch, R. P.; Attenoukon, M.; Kunk, M. J.; McAleer, R. J.; Wathen, B.; Yi, D.

2016-12-01

We have found evidence for dissolution-precipitation creep (DPC) in phyllites and phyllonites naturally deformed at greenschist facies conditions. Since the experiments of Kronenberg et al. (1990) and Mares and Kronenberg (1993) micas are known to be among the weakest of rock-forming minerals. They deform by dislocation glide in their basal plane and when these micas are aligned and contiguous in an orientation favorable for glide they tend to localize strain into shear zones. Therefore, these closed-system experiments suggest that dislocation glide should be the dominant deformation mechanism in mica-rich shear zones from near surface through greenschist facies conditions. In contrast, in naturally deformed rocks we have found strong textural and chemical evidence that micas deform by dissolution-precipitation creep in phyllites at upper and lower greenschist facies conditions. In the Littleton Formation (N.H.) we find retrograde muscovite (pg5)-rich folia (Sn) truncating amphibolite facies Na-rich muscovite and biotite grains that define earlier foliations. Na-rich muscovite grains are also selectively replaced along crenulation axes and boudin necks where plastic and elastic strain are highest. In biotite grade regional metamorphic rocks in the Tananao schist of Taiwan muscovite-rich folia (Sn) truncate crenulated muscovite-biotite schists at high angles. In still lower (chlorite) grade phyllonitic fault zones marking terrane boundaries in southern New England (East Derby shear zone) and in Taiwan (Daugan shear zone) crenulated older fabrics are cut by new undeformed muscovite grains in chlorite-free planar folia. Further evidence for recrystallization rather than dislocation glide comes from the 40Ar/39Ar ages of muscovite in the new Sn folia younger than the age of the truncated folia. The younger ages in each case demonstrate that recrystallization was activated at lower shear stresses than dislocation glide, and that the recrystallization occurred at lower greenschist facies conditions below the closure temperature for diffusion of argon in muscovite. The increase in muscovite/chlorite ratios and change in microchemistry of Sn muscovite, the truncating microstructures, and isotopic results are all incompatible with deformation by dislocation creep.

Did Oligocene crustal thickening precede basin development in northern Thailand? A geochronological reassessment of Doi Inthanon and Doi Suthep

NASA Astrophysics Data System (ADS)

Gardiner, Nicholas J.; Roberts, Nick M. W.; Morley, Christopher K.; Searle, Michael P.; Whitehouse, Martin J.

2016-01-01

The Doi Inthanon and Doi Suthep metamorphic core complexes in northern Thailand are comprised of amphibolite-grade migmatitic gneisses mantled by lower-grade mylonites and metasedimentary sequences, thought to represent Cordilleran-style core complexes exhumed through the mobilization of a low-angle detachment fault. Previous studies have interpreted two metamorphic events (Late Triassic and Late Cretaceous), followed by ductile extension between the late Eocene and late Oligocene, a model which infers movement on the detachment at ca. 40 Ma, and which culminates in a rapid unroofing of the complexes in the early Miocene. The Chiang Mai Basin, the largest such Cenozoic Basin in the region, lies immediately to the east. Its development is related to the extension observed at Doi Inthanon and Doi Suthep, however it is not definitively dated, and models for its development have difficulty reconciling Miocene cooling ages with Eocene detachment movement. Here we present new in-situ LA-ICP-MS and SIMS U-Pb age data of zircon and monazite grains from gneiss and leucogranite samples taken from Doi Inthanon and Doi Suthep. Our new zircon data exhibit an older age range of 221-210 Ma, with younger ages of ca. 72 Ma, and 32-26 Ma. Our monazite data imply an older age cluster at 83-67 Ma, and a younger age cluster of 34-24 Ma. While our data support the view of Indosinian basement being reworked in the Cretaceous, they also indicate a late Eocene-Oligocene tectonothermal event, resulting in prograde metamorphism and anatexis. We suggest that this later event is related to localized transpressional thickening associated with sinistral movement on the Mae Ping Fault, coupled with thickening at the restraining bend of the Mae Yuan Fault to the immediate west of Doi Inthanon. Further, this upper Oligocene age limit from our zircon and monazite data would imply a younger Miocene constraint on movement of the detachment, which, when combined with the previously recorded Miocene cooling ages, has implications for a model for the onset of extension and subsequent development of the Chiang Mai Basin in the early mid-Miocene.

Mineral textural evolution and PT-path of relict eclogite-facies rocks in the Paleoproterozoic Nagssugtoqidian Orogen, South-East Greenland

NASA Astrophysics Data System (ADS)

Müller, Sascha; Dziggel, Annika; Kolb, Jochen; Sindern, Sven

2018-01-01

The Nagssugtoqidian Orogen in South-East Greenland is a deeply eroded, Paleoproterozoic collision orogen. It consists of a variety of Archean and Paleoproterozoic rocks, most notably TTG gneiss, a variety of supracrustal rocks and basic dykes. This study aims at providing new insight into the geodynamic processes and subduction depth of this orogen by investigating the metamorphic evolution of garnet pyroxenite, retrogressed eclogite and amphibolite-facies rocks that are exposed within the Kuummiut Terrane of the Nagssugtoqidian Orogen. The garnet-pyroxenite has a dominant mineral assemblage of garnet, orthopyroxene, clinopyroxene and hornblende, while garnet-amphibolite and garnet-kyanite schist are made up of garnet, hornblende, plagioclase and quartz, and garnet, kyanite, biotite and quartz, respectively. Relicts of, and pseudomorphs after, eclogite-facies mineral assemblages are frequently found within basic metavolcanic rocks and Paleoproterozoic discordant basic dykes. In the retrogressed eclogite, the retrograde mineral reactions ceased prior to completion, resulting in the formation of two domains. A clinopyroxene domain consists of diopside-plagioclase symplectites, which are interpreted to have grown at the expense of omphacite. The symplectites are surrounded and partly replaced by hornblende and plagioclase. Omphacite (XJd 25-42) is preserved in a Na-rich sample, where it occurs in the core of large clinopyroxene and as inclusion in garnet and hornblende. In a garnet domain, garnet is variably replaced by an inner corona of plagioclase and an outer corona of amphibole +/- orthopyroxene and clinopyroxene. The degree of retrogression as well as the type of the retrograde assemblage in both domains appears to be dependent on fluid activity. Large garnet grains preserve Ca-rich cores, interpreted as prograde in origin, while Mg-rich garnet rims formed during eclogite-facies metamorphism and later re-equilibration. Pseudosection modelling combined with conventional geothermobarometry reveals a clockwise PT-evolution, involving eclogite-facies conditions of 17-19 kbar and 740-810 °C, followed by near-isothermal decompression to medium-pressure granulite-facies conditions (13.8-15.4 kbar, 760-880 °C) and subsequent decompression with minor cooling to high-pressure amphibolite-facies grades (8.8-10.9 kbar, 660-840 °C). These data show that rocks of the Kuummiut Terrane were exhumed from 70 to about 30 km into the mid- and lower crust. The PT-path implies that exhumation initially was rapid and tectonically-controlled.

Trondhjemite and metamorphosed quartz keratophyre tuff of the Ammonoosuc volcanics (Ordovician), western New Hampshire and adjacent Vermont and Massachusetts.

USGS Publications Warehouse

Leo, G.W.

1985-01-01

These volcanic rocks consist of a lower, mainly mafic unit of hornblende-plagioclase amphibolite and an upper, mainly felsic metamorphosed quartz keratophyre tuff. They are intruded by sills, dykes and plugs of trondhjemite; which is highly silicic (SiO2, 73-81%), low in Al2O3 (11.3-13.5%) and generally contains <1% K2O. Both trondhjemite and volcanics are calc-alkaline. The major- and minor-element geochemistry of the trondhjemites is closely similar to that of the quartz keratophyre tuff. These rocks were probably produced by partial melting of basaltic source rocks, rather than by fractional crystallization, in view of the virtually bimodal nature of the Ammonoosuc assemblage. The generation of the felsic rocks occurred at deeper levels along a subduction zone dipping eastward.-L.C.H.

Tectono-metamorphic evolution of the Jomolhari massif: Variations in timing of syn-collisional metamorphism across western Bhutan

NASA Astrophysics Data System (ADS)

Regis, Daniele; Warren, Clare J.; Young, David; Roberts, Nick M. W.

2014-03-01

Our current understanding of the rates and timescales of mountain-building processes is largely based on information recorded in U-bearing accessory minerals such as monazite, which is found in low abundance but which hosts the majority of the trace element budget. Monazite petrochronology was used to investigate the timing of crustal melting in migmatitic metasedimentary rocks from the Jomolhari massif (NW Bhutan). The samples were metamorphosed at upper amphibolite to granulite facies conditions (~ 0.85 GPa, ~ 800 °C), after an earlier High-Pressure stage (P > 1.4 GPa), and underwent partial melting through dehydration melting reactions involving muscovite and biotite. In order to link the timing of monazite growth/dissolution to the pressure-temperature (P-T) evolution of the samples, we identified 'chemical fingerprints' in major and accessory phases that were used to back-trace specific metamorphic reactions. Variations in Eu anomaly and Ti in garnet were linked to the growth and dissolution of major phases (e.g. growth of K-feldspar and dehydration melting of muscovite/biotite). Differences in M/HREE and Y from garnet core to rim were instead related to apatite breakdown and monazite-forming reactions. Chemically zoned monazite crystals reacted multiple times during the metamorphic evolution suggesting that the Jomolhari massif experienced a prolonged high-temperature metamorphic evolution from 36 Ma to 18 Ma, significantly different from the P-T-time path recorded in other portions of the Greater Himalayan Sequence (GHS) in Bhutan. Our data demonstrate unequivocally that the GHS in Bhutan consists of units that experienced independent high-grade histories and that were juxtaposed across different tectonic structures during exhumation. The GHS may have been exhumed in response to (pulsed) mid-crustal flow but cannot be considered a coherent block.

Geologic columns for the ICDP-USGS Eyreville B core, Chesapeake Bay impact structure: Impactites and crystalline rocks, 1766 to 1096 m depth

USGS Publications Warehouse

Horton, J. Wright; Gibson, R.L.; Reimold, W.U.; Wittmann, A.; Gohn, G.S.; Edwards, L.E.

2009-01-01

The International Continental Scientific Drilling Program (ICDP)-U.S. Geological Survey (USGS) Eyreville drill cores from the Chesapeake Bay impact structure provide one of the most complete geologic sections ever obtained from an impact structure. This paper presents a series of geologic columns and descriptive lithologic information for the lower impactite and crystalline-rock sections in the cores. The lowermost cored section (1766-1551 m depth) is a complex assemblage of mica schists that commonly contain graphite and fibrolitic sillimanite, intrusive granite pegmatites that grade into coarse granite, and local zones of mylonitic deformation. This basement-derived section is variably overprinted by brittle cataclastic fabrics and locally cut by dikes of polymict impact breccia, including several suevite dikes. An overlying succession of suevites and lithic impact breccias (1551-1397 m) includes a lower section dominated by polymict lithic impact breccia with blocks (up to 17 m) and boulders of cataclastic gneiss and an upper section (above 1474 m) of suevites and clast-rich impact melt rocks. The uppermost suevite is overlain by 26 m (1397-1371 m) of gravelly quartz sand that contains an amphibolite block and boulders of cataclasite and suevite. Above the sand, a 275-m-thick allochthonous granite slab (1371-1096 m) includes gneissic biotite granite, fine- and medium-to-coarse-grained biotite granites, and red altered granite near the base. The granite slab is overlain by more gravelly sand, and both are attributed to debris-avalanche and/or rockslide deposition that slightly preceded or accompanied seawater-resurge into the collapsing transient crater. ?? 2009 The Geological Society of America.

Structural evolution of the Semail Ophiolite metamorphic sole, Wadi Hawasina and Northern Jebel Nakhl Culmination, Oman

NASA Astrophysics Data System (ADS)

Hurtado, C.; Bailey, C.; Visokay, L.; Scharf, A.

2017-12-01

The Semail ophiolite is the world's largest and best-exposed ophiolite sequence, however the processes associated with both oceanic detachment and later emplacement onto the Arabian continental margin remain enigmatic. This study examines the upper mantle section of the ophiolite, its associated metamorphic sole, and the autochthonous strata beneath the ophiolite at two locations in northern Oman. Our purpose is to understand the structural history of ophiolite emplacement and evaluate the deformation kinematics of faulted and sheared rocks in the metamorphic sole. At Wadi Hawasina, the base of the ophiolite is defined by a 5- to 15-m thick zone of penetratively-serpentinized mylonitic peridotite. Kinematic indicators record top-to-the SW (reverse) sense-of-shear with a triclinic deformation asymmetry. An inverted metamorphic grade is preserved in the 300- to 500-m thick metamorphic sole that is thrust over deep-water sedimentary rocks of the Hawasina Group. The study site near Buwah, in the northern Jebel Nakhl culmination, contains a N-to-S progression of mantle peridotite, metamorphic sole, and underlying Jurassic carbonates. Liswanite crops out in NW-SE trending linear ridges in the peridotite. The metamorphic sole includes well-foliated quartzite, metachert, and amphibolite. Kinematic evidence indicates that the liswanite and a serpentinized mélange experienced top to-the north (normal) sense-of-shear. Two generations of E-W striking, N-dipping normal faults separate the autochthonous sequence from the metamorphic sole, and also cut out significant sections of the metamorphic sole. Fabric analysis reveals that the metamorphic sole experienced flattening strain (K<0.2) that accumulated during pure shear-dominated general shear (Wk<0.4). Normal faulting and extension at the Buwah site indicates that post-ophiolite deformation is significant in the Jebel Akhdar and Jebel Nakhl culminations.

Structure and U-Pb zircon geochronology of an Alpine nappe stack telescoped by extensional detachment faulting (Kulidzhik area, Eastern Rhodopes, Bulgaria)

NASA Astrophysics Data System (ADS)

Georgiev, Neven; Froitzheim, Nikolaus; Cherneva, Zlatka; Frei, Dirk; Grozdev, Valentin; Jahn-Awe, Silke; Nagel, Thorsten J.

2016-10-01

The Rhodope Metamorphic Complex is a stack of allochthons assembled during obduction, subduction, and collision processes from Jurassic to Paleogene and overprinted by extensional detachment faults since Middle Eocene. In the study area, the following nappes occur in superposition (from base to top): an orthogneiss-dominated unit (Unit I), garnet-bearing schist with amphibolite and serpentinite lenses (Unit II), greenschist, phyllite, and calcschist with reported Jurassic microfossils (Unit III), and muscovite-rich orthogneiss (Unit IV). U-Pb dating of zircons from a K-feldspar augengneiss (Unit I) yielded a protolith age of ca. 300 Ma. Garnet-bearing metasediment from Unit II yielded an age spectrum with distinct populations between 310 and 250 Ma (detrital), ca. 150 Ma, and ca. 69 Ma (the last two of high-grade metamorphic origin). An orthogneiss from Unit IV yielded a wide spectrum of ages. The youngest population gives a concordia age of 581 ± 5 Ma, interpreted as the age of the granitic protolith. Unit I represents the Lower Allochthon (Byala Reka-Kechros Dome), Unit II the Upper Allochthon (Krumovitsa-Kimi Unit), Unit III the Uppermost Allochthon (Circum-Rhodope Belt), and Unit IV a still higher, far-travelled unit of unknown provenance. Telescoping of the entire Rhodope nappe stack to a thickness of only a few 100 m is due to Late Eocene north directed extensional shearing along the newly defined Kulidzhik Detachment which is part of a major detachment system along the northern border of the Rhodopes. Older top-to-the south mylonites in Unit I indicate that Tertiary extension evolved from asymmetric (top-to-the-south) to symmetric (top-to-the-south and top-to-the-north), bivergent unroofing.

Provenance and tectonic setting of the supra-crustal succession of the Qinling Complex: Implications for the tectonic affinity of the North Qinling Belt, Central China

NASA Astrophysics Data System (ADS)

Shi, Yu; Huang, Qianwen; Liu, Xijun; Krapež, Bryan; Yu, Jinhai; Bai, Zhian

2018-06-01

The Qinling Complex lies in the Qinling orogenic belt of Central China and holds the key to understanding the evolution of this feature. The Qinling Complex comprises a basement complex composed of amphibolite and ecologite, overlain by a supra-crustal succession that has been metamorphosed to the upper greenschist facies at approximately 516-509 Ma. The protoliths of the meta-sedimentary rocks are graywackes, which are divided into lower, middle and upper units. Detrital zircons from nine samples of the supra-crustal succession have ages ranging from 1182 to 1158 Ma for the lower unit, 957 to 955 Ma for the middle unit and 917 to 840 Ma for the upper unit. The lower unit is intruded by a ca. 960 Ma pluton. The bulk compositions of these meta-sedimentary rocks and their detrital zircon ages clearly indicate derivation from Meso- and Neo-proterozoic granites. Thus, we suggest that the sedimentary succession was derived from an arc-related tectonic setting and that none of the detritus was sourced from the southern margin of the North China Block or from the northern and western margins of the South China Block. We conclude that the North Qinling Belt was an independent micro-continental block during the Meso- to Neo-proterozoic.

Trace element behavior and P-T-t evolution during partial melting of exhumed eclogite in the North Qaidam UHPM belt (NW China): Implications for adakite genesis

NASA Astrophysics Data System (ADS)

Zhang, Guibin; Niu, Yaoling; Song, Shuguang; Zhang, Lifei; Tian, Zuolin; Christy, Andrew G.; Han, Lei

2015-06-01

We have studied trace element behavior and timing of decompression melting of UHP rocks during exhumation recorded in the magmatic products, i.e., the melt phase (leucosomes), cumulate (garnetite) and residue (amphibolitized eclogite) from a single outcrop in the south Dulan area, North Qaidam UHPM belt, NW China. Two distinct episodes of partial melting are recognized. First, Grt-free tonalitic-trondhjemitic leucosome melts with higher silica crystallized at 424.0 ± 2.7 Ma. Garnets grew in the leucosome melt but fractionated out to form garnetite cumulates along with Ti-rich phases (rutile and titanite), strengthening the adakitic signature of the leucosome. Later Grt-bearing leucosome melts with an age of 412.4 ± 2.9 Ma cross-cut boudins and layers of amphibolitized eclogite. Geochemical investigation of bulk-rocks and in situ minerals verifies the genetic relationship between the amphibolitized eclogite and the tonalitic-trondhjemitic melts. Zircons from the amphibolitized eclogite have older (> 700 Ma) protolith ages, with subsequent eclogite-facies metamorphism, retrograde granulite-facies overprinting and partial melting. Phase modeling and Zr-in-rutile thermometry calculations in combination with zircon geochronology reveal the evolution P-T-t path for the exhumation and the partial melting of the deeply subducted continental crust at the North Qaidam subduction zone in the Early Paleozoic.

Poly-phase Deformation Recorded in the Core of the Coast Plutonic Complex, Western British Columbia

NASA Astrophysics Data System (ADS)

Hamblock, J. M.; Andronicos, C. L.; Hurtado, J. M.

2006-05-01

The Coast Plutonic Complex of western British Columbia constitutes the largest batholith within the North American Cordillera. The field area for this study is Mt. Gamsby, an unexplored region above the Kitlope River, east of the Coast Shear Zone and at the southern end of the Central Gneiss Complex. The dominant lithologies on Mt. Gamsby include amphibolite and metasedimentary gneiss, gabbro-diorite, and orthogneiss. The amphibolite gneiss contains alternating amphibolite and felsic layers, with chlorite and epidote pervasive in some regions and garnet rare. This unit is commonly migmatized and contains various folds, boudins, and shear zones. The metasedimentary gneiss contains quartz, k-spar, graphite, chlorite, and perhaps cordierite, but appears to lack muscovite and aluminosilicates. The gabbro-diorite is salt and pepper in color and contains ca. 50% pyroxene and plagioclase. The orthogneiss is light in color and plagioclase-rich, with a texture varying from coarse-grained and undeformed to mylonitic. In some regions, this unit contains abundant mafic enclaves. At least four deformational events (D1-4) are observed. The second generation of folding, F2, is dominant in the area and resulted in the production of a large synform during sinistral shearing. The S1 foliation is observed only in the amphibolite gneiss and is orthogonal to S2, creating mushroom- type fold interference patterns. S2 foliations strike NW-SE and dip steeply to the SW, suggesting SW-NE directed shortening. L2 lineations developed on S2 plunge shallowly to the NW and SE, implying strike-slip motion. Although both dextral and sinistral motions are indicated by shear band data, sinistral motion is dominant. The average right and left lateral shear band orientation is nearly identical to S2, suggesting that right and left lateral shearing were synchronous. Foliations within the orthogneiss are parallel to the axes of S2 folds and boudins in the amphibolite gneiss, suggesting that emplacement of orthogneiss was concurrent with S2 deformation of the amphibolite gneiss. Tectonic strains calculated by the Rf-φ method using mafic enclaves in the orthogneiss vary from 4 to 10 within an area <1 km2, suggesting strong strain gradients during D2. S3 foliations strike WNW-ESE to E-W and dip shallowly to the south, suggesting NNE-SSW to N-S shortening. L3 lineations plunge shallowly to the SW and SE, and are associated low-angle shear bands with greenschist facies mineral assemblages which overprint higher temperature assemblages. Deformation phase D4 is characterized by low temperature, brittle deformation as shown by discrete fault surfaces with abundant chlorite. The following tectonic history can be determined based on structural observations. Amphibolite and immature sedimentary material formed from supracrustal (e.g. basalt flows?) and intrusive protoliths. These units were then intruded by the gabbro- diorite, which was deformed by right and left lateral shear zones sometime after crystallization. Both the amphibolite and gabbro-diorite were intruded by the orthogneiss, which was emplaced as sills during right and left lateral shearing and F2 folding. This geologic history is similar to that preserved in other parts of the Coast Plutonic Complex where dextral transpression and sinistral transtension are documented. The localization of low angle normal shear zones with greenschist facies mineral assemblages suggests extension occurred during cooling of the arc.

Disjunctive Grade Variation from Greenschist to Granulite Facies, Siyom Valley, Eastern Arunachal Pradesh, India

NASA Astrophysics Data System (ADS)

Clarke, G. L.; Bhowmik, S. K.; Aitchison, J. C.; Ireland, T. R.

2014-12-01

The Siyom Valley section in eastern Arunachal Pradesh exposes an inverted metamorphic succession (Nandini & Thakur, 2011), metapelitic assemblages increasing in grade northwards from chlorite, through biotite, garnet-staurolite and kyanite-bearing schist to kyanite-sillimanite migmatite. Grade changes are mostly controlled by shallowly north, and northwest-dipping fault structures. Two textural stages of garnet growth can be identified in the ilmenite-bearing amphibolite facies rocks, staurolite having formed late in, or after, deformation responsible for the main penetrative foliation (S2). Kyanite and rutile inclusions in garnet indicate that their growth in migmatite preceded that of matrix sillimanite, ilmenite and cordierite, though unrecrystallized kyanite is also common in the feldspathic matrix. Preliminary data indicate the pronounced tectonic thinning of metasedimentary protoliths during exhumation, and the probability of a pronounced step in grade in the middle part of the river section. Similarities with sections in the Sikkim (Dasgupta et al., 2004) and western Arunachal Pradesh (Goswami et al., 2009) Himalaya reflect the lateral continuity of the south-vergent thrusts that controlled the exhumation of the high-grade rocks, with debate concerning the location and significance of the Main Central Thrust zone begging protolith and metamorphic age data. Dasgupta, S.,Ganguly, J. & Neogi, S., 2004. Inverted metamorphic sequence in the Sikkim Himalayas: crystallization history, P-T gradient and implications. Journal of Metamorphic Geology, 22, 395-412. Goswami, S., Bhowmik, S.K. & Dasgupta, S., 2009. Petrology of a non-classical Barrovian inverted metamorphic sequence from the western Arunachal Himalaya, India. Journal of Asian Earth Sciences, 36, 390-406. Nandini, P. & Thakur, S.S., 2011. Metamorphic evolution of the Lesser Himalayan Crystalline Sequence, Siyom Valley, NE Himalaya, India. Journal of Asian Earth Sciences, 40, 1089-1100

Discordance between Ureteroscopic Biopsy and Final Pathology for Upper Tract Urothelial Carcinoma.

PubMed

Margolin, Ezra J; Matulay, Justin T; Li, Gen; Meng, Xiaosong; Chao, Brian; Vijay, Varun; Silver, Hayley; Clinton, Timothy N; Krabbe, Laura-Maria; Woldu, Solomon L; Singla, Nirmish; Bagrodia, Aditya; Margulis, Vitaly; Huang, William C; Bjurlin, Marc A; Shah, Ojas; Anderson, Christopher B

2018-06-01

We evaluated the discordance between ureteroscopic biopsy and surgical pathology findings for grading and staging upper tract urothelial carcinoma. We also sought to establish preoperative predictors of aggressive tumors. We retrospectively reviewed the records of 314 patients who underwent ureteroscopic biopsy followed by surgical management of upper tract urothelial carcinoma from 2000 to 2016 at a total of 3 institutions. Our primary outcomes were muscle invasive (pT2 or greater) disease at surgical pathology and upgrading of clinical low grade tumors to pathological high grade. At biopsy 61% of the patients had clinical high grade tumors and 21% had subepithelial connective tissue invasion (cT1+). On final pathology 79% of the patients had pathological high grade tumors and 45% had stage pT2 or greater. On multivariate analysis advanced patient age, clinical high grade and cT1+ were independently associated with pT2 or greater. The combined presence of clinical high grade and cT1+ had 86% positive predictive value for muscle invasion while the combined absence of clinical high grade and cT1+ had 80% negative predictive value. The likelihood of missing invasion on biopsy in patients with muscle invasive disease was increased when biopsy fragments were limited to 1 mm or less. Of clinical low grade cases on biopsy 51% were upgraded at surgery. The presence of positive urine cytology was associated with an increased risk of upgrading but this was not statistically significant. Clinical high grade, cT1+ on biopsy and advanced patient age are independent risk factors for muscle invasive upper tract urothelial carcinoma. There is a significant risk of upgrading in patients with clinical low grade tumors on biopsy, especially when urine cytology is positive. The predictive value of biopsy can likely be improved by more extensive ureteroscopic sampling. Copyright © 2018 American Urological Association Education and Research, Inc. Published by Elsevier Inc. All rights reserved.

Instructional and behavior management practices implemented by elementary general education teachers.

PubMed

Reddy, Linda A; Fabiano, Gregory A; Dudek, Christopher M; Hsu, Louis

2013-12-01

This investigation examined 317 general education kindergarten through fifth-grade teachers' use of instructional and behavioral management strategies as measured by the Classroom Strategy Scale (CSS)-Observer Form, a multidimensional tool for assessing classroom practices. The CSS generates frequency of strategy use and discrepancy scores reflecting the difference between recommended and actual frequencies of strategy use. Hierarchical linear models (HLMs) suggested that teachers' grade-level assignment was related to their frequency of using instructional and behavioral management strategies: Lower grade teachers utilized more clear 1 to 2 step commands, praise statements, and behavioral corrective feedback strategies than upper grade teachers, whereas upper grade teachers utilized more academic monitoring and feedback strategies, content/concept summaries, student focused learning and engagement, and student thinking strategies than lower grade teachers. Except for the use of praise statements, teachers' usage of instructional and behavioral management strategies was not found to be related to years of teaching experience or to the interaction of years of teaching experience and grade-level assignment. HLMs suggested that teachers' grade level was related to their discrepancy scores of some instructional and behavioral management strategies: Upper grade teachers had higher discrepancy scores in academic performance feedback, behavioral feedback, and praise than lower grade teachers. Teachers' discrepancy scores of instructional and behavioral management strategies were not found to be related to years of teaching experience or to the interaction of years of teaching experience and grade-level assignment. Implications of results for school psychology practice are outlined. © 2013.

Eurekan deformation on Prins Karls Forland, Svalbard - new insights from Ar40/Ar39 muscovite dating

NASA Astrophysics Data System (ADS)

Faehnrich, Karol; Schneider, David; Manecki, Maciej; Czerny, Jerzy; Myhre, Per Inge; Majka, Jarosław; Kośmińska, Karolina; Barnes, Christopher; Maraszewska, Maria

2017-04-01

Eurekan deformation has been proven to be a complex sequence of tectonic episodes, dominated by compression in the Circum Arctic region. It was associated with early Cenozoic collision of Eurasia, North America and Greenland plates producing fold-thrust belt style of deformation. Timing of this enigmatic event has not yet been extensively resolved by radiometric dating (Piepjohn et al. 2016, Journal of the Geological Society, 173(6), 1007-1024). Reinhardt et al. (2013, Z. Dt. Ges. Geowiss., 164 (1), 131-147) dated syn-tectonic volcanic ashes at c. 60 Ma and 54 Ma on Ellesmere Island, Canada. Tagner et al. (2011, Earth and Planetary Science Letters, 303(3), 203-214) interpreted c. 49-47 Ma 40Ar/39Ar ages on trachyte flows in northern Greenland as peak compression during the Eurekan event. On Svalbard, Tessensohn et al. (2001, Geologisches Jahrbuch, B 91, 83-104) reported K/Ar whole rock ages ranging from c. 67 to 49 Ma for the slates from Svartfjella-Eidembukta-Daudmannsodden Lineament. Bentonite layers in the Central Tertiary Basin are as young as c. 56 Ma (Charles et al. 2011, Geochem. Geophys. Geosyst., 12, 1-19), predating latest deformation. Moreover, Barnes et al (2017, in prep.) applied (U-Th)/He thermochronology along the western margin of Svalbard and resolved Early to Middle Eocene heating, likely documenting burial related to thrusting. Here we present new results from 40Ar/39Ar muscovite dating of ductile to brittle shear zone on Prins Karls Forland, Svalbard, indicating Eurekan age of thrusting. Prins Karls Forland is dominated by Neoproterozoic siliciclastic metasediments (comprising Caledonian basement) regionally metamorphosed to greenschist facies conditions. A ˜1 km wide ductile to brittle shear zone (the Bouréefjellet shear zone) separates the amphibolite facies Pinkie Unit from the lower grade upper structural unit, the Grampianfjella Formation (Faehnrich et al. 2016, EGU 2016). The age of the amphibolite facies metamorphism (c. 370-355 Ma) indicates Ellesmerian tectonism, unlike other higher grade rocks on Svalbard (Kośmińska et al. 2016, EGU 2016). Ten metasedimentary rocks from within the shear zone were collected for dating, with eight muscovite crystals dated per sample via 40Ar/39Ar total fusion. High strain is evinced by mylonitic fabric, mica fish or C' shear zones. Moreover, quartz was dynamically recrystallized with significant grain boundary migration. There is notable age dispersion between the samples with weighted mean ages varying from 45 up to 103 Ma and single grain ages are more than 300 Ma, reflecting partial recrystallization and resetting during Eurekan deformation. Younger ages were obtained from lower structural levels, yielding dates of 44 to 54 Ma for the Eurekan deformation on Prins Karls Forland. We suggest that an Ellesmerian ductile shear zone was reactivated during Eocene (commencing as early as 54 Ma) progressing to brittle conditions which continued after 44 Ma. These are the first documented Eurekan 40Ar/39Ar muscovite deformation ages from Svalbard, and enable to better distinguish individual stages of the Eurekan deformation in the Eocene improving our understanding of relative plate tectonic movements. This work is partially funded by AGH research grant no 11.11.140.319 and the NCN research projects 2013/11/N/ST10/00357 and 2015/17/B/ST10/03114.

Zircon (Hf, O isotopes) as melt indicator: Melt infiltration and abundant new zircon growth within melt rich layers of granulite-facies lenses versus solid-state recrystallization in hosting amphibolite-facies gneisses (central Erzgebirge, Bohemian Massif)

NASA Astrophysics Data System (ADS)

Tichomirowa, Marion; Whitehouse, Martin; Gerdes, Axel; Schulz, Bernhard

2018-03-01

In the central Erzgebirge within the Bohemian Massif, lenses of high pressure and ultrahigh pressure felsic granulites occur within meta-sedimentary and meta-igneous amphibolite-facies felsic rocks. In the felsic granulite, melt rich parts and restite form alternating layers, and were identified by petrology and bulk rock geochemistry. Mineral assemblages representing the peak P-T conditions were best preserved in melanocratic restite layers. In contrast, in the melt rich leucocratic layers, garnet and related HP minerals as kyanite are almost completely resorbed. Both layers display differences in accessory minerals: melanosomes have frequent and large monazite and Fe-Ti-minerals but lack xenotime and apatite; leucosomes have abundant apatite and xenotime while monazite is rare. Here we present a detailed petrographic study of zircon grains (abundance, size, morphology, inclusions) in granulite-facies and amphibolite-facies felsic gneisses, along with their oxygen and hafnium isotope compositions. Our data complement earlier Usbnd Pb ages and trace element data (REE, Y, Hf, U) on zircons from the same rocks (Tichomirowa et al., 2005). Our results show that the degree of melting determines the behaviour of zircon in different layers of the granulites and associated amphibolite-facies rocks. In restite layers of the granulite lenses, small, inherited, and resorbed zircon grains are preserved and new zircon formation is very limited. In contrast, new zircons abundantly grew in the melt rich leucocratic layers. In these layers, the new zircons (Usbnd Pb age, trace elements, Hf, O isotopes) best preserve the information on peak metamorphic conditions due to intense corrosion of other metamorphic minerals. The new zircons often contain inherited cores. Compared to cores, the new zircons and rims show similar or slightly lower Hf isotope values, slightly higher Hf model ages, and decreased oxygen isotope ratios. The isotope compositions (Hf, O) of new zircons indicate partial Hf isotope homogenization in the melt, and melt infiltration from an external source. New zircon was most likely formed by a peritectic reaction with melt above the wet solidus (peritectic zircon). Conversely, the amphibolite-facies host gneisses lack indications of significant melt production. Pre-metamorphic zircons experienced mainly solid-state recrystallization and variable Pb loss with only minor new zircon formation. However, subtle changes in cathodoluminescence pattern, in the Hf and O isotopes, and in the Lu/Hf, Yb/Hf ratios of zircons suggest that small volumes of melt were locally present. In difference to granulites, melt was internally produced. The detection of low degree melts (inferred from zircon geochemistry) is extremely important for the rheology because these amphibolite-facies rocks could act as large scale ductile shear zones. The new zircon data support a different P-T path for closely spaced amphibolite- and granulite-facies rocks.

Chronology of paleozoic metamorphism and deformation in the Blue Ridge thrust complex, North Carolina and Tennessee

DOE Office of Scientific and Technical Information (OSTI.GOV)

Goldberg, S.A.; Dallmeyer, R.D.

1997-05-01

The Blue Ridge province in northwestern North Carolina and northeastern Tennessee records a multiphase collisional and accretionary history from the Mesoproterozoic through the Paleozoic. To constrain the tectonothermal evolution in this region, radiometric ages have been determined for 23 regionally metamorphosed amphibolites, granitic gneisses, and pelitic schists and from mylonites along shear zones that bound thrust sheets and within an internal shear zone. The garnet ages from the Pumpkin Patch a thrust sheet (458, 455, and 451 Ma) are similar to those from the structurally overlying Spruce Pine thrust sheet (460, 456, 455, and 450 Ma). Both thrust sheets exhibitmore » similar upper amphibolite-facies conditions. Because of the high closure temperature for garnet, the garnet ages are interpreted to date growth at or near the peak of Taconic metamorphism. Devonian metamorphic ages are recognized in the Spruce Pine thrust sheet, where Sm-Nd and Rb-Sr garnet ages of 386 and 393 Ma and mineral isochron ages of 397 {+-} 14 and 375 {+-} 27 Ma are preserved. Hornblendes record similar {sup 40}Ar/{sup 39}Ar, Sm-Nd, and Rb-Sr ages of 398 to 379 Ma. Devonian {sup 40}Ar/{sup 39}Ar hornblende ages are also recorded in the structurally lower Pumpkin Patch thrust sheet. The Devonian mineral ages are interpreted to date a discrete tectonothermal event, as opposed to uplift and slow cooling from an Ordovician metamorphic event. The Mississippian mylonitization is interpreted to represent thrusting and initial assembly of crystalline sheets associated with the Alleghanian orogeny. The composite thrust stack of the Blue Ridge complex was subsequently thrust northwestward along the Linville Falls fault during middle Alleghanian orogeny (about 300 Ma).« less

Formation of ore minerals in metamorphic rocks of the German continental deep drilling site (KTB)

NASA Astrophysics Data System (ADS)

Kontny, A.; Friedrich, G.; Behr, H. J.; de Wall, H.; Horn, E. E.; Möller, P.; Zulauf, G.

1997-08-01

The German Continental Deep Drilling Program (KTB) drilled a 9.1 km deep profile through amphibolite facies metamorphic rocks and reached in situ temperatures of 265°C. Each lithologic unit is characterized by typical ore mineral assemblages related to the regional metamorphic conditions. Paragneisses contain pyrrhotite + rutile + ilmenite ± graphite, metabasic units bear ilmenite + rutile + pyrrhotite ± pyrite, and additionally, the so-called variegated units yield pyrrhotite + titanite assemblages. In the latter unit, magnetite + ilmenite + rutile + titanite assemblages related to the lower amphibolite facies breakdown of ilmenite-hematite solid solution also occur locally. Retrograde hydrothermal mineralization which commenced during Upper Carboniferous times is characterized by the following geochemical conditions: (1) low saline Na-K-Mg-Cl fluids with sulfur and oxygen fugacities at the pyrite-pyrrhotite buffer and temperatures of 400-500°C, (2) fluids with CO2, CH4±N2, andpH, Eh, sulfur, and oxygen fugacity in the stability field of graphite + pyrite at temperatures of 280-350° and (3) moderate to high saline Ca-Na-Cl fluids with CH4+ N2; sulfur and oxygen fugacity are in the stability field of pyrrhotite at temperatures <300°C. The latter environment is confirmed by in situ conditions found at the bottom of the deep drilling. Monoclinic, ferrimagnetic pyrrhotite is the main carrier of magnetization which disappears below about 8.6 km, corresponding to in situ temperatures of about 250°C. Below this depth, hexagonal antiferromagnetic pyrrhotite with a Curie temperature of 260°C is the stable phase. Temperature-dependent transformation of pyrrhotite and the reaching of its Curie isotherm within the Earth crust are one of the striking results of the KTB deep drilling project.

Linear geologic structure and magic rock discrimination as determined from infrared data

NASA Technical Reports Server (NTRS)

Offield, T. W.; Rowan, L. C.; Watson, R. D.

1970-01-01

Color infrared photographs of the Beartooth Mountains, Montana show the distribution of mafic dikes and amphibolite bodies. Lineaments that cross grassy plateaus can be identified as dikes by the marked constrast between the dark rocks and the red vegetation. Some amphibolite bodies in granitic terrain can also be detected by infrared photography and their contacts can be accurately drawn due to enchanced contrast of the two types of rock in the near infrared. Reflectance measurements made in the field for amphibolite and granite show that the granite is 25% to 50% more reflective in the near infrared than in the visible region. Further enhancement is due to less atmospheric scattering than in the visible region. Thermal infrared images of the Mill Creek, Oklahoma test site provided information on geologic faults and fracture systems not obtainable from photographs. Subtle stripes that cross outcrop and intervening soil areas and which probably record water distribution are also shown on infrared photographs.

Prioritizing Elementary School Writing Instruction: Cultivating Middle School Readiness for Students with Learning Disabilities

ERIC Educational Resources Information Center

Ciullo, Stephen; Mason, Linda

2017-01-01

Helping elementary students with learning disabilities (LD) prepare for the rigor of middle school writing is an instructional priority. Fortunately, several standards-based skills in upper elementary school and middle school overlap. Teachers in upper elementary grades, specifically fourth and fifth grades, have the opportunity to provide…

POSITION AND MOTION, A SCIENCE UNIT FOR THE UPPER ELEMENTARY GRADES, STUDENT MANUAL.

ERIC Educational Resources Information Center

BERGER, CARL; MONTGOMERY, MARSHALL

THIS MANUAL IS DESIGNED FOR STUDENTS IN UPPER ELEMENTARY GRADES STUDYING THE SCIENCE CURRICULUM IMPROVEMENT STUDY (SCIS) UNIT "POSITION AND MOTION". THE OVERALL STRUCTURE OF THE UNIT FOLLOWS A CYCLE OF PRELIMINARY EXPLORATION, INVENTION OF SPECIFIC CONCEPTS RELATED TO REFERENCE FRAMES, AND DISCOVERY OF THE USEFULNESS OF THE CONCEPT.…

The Benefits of Departmentalization in Upper Elementary Grades for Students and Teachers

ERIC Educational Resources Information Center

Johnson, Malissa Lee

2013-01-01

This study addressed the benefits of departmentalization in upper elementary grades for students and teachers. The variables of gender and classroom structure (departmentalized versus self-contained) were considered for student participants (n = 125). Results for students were evaluated on pre-test and post-test data using the following measures:…

Hierarchical Controlled Remote State Preparation by Using a Four-Qubit Cluster State

NASA Astrophysics Data System (ADS)

Ma, Peng-Cheng; Chen, Gui-Bin; Li, Xiao-Wei; Zhan, You-Bang

2018-06-01

We propose a scheme for hierarchical controlled remote preparation of an arbitrary single-qubit state via a four-qubit cluster state as the quantum channel. In this scheme, a sender wishes to help three agents to remotely prepare a quantum state, respectively. The three agents are divided into two grades, that is, an agent is in the upper grade and other two agents are in the lower grade. In this process of remote state preparation, the agent of the upper grade only needs the assistance of any one of the other two agents for recovering the sender's original state, while an agent of the lower grade needs the collaboration of all the other two agents. In other words, the agents of two grades have different authorities to reconstruct sender's original state.

Metamorphism, argon depletion, heat flow and stress on the Alpine fault

NASA Technical Reports Server (NTRS)

Scholz, C. H.; Beavan, J.; Hanks, T. C.

1978-01-01

The Alpine fault of New Zealand is a major continental transform fault which was uplifted on its southeast side 4 to 11 km within the last 5 m.y. This uplift has exposed the Haast schists, which were metamorphosed from the adjacent Torlesse graywackes. The Haast schists increase in metamorphic grade from prehnite-pumpellyite facies 9-12 km from the fault through the chlorite and biotite zones of the greenschist facies to the garnet-oligoclase zone amphibolite facies within 4 km of the fault. These metamorphic zone boundaries are subparallel to the fault for 350 km along the strike. The K-Ar and Rb-Sr ages of the schists increase with distance from the fault: from 4 m.y. within 3 km of the fault to approximately 110 m.y. 20 km from the fault. Field relations show that the source of heat that produced the argon depletion aureole was the fault itself.

Analysis of airborne imaging spectrometer data for the Ruby Mountains, Montana, by use of absorption-band-depth images

NASA Technical Reports Server (NTRS)

Brickey, David W.; Crowley, James K.; Rowan, Lawrence C.

1987-01-01

Airborne Imaging Spectrometer-1 (AIS-1) data were obtained for an area of amphibolite grade metamorphic rocks that have moderate rangeland vegetation cover. Although rock exposures are sparse and patchy at this site, soils are visible through the vegetation and typically comprise 20 to 30 percent of the surface area. Channel averaged low band depth images for diagnostic soil rock absorption bands. Sets of three such images were combined to produce color composite band depth images. This relative simple approach did not require extensive calibration efforts and was effective for discerning a number of spectrally distinctive rocks and soils, including soils having high talc concentrations. The results show that the high spectral and spatial resolution of AIS-1 and future sensors hold considerable promise for mapping mineral variations in soil, even in moderately vegetated areas.

The 3.5 b.y. old Onverwacht Group: A remnant of ancient oceanic crust

NASA Technical Reports Server (NTRS)

Hoffman, S.

1985-01-01

The interaction between seawater and submarine volcanic rock has had important consequences for the chemistry of the ocean during the Phanerozoic. Most extant terranes have been regionally metamorphosed to the amphibolite and granulite facies, so that their precursor lithologies and structures are not readily determinable. However, the 3.5 b.y. old supracrustal rocks of the Barberton Mountain Land, South Africa, have not been subjected to high grade regional metamorphism, and therefore there was reason to hope that a laboratory investigation might reveal the extent to which these rocks had been exposed to subseafloor hydrothermal activity. Hart and de Wit describe bulk geochemical evidence from the entire suite as well as field evidence which support the concept of hydrothermal activity in the Barberton Mountain Land. Mineralogical and textural features which unequivocally mark it as a submarine sequence emplaced in a midocean ridge/fracture zone or back arc/fracture zone environment are briefly discussed.

Palaeoproterozoic Volcanic Massive Sulphides (VMS) in the Lithuanian crystalline basement: evidences for a back-arc tectonic setting

NASA Astrophysics Data System (ADS)

Skridlaite, Grazina; Siliauskas, Laurynas

2014-05-01

In the southwestern part of the East European Craton (EEC), several events of Palaeoproterozoic volcanic arc magmatic activity were recognized in the concealed crystalline basement. In Lithuania, the TTG suites of 1.89 Ga and 1.86-1.84 Ga were later metamorphosed in amphibolite and granulite facies conditions. Remnants of a volcano-sedimentary sequence metamorphosed in green schist and amphibolite facies conditions were discovered in central and southern Lithuania. In southern Lithuania, the upper part of the Lazdijai 13 (Lz13) drilling (at c. 493 m depth) consists of exhalitic quartz chlorite cherts mixed with andesitic rocks. The rocks are impregnated with magnetite in some places replacing calcite. Most of the magnetite grains are overgrown by a dendritic kovelite, which may have formed while magnetite was still in aqueous surrounding. Other accessory minerals are xenotime, zircon, apatite, Sr-Ba sulphates etc. The cherts are underlain by a metaandesite which volcanic structures were obscured by hydrothermal alteration, i.e. the idiomorphic magnetite crystals and porphyritic plagioclase grains were replaced by clay minerals and quartz or muscovite in many places. Thin metamorphosed mudstone layers turned into garnet, biotite (+/-staurolite) and chlorite schists. The rocks were affected by silicification, chloritization, argilitization and carbonatization. Taking into account the rock composition, micro and macro scale alteration zones and absence of breccia, the whole package resembles an outer part of the VMS stockwork. The lower boundary at 526 m is sharp, marked by a quartz vein, below which lies quartz, biotite (+/- chlorite) bearing schist with minor tremolite (former sandstone). It was intensely affected by silicification, and was enriched in Na, K and Ca. Accessory minerals are monazite, xenotime, apatite and detrital zircon. The schist exhibits fine mineral foliation, and is fine-grained. A 4 m thick granitic vein cuts the rock at 654 m depth, below which there are amphibolites with layers or lenses of skarns formed in marbles. Some amphibolites resemble porphyritic basalts. These might be dikes of basalts, which are common for back arc VMS surroundings. The volcano-clastic rock from the Lz13 yielded c. 1.83 Ga and c. 1.80 Ga ages. The whole rock Sm-Nd isotopic composition points towards juvenile origin of the rock (TDM=2.08 Ga, ɛNd (1.9) +1.8). After the comparison of the obtained data set with VMS deposits formed in different environments, it is most likely that the volcano-sedimentary sequence of Lz13 was formed in a back arc tectonic setting. The volcano-sedimentary sequence can be correlated with the 1.83 Ga Oskarshamn-Jönköping Belt (Mansfeld et al., 2005) and the volcano-sedimentary Vetlanda formation (Makowsky and Mansfeld, 2013) in southeastern Sweden. The c. 1.83-1.80 Ga volcanic arc and back-arc system continues from southeastern Sweden through the Baltic Sea to Lithuania. This is a contribution to the Open Access Centre activities Mansfeld, J., Beunk, F.F. and Barling, J., 2005. GFF, 127: 149-157 Makowsky, F., Mansfeld, J., 2013. 31st Nordic Geological Winter Meeting, Lund, Sweden, 89-90.

Efficiency of Finnish General Upper Secondary Schools: An Application of Stochastic Frontier Analysis with Panel Data

ERIC Educational Resources Information Center

Kirjavainen, Tanja

2012-01-01

Different stochastic frontier models for panel data are used to estimate education production functions and the efficiency of Finnish general upper secondary schools. Grades in the matriculation examination are used as an output and explained with the comprehensive school grade point average, parental socio-economic background, school resources,…

Eco-Inquiry: A Guide to Ecological Learning Experiences for the Upper Elementary/Middle Grades.

ERIC Educational Resources Information Center

Hogan, Kathleen

Eco-Inquiry may be defined as a "whole science" curriculum that embeds hands-on science within thematic multi-dimensional learning experiences. Three modules for the upper elementary and middle grades focus on food webs, decomposition, and nutrient cycling. Each module lasts 4-7 weeks and may be used alone or in sequence. Student…

Coexisting cummingtonite and aluminous hornblende from garnet amphibolite, Boehls Butte area, Idaho, USA

USGS Publications Warehouse

Hietanen, A.

1973-01-01

Electron microprobe analyses of green hornblende and coexisting cummingtonite from garnet amphibolite show identical Fe/Mg ratios ( = 0.9). Cummingtonite is iron-magnesium silicate with very little calcium and aluminum and practically no alkalies. In contrast, the hornblende has 1.5 tetrahedral Al, 0.9 octahedral Al and a considerable amount of Ca and alkalies. Comparison with the hornblendes from the Sierra Nevada shows a higher relative amount of tschemakite molecule in the hornblendes from Idaho where pressures during the recrystallization were higher. ?? 1973.

Hierarchically controlled remote preparation of an arbitrary single-qubit state by using a four-qubit |χ > entangled state

NASA Astrophysics Data System (ADS)

Ma, Peng-Cheng; Chen, Gui-Bin; Li, Xiao-Wei; Zhan, You-Bang

2018-05-01

In this paper, we present a scheme for Hierarchically controlled remote preparation of an arbitrary single-qubit state via a four-qubit |χ > state as the quantum channel. In this scheme, a sender wishes to help three agents to remotely prepare a quantum state, respectively. The three agents are divided into two grades, that is, an agent is in the upper grade and other two agents are in the lower grade. It is shown that the agent of the upper grade only needs the assistance of any one of the other two agents for recovering the sender's original state, while an agent of the lower grade needs the collaboration of all the other two agents. In other words, the agents of two grades have different authorities to recover sender's original state.

Bimodal tholeiitic-dacitic magmatism and the Early Precambrian crust

USGS Publications Warehouse

Barker, F.; Peterman, Z.E.

1974-01-01

Interlayered plagioclase-quartz gneisses and amphibolites from 2.7 to more than 3.6 b.y. old form much of the basement underlying Precambrian greenstone belts of the world; they are especially well-developed and preserved in the Transvaal and Rhodesian cratons. We postulate that these basement rocks are largely a metamorphosed, volcanic, bimodal suite of tholeiite and high-silica low-potash dacite-compositionally similar to the 1.8-b.y.-old Twilight Gneiss - and partly intrusive equivalents injected into the lower parts of such volcanic piles. We speculate that magmatism in the Early Precambrian involved higher heat flow and more hydrous conditions than in the Phanerozoic. Specifically, we suggest that the early degassing of the Earth produced a basaltic crust and pyrolitic upper mantle that contained much amphibole, serpentine, and other hydrous minerals. Dehydration of the lower parts of a downgoing slab of such hydrous crust and upper mantle would release sufficient water to prohibit formation of andesitic liquid in the upper part of the slab. Instead, a dacitic liquid and a residuum of amphibole and other silica-poor phases would form, according to Green and Ringwood's experimental results. Higher temperatures farther down the slab would cause total melting of basalt and generation of the tholeiitic member of the suite. This type of magma generation and volcanism persisted until the early hydrous lithosphere was consumed. An implication of this hypothesis is that about half the present volume of the oceans formed before about 2.6 b.y. ago. ?? 1974.

Chapter L: U.S. Industrial Garnet

USGS Publications Warehouse

Evans, James G.; Moyle, Phillip R.

2006-01-01

The United States presently consumes about 16 percent of global production of industrial garnet for use in abrasive airblasting, abrasive coatings, filtration media, waterjet cutting, and grinding. As of 2005, domestic garnet production has decreased from a high of 74,000 t in 1998, and imports have increased to the extent that as much as 60 percent of the garnet used in the United States in 2003 was imported, mainly from India, China, and Australia; Canada joined the list of suppliers in 2005. The principal type of garnet used is almandite (almandine), because of its specific gravity and hardness; andradite is also extensively used, although it is not as hard or dense as almandite. Most industrial-grade garnet is obtained from gneiss, amphibolite, schist, skarn, and igneous rocks and from alluvium derived from weathering and erosion of these rocks. Garnet mines and occurrences are located in 21 States, but the only presently active (2006) mines are in northern Idaho (garnet placers; one mine), southeastern Montana (garnet placers; one mine), and eastern New York (unweathered bedrock; two mines). In Idaho, garnet is mined from Tertiary and (or) Quaternary sedimentary deposits adjacent to garnetiferous metapelites that are correlated with the Wallace Formation of the Proterozoic Belt Supergroup. In New York, garnet is mined from crystalline rocks of the Adirondack Mountains that are part of the Proterozoic Grenville province, and from the southern Taconic Range that is part of the northern Appalachian Mountains. In Montana, sources of garnet in placers include amphibolite, mica schist, and gneiss of Archean age and younger granite. Two mines that were active in the recent past in southwestern Montana produced garnet from gold dredge tailings and saprolite. In this report, we review the history of garnet mining and production and describe some garnet occurrences in most of the Eastern States along the Appalachian Mountains and in some of the Western States where industrial-grade garnet or its possible occurrence has been reported. Other natural and manmade materials compete with garnet in nearly all of the applications for which garnet can be used; garnet, however, has the advantages that it is reusable, nontoxic, and nonreactive. In addition, garnet produces much less dust than other abrasive materials, and spills are relatively benign and easy to clean up.

Enrichment of trace elements in garnet amphibolites from a paleo-subduction zone: Catalina Schist, southern California

USGS Publications Warehouse

Sorensen, Sorena S.; Grossman, J.N.

1989-01-01

The abundance, P-T stability, solubility, and element-partitioning behavior of minerals such as rutile, garnet, sphene, apatite, zircon, zoisite, and allanite are critical variables in models for mass transfer from the slab to the mantle wedge in deep regions of subduction zones. The influence of these minerals on the composition of subduction-related magmas has been inferred (and disputed) from inverse modelling of the geochemistry of island-arc basalt, or by experiment. Although direct samples of the dehydration + partial-melting region of a mature subduction zone have not been reported from subduction complexes, garnet amphibolites from melanges of circumpacific and Caribbean blueschist terranes reflect high T (>600??C) conditions in shallower regions. Such rocks record geochemical processes that affected deep-seated, high-T portions of paleo-subduction zones. In the Catalina Schist, a subduction-zone metamorphic terrane of southern California, metasomatized and migmatitic garnet amphibolites occur as blocks in a matrix of meta-ultramafic rocks. This mafic and ultramafic complex may represent either slab-derived material accreted to the mantle wedge of a nascent subduction zone or a portion of a shear zone closely related to the slab-mantle wedge contact, or both. The trace-element geochemistry of the complex and the distribution of trace elements among the minerals of garnet amphibolites were studied by INAA, XRF, electron microprobe, and SEM. In order of increasing alteration from a probable metabasalt protolith, three common types of garnet amphibolite blocks in the Catalina Schist are: (1) non-migmatitic, clinopyroxene-bearing blocks, which are compositionally similar to MORB that has lost an albite component; (2) garnet-amphibolite blocks, which have rinds that reflect local interaction between metabasite, metaperidotite, and fluid; and (3) migmatites that are extremely enriched in Th, HFSE, LREE, and other trace elements. These trace-element enrichments are mineralogically controlled by rutile, garnet, sphene, apatite, zircon, zoisite, and allanite. Alkali and alkaline earth elements are much less enriched in the solid assemblage, and thus appear to be decoupled from the other elements in the inferred metasomatic process(es). The compositions of migmatitic garnet amphibolite blocks seem to complement that of "average" island-arc tholeiite. Trace-element metasomatism reflects fluid-solid, rather than melt-solid, interaction. The metasomatic effects indicate that H2O-rich fluid, perhaps with a significant component of Na-Al silicate and alkalis, carried Th, U, Sr, REE, and HFSE. Fractionations of LREE in migmatites resemble those of migmatitic metasedimentary rocks underlying the mafic and ultramafic complex. "Exotic" LREE deposited in allanite in migmatites could have been derived from fluids in equilibrium with subducted sediment. If the paleo-subduction zone represented by the mafic and ultramafic complex of the Catalina Schist had continued its thermal and fluid evolution, a selvage of similarly enriched rocks might have been generated along the slab-mantle wedge contact between ~30 and 85 km depth. Rocks affected by "subduction-zone metasomatism," although rarely recognized at the surface, could be volumetrically significant products of the initiation of subduction and may prove to be geochemical probes of convergent margins that approach the significance of xenoliths in the study of other magmatic environments. ?? 1989.

Bidirectional Relations between Text Reading Prosody and Reading Comprehension in the Upper Primary School Grades: A Longitudinal Perspective

ERIC Educational Resources Information Center

Veenendaal, Nathalie J.; Groen, Margriet A.; Verhoeven, Ludo

2016-01-01

The purpose of this study was to examine the directionality of the relationship between text reading prosody and reading comprehension in the upper grades of primary school. We compared 3 theoretical possibilities: Two unidirectional relations from text reading prosody to reading comprehension and from reading comprehension to text reading prosody…

Geochemistry and metamorphism of the Mouriscas Complex, Ossa-Morena/Central Iberian zone boundary, Iberian Massif, Central Portugal: Implications for the Cadomian and Variscan orogenies

NASA Astrophysics Data System (ADS)

Henriques, S. B. A.; Neiva, A. M. R.; Tajčmanová, L.; Dunning, G. R.

2018-01-01

The Mouriscas Complex is a deformed and metamorphosed predominantly mafic igneous complex of Ediacaran and Ordovician age and crops out at the Ossa-Morena/Central Iberian zone boundary in the Iberian Massif, Central Portugal. It comprises amphibolite with Neoproterozoic protoliths (ca. 544 Ma), protomylonitic felsic dykes derived from younger trondhjemitic protoliths (ca. 483 Ma) and garnet amphibolite derived of even younger dioritic protoliths (ca. 477 Ma). The protoliths of the Neoproterozoic amphibolites are calc-alkaline magmas of basic to intermediate compositions with intraplate and active continental margin affinities and are considered to represent the final phase of the Cadomian arc magmatism. They are interpreted to have originated as coarse-grained intrusions, likely gabbro or diorite and generated from the partial melting of meta-igneous lower crust and mantle. Their emplacement occurred near the Cadomian metamorphic event dated at ca. 540 Ma (P = 7-8 kbar and T = 640-660 °C) which is interpreted to represent a continental collision. During the Late Cambrian-Early Ordovician an extensional episode occurred in the central-southern Iberian Massif and was also observed in other areas of the Variscan Orogen. It led to mantle upwelling and to the development of an aborted intracratonic rift located at the Ossa-Morena/Central Iberian zone boundary and to the opening of the Rheic Ocean to the south of the area studied in present coordinates (i.e., between the Ossa-Morena and South Portuguese Zones). This event has been dated at ca. 477 Ma and was responsible for the melting of deep ancient mafic crust and mantle with formation of bimodal magmatism in an intra-plate setting, as indicated by the protoliths of the protomylonitic felsic dykes with trondhjemitic composition and of the garnet amphibolite. Subsequent Variscan metamorphism took place under amphibolite facies conditions (P = 4-5.5 kbar; T = 600-625 °C) at lower P-T conditions than the Cadomian metamorphic event. It was followed by greenschist retrogression as suggested by the appearance of actinolite rims and formation of chlorite and epidote.

Geodynamic interpretation of the 40Ar/39Ar dating of ophiolitic and arc-related mafics and metamafics of the northern part of the Anadyr-Koryak region

USGS Publications Warehouse

Palandzhyan, S.A.; Layer, P.W.; Patton, W.W.; Khanchuk, A.I.

2011-01-01

Isotope datings of amphibole-bearing mafics and metamafics in the northern part of the Anadyr-Koryak region allow clarification of the time of magmatic and metamorphic processes, which are synchronous with certain stages of the geodynamic development of the northwest segment of the Pacific mobile belt in the Phanerozoic. To define the 40Ar/39Ar age of amphiboles, eight samples of amphibole gabbroids and metamafics were selected during field work from five massifs representing ophiolites and mafic plutons of the island arc. Rocks from terranes of three foldbelts: 1) Pekulnei (Chukotka region), 2) Ust-Belaya (West Koryak region), and 3) the Tamvatnei and El'gevayam subterranes of the Mainits terrane (Koryak-Kamchatka region), were studied. The isotope investigations enabled us to divide the studied amphiboles into two groups varying in rock petrographic features. The first was represented by gabbroids of the Svetlorechensk massif of the Pekulnei Range and by ophiolites of the Tamvatnei Mts.; their magmatic amphiboles show the distribution of argon isotopes in the form of clearly distinguished plateau with an age ranging within 120-129 Ma. The second group includes metamorphic amphiboles of metagabbroids and apogabbro amphibolites of the Ust-Belaya Mts., Pekulnei and Kenkeren ranges (El'gevayam subterranes). Their age spectra show loss of argon and do not provide well defined plateaus the datings obtained for them are interpreted as minimum ages. Dates of amphiboles from the metagabbro of the upper tectonic plate of the Ust-Belaya allochthon points to metamorphism in the suprasubduction environment in the fragment of Late Neoproterozoic oceanic lithosphere in Middle-Late Devonian time, long before the Uda-Murgal island arc system was formed. The amphibolite metamorphism in the dunite-clinopyroxenite-metagabbro Pekulnei sequence was dated to occur at the Permian-Triassic boundary. The age of amphiboles from gabbrodiorites of the Kenkeren Range was dated to be Early Jurassic that confirmed their assignment to the El'gevayam volcanic-plutonic assemblage. These data are consistent with geological concepts and make more precise the available age dates. Neocomian-Aptian 40Ar/39Ar age of amphibolites from the Pekulnei and Tamvatnei gabbroids make evident that mafics of these terranes (varying in geodynamic formation settings and in petrogenesis) were generated in later stages of the development of the West Pekulnei and Mainits-Algan Middle-Late Jurassic-Early Cretaceous island arc systems, presumably due to breakup of island arcs in the Neocomian. ?? 2011 Pleiades Publishing, Ltd.

Closely Reading Informational Texts in the Primary Grades

ERIC Educational Resources Information Center

Fisher, Douglas; Frey, Nancy

2014-01-01

In this article we discuss the differences between close reading in the primary grades and upper elementary grades. We focus on text selection, initial reading. repeated reading, annotation, text-based discussions, and responding to texts.

A treatment for a chronic stroke patient with a plegic hand combining CI therapy with conventional rehabilitation procedures: case report.

PubMed

Bowman, Mary H; Taub, Edward; Uswatte, Gitendra; Delgado, Adriana; Bryson, Camille; Morris, David M; McKay, Staci; Mark, Victor W

2006-01-01

Constraint-Induced Movement therapy (CI therapy) is a recognized rehabilitation approach for persons having stroke with mild to moderately severe motor upper extremity deficits. To date, no rehabilitation treatment protocol has been proven effective that addresses both motor performance and spontaneous upper extremity use in the life situation for chronic stroke participants having severe upper extremity impairment with no active finger extension or thumb abduction. This case report describes treatment of a chronic stroke participant with a plegic hand using a CI therapy protocol that combines CI therapy with selected occupational and physical therapy techniques. Treatment consisted of six sessions of adaptive equipment and upper extremity orthotics training followed by a three-week, six-hour daily intervention of CI therapy plus neurodevelopmental treatment. Outcome measures included the Motor Activity Log for very low functioning patients (Grade 5 MAL), upper extremity portion of the Fugl-Meyer Motor Assessment, Graded Wolf Motor Function Test - for very low functioning patients (gWMFT- Grade 5), and Modified Ashworth Scale. The participant showed improvement on each outcome measure with the largest improvement on the Grade 5 MAL. In follow-up, the participant had good retention of his gains in motor performance and use of his more affected arm for real world activities after 3 months; after a one-week brush-up at 3 months, and at one year post-treatment.

Pressure-temperature evolution of Neoproterozoic metamorphism in the Welayati Formation (Kabul Block), Afghanistan

NASA Astrophysics Data System (ADS)

Collett, Stephen; Faryad, Shah Wali

2015-11-01

The Welayati Formation, consisting of alternating layers of mica-schist and quartzite with lenses of amphibolite, unconformably overlies the Neoarchean Sherdarwaza Formation of the Kabul Block that underwent Paleoproterozoic granulite-facies and Neoproterozoic amphibolite-facies metamorphic events. To analyze metamorphic history of the Welayati Formation and its relations to the underlying Sherdarwaza Formation, petrographic study and pressure-temperature (P-T) pseudosection modeling were applied to staurolite- and kyanite-bearing mica-schists, which crop out to the south of Kabul City. Prograde metamorphism, identified by inclusion trails and chemical zonation in garnet from the micaschists indicates that the rocks underwent burial from around 6.2 kbar at 525 °C to maximum pressure conditions of around 9.5 kbar at temperatures of around 650 °C. Decompression from peak pressures under isothermal or moderate heating conditions are indicated by formation of biotite and plagioclase porphyroblasts which cross-cut and overgrow the dominant foliation. The lack of sillimanite and/or andalusite suggests that cooling and further decompression occurred in the kyanite stability field. The results of this study indicate a single amphibolite-facies metamorphism that based on P-T conditions and age dating correlates well with the Neoproterozoic metamorphism in the underlying Sherdarwaza Formation. The rocks lack any paragenetic evidence for a preceding granulite-facies overprint or subsequent Paleozoic metamorphism. Owing to the position of the Kabul Block, within the India-Eurasia collision zone, partial replacement of the amphibolite-facies minerals in the micaschist could, in addition to retrogression of the Neoproterozoic metamorphism, relate to deformation associated with the Alpine orogeny.

Protolith and metamorphic ages of the Haiyangsuo Complex, eastern China: A non-UHP exotic tectonic slab in the Sulu ultrahigh-pressure terrane

USGS Publications Warehouse

Liou, J.G.; Tsujimori, T.; Chu, W.; Zhang, R.Y.; Wooden, J.L.

2006-01-01

The Haiyangsuo Complex in the NE Sulu ultrahigh-pressure (UHP) terrane has discontinuous, coastal exposures of Late Archean gneiss with amphibolitized granulite, amphibolite, Paleoproterozoic metagabbroic intrusives, and Cretaceous granitic dikes over an area of about 15 km2. The U-Pb SHRIMP dating of zircons indicates that theprotolith age of a garnet-biotite gneiss is >2500 Ma, whereas the granulite-facie metamorphism occurred at around 1800 Ma. A gabbroic intrusion was dated at ???1730 Ma, and the formation of amphibolite-facies assemblages in both metagabbro and granulite occurred at ???340-460 Ma. Petrologic and geochronological data indicate that these various rocks show no evidence of Triassic eclogite-facies metamorphism and Neoproterozoic protolith ages that are characteristics of Sulu-Dabie HP-UHP rocks, except Neoproterozoic inherited ages from post-collisional Jurassic granitic dikes. Haiyangsuo retrograde granulites with amphibolite-facies assemblages within the gneiss preserve relict garnet formed during granulite-facies metamorphism at ???1.85 Ga. The Paleoproterozoic metamorphic events are almost coeval with gabbroic intrusions. The granulite-bearing gneiss unit and gabbro-dominated unit of the Haiyangsuo Complex were intruded by thin granitic dikes at about 160 Ma, which is coeval with post-collisional granitic intrusions in the Sulu terrane. We suggest that the Haiyangsuo Complex may represent a fragment of the Jiao-Liao-Ji Paleoproterozoic terrane developed at the eastern margin of the Sino-Korean basement, which was juxtaposed with the Sulu terrane prior to Jurassic granitic activity and regional deformation. ?? Springer-Verlag 2006.

Diverse mineral compositions, textures, and metamorphic P-T conditions of the glaucophane-bearing rocks in the Tamayen mélange, Yuli belt, eastern Taiwan

NASA Astrophysics Data System (ADS)

Tsai, Chin-Ho; Iizuka, Yoshiyuki; Ernst, W. G.

2013-02-01

This paper presents new petrologic data for high-pressure, low-temperature (HP-LT) metamorphic rocks at Juisui. We reinterpret the so-called "Tamayen block" (Yang and Wang, 1985) or "Juisui block" (Liou, 1981; Beyssac et al., 2008) as a tectonic mélange. It is not a coherent sheet but rather a mixture dominated by greenschist and pelitic schist with pods of serpentinite, epidote amphibolite, and rare blueschist. Four types of glaucophane-bearing rocks are newly recognized in this mélange. Type I is in contact with greenschist lacking glaucophane and garnet. Glaucophane is present only as rare inclusions within pargasite. This type records metamorphic evolution from epidote blueschists-, epidote amphibolite-, to greenschist-facies. Type II contains characteristic zoned amphiboles from barroisite core to Mg-katophorite mantle and glaucophane rim, implying an epidote amphibolite-facies stage overprinted by an epidote blueschists-facies one. Type III includes winchite and indicates P-T conditions of about 6-8 kbar, approaching 400 °C. Type IV contains paragonite but lacks garnet; amphibole shows a Na-Ca core surrounded by a glaucophane rim. This type shows a high-pressure (?) epidote amphibolite-facies stage overprinted by an epidote blueschists-facies one. Amphibole zoning trends and mineral assemblages imply contradictory P-T paths for the four types of glaucophane-bearing rocks—consistent with the nature of a tectonic mélange. The new P-T constraints and petrologic findings differ from previous studies (Liou et al., 1975; Beyssac et al., 2008).

Thermal conductivity of water-saturated rocks from the KTB pilot hole at temperatures of 25 to 300°C

USGS Publications Warehouse

Pribnow, D.; Williams, C.F.; Sass, J.H.; Keating, R.

1996-01-01

The conductivitites of selected gneiss (two) and amphibolite (one) core samples have been measured under conditions of elevated temperature and pressure with a needle-probe. Water-saturated thermal conductivity measurements spanning temperatures from 25 to 300??C and hydrostatic pressures of 0.1 and 34 MPa confirm the general decrease in conductivity with increasing temperature but deviate significantly from results reported from measurements on dry samples over the same temperature range. The thermal conductivity of water-saturated amphibolite decreases with temperature at a rate approximately 40% less than the rate for dry amphibolite, and the conductivity of water-saturated gneiss decreases at a rate approximately 20% less than the rate for dry gneiss. The available evidence points to thermal cracking as the primary cause of the more rapid decrease in dry thermal conductivity with temperature. The effects of thermal cracking were also observed in the water-saturated samples but resulted in a net decrease in room-temperature conductivity of less than 3%. These results highlight the importance of duplicating in-situ conditions when determining thermal conductivity for the deep crust.

An inverted metamorphic field gradient in the central Brooks Range, Alaska and implications for exhumation of high-pressure/low-temperature metamorphic rocks

USGS Publications Warehouse

Patrick, B.; Till, A.B.; Dinklage, W.S.

1994-01-01

During exhumation of the Brooks Range internal zone, amphibolite-facies rocks were emplaced atop the blueschist/greenschist facies schist belt. The resultant inverted metamorphic field gradient is mappable as a series of isograds encountered as one traverses up structural section. Amphibolite-facies metamorphism occurred at ??? 110 Ma as determined from 40Ar 39Ar analysis of hornblende. This contrasts with 40Ar 39Ar phengite cooling ages from the uderlying schist belt, which are clearly older (by 17-22 m.y.). Fabrics in both the amphibolite-facies rocks and schist belt are characterized by repeated cycles of N-vergent crenulation and transposition that was likely associated with out-of-sequence ductile thrusting in the internal zone of the Brooks Range orogen. Contractional deformation occurred in an overall environment of foreland-directed tectonic transport, broadly synchronous with exhumation of the internal zone, and shortening within the thin-skinned fold and thrust belt. These data are inconsistent with a recently postulated mid-Cretaceous episode of lithospheric extension in northern Alaska. ?? 1994.

Age-Grade Distribution, 1984-85. OEA Analytic Report.

ERIC Educational Resources Information Center

New York City Board of Education, Brooklyn. Office of Educational Assessment.

The 1984-85 age-grade distribution for the New York City Public Schools shows that one-third of the city's approximately 850,000 general education and resource room students were above the standard age for their grade. The proportion of overage students increased in the upper grades; in grades nine, ten, and eleven, over half were above standard…

Academic success or failure in nursing students: results of a retrospective observational study.

PubMed

Lancia, Loreto; Petrucci, Cristina; Giorgi, Fabio; Dante, Angelo; Cifone, Maria Grazia

2013-12-01

Nursing student academic failure is a phenomenon of growing international interest, not only because of its economic impact but also because it negatively affects the availability of future nurses in different healthcare systems. To recruit the students with the highest probability of academic success, an open challenge for universities is to recruit students who have previously demonstrated superior scholastic aptitudes that appear to be associated with a greater likelihood of academic success. Documenting the relationship between the selection methods used when selecting nursing students and academic failure will contribute to the international debate concerning the optimisation of the selection strategies. The principal aim of this study was to investigate the role in predicting nursing student academic success of (1) the upper-secondary diploma grades and (2) the score obtained by students in the nursing degree program admission test. A retrospective observational study was conducted. Five cohorts of nursing students, matriculated in consecutive academic years from 2004 to 2008, in an Italian bachelor's degree program were observed retrospectively. Overall, 61.2% of the 1006 considered students concluded their degree within the legal duration allowed for the nursing degree. Students who failed were those who had lowest grades associated with their upper-secondary diploma coursework (p=0.000) and were male (p=0.000). The grades associated with the upper-secondary diploma coursework, unlike the admission test score, correlates positively with the final degree grade and the average value of degree program examination scores. No correlation was found between the upper-secondary diploma coursework grades and the scores obtained in the test for the nursing degree program admission test (r=-0.037). These results suggest that upper-secondary diploma coursework grades are a parameter that should receive great consideration, especially in cases where there are planned numbers of incoming nursing degree students. Copyright © 2013 Elsevier Ltd. All rights reserved.

Geometry of a large-scale low-angle mid-crustal thrust (Woodroffe Thrust, Central Australia)

NASA Astrophysics Data System (ADS)

Wex, Sebastian; Mancktelow, Neil S.; Hawemann, Friedrich; Pennacchioni, Giorgio; Camacho, Alfredo

2015-04-01

Young orogens, such as the Alps, mainly expose the upper part of the continental crust and it is not possible to follow large-scale thrusts (e.g. the Glarus Thrust) to great depth in order to study their changing rheological behavior. This knowledge, however, is crucial for determining the overall kinematic and dynamic response during collision, as middle to lower crustal rocks represent the major part of the total crustal section. Information from deeper parts of the continental crust can only be obtained directly by investigating regions where these levels are now exhumed. The Musgrave Ranges in Central Australia is a very well exposed, semi-desert area, in which numerous large-scale shear zones developed during the Petermann Orogeny around 550 Ma. The most prominent structure is the ˜400 km long E-W trending Woodroffe Thrust, which placed ˜1.2 Ga granulites onto similarly-aged amphibolite and granulite facies gneisses along a generally south-dipping thrust plane with a top-to-north shear sense. Geothermobarometric calculations on the associated mylonites established that the structure developed under mid-crustal conditions (500-650°C, 0.8-1 GPa). Regional P/T variations in the direction of thrusting are small, but show trends consistent with the south-dipping orientation of the thrust plane, which predicts deeper levels and a higher metamorphic grade in the south than in the north. They imply a very low gradient of only around 3°C/km for a distance of some 30 km in the movement direction of the thrust. Combined with a geothermal gradient on the order of 20°C/km, calculated from four separate P/T estimates from the hanging wall and footwall, this regional gradient indicates that the Woodroffe Thrust was originally shallow-dipping at an average angle of only around 9°. This suggests that upper crustal brittle thrusts do not necessarily steepen into the middle to lower crust, but can define very shallow-dipping, large-scale planar features, with dimensions in the order of hundreds of kilometres. Such a geometry would require the rocks to be weak, but field observations (e.g. large volumes of syn-tectonic pseudotachylyte) argue for strong behaviour, involving alternating fast (seismic) fracturing and slow (aseismic) creep.

Does Grading Affect Educational Attainment? A Longitudinal Study

ERIC Educational Resources Information Center

Klapp, Alli

2015-01-01

The purpose of the study was to investigate how grading in primary school affected students' achievement measured by grades in 7th, 8th and 9th Grade and educational attainment in upper secondary school (12th Grade), and how the effect varied as a function of students' cognitive ability, gender and socio-economic status. The data derived from the…

Fluid Enhanced Deformation and Metamorphism in Exhumed Lower Crust from the Northern Madison Range, Southwestern Montana, USA

NASA Astrophysics Data System (ADS)

Condit, Cailey Brown

Deep crustal processes during collisional orogenesis exert first-order controls on the development, scale and behavior of an orogenic belt. The presence or absence of fluids play important roles in these processes by enhancing deformation, catalyzing chemical reactions, and facilitating wholesale alteration of lithologic properties. However, the scales over which these fluid-related interactions occur and the specific feedbacks among them remain poorly constrained. The late Paleoproterozoic Big Sky orogen, expressed as high-grade deep crust exposed in the Laramide basement-cored uplifts of SW Montana, USA, offers an exceptional natural laboratory to address some of these questions. New data are presented from field and structural analysis, petrology, geochemistry, and geochronology in the Northern Madison Range, a key locality for constraining the hinterland-foreland transition of the orogen. Combined with other regional data, the age of high-grade metamorphism youngs by 80-40 Myr across an 100 km transect suggesting propagation of the orogenic core towards its foreland over time. In the southeastern part of the Northern Madison Range, two domains separated by a km-scale ductile shear zone, were transformed by hydrous fluids at significantly different spatial scales. The Gallatin Peak terrane was widely metamorphosed, metasomatized, and penetratively deformed in the presence of fluids at upper amphibolite facies during the Big Sky orogeny. Together, these data suggest that this area was pervasively hydrated and deformed over scales of several kilometers during thermotectonism at 30-25 km paleodepths. In the Moon Lake block, fluid flow at similar crustal depths and temperatures played a more localized but equally important role. Discrete flow along brittle fractures in metagabbronorite dikes led to nucleation of cm-scale ductile shear zones and metasomatic alteration. A model for shear zone evolution is presented that requires feedbacks between mechanical and chemical processes for strain localization. Seismic anisotropy was calculated for one of these shear zones. Deformation-induced crystallographic preferred orientation (CPO) of anisotropic minerals typically produces seismic anisotropy in the deep crust. However, this shear zone deformed by mechanisms that yielded no significant CPO, in part due to the fluid-rich environment, and very low seismic anisotropy, suggesting that high anisotropy does not always correlate with high strain.

The Status of National Values in the Books of Social Studies for the Grades of the Upper Primary Stage in Jordan

ERIC Educational Resources Information Center

Subheyyin, Eid H.; Mawajdeh, Baker S.; Talhouni, Mansour H.; Rfou', Mohammad O.

2017-01-01

This study aimed at determining the most important national values that should be included in the textbooks of social studies for the upper-primary stage grades in Jordan; and then identifying the degree of their inclusion in those books. The study used a descriptive-analytical approach. A study tool which includes twelve national values was…

Validity of Alternative Fitnessgram Upper Body Tests of Muscular Strength and Endurance among Seventh and Eighth Grade Males and Females

ERIC Educational Resources Information Center

Hobayan, Kalani; Patterson, Debra; Sherman, Clay; Wiersma, Lenny

2014-01-01

In a society in which obesity levels have tripled in the past 30 years, the importance of increased fitness levels within the academic setting has become even more critical. The purpose of this study was to investigate the validity of alternative Fitnessgram upper body tests of muscular strength and endurance among seventh and eighth grade males…

Protracted or multiple subduction of metapelites (Rhodope UHP domain, Greece)?

NASA Astrophysics Data System (ADS)

Krohe, A.; Wawrzenitz, N. H.; Mposkos, E.; Romer, R. L.

2012-12-01

The Rhodope domain formed along the suture between the European and the Apulian/Adriatic plate, which collided in the early Tertiary (closure of the Vardar/Axios ocean). Its metamorphic history includes UHP metamorphism documented by diamond inclusions in garnet (Mposkos & Kostopoulos 2001, Perraki et al. 2006, Schmidt et al. 2010), presumably of Jurassic age, and Eocene stages of MP and HP metamorphism. The age of UHPM is still a matter of debate: U-Pb SHRIMP ages extend from 184-172 Ma (monazite in metapelites) to ca. 42 Ma with clusters at 170-160, 150-140, 80-60, 50, 42 Ma, (U-Pb SHRIMP dating of zircon from amphibolitized eclogites and metapelites). These ages are interpreted to date subsequent stages of (U)HP metamorphism and decompression (Liati et al., 2005, Hoinkes et al. 2008, Bauer et al. 2006, Krenn et al 2010). However, these ages are obviously difficult to link with the metamorphic reactions. The metamorphic history has been interpreted in different ways, reflecting: (i) successive accretion of small terranes with rapid subduction and uplift histories (e.g. Liati et al. 2005); (ii) a composite of different tectonic units varying in earlier P-T histories, assembled by shear zones that reflect tectonic erosion and differential exhumation along the plate interface and that are now erased and overprinted (Krohe and Mposkos, 2002, Mposkos et al., 2010). These interpretations imply a different kinematics of the tectonic movements at depths, mechanical processes and process rates. Additionally, a protracted polymetamorphic history of larger volumes of the Rhodope UHP domain may be considered; e.g. the Kimi complex stayed in the lower crust for ca. 50-60 Ma after exhumation of the UHP rocks to this lower crustal level (Mposkos and Krohe, 2006). To constrain a precise age of the HP granulite facies and a minimum age of UHP metamorphism, we conduct an integrated structural, petrologic and geochronological study in a metapelite from the Sidronero Complex. The mineral assemblages Grt-Ky-Bt-Pl-Kfs-Qtz-Rt and Grt-Ky-Bt-Ms-Pl-Qtz-Rt, record a HP granulite facies metamorphism followed by upper amphibolite facies. The rock is particularly well suited for studying the granulite facies metamorphism, as it contains domains that are only weakly overprinted by later metamorphic episodes. ID-TIMS U-Pb ages of single monazite grains and fractions of few grains, that are only locally patchy-zoned and associated with garnet and kyanite, plot along the concordia between 64 to 60 Ma. One date of 55 Ma might represent Pb-loss during later fluid-induced dissolution-reprecipitation, probably related to biotite growth during the amphibolite facies overprint. On the base of these data, a model is discussed, in which rocks from the upper plate and HP-rocks that have been already exhumed, were dragged again into the subduction channel by subduction erosion Bauer et al. 2006, Lithos, 29, 207-228; Hoinkes et al. 2008, 3rd IGC Oslo, UHP-4; Krenn et al 2010, Tectonics, 29, TC4001; Krohe & Mposkos, 2002, Geol. Soc. Sp. Pub. 204, 151-178; Liati, A., 2005, Contrib. Mineral. Petrol., 150, 608-630; Mposkos, & Kostopoulos, 2001, EPSL, 192, 497-506; Mposkos & Krohe, 2006. Can. J. Earth Sci., 43, 1755-1776; Mposkos et al., 2010 Proc. XIX CBGA Congress, 100, 173-178; Perraki et al., 2006, EPSL, 241, 672-685; Schmidt et al., 2010, EJM, 22, 189-198.

A Week for Space

ERIC Educational Resources Information Center

Comstock, Diane

2008-01-01

Space Week focuses on concepts that enable students to make concrete observations in the early grades (K-2) and move to concepts that help students develop their internet research and writing skills in middle and upper grades (Grades 3-5), and culminates with the development of science investigation design skills (Grade 6). To help launch your…

A crustal model of the ultrahigh-pressure Dabie Shan orogenic belt, China, derived from deep seismic refraction profiling

USGS Publications Warehouse

Wang, Chun-Yong; Zeng, Rong-Sheng; Mooney, W.D.; Hacker, B.R.

2000-01-01

We present a new crustal cross section through the east-west trending ultrahigh-pressure (UHP) Dabie Shan orogenic belt, east central China, based on a 400-km-long seismic refraction profile. Data from our profile reveal that the cratonal blocks north and south of the orogen are composed of 35-km-thick crust consisting of three layers (upper, middle, and lower crust) with average seismic velocities of 6.0±0.2 km/s, 6.5±0.1 km/s, and 6.8±0.1 km/s. The crust reaches a maximum thickness of 41.5 km beneath the northern margin of the orogen, and thus the present-day root beneath the orogen is only 6.5 km thick. The upper mantle velocity is 8.0±0.1 km/s. Modeling of shear wave data indicate that Poisson's ratio increases from 0.24±0.02 in the upper crust to 0.27±0.03 in the lower crust. This result is consistent with a dominantly felsic upper crustal composition and a mafic lower crustal composition within the amphibolite or granulite metamorphic facies. Our seismic model indicates that eclogite, which is abundant in surface exposures within the orogen, is not a volumetrically significant component in the middle or lower crust. Much of the Triassic structure associated with the formation of the UHP rocks of the Dabie Shan has been obscured by post-Triassic igneous activity, extension and large-offset strike-slip faulting. Nevertheless, we can identify a high-velocity (6.3 km/s) zone in the upper (<5 km depth) crustal core of the orogen which we interpret as a zone of ultrahigh-pressure rocks, a north dipping suture, and an apparent Moho offset that marks a likely active strike-slip fault.

Petrogenesis and tectonic association of rift-related basic Panjal dykes from the northern Indian plate, North-Western Pakistan: evidence of high-Ti basalts analogous to dykes from Tibet

NASA Astrophysics Data System (ADS)

Sajid, Muhammad; Andersen, Jens; Arif, Mohammad

2017-10-01

Rift related magmatism during Permian time in the northern margin of Indian plate is represented by basic dykes in several Himalayan terranes including north western Pakistan. The field relations, mineralogy and whole rock geochemistry of these basic dykes reveal significant textural, mineralogical and chemical variation between two major types (a) dolerite and (b) amphibolite. Intra-plate tectonic settings for both rock types have been interpreted on the basis of low Zr/Nb ratios (< 10), K/Ba ratios (20-40) and Hf-Ta-Th and FeO-MgO-Al2O3 discrimination diagrams. The compositional zoning in plagioclase and clinopyroxene, variation in olivine compositions and major elements oxide trends indicate a vital role of fractional crystallization in the evolution of dolerites, which also show depletion in rare earth elements (REEs) and other incompatible elements compared to the amphibolites. The equilibrium partial melting models from primitive mantle using Dy/Yb, La/Yb, Sm/Yb and La/Sm ratios show that amphibolite formed by smaller degrees (< 5%) of partial melting than the dolerites (< 10%). The trace elements ratios suggest the origination of dolerites from the subcontinental lithospheric mantle with some crustal contamination. This is consistent with a petrogenetic relationship with Panjal trap magmatism, reported from Kashmir and other parts of north western India. The amphibolites, in contrast, show affinity towards Ocean Island basalts (OIB) with a relatively deep asthenospheric mantle source and minimal crustal contribution and are geochemically similar to the High-Ti mafic dykes of southern Qiangtang, Tibet. These similarities combined with Permian tectonic restoration of Gondwana indicate the coeval origin for both dykes from distinct mantle source during continental rifting related to formation of the Neotethys Ocean.

Geochemical investigation of Archaean Bimodal and Dwalile metamorphic suites, Ancient Gneiss Complex, Swaziland

USGS Publications Warehouse

Hunter, D.R.; Barker, F.; Millard, H.T.

1984-01-01

The bimodal suite (BMS) comprises leucotonalitic and trondhjemitic gneisses interlayered with amphibolites. Based on geochemical parameters three main groups of siliceous gneiss are recognized: (i) SiO2 14%, and fractionated light rare-earth element (REE) and flat heavy REE patterns; (ii) SiO2 and Al2O3 contents similar to (i) but with strongly fractionated REE patterns with steep heavy REE slopes; (iii) SiO2 > 73%, Al2O3 < 14%, Zr ??? 500 ppm and high contents of total REE having fractionated light REE and flat heavy REE patterns with large negative Eu anomalies. The interlayered amphibolites have major element abundances similar to those of basaltic komatiites, Mg-tholeiites and Fe-rich tholeiites. The former have gently sloping REE patterns, whereas the Mg-tholeiites have non-uniform REE patterns ranging from flat (??? 10 times chondrite) to strongly light REE-enriched. The Fe-rich amphibolites have flat REE patterns at 20-30 times chondrite. The Dwalile metamorphic suite, which is preserved in the keels of synforms within the BMS, includes peridotitic komatiites that have depleted light REE patterns similar to those of compositionally similar volcanics in the Onverwacht Group, Barberton, basaltic komatiites and tholeiites. The basaltic komatiites have REE patterns parallel to those of the BMS basaltic komatiites but with lower total REE contents. The Dwalile tholeiites have flat REE patterns. The basic and ultrabasic liquids were derived by partial melting of a mantle source which may have been heterogeneous or the heterogeneity may have resulted from sequential melting of the mantle source. The Fe-rich amphibolites were derived either from liquids generated at shallow levels or from liquids generated at depth which subsequently underwent extensive fractionation. ?? 1984.

The Age and Geodynamic Evolution of the Metamorphic sole rocks from Izmir-Ankara-Erzıncan suture zone (Northern-Turkey)

NASA Astrophysics Data System (ADS)

Melih Çörtük, Rahmi; Faruk Çelik, Ömer; Özkan, Mutlu; Sherlock, Sarah C.; Marzoli, Andrea; Altıntaş, İsmail Emir; Topuz, Gültekin

2016-04-01

The İzmir-Ankara-Erzincan suture zone in northern Turkey is one of the major tectonic zones separating the Pontides to the North from the Anatolide-Tauride block and Kı rşehir Massif to the South. The accretionary complex of the İzmir-Ankara-Erzincan suture zone, near Artova, is composed mainly of peridotites with varying degree serpentinization, metamorphic rocks, basalt, sandstones, pelagic and neritic limestones. The metamorphic rocks are represented by amphibolite, garnet micaschit, calc-schist and marble. The metamorphic rocks were interpreted as the metamorphic sole rocks. Because; (i) They are tectonically located beneath the serpentinized peridotites. (ii) Foliation planes of both the amphibolites and mantle tectonites are parallel to each other. (iii) The metamorphic rocks are crosscut by non-metamorphic dolerite dikes which exhibite Nb and Ta depletion relative to Th enrichment on the N-MORB normalized multi-element spider diagram. The dolerite dikes display flat REE patterns (LaN/YbN=0.85-1.24). These geochemical signatures of the dolerite dikes are indicative of subduction component during their occurrences. Geochemical observations of the amphibolites suggest E-MORB- and OIB-like signatures (LaN/SmN= 1.39-3.14) and their protoliths are represented by basalt and alkali basaltic rocks. Amphiboles from the amphibolites are represented by calcic amphiboles (magnesio-hornblende, tchermakite and tremolite) and they yielded 40Ar-39Ar ages between 157.8 ± 3.6 Ma and 139 ± 11 Ma. These cooling ages were interpreted to be the intra-oceanic subduction/thrusting time of the İzmir-Ankara-Erzincan oceanic domain. This study was funded by TÜBİTAK (Project no: 112Y123).

Petrogenesis and tectonic association of rift-related basic Panjal dykes from the northern Indian plate, North-Western Pakistan: evidence of high-Ti basalts analogous to dykes from Tibet

NASA Astrophysics Data System (ADS)

Sajid, Muhammad; Andersen, Jens; Arif, Mohammad

2018-06-01

Rift related magmatism during Permian time in the northern margin of Indian plate is represented by basic dykes in several Himalayan terranes including north western Pakistan. The field relations, mineralogy and whole rock geochemistry of these basic dykes reveal significant textural, mineralogical and chemical variation between two major types (a) dolerite and (b) amphibolite. Intra-plate tectonic settings for both rock types have been interpreted on the basis of low Zr/Nb ratios (< 10), K/Ba ratios (20-40) and Hf-Ta-Th and FeO-MgO-Al2O3 discrimination diagrams. The compositional zoning in plagioclase and clinopyroxene, variation in olivine compositions and major elements oxide trends indicate a vital role of fractional crystallization in the evolution of dolerites, which also show depletion in rare earth elements (REEs) and other incompatible elements compared to the amphibolites. The equilibrium partial melting models from primitive mantle using Dy/Yb, La/Yb, Sm/Yb and La/Sm ratios show that amphibolite formed by smaller degrees (< 5%) of partial melting than the dolerites (< 10%). The trace elements ratios suggest the origination of dolerites from the subcontinental lithospheric mantle with some crustal contamination. This is consistent with a petrogenetic relationship with Panjal trap magmatism, reported from Kashmir and other parts of north western India. The amphibolites, in contrast, show affinity towards Ocean Island basalts (OIB) with a relatively deep asthenospheric mantle source and minimal crustal contribution and are geochemically similar to the High-Ti mafic dykes of southern Qiangtang, Tibet. These similarities combined with Permian tectonic restoration of Gondwana indicate the coeval origin for both dykes from distinct mantle source during continental rifting related to formation of the Neotethys Ocean.

Can the Metamorphic Basement of Northwestern Guatemala be Correlated with the Chuacús Complex?

NASA Astrophysics Data System (ADS)

Cacao, N.; Martens, U.

2007-05-01

The Chuacús complex constitutes a northward concave metamorphic belt that stretches ca. 150 km south of the Cuilco-Chixoy-Polochic (CCP) fault system in central and central-eastern Guatemala. It represents the basement of the southern edge of the Maya block, being well exposed in the sierra de Chuacús and the sierra de Las Minas. It is composed of high-Al metapelites, amphibolites, quartzofeldspathic gneisses, and migmatites. In central Guatemala the Chuacús complex contains ubiquitous epidote-amphibolite mineral associations, and local relics of eclogite reveal a previous high-pressure metamorphic event. North of the CCP, in the Sierra de Los Cuchumatanes area of western Guatemala, metamorphic rocks have been considered the equivalent of the Chuacús complex and hence been given the name Western Chuacús group, These rocks, which were intruded by granitic rocks and later mylonitized, include chloritic schist and gneiss, biotite-garnet schist, migmatites, and amphibolites. No eclogitic relics have been found within metamorphic rocks in northwestern Guatemala. Petrographic analyses of garnet-biotite schist reveal abundant retrogression and the formation of abundant zeolite-bearing veins associated with intrusion. Although metamorphic conditions in the greenschist and amphibolite facies are similar to those in the sierra de Chuacús, the association with deformed intrusive granites is unique for western Guatemala. Hence a correlation with metasediments intruded by the Rabinal granite in the San Gabriel area of Baja Verapaz seems more feasible than a correlation with the Chuacús complex. This idea is supported by reintegration of the Cenozoic left-lateral displacement along the CCP, which would place the metamorphic basement of western Guatemala north of Baja Verapaz, adjacent to metasediments intruded by granites in the San Gabriel-Rabinal area.

The eye of the field geologist and the mind of the tectonician: one view of dynamic crustal rheology in convergent orogens

NASA Astrophysics Data System (ADS)

Brown, M.

2004-05-01

Orogens record evidence of interaction between converging plates. However, the response of continental crust to tectonic and gravitational loads is dependent on rheology, which is influenced by composition, architecture, thermal profile and strain rate. Crustal rocks undergo melting in deeper parts of orogens. Greywackes and metapelites are the most fertile protoliths, generating 20-50 and 30 vol. % melt respectively at 1 GPa and 1173K; geophysical data suggest >6 but <20 vol. % interconnected melt in deep crust of active orogens. In numerical models of orogens, the transition from coupled doubly-vergent wedge structure to plateau formation and full basal decoupling requires a viscosity drop of 4 orders of magnitude, inferred to be melt weakening. Deformation experiments on granite indicate a dramatic drop in strength (to 100-200 MPa) as the melt wetting transition is approached at 7 vol. % melt, and a more gradual decrease to <1 MPa prior to the drop at the solid-to-liquid transition (RCMP). Important properties of melting systems are viscosity of the melt, rheology of the crystalline framework of grains and permeability of this framework to flow. Permeability is due to an intergranular network of connected pores, compositional layering/fabric and networks of deformation bands; melt distribution is heterogeneous on multiple length scales. The microstructure of anatectic rocks and the magnitude of weakening accompanying melting suggest a limited role for intracrystalline plasticity with increasing vol. % melt and dominance of melt-assisted diffusion creep or diffusion accommodated granular flow. The intrinsic weakness of melt-bearing intervals in the crust makes them ideal detachment horizons. Observations from metasedimentary migmatitic granulites show preservation of (i) early fabrics, suggesting that the strain field emergent under subsolidus conditions controlled initial distribution of melt produced by suprasolidus mica breakdown, and (ii) layering in melt-depleted rocks, implying that they were quasi-continuously drained. Studies of migmatitic granulites demonstrate that melt migrates from grain boundaries to mesoscale networks of structures (mm to m) to steeply-inclined conduits recorded by rod or tabular granite intrusions (m to dm). Melt loss from lower crust yields residual rocks composed of strong minerals (feldspar, pyroxene and garnet) with only minor melt on grain boundaries. Thus, weakening of lower crust due to melting is followed by its strengthening. Around the brittle-to-viscous transition zone granite accumulates in subhorizontal tabular plutons, which implies transient presence of significantly weaker layers in shallow orogenic crust; these are potential detachment horizons. Field studies of exhumed orogens suggest deformation commonly is laterally, transversely and vertically diachronous, reflecting the spatial and temporal variation in the weakening-to-strengthening cycle. There may be important sub-horizontal movement horizons, which allow (partial) decoupling of crustal layers. At upper-to-middle crustal levels rocks are metamorphosed in greenschist-amphibolite facies, with local enhancement by pluton-advected heat to amphibolite-granulite facies and thrust-style brittle-ductile deformation (e.g., Acadian, NH). Rocks from middle crustal levels are in amphibolite facies and have penetrative steep fabrics (e.g., Acadian, western ME) or exhibit a complex network of shallowly- and steeply-dipping fabrics (e.g., St. Malo, France). Rocks from lower crustal levels are in amphibolite-granulite facies and have shallow fabrics due to crustal flow, although these may be steepened by later deformation including core-complex formation (e.g., S. Brittany, France).

High-Intensity Intermittent Training Positively Affects Aerobic and Anaerobic Performance in Judo Athletes Independently of Exercise Mode

PubMed Central

Franchini, Emerson; Julio, Ursula F.; Panissa, Valéria L. G.; Lira, Fábio S.; Gerosa-Neto, José; Branco, Braulio H. M.

2016-01-01

Purpose: The present study investigated the effects of high-intensity intermittent training (HIIT) on lower- and upper-body graded exercise and high-intensity intermittent exercise (HIIE, four Wingate bouts) performance, and on physiological and muscle damage markers responses in judo athletes. Methods: Thirty-five subjects were randomly allocated to a control group (n = 8) or to one of the following HIIT groups (n = 9 for each) and tested pre- and post-four weeks (2 training d·wk−1): (1) lower-body cycle-ergometer; (2) upper-body cycle-ergometer; (3) uchi-komi (judo technique entrance). All HIIT were constituted by two blocks of 10 sets of 20 s of all out effort interspersed by 10 s set intervals and 5-min between blocks. Results: For the upper-body group there was an increase in maximal aerobic power in graded upper-body exercise test (12.3%). The lower-body group increased power at onset blood lactate in graded upper-body exercise test (22.1%). The uchi-komi group increased peak power in upper- (16.7%) and lower-body (8.5%), while the lower-body group increased lower-body mean power (14.2%) during the HIIE. There was a decrease in the delta blood lactate for the uchi-komi training group and in the third and fourth bouts for the upper-body training group. Training induced testosterone-cortisol ratio increased in the lower-body HIIE for the lower-body (14.9%) and uchi-komi (61.4%) training groups. Conclusion: Thus, short-duration low-volume HIIT added to regular judo training was able to increase upper-body aerobic power, lower- and upper-body HIIE performance. PMID:27445856

Significance of Ureteroscopic Biopsy Grade in Patients with Upper Tract Urothelial Carcinoma

PubMed Central

Furukawa, Junya; Miyake, Hideaki; Sakai, Iori; Fujisawa, Masato

2013-01-01

Background The objective of this study was to assess the significance of the ureteroscopic biopsy grade for patients with upper tract urothelial carcinoma (UTUC). Patients and Methods This study included 40 patients who were diagnosed with a single focus of UTUC by ureteroscopic biopsy and subsequently underwent nephroureterectomy. The significance of the biopsy grade as a predictive factor for pathological outcomes of nephroureterectomy was retrospectively analyzed. Results Of these 40 patients, 19 (47.5%) and 21 (52.5%) were diagnosed with low and high grade UTUC, respectively. The ureteroscopic biopsy grade matched the pathological grade of surgically resected specimens in 35 of the 40 cases (87.5%), and there was a significant correlation between the biopsy and pathological grades (p < 0.001). Furthermore, the biopsy grade was also shown to be closely associated with the pathological stage (p < 0.001); that is, only 1 of the 19 patients (5.3%) with biopsy low grade UTUC were pathologically diagnosed as having muscle invasive disease, while 17 of the 21 patients (81.0%) with biopsy high grade UTUC appeared to show tumor invasion into muscle or deeper. Conclusions The grade of UTUC on ureteroscopic biopsy could provide accurate diagnostic information on the final pathology of nephroureterectomy specimens. PMID:24917735

Nature and geodynamic setting of the protoliths of the UHP metamorphic Complex and migmatites in Bixiling area, the Dabie Orogen, China

NASA Astrophysics Data System (ADS)

Li, H.; Jahn, B.; Wang, D.; Yu, H.; Liu, Z.; Hou, G.

2013-12-01

As the largest coesite-bearing mafic-ultramafic body in the Dabie-Sulu orogen, the Bixiling Complex is composed of meta-ultramafic rocks, MgAl-rich eclogites and FeTi-rich eclogites. The FeTi-rich eclogites are further divided into low-Si-high-Fe type (Type I) and high-Si-low-Fe type (Type II) according to their mineral assemblages and bulk chemical composition. Field, petrographic, petrological and geochemical characteristics of these rocks, although suffered an ultra-high pressure metamorphism, still show a magmatic differentiation process among the protoliths of the meta-ultramafic rocks, MgAl-rich eclogites and Type I FeTi-rich eclogites. A small degree of lower crustal contamination occurred during their magma chamber process. Amphibolite is widespread in the periphery of the complex. Non-foliation and fine-grained texture are their obvious characteristics. Geochemical and isotopic affinities suggest that the amphibolites represent a product of complete retrogression from type II FeTi-rich eclogites. The UHP complex is enclosed in granitic gneisses, which variably include two-mica plagioclase gneiss, epidote two-mica plagioclase gneiss, or white-mica plagioclase gneiss. They all show TTG, especially trondjhemitic composition. A migmatite outcrop was found near the northeastern end of the complex. The migmatites consist of dark colored, non-foliated amphibolites and light-colored, fine-grained trondhjemitic gneisses. Field occurrences, microstructures observed under optical microscope and SEM, Sr-Nd isotopic data suggest an origin of partial melting. Chemical composition of two stages of amphiboles occurred in both the amphibolites and the trondhjemitic gneisses also imply a partial melting process occurred. Trace element, Sr-Nd isotope and SHRIMP zircon U-Pb dating of MgAl-rich eclogite, amphibolites and trondhjemite suggest that the migmatites represent a partial melting of crustal materials at about 780Ma, possibly accompanied by the coeval emplacement of a differentiated mafic intrusive body. These rocks were deeply subducted into a mantle depth during the Triassic continental collision between the Yangtze Craton and North China Craton, and thereafter were exhumed to the surface. Their residual geochemical characteristics and spatial / temporal relationship could impose constraints on the tectonic evolution of the Dabieshan UHP terrane.

Late Neoproterozoic metamorphic assemblages along the Pan-African Hamisana Shear Zone, southeastern Egypt: Metamorphism, geochemistry and petrogenesis

NASA Astrophysics Data System (ADS)

Ali-Bik, Mohamed W.; Sadek, Mohamed F.; Ghabrial, Doris Sadek

2014-11-01

A variety of Late Neoproterozoic gneisses and amphibolites are distributed along the N-S trending Hamisana Shear Zone (HSZ), in southeastern Egypt. The HSZ originated after the accretion of the Arabian-Nubian Shield (ANS) and covers an area of about 1500 km2 in southeastern Egypt and northeastern Sudan. The architecture of the northern part of the HSZ is best explained as a tectono-stratigraphic column, in which allochthonous ophiolitic mélange was thrusted onto metamorphosed island-arc assemblages (gneisses and amphibolites). The latter rock units were generally subjected to two successive phases of amphibolite facies metamorphism, followed by a thermal phase and retrograde overprint. The early penetrative, low- to medium-pressure metamorphism (M1) was synchronous with D1-gneissosity and N-S trending lineation, demarcating the high strain HSZ. The mineral assemblages formed during the M1 phase include quartz + andesine + hornblende (I) + biotite (I) in hornblende-biotite gneiss, quartz + andesine + pargasitic hornblende (I) + ferroan pargasitic hornblende (I) + edenitic hornblende (I) in hornblende-schist, quartz + plagioclase + biotite + muscovite in psammopelitic gneiss, and diopside + tremolite + calcite + sphene ± garnet in calc-silicates, being characteristic for amphibolite facies with metamorphic conditions of 600 ± 50 °C and 5-6.5 kbar. The second metamorphic phase (M2) is related to the crystallization of biotite and/or hornblende in S2 foliation demarcating the NE-SW trending dextral shear deformation (D2). The calculated temperature for this M2 phase is about 592 °C. Subsequent thermal events are documented by growth of spinel and scapolite in calc-silicate rocks and of cordierite in psammopelitic gneiss in response to uplift, decomposition and heat provided by the nearby late-formed igneous intrusions. Finally, the rocks reached a temperature of about 530 °C during the cooling retrogressive stage. Based on geological, petrological and geochemical investigations, the island arc assemblages are grouped into: (a) meta-igneous rocks (hornblende-biotite gneiss, biotite gneiss and amphibolites) and (b) metasedimentary rocks (psammopelitic gneiss, hornblende-schist and calc-silicates). Geochemical inspection revealed the non-consanguineous nature of these rock units. They represent subduction-related, theoleiitic and calc-alkaline magmatic rocks and their concomitant sedimentary derivations as well as minor continental shelf calcareous sediments. In terms of maturity, the geochemical signatures of these subduction-related rocks point to an immature volcanic arc origin.

Three-Year Study of Students' Attitudes toward Physical Education: Grades 4-8

ERIC Educational Resources Information Center

Mercier, Kevin; Donovan, Corinne; Gibbone, Anne; Rozga, Kimberly

2017-01-01

Purpose: A relationship exists between attitudes toward physical education and future physical activity. The purpose of this study was to examine changes in attitude toward physical education as students progressed from upper elementary school (Grade 4) through middle school (Grade 8). Method: Three cohorts of students (Cohort 1, Grades 4-6,…

Bidirectional Relations between Text Reading Prosody and Reading Comprehension in the Upper Primary School Grades: A Longitudinal Perspective

PubMed Central

Veenendaal, Nathalie J.; Groen, Margriet A.; Verhoeven, Ludo

2016-01-01

The purpose of this study was to examine the directionality of the relationship between text reading prosody and reading comprehension in the upper grades of primary school. We compared three theoretical possibilities: Two unidirectional relations from text reading prosody to reading comprehension and from reading comprehension to text reading prosody and a bidirectional relation between text reading prosody and reading comprehension. Further, we controlled for autoregressive effects and included decoding efficiency as a measure of general reading skill. Participants were 99 Dutch children, followed longitudinally, from fourth- to sixth-grade. Structural equation modeling showed that the bidirectional relation provided the best fitting model. In fifth-grade, text reading prosody was related to prior decoding and reading comprehension, whereas in sixth-grade, reading comprehension was related to prior text reading prosody. As such, the results suggest that the relation between text reading prosody and reading comprehension is reciprocal, but dependent on grade level. PMID:27667916

Kilbuck terrane: oldest known rocks in Alaska

USGS Publications Warehouse

Box, S.E.; Moll-Stalcup, E. J.; Wooden, J.L.; Bradshaw, J.Y.

1990-01-01

The Kilbuck terrane in southwestern Alaska is a narrow, thin crustal sliver or flake of amphibolite facies orthogneiss. The igneous protolith of this gneiss was a suite of subduction-related plutonic rocks. U-Pb data on zircons from trondhjemitic and granitic samples yield upper-intercept (igneous) ages of 2070 ?? 16 and 2040 ?? 74 Ma, respectively. Nd isotope data from these rocks suggest that a diorite-tonalite-trondhjemite suite (??Nd[T] = +2.1 to +2.7; T is time of crystallization) evolved from partial melts of depleted mantle with no discernible contamination by older crust, whereas a coeval granitic pluton (??Nd[T] = -5.7) contains a significant component derived from Archean crust. Orthogneisses with similar age and Nd isotope characteristics are found in the Idono complex 250 km to the north. Early Proterozoic rocks are unknown elsewhere in Alaska. The possibility that the Kilbuck terrane was displaced from provinces of similar age in other cratons (e.g., Australian, Baltic, Guiana, and west African shields), or from the poorly dated Siberian craton, cannot be excluded. -from Authors

Tectono-metamorphic evolution of high-P/T and low-P/T metamorphic rocks in the Tia Complex, southern New England Fold Belt, eastern Australia: Insights from K-Ar chronology

NASA Astrophysics Data System (ADS)

Fukui, Shiro; Tsujimori, Tatsuki; Watanabe, Teruo; Itaya, Tetsumaru

2012-10-01

The Tia Complex in the southern New England Fold Belt is a poly-metamorphosed Late Paleozoic accretionary complex. It consists mainly of high-P/low-T type pumpellyite-actinolite facies (rare blueschist facies) schists, phyllite and serpentinite (T = 300 °C and P = 5 kbar), and low-P/high-T type amphibolite facies schist and gneiss (T = 600 °C and P < 5 kbar) associated with granodioritic plutons (Tia granodiorite). White mica and biotite K-Ar ages distinguish Carboniferous subduction zone metamorphism and Permian granitic intrusions, respectively. The systematic K-Ar age mapping along a N-S traverse of the Tia Complex exhibits a gradual change. The white mica ages become younger from the lowest-grade zone (339 Ma) to the highest-grade zone (259 Ma). In contrast, Si content of muscovite changes drastically only in the highest-grade zone. The regional changes of white mica K-Ar ages and chemical compositions of micas indicate argon depletion from precursor high-P/low-T type phengitic white mica during the thermal overprinting and recrystallization by granitoids intrusions. Our new K-Ar ages and available geological data postulate a model of the eastward rollback of a subduction zone in Early Permian. The eastward shift of a subduction zone system and subsequent magmatic activities of high-Mg andesite and adakite might explain formation of S-type granitoids (Hillgrove suite) and coeval low-P/high-T type metamorphism in the Tia Complex.

A detrital garnet fingerprint of the Central Swiss Alps

NASA Astrophysics Data System (ADS)

Stutenbecker, Laura; Berger, Alfons; Schlunegger, Fritz

2017-04-01

Detrital garnet is a promising candidate to reliably fingerprint sediment sources in the Alps, which has so far been complicated by the wide range and similarity of some of the lithologies. Garnet is present in most Alpine sediments, is easy to identify, is fairly stable and, most importantly, reflects the type and the metamorphic grade of its source rock in its chemical composition. This study aims to establish fingerprints based on detrital garnet composition for the most important tectonic units of the Central Alps, including European, Penninic and Adriatic basement rocks and their respective meta-sedimentary cover. Sediments collected from modern rivers, which drain representative portions of the individual tectonic units, contain a natural mixture of the various garnet populations present in each unit. We selected six catchments in southwestern Switzerland draining the External Massifs, Helvetic sediments and the Penninic nappe stack at the transition of Alpine greenschist- to amphibolite-facies metamorphism in order to test the variability of Alpine garnets and the role of inherited (pre-Alpine) garnets. Extraordinary grossular- and spessartine-rich garnets of the External massifs, which experienced greenschist facies metamorphism, are clearly distinguishable from generally almandine-rich garnets supplied by the higher-grade metamorphic Penninic nappe stack. The variable pyrope-, grossular- and spessartine-components of these almandine-rich garnets can be used to further distinguish pre-Alpine, Alpine eclogite-facies and low-grade metasedimentary garnets. This fingerprint has the potential to be used for reconstructing sediment sources, transport and dispersal patterns in a variety of settings throughout the Alpine sedimentary record.

The potential of detrital garnet as a provenance proxy in the Central Swiss Alps

NASA Astrophysics Data System (ADS)

Stutenbecker, Laura; Berger, Alfons; Schlunegger, Fritz

2017-04-01

Detrital garnet is a promising candidate to reliably fingerprint sediment sources in the Alps, which has so far been complicated by the wide range and similarity of some of the lithologies. Garnet is present in most Alpine sediments, is easy to identify, is fairly stable and, most importantly, reflects the type and the metamorphic grade of its source rock in its chemical composition. This study aims to establish fingerprints based on detrital garnet composition for the most important tectonic units of the Central Alps, including European, Penninic and Adriatic basement rocks and their respective metasedimentary covers. Sediments collected from modern rivers, which drain representative portions of the individual tectonic units, contain a natural mixture of the various garnet populations present in each unit. We selected six catchments in southwestern Switzerland draining the External massifs, Helvetic sediments and the Penninic nappe stack at the transition of Alpine greenschist- to amphibolite-facies metamorphism in order to test the variability of Alpine garnets and the role of inherited (pre-Alpine) garnets. Extraordinary grossular- and spessartine-rich garnets of the External massifs, which experienced greenschist facies metamorphism, are clearly distinguishable from generally almandine-rich garnets supplied by the higher-grade metamorphic Penninic nappe stack. The variable pyrope, grossular and spessartine components of these almandine-rich garnets can be used to further distinguish pre-Alpine, Alpine eclogite-facies and low-grade metasedimentary garnets. This provenance proxy has the potential to be used for reconstructing sediment sources, transport and dispersal patterns in a variety of settings throughout the Alpine sedimentary record.

Harper Creek and Cuyamaca Reservoir gneisses, CLMSZ: Late Jurassic plutons of the Peninsular Ranges batholith

DOE Office of Scientific and Technical Information (OSTI.GOV)

Miller, J.; Girty, G.H.; Girty, M.S.

1993-04-01

The Cuyamaca Laguna Mountains shear zone (CLMSZ), southern California, has been interpreted to represent east-over-west thrusting resulting from Early Cretaceous arc-continent collision. Near Pine Valley, the western margin of the CLMSZ is underlain by the Harper Creek (HCg) and Cuyamaca Reservoir (CRg) gneisses. U-Pb zircon studies indicate ages of 161 [+-] 17 Ma and 156 [+-] 12 Ma for the Hcg and an age of 158 Ma for the CRg. Geochemically the HCg and CRg are calc-alkaline and peraluminous. Trace element data suggest a magmatic arc setting. Modal and normative mineralogy suggest granodioritic and tonalitic protoliths. Mineral assemblages indicate uppermore » greenschist facies to lower amphibolite grade conditions during deformation. The HCg and CRg were deformed prior to the emplacement of the adjacent 118 [+-] 9 Ma Pine Valley pluton. Structural fabrics described above suggest NE-SW contraction and subvertical extension and are thus compatible with the arc-continent collisional model proposed by earlier workers.« less

Metamorphozed Hercynian granitoids in the Alpine structures of the Central Rhodope, Bulgaria: geotectonic position and geochemistry

NASA Astrophysics Data System (ADS)

Cherneva, Zlatka; Georgieva, Milena

2005-05-01

Orthogneisses of late-Hercynian protolith age crop out in the Central Rhodope high-grade metamorphic complex, which is part of the Alpine orogen in south-eastern Europe. They compose a tectonic unit bordered by late-Alpine extensional shear zones. These rocks reflect Eocene amphibolite facies migmatization (<750 °C/0.9-0.5 GPa). The low-temperature melting favored zircon inheritance and disturbed mainly the LILE protolith compositions. Despite the intense Alpine metamorphic overprint, the major elements, HFSE and REE reflect the initial composition of the Hercynian protolith. A geochemical data set summarizing 200 whole rock analyses testifies to a calc-alkaline magma differentiation producing a compositional range of tonalite and/or granodiorite to granite and leucocratic granite. Geochemical compositions combined with published isotope and age data suggest dominant I-type protoliths and mixed magma sources including crustal and mantle material, and distinguish between older granitoids of volcanic-arc affinity and probably younger ones of late or post-collision origin.

Differentiating Metamorphic Events in a Polymetamorphic Terrane using Zr-in-Ttn thermometry and Titanite U-Pb Geochronology

NASA Astrophysics Data System (ADS)

Kenney, M.; Roeske, S.; Mulcahy, S. R.; Cottle, J. M.; Coble, M. A.

2016-12-01

In polymetamorphic terranes, it is problematic to link ages from geochronometers to metamorphic fabrics and, therefore, to a specific deformation event(s). It is necessary to analyze a mineral which may preserve multiple age domains. Titanite has been shown to retain multiple age and elemental domains in single grains through high-grade metamorphism. In this study, titanite U-Pb geochronology is used to examine whether ages are thermally reset along a sample transect towards a mylonitic shear zone in NW Argentina. This work also seeks to understand the conditions under which titanite resists resetting. A combination of petrographic and electron microprobe analyses reveal the textures and compositional domains in titanite, garnet, and hornblende. Titanite are elongate, wrapped by the mylonitic fabric, and have patchy elemental zoning. Garnet has distinct cores with prograde zoning and thin rims, which appear to be in equilibrium with the fabric defining minerals. Hornblende has inclusion rich cores and thin overgrowth rims in equilibrium with the fabric defining minerals. In-situ U-Pb and trace element data was collected in titanite from four samples, which all preserve lower-intercept ages between 900Ma and 1.0Ga. We observed no correlation between age and elemental domains; these domains correlate with Al and Nb variations. Zr-in-titanite temperatures preserve upper amphibolite facies conditions, 660ºC-710ºC. Given these results, we conclude that titanite U-Pb ages and temperatures reflect original Grenville metamorphism. 40Ar/39Ar hornblende cooling ages, of 515 Ma, suggested titanite may be reset near the shear zone but overprinting P-T of 560ºC and 0.8 GPa, fluid infiltration, and deformation did not cause significant Pb loss. Overprinting conditions and cooling ages suggest that rims of garnet and hornblende correlate to Paleozoic metamorphism, while textural evidence and titanite ages suggest garnet and hornblende cores grew during the Proterozoic.

Variscan tectonics in Dodecanese, Kalymnos island, Greece

NASA Astrophysics Data System (ADS)

Chatziioannou, Eleftheria; Grasemann, Bernhard; Schneider, David; Hubmann, Bernhard; Soukis, Konstantinos

2015-04-01

Kalymnos island is located in the Dodecanese, southeastern Aegean Sea, and geologically appears to be part of the external Hellenides. Pre-Alpidic basement rocks on the Dodecanese islands have been suggested to record compelling similarities with the basement rocks in Eastern Crete with respect to their lithologies and pre-Alpidic metamorphic evolution. The lithotectonic units experienced greenschist to amphibolite facies conditions during the Variscan orogeny. Whereas the rocks in Eastern Crete reveal Alpine high-pressure overprint, the Variscan basement units in the Dodecanese record no or low-grade Alpine metamorphism. A field study of basement rocks below Mesozoic limestones and dolomites in the NW part of Kalymnos near Emporios uncovered a complex history of metamorphism, folding and faulting. Three different tectonic units can be discriminated from top to bottom: a) a quartz-mica schist, b) a white-grey, fossiliferous coarse grained marble and c) a fine-grained fossiliferous blue-grey marble. In the marbles macrofossils such as brachiopods, ammonoid cephalopods (Goniatids?) and crinoids suggest a Middle-Upper Devonian deposition age (Givetian- Frasnian). Structural mapping the area resolved a dominant W-E shortening event, resulting in an overall inverted metamorphic gradient. The lowermost blue-grey marble unit is folded into large-scale upright folds, which are truncated by top-to-east overthrusting of the white-grey marble unit. Whereas deformation mechanisms in the blue-grey marble unit are dominated by dissolution-precipitation creep, the white-grey marble suffered intense crystal plastic deformation with localized high-strain mylonitic shear zones. The uppermost quartz-mica schist unit is separated from the lower units by a cataclastic phyllonitic shear zone. 40Ar/39Ar geochronological dating on white micas from the quartz-mica schists yielded cooling ages between 240 and 334 Ma indicative of Variscan cooling. Our data suggest that this part of the Dodecanese experienced intense Variscan deformation with no high-temperature Alpine overprint.

Alpine extensional detachment tectonics in the Grande Kabylie metamorphic core complex of the Maghrebides (northern Algeria)

NASA Astrophysics Data System (ADS)

Saadallah, A.; Caby, R.

1996-12-01

The Maghrebides are part of the peri-Mediterranean Alpine orogen. They expose in their inner zone inliers of high-grade crystalline rocks surrounded by Oligo-Miocene and younger Miocene cover. Detailed mapping coupled with structural and petrological investigations in the Grande Kabylie massif, and the reinterpretation of the available geochronological data, allow us to refute the traditional concept of rigid behaviour of this massif during Alpine events. We show that the dome geometry, the kinematic and metamorphic evolutions and the age pattern are typical of metamorphic core complexes exhumed by extension. A major low-angle detachment fault defined by mylonites and by younger cataclasites has been traced in the massif. The upper unit encompasses pre-Permian phyllites with Variscan {40Ar }/{39Ar } cooling ages, capped by unconformable Mesozoic to Tertiary cover of the Calcareous Range, both mainly affected by extensive Tertiary brittle deformation and normal faulting. The lower unit exposes in two half-domes a continuous tectonic pile, 6-8 km thick, of amphibolite facies rocks and orthogneisses affected by syndashmetamorphic ductile deformation, devoid of retrogression. The regular increase of paleotemperature downward and the {40Ar }/{39Ar } plateau ages around 80 Ma suggest that the high-temperature foliation and associated WNW-directed shear under a high geothermal gradient relate to extensional tectonics developed during Mesozoic lithospheric thinning of the Variscan south European margin. To the north, the Sidi Alli Bou Nab massif exposes another crustal section affected throughout by WNW-directed extensional shear during {HP }/{HT } syndashmetamorphic thinning and with overall {40Ar }/{39Ar } plateau ages of 25 Ma. The Eocene oblique collisional event responsible for crustal thickening was totally overprinted by this new extensional regime, synchronous with the beginning of the opening of the Western Mediterranean oceanic basin. This was also coeval with south-directed thrusting of foreland nappes to the south. Post-Miocene tectonic events cause significant overprinting.

School Based Accountability and the Distribution of Teacher Quality among Grades in Elementary Schools. Working Paper 75

ERIC Educational Resources Information Center

Fuller, Sarah C.; Ladd, Helen F.

2012-01-01

We use North Carolina data to explore the extent to which teachers in the lower grades (K-2) of elementary school are lower quality than in the upper grades (3-5) and to examine the hypothesis that accountability contributes to a shortfall in teacher quality in the lower grades. Our concern with early elementary grades arises from recent studies…

Equivalency of general biology (for majors) across a state-system

NASA Astrophysics Data System (ADS)

Regier, Kimberly Fayette

General biology courses (for majors) are often transferred from one institution to another. These courses must prepare students for upper division courses in biology. A survey of U.S. college biology faculty was conducted and revealed that more 4-year faculty do not believe that all general biology courses are equivalent. An evaluation of course grades in two upper division biology courses at University of Colorado Denver (N = 2129) based upon course grades in general biology and the type of institution where general biology was taken (2-year school, 4-year, in-residence at UCD, AP credit, CLEP credit, or IB credit) was conducted. Students who transferred general biology credit received lower grades in upper division biology courses and withdrew from upper division biology courses more frequently. Syllabi from a small sample (N = 9) of general biology courses offered at Colorado 2- and 4-year schools show variation in course design. Only 30% of the courses had detailed learning objectives. Sample exams reveal a range in variation between 3-69% of questions requiring higher-order thinking according to Bloom's Taxonomy. Increasing communication between high school, 2-year and 4-year biology faculty is necessary if consistency is to be gained. Professional development for faculty to increase awareness about exam development, curriculum alignment, and curriculum mapping may reduce the disparities between the preparation of students in biology. Transfer student grade outcomes should be further investigated across the state.

Metamorphic P-T-t path retrieved from metapelites in the southeastern Taihua metamorphic complex, and the Paleoproterozoic tectonic evolution of the southern North China Craton

NASA Astrophysics Data System (ADS)

Lu, Jun-Sheng; Zhai, Ming-Guo; Lu, Lin-Sheng; Wang, Hao Y. C.; Chen, Hong-Xu; Peng, Tao; Wu, Chun-Ming; Zhao, Tai-Ping

2017-02-01

The Taihua metamorphic complex in the southern part of the North China Craton is composed of tonalite-trondhjemite-granodiorite (TTG) gneisses, amphibolites, metapelitic gneisses, marbles, quartzites, and banded iron formations (BIFs). The protoliths of the complex have ages ranging from ∼2.1 to ∼2.9 Ga and was metamorphosed under the upper amphibolite to granulite facies conditions with NWW-SEE-striking gneissosity. Metapelitites from the Wugang area have three stages of metamorphic mineral assemblages. The prograde metamorphic mineral assemblage (M1) includes biotite + plagioclase + quartz + ilmenite preserved as inclusions in garnet porphyroblasts. The peak mineral assemblage (M2) consists of garnet porphyroblasts and matrix minerals of sillimanite + biotite + plagioclase + quartz + K-feldspar + ilmenite + rutile + pyrite. The retrograde mineral assemblage (M3), biotite + plagioclase + quartz, occurs as symplectic assemblages surrounding embayed garnet porphyroblasts. Garnet porphyroblasts are chemically zoned. Pseudosection calculated in the NCKFMASHTO model system suggests that mantles of garnet porphyroblasts define high-pressure granulites facies P-T conditions of 12.2 kbar and 830 °C, whereas garnet rims record P-T conditions of 10.2 kbar and 840 °C. Integrating the prograde mineral assemblages, zoning of garnet porphyroblasts with symplectic assemblages, a clockwise metamorphic P-T path can be retrieved. High resolution SIMS U-Pb dating and LA-ICP-MS trace element measurements of the metamorphic zircons demonstrate that metapelites in Wugang possibly record the peak or near peak metamorphic ages of ∼1.92 Ga. Furthermore, 40Ar/39Ar dating of biotite in metapelites suggests that the cooling of the Taihua complex may have lasted until ∼1.83 Ga. Therefore, a long-lived Palaeoproterozoic metamorphic event may define a slow exhumation process. Field relationship and new metamorphic data for the Taihua metamorphic complex does not support the previous model in which the Tran-North China Craton (TNCO) was formed through the collision between the East and West blocks.

Geologic Map of the Clark Peak Quadrangle, Jackson and Larimer Counties, Colorado

USGS Publications Warehouse

Kellogg, Karl S.; Ruleman, Chester A.; Shroba, Ralph R.; Braddock, William A.

2008-01-01

The Clark Peak quadrangle encompasses the southern end of the Medicine Bow Mountains and the northernmost end of the Mummy Range. The Continental Divide traverses the map area and Highway 14 cross the Divide at Cameron Pass, in the southeastern corner of the map. Approximately the eastern half of the map, and a few areas to the west, are underlain by Early Proterozoic plutonic and metamorphic rocks. Most of these basement rocks are part of the ~1,715 Ma Rawah batholith, composed mostly of pinkish, massive to moderately foliated monzogranite and granodiorite intruded by numerous, large pegmatite- aplite bodies. The metamorphic rocks, many of which form large inclusions in the granitic rocks of the Rawah batholith, include biotite-hornblende gneiss, hornblende gneiss, amphibolite, and biotite schist. The crystalline basement rocks are thrust westward along the Medicine Bow thrust over a sequence of sedimentary rocks as old as the Upper Permian Satanka Shale. The Satanka Shale, Middle and Lower Triassic Chugwater group, and a thin sandstone tentatively correlated with the Lower Jurassic and Upper Triassic Jelm Formation are combined as one map unit. This undivided unit is overlain sequentially upward by the Upper Jurassic Sundance Formation, Upper Jurassic Morrison Formation, Lower Cretaceous Dakota Group, Upper and Lower Cretaceous Benton Group, Upper Cretaceous Niobrara Formation, and the Eocene and Paleocene Coalmont Formation. The Late Cretaceous to early Eocene Medicine Bow thrust is folded in places, and several back thrusts produced a complicated thrust pattern in the south part of the map. Early Oligocene magmatism produced rhyolite tuff, dacite and basalt flows, and intermediate dikes and small stocks. A 40Ar/39Ar date on sanidine from one rhyolite tuff is ~28.5 Ma; a similar whole-rock date on a trachybasalt is ~29.6 Ma. A very coarse, unsorted probably pre-Quaternary ridge-top diamicton crops out in the southern part of the quadrangle. Numerous glacial deposits (mostly of Pinedale age), rock glaciers, block-slope deposits, landslide deposits, talus deposits, fan deposits, colluvium, and alluvium comprise the surficial deposits of the map area.

Modified Full Thickness Graded Blepharotomy for Upper Eyelid Retraction Associated With Thyroid Eye Disease in East Asians.

PubMed

Lee, Joonsik; Lee, Hwa; Park, Minsoo; Baek, Sehyun

2016-12-01

To evaluate the functional and cosmetic outcomes of modified full thickness graded blepharotomy when used for East Asian patients with upper eyelid retraction of thyroid eye disease (TED). Medical records of each patient who underwent modified full-thickness blepharotomy at Korea University Guro Hospitals from January 2009 to February 2014 to correct upper eyelid retraction resulting from TED were retrospectively reviewed. Modified full-thickness graded blepharotomies were performed on 22 eyelids of 18 patients. The most common preoperative upper eyelid retraction-associated symptom was asymmetry of the upper eyelid (14 patients, 77.7%) followed by discomfort (10 patients, 55.5%), photophobia (5 patients, 27.7%), and epiphora (4 patients, 22.2%). Most preoperative symptoms improved after blepharotomy (Table 1). Preoperatively, upper eyelid retraction (MRD1; midpupil marginal reflex distance) ranged from 2.3 mm to 6.8 mm (mean, 5.23 ± 0.89) in 22 lids; postoperatively, lid retraction significantly decreased to 3.26 ± 1.23 mm (P = 0.03 by independent t test) (Table 2). Lid retraction was divided into 3 groups according to severity; a severe group (5 eyelids, 27.7%), a moderate group (14 eyelids, 63.6%), and a mild group (3 eyelids, 13.6%). The MRD1 improved regardless of severity (P = 0.03 in the severe group, P = 0.02 in the moderate group, and P = 0.04 in the mild group by independent t test). The MRD1 improvement did not differ significantly among groups (P = 0.08 by Pearson χ t test). At 6 months postoperatively, the midpupil marginal reflex distance was the perfect height in 13 of 22 lids (59.0%), with a mean reduction of 3 mm, whereas 7 of 22 eyelids (31.8%) were at acceptable height and 2 eyelids (9.0%) showed failure. Overall, 18 eyelids (90.9%) exhibited objectively satisfactory results (perfect or acceptable) at 6 months after surgery (Table 3). Modified graded full thickness eyelid blepharotomy is a reliable and safe method for upper eyelid lengthening for East Asian patients with upper eyelid retraction of TED that offers excellent functional and cosmetic results.

U-Pb zircon and CHIME monazite dating of granitoids and high-grade metamorphic rocks from the Eastern and Peninsular Thailand - A new report of Early Paleozoic granite

NASA Astrophysics Data System (ADS)

Kawakami, T.; Nakano, N.; Higashino, F.; Hokada, T.; Osanai, Y.; Yuhara, M.; Charusiri, P.; Kamikubo, H.; Yonemura, K.; Hirata, T.

2014-07-01

In order to understand the age and tectonic framework of Eastern to Peninsular Thailand from the viewpoint of basement (metamorphic and plutonic) geology, the LA-ICP-MS U-Pb zircon dating and the chemical Th-U-total Pb isochron method (CHIME) monazite dating were performed in the Khao Chao, Hub-Kapong to Pran Buri, and Khanom areas in Eastern to Peninsular Thailand. The LA-ICP-MS U-Pb zircon dating of the garnet-hornblende gneiss from the Khao Chao area gave 229 ± 3 Ma representing the crystallization age of the gabbro, and that of the garnet-biotite gneisses gave 193 ± 4 Ma representing the timing of an upper amphibolite facies metamorphism. The CHIME monazite dating of pelitic gneiss from the Khao Chao gneiss gave scattered result of 68 ± 22 Ma, due to low PbO content and rejuvenation of older monazite grains during another metamorphism in the Late Cretaceous to Tertiary time. The U-Pb ages of zircon from the Hua Hin gneissic granite in the Hub-Kapong to Pran Buri area scatter from 250 Ma to 170 Ma on the concordia. Granite crystallization was at 219 ± 2 Ma, followed by the sillimanite-grade regional metamorphism at 185 ± 2 Ma. Monazite in the pelitic gneiss from this area also preserves Early to Middle Jurassic metamorphism and rejuvenation by later contact metamorphism by non-foliated granite or by another fluid infiltration event in the Late Cretaceous to Tertiary time. The Khao Dat Fa granite from the Khanom area of Peninsular Thailand gave a U-Pb zircon age of 477 ± 7 Ma. This is the second oldest granite pluton ever reported from Thailand, and is a clear evidence for the Sibumasu block having a crystalline basement that was formed during the Pan-African Orogeny. The Khao Pret granite gives U-Pb zircon concordia age of 67.5 ± 1.3 Ma, which represents the timing of zircon crystallization from the granitic melt and accompanied sillimanite-grade contact metamorphism against surrounding metapelites and gneisses. Metamorphic rocks in the Doi Inthanon area also share the similar plutono-metamorphic history with the Khanom and the Hub-Kapong to Pran Buri areas. This suggests that these three areas belong to the Sibumasu block, and the Sibumasu block records similar plutono-metamorphic history from Northern to Peninsular Thailand. Relative abundance of oceanic components in the Khao Chao gneiss, their Late Triassic magmatic ages, and the Early Jurassic metamorphic ages prefer the interpretation that the Khao Chao gneiss belongs to the Sukhothai Arc.

Race, disability, and grade: Social relationships in children with autism spectrum disorders.

PubMed

Azad, Gazi F; Locke, Jill; Kasari, Connie; Mandell, David S

2017-01-01

Race is associated with social relationships among typically developing children; however, studies rarely examine the impact of race on social outcomes for children with autism spectrum disorder. This study examined how race (African American, Latino, Asian, or White) in conjunction with disability status (autism spectrum disorders or typically developing) and grade (grades K-2 or 3-5) affects friendships and social networks. The sample comprises 85 children with autism spectrum disorders and 85 typically developing controls matched on race, gender, age/grade, and classroom (wherever possible). Race, disability, and grade each had an independent effect on friendship nominations, and there was an interaction among the three variables. Specifically, children with autism spectrum disorders who were African American or Latino in the upper elementary grades received fewer friendship nominations than typically developing White children in the lower elementary grades. Only the presence of autism spectrum disorders was associated with social network centrality. Our results also suggested that Latino children with autism spectrum disorders in the upper elementary grades were at the highest risk of social isolation. Implications for re-conceptualizing social skills interventions are discussed. © The Author(s) 2016.

Intermediate P/T-type regional metamorphism of the Isua Supracrustal Belt, southern west Greenland: The oldest Pacific-type orogenic belt?

NASA Astrophysics Data System (ADS)

Arai, Tatsuyuki; Omori, Soichi; Komiya, Tsuyoshi; Maruyama, Shigenori

2015-11-01

The 3.7-3.8 Ga Isua Supracrustal Belt (ISB), southwest Greenland, might be the oldest accretionary complex on Earth. Regional metamorphism of the ISB has a potential to constrain the tectonothermal history of the Earth during the Eoarchean. Chemical and modal analyses of metabasite in the study area (i.e., the northeast part of the ISB) show that the metamorphic grade increases from greenschist facies in the northern part of the study area to amphibolite facies in the southern part. To determine the precise metamorphic P-T ranges, isochemical phase diagrams of minerals of metabasite were made using Perple_X. A synthesis of the estimated metamorphic P-T ranges of the ISB indicates that both the metamorphic pressure and temperature increase systematically to the south in the study area from 3 kbar and 380 °C to 6 kbar and 560 °C. The monotonous metamorphic P-T change suggests that the northeast part of the ISB preserves regional metamorphism resulting from the subduction of an accretionary complex although the ISB experienced metamorphic overprints during the Neoarchean. Both the presence of the regional metamorphism and an accretionary complex having originating at subduction zone suggest that the ISB may be the oldest Pacific-type orogenic belt. The progressive metamorphism can be considered as a record of intermediate-P/T type geothermal gradient at the subduction zone in the Eoarchean. Intermediate-P/T type geothermal gradient is typical at the current zones of subducting young oceanic crust, such as in the case of the Philippine Sea Plate in the southwest part of Japan. Considering the fact that almost all metamorphisms in the Archean are greenschist-amphibolite facies, the intermediate-P/T type geothermal gradient at the ISB might have been worldwide in the Archean. This would indicate that the subduction of young micro-plates was common because of the vigorous convection of hot mantle in the Archean.

Proterozoic metamorphism and uplift history of the north-central Laramie Mountains, Wyoming, USA

USGS Publications Warehouse

Patel, S.C.; Frost, B.R.; Chamberlain, K.R.; Snyder, G.L.

1999-01-01

The Laramie Mountains of south-eastern Wyoming contain two metamorphic domains that are separated by the 1.76 Ga. Laramie Peak shear zone (LPSZ). South of the LPSZ lies the Palmer Canyon block, where apatite U-Pb ages are c. 1745 Ma and the rocks have undergone Proterozoic kyanite-grade Barrovian metamorphism. In contrast, in the Laramie Peak block, north of the shear zone, the U-Pb apatite ages are 2.4-2.1 Ga, the granitic rocks are unmetamorphosed and supracrustal rocks record only low-T amphibolite facies metamorphism that is Archean in age. Peak mineral assemblages in the Palmer Canyon block include (a) quartz-biotite-plagioclase-garnet-staurolite-kyanite in the pelitic schists; (b) quartz-biotite-plagioclase-low-Ca amphiboles-kyanite in Mg-Al-rich schists, and locally (c) hornblende-plagioclase-garnet in amphibolites. All rock types show abundant textural evidence of decompression and retrograde re-equilibration. Notable among the texturally late minerals are cordierite and sapphirine, which occur in coronas around kyanite in Mg-Al-rich schists. Thermobarometry from texturally early and late assemblages for samples from different areas within the Palmer Canyon block define decompression from > 7 kbar to < 3 kbar. The high-pressure regional metamorphism is interpreted to be a response to thrusting associated with the Medicine Bow orogeny at c. 1.78-1.76 Ga. At this time, the north-central Laramie Range was tectonically thickened by as much as 12 km. This crustal thickening extended for more than 60 km north of the Cheyenne belt in southern Wyoming. Late in the orogenic cycle, rocks of the Palmer Canyon block were uplifted and unroofed as the result of transpression along the Laramie Peak shear zone to produce the widespread decompression textures. The Proterozoic tectonic history of the central Laramie Range is similar to exhumation that accompanied late-orogenic oblique convergence in many Phanerozoic orogenic belts.

Thermobarometric studies on the Levack Gneisses: Footwall rocks to the Sudbury Igneous Complex

NASA Technical Reports Server (NTRS)

James, R. S.; Peredery, W.; Sweeny, J. M.

1992-01-01

Granulite and amphibolite facies gneisses and migmatites of the Levack Gneiss Complex occupy a zone up to 8 km wide around the northern part of the Sudbury Igneous Complex (SIC). Orthopyroxene- and garnet-bearing tonalitic and semipelitic assemblages of granulite facies grade occur within 3 km of the SIC together with lenses of mafic and pyroxenitic rock compositions normally represented by an amphibole +/- cpx-rich assemblage; amphibolite facies assemblages dominate elsewhere in this terrain. These 2.711-Ga gneisses were introduced by (1) the Cartier Granite Batholith during late Archaean to early Proterozoic time and (2) the SIC, at 1.85 Ga, which produced a contact aureole 1-1.5 km wide in which pyroxene hornfelses are common within 200-300 m of the contact. A suite of 12 samples including both the opx-gt and amphibole-rich rock compositions have been studied. Garnets in the semipelitic gneisses are variably replaced by a plg-bio assemblage. Thermobarometric calculations using a variety of barometers and thermometers reported in the literature suggest that the granulite facies assemblages formed at depths in the 21-28 km range (6-8 kbar). Textures and mineral chemistry in the garnet-bearing semipelitic rocks indicate that this terrain underwent a second metamorphic event during uplift to depth in the 5-11 km range (2-3 kbar) and at temperatures as low as 500-550 C. This latter event is distinct from thermal recrystallization caused by the emplacement of the SIC; it probably represents metamorphism attributable to intrusion of the Cartier Granite Batholith. These data allow two interpretations for the crustal uplift of the Levack Gneisses: (1) The gneisses were tectonically uplifted prior to the Sudbury Event (due to intrusion of the Cartier Batholith); or (2) the gneisses were raised to epizonal levels as a result of meteorite impact at 1.85 Ga.

Upper Elementary Students' Motivation to Read Fiction and Nonfiction

ERIC Educational Resources Information Center

Parsons, Allison Ward; Parsons, Seth A.; Malloy, Jacquelynn A.; Gambrell, Linda B.; Marinak, Barbara A.; Reutzel, D. Ray; Applegate, Mary D.; Applegate, Anthony J.; Fawson, Parker C.

2018-01-01

This research explores upper elementary students' motivation to read fiction and nonfiction. Using expectancy-value theory, the researchers developed separate surveys to measure motivation to read fiction and nonfiction. Researchers administered surveys to 1,104 upper elementary students (grades 3-6) in multiple locations across the United States…

Let's Cut the Cake

ERIC Educational Resources Information Center

Zeybek, Zulfiye; Cross Francis, Dionne I.

2017-01-01

Measurement is an important component of K-grade 12 mathematics curricula. The concepts of area and perimeter of polygons are first introduced in third grade and serve as the basis for teaching in the upper grades. Without a strong understanding of measurement, students will struggle to meaningfully grasp three-dimensional measurement concepts…

Grade Expectations: Redux

ERIC Educational Resources Information Center

Miley, William M.; Gonsalves, Sonia

2004-01-01

We surveyed undergraduate students taking upper level psychology courses about their course and grade expectations as an extension of the work of Gaultney and Cann (2001) with introductory psychology students. More students believed success in a course was measured by good grades rather than by mastery of new material. They wanted effort to play a…

Factors associated with group bullying and psychopathology in elementary school students using child-welfare facilities.

PubMed

Kim, Jun Won; Lee, KounSeok; Lee, Young Sik; Han, Doug Hyun; Min, Kyung Joon; Song, Sung Hwan; Park, Ga Na; Lee, Ju Young; Kim, Jae Ock

2015-01-01

Low socioeconomic status is an important risk factor for child psychiatric problems. Low socioeconomic status is also associated with psychiatric problems later in life. We investigated the effects of group bullying on clinical characteristics and psychopathology in elementary school students using child-welfare facilities. Three hundred and fifty-eight elementary school students using child-welfare facilities were recruited. The School Bullying Self Rating Questionnaire was used to assess group bullying. To evaluate related psychopathology, the Children's Problem-Behavior Screening Questionnaire, the Children's Depression Inventory, the Beck Anxiety Inventory, the Suicidal Ideation Questionnaire, Young's Internet Addiction Scale, and Conners-Wells' Adolescent Self-Report Scale were applied. Samples were classified according to school grade (lower or upper), and each group's characteristics were compared as they related to bullying victims versus non-victims. The prevalence rate of group bullying was 22% in the lower-grade group and 12% in the higher-grade group. Bullying victims in lower grades reported high somatization, depressive symptoms, Internet addiction, and attention deficit hyperactivity disorder tendencies, whereas those in upper grades reported cognitive problems, symptoms of depression and anxiety, suicidal ideation, Internet addiction, and attention deficit hyperactivity disorder tendencies. Somatization and depressive symptoms were significant predictors of bullying in the lower-grade group, and anxiety was a significant predictor of bullying in the upper-grade group. This study demonstrated that elementary school students using child-welfare facilities might have an increased risk of being bullied and that bullying victims may have different psychopathologies depending on their ages.

The Pinkie Unit of the Southwestern Svalbard Caledonian Province and its bearing on distribution of the Torellian-Timanian basement in the High Arctic

NASA Astrophysics Data System (ADS)

Kośmińska, Karolina; Majka, Jarosław; Manecki, Maciej

2015-04-01

Here we present for the first time petrological characteristics of metapelites from the Pinkie Unit (Prins Karls Forland, western Svalbard). Rocks belonging to the Pinkie Unit are represented mainly by laminated quartzites, siliciclastic rocks (sometimes with garnet) and garnet-bearing mica schists. They are overthrust by the lower grade lithologies of the Grampian Group. The mineral composition confirmed by preliminary microscopic observations suggests that the Pinkie rocks were subjected to at least amphibolite facies metamorphism. The metamorphic zoning from chloritoid through staurolite, up to kyanite zone is apparent. This indicates Barrovian type metamorphism. The rocks are strongly deformed, M1 assemblages and D1 structures are overprinted by pervasive D2 mylonitic pattern. This study is focused on kyanite-bearing schists. They consist mainly of garnet, plagioclase, biotite, muscovite, kyanite, quartz and turmaline. Garnet forms anhedral crystals. Its chemical composition is characterized by Alm79-84Sps1-5Prp5-11Grs5-10. The profiles through the garnets are almost flat and they seem to be homogenized most probably during peak temperature at an early stage of retrogression. The Si content in muscovite varies from 3.06 to 3.13. Biotite is characterized by XFe in the range of 0.53 - 0.66. The garnet-biotite-muscovite-plagioclase (GBPM) geothermobarometer (Holdaway, 2001; Wu, 2014) has been used for estimation of pressure - temperature conditions. Preliminary calculations indicate peak metamorphic conditions at 8 - 9 kbar and 650 - 700°C. Our P-T calculations provide further evidence for the Barrovian type of metamorphism along the western coast of Svalbard. The correlation of the Pinkie Unit with other higher grade complexes within Southwestern Svalbard Caledonian Province is still difficult, but the studied rocks resemble the Isbjørnhamna Group of Wedel Jarlsberg Land. This is based on the metamorphic grade, mineral assemblage and probable protolith age (post-950Ma; Kośmińska, unpublished data). If this is a case, the Pinkie Unit will provide another evidence of the Torellian-Timanian (late Neoproterozoic, e.g. Majka et al. 2008) tectonothermal event within the Svalbard's Caledonides. In turn, it can bear important implications for Arctic tectonic reconstructions. This project is financed by NCN research project No 2013/11/N/ST10/00357. References: Holdaway M.J., 2001. Recalibration of the GASP geobarometer in light of recent garnet and plagioclase activity models and versions of the garnet-biotite geothermometer. American Mineralogist, 86, 1117-1129. Majka J., Mazur S., Czerny J., Manecki M., Holm D.K., 2008. Late Neoproterozoic amphibolite facies metamorphism of a pre-Caledonian basement block in southwest Wedel Jarlsberg Land, Spitsbergen: new evidence from U-Th-Pb dating of monazite. Geological Magazine, 145, 822-830. Wu C. M., 2014. Revised empirical garnet-biotite-muscovite-plagioclase (GBMP) geobarometer in metapelites. Journal of Metamorphic Geology. doi: 10.1111/jmg.12115

The Ivrea zone as a model for the distribution of magnetization in the continental crust

NASA Technical Reports Server (NTRS)

Wasilewski, P.; Fountain, D. M.

1982-01-01

Units are identified within the Ivrea zone of northern Italy exhibiting magnetic susceptibilities greater than 0.0005 cgs, saturation magnetization values above 0.009 emu/cu cm, and Curie points as high as 570-580 C. Amphibolites from the granulite-amphibolite facies transition, and the mafic-ultramafic granulite facies lithologies exhibit high values of initial susceptibility and saturation remanence, are laterally continuous, and may be considered as a deep crustal source for long-wavelength anomalies in low-geothermal gradient areas. Evidence is presented which suggests that such mafic-ultramafic bodies as those exposed in the Toce valley were synmetamorphic additions to the base of the crust.

Secondary School Students' Conceptions Relating to Motion under Gravity

ERIC Educational Resources Information Center

Apostolides, Themos; Valanides, Nikos

2008-01-01

The study investigated tenth-, eleventh-, and twelfth-grade students' alternative ideas relating to the motion of a body travelling in the field of gravity with an initial horizontal velocity. The sample of the study consisted of 40 tenth-grade students, and 33 and 40 eleventh-grade students that attended different sections of upper secondary…

Effects of a Year Long Supplemental Reading Intervention for Students with Reading Difficulties in Fourth Grade

ERIC Educational Resources Information Center

Wanzek, Jeanne; Petscher, Yaacov; Al Otaiba, Stephanie; Rivas, Brenna; Jones, Francesca; Kent, Shawn; Schatschneider, Christopher; Mehta, Paras

2017-01-01

Research examining effective reading interventions for students with reading difficulties in the upper elementary grades is limited relative to the information available for the early elementary grades. In the current study, we examined the effects of a multicomponent reading intervention for students with reading comprehension difficulties. We…

Comparative thermometry on pelitic rocks and marbles of the Llano uplift, Texas

DOE Office of Scientific and Technical Information (OSTI.GOV)

Letargo, C.M.R.; Lamb, W.M.

1992-01-01

The Llano Uplift in central Texas is a Grenville-aged metamorphic complex consisting of amphibolite facies assemblages whose development has been attributed to the emplacement of granite plutons between 1.0--1.1 Ga. Temperatures have been obtained from garnet-biotite, garnet-ilmenite, and calcite-dolomite pairs as well as from various silicate equilibria. Application of these geothermometers yield consistent results and are thus indicative of peak conditions attending the amphibolite facies metamorphism. Temperature determined using garnet-biotite and garnet-ilmenite thermometry compare favorably with calcite-dolomite temperatures obtained from marbles in contact with granite plutons in the southeastern part of the uplift. The highest calcite-dolomite temperatures of [approximately]600 Cmore » are obtained from marbles containing an isobarically invariant assemblage consisting of calcite + dolomite + diopside + tremolite + forsterite. At pressures of 2--3 kbar, this isobarically invariant assemblage will be stable at a temperature range of [approximately]600--650 C. Also in close proximity to granites in the southeast uplift is the assemblage muscovite + quartz + k-feldspar + sillimanite [approximately] andalusite which indicate T 650 C and P 2.5 kbar. Assemblages consisting of garnet + sillimanite + quartz + plagioclase (GASP) and garnet + rutile + ilmenite + plagioclase + quartz (GRIPS) are currently being studied to provide additional constraints on pressures of amphibolite facies metamorphism.« less

Validation of image analysis techniques to measure skin aging features from facial photographs.

PubMed

Hamer, M A; Jacobs, L C; Lall, J S; Wollstein, A; Hollestein, L M; Rae, A R; Gossage, K W; Hofman, A; Liu, F; Kayser, M; Nijsten, T; Gunn, D A

2015-11-01

Accurate measurement of the extent skin has aged is crucial for skin aging research. Image analysis offers a quick and consistent approach for quantifying skin aging features from photographs, but is prone to technical bias and requires proper validation. Facial photographs of 75 male and 75 female North-European participants, randomly selected from the Rotterdam Study, were graded by two physicians using photonumeric scales for wrinkles (full face, forehead, crow's feet, nasolabial fold and upper lip), pigmented spots and telangiectasia. Image analysis measurements of the same features were optimized using photonumeric grades from 50 participants, then compared to photonumeric grading in the 100 remaining participants stratified by sex. The inter-rater reliability of the photonumeric grades was good to excellent (intraclass correlation coefficients 0.65-0.93). Correlations between the digital measures and the photonumeric grading were moderate to excellent for all the wrinkle comparisons (Spearman's rho ρ = 0.52-0.89) bar the upper lip wrinkles in the men (fair, ρ = 0.30). Correlations were moderate to good for pigmented spots and telangiectasia (ρ = 0.60-0.75). These comparisons demonstrate that all the image analysis measures, bar the upper lip measure in the men, are suitable for use in skin aging research and highlight areas of improvement for future refinements of the techniques. © 2015 John Wiley & Sons A/S. Published by John Wiley & Sons.

Evolution of crystalline target rocks and impactites in the chesapeake bay impact structure, ICDP-USGS eyreville B core

USGS Publications Warehouse

Horton, J. Wright; Kunk, Michael J.; Belkin, Harvey E.; Aleinikoff, John N.; Jackson, John C.; Chou, I.-Ming

2009-01-01

The 1766-m-deep Eyreville B core from the late Eocene Chesapeake Bay impact structure includes, in ascending order, a lower basement-derived section of schist and pegmatitic granite with impact breccia dikes, polymict impact breccias, and cataclas tic gneiss blocks overlain by suevites and clast-rich impact melt rocks, sand with an amphibolite block and lithic boulders, and a 275-m-thick granite slab overlain by crater-fill sediments and postimpact strata. Graphite-rich cataclasite marks a detachment fault atop the lower basement-derived section. Overlying impactites consist mainly of basement-derived clasts and impact melt particles, and coastal-plain sediment clasts are underrepresented. Shocked quartz is common, and coesite and reidite are confirmed by Raman spectra. Silicate glasses have textures indicating immiscible melts at quench, and they are partly altered to smectite. Chrome spinel, baddeleyite, and corundum in silicate glass indicate high-temperature crystallization under silica undersaturation. Clast-rich impact melt rocks contain α-cristobalite and monoclinic tridymite. The impactites record an upward transition from slumped ground surge to melt-rich fallback from the ejecta plume. Basement-derived rocks include amphibolite-facies schists, greenschist(?)-facies quartz-feldspar gneiss blocks and subgreenschist-facies shale and siltstone clasts in polymict impact breccias, the amphibolite block, and the granite slab. The granite slab, underlying sand, and amphibolite block represent rock avalanches from inward collapse of unshocked bedrock around the transient crater rim. Gneissic and massive granites in the slab yield U-Pb sensitive high-resolution ion microprobe (SHRIMP) zircon dates of 615 ± 7 Ma and 254 ± 3 Ma, respectively. Postimpact heating was <~350 °C in the lower basement-derived section based on undisturbed 40Ar/39Ar plateau ages of muscovite and <~150 °C in sand above the suevite based on 40Ar/39Ar age spectra of detrital microcline.

Measurements of wave velocity and electrical conductivity of an amphibolite from southwestern margin of the Tarim Basin at pressures to 1.0 GPa and temperatures to 700 °C: comparison with field observations

NASA Astrophysics Data System (ADS)

Zhou, Wenge; Fan, Dawei; Liu, Yonggang; Xie, Hongsen

2011-12-01

In situ measurements of elastic wave velocities and electrical conductivities in the three structural directions (normal to foliation Z, perpendicular to lineation in foliation Y and parallel to lineation X) for an amphibolite collected from southwestern margin of the Tarim Basin, northwest China, were carried out in the laboratory. The elastic wave velocity was measured with the combined transmission-reflection method at pressures up to 1.0 GPa (at room temperature) and temperatures up to 700 °C (at 1.0 GPa) and the electrical conductivity was measured with the impedance spectroscopy from 250 to 700 °C at 1.0 GPa. The experimentally determined data included compressional (Vp) and shear wave velocities (Vs), velocity anisotropy (Av), intrinsic pressure and temperature derivatives of Vp and Vs, electrical conductivity (σ), electrical conductivity anisotropy (Aσ) and the parameters of the Arrhenius relationship. Elastic wave velocities increase in the structural directions Z, Y, X, with Vp of 6.63, 6.78 and 6.95 km s-1 and Vs of 3.75, 3.82 and 3.96 km s-1 for Z, Y and X, respectively, at pressure of 1.0 GPa. Elastic wave velocities increase linearly with pressure at room temperature and pressures between 0.25 and 1.0 GPa and decrease linearly with increasing temperature at 1.0 GPa. The pressure coefficients of the sample are in the range of 0.1883-0.2308 km s-1 GPa-1 for Vp and 0.1149-0.1678 km s-1 GPa-1 for Vs. The temperature coefficients are in the range of 2.09-2.35 × 10-4 km s-1 GPa-1 for Vp and 1.28-1.68 × 10-4 km s-1 GPa-1 for Vs. The electrical conductivity increases with increasing temperature, consistent with the Arrhenius relationship. Activation energies for the three structural directions of the amphibolite are in the range of 0.71-0.75 eV. The amphibolite shows velocity anisotropy (4.15-4.86 per cent for Vp and 5.29-5.84 per cent for Vs at 0.25-1.0 GPa) and electrical conductivity anisotropy (11.1-25.2 per cent). Based on the regional crust model and geothermal gradient, velocity and electrical conductivity-depth profiles were calculated for the sample. These profiles were then compared with those derived from seismic reflection/refraction data and from electromagnetic data. Our results showed that the amphibolite sample has Vp and Vs in agreement with those of the middle and lower crust obtained from seismic reflection/refraction data, and σ in accord with that of the lower crust deduced from electromagnetic data. The lower crust of the electromagnetic crust model is roughly equivalent to the middle and lower crust layers of the seismic crust model. Therefore, it is suggest that the amphibolite may be one of the constituents of the present middle and lower crust in the Tarim Basin.

Evidence for ˜80-75 Ma subduction jump during Anatolide-Tauride-Armenian block accretion and ˜48 Ma Arabia-Eurasia collision in Lesser Caucasus-East Anatolia

NASA Astrophysics Data System (ADS)

Rolland, Yann; Perincek, Dogan; Kaymakci, Nuretdin; Sosson, Marc; Barrier, Eric; Avagyan, Ara

2012-05-01

Orogens formed by a combination of subduction and accretion are featured by a short-lived collisional history. They preserve crustal geometries acquired prior to the collisional event. These geometries comprise obducted oceanic crust sequences that may propagate somewhat far away from the suture zone, preserved accretionary prism and subduction channel at the interplate boundary. The cessation of deformation is ascribed to rapid jump of the subduction zone at the passive margin rim of the opposite side of the accreted block. Geological investigation and 40Ar/39Ar dating on the main tectonic boundaries of the Anatolide-Tauride-Armenian (ATA) block in Eastern Turkey, Armenia and Georgia provide temporal constraints of subduction and accretion on both sides of this small continental block, and final collisional history of Eurasian and Arabian plates. On the northern side, 40Ar/39Ar ages give insights for the subduction and collage from the Middle to Upper Cretaceous (95-80 Ma). To the south, younger magmatic and metamorphic ages exhibit subduction of Neotethys and accretion of the Bitlis-Pütürge block during the Upper Cretaceous (74-71 Ma). These data are interpreted as a subduction jump from the northern to the southern boundary of the ATA continental block at 80-75 Ma. Similar back-arc type geochemistry of obducted ophiolites in the two subduction-accretion domains point to a similar intra-oceanic evolution prior to accretion, featured by slab steepening and roll-back as for the current Mediterranean domain. Final closure of Neotethys and initiation of collision with Arabian Plate occurred in the Middle-Upper Eocene as featured by the development of a Himalayan-type thrust sheet exhuming amphibolite facies rocks in its hanging-wall at c. 48 Ma.

Upper Elementary Boys' Participation during Group Singing Activities in Single-Sex and Coeducational Classes

ERIC Educational Resources Information Center

Bazzy, Zadda M.

2010-01-01

As boys in the upper elementary grades become increasingly influenced by peer pressure, many are less likely to participate in singing activities because singing is considered a "feminine" activity. The purpose of this research was to explore if there was an effect on upper elementary boys' level of participation during group singing activities…

Gender Inequities in Grade Two: A Look at Educators and Literature.

ERIC Educational Resources Information Center

Augello, Gina

A study was conducted to determine if second grade teachers use gender biased literature and if these teachers are unintentionally sending biased messages to their students. Sixty-two second grade students and their three teachers were included in this study. The study was conducted in an upper-middle-class suburban elementary school. Several…

The geology of the Inconsolable Range, east-central Sierra Nevada, California

DOE Office of Scientific and Technical Information (OSTI.GOV)

Hathaway, G.M; Reed, W.E.

1993-04-01

Detailed mapping of the Inconsolable Range in the east-central Sierra Nevada reveals a structurally and lithologically complex region of multi-phase intrusions. Some plutons are compositionally-zoned [e.g., Inconsolable (100 Ma) and Lamarck (90 Ma)]; others may be the result of magma mixing. Intrusive borders vary from brittle to ductile and sharp to gradational, and are bounded by contact aureoles of varying metamorphic grade. A shear zone (Long Lake shear zone -- LLSZ) bounds the western margin of the Inconsolable Range for 8 km; this is truncated in the south by the Cretaceous Lamarck intrusive suite, and is tectonically overlain in themore » north by the Bishop Creek Pendant (Ordovician ). The LLSZ is a complex zone of interleaved septa of biotite schists, orthogneisses, aplitic screens, and calc-silicate gneisses approximately 500 to 800 m wide. Preliminary interpretation suggests that the LLSZ is the sheared remnant of a Triassic-Jurassic igneous terrane complete with metasedimentary pendants. Juxtaposition of greenschist facies meta-sedimentary rocks of the Chocolate Peak klippe over highly deformed amphibolite grade meta-igneous rocks of the LLSZ postdates movement along the LLSZ. Metamorphic grades suggest that deeper structural levels are exposed within the LLSZ near its southern terminus. Twenty plutonic lithologies have been mapped and informally named (e.g., Spotted biotite quartz diorite), including 3 compositionally-zoned plutons. Zonation within the Lamarck, Inconsolable, and Spotted intrusions are the result of multiple emplacement events into partially crystallized host plutons. Along the eastern border of the Lamarck intrusive suite field evidence indicates four separate intrusive events. The Inconsolable body is a compositionally-zoned biotite, clinopyroxene, quartz diorite with irregular granodiorite margins. The base of the Spotted intrusion appears to have been magmatically eroded by a pulse of the younger Lamarck intrusion.« less

Geological reconnaissance of some Uruguayan iron and manganese deposits in 1962

USGS Publications Warehouse

Wallace, Roberts Manning

1976-01-01

Three mineralized areas lie in an area near the town of Minas de Corrales in the Departamento de Rivera; they are the Cerro Amelia, the Cerro de Papagayo, and the Cerro Iman. The Cerro Amelia is composed of small bands of iron-rich rock separated by an amphibolitic or mafic rock. Selective mining would be necessary to extract the 31,000 tons per meter of depth of iron-rich rock that ranges from 15 to 40 percent metallic iron. The Cerro de Papagayo district contains many small, rich deposits of ferruginous manganese ore. The ratio of Mn to Fe varies widely within each small deposit as well as from deposit to deposit. Some ferruginous manganese ore contains 50-55 percent manganese dioxide. Although there are many thousands of tons of ore in the district, small-scale mining operations are imperative. One deposit, the Cerro Avestuz manganese mine, was visited. The manganese ore body lies within contorted highly metamorphosed itabirite that contains both hard low grade and soft high grade ferruginous manganese ores estimated to average 40 percent Mn. About 38,000 tons of manganese ore is present in this deposit. The Cerro Iman is a large block of itabirite that contains about 40 percent Fe. The grade is variable and probably runs from less than 35 percent Fe to more than 50 percent Fe. No exploration has been done on this deposit. It is recommended that the Cerro de Iman area be geologically mapped in detail, and that a geological reconnaissance be made of the area that is between the Cuchilla de Corrales and the Cuchilla de Areycua/Cuchilla del Cerro Pelado area.

2.9, 2.36, and 1.96 Ga zircons in orthogneiss south of the Red River shear zone in Viet Nam: evidence from SHRIMP U-Pb dating and tectonothermal implications

NASA Astrophysics Data System (ADS)

Nam, Tran Ngoc; Toriumi, Mitsuhiro; Sano, Yuji; Terada, Kentaro; Thang, Ta Trong

2003-05-01

Orthogneissic rocks coexisting with migmatites and containing small amphibolite lenses are exposed in the center of the metamorphic belt which runs parallel to the Day Nui Con Voi-Red River shear zone in northern Viet Nam. The orthogneiss complex has given some radiogenic dates of Early Proterozoic and Late Archean, which are the oldest ages ever registered for the Southeast Asian continent. Zircon grains separated from three samples of the orthogneiss complex have been dated to establish the protolith age and the timing of high-grade tectonothermal events in the complex. Sixty-five SHRIMP U-Th-Pb analyses of these zircons define three age groups of 2.84-2.91, 2.36, and 1.96 Ga. The age groups correspond to three periods of zircon generation. The oldest ˜2.9 Ga cores indicate a minimum age for the protolith of the orthogneiss complex. Two younger generations (including ˜2.36 Ga outer-cores and ˜1.96 Ga rims) probably grew during later high-grade tectono-metamorphic events, which were previously suggested by K-Ar and 40Ar/ 39Ar cooling ages of ˜2.0 Ga for synkinematic hornblendes. An early thermal history of the orthogneiss complex has been constrained, including a primary magma-crystallization stage starting at ˜2.9 Ga, followed by two Early Proterozoic (˜2.36 and ˜1.96 Ga) high-grade tectonothermal events. The ca. 2.9 Ga protolith age of the orthogneiss complex documented in this study provides new convincing evidence for the presence of Archean rocks in Indochina, and clearly indicates that the crustal evolution of northern Viet Nam started as early as Late Archean time.

Effect of water on the composition of partial melts of greenstone and amphibolite

NASA Technical Reports Server (NTRS)

Beard, James S.; Lofgren, Gary E.

1989-01-01

Closed-system partial melts of hydrated, metamorphosed arc basalts and andesites (greenstones and amphibolites), where only water structurally bound in metamorphic minerals is available for melting (dehydration melting), are generally water-undersaturated, coexist with plagioclase-rich, anhydrous restites, and have compositions like island arc tonalites. In contrast, water-saturated melting at water pressures of 3 kilobars yields strongly peraluminous, low iron melts that coexist with an amphibole-bearing, plagioclase-poor restite. These melt compositions are unlike those of most natural silicic rocks. Thus, dehydration melting over a range of pressures in the crust of island arcs is a plausible mechanism for the petrogenesis of islands arc tonalite, whereas water-saturated melting at pressure of 3 kilobars and above is not.

Origin of Archean migmatites from the Gwenoro Dam area, Zimbabwe-Rhodesia

NASA Astrophysics Data System (ADS)

Condie, Kent C.; Allen, Philip

1980-09-01

Archean migmatites in the vicinity of Gwenoro Dam in Zimbabwe-Rhodesia are composed chiefly of trondhjemite gneiss (TR), mafic tonalite (MT), amphibolite (AM), leuco-trondhjemite veins (LTR), and pegmatites. The gneiss is intruded in nearby areas with small tonalite plutons (TN). Geochemical model studies together with field relationships are consistent with the following model for migmatite production: AM is produced by partial melting of a partly depleted ultramafic parent in which neither garnet nor amphibole remain in the residue; TR and TN are produced by partial melting of undepleted to variably depleted amphibolite in which garnet does not remain in the residue; MT is produced by mixing of plagioclase-rich TR with AM; and LTR represents the solid residue after fractional crystallization of TR.

Emergency pancreatoduodenectomy (whipple procedure) for massive upper gastrointestinal bleeding caused by a diffuse B-cell lymphoma of the duodenum: report of a case.

PubMed

Stratigos, Panagiotis; Kouskos, Efstratios; Kouroglou, Maria; Chrisafis, Ioannis; Fois, Lucia; Mavrogiorgis, Anastasios; Axiotis, Efthimios; Zamtrakis, Sotirios

2007-01-01

We herein report a rare case of a massive upper gastrointestinal (GI) bleeding, caused by high-grade diffuse B-cell lymphoma of the duodenum, secondary to immunoproliferative small intestinal disease (IPSID) and treated with an emergency partial pancreatoduodenectomy. A 42-year-old man was admitted to our hospital because of hematemesis. Upper GI endoscopy was unrevealing because of the copious bleeding. Initially, the patient underwent conservative treatment, thus resulting in the temporary cessation of the bleeding. Later, the hemorrhage massively relapsed. An urgent abdominal ultrasound raised the suspicion of a large, possibly bleeding, neoplasm of the duodenum, which was finally confirmed by abdominal computed tomography. The patient underwent an emergency laparotomy, during which a partial pancreatoduodenectomy was performed (Whipple procedure). Histologically, the tumor was a high-grade B-cell lymphoma of the duodenum. The nearby small intestinal mucosa was suggestive of IPSID. A massive upper GI hemorrhage from a high-grade B-cell non-Hodgkin lymphoma of the duodenum, which develops secondary to IPSID, is a very rare clinical demonstration of this disease. Our case is one of the few reports in the English literature, for which the Whipple procedure has been performed as a curative treatment.

VO2 Max in Variable Type Exercise Among Well-Trained Upper Body Athletes.

ERIC Educational Resources Information Center

Seals, Douglas R.; Mullin, John P.

1982-01-01

The maximal oxygen consumption (VO2 max) of well-trained upper body athletes was compared to that of untrained individuals in four types of exercise: arm cranking, legs only cycling, graded treadmill running, and combined arm cranking and leg cycling. Results of the study showed that well-trained upper body athletes attained a significantly higher…

Exploring Turkish Upper Primary Level Pupils' Understanding of Digestion

ERIC Educational Resources Information Center

Cakici, Yilmaz

2005-01-01

This article reports a study of Turkish children's understanding of digestion in Grades 4 and 5 (ages 10-11). Data collection was carried out through the use of an open-ended questionnaire administered to 283 children in three Turkish primary schools. Follow-up interviews were conducted with 30 children in Grade 4 and 72 children in Grade 5. The…

Classroom Idea-Sparkers: Grading and Student Learning--Ideas for Practice

ERIC Educational Resources Information Center

Wegwert, Joseph C.

2012-01-01

Grading is often seen as a point of conflict with students and, in upper elementary and beyond, with parents. It is a chore that consumes time and saps critical levels of energy better used for creative planning and preparation and face-to-face interactions with students. Grading is sometimes referred to as a "necessary evil," yet many teachers…

The metamorphic sole of New Caledonia ophiolite: 40Ar/39Ar, U-Pb, and geochemical evidence for subduction inception at a spreading ridge

NASA Astrophysics Data System (ADS)

Cluzel, Dominique; Jourdan, Fred; Meffre, SéBastien; Maurizot, Pierre; Lesimple, StéPhane

2012-06-01

Amphibolite lenses that locally crop out below the serpentinite sole at the base of the ophiolite of New Caledonia (termed Peridotite Nappe) recrystallized in the high-temperature amphibolite facies and thus sharply contrast with blueschists and eclogites of the Eocene metamorphic complex. Amphibolites mostly display the geochemical features of MORB with a slight Nb depletion and thus are similar to the youngest (Late Paleocene-Eocene) BABB components of the allochthonous Poya Terrane. Thermochronological data from hornblende (40Ar/39Ar), zircon, and sphene (U-Pb) suggest that these mafic rocks recrystallized at ˜56 Ma. Using various geothermobarometers provides a rough estimate of peak recrystallization conditions of ˜0.5 GPa at ˜800-950°C. The thermal gradient inferred from the metamorphic assemblage (˜60°C km-1), geometrical relationships, and geochemical similarity suggest that these mafic rocks belong to the oceanic crust of the lower plate of the subduction/obduction system and recrystallized when they subducted below young and hot oceanic lithosphere. They were detached from the down-going plate and finally thrust onto unmetamorphosed Poya Terrane basalts. This and the occurrence of slab melts at ˜53 Ma suggest that subduction inception occurred at or near to the spreading ridge of the South Loyalty Basin at ˜56 Ma.

Significance of the Nestos Shearzone in the southern Rhodopes (Northern Greece/Southern Bulgaria)

NASA Astrophysics Data System (ADS)

Nagel, Thorsten; Schmidt, Silke; Janak, Marian; Jahn-Awe, Silke; Froitzheim, Niko; Georgiev, Neven

2010-05-01

The Nestos Shearzone can be traced over 100 kilometers and separates the two main units of the Rhodopes, the Rhodope Terrane in the hangingwall from the Pangaion-Pirin Unit in the footwall. The Rhodope Terrane consists of mingled continental and oceanic basement rocks, intruded by granitic bodies of Cenozoic age. It underwent at least amphibolite facies conditions during the Alpine orogenic cycle and several localities with preserved highpressure and/or ultrahigh-pressure rocks have been found. The age of orogenesis and metamorphism is ambiguous and several Mesozoic and Tertiary cycles may be recorded in that unit. The lowermost level immediately on top of the Nestos Shearzone (Sidironero subunit) mainly consists of rocks derived from a Jurassic arc and appears to show the youngest reported (i.e. Eocene) high-grade metamorphism (including ultra-high-pressure conditions and a subsequent migmatic stage). The underlying Pangaion-Pirin Unit beneath the Nestos Shearzone is build of marbles and Variscan gneisses of disputed Mesozoic paleogeographic position. It is intruded by Oligocene granitoids, which also crosscut the Nestos Shearzone. The Pangaion-Pirin Unit experienced a clockwise PT-path culminating at upper greenschist facies conditions during the Alpine cycle. The Nestos Shearzone is defined by top-to-the-southwest-directed mylonites formed under upper greenschist facies conditions. So far, it has been viewed as a thrust. We present structural and petrological data suggesting that the Nestos Shearzone instead represents a major detachment horizon related to late Eo-Oligocene normal faults in the overlying units. Mylonitisation along the shear zone occurred under conditions postdating peak pressures. The shear zone formed between about 40 Ma and 34 Ma as indicated by the age of high temperature conditions in the hangingwall and the age of Oligocene granitoids crosscutting the mylonites. During this time, pronounced extension and basin formation took place in the hangingwall of the Nestos Shearzone. We propose that the brittle Mesta detachment, which bounds the Mesta Graben to the East, roots into the Nestos Shearzone. Themetamorphic history of the Pangaion-Pirin Unit as well as the proposed young age of the Nestos Shearzone is in conflict with studies proposing that this unit represents an independent microcontinent (Drama) accreted to the future Rhodopes in late Jurassic or early Cretaceous times. Instead, we propose that the Pangaion-Pirin Unit could be derived from the Apulian plate, which would have far reaching consequences for the structural architecture of the Hellenic orogen.

Fatigue of Austempered Ductile Iron with Two Strength Grades in Very High Cycle Regime

NASA Astrophysics Data System (ADS)

Zhang, Jiwang; Li, Wei; Song, Qingpeng; Zhang, Ning; Lu, Liantao

2016-03-01

In this study, Austempered ductile irons (ADIs) with two different strength grades were produced and the fatigue properties were measured at 109 cycles. The results show that the S-N curves give a typical step-wise shape and there is no fatigue limit in the very high cycle fatigue regime. The two grades ADI have the similar fracture behaviors and fatigue failure can initiate from defects at specimen surface and subsurface zone. On the fracture surfaces of some specimens, the `granular-bright-facet' area with rich carbon distribution is observed in the vicinity of the defect. The microstructure affects the crack behaviors at the early propagation stage. The ADI with upper and lower bainite shows higher fatigue strength compared with the ADI with coarse upper bainite.

Part Singing Revisited.

ERIC Educational Resources Information Center

Junda, Mary Ellen

1997-01-01

Maintains that children's success with drones, responsorial singing, and ostinatos in the primary grades can lead naturally to the singing of polyphony and homophony in the upper elementary grades. Recommends teachers using age-appropriate materials, teaching sequentially, and evaluating each instructional step. Lists national standards related to…

Over 400 m.y. metamorphic history of the Fennoscandian lithospheric segment in the Proterozoic (the East European Craton)

NASA Astrophysics Data System (ADS)

Skridlaite, G.; Bogdanova, S.; Taran, L.; Baginski, B.; Krzeminska, E.; Wiszniewska, J.; Whitehouse, M.

2009-04-01

Several Palaeoproterozoic terranes in the Fennoscandian lithospheric segment of the East European Craton (EEC) evolved differently prior to their final amalgamation at c. 1.8 Ga. South-westward younging of the major tectono-thermal events characterizes the Baltic -Belarus region between the Baltic and Ukrainian Shields of the EEC. While at c.1.89-1.87 Ga and 1.85-1.84 Ga rocks of some northern and eastern terranes (Estonia, Belarus and eastern Lithuania) experienced syncollisional, moderate P metamorphism, subduction-related volcanic island arc magmatism still dominated southwestern terranes in Lithuania and Poland. The available age determinations of metamorphic zircon (SIMS/NORDSIM and TIMS methods, Stockholm, SHRIMP method, RSES, ANU, Canberra) and metamorphic monazite (TIMS, Stockholm and EPMA method, Warsaw University) allow to distinguish several metamorphic events related to major orogenic processes: - 1.90-1.87 Ga amphibolite-facies H/MP metamorphism occurred along with emplacements of juvenile TTG-type granitoids in the North Estonian and Lithuanian-Belarus terranes. They are coeval with the main accretionary growth of the crust in the Svecofennian Domain in the Baltic Shield (e.g. Lahtinen et al., 2005). - 1.84-1.79 Ga high-grade metamorphism affected sedimentary and igneous rocks in almost all the terranes and is assumed to have been related to the major aggregation of the EEC (Bogdanova et al, 2006, 2008). In the metasedimentary granulites of western Lithuania, a prograde metamorphism commenced with monazite growth prior garnet at 1.84-1.83 Ga. The sediments and mafic igneous rocks in Lithuania, felsic igneous rocks in NE Poland underwent peak metamorphism and deformation at 1.81-1.79 Ga (zircon and monazite ages). The 1.83-1.79 Ga metamorphism has the same age as a metamorphic imprint and strong shearing of the crust in central Sweden (Andersson et al., 2004). The postcollisional granulite metamorphism of mafic intrusions at 1.80-1.79 Ga in Belarus indicates that the NW-SE collision can have triggered the crustal/mantle disturbance along the Fennoscandia-Sarmatia suture zone. - c. 1.7-1.6 Ga moderate PT metamorphic overprint and deformation of 1.83-1.82 Ga magmatic charnockites and c. 1.8 Ga metamorphic granulites in western Lithuania was recorded by the growth of a new garnet, zircon and monazite. The dated charnockites and metasediments contain metamorphic monazite of both 1.60-1.59 Ga and 1.7-1.65 Ga ages. These metamorphic events can reflect a distal influence of the 1.7-1.6 Ga Gothian orogeny in SW Fennoscandia (e.g. Ahall and Connelly, 2008). - 1.55-1.50 and 1.50-1.45 Ga events. In southern Lithuania, the 1.53-1.50 Ga AMCG magmatism was accompanied by high-grade metamorphism. Deformation and amphibolite facies metamorphism are marked by the 1.55-1.45 Ga 40Ar/39Ar ages of hornblende along EW-trending lineaments in central and southeastern Lithuania and Belarus. There are also indications of shearing and low grade, c. 1.50 Ga, metamorphism of metasedimentary rocks and charnockites in NW Lithuania and NE Poland. Altogether, the coeval AMCG magmatism, local high-grade and widespread low-grade metamorphism, and deformation can be manifestations of the Danopolonian orogeny, particularly prominent around the South Baltic Sea. This is a contribution to the project "The Precambrian structure of Baltica as a control of its recent environment and evolution" of the Visby Programme (the Swedish Institute) and SYNTHESYS project SE-TAF-1535. References Ahall, K.I. and Connelly, J.N., 2008. Precambrian Research, 161(3-4): 452-474. Andersson, U.B. et al., 2004, GFF 126, 16-17. Bogdanova, S. et al., 2006, Geological Society, London Memoirs, 32, pp. 599-628 Bogdanova, S. et al., 2008, Precambrian Research 160, 23-45. Lahtinen, R., et al., 2005. In: Precambrian Geology of Finland - Key to the Evolution of the Fennoscandian Shield. Elsevier, Amsterdam, 481-532

Multi-stage accretion of high pressure rocks and thermal changes in a subduction channel: evidence from Diego de Almagro Island (Chilean Patagonia)

NASA Astrophysics Data System (ADS)

Hyppolito, Thais; Angiboust, Samuel; Juliani, Caetano; Glodny, Johannes; Garcia-Casco, Antonio; Calderon, Mauricio; Chopin, Christian

2016-04-01

The remote Diego de Almagro Island, Chile (51° 30' S) exposes one of the rare vestiges of the Cretaceous paleo-subduction system of western South America. It is constituted by two main tectonic units formed by mafic rocks and metasediments: the high temperature/middle pressure Lázaro unit to the East and the high pressure-low temperature Almagro Complex to the West. We herein focus on the Almagro Complex, a pluri-kilometer thick subducted sequence comprising dominantly metatuffs, but also Grt-micaschists, meta-pillow lavas (showing MORB and OIB signatures) and metacherts (transformed to quartz+garnet-rich layers). Despite its apparent homogeneity, the Almagro Complex is actually composed of two distinct units (Willner et al., 2004) with distinct pressure-temperature-time paths. The Garnet Amphibolite unit (GA) shows three chemically and microstructurally distinct garnet generations that grew and (re)-equilibrated between 1.1 GPa and 1.7 GPa (35-55 km) and between 500°C and 600°C. We report for the first time in Chilean Patagonia the presence of rare relicts of omphacite in equilibrium with garnet in mafic layers together with the finding of chloritoid inclusions in garnet from metasediments, and omphacite and glaucophane inclusions in metatuffs. Our P-T estimates, based on pseudosection modeling, single/multi-equilibrium estimates and Raman spectroscopy of organic matter, demonstrate that rocks from the GA unit reached eclogite facies at around 1.7 to 1.8 GPa. Rb-Sr mineral data for Grt-amphibolites indicates that the amphibolitization overprint - which varies in intensity throughout the GA unit - took place at c. 120 Ma. The Blueschist unit, structurally below the GA unit, comprises lithologies similar to the GA unit but finer grained than the former. On other hand, the Blueschist unit (i) does not show garnet with multiple overgrowths and omphacite crystals as seen in the in GA unit; (ii) exhibits slightly lower peak metamorphic conditions than the GA unit (c. 500 °C, 1.4 GPa); (iii) has not suffered the strong amphibolitization visible in the GA unit, and (iv) records blueschist facies deformation at ~80 Ma (Rb-Sr mineral data). Importantly, this cool 80 Ma old event heterogeneously overprinted the GA rocks as shown by silica-rich (Si = 3.5 pfu) rims around phengite (Si = 3.33 pfu) crystals and glaucophane overgrowths around amphibolite-facies hornblende. The amphibolitization stage recorded by GA unit reveals the presence of a transient warming up of the subduction thermal gradient from 9 °C/ km to c. 14 °C/km at c. 120 Ma. We propose that the GA unit has been subsequently cooled down at around 80 Ma coevally with peak metamorphism in the blueschist unit. Dissolution-overgrowth patterns visible in GA unit garnets may be viewed as the record of short-lived thermal pulses associated with discrete basal accretion events. Lately, GA and blueschist units have been tectonically juxtaposed near the root of the accretionary wedge (at c. 30 km depth) and exhumed coherently. Our P-T-t reconstructions for Diego de Almagro rocks bear implications for reconstructing the physical nature of the subduction interface as well as for the understanding of transient, deep accretionary processes taking place near the roots of the seismogenic zone.

Geochemical and isotopic constraints on the tectonic setting of Serra dos Carajas belt, eastern Para, Brazil

NASA Technical Reports Server (NTRS)

Olszewski, W. J., Jr.; Gibbs, A. K.; Wirth, K. R.

1986-01-01

The lower part of the Serra dos Carajas belt is the metavolcanic and metasedimentary Grao para Group (GPG). The GPG is thought to unconformably overlie the older (but undated) Xingu Complex, composed of medium and high-grade gneisses and amphibolite and greenstone belts. The geochemical data indicate that the GPG has many features in common with ancient and modern volcanic suites erupted through continental crust. The mafic rocks clearly differ from those of most Archean greenstone belts, and modern MORB, IAB, and hot-spot basalts. The geological, geochemical, and isotopic data are all consistent with deposition on continental crust, presumably in a marine basin formed by crustal extension. The isotopic data also suggest the existence of depleted mantle as a source for the parent magmas of the GPG. The overall results suggest a tectonic environment, igneous sources, and petrogenesis similar to many modern continental extensional basins, in contrast to most Archean greenstone belts. The Hammersley basin in Australia and the circum-Superior belts in Canada may be suitable Archean and Proterozoic analogues, respectively.

NaSi⇌CaAl exchange equilibrium between plagioclase and amphibole

NASA Astrophysics Data System (ADS)

Spear, Frank S.

1980-03-01

The exchange equilibrium between plagioclase and amphibole, 2 albite+tschermakite=2 anorthite+glaucophane, has been calibrated empirically using data from natural amphibolites. The partition coefficient, K D, for the exchange reaction is ( X an/ X ab)plag ·(Na, M4/Ca, M4)amph.. Partitioning is systematic between plagioclase and amphibole in suites collected from single exposures, but the solid solutions are highly non-ideal: values of In K D range from -3.0 at X an=0.30 to -1.0 at X an=0.90 in samples from a single roadcut. Changes in both K D and the topology of the ternary reciprocal exchange diagram occur with increasing metamorphic grade. Temperature dependence of In K D is moderate with Δ ¯H≃35 to 47 kcal at X an=0.25; pressure dependence is small with Δ ¯V≃ -0.24 cal/bar. Usefulness of this exchange equilibrium as a geothermometer is restricted by uncertainties in the calculation of the amphibole formula from a microprobe analysis, especially with regard to Na, M4 in amphibole, to approximately ±50 ° C.

Geologic map of the Weka Dur gold deposit, Badakhshan Province, Afghanistan, modified from the 1967 original map compilation of M.P. Guguev and others

USGS Publications Warehouse

Peters, Stephen G.; Stettner, Will R.; Masonic, Linda M.

2014-01-01

The Weka Dur gold deposit lies in a cluster of other gold deposits in Badakhshan Province (Ragh district), such as the Kadar, Nesheb Dur, and Rishaw gold occurrences. These gold occurrences lie within a zone of late Hercynian folding and are most likely related to fluids that originated from orogenic processes. The Weka Dur deposit is the largest recorded gold occurrence in Afghanistan and is hosted in Proterozoic mica schist and amphibolite that is intruded by diabase dikes and other intrusive rocks. The tabular orebody is 350 meters (m) long and 2 m wide and can be traced downdip for 110 m. Mineralization consists of ochreous, brecciated schists containing high gold concentrations along gently and steeply dipping fissures. The brecciated rocks grade to 46.7 grams per ton (g/t) silver and contain arsenopyrite, galena, chalcopyrite, and scheelite. Trenches and adits were constructed, mapped, and sampled during the 1960s. Calculated resources are 958.3 kilograms of gold, averaging 4.1 g/t gold.

Scientific Reasoning and Its Relationship with Problem Solving: The Case of Upper Primary Science Teachers

ERIC Educational Resources Information Center

Alshamali, Mahmoud A.; Daher, Wajeeh M.

2016-01-01

This study aimed at identifying the levels of scientific reasoning of upper primary stage (grades 4-7) science teachers based on their use of a problem-solving strategy. The study sample (N = 138; 32 % male and 68 % female) was randomly selected using stratified sampling from an original population of 437 upper primary school teachers. The…

The Effect of the Involvement within Career Academies by Elective Participation of Eleventh and Twelfth Grade High School Students during the Implementation Year

ERIC Educational Resources Information Center

Johnston, Nancy A.

2010-01-01

The purpose of this study was to determine the effect of elective participation in one of three implementation year Career Academies, Education, Entrepreneurship, or Finance, on upper-class high school academic grades, Grade Point Average, and school academy participation measures. Significance of the junior and senior year of high school, the…

Replicating effective pedagogical approaches from introductory physics to improve student learning of quantum mechanics

NASA Astrophysics Data System (ADS)

Sayer, Ryan Thomas

Upper-level undergraduate students entering a quantum mechanics (QM) course are in many ways similar to students entering an introductory physics course. Numerous studies have investigated the difficulties that novices face in introductory physics as well as the pedagogical approaches that are effective in helping them overcome those difficulties. My research focuses on replicating effective approaches and instructional strategies used in introductory physics courses to help advanced students in an upper-level QM course. I have investigated the use of Just-in-time Teaching (JiTT) and peer discussion involving clicker questions in an upper-level quantum mechanics course. The JiTT approach including peer discussions was effective in helping students overcome their difficulties and improve their understanding of QM concepts. Learning tools, such as a Quantum Interactive Learning Tutorial (QuILT) based on the Doubleslit Experiment (DSE) which I helped develop, have been successful in helping upper-level undergraduate students improve their understanding of QM. Many students have also demonstrated the ability to transfer knowledge from a QuILT based on the Mach-Zehnder interferometer while working on the DSE QuILT. In addition, I have been involved in implementing research-based activities during our semester-long professional development course for teaching assistants (TAs). In one intervention, TAs were asked to grade student solutions to introductory physics problems first using their choice of method, then again using a rubric designed to promote effective problem-solving approaches, then once more at the end of the semester using their choice of method. This intervention found that many TAs have ingrained beliefs about the purposes of grading which include placing the burden of proof on the instructor as well as a belief that grading cannot serve as a formative assessment. I also compared TAs grading practices and considerations when grading student solutions to QM problems versus when grading student solutions to introductory physics. Many TAs penalized students for not explicating the problem solving process more often in the QM context than in the introductory physics context. The implications of these interventions for promoting student learning in QM are discussed.

Predicting Success in Upper-Division Business Communication Classes.

ERIC Educational Resources Information Center

Wilson, Barbara; Plutsky, Susan

1997-01-01

Scores of 102 business communication students on the Descriptive Tests of Language Skills (DTLS) and grades on analytical reports, short assignments, and the overall course were examined. Females received higher course and report grades. The DTLS was a weak predictor of student performance. (SK)

The Neoacadian orogenic core of the souther Appalachians: a Geo-traverse through the migmatitic inner Piedmont from the Brushy Mountains to Lincolnton, North Carolina

USGS Publications Warehouse

Merschat, Arthur J.; Hatcher, Robert D.; Byars, Heather E.; Gilliam, William G.; Eppes, Martha Cary; Bartholomew, Mervin J.

2012-01-01

The Inner Piedmont extends from North Carolina to Alabama and comprises the Neoacadian (360–345 Ma) orogenic core of the southern Appalachian orogen. Bordered to west by the Blue Ridge and the exotic Carolina superterrane to the east, the Inner Piedmont is cored by an extensive region of migmatitic, sillimanite-grade rocks. It is a composite of the peri-Laurentian Tugaloo terrane and mixed Laurentian and peri-Gondwanan affinity Cat Square terrane, which are exposed in several gentle-dipping thrust sheets (nappes). The Cat Square terrane consists of Late Silurian to Early Devonian pelitic schist and metagraywacke intruded by several Devonian to Mississippian peraluminous granitoids, and juxtaposed against the Tugaloo terrane by the Brindle Creek fault. This field trip through the North Carolina Inner Piedmont will examine the lithostratigraphies of the Tugaloo and Cat Square terranes, deformation associated with Brindle Creek fault, Devonian-Mississippian granitoids and charnockite of the Cat Square terrane, pervasive amphibolite-grade Devonian-Mississippian (Neoacadian) deformation and metamorphism throughout the Inner Piedmont, and existence of large crystalline thrust sheets in the Inner Piedmont. Consistent with field observations, geochronology and other data, we have hypothesized that the Carolina superterrane collided obliquely with Laurentia near the Pennsylvania embayment during the Devonian, overrode the Cat Square terrane and Laurentian margin, and squeezed the Inner Piedmont out to the west and southwest as an orogenic channel buttressed against the footwall of the Brevard fault zone.

[Analysis of development, safety and efficacy of percutaneous nephrolithotomy for management of upper urinary tract calculi in pediatric patients].

PubMed

Yu, L P; Xu, T

2017-08-18

To evaluate the development, safety and efficacy of percutaneous nephrolithotomy(PNL) for management of upper urinary tract calculi in pediatric patients. In the study, 77 pediatric patients undergoing 87 PNLs through mini or standard tract for upper urinary tract calculi between January 2005 and December 2016 in Peking University People's hospital were reviewed, including 69 renal calculi, 6 upper ureteral calculi, 12 renal and upper ureteral calculi, 35 single calculi, 43 multiple calculi and 9 staghorn calculi. The development and efficacy of PNL in pediatric patients were studied by analyzing the characteristics and clinical indexes, and by reviewing the associated literature. The Clavien classification system was used to evaluate the complications after PNL. A total of 87 PNLs were performed in 77 pediatric patients. Eighty-one upper urinary tract calculi were managed through a single tract(93.1%), 5 pediatric patients were managed through 2 tracts(5.7%), and 1 pediatric patient was managed through 3 tracts(1.2%). The mean operating time was (77.0±29.8) min. The stone-free rate after one session was 100% for single calculi and 71.2% for multiple or staghorn calculi, 5(5.8%) children underwent auxiliary procedure to remove the residual calculi and the final stone-free rate of PNL was 88.5%. One of the main complications of pediatric PNL was fever. Sixteen (18.4%) had moderate fever(38-39 °C), 5 (5.7%) had high fever (39-40 °C) and there were no severe complications of infection, such as sepsis or septic shock. The mean hemoglobin loss was (10.3±16.1) g/L and the serum creatinine rise was (7.0±13.3) μmol/L. One(1.2%) pediatric patient suffered ureteroscopic lithotripsy because of the obstruction by the residual stone in ureter. No injury of organs or retroperitoneal urinary extravasation occurred. General assessment of the complications showed Clavien grade I complications in 14 (16.1%) pediatric patients, grade II in 7(8.0%) children and grade III in 1(1.2%) children. There was no grade IV or V complications. The overall complication rate was 25.3%. PNL for management of upper urinary tract calculi in pediatric patients is effective. Complications after PNL, as assessed with Clavien classification system, are mild and PNL in pediatric patients is safe.

Extension Within The Australia-Eurasia Collision: The Metamorphic Rocks Of Central Sulawesi, Indonesia

NASA Astrophysics Data System (ADS)

Watkinson, I. M.; Hall, R.; Hennig, J.; Forster, M.

2012-12-01

Low-angle mylonitic fabrics from the metamorphic basement of central Sulawesi reveal a complex history of extension from the late Miocene to the present-day. Sulawesi is situated in the convergent triple junction between the Australian, Eurasian and Philippine Sea plates. The island is cut by the Palu-Koro and Matano faults, major active strike-slip zones that were initiated no earlier than about 5 Ma and have previously been attributed to collision-related processes. Within, and to the north and east of the strike-slip faults, are a suite of metamorphic complexes that include mica schists, schistose amphibolites, gneisses, migmatites, granulites, eclogites, marbles and ultramafic rocks including garnet peridotites. Mylonitic fabrics are widespread throughout the metamorphic rocks. The orientation of the mylonitic foliation is highly variable but typically dips less than 30°. Kinematic indicators record transport directions dominantly between top-to-the-NW and top-to-the-NE. Medium to high-grade mylonites, particularly in the south and west, are associated with ductile boudinage of eclogite and kyanite-bearing layers, 'snowball' garnet porphyroclasts, dynamic recrystallisation of feldspar and amphibole, and mylonitic deformation was locally synchronous with partial melting. Medium to high-grade mylonites are commonly overprinted by isoclinal asymmetric similar folds. Low grade mylonites are characterised by quartz recrystallisation only. Mica growth during mylonitic deformation is recorded by young 40Ar-39Ar plateaux between 5.05 ± 0.01 Ma and 2.07 ± 0.03 Ma in the west and 11.33 ± 0.02 Ma in the east. Undeformed aplitic dykes of similar composition to the migmatite leucosomes locally cross-cut the migmatitic mylonites and have yielded a biotite 40Ar-39Ar plateau of 3.62 ± 0.02 Ma. In the east the mylonitic fabric is cut by a low-angle detachment surface expressed as anomalously corrugated topography. On the basis of lithologic variation, shear-sense directions, 40Ar-39Ar ages and topographic character it is possible to divide the central Sulawesi metamorphic complexes into a series of low-angle ductile shear zones, cut by an upper brittle detachment in the east which may still be active. Uplift of the metamorphic rocks has been largely in response to sequential unroofing along these structures. The system is bounded in the west by the Palu-Koro Fault, which links to subduction beneath north Sulawesi, and which may flatten at depth into a basal detachment below central Sulawesi. Early extension is synchronous with spreading in the North Banda Sea, and may have been driven by east-directed rollback of the Banda Sea. Later extension (post-5 Ma) was driven by subduction rollback in the north, and much of the extensional deformation in central Sulawesi represents the crustal 'tear' marking the southern limit of the effects of northward extension.

Kindergarten: Magic Moments.

ERIC Educational Resources Information Center

Fetzer, Lorelei; Ponder, Darlene

1989-01-01

Argues that the best alternative to assigning children to grades on the basis of birth date alone is to implement a child-centered and process-oriented curriculum for younger children and push back the academic curriculum to the upper grades. Suggests this allows children to develop at their own pace. (RS)

Math Process Standards Series, Grades 3-5

ERIC Educational Resources Information Center

O'Connell, Susan, Ed.

2008-01-01

NCTM's Process Standards support teaching that helps upper elementary level children develop independent, effective mathematical thinking. The books in the Heinemann Math Process Standards Series give every intermediate-grades teacher the opportunity to explore each standard in depth. With language and examples that don't require prior math…

Oncologic results of nephron sparing endoscopic approach for upper tract low grade transitional cell carcinoma in comparison to nephroureterectomy - a case control study.

PubMed

Hoffman, Azik; Yossepowitch, Ofer; Erlich, Yaron; Holland, Ronen; Lifshitz, David

2014-12-02

There is paucity of data as to the results of the endoscopic approach in comparison to the golden standard of nephro-ureterectomy in elective, low grade TCC, patients. Our purpose is to report our results of a nephron sparing approach compared to nephro-ureterectomy in those patients. From a retrospective data base we identified 25 patients and 23 patients who underwent a nephron sparing ureterosocpic resection and nephro-reterectomy for low grade UT-TCC, respectively. The endoscopic technique included endoscopic tumor biopsy followed by primary resection and/or fulguration. The nephron sparing group was followed by bi-annual ureteroscopy and upper tract imaging, timely cystoscopy and urine cytology collection. Data for overall and disease related mortality, bladder and ureteral TCC recurrence and renal function are reported in both groups. Median follow - up time was 26 months. 11 (44%) patients developed bladder recurrence at a median period of 9 months after initial ureteroscopy, compared to 9 (39%) in the NUx group (P < 0.05). Recurrent ureteral low grade TCC was observed in 9 patients (median: 9 months). All were treated endoscopicaly successfully. Renal function remained stable in the nephron sparing group. No disease related mortality was recorded in the nephron-sparing group while one patient died of his disease following NUx. Disease related mortality following a nephron sparing endoscopic approach or nephroureterectomy for low grade upper tract TCC is excellent. However, the nephron sparing approach is associated with a relatively high rate of ureteral and bladder recurrence. Therefore, a stringent follow-up protocol is required.

Extreme extension across Seram and Ambon, eastern Indonesia: Evidence for Banda slab rollback

NASA Astrophysics Data System (ADS)

Pownall, J. M.; Hall, R.; Watkinson, I. M.

2013-04-01

The island of Seram, which lies in the northern part of the 180°-curved Banda Arc, has previously been interpreted as a fold-and-thrust belt formed during arc-continent collision, which incorporates ophiolites intruded by granites thought to have been produced by anatexis within a metamorphic "sole". However, new geological mapping and a re-examination of the field relations cause us to question this model. We instead propose that there is evidence for recent N-S extension that has caused the high-temperature exhumation of hot mantle peridotites, granites, and granulites (the "Kobipoto Complex") beneath low-angle lithospheric detachment faults. Greenschist- to lower-amphibolite facies metapelites and amphibolites of the Tehoru Formation, which comprise the hanging wall above the detachment faults, were overprinted by sillimanite-grade metamorphism, migmatisation and limited localised diatexis to form the Taunusa Complex. Highly aluminous metapelitic garnet + cordierite + sillimanite + spinel + corundum + quartz granulites exposed in the Kobipoto Mountains (central Seram) are intimately associated with the peridotites. Spinel + quartz inclusions in garnet, which indicate that peak metamorphic temperatures for the granulites likely approached 900 °C, confirm that peridotite was juxtaposed against the crust at typical lithospheric mantle temperatures and could not have been part of a cooled ophiolite. Some granulites experienced slight metatexis, but the majority underwent more advanced in situ anatexis to produce widespread granitic diatexites characterised by abundant cordierite and garnet xenocrysts and numerous restitic sillimanite + spinel "clots". These Mio-Pliocene "cordierite granites", which are present throughout Ambon, western Seram, and the Kobipoto Mountains in direct association with peridotites, demonstrate that the extreme extension required to have driven Kobipoto Complex exhumation must have occurred along much of the northern Banda Arc. In central Seram, smeared lenses of peridotites are incorporated with a major left-lateral strike-slip shear zone (the "Kawa Shear Zone"), demonstrating that strike-slip motions likely initiated shortly after the mantle had been partly exhumed by detachment faulting and that the main strike-slip faults may themselves be reactivated and steepened low-angle detachments. The Kobipoto Mountains represent a left-lateral pop-up structure that has facilitated the final stages of exhumation of the high-grade Kobipoto Complex through overlying Mesozoic sedimentary rocks. On Ambon, Quaternary "ambonites" (cordierite + garnet dacites) are evidently the volcanic equivalent of the cordierite granites as they also contain granulite-inherited xenoliths and xenocrysts. The geodynamic driver for mantle exhumation along the detachment faults and strike-slip faulting in central Seram is very likely the same - we interpret the extreme extension to be the result of eastward slab rollback into the Banda Embayment as outlined by the latest plate reconstructions for Banda Arc evolution.

Finnish Primary and Secondary School Students' Interest in Music and Mathematics Relating to Enjoyment of the Subject and Perception of the Importance and Usefulness of the Subject

ERIC Educational Resources Information Center

Tossavainen, Timo; Juvonen, Antti

2015-01-01

Based on an expectancy-value theoretical framework and data (n = 1654) collected in 29 Finnish municipalities using a structured questionnaire, this study examines primary (grades 5-6), lower secondary (grades 7-9) and upper secondary (grades 10-12) students' motivation in music and mathematics. It explores in detail the students' interest in…

Effects of postmortem aging and USDA quality grade on Warner-Bratzler shear force values of seventeen individual beef muscles.

PubMed

Gruber, S L; Tatum, J D; Scanga, J A; Chapman, P L; Smith, G C; Belk, K E

2006-12-01

Forty USDA Select and 40 upper two-thirds USDA Choice beef carcasses were used to determine the effects of postmortem aging on tenderness of 17 individual beef muscles. Biceps femoris-long head, complexus, gluteus medius, infraspinatus, longissimus dorsi, psoas major, rectus femoris, semimembranosus, semitendinosus, serratus ventralis, spinalis dorsi, supraspinatus, tensor fasciae latae, teres major, triceps brachii-long head, vastus lateralis, and vastus medialis muscles were removed from each carcass. Seven steaks (2.54-cm thick) were cut from every muscle, and each steak was assigned to one of the following postmortem aging periods: 2, 4, 6, 10, 14, 21, or 28 d postmortem. After completion of the designated aging period, steaks were removed from storage (2 degrees C, never frozen), cooked to a peak internal temperature of 71 degrees C, and evaluated using Warner-Bratzler shear force (WBSF). Analysis of WBSF revealed a 3-way interaction (P = 0.004) among individual muscle, USDA quality grade, and postmortem aging period. With the exception of the Select teres major, WBSF of all muscles (both quality grades) decreased with increasing time of postmortem storage. Nonlinear regression was used to characterize the extent (aging response) and rate of decrease in WBSF from 2 through 28 d postmortem for each muscle within each quality grade. In general, WBSF of upper two-thirds Choice muscles decreased more rapidly from 2 to 10 d postmortem than did corresponding Select muscles. Muscles that had greater aging responses generally had greater 2-d WBSF values. The upper two-thirds Choice psoas major, serratus ventralis, and vastus lateralis muscles required similar aging times to complete a majority of the aging response (< or =0.1 kg of aging response remaining) compared with analogous Select muscles. The upper two-thirds Choice complexus, gluteus medius, semitendinosus, triceps brachii-long head, and vastus medialis muscles required 4 to 6 d less time to complete a majority of the aging response than did comparable Select muscles. Aging times for Select biceps femoris-long head, infraspinatus, longissimus dorsi, rectus femoris, semimembranosus, spinalis dorsi, supraspinatus, and tensor fasciae latae muscles were > or =7 d longer than those for corresponding upper two-thirds Choice muscles. Results from this study suggest that muscle-to-muscle tenderness differences depend on quality grade and aging time and that postmortem aging should be managed with respect to individual muscle and USDA quality grade.

Geology and mineral deposits of an area in the Departments of Antioquia and Caldas (Subzone IIB), Colombia

USGS Publications Warehouse

Feininger, Tomas; Barrero L., Dario; Castro, Nestor; Hall, R.B.

1973-01-01

The Inventario Minero National (IMN), a four-year cooperative geologic mapping and mineral resources appraisal project, was accomplished under an agreement between the Republic of Colombia and the U. S. Agency for International Development from 1964 through 1969. Subzone IIB, consisting essentially of the east half of Zone comprises nearly 20,000 km2 principally in the Department of Antioquia but including also small parts of the Departments of Caldas and Tolima. The rocks in IIB range from Precambrian to Holocene. Precambrian feldspar-quartz gneiss occupies a mosaic of fault-bounded blocks intruded by igneous rocks between the Oto fault and the Rio Magdalena. Paleozoic rocks are extensive, and include lightly metamorphosed graptolite-bearing Ordovician shale at Cristalina, and a major suite of graphitic quartz-mica schist, feldspathic and aluminous gneiss, quartzite, marble, amphibolite, and other rocks. Syntectonic intrusive gneiss included many of the older rocks during a late Paleozoic(?) orogeny, which was accompanied by Abukuma-type metamorphosing from lowermost greenschist to upper amphibolite facies. A Jurassic diorite pluton bounded by faults cuts volcanic rocks of unknown age east of the Otu fault. Cretaceous rocks are major units. Middle Cretaceous carbonaceous shale, sandstone, graywacke, conglomerate, and volcanic rocks are locally prominent. The Antioquian batholith (quartz diorite) of Late Cretaceous age cuts the middle Cretaceous and older rocks. A belt of Tertiary nonmarine clastic sedimentary rocks crops out along the Magdalena Valley. Patches of Tertiary alluvium are locally preserved in the mountains. Quaternary alluvium, much of it auriferous, is widespread in modern stream valleys. Structurally IIB constitutes part of a vast complex synclinorium intruded concordantly by syntectonic catazonal or mesozonal felsic plutons, and by the later epizonal post-tectonic Antioquian batholith. Previously unrecognized major wrench faults are outstanding structural features of IIB. Some are traceable for several hundred kilometers and probably have displacements measurable in kilometers, although only the Palestina fault, with right-lateral displacement of 27.7 km, is accurately documented. Correlations of rocks mapped in IIB with those of outlying areas including neighboring IIA are discussed.

Paleoproterozoic Keulik-Kenirim Ore-Bearing Gabbro-Peridotite Complex, Kola Region: A New Occurrence of Ferropicritic Magmatism

NASA Astrophysics Data System (ADS)

Smolkin, V. F.; Lokhov, K. I.; Skublov, S. G.; Sergeeva, L. Yu.; Lokhov, D. K.; Sergeev, S. A.

2018-03-01

Comprehensive research of ore-bearing differentiated intrusions of the Keulik-Kenirim structural unit, which represents a fragment of the Paleoproterozoic Pechenga-Varzuga Belt, has been carried out for the first time. The intrusions are subvolcanic by type and lenticular in shape, nearly conformable and steeply dipping. They are made up of peridotite, olivine and plagioclase pyroxenites, and gabbro metamorphosed under amphibolite facies conditions along with host basic volcanics. All intrusive rocks are enriched in TiO2 and FeO. Sulfide Cu-Ni mineralization is represented by disseminated, pocket, and stringer-disseminated types, which are clustered in the peridotitic zone as hanging units and bottom lodes. The Ni content in disseminated ore is estimated at 0.45-0.55 wt % and 1.15-3.32 wt % in ore pockets; the Cu grades are 0.17-0.20 and 0.46-5.65 wt %, respectively. To determine the age of intrusions and metamorphism of intrusive and volcanic rocks, various isotopic systems have been used: Sm-Nd (TIMS) in rock and U-Pb (SIMS SHRIMP) and Lu-Hf (LA-ICP-MS) in zircon. Conclusions on the origin of zircons are based on concentrations of trace elements including REE therein and Hf-Nd correlation in zircons and rocks. The U-Pb system of zircons reflects episodes of igneous rock formation (1982 ± 12 Ma) and their postmagmatic transformation (1938 ± 20 Ma). The last disturbance of the U-Pb isotopic system occurred 700 and 425 Ma. Xenogenic zircons dated from 3.17 to 2.65 Ga have been revealed in the studied samples. These zircons were captured by magma from the Archean basement during its ascent. The intrusions were emplaced synchronously with economic ore formation in the Pechenga ore field (1985 ± 10 Ma). The peak metamorphism of intrusive rocks under amphibolite facies conditions is recorded at 40 Ma later. The differentiated intrusions of the Keulik-Kenirim structural unit are close in their internal structure, mineralogy, and geochemistry, as well as in age and features of related Cu-Ni mineralization to ore-bearing intrusions of the Pechenga ore field, which are derivatives of ferropicritic (ferriferous) magmatism.

Team Teaching at Upper Arlington School.

ERIC Educational Resources Information Center

Jackson, Annette R.

1968-01-01

Team teaching has been used for 4 years in the 10th-grade English classes at Upper Arlington High School near Columbus, Ohio. Units are prepared, presented, and evaluated by teachers working together voluntarily. A 6-day American literature unit introducing Romanticism has been particularly successful. The contrasts between Neoclassicism and…

Building a Trail, Building Character

ERIC Educational Resources Information Center

Elgie, Bill; MacLean, Ross; Dykstra, Rebecca

2007-01-01

In Grade 9, Upper Canada College (UCC) students participate in a week-long outdoor education program in Halton Region, west of Toronto. This week is the culmination of over 60 days of total outdoor education programming between Senior Kindergarten and Grade 9. Activities during the expedition include moving water canoeing, mountain biking, hiking,…

Influence of shovel-shaped incisors on the dental arch crowding in Mongolian females.

PubMed

Hasegawa, Yuh; Terada, Kazuto; Kageyama, Ikuo; Tsukada, Shin-ichi; Uzuka, Satoshi; Nakahara, Rizako; Nakahara, Sen

2009-08-01

The aim of this study was to investigate the influences of shovel-shaped incisors on the dental arch crowding in the samples of modern young female adult Mongolians (belonging to the Khalkha-Mogol grouping) ranged between 18.5 and 25.0 years, with a mean age of 20.7 years. Materials in this study comprised of 33 dental casts. Plaster replicas of the A.S.U. system plaques were used to facilitate standardization in scoring and classify shoveling regarding both upper central and lateral incisors. Dimensions of the dental arch namely, overjet, overbite, arch depth, arch width and irregularity index were measured. The correlation between the shovel shape of the central incisor and the lateral incisor was highly significant. Significantly relations were found between the grades of shoveling and the mesiodistal diameters of upper first molars and lower incisors. Positive correlation was admitted between the shoveling and upper arch depth anterior, and upper arch depth. It may be considered that the grades of shoveling are indirectly related with upper and/or lower anterior crowding. Although crowding is looks like an expression of disharmony between teeth and alveolar arch, it may be caused by multiple etiologic factors interacted directly and/or indirectly.

Success-factors in transition to university mathematics

NASA Astrophysics Data System (ADS)

Bengmark, S.; Thunberg, H.; Winberg, T. M.

2017-11-01

This study examines different factors' relative importance for students' performance in the transition to university mathematics. Students' characteristics (motivation, actions and beliefs) were measured when entering the university and at the end of the first year. Principal component analysis revealed four important constructs: Self-efficacy, Motivation type, Study habits and Views of mathematics. Subsequently, orthogonal partial least squares (OPLS) analysis was used for measuring the constructs' ability to predict students' university mathematics grades. No individual constructs measured at the time of entrance predicted more than 5% of the variation. On the other hand, jointly they predicted 14%, which is almost in pair with upper secondary grades predicting 17%. Constructs measured at the end of the first year were stronger predictors, jointly predicting 37% of the variation in university grades, with Self-efficacy (21%) and Motivation (12%) being the two strongest individual predictors. In general, Study habits were not important for predicting university achievement. However, for students with low upper secondary grades, the textbook and interaction with peers, rather than internet-based resources, contributed positively to achievement. The association between Views of mathematics and performance was weak for all groups and non-existing for students with low grades.

Expression of p27 and its ubiquitin ligase subunit Skp2 in upper urinary tract transitional cell carcinoma.

PubMed

Langner, Cord; von Wasielewski, Reinhard; Ratschek, Manfred; Rehak, Peter; Zigeuner, Richard

2004-09-01

To analyze p27 and S-phase kinase-associated protein 2 (Skp2) expression in upper urinary tract transitional cell carcinoma (TCC) with respect to biologic significance. p27 (p27/kip1) is involved in cell cycle control, and loss of p27 protein expression may result in tumor development and/or progression. The association of p27 with the ubiquitin ligase subunit Skp2 targets p27 for degradation. A total of 53 upper urinary tract TCC specimens were investigated immunohistochemically using a tissue microarray technique. The immunoreactivity of p27 and Skp2 was analyzed with respect to associations with pT stage, grade, and prognosis. Non-neoplastic renal tissue showed p27 immunoreactivity in tubule epithelium and pelvic urothelium, but lacked immunoreactivity for Skp2. In the TCC specimens, p27 immunoreactivity was noted in 47 (89%) of 53 cases. High p27 expression (50% or greater of tumor cell nuclei) tended to decrease with rising tumor stage (14 [45%] of 31 with pT1-pT2 versus 4 [18%] of 22 with pT3; P = 0.076), but was independent of tumor grade (11 [39%] of 28 grade 2 versus 7 [28%] of 25 grade 3-4; P = 0.56). Skp2 immunoreactivity was noted in 32 (60%) of 53 tumors. Skp2 expression increased with rising tumor stage (9 [41%] of 22 pT1 versus 23 [74%] of 31 pT2-pT3; P = 0.023) and tumor grade (12 [43%] of 28 grade 2 versus 20 [80%] of 25 grade 3; P = 0.043) and was associated with angioinvasion (P = 0.017). In multivariate analysis, tumor stage proved to be the only independent prognostic factor regarding disease-free survival. p27 and Skp2 are additional biomarkers in urogenital pathologic findings. The statistically significant association of Skp2 expression with high-grade TCC, as well as the lack of expression in non-neoplastic tissue, suggests that Skp2 could be a promising target for future cancer therapy strategies.

Intra- and interobserver reliability estimates for identification and grading of upper respiratory tract abnormalities recorded in horses at rest and during overground endoscopy.

PubMed

McGivney, C L; Sweeney, J; David, F; O'Leary, J M; Hill, E W; Katz, L M

2017-07-01

Previous studies support good intra- and interobserver agreements for endoscopic evaluation of various upper respiratory tract (URT) diseases in horses. However, these studies mainly assessed resting endoscopic examination videos and/or focussed on a single URT abnormality. To estimate intra- and interobserver agreement for identification and grading of all URT abnormalities from resting and overground endoscopy (OGE) videos of Thoroughbreds. Blinded, fully crossed design. Resting and OGE URT videos for n = 43 Thoroughbreds were retrospectively chosen based on identification of common URT disorders. The videos were randomly evaluated in duplicate by 4 raters blinded to all information including prior URT disorder(s) diagnosis. Abnormalities were graded using well-described ordinal scales. Intra- and interobserver agreements were estimated using Cohen's weighted κ and Krippendorff's α, respectively. Intraobserver agreement was perfect/nearly perfect for arytenoid symmetry at exercise, epiglottic entrapment and epiglottic retroversion, substantial for arytenoid asymmetry at rest, palatal dysfunction (PD), medial deviation of the aryepiglottic folds (MDAF), pharyngeal mucus and epiglottic grade at exercise and moderate for vocal fold collapse (VFC), ventromedial luxation of the apex of the corniculate process of the arytenoid (VLAC), nasopharyngeal collapse (NPC) and epiglottic grade at rest. Interobserver agreement was substantial for arytenoid symmetry at exercise and PD and moderate for arytenoid asymmetry at rest, MDAF, VLAC and epiglottic entrapment. It was only fair for VFC, epiglottic grade at exercise, epiglottic retroversion, pharyngeal mucus and NPC and poor for epiglottic grade at rest. Sample size was insufficient to allow assessment of the effect of one abnormality on the grading of another abnormality. Observers were consistent in grading URT disorders. However, significant disparity in grading existed between observers for some conditions affecting reliability. © 2016 EVJ Ltd.

Geologic Map of Baranof Island, southeastern Alaska

USGS Publications Warehouse

Karl, Susan M.; Haeussler, Peter J.; Himmelberg, Glen R.; Zumsteg, Cathy L.; Layer, Paul W.; Friedman, Richard M.; Roeske, Sarah M.; Snee, Lawrence W.

2015-01-01

This map updates the geology of Baranof Island based on fieldwork, petrographic analyses, paleontologic ages, and isotopic ages. These new data provide constraints on depositional and metamorphic ages of lithostratigraphic rock units and the timing of structures that separate them. Kinematic analyses and thermobarometric calculations provide insights on the regional tectonic processes that affected the rocks on Baranof Island. The rocks on Baranof Island are components of a Paleozoic to Early Tertiary oceanic volcanic arc complex, including sedimentary and volcanic rocks that were deposited on and adjacent to the arc complex, deformed, and accreted. The arc complex consists of greenschist to amphibolite facies Paleozoic metavolcanic and metasedimentary rocks overlain by lower-grade Triassic metasedimentary and metavolcanic rocks and intruded by Jurassic calc-alkaline plutons. The Paleozoic rocks correlate well in age and lithology with rocks of the Sicker and Buttle Lake Groups of the Wrangellia terrane on Vancouver Island and differ from rocks of the Skolai Group that constitute basement to type-Wrangellia in the Wrangell Mountains. The Jurassic intrusive rocks are correlative with plutons that intrude the Wrangellia terrane on Vancouver Island but are lacking in the Wrangell Mountains. The rocks accreted beneath the arc complex are referred to as the Baranof Accretionary Complex in this report and are correlated with the Chugach Accretionary Complex of southern and southeastern Alaska and with the Pacific Rim Complex on Vancouver Island. Stratigraphic correlations between upper- and lower-plate rocks on Baranof Island and western Chichagof Island with rocks on Haida Gwaii and Vancouver Island, in addition to correlative ages of intrusive rocks and restorations of the Fairweather-Queen Charlotte, Chatham Strait, and Peril Strait Faults that define the Baranof-Chichagof block, suggest Baranof Island was near Vancouver Island at the time of initiation of arc magmatism in the Early Jurassic. Early Eocene plutons that intruded the accretionary complex outboard of the arc on Baranof Island are attributed to anatectic melting of trench sediments resulting from subduction of a spreading center. Oligocene intrusive rocks on Baranof Island correlate in age and composition with intrusive rocks in the Kano Plutonic Suite on Haida Gwaii, and similar magmatic sources are inferred.

Physical Activity and School Performance: A Survey among Students Not Qualified for Upper Secondary School

ERIC Educational Resources Information Center

Ericsson, Ingegerd; Cederberg, Margareta

2015-01-01

Background: Many students leave compulsory school without being qualified to apply for national upper secondary school programmes. Despite efforts, the number of unqualified students in Sweden has increased. Grades from compulsory school have direct implications for students' educational futures and the requirement to qualify for an upper…

How To Better Track Effective School Indicators: The Control Chart Techniques.

ERIC Educational Resources Information Center

Coutts, Douglas

1998-01-01

Control charts are practical tools to monitor various school indicators (attendance rates, standardized test scores, grades, and graduation rates) by displaying data on the same scale over time. This article shows how principals can calculate the upper natural-process limit, lower natural-process limit, and upper control limit for attendance. (15…

The Effects of Surface Structure Variables on Performance in Reading Comprehension Tests.

ERIC Educational Resources Information Center

Drum, Priscilla; And Others

1981-01-01

Concludes that reading comprehension tests that are valid for beginning readers should incorporate different factors than tests appropriate for upper elementary readers, since word recognition and word meaning are prime sources of difficulty for younger readers while content density depresses the performance of readers in upper elementary grades.…

A Comparison of Upper Elementary School Children's Attitudes toward Physical Activity.

ERIC Educational Resources Information Center

Folsom-Meek, Sherry L.

This study was conducted to compare upper elementary school children's attitudes toward physical activity, by grade level and gender across six attitude scale subdomains in order to assist physical education teachers in planning programs designed to foster positive attitudes toward physical activity. Subjects (N=429) were 243 girls and 186 boys in…

Teaching New Literacies in Grades 4-6: Resources for 21st-Century Classrooms

ERIC Educational Resources Information Center

Moss, Barbara, Ed.; Lapp, Diane, Ed.

2009-01-01

Upper-elementary students encounter a sometimes dizzying array of traditional and nontraditional texts both in and outside of the classroom. This practical handbook helps teachers in grades 4-6 harness the instructional potential of fiction, poetry, and plays; informational texts; graphic novels; digital storytelling; Web-based and multimodal…

Adult Hispanic ESL Students and Graded Readers

ERIC Educational Resources Information Center

Martinez, Liza E.

2017-01-01

This study examined the extent to which graded readers vis-à-vis scaffolded silent reading (ScSR) resulted in increased vocabulary, reading comprehension, and a positive attitude toward reading. A mixed-methods study was administered to two upper-intermediate adult ESL classes at a community college in southwestern Arizona. Both groups took The…

Fractions as Subtraction: An Activity-Oriented Perspective from Elementary Children

ERIC Educational Resources Information Center

Wood, Marcy B.; Olson, Amy M.; Freiberg, Elizabeth J.; Vega, Ruby I.

2013-01-01

A sample of third-, fourth-, and fifth-grade student responses to the question "What is a fraction?" were examined to gain an understanding of how children in upper elementary grades make sense of fractions. Rather than measure children's understanding of fractions relative to mathematically conventional part-whole constructions of…

The Promise of a Literacy Reform Effort in the Upper Elementary Grades

ERIC Educational Resources Information Center

Walpole, Sharon; Amendum, Steven; Pasquarella, Adrian; Strong, John Z.; McKenna, Michael C.

2017-01-01

We compared year-long gains in fluency and comprehension in grades 3-5 in 3 treatment and 4 comparison schools. Treatment schools implemented a comprehensive school reform (CSR) program called Bookworms. The program employed challenging text and emphasized high text volume, aggressive vocabulary and knowledge building, and contextualized strategy…

History + Mystery = Inquiring Young Historians

ERIC Educational Resources Information Center

Kirchner, Jana; Helm, Allison; Pierce, Kristin; Galloway, Michele

2011-01-01

While social studies content about communities, neighborhood jobs, and maybe even some state history is taught in the early elementary grades, often the upper elementary grades are the first time students learn about the larger progression of history. How do teachers begin to teach the progression of U.S. history and the themes and questions that…

Exploring the Explorers Using Internet Resources

ERIC Educational Resources Information Center

Torrez, Cheryl Franklin; Bush, Gina

2009-01-01

The topic of explorers and exploration is commonly taught in the upper elementary grades. Depending on state and local social studies content standards, teachers will develop a curriculum unit on Explorers of Our State for fourth grade students, a unit on Explorers of the United States for fifth graders, and one on World Explorers for sixth…

Relationship of Self Esteem of the Disadvantaged to School Success.

ERIC Educational Resources Information Center

Frerichs, Allen H.

This study shows that there is a positive correlation between self esteem and academic achievement for inner city black children. Seventy-eight grade 6 black students were divided into the following categories: upper one-third and lower third based on intelligence test scores, standardized reading test scores, and grade point average (GPA) from…

Nutrition Education-Choose Well, Be Well: A Curriculum Guide for the Upper Elementary Grades.

ERIC Educational Resources Information Center

Merklein, Robert, Ed.; Smith, Theodore, Ed.

Part of the "Nutrition Education-Choose Well, Be Well" curriculum series, this guide was developed to help teachers, food service personnel, professionals, and parents provide nutrition education and make nutrition come alive in the classroom, home, or cafeteria. Organized by grade level (from fourth through sixth), activities described…

Effects of an Informational Text Reading Comprehension Intervention for Fifth-Grade Students

ERIC Educational Resources Information Center

Ritchey, Kristen D.; Palombo, Kimberly; Silverman, Rebecca D.; Speece, Deborah L.

2017-01-01

Upper elementary school students who have reading problems may have difficulty in one or more areas of reading, each requiring specific types of interventions. This study evaluated a short-term reading intervention for 46 fifth-grade students with poor reading comprehension. Students were randomly assigned to an intervention or no treatment…

Laser-assisted lipolysis for arm contouring in Teimourian grades I and II: a prospective study of 45 patients.

PubMed

Leclère, Franck Marie; Alcolea, Justo M; Vogt, Peter; Moreno-Moraga, Javier; Mordon, Serge; Casoli, Vincent; Trelles, Mario A

2015-04-01

Upper arm deformities secondary to weight loss or senile elastosis have led to an increased demand for aesthetic contouring procedures. We conducted this study to objectively assess if, in Teimourian low-grade upper arm remodelling, one session of laser-assisted lypolisis (LAL) could result in full patient satisfaction. Between 2011 and 2013, 45 patients were treated for unsightly fat arm Teimourian grade I (15 patients), grade IIa (15 patients) and grade IIb (15 patients) with one session of LAL. The laser used in this study was a 1470-nm diode laser (Alma Lasers, Cesarea, Israel) with the following parameters: continuous mode, 15 W power and transmission through a 600-μm optical fibre. Previous mathematical modelling suggested that 0.1 kJ was required in order to destroy 1 ml of fat. Treatment parameters and adverse effects were recorded.The arm circumference and skin pinch measurements were assessed pre and postoperatively. Patients were asked to file a satisfaction questionnaire. Pain during the anaesthesia and discomfort after the procedure were minimal. Complications included prolonged oedema in 11 patients. The average arm circumference decreased by 4.9 ± 0.4 cm in the right arm (p < 0.01) and 4.7 ± 0.5 cm in the left arm (p < 0.01) in grade I patients, 5.5 ± 0.6 cm in the right arm (p < 0.01) and 5.2 ± 0.5 cm in the left arm (p < 0.01) in grade IIa patients and 5.4 ± 0.5 cm in the right arm (p < 0.01) and 5.3 ± 0.5 cm in the left arm (p < 0.01) in grade IIB patients. The skin tightening effect was confirmed by the reduction of the skin calliper measurements in all three groups. Overall mean opinion of treatment was high for both patients and investigators. Of the 45 patients, all but one would recommend this treatment. A single session of LAL in upper arm remodelling for Teimourian grades I to IIb is a safe and reproducible technique. The procedure allows reduction in the amount of adipose deposits while providing full skin tightening.

DOE Office of Scientific and Technical Information (OSTI.GOV)

Tucker, J. D.; Miller, M. K.; Young, G. A.

Duplex stainless steels are desirable for use in power generation systems due to their attractive combination of strength, corrosion resistance, and cost. However, thermal embrittlement at intermediate homologous temperatures of ~887°F (475°C) and below, via spinodal decomposition, limits upper service temperatures for many applications. New lean grade duplex alloys have improved thermal stability over standard grades and potentially increase the upper service temperature or the lifetime at a given temperature for this class of material. The present work compares the thermal stability of lean grade, alloy 2003 to standard grade, alloy 2205, through a series of isothermal agings between 500°Fmore » (260°C) and 900°F (482°C) for times between 1 and 10,000 hours. Aged samples were characterized by changes in microhardness and impact toughness. Additionally, atom probe tomography was performed to illustrate the evolution of the α-α' phase separation in both alloys at select conditions. Atom probe tomography confirmed that phase separation occurs via spinodal decomposition for both alloys and identified the formation of Ni-Cu-Si-Mn-P clusters in alloy 2205 that may contribute to embrittlement of this alloy. The impact toughness model predictions for upper service temperature show that alloy 2003 can be considered for use in 550°F applications for 80 year service lifetimes based on a Charpy V-notch criteria of 35 ft-lbs at 70°F. Alloy 2205 should be limited to 500°F applications.« less

Provenance and sediment fluxes in the Irrawaddy (Ayeyarwadi) River

NASA Astrophysics Data System (ADS)

Garzanti, Eduardo; Wang, Jiangang; Vezzoli, Giovanni; Limonta, Mara

2016-04-01

The Irrawaddy (Ayeyarwadi) River, still a natural system scarcely affected by human activities, ranks among the five major rivers in the world for its annual suspended load, estimated as 364±60 million tons (Robinson et al., 2007). Sourced in Himalayan glaciers southeast of the eastern Himalayan syntaxis at ca. 28°N, the Irrawaddy originates from the confluence of the Nmai and Mali Rivers, flows southward to receive its major Chindwin tributary in the middle of the central Myanmar Basin, and eventually empties through a nine-armed delta into the Andaman Sea. The compositional fingerprint of bedload sand in the upper Irrawaddy is characterized by common feldspars, medium/high rank of metamorphic rock fragments and high heavy-mineral concentration, reflecting provenance from mid-crustal granitoids, amphibolite-facies and subordinately greenschist-facies rocks widely exposed in the Mogok Belt and Lohit Plutonic Complex. Minor volcanic/metavolcanic and serpentinite grains indicate additional supply from volcanic-arc remnants and the Neotethyan ophiolitic suture. Sand of the Chindwin River has much higher quartz/feldspar ratio and much lower metamorphic indices and heavy-mineral concentration, reflecting provenance mainly from upper crustal sedimentary and very low-grade metasedimentary rocks exposed in the Indo-Burman Ranges (Garzanti et al., 2013). Feldspatho-litho-quartzose to litho-feldspatho-quartzose composition in the lower Irrawaddy is intermediate between that of Chindwin and upper Irrawaddy sand. The slight progressive downstream increase in volcanic rock fragments and chert, and decrease in metamorphic indices, point to additional local supply from volcanic and sedimentary cover rocks. U-Pb age spectra of detrital zircons are characterized by a major cluster between 30 and 150 Ma, corresponding to the long-lasting magmatic activity of the Western Myanmar Arc (Wang et al., 2014), with other clusters at 500-600 Ma and 800-1200 Ma, and a few ages between 1.5 and 2.0 Ga (Limonta et al., 2016). Forward mixing calculations based on integrated petrographic and heavy-mineral data (Garzanti et al., 2012) indicate that 60±10% of the total sediment flux is supplied by the Chindwin River and that upper Irrawaddy sand is supplied mainly by the Nmai headwater branch but also significantly from the Mali branch and left-bank tributaries sourced in the northern Shan Plateau. CITED REFERENCES Garzanti E., Resentini A., Vezzoli G., Andò S., Malusà M., Padoan M. 2012. Forward compositional modelling of Alpine orogenic sediments. Sedimentary Geology 280:149-164. Garzanti E., Limonta M., Resentini A., Bandopadhyay P. C., Najman Y., Andò S., Vezzoli G. 2013. Sediment recycling at convergent plate margins (Indo-Burman Ranges and Andaman-Nicobar Ridge). Earth-Science Reviews 123:113-132. Limonta M., Resentini A., Carter A., Bandopadhyay P.C., Garzanti E. 2016. Provenance of Oligocene Andaman Sandstones (Andaman-Nicobar islands): Ganga-Brahmaputra or Irrawaddy derived? In: Bandyopadhyay P., Carter A. (Eds.). The Andaman-Nicobar accretionary ridge geology, tectonics and hazards, Geological Society of London Memoir, in review. Robinson R.A.J., Bird M.I., Oo N.W., Hoey T.B., Aye M.M., Higgitt D.L., Lu X.X., Swe A., Tun T., Win S. L. 2007. The Irrawaddy River sediment flux to the Indian Ocean: the original nineteenth-century data revisited. The Journal of Geology 115:629-640. Wang J.G., Wu F.Y., Tan X.C., Liu C.Z. 2014. Magmatic evolution of the Western Myanmar Arc documented by U-Pb and Hf isotopes in detrital zircon. Tectonophysics 612:97-105.

Multiphase boudinage: a case study of amphibolites in marble in the Naxos migmatite core

NASA Astrophysics Data System (ADS)

Virgo, Simon; von Hagke, Christoph; Urai, Janos L.

2018-02-01

In multiply deformed terrains multiphase boudinage is common, but identification and analysis of these is difficult. Here we present an analysis of multiphase boudinage and fold structures in deformed amphibolite layers in marble from the migmatitic centre of the Naxos metamorphic core complex. Overprinting between multiple boudinage generations is shown in exceptional 3-D outcrop. We identify five generations of boudinage, reflecting the transition from high-strain high-temperature ductile deformation to medium- to low-strain brittle boudins formed during cooling and exhumation. All boudin generations indicate E-W horizontal shortening and variable direction of bedding parallel extension, evolving from subvertical extension in the earliest boudins to subhorizontal N-S extension during exhumation. Two phases of E-W shortening can be inferred, the first associated with lower crustal synmigmatic convergent flow and the second associated with exhumation and N-S extension, possibly related to movement of the North Anatolian Fault.

The metamorphic record of subduction-accretion processes in the Neoarchaean: the Nuuk region, southern West Greenland.

NASA Astrophysics Data System (ADS)

Dziggel, Annika; Kolb, Jochen

2013-04-01

The Nuuk region of southern West Greenland exposes an exceptionally well preserved section through Archaean mid- to lower continental crust, and therefore provides a natural laboratory to study the tectonic processes in the Archaean. The area mainly consists of amphibolite to granulite facies TTG gneisses, narrow supracrustal belts, and minor late-tectonic granites. It is made up of several distinct terranes, including, from NW to SE, the Færingehavn, Tre Brødre, and Tasiusarsuaq terranes. Extensive high-grade metamorphism and a clockwise PT evolution of the Færingehavn terrane in the Neoarchaean (2.72-2.71 Ga) have been interpreted as a result of crustal thickening and thrusting of the Tasiusarsuaq terrane on top of the Tre Brødre and Færingehavn terranes (Nutman and Friend, 2007). Prior to final collision, the Tasiusarsuaq terrane (the upper plate in a plate tectonic model) underwent a prolonged period of compressive deformation between 2.8 and 2.72 Ga (Kolb et al., 2012). The structural evolution was associated with near-isobaric cooling from medium-pressure granulite facies conditions of ca. 850°C and 7.5 kbar to amphibolite facies conditions of ca. 700°C and 6.5-7 kbar (Dziggel et al., 2012). Despite this long period of crustal convergence, there is no evidence for exhumation and/or loading, pointing to a rheologically weak and unstable Archaean crust perhaps due to low density differences and ongoing melt extraction. Rocks of the structurally underlying Færingehavn terrane record a distinctly different metamorphic evolution. Although generally more strongly retrogressed, relict higher-pressure mineral assemblages in mafic granulites and felsic gneisses record conditions of > 8-9 kbar and >= 750°C, indicating burial to depths of at least 30 km along an apparent geothermal gradient of 20-25°C/km. The peak of metamorphism was followed by isothermal decompression at ca. 2.715 Ga (Nutman and Friend, 2007), indicating rapid exhumation of lower crustal rocks during, or shortly after, the main accretionary event. The existence of dual thermal regimes with contrasting PT paths, as well as the good correlation between the timing of collision, high-pressure metamorphism and rapid exhumation are all consistent with plate-tectonic processes operating in the Neoarchaean. However, the crustal convergence in the Nuuk region was not associated with the extreme crustal thickening observed in many younger orogenic belts, and this likely reflects the generally higher mantle temperatures in the Neoarchaean. The prolonged period of crustal convergence prior to final collision may further indicate that the convergence rates in the Archaean were rather low. Dziggel, A., Diener, J.F.A., Stoltz, N.B., Kolb, J., 2012. Role of H2O in the formation of garnet coronas during near-isobaric cooling of mafic granulites: the Tasiusarsuaq terrane, southern West Greenland. Journal of Metamorphic Geology, 30, 957-972. Kolb, J., Kokfelt, T.F., Dziggel, A., 2012. Geodynamic setting and deformation history of an Archaean terrane at mid-crustal level: the Tasiusarsuaq terrane of southern West Greenland. Precambrian Research, 212-213, 34-56. Nutman, A.P. & Friend, C.R.L., 2007. Adjacent terranes with ca. 2715 and 2650 Ma high-pressure metamorphic assemblages in the Nuuk region of the North Atlantic Craton, southern West Greenland: Complexities of Neoarchaean collisional orogeny. Precambrian Research, 155, 159-203.

Metamorphic sole formation reveals plate interface rheology during early subduction

NASA Astrophysics Data System (ADS)

Mathieu, S.; Agard, P.; Dubacq, B.; Plunder, A.; Prigent, C.

2015-12-01

Metamorphic soles are m to ~500m thick tectonic slices welded beneath most large ophiolites. They correspond to highly to mildly deformed portions of oceanic lithosphere metamorphosed at amphibolite to granulite facies peak conditions. Metamorphic soles are interpreted as formed ≤1-2Ma after intraoceanic subduction initiation by heat transfer from the hot, incipient mantle wegde to the underthrusting lower plate. Their early accretion and exhumation together with the future ophiolite implies at least one jump of the subduction plate interface from above to below the metamorphic sole. Metamorphic soles thus represent one of the few remnants of the very early evolution of the subduction plate interface and provide major constraints on the thermal structure and the effective rheology of the crust and mantle along the nascent slab interface.We herein present a structural and petrological detailed description of the Oman and Turkey metamorphic soles. Both soles present a steep inverted metamorphic structure, with isograds subparallel to the peridotite contact, in which the proportion of mafic rocks, pressure and temperature conditions increase upward. They comprise, as most metamorphic soles worldwide, two main units: (1) a high-grade unit adjacent to the overlying peridotite composed of granulitized to amphibolized metabasalts, with rare metasedimentary interlayers (~800±100ºC at 10±2kbar) and (2) a low-grade greenschist facies unit composed of metasedimentary rocks with rare metatuffs (~500±100ºC at 5±2kbar). We provide for the first time refined P-T peak condition estimations by means of pseudosection modelling and maximum temperature constraints for the Oman low-grade sole by RAMAN thermometry. In order to quantify micro-scale deformations trough the sole, we also present EBSD data on the Oman garnet-bearing and garnet-free high-grade sole.With these new constraints, we finally propose a new conceptual mechanical model for metamorphic sole formation. This model excludes the presence of a continuous inverted metamorphic gradient through the sole but implies the stacking of several homogeneous slivers to constitute the present structure of the sole. These successive thrusts are the result of rheological changes as the plate interface progressively cools.

Upper crustal structure of Alabama from regional magnetic and gravity data: Using geology to interpret geophysics, and vice versa

USGS Publications Warehouse

Steltenpohl, Mark G.; Horton, J. Wright; Hatcher, Robert D.; Zietz, Isidore; Daniels, David L.; Higgins, Michael W.

2013-01-01

Aeromagnetic and gravity data sets obtained for Alabama (United States) have been digitally merged and filtered to enhance upper-crustal anomalies. Beneath the Appalachian Basin in northwestern Alabama, broad deep-crustal anomalies of the continental interior include the Grenville front and New York–Alabama lineament (dextral fault). Toward the east and south, high-angle discordance between the northeast-trending Appalachians and the east-west–trending wedge of overlapping Mesozoic and Cenozoic Gulf Coastal Plain sediments reveals how bedrock geophysical signatures progressively change with deeper burial. High-frequency magnetic anomalies in the Appalachian deformed domain (ADD) correspond to amphibolites and mylonites outlining terranes, while broader, lower-amplitude domains include Paleozoic intrusive bodies and Grenville basement gneiss. Fundamental ADD structures (e.g., the Alexander City, Towaliga, and Goat Rock–Bartletts Ferry faults) can be traced southward beneath the Gulf Coastal Plain to the suture with Gondwanan crust of the Suwannee terrane. Within the ADD, there is clear magnetic distinction between Laurentian crust and the strongly linear, high-frequency magnetic highs of peri-Gondwanan (Carolina-Uchee) arc terranes. The contact (Central Piedmont suture) corresponds to surface exposures of the Bartletts Ferry fault. ADD magnetic and gravity signatures are truncated by the east-west–trending Altamaha magnetic low associated with the Suwannee suture. Arcuate northeast-trending magnetic linears of the Suwannee terrane reflect internal structure and Mesozoic failed-rift trends. Geophysical data can be used to make inferences on surface and subsurface geology and vice versa, which has applicability anywhere that bedrock is exposed or concealed beneath essentially non-magnetic sedimentary cover.

Partial eclogitization of the Ambolten gabbro-norite, north-east Greenland Caledonides

USGS Publications Warehouse

Gilotti, J.A.; Elvevold, S.

1998-01-01

Partially eclogitized igneous bodies composed of gabbro, leucogabbro, anorthosite and cross-cutting diabase dikes are well represented in the North-East Greenland Eclogite Province. A 200 x 100 meter intrusive body on Ambolten Island (78?? 20' N, 19?? 15' W) records a prograde transition from gabbro-norite to eclogite facies coronitic metagabro-norite surrounded by hydrated margins of undeformed to strongly foliated amphibolite. Igneous plagioclase + olivine + enstatite + augite + oxides convert to eclogite facies assemblages consisting of garnet, omphacite, diopside, enstatite, kyanite, zoisite, rutile and pargasitic amphibole through several coronitic reactions. Relict cumulus plagioclase laths are replaced by an outer corona of garnet, an inner corona of omphacite and an internal region of sodic plagioclase, garnet, kyanite, omphacite and zoisite. Olivine and intercumulus pyroxene are partly replaced by metamorphic pyroxenes and amphibole. The corona structures, zoning patterns, diversity of mineral compositions in a single thin section, and preservation of metastable asemblages are characteristic of diffusion-controlled metamorphism. The most extreme disequilibrium is found in static amphibolites, where igneous pyroxenes, plagioclase domains with eclogite facies, assemblages, and matrix amphibole coexist. Complete eclogitization was not attained at Ambolten due to a lack of fluids needed to drive diffusion during prograde and retrograde metamorphism. The P-T conditions of the high-pressure metamorphism are estimated at ??? 750??C and > 18 kbar. Well-equilibrated, foliated amphibolites from the margin of the gabbro-norite supports our contention that the entire North-East Greenland Eclogite Province experienced Caledonian high-pressure metamorphism, even though no eclogite facies assemblages have been found in the quartzofeldspathic host gneisses to date.

Hydrogeological characterisation and prospect of basement Aquifers of Ibarapa region, southwestern Nigeria

NASA Astrophysics Data System (ADS)

Akanbi, Olanrewaju Akinfemiwa

2018-06-01

The present study involved the use of 82 geo-electric soundings, and the measurement of well inventory and conduct of yield tests in 19 wells across the various bedrock terrains of Ibarapa region of southwestern Nigeria. The aim is to proffer solution to the unsustainable yield of the available boreholes in order to effectively exploit the existing groundwater resource in the area. From the geological reports, the area is underlain by four principal crystalline rocks that include porphyritic granite, gneisses, amphibolite and migmatite. The geo-electric studies revealed that the degree and extent of development of the weathered-fractured component varied, leading to diversity in groundwater yield and in aquifer vulnerability to contamination. The thickness of the weathered layer is greater than 18 m in areas underlain by amphibolite and gneisses and less than 13 m within migmatite and porphyritic granite terrains. High groundwater yield greater than 70 m3/day was recorded in wells within the zones of rock contacts and in areas with large concentration of bedrock fractures and elevated locations across the various bedrock terrains. Aquifer vulnerability is low in amphibolite, high in granitic terrains, low to moderate in gneisses and high to moderate in migmatite. Also, wells' depths and terrain elevation have a moderate to strong indirect relationship with groundwater yield in most bedrock terrains, except in high topographic areas underlain by porphyritic granite. Therefore, there is need for modification of well depth in accordance with the terrain elevation and hydrogeological complexity of the weathered-fractured components of the variuos bedrock terrains, so as to ensure a sustainable groundwater yield.

Partial melting under conditions of filter pressing: field and geochemical evidence from the migmatites of NE Minnesota

DOE Office of Scientific and Technical Information (OSTI.GOV)

Sheehan, T.J.; Bauer, R.L.; Nabelek, P.I.

1985-01-01

Amphibolite-grade Archean migmatites in the southern Vermilion Granitic Complex with well-defined paleosome-melanosome and melanosome-leucosome boundaries and with exceptionally wide melanosomes (on the order of centimeters) were studied to elucidate granite-forming processes during high-grade metamorphism. Metagreywacke paleosomes containing 50% plag, 28% qtz, 20% biot and minor hbld, and apat, have (Ce/Yb)/sub N/ = 13.5 to 21 with 650-960 ppm Ba, 42-110 ppm Rb, and 982-1159 ppm Sr. Melanosomes containing 45% plag, 35% biot, 20% hbld and minor qtz and apat, have (Ce/Yb)/sub N/ = 6.8 to 9.3 and have 950-1750 ppm Ba, 41-194 ppm Rb, and 1020-1926 ppm Sr. Leucosomes containingmore » 82% plag, 13% qtz, 5% biot and minor hbld and apat, have overall depleted REE patterns with positive Eu anomalies and 460-750 ppm Ba, 41-43 ppm Rb, and 1876-2106 ppm Sr, suggesting cumulate plagioclase. Mass balance calculations preclude formation of the melanosome from mixing the paleosomes and leucosomes. However, major and trace element modeling suggest that the leucosome formed by in situ partial melting followed by fractional crystallization and filter pressing which resulted in the removal of the residual liquid. Model REE patterns for the melt drive off by this process are REE enriched with a negative Eu anomaly. Such patterns which have been found in some low Sr granites are difficult to produce by simple belting models. Partial melting under conditions of tectonic stress may thus provide an explanation for such granites.« less

Quantitative kinematic analysis within the Khlong Marui shear zone, southern Thailand

NASA Astrophysics Data System (ADS)

Kanjanapayont, Pitsanupong; Grasemann, Bernhard; Edwards, Michael A.; Fritz, Harald

2012-02-01

The NNE trending Khlong Marui shear zone has a strong geomorphic signal with marked fault-strike parallel topographic ridges. The lithologies within the strike-slip zone mainly consist of vertical layers of mylonitic meta-sedimentary rocks associated with orthogneisses, mylonitic granites, and pegmatitic veins. The pegmatitic veins concordantly intrude the mylonitic foliation but were sheared at the rims indicating syn-kinematic emplacement. Microstructures and mineral assemblages suggest that the rocks in the area have been metamorphosed at amphibolite facies and low to medium greenschist facies by the first deformation. The Khlong Marui shear zone was deformed under dextral simple shear flow with a small finite strain. The ductile-to-brittle deformation involves a period of exhumation of lenses of higher grade rocks together with low grade fault rocks probably associated with positive flower structures. The final stage brittle deformation is reflected by normal faulting and formation of proto-cataclasites to cataclasites of the original mylonitic meta-sedimentary host rock. Although clear age-constraints are still missing, we use regional relationships to speculate that earlier dextral strike-slip displacement of the Khlong Marui shear zone was related to the West Burma and Shan-Thai collision and subduction along the Sunda Trench in the Late Cretaceous, while the major exhumation period of the ductile lens was tectonically influenced by the early India-Asia collision. The changing stress field has responded by switching from dextral strike-slip to normal faulting in the Khlong Marui shear zone, and is associated with "escape tectonics" arising from the overall India-Asia collision.

Genomic Characterization of Upper Tract Urothelial Carcinoma.

PubMed

Sfakianos, John P; Cha, Eugene K; Iyer, Gopa; Scott, Sasinya N; Zabor, Emily C; Shah, Ronak H; Ren, Qinghu; Bagrodia, Aditya; Kim, Philip H; Hakimi, A Ari; Ostrovnaya, Irina; Ramirez, Ricardo; Hanrahan, Aphrothiti J; Desai, Neil B; Sun, Arony; Pinciroli, Patrizia; Rosenberg, Jonathan E; Dalbagni, Guido; Schultz, Nikolaus; Bajorin, Dean F; Reuter, Victor E; Berger, Michael F; Bochner, Bernard H; Al-Ahmadie, Hikmat A; Solit, David B; Coleman, Jonathan A

2015-12-01

Despite a similar histologic appearance, upper tract urothelial carcinoma (UTUC) and urothelial carcinoma of the bladder (UCB) tumors have distinct epidemiologic and clinicopathologic differences. To investigate whether the differences between UTUC and UCB result from intrinsic biological diversity. Tumor and germline DNA from patients with UTUC (n=83) and UCB (n=102) were analyzed using a custom next-generation sequencing assay to identify somatic mutations and copy number alterations in 300 cancer-associated genes. We described co-mutation patterns and copy number alterations in UTUC. We also compared mutation frequencies in high-grade UTUC (n=59) and high-grade UCB (n=102). Comparison of high-grade UTUC and UCB revealed significant differences in the prevalence of somatic alterations. Genes altered more commonly in high-grade UTUC included FGFR3 (35.6% vs 21.6%; p=0.065), HRAS (13.6% vs 1.0%; p=0.001), and CDKN2B (15.3% vs 3.9%; p=0.016). Genes less frequently mutated in high-grade UTUC included TP53 (25.4% vs 57.8%; p<0.001), RB1 (0.0% vs 18.6%; p<0.001), and ARID1A (13.6% vs 27.5%; p=0.050). Because our assay was restricted to genomic alterations in a targeted panel, rare mutations and epigenetic changes were not analyzed. High-grade UTUC tumors display a spectrum of genetic alterations similar to high-grade UCB. However, there were significant differences in the prevalence of several recurrently mutated genes including HRAS, TP53, and RB1. As relevant targeted inhibitors are being developed and tested, these results may have important implications for the site-specific management of patients with urothelial carcinoma. Comparison of next-generation sequencing of upper tract urothelial carcinoma (UTUC) with urothelial bladder cancer identified that similar mutations were present in both cancer types but at different frequencies, indicating a potential need for unique management strategies. UTUC tumors were found to have a high rate of mutations that could be targeted with novel therapies. Copyright © 2015 European Association of Urology. Published by Elsevier B.V. All rights reserved.

Constraints on deformation of the Southern Andes since the Cretaceous from anisotropy of magnetic susceptibility

NASA Astrophysics Data System (ADS)

Maffione, Marco; Hernandez-Moreno, Catalina; Ghiglione, Matias C.; Speranza, Fabio; van Hinsbergen, Douwe J. J.; Lodolo, Emanuele

2015-12-01

The southernmost segment of the Andean Cordillera underwent a complex deformation history characterized by alternation of contractional, extensional, and strike-slip tectonics. Key elements of southern Andean deformation that remain poorly constrained, include the origin of the orogenic bend known as the Patagonian Orocline (here renamed as Patagonian Arc), and the exhumation mechanism of an upper amphibolite facies metamorphic complex currently exposed in Cordillera Darwin. Here, we present results of anisotropy of magnetic susceptibility (AMS) from 22 sites in Upper Cretaceous to upper Eocene sedimentary rocks within the internal structural domain of the Magallanes fold-and-thrust belt in Tierra del Fuego (Argentina). AMS parameters from most sites reveal a weak tectonic overprint of the original magnetic fabric, which was likely acquired upon layer-parallel shortening soon after sedimentation. Magnetic lineation from 17 sites is interpreted to have formed during compressive tectonic phases associated to a continuous N-S contraction. Our data, combined with the existing AMS database from adjacent areas, show that the Early Cretaceous-late Oligocene tectonic phases in the Southern Andes yielded continuous contraction, variable from E-W in the Patagonian Andes to N-S in the Fuegian Andes, which defined a radial strain field. A direct implication is that the exhumation of the Cordillera Darwin metamorphic complex occurred under compressive, rather than extensional or strike-slip tectonics, as alternatively proposed. If we agree with recent works considering the curved Magallanes fold-and-thrust belt as a primary arc (i.e., no relative vertical-axis rotation of the limbs occurs during its formation), then other mechanisms different from oroclinal bending should be invoked to explain the documented radial strain field. We tentatively propose a kinematic model in which reactivation of variably oriented Jurassic faults at the South American continental margin controlled the Late Cretaceous to Cenozoic evolution of the Magallanes fold-and-thrust belt, yielding the observed deformation pattern.

INSTRUCTIONAL TELEVISION FOR THE UPPER PRIMARY. A TEACHER GUIDE, SEMESTER II.

ERIC Educational Resources Information Center

DELIKAN, ALFRED; AND OTHERS

TELECAST PROGRAMS FOR THE UPPER PRIMARY GRADES WERE IN ART, MUSIC, PHYSICAL EDUCATION AND SCIENCE. A PREVIEW OF THE CONTENT OF EACH UNIT WAS GIVEN, TOGETHER WITH DETAILED INFORMATION FOR FOLLOWUP ACTIVITY. IN THE ART SERIES, IT WAS RECOMMENDED THAT PUPIL PARTICIPATION TAKE PLACE AS SOON AS POSSIBLE AFTER THE TELECAST. INDIVIDUAL CREATIVITY WAS…

Upper Secondary French Students, Chemical Transformations and the "Register of Models": A Cross-Sectional Study

ERIC Educational Resources Information Center

Cokelez, Aytekin; Dumon, Alain; Taber, Keith S.

2008-01-01

The purpose of this study is to identify how upper secondary school French students (Grade 10-12) interpret chemical transformation with regards to the changes within molecules and atoms, and in terms of intramolecular and/or intermolecular bond breaking. In order to identify and describe the students' assimilated knowledge, four questions were…

Academic Self-Efficacy, Faculty-Student Interactions, and Student Characteristics as Predictors of Grade Point Average

ERIC Educational Resources Information Center

Gosnell, Joan C.

2012-01-01

The purpose of the study was to explore student characteristics, academic self-efficacy, and faculty-student interactions as predictors of grade point average for upper-division (college level third and fourth year) education students at a public 4-year degree-granting community college. The study examined the effects of student characteristics…

Successful Principalship in Norway: Sustainable Ethos and Incremental Changes?

ERIC Educational Resources Information Center

Moller, Jorunn; Vedoy, Gunn; Presthus, Anne Marie; Skedsmo, Guri

2009-01-01

Purpose: The purpose of this paper is to explore whether and how success has been sustained over time in schools which were identified as being successful five years ago. Design/methodology/approach: Three schools were selected for a revisit, and the sample included two combined schools (grade 1-10) and one upper secondary school (grade 11-13). In…

Conversation and Control: Emergent Progressive Pedagogy in the Last of Nebraska's One-Teacher Schools

ERIC Educational Resources Information Center

Swidler, Stephen A.

2005-01-01

This article describes the teaching practices at Upper Rill School, a 1-teacher school in rural Nebraska. With its 8 students, grades 1 through 8, the teacher considers the school?s size and continuity of student enrollment flexible and generative. Subject matter and grade levels are regularly integrated though common curricula. Instruction is…

The Effects of Adult-Oriented Advertising on First, Second, and Third Grade Children across Socioeconomic Bounds.

ERIC Educational Resources Information Center

Lucas, Richard Jay

The purpose of this study was to examine the socializing effect the viewing of adult-oriented commercials has on young children of differing socioeconomic backgrounds. The subjects, 227 children in the first, second, and third grades, included 109 lower-socioeconomic-level black children and 118 white children representing upper-middle-income…

Rights and Responsibilities. User Guide for Grades K-6. My America: Building a Democracy Series.

ERIC Educational Resources Information Center

Fier, Harriet, Ed.; And Others

This user guide covers "Rights and Responsibilities," and offers suggestions for preparatory activities, lessons, and follow-up activities for primary, intermediate, and upper grade students. Goals for the series are to help children: (1) become familiar with the democratic process and active citizenship; (2) recognize what it means to be a…

Using Technology to Support Expository Reading and Writing in Science Classes

ERIC Educational Resources Information Center

Montelongo, Jose A.; Herter, Roberta J.

2010-01-01

Students struggle with the transition from learning to read narrative text in the early grades to reading expository text in the science classroom in the upper grades as they begin reading and writing to gain information. Science teachers can adapt their teaching materials to develop students' reading comprehension and recall by writing summaries…

Learning More about Black Americans. An Instructional Unit for the Upper Elementary Grades.

ERIC Educational Resources Information Center

Montgomery County Public Schools, Rockville, MD.

This instructional unit for grades 4-6 specifies objectives, resources, and lesson plans to help students develop knowledge and appreciation of contributions made by blacks to American society. The activities can be integrated with other program areas, such as language arts, music, and art. For each of four instructional objectives the unit…

Diagnostic Accuracy of Multivariate Universal Screening Procedures for Reading in Upper Elementary Grades

ERIC Educational Resources Information Center

Klingbeil, David A.; Nelson, Peter M.; Van Norman, Ethan R.; Birr, Chris

2017-01-01

We examined the diagnostic accuracy and efficiency of three approaches to universal screening for reading difficulties using retrospective data from 1,307 students in Grades 3 through 5. School staff collected screening data using the Measures of Academic Progress (MAP), a curriculum-based measure (CBM), and running records (RR). The criterion…

RESEARCH IN READING FOR THE MIDDLE GRADES. AN ANNOTATED BIBLIOGRAPHY.

ERIC Educational Resources Information Center

CUTTS, WARREN G.

THIS BULLETIN PRESENTS RESEARCH STUDIES IN READING ON THE UPPER ELEMENTARY GRADE LEVEL DURING THE PERIOD FROM 1955 THROUGH 1960. THIS COMPILATION WAS UNDERTAKEN BY THE OFFICE OF EDUCATION IN AN ATTEMPT TO BRING TOGETHER THE UNPUBLISHED AS WELL AS PUBLISHED STUDIES OF THAT 5-YEAR PERIOD. THE 238 STUDIES WHICH ARE OUTLINED, SUMMARIZED, AND ANNOTATED…

Influence of Property School Wealth on Fifth Grade Student Achievement in Reading and Mathematics

ERIC Educational Resources Information Center

Reyna, Jesus R.

2015-01-01

The purpose of this study was to investigate whether, or to what extent, property wealth of the upper and lower 5% districts, per pupil expenditure, limited English proficient students, economically disadvantaged students, membership, and teacher experience contribute to student achievement in 5th grade reading and mathematics. To do this, the…

Magnetic fabric and Petrofabric of Amphibolites in Eastern Himalaya Syntaxis

NASA Astrophysics Data System (ADS)

Li, Wenjing; Zhang, Junfeng; Xu, Haijun

2017-04-01

The Himalaya orogenic belt was formed by the collision of the Eurasian plate and the Indian plate. There are two syntaxies along the orogenic belt, where the lower crust are extruded because of the strong stress and deep melting. Our samples are from the eastern Himalaya syntaxis, which is near the Namchabarwa Mount. The sample TO-38 is composed of hornblende, garnet, plagioclase, quartz, ilmenite, magnetite and rutile. The hornblendes are strongly deformed and have clear lineation. While the garnets are relative strong and undeformed, they have a white rim of retrograded minerals with S-C fabric. The ilmenites are distributed extensively and are also deformed, with a slight SPO parallel to lineation. The magnetite are almost cubic with no SPO. We obtained the magnetic fabric of sample TO-38 from anisotropy of magnetic susceptibility (AMS) measurements, and crystallographic fabrics from EBSD analysis. The hornblende shows that [001] forms a well defined point maximum parallel to lineation; poles to {110}{010} plot as a girdle normal to the foliation. The ilmenite fabric shows less pronounced distribution of [0001] axis normal to foliation and weak subparallel distribution of [11-20] axis to lineation. The magnetite is very little, and shows no LPO. The AMS measurement shows that the maximum susceptibility direction correspond to the lineation, also parallel to the [11-20] axis of ilmenite and [001] axis of hornblende. The minimum susceptibility direction is parallel to the [0001] axis of ilmenite. The thermomagnetic curves and values of bulk susceptibility reveal a magnetic mineralogy dominated by a mixed contribution of paramagnetic minerals and magnetite. The mean susceptibility are from 7.06×10-3SI to 33.1×10-3SI. We also calculated the seismic anisotropy of amphibolites, and it shows the fast P wave propagate in lineation direction and has a 11.5% anisotropy. Meanwhile, the shear wave splitting polarization is also along the lineation, and has a 6% anisotropy. According to recent geophysical observations, the Tibet mid-lower crust have strong anisotropy, which favors an amphibolite facies mid-lower crust beneath the Tibet. Therefore, the correlation between petrofabric and magnetic fabric of amphibolites can be applied to interpret the deformation and evolution history of Tibetan Plateau.

Assessment of shock effects on amphibole water contents and hydrogen isotope compositions: 1. Amphibolite experiments

NASA Astrophysics Data System (ADS)

Minitti, Michelle E.; Rutherford, Malcolm J.; Taylor, Bruce E.; Dyar, M. Darby; Schultz, Peter H.

2008-02-01

Kaersutitic amphiboles found within a subset of the Martian meteorites have low water contents and variably heavy hydrogen isotope compositions. In order to assess if impact shock-induced devolatilization and hydrogen isotope fractionation were determining factors in these water and isotopic characteristics of the Martian kaersutites, we conducted impact shock experiments on samples of Gore Mountain amphibolite in the Ames Vertical Gun Range (AVGR). A parallel shock experiment conducted on an anorthosite sample indicated that contamination of shocked samples by the AVGR hydrogen propellant was unlikely. Petrographic study of the experimental amphibolite shock products indicates that only ˜ 10% of the shock products experienced levels of damage equivalent to those found in the most highly shocked kaersutite-bearing Martian meteorites (30-35 GPa). Ion microprobe studies of highly shocked hornblende from the amphibolite exhibited elevated water contents (ΔH 2O ˜ 0.1 wt.%) and enriched hydrogen isotope compositions (Δ D ˜ + 10‰) relative to unshocked hornblende. Water and hydrogen isotope analyses of tens of milligrams of unshocked, moderately shocked, and highly shocked hornblende samples by vacuum extraction/uranium reduction and isotope ratio mass spectrometry (IRMS), respectively, are largely consistent with analyses of single grains from the ion microprobe. The mechanisms thought to have produced the excess water in most of the shocked hornblendes are shock-induced reduction of hornblende Fe and/or irreversible adsorption of hydrogen. Addition of the isotopically enriched Martian atmosphere to the Martian meteorite kaersutites via these mechanisms could explain their enriched and variable isotopic compositions. Alternatively, regrouping the water extraction and IRMS analyses on the basis of isotopic composition reveals a small, but consistent, degree of impact-induced devolatilization (˜ 0.1 wt.% H 2O) and H isotope enrichment (Δ D ˜ + 10‰). Extrapolating the shock signature of the regrouped data to grains that experienced Martian meteorite-like shock pressures suggests that shock-induced water losses and hydrogen isotope enrichments could approach 1 wt.% H 2O and Δ D = + 100‰, respectively. If these values are valid, then impact shock effects could explain a substantial fraction of the low water contents and variable hydrogen isotope compositions of the Martian meteorite kaersutites.

Multi-stage barites in partially melted UHP eclogite: implications for fluid/melt activities during deep continental subduction in the Sulu orogenic belt

NASA Astrophysics Data System (ADS)

Wang, Songjie; Wang, Lu

2015-04-01

Barite (BaSO4) is well-known from deep-sea sedimentary environments but has received less attention to its presence in high-grade metamorphic rocks. Recently, barite in ultrahigh pressure (UHP) eclogite has drawn increasing attention from geologists, especially in the Dabie-Sulu orogen, since it is an important indicator for high-salinity fluid events, thus aiding in further understanding HP-UHP fluid / melt evolution. However, its formation time and mechanism in UHP eclogite are still controversial, with three representative viewpoints: (1) Liu et al. (2000) found barite-anhydrite-coesite inclusions in zircon and interpreted them to have formed by UHP metamorphic fluids; (2) Zeng et al. (2007) recognized isolated barite within K-feldspar (Kfs) and Quartz (Qz) surrounded by radial cracks in omphacite, and interpreted Kfs+Qz to be reaction products of potassium-rich fluid/melt and coesite, with the barite formed by prograde metamorphic fluids; (3) Gao et al. (2012) and Chen et al. (2014) found barite-bearing Multiphase Solid (MS) inclusions within garnet and omphacite and assumed that the barite formed by phengite breakdown possibly caused by eclogite partial melting during exhumation, though no direct evidence were proposed. The controversy above is mainly due to the lack of direct formation evidence and absence of a clear link with the metamorphic evolution of UHP eclogite along the subduction-exhumation path. We report detailed petrological and micro-structural analyses revealing four types of barites clearly linked with (1) the prograde, (2) earlier stage of partial melting and (3) later stage of crystallization differentiation, as well as (4) high-grade amphibolite-facies retrogression of a deeply subducted and partially melted intergranular coesite-bearing eclogite from Yangkou Bay, Sulu Orogen. Round barite inclusions (type-I) within UHP-stage garnet and omphacite are formed by internally buffered fluids from mineral dehydration during prograde metamorphism. Zr-in-rutile thermometry shows their formation temperature to be 586-664 oC at 1.5-2.5 GPa. Barite-bearing MS inclusions with Ba-bearing K-feldspar (type-II) connected by Kfs+Pl+Bt veinlets of in-situ phengite breakdown and thin barite veinlets along grain boundaries (type-III) are products of phengite breakdown and induced fluid flow during exhumation. These barites have witnessed the gradational separation process of melt/ fluid from miscibility on/above the second critical endpoint during UHP metamorphism, to immiscibility along the exhumation path of the subducted slab. Associated reactions from pyrite to hematite and goethite with the type-III barite ring surrounding the pyrite provide evidence for a local high oxygen fugacity environment during eclogite partial melting and subsequent melt/fluid crystallization processes. Moreover, large grain barite aggregations (type-IV) modified by amphibole+albite symplectite are most likely formed by release of molecular and hydroxyl water from anhydrous minerals of eclogite during high-grade amphibolite-facies retrogression. The growth of multi-stage barites in UHP eclogite further advances our understanding of fluid/melt transfer, crystallization processes along the subduction-exhumation path of the partially melted eclogite, broadening our knowledge of melt/fluid evolution within subduction-collision zones worldwide. REFERENCES Chen Y.X., et al., 2014, Lithos, 200, 1-21. Liu J.B., et al., 2000, Acta Petrologica Sinica 16(4), 482-484. Zeng L.S., et al., 2007, Chinese Science Bulletin, 52(21), 2995-3001. Gao X.Y., et al., 2012, Journal of Metamorphic Geology, 30(2), 193-212.

Poisson's Ratio and Auxetic Properties of Natural Rocks

NASA Astrophysics Data System (ADS)

Ji, Shaocheng; Li, Le; Motra, Hem Bahadur; Wuttke, Frank; Sun, Shengsi; Michibayashi, Katsuyoshi; Salisbury, Matthew H.

2018-02-01

Here we provide an appraisal of the Poisson's ratios (υ) for natural elements, common oxides, silicate minerals, and rocks with the purpose of searching for naturally auxetic materials. The Poisson's ratios of equivalently isotropic polycrystalline aggregates were calculated from dynamically measured elastic properties. Alpha-cristobalite is currently the only known naturally occurring mineral that has exclusively negative υ values at 20-1,500°C. Quartz and potentially berlinite (AlPO4) display auxetic behavior in the vicinity of their α-β structure transition. None of the crystalline igneous and metamorphic rocks (e.g., amphibolite, gabbro, granite, peridotite, and schist) display auxetic behavior at pressures of >5 MPa and room temperature. Our experimental measurements showed that quartz-rich sedimentary rocks (i.e., sandstone and siltstone) are most likely to be the only rocks with negative Poisson's ratios at low confining pressures (≤200 MPa) because their main constituent mineral, α-quartz, already has extremely low Poisson's ratio (υ = 0.08) and they contain microcracks, micropores, and secondary minerals. This finding may provide a new explanation for formation of dome-and-basin structures in quartz-rich sedimentary rocks in response to a horizontal compressional stress in the upper crust.

New U Pb SHRIMP zircon age for the Schurwedraai alkali granite: Implications for pre-impact development of the Vredefort Dome and extent of Bushveld magmatism, South Africa

NASA Astrophysics Data System (ADS)

Graham, I. T.; De Waal, S. A.; Armstrong, R. A.

2005-12-01

The Schurwedraai alkali granite is one of a number of prominent ultramafic-mafic and felsic intrusions in the Neoarchaean to Palaeoproterozoic sub-vertical supracrustal collar rocks of the Vredefort Dome, South Africa. The alkali granite intruded the Neoarchaean Witwatersrand Supergroup and has a peralkaline to peraluminous composition. A new zircon SHRIMP crystallization age of 2052 ± 14 Ma for the Schurwedraai alkali granite places it statistically before the Vredefort impact event at 2023 ± 4 Ma and within the accepted emplacement interval of 2050-2060 Ma of the Bushveld magmatic event. The presence of the alkali granite and associated small ultramafic-mafic intrusions in the Vredefort collar rocks extends the southern extremity of Bushveld-related intrusions to some 120 km south of Johannesburg and about 150 km south of the current outcrop area of the Bushveld Complex. The combined effect of these ultramafic-mafic and felsic bodies may have contributed to a pronouncedly steep pre-impact geothermal gradient in the Vredefort area, and to the amphibolite-grade metamorphism observed in the supracrustal collar rocks of the Vredefort Dome.

HP LT Variscan metamorphism in the Cubito-Moura schists (Ossa-Morena Zone, southern Iberia)

NASA Astrophysics Data System (ADS)

Booth-Rea, Guillermo; Simancas, José Fernando; Azor, Antonio; Azañón, José Miguel; González-Lodeiro, Francisco; Fonseca, Paulo

2006-12-01

Multi-equilibrium thermobarometry shows that low-grade metapelites (Cubito-Moura schists) from the Ossa-Morena Zone underwent HP-LT metamorphism from 340-370 °C at 1.0-0.9 GPa to 400-450 °C at 0.8-0.7 GPa. These HP-LT equilibriums were reached by parageneses including white K mica, chlorite and chloritoid, which define the earliest schistosity (S 1) in these rocks. The main foliation in the schists is a crenulation cleavage (S 2), which developed during decompression from 0.8-0.7 to 0.4-0.3 GPa at increasing temperatures from 400-450 °C to 440-465 °C. Fe 3+ in chlorite decreased greatly during prograde metamorphism from molar fractions of 0.4 determined in syn-S 1 chlorites down to 0.1 in syn-S 2 chlorites. These new data add to previous findings of eclogites in the Moura schists indicating that a pile of allochtonous rocks situated next to the Beja-Acebuches oceanic amphibolites underwent HP-LT metamorphism during the Variscan orogeny. To cite this article: G. Booth-Rea et al., C. R. Geoscience 338 (2006).

Genomic Biomarkers for the Prediction of Stage and Prognosis of Upper Tract Urothelial Carcinoma.

PubMed

Bagrodia, Aditya; Cha, Eugene K; Sfakianos, John P; Zabor, Emily C; Bochner, Bernard H; Al-Ahmadie, Hikmat A; Solit, David B; Coleman, Jonathan A; Iyer, Gopa; Scott, Sasinya N; Shah, Ronak; Ostrovnaya, Irina; Lee, Byron; Desai, Neil B; Ren, Qinghu; Rosenberg, Jonathan E; Dalbagni, Guido; Bajorin, Dean F; Reuter, Victor E; Berger, Michael F

2016-06-01

Genomic characterization of radical nephroureterectomy specimens in patients with upper tract urothelial carcinoma may allow for thoughtful integration of systemic and targeted therapies. We sought to determine whether genomic alterations in upper tract urothelial carcinoma are associated with adverse pathological and clinical outcomes. Next generation exon capture sequencing of 300 cancer associated genes was performed in 83 patients with upper tract urothelial carcinoma. Genomic alterations were assessed individually and also grouped into core signal transduction pathways or canonical cell functions for association with clinicopathological outcomes. Binary outcomes, including grade (high vs low), T stage (pTa/T1/T2 vs pT3/T4) and organ confined status (pT2 or less and N0/Nx vs greater than pT2 or N+) were assessed with the Kruskal-Wallis and Fisher exact tests as appropriate. Associations between alterations and survival were estimated using the Kaplan-Meier method and Cox regression. Of the 24 most commonly altered genes in 9 pathways TP53/MDM2 alterations and FGFR3 mutations were the only 2 alterations uniformly associated with high grade, advanced stage, nonorgan confined disease, and recurrence-free and cancer specific survival. TP53/MDM2 alterations were associated with adverse clinicopathological outcomes whereas FGFR3 mutations were associated with favorable outcomes. We created a risk score using TP53/MDM2 and FGFR3 status that was able to discriminate between adverse pathological and clinical outcomes, including in the subset of patients with high grade disease. The study is limited by small numbers and lack of validation. Our data indicate that specific genomic alterations in radical nephroureterectomy specimens correlate with tumor grade, stage and cancer specific survival outcomes. Copyright © 2016 American Urological Association Education and Research, Inc. Published by Elsevier Inc. All rights reserved.

Three-Year Study of Students' Attitudes Toward Physical Education: Grades 4-8.

PubMed

Mercier, Kevin; Donovan, Corinne; Gibbone, Anne; Rozga, Kimberly

2017-09-01

A relationship exists between attitudes toward physical education and future physical activity. The purpose of this study was to examine changes in attitude toward physical education as students progressed from upper elementary school (Grade 4) through middle school (Grade 8). Three cohorts of students (Cohort 1, Grades 4-6, n = 96; Cohort 2, Grades 5-7, n = 71; and Cohort 3, Grades 6-8, n = 73) were each followed for 3 years to examine changes in attitudes toward physical education. After an initial increase from Grade 4 to Grade 5, a significant decrease was observed from Grades 5 to 8 in students' positive attitudes toward physical education, with a faster rate of change for girls than boys. This longitudinal study provides further insights regarding the attitudes of students as they progress from Grade 4 to Grade 8 and expands on previous findings identifying decreasing positive attitudes toward physical education as students age, particularly for girls. The results provide evidence to support targeted interventions.

Relationship between colon and kidney: a critical point for percutaneous procedures.

PubMed

Atar, Murat; Hatipoglu, Namik Kemal; Soylemez, Haluk; Penbegul, Necmettin; Bozkurt, Yasar; Gumus, Hatice; Sancaktutar, Ahmet Ali; Kuday, Suzan; Bodakci, Mehmet Nuri

2013-04-01

The aim of this study was to determine the frequency of anatomical variations of the colon associated with the kidney. A retrospective analysis was performed on 1000 consecutive abdominal computed tomography (CT) scans performed between July 2010 and September 2011. A line parallel to the horizontal plane was drawn through the posterior edge of each kidney at three renal levels: upper, middle and lower pole. The bowel between the psoas muscle and the kidney was determined as the interposition of the colon. The amount of perinephric fat was estimated and graded. The total number of patients undergoing CT scans was 1000 (male/female = 510/490). The mean age of patients was 42.2 years. Seventeen patients (1.7%) had retrorenal colon, of which 12 (1.2%) were on the left side, three (0.3%) on the right side and two (0.2%) were bilateral. Of these 17 cases, 11 were found at the lower, two at the middle and four at the upper pole of the kidney. There was grade I perirenal fat tissue in 13 and grade II in four cases. Interposition of the colon was detected in 32 (3.2%) patients, 30 (3%) on the right and two (0.2%) on the left. The grade of perirenal fat tissue in patients with colon interposition was as follows: 25 patients grade I, six patients grade II and one patient grade III. In accessing the lower pole of the kidney, especially on the left side, the risk of colonic injury should be taken into consideration during percutaneous procedures, regardless of the patient's age and gender.

Prevalence of acne vulgaris and its impact of the quality of life among secondary school-aged adolescents in Sohag Province, Upper Egypt.

PubMed

El-Hamd, Mohammed Abu; Nada, Essam El-Din Abdel-Aziz; Moustafa, Mohammed Abdel-Kareem; Mahboob-Allah, Rehab Ahmed

2017-09-01

Acne vulgaris is the most common dermatological condition encountered in adolescents. It was to determine the prevalence of acne vulgaris and its impact of the quality of life among adolescents attending secondary schools in Sohag Province, Upper Egypt. This was a cross-sectional study conducted in randomly selected governmental and technical secondary schools in Sohag Province, Upper Egypt. Approval was taken from the scientific research committee of Sohag Faculty of Medicine and also from Ministry of Education. Every student with acne was subjected to full medical history and local examination of head and neck to assess the severity of acne vulgaris. Assessment of the impact of acne vulgaris on their quality of life was carried out using self-reported validated specific questionnaire, the Cardiff Acne Disability Index (CADI). This study included 994 teenage secondary school students. The overall prevalence of acne vulgaris was 333 (33.5%). The mean age of the students with acne was 16.84±0.87. Acne vulgaris was more common among females than among males (200, 60% vs 133, 40%). The most common form of acne vulgaris was mild 178, 53%, followed by moderate form 135, 41%, and severe form 20, 6%. CADI score was significantly related to the disease grade and it was maximum among those with severe grade, followed by moderate and lastly mild disease grade. Acne vulgaris is a common skin disease and has a valuable impact on quality of life among adolescents attending secondary schools in Sohag Province, Upper Egypt. © 2017 Wiley Periodicals, Inc.

Assessment of thermal embrittlement in duplex stainless steels 2003 and 2205 for nuclear power applications

DOE PAGES

Tucker, J. D.; Miller, M. K.; Young, G. A.

2015-04-01

Duplex stainless steels are desirable for use in power generation systems due to their attractive combination of strength, corrosion resistance, and cost. However, thermal embrittlement at intermediate homologous temperatures of ~887°F (475°C) and below, via spinodal decomposition, limits upper service temperatures for many applications. New lean grade duplex alloys have improved thermal stability over standard grades and potentially increase the upper service temperature or the lifetime at a given temperature for this class of material. The present work compares the thermal stability of lean grade, alloy 2003 to standard grade, alloy 2205, through a series of isothermal agings between 500°Fmore » (260°C) and 900°F (482°C) for times between 1 and 10,000 hours. Aged samples were characterized by changes in microhardness and impact toughness. Additionally, atom probe tomography was performed to illustrate the evolution of the α-α' phase separation in both alloys at select conditions. Atom probe tomography confirmed that phase separation occurs via spinodal decomposition for both alloys and identified the formation of Ni-Cu-Si-Mn-P clusters in alloy 2205 that may contribute to embrittlement of this alloy. The impact toughness model predictions for upper service temperature show that alloy 2003 can be considered for use in 550°F applications for 80 year service lifetimes based on a Charpy V-notch criteria of 35 ft-lbs at 70°F. Alloy 2205 should be limited to 500°F applications.« less

EBSD characterization of pre-Cambrian deformations in conglomerate pebbles (Sierra de la Demanda, Northern Spain)

NASA Astrophysics Data System (ADS)

Puelles, Pablo; Ábalos, Benito; Fernández-Armas, Sergio

2010-05-01

Pre-Cambrian and unconformable earliest Cambrian rocks from the Sierra de la Demanda (N Spain) exhibit field and microstructural relationships that attest to orogenic events recorded by concealed basement rocks. Neoproterozoic foliated slates ("Anguiano Schists") crop out under up to 300 m thick, unfoliated quartz-rich conglomerates ("Anguiano Conglomerates") and quartzites which are stratigraphically ca. 600 m below the oldest, paleontologically dated, pre-trilobitic Cambrian layers (likely older than 520 Ma). The Anguiano Conglomerates contain mm to cm grainsized well-rounded pebbles of various types including monocrystalline quartz, detrital zircon and tourmaline-bearing sandstones, black cherts and metamorphic poly-crystalline quartz aggregates. The undeformed matrix is made of much smaller (diagenetically overgrown) monocrystaline quartz grains and minor amounts of accesory zircon, tourmaline and mica. Black chert pebbles exhibit microstructural evidence of brittle deformation (microfaults and thin veins of syntaxial fibrous quartz). These and the fine-grained sandstone pebbles can also exhibit ductile deformations (microfolds with thickened hinges and axial planar continuous foliations), too. Polycrystalline quartz pebbles exhibit a variety of microstructures that resulted from syn-metamorphic ductile deformations. These are recognisable under the petrographic microscope and include continuous foliations, quartz shape fabrics, various types of subgrain or recrystallized new grain microtextures, and lattice preferred orientations (LPOs). Conventional characterization of quartz fabrics (after oriented structural sections) is challenged in conglomerate pebble thin sections by the difficulty of unraveling in them the complete structural reference framework provided by foliation (whose trace can be unraveled) and lineation orientation (which cannot be directly identified). Quartz in various metamorphic polycrystalline pebbles was studied with the Electron Back-Scatter Diffraction (EBSD) technique. The identification of quartz c-axis point maxima or girdles and their geometrical relationships with respect to -axis arrangements and pebble foliation traces enabled us to identify the operation of basal and prism- and occasionally prism-[c] intracrystalline slip systems. This points to upper-greenschists and amphibolite facies syn-metamorphic deformations. By contrast, black chert and sandstone pebbles and matrix quartz aggregates lack any LPO. The source area of the conglomerates was likely a pre-Cambrian basement that contained penetratively deformed low- to medium-grade metamorphic rocks. Radiometric dating of this metamorphism has not been accomplished so far though it is known that inherited Precambrian sources in the Iberian Peninsula relate notably to Neoproterozoic (Pan-African and Cadomian) orogens, and to a lesser extent to Paleoproterozoic (1.8-2.1 Ga) or Neoarchean (2.4-2.8 Ga) ones. Neoproterozoic (Cadomian) metamorphism of this grade has only been recognized in SW Iberia. If the fabrics here studied were Cadomian, they might be related to the arc-related igneous suites that have been detected or inferred in other realms of the northern Iberian Massif.

The Integration of Mathematics in Physics Problem Solving: A Case Study of Greek Upper Secondary School Students

ERIC Educational Resources Information Center

Meli, Kalliopi; Zacharos, Konstantinos; Koliopoulos, Dimitrios

2016-01-01

This article presents a case study that examines the level of integration of mathematical knowledge in physics problem solving among first grade students of upper secondary school. We explore the ways in which two specific students utilize their knowledge and we attempt to identify the epistemological framings they refer to while solving a physics…

Environmental Education Activities Manual, Book 4: Upper Elementary Activities.

ERIC Educational Resources Information Center

Stapp, William B., Ed.; Cox, Dorothy A., Ed.

This activities book for the upper elementary grades is the fourth book of a series of six books designed to provide developmental K-12 experiences designed to support the basic environmental philosophy of spaceship earth presented in Book 1. The aims of the four activity sections of this book are to aid in developing students to make them more…

Equivalence Reliability among the FITNESSGRAM[R] Upper-Body Tests of Muscular Strength and Endurance

ERIC Educational Resources Information Center

Sherman, Todd; Barfield, J. P.

2006-01-01

This study was designed to investigate the equivalence reliability between the suggested FITNESSGRAM[R] muscular strength and endurance test, the 90[degrees] push-up (PSU), and alternate FITNESSGRAM[R] tests of upper-body strength and endurance (i.e., modified pull-up [MPU], flexed-arm hang [FAH], and pull-up [PU]). Children (N = 383) in Grades 3…

This Land Was Made for You and Me: Teaching for Economic Justice in Upper Elementary and Middle School Grades

ERIC Educational Resources Information Center

Lucey, Thomas A.; Laney, James D.

2009-01-01

Teaching for economic justice can be challenging for upper elementary and middle school teachers. Many teachers may feel uncomfortable with the subject matter and thus avoid addressing sensitive social issues related to economic/financial inequities. This article describes how selected songs and works of visual art, expressions of social protest…

Personality traits measured at baseline can predict academic performance in upper secondary school three years late.

PubMed

Rosander, Pia; Bäckström, Martin

2014-12-01

The aim of the present study was to explore the ability of personality to predict academic performance in a longitudinal study of a Swedish upper secondary school sample. Academic performance was assessed throughout a three-year period via final grades from the compulsory school and upper secondary school. The Big Five personality factors (Costa & McCrae, ) - particularly Conscientiousness and Neuroticism - were found to predict overall academic performance, after controlling for general intelligence. Results suggest that Conscientiousness, as measured at the age of 16, can explain change in academic performance at the age of 19. The effect of Neuroticism on Conscientiousness indicates that, as regarding getting good grades, it is better to be a bit neurotic than to be stable. The study extends previous work by assessing the relationship between the Big Five and academic performance over a three-year period. The results offer educators avenues for improving educational achievement. © 2014 Scandinavian Psychological Associations and John Wiley & Sons Ltd.

Colorado Upper-Division Electrostatics diagnostic: A conceptual assessment for the junior level

NASA Astrophysics Data System (ADS)

Chasteen, Stephanie V.; Pepper, Rachel E.; Caballero, Marcos D.; Pollock, Steven J.; Perkins, Katherine K.

2012-12-01

As part of an effort to systematically improve our junior-level E&M I course, we have developed a tool to assess student conceptual learning of electrostatics at the upper division. Together with a group of physics faculty, we established a list of learning goals for the course that, with results from student observations and interviews, served as a guide in creating the Colorado Upper-Division Electrostatics (CUE) assessment. The result is a 17-question open-ended post-test diagnostic (with an optional 7-question pretest) and an accompanying grading rubric. We present measures of the validation and reliability of the instrument and grading rubric, plus results from 535 students in both standard and interactive-engagement courses across seven institutions as a baseline for the instrument. Overall, we find that the CUE is a valid and reliable measure, and the data herein are intended to be of use to researchers and faculty interested in using the CUE to measure student learning.

Meteorology: Observing, Understanding, and Predicting Weather. Self-Directed Study Units for Grades K-8.

ERIC Educational Resources Information Center

Brown, Mary; Dickinson, Rosemary

This book consists of two complete units on meteorology. The first unit is created for lower elementary students and the second one is for upper elementary grade levels. The units are designed for gifted students and encourage students to be responsible for their own education. Each unit is based on an interdisciplinary approach. Suggestions for…

States' Reading Outcomes of Students Who Are d/Deaf or Hard of Hearing

ERIC Educational Resources Information Center

Easterbrooks, Susan R.; Beal-Alvarez, Jennifer S.

2012-01-01

Historically, researchers have identified that reading outcomes for students in upper grades who are d/Deaf and hard of hearing (d/Dhh) have typically rested around the late 3rd to early 4th grade. In recent years, wide-scale state-level testing has called into question these prognostications. The authors conducted a descriptive, multiunit,…

Liberty and Justice. User Guide for Grades K-6. My America: Building a Democracy Series.

ERIC Educational Resources Information Center

Fier, Harriet, Ed.; And Others

This user guide covers "Liberty and Justice," and offers suggestions for preparatory activities, lessons, and follow-up activities for primary, intermediate, and upper grade students. Goals for the series are to help children: (1) become familiar with the democratic process and active citizenship; (2) recognize what it means to be a citizen in a…

Fostering Writing in Upper Primary Grades: A Study into the Distinct and Combined Impact of Explicit Instruction and Peer Assistance

ERIC Educational Resources Information Center

De Smedt, Fien; Van Keer, Hilde

2018-01-01

As writing is a complex and resource demanding task, high-quality writing instruction is indispensable from primary grades on to support beginning writers in developing effective writing skills. Writing research should therefore provide teachers and schools with evidence-based guidelines for teaching writing in daily practice. In this respect, the…

How Executive Functions Predict Development in Syntactic Complexity of Narrative Writing in the Upper Elementary Grades

ERIC Educational Resources Information Center

Drijbooms, Elise; Groen, Margriet A.; Verhoeven, Ludo

2017-01-01

The aim of this study was to examine the contribution of transcription skills, oral language skills, and executive functions to growth in narrative writing between fourth and sixth grade. While text length and story content of narratives did not increase with age, syntactic complexity of narratives showed a clear developmental progression. Results…

The Rodeo and Cattle Industry -- Its Rich Spanish-Mexican Heritage. A Bilingual-Bicultural Resource Booklet for Teachers, Pre-School through Grade Six.

ERIC Educational Resources Information Center

Archuleta, Lena, Comp.

This teacher resource book describes the Spanish-Mexican contribution to the cattle industry, rodeo, and cowboy culture. It provides background material, resources, and activities for developing a bilingual-bicultural education course for primary, intermediate, and upper grades. The first three sections discuss the cattle industry, American rodeo,…

Multisyllabic Word-Reading Instruction with and without Motivational Beliefs Training for Struggling Readers in the Upper Elementary Grades: A Pilot Investigation

ERIC Educational Resources Information Center

Toste, Jessica R.; Capin, Philip; Vaughn, Sharon

2017-01-01

This randomized controlled trial focused on 59 struggling readers in the third and fourth grades (30 female, 29 male) and examined the efficacy of an intervention aimed at increasing students' multisyllabic word reading (MWR). The study also explored the relative effects of an embedded motivational beliefs (MB) training component. Struggling…

A Task Analysis of a Sport Education Physical Education Season for Fourth Grade Students

ERIC Educational Resources Information Center

Layne, Todd; Hastie, Peter

2015-01-01

Background: Previous research on Sport Education in which the participants were in the primary grades has focused on perceptions of fun and enjoyment as well as other components of motivation. To date, no study in Sport Education has examined the accomplishment of the various instructional and managerial tasks by upper primary school children,…

Joyous Reading: Aspects of Literature Enjoyment for Black/African American Fourth Grade Students

ERIC Educational Resources Information Center

Mosley, Sherea

2017-01-01

This study primarily explores the types of books African American children in a local fourth grade classroom like and enjoy. Books students are interested in reading and other related aspects that contribute to their literary enjoyment are also explored. It is during the upper elementary years that many students who eventually express little or no…

Rewarding Foreign Language Learning: Effects of the Swedish Grade Point Average Enhancement Initiative on Students' Motivation to Learn French

ERIC Educational Resources Information Center

Henry, Alastair

2017-01-01

In order to reinstate interest and motivation for learning foreign languages (FLs) other than English, the Swedish government has recently reformed the system for admission to higher education. Upper secondary students who continue with the FL learnt in secondary school are rewarded with extra credits that considerably enhance their grade point…

Deep and shallow forms of the sulcus for extensor carpi ulnaris.

PubMed

Nakashima, T; Hojo, T; Furukawa, H

1993-12-01

Anatomical variations in the sulcus for the tendon of extensor carpi ulnaris were studied in 240 upper limbs. The sulcus lies between the head and the styloid process on the dorsal surface of the distal end of the ulna. This groove has deep and shallow forms and, rarely, a flat form. The sulcus was classified into 4 grades according to its depth. Grade I, a deep sulcus, was found in 51.3%. Grades II and III are shallow, but the styloid process in grade II is more prominent than in grade III. The former was found in 28.8%, the latter in 14.2%. Grade IV is a flat form. This was rare and found only in 1.3%. This variation was not age-related, but was a congenital feature.

Metamorphic and tectonic evolution of Ceuta peninsula (Internal Rif): new interpretation in the framework of arc and back arc evolution

NASA Astrophysics Data System (ADS)

Homonnay, Emmanuelle; Lardeaux, Jean-Marc; Corsini, Michel; Cenki-Tok, Bénédicte; Bosch, Delphine; Munch, Philippe; Romagny, Adrien; Ouazzani-Touhami, Mohamed

2016-04-01

In the last twenty years, various geophysical investigations have established that the Western Mediterranean opened in a subduction context as a back arc domain. In the Alboran basin the dip of the subduction plane is eastwards or southeastwards depending of considered models. If the geological records of back-arc opening are well-known, the arc-related tectonic and petrologic evolutions are still poorly documented. In order to decipher these markers, we focalised structural, petrological and thermo-chronological studies on the Ceuta peninsula located in the Rif belt, on the western part of the Gibraltar arc to the North of Morocco. The present-day tectonic pile is constituted by: (1) the upper Ceuta unit, composed of High Pressure and High Temperature metapelites retromorphosed under Amphibolite-facies condition, with Ultra-High Pressure relicts, and pyrigarnite and spinel bearing peridotites boudins at its base, (2) the lower Monte Hacho unit, with orthogneisses metamorphosed under Amphibolite-facies conditions. Structural analysis indicates a polyphase tectonic evolution: (1) an earlier deformation phase only observed in the UHP metapelites and characterized by a steep S1 foliation plane, (2) a main deformation phase associated to a pervasive gently dipping S2 foliation plane bearing a L2 stretching lineation and synschistose folds whose axes are parallel to L2 and (3) a late deformation phase which developed S3 foliation plane and L3 stretching lineation coeval with development of narrow normal ductile shear zones. A zone of increasing deformation, several dozen meters wide, is identified as a major ductile shear zone involving the peridotitic lenses at the base of the metapelites of the Ceuta unit and overlaying this upper unit on top of the orthogneisses of the Monte Hacho lower unit. The attitude of mylonitic foliation and stretching and mineral lineations as well as the numerous shear sense indicators observed in the shear zone are consistent with a thrusting toward the NE. Furthermore, biotite-sillimanite bearing S2 foliation affecting the whole of crustal rocks is contemporaneous with the movement on this main ductile thrusting. We combined garnet-biotite and GASP thermo-barometers with thermodynamic modelling (Theriak-Domino) in order to constrain pressure and temperature conditions of D2 and D3 tectono-metamorphic events. P-T conditions of D2 deformation are in the range 7-10kbar and 770-820°C and are compatible with syn-tectonic partial melting. D3 deformation event occurred at 1-7kbar and 400-550°C. These metamorphic conditions reflect abnormally high geothermal gradients during both shortening and thinning and are clearly compatible with the thermal evolution recognized in continental arcs. Preliminary U-Th-Pb (monazite, zircon and xenotime) and previous Ar39/Ar40 (micas) analyses, furnished similar ages around 21 Ma for D2 and D3 events, suggesting a very fast transition from arc to back-arc dynamics.

From an active continental plate margin to continental collision: New constraints from the petrological, structural and geochronological record of the (ultra) high-P metamorphic Rhodope domain (N-Greece)

NASA Astrophysics Data System (ADS)

Mposkos, E.; Krohe, A.; Wawrzenitz, N.; Romer, R. L.

2012-04-01

The Rhodope domain occupies a key area along the suture between the European and the Apulian/Adriatic plate (Schmid et al., 2008), which collided in the early Tertiary (closure of the Vardar/Axios ocean, cf. Mposkos & Krohe, 2006). An integrated study of the geochronological, tectonic and petrological data of the Rhodope domain provides the unique opportunity resolving a 160 my lasting metamorphic evolution (Jurassic to Miocene) of an active plate margin to a high degree. The Greek Rhodope consists of several composite metamorphic complexes bounded by the Nestos thrust and several normal detachment systems. The PT- and structural records of the complexes constrain metamorphic, magmatic and tectonic processes, associated with subduction along a convergent plate margin including UHP metamorphism, MP to HP metamorphism associated with continental collision, and core complex formation linked to Aegean back arc extension. We focus on the Sidironero Complex that shows a polymetamorphic history. This is documented by SHRIMP and LA-ICP-MS U-Pb zircon ages of ca. 150 Ma from garnet-kyanite gneisses that are interpreted to record the HP/UHP metamorphism (Liati, 2005; Krenn et al., 2010). SHRIMP zircon ages of ca. 51 Ma from an amphibolitized eclogite is interpreted by Liati (2005) to record a second Eocene HP metamorphic event. We present new data from an integrated petrological, geochronological and tectonic study. Granulite facies and upper amphibolite facies metamorphic conditions are recorded by the mineral assemblage Grt-Ky-Bt-Pl-Kfs-Qtz-Rt and Grt-Ky-Bt-Ms-Pl-Qtz-Rt, respectively, in deformed migmatitic metapelites. Deformation occurred under granulite facies conditions. Monazites from the matrix, that formed during the granulite facies deformation, lack core/rim structures and are only locally patchy zoned. Monazite chemical compositions are related to varying reaction partners. Single grains and fractions of few grains yield ID-TIMS U-Pb ages that plot along the concordia between 64 to 60 Ma. One date of 55 Ma might represent Pb-loss during later fluid-induced dissolution-reprecipitation. We discuss the following questions: What is the history of the high-P metamorphic rocks in the Sidironero Complex? Were high-P rocks that have been already exhumed again dragged into the subduction channel? Which rocks from the upper plate are affected by high-P metamorphism evincing that subduction erosion is an important mechanism? We reconsider the significance of the P-T-t evolution in the light of the tectonic processes that took place along the depth extension of a convergent plate interface and during subsequent continental collision along the European/Apulian Suture zone. Krenn et al., 2010. Tectonics 29, TC4001. Liati, A., 2005. Contribution to Mineralogy and Petrology 150, 608-630. Mposkos, E. & Krohe, A. 2006. Canadian Journal of Earth Sciences 43, 1755-1776. Schmid S.M., et al. 2008. Swiss Journal of Geoscience 101, 139-183.

Metamorphic evolution and geochronology of the Dunhuang orogenic belt in the Hongliuxia area, northwestern China

NASA Astrophysics Data System (ADS)

Wang, Hao Y. C.; Wang, Juan; Wang, Guo-Dong; Lu, Jun-Sheng; Chen, Hong-Xu; Peng, Tao; Zhang, Hui C. G.; Zhang, Qian W. L.; Xiao, Wen-Jiao; Hou, Quan-Lin; Yan, Quan-Ren; Zhang, Qing; Wu, Chun-Ming

2017-03-01

Garnet-bearing mafic granulites and amphibolites from the Hongliuxia area of the southern Dunhuang orogenic belt, northwestern China, commonly occur as lenses or boudinages enclosed within metapelite or marble, which represent the block-in-matrix feature typical of orogenic mélange. Three to four generations of metamorphic mineral assemblages are preserved in these rocks. In the high-pressure amphibolites, prograde mineral assemblages (M1) occur as inclusions (hornblende + plagioclase + quartz ± chlorite ± epidote ± ilmenite) preserved within garnet porphyroblasts, and formed at 550-590 °C and 7.7-9.2 kbar based on geothermobarometry. The metamorphic peak mineral assemblages (M2) are composed of garnet + hornblende + plagioclase + quartz + clinopyroxene, as well as titanite + zircon + rutile + apatite as accessory minerals in the matrix, and are estimated to have formed at 640-720 °C and 14.1-16.0 kbar. The first retrograde assemblages (M3) are characterized by "white-eye socket" symplectites (hornblende + plagioclase + quartz ± biotite ± epidote ± magnetite) rimming garnet porphyroblasts, which formed at the expense of the garnet rims and adjacent matrix minerals during the decompression stage under P-T conditions of 610-630 °C and 5.6-11.8 kbar. The second retrograde assemblages (M4) are intergrowths of actinolite and worm-like quartz produced by the breakdown of the matrix hornblendes, and formed under P-T conditions of ∼490 °C and ∼2.8 kbar. For the high-pressure mafic granulites, the prograde assemblages (M1) are represented by plagioclase + quartz preserved within the garnet porphyroblasts. The metamorphic peak assemblages (M2) are garnet + matrix minerals (clinopyroxene + plagioclase + quartz + hornblende + rutile + zircon) and were estimated to have formed at ∼680 °C and ∼15.4 kbar. The retrograde assemblages (M3) are characterized by fine-grained patches of hornblende + plagioclase + quartz rimming the garnet porphyroblasts, as well as hornblende rimming clinopyroxene in the matrix, and were inferred to have formed at ∼620 °C and ∼4.2 kbar. For the metapelitic gneiss, the metamorphic peak assemblages are the garnet porphyroblasts plus the matrix minerals (biotite + plagioclase + quartz + ilmenite + zircon), which were estimated to have formed at ∼630 °C and ∼8.9 kbar. The mafic granulites and amphibolites record fairly similar clockwise P-T paths that include nearly isothermal decompression processes, which suggest that they experienced subduction and subsequent rapid tectonic exhumation. SIMS and LA-ICP-MS U-Pb dating of zircons and 40Ar/39Ar dating of hornblende suggest that the metamorphism occurred at ∼430-390 Ma. Field occurrences, different protolith ages of the mafic granulites and amphibolites, and the considerable gap in peak P-T conditions between the amphibolite and mafic granulite boudinages and their country rock may suggest a mélange accumulation process during the Paleozoic caused by the Silurian-Devonian orogeny, which is possibly associated with the closure of the Liuyuan ocean, a branch of the Paleo-Asian ocean near the southern Central Asian Orogenic Belt.

Pressure-temperature-fluid evolution of the Mongolian Altai in the Central Asian Orogenic Belt: evidence from mineral equilibrium modeling and fluid inclusion studies on amphibolite-facies rocks from western Mongolia

NASA Astrophysics Data System (ADS)

Zorigtkhuu, O.-E.

2012-04-01

The Central Asian Orogenic Belt (CAOB), also known as Altaids, located between the Archean Siberian Craton to the north and the Tarim and North China Cratons to the south, is regarded as one of the largest accretionary and collisional orogen in the world. Detailed petrological studies on the CAOB therefore provide useful information of pressure-temperature (P-T) history of the orogeny as well as the tectonic evolution of East Asia. This study reports detailed petrological data, particularly the results of phase equilibrium modeling and fluid inclusion analysis, of pelitic schists and amphibolites from Bodonch area, southwestern Mongolia, which occupies a significant part of the Paleozoic history of the Altai Orogen in the southwestern margin of the CAOB, and discuss pressure-temperature-fluid evolution of the area. The dominant mineral assemblages of pelitic schist in Bodonch area are garnet + kyanite + staurolite + biotite + plagioclase, garnet + biotite + staurolite + cordierite, and garnet + biotite + sillimanite + plagioclase with quartz and ilmenite, while amphibolite contains calcic amphibole + quartz + plagioclase + garnet + ilmenite assemblage. Application of conventional garnet-biotite and garnet-cordierite geothermometers as well as GASP geobarometer gave metamorphic conditions of 615-635°C/8.2-8.9 kbar from kyanite-bearing pelitic schist samples. Slightly higher P-T condition of 640-690°C/6.3-10.7 kbar was obtained by mineral equilibrium modeling of garnet-kyanite-staurolite and garnet-staurolite-cordierite assemblages using Theriak-Domino software. The calculation was made in the system Na2O-CaO-K2O-FeO-MgO-Al2O3-SiO2-H2O (NCKFMASH). We constructed a clockwise P-T path staring from high-pressure amphibolite facies condition within the stability field of kyanite (approximately 650°C/9 kbar) possibly through the stability field of sillimanite by post-peak decompressional cooling. Our petrographical observations of fluid inclusions in pelitic schists identified primary, secondary and pseudosecondary fluid inclusions trapped in quartz grains. The melting temperatures of all the categories of inclusions lie in the narrow range of -57.5 to-56.6°C, close to the triple point of pure CO2. Homogenization of fluids occurs into liquid phase at temperature between -33.3 to +19.4 °C, which convert into densities in the range of 0.78 to 1.09 g/cm3. The estimated CO2 isochores for primary and pseudosecondary high-density inclusions is broadly consistent with the peak metamorphic condition of the studied area. The results, together with the primary and pseudosecondary nature of the inclusions, indicate CO2 was the dominant fluid component during the peak amphibolite-facies metamorphism of the study area. The common occurrences of carbonates and graphite in the study area suggest the origin of CO2 either by oxidation of organic carbon or devolatilization of carbonates in the protolith sedimentary rocks. Key words: P-T condition; geothermobarometry; mineral equilibrium modeling; fluid inclusion; Altai Orogeny; Central Asian Orogenic Belt; Mongolia

Metasomatic Evolution in Tectonically Mixed Zones (Mélange) and Significance for Geochemical Evolution of the Slab-Mantle Interface

NASA Astrophysics Data System (ADS)

Bebout, G. E.; King, R. L.

2012-12-01

Fluid flow focused in highly deformed zones (shear zones), and the physical juxtaposition of chemically disparate rocks (via mechanical mixing) in such zones, can lead to extensive metasomatism, including volume strain, and result in rocks with hybridized compositions little resembling the compositions of the incorporated rock types [1-5]. In the Catalina Schist (California), lawsonite-albite, lawsonite-blueschist, and amphibolite-facies units contain shear zones at scales of meters to kilometers, each containing "blocks" (with more spherical or more tabular dimensions) co-facial in grade with the "matrix" surrounding these blocks [1-3]. Oxygen isotope data for these "mélange" units, and adjacent more "coherent" expanses, indicate enhanced fluid flow in the more strongly deforming mélange zones while fluid flow in coherent domains was dominantly fracture-controlled and episodic. The amphibolite-facies mélange unit shows evidence for km-scale equilibration of varying mineral assemblages with H2O-rich fluids with uniform O and H isotope compositions consistent with a lower-grade metasedimentary source. This unit is believed to have formed largely by mechanical mixing of mafic and ultramafic compositions, partly because of the scarcity of sedimentary blocks. However, the mélange matrix in this unit preserves a number of sedimentary chemical/isotopic characteristics (e.g., Pb isotope compositions [3]) that could reflect the incorporation of sedimentary rocks, with or without fluid-related fractionation, and possibly fluid-mediated additions. Tectonically mixed zones such as these, if volumetrically significant at the slab-mantle interface, could exert disproportionate control on the compositions of hydrous fluids or silicate melts emanating from subducting slabs and entering the forearc to backarc mantle wedge, including those contributing to arc magmatism [1-5]. Geochemical studies of arc lavas should consider the possibility that the "fluids" contributed from slabs to arc source regions bear chemical/isotopic signatures reflecting their interaction with these hybridized zones produced by mixing of varying proportions of sedimentary, mafic, and ultramafic compositions. Also, the high-variance hydrous mineral assemblages created by these coeval mechanical and metasomatic processes (e.g., nearly monomineralic chlorite, talc, and amphibole schists) could play an important role in the volatiles budgets at subduction zones (i.e., having stabilities to P and T significantly higher than those for mineral assemblages in metabasaltic and metasedimentary rocks containing the same mineral phases [1,4]). Field, petrologic/geochemical, theoretical, and geophysical studies should work toward assessment of the volumetric significance, physical properties, and devolatilization histories of these hybridized compositions. [1] Bebout and Barton (2002) Chem. Geol. 187:79-106 [2] King et al. (2006) Ear. Planet. Sci. Lett. 246:288-304 [3] King et al. (2007) Chem. Geol. 239:305-322 [4] Spandler et al. (2008) Contrib. Mineral. Petrol. 155:181-198 [5] Miller et al. (2009) Lithos 107:53-67

Thermobarometric and fluid expulsion history of subduction zones

NASA Astrophysics Data System (ADS)

Ernst, W. G.

1990-06-01

Phanerozoic, unmetamorphosed, weathered, and altered lithotectonic complexes subjected to subduction exhibit the prograde metamorphic facies sequence: zeolite → prehnite-pumpellyite → glaucophane schist → eclogite. Parageneses reflect relatively high-P trajectories, accompanied by semicontinuous devolatilization. The thermal evolution of convergent plate junctions results in early production of high-rank blueschists, high-P amphibolites, and eclogues at depth within narrow subduction zones while the hanging wall lithosphere is still hot. Protracted underflow drains heat from the nonsubducted plate and, even at profound depths, generates very low-T/high-P parageneses. Inclusion studies suggest that two-phase immiscible volatiles (liquid H2O, and gaseous high-hydrocarbons, CH4 and CO2) are evolved in turn during progressive metamorphism of the subducted sections. Expulsion of pore fluids and transitions from weathered and altered supracrustal rocks to zeolite facies assemblages release far more fluid than the better understood higher-grade transformations. Many blueschist parageneses, such as those of the internal Western Alps, have been partially overprinted by later greenschist and/or epidote-amphibolite facies assemblages. Alpine-type postblueschist metamorphic paths involved fairly rapid, nearly adiabatic decompression; some terranes even underwent modest continued heating and fluid evolution during early stages of ascent. Uplift probably occurred as a consequence of the underthrusting of low-density island arc or microcontinental crust along the convergent plate junction, resulting in marked deceleration or cessation of lithospheric underflow, decoupling, and nearly isothermal rise of the recrystallized subduction complex. Other, less common blueschist terranes, such as the eastern Franciscan belt of western California, preserve metamorphic aragonite and other high-P minerals, and lack a low-pressure overprint; physical conditions during retrogression approximately retraced the prograde path or, for early formed high-grade blocks, reflect somewhat higher pressures and lower temperatures. Subducted sections constituting portions of the Franciscan-type of metamorphic belt evidently moved slowly back up the inclined lithospheric plate junction during continued convergence and sustained refrigeration. Upward motion due to isostatic forces was produced by tectonic imbrication of fault suces, laminar return flow in melange zones, and lateral extension of the underplated accretionary prism. The ease with which volatiles are expelled from a subduction complex and migrate upward along the plate junction zone is roughly proportional to the sandstone/shale ratio: low-permeability mudstones tend to maintain fluid values approaching lithostatic, lose strength, and deform chaotically (forming melange belts), whereas permeable sandstone-rich sections retain structural/stratigraphic coherence and fail brittlely (forming coherent terranes). Because of substantial updip expulsion of volatiles during prograde recrystallization, only small amounts of H2O and CO2 are available to support hydration and carbonation of the accretionary complex during its return toward the surface; thus limited back reaction takes place and occurs at low Pfluid/Plithostatic ratios, unless an abundance of volatiles is introduced during uplift.

Usefulness of the comprehensive geriatric assessment in older patients with upper gastrointestinal bleeding: a two-year follow-up study.

PubMed

Pilotto, Alberto; Ferrucci, Luigi; Scarcelli, Carlo; Niro, Valeria; Di Mario, Francesco; Seripa, Davide; Andriulli, Angelo; Leandro, Gioacchino; Franceschi, Marilisa

2007-01-01

The potential usefulness of standardized comprehensive geriatric assessment (CGA) in evaluating treatment and follow-up of older patients with upper gastrointestinal bleeding is unknown. To evaluate the usefulness of the CGA as a 2-year mortality multidimensional prognostic index (MPI) in older patients hospitalized for upper gastrointestinal bleeding. Patients aged > or =65 years consecutively hospitalized for acute upper gastrointestinal bleeding were included. Diagnosis of bleeding was based on clinical and endoscopic features. All patients underwent a CGA that included six standardized scales, i.e., Activities of Daily Living (ADL), Instrumental Activities of Daily Living (IADL), Short Portable Mental Status Questionnaire (SPMSQ), Mini Nutritional Assessment (MNA), Exton-Smith Score (ESS) and Comorbity Index Rating Scale (CIRS), as well as information on medication history and cohabitation, for a total of 63 items. A MPI was calculated from the integrated total scores and expressed as MPI 1 = low risk, MPI 2 = moderate risk, and MPI 3 = severe risk. The predictive value of the MPI for mortality over a 24-month follow-up was calculated. 36 elderly patients (M 16/F 20, mean age 82.8 +/- 7.9 years, range 70-101 years) were included in the study. A significant difference in mean age was observed between males and females (M 80.1 +/- 4.8 vs. F 84.9 +/- 9.3 years; p < 0.05). The causes of upper gastrointestinal bleeding were duodenal ulcer in 38.8%, gastric ulcer in 22.2%, and erosive gastritis in 16.6% of the patients, while 16.6% had gastrointestinal bleeding from unknown origin. The overall 2-year mortality rate was 30.5%. 18 patients (50%) were classified as having a low-risk MPI (mean value 0.18 +/- 0.09), 12 (33.3%) as having a moderate-risk MPI (mean value 0.48 +/- 0.08) and 6 (16.6%) as having a severe-risk MPI (mean value 0.83 +/- 0.06). Higher MPI grades were significantly associated with higher mortality (grade 1 = 12.5%, grade 2 = 41.6%, grade 3 = 83.3%; p = 0.001). Adjusting for age and sex, the prognostic efficacy of MPI for mortality was confirmed and highly significant (odds ratio 10.47, 95% CI 2.04-53.6). CGA is a useful tool for calculating a MPI that significantly predicts the risk of 2-year mortality in older patients with upper gastrointestinal bleeding. Copyright 2007 S. Karger AG, Basel.

Evolution of the Sibişel Shear Zone (South Carpathians): A study of its type locality near Răşinari (Romania) and tectonic implications

NASA Astrophysics Data System (ADS)

Ducea, Mihai N.; Negulescu, Elena; Profeta, Lucia; Sǎbǎu, Gavril; Jianu, Denisa; Petrescu, Lucian; Hoffman, Derek

2016-09-01

The Sibişel Shear Zone is a 1-3 km wide, ductile shear zone located in the South Carpathian Mountains, Romania. In the Rășinari area, the ductile shear zone juxtaposes amphibolite facies rocks of the Lotru Metamorphic Suite against greenschist facies rocks of the Râuşorul Cisnădioarei Formation. The first represents the eroded remnants of Peri-Gondwanan arcs formed between the Neoproterozoic-Silurian (650-430 Ma), regionally metamorphosed to amphibolite facies during the Variscan orogeny (350-320 Ma). The second is composed of metasedimentary and metavolcanic Neoproterozoic-Ordovician (700-497 Ma) assemblages of mafic to intermediate bulk composition also resembling an island arc metamorphosed during the Ordovician (prior to 463 Ma). Between these lie the epidote amphibolite facies mylonitic and ultramylonitic rocks of the Sibișel Formation, a tectonic mélange dominated by mafic actinolite schists attenuated into a high strain ductile shear zone. Mineral Rb-Sr isochrons document the time of juxtaposition of the three domains during the Permian to Early Triassic ( 290-240 Ma). Ductile shear sense indicators suggest a right lateral transpressive mechanism of juxtaposition; the Sibişel shear zone is a remnant Permo-Triassic suture between two Early Paleozoic Gondwanan terranes. A zircon and apatite U-Th/He age transect across the shear zone yields Alpine ages (54-90 Ma apatite and 98-122 Ma zircon); these data demonstrate that the exposed rocks were not subjected to Alpine ductile deformation. Our results have significant implications for the assembly of Gondwanan terranes and their docking to Baltica during Pangea's formation. Arc terranes free of Variscan metamorphism existed until the Early Triassic, emphasizing the complex tectonics of terrane amalgamation during the closure of Paleotethys.

Finite Strain Analysis of the Wadi Fatima Shear Zone in Western Arabia, Saudi Arabia

NASA Astrophysics Data System (ADS)

Kassem, O. M. K.; Hamimi, Z.

2018-03-01

Neoproterozoic rocks, Oligocene to Neogene sediments and Tertiary Red Sea rift-related volcanics (Harrat) are three dominant major groups exposed in the Jeddah tectonic terrane in Western Arabia. The basement complex comprises amphibolites, schists, and older and younger granites unconformably overlain by a post-amalgamation volcanosedimentary sequence (Fatima Group) exhibiting post-accretionary thrusting and thrust-related structures. The older granites and/or the amphibolites and schists display mylonitization and shearing in some outcrops, and the observed kinematic indicators indicate dextral monoclinic symmetry along the impressive Wadi Fatima Shear Zone. Finite strain analysis of the mylonitized lithologies is used to interpret the deformation history of the Wadi Fatima Shear Zone. The measured finite strain data demonstrate that the amphibolites, schists, and older granites are mildly to moderately deformed, where XZ (axial ratios in XZ direction) vary from 2.76 to 4.22 and from 2.04 to 3.90 for the Rf/φ and Fry method respectively. The shortening axes ( Z) have subvertical attitude and are associated with subhorizontal foliation. The data show oblate strain ellipsoids in the different rocks in the studied area and indication bulk flattening strain. We assume that the different rock types have similar deformation behavior. In the deformed granite, the strain data are identical in magnitude with those obtained in the Fatima Group volcanosedimentary sequence. Finite strain accumulated without any significant volume change contemporaneously with syn-accretionary transpressive structures. It is concluded that a simple-shear deformation with constant-volume plane strain exists, where displacement is strictly parallel to the shear plane. Furthermore, the contacts between various lithological units in the Wadi Fatima Shear Zone were formed under brittle to semi-ductile deformation conditions.

Is there an optimal upper instrumented vertebra (UIV) tilt angle to prevent post-operative shoulder imbalance and neck tilt in Lenke 1 and 2 adolescent idiopathic scoliosis (AIS) patients?

PubMed

Kwan, M K; Chan, C Y W

2016-10-01

To investigate whether an optimal upper instrumented vertebra (UIV) tilt angle would prevent 'lateral' shoulder imbalance or neck tilt (with 'medial' shoulder imbalance) post-operatively. The mean follow-up for 60 AIS (Lenke 1 and Lenke 2) patients was 49.3 ± 8.4 months. Optimal UIV tilt angle was calculated from the cervical supine side bending radiographs. Lateral shoulder imbalance was graded using the clinical shoulder grading. The clinical neck tilt grading was as follows: Grade 0: no neck tilt, Grade 1: actively correctable neck tilt, Grade 2: neck tilt that cannot be corrected by active contraction and Grade 3: severe neck tilt with trapezial asymmetry >1 cm. T1 tilt, clavicle angle and cervical axis were measured. UIVDiff (difference between post-operative UIV tilt and pre-operative Optimal UIV tilt) and the reserve motion of the UIV were correlated with the outcome measures. Patients were assessed at 6 weeks and at final follow-up with a minimum follow-up duration of 24 months. Among patients with grade 0 neck tilt, 88.2 % of patients had the UIV tilt angle within the reserve motion range. This percentage dropped to 75.0 % in patients with grade 1 neck tilt whereas in patients with grade 2 and grade 3 neck tilt, the percentage dropped further to 22.2 and 20.0 % (p = 0.000). The occurrence of grade 2 and 3 neck tilt when UIVDiff was <5°, 5-10° and >10° was 9.5, 50.0 and 100.0 %, respectively (p = 0.005). UIVDiff and T1 tilt had a positive and strong correlation (r 2  = 0.618). However, UIVDiff had poor correlation with clavicle angle and the lateral shoulder imbalance. An optimal UIV tilt might prevent neck tilt with 'medial' shoulder imbalance due to trapezial prominence and but not 'lateral' shoulder imbalance.

[Interactive dynamic scalp acupuncture combined with occupational therapy for upper limb motor impairment in stroke: a randomized controlled trial].

PubMed

Wang, Jun; Pei, Jian; Cui, Xiao; Sun, Kexing; Ni, Huanhuan; Zhou, Cuixia; Wu, Ji; Huang, Mei; Ji, Li

2015-10-01

To compare the clinical efficacy on upper limb motor impairment in stroke between the interactive dynamic scalp acupuncture therapy and the traditional scalp acupuncture therapy. The randomized controlled trial and MINIMIZE layering randomization software were adopted. Seventy patients of upper limb with III to V grade in Brunnstrom scale after stroke were randomized into an interactive dynamic scalp acupuncture group and a traditional scalp acupuncture group, 35 cases in each one. In the interactive dynamic scalp acupuncture group, the middle 2/5 of Dingnieqianxiexian (anterior oblique line of vertex-temporal), the middle 2/5 of Dingniehouxiexian (posterior oblique line of vertex-temporal) and Dingpangerxian (lateral line 2 of vertex) on the affected side were selected as the stimulation areas. Additionally, the rehabilitation training was applied during scalp acupuncture treatment. In the traditional scalp acupuncture group, the scalp stimulation areas were same as the interactive dynamic scalp acupuncture group. But the rehabilitation training was applied separately. The rehabilitation training was applied in the morning and the scalp acupuncture was done in the afternoon. The results in Fugl-Meyer for the upper limb motor function (U-FMA), the Wolf motor function measure scale (WM- FT) and the modified Barthel index in the two groups were compared between the two groups before treatment and in 1 and 2 months of treatment, respectively. After treatment, the U-FMA score, WMFT score and the score of the modified Barthel index were all apparently improved as compared with those before treatment (all P < 0.01). The improvement in the U-FMA score after treatment in the interactive dynamic scalp acupuncture group was better than that in the traditional scalp acupuncture group (P < 0.05). For the patients of IV to V grade in Brunnstrom scale, WMFT score in 2 months of treatment and the score of Barthel index after treatment in the interactive dynamic scalp acupuncture group were improved apparently as compared with those in the traditional scalp acupuncture group (P < 0.05, P < 0.01). But, for the patients of III grade in Brunnstrom scale, WMFT score and the score of Barthel index after treatment in the interactive dynamic scalp acupuncture group were not different significantly as compared with those in the traditional scalp acupuncture group (both P > 0.05). For the patients of IV to V grade in Brunnstrom scale in stroke, the interactive dynamic scalp acupuncture therapy achieves the superior improvements of the upper limb motor function and the activity of daily life as compared with the traditional scalp acupuncture therapy, and the longer the treatment lasts, the more apparent the improvements are. For the patients of III grade in Brunnstrom scale, the interactive dynamic scalp acupuncture therapy achieves the similar improvement in the upper limb motor impairment as compared with the traditional scalp acupuncture therapy.

Breaking the Silence: Teaching the Next Generation about Mental Illness. For Upper Elementary Grades. Third Edition.

ERIC Educational Resources Information Center

Susin, Janet; Kaplan, Lorraine; Slater, Louise

This guide provides curriculum lessons for the upper elementary school student that put a human face on mental illness and confront myths passed on from one generation to the next. One in five children will be affected by mental illness at some point in their lives. The goal of these lessons is help students understand that severe mental illnesses…

Family, Community, and School Influences on Resilience among American Indian Adolescents in the Upper Midwest

ERIC Educational Resources Information Center

LaFromboise, Teresa D.; Hoyt, Dan R.; Oliver, Lisa; Whitbeck, Les B.

2006-01-01

This study examines resilience among a sample of American Indian adolescents living on or near reservations in the upper Midwest. Data are from a baseline survey of 212 youth (115 boys and 97 girls) who were enrolled in the fifth through eighth grades. Based upon the definition of resilience, latent class analyses were conducted to identify youth…

Health-Related Fitness and Nutritional Practices: Can They Be Enhanced in Upper Elementary School Students?

ERIC Educational Resources Information Center

Derri, Vassiliki; Aggeloussis, Nikos; Petraki, Christina

2004-01-01

The purpose of the present study was to investigate the effect of an eight-week health-related fitness and nutrition education program on fitness components and dietary habits in upper elementary school students. Forty children from the fifth and sixth grade, 10 to 12 years of age (M= 11.2, SD= 1.1), participated in the study. The experimental…

Mechanisms for Magnesium Isotopic Variation in Low-grade Metamorphosed Mudrocks from the British Caledonides

NASA Astrophysics Data System (ADS)

Wang, S.; Teng, F.; Rudnick, R. L.; Li, S.

2013-12-01

We report Mg isotope ratios for low-grade metamorphosed mudrocks from three lower Paleozoic basins (northern Lake District, southern Lake District and Southern Uplands) in the British Caledonides, previously analyzed for Li, Sr and Nd isotopes (Qiu et al., 2009, GCA), with the aim of understanding the behavior of Mg isotopes during subgreenschist-facies metamorphism, and the processes responsible for Mg isotopic variations in mudrocks. The δ26Mg of mudrocks varies greatly from -0.754 to 0.251, and displays no correlation with metamorphic grade, which ranges from diagenesis to subgreenschist-facies. Thus, low-grade metamorphism has no apparent influence on Mg isotopes. The variations instead likely reflect their provenance and mineralogical components. Samples from the northern Lake District, previously interpreted to derive from ancient, heavily weathered crust have δ26Mg (-0.06 × 0.11 on average) significantly heavier than that of average upper continental crust (~ -0.22), which is consistent with this interpretation. By contrast, mudrocks from the southern Lake District are characterized by low δ26Mg values (from -0.754 to -0.093) that require the presences of an unusually light component. The previously inferred provenance for these rocks of upper continental crust and arc volcanic detritus cannot explain such light isotopic compositions. Rather, such values may reflect the presence of carbonate in these samples and uptake of sea water Mg. Samples from the Southern Uplands, which contain the heaviest Li isotopes and ɛNd, and contain volcanic arc detritus, display Mg isotopic compositions divergent from a 'normal' mantle value (-0.25) towards both high and low δ26Mg values (from -0.742 to -0.079). Therefore, these mudrocks must contain a minimum of three end-members: mature felsic upper continental crust, arc lavas and carbonate. Given that limited Mg isotope fractionation occurs during low-grade metamorphism, Mg isotopes could be a potential tracer of provenance as well as carbonate involvement for fine-grained terrigenous sediments.

Ecology: Learning To Love Our Planet. A Self-Directed Learning Experience. Grades K-8.

ERIC Educational Resources Information Center

Enz, Judith; Diffenderfer, Susan

This self-directed study unit for grades K-3 and 4-8 was developed expressly to transport the student from the position of passive recipient to active participant in his/her own pursuit of knowledge. Within the guide are two complete units: one created for the lower elementary student and one for the upper elementary/middle school student. Units…

Suggestions for Curriculum Development [And] Handbook Upper Elementary Grades, Part B, 4-6. Environmental Education Interdependence: A Concept Approach. Revised.

ERIC Educational Resources Information Center

King, David C.; Long, Cathryn J.

Two booklets comprise the grades 4-6 component of a series of guides for incorporating environmental education into the existing curriculum. Both the guide and handbook emphasize a multidisciplinary approach, use the concept of interdependence as an organizing theme, and offer suggestions for using the local community as a resource to study the…

Gender, Previous Knowledge, Personality Traits and Subject-Specific Motivation as Predictors of Students' Math Grade in Upper-Secondary School

ERIC Educational Resources Information Center

Peklaj, Cirila; Podlesek, Anja; Pecjak, Sonja

2015-01-01

The aim of the study was to examine the relationships between gender, previous knowledge, different personality traits, subject-specific motivational dimensions and students' math grade in secondary school. A total of 386 first-year students (142 boys and 244 girls) from secondary schools in Slovenia (mean age was 15.7 years) participated in the…

Impact of the Developing Mathematical Ideas Professional Development Program on Grade 4 Students' and Teachers' Understanding of Fractions. REL 2017-256

ERIC Educational Resources Information Center

Jayanthi, Madhavi; Gersten, Russell; Taylor, Mary Jo; Smolkowski, Keith; Dimino, Joseph

2017-01-01

Contemporary state math standards emphasize that students must demonstrate an understanding of the mathematical ideas underlying the computations that have typically been the core of the elementary school math curriculum. The standards have put an increased emphasis on the study of fractions in upper elementary grades, which are the years during…

Demographic and Psychological Predictors of Grade Point Average (GPA) in North-Norway: A Particular Analysis of Cognitive/School-Related and Literacy Problems

ERIC Educational Resources Information Center

Saele, Rannveig Grøm; Sørlie, Tore; Nergård-Nilssen, Trude; Ottosen, Karl-Ottar; Goll, Charlotte Bjørnskov; Friborg, Oddgeir

2016-01-01

Approximately 30% of students drop out from Norwegian upper secondary schools. Academic achievement, as indexed by grade point average (GPA), is one of the strongest predictors of dropout. The present study aimed to examine the role of cognitive, school-related and affective/psychological predictors of GPA. In addition, we examined the…

Grades and Withdrawal Rates in Cell Biology and Genetics Based upon Institution Type for General Biology and Implications for Transfer Articulation Agreements

ERIC Educational Resources Information Center

Regier, Kimberly Fayette

2016-01-01

General biology courses (for majors) are often transferred from one institution to another. These courses must prepare students for upper division courses in biology. In Colorado, a Biology Transfer Articulation Agreement that includes general biology has been created across the state. An evaluation was conducted of course grades in two upper…

Twelfth Grade Students' Understanding of Oxidation and Combustion: Using Action Research to Improve Teachers' Practical Knowledge and Teaching Practice

ERIC Educational Resources Information Center

Valanides, Nicos; Nicolaidou, Athanasia; Eilks, Ingo

2003-01-01

Nine 12th grade students, attending the science section of the upper secondary school in Cyprus, were individually interviewed about their understanding of the changes associated with the process of oxidation/combustion. Each student was instructed to firstly predict what would happen when heating a piece of copper wire or a piece of magnesium…

Development and Use of the SCI Inventory to Measure Upper Elementary School Children's Scientific Curiosity and Interests.

ERIC Educational Resources Information Center

Richardson, Rayman Paul

Reported is a study to develop and test an instrument designed to measure the scientific curiosity and science interests of elementary school students. The inventory was administered to 545 students, grades six through nine, in Columbus, Ohio and 1,050 students, grades six and eight, in Portland, Oregon. Total test-retest reliability of the major…

The Effects of Pupil-Corrected Tests and Written Teacher Comments on Learning to Spell in the Upper Elementary Grades.

ERIC Educational Resources Information Center

Lesner, Julius

To determine the effects of teacher comments on spelling test papers, 32 randomly selected fourth- and sixth-grade teachers from low and high socioeconomic area Los Angeles elementary schools used 965 pupils in their regular classes as subjects. The teachers gave the regular weekly spelling test, and one of four evaluation treatments was randomly…

A Teacher's Guide to the Energy 80 Student Booklet for the 1981-82 School Year.

ERIC Educational Resources Information Center

Lord, John, Ed.

This teaching guide was developed for use with Energy 80 program student booklets. Although the program was designed for junior high/middle school students in science/social studies classes, it is indicated that the materials are suitable for use at higher grades and, to a lesser extent, in upper elementary grades. The first 80 pages of the guide…

Ergebnisse einer Lehrerbefragung zum Hintergrund des Englischunterrichts in der Hauptschuloberstufe (Results of a Teacher Questionnaire on the Background of Instruction in English in the Upper Grades of the Hauptschule [9-grade "terminal" school]).

ERIC Educational Resources Information Center

Hellwig, Karlheinz

1980-01-01

The questionnaire dealt with: earmarks of weaker students, parents' attitude, the teachers' training and working conditions, problems of individual instruction, time-frame, existence of professional associations, evaluation of professional conferences, and the use of media. Some evaluations are appended. (IFS/WGA)

The Migration Plans of Upper-Grade Students in Small Towns of Russia

ERIC Educational Resources Information Center

Florinskaia, Iu. F.; Roshchina, T.G.

2006-01-01

This article presents a survey that was carried out in 2004 to assess the level of migration mobility on the part of young inhabitants in the small cities of Russia. The survey was participated in by eleventh-grade (senior) students. The total number of respondents was 500 (100 in each community); 61% were girls and 39% were boys. The statistical…

Computerized Instruction in Translation Strategies for Students in Upper Elementary and Middle School Grades with Persisting Learning Disabilities in Written Language

ERIC Educational Resources Information Center

Niedo, Jasmin; Tanimoto, Steve; Thompson, Robert H.; Abbott, Robert D.; Berninger, Virginia W.

2016-01-01

Students in grades 5 to 9 (ages 10 to 14; 6 girls, 27 boys) who had persisting specific learning disabilities in transcription (handwriting and spelling) completed three kinds of composition tasks requiring translation (thought to written language) on iPads using alternating transcription modes (stylus or keyboard) across every three lessons:…

Clinicopathological characteristics of patients with upper urinary tract urothelial cancer with loss of immunohistochemical expression of the DNA mismatch repair proteins in universal screening.

PubMed

Urakami, Shinji; Inoshita, Naoko; Oka, Suguru; Miyama, Yu; Nomura, Sachio; Arai, Masami; Sakaguchi, Kazushige; Kurosawa, Kazuhiro; Okaneya, Toshikazu

2018-02-01

To assess the detection rate of putative Lynch syndrome-associated upper urinary tract urothelial cancer among all upper urinary tract urothelial cancers and to examine its clinicopathological characteristics. A total of 143 patients with upper urinary tract urothelial cancer who had received total nephroureterectomy were immunohistochemically stained for the expression of mismatch repair proteins MLH1, PMS2, MSH2 and MSH6. For all suspected mismatch repair-deficient cases, MMR genetic testing was recommended and clinicopathological features were examined. Loss of mismatch repair proteins was found in seven patients (5%) who were thus categorized as putative Lynch syndrome-associated upper urinary tract urothelial cancer. Five of these patients showed dual loss of MSH2/MSH6. Two patients were confirmed to be MSH2 germline mutation carriers. Histologically, all seven tumors were low-grade atypical urothelial carcinoma and showed its unique histological features, such as an inverted papilloma-like growth pattern and a villous to papillary structure with mild stratification of tumor cells. Six tumors had no invasion of the muscularis propria. No recurrence or cancer-related deaths were reported in these seven patients. Just three patients met the revised Amsterdam criteria. This is the first report that universally examined mismatch repair immunohistochemical screening for upper urinary tract urothelial cancers. The prevalence (5%) of putative Lynch syndrome-associated upper urinary tract urothelial cancers is much higher than we had expected. We ascertained that putative Lynch syndrome-associated upper urinary tract urothelial cancers were clinically in the early stage and histologically classified into low-grade malignancy with its characteristic pathological features. The clinicopathological characteristics that we found in the present study could become additional possible markers in the diagnosis of Lynch syndrome-associated upper urinary tract urothelial cancers. © 2017 The Japanese Urological Association.

A Rubidium-Strontium study of the Twilight Gneiss, West Needle Mountains, Colorado

USGS Publications Warehouse

Barker, F.; Peterman, Z.E.; Hildreth, R.A.

1969-01-01

The Precambrian trondhjemitic Twilight Gneiss (Twilight Granite of Cross and Howe, 1905b) of the West Needle Mountains, southwestern Colorado, and its interlayered amphibolite and metarhyodacite yield a Rb-Sr isochron of 1,805??35 m.y. A low initial Sr87/Sr86 ratio of 0.7015 implies that metamorphism of these rocks to amphibolite facies took place soon after their emplacement. The mild metamorphism of Uncompahgran age, prior to 1,460 m.y. ago, and Laramide volcanism did not affect the Rb-Sr system in the Twilight. Rb contents of 26.5 to 108 ppm, Sr contents of 114 to 251 ppm, and K2O percentages of 1.23 to 3.64 in the Twilight Gneiss, in conjunction with high K/Rb ratios and the low initial ratio of Sr87/Sr86, lend support to geologic data that suggest the Twilight originated as volcanic or hypabyssal igneous rocks in a basaltic volcanic pile. ?? 1969 Springer-Verlag.

Geochronology of the proterozoic basement of southwesternmost North America, and the origin and evolution of the Mojave crustal province

USGS Publications Warehouse

Barth, Andrew P.; Wooden, Joseph L.; Coleman, Drew S.; Fanning, C. Mark

2000-01-01

The Proterozoic Baldwin gneiss in the central Transverse Ranges of southern California, a part of the Mojave crustal province, is composed of quartzofeldspathic gneiss and schist, augen and granitic gneiss, trondhjemite gneiss, and minor quartzite, amphibolite, metagabbro, and metapyroxenite. Sensitive high resolution ion microprobe (SHRIMP) data indicate that augen and granitic gneisses comprise a magmatic arc intrusive suite emplaced between 1783 ± 12 and 1675 ± 19 Ma, adjacent to or through thinned Archean crust. High U/Th rims on zircons in most samples suggest an early metamorphic event at ∼1741 Ma, but peak amphibolite facies metamorphism and penetrative, west vergent deformation occurred after 1675 Ma. The Baldwin gneiss is part of a regional allochthon emplaced by west vergent deformation over a Proterozoic shelf-slope sequence (Joshua Tree terrane). We hypothesize that emplacement of this regional allochthon occurred during a late Early or Middle Proterozoic arc-continent collision along the western margin of Laurentia.

Distinguishing major lithologic types in rocks of precambrian age in central Wyoming using multilevel sensing, with a chapter on possible economic significance of iron formation discovered by use of aircraft images in the Granite Mountains of Wyoming

NASA Technical Reports Server (NTRS)

Houston, R. S. (Principal Investigator)

1973-01-01

The author has identified the following significant results. Information obtained by remote sensing from three altitude levels: ERTS-1 (565 miles), U-2 (60,000 feet), and C-130 aircraft (15,000 feet) illustrates the possible application of multilevel sensing in mineral exploration. Distinction can be made between rocks of greenstone belts and rocks of granite-granite gneiss areas by using ERTS-1 imagery in portions of the Precambrian of central Wyoming. Study of low altitude color and color infrared photographs of the mafic terrain revealed the presence of metasedimentary rocks with distinct layers that were interpreted as amphibolite by photogeologic techniques. Some of the amphibolite layers were found to be iron formation when examined in the field. To our knowledge this occurrence of iron formation has not been previously reported in the literature.

High-pressure amphibolite facies dynamic metamorphism and the Mesozoic tectonic evolution of an ancient continental margin, east- central Alaska

USGS Publications Warehouse

Dusel-Bacon, C.; Hansen, V.L.; Scala, J.A.

1995-01-01

Ductilely deformed amphibolite facies tectonites comprise two adjacent terranes in east-central Alaska: the northern, structurally higher Taylor Mountain terrane and the southern, structurally lower Lake George subterrane of the Yukon-Tanana terrane. The pressure, temperature, kinematic and age data are interpreted to indicate that the metamorphism of the Taylor Mountain terrane and Lake George subterrane took place during different phases of a latest Palaeozoic through early Mesozoic shortening episode resulting from closure of an ocean basin now represented by klippen of the Seventymile-Slide Mountain terrane. High- to intermediate-pressure metamorphism of the Taylor Mountain terrane took place within a SW-dipping (present-day coordinates) subduction system. High- to intermediate-pressure metamorphism of the Lake George subterrane and the structural contact zone occurred during NW-directed overthrusting of the Taylor Mountain, Seventymile-Slide Mountain and Nisutlin terranes, and imbrication of the continental margin in Jurassic time. -from Authors

Diagnosis and kidney-sparing treatments for upper tract urothelial carcinoma: state of the art.

PubMed

Territo, Angelo; Foerster, Bear; Shariat, Shahrokh F; Rouprêt, Morgan; Gaya, Jose M; Palou, Joan; Breda, Alberto

2018-02-01

Conservative management of upper tract urothelial cancer (UTUC) is becoming increasingly popular: the key to success is correct selection of patients with low-risk UTUC based on size (≤ 2 cm), focality (single lesion), stage (< T2), and grade (low grade). Despite the recent growing interest in the conservative approach to UTUC, the diagnostic process is still a challenge, and kidney-sparing surgery (KSS) is traditionally reserved for patients with contraindications to radical nephroureterectomy. In order to explore the "state of the art" in the diagnosis and conservative treatment of UTUC, a systematic review of the literature was performed. A PubMed, Scopus, and Cochrane search for peer-reviewed studies was performed using the keywords "upper tract urothelial carcinoma" OR "UTUC" OR "upper urinary tract" AND "biopsy" OR "diagnosis" OR "endomicroscopy" OR "imaging" AND "URS" OR "ureteroscopy" OR "kidney-sparing surgery" OR "laser ablation" OR "ureterectomy". We considered as relevant comparative prospective studies (randomized, quasi-randomized, no randomized), retrospective studies, meta-analyses, systematic reviews, and case report series written in the English language. Letters to the editor and contributions written in languages other than English were not considered of value for this review. Eligible articles were reviewed according to the Preferred Reporting Items for Systematic Reviews and Meta-analyses (PRISMA) criteria. Two hundred and sixty-three (263) records were identified using the above-mentioned keywords. Overall, 30 studies were considered relevant for the purpose of this systematic review and for the evidence evaluation process during qualitative synthesis. The outcomes evaluated in this review were the current diagnostic methods and the KSS approaches in UTUC. Furthermore, we included in the review the emerging technology for distinguishing between normal tissue, low-grade UTUC, and high-grade UTUC. Conclusive diagnosis is fundamental to the decision-making process in patients who could benefit from conservative treatment of UTUC. The most relevant diagnostic modalities are computed tomography urography, local urine cytology, and ureteroscopy with acquisition of an adequate biopsy sample for histology. KSS includes the endourological approach and segmental ureterectomy. Promising technology in the endourological management of UTUC helps in providing intraoperative information on UTUC grading and staging, with a high accuracy. Patients treated conservatively have to undergo stringent postoperative follow-up in order to detect and, if necessary, treat any recurrence promptly. Further larger and multicenter studies are needed to confirm these findings.

Lu-Hf Garnet Geochronology Reveals the Tectonic History of Precambrian Rocks in the Southern Rocky Mountains

NASA Astrophysics Data System (ADS)

Aronoff, R.; Andronicos, C.; Vervoort, J. D.; Hunter, R. A.

2014-12-01

Lu-Hf garnet dating of Proterozoic rocks of the southwestern United States provides constraints on the timing and geographic extent of metamorphism associated with the Yavapai, Mazatzal, and newly recognized Picuris orogenies. Prior work focusing on U-Pb dating of plutons and Ar geochronology has left the timing of prograde metamorphism ambiguous, particularly in northern New Mexico and southern Colorado. Because the Lu-Hf system dates the onset of garnet growth, it can constrain the timing of the prograde P-T path. Garnet schist samples from central and northern New Mexico exhibit garnet growth restricted to the time period between ~1460 and 1400 Ma. In the Picuris and Manzano mountains, the oldest Lu-Hf garnet ages predate the U-Pb ages of ~1.4 Ga plutons located near the dated samples. This implies that garnet growth, and therefore the onset of amphibolite facies metamorphism, cannot be driven by contact metamorphism, as has been previously inferred. Garnet-bearing samples from the Needle and Wet Mountains in southern Colorado display a range of garnet ages between ~1750 and 1470 Ma. A garnet gneiss from the Needle Mountains in southwestern Colorado yields an age of 1748 Ma, which is consistent with the Yavapai orogeny. This Lu-Hf garnet age has not been reset by contact metamorphism associated with the emplacement of the ~1.4 Ga Eolus batholith. Anatectic garnet in an orthogneiss from the northern Wet Mountains yields an age of 1601 Ma and is interpreted to date partial melting at the close of the Mazatzal orogeny. A 1476 Ma garnet age from the aureole of the 1440 Ma Oak Creek pluton is interpreted to date upper amphibolite facies metamorphism. The age distribution of these samples shows that rocks in Colorado underwent a complex, poly-metamorphic history, while rocks in New Mexico underwent a single progressive metamorphic event. This contrast implies that the boundary between rocks deformed and metamorphosed during the ~1800-1600 Ma Yavapai and Mazatzal orogenies and those only deformed and metamorphosed during the ~1460-1400 Ma Picuris orogeny lies in northern New Mexico, along what has previously been considered the Mazatzal front. By using Lu-Hf geochronology to directly date a rock-forming mineral, we are better able to reconstruct the tectonic history of this region.

Pre-impact tectonothermal evolution of the crystalline basement-derived rocks in the ICDP-USGS Eyreville B core, Chesapeake Bay impact structure

USGS Publications Warehouse

Gibson, R.L.; Townsend, G.N.; Horton, J. Wright; Reimold, W.U.

2009-01-01

Pre-impact crystalline rocks of the lowermost 215 m of the Eyreville B drill core from the Chesapeake Bay impact structure consist of a sequence of pelitic mica schists with subsidiary metagraywackes or felsic metavolcanic rocks, amphibolite, and calc-silicate rock that is intruded by muscovite (??biotite, garnet) granite and granite pegmatite. The schists are commonly graphitic and pyritic and locally contain plagioclase porphyroblasts, fi brolitic sillimanite, and garnet that indicate middle- to upper-amphibolite-facies peak metamorphic conditions estimated at ??0.4-0.5 GPa and 600-670 ??C. The schists display an intense, shallowly dipping, S1 composite shear foliation with local micrometer- to decimeter-scale recumbent folds and S-C' shear band structures that formed at high temperatures. Zones of chaotically oriented foliation, resembling breccias but showing no signs of retrogression, are developed locally and are interpreted as shear-disrupted fold hinges. Mineral textural relations in the mica schists indicate that the metamorphic peak was attained during D1. Fabric analysis indicates, however, that subhorizontal shear deformation continued during retrograde cooling, forming mylonite zones in which high-temperature shear fabrics (S-C and S-C') are overprinted by progressively lower- temperature fabrics. Cataclasites and carbonate-cemented breccias in more competent lithologies such as the calc-silicate unit and in the felsic gneiss found as boulders in the overlying impactite succession may refl ect a fi nal pulse of low-temperature cataclastic deformation during D1. These breccias and the shear and mylonitic foliations are cut by smaller, steeply inclined anastomosing fractures with chlorite and calcite infill (interpreted as D2). This D2 event was accompanied by extensive chlorite-sericitecalcite ?? epidote retrogression and appears to predate the impact event. Granite and granite pegmatite veins display local discordance to the S1 foliation, but elsewhere they are affected by high-temperature mylonitic shear deformation, suggesting a late-D1 intrusive timing close to the metamorphic peak. The D1 event is tentatively interpreted as a thrusting event associated with westward-verging collision between Gondwana and Laurentia before or during the Permian-Carboniferous Alleghanian orogeny. It is unclear whether subsequent brittle deformation, described here as D2, could be part of regional dextral Alleghanian strike-slip faulting or younger Mesozoic normal faulting. ?? 2009 The Geological Society of America.

Thulium Laser Treatment of Upper Urinary Tract Carcinoma: A Multi-Institutional Analysis of Surgical and Oncological Outcomes.

PubMed

Musi, Gennaro; Mistretta, Francesco A; Marenghi, Carlo; Russo, Andrea; Catellani, Michele; Nazzani, Sebastiano; Conti, Andrea; Luzzago, Stefano; Ferro, Matteo; Matei, Deliu V; Carmignani, Luca; de Cobelli, Ottavio

2018-03-01

To evaluate the efficacy and safety of ureteroscopic thulium laser (TL) treatment of upper urinary tract carcinoma (UTUC). Forty-two consecutive patients underwent conservative TL treatment for UTUC at two referral institutions. All patients underwent preliminary biopsy and then laser vaporization. A 272 μm and 365 μm laser fibers were used with a flexible and semirigid scope, respectively. Ablation was carried out with a 10 to 20 W power. Mean age at surgery was 68 years (SD 10.7). Mean tumor size was 14.3 mm (range 2-30 mm). Preliminary biopsy revealed the presence of low-grade disease in 29 (69.1%) patients, high-grade disease in 4 (9.5%) and 1 carcinoma in situ 1 (2.4%), whereas it was not conclusive in 8 (19%) cases. Final stage was pTa and pTis in 41 (97.6%) and 1 (2.4%) patients, respectively. Thirty eight percent (16) experienced Clavien-Dindo grade I complication, 47.6% (20) grade II, and 2.4% (1) grade III. Five (12%) patients underwent a second-look procedure due to residual disease. Eight (19%) patients experienced clinical recurrence. The median estimated recurrence-free survival was 44 months (SE 3.68). Four patients (9.5%) underwent a nephroureterectomy. Final pathological stage was pTis, pT3 high grade, pTa low grade, and pT0. Median follow-up was 26.3 months (range 2-54 months), and no progression or upstaging of disease occurred. TL management of UTUC is a safe and efficacious conservative treatment. Our experience shows optimal vaporization and hemostatic control in the absence of major complications.

Metamorphism, graphite crystallinity, and sulfide anatexis of the Rampura-Agucha massive sulfide deposit, northwestern India

NASA Astrophysics Data System (ADS)

Mishra, Biswajit; Bernhardt, Heinz-Jurgen

2009-02-01

Located adjacent to the Banded Gneissic Complex, Rampura-Agucha is the only sulfide ore deposit discovered to date within the Precambrian basement gneisses of Rajasthan. The massive Zn-(Pb) sulfide orebody occurs within graphite-biotite-sillimanite schist along with garnet-biotite-sillimanite gneiss, calc-silicate gneisses, amphibolites, and garnet-bearing leucosomes. Plagioclase-hornblende thermometry in amphibolites yielded a peak metamorphic temperature of 720-780°C, whereas temperatures obtained from Fe-Mg exchange between garnet and biotite (580-610°C) in the pelites correspond to postpeak resetting. Thermodynamic considerations of pertinent silicate equilibria, coupled with sphalerite geobarometry, furnished part of a clockwise P- T- t path with peak P- T of ˜6.2 kbar and 780°C, attained during granulite grade metamorphism of the major Zn-rich stratiform sedimentary exhalative deposits orebody and its host rocks. Arsenopyrite composition in the metamorphosed ore yielded a temperature [and log f( S 2)] range of 352°C (-8.2) to 490°C (-4.64), thus indicating its retrograde nature. Contrary to earlier research on the retrogressed nature of graphite, Raman spectroscopic studies on graphite in the metamorphosed ore reveal variable degree of preservation of prograde graphite crystals (490 ± 43°C with a maximum at 593°C). The main orebody is mineralogically simple (sphalerite, pyrite, pyrrhotite, arsenopyrite, galena), deformed and metamorphosed while the Pb-Ag-rich sulfosalt-bearing veins and pods that are irregularly distributed within the hanging wall calc-silicate gneisses show no evidence of deformation and metamorphism. The sulfosalt minerals identified include freibergite, boulangerite, pyrargyrite, stephanite, diaphorite, Mn-jamesonite, Cu-free meneghinite, and semseyite; the last three are reported from Agucha for the first time. Stability relations of Cu-free meneghinite and semseyite in the Pb-Ag-rich ores constrain temperatures at >550°C and <300°C, respectively. Features such as (1) low galena-sphalerite interfacial angles, (2) presence of multiphase sulfide-sulfosalt inclusions, (3) microcracks filled with galena (±pyrargyrite) without any hydrothermal alteration, and (4) high contents of Zn, Ag (and Sb) in galena, indicate partial melting in the PbS-Fe0.96S-ZnS-(1% Ag2S ± CuFeS2) system, which was critical for metamorphic remobilization of the Rampura-Agucha deposit.

Effects of exercise on fitness and health of adults with spinal cord injury: A systematic review.

PubMed

van der Scheer, Jan W; Martin Ginis, Kathleen A; Ditor, David S; Goosey-Tolfrey, Victoria L; Hicks, Audrey L; West, Christopher R; Wolfe, Dalton L

2017-08-15

To synthesize and appraise research testing the effects of exercise interventions on fitness, cardiometabolic health, and bone health among adults with spinal cord injury (SCI). Electronic databases were searched (1980-2016). Included studies employed exercise interventions for a period ≥2 weeks, involved adults with acute or chronic SCI, and measured fitness (cardiorespiratory fitness, power output, or muscle strength), cardiometabolic health (body composition or cardiovascular risk factors), or bone health outcomes. Evidence was synthesized and appraised using Grading of Recommendations Assessment, Development, and Evaluation (GRADE). A total of 211 studies met the inclusion criteria (22 acute, 189 chronic). For chronic SCI, GRADE confidence ratings were moderate to high for evidence showing exercise can improve all of the reviewed outcomes except bone health. For acute SCI, GRADE ratings were very low for all outcomes. For chronic SCI, there was low to moderate confidence in the evidence showing that 2-3 sessions/week of upper body aerobic exercise at a moderate to vigorous intensity for 20-40 minutes, plus upper body strength exercise (3 sets of 10 repetitions at 50%-80% 1-repetition maximum for all large muscle groups), can improve cardiorespiratory fitness, power output, and muscle strength. For chronic SCI, there was low to moderate confidence in the evidence showing that 3-5 sessions per week of upper body aerobic exercise at a moderate to vigorous intensity for 20-44 minutes can improve cardiorespiratory fitness, muscle strength, body composition, and cardiovascular risk. Exercise improves fitness and cardiometabolic health of adults with chronic SCI. The evidence on effective exercise types, frequencies, intensities, and durations should be used to formulate exercise guidelines for adults with SCI. © 2017 American Academy of Neurology.

Identification of neuropathic pain in patients with neck/upper limb pain: application of a grading system and screening tools.

PubMed

Tampin, Brigitte; Briffa, Noelle Kathryn; Goucke, Roger; Slater, Helen

2013-12-01

The Neuropathic Pain Special Interest Group (NeuPSIG) of the International Association for the Study of Pain has proposed a grading system for the presence of neuropathic pain (NeP) using the following categories: no NeP, possible, probable, or definite NeP. To further evaluate this system, we investigated patients with neck/upper limb pain with a suspected nerve lesion, to explore: (i) the clinical application of this grading system; (ii) the suitability of 2 NeP questionnaires (Leeds Assessment of Neuropathic Symptoms and Signs pain scale [LANSS] and the painDETECT questionnaire [PD-Q]) in identifying NeP in this patient cohort; and (iii) the level of agreement in identifying NeP between the NeuPSIG classification system and 2 NeP questionnaires. Patients (n = 152; age 52 ± 12 years; 53% male) completed the PD-Q and LANSS questionnaire and underwent a comprehensive clinical examination. The NeuPSIG grading system proved feasible for application in this patient cohort, although it required considerable time and expertise. Both questionnaires failed to identify a large number of patients with clinically classified definite NeP (LANSS sensitivity 22%, specificity 88%; PD-Q sensitivity 64%, specificity 62%). These lowered sensitivity scores contrast with those from the original PD-Q and LANSS validation studies and may reflect differences in the clinical characteristics of the study populations. The diagnostic accuracy of LANSS and PD-Q for the identification of NeP in patients with neck/upper limb pain appears limited. Copyright © 2013 International Association for the Study of Pain. Published by Elsevier B.V. All rights reserved.

Transdomes: Emplacement of Migmatite Domes in Oblique Tectonic Settings

NASA Astrophysics Data System (ADS)

Teyssier, C. P.; Rey, P. F.; Whitney, D. L.; Mondy, L. S.; Roger, F.

2014-12-01

Many migmatite domes are emplaced within wrench corridors in which a combination of strike-slip and extensional detachment zones (pull-apart, extensional relay, or transfer zones) focus deep-crust exhumation. The Montagne Noire dome (France, Variscan Massif Central) exemplifies wrench-related dome formation and displays the following structural, metamorphic, and geochronologic characteristics of a 'transdome': the dome is elongate in the direction of extension; foliation outlines a double dome separated by a high-strain zone; lineation is shallowly plunging with a fairly uniform trend that parallels the strike of the high-strain zone; subdomes contain recumbent structures overprinted by upright folds that affected upward by flat shear zones associated with detachment tectonics; domes display a large syn-deformation metamorphic gradient from core (upper amphibolite facies migmatite) to margin (down to greenschist facies mylonite); some rocks in the dome core experienced isothermal decompression revealed by disequilibrium reaction textures, particularly in mafic rocks (including eclogite); and results of U-Pb geochrononology indicate a narrow range of metamorphic crystallization from core to mantling schist spanning ~10 Myr. 3D numerical modeling of transdomes show that the dome solicits a larger source region of partially molten lower crust compared to 2D models; this flowing crust creates a double-dome architecture as in 2D models but there are differences in the predicted thermal history and flow paths. In a transtension setting, flow lines converge at depth (radial-centripetal flow) toward the zone of extension and diverge at shallow levels in a more uniform direction that is imposed by upper crust motion and deformation. This evolution produces a characteristic pattern of strain history, progressive fabric overprint, and P-T paths that are comparable to observed dome rocks.

Revised nomenclature and stratigraphic relationships of the Fredericksburg Complex and Quantico Formation of the Virginia Piedmont

USGS Publications Warehouse

Pavlides, Louis

1980-01-01

The Fredericksburg Complex, in part a migmatitic terrane in northeast Virginia, is subdivided on the basis of lithology, as well as aeromagnetic and aeroradiometric data, into two metamorphic suites. These suites are separated by the northeast-trending Spotsylvania lineament, a rectilinear geophysical feature that is probably the trace of an old fault zone. East of the lineament, the Po River Metamorphic Suite, of Proterozoic Z and (or) early Paleozoic age, consists dominantly of biotite gneiss, generally augen gneiss, and lesser amounts of hornblende gneiss and mica schist. West of the Spotsylvania lineament is the Ta River Metamorphic Suite, composed mostly of amphibolite and amphibole gneiss. However, to the southwest, along its strike belt, the Ta River contains abundant biotite gneiss and mica schist. Both the Ta River and Po River contain abundant foliated granitoid and pegmatoid bodies as concordant tabular masses and as crosscutting dikes; these rocks are considered part of the Ta River and Po River Metamorphic Suites. The amphibolitic Holly Corner Gneiss is interpreted to be a western allochthonous equivalent of the Ta River. Both the Ta River and Holly Corner are considered to be coeval, eastern, distal facies of the Lower Cambrian(?) Chopawamsic Formation. The Paleozoic Falls Run Granite Gneiss intrudes the Ta River Metamorphic Suite and the Holly Corner Gneiss; locally the Falls Run is interpreted to have been transported westward with the Holly Corner after intrusion. The Quantico Formation, in the core of the Quantico-Columbia synclinorium, rests with angular unconformity along its northwest and southeast limbs, respectively, on the Chopawamsic Formation and the Ta River Metamorphic Suite. The Quantico Formation is assigned the same Late Ordovician age and similar stratigraphic position as the Arvonia Slate of the Arvonia syncline. The youngest rocks of the area are the granitoid and pegmatoid bodies of the Falmouth Intrusive Suite. They consist of several generations of chiefly dikes and sills that are intrusive into the Fredericksburg Complex and into the Quantico Formation. Granitoid rocks also form small plutons. The Falmouth is isotopically dated as Carboniferous in age. Some of the metavolcanic rocks of the Evington Group and part of the amphibolite gneiss and amphibolite of the Hatcher Complex, named by W. B. Brown in 1969, are probably coeval with the Chopawamsic Formation and hence equivalents of the Ta River Metamorphic Suite and the Holly Corner Gneiss. The biotitic gneiss and granitoid rocks east of the Spotsylvania lineament in the Dillwyn area are considered to be coeval with the Po River Metamorphic Suite.

Long term accretion history (165-70 Ma) recorded by high-pressure rocks of Diego de Almagro Island (Patagonia, Chile): implications for understanding subduction zone interface tectonic processes

NASA Astrophysics Data System (ADS)

Angiboust, Samuel; Hyppolito, Thais; Glodny, Johannes; Cambeses, Aitor; Monié, Patrick; Garcia-Casco, Antonio; Calderon, Mauricio; Juliani, Caetano

2017-04-01

The Diego de Almagro Island preserves one of the rare remnants of the Mesozoic Chilean paleo-accretionary wedge. This complex, formed by MOR-basalts interleaved with metasedimentary rocks, comprises three major tectonic units with distinct P-T-t paths: the HP granulite (Lazaro unit), the garnet amphibolite (GA) and the blueschist (BS) units. HP granulite-facies metamorphic conditions in the Lazaro Unit are attested by Grt-Cpx-Zo-Prg assemblages associated with trondhjemitic leucosomes (c. 1.3 GPa, 750°C). U-Pb SHRIMP dating of zircon metamorphic rims yields a homogeneous age population of 162 ± 2 Ma for this HT event, in agreement with Sm-Nd dating of peritectic garnet (163 ± 2 Ma and 163 ± 18 Ma). In situ white mica Ar-Ar dating and multi-mineral Rb-Sr dating of LT mylonites (c. 450°C) along the base of the Lazaro Unit reveals partial resetting of HT assemblages during deformation between 115 and 72 Ma. GA unit rocks, structurally below the Lazaro unit, locally preserve eclogite facies parageneses (c. 570°C, 1.7 GPa) that underwent a pervasive stage of amphibolitization during decompression down to 1.3 GPa. U-Pb dating of zircon metamorphic rims and Rb-Sr dating indicate that amphibolitization in GA unit took place at 125-120 Ma. GA unit rocks have been also lately overprinted by another HP-LT assemblage as shown by Si-richer phengite rims and small blue amphibole overgrowths. Conversely, the underlying BS unit does not show strong amphibolite facies overprint as seen in GA and Lazaro units and exhibits slightly cooler peak metamorphic conditions (c. 520°C, 1.7 GPa). Rb-Sr and Ar-Ar dating of these blueschists yield deformation ages between 80 and 70 Ma, i.e. 50 Ma younger than the overlying rocks from the GA unit, and 90 Ma younger than Lazaro unit HP-granulites. This new report sheds light on the formation of the youngest and deepest HP rocks exposed along the Chilean subduction margin. The Diego de Almagro Island represents a unique window onto long-term tectonic processes rooted below the base of the accretionary wedge (c. 40-50 km). The exceptionally long residence time of the earlier accreted material -almost 100 Ma-, enables the record of multiple thermal gradient fluctuations and highlights the variability of the subduction interface thermal structure over tens of millions yrs.

Variability Analysis for Effectiveness and Improvement in Classrooms and Schools in Upper Secondary Education in Slovenia: Assessment of/for Learning Analytic Tool

ERIC Educational Resources Information Center

Zupanc, Darko; Urank, Matjaz; Bren, Matevz

2009-01-01

From 1995, data on students' achievement in schools (i.e., teacher's grades) and all data on achievement in the 5-subject group certificate--the "Matura" exam--have been systematically gathered for the entire yearly cohort of students in upper secondary education in Slovenia. This paper describes an on-line data selection system and data…

"Notice the Similarities between the Two Sets …": Imperative Usage in a Corpus of Upper-Level Student Papers

ERIC Educational Resources Information Center

Neiderhiser, Justine A.; Kelley, Patrick; Kennedy, Kohlee M.; Swales, John M.; Vergaro, Carla

2016-01-01

The sparse literature on the use of imperatives in research papers suggests that they are relatively common in a small number of disciplines, but rare, if used at all, in others. The present study addresses the use of imperatives in a corpus of upper-level A-graded student papers from 16 disciplines. A total of 822 papers collected within the past…

Comparative analysis of upper gastrointestinal endoscopy, double-contrast upper gastrointestinal barium X-ray radiography, and the titer of serum anti-Helicobacter pylori IgG focusing on the diagnosis of atrophic gastritis.

PubMed

Yamamichi, Nobutake; Hirano, Chigaya; Takahashi, Yu; Minatsuki, Chihiro; Nakayama, Chiemi; Matsuda, Rie; Shimamoto, Takeshi; Takeuchi, Chihiro; Kodashima, Shinya; Ono, Satoshi; Tsuji, Yosuke; Fujishiro, Mitsuhiro; Wada, Ryoichi; Mitsushima, Toru; Koike, Kazuhiko

2016-04-01

Upper gastrointestinal endoscopy (UGI-ES) and double-contrast upper gastrointestinal barium X-ray radiography (UGI-XR) are two major image-based methods to diagnose atrophic gastritis, which is mostly induced by Helicobacter pylori infection. However, there have been few studies directly comparing them. Atrophic gastritis was evaluated using the data of 962 healthy subjects who underwent UGI-ES and UGI-XR within 1 year. Based on UGI-ES and UGI-XR, 602 subjects did not have atrophic gastritis and 254 subjects did have it. Considering UGI-ES-based atrophic gastritis as the standard, sensitivity and specificity of UGI-XR-based atrophic gastritis were 92.0 % (254/276) and 92.8 % (602/649), respectively. The seven-grade Kimura-Takemoto classification of UGI-ES-based atrophic gastritis showed a strong and significant association with the four-grade UGI-XR-based atrophic gastritis. Sensitivity and specificity of serum anti-Helicobacter pylori IgG to detect UGI-ES/UGI-XR-based atrophic gastritis were 89.4 % (227/254) and 99.8 % (601/602), indicating that atrophic gastritis can be overlooked according to serum anti-Helicobacter pylori IgG alone.

Western redcedar lumber recovery from a western Washington sawmill.

Treesearch

E.E. Matson

1957-01-01

During the summer of 1956 a lumber-recovery study was made at E. C. Miller Lumber Company in Aberdeen, Wash. to determine the grades of lumber that can be expected from western redcedar logs. This sawmill is equipped with a 24-foot carriage, a 10-foot band headrig, a band pony headrig, and an edger. All of the upper grades of lumber are seasoned and then sent to the...

Early Learning and Early Identification Follow-Up Study: Transition from the Early to the Later Childhood Grades, 1990-93.

ERIC Educational Resources Information Center

Marcon, Rebecca A.

As follow-up to an in-depth study of the District of Columbia's early learning programs and their impact, this study provided data on the transition of previously studied children from primary education to upper elementary grades. Academic progress of the original group of pre-kindergarten and Head Start children was studied during years 5 and 6…

Achievement goal profiles and developments in effort and achievement in upper elementary school.

PubMed

Hornstra, Lisette; Majoor, Marieke; Peetsma, Thea

2017-12-01

The multiple goal perspective posits that certain combinations of achievement goals are more favourable than others in terms of educational outcomes. This study aimed to examine longitudinally whether students' achievement goal profiles and transitions between profiles are associated with developments in self-reported and teacher-rated effort and academic achievement in upper elementary school. Participants were 722 fifth-grade students and their teachers in fifth and sixth grade (N = 68). Students reported on their achievement goals and effort in language and mathematics three times in grade 5 to grade 6. Teachers rated students' general school effort. Achievement scores were obtained from school records. Goal profiles were derived with latent profile and transition analyses. Longitudinal multilevel analyses were conducted. Theoretically favourable goal profiles (high mastery and performance-approach goals, low on performance-avoidance goals), as well as transitions from less to more theoretically favourable goal profiles, were associated with higher levels and more growth in effort for language and mathematics and with stronger language achievement gains. Overall, these results provide support for the multiple goal perspective and show the sustained benefits of favourable goal profiles beyond effects of cognitive ability and background characteristics. © 2017 The Authors. British Journal of Education Psychology published by John Wiley & Sons Ltd on behalf of British Psychological Society.

Management, clinical outcomes, and complications of acute cannula-related peripheral vein phlebitis of the upper extremity: A retrospective study.

PubMed

Dunda, S E; Demir, E; Mefful, O J; Grieb, G; Bozkurt, A; Pallua, N

2015-07-01

Acute phlebitis due to peripheral vein catheter use is frequently observed in clinical practice, and requires surgical therapy in severe cases. In this retrospective study, we aimed to increase awareness, evaluate current treatment options, and develop recommendations to optimize treatment outcomes. A total of 240 hospitalized patients with a diagnosis of upper extremity phlebitis from 2006 to 2011 were evaluated in terms of initial clinical features, parameters, co-morbidities and treatment regimes. Severity of phlebitis was graded according to the Baxter scale by assessing clinical symptoms such as pain, erythema, induration, swelling, or palpable venous cord (grade 0-5). Patients were divided in two subgroups: conservative (n = 132) and operative (n = 108) treatment. Surgical intervention rates and severity were higher for cannula insertion in the cubital fossa region than for cannula insertion in the forearm and hand region (p < 0.05). Baxter scale grades were higher in the surgical treatment group than in the conservative treatment group (4.47 vs. 2.67, respectively). The cubital fossa region is vulnerable to severe phlebitis and is not recommended as the first site of choice for cannulation. Phlebitis of Baxter scale grade 4 or 5 should be considered for early surgical intervention. © The Author(s) 2014.

The relationship between continental collision process and metamorphic pattern in the Himalayan collision belts

NASA Astrophysics Data System (ADS)

Oh, Chang-Whan

2015-04-01

Both UHP and HP eclogites are reported from the Kaghan Valley and Tso Morari Massif in the western part of the Himalayan collision belt (Ghazanfar and Chaudhry, 1987; Thakur, 1983). UHP eclogites in the Kaghan record peak metamorphic conditions of 770 °C and 30 kbar (O'Brien et al., 2001) and was retrograded into the epidote-amphibolite or blueschist (580-610 °C, 10-13 kbar; Lombardo and Rolfo, 2000). Sensitive high-resolution ion microprobe dating of zircon reveals that the UHP eclogite formed at ca. 46 Ma (Kaneko et al., 2003; Parrish et al., 2006). The Tso Morari UHP eclogite had formed at 750 °C, > 39 kbar (Mukheerjee et al., 2003; Bundy, 1980) and underwent amphibolite facies retro-grade metamorphism (580 °C, 11 kbar) during uplift (Guillot et al., 2008). Peak metamorphism of the Tso Morari Massif was dated at ca. 53-55 Ma (Leech et al., 2005). Only HP eclogites have been reported from the mid-eastern part of the Himalayan collision belt (Lombardo and Rolfo, 2000; Corrie et al., 2010). The HP eclogite in the mid-eastern part may have formed at ca. > 780 °C and 20 kbar and was overprinted by high-pressure granulite facies metamorphism (780-750°C, 12-10 kbar) at ca. 30 Ma (Groppo et al. 2007; Corrie et al., 2010). HP granulite (890 °C, 17-18 kbar) is reported from the NBS, at the eastern terminus of the Himalayan collision belt; the granulite was subjected to retrograde metamorphism to produce lower-pressure granulite (875-850°C, 10-5 kbar), representing near-isothermal decompression (Liu and Zhong, 1997). The HP granulite metamorphism may have occurred at ca. 22-25 Ma. Along the Himalayan collision belt, peak metamorphism changes eastward from UHP eclogite facies through HP eclogite facies to high-pressure granulite facies, indicating a progressive eastwards decrease in the depth of subduction of continental crust and an eastwards increase in the geothermal gradient. The peak metamorphic ages also decrease from 53-46 Ma in the west to 22-25 Ma in the east indicating propagation of collision towards east. The following collision model of the Himalayan collision belt is proposed based on data published in previous studies. Collision between the Indian and Asian blocks started in the west before ca. 55 Ma. In the western part, the amount of oceanic slab subducted prior to continent collision was enough to pull the continental crust down to the depths of UHP metamorphism, as a wide ocean existed between the Asian and Indian blocks prior to collision. Following UHP metamorphism, oceanic slab break-off started at ca. 55~46 Ma in the west due to the very strong buoyancy of the deeply subducted continental block. In contrast, the subduction of continental crust continued at this time in the middle and eastern parts of the belt. The zone of break-off migrated eastward, initiating a change from steep- to low-angle subduction. Final break-off may have occurred in the easternmost part of the belt at ca. 22-25 Ma. The depth of slab break-off decreased toward the east due to the westward decrease of the amount of subducted oceanic crust along the Himalayan collision belt, resulting eastwards decrease of an uplifting rate due to a decrease in buoyancy of the continental slab. The slower uplift resulted in a longer period of thermal relaxation and a higher geothermal gradient. In the west, the high rate of uplift resulted the epidote amphibolite facies (580-610°C) retrograde metamorphic overprint on the UHP eclogites, whereas the relatively slow uplift in the mid-eastern part caused high-grade granulites (850°C) retrograde metamorphic overprint on the HP eclogites. The study indicates that the metamorphic pattern along the collision belt is strongly related to the amount of subducted oceanic crust between continents before collision and the depth of slab break-off. Therefore metamorphic pattern can be used to interpret both the disappeared and ongoing tectonic process during continental collision.

New Ar/Ar single grain mineral ages from Korean orogenic belts with implications for the Triassic cooling and exhumation history

NASA Astrophysics Data System (ADS)

de Jong, Koenraad; Ruffet, Gilles; Han, Seokyoung

2013-04-01

The Korean peninsula is located in the eastern margin of the Eurasian continent where major late Palaeozoic to early Mesozoic continental collision zones, like the Central Asian Orogenic Belt and the Qinling-Dabie-Sulu Belt, merge with circum-Pacific subduction-accretion systems. Deciphering the tectonic evolution of Korea is thus crucial for the understanding of the amalgamation of East Asia. Classically, research in Korea has focused on the search for (ultra)high-pressure metamorphic rocks and their isotopic dating, most recently applying SHRIMP on Th- and U-bearing accessory minerals, in order to substantiate links with the Qinling-Dabie-Sulu Belt across the Yellow Sea in China. Instead of trying to date peak pressure conditions we focused on 40Ar/39Ar laser-probe step-heating dating of single grains of the fabric-forming minerals muscovite, biotite and amphibole, formed during retrograde recrystallisation and exhumation. This is a big advantage as their growth can be straightforwardly correlated to major phases of the tectono-metamorphic evolution of rocks. This approach helps to meet the major geochronological challenge of obtaining age estimates for the timing of specific tectono-metamorphic events in the Korean orogenic belts. The Korean peninsula comprises a number of Palaeoproterozoic high-grade gneiss terranes; only one of which has been affected by Permo-Triassic metamorphism: the Gyeonggi Massif. We concentrated on the uppermost Gyeonggi Massif and the overlying Imjingang Belt, to the North, and the ill-defined Hongseong zone to the West, both constituted by younger metamorphic rocks. Both belts contain rare lenses of mafic rocks with relics of high-pressure metamorphism. Hornblende from a corona-textured amphibolite from the lowermost part of the Imjingang Belt yielded a U-shaped age spectrum, the base of which is formed by four concordant steps with a weighted mean age of 242.8 ± 2.4 Ma (15% 39Ar release). Muscovites from strongly retrogressed and ductily deformed rocks in the mylonitised top of the Gyeonggi Massif yielded different 1? plateau ages: 242.8 ± 1.0 Ma and 240.3 ± 1.0 Ma for two chlorite-mica schists, and 219.7 ± 0.9 Ma for a garnet-bearing micaceous quartzite. Two amphibolites from Neoproterozoic orthogneiss in the Hongseong area yielded concordant 1? plateau ages of 228.1 ± 1.0 (biotite), 230.1 ± 1.0 (hornblende), and 229.8 ± 1.0 Ma (hornblende from a foliated garnet-bearing corona-textured amphibolite). 40Ar/39Ar laser-probe dating produced robust evidence that cooling and exhumation of once deeply buried rocks in different parts of Korea essentially occurred in middle to late Triassic time. The concordance of hornblende and mica ages in each of the target areas implies a rapid cooling, during at least part of the history, which seems not to have been coeval. This corroborates the observation that our Ar/Ar mineral ages are only a couple of million years younger than CHIME and SHRIMP U-Pb ages in accessory minerals, which are in the 230-255 Ma range in the uppermost Gyeonggi Massif and Imjingang Belt, and between 225-235 Ma in the Hongseong area. However, the much younger muscovite age from the mylonitic quartzite implies a prolonged recrystallization in the ductile shear zone in the uppermost Gyeonggi Massif. This is subject of ongoing research.

An Energy Education Unit for Upper Elementary Grades.

ERIC Educational Resources Information Center

Doyle, Charles

1980-01-01

Describes a two-part energy unit for gifted fifth and sixth graders. Students conduct energy use/waste surveys and participate in a simulation game concerning a particular environmental/energy problem. (SJL)

7 CFR 29.3558 - Type 35.

Code of Federal Regulations, 2011 CFR

2011-01-01

... INSPECTION Standards Official Standard Grades for Dark Air-Cured Tobacco (u.s. Types 35, 36, 37 and Foreign..., Kentucky-Tennessee-Indiana One Sucker, or Dark Air-cured One Sucker, including the upper Cumberland...

7 CFR 29.3558 - Type 35.

Code of Federal Regulations, 2010 CFR

2010-01-01

... INSPECTION Standards Official Standard Grades for Dark Air-Cured Tobacco (u.s. Types 35, 36, 37 and Foreign..., Kentucky-Tennessee-Indiana One Sucker, or Dark Air-cured One Sucker, including the upper Cumberland...

7 CFR 29.3558 - Type 35.

Code of Federal Regulations, 2014 CFR

2014-01-01

... INSPECTION Standards Official Standard Grades for Dark Air-Cured Tobacco (u.s. Types 35, 36, 37 and Foreign..., Kentucky-Tennessee-Indiana One Sucker, or Dark Air-cured One Sucker, including the upper Cumberland...

7 CFR 29.3558 - Type 35.

Code of Federal Regulations, 2012 CFR

2012-01-01

... INSPECTION Standards Official Standard Grades for Dark Air-Cured Tobacco (u.s. Types 35, 36, 37 and Foreign..., Kentucky-Tennessee-Indiana One Sucker, or Dark Air-cured One Sucker, including the upper Cumberland...

7 CFR 29.3558 - Type 35.

Code of Federal Regulations, 2013 CFR

2013-01-01

... INSPECTION Standards Official Standard Grades for Dark Air-Cured Tobacco (u.s. Types 35, 36, 37 and Foreign..., Kentucky-Tennessee-Indiana One Sucker, or Dark Air-cured One Sucker, including the upper Cumberland...

Titanite chronology, thermometry, and speedometry of ultrahigh-temperature (UHT) calc-silicates from south Madagascar: U-Pb dates, Zr temperatures, and lengthscales of trace-element diffusion

NASA Astrophysics Data System (ADS)

Holder, R. M.; Hacker, B. R.

2017-12-01

Calc-silicate rocks are often overlooked as sources of pressure-temperature-time data in granulite-UHT metamorphic terranes due to the strong dependence of calc-silicate mineral assemblages on complex fluid compositions and a lack of thermodynamic data on common high-temperature calc-silicate minerals such as scapolite. In the Ediacaran-Cambrian UHT rocks of southern Madagascar, clinopyroxene-scapolite-feldspar-quartz-zircon-titanite calc-silicate rocks are wide-spread. U-Pb dates of 540-520 Ma from unaltered portions of titanite correspond to cooling of the rocks through upper-amphibolite facies and indicate UHT metamorphism occurred before 540 Ma. Zr concentrations in these domains preserve growth temperatures of 900-950 °C, consistent with peak temperatures calculated by pseudosection modeling of nearby osumilite-bearing gneisses. Younger U-Pb dates (510-490 Ma) correspond to fluid-mediated Pb loss from titanite grains, which occurred below their diffusive Pb-closure temperature, along fractures. The extent of fluid alteration is seen clearly in back-scattered electron images and Zr-, Al-, Fe-, Ce-, and Nb-concentration maps. Laser-ablation depth profiling of idioblastic titanite grains shows preserved Pb diffusion profiles at grain rims, but there is no evidence for Zr diffusion, indicating that it was effectively immobile even at UHT.

Evolution of the Mount Woods Inlier, northern Gawler Craton, Southern Australia: an integrated structural and aeromagnetic analysis

NASA Astrophysics Data System (ADS)

Betts, Peter G.; Valenta, Rick K.; Finlay, Jim

2003-05-01

Structural mapping integrated with interpretation and forward modelling of aeromagnetic data form complimentary and powerful tools for regional structural analysis because both techniques focus on architecture and overprinting relationships. This approach is used to constrain the geometry and evolution of the sparsely exposed Mount Woods Inlier in the northern Gawler Craton. The Mount Woods Inlier records a history of poly-phase deformation, high-temperature metamorphism, and syn- and post-orogenic magmatism between ca. 1736 and 1584 Ma. The earliest deformation involved isoclinal folding, and the development of bedding parallel and axial planar gneissic foliation (S 1). This was accompanied by high-temperature, upper amphibolite to granulite facies metamorphism at ca. 1736 Ma. During subsequent north-south shortening (D 2), open to isoclinal south-southeast-oriented F 2 folds developed as the Palaeoproterozoic successions of the inlier were thrust over the Archaean nuclei of the Gawler Craton. The syn-D 2 Engenina Adamellite was emplaced at ca. 1692 Ma. The post-D 2 history involved shear zone development and localised folding, exhumation of metamorphic rocks, and deposition of clastic sediments prior to the emplacement of the ca. 1584 Ma Granite Balta Suite. The Mount Woods Inlier is interpreted as the northern continuation of the Kimban Orogen.

The Contribution of Vocabulary Knowledge and Spelling to the Reading Comprehension of Adolescents Who Are and Are Not English Language Learners.

PubMed

Reed, Deborah K; Petscher, Yaacov; Foorman, Barbara R

2016-04-01

This study examined the contributions of vocabulary and spelling to the reading comprehension of students in grades 6-10 who were and were not classified as English language learners. Results indicate that vocabulary accounted for greater between-grade differences and unique variance (Δ R 2 = .11 to .31) in comprehension as compared to spelling (Δ R 2 = .01 to .09). However, the contribution of spelling to comprehension was higher in the upper grade levels included in this cross-sectional analysis and functioned as a mediator of the impact of vocabulary knowledge at all levels. The direct effect of vocabulary was strong but lower in magnitude at each successive grade level from .58 in grade 6 to .41 in grade 10 while the indirect effect through spelling increased in magnitude at each successive grade level from .09 in grade 6 to .16 in grade 10. There were no significant differences between the language groups in the magnitude of the indirect impact, suggesting both groups of students relied more on both sources of lexical information in higher grades as compared to students in lower grades.

The Contribution of Vocabulary Knowledge and Spelling to the Reading Comprehension of Adolescents Who Are and Are Not English Language Learners

PubMed Central

Reed, Deborah K.; Petscher, Yaacov; Foorman, Barbara R.

2016-01-01

This study examined the contributions of vocabulary and spelling to the reading comprehension of students in grades 6–10 who were and were not classified as English language learners. Results indicate that vocabulary accounted for greater between-grade differences and unique variance (ΔR2 = .11 to .31) in comprehension as compared to spelling (ΔR2 = .01 to .09). However, the contribution of spelling to comprehension was higher in the upper grade levels included in this cross-sectional analysis and functioned as a mediator of the impact of vocabulary knowledge at all levels. The direct effect of vocabulary was strong but lower in magnitude at each successive grade level from .58 in grade 6 to .41 in grade 10 while the indirect effect through spelling increased in magnitude at each successive grade level from .09 in grade 6 to .16 in grade 10. There were no significant differences between the language groups in the magnitude of the indirect impact, suggesting both groups of students relied more on both sources of lexical information in higher grades as compared to students in lower grades. PMID:27313395

Effects of Nonverbal Problem Solving Treatment on Skills for Externalizing Visual Representation in Upper Elementary Grade Students with and without Dyslexia

ERIC Educational Resources Information Center

Winn, William; Berninger, Virginia; Richards, Todd; Aylward, Elizabeth; Stock, Pat; Lee, Yen-Ling; Lovitt, Dan

2006-01-01

Two groups of twelve dyslexic children and twelve good readers attended a two-week class during the summer following their enrollment in grades 4-6. The topic was the marine environment and focused on the adventures of an orca whale that had lost its family and needed the children's help. The children attended class for three hours each day, 45…

Seeing the Forest, Not the Trees: Essential Technologies for Literacy in the Primary-Grade and Upper Elementary-Grade Classroom

ERIC Educational Resources Information Center

Leu, Donald J.; Forzani, Elena; Timbrell, Nicole; Maykel, Cheryl

2015-01-01

While countless new technologies are appearing in our lives and in school classrooms, we argue that we need to keep in mind our goals in reading before we use any of them. We suggest that a primary goal is to develop the ability to read in order to learn with online information. Technologies that support this goal, especially the Internet, and…

The Revenge of K-12: How Common Core and the New SAT Lower College Standards in the U.S. White Paper No. 122

ERIC Educational Resources Information Center

Phelps, Richard P.; Milgram, R. James

2014-01-01

It is now clear that the original promise to anchor K-12 education to higher education and backmap the Common Core Mathematics Standards (CCMS) from the upper grades down to the primary grades was empty rhetoric. Higher education has scarcely been involved at all, with the exception of the institutions that agreed to place high school students who…

Petrology and physical conditions of metamorphism of calcsilicate rocks from low- to high-grade transition area, Dharmapuri District, Tamil Nadu

NASA Technical Reports Server (NTRS)

Narayana, B. L.; Natarajan, R.; Govil, P. K.

1988-01-01

Calc-silicate rocks comprising quartz, plagioclase, diopside, sphene, scapolite, grossularite-andradite and wollastonite occur as lensoid enclaves within the greasy migmatitic and charnockitic gneisses of the Archaean amphibolite- to granulite-facies transition zone in Dharmapuri district, Tamil Nadu. The calc-silicate rocks are characterized by the absence of K-feldspar and primary calcite, presence of large modal quartz and plagioclase and formation of secondary garnet and zoisite rims around scapolite and wollastonite. The mineral distributions suggest compositional layering. The chemical composition and mineralogy of the calc-silicate rocks indicate that they were derived from impure silica-rich calcareous sediments whose composition is similar to that of pelite-limestone mixtures. From the mineral assemblages the temperature, pressure and fluid composition during metamorphism were estimated. The observed mineral reaction sequences require a range of X sub CO2 values demonstrating that an initially CO2-rich metamorphic fluid evolved with time towards considerably more H2O-rich compositions. These variations in fluid composition suggest that there were sources of water-rich fluids external to the calc-silicate rocks and that mixing of these fluids with those of calc-silicate rocks was important in controlling fluid composition in calc-silicate rocks and some adjacent rock types as well.

Role of Precambrian compositions and fabrics in the development of foreland structures, southern Front Range, Colorado

DOE Office of Scientific and Technical Information (OSTI.GOV)

Chase, R.B.

1985-01-01

The Front Range terminates to the south as three basement-cored uplifts located north and west of the Canon City embayment. Precambrian units consist of foliated and non-foliated granitic rocks, augen gneiss, interlayered schist and gneiss, amphibolite, quartzite, and pegmatite. Precambrian deformations include at least three phases of folding, two phases of crenulation cleavage development, and local mylonitization. Metamorphic conditions reached those of cordierite-sillimanite grade. Paleozoic and Mesozoic sediments surround and overlap the exposed uplifts to form south-plunging arches. Excellent three-dimensional exposure of structural relationships between Precambrian rocks and overlying Phanerozoic sediments is present. Deformation styles in the sedimentary cover aremore » strongly influenced by underlying Precambrian lithologies and structural orientations. Where the crystalline units are granitic, with steeply-dipping foliation or no directional fabric, uplifts are bounded by high angle faults. Some such faults show evidence of repeated movements and reversals dating back to Precambrian time. The boundary between mechanical basement and suprastructure is clearly not defined as the base of the sedimentary section. Balanced cross-sections constructed through the southern Front Range must include contemporaneous flexural folds and thrusts in Precambrian schistose and gneissic rocks as well as in Phanerozoic sedimentary layers.« less

Consistent Top-to-the-foreland Directed Deformation from Floor to Roof in the Seve Nappe Complex (SNC), Jämtland, Sweden

NASA Astrophysics Data System (ADS)

Bender, H.; Ring, U.; Almqvist, B. S. G.; Glodny, J.; Grasemann, B.; Stephens, M. B.

2016-12-01

The recent COSC-1 drilling programme (Lorenz et al., 2015), discovery of microdiamonds (Majka et al., 2014) and discussion of extrusion-wedge tectonics (Grimmer et al., 2015) outline the importance of the Seve Nappe Complex (SNC) and its key role during the Caledonian orogeny. The kinematic evolution of the SNC is crucial for better understanding the entire mountain belt. Thorough structural mapping of the SNC and adjacent units was conducted in western and northern Jämtland, central Sweden. Complementary microstructural investigations strengthen the field observations and show consistent top-to-the-SE directed movement through all studied tectonic units. Amphibolite-facies deformation can be inferred from fabrics in the SNC, which are overprinted by greenschist-facies structures showing the same kinematics throughout the studied section of the nappe stack. These data indicate persistence of the same foreland-directed kinematics over a wide range of pressure-temperature conditions in space and time. Currently proposed models for exhuming high-grade metamorphic rocks in collisional orogens fail to explain these observations and highlight the need for discussing new tectonic concepts for the Scandinavian Caledonides. References: Grimmer et al., 2015, Geology 43 (4); Lorenz et al., 2015, Scientific Drilling 19; Majka et al. 2014, Geology 42 (12).

The Contribution of Segmental and Suprasegmental Phonology to Reading Comprehension

PubMed Central

Veenendaal, Nathalie J.; Groen, Margriet A.; Verhoeven, Ludo

2016-01-01

The aim of the present study was to examine the relation between decoding and segmental and suprasegmental phonology, and their contribution to reading comprehension, in the upper primary grades. Following a longitudinal design, the performance of 99 Dutch primary school children on phonological awareness (segmental phonology) and text reading prosody (suprasegmental phonology) in fourth-grade and fifth-grade, and reading comprehension in sixth-grade were examined. In addition, decoding efficiency as a general assessment of reading was examined. Structural path modeling firstly showed that the relation between decoding efficiency and both measures of phonology from fourth- to fifth grade was unidirectional. Secondly, the relation between decoding in fourth- and fifth-grade and reading comprehension in sixth-grade became indirect when segmental and suprasegmental phonology were added to the model. Both factors independently exerted influence on later reading comprehension. This leads to the conclusion that not only segmental, but also suprasegmental phonology, contributes substantially to children's reading development. PMID:27551159

Upper urinary tract carcinoma in Lynch syndrome cases.

PubMed

Crockett, David G; Wagner, David G; Holmäng, Sten; Johansson, Sonny L; Lynch, Henry T

2011-05-01

Patients with Lynch syndrome are much more likely to have generally rare upper urinary tract urothelial carcinoma but not bladder urothelial carcinoma. While the risk has been quantified, to our knowledge there is no description of how this population of patients with Lynch syndrome and upper urinary tract cancer differs from the general population with upper urinary tract cancer. We obtained retrospective data on a cohort of patients with Lynch syndrome from the Hereditary Cancer Center in Omaha, Nebraska and compared the data to those on a control general population from western Sweden. These data were supplemented by a new survey about exposure to known risk factors. Of the patients with Lynch syndrome 91% had mutations in MSH2 rather than in MSH1 and 79% showed upper tract urothelial carcinoma a mean of 15.85 years after prior Lynch syndrome-type cancer. Median age at diagnosis was 62 years vs 70 in the general population (p <0.0001). Only half of our patients had a significant smoking history and the male-to-female ratio was 0.95. Of patients with Lynch syndrome 51% had urothelial carcinoma in the ureter while it occurred in the renal pelvis in 65% of the general population (p = 0.0013). Similar numbers of high grade tumors were found in the Lynch syndrome and general populations (88% and 74%, respectively, p = 0.1108). Upper urinary tract tumors develop at a younger age and are more likely to be in the ureter with an almost equal gender ratio in patients with Lynch syndrome. It has high grade potential similar to that in the general population. Copyright © 2011 American Urological Association Education and Research, Inc. Published by Elsevier Inc. All rights reserved.

Management of complex regional pain syndrome type I in upper extremity-evaluation of continuous stellate ganglion block and continuous infraclavicular brachial plexus block: a pilot study.

PubMed

Toshniwal, Gokul; Sunder, Rani; Thomas, Ronald; Dureja, G P

2012-01-01

Interventional pain management techniques play an important role in the multidisciplinary approach to management of complex regional pain syndrome (CRPS). In this preliminary study we compared the efficacy of continuous stellate ganglion (CSG) block with that of continuous infraclavicular brachial plexus (CIBP) block in management of CRPS type I of upper extremity. Thirty-three patients with CRPS type I of upper extremity were randomly assigned to either CSG or CIBP group. Patients were treated for 1 week with continuous infusion of 0.125% bupivacaine at 2and 5mL/h, respectively. Catheter was removed at 1 week and patients were followed up for 4 weeks. The outcome was evaluated in terms of neuropathic pain scale score (NPSS), edema scores (Grades 0-2), and range of motion (ROM) of all upper extremity joints (Grades 0-2). CIBP group showed statistically significant improvement in NPSS compared with CSG group during the first 12 hours after the procedures (P value <0.05). After 12 hours, the NPSS was comparable between the groups. At 4 weeks, both groups showed clinically significant improvement in edema score and ROM of all upper extremity joints when compared with the baseline. This preliminary study suggests that CIBP block and CSG block may be feasible and effective interventional techniques for the management of CRPS type I of upper extremities. Hence, we recommend a larger well-randomized, well-controlled, clinical trial to confirm our findings and determine if any significant difference exists between the groups in terms of long-term pain relief and functional restoration. Wiley Periodicals, Inc.

Geochronologic Constraints on Duration of Magma Emplacement and Heat Transfer in the Deep Crust: new data from the Ivrea Zone, Western Alps, Italy

NASA Astrophysics Data System (ADS)

Peressini, G.; Quick, J. E.; Poller, U.; Todt, W.; Mayer, A.; Sinigoi, S.; Hofmann, A. W.

2002-12-01

The Mafic Complex (MC) of the Ivrea Zone is one of the largest gabbro bodies in the Alps (ca 8 km thick and 30 km long); it intruded the already metamorphic volcano-sedimentary sequence of the Kinzigite Formation (KF) at a depth of more than 20 km during the Late Paleozoic. New geochronologic data constrain the duration of the intrusion. The crustal section, uplifted, tilted and exposed in Alpine time, is tectonically bounded, but essentially undisturbed by Alpine tectonics; the internal structure of the MC and its relations with the KF are well preserved. Intrusion of the MC in extending continental crust is suggested by pre-Triassic, high-T, extensional shear zones in the Ivrea Zone, and is consistent with the internal arcuate structure of the MC, which is defined by high-T foliation and banding, that are discordant to the roof of the intrusion. Rocks in the roof of the MC attain upper-amphibolite grade and show evidence of partial melting within about 2 km of the MC. The country rock was melted as a consequence of heat released by the crystallizing mafic body; the chemistry of the mafic rocks was affected by up to 30% crustal contamination that occurred partially in situ, by mixing of the basaltic melts with anatectic melts derived from depleted crustal rocks. A thin (less than 20 m) seam of leucogranite crystallized from anatectic melt is present at the MC-KF contact. Syntectonic intrusion of leucogranite along shear zones within the KF demonstrates migration of anatectic melts to higher crustal levels. U/Pb SHRIMP ages on magmatic zircons range from 295+4 and 287+4 Ma for the MC, and 280+4 Ma for syntectonic leucogranites in the KF. Thus, intrusion of the MC may have taken as long as 10-15 Ma. Nd-Sm mineral isochrones for the MC range from 244 to 274, indicating that the Complex cooled to temperatures below 750C within about 40 Ma of final crystallization. The heat of crystallization of the MC was accommodated by anatexis and assimilation, and syntectonic migration of anatectic melts transferred heat to higher crustal levels.

Duration of a large Mafic intrusion and heat transfer in the lower crust: A SHRIMP U-Pb zircon Study in the Ivrea-Verbano Zone (Western Alps, Italy)

USGS Publications Warehouse

Peressini, G.; Quick, J.E.; Sinigoi, S.; Hofmann, A.W.; Fanning, M.

2007-01-01

The Ivrea-Verbano Zone in the western Italian Alps contains one of the world's classic examples of ponding of mantle-derived, mafic magma in the deep crust. Within it, a voluminous, composite mafic pluton, the Mafic Complex, intruded lower-crustal, high-grade paragneiss of the Kinzigite Formation during Permian-Carboniferous time, and is now exposed in cross-section as a result of Alpine uplift. The age of the intrusion is still debated because the results of geochronological studies in the last three decades on different rock types and with various dating techniques range from 250 to about 300 Ma. Sensitive high-resolution ion microprobe (SHRIMP) U-Pb zircon age determinations on 12 samples from several locations within the Mafic Complex were performed to better constrain the age of the igneous event. The results indicate a long history of magma emplacement and cooling, which reconciles the spread in previously published ages. The main intrusive phase took place at 288 ?? 4 Ma, causing a perturbation of the deep-crustal geotherm, which relaxed to the Sm-Nd closure temperature in garnet-free mafic rocks after about 15-20 Myr of sub-solidus cooling at c. 270 Ma. These results suggest that large, deep crustal plutons, such as those identified geophysically at depths of 10-20 km within extended continental crust (e.g. Yellowstone, Rio Grande Rift, Basin and Range) may have formed rapidly but induced a prolonged thermal perturbation. In addition, the data indicate that a significant thermal event affected the country rock of the Mafic Complex at about 310 Ma. The occurrence of an upper amphibolite- to granulite-facies thermal event in the Kinzigite Formation prior to the main intrusive phase of the Mafic Complex has been postulated by several workers, and is corroborated by other geochronological investigations. However, it remains uncertain whether this event (1) was part of a prolonged perturbation of the deep-crustal geotherm, which started long before the onset of intrusion of the Mafic Complex, or (2) corresponded to the intrusion of the first sills of the Mafic Complex, or (3) was related to an earlier, independent thermal pulse. ?? The Author 2007. Published by Oxford University Press. All rights reserved.

Secondary Education and Health Outcomes in Young People from the Cape Area Panel Study (CAPS)

PubMed Central

2016-01-01

Aim Education is one of the strongest social determinants of health, yet previous literature has focused on primary education. We examined whether there are additional benefits to completing upper secondary compared to lower secondary education in a middle-income country. Methods We performed a longitudinal analysis of the Cape Area Panel Study, a survey of adolescents living in South Africa. We undertook causal modeling using structural marginal models to examine the association between level of education and various health outcomes, using inverse probability weighting to control for sex, age, ethnicity, home language, income, whether employed in past year, region of birth, maternal educational status, marital status, whether currently pregnant and cognitive ability. Educational attainment was defined as primary (grades 1–7), lower secondary (grades 8–9) or upper secondary (grades 10–12). Results Of 3,432 participants, 165 (4.8%) had completed primary education, 646 (18.8%) lower secondary and 2,621 (76.3%) upper secondary. Compared to those completing lower secondary, males completing upper secondary education were less likely to have a health problem (OR 0.49; 95%CI 0.27–0.88; p = 0.02); describe their health as poor (0.52; 0.29–0.95; p = 0.03) or report that health interferes with daily life (0.54; 0.29–0.99; p = 0.047). Females were less likely to have been pregnant (0.45; 0.33–0.61; p<0.001) or pregnant under 18 (0.32; 0.22–0.46; p<0.001); and having had sex under 16 was also less likely (males 0.63; 0.44–0.91; p = 0.01; females 0.39; 0.26–0.58; p<0.001). Cigarette smoking was less likely (males 0.52; 0.38–0.70; p = <0.001; females 0.56; 0.41–0.76; p<0.001), as was taking illicit drugs in males (0.6; 0.38–0.96; p = 0.03). No associations were found between education and alcohol use, psychological distress, obesity, increased waist circumference or hypertension. Conclusion Completing upper secondary education was associated with improved health outcomes compared with lower secondary education. Expanding upper secondary education offers middle-income countries an effective way of improving adolescent health. PMID:27280408

Secondary Education and Health Outcomes in Young People from the Cape Area Panel Study (CAPS).

PubMed

Ward, Joseph L; Viner, Russell M

2016-01-01

Education is one of the strongest social determinants of health, yet previous literature has focused on primary education. We examined whether there are additional benefits to completing upper secondary compared to lower secondary education in a middle-income country. We performed a longitudinal analysis of the Cape Area Panel Study, a survey of adolescents living in South Africa. We undertook causal modeling using structural marginal models to examine the association between level of education and various health outcomes, using inverse probability weighting to control for sex, age, ethnicity, home language, income, whether employed in past year, region of birth, maternal educational status, marital status, whether currently pregnant and cognitive ability. Educational attainment was defined as primary (grades 1-7), lower secondary (grades 8-9) or upper secondary (grades 10-12). Of 3,432 participants, 165 (4.8%) had completed primary education, 646 (18.8%) lower secondary and 2,621 (76.3%) upper secondary. Compared to those completing lower secondary, males completing upper secondary education were less likely to have a health problem (OR 0.49; 95%CI 0.27-0.88; p = 0.02); describe their health as poor (0.52; 0.29-0.95; p = 0.03) or report that health interferes with daily life (0.54; 0.29-0.99; p = 0.047). Females were less likely to have been pregnant (0.45; 0.33-0.61; p<0.001) or pregnant under 18 (0.32; 0.22-0.46; p<0.001); and having had sex under 16 was also less likely (males 0.63; 0.44-0.91; p = 0.01; females 0.39; 0.26-0.58; p<0.001). Cigarette smoking was less likely (males 0.52; 0.38-0.70; p = <0.001; females 0.56; 0.41-0.76; p<0.001), as was taking illicit drugs in males (0.6; 0.38-0.96; p = 0.03). No associations were found between education and alcohol use, psychological distress, obesity, increased waist circumference or hypertension. Completing upper secondary education was associated with improved health outcomes compared with lower secondary education. Expanding upper secondary education offers middle-income countries an effective way of improving adolescent health.

Miocene crustal extension following thrust tectonic in the Lower Sebtides units (internal Rif, Ceuta Peninsula, Spain): Implication for the geodynamic evolution of the Alboran domain

NASA Astrophysics Data System (ADS)

Homonnay, Emmanuelle; Corsini, Michel; Lardeaux, Jean-Marc; Romagny, Adrien; Münch, Philippe; Bosch, Delphine; Cenki-Tok, Bénédicte; Ouazzani-Touhami, Mohamed

2018-01-01

In Western Mediterranean, the Rif belt in Morocco is part of the Gibraltar Arc built during the Tertiary in the framework of Eurasia-Africa convergence. The structural and metamorphic evolution of the internal units of this belt as well as their timing, crucial to constrain the geodynamic evolution of the Alboran Sea, is still largely debated. Our study on the Ceuta Peninsula (Northern Rif) provides new structural, petrological and geochronological data (U-Th-Pb, Ar-Ar), which allow to precise the tectono-metamorphic evolution of the Lower Sebtides metamorphic units with: (1) a syn-metamorphic thrusting event developed under granulite facies conditions (7-10 kbar and 780-820 °C). A major thrust zone, the Ceuta Shear Zone, drove the emplacement of metapelites and peridotitic lenses from the Ceuta Upper Unit over the orthogneisses of the Monte Hacho Lower Unit. This compressional event ended during the Upper Oligocene. (2) an extensional event developed at the boundary between amphibolite and greenschist facies conditions (400-550 °C and 1-3 kbar). During this event, the Ceuta Shear Zone has been reactivated as a normal fault. Normal ductile shear zones contributed to the final exhumation of the metamorphic units during the Early Miocene. We propose that the compressional event is related to the formation of an orogenic wedge located in the upper plate, in a backward position, of the subduction zone driving the geodynamic evolution of the Alboran domain. In this context, the episode of lithospheric thinning could be related to the opening of the Alboran basin in a back-arc position. Furthermore, unlike the previous models proposed for the Rif belt, the tectonic coupling between mantle peridotites and crustal metamorphic rocks occurred in Ceuta Peninsula at a depth of 20-30 km under high temperature conditions, before the extensional event, and thus cannot be related to the back-arc extension. 1, BSE image of monazite. 2, CL image of monazite showing a thin rim zonation. 3, BSE image of zircon. 4, CL image of zircon showing zonation.

Upper Eyelid Fractional CO2 Laser Resurfacing With Incisional Blepharoplasty.

PubMed

Kotlus, Brett S; Schwarcz, Robert M; Nakra, Tanuj

2016-01-01

Laser resurfacing, performed at the same time as blepharoplasty, has most commonly been applied to the lower eyelid skin but can effectively be used on the upper eyelid to reduce rhytidosis and improve skin quality. The authors evaluate the safety and efficacy of this procedure. Fractional CO2 laser resurfacing was performed in conjunction with incisional upper blepharoplasty. The ultrapulsed laser energy was applied to the sub-brow skin, the upper medial canthal skin, and the pretarsal skin in 30 patients. Photos were obtained preoperatively and at 3 months. All patients demonstrated reduction in upper eyelid rhytidosis without any serious complications. Independent rhytidosis grading (0-4) showed a mean improvement of 42%. One patient experienced wound dehiscence that satisfactorily resolved without intervention. Upper eyelid laser resurfacing is effective and can be safely performed at the same time as upper blepharoplasty. This approach reduces or eliminates the need for medial incisions to address medial canthal skin redundancy and rhytidosis and it directly treats upper eyelid wrinkles on residual eyelid and infra-brow skin during blepharoplasty.

Publications - GMC 411 | Alaska Division of Geological & Geophysical

Science.gov Websites

outcrop samples from the 2001 DGGS Salcha River-Pogo project, Big Delta Quadrangle, Alaska Authors . Quadrangle(s): Big Delta Bibliographic Reference Newberry, R.J., 2012, Whole-rock and trace element analyses of two amphibolite outcrop samples from the 2001 DGGS Salcha River-Pogo project, Big Delta Quadrangle

Graphite-(Mo,W)S2 intergrowth as a palaeoenvironmental proxy in metasedimentary rocks

NASA Astrophysics Data System (ADS)

Cabral, Alexandre Raphael; Zeh, Armin; da Silva Viana, Nívea Cristina; Schirmer, Thomas; Lehmann, Bernd

2017-12-01

Molybdenum enrichment in pristine organic-C-rich sedimentary rocks forms the basis for inferring the presence of dissolved oxygen in seawater. Organic matter removes dissolved hexavalent Mo from seawater where anoxic and euxinic conditions are attained. However, it is unknown whether this Mo-based proxy is retained under metamorphic conditions where organic C is no longer preserved. Here, we describe aggregates of graphite and molybdenite (MoS2) containing up to 21 mass per cent of W as tungstenite (WS2) in solid solution. These aggregates are disseminated in a sulfide-rich Mn-silicate-carbonate rock (queluzite), metamorphosed under amphibolite-facies conditions within the Archaean Barbacena greenstone belt in Minas Gerais, Brazil. Our finding indicates that: (i) W is, like Mo, a palaeoenvironmental proxy; (ii) the W proxy is sensitive to high fS2/fO2 environments; (iii) both Mo and W proxies survive amphibolite-facies overprint as (Mo,W)S2 intergrown with graphite. Archaean greenstones are potential candidates for storing palaeoenvironmental information as (Mo,W)S2-graphite intergrowths.

Constraints on crustal hydration below the Colorado plateau from Vp measurements on crustal xenoliths

NASA Astrophysics Data System (ADS)

Padovani, Elaine R.; Hall, Jeremy; Simmons, Gene

1982-04-01

Seismic velocities have been measured as a function of confining pressure to 8 kbar for crustal xenoliths from the Moses Rock Dike and Mule Ear Diatreme, two kimberlite pipes on the Colorado Plateau. Rock types measured include rhyolite, granite, diorite, metasedimentary schists and gneisses, mafic amphibolites and granulites. Many of our samples have been hydrothermally altered to greenschist facies mineral assemblages during transport to the earth's surface. The velocity of compressional waves measured on altered amphibolites and granulites are too low by 0.1-0.3 km/s for such rock types to be characteristic of deep crustal levels. A direct correlation exists between progressive alteration and the presence of microcracks extending into the xenoliths from the kimberlitic host rock. Velocities of pristine samples are compatible with existing velocity profiles for the Colorado Plateau and we conclude that the crust at depths greater than 15 km has probably not undergone a greenschist facies metamorphic event. The xenolith suite reflects a crustal profile similar to that exposed in the Ivrea-Verbano and Strona-Ceneri zones in northern Italy.

40Ar 39Ar Ages and tectonic setting of ophiolite from the Neyriz area, southeast Zagros Range, Iran

USGS Publications Warehouse

Lanphere, M.A.; Pamic, J.

1983-01-01

An ophiolite, considered to be an allochthonous fragment of Tethyan oceanic crust and mantle, crops out near Neyriz in the Zagros Range, Iran. 40Ar 39Ar ages ranging from 76.8 ?? 23.8 Ma to 105 ?? 23.3 Ma were measured on hornblende from five samples of plagiogranite and diabase from the ophiolite. The most precise ages are 85.9 ?? 3.8 Ma for a diabase and 83.6 ?? 8.4 Ma for a plagiogranite. The weighted mean age of hornblende from the five samples is 87.5 ?? 7.2 Ma which indicates that the igneous part of the Neyriz ophiolite formed during the early part of the Late Cretaceous. Pargasite from amphibolite below peridotite of the Neyriz ophiolite has a 40Ar 39Ar age of 94.9 ?? 7.6 Ma. The pargasite age agrees within analytical uncertainty with the ages measured on diabase and plagiogranite. Comparable ages have been measured on igneous rocks from the Samail ophiolite of Oman and on amphibolite below peridotite of the Samail ophiolite. ?? 1983.

Imaging Water in Deformed Quartzites: Examples from Caledonian and Himalayan Shear Zones

NASA Astrophysics Data System (ADS)

Kronenberg, Andreas; Ashley, Kyle; Hasnan, Hasnor; Holyoke, Caleb; Jezek, Lynna; Law, Richard; Thomas, Jay

2016-04-01

Infrared IR measurements of OH absorption bands due to water in deformed quartz grains have been collected from major shear zones of the Caledonian and Himalayan orogens. Mean intragranular water contents were determined from the magnitude of the broad OH absorption at 3400 cm-1 as a function of structural position, averaging over multiple grains, using an IR microscope coupled to a conventional FTIR spectrometer with apertures of 50-100 μm. Images of water content were generated by scanning areas of up to 4 mm2 of individual specimens with a 10 μm synchrotron-generated IR beam and contouring OH absorptions. Water contents vary with structural level relative to the central cores of shear zones and they vary at the grain scale corresponding to deformation and recrystallization microstructures. Gradients in quartz water content expressed over structural distances of 10 to 400 m from the centers of the Moine Thrust (Stack of Glencoul, NW Scotland), the Main Central Thrust (Sutlej valley of NW India), and the South Tibetan Detachment System (Rongbuk valley north of Mount Everest) indicate that these shear zones functioned as fluid conduits. However, the gradients differ substantially: in some cases, enhanced fluid fluxes appear to have increased quartz water contents, while in others, they served to decrease water contents. Water contents of Moine thrust quartzites appear to have been reduced during shear at greenschist facies by processes of regime II BLG/SGR dislocation creep. Intragranular water contents of the protolith 70 m below the central fault core are large (4078 ± 247 ppm, H/106 Si) while mylonites within 5 mm of the Moine hanging wall rocks have water contents of only 1570 (± 229) ppm. Water contents between these extremes vary systematically with structural level and correlate inversely with the extent of dynamic recrystallization (20 to 100%). Quartz intragranular water contents of Himalayan thrust and low-angle detachment zones sheared at upper amphibolite conditions by regime III GBM creep show varying trends with structural level. Water contents increase toward the Lhotse detachment of the Rongbuk valley, reaching 11,350 (± 1095) ppm, whereas they decrease toward the Main Central Thrust exposed in the western part of the Sutlej valley to values as low as 170 (± 25) ppm. Maps of intragranular water content correspond to populations of fluid inclusions, which depend on the history of deformation and dynamic recrystallization. Increases in water content require the introduction of secondary fluid inclusions, generally by brittle microcracking followed by crack healing and processes of inclusion redistribution documented in milky quartz experiments. Decreases in water content result from dynamic recrystallization, as mobile grain boundaries sweep through wet porphyroclasts, leaving behind dry recrystallized grains. Intragranular water contents throughout greenschist mylonites of the Moine thrust are comparable to those of quartz weakened by water in laboratory experiments. However, water contents of upper amphibolite mylonites of the Main Central Thrust are far below those required for water weakening at experimental strain rates and offer challenges to our understanding of quartz rheology.

Deformation sequences of the Day Nui Con Voi metamorphic belt, northern Vietnam

NASA Astrophysics Data System (ADS)

Yeh, M. W.; Lee, T. Y.; Lo, C. H.; Chung, S. L.; Lan, C. Y.; Lee, J. C.; Lin, T. S.; Lin, Y. J.

2003-04-01

The correlation of structure, microstructure and metamorphic assemblages is of fundamental importance to the understanding of the complex tectonic history and kinematics of the Day Nui Con Voi (DNCV) metamorphic belt in Vietnam along the Ailao Shan-Red River (ASRR) shear zone as it provides constraints on the relative timing of the deformation, kinematics and metamorphism. High-grade metamorphic rocks of amphibolite faces showed consistent deformation sequences of three folding events followed by one brittle deformation through all four cross sections from Lao Cai to Viet Tri indicated the DNCV belt experienced similar deformation condition throughout its length. The first deformation event, D1, produced up-right folds (locally preserved) with sub-vertical, NE-SW striking axial planes with dextral sense of shear probably formed during the early phase of the lowermost Triassic Indosinian orogeny. Followed by this compressional event is a gravitational collapsing event, D2, which is the major deformation and metamorphic event characterized by kyanite grade metamorphism and large scale horizontal folds with NW-SE (320) striking sub-horizontal axial pane showing sinsistral sense of shear most likely formed during the Oligocene-Miocene SE extrusion of Indochina peninsula. The 3rd folding event, D3, is a post-metamorphism doming event with NW-SE (310) striking sub-vertical axial plane that folded/tilted the once sub-horizontal D2 axial planes into shallowly (<30 degrees) NE dipping on the NE limb, and SW dipping on the SW limb possibly due to left-lateral movement of the N-S trending Xian Shui He fault system in Mid-Miocene. The outward decreasing of the metamorphic grade from kyanite to garnet then biotite indicated the D3 occurred post metamorphism. Reactivation of the sub-horizontal D2 fold axial planes showed dextral sense of shear possibly due to Late Miocene-Pliocene right-lateral movement of the ASRR shear zone. This right lateral movement continuously deformed the DNCV with brittle fractures such as joints and normal faults (D4) striking NE-SW to E-W and NW-SE.

Comprehensive Genomic Characterization of Upper Tract Urothelial Carcinoma.

PubMed

Moss, Tyler J; Qi, Yuan; Xi, Liu; Peng, Bo; Kim, Tae-Beom; Ezzedine, Nader E; Mosqueda, Maribel E; Guo, Charles C; Czerniak, Bogdan A; Ittmann, Michael; Wheeler, David A; Lerner, Seth P; Matin, Surena F

2017-10-01

Upper urinary tract urothelial cancer (UTUC) may have unique etiologic and genomic factors compared to bladder cancer. To characterize the genomic landscape of UTUC and provide insights into its biology using comprehensive integrated genomic analyses. We collected 31 untreated snap-frozen UTUC samples from two institutions and carried out whole-exome sequencing (WES) of DNA, RNA sequencing (RNAseq), and protein analysis. Adjusting for batch effects, consensus mutation calls from independent pipelines identified DNA mutations, gene expression clusters using unsupervised consensus hierarchical clustering (UCHC), and protein expression levels that were correlated with relevant clinical variables, The Cancer Genome Atlas, and other published data. WES identified mutations in FGFR3 (74.1%; 92% low-grade, 60% high-grade), KMT2D (44.4%), PIK3CA (25.9%), and TP53 (22.2%). APOBEC and CpG were the most common mutational signatures. UCHC of RNAseq data segregated samples into four molecular subtypes with the following characteristics. Cluster 1: no PIK3CA mutations, nonsmokers, high-grade

Adventures in Law and History. Volume I: Native Americans, the Spanish Frontier, and the Gold Rush. A Law and Civic Education Curriculum for Upper Elementary Grades with Units on Rules and Laws, Property, and Authority.

ERIC Educational Resources Information Center

Croddy, Marshall; Degelman, Charles; Doggett, Keri; Hayes, Bill

This is volume one of a two-volume civics curriculum on law and effective citizenship for upper-elementary students. The lessons, set in American historical eras, engage students in cooperative-learning activities, role plays, simulations, readers theater, stories, and guided discussions, which introduce and reinforce law-related and civic…

Shyok Suture Zone, N Pakistan: late Mesozoic Tertiary evolution of a critical suture separating the oceanic Ladakh Arc from the Asian continental margin

NASA Astrophysics Data System (ADS)

Robertson, Alastair H. F.; Collins, Alan S.

2002-02-01

The Shyok Suture Zone (Northern Suture) of North Pakistan is an important Cretaceous-Tertiary suture separating the Asian continent (Karakoram) from the Cretaceous Kohistan-Ladakh oceanic arc to the south. In previously published interpretations, the Shyok Suture Zone marks either the site of subduction of a wide Tethyan ocean, or represents an Early Cretaceous intra-continental marginal basin along the southern margin of Asia. To shed light on alternative hypotheses, a sedimentological, structural and igneous geochemical study was made of a well-exposed traverse in North Pakistan, in the Skardu area (Baltistan). To the south of the Shyok Suture Zone in this area is the Ladakh Arc and its Late Cretaceous, mainly volcanogenic, sedimentary cover (Burje-La Formation). The Shyok Suture Zone extends northwards (ca. 30 km) to the late Tertiary Main Karakoram Thrust that transported Asian, mainly high-grade metamorphic rocks southwards over the suture zone. The Shyok Suture Zone is dominated by four contrasting units separated by thrusts, as follows: (1). The lowermost, Askore amphibolite, is mainly amphibolite facies meta-basites and turbiditic meta-sediments interpreted as early marginal basin rift products, or trapped Tethyan oceanic crust, metamorphosed during later arc rifting. (2). The overlying Pakora Formation is a very thick (ca. 7 km in outcrop) succession of greenschist facies volcaniclastic sandstones, redeposited limestones and subordinate basaltic-andesitic extrusives and flow breccias of at least partly Early Cretaceous age. The Pakora Formation lacks terrigenous continental detritus and is interpreted as a proximal base-of-slope apron related to rifting of the oceanic Ladakh Arc; (3). The Tectonic Melange (<300 m thick) includes serpentinised ultramafic rocks, near mid-ocean ridge-type volcanics and recrystallised radiolarian cherts, interpreted as accreted oceanic crust. (4). The Bauma-Harel Group (structurally highest) is a thick succession (several km) of Ordovician and Carboniferous to Permian-Triassic, low-grade, mixed carbonate/siliciclastic sedimentary rocks that accumulated on the south-Asian continental margin. A structurally associated turbiditic slope/basinal succession records rifting of the Karakoram continent (part of Mega-Lhasa) from Gondwana. Red clastics of inferred fluvial origin ('molasse') unconformably overlie the Late Palaeozoic-Triassic succession and are also intersliced with other units in the suture zone. Reconnaissance further east (north of the Shyok River) indicates the presence of redeposited volcaniclastic sediments and thick acid tuffs, derived from nearby volcanic centres, presumed to lie within the Ladakh Arc. In addition, comparison with Lower Cretaceous clastic sediments (Maium Unit) within the Northern Suture Zone, west of the Nanga Parbat syntaxis (Hunza River) reveals notable differences, including the presence of terrigenous quartz-rich conglomerates, serpentinite debris-flow deposits and a contrasting structural history. The Shyok Suture Zone in the Skardu area is interpreted to preserve the remnants of a rifted oceanic back-arc basin and components of the Asian continental margin. In the west (Hunza River), a mixed volcanogenic and terrigenous succession (Maium Unit) is interpreted to record syn-deformational infilling of a remnant back-arc basin/foreland basin prior to suturing of the Kohistan Arc with Asia (75-90 Ma).

Interfingering of the Frontier Formation and Aspen Shale, Cumberland Gap, Wyoming.

USGS Publications Warehouse

M'gonigle, J.

1982-01-01

The basal part, or the Chalk Creek Member, of the non-marine lower Frontier Formation (Upper Cretaceous) includes a thin coal bed that grades S into a carbonaceous shale. The latter plus associated sandstones and shales pinch out S of Cumberland Gap and lie stratigraphically below the top of the Aspen Shale. The beds in the upper part of the Aspen, in turn, pinch out within the Frontier Formation. The coal bed and equivalent carbonaceous shale represent in-place accumulation of peat. The interfingering suggests that in SW Wyoming the Lower/Upper Cretaceous boundary is within the Chalk Creek Member. -from Author

Effect of ventriculectomy versus ventriculocordectomy on upper airway noise in draught horses with recurrent laryngeal neuropathy.

PubMed

Cramp, P; Derksen, F J; Stick, J A; Nickels, F A; Brown, K E; Robinson, P; Robinson, N E

2009-11-01

Little is known about the efficacy of bilateral ventriculectomy (VE) or bilateral ventriculocordectomy (VCE) in draught horses. To compare the effect of VE and VCE on upper airway noise in draught horses with recurrent laryngeal neuropathy (RLN) by use of quantitative sound analysis techniques. In competitive draught horses with grade 4 RLN, VE and VCE reduce upper airway noise during exercise, but VCE is more effective. Thirty competitive hitch or pulling draught horses with grade 4 RLN were evaluated for upper airway sound during exercise. Respiratory rate (RR), inspiratory (Ti) and expiratory time (Te), the ratio between Ti and Te (Ti/Te), inspiratory (Sli) and expiratory sound levels (Sle), the ratio between Sli and Sle (Sli/Sle), and peak sound intensity of the second formant (F2) were calculated. Eleven horses were treated with VE and 19 with VCE. After 90 days of voice and physical rest and 30 days of work, the horses returned for post operative upper airway sound evaluation and resting videoendoscopy. VE significantly reduced Ti/Te, Sli, Sli/Sle and the sound intensity of F2. Respiratory rate, Ti, Te and Sle were unaffected by VE. VCE significantly reduced Ti/Te, Ti, Te, Sli, Sli/Sle and the sound intensity of F2, while RR and Sle were unaffected. The reduction in sound intensity of F2 following VCE was significantly greater than following VE. After VE and VCE, 7/11 (64%) and 15/18 (83%) owners, respectively, concluded that the surgery improved upper airway sound in their horses sufficiently for successful competition. VE and VCE significantly reduce upper airway noise and indices of airway obstruction in draught horses with RLN, but VCE is more effective than VE. The procedures have few post operative complications. VCE is recommended as the preferred treatment for RLN in draught horses. Further studies are required to evaluate the longevity of the procedure's results.

Radical and sparing surgical treatment of patients with upper urinary tract transitional cell carcinomas (UUT -TCC) - preliminary results.

PubMed

Jabłonowski, Zbigniew; Kędzierski, Robert; Sosnowski, Marek

2011-01-01

Tumors originating from transitional epithelium of the renal pelvis and ureter are infrequent. Their course is asymptomatic at early stages of the disease, and diagnosis and institution of appropriate treatment delayed. The aim of the study is to assess the results of treatment in patients with upper urinary tract transitional cell carcinomas (UUT-TCC). Fifteen patients treated in 2005-2010 for UUT-TCC were qualified for the retrospective study. Clinical symptoms, diagnostic methods, tumor location, clinical stage and histopathological characteristics of the tumors were assessed. Then, the instituted treatment and its results were analyzed. The average follow-up period was 51 month (range 6-65), UUT-TCC accounted for 6.7% of renal tumors treated. Concurrent treated vesical tumors were observed in 4 (26.7%) patients. Primary UUT-TCC was diagnosed in 10 (66.7%) patients. Radical surgery was performed in 10 (66.7%) patients, whereas 5 (33.3%) underwent sparing operations. Macroscopic hematuria was the predominant clinical symptom. In most cases T2-T3 clinical stage (60.0%) and high-grade (66.7%) were observed. Development of an upper urinary tract tumor after treatment of a vesical tumor was noted in 4 (26.7%) patients. During the follow-up period, urinary bladder carcinomas were diagnosed in 5 (33.3%) patients with primary upper urinary tract tumors. Nephroureterectomy remains the standard treatment for UUT-TCC. Organ-sparing surgery is possible in selected patients with low clinical stage and low grade tumors. Patients treated for urinary bladder carcinomas require regular monitoring of the upper urinary tract.

Crystal preferred orientation of amphibole and implications for seismic anisotropy in the crust

NASA Astrophysics Data System (ADS)

Jung, Haemyeong

2016-04-01

Strong seismic anisotropy is often observed in the middle to lower crust and it has been considered to be originated from the crystal preferred orientation (CPO) of anisotropic minerals such as amphibole. Amphibolite is one of the dominant rocks in the middle to lower crust. In this study, crystal preferred orientations of hornblende in amphibolites at Yeoncheon and Chuncheon areas in South Korea were determined by using the electron backscattered diffraction (EBSD)/SEM with HKL Channel 5 software. In Yeoncheon area, hornblende showed two types of CPOs. Type-I CPO is characterized as (100) poles of hornblende aligned subnormal to foliation and [001] axes aligned subparallel to lineation. Type-II CPO is characterized as (100) poles of hornblende aligned subnormal to foliation and (010) poles aligned subparallel to lineation (refer to Ko and Jung, 2015, Nature Communications). In Chuncheon area, three types of CPOs of hornblende were observed. In addition to the type-I and -II CPOs described above, type-III CPO of hornblende was observed in Chuncheon area and it is characterized as (100) poles of hornblende aligned subnormal to foliation and both [001] axes and (010) poles aligned as a girdle subparallel to foliation. Using the observed CPO and the single crystal elastic constant of hornblende, seismic anisotropy of hornblende was calculated. Seismic anisotropy of P-wave was strong in the range of 10.2 - 13.5 %. Seismic anisotropy of S-wave was also strong in the range of 6.9 - 11.2 %. These results show that hornblende deformed in nature can produce a strong CPO, resulting in a strong seismic anisotropy in the middle to lower crust. Taking into account of the CPO of plagioclase in the rock, seismic anisotropies of whole rock turned out to be maximum P-wave anisotropy (Vp) of 9.8% and maximum S-wave anisotropy (Vs) of 8.2%. Therefore, strong seismic anisotropy found in the middle to lower crust in nature can be attributed to the CPO of hornblende in amphibolite.

Production of hybrid granitic magma at the advancing front of basaltic underplating: Inferences from the Sesia Magmatic System (south-western Alps, Italy)

NASA Astrophysics Data System (ADS)

Sinigoi, Silvano; Quick, James E.; Demarchi, Gabriella; Klötzli, Urs S.

2016-05-01

The Permian Sesia Magmatic System of the southwestern Alps displays the plumbing system beneath a Permian caldera, including a deep crustal gabbroic complex, upper crustal granite plutons and a bimodal volcanic field dominated by rhyolitic tuff filling the caldera. Isotopic compositions of the deep crustal gabbro overlap those of coeval andesitic basalts, whereas granites define a distinct, more radiogenic cluster (Sri ≈ 0.708 and 0.710, respectively). AFC computations starting from the best mafic candidate for a starting melt show that Nd and Sr isotopic compositions and trace elements of andesitic basalts may be modeled by reactive bulk assimilation of ≈ 30% of partially depleted crust and ≈ 15%-30% gabbro fractionation. Trace elements of the deep crustal gabbro cumulates require a further ≈ 60% fractionation of the andesitic basalt and loss of ≈ 40% of silica-rich residual melt. The composition of the granite plutons is consistent with a mixture of relatively constant proportions of residual melt delivered from the gabbro and anatectic melt. Chemical and field evidence leads to a conceptual model which links the production of the two granitic components to the evolution of the Mafic Complex. During the growth of the Mafic Complex, progressive incorporation of packages of crustal rocks resulted in a roughly steady state rate of assimilation. Anatectic granite originates in the hot zone of melting crust located above the advancing mafic intrusion. Upward segregation of anatectic melts facilitates the assimilation of the partially depleted restite by stoping. At each cycle of mafic intrusion and incorporation, residual and anatectic melts are produced in roughly constant proportions, because the amount of anatectic melt produced at the roof is a function of volume and latent heat of crystallization of the underplated mafic melt which in turn produces proportional amounts of hybrid gabbro cumulates and residual melt. Such a process can explain the restricted range in isotopic compositions of most rhyolitic and granitic rocks of the Permo-Carboniferous province of Europe and elsewhere. Sheet labelled "XRF standard analyses" reports replicate analyses normalized to 100 obtained by XRF on international standards analyzed along with our samples. Sheet labelled "XRF replicate sample analyses" reports replicate XRF analyses on two samples of our data set. ICP-MS analyses from Acme Analytical Laboratories Ltd. are shown for comparison. Sheet labelled "ICP-MS analyses" reports replicate analyses of trace elements on standard SO18, its official value and replicate analyses of two our samples provided by Acme Analytical Laboratories Ltd. Sheet labelled "kinzigite". Major and trace elements of amphibolite-facies paragneiss samples of the Kinzigite Formation from the roof of the Mafic Complex. In bold data by ICP-MS, other data by XRF. For Ba, Rb and Sr XRF data were included in the average estimate to increase the statistics. The last column reports the average data of amphibolite-facies rocks from the Kinzigite Formation from Schnetger (1994). Sheet labelled "PBB paragneiss". Data for granulite-facies paragneiss samples in the septa of the paragneiss bearing belt (PBB). XRF data for Ba and Sr were included in the average estimate to increase the statistics (Rb excluded because close to detection limit for XRF in many samples). The last column reports the average data of granulite-facies rocks from Val Strona (stronalite) from Schnetger (1994). Sheet labelled "PBB charnockite". Data for charnockitic rocks included in paragneiss septa. XRF data for Ba and Sr were included in the average estimate to increase the statistics (Rb excluded because close to detection limit for XRF in many samples). Sheet labelled "computed crustal assimilant". Reports the average compositions of paragneiss in amphibolite and granulite facies from this work and from Schnetger (1994). The bulk composition of the septa is computed as 70% paragneiss and 30% charnockite, as roughly estimated in the field. The partially depleted assimilant is computed as a 50/50 mixture of amphibolite- and granulite facies rocks. Sheet labelled "anatectic products" includes leucosomes at the roof of the Mafic Complex, anatectic granites from this work and from the Atesina Volcanic district (Rottura et al., 1998). In bold data by ICP-MS, other data by XRF. Sheet labelled "Valle Mosso granite" reports the whole rock compositions of granitic rocks of the pluton, distinguishing samples from upper and lower granite. XRF data for Ba, Rb and Sr were included in the average estimate to increase the statistics. The last column reports the bulk composition of the pluton, estimated as 70% lower and 30% upper granite. Sheet labelled "Rhyolite" reports whole rock and average compositions of rhyolite. Sheet labelled "UMC gabbro" reports whole rock compositions of gabbros from the upper Mafic Complex. Samples are grouped as pertaining to the "Upper Zone" and "Main Gabbro" according the subdivision of Rivalenti et al. (1975). Gt gabbro = garnet-bearing gabbro. In bold data by ICP-MS, other data by XRF. For Ba and Sr XRF data were included in the average estimate to increase the statistics. Sheet labelled "computed average UMC" reports the whole composition of upper Mafic complex, estimated as 30% Upper Zone and 70% Main Gabbro. Sheet labelled "mafic rocks in middle crust" reports the whole rock compositions from the mafic pod PST262, intruded at the boundary between Ivrea Zone and Serie dei Laghi at 287 ± 5 Ma (Klötzli et al., 2014) and mafic dikes and an enclave intruded in the lower Valle Mosso granite. Sheet labelled "mafic volcanic rocks" reports the whole rock compositions of basaltic andesite and andesite from the Sesia Magmatic System. The average composition is computed excluding altered samples and XRF data for trace elements. Sr and Nd isotope data from this work and previous publications. Sheet labelled "compositions for modelling" reports a summary of the average compositions of the components used for the computations. Sheet labelled "Kd used for AFC and FC modelling" reports the Kd values and percent of mineral phases used in the AFC and FC computations (from Claeson and Meurer, 2004; Rollinson, 1993; Green et al., 2000; Namur et al., 2011). Sheet labelled "trace elements modelling" reports the results of AFC, bulk mixing and FC computations on trace elements. The enclosed figure illustrates the bulk mixing lines between Campore and average crust or anatectic granite respectively. Mixing required getting the composition of andesitic basalt with average crust and anatectic granite varies from 33 to 63% respectively (see text for consequences). The AFC path from Campore to andesitic basalts overlaps the bulk mixing lines. The shape of the mixing line between residual and anatectic melt results in the poor sensibility of Nd to the addition of anatectic melt to the residual one (εNd remains within the field of mafic rocks up to 80% addition of anatectic melt). Sheet labelled "major elements modelling" reports the results of mass balance computations on major-elements based on bulk mixing and XL-FRAC (Stormer and Nicholls, 1978). Sheet labelled "EC-RAXFC modelling" reports input data and results obtained by EC-RAXFC code (Bohrson and Spera, 2007) to simulate the energy constrained AFC from Campore to andesitic basalt. Liquidus temperature and specific heat of magma and assimilant (tlm, tla, cpm, cpa) as well as heat of crystallization and fusion (hm, ha) were obtained by Rhyolite-Melts code (Gualda et al., 2012) at P = 6 kbar (intermediate pressure between the roof and the deepest rocks of the Mafic Complex; Demarchi et al., 1998), assuming QFM + 2, and H2O content = 0.5 for Campore and = 1.0 for assimilant (intermediate between kinzigite and stronalite from Schnetger, 1994). Initial temperature of assimilant (tlo) was assumed equal to the solidus temperature (ts), which results around 850° from the experimental melting of natural metapelite (Vielzeuf and Holloway, 1988). Non-linear melting functions were chosen within the range of values suggested by Bohrson and Spera (2007). Recharge magma (R) was set = 0 because the homogeneity of the Upper Mafic Complex is best explained if each new mafic pulse is injected at the new neutral buoyancy level, above a dense and partially depleted restite, and may be treated as a single pulse. X was set = 1 assuming that all anatectic melt enters the mafic magma. Different simulations were run using alternatively bulk partition coefficients of Sr and Nd for the assimilant (Da) reported for "standard" upper crust by Bohrson and Spera (2001; 1.5 and 0.25, respectively), Da estimated from our data set (2.15 and 2.6, respectively) and intermediate values. For the mafic magma, the bulk D values (Dm) of 0.77 for Sr and 0.34 for Nd result from the Kd and percent of mineral phases used in the AFC computation. Lat-long grid for samples reported in OS tables.

Incentivizing advanced mathematics study at upper secondary level: the case of bonus points in Ireland

NASA Astrophysics Data System (ADS)

Treacy, Páraic Thomas

2018-04-01

Secondary level mathematics education in Ireland has recently experienced a period of significant change with the introduction of new curricula and the addition of an incentive to study upper secondary mathematics at the most advanced level (Higher Level). This incentive, typically referred to as 'bonus points', appears to have aided a significant increase in the number of students studying upper secondary mathematics at Higher Level. However, thematic analysis of interviews with experienced upper secondary mathematics examiners and exploration of mathematics diagnostic test data outlined in this paper suggest that the difficulty of the Higher Level upper secondary mathematics final examination in Ireland has reduced since the introduction of the bonus points initiative. The sharp increase in students attempting this examination coupled with a policy of maintaining a consistent proportion of students achieving passing grades was identified as a key reason for this possible reduction in standards.

Petrology and geochronology of crustal xenoliths from the Bering Strait region: Linking deep and shallow processes in extending continental crust

USGS Publications Warehouse

Akinin, V.V.; Miller, E.L.; Wooden, J.L.

2009-01-01

Petrologic, geochemical, and metamorphic data on gneissic xenoliths derived from the middle and lower crust in the Neogene Bering Sea basalt province, coupled with U-Pb geochronology of their zircons using sensitive high-resolution ion microprobe-reverse geometry (SHRIMP-RG), yield a detailed comparison between the P-T-t and magmatic history of the lower crust and magmatic, metamorphic, and deformational history of the upper crust. Our results provide unique insights into the nature of lithospheric processes that accompany the extension of continental crust. The gneissic, mostly maficxenoliths (constituting less than two percent of the total xenolith population) from lavas in the Enmelen, RU, St. Lawrence, Nunivak, and Seward Peninsula fields most likely originated through magmatic fractionation processes with continued residence at granulite-facies conditions. Zircon single-grain ages (n ??? 125) are interpreted as both magmatic and metamorphic and are entirely Cretaceous to Paleocene in age (ca. 138-60 Ma). Their age distributions correspond to the main ages of magmatism in two belts of supracrustal volcanic and plutonic rocks in the Bering Sea region. Oscillatory-zoned igneous zircons, Late Cretaceous to Paleocene metamorphic zircons and overgrowths, and lack of any older inheritance in zircons from the xenoliths provide strong evidence for juvenile addition of material to the crust at this time. Surface exposures of Precambrian and Paleozoic rocks locally reached upper amphibolite-facies (sillimanite grade) to granulite-facies conditions within a series of extension-related metamorphic culminations or gneiss domes, which developed within the Cretaceous magmatic belt. Metamorphic gradients and inferred geotherms (??30-50 ??C/km) from both the gneiss domes and xenoliths aretoo high to be explained by crustal thickening alone. Magmatic heat input from the mantle is necessary to explain both the petrology of the magmas and elevated metamorphic temperatures. Deep-crustal seismic-reflection and refraction data reveal a 30-35-km-thick crust, a sharp Moho and refl ective lower and middle crust. Velocities do not support a largely mafic (underplated) lower crust, but together with xenolith data suggest that Late Cretaceous to early Paleocene maficintrusions are likely increasingly important with depth in the crust and that the elevated temperatures during granulite-facies metamorphism led to large-scale flow of crustal rocks to produce gneiss domes and the observed subhorizontal refl ectivity of the crust. This unique combined data set for the Bering Shelf region provides compelling evidence for the complete reconstitution/re-equilibration of continental crust from the bottom up during mantle-driven magmatic events associated with crustal extension. Thus, despite Precambrian and Paleozoic rocks at the surface and Alaska's accretionary tectonic history, it is likely that a significant portion of the Bering Sea region lower crust is much younger and related to post-accretionary tectonic and magmatic events. ?? 2009 The Geological Society of America.

Assessing Biogenecity of Stromatolites: Return to the Facies

NASA Astrophysics Data System (ADS)

Shapiro, R. S.; Jameson, S.; Rutter, A.; McCarthy, K.; Planavsky, N. J.; Severson, M.

2013-12-01

The discovery of richly microfossiliferous cherty stromatolites near Schreiber and Kakabeka Falls, Ontario, in the 1.9 Ga Gunflint Iron Formation, firmly established the field of pre-Cambrian paleontology. In the half-century since this discovery, paradigm shifts in the ecology of the microfossils as well as the utility of stromatolites as biological markers has caused a re-evaluation of our understanding of the pre-Cambrian fossil record. This research summarizes facies evaluation of the two stromatolite marker beds in the Gunflint-correlative Biwabik Iron Formation of Minnesota. The centimeter-scale microstratigraphy of cores drilled through the central and eastern Mesabi Iron Range was coupled with field descriptions of outcrops and mines in both the Biwabik and Gunflint iron formations. Eight lithologic facies associated with the stromatolites are identified: A) Pebble conglomerate clasts ranging in size of 0.5-3 cm, syneresis cracks, and septarian nodules with medium to coarse grain matrix; B) siltstone with subparallel sub-mm to 5 cm magnetitic and non-magnetic bands; C) stromatolitic boundstone comprising stratiform, pseudocolumnar, domal, undulatory, flat-laminated, dendritic, columnar, and mico-digitate forms and oncoids 0.5 to 2 cm diameter; D) grainstone with medium to coarse siliceous and carbonate ooids and peloids; E) massive green crystalline beds with bands of magnetite, quartz, calcite, disseminated pyrite and localized ankerite; F) autobreccicated fabric of 0.3 to 10 mm clasts; G) medium to coarse sandstone; H) quartzite. Correlation between 11 cores near Hoyt Lakes and 9 cores through the basal stromatolite layer at the MinnTac Mine near Virginia revealed that stromatolites formed both on conglomerate and medium quartz sandstone. Multiple forms of stromatolite may occur in a vertical succession (flat-laminated to undulatory to psuedocolumnar to columnar) or a core may be dominated by one type, typically columnar-stratiform. Where stromatolites do not occur, the interval is autobrecciated with many clasts containing syneresis cracks. Flow-banded iron oxides in these layers are not stromatolitic but likely formed from fluid flow at the boundary between well- and poorly-cemented lithofacies. Mesostructure is similar between collection sites that are essentially unaltered, low-grade diagenetic, and amphibolite-grade metamorphic. Furthermore, mesostructure is consistent in most stromatolites throughout both layers in the Biwabik as well as the Gunflint. These new results provide a much broader context then previous studies and demonstrate that the upper and lower stromatolite horizons in the Biwabik and Gunflint iron ranges are formed in similar facies. Complexity in stromatolite forms occurs on the sub-meter scale, as would be expected for a nearshore, microbially mediated system. However, there appears to be a gradient in the degree of microbial control of stromatolite morphology, with both ';biogenic' and ';abiogenic' forms present. More broadly, this work highlights the importance of field and regional context when deciphering the significance of microbialites.

Microstructural study of the Mertz shear zone, East Antarctica. Implications for deformation processes and seismic anisotropy.

NASA Astrophysics Data System (ADS)

Lamarque, Gaëlle; Bascou, Jérôme; Maurice, Claire; Cottin, Jean-Yves; Ménot, René-Pierre

2015-04-01

The Mertz Shear Zone (MSZ; 146°E 67°S; East Antarctica) is one major lithospheric-scale structure which outcrops on the eastern edge of the Terre Adélie Craton (Ménot et al., 2007) and that could connected with shear zones of South Australia (e.g., Kalinjala or Coorong shear zone (Kleinschmidt and Talarico, 2000; Gibson et al., 2013)) before the Cretaceous opening of the Southern Ocean. Geochronological and metamorphic studies indicated an MSZ activity at 1.7 and 1.5 Ga respectively in amphibolite and greenschists facies conditions. The deformation affects both the intermediate and lower crust levels, without associated voluminous magma injection. Granulite crop out in the area of the MSZ. They were dated at 2.4 Ga (Ménot et al., 2005) and could represent some preserved Neoarchean tectonites. These rocks show various degrees of deformation including penetrative structures that may display comparable features with that observed in amphibolite and greenschists facies rocks, i.e. NS-striking and steeply dipping foliation with weekly plunging lineation. In the field, cinematic indicators for the MSZ argue for a dominant dextral shear sense. We proceed to optical analysis and crystallographic preferred orientation (CPO) measurements using EBSD technique in order to better constrain the deformation processes. Our results highlight (1) a microstructural gradient from highly deformed rocks (mylonites), forming plurimetric large shear bands and showing evidences of plastic deformation, to slightly deformed rocks in preserved cores with no evidences of plastic deformation or with a clear strong static recrystallization; (2) CPO of minerals related with variations on deformation conditions. Feldspar and quartz CPO argue for plastic deformation at high temperature in the most deformed domains and for the absence of deformation or an important stage of static recrystallization in preserved cores; (3) uncommon CPO in orthopyroxene which are characterized by [010]-axes perpendicular to the foliation and [001]-axes parallel to the lineation. These CPO seem to be related to static recrystallization processes. Seismic properties of amphibolite and granulite rocks from the MSZ were calculated in order to evaluate the impact of deformation observed in amphibolite and granulite tectonites to seismic anisotropy. Computations were performed from measured CPO, single crystal elastic stiffness matrix, modal composition and density of characteristic samples. P- and S-waves anisotropies of the cratonic crust affected by the MSZ are small and even tend to be isotropic in the case of S-waves propagating vertically in the crust. These results permit us to better discuss seismic studies and in particular SKS analysis which were recently carried out in this area (Lamarque et al., 2015).

Cascade reservoir flood control operation based on risk grading and warning in the Upper Yellow River

NASA Astrophysics Data System (ADS)

Xuejiao, M.; Chang, J.; Wang, Y.

2017-12-01

Flood risk reduction with non-engineering measures has become the main idea for flood management. It is more effective for flood risk management to take various non-engineering measures. In this paper, a flood control operation model for cascade reservoirs in the Upper Yellow River was proposed to lower the flood risk of the water system with multi-reservoir by combining the reservoir flood control operation (RFCO) and flood early warning together. Specifically, a discharge control chart was employed to build the joint RFCO simulation model for cascade reservoirs in the Upper Yellow River. And entropy-weighted fuzzy comprehensive evaluation method was adopted to establish a multi-factorial risk assessment model for flood warning grade. Furthermore, after determining the implementing mode of countermeasures with future inflow, an intelligent optimization algorithm was used to solve the optimization model for applicable water release scheme. In addition, another model without any countermeasure was set to be a comparative experiment. The results show that the model developed in this paper can further decrease the flood risk of water system with cascade reservoirs. It provides a new approach to flood risk management by coupling flood control operation and flood early warning of cascade reservoirs.

Progression, incidence, and risk factors for intervertebral disc degeneration in a longitudinal population-based cohort: the Wakayama Spine Study.

PubMed

Teraguchi, M; Yoshimura, N; Hashizume, H; Yamada, H; Oka, H; Minamide, A; Nagata, K; Ishimoto, Y; Kagotani, R; Kawaguchi, H; Tanaka, S; Akune, T; Nakamura, K; Muraki, S; Yoshida, M

2017-07-01

The present study examined the progression, incidence, and risk factors for intervertebral disc degeneration (DD) throughout the lumbar spine using magnetic resonance imaging (MRI) in a large population-based cohort. We followed up 617 subjects for more than 4 years as part of the Wakayama Spine Study. 1) "Progression of DD" in each of the entire, upper (L1/2 to L3/4) and lower (L4/5 and L5/S1) lumbar spine was defined as Pfirrmann grade progression at follow-up in at least one disc in the affected region. 2) "Incidence of DD" in each of these regions was defined if all discs were grade 3 or lower (white disc) at baseline, and at least one disc had progressed to grade 4 or higher (black disc) at follow-up. Logistic regression analyses were used to determine the risk factors for progression and incidence of DD. DD progression and incidence in the entire lumbar spine were 52.0% and 31.6% in men, and 60.4% and 44.7% in women, respectively. Women was associated with DD progression in the upper lumbar spine (odds ratio [OR] = 1.68, 95% confidence interval [CI] = 1.18-2.42). Aging was associated with the incidence of DD in each region (entire: OR = 1.14, CI = 1.06-1.14; upper: OR = 1.10, CI = 1.05-1.15; lower: OR = 1.11, CI = 1.05-1.19). Diabetes mellitus (DM) was associated with the incidence of DD in the upper lumbar spine (OR = 6.83, CI = 1.07-133.7). This 4-year longitudinal study is the first to demonstrate DD progression and incidence in the lumbar spine and their risk factors in a large population-based cohort. Copyright © 2017 Osteoarthritis Research Society International. Published by Elsevier Ltd. All rights reserved.

The Effects of Video Feedback Coaching for Teachers on Scientific Knowledge of Primary Students

NASA Astrophysics Data System (ADS)

van Vondel, Sabine; Steenbeek, Henderien; van Dijk, Marijn; van Geert, Paul

2017-04-01

The present study was aimed at investigating the effects of a video feedback coaching intervention for upper-grade primary school teachers on students' cognitive gains in scientific knowledge. This teaching intervention was designed with the use of inquiry-based learning principles for teachers, such as the empirical cycle and the posing of thought-provoking questions. The intervention was put into practice in 10 upper-grade classrooms. The trajectory comprised four lessons, complemented with two premeasures and two postmeasures. The control condition consisted of 11 upper-grade teachers and their students. The success of the intervention was tested using an established standardized achievement test and situated measures. In this way, by means of premeasure and postmeasure questionnaires and video data, an assessment could be made of the change in students' scientific knowledge before, during, and after the intervention. In this study, we primarily focused on the dynamics of students' real-time expressions of scientific knowledge in the classroom. Important indicators of the effect of the intervention were found. Through focusing on the number of explanations and predictions, a significant increase could be seen in the proportion of students' utterances displaying scientific understanding in the intervention condition. In addition, students in the intervention condition more often reasoned on higher complexity levels than students in the control condition. No effect was found for students' scientific knowledge as measured with a standardized achievement test. Implications for future studies are stressed, as well as the importance of enriching the evaluation of intervention studies by focusing on dynamics in the classroom.

Upper Grades Ideas.

ERIC Educational Resources Information Center

Thornburg, David; Beane, Pam

1983-01-01

Presents programming ideas using LOGO, activity for converting flowchart into a computer program, and a Pascal program for generating music using paddles. Includes the article "Helping Computers Adapt to Kids" by Philip Nothnagle; a program for estimating length of lines is included. (JN)

Variation of student numerical and figural reasoning approaches by pattern generalization type, strategy use and grade level

NASA Astrophysics Data System (ADS)

El Mouhayar, Rabih; Jurdak, Murad

2016-02-01

This paper explored variation of student numerical and figural reasoning approaches across different pattern generalization types and across grade level. An instrument was designed for this purpose. The instrument was given to a sample of 1232 students from grades 4 to 11 from five schools in Lebanon. Analysis of data showed that the numerical reasoning approach seems to be more dominant than the figural reasoning approach for the near and far pattern generalization types but not for the immediate generalization type. The findings showed that for the recursive strategy, the numerical reasoning approach seems to be more dominant than the figural reasoning approach for each of the three pattern generalization types. However, the figural reasoning approach seems to be more dominant than the numerical reasoning approach for the functional strategy, for each generalization type. The findings also showed that the numerical reasoning was more dominant than the figural reasoning in lower grade levels (grades 4 and 5) for each generalization type. In contrast, the figural reasoning became more dominant than the numerical reasoning in the upper grade levels (grades 10 and 11).

Unravelling the pre-Variscan evolution of the Habach terrane (Tauern Window, Austria) by U-Pb SHRIMP zircon data

NASA Astrophysics Data System (ADS)

Eichhorn, Roland; Loth, Georg; Kennedy, Allen

2001-08-01

The U-Pb SHRIMP age determinations of zircons from the Habach terrane (Tauern Window, Austria) reveal a complex evolution of this basement unit, which is exposed in the Penninic domain of the Alpine orogen. The oldest components are found in zircons of a metamorphosed granitoid clast, of a migmatitic leucosome, and of a meta-rhyolitic (Variscan) tuff which bear cores of Archean age. The U-Pb ages of discordant zircon cores of the same rocks range between 540 and 520 Ma. It is assumed that the latter zircons were originally also of Archean origin and suffered severe lead loss, whilst being incorporated into Early-Cambrian volcanic arc magmas. The provenance region of the Archean (2.64-2.06 Ga) zircons is assumed to be a terrane of Gondwana affinity: i.e., the West African craton (Hoggar Shield, Reguibat Shield). The Caledonian metamorphism left a pervasive structural imprint in amphibolite facies on rocks of the Habach terrane; it is postdated by discordant zircons of a migmatitic leucosome at <440 Ma (presumably ca. 420 Ma). Alpine and Variscan upper greenschist- to amphibolite-facies conditions caused partial lead loss in zircons of a muscovite gneiss ('white schist') only, where extensive fluid flow and brittle deformation due to its position near a nappe-sole thrust enhanced the grains' susceptibility to isotopic disturbance. The Habach terrane - an active continental margin with ensialic back-arc development - showed subduction-induced magmatic activity approx. between 550 and 507 Ma. Back-arc diorites and arc basalts were intruded by ultramafic sills and subsequently by small patches of mantle-dominated unaltered and (in the vicinity of a major tungsten deposit) altered granitoids. Fore-arc (shales) and back-arc (greywackes, cherts) basin sediments as well as arc and back-arc magmatites were not only nappe-stacked by the Caledonian compressional regime closing the presumably narrow oceanic back-arc basin and squeezing mafic to ultramafic cumulates out of high-level magma chambers (496-482 Ma). It also induced uplift and erosion of deeply rooted crystalline complexes and triggered the development of a successor basin filled with predominantly clastic greywacke-arkosic sediments. The study demonstrates that the basement rocks exposed in the Habach terrane might be the 'missing link' between similar units of the more westerly positioned External domain (i.e., Aar, Aiguilles Rouges, Mont Blanc) and the Austroalpine domain to the east (Oetztal, Silvretta).

Migmatization and low-pressure overprinting metamorphism as record of two pre-Cretaceous tectonic episodes in the Santander Massif of the Andean basement in northern Colombia (NW South America)

NASA Astrophysics Data System (ADS)

Zuluaga, C. A.; Amaya, S.; Urueña, C.; Bernet, M.

2017-03-01

The core of the Santander Massif in the northern Andes of Colombia is dominated by migmatitic gneisses with a < 1.71 Ga protolith and was affected by continuous interactions of oceanic plates to the west and the northwestern corner of the South American continental plate. The exposed metamorphic core of the massif offers a unique opportunity to understand the tectonic evolution of northwestern South America. We present new metamorphic petrology and geochemistry data from the Bucaramanga Gneiss in the Santander Massif to document part of this tectonic evolution from late Proterozoic to Jurassic times. Metapelitic migmatite gneiss, quartz-feldspathic gneiss, and amphibolite from the Bucaramanga Gneiss recorded metamorphic peak conditions in the range of 660-850 °C at pressures of > 7.5 kbar. Lithologies are overprinted by low-pressure metamorphism, related to extensive Jurassic intrusions and linked with growth of cordierite and equilibration of low-pressure mineral assemblages, recorded metamorphic conditions are < 750 °C and < 6.5 kbar. Observed leucosomes display significant compositional variations and can be grouped in three groups: i) Group One leucosomes with high total REE content, high LREE/HREE, and negative Eu anomaly, ii) Group Two leucosomes with low total REE, low LREE/HREE, and positive Eu anomalies, and iii) Group Three leucosomes with relatively low LREE/HREE and strong positive Eu anomaly. Geochemical data support the interpretation that Group Two leucosomes crystallized from melts originated in a partial melting event affecting mostly pelitic and quartz-feldspathic lithologies with fluid-present melting reactions. The evaluation of mesosomes (amphibolite, pelitic and quartz-feldspathic rocks) as potential protoliths or restites indicates that at least two pelitic samples of the analyzed lithologies have characteristics consistent with the occurrence of fluid-present melting reactions involving quartz and feldspar. The leucosomes produced by crystallization of modified partial melts contrast with several other leucosomes that were injected; however, in some cases the melts crystallized as injected leucosomes show consistent geochemistry with partial melting of lithologies geochemically similar to the ones observed in the unit. The migmatization and the low pressure metamorphic overprint are related here to two main tectonic events: an early Paleozoic tectonic pulse produced by subduction of the oceanic crust of the Iapetus Ocean beneath northwestern Gondwana, and an Upper Triassic to Lower Jurassic tectonic pulse produced by subduction of oceanic crust of the proto-Pacific ocean beneath western Pangaea.

The Iceland Deep Drilling Project 4.5 km deep well, IDDP-2, in the seawater-recharged Reykjanes geothermal field in SW Iceland has successfully reached its supercritical target

NASA Astrophysics Data System (ADS)

Friðleifsson, Guðmundur Ó.; Elders, Wilfred A.; Zierenberg, Robert A.; Stefánsson, Ari; Fowler, Andrew P. G.; Weisenberger, Tobias B.; Harðarson, Björn S.; Mesfin, Kiflom G.

2017-11-01

The Iceland Deep Drilling Project research well RN-15/IDDP-2 at Reykjanes, Iceland, reached its target of supercritical conditions at a depth of 4.5 km in January 2017. After only 6 days of heating, the measured bottom hole temperature was 426 °C, and the fluid pressure was 34 MPa. The southern tip of the Reykjanes peninsula is the landward extension of the Mid-Atlantic Ridge in Iceland. Reykjanes is unique among Icelandic geothermal systems in that it is recharged by seawater, which has a critical point of 406 °C at 29.8 MPa. The geologic setting and fluid characteristics at Reykjanes provide a geochemical analog that allows us to investigate the roots of a mid-ocean ridge submarine black smoker hydrothermal system. Drilling began with deepening an existing 2.5 km deep vertical production well (RN-15) to 3 km depth, followed by inclined drilling directed towards the main upflow zone of the system, for a total slant depth of 4659 m ( ˜ 4.5 km vertical depth). Total circulation losses of drilling fluid were encountered below 2.5 km, which could not be cured using lost circulation blocking materials or multiple cement jobs. Accordingly, drilling continued to the total depth without return of drill cuttings. Thirteen spot coring attempts were made below 3 km depth. Rocks in the cores are basalts and dolerites with alteration ranging from upper greenschist facies to amphibolite facies, suggesting that formation temperatures at depth exceed 450 °C. High-permeability circulation-fluid loss zones (feed points or feed zones) were detected at multiple depth levels below 3 km depth to bottom. The largest circulation losses (most permeable zones) occurred between the bottom of the casing and 3.4 km depth. Permeable zones encountered below 3.4 km accepted less than 5 % of the injected water. Currently, the project is attempting soft stimulation to increase deep permeability. While it is too early to speculate on the energy potential of this well and its economics, the IDDP-2 is a milestone in the development of geothermal resources and the study of hydrothermal systems. It is the first well that successfully encountered supercritical hydrothermal conditions, with potential high-power output, and in which on-going hydrothermal metamorphism at amphibolite facies conditions can be observed. The next step will be to carry out flow testing and fluid sampling to determine the chemical and thermodynamic properties of the formation fluids.

Block coals from Indiana: Inferences on changing depositional environment

USGS Publications Warehouse

Mastalerz, Maria; Padgett, P.L.; Eble, C.F.

2000-01-01

Significant differences in coal petrography, palynology and coal quality were found between the Lower Block and Upper Block Coal Members (Brazil Formation, Pennsylvanian) in Daviess County, Indiana. The Lower Block Coal Member ranges in thickness from 51 to 74 cm and the Upper Block Coal Member ranges from 20 to 65 cm. Average sulfur content and ash yield of the Lower Block coal (0.98%, 7.65%) are lower than in the Upper Block coal. Megascopically, the coals show distinct differences. The Lower Block is a banded coal with numerous thin fusain horizons and a thin clay parting in the lower third of the seam. The Upper Block coal has a dulling-upward trend, with a bright clarain found at the base that grades into a clarain and then into a durain in the upper portion of the seam. Vitrinite content of the Lower Block coal ranges from 63% to 78%, with the highest vitrinite content found in the middle portion of the seam. In the Upper Block coal, vitrinite content ranges from 40% to 83%, with the highest values found in the lower part of the seam. Ash yield is higher in the upper part of the Upper Block coal, reaching up to 40%. The Lower Block coal is dominated by lycopod trees and tree ferns. The Upper Block coal shows marked differences in spore assemblages between lower and upper parts of the seam. The lower half is dominated by large lycopod trees and tree ferns, similar to the Lower Block coal. The upper half is dominated by small lycopods, mainly Densosporites and Radiizonates. These differences between the Lower Block and Upper Block Coal Members are significant correlation tools applicable to mining exploration and chronostratigraphy. (C) 2000 Elsevier Science B.V. All rights reserved.Significant differences in coal petrography, palynology and coal quality were found between the Lower Block and Upper Block Coal Members (Brazil Formation, Pennsylvanian) in Daviess County, Indiana. The Lower Block Coal Member ranges in thickness from 51 to 74 cm and the Upper Block Coal Member ranges from 20 to 65 cm. Average sulfur content and ash yield of the Lower Block coal (0.98%, 7.65%) are lower than in the Upper Block coal. Megascopically, the coals show distinct differences. The Lower Block is a banded coal with numerous thin fusain horizons and a thin clay parting in the lower third of the seam. The Upper Block coal has a dulling-upward trend, with a bright clarain found at the base that grades into a clarain and then into a durain in the upper portion of the seam. Vitrinite content of the Lower Block coal ranges from 63% to 78%, with the highest vitrinite content found in the middle portion of the seam. In the Upper Block coal, vitrinite content ranges from 40% to 83%, with the highest values found in the lower part of the seam. Ash yield is higher in the upper part of the Upper Block coal, reaching up to 40%. The Lower Block coal is dominated by lycopod trees and tree ferns. The Upper Block coal shows marked differences in spore assemblages between lower and upper parts of the seam. The lower half is dominated by large lycopod trees and tree ferns, similar to the Lower Block coal. The upper half is dominated by small lycopods, mainly Densosporites and Radiizonates. These differences between the Lower Block and Upper Block Coal members are significant correlation tools applicable to mining exploration and chronostratigraphy.

Software Reviews.

ERIC Educational Resources Information Center

McGrath, Diane, Ed.

1989-01-01

Reviewed are two computer software programs for Apple II computers on weather for upper elementary and middle school grades. "Weather" introduces the major factors (temperature, humidity, wind, and air pressure) affecting weather. "How Weather Works" uses simulation and auto-tutorial formats on sun, wind, fronts, clouds, and…

[Feasibility and short-term efficacy of simplified intensity-modulated radiotherapy and concurrent chemotherapy for neck and upper thoracic esophageal carcinoma].

PubMed

Zhu, Wei-Guo; Yu, Chang-Hua; Han, Ji-Hua; Li, Tao; Zhou, Xi-Lei; Tao, Guang-Zhou

2009-12-01

For neck and upper thoracic esophageal carcinoma, three dimensional conformal radiation therapy (3D-CRT) does not necessarily meet all clinical requirements while intensity modulated radiation therapy (IMRT) may take up a lot of labour power and material resources. This study was to explore the feasibility of simplified IMPT(sIMRT) and concurrent chemotherapy for neck and upper thoracic esophageal carcinoma, and to investigate the acute toxicities and short-term efficacy of this treatment modality. sIMRT plans were designed for 30 patients with neck and upper thoracic esophageal carcinoma. Two target volumes were defined: PTV1, which was designed to irradiate to 64 Gy (2.13 Gy x 30 fractions); PTV2, which was given to 54 Gy (1.8 Gy x 30). The sIMRT plan included five equiangular coplanar beams. All patients concurrently received DDP+5-FU regimen with radiotherapy on d1-5 and d29-33. Chemotherapy was repeated for two cycles 28 days after radiotherapy. The treatment was completed for all patients within 6 weeks, and only one patient had Grade 3 acute bronchitis. The complete response (CR) rate was 90.0% (27/30) and the partial response (PR) rate 10.0% (3/30). Overall response was 100% for esophageal lesions and the CR rate 76.5% (13/17). The PR rate was 23.5% (4/17) in lymph node lesions. The major toxicities observed were Grades I-II leukocytopenia. sIMRT can generate desirable dose distribution for neck and upper thoracic esophageal carcinoma, which is similar to sophisticated IMRT but obviously better than 3D-CRT. The short-term efficacy of sIMRT is satisfactory and its acute toxicities are tolerable.

Active vibration control of functionally graded beams with piezoelectric layers based on higher order shear deformation theory

NASA Astrophysics Data System (ADS)

Bendine, K.; Boukhoulda, F. B.; Nouari, M.; Satla, Z.

2016-12-01

This paper reports on a study of active vibration control of functionally graded beams with upper and lower surface-bonded piezoelectric layers. The model is based on higher-order shear deformation theory and implemented using the finite element method (FEM). The proprieties of the functionally graded beam (FGB) are graded along the thickness direction. The piezoelectric actuator provides a damping effect on the FGB by means of a velocity feedback control algorithm. A Matlab program has been developed for the FGB model and compared with ANSYS APDL. Using Newmark's method numerical solutions are obtained for the dynamic equations of FGB with piezoelectric layers. Numerical results show the effects of the constituent volume fraction and the influence the feedback control gain on the frequency and dynamic response of FGBs.

An Investigation of Bilateral Symmetry During Manual Wheelchair Propulsion.

PubMed

Soltau, Shelby L; Slowik, Jonathan S; Requejo, Philip S; Mulroy, Sara J; Neptune, Richard R

2015-01-01

Studies of manual wheelchair propulsion often assume bilateral symmetry to simplify data collection, processing, and analysis. However, the validity of this assumption is unclear. Most investigations of wheelchair propulsion symmetry have been limited by a relatively small sample size and a focus on a single propulsion condition (e.g., level propulsion at self-selected speed). The purpose of this study was to evaluate bilateral symmetry during manual wheelchair propulsion in a large group of subjects across different propulsion conditions. Three-dimensional kinematics and handrim kinetics along with spatiotemporal variables were collected and processed from 80 subjects with paraplegia while propelling their wheelchairs on a stationary ergometer during three different conditions: level propulsion at their self-selected speed (free), level propulsion at their fastest comfortable speed (fast), and propulsion on an 8% grade at their level, self-selected speed (graded). All kinematic variables had significant side-to-side differences, primarily in the graded condition. Push angle was the only spatiotemporal variable with a significant side-to-side difference, and only during the graded condition. No kinetic variables had significant side-to-side differences. The magnitudes of the kinematic differences were low, with only one difference exceeding 5°. With differences of such small magnitude, the bilateral symmetry assumption appears to be reasonable during manual wheelchair propulsion in subjects without significant upper-extremity pain or impairment. However, larger asymmetries may exist in individuals with secondary injuries and pain in their upper extremity and different etiologies of their neurological impairment.

An Investigation of Bilateral Symmetry During Manual Wheelchair Propulsion

PubMed Central

Soltau, Shelby L.; Slowik, Jonathan S.; Requejo, Philip S.; Mulroy, Sara J.; Neptune, Richard R.

2015-01-01

Studies of manual wheelchair propulsion often assume bilateral symmetry to simplify data collection, processing, and analysis. However, the validity of this assumption is unclear. Most investigations of wheelchair propulsion symmetry have been limited by a relatively small sample size and a focus on a single propulsion condition (e.g., level propulsion at self-selected speed). The purpose of this study was to evaluate bilateral symmetry during manual wheelchair propulsion in a large group of subjects across different propulsion conditions. Three-dimensional kinematics and handrim kinetics along with spatiotemporal variables were collected and processed from 80 subjects with paraplegia while propelling their wheelchairs on a stationary ergometer during three different conditions: level propulsion at their self-selected speed (free), level propulsion at their fastest comfortable speed (fast), and propulsion on an 8% grade at their level, self-selected speed (graded). All kinematic variables had significant side-to-side differences, primarily in the graded condition. Push angle was the only spatiotemporal variable with a significant side-to-side difference, and only during the graded condition. No kinetic variables had significant side-to-side differences. The magnitudes of the kinematic differences were low, with only one difference exceeding 5°. With differences of such small magnitude, the bilateral symmetry assumption appears to be reasonable during manual wheelchair propulsion in subjects without significant upper-extremity pain or impairment. However, larger asymmetries may exist in individuals with secondary injuries and pain in their upper extremity and different etiologies of their neurological impairment. PMID:26125019

The association between gastroesophageal flap valve function and gastroesophageal reflux symptoms.

PubMed

Keskin, O; Kalkan, Ç; Yaman, A; Tüzün, A; Soykan, I

2017-01-01

Upper gastrointestinal endoscopic examination is usually the first step in the evaluation of patients with suspected gastroesopageal reflux disease. The primary aim of this study was to investigate the association between gastroesophageal flap valve function (GEFV) and gastroesophapgeal reflux symptoms in patients undergoing routine upper endoscopy. Patients and methods: 1507 patients were included into the study and the GEFV graded I to IV as follows: Hill I-II: normal GEFV, and Hill III-IV: abnormal GEFV. Patients in abnormal GEFV group had a higher incidence of reflux symptoms compared to normal GEFV group (53.4% vs 47.4% for heartburn p=0.03 and 53.2% vs 42.4% for regurgitation, p<0.01). In abnormal GEFV patients, esophagitis was more common compared to those with normal GEFV (32.6% vs 11.1%, p<0.01). Presence of heartburn and regurgitation (n =556) correlated with Hill III-IV grades (n = 184/556), (sensitivity: 33%, p = 0.003). In contrast, 24.6% (157/638) of patients without reflux symptoms were in abnormal GEFV group. In patients undergoing endoscopy because of reflux symptoms, Grade III-IV valve was detected more commonly in patients with reflux symptoms compared to patients without reflux symptoms (p = 0.01). Patients with abnormal valves (Hill grades III and IV) but without reflux symptoms, esophagitis and hiatal hernia should be evaluated individually by means of the presence of gastroesophageal reflux disease which means that GEFV is not a good indicator of reflux disease. © Acta Gastro-Enterologica Belgica.

Abnormal Gastroesophageal Flap Valve Is Associated With High Gastresophageal Reflux Disease Questionnaire Score and the Severity of Gastroesophageal Reflux Disease in Vietnamese Patients With Upper Gastrointestinal Symptoms.

PubMed

Quach, Duc T; Nguyen, Trang T; Hiyama, Toru

2018-04-30

There have been no studies investigating the distribution of abnormal gastroesophageal flap valve (GEFV) among patients with dyspepsia, non-erosive reflux disease (NERD), and reflux esophagitis (RE) in the same set of patients. The aims of this study are to investigate (1) the association between GEFV and gastroesophageal reflux disease questionnaire (GERDQ) score, and (2) the distribution of abnormal GEFV in Vietnamese patients presenting with upper gastrointestinal symptoms. Three hundred and thirty-one patients recruited in this prospective cross-sectional study were classified into 3 groups: reflux esophagitis (RE), non-erosive reflux disease (NERD) (GERDQ score ≥ 8, no endoscopic mucosal injury), and dyspepsia (GERDQ score < 8, no endoscopic mucosal injury). The GEFV was graded endoscopically according to the Hill classification. GEFV grades I and II were regarded as normal, while grades III and IV were regarded as abnormal GEFV. There were 215 (65.0%) patients with dyspepsia, 55 (16.6%) patients with NERD, and 61 (18.4%) patients with RE. Abnormal GEFV was an independent risk factor for GERD (OR, 2.93; CI 95%, 1.76-4.88) and RE (OR, 3.41; CI 95%, 1.78-6.53). The mean GERDQ score of patients with abnormal GEFV was significantly higher than that of patients with normal GEFV (5.7 ± 2.4 vs 4.9 ± 2.7, P = 0.011). The prevalence of abnormal GEFV gradually increased in patients with dyspepsia (27.4%), NERD (43.6%), grade A RE (56.8%), and grades B/C RE (80.0%) ( P ＜ 0.001). Abnormal GEFV was significantly associated with high GERDQ score. Its prevalence gradually increased in patients with dyspepsia, NERD, and RE, respectively.

Effect of display type, DICOM calibration and room illuminance in bitewing radiographs.

PubMed

Kallio-Pulkkinen, Soili; Huumonen, Sisko; Haapea, Marianne; Liukkonen, Esa; Sipola, Annina; Tervonen, Osmo; Nieminen, Miika T

2016-01-01

To compare observer performance in the detection of both anatomical structures and caries in bitewing radiographs using consumer grade displays with and without digital imaging and communications in medicine (DICOM) calibration, tablets (third generation iPad; Apple, Cupertino, CA) and 6-megapixel (MP) displays under different lighting. 30 bitewing radiographs were blindly evaluated on four displays under bright (510 lx) and dim (16 lx) ambient lighting by two observers. The dentinoenamel junction, enamel and dentinal caries, and the cortical border of the alveolar crests were evaluated. Consensus was considered as reference. Intraobserver agreement was determined. The proportion of equivalent ratings and weighted kappa were used to assess reliability. The proportion of equivalent ratings with consensus differed significantly between uncalibrated and DICOM-calibrated consumer grade display in enamel caries in upper and lower molars in bright (p = 0.013 and p = 0.003) lighting, and in dentinal caries in lower molars in both bright (p = 0.022) and dim (p = 0.004) lighting. The proportion also differed significantly between DICOM-calibrated consumer grade and 6-MP display in dentinal caries in lower molars in bright lighting (p = 0.039), tablet and consumer grade display in enamel caries in upper molars (p = 0.017) in bright lighting, tablet and 6-MP display in dentinal caries in lower molars (p = 0.003) in bright lighting and in enamel caries in lower molars (p = 0.012) in dim lighting. DICOM calibration improves the detection of enamel and dentinal caries in bitewing radiographs, particularly in bright lighting. Therefore, a calibrated consumer grade display can be recommended as a diagnostic tool for viewing bitewing radiographs.

Multi-institutional Evaluation of Upper Urinary Tract Biopsy Using Backloaded Cup Biopsy Forceps, a Nitinol Basket, and Standard Cup Biopsy Forceps.

PubMed

Lama, Daniel J; Safiullah, Shoaib; Patel, Roshan M; Lee, Thomas K; Balani, Jyoti P; Zhang, Lishi; Okhunov, Zhamshid; Margulis, Vitaly; Savage, Stephen J; Uchio, Edward; Landman, Jaime

2018-04-06

To compare the performance of 3 contemporary ureteroscopic biopsy devices for the histopathologic diagnosis of upper tract urothelial carcinoma (UTUC). We retrospectively reviewed 145 patients who underwent 182 urothelial biopsies using 2.4F backloaded cup biopsy forceps, a nitinol basket, or 3F standard cup biopsy forceps at 3 tertiary academic centers between 2011 and 2016. Experienced genitourinary pathologists provided an assessment of each specimen without knowledge of the device used for biopsy. For patients who underwent nephroureterectomy without neoadjuvant chemotherapy within 3 months of biopsy-proven UTUC diagnosis, the biopsy grade was compared with both the grade and stage of the surgical specimen. Biopsy utilization varied among the 3 institutions (P <.0001). Significant variabilities in specimen size (P = .001), the presence of intact urothelium (P = .008), and crush artifact (P = .028) were found among the biopsy devices. The quality of specimens from backloaded cup forceps was rated similarly to the nitinol basket (P >.05) and was favored over standard cup forceps specimens. Grade concordance was not affected by specimen size (P >.05), morphology (P >.1), or location (P >.5). No difference existed among the devices in the rate of acquiring a grade concordant biopsy; however, the backloaded cup forceps provided concordant biopsies that could be distinguished as low- and high-grade (P = .02). The backloaded cup forceps and nitinol basket obtained a higher quality urothelial specimen compared with standard cup forceps. Ureteroscopic biopsy device selection did not significantly impact the accuracy of the histologic diagnosis of UTUC. Copyright © 2018 Elsevier Inc. All rights reserved.

Mineral chemistry of isotropic gabbros from the Manamedu Ophiolite Complex, Cauvery Suture Zone, southern India: Evidence for neoproterozoic suprasubduction zone tectonics

NASA Astrophysics Data System (ADS)

Yellappa, T.; Tsunogae, T.; Chetty, T. R. K.; Santosh, M.

2016-11-01

The dismembered units of the Neoproterozoic Manamedu Ophiolite Complex (MOC) in the Cauvery Suture Zone, southern India comprises a well preserved ophiolitic sequence of ultramafic cumulates of altered dunites, pyroxenites, mafic cumulates of gabbros, gabbro-norites and anorthosites in association with plagiogranites, isotropic gabbros, metadolerites, metabasalts/amphibolites and thin layers of ferruginous chert bands. The isotropic gabbros occur as intrusions in association with gabbroic anorthosites, plagiogranite and metabasalts/amphibolites. The gabbros are medium to fine grained with euhedral to subhedral orthopyroxenes, clinopyroxenes and subhedral plagioclase, together with rare amphiboles. Mineral chemistry of isotropic gabbros reveal that the clinopyroxenes are diopsidic to augitic in composition within the compositional ranges of En(42-59), Fs(5-12), Wo(31-50). They are Ca-rich and Na poor (Na2O < 0.77 wt%) characterized by high-Mg (Mg# 79-86) and low-Ti (TiO2 < 0.35 wt%) contents. The tectonic discrimination plots of clinopyroxene data indicate island arc signature of the source magma. Our study further confirms the suprasubduction zone origin of the Manamedu ophiolitic suite, associated with the subduction-collision history of the Neoproterozoic Mozambique ocean during the assembly of Gondwana supercontinent.

The composite Archaean grey gneisses: Petrological significance, and evidence for a non-unique tectonic setting for Archaean crustal growth

NASA Astrophysics Data System (ADS)

Moyen, Jean-François

2011-04-01

The geodynamic context of formation of the Archaean continental crust is a matter of debate. The crust is largely made of grey gneiss complexes, a composite rock assemblage dominated by granitoids that are generally regarded as belonging to the TTG (tonalite-trondhjemite-granodiorite) series. Using a large database of published TTG and grey gneiss compositions, it is possible to show that the granitoids forming grey gneiss complexes actually belong to at least four main geochemical groups: (i) a potassic component made of granodiorites and formed by melting of existing crustal lithologies; and (ii) three sodic groups (TTG proper) that comprise low, medium and high pressure groups. The geochemistry of the low pressure group is consistent with derivation from a plagioclase and garnet-amphibolite; the medium pressure group was formed in equilibrium with a garnet-rich, plagioclase-poor amphibolite, whereas the high pressure group derived from a rutile-bearing eclogite. As the temperature of melting of metamafic rocks is largely independent from pressure, this corresponds to melting along a range of contrasting geothermal gradients, in turn reflecting a range of tectonic sites for the formation of the Archaean continental crust.

Ultramafic rocks of the western Idaho suture zone: Asbestos Peak and Misery Ridge

DOE Office of Scientific and Technical Information (OSTI.GOV)

Godchaux, M.M.; Bonnichsen, B.

1993-04-01

The Western Idaho Ultramafic Belt extends northward from the town of Weiser to the northern end of Dworshak Reservoir; in its northern portion most of the ultramafic bodies are localized along the suture zone where the Mesozoic oceanic accreted terranes meet the continental craton. Of the twenty bodies investigated, all are small, all are in fault contact with their metavolcanic and metasedimentary host rocks, all have been metamorphosed, and all display deformational fabrics in at least some portion of the outcrop area, suggesting that deformation continued after peak metamorphism. The degree of metamorphism ranges from incipient serpentinization to attainment ofmore » equilibrium in the upper amphibolite facies. Some bodies have been intruded by granitic dikes or pegmatite veins after emplacement, and have locally undergone contact metasomatism. Two particularly complex bodies, Asbestos Peak and Misery Ridge, were chosen for detailed petrographic and chemical study. Asbestos Peak is composed mostly of decussate anthophyllite-talc rock containing isolated patches of harzburgite protolith, and has blackwall border zones. Misery Ridge is composed mostly of coarse-grained sheared tremolite-talc schist without remnant protolith, and lacks true blackwall zones. Both bodies exhibit an unusual and enigmatic hornblende-poikiloblastic garnet-green spinel-skeletal ilmenite assemblage, present in some places as well-defined border zones and in other places as cross-cutting bodies.« less

Regional and contact metamorphism within the Moy Intrusive Complex, Grampian Highlands, Scotland

NASA Astrophysics Data System (ADS)

Zaleski, E.

1985-04-01

In central Scotland, the Moy Intrusive Complex consists of (1) the Main Phase — syntectonic peraluminous granodiorite to granite emplaced at c. 455 Ma, intruded by (2) the Finglack Alaskite — post-tectonic leucocratic granite emplaced at 407+/-5 Ma. The Main Phase was emplaced into country rocks at amphibolite facies temperatures. Rb-Sr dates and a compositional spectrum of decreasing celadonite content in Main Phase muscovite suggest the persistence of c. 550° C temperatures for c. 30 Ma but with a declining pressure regime, i.e. isothermal uplift. The Finglack Alaskite was intruded at high structural level, leading to the development of a contact metamorphic aureole in the Main Phase. The thermal effects of contact metamorphism include intergrowths of andalusite, biotite and feldspar in pseudomorphs after muscovite. This is associated with recrystallized granoblastic quartz. Muscovite breakdown and reaction with adjacent biotite, quartz and feldspar, i.e. a function of local mineral assemblage rather than bulk rock composition, is postulated to explain the occurrence of metamorphic andalusite in a granitoid rock. The Main Phase pluton of the Moy Intrusive Complex lies within a NNE trending belt of c. 450 Ma Caledonian tectonic and magmatic activity paralleling the Moine Thrust, and extending from northern Scotland to the Highland Boundary Fault. Syntectonic ‘S-type’ magmatism with upper crustal source areas implies crustal thickening and suggests an intracratonic orogeny.

Sediment underthrusting within a continental magmatic arc: Coast Mountains batholith, British Columbia

NASA Astrophysics Data System (ADS)

Pearson, David M.; MacLeod, Douglas R.; Ducea, Mihai N.; Gehrels, George E.; Jonathan Patchett, P.

2017-10-01

Though continental magmatic arcs are factories for new continental crust, a significant proportion of continental arc magmas are recycled from supracrustal material. To evaluate the relative contributions of retroarc underthrusting and trench side partial sediment subduction for introducing supracrustal rocks to the middle and lower crust of continental magmatic arcs, we present results from the deeply exposed country rocks of the Coast Mountains batholith of western British Columbia. Prior work demonstrates that these rocks underwent widespread partial melting that contributed to the Coast Mountains batholith. We utilize U-Pb zircon geochronology, Sm-Nd thermochronology, and field-based studies to document the protoliths and early burial history of amphibolite and granulite-facies metasedimentary rocks in the Central Gneiss Complex. U-Pb detrital zircon data from the structurally highest sample localities yielded 190 Ma unimodal age peaks and suggest that retroarc rocks of the Stikine terrane constitute a substantial portion of the Central Gneiss Complex. These supracrustal rocks underwent thrust-related burial and metamorphism at >25 km depths prior to 80 Ma. These rocks may also be underlain at the deepest exposed structural levels by Upper Cretaceous metasedimentary rocks, which may have been emplaced as a result of trench side underplating or intraarc burial. These results further our understanding of the mechanisms of material transport within the continental lithosphere along Cordilleran subduction margins.

Thermal history of a metamorphic core complex

NASA Astrophysics Data System (ADS)

Dokka, R. K.; Mahaffie, M. J.; Snoke, A. W.

Fission track (FT) thermochronology studies of lower plate rocks of the Ruby Mountains-East Humbolt Range metamorphic core complex provide important constraints on the timing an nature of major middle Tertiary extension of northeast Nevada. Rocks analyzed include several varieties of mylonitic orthogneiss as well as amphibolitic orthognesses from the non-mylonitic infrastructural core. Oligocene-age porphyritic biotite granodiorite of the Harrison Pass pluton was also studied. The minerals dated include apatite, zircon, and sphene and were obtained from the same rocks that have been previously studied. FT ages are concordant and range in age from 26.4 Ma to 23.8 Ma, with all showing overlap at 1 sigma between 25.4 to 23.4 Ma. Concordancy of all FT ages from all structural levels indicates that the lower plate cooled rapidly from temperatures above approx. 285 C (assumed sphene closure temperature (2)) to below approx. 150 C (assumed apatite closure temperature) near the beginning of the Miocene. This suggests that the lower plate cooled at a rate of at least approx. 36 deg C/Ma during this event. Rapid cooling of the region is considered to reflect large-scale tectonic denudation (intracrustal thinning), the vertical complement to intense crustal extension. FT data firmly establish the upper limit on the timing of mylonitization during detachment faulting and also coincide with the age of extensive landscape disruption.

Early history and reactivation of the rand thrust, southern California

NASA Astrophysics Data System (ADS)

Postlethwaite, Clay E.; Jacobson, Carl E.

The Rand thrust of the Rand Mountains in the northwestern Mojave Desert separates an upper plate of quartz monzonite and quartzofeldspathic to amphibolitic gneiss from a lower plate of metagraywacke and mafic schist (Rand Schist). The Rand thrust is considered part of the regionally extensive Vincent/Chocolate Mountain thrust system, which is commonly believed to represent a Late Cretaceous subduction zone. The initial direction of dip and sense of movement along the Vincent/Chocolate Mountain thrust are controversial. Microfabrics of mylonites and quartzites from the Rand Mountains were analyzed in an attempt to determine transport direction for this region, but the results are ambiguous. In addition, the southwestern portion of the Rand thrust was found to have been reactivated as a low-angle normal fault after subduction. Reactivation might have occurred shortly after subduction, in which case it could account for the preservation of high-pressure mineral assemblages in the Rand Schist, or it could be related to mid-Tertiary extension in the western United States. In either event, the reactivation might be responsible for the complicated nature of the microfabrics. The Rand Schist exhibits an inverted metamorphic zonation. Isograds in the schist are not significantly truncated by the reactivated segment of the Rand thrust. This indicates that other segments of the Vincent/Chocolate Mountain thrust should be re-evaluated for the possibility of late movement, even if they show an apparently undisturbed inverted metamorphic zonation.

Kinematic evolution of the Mbakop Pan-African granitoids (western Cameroon domain): An integrated AMS and EBSD approach

NASA Astrophysics Data System (ADS)

Bella Nké, B. E.; Njanko, T.; Mamtani, M. A.; Njonfang, E.; Rochette, P.

2018-06-01

This study integrates anisotropy of magnetic susceptibility, microstructural and crystallographic preferred orientation (CPO) data from the Mbakop granitic pluton (MGP; Pan-African age) in order to decipher its kinematic evolution. The MGP lies close to NE-SW branch of Central Cameroon Shear Zone (CCSZ) and is emplaced in gneissic basement. High mean magnetic susceptibility and presence of multi-domain magnetite are recorded. Quartz CPO measured using Electron Backscatter diffraction reveals dominance of rhomb , prism and prism slip in different samples, which is consistent with microstructures developed under upper greenschist/amphibolite facies conditions. Quartz CPO along with other kinematic indicators (feldspar porphyroclasts/mineral fish) indicate non-coaxial deformation was important during tectonic evolution of the MGP. Contrasting sense of shear is recorded implying multi-stage mylonitization in the Western Cameroon Domain. Top-towards-south sense of shear is related to regional D2 deformation (613-585 Ma), while top-towards-north is related to D3 (585-540 Ma). The magnetic fabric in MGP records D3. The obliquity between mean orientation of magnetic foliation (N12°E) and the NE-SW CCSZ branch (N48°E) gives kinematic vorticity number of 0.95. This indicates dominantly simple shear with a minor pure shear component. It is concluded that regional transpression was important during MGP emplacement.

Thermal history of a metamorphic core complex

NASA Technical Reports Server (NTRS)

Dokka, R. K.; Mahaffie, M. J.; Snoke, A. W.

1985-01-01

Fission track (FT) thermochronology studies of lower plate rocks of the Ruby Mountains-East Humbolt Range metamorphic core complex provide important constraints on the timing an nature of major middle Tertiary extension of northeast Nevada. Rocks analyzed include several varieties of mylonitic orthogneiss as well as amphibolitic orthognesses from the non-mylonitic infrastructural core. Oligocene-age porphyritic biotite granodiorite of the Harrison Pass pluton was also studied. The minerals dated include apatite, zircon, and sphene and were obtained from the same rocks that have been previously studied. FT ages are concordant and range in age from 26.4 Ma to 23.8 Ma, with all showing overlap at 1 sigma between 25.4 to 23.4 Ma. Concordancy of all FT ages from all structural levels indicates that the lower plate cooled rapidly from temperatures above approx. 285 C (assumed sphene closure temperature (2)) to below approx. 150 C (assumed apatite closure temperature) near the beginning of the Miocene. This suggests that the lower plate cooled at a rate of at least approx. 36 deg C/Ma during this event. Rapid cooling of the region is considered to reflect large-scale tectonic denudation (intracrustal thinning), the vertical complement to intense crustal extension. FT data firmly establish the upper limit on the timing of mylonitization during detachment faulting and also coincide with the age of extensive landscape disruption.

Ancient Egypt: History 380.

ERIC Educational Resources Information Center

Turk, Laraine D.

"Ancient Egypt," an upper-division, non-required history course covering Egypt from pre-dynastic time through the Roman domination is described. General descriptive information is presented first, including the method of grading, expectation of student success rate, long-range course objectives, procedures for revising the course, major…

Upper Grades Ideas.

ERIC Educational Resources Information Center

Thornburg, David; Beane, Pam

1983-01-01

Presents programs for creating animated characters (Atari), random sentences (Logo), and making a triangle (TRS-80 Level III Basic), and suggestions for creative writing and comparison shopping for computers/software. Also includes "Modems for Micros: Your Computer Can Talk on the Phone" (Bill Chalgren) on telecommunications capabilities of…

Geochemical and Nd isotopic constraints for the origin of Late Archean turbidites from the Yellowknife area, Northwest Territories, Canada

NASA Astrophysics Data System (ADS)

Yamashita, Katsuyuki; Creaser, Robert A.

1999-10-01

A detailed geochemical and isotopic study of Late Archean turbidites and volcanic rocks from the Yellowknife area, Slave province, was undertaken to constrain the nature of exposed crust at the time of 2.6 to 2.7 Ga crustal consolidation. The ɛNdT values of the volcanic rocks range from +1.7 to -4.4. This variation can be produced by assimilation of pre-2.8 Ga basement by a depleted mantle-derived magma, possibly followed by fractional crystallization. The turbidites are typically metamorphosed to greenschist to amphibolite facies, and where metamorphosed to greenschist facies, different units of Bouma sequence can be observed. The different units of Bouma sequence were sampled and analyzed separately to evaluate the possible differences in geochemical and isotopic signatures. The geochemical data presented here is in accord with the previously proposed model that argues for a mixture of 20% mafic-intermediate volcanic rocks, +55% felsic volcanic rocks, and +25% granitic rocks as a source of these turbidites. However, our revised calculation with the new data presented here argues for 1 to 2% input from an ultramafic source, as well as somewhat higher input from mafic-intermediate volcanic sources in the upper shale units compared to the lower sand units. The ɛNdT values of the turbidites generally are lower in the upper shale units compared to the lower sand units. Detailed inspection of trace-element data suggest that this is not an artifact of rare earth element-rich heavy minerals concentrating in the lower sand units of the turbidites, but rather is a result of “unmixing” of detritus with different ɛNdT values during sediment transportation and deposition. The upper shale units of the turbidites are isotopically compatible with a derivation mainly from crustally contaminated volcanic rocks, similar to those exposed in the Yellowknife area. The lower sand units contain a higher proportion of westerly derived plutonic rock detritus, characterized by higher ɛNdT, suggesting that there are area(s) west of Yellowknife not underlain by older (2.8-4.0 Ga) basement. The trace-element characteristics of these turbidites (i.e., Cr, Ni, La, Th, Sc, Eu/Eu∗, and GdN/YbN) are distinct from those of typical post-Archean turbidites. This observation is consistent with the models that predict that the chemical composition of the upper continental crust was slightly different in the Archean compared to post-Archean time.

Monitoring and Early Warning of the 2012 Preonzo Catastrophic Rockslope Failure

NASA Astrophysics Data System (ADS)

Loew, Simon; Gschwind, Sophie; Keller-Signer, Alexandra; Valenti, Giorgio

2015-04-01

In this contribution we describe the accelerated creep stage and early warning system of a 210'000 m3 rock slope failure that occurred in May 2012 above the village of Preonzo (Swiss Alps). The very rapid failure occurred from a larger and retrogressive instability in high-grade metamorphic ortho-gneisses and amphibolites with a total volume of about 350'000 m3 located at an alpine meadow called Alpe di Roscioro. This instability showed clearly visible signs of movements since 1989 and accelerated creep with significant hydro-mechanical forcing since about 1999. Because the instability at Preonzo threatened a large industrial facility and important transport routes a cost-effective early warning system was installed in 2010. The alarm thresholds for pre-alarm, general public alarm and evacuation were derived from 10 years of continuous displacement monitoring with crack extensometers and an automated total station. These thresholds were successfully applied to evacuate the industrial facility and close important roads a few days before the catastrophic slope failure of May 15th, 2012. The rock slope failure occurred in two events, exposing a planar rupture plane dipping 42° and generating deposits in the mid-slope portion with a travel angle of 38°. Two hours after the second rockslide, the fresh colluvial deposits became reactivated in a devastating de-bris avalanche reaching the foot of the slope.

Evaluation of Water Retention in Lumbar Intervertebral Disks Before and After Exercise Stress With T2 Mapping.

PubMed

Chokan, Kou; Murakami, Hideki; Endo, Hirooki; Mimata, Yoshikuni; Yamabe, Daisuke; Tsukimura, Itsuko; Oikawa, Ryosuke; Doita, Minoru

2016-04-01

T2 mapping was used to quantify moisture content of the lumbar spinal disk nucleus pulposus (NP) and annulus fibrosus before and after exercise stress, and after rest, to evaluate the intervertebral disk function. To clarify water retention in intervertebral disks of the lumbar vertebrae by performing magnetic resonance imaging before and after exercise stress and quantitatively measuring changes in moisture content of intervertebral disks with T2 mapping. To date, a few case studies describe functional evaluation of articular cartilage with T2 mapping; however, T2 mapping to the functional evaluation of intervertebral disks has rarely been applied. Using T2 mapping might help detect changes in the moisture content of intervertebral disks, including articular cartilage, before and after exercise stress, thus enabling the evaluation of changes in water retention shock absorber function. Subjects, comprising 40 healthy individuals (males: 26, females: 14), underwent magnetic resonance imaging T2 mapping before and after exercise stress and after rest. Image J image analysis software was then used to set regions of interest in the obtained images of the anterior annulus fibrosus, posterior annulus fibrosus, and NP. T2 values were measured and compared according to upper vertebrae position and degeneration grade. T2 values significantly decreased in the NP after exercise stress and significantly increased after rest. According to upper vertebrae position, in all of the upper vertebrae positions, T2 values for the NP significantly decreased after exercise stress and significantly increased after rest. According to the degeneration grade, in the NP of grade 1 and 2 cases, T2 values significantly decreased after exercise stress and significantly increased after rest. T2 mapping could be used to not only diagnose the degree of degeneration but also evaluate intervertebral disk function. 3.

Diagnostic criteria of traumatic central cord syndrome. Part 3: descriptive analyses of neurological and functional outcomes in a prospective cohort of traumatic motor incomplete tetraplegics.

PubMed

Pouw, M H; van Middendorp, J J; van Kampen, A; Curt, A; van de Meent, H; Hosman, A J F

2011-05-01

Prospective multicenter cohort study. To compare the neurological recovery and functional outcomes between traumatic central cord syndrome (TCCS) patients and motor incomplete tetraplegic patients. European Multicenter Study of human spinal cord injury. In 248 traumatic motor incomplete tetraplegics, initial phase (0-15 days) American Spinal Injury Association (ASIA) impairment grading, upper and lower extremity motor scores (UEMS and LEMS), upper and lower sensory scores and chronic phase (6 or 12 months) neurological outcomes were analyzed. In addition, chronic phase self-care and indoor mobility Spinal Cord Independence Measure (SCIM) items were studied. Tetraplegics were subdivided into three groups: (1) non-TCCS group (UEMSLEMS), (2) intermediate-TCCS group (UEMS=(1-9 points)

Quantum interactive learning tutorial on the double-slit experiment to improve student understanding of quantum mechanics

NASA Astrophysics Data System (ADS)

Sayer, Ryan; Maries, Alexandru; Singh, Chandralekha

2017-06-01

Learning quantum mechanics is challenging, even for upper-level undergraduate and graduate students. Research-validated interactive tutorials that build on students' prior knowledge can be useful tools to enhance student learning. We have been investigating student difficulties with quantum mechanics pertaining to the double-slit experiment in various situations that appear to be counterintuitive and contradict classical notions of particles and waves. For example, if we send single electrons through the slits, they may behave as a "wave" in part of the experiment and as a "particle" in another part of the same experiment. Here we discuss the development and evaluation of a research-validated Quantum Interactive Learning Tutorial (QuILT) which makes use of an interactive simulation to improve student understanding of the double-slit experiment and strives to help students develop a good grasp of foundational issues in quantum mechanics. We discuss common student difficulties identified during the development and evaluation of the QuILT and analyze the data from the pretest and post test administered to the upper-level undergraduate and first-year physics graduate students before and after they worked on the QuILT to assess its effectiveness. These data suggest that on average, the QuILT was effective in helping students develop a more robust understanding of foundational concepts in quantum mechanics that defy classical intuition using the context of the double-slit experiment. Moreover, upper-level undergraduates outperformed physics graduate students on the post test. One possible reason for this difference in performance may be the level of student engagement with the QuILT due to the grade incentive. In the undergraduate course, the post test was graded for correctness while in the graduate course, it was only graded for completeness.

Spatiotemporal evolution of magmatic pulses and regional metamorphism during a Cretaceous flare-up event: Constraints from the Ryoke belt (Mikawa area, central Japan)

NASA Astrophysics Data System (ADS)

Takatsuka, Kota; Kawakami, Tetsuo; Skrzypek, Etienne; Sakata, Shuhei; Obayashi, Hideyuki; Hirata, Takafumi

2018-05-01

The spatiotemporal relationship between granitoid intrusions and low-pressure/temperature type regional metamorphism in the Ryoke belt (Mikawa area) is investigated to understand the tectono-thermal evolution of the upper- to middle-crust during a Cretaceous flare-up event at the Eurasian active continental margin. Three plutono-metamorphic stages are recognized; (1) 99-84 Ma: intrusion of granitoids (99-95 Ma pulse) into the upper crust and high-T regional metamorphism reaching sillimanite-grade (97.0 ± 4.4 Ma to 88.5 ± 2.5 Ma) in the middle crust, (2) 81-75 Ma: intrusion of gneissose granitoids (81-75 Ma Ma pulse) into the middle crust at 19-24 km depth, and (3) 75-69 Ma: voluminous intrusions of massive to weakly-foliated granitoids (75-69 Ma pulse) at 9-13 km depth and formation of contact metamorphic aureoles. Cooling of the highest-grade metamorphic zone below the wet solidus of granitic rocks is estimated at 88.5 ± 2.5 Ma. At ca. 75 Ma, the upper-middle crustal section underwent northward tilting, resulting in the exhumation of regional metamorphic zones to 9-13 km depth. Although the highest-grade metamorphic rocks and the 99-95 Ma pulse granitoids preserve similar U-Pb zircon ages, the absence of spatial association suggests that the regional metamorphic zones were mainly produced by a transient thermal anomaly in the mantle and thermal conduction through the crust, supplemented by localized advection due to granitoid intrusions. The successive emplacement of granitoids into shallow, deep and shallow levels of the crust was probably controlled by the combination of change in thermal structure of the crust and tectonics during granitoid intrusions.

Structural and petrographic constraints on the stratigraphy of the Lapataia Formation, with implications for the tectonic evolution of the Fuegian Andes

NASA Astrophysics Data System (ADS)

Cao, Sebastián J.; Torres Carbonell, Pablo J.; Dimieri, Luis V.

2018-07-01

The structure of the Fuegian Andes central belt is characterized by a first phase of peak metamorphism and ductile deformation, followed by a brittle-ductile thrusting phase including juxtaposition of different (first phase) structural levels; both related to the closure and inversion of the Late Jurassic-Early Cretaceous Rocas Verdes basin. The second phase involved thrust sheets of pre-Jurassic basement, as well as Upper Jurassic and Lower Cretaceous units from the volcanic-sedimentary fill of the basin. Rock exposures in the Parque Nacional Tierra del Fuego reveal a diversity of metamorphic mineral assemblages, dynamic recrystallization grades and associated structures, evidencing a variety of protoliths and positions in the crust during their orogenic evolution. Among the units present in this sector, the Lapataia Formation portrays the higher metamorphic grade reported in the Argentine side of the Fuegian Andes, and since no precise radiometric ages have been established to date, its stratigraphic position remains a matter of debate: the discussion being whether it belongs to the pre-Jurassic basement, or the Upper Jurassic volcanic/volcaniclastic initial fill of the Rocas Verdes basin. The mapping and petrographic/microstructural study of the Lapataia Formation and those of undoubtedly Mesozoic age, allow to characterize the former as a group of rocks with great lithological affinity with the Upper Jurassic metamorphic rocks found elsewhere in the central belt of the Fuegian Andes. The main differences in metamorphic grade are indebted to its deformation at deeper crustal levels, but during the same stages than the Mesozoic rocks. Accordingly, we interpret the regional structure to be associated with the stacking of thrust sheets from different structural levels through the emplacement of a duplex system during the growth of the Fuegian Andes.

Dimensions of adolescent rebellion: Risks for academic failure among high- and low-income youth

PubMed Central

Luthar, Suniya S.; Ansary, Nadia S.

2015-01-01

The central question addressed in this study was whether upper class, suburban teenagers can engage in various problem behaviors and still maintain adequate academic grades, because of environmental safety nets, unlike their low-income, inner-city counterparts. Three problem behavior dimensions were assessed among tenth graders, that is, substance use, delinquency, and low school engagement. Academic achievement was assessed in terms of grades across four major subjects. Variable-based analyses indicated unique links with grades for self-reported delinquency and school disengagement in high- and low-income samples, but for substance use only among the former. Person-based analyses showed that in both schools, grades were clearly compromised among youth with disturbances in all three problem domains. In addition, in the suburban school only, grades were low in the cluster characterized chiefly by high substance use. Results are discussed in terms of stereotypes regarding risks (or lack thereof) stemming from families' socioeconomic status; implications for theory and interventions are also considered. PMID:15971768

The result of adjuvant chemotherapy for localized pT3 upper urinary tract carcinoma in a multi-institutional study.

PubMed

Kawashima, Atsunari; Nakai, Yasutomo; Nakayama, Masashi; Ujike, Takeshi; Tanigawa, Go; Ono, Yutaka; Kamoto, Akihito; Takada, Tsuyosi; Yamaguchi, Yuichiro; Takayama, Hitoshi; Nishimura, Kazuo; Nonomura, Norio; Tsujimura, Akira

2012-10-01

To determine through the analysis of our multi-institutional database whether postoperative adjuvant chemotherapy for upper urinary tract carcinoma with localized invasive upper urinary tract carcinoma (UUTC) is beneficial. A study population of 93 patients with pT3N0/xM0 UUTC was eligible for this study. Clinical features evaluated were sex, tumor location, adjuvant chemotherapy status, tumor pathology (histology, grade, infiltrating growth, lymphovascular invasion (LVI)), and cause of death. Cancer-specific survival (CSS) was estimated by Kaplan-Meier method. Prognostic factors related to CSS were analyzed by Cox proportional hazards regression model for multivariate analysis. In pT3 patients, overall 5-year CSS rate was 68.4% and median CSS time was 31 months (range 3-114 months). In the adjuvant chemotherapy group, 5-year CSS rate was 80.8%, whereas 5-year CSS rate was 64.4% in the non-adjuvant chemotherapy group. By multivariate analysis, adjuvant chemotherapy status was significantly associated with CSS (P = 0.008) were sex, tumor grade, tumor histology, and LVI presence. This study, although it was retrospective study, revealed that adjuvant chemotherapy after RNU may be beneficial in pT3N0/X patients by multivariate analysis. Prospective studies evaluating adjuvant therapy regimens for UTTC are required.

Coteaching with senior students – a way to refine teachers' PCK for teaching chemical bonding in upper secondary school

NASA Astrophysics Data System (ADS)

Schultze, Felix; Nilsson, Pernilla

2018-04-01

During the last decade there has been on-going discussions about students' declining interest and low achievement in science. One of the reasons suggested for this decline is that teachers and students have different frames of reference, whereby teachers sometimes communicate science in the classroom in a way that is not accessible to the students. There is a lack of research investigating the effects of coteaching with senior students in science in upper secondary schools. To improve teaching and to narrow the gap between teachers' and students' different frames of references, this study investigates how an experienced chemistry teacher gains and refines her pedagogical content knowledge (PCK) by cooperating with two grade 12 students (age 18) as coteachers. The teacher and the two coteachers coplanned, cotaught and coevaluated lessons in chemical bonding in a grade 10 upper secondary class. Findings indicate that the coteachers contributed with their own learning experiences to help the teacher understand how students perceive difficult concepts. In such way, the coteachers were mediating between the teacher and the students, thus bridging the gap between the teacher and the students' frames of references. The teachers' PCK was refined which in turn lead to improved teaching strategies.

Characterization of particle deformation during compression measured by confocal laser scanning microscopy.

PubMed

Guo, H X; Heinämäki, J; Yliruusi, J

1999-09-20

Direct compression of riboflavin sodium phosphate tablets was studied by confocal laser scanning microscopy (CLSM). The technique is non-invasive and generates three-dimensional (3D) images. Tablets of 1% riboflavin sodium phosphate with two grades of microcrystalline cellulose (MCC) were individually compressed at compression forces of 1.0 and 26.8 kN. The behaviour and deformation of drug particles on the upper and lower surfaces of the tablets were studied under compression forces. Even at the lower compression force, distinct recrystallized areas in the riboflavin sodium phosphate particles were observed in both Avicel PH-101 and Avicel PH-102 tablets. At the higher compression force, the recrystallization of riboflavin sodium phosphate was more extensive on the upper surface of the Avicel PH-102 tablet than the Avicel PH-101 tablet. The plastic deformation properties of both MCC grades reduced the fragmentation of riboflavin sodium phosphate particles. When compressed with MCC, riboflavin sodium phosphate behaved as a plastic material. The riboflavin sodium phosphate particles were more tightly bound on the upper surface of the tablet than on the lower surface, and this could also be clearly distinguished by CLSM. Drug deformation could not be visualized by other techniques. Confocal laser scanning microscopy provides valuable information on the internal mechanisms of direct compression of tablets.

Free radical scavenging window of infertile patients with polycystic ovary syndrome: correlation with embryo quality.

PubMed

Huang, Bo; Li, Zhou; Ren, Xinling; Ai, Jihui; Zhu, Lixia; Jin, Lei

2017-06-01

The activity of free radicals in follicular fluid was related to ovarian responsiveness, in vitro fertilization (IVF), and embryo transfer success rate. However, studies analyzing the relationship between the free radical scavenging capacity and embryo quality of infertile women with polycystic ovarian syndrome (PCOS) were lacking. The aim of this study was to evaluate the relationship between the free radical scavenging window of women with PCOS and their embryo quality. The free radical scavenging capacity of follicular fluid from women with PCOS was determined by a,a-diphenyl-b-picrylhydrazyl (DPPH), 2,2-azinobis (3-ethylbenzthiazoline-6-sulphonic acid) assay, superoxide radical, and reactive oxygen species (ROS) assay. In the DPPH and ROS assays, the follicular fluid from grades I and II embryos was significantly higher than the follicular fluid from grades III and IVembryos. The lower control limit of DPPH radical scavenging capacity and upper control limit of ROS level were 13.2% and 109.0 cps, respectively. The calculated lower control limit and upper control limit were further confirmed in the follicular fluid of embryos of all grades. These cut-off values of free radical scavenging activity of follicular fluid could assist embryologists in choosing the development of embryos in PCOS patients undergoing IVF.

Ureteroscopic biopsy of upper tract urothelial carcinoma: comparison of basket and forceps.

PubMed

Kleinmann, Nir; Healy, Kelly A; Hubosky, Scott G; Margel, David; Bibbo, Marluce; Bagley, Demetrius H

2013-12-01

To compare two different biopsy devices for upper tract urothelial carcinoma (UTUC) and evaluate the pathologic result obtained by these devices. From January 2008 to December 2010, 414 ureteroscopies were performed and 504 biopsies were taken for evaluation of UTUC. Two biopsy devices were compared: 2.4F stainless steel flat wire basket and 3F cup biopsy forceps. The effect of the biopsy device on obtaining an adequate pathologic specimen was evaluated using univariate and multivariate binary logistic regression analysis. We also investigated whether tumor grade determination was affected by the biopsy device among patients with a diagnostic biopsy. Diagnosis was successful in 63% and 94% in the forceps and basket groups, respectively (P < 0.0001). Among biopsies with a definite diagnosis of UTUC, specific grade was determined in 80% and 93% in the forceps and basket groups, respectively (P = 0.033). In subgroup analysis of tumors larger than 10 mm in diameter, diagnosis was obtained in 80% and 94% in the forceps and basket groups, respectively (P = 0.037). Cytologic evaluation was found to increase diagnostic rates. The stainless steel flat wire basket was shown to be superior to the 3F cup biopsy forceps in terms of obtaining tissue diagnosis and providing specific grade.

Headache in junior high school students: types & characteristics in Thai children.

PubMed

Visudtibhan, Anannit; Boonsopa, Chompoonoot; Thampratankul, Lunliya; Nuntnarumit, Pracha; Okaschareon, Chusak; Khongkhatithum, Chaiyos; Chiemchanya, Surang; Visudhiphan, Pongsakdi

2010-05-01

To survey the prevalence, types, and characteristics of headache in junior high school students. A two-stage study was conducted in seventh grade students in Bangkok, Thailand. A screening self-administered check-list questionnaire and a face-to-face interview followed by physical examination were performed. Headache was diagnosed and classified according to the Second Edition of the Classification of Headache Disorder criteria. 953 students (448 boys and 505 girls, mean-age 13.2 years) in seventh grade, participated in the present study. Eight hundred thirty three students (87.4%) reported of having five episodes of headache in the past three months. After person-to-person interview; there were 121 (12.6%), 116 (12.1%), nine (0.9%), and seven (0.7%) students who had headache attributing to rhinosinusitis/upper respiratory tract infections, migraine, nonspecific headache with upper-limit systolic blood pressure, and tension-type headache respectively. Lack of sleep and stress related to daily school-activities were reported as headache precipitator in 25 and 23 students with migraine, respectively. School absenteeism was documented in four students with migraine. Only one student received migraine prophylactic treatment. Headache was common in Thai grade seven schoolchildren. Awareness of its high prevalence in these age-group children will lead to early identification of students who may need intervention and specific treatment.

Geologic map of upper Eocene to Holocene volcanic and related rocks in the Cascade Range, Washington

USGS Publications Warehouse

Smith, James G.

1993-01-01

For geothermal reasons, the maps emphasize Quaternary volcanic rocks. Large igneous-related geothermal systems that have high temperatures are associated with Quaternary volcanic fields, and geothermal potential declines rapidly as age increases (Smith and Shaw, 1975). Most high-grade recoverable geothermal energy is likely to be associated with silicic volcanism less than 1 Ma. Lower grade (= lower temperature) geothermal resources may be associated with somewhat older rocks; however, volcanic rocks older than about 2 Ma are unlikely geothermal targets (Smith and Shaw, 1975).

Strongly foliated garnetiferous amphibolite clasts in ophiolitic melanges, Yarlung Zangbo Suture Zone, Tibet; Early Cretaceous disruption of a back-arc basin?

NASA Astrophysics Data System (ADS)

Guilmette, C.; Hebert, R.; Wang, C.; Indares, A. D.; Ullrich, T. D.; Dostal, J.; Bedard, E.

2007-12-01

Metre to decameter-size clasts of amphibolite are found embedded in ophiolitic melanges underlying the Yarlung Zangbo Suture Zone Ophiolites, South Tibet, China. These ophiolites and melanges occur at the limit between Indian and Tibetan-derived rocks and represent remnants of an Early Cretaceous intraoceanic supra-subduction zone domain, the Neo-Tethys. In the Saga-Dazuka segment (500 km along-strike), we discovered new occurrences of strongly foliated amphibolites found as clasts in the ophiolitic melange. In garnet-free samples, hornblende is green-blue magnesio-hornblende and cpx is low-Al diopside. In garnet- bearing samples, garnet is almandine with a strong pyrope component (up to 30 mol%) whereas coexisting hornblende is brown Ti-rich tschermakite and clinopyroxene is Al-diopside. Plagioclase composition was ubiquitously shifted to albite during a late metasomatic event. Geochemistry of these rocks indicates that their igneous protoliths crystallized from a slightly differentiated tholeiitic basaltic liquid that did not undergo major fractionation. Trace element patterns reveal geochemical characteristics identical to those of the overlying ophiolitic crust. These are 1) trace element abundances similar to that of N-MORBs or BABBs, 2) a slight depletion of LREE and 3) a moderate to strong Ta-Nb negative anomaly and a slight Ti anomaly. Such characteristics suggest genesis over a spreading center close to a subduction zone, possibly a back-arc basin. Step-heating Ar/Ar plateau ages were obtained from hornblende separates. All ages fall in the range of 123-128 Ma, overlapping the crystallization ages from the overlying ophiolite (126-131 Ma). Pseudosections were built with the THERMOCALC software in the system NCFMASH. Results indicate that the observed assemblage Hb+Pl+Gt+Cpx is stable over a wide range of P-T conditions, between 10-18 kbars and at more than 800°C. Measured mineral modes and solid solution compositions were successfully modeled, indicating equilibrium between 11-13 kbars and 825-850°C, corresponding to high-P granulite facies conditions. In a general way, the geochemistry of the strongly foliated amphibolite clasts suggests that their igneous protolith probably crystallized within the same supra-subduction zone as the crustal rocks from the overlying ophiolite. Then some of these rocks were entrained to mantle depth and were rapidly exhumed, most likely along a lithospheric scale thrust fault underneath the ophiolite. This event corresponds with the end of magmatic activity within the ophiolitic crust and mantle and could be regarded as the inception of a subduction plane at the spreading ridge of a back-arc basin. The whole package was later on obducted over the Indian passive margin, at about 70 Ma. Such a model suggests that closure of the oceanic domain separating India from Eurasia implied disruption of at least one arc-back-arc system, thus requiring at least one early intraoceanic collision or major plate movement reorganization prior to the Late Cretaceous obduction.

Isotopic constraints on contamination processes in the Tonian Goiás Stratiform Complex

NASA Astrophysics Data System (ADS)

Giovanardi, Tommaso; Mazzucchelli, Maurizio; Lugli, Federico; Girardi, Vicente A. V.; Correia, Ciro T.; Tassinari, Colombo C. G.; Cipriani, Anna

2018-06-01

The Tonian Goiás Stratiform Complex (TGSC, Goiás, central Brazil), is one of the largest mafic-ultramafic layered complexes in the world, emplaced during the geotectonic events that led to the Gondwana accretion. In this study, we present trace elements and in-situ U/Pb-Lu-Hf analyses of zircons and 87Sr/86Sr ratios of plagioclases from anorthosites and gabbros of the TGSC. Although formed by three isolated bodies (Cana Brava, Niquelândia and Barro Alto), and characterized by a Lower and Upper Sequence (LS and US), our new U/Pb zircon data confirm recent geochemical, geochronological, and structural evidences that the TGSC has originated from a single intrusive body in the Neoproterozoic. New Hf and Sr isotope ratios construe a complex contamination history for the TGSC, with different geochemical signatures in the two sequences. The low Hf and high Sr isotope ratios of the Lower Sequence (εHf(t) from -4.2 down to -27.5; 87Sr/86Sr = 0.706605-0.729226), suggest the presence of a crustal component and are consistent with contamination from meta-pelitic and calc-silicate rocks found as xenoliths within the Sequence. The more radiogenic Hf isotope ratios and low Sr isotope composition of the Upper Sequence (εHf(t) from 11.3 down to -8.4; 87Sr/86Sr = 0.702368-0.702452), suggest a contamination from mantle-derived metabasalts in agreement with the occurrences of amphibolite xenoliths in the US stratigraphy. The differential contamination of the two sequences is explained by the intrusion of the TGSC in a stratified crust dominated by metasedimentary rocks in its deeper part and metavolcanics at shallower levels. Moreover, the differential thermal gradient in the two crystallizing sequences might have contributed to the preservation and recrystallization of inherited zircon grains in the US and total dissolution or magmatic overgrowth of the LS zircons via melt/rock reaction processes.