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Sample records for acidic plutonic rocks

  1. Plutonic processes recorded in Iceland's volcanic rocks

    NASA Astrophysics Data System (ADS)

    Maclennan, J.

    2013-12-01

    It has long been understood that the compositions of volcanic rocks from basaltic provinces contain information about magmatic differentiation processes. Whole-rock or pillow-rim glass compositions have previously been sucessfully modelled using the single liquid line of descent (LLD) approach. While the expected cumulate products from the crystallisation and differentiation that drives these LLDs can be predicted from the models, this approach provides little information about the physical nature of the chambers that control basaltic evolution. Development in microanalysis now allows for new types of observations to be acquired that can be used to probe the physics of basaltic chambers. Here, we explore three distinct types of observations from the products of young Icelandic volcanic eruptions which can be used to understand plutonic processes in basaltic systems. Ultimately, these observations can be tied to simple physical models of magma chambers, with the aim of quantifying vigour of convection in magma chambers, the related timescales of evolution and the heights of liquid and mush layers in active chambers. The first observation is based on the relationship between the composition of melt inclusions and the forsterite content of their olivine hosts. Certain trace element ratios, such as La/Yb, are effectively passive tracers of mixing of diverse mantle melts under Iceland. The forsterite content of the host olivine tracks the cooling and differentiation of these mixing liquids. The observations indicate the cooling and mixing is concurrent and is likely to be coupled by convection in liquid layers of magma chambers. Relative rates of mixing and cooling can be quantified from these observations and linked to the vigour of convection in the liquid layer of the chamber. The absolute rate of cooling of these chambers is also linked to the Rayleigh number in this layer, and this value can be constrained by geochemical and geological observations from Iceland

  2. Petrology of the Plutonic Rocks of west-central Alaska

    USGS Publications Warehouse

    Miller, Thomas P.

    1970-01-01

    A series of plutons in west-central Alaska defines the Hogatza plutonic belt which extends for about 200 miles in an east-west direction from the northeastern Seward Peninsula to the Koyukuk River. The plutonic rocks have an aggregate area of about 1,200 square miles and their composition, distribution, and possible petrogenesis are discussed for the first time in this report. Field, petrographic and chemical data supported by K/Ar age dating indicate the plutonic rocks are divisible into two suites differing in age, location, and composition. The western plutons are mid-Cretaceous (~100 m.y.) in age and consist of a heterogeneous assemblage of monzonite, syenite, quartz monzonite. Associated with these granitic rocks is a group of alkaline sub-silicic rocks that forma belt of intrusive complexes extending for a distance of at least 180 miles from west-central Alaska to the Bering Sea. The complex at Granite Mountain shows a rare example of zoning from an alkaline rim to a quartz-bearing core. The occurrence of a similar complex at Cape Dezhnev on the easternmost tip of Siberia suggests the alkaline province may extend into Siberia. The easternmost plutons are Late Cretaceous (180 m.y.) in age and composed primarily of granodiorite and quartz monzonite similar to calc-alkaline plutons found throughout the North America Cordillera. The plutons are epizonal and intrude deformed but unmetamorphosed Lower Cretaceous andesitic volcanics and volcanic graywacke which constitute the highly mobile Yukon-Koyukuk volcanogenic province of west-central Alaska. No older rocks have been found within the confines of this vast tract; the occurrence of a bounding ophiolite sequence has lead to the suggestion that the province was formed by large-scale rifting and is underlain by oceanic crust. The possibility of no juvenile sialic crust over much of the area suggests that the potassium-rich magma now represented by the alkaline rocks originated in the mantle. The distribution of the

  3. Apollo 14 inverted pigeonites - Possible samples of lunar plutonic rocks.

    NASA Technical Reports Server (NTRS)

    Papike, J. J.; Bence, A. E.

    1972-01-01

    Analysis of 'inverted pigeonites' found in Apollo 14 samples 14082 and 14083 (a polymict breccia, the 'white rock') by a combination of optical, electron probe, and single-crystal X-ray diffraction techniques. These 'inverted pigeonites' are regarded as samples of plutonic rocks that have been blasted out of the Imbrium Basin. It is also concluded that lunar pigeonites will invert to orthopyroxenes, given sufficiently slow cooling histories even in very anhydrous environments.

  4. Guidelines to classification and nomenclature of Arabian felsic plutonic rocks

    USGS Publications Warehouse

    Ramsay, C.R.; Stoeser, D.B.; Drysdall, A.R.

    1986-01-01

    Well-defined procedures for classifying the felsic plutonic rocks of the Arabian Shield on the basis of petrographic, chemical and lithostratigraphic criteria and mineral-resource potential have been adopted and developed in the Saudi Arabian Deputy Ministry for Mineral Resources over the past decade. A number of problems with conventional classification schemes have been identified and resolved; others, notably those arising from difficulties in identifying precise mineral compositions, continue to present difficulties. The petrographic nomenclature used is essentially that recommended by the International Union of Geological Sciences. Problems that have arisen include the definition of: (1) rocks with sodic, zoned or perthitic feldspar, (2) trondhjemites, and (3) alkali granites. Chemical classification has been largely based on relative molar amounts of alumina, lime and alkalis, and the use of conventional variation diagrams, but pilot studies utilizing univariate and multivariate statistical techniques have been made. The classification used in Saudi Arabia for stratigraphic purposes is a hierarchy of formation-rank units, suites and super-suites as defined in the Saudi Arabian stratigraphic code. For genetic and petrological studies, a grouping as 'associations' of similar and genetically related lithologies is commonly used. In order to indicate mineral-resource potential, the felsic plutons are classed as common, precursor, specialized or mineralized, in order of increasing exploration significance. ?? 1986.

  5. Tertiary epizonal plutonic rocks of the Selway-Bitterroot Wilderness, Idaho County, Idaho

    SciTech Connect

    Motzer, W.E.

    1996-01-01

    Geologic mapping in the Selway-Bitterroot Wilderness identified approximately 731 kmS of epizonal plutonic granitic rocks within the Bitterroot lobe of the Idaho batholith. From north to south, the intrusions are the Rock Lake Creek stock and the Whistling Pig, Running Creek, Bad Luck and Painted Rocks plutons. The stock and plutons consist of medium- to coarse-grained biotite and hornblende-biotite syenorgranite to monzogranite and quartz syenite capped by fine-grained biotite leucogranite. These rocks are intruded by late-synplutonic leucogranite dikes and post plutonic porphyritic rhyolite to rhyodacite and basalt dikes. The medium-grained granitic rocks are high in SiO2, K2O, Na2O, Ga, Th, U, W and Zr, but low in Al7O3, CaO, MgO, Cr, Ni, Co and V. Most of the granites are peraluminous. Rare-earth element (REE) plots (rock sample/chondrite) show enrichment in light REE over heavy REE with strong EU depletions. K-Ar biotite radiometric age determinations for medium-grained granites in all of the plutons range from approximately 51 Ma (Whistling Pig pluton) to 43.7 Ma (Painted Rocks pluton). Petrogenetic studies suggest that the plutons were rapidly emplaced to within 3.0 km of the paleosurface. The types, textures and color of the rocks result from devolatilization of the crystallizing melt and very low-grade hydrothermal alteration. The fluorine-rich melts are the fractionated with accumulate residue; they are considered to be anorogenic (A-type) granites intruded into the center of a metamorphic core complex.

  6. Stoping & Screen Formation In The Wooley Creek Batholith And Andalshatten Pluton: Complex Pluton - Host Rock Interactions During Magma Emplacement

    NASA Astrophysics Data System (ADS)

    Yoshinobu, A. S.; Hargrove, B.

    2010-12-01

    The presence of xenoliths in plutons is often assumed to either be due to stoping or the formation of screens. Stoped blocks are defined as having undergone significant translation, rotation, and/or internal deformation while incorporated in the magma, while screens are considered to be relatively in situ. However, there remains much controversy as to 1) the relative spatial distribution of xenoliths/screens in plutons; 2) the degree to which xenoliths/screens may or may not have moved within the magma; 3) the extent of melting and assimilation xenoliths undergo; and 4) the mechanism by which xenoliths and screens are incorporated into plutons. We describe field and structural relations from the tilted Wooley Creek batholith (WCb) and the mid-crustal Andalshatten pluton (AHp). Both intrusions preserve xenoliths/screens of a variety of lithologies that correspond to the host rocks. The WCb is a 158-155 MA tilted intrusion emplaced into a series of accreted terranes in the Marble Mountains Wilderness, Klamath Mountains, CA. Previous work has demonstrated that the WCb is complexly zoned, and can be divided into three distinct structural units: a structurally deep unit ranging from gabbro to tonalite, a structurally shallow unit ranging from diorite to granite, and an intermediate unit of intensely deformed quartz diorite and tonalite. Numerous xenoliths of metric to centimetric scale occur in this intermediate zone, as well as in proximity to the pluton roof as exposed along the southern contact. While many of these xenoliths have internal structures that are discordant to those found in the host rock, others seem to maintain concordance with the regional bedding, and are identified as screens. In nearly all cases, xenoliths appear partially migmatitic, and veining of the host magma into them is common. The 442 Ma AHp is a large, predominantly granodioritic pluton in the Bindal Batholith. It intrudes four lithologically distinct and structurally complex nappes of the

  7. Uranium-Lead Zircon Ages and Sr, Nd, and Pb Isotope Geochemistry of Selected Plutonic Rocks from Western Idaho

    USGS Publications Warehouse

    Unruh, Daniel M.; Lund, Karen; Kuntz, Mel A.; Snee, Lawrence W.

    2008-01-01

    Across the Salmon River suture in western Idaho, where allochthonous Permian to Cretaceous oceanic rocks are juxtaposed against Proterozoic North American rocks, a wide variety of plutonic rocks are exposed. Available data indicate much variation in composition, source, and structural state of these plutons. The plutonic rocks were long described as the western border zone of the Cretaceous Idaho batholith but limited pre-existing age data indicate more complicated origins. Because the affinity and age of the plutonic rocks cannot be reliably determined from field relations, TIMS U-Pb dating in conjunction with Sr, Nd, and Pb isotopic studies of selected plutons across the suture in western Idaho were undertaken. The data indicate three general groups of plutons including (1) those that intruded the island arc terranes during the Triassic and Jurassic, those that intruded near the western edge of oceanic rocks along the suture in the Early Cretaceous, and the plutons of the Idaho batholith that intruded Proterozoic North American rocks in the Late Cretaceous. Plutons that intruded Proterozoic North American rocks commonly include xenocrystic zircons and in several cases, ages could not be determined. The least radiogenic Sr and most radiogenic Nd are found among the Blue Mountains superterrane island arc samples. Suture-zone plutons have isotopic characteristics that span the range between Idaho batholith and island arc samples but mostly follow island arc signatures. Plutons of the Idaho batholith have the most radiogenic initial Pb and Sr ratios and the least radiogenic Nd of the samples analyzed.

  8. Field Guide to Plutonic and Metamorphic Rocks. Earth Science Curriculum Project Pamphlet Series PS-5.

    ERIC Educational Resources Information Center

    Romey, William D.

    Suggested are methods for the collection of field evidence about processes that form plutonic and metamorphic rock. Description and discussion of these types of rocks are provided. The planning and execution of a successful field trip is discussed. Advanced field projects are also discussed. Included are five appendices, references, and a…

  9. Oxygen isotopic compositions of Central Andean plutonic and volcanic rocks, latitudes 26°-29° south

    NASA Astrophysics Data System (ADS)

    Longstaffe, Frederick J.; Clark, Alan H.; McNutt, Robert H.; Zentilli, Marcos

    1983-07-01

    Oxygen isotope data are reported for 27 igneous rocks of Mesozoic to Quaternary age from the Central Andes. 26-29°S. The plutonic rocks, and most of the volcanics, have δ18O values between 6.2 and 8.3‰. The whole-rock δ 18O values show a weak correlation with initial 87Sr/ 86Sr data. This O-Sr array differs from documented trends for calc-alkaline plutonic suites from California, Scotland and northern Italy, but overlaps with data for volcanic and plutonic rocks from Ecuador, northern Chile and southern Perú. The oxygen isotope results indicate that the magmas evolved without significant contamination from supracrustal rocks (e.g., rocks that experienced 18O enrichment during surficial weathering). The available O, Sr and Pb isotopic data for these rocks are best explained by magma generation in the upper mantle or lower crust. From the Late Mesozoic on, the 87Sr/ 86Sr values were modified at depth by isotopic exchange between the magma and a continually thickening crust of plutonic rocks of Late Precambrian to early Mesozoic age.

  10. Is there a geochemical link between volcanic and plutonic rocks in the Organ Mountains caldera?

    NASA Astrophysics Data System (ADS)

    Memeti, V.; Davidson, J.

    2013-12-01

    Results from separate volcanic and plutonic studies have led to inconsistent conclusions regarding the origins and thus links between volcanic and plutonic systems in continental arcs and the magmatic processes and time scales responsible for their compositional variations. Some have suggested that there is a geochemical and geochronological disconnect between volcanic and plutonic rocks and hence have questioned the existence of magma mush columns beneath active volcanoes. Investigating contemporary volcanic and plutonic rocks that are spatially connected is thus critical in exploring these issues. The ca. 36 Ma Organ Mountains caldera in New Mexico, USA, represents such a system exposing contemporaneous volcanic and plutonic rocks juxtaposed at the surface due to tilting during extensional tectonics along the Rio Grande Rift. Detailed geologic and structural mapping [1] and 40Ar/39Ar ages of both volcanics and plutons [2] demonstrate the spatial and temporal connection of both rock types with active magmatism over >2.5 myr. Three caldera-forming ignimbrites erupted within 600 kyr [2] from this system with a total erupted volume of 500-1,000 km3 as well as less voluminous pre- and post-caldera trachyte and andesite lavas. The ignimbrite sequence ranges from a crystal-poor, high-SiO2 rhyolite at the base to a more crystal-rich, low-SiO2 rhyolite at the top. Compositional zoning with quartz-monzonite at the base grading to syenite and alaskite at the top is also found in the Organ Needle pluton, the main intrusion, which is interpreted to be the source for the ignimbrites [1]. Other contemporaneous and slightly younger plutons have dioritic to leucogranitic compositions. We examined both volcanic and plutonic rocks with petrography and their textural variations with color cathodoluminescence, and used whole rock element and Sr, Nd and Pb isotope geochemistry to constrain magma compositions and origins. Electron microprobe analyses on feldspars have been completed to

  11. Cretaceous plutonic rocks in the Donner Lake-Cisco Grove area, northern Sierra Nevada, California

    USGS Publications Warehouse

    Kulow, Matthew J.; Hanson, Richard E.; Girty, Gary H.; Girty, Melissa S.; Harwood, David S.

    1998-01-01

    The northernmost occurrences of extensive, glaciated exposures of the Sierra Nevada batholith occur in the Donner Lake-Cisco Grove area of the northern Sierra Nevada. The plutonic rocks in this area, which are termed here the Castle Valley plutonic assemblage, crop out over an area of 225 km2 and for the most part are shown as a single undifferentiated mass on previously published geological maps. In the present work, the plutonic assemblage is divided into eight separate intrusive units or lithodemes, two of which each consist of two separate plutons. Compositions are dominantly granodiorite and tonalite, but diorite and granite form small plutons in places. Spectacular examples of comb layering and orbicular texture occur in the diorites. U-Pb zircon ages have been obtained for all but one of the main units and range from ~120 to 114 Ma, indicating that the entire assemblage was emplaced in a narrow time frame in the Early Cretaceous. This is consistent with abundant field evidence that many of the individual phases were intruded penecontemporaneously. The timing of emplacement correlates with onset of major Cretaceous plutonism in the main part of the Sierra Nevada batholith farther south. The emplacement ages also are similar to isotopic ages for gold-quartz mineralization in the Sierran foothills west of the study area, suggesting a direct genetic relationship between the voluminous Early Cretaceous plutonism and hydrothermal gold mineralization.

  12. Prehnite in plutonic and metamorphic rocks of the northern Santa Lucia Range, Salinian block, California

    USGS Publications Warehouse

    Ross, Donald C.

    1976-01-01

    Prehnite is abundant as monomineralic veins, as lenses in biotite, and as discrete patches and apparent primary crystals in both plutonic and metamorphic rocks along the west edge of the Salinian block in the northern Santa Lucia Range. The prehnite appears to be concentrated near the Sur fault zone but is very rare in Franciscan rocks west of the fault zone. The prehnite does not appear to have been derived by local alteration of minerals in the country rocks (either plutonic or metamorphic). I suggest that solutions, derived from a "substratum" (possibly Franciscan graywacke) beneath the tectonically thinned west margin of the Salinian block, migrated through the fractured rocks of the Salinian block near the Sur fault zone and that the chemical and physical nature of these rocks favored selective prehnite deposition.

  13. Corundum-group minerals in rocks of the Khibiny alkaline pluton, Kola Peninsula

    NASA Astrophysics Data System (ADS)

    Mikhailova, Yu. A.; Konopleva, N. G.; Yakovenchuk, V. N.; Ivanyuk, G. Yu.; Men'shikov, Yu. P.; Pakhomovsky, Ya. A.

    2007-12-01

    Five minerals of the corundum group have been identified in the Khibiny pluton with certainty. Corundum proper and karelianite occur only in hornfels after volcanic and sedimentary rocks. Xenoliths of hornfels mark the ring faults that bound foidalite within the field of foyaite. Hematite occurs in hydrothermally altered nepheline syenite and crosscutting hydrothermal veins related to the ring faults. Minerals of the ilmenite-pyrophanite series are present in all rocks of the pluton, including veins. Accessory ilmenite in foyaite varies from the manganese variety and pyrophanite in the inner and outer parts of the pluton to manganese-free ilmenite in zone of the Main Ring Fault. In xenoliths of volcanic rocks and alkaline ultramafic rocks, ilmenite is enriched in magnesium. The zoning in distribution of the above-mentioned minerals and the character of variation in their compositions from margins of the pluton to its center are consistent with the petrochemical zoning formed as a result of foyaite alteration of near ring faults.

  14. Potassium-argon and lead-alpha ages of plutonic rocks, Bokan Mountain area, Alaska

    USGS Publications Warehouse

    Lanphere, M.A.; MacKevett, E.M., Jr.; Stern, T.W.

    1964-01-01

    Most of the granitic rocks in the Bokan Mountain area, southeastern Alaska, are early Paleozoic (probably Ordovician) judged by potassium-argon and lead-alpha age measurements. The Bokan Mountain Granite, the youngest intrusive unit in the area, belongs to a Mesozoic plutonic episode. These age measurements are the first direct evidence for the emplacement of early Paleozoic granitic intrusive rocks close to the Pacific margin of North America.

  15. Potassium-Argon and Lead-Alpha Ages of Plutonic Rocks, Bokan Mountain Area, Alaska.

    PubMed

    Lanphere, M A; Mackevett, E M; Stern, T W

    1964-08-14

    Most of the granitic rocks in the Bokan Mountain area, southeastern Alaska, are early Paleozoic (probably Ordovician) judged by potassium-argon and lead-alpha age measurements. The Bokan Mountain Granite, the youngest intrusive unit in the area, belongs to a Mesozoic plutonic episode. These age measurements are the first direct evidence for the emplacement of early Paleozoic granitic intrusive rocks close to the Pacific margin of North America. PMID:17754670

  16. Physical Properties and Distribution of Intrusive Rocks (Plutons) in the Great Basin

    NASA Astrophysics Data System (ADS)

    Ponce, D. A.; Watt, J. T.; Glen, J. M.

    2010-12-01

    The distribution of intrusive rocks throughout the Great Basin is important because many plutons are associated with base and precious metal mineral deposits, and may provide insights on regional magmatism and tectonism. Combined information on their physical properties and geophysical signatures will allow improvements on their inferred horizontal extent and facilitate modeling their subsurface structure. Physical property measurements of over 1700 plutonic rock samples in the Great Basin, excluding those in the Sierra Nevada, show an average grain density of about 2670 and a range of about 2260 to 3200 kg/m3; show an average saturated bulk density of about 2630 and a range of about 2290 to 3050 kg/m3; an average magnetic susceptibility of about 0.007 and range from essentially non-magnetic to 0.126 SI-units (equivalent to just over 3 per cent magnetite). As a comparison, over 6,000 granitic samples in the Sierra Nevada (Sikora et al., 1991) have an average grain density of about 2690 and a range of about 2420 to 2780 kg/m3; an average magnetic susceptibility of about 0.006 and range from essentially non-magnetic to 0.016 SI-units (equivalent to about 0.4 per cent magnetite). Remanent magnetizations were measured for selected plutons, for example the remanent magnetization of the Ibapah pluton in the Deep Creek Range, Utah is relatively low and has a Koenigsberger ratio (the ratio between remanent and induced magnetization) of about 0.1. In Nevada, previous pluton extents (Grauch et al., 1988; Grauch , 1996) have been only slightly modified. For example, the Cretaceous to Jurassic stock at Blue Mountain, north-central Nevada (Wilden, 1964) is now mapped as a diorite dike swarm (Wyld, 2002) and thought to be mid-Miocene and related to the inception of the Yellowstone Hotspot (Ponce et al, 2010). Magnetic and gravity data indicate that a possible pluton (or other magnetic basement rock), the top of which could be at moderate crustal depths, is skewed from the

  17. Rock-Forming feldspars of the Khibiny alkaline pluton, Kola Peninsula, Russia

    NASA Astrophysics Data System (ADS)

    Ivanyuk, G. Yu.; Pakhomovsky, Ya. A.; Konopleva, N. G.; Kalashnikov, A. O.; Korchak, Yu. A.; Selivanova, E. A.; Yakovenchuk, V. N.

    2010-12-01

    This paper describes the structural-compositional zoning of the well-known Khibiny pluton in regard to rock-forming feldspars. The content of K-Na-feldspars increases inward and outward from the Main foidolite ring. The degree of coorientation of tabular K-Na-feldspar crystals sharply increases in the Main ring zone, and microcline-dominant foyaite turns into orthoclase-dominant foyaite. The composition of K-Na-feldspars in the center of the pluton and the Main ring zone is characterized by an enrichment in Al. This shift is compensated by a substitution of some K and Na with Ba (the Main ring zone) or by an addition of K and Na cations to the initially cation-deficient microcline (the central part of the pluton). Feldspars of volcanosedimentary rocks occurring as xenoliths in foyaite primarily corresponded to plagioclase An15-40, but high-temperature fenitization and formation of hornfels in the Main ring zone gave rise to the crystallization of anorthoclase subsequently transformed into orthoclase and albite due to cooling and further fenitization. Such a zoning is the result of filling the Main ring fault zone within the homogeneous foyaite pluton with a foidolite melt, which provided the heating and potassium metasomatism of foyaite and xenoliths of volcanosedimentary rocks therein. The process eventually led to the transformation of foyaite into rischorrite-lyavochorrite, while xenoliths were transformed into aluminum hornfels with anorthoclase, annite, andalusite, topaz, and sekaninaite.

  18. Petrology and U-Pb geochronology of buried Avalonian plutonic rocks on southeastern Cape Cod

    USGS Publications Warehouse

    Leo, G.W.; Mortensen, J.K.; Barreiro, B.; Phillips, J.D.

    1993-01-01

    Plutonic rocks have been intersected by two separate drill holes on souteastern Cape Cod. Hole CC2 is located about 7 km south of the Nauset anomaly, an east-northeast-trending magnetic lineament that was considered to separate the distinct plutonic zones of Avalon terrane. This drill hole intersected weakly foliated, fairly homogeneous biotite granite. Zircons from this granite give a U-Pb age of 584+9/-8 Ma. Hole CC1 is located about 12 km north of the Nauset anomaly. The drill core intersected foliated, sheared, biotite granodiorite and biotite-hornblende-clinopyroxene-quartz gabbro, metamorphosed to greenschist facies. The deformed and altered state of these rocks, as well as their geochemistry, suggest that their origin and possibly their ages are distinct from the granite in hole CC2. No datable zircons were obtained from rocks in CC1. -from Authors

  19. Spinel-group minerals in rocks of the Khibiny alkaline pluton, Kola Peninsula

    NASA Astrophysics Data System (ADS)

    Ivanyuk, G. Yu.; Pakhomovsky, Ya. A.; Konopleva, N. G.; Yakovenchuk, V. N.; Men'shikov, Yu. P.; Mikhailova, Yu. A.

    2007-12-01

    Seven spinel-group minerals in various geological settings have been revealed in the rocks of the Khibiny pluton. Hercynite, gahnite, and vuorelainenite occur only in xenoliths of hornfels after volcanic and sedimentary rocks, whereas spinel and magnesiochromite occur in alkaline ultramafic rocks of dike series. Franklinite has been discovered in a low-temperature hydrothermal vein. Ubiquitous magnetite is abundant in foyaite, foidolites, alkaline ultrabasic rocks, and pegmatite and hydrothermal veins and may even be the main mineral in some foidolite varieties. The spinel-group minerals are characterized by various chemical compositions due to the fractionation of nepheline syenites resulting in formation of the Main ring of foidolites and apatite-nepheline ore. Like most other minerals found throughout the pluton, magnetite is characterized by variation in the chemical composition along the radial line from the contact with country Proterozoic volcanic rocks to the geometric center of the pluton. Toward the center, the total Ti and Mn contents in magnetite increase from 5 15 up to 40 at %.

  20. Chemistry and petrology of the Apennine Front, Apollo 15. I - KREEP basalts and plutonic rocks. II - Impact melt rocks

    NASA Technical Reports Server (NTRS)

    Simon, S. B.; Papike, J. J.; Laul, J. C.

    1988-01-01

    The mineralogy, petrology, and chemistry of rock fragments for the Apennine Front coarse fines (10-4 and 4-2 mm) have been determined. The data are consistent with a single eruptive event that produced several flows. It is found that most of the plutonic rocks are ferroan in nature, with a few belonging to the Mg-suite. The mineral and bulk chemistry of KREEP basalts and the composition of ferroan anorthosites are discussed. Petrographic studies of 21 impact melts are also presented, showing a variety of textures. It is found that the Apollo 15 impact melts are mixtures of low-K Fra Mauro, KREEP, and plutonic components. The Ni/Ir ratios of the melt rocks are shown to be greater than chondritic values, indicating ancient and/or iron meteorite components.

  1. An underground characterization program for a nuclear fuel waste disposal vault in plutonic rock

    SciTech Connect

    Thompson, P.M.; Everitt, R.A.

    1993-12-31

    The Canadian Nuclear Fuel Waste Management Program (CNFWMP) is developing a concept for disposing of nuclear fuel waste that involves placing and sealing it in a disposal vault excavated 500 to 1,000 m deep in the stable plutonic rock of the Canadian Shield. In this concept, engineered and natural barriers serve to isolate the waste from the biosphere. Since 1983, underground characterization and testing in support of the CNFWMP has been ongoing at the Underground Research Laboratory (URL) in southeastern Manitoba. This paper draws on experience gained at the URL to recommend an approach to underground characterization that would provide the necessary information to make design decisions for a disposal vault in plutonic rock.

  2. Paleoproterozoic layered PGE-bearing Monchetundra pluton, Kola Peninsula: Sm-Nd age of metamorphic alteration of mafic rocks

    NASA Astrophysics Data System (ADS)

    Kunakkuzin, E. L.; Serov, P. A.; Bayanova, T. B.; Nerovich, L. I.; Borisenko, E. S.

    2015-09-01

    The aim of this work is Sm-Nd study of metamorphic alteration of massive gabbronorites from the Monchetundra pluton. The mafic rocks of the pluton are unevenly metamorphosed up to amphibolite facies with the formation of garnet, hornblende, and other minerals. The presence of garnet is a distinctive feature of this pluton in comparison with other Paleoproterozoic PGE-bearing plutons of the eastern part of the Baltic shield: Mt. General'skaya, Fedorovo-Pana, Imandra lopolith, and Monchepluton [9]. The degree of metamorphic alteration of rocks increases near the faults, the largest of which is Monchetundra fault separating the studied pluton from the Monchepluton. This fault was formed about 1.9-2.0 Ga ago according to Sm-Nd and Rb-Sr mineral isochrons for minerals from metagabbro-anorthosites of the M1 well.

  3. Isotopic studies of the late Archean plutonic rocks of the Wind River Range, Wyoming.

    USGS Publications Warehouse

    Stuckless, J.S.; Hedge, C.E.; Worl, R.G.; Simmons, K.R.; Nkomo, I.T.; Wenner, D.B.

    1985-01-01

    Two late Archaean intrusive events were documented in the Wind River Range by isotopic studies of the Rb-Sr and U-Th-Pb systems in whole-rock samples and the U-Pb systematics for zircon. An age of approx 2630(20) m.y. for the Louis Lake batholith and apparent ages of 2504(40) to 2575(50) m.y. for the Bear Ears pluton were obtained. Post-magmatic hydrothermal events approximately Tertiary in age, lowered delta 18O values and disturbed parent-daughter relationships in most of the isotopic systems investigated. The two intrusive units apparently were derived from different protoliths. Initial isotopic ratios and petrochemistry for the Louis Lake batholith are consistent with an early Archaean trondhjemitic to tonalitic source. The protolith for the Bear Ears pluton must have been subjected to high-grade metamorphism that caused loss of Rb and U prior to magma generation. -L.C.H.

  4. Intrusive rocks of the Holden and Lucerne quadrangles, Washington; the relation of depth zones, composition, textures, and emplacement of plutons

    USGS Publications Warehouse

    Cater, Fred W.

    1982-01-01

    The core of the northern Cascade Range in Washington consists of Precambrian and upper Paleozoic metamorphic rocks cut by numerous plutons, ranging in age from early Triassic to Miocene. The older plutons have been eroded to catazonal depths, whereas subvolcanic rocks are exposed in the youngest plutons. The Holden and Lucerne quadrangles span a -sizeable and representative part of this core. The oldest of the formations mapped in these quadrangles is the Swakane Biotite Gneiss, which was shown on the quadrangle maps as Cretaceous and older in age. The Swakane has yielded a middle Paleozoic metamorphic age, and also contains evidence of zircon inherited from some parent material more than 1,650 m.y. old. In this report, the Swakane is assigned an early Paleozoic or older age. It consists mostly of biotite gneiss, but interlayered with it are scattered layers and lenses of hornblende schist and gneiss, clinozoisite-epidote gneiss, and quartzite. Thickness of the Swakane is many thousands of meters, and the base is not exposed. The biotite gneiss is probably derived from a pile of siliceous volcanic rocks containing scattered sedimentary beds and basalt flows. Overlying the Swakane is a thick sequence of eugeosynclinal upper Paleozoic rocks metamorphosed to amphibolite grade. The sequence includes quartzite and thin layers of marble, hornblende schist and gneiss, graphitic schist, and smaller amounts of schist and gneiss of widely varying compositions. The layers have been tightly and complexly folded, and, in places, probably had been thrust over the overlying Swakane prior to metamorphism. Youngest of the supracrustal rocks in the area are shale, arkosic sandstone, and conglomerate of the Paleocene Swauk Formation. These rocks are preserved in the Chiwaukum graben, a major structural element of the region. Of uncertain age, but possibly as old as any of the intrusive rocks in the area, are small masses of ultramafic rocks, now almost completely altered to

  5. Intrusive rocks and plutonic belts of southeastern Alaska, U.S.A.

    USGS Publications Warehouse

    Brew, David A.; Morrell, Robert P.

    1983-01-01

    About 30 percent of the 175,000-km2 area of southeastern Alaska is underlain by intrusive igneous rocks. Compilation of available information on the distribution, composition, and ages of these rocks indicates the presence of six major and six minor plutonic belts. From west to east, the major belts are: the Fairweather-Baranof belt of early to mid-Tertiary granodiorite; the Muir-Chichagof belt of mid-Cretaceous tonalite and granodiorite; the Admiralty-Revillagigedo belt of porphyritic granodiorite, quartz diorite, and diorite of probable Cretaceous age; the Klukwan-Duke belt of concentrically zoned or Alaskan-type ultramafic-mafic plutons of mid-Cretaceous age within the Admiralty-Revillagigedo belt; the Coast Plutonic Complex sill belt of tonalite of unknown, but perhaps mid-Cretaceous, age; and the Coast Plutonic Complex belt I of early to mid-Tertiary granodiorite and quartz monzonite. The minor belts are distributed as follows: the Glacier Bay belt of Cretaceous and(or) Tertiary granodiorite, tonalite, and quartz diorite lies within the Fair-weather-Baranof belt; layered gabbro complexes of inferred mid-Tertiary age lie within and are probably related to the Fairweather-Baranof belt; the Chilkat-Chichagof belt of Jurassic granodiorite and tonalite lies within the Muir-Chichagof belt; the Sitkoh Bay alkaline, the Kendrick Bay pyroxenite to quartz monzonite, and the Annette and Cape Fox trondhjemite plutons, all interpreted to be of Ordovician(?) age, together form the crude southern southeastern Alaska belt within the Muir-Chichagof belt; the Kuiu-Etolin mid-Tertiary belt of volcanic and plutonic rocks extends from the Muir-Chichagof belt eastward into the Admiralty-Revillagigedo belt; and the Behm Canal belt of mid- to late Tertiary granite lies within and next to Coast Plutonic Complex belt II. In addition, scattered mafic-ultramafic bodies occur within the Fairweather-Baranof, Muir-Chichagof, and Coast Plutonic Complex belts I and II. Palinspastic

  6. Plutonic rocks of Jurassic age in the Alaska-Aleutian Range batholith: chemical variation and polarity.

    USGS Publications Warehouse

    Reed, B.I.; Miesch, A.T.; Lanphere, M.A.

    1983-01-01

    Plutonic rocks of Jurassic age exposed on the Pacific side of this batholith form a compositionally continuous calc-alkaline suite that ranges from hornblende gabbro to quartz monzonite. Tonalite and quartz diorite are the dominant rock types. Trend-surface analysis of 102 samples indicates that the direction of slope of the trend is approximately normal to the Jurassic magmatic arc. K2O and SiO2 increase towards the E-SE and the other oxides towards the W-NW. If the chemical trends reflect the approximate geometry of a palaeo-subduction zone, the polarity of the Jurassic magmatic arc is to the NW, i.e. subduction was directed towards the SE. Thus the palaeo-subduction zone is on the opposite side of the arc from the position that has generally been assumed, indicating that the Jurassic plutonic rocks were not generated in response to classical Andean-type convergent plate margins. The magmatic arc may have been formed in an intra-ocean environment and subsequently has been rafted northwards and accreted to this part of the N Pacific rim during the late Mesozoic. Middle and Upper Jurassic clastics underlying Cook Inlet to the SE and derived from the magmatic arc are classified as back-arc deposits, rather than as an arc-trench gap sequence.-L.C.H.

  7. Europium mass balance in polymict samples and implications for plutonic rocks of the lunar crust

    SciTech Connect

    Korotev, R.L.; Haskin, L.A. )

    1988-07-01

    From correlations of SM concentration and Sm/Eu ratio with Th concentration for a large number of polymict samples from various locations in the lunar highlands and the value of 0.91 {mu}g/g for the mean Th concentration of the highlands surface crust obtained by the orbiting gamma-ray experiments. The authors estimate the mean concentrations of Sm and Eu in the lunar surface crust to be between 2 and 3 {mu}g/g Sm and 0.7 and 1.2 {mu}g/g Eu. The compositional trends indicate that there is no significant enrichment or depletion of Eu, on the average, compared to Sm relative to chondritic abundances, i.e., there is no significant Eu anomaly in average upper crust. Although rich in plagioclase ({approximately}70%), the upper crust does not offer evidence for a gross vertical separation of plagioclase from the final liquid from which it crystallized. This and the chondritic ratio of Eu/Al in average highlands material imply that the net effect of the processes that led to formation of the lunar crust was to put most of the Al and incompatible elements in the crust. Among plutonic rocks, only plagioclase in rocks from the magnesian suite can supply the excess Eu in the polymict rocks. Owing to the intermediate value of the mean Mg/Fe ratio of the crust, a significant fraction of the mafic rocks of the lunar highlands must have lower Mg/Fe ratios than the norites and troctolites of the magnesian-suite of plutonic rocks. A large fraction of the plagioclase in the lunar crust is associated not with ferroan anorthosite, but with more mafic rocks. There is little evidence in the Eu data that the lunar crust ever consisted of a thick shell of nearly pure plagioclase, as envisioned in some formulations of the magma ocean model of its formation.

  8. Map showing the distribution and characteristics of plutonic rocks in the Tonopah 1 degree by 2 degrees Quadrangle, central Nevada

    USGS Publications Warehouse

    John, D.A.

    1987-01-01

    The accompanying table includes the name (if any) of the pluton and its location, the age of the pluton (either a radiometric age or an age inferred from field relations), modal composition, texture, mineralogy, hydrothermal alteration and mineralization related to the pluton, the source of mapping shown on this map, and published references on the pluton. Radiometric ages are either published K-Ar and fission track ages or new whole-rock Rb-Sr ages determined by A. C. Robinson on samples collected either for this study or as part of regional Sr-isotope studies by R.W. Kistler and A.C. Robinson. K-Ar ages published prior to 1977 are corrected using the new I.U.C.S. constants (Steiger and Jager, 1977). Muscovite alteration ages are reported for several plutons and represent minimum ages for emplacement of these plutons. Compositional classification follows the T. J. G.S. system (“Streckeisen, 1976) and is based either on modal analyses of slabs or estimates from hand specimens. All modes, unless otherwise noted, were measured in this study. The number of modes determined is shown in parentheses, and the range in volume percent of major minerals is given. Where no modal data are available, the color index (percentage of mafic minerals) and major mafic minerals are given for most plutons. Data tabulated on hydrothermal alteration and mineralization related to plutons are based on observations made during field studies for this project. Clear genetic relation between granitic plutonism and several mineral deposits previously attributed to granitic plutonism were not substantiated, and these inconsistencies are noted in the table.

  9. Emplacement and geochemical evolution of eocene plutonic rocks in the Colville batholith

    SciTech Connect

    Holder, R.W.

    1986-01-01

    Eocene plutonic rocks in the Colville batholith are divided on the basis of field evidence and chemical composition into, in order of decreasing age, (1) several calc-alkalic biotite-hornblende monzodiorite to granodiorite intrusions referred to as the Devils Elbow suite, and (2) compositionally variable calc-alkalic to alkali-calcic intrusions referred to as the Herron Creek suite. These Eocene suites are distinct from older, more voluminous, leucocratic granite and granodiorite intrusions, designated the Keller Butte suite, which are calcic and characteristically lack hornblende. Results of qualitative and computer modeling of major element variation and quantitative models of trace element variation in the chemically coherent Bridge Creek intrusions, a member of the Herron Creek suite, are compatible with fractionation of plagioclase feldspar + hornblende + biotite + magnetite + apatite from a parent magma of andesitic composition to account for the observed variation. Strongly curved variation trends preclude mixing as the primary mechanism for the observed variation. It is suggested that parallel variation trends in the other Eocene intrusions are also the result of crystal fractionation. Lateral chemical variations including a decrease in silica saturation suggest the chemical characteristics of these rocks reflect those of parental magmas derived from the mantle, with an unknown amount of crustal contribution. Rotated and angular xenoliths, discordant contacts, and temporal and spatial proximity to graben structures indicate that the Eocene plutons were passively implaced into the upper crust along graben-bounding faults during graben formation, the earlier stages of which appear to have been contemporaneous with regional mylonitic deformation.

  10. Geochemical evaluation of felsic plutonic rocks in the eastern and southeastern Arabian Shield, Kingdom of Saudi Arabia

    USGS Publications Warehouse

    Du Bray, E.A.; Elliott, James E.; Stoeser, D.B.

    1983-01-01

    In a geochemical evaluation of the eastern and southeastern Arabian Shield, which included collection of 696 rock samples and 694 pan concentrate samples, a province of tin-anomalous granitoid plutons was defined. Pan concentrates collected in and around these plutons were enriched in tin and tungsten relative to the concentrate population. Rock samples of these leucocratic, muscovite-bearing, peraluminous granites contained anomalously high concentrations of lithium, fluorine, beryllium, lead, rubidium, niobium, yttrium, tin, bismuth, silver, and tungsten. Ten tin-anomalous plutons were located in the study area. The plutons are typically small, less than 10 km2 in areal extent, and circular to elliptical in plan view. The resource potential of these latest Proterozoic plutons has not been established; economically exploitable concentrations of tin, tungsten, molybdenum, or zinc may be present, and followup studies are warranted. Further, two of the plutons are characterized by higher than normal total-count radioactivity and have potential for uranium, thorium, or rare-earth element deposits.

  11. Distribution of manganese between coexisting biotite and hornblende in plutonic rocks

    USGS Publications Warehouse

    Greenland, L.P.; Gottfried, D.; Tilling, R.I.

    1968-01-01

    The distribution of manganese between coexisting biotite and hornblende for 80 mineral pairs from igneous rocks of diverse provenance (including Southern California, Sierra Nevada, Boulder, and Boulder Creek batholiths and the Jemez Mountains volcanics) has been determined by neutron activation analysis. Data on the distribution ratio (Kd = Mnhornblende Mnbiotite) indicate that an equilibrium distribution of Mn is closely approached, though not completely attained, in most samples from plutonic environments. Comparison of Kd values of mineral pairs with bulk chemical composition of host rocks reveals no correlation. Because initial crystallization temperatures vary with rock composition, the lack of correlation of composition with Kd suggests that the equilibrium distribution of Mn between biotite and hornblende reflects exchange at subsolidus temperatures rather than initial crystallization temperatures. The highest Kd values are for volcanic rocks, in which rapid quenching prevents subsolidus redistribution of Mn. For sample pairs from the Southern California and Sierra Nevada batholiths there is a positive correlation of Kd with TiO2 content of biotite. Though the evidence is not compelling, Kd may also correlate with the rate of cooling and/or the presence or absence of sphene in the rock. ?? 1968.

  12. Transport and Depositional Model for Large Country Rock Blocks Within the Searchlight Pluton, Southern Nevada

    NASA Astrophysics Data System (ADS)

    Perrault, D. S.; Furbish, D. J.; Miller, C. F.

    2006-05-01

    Searchlight pluton, a steeply tilted, 10 km thick Miocene intrusion in the Colorado River Extensional Corridor, exposes a zone with abundant, 5-400 m long blocks of Proterozoic gneiss. Blocks are present within a pair of subparallel horizons that make up a 2 km-thick zone and extend about 6 km laterally away from the pluton's north margin slightly oblique to the initially subhorizontal boundary between the pluton's middle unit (granite) and lower unit (qtz monzonite). Blocks are a variety of Precambrian metasedimentary gneisses, granitic gneisses, and mylonites. Blocks are commonly polylithologic and well foliated, with long and intermediate dimensions parallel to both their own foliation and that of the granitic host. Their average aspect ratio is ~ 4:1. Blocks within these horizons are interpreted as stoped (detached country rock that experience gravity- induced displacement) based on several lines of evidence. First, the distribution and abundances of blocks are not consistent with an isolated panel of wall rock (screen). The zone is laterally discontinuous (local abundances vary from ~ 0-40 %); transects a gradational (cm-m scale) internal contact at a slightly oblique angle; and tapers away from the pluton's margin. Second, while block foliations are homoclinal and show fairly consistent attitudes from block to block, block foliations are discordant with wall rock foliations at the same stratigraphic level (adjacent north wall). Third, mush disturbance features such as schlieren and enhanced feldspar foliation beneath blocks suggest a downward compaction. We interpret the blocks to have been emplaced after wall collapse events. We are using scaled settling experiments to clarify how blocks move within viscous fluids and interact with crystal mushes. The experiments, involving tabular ceramic blocks with density ρ = 1.75-2.20 g cm-3 settling in shampoo (ρ = 1.02 g cm-3) with viscosity μ = 20.35 Pa s, are scaled to order-of-magnitude by the particle Reynolds

  13. Map showing distribution and classification of felsic plutonic rocks in the eastern Arabian Shield, Kingdom of Saudi Arabia

    USGS Publications Warehouse

    Du Bray, E.A.

    1983-01-01

    This 1:500,000-scale compilation shows the distribution of felsic plutonic rocks, lithologic types, and associated mineralization in an area between lat 21° and 24°30’ N., long 43°30’ and 46° E. It is part of a shieldwide compilation being done within the framework of Saudi Arabian Deputy Ministry for Mineral Resources projects 2.04 and 3.12.

  14. Geochemistry of intrusive rocks associated with the Latir volcanic field, New Mexico, and contrasts between evolution of plutonic and volcanic rocks

    USGS Publications Warehouse

    Johnson, C.M.; Czamanske, G.K.; Lipman, P.W.

    1989-01-01

    Plutonic rocks associated with the Latir volcanic field comprise three groups: 1) ???25 Ma high-level resurgent plutons composed of monzogranite and silicic metaluminous and peralkaline granite, 2) 23-25 Ma syenogranite, and alkali-feldspar granite intrusions emplaced along the southern caldera margin, and 3) 19-23 Ma granodiorite and granite plutons emplaced south of the caldera. Major-element compositions of both extrusive and intrusive suites in the Latir field are broadly similar; both suites include high-SiO2 rocks with low Ba and Sr, and high Rb, Nb, Th, and U contents. Moreover, both intermediateto siliciccomposition volcanic and plutonic rocks contain abundant accessory sphene and apatite, rich in rare-earth elements (REE), as well as phases in which REE's are essential components. Strong depletion in Y and REE contents, with increasing SiO2 content, in the plutonic rocks indicate a major role for accessory mineral fractionation that is not observed in volcanic rocks of equivalent composition. Considerations of the rheology of granitic magma suggest that accessory-mineral fractionation may occur primarily by filter-pressing evolved magmas from crystal-rich melts. More limited accessory-mineral crystallization and fractionation during evolution of the volcanic magmas may have resulted from markedly lower diffusivities of essential trace elements than major elements. Accessory-mineral fractionation probably becomes most significant at high crystallinities. The contrast in crystallization environments postulated for the extrusive and intrusive rocks may be common to other magmatic systems; the effects are particularly pronounced in highly evolved rocks of the Latir field. High-SiO2 peralkaline porphyry emplaced during resurgence of the Questa caldera represents non-erupted portions of the magma that produced the Amalia Tuff during caldera-forming eruption. The peralkaline porphyry continues compositional and mineralogical trends found in the tuff. Amphibole

  15. Rock deformation in hydrothermal systems: the nature of fractures in plutons and their host rocks. Technical progress report

    SciTech Connect

    Norton, D.

    1981-11-01

    The purpose of this program is to accumulate the types of field data which are important for the analysis of magma-hydrothermal systems. The structural effects of thermal processes were identified in order to distinguish the thermally induced deformations from the deformations that occurred subsequent to complete cooling of the system. Mapping techniques were developed to record the structural data on the ground from local domains characteristic of larger areas in the magma chamber, and in the air from low-angle oblique aerial photography of the entire region. The ground system is complete and preliminary testing is currently being carried out to verify the method. The results indicate that granitic crystalline rocks have no structural resistance to thermal perturbations. If nuclear wastes are to be stored in granite, precautionary buffers would have to be incorporated into the system. A total of 30 fossil magma chambers have been studied over the past 2 years. An extensive set of fracture imagery has been collected, together with information related to the geological history of the plutons. Fossil magma chambers in Arizona, Utah, California, Washington, Montana, and British Columbia have been studied.

  16. Forceful emplacement of the Eureka Valley-Joshua Flat-Beer Creek composite pluton into a structural basin in eastern California; internal structure and wall rock deformation

    NASA Astrophysics Data System (ADS)

    Morgan, Sven; Law, Richard; de Saint Blanquat, Michel

    2013-11-01

    Anisotropy of Magnetic Susceptibility parameters have been analyzed at 311 locations in the Eureka Valley-Joshua Flat-Beer Creek (EJB) pluton of eastern California. The large amount of data has allowed for the AMS parameters to be contoured using techniques that both reveal map-scale trends and emphasize small-scale differences. The contour maps suggest that magnetic susceptibility is dominantly controlled by composition of the magma but may also be affected by emplacement-related strain as the magma chamber inflated and forced the wall rocks outward. Pluton construction involved two major pulses of different composition magmas that were emplaced sequentially but with overlapping periods of crystallization. The magmas initially intruded as sill-like bodies into a structural basin. The magnetic foliation of the pluton cuts across internal magmatic contacts on the map scale and is parallel to local contacts between the pluton and surrounding metasedimentary wall rocks. The magnetic fabric is similar in orientation and symmetry to intense flattening strains recorded in the aureole rocks. The metasedimentary wall rocks have been shortened between 60 and 70% and this strain magnitude is approximately equal on the west, south, and east margins of the pluton. Strain in the wall rocks is dominantly flattening and concentrated into a narrow (1 km wide) inner aureole. Mapping of bedding/cleavage intersection lineations south of the pluton indicates that the magma made room for itself by translating the wall rocks outward and rotating the already inward dipping wall rocks of the structural basin to sub-vertical. Stretching of the inner aureole around an expanding magma chamber was responsible for the intense shortening. Limited data on the Marble Canyon pluton to the south of the EJB pluton indicates a very similar emplacement process.

  17. Plutonic and metamorphic xenoliths from the Cascada Tuff, Chihuahua, Mexico, as evidence indicating the composition of the basement rocks beneath the Sierra Madre Occidental

    SciTech Connect

    Duex, T.W.

    1985-01-01

    The Sierra Madre Occidental of western Mexico is composed dominantly of Mid-Tertiary felsic and subordinate mafic volcanic rocks with only sparse outcrops of non-volcanic rocks. There are widely scattered but small exposure of plutonic rocks but regionally metamorphosed rocks are not known to occur in the Sierra. To this date the only known area where plutonic and metamorphic xenoliths have been found is near the village of Basaseachic in western Chihuahua where thick outcrops of the Cascada Tuff occur. The xenoliths are the only known occurrence of regionally metamorphosed rocks for a distance of about 400 km between exposures of Precambrian rocks to the west in Sonora and the east in central Chihuahua. Non-volcanic xenoliths from a few cm to about one meter in diameter occur most abundantly in the upper portions of the Cascada Tuff. They can be divided into four main groups in decreasing order of abundance as follows: (1) coarse-grained phaneritic felsic igneous rocks; (2) cataclastically deformed plutonic rocks; (3) fine-grained phaneritic, mafic to intermediate igneous rocks; and (4) low-grade schistose, gneissic, and non-foliated metamorphic rocks. The lithological composition of the xenoliths is grossly similar to that described for Precambrian metamorphic and plutonic rocks from northern Mexico and the southwestern US.

  18. A tale of 10 plutons - Revisited: Age of granitic rocks in the White Mountains, California and Nevada

    USGS Publications Warehouse

    McKee, E.H.; Conrad, J.E.

    1996-01-01

    40Ar/39Ar incremental heating analysis and conventional K-Ar age determinations on plutonic rocks of the White Mountains define two stages of magmatic emplacement: Late Cretaceous, between ca. 90 Ma and 75 Ma, and Middle-Late Jurassic, between ca. 180 and 140 Ma. The Jurassic stage can be divided into two substages, 180-165 Ma and 150-140 Ma. Thermal effects of the younger plutons on the older granitoids partially to completely reset ages, making it difficult to determine the age of emplacement and cooling of several of the plutons even by 40Ar/39Ar incremental heating analyses. New data together with published ages and regional geochronological synthesis of the Sierra Nevada batholith indicate that regions within the batholith have coherent periods or episodes of magmatic activity. In the White Mountains and Sierra Nevada directly to the west there was little or no activity in Early Jurassic and Early Cretaceous time; magmatism took place during relatively short intervals of 15 m.y. or less in the Middle and Late Jurassic and Late Cretaceous periods. The new K-Ar and 40Ar/39Ar analyses of granitoids from the White Mountains help, but do not completely clarify the complex history of emplacement, cooling, and reheating of the batholith.

  19. Investigation of Plutonic Rocks in Biga Peninsula, NW Turkey, using 3D Normalized Full Gradient of Magnetic Data

    NASA Astrophysics Data System (ADS)

    Ekinci, Y. L.; Yiǧitbaş, E.

    2012-04-01

    Airborne magnetic data of Biga Peninsula were investigated by using 3D Normalized Full Gradient (NFG) technique. The NFG procedure is based on the downward continuation of the potential field data and the NFG amplitude is calculated by dividing the Analytic Signal (AS) of downward continued magnetic data by the average of AS. Application of NFG technique usually enhances the anomalies by computing the anomaly to a level close to the source bodies and points to the boundaries of causative bodies. To that end, a MATLAB based code consisting of a series of linked functions was developed and used for analyses. Study area covers an area of 120 km x 180 km and the data were collected with 1-2 km profile intervals and with about 70 m sampling from 625 m above the ground surface by MTA (General Directorate of Mineral Research and Exploration). 2 km sampling intervals for both north and east directions were used for gridding of the magnetic data. Regional anomalies were approximated by means of element shape functions used in finite element method and then residuals were computed. Prior to the application of 3D NFG, Reduction to the Pole (RTP) transformation was applied to residual data in order to remove the complexity due to the effects of the direction of magnetization and ambient field. RTP transformation process was performed using 55 and 4 degrees for inclination and declination angles, respectively. 3D NFG operation was performed to reduced to pole data for 6 different depth levels (-200, -400, -600, -800, -1000 and -1200 m). Analyzing the resulting anomaly maps of different depth levels together with the geological map (1/500.000) showed that the locations of maximum NFG amplitudes indicate the boundaries of plutonic rocks having high magnetization intensity. Additionally, horizontal and vertical extensions of plutonic rocks were also determined. Keywords: Airborne magnetic data, normalized full gradient, plutonic rocks, Biga Peninsula-Turkey

  20. Geochemistry and geochronology of the volcano-plutonic rocks associated with the Glojeh epithermal gold mineralization, NW Iran

    NASA Astrophysics Data System (ADS)

    Siani, Majid Ghasemi; Mehrabi, Behzad; Azizi, Hossein; Wilkinson, Camilla Maya; Ganerød, Morgan

    2015-08-01

    Eocene to Oligocene volcano-plutonic rocks are widespread throughout NW Iran. The Tarom-Hashtjin metallogenic province is one of the most promising epithermal-porphyry ore mineralized districts in NW Iran. The Glojeh gold deposit, located in the center of this province, is a typical high to intermediate sulfidation epithermal system, spatially and temporally associated with a granite intrusion and associated high-K calc-alkaline to shoshonitic volcano-plutonic rocks. The intrusive complexes of the Glojeh district are characterized by: SiO2 contents of 60.9 to 70.7 wt.%, K2O+Na2O of 7.60 to 8.92 wt.%, and K2O/Na2O ratios of 0.9 to 1.8. They are enriched in light rare earth elements (LREEs), and large ion lithophile elements (LILEs), depleted in high field strength elements (HFSEs), and have weak negative Eu anomalies (Eu/Eu*= 0.5 to 0.9). 40Ar/39Ar geochronology applied to biotite and feldspar, separated from two intrusives (Goljin and Varmarziar), and two feldspar aliquots separated from hydrothermal veins at North Glojeh and South Glojeh, was carried out to constrain magmatic and hydrothermal events. Plagioclase (± sericite), from North Glojeh and South Glojeh produced ages (42.20±0.34 Ma, and 42.56±1.47 Ma respectively) that overlap with the age of the Goljin intrusion (41.87±1.58 Ma). Geochemical data for the volcano-plutonic rocks in the Glojeh district, that have87Sr/86Sr isotopic compositions that range from 0.706344 to 0.708331, suggest an origin involving partial melting of a depleted mantle source during Neo-Tethyan subduction.

  1. Mineral potential of felsic plutonic rocks in the north-central Arabian Shield, Kingdom of Saudi Arabia

    USGS Publications Warehouse

    Moore, W.J.

    1985-01-01

    The muscovite-bearing monzogranites containing anomalous tin and tungsten in rock and (or) wadi sediment samples occur generally east of long 42°30' E. Two of these, Jabal Minya and Jabal Khinzir, are recommended for immediate follow-up studies. Of the alkali granites, most of which occur in the area west of long 42°30' E., the composite plutons of Jabal Hadb ad Dayahin and Jabal Tuqfah have the highest potential for rare-element mineralization and warrant prompt systematic investigation. Evaluation of isolated one- or two-element anomalies should be coordinated with current high-density geochemical prospecting programs of the Riofinex Geological Mission.

  2. Isotopic studies of the Eye-Dashwa Lakes pluton and the long-term integrity of whole-rock and mineral systems

    USGS Publications Warehouse

    Peterman, Zell E.; Kamineni, D.C.

    1990-01-01

    This report presents results of isotopic studies of the Eye-Dashwa Lakes pluton, located near Atikokan, Ontario. Suites of pristine 'unaltered' and 'highly altered' core samples from deep boreholes were used to study Rb-Sr, U-Th-Pb and Sr-Nd systematics, whole-rock Pb isotopes and fission track dating of apatite. The results have been used to investigate natural analogues for radionuclide migration in the geosphere, the tectonic stability of the pluton and the extent of water-rock interaction in fracture zones.

  3. Spectral reflectance and discrimination of plutonic rocks in the 0.45- to 2.45-micron region

    NASA Technical Reports Server (NTRS)

    Blom, R. G.; Abrams, M. J.; Adams, H. G.

    1980-01-01

    Visible and near-infrared field spectral reflectance measurements of plutonic rocks were acquired in the 0.45- to 2.45-micron region with a portable field reflectance spectrometer. These spectra were used to determine spectral signatures for the various rock types and to evaluate the separability of these rocks based on their spectral characteristics. A total of 135 samples were divided into 11 groups based on their mineralogy. These 11 groups approximately correspond to traditional rock classifications and include five granitic groups, three gabbroic groups, and three ultramafic groups. The positions, intensity, and presence of iron, CO3(-2), and Al-OH and Mg-OH absorption bands varied among the 11 groups. Each rock group also had a range of albedos characteristic of the group. Stepwise linear discriminant analysis was performed on the spectral data to determine the separability of the 11 groups. Classification accuracy for 30 equally spaced wavelength bands between 0.45 and 2.45 microns was 78% with 10% serious misclassifications. The same analysis was repeated, limiting the spectral data to the wavelength regions corresponding to the proposed Landsat D thematic mapper scanner.

  4. A 2.5 G.a. reworked sialic crust: Rb-Sr ages and isotopic geochemistry of late archaean volcanic and plutonic rocks from E. Finland

    NASA Astrophysics Data System (ADS)

    Martin, Hervé; Querré, Guirec

    1984-03-01

    In east-central Finland, Archaean terrains present three main lithologic units: a) gneissic basement, emplaced from 2.86 G.a. to 2.62 G.a., b) greenstone belt (2.65 G.a.) and c) calc-alkaline magmatism (2.50 G.a. to 2.40 G.a). Twenty three rocks of the calc-alkaline suite have been chosen for geochronologic and Rb-Sr isotopic studies. These rocks are subdivided into three groups: 1) acid volcanics from Luoma, 2) augen gneiss from Arola, and 3) post kinematik pink leucogranite from Arola. The 2.50±0.10 G.a. age of the Luoma volcanics indicates that they represent the upper part of a greenstone belt composed of a single sequence of volcanic rocks. The ages, initial 87Sr/86Sr (ISr) and major element compositions of the augen gneisses of Arola and Suomussalmi indicate that these rocks are the plutonic equivalents of the Luoma acid volcanics. The Arola pink leucogranite marks the terminal phase of Archaean magmatic activity (from 2.86 G.a. to 2.41 G.a.). This was followed by at least 0.40 G.a. of quiescence. The ISr and major element compositions suggest that the genesis of the calc-alkaline magmatic rocks involved crustal materials, but all their geochemical features cannot be explained without the participation of mafic greenstone belt materials. The first crustal components had low I and low K2O/ Na2O ratios while the younger ones (calc-alkaline magmas) had medium to high ISr and high K2O/Na2O ratios. Thus the petrogenetic processes have changed with time from ensimatic to ensialic, implying major reworking of preexisting crustal materials. This evolution leads to the accretion of the continental crust from the mantle.

  5. Crystal accumulation and compositional trends in a calc-alkaline batholith: implications for correlation of plutonic and volcanic rocks

    NASA Astrophysics Data System (ADS)

    Barnes, C. G.; Coint, N.

    2013-12-01

    -sized magma body (≥ 160 km3) in which both cumulates and differentiates are readily identified. In contrast, differentiates related to lower-zone cumulate rocks are rare, presumably because they intruded higher crustal levels and/or erupted. We conclude that compositional trends of lower-zone rocks are dominated by crystal accumulation and do not accurately reflect magmatic evolution owing to loss of differentiated magmas. If this process is common in such plutons, then the use of bulk-rock compositions to identify consanguineous plutonic and volcanic rocks will be difficult, at best.

  6. Updated paleomagnetic pole from Cretaceous plutonic rocks of the Sierra Nevada, California: Tectonic displacement of the Sierra Nevada block

    USGS Publications Warehouse

    Hillhouse, J.W.; Gromme, S.

    2011-01-01

    We report remanent magnetization measurements from 13 sites in Cretaceous plutonic rocks in the northern Sierra Nevada (38??N-39.5??N). By increasing the number of available paleomagnetic sites, the new data tighten constraints on the displacement history of the Sierra Nevada block and its pre-extensional position relative to interior North America. We collected samples in freshly exposed outcrops along four highway transects. The rocks include diorite, granodiorite, and tonalite with potassium-argon ages (hornblende) ranging from 100 Ma to 83 Ma. By combining our results with previous paleomagnetic determinations from the central and southern Sierra Nevada (excluding sites from the rotated southern tip east of the White Wolf-Kern Canyon fault system), we find a mean paleomagnetic pole of 70.5??N, 188.2??E, A95 = 2.6?? (N = 26, Fisher concentration parameter, K = 118). Thermal demagnetization indicates that the characteristic remanence is generally unblocked in a narrow range within 35 ??C of the Curie temperature of pure magnetite. Small apparent polar wander during the Cretaceous normal-polarity superchron, plus prolonged acquisition of remanence at the site level, may account for the low dispersion of virtual geomagnetic poles and relatively large K value. Tilt estimates based on overlapping sediments, stream gradients, and thermochronology of the Sierra Nevada plutons vary from 0?? to 3?? down to the southwest. Without tilt correction, the mean paleomagnetic pole for the Sierra Nevada is essentially coincident with the North American reference pole during the Cretaceous stillstand (125 Ma to 80 Ma). At 95% confidence, the apparent latitude shift is 1.1?? ?? 3.0?? (positive northward), and the apparent rotation is negligible, 0.0?? ?? 4.7??. Correcting for each degree of tilt, which is limited to 3?? on geologic evidence, increases the rotation anomaly 2.2?? counterclockwise, while the apparent latitude shift remains unchanged. ?? 2011 Geological Society of

  7. Felsic plutonic rocks of the Midyan region, Kingdom of Saudi Arabia—II. Pilot study in chemical classification of Arabian granitoids

    NASA Astrophysics Data System (ADS)

    Ramsay, Colin R.; Odell, John; Drysdall, Alan R.

    A universal classification scheme for felsic plutonic rocks of the Arabian Shield remains an important and elusive objective. The extensive data available for felsic plutonic rocks of the Midyan region, which have been assigned to intrusive suites of the alkali granite, alkali-feldspar granite, monzogranite, granodiorite and trondhjemite associations, provide material for a pilot study. Discriminant analysis of compositional data has yielded multivariate classification functions which successfully assign samples to their proper suites. Functions which use major-oxide values have a better success rate than those based on trace elements, but both are particularly effective in distinguishing samples of the two suites with important mineralizing potential. Test classification of data from another part of the Arabian Shield suggests that the technique and the classification functions are effective beyond the Midyan region. Multivariate discriminant analysis can therefore be used as an aid to mapping, correlating and/or assessing the mineral potential of felsic plutons, and may form the basis for an objective, sensitive and concise classification scheme for Arabian felsic plutonic rocks.

  8. Vein deposits hosted by plutonic rocks in the Croesus Stock and Hailey gold belt mineralized areas, Blaine County, Idaho

    USGS Publications Warehouse

    Worl, Ronald G.; Lewis, Reed S.

    2001-01-01

    Mineral deposits in the Croesus and Hailey gold belt mineralized areas in Blaine County, south-central Idaho, are preciousand base-metal quartz veins that are part of a family of vein deposits spatially and temporally associated with the Idaho batholith. Historic production from these veins has been mainly gold and silver. Host rocks are older border phase plutons of the Idaho batholith that are characterized by more potassium and less sodium as compared to rocks from the main body of the batholith to the west. Host structures are reverse faults that have moderate to shallow dips to the northeast and high-angle normal faults that also strike northwest. The veins are characterized by several generations of quartz and generally sparse sulfide minerals; gold is associated with late-stage comb quartz. The precious-metal ore bodies are in a series of shoots, each of which is as much as 8 ft in width, 400 ft in breadth, and 1,000 ft in pitch length.

  9. Lead isotope compositions of Late Cretaceous and early Tertiary igneous rocks and sulfide minerals in Arizona: Implications for the sources of plutons and metals in porphyry copper deposits

    USGS Publications Warehouse

    Bouse, R.M.; Ruiz, J.; Titley, S.R.; Tosdal, R.M.; Wooden, J.L.

    1999-01-01

    Porphyry copper deposits in Arizona are genetically associated with Late Cretaceous and early Tertiary igneous complexes that consist of older intermediate volcanic rocks and younger intermediate to felsic intrusions. The igneous complexes and their associated porphyry copper deposits were emplaced into an Early Proterozoic basement characterized by different rocks, geologic histories, and isotopic compositions. Lead isotope compositions of the Proterozoic basement rocks define, from northwest to southeast, the Mojave, central Arizona, and southeastern Arizona provinces. Porphyry copper deposits are present in each Pb isotope province. Lead isotope compositions of Late Cretaceous and early Tertiary plutons, together with those of sulfide minerals in porphyry copper deposits and of Proterozoic country rocks, place important constraints on genesis of the magmatic suites and the porphyry copper deposits themselves. The range of age-corrected Pb isotope compositions of plutons in 12 Late Cretaceous and early Tertiary igneous complexes is 206Pb/204Pb = 17.34 to 22.66, 207Pb/204Pb = 15.43 to 15.96, and 208Pb/204Pb = 37.19 to 40.33. These Pb isotope compositions and calculated model Th/U are similar to those of the Proterozoic rocks in which the plutons were emplaced, thereby indicating that Pb in the younger rocks and ore deposits was inherited from the basement rocks and their sources. No Pb isotope differences distinguish Late Cretaceous and early Tertiary igneous complexes that contain large economic porphyry copper deposits from less rich or smaller deposits that have not been considered economic for mining. Lead isotope compositions of Late Cretaceous and early Tertiary plutons and sulfide minerals from 30 metallic mineral districts, furthermore, require that the southeastern Arizona Pb province be divided into two subprovinces. The northern subprovince has generally lower 206Pb/204Pb and higher model Th/U, and the southern subprovince has higher 206Pb/204Pb and

  10. Neodymium, strontium, and lead isotopes in the Maloin Ranch Pluton, Wyoming: Implications for the origin of evolved rocks at anorthosite margins

    SciTech Connect

    Kolker, A.; Hanson, G.N. ); Frost, C.D. ); Geist, D.J. )

    1991-08-01

    Neodymium, strontium, and lead isotopic data are used in this study to investigate the origin of chemically evolved rocks in the Maloin Ranch Pluton, a composite body that borders and intrudes the Laramie Anorthosite. In the Maloin Ranch Pluton, these include ferrodiorite at the base of the intrusion, overalain progressively by fine-grained monzonite, monzosyenite, and porphyritic granite. Biotite gabbro and fine-grained granitic dikes are present locally at various levels of this sequence. The origin of the evolved rocks and their possible relation to associated anorthositic bodies has been much debated. In the Maloin Ranch Pluton, each rock type has distinct isotopic characteristics which, together with trace-element data previously reported, suggest different source characteristics for each member. Strontium and neodymium isotopic data for Maloin Ranch ferrodiorite and Laramie anorthositic rocks show considerable overlap, consistent with a comagmatic relation. Biotite gabbro is chemically and isotopically the most primitive rock type in the Maloin Ranch Pluton. The data suggest that biotite gabbro has a mantle source, but has undergone extensive fractionation in the crust. The authors' results suggest that the remainder (and bulk) of the intrusion formed by partial melting of the lower crust due to the emplacement of the Laramie Anorthosite. Trace-element and isotopic characteristics of the fine-grained monzonite are explained by partial melting of mantle-dervied lower crust, added to the margin of the Archean Wyoming craton at about 1.8 Ga. Neodymium, strontium, and lead isotope data for Maloin Ranch monzosyenite and porphyritic granite also suggest a lower crustal source.

  11. Assessment of gamma radiation exposure and distribution of natural radioactivity in beach sands associated with plutonic rocks of Greece

    NASA Astrophysics Data System (ADS)

    Papadopoulos, Argyrios; Koroneos, Antonios; Christofides, Georgios; Stoulos, Stylianos

    2016-04-01

    This study aims to evaluate the activity concentrations of 238U, 226Ra, 232Th, 228Th and 40K along beaches of Greece associated with plutonic rocks. They range from 6-940, 1-2292, 5-10143, 5-9953 and 27-1319 Bq/kg respectively, with some of them representing the highest values of natural radioactivity measured in sediments in Greece. The investigated beaches include Sithonia peninsula (Chalkidiki, N. Greece), some islands of the Aegean Sea (Mykonos, Paros, Naxos, Serifos, Ikaria), the area of Kavala (N. Greece), Samothraki island, NE Chalkidiki and Maronia (NE Greece). Several of these places are associated with high touristic activity such as Mykonos, Naxos, Paros, Serifos, Ikaria, Sithonia and Kavala. The (% wt.) heavy magnetic fraction (HM) (allanite, amphibole, mica, clinopyroxene, magnetite and hematite), the heavy non-magnetic fraction (HNM) (monazite, zircon, titanite and apatite) and the total heavy fraction (TH), were correlated with the concentrations of the measured radionuclides in the bulk samples. The heavy fractions seem to control the activity concentrations of 238U and 232Th of all the samples, showing some local differences in the main 238U and 232Th mineral carrier. The measured radionuclides in the beach sands were normalized to the respective values measured in the granitic rocks, which are their most probable parental rocks, so as to provide data upon their enrichment or depletion. The highest values of the equivalent dose have been reported in Mykonos, Naxos, Kavala and Sithonia. The annual equivalent dose which should be limited to at least 1 mSv y-1, varies between 0.003 and 0.759 mSv y-1 for tourists and from 0.012 to 3.164 mSv y-1 for local people working on the beach.

  12. Chemistry and petrology of Apollo 17 highland coarse fines - Plutonic and melt rocks

    NASA Technical Reports Server (NTRS)

    Laul, J. C.; Gosselin, D. C.; Galbreath, K. C.; Simon, S. B.; Papike, J. J.

    1989-01-01

    A suite of 21 fragments from the Apollo 17 coarse-fines consists of ferroan anorthosites, anorthositic gabbros, granulitic and regolith breccias, and impact melts. These samples belong to known petrographic and chemical groups. Three ferroan anorthosites were found, including one which appears to be the lowest in REE (La = 0.60X) and probably the purest of the Apollo 17 anorthosites identified thus far. The ferroan suite is a more important component at the Apollo 17 site than previously recognized. The Apollo 17 melt rocks are similar to other samples with LKFM and low-K KREEP compositions and show less diversity in trace elements (REE) than the Apollo 15 melt rocks. Apollo 17 melt rocks consist of aphanitic and poikilitic types that show some compositional variability with identical Ni/Ir, suggesting that either two distinct melt sheets formed by similar projectiles, or compositional heterogeneity within one melt sheet is possible.

  13. On identifying parent plutonic rocks from lunar breccia and soil fragments

    NASA Technical Reports Server (NTRS)

    Haskin, Larry A.; Lindstrom, David J.

    1988-01-01

    Breccia fragments expected from a well-studied boulder of Stillwater anorthosite have been modeled to test the ability to identify parental rock types from examination of breccia and soil fragments. Depending on their size, the boulder fragments give distributions that suggest mixtures of rock types, including monominerallic anorthosite with subordinant amounts of more gabbroic anorthosite, anorthosite, and gabbro for small fragments. The distribution of FeO in samples of lunar ferroan anorthosite (FAN) indicates that FAN has a heterogeneous distribution of mafic minerals like the boulder.

  14. The questa magmatic system: Petrologic, chemical and isotopic variations in cogenetic volcanic and plutonic rocks of the latir volcanic field and associated intrusives, northern New Mexico

    SciTech Connect

    Johnson, C.M.

    1986-01-01

    Field, chemical and isotopic data demonstrate that nearly all igneous rocks at Questa resulted from interactions between mantle-derived parental magmas and the crust. Strontium, neodymium and lead isotope ratios of early andesites to rhyolites (28 to 26 Ma) indicate that these magmas assimilated > 25% lower crust. Injection of basaltic magmas extensively modified the strontium and neodymium but not the lead isotope compositions of the lower crust. Eruption of comendite magmas and the peralkaline Amalia Tuff 26 Ma is correlated with inception of regional extension. Lead isotope ratios identify different sources for the metaluminous granites and the peralkaline rocks. 26 Ma metaluminous granite to granodiorite intrusions have chemical and isotopic compositions to those of the precaldera intermediate-composition rocks, and are interpreted as representing the solidified equivalents of the precaldera magmatic episode. However, both conventional and ion-microprobe isotopic data prohibit significant assimilation of crustal rocks at the level of exposure, suggesting that the plutons were emplaced a relatively crystal-rich mushes which did not have sufficient heat to assimilate country rocks. This suggest that in some cases plutonic rocks are better than volcanic rocks in representing the isotopic compositions of their source regions, because the assimilation potential of crystal-rich magmas is significantly less than that of largely liquid magmas.

  15. The role of pegmatites and acid fluids for REE/HFSE mobilization in the Strange Lake peralkaline granitic pluton, Canada

    NASA Astrophysics Data System (ADS)

    Gysi, A. P.; Williams-Jones, A.

    2012-12-01

    The Strange Lake pluton in Canada is a mid-Proterozoic peralkaline granitic intrusion that is host to a world-class rare earth element (REE), yttrium (Y) and high-field strength element (HFSE) deposit containing more than 50 Mt ore at >1.5 wt.% REE and >3 wt.% Zr. The highest REE/HFSE concentrations are found in pegmatite-rich zones characterized by intense alteration. Previous studies of Strange Lake and other peralkaline and alkaline intrusions, such as Khan Bogd (Mongolia) and Tamazeght (Morocco) plutons have shown that hydrothermal alteration may play an important role in the mobility of the REE/HFSE. However, the fluid chemistry and conditions of alteration (i.e., P, T, pH, fO2, ligand activity) in these systems still need to be constrained to evaluate the importance and scale of such hydrothermal mobilization. We present new data from the B-zone, a pegmatite-rich zone located in NW Strange Lake. The pegmatites are generally zoned and form two main types. The border-type pegmatites consist of quartz, K-feldspar and hematized aegirine, whereas volatile-rich pegmatites consist of hydrothermal quartz and fluorite. Transitions between both types were also observed, with the K-feldspar being partly altered and replaced by Al-Si-rich phyllosilicates. The heavy (H)REE and Zr were primarily concentrated in zirconosilicates such as elpidite, now pseudomorphed by zircon or gittinsite, whereas light (L)REE and Y were concentrated in REE-F-(CO2)-minerals such as fluocerite and bastnäsite. Textural and mineralogical observations indicate that these minerals are primary and were partly to completely leached upon fluid-rock interaction in the pegmatites. Secondary phases include Ca-F-Y-rich minerals, mainly hydrothermal fluorite, that fill vugs and replaced primary REEHFSE minerals. The presence of hydrothermal fluorite veins, micro-veins, vugs and micro-breccia in the most altered parts of the B-zone are interpreted to reflect interaction of the rocks with a F-rich fluid

  16. Processes involved in the formation of magnesian-suite plutonic rocks from the highlands of the Earth's Moon

    NASA Technical Reports Server (NTRS)

    Snyder, Gregory A.; Neal, Clive R.; Taylor, Lawrence A.; Halliday, Alex N.

    1995-01-01

    The earliest evolution of the Moon likely included the formation of a magma ocean and the subsequent development of anorthositic flotation cumulates. This primary anorthositic crust was then intruded by mafic magmas which crystallized to form the lunar highlands magnesian suite. The present study is a compilation of petrologic, mineral-chemical, and geochemical information on all pristine magnesian-suite plutonic rocks and the interpretation of this data in light of 18 'new' samples. Of these 18 clasts taken from Apollo 14 breccias, 12 are probably pristine and include four dunites, two norites, four troctolites, and two anorthosites. Radiogenic isotopic whole rock data also are reported for one of the 'probably pristine' anorthositic troctolites, sample 14303,347. The relatively low Rb content and high Sm and Nd abundances of 14303,347 suggest that this cumulate rock was derived from a parental magma which had these chemical characteristics. Trace element, isotopic, and mineral-chemical data are used to interpret the total highlands magnesian suite as crustal precipitates of a primitive KREEP (possessing a K-, rare earth element (REE)-, and P-enriched chemical signature) basalt magma. This KREEP basalt was created by the mixing of ascending ultramafic melts from the lunar interior with urKREEP (the late, K-, REE-, and P-enriched residuum of the lunar magma ocean). A few samples of the magnesian suite with extremely elevated large-ion lithophile elements (5-10x other magnesian-suite rocks) cannot be explained by this model or any other model of autometasomatism, equilibrium crystallization, or 'local melt-pocket equilibrium' without recourse to an extremely large-ion lithophile element-enriched parent liquid. It is difficult to generate parental liquids which are 2-4 x higher in the REE than average lunar KREEP, unless the liquids are the basic complement of a liquid-liquid pair, i.e., the so-called 'REEP-fraction,' from the silicate liquid immiscibility of ur

  17. Mineral compositions of plutonic rocks from the Lewis Hills massif, Bay of Islands ophiolite

    NASA Technical Reports Server (NTRS)

    Smith, Susan E.; Elthon, Don

    1988-01-01

    Mineral compositions of residual and cumulate rocks from the Lewis Hills massif of the Bay of Islands ophiolite complex are reported and interpreted in the context of magnetic processes involved in the geochemical evolution of spatially associated diabase dikes. The mineral compositions reflect greater degrees of partial melting than most abyssal peridotites do and appear to represent the most depleted end of abyssal peridotite compositions. Subsolidus equilibration between Cr-Al spinal and olivine generally has occurred at temperatures of 700 to 900 C. The spinel variations agree with the overall fractionation of basaltic magmas producing spinels with progressively lower Cr numbers. The compositions of clinopyroxenes suggest that the fractionation of two different magma series produced the various cumulate rocks.

  18. Neutron activation and other analytical data for plutonic rocks from North America and Africa. National Uranium Resource Evaluation

    SciTech Connect

    Price, V.; Fay, W.M.; Cook, J.R.

    1982-09-01

    The objective of this report is to retrieve the elements of an analytical study of granites and associated other plutonic rocks which was begun as a part of the U.S. Department of Energy's National Uranium Resource Evaluation (NURE) program. A discussion of the Savannah River Laboratory (SRL) neutron activation analysis system is given so that a user will understand the linmitations of the data. Enough information is given so that an experienced geochemist can clean up the data set to the extent required by any project. The data are generally good as they are presented. It is intended that the data be read from a magnetic tape written to accompany this report. Microfiche tables of the data follow the text. These tables were prepared from data on the tape, and programs which will read the tape are presented in the section THE DATA TAPE. It is our intent to write a later paper which will include a thoroughly scrubbed data set and a technical discussion of results of the study. 1 figure.

  19. Implementation and compatibility of a North American Volcanic and Plutonic rock database (NAVDAT)

    NASA Astrophysics Data System (ADS)

    Walker, J. D.; Glazner, A. F.; Bowers, T. D.; Straus, A. K.; Farmer, G. L.; Carlson, R. W.; Black, R. A.; Grossman, J. N.

    2002-12-01

    NAVDAT is a database for igneous rocks in western North America that will contain geochemical and age information primarily on Cenozoic rocks. NAVDAT will allow exploration of temporal and spatial patterns in igneous activity, and to connect these patterns with local and regional tectonic development and lithospheric structure. The database will be web-accessible for downloads and queries (navdat.geo.ku.edu). Allied information, such as geologic and geophysical maps, crustal structure, etc., will also be available through a map interface. We have attempted to keep the NAVDAT schema compatible with that for PetDB and GEOROC (petdb.ldeo.columbia.edu, georoc.mpch-mainz.gwdg.de) in order to build consensus on an overall structure for of an igneous rock database. The issues to be addressed by continent-based NAVDAT, however, are somewhat different from ocean-floor based PetDB, and the schema required numerous modifications. We have extended the schema in several areas to meet the needs of the on-land database. Location and age information become critical because we are trying define changes in magma source with time tied to structural position and setting. For this reason, we have added more fields to cover such issues as how a rock is dated and where it is located. In addition, we have implemented an expanded reference section that imports all information available in AGI's Georef database. This should allow for superior query ability. One recurring issue in constructing the NAVDAT database is the inconsistency in the way geochemical data are reported. The following is a suggested publication check-list for geochemists that will enable more robust database construction: 1) all samples must have locations reported as accurately as possible, not just located on a map figure or given as a general location; 2) known sample ages must be given and the method of dating explained (e.g., directly dated, stratigraphically bracketed, or correlated in a regional sense); 3

  20. Tourmaline occurrences within the Penamacor-Monsanto granitic pluton and host-rocks (Central Portugal): genetic implications of crystal-chemical and isotopic features

    NASA Astrophysics Data System (ADS)

    da Costa, I. Ribeiro; Mourão, C.; Récio, C.; Guimarães, F.; Antunes, I. M.; Ramos, J. Farinha; Barriga, F. J. A. S.; Palmer, M. R.; Milton, J. A.

    2014-04-01

    Tourmalinization associated with peraluminous granitic intrusions in metapelitic host-rocks has been widely recorded in the Iberian Peninsula, given the importance of tourmaline as a tracer of granite magma evolution and potential indicator of Sn-W mineralizations. In the Penamacor-Monsanto granite pluton (Central Eastern Portugal, Central Iberian Zone), tourmaline occurs: (1) as accessory phase in two-mica granitic rocks, muscovite-granites and aplites, (2) in quartz (±mica)-tourmaline rocks (tourmalinites) in several exocontact locations, and (3) as a rare detrital phase in contact zone hornfels and metapelitic host-rocks. Electron microprobe and stable isotope (δ18O, δD, δ11B) data provide clear distinctions between tourmaline populations from these different settings: (a) schorl-oxyschorl tourmalines from granitic rocks have variable foititic component (X□ = 17-57 %) and Mg/(Mg + Fe) ratios (0.19-0.50 in two-mica granitic rocks, and 0.05-0.19 in the more differentiated muscovite-granite and aplites); granitic tourmalines have constant δ18O values (12.1 ± 0.1 ‰), with wider-ranging δD (-78.2 ± 4.7 ‰) and δ11B (-10.7 to -9.0 ‰) values; (b) vein/breccia oxyschorl [Mg/(Mg + Fe) = 0.31-0.44] results from late, B- and Fe-enriched magma-derived fluids and is characterized by δ18O = 12.4 ‰, δD = -29.5 ‰, and δ11B = -9.3 ‰, while replacement tourmalines have more dravitic compositions [Mg/(Mg + Fe) = 0.26-0.64], close to that of detrital tourmaline in the surrounding metapelitic rocks, and yield relatively constant δ18O values (13.1-13.3 ‰), though wider-ranging δD (-58.5 to -36.5 ‰) and δ11B (-10.2 to -8.8 ‰) values; and (c) detrital tourmaline in contact rocks and regional host metasediments is mainly dravite [Mg/(Mg + Fe) = 0.35-0.78] and oxydravite [Mg/(Mg + Fe) = 0.51-0.58], respectively. Boron contents of the granitic rocks are low (<650 ppm) compared to the minimum B contents normally required for tourmaline saturation in

  1. The Early Andean Magmatic Province (EAMP): 40Ar/ 39Ar dating on Mesozoic volcanic and plutonic rocks from the Coastal Cordillera, northern Chile

    NASA Astrophysics Data System (ADS)

    Oliveros, Verónica; Féraud, Gilbert; Aguirre, Luis; Fornari, Michel; Morata, Diego

    2006-10-01

    The Early Andean Magmatic Province (EAMP), consists of about 150 000 km 3 of volcanic and plutonic units in the Coastal Cordillera of northern Chile and southern Peru and represents a major magmatic Mesozoic event in the world, for which the precise age of the thick volcanic series was unknown. Thirty 40Ar/ 39Ar analyses were carried out on primary mineral phases of volcanic and plutonic rocks from northern Chile (18°30'-24°S). Reliable plateau and "mini plateau" ages were obtained on plagioclase, amphibole and biotite from volcanic and plutonic rocks, despite widespread strong alteration degree. In the Arica, Tocopilla and Antofagasta (700 km apart) regions, the ages obtained on lava flows constrain the volcanic activity between 164 and 150 Ma and no N-S migration of volcanism is observed. The uppermost lava flows of the volcanic sequence at the type locality of the La Negra Formation extruded at ca. 153-150 Ma, suggesting the end of the volcanic activity of the arc at that time. The oldest volcanic activity occurred probably at ca. 175-170 Ma in the Iquique area, although no plateau age could be obtained. The plutonic bodies of the same regions were dated between ca. 160 and 142 Ma, indicating that they were partly contemporaneous with the volcanic activity. At least one volcanic pulse around 160 Ma is evidenced over the entire investigated reach of the EAMP, according to the ages found in Arica, Tocopilla, Michilla and Mantos Blancos regions. The episodic emplacement of huge amounts of subduction related volcanism is observed throughout the whole Andean history and particularly during the Jurassic (southern Peru, northern Chile and southern Argentina). These events probably correspond to periodic extensional geodynamic episodes, as a consequence of particular subduction conditions, such as change of obliquity of the convergence, change in the subduction angle, slab roll back effect or lower convergence rate, that remain to be precisely defined.

  2. Late-stage sinking of plutons

    USGS Publications Warehouse

    Glazner, A.F.; Miller, D.M.

    1997-01-01

    Many granodiorite to diorite plutons in the Great Basin of western North America are surrounded by rim monoclines or anticlines that suggest relative downward movement of the plutons while wall rocks were hot and ductile. We propose that such plutons rise to a level of approximately neutral buoyancy and then founder as their densities increase ??? 40% during crystallization. Late-stage sinking of intermediate to mafic plutons should be common when wall rocks are rich in weak, low-density minerals such as quartz and calcite. Structures related to sinking will overprint those related to initial pluton emplacement and may be mistaken for regional tectonic structures.

  3. Oxygen 18/oxygen 16 and D/H studies of plutonic granitic and metamorphic rocks across the Cordilleran Batholiths of southern British Columbia

    NASA Astrophysics Data System (ADS)

    Magaritz, Mordeckai; Taylor, Hugh P., Jr.

    1986-02-01

    Hydrogen and oxygen isotope ratios of 500 samples, mainly from granitic plutons, were measured along a 700-km, E-W traverse across the "accreted terranes" of southern British Columbia (latitudes 49°-52°N). Despite the geological complexity and range of intrusive ages (Late Triassic to Tertiary) and although there are "steps" in the isotopic values at some geologic boundaries (e.g., across the Strait of Georgia), two clear patterns emerge: (1) The 18O/16O and D/H ratios of the waters involved in hydrothermal interactions with the granitic rocks show a regular eastward trend of depletion in D and 18O. Enormous areas were affected by the hydrothermal processes, but the most intense alteration is localized along major north trending lineaments (e.g., Okanagan Lake). (2) Independent of the hydrothermal effects, the primary δ18O values of the granitic rocks also change systematically eastward, from +7.0 to +8.5 in Vancouver Island, reaching a minimum of +5.5 to +7.0 in the western and central Coast Plutonic Complex, then increasing progressively from the eastern Coast Batholith to the Okanagan Batholith, and attaining a maximum of +10.0 to +12.0 in the Nelson Batholith. Two groups of samples are unique in their high δD values. The first group is represented by two geographically isolated batholiths (Guichon and Thuya) that were not affected by the Tertiary meteoric-hydrothermal systems and that have therefore preserved their Early Jurassic to Triassic K/Ar ages. The second group is represented by the Jurassic plutons of Vancouver Island; there, the hydrothermal fluids were both D-rich and 18O-rich (δ18O > 0), as evidenced by the fact that feldspars in the altered granites are enriched in 18O relative to coexisting quartz. Both "anomalies" can be explained if these terranes were located closer to the equator and/or in a maritime environment at the time of intrusive and hydrothermal activity, in agreement with available paleomagnetic data. Excluding these anomalous

  4. Structural paragenesis as an indicator of the origin of alkaline rocks in the ijolite-urtite arc of the Khibiny pluton, Kola Peninsula

    NASA Astrophysics Data System (ADS)

    Kulakovsky, A. L.

    2015-03-01

    The results of structural analysis of the ore-bearing complex in the Khibiny pluton are presented. A multistage history of the formation of the ijolite-urtite arc structure has been established. The conic shear zone that determines the structural appearance of the ore-bearing complex is related to the early deformation stage. Only massive ijolite and melteigite are rocks of predeformation matrix. All other rock varieties and apatite ore are syndeformation (gneissic ijolite) or postdeformation (urtite, apatite ore) and thus are not magmatic in origin. The formation of the Paleozoic conic shear zone was most likely predetermined by a Precambrian central-type structure, more precisely, by a binucleus vortex structure related to shearing.

  5. Ulvöspinel from xenoliths of contact-altered volcanic and volcanosedimentary rocks in nepheline syenites of the Khibiny and Lovozero plutons

    NASA Astrophysics Data System (ADS)

    Ivanyuk, G. Yu.; Korchak, Yu. A.; Pakhomovsky, Ya. A.; Men'shikov, Yu. P.; Yakovenchuk, V. N.

    2012-12-01

    Ulvöspinel is a typical accessory mineral of xenoliths of volcanic and volcanosedimentary rocks in alkaline syenites of the Khibiny and Lovozero plutons. Ulvöspinel forms homogeneous Cr- and V-rich grains in slightly altered olivine basalts, basaltic tuffs, and tuffites and is enriched in Mn and Si in the course of contact-metasomatic alteration of these rocks. The strongly reduced conditions of contact metamorphism controlled by ascending flows of hydrocarbon gases and hydrogen sulfide gave rise to the subsolidus decomposition of primary ulvöspinel and Ti-high magnetite with the formation of ilmenite lamellae and then, with decreasing redox potential, of the second-generation latticed ulvöspinel lamellae.

  6. Regional geochemical study of the felsic plutonic rocks in the Nuqrah Quadrangle, sheet 25E, Kingdom of Saudi Arabia

    USGS Publications Warehouse

    Hall, W.E.; Dellinger, David; Selner, G.I.

    1985-01-01

    Pan-concentration samples collected from wadis draining the north end of Jabal Safad contain anomalous Sn, Mo, Pb, and La. Four samples contain 250 to 1,000 ppm of tin. The tin anomaly is associated with a small aplitic pluton intrusive into the Jabal Safad alkalic granite complex. A brief reconnaissance of the area did not reveal any greisen or cassiterite mineralization. However, further exploration work in the area is recommended.

  7. Mesozoic thermal history and timing of structural events for the Yukon-Tanana Upland, east-central Alaska: 40Ar/39Ar data from metamorphic and plutonic rocks

    USGS Publications Warehouse

    Dusel-Bacon, C.; Lanphere, M.A.; Sharp, W.D.; Layer, P.W.; Hansen, V.L.

    2002-01-01

    We present new 40Ar/39Ar ages for hornblende, muscovite, and biotite from metamorphic and plutonic rocks from the Yukon-Tanana Upland, Alaska. Integration of our data with published 40Ar/39Ar, kinematic, and metamorphic pressure (P) and temperature (T) data confirms and refines the complex interaction of metamorphism and tectonism proposed for the region. The oldest metamorphic episode(s) postdates Middle Permian magmatism and predates the intrusion of Late Triassic (215-212 Ma) granitoids into the Fortymile River assemblage (Taylor Mountain assemblage of previous papers). In the eastern Eagle quadrangle, rapid and widespread Early Jurassic cooling is indicated by ???188-186 Ma 40Ar/39Ar plateau ages for hornblende from plutons that intrude the Fortymile River assemblage, and for metamorphic minerals from the Fortymile River assemblage and the structurally underlying Nasina assemblage. We interpret these Early Jurassic ages to represent cooling resulting from northwest-directed contraction that emplaced the Fortymile River assemblage onto the Nasina assemblage to the north as well as the Lake George assemblage to the south. This cooling was the final stage of a continuum of subduction-related contraction that produced crustal thickening, intermediate- to high-P metamorphism within both the Fortymile River assemblage and the structurally underlying Lake George assemblage, and Late Triassic and Early Jurassic plutonism in the Fortymile River and Nasina assemblages. Although a few metamorphic samples from the Lake George assemblage yield Jurassic 40Ar/39Ar cooling ages, most yield Early Cretaceous 40Ar/39Ar ages: hornblende ???135-115 Ma, and muscovite and biotite ???110-108 Ma. We interpret the Early Cretaceous metamorphic cooling, in most areas, to have resulted from regional extension and exhumation of the lower plate, previously tectonically thickened during Early Jurassic and older convergence.

  8. Geochemistry and U-Pb zircon ages of plutonic rocks from the Algodões granite-greenstone terrane, Troia Massif, northern Borborema Province, Brazil: Implications for Paleoproterozoic subduction-accretion processes

    NASA Astrophysics Data System (ADS)

    Costa, Felipe Grandjean da; Palheta, Edney Smith de Moraes; Rodrigues, Joseneusa Brilhante; Gomes, Iaponira Paiva; Vasconcelos, Antonio Maurilio

    2015-04-01

    The Algodões metavolcano-sedimentary sequence is located at the northern margin of the Archean/Paleoproterozoic Troia Massif, northern Borborema Province (NE Brazil). It represents a well-preserved Paleoproterozoic greenstone-like sequence affected by two major plutonic events. The early plutonism, represented by the Cipó orthogneisses, mainly comprises biotite-bearing metatonalites, which share similar geochemical signatures with Archean tonalite-trondjhemite-granodiorite (TTG). For these rocks, we report U-Pb (LA-ICPMS) zircon ages of 2189 ± 14 Ma and 2180 ± 15 Ma. A subsequent plutonic magmatism occurred at ˜2150-2130 Ma and is mainly represented by hornblende-bearing dioritic to tonalitic orthogneisses of the Madalena Suite and São José da Macaoca Complex. Geochemical data indicate that these dioritic/tonalitic orthogneisses have adakitic characteristics and strongly suggest mantle-related magmas. A (sensu stricto) granite plutonism (Serra da Palha orthogneisses) also intruded the Algodões sequence and yielded U-Pb (LA-ICPMS) zircon age of 2150 ± 16 Ma. These granitic orthogneisses show high-K content, A-type characteristics and probably derived from partial melting of a crustal (tonalitic) source. We suggest that the early ˜2190-2160 Ma TTG plutons probably developed in intra-oceanic arc setting, whereas the following ˜2150-2130 Ma adakitic plutons and A-type granitic magmatism developed in response to arc-continent collision.

  9. Comparative geochronology in the reversely zoned plutons of the Bottle Lake Complex, Maine: U-Pb on zircons and Rb-Sr on whole rocks

    USGS Publications Warehouse

    Ayuso, R.A.; Arth, Joseph G.; Sinha, A.K.; Carlson, J.; Wones, D.R.

    1984-01-01

    The Bottle Lake Complex is a composite granitic batholith emplaced into Cambrian to Lower Devonian metasedimentary rocks. Both plutons (Whitney Cove and Passadumkeag River) are very coarse grained hornblende and biotite-bearing granites showing petrographic and geochemical reverse zonation. Two linear whole rock Rb/Sr isochrons on xenolith-free Whitney Cove and Passadumkeag River samples indicate ages of 379??5 m.y. and 381??4 m.y., respectively, in close agreement with published K-Ar ages for biotite from Whitney Cove of 377 m.y. and 379 m.y., and for hornblende 40Ar/39Ar determinations from Passadumkeag River which indicate an age of 378??4 m.y. The initial Sr isotopic ratio for Whitney Cove is 0.70553 and for Passadumkeag River is 0.70414. A whole-rock isochron on a suite of xenoliths from the Passadumkeag River granite indicates a whole rock Rb-Sr age of 496??14 m.y., with an initial Sr isotopic ratio of 0.70262. Two types of zircon exhibiting wide petrographic diversity are evident in variable proportions throughout the batholith. One of these types is preferentially found in a mafic xenolith and it is widely dispersed in the host granites forming discrete grains and probably as inclusions in the other type of zircon. U-Pb analyses of zircons give concordia intercept ages of 399??8 m.y. for Whitney Cove, 388??6 m.y. for Passadumkeag River, 415 m.y. for a mafic xenolith in Passadumkeag River, and 396??32 for combined Whitney Cove and Passadumkeag River granite. The zircons show a spread of up to 20 m.y. in the 207Pb/206Pb ages. Omitting the finest zircon fraction in the Passadumkeag River results in a concordia intercept age of 381??3 m.y., in better agreement with the whole-rock Rb-Sr and mineral K-Ar ages. For the Whitney Cove pluton, exclusion of the finest fraction does not bring the zircon age into agreement with the Rb-Sr data. Age estimates by the whole rock Rb-Sr, mineral K-Ar and Ar-Ar methods suggest that the crystallization age of the plutons is

  10. Sphene (Titanite) as Both Monitor and Driver of Evolution of Felsic Magma: Miocene Volcanic Plutonic and Rocks of the Colorado River Region, NV-AZ, USA

    NASA Astrophysics Data System (ADS)

    Miller, C. F.; Colombini, L. L.; Wooden, J. L.; Mazdab, F. K.; Gualda, G. A.; Claiborne, L. E.; Ayers, J. C.

    2009-05-01

    Sphene is commonly the most abundant accessory mineral in metaluminous to weakly peraluminous igneous rocks. Its relatively large crystals preserve a wide array of zoning patterns and inclusions - notably, abundant other accessories and melt inclusions - and it is a major host for REE, U, Th, and HFSE. Thus it is a valuable repository of information about the history of the magmas from which it forms. Recent development of a Zr-in- sphene thermometer (Hayden et al CMP 155:529 2008) and of sensitive and precise in situ trace element analysis by SHRIMP-RG (Mazdab et al GSA abst 39:6:406 2007) permit more powerful exploitation of this repository. We have initiated a study of sphene in Miocene intrusive and extrusive rocks of the Colorado River extensional corridor for which extensive field, geochemical, and geochronological data provide context. Sphene is present as a late interstitial phase in some gabbros and diorites and common in quartz monzonites and granites. Among extrusive rocks, it occurs as phenocrysts in rhyolite lavas and tuffs that are products of small to giant eruptions (Peach Spring Tuff, >600 km3). Glasses that host sphene in the rhyolites are highly evolved (>76 wt% SiO2). Applying the Zr-in-sphene thermometer (TZr), SHRIMP-RG analyses indicate crystallization T between 730 and 810 C in both plutonic and volcanic rocks. This range is narrower than T estimates for zircon growth (Ti thermometry) for the same suite, which extend to somewhat lower and considerably higher values; zircons also tend to record more events and, evidently, longer histories. Ranges of REE patterns are variable and to some extent sample-specific, but all reveal common characteristics: (1) extremely high concentrations, especially for middle REE (maximum Sm in interiors 10-40x103 x chondrite); (2) deep negative Eu anomalies (Eu/Eu* ca. 0.1-0.2); (3) TZr and REE dropping toward rims - especially pronounced for MREE. Estimated Kds for REE from sphene rims and rhyolite glass or

  11. Assessment of the long-term risk of a meteorite impact on a hypothetical Canadian nuclear fuel waste disposal vault deep in plutonic rock

    SciTech Connect

    Wuschke, D.M.; Whitaker, S.H.; Goodwin, B.W.; Rasmussen, L.R.

    1995-12-31

    Canada has conducted an extensive research program on the safe disposal of nuclear fuel waste. The program has focused on disposal of used fuel in durable containers in an engineered facility or ``vault``, 500 to 1,000 m deep in plutonic rock of the Canadian Shield. This paper describes an assessment of the long-term radiological risk to a critical group, resulting from a meteorite impact on a hypothetical reference disposal vault. The authors assume the critical group is a small rural community which, sometime after the impact, moves to the area contaminated by nuclear fuel waste exposed by the impact. The estimated risk is compared to a risk criterion established by Canada`s nuclear regulatory agency.

  12. Large-scale fluid movement through crustal rocks by transition porosity generation: Feldspar replacement reactions within the Larvik Plutonic Complex, SE-Norway

    NASA Astrophysics Data System (ADS)

    Los, Karin; Verberne, Rick; Plümper, Oliver; Jamtveit, Bjørn; Austrheim, Håkon

    2014-05-01

    Fluid flow through rocks transports heat and mass across the grain to tectonic plate scale. Fluids promote mineral reactions, redistribute elements to form ore deposits, cool the planet and form habitats for life. A fundamental understanding of fluid flow through rocks is central to interpreting geodynamic and geochemical interactions between the geosphere, hydrosphere and biosphere. Some geological systems are open to fluids, but the majority are nearly impermeable. Surprisingly though, even in rocks that are impermeable, evidence for widespread fluid-rock interactions are observed leading to the question: How can fluids migrate through vast amounts of initially impermeable rocks? Here we present work on the Larvik Plutonic Complex (SE-Norway) that provides an ideal natural laboratory to study fluid movement and feldspar re-equilibration reactions. The Larvik Plutonic Complex shows fluid-rock interactions on tens of kilometres. In the field, this is observed as a colour change: the blue larvikite rock is (partly) replaced by red tønsbergite. On the grain scale, mineral replacement is visible as porous crystals surrounding larvikite feldspar relicts. Chemical analysis shows that the alteration is zoned, from non-porous larvikite feldspar at the core to porous albite and orthoclase at the rim. A possible explanation would be infiltration of several fluids; another possibility is a changing fluid activity for Na+ and K+, resulting in a front which shifts during the reaction. The mineral replacement looks pervasive, starting with fluid flowing around the grain boundaries over a long distance. This is followed by slower consumption of the old mineral; the degree of alteration varies throughout the area of interest. Locally, alteration is related to fracture zones with pseudotachylites, which are overprinted by fluids in the vicinity of feldspars. Fluid flow and element mobilisation is controlled by an interaction between grain boundary diffusion and reaction front

  13. Geochronology of plutonic rocks and their tectonic terranes in Glacier Bay National Park and Preserve, southeast Alaska: Chapter E in Studies by the U.S. Geological Survey in Alaska, 2008-2009

    USGS Publications Warehouse

    Brew, David A.; Tellier, Kathleen E.; Lanphere, Marvin A.; Nielsen, Diane C.; Smith, James G.; Sonnevil, Ronald A.

    2014-01-01

    We have identified six major belts and two nonbelt occurrences of plutonic rocks in Glacier Bay National Park and Preserve and characterized them on the basis of geologic mapping, igneous petrology, geochemistry, and isotopic dating. The six plutonic belts and two other occurrences are, from oldest to youngest: (1) Jurassic (201.6–145.5 Ma) diorite and gabbro of the Lituya belt; (2) Late Jurassic (161.0–145.5 Ma) leucotonalite in Johns Hopkins Inlet; (3) Early Cretaceous (145.5–99.6 Ma) granodiorite and tonalite of the Muir-Chichagof belt; (4) Paleocene tonalite in Johns Hopkins Inlet (65.5–55.8 Ma); (5) Eocene granodiorite of the Sanak-Baranof belt; (6) Eocene and Oligocene (55.8–23.0 Ma) granodiorite, quartz diorite, and granite of the Muir-Fairweather felsic-intermediate belt; (7) Eocene and Oligocene (55.8–23.0 Ma) layered gabbros of the Crillon-La Perouse mafic belt; and (8) Oligocene (33.9–23.0 Ma) quartz monzonite and quartz syenite of the Tkope belt. The rocks are further classified into 17 different combination age-compositional units; some younger belts are superimposed on older ones. Almost all these plutonic rocks are related to Cretaceous and Tertiary subduction events. The six major plutonic belts intrude the three southeast Alaska geographic subregions in Glacier Bay National Park and Preserve, from west to east: (1) the Coastal Islands, (2) the Tarr Inlet Suture Zone (which contains the Border Ranges Fault Zone), and (3) the Central Alexander Archipelago. Each subregion includes rocks assigned to one or more tectonic terranes. The various plutonic belts intrude different terranes in different subregions. In general, the Early Cretaceous plutons intrude rocks of the Alexander and Wrangellia terranes in the Central Alexander Archipelago subregion, and the Paleogene plutons intrude rocks of the Chugach, Alexander, and Wrangellia terranes in the Coastal Islands, Tarr Inlet Suture Zone, and Central Alexander Archipelago subregions.

  14. Magnetic properties, acid neutralization capacity, and net acid production of rocks in the Animas River Watershed Silverton, Colorado

    USGS Publications Warehouse

    McCafferty, Anne E.; Yager, Douglas B.; Horton, Radley M.; Diehl, Sharon F.

    2006-01-01

    Federal land managers along with local stakeholders in the Upper Animas River watershed near Silverton, Colorado are actively designing and implementing mine waste remediation projects to mitigate the effects of acid mine drainage from several abandoned hard rock metal mines and mills. Local source rocks with high acid neutralization capacity (ANC) within the watershed are of interest to land managers for use in these remediation projects. A suite of representative samples was collected from propylitic to weakly sericitic-altered volcanic and plutonic rocks exposed in outcrops throughout the watershed. Acid-base accounting laboratory methods coupled with mineralogic and geochemical characterization provide insight into lithologies that have a range of ANC and net acid production (NAP). Petrophysical lab determinations of magnetic susceptibility converted to estimates for percent magnetite show correlation with the environmental properties of ANC and NAP for many of the lithologies. A goal of our study is to interpret watershed-scale airborne magnetic data for regional mapping of rocks that have varying degrees of ANC and NAP. Results of our preliminary work are presented here.

  15. Equilibrium partitioning and subsequent re-distribution of halogens among apatite-biotite-amphibole assemblages from mantle-derived plutonic rocks: Complexities revealed

    NASA Astrophysics Data System (ADS)

    Teiber, Holger; Scharrer, Manuel; Marks, Michael A. W.; Arzamastsev, Andrei A.; Wenzel, Thomas; Markl, Gregor

    2015-04-01

    The concentration of halogens in apatite, biotite and amphibole is investigated for a large variety of mantle-derived plutonic rocks (gabbros, diorites, monzonites, olivine- and pyroxene-bearing monzonitic to granitic rocks, syenites, carbonatites and a phoscorite). In all rocks studied, apatite occurs as an early magmatic phase, whereas biotite and amphibole may occur either as a late magmatic phase or as late-stage, potentially hydrothermal product replacing precursor olivine, pyroxene and Fe-Ti oxides (ilmenite and magnetite). Based on electron microprobe analyses for F and Cl and detailed textural observations, we test existing models of halogen partitioning between apatite and biotite. Bromine concentration data for apatite, biotite and amphibole are used to further refine our understanding of the geochemical similarities and differences between Cl and Br during magmatic and hydrothermal processes. Our data suggests that F and Cl contents in apatite, biotite and amphibole can indeed be useful monitors of the halogen systematics in magmas, but they may also be subject to post-magmatic changes to variable extents. The relatively small radius and compatible F cation seems to be less prone to post-magmatic alteration and is likely to best reflect the original magmatic halogen abundances - especially in apatite. However, the larger and probably more incompatible Cl anion, is more easily re-mobilized as reflected by strong redistribution of Cl in biotite and amphibole which have been clearly overprinted by hydrothermal fluids. In certain cases, the ability of halogens to re-distribute themselves after magmatic equilibrium partitioning (as emphasized by our data) suggests that observed partitioning (especially between apatite and biotite) may also be used as a very sensitive indicator for post-magmatic hydrothermal processes.

  16. A numerical method for retrieving high oxygen isotope temperatures from plutonic igneous rocks: An example from the Laramie Anorthosite Complex, Wyoming, USA

    SciTech Connect

    Farquhar, J.; Chacko, T. . Dept. of Geology); Frost, B.R. )

    1992-01-01

    The Sybille Pit is a late-stage magnetite-ilmenite-plagioclase-bearing differentiate of the Laramie Anorthosite with a wide range of grain sizes and modal mineralogy. This variability makes Sybille an ideal locality in which to study the factors that affect isotopic thermometry in plutonic environments. The authors have developed a numerical model based on isotope exchange trajectories that retrieves close to magmatic temperatures for samples from Sybille. This method is based on the premise that hand sample-scale sub-systems close to exchange with each other at temperatures that exceed those of the constituent minerals. The temperature of hand-sample scale closure is retrieved by back calculating the isotope exchange trajectories to the temperature at which two samples with widely different model compositions are in isotopic equilibrium. Application of these methods to samples from Sybille provides promising results. Whereas conventional isotopic thermometry of individual samples yields a wide range of temperatures ([approximately]600 to > 1000 C) depending on the mineral-pair chosen, application of this numerical model to multiple samples yields temperatures of 1,070 [+-] 100 C which corresponds closely to the inferred solidus for these rocks.

  17. Part 1. Stratigraphy, structure and petrology of the Peterborough 1.5-minute quadrangle, New Hampshire and part 2. Graphite textural and isotropic variations in plutonic rocks, south-central New Hampshire

    NASA Astrophysics Data System (ADS)

    Duke, E. F.

    The stratigraphy of the Merrimack Synclinorium in the Peterborough quadrangle is reinterpreted and correlated with fossil dated Silurian-Lower Devonian strata of western Maine. The earliest phase of the Acadian Orogeny produced west directed fold thrust nappes in this area. The Kinsman Quartz Monzonite was intruded along axial surfaces of these structures, locally establishing peak metamorphic conditions in the wall rocks. Intrusion of the Kinsman was closely followed by mafic intrusions of the Spaulding Quartz. Dorite possibly accompanying west northwest F sub 2 folding, and peak metamorphic conditions were reached in adjacent rocks. Graphite occurs in two distinct textural varieties in syntectonic granifolds of the New Hampshire Plutonic Series and in associated metasedimentary wall rocks. Textural characteristics indicate that coarse graphite flakes (0.1 to 1.0mm) were present at an early stage of crystallization of the igneous rocks and may represent xenocrystic material assimilated from the wall rocks.

  18. Age and tectonic setting of subsurface plutonic rocks in south Alabama: Implications for igneous activity along the Alleghanian suture

    SciTech Connect

    Guthrie, G.M. ); Steltenpohl, M.G. . Dept. of Geology); Heatherington, A.L. . Dept. of Geology); Kunk, M.J. ); Defant, M.S. . Dept. of Geology); Salpas, P.A. )

    1994-03-01

    The proposed Alleghanian suture between ancestral North America and Suwannee terrane Gondwana crust trends east-west beneath coastal plain sediments from South Carolina to Alabama. Three distinct intrusive suites in south Alabama have been examined to determine their possible relationships with the suture. The first suite consists of rhyolite, andesite, andesitic breccia, and granodiorite and forms the stratigraphic base of the Suwannee terrane. Calc-alkaline metaluminous granodiorite yields a whole-rock depleted mantle Nd model age of 1,023 Ma, a U-Pb zircon crystallization age of 625 Ma, and a [sup 40]Ar/[sup 39]Ar cooling age (ca. 500 C) of ca. 612 Ma. The second suite comprises felsic granophyre, pyroxenite, and diabase. Metaluminous granophyre follows a calc-alkaline trend with pyroxenite. Trace element ratios (Ta/Yb and Rb/Yb+Ta) indicate a volcanic or syn-collisional arc environment. Biotite separates from granodiorite yield a [sup 40]Ar/[sup 39]Ar cooling age (ca. 300 C) of ca. 329 Ma. Pyroxenite and granophyre Nd model ages are 1,062 and 1,090 Ma, respectively. The third suite comprises high-iron quartz-normative tholeiitic diabase, gabbro, and basalt. These rocks have Ta/Yb and Rb/Yb+Ta ratios similar to within plate magmas, and are correlated with the Lower Jurassic North American diabase suite because of geochemical similarities and intrusive contacts with the Upper Triassic-Lower Jurassic Newark Group.

  19. Cogenetic Rock Fragments from a Lunar Soil: Evidence of a Ferroan Noritic-Anorthosite Pluton on the Moon

    NASA Technical Reports Server (NTRS)

    Jolliff, B. L.; Haskin, L. A.

    1995-01-01

    The impact that produced North Ray Crater, Apollo 16 landing site, exhumed rocks that include relatively mafic members of the lunar ferroan anorthositic suite. Bulk and mineral compositions indicate that a majority of 2-4 mm lithic fragments from sample 67513, including impact breccias and monomict igneous rocks, are related to a common noritic-anorthosite precursor. Compositions and geochemical trends of these lithic fragments and of related samples collected along the rim of North Ray Crater suggest that these rocks derived from a single igneous body. This body developed as an orthocumulate from a mixture of cumulus plagioclase and mafic intercumulus melt, after the plagioclase had separated from any cogenetic mafic minerals and had become concentrated into a crystal mush (approximately 70 wt% plagioclase, 30 wt% intercumulus melt). We present a model for the crystallization of the igneous system wherein "system" is defined as cumulus plagioclase and intercumulus melt. The initial accumulation of plagioclase is analogous to the formation of thick anorthosites of the terrestrial Stillwater Complex; however, a second stage of formation is indicated, involving migration of the cumulus-plagioclase-intercumulus-melt system to a higher crustal level, analogous to the emplacement of terrestrial massif anorthosites. Compositional variations of the lithic fragments from sample 67513 are consistent with dominantly equilibrium crystallization of intercumulus melt. The highly calcic nature of orthocumulus pyroxene and plagioclase suggests some reaction between the intercumulus melt and cumulus plagioclase, perhaps facilitated by some recrystallization of cumulus plagioclase. Bulk compositions and mineral assemblages of individual rock fragments also require that most of the mafic minerals fortned in close contact with cumulus plagioclase, not as separate layers. The distribution of compositions (and by inference, modes) has a narrow peak at anorthosite and a broader, larger

  20. Acidic Plutonism in the Izu-Ogasawara (Bonin)-Mariana (IBM) Arc and Growth of Arc Crust: Petrological and Geochemical Characteristics of the Tonalite at the Komahashi-Daini Seamount and Difference From the Tanzawa Plutonic Complex

    NASA Astrophysics Data System (ADS)

    Haraguchi, S.; Ishii, T.

    2003-12-01

    Recent seismic refraction and reflection data suggest that the continents are underlain by mafic lower crust and felsic middle crust. Petrogenesis of granitic middle crust layers is important for understanding the formation and evolution of continental crust. In modern tectonic regimes, tonalitic rocks and chemically equivalent volcanic rocks occur in island arcs and active continental margins. Thus, the petrogenesis of tonalite and related rocks in intra-oceanic arc settings is of great importance in understanding the processes of both recent island arc and continental crust formation. The Komahashi-Daini Seamount, in the northern Kyushu-Palau Ridge in the northern Philippine Sea plate, was investigated by the Japanese Geodynamics Project (GDP) cruises in the 1970's, and by the R/V Tansei-maru (Ocean Research Institute, University of Tokyo) in the 1990's. Plutonic rocks were dredged from the seamount, and have great importance for understanding the processes of island arc and continental crust formation. The petrographical and geochemical characteristics of the Komahashi-Daini Seamount tonalite are summarized as follows: (1) These tonalites are classified into biotite-hornblende tonalite and hornblende tonalite. Phenocrysts, especially plagioclase, show common lamellar twins and oscillatory zoning patterns; (2) This tonalite show low content of bulk LILE, and classified into low-K calc-alkaline, 1 to 8 wt.% MgO with 55 to 75 wt.% SiO2; (3) This tonalite shows roughly parallel and increasing total REE content with increasing SiO2 content, except for increasingly strong negative Eu anomaly at higher SiO2. These factors indicate that the Komahashi-Daini Seamount tonalite was produced by fractional crystallization. The parent magma of this tonalite is considered lower than 56 wt.% SiO2. Based on this relationship, we concluded that the source for the parental magma was arc mantle peridotite. We compared these tonalites with typical tonalite, i.e., Tanzawa Complex

  1. Early Paleozoic alkalic and calc-alkalic plutonism and associated contact metamorphism, central Virginia Piedmont

    USGS Publications Warehouse

    Pavlides, Louis; Arth, Joseph G.; Sutter, J.F.; Stern, T.W.; Cortesini, Henry, Jr.

    1994-01-01

    Early Paleozoic plutonism in the central Virginia Piedmont consists of the igneous Lahore Complex and Ellisville Pluton. The Lahore Complex consists of a small altered mafic pluton intruded by the shoshonitic, alkalic monzonites of the Lahore Pluton (-450 Ma) that, in turn, is intruded by the calc-alkaline, granodioritic Ellisville Pluton (-440 Ma). These plutons were emplaced at about 760aC at a depth of 12 to 18 km within greenschist-facies rocks and are enclosed by contact-metamorphosed rocks.

  2. Acid rock drainage and climate change

    USGS Publications Warehouse

    Nordstrom, D.K.

    2009-01-01

    Rainfall events cause both increases and decreases in acid and metals concentrations and their loadings from mine wastes, and unmined mineralized areas, into receiving streams based on data from 3 mines sites in the United States and other sites outside the US. Gradual increases in concentrations occur during long dry spells and sudden large increases are observed during the rising limb of the discharge following dry spells (first flush). By the time the discharge peak has occurred, concentrations are usually decreased, often to levels below those of pre-storm conditions and then they slowly rise again during the next dry spell. These dynamic changes in concentrations and loadings are related to the dissolution of soluble salts and the flushing out of waters that were concentrated by evaporation. The underlying processes, pyrite oxidation and host rock dissolution, do not end until the pyrite is fully weathered, which can take hundreds to thousands of years. These observations can be generalized to predict future conditions caused by droughts related to El Ni??o and climate change associated with global warming. Already, the time period for dry summers is lengthening in the western US and rainstorms are further apart and more intense when they happen. Consequently, flushing of inactive or active mine sites and mineralized but unmined sites will cause larger sudden increases in concentrations that will be an ever increasing danger to aquatic life with climate change. Higher average concentrations will be observed during longer low-flow periods. Remediation efforts will have to increase the capacity of engineered designs to deal with more extreme conditions, not average conditions of previous years.

  3. A Tale of Two Plutons: Using Monazite to Reconstruct the Fluid History of Contact Metamorphic Aureoles

    NASA Astrophysics Data System (ADS)

    Ayers, J. C.; Crombie, S.; Miller, C.; Luo, Y.; Loflin, M.

    2006-12-01

    The rare earth phosphate monazite can be a powerful tool for characterizing the timing and spatial extent of fluid infiltration during contact metamorphism. We used an ion microprobe to investigate how wallrock monazite responded to the intrusion of two different granitic plutons, the Cretaceous Birch Creek Pluton (BCP) in the White Mountains of eastern California and the Miocene Searchlight pluton in southern Nevada. The contact metamorphic aureoles of both plutons contain monazite and display evidence of alteration by acidic magmatic fluids (sericitization). Contact metamorphism occurred at conditions under which monazite in granitic systems has been shown to be susceptible to hydrothermal alteration: mildly acidic fluids at temperatures of ~250-400C and pressures of ~0.15-0.4 GPa. Monazite from the hydrothermal aureole of the BCP records the infiltration of magmatic fluids into the Early Cambrian Deep Spring Formation (DSF) containing metaquartzites and metasandstones. Monazites in the DSF < 0.6 km from the contact show patchy zoning and have Th-Pb ages and oxygen isotope compositions similar to monazites in the Birch Creek granite but different from monazites > 0.6 km from the contact, suggesting that they dissolved and reprecipitated in infiltrating magmatic fluids. In contrast, the stable isotope compositions of monazites and host rocks (Proterozoic gneisses and the Cretaceous Ireteba granite) on the flanks of the Searchlight pluton do not show evidence of hydrothermal alteration, even though many of the monazites display patchy zoning and ages corresponding to the Searchlight intrusion. The Searchlight gold-silver-copper mining district is primarily located in the roof of the Searchlight intrusion, which contains rocks that were intensely hydrothermally altered but contain no monazite. Searchlight magmatic fluids were strongly focused into the roof zone, with little or no fluid escaping out the sides of the Searchlight pluton during crystallization. Monazite

  4. A statistical approach to the volcanic-plutonic connection

    NASA Astrophysics Data System (ADS)

    Schoene, B.; Keller, C.; Samperton, K. M.; Barboni, M.; Husson, J. M.

    2013-12-01

    The geochemical relationship between volcanic and plutonic rocks - whether the two are geochemically identical, or if the choice between eruption or intrusion is correlated with magma chemistry - represents a major unanswered question in igneous petrology. In one endmember scenario, felsic to intermediate plutons represent the unerupted residue from which crystal-poor eruptible melts are extracted. At the other end of the spectrum, it is argued that a nearly the entire volume of magma is evacuated during eruption, and that the probability of eruption versus intrusion is instead largely a function of magma flux. In the first scenario, parental magmas originating at depth experience substantial fractionation during volcanic melt extraction, leading to complementary volcanic and plutonic reservoirs. In the second endmember scenario, volcanic/plutonic fractionation in the middle to upper crust is negligible, predicting no geochemical difference between volcanic and plutonic rocks. A third endmember scenario that is not exclusive from the other two predicts differences between volcanic and plutonic rocks if geochemical characteristics are correlated with the eventual eruptibility of magma. Deciphering the relative importance of each of these models is important for understanding both the long-term geochemical balance of the crust and mantle due to increased erosion and recycling of volcanic rocks and also for understanding magma transport dynamics. We have compared the geochemistry of ~500,000 volcanic and plutonic rocks from a range of tectonic settings by Monte Carlo bootstrap analysis in order to produce maximally representative average compositions. The results indicate that while volcanic and plutonic rocks in general show remarkably similar major element trends, intermediate to felsic plutonic rocks, for a given silica content, display clear enrichments in Sr and Ba and depletions in Zr, Hf, and HREEs relative to their volcanic equivalents. More subtly

  5. PASSIVE TREATMENT OF ACID ROCK DRAINAGE FROM A SUBSURFACE MINE

    EPA Science Inventory

    Acidic, metal-contaminated drainages are a critical problem facing many areas of the world. Acid rock drainage results when metal sulfide minerals, particularly pyrite, are oxidized by exposure to oxygen and water. The deleterious effects of these drainages on receiving streams a...

  6. PRECIPITATION OF PLUTONOUS PEROXIDE

    DOEpatents

    Barrick, J.G.; Manion, J.P.

    1961-08-15

    A precipitation process for recovering plutonium values contained in an aqueous solution is described. In the process for precipitating plutonium as plutonous peroxide, hydroxylamine or hydrazine is added to the plutoniumcontaining solution prior to the addition of peroxide to precipitate plutonium. The addition of hydroxylamine or hydrazine increases the amount of plutonium precipitated as plutonous peroxide. (AEC)

  7. Petrology and radiogeology of the Stripa pluton

    SciTech Connect

    Wollenberg, H.; Flexser, S.; Andersson, L.

    1980-12-01

    Both the quartz monzonite and the metavolcanic leptite which it intruded are strongly fractured. Two stages of fracture filling are evident; an earlier stage encompassing quartz, sericite, feldspar, epidote, and chlorite, and a later stage dominated by carbonate minerals. The Stripa quartz monozite is chemically and mineralogically distinct from other plutons in the region. Muscovite is the predominant mica in the quartz monzonite; biotite has been altered to chlorite, hornblende is absent, and accessory minerals are scarce. In contrast, in other plutons in the Stripa region, biotite and hornblende are prominent mafic minerals and accessory minerals are abundant. The Stripa quartz monzonite is also considerably more radioactive than the the leptite and other plutons in the region. Uranium and thorium abundances are both approx. 30 ppM, considerably higher than in normal granitic rocks where the thorium-to-uranium ratio generally exceeds 2. Potassium-argon dating of muscovite from the Stripa quartz monzonite indicates that this rock may be older, at 1691 million years than granitic rock of the neighboring Gusselby and Kloten massifs, whose ages, based on K-Ar dating of biotite, are respectively 1604 and 1640 m.y. Heat flow and heat productivity considerations show that although Stripa quartz monzonite contains high abundances of radioelements, the pluton has little efect on the regional heat flow. If it occurs in a layered plutonic setting, it is not more than 1.5 km thick; otherwise it may comprise a stock, dike, or border phase that is relatively small compared with the large granitic plutons exposed in the region.

  8. Petrology and radiogeology of the Stripa pluton

    SciTech Connect

    Wollenberg, Harold; Flexser, Steve; Andersson, Lennart

    1980-12-01

    To better define the character of the rock encompassing the thermomechanical and hydrological experiments at the Stripa mine in central Sweden, and to help determine the size of the Stripa pluton, detailed studies were conducted of the petrology and radiogeology of the quartz monzonite and adjacent rocks. Petrologic studies emphasized optical petrography, with supplementary X-ray diffraction, X-ray fluorescence and microprobe analyses. Radiogeologic investigations were based primarily on surface and underground gamma-ray spectrometric measurements of uranium, thorium and potassium, supplemented by laboratory gamma spectrometric analyses and fission-track radiographic determinations of the locations and abundance of uranium in the rock matrix. Both the quartz monzonite and the metavolcanic leptite which it intruded are strongly fractured. Two stages of fracture filling are evident; an earlier stage encompassing quartz, sericite, feldspar, epidote, and chlorite, and a later stage dominated by carbonate minerals. The Stripa quartz monzonite is chemically and mineralogically distinct from other plutons in the region. Muscovite is the predominant mica in the quartz monzonite; biotite has been altered to chlorite, hornblende is absent, and accessory minerals are scarce. In contrast, in other plutons in the Stripa region biotite and hornblende are prominent mafic minerals and accessory minerals are abundant. The Stripa quartz monzonite is also considerably more radioactive than the leptite and other plutons in the region. Uranium and thorium abundances are both- 30 ppm, considerably higher than in "normal" granitic rocks where the thorium-to-uranium ratio generally exceeds 2. Potassium-argon dating of muscovite from the Stripa quartz monzonite indicates that this rock may be older, at 1691 million years than granitic rock of the neighboring Gusselby and Kloten massifs, whose ages, based on K-Ar dating of biotite, are respectively 1604 and 1640 m.y. Heat flow and heat

  9. Relationship of voluminous ignimbrites to continental arc plutons: Petrology of Jurassic ignimbrites and contemporaneous plutons in southern California

    USGS Publications Warehouse

    Fohey-Breting, N. K.; Barth, A.P.; Wooden, J.L.; Mazdab, F.K.; Carter, C.A.; Schermer, E.R.

    2010-01-01

    Volcanism was broadly associated in both space and time with Mesozoic plutonism in the Cordillera continental margin arc, but the precise petrogenetic relationships between volcanic rocks and adjacent zoned plutons are not known. Igneous rocks in a tilted crustal section in California include four laterally extensive Jurassic ash flow tuffs from 550 to >1100 m thick underlain at deeper structural levels by Jurassic plutons. Zircon geochronology confirms previous correlations of individual tuffs, suggesting ignimbrites with eruptive volumes up to 800 km3 were deposited both during the apparent Early Jurassic plutonic lull as well as contemporaneous with solidification of regionally widespread Middle and Late Jurassic plutons. The tuffs are weakly to strongly porphyritic (5 to 55% phenocrysts) monotonous intermediate porphyritic dacite to low-silica rhyolite and show strong bulk rock chemical affinity to contemporaneous plutons. Trace element compositions of zircons from the tuffs and contemporaneous plutonic rocks record large and consistent differences in Hf/Zr and REE over similar ranges in Ti abundances, supporting bulk compositional similarities and illuminating similarities and variations in thermal histories despite the effects of hydrothermal alteration. ?? 2009 Elsevier B.V. All rights reserved.

  10. Multiphase groundwater flow near cooling plutons

    USGS Publications Warehouse

    Hayba, D.O.; Ingebritsen, S.E.

    1997-01-01

    We investigate groundwater flow near cooling plutons with a computer program that can model multiphase flow, temperatures up to 1200??C, thermal pressurization, and temperature-dependent rock properties. A series of experiments examines the effects of host-rock permeability, size and depth of pluton emplacement, single versus multiple intrusions, the influence of a caprock, and the impact of topographically driven groundwater flow. We also reproduce and evaluate some of the pioneering numerical experiments on flow around plutons. Host-rock permeability is the principal factor influencing fluid circulation and heat transfer in hydrothermal systems. The hottest and most steam-rich systems develop where permeability is of the order of 10-15 m2. Temperatures and life spans of systems decrease with increasing permeability. Conduction-dominated systems, in which permeabilities are ???10-16m2, persist longer but exhibit relatively modest increases in near-surface temperatures relative to ambient conditions. Pluton size, emplacement depth, and initial thermal conditions have less influence on hydrothermal circulation patterns but affect the extent of boiling and duration of hydrothermal systems. Topographically driven groundwater flow can significantly alter hydrothermal circulation; however, a low-permeability caprock effectively decouples the topographically and density-driven systems and stabilizes the mixing interface between them thereby defining a likely ore-forming environment.

  11. Miscellaneous investigations series: Bedrock geologic map of the Lone Mountain pluton area, Esmeralda County, Nevada

    SciTech Connect

    Maldonado, F.

    1984-12-31

    The joint attitudes were measured in the field and plotted on aerial photos at a scale of 1:24,000. The pluton is intensely jointed, primarily as a result of cooling and movement of the magma within a northwest-trending stress field. Foliation, in general, is poorly developed, and quality varies from area to area, but it is best developed close to the contacts with the metasedimentary rocks. A prominent northwest foliation direction was observed that parallels the northwest elongation of the exposed pluton. Faults in the pluton are difficult to identify because of the homogeneity of the rock. Several faults were mapped in the northern part of the area where they have a northeast trend and intersect the northwest-trending lamprophyre dikes with little apparent displacement. A major fault that bounds the northern part of the pluton is downthrown to the north and strikes northeast. This fault offsets the alluvium, the metasedimentary rocks, and the pluton and forms fault scraps as high as 10 m. Aeromagnetic data (US Geological Survey, 1979) suggest the following: (1) the local magnetic highs in the central part of the Lone Mountain pluton are probably related to topographic highs (peaks) where the flight lines are closer to the pluton; (2) a magnetic low in the northeastern part of Lone Mountain coincides with the pluton-country rock contact, which may be very steep; (3) the contours for the southwestern part of the mapped area indicate that the pluton-country rock contact is not as steep as that in the northeastern part and that the pluton probably coalesces at depth with the Weepah pluton, a pluton exposed south of the mapped area; and (4) the contours for the area of the Lone Mountain pluton express a northwest-trending gradient that parallels the northwest elongation of the Lone Mountain pluton and the northwest-trending stress field. 10 refs.

  12. Polymerization on the rocks: beta-amino acids and arginine

    NASA Technical Reports Server (NTRS)

    Liu, R.; Orgel, L. E.; Bada, J. L. (Principal Investigator)

    1998-01-01

    We have studied the accumulation of long oligomers of beta-amino acids on the surface of minerals using the 'polymerization on the rocks' protocol. We find that long oligopeptides of beta-glutamic acid which cannot be formed in homogeneous aqueous solution are accumulated efficiently on the surface of hydroxylapatite using 1-ethyl-3-(3-dimethylaminopropyl) carbodiimide (EDAC) as condensing agent. The EDAC-induced oligomerization of aspartic acid on hydroxylapatite proceeds even more efficiently. Hydroxylapatite can also facilitate the ligation of the tripeptide (glu)3. The 'polymerization on the rocks' scenario is not restricted to negatively-charged amino acids. Oligoarginines are accumulated on the surface of illite using carbonyldiimidizole (CDI) as condensing agent. We find that FeS2 catalyzes the CDI-induced oligomerization of arginine, although it does not adsorb oligoarginines. These results are relevant to the formation of polypeptides on the primitive earth.

  13. Net Acid Production, Acid Neutralizing Capacity, and Associated Mineralogical and Geochemical Characteristics of Animas River Watershed Igneous Rocks Near Silverton, Colorado

    USGS Publications Warehouse

    Yager, Douglas B.; Choate, LaDonna; Stanton, Mark R.

    2008-01-01

    This report presents results from laboratory and field studies involving the net acid production (NAP), acid neutralizing capacity (ANC), and magnetic mineralogy of 27 samples collected in altered volcanic terrain in the upper Animas River watershed near Silverton, Colo., during the summer of 2005. Sampling focused mainly on the volumetrically important, Tertiary-age volcanic and plutonic rocks that host base- and precious-metal mineralization in the study area. These rocks were analyzed to determine their potential for neutralization of acid-rock drainage. Rocks in the study area have been subjected to a regional propylitic alteration event, which introduced calcite, chlorite (clinochlore), and epidote that have varying amounts and rates of acid neutralizing capacity (ANC). Locally, hydrothermal alteration has consumed any ANC and introduced minerals, mainly pyrite, that have a high net acid production (NAP). Laboratory studies included hydrogen pyroxide (H2O2) acid digestion and subsequent sodium hydroxide (NaOH) titration to determine NAP, and sulfuric acid (H2SO4) acid titration experiments to determine ANC. In addition to these environmental rock-property determinations, mineralogical, chemical, and petrographic characteristics of each sample were determined through semiquantitative X-ray diffractometry (Rietveld method), optical mineralogy, wavelength dispersive X-ray fluorescence, total carbon-carbonate, and inductively coupled plasma?mass spectrometric analysis. An ANC ranking was assigned to rock samples based on calculated ANC quantity in kilograms/ton (kg/t) calcium carbonate equivalent and ratios of ANC to NAP. Results show that talus near the southeast Silverton caldera margin, composed of andesite clasts of the Burns Member of the Silverton Volcanics, has the highest ANC (>100 kg/t calcium carbonate equivalent) with little to no NAP. The other units found to have moderate to high ANC include (a) andesite lavas and volcaniclastic rocks of the San Juan

  14. Petrology and Geochemistry of Neoproterozoic Arc Plutons Beneath the Atlantic Coastal Plain, SRS, SC

    SciTech Connect

    Maryak, M.

    1998-10-21

    In this report is presented first a brief review of the regional geologic setting of the Savannah River Site, descriptions of the plutonic rock units sampled here, whole rock geochemical data on the plutonic igneous rocks, and finally, a discussion of how the crystalline basement rocks of the Savannah River Site formed and how they may correlate with other terranes exposed in the Piedmont of the Carolinas, Georgia, and Virginia.

  15. Petrogenesis of the reversely-zoned Turtle pluton, southeastern California

    SciTech Connect

    Allen, C.M.

    1989-01-01

    Few plutons with a reversed geometry of a felsic rim and mafic core have been described in the geologic literature. The Turtle pluton of S.E. California is an intrusion composed of a granitic rim and granodioritic core and common microgranitoid enclaves. Field observations, mineral textures and chemistries, major and trace element geochemistry, and isotopic variability support a petrogenetic model of in situ, concomitant, magma mixing and fractional crystallization of rhyolitic magma progressively mixed with an increasing volume of andesitic magma, all without chemical contribution from entrained basaltic enclaves. Hornblende geobarometry indicates the Turtle pluton crystallized at about 3.5 kb. A crystallization sequence of biotite before hornblende (and lack of pyroxenes) suggests the initial granitic magma contained less than 4 wt% H{sub 2}O at temperatures less than 780C. U-Pb, Pb-Pb, Rb-Sr and oxygen isotope studies indicate the terrane intruded by the Turtle pluton is 1.8 Ga, that the Turtle pluton crystallized at 130 Ma, that the Target Granite and garnet aplites are about 100 Ma, and that these intrusions were derived from different sources. Models based on isotopic data suggest the rhyolitic end member magma of the Turtle pluton was derived from mafic igneous rocks, and was not derived from sampled Proterozoic country rocks. Similarity of common Sr and Pb isotopic ratios of these rocks to other Mesozoic intrusions in the Colorado River Region suggest the Turtle pluton and Target Granite have affinities like rocks to the east, including the Whipple Mountains and plutons of western Arizona. P-T-t history of the southern Turtle Mountains implies uplift well into the upper crust by Late Cretaceous time so that the heating and deformation events of the Late Cretaceous and Tertiary observed in flanking ranges did not affect the study area.

  16. Application of Thermal Infrared Multiband Scanner (TIMS) data to mapping of Plutonic and stratified rock and assemblages in accreted terrains of the Northern Sierra, California

    NASA Technical Reports Server (NTRS)

    Taranik, James V.; Davis, David; Borengasser, Marcus

    1986-01-01

    The Thermal Infrared Multispectral Scanner (TIMS) data were acquired over the Donner Pass area in California on September 12, 1985. The higher peaks in the area approach 9,200 feet in elevation, while the canyon of the north fork of the American River is only 3000 feet in elevation. The vegetation is dominated by conifers, although manzanita and other shrubs are present in areas where soils have developed. The data contain noise patterns which cut across scan lines diagonally. The TIMS data were analyzed using both photointerpretative and digital processing techniques. Preliminary image interpretation and field analysis confirmed that TIMS image data displays the chert units and silicic volcanics as bright red. The imagery appears to display zoning in the batholithic and hypabyssal intrusive rocks, although this was not field checked at this time. Rocks which appear to be more dioritic in composition appear purple on the imagery, while rocks more granitic in composition appear shades of red and pink. Areas that have more than 40% vegetative cover appear green on the imagery.

  17. Petrology of Aztec Wash pluton, Eldorado Mountains, southern Nevada

    SciTech Connect

    Falkner, C.M.; Miller, C.F. ); Wooden, J.L. )

    1993-04-01

    Aztec Wash pluton, a 50 km[sup 2] intrusive complex in the northern Eldorado Mountains, was emplaced ca. 16 Ma (Faulds et al., 1990) during extension within the Colorado River Corridor. The pluton displays extreme compositional variability, ranging from olivine gabbro (ca. 50 wt% SiO[sub 2]) to highly evolved aplite (76% SiO[sub 2]). Most of the intrusion is medium grained, homogeneous granite (ca. 72% SiO[sub 2]), but 1/3 is highly heterogeneous and dominated by mafic to intermediate rocks; a 6 [times] 3km, N-S mafic zone almost bisects the pluton. Well-displayed magma mingling and late mafic and felsic dikes verify the coexistence of mafic and felsic melts. Hornblende barometry indicates that the entire exposed portion of Aztec Wash pluton was emplaced at very shallow depth (pluton has undergone little tilting. Mafic dikes that preceded emplacement of the pluton are variably dipping and in some cases sub horizontal, possibly suggesting a more complex pre-pluton deformational history. The authors propose the following emplacement history for Aztec Wash pluton: felsic magma intruded shallow levels of crust; the base of the magma chamber was intruded by basalt; after the upper portion of the initial magma was largely crystallized, basalt ascended into, perhaps remobilized, and mingled with felsic magma; this ascent may have been facilitated by E-W extension of the crystallizing pluton; more discrete syn- to post-pluton, mafic to felsic dikes mark additional intrusive pulses triggered by basalt intrusion and extensional fracturing. Field relations suggest that the mingling led to mixing in both the main units and the late dikes, but geochemical data indicate that mixing, if it occurred, was not a simple 2-end member process.

  18. LA-ICP MS zircon dating, whole-rock and Sr-Nd-Pb-O isotope geochemistry of the Camiboğazı pluton, Eastern Pontides, NE Turkey: Implications for lithospheric mantle and lower crustal sources in arc-related I-type magmatism

    NASA Astrophysics Data System (ADS)

    Kaygusuz, Abdullah; Arslan, Mehmet; Siebel, Wolfgang; Sipahi, Ferkan; İlbeyli, Nurdane; Temizel, İrfan

    2014-04-01

    Late Cretaceous I-type plutons are widespread in the Eastern Pontides, NE Turkey. The studied Camiboğazı pluton is a composite pluton consisting of diorite, tonalite, monzodiorite, monzonite, quartz monzonite, granite, and mafic microgranular enclaves (MMEs). Laser ablation ICP-MS U-Pb dating of zircon yielded crystallization ages of 76.21 ± 0.79 Ma, 75.65 ± 0.50 Ma, 75.04 ± 0.83 Ma, and 74.73 ± 0.86 Ma for diorite, monzodiorite, monzonite, and granite, respectively. The rocks of the pluton have I-type, high-K to shoshonitic and metaluminous character, displaying whole-rock geochemical features of arc-related granites. They are enriched in large-ion lithophile and light rare-earth elements, and depleted in high-field-strength elements. Major element variations can be attributed to fractionation of plagioclase, clinopyroxene, hornblende, and Fe-Ti oxides. The rocks show considerable variation in 87Sr/86Sr(i) (0.70498 to 0.70622), ɛNd(i) (- 2.79 to - 0.36), δ18O values (+ 6.3 to + 11.4) and Nd model ages (TDM) (0.81 Ga to 1.26 Ga). Besides, they have (206Pb/204Pb) = 18.44-19.09, (207Pb/204Pb) = 15.64-15.69, and (208Pb/204Pb) = 38.37-38.89. Although isotope signatures of the mafic microgranular enclaves (MMEs) (87Sr/86Sr(i) = 0.70551 to 0.70622; ɛNd(i) = - 2.9 to - 1.23; δ18O = + 8.3 to + 9.7) are largely similar to the host rocks, MMEs are characterized by relatively high Mg-numbers (32-36), low contents of SiO2 (52-56 wt.%) and low ASI (0.7-0.9). Estimated crystallization temperatures for the rocks of the pluton range from 735 ± 58 °C to 844 ± 24 °C and a shallow intrusion depth (< 10 km) is estimated from Al-in-hornblende thermobarometry. Whole-rock geochemical and isotopic data suggest magma generation by dehydration melting of an amphibolite-type lower crustal component with additional input of a subcontinental lithospheric mantle component. Furthermore, Sr-Nd isotope mixing model reveals ~ 30% to 40% lower crustal magma contribution to the mantle

  19. Petrogenesis of collision-related plutonics in Central Anatolia, Turkey

    NASA Astrophysics Data System (ADS)

    Ilbeyli, N.; Pearce, J. A.; Thirlwall, M. F.; Mitchell, J. G.

    2004-02-01

    Central Anatolia exhibits good examples of calc-alkaline and alkaline magmatism of similar age in a collision-related tectonic setting (continent-island arc collision). In the Central Anatolia region, late Cretaceous post-collisional plutonic rocks intrude Palaeozoic-Mesozoic metamorphic rocks overthrust by Upper Cretaceous ophiolitic units to make up the Central Anatolian Crystalline Complex. In the complex, three different intrusive rock types may be recognised based on their geochemical characteristics: (i) calc-alkaline (Behrekdag, Cefalikdag, and Celebi); (ii) subalkaline-transitional (Baranadag); and (ii) alkaline (Hamit). The calc-alkaline and subalkaline plutonic rocks are metaluminous I-type plutons ranging from monzodiorite to granite. The alkaline plutonic rocks are metaluminous to peralkaline plutons, predominantly A-type, ranging from nepheline monzosyenite to quartz syenite. All intrusive rocks show enrichment in LILE and LREE relative to HFSE, and have high 87Sr/ 86Sr and low 143Nd/ 144Nd ratios. These characteristics indicate an enriched mantle source region(s) carrying a subduction component inherited from pre-collision subduction events. The tectonic discrimination diagram of Rb vs. (Y+Nb) suggests that the calc-alkaline, subalkaline, and alkaline plutonic rocks have been affected by crustal assimilation combined with fractional crystallisation processes. The coexistence of calc-alkaline and alkaline magmatism in the Central Anatolian Crystalline Complex may be attributed to mantle source heterogeneity before collision. The former carries a smaller intraplate component and pre-subduction enrichment compared to the latter. Either thermal perturbation of the metasomatised lithosphere by delamination of the thermal boundary layer (TBL), or removal of a subducted plate (slab breakoff) is the likely mechanism for the initiation of the post-collisional magmatism in the Complex.

  20. The Solarya Volcano-Plutonic Complex (NW Turkey): Petrography, Petrogenesis and Tectonic Implications

    NASA Astrophysics Data System (ADS)

    Ünal, Alp; Kamacı, Ömer; Altunkaynak, Şafak

    2014-05-01

    The post collisional magmatic activity produced several volcano-plutonic complexes in NW Anatolia (Turkey) during the late Oligocene- Middle Miocene. One of the major volcano-plutonic complexes, the Solarya volcano-plutonic complex is remarkable for its coeval and cogenetic plutonic (Solarya pluton), hypabysal and volcanic rocks of Early Miocene (24-21 Ma) age. Solarya pluton is an epizonal pluton which discordantly intruded into metamorphic and nonmetamorphic basement rocks of Triassic age. It is a N-S trending magmatic body covering an area of 220 km2,approximatelly 20 km in length and 10 km in width. Based on the field and petrographic studies, three main rock groups distinguished in Solarya pluton; K-feldspar megacrystalline granodiorite, microgranite-granodiorite and haplogranite. Porphyritic and graphic-granophyric textures are common in these three rock groups. Pluton contains magmatic enclaves and syn-plutonic dykes of dioritic composition. Hypabyssal rocks are represented by porphyritic microdiorite and porphyritic quartz-diorite. They form porphyry plugs, sheet inrusions and dykes around the pluton. Porphyrites have microcrystalline-cryptocrystalline groundmass displaying micrographic and granophyric textures. Petrographically similar to the hypabyssal rocks, volcanic rocks are formed from andesitic and dasitic lavas and pyroclastic rocks. Plutonic, hypabyssal and volcanic rocks of Solarya volcano-plutonic complex show similar major-trace element and Sr-Nd-Pb isotopic compositions, indicating common magmatic evolution and multicomponent melt sources including mantle and crustal components. They are mainly metaluminous, medium to high-K calc alkaline rocks and display enrichment in LILE and depletion in Nb, Ta, P and Ti. They have initial 87Sr/86Sr values of 0.70701- 0.70818 and 143Nd/144Nd values of 0.51241-0.51250. These geochemical characteristics and isotopic signatures are considered to reflect the composition of the magmas derived from a

  1. Survey of lunar plutonic and granulitic lithic fragments

    NASA Technical Reports Server (NTRS)

    Bickel, C. E.; Warner, J. L.

    1978-01-01

    A catalog of lunar plutonic rocks and granulitic impactites belonging to the ANT suite has been compiled. The coarser-grained, plutonic rocks in the compilation are probably pristine; they belong to two groups, Mg-rich plutonic rocks and anorthosites, with a preponderance of the latter type. The granulitic impactites, however, have bulk and mineral compositions that fall between the two groups defined by the pristine nonmare samples of Warren and Wasson (1977). Thus the granulitic impactites may have originated by metamorphism of mixed impactites in early breccia sheets. The catalog, representative of the lunar crust before the end of heavy bombardment, suggests a crust with over 78 vol. % plagioclase and about equal proportions of material with noritic and troctolitic affinity.

  2. Silicon Isotope Fractionation During Acid Water-Igneous Rock Interaction

    NASA Astrophysics Data System (ADS)

    van den Boorn, S. H.; van Bergen, M. J.; Vroon, P. Z.

    2007-12-01

    Silica enrichment by metasomatic/hydrothermal alteration is a widespread phenomenon in crustal environments where acid fluids interact with silicate rocks. High-sulfidation epithermal ore deposits and acid-leached residues at hot-spring settings are among the best known examples. Acid alteration acting on basalts has also been invoked to explain the relatively high silica contents of the surface of Mars. We have analyzed basaltic-andesitic lavas from the Kawah Ijen volcanic complex (East Java, Indonesia) that were altered by interaction with highly acid (pH~1) sulfate-chloride water of its crater lake and seepage stream. Quantitative removal of major elements during this interaction has led to relative increase in SiO2 contents. Our silicon isotope data, obtained by HR-MC-ICPMS and reported relative to the NIST RM8546 (=NBS28) standard, show a systematic increase in &δ&&30Si from -0.2‰ (±0.3, 2sd) for unaltered andesites and basalts to +1.5‰ (±0.3, 2sd) for the most altered/silicified rocks. These results demonstrate that silicification induced by pervasive acid alteration is accompanied by significant Si isotope fractionation, so that alterered products become isotopically heavier than the precursor rocks. Despite the observed enrichment in SiO2, the rocks have experienced an overall net loss of silicon upon alteration, if Nb is considered as perfectly immobile. The observed &δ&&30Si values of the alteration products appeared to correlate well with the inferred amounts of silicon loss. These findings would suggest that &28Si is preferentially leached during water-rock interaction, implying that dissolved silica in the ambient lake and stream water is isotopically light. However, layered opaline lake sediments, that are believed to represent precipitates from the silica-saturated water show a conspicuous &30Si-enrichment (+1.2 ± 0.2‰). Because anorganic precipitation is known to discriminate against the heavy isotope (e.g. Basile- Doelsch et al., 2006

  3. Geophysical modeling and structure of Ushuaia Pluton, Fuegian Andes, Argentina

    NASA Astrophysics Data System (ADS)

    Peroni, Javier Ignacio; Tassone, Alejandro Alberto; Menichetti, Marco; Cerredo, María Elena

    2009-10-01

    Within the area of Ushuaia Bay (Tierra del Fuego, southernmost South America) the deformed Lower Cretaceous sedimentary rocks of Yahgán Formation host the Ushuaia Pluton. The intrusive body is oval in map view; it is compositionally varied with rocks ranging from the ultrabasic to the mesosiliceous realm. The emplacement time is constrained within the Albian-Cenomanian span by new amphibole K/Ar data. Meso- and microstructures of Ushuaia Pluton and its host indicate a synkinematic emplacement with a dominant extensional component. A set of transcurrent and normal faults related to the sinistral strike-slip Beagle Channel Fault System affects the pluton and its host. On the basis of aeromagnetic data combined with field information, a new model is presented for the Ushuaia Pluton. Modeling results fit well with a laccolithic body with an estimated volume of around 111 km 3. The model pluton cross-section displays a central zone with an average thickness of 2000 m which progressively thins toward the margins (˜ 500 m) and a southern root which reaches 5000 m deep. The combined structural and geophysical model supports a transtensive scenario for the Ushuaia Pluton emplacement at Early-Late Cretaceous boundary.

  4. Bibliography for acid-rock drainage and selected acid-mine drainage issues related to acid-rock drainage from transportation activities

    USGS Publications Warehouse

    Bradley, Michael W.; Worland, Scott C.

    2015-01-01

    Acid-rock drainage occurs through the interaction of rainfall on pyrite-bearing formations. When pyrite (FeS2) is exposed to oxygen and water in mine workings or roadcuts, the mineral decomposes and sulfur may react to form sulfuric acid, which often results in environmental problems and potential damage to the transportation infrastructure. The accelerated oxidation of pyrite and other sulfidic minerals generates low pH water with potentially high concentrations of trace metals. Much attention has been given to contamination arising from acid mine drainage, but studies related to acid-rock drainage from road construction are relatively limited. The U.S. Geological Survey, in cooperation with the Tennessee Department of Transportation, is conducting an investigation to evaluate the occurrence and processes controlling acid-rock drainage and contaminant transport from roadcuts in Tennessee. The basic components of acid-rock drainage resulting from transportation activities are described and a bibliography, organized by relevant categories (remediation, geochemical, microbial, biological impact, and secondary mineralization) is presented.

  5. Reduction of acid rock drainage using steel slag in cover systems over sulfide rock waste piles.

    PubMed

    de Almeida, Rodrigo Pereira; Leite, Adilson do Lago; Borghetti Soares, Anderson

    2015-04-01

    The extraction of gold, coal, nickel, uranium, copper and other earth-moving activities almost always leads to environmental damage. In metal and coal extraction, exposure of sulfide minerals to the atmosphere leads to generation of acid rock drainage (ARD) and in underground mining to acid mine drainage (AMD) due to contamination of infiltrating groundwater. This study proposes to develop a reactive cover system that inhibits infiltration of oxygen and also releases alkalinity to increase the pH of generated ARD and attenuate metal contaminants at the same time. The reactive cover system is constructed using steel slag, a waste product generated from steel industries. This study shows that this type of cover system has the potential to reduce some of the adverse effects of sulfide mine waste disposal on land. Geochemical and geotechnical characterization tests were carried out. Different proportions of sulfide mine waste and steel slag were studied in leachate extraction tests. The best proportion was 33% of steel slag in dry weight. Other tests were conducted as follows: soil consolidation, saturated permeability and soil water characteristic curve. The cover system was numerically modeled through unsaturated flux analysis using Vadose/w. The solution proposed is an oxygen transport barrier that allows rain water percolation to treat the ARD in the waste rock pile. The results showed that the waste pile slope is an important factor and the cover system must have 5 m thickness to achieve an acceptable effectiveness. PMID:25750056

  6. Thermal maturation of incrementally assembled plutons

    NASA Astrophysics Data System (ADS)

    Davis, J.; Coleman, D. S.; Heizler, M. T.

    2009-12-01

    The Cretaceous zoned intrusive suites of the Sierra Nevada batholith (SNB) were each assembled over 8-11 million years through incremental amalgamation of sheeted intrusions. Emplacement as small sheet-like increments inhibits development of a voluminous zone of melt bearing rock; instead the active magma body represents only a small portion of the total volume intruded. Plutons formed incrementally will have a protracted thermal history (T-t) that can be elucidated using thermochronologic techniques yielding insights into the thermal evolution of the lithosphere at magma chamber-pluton scales. Thermal histories are derived for plutons from the dike-like John Muir Intrusive Suite (JMIS) and the laccolithic Mount Whitney Intrusive Suite (MWIS), both located in the eastern-central SNB, by correlating estimated zircon saturation and argon closure temperatures with U-Pb zircon and titanite, 40Ar/39Ar amphibole, biotite, and K-feldspar ages. Close agreement among zircon and hornblende ages indicate rapid cooling following intrusion. However, hornblende and biotite ages are separated by 6-9 million years indicating slow protracted cooling. We interpret these data to reflect the thermal maturation of an incrementally assembled magma system in which temperatures cycled between ~500-300°C for millions of years. Hornblende ages were not reset by younger intrusions, therefore maximum reheating temperatures did not exceed ~500°C for geologically significant durations. T-t cooling curves from the intrusive suites are used to calibrate finite difference numerical simulations of pluton assembly. Intrusion geometries are modeled (HEAT 3D, Wohletz, 2007) by stacking horizontal increments from the top-down and bottom-up and vertical increments are emplaced syntaxially and antitaxially and are designed to generate plutons of the approximate dimensions, depth of emplacement, and age range of the Sierran suites. Numerical simulations yield the following general observations: 1) an

  7. Pyroxenes of the Khibiny alkaline pluton, Kola Peninsula

    NASA Astrophysics Data System (ADS)

    Yakovenchuk, V. N.; Ivanyuk, G. Yu.; Pakhomovsky, Ya. A.; Men'shikov, Yu. P.; Konopleva, N. G.; Korchak, Yu. A.

    2008-12-01

    Seven pyroxene varieties were identified in nepheline syenites and foidolites of the Khibiny pluton: enstatite, ferrosilite, diopside, hedenbergite, augite, aegirine-augite, and aegirine. Enstatite and augite are typical of alkaline and ultramafic rocks of dike series. Ferrosilite was found in country quartzitic hornfels. Diopside is a rock-forming mineral in alkaline and ultramafic rocks, alkali gabbroids, hornfels in xenoliths of volcanic and sedimentary rocks and foyaite, melteigite-urtite that assimilate them, and certain hydrothermal pegmatite veins. Hedenbergite was noted in hornfels from xenoliths of volcanic and sedimentary rocks and in a hydrothermal pegmatite vein at Mount Eveslogchorr. Aegirine-augite is the predominant pyroxene in all types of nepheline syenites, phonolites and tinguaites, foidolites, alkaline and ultramafic rocks of dike series, fenitized wall rocks surrounding the pluton, and xenoliths of Devonian volcanic and sedimentary rocks. Aegirine is an abundant primary or, more often, secondary mineral in nepheline syenites, foidolites, and hydrothermal pegmatite veins. It occurs as separate crystals, outer zones of diopside and aegirine-augite crystals, and homoaxial pseudomorphs after Na-Ca amphiboles. Microprobe analyses of 265 pyroxenes samples allowed us to distinguish ten principal trends of isomorphic replacement and corresponding typomorphic features of pyroxenes. Compositional variations in clinopyroxenes along the sampled 35-km profile from the margin of the Khibiny pluton to its center confirm the symmetric zoning of the foyaite pluton relative to semicircular faults of the Minor Arc and the Main (Central) Ring marked by Devonian volcanic and sedimentary rocks, foidolites, and related metasomatic rocks (rischorrite, albitite, and aegirinite). Changes in the composition of pyroxenes are explained mainly by the redistribution of elements between coexisting minerals of foyaites in the process of their intense differentiation under the

  8. Mafic enclaves in the Wilson Ridge Pluton, northwestern Arizona: Implications for the generation of a calc-alkaline intermediate pluton in an extensional environment

    NASA Astrophysics Data System (ADS)

    Larsen, Lance L.; Smith, Eugene I.

    1990-10-01

    The Wilson Ridge pluton is an epizonal calc-alkaline pluton that formed about 13.5 Ma during a period of mid-Miocene extension. Faulting and erosional dissection provide a cross section of the pluton. The apex of the pluton, in the Boulder Wash area, Nevada, is composed of hypabyssal quartz monzonite and dacite. The base of the pluton is 20 km to the south where quartz monzodiorite, monzodiorite, and diorite are in low-angle intrusive contact with Precambrian basement. The pluton was separated from cogenetic volcanic rocks in the River Mountains by movement along the Saddle Island detachment fault at about 13.4 Ma. The River Mountains now lie 20 km to the west of the pluton. The Wilson Ridge pluton is composed of the Teakettle Pass suite consisting of foliated monzodiorite and quartz monzodiorite and unfoliated quartz monzonite and the older Horsethief Canyon diorite. Rocks of the pluton contain 2-4 modal percent sphene. Intermediate rocks of the Teakettle Pass suite contain abundant basaltic and diorite enclaves. Basaltic enclaves are lensoidal and pillow-like and commonly have crenulate and fine-grained margins. Enclaves are chemically similar to mafic dikes of the Wilson Ridge pluton and to cogenetic alkali basalt flows in the River Mountains. They probably represent blobs of mafic liquid that commingled and mechanically mixed with felsic magma to produce the intermediate rocks of the pluton. Basaltic enclaves commonly occur as inclusion-rich zones that represent synplutonic mafic dikes that were injected into a quartz monzonite host. Mafic magma was entrained and mechanically broken down by magmatic flow shear. A continuum in shape exists from enclaves that are bulbous and ellipsoidal to those that are thin, tabular mafic selvages and schlieren and ultimately to the mafic component in foliated quartz monzodiorite and monzodiorite. Diorite enclaves have angular contacts with host rocks and are interpreted as xenoliths. Field evidence and major and trace element

  9. Dyking Mechanism and Melting transfer, Misho granitoid Pluton (NW of Iran)

    NASA Astrophysics Data System (ADS)

    Mehri, M.; Mohssen, M.

    2009-04-01

    Misho granitoid pluton are exposed in NW of Misho elevation and SW of Marand depression (Nw of Iran). Mineralogical paragenesis of pluton contain unhedral to sub-hedral quartz, alkaline feldspar (microcline and sub-hedral to unhedral orthoclase), two type biotites, subhedral to euhedral plagioclase (oligoclase to albite), two type zircon, magmatic epidote, sphene and apatite. Pluton, samples show geochemical characteristic of syn - to post - collisional environment, s-type granite and allocktonous. Pluton located in faulted area with Paleozoic respect dating. Source rocks of Pluton are meta - graywake and meta - pelite mixed. One type of zircon and biotite are restitic. Pluton samples have textures that indicate the effect and evidence of pressure syn - crystallization. Field geological, mineralogical and geochemical characteristic of samples from this pluton associated with enclaves riched in mica and shapes of pluton suggest quick arising and dyking mechanism as main mechanism for melt transfer. This caused restitic zircon and biotite remained, there for main mechanism of arising and generation of this pluton are dyking with propagation of fractures so that diaprism process and mechanism have very low role and effect in emplacement and melt transfer of Misho granitoid. Key Words: Misho Pluton, Restitic biotite, Arising mechanism, Dyking

  10. Dyking Mechanism and Melting transfer, Misho granitoied Pluton (NW of Iran)

    NASA Astrophysics Data System (ADS)

    Mehri, M.; Mohssen, M.; Arezoo, S.; Aram, S.

    2009-04-01

    Misho granitoid pluton are exposed in NW of Misho elevation and SW of Marand depression (In Iran). Mineralogical paragenesis of pluton contain unhedral to sub â€" hedral quartz , alkaline feldspar (microcline and sub - hedral to unhedral orthoclase) , two type biotites , subhedral to euhedral plagioclase (oligoclase to albite) , two type zircon , magmatic epidote , sphene and apatite. Pluton ,s samples show geochemical charactrestic of syn â€" to post â€" collisional environment , s â€" type granite and allocktonous. Pluton located in faulted area with Paleozoic respect dating. Source rocks of Pluton are meta â€" graywake and meta â€" pelite mixed. One type of zircon and biotite are restitic. Pluton , s samples have textures that indicate the effect and evidence of pressure syn â€" crystallization. Field geological , mineralogical and geochemical characteristic of samples from this pluton associated with enclaves riched in mica and shapes of pluton suggest quick arising and dyking mechanism as main mechanism for melt transfer . this caused restitic zircon and biotite remained , There for main mechanism of arising and generation of this pluton are dyking with propagation of fractures so that diaprism process and mechanism have very low role and effect in emplacement and melt ,s transfer of Misho granitoid. Key Words: Misho Pluton , Restitic biotite , Arising mechanism , Dyking

  11. Acid-rock drainage at Skytop, Centre County, Pennsylvania, 2004

    USGS Publications Warehouse

    Hammarstrom, Jane M.; Brady, Keith; Cravotta, Charles A., III

    2005-01-01

    Recent construction for Interstate Highway 99 (I?99) exposed pyrite and associated Zn-Pb sulfide minerals beneath a >10-m thick gossan to oxidative weathering along a 40-60-m deep roadcut through a 270-m long section of the Ordovician Bald Eagle Formation at Skytop, near State College, Centre County, Pennsylvania. Nearby Zn-Pb deposits hosted in associated sandstone and limestone in Blair and Centre Counties were prospected in the past; however, these deposits generally were not viable as commercial mines. The pyritic sandstone from the roadcut was crushed and used locally as road base and fill for adjoining segments of I?99. Within months, acidic (pH1,000 mg/L), seep waters at the base of the cut contain >100 mg/L dissolved Zn and >1 mg/L As, Co, Cu, and Ni. Lead is relatively immobile (<10 ?g/L in seep waters). The salts sequester metals and acidity between rainfall events. Episodic salt dissolution then contributes pulses of contamination including acid to surface runoff and ground water. The Skytop experience highlights the need to understand dynamic interactions of mineralogy and hydrology in order to avoid potentially negative environmental impacts associated with excavation in sulfidic rocks.

  12. A Sustainable Approach for Acid Rock Drainage Treatment using Clinoptilolite

    NASA Astrophysics Data System (ADS)

    Li, L. Y.; Xu, W.; Grace, J. R.

    2009-04-01

    Problems related to acid rock drainage (ARD) occur along many highways of British Columbia. The ARD problem at Pennask Creek along Highway 97C in the Thompson-Okanagan region is an ideal site for pilot study to investigate a possible remediation solution. The highway was opened in 1991. An ARD problem was identified in 1997. Both sides of Highway 97C are producing acidified runoff from both cut rock surface and a fractured ditch. This runoff eventually enters Pennask Creek, the largest spawning source of rainbow trout in British Columbia. The current remediation technique using limestone for ARD treatment appears to be unnecessarily expensive, to generate additional solid waste and to not be optimally effective. A soil mineral natural zeolite - clinoptilolite - which is inexpensive and locally available, has a high metal adsorption capacity and a significant buffering capacity. Moreover, the clinoptilolite materials could be back-flushed and reused on site. An earlier batch adsorption study from our laboratory demonstrated that clinoptilolite has a high adsorption capacity for Cu, Zn, Al, with adsorption concentrations 131, 158 and 215 mg/kg clinoptilolite, respectively, from ARD of pH 3.3. Removal of metals from the loaded clinoptilolite by back-flushing was found to depend on the pH, with an optimum pH range for extraction of 2.5 to 4.0 for a contact time of one hour. The rank of desorption effectiveness was EDTA > NaCl > NaNO3 > NaOAC > NaHCO3 > Na2CO3 > NaOH > Ca(OH)2. A novel process involving cyclic adsorption on clinoptilolite followed by regeneration of the sorbent by desorption is examined for the removal of heavy metals from acid rock drainage. Experimental results show that the adsorption of zinc and copper depends on the pH and on external mass transfer. Desorption is assisted by adding NaCl to the water. A slurry bubble column was able to significantly reduce the time required for both adsorption and desorption in batch tests. XRD analysis indicated

  13. Rocks.

    ERIC Educational Resources Information Center

    Lee, Alice

    This science unit is designed for limited- and non-English speaking students in a Chinese bilingual education program. The unit covers rock material, classification, characteristics of types of rocks, and rock cycles. It is written in Chinese and simple English. At the end of the unit there is a list of main terms in both English and Chinese, and…

  14. Symmagmatic folding of the base of the Bergell pluton, Central Alps

    NASA Astrophysics Data System (ADS)

    Davidson, C.; Rosenberg, C.; Schmid, S. M.

    1996-11-01

    Evidence for magmatic, submagmatic and solid-state deformation in tonalite, granodiorite and country rocks found at the deep-seated floor (22-26 km) of the Bergell pluton demonstrates that final emplacement and crystallization occurred during regional deformation of the pluton and the underlying country rocks. After northward emplacement over the country rocks, but before complete crystallization, the floor of the pluton was folded during simultaneous N-S shortening and E-W stretching. This is evidenced by synmagmatic folds with E-W striking, nearly vertical axial planes, and by regional east-plunging stretching lineations in the country rocks which are parallel to the regional-scale fold axes and the magmatic mineral lineations in the pluton. Opposite senses of shear from the well-foliated, occasionally mylonitic contact suggest that deformation was mostly accomplished by pure shear. Synmagmatic deformation is related to late-stage N-S shortening of the Alpine orogen and shows that the still partially molten pluton responded to low differential stress very much like the country rocks deformed in the solid-state at high temperatures. Post-emplacement tilting associated with backthrusting along the Insubric mylonites led to the exposure of the pluton's floor at its present-day western margin.

  15. Typomorphism of fluorapatite in the Khibiny alkaline pluton, Kola Peninsula

    NASA Astrophysics Data System (ADS)

    Konopleva, N. G.; Ivanyuk, G. Yu.; Pakhomovsky, Ya. A.; Yakovenchuk, V. N.; Mikhailova, Yu. A.

    2014-12-01

    The zoning of accessory and rock-forming fluorapatite in the Khibiny pluton is discussed in its content, morphology, and chemical composition. The concentrations of Na, REE, and Si impurities in fluorapatite decrease from the margin and center of the pluton to the Major Ring, composed of melteigiteurtite and rischorrite. Within this structure, the purest apatite is characteristic of the high-grade ore in large deposits, where it occurs free of Na, and REE, as well as Sr in place of Ca. The fractal dimension of fluorapatite aggregates in all textural types of apatite-nepheline rocks (ores) corresponds to the dimension of fractures. Along with mineralogy of apatite-nepheline rocks and zoning of host foidolite, this feature indicates the superimposed character of apatite mineralization.

  16. Granite intrusion by externally induced growth and deformation of the magma reservoir, the example of the Plasenzuela pluton, Spain

    NASA Astrophysics Data System (ADS)

    Castro, Antonio; Fernández, Carlos

    1998-09-01

    The Plasenzuela pluton in the Central Extremadura batholith in the southern Iberian Massif, is an example of permissive emplacement in relation to the tectonic development of extensional fractures in the upper continental crust. Paradoxically, this pluton has a concordant structural pattern which is classically attributed to diapirism or ballooning. This pattern consists of the following elements: (a) nearly elliptical shape in the horizontal section; (b) conformity of the pre-existing aureole structures to the shape of the pluton contacts; and (c) development of a crenulation cleavage, parallel to the contacts, in the vicinity of the pluton walls. All these features have been interpreted in many plutons as resulting from the pushing-aside of the country rock structures due to the expansion of the pluton. However, the detailed structural relationships in the aureole do not favour a forceful emplacement mechanism. By contrast, these relationships constitute prime evidence of permissive intrusion in extensional fractures. According to this interpretation, the concordant shape of the pluton was acquired by syn-plutonic opening of a mixed tensional-shear fracture, parallel to the main foliation in the host rocks, and by folding of the fracture walls together with the previous anisotropy of the country rocks. This is a growth-deformation process that can operate at local conditions in the upper continental crust giving rise to concordant syn-tectonic plutons.

  17. Late Silurian plutons in Yucatan

    NASA Astrophysics Data System (ADS)

    Steiner, M. B.; Walker, J. Douglas

    1996-08-01

    U-Pb measurements of zircons from two composite plutons in the Maya Mountains of the Yucatan Block (Belize) give Late Silurian ages. Zircons from one of the five compositional phases of the Mountain Pine Ridge pluton yield an age of 418±3.6 Ma. A second compositional phase gives a minimum age of 404 Ma, and zircons from a third phase, although plagued with high common Pb, yield ages consistent with the other two. Zircons from one compositional phase of the Hummingbird-Mullins River pluton indicate an age of about 410-420 Ma. These data demonstrate that two of the three Maya Mountains plutons residing among the strata of the Late Pennsylvanian through Permian Santa Rosa Group are older than that sedimentation. Although the third pluton was not dated, both the similarity of sedimentary facies patterns adjacent to it to those adjacent to one of the plutons dated as Late Silurian and a published single Rb-Sr age of 428 ± 41 Ma suggest this third pluton also was emergent during Santa Rosa deposition. Thus the new U/Pb dates and other data suggest that all three Maya Mountains plutons pre-date Late Carboniferous sedimentation and that none intrude the Santa Rosa Group. Although very uniform ages of about 230 Ma amongst all plutons, derived from abundant earlier dating by the K-Ar system, led to the conclusion that intrusion mostly had occurred in the Late Triassic, the U-Pb ages (obtained from the same sites as the K-Ar dates) demonstrate that the K-Ar ages do not derive from a Late Triassic intrusive episode. The K-Ar dates probably are a signature of the rifting associated with Pangean breakup and formation of the Gulf of Mexico. In a reconstructed Pangea, the position of the Maya Mountains Late Silurian plutons suggests that the Late Silurian Acadian-Caledonian orogen of eastern North America extended through the region of the future Gulf of Mexico. Finally, the U-Pb ages of the Maya Mountains plutons are the same as those of a group of shocked zircons found in the

  18. Acid rock drainage and rock weathering in Antarctica: important sources for iron cycling in the Southern Ocean.

    PubMed

    Dold, B; Gonzalez-Toril, E; Aguilera, A; Lopez-Pamo, E; Cisternas, M E; Bucchi, F; Amils, R

    2013-06-18

    Here we describe biogeochemical processes that lead to the generation of acid rock drainage (ARD) and rock weathering on the Antarctic landmass and describe why they are important sources of iron into the Antarctic Ocean. During three expeditions, 2009-2011, we examined three sites on the South Shetland Islands in Antarctica. Two of them displayed intensive sulfide mineralization and generated acidic (pH 3.2-4.5), iron-rich drainage waters (up to 1.78 mM Fe), which infiltrated as groundwater (as Fe(2+)) and as superficial runoff (as Fe(3+)) into the sea, the latter with the formation of schwertmannite in the sea-ice. The formation of ARD in the Antarctic was catalyzed by acid mine drainage microorganisms found in cold climates, including Acidithiobacillus ferrivorans and Thiobacillus plumbophilus. The dissolved iron (DFe) flux from rock weathering (nonmineralized control site) was calculated to be 0.45 × 10(9) g DFe yr(-1) for the nowadays 5468 km of ice-free Antarctic rock coastline which is of the same order of magnitude as glacial or aeolian input to the Southern Ocean. Additionally, the two ARD sites alone liberate 0.026 and 0.057 × 10(9) g DFe yr(-1) as point sources to the sea. The increased iron input correlates with increased phytoplankton production close to the source. This might even be enhanced in the future by a global warming scenario, and could be a process counterbalancing global warming. PMID:23682976

  19. Mixing-controlled uncertainty in long-term predictions of acid rock drainage from heterogeneous waste-rock piles

    NASA Astrophysics Data System (ADS)

    Pedretti, D.; Beckie, R. D.; Mayer, K. U.

    2015-12-01

    The chemistry of drainage from waste-rock piles at mine sites is difficult to predict because of a number of uncertainties including heterogeneous reactive mineral content, distribution of minerals, weathering rates and physical flow properties. In this presentation, we examine the effects of mixing on drainage chemistry over timescales of 100s of years. We use a 1-D streamtube conceptualization of flow in waste rocks and multicomponent reactive transport modeling. We simplify the reactive system to consist of acid-producing sulfide minerals and acid-neutralizing carbonate minerals and secondary sulfate and iron oxide minerals. We create multiple realizations of waste-rock piles with distinct distributions of reactive minerals along each flow path and examine the uncertainty of drainage geochemistry through time. The limited mixing of streamtubes that is characteristic of the vertical unsaturated flow in many waste-rock piles, allows individual flowpaths to sustain acid or neutral conditions to the base of the pile, where the streamtubes mix. Consequently, mixing and the acidity/alkalinity balance of the streamtube waters, and not the overall acid- and base-producing mineral contents, control the instantaneous discharge chemistry. Our results show that the limited mixing implied by preferential flow and the heterogeneous distribution of mineral contents lead to large uncertainty in drainage chemistry over short and medium time scales. However, over longer timescales when one of either the acid-producing or neutralizing primary phases is depleted, the drainage chemistry becomes less controlled by mixing and in turn less uncertain. A correct understanding of the temporal variability of uncertainty is key to make informed long-term decisions in mining settings regarding the management of waste material.

  20. Calc-alkaline plutonism along the Pacific rim of southern Alaska

    USGS Publications Warehouse

    Hudson, Travis

    1979-01-01

    Field, petrology, and age data on southern Alaska plutonic rocks now enable the delineation of eight calc-alkaline plutonic belts. These belts of plutons or batholithic complexes are curvilinear to linear and trend parallel or subparallel to the continental margin. The belts represent the principal loci of emplacement for plutons of specific ages and although there is spatial or temporal overlap in some cases, they are more commonly spatially and temporally distinct. Intermediate lithologies such as quartz diorite, tonalite, and granodiorite dominate in most of the Belts but granodiorite and granite characterize one. The belts are of Mesozoic or Cenozoic age and plutonism began in six of them at about 195, 175, 120, 75, 60, and 40 m.y. ago; age relations in two are poorly known. Recognition of the belts is important for future studies of regional geology, tectonism, and magmatism along the Pacific rim of southern Alaska.

  1. Amphiboles of the Khibiny alkaline pluton, Kola Peninsula, Russia

    NASA Astrophysics Data System (ADS)

    Konopleva, N. G.; Ivanyuk, G. Yu.; Pakhomovsky, Ya. A.; Yakovenchuk, V. N.; Men'shikov, Yu. P.; Korchak, Yu. A.

    2008-12-01

    The rocks of the Khibiny pluton contain 25 amphibole varieties, including edenite, fluoredenite, kaersutite, pargasite, ferropargasite, hastingsite, magnesiohastingsite, katophorite, ferrikatophorite, magnesiokatophorite, magnesioferrikatophorite, magnesioferrifluorkatophorite, ferrimagnesiotaramite, ferrorichterite, potassium ferrorichterite, richterite, potassium richterite, potassium fluorrichterite, arfvedsonite, potassium arfvedsonite, magnesioarfvedsonite, magnesioriebeckite, ferriferronyboite, ferrinyboite, and ferroeckermannite. The composition of rock-forming amphiboles changes symmetrically relative to the Central Ring of the pluton; i.e., amphiboles enriched in K, Ca, Mg, and Si are typical of foyaite near and within the Central Ring. The Fe and Mn contents in amphiboles increase in the direction from marginal part of the pluton to its center. Foyaite of the marginal zone contains ferroeckermannite, richterite, arfvedsonite, and ferrorichterite; edenite is typical of foyaite and hornfels of the Minor Arc. Between the Minor Arc and the Central Ring, foyaite contains ferroeckermannite, arfvedsonite, and richterite; amphiboles in rischorrite, foidolite and hornfels of the Central Ring are (potassium) arfvedsonite, (potassium) richterite, magnesiokatophorite, magnesioarfvedsonite, ferroeckermannite, and ferriferronyboite; amphiboles in foyaite within the Central Ring, in the central part of the pluton, are arfvedsonite, magnesioarfvedsonite, ferriferronyboite, katophorite, and richterite. It is suggested that such zoning formed due to the alteration of foyaite by a foidolite melt intruded into the Main (Central) Ring Fault.

  2. Evaluation of Acid Producing Potential of Road-cut Rock Slopes

    NASA Astrophysics Data System (ADS)

    Min, K.; Han, D.

    2006-12-01

    Acid rock drainage (ARD) developed as a result of road construction represents a number of technical, environmental, and social problems. Engineering impacts from ARD, the product of atmospheric oxidation of rock-forming sulfide minerals, including degradation of surface water quality, disintegration of construction materials, and structural damage of buildings, have been documented widely around the world. To characterize the ARD and to evaluate acid producing potential of road-cut rocks, samples of rocks and water were collected from two road-cut sites of shale to phyllite showing such visual indicators of ARD as orange iron precipitates along streambed and rocks. Acid Base Accounting (ABA) test, the most commonly applied static test to evaluate the potential acidity, and X-ray diffraction (XRD) analysis were performed for fifteen rock samples. In terms of NAPP (Net Acid Producing Potential) and NAGpH (pH of Net Acid Generation), seven, four, and four rock samples were classified into a PAF (potentially acid forming) group, a NAF (non-acid forming) group, and an uncertain group, respectively. Water samples with low pH of 4.4, low DO (dissolved oxygen), and high contents of heavy metals and sulfate ion showed the generation of ARD in the studied area, which confirmed the applicability of ABA test to prediction of ARD in road-cut rock slopes. Evaluation of acid producing potential of earth materials should be an essential step in the pre-design stage of construction works especially in the vicinity of mining areas.

  3. Amino acids and hydrocarbons approximately 3,800-Myr old in the Isua rocks, southwestern Greenland

    NASA Technical Reports Server (NTRS)

    Nagy, B.; Engel, M. H.; Zumberge, J. E.; Ogino, H.; Chang, S. Y.

    1981-01-01

    Results of an analysis of amino acids and hydrocarbons found in the Isua banded iron formation, which contains the oldest known rocks on earth, are discussed. Similarities are pointed out between the relative amino acid abundances of the Isua rocks and those of lichens found on their surfaces, and a lack of substantial racemization indicated by the low D/L ratios in the 3800-million year old rock samples is noted. Experimental results showing the possibility of amino acid diffusion from lichens into the rocks are presented. Comparisons of the Isua rock amino acid D/L ratios with those reported for samples from other regions indicates that none of the Isua amino acids are older than a few tens of thousands to a few hundred thousand years. Analyses of the saturated hydrocarbons of the Isua samples reveals no odd carbon number preference, which may indicate antiquity, however laboratory experiments have shown that amino acids and aromatic and saturated aliphatic hydrocarbons could not have survived the metamorphic history of the Isua rocks. The evidence presented thus suggests that the amino acids and hydrocarbons found are not of the age of the sediments.

  4. Operational Lessons Leaned During bioreactor Demonstrations for Acid Rock Drainage Treatment

    EPA Science Inventory

    The U.S. Environmental Protection Agency's Mine Waste Technology Program (MWTP) has emphasized the development of biologically-based treatment technologies for acid rock drainage (ARD). Progressively evolving technology demonstrations have resulted in significant advances in sulf...

  5. Operational Lessons Learned During Bioreactor Demonstrations for Acid Rock Drainage Treatment

    EPA Science Inventory

    The U.S. Environmental Protection Agency’s Mine Waste Technology Program (MWTP) has emphasized the development of biologically-based treatment technologies for acid rock drainage (ARD). Progressively evolving technology demonstrations have resulted in significant advances in sul...

  6. Testing the role of silicic acid and bioorganic materials in the formation of rock coatings

    NASA Astrophysics Data System (ADS)

    Kolb, Vera M.; Philip, Ajish I.; Perry, Randall S.

    2004-11-01

    Silica, amino acids, and DNA were recently discovered in desert varnish. In this work we experimentally test the proposed role of silicic acid and bio-chemicals in the formation of desert varnish and other rock coatings. We have developed a protocol in which the rocks were treated with a mixture of silicic acid, sugars, amino acids, metals and clays, under the influence of heat and UV light. This protocol reflects the proposed mechanism of the polymerization of silicic acid with the biooganic materials, and the laboratory model for the natural conditions under which the desert varnish is formed. Our experiments produced coatings with a hardness and morphology that resemble the natural ones. These results provide a support for the role of silicic acid in the formation of rock coatings. Since the hard silica-based coatings preserve organic compounds in them, they may serve as a biosignature for life, here or possibly on Mars.

  7. Testing the Role of Silicic Acid and Bioorganic Materials in the Formation of Rock Coatings

    SciTech Connect

    Kolb, Vera; Philip, Ajish I.; Perry, Randall S.

    2004-12-01

    Silica, amino acids, and DNA were recently discovered in desert varnish. In this work we experimentally test the proposed role of silicic acid and bio-chemicals in the formation of desert varnish and other rock coatings. We have developed a protocol in which hte rocks were treated with a mixture of silicic acid, sugars, amino acids, metals and clays, under the influence of heat and UV light. This protocol reflects the proposed mechanism of hte polymerization of silicic acid with the bioorganic materials, and the laboratory model for the natural conditions under which the desert varnish is formed. Our experiments produced coatings with a hardness and morphology that resemble the nature ones. These results provide a support for the role of silicic acid in the formation of rock coatings. Since the hard silica-based coatings preserve organic compounds in them, they may serve as a biosignature for life, here or possibly Mars.

  8. Interactions between plutonism and detachments during metamorphic core complex formation, Serifos Island (Cyclades, Greece)

    NASA Astrophysics Data System (ADS)

    Rabillard, Aurélien; Arbaret, Laurent; Jolivet, Laurent; Le Breton, Nicole; Gumiaux, Charles; Augier, Romain; Grasemann, Bernhard

    2015-06-01

    In order to better understand the interactions between plutonic activity and strain localization during metamorphic core complex formation, the Miocene granodioritic pluton of Serifos (Cyclades, Greece) is studied. This pluton (11.6-9.5 Ma) intruded the Cycladic Blueschists during thinning of the Aegean domain along a system of low-angle normal faults belonging to the south dipping West Cycladic Detachment System (WCDS). Based on structural fieldwork, together with microstructural observations and anisotropy of magnetic susceptibility, we recognize a continuum of deformation from magmatic to brittle conditions within the magmatic body. This succession of deformation events is kinematically compatible with the development of the WCDS. The architecture of the pluton shows a marked asymmetry resulting from its interaction with the detachments. We propose a tectonic scenario for the emplacement of Serifos pluton and its subsequent cooling during the Aegean extension: (1) A first stage corresponds to the metamorphic core complex initiation and associated southwestward shearing along the Meghàlo Livadhi detachment. (2) In the second stage, the Serifos pluton has intruded the dome at shallow crustal level, piercing through the ductile/brittle Meghàlo Livadhi detachment. Southwest directed extensional deformation was contemporaneously transferred upward in the crust along the more localized Kàvos Kiklopas detachment. (3) The third stage was marked by synmagmatic extensional deformation and strain localization at the contact between the pluton and the host rocks resulting in nucleation of narrow shear zones, which (4) continued to develop after the pluton solidification.

  9. Emplacement, rapid burial, and exhumation of 90-Ma plutons in southeastern Alaska

    USGS Publications Warehouse

    Himmelberg, G.R.; Haeussler, P.J.; Brew, D.A.

    2004-01-01

    In southeastern Alaska, granodiorite-tonalite plutons of the Admiralty-Revillagigedo belt intruded the Jurassic-Cretaceous Gravina belt along the eastern side of the Alexander terrane around 90 Ma. These plutons postdate some deformation related to a major contractional event between the previously amalgamated Wrangellia and Alexander terranes and the previously accreted terranes of the North American margin. We studied the aureole mineral assemblages of these plutons near Petersburg, Alaska, determined pressure and temperature of equilibration, and examined structures that developed within and adjacent to these plutons. Parallelism of magmatic and submagmatic fabrics with fabrics in the country rock indicates synchroneity of pluton emplacement with regional deformation and suggests that magma transport to higher crustal levels was assisted by regional deformation. Replacement of andalusite by kyanite or sillimanite indicates crustal thickening soon after pluton emplacement. Regional structural analysis indicates the crustal thickening was accomplished by thrust burial. Thermobarometric analyses indicate the aureoles reached near-peak temperatures of 525 to 635 ??C at pressures of 570 to 630 MPa. Consideration of the rate of thermal decay of the aureoles suggests that burial was rapid and occurred at rates around 5 to 8 mm/year. Structural observations indicate there was contractional deformation before, during, and after emplacement of the 90-Ma plutons. Initial exhumation of the Admiralty-Revillagedo belt in the Petersburg area may have occurred along a thrust west of the pluton belt within the Gravina belt. ?? 2004 NRC Canada.

  10. Typochemistry of rinkite and products of its alteration in the Khibiny Alkaline pluton, Kola Peninsula

    NASA Astrophysics Data System (ADS)

    Konopleva, N. G.; Ivanyuk, G. Yu.; Pakhomovsky, Ya. A.; Yakovenchuk, V. N.; Mikhailova, Yu. A.; Selivanova, E. A.

    2015-12-01

    The occurrence, morphology, and composition of rinkite are considered against the background of zoning in the Khibiny pluton. Accessory rinkite is mostly characteristic of foyaite in the outer part of pluton, occurs somewhat less frequently in foyaite and rischorrite in the central part of pluton, even more sparsely in foidolites and apatite-nepheline rocks, and sporadically in fenitized xenoliths of the Lovozero Formation. The largest, up to economic, accumulations of rinkite are related to the pegmatite and hydrothermal veins, which occur in nepheline syenite on both sides of the Main foidolite ring. The composition of rinkite varies throughout the pluton. The Ca, Na, and F contents in accessory rinkite and amorphous products of its alteration progressively increase from foyaite and fenitized basalt of the Lovozero Formation to foidolite, rischorrite, apatite-nepheline rocks, and pegmatite-hydrothermal veins.

  11. Volcanic-plutonic parity and the differentiation of the continental crust.

    PubMed

    Keller, C Brenhin; Schoene, Blair; Barboni, Melanie; Samperton, Kyle M; Husson, Jon M

    2015-07-16

    The continental crust is central to the biological and geological history of Earth. However, crustal heterogeneity has prevented a thorough geochemical comparison of its primary igneous building blocks-volcanic and plutonic rocks-and the processes by which they differentiate to felsic compositions. Our analysis of a comprehensive global data set of volcanic and plutonic whole-rock geochemistry shows that differentiation trends from primitive basaltic to felsic compositions for volcanic versus plutonic samples are generally indistinguishable in subduction-zone settings, but are divergent in continental rifts. Offsets in major- and trace-element differentiation patterns in rift settings suggest higher water content in plutonic magmas and reduced eruptibility of hydrous silicate magmas relative to dry rift volcanics. In both tectonic settings, our results indicate that fractional crystallization, rather than crustal melting, is predominantly responsible for the production of intermediate and felsic magmas, emphasizing the role of mafic cumulates as a residue of crustal differentiation. PMID:26178961

  12. Anatomy of the Cretaceous Hobenzan pluton, SW Japan: Internal structure of a small zoned pluton, and its genesis

    NASA Astrophysics Data System (ADS)

    Imaoka, Teruyoshi; Nakashima, Kazuo; Kamei, Atsushi; Hayasaka, Yasutaka; Ogita, Yasuo; Ikawa, Toshiyuki; Itaya, Tetsumaru; Takahashi, Yoshio; Kagami, Hiroo

    2014-11-01

    Field, petrographic, geochemical, and K-Ar and U-Pb age data were used to elucidate the internal structure of the Cretaceous Hobenzan pluton, SW Japan, and the processes which generated that structure. The pluton is elongated E-W with dimensions of about 6.5 × 2.0 km (13 km2), and was emplaced at ~ 95 Ma as a pluton in accretionary complexes. The pluton contains an early tonalite, but most of the body consists of later granitoids that show a continuous differentiation series from biotite-hornblende granodiorite (GD) to hornblende-biotite granite (HBG) and biotite granite (BG). The contacts between the GD and HBG are gradational. The pluton provides an exceptional cross-sectional view of a simple cooling magma body. The GD shows no vertical variations in modal and chemical compositions, whereas the HBG displays differentiation from the lowermost exposure to the top of the pluton. Initial Sr isotope ratios (SrI) in the HBG increase from the lower part to the top of the pluton. The granitoids show continuous compositional variations from 65 to 79 wt.% SiO2 (anhydrous basis), and magmatic differentiation was dominantly controlled by crystal fractionation of hornblende and plagioclase. Field, elemental and Sr-Nd isotope data are consistent with limited operation of assimilation with pelitic rocks and fractional crystallization (AFC), in which assimilation increased with higher degrees of differentiation. The Hobenzan pluton retains a history of granitoid magma evolution in a subvolcanic magma reservoir. The GD formed as a rigid sponge, and melt fraction increases inwards from the walls, forming the HBG mush by fractional crystallization, coupled with small degrees of assimilation of adjacent schists. A more evolved and enriched low-density melt segregated from the mushy cumulate of the HBG by incomplete crystal-melt separation, and moved upwards with the assistance of gas-driven filter pressing, as indicated by the presence of miarolitic cavities, thus forming the BG

  13. An AMS study of the Takidani pluton (Japan)

    NASA Astrophysics Data System (ADS)

    Hartung, Eva; Caricchi, Luca; Floess, David; Wallis, Simon; Harayama, Satoru

    2016-04-01

    Large plutonic bodies are typically constructed incrementally often by under-accretion of distinct successive magma pulses. Petrography and geochemistry of the Takidani Pluton (1.54 Ma ± 0.23 Ma) in the Northern Japanese Alps show that the chemical and textural variability observed at the roof of this intrusion is best explained by the segregation of residual melt from a crystallising magma body. We carried out a magnetic susceptibility survey (bulk susceptibility and anisotropy of magnetic susceptibility) to identify the structures associated with the emplacement and extraction of residual melts from a magmatic mush. Additionally, we determined shape preferred orientations (SPO) of amphibole at several locations within the Takidani pluton. From bottom to top of the intrusion, the bulk susceptibility is about constant in the main granodioritic part, decreases roofwards within the porphyritic unit, before increasing again within the marginal granodiorite close to the contact with the overlaying Hotaka Andesite. Such variability mimics the major and trace elements compositional variability measured in the whole rock samples. Magnetic foliations are observed at the western tectonic contact of the pluton potentially indicating overprint, while most other magnetic fabrics across the pluton are characterised by triaxial ellipsoids of magnetic susceptibility or magnetic lineations. Our preliminary data and the lack of internal contacts indicate that Takidani Pluton was likely emplaced as a series of successive magma pulses finally merging to produce a large connected magma body. While amphibole foliations may likely be the results of super-solidus tectonic overprint, anisotropy of magnetic susceptibility data may be related to post-emplacement melt segregation.

  14. Near-roof structure and crack-seal emplacement, Colosseum pluton, Sierra Nevada, California

    NASA Astrophysics Data System (ADS)

    Bartley, J. M.; Glazner, A. F.; Coleman, D. S.

    2011-12-01

    Field evidence from diverse localities indicates that dike-like granitic plutons are emplaced by magmatic crack-seal, yielding plutons that are essentially huge composite dikes. Plutons that are equant in map view may also form by crack-seal from increments that are subhorizontal and vertically stacked, but field evidence to assess this hypothesis is scarce. Here we present evidence that the Late Cretaceous, granitic Colosseum pluton of Moore (1963), which crops out along the Sierra Nevada crest southwest of Big Pine, California, may have been emplaced as horizontal sheets by crack-seal. The equant outcrop pattern of the elliptical, 2x3 km Colosseum pluton as mapped by Moore (1963) mainly reflects Pleistocene glacial erosion that cut ~600 m down through the pluton's gently sloping roof contact. Moore mapped a steep eastern contact with the Spook pluton, but our field observations suggest that the Spook and Colosseum plutons may be the same. This would imply that the pluton is much larger and that the map pattern is not elliptical. Additionally, the exposed intrusive contact everywhere dips gently, but the eastern intrusive contact has been cut off by the Sierran frontal fault. If so, up to 2.5 km of largely unexplored vertical relief in the pluton is exposed on the eastern escarpment of the Sierra Nevada. Geologic and bulk magnetic susceptibility mapping of near-roof rocks revealed the following. (1) Although the intrusive contact sharply truncates wall-rock foliation, xenoliths are absent, even at contacts, indicating that stoping was an insignificant process. (2) The pluton contains a subhorizontal sheet of leucogranite that is broadly concordant with the roof but bounded both above and below by more typical biotite granodiorite. This sheet may represent one or more intrusive increments. (3) Along the western contact, thin tabular apophyses of the pluton intrude its subvertically layered and foliated roof. Although some of these dip steeply and are concordant

  15. Strontium and oxygen isotopic variations in Mesozoic and Tertiary plutons of central Idaho

    USGS Publications Warehouse

    Fleck, R.J.; Criss, R.E.

    1985-01-01

    Regional variations in initial 87Sr/86Sr ratios (ri) of Mesozoic plutons in central Idaho locate the edge of Precambrian continental crust at the boundary between the late Paleozoic-Mesozoic accreted terranes and Precambrian sialic crust in western Idaho. The ri values increase abruptly but continuously from less than 0.704 in the accreted terranes to greater than 0.708 across a narrow, 5 to 15 km zone, characterized by elongate, lens-shaped, highly deformed plutons and schistose metasedimentary and metavolcanic units. The chemical and petrologic character of the plutons changes concomitantly from ocean-arc-type, diorite-tonalite-trondhjemite units to a weakly peraluminous, calcic to calcalkalic tonalite-granodiorite-granite suite (the Idaho batholith). Plutons in both suites yield Late Cretaceous ages, but Permian through Early Cretaceous bodies are confined to the accreted terranes and early Tertiary intrusions are restricted to areas underlain by Precambrian crust. The two major terranes were juxtaposed between 75 and 130 m.y. ago, probably between 80 and 95 m.y. Oxygen and strontium isotopic ratios and Rb and Sr concentrations of the plutonic rocks document a significant upper-crustal contribution to the magmas that intrude Precambrian crust. Magmas intruding the arc terranes were derived from the upper mantle/subducted oceanic lithosphere and may have been modified by anatexis of earlier island-arc volcanic and sedimentary units. Plutons near the edge of Precambrian sialic crust represent simple mixtures of the Precambrian wall-rocks with melts derived from the upper mantle or subducted oceanic lithosphere with ri of 0.7035. Rb/Sr varies linearly with ri, producing "pseudoisochrons" with apparent "ages" close to the age of the wall rocks. Measured ??18O values of the wall rocks are less than those required for the assimilated end-member by Sr-O covariation in the plutons, however, indicating that wall-rock ??18O was reduced significantly by exchange with

  16. Magnetic Fabrics and Their Relationship with the Emplacement of the Piracaia Pluton, se Brazil

    NASA Astrophysics Data System (ADS)

    Raposo, M. B.; Pressi, L. F.; Janasi, V. D.

    2010-12-01

    Magnetic fabric and rock magnetism studies were performed on the four units of the 578 +/- 3 Ma-old Piracaia pluton (NW of São Paulo State, southern Brazil). This intrusion is roughly elliptical (~ 32 km2), composed of (i) coarse-grained monzodiorite (MZD-c), (ii) fine-grained monzodiorite (MZD-f) which is predominant in the pluton, (iii) monzonite heterogeneous (MZN-het), and (iv) quartz syenite (Qz-Sy). Magnetic fabrics were determined by applying both anisotropy of low-field magnetic susceptibility (AMS) and anisotropy of anhysteretic remanent magnetization (AARM). The two fabrics are coaxial. The parallelism between AMS and AARM tensors excludes the presence of a single domain (SD) effect on the AMS fabric of the units. Several rock-magnetism experiments performed in one specimen from each sampled unit show that for all units the magnetic susceptibility and magnetic fabrics are carried by magnetite grains. Foliations and lineations in the units were successful determined by applying magnetic methods. Most of the magnetic foliations are steeply dipping or vertical in all units, and are roughly parallel to the foliation measured in the field and in the rocks which surround the pluton. In contrast, the magnetic lineations present mostly low plunges for the whole pluton. However, for two sites they are steep. Thin section analysis show that rocks from the Piracaia pluton were affected by the regional strain during and after emplacement since magmatic foliation evolves to solid-state deformation in the north and south of the pluton, indicating clearly that magnetic fabrics are related to this strain. Otherwise, the lack of solid-state deformation at outcrop scale and in thin sections precludes deformation in the SW of the pluton. This evidence allows us to interpret the observed magnetic fabrics as primary in origin (magmatic) acquired when the rocks were solidified as a result of magma flow, in which steeply plunging magnetic lineation suggests that a feeder zone

  17. Late Jurassic plutonism in the southwest U.S. Cordillera

    USGS Publications Warehouse

    Barth, A.P.; Wooden, J.L.; Howard, K.A.; Richards, J.L.

    2008-01-01

    Although plate reconstructions suggest that subduction was an approximately steady-state process from the mid-Mesozoic through the early Tertiary, recent precise geochronologic studies suggest highly episodic emplacement of voluminous continental-margin batholiths in the U.S. Cordillera. In central and southern California and western Arizona, major episodes of batholithic magmatism are known to have occurred in Permian-Triassic, Middle Jurassic, and late Early to Late Cretaceous time. However, recent studies of forearc-basin and continental-interior sediments suggest that Late Jurassic time was probably also a period of significant magmatism, although few dated plutons of this age have been recognized. We describe a belt of Late Jurassic plutonic and hypabyssal rocks at least 200 km in length that extends from the northwestern Mojave Desert through the Transverse Ranges. The belt lies outboard of both the voluminous Middle Jurassic arc and the ca. 148 Ma Independence dike swarm at these latitudes. The plutons include two intrusive suites emplaced between 157 and 149 Ma: a calc-alkaline suite compositionally unlike Permian-Triassic and Middle Jurassic mon-zonitic suites but similar to Late Cretaceous arc plutons emplaced across this region, and a contemporaneous but not comagmatic alkaline suite. The Late Jurassic was thus a time of both tectonic and magmatic transitions in the southern Cordillera. ?? 2008 The Geological Society of America.

  18. Observations on lichens, granite rock outcrops and acid rain

    SciTech Connect

    Not Available

    1980-06-01

    Lichen sensitivity to the synergistic effects of acid rain and toxic metals in the Atlanta, Georgia area is discussed. The disappearance of lichens on Stone Mountain after the placement of a safety galvinized fence lead to the observations of possible acid rain effects on population dynamics of the lichen community.

  19. Reconnaissance geochemical exploration of plutons of syenite and shonkinite, southern Asir, Kingdom of Saudi Arabia

    SciTech Connect

    Overstreet, W.C.; Assegaff, A.B.; Hussain, M.A.; Naqvi, M.I.; Selner, G.I.; Matzko, J.J.

    1985-01-01

    Reconnaissance geochemical exploration for rare metals in plutons of syenite and shonkinite disclosed generally less than 20 ppM Nb in rocks, wadi sediments, and concentrates. The sparsity of Nb is accompanied by low values for La, Sn, W, Y, and Zr and relatively high but insignificant values for Be and Mo. Base and precious metals are either below their respective limits of determination in the various sample media or are present at background levels commensurate with average crustal abundances in felsic rocks. Pegmatite dikes associated with the syenite plutons are rare and lack vermiculite. The present investigation disclosed no possible ore deposits in the plutons covered by the field work. Known kyanite-topaz-natroalunite rocks in the vicinity of the surveyed areas should be examined for possible deposits of Cu, Mo, or Au associated with high-alumina hydrothermal deposits. 27 refs., 7 figs., 21 tabs.

  20. Natural radioactivity levels in granitic plutons and groundwaters in Southeast part of Eskisehir, Turkey.

    PubMed

    Orgün, Y; Altinsoy, N; Gültekin, A H; Karahan, G; Celebi, N

    2005-08-01

    The present work investigated the radioactivity level of the granitoid plutons and its effect on the groundwaters in the southeast part of Eskisehir. Fourteen granitic samples from the Kaymaz and Sivrihisar plutons and 11 groundwater samples from the near vicinity of the pluton were analyzed. The activity concentrations measured for (238)U and (232)Th ranged from 43.59+/-2 to 651.80+/-24 Bq/kg, and 51.16+/-3 to 351.94+/-13 Bq/kg, respectively. The activity concentrations obtained for (40)K varied from 418.50+/-17 to 1618.03+/-66 Bq/kg. The absorbed dose rates in air outdoors ranged from 87.14 to 531.81 nGy/h. All the results obtained from the Kaymaz pluton are higher than those from the Sivrihisar. The U (ave. 16.6 ppm) and Th (ave. 49.9 ppm) values of the Kaymaz pluton are higher than the average concentrations of the magmatic rocks of granitic composition. These results are consistent with high dose rates of the pluton. The gross-alpha activities in the groundwater samples ranged from 0.009 to 1.64 Bq/l and the gross-beta activities from 0.006 to 0.89 Bq/l. The highest gross-alpha value was found in the sample taken from near the Kaymaz pluton. The concentrations of (222)Rn varied from 0.060 to 0.557 Bq/l. PMID:15921915

  1. Multiple mafic and felsic magma interaction as exhibited in the Dartmouth Pluton, Avalon zone, southeastern Massachusetts

    SciTech Connect

    Hamidzada, N.A.; Hermes, O.D.; Murray, D.P. . Dept. of Geology)

    1993-03-01

    Dioritic to quartz monzonitic rocks of the Dartmouth Pluton exhibit excellently preserved, diverse features produced by mingling and mixing of mafic and felsic magma during multiple events. The related mafic and hybridized intermediate composition rocks occur both as discrete outcrop-sized masses or as enclaves within quartz monzonite or early-stage mixed rocks. Enclaves are rounded, lack chilled margins, and in some cases exhibit cuspate margins; they range in size from 1m--<1cm. Outcrops dominated by dioritic rock consist of well developed mafic pillows with inter-pillow infillings of hybridized rock that had been subjected to magma mixing during or prior to the final mingling process. Dioritic rocks are fine-grained with sparse plagioclase phenocrysts; they contain small, darker-colored enclaves indicative of preceding magma interaction. Major and trace element variation diagrams for this suite of rocks exhibit general linear trends consistent with mixing processes. Overall, field, petrographic, and geochemical relationships in the Dartmouth Pluton demonstrate: (1) widespread mingling of mafic and felsic magma, (2) variable degrees of mafic and felsic magma mixing, and (3) multiple and repeated episodes of mafic and felsic magma interaction. Significantly, some spatially associated dioritic and granitic rocks, including a 595 Ma alkali feldspar granite formerly considered to be part of the Dartmount Pluton, are geochemically related. Field mapping demonstrates that rocks of the mixed suite are intrusive into these rocks, thus establishing a maximum age, but raising the questions that the suite may be considerably younger.

  2. Conceptual models of the formation of acid-rock drainage at road cuts in Tennessee

    USGS Publications Warehouse

    Bradley, Michael W.; Worland, Scott; Byl, Tom

    2015-01-01

    Pyrite and other minerals containing sulfur and trace metals occur in several rock formations throughout Middle and East Tennessee. Pyrite (FeS2) weathers in the presence of oxygen and water to form iron hydroxides and sulfuric acid. The weathering and interaction of the acid on the rocks and other minerals at road cuts can result in drainage with low pH (< 4) and high concentrations of trace metals. Acid-rock drainage can cause environmental problems and damage transportation infrastructure. The formation and remediation of acid-drainage from roads cuts has not been researched as thoroughly as acid-mine drainage. The U.S Geological Survey, in cooperation with the Tennessee Department of Transportation, is conducting an investigation to better understand the geologic, hydrologic, and biogeochemical factors that control acid formation at road cuts. Road cuts with the potential for acid-rock drainage were identifed and evaluated in Middle and East Tennessee. The pyrite-bearing formations evaluated were the Chattanooga Shale (Devonian black shale), the Fentress Formation (coal-bearing), and the Precambrian Anakeesta Formation and similar Precambrian rocks. Conceptual models of the formation and transport of acid-rock drainage (ARD) from road cuts were developed based on the results of a literature review, site reconnaissance, and the initial rock and water sampling. The formation of ARD requires a combination of hydrologic, geochemical, and microbial interactions which affect drainage from the site, acidity of the water, and trace metal concentrations. The basic modes of ARD formation from road cuts are; 1 - seeps and springs from pyrite-bearing formations and 2 - runoff over the face of a road cut in a pyrite-bearing formation. Depending on site conditions at road cuts, the basic modes of ARD formation can be altered and the additional modes of ARD formation are; 3 - runoff over and through piles of pyrite-bearing material, either from construction or breakdown

  3. Apatite trace element and halogen compositions as petrogenetic-metallogenic indicators: Examples from four granite plutons in the Sanjiang region, SW China

    NASA Astrophysics Data System (ADS)

    Pan, Li-Chuan; Hu, Rui-Zhong; Wang, Xin-Song; Bi, Xian-Wu; Zhu, Jing-Jing; Li, Chusi

    2016-06-01

    The abundances of trace elements including Sr, Ga and rare earth elements (REE) and halogens in apatite crystals from four intermediate-felsic plutons in the Zhongdian terrane in the Sanjiang region have been determined using electron microprobe and laser ablation inductively coupled plasma mass spectrometry to evaluate the potential of apatite as a petrogenic-metallogenic indicator. The selected plutons include one that is not mineralized (the Triassic Xiuwacu pluton, or the TXWC pluton), one that hosts a porphyry-type Cu deposit (the Pulang pluton, or the PL pluton), one that hosts a porphyry-type Mo deposit (the Tongchanggou pluton, or the TCG pluton), and one that hosts a vein-type Mo deposit (the Cretaceous Xiuwacu pluton, or the CXWC pluton). Except for the CXWC pluton, the other three plutons have adakite-like trace element signatures in whole rocks. The results from this study show that REE, Sr and halogens in apatite can be used to track magma compositions, oxidation states and crystallization history. Apatite crystals from the adakite-like plutons are characterized by much higher Sr/Y and δEu than the non-adakite-type pluton. This means that apatite, which is not susceptible to alteration, is a useful tool for identifying the adakite-like plutons that no longer preserve the initial Sr/Y ratios in whole rocks due to weathering and hydrothermal alteration. Based on apatite Ga contents and δEu values, it is inferred that the parental magmas for the two adakite-like plutons containing porphyry-type Cu and Mo mineralization are more oxidized than that for the non-adakite-type pluton containing vein-type Mo mineralization. Apatite crystals from the vein-type Mo deposit have much lower Cl/F ratios than those from the porphyry-type Cu and Mo deposits. Apatite crystals from the adakite-like pluton without Cu or Mo mineralization is characterized by much lower Cl/F ratios than those from the adakite-like plutons that host the porphyry-type Cu and Mo deposits. The

  4. The Crabtree Creek pluton: A deformed Mid-Paleozoic( ) stitching pluton on the west flank of the Raleigh metamorphic belt

    SciTech Connect

    Blake, E.F. . Dept. of Earth Sciences); Stoddard, E.F. . Dept. of MEAS)

    1993-03-01

    Crystalline rocks on the west flank of the Alleghanian-aged Raleigh metamorphic belt are subdivided into four west-dipping lithotectonic terranes in the Falls Lake and north Raleigh areas. The rocks of these terranes are separated from east to west on the basis of bulk rock composition, metamorphic textural characteristics, and discrete structural discontinuities into the Raleigh terrane (RT), Crabtree terrane (CT), Falls Lake melange (FLM), and the volcanogenic Carolina slate belt (CSB). The RT and CT are separated by the dextral shear Nutbush Creek fault zone, while the Falls Lake thrust juxtaposes the CT and FLM. The structural character of the discontinuity separating the FLM and the CSB is unclear, although thrusting has been proposed. The results of geologic mapping in the Raleigh West 7.5[prime] quadrangle for the NC Geological Survey's COGEOMAP project in the Raleigh 1[degree] sheet indicate that only the CSB and CT are exposed west of I-440 between US 70 and I-40. This confirms the mapping results of Horton and others that the melange pinches out in north Raleigh just north of US 70. South of US 70, a large orthogneiss body, the Crabtree Creek composite granitic pluton, occupies the same relative position as the melange, separating mafic and intermediate metavolcanic rocks of the CSB from nonlineated and lineated interlayered schists and gneisses of the CT. The pluton is subdivided into a foliated leucocratic, medium grained muscovite granitic orthogneiss, and a foliated leucocratic to mesocratic medium to coarse grained muscovite [plus minus] biotite granitic orthogneiss containing abundant porphyroclastic disks, rods, and knobs of quartz. Because its lobes locally display intrusive contacts with metavolcanic and metasedimentary rocks of both terranes, the Crabtree Creek pluton represents an intrusion that stitched the two terranes together.

  5. 7th international conference on acid rock drainage

    SciTech Connect

    Barnhisel, R.I.

    2006-07-01

    This meeting also serves as the 23rd annual meeting of the American Society of Mining and Reclamation. The papers discussed various aspects of acid mine drainage including its impact, sustainability issues, case studies, lessons learned, characterization, closure/land use issues, emerging technologies, forestry/ecology, abandoned mine lands, modelling, pit lakes/backfill, soils and overburden, and treatment.

  6. Late Cretaceous and early Tertiary plutonism and deformation in the Skagit Gneiss Complex, north Cascade Range, Washington and British Columbia

    USGS Publications Warehouse

    Haugerud, R.A.; Van Der Heyden, P.; Tabor, R.W.; Stacey, J.S.; Zartman, R.E.

    1991-01-01

    The Skagit Gneiss Complex forms a more-or-less continuous terrane within the North Cascade Range. The complex comprises abundant plutons intruded at mid-crustal depths into a variety of metamorphosed supracrustal rocks of both oceanic and volcanic-arc origin. U-Pb zircon ages from gneissis plutons within and near the Skagit Gneiss Complex indicate magmatic crystallziations between 75 and 60 Ma. Deformation, recrystallization, and migmatization in part postdate intrusion of the 75-60 Ma plutons. This latest Cretaceous and earliest Tertiary plutonism and migmatization may reflect thermal relaxation following early Late Cretaceous orogeny. The complex was ductilely extended northwest-southeast shortly after intrusion of granite dikes at ~45 Ma, but before emplacement of the earliest (~34 Ma) plutons of the Cascade arc. -from Authors

  7. A Comparative Size-Composition-Distribution Analysis Of Xenoliths In Plutons

    NASA Astrophysics Data System (ADS)

    Gates, K.; Marko, W. T.; Yoshinobu, A. S.

    2012-12-01

    Field geologists and petrologists have long recognized the significance of xenoliths both in terms of their presence, as well as their conspicuous absence within plutonic rocks. However, few quantitative studies exist on the size and distribution of xenoliths in plutons. We report an exploratory set of size, composition, and distribution studies of xenoliths from a variety of different plutons of granodiorite to diorite composition that bear on processes of xenolith a) incorporation into magmas, b) deformation and displacement in magma chambers, c) preservation in magmas, and d) dissolution and melting in magmas. Four plutons, assembled at depths ranging from subvolcanic to 25 km, have been studied in detail (Jackass Lakes granodiorite, CA; Andalshatten granodiorite and Vega granodiorite, Norway; and Wooley Creek qtz-diorite, CA); two additional plutons (Krakfjellet, Norway, Main Donegal, Ireland) have been evaluated based on published observations. The following observations are summarized: 1) xenoliths in the studied intrusions range in size from sub-mm2 to > km2 and from << 1 to > 8% of total intrusion area, exclusive of screens that may be attached to the host rocks in 3D; 2) in plutons that intrude metasedimentary host rocks, xenoliths of carbonate/quartzite/bte-schist are common whereas pelite and pelitic migmatite are uncommon; 3) statistical size-frequency analysis of a variety of xenolith lithologies display fractal dimensions with D ~ 1 to 3 in log space over a range of sizes. However, in most cases, the density of small xenolith sizes diminishes; 4) plutons with compositions corresponding to higher solidi (e.g., tonalites, qtz diorites, gabbros, etc.) tend to contain migmatitic xenoliths (where bulk composition is appropriate), some of which underwent partial melting in situ; 5) virtually all xenoliths from mm to km in scale have been displaced relative to a fixed host-rock reference frame; none can be shown to be in situ; 6) in all plutons examined

  8. COMPOST-FREE BIOREACTOR TREATMENT OF ACID ROCK DRAINAGE LEVIATHAN MINE, CALIFORNIA INNOVATIVE TECHNOLOGY EVALUATION REPORT

    EPA Science Inventory

    As part of the Superfund Innovative Technology Evaluation (SITE) program, an evaluation of the compost-free bioreactor treatment of acid rock drainage (ARD) from the Aspen Seep was conducted at the Leviathan Mine Superfund site located in a remote, high altitude area of Alpine Co...

  9. COMPOST-FREE BIOLOGICAL TREATMENT OF ACID ROCK DRAINAGE, TECHNICAL EVALUATION BULLETIN

    EPA Science Inventory

    As part of the Superfund Innovative Technology Evaluation (SITE) program, an evaluation of the compost-free bioreactor treatment of acid rock drainage (ARD) from the Aspen Seep was conducted at the Leviathan Mine Superfund site located in a remote, high altitude area of Alpine Co...

  10. COMPOST-FREE BIOREACTOR TREATMENT OF ACID ROCK DRAINAGE - TECHNOLOGY CAPSULE

    EPA Science Inventory

    As part of the Superfund Innovative Technology Evaluation (SITE) program, an evaluation of the compost-free bioreactor treatment of acid rock drainage (ARD) from the Aspen Seep was conducted at the Leviathan Mine Superfund site located in a remote, high altitude area of Alpine Co...

  11. Aqueous Alteration of Mars-Analog Rocks Under an Acidic Atmosphere

    NASA Technical Reports Server (NTRS)

    Bullock, M. A.; Moore, J. M.; Mellon, M. T.

    2001-01-01

    The wind-blown fines of Mars have high amounts of salts that are easily mobilized by water. We report on laboratory experiments that produce brines from the interaction of water with Mars-analog rocks and a simulated acidic Mars paleoatmosphere. Additional information is contained in the original extended abstract.

  12. PHYSICAL SOLUTIONS FOR ACID ROCK DRAINAGE AT REMOTE SITES DEMONSTRATION PROJECT

    EPA Science Inventory

    This report summarizes the results of Mine Waste Technology Program, Activity III, Project 42, Physical Solutions for Acid Rock Drainage at Remote Sites, funded by the U.S. Environmental Protection Agency (EPA) and jointly administered by EPA and the U.S. Department of Energy. A...

  13. Distinctly different parental magmas for calc-alkaline plutons and tholeiitic lavas in the central and eastern Aleutian arc

    NASA Astrophysics Data System (ADS)

    Cai, Yue; Rioux, Matthew; Kelemen, Peter B.; Goldstein, Steven L.; Bolge, Louise; Kylander-Clark, Andrew R. C.

    2015-12-01

    Cenozoic calc-alkaline plutons that comprise the middle crust of the central and eastern Aleutians have distinct isotopic and elemental compositions compared to Holocene tholeiitic lavas in the same region, including those from the same islands. Therefore the Holocene lavas are not representative of the net magmatic transfer from the mantle into the arc crust. Compared to the lavas, the Eocene to Miocene (9-39 Ma) intermediate to felsic plutonic rocks show higher SiO2 at a given Fe/Mg ratio, and have higher εNd-εHf values and lower Pb-Sr isotope ratios. However, the plutonic rocks strongly resemble calc-alkaline Holocene volcanics with more "depleted" isotope ratios in the western Aleutians, whose composition has been attributed to significant contributions from partial melting of subducted basaltic oceanic crust. These data could reflect a temporal variation of central and eastern Aleutian magma source compositions, from predominantly calc-alkaline compositions with more "depleted" isotope ratios in the Paleogene, to tholeiitic compositions with more "enriched" isotopes more recently. Alternatively, the differences between central Aleutian plutonic and volcanic rocks may reflect different transport and emplacement processes for the magmas that form plutons versus lavas. Calc-alkaline parental magmas, with higher SiO2 and high viscosity, are likely to form plutons after extensive mid-crustal degassing of initially high water contents. This conclusion has overarching importance because the plutonic rocks are chemically similar to bulk continental crust. Formation of similar plutonic rocks worldwide may play a key role in the genesis and evolution of continental crust.

  14. Evidence from the Farmington pluton for early Devonian subduction-related magmatism in the Carolina zone of central North Carolina

    NASA Astrophysics Data System (ADS)

    Esawi, E. K.

    2004-04-01

    The Concord plutonic suite consists of numerous gabbroic plutons scattered throughout the Carolina terrane with ages that cluster around 400 Ma. The Farmington pluton is located on the northeastern part of the Mocksville complex and consists mostly of gabbronorites and troctolites. Field, geochemical, and P-T studies of the Farmington gabbros suggest that the rocks are genetically related and formed by transitional to calc-alkaline differentiation of mafic magma. The pluton was formed in a moderate-pressure environment (˜6 kbar) and underwent limited differentiation after emplacement. The overall geological and geochemical features of the Farmington pluton are consistent with a transitional to arc origin. The Concord plutonic suite does not fit well in classical tectonothermal models suggested for the evolution of the Appalachian orogen. However, Field and geochemical data in this report and other data reported recently suggest that the origin of the Farmington pluton and possibly the Concord plutonic suite is that the suite represents a continuous to semi-continuous Taconian-Acadian magmatic event(s).

  15. Petrology of Quaternary volcanic rocks and related plutonic xenoliths from Gölcük volcano, Isparta Angle, Turkey: Origin and evolution of the high-K alkaline series

    NASA Astrophysics Data System (ADS)

    Platevoet, Bernard; Elitok, Ömer; Guillou, Hervé; Bardintzeff, Jacques-Marie; Yagmurlu, Fuzuli; Nomade, Sébastien; Poisson, André; Deniel, Catherine; Özgür, Nevzat

    2014-10-01

    The Quaternary volcanism of Isparta, south-western Anatolia, belongs to the post-collisional alkali-potassic to ultrapotassic magmatism, active since Miocene, from Afyon to Isparta. In the so-called Isparta Angle, the magmatism is contemporaneous with the Aegean extensional regime initiated during the Late Miocene and active throughout the Pliocene and Quaternary. The Gölcük volcano-forming stages consist of three main eruptive cycles: Cycle I comprising 200 m-thick pyroclastic flow deposits; Cycle II consisting of tephriphonolitic lava dome-flows extruded throughout the caldera; and Cycle III characterized by tuff-ring deposits related to the last phreatoplinian events. These late explosive events sampled plutonic xenoliths that allow to better constrain magma fractionation processes that operated at depth in the magma chamber. Magma evolution was first controlled by accumulation of clinopyroxene, phlogopite and apatite, then by phlogopite, amphibole and feldspars, with apatite, magnetite, titanite and zircon as accessories. Crystallization of clinopyroxene, phlogopite and amphibole probably controlled the silica-saturation trend of the whole series and faithfully reflect intensive H2O variations in the magma that were responsible of explosive cyclic events. The parental magma may have had a lamprophyric-tephritic composition. Trace element and isotope ratios indicate a prevalent asthenospheric source versus lithospheric one. Geochemical features, such as strong enrichment of LILE, REE, HFSE in the Gölcük magma point to the involvement of a asthenospheric OIB-type melt with a possible carbonatitic component, that interacted with remnants of the delaminated lithosphere during upwelling.

  16. X-ray microtomography of hydrochloric acid propagation in carbonate rocks.

    PubMed

    Machado, A C; Oliveira, T J L; Cruz, F B; Lopes, R T; Lima, I

    2015-02-01

    Acid treatments are used in the oil and gas industry, to increase the permeability of the carbonate reservoirs by creating preferential channels, called wormholes. Channels formation is strongly influenced by acid type and injection rate. The aim of this study is to evaluate some characteristics of the microporous system of carbonate rocks, before and after acidizing. For that purpose X-ray high-resolution microtomography was used. The results show that this technique can be used as a reliable method to analyze microstructural characteristics of the wormholes. PMID:25485884

  17. 4-Dimensional Insights into Silicic Magma Reservoir Assembly from Late Miocene Southern Andean Plutons

    NASA Astrophysics Data System (ADS)

    Schaen, A. J.; Garibaldi, N.; Singer, B. S.; Schoene, B.; Cottle, J. M.; Tikoff, B.; Gutiérrez, F. J.; Jicha, B. R.; Payacán, I. J.

    2015-12-01

    Linking the development of magmatic flow fabrics to the T-X-t history of intraplutonic domains using modern structural and petrochronologic methods offers a frontier along which to explore for eruptability in plutonic rocks and better understand how shallow magma systems are assembled. The ~6.2 Ma Risco Bayo and Huemul plutons in the Chilean Andes (~36°S) exhibit a similar compositional spectrum and footprint to the active Laguna del Maule rhyolitic volcanic field nearby. The plutons comprise distinct lithological domains-each on the order of a few km3: gabbro to granite in Risco Bayo and granodiorite to leucogranite in Huemul. Whole rock variations and 87Sr/86Sr ratios highlight the importance of AFC processes during pluton assembly. Mixing and mingling of magma batches is observed geochemically and in the field as abundant mafic enclaves. U-Pb CA-ID-TIMS zircon ages of 6.36 to 6.18 Ma in Risco Bayo granodiorite and Huemul miarolitic leucogranite overlap with their 40Ar/39Ar biotite ages of ~6.24 Ma, suggesting coeval zircon saturation, emplacement, and rapid cooling of two compositionally and structurally distinct domains. A granodiorite domain within Huemul has a more protracted crystallization history and zircons with lower REE than in the adjacent miarolitic leucogranite, suggesting pluton construction by pulses on 10 to 100 kyr timescales. Al-in-hornblende barometry constrains emplacement to 3-4 km depth. Observations from Laguna del Maule (extrusion/intrusion rates, spatio-temporal pattern of mafic/rhyolitic volcanism, etc.) provide volcanic parallels with which to help interpret pluton assembly. AMS fabrics suggest possible upward migration of magma associated with decompression. Late Miocene silicic ignimbrites nearby are also being investigated to determine if they represent erupted products from the Risco Bayo-Huemul plutonic system.

  18. Evolution of Mayurbhanj Granite Pluton, eastern Singhbhum, India: a case study of petrogenesis of an A-type granite in bimodal association

    NASA Astrophysics Data System (ADS)

    Misra, Saumitra; Sarkar, Subha Sankar; Ghosh, Sambhunath

    2002-11-01

    The A-type Mayurbhanj Granite Pluton (˜3.09 Ga), occurring along the eastern margin of the Singhbhum-Orissa Craton, eastern India, represents the final phase of acid plutonism in this crustal block of Archean age. The granite shows a bimodal association with a voluminous gabbroid body, exposed mainly along its western margin, and is associated with the Singhbhum Shear zone. The granite pluton is composed mainly of a coarse ferrohastingsite-biotite granite phase, with an early fine-grained granophyric microgranitic phase and a late biotite aplogranitic phase. Petrogenetic models of partial melting, fractional crystallisation and magma mixing have been advocated for the evolution of this pluton. New data, combined with earlier information, suggest that two igneous processes were responsible for the evolution of the Mayurbhanj Granite Pluton: partial melting of the Singhbhum Granite; followed by limited amount of mixing of acid and basic magmas in an anorogenic extensional setting. The necessary heat for partial melting was provided by the voluminous basaltic magma, now represented by the gabbroid body, emplaced at a shallow crustal level and showing a bimodal association with the Mayurbhanj Granite Pluton. The Singhbhum Shear Zone provided a possible channel way for the emplacement of the basic magma during crustal extension. It is concluded that all three phases of the Mayurbhanj Granite Pluton were derived from the same parent magma, generated by batch partial melting of the Singhbhum Granite at relatively high temperatures (˜980 °C) and low pressures (4 to <2 kbar) under anhydrous conditions. The coarse ferrohastingsite biotite granite phase shows evidence of limited and heterogeneous assimilation of country rock metasediments. However, the early microgranite phase and late aplogranite phase have not assimilated any metasediments. Compositional irregularities observed along the western margin of the Mayurbhanj Granite Pluton in contact with the gabbro body

  19. Contact metamorphism associated with emplacement of the Papoose Flat pluton, Inyo Mountains, California

    SciTech Connect

    Nyman, M.W.; Law, R.D.; Morgan, S.S. )

    1992-01-01

    Petrologic investigation of marbles and calc-silicates found within L-S tectonites from the western part of the Papoose Flat pluton's aureole has been undertaken to determine the wallrock thermal gradients associated with pluton emplacement. Temperatures of metamorphism of marbles were determined using Cal-Dol geothermometry coupled with constrains from phase equilibria of both carbonates and interbedded pelites. Throughout the aureole maximum temperatures for samples closest to the contact range from 475--500 C. The phase assemblage in these samples is Cal-Dol-Qtz-Ms-Phl [+-] Hb [+-] Chl. Temperatures decrease rapidly to ambient country rock conditions within 30--90 m away from the contact. Thermal gradients around the strongly deformed western margin of the pluton appear to all be linear and fall into three distinct groups: Type 1. gradients of 0--2.5 C/10m, Type 2. gradients of 13--18 C/10m and, Type 3. gradients of 47--59 C/10m. The strongly deformed nature of the contact rocks supports post- or synmetamorphic thinning of the aureole whereas the presence of skarn mineralization and strongly altered pelitic aureole rocks suggest a convective control to the thermal gradients. Portions of the aureole which have Type 1 gradients may represent areas where (1) convection was more efficient and therefore maintained a relatively steady state thermal profile, (2) introduction of new magma batches during pluton emplacement kept aureole temperatures constant or (3) the pluton-wallrock contact is oriented such that each sample locality is equidistant from the pluton margin. Thermal modeling using both convective and conductive parameters is currently being undertaken to further evaluate these models.

  20. Structure and emplacement of granite plutons in the Paleoproterozoic crust of Eastern Burkina Faso: rheological implications

    NASA Astrophysics Data System (ADS)

    Vegas, Nestor; Naba, Seta; Bouchez, Jean Luc; Jessell, Mark

    2008-11-01

    The Fada N'Gourma area in Burkina Faso is underlain by Paleoproterozoic rocks that make the northeastern West-African Craton. This region is composed of NE-trending volcano-sedimentary belts and foliated tonalites, affected by several shear zones. A generation of younger, ˜2100 Ma-old, non-foliated biotite-bearing granites intrudes the former rock units. We have investigated the younger granite pluton of Kouare that was previously considered as forming a single body with the pluton of Satenga to the west, a pluton which likely belongs to the ˜20 Ma more recent Tenkodogo-Yamba batholith. Magnetic fabric measurements have been combined with microstructural observations and the analysis of field and aeromagnetic data. The granite encloses angular enclaves of the host tonalites. Magmatic microstructures are preserved inside the pluton and solid-state, high-temperature deformation features are ubiquitous at its periphery. The presence of steeply plunging lineations in the pluton of Kouare and its adjacent host-rocks suggests that large volumes of granitic magmas became crystallized while they were ascending through the crust that was softened and steepened close to the contact. Around Kouare, the foliation in the host tonalites conforms with a map-scale, Z-shaped fold in between NNE-trending shear zones, implying a bulk clockwise rotation of the material contained in-between the shear zones, including the emplacing pluton. Regionally, the Fada N'Gourma area is concluded to result from NW-shortening associated with transcurrent shearing and vertical transfer of granitic magmas. This study concludes that the ˜2200 Myears old juvenile crust of Burkina Faso was brittle before the intrusion of the biotite-granites, became softened close to them and that gravity-driven and regional scale wrench tectonics were active together.

  1. In Situ Assimilation Tracked By Trace Element Variation in Augite: Sausfjellet Pluton, North-Central Norway

    NASA Astrophysics Data System (ADS)

    Barnes, C. G.; Coint, N.; Yoshinobu, A. S.; Prestvik, T.; Barnes, M. A. W.

    2014-12-01

    The Sausfjellet pluton is a sub-circular, 445 Ma pluton in the Bindal Batholith. It was intruded into mid-crustal level (~700 MPa), high-grade rocks during Taconian assembly of the Helgeland Nappe Complex. Stage 1 of the pluton is massive pyroxene hornblende gabbro with poikilitic hornblende. Stage 2, the subject of this study, occupies the central and western parts of the pluton and is gradationally zoned from central, layered, xenolith-rich hornblende biotite two-pyroxene diorite + anorthosite, to western, massive, xenolith-poor hornblende biotite three-pyroxene quartz monzonite. Bulk-rock compositions are consistent with widespread accumulation of pyroxene + plagioclase. In order to separate effects of accumulation from assimilation, trace element zoning profiles in augite were used as a proxy for changes in melt composition. Augite is normally zoned, with incompatible elements increasing from cores to rims. However, trace element variation among samples plots as multiple trends that can be resolved into two broad groups that correspond to the central and western zones. Augite in the layered central zone has lower abundances of REE, Pb and Hf and higher abundances of Cr, V, Ni, Sr, and P compared to the western zone. The two trends intersect at low concentrations of incompatible elements such as Zr. Calculation of melts in equilibrium with augite, combined with AFC-type modeling, suggest that variation in augite Zr contents requires assimilation of Zr-rich rocks in all Stage 2 rocks. In the western zone, increases in Zr, Hf, REE and Pb suggest assimilation of Neoproterozoic gneisses that are host to the western zone; this conclusion is consistent with bulk-rock δ18O values. We conclude that assimilation of host rocks was widespread in this mid-crustal magma body, and that augite preserves a trace element record of differentiation (AFC) that is difficult to identify using bulk-rock compositions alone.

  2. Rho Kinase ROCK2 Mediates Acid-Induced NADPH Oxidase NOX5-S Expression in Human Esophageal Adenocarcinoma Cells

    PubMed Central

    Cao, Weibiao

    2016-01-01

    Mechanisms of the progression from Barrett’s esophagus (BE) to esophageal adenocarcinoma (EA) are not fully understood. We have shown that NOX5-S may be involved in this progression. However, how acid upregulates NOX5-S is not well known. We found that acid-induced increase in NOX5-S expression was significantly decreased by the Rho kinase (ROCK) inhibitor Y27632 in BE mucosal biopsies and FLO-1 EA cells. In addition, acid treatment significantly increased the Rho kinase activity in FLO-1 cells. The acid-induced increase in NOX5-S expression and H2O2 production was significantly decreased by knockdown of Rho kinase ROCK2, but not by knockdown of ROCK1. Conversely, the overexpression of the constitutively active ROCK2, but not the constitutively active ROCK1, significantly enhanced the NOX5-S expression and H2O2 production. Moreover, the acid-induced increase in Rho kinase activity and in NOX5-S mRNA expression was blocked by the removal of calcium in both FLO-1 and OE33 cells. The calcium ionophore A23187 significantly increased the Rho kinase activity and NOX5-S mRNA expression. We conclude that acid-induced increase in NOX5-S expression and H2O2 production may depend on the activation of ROCK2, but not ROCK1, in EA cells. The acid-induced activation of Rho kinase may be mediated by the intracellular calcium increase. It is possible that persistent acid reflux present in BE patients may increase the intracellular calcium, activate ROCK2 and thereby upregulate NOX5-S. High levels of reactive oxygen species derived from NOX5-S may cause DNA damage and thereby contribute to the progression from BE to EA. PMID:26901778

  3. Petrogenesis of the Barcroft pluton, northern White-Inyo Mountains, east-central California

    NASA Astrophysics Data System (ADS)

    Ernst, W. G.

    2013-03-01

    The White-Inyo Range lies within the regional transition from Paleozoic-Precambrian North American continental basement to outboard Mesozoic and younger accreted terranes and a superimposed Andean-type arc. In the central White Mountains, the metaluminous Barcroft granodiorite invaded a major NE-striking, SE-dipping high-angle reverse fault—the Barcroft break. Because it is a relatively isolated igneous body and is well exposed over an elevation range of 1,500-4,000 m, its thermal history and that of the surrounding superjacent section are clearer than those of nearly coeval, crowded plutons emplaced in the hotter Sierra Nevada belt. The Barcroft pluton was emplaced as a compositionally heterogeneous series of areally scattered melt pulses episodically injected over the approximate interval 167-161 Ma. The oldest dated rocks are relatively quartzofeldspathic, whereas the youngest is more ferromagnesian, suggesting progressive partial fusion of a relatively mafic protolith. Heavy rare earth-enriched zircons indicate that Barcroft melts were derived at mid-crustal depths from a previously emplaced metabasaltic protolith containing plagioclase but lacking garnet. Granodioritic magma genesis involved the possible mixing of mafic and felsic melts, as well as very minor assimilation of country rocks, but mainly by fractional fusion and crystallization. Bulk chemical, rare earth, and isotopic data suggest that analyzed Barcroft rocks are members of a single suite. Granodioritic rocks are slightly more magnetite-rich at higher elevations on the NE, nearer the roof of the pluton. Earlier thermobarometry chronicled cooling and re-equilibration of the Barcroft pluton from its margins inward, as well as from mid-crustal generation depths of ~25 km through ascent and stalling at ~10-12 km. Refractory phase assemblages crystallized along the pluton margins, whereas subsolidus minerals in the interior of the of body continued to exchange with upper crustal deuteric and

  4. Use of olivine and plagioclase saturation surfaces for the petrogenetic modeling of recrystallized basic plutonic systems

    NASA Technical Reports Server (NTRS)

    Hanson, G. N.

    1983-01-01

    During petrogenetic studies of basic plutonic rocks, there are at least three major questions to be considered: (1) what were the relative proportions of cumulate crystals and intercumulus melt in a given sample? (2) what is the composition and variation in composition of the melts within the pluton? and (3) what is the original composition of the liquids, their source and evolution prior to the time of emplacement? Use of both saturation surfaces can place strong limits on the compositions of potential cumulate phases and intercumulus melts. Consideration of appropriate trace elements can indicate whether a sample is an orthocumulate, adcumulate or mesocumulate. Thus, when trace element and petrographic data are considered together with the saturation surfaces, it should be possible to begin to answer the three major questions given above, even for strongly recrystallized basic plutons.

  5. Berdyaush pluton of rapakivi granites, South Urals: New data on the geological structure and geodynamic evolution

    NASA Astrophysics Data System (ADS)

    Snachev, V. I.; Bazhin, E. A.

    2016-01-01

    The new version of the geological structure of the Berdyaush pluton (a single intrusion of rapakivi granites in the Urals) presented in this paper is significantly distinct from the previous structural schemes. Rapakivi granites compose no more than 10-20% of the area of the pluton and they are widespread only in its northeastern and southwestern flanks. The contacts between gabbro (I phase), hybrid syenodiorites (II phase), and rapakivi granites (III phase) are transitional, metasomatic. The hybrid syenodiorites and rapakivi granites are formed after gabbroic rocks as a result of their intense thermal and metasomatic transformation by the deep fluids. The driving force of this process could be the unilateral compression of the Berdyaush pluton resulting from formation of the eastward continental rift in the beginning of the Middle Riphean.

  6. Magnetic fabrics and their relationship with the emplacement of the Piracaia pluton, SE Brazil

    NASA Astrophysics Data System (ADS)

    Raposo, M. Irene B.; Pressi, Leonardo Frederico; de Assis Janasi, Valdecir

    2012-04-01

    Magnetic fabric and rock-magnetism studies were performed on the four units of the 578 ± 3-Ma-old Piracaia pluton (NW of São Paulo State, southern Brazil). This intrusion is roughly elliptical (~32 km2), composed of (i) coarse-grained monzodiorite (MZD-c), (ii) fine-grained monzodiorite (MZD-f), which is predominant in the pluton, (iii) monzonite heterogeneous (MZN-het), and (iv) quartz syenite (Qz-Sy). Magnetic fabrics were determined by applying both anisotropy of low-field magnetic susceptibility (AMS) and anisotropy of anhysteretic remanent magnetization (AARM). The two fabrics are coaxial. The parallelism between AMS and AARM tensors excludes the presence of a single domain (SD) effect on the AMS fabric of the units. Several rock-magnetism experiments performed in one specimen from each sampled units show that for all of them, the magnetic susceptibility and magnetic fabrics are carried by magnetite grains, which was also observed in the thin sections. Foliations and lineations in the units were successfully determined by applying magnetic methods. Most of the magnetic foliations are steeply dipping or vertical in all units and are roughly parallel to the foliation measured in the field and in the country rocks. In contrast, the magnetic lineations present mostly low plunges for the whole pluton. However, for eight sites, they are steep up to vertical. Thin-section analyses show that rocks from the Piracaia pluton were affected by the regional strain during and after emplacement since magmatic foliation evolves to solid-state fabric in the north of the pluton, indicating that magnetic fabrics in this area of the pluton are related to this strain. Otherwise, the lack of solid-state deformation at outcrop scale and in thin sections precludes deformation in the SW of the pluton. This evidence allows us to interpret the observed magnetic fabrics as primary in origin (magmatic) acquired when the rocks were solidified as a result of magma flow, in which steeply

  7. Reconstruction of mid-crustal pluton assembly and evolution using trace elements in augite: Sausfjellet pluton, Bindal batholith, north-central Norway.

    NASA Astrophysics Data System (ADS)

    Coint, Nolwenn; Barnes, Calvin; Yoshinobu, Aaron; Prestvik, Tore; Barnes, Melanie

    2013-04-01

    The Sausfjellet pluton is a 445 Ma gabbroic to monzonitic body of 7 Km in diameter emplaced in two stages at ~700 MPa pressure. Stage 1 is a coarse pyroxene hornblende gabbro. Stage 2 intrudes a steep contact between marbles on the east and pelitic migmatites on the west. Stage 2 displays a gradational transition from hornblende biotite two-pyroxene diorite to hornblende biotite three-pyroxene quartz monzonite. This transition is accompanied by a decrease in the An content of normally-zoned plagioclase from An61 to An27. Much of the pluton consists of cumulate rocks, as illustrated by the presence of anorthosite and pyroxene-rich layers. In the western part of the intrusion, hosted by metapelitic rocks, incompatible element concentrations and bulk-rock ^18O increase to levels that cannot be explained by fractional crystallization. These increases were originally explained by AFC processes, but because of the cumulative nature of the rocks, it is difficult to assess magmatic processes using bulk rock compositions. Therefore, we analyzed trace element contents and core-to-rim zoning in augite as a proxy to track changes in melt composition. Augite is normally zoned, with lower incompatible element abundances in the cores than in the rims, consistent with evolution of the melt by fractional crystallization. However, instead of plotting along a single differentiation trend, augite compositions define two trends, which is inconsistent with a closed system. The most mafic rocks define a trend with lower REE contents and smaller (negative) Eu anomalies compared to those from the more evolved part of the pluton, although the two trends overlap in Zr content. The two trends correspond to the central, more mafic zone that intrudes marble and the western, more evolved zone that intrudes metapelites. The trend associated with the western zone consists of the same samples that show bulk-rock ^18O enrichment, and is best explained as resulting from assimilation of the host

  8. The Ajo Mining District, Pima County, Arizona--Evidence for Middle Cenozoic Detachment Faulting, Plutonism, Volcanism, and Hydrothermal Alteration

    USGS Publications Warehouse

    Cox, Dennis P.; Force, Eric R.; Wilkinson, William H.; More, Syver W.; Rivera, John S.; Wooden, Joseph L.

    2006-01-01

    Introduction: The Ajo porphyry copper deposit and surrounding Upper Cretaceous rocks have been separated from their plutonic source and rotated by detachment faulting. Overlying middle Cenozoic sedimentary and volcanic rocks have been tilted and show evidence for two periods of rotation. Following these rotations, a granitic stock (23.7?0.2 Ma) intruded basement rocks west of the Ajo deposit. This stock was uplifted 2.5 km to expose deep-seated Na-Ca alteration.

  9. Aerobic bacterial pyrite oxidation and acid rock drainage during the Great Oxidation Event.

    PubMed

    Konhauser, Kurt O; Lalonde, Stefan V; Planavsky, Noah J; Pecoits, Ernesto; Lyons, Timothy W; Mojzsis, Stephen J; Rouxel, Olivier J; Barley, Mark E; Rosìere, Carlos; Fralick, Phillip W; Kump, Lee R; Bekker, Andrey

    2011-10-20

    The enrichment of redox-sensitive trace metals in ancient marine sedimentary rocks has been used to determine the timing of the oxidation of the Earth's land surface. Chromium (Cr) is among the emerging proxies for tracking the effects of atmospheric oxygenation on continental weathering; this is because its supply to the oceans is dominated by terrestrial processes that can be recorded in the Cr isotope composition of Precambrian iron formations. However, the factors controlling past and present seawater Cr isotope composition are poorly understood. Here we provide an independent and complementary record of marine Cr supply, in the form of Cr concentrations and authigenic enrichment in iron-rich sedimentary rocks. Our data suggest that Cr was largely immobile on land until around 2.48 Gyr ago, but within the 160 Myr that followed--and synchronous with independent evidence for oxygenation associated with the Great Oxidation Event (see, for example, refs 4-6)--marked excursions in Cr content and Cr/Ti ratios indicate that Cr was solubilized at a scale unrivalled in history. As Cr isotope fractionations at that time were muted, Cr must have been mobilized predominantly in reduced, Cr(III), form. We demonstrate that only the oxidation of an abundant and previously stable crustal pyrite reservoir by aerobic-respiring, chemolithoautotrophic bacteria could have generated the degree of acidity required to solubilize Cr(III) from ultramafic source rocks and residual soils. This profound shift in weathering regimes beginning at 2.48 Gyr ago constitutes the earliest known geochemical evidence for acidophilic aerobes and the resulting acid rock drainage, and accounts for independent evidence of an increased supply of dissolved sulphate and sulphide-hosted trace elements to the oceans around that time. Our model adds to amassing evidence that the Archaean-Palaeoproterozoic boundary was marked by a substantial shift in terrestrial geochemistry and biology. PMID:22012395

  10. The Effects of Acid Rock Drainage (ARD) on Fluorescent Dissolved Organic Matter (DOM)

    NASA Astrophysics Data System (ADS)

    Lee, R. H.; Gabor, R. S.; SanClements, M.; McKnight, D. M.

    2011-12-01

    Located in the Rocky Mountains of central Colorado, the catchments drained by the headwaters of the Snake River are dominated by metal- and sulfide-rich bedrock. The breakdown of these minerals results in acidic metal-rich waters in the Snake (pH ~3) that persist until the confluence with Deer Creek (pH ~7). Previous research has been conducted examining the interactions of acid-rock drainage (ARD) and dissolved organic matter (DOM), but the effects of ARD on DOM production is not as well understood. In a synoptic study, samples of creek water were collected at evenly spaced intervals along the length of a tributary to the Snake River which drains an area with ARD. At each sampling location, water samples were collected and pH, conductivity, and temperature were measured. Water samples were analyzed for metal chemistry, and the DOM was analyzed with UV-Vis and fluorescence spectroscopy. The character of the DOM was described using PARAFAC and index calculations. This work demonstrates that the introduction of acid and dissolved metal species has notable effects on DOM composition. Preliminary data suggests that the introduction of acid drainage is responsible for the formation of a fluorophore not accounted for in the Cory and McKnight PARAFAC model. Both high concentrations of heavy metals (e.g. zinc) and the novel fluorophore are present downstream from a mining site, which indicates it as a possible source of both species. The data suggest a link between the introduction of fluorophores in acidic waters and acidophile populations at the source of the acid rock drainage.

  11. Rapid Intradeformational Emplacement of the Big Hole Canyon Pluton Into the Sevier Fold-Thrust Belt, Southwest Montana.

    NASA Astrophysics Data System (ADS)

    Hespenheide, M. A.

    2002-12-01

    The Big Hole Canyon pluton (BHCp) is a Late Cretaceous pluton emplaced within the Sevier fold-and-thrust belt of the western North American Cordillera. The pluton is exposed over 60km2 and a thickness of ~1400m. Combined anisotropy of magnetic susceptibility (AMS), structural, and field studies document a clear pattern of magmatic flow radiating from at least three subvertical conduits <100m wide and ~300 to ~800m long. Interpreted flow plunges change rapidly to subhorizontal fabrics across the rest of the pluton, matching the expected pattern for laccolithic emplacement. Ascent conduits within the Big Hole Canyon pluton are coincident with the fold axis of an anticline above a thrust ramp, suggesting that the magma ascended up the fault of the fault-bend-fold. Geobarometry and stratigraphic reconstructions indicate an emplacement depth of approximately ~3km. Preliminary thermal modeling indicates that the BHCp was emplaced in 250,000 years, likely between periods of regional shortening deformation. Rapid magma ascent rates calculated by dike flow modeling and implied by entrained wall-rock xenoliths may indicate sequential magma injection into the pluton; an absence of chill margins between phases within the pluton indicates that sequential injections must have taken place quickly enough that the magmas did not have time to cool below the solidus temperature. The geometry and location of the BHCp suggest that magma used a pre-existing fault as a mechanical discontinuity for both ascent and emplacement. Continued intrusion of magma had a sufficient amount of driving pressure to stretch, shear, and lift the roof of the pluton. Detailed field mapping, structural studies, AMS, and thermobarometry indicate that the Late Cretaceous Big Hole Canyon pluton was emplaced as a laccolith at the top of a pre-existing fault-bend-fold in the frontal portion of the Sevier fold-thrust belt.

  12. On the neutralization of acid rock drainage by carbonate and silicate minerals

    NASA Astrophysics Data System (ADS)

    Sherlock, E. J.; Lawrence, R. W.; Poulin, R.

    1995-02-01

    The net result of acid-generating and-neutralizing reactions within mining wastes is termed acid rock drainage (ARD). The oxidation of sulfide minerals is the major contributor to acid generation. Dissolution and alteration of various minerals can contribute to the neutralization of acid. Definitions of alkalinity, acidity, and buffer capacity are reviewed, and a detailed discussion of the dissolution and neutralizing capacity of carbonate and silicate minerals related to equilibium conditions, dissolution mechanism, and kinetics is provided. Factors that determine neutralization rate by carbonate and silicate minerals include: pH, PCO 2, equilibrium conditions, temperature, mineral composition and structure, redox conditions, and the presence of “foreign” ions. Similar factors affect sulfide oxidation. Comparison of rates shows sulfides react fastest, followed by carbonates and silicates. The differences in the reaction mechanisms and kinetics of neutralization have important implications in the prediction, control, and regulation of ARD. Current static and kinetic prediction methods upon which mine permitting, ARD control, and mine closure plans are based do not consider sample mineralogy or the kinetics of the acid-generating and-neutralizing reactions. Erroneous test interpretations and predictions can result. The importance of considering mineralogy for site-specific interpretation is highlighted. Uncertainty in prediction leads to difficulties for the mine operator in developing satisfactory and cost-effective control and remediation measures. Thus, the application of regulations and guidelines for waste management planning need to beflexible.

  13. Melt segregation evidence from a young pluton, Takidani Granodiorite (Japan)

    NASA Astrophysics Data System (ADS)

    Hartung, Eva; Caricchi, Luca; Floess, David; Wallis, Simon; Harayama, Satoru; Chiaradia, Massimo; Kouzmanov, Kalin

    2016-04-01

    We are presenting new petrological data from one of the youngest exposed plutons in the world, the Takidani Granodiorite (Japan), which has been suggested as a source for large volume ignimbrites (> 300km3). Takidani Granodiorite (1.54 Ma ± 0.23 Ma) is located within the active Norikura Volcanic Chain in the Northen Japan Alps and has been previously linked to large andesitic (1.76 Ma ± 0.17 Ma) and rhyolitic eruptions (1.75 Ma ± 0.17 Ma). The pluton is vertically zoned and consists of granites (67 to 68 wt.% SiO2) in the lower section, granodiorites (65 to 66 wt.% SiO2) in the middle section, a chemically more evolved fine-grained porphyritic unit (67 to 71 wt.% SiO2) near the roof and a marginal granodiorite at the roof (67 to 68 wt.% SiO2). The porphyritic texture of the more evolved unit near the roof indicates rapid crystallisation, which could be the result of the late intrusion of this unit at the roof of the magmatic system. However, no sharp contact is found between the underlying granodiorite and the porphyritic unit. Instead, a gradual change in rock fabric, whole-rock chemistry and mineralogy is observed suggesting that melt was extracted from the granodiorite. Electron microprobe analyses of plagioclases show three main crystal populations (Type I, II and III) with distinct anorthite and Fe contents. Type I plagioclase (An30‑40) occurs dominantly within the marginal granodiorite at the roof. Type II plagioclase (An40‑45) are common in the granodiorite and porphyritic unit. Type III plagioclase (An45‑50) is predominantly present in the granite. All plagioclase populations share a common sodic rim (An22) across the different units. Takidani Granodiorite rocks are compared to crystallisation experiments from similar magmatic suites. Emplacement conditions of the Takidani Granodiorite are obtained from the latter as well as barometry, thermometry and hygrometry indicating that magmas were ultimately emplaced at around 200 MPa, 850° C to 875° C

  14. Applicability Comparison of Methods for Acid Generation Assessment of Rock Samples

    NASA Astrophysics Data System (ADS)

    Oh, Chamteut; Ji, Sangwoo; Yim, Giljae; Cheong, Youngwook

    2014-05-01

    Minerals including various forms of sulfur could generate AMD (Acid Mine Drainage) or ARD (Acid Rock Drainage), which can have serious effects on the ecosystem and even on human when exposed to air and/or water. To minimize the hazards by acid drainage, it is necessary to assess in advance the acid generation possibility of rocks and estimate the amount of acid generation. Because of its relatively simple and effective experiment procedure, the method of combining the results of ABA (Acid Base Accounting) and NAG (Net Acid Generation) tests have been commonly used in determining acid drainage conditions. The simplicity and effectiveness of the above method however, are derived from massive assumptions of simplified chemical reactions and this often leads to results of classifying the samples as UC (Uncertain) which would then require additional experimental or field data to reclassify them properly. This paper therefore, attempts to find the reasons that cause samples to be classified as UC and suggest new series of experiments where samples can be reclassified appropriately. Study precedents on evaluating potential acid generation and neutralization capacity were reviewed and as a result three individual experiments were selected in the light of applicability and compatibility of minimizing unnecessary influence among other experiments. The proposed experiments include sulfur speciation, ABCC (Acid Buffering Characteristic Curve), and Modified NAG which are all improved versions of existing experiments of Total S, ANC (Acid Neutralizing Capacity), and NAG respectively. To assure the applicability of the experiments, 36 samples from 19 sites with diverse geologies, field properties, and weathering conditions were collected. The samples were then subject to existing experiments and as a result, 14 samples which either were classified as UC or could be used as a comparison group had been selected. Afterwards, the selected samples were used to conduct the suggested

  15. Tectonic rotations and internal structure of Eocene plutons in Chuquicamata, northern Chile

    NASA Astrophysics Data System (ADS)

    Somoza, R.; Tomlinson, A. J.; Zaffarana, C. B.; Singer, S. E.; Puigdomenech Negre, C. G.; Raposo, M. I. B.; Dilles, J. H.

    2015-07-01

    A paleomagnetic and AMS study on Eocene plutonic complexes in the Calama area, northern Chile, reveals high-temperature, high-coercivity magnetizations of dominantly thermoremanent origin and magnetic fabrics controlled by magnetite. The paleomagnetic results indicate that ~ 43 Ma plutons underwent clockwise tectonic rotation, whereas adjacent ~ 39 Ma plutons did not undergo discernible rotation. This points to a middle Eocene age for the younger tectonic rotations associated with the Central Andean Rotation Pattern in the Chuquicamata-Calama area. The petrofabric in these rocks formed under conditions ranging from purely magmatic (i.e. before full crystallization) to low-temperature solid-state deformation. AMS and paleomagnetism suggest that the plutonic bodies were formed by progressive amalgamation of subvertical magma sheets spanning multiple magnetic polarity chrons. The parallelism between magmatic and tectonic foliations suggests that regional tectonic stress controlled ascent, emplacement and rock deformation during cooling. In this context, we suggest that magma ascent and emplacement in the upper crust likely exploited Mesozoic structures which were locally reactivated in the Eocene.

  16. Constraints on the depth of generation and emplacement of a magmatic epidote-bearing quartz diorite pluton in the Coast Plutonic Complex, British Columbia

    USGS Publications Warehouse

    Chang, J.M.; Andronicos, C.L.

    2009-01-01

    Petrology and P-T estimates indicate that a magmatic epidote-bearing quartz diorite pluton from Mt. Gamsby, Coast Plutonic Complex, British Columbia, was sourced at pressures below ???1.4 GPa and cooled nearly isobarically at ???0.9 GPa. The P-T path indicates that the magma was within the stability field of magmatic epidote early and remained there upon final crystallization. The pluton formed and crystallized at depths greater than ???30 km. REE data indicate that garnet was absent in the melting region and did not fractionate during crystallization. This suggests that the crust was less than or equal to ???55 km thick at 188 Ma during the early phases of magmatism in the Coast Plutonic Complex. Late Cretaceous contractional deformation and early Tertiary extension exhumed the rocks to upper crustal levels. Textures of magmatic epidote and other magmatic phases, combined with REE data, can be important for constraining the P-T path followed by magmas. ?? 2009 Blackwell Publishing Ltd.

  17. Methods for estimation of long-term non-carbonate neutralisation of acid rock drainage.

    PubMed

    Miller, Stuart D; Stewart, Warwick S; Rusdinar, Yuni; Schumann, Russell E; Ciccarelli, Joseph M; Li, Jun; Smart, Roger St C

    2010-04-01

    In the long-term phase of an acid rock drainage (ARD) evolution profile, after any short-term neutralisation capacity provided by carbonate minerals is exhausted, the net acid release is a product of a declining acid generation rate (AGR) and a slower, long-term acid neutralisation rate mainly provided by gangue silicate minerals. At some point, the AGR and the non-carbonate acid neutralisation rate (ANRnc) will be similar. Matching of the AGR and ANRnc near 10mg H(2)SO(4)/kg/week is demonstrated in data from 10-year columns. This long-term neutralisation is not measured at present in any accepted assessment tests. Methods to estimate ANRnc, based on silicate mineralogy and solution assays from long-term column leach tests, are compared. Good agreement is demonstrated between rates measured from the solution assay data and those calculated from mineralogy using kinetic databases. More rigorous analysis of the leachate chemistry of selected long-term leach tests also suggests possible cover design criteria based on the maximum AGR that will maintain a pH>4 in leachate from ARD materials. The data show a distinct break at an AGR of 3mg H(2)SO(4)/kg/week, below which no leachate pH is less than 4. The results indicate that an AGR of 10t H(2)SO(4)/ha/year is conservative and a suitable cover design target for ARD control that would be matched by ANRnc. PMID:20097405

  18. Chemical stability of acid rock drainage treatment sludge and implications for sludge management

    SciTech Connect

    Danny M. McDonald; John A. Webb; Jeff Taylor

    2006-03-15

    To assess the chemical stability of sludges generated by neutralizing acid rock drainage (ARD) with alkaline reagents, synthetic ARD was treated with hydrated lime (batch and high-density sludge process), limestone, and two proprietary reagents (KB-1 and Bauxsol). The amorphous metal hydroxide sludge produced was leached using deionized water, U.S. EPA methods (toxicity characteristic leaching procedure, synthetic precipitation leaching procedure), and the new strong acid leach test (SALT), which leaches the sludge with a series of sulfuric acid extractant solutions; the pH decreases by {approximately} 1 pH unit with each test, until the final pH is {approximately}2. Sludges precipitated by all reagents had very similar leachabilities except for KB-1 and Bauxsol, which released more aluminum. SALT showed that lowering the pH of the leaching solution mobilized more metals from the sludges. Iron, aluminum, copper, and zinc began to leach at pH 2.5-3, {approximately}4.5, {approximately}5.5, and 6-6.5, respectively. The leachability of ARD treatment sludges is determined by the final pH of the leachate. A higher neutralization potential (e.g., a greater content of unreacted neutralizing agent) makes sludges inherently more chemically stable. Thus, when ARD or any acidic metalliferous wastewater is treated, a choice must be made between efficient reagent use and resistance to acid attack. 26 refs., 5 figs., 2 tabs.

  19. Chemical stability of acid rock drainage treatment sludge and implications for sludge management.

    PubMed

    McDonald, Danny M; Webb, John A; Taylor, Jeff

    2006-03-15

    To assess the chemical stability of sludges generated by neutralizing acid rock drainage (ARD) with alkaline reagents, synthetic ARD was treated with hydrated lime (batch and high-density sludge process), limestone, and two proprietary reagents (KB-1 and Bauxsol). The amorphous metal hydroxide sludge produced was leached using deionized water, U.S. EPA methods (toxicity characteristic leaching procedure, synthetic precipitation leaching procedure), and the new strong acid leach test (SALT), which leaches the sludge with a series of sulfuric acid extractant solutions; the pH decreases by approximately 1 pH unit with each test, until the final pH is approximately 2. Sludges precipitated by all reagents had very similar leachabilities except for KB-1 and Bauxsol, which released more aluminum. SALT showed that lowering the pH of the leaching solution mobilized more metals from the sludges. Iron, aluminum, copper, and zinc began to leach at pH 2.5-3, approximately 4.5, approximately 5.5, and 6-6.5, respectively. The leachability of ARD treatment sludges is determined by the final pH of the leachate. A higher neutralization potential (e.g., a greater content of unreacted neutralizing agent) makes sludges inherently more chemically stable. Thus, when ARD or any acidic metalliferous wastewater is treated, a choice must be made between efficient reagent use and resistance to acid attack. PMID:16570625

  20. Impacts on water quality and biota from natural acid rock drainage in Colorado's Lake Creek watershed

    USGS Publications Warehouse

    Bird, D.A.; Sares, Matthew A.; Policky, Greg A.; Schmidt, Travis S.; Church, Stanley E.

    2006-01-01

    Colorado's Lake Creek watershed hosts natural acid rock drainage that significantly impacts surface water, streambed sediment, and aquatic life. The source of the ARD is a group of iron-rich springs that emerge from intensely hydrothermally altered, unexploited, low-grade porphyry copper mineralization in the Grizzly Peak Caldera. Source water chemistry includes pH of 2.5 and dissolved metal concentrations of up to 277 mg/L aluminum, 498 mg/L iron, and 10 mg/L copper. From the hydrothermally altered area downstream for 27 kilometers to Twin Lakes Reservoir, metal concentrations in streambed sediment are elevated and the watershed experiences locally severe adverse impacts to aquatic life due to the acidic, metal-laden water. The water and sediment quality of Twin Lakes Reservoir is sufficiently improved that the reservoir supports a trout fishery, and remnants of upstream ARD are negligible.

  1. Acid-neutralizing potential of minerals in intrusive rocks of the Boulder batholith in northern Jefferson County, Montana

    USGS Publications Warehouse

    Desborough, George A.; Briggs, Paul H.; Mazza, Nilah; Driscoll, Rhonda

    1998-01-01

    Experimental studies show that fresh granitic rocks of the Boulder batholith in the Boulder River headwaters near Basin, Montana have significant acid-neutralizing potential and are capable of neutralizing acidic water derived from metal-mining related wastes or mine workings. Laboratory studies show that in addition to the acidneutralizing potential (ANP) of minor amounts of calcite in these rocks, biotite, tremolite, and feldspars will contribute significantly to long-term ANP. We produced 0.45 micrometer-filtered acidic (pH = 2.95) leachate for use in these ANP experiments by exposing metal-mining related wastes to deionized water in a waste:leachate ratio of 1:20. We then exposed these leachates to finely-ground and sized fractions of batholith rocks, and some of their mineral fractions for extended and repeated periods, for which results are reported here. The intent was to understand what reactions of metal-rich acidic water and fresh igneous rocks would produce. The reactions between the acidic leachates and the bulk rocks and mineral fractions are complex. Factors such as precipitation of phases like Fe-hydroxides and Alhydroxides and the balance between dissolved cations and anions that are sulfate dominated complicate analysis of the results. Research by others of acid neutralization by biotite and tremolite attributed a rise in pH to proton (H+) adsorption in sites vacated by K, Mg, and Ca. Destruction of the silicate framework and liberation of associated structural hydroxyl ions may contribute to ANP. Studies by others have indicated that the conversion of biotite to a vermiculite-type structure by removal of K at a pH of 4 consumes about six protons for every mole of biotite, but at a pH of 3 there is pronounced dissolution of the tetrahedral lattice. The ANP of fresh granitic rocks is much higher than anticipated. The three bulk Boulder igneous rock samples studied have minimum ANP equivalent to about 10-14 weight percent calcite. This ANP is in

  2. Immobilization and phytotoxicity of Pb in contaminated soil amended with γ-polyglutamic acid, phosphate rock, and γ-polyglutamic acid-activated phosphate rock.

    PubMed

    Zhu, Jun; Cai, Zhijian; Su, Xiaojuan; Fu, Qingling; Liu, Yonghong; Huang, Qiaoyun; Violante, Antonio; Hu, Hongqing

    2015-02-01

    Pot experiments were conducted to investigate the effects of γ-polyglutamic acid (γ-PGA), phosphate rock (PR), and γ-PGA-activated PR (γ-PGA-PR) on the immobilization and phytotoxicity of Pb in a contaminated soil. The proportion of residual Pb (Re-Pb) in soil was reduced by the addition of γ-PGA but was increased by the application of PR and γ-PGA-PR. The addition of γ-PGA in soil improved the accumulation of Pb in pak choi and decreased the growth of pak choi, suggesting the intensification of Pb phytotoxicity to pak choi. However, opposite effects of PR and γ-PGA-PR on the phytotoxicity of Pb to pak choi in soil were observed. Moreover, in the examined range, γ-PGA-PR activated by a higher amount of γ-PGA resulted in a greater proportion of Re-Pb in soil and weaker phytotoxicity of Pb to pak choi. The predominance of γ-PGA-PR in relieving the phytotoxicity of Pb was ascribed mainly to the increase of soil pH and available phosphate after the amendment, which could facilitate the precipitation of Pb in soil and provide pak choi with more phosphorus nutrient. PMID:25196962

  3. Numerical modeling of forceful pluton emplacement and associated deformation at different crustal levels - instantaneous, continuous or episodic intrusion?

    NASA Astrophysics Data System (ADS)

    Chen, Y.; Nabelek, P. I.

    2015-12-01

    The Papoose Flat pluton in the White-Inyo Range, California, is one of the best examples of forceful magma emplacement at mid-crustal levels that is revealed by a highly strained aureole. A thermo-rheological 2-D model of the pluton and its aureole is proposed. We explored how the frequency of magma input, from instantaneous to continuous to the bottom of the laccolith, affects the ductile width of the aureole and the crystallinity of the pluton, which has implications for eruption of magma. We modeled these aspects at mid- and upper-crustal levels. The pluton was assumed to be 5 km thick in the middle and 13 km wide. Except for instantaneous growth, pluton was assumed to grow over 5 m.y. The aureole was assumed to have power-law rheology of quartz with dependence on H2O fugacity, which was calculated using the CORK equation (Holland & Powell, 1991) Our result shows that the bottom of the Papoose Flat pluton was emplaced at the brittle-ductile transition zone of the crust. The crustal rheology profile assisted the softening of rocks around the pluton. The simulated temperature and strength profiles confirm that ductile deformation was related to thermal weakening (Saint-Blanquat et al., 2001). Results of incremental growth calculations show that the pluton remains hot and only partially crystalline for millions of years when it grows by frequent input of small batches of liquid. At the mid-crustal level, the ductile region around the pluton is much wider and exists longer than at the shallow crustal level. Brittle rheology is dominant during the late stage growth at the shallow depth. When the pluton grows instantly or by only few episodes of large batches of input, the mobile part of the pluton is thin and the ductile aureole is narrower. High-frequency incremental growth by smaller magma batches produces a large volume of mobile magma that has the potential to induce internal magmatic layering that may be reflected in aligned acquired magnetic susceptibility (AMS

  4. Incorporating Geochemical And Microbial Kinetics In Reactive Transport Models For Generation Of Acid Rock Drainage

    NASA Astrophysics Data System (ADS)

    Andre, B. J.; Rajaram, H.; Silverstein, J.

    2010-12-01

    Acid mine drainage, AMD, results from the oxidation of metal sulfide minerals (e.g. pyrite), producing ferrous iron and sulfuric acid. Acidophilic autotrophic bacteria such as Acidithiobacillus ferrooxidans and Leptospirillum ferrooxidans obtain energy by oxidizing ferrous iron back to ferric iron, using oxygen as the electron acceptor. Most existing models of AMD do not account for microbial kinetics or iron geochemistry rigorously. Instead they assume that oxygen limitation controls pyrite oxidation and thus focus on oxygen transport. These models have been successfully used for simulating conditions where oxygen availability is a limiting factor (e.g. source prevention by capping), but have not been shown to effectively model acid generation and effluent chemistry under a wider range of conditions. The key reactions, oxidation of pyrite and oxidation of ferrous iron, are both slow kinetic processes. Despite being extensively studied for the last thirty years, there is still not a consensus in the literature about the basic mechanisms, limiting factors or rate expressions for microbially enhanced oxidation of metal sulfides. An indirect leaching mechanism (chemical oxidation of pyrite by ferric iron to produce ferrous iron, with regeneration of ferric iron by microbial oxidation of ferrous iron) is used as the foundation of a conceptual model for microbially enhanced oxidation of pyrite. Using literature data, a rate expression for microbial consumption of ferrous iron is developed that accounts for oxygen, ferrous iron and pH limitation. Reaction rate expressions for oxidation of pyrite and chemical oxidation of ferrous iron are selected from the literature. A completely mixed stirred tank reactor (CSTR) model is implemented coupling the kinetic rate expressions, speciation calculations and flow. The model simulates generation of AMD and effluent chemistry that qualitatively agrees with column reactor and single rock experiments. A one dimensional reaction

  5. Mechanism of Mesozoic Volcanism in Northeastern China: Evidence from New Distribution Maps of Volcanic Rock and Petrogenesis of Acid Rock in Deep Songliao Basin

    NASA Astrophysics Data System (ADS)

    Meng, Fanchao; Liu, Jiaqi; Rasskazov, Sergei; Gao, Jinliang; Zhang, Yutao

    2014-05-01

    Northeastern China is located in the eastern segment of the Central Asian Orogenic belt, which is characterized by widespread Mesozoic volcanic rocks. At present, there are two different opinions concerning the mechanism of volcanism: one proposal is that volcanism was associated with the closure of Mongolia-Okhotsk (MO) Bay, but another suggestion is that the Mesozoic volcanism is controlled by the subduction of Paleo-Pacific plate. However, most studies have mainly focused on the Mesozoic volcanic rocks in Great Xing'an Range(GXR), lack of evidence from Songliao Basin. In order to exactly reveal the mechanism of volcanic rocks in Northeastern China, five new distribution maps of volcanic rocks in Northeast China are drawn and petrogenesis of Mesozoic volcanic rocks in Songliao Basin are obtained. Based on 1: 50000 geological maps, five distribution maps of volcanic rocks (1:2000000) in Northeastern China are recompiled: Early Jurassic, Middle Jurassic, Late Jurassic, Early Cretaceous, and Late Cretaceous. The Early Jurassic volcanic rocks predominantly occur in the eastern Heilongjiang-Jilin province, with minor in Manzhouli in the western. The Middle Jurassic volcanic rocks are mainly founded in the western Liaoning provinces. The Early-Middle Jurassic volcanic rocks(170-146Ma) belong chemically to sub-alkaline series, implying an active continental margin setting. The Late Jurassic volcanic rocks(146-122Ma) mainly occur in the western GXR area, and the magma derived from enriched lithospheric mantle which is closely associated with the subduction of MO plate. The Early Cretaceous volcanic rocks(122-102Ma), widespread in GXR and Songliao basin, are mainly acid and erupt in extensional setting, probably associated with the lithospheric thinning and asthenospheric mantle upwelling caused by subduction of the Paleo-Pacific plate beneath eastern China. Constraints on the timing of MO Bay closure and the motion direction of Paleo-Pacific plate, we infer that:(1) In

  6. Source variation for Mesozoic granitoid plutons in the White-Inyo Range, California, and implications for changes in the lithospheric structure

    NASA Astrophysics Data System (ADS)

    Gammel, E.; Nabelek, P. I.; Phillips, E. H. W.; Scott, S. R.; Sims, K. W. W.

    2015-12-01

    shallower lithospheric material, or (2) two source materials are present at all times with varying degrees of mixing; older plutons represent a greater degree of mixing whereas younger plutons are primarily unmixed. Whole rock isotopic data and amphibole, pyroxene, feldspar compositional data will be used to explore these hypotheses.

  7. River Valley pluton, Ontario - A late-Archean/early-Proterozoic anorthositic intrusion in the Grenville Province

    NASA Technical Reports Server (NTRS)

    Ashwal, Lewis D.; Wooden, Joseph L.

    1989-01-01

    This paper presents Nd, Sr, and Pb isotopic data indicating a late-Archean/early-Proterozoic age for the River Valley anorthositic pluton of the southwestern Grenville Province of Sudbury, Ontario. Pb-Pb isotopic data on 10 whole-rock samples ranging in composition from anorthosite to gabbro yield an age of 2560 + or - 155 Ma. The River Valley pluton is thus the oldest anorthositic intrusive yet recognized within the Grenville Province. The Sm-Nd isotopic system records an age of 2377 + or - 68 Ma. High Pb-208/Pb-204 of deformed samples relative to igneous-textured rocks implies Th introduction and/or U loss during metamorphism in the River Valley area. Rb-Sr data from igneous-textured and deformed samples and from mineral separates give an age of 2185 + or - 105 Ma, indicating substantial disturbance of the Rb-Sr isotopic system.

  8. River Valley pluton, Ontario: A late-Archean/early-Proterozoic anorthositic intrusion in the Grenville Province

    SciTech Connect

    Ashwal, L.D. ); Wooden, J.L. )

    1989-03-01

    The River Valley pluton is a ca. 100 km{sup 2} body of anorthositic and gabbroic rocks located about 50 km northeast of Sudbury, Ontario. The pluton is situated entirely within the Grenville Province, but its western margin is a series of imbricate thrust faults associated with the Grenville Front Tectonic Zone. It is dominated by coarse leuconorite and leucogabbro, with lesser anorthosite, gabbro, and rare ultramafics. Igneous textured rocks are abundant and consist of plagioclase (An{sub 60-70}) charged with Fe-Ti oxide inclusions, low Ca pyroxene (orthopyroxene and/or inverted pigeonite) and augite. The most unfractionated rocks are minor olivine gabbros with Fo{sub 70-80}. A variety of deformed and recrystallized equivalents of the igneous-textured rocks is also present, and these are composed largely of calcic plagioclase and hornblende. An Sm-Nd isochron from 3 igneous-textured leucogabbros and an augite mineral separate gives 2,377 {plus minus} 68 Ma, implying slight disturbance of the Sm-Nd whole-rock-mineral system during later metamorphism. The Rb-Sr system has been substantially disturbed, giving an age of 2,185 {plus minus} 105 Ma, which is similar to internal Pb-Pb isochron ages of 2,165 {plus minus} 130 Ma and 2,100 {plus minus} 35 Ma for two igneous-textured rocks. Initial isotopic ratios for the River Valley pluton correspond to single-stage model parameters of {mu} = 8.06, {epsilon}{sub Nd} = O to {minus}3, and I{sub Sr} = 0.7015 to 0.7021. Collectively, these suggest either an enriched mantle source or crustal contamination of a mantle-derived magma. The crustal component involved must have been older and more radiogenic than the majority of rocks exposed at the surface in the nearby Superior Province.

  9. Magmatic and metamorphic belts and plutonic-metamorphic complexes of southeastern Alaska

    SciTech Connect

    Brew, D.A.; Himmelberg, G.R.; Ford, A.B.; Loney, R.A. . Branch of Alaskan Geology Univ. of Missouri, Columbia, MO . Dept. of Geology)

    1993-04-01

    The Cordilleran orogen in southeastern Alaska includes 24 distinct magmatic belts, ranging in age from Cambrian to Holocene, that are defined by map relations, lithology, age, and chemical composition. The youngest magmatic features are Quaternary-age pre- and post-glacial volcanic rocks that occur in three major fields in the region, as well as in isolated locations. Cenozoic magmatic features consist of four major and three minor belts. The major Tkope-Portland Peninsula belt of Oligocene age includes both volcanic and plutonic rocks. The major calcalkalic Coast Mountains belt of early and middle Eocene age is the single largest magmatic feature of the region. Early Tertiary and latest Cretaceous magmatism is represented by the major calcalkalic great tonalite sill belt, a remarkable long and narrow feature along the west side of the Coast Mountains. Cretaceous and Jurassic intrusive rocks occur in five major belts and two minor belts in the region and Paleozoic intrusive rocks occur in four major and two minor belts. The three major plutonic-metamorphic complexes (PMC), from east to west, are: the Coast PMC in the Coast Mountains; the Glacier Bay-Chichag of plutonic complex (Chugach MC) in the northern outer islands. The Coast PMC records dynamothermal and regional contact metamorphic events related to regional plutonism within several juxtaposed terranes; its lengthy and complicated history is related to the Late Cretaceous collision of the Alexander and Wrangellia terranes and the Gravina overlap assemblage to the west against the Yukon prong and Stikine terrane to the east. The relatively simple Glacier Bay PC history is recorded as the roots of a Late Jurassic through late Early Cretaceous island arc that probably developed during the early stages of the above tectonic event. The complicated Chugach MC history developed during and after the Late Cretaceous collision of the Chugach terrane with the Wrangellia and Alexander terranes.

  10. Asymmetric textural and structural patterns of a granitic body emplaced at shallow levels: The La Chinchilla pluton, northwestern Argentina

    NASA Astrophysics Data System (ADS)

    Macchioli Grande, M.; Alasino, P. H.; Rocher, S.; Larrovere, M. A.; Dahlquist, J. A.

    2015-12-01

    New mapping and a detailed structural study of the La Chinchilla stock, Sierra de Velasco, NW Argentina, suggest an asymmetrical shape of the pluton and provide strong evidence for its shallow emplacement depth. The pluton is a Lower Carboniferous monzogranite composed of K-feldspar, quartz, plagioclase and biotite. It exhibits an internal asymmetric textural zoning, defined by porphyritic granite in the southeastern region to equigranular granite in the northwestern region. The presence of subhorizontal dikes in the northwestern area, where the contacts dip shallowly, and subvertical dikes intruding the host rock nearby steep-dipping intrusive contacts in the southeastern region are compatible with an overall asymmetrical shape and internal structure of this pluton. Considering published crystallization ages, a dominant strain field occurring at around 12 Ma is inferred based on magmatic fabrics in the pluton and its host rock (the Huaco pluton), with a principal shortening direction oriented SW-NE, consistent with the general NW-SE strike of the body. Field evidence supports brittle fracturing and block displacement as the dominant emplacement mechanism, suggesting that magmatic stoping dominated during the late stage of the evolution of the magma chamber.

  11. Thermal evolution of plutons: a parameterized approach

    SciTech Connect

    Spera, F.

    1980-01-18

    A conservation-of-energy equation was derived for the spatially averaged magma temperature in a spherical pluton undergoing simultaneous crystallization and both internal (magma) and external (hydrothermal fluid) thermal convection. The model accounts for the dependence of magma viscosity on crystallinity, temperature, and bulk composition; it includes latent heat effects and the effects of different initial water concentrations in the melt, and quantitatively considers the role that large volumes of circulatory hydrothermal fluids play in dissipating heat. The nonlinear ordinary differential equation describing these processes was solved for a variety of magma compositions, initial temperatures, initial crystallinities, volume ratios of hydrothermal fluid to magma, and pluton sizes. These calculations are graphically summarized in plots of the average magma temperature versus time after emplacement. Solidification times, defined as the time necessary for magma to cool from the initial emplacement temperature to the solidus temperature vary as R/sup 1/ /sup 3/, where R is the pluton radius. The solidification time of a pluton with a radius of 1 kilometer is 5 x 10/sup 4/ years; for an otherwise identical pluton with a radius of 10 kilometers, the solidification time is approx. 10/sup 6/ years. The water content has a marked effect on the solidification time. A granodiorite pluton with a radius of 5 kilometers and either 0.5 or 4 percent (by weight) water cools in 3.3 x 10/sup 5/ or 5 x 10/sup 4/ years, respectively. Convection solidification times are usually but not always less than conduction cooling times. 2 figures.

  12. Availability of elements in tundra soils on acidic and ultramafic rocks in the Polar Urals

    NASA Astrophysics Data System (ADS)

    Kataeva, M. N.

    2013-02-01

    The chemical properties of soils and their particle-size distribution in ecotopes of the Polar Urals mountain tundra were considered in relation with the lithological and geochemical features of the parent rocks. In the soils of ecotopes on the ultramafic massif, the contents of the total Ni (2830 mg/kg) and the total Cr (2327 mg/kg) were found to exceed their clarke values, which suggested the accumulation of these elements by plants and their migration with water. In the soils of the ultramafic massif, the average content of mobile Ni was 46.8 mg/kg, which exceeded the Ni MPC by 11.7 times. The average concentration of mobile Cr in the soils of the massif made up 0.35 MPC. In the soils of geochemical acidic rocks, the contents of mobile Ni and Cr were lower than their MPC levels. A higher content of particles with an average diameter ≥5 μm was found in the soils of the ultramafic massif.

  13. Extreme carbon dioxide concentrations in acidic pit lakes provoked by water/rock interaction.

    PubMed

    Sánchez-España, Javier; Boehrer, Bertram; Yusta, Iñaki

    2014-04-15

    We quantify the gas pressure and concentration of a gas-charged acidic pit lake in SW Spain. We measured total dissolved gas pressure, carbon dioxide (CO2) concentration, major ion concentration, isotopic composition of dissolved inorganic carbon (δ(13)C(DIC)), and other physicochemical parameters. CO2 is the dominant dissolved gas in this lake and results mainly from carbonate dissolution during the interaction of acidic water with wall rocks, followed by diffusive and advective transport through the water column. The δ(13)C(DIC) values suggest that the biological contribution is comparatively small. Maximum CO2 concentrations higher than 0.1 M (∼5000 mg/L) have been measured, which are only comparable to those found in volcanic crater lakes. The corresponding gas pressures of CO2 alone (pCO2 ∼3.6 bar) imply 60% saturation relative to local pressure at 50 m depth. High CO2 concentrations have been observed in other pit lakes of the region. We recommend gas-specific monitoring in acidic pit lakes and, if necessary, the design of feasible degassing strategies. PMID:24628479

  14. The Granite Aqueduct and Advection of Water and Heat Through Plutonic Terranes

    NASA Astrophysics Data System (ADS)

    Glazner, A. F.; Bartley, J. M.; Law, B.; Coleman, D. S.

    2011-12-01

    Although water plays a critical role in the genesis and movement of magma, it is largely lost from rocks upon crystallization. Observation of active volcanoes, analysis of magmatic inclusions, and experimental petrology indicate that intermediate magmas in subduction zones are water-rich, containing 5 wt% or more H2O. Carmichael (2002) wrote of the "andesite aqueduct" that conveys copious amounts of water from magma source regions in subduction zones to the surface and atmosphere. We suggest that this water plays a significant role in the thermal and textural history of the plutonic rocks through which it passes. A dacite magma with 5 wt% H2O crystallizes to granodiorite with ~0.5 wt% H2O, releasing >100 kg of H2O per m3. Field and geochronological data indicate that many sheet-like plutons are constructed from the top down, typically over 1 m.y. or more, likely bathing earlier pulses in ascending water released from later pulses. For a 5 km thick pluton, this release amounts to a condensed-water equivalent depth of ~500 m per unit of horizontal area, a truly vast amount. Plutons preserve abundant evidence for late-stage fluid transfer via a "granite aqueduct." For example, the Tuolumne Intrusive Suite of California is cut by myriad hydrothermally altered pipes that are typically found within or near aplite-pegmatite dikes (Mustart & Horrigan, 2000). The pipes attest to focused fluid flow, and the dikes themselves are the crystallized remnants of late-stage magmatic liquids. Upward advection of heat through dikes and pipes transfers thermal energy from newly crystallizing magma increments to older ones above much more efficiently and rapidly than thermal conduction, and could account for the widespread and profound recrystallization that produces the large grain size and low-temperature mineral assemblages of many granitic rocks. Although the concept that plutons represent the frozen record of huge, highly liquid magma chambers is losing favor, some recent studies

  15. Petrogenesis of Mesoproterozoic granitic plutons, eastern Llano Uplift, central Texas, USA

    NASA Astrophysics Data System (ADS)

    Smith, R. K.; Gray, Walt; Gibbs, Tyson; Gallegos, M. A.

    2010-08-01

    The Llano Uplift of central Texas is a gentle structural dome exposing ˜ 1370 to 1230 Ma metaigneous and metasedimentary rocks of Grenville affinity along the southern margin of Laurentia. The metamorphic rocks were subsequently intruded by ˜ 1119 to 1070 Ma late syn- to post-tectonic granites collectively known as the Town Mountain Granite (TMG). The eastern most of the TMG, the Marble Falls (MF), Kingsland (KL), and Lone Grove (LG) plutons, are metaluminous to marginally peraluminous, high-K, calc-alkaline, ferroan, biotite-calcic amphibole granites [Fe/(Fe + Mg) = 0.71-0.92 and 0.78-0.91 for biotite and calcic amphibole, respectively] displaying distinct variation trends with increasing silica content. They are chemically and texturally zoned and have mineralogical and chemical characteristics similar to A-type granites; i.e., 1) Fe-rich biotites, calcic amphiboles, accessory fluorite, and sporadic rapakivi texture, 2) high K 2O (> 4 wt.%), 3) low Al 2O 3 (< 16 wt.%) and CaO (< 3 wt.%), 4) high Fe/(Fe + Mg), 5) enrichments in Zr, Nb, REE, Ga/Al, and 6) depleted Eu. However, in contrast to typical A-type granites (having low Sr and Ba) the MF, KL,and LG plutons are enriched in Sr and Ba; i.e., up to 229 ppm and 1090 ppm, respectively. On granite discrimination diagrams [(K 2O + Na 2O)/CaO vs. Zr + Nb + Ce + Y (ppm) and Zr (ppm) vs. Ga/Al*10,000] the KL and MF plutons plot within the A-type field, whereas the LG pluton compositions are divided between A-type and fractionated granite fields (I-, S- and M-types). On tectonic discrimination diagrams (Y vs. Nb ) the MF and KL granites plot in the "within-plate" granite field, but the LG pluton plots across several fields including "within-plate" and "volcanic arc plus syn-collisional" fields. Consequently the tectonic classification on a geochemical basis for the LG pluton is unclear. Based on thermal metamorphic mineral assemblages, normative Q-Ab-Or plots, and Q-Ab-Or-H 2O experimental data (Johannes and Holtz

  16. A paleomagnetic and stable isotope study of the pluton at Rio Hondo near Questa, New Mexico: implications for CRM related to hydrothermal alteration

    USGS Publications Warehouse

    Hagstrum, J.T.; Johnson, C.M.

    1986-01-01

    Paleomagnetic and rock magnetic data combined with stable isotope data from the middle Tertiary pluton along the Rio Hondo in northern New Mexico suggest that its magnetic remanence has both thermal (TRM) and high-temperature chemical (CRM) components. Oxygen isotope temperatures indicate that magnetite associated with the more rapidly cooled higher levels of the pluton, and with mafic inclusions and cogenetic rhyolitic dikes sampled at lower levels of exposure, ceased subsolidus recrystallization and isotopic exchange above its Curie temperature (580??C) in the presence of a magmatic fluid. Continued cooling imparted a TRM to these portions of the pluton. The more slowly cooled granodiorite at lower levels has quartz-magnetite isotopic temperatures that are below the Curie temperature of magnetite implying that its magnetization is high-temperature CRM. Sub-Curie isotopic temperatures for other granitic plutons in the western U.S.A. suggest that CRM may be commonly derived from subsolidus interactions between magnetite and magmatic fluids in plutonic rocks. A meteoric-hydrothermal system generated by the cooling Rio Hondo pluton, and not by younger adjacent intrusions, resulted in limited alteration along zones of high permeability near the southern margin of the Rio Hondo pluton, and in more prevasive alteration of the pluton to the north. The meteoric-hydrothermal alteration occurred at relatively high temperatures (> 350??C) and, with the exception of local chloritization, caused little visible alteration of the rocks. The isotopic ratios indicate that little of the magnetite could have grown from or exchanged with a meteoric-hydrothermal fluid. ?? 1986.

  17. Treatment of acid rock drainage using a sulfate-reducing bioreactor with zero-valent iron.

    PubMed

    Ayala-Parra, Pedro; Sierra-Alvarez, Reyes; Field, James A

    2016-05-01

    This study assessed the bioremediation of acid rock drainage (ARD) in flow-through columns testing zero-valent iron (ZVI) for the first time as the sole exogenous electron donor to drive sulfate-reducing bacteria in permeable reactive barriers. Columns containing ZVI, limestone or a mixture of both materials were inoculated with an anaerobic mixed culture and fed a synthetic ARD containing sulfuric acid and heavy metals (initially copper, and later also cadmium and lead). ZVI significantly enhanced sulfate reduction and the heavy metals were extensively removed (>99.7%). Solid-phase analyses showed that heavy metals were precipitated with biogenic sulfide in the columns packed with ZVI. Excess sulfide was sequestered by iron, preventing the discharge of dissolved sulfide. In the absence of ZVI, heavy metals were also significantly removed (>99.8%) due to precipitation with hydroxide and carbonate ions released from the limestone. Vertical-profiles of heavy metals in the columns packing, at the end of the experiment, demonstrated that the ZVI columns still had excess capacity to remove heavy metals, while the capacity of the limestone control column was approaching saturation. The ZVI provided conditions that enhanced sulfate reduction and generated alkalinity. Collectively, the results demonstrate an innovative passive ARD remediation process using ZVI as sole electron-donor. PMID:26808248

  18. Thondhjemite of the Talkeetna Mountains: An unusually large low-K pluton in Alaska's Peninsular terrane

    SciTech Connect

    Ford, A.B.; Arth, J.G.; Csejtey, B. )

    1993-04-01

    An unusually large, elongate Jurassic pluton of trondhjemite, about 120- by 10--15 km in dimensions, intruded Jurassic plutonic and metamorphic rocks of the Peninsular terrane in the central Talkeetna Mountains of south-central Alaska. Muscovite and biotite yield minimum ages of 150--145 Ma. The N40[degree]E-trending body is concordant with regional structures. It is the youngest member of a subduction-related Jurassic plutonic suite in the Peninsular terrane that, along with Wrangellia, was accreted to the North American continent in the middle Cretaceous. Rocks, commonly sheared, are medium to coarse grained and leucocratic (CI = 3--9). Biotite is the chief mafic mineral. Minor muscovite and garnet are common and green hornblende rare. Samples (n = 27) from the body's entire length have an average Mg[number sign] of 45 and an SiO[sub 2] continuum of 67--74% (avg. 70.7%). High Al[sub 2]O[sub 3] (14.4--17.9%, avg. 16.5%) is typical of continental trondhjemite. Averages for Zr (109 ppm) and Nb (3.5 ppm) and the ratios K/Rb (491) and Zr/Nb (34) are typical of orogenic igneous rocks of subduction origin. Four samples analyzed have low ([sup 87]Sr/[sup 86]Sr)[sub i] (avg. 0.7036). Very low Rb/Sr (avg. 0.027) is similar to Idaho batholith trondhjemites. REE patterns with low to moderate LREE and HREE with flat patterns and low contents suggest residual garnet or hornblende during partial melting or fractionation. The pluton appears homogeneous in outcrop. However, some geographic variations in chemistry, as in SiO[sub 2] contents and especially in Eu/Eu[sup *], suggest existence of perhaps three regionally separate plumbing systems, or chambers in which different processes such as plagioclase accumulation or hornblende fractionation were active.

  19. Petrology of the igneous rocks

    NASA Technical Reports Server (NTRS)

    Mccallum, I. S.

    1987-01-01

    Papers published during the 1983-1986 period on the petrology and geochemistry of igneous rocks are discussed, with emphasis on tectonic environment. Consideration is given to oceanic rocks, subdivided into divergent margin suites (mid-ocean ridge basalts, ridge-related seamounts, and back-arc basin basalts) and intraplate suites (oceanic island basalts and nonridge seamounts), and to igneous rocks formed at convergent margins (island arc and continental arc suites), subdivided into volcanic associations and plutonic associations. Other rock groups discussed include continental flood basalts, layered mafic intrusions, continental alkalic associations, komatiites, ophiolites, ash-flow tuffs, anorthosites, and mantle xenoliths.

  20. Introduction to the Apollo collections. Part 1: Lunar igneous rocks

    NASA Technical Reports Server (NTRS)

    Mcgee, P. E.; Warner, J. L.; Simonds, C. H.

    1977-01-01

    The basic petrographic, chemical, and age data is presented for a representative suite of igneous rocks gathered during the six Apollo missions. Tables are given for 69 samples: 32 igneous rocks and 37 impactites (breccias). A description is given of 26 basalts, four plutonic rocks, and two pyroclastic samples. The textural-mineralogic name assigned each sample is included.

  1. Record of Hybridization Preserved in Zircon, Aztec Wash Pluton, NV

    NASA Astrophysics Data System (ADS)

    Bromley, S. A.; Miller, C. F.; Claiborne, L. L.; Wooden, J. L.; Mazdab, F. K.

    2007-12-01

    The mid-Miocene Aztec Wash pluton comprises a smaller granite zone and a larger, highly heterogeneous zone in which evidence for interaction between basaltic and granitic magmas is ubiquitous. Granitic rocks in both zones show textural and compositional evidence for crystal accumulation and melt fractionation. In the heterogeneous zone, basalts have chilled, crenulate margins against granitic rocks, and there is widespread evidence for mechanical contamination of each lithology (coarse resorbed alkali feldspar in fine-grained mafic rock; mafic enclaves in granite). "Grey rocks" of intermediate composition are exposed on dm to 100's of m-scale as enclaves, pods, and initially subhorizontal sheets. They are variable texturally, but most are dominantly fine- grained and equigranular. Textures of grey rocks are consistent with rapid solidification from melt-rich magma, and, in combination with isotopic compositions intermediate between felsic and mafic rocks of the pluton, suggest an origin by near-complete homogenization of a hybrid melt (Bleick et al. 2005; Ericksen 2005). The elemental chemistry of zircon preserves information about the evolving magmatic environment in which it was hosted (Claiborne et al., 2006). Owing to its slow dissolution rate, it has the potential to survive periods of undersaturation with only partial resorption. Thus, it may record drastic shifts in T and melt chemistry that would accompany mafic-felsic hybridization. We are investigating zircon zoning patterns by cathodoluminescence (CL) and elemental compositions by SHRIMP-RG to evaluate the record of processes that they preserve. Temperatures of zircon growth are estimated using Ti-in-zircon thermometry (Watson et al. 2006), assuming a(TiO2) of ca. 0.7 (sphene +/-ilmenite are ubiquitous). Zircons from the granite zone yield estimated T's of 700-860 C, whereas those from grey rocks range from 710- 910 C. While both granite and grey zircon populations show dramatic T variations among and

  2. In situ calcite formation in limestone-saturated water leaching of acid rock waste.

    PubMed

    Smart, Roger St C; Miller, Stuart D; Stewart, Warwick S; Rusdinar, Yuni; Schumann, Russell E; Kawashima, Nobuyuki; Li, Jun

    2010-07-15

    The result of leaching of a 75% acid rock/25% limestone column with limestone-saturated solution has shown that the pH of the effluent recovered from 2.5, after apparent loss of acid neutralizing capacity after 4 years with water leaching, to pH 7 in less than 3 years. Bulk assay results, XRD and SEM/EDS analyses of samples from the column at 384 weeks (pH 3.6) and 522 weeks (pH 6.9) during this recovery have suggested that this is due to formation in situ of fine calcite. Calcite, initially blended to the column material at 25 wt.% was not found in the XRD of the 384 week sample but is clearly found in the 522 week XRD. This increased calcite content appears to be derived from the limestone-saturated water as finely divided solid precipitated in the drying cycles in the column. This result is confirmed by assessment of the 522 week sample as non-acid forming. Loss of some reactive aluminosilicate minerals, formation of secondary, precipitated, surface-attached gypsum and loss of fine secondary jarosite occurs across this pH range but fine, surface-attached jarosite is still found in the 522 week sample implying relatively slow dissolution kinetics. In comparison with the 384 week sample, armouring of highly reacted pyrite particles by surface layers of iron oxyhydroxides and aluminosilicates has become more extensive at 522 weeks after return of the pH to neutral values. This is consistent with results from Freeport field samples from limestone blended test pads where pyrite armouring was also substantially increased at higher pH. The results suggest that it may be possible to effectively maintain neutral pH and passivate pyrite, reducing oxidation rates by more than an order of magnitude, using limestone-saturated solution dump feed rather than bulk limestone blending or covers. PMID:20452647

  3. Biochar enhances Aspergillus niger rock phosphate solubilization by increasing organic acid production and alleviating fluoride toxicity.

    PubMed

    Mendes, Gilberto de Oliveira; Zafra, David Lopez; Vassilev, Nikolay Bojkov; Silva, Ivo Ribeiro; Ribeiro, José Ivo; Costa, Maurício Dutra

    2014-05-01

    During fungal rock phosphate (RP) solubilization, a significant quantity of fluoride (F(-)) is released together with phosphorus (P), strongly inhibiting the process. In the present study, the effect of two F(-) adsorbents [activated alumina (Al2O3) and biochar] on RP solubilization by Aspergillus niger was examined. Al2O3 adsorbed part of the F(-) released but also adsorbed soluble P, which makes it inappropriate for microbial RP solubilization systems. In contrast, biochar adsorbed only F(-) while enhancing phosphate solubilization 3-fold, leading to the accumulation of up to 160 mg of P per liter. By comparing the values of F(-) measured in solution at the end of incubation and those from a predictive model, it was estimated that up to 19 mg of F(-) per liter can be removed from solution by biochar when added at 3 g liter(-1) to the culture medium. Thus, biochar acted as an F(-) sink during RP solubilization and led to an F(-) concentration in solution that was less inhibitory to the process. In the presence of biochar, A. niger produced larger amounts of citric, gluconic, and oxalic acids, whether RP was present or not. Our results show that biochar enhances RP solubilization through two interrelated processes: partial removal of the released F(-) and increased organic acid production. Given the importance of organic acids for P solubilization and that most of the RPs contain high concentrations of F(-), the proposed solubilization system offers an important technological improvement for the microbial production of soluble P fertilizers from RP. PMID:24610849

  4. Biochar Enhances Aspergillus niger Rock Phosphate Solubilization by Increasing Organic Acid Production and Alleviating Fluoride Toxicity

    PubMed Central

    Mendes, Gilberto de Oliveira; Zafra, David Lopez; Vassilev, Nikolay Bojkov; Silva, Ivo Ribeiro; Ribeiro, José Ivo

    2014-01-01

    During fungal rock phosphate (RP) solubilization, a significant quantity of fluoride (F−) is released together with phosphorus (P), strongly inhibiting the process. In the present study, the effect of two F− adsorbents [activated alumina (Al2O3) and biochar] on RP solubilization by Aspergillus niger was examined. Al2O3 adsorbed part of the F− released but also adsorbed soluble P, which makes it inappropriate for microbial RP solubilization systems. In contrast, biochar adsorbed only F− while enhancing phosphate solubilization 3-fold, leading to the accumulation of up to 160 mg of P per liter. By comparing the values of F− measured in solution at the end of incubation and those from a predictive model, it was estimated that up to 19 mg of F− per liter can be removed from solution by biochar when added at 3 g liter−1 to the culture medium. Thus, biochar acted as an F− sink during RP solubilization and led to an F− concentration in solution that was less inhibitory to the process. In the presence of biochar, A. niger produced larger amounts of citric, gluconic, and oxalic acids, whether RP was present or not. Our results show that biochar enhances RP solubilization through two interrelated processes: partial removal of the released F− and increased organic acid production. Given the importance of organic acids for P solubilization and that most of the RPs contain high concentrations of F−, the proposed solubilization system offers an important technological improvement for the microbial production of soluble P fertilizers from RP. PMID:24610849

  5. Pluton accommodation at high strain rates in the upper continental crust. The example of the Central Extremadura batholith, Spain

    NASA Astrophysics Data System (ADS)

    Fernández, Carlos; Castro, Antonio

    1999-08-01

    Emplacement in the tensional bridge of a stepped dextral shear zone system is proposed for the Central Extremadura batholith (Spain). The country rocks show a pervasive anisotropy that conditioned the style of the structures developed as a consequence of the transference of displacement from the stepped shear zones to the releasing area. The kinematic evolution of the resulting megakink fold provided the volume increase necessary for the granite emplacement. Thermal and kinematic models suggest that the growth of individual plutons took place in periods of no more than several hundred to a few thousand years. Fast strain rates (10 -10-10 -11 s -1) must concentrate in local structures (e.g. initiation of kink folds) even in zones deforming as a whole under typical strain rates (10 -14±1 s -1). Granite plutons might be used as strain-rate gauges for syn-plutonic structures.

  6. The chemical and isotopic differentiation of an epizonal magma body: Organ Needle pluton, New Mexico

    USGS Publications Warehouse

    Verplanck, P.L.; Farmer, G.L.; McCurry, M.; Mertzman, S.A.

    1999-01-01

    Major and trace element, and Nd and Sr isotopic compositions of whole rocks and mineral separates from the Oligocene, alkaline Organ Needle pluton (ONP), southern New Mexico, constrain models for the differentiation of the magma body parental to this compositionally zoned and layered epizonal intrusive body. The data reveal that the pluton is rimmed by lower ??(Nd) (~-5) and higher 87Sr/86Sr (~0.7085) syenitic rocks than those in its interior (??(Nd) ~ 2, 87Sr/86Sr ~0.7060) and that the bulk compositions of the marginal rocks become more felsic with decreasing structural depth. At the deepest exposed levels of the pluton, the ??(Nd)~-5 lithology is a compositionally heterogeneous inequigranular syenite. Modal, compositional and isotopic data from separates of rare earth element (REE)-bearing major and accesory mineral phases (hornblende, titanite, apatite, zircon) demonstrate that this decoupling of trace and major elements in the inequigranular syenite results from accumulation of light REE (LREE)-bearing minerals that were evidently separated from silicic magmas as the latter rose along the sides of the magma chamber. Chemical and isotopic data for microgranular mafic enclaves, as well as for restite xenoliths of Precambrian granite wall rock, indicate that the isotopic distinction between the marginal and interior facies of the ONP probably reflects assimilation of the wall rock by ??(Nd) ~-2 mafic magmas near the base of the magma system. Fractional crystallization and crystal liquid separation of the crystally contaminated magma at the base and along the margins of the chamber generated the highly silicic magmas that ultimately pooled at the chamber top.

  7. Geochemical Relationships between Volcanic and Plutonic Upper to Mid Crustal Exposures of the Rosario Segment, Alisitos Arc (Baja California, Mexico): An Outstanding Field Analog to the Izu-Bonin-Mariana Arc

    NASA Astrophysics Data System (ADS)

    Morris, R.; DeBari, S. M.; Busby, C. J.; Medynski, S.

    2015-12-01

    Exposed paleo-arcs, such as the Rosario segment of the Cretaceous Alisitos Arc in Baja California, Mexico, provide an opportunity to explore the evolution of arc crust through time. Remarkable 3-D exposures of the Rosario segment record crustal generation processes in the volcanic rocks and underlying plutonic rocks. In this study, we explore the physical and geochemical connection between the plutonic and volcanic sections of the extensional Alisitos Arc, and elucidate differentiation processes responsible for generating them. These results provide an outstanding analog for extensional active arc systems, such as the Izu-Bonin-Mariana (IBM) Arc. Upper crustal volcanic rocks have a coherent stratigraphy that is 3-5 km thick and ranges in composition from basalt to dacite. The most felsic compositions (70.9% SiO2) are from a welded ignimbrite unit. The most mafic compositions (51.5% SiO2, 3.2% MgO) are found in basaltic sill-like units. Phenocrysts in the volcanic units include plagioclase +/- amphibole and clinopyroxene. The transition to deeper plutonic rocks is clearly an intrusive boundary, where plutonic units intrude the volcanic units. Plutonic rocks are dominantly a quartz diorite main phase with a more mafic, gabbroic margin. A transitional zone is observed along the contact between the plutonic and volcanic rocks, where volcanics have coarsely recrystallized textures. Mineral assemblages in the plutonic units include plagioclase +/- quartz, biotite, amphibole, clinopyroxene and orthopyroxene. Most, but not all, samples are low K. REE patterns are relatively flat with limited enrichment. Normalization diagrams show LILE enrichment and HFSE depletion, where trends are similar to average IBM values. We interpret plutonic and volcanic units to have similar geochemical relationships, where liquid lines of descent show the evolution of least to most evolved magma types. We provide a model for the formation and magmatic evolution of the Alisitos Arc.

  8. Oil sands thickened froth treatment tailings exhibit acid rock drainage potential during evaporative drying.

    PubMed

    Kuznetsov, Petr; Kuznetsova, Alsu; Foght, Julia M; Siddique, Tariq

    2015-02-01

    Bitumen extraction from oil sands ores after surface mining produces different tailings waste streams: 'froth treatment tailings' are enriched in pyrite relative to other streams. Tailings treatment can include addition of organic polymers to produce thickened tailings (TT). TT may be further de-watered by deposition into geotechnical cells for evaporative drying to increase shear strength prior to reclamation. To examine the acid rock drainage (ARD) potential of TT, we performed predictive analyses and laboratory experiments on material from field trials of two types of thickened froth treatment tailings (TT1 and TT2). Acid-base accounting (ABA) of initial samples showed that both TT1 and TT2 initially had net acid-producing potential, with ABA values of -141 and -230 t CaCO₃ equiv. 1000 t(-1) of TT, respectively. In long-term kinetic experiments, duplicate ~2-kg samples of TT were incubated in shallow trays and intermittently irrigated under air flow for 459 days to simulate evaporative field drying. Leachates collected from both TT samples initially had pH~6.8 that began decreasing after ~50 days (TT2) or ~250 days (TT1), stabilizing at pH~2. Correspondingly, the redox potential of leachates increased from 100-200 mV to 500-580 mV and electrical conductivity increased from 2-5 dS m(-1) to 26 dS m(-1), indicating dissolution of minerals during ARD. The rapid onset and prolonged ARD observed with TT2 is attributed to its greater pyrite (13.4%) and lower carbonate (1.4%) contents versus the slower onset of ARD in TT1 (initially 6.0% pyrite and 2.5% carbonates). 16S rRNA gene pyrosequencing analysis revealed rapid shift in microbial community when conditions became strongly acidic (pH~2) favoring the enrichment of Acidithiobacillus and Sulfobacillus bacteria in TT. This is the first report showing ARD potential of TT and the results have significant implications for effective management of pyrite-enriched oil sands tailings streams/deposits. PMID:25306090

  9. Using Oxygen Isotopes of Zircon to Evaluate Magmatic Evolution and Crustal Contamination in the Halifax Pluton, Nova Scotia

    NASA Astrophysics Data System (ADS)

    Murray, K. E.; Lackey, J.; Valley, J. W.; Nowak, R.

    2007-12-01

    Oxygen isotope analysis of zircon (Zrc) is well suited for parsing out the magmatic history in granitoids. The Halifax pluton is the largest pluton (1060 km2) in the peraluminous South Mountain batholith. The Halifax pluton is mapped as a concentrically zoned body, with outer units comprising granodiorite, monzogranite and a mafic porphyry; these units are locally rich in metasedimentary xenoliths and magmatic enclaves. The exterior units surround a more felsic core of leucogranite [1]. Previous oxygen isotope studies of the pluton report high whole rock δ18O values that range from 10.7-11.7‰ [2], and indicate a significant supracrustal component in the source of the pluton. We report the first δ18O(Zrc) values from the Peggy's Cove monzogranite and an associated mafic porphyry. Samples were collected across 30 km of discontinuous exposures of the monzogranite. Values of δ18O(Zrc) vary from 7.71-8.26‰ (average = 8.15±±0.32‰(2 S.D.); n = 10). Small but systematic E-W regional variation in δ18O(Zrc) values suggests heterogeneous magmatic contamination within the monzogranite. Meter-scale magmatic enclaves, observed in close association with pods of diverse xenoliths and smaller enclaves at the western Cranberry Head locality, are slightly enriched in δ18O relative to the host monzogranite. These data combined support a model of magma mingling and heterogeneous mixing at the rim of the pluton, with contamination by high-δ18O rocks. Additional high-δ18O(Zrc) data from granodiorites on the northern margin of the Halifax pluton concur with these observations [3]. Typically, closed magmatic systems show increasing δ18O with SiO2 because more felsic magmas have a greater percentage of high-δ18O minerals such as quartz and feldspar. Thus, the Halifax pluton appears to exhibit an enrichment trend opposite of what would be expected of a closed evolving system. Emplacement mechanisms for the Halifax pluton proposed by previous workers suggest that the outer

  10. In-Situ and Experimental Evidence for Acidic Weathering of Rocks and Soils on Mars

    NASA Technical Reports Server (NTRS)

    Hurowitz, J. A.; McLennan, S. M.; Tosca, N. J.; Arvidson, R. E.; Michalski, J. R.; Ming, D.; Schroeder, C.; Squyres, S. W.

    2006-01-01

    Experimental data for alteration of synthetic Martian basalts at pH=0-1 indicate that chemical fractionations at low pH are vastly different from those observed during terrestrial weathering. Rock analyses from Gusev crater are well described by the relationships apparent from low pH experimental alteration data. A model for rock surface alteration is developed which indicates that a leached alteration zone is present on rock surfaces at Gusev. This zone is not chemically fractionated to a large degree from the underlying rock interior, indicating that the rock surface alteration process has occurred at low fluid-to-rock ratio. The geochemistry of natural rock surfaces analyzed by APXS is consistent with a mixture between adhering soil/dust and the leached alteration zone. The chemistry of rock surfaces analyzed after brushing with the RAT is largely representative of the leached alteration zone. The chemistry of rock surfaces analyzed after grinding with the RAT is largely representative of the interior of the rock, relatively unaffected by the alteration process occurring at the rock surface. Elemental measurements from the Spirit, Opportunity, Pathfinder and Viking 1 landing sites indicate that soil chemistry from widely separated locations is consistent with the low-pH, low fluid to rock ratio alteration relationships developed for Gusev rocks. Soils are affected principally by mobility of FeO and MgO, consistent with alteration of olivine-bearing basalt and subsequent precipitation of FeO and MgO bearing secondary minerals as the primary control on soil geochemistry.

  11. Distinctly different parental magmas for plutons and lavas in the central Aleutian arc

    NASA Astrophysics Data System (ADS)

    Cai, Y.; Rioux, M. E.; Kelemen, P. B.; Goldstein, S. L.; Bolge, L.; Kylander-Clark, A. R.

    2014-12-01

    While it is generally agreed that continental crust is generated by arc magmatism, average arc lavas are basaltic while the bulk continental crust is andesitic, and this has led to many models for secondary reprocessing of the arc crust in order to form continental crust. We report new data on calc-alkaline plutons in the central Aleutians showing that they have distinctly different sources compared to Holocene tholeiitic lavas. Therefore the lavas are not representative of the net magmatic transfer from the mantle into the arc crust. Eocene to Miocene (9-39 Ma) intermediate to felsic plutonic rocks from the central Aleutian arc show higher SiO2 at a given Mg#, higher ɛNd- and ɛHf-values, and lower Pb isotope ratios than Holocene volcanic rocks from the same region. Instead, the plutonic rocks resemble volcanics from the western Aleutians isotopically, and have chemical compositions similar to bulk continental crust. These data could reflect temporal variation of Aleutian magma source compositions, from Eocene-Miocene "isotopically depleted" and predominantly calc-alkaline to Holocene "isotopically enriched" and predominantly tholeiitic. Alternatively, they may reflect different transport and emplacement processes for the magmas that form plutons and lavas: calc-alkaline magmas with higher Si content and high viscosity may preferentially form plutons, perhaps after extensive mid-crustal degassing of initially high water contents. The latter case implies that the upper and middle arc crust is more like the calc-alkaline bulk composition of the continental crust than the lavas alone. Crustal reprocessing mechanisms that preserve upper and middle arc crust, while removing lower arc crust, can account for the genesis and evolution of continental crust. Since gabbroic lower arc crust extends from ca 20-40 km depth, and is density stable over most of this depth range, "delamination" of dense lithologies [1] may not be sufficient to accomplish this. Alternatively

  12. Evolution and geochemistry of the Tertiary calc-alkaline plutons in the Adak Island region of the central Aleutian oceanic island arc

    NASA Astrophysics Data System (ADS)

    Kay, Suzanne; Citron, Gary P.; Kay, Robert W.; Jicha, Brian; Tibbetts, Ashley

    2014-05-01

    Calc-alkaline plutons are major crustal building blocks of continental margin mountain belts like the Mesozoic to Tertiary Andes and the Sierra Nevada, but are rare in oceanic island arcs. Some of the most calc-alkaline I-type island arc plutons are in the Central Aleutians with the most extreme signatures, as indicated by FeO/MgO ratios of < ~2 at 48-70% wt. % SiO2, in the ~10 km wide Oligocene Hidden Bay pluton on southern Adak Island and the 10 km wide Miocene Kagalaska pluton to the north on eastern Adak and the adjacent Kagalaska Island. Although small compared to most continental plutons, similarities in intrusive units, mineralogy and chemistry suggest common formation processes. The Aleutian calc-alkaline plutonic rocks mainly differ from continental plutons in having more oceanic like isotopic (87Sr/86Sr = 0.703-0.7033; Epsilon Nd = 9-7.8) and LIL (e.g., higher K/Rb) ratios. The Adak region plutons differ from Tertiary plutons on Unalaska Island further east in being more K-rich and in having a more oxidized and lower-temperature mineralogy. From a regional perspective, the Adak area plutons intrude Eocene/Oligocene Finger Bay Formation mafic volcanic and sedimentary rocks and postdate the small ~38 Ma tholeiitic Finger Bay pluton. The chemistry of these older magmatic rocks is basically similar to that of young Central Aleutian magmatic rocks with boninites and arc tholeiitic magmas seemingly being absent. The formation of the calc-alkaline plutons seems to require a sufficient crustal thickness, fluid concentration and contractional stress such that magma chambers can stabilize significant amounts of pargasitic hornblende. Seismic receiver function analyses (Janiszewski et al., 2013) indicate the modern Adak crust is ~ 37 km thick. Existing and new hornblende, plagioclase and biotite Ar/Ar ages from 16 Hidden Bay pluton and Gannet Lake stock gabbro, porphyritic diorite, diorite, granodiorite, leucogranodiorite and aplite samples range from 34.6 to 30

  13. Trace metal mobilization from oil sands froth treatment thickened tailings exhibiting acid rock drainage.

    PubMed

    Kuznetsova, Alsu; Kuznetsov, Petr; Foght, Julia M; Siddique, Tariq

    2016-11-15

    Froth treatment thickened tailings (TT) are a waste product of bitumen extraction from surface-mined oil sands ores. When incubated in a laboratory under simulated moist oxic environmental conditions for ~450d, two different types of TT (TT1 and TT2) exhibited the potential to generate acid rock drainage (ARD) by producing acid leachate after 250 and 50d, respectively. We report here the release of toxic metals from TT via ARD, which could pose an environmental threat if oil sands TT deposits are not properly managed. Trace metal concentrations in leachate samples collected periodically revealed that Mn and Sr were released immediately even before the onset of ARD. Spikes in Co and Ni concentrations were observed both pre-ARD and during active ARD, particularly in TT1. For most elements measured (Fe, Cr, V, As, Cu, Pb, Zn, Cd, and Se), leaching was associated with ARD production. Though equivalent acidification (pH2) was achieved in leachate from both TT types, greater metal release was observed from TT2 where concentrations reached 10,000ppb for Ni, 5000ppb for Co, 3000ppb for As, 2000ppb for V, and 1000ppb for Cr. Generally, metal concentrations decreased in leachate with time during ARD and became negligible by the end of incubation (~450d) despite appreciable metals remaining in the leached TT. These results suggest that using TT for land reclamation purposes or surface deposition for volume reduction may unfavorably impact the environment, and warrants application of appropriate strategies for management of pyrite-enriched oil sands tailings streams. PMID:27443453

  14. Reclamation of acidic, denuded copper basin land: Revegetation performance of phosphate rock vs other nutrient sources

    SciTech Connect

    Soileau, J.M.; Sikora, F.J.; Maddox, J.J.; Kelsoe, J.J.

    1996-12-31

    Open pit smelting of Copper ore about 100 years ago resulted in approximately 9,300 ha of severely eroded, very acidic (pH 4.0 to 5.0) soils at Copper Basin, Tennessee. Along with other essential nutrients, phosphorus (P) amendments are critical for long-term productivity and sustainability of vegetation on this depleted soil. A field study was conducted (1992-1995) to compare revegetation from surface-applied North Carolina phosphate rock (PR) and triple superphosphate (TSP) at 20, 59, and 295 kg P ha{sup -1}, and to determine benefits of starter NPK tree tablets. The experimental design consisted of 7.3 x 9.1 m replicated plots, each planted to 20 loblolly pine seedlings and aerially seeded with a mixture of grasses and legumes. Tree survivability was high from all treatments. Through the third year, tree height and diameter increased with increasing P to 59 kg P ha without fertilizer tablets. There were no pine growth differences between PR and TSP. Weeping lovegrass has been the dominant cover crop through 1995, with increased stimulation to tree tablets and surface P. Tall fescue (KY 31), sericea lespedeza, and black locust responded more to PR than to TSP. Surface soil pH increased, and 0.01 M SrCl{sub 2} extractable Al decreased, with increasing rate of PR. For future loblolly pine plantings in the Copper Basin, this study suggests there is no benefit to applying both tree tablets and surface P at rates above 59 kg P ha{sup -1}. For reclaiming land with high acidity and low P fertility, PR has significant benefits. In reclaiming steep, gullied land, there is great potential for aerial application of PR and/or pelletized liming agents.

  15. Insights Into the Formation of Rhyolite From the Searchlight Pluton: Evidence from Oriented Quartz Clusters

    NASA Astrophysics Data System (ADS)

    Froemming, N.; Deering, C. D.; Beane, R. J.; Bachmann, O.

    2012-12-01

    The Miocene Searchlight pluton (SLP) in the Colorado River extensional corridor of southern Nevada, is well-exposed and tilted near-vertical for exceptional cross-sectional study of magma reservoir dynamics and crystal fractionation of a mid- to upper-crustal pluton (3 to 13 km depth). The upper quartz monzonite section is dominated by minerals in apparent random orientation with a medium- to fine-grained texture due to direct contact with the cold host rock. The middle granitic section is dominated by coarse-grained quartz and feldspar, and interpreted to be a zone of extracted liquid from an intermediate magma. The lower monzonite section is composed of coarse-grained plagioclase and potassium feldspar. We used the crystallographic orientations of quartz clusters, as determined by Electron Backscatter Diffraction (EBSD), to test for crystal accumulation in the SLP. Clusters of quartz crystals with matched dipyramidal faces (parallel or Esterel twin orientation) may indicate a period of crystal accumulation. By analyzing representative samples from each section of the pluton, we found that the lower section (intermediate cumulate) and upper section (crystallization front) do not have quartz clusters with matched dipyramidal faces. Although plagioclase grains are aligned in the lower section, the late crystallization of quartz appears to have prevented aligned or preferred growth orientations. In contrast, the middle section has a high percentage of quartz clusters with matched dipyramidal faces - similar to that found in granite porphyry of the Vinalhaven pluton, Maine. The aligned grains may have formed by fractional crystallization, compaction and synneusis of the early forming quartz in this granitic section. We interpret the middle section of the Searchlight pluton as being similar to shallow, upper crustal plutons (3-8 km depth) such as Vinalhaven pluton. The deep vertical exposure of the SLP, shows that the middle section was formed from periodic episodes of

  16. Dealumination of clinoptilolite and its effect on zinc removal from acid rock drainage.

    PubMed

    Xu, Wanjing; Li, Loretta Y; Grace, John R

    2014-09-01

    Clinoptilolite, a natural zeolite, is capable of removing heavy metals from acid rock drainage (ARD). Previous studies have neglected the dealumination of clinoptilolite and its impact during remediation. This study observed the dealumination of clinoptilolite during ARD remediation in a slurry bubble column (SBC), and investigated its impact on the capture of zinc. Uptake tests were performed with natural ARD and various sorbent average particle diameters from 300 to 1400μm, superficial gas velocities from 0.08 to 0.23ms(-1), initial aqueous pH from 2 to 6, Zn concentrations from 15 to 215ppm and sorbent/solution mass ratios from 25 to 400gkg(-1) to test zinc uptake. Dealumination of clinoptilolite was sometimes observed during the uptake process. Increased Al in the aqueous phase led to co-precipitation of Zn-Al colloid, enhanced by abundant sulfate in solution. The unit zinc uptake of the Al colloid was found to be much higher than for the raw clinoptilolite. PMID:24997948

  17. Algae as an electron donor promoting sulfate reduction for the bioremediation of acid rock drainage.

    PubMed

    Ayala-Parra, Pedro; Sierra-Alvarez, Reyes; Field, Jim A

    2016-11-01

    This study assessed bioremediation of acid rock drainage in simulated permeable reactive barriers (PRB) using algae, Chlorella sorokiniana, as the sole electron donor for sulfate-reducing bacteria. Lipid extracted algae (LEA), the residues of biodiesel production, were compared with whole cell algae (WCA) as an electron donor to promote sulfate-reducing activity. Inoculated columns containing anaerobic granular sludge were fed a synthetic medium containing H2SO4 and Cu(2+). Sulfate, sulfide, Cu(2+) and pH were monitored throughout the experiment of 123d. Cu recovered in the column packing at the end of the experiment was evaluated using sequential extraction. Both WCA and LEA promoted 80% of sulfate removal (12.7mg SO4(2-) d(-1)) enabling near complete Cu removal (>99.5%) and alkalinity generation raising the effluent pH to 6.5. No noteworthy sulfate reduction, alkalinity formation and Cu(2+) removal were observed in the endogenous control. In algae amended-columns, Cu(2+) was precipitated with biogenic H2S produced by sulfate reduction. Formation of CuS was evidenced by sequential extraction and X-ray diffraction. LEA and WCA provided similar levels of electron donor based on the COD balance. The results demonstrate an innovative passive remediation system using residual algae biomass from the biodiesel industry. PMID:27318730

  18. Pennsylvanian pluton stitching of Wrangellia and the Alexander terrane, Wrangell Mountains, Alaska

    SciTech Connect

    Gardner, M.C.; Bergman, S.C.; Cushing, G.W. ); Plafker, G. ); Campbell, R.B.; Dodds, C.J. ); McClelland, W.C. ); Mueller, P.A. ); MacKevett, E.M. Jr.

    1988-11-01

    A quartz monzonite-syenite-alkali granite plutonic complex in eastern Alaska crosscuts the contact of the Alexander terrane and Wrangellia and intrudes the basement rocks of both terranes. Zircon U-Pb data indicate an intrusion age of 309 {plus minus} 5 Ma (Middle Pennsylvanian) for the pluton, and {sup 40}K-{sup 40}Ar age for hornblende separates indicate cooling to about 450 C during Middle Pennsylvanian-Early Permian time. The new field relations and age data demonstrate the Wrangellia and the Alexander terrane were contiguous during the Middle Pennsylvanian. This conclusion provides an important new constraint on paleogeographic reconstructions of the northwest Cordillera, and necessitates reassessment of stratigraphic and paleomagnetic data that were cited as evidence that the terranes evolved separately until the late Mesozoic.

  19. Genesis and evolution of water in a two-mica pluton: A hydrogen isotope study

    USGS Publications Warehouse

    Brigham, R.H.; O'Neil, J.R.

    1985-01-01

    Measurements were made of the hydrogen isotope composition of 74 samples of muscovite, biotite, vein quartz and whole rocks from the Papoose Flat pluton, eastern California, U.S.A., and adjacent metamorphic and sedimentary rocks in order to elucidate the genesis and evolution of water and hydrous minerals in a two-mica granodiorite. Electron microprobe analyses were made of all micas so that the Suzuoki-Epstein equation could be used in evaluating the data. Based on experimental, theoretical and textural evidence of mica paragenesis, a model of hydrogen isotope fractionation between an aqueous vapor and a magma during crystallization has been constructed. This model accounts for the observed hydrogen isotope relations and implies that primary hydrogen isotope compositions have been preserved in a large portion of the pluton. The ?? D-values of biotites vary widely over the range -103 to -66% with most values lying between -90 and -70??? Muscovites, on the other hand, are isotopically more uniform and have ?? D-values of -61 to -41??? with most values lying between -50 and -46??? These data are consistent with the interpretation that biotite formed over a long period of crystallization whereas muscovite formed in a narrow interval, presumably during the final stages of crystallization when alumina and water contents were at their highest. Only 8 of the 21 muscovite-biotite pairs analyzed are in hydrogen isotope equilibrium as calculated from the Suzuoki-Epstein equation. Biotites in the western half of the pluton have relatively low ?? D-values of around -85???, whereas those in the eastern half have higher values of up to -66??? This pattern is a consequence of a loss of permeability associated with the syn-intrusive deformation of the western margin of the pluton. This loss of permeability enhanced the preservation of primary hydrogen isotope relations there by diverting water evolved from the magma out through the eastern half of the pluton where some deuteric

  20. Petrogenesis and geodynamic implications of the Xiema and Ziyunshan plutons in Hunan Province, South China

    NASA Astrophysics Data System (ADS)

    Wang, Kai-Xing; Chen, Wei-Feng; Chen, Pei-Rong; Ling, Hong-Fei; Huang, Hui

    2015-11-01

    To understand the Mesozoic tectonic settings of the South China Block, samples collected from the Xiema and Ziyunshan plutons were analyzed with respect to zircon age, whole-rock and biotite chemical composition, whole-rock Sr-Nd and zircon Hf isotopic composition. Petrographic analysis and zircon LA-ICP-MS dating reveal that the Xiema pluton and the outer portion of the Ziyunshan pluton are composed of Late Triassic (Indosinian) biotite granodiorites and quartz monzonites with contemporaneous mafic microgranular enclaves (hereafter MMEs), whereas the inner part of the Ziyunshan pluton consists of Early Jurassic (Yanshanian) biotite granites and two-mica granites. Elemental and isotopic geochemical characteristics demonstrate that the Late Triassic granites are I-type granites and the Early Jurassic granites are S-type granites; furthermore, the data suggest that the two types of granites originated from different sources. The Late Triassic granites were mainly derived from the partial melting of Proterozoic meta-greywacke and meta-basalts at temperatures of 758-814 °C and log(fO2) values of -13 to -12. The residual mineral phases contain plagioclase, clinopyroxene/orthopyroxene, and quartz. At melting temperatures of 738-772 °C and log(fO2) values ranging from -15 to -13, the Early Jurassic granites originated from the partial melting of Proterozoic greywacke, with K-feldspar, ilmenite, clinopyroxene/orthopyroxene, and zircon serving as residues in the source. Geochronology and geochemistry data suggest that the Late Triassic granites were formed under the extension environment caused by the Early Mesozoic post multi-plate convergence tectonic setting, whereas the Early Jurassic granites formed in an intracontinental extensional setting.

  1. Neutralization/prevention of acid rock drainage using mixtures of alkaline by-products and sulfidic mine wastes.

    PubMed

    Alakangas, Lena; Andersson, Elin; Mueller, Seth

    2013-11-01

    Backfilling of open pit with sulfidic waste rock followed by inundation is a common method for reducing sulfide oxidation after mine closure. This approach can be complemented by mixing the waste rock with alkaline materials from pulp and steel mills to increase the system's neutralization potential. Leachates from 1 m3 tanks containing sulfide-rich (ca.30 wt %) waste rock formed under dry and water saturated conditions under laboratory conditions were characterized and compared to those formed from mixtures. The waste rock leachate produced an acidic leachate (pH<2) with high concentrations of As (65 mg/L), Cu (6 mg/L), and Zn (150 mg/L) after 258 days. The leachate from water-saturated waste rock had lower concentrations of As and Cu (<2 μg/L), Pb and Zn (20 μg/L and 5 mg/L), respectively, and its pH was around 6. Crushed (<6 mm) waste rock mixed with different fractions (1-5 wt %) of green liquid dregs, fly ash, mesa lime, and argon oxygen decarburization (AOD) slag was leached on a small scale for 65 day, and showed near-neutral pH values, except for mixtures of waste rock with AOD slag and fly ash (5% w/w) which were more basic (pH>9). The decrease of elemental concentration in the leachate was most pronounced for Pb and Zn, while Al and S were relatively high. Overall, the results obtained were promising and suggest that alkaline by-products could be useful additives for minimizing ARD formation. PMID:23740301

  2. Radiological, chemical and morphological characterizations of phosphate rock and phosphogypsum from phosphoric acid factories in SW Spain.

    PubMed

    Rentería-Villalobos, Marusia; Vioque, Ignacio; Mantero, Juan; Manjón, Guillermo

    2010-09-15

    In this work, radiological, chemical, and also morphological characterization was performed in phosphate rock and phosphogypsum samples, in order to understand the behavior of toxic elements. Characterization was carried out using X-ray diffraction (XRD), X-ray fluorescence (XRF), gamma spectrometry and scanning electron microscopy with energy-dispersive X-ray analysis (SEM-EDX). Our results show that the phosphate rock was mainly composed of fluorapatite, calcite, perovskite, quartz, magnetite, pyrite and kaolinite, whereas phosphogypsum only exhibited dihydrated calcium sulfate. The activity concentration of U-series radioisotopes in phosphate rock was around 1640 Bq/kg. (226)Ra and (210)Pb tend to be distributed into phosphogypsum by up to 80%, whereas the fraction of U-isotopes is 10%. The most abundant trace elements in phosphate rock were Sr, Cr, V, Zn, Y, Ni and Ba. Some elements, such as Ba, Cd, Cu, La, Pb, Se, Sr, Th and Y, were enriched in the phosphogypsum. This enrichment may be attributed to an additional input associated to the sulfuric acid used for the phosphoric acid production. Furthermore, results from SEM-EDX demonstrated that toxic elements are not distributed homogeneously into phosphogypsum. Most of these elements are concentrated in particles <20 microm of high porosity, and could be easily mobilized by leaching and/or erosion. PMID:20537794

  3. Mingled mafic and felsic magmas in the Jurassic Eagle Mountain pluton, southeastern California

    SciTech Connect

    Mayo, D.P. . Dept. of Geological Sciences); Wooden, J.L. )

    1993-04-01

    The metalluminous, compositionally expanded Eagle Mountain pluton ([approx] 165 Ma) was epizonally emplaced within Proterozoic metaigneous and Proterozoic-Paleozoic metasedimentary rocks in the Eagle Mountains of southeastern California. The evolution of the pluton involved mingling and partial mixing between mafic and felsic magmas. Heterogeneous rocks consisting of discrete biotite-clinopyroxene microdioritic enclaves (49--54% SiO[sub 2]) enclosed in hornblende-biotite granodiorite (57--61% SiO[sub 2]) grade into complexly mingled microdiorite and granodiorite as the proportion of microdiorite increases. The dioritic enclaves are notably potassic (2.1 [+-] .2 wt. %), containing abundant biotite (up to 23%) and interstitial patches of K-feldspar. These features are attributed to selective potassium enrichment of dioritic magma by diffusion during mingling with host granodioritic magma. A similar phenomenon was observed in experiments by Johnston and Wyllie, and attributed to relatively rapid diffusion of potassium from felsic to mafic magma. Calculated Sr[sub i] for the enclaves, intermediate dioritoids, and three of four analyzed host rocks cluster at 0.7085 [+-] 0.0002. Several homogeneous monzogranites not associated with enclaves have slightly higher Sr[sub i] (up to 0.7094) and define two separate mixing/AFC arrays on a plot of Sr[sub i] vs. 1/Sr, both anchored at the cluster of less radiogenic rocks. Alternatively, relatively rapid self-diffusion of Sr may have contributed to isotopic homogeneity during mingling of magmas from isotopically distinct sources.

  4. Reworked old crust-derived shoshonitic magma: The Guarany pluton, Northeastern Brazil

    NASA Astrophysics Data System (ADS)

    Ferreira, Valderez P.; Sial, Alcides N.; Pimentel, Marcio M.; Armstrong, Richard; Guimarães, Ignez P.; da Silva Filho, Adejardo F.; de Lima, Mariucha Maria C.; da Silva, Thyego R.

    2015-09-01

    The 572 Ma Guarany stock consists of magmatic epidote-bearing hornblende monzodiorite to biotite granite that intruded Paleoproterozoic orthogneisses about 10 km inland from the coast in northeastern Brazil. Co-magmatic diorite enclaves and dikes are abundant throughout the pluton. The monzodiorite-granite pluton and diorite enclaves are shoshonitic and display continuous trends in variation diagrams. They display chemical and isotopic characteristics of crustal melts, such as enrichment in incompatible elements, high back-calculated initial 87Sr/86Sr ratios (avg. 0.71253), negative εNd (0.57Ga) values (avg. - 14.58), as well as high and variable (+ 9.1 to + 11.1‰VSMOW) δ18O (zircon) values. Correlations between O-isotope and whole-rock silica contents, as well as initial 87Sr/86Sr ratios with 1/Sr concentrations, suggest hybridization of a lower continental crustal melt with more felsic crustal rocks, concomitant with fractional crystallization. Amphibole chemistry and whole rock Zr, TiO2 and P2O5 contents suggest magma solidification at a pressure ~ 7 kbar and near liquidus temperature ~ 900 °C. The parental magma was likely formed by partial melting of old (tDM = 2.0 Ga) amphibolitic lower continental crustal rocks, in a post-collisional setting, probably triggered by underplating of mantle-derived mafic magma during the period of relaxation after collision.

  5. Charon Cryovolcanism and Plutonian Plutonics

    NASA Astrophysics Data System (ADS)

    Desch, S. J.; Neveu, M.

    2013-12-01

    Extrusion of cold material from the interior of icy bodies, or cryovolcanism, has been observed on Enceladus and Triton. It may explain the observed evidence for a young surface on Charon (Pluto's surface is masked by frosts). Here, we evaluate 3 prerequisites for cryovolcanism on Pluto and Charon, and make testable predictions for the 2015 New Horizons flyby. 1. Subsurface liquid: Thermal evolution models of Pluto and Charon suggest that they should have differentiated into a rocky core and an icy mantle, and retained a liquid layer for many Gyr, possibly until today (Desch et al. 2009; Robuchon and Nimmo 2011; Rubin et al., in revision). Primordial volatile antifreezes (ammonia, methanol) enhance liquid persistence on Pluto, and are required for liquid on Charon. 2. Cryovolcanic processes: At the frigid temperatures (40-60 K) of Pluto's and Charon's surfaces, ice is brittle: diapirism and effusive volcanism are unlikely. Explosive volcanism can occur if cracks, resulting from freezing, develop in the ice shell. Water can then ascend in the crack up to the water/ice hydrostatic level, but cannot progress further unless the negative buoyancy of water in ice is overcome. This can happen via two mechanisms. First, the headspace pressure (difference between surrounding hydrostatic and crack water column pressures) inside cracks decreases as the crack's length increases. This can lead to the exsolution of volatiles from water to make a low-density foam (Crawford and Stevenson 1988). Here, we show that exsolution of non-polar volatiles such as H2, N2, Ar, CH4, CO, and CO2 allows crack propagation by positive buoyancy. However, exsolution does not happen a dwarf planets retains a primordial ice-rock crust like those modeled by Desch et al. 2009; it acts as a pressure seal to keep the volatiles dissolved. In the second mechanism, the negative buoyancy is overcome by the pressurization of water as the body cools and freezes (Fagents 2003; Manga and Wang 2007). Although

  6. Search for underground openings for in situ test facilities in crystalline rock

    SciTech Connect

    Wollenberg, H.A.; Strisower, B.; Corrigan, D.J.; Graf, A.N.; O'Brien, M.T.; Pratt, H.; Board, M.; Hustrulid, W.

    1980-01-01

    With a few exceptions, crystalline rocks in this study were limited to plutonic rocks and medium to high-grade metamorphic rocks. Nearly 1700 underground mines, possibly occurring in crystalline rock, were initially identified. Application of criteria resulted in the identification of 60 potential sites. Within this number, 26 mines and 4 civil works were identified as having potential in that they fulfilled the criteria. Thirty other mines may have similar potential. Most of the mines identified are near the contact between a pluton and older sedimentary, volcanic and metamorphic rocks. However, some mines and the civil works are well within plutonic or metamorphic rock masses. Civil works, notably underground galleries associated with pumped storage hydroelectric facilities, are generally located in tectonically stable regions, in relatively homogeneous crystalline rock bodies. A program is recommended which would identify one or more sites where a concordance exists between geologic setting, company amenability, accessibility and facilities to conduct in situ tests in crystalline rock.

  7. 8,9-Epoxyeicosatrienoic acid analog protects pulmonary artery smooth muscle cells from apoptosis via ROCK pathway

    SciTech Connect

    Ma, Jun; Zhang, Lei; Li, Shanshan; Liu, Shulin; Ma, Cui; Li, Weiyang; Falck, J.R.; Manthati, Vijay L.; Reddy, D. Sudarshan; Medhora, Meetha; Jacobs, Elizabeth R.; Zhu, Daling

    2010-08-15

    Epoxyeicosatrienoic acids (EETs), metabolites of arachidonic acid (AA) catalyzed by cytochrome P450 (CYP), have many essential biologic roles in the cardiovascular system including inhibition of apoptosis in cardiomyocytes. In the present study, we tested the potential of 8,9-EET and derivatives to protect pulmonary artery smooth muscle cells (PASMCs) from starvation induced apoptosis. We found 8,9-epoxy-eicos-11(Z)-enoic acid (8,9-EET analog (214)), but not 8,9-EET, increased cell viability, decreased activation of caspase-3 and caspase-9, and decreased TUNEL-positive cells or nuclear condensation induced by serum deprivation (SD) in PASMCs. These effects were reversed after blocking the Rho-kinase (ROCK) pathway with Y-27632 or HA-1077. Therefore, 8,9-EET analog (214) protects PASMC from serum deprivation-induced apoptosis, mediated at least in part via the ROCK pathway. Serum deprivation of PASMCs resulted in mitochondrial membrane depolarization, decreased expression of Bcl-2 and enhanced expression of Bax, all effects were reversed by 8,9-EET analog (214) in a ROCK dependent manner. Because 8,9-EET and not the 8,9-EET analog (214) protects pulmonary artery endothelial cells (PAECs), these observations suggest the potential to differentially promote apoptosis or survival with 8,9-EET or analogs in pulmonary arteries.

  8. Manifestation of Preferential Flow and Nitrate Transport in Central European Soils on Acid Crystalline Rocks

    NASA Astrophysics Data System (ADS)

    Dolezal, F.; Cislerova, M.; Vogel, T.; Zavadil, J.; Vacek, J.; Kvitek, T.; Prazak, P.; Nechvatal, M.; Bayer, T.

    2006-12-01

    Large areas of Central Europe are occupied by highlands and peneplains of medium altitudes, built by acid crystalline rocks. The soils overlying them are typically of medium textures. They are neither markedly water- repellent nor greatly swelling and shrinking. These landscapes are characterized by high vulnerability of water bodies, both surface and subsurface. The existing methodologies of vulnerability assessment regard the heavier among these soils as little vulnerable to diffuse pollution, while in reality they may be virtually equally vulnerable, because of the short-circuiting effect of preferential flow and transport. Our experiment site was Valeèov (49° 38' 40" N, 14° 30' 25" E, 461 m a.s.l.) in the Bohemo-Moravian highland, with average annual precipitation 660 mm and average annual air temperature 7.2 ° C. The field trials, starting from 2001, were focused on growing potato under different conditions. Soil moisture content was measured by Theta- probe capacitance sensors, soil water suction by Watermark sensors and tensiometers. Nitrate leaching was monitored by soil solution sampling with ceramic suction cups and zero-tension lysimeters. The hydraulic conductivity of the soil was measured on small cores and by suction and pressure infiltrometers. The following preferential flow manifestations are analyzed and quantified: a) the spatial variability of soil moisture content and suction after rainstorms, b) the spatial and temporal variability of soil's hydraulic conductivity and its dependence on soil moisture content, c) the spatial variability of percolation volumes in parallel lysimeters, d) the variability of nitrate concentrations in the lysimeter leachate, e) the apparent absence of correlation between leachate volumes and leachate concentrations in lysimeters, f) the lower mean and higher variance of leachate concentrations in lysimeters, in comparison with those in suction cups.

  9. Attached and Unattached Bacterial Communities in a 120-Meter Corehole in an Acidic, Crystalline Rock Aquifer

    PubMed Central

    Lehman, R. Michael; Roberto, Francisco F.; Earley, Drummond; Bruhn, Debby F.; Brink, Susan E.; O'Connell, Sean P.; Delwiche, Mark E.; Colwell, Frederick S.

    2001-01-01

    The bacteria colonizing geologic core sections (attached) were contrasted with those found suspended in the groundwater (unattached) by examining the microbiology of 16 depth-paired core and groundwater samples using a suite of culture-independent and culture-dependent analyses. One hundred twenty-two meters was continuously cored from a buried chalcopyrite ore hosted in a biotite-quartz-monzonite porphyry at the Mineral Park Mine near Kingman, Ariz. Every fourth 1.5-m core was acquired using microbiologically defensible methods, and these core sections were aseptically processed for characterization of the attached bacteria. Groundwater samples containing unattached bacteria were collected from the uncased corehole at depth intervals corresponding to the individual cores using an inflatable straddle packer sampler. The groundwater was acidic (pH 2.8 to 5.0), with low levels of dissolved oxygen and high concentrations of sulfate and metals, including ferrous iron. Total numbers of attached cells were less than 105 cells g of core material−1 while unattached cells numbered about 105 cells ml of groundwater−1. Attached and unattached acidophilic heterotrophs were observed throughout the depth profile. In contrast, acidophilic chemolithotrophs were not found attached to the rock but were commonly observed in the groundwater. Attached communities were composed of low numbers (<40 CFU g−1) of neutrophilic heterotrophs that exhibited a high degree of morphologic diversity, while unattached communities contained higher numbers (ca. 103 CFU ml−1) of neutrophilic heterotrophs of limited diversity. Sulfate-reducing bacteria were restricted to the deepest samples of both core and groundwater. 16S ribosomal DNA sequence analysis of attached, acidophilic isolates indicated that organisms closely related to heterotrophic, acidophilic mesophiles such as Acidiphilium organovorum and, surprisingly, to the moderately thermophilic Alicyclobacillus acidocaldarius were present

  10. Syn-extensional plutonism and peak metamorphism in the albion-raft river-grouse creek metamorphic core complex

    USGS Publications Warehouse

    Strickland, A.; Miller, E.L.; Wooden, J.L.; Kozdon, R.; Valley, J.W.

    2011-01-01

    The Cassia plutonic complex (CPC) is a group of variably deformed, Oligocene granitic plutons exposed in the lower plate of the Albion-Raft River- Grouse Creek (ARG) metamorphic core complex of Idaho and Utah. The plutons range from granodiorite to garnet-bearing, leucogranite, and during intrusion, sillimanite- grade peak metamorphism and ductile attenuation occurred in the country rocks and normal-sense, amphibolite-grade deformation took place along the Middle Mountain shear zone. U-Pb zircon geochronology from three variably deformed plutons exposed in the lower plate of the ARG metamorphic core complex revealed that each zircon is comprised of inherited cores (dominantly late Archean) and Oligocene igneous overgrowths. Within each pluton, a spread of concordant ages from the Oligocene zircon overgrowths is interpreted as zircon recycling within a long-lived magmatic system. The plutons of the CPC have very low negative whole rock ??Nd values of -26 to -35, and initial Sr values of 0.714 to 0.718, consistent with an ancient, crustal source. Oxygen isotope ratios of the Oligocene zircon overgrowths from the CPC have an average ??18O value of 5.40 ?? 0.63 permil (2SD, n = 65) with a slight trend towards higher ??18O values through time. The ??18O values of the inherited cores of the zircons are more variable at 5.93 ?? 1.51 permil (2SD, n = 29). Therefore, we interpret the plutons of the CPC as derived, at least in part, from melting Archean crust based on the isotope geochemistry. In situ partial melting of the exposed Archean basement that was intruded by the Oligocene plutons of the CPC is excluded as the source for the CPC based on field relationships, age and geochemistry. Correlations between Ti and Hf concentrations in zircons from the CPC suggest that the magmatic system may have become hotter (higher Ti concentration in zircon) and less evolved (lower Hf in zircon concentration) through time. Therefore, the CPC represents prolonged or episodic magmatism

  11. Petrological imaging of an active pluton beneath Cerro Uturuncu, Bolivia

    NASA Astrophysics Data System (ADS)

    Muir, Duncan D.; Blundy, Jon D.; Hutchinson, Michael C.; Rust, Alison C.

    2014-03-01

    Uturuncu is a dormant volcano in the Altiplano of SW Bolivia. A present day ~70 km diameter interferometric synthetic aperture radar (InSAR) anomaly roughly centred on Uturuncu's edifice is believed to be a result of magma intrusion into an active crustal pluton. Past activity at the volcano, spanning 0.89 to 0.27 Ma, is exclusively effusive and almost all lavas and domes are dacitic with phenocrysts of plagioclase, orthopyroxene, biotite, ilmenite and Ti-magnetite plus or minus quartz, and microlites of plagioclase and orthopyroxene set in rhyolitic groundmass glass. Plagioclase-hosted melt inclusions (MI) are rhyolitic with major element compositions that are similar to groundmass glasses. H2O concentrations plotted versus incompatible elements for individual samples describe a trend typical of near-isobaric, volatile-saturated crystallisation. At 870 °C, the average magma temperature calculated from Fe-Ti oxides, the average H2O of 3.2 ± 0.7 wt% and CO2 typically <160 ppm equate to MI trapping pressures of 50-120 MPa, approximately 2-4.5 km below surface. Such shallow storage precludes the role of dacite magma emplacement into pre-eruptive storage regions as being the cause of the observed InSAR anomaly. Storage pressures, whole-rock (WR) chemistry and phase assemblage are remarkably consistent across the eruptive history of the volcano, although magmatic temperatures calculated from Fe-Ti oxide geothermometry, zircon saturation thermometry using MI and orthopyroxene-melt thermometry range from 760 to 925 °C at NNO ± 1 log. This large temperature range is similar to that of saturation temperatures of observed phases in experimental data on Uturuncu dacites. The variation in calculated temperatures is attributed to piecemeal construction of the active pluton by successive inputs of new magma into a growing volume of plutonic mush. Fluctuating temperatures within the mush can account for sieve-textured cores and complex zoning in plagioclase phenocrysts

  12. Application of potential phosphate-solubilizing bacteria and organic acids on phosphate solubilization from phosphate rock in aerobic rice.

    PubMed

    Panhwar, Qurban Ali; Jusop, Shamshuddin; Naher, Umme Aminun; Othman, Radziah; Razi, Mohd Ismail

    2013-01-01

    A study was conducted at Universiti Putra Malaysia to determine the effect of phosphate-solubilizing bacteria (PSB) and organic acids (oxalic & malic) on phosphate (P) solubilization from phosphate rock (PR) and growth of aerobic rice. Four rates of each organic acid (0, 10, 20, and 30 mM), and PSB strain (Bacillus sp.) were applied to aerobic rice. Total bacterial populations, amount of P solubilization, P uptake, soil pH, and root morphology were determined. The results of the study showed significantly high P solubilization in PSB with organic acid treatments. Among the two organic acids, oxalic acid was found more effective compared to malic acid. Application of oxalic acid at 20 mM along with PSB16 significantly increased soluble soil P (28.39 mg kg(-1)), plant P uptake (0.78 P pot(-1)), and plant biomass (33.26 mg). Addition of organic acids with PSB and PR had no influence on soil pH during the planting period. A higher bacterial population was found in rhizosphere (8.78 log10 cfu g(-1)) compared to the nonrhizosphere and endosphere regions. The application of organic acids along with PSB enhanced soluble P in the soil solution, improved root growth, and increased plant biomass of aerobic rice seedlings without affecting soil pH. PMID:24288473

  13. Petrography and mineral chemistry of the composite Deboullie Pluton, northern Maine, USA: implications for the genesis of Cu-Mo mineralization

    USGS Publications Warehouse

    Loferski, P.J.; Ayuso, R.A.

    1995-01-01

    Biotite and apatite mineral chemistry, particularly halogen abundances and ratios, are used to investigate the relation of the two contrasting parts of the Deboullie composite pluton (syenite-granodiorite) located in northern Maine. Biotite mineral chemistry helps to classify the weakly developed porphyry-style mineralization (Cu-Mo) associated with syenitic rocks of the Deboullie pluton. Biotite and apatite occur within the matrix of the rocks and within small multiphase inclusions hosted by clinopyroxene. The inclusions are interpreted to be crystallized melt inclusions rather than solid inclusions, that were trapped by clinopyroxene during growth. The multiphase inclusions consist of K-feldspar + quartz + biotite + apatite + magnetite. On a regional scale, biotite compositions from granitic plutons in Maine do not vary in a systematic manner. -from Authors

  14. Phosphate Stability in Diagenetic Fluids Constrains the Acidic Alteration Model for Lower Mt. Sharp Sedimentary Rocks in Gale Crater, Mars

    NASA Technical Reports Server (NTRS)

    Berger, J. A.; Schmidt, M. E.; Izawa, M. R. M.; Gellert, R.; Ming, D. W.; Rampe, E. B.; VanBommel, S. J.; McAdam, A. C.

    2016-01-01

    The Mars rover Curiosity has encountered silica-enriched bedrock (as strata and as veins and associated halos of alteration) in the largely basaltic Murray Fm. of Mt. Sharp in Gale Crater. Alpha Particle X-ray Spectrometer (APXS) investigations of the Murray Fm. revealed decreasing Mg, Ca, Mn, Fe, and Al, and higher S, as silica increased (Fig. 1). A positive correlation between SiO2 and TiO2 (up to 74.4 and 1.7 wt %, respectively) suggests that these two insoluble elements were retained while acidic fluids leached more soluble elements. Other evidence also supports a silica-retaining, acidic alteration model for the Murray Fm., including low trace element abundances consistent with leaching, and the presence of opaline silica and jarosite determined by CheMin. Phosphate stability is a key component of this model because PO4 3- is typically soluble in acidic water and is likely a mobile ion in diagenetic fluids (pH less than 5). However, the Murray rocks are not leached of P; they have variable P2O5 (Fig. 1) ranging from average Mars (0.9 wt%) up to the highest values in Gale Crater (2.5 wt%). Here we evaluate APXS measurements of Murray Fm. bedrock and veins with respect to phosphate stability in acidic fluids as a test of the acidic alteration model for the Lower Mt. Sharp rocks.

  15. Geologic and mineralogic controls on acid and metal-rich rock drainage in an alpine watershed, Handcart Gulch, Colorado

    USGS Publications Warehouse

    Bove, Dana J.; Caine, Jonathan S.; Lowers, Heather

    2012-01-01

    The surface and subsurface geology, hydrothermal alteration, and mineralogy of the Handcart Gulch area was studied using map and drill core data as part of a multidisciplinary approach to understand the hydrology and affects of geology on acid-rock drainage in a mineralized alpine watershed. Handcart Gulch was the locus of intense hydrothermal alteration that affected an area of nearly 3 square kilometers. Hydrothermal alteration and accompanied weak mineralization are spatially and genetically associated with small dacite to low-silica rhyolite stocks and plugs emplaced about 37-36 Ma. Felsic lithologies are commonly altered to a quartz-sericite-pyrite mineral assemblage at the surface, but alteration is more variable in the subsurface, ranging from quartz-sericite-pyrite-dominant in upper core sections to a propylitic variant that is more typical in deeper drill core intervals. Late-stage, hydrothermal argillic alteration [kaolinite and(or) smectite] was superimposed over earlier-formed alteration assemblages in the felsic rocks. Smectite in this late stage assemblage is mostly neoformed resulting from dissolution of chlorite, plagioclase, and minor illite in more weakly altered rocks. Hydrothermally altered amphibolites are characterized by biotitic alteration of amphibole, and subsequent alteration of both primary and secondary biotite to chlorite. Whereas pyrite is present both as disseminations and in small veinlets in the felsic lithologies, it is mostly restricted to small veinlets in the amphibolites. Base-metal sulfides including molybdenite, chalcopyrite, sphalerite, and galena are present in minor to trace amounts in the altered rocks. However, geologic data in conjunction with water geochemical studies indicate that copper mineralization may be present in unknown abundance in two distinct areas. The altered rocks contain an average of 8 weight percent fine pyrite that is largely devoid of metals in the crystal structure, which can be a significant

  16. Acid-rain related reconnaissance of water, rock, soil, and sediment chemistry in the Adirondacks during Fall, 1981

    SciTech Connect

    Not Available

    1981-01-01

    This study suggests strongly that inorganic chemical processes, with sulfate and nitrate input from atmospheric deposition and the absence of buffering from carbonate rock, cannot simply account for either the pH or the aluminum concentrations observed in Adirondack surface waters. Instead, organic acids originating from water flow through organic soil layers and wetlands are indicated as possible causes of increased acidity and aluminum concentrations. There are also indications that sulfides in bedrock and the sulfur utilized by vegetation may be important surface-water sulfate sources. Further, in part of the Adirondacks, weathering of calcium-containing non-carbonate aluminosilicate bedrock apparently keeps surface water from reaching ''critical'' acidity levels. Also, appreciable concentrations of heavy metals and persistent insecticides associated with the organic material in some soils and sediments. If mobilized into the food chain, these materials could be causing adverse ecological effects usually attributed to acid precipitation. Recommendations are included for further studies. 13 figs., 29 tabs. (PSB)

  17. Relationships between subduction and extension in the Aegean region: evidence from granite plutons of the Biga Peninsula, NW Turkey

    NASA Astrophysics Data System (ADS)

    Black, K. N.; Catlos, E. J.; Oyman, T.; Demirbilek, M.

    2012-04-01

    The Biga Peninsula is a tectonically complex region in western Turkey characterized by Tethyan sutures overprinted by extensional grabens, active fault strands of the North Anatolian Shear Zone, and numerous granitoid plutons. Two end-member models for the initiation of extension in the Biga region have been proposed, both of which focus on the role of igneous assemblages. The first model involves the emplacement of a hot mantle plume that thins and weakens crust and isostatic doming drives extension. The second has regional tensional stresses as the driving force, and magmatism is a consequence of decompression. Here we focus on understanding the timing and geochemical evolution of three granitoid plutons located in and just south of the Biga Peninsula to understand which end-member model could be applicable to the Aegean region. The Kestanbolu pluton is located north of the proposed Vardar Suture Zone, whereas the Eybek and Kozak plutons are north of the Izmir-Ankara Suture Zone. These sutures may mark regions of the closure of branches of the NeoTethyan Ocean. To better understand their sources and tectonic evolution, we acquired geochemical and geochronological data, and cathodoluminescence (CL) images of the rocks. Previously reported ages of the plutons range from Late Eocene to Middle Miocene. Here we acquired in situ (in thin section) ion microprobe U-Pb ages of zircon grains found in a range of textural relationships. Ages from the Kozak pluton range from 37.8±5.4 Ma to 10.3±2.4 Ma (238U/206Pb, ±1σ) with two ages from a single grain of 287±26 Ma and 257±18 Ma. We also found Oligocene to Late Miocene zircon grains in the Kestanbolu pluton, whereas zircons from the Eybek pluton range from 34.3±4.8 Ma to 21.2±1.7 Ma. Samples collected from the Kozak and Eybek plutons are magnesian, calc-alkalic, and metaluminous, whereas the Kestanbolu rocks are magnesian, alkali-calcic, and metaluminous with one ferroan sample and one peraluminous sample. Trace

  18. Thermochronology and Cooling Histories of Intrusive Suites: Implications for Incremental Pluton Assembly

    NASA Astrophysics Data System (ADS)

    Davis, J.; Coleman, D.; Heizler, M.

    2007-12-01

    Debate persists about the timescales and mechanisms of pluton emplacement and batholith formation. An understanding of whether plutons accumulate as large masses of magma or as an incremental series of pulses, in which the active magma body is small relative to the final pluton, is important for understanding the relationship between volcanoes and plutons. If volcanic eruptions < 1000 km3 are the most common size and large ignimbrites are rare, it follows that most plutons should record accumulations of small volumes of melt that were emplaced over long time intervals (millions to tens of millions of years) and therefore preserve predictable, protracted thermal histories. Modeling predicts observable differences in thermal histories of plutons and their aureoles that can be tested through thermochronology. Application of multiple chronometers (zircon and titanite U-Pb TIMS; hornblende, biotite, and K-feldspar 40Ar/39Ar; zircon and titanite (U-Th)/He) combined with K-feldspar multiple diffusion domain (MDD) modeling were used to determine the thermal history and to calibrate thermal models of two eastern California, Sierra Nevada batholith intrusive suites; the dike-like John Muir Intrusive Suite (JMIS) and the laccolithic Mt. Whitney Intrusive Suite (MWIS), and their wall rocks. Preliminary results of (U-Th)/He zircon data from the JMIS and its wall rock (the Tinemaha granodiorite) show a tight cluster of dates ranging from 75.6 to 70.4 Ma. The JMIS is thought to be mesozonal (8 to 11 km) and these data are interpreted as resulting from exhumation and additional 40Ar/39Ar data are required to determine if the thermal history reflects incremental intrusions. In contrast to the JMIS, preliminary (U-Th)/He zircon data from the MWIS and its wall rock (the Bullfrog pluton) show a wide range in dates ranging from 91.4 to 74.6 Ma that are interpreted to reflect reheating events. Amphibole 40Ar/39Ar inverse isochron dates, K- feldspar age spectra, and (U-Th)/He zircon data

  19. Evidence for multiple mechanisms of crustal contamination of magma from compositionally zoned plutons and associated ultramafic intrusions of the Alaska Range

    USGS Publications Warehouse

    Reiners, P.W.; Nelson, B.K.; Nelson, S.W.

    1996-01-01

    Models of continental crustal magmagenesis commonly invoke the interaction of mafic mantle-derived magma and continental crust to explain geochemical and petrologic characteristics of crustal volcanic and plutonic rocks. This interaction and the specific mechanisms of crustal contamination associated with it are poorly understood. An excellent opportunity to study the progressive effects of crustal contamination is offered by the composite plutons of the Alaska Range, a series of nine early Tertiary, multiply intruded, compositionally zoned (peridotite to granite) plutons. Large initial Sr and Nd isotopic contrasts between the crustal country rock and likely parental magmas allow evaluation of the mechanisms and extents of crustal contamination that accompanied the crystallization of these ultramafic through granitic rocks. Three contamination processes are distinguished in these plutons. The most obvious of these is assimilation of crustal country rock concurrent with magmatic fractional crystallization (AFC), as indicated by a general trend toward crustal-like isotopic signatures with increasing differentiation. Second, many ultramafic and mafic rocks have late-stage phenocryst reaction and orthocumulate textures that suggest interaction with felsic melt. These rocks also have variable and enriched isotopic compositions that suggest that this felsic melt was isotopically enriched and probably derived from crustal country rock. Partial melt from the flysch country rock may have reacted with and contaminated these partly crystalline magmas following the precipitation and accumulation of the cumulus phenocrysts but before complete solidification of the magma. This suggests that in magmatic mush (especially of ultramafic composition) crystallizing in continental crust, a second distinct process of crustal contamination may be super-imposed on AFC or magma mixing involving the main magma body. Finally, nearly all rocks, including mafic and ultramafic rocks, have (87Sr

  20. Is the southeast Coast Plutonic Complex the consequence of accretion of the insular superterrane Evidence from U-Pb zircon geochronometry in the northern Washington Cascades

    SciTech Connect

    Walker, N.W. ); Brown, E.H. )

    1991-07-01

    Zircon U-Pb geochronometry of orthogneisses and plutons in the southwestern crystalline core of the North Cascades, coupled with fabric and textural studies of the orthogneisses, plutons, and their metamorphic host rocks, indicates extensive synmetamorphic plutonism at 89-96 Ma. Metamorphic mineral assemblages define a culmination composed of an axial kyanite-sillimanite zone rimmed by lower grade zones. High-grade index minerals are typically syntectonic to posttectonic. Metamorphic fabrics are characterized by an orogen-parallel, northwest-striking, steep foliation that contains a subhorizontal stretching and mineral lineation interpreted to be the product of ductile strike-slip deformation. This fabric is crosscut by 96-92 Ma plutons yet is imprinted on 92-89 Ma orthogneisses, suggesting spatially diachronous fabric development during orogeny. Documentation of the spatial and temporal coincidence of magmatism with the peak of orogeny, together with the kinematic significance of the metamorphic fabric, precludes generation of the metamorphic fabric and plutons in response to thrust loading. The authors suggest that this part of the Coast Plutonic Complex evolved as a transpressional magmatic arc.

  1. Zircon U-Pb ages and tectonic implications of Paleozoic plutons in northern West Junggar, North Xinjiang, China

    NASA Astrophysics Data System (ADS)

    Chen, Jia-Fu; Han, Bao-Fu; Ji, Jian-Qing; Zhang, Lei; Xu, Zhao; He, Guo-Qi; Wang, Tao

    2010-03-01

    North Xinjiang, Northwest China, is made up of several Paleozoic orogens. From north to south these are the Chinese Altai, Junggar, and Tian Shan. It is characterized by widespread development of Late Carboniferous-Permian granitoids, which are commonly accepted as the products of post-collisional magmatism. Except for the Chinese Altai, East Junggar, and Tian Shan, little is known about the Devonian and older granitoids in the West Junggar, leading to an incomplete understanding of its Paleozoic tectonic history. New SHRIMP and LA-ICP-MS zircon U-Pb ages were determined for seventeen plutons in northern West Junggar and these ages confirm the presence of Late Silurian-Early Devonian plutons in the West Junggar. New age data, combined with those available from the literature, help us distinguish three groups of plutons in northern West Junggar. The first is represented by Late Silurian-Early Devonian (ca. 422 to 405 Ma) plutons in the EW-striking Xiemisitai and Saier Mountains, including A-type granite with aegirine-augite and arfvedsonite, and associated diorite, K-feldspar granite, and subvolcanic rocks. The second is composed of the Early Carboniferous (ca. 346 to 321 Ma) granodiorite, diorite, and monzonitic and K-feldspar granites, which mainly occur in the EW-extending Tarbgatay and Saur (also spelled as Sawuer in Chinese) Mountains. The third is mainly characterized by the latest Late Carboniferous-Middle Permian (ca. 304 to 263 Ma) granitoids in the Wuerkashier, Tarbgatay, and Saur Mountains. As a whole, the three epochs of plutons in northern West Junggar have different implications for tectonic evolution. The volcano-sedimentary strata in the Xiemisitai and Saier Mountains may not be Middle and Late Devonian as suggested previously because they are crosscut by the Late Silurian-Early Devonian plutons. Therefore, they are probably the eastern extension of the Early Paleozoic Boshchekul-Chingiz volcanic arc of East Kazakhstan in China. It is uncertain at

  2. Melt Extraction Zones in Shallow Arc Plutons: Insights from Fisher Lake Orbicules and Comb Layers, Northern Sierra Nevada

    NASA Astrophysics Data System (ADS)

    McCarthy, A. J.; Muntener, O.

    2015-12-01

    Identifying the processes behind magma flow structures and complex sheeted zones within otherwise near-homogeneous shallow plutons is fundamental in order to understand the mechanisms of melt transport, magma differentiation, crustal recycling and growth of mid-upper crustal plutons. The Cretaceous gabbro-diorite pluton of Fisher Lake, Northern Sierra Nevada (USA), contains multiple m-sized orbicule and magma-breccia bodies as well as orbicule- and comb layer-bearing dikes. Olivine-bearing norites, hornblende diorites and gabbros which have crystallized at low pressure (2kbar) from hydrous basaltic-andesite melts form texturally diverse orbicule cores which act as nuclei for comb layers. Rising hydrous mafic melts remobilizing low pressure cumulates and/or crystal mushes are injected at the contact between cooling plutons prior to the initiation of comb layer growth. Multiple generations of melt injections are attested by the presence of magma-breccia bodies which incorporate fractured, disaggregated fragments of pre-existing orbicule and comb layer bodies. The cumulate signature of the orbicule-bearing matrix indicates that interstitial melt was extracted towards shallower depth. Though orbicule and comb layer bodies have been variously ascribed to melt migration within cooling plutons, magma mixing or fluid flow, we propose an alternative interpretation where these m-scale features represent localized subvertical channels formed during the extraction of multiple batches of hydrous melts within a volcanic plumbing system or shallow plutonic feeder zone. These features thus preserve unique evidence of upper-crustal melt migration processes during the transfer of hydrous mafic melts towards shallower depth. Geochemical gradients between decompressing liquids and crystallizing cumulates are the main driving force for crystallization. We will illustrate examples of this process on the basis of field observations, textural data, whole rock and mineral geochemistry.

  3. The relationship between adakitic, calc-alkaline volcanic rocks and TTGs: implications for the tectonic setting of the Karelian greenstone belts, Baltic Shield

    NASA Astrophysics Data System (ADS)

    Samsonov, A. V.; Bogina, M. M.; Bibikova, E. V.; Petrova, A. Yu.; Shchipansky, A. A.

    2005-01-01

    Two types of coeval acid-intermediate rocks with different petrological, geochemical and isotopic features have been discovered among volcanic rocks and surrounding synkinematic tonalite-trondhjemite-granodiorite (TTG) plutons of Late Archaean greenstone belts in the Karelian granite-greenstone terrane. Type-1 rocks comprise trondhjemites and sub-volcanic, occasionally volcanic dacite-rhyolite rocks. They are characterized by high Sr, low Y and HREE contents, high Sr/Y ratios, and strongly fractionated REE patterns with no significant positive or negative Eu anomaly. Initial ɛNd is positive, indicating a generation from juvenile source with little or no contribution of ancient continental crust. Type 2 is represented by diorite-granodiorites and calc-alkaline basalt-andesite-dacite-rhyolite (BADR) series. As compared to type 1, these rocks differ by their lower Sr, higher Y and HREE contents, lower Sr/Y ratios and less fractionated HREE patterns with negative Eu anomalies. Initial ɛNd varies from negative to positive values, thus indicating a variable contribution of sialic crust. Geochemistry of the two magmatic series suggests their formation in a convergent plate margin setting. The type-1 rocks resemble Phanerozoic adakites, which represent slab-derived melts contaminated by overlying mantle wedge. The type-2 rocks resemble BADR series, which were derived from a mantle wedge metasomatized by slab-derived fluids and melts, with subsequent variable crustal contamination. The spatial distribution of these two types of magmatic series defines the asymmetry of the studied granite-greenstone structures, which presumably reflects the primary lateral zoning of island arc formed under specific thermal conditions in the Archaean mantle. Adakite melts upraised to the surface in the frontal part of the island arc, where mantle wedge was thin, showing no or little interaction with metasomatized mantle, and formed adakite-type plutonic and sub-volcanic rocks. At greater

  4. Formation of composite dykes by contact remelting and magma mingling: The Shaluta pluton, Transbaikalia (Russia)

    NASA Astrophysics Data System (ADS)

    Litvinovsky, B. A.; Zanvilevich, A. N.; Katzir, Y.

    2012-10-01

    A unique opportunity to study the source areas, from which composite dykes were injected, occurs in the Shaluta pluton, Transbaikalia, Russia. The major quartz syenite pluton was intruded by several synplutonic gabbro bodies of various sizes. Investigations of the contact zones between gabbro and host syenite showed that liquid basalt magma intruded the incompletely crystallized coarse-grained quartz syenite with T = 700-720 °C and caused contact remelting of the silicic rock at about 900-950 °C. Mechanical interaction between newly formed silicic melt and partially crystallized mafic magma resulted in extensive magma mingling. Chemical interaction was exhibited by migration of MgO, CaO, FeO∗, Sr, H2O and Cl from the basalt magma, whereas silica, alkalis, Rb and Ba migrated from the silicic refusion zone into the crystallized gabbro. Presence of melt inclusions with homogenization temperature ranging from 640 to 790 °C in quartz and attaining 850-900 °C in late clinopyroxene indicates that at least part of newly formed minerals crystallized from the hybrid melt. Mingled magmatic material was squeezed out inwards, into the host solid quartz syenite pluton and formed dyke-like apophyses that can be traced for a distance of 60-70 m from the contact zone. Apophyses have the same dimensions, structure and composition as typical composite dykes that are common in the roof pendant over the gabbro bodies and nearby the gabbro exposures.

  5. Ti in zircon from the Boggy Plain zoned pluton: implications for zircon petrology and Hadean tectonics

    NASA Astrophysics Data System (ADS)

    Ickert, R. B.; Williams, I. S.; Wyborn, D.

    2011-08-01

    The understanding of zircon crystallization, and of the Ti-in-zircon thermometer, has been enhanced by Ti concentration measurements of zircon from a small, concentrically zoned pluton in south-eastern Australia, the Boggy Plain zoned pluton (BPZP). Zircon crystals from rocks ranging in composition from gabbro to aplite were analysed for U-Th-Pb dating and Ti concentrations by an ion microprobe. Geochronological data yield a 206Pb/238U age of 417.2 ± 2.0 Ma (95% confidence) and demonstrate the presence of older inherited or xenocrystic zircon. Titanium measurements ( n = 158) yield a mean Ti concentration of 11.7 ± 6.1 ppm (2SD) which corresponds to a mean crystallization temperature of 790°C for an α-TiO2 = 0.74 (estimated using mineral equilibria), or 760°C for an α-TiO2 = 1.0. Apparent zircon crystallization temperatures are similar in all intrusive phases, although the gabbro yields slightly higher values, indicating that crystallization occurred at the same temperature in all rock types. This finding is consistent with previous work on the BPZP, which indicates that liquid-crystal sorting (crystal fractionation) was the dominant control on chemical differentiation, and that late, differentiated liquids were similar in composition for all rock types. A simple forward model approximately predicts the range of crystallization temperatures, but not the shape of the distributions, due to sampling biases and complexities in the cooling and crystallization history of the pluton. The distribution of Ti concentrations has a mode at a higher Ti (higher temperature) than the sample set of Hadean detrital zircon. This is consistent with the hypothesis that the skew to low-T in the Hadean dataset is due to the presence of zircon that crystallized from wet anatectic melts.

  6. The Middle Fork Plutonic Complex: A plutonic association of coeval peralkaline and metaluminous magmas in the north-central Alaska Range

    SciTech Connect

    Solie, D.N.

    1988-01-01

    The 57 m.y. Middle Fork Plutonic Complex (MFPC) intrudes Paleozoic metasedimentary rocks south of the Farewell Fault zone in the north-central Alaska Range. Though spatially related to the late Cretaceous - Early Tertiary subduction-related Alaska Range batholith, MFPC is more characteristic of an extensional or anorogenic setting. A swarm of basalt, hawaiite and rhyolite dikes east of the complex intruded, and was intruded by, the plutonic rocks. Approximately 30% of the exposed rock in the 125 km[sup 2] complex is hedenbergite - fayalite syenite, [approx equal]20% is peralkalin arfvedsonite-biotite alkali-feldspar granite (AF granite), and [le]20% is pyroxene-olivine-biotite gabbro. The rest is a mixed unit including clinopyroxene-biotite-amphibole diorite, and hornblende-biotite granite (HB granite). K-Ar and Rb-Sr radiometric dating of rock types shows that they are coeval. Their close spatial and temporal relationships led to complex magmatic interactions. Calculated initial [sup 87]Sr/[sup 86]Sr for gabbro and diorite group is around 0.705 to 0.706. HB granites are heterogeneous, but fall mostly around 0.707 to 0.708. Hypersolvus syenites and AF granites form an isochron with initial [sup 87]Sr/[sup 86]Sr of 0.70965. These groupings suggest that at least three different magmas formed the MFPC; scatter of isotopic data reflects mutual contamination and assimilation. Consanguinous hypersolvus syenite and AF granite mineralogy appears to be controlled by fluorine in the magma chamber. Eruptive stratigraphy, as predicted by intrusive history of MFPC, compares favorably with volcanic stratigraphies of peralkaline volcanic systems worldwide, and MFPC may be modelled as the root zone of a peralkaline volcanic system.

  7. Model of formation of the Khibiny-Lovozero ore-bearing volcanic-plutonic complex

    NASA Astrophysics Data System (ADS)

    Arzamastsev, A. A.; Arzamastseva, L. V.; Zhirova, A. M.; Glaznev, V. N.

    2013-09-01

    The paper presents the results of a study of the large Paleozoic ore-magmatic system in the northeastern Fennoscandian Shield comprising the Khibiny and Lovozero plutons, the Kurga intrusion, volcanic rocks, and numerous alkaline dike swarms. As follows from the results of deep drilling and 3D geophysical simulation, large bodies of rocks pertaining to the ultramafic alkaline complex occur at the lower level of the ore-magmatic system. Peridotite, pyroxenite, melilitolite, melteigite, and ijolite occupy more than 50 vol % of the volcanic-plutonic complex within the upper 15 km accessible to gravity exploration. The proposed model represents the ore-magmatic system as a conjugate network of mantle magmatic sources localized at different depth levels and periodically supplying the melts belonging to the two autonomous groups: (1) ultramafic alkaline rocks with carbonatites and (2) alkali syenites-peralkaline syenites, which were formed synchronously having a common system of outlet conduits. With allowance for the available isotopic datings and new geochronological evidence, the duration of complex formation beginning from supply of the first batches of melt into calderas and up to postmagmatic events, expressed in formation of late pegmatoids, was no less than 25 Ma.

  8. A possible concealed pluton in Beaverhead and Madison Counties, Montana, and Clark County, Idaho

    USGS Publications Warehouse

    Witkind, Irving Jerome

    1974-01-01

    A northeast-trending magnetic anomaly in parts of Beaverhead and Madison Counties, Mont., and Clark County, Idaho, may reflect the trend, shape, and size of a concealed pluton. The type of rock that forms the pluton(?) is unknown. A small volcanic pipe, possibly a diatreme, is at the southeast end of the high. The pipe, about 92 m (300 ft) in diameter, consists of a rubbly basalt-like matrix through which are scattered xenoliths of Precambrian crystalline rocks and of various Paleozoic and Mesozoic strata. It is uncertain whether the juxtaposition of the pipe and the magnetic high is meaningful or is merely fortuitous. Although no mineralized rock was found in the area underlain by the anomaly, placer gold has been found nearby. Some 113 km (70 mi) to the west, in Custer and Lemhi Counties, Idaho, a similar northeast-trending magnetic high marks the site of the Gilmore mining district. The similarities in trend, shape, and magnitude between the two anomalies suggest that the high in Beaverhead and Madison Counties should be investigated for undetected mineral deposits, possibly by a geochemical survey.

  9. River Valley pluton, Ontario: A late-Archean/early-Proterozoic anorthositic intrusion in the Grenville Province

    USGS Publications Warehouse

    Ashwal, L.D.; Wooden, J.L.

    1989-01-01

    The River Valley pluton is a ca. 100 km2 body of anorthositic and gabbroic rocks located about 50 km northeast of Sudbury, Ontario. The pluton is situated entirely within the Grenville Province, but its western margin is a series of imbricate thrust faults associated with the Grenville Front Tectonic Zone. It is dominated by coarse leuconorite and leucogabbro, with lesser anorthosite, gabbro, and rare ultramafics. Igneous textured rocks are abundant and consist of plagioclase (An60-70) charged with Fe-Ti oxide inclusions, low Ca pyroxene (orthopyroxene and/or inverted pigeonite) and augite. The most unfractionated rocks are minor olivine gabbros with Fo70-80. A variety of deformed and recrystallized equivalents of the igneous-textured rocks is also present, and these are composed largely of calcic plagioclase and hornblende. Ten samples, including both igneous and deformed lithologies give a Pb-Pb whole-rock isochron of 2560??155Ma, which is our best estimate of the time of primary crystallization. The River Valley pluton is thus the oldest anorthositic intrusive yet reported from the Grenville Province, but is more calcic and augitic than typical massifs, and lacks their characteristic Fe-Ti oxide ore deposits. The River Valley body may be more akin to similar gabbro-anorthosite bodies situated at the boundary between the Archean Superior Province and Huronian supracrustal belt of the Southern Province west of the Grenville Front. An Sm-Nd isochron from 3 igneous-textured leucogabbros and an augite mineral separate gives 2377 ?? 68 Ma, implying slight disturbance of the Sm-Nd whole-rock-mineral system during later metamorphism. The Rb-Sr system has been substantially disturbed, giving an age of 2185 ?? 105 Ma, which is similar to internal Pb-Pb isochron ages of 2165 ?? 130 Ma and 2100 ?? 35 Ma for two igneous-textured rocks. It is uncertain whether these ages correspond to a discrete event at this time or represent a partial resetting of the Rb-Sr and Pb

  10. Climate change and increased zinc concentrations in a Rocky Mountain acid rock drainage stream

    NASA Astrophysics Data System (ADS)

    Crouch, C. M.; Todd, A. S.; McKnight, D. M.

    2009-12-01

    The Snake River Watershed in Colorado is impacted by acid rock drainage (ARD) originating from both natural sources and sources associated with the historic mining in the watershed. Downstream of mines, the high metal ion concentrations, low pH, and metal oxide deposition cause contamination which disrupts ecosystem functions, impairs biological diversity, and contaminates surface and groundwater drinking supplies. One obvious measure of the severity of this contamination is that the self-sustaining trout populations in the watershed are quite sparse. While elevated concentrations of numerous trace metals are present, dissolved zinc is used as an indicator of trout habitat water quality because the fish are so impacted by its presence. Water quality was monitored along the Snake River from 1980 to 1990 and since then less frequent sampling was conducted as part of research studies and efforts to designate portions of the watershed for mitigation. Metals concentrations during the seasonal low flows of September and October have been observed to increase significantly over that time. In particular, at a site in the headwaters well above the historic mining impacts, zinc concentrations, which were measured between 0.3 and 0.4 mg/L through the 1980s, have now exceeded 1.2 mg/L in the past several years. This four-fold increase in zinc concentrations is associated with an increase in sulfate concentrations, which indicates that these water quality changes are driven primarily by accelerated natural weathering of pyrite in the watershed. The observed increase in natural ARD - possibly the result of climate change - may have implications for mitigation. Currently, these trends are being evaluated by reanalyzing the archived samples to delineate the spatial and temporal changes in contamination. Processes which may be driving the accelerated natural weathering include the earlier occurrence of peak snowmelt due to climate change which causes lower stream flows and drier

  11. Mineral associations produced by sodic-calcic hydrothermal alteration in the Buffalo Mountain pluton, north-central Nevada

    SciTech Connect

    McBride, D. . Dept. of Geology and Geography)

    1993-03-01

    Sodic-calcic (Na-Ca) hydrothermal alteration is prevalent throughout Mesozoic-age arc igneous rocks in the western US. The middle Jurassic Buffalo Mountain pluton, located in north-central Nevada, contains particularly well developed Na-Ca metasomatism. The Buffalo Mountain pluton is composed of porphyritic syenite, quartz monzonite, small bordering stocks (which account for less than 1% of the pluton), and an extensive felsic dike swarm. Quartz monzonite intruded syenite and constitutes the majority of the surface area. Unaltered porphyritic syenite is composed of perthite, plagioclase, quartz, augite, hornblende, biotite, olivine, magnetite, and other minerals accounting for less than 1% of the rock. Unaltered quartz monzonite is an aggregate of K-feldspar, plagioclase, quartz, biotite, hornblende, and accessory minerals accounting for less than 1% of the rock. The dikes cut both phases of the total intrusive rock body and are closely related in space to zones of Na-Ca alteration. Alteration variably affects all igneous rock types and exists as both fracture-controlled and pervasive Na-Ca alteration. Sodic-calcic alteration resulted in the following mineral reactions: K-feldspar is replaced by chalky-colored plagioclase, and primary mafic minerals react to form pale green diopside or, less commonly, actinolite. Garnet, scapolite, and epidote are often spatially associated with Na-Ca altered rocks. The fact that Na-Ca alteration occurs most commonly in and around dikes suggests that they might have been the source of channel for fluid entry into the surrounding igneous rocks. Further study will seek to constrain the origins and pathways of Na-Ca fluids.

  12. Redox potential of the Khibiny magmatic system and genesis of abiogenic hydrocarbons in alkaline plutons

    NASA Astrophysics Data System (ADS)

    Ryabchikov, I. D.; Kogarko, L. N.

    2009-12-01

    The temperature and redox conditions of the crystallization of rocks from the Khibiny alkaline pluton have been estimated based on an analysis of coexisting magnetite, ilmenite, titanite, and pyroxene. Under redox conditions characteristic of the Khibiny Complex, CO2 is contained in fluid and carbonate anions are contained in melt at high temperature; then graphite is released and an appreciable amount of hydrocarbons appear at a lower temperature as products of reaction of graphite with fluid. Abiogenic hydrocarbons can arise in igneous complexes owing to a processes distinct from Fischer-Tropsch synthesis.

  13. Deformation within the cannibal creek pluton and its aureole, Queensland, Australia: a re-evaluation of ballooning as an emplacement mechanism

    NASA Astrophysics Data System (ADS)

    Godin, Paul

    1994-05-01

    Structures within the foliated Cannibal Creek granite and its deformed aureole indicate that the pluton appears to have been emplaced after a minimum of two strong regional deformation events ( D1, D2), that contact metamorphic porphyroblast growth began during the early stages of a third aureole-centred event ( Da) and that a fourth weak deformation overprints all earlier structures, at least within the strain-softened aureole. The aureole deformation ( Da) is most strongly developed at the pluton contact, decreasing in intensity both inwards to the core, and outwards into the wall rock. Earlier interpretations linking ( Da) strain to expansion (ballooning) of the pluton during emplacement are no longer favoured. Previously discussed diagnostic criteria of ballooning, such as closed elliptical trend lines for the aureole foliation, and new field evidence, such as radial magmatic lineations and moderate to high-temperature solid-state deformation of external sheath dykes, are either ambiguous or point strongly toward syn- to pre-tectonic emplacement of a piercement diapir. Less than 30% of the pluton volume appears to have been accommodated by wall rock shortening as the result of ballooning or diapiric ascent. The rest was likely accommodated by a combination of broad wavelength regional doming (1-5 mm year -1) above the pluton, far field redistribution of mass into the source area plus or minus some component of diapiric backflow, stoping, assimilation and dilation in fault bends or fold hinges.

  14. Jurassic plutons in the Desolation wilderness, northern Sierra Nevada batholith, California: A new segment in the Jurassic magmatic arc

    SciTech Connect

    Sabine, C. . Quaternary Sciences Center)

    1993-04-01

    A 164[+-]7 Ma U-P zircon date establishes a Middle- to Late-Jurassic age for the Pyramid Peak granite and synplutonic dioritoids and hybrid rocks that comprise the Crystal Range suite, located southwest of Lake Tahoe. A Jurassic age is also assigned to the Keiths Dome quartz monzonite and the Desolation Valley and Camper Flat granodiorites (Loomis', 1983, Early Granitic Group) which are distinctly older than surrounding Cretaceous granitoids. The Keiths Dome quartz monzonite, the oldest pluton of the group, may be as old as 180 Ma and is distinguished by ductile shear zones and recrystallization textures which indicate an episode of deformation not undergone by other plutons. The Camper flat and Desolation Valley granodiorites are the youngest plutons of the group. ENE-trending microdiorite dikes filled extensional fractures, perpendicular to the direction of shortening, in all Jurassic plutons but on none of the Cretaceous bodies. Jurassic plutons may help constrain ages of metasedimentary and metavolcanic rocks and associated structures in the Mount Tallac roof pendant. The Pyramid Peak granite intrudes the Sailor Canyon Formation which bears Late Pliensbachian ammonites (Fisher, 1990), and the Keiths Dome quartz monzonite intrudes the overlying Tuttle Lake Formation and transects faults and shear zones in the pendant. Initial Sr isotope ratios for the Pyramid Peak granite range between 0.705427 and 0.706874, spanning the 0.706 value taken by some to mark the western limit of sialic lower crust. Data suggest an isotopically mixed source containing mantle and crustal components. Such an environment is not inconsistent with a passive continental margin where mafic magma invades rifted continental crust.

  15. Isotopic constraints on the petrogenesis of jurassic plutons, Southeastern California

    USGS Publications Warehouse

    Mayo, D.P.; Anderson, J.L.; Wooden, J.L.

    1998-01-01

    The 165 Ma Eagle Mountain intrusion is a heterogeneous, enclave-bearing, metaluminous remnant of the Cordilleran Jurassic arc that cuts regionally metamorphosed pre-Mesozoic rocks in the southeastern Mojave Desert of California. The main phase of the intrusion consists of granodiorite to tonalite host facies, diorite mixed facies, and homogeneous monzogranite facies. The host facies contains microdiorite enclaves interpreted as intermingled masses of mafic magma. Late-phase leucogranite stocks cut the main phase. Mineral equilibria indicate emplacement at ???6.5 km depth, with solidus temperatures ranging from 760??C for diorite to 700??C for felsic granodiorite. Although uniform radiogenic-isotope compositions (Sri = 0.7085, ???Ndi = -9.4) suggest derivation from a single source, no known source has the composition required. A hybrid source is proposed, consisting of various proportions of juvenile mantle and recycled lower crust. Calculations indicate that the source of the Eagle Mountain intrusion comprised >60% juvenile mantle and <40% recycled crust. On the basis of their isotopic compositions, other mafic Jurassic plutons in the region were derived from sources containing different proportions of mantle and crustal components.

  16. Tectonic significance of granitoid plutons from the Andasibe paragneiss belt, east-central Madagascar

    NASA Astrophysics Data System (ADS)

    Raharimahefa, T.

    2013-12-01

    The understanding of the crustal evolution of the central Madagascar is of major significance in the study of the Precambrian basement of Madagascar and the greater Gondwana supercontinent. The study area, known as Andasibe paragneiss defines a fold belt that stretches from Ambatondrazaka to Soavina area in eastern Madagascar and is intruded by extensive granitoid intrusions. The western part of Andasibe paragneiss lies within the crustal scale Angavo shear zone, and is characterized by fine to medium-grained foliated paragneiss, which also include biotite-hornblende gneiss, migmatitic quartzofeldspathic gneiss, sillimanite-bearing gneiss, garnet-bearing gneiss, graphitic gneiss intercalates with schist, quartzite, muscovite-bearing gneiss and marble. Three samples of granitoid plutons intruding the Andasibe paragneiss yielded isotope dilution-thermal ionization mass spectrometry (ID-TIMS) U-Pb zircon ages of 801.2×3.8Ma, 776.5×4.4Ma and 772.1×4.2Ma. These dates are interpreted to represent the crystallization ages of these rocks and are comparable to other reported U-Pb emplacement ages for granitoid plutons within and along the north-central margin of the Angavo shear zone, which are suggested to be related to ca. 820 Ma successor-arc plutonism. These granitoids pre-dates the Angavo shear zone and folds affecting the plutons foliation are believed to have formed during the East-African Orogen, which in this part of the Malagasy Precambrian basement, is considered to have associated with Neoproterozoic extensive magmatism ca. 820 Ma to 540 Ma.

  17. Reactivity of Hontomín carbonate rocks to acidic solution injection: reactive "push-pull" tracer tests results

    NASA Astrophysics Data System (ADS)

    De Gaspari, Francesca; Cabeza, Yoar; Luquot, Linda; Rötting, Tobias; Saaltink, Maarten W.; Carrera, Jesus

    2014-05-01

    Several field tests will be carried out in order to characterize the reservoir for CO2 injection in Hontomín (Burgos, Spain) as part of the Compostilla project of "Fundación Ciudad de la Energía" (CIUDEN). Once injected, the dissolution of the CO2 in the resident brine will increase the acidity of the water and lead to the dissolution of the rocks, constituted mainly by carbonates. This mechanism will cause changes in the aquifer properties such as porosity and permeability. To reproduce the effect of the CO2 injection, a reactive solution with 2% of acetic acid is going to be injected in the reservoir and extracted from the same well (reactive "push-pull" tracer tests) to identify and quantify the geochemical reactions occurring into the aquifer. The reactivity of the rock will allow us also to evaluate the changes of its properties. Previously, theoretical calculations of Damkhöler numbers were done to determine the acid concentrations and injection flow rates needed to generate ramified-wormholes patterns, during theses "push-pull" experiments. The aim of this work is to present the results and a preliminary interpretation of the field tests.

  18. Static corrosion of construction materials exposed to superphosphoric acid made from various sources of phosphate rock

    SciTech Connect

    Nguyen, D.T.; McDonald, C.L.; McGill, K.E.

    1994-10-01

    Corrosion tests were performed with various construction materials, such as carbon steel, cast iron, stainless steels, nickel and nickel-based alloys, copper and its alloys, aluminum alloy, zirconium alloy, and tantalum, exposed to wet-process superphosphoric acids (approximately 70% P{sub 2}O{sub 5}) from all the suppliers in the United States and to a technical-grade (55% P{sub 2}O{sub 5}) acid made by the electric furnace process. The study was conducted in response to reports from pipe-reactor users of excessive corrosion by superphosphoric acids and electric furnace acid. Test temperatures were ambient (approximately 21{degrees}C or 70{degrees}F), 66{degrees}C (150{degrees}F), and 93{degrees}C (200{degrees}F). Test results showed that temperature was a significant factor in acid corrosivity. Electric furnace acid was more corrosive than the superphosphoric acids. Carbon steel, cast iron, and aluminum alloy were not resistant to either the superphosphoric acids or the electric furnace acid. Nickel-chromium (Ni-Cr) and nickel-molybdenum (Ni-Mo) based alloys and tantalum exhibited adequate corrosion resistance in the superphosphoric acids and the electric furnace acid. Stainless steels performed well in all test acids at all test temperatures with some exceptions in the electric furnace acid at 93{degrees}C. Zirconium alloy, copper and its alloys, pure nickel, and Monel 400 provided adequate corrosion resistance to all test acids at ambient temperature only.

  19. Tectonomagmatic origin of Precambrian rocks of Mexico and Argentina inferred from multi-dimensional discriminant-function based discrimination diagrams

    NASA Astrophysics Data System (ADS)

    Pandarinath, Kailasa

    2014-12-01

    Several new multi-dimensional tectonomagmatic discrimination diagrams employing log-ratio variables of chemical elements and probability based procedure have been developed during the last 10 years for basic-ultrabasic, intermediate and acid igneous rocks. There are numerous studies on extensive evaluations of these newly developed diagrams which have indicated their successful application to know the original tectonic setting of younger and older as well as sea-water and hydrothermally altered volcanic rocks. In the present study, these diagrams were applied to Precambrian rocks of Mexico (southern and north-eastern) and Argentina. The study indicated the original tectonic setting of Precambrian rocks from the Oaxaca Complex of southern Mexico as follows: (1) dominant rift (within-plate) setting for rocks of 1117-988 Ma age; (2) dominant rift and less-dominant arc setting for rocks of 1157-1130 Ma age; and (3) a combined tectonic setting of collision and rift for Etla Granitoid Pluton (917 Ma age). The diagrams have indicated the original tectonic setting of the Precambrian rocks from the north-eastern Mexico as: (1) a dominant arc tectonic setting for the rocks of 988 Ma age; and (2) an arc and collision setting for the rocks of 1200-1157 Ma age. Similarly, the diagrams have indicated the dominant original tectonic setting for the Precambrian rocks from Argentina as: (1) with-in plate (continental rift-ocean island) and continental rift (CR) setting for the rocks of 800 Ma and 845 Ma age, respectively; and (2) an arc setting for the rocks of 1174-1169 Ma and of 1212-1188 Ma age. The inferred tectonic setting for these Precambrian rocks are, in general, in accordance to the tectonic setting reported in the literature, though there are some inconsistence inference of tectonic settings by some of the diagrams. The present study confirms the importance of these newly developed discriminant-function based diagrams in inferring the original tectonic setting of

  20. Solution of rocks and refractory minerals by acids at high temperatures and pressures. Determination of silica after decomposition with hydrofluoric acid

    USGS Publications Warehouse

    May, I.; Rowe, J.J.

    1965-01-01

    A modified Morey bomb was designed which contains a removable nichromecased 3.5-ml platinium crucible. This bomb is particularly useful for decompositions of refractory samples for micro- and semimicro-analysis. Temperatures of 400-450?? and pressures estimated as great as 6000 p.s.i. were maintained in the bomb for periods as long as 24 h. Complete decompositions of rocks, garnet, beryl, chrysoberyl, phenacite, sapphirine, and kyanite were obtained with hydrofluoric acid or a mixture of hydrofluoric and sulfuric acids; the decomposition of chrome refractory was made with hydrochloric acid. Aluminum-rich samples formed difficultly soluble aluminum fluoride precipitates. Because no volatilization losses occur, silica can be determined on sample solutions by a molybdenum-blue procedure using aluminum(III) to complex interfering fluoride. ?? 1965.

  1. Lead isotope systematics of some igneous rocks from the Egyptian Shield

    NASA Technical Reports Server (NTRS)

    Gillespie, J. G.; Dixon, T. H.

    1983-01-01

    Lead isotope data on whole-rock samples and two feldspar separates for a variety of Pan-African (late Precambrian) igneous rocks for the Egyptian Shield are presented. It is pointed out that the eastern desert of Egypt is a Late Precambrian shield characterized by the widespread occurrence of granitic plutons. The lead isotope ratios may be used to delineate boundaries between Late Precambrian oceanic and continental environments in northeastern Africa. The samples belong to three groups. These groups are related to a younger plutonic sequence of granites and adamellites, a plutonic group consisting of older tonalites to granodiorites, and the Dokhan volcanic suite.

  2. Climate Change and Water Quality in the Rocky Mountains: challenges of too much summer for addressing acid rock drainage (Invited)

    NASA Astrophysics Data System (ADS)

    McKnight, D. M.; Crouch, C. M.; Rue, G. P.

    2013-12-01

    A major water quality concern in the Rocky Mountains is acid rock drainage, which causes acidic conditions and high metal concentrations. The 30-year water quality record for the Snake River watershed in Colorado, USA, shows that for the summer low-flow period zinc concentrations have increased four- to six-fold concurrently with a two- to three week advancement in spring snowmelt. We found that the main source of acidity, zinc and other metals, including rare earth elements to the upper Snake River was a tributary draining an alpine area rich in disseminated pyrite. By conducting a tracer experiment in this tributary, we demonstrated that more than half of the trace metal and acidity loading entered in an upper steep, rocky reach where the tributary is fed by an alpine spring. Another increase in flow and metal loading occurred where the tributary flows through a gently-sloped wetland area containing a bog iron deposit. Analysis of the tracer experiment indicated a significant increase in hyporheic exchange along this wetland reach, where decreases in pH of the water exchanging in the hyporheic zone may be mobilizing metals that had been sequestered in the wetland through sorption to iron oxides. One possible scenario is that decreasing pH in the upper reach has reached a threshold, resulting in mobilization of metals from the hyporheic zone of the wetland. This study illustrates how changes in hydrologic regime may cause changes in biogeochemical processes that exacerbate the danger to aquatic ecosystems associated with acid rock drainage.

  3. A 2 Million Year History of Plutonism and Volcanism in the Searchlight Magma System, Eldorado Mountains, Nevada (USA)

    NASA Astrophysics Data System (ADS)

    Miller, J.; Miller, C.; Wooden, J.; Perrault, D.; Hodge, K.; Faulds, J.; Cates, N.; Means, M.

    2006-12-01

    Subvolcanic plutons provide an important record of magma processing and solidification of upper crustal magma bodies but rarely can they be compared with volcanic output from the same magma system. In the Colorado River extensional corridor of southern Nevada, steep tilting caused by crustal extension has exposed outstanding examples of large intrusions that have complementary volcanic output. One of the best examples is the 12 km thick Searchlight pluton and its overlying volcanic cover. Earlier work in the pluton documented vertical growth, wherein crystal accumulation (mafic quartz monzonite cumulate) and roof-down solidification (upper quartz monzonite) resulted in segregation of evolved felsic melt in the chamber interior (middle granite). This general evolutionary sequence is mirrored by lava flow stratigraphy in steeply tilted volcanic sections that are structurally above the roof of Searchlight pluton. We have obtained more than 400 ion microprobe U/Pb zircon ages (Stanford/USGS SHRIMP-RG) on more than 20 samples for the pluton and overlying volcanic rocks in order to temporally link the volcanic rocks with the intrusive rocks. The oldest unit from Searchlight pluton is a gabbro pod near the northern margin of the lower Searchlight quartz monzonite that yielded a 206Pb/238U age of 17.7±0.3 Ma (all age errors reported are 1σ; MSWD ~1 or lower except where noted) but the main lower quartz monzonite from structurally deep has a 206Pb/238U age of 16.9±0.2 Ma. This age is the same age as trachydacite porphyry dikes and pods (16.6±0.3 Ma) that intrude upper Searchlight (but not lower Searchlight) and an identical trachydacite lava flow from near the base of a sequence of trachydacite flows above the pluton (16.9±0.4 Ma; MSWD 1.9). Samples of the middle granite and a gabbro that interacts with the granite are interpreted to be the last materials to solidify in the pluton and have 206Pb/238U ages ranging from 15.9-16.2 Ma but with MSWD's >3. Distinct age peaks

  4. Agronomic effectiveness of biofertilizers with phosphate rock, sulphur and Acidithiobacillus for yam bean grown on a Brazilian tableland acidic soil.

    PubMed

    Stamford, N P; Santos, P R; Santos, C E S; Freitas, A D S; Dias, S H L; Lira, M A

    2007-04-01

    Phosphate rocks have low available P and soluble P fertilizers have been preferably used in plant crop production, although economic and effective P sources are needed. Experiments were carried out on a Brazilian Typic Fragiudult soil with low available P to evaluate the agronomic effectiveness of phosphate rock (PR) compared with soluble phosphate fertilizer. Yam bean (Pachyrhizus erosus) inoculated with rhizobia (strains NFB 747 and NFB 748) or not inoculated was the test crop. Biofertilizers were produced in field furrows by mixing phosphate rock (PR) and sulphur inoculated with Acidithiobacillus (S+Ac) in different rates (50, 100, 150 and 200 g S kg(-1) PR), with 60 days of incubation. Treatments were carried out with PR; biofertilizers B(50), B(100), B(150), B(200); triple super phosphate (TSP); B(200) without Acidithiobacillus and a control treatment without P application (P(0)). TSP and biofertilizers plus S inoculated with Acidithiobacillus increased plant growth. Soil acidity and available P increased when biofertilizers B(150) and B(200) were applied. We conclude that biofertilizers may be used as P source; however, long term use will reduce soil pH and potentially reduce crop growth. PMID:16815009

  5. Jim River and Hodzana plutons, Alaska: the role of assimilation in the petrogenesis of syenite and granite

    SciTech Connect

    Blum, J.D.; Blum, A.E.; Dillon, J.T.

    1985-01-01

    Early Cretaceous plutonic rocks in central Alaska intrude both Devonian to Jurassic oceanic rocks of the Angayuchum terrane (AT) and early Paleozoic to Precambrian continental metasediments of the Ruby terrane (RT). Most plutons intrude only the RT and are biotite and two-mice granite. The Hodzana pluton intrudes both fault-bounded terranes, constraining movement between them to the emplacement age of about 110 million years, and is mainly biotite-amphibole granite with some monzodiorite. Modal and chemical data from the Jim River and Hodzana plutons define two distinct compositional trends. One trend is monzonitic to syenitic while the other is mostly granitic. The two suites are the same age, yet cannot be related by simple differentiation due to a pronounced chemical discontinuity. Rb-Sr whole-rock isochrons yield an age of 112 million years and (87Sr/86Sr)o of .7078 for the syenitic suite, and an age of 108 million years and (87Sr/86Sr)o of .7079 for the granitic suite. The authors suggest that the monzonite represents a primary magma that formed in the lower crust or mantle and initiated upper crustal melting as it intruded the AT and RT. Assimilation of continental crust could have allowed the portion of the magma that intruded the RT to evolve from a monzonite to a granite. Fractionation of these two parent magmas may have resulted in the contemporaneous syenitic and granitic suites. The two suites may reflect the contrasting composition of assimilated wallrock across the AT-RT boundary. Isotopic studies of the wallrocks are in progress and may help to constrain the amount and composition of crust that was assimilated where the magma intruded the AT versus the RT.

  6. Polymerization on the rocks: negatively-charged alpha-amino acids

    NASA Technical Reports Server (NTRS)

    Hill, A. R. Jr; Bohler, C.; Orgel, L. E.; Bada, J. L. (Principal Investigator)

    1998-01-01

    Oligomers of the negatively-charged amino acids, glutamic acid, aspartic acid, and O-phospho-L-serine are adsorbed by hydroxylapatite and illite with affinities that increase with oligomer length. In the case of oligo-glutamic acids adsorbed on hydroxylapatite, addition of an extra residue results in an approximately four-fold increase in the strength of adsorption. Oligomers much longer than the 7-mer are retained tenaciously by the mineral. Repeated incubation of short oligo-glutamic acids adsorbed on hydroxylapatite or illite with activated monomer leads to the accumulation of oligomers at least 45 units long. The corresponding reactions of aspartic acid and O-phospho-L-serine on hydroxylapatite are less effective in generating long oligomers, while illite fails to accumulate substantial amounts of long oligomers of aspartic acid or of O-phospho-L-serine.

  7. The Tynong pluton, its mafic synplutonic sheets and igneous microgranular enclaves: the nature of the mantle connection in I-type granitic magmas

    NASA Astrophysics Data System (ADS)

    Clemens, J. D.; Regmi, K.; Nicholls, I. A.; Weinberg, R.; Maas, R.

    2016-04-01

    In the Lachlan Orogen of south-eastern Australia, the high-level, postorogenic, 368-Ma, I-type Tynong pluton contains granitic to granodioritic rocks that crystallised from a variety of mainly crustally derived magmas emplaced in the shallow crust, in an extensional regime. The isotopic characteristics of the main plutonic rocks are relatively unevolved (87Sr/86Sr t ~ 0.705-0.706 and ɛNd t ~ -0.4 to 0.6), suggesting source rocks not long separated from the mantle. We infer that arc mafic to intermediate rocks and associated immature greywackes formed the main crustal source rocks and that these are located in the largely unexposed Neoproterozoic-Cambrian Selwyn Block that forms the basement. As exposed near its southern margin, the pluton also contains minor, pillowed sheet-like intrusions of quartz dioritic rock that show mainly mingling structures with the enclosing granodiorites, as well as some hybrid pods and fairly abundant igneous microgranular enclaves that we infer to have been derived from the quartz dioritic sheets. Despite this evidence of direct mantle input into the Tynong magma system, the main granodioritic series do not appear to have been formed by magma mixing processes. Of any I-type granite in the region, the Tynong pluton has perhaps the most direct connection with mantle magmas. Nevertheless, the main mantle connection here is probably in the mantle-derived protolith for these crustal magmas and in the mantle thermal event that gave rise to melting of the deep crust in the Selwyn Block. This degree of mantle connectedness seems typical for I-type granitic rocks worldwide.

  8. Stabile Chlorine Isotope Study of Martian Shergottites and Nakhlites; Whole Rock and Acid Leachates and Residues

    NASA Technical Reports Server (NTRS)

    Nakamura, N.; Nyquist, L. E.; Reese, Y.; Shih, C-Y; Fujitani, T.; Okano, O.

    2011-01-01

    We have established a precise analytical technique for stable chlorine isotope measurements of tiny planetary materials by TIMS (Thermal Ionization Mass Spectrometry) [1], for which the results are basically consistent with the IRMS tech-nique (gas source mass spectrometry) [2,3,4]. We present here results for Martian shergottites and nakhlites; whole rocks, HNO3-leachates and residues, and discuss the chlorine isotope evolution of planetary Mars.

  9. The mafic rocks of Shao La (Kharta, S. Tibet): Ordovician basaltic magmatism in the greater himalayan crystallines of central-eastern Himalaya

    NASA Astrophysics Data System (ADS)

    Visonà, Dario; Rubatto, Daniela; Villa, Igor M.

    2010-04-01

    In the Kharta area, east of Mount Everest, the Greater Himalayan Crystallines are significantly richer in mafic rocks than the surrounding areas, Sikkim-West Bhutan and Makalu-Cho Oyu. These rocks are lenses with a complex metamorphic history. The mafic lenses of Shao La, in the Greater Himalayan Sequence south of Kharta, are here considerated as dismembered dykes apparently escaped the Himalayan high-temperature metamorphism and only record a low-grade metamorphic event. They are calc-alkaline medium-K basalts to basaltic andesites, consisting of plagioclase (core 62% An and rim 55% An), augite (Wo 43-47En36 36-37Fs 16-20), hypersthene (Wo 1.6-3.3En 50-52Fs 46-48), and minor brown hornblende, biotite and ilmenite. They show strong enrichment in low ionic potential elements relative to high-field-strength elements, and only minor Ce and P enrichment with respect to MORB. Combined Sr-Nd systematics suggest contamination of a basic magma from a subcontinental mantle source with a small amount of crust (about 4 vol.%). This in turn indicates that the Shao La basalts and basaltic andesites have the geochemical fingerprint of a supra-subduction zone magma. U-Pb dating of zircon from one sample yielded an age of 457 ± 6 Ma for the crystallisation of the Shao La basic rocks, assigning them to the Cambro-Ordovician Bhimphedian orogenic event. The age and geochemical characteristics of the Shao La rocks are similar to those of the basic rocks of the Cambro-Ordovician Mandi pluton further west. This suggests the existence of an extensive supra-subduction zone magmatism along the Indian margin of Gondwana. Like the bimodal granite-gabbro magmatism in the Mandi-Kaplas area, the Shao La basic rocks are contemporaneous with the emplacement of granitic plutons in the Everest-Kharta area. This acid plutonism is interpreted as crustal melt triggered by the upwelling of metasomatised mantle in a back-arc setting. The age of basic and acidic plutonism in the Everest-Kharta area is

  10. From Migmatites to Plutons: Power Law Relationships in the Evolution of Magmatic Bodies

    NASA Astrophysics Data System (ADS)

    Soesoo, Alvar; Bons, Paul D.

    2015-07-01

    Magma is generated by partial melting from micrometre-scale droplets at the source and may accumulate to form >100 km-scale plutons. Magma accumulation thus spans well over ten orders of magnitude in scale. Here we provide measurements of migmatitic leucosomes and granitic veins in drill cores from the Estonian Proterozoic basement and outcrops at Masku in SW Finland and Montemor-o-Novo, central Portugal. Despite the differences in size and number of measured leucosomes and magmatic veins, differences in host rock types and metamorphic grades, the cumulative width distribution of the studied magmatic leucosomes/veins follows a power law with exponents usually between 0.7 and 1.8. Published maps of the SE Australian Lachlan Fold Belt were used to investigate the distribution of granitoid pluton sizes. The granites occupy ca. 22 % of the 2.6 × 105 km2 area. The cumulative pluton area distributions show good power law distributions with exponents between 0.6 and 0.8 depending on pluton area group. Using the self-affine nature of pluton shapes, it is possible to estimate the total volume of magma that was expelled from the source in the 2.6 × 105 km2 map area, giving an estimated 0.8 km3 of magma per km2. It has been suggested in the literature that magma batches in the source merge to form ever-bigger batches in a self-organized way. This leads to a power law for the cumulative distribution of magma volumes, with an exponent m V between 1 for inefficient melt extraction, and 2/3 for maximum accumulation efficiency as most of the volume resides in the largest batches that can escape from the source. If m V ≥ 1, the mass of the magma is dominated by small batches; in case m = 2/3, about 50 % of all magma in the system is placed in a single largest batch. Our observations support the model that the crust develops a self-organized critical state during magma generation. In this state, magma batches accumulate in a non-continuous, step-wise manner to form ever

  11. From steep feeders to tabular plutons - Emplacement controls of syntectonic granitoid plutons in the Damara Belt, Namibia

    NASA Astrophysics Data System (ADS)

    Hall, Duncan; Kisters, Alexander

    2016-01-01

    Granitoid plutons in the deeply eroded south Central Zone of the Damara Belt in Namibia commonly show tabular geometries and pronounced stratigraphic controls on their emplacement. Subhorizontal, sheet-like pluton geometries record emplacement during regional subhorizontal shortening, but the intrusion of spatially and temporally closely-related granitoid plutons at different structural levels and in distinct structural settings suggests independent controls on their levels of emplacement. We describe and evaluate the controls on the loci of the dyke-to-sill transition that initiated the emplacement of three syntectonic (560-530 Ma) plutons in the basement-cover stratigraphy of the Erongo region. Intrusive relationships highlight the significance of (1) rigidity anisotropies associated with competent sedimentary packages or pre-existing subhorizontal granite sheets and (2) rheological anisotropies associated with the presence of thick ductile marble horizons. These mechanical anisotropies may lead to the initial deflection of steep feeder conduits as well as subsequent pluton assembly by the repeated underaccretion of later magma batches. The upward displacement of regional isotherms due to the heat advection associated with granite emplacement is likely to have a profound effect on the mechanical stratification of the upper crust and, consequently, on the level at which granitoid pluton emplacement is initiated. In this way, pluton emplacement at progressively shallower crustal depths may have resulted in the unusually high apparent geothermal gradients recorded in the upper crustal levels of the Damara Belt during its later evolution.

  12. Character of the pre-Mesozoic basement along the edge of the western US craton: Pb isotopic evidence from Mesozoic plutonism

    SciTech Connect

    Wooden, J.L.; Kistler, R.W.; Robinson, A.; Tosdal, R.M. ); Wright, J.E. . Dept. of Geology and Geophysics)

    1993-04-01

    The pre-Mesozoic cratonic crust of the western US was a composite of provinces composed mostly of Archean and Early Proterozoic rocks that had been truncated by Late Proterozoic rifting and had some new Paleozoic crust added along the western edge. Mesozoic and younger geologic events greatly obscured this pre-Mesozoic basement along the craton edge. However, the Pb isotopic signatures of Mesozoic plutons provide significant clues to the character of the crust in which they formed or were emplaced because of a strong contrast in Pb concentration between low-Pb, mantle-derived melts and Pb-rich crust. Thus, magmas whether derived from the crust or the mantle with subsequent crustal interaction, will likely have Pb isotopic compositions that reflect those of the crust. In the western US the Pb isotopic compositions of Mesozoic plutonic rocks have strong regional characteristics. Within the Early Proterozoic Mojave crustal province, Mesozoic plutonic rocks have a large range of 206Pb/204Pb ratios that plot above the crustal average, relatively high 207Pb/204Pb ratios that suggest an Archean contribution, and Pb and Sr isotopic compositions that are not correlated and that do not distinguish age groups. At the southern and western edge of this province where some 1.1 Ga rocks are exposed, 208Pb/204Pb ratios lie along the average crust model curve. These data suggest that any individual pluton provides a composite Pb isotopic composition for a discrete vertical section of the crust. Pb isotopic compositions of plutons in the Sierra Nevada and Great Basin are very different from those described above with 206Pb/204Pb ratios starting at 18.6, well-correlated Pb isotopic trends starting below the crustal model but extending to values that require input from the very radiogenic Wyoming province Archean crust, and good correlations between Pb and (1) Sr isotopic compositions and (2) W-E geographic position.

  13. Death Valley turtlebacks: Mesozoic contractional structures overprinted by Cenozoic extension and metamorphism beneath syn-extensional plutons

    NASA Astrophysics Data System (ADS)

    Pavlis, T. L.; Miller, M.; Serpa, L.

    2008-07-01

    -thrust belts. Our work to the east of Death Valley suggests these thrusts were part of a NW trending thrust system that overprinted an older NE trending fold-thrust system that tracks into the Death Valley region from Nevada. These NW trending thrusts probably underlie all of the southern Black Mountains (south of the turtlebacks) and we suggest that pre-extensional structural relief along these basement thrusts placed basement at shallow crustal levels throughout what is now the Black Mountains; a conclusion consistent with the absence of rocks younger than Cambrian beneath Tertiary unconformities throughout the southern Death Valley region. In Late Miocene time, a major detachment system formed and the turtlebacks represent a mid-crustal shear zone developed during that time period, but this system is older, and structurally beneath younger detachments systems that comprise the Amargosa fault system. During motion on the detachment, an ~2km thick plutonic sheet was emplaced along the shear zone forming the Miocene plutonic assemblages of the Black Mountains, and produced upper amphibolite facies metamorphic assemblages along the floor of the pluton in what are now the Copper Canyon and Mormon Point turtlebacks, but the Badwater Turtleback escaped this metamorphism due to a different structural position. Motion continued along the floor of the pluton but syn-extensional folding produced structural relief along folds with axes parallel to the extension direction. Ultimately a new detachment system cut obliquely across the older extensional system, removing the roof of the pluton, but cutting down to its floor in the turtlebacks. This fault system formed a complex detachment system updip in the famous 'Amargosa Chaos', and removing the entire cover sequence from the Black Mountains (~10-12km of crustal section). The turtlebacks are therefore a composite structure in which extension contemporaneous with folding, presumably as a result of distributed transcurrent motion during

  14. Quartz and feldspar zoning in the eastern Erzgebirge volcano-plutonic complex (Germany, Czech Republic): evidence of multiple magma mixing

    NASA Astrophysics Data System (ADS)

    Müller, Axel; Breiter, Karel; Seltmann, Reimar; Pécskay, Zoltán

    2005-03-01

    Zoned quartz and feldspar phenocrysts of the Upper Carboniferous eastern Erzgebirge volcano-plutonic complex were studied by cathodoluminescence and minor and trace element profiling. The results verify the suitability of quartz and feldspar phenocrysts as recorders of differentiation trends, magma mixing and recharge events, and suggest that much heterogeneity in plutonic systems may be overlooked on a whole-rock scale. Multiple resorption surfaces and zones, element concentration steps in zoned quartz (Ti) and feldspar phenocrysts (anorthite content, Ba, Sr), and plagioclase-mantled K-feldspars etc. indicate mixing of silicic magma with a more mafic magma for several magmatic phases of the eastern Erzgebirge volcano-plutonic complex. Generally, feldspar appears to be sensitive to the physicochemical changes of the melt, whereas quartz phenocrysts are more stable and can survive a longer period of evolution and final effusion of silicic magmas. The regional distribution of mixing-compatible textures suggests that magma mingling and mixing was a major process in the evolution of these late-Variscan granites and associated volcanic rocks. Quartz phenocrysts from 14 magmatic phases of the eastern Erzgebirge volcano-plutonic complex provide information on the relative timing of different mixing processes, storage and recharge, allowing a model for the distribution of magma reservoirs in space and time. At least two levels of magma storage are envisioned: deep reservoirs between 24 and 17 km (the crystallisation level of quartz phenocrysts) and subvolcanic reservoirs between 13 and 6 km. Deflation of the shallow reservoirs during the extrusion of the Teplice rhyolites triggered the formation of the Altenberg-Teplice caldera above the eastern Erzgebirge volcano-plutonic complex. The deep magma reservoir of the Teplice rhyolite also has a genetic relationship to the younger mineralised A-type granites, as indicated by quartz phenocryst populations. The pre

  15. Paleocene plutonism and its tectonic implications, North Cascades, Washington

    SciTech Connect

    Miller, R.B. ); Bowring, S.A. ); Hoppe, W.J. )

    1989-09-01

    U-Pb zircon geochronology has identified a northwest-trending belt of Paleocene (68-59 Ma) plutons within the crystalline core of the North Cascades. Most of these plutons show amphibolite facies assemblages and solid-state foiliation. They document extensive Paleogene dynamothermal metamorphism in the core, and combined with other recent studies, demonstrate ongoing metamorphism from mid-Cretaceous to mid-Eocene time. The Paleocene plutons were emplaced during an interval that marked a magmatic lull throughout much of the northern Cordillera. The distribution of latest Cretaceous and Paleocene plutons suggests that magmatism in the North Cascades core records the same eastward retreat that occurred farther north in the Cordillera.

  16. Rocks of the early lunar crust

    NASA Technical Reports Server (NTRS)

    James, O. B.

    1980-01-01

    Data are summarized which suggest a model for the early evolution of the lunar crust. According to the model, during the final stages of accretion, the outer part of the moon melted to form a magma ocean approximately 300 km deep. This ocean fractionated to form mafic and ultramafic cumulates at depth and an overlying anorthositic crust made up of ferroan anorthosites. Subsequent partial melting in the primitive mantle underlying the crystallized magma ocean produced melts which segregated, moved upward, intruded the primordial crust, and crystallized to form layered plutons consisting of Mg-rich plutonic rocks. Intense impact bombardment at the lunar surface mixed and melted the rocks of the two suites to form a thick layer of granulated debris, granulitic breccias, and impact-melt rocks.

  17. Ductile strain rate recorded in the Symvolon syn-extensional plutonic body (Rhodope core complex, Greece)

    NASA Astrophysics Data System (ADS)

    Cirrincione, Rosolino; Fazio, Eugenio; Ortolano, Gaetano; Fiannacca, Patrizia; Kern, Hartmut; Mengel, Kurt; Pezzino, Antonino; Punturo, Rosalda

    2016-04-01

    The present contribution deals with quantitative microstructural analysis, which was performed on granodiorites of the syn-tectonic Symvolon pluton (Punturo et al., 2014) at the south-western boundary of the Rhodope Core Complex (Greece). Our purpose is the quantification of ductile strain rate achieved across the pluton, by considering its cooling gradient from the centre to the periphery, using the combination of a paleopiezometer (Shimizu, 2008) and a quartz flow law (Hirth et al., 2001). Obtained results, associated with a detailed cooling history (Dinter et al., 1995), allowed us to reconstruct the joined cooling and strain gradient evolution of the pluton from its emplacement during early Miocene (ca. 700°C at 22 Ma) to its following cooling stage (ca. 500-300°C at 15 Ma). Shearing temperature values were constrained by means of a thermodynamic approach based on the recognition of syn-shear assemblages at incremental strain; to this aim, statistical handling of mineral chemistry X-Ray maps was carried out on microdomains detected at the tails of porphyroclasts. Results indicate that the strain/cooling gradients evolve "arm in arm" across the pluton, as also testified by the progressive development of mylonitic fabric over the magmatic microstructures approaching the host rock. References • Dinter, D. A., Macfarlane, A., Hames, W., Isachsen, C., Bowring, S., and Royden, L. (1995). U-Pb and 40Ar/39Ar geochronology of the Symvolon granodiorite: Implications for the thermal and structural evolution of the Rhodope metamorphic core complex, northeastern Greece. Tectonics, 14 (4), 886-908. • Shimizu, I. (2008). Theories and applicability of grain size piezometers: The role of dynamic recrystallization mechanisms. Journal of Structural Geology, 30 (7), 899-917. • Hirth, G., Teyssier, C., and Dunlap, J. W. (2001). An evaluation of quartzite flow laws based on comparisons between experimentally and naturally deformed rocks. International Journal of Earth

  18. Experimental Acid Weathering of Fe-Bearing Mars Analog Minerals and Rocks: Implications for Aqueous Origin of Hematite-Bearing Sediments in Meridiani Planum, Mars

    NASA Technical Reports Server (NTRS)

    Golden, D. C.; Koster, A. M.; Ming, D. W.; Morris, R. V.; Mertzman, S. A.

    2011-01-01

    A working hypothesis for Meridiani evaporite formation involves the evaporation of fluids derived from acid weathering of Martian basalts and subsequent diagenesis [1, 2]. However, there are no reported experimental studies for the formation of jarosite and gray hematite (spherules), which are characteristic of Meridiani rocks from Mars analog precursor minerals. A terrestrial analog for hematite spherule formation from basaltic rocks under acidic hydrothermal conditions has been reported [3], and we have previously shown that the hematite spherules and jarosite can be synthetically produced in the laboratory using Fe3+ -bearing sulfate brines under hydrothermal conditions [4]. Here we expand and extend these studies by reacting Mars analog minerals with sulfuric acid to form Meridiani-like rock-mineral compositions. The objective of this study is to provide environmental constraints on past aqueous weathering of basaltic materials on Mars.

  19. Acid wash of second cycle solvent in the recovery of uranium from phosphate rock

    SciTech Connect

    York, W.R.

    1984-02-07

    Entrainment of contaminated water in the organic phase and poor phase disengagement is prevented in the second cycle scrubber, in a two cycle-uranium recovery process, by washing the organic solvent stream containing entrained H/sub 3/PO/sub 4/ from the second cycle extractor, with a dilute aqueous sulfuric or nitric acid solution in an acid scrubber, prior to passing the solvent stream into the second cycle stripper.

  20. The role of felsic microgranular enclaves on the evolution of some Neoproterozoic granite plutons in SE Brazil

    NASA Astrophysics Data System (ADS)

    Alves, Adriana; Janasi, Valdecir A.; Pereira, Giovanna

    2010-05-01

    Recent studies of granite petrogenesis are strongly influenced by the finding that mafic microgranular enclaves (mme) witness frequent and volumetrically significant contribution of mantle-derived magmas to the origin and evolution of granitic melts, be it as a heat source and/or as a source compositional diversity. On the other hand, the origin of felsic microgranular enclaves (fme) is still a matter of debate; current hypotheses consider them as fragments of chilled margins, products of protracted hybridization between invading basic magmas and resident granite mushes or products of interaction between fairly similar melts. Felsic microgranular enclaves are widespread in various granite plutons from SE Brazil, in many cases surpassing mme in size and volume. Two groups of occurrences are studied in more detail illustrate different scenarios, with and without clear connections with mafic magmas. In the Mauá and Mogi das Cruzes plutons, made up of (muscovite)-biotite monzogranite, only fme occur, and the participation of more mafic melts is not evident from field structures or from whole rock and mineral chemical/isotope data. Our preferred model relate the fme to self-mixing events, suggesting mingling/mixing between highly viscous and chemically similar felsic endmembers. In the Itu Batholith, mme enclaves occur, albeit in very different volumes, in three chemically distinct plutons, all with A-type chemical affinities, In the rapakivi Salto Pluton, fme are large (dm to meter-sized) and widespread, except in a central body of porphyry granite. Scattered cm-sized mme of variable composition, some clearly brought as inclusions in the fme, are thought to represent different stages of hybridization, as indicated by disequilibrum features common also in the host syenogranites (rapakivi texture; mafic-rimmed quartz). The enclave assemblage of the Cabreúva Pluton is similarly dominated by fme, but larger mme and small diorite occurrences are evidence that basic magmas

  1. The 13 Ma Monts Ballons alkalic plutonic suite, Kerguelen Archipelago, Indian Ocean

    NASA Astrophysics Data System (ADS)

    Loftus, T.; Weis, D.; Scoates, J. S.; Giret, A.

    2011-12-01

    The 12.955 ± 0.011 Ma (U-Pb zircon) Monts Ballons plutonic suite comprises several small alkalic intrusions (0.3 km2) that were emplaced into older (~25 Ma) flood basalts in the central region of the Kerguelen Archipelago, a major oceanic island in the southern Indian Ocean related to magmatic activity associated with the long-lived (130 million years) Kerguelen mantle plume. The Monts Ballons intrusions contain a suite of rocks ranging from amphibole gabbros to nepheline syenites (silica-undersaturated suite) and are amongst the most alkalic rock types on the archipelago [1]. They represent the products of small degrees of melting of the Kerguelen mantle plume source. Samples from the Monts Ballons suite are enriched in highly incompatible trace elements with sub-parallel normalized trace element patterns. They define a small range of radiogenic isotopic ratios, and lie at the low end of Hf-Nd-Pb isotopic fields in comparison to the majority of volcanic and plutonic rocks on the archipelago, with average values at 13 Ma of ɛHf=-0.8±1.5, ɛNd=-1.2±07 and 206Pb/204Pb=18.2. Values of 87Sr/86Sr at 0.7052±2 fall within the range of the composition of the enriched Kerguelen plume as defined by basalts from the Courbet Peninsula [2]. The Monts Ballons compositions bridge a gap between the radiogenic compositions of the 25-24 Ma mildly alkalic flood basalts from Mt. Crozier and Baie Charrier and the less radiogenic lavas of the young (<10 Ma) alkalic rocks of the Upper Miocene Series and the recent Mt. Ross stratovolcano [3]. The Monts Ballons chemistry does not show any evidence for continental input to account for these enriched signatures typical of the Kerguelen plume. The magmas that crystallized to form the high-level Monts Ballons plutonic suite derive from the source of the enriched Kerguelen mantle plume and subsequently interacted and assimilated some of the underlying Cretaceous Kerguelen Plateau during ascent. [1] Scoates et al. (2006) Contrib. Min

  2. Origin of saline, neutral-pH, reduced epithermal waters by reaction of acidic magmatic gas condensates with wall rock

    SciTech Connect

    Reed, M.H. . Dept. of Geological Sciences)

    1993-04-01

    Fluid inclusions in quartz and sphalerite of epithermal veins containing galena, sphalerite and chalcopyrite with silver sulfides and electrum commonly have salinities of 2 to 10 weight percent NaCl equivalent. Examples include Bohemia, OR, Comstock, NV, and Creede, CO. Salinities in such base metal-rich systems are apparently greater than those in gold-adularia, base metal-poor systems such as Sleeper, NV, Republic, WA, and Hishikare, Kyushu. Saline epithermal fluids are commonly assumed to have been derived from saline magmatic brines, from local host formations, as has been suggested for Creede, or from evaporative concentration (boiling) of more dilute meteoric ground water. Another possibility, which may be the most common origin, is reaction of wall rocks with magmatic gas condensates rich in HCl and sulfuric acid. A mixture of one part Augustine Volcanic gas condensate in 10 parts cold ground water has a pH of 0.7 and the dominant cation is H[sup +] by a factor of 10[sup 4]. Calculated reaction of this condensate mixture with andesite at 300 C to a water/rock ratio (w/r) of 4.6 yields an NaCl-dominated fluid with a total salinity of 2.1 wt %. and pH 3.7. Further reaction, to w/r 0.14 yields a fluid salinity of 2.6 wt % and pH of 5.7; this fluid is in equilibrium with a propylitic alteration assemblage. Aqueous sulfide accumulates during the rock reaction as sulfate is reduced to sulfide when ferrous iron is oxidized to ferric iron. Sulfide concentration in the latter fluid is 32 ppm, far exceeding sulfate concentration. In the overall reaction, hydrogen ion is exchanged for base cations (including base metals) and sulfate is reduced to sulfide.

  3. Development of modal layering in granites: a case study from the Carna Pluton, Connemara, Ireland

    NASA Astrophysics Data System (ADS)

    McKenzie, Kirsty; McCarthy, William; Hunt, Emma

    2016-04-01

    Modal layering in igneous rocks uniquely record dynamic processes operating in magma chambers and also host a large proportion of Earth's strategic mineral deposits. This research investigates the origin of biotite modal layering and primary pseudo-sedimentary structures in felsic magmas, by using a combination of Crystal Size Distribution (CSD) analysis and Electron Probe Microanalysis (EPMA) to determine the mechanisms responsible for the development of these structures in the Carna Pluton, Connemara, Ireland. The Carna Pluton is a composite granodiorite intrusion and is one of five plutons comprising the Galway Granite Complex (425 - 380 Ma). Prominent 30 cm thick modal layers are defined by sharp basal contacts to a biotite-rich (20%) granite, which grades upward over 10 cm into biotite-poor, alkali-feldspar megacrystic granite. The layering strikes parallel to, and dips 30-60° N toward the external pluton contact. Pseudo-sedimentary structures (cross-bedding, flame structures, slumping and crystal graded bedding) are observed within these layers. Petrographic observations indicate the layers contain euhedral biotite and fresh undeformed quartz and feldspar. Throughout the pluton, alkali-feldspar phenocrysts define a foliation that is sub-parallel to the strike of biotite modal layers. Together these observations indicate that the intrusion's concentric foliation, biotite layers and associated structures formed in the magmatic state and due to a complex interaction between magma flow and crystallisation processes. Biotite CSDs (>250 crystals per sample) were determined for nine samples across three biotite-rich layers in a single unit. Preliminary CSD results suggest biotite within basal contacts accumulated via fractional crystallisation within an upward-growing crystal pile, likely reflecting the yield strength of the magma as a limiting factor to gravitational settling of biotite. This is supported by the abrupt decrease in mean biotite crystal size across

  4. C3 Photosynthesis and Crassulacean Acid Metabolism in a Kansas Rock Outcrop Succulent, Talinum calycinum Engelm. (Portulacaceae) 1

    PubMed Central

    Martin, Craig E.; Zee, Aaron Klaas

    1983-01-01

    The potential for Crassulacean acid metabolism (CAM) was investigated in the sandstone outcrop succulent Talinum calycinum in central Kansas. Field studies revealed CAM-like diurnal acid fluctuations in these plants. These fluctuations persisted under all moisture and temperature regimes in the laboratory. Despite this CAM-like acid metabolism, simultaneous gravimetric determinations of day- and nighttime transpiration rates indicated the presence of a C3 gas exchange pattern. Subsequent analyses of diurnal CO2 and H2O exchange patterns under well-watered conditions and after 3, 5, and 7 days of drought confirmed these findings, though low rates of nocturnal CO2 uptake were observed on the fifth night after continuous drought. Finally, the δ13C/12C value of this succulent, −27.8‰, emphasizes the insignificance of any nocturnal CO2 uptake in the lifelong accumulation of carbon in this species. Thus, it is proposed that T. calycinum is a C3 plant with some CAM characteristics, including the ability to re-fix respiratory CO2 at night under all moisture regimes, potentially resulting in a conservation of carbon, and occasionally to fix atmospheric CO2 at night. These findings may prove to be common among rock outcrop succulents. PMID:16663289

  5. Comparison of hot hydroxylamine hydrochloride and oxalic acid leaching of stream sediment and coated rock samples as anomaly enhancement techniques

    USGS Publications Warehouse

    Filipek, L.H.; Chao, T.T.; Theobald, P.K., Jr.

    1982-01-01

    A hot hydroxylamine hydrochloride (H-Hxl) extraction in 25% acetic acid is compared with the commonly used oxalic acid extraction as a method of anomaly enhancement for Cu and Zn in samples from two very different metal deposits and climatic environments. Results obtained on minus-80-mesh stream sediments from an area near the Magruder massive sulfide deposit in Lincoln County, Georgia, where the climate is humid subtropical, indicate that H-Hxl enhances the anomaly for Cu by a factor of 2 and for Zn by a factor of 1.5, compared to the oxalic method. Analyses of Fe oxide-coated rock samples from outcrops overlying the North Silver Bell porphyry copper deposit near Tucson, Arizona, where the climate is semi-arid to arid, indicate that both techniques effectively outline the zones of hydrothermal alteration. The H-Hxl extraction can also perform well in high-carbonate or high-clay environments, where other workers have suggested that oxalic acid is not very effective. Therefore, the H-Hxl method is recommended for general exploration use. ?? 1982.

  6. Uncertainty quantification and integration of machine learning techniques for predicting acid rock drainage chemistry: a probability bounds approach.

    PubMed

    Betrie, Getnet D; Sadiq, Rehan; Morin, Kevin A; Tesfamariam, Solomon

    2014-08-15

    Acid rock drainage (ARD) is a major pollution problem globally that has adversely impacted the environment. Identification and quantification of uncertainties are integral parts of ARD assessment and risk mitigation, however previous studies on predicting ARD drainage chemistry have not fully addressed issues of uncertainties. In this study, artificial neural networks (ANN) and support vector machine (SVM) are used for the prediction of ARD drainage chemistry and their predictive uncertainties are quantified using probability bounds analysis. Furthermore, the predictions of ANN and SVM are integrated using four aggregation methods to improve their individual predictions. The results of this study showed that ANN performed better than SVM in enveloping the observed concentrations. In addition, integrating the prediction of ANN and SVM using the aggregation methods improved the predictions of individual techniques. PMID:24852616

  7. Effects of acid rock drainage on stocked rainbow trout (Oncorhynchus mykiss): an in-situ, caged fish experiment.

    PubMed

    Todd, Andrew S; McKnight, Diane M; Jaros, Chris L; Marchitto, Thomas M

    2007-07-01

    In-situ caged rainbow trout (Oncorhynchus mykiss) studies reveal significant fish toxicity and fish stress in a river impacted by headwater acid rock drainage (ARD). Stocked trout survival and aqueous water chemistry were monitored for 10 days at 3 study sites in the Snake River watershed, Colorado, U.S.A. Trout mortality was positively correlated with concentrations of metals calculated to be approaching or exceeding conservative toxicity thresholds (Zn, Mn, Cu, Cd). Significant metal accumulation on the gills of fish stocked at ARD impacted study sites support an association between elevated metals and fish mortality. Observations of feeding behavior and significant differences in fish relative weights between study site and feeding treatment indicate feeding and metals-related fish stress. Together, these results demonstrate the utility of in-situ exposure studies for stream stakeholders in quantifying the relative role of aqueous contaminant exposures in limiting stocked fish survival. PMID:17180429

  8. Oxalic-acid leaching of rock, soil, and stream-sediment samples as an anomaly-accentuated technique

    USGS Publications Warehouse

    Alminas, Henry V.; Mosier, Elwin L.

    1976-01-01

    In many instances total-rock and sieved-soil and stream-sediment samples lack the sensitivity and contrast required for reconnaissance exploration and necessary in the search for blind ore deposits. Heavy-mineral concentrates incorporate the required sensitivity and contrast but are overly expensive for two reasons: time-consuming sample preparation is required to obtain them, and they cannot be easily derived from all bulk-sample types. Trace-metal-content comparisons of the oxalic-acid-leachable portions with heavy-mineral concentrates show that the leachates are equal to the heavy-mineral concentrates in sensitivity and contrast. Simplicity of preparation and the resultant cost savings are additional advantages of this proposed method.

  9. Petrogenesis of the Mesozoic Zijinguan mafic pluton from the Taihang Mountains, North China Craton: Petrological and Os-Nd-Sr isotopic constraints

    NASA Astrophysics Data System (ADS)

    Liu, An-Kun; Chen, Bin; Suzuki, Katsuhiko; Liu, Ling

    2010-09-01

    Mantle peridotites show low Re/Os ratios and sub-chondritic 187Os/ 188Os ratios (<0.13), which contrast sharply with the radiogenic Os isotopic composition of continental crust (e.g., 187Os/ 188Os = 6 ˜ 80 for the Archean rocks). This provides a potential to use the Re-Os isotopes of mantle-derived magmas to trace the processes of mantle-crust interaction. We report petrological and Os isotopic data for the Zijinguan Cretaceous mafic pluton from the North China Craton to place constraints on their petrogenesis, mantle source characteristics, and the role of crustal contamination. The mafic pluton consists of hornblende pyroxenites, hornblende gabbros and gabbrodiorites. These rocks are enriched in LILE (e.g., Ba and Sr) and LREE, depleted in HFSE (e.g., Nb, Zr). They possess radiogenic Os isotopic compositions with 187Os/ 188Os = 0.187-0.603, and EM1-like Sr-Nd isotopic compositions (I Sr = 0.7058-0.7066, ɛNd( t) = -13.8 to -18.2). Petrography and elemental data suggest a significant fractionation and accumulation of olivine + pyroxene + hornblende in forming the mafic pluton. Clinopyroxene and plagioclase from the gabbrodiorites show complicated compositional zoning, suggesting a process of magma recharge in the late-stage of magma evolution. This is supported by their higher ɛNd( t) values (-14) than the other two rock types (-15 to -18). The parental magmas to the mafic pluton should be hydrous, which originated from an old, enriched lithospheric mantle, and were significantly contaminated by Precambrian mafic lower crust and TTG gneisses during magma evolution, as is suggested by the highly radiogenic Os- and unradiogenic Nd isotopic compositions of the mafic pluton.

  10. Petrogenetic evolution of the Early Miocene Alaçamdağ volcano-plutonic complex, northwestern Turkey: implications for the geodynamic framework of the Aegean region

    NASA Astrophysics Data System (ADS)

    Erkül, Sibel Tatar

    2012-01-01

    Extensional-tectonic processes have generated extensive magmatic activity that produced volcanic/plutonic rocks along an E-W-trending belt across north-western Turkey; this belt includes granites and coeval volcanic rocks of the Alaçamdağ volcano-plutonic complex. The petrogenesis of the Early Miocene Alaçamdağ granitic and volcanic rocks are here investigated by means of whole-rock Sr-Nd isotopic data along with field, petrographic and whole-rock geochemical studies. Geological and geochemical data indicate two distinct granite facies having similar mineral assemblages, their major distinguishing characteristic being the presence or absence of porphyritic texture as defined by K-feldspar megacrysts. I-type Alaçamdağ granitic stocks have monzogranitic-granodioritic compositions and contain a number of mafic microgranular enclaves of monzonitic, monzodioritic/monzogabbroic composition. Volcanic rocks occur as intrusions, domes, lava flows, dykes and volcanogenic sedimentary rocks having (first episode) andesitic and dacitic-trachyandesitic, and (second episode) dacitic, rhyolitic and trachytic-trachydacitic compositions. These granitic and volcanic rocks are metaluminous, high-K, and calc-alkaline in character. Chondrite-normalised rare earth element patterns vary only slightly such that all of the igneous rocks of the Alaçamdağ have similar REE patterns. Primitive-mantle-normalised multi-element diagrams show that these granitic and volcanic rocks are strongly enriched in LILE and LREE pattern, high (87Sr/86Sr)i and low ɛ Nd( t) ratios suggesting Alaçamdağ volcano-plutonic rocks to have been derived from hybrid magma that originated mixing of co-eval lower crustal-derived more felsic magma and enriched subcontinental lithospheric mantle-derived more mafic magmas during extensional processes, and the crustal material was more dominant than the mantle contribution. The Alaçamdağ volcano-plutonic complex rocks may form by retreat of the Hellenic

  11. Phosphorus leaching in an acid tropical soil "recapitalized" with phosphate rock and triple superphosphate.

    PubMed

    Gikonyo, Esther W; Zaharah, Abdul R; Hanafi, Mohamed M; Anuar, Rahim A

    2010-01-01

    With high rates of phosphorus applied to increase "capital P" as a stock for plant uptake over several years, the question of P leaching is inevitable. We conducted an intact soil column experiment in the field to evaluate P leached from soils treated with triple superphosphate (TSP) and Gafsa phosphate rock (GPR) at 300, 600, and 900 kg P ha-1 with and without integration of cattle manure. The lysimeters, made from PVC tubes of 30-cm length, were inserted into the soil up to the 25-cm depth. The tubes were fitted with a resin bag containing a mixture of cation and anion exchange resin (50:50) at the lower end of the tube inserted into the soil. The tubes, arranged in a completely randomized design, were sampled randomly at 10-week intervals for 12 months. Phosphorus extractable from the top- and subsoil at the end of experiment and leached P were determined. More P was leached out from TSP (threefold) compared to GPR, and the amount of P leached increased with increasing rates of P fertilizer applied. Application of manure intensified the amounts of P leached from TSP, particularly at the 6-month sampling time. There was hardly any substantial P leached from the soil treated with GPR. Thus, for effective and efficient long-term P fertilizer management strategies, choosing the right P fertilizer source and monitoring P losses through leaching has to be done for enhanced fertilizer use efficiency and thus reducing P pollution of ground waters. PMID:20694445

  12. Kilbuck terrane: Oldest known rocks in Alaska

    SciTech Connect

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

    1990-12-01

    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 2,070 {plus minus}16 and 2,040 {plus minus}74 Ma, respectively. Nd isotope data from these rocks suggest that a diorite-tonalite-trondhjemite suite ({epsilon}{sub 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 ({epsilon}{sub Nd}(T) = {minus}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. However, Phanerozoic plutons cutting several continental terranes in Alaska (southern Brooks Range and Ruby, Seward, and Yukon-Tanana terranes) have Nd isotope compositions indicative of Early Proterozoic (or older) crustal components that could be correlative with rocks of the Kilbuck terrane. Rocks with similar igneous ages in cratonal North America are rare, and those few that are known have Nd isotope compositions distinct from those of the Kilbuck terrane. Conversely, provinces with Nd model ages of 2.0-2.1 Ga are characterized by extensive 1.8 Ga or younger plutonism, which is unknown in the Kilbuck terrane. At present the case for a North American parentage of the Kilbuck terrane is not compelling. 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.

  13. Rho/ROCK acts downstream of lysophosphatidic acid receptor 1 in modulating P2X3 receptor-mediated bone cancer pain in rats

    PubMed Central

    Wu, Jing-xiang; Yuan, Xiao-min; Wang, Qiong; Wei, Wang

    2016-01-01

    Background Lysophosphatidic acid receptor 1 and Rho/ROCK signaling is implicated in bone cancer pain development. However, it remains unknown whether the two signaling pathways function together in P2X3 receptor-mediated bone cancer pain. Results In this study, using a rat model of bone cancer, we examined the expression of P2X3 and lysophosphatidic acid receptor 1 in rat dorsal root ganglion neurons and further dissected whether lysophosphatidic acid receptor 1 and Rho/ROCK-mediated pathways interacted in modulating rat pain behavior. Bone cancer was established by inoculating Walker 256 cells into the left tibia of female Wistar rats. We observed a gradual and yet significant decline in mean paw withdrawal threshold in rats with bone cancer, but not in control rats. Our immunohistochemical staining revealed that the number of P2X3- and lysophosphatidic acid receptor 1-positive dorsal root ganglion neurons was significantly greater in rats with bone cancer than control rats. Lysophosphatidic acid receptor 1 blockade with VPC32183 significantly attenuated decline in mean paw withdrawal threshold. Flinching behavior test further showed that lysophosphatidic acid receptor 1 inhibition with VPC32183 transiently but significantly attenuated α,β-meATP-induced increase in paw lift time per minute. Rho inhibition by intrathecal BoTXC3 caused a rapid reversal in decline in mean paw withdrawal threshold of rats with bone cancer. Flinching behavior test showed that BoTXC3 transiently and significantly attenuated α,β-meATP-induced increase in paw lift time per minute. Similar findings were observed with ROCK inhibition by intrathecal Y27632. Furthermore, VPC32183 and BoTXC3 effectively aborted the appearance of lysophosphatidic acid-induced calcium influx peak. Conclusions Lysophosphatidic acid and its receptor LPAR1, acting through the Rho-ROCK pathway, regulate P2X3 receptor in the development of both mechanical and spontaneous pain in bone cancer. PMID:27094551

  14. A petrologic comparison of Triassic plutonism in the San Gabriel and Mule Mountains, southern California

    SciTech Connect

    Barth, A.P. ); Tosdal, R.M.; Wooden, J.L. )

    1990-11-10

    Triassic magmatism in the southwest US Cordillera forms a semicontinuous magmatic arc extending from northwestern Nevada to southeastern California. Quartz monzodioritic and quartz monzonitic rocks and associated diorites and granites are widespread in southeastern California, and the authors suggest that these rocks represent exposure of a structurally deeper part of the Triassic arc, where it was emplaced into comparatively thick Proterozoic crust. Elemental and isotopic data suggest that Triassic quartz monzodiorites and quartz monzonites in the Mule and San Gabriel Mountains were derived from a relatively undepleted, nonradiogenic mafic lithospheric source, with virtually no upper crustal interaction. Very limited data for associated Triassic ( ) diorites indicate a wide range in composition and a surprisingly radiogenic isotopic signature. Younger Triassic( ) granites record a strong geochemical signature of interaction with continental crust, including inherited zircon and high initial Sr ratios but comparatively less radiogenic Pb isotopic compositions. The major and trace element geochemistry of Late Triassic plutonic rocks in southeastern California is similar in many respects to akalic components of the Triassic arc in the Mojave Desert. However, contemporaneous rocks farther north have a calc-alkalic signature, perhaps reflecting the variation in age and composition of lithosphere across which the Triassic arc was constructed.

  15. A topaz- and amazonite-bearing leucogranite pluton in eastern Xinjiang, NW China and its zoning

    NASA Astrophysics Data System (ADS)

    Gu, Lian-xing; Zhang, Zun-zhong; Wu, Chang-zhi; Gou, Xiao-qin; Liao, Jing-juan; Yang, Hao

    2011-10-01

    The highly evolved Baishitouquan (BST) beryl-mineralised and topaz-bearing amazonite granite pluton is situated in the eastern Tianshan orogen of northwestern China. This pluton exhibits five well-exposed lithological zones, which, gradational from the lowest level, are leucogranite (zone-a), amazonite-bearing granite (zone-b), amazonite granite (zone-c), topaz-bearing amazonite granite (zone-d) and topaz albite granite (zone-e). The rocks are composed mainly of quartz, albite, and K-feldspar with varying amounts of topaz and amazonite. Quartz and topaz phenocrysts are the earliest phases that crystallised from the melt. Amazonite which replaced albite and K-feldspar was formed at the late magmatic stage or during the magmatic-hydrothermal transition. Geochemically, this pluton is characterised by high F (>2 wt.%) and Rb (499.5-1087.04 ppm), low P 2O 5 (⩽0.06 wt.%), Na 2O > K 2O, A/NKC = 1.00-1.11, low ratios of K/Rb, Al/Ga, Y/Ho, Zr/Ha and Nb/Ta, Σ14 REE = 28.6-231.9 ppm with gull wing-shaped distribution patterns (La CN/Lu CN = 0.11-0.68, Eu/Eu * = 0.0005-0.0110) and tetrad effects, and δ 18O = 9.75-7.32‰. Melt and fluid-melt inclusions coexist with liquid and vapour inclusions. The rocks were originated from a highly evolved granitic magma. The BST pluton exhibits transition in the following aspects from zone-a to zone-e: (1) As quartz and topaz phenocrysts progressively increase in size and crystal euhedral shape, rock textures change from equigranular to porphyritic. (2) Amazonite begins to appear in zone-b and becomes most concentrated in zone-c, whereas topaz begins to appear in zone-d becoming highly concentrated in zone-e. (3) Li and (Al + Ti) increase in white mica. (4) Petrochemically, there are general trends of increasing F, Al 2O 3 and Na 2O, and decreasing SiO 2, (Fe 2O 3 + FeO + MgO + MnO) and K 2O. Plots of normative compositions on the Qz-Ab-Or diagram move gradually towards the Ab apex. (5) Overall, Cr, Ni, Co, V, W, Nb, Zr, U, Th and Y

  16. Magma accumulation rates and thermal histories of plutons of the Sierra Nevada batholith, CA

    NASA Astrophysics Data System (ADS)

    Davis, Jesse W.; Coleman, Drew S.; Gracely, John T.; Gaschnig, Richard; Stearns, Michael

    2012-03-01

    Zircon U-Pb geochronology results indicate that the John Muir Intrusive Suite of the central Sierra Nevada batholith, California, was assembled over a period of at least 12 Ma between 96 and 84 Ma. Bulk mineral thermochronology (U-Pb zircon and titanite, 40Ar/39Ar hornblende and biotite) of rocks from multiple plutons comprising the Muir suite indicates rapid cooling through titanite and hornblende closure following intrusion and subsequent slow cooling through biotite closure. Assembly of intrusive suites in the Sierra Nevada and elsewhere over millions of years favors growth by incremental intrusion. Estimated long-term pluton assembly rates for the John Muir Intrusive Suite are on the order of 0.001 km3 a-1 which is inconsistent with the rapid magma fluxes that are necessary to form large-volume magma chambers capable of producing caldera-forming eruptions. If large shallow crustal magma chambers do not typically develop during assembly of large zoned intrusive suites, it is doubtful that the intrusive suites represent cumulates left behind following caldera-forming eruptions.

  17. Zircon U-Pb ages, geochemical and Sr-Nd-Pb-Hf isotopic constraints on petrogenesis of the Tarom-Olya pluton, Alborz magmatic belt, NW Iran

    NASA Astrophysics Data System (ADS)

    Nabatian, Ghasem; Jiang, Shao-Yong; Honarmand, Maryam; Neubauer, Franz

    2016-02-01

    A petrological, geochemical and Sr-Nd-Pb isotopic study was carried out on the Tarom-Olya pluton, Iran, in the central part of the Alpine-Himalayan orogenic belt. The pluton is composed of diorite, monzonite, quartz-monzonite and monzogranite, which form part of the Western Alborz magmatic belt. LA-ICP-MS analyses of zircons yield ages from 35.7 ± 0.8 Ma to 37.7 ± 0.5 Ma, interpreted as the ages of crystallization of magmas. Rocks from the pluton have SiO2 contents ranging from 57.0 to 69.9 wt.%, high K2O + Na2O (5.5 to 10.3 wt.%) and K2O/Na2O ratio of 0.9 to 2.0. Geochemical discrimination criteria show I-type and shoshonitic features for the studied rocks. All investigated rocks are enriched in light rare earth elements (LREEs), large ion lithophile elements (LILEs), depleted in high-field strength elements (HFSEs), and show weak or insignificant Eu anomalies (Eu/Eu* = 0.57-1.02) in chondrite-normalized trace element patterns. The Tarom-Olya pluton samples also show depletions in Nb, Ta and Ti typical of subduction-related arc magmatic signatures. The samples have relatively low ISr (0.7047-0.7051) and positive εNd(36 Ma) (+ 0.39 to + 2.10) values. The Pb isotopic ratios show a (206Pb/204Pb)i ratio of 18.49-18.67, (207Pb/204Pb)i ratio of 15.58-15.61 and (208Pb/204Pb)i ratio of 38.33-38.77. The εHf(t) values of the Tarom-Olya pluton zircons vary from - 5.9 to + 8.4, with a peak at + 2 to + 4. The depleted mantle Hf model ages for the Tarom-Olya samples are close to 600 Ma. These isotope evidences indicate contribution of juvenile sources in petrogenesis of the Tarom-Olya pluton. Geochemical and isotopic data suggest that the parental magma of the Tarom-Olya pluton was mainly derived from a sub-continental lithospheric mantle source, which was metasomatized by fluids and melts from the subducted Neotethyan slab with a minor crustal contribution. Subsequent hot asthenospheric upwelling and lithospheric extension caused decompression melting in the final stage of

  18. Acid neutralizing capacity and leachate results for igneous rocks, with associated carbon contents of derived soils, Animas River AML site, Silverton, Colorado

    USGS Publications Warehouse

    Yager, Douglas B.; Stanton, Mark R.; Choate, LaDonna M.; Burchell, Alison

    2009-01-01

    Mine planning efforts have historically overlooked the possible acid neutralizing capacity (ANC) that local igneous rocks can provide to help neutralize acidmine drainage. As a result, limestone has been traditionally hauled to mine sites for use in neutralizing acid drainage. Local igneous rocks, when used as part of mine life-cycle planning and acid mitigation strategy, may reduce the need to transport limestone to mine sites because these rocks can contain acid neutralizing minerals. Igneous hydrothermal events often introduce moderately altered mineral assemblages peripheral to more intensely altered rocks that host metal-bearing veins and ore bodies. These less altered rocks can contain ANC minerals (calcite-chlorite-epidote) and are referred to as a propylitic assemblage. In addition, the carbon contents of soils in areas of new mining or those areas undergoing restoration have been historically unknown. Soil organic carbon is an important constituent to characterize as a soil recovery benchmark that can be referred to during mine cycle planning and restoration.
    This study addresses the mineralogy, ANC, and leachate chemistry of propylitic volcanic rocks that host polymetallic mineralization in the Animas River watershed near the historical Silverton, Colorado, mining area. Acid titration tests on volcanic rocks containing calcite (2 – 20 wt %) and chlorite (6 – 25 wt %), have ANC ranging from 4 – 146 kg/ton CaCO3 equivalence. Results from a 6-month duration, kinetic reaction vessel test containing layered pyritic mine waste and underlying ANC volcanic rock (saturated with deionized water) indicate that acid generating mine waste (pH 2.4) has not overwhelmed the ANC of propylitic volcanic rocks (pH 5.8). Sequential leachate laboratory experiments evaluated the concentration of metals liberated during leaching. Leachate concentrations of Cu-Zn-As-Pb for ANC volcanic rock are one-to-three orders of magnitude lower when compared to leached

  19. Metamorphic facies map of Southeastern Alaska; distribution, facies, and ages of regionally metamorphosed rocks

    USGS Publications Warehouse

    Dusel-Bacon, Cynthia; Brew, D.A.; Douglass, S.L.

    1996-01-01

    Nearly all of the bedrock in Southeastern Alaska has been metamorphosed, much of it under medium-grade conditions during metamorphic episodes that were associated with widespread plutonism. The oldest metamorphisms affected probable arc rocks near southern Prince of Wales Island and occurred during early and middle Paleozoic orogenies. The predominant period of metamorphism and associated plutonism occurred during Early Cretaceous to early Tertiary time and resulted in the development of the Coast plutonic-metamorphic complex that extends along the inboard half of Southeastern Alaska. Middle Tertiary regional thermal metamorphism affected a large part of Baranof Island.

  20. Palaeomagnetic constraints from granodioritic plutons (Jiaodong Peninsula): New insights on Late Mesozoic continental extension in Eastern Asia

    NASA Astrophysics Data System (ADS)

    Charles, Nicolas; Chen, Yan; Augier, Romain; Gumiaux, Charles; Lin, Wei; Faure, Michel; Monié, Patrick; Choulet, Flavien; Wu, Fuyuan; Zhu, Rixiang; Wang, Qingchen

    2011-08-01

    Mechanism and kinematics of the Late Mesozoic continental extension event of Eastern Asia are still debated. In order to better constrain its evolution, two granodioritic plutons of the Jiaodong Peninsula have been chosen as targets for a time-constrained palaeomagnetic study. Indeed, plutons are devoid of visible deformation, did not experience rotation along horizontal axis and are precisely dated by U/Pb and 40Ar/ 39Ar methods. Multidomain (MD) magnetite has been identified as the principal magnetic remanent carrier. The interpolation of existing and new U/Pb and 40Ar/ 39Ar ages revealed that characteristic remanent magnetisation was acquired in a narrow range of 116 ± 2 Ma. Twenty out of 27 sites present stable magnetic directions calculated from high-temperature or high-coercive components. The observations of the solo normal magnetic polarity for this palaeomagnetic collection and of the magnetic remanent age consistent with the Cretaceous Normal Superchron (CNS) argue that the characteristic magnetic remanence may be considered as primary. Detailed field observations of the intrusive relationship between the plutons and country rocks and Anisotropy of Magnetic Susceptibility (AMS) study reveal the absence of the subsequent deformation of plutons, or rigid rotation of plutons along a horizontal axis. Two palaeomagnetic poles have been therefore calculated from these plutons. Among 12 out 15 Cretaceous palaeomagnetic poles, including the two new poles provided by this study, from the Jiaodong Peninsula and on both sides of Tan-Lu and Muping-Jimo faults are statistically consistent. As a result, the Jiaodong Peninsula behaved as a rigid block as internal deformation appears negligible. The remaining three derived poles are probably due to the secular variation or/and the vicinity of fault zones near of the palaeomagnetic sampling site. Thus, they can not be applied to the peninsula-scaled tectonics. Comparison of these time-constrained Cretaceous

  1. Domain-level rocking motion within a polymerase that translocates on single-stranded nucleic acid

    SciTech Connect

    Li, Huiyung; Li, Changzheng; Zhou, Sufeng; Poulos, Thomas L.; Gershon, Paul David

    2013-04-01

    An X-ray crystallographic structure is described for unliganded Vaccinia virus poly(A) polymerase monomer (VP55), showing the first domain-level structural isoforms among either VP55, it’s processivity factor VP39, or the VP55-VP39 heterodimer. The occurrence of domain-level motion specifically in monomeric VP55 is consistent with the finding that the monomeric protein undergoes saltatory translocation whereas the heterodimer does not. Vaccinia virus poly(A) polymerase (VP55) is the only known polymerase that can translocate independently with respect to single-stranded nucleic acid (ssNA). Previously, its structure has only been solved in the context of the VP39 processivity factor. Here, a crystal structure of unliganded monomeric VP55 has been solved to 2.86 Å resolution, showing the first backbone structural isoforms among either VP55 or its processivity factor (VP39). Backbone differences between the two molecules of VP55 in the asymmetric unit indicated that unliganded monomeric VP55 can undergo a ‘rocking’ motion of the N-terminal domain with respect to the other two domains, which may be ‘rigidified’ upon VP39 docking. This observation is consistent with previously demonstrated experimental molecular dynamics of the monomer during translocation with respect to nucleic acid and with different mechanisms of translocation in the presence and absence of processivity factor VP39. Side-chain conformational changes in the absence of ligand were observed at a key primer contact site and at the catalytic center of VP55. The current structure completes the trio of possible structural forms for VP55 and VP39, namely the VP39 monomer, the VP39–VP55 heterodimer and the VP55 monomer.

  2. Granitoid emplacement by multiple sheeting during Variscan dextral transpression: The Saint-Laurent - La Jonquera pluton (Eastern Pyrenees)

    NASA Astrophysics Data System (ADS)

    Olivier, Philippe; Druguet, Elena; Castaño, Lina Marcela; Gleizes, Gérard

    2016-01-01

    The structural study of the Saint-Laurent - La Jonquera pluton (Eastern Pyrenees), a Variscan composite laccolithic intrusion emplaced in metasedimentary and gneissic rocks of the Roc de Frausa dome, by means of the anisotropy of magnetic susceptibility (AMS) technique has allowed the determination of the nature and orientation of its magmatic fabrics. The magmatic foliation has a predominant NE-SW strike and the mean lineation is also NE-SW trending with a shallow plunge. A strain gradient is measured so that the tonalites to granodiorites that form the basal parts of the pluton, and are intruded into amphibolite-facies metamorphic rocks, recorded the highest anisotropies, whereas the monzogranites and leucogranites, emplaced into upper crustal, low-grade metamorphic rocks, are weakly deformed. These results point to the synkinematic sequential emplacement of multiple granitoid sheets, from less to more differentiated magmatic stages, during the Late Carboniferous D2 event characterized by an E-W-trending dextral transpression. The magmatic foliation appears locally disturbed by the effects of two tectonic events. The first of them (D3) produced mylonitization of granitoids along NW-SE retrograding shear zones and open folds in the host Ediacaran metasediments of the Roc de Frausa massif, likely during late Variscan times. Interference between D2 and D3 structures was responsible for the dome geometry of the whole Roc de Frausa massif. The second and last perturbation consisted of local southward tilting of the granitoids coupled to the Mesozoic-Cenozoic cover during the Alpine.

  3. Exploring the plutonic crust at a fast-spreading ridge:new drilling at Hess Deep

    SciTech Connect

    Gillis, Kathryn M.; Snow, Jonathan E.; Klaus, Adam; Guerin, Gilles; Abe, Natsue; Akizawa, Norikatsu; Ceuleneer, Georges; Cheadle, Michael J.; Adriao, Alden de Brito; Faak, Kathrin; Falloon, Trevor J.; Friedman, Sarah A.; Godard, Marguerite M.; Harigane, Yumiko; Horst, Andrew J.; Hoshide, Takashi; Ildefonse, Benoit; Jean, Marlon M.; John, Barbara E.; Koepke, Juergen H.; Machi, Sumiaki; Maeda, Jinichiro; Marks, Naomi E.; McCaig, Andrew M.; Meyer, Romain; Morris, Antony; Nozaka, Toshio; Python, Marie; Saha, Abhishek; Wintsch, Robert P.

    2013-02-28

    Integrated Ocean Drilling Program (IODP) Hess Deep Expedition 345 was designed to sample lower crustal primitive gabbroic rocks that formed at the fast-spreading East Pacific Rise (EPR) in order to test models of magmatic accretion and the intensity of hydrothermal cooling at depth. The Hess Deep Rift was selected to exploit tectonic exposures of young EPR plutonic crust, building upon results from ODP Leg 147 as well as more recent submersible, remotely operated vehicle, and near-bottom surveys. The primary goal was to acquire the observations required to test end-member crustal accretion models that were in large part based on relationships from ophiolites, in combination with mid-ocean ridge geophysical studies. This goal was achieved with the recovery of primitive layered olivine gabbros and troctolites with many unexpected mineralogical and textural relationships, such as the abundance of orthopyroxene and the preservation of delicate skeletal olivine textures.

  4. Magmatic and solid state structures of the Abu Ziran pluton: Deciphering transition from thrusting to extension in the Eastern Desert of Egypt

    NASA Astrophysics Data System (ADS)

    Fritz, Harald; Loizenbauer, Jürgen; Wallbrecher, Eckart

    2014-11-01

    The 606 Ma old Abu Ziran granite of the Eastern Desert of Egypt intruded the southern margin of the Meatiq dome in a sinistral shear extensional setting. Its emplacement was enabled by a system of NW-trending sinistral shears, related Riedel shears and N-S extensional shear zones and faults. Magmatic flow was east-directed and controlled by Riedel shears that progressively rotated to an orientation favourable for extension. Strain markers that document magmatic flow show eastward decreasing strain together with strain increase from pluton centre to margins. This is explained by Newtonian flow between non-parallel plates and differences in flow velocities across the pluton. Solid state fabrics including shear fabrics, orientation of late magmatic dykes and quartz tension gashes, together with quartz C-axes distributions, document southward extensional shear within the solidified pluton and adjacent host rocks. Extensional shear is correlated with exhumation of the Meatiq dome coeval and soon after pluton solidification (585 Ma). Pressure temperature evolutionary paths, derived from fluid inclusions, show a clockwise path with exhumation by isothermal decompression in the Meatiq dome. By contrast, the overlying volcanosedimentary nappes experienced an anti-clockwise path released by temperature rise due to pluton emplacement followed by isobaric cooling. Quartz fabrics indicate high-temperature coaxial N-S flow in the northern Meatiq dome and lower-temperature, non-coaxial southward flow within the overlaying superficial nappe. This is explained by the exhumation process itself that progressively localised into simple shear domains when rocks approached higher crustal levels. Late extension at ca. 580 Ma was pure shear dominated and resulted in reversal of shear, now dextral, in the western Meatiq shear zone.

  5. Pseudomonas fluorescens ATCC 13525 containing an artificial oxalate operon and Vitreoscilla hemoglobin secretes oxalic acid and solubilizes rock phosphate in acidic alfisols.

    PubMed

    Yadav, Kavita; Kumar, Chanchal; Archana, G; Naresh Kumar, G

    2014-01-01

    Oxalate secretion was achieved in Pseudomonas fluorescens ATCC 13525 by incorporation of genes encoding Aspergillus niger oxaloacetate acetyl hydrolase (oah), Fomitopsis plaustris oxalate transporter (FpOAR) and Vitreoscilla hemoglobin (vgb) in various combinations. Pf (pKCN2) transformant containing oah alone accumulated 19 mM oxalic acid intracellularly but secreted 1.2 mM. However, in the presence of an artificial oxalate operon containing oah and FpOAR genes in plasmid pKCN4, Pf (pKCN4) secreted 13.6 mM oxalate in the medium while 3.6 mM remained inside. This transformant solubilized 509 μM of phosphorus from rock phosphate in alfisol which is 4.5 fold higher than the Pf (pKCN2) transformant. Genomic integrants of P. fluorescens (Pf int1 and Pf int2) containing artificial oxalate operon (plac-FpOAR-oah) and artificial oxalate gene cluster (plac-FpOAR-oah, vgb, egfp) secreted 4.8 mM and 5.4 mM oxalic acid, released 329 μM and 351 μM P, respectively, in alfisol. The integrants showed enhanced root colonization, improved growth and increased P content of Vigna radiata plants. This study demonstrates oxalic acid secretion in P. fluorescens by incorporation of an artificial operon constituted of genes for oxalate synthesis and transport, which imparts mineral phosphate solubilizing ability to the organism leading to enhanced growth and P content of V. radiata in alfisol soil. PMID:24705024

  6. High temperature fracturing and ductile deformation during cooling of a pluton: The Lake Edison granodiorite (Sierra Nevada batholith, California)

    NASA Astrophysics Data System (ADS)

    Pennacchioni, Giorgio; Zucchi, Eleonora

    2013-05-01

    In the Bear Creek area of the Sierra Nevada batholith, California, the high temperature postmagmatic deformation structures of the Lake Edison granodiorite include steeply-dipping orthogneiss foliations, joints, and ductile shear zones that nucleated on joints and leucocratic dykes. Exploitation of segmented joints resulted in sharply bounded, thin shear zones and in large slip gradients near the shear zone tips causing the deformation of the host rock at contractional domains. The orthogneiss foliation intensifies towards the contact with the younger Mono Creek granite and locally defines the dextral Rosy Finch Shear Zone (RFSZ), a major kilometre-wide zone crosscutting the pluton contacts. Joints predominantly strike at N70-90°E over most of the Lake Edison pluton and are exploited as sinistral shear zones, both within and outside the RFSZ. In a narrow (˜250 m thick) zone at the contact with the younger Mono Creek granite, within the RFSZ, the Lake Edison granodiorite includes different sets of dextral and sinistral shear zones/joints (the latter corresponding to the set that dominates over the rest of the Lake Edison pluton). These shear zones/joints potentially fit with a composite Y-R-R' shear fracture pattern associated with the RFSZ, or with a pattern consisting of Y-R-shear fractures and rotated T' mode I extensional fractures. The mineral assemblage of shear zones, and the microstructure and texture of quartz mylonites indicate that ductile deformation occurred above 500 °C. Joints and ductile shearing alternated and developed coevally. The existing kinematic models do not fully capture the structural complexity of the area or the spatial distribution of the deformation and magmatic structures. Future models should account more completely for the character of ductile and brittle deformation as these plutons were emplaced and cooled.

  7. Petrogenesis of the Dengzhazi A-type pluton from the Taihang-Yanshan Mesozoic orogenic belts, North China Craton

    NASA Astrophysics Data System (ADS)

    Xiaolu, Niu; Bin, Chen; Xu, Ma

    2011-05-01

    The voluminous Mesozoic monzonitic to monzogranitic rocks in the north China craton (NCC) mostly show high-K calc-alkaline and I-type granitoids features. The Dengzhazi granitic pluton, however, shows features typical of A-type granites. The A-type pluton was emplaced in the Taihang-Yanshan orogenic belts of the northern margin of the NCC, with zircon U-Pb ages of around 140 Ma. The Dengzhazi A-type granites are characterized by high SiO 2 (70.2-77.7 wt.%), K 2O + Na 2O, Zr, Nb, Ga, Zn, and Y contents as well as high Ga/Al ratios, and extremely low CaO, Ba, Sr. In addition, they show high zircon saturation temperatures (870-950 °C), low water and low oxygen fugacity. All these features are consistent with the A-type affinity of the pluton. In situ Hf isotopic analyses for the dated zircons show relatively small range of ɛHf( t) (-13 to -17). They also have homogeneous initial Nd isotopic compositions with ɛNd( t) ranging from -15.1 to -16.3. The Hf and Nd isotopic data suggest that the Dengzhazi A-type granites originated from a homogeneous crustal source, probably the Archean mafic-intermediate granulites. Taking into account the high temperatures, the low H 2O and fO 2 of the magma system, we believe that partial melting of the granulites should have been triggered by underplating of mantle-derived magmas at the base of the mafic lower crust in an extensional regime. The Dengzhazi A-type granite is the oldest pluton of the Taihang-Yanshan Mesozoic magma belts, signifying the commencement of extensive underplating of mafic magmas, and thus of lithospheric thinning in the northern NCC.

  8. Selective Precipitation of Thorium lodate from a Tartaric Acid-Hydrogen Peroxide Medium Application to Rapid Spectrophotometric Determination of Thorium in Silicate Rocks and in Ores

    USGS Publications Warehouse

    Grimaldi, F.S.

    1957-01-01

    This paper presents a selective iodate separation of thorium from nitric acid medium containing d-tartaric acid and hydrogen peroxide. The catalytic decomposition of hydrogen peroxide is prevented by the use of 8quinolinol. A few micrograms of thorium are separated sufficiently clean from 30 mg. of such oxides as cerium, zirconium, titanium, niobium, tantalum, scandium, or iron with one iodate precipitation to allow an accurate determination of thorium with the thoronmesotartaric acid spectrophotometric method. The method is successful for the determination of 0.001% or more of thorium dioxide in silicate rocks and for 0.01% or more in black sand, monazite, thorite, thorianite, eschynite, euxenite, and zircon.

  9. Petrochemistry of ultrapotassic tephrites and associated cognate plutonic xenoliths with carbonatite affinities from the late Quaternary Qa’le Hasan Ali maars, central Iran

    NASA Astrophysics Data System (ADS)

    Saadat, S.; Stern, C. R.; Moradian, A.

    2014-08-01

    The Quaternary Qa’le Hasan Ali (QHA) maars in central Iran occur at the intersection of the north-south Nayband fault, which defines the western boundary of the Lut micro-continental block, and a system of northwest-southeast faults, subparallel to the Zagros suture zone, that formed during the Arabian-Eurasian collision. These post-collisional maars intrude Eocene volcanic rocks of the Urumieh-Dokhtar magmatic belt, which was generated by the subduction of Neotethys oceanic lithosphere below Iran. The highly potassic, Ti-phlogopite + Mg-rich (Fo89-92) olivine + diopside-augite + aegirine-augite basanite tephrites forming the tuff rims of the QHA maars contain tephrite-coated plutonic xenoliths, some of which are interpreted as co-genetic with the tephrites based on their similar mineralogy and Sr isotopic composition (87Sr/86Sr = 0.70590). Cognate plutonic xenoliths have up to ∼20 vol% calcite, considered to be magmatic calcite because of (1) its grain size, which is similar to feldspars and aegirine-augite pyroxenes in these rocks, (2) the occurrence of fine-grained inclusions of pyroxene and apatite within these calcite grains, and (3) the similarity of the Sr-isotopic composition of this calcite with the other minerals in these rocks. The fact that the magmatic calcite has remained intact and did not volatilize during the transport of these xenoliths to the surface in the hot tephrite magma implies a short transit time, indicating that they are samples of a shallow plutonic complex, as does the presence of anorthoclase in these plutonic xenoliths. Their high modal proportion of magmatic calcite suggests that this shallow plutonic complex has affinities with carbonatites. The magmatic calcite-bearing plutonic xenoliths have high LREE/HREE ratios and contain REE-rich allanite (with up to ∼20 wt% LREE) and britholite (∼60 wt% LREE) that make up ∼3 modal percent of the most calcite-rich samples. Similar to many post-collisional highly potassic rocks

  10. Emplacement mechanism of the Middle-Late Jurassic Qitianling pluton and its implications on the Mesozoic tectonics of South China Block

    NASA Astrophysics Data System (ADS)

    Liu, Hongsheng; Chen, Yan; Faure, Michel; Scaillet, Bruno; Wang, Bo; Martelet, Guillaume; Huang, Fangfang; Zhu, Jinchu; Wang, Rucheng; Erdmann, Saskia

    2016-04-01

    The widespread Mesozoic magmatism that extends about 1500km along the NE-SW strike and 800km wide in the southeastern part of the South China Block is a remarkable feature that has attracted the attention of geoscientists since 1940's. Numerous studies have been carried out, and consequently, several geodynamic models related to the emplacement mechanism have been proposed, based essentially on petrology, geochronology, and (isotopic) geochemistry. Recently, a general consensus is apparently achieved within the geosciences community on the tectonic contexts of the South China Block during the Triassic (compressive) and Cretaceous (extensive) periods, however the tectonic setting of the Jurassic is still in debate, moreover the Jurassic magmatism is closely related to abundant mineralization of rare metal elements. Due to the similarities in age, rock type and major geochemical feature of Jurassic granite, the Qitianling granitic pluton, situated in the Nanling area and dated at ca. 157 Ma, was chosen as the target of this study among 41 visited plutons. Previous studies divide the Qitianling pluton into three petrographic facies, namely: i) Bt + Qtz + Fsd + Amp, ii) Bt + Qtz + Fsd + (Amp) , iii) Bt + Qtz + Fsd. Zircon U-Pb dating indicate the age peak of these different facies at 161Ma, 157-156Ma and 149Ma, respectively. The field observation shows that: 1) the granite is isotropic without visible preferred mineral orientation or deformation; 2) the contact between the granite and country rocks is sharp, with a 1-10m narrow thermal aureole, but without any visible deformation. The microscopic observation on the thin sections of wall rocks and granite doesn't show any mineral preferred orientation consisting to the field observation. Therefore, a total of 53 sampling sites and 318 oriented cores were collected from the Qitianling pluton for an Anisotropy of Magnetic Susceptibility (AMS) study. The investigation on rock magnetism shows the pseudo

  11. Geology and geochemistry of the Mount Riley-Mount Cox pluton, Dona Ana County, New Mexico

    SciTech Connect

    Zimbelman, D.R.; Siems, D.F.; Kilburn, J.E.; Hubert, A.E.

    1985-01-01

    The Mount Riley-Mount Cox area is comprised of a relatively homogeneous pluton of rhyodacite rising some 1600 feet above the La Mesa surface. The pluton, of apparent Tertiary age, intrudes Cretaceous sedimentary rocks and Tertiary ( ) latite and tuff. The rhyodacite is holocrystalline, light gray to pinkish gray, porphyritic to microporphyritic, and locally banded. Phenocrysts include hornblende, quartz, biotite, and calcite. The phenocrysts range in size from 0.2 to 2 mm and make up one to fifteen percent of the rock. The phenocrysts often display a glomerophyric texture within a trachytic groundmass. The groundmass ranges from cryptocrystalline to very fine grained and is composed of plagioclase, quartz, potassium feldspar, hornblende/biotite, and iron-oxide material. Locally, the rhyodacite displays millimeter-scale banding and a poikilitic texture consisting of quartz oikiocrysts and plagioclase chadocrysts. The rhyodacite averages 68.74%, SiO/sub 2/, 0.39% TiO/sub 2/, 16.40% Al/sub 2/O/sub 3/, 2.87% Fe/sub t/, 0.10% MnO, 1.21% MgO, 2.56% CaO, 3.79% Na/sub 2/O, and 3.96% K/sub 2/O. The rhyodacite is cut by veins and veinlets of brown to white calcite. The veins attain a maximum thickness of one meter, are locally bordered by calcite-cemented breccia zones, and locally include pyrite. The veins trend north or northwest, consistent with regional trends for the Rio Grande rift and the Texas Lineament, respectively. Sixty-five samples of rhyodacite, breccia, and vein were analyzed for 31 elements by emission-spectrographic methods. Trace-element data suggestive of hydrothermal mineralization was not recognized.

  12. Petrology and geochemistry of the Russian peak pluton, Klamath Mountains, northern California

    SciTech Connect

    Cotkin, S.J.

    1987-01-01

    The Jurassic Russian Peak pluton consists of an older peridotite-to-quartz diorite complex intruded by younger granodiorite. U-Pb ages of 159 Ma have been obtained for both units. The peridotite-to-quartz diorite complex consists principally of quartz diorite; however, cumulate ultramafic rocks occur where it is in contact with Ordovician serpentinite, and the following zonation from serpentinite to quartz diorite is present: peridotite, pyroxenite, hornblendite, eucrite, and diorite. In order to evaluate the petrogenesis of the pluton a combination of field, petrographic, microprobe, X-ray fluorescence, and instrumental neutron activation analysis, and Rb-Sr data have been collected. Major and trace element modeling indicates that quartz-rich quartz diorite formed by crystallization, quartz-poor quartz diorite by accumulation of crystals plus trapped liquid, and ultramafic rocks by assimilation of serpentinite. Granodiorite on the other hand can be modeled by crystallization alone, with the precipitation of plagioclase, amphibole, and biotite accounting for the major and minor element variations. REE modeling indicates that a garnet-clinopyroxene amphibolite is a plausible source. A variety of techniques have been used to decipher the conditions of crystallization in each unit, including a comparison of paragenesis with crystallization experiments, geological thermometry and barometry, and phase equilibria. Pressure of intrusion is considered to have been approximately 3 kbar. The peridotite-to-quartz diorite complex intruded at about 1000/sup 0/C and was completely crystalline at 790/sup 0/C. Granodiorite intruded at somewhat lower temperatures and was completely crystalline at about 700/sup 0/C. The oxygen fugacity for both units was slightly above QFM. At its solidus, granodiorite was saturated with H/sub 2/O, which may account for the pervasive deuteric alteration of this unit.

  13. Review of potential host rocks for radioactive waste disposal in the Piedmont Province of Georgia

    SciTech Connect

    Wenner, D.B.; Gillon, K.A.

    1980-10-01

    A literature study was conducted on the Piedmont province of Georgia to designate areas that may be favorable for field exploration for consideration of a repository for storage of radioactive waste. The criteria utilized in such a designation was based upon consideration of the rock unit having favorable geological, geotechnical, and geohydrological features. The most important are that the rock unit have: (1) satisfactory unit dimensions (> 100 km/sup 2/ outcrop area and at least 1500 meters (approx. 5000 feet) depth of a continuous rock type); and (2) acceptable geohydrological conditions. Among all rock types, it is concluded that the granites of the large post-metamorphic plutons and large, homogeneous orthogneissic units offer the most favorable geologic settings for exploration for siting a radioactive waste repository. Virtually all other rock types, including most metavolcanic and metasedimentary lithologies have unacceptable unit dimensions, generally unfavorable geohydrologic settings, and deleterious mechanical and physical geotechnical properties. After consideration of all major lithologies that comprise the Georgia Piedmont, the following units were deemed favorable: (1) the Elberton Pluton; (2) the Siloam Pluton; (3) the Sparta Pluton; (4) two unnamed plutons adjacent to the Snelson body of S.W. Georgia; (5) the Lithonia Gneiss; (6) basement orthogneisses and charnockites of the Pine Mountain Belt.

  14. Treatment and prevention of ARD using silica micro encapsulation[Acid Rock Drainage

    SciTech Connect

    Mitchell, P.; Rybock, J.; Wheaton, A.

    1999-07-01

    In response to the known drawbacks of liming and the ever-increasing regulatory demands on the mining industry, KEECO has developed a silica micro encapsulation (SME) process. SME is a cost-effective, high performance reagent that is utilized in conjunction with simple chemical delivery systems. By encapsulating metals in a silica matrix formation and rapidly precipitating them into a sand-like sludge, it offers all the advantages of liming without the negative drawbacks. Utilizing an injection technique via a high shear mixing device, a slurry form of the SME product called KB-1{trademark} was applied to ARD at the Bunker Hill Mine in Idaho and to ARD pumped from collection ponds at a remote mine site in the Sierra Nevada Mountains. Flow rates at both sites ranged form 500 to 800 gallons per minute. Treated water from the Bunker Hill Mine operation achieved the site's NPDES criteria for all evaluated metals and US Drinking Water quality for arsenic, cadmium, chromium, lead and zinc with a dosage rate of 1.34 grams KB-1{trademark} per liter. Treated water from the Sierra Nevada project focused on the control of aluminum, arsenic, copper, iron and nickel. All water samples displayed a >99.5% reduction in these metals, as well as an 84%--87% reduction in the concentration of sulfate. Testing on sludge generated form both operations achieved TCLP Action Limits. The SME process is currently under evaluation as a means to coat the pyrite surfaces of newly generated mine tailings to prevent oxidation and future acid generation.

  15. Natural radioactivity and radiation index of the major plutonic bodies in Greece.

    PubMed

    Papadopoulos, A; Christofides, G; Koroneos, A; Papadopoulou, L; Papastefanou, C; Stoulos, S

    2013-10-01

    The natural radioactivity of the major plutonic bodies in Greece, as well as the assessment of any potential health hazard due to their usage as decorative building materials is studied. One hundred and twenty one samples from every major plutonic body in Greece, including various rock-types from gabbro to granite, have been measured for their natural radioactivity using γ-spectrometry methodology. According to the experimental results, the natural radioactivity levels were ranged up to 315 Bq kg(-1) for (226)Ra, up to 376 Bq kg(-1) for (232)Th and up to 1632 Bq kg(-1) for (40)K, with arithmetic mean values and standard deviations of 74 (±51), 85 (±54) and 881 (±331) Bq kg(-1) respectively, which are below the international representative mean values for granite stones. The excess on the effective dose received annually indoors due to granite tiles usage is estimated considering a standard room model where granite tiles with 1.5 cm in thickness cover only the floor of the room. The increment on the external γ-radiation effective dose rate shows a Gaussian distribution well dispersed below 0.3 mSv y(-1), presenting a mean value of 0.14 (±0.06) mSv y(-1). In case of the internal α-radiation a log-normal distribution is appeared scattering below 0.5 mSv y(-1) with a mean value 0.19 (±0.13) mSv y(-1), for a well-ventilated living environment. In case of a poor-ventilated room the increment on internal effective dose rate is estimated with a mean value 0.27 (±0.19) mSv y(-1) scattering below 0.8 mSv y(-1). The majority of the samples increase the external as well as the internal dose less than 30% of the maximum permitted limit of the effective dose rate. Therefore, at least from radiological point of view, the plutonic rocks of Greece could be safely used as decorative building materials. PMID:23827232

  16. Zinc isotope investigation of surface and pore waters in a mountain watershed impacted by acid rock drainage.

    PubMed

    Aranda, Suzan; Borrok, David M; Wanty, Richard B; Balistrieri, Laurie S

    2012-03-15

    The pollution of natural waters with metals derived from the oxidation of sulfide minerals like pyrite is a global environmental problem. However, the metal loading pathways and transport mechanisms associated with acid rock drainage reactions are often difficult to characterize using bulk chemical data alone. In this study, we evaluated the use of zinc (Zn) isotopes to complement traditional geochemical tools in the investigation of contaminated waters at the former Waldorf mining site in the Rocky Mountains, Colorado, U.S.A. Geochemical signatures and statistical analysis helped in identifying two primary metal loading pathways at the Waldorf site. The first was characterized by a circumneutral pH, high alkalinity, and high Zn/Cd ratios. The second was characterized by acidic pHs and low Zn/Cd ratios. Zinc isotope signatures in surface water samples collected across the site were remarkably similar (the δ(66)Zn, relative to JMC 3-0749-L, for most samples ranged from 0.20 to 0.30‰±0.09‰ 2σ). This probably suggests that the ultimate source of Zn is consistent across the Waldorf site, regardless of the metal loading pathway. The δ(66)Zn of pore water samples collected within a nearby metal-impacted wetland area, however, were more variable, ranging from 0.20 to 0.80‰±0.09‰ 2σ. Here the Zn isotopes seemed to reflect differences in groundwater flow pathways. However, a host of secondary processes might also have impacted Zn isotopes, including adsorption of Zn onto soil components, complexation of Zn with dissolved organic matter, uptake of Zn into plants, and the precipitation of Zn during the formation of reduced sulfur species. Zinc isotope analysis proved useful in this study; however, the utility of this isotopic tool would improve considerably with the addition of a comprehensive experimental foundation for interpreting the complex isotopic relationships found in soil pore waters. PMID:22326318

  17. Microbacter margulisiae gen. nov., sp. nov., a propionigenic bacterium isolated from sediments of an acid rock drainage pond.

    PubMed

    Sánchez-Andrea, Irene; Sanz, Jose Luis; Stams, Alfons J M

    2014-12-01

    A novel anaerobic propionigenic bacterium, strain ADRI(T), was isolated from sediment of an acid rock drainage environment (Tinto River, Spain). Cells were small (0.4-0.6×1-1.7 µm), non-motile and non-spore-forming rods. Cells possessed a Gram-negative cell-wall structure and were vancomycin-resistant. Strain ADRI(T) utilized yeast extract and various sugars as substrates and formed propionate, lactate and acetate as major fermentation products. The optimum growth temperature was 30 °C and the optimum pH for growth was pH 6.5, but strain ADRI(T) was able to grow at a pH as low as 3.0. Oxidase, indole formation, and urease and catalase activities were negative. Aesculin and gelatin were hydrolysed. The predominant cellular fatty acids of strain ADRI(T) were anteiso-C15 : 0 (30.3 %), iso-C15 : 0 (29.2 %) and iso-C17 : 0 3-OH (14.9 %). Major menaquinones were MK-8 (52 %) and MK-9 (48 %). The genomic DNA G+C content was 39.9 mol%. Phylogenetically, strain ADRI(T) was affiliated to the family Porphyromonadaceae of the phylum Bacteroidetes. The most closely related cultured species were Paludibacter propionicigenes with 16S rRNA gene sequence similarity of 87.5 % and several species of the genus Dysgonomonas (similarities of 83.5-85.4 % to the type strains). Based on the distinctive ecological, phenotypic and phylogenetic characteristics of strain ADRI(T), a novel genus and species, Microbacter margulisiae gen. nov., sp. nov., is proposed. The type strain is ADRI(T) ( = JCM 19374(T) = DSM 27471(T)). PMID:25201913

  18. Lysophosphatidic acid induces YAP-promoted proliferation of human corneal endothelial cells via PI3K and ROCK pathways

    PubMed Central

    Hsueh, Yi-Jen; Chen, Hung-Chi; Wu, Sung-En; Wang, Tze-Kai; Chen, Jan-Kan; Ma, David Hui-Kang

    2015-01-01

    The first two authors contributed equally to this work.Silence of p120-catenin has shown promise in inducing proliferation in human corneal endothelial cells (HCECs), but there is concern regarding off-target effects in potential clinical applications. We aimed to develop ex vivo expansion of HCECs using natural compounds, and we hypothesized that lysophosphatidic acid (LPA) can unlock the mitotic block in contact-inhibited HCECs via enhancing nuclear translocation of yes-associated protein (YAP). Firstly, we verified that exogenous YAP could induce cell proliferation in contact-inhibited HCEC monolayers and postconfluent B4G12 cells. In B4G12 cells, enhanced cyclin D1 expression, reduced p27KIP1/p21CIP1 levels, and the G1/S transition were detected upon transfection with YAP. Secondly, we confirmed that LPA induced nuclear expression of YAP and promoted cell proliferation. Moreover, PI3K and ROCK, but not ERK or p38, were required for LPA-induced YAP nuclear translocation. Finally, cells treated with LPA or transfected with YAP remained hexagonal in shape, in addition to unchanged expression of ZO-1, Na/K-ATPase, and smooth muscle actin (SMA), suggestive of a preserved phenotype, without endothelial–mesenchymal transition. Collectively, our findings indicate an innovative strategy for ex vivo cultivation of HCECs for transplantation and cell therapy. PMID:26029725

  19. Exploring Elongation-Inclination Relationships in Datasets from Plutons and Remagnetized Sediments: Examples from the North Cascades and the Blue Mountains

    NASA Astrophysics Data System (ADS)

    Housen, B. A.

    2014-12-01

    Tectonic applications of paleomagnetism rely upon establishment of paleohorizontal at the time of magnetization. Paleohorizontal can be established in sedimentary rocks and volcanics, but is poorly constrained in plutonic rocks and areas that have experienced regional remagnetizations. This study will explore another latitudinal-dependent property of the geomagnetic field- elongation of elliptical distributions of directional data- to evaluate whether the combination of elongation and inclination can be used to constrain effects of tilt or other paleohorizontal uncertainties in paleomagnetic datasets. This work is inspired by the application of the E-I relationship proposed by Tauxe and Kent (2004) to evaluate effects of inclination error in sedimentary rocks. The first example is from the Blue Mountains of eastern OR. Remagnetized Permian-Jurassic sedimentary rocks (Hillhouse et al, 1982, Harbert et al, 1995, Housen, 2007, Kalk, 2008) have magnetizations that match those of Late Jurassic-Early Cretaceous plutons (Wilson and Cox, 1980, Housen, 2007). Directions from 64 sites of these rocks yields a mean of D = 33°, I = 64°, k= 26, α95 = 3.7°. The E-I method can be used to determine the effects of calculated paleohorizontal errors by finding an optimal paleohorizontal error that results in the best agreement between E and I for a set of data. For the Blue Mountains rocks, the optimal E-I relationship yields a corrected inclination of I = 65° (+7°/-4°), and estimated paleolatitude of 47°N (42° to 57°). The second example is from the Cretaceous Mt Stuart batholith in the North Cascades of central WA- these 95-88 Ma plutonic rocks have well defined magnetizations (Housen et al, 2003). Directions from 89 samples have a mean of D = 350°, I=44°, k=50, α95 = 2.1°. The E-I relationship suggests a corrected mean inclination of I=46° (+12°/-3°), and estimated paleolatitude of 27°N (25° to 39°). For the Blue Mountains, this comparison indicates that the

  20. The link between volcanism and plutonism in epizonal magma systems; high-precision U-Pb zircon geochronology from the Organ Mountains caldera and batholith, New Mexico

    NASA Astrophysics Data System (ADS)

    Rioux, Matthew; Farmer, G. Lang; Bowring, Samuel A.; Wooton, Kathleen M.; Amato, Jeffrey M.; Coleman, Drew S.; Verplanck, Philip L.

    2016-02-01

    The Organ Mountains caldera and batholith expose the volcanic and epizonal plutonic record of an Eocene caldera complex. The caldera and batholith are well exposed, and extensive previous mapping and geochemical analyses have suggested a clear link between the volcanic and plutonic sections, making this an ideal location to study magmatic processes associated with caldera volcanism. Here we present high-precision thermal ionization mass spectrometry U-Pb zircon dates from throughout the caldera and batholith, and use these dates to test and improve existing petrogenetic models. The new dates indicate that Eocene volcanic and plutonic rocks in the Organ Mountains formed from ~44 to 34 Ma. The three largest caldera-related tuff units yielded weighted mean 206Pb/238U dates of 36.441 ± 0.020 Ma (Cueva Tuff), 36.259 ± 0.016 Ma (Achenback Park tuff), and 36.215 ± 0.016 Ma (Squaw Mountain tuff). An alkali feldspar granite, which is chemically similar to the erupted tuffs, yielded a synchronous weighted mean 206Pb/238U date of 36.259 ± 0.021 Ma. Weighted mean 206Pb/238U dates from the larger volume syenitic phase of the underlying Organ Needle pluton range from 36.130 ± 0.031 to 36.071 ± 0.012 Ma, and the youngest sample is 144 ± 20 to 188 ± 20 ka younger than the Squaw Mountain and Achenback Park tuffs, respectively. Younger plutonism in the batholith continued through at least 34.051 ± 0.029 Ma. We propose that the Achenback Park tuff, Squaw Mountain tuff, alkali feldspar granite and Organ Needle pluton formed from a single, long-lived magma chamber/mush zone. Early silicic magmas generated by partial melting of the lower crust rose to form an epizonal magma chamber. Underplating of the resulting mush zone led to partial melting and generation of a high-silica alkali feldspar granite cap, which erupted to form the tuffs. The deeper parts of the chamber underwent continued recharge and crystallization for 144 ± 20 ka after the final eruption. Calculated magmatic

  1. Natural radioactivity distribution and gamma radiation exposure of beach sands close to Kavala pluton, Greece

    NASA Astrophysics Data System (ADS)

    Papadopoulos, Argyrios; Koroneos, Antonios; Christofides, Georgios; Stoulos, Stylianos

    2015-10-01

    This study aims to evaluate the activity concentrations of 238U, 226Ra, 232Th, 228Th and 40K along the beaches of Kavala being adjacent to the rock-types of the Kavala pluton. These ranged from 14-940, 16-1710, 26- 4547, 27-4488 and 194-1307 Bq/kg respectively, representing the highest values of natural radioactivity measured in sediments of Greece. The (%wt.) heavy magnetic (HM) (allanite, amphibole, mica, clinopyroxene, magnetite and hematite) fraction, the heavy non-magnetic (HNM) (monazite, zircon, titanite and apatite) fraction and the total heavy fraction (TH), were correlated with the concentrations of the measured radionuclides in the bulk samples. The heavy fractions seem to control the activity concentrations of 238U and 232Th of all the samples, showing some local differences in the main 238U and 232Th mineral carrier. The measured radionuclides in the beach sands were normalized to the respective values measured in the granitic rocks, which are their most probable parental rocks, so as to provide data upon their enrichment or depletion. The annual equivalent dose varies between 0.01 and 0.35 mSv y-1 for tourists and from 0.03 to 1.48 mSv y-1 for local people working on the beach.

  2. Reconnaissance geochemical exploration of the plutons of quartz monzonite and granite in the Jabal Lababa and Ar Rayth areas, Southern Asir, Kingdom of Saudi Arabia

    SciTech Connect

    Overstreet, W.C.; Assegaff, A.B.; Jambi, M.; Hussain, M.A.; Selner, G.I.; Matzko, J.J.

    1985-01-01

    Geochemical reconnaissance for rare metals in plutons of albite-muscovite granite and quartz monzonite in the vicinity of Jabal Lababa disclosed positive geochemical anomalies for beryllium, tantalum, thorium, lanthanum, niobium, tin, yttrium, and zirconium. The low anomalous values for the rare metals in rocks and the short mechanical dispersion trains, seldom exceeding 4 km in length, of rare-metal-bearing heavy minerals, are interpreted to indicate that primary deposits of these metals are lacking, and any placers would be small and low in tenor. Small positive anomalies for barium were detected at scattered localities in the metasediments adjacent to the plutons in the Jabal Lababa area. Positive anomalies for the precious metals are lacking, and the low values observed for base metals do not indicate the presence of sulfide deposits. The abundant quartz lag gravel in the eastern part of the area is unmineralized. Small books of muscovite are present in some pegmatite, but is of non-commercial volume and quality. A subcircular structure at the coast of the Red Sea near the month of Wadi Nahb should be tested to determine if it is a buried salt dome. Three nonmagnetic high-density concentrates containing 1000 to 15,000 ppm lead were found on the granitic pluton near Ar Rayth. The source of the lead is not galena, and high values for lead appear to be characteristic of the pluton but do not indicate an ore deposit. 74 refs., 11 figs., 43 tabs.

  3. Remarkable isotopic and trace element trends in potassic through sodic Cretaceous plutons of the Yukon-Koyukuk Basin, Alaska, and the nature of the lithosphere beneath the Koyukuk terrane

    USGS Publications Warehouse

    Arth, Joseph G.; Criss, Robert E.; Zmuda, Clara C.; Foley, Nora K.; Patton, W.W., Jr.; Miller, T.P.

    1989-01-01

    During the period from 110 to 80 m.y. ago, a 450-km-long magmatic belt was active along the northern margin of Yukon-Koyukuk basin and on eastern Seward Peninsula. The plutons intruded Upper Jurassic(?) and Lower Cretaceous volcanic arc rocks and Cretaceous sedimentary rocks in Yukon-Koyukuk basin and Proterozoic and lower Paleozoic continental rocks in Seward Peninsula. Within Yukon-Koyukuk basin, the plutons vary in composition from calc-alkalic plutons on the east to potassic and ultrapotassic alkalic plutons on the west. Plutons within Yukon-Koyukuk basin were analyzed for trace element and isotopic compositions in order to discern their origin and the nature of the underling lithosphere. Farthest to the east, the calc-alkalic rocks of Indian Mountain pluton are largely tonalite and sodic granodiorite, and have low Rb (average 82 ppm), high Sr (>600 ppm), high chondrite-normalized (cn) Ce/Yb (16–37), low δ18O (+6.5 to +7.1), low initial 87Sr/86Sr (SIR) (0.704), and high initial 143Nd/144Nd (NIR) (0.5126). These rocks resemble those modelled elsewhere as partial melts and subsequent fractionates of basaltic or gabbroic metaigneous rocks, and may be products of melting in the deeper parts of the Late Jurassic(?) and Early Cretaceous volcanic arc. Farthest to the west, the two ultrapotassic bodies of Selawik and Inland Lake are high in Cs (up to 93 ppm), Rb (up to 997 ppm), Sr, Ba, Th, and light rare earth elements, have high (Ce/Yb)cn (30, 27), moderate to low δ18O (+8.4, +6.9), high SIR (0.712, 0.710), and moderate NIR (0.5121–0.5122). These rocks resemble rocks of Australia and elsewhere that were modelled as melts of continental mantle that had been previously enriched in large cations. This mantle may be Paleozoic or older. The farthest west alkalic pluton of Selawik Hills is largely monzonite, quartz monzonite, and granite; has moderate Rb (average 284 ppm), high Sr (>600 ppm), high (Ce/Yb)cn (15–25), moderate δ18O (+8.3 to +8.6), high SIR (0.708

  4. Constraints on ages of Taconian and Acadian deformation from zircon evaporation ages of felsic plutons from western Massachusetts

    SciTech Connect

    Williamson, B.F.; Karabinos, P. . Dept. of Geology)

    1993-03-01

    New dates on three felsic plutons constrain the age of Taconian and Acadian deformation in western Massachusetts. The tonalitic Hallockville Pond Gneiss intrudes the Moretown Formation of the Rowe-Hawley belt and shows deformation comparable in degree and orientation to that of the surrounding rocks. The Middlefield Granite, a quartz monzonite, intrudes the Rowe and Moretown Formations at their contact. The Williamsburg Granodiorite, of minimum-melt composition, intrudes Silurian and Devonian formations of the Connecticut Valley Synclinorium, east of the Row-Hawley belt, and contains no obvious deformation fabric. [sup 207]Pb/[sup 206]Pb single-grain zircon evaporation ages for these plutons are as follows: the Hallockville Pond Gneiss, 484 [plus minus] 7 Ma; the Middlefield Granite, 447 [plus minus] 3 Ma (weighted average of 4 grains); and the Williamsburg Granodiorite, 373 [plus minus] 5 Ma (weighted average of 3 grains). The Moretown Formation, presently correlated with the Middle Ordovician Beauceville Formation in Quebec, must be older than 484 Ma (Early Ordovician), the age of the intruding Hallockville Pond Gneiss, which might be related to rocks in the proposed Shelburne Falls arc of similar age (Karabinos and Tucker, 1992). Field relations and the age of the Middlefield Granite show that if the Rowe-Moretown contact is a fault, one interpretation suggested by Stanley and Hatch (1988) and advocated by Ratcliffe et al. (1992), then Taconian thrusting in this area ended by 447 Ma because the pluton is not offset by faults. The 373 Ma age of the unfoliated Williamsburg Granodiorite, together with a U-Pb zircon age on a strongly deformed sill in the Granville dome of 376 [plus minus] 4 Ma, tightly constrains the timing of the main phase of Acadian deformation in western Massachusetts.

  5. Indoor radon risk associated to post-tectonic biotite granites from Vila Pouca de Aguiar pluton, northern Portugal.

    PubMed

    Martins, L M O; Gomes, M E P; Teixeira, R J S; Pereira, A J S C; Neves, L J P F

    2016-11-01

    At Vila Pouca de Aguiar area, northern Portugal, crops out a post-tectonic Variscan granite pluton, related with the Régua-Vila Real-Verín fault zone, comprising three types of biotite granites. Among these granites, PSG granite yield the highest average contents of U, probably due to its enrichment in accessory U-bearing minerals such as zircon. In the proximity of faults and joints, these granites are often affected by different degrees of hydrothermal alteration, forming reddish altered rocks, commonly known as "episyenites". These altered rocks are probably associated to the occurrence of hydrothermal processes, which led to uranium enrichment in the most advanced stages of episyenitization. In these granites, both average gamma absorbed dose rates in outdoor and indoor air are higher than those of the world average. Furthermore, even in the worst usage scenario, all these granites can be used as a building material, since their annual effective doses are similar to the limit defined by the European Commission. The geometric mean of radon activity of 91 dwellings located at the Vila Pouca de Aguiar pluton is 568Bqm(-3), exceeding that of other northern Portuguese granites. Measurements carried out during a winter season, indicate that 62.6% of the analysed dwellings yield higher indoor radon average values than the Portuguese legislation limit (400Bqm(-3)), and annual effective doses due higher than the world's average value (1.2mSvy(-1)). The interaction of geogenic, architectural and anthropogenic features is crucial to explain the variance in the geometric mean of radon activity of dwellings from Vila Pouca de Aguiar pluton, but the role of geologic faults is probably the most important decisive factor to increase the indoor radon concentration in dwellings. Hence, the development of awareness campaigns in order to inform population about the incurred radiological risks to radon exposure are highly recommended for this specific area. PMID:27448957

  6. Diel cycling of zinc in a stream impacted by acid rock drainage: Initial results from a new in situ Zn analyzer

    USGS Publications Warehouse

    Chapin, T.P.; Nimick, D.A.; Gammons, C.H.; Wanty, R.B.

    2007-01-01

    Recent work has demonstrated that many trace metals undergo dramatic diel (24-h) cycles in near neutral pH streams with metal concentrations reproducibly changing up to 500% during the diel period (Nimick et al., 2003). To examine diel zinc cycles in streams affected by acid rock drainage, we have developed a novel instrument, the Zn-DigiScan, to continuously monitor in situ zinc concentrations in near real-time. Initial results from a 3-day deployment at Fisher Creek, Montana have demonstrated the ability of the Zn-DigiScan to record diel Zn cycling at levels below 100 ??g/l. Longer deployments of this instrument could be used to examine the effects of episodic events such as rainstorms and snowmelt pulses on zinc loading in streams affected by acid rock drainage. ?? Springer Science+Business Media B.V. 2006.

  7. IS ISLAND PARK A HOT DRY ROCK SYSTEM?

    USGS Publications Warehouse

    Hoover, D.B.; Pierce, Herbert A.; Long, C.L.

    1985-01-01

    The Island Park-Yellowstone National Park region comprises a complex caldera system which has formed over the last 2 m. y. The caldera system has been estimated to contain 50% of the total thermal energy remaining in all young igneous systems in the United States. As the result of a reexamination of the data and recent electrical work in the area, the authors now postulate that much of the area where the first- and second-stage calderas developed is underlain by a solidified but still hot pluton. They postulate that the pluton represents a significant hot-dry-rock resource for the United States.

  8. Performance of an open limestone channel for treating a stream affected by acid rock drainage (León, Spain).

    PubMed

    Santofimia, Esther; López-Pamo, Enrique

    2016-07-01

    The generation of acid rock drainage (ARD) was observed after the oxidation dissolution of pyrite-rich black shales, which were excavated during the construction of a highway in León (Spain). ARDs are characterized by the presence of high concentrations of sulfate and metals (Al, Fe, Mn, Zn, Cu, Co, Ni, Th, and U) that affect the La Silva stream. Dissolved element concentrations showed values between one and four orders of magnitude higher than those of natural waters of this area. A passive treatment system was constructed; the aim of which was to improve the quality of the water of the stream. This work provides a hydrochemical characterization of the La Silva stream after its transit through the different elements that constitute the passive treatment system (open limestone channel (OLC), small ponds, and a wetland), during its first year of operation. The passive treatment system has two sections separated by a tunnel 230 m long. The first section, which stretches between the highway and the tunnel entrance, is an OLC 350 m long with a slope of 16 %. The second section, which stretches from the tunnel exit to the end wetland, has a length of 700 m and a slope of 6 %; it is in this section where six small ponds are located. In the first section of this passive treatment system, the OLC was effectively increasing the pH from 3 to 4-4.5 and eliminating all of the dissolved Fe and the partially dissolved Al. These elements, after hydrolysis at a pH 3-3.5 and 4-4.5, respectively, had precipitated as schwertmannite and hydrobasaluminite, while other dissolved metals were removed totally or partially for adsorption by the precipitates and/or by coprecipitation. The second section receives different inputs of water such as ARDs and natural waters. After exiting the treatment system, the stream is buffered by Al at a pH of 4-4.3, showing high Al concentrations (19-101 mg/L) but with a complete removal of dissolved Fe. Unfortunately, the outflow shows similar or

  9. Crustal-scale perspective on the rapid development of Oligocene silicic calderas and related underlying plutonic systems, western Nevada USA

    NASA Astrophysics Data System (ADS)

    Colgan, J. P.; John, D. A.; Henry, C.; Watts, K. E.

    2015-12-01

    Geologic mapping, U-Pb zircon ages, and 40Ar/39Ar sanidine ages document the timing and extent of Oligocene magmatism in the southern Stillwater Range and Clan Alpine Mountains of western Nevada, where Miocene extension has exposed five nested silicic calderas and related granitic plutons to crustal depths locally ≥9 km. The ≤29.4-28.8 Ma Job Canyon caldera in the Stillwater Range is filled with ~4 km of intracaldera tuff and lava flows; the 28.4 Ma IXL pluton intrudes intracaldera tuff and extends to ≥9 km depth. The 29 Ma Deep Canyon caldera covers ~250 km2 of the Clan Alpine Mountains, but only the upper ~1 km is exposed. The ≤26.0-25.2 Ma Poco Canyon caldera in the Stillwater Range is filled with two distinct intracaldera tuffs totaling 4.5 km thick, underlain by the 24.8 Ma Freeman Creek pluton exposed to depths ≥8 km. The small 25.3 Ma Louderback Mountains caldera in the SW Clan Alpine Mountains is filled with ~600 m of intracaldera tuff deposited on Oligocene rhyolite lava flows. The 25.1 Ma Elevenmile Canyon caldera spans ~1600 km2 in the Stillwater Range, Clan Alpine Mountains, and Desatoya Mountains, where it overlaps or cross cuts older calderas. Its total volume is ≥2500 km3, mostly consisting of the 1-4 km thick tuff of Elevenmile Canyon. 24.9-25.5 Ma silicic intrusive rocks underlie the Louderback Mountains and Elevenmile Canyon calderas to depths ≥6-8 km, locally surrounding septa of basement rock and older Oligocene igneous rocks. Two magmatic pulses, each lasting ~1 m.y. and associated with the 29 and 25 Ma caldera complexes, replaced almost the entire Mesozoic upper crust with Oligocene intrusive and extrusive rock to depths ≥9 km over a 1500 km2 area (pre-extension). Magma emplacement was most likely accommodated by downward transfer of country rocks and accompanied by isostatic surface uplift. If other Great Basin calderas are similar, the dense concentration of shallowly exposed calderas in central Nevada may be underlain by a

  10. [Analysis of X-Ray Fluorescence Spectroscopy and Plasma Mass Spectrometry of Pangxidong Composite Granitoid Pluton and Its Implications for Magmatic Differentiation].

    PubMed

    Zeng, Chang-yu; Ding, Ru-xin; Li, Hong-zhong; Zhou, Yong-zhang; Niu, Jia; Zhang, Jie-tang

    2015-11-01

    Pangxidong composite granitoid pluton located in the southwestern margin of Yunkai massif. The metamorphic grade of this pluton increases from outside to inside, that is, banded-augen granitic gneisses, gneissoid granites and granites distribute in order from edge to core. X-Ray Fluorescence Spectroscopy and Plasma Mass Spectrometry are conducted to study the geochemical characteristics of the three types of rocks. The result shows that all the three types of rocks are peraluminous rocks and their contents of main elements and rare earth elements change gradually. From granitic gneisses to granites, the contents of Al₂O₃, CaO, MgO, TiO₂, total rare earth elements and light rare earth elements increase, but the contents of SiO₂ and heavy rare earth elements decrease. It is suggested that the phylogenetic relationship exists between granitic gneisses, gneissoid granites and granites during the multi-stage tectonic evolution process. Furthermore, the remelting of metamorphosed supracrustal rocks in Yunkai massif is probably an important cause of granitoid rocks forming. The evolutionary mechanism is probably that SiO₂ and heavy rare earth elements were melt out from the protolith and gradually enriched upward, but Al₂O₃, CaO, MgO, TiO₂ and light rare earth elements enriched downward. PMID:26978933

  11. There's more than one way to build a caldera magma chamber: Evidence from volcanic-plutonic relationships at three faulted Rio-Grande-rift calderas

    NASA Astrophysics Data System (ADS)

    Zimmerer, M. J.; McIntosh, W. C.

    2011-12-01

    The temporal and chemical relationships of volcanic and plutonic rocks of the Questa (NM), Mt. Aetna (CO), and Organ caldera (NM) complexes were investigated to establish the origin of these silicic magmas. Rio Grande Rift faulting at these systems has exposed both intracaldera sequences and subvolcanic plutons. Ar/Ar and U/Pb ages reveal the timing of volcanic activity and pluton emplacement and cooling. We observe a link between ignimbrite zoning patterns and the temporal-chemical relationship of volcanic and plutonic rocks. The Questa caldera erupted the high-SiO2 peralkaline Amalia Tuff (AT) at 25.4 Ma. Volumetrically minor phases of two resurgent plutons and a ring dike are compositionally similar to the AT. The age of the ring dike (25.4 Ma) is indistinguishable to AT, suggesting that the peralkaline intrusions are nonerupted AT. The remaining pluton ages are 100 ka to 6.1 Ma younger than AT and are too young to be the AT residual crystal mush. The Mt. Princeton batholith and nested Mt. Aetna caldera are interpreted to be the sources for the 37.3 Ma, low-SiO2 rhyolitic Wall Mountain Tuff (WMT) and the 34.3 Ma, dacitic Badger Creek Tuff (BCT). U/Pb and Ar/Ar ages of Mt. Princeton batholith (36.5 to 35.1 Ma) indicate that it was emplaced and rapidly cooled during the interval between the WMT and BCT eruptions, and that any WMT age intrusions are now eroded. During the eruption of the BCT, the fully crystallized Mt. Princeton batholith collapsed into the Mt. Aetna caldera. Intrusions along the margins of the Mt. Aetna caldera are compositionally identical the BCT and contain zircons 100 to 500 ka older than the tuff, suggesting that the BCT magma chamber was incrementally emplaced prior to caldera eruption. The Organ caldera complex erupted three ignimbrites: a basal high-silica 36.5 Ma rhyolite, a middle intermediate-silica 36.2 Ma rhyolite, and an upper 36.0 Ma low-silica rhyolite. The intracaldera sequence is intruded by the Organ Needle pluton. U/Pb zircon

  12. K Ar ages of plutonism and mineralization at the Shizhuyuan W Sn Bi Mo deposit, Hunan Province, China

    NASA Astrophysics Data System (ADS)

    Yin, Jingwu; Kim, Sang Jung; Lee, Hyun Koo; Itay, Tetsumaru

    2002-01-01

    The Qianlishan granite complex, situated 16 km southeast of Chenzhou City, Hunan Province, China, hosts the Shizhuyuan W-Sn-Bi-Mo deposit. This complex, which intruded the Protozoic metasedimentary rocks and the Devonian clastic sedimentary and carbonate rocks, consists of mainly medium- to coarse-grained biotite granites and minor amounts of fine-grained biotite granite in addition to granite and quartz porphyry. K-Ar ages suggest three episodes of plutonism: the medium- to coarse-grained biotite granite (before 152 Ma), the fine-grained biotite granite (137 Ma), and the granite porphyry (129-131 Ma). Muscovite ages of the greisen are 145-148 Ma, suggesting that the W-Sn-Bi-Mo mineralization was related to the main, medium- to coarse-grained biotite granites. The K-Ar age of the hydrothermal vein mineralization is 92 Ma and is probably related to the porphyries.

  13. Gravimetric, radiometric, and magnetic susceptibility study of the Paleoproterozoic Redenção and Bannach plutons, eastern Amazonian Craton, Brazil: Implications for architecture and zoning of A-type granites

    NASA Astrophysics Data System (ADS)

    de Oliveira, Davis Carvalho; Dall'Agnol, Roberto; Corrêa da Silva, João Batista; Costa de Almeida, José Arimatéia

    2008-02-01

    The 1.88 Ga, anorogenic, A-type Redenção and Bannach granites, representative of the Jamon suite and associated dikes, are intrusive in Archean granitoids of the Rio Maria Granite-Greenstone Terrane in the eastern Amazonian Craton in northern Brazil. Petrographic and geochemical aspects associated with magnetic susceptibility and gamma-ray spectrometry data show that the Redenção and the northern part of Bannach plutons are normally zoned. They were formed by two magmatic pulses: (1) a first magma pulse was fractionated in situ after emplacement at shallow crustal level, generating a series of coarse, even-grained monzogranites with variable modal proportions of biotite and hornblende; and (2) a second, slightly younger magma pulse, located to the center of the plutons, was composed of a more evolved liquid from which even-grained leucogranites derived. Gravity modeling indicates that the Redenção and Bannach plutons are sheeted-like composite intrusions, approximately 6 and 2 km thick, respectively. These plutons follow the general power law for laccolith dimension and are similar in this respect to classical rapakivi granite plutons. Gravity data suggest that the growth of the northern part of the Bannach pluton resulted from the amalgamation of smaller sheeted-like plutons that intruded in sequence from northwest to southeast. The Jamon suite plutons were emplaced in an extensional tectonic setting, and the stress was oriented approximately NNE-SSW to ENE-WSW, as indicated by the occurrence of diabase and granite porphyry dyke swarms, orientated WNW-ESE to NNW-SSE and coeval with the Jamon suite. The 1.88 Ga A-type granite plutons and stocks of Carajás are disposed along a belt that follows the general trend defined by the dikes. The inferred tabular geometry of the studied plutons and the high contrast of viscosity between the granites and their Archean country rocks can be explained by magma transport via dikes.

  14. Onset of Grain Boundary Migration and Drastic Weakening of Quartzite during increasing grade of Metamorphism in the Contact Aureole surrounding the Eureka Valley-Joshua Flat-Beer Creek pluton, California, USA

    NASA Astrophysics Data System (ADS)

    Morgan, S. S.; Student, J. J.; Jakeway, J.

    2015-12-01

    The Eureka Valley-Joshua Flat-Beer Creek (EJB) pluton in eastern California is surrounded by a ~1.3 km wide intensely deformed concordant aureole of metasedimentary rocks. South of the pluton, the Harkless Quartzite can be mapped from where it is located outside the aureole, with its regional strike through the transition into the aureole and concordancy with the pluton. The transition into concordancy, which is fairly abrupt, occurs over a distance of less than 100 m. Across this transition the bedding rotates close to 90° to become subvertical. Here the metasedimentary formations in the aureole have undergone 65% shortening. A suite of Harkless Quartzite samples was collected starting at 2.3 km south of the pluton, across the transition into concordancy at 1.3 km, and to within 450m from the pluton contact. Microstructurally, the transition is defined by changes in the dominant recrystallization mechanisms. At 2.3 km from the pluton, subgrain rotation recrystallization (SGR) plus grain boundary migration (GBM) operate together and many sedimentary grains (rounded grain boundaries) exist. As the pluton is approached, SGR decreases, GBM increases, and rounded grain boundaries slowly disappear. The abrupt transition into concordancy is marked by the final disappearance of SGR and rounded grain boundaries and extensive GBM. The transition is not completely smooth, and other variables such as pinning and amount of fluid inclusions seem to have a strong local affect on the dominant recrystallization mechanism. We suspect that the onset of extensive GBM allows for the diffusion of water into the crystal lattice which results in the drastic weakening and rotation of metasedimentary formations into concordancy.

  15. Tilted middle Tertiary ash-flow calderas and subjacent granitic plutons, southern Stillwater Range, Nevada: cross sections of an Oligocene igneous center

    USGS Publications Warehouse

    John, D.A.

    1995-01-01

    Steeply tilted late Oligocene caldera systems in the Stillwater caldera complex record a number of unusual features including extreme thickness of caldera-related deposits, lack of evidence for structural doming of the calderas and preservation of vertical compositional zoning in the plutonic rocks. The Stillwater caldera complex comprises three partly overlapping ash-flow calderas and subjacent plutonic rocks that were steeply tilted during early Miocene extension. The Job Canyon caldera, the oldest (ca. 29-28 Ma) caldera, consists of two structural blocks. The 25 to 23 Ma Poco Canyon and Elevenmile Canyon calderas and underlying Freeman Creek pluton overlap in time and space with each other. Caldera collapse occurred mostly along subvertical ring-fracture faults that penetrated to depths of >5 km and were repeatedly active during eruption of ash-flow tuffs. The calderas collapsed as large piston-like blocks, and there is no evidence for chaotic collapse. Preserved parts of caldera floors are relatively flat surfaces several kilometers across. -from Author

  16. Magnetic fabric and zircon U Pb geochronology of the Itaoca pluton: Implications for the Brasiliano deformation of the southern Ribeira Belt (SE Brazil)

    NASA Astrophysics Data System (ADS)

    Salazar, Carlos A.; Archanjo, Carlos J.; Babinski, Marly; Liu, Dunyi

    2008-11-01

    The Itaoca pluton consists of porphyritic monzogranite that intruded the upper crust into low-grade metasedimentary rocks of the Apiaí Domain (Ribeira Belt). Anisotropy of magnetic susceptibility and zircon U-Pb (Shrimp) geochronology were combined to determine pluton emplacement mechanisms and its chronology relative to the collision structures of the Paranapiacaba (Brasiliano II) orogenic system. Magnetic susceptibility ranges between 4 and 38 × 10 -3 SI, and thermomagnetic measurements indicate multidomain magnetite is the main carrier of anisotropy. The pluton shows an "onion-skin" structure roughly elongated to the northeast with its hinge zone including kilometer-wide roof-pendants. Magnetic lineations are variable in orientation in consistency with the dominant oblate symmetry of the magnetic fabric. A distinct NE-trending point-maxima, however, indicates the mean lineation is parallel to the stretching direction of the transpressive deformation that affected the regional host rocks. Prismatic zircon from the monzogranite, both in the core and in the finely-zoned margins, yielded an age of 623 ± 10 Ma. These results suggest the magmatic fabric recorded the earlier strain increments of the regional shear deformation. It may correspond to the transition from continental arc to collision tectonics of the southern Ribeira Belt.

  17. Age and zircon inheritance of eastern Blue Ridge plutons, southwestern North Carolina and northeastern Georgia, with implications for magma history and evolution of the southern Appalachian origin

    SciTech Connect

    Miller, C.F.; Hatcher, R.D. Jr.; Ayers, J.C.; Coath, C.D.; Harrison, T.M.

    2000-02-01

    High-resolution ion microprobe analysis of zircon has provided ages for previously undated plutons of the high-grade eastern Blue Ridge of northeastern Georgia and southwestern North Carolina. These data, together with backscattered electron imaging, reveal the presence of nearly ubiquitous inherited cores of highly variable age and magmatic rims that have experienced variable Pb loss, thus making interpretation of conventional U-Pb analyses very difficult. Ion probe rim analyses indicate that the plutons were emplaced during both the mod-Ordovician and mid-Devonian. Zircons from all intrusions have predominantly 1.0 to 1.25 Ga cores (Grenvillian). In addition, both Devonian and Ordovician plutons have smaller populations of Late Proterozoic-early Paleozoic (0.5--0.75 Ga), Middle Proterozoic (1.4 Ga), and Late Archean (2.6--2.9 Ga) cores. The ubiquitous, round cores and thick magmatic rims suggest significant resorption and then protracted growth within the melts. Zircon saturation temperatures based on whole-rock ({approximately}melt) Zr concentrations are lower than expected for magma generation (710--760 C). Zirconium concentrations may not reflect saturation at maximum temperature, if melting was very rapid (<{approximately}10{sup 5} yrs), or if zircon cores represent grains that were shielded from melt inside host grains for much of the magmatic history. Ages of magmatic and inherited zones of zircon from the plutons demonstrate that similar crust underlay the eastern Blue Ridge during both Taconian and Acadian orogenies, that there was no single episode of voluminous magmatism, and that metamorphism and deformation began before 470 Ma and continued after 370 Ma. These plutons do not constitute a significant convergence-related arc, though it is possible that they represent a displaced part of an arc that lies primarily to the east (in the Inner Piedmont?).

  18. Paleomagnetism and magnetic fabric of Miocene plutons of the Tonalá shearz zone, Chiapas, Mexico: evidence of rotation of the remanence vector

    NASA Astrophysics Data System (ADS)

    Molina-Garza, Roberto S.; Geissman, John W.

    2016-04-01

    The Late Miocene plutons of coastal Chiapas are elongated parallel to the Tonalá mylonite belt, and some plutons show asymmetric outcrop patterns with sheared tails that trail behind the intrusions. Plutons were emplaced within a transpressional sinistral shear zone. Magnetic fabrics in the plutons are well-developed, and are subparallel to the structural trend of the Tonalá mylonitic belt, but locally magmatic fabrics are preserved. Magnetic fabrics in undeformed granites with igneous textures are also subparallel to the shear zone axis. Strongly deformed plutons have Ṕvalues as high as 1.7. Fabric ellipsoids are predominantly oblate, but they are triaxial in sites with igneous textures. Characteristic magnetizations reside in a cubic phase, such as low-Ti magnetite, but abundant particles in the MD range prevent isolating a stable magnetization in many of the sites. Site means are NW to NE directed, and of moderate positive inclination (or its antipodal), but locally they are very discordant in declination. The overall mean, discarding highly discordant sites is of D= 359.5 and I=41.9 (k=14.2, alpha95=8.1), which is nearly concordant with the NA reference direction indicating gentle northward tilt of less than about 10°. We explain the highly discordant directions as caused by continuing, progressive, deformation in the transpressive shear zone of a thermochemical remanence acquired during deformation. Deformation resulted in rotations, both in a clockwise and an anticlockwise sense. These results are interpreted as paleomagnetic vectors affected by distortional strain, which based on AMS exceed 40% shortening and accommodate shape and volume change in the rock.

  19. Zircon U-Pb geochronology, Sr-Nd-Hf isotopic composition and geological significance of the Late Triassic Baijiazhuang and Lvjing granitic plutons in West Qinling Orogen

    NASA Astrophysics Data System (ADS)

    Duan, Meng; Niu, Yaoling; Kong, Juanjuan; Sun, Pu; Hu, Yan; Zhang, Yu; Chen, Shuo; Li, Jiyong

    2016-09-01

    The Qinling Orogen was a consequence of continental collision of the South China Craton with the North China Craton in the Triassic and caused widespread granitoid magmatism. However, the petrogenesis of these granitoids remains controversial. In this paper, we choose the Baijiazhuang (BJZ) and Lvjing (LJ) plutons in the West Qinling Orogen for a combined study of the zircon U-Pb geochronology, whole-rock major and trace element compositions and Sr-Nd-Hf isotopic characteristics. We obtained zircon crystallization ages of ~ 216 Ma and ~ 212 Ma for the BJZ and the LJ plutons, respectively. The granitoid samples from both plutons have high K2O metaluminous to peraluminous compositions. They are enriched in large ion lithophile elements (LILEs), light rare earth elements (LREEs) and depleted in high field-strength elements (HFSEs) with significant negative Eu anomalies. The BJZ samples have initial Sr isotopic ratios of 0.7032 to 0.7078, εNd(t) of - 10.99 to - 8.54 and εHf (t) of - 10.22 to - 6.41. The LJ granitoids have initial Sr isotopic ratios of 0.7070 to 0.7080, εNd(t) of - 5.37 to - 4.58 and εHf(t) of - 3.64 to - 1.78. The enriched isotopic characteristics of the two plutons are consistent with their source being dominated by ancient continental crust. However, two BJZ samples show depleted Sr isotope compositions, which may infer possible involvement of mantle materials. Mantle-derived melt, which formed from partial melting of mantle wedge peridotite facilitated by dehydration of the subducted/subducting Mianlue ocean crust, provide the required heat for the crustal melting while also contributing to the compositions of these granitoids. That is, the two granitic plutons are magmatic responses to the closure of the Mianlue ocean basin and the continental collision between the Yangtze and South Qinling crustal terranes.

  20. The plutonic-volcanic connection: are we even on the right track? (Invited)

    NASA Astrophysics Data System (ADS)

    Lundstrom, C.; Chakraborty, P.; Zambardi, T.

    2013-12-01

    The connection between silicic volcanic and plutonic rocks is full of contradictions. Foremost, granitic plutons reflect long slow incremental emplacement yet vast amounts of aphyric ignimbrite can be erupted rapidly. Heat flow, geophysical tomography, geochronology, geochemistry and petrology all provide observations, yet we are far from any consensus. The two most popular suggestions for forming ignimbrites, extraction of partial melt from a granitic upper crust reservoir or lower crustal hot zone melting, are each inconsistent with some observations/constraints. 100% melting of a granite mush, which may be consistent with many observations, was previously proposed1 but dismissed due to the large amount of latent heat needed to completely melt a mush. This work first presents new non-traditional isotope ratio data (Fe, Si) for plutonic and volcanic rocks suites showing that like Harker diagrams, volcanics and plutonics produce identical systematic behavior with differentiation. δ56Fe forms upwardly curving trends with increasing silica whereas δ30Si increases linearly. The logical deduction is that volcanics reflect 100% mobilization of a granite mush (not necessarily melting). While the origin of NTSI variations remains debated, the systematic NTSI trends are consistent with prediction of a top-down thermal migration zone refining (TMZR) process2. In part 2, we assume TMZR generates a granitic mush and propose that an instability in this mush leads to a runaway effect that results in eruption of aphyric ignimbrite. Experiments show that wet andesite evolves to granite at the cold (400°C) end of a thermal gradient3 with hydrous peralkaline melt existing interstitially. Previous work4 shows that such melts show retrograde immiscibility, segregating into a water rich melt and a water poor melt with temperature increase. Thus, as the mush builds down into hot crust, it crosses the immiscibility boundary triggering release of the water-rich phase; buoyant rise and

  1. Influence of the Trojan Nickel Mine on surface water quality, Mazowe valley, Zimbabwe: Runoff chemistry and acid generation potential of waste rock

    NASA Astrophysics Data System (ADS)

    Lupankwa, Keretia; Love, David; Mapani, Benjamin; Mseka, Stephen; Meck, Maideyi

    The impacts of mining on the environment depend on the nature of the ore body, the type of mining and the size of operation. The focus of this study is on Trojan Nickel Mine which is located 90 km north of Harare, Zimbabwe. It produces nickel from iron, iron-nickel and copper-nickel sulphides and disposes of waste rock in a rock dump. Surface water samples were taken at 11 points selected from a stream which drains the rock dump, a stream carrying underground water and the river into which these streams discharge. Samples were analysed for metals using atomic absorption spectrometry, for sulphates by gravitation and for carbonates and bicarbonates by back titration. Ninteen rock samples were collected from the dump and static tests were performed using the Sobek acid base accounting method. The results show that near neutral runoff (pH 7.0-8.5) with high concentrations of sulphate (over 100 mg/L) and some metals (Pb > 1.0 mg/L and Ni > 0.2 mg/L) emanates from the dump. This suggests that acid mine drainage is buffered in the dump (probably by carbonates). This is supported by the static tests, which show that the fine fraction of dump material neutralises acid. Runoff from the dump flows into a pond. Concentrations of sulphates and metals decrease after the dump runoff enters the pond, but sufficient remains to increase levels of calcium, sulphate, bicarbonate, iron and lead in the Pote River. The drop in concentrations at the pond indicates that the settling process has a positive effect on water quality. This could be enhanced by treating the pond water to raise pH, thus precipitating out metals and decreasing their concentrations in water draining from the pond.

  2. Oxygen Isotope Perspectives on Magma Sources and Pluton Assembly in Convergent Margin Batholiths

    NASA Astrophysics Data System (ADS)

    Lackey, J.

    2008-12-01

    Oxygen isotope (δ18O) analysis of zircon in the Sierra Nevada batholith (SNB) yields fresh insight on the origin of this and other convergent margin batholiths. Zircon precisely and accurately maps (δ18O) variation by circumventing the effects of differentiation and sub-solidus alteration[1]. New temporal and spatial δ18O patterns are recognized, and the findings have bearing in current debates on the tempo and mode of pluton and intrusive suite assembly [2-4]. At large scales, regional belts of high and low δ18O reveal markedly contrasting budgets of crust and mantle in magma sources at different points during formation of the batholith. Contrary to original thinking, recycling of supracrustal rocks is greater in the western than eastern SNB. Gradients of δ18O show variable input of crust and mantle within these regional belts; however, sharp shifts in δ18O between some belts suggest pre-batholith lithospheric breaks. Generally, δ18O breaks do not coincide with the 0.706 Sri line suggesting isotopic decoupling, either in sources or during crustal contamination. Where present, crustal contamination is limited to veneers on plutons, and is largely restricted to the western SNB. Careful investigation of individual intrusive suites, reveals details of source longevity. In the Tuolumne suite, limited variability of δ18O suggests remarkably source homogeneity despite evidence for protracted emplacement[2,4]. In contrast, the John Muir suite shows distinct trends in its older and younger plutons, with a δ18O transition recorded in the Lake Edison granodiorite. Thus, some suites may draw from stable sources over several million years, with differentiation in the upper crust creating zoning and textural diversity; others record source switching or depletion of sources. Over time, shifts in δ18O in the SNB are punctuated by major pulses of magmatism suggesting reorganization of sources, likely in response to intra-arc deformation[5]. Overall, results show that a

  3. Origin and interaction of some alkalic and silicic plutons in the Vermilion Granitic Complex, NE Minnesota

    SciTech Connect

    McCall, G.W.; Nabelek, P.I.; Bauer, R.L.; Glascock, M.D.

    1985-01-01

    Alkalic gabbros and tonalites comprise a significant portion of the Archaean crust in the Vermilion Granitic Complex of NE Minnesota. The origin of these and associated rocks has been modeled using major and trace element approaches. Samples of the alkalic gabbro collected from three different intrusions have similar major element, REE, and transition metal concentrations. The REE patterns of these rocks can be modeled as the result of 1% to 3% melting of an undepleted garnet herzolite mantle with REE concentrations three times that of chondrites. However, their Al/sub 2/O/sub 3//CaO ratios of 2 - 3, Sr content of 900-1400 ppm and Ba of 100 - 1600 ppm suggest that the source may have been an enriched, metasomatized mantle. The hornblendites associated with these alkalic rocks have REE patterns which are consistent with crystallization and accumulation from the gabbroic magma. Major and trace element modeling suggest that the granitic dikes which are common throughout the area may be residual liquids formed by 60% crystallization of plagioclase, biotite, hornblende and apatite from the nearby tonalites such as the Burntside of Wakemup Bay plutons. Porphyritic hornblende monzonites composed of centimeter sized hornblende crystals floating in a granitic matrix occur locally. The field relations as well as the major and trace element data are consistent with the formation of these monzonitic rocks by mixing of the granite with partially consolidated hornblendite. These results suggest a complex interaction between alkalic gabbros and tonalites involving fractionation and mixing during the development of the Archaean crust of NE Minnesota.

  4. Petrological and geochemical constraints on granitoid formation: The Waldoboro Pluton Complex, Maine

    SciTech Connect

    Barton, M. . Dept. of Geological Science); Sidle, W.S. )

    1992-01-01

    The Waldoboro Pluton Complex (WPC) comprises seven units ranging from qtz-diorite to aplite. The country rocks are biotite-rich metagraywackes with minor shales mostly belonging to the Proterozoic Z-Ordovician Bucksport Formation. Field evidence strongly suggests that the WPC formed in-situ: contacts with the country rock are cryptic, transitional and concordant; restitic minerals in the granitoids are identical to those in the country rocks; prolific metasedimentary enclaves in the WPC are locally derived. Major and trace element data for country rock and the most voluminous units of the WPC define consistent linear trends suggesting limited melt segregation and retention of a high proportion of restite. Mixing models and partial melting models require 54--76% melting for generation of the gneissic granites and two-mica granites. Garnet-biotite geothermometry and garnet-Al[sub 2]SiO[sub 5]-SiO[sub 2]-plagioclase geobarometry indicate that the WPC formed at T = 740--780 C and P = 0.4--0.7 GPa. Published experimental data show that < 50% melting is likely under these conditions if melting is controlled by dehydration reactions. Bucksport lithologies contain < 20% biotite, suggesting that the maximum amount of melt that could have formed by dehydration melting is < 20%, even if all biotite was consumed during melting. It seems probable that a free fluid phase was required to generate the WPC. Migmatization is apparent in all lithologies (including amphibolites) in the vicinity of the WPC, consistent with fluid-present melting. Fluid may have ingressed along the St. George thrust, but the source of the fluid is unknown.

  5. Mid-crustal emplacement and deformation of plutons in an Andean-style continental arc along the northern margin of the North China Block and tectonic implications

    NASA Astrophysics Data System (ADS)

    Zhang, Shuan-Hong; Zhao, Yue

    2013-11-01

    Outcrop mapping and thermobarometrical, thermochronological and microstructural analyses in five Late Carboniferous-Early Permian arc plutons in the northern North China Block (NCB) indicate a transition of tectonic regime from arc-perpendicular contraction to transpression and successive uplift and exhumation of the crustal rocks during magma emplacement and construction of the continental arc system. The early emplaced Daguangding and Boluonuo plutons (324-302 Ma) display well-developed, penetrative, moderately to steeply dipping magmatic foliations and high-temperature sub-solidus foliations that are parallel to host rock foliation near the contact. Widespread high-temperature sub-solidus foliations in these plutons indicate that they are syn-tectonic with N-S, arc-perpendicular shortening and record arc construction at a convergent continental margin. However, the late emplaced Tianqiao and Xianghuangqi-Wudaoyingzi plutons (288-274 Ma) display relatively weak magmatic fabrics at their margins and lack sub-solidus foliations and pluton-related ductile deformation of the contact host rocks. These structural differences likely reflect a kinematic transition from early arc-perpendicular contraction to late sinistral transpression during continental arc formation. Aluminum-in-hornblende barometry shows that their estimated emplacement depths decrease gradually from the Late Carboniferous (18.7 ± 0.8 km) to Early Permian (13.8 ± 0.9 km), indicating successive exhumation of the crustal rocks at an average rate of ca. 123 mm/ka over 40 million years of arc formation. 40Ar/39Ar thermochronological results show that cooling of the continental crust was very slow (4.9 °C/Ma) during arc construction in the Late Carboniferous-Late Permian but increased significantly during the Late Permian-Middle Triassic after arc termination. The mid-crust of the northern NCB remained very hot (> 530 °C) during arc construction and emplacement of the arc batholiths. Combined with

  6. Geochemistry and Geochronology of Eocene Plutons in Northeastern Washington: A Test of Farallon Slab Rollback as a Cause of the Challis Event

    NASA Astrophysics Data System (ADS)

    Caulfield, L.; Tepper, J. H.

    2015-12-01

    The causes of widespread magmatism and extension that affected the Pacific Northwest during the Eocene "Challis Event" are poorly understood. Two models that have been advanced to explain this activity are passage of a slab window (e.g., Haeussler et al., 2011) and rollback of the subducting Farallon slab following accretion of Siletzia (Schmandt and Humphreys, 2011). Both scenarios would have resulted in widespread magmatism but with different temporal patterns. Based on reconstructed plate motion vectors magmatism related to a slab window should produce a younging-to-the-NW pattern whereas magmatism associated with slab rollback should young to the S or SW. Existing dates on Eocene igneous units in NE Washington appear to show an overall younging to the SW, consistent with the slab rollback model. However, many of these dates (mainly K-Ar) have large uncertainties so we are conducting a U-Pb dating and geochemical survey of Eocene plutons across the region. An initial set of zircon U-Pb ages (by LA-MC-ICP-MS) from five intrusions in east-central WA range from 50.7 - 46.7 Ma and young to the SW, a trend similar to that observed among Eocene rocks in the Idaho Batholith (Gaschnig et al., 2013). To further investigate this pattern we are dating an additional ten plutonic units that define a ~100 km SW-NE transect through NE WA. From NE to SW the units in this transect are (with dates from WA DNR mapping) as follows: Sheppard granite (undated), Herron Creek intrusion (51.4 +/- 1.9 Ma), Mt. Bonaparte pluton (52.8 +/- 2.6 Ma), Daisy Trail granite (49.9 +/- 0.3 Ma), Swimptkin Creek pluton (48.2 +/- 1.2 Ma), Moses pluton (48.6 +/- 1.2 Ma), Keller Butte granite (52.9 +/- 0.4 Ma), Johnny George plutonic complex (49.9 +/- 0.45 Ma), Manilla Creek (undated), and Swawilla Basin pluton (58.8 +/- 2.2 Ma). Results of this study should lead to a better understanding of the cause(s) of Challis magmatism and specifically its relationship to the ~50-48 Ma accretion of Siletzia.

  7. The relationship between plutonism and volcanism: zircon ages from granitoid clasts in recent pyroclastic deposits from Tarawera volcano

    NASA Astrophysics Data System (ADS)

    Shane, P. A.; Storm, S.; Schmitt, A. K.; Lindsay, J.

    2011-12-01

    In Quaternary magmatic systems that have not undergone extensive uplift that would expose their intrusive roots, co-magmatic (and xenolithic) plutonic clasts entrained in eruptive deposits are an important source of information on the temporal relationship between plutonism and volcanism. Granitoid clasts in pyroclastic deposits of the 0.7 ka (Kaharoa) eruption from the Tarawera volcano of the Okataina Volcanic Centre (OVC), New Zealand, provide a rare insight to the plutonic processes beneath one of the most productive Quaternary rhyolite centers on Earth. SIMS U-Th and U-Pb data on 79 granitoid zircon crystals from six clasts reveal a unimodal age spectrum yielding a weighted average model age of 211 ± 4 ka (MSWD = 1.1). This crystallization event coincides with relative quiescence in OVC volcanism. A few outlier antecrysts date back to ~700 ka, a period significantly longer than the known volcanic record at OVC (probably ~330 ka). In contrast, zircon crystallization in co-erupted pumice and lava of the 0.7 ka Kaharoa event, and that of the three preceding rhyolite eruptions, occurred mostly during 0-50 ka. Thus, the granitoid clasts represent part of the system immediately beneath the volcano that survived assimilation and/or destruction in subsequent eruption and caldera collapse episodes. Brittle deformation features, incipient alteration and low-d18O whole-rock compositions (+3%) are consistent with a shallow solid carapace that has interacted with hydrothermal fluids. However, d18O SIMS analyses of zircons (+5.4 ± 0.2 %; n = 11) are consistent with magmatic compositions, and thus meteoric interaction occurred post-emplacement. The Kaharoa granitoids contrast with those ejected in the ~60 ka caldera-forming Rotoiti event, that were partly molten and display zircon age spectra indistinguishable from that in co-erupted pumices, suggesting the latter were derived from contemporaneous crystal mush. The 0.7 ka Kaharoa case shows that, over time, eruptible parts

  8. Magmatic and crustal differentiation history of granitic rocks from Hf-O isotopes in zircon.

    PubMed

    Kemp, A I S; Hawkesworth, C J; Foster, G L; Paterson, B A; Woodhead, J D; Hergt, J M; Gray, C M; Whitehouse, M J

    2007-02-16

    Granitic plutonism is the principal agent of crustal differentiation, but linking granite emplacement to crust formation requires knowledge of the magmatic evolution, which is notoriously difficult to reconstruct from bulk rock compositions. We unlocked the plutonic archive through hafnium (Hf) and oxygen (O) isotope analysis of zoned zircon crystals from the classic hornblende-bearing (I-type) granites of eastern Australia. This granite type forms by the reworking of sedimentary materials by mantle-like magmas instead of by remelting ancient metamorphosed igneous rocks as widely believed. I-type magmatism thus drives the coupled growth and differentiation of continental crust. PMID:17303751

  9. Geochemical Database for the Boulder Batholith and Its Satellitic Plutons, Southwest Montana

    USGS Publications Warehouse

    du Bray, Edward A.; Lund, Karen; Tilling, Robert I.; Denning, Paul D.; DeWitt, Ed

    2009-01-01

    Geochemical data presented in this report pertain to Cretaceous igneous intrusions of the Boulder batholith and its satellitic plutons in southwest Montana. The geographic area addressed in this compilation is approximately bounded by lats 45.6 deg and 46.7 deg N. and longs 112.75 deg and 111.5 deg W. These data were compiled in order to establish the geologic framework for world-class mineral deposits of the Butte district. Although these deposits and their host rocks have been the subject of many investigations, the petrologic characteristics of associated intrusive rocks have not been systematically compiled, synthesized, or interpreted. Abundant late Mesozoic intrusions in the study area are probably byproducts of subduction-related processes, including back-arc magmatism that prevailed along the west edge of the North American plate during this interval. The ultimate goal of this effort will be an evaluation of the time-space-compositional evolution of Mesozoic magmatism associated with the Boulder batholith and identification of genetic associations between magmatic and mineralizing processes in this region.

  10. Formation of lower continental crust by relamination of buoyant arc lavas and plutons

    NASA Astrophysics Data System (ADS)

    Kelemen, Peter B.; Behn, Mark D.

    2016-03-01

    The formation of the Earth's continents is enigmatic. Volcanic arc magmas generated above subduction zones have geochemical compositions that are similar to continental crust, implying that arc magmatic processes played a central role in generating continental crust. Yet the deep crust within volcanic arcs has a very different composition from crust at similar depths beneath the continents. It is therefore unclear how arc crust is transformed into continental crust. The densest parts of arc lower crust may delaminate and become recycled into the underlying mantle. Here we show, however, that even after delamination, arc lower crust still has significantly different trace element contents from continental lower crust. We suggest that it is not delamination that determines the composition of continental crust, but relamination. In our conceptual model, buoyant magmatic rocks generated at arcs are subducted. Then, upon heating at depth, they ascend and are relaminated at the base of the overlying crust. A review of the average compositions of buoyant magmatic rocks -- lavas and plutons -- sampled from the Aleutians, Izu-Bonin-Marianas, Kohistan and Talkeetna arcs reveals that they fall within the range of estimated major and trace elements in lower continental crust. Relamination may thus provide an efficient process for generating lower continental crust.

  11. Metamorphism and plutonism in the Quetico Belt, Superior Province, N.W. Ontario

    NASA Technical Reports Server (NTRS)

    Percival, J. A.

    1986-01-01

    The Quetico Belt lies between the metavolcanic Wawa-Shebandowan and Wabigoon Belts. It consists of marginal metasedimentary rocks and central pelitic, gneissic and plutonic rocks. Metamorphism is Barrovian, at depths less than 10 km, and grade increases from margins to core of the belt: the outermost pelites are at chlorite-muscovite grade; inward a garnet-andalusite zone formed throughout the inner margin; and the central zone ranges form garnet-andalusite in the west and garnet-sillimanite-muscovite to garnet-sillimanite-cordierite and rare kyanite 6 to 150 km to the east. This increase is correlated with granitic intrusives. Migmatites in the core have intrusive leucosomes in the west and locally derived ones in the east. Isograd surfaces are steep where the belt is narrow and dip gently where it is wide. The Quetico Park intrusive complex of the central region of the Quetico Belt shows a zonation across it 20 to 50 km width from older, medium grained biotite composition to younger, coarse to pegmatitic granitic composition. Sediment of the Quetico basin had its source in the bordering metavolcanic belts and was deposited ca. 2.75 to 2.70 Ga ago. Boundaries of the belt dip inward, so it essentially is a graben of inter-arc or back-arc type.

  12. Magma flow recorded by magmatic and magnetic fabrics in a shallow granitic pluton: La Gloria Pluton, central Chile

    NASA Astrophysics Data System (ADS)

    Payacán, I. J.; Gutiérrez, F. J.; Gelman, S. E.; Bachmann, O.; Parada, M. A.

    2013-12-01

    To better understand the dynamics of a small, shallow, silicic magma reservoir, magmatic and magnetic (AMS) fabrics are compared in samples obtained from La Gloria Pluton (LGP), a 10 Ma granitic intrusion located in southern Andes. The magnetic fabric of LGP, mainly given by magnetite, is characterized by oblate shapes. Magnetic lineations have a NW trend with subhorizontal dip, following the main pluton elongation, while magnetic foliation planes have dips varying gradually from vertical at the walls to subhorizontal toward the center and the roof of the pluton. On the basis of numerical simulations, magnetic fabric was interpreted to represent the shear record induced by magmatic convection along solidification fronts as the reservoir reached its rheological locking point. Magmatic fabric (mineral orientation) was determined on 12 samples along the pluton. Three mutually orthogonal thin sections were produced for each sample, perpendicular to the AMS tensor axes. Size and orientation of individual crystals were obtained by image analysis. A 2-D tensor for two mineral groups (plagioclase and amphibole+biotitie) was defined in each mineral plane projecting the crystal lengths on the main crystal orientation (given by Bingham statistics). A 3-D magmatic fabric tensor was obtained. In order to compare the magmatic and magnetic fabrics, magmatic anisotropy parameters were defined similar to the AMS tensors. Magmatic fabric and anisotropy parameter values vary depending on the location inside the pluton: (1) Samples located at the borders exhibit vertical foliations and lineations with a NW trend, similar to the magnetic fabric tensors and higher anisotropy values for plagioclase than amphibole+biotite,; (2) samples located at the center of the LGP commonly present subvertical foliations/lineations, which differ from the magnetic fabric, and higher magmatic anisotropy degree values for amphibole+biotite than plagioclase. Based on numerical simulations of the fluid

  13. The Swansea Plutonic Suite: Synextensional magmatism in the Buckskin and Rawhide Mountains, west-central Arizona

    SciTech Connect

    Bryant, B.; Nealey, L.D. . Denver Federal Center); Wooden, J.L. )

    1993-04-01

    About 200 km[sup 2] of the crystalline rocks exposed below the Buckskin-Rawhide detachment fault in west-central Arizona consists of gabbro to granite of the 20--30 Ma Swansea Plutonic Suite. Gabbro is only locally mylonitized and is intruded by more felsic rocks of the suite. The felsic rocks have a well-developed mylonitic texture and northeast-trending mineral lineation formed by ductily deformed quartz grains and aggregates. The felsic rocks are generally fine to medium grained except for a distinctive porphyritic phase, in which K-feldspar phenocrysts (now porphyroclasts) are as much as 3 cm in diameter. The suite is calcic to alkali calcic, metaluminous to weakly peraluminous (A/CNK = 0.7--1), and has average Th/U of 4.8 and Rb/Sr of 0.11. It shows a wide range in total rare-earth abundances (REE = 132--393 ppm), light to heavy REE enrichment (chondrite normalized [CN] La/Yb = 3--52), and heavy REE enrichment (CN Yb = 2.6--24.5). Intermediate and silicic members are depleted in HREE compared with mafic members, indicating magmatic control by clinopyroxene with or without amphibole or garnet. The porphyritic phase has the highest total REE and HREE abundances. Lead isotope ratios cluster in tight groups between reference lines for the Mohave and central Arizona crustal provinces. Lead in the porphyritic phase is distinctly less radiogenic than in the other phases. U-Pb zircon age of a granite in the suite is 21 [+-] 1.5 Ma. Upper intercept of the discordia line is 1,420 [+-] 54 Ma, indicating that 1,400-Ma rock dominates the source region for at least the felsic rocks of the suite. The suite was emplaced during the beginning and early phases of crustal extension and was probably pulled southwest out from beneath the Colorado Plateau transition zone as extension progressed. Thus the suite may represent roots of subaerial volcanic centers at the margin of the transition zone, which chemically resemble rocks of the suite in major-element chemistry.

  14. Subvolcanic mafic to intermediate dike-systems: constraints on post-plutonic activity (S-Adamello, N-Italy)

    NASA Astrophysics Data System (ADS)

    Hurlimann, N.; Muntener, O.; Ulmer, P.

    2010-12-01

    Various scales of dike geometries provide a record of strain during their emplacement. Distinct dike generations might record strain-evolution through time. In addition, dike rocks are generally close to liquid compositions, in particular mafic compositions, relative to plutonic rocks. Here we present field evidence of structural relationships and first petrological and geochemical data that characterize the evolution of post-batholith subvolcanic magmatic activity during cooling of a plutonic-suite in the Southern Adamello massif (Italy). At least three different generations of mafic to intermediate dikes of picrobasaltic to andesitic composition postdate a succession of large volume pluton emplacement [1,2,3]. Early, partially deformed dike generations appear to reflect more local strain whereas later ones reflect a much more regional strain pattern that appears to be independent of interplutonic and wallrock contacts. Subvertical dikes are characterized by composite, multiple stage textures and are often phenocryst/xenocryst-rich whereas subhorizontal types are related to simpler one stage or pulse emplacement. Subhorizontal types show a wide range of phenocryst phases such as olivine, clinopyroxene, amphibole and plagioclase. Evolved phases such as allanite-epidote, titanite, apatite and zircon are mainly associated with more felsic zones or bands within the dikes. Plagioclase in these felsic zones shows a large range of compositional variation. Such felsic zones appear to represent evolved liquid segregations from rather closed system fractionation (equilibrium crystallization). Bulk rock geochemistry and petrography indicate an evolution to more evolved magmas towards younger generations and pulses. Particularly the later dike generations carry variable proportions of xenocrystic material. Major and trace element concentrations of bulk rocks indicate that aphyric dike margins in single pulse systems display a more evolved ‘hydraulic head’ followed by a

  15. Talking Rocks.

    ERIC Educational Resources Information Center

    Rice, Dale; Corley, Brenda

    1987-01-01

    Discusses some of the ways that rocks can be used to enhance children's creativity and their interest in science. Suggests the creation of a dramatic production involving rocks. Includes basic information on sedimentary, igneous, and metamorphic rocks. (TW)

  16. Significant Enrichment of Polyunsaturated Fatty Acids (PUFAs) in the Lipids Extracted by Supercritical CO2 from the Livers of Australian Rock Lobsters (Jasus edwardsii).

    PubMed

    Nguyen, Trung T; Zhang, Wei; Barber, Andrew R; Su, Peng; He, Shan

    2015-05-13

    Australian rock lobster (Jasus edwardsii) liver contains approximately 24.3% (w/w) lipids, which can contain a high amount of polyunsaturated fatty acids (PUFAs). However, this material has been found to be contaminated with arsenic (240 mg/kg) and cadmium (8 mg/kg). The high level of contaminants in the raw material and the large amount of PUFAs in the lipids prove a significant challenge in the extraction of high-quality lipids from this byproduct by conventional methods. Supercritical carbon dioxide (SC-CO2) extraction is a highly promising technology for lipid extraction with advantages including low contamination and low oxidation. The technique was optimized to achieve nearly 94% extraction of lipids relative to conventional Soxhlet extraction in Australian rock lobster liver at conditions of 35 MPa and 50 °C for 4 h. The extracted lipids are significantly enriched in PUFAs at 31.3% of total lipids, 4 times higher than those in the lipids recovered by Soxhlet extraction (7.8%). Specifically, the concentrations of docosahexaenoic acid (DHA) and eicosapentaenoic acid (EPA) in SC-CO2 extraction are 7 times higher than those obtained by Soxhlet extraction. Moreover, very small amounts of toxic heavy metals such as lead (Pb), arsenic (As), mercury (Hg), and cadmium (Cd) were detected in the SC-CO2-extracted lipids, 0.5-27 times lower than those in the Soxhlet-extracted lipids, which are 40-200 times lower than the regulatory limit maximum values. The low levels of contaminants and the high proportion of PUFAs (dominated by DHA and EPA) found in the SC-CO2-extracted lipids from Australian rock lobster liver suggest that the material could potentially be used as a valuable source of essential fatty acids for human consumption. PMID:25905456

  17. Developing the ability to model acid-rock interactions and mineral dissolution during the RMA stimulation test performed at the Soultz-sous-Forêts EGS site, France

    NASA Astrophysics Data System (ADS)

    Portier, Sandrine; Vuataz, François D.

    2010-07-01

    The Soultz Enhanced Geothermal System (EGS) reservoir's response to chemical stimulation is assessed by numerical simulation of coupled thermo-hydraulic-chemical processes. To assess chemical interactions between host rocks and a mixture of HCl and HF as well as its potential effects on the Soultz EGS reservoir, new modelling efforts using the FRACHEM code have been initiated. This article presents the model calibration and results. Simulations consider realistic conditions with available data sets from the EGS system at Soultz. Results indicate that the predicted amount of fracture sealing minerals dissolved by injection of a mixture of acids Regular Mud Acid (RMA) was consistent with the estimated amount from the test performed on GPK4 well at Soultz EGS site. Consequently reservoir porosity and permeability can be enhanced especially near the injection well by acidizing treatment.

  18. Deeply Eroded Massif Anorthosite and Nepheline Syenite of the Chimakurti-Uppalapadu Plutons, Peninsular India: Cospatial but not Comagmatic

    NASA Astrophysics Data System (ADS)

    Kumar, K.; Frost, C. D.; Frost, B. R.

    2001-12-01

    plagioclase buoyancy and re-melting) of tholeiitic magma. The calculated parental liquid REE concentrations to the CAG suite show LREE-enriched patterns with positive Eu anomalies, similar to the proposed parental liquids to other massif anorthosites. The HQF series represents residual liquids to the parental magma that produced CAG suite, but with crustal inputs. Attempts to model the derivation of Si-oversaturated HQF series from Si-undersaturated NS and vice-versa were not successful. The NS could be the end product of a long liquid-line-of-descent of mantle-derived alkali basaltic magma or a partial melt of shallow melting of metasomatised mantle or alkali basalt. The second possibility is favored because of the predominance of felsic rocks and almost complete absence of mafic rocks in the Uppalapadu pluton. This study strongly suggests that 1) the ultimate source for massif anorthosites is tholeiitic mantle and the early stage of differentiation is dominated by Al-rich clinopyroxene fractionation, 2) the cospatial anorthosites and nepheline syenites are not cogenetic, but the nepheline syenites require an alkalic source. This magmatic association in the Prakasam Province is akin to the coeval alkalic and tholeiitic basalt magmatism of many rift-related environments.

  19. An integrated zircon geochronological and geochemical investigation into the Miocene plutonic evolution of the Cyclades, Aegean Sea, Greece: part 2—geochemistry

    NASA Astrophysics Data System (ADS)

    Bolhar, Robert; Ring, Uwe; Kemp, Anthony I. S.; Whitehouse, Martin J.; Weaver, Steve D.; Woodhead, Jon D.; Uysal, I. Tonguc; Turnbull, Rose

    2012-12-01

    Zircons from 14 compositionally variable granitic rocks were examined in detail using CL image-guided micro-analysis to unravel the complex magmatic history above the southward retreating Hellenic subduction zone system in the Aegean Sea. Previously published U-Pb ages document an episodic crystallisation history from 17 to 11 Ma, with peraluminous (S-type) granitic rocks systematically older than closely associated metaluminous (I-type) granitic rocks. Zircon O- and Hf isotopic data, combined with trace element compositions, are highly variable within and between individual samples, indicative of open-system behaviour involving mantle-derived melts and evolved supracrustal sources. Pronounced compositional and thermal fluctuations highlight the role of magma mixing and mingling, in accord with field observations, and incremental emplacement of distinct melt batches coupled with variable degrees of crustal assimilation. In the course of partial fusion, more fertile supracrustal sources dominated in the earlier stages of Aegean Miocene magmatism, consistent with systematically older crystallisation ages of peraluminous granitic rocks. Differences between zircon saturation and crystallisation temperatures (deduced from zircon Ti concentrations), along with multimodal crystallisation age spectra for individual plutons, highlight the complex and highly variable physico-compositional and thermal evolution of silicic magma systems. The transfer of heat and juvenile melts from the mantle varied probably in response to episodic rollback of the subducting lithospheric slab, as suggested by punctuated crystallisation age spectra within and among individual granitic plutons.

  20. Distribution of elements in biotite-hornblende pairs and in an orthopyroxene-clinopyroxene pair from zoned plutons, northern Sierra Nevada, California

    USGS Publications Warehouse

    Hietanen, A.

    1971-01-01

    Distribution of major and minor elements has been determined for five hornblende-biotite pairs from hornblende-biotite quartz diorite and monzotonalite and for a clinopyroxene-orthopyroxene pair from pyroxene diorite collected from the border zones and centers of zoned plutons in the northern Sierra Nevada, California. The distribution coefficients Kd [Mg/Fe] for biotite/hornblende are of the same magnitude (0.61-0.67) for both the mafic border zone and the silicic center. For comparison, KD [Mg/Fe] values for biotite/hornblende from plutonic rocks of the central Sierra Nevada and the southern California batholith were calculated from data published by others. Rocks of the oldest age group (ca. 150 m.y.) in the central Sierra Nevada have an average distribution coefficient, KD, of 0.64, close to the average KD in the study area, where K-Ar dates are 143 to 129 m.y. The intermediate age group has an average KD=0.81, and the youngest group has KD=0.77. KD [Mg/Fe] for biotite/hornblende from the southern California batholith is 0.83, close to the average of the intermediate age group in the central Sierra Nevada. The calculated difference in pressure of crystallization between rocks of the Feather River area and the southern California batholith is 1 kb; the rocks of the Feather River area being crystallized at a higher pressure. This is in good agreement with the low-pressure contact metamorphism in the south (pyroxene hornfels facies), as compared with a medium-pressure metamorphism around the northern plutons, where andalusitesillimanite-cordierite and andalusite-staurolite subfacies of the amphibolite facies indicate pressures of about 4 kb. Trace elements Cr, V, Ni, Co, Ga are distributed equally between biotite and hornblende, whereas Ba and possibly Cu are concentrated in biotite and Sr and Sc and possibly Zr in hornblende. ?? 1971 Springer-Verlag.

  1. The displaced eugeoclinal rocks in the El Paso Mountains and northern Mojave Desert: A Triassic sliver

    SciTech Connect

    Miller, J.S.; Glazner, A.F. . Dept. of Geology); Walker, J.D.; Martin, M.W. . Dept. of Geology)

    1993-04-01

    Many workers have drawn attention to the displaced eugeoclinal rocks in the northern Mojave Desert and El Paso Mountains and their importance in models for the development of an active continental margin in the western Cordillera. Existing models can generally for either strike-slip juxtaposition or thrust emplacement. New field data, U-Pb zircon geochronology, and isotopic data for metasedimentary rocks and plutons in the northern Mojave Desert and El Paso Mountains shed light on the timing and mechanism of emplacement of the eugeoclinal allocthon. The observations and data above indicate that Early Triassic plutons in the northern Mojave Desert came through oceanic lithosphere but later Jurassic plutons intercepted continental lithosphere. The authors suggest a model where eugeoclinal rocks were deposited on oceanic crust which was initially brought southward along a strike-slip fault and later thrust eastward over the cratonal assemblage. Permian thrusting is incompatible with their data and observations. Intrusion of lower Triassic strata by Early Triassic plutons in the Lane Mountain area permits some Early Triassic thrusting but the oceanic affinity of the plutons implies that thrusting did not involve continental lithosphere.

  2. A hybrid origin for two Cretaceous monzonitic plutons in eastern Zhejiang Province, Southeast China: Geochronological, geochemical, and Sr-Nd-Hf isotopic evidence

    NASA Astrophysics Data System (ADS)

    Liu, Liang; Qiu, Jian-Sheng; Zhao, Jiao-Long

    2016-01-01

    Monzonites can provide important information about the nature of the mantle sources and the mechanism of crust-mantle interactions. However, details on the origin of Late Mesozoic monzonites in the Southeastern China remain poorly constrained. This paper presents whole-rock geochemical, Sr-Nd isotopic and zircon U-Pb and Hf isotopic data for two monzonitic plutons (Huangtanyang and Kanggu) in eastern Zhejiang Province, with the aim of elucidating their petrogenesis, and providing important insights into the process of crust-mantle interaction. LA-ICP-MS zircon U-Pb dating results imply that the Huangtanyang and Kanggu quartz monzonites were emplaced in Cretaceous (104-109 Ma). All quartz monzonites are intermediate to acidic, metaluminous to weakly peraluminous, subalkaline, and K-rich in composition. They are enriched in large ion lithophile (e.g., Rb, Ba and Pb) and light rare earth elements, depleted in high-field strength elements (e.g., Nb, Ta, and Ti), and show weakly negative or no Eu anomalies (δEu = 0.78-1.02). All quartz monzonites have homogeneous initial ISr values (0.7084-0.7090) and εNd(t) values (-7.50 to -6.84). They are characterised by highly variable zircon Hf isotopic compositions, with εHf(t) values ranging from -13.3 to -5.7. The combined geochemical evidences (such as high Mg# values, low Nb/U and Ta/U ratios, and variable zircon Hf isotopic compositions) suggests that both depleted asthenospheric and metasomatically enriched mantle components were involved in the formation of the monzonites. The existence of some zircons with unusually low εHf(t) values (low to -13.3) and Palaeoproterozoic two-stage Hf model ages from the Huangtanyang and Kanggu quartz monzonites also argues strongly for Palaeoproterozoic crustal involvement. Magma mixing played a dominated role in the genesis of these monzonites, as indicated by their wide range in zircon Hf isotopic compositions and the occurrence of mafic microgranular enclaves (MMEs). The MMEs show

  3. Arc petrogenesis in southern Ireland and the Isle of Man: Implications for Ordovician accretionary history and constraints from Late Caledonian plutonism

    NASA Astrophysics Data System (ADS)

    Fritschle, Tobias; Daly, J. Stephen; Whitehouse, Martin J.; McConnell, Brian; Buhre, Stephan

    2016-04-01

    Peri-Laurentian and peri-Gondwanan magmatic arcs and microcontinents, and their attendant sedimentary basins were assembled during the Caledonian Orogeny (c. 490 - 400 Ma) to form the Irish and British lithosphere. Accretion of these terranes to Laurentia and subsequent closure of the Iapetus Ocean initiated the generation of widespread Late Caledonian plutons (c. 425 - 400 Ma). Petrogenetic investigation of Ordovician arc-related rocks aims to test possible terrane affinities, using geochemical data from the arcs and related rocks as well as isotopic signatures preserved within Late Caledonian granites. SIMS zircon U-Pb geochronology has provided middle to early Ordovician ages for volcanic rocks with arc affinities from Avoca (Ireland, c. 463 Ma) and a newly discovered volcanic sequence from Port-e-Vullen (Isle of Man, c. 473 Ma). Granitic rocks from Leinster (Ireland), interpreted as arc plutons, yielded late to middle Ordovician ages of c. 457 - 454 Ma (Croghan Kinshelagh) and c. 462 - 459 Ma (Graiguenamanagh), similar to the c. 457 Ma age of the Dhoon Granite (Isle of Man). Oxygen isotopic compositions of zircons from the Ordovician volcanic and plutonic rocks are close to or slightly heavier than mantle values (δ18O generally < 7 ‰). Lu-Hf zircon compositions suggest different terrane affinities: relatively juvenile ɛHfT values (c. +8.5 - +5.3) for the Avoca volcanics are similar to those of the older unit of the Croghan Kinshelagh Granite, whereas the Port-e-Vullen volcanics and the Graiguenamanagh Granite have less radiogenic ɛHfT values (c. +4.4 - +1.3). The present-day geographic distribution of these rocks and petrogenetic inferences from their North American correlatives invite comparison with the Avalonian and the Ganderian microcontinent, respectively[1]. These constraints are supported by inherited zircons and corresponding isotopic analyses. ɛHfT values (c. +11.5 - +1.5) from magmatic zircons of the Dhoon Granite and the younger unit of the

  4. Sr and Pb isotopic geochemistry of feldspars and implications for the growth of megacrysts in plutonic settings.

    NASA Astrophysics Data System (ADS)

    Munnikhuis, J.; Glazner, A. F.; Coleman, D. S.; Mills, R. D.

    2015-12-01

    Why megacrystic textures develop in silicic igneous rocks is still unknown. One hypothesis is that these crystals nucleate early in a magma chamber with a high liquid content. A supportive observation of this hypothesis is areas in plutons with high concentrations of megacrysts suggesting flow sorting. Another group of hypotheses suggest megacrystic textures form during protracted late-stage coarsening in a low-melt, interlocked matrix due to either thermal oscillations from incremental pluton emplacement, or Ostwald ripening. Isotopic analyses of large, euhedral K-feldspar megacrysts from the Cretaceous intrusive suites of the Sierra Nevada batholith (SNB) provide new insight into their origin. Megacrysts from the SNB reach the decimeter scale, are Or rich (85-90%), are perthitic, and host mineral inclusions of nearly all phases in the host rock. In-situ micro-drilling of transects, from core to rim, of the alkali feldspars provides material for Sr and Pb isotopic analyses by thermal ionization mass spectrometry (TIMS). Preliminary 87Sr/86Sr(i) isotopic data from samples from the Cathedral Peak Granodiorite, of the Tuolumne Intrusive Suite range from 0.706337 to 0.706452 (~1.6ɛSr) near the cores, whereas a sawtooth pattern with larger variability, 0.706179 to 0.706533 (~5ɛSr), occurs nears the rims. We interpret these preliminary data to indicate that the late portion of growth (i.e. crystal rim) was dominated by either cannibalism of small K-feldspar crystals with isotopic variability, or by addition of isotopically diverse late components to the magma. By comparing the Sr and Pb isotopic stratigraphy of megacrysts from a variety of rock matrices and different granitoids in the SNB isotopic trends can be evaluated to determine if crystals sizes are dependent on disequilibrium processes or grow at a steady state.

  5. Numerical simulations of late-stage magma flow in La Gloria pluton, central Chile

    NASA Astrophysics Data System (ADS)

    Gutierrez, F. J.; Payacan, I.; Bachmann, O.; Parada, M.

    2012-12-01

    along solidification fronts. The core of the chamber remains at temperatures above the solidus as a consequence of thermal insulation from the colder host rocks, ultimately surviving up to 20 k.y. This allows enough time for extraction of residual leucogranitic melt and late magmatic reactive processes. The model explains (1) the previously determined compositional and mineralogical zoning pattern in the pluton; (2) late magmatic mineral re-equilibration recorded in samples from the core of the pluton; (3) the late-stage liquid extraction from a crystal mush, producing leucogranite dikes found in several areas around LGP; and (4) the AMS and mineral orientation data. This research has been developed by the FONDECYT N°11100241 and PBCT-PDA07 projects granted by Chilean National Commission for Science and Technology (CONICYT ). FG and OB were supported by U.S. National Science Foundation (NSF) grant EAR-080982 during the completion of this research. Temperature of the magma: (A) maximum and minimum value on time; and (B) cross section of the model at 3.5 kyr of simulation.

  6. Geologic and hydrologic controls on the economic potential of hydrothermal systems associated with upper crustal plutons

    NASA Astrophysics Data System (ADS)

    Weis, Philipp; Driesner, Thomas; Scott, Samuel; Lecumberri-Sanchez, Pilar

    2016-04-01

    Heat and mass transport in hydrothermal systems associated with upper crustal magmatic intrusions can result in resources with large economic potential (Kesler, 1994). Active hydrothermal systems can form high-enthalpy geothermal reservoirs with the possibility for renewable energy production. Fossil continental or submarine hydrothermal systems may have formed ore deposits at variable crustal depths, which can be mined near today's surface with an economic profit. In both cases, only the right combination of first-order geologic and hydrologic controls may lead to the formation of a significant resource. To foster exploration for these hydrothermal georesources, we need to improve our understanding of subsurface fluxes of mass and energy by combining numerical process modelling, observations at both active and fossil systems, as well as knowledge of fluid and rock properties and their interactions in natural systems. The presentation will highlight the role of non-linear fluid properties, phase separation, salt precipitation, fluid mixing, permeability structure, hydraulic fracturing and the transition from brittle to ductile rock behavior as major geologic and hydrologic controls on the formation of high-enthalpy and supercritical geothermal resources (Scott et al., 2015), and magmatic-hydrothermal mineral resources, such as porphyry copper, massive sulfide and epithermal gold deposits (Lecumberri-Sanchez et al., 2015; Weis, 2015). References: Kesler, S. E., 1994: Mineral Resources, economics and the environment, New York, McMillan, 391. Lecumberri-Sanchez, P., Steele-MacInnis, M., Weis, P., Driesner, T., Bodnar, R.J. (2015): Salt precipitation in magmatic-hydrothermal systems associated with upper crustal plutons. Geology, v. 43, p. 1063-1066, doi:10.1130/G37163.1 Scott, S., Driesner, T., Weis, P. (2015): Geologic controls on supercritical geothermal resources above magmatic intrusions. Nature Communications, 6:7837 doi: 10.1038/ncomms8837 Weis, P. (2015): The

  7. Spatial distribution analysis of igneous textures: Numerical modeling and interpretation of crystal accumulation in plutons

    NASA Astrophysics Data System (ADS)

    Špillar, Václav; Dolejš, David

    2014-05-01

    systematic and progressive decrease in melt extraction towards the pluton roof. The melt extraction has appeared at initial phenocryst crystallinities of ~10 %. By contrast, olivine crystal patterns in the cumulate zone of komatiite flows record degree of melt extraction up to over 80 % (crystal accumulation by a factor of three). The modeling is consistent with the phenocrysts in porphyritic rocks being early crystals, possibly displaced from their original site, rather than the late-stage products coarsened during the period of subsolidus annealing. Our results provide an approach and constraining parameters to quantitatively assess the mechanical mobility and the role of crystal accumulation during the magma emplacement and pluton construction based on textural record.

  8. Origin and evolution of calcalkaline plutons in the Northeast Kingdom batholith, Vermont

    SciTech Connect

    Ayuso, R.A.; Arth, J.G.

    1985-01-01

    Geochemical and petrographic study of five calcalkaline Devonian plutons in the Northeast Kingdom batholith suggests that they were generated from similar sources but evolved differently. The modally homogeneous Willoughby granite (WG) and the Derby granodiorite (DG) are the most aluminous plutons and contain muscovite and biotite (+/- garnet). The West Charleston diorite (WCD) and the Nulhegan granodiorite (NG) are relatively mafic plutons containing pyroxene, hornblende, and biotite. The Echo Pond (EP) has a granodioritic core but is dioritic along its southern margin. Regular variations of major and trace elements are found in NG and in the relatively sodic DG. More erratic chemical variations are found for WG. The more mafic plutons have higher Sr and lower Rb, Nb and Ta compared to the more felsic WG and DG. Rare-earth patterns for all plutons show higher light than heavy rare-earths. However, the more mafic plutons are comparatively less enriched, have smaller Eu anomalies, and tend to have higher contents of heavy rare earths than the WG and DG. The felsic Willoughby pluton is the best candidate for an upper crustal minimum melt. A deeper origin for the more mafic plutons is likely. Significant differences in the rare earths and ferromagnesian elements indicate that the WG, DG, and EP cannot be related by a simple fractionation scheme to the more mafic plutons.

  9. Discrimination of alkalinity in granitoid Rocks: A potential TIMS application

    NASA Technical Reports Server (NTRS)

    Ruff, Steven W.

    1995-01-01

    In mineral exploration, the ability to distinguish and map petrochemical variations of magmatic rocks can be a useful reconnaissance tool. Alkalinity is one such petrochemical parameter and is used in the characterization of granitoid rocks. In quartz normative plutonic rocks, alkalinity is related to the composition and abundance of feldspars. Together with quartz abundance, knowledge of feldspar modes allows the classification of these igneous rocks according to the Streckeisen diagram. Alternative classification schemes rely on whole rock geochemistry instead of mineral identifications. The relative ease of obtaining whole rock analyses means that geochemical classifications tend to be favored in exploration geology. But the technique of thermal infrared spectroscopy of rocks yields information on mineralogy and is one that can be applied remotely. The goal of the current work then is to establish whether data from TIMS can be used to distinguish the mineralogical variations that relate to alkalinity. An ideal opportunity to test this thesis arises from the work presented in a paper by Dewitt (1989). This paper contains the results of mapping and analysis of Proterozoic plutonic rocks in north-central Arizona. The map resulting from this work delineates plutons according to alkalinity in an effort to establish a trend or polarity in the regional magmatism. Also contained within this paper are brief descriptions of the mineralogy of half of the region's plutons. This combination of mineralogical and geochemical information was the rationale behind choosing this area as a site for TIMS over flights. A portion of the region centered on the northern Bradshaw Mountains was selected because it contains plutons of all three alkalinity classifications (alkali-calcic, calc-alkalic, and calic) present on DeWitt's map within a relatively small area. The site was flown in August of 1994 and the data received a few days before the writing of this manuscript. Most of this

  10. On the reliability of AMS in ilmenite-type granites: an insight from the Marimanha pluton, central Pyrenees

    NASA Astrophysics Data System (ADS)

    Oliva-Urcia, B.; Casas, A. M.; Ramón, M. J.; Leiss, B.; Mariani, E.; Román-Berdiel, T.

    2012-04-01

    The anisotropy of magnetic susceptibility (AMS) at room temperature has been used for decades to obtain the petrofabric orientation in granites as a kinematic marker to establish models explaining the emplacement of plutons. To assess the significance of AMS in terms of mineral orientation, we have performed a multidisciplinary study at five sites of an ilmenite-type pluton (Marimanha, central Pyrenees) with significant facies changes. To test the reliability of AMS measurements at room temperature, the following methods were applied: low temperature AMS; image analyses and X-ray texture goniometry (XTG) of biotites; and electron backscatter diffraction (EBSD) to obtain c-axes directions of quartz. The total (para-, ferro- and dia-)magnetic fabric analysed by AMS is compared with the paramagnetic fabric (low-T AMS), mica orientation (with image analyses and XTG) and the diamagnetic fabric (EBSD). Results indicate that weakly oriented paramagnetic minerals can give well-defined magnetic fabrics (AMS at room and low temperatures). Furthermore, the AMS ellipsoid is the result of composite biotite fabrics resulting from both orientation and spatial distribution of crystals, as demonstrated by 2-D mathematical models presented in this study. AMS is the most effective technique for quickly measuring composite fabrics. In addition, the advantage of using AMS analyses is twofold: (1) it is a fast way of analysing standard samples that can give clues for subsequent image/mineral orientation analysis and (2) it is a volume-related method that gives a picture of the rock fabric as a whole.

  11. Assimilation of the plutonic roots of the Andean arc controls variations in U-series disequilibria at Volcan Llaima, Chile

    NASA Astrophysics Data System (ADS)

    Reubi, O.; Bourdon, B.; Dungan, M. A.; Koornneef, J. M.; Sellés, D.; Langmuir, C. H.; Aciego, S.

    2011-02-01

    U-series disequilibria provide important constraints on the processes and time scales of melt production, differentiation, and transport in subduction settings. Such constraints, which are essential for understanding the chemical evolution of the continental crust, are conventionally based on the assumption that the U-series disequilibria measured in mafic lavas are produced during mantle metasomatism and melting, and that intracrustal differentiation and assimilation have limited impacts. Here we show that mantle-derived U-series disequilibria in mafic lavas erupted at Volcán Llaima, Chile are significantly diminished by assimilation of plutonic rocks forming Llaima's subvolcanic basement. This contamination process is extremely subtle in terms of "classical" indicators of crustal assimilation like Sr, Nd or Pb isotopes because it is a manifestation of assimilative recycling of the plutonic roots of the arc. This process results in variations in U-series disequilibria and incompatible trace element ratios that are significant compared to regional and global variability in arc magmas. Furthermore, it yields linear correlations between U-series excesses and incompatible trace element ratios that are generally interpreted as slab-fluid indicators and chronometers, or tracers of sediment recycling in subduction zone. Cannibalization of ancestral magmas by ascending melts warrants careful evaluation when considering the components and chemical fluxes in subduction zones. Linear arrays defined by activity ratios of U-series nuclides with different half-lives may be the most reliable indicators of assimilative recycling of ancestral intrusive magmas.

  12. Near conductive cooling rates in the upper-plutonic section of crust formed at the East Pacific Rise

    NASA Astrophysics Data System (ADS)

    Faak, Kathrin; Coogan, Laurence A.; Chakraborty, Sumit

    2015-08-01

    A new geospeedometer, based on diffusion modeling of Mg in plagioclase, is used to determine cooling rates of the upper section of the lower oceanic crust formed at fast-spreading mid-ocean ridges. The investigated natural sample suites include gabbroic rocks formed at three different locations along the fast-spreading East Pacific Rise. These samples cover a depth interval of 0-840 m below the sheeted dike/gabbro boundary and therefore allow the variation of cooling rate as a function of depth within the upper plutonic sequence to be determined. We demonstrate that the cooling rates we obtained are robust (reproducible and consistent across different vertical sections at fast spreading ridges) and decrease significantly with increasing sample depth (covering almost 4 orders of magnitude, ranging from ∼1 °C y-1 for the shallowest samples to 0.0003 °C y-1 for the deepest samples). Both the absolute cooling rates, and the rate of decrease of cooling rate with depth, are consistent with conductive thermal models. In contrast, the absolute cooling rates determined from the deeper samples (>300 m below DGB), and the large decrease in cooling rate with depth are inconsistent with thermal models that include substantial cooling by off-axis hydrothermal circulation within the upper plutonic section of the crust.

  13. Late Paleozoic granitic rocks of the Chukchi Peninsula: Composition and location in the structure of the Russian Arctic

    NASA Astrophysics Data System (ADS)

    Luchitskaya, M. V.; Sokolov, S. D.; Kotov, A. B.; Natapov, L. M.; Belousova, E. A.; Katkov, S. M.

    2015-07-01

    An Early Carboniferous (352-359 Ma) U-Pb (TIMS, SIMS) age is established for granitic rocks of the Kibera pluton, quartz sienites of the Kuekvun pluton, and granites from the pebbles in the basement of Carboniferous rocks of the Kuul and Kuekvun uplifts in the Central Chukotka region. These data support the suggestion of granitic magmatism to occur in the region in the Late Paleozoic. The petrogeochemistry of most granitic rocks of the Kibera and Kuekvun plutons is similar to that of I-type granites, and their age coincides with tectonic events of Ellesmerian Orogeny in the Arctic region at the Late Devonian-Early Carboniferous boundary. The Devonian-Early Carboniferous granitic complexes extend to the territories of the Arctic Alaska, Yukon, and Arctic Canada, which indicates a common geological evolution within the Chukotka-Arctic Alaska block, which experienced a motion away from Arctic Canada.

  14. Decompressional metamorphic P-T paths from kyanite-sillimanite-andalusite bearing rocks in north-central New Mexico

    SciTech Connect

    Daniel, C.G.; Thompson, A.G.; Grambling, J.A. . Dept. of Earth and Planetary Sciences)

    1992-01-01

    Proterozoic rocks in six uplifts in northern and central New mexico display decompressional metamorphic P-T paths, apparently, related to crustal extension at a time near 1,440 Ma. Metamorphic P-T paths from the Picuris, Rincon, Truchas, Rio Mora, Sandia and southern Manzano Mountains are constrained by three independent techniques: (1) Al[sub 2]SiO[sub 5] and other mineral parageneses; (2) the Gibbs method applied to compositional zoning in garnet and plagioclase; and (3) a new technique based upon Fe[sup 3+] and Mn[sup 3+] zoning in andalusite. Aluminum silicate textures suggest that kyanite and subsequent sillimanite (commonly aligned parallel to the regional foliation and lineation) are earlier than andalusite, which overprints foliation. The decompressional P-T paths are interpreted to reflect crustal extension. Contact metamorphic aureoles associated with the Priest pluton in the southern Manzano and the Sandia Granite in the Sandia Mountains place constraints upon the timing of the Ky-Sil-And metamorphism. In the southern Manzano Mountains metamorphic isograds marking the first appearance of staurolite and (closer to the pluton) sillimanite are parallel to the margin of the 1,440 Ma Priest quartz monzonite pluton. Similarly, isograds also surround the NW margin of the 1,420 Ma Sandia pluton. The regional metamorphism appears to have coincided with and to have been enhanced by the emplacement of the plutons. Because plutonism and regional metamorphism appear to have been synchronous, pluton emplacement occurred during decompression.

  15. Zircon U-Pb Ages Chronicle 3 Myr of Episodic Crystallization in the Composite Miocene Tatoosh Pluton, Mount Rainier National Park, Washington Cascades

    NASA Astrophysics Data System (ADS)

    Bacon, C. R.; Du Bray, E. A.; Wooden, J. L.; Mazdab, F. K.

    2007-12-01

    Zircon geochronology of upper crustal plutons can constrain longevities of intermediate to silicic magmatic systems. As part of a larger study of the geochemistry and metallogeny of Tertiary Cascades magmatic arc rocks, we used the USGS-Stanford SHRIMP RG to determine 20 to 28 238U-206Pb ages for zircons from each of 6 quartz monzodiorite (qmd), quartz monzonite (qm), or granodiorite (grd) samples representative of the Tatoosh pluton, and one grd from the nearby Carbon River stock. The 7x12 km composite Tatoosh pluton, discontinuously exposed on the south flank of Mount Rainier, consists of at least 4 petrographic/compositional phases, here termed Pyramid Peak, Nisqually, Reflection Lake, and Tatoosh. These collectively intrude gently folded and weakly metamorphosed basaltic andesite flows and volcaniclastic rocks of the Eocene Ohanapecosh Formation, silicic ignimbrites and sedimentary rocks of the Oligocene Stevens Ridge Formation, and basaltic to intermediate volcanic rocks of the Miocene Fifes Peak Formation. Histograms and relative probability plots of U- Pb ages indicate 2 to 4 age populations within each sample. The weighted mean age of each of the youngest populations (all ±2σ) is interpreted as the time of final solidification: Pyramid Peak qmd (58.5% SiO2) 17.4±0.2 Ma, Nisqually grd (in Paradise Valley; 65.4% SiO2) 16.7±0.2 Ma, Nisqually grd (at Christine Falls; 66.4% SiO2) 17.3±0.2 Ma, Reflection Lake qm (along Pinnacle Peak trail; 66.6% SiO2) 17.1±0.2 Ma, Tatoosh grd (in Stevens Canyon; 67.8% SiO2) 18.2±0.2 Ma, Tatoosh grd (south of Louise Lake; 69.3% SiO2) 19.3±0.1 Ma, and Carbon River grd (68.0% SiO2) 17.4±0.3 Ma. The older Nisqually grd age is indistinguishable from a TIMS zircon age of 17.5±0.1 Ma reported by Mattinson (GSA Bulletin 88:1509-1514, 1977) for grd from a nearby locality. None of the 164 SHRIMP-RG U-Pb ages, including cores, is older than 21 Ma. The relatively small, high-level pluton likely was emplaced and solidified in pulses

  16. Integrating field, microstructures, magnetic fabrics, metamorphic studies to establish Yavapai-Mazatazal-aged syntectonic pluton emplacement and strain localization in the Tusas Mountains, New Mexico

    NASA Astrophysics Data System (ADS)

    Davis, P.; Kruckenberg, S. C.

    2012-12-01

    Paleoproterozoic metamorphic rocks in the northern Tusas Mountains of New Mexico record the conditions of deposition, deformation and tectonic processes during assembly and stabilization of these rocks to the southern margin of the Laurentian craton. Metasedimentary and metavolcanic supracrustal rocks of the Vadito and Hondo groups comprise the majority of exposures, detrital zircon from within these units constrain the age of deposition ca. 1.70 Ga. - the Yavapai-Mazatazal temporal orogenic boundary. P-T conditions are ~425-600 C and 4-6 kbars. Two pervasive fold and fabric events are regionally displayed that have been locally modified by a third deformation event. Regional constraints on tectonism timing are mixed, with recent work showing that tectonism occurred ca. 1.4 Ga. Two orthogneiss bodies, the Tres Piedras (TP) and Tusas Mountain (TM) granites, were emplaced into supracrustal host rocks at ca. 1.69 Ga. Several datasets that include mapping and characterization of metamorphic assemblages, EBSD microstructural analysis, and anisotropy of magnetic susceptibility analyses suggest that emplacement was syntectonic. Metamorphic assemblages show a field-gradient that is roughly concentric to the TP and TM plutons from greenschist facies (ca. 400-425 C) in the distant country rock, to upper amphibolite facies (ca. 650 C) near the pluton contacts. This is a new discovery for the region, as most of northern New Mexico displays a regional amphibolite facies signature. Quartz and feldspar microstructures suggest that the body of both plutons record non-coaxial deformation from near solidus to high-T conditions (>600 C). Muscovite inclusions in cm-scale euhedral microcline grains are aligned with S1, and isoclinal folds in the TP lack an axial planar fabric. Measurement of the anisotropy of magnetic susceptibility (AMS) suggest that the orientation of magmatic fabrics within these plutons are consistent with principal regional fabrics (D1) recorded in the

  17. Structural characterization of the Misajé granitic pluton (NW Cameroon): constraints from magnetic and field observations

    NASA Astrophysics Data System (ADS)

    Fozing, Eric Martial; Njanko, Théophile; Naba, Séta; Kwékam, Maurice; Njonfang, Emmanuel; Rochette, Pierre

    2015-12-01

    The Misajé granitic pluton, emplaced between 569 and 560 Ma in an amphibolitic and gneissic host rock, comprises four petrographic units namely biotite-hornblende granite (BHG), granodiorite (Gd), biotite granite (BG), and leucocratic granite (LG). Four major tectonic events have been described in the studied area: a D1-early tectonic event, responsible of the E-W flat foliation which has been progressively transposed by a D2 tectonic event. A D2 event has developed heterogeneous simple shear in a dextral transpressive context with moderate to strong dipping NE-SW striking foliation; a D3 tectonic event has lead to a sinistral N-S ductile shear characterized by N- to ENE-striking foliation and E-W strike-slip shear corridors and a D4 tectonic event that developed N-S dextral ductile strike-slip deformation. The magnetic study of the pluton, based on the AMS parameters, reveals the coexistence of both paramagnetic (dominated by iron-bearing silicates; 54 % of sites) and ferromagnetic (due to the occurrence of PSD and MD grains of magnetite or other ferromagnetic minerals; 46 % of sites) behaviors. Magnetic foliation shows best poles at 55/82 for the whole pluton, 95/32 in BHG, and 273/83 in BG, and the magnetic lineation trends are mostly NNE-SSW with best lines at 210/8, 198/19, and 36/3, respectively. The trend of the magnetic lineation in BG indicates an S-shape trajectory, suggesting a sinistral sense of shear motion along discrete E-W corridors situated at the northern and southern ends. Kinematic indicators in BG point to a sinistral sense of shear, suggesting its emplacement during the D3 event. The close relationship between K 1 and K 3 points to a syn-kinematic emplacement and crystallization of the Misajé granitic pluton during the Pan-African event, and the tectonic evolution of the study area is considered to be coeval with the tectonic evolution of the trans-Saharan Pan-African belt of eastern Nigeria.

  18. Why are plutons dry? Outgassing mechanisms of crustal magmatic bodies

    NASA Astrophysics Data System (ADS)

    parmigiani, andrea; Huber, Christian; Bachmann, Olivier; Leclaire, Sébastien

    2016-04-01

    Magma bodies crystallizing to completion within the crust (i.e., forming plutons) typically undergo significant amounts of second boiling (i.e. cooling and crystallization of dominantly anhydrous minerals lead to volatile saturation and bubble nucleation/growth). The low water content (< 1 wt % H2O) and vanishing residual porosity of most plutons, despite the high volatile concentrations of their magma sources (commonly > 6 wt % H2O for evolved compositions in subduction zones), testify that outgassing from crystalline mushy reservoirs must be an efficient and widespread process. Understanding this outgassing mechanism is key to understand how volatiles are transferred from mantle depths to the surface. From the hydrodynamics point of view, the mass balance of exsolved volatiles in these plutonic bodies is controlled by the difference between the rate of degassing (formation of bubbles by 2nd boiling) and outgassing (transport of gas out of the magma body). In this study, we use pore-scale multiphase modeling to constrain these rates as function of the crystal and volatile contents in the magma. Because second boiling is a slow process, one can consider equilibrium degassing as a valid assumption. Outgassing, on the other end, is controlled by the competition between buoyancy, capillary and viscous forces. Our numerical simulations are used to determine the most efficient setting for gas to escape its magmatic trap. The high viscosity of interstitial melts and capillary forces (due to the non-wetting nature of the gas phase with most of the mineral phases in magmatic systems) strongly limits gas transport until vertically extensive gas channels are generated. We show that channels can readily form in volatile-rich coarse-grained mush zones in the upper crust, and allow efficient outgassing at crystallinities around 50-75 vol%, when millimetric bubbles can still win capillary resistive forces.

  19. Assessment of zinc loading in an acid rock drainage alpine catchment using a tracer-injection and synoptic-sampling study

    NASA Astrophysics Data System (ADS)

    Crouch, C. M.; McKnight, D. M.; Todd, A.

    2010-12-01

    Seasonal low flow conditions in acid rock drainage (ARD) streams result in increased acidity and metal ion concentrations - changes that have been shown to become more pronounced with longer dry periods. These resulting increases in acidity and metals concentrations may pose an increasing danger to aquatic ecosystems and drinking water supplies. For example, in many ARD-impacted mountain streams, fish populations are not self-sustaining. The study site in the Upper Snake River watershed in Colorado is an alpine catchment impacted by acid rock drainage thought to originate from the natural weathering of pyrite whereas the main stem of the Snake River and its other tributaries are impacted by accelerated ARD resulting from historic mining activities. Because concentrations toxic to aquatic life persist well downstream of the ARD inputs, dissolved zinc is the primary metal of concern in this study. A compilation of historic data from the Snake River Watershed during the low flow months of September and October indicates that zinc concentrations have increased four-fold over the past 30 years. We hypothesize that this increase is due to changes in groundwater flow patterns caused by climate change and associated earlier peak snowmelt (by 2-3 weeks), resulting in lower stream flows and drier soils in late summer. The observed increase in background metals concentrations has implications for mitigation of former mining sites. A synoptic study to identify discrete surface water sources of zinc loading indicated a significant input from a tributary on the north side of the catchment. Zinc concentrations here measured an order of magnitude higher than in the main stem of the stream, and were correlated with increases in sulfate, hardness, and total metals, supporting our contention that increasing zinc concentrations are driven by the acceleration of ARD in the watershed. The current research further investigates sources of metal-rich inflows to the tributary using a tracer

  20. Protracted late magmatic stage of the Caleu pluton (central Chile) as a consequence of heat redistribution by diking: Insights from zircon data and thermal modeling

    NASA Astrophysics Data System (ADS)

    Molina, Pablo G.; Parada, Miguel A.; Gutiérrez, Francisco J.; Ma, Changqian; Li, Jianwei; Yuanyuan, Liu; Reich, Martin; Aravena, Álvaro

    2015-06-01

    Zircon U-Pb geochronology and geochemistry are combined with whole-rock composition and thermal modeling to decipher the late magmatic stage of the composite Cretaceous Caleu pluton, which consists of four lithological zones: Gabbro-Diorite Zone (GDZ), Quartz Monzodiorite Zone (QMDZ), Granodiorite Zone (GZ) and Monzogranite Zone (MGZ). The four lithological zones include felsic dikes and veins of variable thickness and distribution. Zircons of four representative samples, each from the mentioned zones, were dated and chemically analyzed. The U-Pb ages exhibit sample-scale scatter derived from protracted zircon crystallization. At pluton scale the ages are substantially overlapped with a subtle decrease of ages from mafic to felsic sample; the latter has a normal age span distribution with a mean age of 94.68 ± 0.71 (2σ confidence) and a MSWD of 0.95. Zircon grains from the uppermost zone of the pluton, where the QMDZ is emplaced, have the highest REE and HFSE contents. Zircon crystallization temperatures oscillate between 680 and 850 °C, regardless of the zircon age and sample composition. Differences in temperature and age of zircon crystallization of up to 185 °C and 2.6 Myr were identified at sample scale, respectively. Numerical modeling indicates that the melts from which zircon crystallized are highly crystalline (mostly higher than 60% crystal) and resemble MGZ in compositions. Time-dependent thermal models were performed to account for preservation of the system above solidus temperature for long time intervals consistent with those of zircon crystallization. Two non-exclusive scenarios for the late-stage development of Caleu pluton were considered: (i) pluton construction by magma pulses assembled incrementally and (ii) upward transport of residual melts by diking through a mush system to yield heat redistribution to the levels where the samples collected. The first scenario does not preserve residual melts for intervals as long as 2.6 Myr unless an

  1. U-Pb geochronology and geochemistry of Bibi-Maryam pluton, eastern Iran: Implication for the late stage of the tectonic evolution of the Sistan Ocean

    NASA Astrophysics Data System (ADS)

    Delavari, Morteza; Amini, Sadraddin; Schmitt, Axel K.; McKeegan, Kevin D.; Mark Harrison, T.

    2014-07-01

    The Bibi-Maryam pluton crops out in the Sistan suture zone, eastern Iran. This pluton is a 1.5 × 2 km stock composed of leucocratic tonalite, granodiorite and granite. U-Pb zircon geochronology of a leucogranite indicates an emplacement age of 58.6 ± 2.1 Ma (95% confidence). The Bibi-Maryam rock suite is sodic with elevated Na2O/K2O (2.9 to 5.5), Sr/Y (15.6-62.2), La/Yb (13.3-22.2), and low MgO (0.86-1.81) abundances. It lacks significant Eu anomalies. Because of these geochemical characteristics, Bibi-Maryam rocks are similar to high-SiO2 adakites. Trace element modeling indicates that the Bibi-Maryam adakitic rocks could be produced by 5-8% non-modal batch partial melting from a source with composition of 95% N-MORB + 5% sediment in the presence of 35-40% amphibole + 5-10% garnet + 55-60% clinopyroxene + 1% apatite + 1% rutile. This source mineralogy is similar to hornblende eclogite or garnet amphibolites. Collectively, these data provide new constraints for the evolution of the Sistan suture zone and suggest that the Bibi-Maryam pluton formed via slab melting in an oceanic arc and pre-plate collision tectonic setting. This implies that the closure of the Sistan Ocean and Lut-Afghan continental blocks collision happened after the Bibi-Maryam emplacement at 58.6 ± 2.1 Ma.

  2. Geology of crystalline rocks of northern Fiordland: details of the granulite facies Western Fiordland Orthogneiss and associated rock units

    USGS Publications Warehouse

    Bradshaw, J.Y.

    1990-01-01

    A c. 700 km2 area of northern Fiordland (South Island, New Zealand) is described in which Early Cretaceous high-pressure metamorphic rocks and virtually unmetamorphosed plutonic rocks occur. The dominant rocks are orthogneisses developed from synmetamorphic basic-intermediate intrusive complexes, the youngest and most widespread of which is the Early Cretaceous Western Fiordland Orthogneiss (WFO). The latter has undergone granulite facies metamorphism and occurs throughout much of western Fiordland. WFO was emplaced synkinematically in a subduction-related magmatic arc. A collisional event during or immediately following magma emplacement resulted in crustal thickening equivalent to onloading of a 20 km thick section over rocks already buried at mid-crustal depths. This event was responsible for peak load pressures of c. 12-13 kbar. The steeply dipping Surprise Creek Fault juxtaposes high-pressure metamorphic rocks of western and central Fiordland against virtually unmetamorphosed gabbroic rocks of the Early Cretaceous Darran Complex. -from Author

  3. The River Mountains Volcanic Section - Wilson Ridge Pluton, a Long Lived Multiphase Mid- Tertiary Igneous System in Southern Nevada and Northwestern Arizona, USA

    NASA Astrophysics Data System (ADS)

    Honn, D. K.; Simon, A. C.; Smith, E. I.; Spell, T. L.

    2007-12-01

    206Pb/238U zircon dates (LA-ICPMS) from 106-40 μm spots on 49 zircons suggest the Wilson Ridge Pluton in northwestern Arizona and its corresponding volcanic cover in the River Mountains of southern Nevada represent a complex multiphase igneous system active for 4.2 million years (based on a zircon core-rim pair) to a maximum of 7.2 million years (from two zircon rim dates 18.9 ± 0.8 to 13.1 ± 0.6 Ma). This period of activity is significantly longer than the 500 thousand year interval (12.99 ± 0.02 to 13.45 ± 0.02) determined by 40Ar/39Ar sanidine, biotite, hornblende, and whole rock dates. The 40Ar/39Ar dates only reflect the time when the igneous system cooled to mineral closure temperatures during emplacement in the upper crust. Zircon xenocrysts identified in cathodoluminescence images range in age from 1517.5 ± 11.2 Ma to 21.3 ± 0.8 Ma. Inherited zircon cores are as much as 8.9 million years older than their rims. Zircon dates correspond to pluton stratigraphy with late stage dikes at 15.3 Ma (mean age based on 9 dates), quartz monzonite intermediate in composition and age (mean age 15.5 Ma based on 20 dates), and the oldest unit, the Horsethief Canyon diorite (mean age 17.5 Ma based on 6 dates). Although the mean ages correspond to stratigraphy, the spread of ages for each unit overlaps, therefore these correlations are preliminary. The River Mountains volcanic section lies 20 km to the west of the pluton and may have been separated from it by west directed motion along the Saddle Island detachment fault. The River Mountains volcanic section and the Wilson Ridge Pluton are considered a single igneous system as demonstrated by major and trace element geochemistry, whole rock isotopic analyses (Sr and Nd), previous 40Ar/39Ar and K-Ar dates, mafic enclave chemistry, extensive magnesio-riebeckite alteration unique to both the River Mountains volcanic and Wilson Ridge Plutonic sections, and the location of the Saddle Island fault. Preliminary zircon dates

  4. Structural evolution of the Rieserferner Pluton: insight into the localization of deformation and regional tectonics implications

    NASA Astrophysics Data System (ADS)

    Ceccato, Alberto; Pennacchioni, Giorgio

    2016-04-01

    The Rieserferner pluton (RFP, Eastern Alps, 32.2±0.4 Ma, Romer et al. 2003) represents a relatively deep intrusion (12-15 km; Cesare, 1994) among Periadriatic plutons. The central portion of the RFP consists of dominant tonalites and granodiorites that show a sequence of solid-state deformation structures developed during pluton cooling and exhumation. This sequence includes: (1) quartz veins, filling two set of steeply-dipping joints trending respectively E-W and NW-SE, commonly showing a millimetric grain size and associated with strike-slip displacement. (2) Quartz- and locally epidote-filled shallowly E-dipping joint set, commonly exploited as discrete derived from both the quartz veins and the host tonalite. These mylonites show a composite sense of shear with a first stage of left-lateral strike-slip followed by a top-to-E dip-slip (normal) movement. The synmylonitic assemblage includes biotite + plagioclase + white mica + epidote ± sphene ± garnet. (3) Set of N-S-trending steeply-dipping joints. These joints are concentrated in zones 1-2 m wide, separated by otherwise un-jointed domains a few tens to hundred meters wide, and are commonly exploited as brittle-ductile faults with dominant dip-slip (normal) kinematics. The mineral assemblage of fault rocks includes white mica + calcite ± chlorite ± quartz. The joints/faults are locally involved in folding. (4) Mafic dikes, dated at 26.3±3 Ma (Steenken et al., 2000), locally injecting the N-S trending set of joints. (5) Cataclasite- and pseudotachylyte-bearing faults also forming a set of steeply-dipping N-S-trending structures. These faults are commonly associated with epidote veins surrounded by bleaching haloes. (6) Zeolite-bearing faults marked by whitish cataclasites, fault gouges and mirror-like surfaces. These faults have a complex oblique- to strike-slip kinematics with an overall N-S trending lineation. As observed in other plutons (e.g. Adamello; Pennacchioni et al., 2006), the network of

  5. Sheeted and bulbous pluton intrusion mechanisms of a small granitoid from southeastern Australia: implications for dyke-to-pluton transformation during emplacement

    NASA Astrophysics Data System (ADS)

    Fowler, T. J.

    1994-06-01

    The small late syn-tectonic Carboniferous Davys Creek Granite (DCG) of southeastern Australia consists of microgranitic intrusive bodies of diverse geometry and structure. These bodies include: (1) subvertical concordant sheets; (2) bulbous peneconcordant plutons with apophyses and discordant lobes; and (3) subvertical dykes and stocks. The sequence of changing intrusive style is broadly 1-2-3. Transition from 1 to 2 was probably a response to rising magma pressures or declining tectonic stresses. The λ parameter of Emerman and Marrett (1990), which discriminates between stable sheet-like and potential stock/pluton/batholith emplacement modes, adequately predicts the transitions between sheet and pluton emplacements for the DCG. Ductile dyking along actively forming foliations appears to have been an important early intrusive mechanism. A transition from sheet to bulbous pluton intrusion style is suggested to have been in response to magma pressure increases.

  6. Phase equilibria of a fluorine-rich leucogranite from the St. Austell pluton, Cornwall

    SciTech Connect

    Weidner, J.R.; Martin, R.F.

    1987-06-01

    Highly evolved leucogranitic rocks in the St. Austell pluton, Cornwall, of Hercynian age, contain accessory muscovite, topaz and fluorite. The authors have studied the H/sub 2/O-saturated melting behavior of one representative sample. Its solidus and liquidus pass through the points 663 and 725/sup 0/C, respectively, at 1 kbar, 640 and 665/sup 0/C at 2 kbar, 610 and 717/sup 0/C at 4 kbar, and 608 and 700+/sup 0/C at 8 kbar. Plagioclase is on the liquidus at low pressure, and topaz is on the liquidus at 4 kbar. The fluorite is consumed in the formation of the first-formed liquid. Calcium can partition into an evolved granitic melt if complexed by fluorine. The fluorite appears to be largely primary in fresh fluorite granite at St. Austell, and not to reflect the albitization of oligoclase in the surrounding biotite granite. Such fluorine-rich leucogranites can be expected to be of subsolvus character.

  7. 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

  8. Novel long-chain anteiso-alkanes and anteiso-alkanoic acids in Antarctic rocks colonized by living and fossil cryptoendolithic microorganisms

    NASA Technical Reports Server (NTRS)

    Matsumoto, G. I.; Friedmann, E. I.; Watanuki, K.; Ocampo-Friedmann, R.

    1992-01-01

    Saponified extracts of rock samples colonized by cryptoendolithic microbial communities from the McMurdo Dry Valleys of Southern Victoria Land, Antarctica, were separated into hydrocarbon and fatty acid fractions by silica gel column chromatography. Hydrocarbons and methyl esters of fatty acids were analyzed by capillary gas chromatography-mass spectrometry. Unusually, a suite of long-chain anteiso-alkanes (a-C20 to a-C30) and anteiso-alkanoic acids (a-C20 to a-C30) were detected in many samples, together with straight-chain, branched and/or cyclic and acyclic isoprenoid compounds. These novel compounds are probably derived from unidentified heterotrophic bacteria or symbiotic processes in a unique microbial community in the Antarctic cold desert and suggest the occurrence of a special biosynthetic pathway. Long-chain anteiso-alkanes are probably formed through microbial decarboxylation of corresponding anteiso-alkanoic acids. They may serve as new biomarkers in environmental and geochemical studies.

  9. Three-dimensional shape and emplacement of the Cardenchosa deformed pluton (Variscan Orogen, southwestern Iberian Massif)

    NASA Astrophysics Data System (ADS)

    Simancas, J. Fernando; Galindo-Zaldívar, Jesús; Azor, Antonio

    2000-04-01

    The Cardenchosa pluton is a Lower Carboniferous Variscan granite located in the southwestern Iberian Massif. It intruded along the contact between the Sierra Albarrana and Azuaga tectonic units. To the northwest the pluton connects with the left-lateral Azuaga fault. The pluton appears in the footwall of the low-angle normal Casa del Café fault, which crops out to the west of the granite. Gravimetric modelling shows the pluton to have a flat bottom at a depth of 2 km. Strain analysis of post-emplacement deformation of the pluton indicates that: (a) the deformation of the pluton accommodates the displacement of the Azuaga fault; and (b) the pluton prior to the solid state deformation was a lens-shaped laccolith of approximately 10 km diameter and 2 km thickness. The Cardenchosa pluton was a single pulse of magma trapped in a rheological discontinuity of the upper crust (the contact between the Sierra Albarrana and Azuaga units). The magma would ascend through dikes since no root has been detected. The tectonic scenario during the intrusion was one of regional extension.

  10. Mid-Neoproterozoic ridge subduction and magmatic evolution in the northeastern margin of the Indochina block: Evidence from geochronology and geochemistry of calc-alkaline plutons

    NASA Astrophysics Data System (ADS)

    Qi, Xuexiang; Santosh, M.; Zhao, Yuhao; Hu, Zhaocuo; Zhang, Chao; Ji, Fengbao; Wei, Cheng

    2016-04-01

    The mid-Neoproterozoic medium- to high-K calc-alkaline magmatic rocks in the northeastern margin of the Indochina block, SW China, provide important insights into the relationship of the Indochina block with the Gondwana supercontinent. Here we report zircon LA-ICP-MS U-Pb data from the early and late stage plutons which yield weighted mean 206Pb/238U ages of 765 Ma and 732-739 Ma suggesting mid-Neoproterozoic emplacement. The zircon εHf(t) values show a range of - 3.2 to + 2.4 (average + 0.1 ± 0.9) with TDMC of 1510 to 1870 Ma for the early plutons, and - 5.4 to + 5.1 (average + 2.1 to - 3.9) with TDMC of 1366 to 1985 Ma for late plutons. Both groups show similar geochemical characteristics including high Mg#, enrichment of LILE and LREE, slight negative Eu anomalies, and strongly negative Nb, Ta and Ti anomalies, with all the samples falling within the continental/island arc field in tectonic discrimination diagrams. These features suggest that the early and late stage magmas were produced by the mixing of mantle-derived magma and crust-derived magma in different proportion within an active continental margin, in subduction-related continental-arc tectonic setting. The linear zoning and roughly parallel distribution of the two generations of intrusions with a hiatus of 20 Ma might suggest an episode of ridge subduction with asthenosphere upwelling through the slab window that generated the second phase of plutons.

  11. Petrographic and crystallographic study of silicate minerals in lunar rocks

    NASA Technical Reports Server (NTRS)

    Carmichael, I. S. E.; Turner, F. J.; Wenk, H. R.

    1974-01-01

    Optical U-stage measurements, chemical microprobe data, and X-ray procession photographs of a bytownite twin group from rock 12032,44 are compared. Sharp but weak b and no c-reflections were observed for this An89 bytownite indicating a partly disordered structure. Euler angles, used to characterize the orientation of the optical indicatrix, compare better with values for plutonic than for volcanic plagioclase. This indicates that structural and optical properties cannot be directly correlated.

  12. Subsurface Geology of the Fenton Hill Hot Dry Rock Geothermal Energy Site

    SciTech Connect

    Levey, Schon S.

    2010-12-01

    The Precambrian rock penetrated by wells EE-2A and -3A belongs to one or more granitic to granodioritic plutons. The plutonic rock contains two major xenolith zones of amphibolite, locally surrounded by fine-grained mafic rock of hybrid igneous origin. The granodiorite is cut by numerous leucogranite dikes that diminish in abundance with depth. The most prominent structural feature is the main breccia zone, in which the rock is highly fractured and moderately altered. This zone is at least 75 m thick and is of uncertain but near-horizontal orientation. Fracture abundance decreases with increasing depth below the main breccia zone, and fractures tend to be associated with leucogranite dikes. This association suggests that at least some of the fractures making up the geothermal reservoir are of Precambrian age or have long-range orientations controlled by the presence of Precambrian-age granitic dikes.

  13. Effects of low molecular weight organic acids on the immobilization of aqueous Pb(II) using phosphate rock and different crystallized hydroxyapatite.

    PubMed

    Wei, Wei; Cui, Jing; Wei, Zhenggui

    2014-06-01

    Understanding the effects of low molecular weight organic acids (LMWOAs) on the transformation of Pb(II) to geochemically stable pyromorphite (PY) by apatite materials (AMs), has considerable benefits for risk assessment and remediation strategies for contaminated water and soil. In this study, we systematically investigated the immobilization of Pb(II) from aqueous solution by natural phosphate rock (PR) and different crystallized hydroxyapatite (HAp) in the absence and presence of LMWOAs (oxalic, malic and citric acids). The results indicated that the effectiveness of PR and HAp in immobilizing Pb(II) followed in descending order by HAp2 (the poorly crystallized HAp), HAp1 (the well crystallized HAp) and PR, regardlessof the presence of LMWOAs. The presence of malic and citric acids significantly decreased the immobilizationefficiency of Pb(II) by HAp1 and PR, clarifying the lower adsorption affinities of Pb(II)-organic acid complexes on HAp1 and PR rather than Pb(II) ion. On thecontrary, oxalic acid could markedly enhance the removal of Pb(II) from aqueous solution by HAp1 and PR through the formation of lead oxalate, which was confirmed by FT-IR and XRDanalysis. Results also showed that LMWOAs had little promoting or inhibiting effect on the immobilization of Pb(II) by HAp2. This study suggested that the ubiquity of LMWOAs in natural environments could retard the transformation efficiency of Pb(II) to PY by AMs, especiallyin thepresenceof oxalic acid, and the poorly crystallized HAp2 had great potential to remediate Pb(II)-contaminated water and soil due to its insusceptibility to LMWOAs. PMID:24216261

  14. Rock Art

    ERIC Educational Resources Information Center

    Henn, Cynthia A.

    2004-01-01

    There are many interpretations for the symbols that are seen in rock art, but no decoding key has ever been discovered. This article describes one classroom's experiences with a lesson on rock art--making their rock art and developing their own personal symbols. This lesson allowed for creativity, while giving an opportunity for integration…

  15. Rock Finding

    ERIC Educational Resources Information Center

    Rommel-Esham, Katie; Constable, Susan D.

    2006-01-01

    In this article, the authors discuss a literature-based activity that helps students discover the importance of making detailed observations. In an inspiring children's classic book, "Everybody Needs a Rock" by Byrd Baylor (1974), the author invites readers to go "rock finding," laying out 10 rules for finding a "perfect" rock. In this way, the…

  16. Collecting Rocks.

    ERIC Educational Resources Information Center

    Barker, Rachel M.

    One of a series of general interest publications on science topics, the booklet provides those interested in rock collecting with a nontechnical introduction to the subject. Following a section examining the nature and formation of igneous, sedimentary, and metamorphic rocks, the booklet gives suggestions for starting a rock collection and using…

  17. Tectono-magmatic evolution of sheeted plutonic bodies along the north Giudicarie line (northern Italy)

    NASA Astrophysics Data System (ADS)

    Martin, S.; Prosser, G.; Morten, L.

    1993-04-01

    Tectonized slices of foliated quartz-diorite/ quartz-gabbro rocks are exposed along the north Giudicarie line between Dimaro and Rumo (Western Trentino region, north-east Italy). They show geochemical and mineralogical similarities with the north-east corner of the Adamello batholith (Presanella pluton) and may be regarded as a northern apophysis lamella of Adamello. The intrusive bodies were emplaced within the Adria crust at a relatively shallow depth (approximatelyP_{{text{H}}_{text{2}} {text{O}}} equal to 3 kbar) along a proto-Giudicarie line under transtensive conditions during late Oligocene. Only near Rumo has contact metamorphism on the Austroalpine basement been observed, whereas in other outcrops it has been tectonically removed by later movements along the Giudicarie line. In the Samoclevo lamella a magmatic flow texture, which developed during the emplacement of a crystal mush at shallow depth, is recorded by the preferred alignment of plagioclase and hornblende. A solid state foliation, outlined by quartz crystal aggregates, green hornblende and biotite, has been observed mostly in the Rumo lamella. This indicates that a later ductile deformation, which developed under decreasing temperatures, overprinted the intrusive rocks. This deformation probably reflects late Oligocene strike-slip movements along the Tonale and Giudicarie lines. Finally semi-brittle to brittle deformation overprints the foliated igneous lamellae producing cataclasites and pseudotachylites. Sometimes these structures are subsequently cut by prehnite and epidote bearing veins. During this event, the intrusive lamellae were decoupled from their contact aureole and carried over the Insubric Flysch of the southern Alps. This last tectonic phase may be correlated to the Upper Miocene neo-Alpine transpressive event along the Giudicarie Line.

  18. The Paradox of the Axial Melt Lens: Petrology and Geochemistry of the Upper Plutonics at Hess Deep

    NASA Astrophysics Data System (ADS)

    Lissenberg, C. J.; Loocke, M. P.; MacLeod, C. J.

    2014-12-01

    The axial melt lens (AML) is a steady-state magma-rich body located at the dyke-gabbro transition at intermediate- and fast-spreading ridges. It is widely believed to be the reservoir from which mid-ocean ridge basalt (MORB) is erupted. The paradox of the axial melt lens is that the plutonic rocks that occur at this level are far too evolved to be in equilibrium with MORB, which is basaltic by definition; hence, the plutonic and volcanic records do not match. We explore this paradox by study of the first comprehensive sample suite of the uppermost plutonics of a fast-spreading ridge, taken by remotely-operated vehicle from the Hess Deep rift during cruise JC21. 23 samples (8 dolerites, 14 gabbronorites, and 1 gabbro) were collected from a section containing the transition from the uppermost gabbroic section into sheeted dykes. We present the results of a detailed petrographic and microanalytical investigation of these samples. They are dominated by evolved, varitextured (both in hand sample and thin section) oxide gabbronorites; olivine occurs in only one sample. A preponderance of the samples have positive Eu/Eu* and Sr/Sr*, indicating a cumulate origin. However, the minerals have evolved compositions, and are in equilibrium with melts significantly more evolved than East Pacific Rise MORB. Furthermore, the trace element contents of clinopyroxene differ significantly from clinopyroxene in equilibrium with MORB, being more enriched in incompatible elements. To account for both the evidence of derivation of MORB from the AML and the evolved nature of its rock record, we posit that the AML must be fed by melts on two different timescales: continual low-volume feeding by evolved interstitial melt from the cumulus pile below is augmented episodically by delivery of high volumes of more primitive melt. The latter episodes may trigger eruptions; hence the primitive melts are held in the magma chamber for only short periods, and erupt on the seafloor before significant

  19. Laboratory duplication of comb layering in the Rhum pluton. [igneous rocks with comb layered texture

    NASA Technical Reports Server (NTRS)

    Donaldson, C. H.

    1977-01-01

    A description is provided of the texture of harrisite comb layers, taking into account the results of crystallization experiments at controlled cooling rates, which have reproduced the textural change from 'cumulate' to comb-layered harrisite. Melted samples of harrisite were used in the dynamic crystallization experiments considered. The differentiation of a cooling rate run with respect to olivine grain size and shape is shown and three possible origins of hopper olivine in differentiated crystallization runs are considered. It is found that olivine nucleation occurred throughout cooling, except for the incubation period during early cooling. The elongate combed olivines in harrisite apparently grew as the magma locally supercooled to at least 30 C. It is suggested that the branching crystals in most comb layers, including comb-layered harrisite, probably grew along thermal gradients.

  20. Europium mass balance in polymict samples and implications for plutonic rocks of the lunar crust

    NASA Technical Reports Server (NTRS)

    Korotev, Randy L.; Haskin, Larry A.

    1988-01-01

    The mean concentrations of Sm and Eu in the lunar surface crust were analyzed by correlating the Sm concentration and the Sm/Eu ratio with Th concentration obtained from published data on a large number of polymict samples from various locations in the lunar highlands, and using the value of 0.91 microg/g for the mean Th concentration of the highlands surface crust obtained by the orbiting gamma-ray experiments. The mean concentration of Sm in the lunar surface crust was found to be between 2 and 3 microg/g, and that of Eu between 0.7 and 1.2 microg/g. The results indicate that there is no significant enrichment or depletion of Eu, compared to Sm, relative to chondritic abundances; i.e., there is no significant 'Eu anomaly' in average upper crust, contrary to predictions by some earlier investigators.

  1. Late Paleozoic crustal history of central coastal Queensland interpreted from geochemistry of Mesozoic plutons: The effects of continental rifting

    USGS Publications Warehouse

    Allen, C.M.; Wooden, J.L.; Chappell, B.W.

    1997-01-01

    The eastern margin of Australia is understood to be the result of continental rifting during the Cretaceous and Tertiary. Consistent with this model, Cretaceous igneous rocks (granites to basalts) in a continental marginal setting near Bowen, Queensland are isotonically retarded, having isotopic ratios similar to those of most island arcs (Sri = 0.7030-0.7039, ??Nd = +6.46 to +3.00 and 206Pb/204Pb = 18.44-18.77, 207Pb/204Pb = 15.552-15.623, and 208Pb/204Pb = 37.90-38.52). These isotopic signatures are much less evolved than the Late Carboniferous-Permian batholith that many Cretaceous plutons intrude. As rocks ranging in age from about 300-100 Ma are well exposed near Bowen, we can track magma evolution through time. The significant change of magma source occurred much earlier than the Cretaceous based on the fact that Triassic granites in the same area are also isotonically primitive. We attribute the changes of magma composition to crustal rifting during the Late Permian and earliest Triassic. The Cretaceous rocks (actually latest Jurassic to Cretaceous, 145-98 Ma) themselves show compositional trends with time. Rocks of appropriate mineralogy for Al-in-hornblende geobarometry yield pressures ranging from 250 to 80 MPa for rocks ranging in age from 145 to 125 Ma, respectively. More significantly, this older group is relatively compositionally restricted, and is Sr-rich, and Y- and Zr-poor compared to 120-98 Ma rocks. This younger groups is bimodal, being comprised principally of basalts and rhyolites (granites). REE patterns for a given rock type, however, do not differ with age tribute these relatively subtle trace element differences to small differences in conditions (T, aH2O) at the site of melting. Cretaceous crustal rifting can explain the range of rock types and the spatial distribution of rocks < 120 Ma in a longitudinal strip between and overlapping with provinces of older Cretaceous intrusions. A subduction-related setting is assigned to the 145-125 Ma

  2. Age and intrusive relations of the Lamarck granodiorite and associated mafic plutons, Sierra Nevada, California

    SciTech Connect

    Joye, J.L.; Bachl, C.A.; Miller, J.S.; Glazner, A.F. . Dept. of Geology); Frost, T.P. ); Coleman, D.S. . Dept. of Earth, Atmospheric and Planetary Sciences)

    1993-04-01

    The compositionally zoned Late Cretaceous Lamarck granodiorite, west of Bishop, hosts numerous mafic intrusions ranging from hornblende gabbro to mafic granodiorite. Frost and Mahood (1987) suggested from field relations that the Lamarck and the associated mafic plutons were co-intrusive. Contact relations between the Lamarck host and the mafic intrusions are variable (sharp to diffuse) and in places suggest commingling. In order to constrain the intrusive relationships between the Lamarck and its associated mafic plutons, the authors have analyzed feldspars from the Mt. Gilbert pluton and the Lamarck granodiorite to see if feldspar compositions in the Mt. Gilbert overlap those in the Lamarck host and determined U-Pb zircon ages for the Mt. Gilbert and Lake Sabrina plutons to see if they have the same age as the Lamarck granodiorite. Feldspars from the Lamarck granodiorite are normally zoned and range compositionally from An[sub 38--32]; those in the Mt. Gilbert diorite are also normally zoned but range compositionally from An[sub 49--41] and do not overlap the Lamarck host. Four to five zircon fractions from each pluton were handpicked and dated using U-Pb methods. The Mt. Gilbert mafic diorite has a concordant age of 92.5 Ma and the Lake Sabrina diorite has a concordant age of 91.5 Ma. Ages for the two plutons overlap within error, but multiple fractions from each suggest that the Lake Sabrina pluton is slightly younger than the Mt. Gilbert pluton. These data and field relationships indicate: (1) plagioclase phenocrysts in the Mt. Gilbert pluton were not derived from the Lamarck granodiorite despite their textural similarity; but (2) the Lamarck granodiorite and its associated mafic plutons are co-intrusive as supported by the close agreement of the ages with the crystallization age obtained by Stern and others for the Lamarck granodiorite.

  3. Temporal Evolution of Volcanic and Plutonic Magmas Related to Porphyry Copper Ores Based on Zircon Geochemistry

    NASA Astrophysics Data System (ADS)

    Dilles, J. H.; Lee, R. G.; Wooden, J. L.; Koleszar, A. M.

    2015-12-01

    Porphyry Cu (Mo-Au) and epithermal Au-Ag ores are globally associated with shallow hydrous, strongly oxidized, and sulfur-rich arc intrusions. In many localities, long-lived magmatism includes evolution from early andesitic volcanic (v) and plutonic (p) rocks to later dacitic or rhyolitic compositions dominated by plutons. We compare zircon compositions from three igneous suites with different time spans: Yerington, USA (1 m.y., p>v), El Salvador, Chile (4 m.y., p>v), and Yanacocha, Peru (6 m.y., v>p). At Yerington granite dikes and ores formed in one event, at ES in 2 to 3 events spanning 3 m.y., and at Yanacocha in 6 events spanning 5 m.y. At both ES and Yanacocha, high-Al amphiboles likely crystallized at high temperature in the mid-crust and attest to deep magmas that periodically recharged the shallow chambers. At Yanacocha, these amphiboles contain anhydrite inclusions that require magmas were sulfur-rich and strongly oxidized (~NNO+2). The Ti-in-zircon geothermometer provides estimates of 920º to 620º C for zircon crystallization, and records both core to rim cooling and locally high temperature rim overgrowths. Ore-related silicic porphyries yield near-solidus crystallization temperatures of 750-650°C consistent with low zircon saturation temperatures. The latter zircons have large positive Ce/Ce* and small negative Eu/Eu*≥0.4 anomalies attesting to strongly oxidized conditions (Ballard et al., 2001), which we propose result from crystallization and SO2 loss to the magmatic-hydrothermal ore fluid (Dilles et al., 2015). The Hf, REE, Y, U, and Th contents of zircons are diverse in the magma suites, and Th/U vs Yb/Gd plots suggest a dominant role of crystal fractionation with lesser roles for both crustal contamination and mixing with high temperature deep-sourced mafic magma. Ce/Sm vs Yb/Gd plots suggest that magma REE contents at <900°C are dominated by early crystallization of hornblende and apatite, and late crystallization (~<780°C) of titanite

  4. Inferring a deep-crustal source terrane from a high-level granitic pluton: the Strathbogie Batholith, Australia

    NASA Astrophysics Data System (ADS)

    Clemens, J. D.; Phillips, G. N.

    2014-11-01

    The Strathbogie Igneous Complex is comprised of the ignimbritic rocks of the Violet Town Volcanics and the granitic rocks of the Strathbogie batholith. It is Late Devonian in age and postorogenic-extensional in tectonic setting. The batholith was constructed from peraluminous, metasediment-derived magmas emplaced as several internally heterogeneous plutons. Chemical variation in the magmas was largely inherited from the protolith rather than having been produced by differentiation (crystal-liquid separation) or magma mixing. The Strathbogie magmas formed during a granulite-facies metamorphic event that caused partial melting of the rocks of the Proterozoic Selwyn Block, which forms the basement in this region. The chemistry of the Strathbogie batholith, the Violet Town Volcanics and various other felsic complexes of similar age, implies that the Selwyn Block here originally consisted of andesite, dacite, greywacke and pelite, probably deposited in a back-arc extensional setting. The sedimentary components of this protolith may have been deposited in a basin that was extending and deepening with time, so that the sediments contained progressively higher ratios of clay to volcanic materials. Much later, in the Late Devonian, extensional tectonics allowed the emplacement of mantle magmas into the deep and middle crust, causing the low-pressure granulite-facies metamorphic event that was responsible for the production of the crustal components in the granitic magmas of Central Victoria.

  5. {sup 40}Ar/{sup 39}Ar thermochronology and thermobarometry of metamorphism, plutonism, and tectonic denudation in the Old Woman Mountains area, California

    SciTech Connect

    Foster, D.A.; Miller, C.F.; Harrison, T.M.; Hoisch, T.D.

    1992-02-01

    Discrimination of individual tectonometamorphic events in polymetamorphosed terranes requires a comprehensive understanding of the relative timing and conditions of metamorphism and plutonism. We have applied a combination of {sup 40}Ar/{sup 39} Ar thermochronology, petrology, and thermobarometry to reconstruct the complex Early Proterozoic through early Cenozoic tectonic and metamorphic evolution of continental crust in the Old Woman Mountains area, southeastern California. Strong Mesozoic thermal events obscure the earlier history in much of the Old Woman Mountains area. In those areas where Early Proterozoic rocks underwent only lower-greenschist-facies metamorphism during the Mesozoic, thermobarometry of pelitic schists indicates that Proterozoic metamorphism occurred at 9 to 11 kbar and {approximately}700 {degrees}C. {sup 40}Ar/{sup 39}Ar ages of hornblende from samples of interbedded Proterozoic amphibolite indicate that this high-grade metamorphism took place before 1600 Ma. The relatively high-pressure conditions of Early Proterozoic metamorphism in the Old Woman Mountains area contrast with the low-pressure granulite-facies metamorphism that occurred elsewhere in the Mojave Desert at this time. {sup 40}Ar/{sup 39}Ar analyses of hornblende from Proterozoic rocks within Mesozoic shear zones and hornblende barometry from Jurassic intrusive rocks suggest that tectonism and burial of Paleozoic strata to >10 km began between 170 and 150 Ma. This tectonism resulted in regional greenschist-facies metamorphism. Late-stage mineral assemblages in Proterozoic and Paleozoic pelitic rocks in the Old Woman Mountains area indicate an increase in metamorphic grade from greenschist to upper amphibolite facies toward Later Cretaceous Plutons of the 73 Ma Old Woman-Piute batholith. Barometric calculations from garnet-bearing metamorphic rocks suggest that this Cretaceous metamorphism took place at 3.5 to 5.0 kbar in the Old Woman Mountains. 68 refs., 11 figs., 3 tabs.

  6. Comprehensive Pb-Sr-Nd-Hf isotopic, trace element, and mineralogical characterization of mafic to ultramafic rock reference materials

    NASA Astrophysics Data System (ADS)

    Fourny, Anaïs.; Weis, Dominique; Scoates, James S.

    2016-03-01

    Controlling the accuracy and precision of geochemical analyses requires the use of characterized reference materials with matrices similar to those of the unknown samples being analyzed. We report a comprehensive Pb-Sr-Nd-Hf isotopic and trace element concentration data set, combined with quantitative phase analysis by XRD Rietveld refinement, for a wide range of mafic to ultramafic rock reference materials analyzed at the Pacific Centre for Isotopic and Geochemical Research, University of British Columbia. The samples include a pyroxenite (NIM-P), five basalts (BHVO-2, BIR-1a, JB-3, BE-N, GSR-3), a diabase (W-2), a dolerite (DNC-1), a norite (NIM-N), and an anorthosite (AN-G); results from a leucogabbro (Stillwater) are also reported. Individual isotopic ratios determined by MC-ICP-MS and TIMS, and multielement analyses by HR-ICP-MS are reported with 4-12 complete analytical duplicates for each sample. The basaltic reference materials have coherent Sr and Nd isotopic ratios with external precision below 50 ppm (2SD) and below 100 ppm for Hf isotopes (except BIR-1a). For Pb isotopic reproducibility, several of the basalts (JB-3, BHVO-2) require acid leaching prior to dissolution. The plutonic reference materials also have coherent Sr and Nd isotopic ratios (<50 ppm), however, obtaining good reproducibility for Pb and Hf isotopic ratios is more challenging for NIM-P, NIM-N, and AN-G due to a variety of factors, including postcrystallization Pb mobility and the presence of accessory zircon. Collectively, these results form a comprehensive new database that can be used by the geochemical community for evaluating the radiogenic isotope and trace element compositions of volcanic and plutonic mafic-ultramafic rocks.

  7. Whole-Rock Geochemistry and Zircon U-Pb Isotopes of the Late Cretaceous Granitoids of the Eastern Taurus (turkey): Implications for Petrogenesis and Geodynamic Setting

    NASA Astrophysics Data System (ADS)

    Beyarslan, Melahat; Lin, Yu-Chin; Chung, Sun-Lin; Feyzi Bingol, Ahmet; Yildirim, Esra

    2015-04-01

    The granitoid plutons out crop largely in the Eastern Taurus, in Turkey. New data, including a combination of field relation, U-Pb zircon geochronology and rock geochemistry on the granitoids in the Eastern Taurus of the Tethyan orogen in Turkey, come from four plutons ( Pertek, Baskil, Göksun and Şifrin). Pertek, Baskil and Göksun plutons consist mainly of diorite, quartz-diorites, tonalite, granodiorites and granites of I-type, with minor monzonite, the Şifrin pluton consists of syenogranite, syenite, monzogranite, monzonite. U-Pb zircon geochronology of four samples of diorite and granite from Pertek and Baskil plutons indicate ages of 86±2 - 79 ± 1Ma. U-Pb zircon geochronology of four samples from the Şifrin granitoid yield ages 77±1-72±1 Ma. Considering these ages, emplacement of the plutons took place during Late Cretaceous (Santonian-Campanian), from 86 to 72 Ma. Although the SiO2 of rocks forming granitoids varies in wide range ( 46.792- 74.092 wt%), they show arc and syn-collision geochemical affinity, with enrichment of LILE (K, Rb, Sr and Ba) and depletion of HFSE (Nb, Ta and Ti) and P. Geochemical data indice that the diorite, tonalite and granodiorite are low-K tholeiite, monzodiorite, monzogranite, granite and K-granite are calc-alkaline and high-K calc-alkaline and monzonite, syenomonzonite and syenite of Şifrin pluton and some samples of the Pertek pluton are shoshonitic. The Eastern Taurus granitoids would be formed by partial melting of possible juvenile arc-derived rocks during subduction of the South Branch of the Neo-Tethyan oceanic crust and subsequent arc-continent collision.

  8. Geochemistry and U-Pb SHRIMP zircon chronology of granitoids and microgranular enclaves from Jhirgadandi Pluton of Mahakoshal Belt, Central India Tectonic Zone, India

    NASA Astrophysics Data System (ADS)

    Bora, Sita; Kumar, Santosh; Yi, Keewook; Kim, Namhoon; Lee, Tae Ho

    2013-07-01

    The northern part of Central India Tectonic Zone (CITZ) is delineated by an arc-shaped supracrustal belt commonly referred to as Mahakoshal Belt, which is considered as a product of intense rifting of sialic crust that occurred at ca 2400-2600 Ma. Several granitoid plutons intrude the Parsoi Formation of Mahakoshal Belt. Among these, an elliptical small stock-like granitoid body trending E-W is exposed in and around Jhirgadandi region of Mahakoshal Belt, referred herein as Jhirgadandi Pluton. It is composed of minor amount of mafic rocks (diorite) and predominant granitoids. Country-rock pelitic xenoliths and microgranular enclaves (ME) are commonly hosted in granitoids but are absent in diorite. The ME exhibit typical magmatic texture with a Bt(±Cpx ± Hbl)-Pl-Kf-Qtz-Mag-Ap assemblage, similar to that in host granitoids but with contrasting mineral proportions. Whole-rock molar Al2O3/(CaO + Na2O + K2O) (A/CNK) ratios of diorite (0.63-0.72), ME (0.69-1.21) and granitoids (0.83-1.05) suggest their nature largely metaluminous (I-type) to rarely peraluminous (S-type) granitoids. On most binary plots involving silica, two distinct compositional paths can be recognized; one formed by an array of differentiating diorite and ME, and another by fractionating granitoids gradually depleting in compatible elements. It is most likely that ME were generated by progressive and concurrent mixing of coeval pristine mafic (diorite) and granitoid magmas and fractionation processes. However, coherent and identical trace elements (except for Sr, Th, Y and Ni) and REE patterns for ME-granitoid pairs most likely suggest partial to near-complete chemical equilibration through varying degrees of diffusion process across the ME - partly crystalline host granitoid boundary. High-precision U-Pb SHRIMP zircon 206Pb/238U ages for ME (1758 ± 19 Ma) and host granitoid (1753 ± 9.1 Ma) from Jhirgadandi Pluton further support the notion that they were coeval. The obtained age (˜1750 Ma) of

  9. Fractionation of Cu and Zn isotopes during adsorption onto amorphous Fe(III) oxyhydroxide: Experimental mixing of acid rock drainage and ambient river water

    NASA Astrophysics Data System (ADS)

    Balistrieri, Laurie S.; Borrok, David M.; Wanty, Richard B.; Ridley, W. Ian

    2008-01-01

    Fractionation of Cu and Zn isotopes during adsorption onto amorphous ferric oxyhydroxide is examined in experimental mixtures of metal-rich acid rock drainage and relatively pure river water and during batch adsorption experiments using synthetic ferrihydrite. A diverse set of Cu- and Zn-bearing solutions was examined, including natural waters, complex synthetic acid rock drainage, and simple NaNO3 electrolyte. Metal adsorption data are combined with isotopic measurements of dissolved Cu (65Cu/63Cu) and Zn (66Zn/64Zn) in each of the experiments. Fractionation of Cu and Zn isotopes occurs during adsorption of the metal onto amorphous ferric oxyhydroxide. The adsorption data are modeled successfully using the diffuse double layer model in PHREEQC. The isotopic data are best described by a closed system, equilibrium exchange model. The fractionation factors (αsoln-solid) are 0.99927 ± 0.00008 for Cu and 0.99948 ± 0.00004 for Zn or, alternately, the separation factors (Δsoln-solid) are -0.73 ± 0.08‰ for Cu and -0.52 ± 0.04‰ for Zn. These factors indicate that the heavier isotope preferentially adsorbs onto the oxyhydroxide surface, which is consistent with shorter metal-oxygen bonds and lower coordination number for the metal at the surface relative to the aqueous ion. Fractionation of Cu isotopes also is greater than that for Zn isotopes. Limited isotopic data for adsorption of Cu, Fe(II), and Zn onto amorphous ferric oxyhydroxide suggest that isotopic fractionation is related to the intrinsic equilibrium constants that define aqueous metal interactions with oxyhydroxide surface sites. Greater isotopic fractionation occurs with stronger metal binding by the oxyhydroxide with Cu > Zn > Fe(II).

  10. Fractionation of Cu and Zn isotopes during adsorption onto amorphous Fe(III) oxyhydroxide: Experimental mixing of acid rock drainage and ambient river water

    USGS Publications Warehouse

    Balistrieri, L.S.; Borrok, D.M.; Wanty, R.B.; Ridley, W.I.

    2008-01-01

    Fractionation of Cu and Zn isotopes during adsorption onto amorphous ferric oxyhydroxide is examined in experimental mixtures of metal-rich acid rock drainage and relatively pure river water and during batch adsorption experiments using synthetic ferrihydrite. A diverse set of Cu- and Zn-bearing solutions was examined, including natural waters, complex synthetic acid rock drainage, and simple NaNO3 electrolyte. Metal adsorption data are combined with isotopic measurements of dissolved Cu (65Cu/63Cu) and Zn (66Zn/64Zn) in each of the experiments. Fractionation of Cu and Zn isotopes occurs during adsorption of the metal onto amorphous ferric oxyhydroxide. The adsorption data are modeled successfully using the diffuse double layer model in PHREEQC. The isotopic data are best described by a closed system, equilibrium exchange model. The fractionation factors (??soln-solid) are 0.99927 ?? 0.00008 for Cu and 0.99948 ?? 0.00004 for Zn or, alternately, the separation factors (??soln-solid) are -0.73 ?? 0.08??? for Cu and -0.52 ?? 0.04??? for Zn. These factors indicate that the heavier isotope preferentially adsorbs onto the oxyhydroxide surface, which is consistent with shorter metal-oxygen bonds and lower coordination number for the metal at the surface relative to the aqueous ion. Fractionation of Cu isotopes also is greater than that for Zn isotopes. Limited isotopic data for adsorption of Cu, Fe(II), and Zn onto amorphous ferric oxyhydroxide suggest that isotopic fractionation is related to the intrinsic equilibrium constants that define aqueous metal interactions with oxyhydroxide surface sites. Greater isotopic fractionation occurs with stronger metal binding by the oxyhydroxide with Cu > Zn > Fe(II).

  11. The link between volcanism and plutonism in epizonal magma systems; high-precision U–Pb zircon geochronology from the Organ Mountains caldera and batholith, New Mexico

    USGS Publications Warehouse

    Rioux, Matthew; Farmer, Lang; Bowring, Samuel; Wooton, Kathleen M.; Amato, Jeffrey M.; Coleman, Drew S.; Verplanck, Philip L.

    2016-01-01

    The Organ Mountains caldera and batholith expose the volcanic and epizonal plutonic record of an Eocene caldera complex. The caldera and batholith are well exposed, and extensive previous mapping and geochemical analyses have suggested a clear link between the volcanic and plutonic sections, making this an ideal location to study magmatic processes associated with caldera volcanism. Here we present high-precision thermal ionization mass spectrometry U–Pb zircon dates from throughout the caldera and batholith, and use these dates to test and improve existing petrogenetic models. The new dates indicate that Eocene volcanic and plutonic rocks in the Organ Mountains formed from ~44 to 34 Ma. The three largest caldera-related tuff units yielded weighted mean 206Pb/238U dates of 36.441 ± 0.020 Ma (Cueva Tuff), 36.259 ± 0.016 Ma (Achenback Park tuff), and 36.215 ± 0.016 Ma (Squaw Mountain tuff). An alkali feldspar granite, which is chemically similar to the erupted tuffs, yielded a synchronous weighted mean 206Pb/238U date of 36.259 ± 0.021 Ma. Weighted mean 206Pb/238U dates from the larger volume syenitic phase of the underlying Organ Needle pluton range from 36.130 ± 0.031 to 36.071 ± 0.012 Ma, and the youngest sample is 144 ± 20 to 188 ± 20 ka younger than the Squaw Mountain and Achenback Park tuffs, respectively. Younger plutonism in the batholith continued through at least 34.051 ± 0.029 Ma. We propose that the Achenback Park tuff, Squaw Mountain tuff, alkali feldspar granite and Organ Needle pluton formed from a single, long-lived magma chamber/mush zone. Early silicic magmas generated by partial melting of the lower crust rose to form an epizonal magma chamber. Underplating of the resulting mush zone led to partial melting and generation of a high-silica alkali feldspar granite cap, which erupted to form the tuffs. The deeper parts of the chamber underwent continued recharge and crystallization for 144 ± 20 ka after the

  12. Reassessment of the Role of Magmatism in the Evolution of the Catalina MCC: Evidence for a Felsic-Intermediate Pluton at Shallow Depths

    NASA Astrophysics Data System (ADS)

    Terrien, J. J.; Finn, C. A.; Baldwin, S. L.

    2005-12-01

    the pluton is ~ 30 km wide and ~ 100 km long. The exact timing of pluton emplacement is presently unknown, although available thermochronologic data indicates it has to be >14 Ma. The aeromagnetic map patterns show the body is cut by the Basin and Range high angle Pirate fault, which cuts the NW side of the Santa Catalina Mountains and is assumed to be 12-6 Ma. The NW-SE-trending profile exhibits topographic valleys that cut the top boundary surface of the pluton and correspond to drainages at the surface, interpreted as corrugation surfaces. The axes of the corrugation surfaces trend SW-NE and thus suggests the timing of pluton emplacement is related to the extension along the Catalina detachment fault. Future work will include modeling the heat flow for the region. Several heat flow models will be considered using crystallization ages of magmatic rocks exposed at the surface as initial conditions.

  13. Plutonism, oblique subduction, and continental growth: An example from the Mesozoic of California

    SciTech Connect

    Glazner, A.F. )

    1991-08-01

    Major episodes of Mesozoic plutonism in California correlate with periods of oblique subduction and trench-parallel transport of western California along intrabatholithic faults. Major episodes of plutonism occurred in the Late Jurassic, during left-oblique convergence, and in the mid-Cretaceous, during right-oblique convergence. In contrast, a conspicuous lull in plutonism (but continuation of volcanism) in the earliest Cretaceous coincides with a time when the North America-Farallon convergence vector, although large in magnitude, was oriented perpendicular to the trench. This correlation suggests that plutonism is facilitated by strike-slip faulting within the batholithic belt; one explanation, which helps to solve the plutonic room problem, is that plutons are passively emplaced at releasing bends in the strike-slip faults, and volume is conserved by thrusting at the trench. If this correlation is generally applicable, then it implies that mid-crustal plutonism is limited beneath areas in which the convergence vector is subperpendicular to the trench. Continental growth in such areas may occur dominantly by volcanism.

  14. Late Proterozoic and Silurian alkaline plutons within the southeastern New England Avalon zone

    SciTech Connect

    Hermes, O.D. ); Zartman, R.E. )

    1992-07-01

    Distinct pulses of quartz-bearing, alkaline plutonism and volcanism are known to have occurred in the Avalon zone of southeastern New England during the Late Ordovician, Early Silurian, Devonian, and Carboniferous. Zircon separates from the Franklin and Dartmouth plutons demonstrate that two additional, previously unrecognized periods of alkaline magmatism occurred. The Franklin pluton yields an age of 417 {plus minus} 6 Ma (Late Silurian), whereas the Dartmouth pluton is Late Proterozoic (595 {plus minus} 5 Ma) and markedly older than the other plutons of alkaline affinity. The new ages further emphasize the episodic nature and long-term duration of such alkaline igneous events within the southeastern New England Avalon zone. The Dartmouth pluton may represent a post-collisional alkaline granite emplaced in the Late Proterozoic, almost immediately after a major period of calcalkaline igneous activity that accompanied plate convergence and continental accretion. The abrupt change from orogenic calcalkaline igneous activity to post-collisional alkaline granite, followed by younger episodes of anorogenic emplacement, is remarkably similar to igneous events reported from pan-African mobile belts widespread throughout Africa. In addition, parts of the Dartmouth pluton exhibit features indicative of mixing and commingling of felsic and mafic melts that are associated with coevally formed mylonitic fabrics. Because these fabrics are conformable to those in adjacent gneisses, but discordant with Alleghanian fabrics in the nearby Carboniferous Narragansett basin, they represent some of the best candidates for pre-Alleghanian structures thus far identified in the southeastern New England Avalon zone.

  15. Xenolith incorporation, distribution, and dissemination in a mid-crustal granodiorite, Vega pluton, central Norway

    NASA Astrophysics Data System (ADS)

    Marko, W.; Barnes, M.; Vietti, L.; McCulloch, L.; Anderson, H.; Barnes, C.; Yoshinobu, A.

    2005-12-01

    and populations of primarily gneissic and/or schistose xenoliths. We suggest that dissemination of xenoliths throughout the intrusion may have resulted from disaggregation and incorporation of the residuum from the source region, as well as dyking and stoping of host rocks incorporated during magma migration. Mechanical rock fragmentation studies suggest that particle size - frequency distributions commonly display log-linear relationships. The apparent absence of such a distribution suggests that thermally induced fracturing (stoping) may not be the only processes controlling xenolith size distribution. Furthermore, intrusion mineralogies appear consistent with possible dehydration melting reactions in diatexitic components of the intrusion. Host rocks do not appear to have been involved in melting reactions and have structures, which are both discordant and concordant to the pluton host rock contact. Several map scale xenoliths of calc-silicate and quartzite are also included in the intrusion and dykes are observed at several scales within the host rocks. The absence of stock work or net-veining in the Vega host rocks argues to limit a wide range of xenolith size contributions to the magma via dyking. Furthermore, small xenoliths (xenocrysts) size-frequency distributions may be governed in part by thermodynamic and chemical processes including dissolution, crystallization, and melting of smaller crystals and aggregates.

  16. 'Earhart' Rock

    NASA Technical Reports Server (NTRS)

    2004-01-01

    This false-color image taken by NASA's Mars Exploration Rover Opportunity shows a rock informally named 'Earhart' on the lower slopes of 'Endurance Crater.' The rock was named after the pilot Amelia Earhart. Like 'Escher' and other rocks dotting the bottom of Endurance, scientists believe fractures in Earhart could have been formed by one of several processes. They may have been caused by the impact that created Endurance Crater, or they might have arisen when water leftover from the rock's formation dried up. A third possibility is that much later, after the rock was formed, and after the crater was created, the rock became wet once again, then dried up and developed cracks. Rover team members do not have plans to investigate Earhart in detail because it is located across potentially hazardous sandy terrain. This image was taken on sol 219 (Sept. 4) by the rover's panoramic camera, using its 750-, 530- and 430-nanometer filters.

  17. Calcic myrmekite in anorthositic and gabbroic rocks

    SciTech Connect

    Schiffries, C.M.; Dymek, R.F.

    1985-01-01

    Myrmekite is a common feature of granitic plutonic rocks and quartzo-feldspathic gneisses, but it is rarely reported in anorthositic and gabbroic rocks. The authors have identified myrmekitic intergrowths of quartz and calcic plagioclase in a variety of plagioclase-rich cumulate rocks, including samples from a number of massif anorthosites and layered igneous intrusions. It appears that calcic myrmekite has been frequently overlooked, and is a common accessory feature in these rock types. Chemical and textural characteristics of myrmekite in the St-Urbain massif anorthosite (Quebec) and the Bushveld Igneous Complex (South Africa) have several features in common, but this myrmekite appears to be fundamentally different from that described by most previous investigators. Whereas myrmekite typically consists of a vermicular intergrowth of sodic plagioclase and quartz that occurs adjacent to alkali feldspar, the intergrowths in these rocks contain highly calcic plagioclase and lack the intervening alkali feldspar. In addition, the plagioclase in the myrmekite is more calcic than that in the surrounding rock. The boundary between the myrmekite and the host material is generally extremely sharp, although reverse zoning of host plagioclase may obscure the contact in some cases. The textural and chemical evidence is consistent with a replacement origin for these intergrowths; the proportion of quartz in the myrmekite is in close agreement with the predicted amount of silica that is generated by the theoretical replacement reaction. It appears that water played a key role in the replacement process.

  18. Science Rocks!

    ERIC Educational Resources Information Center

    Prestwich, Dorothy; Sumrall, Joseph; Chessin, Debby A.

    2010-01-01

    It all began one Monday morning. Raymond could not wait to come to large group. In his hand, he held a chunk of white granite he had found. "Look at my beautiful rock!" he cried. The rock was passed around and examined by each student. "I wonder how rocks are made?" wondered one student. "Where do they come from?" asked another. At this moment, a…

  19. An Archean Geomagnetic Reversal in the Kaap Valley Pluton, South Africa

    PubMed

    Layer; Kroner; McWilliams

    1996-08-16

    The Kaap Valley pluton in South Africa is a tonalite intrusion associated with the Archean Barberton Greenstone Belt. Antipodal paleomagnetic directions determined from the central and marginal parts of the pluton record a geomagnetic reversal that occurred as the pluton cooled. The age of the reversal is constrained by an 40Ar/39Ar plateau age from hornblende at 3214 +/- 4 million years, making it the oldest known reversal. The data presented here suggest that Earth has had a reversing, perhaps dipolar, magnetic field since at least 3.2 billion years ago. PMID:8688075

  20. Tectonic setting of the Sandia pluton: An orogenic 1.4 Ga granite in New Mexico

    NASA Astrophysics Data System (ADS)

    Kirby, Eric; Karlstrom, Karl E.; Andronicos, Chris L.; Dallmeyer, R. David

    1995-02-01

    Structural studies of the circa 1.42 Ga Sandia pluton and its aureole document significant deformation synchronous with pluton emplacement and call into question the "anorogenic" label associated with this and other 1.4 Ga granites in the southwestern United States. The SE margin of the pluton is a 1- to 2-km-wide NW dipping ductile shear zone. Field and microstructural observations (melt-filled shear bands, high-temperature dynamic recrystallization of K-feldspar megacrysts, and crosscutting pegmatite dikes) indicate that top-to-the-NW (normal) movement in the shear zone took place in the presence of melt. Subparallel magmatic fabrics north of and structurally above the shear zone contain kinematic indicators consistent with top-to-the-NW shear sense, suggesting that over large regions of the pluton, magmatic flow mimicked solid-state strain. In the northern aureole, contact metamorphic aluminosilicate porphyroblasts grew during the formation of a NE striking crenulation cleavage (S3) and related folds of late-stage pegmatite dikes. These features document the synchroneity of magma emplacement, shortening, and metamorphism and indicate that the Sandia pluton is syntectonic, not anorogenic. We interpret the kinematic consistency of structural elements from the base of the pluton, the interior of the pluton, and the northern aureole to reflect a regional (larger than the pluton) strain field and suggest that the "orogeny" recorded in and around the Sandia pluton involved a three dimensional strain field with subhorizontal extension (N-S) and contraction (E-W) directions. N-S extension is documented by the orientation of mineral lineations and movement directions in the basal shear zone and in high-strain zones in the northern aureole and by the orientations of tabular pegmatite and aplite dikes in the pluton and aureole. East to SE shortening is documented in the northern aureole by orientations of folded pegmatite dikes and associated S3 crenulation cleavage, and

  1. Rock flows

    NASA Technical Reports Server (NTRS)

    Matveyev, S. N.

    1986-01-01

    Rock flows are defined as forms of spontaneous mass movements, commonly found in mountainous countries, which have been studied very little. The article considers formations known as rock rivers, rock flows, boulder flows, boulder stria, gravel flows, rock seas, and rubble seas. It describes their genesis as seen from their morphological characteristics and presents a classification of these forms. This classification is based on the difference in the genesis of the rubbly matter and characterizes these forms of mass movement according to their source, drainage, and deposit areas.

  2. Neutralization of sulfuric acid and immobilization of heavy metals in an acid rock drainage stream, East Mancos River, San Juan National Forest, Colorado

    SciTech Connect

    Meyer, W.A.; Parnell, R.A. Jr.; Bennett, J.B. . Dept. of Geology)

    1993-04-01

    The East Mancos River of Southwestern Colorado is a stream naturally acidified by sulfuric acid produced by outcrops in its stream bed. In the headwaters of the river, two 20m dipslope exposures of fault breccias in the Entrada Sandstone are mineralized by pyrite, chalcopyrite, sphalerite, and galena. Over a 13.4 km distance downstream, solution chemistry rapidly changes and a sequence of inorganic then organic stream coatings are observed. To describe the natural geochemical processes controlling acid anion and heavy metal concentrations in the river, five longitudinal profiles were completed during 1991 and 1992. Complete inorganic chemical analyses of 0.1 [mu]m filtered samples were performed. At each of the 16 water sampling stations, stream discharge was measured, and stream bed grab samples were collected for organic and inorganic characterization by optical petrography, x-ray diffraction, loss on ignition, and selective chemical dissolution. Sulfate, iron, aluminum, copper, zinc and hydrogen ion concentrations decrease steadily downstream. Moving downstream, the amount and composition of ferric oxyhydroxide precipitates decreases rapidly below the breccias. The co-existing iron phases include lepidocroicite, goethite, feroxyhyte, and ferrihydrite. At threshold stream compositions, epilithic coverings of bacteria and algae occur as iron precipitation ceases. Natural neutralization of sulfur acid and loss of heavy metals from solution occurs in excess of that expected by simple dilution of the initial acidic stream water. Abundances and compositions of stream bed precipitates are consistent with the observed losses of ions from the co-existing solution.

  3. Characterization of anthropogenic and natural sources of acid rock drainage at the Cinnamon Gulch abandoned mine land inventory site, Summit County, Colorado

    USGS Publications Warehouse

    Bird, D.A.

    2003-01-01

    Colorado's Cinnamon Gulch releases acid rock drainage (ARD) from anthropogenic and natural sources. In 2001, the total discharge from Cinnamon Gulch was measured at 1.02 cfs (29 L/s) at base flow and 4.3 cfs (122 L/s) at high flow (spring runoff). At base flow, natural sources account for 98% of the discharge from the watershed, and about 96% of the chemical loading. At high flow, natural sources contribute 96% of discharge and 92 to 95% of chemical loading. The pH is acidic throughout the Cinnamon Gulch watershed, ranging from 2.9 to 5.4. At baseflow, nearly all of the trace metals analyzed in the 18 samples exceeded state hardness-dependent water quality standards for aquatic life. Maximum dissolved concentrations of selected constituents included 16 mg/ L aluminum, 15 mg/L manganese, 40 mg/L iron, 2 mg/L copper, 560 ??g/L lead, 8.4 mg/L zinc, and 300 mg/L sulfate. Average dissolved concentrations of selected metals at baseflow were 5.5 mg/L aluminum, 5.5 mg/L manganese, 14 ??g/L cadmium, 260 ??g/L copper, 82 ??g/L lead, and 2.8 mg/L zinc.

  4. Double-layer mode of acid intrusive rocks from Xiuwacu Porphyry Mo deposit, Northwestern Yunnan SW China: U-Pb geochronology evidence

    NASA Astrophysics Data System (ADS)

    Yu, Haijun; Li, Wenchang

    2016-04-01

    Recent research infer that, the south-north extension of the Xiuwacu-Tongchanggou acidic intrusive belt along the Geza island arc have been developed of intense molybdenum-mutimetallic mineralization(Li et al., 2012, 2013; Yu et al., 2015). The northern section of this intrusive belt exposed widly and occur much monzonitic granite, biotite-granite, granodiorite, biotite-monzogranite; while in southern section, intrusions are cocealed. The Tongchanggou district in south section have been obtained large breakthrough of porphyry-skarn type molybdenum-multimetallic deposits exploration recent years(Yu et al., 2014), the Mo-W mineral resources also increased year after year in north section of the belt. The Mo-mineral resouree potential of porphyry-skarn type Mo-mutimetallic deposits in whole area are tremendous. Xiuwacu Porphyry molybdenum deposit was explored in Geza island arc, and widespread Biotite granite and monzonitic granite that is closely related to mineralization. We have understood poorly about this ore deposit for the harsh geographical circumstance, through, some referential result in chronology have accumulated, it still lack of systematic lithogeochemical study and reliable chronology data about intrusions. We yield biotite granite and monzonitic zircons U-Pb ages(200.93±0.65Ma, 83.57±0.32Ma, respectively) of Xiuwacu. There are two periods of intermediate-acid intrusive rocks of Xiuwacu area. Indosinian Biotite granite and Yanshanian monzonitic granite were formed as superposition phenomenon.

  5. Age and composition of igneous rocks, Edna Mountain quadrangle, Humboldt County, Nevada

    USGS Publications Warehouse

    Erickson, Ralph L.; Silberman, Miles L.; Marsh, S.P.

    1978-01-01

    Six pulses of igneous activity ranging in age from Jurassic to Pliocene have been identified in the Edna Mountain quadrangle, Humboldt County, Nev. Porphyritic syenite am! quartz monzonite of Jurassic age (146-164 million years) at Buffalo Mountain are highly potassic through a wide range in SiO2 content from olivine-bearing syenite to quartz-rich monzonite, and their composition contrasts sharply with plutons elsewhere in north-central Nevada. Granodiorite and quartz monzonite plutons of Cretaceous age (88- 106 m.y.) are chemically and mineralogically similar to other calc-alkaline plutons in north-central Nevada. Four episodes of Tertiary volcanism include rhyolite ashflow tuffs and slightly younger andesitic basalt flows and tuffs of Oligocene age, rhyolite vitrophyre of late Miocene age, and olivine basalt flows of Pliocene age. Their age and mineralogical and chemical compositions are similar to other Tertiary volcanic rocks in north-central Nevada.

  6. Strain Localization Within a Syn-Tectonic Pluton in a Back-Arc Extensional Context: the Naxos granodiorite (Cyclades, Greece)

    NASA Astrophysics Data System (ADS)

    Bessiere, Eloïse; Rabillard, Aurélien; Arbaret, Laurent; Jolivet, Laurent; Augier, Romain; Menant, Armel

    2016-04-01

    Naxos Island is part of the central Cyclades (Aegean Sea, Greece) where a series of migmatite-cored metamorphic domes were exhumed below large-scale detachment systems during a Cenozoic back-arc extension. On Naxos, the Miocene exhumation history of the high-temperature metamorphic dome was notably achieved through two anastomosing and closely spaced top-to-the-north detachments belonging to the Naxos-Paros detachment system. According to previous contributions, the late exhumation stages were accompanied by the emplacement of a syn-kinematic I-type granodiorite that intruded a ductile-then-brittle detachment. Later the detachment migrated at the interface between the pluton and the metamorphic unit under ductile-to-brittle conditions. To clarify how extensional deformation was precisely distributed within the pluton, a multi-scale approach from field observations to laboratory investigations was undertaken. Through macro- to micro-structural observations, we show a continuous deformation history from magmatic to solid-state ductile/brittle conditions under an overall north-directed shearing deformation. The early magmatic or sub-solidus deformation is evidenced in a large part of the granodiorite, notably in its southern part where the original intrusive contact is still preserved. Solid-state deformation is recorded further north when approaching the detachment zone, highlighted by a thicker cataclastic zone and numerous pseudotachylite veins. From these field observations, we defined six strain facies, leading us to propose a qualitative strain map of the Naxos granodiorite. Based on field pictures and X-ray tomography of oriented samples collected along the strain gradient, we quantified the intensity of mineralogical fabrics in 2D and 3D. This step required the treatment of 600 rocks samples and pictures using SPO2003 (Shape Preferred Orientation) and Intercepts2003. Measured shape variations of the strain ellipsoid thus corroborate the large-scale strain

  7. Petrochemistry and petrology of I-type granitoids in an arc setting: the composite Torul pluton, Eastern Pontides, NE Turkey

    NASA Astrophysics Data System (ADS)

    Kaygusuz, Abdullah; Siebel, Wolfgang; Şen, Cüneyt; Satir, Muharrem

    2008-07-01

    The Upper Cretaceous Torul pluton, located in the Eastern Pontides, is of sub-alkaline affinity and displays features typical of volcanic arc granitoids. It is a composite pluton consisting of granodiorite, biotite hornblende monzogranite, quartz monzodiorite, quartz monzonite and hornblende biotite monzogranite. The oldest syenogranite (77.9 ± 0.3 Ma) and the youngest quartz diorite form small stocks within the pluton. Samples from the granodiorites, biotite hornblende monzogranites, quartz monzodiorites, quartz monzonites and hornblende biotite monzogranites have SiO2 between 57 and 68 wt% and display high-K calc-alkaline, metaluminous to peraluminous characteristics. Chondrite-normalized REE patterns are fractionated (Lacn/Lucn = 6.0-14.2) with pronounced negative Eu anomalies (Eu/Eu* = 0.59-0.84). Initial ɛNd(i) values vary between -3.1 and -4.1, initial 87Sr/86Sr values between 0.7058 and 0.7072, and δ18O values between +4.4 and +7.3‰. The quartz diorites are characterized by relatively high Mg-number of 36-38, low contents of Na2O (2.3-2.5 wt%) and SiO2 (52-55 wt%) and medium-K calc-alkaline, metaluminous composition. Chondrite-normalized REE patterns are relatively flat [(La/Yb)cn = 2.8-3.3; (Tb/Yb)cn = 1.2] and show small negative Eu anomalies (Eu/Eu* = 0.74-0.76). Compared to the other rock types, radiogenic isotope signatures of the quartz diorites show higher 87Sr/86Sr (0.7075-0.7079) and lower ɛNd(i) (-4.5 to -5.3). The syenogranites have high SiO2 (70-74 wt%) and display high-K calc-alkaline, peraluminous characteristics. Their REE patterns are characterized by higher Lacn/Lucn (12.9) and Eu/Eu* (0.76-0.77) values compared to the quartz diorites. Isotopic signatures of these rocks [ɛNd(i) = -4.0 to -3.3; 87Sr/86Sr(i) = 0.7034-0.7060; δ18 O = + 4.9 to + 8.2] are largely similar to the other rock types but differ from that of the quartz diorites. Fractionation of plagioclase, hornblende, pyroxene and Fe-Ti oxides played an important role in the

  8. Late magmatic stage of the zoned Caleu pluton (Central Chile): insights from zircon crystallization conditions

    NASA Astrophysics Data System (ADS)

    Molina, P. G.; Parada, M.; Gutierrez, F. J.; Chang-Qiang, M.; Jianwei, L.; Yuanyuan, L.

    2012-12-01

    The Caleu pluton consists of three N-S elongated lithological zones: Gabbro-Diorite Zone (GDZ), Tonalite Zone (TZ) and Granodiorite Zone (GZ); western, middle and eastern portions of the pluton, respectively. The zones are thought to be previously differentiated in a common, isotopically depleted (Sr-Nd), subjacent magma reservoir at a 4 kbar equivalent depth. The emplacement should have occurred at the climax of the Cretaceous rifting. We present preliminary results of U238/Pb206 zircon geochronology; zircon saturation, Tsat(Zrn), and crystallization temperatures (Ti-in-Zrn); as well as relative oxidation states at time of crystallization, based on: (i) the sluggish REE and HFSE subsolidus diffusivities in zircon; (ii) the behavior of Ti4+↔Si4+ and Ce4+↔Zr4+ isovalent replacement, in addition to a constrained TiO2 activity in almost all typical crustal rocks; and (iii) relative oxidation states at time of crystallization, respectively. The latter are obtained by interpolation of the partition coefficients of trivalent (REE) and tetravalent (HFSE) curves in Onuma diagrams for each zircon, and then estimating relative Ce(IV)/Ce(III) ratios. Results obtained from 4 samples (a total of 77 zircon grains) collected from the three mentioned lithological zones indicate U/Pb ages of approximately 99.5 ±1.5 Ma, 96.8 ±0.6 Ma, and 94.4 +2.2 -0.8 Ma; and Ti-in Zrn ranges of ca. 720-870°C, ca. 680-820°C and ca. 750-840°C, for the GDZ, TZ and GZ samples, respectively. On the other hand Tsat(Zrn) of ca. 750-780°C in the TZ, and ca. 830-890°C in the GZ, were obtained. As expected saturation temperatures are similar or higher than Ti-in-Zrn obtained in zircon grains of TZ and GZ, respectively. Cathodoluminiscence images in zircon suggest a magmatic origin, due to absence of complex zoning patterns and fairly well conserved morphologies. Exceptionally the GDZ sample zircons show evidence of inheritance, indicating a xenocrystic and/or antecrystic origin. A relative Ce

  9. Geochemical and geochronologic analysis of the plutonic basement of the Tacaná Volcano Complex, Chiapas México.

    NASA Astrophysics Data System (ADS)

    Paul William, L.

    2006-12-01

    The Tacana Volcano Complex (TVC) is located on the border between the State of Chiapas, southern Mexico, and Guatemala. This volcanic complex has been described as the last volcano in the northwest part of the Central American Volcanic Arc (CAVA). The region where the TVC was emplaced is influenced by the transpressional boundary formed by the shear movement between the North American and Caribbean Plates and the compressive stress by the subduction of the Cocos Plate under the North American Plate. The most recently study about TVC was by García-Palomo et al. (2004), who summarized the chronology of the TVC from basement formation to its recent activity and report that the active TVC lies on igneous basement rocks that were formed by two magmatic processes during the Mesozoic and Cenozoic. In this work, we present the results of detailed petrographic, geochemical and geochronologic analyses obtained from plutonic rocks in the basement of the TVC zone. The results show that t this basement (granites: SiO2 of 64.64 to 65.29 wt%, granodiorites: SiO2 of 60.18 wt%, and gabbros: SiO2 of 51.67 wt%) belongs to the suite of plutonic rocks of an orogenic environment. The granites are classified as both S-type peraluminosus granites derived form partial melting of continental crust, characterized by minerals such as quartz, k-feldspar, biotite, hornblende and some Fe-Ti oxides and I-type metaluminous granites derived from subduction processes with the main mineral phases being quartz, k-feldspar, hornblende, biotite and Fe-Ti oxides. The ages thus far obtained (K- Ma to 12.65 +/- 0.08 Ma) suggest that there were at least nine periods of magmatic activity that produced granitic and mafic magmas. Reference: Garcia-Palomo, A., Macias, J.L., Arce, J.L., Mora, J.C., Hughes, S., Saucedo, R., Espindola, J.M., Escobar, R., and Layer, P., (2004). GSA Special Paper 412, p 39-57.

  10. Ancient oceanic crust in island arc lower crust: Evidence from oxygen isotopes in zircons from the Tanzawa Tonalitic Pluton

    NASA Astrophysics Data System (ADS)

    Suzuki, Kazue; Kitajima, Kouki; Sawaki, Yusuke; Hattori, Kentaro; Hirata, Takafumi; Maruyama, Shigenori

    2015-07-01

    Knowledge of the lithological variability and genesis of island arc crust is important for understanding continental growth. Although the volcanic architecture of island arcs is comparatively well known, the nature of island arc middle- and lower-crust remains uncertain owing to limited exposure. One of the best targets for deciphering the evolution of an island arc system is the Tanzawa Tonalites (4-9 Ma), in the intra-oceanic Izu-Bonin-Mariana arc. These tonalities which occupied a mid-crustal position were generated by partial melting of lower crust. To constrain protoliths of the plutonic rocks in the island arc lower crust, in-situ O-isotopic analysis using an IMS-1280 Secondary Ion Mass Spectrometer was carried out on 202 zircon grains separated from 4 plutons in the Tanzawa Tonalite. δ18O value of the zircons ranges from 4.1‰ to 5.5‰ and some zircons have δ18O slightly lower than the mantle range. The low zircon δ18O values from the Tanzawa Tonalite suggest that their protoliths involved materials with lower δ18O values than those of the mantle. Hydrothermally altered gabbros in the lower oceanic crust often have lower δ18O values than mantle and can be primary components of arc lower crust. The Tanzawa Tonalite is interpreted to have been formed by partial melting of island arc lower crust. Thus the low δ18O values in zircons from the Tanzawa Tonalites may originate by melting of the hydrothermally altered gabbro. Ancient oceanic crustal material was likely present in the Izu-Bonin-Mariana arc lower crust, at the time of formation of the Tanzawa Tonalites.

  11. 'Tetl' Rock

    NASA Technical Reports Server (NTRS)

    2004-01-01

    This image, taken by the panoramic camera on NASA's Mars Exploration Rover Spirit during the rover's trek through the 'Columbia Hills' at 'Gusev Crater,' shows the horizontally layered rock dubbed 'Tetl.' Scientists hope to investigate this rock in more detail, aiming to determine whether the rock's layering is volcanic or sedimentary in origin. If for some reason this particular rock is not favorably positioned for grinding and examination by the toolbox of instruments on the rover's robotic arm, Spirit will be within short reach of another similar rock, dubbed 'Coba.' Spirit took this image on its 264th martian day, or sol (Sept. 29, 2004). This is a false-color composite image generated from the panoramic camera's 750-, 530-, and 430-nanometer filters.

  12. Iron variation within a granitic pluton as determined by near-infrared reflectance

    NASA Technical Reports Server (NTRS)

    Baird, A. K.

    1984-01-01

    One-hundred fifty-one previously chemically analyzed samples of tonalite from the Lakeview Mountains pluton, southern California batholith, were analyzed for their iron content using near-infrared spectrophotometry. Compared to the earlier analyses of the same sample set by X-ray fluorescence spectrography, the infrared data have higher analytical variance but clearly define patterns of compositional zonation in the pluton which are closely similar to those patterns obtained from X-ray data; petrogenetic interpretations for the pluton would be the same from either data set. Infrared spectral data can be obtained directly in the field with relatively simple instruments and field measurements can be made to average local heterogeneities that often mask significant plutonic variations.

  13. Geochemistry of granitoid rocks from the western Superior Province: Evidence for 2- and 3-stage crustal evolution models

    NASA Technical Reports Server (NTRS)

    Beakhouse, G. P.; errane) are discussed.

    1986-01-01

    The Superior Province is divisible into subprovinces that can be classified as greenstone-tonalite, paragneiss, or batholitic terranes and are distinguished by differences in lithologic proportions, metamorphic grade, and structural style. The origin and significance of contrasting geochemical characteristics of plutonic rocks from the Winnipeg River subprovince (a batholithic terrane) and the Wabigoon subprovince (a greenstone-tonalite terrane) are discussed.

  14. Review of potential host rocks for radioactive waste disposal in the southeast United States-Southern Piedmont subregion

    SciTech Connect

    Not Available

    1980-10-01

    A literature study was conducted on the geology of the Southern Piedmont province in the states of Maryland, Virginia, North Carolina, South Carolina, and Georgia. The purpose was to identify geologic areas potentially suitable for containment of a repository for the long-term isolation of solidified radioactive waste. The crystalline rocks of the Southern Piedmont province range in age from Precambrian to Paleozoic, and are predominantly slates, phyllites, argillites, schists, metavolcanics, gneisses, gabbros, and granites. These rock units were classified as either favorable, potentially favorable, or unfavorable as potential study areas based on an evaluation of the geologic, hydrologic, and geotechnical characteristics. No socio-economic factors were considered. Rocks subjected to multiple periods of deformation and metamorphism, or described as highly fractured, or of limited areal extent were generally ranked as unfavorable. Potentially favorable rocks are primarily the high-grade metamorphic gneisses and granites. Sixteen areas were classified as being favorable for additional study. These areas are primarily large igneous granite plutons as follows: the Petersburg granite in Virginia; the Rolesville-Castallia, Churchland, and Landis plutons in North Carolina; the Liberty Hill, Winnsboro, and Ogden plutons in South Carolina; and the Siloam, Elberton, and six unnamed granite plutons in Georgia.

  15. Mapping brittle fracture zones in three dimensions: high resolution traveltime seismic tomography in a granitic pluton

    NASA Astrophysics Data System (ADS)

    Martí, D.; Carbonell, R.; Tryggvason, A.; Escuder, J.; Pérez-Estaún, A.

    2002-04-01

    Fractured and altered zones within a granitic pluton are mapped in three dimensions by means of high resolution seismic traveltime tomography. The input traveltimes were picked from offset and azimuth variable vertical seismic profiles (OVSP) acquired in three boreholes and from seismic shot gathers of four CDP high resolution seismic reflection profiles recorded on the surface. For the OVSP data a hydrophone streamer placed in the boreholes recorded the acoustic energy generated (a signal with a frequency content between 15 to 150 Hz) by a Vibroseis truck at source points distributed every 30 m in a rectangular grid of 620 m by 150 m. The combination of borehole and surface seismic data resulted in an increase in the ray density of the shallow subsurface. The tomographic algorithm uses a variable model grid, with a finer grid spacing close to the surface were ray density is highest and the velocity variations are strongest. Therefore the resulting velocity models feature more detail at shallow levels. A simple and smooth starting velocity model was derived from P -wave velocity logs. Careful surface geological mapping, and borehole geophysical data, P - and S -wave velocity logs and Poisson's ratio depth functions, provided key constraints for a physically reasonable 3-D interpretation of the tomograms. The low velocity anomalies constrained by the tomographic images were interpreted as unconsolidated rock, fractures and altered zones which correlate with structures mapped at the surface or velocity anomalies identified in the logs. Subsequent resolution analysis revealed that the derived velocity model is well constrained to depths of 60 m.

  16. Mineral-Scale and Regional Isotopic Heterogeneity within the Kiglapait Intrusion and Other Mafic Intrusions of the ca. 1.3 Ga Nain Plutonic Suite, Labrador

    NASA Astrophysics Data System (ADS)

    Weis, D.; Morse, S. A.; Scoates, J. S.

    2004-05-01

    For years, stratigraphic variations in the radiogenic isotopic compositions of whole rocks from layered intrusions have been used to document compositional changes (e.g., magma recharge, mixing, contamination) associated with the filling, crystallization, and cooling of crustal magma chambers. However, recent studies are revealing pronounced isotopic disequilibrium or heterogeneity between minerals from many major layered intrusions, including Pb isotopes in coexisting plagioclase and sulfide from the Bushveld (Mathez & Waight, 2003, GCA) and the Stillwater (McCallum et al, 1999, CMP), Sr and Nd isotopes in whole rock, plagioclase, and clinopyroxene from the Skaergaard (McBirney & Creaser, 2003, JP), and Sr isotopes in single plagioclase crystals from the Rum layered intrusion (Tepley & Davidson, 2003, CMP). Except for the Stillwater intrusion, these isotopic variations are not related to low-temperature secondary alteration. Instead, slow cooling (105-106 years) of these large bodies from near-liquidus to subsolidus temperatures appears to allow for complex geochemical evolution of partially molten systems. Proterozoic anorthosite plutonic suites are especially attractive targets for investigating the significance and extent of isotopic differences between crystals, whole rocks, and different intrusions given their typically protracted emplacement histories, range of magma compositions, and slow cooling at mid-crustal depths. To this list of intrusions that record mineral-mineral isotopic disequilibrium, we can add the large 1308 Ma troctolitic Kiglapait layered intrusion in the Nain Plutonic Suite, Labrador. Plagioclase separates and whole rocks show significant differences in both measured and initial Pb isotopic compositions. Bulk mafics and separated minerals (apatite, magnetite, augite and olivine) give internal Pb-Pb and U-Pb isochron ages consistent with the crystallization age. Measured 206Pb/204Pb is highest in apatite (30-73), indicating that apatite is

  17. Petrology, geochemistry and thermobarometry of the northern area of the Flamenco pluton, Coastal Range batholith, northern Chile. A thermal approach to the emplacement processes in the Jurassic andean batholiths

    NASA Astrophysics Data System (ADS)

    Rodríguez, Natalia; Díaz-Alvarado, Juan; Rodríguez, Carmen; Riveros, Karl; Fuentes, Paulina

    2016-04-01

    The Flamenco pluton is part of a N-S alignment of Late Triassic to Early Jurassic intrusive belt comprising the westernmost part of the Coastal Range batholith in northern Chile. The Jurassic-Cretaceous voluminous magmatism related to subduction in the western active continental margin of Gondwana is emplaced in the predominantly metasedimentary Paleozoic host-rocks of the Las Tórtolas formation, which in the northern area of the Flamenco pluton present an intense deformation, including the Chañaral mélange. Geochemically, the Flamenco pluton shows a wide compositional variability (SiO2 between 48wt % and 67wt %). Gabbros, Qtz-diorites and tonalites, mesocratic and leucocratic granodiorites are classified as calc-alkaline, calcic, magnesian and metaluminous magmatism. Flamenco granitoids define cotectic linear evolution trends, typical of magmatic fractionation processes. Geochemical trends are consistent with magmas evolved from undersaturated and low-pressure melts, even though the absence of transitional contacts between intrusive units precludes in-situ fractionation. Although some granodioritic samples show crossed geochemical trends that point to the compositional field of metasediments, and large euhedral prismatic pinnite-biotite crystals, typical Crd pseudomorph, are observed in contact magmatic facies, geochemical assimilation processes are short range, and the occurrence of host-rocks xenoliths is limited to a few meters from the pluton contact. A thermal approach to the emplacement process has been constrained through the thermobarometric results and a 2D thermo-numerical model of the contact aureole. Some Qtz-diorites and granodiorites located in the north area of the pluton exhibit granulitic textures as Hbl-Pl-Qtz triple junctions, poikiloblastic Kfs and Qtz recrystallization. The Hbl-Pl pairs have been used for the thermobarometric study of this metamorphic process, resulting granoblastic equilibrium temperatures between 770 and 790 °C, whereas

  18. Contrasting petrogenesis of Mg-K and Fe-K granitoids and implications for post-collisional magmatism: Case study from the Late-Archean Matok pluton (Pietersburg block, South Africa)

    NASA Astrophysics Data System (ADS)

    Laurent, O.; Rapopo, M.; Stevens, G.; Moyen, J. F.; Martin, H.; Doucelance, R.; Bosq, C.

    2014-05-01

    This study investigates the origin of the 2.69 Ga-old Matok pluton, emplaced in the Pietersburg block, northern Kaapvaal Craton (South Africa), forthwith after a major tectono-metamorphic event ascribed to continent-continent collision. The Matok pluton consists of diorites, granodiorites and monzogranites. Petrography and whole-rock major- and trace element compositions of the Matok samples are similar to those of post-collisional Fe-K suites, which are very common in Proterozoic terranes. These granitoids are particularly rich in FeOt, TiO2, P2O5, span a wide range of SiO2 contents and display elevated concentrations in K2O, Ba, HFSE and REE, with moderately fractionated REE patterns.

  19. The northern coast plutonic-metamorphic complex, southeastern Alaska and northwestern British Columbia</