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Sample records for active orogenic systems

  1. Thermo-kinematic evolution of the Annapurna-Dhaulagiri Himalaya, central Nepal: The Composite Orogenic System

    NASA Astrophysics Data System (ADS)

    Parsons, A. J.; Law, R. D.; Lloyd, G. E.; Phillips, R. J.; Searle, M. P.

    2016-04-01

    The Himalayan orogen represents a "Composite Orogenic System" in which channel flow, wedge extrusion, and thrust stacking operate in separate "Orogenic Domains" with distinct rheologies and crustal positions. We analyze 104 samples from the metamorphic core (Greater Himalayan Sequence, GHS) and bounding units of the Annapurna-Dhaulagiri Himalaya, central Nepal. Optical microscopy and electron backscatter diffraction (EBSD) analyses provide a record of deformation microstructures and an indication of active crystal slip systems, strain geometries, and deformation temperatures. These data, combined with existing thermobarometry and geochronology data are used to construct detailed deformation temperature profiles for the GHS. The profiles define a three-stage thermokinematic evolution from midcrustal channel flow (Stage 1, >700°C to 550-650°C), to rigid wedge extrusion (Stage 2, 400-600°C) and duplexing (Stage 3, <280-400°C). These tectonic processes are not mutually exclusive, but are confined to separate rheologically distinct Orogenic Domains that form the modular components of a Composite Orogenic System. These Orogenic Domains may be active at the same time at different depths/positions within the orogen. The thermokinematic evolution of the Annapurna-Dhaulagiri Himalaya describes the migration of the GHS through these Orogenic Domains and reflects the spatial and temporal variability in rheological boundary conditions that govern orogenic systems.

  2. Young orogenic gold mineralisation in active collisional mountains, Taiwan

    NASA Astrophysics Data System (ADS)

    Craw, Dave; Upton, Phaedra; Yu, Bing-Sheng; Horton, Travis; Chen, Yue-Gau

    2010-10-01

    Gold-bearing vein systems in the high mountains of Taiwan are part of the youngest tectonic-hydrothermal system on Earth. Tectonic collision initiated in the Pliocene has stacked Eocene-Miocene marine sedimentary rocks to form steep mountains nearly 4 km high. Thinner portions of the sedimentary pile (˜5 km) are currently producing hydrocarbons in a fold and thrust belt, and orogenic gold occurs in quartz veins in thicker parts of the pile (˜10 km) in the Slate Belt that underlies the mountains. Metamorphic fluids (2-5 wt.% NaCl equivalent) are rising from the active greenschist facies metamorphic zone and transporting gold released during rock recrystallisation. Metamorphic fluid flow at the Pingfengshan historic gold mine was focussed in well-defined (4 km3) fracture zones with networks of quartz veins, whereas large surrounding volumes of rock are largely unveined. Gold and arsenopyrite occur in several superimposed vein generations, with ankeritic alteration of host rocks superimposed on chlorite-calcite alteration zones as fluids cooled and became out of equilibrium with the host rocks. Mineralising fluids had δ18O near +10‰, δ13C was between -1‰ and -6‰ and these fluids were in isotopic equilibrium with host rocks at ˜350°C. Ankeritic veins were emplaced in extensional sites in kink fold axial surfaces, formed as the rock mass was transported laterally from compressional to extensional regimes in the orogen. Rapid exhumation (>2 mm/year) of the Slate Belt is causing a widespread shallow conductive thermal anomaly without igneous intrusions. Meteoric water is penetrating into the conductive thermal anomaly to contribute to crustal fluid flow and generate shallow boiling fluids (˜250°C) with fluid temperature greater than rock temperature. The meteoric-hydrothermal system impinges on, but causes only minor dilution of, the gold mineralisation system at depth.

  3. Depositional environments and fluvial system changes in the dinosaur-bearing Sânpetru Formation (Late Cretaceous, Romania): Post-orogenic sedimentation in an active extensional basin

    NASA Astrophysics Data System (ADS)

    Therrien, François

    2006-12-01

    The Sânpetru Formation (Haţeg Basin, Romania) was deposited in an active extensional basin in response to the post-orogenic collapse of the Southern Carpathians. Despite being one of the best exposed latest Cretaceous continental successions of Eastern Europe and having great potential to improve knowledge about the Mesozoic evolution of the Carpathian orogen and the latest Cretaceous terrestrial paleoenvironments of Europe, this formation has been the subject of limited sedimentologic research. Fourteen stratigraphic sections were measured in the Sânpetru Formation throughout an 860-m-thick interval exposed along the Sibişel Valley in order to conduct the most detailed stratigraphic and sedimentologic study of this formation to date. The Sânpetru Formation is a repetitive succession of fining-upward units composed of stratified and structureless sandstones, conglomerates, and mudstones. Facies analysis reveals that the Sânpetru Formation was deposited by braided streams that flowed through a symmetrical, extensional basin. The low variability of paleocurrent direction, the sheet-like architecture of the deposits, and the paucity of channel-shaped scours indicate poorly channelized flow across a shallow, broad braidplain. Small-scale fluctuations in sandstone/mudstone ratio and maximum grain size of channel deposits in the lower Sânpetru Formation reflect autocyclic shifts in paleochannel position. In the upper Sânpetru Formation, sandstone/mudstone ratios and maximum grain size of channel deposits increase, paleocurrent direction changes significantly, and hydromorphic paleosols become the sole type of paleosols present. These changes reflect an episode of rapid uplift of the source area and the basinward creation of accommodation space below the local water table, which resulted in the creation of extensive wetlands. The wetlands of the upper Sânpetru Formation were not an environment favorable for the formation of dinosaur bonebeds, which are found in

  4. A Paleozoic Japan-type subduction-accretion system in the Beishan orogenic collage, southern Central Asian Orogenic Belt

    NASA Astrophysics Data System (ADS)

    Song, Dongfang; Xiao, Wenjiao; Windley, Brian F.; Han, Chunming; Tian, Zhonghua

    2015-05-01

    Magmatic arcs ascribed to oceanic lithosphere subduction played a dominant role in the construction of the accretionary Central Asian Orogenic Belt (CAOB). The Beishan orogenic collage, situated between the Tianshan Orogen to the west and the Inner Mongolia Orogen to the east, is a key area to understanding the subduction and accretionary processes of the southern CAOB. However, the nature of magmatic arcs in the Beishan and the correlation among different tectonic units along the southern CAOB are highly ambiguous. In order to investigate the subduction-accretion history of the Beishan and put a better spatial and temporal relationship among the tectonic belts along the southern CAOB, we carried out detailed field-based structural geology and LA-ICP-MS zircon U-Pb geochronological as well as geochemical studies along four cross-sections across crucial litho-tectonic units in the central segment of the Beishan, mainly focusing on the metamorphic assemblages and associated plutons and volcanic rocks. The results show that both the plutonic and volcanic rocks have geochemical characteristics similar to those of subduction-related rocks, which favors a volcanic arc setting. Zircons from all the plutonic rocks yield Phanerozoic ages and the plutons have crystallization ages ranging from 464 ± 2 Ma to 398 ± 3 Ma. Two volcanic-sedimentary rocks yield zircons with a wide age range from Phanerozoic to Precambrian with the youngest age peaks at 441 Ma and 446 Ma, estimated to be the time of formation of the volcanic rocks. These new results, combined with published data on ophiolitic mélanges from the central segment of the Beishan, favor a Japan-type subduction-accretion system in the Cambrian to Carboniferous in this part of the Paleo-Asian Ocean. The Xichangjing-Niujuanzi ophiolite probably represents a major suture zone separating different tectonic units across the Beishan orogenic collage, while the Xiaohuangshan-Jijitaizi ophiolitic mélange may represent a

  5. Association of orogenic activity with the Ordovician radiation of marine life

    NASA Technical Reports Server (NTRS)

    Miller, A. I.; Mao, S.

    1995-01-01

    The Ordovician radiation of marine life was among the most substantial pulses of diversification in Earth history and coincided in time with a major increase in the global level of orogenic activity. To investigate a possible causal link between these two patterns, the geographic distributions of 6576 individual appearances of Ordovician vician genera around the world were evaluated with respect to their proximity to probable centers of orogeny (foreland basins). Results indicate that these genera, which belonged to an array of higher taxa that diversified in the Middle and Late Ordovician (trilobites, brachiopods, bivalves, gastropods, monoplacophorans), were far more diverse in, and adjacent to, foreland basins than they were in areas farther removed from orogenic activity (carbonate platforms). This suggests an association of orogeny with diversification at that time.

  6. Acadian orogen Which Acadian orogen

    SciTech Connect

    Ludman, A. )

    1993-03-01

    The Acadian orogeny is widely viewed as the climactic event in much of the Northern Appalachians, resulting from the closing of one or more ocean basins and the accretion of the Avalonian continent to ancestral North America. Unconformities have traditionally dated the Acadian orogeny as Middle Devonian in the east and Late Middle to Late Devonian in the western part of the orogen. The recent recognition that several post-Acadian'' plutons are actually Late Silurian suggests that the tectonic models are too simplistic; that accretion previously attributed to a Devonian (Acadian) event may have been a two-stage process: Late Silurian (Salinic ) and Acadian sensu stricto; that orogenic activity may have been continuous from Taconian through Acadian'' times. Differences between the records of the Taconic (Ordovician) and Acadian orogenies suggest different plate interactions: near-orthogonal subduction for the former vs transcurrent faulting for the latter as the dominant mechanisms. Distribution of Salinic'' unconformities across the Northern Appalachian orogen in Maine suggests that accretion of Avalon may have been completed by that Silurian event, but faunal provincialities displayed by fossils as young as Early Devonian in terranes bordering the Fredericton Trough argue for later (Devonian) accretion. A further complication is the imprecise knowledge of the extent to which post-Devonian tectonism is responsible for the current terrane configuration in the Northern Appalachians. Alleghenian folding and thrusting is well-established in some areas where post-Acadian (Carboniferous) strata are present, and is now being documented in older rocks in eastern Maine as well: transcurrent faulting as young as post-Mesozoic( ) along the Norumbega Fault Zone; east-directed thrusting involving the Early Devonian Center Pond pluton.

  7. A Numerical SImulation of the Goshen Tornado Observed During Vortex 2: An Orogenic Convective System

    NASA Astrophysics Data System (ADS)

    Tripoli, G. J.; Trevorrow, S. T.; Büker, M.

    2014-12-01

    A numerical simulation of the Goshen 2009 tornado observed during Vortex 2 is presented. The simulation is initialized from the North American Regional Reanalysis data set on the scale of the North American continent. The observed Goshen County tornadic supercell evolves in the simulation from the regional slope flow embedded an a favorable synoptic environment. A supercell and tornado were produced by the simulation in the approximate location and precise time that observations were made of the event by the Vortex 2 team. This was withoiut additional assimilation of high resolution observations beyond the standard data contributing to the 1500 UTC 35 km NARR analysis 7 hours prior to the observed tornado. The simulation can be and is compared directly to Vortex 2 Doppler observations. The process of orogenic storm organization driven by the interaction of topography and the large scale environment is discussed. It is hypothesized that the unusually high predictability of the timing and location as well as the system structure and attendant weather including tornado activity was the result of a highly predictable diurnal slope flow environment that constrained and so reduced the uncertainty of the simulation outcome.

  8. Active Tectonics in crossroads of an evolving orogen and morphological consequences: Anatolia

    NASA Astrophysics Data System (ADS)

    Koral, Hayrettin

    2016-04-01

    Anatolia lies in a curved setting of the active Alpine Mountain Range and is located in crossroads of the European and Asian terrains. It is one of the fastest deforming land in the world, manifested by seismicity, characteristic landforms and GPS measurements. Active tectonics in Anatolia provides not only a comparable geological model for the past orogens, but also a laboratory case for morphological consequences of an orogenic processes. Anatolia comprise different tectonic subsettings with its own characteristics. Northern part is influenced by tectonic characteristics of the Black Sea Basin, the Pontides and the Caucasian Range; northwestern part by the Balkanides; eastern-southeastern part by the Bitlis-Zagros suture; and south-southwestern part by the eastern Mediterranean subduction setting. Much of its present tectonic complexity was inherited from the convergence dominant plate tectonic setting of the platelets prior to the Middle-Neogene. Beginning about 11 Ma ago, the deformed and uplifted landmass unable to accommodate further deformation in Anatolia and ongoing tectonic activity gave rise to rearrangement of tectonic forces and westerly translational movements. Formation of major strike-slip faults in Anatolia including the North and East Anatolian Faults and a new platelet called the Anatolian Plate are the consequences of this episode. Such change in the tectonic regime has led to modification of previously-formed landscape, modification and sometimes termination of previously-formed basins. Evidence is present in the Plio-Quaternary stratigraphy, tectonic characteristics and morphology of the well-studied areas. This presentation will discuss active tectonic features of the northwestern, southwestern and eastern Anatolian subsettings and their influence on morphology that is closely related to sites of pre-historical human settlement.

  9. Stress Dynamics of Magma Activity during Orogenic Evolution: An Example from Kinmen Island, SE China

    NASA Astrophysics Data System (ADS)

    Chen, Ping-Chuan; Yeh, En-Chao; Lin, Jian-Wei; Lee, Chi-Yu; Chen, Rou-Fei; Lin, Wayne; Hsieh, Pei-Shan; Lin, Cheng-Kuo; Iizuka, Yoshiyuki

    2016-04-01

    During orogeny, a mountain belt experienced different orogenic stages with various conditions of temperature, pressure, stress and fluid pressure. The speculation, that the orogenic stresses evolve from reverse faulting via strike-slip faulting to normal faulting stress regimes corresponding to syn-orogenic, post-orogenic and an-orogenic stage respectively, has been proposed but has not been proved yet. Here we report the study of dikes from Kinmen Island can shed light on understanding the stress evolution of orogeny. The Kinmen Island, located in the southeastern continental margin of Mainland China, cropped out the middle to lower crust of NE structural grain, which was experienced deformation and metamorphism during Late Yenshanian Orogeny(LYO). Based on previous studies of geochemistry, geochronology, and P-T conditions, various types of dike have been identified. They are syn-orognic dikes of amphibolite (130-110Ma), post-orogenic dikes of pegmatite and aplite (110-100Ma), and an-orogenic dike of gabbro (94-76Ma). During syn-orogenic stage of LYO, dike intrusion appeared as low-angle dip, which reflected that reverse faulting regime and horizontal maximum stress direction in E-W orientation. In post-orogenic stage, stress would be divided into two sub-stages. The early one was strike-slip faulting regime and horizontal maximum stress was in NW-SE orientation. The late one was normal faulting regime and horizontal maximum stress direction returned to E-W orientation. Finally, an-orogenic dike intrusion striked NE-SW with vertical dip, which displayed that normal faulting regime and NE-SW horizontal maximum stress direction. Our observation is consistent with the expected stress evolution during orogeny. Deviatoric stresses from new findings were decreased at early post-orogenic stage but increased after late post-orogenic stage, indicating the change of fluid pressure ratio with time. The spatiotemporal variation of stress field might be suggested the change

  10. Orogenic Response to Augmented Erosion Associated with Northern Hemisphere Glaciation: The St. Elias Orogen of Alaska

    NASA Astrophysics Data System (ADS)

    Berger, A. L.; Gulick, S. P.; Spotila, J. A.; Worthington, L. L.; Upton, P.; Jaeger, J. M.; Pavlis, T. L.

    2009-12-01

    Active orogens are thought to behave as internally deforming critical-taper wedges that are in rough long-term equilibrium with regional boundary conditions. Deformation, kinematics, and the thermal evolution of orogenic systems are therefore believed to be significantly influenced by spatial and temporal variations in climate. The exact role of cryosphere-geosphere interactions in natural systems, however, continues to be elusive. Here we quantify the spatial patterns of denudation and deformation, and their temporal variations, in the heavily glaciated St Elias orogen in southern Alaska. The tractable size and high latitude of the St. Elias orogen provides an ideal setting to address the real world orogenic response to focused denudation and climate change. Independent of any known change in regional tectonic convergence rate, the St. Elias orogen was subjected to the most severe transition in climate during Cenozoic time, the Late Neogene and Pleistocene onset and advance of glaciers. Low-temperature bedrock thermochronometry, thermokinematic modelling, and offshore seismic reflection and borehole data demonstrate an association between augmented glacial denudation and orogenic evolution. Coeval with the onset of enhanced glacier coverage in mid-Pleistocene time, onshore denudation and offshore sedimentation accelerated ~ten-fold, with the highest rates of exhumation (4 km/Myr (±25%)) located around a narrow zone where the mean Quaternary glacial equilibrium line altitude (ELA) intersects mean topography on the windward flank of the orogen. This climatically driven mass redistribution coincided with the transfer of strain away the seaward deformation front as well as accelerated motion along both a backthrust running the length of the orogen and a series of forethrusts that lie beneath the zone of highest glacial flux. In a cause and effect response, the expansion of glaciers thus appears to have driven an orogen scale structural reorganization leading to the

  11. Extensional deformation structures within a convergent orogen: The Val di Lima low-angle normal fault system (Northern Apennines, Italy)

    NASA Astrophysics Data System (ADS)

    Clemenzi, Luca; Molli, Giancarlo; Storti, Fabrizio; Muchez, Philippe; Swennen, Rudy; Torelli, Luigi

    2014-09-01

    A low-angle extensional fault system affecting the non metamorphic rocks of the carbonate dominated Tuscan succession is exposed in the Lima valley (Northern Apennines, Italy). This fault system affects the right-side-up limb of a kilometric-scale recumbent isoclinal anticline and is, in turn, affected by superimposed folding and late-tectonic high-angle extensional faulting. The architecture of the low-angle fault system has been investigated through detailed structural mapping and damage zone characterization. Pressure-depth conditions and paleofluid evolution of the fault system have been studied through microstructural, mineralogical, petrographic, fluid inclusion and stable isotope analyses. Our results show that the low-angle fault system was active during exhumation of the Tuscan succession at about 180°C and 5 km depth, with the involvement of low-salinity fluids. Within this temperature - depth framework, the fault zone architecture shows important differences related to the different lithologies involved in the fault system and to the role played by the fluids during deformation. In places, footwall overpressuring influenced active deformation mechanisms and favored shear strain localization. Our observations indicate that extensional structures affected the central sector of the Northern Apennines thrust wedge during the orogenic contractional history, modifying the fluid circulation through the upper crust and influencing its mechanical behavior.

  12. Syn- and post-orogenic alkaline magmatism in a continental arc: Along-strike variations in the composition, source, and timing of igneous activity in the Ross Orogen, Antarctica

    NASA Astrophysics Data System (ADS)

    Hagen-Peter, G.; Cottle, J. M.

    2013-12-01

    Neoproterozoic-Paleozoic convergence and subduction along the margin of East Gondwana (Australia, New Zealand, Antarctica) resulted in a belt of deformed and metamorphosed sedimentary rocks and batholith-scale igneous intrusions comparable in size to the present day Andes. Mid-crustal levels of this belt, known as the Ross Orogen in Antarctica, are exposed in the basement of the Cenozoic Transantarctic Mountains, providing snapshots of the intrusive magma system of a major continental arc. Whole rock major- and trace-element geochemistry, Hf isotopes in zircon, and U-Pb geochronology have identified along-strike variations in the composition, source, and timing of magmatism along ~200 km of the southern Victoria Land segment of the orogen. There is an apparent younging of the igneous activity from south to north. New U-Pb ages for intrusive rocks from the Koettlitz Glacier Alkaline Province (KGAP) reveal that igneous activity spanned ca. 565-500 Ma (~30 m.y. longer than previously recognized), while immediately to the north in the Dry Valleys area most igneous activity was confined to a relatively short period (ca. 515-495 Ma). Alkaline and subalkaline igneous rocks occur in both the Dry Valleys area and the KGAP, but alkaline rocks in the Dry Valleys are restricted to the latest phase of magmatism. Na-alkaline rocks in the KGAP, including nepheline syenites, carbonatites, and A-type granites, range in age from ca. 545-500 Ma and overlap in age with more typical subduction/collision-related I- and S-type granites elsewhere in southern Victoria Land. Strong enrichments in the LILE and LREE and high LILE/HFSE and LREE/HREE of samples from the KGAP reveal a source enriched in aqueous-mobile elements, potentially a strongly metasomatized mantle wedge beneath the arc. In the Dry Valleys area, rocks with alkali-calcic composition constitute only the youngest intrusions (505-495 Ma), apparently reflecting a shift to post-orogenic magmatism. Zircons from Dry Valleys

  13. Late-stage orogenic processes: How to link surface motion with distinct lithospheric processes

    NASA Astrophysics Data System (ADS)

    Neubauer, F.; Heberer, B.

    2009-04-01

    There is still a lack of knowledge of surface expression caused by deep-seated lithospheric processes, and how such processes could be distinguished from other, e.g. climate-induced, surface processes like denudation. Surface expressions of deep-seated lithospheric processes in convergent settings are expected to have been long-lived and to show large wave-length structures creating a dynamic topography (Wortel and Spakman, 2000; Cloetingh and Ziegler, 2007). Resulting continent-continent collisional orogens are bivergent, and the principal vergency of collisional orogens is controlled by the previous subduction of oceanic lithosphere (Beaumont et al., 1996). A number of tectonic processes are shown to be active during late orogenic phases and these processes particularly result in specific patterns of surface uplift and denudation of the evolving orogens as well as subsidence in the associated foreland basin. A number of these processes are not fully understood. Late-stage orogenic processes include, among others, slab break-off, slab delamination respectively of lithospheric roots, back-thrusting, tectonic indentation and consequent orogen-parallel lateral extrusion and formation of Subduction-Transform Edge Propagator (STEP) faults acting on the subducting lithosphere (Molnar and Tapponnier, 1975; Wortel and Spakman, 2000; Ratschbacher et al., 1991; Govers and Wortel, 2005). Here, we discuss these processes mainly in terms of their near-surface geological expressions within the orogen and the associated foreland basins, and how these processes could be distinguished by such geological features. We also show distinct theoretical models applied to the arcuate Alpine-Balkan-Carpathian-Dinaric system, which is driven by the oblique convergence of Africa-Europe. Slab-break-off results in lateral orogen-parallel migration of sharp subsidence in a linear belt in front of the slab window, coupled subsidence and subsequent uplift/basin inversion of peripheral foreland

  14. Pre-orogenic structural inheritances control on the Provence thrust system, SE France

    NASA Astrophysics Data System (ADS)

    Bestani, Lucie; Espurt, Nicolas; Lamarche, Juliette; Hollender, Fabrice; Bellier, Olivier

    2015-04-01

    The Provence thrust system located to the southeast of France corresponds to the foreland of the Pyrenean and Alps belts, characteristic of the late Cretaceous-Eocene and Miocene to present-day compressions respectively. Paleozoic-Mesozoic pre-orogenic substratum geometry still raise questions and the shortening of Provence and associated partitioning among these two compressional events, which are responsible for the present Provence foreland structure has never been precisely quantified. The Provence foreland is divided into two parts by the Middle-Durance and Aix-en-Provence faults system: the western and eastern Provence. The Middle Durance/Aix-en-Provence faults system is inherited from Paleozoic times and is responsible for strong thickness variations in the Mesozoic sedimentary pile ranging from 3 (easternpart) to ~10 km (western part). N-S balanced cross sections (~130 km) between the Baronnies to the north and the Mediterranean Sea to the south reveal that the Provence foreland structure results of 91% of the Pyrenean shortening. The Alpine compression led to minor reactivation of Pyrenean-Provence structures with a Miocene shortening of ~650 m (0.5%). Cross-section balancing shows an along-strike heterogeneous total horizontal shortening from ~7.6 km (6%) in the west to ~51 km (27%) in the east. These results show that during the Pyrenean-Provence compression, the Middle Durance/Aix-en-Provence faults system played the role of an oblique transfer zone between the western and eastern Provence domains and separated two contrasted structural domains. Eastward where the sedimentary pile is thin (<4 km), the inversion of deep-seated late Paleozoic-Triassic extensional structures induced a thick-skin style. On the contrary, westward where the sedimentary pile is thick (>7km), the reactivation of basement structures is not necessary involved in the accommodation of the shortening, leading to a thin-skinned tectonics above Triassic series. Paleozoic basement

  15. The initiation of orogenic margin reverse faulting

    NASA Astrophysics Data System (ADS)

    Bailey, R. C.

    2002-04-01

    Laboratory values of rock friction coefficients suggest that reverse faulting should be very difficult to initiate by simple horizontal compression of the crust. Values of stresses required by Andersonian faulting may be an order of magnitude higher than those actually present in orogenic margins. A simple stress balance calculation shows that the effect of the excess lithostatic pressure under an elevated orogen, if transmitted laterally through a crustal ductile layer to the orogenic margin, is to provide sufficient hydraulic lift under the orogen flanks to initiate reverse faulting by direct lift, even with rock friction coefficients of order 0.8. The required orogenic elevation above surrounding ``normal'' lithosphere is about one fifth of the thickness of the brittle crust of the orogen. This elevation may be as small as 2 km in tectonically active regions. The mechanism works even in the absence of regional lithospheric compressive stresses.

  16. Sediment-hosted/orogenic gold mineral systems exploration using PALSAR remote sensing data in Peninsular Malaysia

    NASA Astrophysics Data System (ADS)

    Beiranvand Pour, Amin; Hashim, Mazlan

    2016-06-01

    The Bentong-Raub Suture Zone (BRSZ) is genetically related to the sediment-hosted/orogenic gold deposits associated with the major lineaments and form-lines in the Central Gold Belt of Peninsular Malaysia. In this investigation, the Phased Array type L-band Synthetic Aperture Radar (PALSAR) satellite remote sensing data were used to analyse major geological structures in Peninsular Malaysia and provide detailed characterization of lineaments and form-lines in the BRSZ, as well as its implications for sediment-hosted/orogenic gold exploration in tropical environments. The pervasive array of N-S faults in the study area and surrounding terrain is mainly linked to the N-S trending of the BRSZ Suture Zone. N-S striking lineaments are often cut by younger NE-SW and NW-SE-trending lineaments. Three generations of folding event have been discerned from remote sensing structural analysis. Gold mineralized trends lineaments are associated with the intersection of N-S, NE-SW, NNW-SSE and ESE-WNW faults and curvilinear features in shearing and alteration zones. Compressional tectonics structures such as NW-SE trending thrust, ENE-WSW oriented faults in mylonite and phyllite, recumbent folds and asymmetric anticlines in argillite are high potential zones for gold prospecting.

  17. New geomorphic data on the active Taiwan orogen: A multisource approach

    NASA Technical Reports Server (NTRS)

    Deffontaines, B.; Lee, J.-C.; Angelier, J.; Carvalho, J.; Rudant, J.-P.

    1994-01-01

    A multisource and multiscale approach of Taiwan morphotectonics combines different complementary geomorphic analyses based on a new elevation model (DEM), side-looking airborne radar (SLAR), and satellite (SPOT) imagery, aerial photographs, and control from independent field data. This analysis enables us not only to present an integrated geomorphic description of the Taiwan orogen but also to highlight some new geodynamic aspects. Well-known, major geological structures such as the Longitudinal Valley, Lishan, Pingtung, and the Foothills fault zones are of course clearly recognized, but numerous, previously unrecognized structures appear distributed within different regions of Taiwan. For instance, transfer fault zones within the Western Foothills and the Central Range are identified based on analyses of lineaments and general morphology. In many cases, the existence of geomorphic features identified in general images is supported by the results of geological field analyses carried out independently. In turn, the field analyses of structures and mechanisms at some sites provide a key for interpreting similar geomorphic featues in other areas. Examples are the conjugate pattern of strike-slip faults within the Central Range and the oblique fold-and-thrust pattern of the Coastal Range. Furthermore, neotectonic and morphological analyses (drainage and erosional surfaces) has been combined in order to obtain a more comprehensive description and interpretation of neotectonic features in Taiwan, such as for the Longitudinal Valley Fault. Next, at a more general scale, numerical processing of digital elevation models, resulting in average topography, summit level or base level maps, allows identification of major features related to the dynamics of uplift and erosion and estimates of erosion balance. Finally, a preliminary morphotectonic sketch map of Taiwan, combining information from all the sources listed above, is presented.

  18. Crimean orogene: A nappe interpretation

    SciTech Connect

    Popadyuk, I.V.; Smirnov, S.E. )

    1993-09-01

    On the International Tectonic Map of Europe, the Crimean orogene presents a structure that has no analog in the Alpine orogenic belt. The Crimean mountain system lacks nappe structures of Alpine age. Its geosynclinal folding deformation is restricted to the Tavria flysch formation, previously dated as Triassic-Liassic. Therefore, the Crimean orogene was considered as the Kimmerian tectonotype. In our model, the Crimean orogene is characterized by nappe structures. The Yayla nappe is composed to Upper Jurassic and Neocomian sediments and is located below the Tavrian nappe, which consists of the Tavrian flysch formation. We dated the age of the Tavrian formation as Hauterivian-Aptian on the basis of published ammonite finds in the stratotype section. Nappe displacements are dated roughly as Austrian (albian) by the occurrence of upper-middle Albian sediments below the nappes and the Upper Cretaceous age of their neoautochthonous sedimentary cover. These north-vergent nappes have a horizontal displacement of about 20 km. In the eastern part of the orogene, these nappe structures were overprinted by Laramide-Savic (Paleocene and end Oligocene-early Miocene) deformations, as evident in the Kerch peninsula. The nature of these late deformation is not clear. The hydrocarbon potential of the prenapping autochthonous series has not yet been studied. Exploration for oil and gas in the Crimean sector of the Black Sea must take the suggested model and its implications into account.

  19. Accretionary orogens through Earth history

    USGS Publications Warehouse

    Cawood, Peter A.; Kroner, A.; Collins, W.J.; Kusky, T.M.; Mooney, W.D.; Windley, B.F.

    2009-01-01

    Accretionary orogens form at intraoceanic and continental margin convergent plate boundaries. They include the supra-subduction zone forearc, magmatic arc and back-arc components. Accretionary orogens can be grouped into retreating and advancing types, based on their kinematic framework and resulting geological character. Retreating orogens (e.g. modern western Pacific) are undergoing long-term extension in response to the site of subduction of the lower plate retreating with respect to the overriding plate and are characterized by back-arc basins. Advancing orogens (e.g. Andes) develop in an environment in which the overriding plate is advancing towards the downgoing plate, resulting in the development of foreland fold and thrust belts and crustal thickening. Cratonization of accretionary orogens occurs during continuing plate convergence and requires transient coupling across the plate boundary with strain concentrated in zones of mechanical and thermal weakening such as the magmatic arc and back-arc region. Potential driving mechanisms for coupling include accretion of buoyant lithosphere (terrane accretion), flat-slab subduction, and rapid absolute upper plate motion overriding the downgoing plate. Accretionary orogens have been active throughout Earth history, extending back until at least 3.2 Ga, and potentially earlier, and provide an important constraint on the initiation of horizontal motion of lithospheric plates on Earth. They have been responsible for major growth of the continental lithosphere through the addition of juvenile magmatic products but are also major sites of consumption and reworking of continental crust through time, through sediment subduction and subduction erosion. It is probable that the rates of crustal growth and destruction are roughly equal, implying that net growth since the Archaean is effectively zero. ?? The Geological Society of London 2009.

  20. Provenance of Cretaceous trench slope sediments from the Mesozoic Wandashan Orogen, NE China: Implications for determining ancient drainage systems and tectonics of the Paleo-Pacific

    NASA Astrophysics Data System (ADS)

    Sun, Ming-Dao; Xu, Yi-Gang; Wilde, Simon A.; Chen, Han-Lin

    2015-06-01

    The Wandashan Orogen of NE China is a typical accretionary orogen related to Paleo-Pacific subduction. The Raohe Complex, as a major part of the orogen, consists of mid-Triassic to mid-Jurassic radiolarian chert and intraoceanic igneous rocks in an accretionary prism overlain by weakly sheared terrestrial-sourced clastic trench slope sediments. Sensitive high-resolution ion microprobe U-Pb dating and LA-MC-ICPMS Hf isotopic analysis of detrital zircons from the terrestrial-sourced Yongfuqiao Formation sandstone show that most zircons are Phanerozoic (90%): 140-150 Ma (10%), 180-220 Ma (25%), 240-270 Ma (15%), 300-360 Ma (15%), 391-395 Ma (3%), and 450-540 Ma (20%), whereas 10% are Precambrian in age. About 90% of the zircons have ɛHf(t) values ranging from +11.1 to -12.8. This suggests that the major provenance of the trench slope sediments was from the adjacent eastern segment of the Central Asian Orogenic Belt and the Jiamusi Block. The age of the Yongfuqiao Formation is constrained to the earliest Cretaceous, which represents the accretion time of the mid-Triassic to mid-Jurassic oceanic complexes. When compared with the Mino Complex in Japan and the Tananao Complex in Taiwan, three different provenances are identified suggesting three ancient drainage systems which transported sediments from NE China, North China, and South China to the Paleo-Pacific subduction-accretion system.

  1. Deciphering the Late Quaternary fluvial dynamics at the foothill of an active orogen - the example of the Transcaucasian depression in eastern Georgia

    NASA Astrophysics Data System (ADS)

    von Suchodoletz, Hans; Faust, Dominik

    2013-04-01

    Generally, the dynamics of fluvial systems can be triggered by climate, tectonics, anthropogenic activity or internal mechanisms. The lowland of the Transcaucasian depression is located between the Greater Caucasus in the north and the Lesser Caucasus in the south. Both mountainous massifs form a part of the Alpidic orogenic belt and are thus characterized by a high tectonic activity. During the Weichselian glaciation, due to their altitude >3000 m the massifs were strongly glaciated. During the last years, we investigated fluvial sediment sequences of several rivers that originate from the mountain belts and cross the eastern semi-arid part of the Transcauscasian depression towards the Caspian Sea (e.g. Algeti, Khrami, Kura, Alazani), in order to decipher changes of their fluvial dynamics during the past. The investigated sediments of Late Pleistocene and Holocene age show thicknesses up to 50 m and are mostly well outcropped. Our morphologic, sedimentologic and chronostratigraphic investigations of different sediment sequences demonstrate distinctive changes of the fluvial dynamics between the Late Pleistocene and the Holocene, and show that high-frequent Holocene changes of the fluvial pattern of the rivers are probably linked to climatic and/or anthropogenic triggers. Additionally, on a longer time scale the fluvial dynamics of the rivers is obviously controlled by ongoing tectonic processes.

  2. Neoarchean orogenic, magmatic and hydrothermal events in the Kalgoorlie-Kambalda area, Western Australia: constraints on gold mineralization in the Boulder Lefroy-Golden Mile fault system

    NASA Astrophysics Data System (ADS)

    Mueller, Andreas G.; Hagemann, Steffen G.; McNaughton, Neal J.

    2016-08-01

    The Boulder Lefroy-Golden Mile (BLF-GMF) fault system is the most intensely mineralized structure (>2150 t Au to 2015) in the Archean Yilgarn Craton, Western Australia. The fault system links the Kalgoorlie and Kambalda mining districts in the Eastern Goldfields Province, a continental-margin orogen subdivided into the western Kalgoorlie ensialic rift and the eastern Kurnalpi volcanic arc. After rifting, the 2.73-2.66 Ga greenstone-greywacke succession in the Kalgoorlie-Kambalda area underwent five phases of orogenic deformation, predominantly during ENE-WSW shortening: D1 upright folding at ca. 2680 Ma, D2 sinistral strike-slip faulting at 2678-2663 Ma, D3 folding of late conglomerate-turbidite successions at 2665-2655 Ma, D4 dextral strike-slip faulting at 2655-2640 Ma and D5 east-northeast-striking normal faulting. Regional prehnite-pumpellyite to greenschist facies burial metamorphism took place during D1 and D3 crustal thickening, and amphibolite facies aureoles formed around granite batholiths during and after D3 at 400 ± 100 MPa pressure. The D2 BLF offsets D1 folds by 12 km SW-side south and contains a porphyry dyke (2676 ± 7 Ma) boudinaged by transtensional oblique-slip along a line pitching 21° southeast. The BLF is linked by transverse D2 thrusts to other sinistral faults recording strike-slip until 2663 ± 7 Ma. Late D2 strike-slip movement alternated with early D3 shortening. D3 thrusts accommodated strain in fault blocks of rigid mafic-ultramafic volcanic rocks consolidated during D1, while the sedimentary rocks in D3 synclines were foliated at high strain. Biotite-sericite alteration and gold-pyrite mineralization in the BLF-GMF system took place at 11 ± 4 km burial depth in faults active during D2 and D3. The Golden Mile (1708 t Au) and other deposits are associated with stocks and dykes of high-Mg monzodiorite-tonalite porphyry, part of a late-orogenic (2665-2645 Ma) mantle-derived suite of adakitic affinity. Hornblende and apatite compositions

  3. Late-stage orogenic processes: How to link surface motion with distinct lithospheric processes

    NASA Astrophysics Data System (ADS)

    Neubauer, F.; Heberer, B.

    2009-04-01

    There is still a lack of knowledge of surface expression caused by deep-seated lithospheric processes, and how such processes could be distinguished from other, e.g. climate-induced, surface processes like denudation. Surface expressions of deep-seated lithospheric processes in convergent settings are expected to have been long-lived and to show large wave-length structures creating a dynamic topography (Wortel and Spakman, 2000; Cloetingh and Ziegler, 2007). Resulting continent-continent collisional orogens are bivergent, and the principal vergency of collisional orogens is controlled by the previous subduction of oceanic lithosphere (Beaumont et al., 1996). A number of tectonic processes are shown to be active during late orogenic phases and these processes particularly result in specific patterns of surface uplift and denudation of the evolving orogens as well as subsidence in the associated foreland basin. A number of these processes are not fully understood. Late-stage orogenic processes include, among others, slab break-off, slab delamination respectively of lithospheric roots, back-thrusting, tectonic indentation and consequent orogen-parallel lateral extrusion and formation of Subduction-Transform Edge Propagator (STEP) faults acting on the subducting lithosphere (Molnar and Tapponnier, 1975; Wortel and Spakman, 2000; Ratschbacher et al., 1991; Govers and Wortel, 2005). Here, we discuss these processes mainly in terms of their near-surface geological expressions within the orogen and the associated foreland basins, and how these processes could be distinguished by such geological features. We also show distinct theoretical models applied to the arcuate Alpine-Balkan-Carpathian-Dinaric system, which is driven by the oblique convergence of Africa-Europe. Slab-break-off results in lateral orogen-parallel migration of sharp subsidence in a linear belt in front of the slab window, coupled subsidence and subsequent uplift/basin inversion of peripheral foreland

  4. The Ediacaran Rio Doce magmatic arc revisited (Araçuaí-Ribeira orogenic system, SE Brazil)

    NASA Astrophysics Data System (ADS)

    Tedeschi, Mahyra; Novo, Tiago; Pedrosa-Soares, Antônio; Dussin, Ivo; Tassinari, Colombo; Silva, Luiz Carlos; Gonçalves, Leonardo; Alkmim, Fernando; Lana, Cristiano; Figueiredo, Célia; Dantas, Elton; Medeiros, Sílvia; De Campos, Cristina; Corrales, Felipe; Heilbron, Mônica

    2016-07-01

    Described half a century ago, the Galiléia tonalite represents a milestone in the discovery of plate margin magmatic arcs in the Araçuaí-Ribeira orogenic system (southeastern Brazil). In the 1990's, analytical studies on the Galiléia tonalite finally revealed the existence of a Late Neoproterozoic calc-alkaline magmatic arc in the Araçuaí orogen. Meanwhile, the name Rio Doce magmatic arc was applied to calc-alkaline plutons found in the Araçuaí-Ribeira boundary. After those pioneer studies, the calc-alkaline plutons showing a pre-collisional volcanic arc signature and age between 630 Ma and 585 Ma have been grouped in the G1 supersuite, corresponding to the Rio Doce arc infrastructure. Here, we revisit the Rio Doce arc with our solid field knowledge of the region and a robust analytical database (277 lithochemical analyses, and 47 U-Pb, 53 Sm-Nd, 25 87Sr/86Sr and 7 Lu-Hf datasets). The G1 supersuite consists of regionally deformed, tonalitic to granodioritic batholiths and stocks, generally rich in melanocratic to mesocratic enclaves and minor gabbroic to dioritic plutons. Gabbroic to dioritic enclaves show evidence of magma mixing processes. The lithochemical and isotopic signatures clearly reveal a volcanic arc formed on a continental margin setting. Melts from a Rhyacian basement form the bulk of the magma produced, whilst gabbroic plutons and enclaves record involvement of mantle magmas in the arc development. Tonalitic stocks (U-Pb age: 618-575 Ma, εNd(t): -5.7 to -7.8, Nd TDM ages: 1.28-1.68 Ga, 87Sr/86Sr(t): 0.7059-0.7118, and εHf(t): -5.2 to -11.7) form the northernmost segment of the Rio Doce arc, which dies out in the ensialic sector of the Araçuaí orogen. At arc eastern and central zones, several batholiths (e.g., Alto Capim, Baixo Guandu, Galiléia, Muniz Freire, São Vítor) record a long-lasting magmatic history (632-580 Ma; εNd(t): -5.6 to -13.3; Nd TDM age: 1.35-1.80 Ga; 87Sr/86Sr(t): 0.7091-0.7123). At arc western border, the magmatic

  5. Age, tectonic evolution and origin of the Aswa Shear Zone in Uganda: Activation of an oblique ramp during convergence in the East African Orogen

    NASA Astrophysics Data System (ADS)

    Saalmann, K.; Mänttäri, I.; Nyakecho, C.; Isabirye, E.

    2016-05-01

    Shear Zone activation is linked to underthrusting of the Congo Craton and coeval high-grade metamorphism and intense deformation in the orogen interior. During E-W convergence between ca. 690 and 650 Ma, the NE-dipping ASZ was activated as an oblique ramp leading to deflection of the transport direction and concentration of non-coaxial strain and sinistral shear along the shear zone system. During progressive convergence, between ca. 645 and 620 Ma, sinistral shearing along ASZ changed to ductile-brittle deformation mechanisms, while thrusting took place in Pan-African belts in eastern and western Uganda. Late-orogenic brittle sinistral reactivation of the ASZ can be regarded as the result of continent collision and closure of the Mozambique ocean further to the east, that potentially caused lateral escape manifested in NW-SE striking sinistral shear zones in Kenya and the southern Arabina-Nubian Shield between 620 and 570 Ma.

  6. Age, tectonic evolution and origin of the Aswa Shear Zone in Uganda: Activation of an oblique ramp during convergence in the East African Orogen

    NASA Astrophysics Data System (ADS)

    Saalmann, K.; Mänttäri, I.; Nyakecho, C.; Isabirye, E.

    2016-05-01

    . Early Aswa Shear Zone activation is linked to underthrusting of the Congo Craton and coeval high-grade metamorphism and intense deformation in the orogen interior. During E-W convergence between ca. 690 and 650 Ma, the NE-dipping ASZ was activated as an oblique ramp leading to deflection of the transport direction and concentration of non-coaxial strain and sinistral shear along the shear zone system. During progressive convergence, between ca. 645 and 620 Ma, sinistral shearing along ASZ changed to ductile-brittle deformation mechanisms, while thrusting took place in Pan-African belts in eastern and western Uganda. Late-orogenic brittle sinistral reactivation of the ASZ can be regarded as the result of continent collision and closure of the Mozambique ocean further to the east, that potentially caused lateral escape manifested in NW-SE striking sinistral shear zones in Kenya and the southern Arabina-Nubian Shield between 620 and 570 Ma.

  7. Structural evolution of the Irtysh Shear Zone (northwestern China) and implications for the amalgamation of arc systems in the Central Asian Orogenic Belt

    NASA Astrophysics Data System (ADS)

    Li, Pengfei; Sun, Min; Rosenbaum, Gideon; Cai, Keda; Yu, Yang

    2015-11-01

    The NW-SE Irtysh Shear Zone is a major tectonic boundary in the Central Asian Orogenic Belt (CAOB), which supposedly records the amalgamation history between the peri-Siberian orogenic system and the Kazakhstan/south Mongolia orogenic system. However, the tectonic evolution of the Irtysh Shear Zone is not fully understood. Here we present new structural and geochronological data, which together with other constraints on the timing of deformation suggests that the Irtysh Shear Zone was subjected to three phases of deformation in the late Paleozoic. D1 is locally recognized as folded foliations in low strain areas and as an internal fabric within garnet porphyroblasts. D2 is represented by a shallowly dipping fabric and related ˜ NW-SE stretching lineations oriented sub-parallel to the strike of the orogen. D2 foliations are folded by ˜ NW-SE folds (F3) that are bounded by a series of mylonite zones with evidence for sinistral/reverse kinematics. These fold and shear structures are kinematically compatible, and thus interpreted to result from a transpressional deformation phase (D3). Two samples of mica schists yielded youngest detrital zircon peaks at ˜322 Ma, placing a maximum constraint on the timing of D1-D3 deformation. A ˜ NE-SW granitic dyke swarm (˜252 Ma) crosscuts D3 fold structures and mylonitic fabrics in the central part of the shear zone, but is displaced by a mylonite zone that represents the southern boundary of the Irtysh Shear Zone. This observation indicates that the major phase of D3 transpressional deformation took place prior to ˜252 Ma, although later phases of reactivation in the Mesozoic and Cenozoic are likely. The late Paleozoic deformation (D1-D3 at ˜322-252 Ma) overlaps in time with the collision between the Chinese Altai and the intra-oceanic arc system of the East Junggar. We therefore interpret that three episodes of late Paleozoic deformation represent orogenic thickening (D1), collapse (D2), and transpressional deformation (D3

  8. When sink becomes source: Importance of sediment recycling in linked orogen-basin systems

    NASA Astrophysics Data System (ADS)

    Romans, Brian W.; Fosdick, Julie C.; Hubbards, Stephen M.; Fildani, Andrea

    2013-04-01

    Much of the recent research on sedimentary system dynamics has focused on extant systems where the linkage of sediment production from eroding highlands can be directly linked to deposition in lowlands and/or offshore basins. Studies of such systems, typically late Pleistocene to Holocene in age, are especially valuable for quantitative constraints such as system morphometrics (e.g., longitudinal profiles, basin volumes, etc.) and rates of processes (e.g., erosion/denudation, sediment accumulation, etc.), which can be measured directly or estimated with relatively high certainty. Moreover, information about climate and tectonic forcings that are independent to the system is explicitly known for extant systems. However, an understanding of longer-term (>105 yr) evolution can only be gained through the investigation of ancient systems. Such systems are either buried in the subsurface, which requires geophysical remote sensing and/or drilling, or exposed at the Earth's surface as outcrops as the result of uplift and exhumation. The dynamic linkage of mountain belt and adjacent basin makes foreland basin systems ideal natural laboratories to address long-term sedimentary system evolution. In this presentation, we highlight important issues and challenges that sedimentary systems research is currently facing, with an emphasis on sediment recycling during progressive stages of basin development. In this context, we focus on sedimentary systems in which multiple episodes of uplift and erosion of the primary depocenter led to a history whereby basin material was repeatedly recycled. The spatial and temporal aspects of sediment recycling have implications for how provenance signals (based on composition, crystallization or metamorphic age information, thermal history, etc.) are used. Additionally, improved constraints regarding the timescales and magnitude of sediment recycling have implications for system-scale modeling. Key parameters such as total sediment volumes and

  9. Hydrothermal activity during tectonic building of the Variscan orogen recorded by U-Pb systematics of xenotime in the Grès Armoricain formation, Massif Armoricain, France

    NASA Astrophysics Data System (ADS)

    Tartèse, Romain; Poujol, Marc; Gloaguen, Eric; Boulvais, Philippe; Drost, Kerstin; Košler, Jan; Ntaflos, Theodoros

    2015-08-01

    In the Saint-Aubin-des-Châteaux deposit (Massif Armoricain, France), the Ordovician Grès Armoricain sandstones have undergone several fluid-rock interaction events, including diagenetic cementation and orogenic base metal-As-Sb-Au mineralisation. Ironstone layers interbedded in the sandstones contain several generations of spectacular authigenic xenotime overgrowths that formed around detrital zircon grains in response to successive hydrothermal events. Textural and chemical characterisations allow to distinguish three generations of xenotime overgrowths, differing notably in their REE characteristics. In-situ U-Pb data obtained on these xenotime overgrowths show that their U-Pb systematics were largely disturbed by successive hydrothermal events over about 90 Ma between ~ 330 and ~ 420 Ma, a time interval encompassing most phases of the construction of the Variscan orogen in France. The younger dates cluster around ~ 330-340 Ma and likely correspond to the age of the deposition of massive sulphides and base-metals in the Saint-Aubin-des-Châteaux deposits, which is consistent with the structural contexts where they formed. Finally, this study shows that similarly to monazite, another phosphate widely used for U-Pb and Th-Pb dating studies, the U-Pb chronometric system in xenotime appears to be highly sensitive to fluid circulations.

  10. Early Cretaceous tectono-magmatic activity and tectonic implications along the Sulu Orogenic Belt - case study of the Dashan complex

    NASA Astrophysics Data System (ADS)

    Liu, Yanghe; Liu, Junlai; Shi, Xiaoxiao; Yuan, Fengjie; Ni, Jinlong; Wu, Wenbin; Chen, Xiaoyu

    2016-04-01

    The tectonic extension of the eastern Eurasian continent during the Early Cretaceous resulted in widespread occurrence of metamorphic core complexes, wide rifts and related magmatic emplacement, among which the Dashan complex of the Jiaonan orogenic belt is a typical example. The complex is a complex massif of several types of granitic rocks. The core of the complex is composed of massive porphry-bearing biotite-hornblende granitoid without any evidence of ductile deformation. Mylonitized augen quartz monzonite and granodiorite constitute the margin of the complex. A transition zone is composed of porphyritic biotite-hornblende monzonite with weakly orientated K-feldspar phenocryst and mafic microgranular enclave. The foliations along the northwestern margin of the complex dip to NW at with dip angles of about 38°, and along the southwestern and northeastern margins to SE with dip angles of about 45°. Stretching lineations are constantly plunging WNW-ESE with pitch angles between 10° and 40°, which is consistent with the orientation of lineations in the other regions in eastern China. The granites,porphyritic monzogranite and the mafic microgranular enclaves in monzogranite are dated of ca.126Ma. The similarities in ages of crystallization of the monzogranite and its MME's implies the existence of magmatic mixing processes. Meanwhile, the mylonitized augen quartz monzonite and granodiorite along the margins of the complex possess crystallization ages of 129.8±1.1Ma and 132.7±2.8Ma, respectively. The petrographical zonation , structural characteristics and the systematical zircon U-Pb geochronology of the granitic rocks may suggest that the Dashan complex has experienced multistage emplacement under the same tectonic extension setting. In despite of the location of the complex near the Tanlu fault zone, the remarkable consistency of the orientations of stretching lineation of the Dashan complex to those from the other parts of the eastern China area implies

  11. Tectonic stress evolution in the Pan-African Lufilian Arc and its foreland (Katanga, DRC): orogenic bending, late orogenic extensional collapse and transition to rifting

    NASA Astrophysics Data System (ADS)

    Kipata, M. L.; Delvaux, D.; Sebagenzi, M. N.; Cailteux, J.; Sintubin, M.

    2012-04-01

    Between the paroxysm of the Lufilian orogeny at ~ 550 Ma and the late Neogene to Quaternary development of the south-western branch of the East African rift system, the tectonic evolution of the Lufilian Arc and Kundelungu foreland in the Katanga region of the Democratic Republic of Congo remains poorly unknown although it caused important Cu-dominated mineral remobilizations leading to world-class ore deposits. This long period is essentially characterized by brittle tectonic deformations that have been investigated by field studies in open mines spread over the entire arc and foreland. Paleostress tensors were computed for a database of 1450 fault-slip data by interactive stress tensor inversion and data subset separation, and the relative succession of 8 brittle deformation events established. The oldest brittle structures observed are related to the Lufilian brittle compressional climax (stage 1). They have been re-oriented during the orogenic bending that led to the arcuate shape of the belt. Unfolding the stress directions from the first stage allows to reconstruct a consistent NE-SW direction of compression for this stage. Constrictional deformation occurred in the central part of the arc, probably during orogenic bending (Stage 2). After the orogenic bending, a sequence of 3 deformation stages marks the progressive onset of late-orogenic extension: strike-slip deformations (stages 3-4) and late-orogenic arc-parallel extension (stage 5). It is proposed that these 3 stages correspond to orogenic collapse. In early Mesozoic, NW-SE compression was induced by a transpressional inversion, interpreted as induced by far-field stresses generated at the southern active margin of Gondwana (stage 6). Since then, this region was affected by rift-related extension, successively in a NE-SW direction (stage 7, Tanganyika trend) and NW-SE direction (stage 8, Moero trend).

  12. 'Extra-regional' strike-slip fault systems in Chile and Alaska: the North Pacific Rim orogenic Stream vs. Beck's Buttress

    NASA Astrophysics Data System (ADS)

    Redfield, T. F.; Scholl, D. W.; Fitzgerald, P. G.

    2010-12-01

    The ~2000 km long Denali Fault System (DFS) of Alaska is an example of an extra-regional strike-slip fault system that terminates in a zone of widely-distributed deformation. The ~1200 km long Liquiñe-Ofqui Fault Zone (LOFZ) of Patagonia (southern Chile) is another. Both systems are active, having undergone large-magnitude seismic rupture is 2002 (DFS) and 2007 (LOFZ). Both systems appear to be long-lived: the DFS juxtaposes terranes that docked in at least early Tertiary time, whilst the central LOFZ appears to also record early Tertiary or Mesozoic deformation. Both fault systems comprise a relatively well-defined central zone where individual fault traces can be identified from topographic features or zones of deformed rock. In both cases the proximal and distal traces are much more diffuse tributary and distributary systems of individual, branching fault traces. However, since their inception the DFS and LOFZ have followed very different evolutionary paths. Copious Alaskan paleomagnetic data are consistent with vertical axis small block rotation, long-distance latitudinal translation, and a recently-postulated tectonic extrusion towards a distributary of subordinate faults that branch outward towards the Aleution subduction zone (the North Pacific Rim orogenic Stream; see Redfield et al., 2007). Paleomagnetic data from the LOFZ region are consistent with small block rotation but preclude statistically-significant latitudinal transport. Limited field data from the southernmost LOFZ suggest that high-angle normal and reverse faults dominate over oblique to strike-slip structures. Rather than the high-angle oblique 'slivering regime' of the southeasternmost DFS, the initiation of the LOFZ appears to occur across a 50 to 100 km wide zone of brittly-deformed granitic and gneissic rock characterized by bulk compression and vertical pathways of exhumation. In both cases, relative plate motions are consistent with the hypothetical style, and degree, of offset, leading

  13. Geomorphic response of an active metamorphic core-complex in a collisional orogen: Example from the Lunggar Shan, Southern Tibet

    NASA Astrophysics Data System (ADS)

    Taylor, M. H.; Kapp, P. A.; Stockli, D. F.

    2008-07-01

    We present structural and neotectonic mapping from the Lunggar Shan rift in southern Tibet. The Lunggar Shan is a N-trending mountain range ~70 km long N-S and up to 40 km wide E-W. The Lunggar Shan is bounded on its east side by a low-angle (<40°) east-dipping detachment fault that juxtaposes mylonitic gneiss and variably deformed granites in its footwall against alluvial fans and Neogene gravels in its hangingwall. Foliations in the mylonitic footwall dip < 40° east and stretching lineations are east plunging. The range front detachment is presently inactive as indicated by undisturbed moraines and Quaternary sediments that overlie it. However, we consider the Lunggar Shan detachment to be an active structure, as inferred by range parallel fault scarps cutting Quaternary alluvium located 4-5 km into the hangingwall basin, with >40 m of throw on individual scarps. An intriguing observation is that an intrabasinal topographic high is actively developing near areas of inferred maximum extension, with lacustrine sediments being uplifted and eroded. This observation indicates that the rift basin initially developed as a typical half-graben system that underwent a transition from deposition, to uplift and erosion perhaps as a result of isostatic rebound of the footwall at depth, warping the overlying hangingwall basin. If correct, the Lunggar Shan may represent a modern analogue to the supradetachment basin model.

  14. Inheritance and refertilization of Upper Mantle rocks in Alpine type orogens and rift systems: what and why

    NASA Astrophysics Data System (ADS)

    Muntener, O.

    2015-12-01

    Mantle peridotites and their serpentinized counterparts from ocean-continent transition zones (OCT's) and (ultra-) slow spreading ridges question a series of 'common beliefs' that have been applied to understand Alpine-type collisional orogens in the framework of the ophiolite concept. I will show that inherited mantle signatures play a key role for the interpretation of ophiolites, and similar processes are relevant for present-day passive margins. Field data and petrology demonstrates that ancient, thermally undisturbed, pyroxenite-veined subcontinental mantle formed parts of the ocean floor next to thinned continental crust. These heterogeneities might comprise an ancient subduction component. Mantle upwelling and decompression melting during rifting forms partial melts that enter a thick conductive lithospheric mantle and inevitably leads to freezing of the melt and refertilization of the lithospheric mantle. Mafic bodies (gabbros, basalts) are small and discontinous. The abundance of plagioclase peridotites in the Alpine ophiolites and elswhere along rifted margins are interpreted as recorders of refertilization processes related to thinning and exhumation of mantle lithosphere. Similar features are found (ultra-) slow spreading ridges. Another important result is the discovery of extremely refractory Nd-isotopic compositions with highly radiogenic 147Sm/144Nd, which indicates that partial melting processes and Jurassic magmatism in the Western Tethys are locally decoupled. Although the isotopic variability along ridges is generally explained by mantle heterogeneities such as pyroxenites, an alternative is that these depleted domains represent snapshots of melting processes that are related to Permian and/or even older crust forming processes, and during the most recent decompression they were unffected by (further) melting. Similarly, refractory rocks from rifted margins and (ultra-) slow spreading ridges have been interpreted to represent ancient melting

  15. Kinematics of back-arc extension driven by the interference of subduction and/or collisional zones: application to a number of Mediterranean orogens

    NASA Astrophysics Data System (ADS)

    Matenco, L.; Cloetingh, S.

    2013-12-01

    The large number and distribution of roll-back systems in Mediterranean orogens infers the possibility of interacting extensional back-arc deformation driven by different slabs. Classical models of orogenic evolution assume that such back arc basins form in the hinterland of orogens, collapsing the upper plate above oceanic subduction zones. This is a common characteristic thought to apply to all low-topography orogens of Mediterranean type driven by the fast roll-back of genetically related slabs, or to other analogues such as the Miocene to recent evolution of the SE Asia subduction zones. This extension may take place far at the interior of the upper plate, as is the case in various segments of the Carpathians or in the core of the SE Asian domain, but in most cases of the Dinarides, Apennines or Hellenides it take place superposed or far into the foreland when compared with the position of oceanic suture zones. Mediterranean orogens often diverge from the typical scenario by widespread extensional deformation taking place during moments of continent-continent collision and by the interference of such deformation driven by different subduction zones. For instance, the formation of the Pannonian back-arc basin is generally related to the rapid Miocene roll-back of a slab attached to the European continent. The present-day extensional geometry of the Pannonian back-arc formed essentially during the Carpathians collision and was also driven by an additional Middle Miocene roll-back of a Dinaridic slab. In other orogenic systems, the back-arc extension takes place during continent-continent collision along major detachments that are located in the core of the orogen (Rif, Betics), in the accreted crustal material of the lower plate (Apennines, Dinarides) or even in a presumed former fore-arc (Aegean, Sunda-Banda arc). In all these subduction zones, collision has largely duplicated crustal blocks from the lower plate and has gradually shifted subduction zone far

  16. Predictive mapping of prospectivity for orogenic gold in Uganda

    NASA Astrophysics Data System (ADS)

    Herbert, Sarah; Woldai, Tsehaie; Carranza, Emmanuel John M.; van Ruitenbeek, Frank J. A.

    2014-11-01

    Integration of enhanced regional geo-datasets has facilitated new geological interpretation and modelling of prospectivity for orogenic gold in southwestern Uganda. The geo-datasets include historical geological maps, geological field data, digital terrain models, Landsat TM data and airborne geophysical data. The study area, bordered by the western branch of the East African Rift, covers a range of different aged terranes including the Archaean basement gneisses, Palaeoproterozoic volcano-sedimentary Buganda Toro Belt, Mesoproterozoic clastic sedimentary Karagwe Ankolean Belt and several outliers of undeformed Neoproterozoic sediments. The mineral systems approach to practical exploration targeting requires a framework to link conceptual models of mineralisation with available data. A conceptual model requires good understanding of key processes and their timing within the geodynamic history of an area. The challenge is that processes cannot be mapped, only their results or effects. In this study, a district-scale (1:100,000) investigation is considered appropriate given the scarcity of geological information and the absence of world-renowned gold deposits in southwestern Uganda. At this scale of orogenic gold mineral systems understanding, evidence for the source of gold, active pathways and the physical traps are considered critical. Following the mineral system approach, these processes critical to orogenic gold systems are translated into district-scale mappable proxies using available regional-scale datasets. Tectono-stratigraphic domains, mantle indicators and gold occurrences represent the “source of gold” as a critical process. Zones of hydrothermal alteration were extracted from radiometric data, structures involved in the orogenies and terrane contacts were extracted to represent the active pathway as a critical process and finally the physical throttle is represented by rheological contrasts and geological complexity. Then, the knowledge

  17. New views on the structure and evolution of the Andes-Altiplano orogenic system: Are collision- and subduction-type mountain belts mechanically different?

    NASA Astrophysics Data System (ADS)

    Riesner, M.; Armijo, R.; Lacassin, R.; Simoes, M.; Carrizo, D.; Fuentes, G.

    2014-12-01

    The Andes-Altiplano orogenic system, one of the most significant topographic feature on Earth, is the case example of subduction-type mountain belts. This latter conceptual model considers that the overall structure of the mountain belt forms antithetic to the subduction zone which marks the main plate interface, and as such poses several mechanical issues. Recent studies challenged this view, by proposing a model of the Andes involving an embryonic west-vergent intracontinental subduction, synthetic to the subduction zone and thus geometrically comparable to alpine-type collision belts. Here, we compare these two models of the Andes, by re-evaluating a cross-section of the range at the latitude of Santiago del Chile (33.5 °S). A particular structure, the east-vergent Aconcagua fold-and-thrust belt (AFTB), appears critical in discussing and discriminating between these two views. We revise the structural geometry of the AFTB based on satellite imagery, digital elevation models, existing geological maps and field observations. We propose a new 3D cartography and cross-section of the AFTB and conclude that the AFTB develops over a 2-3 km deep décollement, with a finite shortening of ~13 km. We integrate the AFTB to the well-documented fold and thrust belt forming the western flank of the belt and find that it is a relatively secondary feature of the Andes. From kinematic modelling using Move software (Midland Valley Ltd), we build a crustal-scale evolutionary model showing the progressive shortening of the Andean margin. We find that the AFTB can be modelled as a secondary east-verging structure, passively transported westward atop a basement ramp anticline forming the Frontal Cordillera. This evolutionary model is discussed and constrained in perspective of available thermochronology data. Our model therefore suggests that the Andes orogen can be mechanically modelled as an alpine-type collision belt, challenging our long-standing view of subduction-type mountain-belts.

  18. New (U-Th)/He titanite data from a complex orogen-passive margin system: A case study from northern Mozambique

    NASA Astrophysics Data System (ADS)

    Bauer, Friederike U.; Jacobs, Joachim; Emmel, Benjamin U.; van Soest, Matthijs C.

    2016-08-01

    New titanite (U-Th)/He (He) data on basement rocks from NE Mozambique are presented. The objective was to test the applicability of titanite He thermochronology in an orogen-passive margin setting and to better constrain the exhumation history across the Lurio Belt, a major structural discontinuity in Mozambique. Therefore, samples from existing geochronological and thermochronological studies were dated using titanite He thermochronology. Resulting titanite He data (from abraded crystals) provide average cooling ages from 178 ± 15 to 383 ± 23 Ma. The data fit well into the age pattern obtained from previous thermochronological studies in NE Mozambique, revealing differential exhumation across the Lurio Belt. The basement to the north experienced earlier cooling than that to the south, while overall youngest titanite He ages are from the Lurio Belt, indicating reactivation linked to the post-collisional extension and break-up of Gondwana. Thermal history modelling revealed two possibilities, able to account for the different cooling histories of NE Mozambique since initial Gondwana break-up in Permian times: One involves a transient sedimentary overburden that buried and (re)heated the southern basement, with subsequent basin inversion at ∼250 Ma in response to rift shoulder uplift. The second model implies delayed cooling of the southern basement, possibly due to delamination of the crustal root shortly after Gondwana formation. The formerly upwelling asthenosphere and the subsequently formed sag basin might have caused a prolonged thermal effect. Titanite He ages and thermal histories point to rift shoulder uplift of the southern part and increased thermal activity within the reactivated Lurio Belt, signifying first rifting activities as precursor of Gondwana break-up.

  19. Ore geology and fluid inclusion geochemistry of the Tiemurt Pb-Zn-Cu deposit, Altay, Xinjiang, China: A case study of orogenic-type Pb-Zn systems

    NASA Astrophysics Data System (ADS)

    Zhang, Li; Zheng, Yi; Chen, YanJing

    2012-04-01

    The Tiemurt Pb-Zn-Cu deposit is hosted in a Devonian volcanic-sedimentary basin of the Altay orogenic belt, and is thus interpreted to have formed by sea-floor hydrothermal exhalation in previous studies. Our investigation discovered that the deposit is not stratiform or stratabound, but structure-controlled instead. The hydrothermal ore-forming process can be divided into the early, middle and late stage, represented by pyrite-quartz, polymetallic sulfide-quartz and carbonate-quartz veinlets, respectively. The early-stage veins and contained minerals are structurally deformed and brecciated, suggesting a compressional or transpressional tectonic regime. The middle-stage veinlets intrude and infill the fissures of the early-stage assemblages, and show no deformation, suggesting a tensional shear setting. The late-stage veinlets mostly infill open-space fissures that crosscut veins and replacements formed in the earlier stages. Four types of fluid inclusions (FIs), including aqueous (type W), carbonic-aqueous (type C), pure carbonic (type PC) and solid-bearing (type S), are identified at the Tiemurt deposit. The early-stage minerals contain the C- and W-type primary FIs that are totally homogenized at temperatures of 330-390 °C with low salinities of 0.8-11.9 wt.% NaCl eqv.; whilst the late-stage quartz or calcite contains only the W-type FIs with homogenization temperatures of 118-205 °C, and salinities of 1.4-3.4 wt.% NaCl eqv. This indicates that the ore fluid system evolved from CO2-rich, probably metamorphic to CO2-poor, meteoric fluids; and that a significant CO2-escape must have occurred. All the four types of FIs can be only observed in the middle-stage minerals, and even in a microscopic domain of a crystal, representing an association trapped from a boiling fluid system. These FIs homogenize at temperatures ranging from 270 to 330 °C, with two salinity clusters of 1.9-14.5 and 37.4-42.4 wt.% NaCl eqv., respectively. This implies that metal precipitation

  20. The Development of Topography in Ancient and Active Orogens: Case Studies of Landscape Evolution in the Southern Appalachians, USA and Crete, Greece

    NASA Astrophysics Data System (ADS)

    Gallen, Sean Francis

    Understanding the development of topography is fundamental to the geosciences. Topography represents the sum of all tectonic and geodynamic processes that force the earth's surface upward paired with those that act to bring it down. Spatial and temporal changes in topographic relief can modulate the various feedbacks between atmospheric, earth surface and rock exhumation processes, sediment flux, and the magnitude and style of gravity driven natural hazards. Plate tectonics provides the first-order framework necessary to understand how topography is built through the interaction of lithospheric plates. However, density contrasts in the mantle can also influence the elevation of the earth's surface through dynamic topography, while poorly understood nuances of mountain building at convergent margins complicate drawing direct connections between tectonics and topography. Such linkages are further confounded by non-linearity between rock uplift and erosion, variations in rates of deformation, changes in climate and the properties of bedrock. Great advances in our understanding of the evolution of topography have been achieved, yet numerous questions remain regarding the evolution of topography in ancient and active orogens. This research addresses knowledge gaps in the development of topography through case-studies of landscape evolution in the southern Appalachians Mountains, USA and the forearc overlying the Hellenic subduction zone. Chapter 1 explores the origins of modern topographic relief in the southern Appalachians, where tectonic activity ceased prior to 200 Ma. Conventional theories invoked to explain modern relief in the region are challenged. Quantitative analyses of digital elevation models and numerical modeling are coupled to provide the magnitudes and timing of changes in topographic relief. The results suggest that the southern Appalachians experienced a phase of topographic rejuvenation during the Miocene that increased the distance between the

  1. Simultaneous Miocene Extension and Shortening in the Himalayan Orogen

    NASA Astrophysics Data System (ADS)

    Hodges, K. V.; Parrish, R. R.; Housh, T. B.; Lux, D. R.; Burchfiel, B. C.; Royden, L. H.; Chen, Z.

    1992-11-01

    The South Tibetan detachment system separates the high-grade metamorphic core of the Himalayan orogen from its weakly metamorphosed suprastructure. It is thought to have developed in response to differences in gravitational potential energy produced by crustal thickening across the mountain front. Geochronologic data from the Rongbuk Valley, north of Qomolangma (Mount Everest) in southern Tibet, demonstrate that at least one segment of the detachment system was active between 19 and 22 million years ago, an interval characterized by large-scale crustal thickening at lower structural levels. These data suggest that decoupling between an extending upper crust and a converging lower crust was an important aspect of Himalayan tectonics in Miocene time.

  2. Upper Triassic turbidites of the northern Tethyan Himalaya (Langjiexue Group): the terminal of a sediment-routing system sourced in the Gondwanide Orogen

    NASA Astrophysics Data System (ADS)

    Wang, Jian-Gang; Wu, Fu-Yuan; Garzanti, Eduardo; Hu, Xiu-Mian; Ji, Wei-Qiang; Liu, Zhi-Chao; Liu, Xiao-Chi

    2016-04-01

    zircons with uniform ɛHf(t) values from -5 to +10 are incompatible with any nearby source, including the Qiantang Block, the Lhasa Block or the India subcontinent, and indicate instead supply from a long-lived magmatic-arc terrane. Considering what is known about Late Triassic paleogeography, a plausible source for Langjiexue sediments is represented by the Gondwanide Orogen, generated during subduction of the pan-Pacific oceanic lithosphere beneath southeastern Gondwana. This scenario is supported by the age range and Hf isotopic signatures of Late Paleozoic-Early Mesozoic zircons contained in Langjiexue turbidites as in coeval turbidites exposed in western Myanmar (Sevastjanova et al., 2016). New data are needed to confirm/falsify the existence of a thousands-km-long sediment-routing system similar to the modern Amazon, which - sourced in a cordillera-type orogen rising along the southeastern margin of Gondwana - crossed an entire continent to feed turbiditic fans now exposed from western Myanmar to the northern Tethys Himalaya.

  3. Mantle refertilization and magmatism in old orogenic regions: The role of late-orogenic pyroxenites

    NASA Astrophysics Data System (ADS)

    France, Lydéric; Chazot, Gilles; Kornprobst, Jacques; Dallai, Luigi; Vannucci, Riccardo; Grégoire, Michel; Bertrand, Hervé; Boivin, Pierre

    2015-09-01

    Pyroxenites and garnet pyroxenites are mantle heterogeneities characterized by a lower solidus temperature than the enclosing peridotites; it follows that they are preferentially involved during magma genesis. Constraining their origin, composition, and the interactions they underwent during their subsequent evolution is therefore essential to discuss the sources of magmatism in a given area. Pyroxenites could represent either recycling of crustal rocks in mantle domains or mantle originated rocks (formed either by olivine consuming melt-rock reactions or by crystal fractionation). Petrological and geochemical (major and trace elements, Sr-Nd and O isotopes) features of xenoliths from various occurrences (French Massif-Central, Jordan, Morocco and Cameroon) show that these samples represent cumulates crystallized during melt percolation at mantle conditions. They formed in mantle domains at pressures of 1-2 GPa during post-collisional magmatism (possibly Hercynian for the French Massif-Central, and Panafrican for Morocco, Jordan and Cameroon). The thermal re-equilibration of lithospheric domains, typical of the late orogenic exhumation stages, is also recorded by the samples. Most of the samples display a metasomatic overprint that may be either inherited or likely linked to the recent volcanic activity that occurred in the investigated regions. The crystallization of pyroxenites during late orogenic events has implications for the subsequent evolution of the mantle domains. The presence of large amounts of mantle pyroxenites in old orogenic regions indeed imparts peculiar physical and chemical characteristics to these domains. Among others, the global solidus temperature of the whole lithospheric domain will be lowered; in turn, this implies that old orogenic regions are refertilized zones where magmatic activity would be enhanced.

  4. An investigation of lithospheric structure and evolution in convergent orogenic systems using seismic receiver functions and surface wave analysis

    NASA Astrophysics Data System (ADS)

    Calkins, Joshua A.

    Whether by accretion, magmatic addition, or refinement of more mafic lithologies, continental arcs are likely zones for the creation of "average" continental crust with intermediate silica content. This dissertation contains the results of broadband seismic studies carried out in two field areas, an active subduction zone and the remnants of an extinct arc, with the aim of understanding lithospheric evolution at convergent margins. The analytical techniques of receiver function calculation and surface wave tomography are applied to data sets collected above the Andean subduction zone in Chile and western Argentina and in the Coast Mountains Batholith of central British Columbia. We present the first in-depth comparison of receiver functions calculated using the high frequencies available in records of intermediate-depth local earthquakes with those calculated from the lower frequency data in records of larger teleseismic events. The comparison reveals that the lower crust beneath the Western Sierras Pampeanas contains a gradational velocity increase over ˜20km above a small velocity step at the Moho. Surface wave tomography confirms the existence of an unusually high velocity anomaly in the mantle above the slab and yields estimates of slab thickness on the order of 50 km. To the south of the flat slab region, we see evidence of active mantle wedge convection above the steep slab, but no evidence of the lithosphere-asthenosphere boundary beneath the subducting Nazca plate. In the Coast Mountains Batholith (CMB), receiver functions image a bright, continuous Moho throughout the study region. Combined with petrologic modeling, the receiver function data point toward convective removal of any ultramafic root that formed beneath the CMB. Low absolute shear wave velocities in the upper mantle resolved via surface wave analysis strengthen the case for root removal beneath the eastern section of the CMB. On the far western edge of the CMB, we find evidence of a partially

  5. The Wassa deposit: A poly-deformed orogenic gold system in southwest Ghana - Implications for regional exploration

    NASA Astrophysics Data System (ADS)

    Perrouty, Stéphane; Jessell, Mark W.; Bourassa, Yan; Miller, John; Apau, Daniel; Siebenaller, Luc; Velásquez, Germán; Baratoux, Lenka; Aillères, Laurent; Béziat, Didier; Salvi, Stefano

    2015-12-01

    The Ashanti greenstone belt in southwest Ghana hosts many gold deposits distinguished by different timing and structural contexts. This study investigates the evolution of the Wassa system by integrating field and geophysical observations. This 4 million ounces (past production and current resources) gold deposit is interpreted to represent the oldest gold mineralization event in West Africa with gold-bearing pyrites aligned and stretched within the S1 ductile fabric. Mineralized quartz-carbonate veins were strongly deformed during the D1 deformation event. Three additional folding events are characterized by hectometer-scale tight to isoclinal folds, by a kilometer-scale synform fold centered on the mine and by a late recumbent metric-scale folds. Because of its early timing, the Wassa system represents a new poly-deformed deposit type in West Africa and highlights a potential for new discoveries in the underexplored meta-volcanic and meta-sedimentary Sefwi Group. Timing of the gold mineralization at the Wassa mine makes this deposit type a possible candidate for the source of the gold contained in the Tarkwa paleoplacer.

  6. Giant quartz vein systems in accretionary orogenic belts: the evidence for a metamorphic fluid origin from δ 15N and δ 13C studies

    NASA Astrophysics Data System (ADS)

    Jia, Yiefei; Kerrich, Robert

    2000-12-01

    Nitrogen isotope compositions of hydrothermal micas in giant structurally hosted quartz vein systems place constraints on the origin of the hydrothermal fluids. The vein systems are from Neoarchean terranes in the Superior Province of Canada, and the Norseman terrane, Western Australia. The four quartz vein systems studied in different terranes formed at metamorphic grades ranging from lower greenschist to lower amphibolite facies, coevally with metamorphism of the host terrane. Nitrogen resides predominantly as NH 4+ in hydrothermal mica. For lower to upper greenschist facies quartz veins, N contents and δ 15N values of micas are between 40 and 200 ppm and 15‰ and 21‰, respectively, whereas in quartz veins formed at the greenschist to amphibolite transition and lower amphibolite facies, micas have N contents of 20-70 ppm and δ 15N of 11-24‰. In contrast, micas and K-feldspars from granitoids in the Neoarchean Abitibi and Red Lake greenstone belts are characterized by systematically lower δ 15N of -5‰ to 5‰, and generally lower N contents of 20-50 ppm, comparable to other granitoids. Carbon and oxygen isotope compositions of hydrothermal ferroan dolomite and calcite show systematic depletions with increasing metamorphic grade. The mean values range from -2.2‰ to -3.7‰ for δ 13C and 13.8‰ to 12.3‰ for δ 18O in veins formed at lower to upper greenschist facies, but from -5.8‰ to -7.1‰ for δ 13C and 11.4‰ to 9.8‰ for δ 18O at higher metamorphic grades. Nitrogen isotope compositions rule out mantle (δ 15N mean=-5‰), magmatic (δ 15N=-5‰ to <10‰), or meteoric fluids (δ 15N mean=4.4±2.0‰) for the quartz veins. Accordingly, the results are consistent with fluids derived from metamorphic dehydration of oceanic crust and sediments within accretionary orogenic belts.

  7. The U-Pb age and Hf isotope record of detrital zircons from Paleozoic sedimentary rocks of the proto-Andean accretionary orogen

    NASA Astrophysics Data System (ADS)

    Bahlburg, Heinrich

    2010-05-01

    The global record of detrital zircon ages is frequently interpreted as reflecting cycles of supercontinent assembly and dispersal. When peaks in zircon age distributions are combined with data on the relative production of juvenile crust through time, a coincidence between the data sets is discernible for events mainly in the Archean and Paleoproterozoic. Hawkesworth et al. (2009) recently concluded that peaks in U-Pb detrital ages (n=7000; Campbell and Allen, 2008) and juvenile crust production do not always coincide on a global scale, and that a link to supercontinent cycles may in fact not exist. The reason for this is seen in the poor preservation potential of juvenile magmatic arc crust of accretionary orogens relative to continental collisional systems. This is significant as juvenile crust tends to be produced at active margins where it is also prone to destruction by subduction erosion. Granitic magmatic systems in collisional mountain belts, which later may become prolific sources of detrital zircons when eroded, are often formed by partial melting of preexisting crust. They may be volumetrically smaller than arc systems but have a better preservation potential due to their position in the interior of the evolving orogenic belts. The difference in formation and preservation potential is seen as a potential bias of the detrital zircon record towards collisional mountain belts. In contrast, non-collisional accretionary orogens should have detrital zircon age records free of this bias. The SW Amazonia Orogenic System evolved by the episodic accretion of marginal orogenic belts to Amazonia from c. 2.3 to 0.9 Ga. From 0.9 to 0.25 Ga it was superseded by the Andean portion of the Terra Australis accretionary orogen. Recent reconsiderations of paleomagnetic data (e.g. Evans et al., 2010) together with the tectonic evolution of these orogens indicate that they reflect a c. 2 Ga long orogenic history free of major continental collisions. A compilation of U

  8. Late Paleozoic tectonic evolution of the Central Asian Orogenic Belt: Constraints from multiple arc-basin systems in Altai-Junggar area, NW China

    NASA Astrophysics Data System (ADS)

    Li, D.

    2015-12-01

    In this study, we report results from integrated geological, geophysical and geochemical investigations on the Wulungu Depression of the Junggar Basin to understand the Late Paleozoic continental growth of the Junggar area and its amalgamation history with the Altai terrane, within the broad tectonic evolution of the Altai-Junggar area. Based on seismic and borehole data, the Wulungu Depression can be divided into two NW-trending tectonic units by southward thrust faults. The Suosuoquan Sag is composed of gray basaltic andesite, andesite, tuff, tuffaceous sandstone and tuffite, and the overlying Early Carboniferous volcano-sedimentary sequence with lava gushes and marine sediments from a proximal juvenile provenance, compared to the andesite in the Hongyan High. The SIMS Zircon U-Pb ages for andesites from Late Paleozoic strata indicate that these volcanics in Suosuoquan Sag and Hongyan High erupted at 376.3Ma and 313.4Ma, respectively. Most of the intermediate-mafic volcanic rocks exhibit calc-alkaline affinity, low initial 87Sr/86Sr and positive ɛNd(t) and ɛHf(t) values. Furthermore, these rocks have high Th/Yb and low Ce/Pb and La/Yb ratios as well as variable Ba/Th and Ba/La ratios. These features imply that the rocks were derived from partial melting of a mantle wedge metasomatized by subduction-related components in an island arc setting. The basin filling pattern and the distribution of island arc-type volcanics and their zircon Hf model ages with the eruptive time suggest that the Wulungu Depression represents an island arc-basin system with the development of a Carboniferous retro-arc basin. The gravity and magnetic anomaly data suggest that Altai-Junggar area incorporates three arc-basin belts from north to south: the Karamaili-Luliang-Darbut, Yemaquan-Wulungu, and Dulate-Fuhai-Saur. The recognition of the Wulungu arc-basin system demonstrates that the northern Junggar area is built by amalgamation of multiple Paleozoic linear arcs and accretionary

  9. Pn anisotropic tomography under the entire Tienshan orogenic belt

    NASA Astrophysics Data System (ADS)

    Zhou, Zhigang; Lei, Jianshe

    2015-11-01

    We present a new anisotropic tomography of the uppermost mantle under the Tienshan orogenic belt and surrounding regions using a number of Pn arrival-time data hand-picked from portable seismic stations and chosen from the Xinjiang provincial observation bulletins and the EHB datasets. Our results exhibit prominent lateral heterogeneities in the study region. Distinct low-velocity anomalies are visible under the tectonically active regions, such as the Tienshan orogenic belt and western Kunlun Mountains, whereas pronounced high-velocity anomalies are imaged beneath the stable blocks, such as the Kazakh shield, the Junggar, Tarim, Qaidam, and Turpan-Hami basins, and the Tajik depression. Most strong earthquakes (Ms > 7.0) are mainly distributed along the transition zone of high to low velocity anomalies, suggesting a possible correlation between the strong earthquakes and the upper mantle structure. The fast directions of Pn anisotropy beneath the Tienshan orogenic belt are generally parallel to its striking orientation, whereas those beneath Pamir show a northward arc-shaped distribution. The Pn fast-velocity directions on the boundaries of the Kazakh shield and the Tarim and Junngar basins are approximately perpendicular to the strike of the Tienshan orogenic belt. By integrating with previous findings, our results suggest that the Tarim and Kazakh lithospheric materials could have underthrusted beneath the Tienshan orogenic belt that leads to the hot mantle material upwelling under the Tienshan orogenic belt, which is attributable to the Indo-Asian collision. These dynamic processes could play important roles in the Tienshan mountain building.

  10. Age and geochemistry of Silurian gabbroic rocks in the Tongbai orogen, central China: Implications for the geodynamic evolution of the North Qinling arc-back-arc system

    NASA Astrophysics Data System (ADS)

    Wang, Hao; Wu, Yuan-Bao; Qin, Zheng-Wei; Zhu, Liu-Qin; Liu, Qian; Liu, Xiao-Chi; Gao, Shan; Wijbrans, Jan R.; Zhou, Lian; Gong, Hu-Jun; Yuan, Hong-Lin

    2013-10-01

    The tectonic properties of the Erlangping unit and the subduction polarity of oceanic basins in the North Qinling-Tongbai orogen have been the focus of debate for more than twenty years. The resolution of these controversies hinges on the refined constraints on the location and nature of subduction-related magmatism. In this contribution, we provide a combined study of zircon U-Pb ages, major and trace element geochemistry, and Sr-Nd-Hf isotope compositions of gabbroic rocks from the Erlangping unit in the Tongbai orogen. U-Pb dating of zircons from two gabbroic diorite samples yielded two weighted mean ages of 443 ± 3 and 440 ± 4 Ma. The Erlangping gabbroic rocks are tholeiitic in composition with variable MgO (4.48-8.17%), and low K2O (0.25-1.01%) and TiO2 (0.60-1.79%) contents. They are characterized by enrichment of LILEs, depletion of HFSEs, and highly positive whole-rock ɛNd(t) (3.76-5.68) and zircon ɛHf(t) (12.0-12.1) values. The geochemical features indicate that the Erlangping gabbroic rocks were derived from a depleted lithospheric mantle that had been exposed to metasomatism by slab-derived fluid shortly before their generation. Their occurrence, coupled with coeval granitoids with highly positive ɛNd(t) values, manifest significant crustal growth in the North Qinling-Tongbai orogen during the late Ordovician-Silurian. In addition, the Erlangping gabbroic rocks have low Sr/Y (7.32-26.2) and (La/Yb)N (1.34-4.07) ratios, but high HREEs, Y and Sc contents. This implies that their mantle source had no residual garnet, and thus partial melting of the lithospheric mantle occurred under relatively low-pressure conditions. The generation of the Erlangping gabbroic rocks might result from incipient rifting of the Erlangping back-arc basin induced by the northward subduction of the Paleotethyan Shangdan Ocean. Taking into account the ca. 490 Ma collision between the Erlangping arc and North Qinling microcontinent, we suggested that the evolution of the North

  11. Ambient tremors in a collisional orogenic belt

    USGS Publications Warehouse

    Chuang, Lindsay Yuling; Chen, Kate Huihsuan; Wech, Aaron G.; Byrne, Timothy; Peng, Wei

    2014-01-01

    Deep-seated tectonic tremors have been regarded as an observation tied to interconnected fluids at depth, which have been well documented in worldwide subduction zones and transform faults but not in a collisional mountain belt. In this study we explore the general features of collisional tremors in Taiwan and discuss the possible generation mechanism. In the 4 year data, we find 231 ambient tremor episodes with durations ranging from 5 to 30 min. In addition to a coseismic slip-induced stress change from nearby major earthquake, increased tremor rate is also highly correlated with the active, normal faulting earthquake swarms at the shallower depth. Both the tremor and earthquake swarm activities are confined in a small, area where the high attenuation, high thermal anomaly, the boundary between high and low resistivity, and localized veins on the surfaces distributed, suggesting the involvement of fluids from metamorphic dehydration within the orogen.

  12. Reconstructing multiple arc-basin systems in the Altai-Junggar area (NW China): Implications for the architecture and evolution of the western Central Asian Orogenic Belt

    NASA Astrophysics Data System (ADS)

    Li, Di; He, Dengfa; Tang, Yong

    2016-05-01

    The Altai-Junggar area in northwestern China is a critical region to gain insights on the tectonic framework and geological evolution of the western Central Asian Orogenic Belt (CAOB). In this study, we report results from integrated geological, geochemical and geophysical investigations on the Wulungu Depression of the Junggar Basin to determine the basement nature of the basin and understand its amalgamation history with the Chinese Altai, within the broad tectonic evolution of the Altai-Junggar area. Based on borehole and seismic data, the Wulungu Depression is subdivided into two NW-trending tectonic units (Suosuoquan Sag and Hongyan High) by southward-vergent thrust faults. The Suosuoquan Sag consists of the Middle-Late Devonian basaltic andesite, andesite, dacite, tuff, tuffaceous sandstone and tuffite, and the overlying Early Carboniferous volcano-sedimentary sequence with lava flows and shallow marine sediments from a proximal juvenile provenance (zircon εHf(t) = 6.0-14.9), compared to the Late Carboniferous andesite and rhyolite in the Hongyan High. Zircon SIMS U-Pb ages for dacites and andesites indicate that these volcanics in the Suosuoquan Sag and Hongyan High erupted at 376.3 Ma and 313.4 Ma, respectively. The Middle-Late Devonian basaltic andesites from well LC1 are calc-alkaline and exhibit primitive magma-like MgO contents (7.9-8.6%) and Mg# values (66-68), with low initial 87Sr/86Sr (0.703269-0.704808) and positive εNd(t) values (6.6-7.6), and relatively high Zr abundance (98.2-116.0 ppm) and Zr/Y ratios (5.1-5.4), enrichment in LREEs and LILEs (e.g., Th and U) and depletion in Nb, Ta and Ti, suggesting that they were probably derived from a metasomatized depleted mantle in a retro-arc extensional setting. The well LC1 andesitic tuffs, well L8 dacites, well WL1 dacitic tuffs and well L5 andesites belong to calc-alkaline and metaluminous to peraluminous (A/CNK = 0.8-1.7) series, and display low Mg# values (35-46) and variably positive εNd(t) (4

  13. Orogen-parallel extension and exhumation enhanced by denudation in the trans-Himalayan Arun River gorge, Ama Drime Massif, Tibet-Nepal

    NASA Astrophysics Data System (ADS)

    Jessup, Micah J.; Newell, Dennis L.; Cottle, John M.; Berger, Aaron L.; Spotila, James A.

    2008-07-01

    Focused denudation and mid-crustal flow are coupled in manyactive tectonic settings, including the Himalaya, where exhumationof mid-crustal rocks accommodated by thrust faults and low-angledetachment systems during crustal shortening is well documented.New structural and (U-Th)/He apatite data from the Mount Everestregion demonstrate that the trans-Himalayan Ama Drime Massifhas been exhumed at a minimum rate of ~1 mm/yr between 1.5 and3.0 Ma during orogen-parallel extension. The Ama Drime Massifoffsets the South Tibetan detachment system, and therefore theSouth Tibetan detachment system is no longer capable of accommodatingsouth-directed mid-crustal flow or coupling it with focuseddenudation. Previous investigations interpreted the NNE-SSW-strikingshear zone on the west side of the Ama Drime Massif as the MainCentral thrust zone; however, our data show that the Ama DrimeMassif is bounded on either side by 100-300-m-thick normal-senseshear zone and detachment systems that are kinematically linkedto young brittle faults that offset Quaternary deposits andrecord active orogen-parallel extension. When combined withexisting data, these results suggest that the Ama Drime Massifwas exhumed during orogen-parallel extension that was enhancedby, or potentially coupled with, denudation in the trans-HimalayanArun River gorge. This model provides important insights intothe mechanisms that exhumed trans-Himalayan antiformal structuresduring orogen-parallel extension along the southern margin ofthe Tibetan Plateau.

  14. Granitoids and Crustal Growth in the East- Kunlun Orogenic Belt

    NASA Astrophysics Data System (ADS)

    Mo, X.; Luo, Z.; Deng, J.; Yu, X.; Liu, C.; Yuan, W.; Bi, X.

    2011-12-01

    1MO Xuanxue, 1LUO Zhaohua, 1DENG Jinfu,1YU Xuehui, 2LIU Chengdong, 1Yuan Wanming, 1Bi Xianmei 1China University of Geosciences, Beijing, 100083; 2Donghua University of Technology, Nanchang, 330013 Abstract: The East- Kunlun orogenic belt (abbrev. EKOB) is one of major tectono-magmatic belts in the Tibetan plateau. Four stages of granitoid plutonism took place in Precambrian (the Proterozoic), early Paleozoic (∈-D3), late Paleozoic- early Mesozoic (D3-T3), and late Mesozoic- Cenozoic (after early Jurassic), respectively. Among them, the late Paleozoic- early Mesozoic, especially Triassic granitoids are predominant. The basement of EKOB formed in late Paleo- Proterozoic. The early Paleozoic tectono-magmatic event sequence is comparable to that in the North- Qilian orogenic belt, and became a part of the Qilian- East- Kunlun Caledonian orogenic system. However, EKOB had been involved in the Paleo- Tethyan tectonic regime during late Paleozoic- early Mesozoic period, and yield an integrated Variscian- Indo-Chinese orogenic cycle, similar to the Sanjiang Paleo-Tethyan orogeny. The south- Kunlun suture zone then defined the main boundary between the north and the south China. Subsequently, EKOB has been involved in the Tibetan collisional orogenic system in the Cenozoic since Indo- Eurasia collision. While the continental crust of EKOB mainly formed in late Paleo- Proterozoic, juvenile crust was also generated in the Phanerozoic time, similar to the Xing'anling- Mongolia, the Gangdese and the Andes orogenic belts. There are abundant conclusive evidences of underplating and magma mixing in the East- Kunlun granitoid belt (Fig.1). Initiate values of 87Sr/86Sr of the East- Kunlun granitoids are mostly less than 0.710 and ɛNd(t)values of them range from -9.2 to +3.6. Those imply that inputting of mantle materials and mixing between mantle- and crust- derived materials played an important role in crustal generation and evolution in EKOB during the Phanerozoic time

  15. Proterozoic orogens in southern Peninsular India: Contiguities and complexities

    NASA Astrophysics Data System (ADS)

    Chetty, T. R. K.; Santosh, M.

    2013-12-01

    The Precambrian terranes of southern Peninsular India have been central to discussions on the history of formation and breakup of supercontinents. Of particular interest are the Proterozoic high grade metamorphic orogens at the southern and eastern margins of the Indian shield, skirting the 3.4 Ga Dharwar craton which not only preserve important records of lower crustal processes and lithospheric geodynamics, but also carry imprints of the tectonic framework related to the assembly of the major Neoproterozoic supercontinents - Rodinia and Gondwana. These Proterozoic orogens are described as Southern Granulite Terrane (SGT) in the southern tip and the Eastern Ghats Mobile Belt (EGMB) in the eastern domains of the peninsula. The contiguity of these orogens is broken for a distance of ˜400 km and disappears in the Bay of Bengal. These orogens expose windows of middle to lower crust with well-preserved rock records displaying multiple tectonothermal events and multiphase exhumation paths.Recent studies in these orogens have led to the recognition of discrete crustal blocks or terranes separated by major shear zone systems, some of which represent collisional sutures. The SGT and EGMB carry several important features such as fold-thrust tectonics, regional granulite facies metamorphism of up to ultrahigh-temperature conditions in some cases, multiple P-T paths, development of lithospheric shear zones, emplacement of ophiolites, presence of alkaline and anorthositic complexes, development of crustal-scale "flower structures", transpressional strains, and reactivation tectonics. A heterogeneous distribution of different metamorphic and magmatic assemblages with distinct spatial and temporal strain variations in shaping the fabric elements in different blocks is identified. Both EGMB and SGT share a common transpressional deformation history during the latest Neoproterozoic characterized by the steepening of the initial low angle crustal scale structures leading to a

  16. Part I: Neoacadian to Alleghanian foreland basin development and provenance in the central appalachian orogen, pine mountain thrust sheet Part II: Structural configuration of a modified Mesozoic to Cenozoic forearc basin system, south-central Alaska

    NASA Astrophysics Data System (ADS)

    Robertson, Peter Benjamin

    . Four samples of Lower Mississippian to Middle Pennsylvanian sandstone were collected from the hanging wall (n = 3) and footwall (n = 1) of the Pine Mountain thrust sheet at Pound Gap to determine sediment provenance in this long-lived foreland basin system. Paleocurrent indicators considered in the context of the regional foreland basin system suggest transverse regional drainage during the development of Early and Late Mississippian delta complexes. Eustatic fall during the early stages of the Alleghanian orogeny to the east saw a shift in regional drainage with the development of a southwestward-flowing and axial braided river system in Early Pennsylvanian time followed by Middle Mississippian transgression of a fluvio-deltaic complex. Detrital zircon U-Pb age data from Lower Mississippian to Lower Pennsylvanian sandstone support regional interpretations of sediment sourcing from probably recycled foreland basin strata along the east Laurentian margin, whereas compositionally immature Middle Pennsylvanian sediment was sourced by a limited distribution of east Laurentia sources reflecting thrust belt migration into the adjacent foreland basin system during Alleghanian orogenesis. In addition, the stratigraphy of the foreland basin system in the central Appalachian basin is significantly different compared to the stratigraphic record that is typified for foreland basin systems and suggests that the Carboniferous Appalachian foreland basin system investigated in this study does not fit the typical foreland basin model that is used widely today for both ancient and modern systems. Possible factors that produce the observed discrepancies between the central Appalachian and typical foreland basin systems may include differences in the timing, type, and frequency of orogenic events leading to foreland basin development, related variations in the rheology of the underlying lithosphere, and whether forebulge migration is mechanically static or mobile. The Cordilleran margin

  17. The Capricorn Orogen Passive source Array (COPA) in Western Australia

    NASA Astrophysics Data System (ADS)

    Gessner, K.; Yuan, H.; Murdie, R.; Dentith, M. C.; Johnson, S.; Brett, J.

    2015-12-01

    COPA is the passive source component of a multi-method geophysical program aimed at assessing the mineral deposits potential of the Proterozoic Capricorn Orogen. Previous results from the active source surveys, receiver functions and magnetotelluric studies show reworked orogenic crust in the orogen that contrasts with more simple crust in the neighbouring Archean cratons, suggesting progressive and punctuated collisional processes during the final amalgamation of the Western Australian craton. Previous seismic studies are all based on line deployment or single station analyses; therefore it is essential to develop 3D seismic images to test whether these observations are representative for the whole orogen. With a careful design that takes advantage of previous passive source surveys, the current long-term and short-term deployments span an area of approximately 500 x 500 km. The 36-month total deployment can guarantee enough data recording for 3D structure imaging using body wave tomography, ambient noise surface wave tomography and P- and S-wave receiver function Common Conversion Point (CCP) stacking techniques. A successive instrument loan from the ANSIR national instrument pool, provided 34 broadband seismometers that have been deployed in the western half of the orogen since March 2014. We expect approximately 40-km lateral resolution near the surface for the techniques we propose, which due to low frequency nature of earthquake waves will degrade to about 100 km near the base of the cratonic lithosphere, which is expected at depths between 200 to 250 km. Preliminary results from the first half of the COPA deployment will be presented in the light of the hypotheses that 1) distinct crustal blocks can be detected continuously throughout the orogen (using ambient noise/body wave tomography); 2) distinct lithologies are present in the crust and upper mantle across the orogen (using receiver function CCP images); and 3) crustal and lithosphere deformation along

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

    NASA Astrophysics Data System (ADS)

    Wang, Songjie; Wang, Lu

    2015-04-01

    Barite (BaSO4) is well-known from deep-sea sedimentary environments but has received less attention to its presence in high-grade metamorphic rocks. Recently, barite in ultrahigh pressure (UHP) eclogite has drawn increasing attention from geologists, especially in the Dabie-Sulu orogen, since it is an important indicator for high-salinity fluid events, thus aiding in further understanding HP-UHP fluid / melt evolution. However, its formation time and mechanism in UHP eclogite are still controversial, with three representative viewpoints: (1) Liu et al. (2000) found barite-anhydrite-coesite inclusions in zircon and interpreted them to have formed by UHP metamorphic fluids; (2) Zeng et al. (2007) recognized isolated barite within K-feldspar (Kfs) and Quartz (Qz) surrounded by radial cracks in omphacite, and interpreted Kfs+Qz to be reaction products of potassium-rich fluid/melt and coesite, with the barite formed by prograde metamorphic fluids; (3) Gao et al. (2012) and Chen et al. (2014) found barite-bearing Multiphase Solid (MS) inclusions within garnet and omphacite and assumed that the barite formed by phengite breakdown possibly caused by eclogite partial melting during exhumation, though no direct evidence were proposed. The controversy above is mainly due to the lack of direct formation evidence and absence of a clear link with the metamorphic evolution of UHP eclogite along the subduction-exhumation path. We report detailed petrological and micro-structural analyses revealing four types of barites clearly linked with (1) the prograde, (2) earlier stage of partial melting and (3) later stage of crystallization differentiation, as well as (4) high-grade amphibolite-facies retrogression of a deeply subducted and partially melted intergranular coesite-bearing eclogite from Yangkou Bay, Sulu Orogen. Round barite inclusions (type-I) within UHP-stage garnet and omphacite are formed by internally buffered fluids from mineral dehydration during prograde metamorphism

  19. Uncoupled O and Hf isotopic systems in zircon from the contrasting granite suites of the New England Orogen, eastern Australia: Implications for studies of Phanerozoic magma genesis

    NASA Astrophysics Data System (ADS)

    Jeon, Heejin; Williams, Ian S.; Bennett, Vickie C.

    2014-12-01

    The Permo-Triassic granites of the New England Orogen, eastern Australia, were emplaced into a volcanic arc complex accreted to the eastern Gondwana margin in the Late Devonian or Early Carboniferous. Zircon U-Pb dating shows that the S-type Hillgrove (∼297 Ma) and Bundarra (∼287 Ma) Supersuites predated intrusion of the I-type Moonbi Supersuite (∼250 Ma) by up to 50 Ma. The high δ18Ozrn of the S-type granites (10.0-11.5‰), and range of U-Pb ages (∼370-300 Ma) and δ18Ozrn (∼5-10‰) of their inherited zircon cores, show that their source rocks were predominantly weathered Carboniferous volcaniclastics, the youngest deposited < 25 Ma before the granites were emplaced. In contrast, the lower δ18Ozrn (6.9-7.8‰) and lack of inheritance in the I-type granites is consistent with a zircon poor, more juvenile source, probably a mafic igneous underplate mixed with a small amount of volcanogenic and/or oceanic sediment. Despite the differences in source materials, the εHf(t) values of all granites, both S- and I-type, are similar (+5.0 ± 0.5 cf. +5.9 ± 0.5), consistent with both the mafic and sedimentary components in the granite sources being relatively young and similar in Hf isotopic composition at the time of granite genesis. In young, isotopically juvenile orogens, the O isotopic composition of well-dated igneous and inherited zircon can be a much more sensitive indicator of petrogenetic processes than the zircon Hf isotopic compositions alone.

  20. Curved orogen and syntaxes formation during subduction and collision

    NASA Astrophysics Data System (ADS)

    Bajolet, F.; Replumaz, A.; Faccenna, C.; Lainé, R.

    2012-04-01

    The sustained convergence between India and Asia with successive stages of oceanic subduction, continental subduction and continental collision has lead to the formation of the Tibetan plateau while the Himalayan orogenic front acquired an arcuate shape convex toward the South. The Indian plate is bounded by north-south strike-slip faults, which accommodate a large indentation of Asia, between two oceanic subductions, beneath Makran to the west, beneath Indonesia to the east. Two syntaxes formed at both east and west termination of the Himalayan orogenic front at the transition between Indian and Asian plates. In order to better understand this particular configuration, we performed analog experiments at the Laboratory of Experimental Tectonics of Roma TRE to simulate, at the scale of the mantle - lithosphere system, the mechanics of the indentation process. The configuration is set to drive the India indenter towards the Asian continent with a motor-controlled-piston, to simulate far field stresses necessary for indentation. In particular, we test (1) which geometry and rheological parameters favor arcuate orogen and syntaxes formation, (2) what are the consequences on the topography of both the orogenic front and the plateau, and (3) how they relate with the subduction/collision dynamics. The setup is composed of a subducting and an overriding plate made of visco-elastic silicone putty, floating on low-viscosity syrup simulating the asthenosphere. The subducting plate simulates an oceanic lithosphere followed by a continental indenter (analog for the Indian craton) flanked or not by oceans (analog for Makran and Indonesian domains), while the upper continental plate simulates the Tibetan plateau. Results show that the curvature of the orogen and syntaxes' formation are primarily controlled by the strength and gravitational potential energy of the upper plate, and the shape of the subducting plate. A relatively strong upper plate flanked by oceans leads to a

  1. And the Variscan Orogen Buckled

    NASA Astrophysics Data System (ADS)

    Pastor-Galán, D.; Groenewegen, T.; Gutiérrez-Alonso, G.; Langereis, C. G.

    2013-12-01

    Oroclines are the largest scale folds in nature, and as folds can be produced by bending or by buckling. The most commonly invoked bending mechanisms are indentation (the Himalayan syntaxes) and slab roll-back (The Calabria Arc) whereas buckling usually are commonly related with collision of the apex of ribbon continents along strike (Alaskan oroclines). In Western Europe the tectonostratigraphic zonation of Variscan orogen shows a complex 'S' shape pattern recently interpreted as a double orocline consisting of a northern and southern arc. The northern arc, known as Cantabria-Asturias Arc or Cantabrian Orocline, was developed after closure of the Rheic Ocean and the building and collapse of the Variscan orogenic edifice and, therefore, is considered post-Variscan in age. On the other hand, neither the geometry nor the kinematics of the so-called Central Iberian orocline, situated at the south of the Iberian peninsula are properly known. However, it seems reasonable to think that both oroclines developed at the same time as other coupled oroclines, such as the New England oroclines or the Carpathian oroclines. The particular paleogeography of the Variscan belt in Pangea and the kinematics of the oroclinal formation make impossible the mechanisms of indentation or buckling of a ribbon continent. The occurrence of an intense syn- and slightly post-Cantabrian orocline magmatic event (310-290 Ma) has been linked to the development of the orocline(s) due to the particular spatial-temporal distribution of these post-tectonic granitoids and its isotopic signature which would imply that the oroclines (if synchronous) are thick-skinned. This magmatic pulse has also been interpreted as due to slab roll-back. We present widespread evidences of buckling around the whole orocline at different lithospheric levels and new insights of the particular geometry of the southern orocline which is difficult to reconcile with a roll-back related origin. Therefore, a major change in the

  2. Zagros fold belt: orogenic accretion from obduction to collision

    NASA Astrophysics Data System (ADS)

    Vergés, Jaume; Saura, Eduard; Casciello, Emilio; Fernandez, Manel; Garcia-Castellanos, Daniel; Jiménez-Munt, Ivone; Torne, Montserrat; Villaseñor, Antonio

    2014-05-01

    The Zagros orogenic system comprises an exceptionally wide deformation zone between Arabia and Eurasia, embracing the entire Iran, and resulting from the closure of the Neotethys Ocean through its protracted NE-dipping subduction beneath Eurasia. The ~2000-km long, NW-SE trending Zagros fold belt is at the front of this orogenic system formed by the Sanandaj-Sirjan Zone and the Urumieh-Dokhtar Magmatic Arc, which are parallel to the main tectonic grain and have different geodynamic significance. The Zagros fold belt deforms 10-12-km thick Arabian sedimentary cover, which records compressive deformation since Late Cretaceous times. These tectonic events and their sequence have been studied in greater detail in the last ten years, mainly due to the profusion of dating of the syntectonic marine and non-marine sediments in the foreland basin. Despite these new data, and taking in account that there is a general consensus that the Zagros orogeny occurred during the complete consumption of the Neotethys Ocean, tectonic interpretations differ and ages of major geodynamic events remain controversial. Our studies confirm that the early Amiran foreland basin depocenter migrated from Campanian to Eocene (c. 83-52.7 Ma) after the onset of young Tethyan intra-oceanic obduction on top of the Arabian plate margin at the Cenomanian-Turonian boundary (~93 Ma). This migration is coeval with a mild but far-reaching deformation as indicated by punctuated growth strata patterns. A younger deformation event shaped the present geometry of the magnificent Zagros fold belt, overprinting the previous phase. Deformation along the High Zagros Fault was active from 20 Ma to at least 7.5 Ma. Folding in the Lurestan was active from at least ~13.5 Ma in the NE, migrating to the SW where it possibly terminated at about 2.5-1.5 Ma. In the Fars, deformation onset is dated at 14.5 Ma migrating SW-wards to the Persian Gulf coastline where the folds are still active. We propose a simple 2D kinematic

  3. Structural inversion of the Tamworth Belt: Insights into the development of orogenic curvature in the southern New England Orogen, Australia

    NASA Astrophysics Data System (ADS)

    Phillips, G.; Robinson, J.; Glen, R.; Roberts, J.

    2016-05-01

    The middle to late Permian Hunter Bowen Event is credited with the development of orogenic curvature in the southern New England Orogen, yet contention surrounds the structural dynamics responsible for the development of this curvature. Debate is largely centred on the roles of orogen parallel strike-slip and orogen normal extension and contraction to explain the development of curvature. To evaluate the dynamic history of the Hunter Bowen Event, we present new kinematic reconstructions of the Tamworth Belt. The Tamworth Belt formed as a Carboniferous forearc basin and was subsequently inverted during the Hunter Bowen Event. Kinematic reconstructions of the Tamworth Belt are based on new maps and cross-sections built from a synthesis of best-available mapping, chronostratigraphic data and new interpretations of depth-converted seismic data. The following conclusions are made from our study: (i) the Hunter Bowen Event was dominantly driven by margin normal contraction (east-west shortening; present-day coordinates), and; (ii) variations in structural style along the strike of the Tamworth Belt can be explained by orthogonal vs. oblique inversion, which reflects the angular relationship between the principal shortening vector and continental-arc margin. Given these conclusions, we suggest that curvature around the controversial Manning Bend was influenced by the presence of primary curvature in the continental margin, and that the Hastings Block was translated along a sinistral strike-slip fault system that formed along this oblique (with respect to the regional east-west extension and convergence direction) part of the margin. Given the available temporal data, the translation of the Hastings Block took place in the Early Permian (Asselian) and therefore preceded the Hunter Bowen Event. Accordingly, we suggest that the Hunter Bowen Event was dominantly associated with enhancing curvature that was either primary in origin, or associated with fault block translation

  4. Crustal Seismic Anisotropy Produced by Rock Fabric Terranes in the Taiwan Central Range Deformational Orogen: Integrative Study Combining Rock Physics, Structural Geology, and Passive/Active-Source Seismology

    NASA Astrophysics Data System (ADS)

    Okaya, D. A.; Ross, Z.; Christensen, N. I.; Wu, F. T.; Byrne, T. B.

    2014-12-01

    The island of Taiwan is currently under construction due to the collision of the northwestern corner of the Philippine Sea plate and the embedded Luzon island arc with the larger continental Eurasian plate. This collision is responsible for the current growth of the Central Range that dominates the eastern half of the island. An international collaboration involving several USA and Taiwan universities and academic institutions was formed to study how the orogen evolves through time and to understand the role of a colliding island arc in mountain building. The project, Taiwan Integrated Geodynamics Research (TAIGER), was funded by NSF-Continental Dynamics and Taiwan National Science Council. The Central Range grows at one of the most rapid rates of uplift in the world, exposing metamorphic rocks that were once at least 10 km deep. The range offers unique opportunities for studies of crustal seismic anisotropy for two major reasons: (1) its geological makeup is conducive for producing crustal seismic anisotropy; that is, the rocks are highly foliated; and (2) a seismological data volume of significant breadth offers extensive coverage of sources and recording stations throughout the region. We carried out a crustal shear wave splitting study by data mining 3300 local earthquakes collected in the TAIGER 2009 sea-land experiment. We used an automated P and S wave arrival time picking method (Ross and Ben-Zion, 2014) applied to over 100,000 event-station pairs. These data were analyzed for shear-wave splitting using the MFAST automated package (Savage et al., 2010), producing 3300 quality shear wave split measurements. The splitting results were then station-averaged. The results show NNE to NE orientation trends that are consistent with regional cleavage strikes. Average crustal shear wave split time is 0.244 sec. These measurements are consistent with rock physics measurements of Central Range slate and metamorphic acoustic velocities. The splits exhibit orientations

  5. Structural controls on Tertiary orogenic gold mineralization during initiation of a mountain belt, New Zealand

    NASA Astrophysics Data System (ADS)

    Craw, D.; Begbie, M.; MacKenzie, D.

    2006-10-01

    Two types of structurally controlled hydrothermal mineralization have occurred during folding of fissile schist in southern New Zealand: fold-related mineralization and normal fault-related mineralization. Both types have the same mineralogy and textures, and are dominated by quartz-ankerite veins and silicified breccias with ankeritic alteration. Most mineralized zones are thin (centimetre scale), although host schist is commonly impregnated with ankerite up to 20 m away. Thick (up to 5 m wide) mineralized zones are generally gold-bearing and contain pyrite and arsenopyrite with stibnite pods locally. Some of these auriferous zones have been extensively mined historically despite rugged topography and difficult access. Mineralization occurred during regional tectonic compression in the initial stages of development of the Southern Alps mountain belt at the Pacific-Australian plate boundary in the Miocene. Most of the gold-bearing deposits occur in east to south-east, striking normal faults that cut across mesoscopic folds in a belt that coincides with the southern termination of a regional-scale north trending antiform. Mineralized zones have similar structural control and relative timing to a nearby swarm of Miocene lamprophyre dykes and carbonatites. Limited stable isotopic data (C and O) and trace element geochemistry suggest that there was probably no genetic link between the igneous activity and gold mineralization. However, these two types of fluid flow have been controlled by the same tectonically created crustal plumbing system. This Miocene hydrothermal activity and gold deposition demonstrates that orogenic (mesothermal) mineralization can occur during the inception of an orogenic belt, not just in the latter stages as is commonly believed. These Miocene structures have been preserved in the orogen because the locus of uplift has moved northwards, so the early-formed gold deposits have not yet been structurally overprinted or eroded.

  6. Porphyry molybdenum deposits in the Tianshan-Xingmeng orogenic belt, northern China

    NASA Astrophysics Data System (ADS)

    Zeng, Qingdong; Qin, Kezhang; Liu, Jianming; Li, Guangming; Zhai, Mingguo; Chu, Shaoxiong; Guo, Yunpeng

    2015-06-01

    Molybdenum (Mo) exploration activity in China has increased tremendously over the past decade, and China is now known to have the largest Mo reserves in the world. The Tianshan-Xingmeng orogenic belt, the second largest Mo metallogenic belt, possesses over 8.2 Mt of Mo reserves. Porphyry Mo deposits contain 99 % of the Mo reserves in the Tianshan-Xingmeng orogenic belt; other Mo deposits contain 1 % of the Mo reserves. Five subtypes of the porphyry Mo deposits can be distinguished by deposit associations, such as Mo, Mo-Cu, Mo-W, Mo-Pb-Zn-Ag, and Cu-Mo deposits. These porphyry Mo deposits are formed at different stages: during the Ordovician, Devonian, Carboniferous, Late Permian, Triassic, Jurassic, and Cretaceous Periods. The polystage porphyry Mo mineralizations indicate that polystage tectonic-magmatic activity occurred in the orogenic belt. The Ordovician-Carboniferous porphyry Cu-Mo deposits are formed in an island-arc setting; the Late Permian porphyry Mo deposits are formed in a syn-collisional tectonic setting; and the Triassic porphyry Mo deposits are formed in a syn-collisional to post-collisional tectonic setting. The Ordovician-Triassic porphyry deposits are related to the Paleo-Asian Ocean tectonic system. The Jurassic porphyry Mo deposits are formed at the eastern margin of the Asian continent and are associated with a Paleo-Pacific plate-subduction tectonic setting. Cretaceous porphyry Mo deposits are formed in a lithospheric thinning setting and are related to the rollback of the Paleo-Pacific subduction plate.

  7. Paleozoic tectonics of the Ouachita Orogen through Nd isotopes

    SciTech Connect

    Gleason, J.D.; Patchett, P.J.; Dickinson, W.R.; Ruiz, J. . Dept. of Geosciences)

    1992-01-01

    A combined isotopic and trace-element study of the Late Paleozoic Ouachita Orogenic belt has the following goals: (1) define changing provenance of Ouachita sedimentary systems throughout the Paleozoic; (2) constrain sources feeding into the Ouachita flysch trough during the Late Paleozoic; (3) isolate the geochemical signature of proposed colliding terranes to the south; (4) build a data base to compare with possible Ouachita System equivalents in Mexico. The ultimate aim is to constrain the tectonic setting of the southern margin of North America during the Paleozoic, with particular emphasis on collisional events leading to the final suturing of Pangea. Nd isotopic data identify 3 distinct groups: (1) Ordovician passive margin sequence; (2) Carboniferous proto-flysch (Stanley Fm.), main flysch (Jackfork and Atoka Fms.) and molasse (foreland Atoka Fm.); (3) Mississippian ash-flow tuffs. The authors interpret the Ordovician signature to be essentially all craton-derived, whereas the Carboniferous signature reflects mixed sources from the craton plus orogenic sources to the east and possibly the south, including the evolving Appalachian Orogen. The proposed southern source is revealed by the tuffs to be too old and evolved to be a juvenile island arc terrane. They interpret the tuffs to have been erupted in a continental margin arc-type setting. Surprisingly, the foreland molasse sequence is indistinguishable from the main trough flysch sequence, suggesting the Ouachita trough and the craton were both inundated with sediment of a single homogenized isotopic signature during the Late Carboniferous. The possibility that Carboniferous-type sedimentary dispersal patterns began as early as the Silurian has important implications for the tectonics and paleogeography of the evolving Appalachian-Ouachita Orogenic System.

  8. Part I: Neoacadian to Alleghanian foreland basin development and provenance in the central appalachian orogen, pine mountain thrust sheet Part II: Structural configuration of a modified Mesozoic to Cenozoic forearc basin system, south-central Alaska

    NASA Astrophysics Data System (ADS)

    Robertson, Peter Benjamin

    . Four samples of Lower Mississippian to Middle Pennsylvanian sandstone were collected from the hanging wall (n = 3) and footwall (n = 1) of the Pine Mountain thrust sheet at Pound Gap to determine sediment provenance in this long-lived foreland basin system. Paleocurrent indicators considered in the context of the regional foreland basin system suggest transverse regional drainage during the development of Early and Late Mississippian delta complexes. Eustatic fall during the early stages of the Alleghanian orogeny to the east saw a shift in regional drainage with the development of a southwestward-flowing and axial braided river system in Early Pennsylvanian time followed by Middle Mississippian transgression of a fluvio-deltaic complex. Detrital zircon U-Pb age data from Lower Mississippian to Lower Pennsylvanian sandstone support regional interpretations of sediment sourcing from probably recycled foreland basin strata along the east Laurentian margin, whereas compositionally immature Middle Pennsylvanian sediment was sourced by a limited distribution of east Laurentia sources reflecting thrust belt migration into the adjacent foreland basin system during Alleghanian orogenesis. In addition, the stratigraphy of the foreland basin system in the central Appalachian basin is significantly different compared to the stratigraphic record that is typified for foreland basin systems and suggests that the Carboniferous Appalachian foreland basin system investigated in this study does not fit the typical foreland basin model that is used widely today for both ancient and modern systems. Possible factors that produce the observed discrepancies between the central Appalachian and typical foreland basin systems may include differences in the timing, type, and frequency of orogenic events leading to foreland basin development, related variations in the rheology of the underlying lithosphere, and whether forebulge migration is mechanically static or mobile. The Cordilleran margin

  9. Metamorphic origin of ore-forming fluids for orogenic gold-bearing quartz vein systems in the North American Cordillera: constraints from a reconnaissance study of δ15N, δD, and δ18O

    USGS Publications Warehouse

    Jia, Y.; Kerrich, R.; Goldfarb, R.

    2003-01-01

    The western North American Cordillera hosts a large number of gold-bearing quartz vein systems from the Mother Lode of southern California, through counterparts in British Columbia and southeastern Alaska, to the Klondike district in central Yukon. These vein systems are structurally controlled by major fault zones, which are often reactivated terrane-bounding sutures that formed in orogens built during accretion and subduction of terranes along the continental margin of North America. Mineralization ages span mid-Jurassic to early Tertiary and encompass much of the evolution ofthe Cordilleran orogen. Nitrogen contents and ??15N values of hydrothermal micas from veins are between 130 and 3,500 ppm and 1.7 to 5.5 per mil, respectively. These values are consistent with fluids derived from metamorphic dehydration reactions within the Phanerozoic accretion-subduction complexes, which have ??15N values of 1 to 6 per mil. The ??18O values of gold-bearing vein quartz from different locations in the Cordillera are between 14.6 and 22.2 per mil but are uniform for individual vein systems. The ??D values of hydrothermal micas are between -110 and -60 per mil. Ore fluids have calculated ??18O values of 8 to 16 per mil and ??D values of -65 to -10 per mil at an estimated temperature of 300??C; ??D values of ore fluids do not show any latitudinal control. These results indicate a deep crustal source for the ore-forming fluids, most likely of metamorphic origin. Low ??DH2O values of -120 to -130 per mil for a hydrous muscovite from the Sheba vein in the Klondike district reflect secondary exchange between recrystallizing mica and meteoric waters. Collectively, the N, H, and O isotope compositions of ore-related hydrothermal minerals indicate that the formation of these gold-bearing veins involved dilute, aqueous carbonic, and nitrogen-bearing fluids that were generated from metamorphic dehydration reactions at deep crustal levels. These data are not consistent with either mantle

  10. Recognizing remnants of magma-poor rifted margins in high-pressure orogenic belts: The Alpine case study

    NASA Astrophysics Data System (ADS)

    Beltrando, Marco; Manatschal, Gianreto; Mohn, Geoffroy; Dal Piaz, Giorgio Vittorio; Vitale Brovarone, Alberto; Masini, Emmanuel

    2014-04-01

    Magma-poor rifted margins are being increasingly recognized in present-day Atlantic-type systems. However, findings of fossil areas floored by exhumed mantle or hyper-extended crust are comparatively rare within orogenic belts that were originated through the inversion of pre-existing rifted margins. This discrepancy may be due to the common reactivation of lithological contacts during subduction/orogeny, potentially masking pre-orogenic relationships, and, most importantly, to the frequent lack of a pre-orogenic layer-cake architecture, hindering retro-deformation of multiply deformed tectonic units. This study outlines a methodology to detect sections of magma-poor, hyper-extended rifted margins without a layer-cake architecture in multiply deformed/metamorphosed terrains. This approach is defined by comparison to well studied examples of fossil analogues preserved in weakly deformed parts of Alpine orogens. In the latter domains, continental basement and hydrated peridotites were exhumed at the basin floor during Jurassic rifting along long-offset detachment systems. Extensional geometries locally resulted in tectonic sampling of laterally discontinuous slivers of allochthonous continental basement and pre-rift sediments from the hanging wall blocks. Lithostratigraphic associations consisting of continental basement rocks directly juxtaposed with syn- to post-rift meta-sediments and/or serpentinized subcontinental mantle are widespread within sections of Alpine-type orogenic belts that underwent high- to ultra-high-pressure metamorphism. However, similar associations may arise from a variety of processes other than rift-related lithospheric thinning in magma-poor environments, including subduction mélange dynamics or deposition of sedimentary mélanges along convergent/divergent margins. The partial preservation of rift-related lithostratigraphic associations may still be assessed, despite the lack of biostratigraphic evidence, by (1) the consistency of the

  11. Fluid inclusion and H-O-C isotope geochemistry of the Yaochong porphyry Mo deposit in Dabie Shan, China: a case study of porphyry systems in continental collision orogens

    NASA Astrophysics Data System (ADS)

    Wang, Pin; Chen, Yan-Jing; Fu, Bin; Yang, Yong-Fei; Mi, Mei; Li, Zhong-Lie

    2014-04-01

    The Yaochong porphyry Mo deposit in Xinxian County, Henan Province, China, is located in the Hong'an terrane, that is, the western part of the Dabie orogen. The Dabie orogen is part of a >1,500 km long, Triassic continental collision belt between the North China Block and the South China Block. Four types of vein are present. Paragenetically, from early to late, they are as follows: stage 1 quartz + K-feldspar ± pyrite ± magnetite vein; stage 2 quartz + K-feldspar + molybdenite ± pyrite vein; stage 3 quartz + polymetallic sulfides ± K-feldspar vein; and stage 4 quartz ± carbonate ± fluorite vein. Four compositional types of fluid inclusion, pure CO2, CO2 bearing, aqueous, and solid bearing, are present in quartz from the first three stages; only low-salinity aqueous fluid inclusions occur in quartz from the last stage. All the estimated salinities are ≤13.1 wt% NaCl eq., and no halite crystals were identified. Homogenization temperatures for the fluid inclusions from stages 1 to 4 are in the ranges of 262-501, 202-380, 168-345, and 128-286 °C, respectively, and estimated depths decrease from 6.9 to 8.9 km, through 6.2-7.2, to ~4.7 km. Quartz separates from the veins yielded a δ18O value of 7.7-11.2 ‰, corresponding to δ18OH2O values of -1.3 to 6.9 ‰ using temperature estimates from fluid inclusion data; δDH2O values of fluid inclusion vary from -80 to -55 ‰, and δ13CCO2 from -2.3 to 2.7 ‰, suggesting that the ore-fluids evolved from magmatic to meteoric sources. We conclude that the ore-forming fluid system at Yaochong was initially high temperature, high salinity, and CO2-rich and then progressively evolved to CO2-poor, lower salinity, and lower temperature, by mixing with meteoric water, which results in ore precipitation.

  12. Synchronous unroofing and faulting in the Precordillera of Argentina: thermochronometric constraints on fault-propagation in a thin- to thick-skinned orogenic system

    NASA Astrophysics Data System (ADS)

    Fosdick, J. C.; Carrapa, B.

    2013-12-01

    Mass removal via erosion is an important process that interacts with deformation in convergent mountain belts such as the Andes, and improved quantification of denudation is critical for elucidating spatio-temporal patterns of deformation. We report new apatite and zircon (U-Th)/He (AHe, ZHe) and apatite fission track (AFT) results from the Precordillera of Argentina that record Neogene fault-related unroofing during growth of the Andean retroarc fold-and-thrust belt. The Precordillera fold-and-thrust belt of Argentina is located west of the thick-skinned Sierras Pampeanas and evolved concurrently with the Bermejo retroarc foreland basin since at least the early Miocene. At the Rio Jáchal latitude (30°S), most crustal shortening associated with the Andean orogen is accommodated across the Precordillera, however, its unroofing record remains poorly constrained. Here we test the relationships between thrust faulting and exhumation and quantify the erosional input of sediments to the foreland basin. ZHe samples from Silurian-Carboniferous metasedimentary rocks collected across the Rio Jáchal transect yield entirely Permo-Triassic cooling ages, indicating that the present-day erosional depth of the Precordillera has resided above the ZHe partial retention zone (PRZ) throughout Mesozoic-Cenozoic time. Preliminary AFT data of the Precordillera also indicate mixed pre-Cenozoic ages. ZHe and AFT ages provide a nominal <6-7 km maximum constraint on the degree of erosion associated with Andean deformation, despite over 50% shortening. In contrast, AHe dates range between ~2 to 16 Ma and track eastward with the progressive faulting of the Blanca, San Roque, and Niquivil thrust sheets from ~16 to 2 Ma. Cooling related to out-of-sequence thrusting is also reflected by the AHe results; the youngest AHe ages (5-2 Ma) are located along the margins of the Iglesia piggy-back basin and the Las Salinas anticline at the eastern boundary between the Precordillera and Pampean craton

  13. Rapid exhumation of deep crust in an obliquely convergent orogen: The Kaoko Belt of the Damara Orogen

    NASA Astrophysics Data System (ADS)

    Foster, David A.; Goscombe, Ben D.; Gray, David R.

    2009-08-01

    The exhumation of deep crustal rocks and juxtaposition of structural-metamorphic domains from different depths in a transpressional orogen may occur during the prograde evolution of the orogen by vertical extrusion or during the retrograde evolution of the orogen via extension. Metamorphic petrology, kinematics, and thermochronology of strike-slip shear zones in the Kaoko Belt of the Damara Orogen are used to evaluate extrusion and extension processes in this transpressional orogen. Mineral assemblages and deformation mechanisms record shearing at pressures of 4-6 kbar and temperatures of ˜550°C for the Three Palms mylonite zone, 600-650°C for the Purros mylonite zone, and ˜630-700°C for the Village and Khumib mylonite zones. The Three Palms mylonite zone, which separates the accreted Coastal Terrane from the former passive margin of the Congo Craton, exhibits progressive deformation during decreasing temperatures through lower greenschist facies and into the brittle field, with consistent oblique normal shear indicators. Lower-temperature fabrics and brittle features also overprint the Village mylonite zone. The 207Pb-206Pb (titanite) and 40Ar/39Ar (hornblende, muscovite, and biotite) data indicate rapid cooling, at rates of 30-100°C/Ma, of all high-grade structural domains in the core of the Kaoko Belt between circa 535 and 525 Ma, which is about 20-30 Ma younger then peak metamorphism. The 40Ar/39Ar data from synkinematic muscovite fish in the retrograde shear zone assemblages indicate that the Khumib, Village, and Three Palms mylonite zones were actively deforming at temperatures below 350°C at circa 530-524 Ma. These data indicate that the high-grade metamorphic rocks of the Kaoko were rapidly exhumed and juxtaposed after the main transpressive deformation by oblique extension. Reactivation of the shear zones and tectonic exhumation of high-grade structural domains from beneath the accreted Coastal Terrane was caused by collision in the Damara Belt and

  14. Exhumation at orogenic indentor corners under long-term glacial conditions: Example of the St. Elias orogen, Southern Alaska

    NASA Astrophysics Data System (ADS)

    Spotila, James A.; Berger, Aaron L.

    2010-07-01

    Syntaxial bends in convergent plate boundaries, or indentor corners, display some of the most intriguing deformation patterns on Earth and are type localities for "aneurysms" of coupled erosion, thermal weakening, and strain. The St. Elias orogen in Alaska is a small, young convergent system that has been dominated by a glacial climate for much of its history and exhibits two prominent indentor corners that are not well understood. We have added 40 new apatite (U-Th)/He ages to the already extensive dataset for the low-temperature cooling history of this orogen to constrain the pattern of exhumation in these indentor corners. Ages from the western syntaxis show minor variation across the structural hinge, suggesting that the bend has little effect on the pattern of exhumation and that structures, including the Bagley fault, connect smoothly from the orogen core to the subduction zone to the southwest. Rock uplift on the north flank of the range appears to increase steadily towards the eastern syntaxis, which represents the apex in the right-angle bend between a transform fault in the south and the collision zone in the west. Based on age-elevation relationships, zones of relative rock uplift can be defined in which the Mt. Logan massif, or the area just north of the eastern syntaxis, experienced ˜ 4.8 km greater rock uplift than background levels northwest of the western syntaxis. A bulge in relative rock uplift is symmetric about the hinge in the eastern indentor corner. However, rates of denudation in this bulge are not as rapid as the core of the fold and thrust belt and are lower than those implied by detrital cooling ages from beneath the Seward Glacier. This implies that a large bull's eye of ultra-rapid (˜ 5 mm/yr) exhumation does not occur and that the subpopulation of young detrital ages may be sourced from a narrow transpressional zone along the Fairweather fault. Unlike the Himalayan syntaxes, it thus appears that an aneurysm of coupled erosion

  15. Orogen styles in the East African Orogen: A review of the Neoproterozoic to Cambrian tectonic evolution

    NASA Astrophysics Data System (ADS)

    Fritz, H.; Abdelsalam, M.; Ali, K. A.; Bingen, B.; Collins, A. S.; Fowler, A. R.; Ghebreab, W.; Hauzenberger, C. A.; Johnson, P. R.; Kusky, T. M.; Macey, P.; Muhongo, S.; Stern, R. J.; Viola, G.

    2013-10-01

    The East African Orogen, extending from southern Israel, Sinai and Jordan in the north to Mozambique and Madagascar in the south, is the world´s largest Neoproterozoic to Cambrian orogenic complex. It comprises a collage of individual oceanic domains and continental fragments between the Archean Sahara-Congo-Kalahari Cratons in the west and Neoproterozoic India in the east. Orogen consolidation was achieved during distinct phases of orogeny between ∼850 and 550 Ma. The northern part of the orogen, the Arabian-Nubian Shield, is predominantly juvenile Neoproterozoic crust that formed in and adjacent to the Mozambique Ocean. The ocean closed during a protracted period of island-arc and microcontinent accretion between ∼850 and 620 Ma. To the south of the Arabian Nubian Shield, the Eastern Granulite-Cabo Delgado Nappe Complex of southern Kenya, Tanzania and Mozambique was an extended crust that formed adjacent to theMozambique Ocean and experienced a ∼650-620 Ma granulite-facies metamorphism. Completion of the nappe assembly around 620 Ma is defined as the East African Orogeny and was related to closure of the Mozambique Ocean. Oceans persisted after 620 Ma between East Antarctica, India, southern parts of the Congo-Tanzania-Bangweulu Cratons and the Zimbabwe-Kalahari Craton. They closed during the ∼600-500 Ma Kuungan or Malagasy Orogeny, a tectonothermal event that affected large portions of southern Tanzania, Zambia, Malawi, Mozambique, Madagascar and Antarctica. The East African and Kuungan Orogenies were followed by phases of post-orogenic extension. Early ∼600-550 Ma extension is recorded in the Arabian-Nubian Shield and the Eastern Granulite-Cabo Delgado Nappe Complex. Later ∼550-480 Ma extension affected Mozambique and southern Madagascar. Both extension phases, although diachronous,are interpreted as the result of lithospheric delamination. Along the strike of the East African Orogen, different geodynamic settings resulted in the evolution of

  16. Orogen styles in the East African Orogen: A review of the Neoproterozoic to Cambrian tectonic evolution☆

    PubMed Central

    Fritz, H.; Abdelsalam, M.; Ali, K.A.; Bingen, B.; Collins, A.S.; Fowler, A.R.; Ghebreab, W.; Hauzenberger, C.A.; Johnson, P.R.; Kusky, T.M.; Macey, P.; Muhongo, S.; Stern, R.J.; Viola, G.

    2013-01-01

    The East African Orogen, extending from southern Israel, Sinai and Jordan in the north to Mozambique and Madagascar in the south, is the world́s largest Neoproterozoic to Cambrian orogenic complex. It comprises a collage of individual oceanic domains and continental fragments between the Archean Sahara–Congo–Kalahari Cratons in the west and Neoproterozoic India in the east. Orogen consolidation was achieved during distinct phases of orogeny between ∼850 and 550 Ma. The northern part of the orogen, the Arabian–Nubian Shield, is predominantly juvenile Neoproterozoic crust that formed in and adjacent to the Mozambique Ocean. The ocean closed during a protracted period of island-arc and microcontinent accretion between ∼850 and 620 Ma. To the south of the Arabian Nubian Shield, the Eastern Granulite–Cabo Delgado Nappe Complex of southern Kenya, Tanzania and Mozambique was an extended crust that formed adjacent to theMozambique Ocean and experienced a ∼650–620 Ma granulite-facies metamorphism. Completion of the nappe assembly around 620 Ma is defined as the East African Orogeny and was related to closure of the Mozambique Ocean. Oceans persisted after 620 Ma between East Antarctica, India, southern parts of the Congo–Tanzania–Bangweulu Cratons and the Zimbabwe–Kalahari Craton. They closed during the ∼600–500 Ma Kuungan or Malagasy Orogeny, a tectonothermal event that affected large portions of southern Tanzania, Zambia, Malawi, Mozambique, Madagascar and Antarctica. The East African and Kuungan Orogenies were followed by phases of post-orogenic extension. Early ∼600–550 Ma extension is recorded in the Arabian–Nubian Shield and the Eastern Granulite–Cabo Delgado Nappe Complex. Later ∼550–480 Ma extension affected Mozambique and southern Madagascar. Both extension phases, although diachronous,are interpreted as the result of lithospheric delamination. Along the strike of the East African Orogen, different geodynamic settings

  17. Tectonic and Topographic Effects of Collision Between Two Orogens

    NASA Astrophysics Data System (ADS)

    Forte, A. M.; Cowgill, E.

    2013-12-01

    Although collisions between small orogens may be common during the early stages of orogeny as small, intervening basins and back-arcs are consumed during progressive collision, the structural, topographic and stratigraphic expressions of such events are poorly understood. Investigation of the Greater Caucasus (GC) and Lesser Caucasus (LC) in the Arabia-Eurasia collision zone, suggests that incipient collision can drive an orogen out of steady state, causing significant structural and topographic departures from the predictions of a simple steady-state bivergent orogenic wedge model. The W-NW striking GC form the northern margin of the Arabia-Eurasia collision between the Black and Caspian Seas and represent the main locus of NE-SW shortening within the central portion (40° to 50°E) of the collision. Strong tectonic and climatic gradients characterize the GC along their 1000 km length, including an eastward increase in GPS-derived convergence rates from 2 to 10 mm/yr, and an eastward decrease in mean annual precipitation from 100 to 20 cm/yr. The existence of the GC as a significant topographic and structural feature is recent, with rapid exhumation beginning at 5 Ma. Importantly, the first order architecture of the GC remains enigmatic. Previous workers suggest the range is well explained as a bivergent orogenic wedge with a south-facing pro-wedge. However both the location of active structures and the topographic expression of the range significantly depart from predictions of a standard, steady-state, bivergent orogenic wedge model. Topographically, the GC are atypically symmetric across-strike, with nearly equal retro- and pro-wedge widths. Also unexpected is the consistent location of the topographic crest of the range north,of the main drainage divide and towards the retro-wedge by up to 40 km in the center of the range. Stratigraphic records along the SE margin of the GC indicate Plio-Pleistocene-aged alluvial fans were an order of magnitude larger than

  18. The Tyrrhenian stage geodinamic evolution of Apenninic-Maghrebian orogen (Southern Apennines and Sicily)

    NASA Astrophysics Data System (ADS)

    Lentini, F.; Carbone, S.; Barreca, G.

    2009-04-01

    detachments occurred with further forward transport, which generated repeated slices with an apparent increase to the original thickness. . The Alpine Tethydes are composed of sedimentary sequences, which were deposited in the Alpine Tethys, and originally were located between the European and the Panormide/Apenninic Block. They are represented by allochthonous far travelled tectonic units, resting on both the Panormide/Apenninic Platforms and the Ionides. The Calabride Chain originated by the delamination of the European margin. This roof thrust system includes nappes of Hercynian basement with remains of the original Meso-Cenozoic covers deformed during the Paleogene and sutured by the Late Oligocene-Early Burdigalian Capo d'Orlando Flysch. The geological, geophysical data and the volcanological characters permit to restore the palaeogeography and the geodynamic evolution, and allow to recognize three orogenic stages: the Eo-Alpine, originated during Cretaceous-Eocene times, evident in the western Calabria, in the Tyrrhenian basin and the Alpine Corsica; the Balearic stage (Late Oligocene-Early Miocene), in which the Corsica-Sardinia block rotated and collided with the Adria-Africa margins with thrusting of the Alpine Tethydes over Panormide/Apenninic platforms; and the Tyrrhenian stage (Middle Miocene to Present), when the onset of the Tyrrhenian back-arc basin occurred and after the closure of the interposed Palaeoionian branches the Ionides were tectonically transported onto the foreland blocks. The CROP crustal sections allow to distinguish thickness and distribution of the crusts in this area of the Mediterranean Sea, and their clear influence on geodynamic evolution of the Tyrrhenian stage. They confirm that both the foreland blocks extend below the orogenic belt, reaching the Tyrrhenian margins, with a gradual thinning and a transition to a Palaeo-Ionian slab, probably not active at present time, from which the Ionides detached and overrode the ETS. The

  19. Sand fairway mapping as a tool for tectonic restoration in orogenic belts

    NASA Astrophysics Data System (ADS)

    Butler, Rob

    2016-04-01

    geomorphology. The stratigraphic records are preserved in many parts of the Alpine-Mediterranean region. Examples are drawn from the Eo-Oligocene of the western Alps and the early Miocene of the Maghreb-Apennine system to illustrate how turbidite sedimentology, linked to studies of basin structure, can inform understanding of tectonic processes on regional and local scales. In both examples, sediment was delivered across deforming basin arrays containing contractional structures, sourced from beyond the immediate orogenic segments. The depositional systems show that multiple structures were active in parallel, rather than develop in any particular sequence. Both systems show that significant deformation occurs, emerging to the syn-orogenic surface ahead of the main orogenic wedge. The cycling of uplift and subsidence of "massifs" can be significantly more complex that the histories resolved from thermochronological data alone.

  20. Active optical zoom system

    DOEpatents

    Wick, David V.

    2005-12-20

    An active optical zoom system changes the magnification (or effective focal length) of an optical imaging system by utilizing two or more active optics in a conventional optical system. The system can create relatively large changes in system magnification with very small changes in the focal lengths of individual active elements by leveraging the optical power of the conventional optical elements (e.g., passive lenses and mirrors) surrounding the active optics. The active optics serve primarily as variable focal-length lenses or mirrors, although adding other aberrations enables increased utility. The active optics can either be LC SLMs, used in a transmissive optical zoom system, or DMs, used in a reflective optical zoom system. By appropriately designing the optical system, the variable focal-length lenses or mirrors can provide the flexibility necessary to change the overall system focal length (i.e., effective focal length), and therefore magnification, that is normally accomplished with mechanical motion in conventional zoom lenses. The active optics can provide additional flexibility by allowing magnification to occur anywhere within the FOV of the system, not just on-axis as in a conventional system.

  1. Exploration of the Banda orogen, Indonesia

    SciTech Connect

    Harris, R.A. ); Audley-Charles, M.G. ); Tobing, S.L. )

    1990-06-01

    An integrated geologic evaluation of the late Miocene to present Banda orogen and its petroleum potential is in progress. The focus of the investigation involves sedimentary sections of the NW Australian continental margin incorporated into the Banda orogen. The islands of Timor and Seram, and several other islands throughout the Banda orogenic arc, are the closest exposed lithostratigraphic equivalents of the hydrocarbon producing NW Australian subsurface stratigraphy. Hydrocarbon occurrences are well documented on many of the islands, and over 13 million barrels of oil have been produced from the Bula field in Seram. Recent studies of seeps in Timor and associated stratigraphic, structural, and geochemical relations indicate that (1) oil and gas seeps occur throughout the Permian to Pliocene stratigraphic section; (2) bituminous limestones of the Triassic Aituti Formation are the most likely source for many of the seeps; (3) preliminary geochemical analyses of the oils indicate a mixed terrestrial and marine organic source, and suggest a genetic link between the Aitutu oils and oils seeping from Tertiary reservoirs; (4) triterpane and sterane parameters indicate some of these oils are highly mature; (5) palynomorph coloration, conodont alteration, and clay mineralogy data yield paleotemperature estimates in the range of hydrocarbon generation from much of the pre-rift sequence (Permian-Jurassic); (6) structural modeling suggests that the initial decollement zone of the orogenic wedge formed near the Jurassic breakup unconformity of the underthrust NW Australian margin, imbricating the post-rift sequence; (7) in Timor and Seram the decollement has stepped to deeper levels involving prerift sequences that form structural culminations in the core of the orogen. The culminations are expressed as topographic highs as in New Guinea and Oman.

  2. Paleozoic orogens in New England, USA

    USGS Publications Warehouse

    Robinson, P.; Tucker, R.D.; Bradley, D.; Berry, H.N., IV; Osberg, P.H.

    1998-01-01

    Stratigraphy and isotope geochronology in the crystalline core of the Appalachians suggest revised interpretations of the extent, nature and timing of Paleozoic orogens in New England. Five major episodes of magmatism, deformation, and high-grade regional metamorphism are recognized: Taconian (455-442 Ma), Acadian (423-385 Ma), Neo-Acadian (366-350 Ma), Late Pennsylvanian (300-290 Ma) and Alleghanian (280-260 Ma). In the Taconian, the passive margin of Laurentia was subducted below a complex magmatic arc lasting from 480 to 442 Ma, founded in part on continental crust of a Medial New England terrane with possible affinities with Amazonia. Questions about Medial New England involve its coherence as a single plate, and the nature of its underlying crust. The Acadian began in Late Silurian as a collision between the amalgamated Laurentia-Medial New England and outer belts of Composite Avalon along a cryptic suture in coastal Maine, and progressed northwestward to the Connecticut Valley basin by mid-Devonian. Tonalitic-granitic magmatism and up to granulite-facies metamorphism culminated in Early Devonian, possibly tied to lithospheric detachment below the subducting northwestern plate and consequent asthenosphere upwelling. Newly discovered Neo-Acadian Late Devonian to Early Mississippian tonalitic-granitic magmatism, up to granulite-facies metamorphism, and severe deformation in central Massachusetts took place in a plate context poorly understood. Late Pennsylvanian effects include magmatism, metamorphism, and deformation near south New England gneiss domes and the Sebago batholith, and development of the right-lateral Norumbega fault system. Permian Alleghanian effects include penetrative deformation, granitic intrusions and up to sillimanite-grade metamorphism of Pennsylvanian beds in southeastern New England. These last two episodes relate to the arrival of Africa.

  3. The Effects of Gravitational Instability on the Tectonic Evolution of Continental Orogens

    NASA Astrophysics Data System (ADS)

    Gemmer, L.; Houseman, G. A.

    2005-05-01

    Convergent continental orogens have been the research focus of numerous geological and geophysical surveys and dynamical modeling studies, but the mechanisms controlling the evolution of these systems are still under debate. The temporal and spatial distribution of tectonic processes in orogenic regions is complex, and the interplay between buoyancy forces and regional tectonics in some of these systems is still not well understood. In several cases the extensional collapse of mountain belts is associated with dramatic thinning of the mantle part of the lithosphere, more so than the crust. A key region for investigating these processes is the Carpathian-Pannonian system of eastern Europe, where rapid extension took place in the Pannonian Basin simultaneously with contractional deformation in the surrounding orogens. Previous studies show that gravitational instabilities may play a fundamental role in the tectonics of mountain ranges. In general, the lithosphere is colder and thereby denser than the underlying asthenosphere. Under some circumstances this may cause the lithosphere to sink into the underlying asthenosphere. We use dynamic numerical models to investigate how such gravitational instabilities may affect the evolution of continental orogens. We show how a crust initially thickened by localized convergence may promote lithospheric gravitational instabilities that cause the collapse of high topography and focused, depth-variable lithospheric thinning developing simultaneously with contractional deformation and lithospheric downwelling in the adjacent areas. We investigate the relative importance of buoyancy and regional tectonics in convergent continental orogens and show how density and viscosity (Newtonian or non-Newtonian) affect the evolution of a model system. We investigate the distribution and amplitude of lithospheric downwelling and examine how the instability develops adjacent to the corner of an initially rectangular region of thickened crust in

  4. Post-orogenic thermal evolution of newborn Archean continents

    NASA Astrophysics Data System (ADS)

    Jaupart, C.; Mareschal, J.-C.

    2015-12-01

    The post-orogenic thermal evolution of newborn cratons in the Archean is marked by high-temperature metamorphism and plutonic activity that lag accretion by several tens of million years. The source of the heat that is required remains controversial. Here, we show that such late activity is consistent with the thermal evolution of new continental crust that adjusts to heat released by radioactive decay. Quantitative results depend on the total amount of radioactive elements in the newborn crust. Using heat flow and heat production data from the Archean Superior Province of the Canadian Shield, we show that temperatures ≈800-900 °C were reached in the lower crust a few tens of million years after the final accretion event. The timing of post-orogenic metamorphism is sensitive to the thermal structure acquired at the end of accretion. For the Superior Province, the relatively short time-lag between the end of accretion and metamorphism suggests that the lithosphere was thin or had been heated up by sustained magma percolation.

  5. Tracking basement cross-strike discontinuities in the Indian crust beneath the Himalayan orogen using gravity data - relationship to upper crustal faults

    NASA Astrophysics Data System (ADS)

    Godin, Laurent; Harris, Lyal B.

    2014-07-01

    The Himalaya is the result of the on-going convergence and collision of India and Asia. The internal configuration and processes that govern the rise of the Himalayan Mountains and Tibetan Plateau are crucial to understand continental collision zones. However, knowledge of the prior configuration of the colliding plates is equally important, since inherited (pre-orogenic/basement) structures can undeniably influence the development of the orogenic architecture throughout the orogen's cycle of collision and eventual collapse. Three northeast-trending palaeotopographic ridges of faulted Precambrian Indian basement underlie the Ganga basin south of the Himalaya. Our paper illustrates a crustal-scale fault origin for these ridges and succeeds in determining how far north beneath the Himalayan system they extend and how they ultimately govern the location of upper crustal faults in southern Tibet. Spectrally filtered EGM2008 Bouguer gravity data and edges in its horizontal gradient at different source depths (`gravity worms') over northern Peninsular India, the Himalaya and southern Tibet reveal several continuous Himalayan cross-strike discontinuities interpreted to represent crustal faults. Gravity lineaments in Peninsular India coincide with edges of the Precambrian basement ridges and megakinks up to 100 km wide develop in foreland cover sequences between the interpreted basement faults. The interpreted basement faults project northward beneath the Himalayan system and southern Tibet. Our results suggest that several active Himalayan cross-strike faults, such as the ones related to many graben in southern Tibet, are rooted in the underplated Indian lower crust or step en échelon along interpreted basement faults. Our interpretation thus suggests that south Tibet graben are spatially related to deep-seated crustal-scale faults rooted in the underplated Indian crust. These major discontinuities partition the Himalayan range into distinct zones, and could ultimately

  6. GEOPHYSICS. Layered deformation in the Taiwan orogen.

    PubMed

    Huang, T-Y; Gung, Y; Kuo, B-Y; Chiao, L-Y; Chen, Y-N

    2015-08-14

    The underthrusting of continental crust during mountain building is an issue of debate for orogens at convergent continental margins. We report three-dimensional seismic anisotropic tomography of Taiwan that shows a nearly 90° rotation of anisotropic fabrics across a 10- to 20-kilometer depth, consistent with the presence of two layers of deformation. The upper crust is dominated by collision-related compressional deformation, whereas the lower crust of Taiwan, mostly the crust of the subducted Eurasian plate, is dominated by convergence-parallel shear deformation. We interpret this lower crustal shearing as driven by the continuous sinking of the Eurasian mantle lithosphere when the surface of the subducted plate is coupled with the orogen. The two-layer deformation clearly defines the role of subduction in the formation of the Taiwan mountain belt. PMID:26273051

  7. The Palaeoproterozoic crustal evolution: evidences from granulite-gneiss belts, collisional and accretionary orogens

    NASA Astrophysics Data System (ADS)

    Mints, M. V.; Konilov, A. N.

    2003-04-01

    The Palaeoproterozoic juvenile assemblages were emplaced within two types of mobile belts: (1) high-grade or "granulite-gneiss" belts; (2) low- and medium-grade volcano-sedimentary and volcano-plutonic belts. Type (1) belts resulted from plume-induced heating, magmatism, emergence of riftogenic basins and volcano-tectonic depressions, their filling with rift-type sediments and juvenile but strongly contaminated lavas and ash-flow deposits, high-grade recrystallization of the lower- and mid-crustal assemblages including the filling of the basins and depressions that followed in intraplate and back-arc settings, and final thrusting and exhumation caused by collision-related tectonism. Type (2) belts represent sutures containing MORB- and arc-related assemblages, together with initial rift-related assemblages formed during evolution of the short-lived, mainly Red Sea-type oceans (intracontinental collisional orogens) and systems of oceanic, island-arc and back-arc terranes amalgamated along continent margins (peripheral accretionary orogens). Palaeoproterozoic history can be subdivided into five periods: (1) 2.51-2.44 Ga superplume activity and displacement of Fennoscandia; (2) 2.44-2.0 (2.11) Ga quiescent within-plate development complicated by local plume- and plate tectonics-related processes; (3) a 2.0-1.95 Ga superplume event; (4) 1.95-1.75 (1.71) Ga combined plume- and plate tectonics-related evolution, resulting in the partial disruption of the continental crust, and formation of accretionary orogens along some margins of the supercontinent and rebirth of the supercontinent entity, and (5) < 1,75 Ga post- and anorogenic magmatism and metamorphism. Magmatic and thermal activity during the early Palaeoproterozoic was almost exclusively concentrated within Laurentia (comprising North American and Fennoscandian cratons). In contrast, late Palaeoproterozoic assemblages are distributed within all continents. The simultaneous appearance of within-plate plume

  8. Tectono-metamorphic evolution of the internal zone of the Pan-African Lufilian orogenic belt (Zambia): Implications for crustal reworking and syn-orogenic uranium mineralizations

    NASA Astrophysics Data System (ADS)

    Eglinger, Aurélien; Vanderhaeghe, Olivier; André-Mayer, Anne-Sylvie; Goncalves, Philippe; Zeh, Armin; Durand, Cyril; Deloule, Etienne

    2016-01-01

    The internal zone of the Pan-African Lufilian orogenic belt (Zambia) hosts a dozen uranium occurrences mostly located within kyanite micaschists in a shear zone marking the contact between metasedimentary rocks attributed to the Katanga Neoproterozoic sedimentary sequence and migmatites coring domes developed dominantly at the expense of the pre-Neoproterozoic basement. The P-T-t-d paths reconstructed for these rocks combining field observations, microstructural analysis, metamorphic petrology and thermobarometry and geochronology indicate that they have recorded burial and exhumation during the Pan-African orogeny. Both units of the Katanga metasedimentary sequence and pre-Katanga migmatitic basement have underwent minimum peak P-T conditions of ~ 9-11 kbar and ~ 640-660 °C, dated at ca. 530 Ma by garnet-whole rock Lu-Hf isochrons. This suggests that this entire continental segment has been buried up to a depth of 40-50 km with geothermal gradients of 15-20 °C.km- 1 during the Pan-African orogeny and the formation of the West Gondwana supercontinent. Syn-orogenic exhumation of the partially molten root of the Lufilian belt is attested by isothermal decompression under P-T conditions of ~ 6-8 kbar at ca. 530-500 Ma, witnessing an increase of the geothermal gradients to 25-30 °C·km- 1. Uranium mineralizations that consist of uraninite and brannerite took place at temperatures ranging from ~ 600 to 700 °C, and have been dated at ca. 540-530 Ma by U-Pb ages on uraninite. The main uranium deposition thus occurred at the transition from the syn-orogenic burial to the syn-orogenic exhumation stages and has been then partially transposed and locally remobilized during the post-orogenic exhumation accommodated by activation of low-angle extensional detachment.

  9. Seismogenic nodes in the Mediterranean orogenic belt

    NASA Astrophysics Data System (ADS)

    Gorshkov, A.; Panza, G.; Soloviev, A.; Aoudia, A.

    2003-04-01

    The central segment of the Mediterranean orogenic belt (the Apennines, Alps, Carpathians, Balkanides, and Dinarides) has been studied to identify seismogenic nodes, specific structures formed at the intersections of fault zones. The nodes have been delineated with the morphostructural zoning (MSZ) based on the concept that the lithosphere is built-up by different-scale blocks, separated by mobile boundaries. With MSZ we compiled the morphostructural map (scale 1:1,000,000) for the study region using the GIS technology. The map shows the hierarchical block-structure of the region, the boundary zones bounding blocks, and the loci of the nodes. Three-level hierarchy has been established for the blocks and their boundaries. All the recorded M >= 6.0 earthquakes nucleate at the nodes delineated by MSZ, i.e. ignoring the seismic record. The nodes capable of M >= 6.5 earthquakes are identified with the criteria of high seismicity nodes, previously derived from pattern recognition in the Pamirs -Tien Shan region. In the study region, with the employed criteria 29 out of the 33 nodes, hosting the observed M >= 6.5 events, have been classified as prone to M >= 6.5 earthquakes. With the exception of the Carpatho-Balkanides system, where the recognition procedure is inapplicable due to the insufficient number of sample nodes for the learning stage, we recognized the seismogenic nodes (D), prone to M >= 6.0 earthquakes, with the pattern recognition algorithm CORA-3. The recognition is performed using geomorphic, morphostructural, and gravity parameters relevant to seismicity. The majority of D nodes is associated with the first and second rank boundaries, i.e. larger earthquakes originate at the boundaries of larger blocks. Characteristic traits of D nodes selected by CORA-3 suggest an increased fragmentation of the crust and high intensity of tectonic movements in the D nodes vicinities. We identify a number of D nodes, where strong earthquakes are not recorded till present

  10. Linkages of Erosion, Tectonics, and Climate in a Glacial Setting: Lessons Learned in Alaska's St. Elias Orogen

    NASA Astrophysics Data System (ADS)

    Spotila, J. A.; Berger, A. L.

    2009-12-01

    A microplate collision in the southern Alaskan syntaxis provides useful analogies and lessons for the erosive-tectonic coupling that occur at Earth’s other great orogens. The St. Elias orogen is a relatively small collision produced by impingement of the Yakutat terrane in the transform-subduction crook of the northernmost Pacific-North America plate boundary. Due to convergence rates comparable to those in the Himalaya and a severe maritime glacial climate, deformation and rock uplift in this orogen rival Earth’s most extreme tectonic environments. Ongoing multidisciplinary investigations have documented several key phenomena that are relevant to orogenic processes worldwide. Previously obtained bedrock thermochronometry has revealed that glaciers exert an important control on tectonic crustal efflux. Long-term denudation is focused where mean Quaternary glacial ELA intersects the windward flank of the orogen. Quaternary enhancement of glaciation also appears to have dramatically accelerated denudation and forced a reorganization of orogenic wedge architecture. These results imply that glaciers are more significant to orogenic belts than implied by the topographic “buzz saw” hypothesis, in that they actually dictate long-term patterns of strain and mass transfer at the orogen-scale. New data refine the spatial and temporal patterns of exhumation in the orogen and enable more robust assessment of flux steady-state, or how exhumation has kept pace with tectonic crustal influx. Results suggest that, despite the presence of such an efficient erosive system, a component of tectonic influx is likely accommodated by subduction or lateral advection via intraplate transform faults. We suggest that a continuous dextral fault connects the mapped Totschunda-Denali and Fairweather faults, enabling a significant component of plate convergence to bypass the orogen. Finally, the refined pattern of exhumation sheds light onto the possible existence of tectonic

  11. The role of lateral lithospheric strength heterogeneities in orogenic plateau growth: Insights from 3-D thermo-mechanical modeling

    NASA Astrophysics Data System (ADS)

    Chen, Lin; Gerya, Taras V.

    2016-04-01

    Preexisting lateral variations in crustal thickness and lithospheric thermal state are documented for the formation of some orogenic plateaux. Here we use high-resolution 3-D thermo-mechanical simulations to investigate the influence of preexisting lateral lithospheric strength heterogeneity on the growth of orogenic plateau. The modeling results illustrate an episodic scenario for plateau growth: (1) an early rapid growth stage, characterized by rapid surface uplift and intensive crustal buckling and thickening; (2) an outward spreading stage, characterized by significant lateral expansion of the plateau edges; and (3) a mature stage, characterized by the development of the intracrustal partial melting and subduction of the surrounding lithosphere under the plateau. Sensitivity analyses indicate that lateral variation in crustal thickness favors outward spreading of orogenic plateau, while lateral variation in geothermal gradient favors crustal buckling. The model in absence of lateral strength heterogeneity leads to progressive migration of orogenic belt. Our models show that the plateau's lower crust is largely coupled with underlying lithospheric mantle and does not flow into the surrounding lithospheres, casting doubt on the lower crust flow model. We suggest that the Himalayan-Tibetan orogenic system can be best understood within the framework that the proto-southern Asian margin was fairly weak prior to the India-Asia collision to steer the formation of a large hot orogenic plateau there.

  12. Solar cell activation system

    SciTech Connect

    Apelian, L.

    1983-07-05

    A system for activating solar cells involves the use of phosphorescent paint, the light from which is amplified by a thin magnifying lens and used to activate solar cells. In a typical system, a member painted with phosphorescent paint is mounted adjacent a thin magnifying lens which focuses the light on a predetermined array of sensitive cells such as selenium, cadmium or silicon, mounted on a plastic board. A one-sided mirror is mounted adjacent the cells to reflect the light back onto said cells for purposes of further intensification. The cells may be coupled to rechargeable batteries or used to directly power a small radio or watch.

  13. The Western Chugach-St. Elias Orogen, Alaska: Strain Partitioning and the Effect of Glacial Erosion

    NASA Astrophysics Data System (ADS)

    Berger, A. L.; Spotila, J. A.

    2006-12-01

    The ongoing collision between the Yakutat terrane and the North American plate in southeastern Alaska's St. Elias orogen is a modern analog for the tectonic processes which produced, and shaped, much of the Cordillera. With convergence rates comparable to that of the Himalaya (>4 cm/yr), a young and dynamic zone of thin-skinned interplate deformation has constructed the highest coastal relief on Earth, and given rise to the second and third highest peaks in North America (5,959 and 5,489 m). The orogen receives upwards of 4 m precipitation annually, has been heavily glaciated for the last 5 Ma, and contains some of the fastest short-term erosion rates known. Over the last few years, evidence has steadily mounted that within such tectonic settings, climate and tectonics exist as a coupled system (i.e. Taiwan and Nanga Parbat). Our ongoing research, aimed at quantifying spatial patterns in exhumation rate as well as the location of active structures within the western half of the St. Elias orogen, bolsters this new paradigm. Bedrock ([U-Th]/He) cooling ages in apatite show that exhumation is currently focused on the windward side of the orogen. Time- averaged, long-term, exhumation rates near the coast are generally ~2-3 mm/yr, versus <0.5 mm/yr on the leeward side of the range. However, the rapid exhumation rates along the windward flank are not spatially uniform with the highest rates measured thus far >~5.5 mm/yr (0.4 Ma cooling age) situated near the Bering and Steller Glaciers. This locus of exhumation could reflect a redistribution of strain by focused erosion beneath these large outlet glaciers. Yet, the structural mechanism of this focused strain is still speculative. Pairs of helium ages spanning the foot-wall and hanging-wall of the Chugach-St. Elias thrust, the suture between the North American plate and colliding Yakutat terrane, imply that the thrust became inactive at some time between 2 and 5 Ma. Because of the coincidence in timing between this

  14. The Tyrrhenian stage geodinamic evolution of Apenninic-Maghrebian orogen (Southern Apennines and Sicily)

    NASA Astrophysics Data System (ADS)

    Lentini, F.; Carbone, S.; Barreca, G.

    2009-04-01

    detachments occurred with further forward transport, which generated repeated slices with an apparent increase to the original thickness. . The Alpine Tethydes are composed of sedimentary sequences, which were deposited in the Alpine Tethys, and originally were located between the European and the Panormide/Apenninic Block. They are represented by allochthonous far travelled tectonic units, resting on both the Panormide/Apenninic Platforms and the Ionides. The Calabride Chain originated by the delamination of the European margin. This roof thrust system includes nappes of Hercynian basement with remains of the original Meso-Cenozoic covers deformed during the Paleogene and sutured by the Late Oligocene-Early Burdigalian Capo d'Orlando Flysch. The geological, geophysical data and the volcanological characters permit to restore the palaeogeography and the geodynamic evolution, and allow to recognize three orogenic stages: the Eo-Alpine, originated during Cretaceous-Eocene times, evident in the western Calabria, in the Tyrrhenian basin and the Alpine Corsica; the Balearic stage (Late Oligocene-Early Miocene), in which the Corsica-Sardinia block rotated and collided with the Adria-Africa margins with thrusting of the Alpine Tethydes over Panormide/Apenninic platforms; and the Tyrrhenian stage (Middle Miocene to Present), when the onset of the Tyrrhenian back-arc basin occurred and after the closure of the interposed Palaeoionian branches the Ionides were tectonically transported onto the foreland blocks. The CROP crustal sections allow to distinguish thickness and distribution of the crusts in this area of the Mediterranean Sea, and their clear influence on geodynamic evolution of the Tyrrhenian stage. They confirm that both the foreland blocks extend below the orogenic belt, reaching the Tyrrhenian margins, with a gradual thinning and a transition to a Palaeo-Ionian slab, probably not active at present time, from which the Ionides detached and overrode the ETS. The

  15. Collapse and Melting in a Confined Orogenic Belt: Preliminary Results From the Neoproterozoic Araçuaí Belt of Eastern Brazil

    NASA Astrophysics Data System (ADS)

    Whittington, A.; Connelly, J.; Pedrosa-Soares, A.; Marshak, S.; Alkmim, F.

    2001-12-01

    The Neoproterozoic Araçuaí belt of eastern Brazil records the closure of a Red Sea-type basin between the São Francisco and Congo cratons of West Gondwana, and is part of the Brasiliano (Pan-African) orogenic system. In its southern part this basin contained oceanic crust, so that closure involved subduction and arc magmatism prior to continental collision. In its northern part, the basin was entirely ensialic. After the cessation of subduction, a period of magmatic quiescence and possible plateau development ended with the collapse of the orogen. Extensional structures are observed across the preserved Brazilian portion of the orogen (the eastern segment of the orogen is now in West Africa). Six distinct syn- to post- kinematic granite suites were emplaced within the orogen, although the temporal relation of the different granite suites to contractional and post-collision extensional tectonism has remained enigmatic. Preliminary U-Pb ages for key granite suites are related to the structural history of the orogen, placing important constraints on the timing and duration of orogenic collapse. The age of the northernmost pluton of the subduction-related (G1) granite suite is consistent with published ages for this suite of 625 to 575 Ma. The G2 suite consists of an "anatectic sea" of variably foliated S-type migmatitic leucosomes, leucogranitic sheets and plutons, commonly associated with locally extensional mesoscopic shear zones. This migmatite-leucogranite association covers >75% of the outcrop over an area of ~20,000 km2. A preliminary U-Pb zircon age of ca. 536 Ma from a well-foliated G2 pluton is significantly younger than published ages from other G2 bodies (590 to 570 Ma). Bodies sampled from the other suites are: an I-type granite showing flow foliation but little or no tectonic fabric (G3I suite), an undeformed S-type leucogranite (G4 suite), and an undeformed I-type granite containing dioritic enclaves (G5 suite). Preliminary U-Pb zircon ages from all

  16. Asymmetric vs. symmetric deep lithospheric architecture of intra-plate continental orogens

    NASA Astrophysics Data System (ADS)

    Calignano, Elisa; Sokoutis, Dimitrios; Willingshofer, Ernst; Gueydan, Frédéric; Cloetingh, Sierd

    2015-08-01

    The initiation and subsequent evolution of intra-plate orogens, resulting from continental plate interior deformation due to transmission of stresses over large distances from the active plate boundaries, is controlled by lateral and vertical strength contrasts in the lithosphere. We present lithospheric-scale analogue models combining 1) lateral strength variations in the continental lithosphere, and 2) different vertical rheological stratifications. The experimental continental lithosphere has a four-layer brittle-ductile rheological stratification. Lateral heterogeneity is implemented in all models by increased crustal strength in a central narrow block. The main investigated parameters are strain rate and strength of the lithospheric mantle, both playing an important role in crust-mantle coupling. The experiments show that the presence of a strong crustal domain is effective in localizing deformation along its boundaries. After deformation is localized, the evolution of the orogenic system is governed by the mechanical properties of the lithosphere such that the final geometry of the intra-plate mountain depends on the interplay between crust-mantle coupling and folding versus fracturing of the lithospheric mantle. Underthrusting is the main deformation mode in case of high convergence velocity and/or thick brittle mantle with a final asymmetric architecture of the deep lithosphere. In contrast, lithospheric folding is dominant in case of low convergence velocity and low strength brittle mantle, leading to the development of a symmetric lithospheric root. The presented analogue modelling results provide novel insights for 1) strain localization and 2) the development of the asymmetric architecture of the Pyrenees.

  17. Production Systems. Laboratory Activities.

    ERIC Educational Resources Information Center

    Gallaway, Ann, Ed.

    This production systems guide provides teachers with learning activities for secondary students. Introductory materials include an instructional planning outline and worksheet, an outline of essential elements, domains and objectives, a course description, and a content outline. The guide contains 30 modules on the following topics: production…

  18. Communication Systems. Laboratory Activities.

    ERIC Educational Resources Information Center

    Sutherland, Barbara, Ed.

    This communication systems guide provides teachers with learning activities for secondary students. Introductory materials include an instructional planning outline and worksheet, an outline of essential elements, a list of objectives, a course description, and a content outline. The guide contains 32 modules on the following topics: story…

  19. Crustal Development in the Northeast Asian Orogenic Belt and its comparison with the Central Asian Orogenic Belt

    NASA Astrophysics Data System (ADS)

    Jahn, Bor-ming

    2016-04-01

    The Northeast Asian Orogenic Belt is a Mesozoic-Cenozoic accretionary orogenic collage, and it constitutes the northern and principal part of the "Nipponides" (Sengor and Natal'in, 1996). The tectonic framework was formed in Mesozoic and Cenozoic, and it continues to evolve along the modern Pacific arc-trench systems. Generally, a oceanward younging of tectonic units may be discerned, but such a simple pattern is disrupted in many places by extensive strike-slip faulting, most of which is left-lateral. In this talk, the issue of crustal development in the sector of Sikhote-Alin and Japanese Islands will be discussed based on the geochemical and isotopic analyses of granitoids that intruded in various tectonostratigraphic terrains. The majority of granitoids in the NE Asian Orogenic Belt formed from Jurassic to late Cenozoic, with Cretaceous as the dominant period of granitic magmatism and tectonothermal events. A few Early Paleozoic granitic rocks (500 to 450 Ma) have been identified in SW Japan (Kurosegawa Belt) as well as in NE Japan (Kitakami Belt), among them the ca. 500 Ma diorites and tonalites of southern Kitakami are the oldest rocks in Japan and interpreted as the first TTG crust of proto-Japan (Isozaki et al., 2015). Cretaceous granitoids are widespread in Sikhote-Alin and in NE and SW Japan. However, granitoids were emplaced only in the Cenozoic in Sakhalin (ca. 44 - 42 Ma) and Hokkaido (45, 37 and 18 Ma). Most granitoids from Sikhote-Alin are of I-type and have ISr = 0.7040 to 0.7083, and ɛNd(T) = +3.0 to -6.0 (mostly 0 to -5). The Sr-Nd isotopic data fall within the range of granitoids from SW Japan (0.704 to 0.712; +5.0 to -13.0), and the data of Cretaceous granitoids from Sikhote-Alin and SW Japan overlap almost completely. The Cenozoic granitoids of Hokkaido are characterized by ISr = 0.7044 - 0.7061, ɛNd(T) = +1.0 to +4.7, and Sm-Nd model-1 ages = 400-1000 Ma. This is remarkably similar to the Sakhalin granitoids with ISr = 0.7047 - 0.7050,

  20. ADASY (Active Daylighting System)

    NASA Astrophysics Data System (ADS)

    Vázquez-Moliní, Daniel; González-Montes, Mario; Fernández-Balbuena, Antonio Á.; Bernabéu, Eusebio; García-Botella, Ángel; García-Rodríguez, Lucas; Pohl, Wilfried

    2009-08-01

    The main objective of ADASY (Active Daylighting System) work is to design a façade static daylighting system oriented to office applications, mainly. The goal of the project is to save energy by guiding daylight into a building for lighting purpose. With this approach we can reduce the electrical load for artificial lighting, completing it with sustainable energy. The collector of the system is integrated on a vertical façade and its distribution guide is always horizontal inside of the false ceiling. ADASY is designed with a specific patent pending caption system, a modular light-guide and light extractor luminaire system. Special care has been put on the final cost of the system and its building integration purpose. The current ADASY configuration is able to illuminate 40 m2 area with a 300lx-400lx level in the mid time work hours; furthermore it has a good enough spatial uniformity distribution and a controlled glare. The data presented in this study are the result of simulation models and have been confirmed by a physical scaled prototype. ADASY's main advantages over regular illumination systems are: -Low maintenance; it has not mobile pieces and therefore it lasts for a long time and require little attention once installed. - No energy consumption; solar light continue working even if there has been a power outage. - High quality of light: the colour rendering of light is very high - Psychological benefits: People working with daylight get less stress and more comfort, increasing productivity. - Health benefits

  1. Tectonic controls of Mississippi Valley-type lead-zinc mineralization in orogenic forelands

    USGS Publications Warehouse

    Bradley, D.C.; Leach, D.L.

    2003-01-01

    Most of the world's Mississippi Valley-type (MVT) zinc-lead deposits occur in orogenic forelands. We examine tectonic aspects of foreland evolution as part of a broader study of why some forelands are rich in MVT deposits, whereas others are barren. The type of orogenic foreland (collisional versus Andean-type versus inversion-type) is not a first-order control, because each has MVT deposits (e.g., Northern Arkansas, Pine Point, and Cevennes, respectively). In some MVT districts (e.g., Tri-State and Central Tennessee), mineralization took place atop an orogenic forebulge, a low-amplitude (a few hundred meters), long-wavelength (100-200 km) swell formed by vertical loading of the foreland plate. In the foreland of the active Banda Arc collision zone, a discontinuous forebulge reveals some of the physiographic and geologic complexities of the forebulge environment, and the importance of sea level in determining whether or not a forebulge will emerge and thus be subject to erosion. In addition to those on extant forebulges, some MVT deposits occur immediately below unconformities that originated at a forebulge, only to be subsequently carried toward the orogen by the plate-tectonic conveyor (e.g., Daniel's Harbour and East Tennessee). Likewise, some deposits are located along syn-collisional, flexure-induced normal and strike-slip faults in collisional forelands (e.g., Northern Arkansas, Daniel's Harbour, and Tri-State districts). These findings reveal the importance of lithospheric flexure, and suggest a conceptual tectonic model that accounts for an important subset of MVT deposits-those in the forelands of collisional orogens. The MVT deposits occur both in flat-lying and in thrust-faulted strata; in the latter group, mineralization postdated thrusting in some instances (e.g., Picos de Europa) but may have predated thrusting in other cases (e.g., East Tennessee).

  2. On the orogenic status of the Central Alps

    NASA Astrophysics Data System (ADS)

    Rahn, M. K.

    2003-04-01

    In a simplified way, the history of every orogen can be divided into an initial stage of formation, an intermediate stage of maturity and a final stage of decay. For the Central European Alps, the initial stage started with the continent-continent collision in the Eocene. The intermediate stage may be divided into several substages of quiescence and further growth. The youngest stage of growth, the Grindelwald stage, has led to shortening and thrusting within the Central crystalline massifs (Aar, Gotthard) and to major exhumation of these units and possibly a northward thrusting of the overlying sediments (Helvetic nappes) onto more external basin sediments (Molasse Basin). During the last 10 myr, however, the Central Alps are characterized by the formation of dome structures aligned along a major thrust zone (Penninic front thrust) that seems to have acted in a normal sense since that time. A contoured compilation of fission track apatite ages reveals the absence of structures with compressional movements during that time interval. Compression was restricted to the northern Alpine border and to the Jura Mountains, an external chain of thin-skin tectonic folds and thrust faults, which is separated from the Alpine body by some tens of kilometres of tectonically undisturbed sediments of the Molasse Basin. Folding and thrusting in the Jura Mountains, starting some time between 9 and 5 Ma and being completed at about 3.5 Ma, was contemporaneous to exhumation and erosion in the Molasse Basin. The Alpine border thrust, where Helvetic sediments thrust on top of Molasse Basin sediments towards N to NW has been active at around 10 Ma. Younger, N-directed thrusting can also be showm from boreholes within nearby Molasse sediments. During the last few myr, the Central Alps, however, seem to have been dominated by normal faulting and doming, indicating that the general status of the Central Alps is that of a quiet or even decaying orogen.

  3. How does the mid-crust accommodate deformation in large, hot collisional orogens? A review of recent research in the Himalayan orogen

    NASA Astrophysics Data System (ADS)

    Cottle, John M.; Larson, Kyle P.; Kellett, Dawn A.

    2015-09-01

    The presence of hot, weak crust is a central component of recent hypotheses that seek to explain the evolution of continent-continent collisions, and in particular may play an important role in accommodating the >3000 km of convergence within the Himalaya-Tibetan collision over the last ˜55 Myr. Models that implicate flow of semi-viscous midcrustal rocks south toward the front of the Himalayan orogen, 'channel flow', are able to account for many geologic observations in the Himalaya, while alternative models of collision, particularly 'thrust-wedge taper', demonstrate that much of the observed geology could have formed in the absence of a low-viscosity mid-crustal layer. Several recent studies, synthesized here, have prompted a shift from initial assumptions that channel flow and thrust-wedge taper processes are by definition mutually exclusive. These new studies reveal the presence of several tectonometamorphic discontinuities in the midcrust that appear to reflect a continuum of deformation in which both channel- and wedge-type processes operate in spatially and temporally distinct domains within the orogen, and further, that the system may migrate back and forth between these types of behavior. This continuum of deformation styles within the collisional system is of crucial importance for explaining the evolution of the Himalayan orogen and, hence, for understanding the evolution of Earth's many continent-continent collision zones.

  4. Visualizing the sedimentary response through the orogenic cycle using multi-dimensional scaling

    NASA Astrophysics Data System (ADS)

    Spencer, C. J.; Kirkland, C.

    2015-12-01

    connect the evolutionary patterns of detrital zircon age spectra to the geodynamics of an orogenic system, which in many cases is a direct function of proximity to the orogenic front.

  5. Neoproterozoic, Paleozoic, and Mesozoic granitoid magmatism in the Qinling Orogen, China: Constraints on orogenic process

    NASA Astrophysics Data System (ADS)

    Wang, Xiaoxia; Wang, Tao; Zhang, Chengli

    2013-08-01

    The Qinling Orogen is one of the main orogenic belts in Asia and is characterized by multi-stage orogenic processes and the development of voluminous magmatic intrusions. The results of zircon U-Pb dating indicate that granitoid magmatism in the Qinling Orogen mainly occurred in four distinct periods: the Neoproterozoic (979-711 Ma), Paleozoic (507-400 Ma), and Early (252-185 Ma) and Late (158-100 Ma) Mesozoic. The Neoproterozoic granitic magmatism in the Qinling Orogen is represented by strongly deformed S-type granites emplaced at 979-911 Ma, weakly deformed I-type granites at 894-815 Ma, and A-type granites at 759-711 Ma. They can be interpreted as the products of respectively syn-collisional, post-collisional and extensional setting, in response to the assembly and breakup of the Rodinia supercontinent. The Paleozoic magmatism can be temporally classified into three stages of 507-470 Ma, 460-422 Ma and ˜415-400 Ma. They were genetically related to the subduction of the Shangdan Ocean and subsequent collision of the southern North China Block and the South Qinling Belt. The 507-470 Ma magmatism is spatially and temporally related to ultrahigh-pressure metamorphism in the studied area. The 460-422 Ma magmatism with an extensive development in the North Qinling Belt is characterized by I-type granitoids and originated from the lower crust with the involvement of mantle-derived magma in a collisional setting. The magmatism with the formation age of ˜415-400 Ma only occurred in the middle part of the North Qinling Belt and is dominated by I-type granitoid intrusions, and probably formed in the late-stage of a collisional setting. Early Mesozoic magmatism in the study area occurred between 252 and 185 Ma, with the cluster in 225-200 Ma. It took place predominantly in the western part of the South Qinling Belt. The 250-240 Ma I-type granitoids are of small volume and show high Sr/Y ratios, and may have been formed in a continental arc setting related to subduction

  6. Neutron activation analysis system

    DOEpatents

    Taylor, M.C.; Rhodes, J.R.

    1973-12-25

    A neutron activation analysis system for monitoring a generally fluid media, such as slurries, solutions, and fluidized powders, including two separate conduit loops for circulating fluid samples within the range of radiation sources and detectors is described. Associated with the first loop is a neutron source that emits s high flux of slow and thermal neutrons. The second loop employs a fast neutron source, the flux from which is substantially free of thermal neutrons. Adjacent to both loops are gamma counters for spectrographic determination of the fluid constituents. Other gsmma sources and detectors are arranged across a portion of each loop for deterMining the fluid density. (Official Gazette)

  7. Orogenic gold: Common or evolving fluid and metal sources through time

    NASA Astrophysics Data System (ADS)

    Goldfarb, Richard J.; Groves, David I.

    2015-09-01

    generations, many which are not related to ore formation. Radiogenic isotopes, such as those of Pb, Sr, Nd, Sm, and Os, measured on hydrothermal minerals are even more difficult to interpret for defining metal source, particularly as the low-salinity ore fluids transport limited amounts of these elements and significant amounts of these may be locally added to the minerals during alteration reactions at the sites of gold deposition. Noble gas and halogen data are equally equivocal. Fluid exsolution from granitoids emplaced into the upper and middle crust, metamorphism of the crust, or fluids entering trans-crustal fault zones from below the crust all remain as permissive scenarios associated with orogenic gold formation, as the abundant geochemical data are equivocal. However, geological and geochronological data weigh heavily against a magmatic-hydrothermal model in the upper to middle crust. There is no universal temporal association between orogenic gold and magmatism, and where there is an overlap in age, there is no specific type of magmatism consistently associated with gold formation, nor element zonation around any specific pluton. A crustal metamorphic model for fluid and metal sources is very consistent with geological, geochronological, and geochemical data, although metamorphism on a regional scale that releases these components into major fault zones can be associated with many processes along active continental margins. These can include crustal thickening and radiogenic heating, slab rollback and heating during crustal extension, or subduction of a spreading ridge heating the base of an accretionary prism. In rare examples where Phanerozoic orogenic gold deposits are hosted in Precambrian high-grade metamorphic terranes, fluids and metals must, however, enter a transcrustal fault system from a sub-crustal source. This could either be a devolatilized, subducted, relatively flat, perhaps stalled slab and its overlying sediment, or the corner of the fertilized

  8. The St. Elias orogen as an early stage in the development of indentor corners: Initial results from the STEEP project

    NASA Astrophysics Data System (ADS)

    Pavlis, T. L.; Bruhn, R. L.; Koons, P.; Berger, A.; Spotila, J.; Barker, A.; Chapman, J.; Doser, D.; Pavlis, G.

    2006-12-01

    The actively deforming St. Elias orogen of southern Alaska is developed at the transition between the Aleutian trench and the Queen Charlottes transform, and has produced a "one sided" indentor corner as the collided block has been carried obliquely into the subduction-transform transition. A distinctive feature generated within this evolving corner is a 90o bend in the suture at the western edge of the orogen that is associated with a refolding of earlier thin-skinned fold-thrust systems in the collided block. The refolding is recognizable in the area between the bent suture and a major glacial valley, the Bering Glacier, but is absent to the east. Bruhn et al. (2004, GSAB) used this observation to infer an active structure along the Bering Glacier, and speculated that the refolding may be active. New data collected as part of the St. Elias Erosion and tectonics Project (STEEP) provides support for this hypothesis from two observations: 1) clear evidence that many of the hundreds of surface ruptures in this region represent fault-scarps-- probably representing fold-related, bedding- plane slip during refolding; and 2) extremely young (locally <500Ka) U-Th-He apatite cooling ages just west of the Bering Glacier are consistent with the hypothesis of an active structure along the glacial valley. However, young cooling ages to the east of the Bering Glacier as well as geomorphology suggest that at least one of the fold-thrust belt structures is also active, indicating that the interplay of active faults is complex. Additional support for active deformation along the Bering Glacier comes from the spatial distribution of seismicity between the Bering Glacier and Bagley icefield and these observations should be further constrained as data are obtained from the new STEEP broadband seismic network in the area. Analog (sand) and numerical models suggest that this type of feature can originate as the indentor is driven into the corner through a variable vertical axis

  9. European Neutron Activation System.

    2013-01-11

    Version 03 EASY-2010 (European Activation System) consists of a wide range of codes, data and documentation all aimed at satisfying the objective of calculating the response of materials irradiated in a neutron flux. The main difference from the previous version is the upper energy limit, which has increased from 20 to 60 MeV. It is designed to investigate both fusion devices and accelerator based materials test facilities that will act as intense sources of high-energymore » neutrons causing significant activation of the surrounding materials. The very general nature of the calculational method and the data libraries means that it is applicable (with some reservations) to all situations (e.g. fission reactors or neutron sources) where materials are exposed to neutrons below 60 MeV. EASY can be divided into two parts: data and code development tools and user tools and data. The former are required to develop the latter, but EASY users only need to be able to use the inventory code FISPACT and be aware of the contents of the EAF library (the data source). The complete EASY package contains the FISPACT-2007 inventory code, the EAF-2003, EAF-2005, EAF-2007 and EAF-2010 libraries, and the EASY User Interface for the Window version. The activation package EASY-2010 is the result of significant development to extend the upper energy range from 20 to 60 MeV so that it is capable of being used for IFMIF calculations. The EAF-2010 library contains 66,256 reactions, almost five times more than in EAF-2003 (12,617). Deuteron-induced and proton-induced cross section libraries are also included, and can be used with EASY to enable calculations of the activation due to deuterons and proton [2].« less

  10. Deep Seismic Reflection Profiles Reveal The Crust Structures Beneath Xing'an-Mongolian Orogenic Belt and Its Neighboring Area

    NASA Astrophysics Data System (ADS)

    Hou, H.; Gao, R.; Keller, R. G.; Li, Q.; Li, W.; Li, H.; Xiong, X.; Guo, L.

    2012-12-01

    The Xing'an-Mongolia orogenic belt (XMOB) as the eastern part of the CAOB (Central Asian Orogenic Belt) is one of the remarkably reworked and crustal accretionary belts during the Phanerozoic in the world. It is located between the northern margin of the North China craton and the southern margin of the Siberia craton and is characterized by large-scale Mesozoic magmatism, and forms a key part of the NE-trending Mesozoic magmatic belt in East China. Therefore, it will be of great importance to study the contact relationship between these blocks, which will prodive important information on the study of mineralization and assessment of earthquake disaster. A major problem with all previous publications on Xing'an-Mongolian Orogenic belt was the lack of a seismic section which could potentially image the zone or the dominant vergence of crustal structures at depth. In the view of above, deep seismic profiling data acquisition finished in last three years and the newly processing seismic reflection profiles in this belt were possible under the support of SinoProbe project and China Geological Survey. As we not only focuse on the deep structures of crust, but also carry about the relationships between the shallow reflection fabrics with surface geology. Therefore, different with oil industrial data accquistion, we develop some deep seismic reflection techniques such as three levels of explosive shots were adopted for enough energy reflected from all crust, long offset with single side length of 15 km on symmetrical for the modeling of shallow crust by use of tomographic method, meanwhile we share the shots large than 500 kg with seismic refraction survey line providing more rays for modeling deep velocity strucutre. The seismic reflection data were mainly using the seismic processing package ProMAX and the CGG processing system, following the processing steps with special methods such as tomographic inversion static corrections, surface-consistent amplitude compensation

  11. Extreme mass flux from the glaciated, collisional St. Elias Orogen: Preliminary results from IODP Expedition 341 (Invited)

    NASA Astrophysics Data System (ADS)

    Gulick, S. P.; Jaeger, J. M.

    2013-12-01

    Integrated Ocean Drilling Program Expedition 341 drilled a cross-margin transect to investigate the linkages between global climate change, modification of the dynamics of surficial processes, and subsequent tectonic responses. The Gulf of Alaska (GoA) borders the St. Elias orogen, the highest coastal mountain range on Earth. Exp. 341 drilled five sites within a regional seismic reflection grid that spans from the distal Surveyor Fan to the continental shelf. More than 3000 m of high-quality core coupled with seismic reflection profiles collected with nested vertical resolution allows us to address the major objectives of drilling in the GoA. These objectives were to: 1) document the tectonic response of an active orogenic system to late Miocene to recent climate change; 2) establish the timing of advance/retreat phases of the northern Cordilleran ice sheet to test its relation to dynamics of other global ice sheets; 3) implement an expanded source-to-sink study of the interactions between glacial, tectonic, and oceanographic processes responsible for creation of one of the thickest Neogene high-latitude continental margin sequences; 4) understand the dynamics of productivity, nutrients, freshwater input to the ocean, and ocean circulation in the northeast Pacific and their role in the global carbon cycle, and 5) document the spatial and temporal behavior of the geomagnetic field at extremely high temporal resolution in an under-sampled region of the globe. The Exp. 341 cross-margin transect discovered transitions in sediment accumulation rates from >100 m/Ma at the distal site to > 1000 m/Ma in the proximal fan, slope and on the continental shelf that provide a telescoping view of strata formation from the Miocene to the Holocene. Complete recovery and development of spliced sedimentary records of the Pleistocene through Holocene were achieved at the distal, proximal, and slope Sites U1417, U1418, and U1419, respectively, because of exceptional piston core

  12. Sources of ore-forming fluids and formation environments of orogenic Au deposits in the Main Uralian Fault zone (Southern Urals)

    NASA Astrophysics Data System (ADS)

    Znamenskii, S. E.; Puchkov, V. N.; Michurin, S. V.

    2015-09-01

    The analysis of stable S, C, and O isotopes in minerals combined with the results of structural studies of orogenic gold deposits in carbonaceous shales of the Main Uralian Fault in the South Urals reveals that orogenic gold mineralization was formed during two stages of Late Paleozoic collisional deformations: early (thrust formation) and late (wrench faulting). The leading role in hydrothermal ore-forming systems of the first stage belonged to fluids of metamorphic origin, while at the second sage they were magmatogenic.

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

    USGS Publications Warehouse

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

    2000-01-01

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

  14. Paleozoic Orogens of Mexico and the Laurentia-Gondwana Connections: an Update

    NASA Astrophysics Data System (ADS)

    Ortega-Gutierrez, F.

    2009-05-01

    The present position of Mexico in North America and the fixist tectonic models that prevailed prior to the seventies of the past century, have considered the main Paleozoic tectonic systems of Mexico as natural extensions of the orogens that fringed the eastern and southern sides of the Laurentian craton. Well known examples of pre-Mesozoic orogens in Mexico are the Oaxacan, Acatlan, and Chiapas polymetamorphic terranes, which have been correlated respectively with the Grenville and Appalachian-Ouachitan orogens of eastern North America. Nonetheless, several studies conducted during the last decade in these Mexican orogenic belts, have questioned their Laurentian connections, regarding northwestern Gondwana instead as the most plausible place for their birth and further tectonic evolution. This work pretends to approach the problem by briefly integrating the massive amount of new geological information, commonly generated through powerful dating methods such as LA-ICPM-MS on detrital zircon of sedimentary and metasedimentary units in the Paleozoic crustal blocks, which are widely exposed in southern and southeastern Mexico. The Acatlan Complex bears the closest relationships to the Appalachian orogenic system because it shows thermotectonic evidence for opening and closure of the two main oceans involved in building the Appalachian mountains in eastern Laurentia, whereas two other Paleozoic terranes in NW and SE Mexico, until recently rather geologically unknown, may constitute fundamental links between the Americas for the last-stage suturing and consolidation of western Pangea. The buried basement of the Yucatan platform (400,000 squared km) on the other hand, remains as one of the most relevant problems of tectonostratigraphic correlations across the Americas, because basement clasts from the Chicxulub impact ejecta reveal absolute and Nd-model ages that suggest close Gondwanan affinities. Major changes in the comprehension of the Paleozoic orogens in Mexico

  15. The deep structure of Alpine-type orogens: how important is rift-inheritance?

    NASA Astrophysics Data System (ADS)

    Tugend, Julie; Manatschal, Gianreto; Mohn, Geoffroy

    2016-04-01

    Collisional belts are commonly thought to result from the closure of oceanic basins and subsequent inversion of former rifted margins. The formation and evolution of collisional belts should therefore be closely interlinked with the initial architecture of former rifted margins. Reflection and refraction seismic data from present-day magma-poor rifted margins show the omnipresence of hyperextended domains (severely thinned continental crust (<10 km) and/or exhumed serpentinized mantle with minor magmatic additions) between unequivocal continental and oceanic domains. Integrating these new observations and exploring their impact on mountain building processes may result in alternative interpretations of the lithospheric structure of collisional orogens. We focus on the Pyrenees and Western to Central Alps, respectively resulting from the inversion of a Late Jurassic to Mid Cretaceous and an Early to Mid Jurassic rift system eventually floored by hyperextended crust, exhumed mantle or proto-oceanic crust. The rift-related pre-collisional architecture of the Pyrenees shows many similarities with that proposed for the Alps; although the width of the hyperextended and in particular of the proto-oceanic domains is little constrained. Contrasting with the Pyrenees, remnants of these domains are largely affected by orogeny-related deformation and show a HP-LT to HT-MP metamorphic overprint in the Alps. Nevertheless, in spite of the occurrence of these highly deformed and metamorphosed rocks constituting the internal parts of the Alps, the overall crustal and lithospheric structure looks surprisingly comparable. High resolution tomographic images across both orogens unravel the occurrence of a velocity anomaly dipping underneath the internal domains and progressively attenuated at depth that we interpret as former hyperextended domains subducted/underthrusted during collision. This interpretation contrasts with the classical assumption that the subducted material is made of

  16. Technology Systems. Laboratory Activities.

    ERIC Educational Resources Information Center

    Brame, Ray; And Others

    This guide contains 43 modules of laboratory activities for technology education courses. Each module includes an instructor's resource sheet and the student laboratory activity. Instructor's resource sheets include some or all of the following elements: module number, course title, activity topic, estimated time, essential elements, objectives,…

  17. Basin-mountain structures and hydrocarbon exploration potential of west Junggar orogen in China

    NASA Astrophysics Data System (ADS)

    Wu, Xiaozhi; He, Dengfa; Qi, Xuefeng

    2016-04-01

    Situated in northern Xinjiang, China, in NE-SW trend, West Junggar Orogen is adjacent to Altai fold belt on the north with the Ertix Fault as the boundary, North Tianshan fold belt on the south with the Ebinur Lake Strike-slip Fault as the boundary, and the Junggar Basin on the southeast with Zaire-Genghis Khan-Hala'alat fold belt as the boundary. Covering an area of about 10×104 km2 in China, there are medium and small intermontane basins, Burqin-Fuhai, Tacheng, Hefeng and Hoxtolgay, distributing inside the orogen. Tectonically West Junggar Orogen lies in the middle section of the Palaeo-Asian tectonic domain where the Siberia, Kazakhstan and Tarim Plates converge, and is the only orogen trending NE-SW in the Palaeo-Asian tectonic domain. Since the Paleozoic, the orogen experienced pre-Permian plate tectonic evolution and post-Permian intra-plate basin evolution. Complex tectonic evolution and multi-stage structural superimposition not only give rise to long term controversial over the basin basement property but also complex basin-mountain coupling relations, structures and basin superimposition modes. According to analysis of several kinds of geological and geophysical data, the orogen was dominated by compressive folding and thrust napping from the Siberia plate in the north since the Late Paleozoic. Compressive stress weakened from north to south, corresponding to subdued vertical movement and enhanced horizontal movement of crustal surface from north to south, and finally faded in the overthrust-nappe belt at the northwest margin of the Junggar Basin. The variation in compressive stress is consistent with the surface relief of the orogen, which is high in the north and low in the south. There are two kinds of basin-mountain coupling relationships, i.e. high angle thrusting and overthrusting and napping, and two kinds of basin superimposition modes, i.e. inherited and progressive, and migrating and convulsionary modes. West Junggar orogen has rich oil and gas

  18. Linking magmatism with collision in an accretionary orogen

    PubMed Central

    Li, Shan; Chung, Sun-Lin; Wilde, Simon A.; Wang, Tao; Xiao, Wen-Jiao; Guo, Qian-Qian

    2016-01-01

    A compilation of U-Pb age, geochemical and isotopic data for granitoid plutons in the southern Central Asian Orogenic Belt (CAOB), enables evaluation of the interaction between magmatism and orogenesis in the context of Paleo-Asian oceanic closure and continental amalgamation. These constraints, in conjunction with other geological evidence, indicate that following consumption of the ocean, collision-related calc-alkaline granitoid and mafic magmatism occurred from 255 ± 2 Ma to 251 ± 2 Ma along the Solonker-Xar Moron suture zone. The linear or belt distribution of end-Permian magmatism is interpreted to have taken place in a setting of final orogenic contraction and weak crustal thickening, probably as a result of slab break-off. Crustal anatexis slightly post-dated the early phase of collision, producing adakite-like granitoids with some S-type granites during the Early-Middle Triassic (ca. 251–245 Ma). Between 235 and 220 Ma, the local tectonic regime switched from compression to extension, most likely caused by regional lithospheric extension and orogenic collapse. Collision-related magmatism from the southern CAOB is thus a prime example of the minor, yet tell-tale linking of magmatism with orogenic contraction and collision in an archipelago-type accretionary orogen. PMID:27167207

  19. Linking magmatism with collision in an accretionary orogen

    NASA Astrophysics Data System (ADS)

    Li, Shan; Chung, Sun-Lin; Wilde, Simon A.; Wang, Tao; Xiao, Wen-Jiao; Guo, Qian-Qian

    2016-05-01

    A compilation of U-Pb age, geochemical and isotopic data for granitoid plutons in the southern Central Asian Orogenic Belt (CAOB), enables evaluation of the interaction between magmatism and orogenesis in the context of Paleo-Asian oceanic closure and continental amalgamation. These constraints, in conjunction with other geological evidence, indicate that following consumption of the ocean, collision-related calc-alkaline granitoid and mafic magmatism occurred from 255 ± 2 Ma to 251 ± 2 Ma along the Solonker-Xar Moron suture zone. The linear or belt distribution of end-Permian magmatism is interpreted to have taken place in a setting of final orogenic contraction and weak crustal thickening, probably as a result of slab break-off. Crustal anatexis slightly post-dated the early phase of collision, producing adakite-like granitoids with some S-type granites during the Early-Middle Triassic (ca. 251–245 Ma). Between 235 and 220 Ma, the local tectonic regime switched from compression to extension, most likely caused by regional lithospheric extension and orogenic collapse. Collision-related magmatism from the southern CAOB is thus a prime example of the minor, yet tell-tale linking of magmatism with orogenic contraction and collision in an archipelago-type accretionary orogen.

  20. Rotund versus skinny orogens: Well-nourished or malnourished gold?

    USGS Publications Warehouse

    Goldfarb, R.J.; Groves, D.I.; Gardoll, S.

    2001-01-01

    Orogenic gold vein deposits require a particular conjunction of processes to form and be preserved, and their global distribution can be related to broad-scale, evolving tectonic processes throughout Earth history. A heterogeneous distribution of formation ages for these mineral deposits is marked by two major Precambrian peaks (2800-2555 Ma and 2100-1800 Ma), a singular lack of deposits for 1200 m.y. (1800-600 Ma), and relatively continuous formation since then (after 600 Ma). The older parts of the distribution relate to major episodes of continental growth, perhaps controlled by plume-influenced mantle overturn events, in the hotter early Earth (ca. 1800 Ma or earlier). This worldwide process allowed preservation of gold deposits in cratons, roughly equidimensional, large masses of buoyant continental crust. Evolution to a less episodic, more continuous, modern-style plate tectonic regime led to the accretion of volcano-sedimentary complexes as progressively younger linear orogenic belts sorrounding the margins of the more buoyant cratons. The susceptibility of these linear belts to uplift and erosion can explain the overall lack of orogenic gold deposits at 1800-600 Ma, their exposure in 600-50 Ma orogens, the increasing importance of placer deposits back through the Phanerozoic since ca. 100 Ma, and the absence of gold deposits in orogenic belts younger than ca. 50 Ma.

  1. Linking magmatism with collision in an accretionary orogen.

    PubMed

    Li, Shan; Chung, Sun-Lin; Wilde, Simon A; Wang, Tao; Xiao, Wen-Jiao; Guo, Qian-Qian

    2016-01-01

    A compilation of U-Pb age, geochemical and isotopic data for granitoid plutons in the southern Central Asian Orogenic Belt (CAOB), enables evaluation of the interaction between magmatism and orogenesis in the context of Paleo-Asian oceanic closure and continental amalgamation. These constraints, in conjunction with other geological evidence, indicate that following consumption of the ocean, collision-related calc-alkaline granitoid and mafic magmatism occurred from 255 ± 2 Ma to 251 ± 2 Ma along the Solonker-Xar Moron suture zone. The linear or belt distribution of end-Permian magmatism is interpreted to have taken place in a setting of final orogenic contraction and weak crustal thickening, probably as a result of slab break-off. Crustal anatexis slightly post-dated the early phase of collision, producing adakite-like granitoids with some S-type granites during the Early-Middle Triassic (ca. 251-245 Ma). Between 235 and 220 Ma, the local tectonic regime switched from compression to extension, most likely caused by regional lithospheric extension and orogenic collapse. Collision-related magmatism from the southern CAOB is thus a prime example of the minor, yet tell-tale linking of magmatism with orogenic contraction and collision in an archipelago-type accretionary orogen. PMID:27167207

  2. Strong imprint of past orogenic events on the thermochronological record

    NASA Astrophysics Data System (ADS)

    Braun, Jean

    2016-06-01

    Using a simple solution to the heat conduction equation, I show how, at the end of an orogenic event, the relaxation of isotherms from a syn-orogenic advection-dominated geometry to a post-orogenic conduction-dominated geometry leads to the creation of a thick iso-age crustal layer. Subsequent erosion of this layer yields peculiar age-elevation profiles and detrital age distributions that cannot be easily interpreted using traditional techniques. I illustrate these points by using a simple analytical solution of the heat equation as well as a transient, three-dimensional numerical model. I also demonstrate that the age of the end of an orogenic event is so strongly imprinted in the thermochronological record that it erases most of the information pertaining to the orogenic phase itself and the subsequent isostatically-driven exhumation. The concept is used to explain two thermochronological datasets from the Himalayas and demonstrate that their most likely interpretation involves the sudden interruption of extremely fast exhumation accommodated by movement along the South Tibetan Detachment in the Higher Himalayas around 15 Ma.

  3. Non-tectonic base level forcings drive widespread transient incision and relief production in the waning Appalachian orogen

    NASA Astrophysics Data System (ADS)

    Prince, P. S.; Richardson, R. P.

    2012-12-01

    The development of knickpoints and steep bedrock gorges within otherwise low-relief landscapes of the Appalachian Highlands has long interested geomorphologists. While large tracts of muted Appalachian topography appear consistent with slow, steady exhumation of a thickened crustal root, active gorge development into lower-relief uplands suggests that Appalachian river systems have been re-energized to incise into bedrock and increase relief. Orogen-scale analysis of incision patterns, fluvial profiles, and surficial deposits indicate that two main sources of non-tectonic base level drop superimposed on the slowly-exhuming Appalachian landscape can explain the Cenozoic relief production observed. Along the Eastern Continental Divide on the southeast margin of the Highlands, repeated capture of headwaters of elevated, landward-draining streams of the Blue Ridge by Atlantic basin streams maintains the oversteepened slopes and bedrock gorges of the Blue Ridge Escarpment zone. Capture events induce a transient erosional response in which rapid knickpoint retreat carves deep gorges into the captured basin, ultimately adjusting topography to match the rest of the Atlantic slope. In the lower reaches of landward Appalachian rivers still following courses to the continental interior, hillslope steepening in the wake of migrating knickpoints is apparent against the backdrop of a comparatively low-relief upland. This landscape suggests that landward base level drop, possibly due to rapid, glacially-forced Plio-Pleistocene drainage rearrangement, has initiated transgressive waves of incision to adjust Highlands topography to the recently-established continental interior drainage pattern. Encroachment of both the post-rift seaward base level and the modern landward base level forces a rapid release of potential energy stored in the elevated Highlands, energizing streams to incise into bedrock without the introduction of new tectonic energy. The southern Appalachian landscape

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

    NASA Astrophysics Data System (ADS)

    Brown, M.

    2004-05-01

    Orogens record evidence of interaction between converging plates. However, the response of continental crust to tectonic and gravitational loads is dependent on rheology, which is influenced by composition, architecture, thermal profile and strain rate. Crustal rocks undergo melting in deeper parts of orogens. Greywackes and metapelites are the most fertile protoliths, generating 20-50 and 30 vol. % melt respectively at 1 GPa and 1173K; geophysical data suggest >6 but <20 vol. % interconnected melt in deep crust of active orogens. In numerical models of orogens, the transition from coupled doubly-vergent wedge structure to plateau formation and full basal decoupling requires a viscosity drop of 4 orders of magnitude, inferred to be melt weakening. Deformation experiments on granite indicate a dramatic drop in strength (to 100-200 MPa) as the melt wetting transition is approached at 7 vol. % melt, and a more gradual decrease to <1 MPa prior to the drop at the solid-to-liquid transition (RCMP). Important properties of melting systems are viscosity of the melt, rheology of the crystalline framework of grains and permeability of this framework to flow. Permeability is due to an intergranular network of connected pores, compositional layering/fabric and networks of deformation bands; melt distribution is heterogeneous on multiple length scales. The microstructure of anatectic rocks and the magnitude of weakening accompanying melting suggest a limited role for intracrystalline plasticity with increasing vol. % melt and dominance of melt-assisted diffusion creep or diffusion accommodated granular flow. The intrinsic weakness of melt-bearing intervals in the crust makes them ideal detachment horizons. Observations from metasedimentary migmatitic granulites show preservation of (i) early fabrics, suggesting that the strain field emergent under subsolidus conditions controlled initial distribution of melt produced by suprasolidus mica breakdown, and (ii) layering in melt

  5. Cumberland batholith, Trans-Hudson Orogen, Canada: Petrogenesis and implications for Paleoproterozoic crustal and orogenic processes

    NASA Astrophysics Data System (ADS)

    Whalen, Joseph B.; Wodicka, Natasha; Taylor, Bruce E.; Jackson, Garth D.

    2010-06-01

    Large volume, plutonic belts, such as the ˜ 221,000 km 2, ca. 1.865-1.845 Ga Cumberland batholith (CB) of the Trans-Hudson Orogen in Canada, are major components of Paleoproterozoic orogenic belts. In many cases, they have been interpreted as continental arc batholiths. The petrogenesis and tectonic context of the CB and implications for crustal growth and recycling are interpreted herein based on a 900 km geochemical-isotopic (Nd-O) transect across it and into granitoid plutons within bounding Archean cratons in central and southern Baffin Island. The mainly granulite grade CB, emplaced over an age span of between 14 and 24 Ma, consists mainly of high-K to shoshonitic monzogranite and granodiorite, but also includes low- and medium-K granitoid rocks. Metaluminous to slightly peraluminous compositions and δ 18O (VSMOW) values (+ 6 to + 10‰) indicate derivation from infracrustal (I-type) sources. ɛ Nd 1.85 Ga signatures (- 12 to - 2) of both mafic and felsic units suggest a dominance of evolved sources. Isotopic signatures in the interior of the CB (- 2 to - 7) are more radiogenic than those within Archean domains in central (- 8 to - 15) and southern (- 5 to - 19) Baffin Island. The isotopic transect is interpreted as 'imaging' an accreted microcontinental block (Meta Incognita) and bounding Archean cratons. The CB includes granites of arc, within-plate (A-type) and post-collisional affinity and volumetrically minor mafic rocks with both arc and non-arc features. (La/Yb) CN and Sr/Y values range from < 1 to 225 and < 1 to 611, respectively. In these respects, some CB granitoid rocks resemble Paleozoic adakitic granites, interpreted as partial melts of greatly thickened crust within post-collisional settings, such as Tibet. Thus, the CB likely encompasses various non-consanguineous magmatic suites generated at deep- to mid-crustal depths. Although CB granitoid rocks undoubtedly had important crustal sources, it is hard to assess the relative contribution of

  6. How Orogen-scale Exhumed Strike-slip Faults Initiate

    NASA Astrophysics Data System (ADS)

    Cao, S.; Neubauer, F.

    2015-12-01

    Orogen-scale strike-slip faults present one the most important geodynamic processes affecting the lithosphere-asthenosphere system. In specific subtypes, faulting is virtually initiated along hot-to-cool boundaries, e.g. at such of hot granite intrusions or metamorphic core complexes to cool country rocks. Such fault zones are often subparallel to mountain ranges and expose a wide variety of mylonitic, cataclastic and non-cohesive fault rocks, which were formed at different structural levels of the crust and are stacked within each other ("telescoping"). Exhumation of rocks is, therefore, a common feature of such strike-slip faults implying major transtensive and/or transpressive processes accompanying pure strike-slip motion. The hot-to-cool thermal structure across the fault zone significantly influences the physical fault rock properties. One major question is how and where a major strike-slip initiates and further development. Here, we propose a model in which major continental exhumed strike-slip faults potentially evolve along rheologically weak zones such as plutons or margins of metamorphic complexes. As an example, we propose a model for the Ailao Shan-Red River (ASRR) fault, SE Asia, which initiated along the edge of a plutonic belt and evolved in response to India-Asia collision with four tectonic phases.

  7. Portable active interrogation system.

    SciTech Connect

    Moss, C. E.; Brener, M. W.; Hollas, C. L.; Myers, W. L.

    2004-01-01

    The system consists of a pulsed DT neutron generator (5 x 10{sup 7} n/s) and a portable but high intrinsic efficiency, custom-designed, polyethylene-moderated {sup 3}He neutron detector. A multichannel scaler card in a ruggedized laptop computer acquires the data. A user-friendly LabVIEW program analyzes and displays the data. The program displays a warning message when highly enriched uranium or any other fissionable materials is detected at a specified number of sigmas above background in the delayed region between pulses. This report describes the system and gives examples of the response of the system to highly enriched uranium and some other fissionable materials, at several distances and with various shielding materials.

  8. Tandem suturing and disarticulation of the Taiwan orogen revealed by its neotectonic elements

    NASA Astrophysics Data System (ADS)

    Shyu, J. Bruce H.; Sieh, Kerry; Chen, Yue-Gau

    2005-04-01

    Taiwan's numerous active faults and folds demarcate distinct eastern and western neotectonic belts. The western belt results from the attachment and subsequent detachment of a sliver of continental lithosphere to the Eurasian continental margin. The eastern belt is the product of the same continental sliver docking with and then separating from the Luzon volcanic arc. Thus, the active Taiwan orogen is a tandem suturing and tandem disengagement of a volcanic arc and a continental sliver to and from the Eurasian continental margin. This progressive suturing and separation is a superb, living demonstration of the fundamental weakness of lithospheric sutures. Furthermore, this neotectonic architecture provides the basis for understanding the Taiwan's seismic sources.

  9. Window into the Caledonian orogen: Structure of the crust beneath the East Shetland platform, United Kingdom

    USGS Publications Warehouse

    McBride, J.H.; England, R.W.

    1999-01-01

    Reprocessing and interpretation of commercial and deep seismic reflection data across the East Shetland platform and its North Sea margin provide a new view of crustal subbasement structure beneath a poorly known region of the British Caledonian orogen. The East Shetland platform, east of the Great Glen strike-slip fault system, is one of the few areas of the offshore British Caledonides that remained relatively insulated from the Mesozoic and later rifting that involved much of the area around the British Isles, thus providing an "acoustic window" into the deep structure of the orogen. Interpretation of the reflection data suggests that the crust beneath the platform retains a significant amount of its original Caledonian and older architecture. The upper to middle crust is typically poorly reflective except for individual prominent dipping reflectors with complex orientations that decrease in dip with depth and merge with a lower crustal layer of high reflectivity. The three-dimensional structural orientation of the reflectors beneath the East Shetland platform is at variance with Caledonian reflector trends observed elsewhere in the Caledonian orogen (e.g., north of the Scottish mainland), emphasizing the unique tectonic character of this part of the orogen. Upper to middle crustal reflectors are interpreted as Caledonian or older thrust surfaces that were possibly reactivated by Devonian extension associated with post-Caledonian orogenic collapse. The appearance of two levels of uneven and diffractive (i.e., corrugated) reflectivity in the lower crust, best developed on east-west-oriented profiles, is characteristic of the East Shetland platform. However, a north-south-oriented profile reveals an interpreted south-vergent folded and imbricated thrust structure in the lower crust that appears to be tied to the two levels of corrugated reflectivity on the east-west profiles. A thrust-belt origin for lower crustal reflectivity would explain its corrugated

  10. The boundary between the eastern and western domains of the Pyrenean Orogen: a Cenozoic triple junction zone in Iberia?

    NASA Astrophysics Data System (ADS)

    Tavani, S.

    2012-04-01

    The Cantabrian Transitional Area (CTA) is located in the eastern portion of the Cantabrian Mountain Range of the northern Spain. It represents the most important internal boundary within the Upper Cretaceous to Cenozoic E-W elongated Pyrenean Orogen. In the south-verging portion of this orogen, the CTA divides the western thick-skinned Cantabrian Domain, which accommodated for a limited portion of the total N-S oriented orogenic shortening, from the Pyrenean realm to the east, where the south-verging frontal structures are characterised by a marked thiN-Skin style of deformation, and significantly contributed to accommodate the total shortening. In the Cantabrian Transitional Area, Cenozoic syn-orogenic left-lateral, right-lateral and reverse dip-slip movements have occurred along different directions, postdating early-orogenic extensional structures. The latter indicate that the southern portion of the study area formed the eastern termination of the northward concave roughly E-W oriented proto Duero Foreland Basin. This basin was flanked to the north by the thick-skinned proto Cantabrian Belt, which included in its easternmost part the northern portion of the Cantabrian Transitional Area. Onset of right-lateral strike-slip tectonics along the WNW-ESE striking Ubiernal-Venatniella Fault System, which locates to the SW of the CTA and crosses the entire Cantabrian Belt and its formerly southern foreland basin, caused the dislocation of the belt-foredeep system. Contextually, thiN-Skinned structures belonging to the eastern domain of the Pyrenean Orogen laterally propagated and incorporated the eastern part of the proto Duero Foreland Basin. Coexistence of right-lateral and reverse movements to the west and to the east, respectively, determined the onset of an intrabelt compression at the boundary between the Cantabrian and Pyrenean domains, which was the ultimate act of the fusion of the two domains into a single orogen. Paradoxically, this fusion has basically

  11. Hillslope response to knickpoint migration in the Southern Appalachians: Implications for the evolution of post-orogenic landscapes

    USGS Publications Warehouse

    Wegmann, S.F.G.; Franke, K.L.; Hughes, S.; Lewis, R.Q.; Lyons, N.; Paris, P.; Ross, K.; Bauer, J.B.; Witt, A.C.

    2011-01-01

    The southern Appalachians represent a landscape characterized by locally high topographic relief, steep slopes, and frequent mass movement in the absence of significant tectonic forcing for at least the last 200 Ma. The fundamental processes responsible for landscape evolution in a post-orogenic landscape remain enigmatic. The non-glaciated Cullasaja River basin of south-western North Carolina, with uniform lithology, frequent debris flows, and the availability of high-resolution airborne lidar DEMs, is an ideal natural setting to study landscape evolution in a post-orogenic landscape through the lens of hillslope-channel coupling. This investigation is limited to channels with upslope contributing areas >2.7 km2, a conservative estimate of the transition from fluvial to debris-flow dominated channel processes. Values of normalized hypsometry, hypsometric integral, and mean slope vs elevation are used for 14 tributary basins and the Cullasaja basin as a whole to characterize landscape evolution following upstream knickpoint migration. Results highlight the existence of a transient spatial relationship between knickpoints present along the fluvial network of the Cullasaja basin and adjacent hillslopes. Metrics of topography (relief, slope gradient) and hillslope activity (landslide frequency) exhibit significant downstream increases below the current position of major knickpoints. The transient effect of knickpoint-driven channel incision on basin hillslopes is captured by measuring the relief, mean slope steepness, and mass movement frequency of tributary basins and comparing these results with the distance from major knickpoints along the Cullasaja River. A conceptual model of area-elevation and slope distributions is presented that may be representative of post-orogenic landscape evolution in analogous geologic settings. Importantly, the model explains how knickpoint migration and channel- hillslope coupling is an important factor in tectonically-inactive (i

  12. Rift inheritance in orogenes: a case study from the Western Pyrenees

    NASA Astrophysics Data System (ADS)

    Masini, E.; Manatschal, G.; Tugend, J.; Kusznir, N. J.; Flament, J.

    2012-12-01

    In plate tectonics, there is a general assumption that rifted margins represent most of the former material accreted into collisional orogenic prisms. In this regard, the former architecture, structures and composition of rifted margins, i.e. the pre-orogenic inheritances, play undoubtedly a major role during tectonic inversion. Studies have shown that rifted margins are more complex than a succession of tilted blocks. Indeed, the discovery of hyper-extended domains, where low-angle detachments replace high-angle normal faults and mantle material is exhumed to the seafloor implies a revision of the margin's template used in orogenic models. Because of overprint, the role of rift inheritance in orogenes remains often underestimated. The Pyrenees, located along the Iberian-European plate boundary, can be considered as one of the best places to study the reactivation of hyper-extended rifts. In this orogen, the Late Cretaceous and Tertiary convergence overprints a Latest Jurassic to Lower Cretaceous intracontinental rift linked with the opening of the North Atlantic. There, Albian hyper-extended rift basins developed where deep crustal and mantle rocks were exhumed along low-angle detachments to the seafloor. In this work we discuss the example of the Mauléon-Arzacq domain, which escaped from the most pervasive deformation because of its specific location between the western termination of the chain and the Bay of Biscay oceanic domain. Combining field study with subsurface geophysical and drillhole data, we show that the overall rift domain is asymmetric. The northern European upper plate is on the hangingwall of low-angle detachment systems affecting the southern Iberian Lower plate. The upper plate records depth-dependent crustal thinning and the development of a syn-rift sag basin. In contrast, the lower plate resulted from the hyper-extension of Iberian continental crust accommodated at the surface by two diachronous top-basement detachment systems. The first

  13. Orogenic plateau growth in the Zagros of Iran

    NASA Astrophysics Data System (ADS)

    Allen, Mark; Blanc, Eric; Saville, Christopher

    2010-05-01

    This paper concerns how Turkish-Iranian plateau grows by incorporating the Zagros fold and thrust belt. The plateau's tectonic boundary can be defined as the limit of significant seismogenic thrusting, which occurs close to the regional 1 km elevation contour. The geomorphic boundary is less distinct, but occurs northeast of the limit of active thrusting, because of a time lag during which mountainous relief converts to the subdued plateau geomorphology. Most of the High Zagros and ~25,000 km2 of the Zagros Simple Folded Zone behave as part of the plateau. The Dezful Embayment is a low strain zone in the western Zagros Simple Folded Zone, implying locally strong basement. Deformation is correspondingly more intense northeast of the Embayment, where the highest elevations and steepest slopes in the Zagros occur. As a consequence of the Embayment, lateral plateau growth is more limited in the western Zagros than the east (Fars). A more uniform structure across the Fars region has produced a lower orogenic taper, and a wider region of the Zagros behaves as part of the Turkish-Iranian plateau. Climatic variation along the Zagros is likely to act as a positive feedback on this tectonic variation, although the rates are not well-constrained. Relatively high orographic precipitation northeast of the Dezful Embayment promotes exhumation. The more arid climate in the Fars region should subdue exhumation, implying quicker crustal thickening and elevation for any given shortening. This enhances lateral plateau growth. Regional plateau elevations >1 km may relate to underlying warm and partially molten mantle.

  14. Active Response Gravity Offload System

    NASA Technical Reports Server (NTRS)

    Valle, Paul; Dungan, Larry; Cunningham, Thomas; Lieberman, Asher; Poncia, Dina

    2011-01-01

    The Active Response Gravity Offload System (ARGOS) provides the ability to simulate with one system the gravity effect of planets, moons, comets, asteroids, and microgravity, where the gravity is less than Earth fs gravity. The system works by providing a constant force offload through an overhead hoist system and horizontal motion through a rail and trolley system. The facility covers a 20 by 40-ft (approximately equals 6.1 by 12.2m) horizontal area with 15 ft (approximately equals4.6 m) of lifting vertical range.

  15. Exhumed Himalayan-type syntaxis in the Grenville orogen, northeastern Laurentia

    NASA Astrophysics Data System (ADS)

    Gates, Alexander E.; Valentino, David W.; Chiarenzelli, Jeffrey R.; Solar, Gary S.; Hamilton, Michael A.

    2004-04-01

    A deep-seated analog of the syntaxis developed in the Tibetan Plateau occurs in the Grenville Orogen of eastern Laurentia. During the final assembly of Rodinia, Amazonia collided with Laurentia and produced a series of large, conjugate, transcurrent, shear systems and pervasive strike-slip deformation that overprinted compressional structures related to the Ottawan Orogeny (the last orogenic phase of what is considered Grenvillian). A northeast-striking dextral system at least 35-km wide developed in the Reading Prong of New York (locally known as the Hudson Highlands), New Jersey, and Pennsylvania. U-Pb SHRIMP zircon geochronology and Ar/Ar thermochronology on the lowest grade cataclasites constrain the age of movement between 1008 and 876 Ma. A 60-km-wide, east-west striking, sinistral shear system developed across the central Adirondack Highlands. This system overprints rocks with granulite-facies metamorphic assemblages containing ca. 1050 Ma metamorphic zircons and is cut by a swarm of 950 Ma leucogranites. The timing, geometric relationships, and shear sense of the Adirondacks and Reading Prong shear systems suggest a conjugate system within a syntaxis with bulk compression directed ENE-WSW. This tectonic scenario invokes a component of strike-parallel deformation during the Ottawan Orogeny and provides a kinematic mechanism for an otherwise enigmatic, synchronous, late (ca. 930 Ma) extensional event including the Carthage-Colton mylonite zone in the northwest Adirondacks and Canada.

  16. The JET Neutron Activation System

    NASA Astrophysics Data System (ADS)

    Roquemore, A. L.; Bertalot, L.; Esposito, B.; Jarvis, O. N.; Loughlin, M. J.; Sadler, G.; van Belle, P.

    1997-11-01

    The JET activation system provides the absolute value of the neutron yields as well as a check on the linearity of other neutron detector systems. The total neutron yield is standardized to one irradiation end reentrant in the top of the vessel, while the results from the other seven irradiation ends are normalized to this standard end and provide redundancy as well as information on the plasma position. A pneumatic transfer system is used to transfer up to five capsules containing elemental foils for a single discharge on JET. Eleven different elemental foils have been utilized to determine the yields from both DD and DT plasmas. By placing several different foils with different activation energy thresholds in a single capsule for one DT discharge, neutron spectral information has been obtained by use of the SAND-II unfolding code. A description of the activation system hardware and calibration of the activation detector system will be presented along with the results from the DT neutron calibration campaign.

  17. Sedimentary basin evolution and the link with the deformation of surrounding orogens in European case-studies

    NASA Astrophysics Data System (ADS)

    Matenco, Liviu

    2014-05-01

    major extensional structures during the subsequent back-arc evolution. In all these areas, understanding the quantitative evolution of sedimentary basins means critically the understanding of the exhumation of surrounding mountains and subsequent sediment routing. All these findings demonstrate that the legacy of defining strain localization and rheological contrast at regional level driven by orogenic activity or activation of extensional basins is larger that commonly thought. References Ziegler, P.A., Cloetingh, S., van Wees, J.-D., 1995. Dynamics of intra-plate compressional deformation: the Alpine foreland and other examples. Tectonophysics 252, 7-22. Ziegler, P.A., van Wees, J.-D., Cloetingh, S., 1998. Mechanical controls on collision-related compressional intraplate deformation. Tectonophysics 300, 103-129. Ziegler, P.A., Cloetingh, S., 2004. Dynamic processes controlling evolution of rifted basins. Earth-Science Reviews 64, 1-50. Ziegler, P.A., Schumacher, M.E., Dezes, P., Van Wees, J.D., Cloetingh, S., 2006. Post-Variscan evolution of the lithosphere in the area of the European Cenozoic Rift System. Geological Society, London, Memoirs 32, 97-112.

  18. Modeling approaches for active systems

    NASA Astrophysics Data System (ADS)

    Herold, Sven; Atzrodt, Heiko; Mayer, Dirk; Thomaier, Martin

    2006-03-01

    To solve a wide range of vibration problems with the active structures technology, different simulation approaches for several models are needed. The selection of an appropriate modeling strategy is depending, amongst others, on the frequency range, the modal density and the control target. An active system consists of several components: the mechanical structure, at least one sensor and actuator, signal conditioning electronics and the controller. For each individual part of the active system the simulation approaches can be different. To integrate the several modeling approaches into an active system simulation and to ensure a highly efficient and accurate calculation, all sub models must harmonize. For this purpose, structural models considered in this article are modal state-space formulations for the lower frequency range and transfer function based models for the higher frequency range. The modal state-space formulations are derived from finite element models and/or experimental modal analyses. Consequently, the structure models which are based on transfer functions are directly derived from measurements. The transfer functions are identified with the Steiglitz-McBride iteration method. To convert them from the z-domain to the s-domain a least squares solution is implemented. An analytical approach is used to derive models of active interfaces. These models are transferred into impedance formulations. To couple mechanical and electrical sub-systems with the active materials, the concept of impedance modeling was successfully tested. The impedance models are enhanced by adapting them to adequate measurements. The controller design strongly depends on the frequency range and the number of modes to be controlled. To control systems with a small number of modes, techniques such as active damping or independent modal space control may be used, whereas in the case of systems with a large number of modes or with modes that are not well separated, other control

  19. Noble gases fingerprint a metasedimentary fluid source in the Macraes orogenic gold deposit, New Zealand

    NASA Astrophysics Data System (ADS)

    Goodwin, Nicholas R. J.; Burgess, Ray; Craw, Dave; Teagle, Damon A. H.; Ballentine, Chris J.

    2016-04-01

    The world-class Macraes orogenic gold deposit (˜10 Moz resource) formed during the late metamorphic uplift of a metasedimentary schist belt in southern New Zealand. Mineralising fluids, metals and metalloids were derived from within the metasedimentary host. Helium and argon extracted from fluid inclusions in sulphide mineral grains (three crush extractions from one sample) have crustal signatures, with no evidence for mantle input (R/Ra = 0.03). Xenon extracted from mineralised quartz samples provides evidence for extensive interaction between fluid and maturing organic material within the metasedimentary host rocks, with 132Xe/36Ar ratios up to 200 times greater than air. Similarly, I/Cl ratios for fluids extracted from mineralised quartz are similar to those of brines from marine sediments that have interacted with organic matter and are ten times higher than typical magmatic/mantle fluids. The Macraes mineralising fluids were compositionally variable, reflecting either mixing of two different crustal fluids in the metasedimentary pile or a single fluid type that has had varying degrees of interaction with the host metasediments. Evidence for additional input of meteoric water is equivocal, but minor meteoric incursion cannot be discounted. The Macraes deposit formed in a metasedimentary belt without associated coeval magmatism, and therefore represents a purely crustal metamorphogenic end member in a spectrum of orogenic hydrothermal processes that can include magmatic and/or mantle fluid input elsewhere in the world. There is no evidence for involvement of minor intercalated metabasic rocks in the Macraes mineralising system. Hydrothermal fluids that formed other, smaller, orogenic deposits in the same metamorphic belt have less pronounced noble gas and halogen evidence for crustal fluid-rock interaction than at Macraes, but these deposits also formed from broadly similar metamorphogenic processes.

  20. Erosion and Sediment Transport Across Pronounced Topographic and Climatic Gradients in the Himalayan Orogen

    NASA Astrophysics Data System (ADS)

    Strecker, M. R.; Bookhagen, B.

    2014-12-01

    The interaction between the NW-directed trajectories of moisture transport associated with the Indian Summer Monsoon circulation and the high topography of the Himalayan orogen results in one of the most efficient orographic barriers on Earth. The steep topographic gradients, the impact of focused rainfall along the southern flank of the range, and northward shifts of rainfall during frequent intensified Indian Summer Monsoons are responsible for an efficient erosional regime, with some of the highest known erosion rates. The spatiotemporal correlation between various topographic, tectonic, climatic, and exhumational phenomena in this region has resulted in the formulation of models of possible long-term erosional and tectonic feedback processes that drive the lateral expansion and vertical growth of the mountain belt. However, despite an increase in thermochronologic, cosmogenic radionuclide, and sedimentological datasets that help explain the underlying mechanisms, the true nature of these relationships is still unclear and controversies particularly exist concerning the importance of the different forcing factors that drive exhumation and, ultimately, deformation. Here, we synthesize and assess these controversies with observations from studies conducted perpendicular to and along strike of the orogen, and combine them with our new basin-wide erosion-rate data from the Sutlej Valley in the NW Himalaya. In our regional comparison we highlight the importance of large river systems and climate-controlled aspects of weathering concerning fluvial mass distribution as there appear to be positive feedbacks between tectonics and surface processes. In contrast, observations from smaller catchments along the orogenic front suggest a negative correlation. Similar to other environments with steep topographic and climatic gradients, our observations from the Sutlej catchments emphasize that erosional processes in the Himalayan realm are most efficient in geomorphic

  1. A new lithostratigraphic framework for the Anti-Atlas Orogen, Morocco

    NASA Astrophysics Data System (ADS)

    Thomas, R. J.; Fekkak, A.; Ennih, N.; Errami, E.; Loughlin, S. C.; Gresse, P. G.; Chevallier, L. P.; Liégeois, J.-P.

    2004-06-01

    A new lithostratigraphic nomenclatural framework is proposed for the Anti-Atlas Orogen of Morocco, to replace the previous chronostratigraphic scheme. All the lithostratigraphic units of the Anti-Atlas Orogen are well represented in the Sirwa, Kerdous and Sarhro inliers and examples from these areas are given prominence, though correlates in other areas are given, where known. The oldest, Palaeoproterozoic, rocks of the cratonic basement form the northern part of the West African Craton and can be subdivided into a series of Complexes (made up of constituent Groups, Suites etc.), depending on geographical outcrop (e.g. the Zenaga and Kerdous Complexes in the Sirwa and Kerdous inliers respectively). The Neoproterozoic rocks deposited on this basement are termed the Anti-Atlas Supergroup, within which five groups of volcano-sedimentary units ( Taghdout, Jbel Lkst, Sarhro, Iriri, and Bou Azzer Groups) and various intrusive igneous rocks are recognised (e.g. Ifzwane and Toudma Suites). These units are related to the earliest passive margin, oceanic and island-arc development phases of the orogen between ˜800 and 660 Ma. The earliest Pan-African deformation (at ˜660 Ma) resulted from closure of the ocean basin, SW-directed thrusting and accretion of the island-arc remnants. Continued prolonged convergence gave rise to a sinistral transpressional regime in which late syn- to post-tectonic continental volcanic and clastic sequences of the Ouarzazate Supergroup were deposited. The first rocks of this new tectonic regime were deposited in narrow, tectonically active, strike-slip pull-apart rift basins ( Bou Salda, Mgouna, Tafrawt and Anzi Groups) associated with intrusion of high-K calc-alkaline granitoid batholiths (e.g. Assarag, Bardouz Suites) and the juxtaposition of ophiolitic remnants in major strike-slip shear belts. These were followed by the deposition of the much more areally extensive continental volcano-sedimentary molasse, the volcanic components of which

  2. Rivers, re-entrants, and 3D variations in orogenic wedge development: a case study of the NW Indian Himalaya

    NASA Astrophysics Data System (ADS)

    Webb, A. G.; Yu, H.; Hendershott, Z.

    2010-12-01

    Orogenic wedges are standard elements of collisional plate tectonics, from accretionary prisms to retro-arc basins. Recent study of orogenic wedge development has focused on links between mechanisms of internal deformation and surface processes. Models of orogenic wedges are commonly presented in the cross-section plane, which is generally effective as wedges largely develop via plane strain. The 3rd dimension can be utilized to explore effects of differences in controlling parameters on wedge evolution. We are investigating a stretch of the western Himalayan orogenic wedge that has two prominent changes in along-strike morphology: (1) a tectonic window (the Kullu Window) that appears to be strongly influenced by erosion along the 3rd largest river in the Himalayan system, the Sutlej River and (2) the Kangra Re-entrant, the largest re-entrant along the Himalayan arc. In addition to the along-strike heterogeneity, a key advantage of the proposed study area is its rich stratigraphy, with the most known diversity in the Himalayan arc. The stratigraphic wealth, combined with the along-strike heterogeneity in exposure level, offers a high resolution view of regional structural geometry. Our preliminary reconstructions suggest that the Sutlej River erosion increases the exposure depth and shortening budget across a narrow segment of the orogen, strongly warping the Kullu Window. Previous models have suggested that the out-of-sequence Munsiari thrust is the main structure associated with Kullu window formation, while our work suggests that most of this uplift and warping is accomplished by antiformal stacking of basement thrust horses. Late Miocene ages (U-Pb ages of zircons and Th-Pb ages of monazites) from a leucogranite in the core of the Kullu Window along the Sutlej River further suggests that this segment of the orogen represents a middle ground between plane strain orogenic wedge development and a tectonic aneurysm model. We have constructed a palinspastic

  3. Taconic plate kinematics as revealed by foredeep stratigraphy, Appalachian Orogen

    USGS Publications Warehouse

    Bradley, D.C.

    1989-01-01

    Destruction of the Ordovician passive margin of eastern North America is recorded by an upward deepening succession of carbonates, shales, and flysch. Shelf drowning occurred first at the northern end of the orogen in Newfoundland, then at the southern end of the orogen in Georgia, and finally in Quebec. Diachronism is attributed to oblique collision between an irregular passive margin, that had a deep embayment in Quebec, and at least one east dipping subduction complex. The rate of plate convergence during collision is estimated at 1 to 2 cm/yr, and the minimum width of the ocean that closed is estimated at 500 to 900 km. The drowning isochron map provides a new basis for estimating tectonic transport distances of four of these allochthons (about 165 to 450 km), results not readily obtained by conventional structural analysis. -Author

  4. The activation system EASY-2007

    NASA Astrophysics Data System (ADS)

    Forrest, R. A.; Kopecky, J.

    2009-04-01

    Safety and waste management of materials for ITER, IFMIF and future power plants require knowledge of the activation caused by irradiation with neutrons, or in the case of IFMIF, deuterons. The European Activation System has been developed for such calculations and a new version was released earlier this year. This contains a large amount of nuclear data in the European Activation File covering neutron-, deuteron- and proton-induced cross sections. These data are input to the FISPACT code for activation calculations. EASY-2007 is being validated using integral and differential measurements. However, only a minority of reactions have experimental support and a statistical method is described that can test the complete library. Importance diagrams are useful in finding the dominant nuclides formed following irradiation and the reactions responsible for their production. These diagrams now cover energies above 20 MeV and examples of new dominant nuclides and reactions relevant to IFMIF are given.

  5. Jurassic sedimentary basins in the Central Asian orogenic belt

    SciTech Connect

    Bebeshev, I.I.

    1995-05-01

    The principal stages of development of Jurassic sedimentary basins (from their origin to the end of their existence) in the Central Asian orogenic belt are considered. The interrelations of the basins with the surrounding paleorises are investigated. Paleogeographic maps are compiled representing the evolution of paleolandscapes and revealing their interrelations in space and time for each stage. Areas with the highest prospects for coal are found.

  6. Possible genetic link between I-type granite and orogenic gold deposits in Egypt (metamorphic-magmatic interaction?)

    NASA Astrophysics Data System (ADS)

    Abd El Monsef, Mohamed

    2015-04-01

    The orogenic gold deposits are a distinctive type of deposits that revealed unique temporal and spatial association with an orogeny. Where, the system of gold veins and related ore minerals was confined to hydrothermal solutions formed during compressional to transpressional deformation processes at convergent plate margins in accretionary and collisional orogens, with the respect to ongoing deep-crustal, subduction-related thermal processes. In Egypt, most of vein-type and dyke-type gold mineralization are restricted to granitic rocks or at least near of granitic intrusion that seems to have had an important influence on gold mineralization. Shear zone-related, mesothermal gold deposits of Fatira and Gidami mines in the northern Eastern Desert of Egypt are found within granitic bodies or at the contact between granites and metavolcanic rocks. The hosting-granitic rocks in Fatira and Gidami areas are mainly of granodioritic composition (I-Type granite) which is related to calc-alkaline magmatic series. However, Fatira granitoids were developed within island arc tectonic settings related to mature island arc system (Late-orogenic stage), at relatively low temperature (around 660° C) and medium pressure between (5 - 10 Kbar). On the other hand, Gidami granitoids were developed during the collision stage in continental arc regime related to active continental margin (Syn-orogeny), which were crystallized at relatively high temperature (700-720° C) and low pressure (around 0.1 Kbar). The ore mineralogy includes pyrite, chalcopyrite, sphalerite, covellite, ilmenite, goethite ± pyrrhotite ± pentlandite ± galena ± molybdenite. Native gold is detected only in Gidami mineralization as small inclusions within pyrite and goethite or as tiny grains scattered within quartz vein (in close proximity to the sulfides). In Fatira deposits, it is detected only by microprobe analysis within the crystal lattice of pyrite and jarosite. Fluid inclusions study for the mineralized

  7. Orogenic plateau magmatism of the Arabia-Eurasia collision zone

    NASA Astrophysics Data System (ADS)

    Allen, M. B.; Neill, I.; Kheirkhah, M.; van Hunen, J.; Davidson, J. P.; Meliksetian, Kh.; Emami, M. H.

    2012-04-01

    Magmatism is a common feature of high plateaux created during continental collision, but the causes remain enigmatic. Here we study Pliocene-Quaternary volcanics from the active Arabia-Eurasia collision zone, to determine the chemistry of these rocks and their relations to faulting and deeper lithospheric structure. The great majority of the centres lie within the overriding Eurasian plate in Iran, eastern Turkey and Armenia , implying that mantle fertilised by pre-collision subduction processes plays a significant role in magma generation. The composition of the Pliocene-Quaternary centres is extremely variable, ranging from OIB-like alkali basalts, to intermediate types resembling mature continental arc lavas, to potassic and even ultrapotassic lavas. These centres are erupted across a mosaic of pre-Cenozoic suture zones and heterogeneous lithospheric blocks. The chemical diversity implies a range of partial melting conditions operating on lithospheric and perhaps sub-lithospheric sources. Published data show a thick (>200 km) lithospheric keel beneath the Arabia-Eurasia suture, thinning to near normal thicknesses (~120 km) across much of central and northern Iran. Thin mantle lithosphere under eastern Turkey (max. ~30 km) may relate to the region's juvenile, accretionary lithosphere. These variable thicknesses are constraints on the cause of the melting in each area, and the degree of variation suggests that no one mechanism applies across the plateau. Various melting models have been suggested. Break-off of the subducted Neo-Tethyan oceanic slab is supported by tomographic data, which may have permitted melting related to adiabatic ascent of hot asthenosphere under areas where the lithosphere is thin. This seems a less plausible mechanism where the lithosphere is at normal or greater than normal thickness. The same problem applies to postulated lower lithosphere delamination. Isolated pull-aparts may account for the location of some centres, but are not

  8. Tale of three cratons: Tectonostratigraphic anatomy of the Damara orogen in northwestern Namibia and the assembly of Gondwana

    NASA Astrophysics Data System (ADS)

    Prave, Anthony R.

    1996-12-01

    The Neoproterozoic Damara orogen in Namibia records the Gondwanan assembly of the Congo Kalahari Rio de la Plata cratons. Sedimentological and stratigraphic analyses of the Otavi (mostly carbonate) and Mulden (siliciclastic molasse) Groups exposed along the southwestern margin of the Congo craton indicate that foreland-basin orogenesis began during middle Otavi (ca. 600 750 Ma); this time frame is earlier than that for the Nama foreland (ca. 550 Ma) on the Kalahari craton. Evidence for this interpretation includes (1) an intra-Otavi angular unconformity; (2) concomitant development of increasing accommodation space, basin segmentation, and backstepping depositional systems composed mostly of deep-basin and slope hemipelagic and sediment gravity-flow deposits; and (3) a near reversal in paleocurrents (initially northward off the Congo craton, then switching to southeastward from a west-northwestern orogen). Thus, Congo Rio de la Plata suturing predated Congo-Kalahari suturing during the assembly of Gondwana.

  9. The crust-mantle interaction in continental subduction channels: Zircon evidence from orogenic peridotite in the Sulu orogen

    NASA Astrophysics Data System (ADS)

    Li, Hai-Yong; Chen, Ren-Xu; Zheng, Yong-Fei; Hu, Zhaochu

    2016-02-01

    A combined secondary ion mass spectrometer and laser ablation-(multicollector)-inductively coupled plasma mass spectrometer study of zircon U-Pb ages, trace elements, and O and Hf isotopes was carried out for orogenic peridotite and its host gneiss in the Sulu orogen. Newly grown zircon domains exhibit weak zoning or no zoning, relatively low Th/U ratios (<0.1), low heavy rare earth element (HREE) contents, steep middle rare earth element-HREE patterns, negative Eu anomalies, and negative to low δ18O values of -11.3 to 0.9‰ and U-Pb ages of 220 ± 2 to 231 ± 4 Ma. Thus, these zircons would have grown from metasomatic fluids during the early exhumation of deeply subducted continental crust. The infiltration of metasomatic fluids into the peridotite is also indicated by the occurrence of hydrous minerals such as amphibole, serpentine, and chlorite. In contrast, relict zircon domains exhibit magmatic zircon characteristics. Their U-Pb ages and trace element and Hf-O isotope compositions are similar to those for protolith zircons from ultrahigh-pressure metamorphic rocks in the Dabie-Sulu orogenic belt. Thus, these relict magmatic zircons would be physically transported into the peridotite by metasomatic fluids originated from the deeply subducted continental crust. Therefore, the peridotite underwent metasomatism by aqueous solutions derived from dehydration of the deeply subducted continental crust during the early exhumation. It is these crustally derived fluids that would have brought not only such chemical components as Zr and Si but also tiny zircon grains from the deeply subducted crustal rocks into the peridotite at the slab-mantle interface in continental subduction channels. As such, the orogenic peridotite records the crust-mantle interaction at the deep continental subduction zone.

  10. Orogenic structural inheritance and rifted passive margin formation

    NASA Astrophysics Data System (ADS)

    Salazar Mora, Claudio A.; Huismans, Ritske S.

    2016-04-01

    Structural inheritance is related to mechanical weaknesses in the lithosphere due to previous tectonic events, e.g. rifting, subduction and collision. The North and South Atlantic rifted passive margins that formed during the breakup of Western Gondwana, are parallel to the older Caledonide and the Brasiliano-Pan-African orogenic belts. In the South Atlantic, 'old' mantle lithospheric fabric resulting from crystallographic preferred orientation of olivine is suggested to play a role during rifted margin formation (Tommasi and Vauchez, 2001). Magnetometric and gravimetric mapping of onshore structures in the Camamu and Almada basins suggest that extensional faults are controlled by two different directions of inherited older Brasiliano structures in the upper lithosphere (Ferreira et al., 2009). In the South Atlantic Campos Basin, 3D seismic data indicate that inherited basement structures provide a first order control on basin structure (Fetter, 2009). Here we investigate the role of structural inheritance on the formation of rifted passive margins with high-resolution 2D thermo-mechanical numerical experiments. The numerical domain is 1200 km long and 600 km deep and represents the lithosphere and the sublithospheric mantle. Model experiments were carried out by creating self-consistent orogenic inheritance where a first phase of orogen formation is followed by extension. We focus in particular on the role of varying amount of orogenic shortening, crustal rheology, contrasting styles of orogen formation on rifted margin style, and the time delay between orogeny and subsequent rifted passive formation. Model results are compared to contrasting structural styles of rifted passive margin formation as observed in the South Atlantic. Ferreira, T.S., Caixeta, J.M., Lima, F.D., 2009. Basement control in Camamu and Almada rift basins. Boletim de Geociências da Petrobrás 17, 69-88. Fetter, M., 2009. The role of basement tectonic reactivation on the structural evolution

  11. Crustal Shear Wave Anisotropy in the Taiwan Orogen

    NASA Astrophysics Data System (ADS)

    Rau, R.; Yang, C.

    2002-12-01

    Crustal shear wave anisotropy is analyzed in seismograms from local earthquakes (1.5 < M < 4.5) recorded at 75 permanent network stations in Taiwan during the period between 1991 and 2000. We investigate the origin of Taiwan crustal anisotropy by analyzing splitting in recorded shear waves, which can be characterized by a fast polarization direction and a time delay between fast and slow shear waves. Particle motion analysis and cross-correlation method are applied to estimate the splitting parameters of local shear waves. Clear evidence of shear wave splitting with split times of 0.02 to 0.2 s is found in about 75% of the stations studied. Stations in Coastal Plain, the foreland basin, show consistent alignment of the fast polarization directions that are parallel to the directions of local maximum horizontal compressive stress. Around the Chukou fault in the foothills region, fast shear-wave polarization directions of over 20 earthquakes recorded at station TWL are normal to the direction of local maximum horizontal compressive stress and parallel to the NE-SW trend of this east-dipping thrust fault. Except TWL, all the stations in foothills show large scatter in measured shear-wave polarizations. In the southern Central Range, two stations with a stable polarization direction of NNE-SSW, which is consistent with the local preferential mineral orientation, are found near the ChaoChou fault system. Two persistent polarization directions of fast shear wave are observed in a station (STY) near the boundary between the foothills and the southern Central Range: NW-SE direction for earthquakes located beneath the foothills and NE-SW direction for earthquakes coming under the Central Range. Our study indicates that the crustal anisotropy beneath the Taiwan orogen cannot be simply explained by the hypothesis of extensive dilatancy anisotropy (EDA), where parallel alignment of fluid-filled fractures produces the anisotropy. Other factors, such as intrinsic rock anisotropy

  12. Zirconolite, zircon and monazite-(Ce) U-Th-Pb age constraints on the emplacement, deformation and alteration history of the Cummins Range Carbonatite Complex, Halls Creek Orogen, Kimberley region, Western Australia

    NASA Astrophysics Data System (ADS)

    Downes, Peter J.; Dunkley, Daniel J.; Fletcher, Ian R.; McNaughton, Neal J.; Rasmussen, Birger; Jaques, A. Lynton; Verrall, Michael; Sweetapple, Marcus T.

    2016-04-01

    In situ SHRIMP U-Pb dating of zirconolite in clinopyroxenite from the Cummins Range Carbonatite Complex, situated in the southern Halls Creek Orogen, Kimberley region, Western Australia, has provided a reliable 207Pb/206Pb age of emplacement of 1009 ± 16 Ma. Variably metamict and recrystallised zircons from co-magmatic carbonatites, including a megacryst ~1.5 cm long, gave a range of ages from ~1043-998 Ma, reflecting partial isotopic resetting during post-emplacement deformation and alteration. Monazite-(Ce) in a strongly foliated dolomite carbonatite produced U-Th-Pb dates ranging from ~900-590 Ma. Although the monazite-(Ce) data cannot give any definitive ages, they clearly reflect a long history of hydrothermal alteration/recrystallisation, over at least 300 million years. This is consistent with the apparent resetting of the Rb-Sr and K-Ar isotopic systems by a post-emplacement thermal event at ~900 Ma during the intracratonic Yampi Orogeny. The emplacement of the Cummins Range Carbonatite Complex probably resulted from the reactivation of a deep crustal structure within the Halls Creek Orogen during the amalgamation of Proterozoic Australia with Rodinia over the period ~1000-950 Ma. This may have allowed an alkaline carbonated silicate magma that was parental to the Cummins Range carbonatites, and generated by redox and/or decompression partial melting of the asthenospheric mantle, to ascend from the base of the continental lithosphere along the lithospheric discontinuity constituted by the southern edge of the Halls Creek Orogen. There is no evidence of a link between the emplacement of the Cummins Range Carbonatite Complex and mafic large igneous province magmatism indicative of mantle plume activity. Rather, patterns of Proterozoic alkaline magmatism in the Kimberley Craton may have been controlled by changing plate motions during the Nuna-Rodinia supercontinent cycles (~1200-800 Ma).

  13. Late Mesozoic deformations of the Verkhoyansk-Kolyma orogenic belt, Northeast Russia

    NASA Astrophysics Data System (ADS)

    Fridovsky, Valery

    2016-04-01

    The Verkhoyansk-Kolyma orogenic belt marks the boundary between the Kolyma-Omolon superterrane (microcontinent) and the submerged eastern margin of the North Asian craton. The orogenic system is remark able for its large number of economically viable gold deposits (Natalka, Pavlik, Rodionovskoe, Drazhnoe, Bazovskoe, Badran, Malo-Tarynskoe, etc.). The Verkhoyansk - Kolyma orogenic belt is subdivided into Kular-Nera and the Polousny-Debin terranes. The Kular-Nera terrane is mainly composed of the Upper Permian, Triassic, and Lower Jurassic black shales that are metamorphosed at lower greenschist facies conditions. The Charky-Indigirka and the Chai-Yureya faults separate the Kular-Nera from the Polousny-Debin terrane that is predominantly composed of the Jurassic flyschoi dturbidites. The deformation structure of the region evolved in association with several late Mesozoic tectonic events that took place in the north-eastern part ofthe Paleo-Pacific. In Late Jurassic-Early Cretaceous several generations of fold and thrust systems were formed due to frontal accretion of the Kolyma-Omolon superterrane to the eastern margin of the North Asian craton.Thrusting and folding was accompanied by granitic magmatism, metamorphic reworking of the Late Paleozoic and the Early Mesozoic sedimentary rocks, and formation of Au-Sn-W mineralization. Three stages of deformation related to frontal accretion can be distinguished. First stage D1 has developed in the north-eastern part of the Verkhoyansk - Kolyma orogenic belt. Early tight and isoclinal folds F1 and assosiated thrusts are characteristic of D1. Major thrusts, linear concentric folds F2 and cleavage were formed during D2. The main ore-controlling structures are thrust faults forming imbricate fan systems. Frontal and oblique ramps and systems of bedding and cross thrusts forming duplexes are common. It is notable that mineralized tectonized zones commonly develop along thrusts at the contacts of rocks of contrasting competence

  14. Role of Neogene Exhumation and Sedimentation on Critical-Wedge Kinematics in the Zagros Orogenic Belt, Northeastern Iraq, Kurdistan

    NASA Astrophysics Data System (ADS)

    Koshnaw, R. I.; Horton, B. K.; Stockli, D. F.; Barber, D. E.; Tamar-Agha, M. Y.; Kendall, J. J.

    2014-12-01

    The Zagros orogenic belt and foreland basin formed during the Cenozoic Arabia-Eurasia collision, but the precise histories of shortening and sediment accumulation remain ambiguous, especially at the NW extent of the fold-thrust belt in Iraqi Kurdistan. This region is characterized by well-preserved successions of Cenozoic clastic foreland-basin fill and deformed Paleozoic-Mesozoic hinterland bedrock. The study area provides an excellent opportunity to investigate the linkage between orogenic wedge behavior and surface processes of erosion and deposition. The aim of this research is to test whether the Zagros orogenic wedge advanced steadily under critical to supercritical wedge conditions involving in-sequence thrusting with minimal erosion or propagated intermittently under subcritical condition involving out-of-sequence deformation with intense erosion. These endmember modes of mountain building can be assessed by integrating geo/thermochronologic and basin analyses techniques, including apatite (U-Th)/He thermochronology, detrital zircon U-Pb geochronology, stratigraphic synthesis, and seismic interpretations. Preliminary apatite (U-Th)/He data indicate activation of the Main Zagros Fault (MZF) at ~10 Ma with frontal thrusts initiating at ~8 Ma. However, thermochronometric results from the intervening Mountain Front Flexure (MFF), located between the MZF and the frontal thrusts, suggest rapid exhumation at ~6 Ma. These results suggest that the MFF, represented by the thrust-cored Qaradagh anticline, represents a major episode of out-of-sequence deformation. Detrital zircon U-Pb analyses from the Neogene foreland-basin deposits show continuous sediment derivation from sources to the NNE in Iraq and western Iran, suggesting that out-of-sequence thrusting did not significantly alter sedimentary provenance. Rather, intense hinterland erosion and recycling of older foreland-basin fill dominated sediment delivery to the basin. The irregular distribution of

  15. A Major Out of Sequence Fault in Central Range and Its Implication to Mountain Building Process of Taiwan Orogenic Belt

    NASA Astrophysics Data System (ADS)

    Lee, Y. H.

    2015-12-01

    A Major Out of Sequence Fault in Central Range and Its Implication to Mountain Building Process of Taiwan Orogenic Belt Yuan-Hsi Lee1, Wei Lo2, Wei-Hau Wang1, Tim-Byrne 3, Ruey-Juen Rau 41. Department of Earth and Environmental Sciences, National Chung Cheng University, Taiwan, R.O.C. 2. Department of Materials and Mineral Resources Engineering, Taipei, National Taipei University of Technology, Taiwan, R.O.C. 3. Center for Integrative Geosciences, University of Connecticut, Storrs, CT, USA 4. Department of Earth Science, National Chen-Kung University, Taiwan, R.O.C. Taiwan mountain belt results from collision between Eurasia continental crust and Philippine Sea plate that result in exposing the metamorphic complex with high exhumation rate in eastern Central Range of Taiwan orogenic belt. In this study we combine with field survey, zircon fission track (ZFT), metamorphic grade, and tomography data to identify there exists a major out of sequence fault (MOSF) in eastern Central Range of Taiwan orogenic belt. This MOSF extends from north to south of eastern central Range with several segments and the total length is more than 250 km. The ZFT shows total annealing age of ca.1-3 Ma on the hanging wall and partial annealing ages on the foot wall. The seismicity data indicates the MOSF is still active from central to southern central Range. We consider that the MOSF is related with crustal channel flow in depth. To the western side of crustal flow it shows thrusting mechanism associated with MOSF and the normal faults (or normal shearing zone) develop in eastern side of the crustal channel flow. This crustal channel flow is also related with exposing the metamorphic complex in Central Range that is important mechanism for the mountain building process of Taiwan orogenic belt.

  16. Crustal structure of the south-western termination of the Alpine Pyrenean-Cantabrian Orogen (NW Iberian Peninsula)

    NASA Astrophysics Data System (ADS)

    Rodríguez Fernández, L. R.; Pedrera, A.; Pous, J.; Ayala, C.; González Menéndez, L.; Ibarra, P.; Martín-González, F.; González Cuadra, P.; Seillé, H.

    2015-11-01

    The structure of the western termination of the Alpine Pyrenean-Cantabrian Orogen (NW Iberian Peninsula) has been under debate during the last years. We present new results derived from a new magnetotelluric profile that runs through the western Cantabrian Mountains and the León Mountains, together with gravity data, structural field data and petrological modeling that allows the crustal structure of the sector to be clarified. In the Cantabrian Mountains, the overall Alpine structure is a regional monoclinal flexure that corresponds to the back-limb of E-W trending and north-dipping thrust system. It is formed by a connected thrust-fault splay that overturns the Cenozoic sediments of the Bierzo basin, probably rooted in a detachment at 15 km depth. Further to the South, in the León Mountains, we propose a "pop-up" geometry characterized by high-angle dipping reverse faults that extend toward the lower crust probably causing uplift and the erosion of the early foreland basin. Apatite fission-track and paleontological data suggests that uplift and exhumation of the León Mountains occurred later than in the Cantabrian Mountains. Uplift started in the Middle and Upper Miocene in the León Mountains linked to the activity of the highlighted "pop-up" structure whereas it took place during the Oligocene in the Cantabrian Mountains.

  17. Structural geometry of an exhumed UHP terrane in the eastern Sulu Orogen, China: Implications for continental collisional processes

    NASA Astrophysics Data System (ADS)

    Wang, Lu; Kusky, Timothy M.; Li, Sanzhong

    2010-04-01

    High-precision 1:200-1:1000 mapping of Yangkou Bay, eastern Sulu orogen, defines the structural geometry and history of one of the world's most significant UHP (ultrahigh-pressure) belts. At least four stages of folds are recognized in UHP eclogites and associated quartzo-feldspathic gneiss. UHP eclogite facies rootless F 1 and isoclinal F 2 folds are preserved locally in coesite-eclogite. Mylonitic to ultramylonitic quartzo-feldspathic and coesite-eclogite shear zones separate small-scale 5-10-m-thick nappes of ultramafic-mafic UHP rocks from banded quartzo-feldspathic gneiss. These shear zones are folded, and progressively overprinted by amphibolite-greenschist facies shear zones. The prograde to retrograde D 1-D 5 deformation sequence is explained by deep subduction of offscraped thrust slices of lower continental or oceanic crust from the down-going plate, caught between the colliding North and South China cratons in the Mesozoic. After these slices were structurally isolated along the plate interface, they were rolled in the subduction channel during exhumation and structural juxtaposition with quartzo-feldspathic gneisses, forming several generations of folds, sequentially lower-grade foliations and lineations, and intruded by in situ and exotically derived melts. Shear zones formed during different deformation generations are wider with lower grades, suggesting that deep-crustal/upper mantle deformation operates more efficiently, perhaps with more active crystallographic slip systems, than deformation at mid-upper crustal levels.

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

    NASA Astrophysics Data System (ADS)

    Wang, L.; Kusky, T.

    2009-12-01

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

  19. Late-orogenic, post-orogenic, and anorogenic granites: Distinction by major-element and trace-element chemistry and possible origins

    SciTech Connect

    Rogers, J.J.W.; Greenberg, J.K. )

    1990-05-01

    Granites classified into four categories based solely on tectonics of occurrence and associated rock types also have compositional characteristics that are consistent within groups and different among groups. Orogenically related granites include late-orogenic varieties (LO) associated with calc-alkaline batholiths, and post-orogenic varieties (PO), which occur in broad zones of isolated diapiric plutons in recently deformed orogenic belts. Inclined REE patterns, moderate Sr contents, and K{sub 2}O-SiO{sub 2} relationships show that late-orogenic granites formed by fractionation of plagioclase, clinopyroxene, and amphibole from calcalkaline magmas. Flatter REE patterns and K{sub 2}O contents near 5%, plus the absence of associated magmatic rocks, indicate that the post-orogenic granites developed by partial melting of subduction-produced mafic/intermediate magmatic rocks. Both the late- and post-orogenic granites can be part of material newly added to continental crust as a result of orogeny. Anorogenic granites in anorthosite/rapakivi complexes (AR) or alkaline ring complexes (RC) have LIL contents too high to have been equilibrated with a mafic mineral assemblage. These anorogenic rocks probably formed by partial melting of preexisting sialic crust and do not represent new crustal increment.

  20. The evolution of a Gondwanan collisional orogen: A structural and geochronological appraisal from the Southern Granulite Terrane, South India

    NASA Astrophysics Data System (ADS)

    Plavsa, Diana; Collins, Alan S.; Foden, John D.; Clark, Chris

    2015-05-01

    Gondwana amalgamated along a suite of Himalayan-scale collisional orogens, the roots of which lace the continents of Africa, South America, and Antarctica. The Southern Granulite Terrane of India is a generally well-exposed, exhumed, Gondwana-forming orogen that preserves a record of the tectonic evolution of the eastern margin of the East African Orogen during the Ediacaran-Cambrian (circa 600-500 Ma) as central Gondwana formed. The deformation associated with the closure of the Mozambique Ocean and collision of the Indian and East African/Madagascan cratonic domains is believed to have taken place along the southern margin of the Salem Block (the Palghat-Cauvery Shear System, PCSS) in the Southern Granulite Terrane. Investigation of the structural fabrics and the geochronology of the high-grade shear zones within the PCSS system shows that the Moyar-Salem-Attur shear zone to the north of the PCSS system is early Paleoproterozoic in age and associated with dextral strike-slip motion, while the Cauvery shear zone (CSZ) to the south of the PCSS system can be loosely constrained to circa 740-550 Ma and is associated with dip-slip dextral transpression and north side-up motion. To the south of the proposed suture zone (the Cauvery shear zone), the structural fabrics of the Northern Madurai Block suggest four deformational events (D1-D4), some of which are likely to be contemporaneous. The timing of high pressure-ultrahigh temperature metamorphism and deformation (D1-D3) in the Madurai Block (here interpreted as the southern extension of Azania) is constrained to circa 550-500 Ma and interpreted as representing collisional orogeny and subsequent orogenic collapse of the eastern margin of the East African Orogen. The disparity in the nature of the structural fabrics and the timing of the deformation in the Salem and the Madurai Blocks suggest that the two experienced distinct tectonothermal events prior to their amalgamation along the Cauvery shear zone during the

  1. Flow of deep crust in orogens, associated surface dynamics, and the stabilization of continents

    NASA Astrophysics Data System (ADS)

    Teyssier, C. P.; Whitney, D. L.; Mulch, A.; Rey, P. F.

    2013-12-01

    Mountain building throws continental crust into an unstable state; subsequent stabilization of continental crust takes various forms, but flow of low-viscosity crust is the most common. Some of this low-viscosity crust remains at depth- it is the crust we see in the deep portions of Archean and Proterozoic cratons, typically granulite-migmatite terrains that have recorded ~10 kbar pressure, 600-800°C temperature, and intense deformation dominated by subhorizontal fabrics. In some places though, this deep crust reached the surface during the orogenic cycle. This is the case in the North American Cordillera where the deep crust leaked toward the surface and formed a series of metamorphic complexes that are cored by migmatite domes. Within the domes, complex structural overprints and decompression metamorphic paths indicate large-magnitude horizontal and vertical flow of partially molten crust relative to mantling rocks. No matter how the crust reached partial melting (thermal relaxation and/or heating) during continental under-thrusting, crustal thickening, lithosphere foundering, slab break-off, or slab window, the end result is one of an orogenic crust that contains a low viscosity layer at depth. This layer is mobile and opportunistic: it flows laterally and therefore helps keep a flat Moho; it may flow from a thick plateau and thicken the foreland region (mechanism of plateau growth); it fills gaps that open in the upper crust and therefore enhances orogenic collapse by transferring material from deep to shallow levels; ultimately, flow of this layer stabilizes the crust and may bring the end of orogeny. Thermal and mechanical numerical modeling can help evaluate quantitatively the relative importance of crust thickness, geothermal gradients, and tectonic boundary conditions in the evolution of orogenic systems. In the simple case of steady extension of a layered crust, results show that upper-crust extension is dynamically linked to lower crustal flow until

  2. Asymmetric gravitational spreading - Analogue experiments on the Svecofennian orogen

    NASA Astrophysics Data System (ADS)

    Nikkilä, Kaisa; Korja, Annakaisa; Koyi, Hemin; Eklund, Olav

    2015-04-01

    Over-thickened orogenic crust may suffer from rheological, gravitational and topographical unbalancing resulting in discharging via gravitational spreading. If the thickened orogen is also hot, then increased temperature may reduce the viscosity of the crust that may induce large-scale horizontal flow. The effect of flow on the crustal architecture has previously been modeled with symmetric two-way spreading or asymmetric one- or two-way spreading (like channel flow) experiments. Most models do not take into account of the contrasting mechanical properties of the juxtaposed terranes. We have made analogue experiments to study gravitational one-way spreading and the interplay between two crustal blocks with contrasting rheological properties. The models are 3 cm thick replicas of 60 km thick crust. They have three horizontal layers representing strong lower, weak middle and brittle upper crust. The models have cuts to study the effect of inherited crustal-scale weakness zones. The experiments have been conducted within a large centrifuge in the Hans Ramberg Tectonic Laboratory at Uppsala University. The analogue models propose that asymmetric, unilateral flow has different effect on the contrasting crustal units, in both horizontal and vertical directions. The laterally heterogeneous crust flows towards the direction of extension, and it rotates and extends the pre-existing weakness zones. The weakness zones facilitate exhumation and they increase strain rate. The weakness zones split the crust into subblocks, which stretch individually and which may show signatures of compression or rotation. The changes in thickness of the model reflect changes in the layers, which may thin or thicken depending on the mechanical properties of crustal layers. A consequence of this the total amount of flattening is less than the model extension. The results are compared to geophysical and geological data from Precambrian Svecofennian orogen in Fennoscandia. The comparison suggest

  3. Convergence rate controls seismicity styles in collision orogens

    NASA Astrophysics Data System (ADS)

    Dal Zilio, Luca; van Dinther, Ylona; Gerya, Taras

    2016-04-01

    The 25 April 2015 Mw 7.8 Gorkha earthquake in Nepal resulted from the unzipping of the previously locked Main Himalayan Thrust (MHT) fault, along which the Himalayan wedge is thrust over India. Strong ground shaking caused the collapse of more than half a million homes, killing more than 8500 people. Can such a large magnitude event also occur within the populated European Alps? Or is there a distinctly different seismicity pattern in different orogens? We show that their long-term seismicity patterns are indeed different and that their differences can be explained by a single parameter: their convergence rate. To do so we present the first self-consistent seismic cycle model for continental collisional margins. We use the viscoelastoplastic continuum Seismo-Thermo-Mechanical model (STM) validated for seismic cycle applications against a laboratory model (van Dinther et al., 2013a) and natural observations (van Dinther et al., 2013b), which includes Drucker-Prager plasticity and spontaneous rupture events governed by strongly rate-dependent friction. The 2-D model setup consists of two continental plates separated by an oceanic plate, in which the incipient subduction phase is followed by collisional orogeny. Results show the physically consistent spontaneous emergence of complex rupture paths, both on and off the main frontal thrust. These off-main frontal thrust events within the upper and lower plate complement the main frontal thrust seismicity leading to a Gutenberg-Richter frequency-magnitude distribution. This is a key observational feature of seismicity, which is typically not reproduced in seismic cycle models. The range of simulated b-values agrees with natural ranges, as we observe values from 0.97 up to 1.25 for convergence rates decreasing from 5 to 1 cm/yr. Decreasing convergence rates thus lead to relatively larger amounts of smaller earthquakes (increasing b-value) and lower maximum magnitudes. This change in b-value also observed to corresponds to

  4. Active thermal control system evolution

    NASA Technical Reports Server (NTRS)

    Petete, Patricia A.; Ames, Brian E.

    1991-01-01

    The 'restructured' baseline of the Space Station Freedom (SSF) has eliminated many of the growth options for the Active Thermal Control System (ATCS). Modular addition of baseline technology to increase heat rejection will be extremely difficult. The system design and the available real estate no longer accommodate this type of growth. As the station matures during its thirty years of operation, a demand of up to 165 kW of heat rejection can be expected. The baseline configuration will be able to provide 82.5 kW at Eight Manned Crew Capability (EMCC). The growth paths necessary to reach 165 kW have been identified. Doubling the heat rejection capability of SSF will require either the modification of existing radiator wings or the attachment of growth structure to the baseline truss for growth radiator wing placement. Radiator performance can be improved by enlarging the surface area or by boosting the operating temperature with a heat pump. The optimal solution will require both modifications. The addition of growth structure would permit the addition of a parallel ATCS using baseline technology. This growth system would simplify integration. The feasibility of incorporating these growth options to improve the heat rejection capacity of SSF is under evaluation.

  5. Kinematics of post-orogenic extension and exhumation of the Taku Schist, NE Peninsular Malaysia

    NASA Astrophysics Data System (ADS)

    Md Ali, M. A.; Willingshofer, E.; Matenco, L.; Francois, T.; Daanen, T. P.; Ng, T. F.; Taib, N. I.; Shuib, M. K.

    2016-09-01

    Recent studies imply that the formation and evolution of many SE Asian basins was driven by extensional detachments or systems of low-angle normal faults that created significant crustal exhumation in their footwalls. In this context, the architecture of the Triassic Indosinian orogen presently exposed in Peninsular Malaysia is compatible with significant extension post-dating the orogenic event. In this study we performed a kinematic analysis based on fieldwork and microstructural observations in the Taku Schist, Kemahang granite and the surrounding Gua Musang sediments of northern Peninsular Malaysia in order to shed light on processes related to the build-up and subsequent demise of the Indosinian orogen. The first three phases of deformation were related to an overall period of E-W oriented contraction and burial metamorphism. These phases of deformation are characterized by isoclinal folding with flat lying axial plane cleavages (D1), asymmetrical folding, top-to-the-W-SW shearing (D2) and upright folding (D3). All are in general agreement with observations of the previously inferred Permo-Triassic Indosinian orogeny. During these times, the Taku Schist, a sequence of Paleozoic clastic sediments with mafic intercalations was metamorphosed to amphibolite facies. These rocks are most likely equivalent to the ones exposed in the Bentong-Raub suture zone. Structural relations suggest that the Triassic Kemahang pluton is syn-kinematic, which provides important constraints for the timing of these contractional events. We demonstrate that the overall shortening was followed by a hitherto undescribed extension in NW-SE direction resulting in the formation of a large-scale detachment, the Taku detachment, in northern Peninsular Malaysia. Extension probably reactivated the former subduction plane as a detachment and exhumed previously buried and metamorphosed rocks of similar lithological composition to the neighboring Bentong-Raub suture zone. Such a mechanism is

  6. Plume-orogenic lithosphere interaction recorded in the Haladala layered intrusion in the Southwest Tianshan Orogen, NW China

    NASA Astrophysics Data System (ADS)

    He, Peng-Li; Huang, Xiao-Long; Xu, Yi-Gang; Li, Hong-Yan; Wang, Xue; Li, Wu-Xian

    2016-03-01

    The plume-orogenic lithosphere interaction may be common and important for the generation of large igneous provinces. The information regarding such a process is recorded by the Haladala gabbroic intrusion (~300 Ma), the largest layered ultramafic-mafic intrusion hosting V-Ti magnetite deposits in the Southwest Tianshan Orogen, NW China. The Haladala gabbros exhibit unfractionated chondrite-normalized rare earth element patterns with negative Nb and Ta anomalies and positive Pb anomaly on the primitive mantle-normalized multielement variation diagram. They are characterized by low initial Sr isotopes, slightly decoupled but high positive bulk rock ɛNd(t) and ɛHf(t), and high 207Pb/204Pb and 208Pb/204Pb relative to 206Pb/204Pb, delineating a DUPAL signature in the sources. The Haladala gabbros cannot be arc or postcollisional magmatism, given the lack of hydrous minerals and low K contents, respectively. This is further supported by the relatively low oxygen fugacity required for the gradual enrichment of V-Ti magnetite during the magma fractionation and by an overall anhydrous mantle source suggested by troctolite mineral assemblage (olivine + plagioclase). The emplacement age of the Haladala gabbros is identical to that of the Wajilitag kimberlites in the Tarim's interior, which have been interpreted as the first magmatic expression of the Tarim mantle plume. We thus propose that the Haladala gabbroic intrusion was generated in a hybrid geodynamic setting in which the Southwest Tianshan Orogen was impacted by an upwelling mantle plume. In this sense, the Haladala layered gabbroic intrusion records the early phase of magmatism of the Tarim plume, which was preferentially emplaced in a lithospheric weak zone.

  7. Groundwater flow within a sub-aerial orogenic wedge subject to depth-dependent permeability structure

    NASA Astrophysics Data System (ADS)

    Pollyea, R.; Van Dusen, E.; Fischer, M. P.

    2014-12-01

    In recent years, investigators have revisited the problem of basin-scale fluid flow with an emphasis on depth-dependent permeability, which is a frequently observed geological phenomenon that is seldom accounted for in basin-scale flow models. These recent investigations have shown that depth-dependent permeability at the basin scale strongly influences the relationship between sub-basin and regional-scale flow paths. Here, we revisit topography driven fluid flow within a foreland basin using a numerical modeling experiment designed to assess first-order fluid system behavior when permeability decreases systematically with depth. Critical taper theory is invoked to define two-dimensional basin geometry, and three sub-aerially exposed orogenic wedge models are presented with critical taper angles of 2°, 4°, and 10°. To assess the combined influence of topographic slope and depth-dependent permeability, a constant rate infiltration is applied at the wedge surface and a transient simulation is performed within each model for 500,000 years. Our results suggest that fluid system structure within the narrowly tapering orogenic wedge (2°) is explained by recent investigations applying depth-decaying permeability to the classic Tóth basin; however, increasing topographic slope beyond 3° results in a fundamentally different fluid system architecture. As topographic slope increases, fluid system structure is characterized by (1) dominant regional flow paths and little, if any, sub-basin scale fluid circulation, (2) shallow meteoric water penetration, (3) a stratified distribution of groundwater residence time without pronounced stagnation points. Moreover, for a given detachment slope, these effects become more pronounced as topographic gradient increases.

  8. Morphometric properties of the trans-Himalayan river catchments: Clues towards a relative chronology of orogen-wide drainage integration

    NASA Astrophysics Data System (ADS)

    Ghosh, Parthasarathi; Sinha, Sayan; Misra, Arindam

    2015-03-01

    The geomorphological evolution of the Himalayan mountain belt both in terms of crustal deformation and concomitant erosion by surface processes has been suggested to have a profound influence on a number of earth system processes and has been extensively researched through a number of different techniques. The huge catchments of the trans-Himalayan rivers are the product of long-term fluvial erosion of the landscape. This work attempts to understand their evolution through a study of drainage network, morphology, and internal organization of the smaller watersheds nested within each catchment. Using morphometric techniques applied to an orogen-wide digital elevation data grid, we characterized the drainage network structure and catchment of all the 18 trans-Himalayan rivers situated between the exits of the Indus and Brahmaputra rivers and constructed rectangular approximations of the catchment geometries. With the help of catchment dimensions measured transverse and parallel to the strike of the orogen, and by analyzing the dimension and spatial dispositions of the rectangular approximations, we demonstrate that the trans-Himalayan catchment shapes cannot be explained only as a product of the headward enlargement of drainage networks on a topographic slope, or orogenic taper. Within individual catchments we identified the existence of drainage components (watersheds) that are organized in a systematic manner with respect to the first-order physiographic features of the Himalayas, formed at different periods of geological time. Each of them shows distinct morphometric characteristics that are indicative of differences in processes and / or time scale involved in their formation. The hypsometric properties of the watersheds occupying the upper part of the catchments suggest that they are the remnants of pre-orogenic drainage that became confined to the leeward side of the Himalayas before the advent of monsoon circulation. The shape and organization of the

  9. The Oligocene Alps: Domal unroofing and drainage development during early orogenic growth

    NASA Astrophysics Data System (ADS)

    Garzanti, Eduardo; Malusà, Marco G.

    2008-04-01

    Tertiary evolution of the Alps-Apennines orogenic couple, but also for general relationships among tectonic activity, relief formation, drainage development, erosion distribution, and long-distance sediment transfer during continental collision and orogenic growth.

  10. Continuation of the New England Orogen, Australia, beneath the Queensland Plateau and Lord Howe rise

    USGS Publications Warehouse

    Mortimer, N.; Hauff, F.; Calvert, A.T.

    2008-01-01

    Greywacke, argillite, greyschist and hypabyssal igneous rocks have been obtained from an Ocean Drilling Program core on the Queensland Plateau and from xenoliths in a volcanic breccia dredged from the crest of the Lord Howe Rise. Low to intermediate detrital quartz contents, 260-240 Ma K-Ar ages, and only moderately radiogenic Sr and Nd isotope compositions, suggest a correlation with the New England Orogen of eastern Australia, rather than with Australia's Lachlan Orogen or other adjacent geological provinces. Our results indicate that the New England Orogen terranes continue towards New Zealand at least as far as the southern Lord Howe Rise. The projected offshore boundaries of the major east Australian orogens are now known with more confidence, and do not appear to require any major cross-orogen offsets.

  11. Tectonic processes during oblique collision: Insights from the St. Elias orogen, northern North American Cordillera

    USGS Publications Warehouse

    Pavlis, T.L.; Picornell, C.; Serpa, L.; Bruhn, R.L.; Plafker, G.

    2004-01-01

    Oblique convergence in the St. Elias orogen of southern Alaska and northwestern Canada has constructed the world's highest coastal mountain range and is the principal driver constructing all of the high topography in northern North America. The orogen originated when the Yakutat terrane was excised from the Cordilleran margin and was transported along margin-parallel strike-slip faults into the subduction-transform transition at the eastern end of the Aleutian trench. We examine the last 3 m.y. of this collision through an analysis of Euler poles for motion of the Yakutat microplate with respect to North America and the Pacific. This analysis indicates a Yakutat-Pacific pole near the present southern triple junction of the microplate and' predicts convergence to dextral-oblique convergence across the offshore Transition fault, onland structures adjacent to the Yakutat foreland, or both, with plate speeds increasing from 10 to 30 mm/yr from southeast to northwest. Reconstructions based on these poles show that NNW transport of the collided block into the NE trending subduction zone forced contraction of EW line elements as the collided block was driven into the subduction-transform transition. This suggests the collided block was constricted as it was driven into the transition. Constriction provides an explanation for observed vertical axis refolding of both earlier formed fold-thrust systems and the collisional suture at the top of the fold-thrust stack. We also suggest that this motion was partially accommodated by lateral extrusion of the western portion of the orogen toward the Aleutian trench. Important questions remain regarding which structures accommodated parts of this motion. The Transition fault may have accommodated much of the Yakutat-Pacific convergence on the basis of our analysis and previous interpretations of GPS-based geodetic data. Nonetheless, it is locally overlapped by up to 800 m of undeformed sediment, yet elsewhere shows evidence of young

  12. Sedimentary basinal responses to a Late Precambrian Wilson Cycle: the Damara Orogen and Nama Foreland, Namibia

    NASA Astrophysics Data System (ADS)

    Stanistreet, Ian G.; Kukla, Peter A.; Henry, George

    In the Damara Orogen sedimentary basinal responses are important in recording the evolution of the fold belt. Here we integrate sedimentological patterns and tectonics to characterise the basin development of both the pre- to syn-orogenic Damara Sequence and the syn- to post-orogenic Nama Group. The evolution of an entire Late Proterozoic Wilson Cycle involved initial rifting, with the opening of two oceanic arms through convergence to collision and foreland basin development. Rift initiation (stage 1) took place along old tectonic weaknesses and extensional rift basins (stage 2) were filled by continental sediments and alkaline/bimodal volcanics. Two oceanic openings occurred: (i) the Adamastor Ocean (stage 3) produced a break-up unconformity and eastward transgression over the Kalahari and Congo Cratons; and (ii) the Khomas Sea gulf subsequently developed betwen the two cratons (stage 4) and is associated with break-up unconformities, and ultimately the development of mature shleves (stage 5). In the latter opening, we envisage an anticlockwise rotation of the Kalahari Craton with respect to the Congo Craton. During convergence the closing Khomas Sea produced an accretionary prism/arc/retro-arc system (stage 6) and the first deformation phase in the Southern Zone. The Khomas Orogeny records the collision between the Kalahari and Congo Cratons (stage 7) including the obduction of oceanic elements onto the Kalahari Craton foreland, and caused the second and third deformation phases in the Southern Zone and first and second deformation phases in the Central Zone. A peripheral foreland basin and peripheral bulge on the Kalahari Craton resulted, which respectively contained and affected the marine and fluvial Nama Group sedimentation. A complementary hinterland basin accepted Mulden Group sediments on the Congo Craton. Ultimately the collision of the South American continent with the newly reconstituted African foreland (stage 8) caused the Adamastor Orogeny and

  13. Crustal channel flows: 2. Numerical models with implications for metamorphism in the Himalayan-Tibetan orogen

    NASA Astrophysics Data System (ADS)

    Jamieson, Rebecca A.; Beaumont, Christopher; Medvedev, Sergei; Nguyen, Mai H.

    2004-06-01

    Results from a thermal-mechanical model (HT1) that includes midcrustal channel flow are compatible with many features of the Himalayan-Tibetan system. Radioactive self-heating and rheological weakening of thickened model orogenic crust lead to the formation of a hot, low-viscosity midcrustal channel and a broad plateau. Channel material, corresponding to the Greater Himalayan Sequence (GHS), flows outward from beneath the plateau in response to topographically induced differential pressure. At the plateau flank it is exhumed by focused surface denudation and juxtaposed with cooler, newly accreted material corresponding to the Lesser Himalayan Sequence (LHS). The model channel is bounded by coeval thrust and normal sense ductile shear zones, interpreted to represent the Main Central Thrust (MCT) zone and South Tibetan Detachment system, respectively. Inverted metamorphism associated with the model MCT zone results from distributed ductile shear along the MCT and extrusion of the hot channel. A variety of model P-T-t path styles, resembling those observed in the GHS and LHS, are produced for points traveling through contrasting tectonic regimes that coexist in different parts of the model. Predicted times of peak metamorphism, cooling, and erosion of metamorphic facies are generally compatible with observations, although model GHS cooling ages are too young. The times of M1 and M2 metamorphic "events" observed in the GHS correspond to model times of maximum burial and maximum heating, respectively. The results highlight the need to integrate tectonics and metamorphism in continental collision models and demonstrate the importance of lateral transport of both heat and material in large hot orogens.

  14. Manually controlled neutron-activation system

    NASA Astrophysics Data System (ADS)

    Johns, R. A.; Carothers, G. A.

    1982-01-01

    A manually controlled neutron activation system, the Manual Reactor Activation System, was designed and built and has been operating at one of the Savannah River Plant's production reactors. With this system, samples can be irradiated for up to 24 hours and pneumatically transferred to a shielded repository for decay until their activity is low enough for them to be handled at a radiobench. The Manual Reactor Activation System was built to provide neutron activation of solid waste forms for the Alternative Waste Forms Leach Testing Program. Neutron activation of the bulk sample prior to leaching permits sensitive multielement radiometric analyses of the leachates.

  15. Disclosing the Paleoarchean to Ediacaran history of the São Francisco craton basement: The Porteirinha domain (northern Araçuaí orogen, Brazil)

    NASA Astrophysics Data System (ADS)

    Silva, Luiz Carlos da; Pedrosa-Soares, Antonio Carlos; Armstrong, Richard; Pinto, Claiton Piva; Magalhães, Joana Tiago Reis; Pinheiro, Marco Aurélio Piacentini; Santos, Gabriella Galliac

    2016-07-01

    This geochronological and isotopic study focuses on one of the Archean-Paleoproterozoic basement domains of the São Francisco craton reworked in the Araçuaí orogen, the Porteirinha domain, Brazil. It also includes a thorough compilation of the U-Pb geochronological data related to the adjacent Archean and Rhyacian terranes from the São Francisco craton and Araçuaí orogen. The main target of this study is the TTG gneisses of the Porteirinha complex (Sample 1). The gneiss dated at 3371 ± 6 Ma unraveled a polycyclic evolution characterized by two metamorphic overprinting episodes, dated at 3146 ± 24 Ma (M1) and ca. 600 Ma (M2). The former (M1) is so far the most reliable evidence of the oldest metamorphic episode ever dated in Brazil. The latter (M2), in turn, is endemic in most of the exposed eastern cratonic margin within the Araçuaí orogen. Whole-rock Sm-Nd analysis from the gneiss provided a slightly negative εNd(t3370) = - 0.78 value, and a depleted mantle model (TDM) age of 3.5 Ga, indicating derivation mainly from the melting of a ca. 3.5 Ga tholeiitic source. Sample 2, a K-rich leuco-orthogneiss from the Rio Itacambiriçu Complex, was dated at 2657 ± 25 Ma and also presents a ca. 600 Ma M2 overprinting M2 age. The other two analyses were obtained from Rhyacian granitoids. Sample 3 is syn-collisional, peraluminous leucogranite from the Tingui granitic complex, showing a crystallization age of 2140 ± 14 Ma and strong post-crystallization Pb*-loss, also ascribed to the Ediacaran overprinting. Accordingly, it is interpreted as a correlative of the late Rhyacian (ca. 2150-2050 Ma) collisional stage of the Mantiqueira orogenic system/belt (ca. 2220-2000 Ma), overprinted by the Ediacaran collage. Sample 4 is a Rhyacian post-orogenic (post-collisional), mixed-source, peralkaline, A1-type suite, with a crystallization age of 2050 ± 10 Ma, presenting an important post-crystallization Pb*-loss related to Ediacaran collision. The focused region records some

  16. Wave activated power generation system

    SciTech Connect

    Ono, Y.

    1983-08-09

    A wave activated power generation system of the float type is disclosed, comprising at least one piston-cylinder device having an anchored cylinder and a piston slidable in the cylinder and cooperating with the cylinder to form a pumping chamber above the piston and a low pressure chamber below the piston. The cylinder has an intake port and an exhaust port both formed at an upper port thereof to communicate with the pumping chamber and each provided with a check valve. A float is connected through a cable to the piston of the piston- cylinder device. A pair of fluid storages are connected to the intake port and the exhaust port of the pumping chamber, respectively. A waterwheel generator is driven by the fluid flowing from one of the fluid storages to another. A pressure regulating device is connected to the low pressure chamber so as to maintain the low pressure chamber at a pressure lower than the pressure in the pumping chamber, the difference in pressure ceaselessly applying a downward force on the piston to keep the cable in a tensed condition.

  17. The Velay dome (French Massif Central): melt generation and granite emplacement during orogenic evolution

    NASA Astrophysics Data System (ADS)

    Ledru, P.; Courrioux, G.; Dallain, C.; Lardeaux, J. M.; Montel, J. M.; Vanderhaeghe, O.; Vitel, G.

    2001-12-01

    This paper is a synthesis of available data on the Velay dome that include both small- and large-scale lithologic and structural mapping, strain analysis, isotope geochemistry, geochronology and pressure-temperature estimates. The Velay dome, one of the largest granite-migmatite domes of the Variscan Belt, formed during orogenic collapse at around 300 Ma. Its study allows an assessment of the thermal and geodynamic context leading to voluminous crustal anatexis of the Variscan orogenic crust. A first melting stage developed in connection with south-verging thrust zones during the Early Carboniferous, leading to a crustal thickening estimated at 20 km minimum. The involvement of fertile lithologies and the intrusion of plutons of deep origin contributed to the development of water-saturated melts. The volume of biotite granite extracted from melt during this period was limited. The second phase of melting, corresponded to generalized melting of gneiss achieved by biotite-dehydration melting reactions and accompanied by the generation of cordierite-bearing granites. At this stage, crustal-scale detachment faults were active and partially obliterated the earlier structures. The new structures were progressively tilted to the vertical at the margin of the Velay dome due to the southward and lateral ballooning of the granitic dome. The reconstructed P, T path indicate that the large volume of melt produced was a consequence of a significant increase in temperature at the onset of biotite dehydration melting. At the base of the crust, this melting event is coeval with granulite facies metamorphism associated to underplating of mantle-derived magmas as suggested by the geochemical signature of Late Paleozoic lower crustal xenoliths sampled by Cenozoic volcanoes and with the isotopic signature of the late granitic intrusions. Accordingly, it is proposed that asthenospheric upwelling was responsible for the temperature increase favoring melting of hydrous minerals.

  18. Magnetic constraints on the thermal evolution of a collapsing orogen

    NASA Astrophysics Data System (ADS)

    Platzman, Ellen

    2002-06-01

    The thermal evolution of an orogen undergoing late-stage extension was investigated using rock magnetic properties of a suite of mafic dyke rocks affected by greenschist facies metamorphism in the internal zones of the Betic Cordillera, southern Spain. The natural remanent magnetization (NRM) in the dykes intruded into the lowest geological unit is made up of up to three components. The lowest temperature component (LT) is in the direction of the present day magnetic field and is believed to be a chemical remanent magnetization (CRM) or viscous remanent magnetization (VRM) acquired in the recent magnetic field. The intermediate temperature (IT) component unblocked between 200°C and 450°C is thought to be largely a thermoviscous overprint acquired during metamorphism. This component is carried by either primary or authogenic sulfides and low-unblocking temperature magnetite. The component of magnetization with the highest blocking temperature (HT) is isolated above 450°C and is interpreted as the primary component of remanent magnetization. It is most likely that this component is carried by magnetite that resides in the plagioclase and has been shielded from the metamorphism, which transformed most of the original magnetite to metamorphic amphibole, chlorite and biotite. Thermal demagnetization of these dykes separates the IT overprint from the HT primary remanence at a sharp junction occurring at 450°C. For single domain grains this translates to a peak palaeotemperature in the natural sample of approximately 370°C, which is close to the estimated temperature experienced by the greenschist facies country rocks (400°C). In contrast, results obtained from a dyke that is intruded into an overlying weakly metamorphosed geological unit, indicates that temperatures only reached about 175°C in this unit. These results are consistent with temperatures deduced from geological constraints and they imply that between 4 and 6 km of section has been removed between the

  19. Lithotectonic framework and continental collisional reworking in the eastern part of the Sveconorwegian orogen

    NASA Astrophysics Data System (ADS)

    Andersson, Jenny; Möller, Charlotte; Stephens, Michael B.

    2013-04-01

    -to-the-ESE displacement followed by top-to-the-W extension. It forms a major structural, metamorphic and lithological terrane boundary. Lithotectonic units west thereof have been displaced out of their original tectonic context and cannot be directly linked to the remainder of the pre-Sveconorwegian Fennnoscandian Shield. Thus, considerable displacement must be accounted for. The Idefjorden terrane is the easternmost allochthonous belt of the orogen, directly overlying the Eastern Segment. It constitutes a patchwork of metamorphic sub-domains where high-grade complexes are juxtaposed against domains that show little or no imprint of Sveconorwegian reworking. Crustal thickening recorded by high-pressure granulite facies metamorphism (1.0-1.5 GPa and 700-740°C) has been dated at 1.05-1.02 Ga, i.e. at least 30 Ma earlier than the high-pressure metamorphism in the underlying Eastern Segment. The structural grain is orogen-parallel (in contrast to that in the Eastern Segment), with N-S-trending ductile fabrics, including fold axes, regional deformation zones and tectonic contacts of metamorphic complexes. The high- and medium-pressure metamorphism of the Eastern Segment (0.99-0.97 Ga) and the Idefjorden terrane (1.05-1.02 Ga) testifies to deep subduction of the Fennoscandian continental crust during the Sveconorwegian orogeny, broadly corresponding to the Rigolet and Ottawan phases of the Grenvillian orogeny, respectively. Both events are diagnostic of collisional orogeny, with syn-metamorphic intrusive activity limited to local dyke intrusion.

  20. Proterozoic collisional tectonism in the Trans-Hudson orogen, Saskatchewan

    SciTech Connect

    Bickford, M.E.; Chiarenzelli, J.R.; Van Schmus, W.R. ); Collerson, K.D. ); Lewry, J.F. )

    1990-01-01

    Isotopic and structural data from the juvenile Reindeer zone of the Trans-Hudson orogen, northern Saskatchewan, indicate a pre-1.85 Ga thermotectonic event, possibly reflecting arc-continent collision, followed by a more extensive, nappe-forming, ca. 1.83-1.80 Ga thermotectonism during terminal continent-continent collision. Preliminary data from the adjacent, ensialic Cree Lake zone suggest high-grade reworking of Archean crust by the pre-1.85 Ga event. In the Rae province to the west, high-grade metamorphism and reworking of Archean crust occurred about 2.0 Ga and may be related to the formation of the coeval Taltson magmatic zone.

  1. Possible Subcrustal Anisotropic Fabric Beneath the Grenville Orogen

    NASA Astrophysics Data System (ADS)

    Frederiksen, A. W.; Miong, S.; Eaton, D. W.

    2004-05-01

    The Proterozoic Grenville Orogen, which forms the southeastern edge of the Canadian Shield, is the result of extensive crustal shortening and deformation during the interval 1.3-0.98 Ga. The degree to which this crustal deformation is reflected in the underlying mantle is uncertain, though LITHOPROBE detection of a preserved subduction zone (Calvert et al., 1995) in adjacent Archean terranes indicates that relict Precambrian features are preserved below the crust. A number of permanent CNSN stations (e.g., SADO, GAC, KGNO, etc.) are located on or near the Grenville, and have large archives of teleseismic data available; the more recent deployment of the dense Ontario POLARIS network provides additional constraints. We examine teleseismic receiver functions from POLARIS and CNSN stations for transverse-component energy beneath the Moho; early results indicate a complex structure involving multiple anisotropic domains that do not correlate with SKS splitting results.

  2. Distant effects in bivergent orogenic belts - How retro-wedge erosion triggers resource formation in pro-foreland basins

    NASA Astrophysics Data System (ADS)

    Hoth, Silvan; Kukowski, Nina; Oncken, Onno

    2008-08-01

    Timeseries derived from two-dimensional sandbox simulations involving surface erosion are taken for the first time to be implemented into flexure calculations of foreland basins. Based on our results we highlight that orogenic systems are a four component system, consisting of a pro-foreland basin, a pro-wedge, a retro-wedge, and a retro-foreland basin. These four components are mechanically coupled via the load dependence of tectonic faulting [Mandl, G., 1988. Mechanics of tectonic faulting, 1st Edition. Elsevier, Amsterdam.] and the finite flexural rigidity of lithospheric plates [Beaumont, C., 1981. Foreland basins. Geophys. J. R. Astron. Soc. 5 (2), 291-329.]. We further demonstrate that the impact of pro-wedge erosion is most pronounced within the pro-wedge but also modifies the shape and size of the retro-wedge, which in turn changes the geometry and propagation velocity of the retro-foreland basin and vice versa. This suggests that one out of the four components of an orogenic system cannot be fully understood without recognition of the other three components. Thus, spatial separation between processes or observations does not necessarily imply their physical independence. This conceptual model is applied in a case study to the Pyrenean orogenic wedge and its Ebro and Aquitaine foreland basins. Our analysis suggests that the Pyrenean pro- and retro-wedge are mechanically coupled and that this coupling manifests itself in the migration of depocentres in both foreland basins. We finally explore implications for the formation of Mississippi Valley Type deposits.

  3. A reconsideration of Pan African orogenic cycle in the Anti-Atlas Mountains, Morocco

    NASA Astrophysics Data System (ADS)

    Hefferan, Kevin; Soulaimani, Abderrahmane; Samson, Scott D.; Admou, Hassan; Inglis, Jeremy; Saquaque, Ali; Latifa, Chaib; Heywood, Neil

    2014-10-01

    For over 50 years the Pan African orogeny has been recognized as a Neoproterozoic tectonothermal episode affecting West Africa 800-550 Ma. As such, the Pan African events are similar to the Appalachian orogenic cycle extending from ∼1100 to 250 Ma and the Cordilleran orogenic cycle of 350 Ma to the present. A significant difference is that the Appalachian orogenic cycle has long been recognized as consisting of separate Grenville, Taconic, Acadian and Alleghenian orogenies. Similarly, the Cordilleran orogenic cycle consists of distinct Antler, Sonoma, Nevadan, Sevier, Laramide and ongoing Cascadian-Andean orogenies. Failure to distinguish individual tectonic events in the Anti-Atlas Mountains has been attributable to the dearth of radiometric dates in this region. Since 2000, precision geochronologic dating in the Anti-Atlas Mountains, Morocco, has provided a means by which it is now appropriate to designate a Pan African orogenic cycle consisting of separate distinct orogenic events. We herein propose the following distinct orogenic events in the Anti-Atlas Mountains of Morocco: Iriri-Tichibanine orogeny (760-700 Ma), Bou Azzer orogeny (680-640 Ma) and the WACadomian orogeny (620-555 Ma).

  4. Seismic anisotropy and mantle creep in young orogens

    USGS Publications Warehouse

    Meissner, R.; Mooney, W.D.; Artemieva, I.

    2002-01-01

    Seismic anisotropy provides evidence for the physical state and tectonic evolution of the lithosphere. We discuss the origin of anisotropy at various depths, and relate it to tectonic stress, geotherms and rheology. The anisotropy of the uppermost mantle is controlled by the orthorhombic mineral olivine, and may result from ductile deformation, dynamic recrystallization or annealing. Anisotropy beneath young orogens has been measured for the seismic phase Pn that propagates in the uppermost mantle. This anisotropy is interpreted as being caused by deformation during the most recent thermotectonic event, and thus provides information on the process of mountain building. Whereas tectonic stress and many structural features in the upper crust are usually orientated perpendicular to the structural axis of mountain belts, Pn anisotropy is aligned parallel to the structural axis. We interpret this to indicate mountain-parallel ductile (i.e. creeping) deformation in the uppermost mantle that is a consequence of mountain-perpendicular compressive stresses. The preferred orientation of the fast axes of some anisotropic minerals, such as olivine, is known to be in the creep direction, a consequence of the anisotropy of strength and viscosity of orientated minerals. In order to explain the anisotropy of the mantle beneath young orogens we extend the concept of crustal 'escape' (or 'extrusion') tectonics to the uppermost mantle. We present rheological model calculations to support this hypothesis. Mountain-perpendicular horizontal stress (determined in the upper crust) and mountain-parallel seismic anisotropy (in the uppermost mantle) require a zone of ductile decoupling in the middle or lower crust of young mountain belts. Examples for stress and mountain-parallel Pn anisotropy are given for Tibet, the Alpine chains, and young mountain ranges in the Americas. Finally, we suggest a simple model for initiating mountain parallel creep.

  5. A Reconsideration of Pan African Orogenic Cycle in the Anti-Atlas Mountains, Morocco

    NASA Astrophysics Data System (ADS)

    Hefferan, K. P.; Soulaimani, A.; Samson, S. D.; Admou, H.; Inglis, J.; Saquaque, A.; Heywood, N. C.

    2013-12-01

    The term 'Pan African' orogeny was first proposed in 1964 for a tectonothermal event in Africa ~ 500+/- 50 Ma. Over the past 50 years, the Pan African orogeny has been extended to as much as ~1050-450 Ma and recognized in other Gondwanan continents where regional names such as Brasiliano (South America), Adelaidean (Australian) and Bearmore (Antarctica) have been applied. The Pan African time span of ~500 million years is much longer than any Phanerozoic orogeny. However, it does correlate with time ranges of well defined Phanerozoic orogenic cycles such as the Appalachian cycle, extending from ~1,100 to 250 Ma, and the Cordilleran cycle of ~350 Ma to the present. A significant difference of course is that the Appalachian orogenic cycle has long been recognized as consisting of separate Grenville, Taconic, Acadian and Alleghenian orogenies. Similarly, the Mesozoic-Cenozoic Cordilleran orogenic cycle consists of distinct Antler, Sonoma, Nevadan, Sevier, Laramide and ongoing Cascadian-Andean orogenies. Until recently, the absence of precise geochronology in West Africa has prevented a more refined analysis of individual orogenic events within the Pan-African orogenic cycle. Since 2000, precision geochronologic dating by various researchers in the Anti-Atlas Mountains, Morocco, has provided critical data by which it is now appropriate to designate a Pan African orogenic cycle consisting of three separate orogenic events. We herein propose the following distinct orogenic events in the Anti-Atlas Mountains of Morocco: Iriri-Tichibanine orogeny (750-700 Ma), Bou Azzer orogeny (660-640 Ma) and the WACadomian orogeny (620-580 Ma). Generalized tectonic map of the Anti-Atlas Mountain inliers (Adapted from Ennih and Liégeois, 2008). Geodynamic model of the Pan African orogenic cycle in the Anti-Atlas Mountains. Modified from Walsh et al. (2012) and incorporating ideas from Thomas et al. (2002) and El Hadi et al. (2012).

  6. The early Cretaceous orogen-scale Dabieshan metamorphic core complex: implications for extensional collapse of the Triassic HP-UHP orogenic belt in east-central China

    NASA Astrophysics Data System (ADS)

    Ji, Wenbin; Lin, Wei; Faure, Michel; Shi, Yonghong; Wang, Qingchen

    2016-03-01

    The Dabieshan massif is famous as a portion of the world's largest HP-UHP metamorphic belt in east-central China that was built by the Triassic North-South China collision. The central domain of the Dabieshan massif is occupied by a huge migmatite-cored dome [i.e., the central Dabieshan dome (CDD)]. Origin of this domal structure remains controversial. Synthesizing previous and our new structural and geochronological data, we define the Cretaceous Dabieshan as an orogen-scale metamorphic core complex (MCC) with a multistage history. Onset of lithospheric extension in the Dabieshan area occurred as early as the commencement of crustal anatexis at the earliest Cretaceous (ca. 145 Ma), which was followed by primary (early-stage) detachment during 142-130 Ma. The central Dabieshan complex in the footwall and surrounding detachment faults recorded a consistently top-to-the-NW shearing. It is thus inferred that the primary detachment was initiated from a flat-lying detachment zone at the middle crust level. Removal of the orogenic root by delamination at ca. 130 Ma came into the extensional climax, and subsequently isostatic rebound resulted in rapid doming. Along with exhumation of the footwall, the mid-crustal detachment zone had been warped as shear zones around the CDD. After 120 Ma, the detachment system probably experienced a migration accommodated to the crustal adjustment, which led to secondary (late-stage) detachment with localized ductile shearing at ca. 110 Ma. The migmatite-gneiss with HP/UHP relicts in the CDD (i.e., the central Dabieshan complex) was product of the Cretaceous crustal anatexis that consumed the deep-seated part of the HP-UHP slices and the underlying para-autochthonous basement. Compared with the contemporaneous MCCs widely developed along the eastern margin of the Eurasian continent, we proposed that occurrence of the Dabieshan MCC shares the same tectonic setting as the "destruction of the North China craton". However, geodynamic trigger

  7. What Is an Activity? Appropriating an Activity-Centric System

    NASA Astrophysics Data System (ADS)

    Yarosh, Svetlana; Matthews, Tara; Moran, Thomas P.; Smith, Barton

    Activity-Centric Computing (ACC) systems seek to address the fragmentation of office work across tools and documents by allowing users to organize work around the computational construct of an Activity. Defining and structuring appropriate Activities within a system poses a challenge for users that must be overcome in order to benefit from ACC support. We know little about how knowledge workers appropriate the Activity construct. To address this, we studied users’ appropriation of a production-quality ACC system, Lotus Activities, for everyday work by employees in a large corporation. We contribute to a better understanding of how users articulate their individual and collaborative work in the system by providing empirical evidence of their patterns of appropriation. We conclude by discussing how our findings can inform the design of other ACC systems for the workplace.

  8. Geochronology of the Baie Verte Peninsula, Newfoundland: implications for the tectonic evolution of the Humber and Dunnage Zones of the Appalachian Orogen

    SciTech Connect

    Dallmeyer, R.D.; Hibbard, J.

    1984-09-01

    U-Pb analyses of zircon from the Burlington Granodiorite suggest intrusion at c. 460-465 Ma. Hornblende and biotite from central portions of the pluton record markedly younger /sup 40/Ar//sup 39/Ar plateau dates (410-420 Ma) which are interpreted to date contact metamorphic effects associated with the widespread emplacement of Silurian-Devonian igneous suites. Northern portions of the Burlington Granodiorite are polydeformed and regionally metamorphosed. Hornblende and biotite from this terrane yield /sup 40/Ar//sup 39/Ar plateau ages of 345-350 Ma. U-Pb analyses of zircon from the Dunamagon Granite indicate emplacement at c. 440-460 Ma, thereby providing an upper limit for tectonic juxtapositioning of the Humber and Dunnage Zones along the Baie Verte Line. Similar ages are also recorded by hornblende and biotite throughout northerly portions of the Mings Bight (Humber Zone) and Pacquet Harbour (Dunnage Zone) Groups. These results indicate that the tectonic evolution of the Baie Verte Line as polygenetic, and involved: (1) regionally significant tectonothermal activity prior to the Middle Ordovician and (2) Middle to Late Paleozoic tectonothermal activity centered along easterly segments of the Baie Verte Line. The regional metamorphism associated with this orogenic activity altered primary U-Pb and Rb-Sr isotopic systems within various igneous suites exposed in northeastern portions of the Burlington Peninsula, which may explain some inconsistent geochronological results previously obtained. 54 references, 6 figures, 5 tables.

  9. The Influence of Climate Change in Active Convergent Systems

    NASA Astrophysics Data System (ADS)

    Scarselli, S.; Simpson, G. H.; Allen, P. A.; Minelli, G.

    2006-12-01

    The link between tectonics, surface erosion, and climate in the evolution of mountain belts has been observed in several natural systems (Sinclair & Allen, 1992; Norris & Cooper, 1997; Pavlis et al., 1997; Willett et al., 2006) and numerous theoretical and applied studies have been carried out in the last several years ( Willett et al., 2002; Simpson, 2004 a, c). This relation is particularly sensitive in active convergent orogenic wedges where the efficiency of surface mass transport and climatic change controls the spatial distribution of deformation and sedimentation and degree of crustal thickening (Beaumont et al., 1992; Willett, 1999; Simpson, 2006). This study focus on the effect of climatic changes, leading to palaeogeographic changes, in an active convergent system. In particular, the effects produced by relative sea-level changes and efficiency of the erosional processes have been tested using a two dimensional mechanical model (Simpson, 2006). The model is suited to study deformation, erosion and sedimentation in fold-thrust belts and foreland basins. Two effects of the relative sea-level changes, and in particular in the case of the relative sea-level drop occurring during deformation, can be potentially important for the mechanical behavior of the surrounding crust. Firstly, gravitational water loads above the deforming rocks could be decreased. Secondly, the replacement of submarine with subaerial conditions could probably increase erosion rates, especially within the river system. Both effects would tend to amplify local deformation rates leading to a major pulse of deformation (Simpson, 2006) and to the formation of complex three dimensional deformation patterns (Simpson, 2004). Finally, this model has been used to evaluate the effect of the Messinian salinity crisis in the Mediterranean basin and in particular in the Northern Apennines evolution (Italy). References: Beaumont, C.; Fullsack, P. & Hamilton J., (1992). In: Thrust Tectonics (Ed by K

  10. Signature of Cenozoic orogenic movements in combustion metamorphic rocks: mineralogy and geochronology (example of the Salair-Kuznetsk Basin transition)

    SciTech Connect

    Novikov, I.S.; Sokol, E.V.; Travin, A.V.; Novikova, S.A.

    2008-06-15

    Cenozoic combustion metamorphic (CM) complexes produced by fossil natural coal fires are widespread at range-basin junctions worldwide. Large-scale fires accompany the initial orogenic phases as fresh coal-bearing strata become drawn into the aeration zone as a result of crustal deformation. In combustion metamorphism, the protolith melts to different degrees either into ferrous basic paralava or in glassy clinker. The melt rocks have a phase composition favorable for Ar-40/Ar-39 dating of ignition coeval with the onset of each episode in Late Cenozoic orogenic events. We suggest an algorithm providing correct Ar-40/Ar-39 age determination of CM rocks followed by well-grounded geological interpretation and test the new approach on melt rocks from the Kuznetsk Coal Basin. Paralava samples were dated by Ar-40/Ar-39 incremental heating and the isotope ratios were corrected for Ca-, Cl-, and K-derived Ar isotopic interferences. The interpretation of age-spectrum results was checked against internal and external criteria. The former were plateau and isochrone ages and the latter included the so-called 'couple criterion' and conventional relative ages inferred from geological and stratigraphic evidence. As a result, we distinguished two groups of dates for combustion metamorphic events bracketed between 1.2 {+-} 0.4 and 0.2 {+-} 0.3 Ma. The older ages represent rocks in the western edge of the Prokopievsk-Kiselevsk block of the Salair zone and the younger dates correspond to those in its eastern edge. The reported dates record the time when the fault boundaries of the blocks were rejuvenated during recent activity and the block accreted to the Salair orogenic area as a submontane step. The suggested approach to the choice of objects, classification of rocks, and interpretation of Ar-40/Ar-39 spectra is universal and can be practiced in any area of combustion metamorphism.

  11. Pressure-temperature-deformation-time of the ductile Alpine shearing in Corsica: From orogenic construction to collapse

    NASA Astrophysics Data System (ADS)

    Rossetti, Federico; Glodny, Johannes; Theye, Thomas; Maggi, Matteo

    2015-03-01

    Definition of the Tertiary tectono-metamorphic history of Alpine Corsica is a key task to decipher the space-time linkage between the Alpine and Apennine subduction systems in the Mediterranean region. Alpine Corsica exposes a nappe stack of oceanic- and continental-derived units, structurally juxtaposed onto the former European continental margin (Hercynian Corsica). Still uncertain is the timing of involvement of the continental-derived units in orogenic construction and shift to regional extension. This paper focuses on reconstruction of the pressure-temperature-deformation-time evolution of selected ductile shear zones activated during transition from the tectonic underplating to the extensional reworking stages. New Rb-Sr mineral age data, integrated with structural and thermobarometric investigations constrain the waning stages of the high-pressure (from blueschist to greenschist facies metamorphic conditions) top-to-the-W thrusting of the HP, oceanic-derived realm (Schistes Lustrés Complex) onto the Hercynian Corsica along the East Tenda Shear Zone in the early Oligocene (from ~ 32 to ~ 27 Ma). This early compressional evolution is overprinted by a major phase of retrogressive, syn-greenschist top-to-the-E extensional shearing in the Schistes Lustrés Complex with the last episode of deformation-related ductile recrystallization recorded during the early Miocene at ~ 20-21 Ma, in a continuum transition from ductile to brittle shearing. The same early Miocene Rb-Sr deformation ages are recovered from the ductile-to-brittle top-to-the-E reactivation domains within the East Tenda Shear Zone, documenting that transition from compression to extension in Alpine Corsica occurred during the late Oligocene-early Miocene time lapse. Implications of these data are discussed in the broader context of the Tertiary geodynamic evolution of the Central Mediterranean region.

  12. Data base management systems activities

    NASA Technical Reports Server (NTRS)

    1983-01-01

    The Data Management System-1100 is designed to operate in conjunction with the UNIVAC 1100 Series Operating System on any 1100 Series computer. DMS-1100 is divided into the following four major software components: (1) Data Definition Languages (DDL); (2) Data Management Routine (DMR); (3) Data Manipulation Languages (DML); and (4) Data Base Utilities (DBU). These software components are described in detail.

  13. Orbiter active thermal control system description

    NASA Technical Reports Server (NTRS)

    Laubach, G. E.

    1975-01-01

    A brief description of the Orbiter Active Thermal Control System (ATCS) including (1) major functional requirements of heat load, temperature control and heat sink utilization, (2) the overall system arrangement, and (3) detailed description of the elements of the ATCS.

  14. Contrasting Triassic ferroan granitoids from northwestern Liaoning, North China: Magmatic monitor of Mesozoic decratonization and a craton-orogen boundary

    NASA Astrophysics Data System (ADS)

    Zhang, Xiaohui; Yuan, Lingling; Xue, Fuhong; Zhang, Yanbin

    2012-07-01

    The diversity exhibited by ferroan granitoids testifies to multiple distinct crustal and mantle processes generally within extensional environments and thus holds the key to monitoring important geodynamic and crustal evolutionary processes and calibrating terrane tectonic affinity. This study documents three Middle to Late Triassic ferroan granitoid suites from northwestern Liaoning, North China, and proposes distinct petrogenetic scenarios for each. The Middle Triassic (ca. 238 Ma) Ping'andi (PAD) granites are mainly calc-alkali and peraluminous. Their radiogenic whole-rock Nd and zircon Hf isotopic signatures argue for an origin consistent with partial melting of a juvenile quartzofeldspathic crust formed by prior mantle-derived magmatic underplating and their differentiations. By contrast, the Late Triassic (ca. 220 Ma) Dashaoleng (DSL) and Sijiazi (SJZ) suites show an evolved character from alkali-calcic to alkali and from metaluminous to peraluminous. Their variably evolved whole-rock Sr-Nd and mixed zircon Hf isotopic compositions suggest that both suites were formed by variable mixing between depleted mantle-derived mafic magma and old crust-derived felsic magma, with distinctively higher input from juvenile components in the DSL suite. These contrasting ferroan granitoid suites not only provide a spatial marker for monitoring juxtaposition of the North China Craton (NCC) and the Central Asian Orogenic Belt (CAOB) along a lithospheric-scale boundary fault in the region, but also present a temporal snapshot that records a southwardly-progressing crustal growth scenario possibly in response to lithospheric dripping within a post-orogenic extensional regime. The cratonic scale synthesis further indicates that diachronous decratonization pattern of the NCC might record episodic response of the craton to evolved plate tectonic processes with two contrasting Phanerozoic orogenic systems.

  15. Experiment system of LAMOST active optics

    NASA Astrophysics Data System (ADS)

    Cui, Xiangqun; Su, Ding; Li, Guoping; Yao, Zhengqiu; Zhang, Zhengcao; Li, Yeping; Zhang, Yong; Wang, You; Xu, Xinqi; Wang, Hai

    2004-10-01

    Active optics is the most difficult part in LAMOST project. Especially for the segmented reflecting Schmidt plate Ma, in which both segmented mirror active optics and thin mirror (or deformable mirror) active optics are applied. To test and optimize the thin mirror active optics of Ma, and to approach the reality of operating environment of the telescope, an outdoor experiment system has been established. This experiment system is also a `small LAMOST" with one sub-mirror of the primary mirror Mb and one sub-mirror of the Schmidt plate Ma, and with full scale in spacing (40 meters) between Ma and Mb. many parts of LAMOST were tested in the experiment system except segmented mirror active optics. Especially for force actuators, thin mirror support system, friction driving of the alt-azimuth mounting and its control system, wave front test along such a long optical path. This paper presents the experiment system, research and developments, and some experiment results.

  16. Modeling Cytoskeletal Active Matter Systems

    NASA Astrophysics Data System (ADS)

    Blackwell, Robert

    Active networks of filamentous proteins and crosslinking motor proteins play a critical role in many important cellular processes. One of the most important microtubule-motor protein assemblies is the mitotic spindle, a self-organized active liquid-crystalline structure that forms during cell division and that ultimately separates chromosomes into two daughter cells. Although the spindle has been intensively studied for decades, the physical principles that govern its self-organization and function remain mysterious. To evolve a better understanding of spindle formation, structure, and dynamics, I investigate course-grained models of active liquid-crystalline networks composed of microtubules, modeled as hard spherocylinders, in diffusive equilibrium with a reservoir of active crosslinks, modeled as hookean springs that can adsorb to microtubules and and translocate at finite velocity along the microtubule axis. This model is investigated using a combination of brownian dynamics and kinetic monte carlo simulation. I have further refined this model to simulate spindle formation and kinetochore capture in the fission yeast S. pombe. I then make predictions for experimentally realizable perturbations in motor protein presence and function in S. pombe.

  17. High speed hybrid active system

    NASA Astrophysics Data System (ADS)

    Gonzalez, Ignacio F.; Chang, Fu-Kuo; Qing, Peter X.; Kumar, Amrita; Zhang, David

    2005-05-01

    A novel piezoelectric/fiber-optic system is developed for long-term health monitoring of aerospace vehicles and structures. The hybrid diagnostic system uses the piezoelectric actuators to input a controlled excitation to the structure and the fiber optic sensors to capture the corresponding structural response. The aim of the system is to detect changes in structures such as those found in aerospace applications (damage, cracks, aging, etc.). This system involves the use of fiber Bragg gratings, which may be either bonded to the surface of the material or embedded within it in order to detect the linear strain component produced by the excitation waves generate by an arbitrary waveform generator. Interrogation of the Bragg gratings is carried out using a high speed fiber grating demodulation unit and a high speed data acquisition card to provide actuation input. With data collection and information processing; is able to determine the condition of the structure. The demands on a system suitable for detecting ultrasonic acoustic waves are different than for the more common strain and temperature systems. On the one hand, the frequency is much higher, with typical values for ultrasonic frequencies used in non-destructive testing ranging from 100 kHz up to several MHz. On the other hand, the related strain levels are much lower, normally in the μstrain range. Fiber-optic solutions for this problem do exist and are particularly attractive for ultrasonic sensing as the sensors offer broadband detection capability.

  18. Srsbnd Ndsbnd Pb isotopic compositions of Early Cretaceous granitoids from the Dabie orogen: Constraints on the recycled lower continental crust

    NASA Astrophysics Data System (ADS)

    He, Yongsheng; Li, Shuguang; Hoefs, Jochen; Kleinhanns, Ilka C.

    2013-01-01

    In order to characterize the recycled lower continental crust (LCC) in the Dabie orogen, 17 Early Cretaceous low-Mg adakitic (LMA) and 9 normal (non-adakitic) granitoids have been investigated for Srsbnd Ndsbnd Pb isotopes. Combined with literature data, LMA have low ƐNd(t) (- 27.8 to - 14.7) and 206Pb/204Pb(i) (15.69-17.16) and low to moderately high 87Sr/86Sr(i) (0.7066 to 0.7087) ratios. Normal granitoids yield isotope ratios similar to adakitic rocks, except a few with 87Sr/86Sr (i) up to 0.7105. Dabie LMA define a linear trend parallel to the North Hemisphere Reference Line (NHRL) in a 208Pb/204Pb(i)- 206Pb/204Pb(i) diagram. For a given 206Pb/204Pb(i), the 208Pb/204Pb(i) or ∆8/4 (152-217) of Dabie LMA are close to the majority of UHP gneisses and the Neoproterozoic mafic rocks from the northern margin of the South China Block (SCB), but significantly higher than adakitic rocks from the North China Block (∆8/4 < 150). Considering the commonly present Neoproterozoic inherited zircons, we suggest that the LMA in the Dabie orogen are derived from a thickened LCC that could be dominantly composed of ancient SCB lower crust. The Srsbnd Ndsbnd Pb isotopic composition of LMA are similar to those of Post-Collisional Mafic Igneous rocks (PCMI) from the Dabie orogen, but different to exhumed UHP rocks. The Srsbnd Ndsbnd Pb isotopic system of the mantle source of the PCMI could be enriched in components dominantly from delaminated LCC of the Dabie orogen instead of deeply subducted continental crust, which is in contrast to O- and C-isotope data by [Zhao, Z.F., Zheng, Y.F., Wei, C.S., Wu, Y.B., Chen, F.K., and Jahn, B.M., 2005. Zircon Usbnd Pb age, element and Csbnd O isotope geochemistry of post-collisional mafic-ultramafic rocks from the Dabie orogen in east-central China. Lithos 83(1-2), 1-28; Dai, L.Q., Zhao, Z.F., Zheng, Y.F., Li, Q.L., Yang, Y.H., and Dai, M.N., 2011. Zircon Hfsbnd O isotope evidence for crust-mantle interaction during continental deep

  19. Crustal structure and evolution of the Trans-Hudson orogen: Results from seismic reflection profiling

    NASA Astrophysics Data System (ADS)

    Baird, D. J.; Nelson, K. D.; Knapp, J. H.; Walters, J. J.; Brown, L. D.

    1996-04-01

    A 400-km-long deep seismic reflection transect across northeastern Montana and northern North Dakota reveals the crustal-scale structural fabric of the Early Proterozoic Trans-Hudson orogen beneath the Williston basin. Comparison with deep seismic reflection data across the Canadian portion of the same orogen ˜700 km to the north reveals first-order similarities in crustal architecture but documents significant along-strike variation in orogenic evolution. Both transects display a broad crustal-scale antiform axial to the orogen. In the north, geologic data suggest that this antiform is cored by an Archean microcontinent. In the south, west dipping reflections on the western flank of the antiform extend from the upper crust to the uppermost mantle and truncate prominent subhorizontal lower crustal reflections of the Archean Wyoming craton. Within the Wyoming craton, the eastern limit of east dipping midcrustal reflections coincides with the subsurface age boundary between the craton and the Early Proterozoic Trans-Hudson orogen as interpreted from potential field and drill core data. On the basis of subsurface geochronologic data from the crystalline basement and by analogy with the Glennie domain within the exposed Trans-Hudson orogen in Canada, we suggest that the southern antiform is cored by an Archean crustal fragment that was caught up in the terminal collision of the Wyoming and Superior cratons during Hudsonian orogeny. The eastern side of the Trans-Hudson orogen is characterized on both seismic transects by predominantly east dipping crustal penetrating reflections. We interpret the easterly dip of these reflections as evidence that the Superior province was thrust westward over the interludes of the orogen during terminal collision. Although juvenile Early Proterozoic terranes characterize the exposed segment of the Trans-Hudson orogen in Canada, limited drill core information within the Dakota segment of the orogen shows a predominance of granulitic

  20. The geometries and development of late orogenic strike-slip faults

    NASA Astrophysics Data System (ADS)

    Anderson, M. W.; Peacock, D. C. P.

    2003-04-01

    Strike-slip faults are commonly the final phase of contraction in orogenic belts, occurring when the folds have locked-up and the thrusts have become too steep for further displacement to occur. Where the maximum stress axis (sigma1) is perpendicular to the orogenic belt (i.e. pure shear), the strike-slip faults are conjugate and represent strike-perpendicular shortening and necessary strike-parallel extension. An example of such behaviour occurs in the steeply dipping Silurian sandstones and shales in Kirkcudbrightshire, in the Southern Uplands of Scotland. If sigma1 is at ~ 70°; to the strike of the orogenic belt, the conjugate strike-slip faults become asymmetric. One set of strike-slip faults occurs at a high angle to the strike of bedding, and the conjugate set has a ramp-flat trajectory across steeply dipping beds. An example of this behaviour occurs in the steeply dipping Silurian turbidites at Ardglass, in the Longford-Down terrane of Northern Ireland. If sigma1 is at a lower angle to the orogenic belt (i.e. transpression), one set of strike-slip faults tends to dominate. In some cases, the dominant strike-slip fault set is parallel to the strike of the orogenic belt, the Caledonian-age Great Glen Fault of Scotland being such an example. In other cases, block rotation occurs on the set of strike-slip faults that are at a high angle to the orogenic belt, as in the Variscan Orogenic Belt of SW England. An annulus model is presented to illustrate the variations in geometries of late-orogenic strike-slip faults from pure shear to transpression.

  1. How is Silurian-Early Devonian faulting in the North America continental interior related to orogenic processes at plate boundaries? A working hypothesis from the Canadian North

    NASA Astrophysics Data System (ADS)

    Pinet, Nicolas

    2015-04-01

    The Paleozoic Appalachian/Franklinian orogen that rims the North America continent on its eastern and northern sides is comparable in size with Tethyan orogenic belts. However, the far-field effects in the continental interior of the multiple Ordovician to Carboniferous deformation phases that built the orogen were relatively minor if compared with those associated with the Himalayas and Alps, a characteristics related to the high integrated strength of the North American craton. Despite the generally little deformation of the continental interior, two regional-scale tectonic features preserved evidence of significant Paleozoic tectonism: the fault bounded Hudson Bay Central High (HBCH) and the Boothia uplift/Cornwallis fold belt (BUCF) in the Canadian Arctic. In the Hudson Bay intracratonic basin, the lower part of the sedimentary succession (Upper Ordovician to Lower Devonian) is cut by high-angle faults and overlain by a saucer-shape, essentially underformed sedimentary package (Middle to Upper Devonian). The main structural feature is the NNW-trending HBCH that extends for a minimum length of 500 km with normal faults characterized by throws up to 500 m that were mainly active during the Silurian - Early Devonian period. The >700-km long, N-trending BUCF is nearly perpendicular to the deformation front of the Franklinian mobile belt. In its southern segment (Boothia uplift), its western side is characterized by an east-dipping reverse fault zone that puts Precambrian rocks over Paleozoic strata. In its northern segment (Cornwallis fold belt), the Paleozoic succession is involved in open folds and cuts by steeply dipping reverse faults. Syn-tectonic clastic sediments constrain the age of structures to the latest Silurian-Early Devonian. Comparison of the HBCH and BUCF indicates that they are grossly parallel, partly contemporaneous but with different kinematics. This kinematic variability may be explained if they are genetically linked with different segments of

  2. Tectonic evolution of the western Kunlun orogenic belt, western China

    NASA Astrophysics Data System (ADS)

    Zhihong, Wang

    2004-11-01

    The western Kunlun orogenic belt in western China evolved through the development of a large subduction-accretionary complex, including flysch sediments and granitic plutons, and by collision of three terranes, namely the North and South Kunlun and Karakorum-Qiangtang blocks from the early Paleozoic to the early Mesozoic. North-dipping subduction of the Paleo-Tethys ocean beneath the Kunlun terranes, which may have commenced in the Cambrian, produced an early Paleozoic Andean-type magmatic arc on the South Kunlun, and a marginal back arc basin, represented by the early Paleozoic Oytag-Kudi ophiolite belt, between the North and South Kunlun. A northward subduction zone consumed the basin and the young, hot upper plate lithosphere was obducted southward onto the South Kunlun following closure of the basin. This resulted in collision of the North and South Kunlun in the early Devonian. Continuous northward subduction of Paleo-Tethys resulted in the development of a Carboniferous-Triassic magmatic arc, and a back arc rifting sequence composed of the Carboniferous to Permian carbonates and clastic sediments on the North and South Kunlun terranes. The Paleo-Tethys ocean finally closed in the late Triassic-early Jurassic, when the Kunlun and Karakorum-Qiangtang blocks were accreted, with the Kara-Kunlun accretionary prism marking their suture zone.

  3. Late Paleozoic orogenic episodes, Trans-Pecos Texas

    SciTech Connect

    Muehlberger, W.R. . Dept. of Geological Sciences)

    1993-04-01

    The onset of the Ouachita orogeny is marked by the absence of rock of Early Mississippian age. This is interpreted to be the result of the narrowing of the trans-equatorial seaway between North America and the oncoming South American plate. Foredeep filling (Pulse I) began in Early Meramecian time with northward-prograding Tesnus Fm siliciclastic turbidites. Pulse 2 began in Atokan time with northward-prograding siliciclastic turbidites of the Haymond Fm. The thrust belt to the south had now intersected the edge of the NAm carbonate platform as shown by clasts of Middle Cambrian carbonates, as well as Ouachita facies clasts, and rounded clasts of Precambrian quartzite, metarhyolite, and gneiss of unknown source. During Late Pennsylvanian time deltaic sediments prograded across the Marathon region into the southern Permian Basin (Gaptank Fm). In Early Wolfcampian time (Pulse 3), all these units were translated on the Dugout Creek thrust, then (Pulse 4 ) translated finally on a frontal imbricate before deposition of Upper Wolfcampian units across the eroded toes of the thrust sheets. Permian Basin orogenic phases parallel those outlined above. Transgressive clastics from the south and the subdivision of the earlier broad, shallow Tobosa Basin into the uplifts and basins that characterize the Permian Basin began in the Mississippian and became prominent structural units by Late Mississippian time.

  4. The Andes as a peripheral orogen of the breaking-up Pangea

    NASA Astrophysics Data System (ADS)

    Lomize, M. G.

    2008-05-01

    Formation conditions of the peripheral orogen are expressed most fully in the Central Andes, a mountain system almost not yielding in height to the Himalayan-Tibetan system but formed at the margin of ocean without any relations to intercontinental collision. The marine transgression and rejuvenation of subduction in the Early Jurassic during the origination of foldbelt at the margin of Pangea marked the transition to a new supercontinental cycle, and the overall further evolution began and continues now in the frame of the first half of this cycle. The marginal position of this belt above the subduction zone, the rate and orientation of convergence of the lithospheric plates, the age of “absolute” movement of the continental plate, variation in slab velocity, and subduction of heterogeneities of the oceanic crust were the crucial factors that controlled the evolution of the marginal foldbelt. At the stage of initial subsidence (Jurassic-Mid-Cretaceous), during extension of the crust having a moderate thickness (30-35 km), the Andean continental margin comprises the full structural elements of an ensialic island arc that resembled the present-day Sunda system. These conditions changed with the separation and onset of the western drift of the South American continent. Being anchored in the mantle and relatively young, the slab of the Andean subduction zone served as a stop that brought about compression that controlled the subsequent evolution. Due to the contribution of deep magma sources along with marine sediments and products of tectonic erosion removed to a depth, the growth of crust above the subduction zone was favorable for heating of the crust. By the middle Eocene, when compression enhanced owing to the acceleration of subduction, the thermal evolution of the crust had already prepared the transition to the orogenic stage of evolution, i.e., to the progressive viscoplastic shortening and swelling of the mechanically weakened lower crust and the

  5. Centrally activated pipe snubbing system

    DOEpatents

    Cawley, William E.

    1985-01-01

    An electromechanical pipe snubbing system and an electromechanical pipe snubber. In the system, each pipe snubber, in a set of pipe snubbers, has an electromechanical mechanism to lock and unlock the snubber. A sensor, such as a seismometer, measures a quantity related to making a snubber locking or unlocking decision. A control device makes an electrical connection between a power supply and each snubber's electromechanical mechanism to simultaneously lock each snubber when the sensor measurement indicates a snubber locking condition. The control device breaks the connection to simultaneously unlock each snubber when the sensor measurement indicates a snubber unlocking condition. In the snubber, one end of the shaft slides within a bore in one end of a housing. The other end of the shaft is rotatably attached to a pipe; the other end of the housing is rotatively attached to a wall. The snubber's electromechanical mechanism locks the slidable end of the shaft to the housing and unlocks that end from the housing. The electromechanical mechanism permits remote testing and lockup status indication for each snubber.

  6. Strong Lg-wave attenuation in the Middle East continental collision orogenic belt

    NASA Astrophysics Data System (ADS)

    Zhao, Lian-Feng; Xie, Xiao-Bi

    2016-04-01

    Using Lg-wave Q tomography, we construct a broadband crustal attenuation model for the Middle East. The QLg images reveal a relationship between attenuation and geological structures. Strong attenuation is found in the continental collision orogenic belt that extends from the Turkish and Iranian plateau to the Pamir plateau. We investigate the frequency dependence of QLg in different geologic formations. The results illustrate that QLg values generally increase with increasing frequency but exhibit complex relationships both with frequency and between regions. An average QLg value between 0.2 and 2.0 Hz, QLg (0.2-2.0 Hz), may be a critical index for crustal attenuation and is used to infer the regional geology. Low-QLg anomalies are present in the eastern Turkish plateau and correlate well with low Pn-velocities and Cenozoic volcanic activity, thus indicating possible partial melting within the crust in this region. Very strong attenuation is also observed in central Iran, the Afghanistan block, and the southern Caspian Sea. This in line with the previously observed high crustal temperature, high-conductivity layers, and thick marine sediments in these areas, suggests the high Lg attenuation is caused by abnormally high tectonic and thermal activities.

  7. Syn-orogenic extensional pulses within the contractional history of thrust wedges. The Val di Lima low-angle normal fault case study, Northern Apennines, Italy.

    NASA Astrophysics Data System (ADS)

    Clemenzi, Luca; Molli, Giancarlo; Storti, Fabrizio; Muchez, Philippe; Swennen, Rudy; Torelli, Luigi

    2014-05-01

    In this contribution we describe the Val di Lima low-angle fault system, a kilometric-scale extensional structure exposed in the central sector of the Northern Apennines thrust wedge, Italy. The low-angle extensional fault system delaminates the right-side-up limb of a km-scale recumbent isoclinal anticline that affects the carbonate-dominated Late Triassic to early Early Miocene non-metamorphic Tuscan succession. The low-angle fault system, in turn, is affected by superimposed folding and late-tectonic high-angle extensional faulting. The three-dimensional configuration of the low-angle fault system has been investigated through detailed structural mapping and restoration of the superimposed deformations, while the fault damage zone architecture has been characterized in outcrops with appropriate exposure. Pressure-depth conditions and palaeofluid evolution of the fault system have been studied through microstructural, mineralogical, petrographic, fluid inclusion and stable isotope analysis of fault rocks and fault-related calcite and quartz veins. Our results show that the low-angle fault system was active during exhumation of the Tuscan succession, at estimated conditions of about 180°C and 5.2 km depth. The fault system had a twofold influence on fluid circulation within the orogenic wedge: i) it allowed the migration of low-salinity fluids, due to the increased permeability along the fault zone; ii) it favored footwall fluid overpressures where the fault core acted as an efficient hydraulic barrier. Abundant fluid circulation in fault damage zones also characterized the late-stage evolution of the low-angle fault system, allowing the recrystallization of calcite veins and limestone host rocks at shallower conditions (~ 4 km). Within this P-T framework, the fault zone architecture shows important differences, related to the different lithologies involved in the fault system and to the role played by the fluids during deformation. In particular, footwall fluid

  8. Active microrheology in active matter systems: Mobility, intermittency, and avalanches.

    PubMed

    Reichhardt, C; Reichhardt, C J Olson

    2015-03-01

    We examine the mobility and velocity fluctuations of a driven particle moving through an active matter bath of self-mobile disks for varied density or area coverage and varied activity. We show that the driven particle mobility can exhibit nonmonotonic behavior that is correlated with distinct changes in the spatiotemporal structures that arise in the active media. We demonstrate that the probe particle velocity distributions exhibit specific features in the different dynamic regimes and identify an activity-induced uniform crystallization that occurs for moderate activity levels and is distinct from the previously observed higher activity cluster phase. The velocity distribution in the cluster phase has telegraph noise characteristics produced when the probe particle moves alternately through high-mobility areas that are in the gas state and low-mobility areas that are in the dense phase. For higher densities and large activities, the system enters what we characterize as an active jamming regime. Here the probe particle moves in intermittent jumps or avalanches that have power-law-distributed sizes that are similar to the avalanche distributions observed for nonactive disk systems near the jamming transition. PMID:25871116

  9. Aeromagnetic study of the Hengshan-Wutai-Fuping region: Unraveling a crustal profile of the Paleoproterozoic Trans-North China Orogen

    NASA Astrophysics Data System (ADS)

    Zhang, Jian; Zhao, Guochun; Shen, Wenlue; Li, Sanzhong; Sun, Min

    2015-11-01

    An integrated crustal profile of the intervening Trans-North China Orogen (TNCO) is one of the key issues to understanding the tectonic evolution of the North China Craton. However, the existing geological studies focus only on the surface-mapping based petrological, geochemical and structural analysis, but lack subsurface geophysical evidence and thus make the crustal profile interpretations ambiguous. In contrast, the current geophysical data covers a very large-scale lithospheric mantle and fails to image the detailed structural pattern of the orogenic crust. To achieve this goal, we present high-resolution aeromagnetic data for the Hengshan-Wutai-Fuping region, the largest exposure of the central TNCO. The reduced-to-pole magnetic anomaly map firstly verifies the regional tectonic subdivision that the high-grade metamorphic terranes (i.e. Hengshan and Fuping Complexes) are consistent with high-magnetic responses and long-wavelength anomalies, intervened by a low-grade terrane (Wutai Complex) characterized by low-magnetic responses and short-wavelength anomalies. 3D Euler deconvolution reveals that the tendencies of the clustered solutions show large consistence with the major structural pattern of the region which is characterized by a fan-shaped doubly-vergent orogenic wedge. Upward continuation further shows that the northwest part of the orogen yields a thicker crust and is most likely located closer to the paleosubduction zone. The new aeromagnetic data, combined with structural, petrological and metamorphic data indicate that an eastward-dipping subduction zone was most possibly active before the collision of the Western and Eastern Blocks, leading to the formation of the TNCO and the final amalgamation of the North China Craton.

  10. Seismic Tomography Reveals Breaking Crust and Lithosphere Beneath a Classic Orogen

    NASA Astrophysics Data System (ADS)

    Byrne, T. B.; Rau, R.; Kuo-Chen, H.; Lee, Y.; Ouimet, W. B.; Van Soest, M. C.; Huang, C.; Wu, F. T.

    2013-12-01

    The orogenic system in Taiwan is often considered a classic example of an accretionary prism that has grown to a steady-state size and shape above an also steady subduction zone. A new study of vertical and horizontal sections of a tomographic velocity model created by Kuo-Chen et al. (2012) show, however, both a well-developed crack in the subducted crust beneath southern Taiwan and a discontinuous lithosphere beneath northern Taiwan, suggesting that slab breakoff is actively occurring beneath Taiwan. The transition from slab breakoff to cracking crust in southern Taiwan also suggests that slab breakoff is propagating southward, consistent an oblique collision. The crack in the subducting crust is revealed by progressively deeper horizontal sections of the local-scale tomographic model. The sections show an ellipsoidal-shaped area of high velocity that plunges southeast, oblique to all of the regional trends. Taking into account the dip of the slab, however, the area of high velocity is nearly parallel to previously recognized fracture zone in the Eurasian continental margin. We interpret the area of high velocity to be a crack in the Eurasian crust that is filled high velocity Eurasian mantle. Support for this interpretation comes from: 1) new exhumation cooling data from Mt Yu, the highest peak in Taiwan; 2) a recent leveling survey along the South Cross-Island Highway that shows unusually high rates of surface uplift (up to 15 mm/yr; Ching et al., 2011); 3) Vp attenuation studies that suggest anomalously high temperatures and/or the presence of fluids; 4) earthquake focal mechanisms in the core of the southern Central Range that are dominated by NE-SW extension; and finally, 5) the core of the southern Central Range preserves anomalous areas of low topographic relief that straddle the crest of the range. The areas of low relief are fringed by stream channels with relatively high stream gradient indexes and do not appear related to weaker rock types, glacial

  11. Continental Construction and Crustal Growth of Central Asian Orogenic Belt in Mongolia

    NASA Astrophysics Data System (ADS)

    Schulmann, K.; Guy, A.; Lehmann, J.; Seltmann, R.; Lexa, O.

    2013-12-01

    The geophysical and geochemical data document crustal growth and continent construction processes responsible for episodic formation of Central Asian Orogenic Belt (CAOB) crust in Mongolia. Here, well-defined Cambrian suture rims the western borders of Proterozoic continental fragments in Mongolia and Russia (1200 to 700 Ma). This arcuate suture zone is defined by numerous ophiolites (800-560 Ma) originated by Early Cambrian obduction of young (Late Proterozoic) oceanic basins and magmatic arcs. The juvenile crust further south is built by gneisses a metasediments dated at 530-470 Ma interpreted as a Cambro-Ordovician accretionary prism intruded by juvenile Devono-Carboniferous Japan type magmatic arcs. The southerly mantle fragments covered by Silurian cherts, Devonian basaltic volcanics and late Devonian volcanoclastic sediments are interpreted as an oceanic crust of back arc and oceanic arc affinity. Following scenario is proposed: 1) Proterozoic basement blocks formed N-S trending zone documented by the shape of Early Cambrian suture, 2) Devono-Carboniferous magmatic arcs were emplaced during E-W shortening event along western margin of this zone leading to moderate crustal shortening, 3) the intra oceanic ophiolites were thrust over Devonian volcanoclastics during Late Carboniferous in the E-W direction. All that suggests that the early Devonian (Phillipiny sea type) back arc spreading was replaced by 50 to 80 My lasting E-W compressive regime during prolonged activity of north trending Mongol-Okhotsk Pacific type subduction zone. The change in tectonic movements from E-W to N-S is responsible for oroclinal bending of trail of Mongolian microcontinents and scissor-like closure of Mongol Okhotsk (Pacific ocean embayment) ocean. We conclude that both crustal growth and crustal construction are episodic in the CAOB. The former process occurred in two main episodes related to Pacific subduction, while the continental construction is a complex sequence of two peri

  12. Time-space focused intrusion of genetically unrelated arc magmas in the early Paleozoic Ross-Delamerian Orogen (Morozumi Range, Antarctica)

    NASA Astrophysics Data System (ADS)

    Rocchi, S.; Di Vincenzo, G.; Dini, A.; Petrelli, M.; Vezzoni, S.

    2015-09-01

    The growth of continental crust in accretionary orogenic belts takes place through repeated cycles of subduction-accretion of rock units from continental and oceanic magmatic arcs, supra-subduction zone backarcs and forearcs loaded with continent-derived materials. An ancient example relevant to magmatic arc accretion models is represented by the remnants of the Cambrian-Ordovician Ross Orogen in the Morozumi Range, Victoria Land (Antarctica). There, late Neoproterozoic phyllites host an intrusive complex which preserves a remarkably uncommon record of genetically unrelated magma pulses emplaced under a variable stress regime in a short time span: (1) a dominant K-feldspar-phyric granite, (2) fine-grained dioritic stocks and dykes, (3) a peraluminous granite; and (4) a tonalitic-granodioritic dyke swarm. Laserprobe U-Pb zircon dates cluster at late Cambrian times for all these units, yet they carry differential cargoes of relict cores. Unique geochemical-isotopic signatures for both the less evolved magmas (diorite and dyke tonalite) and the most acidic ones (granite and peraluminous granite) indicate that each one of them originated from distinct sources at depth. Additionally, field relationships and chemical evolutionary trends testify for a variety of shallow level open-system processes, such as magma mingling/mixing between diorite and main granite magmas, as well as progressive incorporation of the host schists by the dyke tonalite magma. In summary, crustal growth in the Morozumi intrusive complex was contributed by fresh mantle magma issuing from the metasomatised mantle wedge, while the production of other melts did recycle different crustal portions/layers: the main granite derived from Grenville-age granulitic lower crust; the peraluminous granite from late Proterozoic upper crust, and the tonalite magmas derived from subduction erosion-enriched subarc mantle and evolved by ingestion of local metasedimentary rocks. Overall, the Morozumi intrusive complex

  13. PASS: Creating Physically Active School Systems

    ERIC Educational Resources Information Center

    Ciotto, Carol M.; Fede, Marybeth H.

    2014-01-01

    PASS, a Physically Active School System, is a program by which school districts and schools utilize opportunities for school-based physical activity that enhance overall fitness and cognition, which can be broken down into four integral parts consisting of connecting, communicating, collaborating, and cooperating. There needs to be an…

  14. Active impedance matching of complex structural systems

    NASA Technical Reports Server (NTRS)

    Macmartin, Douglas G.; Miller, David W.; Hall, Steven R.

    1991-01-01

    Viewgraphs on active impedance matching of complex structural systems are presented. Topics covered include: traveling wave model; dereverberated mobility model; computation of dereverberated mobility; control problem: optimal impedance matching; H2 optimal solution; statistical energy analysis (SEA) solution; experimental transfer functions; interferometer actuator and sensor locations; active strut configurations; power dual variables; dereverberation of complex structure; dereverberated transfer function; compensators; and relative power flow.

  15. Distribution of strain rates in the Taiwan orogenic wedge

    NASA Astrophysics Data System (ADS)

    Mouthereau, F.; Fillon, C.; Ma, K.-F.

    2009-07-01

    To constrain the way Eurasian crust is accreted to the Taiwan orogenic wedge we investigate the present-day 3D seismogenic deformation field using the summation of 1129 seismic moment tensors of events ( Mw > 4) covering a period of 11 years (1995 to 2005). Based on the analysis of the principal strain-rate field, including dilatation and maximum shear rates, we distinguish four domains. Domain I comprises the Coastal Plain and the Western Foothills. It is mainly contractional in both the horizontal plane and in cross-section. Domain II comprises the eastern Western Foothills, the Hsuehshan Range and the Backbone Range. It is characterized by the highest contraction rates of 10 - 6 yr - 1 in association with area expansion in cross-section and area contraction in the horizontal plane. Domain III corresponds to the Central Range. It is characterized by area contraction in cross-section and area expansion in the horizontal plane. The maximum contractional axis is typically low and plunges ~ 30°E. Extension is larger, horizontal and strikes parallel to the axis of the mountain range. Domain IV corresponding to the Coastal Range and offshore Luzon Arc shows deformation patterns similar to domain II. This seismogenic strain-rate field, which is found in good agreement with the main features of the geodetic field, supports shortening within a thick wedge whose basal décollement is relatively flat and located in the middle-to-lower crust > 20 km. The east plunges of maximum strain-rate axes below the Central Range argue for the development of top-to-the-east transport of rocks resulting from the extrusion of the whole crust along west-dipping crustal-scale shear zones. The study of seismogenic strain rates argues that the initiation of subduction reversal has already started in the Taiwan collision domain.

  16. Propagation tectonics and multiple accretionary processes of the Qinling Orogen

    NASA Astrophysics Data System (ADS)

    Dong, Yunpeng; Zhang, Xiaoning; Liu, Xiaoming; Li, Wei; Chen, Qing; Zhang, Guowei; Zhang, Hongfu; Yang, Zhao; Sun, Shengsi; Zhang, Feifei

    2015-05-01

    The Qinling Orogen was built through collision between the North China and South China Blocks. Previous detailed geological, geochemical and geochronological investigations revealed that the mountain range can be divided into four tectonic units with distinct tectono-lithostratigraphy, which are, from north to south, the southern sector of the North China Block, North Qinling Belt, South Qinling Belt and northern sector of the South China Block, separated by the Kuanping, Shangdan and Mianlue sutures. According to the petrology, geochemistry and geochronology of ophiolitic mélanges and related magmatic rocks, as well as the features of sedimentary units, we think that the North China Block, the North Qinling Belt and the South China Block were originally independent continental units while the South Qinling Belt had been the northern part of the South China Block. These units experienced three episodes of accretionary tectonic processes and amalgamation from south to north. The Neoproterozoic accretion took place along the Luonan-Luanchuan Fault and Kuanping ophiolitic mélange belt as a result of southward subduction and subsequent collision between the North Qinling and North China Blocks during ca. 1.0-0.8 Ga related to the formation of the supercontinent of Rodinia. The Paleozoic accretion occurred along the Shangdan suture resulted from northward subduction of oceanic lithosphere in the Early Paleozoic and subsequent continental subduction in the Late Paleozoic. Late Triassic accretion took place along the Mianlue suture between the South Qinling and South China Blocks due to northward subduction of the Mianlue oceanic lithosphere during the Permian-Early Triassic and subsequent collision in the Late Triassic. After the Late Triassic collision along the Mianlue suture the whole Qinling Mountain range entered the phase of intense intracontinental deformation.

  17. Petrogenesis and U-Pb zircon chronology of felsic tuffs interbedded with turbidites (Eastern Pontides Orogenic Belt, NE Turkey): Implications for Mesozoic geodynamic evolution of the eastern Mediterranean region and accumulation rates of turbidite sequences

    NASA Astrophysics Data System (ADS)

    Eyuboglu, Yener

    2015-01-01

    The Meso-Cenozoic geodynamic evolution of the Eastern Pontides Orogenic Belt, which is one of the key areas of the Alpine-Himalayan system, is still controversial due to lack of systematic geological, geophysical, geochemical and chronological data. The prevailing interpretation is that this belt represents the southern margin of Eurasia during the Mesozoic and its geodynamic evolution is related to northward subduction of oceanic lithosphere. This paper reports the first detailed geological, geochemical and chronological data from felsic tuffs interbedded with late Cretaceous turbidites in the Southern Zone of the Eastern Pontides Orogenic Belt. Individual tuff layers are thin, mostly < 2 m in thickness, implying that these are dominantly air-fall tuffs. Petrographic data indicate that the felsic tuffs, which exhibit various degrees of alteration, can be classified as crystal-rich and crystal-poor tuffs. The crystal-poor tuffs consist mainly of 45-65% devitrified glass shards and 10-20% broken quartz crystals, whereas the crystal-rich tuffs consist of > 50% crystals. The zircon U-Pb data show three statistically distinct ages at 84, 81 and 77 Ma, with uncertainties of about 1 Ma, suggesting that tuff-forming late Cretaceous magmatism started about 84 Ma ago and was episodically active over a minimum of 7 Ma. The age data also indicate that the average accumulation rate of the turbiditic sequence that hosts the felsic tuffs remained constant between 36 and 40 cm/10 ky. Their enrichment in LIL and LRE elements relative to HFS and HRE elements, and also strongly negative Nb, Ta and Ti anomalies, are consistent with those of magmas generated by subduction-related processes. The tuffs have relatively low initial ratios of 143Nd/144Nd (0.512296-0.512484; εNd: - 2.1 and - 7.2) and 87Sr/86Sr (0.704896-0.706159). Their initial Pb isotopic compositions range from 18.604 to 18.646 for 206Pb/204Pb, from 15.644 to 15.654 for 207Pb/206Pb and from 38.712 to 38.763 for 208Pb/204

  18. Influence of syn-sedimentary faults on orogenic structures in a collisional belt: Insights from the inner zone of the Northern Apennines (Italy)

    NASA Astrophysics Data System (ADS)

    Brogi, Andrea

    2016-05-01

    This paper discusses the possible influence of syn-sedimentary structures on the development of orogenic structures during positive tectonic inversion in the inner Northern Apennines (Italy). Examples from key areas located in southern Tuscany provided original cartographic, structural and kinematics data for Late Oligocene-Early Miocene thrusts, organized in duplex systems, verging in the opposite direction of the foreland propagation (back-thrusts), which affected the Late Triassic-Oligocene sedimentary succession of the Tuscan Domain, previously affected by pre-orogenic structures. These latter consist of mesoscopic-to cartographic-scale Jurassic syn-sedimentary normal faults and extensional structures, which gave rise to effective stratigraphic lateral variation and mechanical heterogeneities. Structural analysis of both syn-sedimentary faults and back-thrusts were therefore compared in order to discuss the possible role of the pre-existing anisotropies in influencing the evolution of the back-thrusts. As a result, it can be reasonably proposed that back-thrusts trajectories and stacking pattern were controlled by relevant syn-sedimentary normal faults; these latter were reactivated, in some cases, if properly oriented. Such an issue adds new inputs for discussing the potential role of structural inheritance during tectonic inversions, and helps to better understand the processes suitable for the development of back-thrusts in the inner zones of orogenic belts, as it is the case of the inner Northern Apennines.

  19. Controls of erosional denudation in the orogen on foreland basin evolution: The Oligocene central Swiss Molasse Basin as an example

    NASA Astrophysics Data System (ADS)

    Schlunegger, Fritz; Jordan, Teresa E.; Klaper, Eva Maria

    1997-10-01

    A high-resolution three-dimensional reconstruction of the 25-m.y.-old central Swiss Molasse Basin reveals two sedimentary domains separated by a ˜5-km-wide flood-plain. The proximal domain of the basin attained a width of 20 km, and its basement is steeply flexed (6°-7° dip). Petrographic data indicate that it was filled by sediment from the Rigi dispersal system derived from the central Alps of eastern Switzerland and by locally sourced bajadas. In contrast, the distal sedimentary domain, located farther north, was gently dipping (<2°) and was filled by the meandering Lac Léman and Honegg dispersal systems. Chronological data reveal that sedimentation in the northern proximal part of the basin started at ˜27 Ma, when sediment supply to the basin started to increase. Deflection of the foreland plate at ˜25 Ma is successfully simulated by flexural modeling of the thrust load and the sediment load. The model reveals that the Lac Léman and Honegg dispersal systems are located on a buried flexural bulge. Furthermore, it shows that burial and suppression of the flexural bulge at ˜27 Ma as well as an increase of the basin wavelength were controlled by the contemporaneous increase in the sediment supply rate of the Rigi system. The model presented suggests that the tectonic subsidence of the Molasse Basin was mainly controlled by tectonic events in the northern part of the orogen, within ˜70 km distance from the tip of the orogenic wedge. Crustal thickening in this part of the orogen is reflected in the proximal Molasse by sedimentary cycles characterized by an increase in the sediment accumulation rates up section and by the presence of locally sourced bajada fans at the top of each cycle. Although south vergent back thrusting along the Insubric Line ˜150 km south of the foreland basin contributed little to flexure, it resulted in an increase of the sediment supply to the foreland basin. This is reflected in the Molasse by coarsening and thickening upward

  20. Phase Transitions in Model Active Systems

    NASA Astrophysics Data System (ADS)

    Redner, Gabriel S.

    The amazing collective behaviors of active systems such as bird flocks, schools of fish, and colonies of microorganisms have long amazed scientists and laypeople alike. Understanding the physics of such systems is challenging due to their far-from-equilibrium dynamics, as well as the extreme diversity in their ingredients, relevant time- and length-scales, and emergent phenomenology. To make progress, one can categorize active systems by the symmetries of their constituent particles, as well as how activity is expressed. In this work, we examine two categories of active systems, and explore their phase behavior in detail. First, we study systems of self-propelled spherical particles moving in two dimensions. Despite the absence of an aligning interaction, this system displays complex emergent dynamics, including phase separation into a dense active solid and dilute gas. Using simulations and analytic modeling, we quantify the phase diagram and separation kinetics. We show that this nonequilibrium phase transition is analogous to an equilibrium vapor-liquid system, with binodal and spinodal curves and a critical point. We also characterize the dense active solid phase, a unique material which exhibits the structural signatures of a crystalline solid near the crystal-hexatic transition point, as well as anomalous dynamics including superdiffusive motion on intermediate timescales. We also explore the role of interparticle attraction in this system. We demonstrate that attraction drastically changes the phase diagram, which contains two distinct phase-separated regions and is reentrant as a function of propulsion speed. We interpret this complex situation with a simple kinetic model, which builds from the observed microdynamics of individual particles to a full description of the macroscopic phase behavior. We also study active nematics, liquid crystals driven out of equilibrium by energy-dissipating active stresses. The equilibrium nematic state is unstable in these

  1. Active imaging system with Faraday filter

    DOEpatents

    Snyder, J.J.

    1993-04-13

    An active imaging system has a low to medium powered laser transmitter and receiver wherein the receiver includes a Faraday filter with an ultranarrow optical bandpass and a bare (nonintensified) CCD camera. The laser is locked in the vicinity of the passband of the Faraday filter. The system has high sensitivity to the laser illumination while eliminating solar background.

  2. Active imaging system with Faraday filter

    DOEpatents

    Snyder, James J.

    1993-01-01

    An active imaging system has a low to medium powered laser transmitter and receiver wherein the receiver includes a Faraday filter with an ultranarrow optical bandpass and a bare (nonintensified) CCD camera. The laser is locked in the vicinity of the passband of the Faraday filter. The system has high sensitivity to the laser illumination while eliminating solar background.

  3. Early Cretaceous extensional reworking of the Triassic HP-UHP metamorphic orogen in Eastern China

    NASA Astrophysics Data System (ADS)

    Lin, Wei; Ji, Wenbin; Faure, Michel; Wu, Lin; Li, Qiuli; Shi, Yonghong; Scharer, Urs; Wang, Fei; Wang, Qingchen

    2015-11-01

    Corresponding to the Early Mesozoic continental subduction between the North China Block (NCB) and the South China Block (SCB), the Tongbaishan-Hong'an-Dabieshan-Sulu massifs are famous for their HP-UHP metamorphism. More than 50% of the HP-UHP Orogenic Belt was significantly reworked by Early Cretaceous extensional tectonics. This Early Cretaceous event with a fast cooling period, at 130-120 Ma, superimposed on the Early Mesozoic HP-UHP orogenic belt and intensively changed the architecture of this orogen. Each individual segment documents different Early Cretaceous extensional structures, namely the central Tongbaishan domain is a metamorphic core complex (MCC) represented by an A-type non-cylindrical antiform; the central Dabieshan domain is a typical Cordilleran-type migmatite-cored MCC; the Southern Sulu UHP domain is a "wedge-shaped" structure exhumed by a simple detachment fault. These late stage extensional structures expose the previous HP-UHP orogenic belt as fragments along the NCB-SCB boundary. The geodynamic setting of this Early Cretaceous extensional tectonics along the HP-UHP orogen is a part of a 1000 km-scale crustal extension belt that is widespread in eastern Eurasia continent from Trans-Baikal to the central part of SCB. Convective erosion or delamination of the mantle lithosphere might be considered as a possible mechanism for mantle removal.

  4. Early Cretaceous extensional reworking of the Triassic HP-UHP metamorphic orogen in Eastern China

    NASA Astrophysics Data System (ADS)

    Lin, W.; Ji, W.; Faure, M.; Wu, L.; Li, Q. L.; Shi, Y.; Scharer, U.; Wang, F.; Wang, Q.

    2015-12-01

    Corresponding to the Early Mesozoic continental subduction between the North China Block (NCB) and the South China Block (SCB), the Tongbaishan-Hong'an-Dabieshan-Sulu massifs are famous for their HP-UHP metamorphism. More than 50% of the HP-UHP Orogenic Belt was significantly reworked by Early Cretaceous extensional tectonics. This Early Cretaceous event with a fast cooling period, at 130-120 Ma, superimposed on the Early Mesozoic HP-UHP orogenic belt and intensively changed the architecture of this orogen. Each individual segment documents different Early Cretaceous extensional structures, namely the central Tongbaishan domain is a metamorphic core complex (MCC) represented by an A-type non-cylindrical antiform; the central Dabieshan domain is a typical Cordilleran-type migmatite-cored MCC; the Southern Sulu UHP domain is a "wedge-shaped" structure exhumed by a simple detachment fault. These late stage extensional structures expose the previous HP-UHP orogenic belt as fragments along the NCB-SCB boundary. The geodynamic setting of this Early Cretaceous extensional tectonics along the HP-UHP orogen is a part of a 1000 km-scale crustal extension belt that is widespread in eastern Eurasia continent from Trans-Baikal to the central part of the South China Block. Convective erosion or delamination of the mantle lithosphere might be considered as a possible mechanism for mantle removal.

  5. Crustal Architecture along BABEL and FIRE profiles - Insight in the Growth of the Svecofennian Orogen

    NASA Astrophysics Data System (ADS)

    Korja, Annakaisa

    2016-04-01

    The Precambrian Svecofennian orogen is characterized by LP- HT metamorphism and voluminous granitoid magmatism that usually develop in transitional to plateau stages of a collisional orogeny. Deep seismic reflection profiles BABEL and FIRE have been interpreted using PURC concepts: prowedge, retrowedg, uplifted plug, subduction conduit and elevated plateau. BABEL profiles image a transitional orogen with several nuclei displaying prowedge-uplifted plug-retrowedge architecture above paleo-subduction conduits. Prowedge and -continent are on the south-southwestern side and retrowedge and -continent on the north-northwestern side. This implies a long-lived southwesterly retreating convergent margin, where transitional accretionary orogens have developed. FIRE1-3 profiles images a hot orogen with a pronounced super-infra structure, typical of an elevated plateau stage, below the Central Finland Granitoid Complex. Large volumes of granitoid intrusions suggest large scale melting of the middle and/or lower crust. Reflection structures, analogue and numerical modeling suggest midcrustal flow. The plateau is flanked by prowedges that are characterized by HT-LP migmatite belts. The Svecofennian orogeny has progressed to an elevated plateau stage in the thickest core of the orogen, west of the arc-continent collision zone.

  6. Non-volcanic tremors, low-frequency earthquake swarms, and their association with orogenic fluid flow in Taiwan

    NASA Astrophysics Data System (ADS)

    Chen, K. H.; Kim, A.; Chuang, Y. L.; Peng, W.; Leu, T.

    2012-12-01

    Taiwan is a young transpressive orogen exhibiting high uplift and exhumation. Under the southern flank of Central Range, two types of seismic activities typically observed in volcanic region are found to occur closely in space. Swarms of earthquakes showing vertical planar features occur frequently at a depth range of 0-20 km, whereas some shallow events (< 7 km) reveal the characteristics similar to volcanic low-frequency earthquakes: (1) dominant by ~ 2 Hz (2) lack of S phases (3) long coda. Below the swarm events, the deep-seated, ambient tremors are also observed. Spatial correlation between deeper tremor and shallow low-frequency swarm events indicates a common generation mechanism. These two seismic activities are confined in a small area where the localized veining, anomalous magnetic and thermal anomalies are distributed, suggesting the involvement of fluid-pressure processes within the orogen. Here we pay special attention to develop an automatic detection scheme for Taiwan tremors. Using this method we find 87 tremor episodes with duration ranging from 5 to 30 minutes. The tremors activity appears to have increased at the time of local M6 earthquakes. In March 2008, an active swarm composed of 632 events (M0.4-5.2) occurred only two days apart of the preceding tremor episode (duration 60 minutes). The possible spatial and temporal relationship between ambient tremors and earthquake swarms provides a rare opportunity for the understanding of tremor source model. Here we examine if the swarms are induced by shear stress increases due to slip events along the decollement underneath Central Range. Other than slip model, fluid-filled cracks model is also examined. Moment tensor inversion will be used to determine focal mechanism of the low-frequency earthquake swarms, to investigate the fluids related volume changes.

  7. System for objective assessment of fetal activity.

    PubMed

    Kaluzynski, K J; Kret, T; Czajkowski, K; Sieńko, J; Zmigrodzki, J

    2011-07-01

    Fetal activity is an important indicator of fetal well-being. It is proposed to assess this activity using the pulsed wave Doppler method to collect fetal activity data and dedicated software for on-line processing. The system, addressed to 3rd trimester pregnancies, provides information on presence of pseudobreathing, the heart rate trace, the fetal movement trace, the movement velocity spectrogram, histograms of the velocity and acceleration of both the body movements and pseudobreathing, parameters of these histograms (mean values, standard deviations, shape descriptors), and cumulative counts of the velocity histograms. These parameters form the feature vector of the fetal activity. The system was validated by simultaneous echographic and cardiotocographic recordings and during oxytocin challenge tests. Feature vectors obtained from 1h recordings in 61 pregnancies were submitted to multivariate analysis of variance. Activity patterns of physiological cases and "borderline pathologies" were discriminated using reduced feature vectors, containing cumulative counts of velocity histograms. PMID:21277248

  8. Active containment systems incorporating modified pillared clays

    SciTech Connect

    Lundie, P. |; McLeod, N.

    1997-12-31

    The application of treatment technologies in active containment systems provides a more advanced and effective method for the remediation of contaminated sites. These treatment technologies can be applied in permeable reactive walls and/or funnel and gate systems. The application of modified pillared clays in active containment systems provides a mechanism for producing permeable reactive walls with versatile properties. These pillared clays are suitably modified to incorporate reactive intercalatants capable of reacting with both a broad range of organic pollutants of varying molecular size, polarity and reactivity. Heavy metals can be removed from contaminated water by conventional ion-exchange and other reactive processes within the clay structure. Complex contamination problems can be addressed by the application of more than one modified clay on a site specific basis. This paper briefly describes the active containment system and the structure/chemistry of the modified pillared clay technology, illustrating potential applications of the in-situ treatment process for contaminated site remediation.

  9. A tear fault boundary between the Taiwan orogen and the Ryukyu subduction zone

    NASA Astrophysics Data System (ADS)

    Lallemand, Serge E.; Liu, Char-Shine; Font, Yvonne

    1997-06-01

    More than twenty seismic lines were analysed across the intersection of the Taiwan orogen and the Ryukyu arc-forearc system. The main results of this study concern the recognition of two superposed sedimentary basins that were previously unknown. We have named the recent one the Hoping Basin and the older, tectonized one the Suao Basin. The Suao Basin, containing sediments more than 3 km thick, records subsidence of about 3 km on its southwestern portion after being shortened in the direction of plate convergence. On the basis of seismicity, gravity, present-day plate kinematics as well as seismic reflection data, we relate the dramatic subsidence of the Suao Basin to the initiation of a WNW-trending tear fault within the Philippine Sea plate. This tear fault decouples the subducting Philippine Sea plate to the northeast and the apparent overthrusting Philippine Sea plate in the Coastal Range to the southwest. Back-arc rifting may thus occur in the westernmost section of the Okinawa trough above the sinking Philippine Sea slab while lithospheric shortening prevails south of Hualien. As a consequence, the triangular area located southwest of the tear fault, between the Taiwan coastline and the toe of the Yaeyama ridge, no longer belongs to the Ryukyu forearc. It is now passively transported with the non-subducting portion of the Philippine Sea plate. We propose an evolutionary model for the relative chronology of tectono-sedimentary events in this region over the last 5 m.y.

  10. Protection of Active Distribution Systems with DGs

    NASA Astrophysics Data System (ADS)

    Akila, Abdelrahman Ahmed; Helal, Ahmed; Eldesouki, Hussein

    2015-10-01

    Distribution systems are traditionally designed as radial passive systems fed from a single source. Protection coordination of such systems has been easily established assuming the system radiality. Insertion of distributed generators (DGs) into distribution systems makes the distribution system to be more active which causes redistribution of fault currents magnitudes and directions. This causes negative impacts on the original protection system coordination, since the distribution system losses its radiality and passiveness. Recently protection coordination in the presence of distributed generation has been paid a great attention. Researchers proposed various solutions to solve the protection coordination problem caused by adding DG into the distribution network. In this paper, the proposed solutions for the protection coordination problem considering the DG insertion will be illustrated, classified, and criticized.

  11. Mechanical model for subduction-collision tectonics of Alpine-type compressional orogens

    NASA Astrophysics Data System (ADS)

    Beaumont, Christopher; Ellis, Susan; Hamilton, Juliet; Fullsack, Philippe

    1996-08-01

    Alpine-type orogens are characterized by three distinct convergent tectonic phases: subduction with deformation that has primarily single vergence, a transition from subduction to collision, and continental collision with double vergence. Although the Cenozoic history of the European Alps has additional complexities, a mechanical explanation for these three phases would provide the necessary crustal-scale framework in which to develop an understanding of the smaller-scale processes. We present results from a simple numerical model, which explain the mechanics of these three phases as a consequence of the changing buoyancy of the lithosphere subducted beneath the orogen. The development and exhumation of a subduction complex, suture zone, and basement nappe stack (Piemont suture, Penninic Nappes); the presence of a crustal-scale back fold and thrust (Insubric Line); and uplift of basement on the pro- (European) side of the orogen (external basement massifs) may be explained as a simple consequence of changing dynamics during the transition from subduction to collision.

  12. Neogene coupling between Kuqa Basin and Southern Tien Shan Orogen, Northwestern China.

    PubMed

    He, Guang-Yu; Chen, Han-Lin

    2004-08-01

    Based on the sedimentary and subsiding features of Kuqa foreland basin, this paper presents the following characteristics of Neogene coupling relationship between Kuqa Basin and Southern Tien Shan Orogen, Northwestern China: (1) The Southern Tien Shan Orogen underwent Neogene uplifting of 4 km in height and the Kuqa Basin underwent Neogene subsidence of 4-6 km in depth accordingly beginning in 25 Ma; (2) The Southern Tien Shan Orogen moved continuously toward the Kuqa Basin, with largest structural shortening rate of greater than 53.7%, and the north boundary of the Kuqa Basin retreated continuously southward accordingly since the Miocene; (3) There are two subsidence centers with high subsiding rates and large subsiding extent, located in the eastern and western Kuqa Basin respectively, with the subsiding maximizing in the deposition period of Kuqa Formation. PMID:15236483

  13. Architecture of orogenic belts and convergent zones in Western Ishtar Terra, Venus

    NASA Technical Reports Server (NTRS)

    Head, James W.; Vorderbruegge, R. W.; Crumpler, L. S.

    1989-01-01

    Linear mountain belts in Ishtar Terra were recognized from Pioneer-Venus topography, and later Arecibo images showed banded terrain interpreted to represent folds. Subsequent analyses showed that the mountains represented orogenic belts, and that each had somewhat different features and characteristics. Orogenic belts are regions of focused shortening and compressional deformation and thus provide evidence for the nature of such deformation, processes of crustal thickening (brittle, ductile), and processes of crustal loss. Such information is important in understanding the nature of convergent zones on Venus (underthrusting, imbrication, subduction), the implications for rates of crustal recycling, and the nature of environments of melting and petrogenesis. The basic elements of four convergent zones and orogenic belts in western Ishtar Terra are identified and examined, and then assess the architecture of these zones (the manner in which the elements are arrayed), and their relationships. The basic nomenclature of the convergent zones is shown.

  14. Remagnetization and orogenic fluids: testing the hypothesis in the central Appalachians

    NASA Astrophysics Data System (ADS)

    Elmore, R. Douglas; Kelley, Jeff; Evans, Mark; Lewchuk, Michael T.

    2001-03-01

    Palaeomagnetic and geochemical studies on Devonian sedimentary rocks in the Valley and Ridge province in West Virginia indicate that the hypothesized relationship between orogenic fluids and remagnetization is not straightforward. The Helderberg Group, an aquitard, and the Oriskany Formation, a palaeoaquifer, both contain similar, synfolding late Palaeozoic chemical remanent magnetizations (CRMs) residing in magnetite. The results from the Oriskany Formation are consistent with remagnetization by orogenic fluids because the unit contains geochemical evidence for the migration of such fluids. In contrast, there is no geochemical evidence for the widespread migration of orogenic fluids into the Helderberg Group and thus the CRM cannot be related to such fluids. Another remagnetization mechanism, which remains elusive, must be responsible for the CRM in the Helderberg Group.

  15. Aging assessment for active fire protection systems

    SciTech Connect

    Ross, S.B.; Nowlen, S.P.; Tanaka, T.

    1995-06-01

    This study assessed the impact of aging on the performance and reliability of active fire protection systems including both fixed fire suppression and fixed fire detection systems. The experience base shows that most nuclear power plants have an aggressive maintenance and testing program and are finding degraded fire protection system components before a failure occurs. Also, from the data reviewed it is clear that the risk impact of fire protection system aging is low. However, it is assumed that a more aggressive maintenance and testing program involving preventive diagnostics may reduce the risk impact even further.

  16. Active Displacement Control of Active Magnetic Bearing System

    NASA Astrophysics Data System (ADS)

    Kertész, Milan; Kozakovič, Radko; Magdolen, Luboš; Masaryk, Michal

    2014-12-01

    The worldwide energy production nowadays is over 3400 GW while storage systems have a capacity of only 90 GW [1]. There is a good solution for additional storage capacity in flywheel energy storage systems (FES). The main advantage of FES is its relatively high efficiency especially with using the active magnetic bearing system. Therefore there exist good reasons for appropriate simulations and for creating a suitable magneto-structural control system. The magnetic bearing, including actuation, is simulated in the ANSYS parametric design language (APDL). APDL is used to create the loops of transient simulations where boundary conditions (BC) are updated based upon a "gap sensor" which controls the nodal position values of the centroid of the shaft and the current density inputs onto the copper windings.

  17. Reconciling the detrital zircon record and crustal growth within juvenile accretionary orogens

    NASA Astrophysics Data System (ADS)

    Spencer, C. J.; Cawood, P. A.; Roberts, N. M. W.

    2014-12-01

    Ancient cratons are generally characterised by Archaean cores surrounded by Proterozoic accretionary belts with large volumes of juvenile crust. Their crustal growth histories provide important insights into the genesis of continents and orogenic evolution. Whole-rock and detrital zircon isotopic studies are often used to deduce those histories, but the extent to which representative lithologies within the orogens are reliably sampled for such studies is not well established. This is especially true in cases where juvenile, zircon-poor mafic crust comprises a significant proportion of an orogen such as the East African (0.8-0.5 Ga), Namaqua-Natal (1.2-1.0 Ga), Trans-Hudson (1.9-1.8 Ga), and Kola (2.5 Ga). In particular, the Mesoproterozoic Namaqua-Natal orogenic belt (NNO) fringing the Kalahari Craton is a case in point in which Nd isotopic studies of whole-rock outcrop samples and U-Pb-Hf isotopic studies of detrital zircons from sediments of the Orange River (which drains the NNO) show different crust-formation ages and proportions of new and reworked crustal material. We hypothesise that this discrepancy is due to biasing of the detrital zircon record towards felsic rocks. Understanding the representative nature of the crustal archive preserved in detrital zircons remains critical for many studies of crustal evolution. We present data that: (a) addresses the scale of potential bias within an accretionary orogen containing large proportions of juvenile material, (b) demonstrates how the whole-rock and detrital zircon records can be reconciled for the Namaqua-Natal orogen to start, and (c) can be used to evaluate the effect of zircon bias on previous crustal growth models.

  18. Porphyry copper assessment of the Central Asian Orogenic Belt and eastern Tethysides: China, Mongolia, Russia, Pakistan, Kazakhstan, Tajikistan, and India: Chapter X in Global mineral resource assessment

    USGS Publications Warehouse

    Mihalasky, Mark J.; Ludington, Stephen; Hammarstrom, Jane M.; Alexeiev, Dmitriy V.; Frost, Thomas P.; Light, Thomas D.; Robinson, Gilpin R., Jr.; Briggs, Deborah A.; Wallis, John C.; Miller, Robert J.; Bookstrom, Arthur A.; Panteleyev, Andre; Chitalin, Andre; Seltmann, Reimar; Guangsheng, Yan; Changyun, Lian; Jingwen, Mao; Jinyi, Li; Keyan, Xiao; Ruizhao, Qiu; Jianbao, Shao; Gangyi, Shai; Yuliang, Du

    2015-01-01

    The U.S. Geological Survey collaborated with international colleagues to assess undiscovered resources in porphyry copper deposits in the Central Asian Orogenic Belt and eastern Tethysides. These areas host 20 known porphyry copper deposits, including the world class Oyu Tolgoi deposit in Mongolia that was discovered in the late 1990s. The study area covers major parts of the world’s largest orogenic systems. The Central Asian Orogenic Belt is a collage of amalgamated Precambrian through Mesozoic terranes that extends from the Ural Mountains in the west nearly to the Pacific Coast of Asia in the east and records the evolution and final closure of the Paleo-Asian Ocean in Permian time. The eastern Tethysides, the orogenic belt to the south of the Central Asian Orogenic Belt, records the evolution of another ancient ocean system, the Tethys Ocean. The evolution of these orogenic belts involved magmatism associated with a variety of geologic settings appropriate for formation of porphyry copper deposits, including subduction-related island arcs, continental arcs, and collisional and postconvergent settings. The original settings are difficult to trace because the arcs have been complexly deformed and dismembered by younger tectonic events. Twelve mineral resource assessment tracts were delineated to be permissive for the occurrence of porphyry copper deposits based on mapped and inferred subsurface distributions of igneous rocks of specific age ranges and compositions. These include (1) nine Paleozoic tracts in the Central Asian Orogenic Belt, which range in area from about 60,000 to 800,000 square kilometers (km2); (2) a complex area of about 400,000 km2 on the northern margin of the Tethysides, the Qinling-Dabie tract, which spans central China and areas to the west, encompassing Paleozoic through Triassic igneous rocks that formed in diverse settings; and (3) assemblages of late Paleozoic and Mesozoic rocks that define two other tracts in the Tethysides, the 100

  19. Gamma Band Activity in the Reticular Activating System

    PubMed Central

    Urbano, Francisco J.; Kezunovic, Nebojsa; Hyde, James; Simon, Christen; Beck, Paige; Garcia-Rill, Edgar

    2012-01-01

    This review considers recent evidence showing that cells in three regions of the reticular activating system (RAS) exhibit gamma band activity, and describes the mechanisms behind such manifestation. Specifically, we discuss how cells in the mesopontine pedunculopontine nucleus (PPN), intralaminar parafascicular nucleus (Pf), and pontine subcoeruleus nucleus dorsalis (SubCD) all fire in the beta/gamma band range when maximally activated, but no higher. The mechanisms behind this ceiling effect have been recently elucidated. We describe recent findings showing that every cell in the PPN have high-threshold, voltage-dependent P/Q-type calcium channels that are essential, while N-type calcium channels are permissive, to gamma band activity. Every cell in the Pf also showed that P/Q-type and N-type calcium channels are responsible for this activity. On the other hand, every SubCD cell exhibited sodium-dependent subthreshold oscillations. A novel mechanism for sleep–wake control based on well-known transmitter interactions, electrical coupling, and gamma band activity is described. The data presented here on inherent gamma band activity demonstrates the global nature of sleep–wake oscillation that is orchestrated by brainstem–thalamic mechanism, and questions the undue importance given to the hypothalamus for regulation of sleep–wakefulness. The discovery of gamma band activity in the RAS follows recent reports of such activity in other subcortical regions like the hippocampus and cerebellum. We hypothesize that, rather than participating in the temporal binding of sensory events as seen in the cortex, gamma band activity manifested in the RAS may help stabilize coherence related to arousal, providing a stable activation state during waking and paradoxical sleep. Most of our thoughts and actions are driven by pre-conscious processes. We speculate that continuous sensory input will induce gamma band activity in the RAS that could participate in the processes of

  20. Traveling and Resting Crystals in Active Systems

    NASA Astrophysics Data System (ADS)

    Menzel, Andreas M.; Löwen, Hartmut

    2013-02-01

    A microscopic field theory for crystallization in active systems is proposed which unifies the phase-field-crystal model of freezing with the Toner—Tu theory for self-propelled particles. A wealth of different active crystalline states are predicted and characterized. In particular, for increasing strength of self-propulsion, a transition from a resting crystal to a traveling crystalline state is found where the particles migrate collectively while keeping their crystalline order. Our predictions, which are verifiable in experiments and in particle-resolved computer simulations, provide a starting point for the design of new active materials.

  1. Plate tectonics and orogenic research after 25 years: Synopsis of a Tethyan perspective

    NASA Astrophysics Data System (ADS)

    Şengör, A. M. Celâl

    1991-02-01

    Orogeny, the process by which the earth's prominent mountain ranges are constructed, is herein defined as a collective term for convergent margin processes. The recognition that strains and displacements of very considerable magnitude occur along all of the three dimensions within an orogenic belt has grown gradually during the last two centuries. Investigation of orogenic belts along cross-sections reveals that there are a large number of types of orogenic belts. These are divided into four main orders ( transpressional, subduction-controlled, obduction-controlled, and collision-controlled) consisting of two superfamilies, eight families, and twenty genera. Cross-sectional studies of orogenic belts show that the cross-sectional area during orogeny is not conserved. Similarly, map-view studies of orogenic belts reveal that an absolute minimum of 60% (by length) of them display significant strike-slip motion along their trend which leads also to a non-conservation of the cross-sectional area during orogeny. Thus, rigorous line and area balancing across orogenic belts now is not possible. Large orogenic belts are commonly made up of tectonic collages of microcontinents, island arcs, and accretionary complexes, generally disrupted to form smaller, fault-bounded tectonic entities of diverse sorts. The recently developed "terrane analysis" was developed to aid the study of these but it resembles the early concepts of Alpine nappes and is found to be a retrogressive step in tectonic research mainly because of its disclaim of most genetic connotations. The temporal aspects of orogeny have been debated for over 200 years in terms of continuous vs. world-wide, synchronously episodic orogeny. Plate tectonics has provided a rigorous rationale and something approaching a consensus for continuous orogeny. I conclude that there are as yet no shortcuts to establishing the kinematics of continental deformation except by the traditional methods of field geology aided by relevant

  2. Crustal Structure of the Dabie Orogenic Belt (eastern China) Inferred from Gravity and Magnetic Data

    NASA Astrophysics Data System (ADS)

    Yang, Y.; Li, Y.

    2012-12-01

    This study investigates the utility of the potential fields (gravity and magnetics) in orogenic belt settings as observed in the Dabie orogenic belt. The methods applied are Euler deconvolution on the magnetic data, continuous wavelet transform (CWT), and the gravity forward modeling. We devise a 500km long profile I, which trends N21°E and begins in the north within the Hefei basin of the North China craton, passes through the Dabie orogen, and ends in the Yangtze craton. The Euler deconvolution on the magnetic signal provides depth estimation for magnetized sources along the profile. The CWT method is then adopted to characterize the underground density interfaces of gravity field, which provides a useful constraint for the forward modeling of the profile I. Finally we present a crustal cross section through the Dabie orogenic belt, derived from the gravity forward modeling results with integration of source depth estimations from the gravity and magnetic data. As indicated by the forward gravity modeling results, there are low density bodies in the central orogen, which are probably due to the over-thickened crustal materials formed during the continuous convergence between the North China craton (NCC) and the Yangtze craton after break-off of the subducted slab. After the delamination or mountain root removal in the Dabie orogen, the asthenosphere upwelled to replace the volume previously occupied by the delaminated lithosphere. Under the extensional environment in the early Cretaceous, the upwelling mantle was metasomatised and partially melted to produce the parental magma of the post-collisional mafic-ultramafic intrusive rocks. Two anomalous denser materials with low magnetization in the lower crust and upper mantle of the Dabie orogen can be recognized in the CWT-based spectral analysis result on the magnetic data, which may be inferred as sequence of mass transport from the metasomatised mantle. Figure 1. A profile view from the Dabie orogen along the

  3. Basin-mountain structures and hydrocarbon exploration potential of west Junggar orogen in China

    NASA Astrophysics Data System (ADS)

    Wu, X.; Qi, X.; Zheng, M.

    2015-12-01

    Situated in northern Xinjiang, China, in NE-SW trend, West Junggar Orogen is adjacent to Altai fold belt on the north with the Ertix Fault as the boundary, North Tianshan fold belt on the south with the Ebinur Lake Strike-slip Fault as the boundary, and the Junggar Basin on the southeast with Zaire-Genghis Khan-Hala'alat fold belt as the boundary. Covering an area of about 10×104 km2 in China, there are medium and small intermontane basins, Burqin-Fuhai, Tacheng, Hefeng and Hoxtolgay, distributing inside the orogen. Tectonically West Junggar Orogen lies in the middle section of the Palaeo-Asian tectonic domain where the Siberia, Kazakhstan and Tarim Plates converge, and is the only orogen trending NE-SW in the Palaeo-Asian tectonic domain. Since the Paleozoic, the orogen experienced pre-Permian plate tectonic evolution and post-Permian intra-plate basin evolution. Complex tectonic evolution and multi-stage structural superimposition not only give rise to long term controversial over the basin basement property but also complex basin-mountain coupling relations, structures and basin superimposition modes. According to analysis of several kinds of geological and geophysical data, the orogen was dominated by compressive folding and thrust napping from the Siberia plate in the north since the Late Paleozoic. Compressive stress weakened from north to south, corresponding to subdued vertical movement and enhanced horizontal movement of crustal surface from north to south, and finally faded in the overthrust-nappe belt at the northwest margin of the Junggar Basin. The variation in compressive stress is consistent with the surface relief of the orogen, which is high in the north and low in the south. There are two kinds of basin-mountain coupling relationships, i.e. high angle thrusting and overthrusting and napping, and two kinds of basin superimposition modes, i.e. inherited and progressive, and migrating and convulsionary modes. West Junggar orogen has rich oil and gas

  4. Reconciling competing models for the tectono-stratigraphic zonation of the Variscan orogen in Western Europe

    NASA Astrophysics Data System (ADS)

    Murphy, J. Brendan; Quesada, Cecilio; Gutiérrez-Alonso, Gabriel; Johnston, Stephen T.; Weil, Arlo

    2016-06-01

    The Late Paleozoic Variscan orogen in Europe is the result of convergence and collision between Laurussia and Gondwana during closure of the Rheic Ocean. The orogen is divided into tectonostratigraphic zones that have a distinct curvature (Ibero-Armorican Arc, IAA) and record the Late Cambrian-Early Ordovician opening of the Rheic Ocean, the migration of terranes from the Gondwanan margin towards Laurussia, as well as the closure of that ocean and development of the IAA. Three models have emerged to explain the distribution of tectonostratigraphic zones:

  5. Unraveling complex orogenic histories by integrating Foliation Intersection Axis (FIA) orientation data with thermodynamic modeling: the Swat area case study, NW Himalaya

    NASA Astrophysics Data System (ADS)

    Sayab, M.; Shah, S. Z.; Aerden, D. G.

    2012-12-01

    Barrovian-type mineral assemblages typically result from regional- to plate-scale collision tectonics and resulting clockwise P-T paths. Inclusion trail patterns preserved within such assemblages can provide important information about the kinematics of an orogen and of orogenic processes in general. We have measured Foliation Intersection Axes (FIA) preserved in garnet porphyroblasts of a metapelitic sequence exposed south of the Main Mantle Thrust in the Swat region of the NW Himalaya, Pakistan. This area underwent multiply deformation and metamorphism from ca. 55 to 38 Ma as part of the Himalayan orogen. Metamorphic garnets in the area contain spiral, sigmoidal, millipede and straight inclusion trails that represent progressive stages of a complex succession of deformations during this period. Spiral trails are commonly truncated by the matrix foliation, whereas the other types can be followed in the matrix indicating an older age of the spiral garnets. Determination of FIA for these garnets using two complementary techniques reveals two main FIA sets with broadly E-W versus N-S trends. Relative timing criteria indicate an older age of the E-W trending FIA consistent with development during progressive N-S crustal shortening, thrusting and convergence between the Indian plate and Kohistan-Ladakh Island Arc (KLIA). Younger N-S trending FIA formed in response to E-W crustal shortening as a result of orogen-parallel compression. The trends of FIA sub-classes suggest a progressive rotation of about 125° in the orientation of collision between the Indian Plate and KLIA. In order to estimate P-T conditions during this orogenic evolution, representative samples preserving different geometric types of inclusion trails in garnets (FIAs) are modeled in the chemical system MnNCKFMASH using THERMOCALC 3.33. A sophisticated clockwise P-T-t-d path is obtained that brackets metamorphic conditions during the N-S shortening (M1 metamorphism) between 4.0-8.7 kbars and 495-565o

  6. Distributed control system for active mirrors

    NASA Astrophysics Data System (ADS)

    Rodriguez-Ramos, Luis F.; Williams, Mark R.; Castro, Javier; Cruz, A.; Gonzalez, Juan C.; Mack, Brian; Martin, Carlos; Pescador, German; Sanchez, Vicente; Sosa, Nicolas A.

    1994-06-01

    This paper presents the IAC (Instituto de Astrofisica de Canaries, Spain) proposal of a distributed control system intended for the active support of a 8 m mirror. The system incorporates a large number of compact `smart' force actuators, six force definers, and a mirror support computer (MSC) for interfacing with the telescope control system and for general housekeeping. We propose the use of a network for the interconnection of the actuators, definers and the MSC, which will minimize the physical complexity of the interface between the mirror support system and the MSC. The force actuator control electronics are described in detail, as is the system software architecture of the actuator and the MSC. As the network is a key point for the system, we also detail the evaluation of three candidates, before electing the CAN bus.

  7. Flexural bending-induced plumelets and their seamounts in accretionary (Japanese-style) and collisional (Tethyan-style) orogenic belts

    NASA Astrophysics Data System (ADS)

    Hirano, N.; Dilek, Y.

    2015-12-01

    Seamounts and seamount chains are common in both the upper and lower plates of active subduction zones. Their OIB-type volcanic products are distinctly different from suprasubduction zone (arc, forearc and backarc) generated volcanic rocks in terms of their compositions and mantle sources. Tectonic accretion of such seamounts into the Japanese archipelago in the NW Pacific and into subduction-accretion complexes and active margins of continents/microcontinents within the Tethyan realm during the Cretaceous played a significant role in continental growth. Seamount assemblages comprise alkaline volcanic rocks intercalated with radiolarian and hemipelagic chert, and limestone, and may also include hypabyssal dolerite and gabbro intrusions. In the Tethyan orogenic belts these seamount rocks commonly occur as km-scale blocks in mélange units beneath the late Jurassic - Cretaceous ophiolites nappes, whereas on the Japanese islands they form discrete, narrow tectonic belts within the late Jurassic - Cretaceous accretionary prism complexes. We interpret some of these OIB occurrences in the Japanese and Tethyan mountain belts as asperities in downgoing oceanic plates that formed in <10 million years before their accretion. Their magmas were generated by decompressional melting of upwelling asthenosphere, without any significant mantle plume component, and were brought to the seafloor along deep-seated brittle fractures that developed in the flexed, downgoing lithosphere as it started bending near a trench. The modern occurrences of these "petit-spot volcanoes" are well established in the northwestern Pacific plate, off the coast of Japan. The proposed mechanism of the formation of these small seamounts better explains the lack of hotspot trails associated with their occurrence in the geological record. Magmatic outputs of such flexural bending-induced plumelets should be ubiquitious in the accretionary (Japanese-style) and collisional (Tethyan-style) orogenic belts.

  8. Trans-Hudson Orogen of North America and Himalaya-Karakoram-Tibetan Orogen of Asia: Structural and thermal characteristics of the lower and upper plates

    NASA Astrophysics Data System (ADS)

    St-Onge, Marc R.; Searle, Michael P.; Wodicka, Natasha

    2006-08-01

    The Trans-Hudson Orogen (THO) of North America and the Himalaya-Karakoram-Tibetan Orogen (HKTO) of Asia preserve a Paleoproterozoic and Cenozoic record, respectively, of continent-continent collision that is notably similar in scale, duration and character. In THO, the tectonothermal evolution of the lower plate involves (1) early thin-skinned thrusting and Barrovian metamorphism, (2) out-of-sequence thrusting and high-T metamorphism, and (3) fluid-localized reequilibration, anatexis, and leucogranite formation. The crustal evolution of the Indian lower plate in HKTO involves (1) early subduction of continental crust to ultrahigh pressure (UHP) eclogite depths, (2) regional Barrovian metamorphism, and (3) widespread high-T metamorphism, anatexis, and leucogranite formation. The shallow depths of the high-T metamorphism in HKTO are consistent with early to mid-Miocene ductile flow of an Indian lower plate midcrustal channel, from beneath the southern Tibetan Plateau to the Greater Himalaya. Melt weakening of the lower plate in THO is not observed at a similar scale probably due to the paucity of pelitic lithologies. Tectonothermal events in the upper plate of both orogens include precollisional accretion of crustal blocks, emplacement of Andean-type plutonic suites, and high-T metamorphism. Syncollisional to postcollisional events include emplacement of garnet-biotite-muscovite leucogranites, anatectic granites, and sporadic metamorphism (up to 90 Myr following the onset of collision in THO). Comparing the type and duration of tectonothermal events for THO and HKTO supports the notion of tectonic uniformitarianism for at least the later half of dated Earth history and highlights the complementary nature of the rock record in an older "exhumed" orogen compared to one undergoing present-day orogenesis.

  9. Timing and climatic drivers for glaciation across monsoon-influenced regions of the Himalayan-Tibetan orogen

    NASA Astrophysics Data System (ADS)

    Murari, Madhav K.; Owen, Lewis A.; Dortch, Jason M.; Caffee, Marc W.; Dietsch, Craig; Fuchs, Markus; Haneberg, William C.; Sharma, Milap C.; Townsend-Small, Amy

    2014-03-01

    Mapping and thirty-eight 10Be terrestrial cosmogenic nuclide (TCN) ages help define the timing of glaciation in the monsoon-influenced Greater Himalaya in central Garwhal, India. Glacial landforms in central Garwhal are present only within a few kilometers of the present glaciers and all date to less than ˜12.5 ka. This suggests that the Lateglacial and/or Holocene glacial advances were more extensive than their predecessors and hence destroyed or buried evidence for earlier glaciation or that other processes, such as intensive fluvial erosion and/or hillslope mass movements, have destroyed evidence of earlier glaciation. Prominent laterofrontal moraines date to the Lateglacial, the Early Holocene, and the Neoglaciation. Moraines next to the active ice and boulders on contemporary glaciers date to 101-102 years before present. This suggests only a minor glacial advance during the Little Ice Age occurred in central Garhwal. These young ages indicate that inheritance of TCNs in areas that were recently glaciated is very small and likely has little effect when considering TCN ages on moraines older than the global Last Glacial Maximum. The new 10Be ages are combined with 1081 recalculated 10Be ages from previous studies to develop a regional framework of glaciation across the monsoon-influenced and adjacent regions of the Himalayan-Tibetan orogen. We separate what appears to be continuous glaciation into 27 regional glacial stages (plus 2 tentative glacial stages) that are termed monsoonal Himalayan-Tibetan stages (MOHITS). The regional glacial stages cover a wide chronologic range that includes: five regional glacial stages older than the Last Glacial cycle (MOHITS 13 at 483 ± 38 ka to MOHITS 5E at 122 ± 15 ka); thirteen regional glacial stages within the Last Glacial cycle (MOHITS 5B at 91 ± 15 ka to MOHITS 2A at 12.9 ± 0.9 ka); and eleven regional glacial stages during the Holocene (MOHITS 1k at 11.4 ± 0.7 ka to MOHITS 1A at 0.4 ± 0.1 ka). There are strong

  10. Modular System to Enable Extravehicular Activity

    NASA Technical Reports Server (NTRS)

    Sargusingh, Miriam J.

    2011-01-01

    The ability to perform extravehicular activity (EVA), both human and robotic, has been identified as a key component to space missions to support such operations as assembly and maintenance of space system (e.g. construction and maintenance of the International Space Station), and unscheduled activities to repair an element of the transportation and habitation systems that can only be accessed externally and via unpressurized areas. In order to make human transportation beyond lower earth orbit (BLEO) practical, efficiencies must be incorporated into the integrated transportation systems to reduce system mass and operational complexity. Affordability is also a key aspect to be considered in space system development; this could be achieved through commonality, modularity and component reuse. Another key aspect identified for the EVA system was the ability to produce flight worthy hardware quickly to support early missions and near Earth technology demonstrations. This paper details a conceptual architecture for a modular extravehicular activity system (MEVAS) that would meet these stated needs for EVA capability that is affordable, and that could be produced relatively quickly. Operational concepts were developed to elaborate on the defined needs and define the key capabilities, operational and design constraints, and general timelines. The operational concept lead to a high level design concept for a module that interfaces with various space transportation elements and contains the hardware and systems required to support human and telerobotic EVA; the module would not be self-propelled and would rely on an interfacing element for consumable resources. The conceptual architecture was then compared to EVA Systems used in the Shuttle Orbiter, on the International Space Station to develop high level design concepts that incorporate opportunities for cost savings through hardware reuse, and quick production through the use of existing technologies and hardware designs

  11. Understanding erosion rates in the Himalayan orogen: A case study from the Arun Valley

    NASA Astrophysics Data System (ADS)

    Olen, Stephanie M.; Bookhagen, Bodo; Hoffmann, Bernd; Sachse, Dirk; Adhikari, D. P.; Strecker, Manfred R.

    2015-10-01

    Understanding the rates and pattern of erosion is a key aspect of deciphering the impacts of climate and tectonics on landscape evolution. Denudation rates derived from terrestrial cosmogenic nuclides (TCNs) are commonly used to quantify erosion and bridge tectonic (Myr) and climatic (up to several kiloyears) time scales. However, how the processes of erosion in active orogens are ultimately reflected in 10Be TCN samples remains a topic of discussion. We investigate this problem in the Arun Valley of eastern Nepal with 34 new 10Be-derived catchment-mean denudation rates. The Arun Valley is characterized by steep north-south gradients in topography and climate. Locally, denudation rates increase northward, from <0.2 mm yr-1 to ~1.5 mm yr-1 in tributary samples, while main stem samples appear to increase downstream from ~0.2 mm yr-1 at the border with Tibet to 0.91 mm yr-1 in the foreland. Denudation rates most strongly correlate with normalized channel steepness (R2 = 0.67), which has been commonly interpreted to indicate tectonic activity. Significant downstream decrease of 10Be concentration in the main stem Arun suggests that upstream sediment grains are fining to the point that they are operationally excluded from the processed sample. This results in 10Be concentrations and denudation rates that do not uniformly represent the upstream catchment area. We observe strong impacts on 10Be concentrations from local, nonfluvial geomorphic processes, such as glaciation and landsliding coinciding with areas of peak rainfall rates, pointing toward climatic modulation of predominantly tectonically driven denudation rates.

  12. Active Annuloplasty System for Mitral Valve Insufficiency

    NASA Astrophysics Data System (ADS)

    Díaz Lantada, Andrés; Lafont, Pilar; Rada, Ignacio; Jiménez, Antonio; Hernández, José Luis; Lorenzo-Yustos, Héctor; Muñoz-García, Julio

    Active materials are capable of responding in a controlled way to different external physical or chemical stimuli by changing some of their properties. These materials can be used to design and develop sensors, actuators and multifunctional systems with a large number of applications for developing medical devices.

  13. METALS DISTRIBUTIONS IN ACTIVATED SLUDGE SYSTEMS

    EPA Science Inventory

    This project developed models to predict the distribution of metals in activated sludge system process streams. The data used to develop the models were obtained through extended pilot studies from a previous project. The objectives of the study were to evaluate the effects of wa...

  14. Supporting Classroom Activities with the BSUL System

    ERIC Educational Resources Information Center

    Ogata, Hiroaki; Saito, Nobuji A.; Paredes J., Rosa G.; San Martin, Gerardo Ayala; Yano, Yoneo

    2008-01-01

    This paper presents the integration of ubiquitous computing systems into classroom settings, in order to provide basic support for classrooms and field activities. We have developed web application components using Java technology and configured a classroom with wireless network access and a web camera for our purposes. In this classroom, the…

  15. Design of nutrient removal activated sludge systems.

    PubMed

    Manga, J; Ferrer, J; Seco, A; Garcia-Usach, F

    2003-01-01

    A mechanistic mathematical model for nutrient and organic matter removal was used to describe the behavior of a nitrification denitrification enhanced biological phosphorus removal (NDEBPR) system. This model was implemented in a user-friendly software DESASS (design and simulation of activated sludge systems). A 484-L pilot plant was operated to verify the model results. The pilot plant was operated for three years over three different sludge ages. The validity of the model was confirmed with data from the pilot plant. Also, the utility of DESASS as a valuable tool for designing NDEBPR systems was confirmed. PMID:12906279

  16. Targeted activation in deterministic and stochastic systems

    NASA Astrophysics Data System (ADS)

    Eisenhower, Bryan; Mezić, Igor

    2010-02-01

    Metastable escape is ubiquitous in many physical systems and is becoming a concern in engineering design as these designs (e.g., swarms of vehicles, coupled building energetics, nanoengineering, etc.) become more inspired by dynamics of biological, molecular and other natural systems. In light of this, we study a chain of coupled bistable oscillators which has two global conformations and we investigate how specialized or targeted disturbance is funneled in an inverse energy cascade and ultimately influences the transition process between the conformations. We derive a multiphase averaged approximation to these dynamics which illustrates the influence of actions in modal coordinates on the coarse behavior of this process. An activation condition that predicts how the disturbance influences the rate of transition is then derived. The prediction tools are derived for deterministic dynamics and we also present analogous behavior in the stochastic setting and show a divergence from Kramers activation behavior under targeted activation conditions.

  17. Green Bank Telescope active surface system

    NASA Astrophysics Data System (ADS)

    Lacasse, Richard J.

    1998-05-01

    During the design phase of the Green Bank Telescope (GBT), various means of providing an accurate surface on a large aperture paraboloid, were considered. Automated jacks supporting the primary reflector were selected as the appropriate technology since they promised greater performance and potentially lower costs than a homologous or carbon fiber design, and had certain advantages over an active secondary. The design of the active surface has presented many challenges. Since the actuators are mounted on a tipping structure, it was required that they support a significant side-load. Such devices were not readily available commercially so they had to be developed. Additional actuator requirements include low backlash, repeatable positioning, and an operational life of at least 230 years. Similarly, no control system capable of controlling the 2209 actuators was commercially available. Again a prime requirement was reliability. Maintaining was also a very important consideration. The system architecture is tree-like. An active surface 'master-computer' controls interaction with the telescope control system, and controls ancillary equipment such as power supplies and temperature monitors. Two slave computers interface with the master- computer, and each closes approximately 1100 position loops. For simplicity, the servo is an 'on/off' type, yet achieves a positioning resolution of 25 microns. Each slave computer interfaces with 4 VME I/O cards, which in turn communicate with 140 control modules. The control modules read out the positions of the actuators every 0.1 sec and control the actuators' DC motors. Initial control of the active surface will be based on an elevation dependant structural model. Later, the model will be improved by holographic observations.Surface accuracy will be improved further by using laser ranging system which will actively measure the surface figure. Several tests have been conducted to assure that the system will perform as desired when

  18. sup 40 Ar/ sup 39 Ar polyorogenic mineral age record within the southern Mauritanide orogen (M'Bout-Bakel region) West Africa

    SciTech Connect

    Dallmeyer, R.D. ); Lecorche, J.P. )

    1990-12-01

    The southern Mauritanide orogen exposed between M'Bout and Bakel is characterized by several internally imbricated, polydeformed, and variably metamorphosed infrastructural allochthons. {sup 40}Ar/{sup 39}Ar incremental-release ages recorded by hornblende within undeformed granodiorite of the Guidimakha Complex suggest post-magmatic cooling through appropriate argon closure temperatures at approx 670 Ma. {sup 40}Ar/{sup 39}Ar ages recorded by muscovite within lithologic elements of both the Guidimakha Complex and the Diala-Bouanze Series suggest initial regional metamorphism (associated with Pan-African I orogenesis) was following by cooling through muscovite argon closure temperatures between approx 600 and 620 Ma. Slight rejuvenation of muscovite argon systems occurred locally between approx 325 and 350 Ma. Muscovite and whole-rock slate/phyllite argon systems within metavolcanic and metavolcaniclastic components of the infrastructural calc-alkaline igneous complex (easternmost sectors of the M'Bout Series) record {sup 40}Ar/{sup 39}Ar plateau age of approx 300 to 320 Ma. Muscovite and whole-rock slate/phyllite argon systems within westernmost portions of the study area (western portions of the M'Bout Series) record {sup 40}Ar/{sup 39}Ar plateau ages of approx 267 to 312 Ma. All foreland units within the M'Bout-Bakel area were affected by post-Emsian folding. Effects of this tectonic activity are widespread throughout the parautochthon and western metamorphic sequences. These effects include emplacement of suprastructural ( ) allochthons and local reactivation of older thrust faults within infrastructural units.

  19. Active gated imaging in driver assistance system

    NASA Astrophysics Data System (ADS)

    Grauer, Yoav

    2014-04-01

    In this paper, we shall present the active gated imaging system (AGIS) in relation to the automotive field. AGIS is based on a fast-gated camera and pulsed illuminator, synchronized in the time domain to record images of a certain range of interest. A dedicated gated CMOS imager sensor and near infra-red (NIR) pulsed laser illuminator, is presented in this paper to provide active gated technology. In recent years, we have developed these key components and learned the system parameters, which are most beneficial to nighttime (in all weather conditions) driving in terms of field of view, illumination profile, resolution, and processing power. We shall present our approach of a camera-based advanced driver assistance systems (ADAS) named BrightEye™, which makes use of the AGIS technology in the automotive field.

  20. Shear Zone Development and Rheology in the Deep Orogenic Crust

    NASA Astrophysics Data System (ADS)

    Marsh, J. H.; Johnson, S. E.; Gerbi, C. C.; Culshaw, N. G.

    2008-12-01

    Within the Central Gneiss Belt (CGB) of the southwestern Grenville Province, Ontario, Canada, a number of allocthonous lithotectonic domains are juxtaposed along crustal-scale shear zones. Extensive exposure of variably reworked granulites of the interior Parry Sound domain (iPSD) has enabled investigation of the structural and petrologic character of domain-bounding shear zones within the deep orogenic crust. Recent detailed mapping and structural data collected along the southwestern margin of the iPSD is consistent with the suggestion of Culshaw et al. (in prep) that spaced outcrop-scale shear zones have coalesced and progressively reworked layered granulites into a transposed amphibolite-facies tectonite. The tectonites comprise the Twelve Mile Bay Shear Zone (TMBSZ), which separates the iPSD from para-autocthonous rocks to the south. This study investigates the grain- and outcrop-scale mechanisms involved in shear zone development and attempts to quantify the associated changes in rock rheology. Northwest of TMBSZ, samples collected across individual outcrop-scale shear zones (i.e., across large strain gradients) have distinct differences in mineralogy and microstructure. In mafic layers the original granulite texture and cpx + opx + pl + hbl +/- grt assemblage is commonly retained away from the shear zones within unsheared "panels". With proximity to the shear zones pyroxenes and garnet are progressively consumed in hydration reactions producing hornblende and biotite, which define a new planar foliation within the highly attenuated and deflected layering. Felsic layers generally have only minor mineralogical changes across the zones, but develop an increasingly intense and recrystallized structural fabric into the sheared margin. The shear zones are commonly cored by variably deformed pegmatite dikes that were emplaced prior to, or during the early stages of shearing. Evidence for incipient shear zone formation along mineralized fracture sets that cut

  1. Modular System to Enable Extravehicular Activity

    NASA Technical Reports Server (NTRS)

    Sargusingh, Miriam J.

    2012-01-01

    The ability to perform extravehicular activity (EVA), both human and robotic, has been identified as a key component to space missions to support such operations as assembly and maintenance of space systems (e.g. construction and maintenance of the International Space Station), and unscheduled activities to repair an element of the transportation and habitation systems that can only be accessed externally and via unpressurized areas. In order to make human transportation beyond lower Earth orbit (LEO) practical, efficiencies must be incorporated into the integrated transportation systems to reduce system mass and operational complexity. Affordability is also a key aspect to be considered in space system development; this could be achieved through commonality, modularity and component reuse. Another key aspect identified for the EVA system was the ability to produce flight worthy hardware quickly to support early missions and near Earth technology demonstrations. This paper details a conceptual architecture for a modular EVA system that would meet these stated needs for EVA capability that is affordable, and that could be produced relatively quickly. Operational concepts were developed to elaborate on the defined needs, and to define the key capabilities, operational and design constraints, and general timelines. The operational concept lead to a high level design concept for a module that interfaces with various space transportation elements and contains the hardware and systems required to support human and telerobotic EVA; the module would not be self-propelled and would rely on an interfacing element for consumable resources. The conceptual architecture was then compared to EVA Systems used in the Space Shuttle Orbiter, on the International Space Station to develop high level design concepts that incorporate opportunities for cost savings through hardware reuse, and quick production through the use of existing technologies and hardware designs. An upgrade option

  2. Post-collisional magmatism in the central East African Orogen: The Maevarano Suite of north Madagascar

    USGS Publications Warehouse

    Goodenough, K.M.; Thomas, Ronald J.; De Waele, B.; Key, R.M.; Schofield, D.I.; Bauer, W.; Tucker, R.D.; Rafahatelo, J.-M.; Rabarimanana, M.; Ralison, A.V.; Randriamananjara, T.

    2010-01-01

    Late tectonic, post-collisional granite suites are a feature of many parts of the Late Neoproterozoic to Cambrian East African Orogen (EAO), where they are generally attributed to late extensional collapse of the orogen, accompanied by high heat flow and asthenospheric uprise. The Maevarano Suite comprises voluminous plutons which were emplaced in some of the tectonostratigraphic terranes of northern Madagascar, in the central part of the EAO, following collision and assembly during a major orogeny at ca. 550 Ma. The suite comprises three main magmatic phases: a minor early phase of foliated gabbros, quartz diorites, and granodiorites; a main phase of large batholiths of porphyritic granitoids and charnockites; and a late phase of small-scale plutons and sheets of monzonite, syenite, leucogranite and microgranite. The main phase intrusions tend to be massive, but with variably foliated margins. New U-Pb SHRIMP zircon data show that the whole suite was emplaced between ca. 537 and 522 Ma. Geochemically, all the rocks of the suite are enriched in the LILE, especially K, and the LREE, but are relatively depleted in Nb, Ta and the HREE. These characteristics are typical of post-collisional granitoids in the EAO and many other orogenic belts. It is proposed that the Maevarano Suite magmas were derived by melting of sub-continental lithospheric mantle that had been enriched in the LILE during earlier subduction events. The melting occurred during lithospheric delamination, which was associated with extensional collapse of the East African Orogen. ?? 2009 Natural Environment Research Council.

  3. Relating orogen width to shortening, erosion, and exhumation during Alpine collision

    NASA Astrophysics Data System (ADS)

    Rosenberg, C. L.; Berger, A.; Bellahsen, N.; Bousquet, R.

    2015-06-01

    We investigate along-strike width changes of the thickened, accreted lower plate (TALP) in the Central and in the Eastern Alps. We set the width of the TALP in relation to the inferred amount of collisional shortening and exhumation along six orogen-scale cross sections. Taking the present-day, along-strike gradients in the amount of collisional shortening to represent the temporal evolution of the collisional wedge, it may be concluded that the cross-sectional area of the TALP diminishes during ongoing shortening, indicating that the erosional flux outpaced the accretionary flux. Higher amounts of collisional shortening systematically coincide with smaller widths of the TALP and dramatic increases of the reconstructed eroded rock column. Higher amounts of shortening also coincide with larger amplitudes of orogen-scale, upright folds, with higher exhumation and with higher exhumation rates. Hence, erosion did play a major role in reducing by >30 km the vertical crustal thickness in order to accommodate and allow shortening by folding. Long-term climate differences cannot explain alternating changes of width by a factor of almost 2 along straight segments of the orogen on length scales less than 200 km, as observed from the western Central Alps to the easternmost Eastern Alps. Sedimentary or paleontological evidences supporting such paleo-climatic differences are lacking, suggesting that erosional processes did not directly control the width of the orogen.

  4. Crustal structure and orogenic material budget in the west central Pyrenees

    NASA Astrophysics Data System (ADS)

    Teixell, Antonio

    1998-06-01

    Surface and subsurface data are combined to construct a crustal-scale cross section of the western central Pyrenees (France and Spain) at the boundary between the European and Iberian plates. The position of Moho reflections in the ECORS-Arzacq reflection profile suggests a tectonic wedge of European crust and upper mantle had indented the Iberian plate at lower crustal levels. The European wedge is overlain by an upper, Iberian wedge thus constituting a double (stacked) wedge geometry. The upper wedge was delaminated and deformed giving rise to the Pyrenean orogenic prism, manifested as a bivergent fan in upper crustal levels. The underthrust lower Iberian plate has been imaged to depths of 55-60 km, but crustal budget considerations based on a palinspastic reconstruction require that this continental root subducted to depths up to 90 km. Total orogenic contraction calculated from surface structures is about 75-80 km, which was accomplished between the latest Cretaceous and the early Miocene at an averaged rate of 1.2 mm/yr. Consistent with these moderate values, exhumation of the orogen is much less than in the more shortened eastern parts of the range. Paleozoic basement and preorogenic Mesozoic rocks are little eroded, and much of the exhumation involved cannibalization of early foreland basins, which once covered the entire, poorly emergent orogen at this transect. This resulted in a continuous process of sediment recycling and, coupled with a considerable lateral arrival of material, a bulk negative erosion-sedimentation budget.

  5. Paleomagnetic data from the New England Orogen (eastern Australia) and implications for oroclinal bending

    NASA Astrophysics Data System (ADS)

    Shaanan, Uri; Rosenbaum, Gideon; Pisarevsky, Sergei; Speranza, Fabio

    2015-11-01

    Orogenic curvatures (oroclines) are common in modern and ancient orogens, but the geodynamic driving forces of many oroclines remain controversial. Here we focus on the New England oroclines of eastern Australia, the formation of which had been previously broadly constrained to the Early-Middle Permian. This time interval encompasses periods of both back-arc extension (at ~ 300-280 Ma) and subsequent contractional deformation (Hunter-Bowen Orogeny) that commenced at ~ 270 Ma along the paleo-Pacific and Gondwanan subduction plate boundary. We present new paleomagnetic data from volcanic rocks that were extruded during the transition from extension to contraction (at ~ 272 Ma), and we show that the oroclinal structure must have formed prior to the emplacement of the volcanic rocks. Our results thus indicate that oroclinal bending in the southernmost New England Orogen has been completed prior to the onset of Middle Permian contractional deformation. It is therefore concluded that the oroclines have likely formed during back-arc extension, and that a major contribution to the orogenic curvature was driven by trench retreat.

  6. Optically Active Porphyrin and Phthalocyanine Systems.

    PubMed

    Lu, Hua; Kobayashi, Nagao

    2016-05-25

    This review highlights and summarizes various optically active porphyrin and phthalocyanine molecules prepared using a wide range of structural modification methods to improve the design of novel structures and their applications. The induced chirality of some illustrative achiral bis-porphyrins with a chiral guest molecule is introduced because these systems are ideal for the identification and separation of chiral biologically active substrates. In addition, the relationship between CD signal and the absolute configuration of the molecule is analyzed through an analysis of the results of molecular modeling calculations. Possible future research directions are also discussed. PMID:27186902

  7. Lithosphere structure of the west Qinling orogenic belt revealed by deep seismic reflection profile

    NASA Astrophysics Data System (ADS)

    Wang, H.

    2009-12-01

    The west Qinling orogen located in the northeastern margin of the Qinghai-Tibet plateau, is transformation zone between the N-S-trending and E-W-trending tectonics in the Chinese continent. Further study of the fine crust structure of the west Qinling orogen and its relationships with surrounding basins have very important significance for understanding tectonic response of the northeastern margin of the plateau about collision convergence of the Indian block and Asian block and learning formation and evolution of the plateau. In 2009, we reprocessed the data of the Tangke-Hezuo deep seismic reflection profiles collected in 2004 across the west Qinling orogen and the northern Songpan block. The new results show the lithosphere fine structure of the west Qinling orogen. Reflection features indicate that an interface at 6.0-7.0s (TWT) divided the crust into the upper and lower crust, whose structural style and deformation are totally different. Integrating geological data, we deduce that the interface at 6.0-7.0s (depth with 18-21 km) was the basement detachment, which made deformation decoupled of the upper and lower crust. The multi-layered reflections in the upper crust reveal the sedimentary covers of the west Qinling orogen, disclose the thickness of the various structure layer and deformation degree, and provide a basis for the prospective evaluation of a multi-metallic mineral and energy exploration. The north dipping strong reflection characteristics of the lower crust in the west Qinling orogen constituted imbricate structure, such imbricate structural features provide seismology evidence for researching the west Qinling thrusting toward the northern Songpan block, and have great significance for studying formation and evolution of the Songpan-Garze structure. Moho reflections are observed around 17.0-17.2s, characterized by nearly horizontal reflections, which implies the west Qinling orogen underwent an intense extension post orogeny caused the lithosphere

  8. Transient and Steady-State Kinematic Response to Erosional Forcing in an Orogenic Wedge: Sandbox Perspective

    NASA Astrophysics Data System (ADS)

    Cruz, L.; Teyssier, C.; Annia, F.; Take, A.

    2005-12-01

    The evolution of orogens is highly affected by surface processes that control mass distribution. Transportation and redistribution of mass at the Earth's surface modifies the gravitational load and alters the stress field and kinematics within orogens. We explore the role of asymmetric erosion, indenter dip angle, and flux steady/non-steady state in determining the patterns of deformation and exhumation in doubly-sided orogenic wedges. In our analogue model, shortening of the orogen is driven by rigid indenters, represented by Plexiglas wedged blocks (35 and 70 degrees) that deform a non-cohesive dry Coulomb material (walnut shells) representing crustal material. Three end-member erosional scenarios are considered. In the first case, erosion is not applied, and thus the doubly-sided orogenic wedge evolves without restraints (non-steady state). In the second case, erosion is concentrated solely on the indenters side of the orogen (retrowedge), and in the third case, erosion is focused on the flank opposite to the indenter side (prowedge). In the last two cases, steady-state conditions were present in the middle stages of shortening. Strain and exhumation were calculated using displacement fields from 2D particle image velocimetry (PIV analysis). In the three cases, the model deforms as a combination of lateral compaction and localization of strain in shear bands. In the early stages of deformation, a "pop-up" structure develops, bounded by a fore-shear on the front and a back-shear toward the indenter. As deformation continues, a new fore-shear develops, and the previous one remains inactive and is passively pushed up the wedge. In the case of no erosion, the old fore-shears rotate slightly toward the indenter, and the shear bands evolve to steeply dipping structures. In the case of retrowedge erosion, the old fore-shears back rotate toward the indenter, and the shear bands evolve to shallowly dipping structures. In the case of prowedge erosion, old fore

  9. Control Systems Cyber Security Standards Support Activities

    SciTech Connect

    Robert Evans

    2009-01-01

    The Department of Homeland Security’s Control Systems Security Program (CSSP) is working with industry to secure critical infrastructure sectors from cyber intrusions that could compromise control systems. This document describes CSSP’s current activities with industry organizations in developing cyber security standards for control systems. In addition, it summarizes the standards work being conducted by organizations within the sector and provides a brief listing of sector meetings and conferences that might be of interest for each sector. Control systems cyber security standards are part of a rapidly changing environment. The participation of CSSP in the development effort for these standards has provided consistency in the technical content of the standards while ensuring that information developed by CSSP is included.

  10. Advanced extravehicular activity systems requirements definition study

    NASA Technical Reports Server (NTRS)

    1988-01-01

    A study to define the requirements for advanced extravehicular activities (AEVA) was conducted. The purpose of the study was to develop an understanding of the EVA technology requirements and to map a pathway from existing or developing technologies to an AEVA system capable of supporting long-duration missions on the lunar surface. The parameters of an AEVA system which must sustain the crewmembers and permit productive work for long periods in the lunar environment were examined. A design reference mission (DRM) was formulated and used as a tool to develop and analyze the EVA systems technology aspects. Many operational and infrastructure design issues which have a significant influence on the EVA system are identified.

  11. From orogenic collapse to rifting ; structures of the South China Sea

    NASA Astrophysics Data System (ADS)

    Pubellier, M.; Chan, L. S.; Chamot Rooke, N.; Shen, W.; Ringenbach, J. C.

    2009-04-01

    The opening of the South China Sea has been a matter of debate for many years because of its internal structure, the differences between the conjugate margins and the variations of rifting and spreading directions. Although it is considered as being a back-arc basin, it is not sitting directly above a subduction zone, and the rifting process lasted for an unusually long duration. Among the specific characteristics is the early phase of rifting which took place early in place of the former Yanshanian andean-type mountain range. This stage is marked by narrow basins filled with deformed conglomerate, and initiated around 70My ago within a framework where the oblique subduction marked by igneous activity and ductile wrench faults, was replaced by orogenic collapse. The rifting stage is marked by Eocene syntectonic normal faults and occasional volcanics centres and has proceeded from NW-SE to NS extension. The NW stretching created at least two aborted basins which remained at rift stage. Extension was followed by spreading from 33 to ~20 Ma in the South China Sea. The ocean floor spreading also changed direction to NW-SE with a propagator inside the Sunda shelf from 20 to 17My ago. However the propagator opening implies that deformation is also taken by rifting around a southern wedge which in turn created strain inside the thinned crust. Another extension parallel to the margin is also observed althought the spreading was in process. The southward motion of the southern conjugate margin was later accommodated by its subduction beneath the NW Borneo wedge until completion of the Proto South China Sea subduction. Variations of rifting spreading through time and variations of structural styles are discussed in terms of boundary forces acting to the SE.

  12. Vestiges of The Peri-rodinian Ocean: Sliced, Diced, Recycled But Preserved In Younger Orogens

    NASA Astrophysics Data System (ADS)

    Murphy, J. B.; Nance, R. D.; Keppie, J. D.; Dostal, J.

    Just as the amalgamation and dispersal of Pangea exerted a first-order influence on tectonothermal events in the Phanerozoic, Middle to late Proterozoic global scale tec- tonics were profoundly influenced by the amalgamation and subsequent breakup of the supercontinent Rodinia. Most tectonic studies of the evolution of Rodinia concentrate on the near-field effects of these events such as the collisional orogenies that result in its amalgamation and the sedimentary rift-drift record of its breakup. However, ves- tiges of the far field effects of these events are also preserved and their tectonothermal evolution can provide additional constraints on supercontinent configuration and the timing of breakup. During the time interval of Rodinian amalgamation, for exam- ple, ensimatic subduction and plume activity in the peri-Rodinian ocean resulted in the formation of oceanic crust with ca. 1.0 Ga Sm-Nd depleted mantle model (TDM) ages. Vestiges of this crust are now preserved in the terranes that subsequently accreted along the margins of the dispersing continents, including the peri-Gondwanan terranes (e.g. Avalonia, Carolina, Iberia) of eastern North America and Europe, the Tocantins orogenic belt of Brazil, and the terranes of the Arabian-Nubian Shield. The Neopro- terozoic tectonothermal evolution of these terranes was a far-field response to Rodinia breakup, in the same way that the Mesozoic and Cenozoic evolution of western North America was a far-field response to the breakup of Pangea. Hence, the Neoproterozoic histories of these terranes are geodynamically linked to that of Rodinia and so provide constraints on its configuration and the timing of its major tectonothermal events.

  13. Tectonic, magmatic, and metallogenic evolution of the Late Cretaceous arc in the Carpathian-Balkan orogen

    NASA Astrophysics Data System (ADS)

    Gallhofer, Daniela; Quadt, Albrecht von; Peytcheva, Irena; Schmid, Stefan M.; Heinrich, Christoph A.

    2015-09-01

    The Apuseni-Banat-Timok-Srednogorie Late Cretaceous magmatic arc in the Carpathian-Balkan orogen formed on the European margin during closure of the Neotethys Ocean. It was subsequently deformed into a complex orocline by continental collisions. The Cu-Au mineralized arc consists of geologically distinct segments: the Apuseni, Banat, Timok, Panagyurishte, and Eastern Srednogorie segments. New U-Pb zircon ages and geochemical whole rock data for the Banat and Apuseni segments are combined with previously published data to reconstruct the original arc geometry and better constrain its tectonic evolution. Trace element and isotopic signatures of the arc magmas indicate a subduction-enriched source in all segments and variable contamination by continental crust. The magmatic arc was active for 25 Myr (~92-67 Ma). Across-arc age trends of progressively younger ages toward the inferred paleo-trench indicate gradual steepening of the subducting slab away from the upper plate European margin. This leads to asthenospheric corner flow in the overriding plate, which is recorded by decreasing 87Sr/86Sr (0.70577 to 0.70373) and increasing 143Nd/144Nd (0.51234 to 0.51264) ratios over time in some segments. The close spatial relationship between arc magmatism, large-scale shear zones, and related strike-slip sedimentary basins in the Timok and Pangyurishte segments indicates mild transtension in these central segments of the restored arc. In contrast, the Eastern Srednogorie segment underwent strong orthogonal intraarc extension. Segmental distribution of tectonic stress may account for the concentration of rich porphyry Cu deposits in the transtensional segments, where lower crustal magma storage and fractionation favored the evolution of volatile-rich magmas.

  14. Thin visous sheet modelling of orogen scale deformation. The Eastern Alps in plan view

    NASA Astrophysics Data System (ADS)

    Robl, J.; Stuewe, K.

    2003-04-01

    We present first results of a new numerical model to describe the dynamic evolution of the eastern Alps in plan view on the orogen scale. We investigate the influence of boundary conditions, gravitational potential energy, rheology contrast of major tectonic units and internal structures on the deformation field. We aim at estimating the Argan number of the Eastern Alps and to calculate slip rates along big lineaments that represent the northern and southern border of the Austro-Alpine extrusion corridor. A further aim is to predict the position and the activity of major faults where they disappear below quartenary sediments. All calculation are perfomed with the mechanical finite element code BASIL that allows computation on a thin visous sheet. The starting conditons are controlled by the varying crustal thickness of the region and by the rheolgy of the Adriatic indenter in the south, the Bohemian massif in the north and the Eastern Alps inbetween. We assume that the Eastern Alps are fixed to the north and the west while the southern boundary moves northward at a rate of 6-8 mm /y. The geodynamic setting in the east changed over the last 5 my. While a roll back subduction zone beneath the Carparthian belt accompanied by extension, crustal thinning and basin formation controlled the deformation of the Eastern Alps until the Miocene. Later on subduction stopped and the overall stress field changed from extension to compression resulting in uplift of many basins and the lack sediments younger than Pliocene. This well known variation of plate tectonic scenarios over the last 5 my allows us to place tight constraints for the boundary conditions of our model. Although our work is only now in progress, we can report some promising results: some of the kinematics and mechaniscs predicted by our modelling are consistent with field observations of the structural geologists and geodeticists.

  15. Active State Model for Autonomous Systems

    NASA Technical Reports Server (NTRS)

    Park, Han; Chien, Steve; Zak, Michail; James, Mark; Mackey, Ryan; Fisher, Forest

    2003-01-01

    The concept of the active state model (ASM) is an architecture for the development of advanced integrated fault-detection-and-isolation (FDI) systems for robotic land vehicles, pilotless aircraft, exploratory spacecraft, or other complex engineering systems that will be capable of autonomous operation. An FDI system based on the ASM concept would not only provide traditional diagnostic capabilities, but also integrate the FDI system under a unified framework and provide mechanism for sharing of information between FDI subsystems to fully assess the overall health of the system. The ASM concept begins with definitions borrowed from psychology, wherein a system is regarded as active when it possesses self-image, self-awareness, and an ability to make decisions itself, such that it is able to perform purposeful motions and other transitions with some degree of autonomy from the environment. For an engineering system, self-image would manifest itself as the ability to determine nominal values of sensor data by use of a mathematical model of itself, and selfawareness would manifest itself as the ability to relate sensor data to their nominal values. The ASM for such a system may start with the closed-loop control dynamics that describe the evolution of state variables. As soon as this model was supplemented with nominal values of sensor data, it would possess self-image. The ability to process the current sensor data and compare them with the nominal values would represent self-awareness. On the basis of self-image and self-awareness, the ASM provides the capability for self-identification, detection of abnormalities, and self-diagnosis.

  16. Research on an Active Seat Belt System

    NASA Astrophysics Data System (ADS)

    Kawashima, Takeshi

    In a car crash, permanent injury can be avoided if deformation of an occupant's rib cage is maintained within the allowable value. In order to realize this condition, the occupant's seat belt tension must be instantaneously adjusted by a feedback control system. In this study, a seat belt tension control system based on the active shock control system is proposed. The semi-active control law used is derived from the sliding mode control method. One advantage of this proposed system is that it does not require a large power actuator because the seat belt tension is controlled by a brake mechanism. The effectiveness is confirmed by numerical simulation using general parameters of a human thorax and a passenger car in a collision scenario with a wall at a velocity of 100 km/h. The feasibility is then confirmed with a control experiment using a scale model of about 1/10 scale. The relative displacement of the thorax model approaches the allowable value smoothly along the control reference and settles near this value. Thus, the proposed seat belt tension control system design is established.

  17. Multipurpose active/passive motion compensation system

    SciTech Connect

    Sullivan, R.A.; Clements, R.E.; Davenport, M.R.

    1984-05-01

    A microprocessor-controlled active/passive motion compensation system has been developed for deploying a variety of geotechnical in-situ testing devices with mobile drilling rigs from low-cost service vessels. The light-weight rotary heave compensator incorporates a hydraulic motor as the compensator actuator and a servo-controlled closed loop pump to reduce the air storage and power requirements. Unique features of the system are the use of inertial sensors to measure three components of boat motion, the ability to run the system in active/passive or passive modes, and the ability to automatically lower the drillstring at a constant velocity while maintaining motion compensation. Quantitative measurements made during sea trials offshore California yielded motion compensation accuracy approaching 98 percent which is much better than the compensation achieved with passive systems. Results are presented from offshore in-situ testing with a cone penetrometer, a vane shear device, and a suspension PS logger. The system can also be used for other offshore applications.

  18. Active laser system for sea ice control

    NASA Astrophysics Data System (ADS)

    Evtikhiev, Nickolay N.; Gaponov, Alexandr E.; Kuluba, Yury N.; Matous, Vladislav I.; Radominov, Oleg E.; Tuzikov, Vladimir Z.; Vargaftic, Vasiliy N.

    1997-01-01

    The airborne systems are used for complex investigations of coastline very successfully, for example it can be used to measure the depth of the sea, to discover the reefs and so on. Such information may be used in navigation too. The specific conditions of navigation in the North and Pole seas defines the necessity of exact knowledge about the ice cracks in order to find the possible direction of the ship movement. The active optical system, working in the near IR region, has many advantages before the passive one, especially if it is necessary to work during the polar night and at bad weather conditions. In this article we discuss the demands to the laser active airborne systems, that given the accurate picture of the ice with high resolution in the daytime and nighttime conditions. Such system based on the laser, mechanical scanner and avalanche photodiode is very compact, reliable and informative. The picture of the ice surface can be shown on the TV monitor, can be written to the memory and can be delivered to the processing center by the radiochannel. The experimental results are shown together with results of this system probing in the conditions of the North Pole Ocean.

  19. PCM Passive Cooling System Containing Active Subsystems

    NASA Technical Reports Server (NTRS)

    Blanding, David E.; Bass, David I.

    2005-01-01

    A multistage system has been proposed for cooling a circulating fluid that is subject to intermittent intense heating. The system would be both flexible and redundant in that it could operate in a basic passive mode, either sequentially or simultaneously with operation of a first, active cooling subsystem, and either sequentially or simultaneously with a second cooling subsystem that could be active, passive, or a combination of both. This flexibility and redundancy, in combination with the passive nature of at least one of the modes of operation, would make the system more reliable, relative to a conventional cooling system. The system would include a tube-in-shell heat exchanger, within which the space between the tubes would be filled with a phase-change material (PCM). The circulating hot fluid would flow along the tubes in the heat exchanger. In the basic passive mode of operation, heat would be conducted from the hot fluid into the PCM, wherein the heat would be stored temporarily by virtue of the phase change.

  20. Active Aircraft Pylon Noise Control System

    NASA Technical Reports Server (NTRS)

    Thomas, Russell H. (Inventor); Czech, Michael J (Inventor); Elmiligui, Alaa A. (Inventor)

    2015-01-01

    An active pylon noise control system for an aircraft includes a pylon structure connecting an engine system with an airframe surface of the aircraft and having at least one aperture to supply a gas or fluid therethrough, an intake portion attached to the pylon structure to intake a gas or fluid, a regulator connected with the intake portion via a plurality of pipes, to regulate a pressure of the gas or fluid, a plenum chamber formed within the pylon structure and connected with the regulator, and configured to receive the gas or fluid as regulated by the regulator, and a plurality of injectors in communication with the plenum chamber to actively inject the gas or fluid through the plurality of apertures of the pylon structure.

  1. Stable isotope and Ar/Ar evidence of prolonged multiscale fluid flow during exhumation of orogenic crust: Example from the Mont Blanc and Aar Massifs (NW Alps)

    NASA Astrophysics Data System (ADS)

    Rossi, M.; Rolland, Y.

    2014-09-01

    The spatial and temporal scales and the geometry of fluid pathways in a collisional orogen are investigated using stable isotope analysis (O, C, and H) and 40Ar/39Ar dating of vein minerals formed at circa 11-16 Ma in the Mont Blanc and the Aar External Crystalline Massifs. In both massifs 40Ar/39Ar dating of veins adularia provides evidence for progressive crystallization from 16 to 9 Ma, and mainly at 11-12 Ma following veins opening during shear zone activity. The fluid flow duration thus ranges from 4 to 5 Ma in the two massifs. The δ18O values of vein quartz and calcite are similar to those of undeformed crystalline and sedimentary host rocks, suggesting rock buffering, while carbon isotope ratios of vein calcites fall into three compositional groups. A-type veins have δ13C values that are buffered by the Helvetic metasediments, which suggests that these veins formed in a closed system from a locally derived CO2-rich fluid. The fluid in equilibrium with C-type veins has depleted δ13C values similar to mantle-CO2, while the intermediate δ13C values of B-type veins suggest mixing between the A-type and C-type fluids. These results are in agreement with crustal- to lithosphere-scale upward vertical fluid flow along vertical shear zones related to the strike-slip system bounding the Adriatic block since 16-20 Ma, connecting a deep-seated fluid to some downward flow in the sedimentary cover of External Crystalline Massifs.

  2. The generation, segregation, ascent and emplacement of granite magma: the migmatite-to-crustally-derived granite connection in thickened orogens

    NASA Astrophysics Data System (ADS)

    Brown, Michael

    1994-04-01

    , consistent with a pulsed magma supply. Some examples cited in the literature of diapiric emplacement may be interpreted better as local ballooning by magmatic flow of granite after upward transport along shear zones. Thus, granite contact relationships likely reflect local emplacement mechanisms rather than regional, crustal-scale ascent mechanisms. A general model for granite magma genesis, ascent and emplacement that may apply to other orogenic belts is developed from relationships interpreted from different crustal levels exposed within the late-Precambrian Cadomian orogenic belt of northwest France. Here, thickening of a volcano-sedimentary basin during transpression led to upper amphibolite facies water-rich volatile phase-present anatexis and development of migmatites (St. Malo migmatite belt) and granite melt production (Mancellian granites), with some evidence of dehydration melting in granites emplaced at the highest structural level. Transcurrent shear was regionally focussed within this zone of softened crust. Granite magma was transported to higher crustal levels in megadike bodies (c. 0.5-1 km width), themselves constructed from multiple sheets, located within major ductile shear zones. Magma entered the shear zones at points of local extension and was expelled upwards in zones of compression, a mechanism referred to as strike slip dilatancy pumping. The shear zones are inferred to have been linked to major brittle fault zones in the upper crust, and extensional jogs within such systems have provided sites for assembly of plutons (tens of km across) from magmas arriving from below. Granite is generated also by decompression melting during uplift of orogenic belts and commonly has an important role to play in exhumation of the high-grade cores of thickened orogens. The Variscan metamorphic belt of western France provides an example of these interactions between tectonic processes and granite in a thickened orogen. Here, the Eo-Variscan to Variscan P- T- t- d

  3. Spontaneous activity in the developing auditory system.

    PubMed

    Wang, Han Chin; Bergles, Dwight E

    2015-07-01

    Spontaneous electrical activity is a common feature of sensory systems during early development. This sensory-independent neuronal activity has been implicated in promoting their survival and maturation, as well as growth and refinement of their projections to yield circuits that can rapidly extract information about the external world. Periodic bursts of action potentials occur in auditory neurons of mammals before hearing onset. This activity is induced by inner hair cells (IHCs) within the developing cochlea, which establish functional connections with spiral ganglion neurons (SGNs) several weeks before they are capable of detecting external sounds. During this pre-hearing period, IHCs fire periodic bursts of Ca(2+) action potentials that excite SGNs, triggering brief but intense periods of activity that pass through auditory centers of the brain. Although spontaneous activity requires input from IHCs, there is ongoing debate about whether IHCs are intrinsically active and their firing periodically interrupted by external inhibitory input (IHC-inhibition model), or are intrinsically silent and their firing periodically promoted by an external excitatory stimulus (IHC-excitation model). There is accumulating evidence that inner supporting cells in Kölliker's organ spontaneously release ATP during this time, which can induce bursts of Ca(2+) spikes in IHCs that recapitulate many features of auditory neuron activity observed in vivo. Nevertheless, the role of supporting cells in this process remains to be established in vivo. A greater understanding of the molecular mechanisms responsible for generating IHC activity in the developing cochlea will help reveal how these events contribute to the maturation of nascent auditory circuits. PMID:25296716

  4. Alkali-calcic and alkaline post-orogenic (PO) granite magmatism: petrologic constraints and geodynamic settings

    NASA Astrophysics Data System (ADS)

    Bonin, Bernard; Azzouni-Sekkal, Abla; Bussy, François; Ferrag, Sandrine

    1998-12-01

    The end of an orogenic Wilson cycle corresponds to amalgamation of terranes into a Pangaea and is marked by widespread magmatism dominated by granitoids. The post-collision event starts with magmatic processes still influenced by subducted crustal materials. The dominantly calc-alkaline suites show a shift from normal to high-K to very high-K associations. Source regions are composed of depleted and later enriched orogenic subcontinental lithospheric mantle, affected by dehydration melting and generating more and more K- and LILE-rich magmas. In the vicinity of intra-crustal magma chambers, anatexis by incongruent melting of hydrous minerals may generate peraluminous granitoids bearing mafic enclaves. The post-collision event ends with emplacement of bimodal post-orogenic (PO) suites along transcurrent fault zones. Two suites are defined, (i) the alkali-calcic monzonite-monzogranite-syenogranite-alkali feldspar granite association characterised by [biotite+plagioclase] fractionation and moderate [LILE+HFSE] enrichments and (ii) the alkaline monzonite-syenite-alkali feldspar granite association characterised by [amphibole+alkali feldspar] fractionation and displaying two evolutionary trends, one peralkaline with sodic mafic mineralogy and higher enrichments in HFSE than in LILE, and the other aluminous biotite-bearing marked by HFSE depletion relative to LILE due to accessory mineral precipitation. Alkali-calcic and alkaline suites differ essentially in the amounts of water present within intra-crustal magma chambers, promoting crystallisation of various mineral assemblages. The ultimate enriched and not depleted mantle source is identical for the two PO suites. The more primitive LILE and HFSE-rich source rapidly replaces the older orogenic mantle source during lithosphere delamination and becomes progressively the thermal boundary layer of the new lithosphere. Present rock compositions are a mixture of major mantle contribution and various crustal components

  5. SVM-based base-metal prospectivity modeling of the Aravalli Orogen, Northwestern India

    NASA Astrophysics Data System (ADS)

    Porwal, Alok; Yu, Le; Gessner, Klaus

    2010-05-01

    The Proterozoic Aravalli orogen in the state of Rajasthan, northwestern India, constitutes the most important metallogenic province for base-metal deposits in India and hosts the entire economically viable lead-zinc resource-base of the country. The orogen evolved through near-orderly Wilson cycles of repeated extensional and compressional tectonics resulting in sequential opening and closing of intracratonic rifts and amalgamation of crustal domains during a circa 1.0-Ga geological history from 2.2 Ga to 1.0 Ga. This study develops a conceptual tectonostratigraphic model of the orogen based on a synthesis of the available geological, geophysical and geochronological data followed by deep-seismic-reflectivity-constrained 2-D forward gravity modeling, and links it to the Proterozoic base-metal metallogeny in the orogen in order to identify key geological controls on the base-metal mineralization. These controls are translated into exploration criteria for base-metal deposits, validated using empirical spatial analysis, and used to derive input spatial variables for model-based base-metal prospectivity mapping of the orogen. A support vector machine (SVM) algorithm augmented by incorporating a feature selection procedure is used in a GIS environment to implement the prospectivity mapping. A comparison of the SVM-derived prospectivity map with the ones derived using other established models such as neural-networks, logistic regression, and Bayesian weights-of-evidence indicates that the SVM outperforms other models, which is attributed to the capability of the SVM to return robust classification based on small training datasets.

  6. Voice activity detection for speaker verification systems

    NASA Astrophysics Data System (ADS)

    Borowski, Filip

    2008-01-01

    Complex algorithm for speech activity detection was presented in this article. It is based on speech enhancement, features extraction and final detection algorithm. The first one was published in ETSI standard as a module of "Advanced front-end feature extraction algorithm" in distributed speech recognition system. It consists of two main parts, noise estimatiom and Wiener filtering. For the final detection modified linear prediction coefficients and spectral entropy features are extracted form denoised signal.

  7. Light and immune systems: activation of immunological activities

    NASA Astrophysics Data System (ADS)

    Huang, Zheng; Liu, Hong; Chen, Wei R.

    2006-02-01

    Light has been used to treat diseases for hundreds of years. Convenient and powerful light sources such as lasers make photomedicine a major branch in diseases treatment and detection. Originally, light was often used for local treatment, using photomechanical, photochemical, photothermal reactions and photomodulation as the major mechanisms. More and more investigators have become interested in the systemic effects of light, particularly in its effects on immune systems. Much work has been done to activate and/or enhance the host immune system to combat cancer, either using light as a direct tool or as an adjuvant method. Light has long been used for assisting disease detection and diagnosis. Advances in light technology have made photo-diagnostics ever more precise spatially and temporally. Many techniques facilitate observation of bio-molecule interactions and other biological processes at the cellular level, hence providing opportunities to detect and monitor immune activities. This manuscript will review recent photo-immunological research in treatment of cancer. The recent development of combination therapies involving lasers will be presented. Specifically, the results of cancer treatment using laser photothermal interaction, either with or without additional immunological stimulation will be discussed. The immunological effects of photodynamic therapy (PDT), and of its combination with immunotherapy in cancer treatment will also be discussed. Much interest has been recently concentrated in the immunological responses after laser treatment. Such responses at cellular and molecular levels will be discussed. The effect of these treatment modalities on the distant metastases also showed promise of light induced antitumor immunity. The combination therapy and induced immunological responses appear to be the key for long-term control of tumors.

  8. Post-orogenic exhumation history of a Variscan mid-crustal basement in Galicia (NW Spain)

    NASA Astrophysics Data System (ADS)

    Grobe, Rene; Alvarez-Marrón, Joaquina; Glasmacher, Ulrich A.; Stuart, Finlay; Castañeda-Zarauz, A.

    2010-05-01

    The present study aims to quantify the complex post-orogenic history of cooling, denudation, and long-term landscape evolution of a mid-crustal section of Variscan basement in Galicia (NW Spain). We use apatite fission-track and apatite (U-Th)/He thermochronological techniques combined with time-temperature (t-T) path modelling using the software code HeFTy©. The topography is characterized by an extensive, low relief area at ~500 m elevation in central Galicia, and a WNW-ESE ridge that reaches up to 1000 m to the North. The area experienced two major tectonic events since the end of the Variscan orogeny in the Late Palaeozoic: 1) continental break-up and Mesozoic rifting leading to the opening of the Atlantic Ocean and the Bay of Biscay, and 2) limited convergence between Iberia and Eurasia since Middle Eocene times. Apatite fission-track ages range from 68.1 ± 5.0 Ma to 174.5 ± 7.7 Ma and apatite (U-Th)/He ages range from 73.6 ± 5.4 to 147.1 ± 16.6 Ma. Age-elevation plots and t-T path modelling suggest a tectonothermal evolution with faster exhumation associated to faulting during Mesozoic rifting. In particular, two major fault systems trending WNW-ESE and NNE-SSW, the As Pontes and the Lugo faults respectively separate areas with the fastest exhumation around 115 Ma from areas with overall slow exhumation since 200-150 Ma. A landscape of subdued topography in central Galicia was acquired prior to Eocene convergence. The higher elevation areas along the northern ridge formed since Middle Eocene times due to fault reactivation and minor exhumation occurred along the fault escarpment.

  9. Uplift mechanism of orogens inferred from GRACE temporal gravity changes - example of Qinghai-Tibet

    NASA Astrophysics Data System (ADS)

    Braitenberg, C. F.; Shum, C. K.

    2015-12-01

    Orogenic areas are subject to uplift and horizontal deformation as observed by present-day global positioning system and repeated leveling measurements. Crustal mass is conservative and less dense than the mantle, thus the horizontal shortening must be accompanied by crustal thickening and horizontal extrusion. According to the level of isostatic compensation, the thickening is partitioned into topographic uplift and Moho deepening. We investigate the mass change induced gravity signal and discuss whether this signal could be detected using terrestrial or satellite gravity observations. An example is the Qinghai-Tibet plateau, for which we model crustal thickening and calculate the expected gravity signal. The predictions are compared with present-day gravity changes observed by GRACE and with published in situ absolute gravity rates. It is found that the crustal thickening signal cannot be neglected and that it contributes significantly to the observed signal. Those studies with focus on the glacier and hydrologic mass fluxes should be aware that, if neglected, the crustal signal could introduce a significant bias. The GRACE observations give a positive gravity rate over central Tibetan Plateau, unexplained by the hydrologic or cryospheric signals, and a negative rate over the Himalayas and at its foothill, which is attributable to a prolonged hydrologic drought and/or depletion of groundwater. Our model shows that the positive gravity rate could be explained by elevation uplift, and a stable or upwelling Moho. The negative gravity change signal is due primarily to the strong elevation-gradient at the foothill of the Himalayas, and to an uplift accompanied by crustal thickening and Moho lowering. Finally, we place constraints and requirements on future gravity missions, for the feasibility to more accurately observe this signal, and to separate it from the background hydrologic and cryospheric processes.

  10. Orogenic structure of the Eastern Alps, Europe, from TRANSALP deep seismic reflection profiling

    NASA Astrophysics Data System (ADS)

    Lüschen, Ewald; Lammerer, Bernd; Gebrande, Helmut; Millahn, Karl; Nicolich, Rinaldo; Transalp Working Group

    2004-09-01

    The TRANSALP Group, comprising of partner institutions from Italy, Austria and Germany, acquired data on a 340 km long deep seismic reflection line crossing the Eastern Alps between Munich and Venice. Although the field work was split into four campaigns, between fall 1998 and summer 2001, the project gathered for the first time a continuous profile across the Alps using consistent field acquisition and data processing parameters. These sections span the orogen itself, at its broadest width, as well as the editor Fred Davey and the two adjacent basins. Vibroseis and explosion data, complementary in their depth penetration and resolution characteristics, were obtained along with wide-angle and teleseismic data. The profile shows a bi-vergent asymmetric structure of the crust beneath the Alpine axis which reaches a maximum thickness of 55 km, and 80-100 km long transcrustal ramps, the southward dipping 'Sub-Tauern-Ramp' and the northward-dipping 'Sub-Dolomites-Ramp'. Strongly reflective patterns of these ramps can be traced towards the north to the Inn Valley and towards the south to the Valsugana thrust belt, both of which show enhanced seismicity in the brittle upper crust. The seismic sections do not reveal any direct evidence for the presence of the Periadriatic Fault system, the presumed equivalent to the Insubric Line in the Western Alps. According to our new evolutionary model, the Sub-Tauern-Ramp is linked at depth with remnants of the subducted Penninic Ocean. The 'crocodile'-type model describes an upper/lower crustal decoupling and wedging of both the European and the Adriatic-African continents.

  11. The Ust-Belaya ophiolite terrane, West Koryak Orogen: Isotopic dating and paleotectonic interpretation

    NASA Astrophysics Data System (ADS)

    Palandzhyan, S. A.

    2015-03-01

    The Ust-Belaya ophiolite terrane in the West Koryak Orogen, which is the largest in northeastern Asia, consists of three nappe complexes. The upper Ust-Belaya Nappe is composed of a thick (>5 km) sheet of fertile peridotites and mafic rocks (remnants of the proto-Pacific lithosphere); its upper age boundary is marked by Late Neoproterozoic plagiogranites. In the middle Tolovka-Otrozhny Nappe, the Late Precambrian lherzolite-type ophiolites are supplemented by fragments of tectonically delaminated harzburgite-type ophiolites, which make up the Tolovka rock association. The isotopic age of metadacite (K-Ar method, whole-rock sample) and zircons from plagiogranite porphyry (U-Pb method, SHRIMP) determines the upper chronological limit of the Tolovka ophiolites as 262-265 Ma ago. It is suggested that igneous rocks of these ophiolites were generated in a backarc basin during the Early Carboniferous and then incorporated into the fold-nappe structure in the Mid-Permian. This was the future basement of the Koni-Taigonos arc, where the Early Carboniferous ophiolites together with Late Neoproterozoic precursors were subject to low-temperature metamorphism and intruded by plagiogranite porphyry dikes in Permian-Triassic. The polymicte serpentinite mélange, which was formed in the accretionary complex of the Koni-Taigonos arc comprises rock blocks of the upper units of Late Precambrian ophiolites (in particular, plagiogranite), the overlying Middle to Upper Devonian and Early Carboniferous deposits, as well as Early Carboniferous (?) Tolovka ophiolites and meta-ophiolites. Mélange of this type with inclusions of Late Precambrian "oceanic" granitoids also developed in the lower Utyosiki Nappe composed of Middle Jurassic-Lower Cretaceous sedimentary and volcanic sequences, the formation of which was related to the next Uda-Murgal island-arc systems.

  12. Late Paleozoic tectonic evolution and concentrated mineralization in Balkhash and West Junggar, western part of the Central Asian Orogenic Belt

    NASA Astrophysics Data System (ADS)

    Dong, Shuwen; Chen, Xuanhua; Chen, Zhengle

    2016-04-01

    The Central Asia Orogenic Belt (CAOB) is an important area with significant growth of the crust and metallogeny in the Late Paleozoic. The Balkhash-Junggar tectono-metallogenic belt consists of the Balkhash, the West Junggar, and the East Junggar tectono-metallogenic belts in western part of the Central Asian Orogenic Belt (CAOB). According to the structural geological relationship, the East Junggar, the West Junggar, and the Balkhash belts are considered to be once a continuous E-W-trending tectono-metallogenic belt in Late Carboniferous. The West Junggar belt is featured with NE-trending left-lateral strike-slip faulting tectonic system (WJTS), while the left-lateral strike-slip faults are E-W-trending in the Balkhash belt. The WJTS consists of the Darabut, the Mayile, and the Baerluke faults, and the blocks among them. All these left-lateral strike-slip faults are forming due to the transition of tectonic settings from syn-collisional orogeny to post-collisional extension during the closure of the ocean (the Junggar Sea) in Late Carboniferous, with significant intrusion of batholiths and crust growth occurred in this period. These faults are truncated by the right-lateral strike-slip faults, such as the Chingiz-Junggar fault, and the Central Balkhash fault in Mesozoic. The Balkhash-Junggar tectono-metallogenic belt is important for the occurrence of many well-known super-large and large porphyry Cu-Mo deposits (such as the Kounrad, the Aktogai, the Borly, and the Baogutu deposits), large skarn Cu deposits (in the Sayak ore-filed), large rare metal deposits (such as the East Kounrad, the Zhanet, and the Akshatau deposits), and large gold deposits (such as the Hatu deposit). Zircon U-Pb ages, Re-Os isotopic dating of molybdenites, 40Ar/39Ar thermochronology of hornblendes, muscovites, biotites, and K-feldspars, and zircon and apatite fission track (FT) and (U-Th)/He dating and thermal history modeling, provide a multidisciplinary approach to constrain the whole

  13. Active polarimeter optical system laser hazard analysis.

    SciTech Connect

    Augustoni, Arnold L.

    2005-07-01

    A laser hazard analysis was performed for the SNL Active Polarimeter Optical System based on the ANSI Standard Z136.1-2000, American National Standard for Safe Use of Lasers and the ANSI Standard Z136.6-2000, American National Standard for Safe Use of Lasers Outdoors. The Active Polarimeter Optical System (APOS) uses a pulsed, near-infrared, chromium doped lithium strontium aluminum fluoride (Cr:LiSAF) crystal laser in conjunction with a holographic diffuser and lens to illuminate a scene of interest. The APOS is intended for outdoor operations. The system is mounted on a height adjustable platform (6 feet to 40 feet) and sits atop a tripod that points the beam downward. The beam can be pointed from nadir to as much as 60 degrees off of nadir producing an illuminating spot geometry that can vary from circular (at nadir) to elliptical in shape (off of nadir). The JP Innovations crystal Cr:LiSAF laser parameters are presented in section II. The illuminating laser spot size is variable and can be adjusted by adjusting the separation distance between the lens and the holographic diffuser. The system is adjusted while platform is at the lowest level. The laser spot is adjusted for a particular spot size at a particular distance (elevation) from the laser by adjusting the separation distance (d{sub diffuser}) to predetermined values. The downward pointing angle is also adjusted before the platform is raised to the selected operation elevation.

  14. Global Positioning System Synchronized Active Light Autonomous Docking System

    NASA Technical Reports Server (NTRS)

    Howard, Richard T. (Inventor); Book, Michael L. (Inventor); Bryan, Thomas C. (Inventor); Bell, Joseph L. (Inventor)

    1996-01-01

    A Global Positioning System Synchronized Active Light Autonomous Docking System (GPSSALADS) for automatically docking a chase vehicle with a target vehicle comprising at least one active light emitting target which is operatively attached to the target vehicle. The target includes a three-dimensional array of concomitantly flashing lights which flash at a controlled common frequency. The GPSSALADS further comprises a visual tracking sensor operatively attached to the chase vehicle for detecting and tracking the target vehicle. Its performance is synchronized with the flash frequency of the lights by a synchronization means which is comprised of first and second internal clocks operatively connected to the active light target and visual tracking sensor, respectively, for providing timing control signals thereto, respectively. The synchronization means further includes first and second Global Positioning System receivers operatively connected to the first and second internal clocks, respectively, for repeatedly providing simultaneous synchronization pulses to the internal clocks, respectively. In addition, the GPSSALADS includes a docking process controller means which is operatively attached to the chase vehicle and is responsive to the visual tracking sensor for producing commands for the guidance and propulsion system of the chase vehicle.

  15. Global Positioning System Synchronized Active Light Autonomous Docking System

    NASA Technical Reports Server (NTRS)

    Howard, Richard (Inventor)

    1994-01-01

    A Global Positioning System Synchronized Active Light Autonomous Docking System (GPSSALADS) for automatically docking a chase vehicle with a target vehicle comprises at least one active light emitting target which is operatively attached to the target vehicle. The target includes a three-dimensional array of concomitantly flashing lights which flash at a controlled common frequency. The GPSSALADS further comprises a visual tracking sensor operatively attached to the chase vehicle for detecting and tracking the target vehicle. Its performance is synchronized with the flash frequency of the lights by a synchronization means which is comprised of first and second internal clocks operatively connected to the active light target and visual tracking sensor, respectively, for providing timing control signals thereto, respectively. The synchronization means further includes first and second Global Positioning System receivers operatively connected to the first and second internal clocks, respectively, for repeatedly providing simultaneous synchronization pulses to the internal clocks, respectively. In addition, the GPSSALADS includes a docking process controller means which is operatively attached to the chase vehicle and is responsive to the visual tracking sensor for producing commands for the guidance and propulsion system of the chase vehicle.

  16. Dislocation boundaries and active slip systems

    SciTech Connect

    Wert, J.A.; Hansen, N.

    1995-11-01

    Part of the dislocations which have participated in the plastic deformation of a polycrystalline metal are stored in dislocation boundaries in a two- or three-dimensional arrangement. The dislocation in such boundaries can be analyzed by determining the misorientation between neighboring crystallites and the boundary orientation. Information about the dislocations in the boundaries can also be obtained by an analysis of active slip systems based on the crystallite orientation and the imposed stress or strain state in combination with appropriate constraint conditions. In the present paper an analysis of the boundary dislocation structure and of the slip systems has been conducted for pure aluminium cold-rolled to a von Mises strain of 0.41. The results show that a substantial majority of dislocations in different types of dislocation boundaries are from the primary and conjugate slip system in the adjoining crystallites. A basis is therefore provided for integrating deformation structure observations with plastic deformation behavior.

  17. Extravehicular Activity (EVA) 101: Constellation EVA Systems

    NASA Technical Reports Server (NTRS)

    Jordan, Nicole C.

    2007-01-01

    A viewgraph presentation on Extravehicular Activity (EVA) Systems is shown. The topics include: 1) Why do we need space suits? 2) Protection From the Environment; 3) Primary Life Support System (PLSS); 4) Thermal Control; 5) Communications; 6) Helmet and Extravehicular Visor Assy; 7) Hard Upper Torso (HUT) and Arm Assy; 8) Display and Controls Module (DCM); 9) Gloves; 10) Lower Torso Assembly (LTA); 11) What Size Do You Need?; 12) Boot and Sizing Insert; 13) Boot Heel Clip and Foot Restraint; 14) Advanced and Crew Escape Suit; 15) Nominal & Off-Nominal Landing; 16) Gemini Program (mid-1960s); 17) Apollo EVA on Service Module; 18) A Bold Vision for Space Exploration, Authorized by Congress; 19) EVA System Missions; 20) Configurations; 21) Reduced Gravity Program; and 22) Other Opportunities.

  18. The synchronous active neutron detection assay system

    SciTech Connect

    Pickrell, M.M.; Kendall, P.K.

    1994-08-01

    We have begun to develop a novel technique for active neutron assay of fissile material in spent nuclear fuel. This approach will exploit a 14-MeV neutron generator developed by Schlumberger. The technique, termed synchronous active neutron detection (SAND), follows a method used routinely in other branches of physics to detect very small signals in presence of large backgrounds. Synchronous detection instruments are widely available commercially and are termed ``lock-in`` amplifiers. We have implemented a digital lock-in amplifier in conjunction with the Schlumberger neutron generator to explore the possibility of synchronous detection with active neutrons. The Schlumberger system can operate at up to a 50% duty factor, in effect, a square wave of neutron yield. Results are preliminary but promising. The system is capable of resolving the fissile material contained in a small fraction of the fuel rods in a cold fuel assembly; it also appears resilient to background neutron interference. The interrogating neutrons appear to be non-thermal and penetrating. Work remains to fully explore relevant physics and optimize instrument design.

  19. Active Thermal Control System Development for Exploration

    NASA Technical Reports Server (NTRS)

    Westheimer, David

    2007-01-01

    All space vehicles or habitats require thermal management to maintain a safe and operational environment for both crew and hardware. Active Thermal Control Systems (ATCS) perform the functions of acquiring heat from both crew and hardware within a vehicle, transporting that heat throughout the vehicle, and finally rejecting that energy into space. Almost all of the energy used in a space vehicle eventually turns into heat, which must be rejected in order to maintain an energy balance and temperature control of the vehicle. For crewed vehicles, Active Thermal Control Systems are pumped fluid loops that are made up of components designed to perform these functions. NASA has been actively developing technologies that will enable future missions or will provide significant improvements over the state of the art technologies. These technologies have are targeted for application on the Crew Exploration Vehicle (CEV), or Orion, and a Lunar Surface Access Module (LSAM). The technologies that have been selected and are currently under development include: fluids that enable single loop ATCS architectures, a gravity insensitive vapor compression cycle heat pump, a sublimator with reduced sensitivity to feedwater contamination, an evaporative heat sink that can operate in multiple ambient pressure environments, a compact spray evaporator, and lightweight radiators that take advantage of carbon composites and advanced optical coatings.

  20. Differential decay of the East-African Antarctic Orogen : an integrated examination of Northeastern Mozambique

    NASA Astrophysics Data System (ADS)

    Ueda, K.; Jacobs, J.; Emmel, B.; Thomas, R. J.; Matola, R.

    2009-04-01

    In Northeastern Mozambique, the late Proterozoic - early Paleozoic East African-Antarctic Orogen can be subdivided into two major blocks that exhibit some relevant differences. The line of divide is represented by the Lurio Belt, a kinematically poorly constrained shear zone that also marks the conceptual northern limit of frequent late-tectonic granitoid intrusions. Moreover, far-travelled granulite-facies nappes cover a much larger area north of this belt (Viola et. al, 2008), giving rise to the assumption of different exhumation and present exposure levels. U/Pb data from previous surveys (e.g., Norconsult consortium, 2007) show coeval high-grade metamorphism in the whole region between c. 610 - 550 Ma, while the block south of the Lurio Belt also shows continuing metamorphism until c. 490 Ma that can be related to extension. Geothermobarometry for samples from within the Lurio Belt (Engvik et. al, 2007) indicates rapid exhumation after high-pressure granulite facies metamorphism and is consistant with the assumption of long tectonic activity. A possible model for the outlined pattern is the delamination of the orogenic root only in the southern part, followed by rapid mechanical thinning as well as by isostatic accommodation along the Lurio Belt. A valuable marker was identified in the metasedimentary Mecuburi group that overlies the southern basement. U/Pb analysis of detrital zircons have yielded a maximum deposition age of c. 600 Ma, while metamorphism is recorded until c. 505 Ma. Investigations of the relationship between metasediments and older basement show that the basal contact is a fairly preserved depositional contact, allowing to suppose a conjoint post-depositional evolution. It is notable that the timing of deposition shortly follows the onset of the main, widespread high-grade metamorphism. Relatively high but variable degrees of migmatisation in the Mecuburi Group require a phase of burial from surface to deep levels after 600 Ma, followed by

  1. Advanced Active Thermal Control Systems Architecture Study

    NASA Technical Reports Server (NTRS)

    Hanford, Anthony J.; Ewert, Michael K.

    1996-01-01

    The Johnson Space Center (JSC) initiated a dynamic study to determine possible improvements available through advanced technologies (not used on previous or current human vehicles), identify promising development initiatives for advanced active thermal control systems (ATCS's), and help prioritize funding and personnel distribution among many research projects by providing a common basis to compare several diverse technologies. Some technologies included were two-phase thermal control systems, light-weight radiators, phase-change thermal storage, rotary fluid coupler, and heat pumps. JSC designed the study to estimate potential benefits from these various proposed and under-development thermal control technologies for five possible human missions early in the next century. The study compared all the technologies to a baseline mission using mass as a basis. Each baseline mission assumed an internal thermal control system; an external thermal control system; and aluminum, flow-through radiators. Solar vapor compression heat pumps and light-weight radiators showed the greatest promise as general advanced thermal technologies which can be applied across a range of missions. This initial study identified several other promising ATCS technologies which offer mass savings and other savings compared to traditional thermal control systems. Because the study format compares various architectures with a commonly defined baseline, it is versatile and expandable, and is expected to be updated as needed.

  2. Noninvasive ambulatory measurement system of cardiac activity.

    PubMed

    Pino, Esteban J; Chavez, Javier A P; Aqueveque, Pablo

    2015-08-01

    This work implements a noninvasive system that measures the movements caused by cardiac activity. It uses unobtrusive Electro-Mechanical Films (EMFi) on the seat and on the backrest of a regular chair. The system detects ballistocardiogram (BCG) and respiration movements. Real data was obtained from 54 volunteers. 19 of them were measured in the laboratory and 35 in a hospital waiting room. Using a BIOPAC acquisition system, the ECG was measured simultaneously to the BCG for comparison. Wavelet Transform (WT) is a better option than Empirical Mode Decomposition (EMD) for signal extraction and produces higher effective measurement time. In the laboratory, the best results are obtained on the seat. The correlation index was 0.9800 and the Bland-Altman limits of agreement were 0.7136 ± 4.3673 [BPM]. In the hospital waiting room, the best results are also from the seat sensor. The correlation index was 0.9840, and the limits of agreement were 0.4386 ± 3.5884 [BPM]. The system is able to measure BCG in an unobtrusive way and determine the cardiac frequency with high precision. It is simple to use, which means the system can easily be used in non-standard settings: resting in a chair or couch, at the gym, schools or in a hospital waiting room, as shown. PMID:26738057

  3. Velocity distribution in active particles systems

    PubMed Central

    Marconi, Umberto Marini Bettolo; Gnan, Nicoletta; Paoluzzi, Matteo; Maggi, Claudio; Di Leonardo, Roberto

    2016-01-01

    We derive an analytic expression for the distribution of velocities of multiple interacting active particles which we test by numerical simulations. In clear contrast with equilibrium we find that the velocities are coupled to positions. Our model shows that, even for two particles only, the individual velocities display a variance depending on the interparticle separation and the emergence of correlations between the velocities of the particles. When considering systems composed of many particles we find an analytic expression connecting the overall velocity variance to density, at the mean-field level, and to the pair distribution function valid in the limit of small noise correlation times. Finally we discuss the intriguing analogies and main differences between our effective free energy functional and the theoretical scenario proposed so far for phase-separating active particles. PMID:27001289

  4. Velocity distribution in active particles systems

    NASA Astrophysics Data System (ADS)

    Marconi, Umberto Marini Bettolo; Gnan, Nicoletta; Paoluzzi, Matteo; Maggi, Claudio; di Leonardo, Roberto

    2016-03-01

    We derive an analytic expression for the distribution of velocities of multiple interacting active particles which we test by numerical simulations. In clear contrast with equilibrium we find that the velocities are coupled to positions. Our model shows that, even for two particles only, the individual velocities display a variance depending on the interparticle separation and the emergence of correlations between the velocities of the particles. When considering systems composed of many particles we find an analytic expression connecting the overall velocity variance to density, at the mean-field level, and to the pair distribution function valid in the limit of small noise correlation times. Finally we discuss the intriguing analogies and main differences between our effective free energy functional and the theoretical scenario proposed so far for phase-separating active particles.

  5. A Group Recommender System for Tourist Activities

    NASA Astrophysics Data System (ADS)

    Garcia, Inma; Sebastia, Laura; Onaindia, Eva; Guzman, Cesar

    This paper introduces a method for giving recommendations of tourist activities to a group of users. This method makes recommendations based on the group tastes, their demographic classification and the places visited by the users in former trips. The group recommendation is computed from individual personal recommendations through the use of techniques such as aggregation, intersection or incremental intersection. This method is implemented as an extension of the e-Tourism tool, which is a user-adapted tourism and leisure application, whose main component is the Generalist Recommender System Kernel (GRSK), a domain-independent taxonomy-driven search engine that manages the group recommendation.

  6. Influenza virus activation of the interferon system

    PubMed Central

    Killip, Marian J.; Fodor, Ervin; Randall, Richard E.

    2015-01-01

    The host interferon (IFN) response represents one of the first barriers that influenza viruses must surmount in order to establish an infection. Many advances have been made in recent years in understanding the interactions between influenza viruses and the interferon system. In this review, we summarise recent work regarding activation of the type I IFN response by influenza viruses, including attempts to identify the viral RNA responsible for IFN induction, the stage of the virus life cycle at which it is generated and the role of defective viruses in this process. PMID:25678267

  7. System and method for monitoring cellular activity

    NASA Technical Reports Server (NTRS)

    Bearman, Gregory H. (Inventor); Fraser, Scott E. (Inventor); Lansford, Russell D. (Inventor)

    2002-01-01

    A system and method for monitoring cellular activity in a cellular specimen. According to one embodiment, a plurality of excitable markers are applied to the specimen. A multi-photon laser microscope is provided to excite a region of the specimen and cause fluorescence to be radiated from the region. The radiating fluorescence is processed by a spectral analyzer to separate the fluorescence into respective wavelength bands. The respective bands of fluorescence are then collected by an array of detectors, with each detector receiving a corresponding one of the wavelength bands.

  8. LDEF active optical system components experiment

    NASA Technical Reports Server (NTRS)

    Blue, M. D.

    1991-01-01

    A preliminary report on the Active Optical System Components Experiment is presented. This experiment contained 136 components in a six-inch deep tray including lasers, infrared detectors and arrays, ultraviolet light detectors, light-emitting diodes, a light modulator, flash lamps, optical filters, glasses, and samples of surface finishes. The experimental results for those component characteristics appear as much related to the passage of time as to the effects of the space environment, but organic materials and extreme-infrared reflectivity of black paints show unexpected changes.

  9. LDEF active optical system components experiment

    NASA Technical Reports Server (NTRS)

    Blue, M. D.

    1992-01-01

    A preliminary report on the Active Optical System Components Experiment is presented. This experiment contained 136 components in a six inch deep tray including lasers, infrared detectors and arrays, ultraviolet light detectors, light-emitting diodes, a light modulator, flash lamps, optical filters, glasses, and samples of surface finishes. Thermal, mechanical, and structural considerations leading to the design of the tray hardware are discussed. In general, changes in the retested component characteristics appear as much related to the passage of time as to the effects of the space environment, but organic materials, multilayer optical interference filters, and extreme-infrared reflectivity of black paints show unexpected changes.

  10. System and method for monitoring cellular activity

    NASA Technical Reports Server (NTRS)

    Bearman, Gregory H. (Inventor); Fraser, Scott E. (Inventor); Lansford, Russell D. (Inventor)

    2004-01-01

    A system and method for monitoring cellular activity in a cellular specimen. According to one embodiment, a plurality of excitable markers are applied to the specimen. A multi-photon laser microscope is provided to excite a region of the specimen and cause fluorescence to be radiated from the region. The radiating fluorescence is processed by a spectral analyzer to separate the fluorescence into respective wavelength bands. The respective bands of fluorescence are then collected by an array of detectors, with each detector receiving a corresponding one of the wavelength bands.

  11. Analog VLSI system for active drag reduction

    SciTech Connect

    Gupta, B.; Goodman, R.; Jiang, F.; Tai, Y.C.; Tung, S.; Ho, C.M.

    1996-10-01

    In today`s cost-conscious air transportation industry, fuel costs are a substantial economic concern. Drag reduction is an important way to reduce costs. Even a 5% reduction in drag translates into estimated savings of millions of dollars in fuel costs. Drawing inspiration from the structure of shark skin, the authors are building a system to reduce drag along a surface. Our analog VLSI system interfaces with microfabricated, constant-temperature shear stress sensors. It detects regions of high shear stress and outputs a control signal to activate a microactuator. We are in the process of verifying the actual drag reduction by controlling microactuators in wind tunnel experiments. We are encouraged that an approach similar to one that biology employs provides a very useful contribution to the problem of drag reduction. 9 refs., 21 figs.

  12. Spontaneous Oscillations in an Active Matter System

    NASA Astrophysics Data System (ADS)

    Hayes, Robert; Tsang, Boyce; Granick, Steve

    Active matter (which consumes energy to move about) can organize into dynamic structures more interesting than those possible at steady-state. Here we show spontaneous periodic self-assembly in a simple three-component system of water, oil phase, and surfactant at constant room temperature, with emphasis on one model system. Benchtop experiments show that liquid crystal oil droplets spontaneously and collectively oscillate like a `beating heart' for several hours; contract, relax, and subsequently re-contract in a petri dish at a rate of a few `beats' per minute. These oscillations, emergent from the cooperative interaction of the three components, are driven by the competition between positive and negative feedback processes. This illustration of feedback in action reveals a new way to program self-assembled structures to vary with time.

  13. Actively controlled vibration welding system and method

    SciTech Connect

    Cai, Wayne W.; Kang, Bongsu; Tan, Chin-An

    2013-04-02

    A vibration welding system includes a controller, welding horn, an active material element, and anvil assembly. The assembly may include an anvil body connected to a back plate and support member. The element, e.g., a piezoelectric stack or shape memory alloy, is positioned with respect to the assembly. The horn vibrates in a desirable first direction to form a weld on a work piece. The element controls any vibrations in a second direction by applying calibrated response to the anvil body in the second direction. A method for controlling undesirable vibrations in the system includes positioning the element with respect to the anvil assembly, connecting the anvil body to the support member through the back plate, vibrating the horn in a desirable first direction, and transmitting an input signal to the element to control vibration in an undesirable second direction.

  14. Active alignment/contact verification system

    DOEpatents

    Greenbaum, William M.

    2000-01-01

    A system involving an active (i.e. electrical) technique for the verification of: 1) close tolerance mechanical alignment between two component, and 2) electrical contact between mating through an elastomeric interface. For example, the two components may be an alumina carrier and a printed circuit board, two mating parts that are extremely small, high density parts and require alignment within a fraction of a mil, as well as a specified interface point of engagement between the parts. The system comprises pairs of conductive structures defined in the surfaces layers of the alumina carrier and the printed circuit board, for example. The first pair of conductive structures relate to item (1) above and permit alignment verification between mating parts. The second pair of conductive structures relate to item (2) above and permit verification of electrical contact between mating parts.

  15. Active balance system and vibration balanced machine

    NASA Technical Reports Server (NTRS)

    Qiu, Songgang (Inventor); Augenblick, John E. (Inventor); Peterson, Allen A. (Inventor); White, Maurice A. (Inventor)

    2005-01-01

    An active balance system is provided for counterbalancing vibrations of an axially reciprocating machine. The balance system includes a support member, a flexure assembly, a counterbalance mass, and a linear motor or an actuator. The support member is configured for attachment to the machine. The flexure assembly includes at least one flat spring having connections along a central portion and an outer peripheral portion. One of the central portion and the outer peripheral portion is fixedly mounted to the support member. The counterbalance mass is fixedly carried by the flexure assembly along another of the central portion and the outer peripheral portion. The linear motor has one of a stator and a mover fixedly mounted to the support member and another of the stator and the mover fixedly mounted to the counterbalance mass. The linear motor is operative to axially reciprocate the counterbalance mass.

  16. Progression from South-Directed to Orogen-Parallel Mid-Crustal Flow on the Southern Margin of the Tibetan Plateau, Ama Drime Massif, Tibet

    NASA Astrophysics Data System (ADS)

    Jessup, M. J.; Cottle, J. M.; Newell, D. L.; Berger, A. L.; Spotila, J. A.

    2008-12-01

    In the South Tibetan Himalaya, two major detachment systems are exposed in the Ama Drime and Mount Everest Massifs. These structures represent a fundamental shift in the dynamics of the Himalayan orogen, recording a progression from south-directed to orogen-parallel mid-crustal flow and exhumation. The South Tibetan detachment system (STDS) accommodated exhumation of the Greater Himalayan series (GHS) until the Middle Miocene. A relatively narrow mylonite zone that progressed into a brittle detachment accommodated exhumation of the GHS. Northward, in the down-dip direction (Dzakaa Chu and Doya La), a 1-km-wide distributed zone of deformation that lacks a foliation-parallel brittle detachment characterizes the STDS. Leucogranites in the footwall of the STDS range between 17-18 Ma. Previously published 40Ar/39Ar ages suggest that movement on the STDS ended by ~ 16 Ma in Rongbuk Valley and ~ 13 Ma near Dinggye. This once continuous section of the STDS is displaced by the trans- Himalayan Ama Drime Massif and Xainza-Dinggye graben. Two oppositely dipping normal faults and shear zones that bound the Ama Drime Massif record orogen-parallel extension. During exhumation, deformation was partitioned into relatively narrow (100-300-m-thick) mylonite zones that progressed into brittle faults/detachments, which offset Quaternary deposits. U(-Th-)Pb geochronology of mafic lenses suggests that the core of the ADM reached granulite facies at ~ 15 Ma. Leucogranites in the footwall of the detachment faults range between 12-11 Ma: significantly younger than those related to movement on the STDS. Previously published 40Ar/39Ar ages from the eastern limb of the Ama Drime Massif suggest that exhumation progressed into the footwall of the Nyüonno detachment between ~ 13-10 Ma. (U-Th)/He apatite ages record a minimum exhumation rate of ~ 1mm/yr between 1.5-3.0 Ma that was enhanced by focused denudation in the trans-Himalayan Arun River gorge. Together these bracket the timing (~ 12 Ma

  17. Testing models of orogen exhumation using zircon (U-Th)/He thermochronology: Insight from the Ligurian Alps, Northern Italy

    NASA Astrophysics Data System (ADS)

    Maino, Matteo; Dallagiovanna, Giorgio; Dobson, Katherine J.; Gaggero, Laura; Persano, Cristina; Seno, Silvio; Stuart, Finlay M.

    2012-08-01

    Testing models of orogen exhumation requires precise constraint of the time-temperature paths of the exhumed rocks. The zircon (U-Th)/He (ZHe) thermochronometer has a closure temperature of ~ 140-210 °C, and can provide temporal constraints on the exhumation history of rocks through a thermal range which crucially corresponds the onset of brittle behaviour of an exhuming orogen. We performed ZHe analyses to test the existing contradictory models for the exhumation of the Ligurian Alps. The ZHe ages indicate a very rapid (1.3-6.8 mm/yr) and southward migrating exhumation of the orogen between ~ 32 and 25 Ma. These high exhumation rates are unique within the Alpine belt and cannot be reconciled with existing geodynamic models of the evolution of the Ligurian Alps. We propose a model of tectonic denudation via detachment accomplished in the shallowest crust (< 5 km) as a result of the last orogenic phase of extension.

  18. Next Generation Active Buffet Suppression System

    NASA Technical Reports Server (NTRS)

    Galea, Stephen C.; Ryall, Thomas G.; Henderson, Douglas A.; Moses, Robert W.; White, Edward V.; Zimcik, David G.

    2003-01-01

    Buffeting is an aeroelastic phenomenon that is common to high performance aircraft, especially those with twin vertical tails like the F/A-18, at high angles of attack. These loads result in significant random stresses, which may cause fatigue damage leading to restricted capabilities and availability of the aircraft. This paper describes an international collaborative research activity among Australia, Canada and the United States involving the use of active structural control to alleviate the damaging structural response to these loads. The research program is being co-ordinated by the Air Force Research Laboratory (AFRL) and is being conducted under the auspices of The Technical Cooperative Program (TTCP). This truly unique collaborative program has been developed to enable each participating country to contribute resources toward a program that coalesces a broad range of technical knowledge and expertise into a single investigation. This collaborative program is directed toward a full-scale test of an F/A-18 empennage, which is an extension of an earlier initial test. The current program aims at applying advanced directional piezoactuators, the aircraft rudder, switch mode amplifiers and advanced control strategies on a full-scale structure to demonstrate the enhanced performance and capability of the advanced active BLA control system in preparation for a flight test demonstration.

  19. The synchronous active neutron detection assay system

    SciTech Connect

    Pickrell, M.M.; Kendall, P.K.

    1994-09-01

    The authors have begun to develop a novel technique for active neutron assay of fissile material in spent nuclear fuel. They are using a Schlumberger neutron generator for the direct measurement of the fissile material content in spent fuel, in place of the indirect measures used at present. The technique they are investigating is termed synchronous active neutron detection (SAND). It closely follows a method that has been used routinely in other branches of physics for the detection of very small signals in the presence of large backgrounds. Synchronous detection instruments are widely available commercially and are termed ``lock-in`` amplifiers. They have implemented a digital lock-in amplifier in conjunction with the Schlumberger neutron generator to explore the possibility of synchronous detection with active neutrons. The results to data are preliminary but quite promising. The system is capable of resolving the fissile material contained in a small fraction of the fuel rods in a cold fuel assembly. It also appears to be quite resilient to background neutron interference.

  20. Axial Belt Provenance: modern river sands from the core of collision orogens

    NASA Astrophysics Data System (ADS)

    Resentini, A.; Vezzoli, G.; Paparella, P.; Padoan, M.; Andò, S.; Malusà, M.; Garzanti, E.

    2009-04-01

    Collision orogens have a complex structure, including diverse rock units assembled in various ways by geodynamic processes. Consequently, orogenic detritus embraces a varied range of signatures, and unravelling provenance of clastic wedges accumulated in adjacent foreland basins, foredeeps, or remnant-ocean basins is an arduous task. Dickinson and Suczek (1979) and Dickinson (1985) recognized the intrinsically composite nature of orogenic detritus, but did not attempt to establish clear conceptual and operational distinctions within their broad "Recycled Orogenic Provenance". In the Alpine and Himalayan belts, the bulk of the detritus is produced by focused erosion of the central backbone of the orogen, characterized by high topography and exhumation rates (Garzanti et al., 2004; Najman, 2006). Detritus derived from such axial nappe pile, including slivers of thinned continental-margin lithosphere metamorphosed at depth during early collisional stages, has diagnostic general features, which allows us to define an "Axial Belt Provenance" (Garzanti et al., 2007). In detail, "Axial Belt" detrital signatures are influenced by metamorphic grade of source rocks and relative abundance of continental versus oceanic protoliths, typifying distinct subprovenances. Metasedimentary cover nappes shed lithic to quartzolithic detritus, including metapelite, metapsammite, and metacarbonate grains of various ranks; only amphibolite-facies metasediments supply abundant heavy minerals (e.g., almandine garnet, staurolite, kyanite, sillimanite, diopsidic clinopyroxene). Continental-basement nappes shed hornblende-rich quartzofeldspathic detritus. Largely retrogressed blueschist to eclogite-facies metaophiolites supply albite, metabasite and foliated antigorite-serpentinite grains, along with abundant heavy minerals (epidote, zoisite, clinozoisite, lawsonite, actinolitic to barroisitic amphiboles, glaucophane, omphacitic clinopyroxene). Increasing metamorphic grade and deeper

  1. Systemic lupus erythematosus activity. An operational definition.

    PubMed

    Liang, M H; Stern, S; Esdaile, J M

    1988-04-01

    Improved diagnosis and treatment have reduced mortality from SLE and present us with an opportunity to consider SLE in finer distinctions than alive or dead. Although much has been learned about SLE without a gold standard of disease activity or a universally agreed-upon definition of SLE activity, standardization of one or more measures would greatly enhance our ability to compare results from different centers and to communicate more precisely. It is unlikely that any of the existing measures or any ones to be developed will completely satisfy everyone's needs but it is pointless to proliferate new ones without testing their metric properties. Some differences in concept are desirable, particularly for investigators who have specialized interests or insights, but each should meet criteria of reliability and validity and have explicit definitions of terms, rules for their ascertainment, and the time period covered. Moreover, agreement on minimum essential elements of any SLE activity measure and their operational definitions would be a boon. SLE activity is one dimension in the disease pathway of lupus and implies a continuous phenomena that is potentially reversible. Organ damage, another point in the path of causation, connotes irreversible disease. We recommend that minimum essential elements be based on their frequency of occurrence, biological sensibleness, and the likelihood that degrees of activity can be rated reliably to show a change in a clinical state. The rating should be independent of whether a therapy is employed. Since activity is always considered with severity, the two dimensions could be recognized in the scale. Severity can be used to expand a scale's gradations if a symptom or sign is present. Severity could be rated by the need to treat with immunosuppressive agents, the need to follow the patient more closely, or the functional or prognostic consequences of the manifestation. For every organ system clinical judgment should be used to decide

  2. Nappe-Bounding Shear Zones Initiated On Syn-Tectonic, Pegmatite-Filled Extensional Shear Fractures During Deep-Crustal Nappe Flow In A Large Hot Orogen

    NASA Astrophysics Data System (ADS)

    Culshaw, Nicholas; Gerbi, Christopher; Marsh, Jeffrey; Regan, Peter

    2014-05-01

    The Central Gneiss Belt (CGB) of the Proterozoic western Grenville Province is an extensive exposure of the mid-crustal levels (upper amphibolite facies, lesser granulites) of a large hot orogen. Numerical models give a credible prediction of structure and metamorphism accompanying CGB deep-crustal nappe flow and define a temporal framework based on four developmental phases: thickening, heating, nappe-flow and post convergence extensional spreading. These phases are diachronous in direction of orogen propagation and imply a spatial framework: externides (close to orogen-craton boundary) containing moderately inclined thickening and/or extensional structures, and internides containing thickening structures overprinted by sub-horizontal nappe flow structures, which may be locally overprinted by those due to extensional spreading. Although on average of granitoid composition, CGB nappes differ in rheology, varying from fertile and weak (unmetamorphosed before Grenville, meltable) to infertile and strong (metamorphosed at high grade before Grenville, unmeltable) or mixed fertile-infertile protoliths. Deformation style varies from diffuse in fertile nappes, weakened by pervasive melting, to localised in shear zones on boundaries or interiors of infertile nappes. Specifically, in terms of deformation phase and location within the orogen, shear zones occur as: thickening structures of externides, early thickening- and later overprinting nappe-flow structures of infertile internide nappes, and extension-related shear zones in externides and internides. Many of the nappe-flow shear zones of the internides are associated with pegmatites. One example has been recognized of a preserved progression from small-scale fracture arrays to regional shear zone. The sequence is present on a km-scale and initiates in the interior of a nappe of layered granulite with arrays of pegmatite filled extensional-shear fractures (mm to cm width) displaying amphibolized margins. The fracture

  3. Key role of Upper Mantle rocks in Alpine type orogens: some speculations derived from extensional settings for subduction zone processes and mountain roots

    NASA Astrophysics Data System (ADS)

    Müntener, Othmar

    2016-04-01

    Orogenic architecture and mountain roots are intrinsically related. Understanding mountain roots largely depends on geophysical methods and exhumed high pressure and high temperature rocks that might record snapshots of the temporal evolution at elevated pressure, temperatures and/or fluid pulses. If such high pressure rocks represent ophiolitic material they are commonly interpreted as exhumed remnants of some sort of 'mid-ocean ridge' processes. Mantle peridotites and their serpentinized counterparts thus play a key role in understanding orogenic architecture as they are often considered to track suture zones or ancient plate boundaries. The recognition that some mantle peridotites and their serpentinized counterparts are derived from ocean-continent transition zones (OCT's) or non-steady state (ultra-)slow plate separation systems question a series of 'common beliefs' that have been applied to understand Alpine-type collisional orogens in the framework of the ophiolite concept. Among these are: (i) the commonly held assumption of a simple genetic link between mantle melting and mafic (MORB-type) magmatism, (ii) the commonly held assumption that mélange zones represent deep subduction zone processes at the plate interface, (iii) that pre-collisional continental crust and oceanic crust can easily be reconstructed to their original thickness and used for reconstructions of the size of small subducted oceanic basins as geophysical data from rifted margins increasingly indicate that continental crust is thinned to much less than the average 30-35 kilometers over a large area that might be called the 'zone of hyperextension', and (iv) the lack of a continuous sheet of mafic oceanic crust and the extremely short time interval of formation results in a lack of 'eclogitization potential' during convergence and hence a lack of potential for subsequent slab pull and, perhaps, a lack of potential for 'slab-breakoff'. Here we provide a synopsis of mantle rocks from the

  4. A new melanoma diagnosis active support system.

    PubMed

    Fiorini, R A; Dacquino, G; Laguteta, G

    2004-01-01

    The aim of this paper is to present the operational performance of a new MDASS (Melanoma Diagnosis Active Support System) prototype able to distil optimal knowledge from acquired data to automatically capture and reliably discriminate and quantify the stage of disease evolution. Automated classification dermatoscopical parameters can be divided into two main classes: Size Descriptor (point size, local, and global) and Intrinsic Descriptor (morphological, geometrical, chromatic, others). Usually elementary geometric shape robust and effective characterization, invariant to environment and optical geometry transformations, on a rigorous mathematical level is a key and computational intensive problem. MDASS uses GEOGINE (GEOmetrical enGINE), a state-of-the-art OMG (Ontological Model Generator) based on n-D Tensor Moment Invariants for shape/texture effective description. MDASS main results show robust disease classification procedure with distillation of minimal reference grids for pathological cases and they ultimately achieve effective early diagnosis of melanocytic lesion. System results are validated by carefully designed experiments with certified clinical reference database. Overall system operational performance is presented. Finally, MDASS error analysis and computational complexity are addressed and discussed. PMID:17270962

  5. Early proterozoic evolution of the saskatchewan craton and its allochthonous coyer, trans-hudson Orogen

    USGS Publications Warehouse

    Chiarenzelli, J.; Aspler, L.; Villeneuve, M.; Lewry, J.

    1998-01-01

    The composition, chronology, and structural relations of the Saskatchewan Craton and enveloping mylonitic rocks exposed in basement windows of the Glennie Domain, Trans-Hudson Orogen, have been determined by geochemical, geochronologic, and structural studies accompanying detailed field mapping. Basement windows lie along the hinge zone of a regional crustal culmination and consist mostly of 2.4-2.5 Ga felsic plutonic rocks enveloped by the Nistowiak Thrust. The Nistowiak Thrust is a folded, 1-2 km thick, upper amphibolite facie??s mylonite zone formed during emplacement of the Flin Flon-Glennie Complex across the Saskatchewan Craton. It is likely correlative to the Pelican Thrust, which envelops basement windows in the Hanson Lake Block -100 km to the east. An internal high strain zone within the overlying nappe pile, the Guncoat Thrust, is composed primarily of mylonitized porphyroclastic pelitic and psammitic migmatites. U-Pb geochronological results suggest calc-alkaline plutonism from 1889-1837 Ma, thrust stacking, peak metamorphism and associated anatexis between 1837 and 1809 Ma, isotopic closure of titanite at 1790-1772 Ma, and intrusion of late granitic rocks at 1770-1762 Ma. This is in agreement with ages from the Hanson Lake Block, and La Ronge, Kisseynew, and Flin-Flon domains in Saskatchewan and Manitoba, and from the Ungava-Baffin portion of Trans-Hudson Orogen, suggesting broadly synchronous thermotectonic processes along a strike length of 2000 km. We speculate that the Saskatchewan Craton, rather than representing an exotic continental fragment, rifted from the Superior and/or Hearne Provinces at ca. 2.1 Ga and that the Trans-Hudson Orogen is an internal orogen. In this scenario the Maniwekan Ocean, developed between the Rae-Hearne and Superior cratons, opened and closed about similar pole(s) of plate motion. ?? 1998 by The University of Chicago. All rights reserved.

  6. The structure, stratigraphy, tectonostratigraphy, and evolution of the southernmost part of the Appalachian Orogen

    SciTech Connect

    Higgins, M.W.; Atkins, R.L.; Crawford, T.J.; Crawford, R.F. III; Brooks, R.; Cook, R.B.

    1988-01-01

    The southernmost part of the Appalachian Orogen is composed of three stacks of folded thrust sheets, which preserve rocks formed in a variety of environments that virtually spanned the Iapetus Ocean. All of the metamorphism, deformation, and plutonism in the southernmost Appalachians can be related to the movement of the thrust sheets and stacks. Thrusting took place continuously from Early Ordovician through Carboniferous time. An account is given of the origins, assembly, transport, and arrival of the thrust sheets and stacks.

  7. Central Appalachian Exotic Terranes and Exposures of Former Orogenic Middle Crust

    NASA Astrophysics Data System (ADS)

    Martin, A. J.

    2015-12-01

    In the northern and southern Appalachians, rocks that formed Paleozoic orogenic middle crust mostly are exposed within or directly inboard of terranes that originated near Gondwana. Most outcrops of the Paleozoic orogenic middle crust of the eastern edge of Laurentia occur adjacent to these exotic terranes. However, a narrow belt of Paleozoic orogenic middle crust is exposed in the Piedmont of the central Appalachians despite the absence of recognized exotic terranes. The presence of these deformed, amphibolite facies rocks raises the questions: "Did central Appalachian orogeny occur in the absence of accreted exotic terranes?" and, more generally, "Is exotic terrane collision required for exhumation of Appalachian former middle crust?" Previous U/Pb isotopic dating of spots in detrital zircon revealed the presence of Gondwanan terranes in three locations in the central Appalachians: central Virginia, central Maryland, and southeastern Pennsylvania. Two new samples collected near the discovery locations in Virginia and Maryland yielded prominent peaks in zircon U/Pb age distributions at ca. 630-610 Ma, confirming the Gondwanan affinity of these rocks. Hf isotopic compositions of spots in these upper Neoproterozoic zircon grains range to both more and less depleted than spots in zircon from the few possible Laurentian granitic sources, consistent with derivation of the zircon from Gondwana. Abundant 1700-1000 Ma detrital zircon rules out the West Africa Craton as a potential source; Amazonia is the most likely ultimate source of the zircon. The extent of the exotic terrane(s) in the central Appalachian Piedmont remains enigmatic due to uncertain connections between isolated exposures of the terrane(s). Nevertheless, the discovery of one or more exotic terranes in the central Appalachian Piedmont underscores the relationship between exotic terranes and exposed former middle crust in the Appalachians. This relationship may be a feature of several other major

  8. Formation of Secondary Lherzolite and Refertilization of the Subcontinental Lithospheric Mantle: The Record of Orogenic Peridotites

    NASA Astrophysics Data System (ADS)

    Garrido, Carlos J.; Varas-Reus, María Isabel; Bodinier, Jean-Louis; Marchesi, Claudio; Bosch, Delphine; Hidas, Károly

    2016-04-01

    Correlations observed between major and minor transition elements in tectonically-emplaced orogenic peridotites have classically been ascribed to variable degrees of melt extraction. There is a growing body of evidence indicating that these chemical variations mostly reflect melt redistribution and near solidus reactions superimposed onto previous melting depletion events. Here we will assess this hypothesis using a large database of peridotites from orogenic peridotites in the westernmost Mediterranean (Ronda and Beni Bousera peridotites). We show that lherzolite samples show some trends in major elements and modal variations that are inconsistent with their interpretation as depleted MORB mantle (DMM). These trends are more consistent with the secondary formation of lherzolites by refertilization processes involving a least two different near-solidus, melt-processes: refertilization by pyroxenite-derived melts and by hydrous melts leading, respectively, to secondary lherzolites with Ol/Opx and Cpx/Opx ratios greater than those expected from residues from a primitive upper mantle source. Together with their N-MORB, LREE-depleted pattern, their fertile lherzolitic composition may have been acquired as a result of melt-rock interaction processes associated with the thermomechanical erosion of lithospheric mantle by asthenosphere. Major refertilization of depleted subcontinental mantle is an alternative to the small degrees of melt extraction to account for LREE depletion in otherwise fertile orogenic lherzolites.

  9. Extreme variation of sulfur isotopic compositions in pyrite from the Qiuling sediment-hosted gold deposit, West Qinling orogen, central China: an in situ SIMS study with implications for the source of sulfur

    NASA Astrophysics Data System (ADS)

    Chen, Lei; Li, Xian-hua; Li, Jian-wei; Hofstra, Albert H.; Liu, Yu; Koenig, Alan E.

    2015-08-01

    high δ34S values. The variations in Au content and sulfur isotopic compositions across a single ore-stage pyrite grain may reflect displacement of indigenous groundwater with low δ34S values by auriferous metamorphic fluids with high δ34S values. The very low-grade metamorphism of the host rocks and the metamorphic derivation of sulfur for the ore pyrite indicate that the Qiuling sediment-hosted gold deposit is an epizonal manifestation of an orogenic gold system in the West Qinling orogen.

  10. Foreland-forearc collisional granitoid and mafic magmatism caused by lower-plate lithospheric slab breakoff: The Acadian of Maine, and other orogens

    USGS Publications Warehouse

    Schoonmaker, A.; Kidd, W.S.F.; Bradley, D.C.

    2005-01-01

    During collisional convergence, failure in extension of the lithosphere of the lower plate due to slab pull will reduce the thickness or completely remove lower-plate lithosphere and cause decompression melting of the asthenospheric mantle; magmas from this source may subsequently provide enough heat for substantial partial melting of crustal rocks under or beyond the toe of the collisional accretionary system. In central Maine, United States, this type of magmatism is first apparent in the Early Devonian West Branch Volcanics and equivalent mafic volcanics, in the slightly younger voluminous mafic/silicic magmatic event of the Moxie Gabbro-Katahdin batholith and related ignimbrite volcanism, and in other Early Devonian granitic plutons. Similar lower-plate collisional sequences with mafic and related silicic magmatism probably caused by slab breakoff are seen in the Miocene-Holocene Papuan orogen, and the Hercynian-Alleghenian belt. Magmatism of this type is significant because it gives evidence in those examples of whole-lithosphere extension. We infer that normal fault systems in outer trench slopes of collisional orogens in general, and possibly those of oceanic subduction zones, may not be primarily due to flexural bending, but are also driven by whole-lithosphere extension due to slab pull. The Maine Acadian example suggests that slab failure and this type of magmatism may be promoted by pre-existing large margin-parallel faults in the lower plate. ?? 2005 Geological Society of America.

  11. Activity systems in the inquiry classroom

    NASA Astrophysics Data System (ADS)

    Wortham, Donald William

    Inquiry science, as called for by reform-minded organizations such as the National Research Council (1996), offers a platform with the potential for introducing all students to the practice of science while maintaining focus on key concepts and theories. This project followed two small groups as they completed an inquiry unit on genetics at a Midwestern high school. I investigated whether levels of student-to-teacher, student-to-student, student-apparatus, and student-concept connections were approximately equal across all students in each of the two groups. I found differences among students in levels of student-to-teacher, student-to-student, and student-concept connections. From a situated idiopathic perspective, these differences may indicate different levels of opportunity-to-learn. At a more abstract (nomothetic) level, these differences may be due to emergent divisions of labor (roles) within the two groups. From the perspective of Activity Theory (Leont'ev, 1978; Engestrom, 1987), roles serve as important mediators that simultaneously allow the social unit to accomplish its objectives, while shaping the development of participants. I describe three roles that capture modes of participation for students interacting in the small groups, and that may contribute to what Engestrom (2001) calls subject-producing activity systems: networked contributor, social member, and isolate. This paper also describes tools for teachers and researchers to use in identifying levels of mediation and roles as they occur in small groups.

  12. Timing of magmatism and migmatization in the 2.0-1.8 Ga accretionary Svecokarelian orogen, south-central Sweden

    NASA Astrophysics Data System (ADS)

    Johansson, Åke; Stephens, Michael B.

    2016-07-01

    The Palaeoproterozoic (2.0-1.8 Ga) Svecokarelian orogen in central Sweden consists of a low-pressure, predominantly medium-grade metamorphic domain (central part of Bergslagen lithotectonic unit), enclosed to the north and south by low-pressure migmatite belts. Two periods of metamorphism (1.87-1.85 and 1.83-1.79 Ga) are known in the migmatite belts. In this study, new U-Th-Pb ion microprobe data on zircon and monazite from twelve samples of locally migmatized gneisses and felsic intrusive bodies determine both protolith and metamorphic ages in four sample areas north of Stockholm, inside or immediately adjacent to the medium-grade metamorphic domain. Two orthogneiss samples from the Rimbo area yield unusually old protolith ages of 1909 ± 4 and 1908 ± 4 Ma, while three orthogneisses from the Skutskär and Forsmark areas yield more typical protolith ages between 1901 ± 3 and 1888 ± 3 Ma. Migmatized paragneiss samples from this and two earlier studies contain a significant detrital component sourced from this 1.9 Ga magmatic suite. They are interpreted to be deposited contemporaneously with or shortly after this magmatism. Migmatization of the paragneiss at Rimbo was followed by intrusion of leucogranite at 1846 ± 3 Ma. Even in the other sample areas to the north (Hedesunda-Tierp, Skutskär and Forsmark), metamorphism including migmatization is constrained to the 1.87-1.85 Ga interval and penetrative ductile deformation is limited by earlier studies in the Forsmark area to 1.87-1.86 Ga. However, apart from a metamorphic monazite age of 1863 ± 1 Ma, precise ages were not possible to obtain due to the presence of only partially reset recrystallized domains in zircon, or highly discordant U-rich metamict and altered metamorphic rims. Migmatization was contemporaneous with magmatic activity at 1.87-1.84 Ga in the Bergslagen lithotectonic unit involving a mantle-derived component, and there is a spatial connection between migmatization and this magmatic phase in the

  13. Linking collisional and accretionary orogens during Rodinia assembly and breakup: Implications for models of supercontinent cycles

    NASA Astrophysics Data System (ADS)

    Cawood, Peter A.; Strachan, Robin A.; Pisarevsky, Sergei A.; Gladkochub, Dmitry P.; Murphy, J. Brendan

    2016-09-01

    Periodic assembly and dispersal of continental fragments has been a characteristic of the solid Earth for much of its history. Geodynamic drivers of this cyclic activity are inferred to be either top-down processes related to near surface lithospheric stresses at plate boundaries or bottom-up processes related to mantle convection and, in particular, mantle plumes, or some combination of the two. Analysis of the geological history of Rodinian crustal blocks suggests that internal rifting and breakup of the supercontinent were linked to the initiation of subduction and development of accretionary orogens around its periphery. Thus, breakup was a top-down instigated process. The locus of convergence was initially around north-eastern and northern Laurentia in the early Neoproterozoic before extending to outboard of Amazonia and Africa, including Avalonia-Cadomia, and arcs outboard of Siberia and eastern to northern Baltica in the mid-Neoproterozoic (∼760 Ma). The duration of subduction around the periphery of Rodinia coincides with the interval of lithospheric extension within the supercontinent, including the opening of the proto-Pacific at ca. 760 Ma and the commencement of rifting in east Laurentia. Final development of passive margin successions around Laurentia, Baltica and Siberia was not completed until the late Neoproterozoic to early Paleozoic (ca. 570-530 Ma), which corresponds with the termination of convergent plate interactions that gave rise to Gondwana and the consequent relocation of subduction zones to the periphery of this supercontinent. The temporal link between external subduction and internal extension suggests that breakup was initiated by a top-down process driven by accretionary tectonics along the periphery of the supercontinent. Plume-related magmatism may be present at specific times and in specific places during breakup but is not the prime driving force. Comparison of the Rodinia record of continental assembly and dispersal with that

  14. Gold enrichment and Bi-mineral assemblages in ores: Examples from shield and orogenic areas

    NASA Astrophysics Data System (ADS)

    Ciobanu, C. L.; Cook, N. J.; Pring, A.

    2003-04-01

    Gold deposits in metamorphic terranes, like their counterparts in hydrothermal areas, commonly contain small quantities of Bi-tellurides/selenides (BTS) or Bi-sulpho-salts (Bi-ss). These mineral groups, although eclectic in character, have the potential to offer real and hitherto-untapped information on processes of ore formation and evolution, since BTS speciation, paragenesis and assemblages lie at the heart of ideas covering mechanisms of Au-enrichment, fluid-driven infiltration and sulphide modularity. A systematic study of the distribution of BTS in Au-enriched ores from 25 deposits in the Fennoscandian/Ukrainian Shields and in European Phanerozoic orogenic belts allows comparison of telluride speciation and association and construction of a qualitative diagram for Bi-telluride stability in fS_2-fO_2 space on the basis of Bi/Te+Se+S (R{Bi/Te}). Tsumoite (BiTe) stability separates reducing environ-ments where Bi-tellurides with R{Bi/Te}>1 are associated with native Bi and maldonite, and oxidizing environments where Bi-tellurides with R{Bi/Te}<1 are associated with Au-Ag-bearing tellurides and native Te. BTS are closely associated with Au, due to incorporation within Bi{melt} above 271^oC. Such melts are powerful "scavengers" for Au, especially at the main fS_2/fO_2 buffers. Overall compositions of Bi-Te-Se-Aumelts, as seen in resultant BTS associations, reflect the reducing/oxidizing character of source fluids. Telluride speciation has implications for discriminating overprinting events, with focus on local Au-enrichment at metamorphic peaks, during retrograde stages in skarn and secondary boiling in porphyry, irrespective of age or deposit type. Unlike tellurides, Bi-ss are not necessarily genetically related to Au-enrich-ment. Instead, speciation and compositional variation relate to primary fluid sources and may be specific to regional/orefield trends. Nevertheless, as many sulphosalts form polysomatic series, they can adjust chemical variation via

  15. Orogenic front propagation in the basement involved Malargüe fold and thrust belt, Neuquén Basin, (Argentina)

    NASA Astrophysics Data System (ADS)

    Branellec, Matthieu; Nivière, Bertrand; Callot, Jean-Paul; Ringenbach, Jean-Claude

    2015-04-01

    The Malargüe fold and thrust belt (MFTB) and the San Rafael Block (SRB) are located in the northern termination of the Neuquén basin in Argentina. This basin is a wide inverted intracratonic sag basin with polyphased evolution controlled at large scale by the dynamic of the Pacific subduction. By late Triassic times, narrow rift basins developed and evolved toward a sag basin from middle Jurassic to late Cretaceous. From that time on, compression at the trench resulted in various shortening pulses in the back-arc area. Here we aim to analyze the Andean system at 35°S by comparing the Miocene structuration in the MFTB and the current deformation along the oriental border or the San Rafael Block. The main structuration stage in the MFTB occurred by Miocene times (15 to 10 Ma) producing the principal uplift of the Andean Cordillera. As shown by new structural cross sections, Triassic-early Jurassic rift border faults localized the Miocene compressive tectonics. Deformation is compartmentalized and does not exhibit a classical propagation of homogeneous deformation sequence expected from the critical taper theory. Several intramontane basins in the hangingwall of the main thrusts progressively disconnected from the foreland. In addition, active tectonics has been described in the front of the MFTB attesting for the on-going compression in this area. 100 km farther to the east, The San Rafael Block, is separated from the MFTB by the Rio Grande basin. The SRB is mostly composed of Paleozoic terranes and Triassic rift-related rocks, overlain by late Miocene synorogenic deposits. The SRB is currently uplifted along its oriental border along several active faults. These faults have clear morphologic signatures in Quaternary alluvial terraces and folded Pleistocene lavas. As in the MFTB, the active deformation localization remains localized by structural inheritance. The Andean system is thus evolving as an atypical orogenic wedge partly by frontal accretion at the front

  16. ROVER: A prototype active vision system

    NASA Astrophysics Data System (ADS)

    Coombs, David J.; Marsh, Brian D.

    1987-08-01

    The Roving Eyes project is an experiment in active vision. We present the design and implementation of a prototype that tracks colored balls in images from an on-line charge coupled device (CCD) camera. Rover is designed to keep up with its rapidly changing environment by handling best and average case conditions and ignoring the worst case. This allows Rover's techniques to be less sophisticated and consequently faster. Each of Rover's major functional units is relatively isolated from the others, and an executive which knows all the functional units directs the computation by deciding which jobs would be most effective to run. This organization is realized with a priority queue of jobs and their arguments. Rover's structure not only allows it to adapt its strategy to the environment, but also makes the system extensible. A capability can be added to the system by adding a functional module with a well defined interface and by modifying the executive to make use of the new module. The current implementation is discussed in the appendices.

  17. The tectonic frame of the Variscan Alleghanian orogen in Southern Europe and Northern Africa

    NASA Astrophysics Data System (ADS)

    Simancas, J. Fernando; Tahiri, Abdelfatah; Azor, Antonio; Lodeiro, Francisco González; Martínez Poyatos, David J.; El Hadi, Hassan

    2005-04-01

    By confronting different geological and geophysical data, we attempt to reconstruct the Variscan-Alleghanian orogenic belt, with especial emphasis on the links between Iberia, northwest Africa, and northeast America. The northern Iberia transect corresponds to the rifted margin of Gondwana, inverted during the Variscan orogeny and overthrust in its westernmost sector by a pile of allochthonous units, some of them with oceanic affinity and witnessing an orogenic suture. The southern Iberia section reveals two sutures at both boundaries of a terrane closely tied to Gondwana, namely the Ossa-Morena Zone. The southern boundary of this zone (i.e., the contact with the South Portuguese Zone) is enhanced by amphibolites with oceanic affinity and probably represents the suture of the Rheic Ocean. The Moroccan Variscides can be divided into: (i) a western external zone, namely the Coastal Block and the Central Massif; (ii) an internal zone, namely the Eastern Meseta; (iii) an eastern external zone represented in the Anti Atlas region; and (iv) the African cratonic foreland. Since neither ophiolites nor eclogites crop out along this transect of the orogen, we consider it to be an incomplete transect, lacking the main suture zone (Rheic Ocean). Stratigraphic and faunal affinities between the Moroccan Meseta, on the one hand, and the Central Iberian, Western Asturian-Leonese, and Cantabrian zones of Iberia, on the other hand, suggest that they may well have been part of a common pre-orogenic domain at the margin of Gondwana. On the contrary, there are no counterparts in Morocco for the Ossa-Morena Zone. Thus, the northern Iberia palaeogeographic zones would prolong in the Moroccan Meseta through an eastward arcuate structure, while the suture of the Rheic Ocean would do so offshore Morocco. In our reconstruction, an Avalonian spur (Grand Banks indentor), which included the Caledonian Sehoul block in northern Morocco and the crust of the South Portuguese Zone in SW Iberia

  18. Distribution, microfabric, and geochemical characteristics of siliceous rocks in central orogenic belt, China: implications for a hydrothermal sedimentation model.

    PubMed

    Li, Hongzhong; Zhai, Mingguo; Zhang, Lianchang; Gao, Le; Yang, Zhijun; Zhou, Yongzhang; He, Junguo; Liang, Jin; Zhou, Liuyu; Voudouris, Panagiotis Ch

    2014-01-01

    Marine siliceous rocks are widely distributed in the central orogenic belt (COB) of China and have a close connection to the geological evolution and metallogenesis. They display periodic distributions from Mesoproterozoic to Jurassic with positive peaks in the Mesoproterozoic, Cambrian--Ordovician, and Carboniferous--Permian and their deposition is enhanced by the tensional geological settings. The compressional regimes during the Jinning, Caledonian, Hercynian, Indosinian, and Yanshanian orogenies resulted in sudden descent in their distribution. The siliceous rocks of the Bafangshan-Erlihe ore deposit include authigenic quartz, syn-depositional metal sulphides, and scattered carbonate minerals. Their SiO2 content (71.08-95.30%), Ba (42.45-503.0 ppm), and ΣREE (3.28-19.75 ppm) suggest a hydrothermal sedimentation origin. As evidenced by the Al/(Al + Fe + Mn), Sc/Th, (La/Yb) N, and (La/Ce) N ratios and δCe values, the studied siliceous rocks were deposited in a marginal sea basin of a limited ocean. We suggest that the Bafangshan-Erlihe area experienced high- and low-temperature stages of hydrothermal activities. The hydrothermal sediments of the former stage include metal sulphides and silica, while the latter was mainly composed of silica. Despite the hydrothermal sedimentation of the siliceous rocks, minor terrigenous input, magmatism, and biological activity partly contributed to geochemical features deviating from the typical hydrothermal characteristics. PMID:25140349

  19. Distribution, Microfabric, and Geochemical Characteristics of Siliceous Rocks in Central Orogenic Belt, China: Implications for a Hydrothermal Sedimentation Model

    PubMed Central

    Li, Hongzhong; Zhai, Mingguo; Zhang, Lianchang; Gao, Le; Yang, Zhijun; Zhou, Yongzhang; He, Junguo; Liang, Jin; Zhou, Liuyu; Voudouris, Panagiotis Ch.

    2014-01-01

    Marine siliceous rocks are widely distributed in the central orogenic belt (COB) of China and have a close connection to the geological evolution and metallogenesis. They display periodic distributions from Mesoproterozoic to Jurassic with positive peaks in the Mesoproterozoic, Cambrian—Ordovician, and Carboniferous—Permian and their deposition is enhanced by the tensional geological settings. The compressional regimes during the Jinning, Caledonian, Hercynian, Indosinian, and Yanshanian orogenies resulted in sudden descent in their distribution. The siliceous rocks of the Bafangshan-Erlihe ore deposit include authigenic quartz, syn-depositional metal sulphides, and scattered carbonate minerals. Their SiO2 content (71.08–95.30%), Ba (42.45–503.0 ppm), and ΣREE (3.28–19.75 ppm) suggest a hydrothermal sedimentation origin. As evidenced by the Al/(Al + Fe + Mn), Sc/Th, (La/Yb)N, and (La/Ce)N ratios and δCe values, the studied siliceous rocks were deposited in a marginal sea basin of a limited ocean. We suggest that the Bafangshan-Erlihe area experienced high- and low-temperature stages of hydrothermal activities. The hydrothermal sediments of the former stage include metal sulphides and silica, while the latter was mainly composed of silica. Despite the hydrothermal sedimentation of the siliceous rocks, minor terrigenous input, magmatism, and biological activity partly contributed to geochemical features deviating from the typical hydrothermal characteristics. PMID:25140349

  20. Partial melting in amphibolites in a deep section of the Sveconorwegian Orogen, SW Sweden

    NASA Astrophysics Data System (ADS)

    Hansen, Edward; Johansson, Leif; Andersson, Jenny; LaBarge, Leah; Harlov, Daniel; Möller, Charlotte; Vincent, Stephanie

    2015-11-01

    Garnet amphibolite metataxites at the Steningekusten Nature Reserve in southwestern Sweden contain tonalitic patches and veins. Whole rock chemistry suggests that the protoliths were mafic igneous rocks with alkaline affinities. Orthopyroxene megacrysts are present in leucosome in parts of these garnet amphibolites but absent in others. Orthopyroxene megacrysts were formed by vapor-absent melting initiated by incongruent melting of biotite followed by the breakdown of hornblende. The net reaction was Bt + Hbl + Pl +/- Qtz ↔ Opx + Melt + Cpx + Gt. Melting occurred at pressures of approximately 1 GPa and temperatures which probably exceeded 800 °C. Pyroxenes are surrounded by hornblende-quartz symplectites, and hornblende in these coronas has distinctly lower concentrations of (Na + K) and Ti than that in adjacent mesosome. The hornblende rims formed upon cooling and reaction with crystallizing melt. This created a barrier to further reaction thus preserving the orthopyroxene megacrysts. Garnet amphibolite metatexites lacking pyroxene megacrysts have features characteristic of vapor-present melting including lack of peritectic phases predicted by vapor-absent melting reactions, larger amounts of leucosome (14 versus 7%), and less distinct melanosomes. The variation in these migmatites reflects open system behavior, either on a regional scale with the migration of aqueous fluids into the amphibolites or on a local scale with the migration of melt within the amphibolites. Zircons from all units have CL-dark core domains that are dated at 1415-1390 Ma. The core zones are cut and overgrown by CL-dark and CL-bright rims that are dated at 975-965 Ma. The zircon rims are thin in the mesosome but are thicker in the leucosome suggesting that they formed during migmatization. New growth of zircon associated with migmatization at ca. 970 Ma corresponds to the timing of crustal scale partial melting in the deep regions of the Sveconorwegian orogen, synchronous with east

  1. Late Devonian Anoxia Events in the Central Asian Orogenic Belt: a Global Phenomenon

    NASA Astrophysics Data System (ADS)

    Carmichael, S. K.; Waters, J. A.; Suttner, T. J.; Kido, E.; DeReuil, A. A.; Moore, L. M.; Batchelor, C. J.

    2013-12-01

    Atmospheric CO2 values decreased dramatically during the Middle Devonian due to the rapid rise of land plants. These changing environmental conditions resulted in widespread anoxia and extinction events throughout the Late Devonian, including the critical Kellwasser and Hangenberg anoxia events, which are associated with major mass extinctions at both the beginning and end of the Famennian Stage of the Late Devonian. Fammenian sediments in northwestern Xinjiang Province, China, represent a highly fossiliferous shallow marine setting associated with a Devonian oceanic island arc complex. Analysis of multiple geochemical proxies (such as U/Th, Ba, normalized P2O5, V/Cr, Zr), magnetic susceptibility, and mineralogical data (biogenic apatite and pyrite framboids) indicates that these Famennian sequences record not only the Upper Kellwasser Anoxic Event at the Frasnian/Famennian (F/F) boundary but also the rebound from the F/F extinction event. Preliminary evidence suggests that the Hangenberg Anoxic Event can also be recognized in the same sequence, although our biostratigraphic control is less precise. Previous studies of the Kellwasser and Hangenberg Events have been performed on continental shelf environments of Laurussia, Gondwana, Siberia, and South China. The Devonian formations of northwest Xinjiang in this study, however, are part of the Central Asian Orogenic Belt (CAOB), which is thought to have formed as part of a complex amalgamation of intra-oceanic island arcs and continental fragments prior to the end of the latest Carboniferous. These results allow us to confirm the presence of the Kellwasser and Hangenberg Events in the open oceanic part of Paleotethys, indicating that both events were global in scope. The presence of an abundant diverse Famennian fauna between these anoxia/extinction events suggests that the shallow marine ecosystems in the CAOB were somewhat protected due to their tectonic location and relative isolation within an open ocean system

  2. Orogenic-type copper-gold-arsenic-(bismuth) mineralization at Flatschach (Eastern Alps), Austria

    NASA Astrophysics Data System (ADS)

    Raith, Johann G.; Leitner, Thomas; Paar, Werner H.

    2015-10-01

    Structurally controlled Cu-Au mineralization in the historic Flatschach mining district (Styria, Austria) occurs in a NE-SW to NNE-WSW oriented vein system as multiple steep-dipping calcite-(dolomite)-quartz veins in amphibolite facies metamorphic rocks (banded gneisses/amphibolites, orthogneisses, metagranitoids) of the poly-metamorphosed Austroalpine Silvretta-Seckau nappe. Vein formation postdated ductile deformation events and Eoalpine (Late Cretaceous) peak metamorphism but predated Early to Middle Miocene sediment deposition in the Fohnsdorf pull-apart basin; coal-bearing sediments cover the metamorphic basement plus the mineralized veins at the northern edge of the basin. Three gold-bearing ore stages consist of a stage 1 primary hydrothermal (mesothermal?) ore assemblage dominated by chalcopyrite, pyrite and arsenopyrite. Associated minor minerals include alloclasite, enargite, bornite, sphalerite, galena, bismuth and matildite. Gold in this stage is spatially associated with chalcopyrite occurring as inclusions, along re-healed micro-fractures or along grain boundaries of chalcopyrite with pyrite or arsenopyrite. Sericite-carbonate alteration is developed around the veins. Stage 2 ore minerals formed by the replacement of stage 1 sulfides and include digenite, anilite, "blue-remaining covellite" (spionkopite, yarrowite), bismuth, and the rare copper arsenides domeykite and koutekite. Gold in stage 2 is angular to rounded in shape and occurs primarily in the carbonate (calcite, Fe-dolomite) gangue and less commonly together with digenite, domeykite/koutekite and bismuth. Stage 3 is a strongly oxidized assemblage that includes hematite, cuprite, and various secondary Cu- and Fe-hydroxides and -carbonates. It formed during supergene weathering. Stage 1 and 2 gold consists mostly of electrum (gold fineness 640-860; mean = 725; n = 46), and rare near pure gold (fineness 930-940; n = 6). Gold in stage 3 is Ag-rich electrum (fineness 350-490, n = 12), and has a

  3. Miocene magmatism and tectonics within the Peri-Alboran orogen (western Mediterranean)

    NASA Astrophysics Data System (ADS)

    El Azzouzi, M.; Bellon, H.; Coutelle, A.; Réhault, J.-P.

    2014-07-01

    The aim of this paper concerns Miocene igneous activity in the Alboran Sea and Peri-Alboran area (northern Morocco, western Algeria and Betic Cordilleras in Spain), considering its age and its location with regard to major tectonics structures. We have compiled previous K-Ar isotopic ages of lavas and plutonic boulders and intrusives with an error of ±1σ and completed this set by a new K-Ar isotopic age for andesitic tuffites from Alboran Island. Geochemistry of most of these samples has been considered after previous analyses completed with new data for Spain magmatism. These two sets of data allow us to place the magmatic activity within the regional stratigraphy and tectonics and their chronological framework of the three major tectonic phases of the Maghrebian orogen, at 17 Ma (Burdigalian), 15 Ma (Langhian) and 9 Ma (Tortonian). Petro-geochemical characteristics are compared through time and geographical locations. A major goal of this coupled approach is to help the elaboration of possible geodynamical processes. As an application, we present the case study of the Dellys, Djinet and Thenia region (east of Algiers) where the successive magmatic events between 19.4 ± 1 and 11.6 ± 0.5 Ma are closely related to the local tectonics and sedimentation. The Peri-Alboran igneous activity is placed in a multidisciplinary framework. Timing of activity is defined according to the ages of the neighbouring sedimentary units and the K-Ar ages of igneous rocks. In Spain, the Cabo de Gata-Carboneras magmatic province displays late Oligocene and early Miocene leucogranitic dikes, dated from 24.8 ± 1.3 to 18.1 ± 1.2 Ma; three following andesitic to rhyolitic events took place around 15.1 ± 0.8 to 14.0 ± 0.7 Ma, 11.8 ± 0.6 to 9.4 ± 0.4 Ma, 8.8 ± 0.4 to 7.9 ± 0.4 Ma; this last event displays also granitic rocks. Lamproitic magmas dated between 8.4 ± 0.4 and 6.76 ± 0.04 Ma were emplaced after the Tortonian phase. In Morocco, after the complex building of the Ras Tarf

  4. The Kharapeh orogenic gold deposit: Geological, structural, and geochemical controls on epizonal ore formation in West Azerbaijan Province, Northwestern Iran

    USGS Publications Warehouse

    Niroomand, Shojaeddin; Goldfarb, Richard J.; Moore, Farib; Mohajjel, Mohammad; Marsh, Erin E.

    2011-01-01

    part of a diachronous gold event during the middle to late Tertiary throughout the SSZ and during the final stages of the Zagros orogeny. The proximity of Kharapeh to the main tectonic suture of the orogen, well-developed regional fold systems with superimposed complex fracture geometries, and recognition of nearby volcanogenic massive sulfide systems that suggest a region characterized by sulfur- and metal-rich crustal rocks, collectively indicate an area of the SSZ with high favorability for undiscovered gold resources.

  5. Evolution and Metallogenesis of the Great Serpentinite Belt in the New England Orogen, N.S.W. Australia

    NASA Astrophysics Data System (ADS)

    Manton, R. J.; Buckman, S.; Nutman, A.

    2013-12-01

    Current tectonic interpretations of disrupted ophiolitic complexes and scattered HP/LT eclogite-blueschist blocks within the New England Orogen are still problematic due to limited or unreliable geochronological data. Ophiolitic, island-arc and accretionary complex terranes are contained or spatially associated within the 'alpine-type' Great Serpentinite Belt, which is controlled by the ~350km long, NNW-SSE orientated, Peel-Manning Fault System. The Cambro-Ordovician blocks within the mélange contrast with the Permian emplacement age for the serpentinite. Early Cambrian (530 Ma) ages of the igneous zircons extracted from plagiogranites and tonalities record the formation of the ophiolitic protolith making them the oldest rocks in eastern Australia (Aitchison et al., 1992 Geology v. 20). The timing of serpentinite emplacement is problematic. The minimum age is constrained by the stitching pluton of the Late Permian Moonbi Adamellite (256 × 4 Ma) and the presence of serpentinite clasts within adjacent Early? Permian Manning Group rocks. However, the maximum emplacement age is less well constrained and limited to the absence of serpentinite clasts in older adjacent Carboniferous sedimentary rocks, thereby suggesting the serpentinite belt was not exposed until the Early Permian. In this study we present zircon U-Pb dates and REE chemistry of an eclogite block in the serpentinite belt at Attunga. REE chemistry of the zircons shows an age of 492 × 13 Ma for high pressure metamorphism. Igneous inheritance in metamorphic zircon has an age of ~530 Ma. Titanium in zircon thermometry (zircon + rutile + quartz) indicate high pressure zircon growth at 650 - 700°C. This is higher than the previously calculated 290 - 600°C, which was based on the distribution of Fe and Mg between co-existing garnet and pyroxene (Shaw and Flood 1974, AJES v. 21). We interpret this block as being a portion of the metamorphic sole of the original ophiolite. Ongoing studies will further

  6. Distinct magnetic fabric in weakly deformed sediments from extensional basins and fold-and-thrust structures in the Northern Apennine orogenic belt (Italy)

    NASA Astrophysics Data System (ADS)

    Caricchi, Chiara; Cifelli, Francesca; Kissel, Catherine; Sagnotti, Leonardo; Mattei, Massimo

    2016-02-01

    We report on results from anisotropy of magnetic susceptibility (AMS) analyses carried out on weakly deformed fine-grained sediments from the Northern Apennine orogenic system (Italy). We sampled 63 sites from preorogenic, synorogenic, and postorogenic sequences, which differ in age, composition, depositional environment, degrees of deformation, and tectonic regimes. The magnetic fabric is typical of weakly deformed sediments, with a magnetic foliation subparallel to the bedding plane and a magnetic lineation well defined in this plane. Northern Apennine chain deposits are characterized by strongly oblate magnetic susceptibility ellipsoids, indicating that the magnetic fabric is the result of both compaction process and tectonic load experienced by the sediments during diagenesis and orogenic events. The orientation of magnetic lineation is significantly different depending whether the studied sites underwent extensional or compressional tectonic regimes. In the Northern Apennine chain, the magnetic lineation is mostly oriented NNW-SSE, parallel to the main compressional structures. It suggests a tectonic origin of the magnetic lineation with an acquisition related to the Apennines compressional phases. In the extensional Tuscan Tyrrhenian margin, magnetic lineation is oriented ENE-WSW, almost perpendicular to the main extensional faults, which represent the main deformation elements of the area. Our results demonstrate a close relationship between the shape and orientation of magnetic fabric and the tectonic history of rocks, confirming that AMS represents a valuable tool to investigate the tectonic history of weakly deformed sedimentary rocks.

  7. Proto-Pacific-margin source for the Ordovician turbidite submarine fan, Lachlan Orogen, southeast Australia: Geochemical constraints

    NASA Astrophysics Data System (ADS)

    Offler, R.; Fergusson, C. L.

    2016-04-01

    diagrams involving major, trace and REE strongly support a collisional/continental volcanic arc setting that was substantially eroded to produce the plutonic detritus observed in the sandstones. The collisional setting accords with that proposed previously by other authors who suggested that it developed during the Delamerian Orogeny, resulting in the uplifted source areas providing detritus that inundated the backarc and forearc sites of the Macquarie Arc. Some of the detritus, however, may have been derived from a continental arc that existed in the late Cambrian along the margin of the Ross Orogen. Based on palaeocurrent analyses in previous studies and shoshonitic signature of the detritus, it is proposed that the Cambrian volcanics along the eastern active margin of Gondwana provided much of the detritus in the Adaminaby Group. Zircons with the Grenvillian signature suggest that some detritus were also derived from the Ross Orogen.

  8. Drainage divide migration induced by rainfall gradient in orogenic landscape and the split of the associated drainage networks

    NASA Astrophysics Data System (ADS)

    Bonnet, S.

    2009-12-01

    discharge within drainage basins, divide migration drives a narrowing of the channels so that channel erosion progressively localizes within the floodplains, whose abandoned parts are subsequently uplifted. Even if channels cannot be observed directly during experiments because of opacity during rainfall, a careful examination at the time-step evolution of the experimental landscape shows that the location of the newly-formed trunk channels after splitting is intimately linked to the former geometry of the upstream tributaries of the channel network. The network splitting mechanism most likely occurs at the tributaries’ junction and lies in the combination of channel narrowing due to the decrease of discharge associated to the existence of an uplift forcing. This enables flows coming from the tributaries to disconnect in place of a former single channel. The mechanism of drainage network splitting relates to a very unstable landscape whose characteristics, as exemplified by the Aconquija range in Argentina, provide the first possibility to demonstrate and investigate divide migration in active orogens through the coeval dynamics of the associated drainage networks.

  9. Large landslides lie low: Vertical domains of denudation processes in the arid Himalaya-Karakoram orogen

    NASA Astrophysics Data System (ADS)

    Blöthe, Jan Henrik

    2014-05-01

    Large bedrock landslides (defined here as affecting >0.1 km2 in planform area) are thought to substantially contribute to denuding active mountain belts, and limiting the growth of topographic relief produced by concurrent tectonic uplift and fluvial or glacial incision. While most research on large landslides has focused on tectonically active, humid mountain belts with varying degrees of rainstorm and earthquake activity, lesser attention has been devoted to arid mountain belts. Especially in the Himalaya, where high denudation rates are commonly associated with high landslide activity, previous work has largely ignored landslide processes in the arid compartments of the orogen. This was motivation for us to compile a landslide inventory covering the arid Himalaya-Karakoram of NW India and N Pakistan within the Indus catchment. Our data set contains 493 rock-slope failures that we compiled from published studies and mapping from remote sensing imagery. Using an empirical volume-area scaling approach we estimate the total landslide volume at >250 km3. This is more than thousand times the contemporary annual sediment load in the Indus River. We analyse the distribution of these volumetrically significant landslides with respect to the regional hypsometry, contemporary glacier cover, and the distribution of rock glaciers. We find that large bedrock landslides in the arid Himalaya-Karakoram region preferentially detach near or from below the study area's median elevation, while glaciers and rock glaciers occupy higher elevations almost exclusively. This trend holds true for both the study area and parts thereof. The largest and highest-lying landslides occur in the Karakoram mountains, where local relief exceeds 6 km, and >90% of the landslide areas lie below the region's median elevation. Our analysis reveals a hitherto unrecognized vertical layering of denudation processes, with landslides chiefly operating below the median elevation, whereas mass transport by

  10. High-pressure metamorphism in the southern New England Orogen: Implications for long-lived accretionary orogenesis in eastern Australia

    NASA Astrophysics Data System (ADS)

    Phillips, G.; Offler, R.; Rubatto, D.; Phillips, D.

    2015-09-01

    New geochemical, metamorphic, and isotopic data are presented from high-pressure metamorphic rocks in the southern New England Orogen (eastern Australia). Conventional and optimal thermobarometry are augmented by U-Pb zircon and 40Ar/39Ar phengite dating to define pressure-temperature-time (P-T-t) histories for the rocks. The P-T-t histories are compared with competing geodynamic models for the Tasmanides, which can be summarized as (i) a retreating orogen model, the Tasmanides formed above a continuous, west dipping, and eastward retreating subduction zone, and (ii) a punctuated orogen model, the Tasmanides formed by several arc accretion, subduction flip, and/or transference events. Whereas both scenarios are potentially supported by the new data, an overlap between the timing of metamorphic recrystallization and key stages of Tasmanides evolution favors a relationship between a single, long-lived subduction zone and the formation, exhumation, and exposure of the high-pressure rocks. By comparison with the retreating orogen model, the following links with the P-T-t histories emerge: (i) exhumation and underplating of oceanic eclogite during the Delamerian Orogeny, (ii) recrystallization of underplated and exhuming high-pressure rocks at amphibolite facies conditions coeval with a period of rollback, and (iii) selective recrystallization of high-pressure rocks at blueschist facies conditions, reflecting metamorphism in a cooled subduction zone. The retreating orogen model can also account for the anomalous location of the Cambrian-Ordovician high-pressure rocks in the Devonian-Carboniferous New England Orogen, where sequential rollback cycles detached and translated parts of the leading edge of the overriding plate to the next, younger orogenic cycle.

  11. Late Carboniferous collision between the Tarim and Kazakhstan-Yili terranes in the western segment of the South Tian Shan Orogen, Central Asia, and implications for the Northern Xinjiang, western China

    NASA Astrophysics Data System (ADS)

    Han, Bao-Fu; He, Guo-Qi; Wang, Xue-Chao; Guo, Zhao-Jie

    2011-12-01

    The Tian Shan of Central Asia is located in the southwestern part of the Central Asian Orogenic Belt (CAOB, also known as the Central Asian Orogenic System or CAOS). Formation of the South Tian Shan Orogen is a diachronous, scissors-like process during the Paleozoic and its western segment in China-Kyrgyzstan contiguous regions is accepted as the site of the final collision zone between the Tarim craton to the south and the Kazakhstan-Yili terrane to the north in the Late Paleozoic. However, when the final collision occurred is still in hot debate. Particularly, an end-Permian to Triassic collisional model is recently proposed for the western segment of the South Tian Shan Orogen. This even leads to the speculation that the complicated accretion-collision processes in the Northern Xinjiang of western China, which involved the terrane amalgamation in the East and West Junggar and the collision between the Altai and Kazakhstan terranes and between the Yili-Central Tian Shan and Junggar terranes, were finally terminated during the end-Permian to mid-Triassic, rather than the Late Paleozoic as usually accepted. Obviously, the western segment of the South Tian Shan Orogen also presents the key issue associated with the termination time of accretion-collision processes in the Northern Xinjiang. A collisional model that is derived from the knowledge of the Himalayan Orogen is helpful for establishing a sequence of major tectonothermal events in the western segment of the South Tian Shan Orogen and constraining the time of collision between the Tarim craton and the Kazakhstan-Yili terrane. For the western segment of the South Tian Shan Orogen, the end-Permian to Triassic collisional model is mainly based on Triassic zircon U-Pb ages of 234 to 226 Ma from the West Tian Shan eclogite and two suspected Late Permian radiolarian specimens Albaillella excelsa Ishiga, Kito and Imoto (?) from the Baleigong ophiolitic mélange. Actually, the poor preservation of the two radiolarian

  12. Late Cryogenian-Ediacaran history of the Arabian-Nubian Shield: A review of depositional, plutonic, structural, and tectonic events in the closing stages of the northern East African Orogen

    NASA Astrophysics Data System (ADS)

    Johnson, P. R.; Andresen, A.; Collins, A. S.; Fowler, A. R.; Fritz, H.; Ghebreab, W.; Kusky, T.; Stern, R. J.

    2011-10-01

    affected by oblique (transpressional) convergence of continental blocks that formed eastern and western Gondwana—the pANS was approaching the Saharan Metacraton; north-trending shear and shortening zones developed in the southern ANS; and northwest-trending strike-slip shear zones of the Najd fault system dominated farther north. In the northwestern ANS, convergence and Najd transpression buckled the crust causing structural highs with domes of gneissic infracrust overlain by supracrust composed of ophiolitic and volcanosedimentary assemblages dating from the Tonian-middle Cryogenian period of island-arc activity. The supracrust was extensively translated to the northwest above a high-strain zone. Extension and tectonic escape augmented exhumation of the gneissic infracrust particularly between ˜620-580 Ma. In the northeastern ANS, linear belts of gneiss formed from reworked older intrusive bodies or syntectonic intrusions that were emplaced along Najd faults. By ˜620 Ma a marine basin on the eastern margin of the pANS (present coordinates) was beginning to close. A thick sedimentary assemblage (Abt formation) in this basin underwent metamorphism and folding, and subduction-related magmatism and volcanism farther into this basin (Al Amar arc; >690-615 Ma) was coming to an end. Amalgamation of the Abt formation, Al Amar arc, and the pANS occurred between ˜620 and ˜605 Ma, and terminal collision between the pANS and the Saharan Metacraton was complete by ˜580 Ma. At this time, the ANS was fully assembled. Granite magmatism continued until ˜565-560 Ma and orogeny ceased by ˜550 Ma. During these terminal events, the region underwent strong chemical weathering and became a vast low-relief surface on which Lower Paleozoic sandstone was eventually deposited.

  13. Palaeozoic - Mesozoic tectonics of the western Transbaikalian segment of the Central Asian Orogenic Belt

    NASA Astrophysics Data System (ADS)

    Gladkochub, Dmitry; Donskaya, Tatiana; Mazukabzov, Anatoly

    2014-05-01

    The western Transbaikalian segment of the Central Asian Orogenic Belt (CAOB) is a key to understand a scenario of gradual growth of continental crust in this part of the Northern Eurasia. In general this growth was directly controlled by long-living processes related to interaction of the southern margin of the Siberian craton with different units of the Palaeo-Asian and Mongol-Okhotsk oceans. The Neoproterozoic activity within this area was related to opening and development of the Palaeo-Asian Ocean. The early Palaeozoic stage was characterized by collision of numerous terranes (microcontinents, relicts of island arcs and back-arc basins, etc.) with the southern flank of the Siberian craton. These events reflect an early stage of Palaeo-Asian Ocean closure and the beginning of CAOB building. Since the late Palaeozoic the development of the Transbaikalian segment of the CAOB was related to the evolution of the Mongol-Okhotsk Ocean. Late Silurian - middle Devonian clastic and carbonate sediments were deposited along a passive margin of the Mongol-Okhotsk Ocean. The low-angle subduction of oceanic lithosphere of the Mongol-Okhotsk Ocean beneath the Siberian continent started in the middle Devonian. In the early to late Carboniferous, a steeper dip of subduction led to tectonic switching from extension to compression. This period was characterized by compression, metamorphism, deformations and thickening of continental crust. Autochthonous biotite granites of the Angara-Vitim batholith (ca. 320-300 Ma) were emplaced during this phase. Destruction of the subducted slab and roll-back toward the ocean in the late Carboniferous - early Permian caused extension of continental lithosphere and magmatic input from the mantle into the continental crust. These processes were responsible for voluminous magmatism that is spectacularly represented by allochthonous granitoids of the Angara-Vitim batholith and magmatic rocks of the western Transbaikalian belt (ca. 300-270 Ma). In

  14. Preliminary design activities for solar heating and cooling systems

    NASA Technical Reports Server (NTRS)

    1978-01-01

    Information on the development of solar heating and cooling systems is presented. The major emphasis is placed on program organization, system size definition, site identification, system approaches, heat pump and equipment design, collector procurement, and other preliminary design activities.

  15. Geology and metallogeny of the Ar Rayn terrane, eastern Arabian shield: Evolution of a Neoproterozoic continental-margin arc during assembly of Gondwana within the East African orogen

    USGS Publications Warehouse

    Doebrich, J.L.; Al-Jehani, A. M.; Siddiqui, A.A.; Hayes, T.S.; Wooden, J.L.; Johnson, P.R.

    2007-01-01

    characteristics of the Ar Rayn terrane are analogous to the Andean continental margin of Chile, with opposite subduction polarity. The Ar Rayn terrane represents a continental margin arc that lay above a west-dipping subduction zone along a continental block represented by the Afif composite terrane. The concentration of epithermal, porphyry Cu and IOCG mineral systems, of central arc affiliation, along the AAF suggests that the AAF is not an ophiolitic suture zone, but originated as a major intra-arc fault that localized magmatism and mineralization. West-directed oblique subduction and ultimate collision with a land mass from the east (East Gondwana?) resulted in major transcurrent displacement along the AAF, bringing the eastern part of the arc terrane to its present exposed position, juxtaposed across the AAF against a back-arc basin assemblage represented by the Abt schist of the Ad Dawadimi terrane. Our findings indicate that arc formation and accretionary processes in the Arabian shield were still ongoing into the latest Neoproterozoic (Ediacaran), to about 620-600 Ma, and lead us to conclude that evolution of the Ar Rayn terrane (arc formation, accretion, syn- to postorogenic plutonism) defines a final stage of assembly of the Gondwana supercontinent along the northeastern margin of the East African orogen. ?? 2007 Elsevier B.V. All rights reserved.

  16. Chemical remagnetization and paleomagnetic dating of fluid migration events: Testing the orogenic fluid hypothesis

    SciTech Connect

    Douglas, E.R. )

    1993-11-01

    Remagnetization, the acquisition of a secondary magnetization, is now recognized as a widespread phenomenon in sedimentary rocks. The recognition that many sedimentary rocks were remagnetized long after deposition has not only led to a reevaluation of the paleomagnetic database, but also has led to a new application of the paleomagnetic method to other areas of earth science. Many secondary magnetizations are tangible evidence of a chemical event caused by rock-fluid interactions. Recent studies demonstrate that isolation of a chemical remanent magnetization (CRM) and comparison of the corresponding pole position to the apparent polar wander path can provide essential constraints on the timing of a diagenetic event. Many CRMs can be spatially correlated with orogenic belts and temporally related to orogeny. In this talk several case studies will be presented where paleomagnetic and geochemical results are used to date diagenetic events and test the role of orogenic fluids as agents of remagnetization. The Ordovician Viola Limestone contains a pervasive Pennsylvanian CRM and a localized Permian CRM that occurs in a halo around veins mineralized by saline radiogenic fluids. The Permian CRM can be related to alteration by the basinal fluids. The pervasive CRM, which is similar to many other CRMs that have been related to orogenic fluids, occurs in relatively unaltered limestone. The acquisition of this CRM was caused by an as yet unidentified chemical mechanism that was not triggered by externally-derived fluids. Preliminary results, however, suggest a connection between the CRM and organic matter in the limestone. Radiogenic Cambrian-Ordovician dolomites near the Ouachita Mountains in southern Oklahoma that have been altered by basinal fluids contain a late Paleozoic CRM. Understanding the origin of these CRMs will require tests of mechanisms that do not rely on externally-derived fluids.

  17. Linked basin sedimentation and orogenic uplift: The Neogene Barinas basin sediments derived from the Venezuelan Andes

    NASA Astrophysics Data System (ADS)

    Erikson, Johan P.; Kelley, Shari A.; Osmolovsky, Peter; Verosub, Kenneth L.

    2012-11-01

    The Venezuelan Andes are an asymmetric, doubly vergent orogen that is flanked on its southeastern side by the Barinas basin. Analyses of sedimentary facies, sandstone petrography, apatite fission-tracks, and magnetostratigraphy were completed on a 1750-m section of the syn-orogenic Neogene Parángula and Río Yuca formations in the Barinas side foothills of the Venezuelan Andes. Our sedimentary facies analyses record a progression of sedimentary environments from floodplain and floodplain channel deposits through the 560-m thick Parángula Formation transitioning to distal alluvial fan deposits in the lower Río Yuca Formation and finally to an alternation of distal alluvial fan and two, ˜100-m thick organic-rich lacustrine deposits in the upper third of the section. Major- and minor-mineral petrographic analysis reveals unroofing of the Venezuelan Andes, with quartz arenite composition low in the section succeeded by metamorphic and igneous clasts and potassium feldspar appearing near the base of the Río Yuca Formation. Apatite fission-track (AFT) analysis of sandstones and pebbles generated ages of 11.2 ± 1.3 - 13.8 ± 2.0 Ma over ˜1100 m of stratigraphic section. Thermal modeling of the detrital AFT and vitrinite data from the lower Río Yuca Formation indicates exhumation of the source area was occurring by 12-13 Ma, surface exposure at 10-9 Ma, maximum burial by 4-2 Ma and exhumation of the sedimentary package starting 3-2 Ma. Accumulation of the Río Yuca Formation is contemporaneous with a basinward migration of the deformation front. Regional considerations indicate that the Venezuelan Andes evolved from a primarily singly vergent orogen to its current double vergence over the interval of Neogene-Quaternary sedimentation.

  18. Middle Miocene paleoaltimetry of southern Tibet: Implications for the role of mantle thickening and delamination in the Himalayan orogen

    NASA Astrophysics Data System (ADS)

    Currie, Brian S.; Rowley, David B.; Tabor, Neil J.

    2005-03-01

    The stable isotope composition of pedogenic and early diagenetic carbonates from the Oiyug Basin of southern Tibet allows model estimates of the paleoaltimetry of the Tibetan Plateau for the middle Miocene. Pedogenic calcium carbonate nodules have average δ18Occ values of -19.6‰, whereas nodular lacustrine dolomites range in composition from -7.6‰ to -5.5‰. The most negative of the carbonate isotope values can be used to constrain the oxygen isotope composition of paleoprecipitation, from which model estimates of paleoaltimetry can be made. Model results indicate that the southern Tibetan Plateau achieved elevations of ˜5200 +1370/-605 m by at least 15 Ma. Our results are identical within uncertainty to previous workers' paleoelevation estimates based on Oiyug Basin fossil floral physiognomy. This is the first time that two paleoaltimeters have been directly compared and are in accord. Collectively, these data strongly support tectonic models in which thickening of mantle lithosphere beneath the domain of crustal thickening and subsequent detachment of the mantle lithosphere plays an indiscernible role in the elevation history of this part of the Himalaya-Tibet orogenic system.

  19. Sediment yield along the Andes: continental budget, regional variations, and comparisons with other basins from orogenic mountain belts

    NASA Astrophysics Data System (ADS)

    Latrubesse, Edgardo M.; Restrepo, Juan D.

    2014-07-01

    We assess the sediment yield at 119 gauging stations distributed from Colombia to Patagonia, covering the different morphotectonic and morphoclimatic settings of the Andes. The most productive areas are the Meta River basin within the northern Andes and the Bolivian and northern Argentina-Chaco systems, which produce an average of 3345, 4909 and 2654 t km2 y- 1 of sediment, respectively. The rivers of the northern and central Andes (excluding the Pacific watersheds of Peru, northern Chile, and central Argentina) have a weighted mean sediment yield of 2045 t km- 2 y- 1 and produce 2.25 GTy- 1 of total sediment. A major constraint estimating the Andean continental budget of sediment yield lies in the lack of gauging data for the Peruvian region. Using the available gauge stations, the regional sediment yield appears underestimated. Assuming a higher value of sediment yield for the Peruvian Andes, the total budget for the whole central Andes could range between 2.57 GT y- 1 and 3.44 GT y- 1. A minimum of ~ 0.55 GT y- 1 and a probable maximum of ~ 1.74 GT y- 1 of sediment are deposited in the intramontane and surrounding proximal sedimentary basins. The magnitude of sediment yield in the Andes is comparable to other rivers draining orogenic belts around the world.

  20. Zongo-San Gaban zone: Eocene foreland boundary of the Central Andean orogen, northwest Bolivia and southeast Peru

    SciTech Connect

    Farrar, E.; Clark, A.H.; Kontak, D.J.; Archibald, D.A.

    1988-01-01

    Discordant muscovite and biotite K-Ar dates of samples taken in six transects through the Cordillera Oriental of southeast Peru and northwest Bolivia, combined with /sup 40/Ar//sup 39/Ar age spectra, reveal a northwest-trending, structurally cryptic, tectonothermal zone of late Eocene age (ca. 38 Ma) that overprints Triassic and older igneous and metamorphic rocks. The zone is at least 450 km long but is less than 25 km wide; temperatures along its northeast boundary are estimated to have reached 350/sup 0/C. No Paleogene magmatism has been recognized that could account for the thermal resetting of the K-Ar isotopic system. Uplift, erosion, and southwest-verging thrusting accompanied the development of this domain, which defined the foreland boundary of the orogen prior to inception of northeast-verging Andean thrusting in Miocene time. It is proposed that this tectonothermal zone, the Zongo-San Gaban zone (ZSGZ), which involves thrusting and basement shortening, is the southerly manifestation of the Incaic compressional deformation, which produced the thin-skinned Maranon thrust and fold belt (MTFB) north of the Abancay deflection of central Peru.

  1. Multiple thermal events in the Grenvillian orogenic cycle: geochronologic evidence from the northern Reading Prong, New York-New Jersey

    SciTech Connect

    Grauch, R.I.; Aleinikoff, J.N.

    1985-01-01

    The Grenville terrane of the northern Reading Prong, New York-New Jersey, has a far more complex thermal history than previously recognized. U-Pb zircon ages record at least five discrete thermal events between about 1300 and 900 Ma: (1) 1230 +/- 20 Ma--metamorphism of paragneiss; (2) 1150 +/- 30 Ma--crystallization of Storm King-type granite, protoliths of a leucogneiss, and a member of the Fordham Gneiss; (3) 1090 +/- 10 Ma--crystallization of a hornblende gneiss and the Canopus pluton; (4) 1015 +/- Ma--regional metamorphism, crystallization of the Canada Hill granite and pegmatitic alaskites; (5) 965 +/- 10 Ma--crystallization of pegmatites, formation of a monazite-xenotime rock, and closure of the U-Pb whole-rock system. Another problem that arises from these results is the past correlation throughout the Reading Prong of lithologic sequences whose zircon ages apparently do not agree. This complex sequence of Middle Proterozoic thermal events in the central Appalachians correlates fairly well with events recorded in the Grenville terrane of eastern Ontario, where at least two major orogenic events between 1300 and 900 Ma have been identified. The fit with identified events in the Adirondacks of northern New York and with Precambrian events of the southern Appalachians is not as good, but the early approx. = 1230 Ma and the late approx. = 960 Ma events seem to be present in both regions.

  2. Activity Systems and Moral Reasoning: An Intervention Study

    ERIC Educational Resources Information Center

    Wardi, Eva; Helkama, Klaus

    2015-01-01

    Seventeen social educator students were taught to analyze their work activity by means of a Vygotsky-inspired method, drawing on Engeström's notion of an activity system. The method aimed at increasing the consciousness of the students of the structure of work activity system. The participants wrote two accounts of their field-work practice…

  3. New approaches to enhance active steering system functionalities: preliminary results

    NASA Astrophysics Data System (ADS)

    Serarslan, Benan

    2014-09-01

    An important development of the steering systems in general is active steering systems like active front steering and steer-by-wire systems. In this paper the current functional possibilities in application of active steering systems are explored. A new approach and additional functionalities are presented that can be implemented to the active steering systems without additional hardware such as new sensors and electronic control units. Commercial active steering systems are controlling the steering angle depending on the driving situation only. This paper introduce methods for enhancing active steering system functionalities depending not only on the driving situation but also vehicle parameters like vehicle mass, tyre and road condition. In this regard, adaptation of the steering ratio as a function of above mentioned vehicle parameters is presented with examples. With some selected vehicle parameter changes, the reduction of the undesired influences on vehicle dynamics of these parameter changes has been demonstrated theoretically with simulations and with real-time driving measurements.

  4. Four Years of Absolute Gravity in the Taiwan Orogen (AGTO)

    NASA Astrophysics Data System (ADS)

    Mouyen, Maxime; Masson, Frédéric; Hwang, Cheinway; Cheng, Ching-Chung; Le Moigne, Nicolas; Lee, Chiung-Wu; Kao, Ricky; Hsieh, Nicky

    2010-05-01

    AGTO is a scientific project between Taiwanese and French institutes, which aim is to improve tectonic knowledge of Taiwan primarily using absolute gravity measurements and permanent GPS stations. Both tools are indeed useful to study vertical movements and mass transfers involved in mountain building, a major process in Taiwan located at the convergent margin between Philippine Sea plate and Eurasian plate. This convergence results in two subductions north and south of Taiwan (Ryukyu and Manilla trenches, respectively), while the center is experiencing collision. These processes make Taiwan very active tectonically, as illustrated by numerous large earthquakes and rapid uplift of the Central Range. High slopes of Taiwan mountains and heavy rains brought by typhoons together lead to high landslides and mudflows risks. Practically, absolute gravity measurements have been yearly repeated since 2006 along a transect across south Taiwan, from Penghu to Lutao islands, using FG5 absolute gravimeters. This transect contains ten sites for absolute measurements and has been densified in 2008 by incorporating 45 sites for relative gravity measurements with CG5 gravimeters. The last relative and absolute measurements have been performed in November 2009. Most of the absolute sites have been measured with a good accuracy, about 1 or 2 ?Gal. Only the site located in Tainan University has higher standard deviation, due to the city noise. We note that absolute gravity changes seem to follow a trend in every site. However, straightforward tectonic interpretation of these trends is not valuable as many non-tectonic effects are supposed to change g with time, like groundwater or erosion. Estimating and removing these effects leads to a tectonic gravity signal, which has theoretically two origins : deep mass transfers around the site and vertical movements of the station. The latter can be well constrained by permanent GPS stations located close to the measurement pillar. Deep mass

  5. Four Years of Absolute Gravity in the Taiwan Orogen (AGTO)

    NASA Astrophysics Data System (ADS)

    Mouyen, M.; Masson, F.; Hwang, C.; Cheng, C.; Le Moigne, N.; Lee, C.; Kao, R.; Hsieh, N.

    2009-12-01

    AGTO is a scientific project between Taiwanese and French institutes which aim is to improve tectonic knowledge of Taiwan primarily using absolute gravity measurements and permanent GPS stations. Both tools are indeed useful to study vertical movements and mass transfers involved in mountain building, a major process in Taiwan located at the convergent margin between Philippine Sea plate and Eurasian plate. This convergence results in two subductions north and south of Taiwan (Ryukyu and Manilla trenches, respectively), while the center is experiencing collision. These processes make Taiwan very active tectonically, as illustrated by numerous large earthquakes and rapid uplift of the Central Range. High slopes of Taiwan mountains and heavy rains brought by typhoons together lead to high landslides and mudflows risks. Practically, absolute gravity measurements have been yearly repeated since 2006 along a transect across south Taiwan, from Penghu to Lutao island, using FG5 absolute gravimeters. This transect contains ten sites for absolute measurements and has been densified in 2008 by incorporating 45 sites for relative gravity measurements with CG5 gravimeters. At the end of 2009, the relative gravity network will be densified again in its eastern part, i.e. in the Longitudinal Valley and the Central Range. A fourth set of absolute gravity measurements will also be performed at the same period. Most of the absolute sites have been measured with a good accuracy, about 1 or 2 μGal. Only the site located in Tainan University has higher standard deviation, due to the city noise. The stronger change in gravity reaches -7 μGal a -1 west of the Longitudinal Valley and might be explained by tectonic movement along a fault. A large decrease of -5 μGal a-1 is also measured in Tainan city and could be correlated with uplift of this region, also denoted by InSAR, leveling and GPS. Changes occurring in the Central Range are more difficult to interpret due to the small

  6. Flake tectonics in the Sulu orogen in eastern China as revealed by seismic tomography

    NASA Astrophysics Data System (ADS)

    Xu, Peifen; Liu, Futian; Ye, Kai; Wang, Qingchen; Cong, Bolin; Chen, Hui

    2002-05-01

    Seismic tomographic image reveals a crocodile-like P-waves velocity structure beneath the Sulu orogenic belt, which marks the subduction/collision zone between the Sino-Korean block (SK) and Yangtze block (YZ) in eastern China. It may imply that the upper crust of the YZ was detached from its lower crust and thrust over the SK for a maximum of ~400 km in the Sulu region, whereas the remnant of the subducted Yangtze lithosphere was lay beneath the SK. This crustal detached structure (flake tectonics) might have occurred after the Triassic subduction/collision.

  7. Process of activation of a palladium catalyst system

    DOEpatents

    Sobolevskiy, Anatoly; Rossin, Joseph A.; Knapke, Michael J.

    2011-08-02

    Improved processes for activating a catalyst system used for the reduction of nitrogen oxides are provided. In one embodiment, the catalyst system is activated by passing an activation gas stream having an amount of each of oxygen, water vapor, nitrogen oxides, and hydrogen over the catalyst system and increasing a temperature of the catalyst system to a temperature of at least 180.degree. C. at a heating rate of from 1-20.degree./min. Use of activation processes described herein leads to a catalyst system with superior NOx reduction capabilities.

  8. Fluid-assisted melting in a collisional orogen

    NASA Astrophysics Data System (ADS)

    Berger, A.; Burri, T.; Engi, M.; Roselle, G. T.

    2003-04-01

    The Southern Steep Belt (SSB) of the Central Alps is the location of backthrusting during syn- to post-collisional deformation. From its metamorphic evolution and lithological contents the SSB has been interpreted as a tectonic accretion channel (TAC [1]). The central part of the SSB is additionally characterized by anatexites, leucogranitic aplites and pegmatites. Dehydration melting of muscovite is rare but did occurr locally. Moreover, no evidence of dehydration melting of biotite has been formed in that products of incongruent melting reactions (garnet, opx or cordierite) are missing. The melts are mainly produced by the infiltration of an external aqueous fluid. The fluids must have originated from the breakdown of hydrous minerals at temperatures below the water saturated solidus of the quartz-feldspar-system, such that the liberated fluids could not been trapped in the melt. Using the thermal modeling program MELONPIT [2] and assuming that solid fragments ascended in combination with tectonic accreated radioactive material, a complex thermal evolution inside the TAC has been derived. During subduction of the downgoing plate, isotherms were locally inverted, then subsequently relaxed, when subduction slowed down. At the collisional stage a small region develope, where the isotherms were still bent, and where temperatures increased during decompression. Assuming that dehydration reactions were followed by upward flow of fluids released from this region fluid present partial melting was triggered. The flow direction of the fluid was controlled by the pressure gradient and the steeply oriented foliations in the SSB. According to the model, the area of upward flowing fluids should be limited to the SSB. This is consistent with the observed regional distribution of leucosomes derived from in-situ melts. [1] Engi et al. (2001) Geology 29: 1143-1146 [2] Roselle et al. (2002) Am. J. Sci. 302: 381-409

  9. Late Paleozoic closure of the Ob-Zaisan Ocean along the Irtysh/Chara shear zone and implications for arc amalgamation and oroclinal bending in the western Central Asian Orogenic Belt

    NASA Astrophysics Data System (ADS)

    Li, Pengfei; Sun, Min; Rosenbaum, Gideon

    2016-04-01

    The Irtysh/Chara Shear Zone is one of the largest strike-slip systems in the Central Asian Orogenic Belt (CAOB). It records collisional processes of the peri-Siberian orogenic system with the West Junggar-Kazakhstan-Tianshan orogenic system following the closure of the Ob-Zaisan Ocean, but the exact timing of these events remains enigmatic. We conducted detailed structural analysis along the Irtysh Shear Zone (NW China), which together with new geochronological data allows us to reconstruct the tectonic evolution during the final closure of the Ob-Zaisan Ocean. Our results showed that subduction-accretion processes lasted at least until the Late Carboniferous in the Chinese Altai and the East/West Junggar. The subsequent arc amalgamation is characterized by a cycle of crustal thickening, orogenic collapse and transpressional thickening. On a larger scale, the West Junggar- Kazakhstan -Tianshan orogenic system defines a U-shape oroclinal structure (e.g. Xiao et al., 2010). A major phase of oroclinal bending that involved ~110° rotation may have occurred during the Late Devonian to Early Carboniferous (Levashova et al., 2012). Previous authors have linked oroclinal bending with the late Paleozoic amalgamation of the western CAOB, and proposed that a quasi-linear West Junggar- Kazakhstan -Tianshan orogenic system was buckled during the convergence of the Siberian and Tarim cratons following the closure of the Ob-Zaisan Ocean (in the north) and the South Tianshan Ocean (in the south) (e.g. Abrajevitch et al., 2008). This model, however, is not supported by our new data that constrain the closure of the Ob-Zaisan Ocean to the Late Carboniferous. Alternatively, we propose that oroclinal bending may have involved two phases of bending, with the ~110° rotation in the Late Devonian to Early Carboniferous possibly associated with trench retreat. Further tightening may have occurred in response to the convergence of the Siberian and Tarim cratons during the Late

  10. Deep Crustal Metamorphic Carbon Cycling in Collisional Orogens: What do we Really Know?

    NASA Astrophysics Data System (ADS)

    Ague, J.

    2012-12-01

    The classic study of Bowen (1940) showed that CO2 is lost during metamorphic heating of common carbonate-bearing rocks. Despite tremendous progress in our understanding of devolatilization since Bowen's time, the fact remains that the metamorphic CO2 flux from active mountain belts is one of the most poorly-understood components of the global C cycle. A basic question is: do large fluid fluxes accompany collisional orogenesis? It has been argued that metamorphic rocks are overpressured and, thus, permeability is low and fluid fluxes are limited. In contrast, field-based studies commonly estimate large time-integrated fluxes of the order of 103 m3 m-2 or more. These opposing viewpoints can be reconciled by recognizing that large fluxes can pass through rocks on geologic timescales even if permeability is low, and that transient events such as fracturing can greatly increase permeability and facilitate flow. Large regional fluxes make possible significant CO2 transfer from the deep roots of mountain belts to the shallow hydrosphere and atmosphere. Important prograde CO2 release processes include "internally-buffered" reactions, fluid infiltration, carbonate mineral dissolution, and oxidation of graphite (or diamond). The relative roles of these processes, particularly the latter two, are topics of active research. Regardless of process, however, field-based results commonly show prograde loss of 10 to 15 kg CO2 per 100 kg rock for a range of carbonate mineral-bearing lithologies from sub-greenschist to upper amphibolite facies metamorphism. Could this CO2 make a real difference to C cycling? A new assessment of the mean loss of CO2 from metamorphic sequences in New England, USA, for example, yields a minimum release rate of about 1018 mol Ma-1 during the Acadian orogeny (Devonian). This is comparable to Kerrick and Caldeira's (1993) threshold needed to affect global atmospheric temperatures. Flow around large, deep-seated intrusions could easily produce even larger

  11. Tectonics of the zagros orogenic belt of iran: new data and interpretations

    NASA Astrophysics Data System (ADS)

    Alavi, Mehdi

    1994-01-01

    The Zagros orogenic belt of Iran is the result of the opening and closure of the Neo-Tethys oceanic realm, and consists, from northeast to southwest, of three parallel tectonic subdivisions: (1) the Urumieh-Dokhtar Magmatic Assemblage; (2) the Sanandaj-Sirjan Zone; and (3) the Zagros Simply Folded Belt. Recent detailed and reconnaissance mapping and stratigraphie-structural analyses in various parts of the belt indicate that the tectonics of the Sanandaj-Sirjan Zone is dominated by either large-scale composite duplex structures or low- and high-angle NE-dipping imbricate systems. These thrust systems have transported numerous horses and sheets (nappes) of metamorphosed and non-metamorphosed Phanerozoic rocks for tens or possibly hundreds of kilometers. Stratigraphic evidence and synorogenic conglomerates indicate that thrusting was initiated in the Late Cretaceous and has continued episodically since that time. Shear sense indicators in various parts of the zone reveal a NE-SW direction of transport. Thrust systems generated in each episode are superimposed upon the previous structures, cutting across and displacing them and producing complicated stacks of thrust sheets. Southwestward transport and stacking of the thrust sheets has resulted in an increase of about 10-15 km in the thickness of the continental crust in the southwestern part of this zone. The so-called z"Main Zagros Thrust", which has been traditionally considered as the boundary between the Sanandaj-Sirjan Zone and the Zagros Simply Folded Belt, is by no means a single "high-angle reverse fault", nor is it a narrow zone of "crushed rocks" but a series of low-angle thrusts locally cut by normal faults. These thrusts are indistinguishable from those mapped in the Sanandaj-Sirjan Zone, and are geometrically part of the Sanandaj-Sirjan Zone structures. There is no single thrust among them that can be singled out and referred to as the "Main" one. The boundary of the Sanandaj-Sirjan Zone with the Urumieh

  12. Student Activity Funds: Creating a System of Controls That Work.

    ERIC Educational Resources Information Center

    Cuzzetto, Charles

    1995-01-01

    Although student-activity funds usually represent a small portion of school-system monies, their very nature makes them a high risk. Outlines three steps for maintaining an efficient and effective system of controls over student-activity funds: (1) identifying control issues; (2) designing a control system; and (3) using checks and balances.…

  13. Active fluidization in dense glassy systems.

    PubMed

    Mandal, Rituparno; Bhuyan, Pranab Jyoti; Rao, Madan; Dasgupta, Chandan

    2016-07-20

    Dense soft glasses show strong collective caging behavior at sufficiently low temperatures. Using molecular dynamics simulations of a model glass former, we show that the incorporation of activity or self-propulsion, f0, can induce cage breaking and fluidization, resulting in the disappearance of the glassy phase beyond a critical f0. The diffusion coefficient crosses over from being strongly to weakly temperature dependent as f0 is increased. In addition, we demonstrate that activity induces a crossover from a fragile to a strong glass and a tendency of active particles to cluster. Our results are of direct relevance to the collective dynamics of dense active colloidal glasses and to recent experiments on tagged particle diffusion in living cells. PMID:27380935

  14. Active vibration control of lightweight floor systems

    NASA Astrophysics Data System (ADS)

    Baader, J.; Fontana, M.

    2016-04-01

    Wide-span and lightweight floors are often prone to structural vibrations due to their low resonance frequency and poor material damping. Their dynamic behaviour can be improved using passive, semi-active or active vibration control devices. The following article proposes a novel method for the controller synthesis for active vibration control. An existing passive TMD (tuned mass damper) is modelled and equipped with an actuator in order to provide more efficient damping. Using an iterative optimization approach under constraints, an optimal controller is found which minimizes a quadratic cost function in frequency domain. A simulation of an existing test bench shows that the active vibration control device is able to provide increased damping compared to the passive TMD.

  15. Power System Considerations and Test Activities

    NASA Technical Reports Server (NTRS)

    Miller, J.

    1983-01-01

    The potential benefits of an IPACS system compared to NiCd and/or Regen Fuel Cell systems are summarized. The benefits are: (1) significant life cycle cost savings; (2) total weight to orbit savings (30 yrs) as much as 10 times; (3) end to end efficiency increase results in approximately 10 kW reduction in array size(6%); (4) motor/generator controller regulation during discharge simplifies distribution system; and (5) momentum stored for attitude control increased by 4 times.

  16. A comparative analysis of pre-Silurian crustal building blocks of the northern and the southern Appalachian orogen

    USGS Publications Warehouse

    Hibbard, J.P.; van Staal, C.R.; Rankin, D.W.

    2007-01-01

    The New York promontory serves as the divide between the northern and southern segments of the Appalachian orogen. Antiquated subdivisions, distinct for each segment, implied that they had lithotectonic histories that were independent of each other. Using new lithotectonic subdivisions we compare first order features of the pre-Silurian orogenic 'building blocks' in order to test the validity of the implication of independent lithotectonic histories for the two segments. Three lithotectonic divisions, termed here the Laurentian, Iapetan, and the peri-Gondwanan realms, characterize the entire orogen. The Laurentian realm, composed of native North American rocks, is remarkably uniform for the length of the orogen. It records the multistage Neoproterozoic-early Paleozoic rift-drift history of the Appalachian passive margin, formation of a Taconic Seaway, and the ultimate demise of both in the Middle Ordovician. The Iapetan realm encompasses mainly oceanic and magmatic arc tracts that once lay within the Iapetus Ocean, between Laurentia and Gondwana. In the northern segment, the realm is divisible on the basis of stratigraphy and faunal provinciality into peri-Laurentian and peri-Gondwanan tracts that were amalgamated in the Late Ordovician. South of New York, stratigraphic and faunal controls decrease markedly; rock associations are not inconsistent with those of the northern Appalachians, although second-order differences exist. Exposed exotic crustal blocks of the peri-Gondwanan realm include Ganderia, Avalonia, and Meguma in the north, and Carolinia in the south. Carolinia most closely resembles Ganderia, both in early evolution and Late Ordovician-Silurian docking to Laurentia. Our comparison indicates that, to a first order, the pre-Silurian Appalachian orogen developed uniformly, starting with complex rifting and a subsequent drift phase to form the Appalachian margin, followed by the consolidation of Iapetan components and ending with accretion of the peri

  17. Geodynamic implications for the formation of the Betic-Rif orogen from magnetotelluric studies

    NASA Astrophysics Data System (ADS)

    Martí, A.; Queralt, P.; Roca, E.; Ledo, J.; Galindo-ZaldíVar, J.

    2009-01-01

    Magnetotelluric data from the central Betics mountains (Spain) have been used to determine the electrical resistivity of the crust after a three-dimensional (3D) interpretive approach. At shallow levels (<2 km), the resulting model shows good correlation between the geoelectric structures and the geologic units. At greater depths (>3 km), the most striking and well-resolved feature of the model is an upper-middle crust conductive body, located at the core of the Internal Betics antiform. This approximately 14-km-thick body is interpreted as basic or ultrabasic rocks containing a conducting mineral phase. Its structural location above the sole thrust of the Betic orogen and beneath the Nevado-Filábride complex confirms the presence of a major suture zone between this complex and the autochthonous Iberian plate. This suture may correspond to an ancient oceanic or transitional domain developed between Iberia and the Alboran Domain during the opening of the Tethys Ocean, partially subducted and closed during the development of the Betic orogen. The possible geodynamic scenarios for the Betics have been reconsidered, taking into account this new constraint.

  18. Ediacaran 2,500-km-long synchronous deep continental subduction in the West Gondwana Orogen.

    PubMed

    Ganade de Araujo, Carlos E; Rubatto, Daniela; Hermann, Joerg; Cordani, Umberto G; Caby, Renaud; Basei, Miguel A S

    2014-01-01

    The deeply eroded West Gondwana Orogen is a major continental collision zone that exposes numerous occurrences of deeply subducted rocks, such as eclogites. The position of these eclogites marks the suture zone between colliding cratons, and the age of metamorphism constrains the transition from subduction-dominated tectonics to continental collision and mountain building. Here we investigate the metamorphic conditions and age of high-pressure and ultrahigh-pressure eclogites from Mali, Togo and NE-Brazil and demonstrate that continental subduction occurred within 20 million years over at least a 2,500-km-long section of the orogen during the Ediacaran. We consider this to be the earliest evidence of large-scale deep-continental subduction and consequent appearance of Himalayan-scale mountains in the geological record. The rise and subsequent erosion of such mountains in the Late Ediacaran is perfectly timed to deliver sediments and nutrients that are thought to have been necessary for the subsequent evolution of sustainable life on Earth. PMID:25319269

  19. Devonian sedimentation in the Xiqingshan Mountains: Implications for paleogeographic reconstructions of the SW Qinling Orogen

    NASA Astrophysics Data System (ADS)

    Yan, Zhen; Aitchison, Jonathan C.; Fu, Changlei; Guo, Xianqing; Xia, Wenjing; Niu, Manlan

    2016-08-01

    The Qinling Orogen between the North China and Yangtze plates comprises various accreted and collisional terranes, recording the evolution of the Proto-Tethyan Ocean and the formation of east Asia. Knowledge of the provenance and tectonic setting of a thick succession of E-W striking Devonian sedimentary rocks sandwiched tectonically between the Shangdan and Mianlue ophiolitic suture zones in this belt is essential to understanding the evolution of the Qinling Orogen and the assembly of the North China and Yangtze plates during the Late Paleozoic. Systematic studies of the Devonian sedimentary facies in the Xiqingshan Mountains indicate the northern margin of the South Qinling belt was uplifted prior to the Early Devonian. Lower Devonian sandstones are dominated by feldspathic litharenite (Q12-31F18-37L40-65), indicative of a continental arc derivation. Detrital zircon U-Pb data demonstrate that the Lower and Middle Devonian sandstones were derived respectively from ca. 770 Ma and ca. 400 Ma felsic arc-related magmatic sources. Devonian sedimentation in the Xiqingshan Mountains is interpreted to have occurred in a foreland basin between the Yangtze plate and the North Qinling continental arc.

  20. Modelling the thermal evolution of orogens: where’s the heat?

    NASA Astrophysics Data System (ADS)

    Healy, D.; Clark, C.

    2009-12-01

    Our understanding of heat transfer during orogenesis has largely been shaped by the seminal work of England & Thompson (1984). These authors explored P-T-t paths in thickened crust as a function of radiogenic heat production, mantle heat flow, thermal conductivity and rates of erosion. In this contribution we incorporate recent experimental data on the temperature dependence of thermal conductivity and field observations of heat producing elements in exposed orogenic roots into 1D thermal models of regional metamorphism. We identify distinct tectonic processes responsible for heat flow perturbations in thickened crust and compare the temporal evolution of temperature with depth (pressure) for each case. Several recent papers have presented ad hoc combinations of these processes and we seek to clarify the contribution of each process to the total heat orogenic heat budget. We present sensitivity analyses to key model parameters for each case and discuss the scope for separating the relative contribution of each process from field data such as metamorphic field gradients and pressure-temperature-time paths.

  1. Shallow, old, and hydrologically insignificant fault zones in the Appalachian orogen

    NASA Astrophysics Data System (ADS)

    Malgrange, Juliette; Gleeson, Tom

    2014-01-01

    The permeability of fault zones impacts diverse geological processes such as hydrocarbon migration, hydrothermal fluid circulation, and regional groundwater flow, yet how fault zones affect groundwater flow at a regional scale (1-10 km) is highly uncertain. The objective of this work is to determine whether faults affect regional patterns of groundwater flow, by using radioactive radon and chloride to quantify groundwater discharge to lakes underlain by faults and not underlain by faults. We sampled lakes overlying the Paleozoic Appalachian fold and thrust belt in the Eastern Townships in Québec, and compared our results to a previous study in a crystalline watershed in the Canadian Shield. The field data was analyzed with an analytical geochemical mixing model. The uncertainties of model parameters were assessed in a sensitivity analysis using Monte Carlo simulation, and the difference between lakes tested with statistical analysis. While the model results indicate non-negligible groundwater discharge for most of the lakes in the Paleozoic orogen, the difference between the groundwater discharge rate into the lakes located on faults and the other lakes is not statistically significant. However, the groundwater discharge rate to lakes in the Paleozoic orogeny is significantly higher than lakes that overlay crystalline bedrock, which is consistent with independent estimates of permeability. The rate of groundwater discharge is not significantly enhanced or diminished around the thrust fault zones, suggesting that in a regional scale, permeability of fault zones is not significantly different from the bedrock permeability at shallow depth in this old, tectonically- inactive orogen.

  2. Crustal structure of the alaska range orogen and denali fault along the richardson highway

    USGS Publications Warehouse

    Fisher, M.A.; Pellerin, L.; Nokleberg, W.J.; Ratchkovski, N.A.; Glen, J.M.G.

    2007-01-01

    A suite of geophysical data obtained along the Richardson Highway crosses the eastern Alaska Range and Denali fault and reveals the crustal structure of the orogen. Strong seismic reflections from within the orogen north of the Denali fault dip as steeply as 25?? north and extend downward to depths between 20 and 25 km. These reflections reveal what is probably a shear zone that transects most of the crust and is part of a crustal-scale duplex structure that probably formed during the Late Cretaceous. These structures, however, appear to be relict because over the past 20 years, they have produced little or no seismicity despite the nearby Mw = 7.9 Denali fault earthquake that struck in 2002. The Denali fault is nonreflective, but we interpret modeled magnetotelluric (MT), gravity, and magnetic data to propose that the fault dips steeply to vertically. Modeling of MT data shows that aftershocks of the 2002 Denali fault earthquake occurred above a rock body that has low electrical resistivity (>10 ohm-m), which might signify the presence of fluids in the middle and lower crust. Copyright ?? 2007 The Geological Society of America.

  3. Description of data base management systems activities

    NASA Technical Reports Server (NTRS)

    1983-01-01

    One of the major responsibilities of the JPL Computing and Information Services Office is to develop and maintain a JPL plan for providing computing services to the JPL management and administrative community that will lead to improved productivity. The CISO plan to accomplish this objective has been titled 'Management and Administrative Support Systems' (MASS). The MASS plan is based on the continued use of JPL's IBM 3032 Computer system for administrative computing and for the MASS functions. The current candidate administrative Data Base Management Systems required to support the MASS include ADABASE, Cullinane IDMS and TOTAL. Previous uses of administrative Data Base Systems have been applied to specific local functions rather than in a centralized manner with elements common to the many user groups. Limited capacity data base systems have been installed in microprocessor based office automation systems in a few Project and Management Offices using Ashton-Tate dBASE II. These experiences plus some other localized in house DBMS uses have provided an excellent background for developing user and system requirements for a single DBMS to support the MASS program.

  4. Hybrid energy storage systems utilizing redox active organic compounds

    DOEpatents

    Wang, Wei; Xu, Wu; Li, Liyu; Yang, Zhenguo

    2015-09-08

    Redox flow batteries (RFB) have attracted considerable interest due to their ability to store large amounts of power and energy. Non-aqueous energy storage systems that utilize at least some aspects of RFB systems are attractive because they can offer an expansion of the operating potential window, which can improve on the system energy and power densities. One example of such systems has a separator separating first and second electrodes. The first electrode includes a first current collector and volume containing a first active material. The second electrode includes a second current collector and volume containing a second active material. During operation, the first source provides a flow of first active material to the first volume. The first active material includes a redox active organic compound dissolved in a non-aqueous, liquid electrolyte and the second active material includes a redox active metal.

  5. The Grenville Orogenic Cycle (ca. 1350-1000 Ma): an Adirondack perspective

    NASA Astrophysics Data System (ADS)

    McLelland, James; Daly, J. Stephen; McLelland, Jonathan M.

    1996-11-01

    The Adirondack Mountains are characterized by three major events that took place during the interval ca. 1350-1000 Ma. The earliest of these is the arc-related Elzevirian Orogeny (ca. 1350-1185 Ma) during which substantial volumes of juvenile calc-alkaline crust were added to the Adirondacks as well as to the northwest segment of the Central Metasedimentary Belt. Data from the southwestern United States as well as from Ireland and Baltica indicate that Elzevirian magmatism and orogeny were of global dimensions. Within the southwestern sector of the Grenville Province, the Elzevirian Orogeny culminated at ca. 1185 Ma when accretion of all outboard terranes was completed. Compressional orogeny related to this convergence resulted in overthickened crust and lithosphere which subsequently delaminated giving rise to orogen collapse and AMCG magmatism that swept southeastward from the Frontenac Terrane into the Adirondack Highlands during the interval ca. 1180-1130 Ma. Localized compressional events within neighboring parts of the Grenville Province emphasize the continued existence of contraction during this interval, although crustal extension caused local in sedimentary basins in which were deposited the Flinton and the St. Boniface Groups. The Adirondacks have not yet provided any record of events within the interval ca. 1125-1100 Ma, although there is evidence of contraction elsewhere in the southwestern Grenville Province at that time. At 1100-1090 Ma the northern Adirondack Highlands were invaded by mildly A-type hornblende granites (Hawkeye suite) that are interpreted to be the result of local crustal thinning contemporaneous with rifting and mafic magmatism taking place in the Midcontinent rift. Immediately following, at ca. 1090 Ma, the global-scale continental collision of the Ottawan Orogeny was initiated. Strong convergence, deformation, and metamorphism continued to at least ca. 1070 Ma, and rocks older than this are profoundly affected by this event

  6. Experimental acquisition system for impedance tomography with active electrode approach.

    PubMed

    Rigaud, B; Shi, Y; Chauveau, N; Morucci, J P

    1993-11-01

    An experimental system for impedance tomography has been constructed. The acquisition system uses 16 multifunctional active electrodes, each including a current source and a voltage buffer. Images of active and reactive parts of different target impedances in a phantom filled with liquid have been obtained. The system performance has been compared with those of other systems using either a mesh phantom or rods as point sources used for the determination of the modulation transfer function. PMID:8145585

  7. An analysis of the daily precipitation variability in the Himalayan orogen using a statistical parameterisation and its potential in driving landscape evolution models with stochastic climatic forcing

    NASA Astrophysics Data System (ADS)

    Deal, Eric; Braun, Jean

    2015-04-01

    A current challenge in landscape evolution modelling is to integrate realistic precipitation patterns and behaviour into longterm fluvial erosion models. The effect of precipitation on fluvial erosion can be subtle as well as nonlinear, implying that changes in climate (e.g. precipitation magnitude or storminess) may have unexpected outcomes in terms of erosion rates. For example Tucker and Bras (2000) show theoretically that changes in the variability of precipitation (storminess) alone can influence erosion rate across a landscape. To complicate the situation further, topography, ultimately driven by tectonic uplift but shaped by erosion, has a major influence on the distribution and style of precipitation. Therefore, in order to untangle the coupling between climate, erosion and tectonics in an actively uplifting orogen where fluvial erosion is dominant it is important to understand how the 'rain dial' used in a landscape evolution model (LEM) corresponds to real precipitation patterns. One issue with the parameterisation of rainfall for use in an LEM is the difference between the timescales for precipitation (≤ 1 year) and landscape evolution (> 103 years). As a result, precipitation patterns must be upscaled before being integrated into a model. The relevant question then becomes: What is the most appropriate measure of precipitation on a millennial timescale? Previous work (Tucker and Bras, 2000; Lague, 2005) has shown that precipitation can be properly upscaled by taking into account its variable nature, along with its average magnitude. This captures the relative size and frequency of extreme events, ensuring a more accurate characterisation of the integrated effects of precipitation on erosion over long periods of time. In light of this work, we present a statistical parameterisation that accurately models the mean and daily variability of ground based (APHRODITE) and remotely sensed (TRMM) precipitation data in the Himalayan orogen with only a few

  8. Practical engineering: control of active systems using the stagnation temperature

    SciTech Connect

    Lunde, P.J.

    1982-04-01

    Solar active systems with flat plate collectors are discussed with reference to the temperature at which the system should be activated. It is concluded that the system should be activated when the stagnation temperature (temperature under the absorber plate when no fluid is circulating) equals the temperature of the fluid in storage. A thermistor Wheatstone bridge control system is described which will eliminate pump relay chatter and the permissible control differential is calculated from the collector efficiency curve. To avoid dedication of an entire collector to house the control system, a method is described for determining the stagnation temperature using a portion of an active collector. For an active solar hot water system, a calculation is carried out to show that a 2/sup 0/F temperature differential (stagnation temperature-storage temperature) is satisfactory. (MJJ)

  9. Electricity/Electronics Systems. Laboratory Activities.

    ERIC Educational Resources Information Center

    Sutherland, Barbara, Ed.

    This electricity/electronics guide provides teachers with learning activities for secondary students. Introductory materials include an instructional planning outline and worksheet, an outline of essential elements, a list of objectives, a course description, and a content outline. The guide contains 35 modules on the following topics: electrical…

  10. The Permian post-orogenic collapse in the Alps: insights from the Campo unit (Austroalpine nappes, N-Italy, SE-Switzerland)

    NASA Astrophysics Data System (ADS)

    Petri, Benoît; Mohn, Geoffroy; Štípská, Pavla; Manatschal, Gianreto; Schulmann, Karel

    2014-05-01

    the ~290 Ma (U-Pb on zircon) mafic intrusion give conditions of ~6 kbar and > 900°C. Our results bring constrains on the thermal and mechanical relation between the pluton and the host rock in the middle crust and confirm the mid-crustal position of the Campo unit during the Permian. Furthermore, this study highlights the contrasted evolution of mid-crustal levels compared to lower-crustal systems such as the Ivrea zone. Eventually at a larger scale, these results provide insights on the tectonic and magmatic processes and thermal conditions of the continental crust during Variscan post-orogenic evolution.

  11. A network extraction tool for mineral exploration: a case study from the Wopmay Orogen, Northwest Territories, Canada

    NASA Astrophysics Data System (ADS)

    Lee, Madeline; Morris, William; Harris, Jeff; Leblanc, George

    2012-03-01

    Many mineral exploration initiatives target regional- and local-scale lineaments (e.g. fault systems and dyke swarms) as they may act as conduits for mineralized fluids. In this work, we apply an automatic lineament `network extraction' method that draws on similar processes as the Blakely-Simpson peak detection algorithm and a stream network extraction algorithm commonly used in the mapping of drainage patterns from a topographic surface (e.g. DEM, DTM) within a Geographic Information System (GIS) environment. We apply the network extraction algorithm to a magnetic surface (grid) rather than a topographic surface. The method uses a simple quadratic surface across a 3×3 window to determine the degree of surface slope and if the centre cell of the window represents a localised low point in the surface. Thus this routine is particularly effective at identifying magnetic lows that may represent faults, which have undergone magnetite depletion (e.g. hematization). These lineament solutions provide insight into mineral exploration vectors through the computation of rose diagrams, fracture density plots and intersection locations. These diagrams, plots, and locations are used in conjunction with other geophysical layers (e.g. radiometrics) to help identify potential mineral exploration targets. We successfully applied this algorithm to an aeromagnetic dataset from the Wopmay Orogen in Northwestern Canada. This area is characterised by extensive regional and localised fault systems and dyke swarms, along with promising polymetallic hydrothermal mineral occurrences. Key areas for follow up exploration are identified through a combined study of geophysical grids and lineament analysis.

  12. Geochronological and geochemical constraints on the Lüliang Group in the Lüliang Complex: Implications for the tectonic evolution of the Trans-North China Orogen

    NASA Astrophysics Data System (ADS)

    Liu, Chaohui; Zhao, Guochun; Liu, Fulai; Shi, Jianrong

    2014-06-01

    The Lüliang Complex is located at the western margin of the middle segment of the Trans-North China Orogen, along which the Western and Eastern Blocks amalgamated to form the basement of the North China Craton. The complex consists of the late Neoarchean to Paleoproterozoic granitic plutons and meta-supracrustal rocks, of which the latter are subdivided into the Jiehekou, Lüliang, Yejishan, and Heichashan/Lanhe Groups. The Lüliang Group is composed mainly of siliciclastic rocks in the lower part and volcanic rocks in the upper part, all of which have been metamorphosed from greenschist- to amphibolite-facies. U-Pb ages of detrital zircons from meta-sedimentary rocks in the Lüliang Group yield four populations of 3061-2920 Ma, 2790-2600 Ma, 2599-2280 Ma and 2211-2202 Ma, suggesting that their provenances were derived mainly from the Lüliang and Taihua Complexes in the Trans-North China Orogen. The meta-volcanic rocks give igneous zircon U-Pb ages of 2209-2178 Ma and εHf(t) values of - 0.8 to + 3.6. Geochemically, they are subalkaline basalts and andesites that can be classified into two groups, of which one group has flat LREEs, weak enrichment in LREEs relative to HREEs and flat HREEs and displays E-MORB-like spider diagrams with the exception of insignificantly negative Nb-Ta, Zr-Hf and Ti anomalies. In contrast, the other group displays stronger LREE fractionation, stronger enrichment in LREEs relative to HREEs and mildly fractionated HREEs and is characterized by “spiky” spider diagrams similar to arc volcanic rocks. The first group is interpreted to have originated from a Neoarchean E-MORB source, whereas the second group shows inputs of newly subduction-derived fluids in the mantle source. These geochronological and geochemical signatures indicate the existence of an 2.2-2.1 Ga continental back-arc system in the Lüliang Complex of the Trans-North China Orogen, which is consistent with the model that the collision between the Eastern and Western

  13. Kinematic evolution of an intracontinental convergent orogen from the analysis of syntectonic sediments in piggy-back basins. Application to the South-Central Pyrenees

    NASA Astrophysics Data System (ADS)

    Beamud, Elisabet; Muñoz, Josep Anton; Garcés, Miguel; Fitzgerald, Paul G.; Cabrera, Lluis

    2014-05-01

    The Pyrenees are an asymmetric, doubly vergent orogen formed by the collision between the European and Iberian plates from late Cretaceous to Miocene times. The high subsidence rates in the South-Central Pyrenees intramontane basins and the fact that the South Pyrenean foreland basin became endorheic from Late Eocene until Middle Miocene times favoured an unusual and excellent preservation of thick packages of synorogenic sediments on its southern flank. Analysis of synorogenic sediments preserved in sedimentary basins adjacent to an orogen contributes significantly towards a better understanding of the coupled evolution of the mountain belt and the basin. Geometric relationships between tectonic structures and synorogenic materials provide a relative chronology of events, however the precise timing and rate of deposition and deformation can only be attained with absolute ages. Magnetostratigraphy provides near-continuous absolute ages of sedimentary successions, allowing timing and quantification of the tectonic processes to be determined when applied to syntectonic sediments. Additionally, ages provided by detrital thermochronology, especially if combined with in-situ thermochronology of the source region, yield constraints on the exhumation (timing, magnitudes and rates) and tectonic history of the orogen as well as changes in sediment provenance and landscape evolution. In this work we present the Cenozoic kinematic evolution of the South-Central Pyrenees, integrating structural, sedimentological, magnetostratigraphic, magnetotectonic and thermochronological analyses of synorogenic strata. The magnetostratigraphic and thermochronological ages obtained permit the link between the sedimentation rates in the surrounding basins and the exhumation rates in the hinterland. This reveals that accommodation space was the main control on sedimentation rates within the piggy-back basins. Our results highlight a strong relationship between the structural evolution of the

  14. MARS PATHFINDER PYRO SYSTEMS SWITCHING ACTIVITY

    NASA Technical Reports Server (NTRS)

    1996-01-01

    The Mars Pathfinder lander is subjected to electrical and functional tests of its pyrotechic petal deployer system by Jet Propulsion Laboratory (JPL) engineers and technicians in KSC's Spacecraft Assembly and Encapsulation Facility (SAEF-2). When the lander touches down on the surface of Mars next year, the pyrotechnic system will deploy its three petals open like a flower and allow the Sojourner autonomous rover to explore the Martian surface. The Mars Pathfinder is scheduled for launch aboard a Delta II expendable launch vehicle on Dec. 2, the beginning of a 24-day launch period. JPL is managing the Mars Pathfinder project for NASA.

  15. PEGASUS: Designing a System for Supporting Group Activity

    ERIC Educational Resources Information Center

    Kyprianidou, Maria; Demetriadis, Stavros; Pombortsis, Andreas; Karatasios, George

    2009-01-01

    Purpose: The purpose of this paper is to present the design and first results of the integration of a web-based system person-centred group-activity support system (PEGASUS) in university instruction, as a means for advancing person-centred learning by supporting group activity. The PEGASUS is expected to help students and teachers in two distinct…

  16. Applying an Activity System to Online Collaborative Group Work Analysis

    ERIC Educational Resources Information Center

    Choi, Hyungshin; Kang, Myunghee

    2010-01-01

    This study determines whether an activity system provides a systematic framework to analyse collaborative group work. Using an activity system as a unit of analysis, the research examined learner behaviours, conflicting factors and facilitating factors while students engaged in collaborative work via asynchronous computer-mediated communication.…

  17. Entry-Level Activities in System Consultation

    ERIC Educational Resources Information Center

    Hylander, Ingrid

    2014-01-01

    System-level consultation or organizational development in schools is an area in great need of theoretical models and definitions. The three articles in this special issue provide a unique learning opportunity not only for consultation across borders but also for consultation within the same nation. In my commentary, I limit my remarks to a few…

  18. Methodology for the systems engineering process. Volume 1: System functional activities

    NASA Technical Reports Server (NTRS)

    Nelson, J. H.

    1972-01-01

    Systems engineering is examined in terms of functional activities that are performed in the conduct of a system definition/design, and system development is described in a parametric analysis that combines functions, performance, and design variables. Emphasis is placed on identification of activities performed by design organizations, design specialty groups, as well as a central systems engineering organizational element. Identification of specific roles and responsibilities for doing functions, and monitoring and controlling activities within the system development operation are also emphasized.

  19. From hyper-extended rifts to orogens: the example of the Mauléon rift basin in the Western Pyrenees (SW France)

    NASA Astrophysics Data System (ADS)

    Masini, E.; Manatschal, G.; Tugend, J.

    2011-12-01

    An integral part of plate tectonic theory is that the fate of rifted margins is to be accreted into mountain belts. Thus, rift-related inheritance is an essential parameter controlling the evolution and architecture of collisional orogens. Although this link is well accepted, rift inheritance is often ignored. The Pyrenees, located along the Iberian and European plate boundary, can be considered as one of the best places to study the reactivation of former rift structures. In this orogen the Late Cretaceous and Tertiary convergence overprints a Late Jurassic to Lower Cretaceous complex intracontinental rift system related to the opening of the North Atlantic. During the rifting, several strongly subsiding basins developed in the axis of the Pyrenees showing evidence of extreme crustal extension and even locale mantle exhumation to the seafloor. Although the exact age and kinematics of rifting is still debated, these structures have an important impact in the subsequent orogenic overprint. In our presentation we discuss the example of the Mauléon basin, which escaped from the most pervasive deformations because of its specific location at the interface between the western termination of the chain and the Bay of Biscay oceanic realm. Detailed mapping combined with seismic reflection, gravity data and industry wells enabled to determine the 3D rift architecture of the Mauléon basin. Two major diachronous detachment systems can be mapped and followed through space. The Southern Mauléon Detachment (SMD) develops first, starts to thin the crust and floors the Southern Mauléon sub-Basin (SMB). The second, the Northern Mauléon Detachment (SMD) is younger and controls the final crustal thinning and mantle exhumation to the north. Both constitute the whole Mauléon basin. Like at the scale of the overall Pyrenees, the reactivation of the Mauléon Basin increases progressively from west to east, which enables to document the progressive reactivation of an aborted hyper

  20. A microscopic field theoretical approach for active systems

    NASA Astrophysics Data System (ADS)

    Alaimo, F.; Praetorius, S.; Voigt, A.

    2016-08-01

    We consider a microscopic modeling approach for active systems. The approach extends the phase field crystal (PFC) model and allows us to describe generic properties of active systems within a continuum model. The approach is validated by reproducing results obtained with corresponding agent-based and microscopic phase field models. We consider binary collisions, collective motion and vortex formation. For larger numbers of particles we analyze the coarsening process in active crystals and identify giant number fluctuation in a cluster formation process.

  1. Motor Cortex Activity Organizes the Developing Rubrospinal System

    PubMed Central

    Williams, Preston T.J.A.

    2015-01-01

    The corticospinal and rubrospinal systems function in skilled movement control. A key question is how do these systems develop the capacity to coordinate their motor functions and, in turn, if the red nucleus/rubrospinal tract (RN/RST) compensates for developmental corticospinal injury? We used the cat to investigate whether the developing rubrospinal system is shaped by activity-dependent interactions with the developing corticospinal system. We unilaterally inactivated M1 by muscimol microinfusion between postnatal weeks 5 and 7 to examine activity-dependent interactions and whether the RN/RST compensates for corticospinal tract (CST) developmental motor impairments and CST misprojections after M1 inactivation. We examined the RN motor map and RST cervical projections at 7 weeks of age, while the corticospinal system was inactivated, and at 14 weeks, after activity returned. During M1 inactivation, the RN on the same side showed normal RST projections and reduced motor thresholds, suggestive of precocious development. By contrast, the RN on the untreated/active M1 side showed sparse RST projections and an immature motor map. After M1 activity returned later in adolescent cat development, RN on the active M1/CST side continued to show a substantial loss of spinal terminations and an impaired motor map. RN/RST on the inactivated side regressed to a smaller map and fewer axons. Our findings suggest that the developing rubrospinal system is under activity-dependent regulation by the corticospinal system for establishing mature RST connections and RN motor map. The lack of RS compensation on the non-inactivated side can be explained by development of ipsilateral misprojections from the active M1 that outcompete the RST. SIGNIFICANCE STATEMENT Skilled movements reflect the activity of multiple descending motor systems and their interactions with spinal motor circuits. Currently, there is little insight into whether motor systems interact during development to

  2. MARS PATHFINDER PYRO SYSTEMS SWITCHING ACTIVITY

    NASA Technical Reports Server (NTRS)

    1996-01-01

    The Mars Pathfinder lander is subjected to a electrical and functional tests of its pyrotechic petal deployer system by Jet Propulsion Laboratory (JPL) engineers and technicians in KSC's Spacecraft Assembly and Encapsulation Facility (SAEF-2). In the background is the Pathfinder cruise stage, which the lander will be mated to once its functional tests are complete. The lander will remain attached to this stage during its six-to-seven-month journey to Mars. When the lander touches down on the surface of Mars next year, the pyrotechnic system will deploy its three petals open like a flower and allow the Sojourner autonomous rover to explore the Martian surface. The Mars Pathfinder is scheduled for launch aboard a Delta II expendable launch vehicle on Dec. 2, the beginning of a 24-day launch period. JPL is managing the Mars Pathfinder project for NASA.

  3. MARS PATHFINDER PYRO SYSTEMS SWITCHING ACTIVITY

    NASA Technical Reports Server (NTRS)

    1996-01-01

    The Mars Pathfinder lander is subjected to a electrical test of its pyrotechnic system by Jet Propulsion Laboratory (JPL) engineers Lorraine Garcia (foreground) and Linda Robeck in KSC's Spacecraft Assembly and Encapsulation Facility (SAEF-2). A wheel of the Sojourner autonomous rover, which is attached to one of the lander's petals, can be seen behind the lander. When the lander touches down on the surface of Mars next year, the pyrotechnic system will deploy its three petals open like a flower and allow the rover to explore the Martian surface. The Mars Pathfinder is scheduled for launch aboard a Delta II expendable launch vehicle on Dec. 2, the beginning of a 24-day launch period. JPL is managing the Mars Pathfinder project for NASA.

  4. MARS PATHFINDER PYRO SYSTEMS SWITCHING ACTIVITY

    NASA Technical Reports Server (NTRS)

    1996-01-01

    The Mars Pathfinder lander is subjected to a test of its pyrotechnic system by Jet Propulsion Laboratory (JPL) engineer Jerry Gutierrez in KSC's Spacecraft Assembly and Encapsulation Facility (SAEF-2). A wheel of the Sojourner autonomous rover, which is attached to one of the lander's petals, can be seen behind the lander. When the lander touches down on the surface of Mars next year, the pyrotechnic system will deploy its three petals open like a flower and allow the rover to explore the Martian surface. The Mars Pathfinder is scheduled for launch aboard a Delta II expendable launch vehicle on Dec. 2, the beginning of a 24-day launch period. JPL is managing the Mars Pathfinder project for NASA.

  5. A fuselage/tank structure study for actively cooled hypersonic cruise vehicles: Active cooling system analysis

    NASA Technical Reports Server (NTRS)

    Stone, J. E.

    1975-01-01

    The effects of fuselage cross section and structural arrangement on the performance of actively cooled hypersonic cruise vehicles are investigated. An active cooling system which maintains the aircraft's entire surface area at temperatures below 394 K at Mach 6 is developed along with a hydrogen fuel tankage thermal protection system. Thermodynamic characteristics of the actively cooled thermal protection systems established are summarized. Design heat loads and coolant flowrate requirements are defined for each major structural section and for the total system. Cooling system weights are summarized at the major component level. Conclusions and recommendations are included.

  6. Ain't No Mountain High Enough: Reconstructing Paleoelevation of Eroded Orogens

    NASA Astrophysics Data System (ADS)

    Mulch, A.; Teyssier, C.; Chamberlain, C. P.; Vennemann, T.; Cosca, M.; Wells, M.

    2004-12-01

    Quantitative paleoelevation reconstructions are a key element in understanding the relationships among uplift, erosion, and the demise of orogens. We present a new approach of determining paleoelevation based on the stable isotope composition of meteoric water that interacted with detachment mylonite during exhumation and uplift. Provided that this interaction is precisely dated and temporally linked to the stable isotope record in syntectonic basins this approach relates the tectonic, sedimentary and climate history of the orogen. Hydrogen, oxygen and Ar-Ar data from extensional detachments of the Shuswap, Kettle and Raft River core complexes and their adjacent basins, allow us to reconstruct discrete episodes in the Cenozoic elevation history of the North American Cordillera. Our data are consistent with a southward migration of a topographic high from Eocene to Miocene times, as reflected in the sequential onset of detachment faulting and extensional collapse in the Cordilleran hinterland. The integrated oxygen and hydrogen isotope data show that meteoric waters infiltrating the early to middle Eocene (49.0 - 47.0 Ma) eastern detachments of the Shuswap (British Columbia) and Kettle (Washington) core complexes had very negative hydrogen isotope values (-135 and -120 permil, respectively). These results require mean elevations in excess of 4000 m immediately preceding the timing of extensional deformation. Preliminary hydrogen (meteoric fluid compositions of -100 to -110 permil) and oxygen isotope data from Oligocene and Miocene mylonites of the Raft River complex (Utah) indicate that at lower latitudes high elevations persisted until Oligocene/Miocene times, a conclusion consistent with stable isotope data derived from syntectonic sedimentary deposits in the adjacent Elko Basin (Nevada). The coupled Eocene to Miocene data sets derived from rocks that at the time were at several km depth indicate that crustal thickening prior to detachment faulting resulted in

  7. Lawsonite Blueschists in Recycled Mélange Involved in K-Rich Orogenic Magmatism

    NASA Astrophysics Data System (ADS)

    Wang, Y.; Prelevic, D.; Foley, S. F.; Buhre, S.; Galer, S. J. G.

    2014-12-01

    The origin of K-rich orogenic magmatism in the Alpine-Himalayan belt and its relationship to the large-scale elevations in several massifs of the orogen is controversial, particularly the significance of the widespread presence of a geochemical signal typical for recycled continental crust. Two competing scenarios invoke direct melting of continental crust during deep intercontinental subduction and removal of heavily metasomatised mantle lithosphere by delamination into the convecting mantle. Here we investigate the coupling of high Th/La ratio with crustal isotopic signatures in K-rich orogenic lavas that does not occur in volcanic rocks from other collisional environments to distinguish between these two models. High-pressure experimental results on a phyllite representing upper crustal composition and a detailed mineral and geochemical study of blueschists from Tavşanlı mélange, Turkey, indicate that this geochemical fingerprint originates by melting of subducted mélange. Melting of crust at the top of the subducted continental lithosphere cannot produce observed fingerprint, whereas lawsonites, especially those with terrigenous sediment origin from blueschists with high Th/La can. Lawsonites that grow in various components of a subduction mélange inherit the geochemical characteristics of either oceanic or continental protoliths. It is currently uncertain whether those carrying the high Th/La signature originate by direct melting of continental blocks in the mélange or by the introduction of supercritical fluids from lawsonite blueschist of continental origin that infiltrate oceanic sediment blocks. Either way, the high Th/La is later released into subsequently formed melts. This confirms the supposition that lawsonite is the main progenitor of the high Th/La and Sm/La ratio. However, lawsonite must break down completely to impart this unique feature to subsequent magmas. The source regions of the potassic volcanic rocks consist of blueschist facies m

  8. New constraints on fluid sources in orogenic gold deposits, Victoria, Australia

    NASA Astrophysics Data System (ADS)

    Fu, Bin; Kendrick, Mark A.; Fairmaid, Alison M.; Phillips, David; Wilson, Christopher J. L.; Mernagh, Terrence P.

    2012-03-01

    Fluid inclusion microthermometry, Raman spectroscopy and noble gas plus halogen geochemistry, complemented by published stable isotope data, have been used to assess the origin of gold-rich fluids in the Lachlan Fold Belt of central Victoria, south-eastern Australia. Victorian gold deposits vary from large turbidite-hosted `orogenic' lode and disseminated-stockwork gold-only deposits, formed close to the metamorphic peak, to smaller polymetallic gold deposits, temporally associated with later post-orogenic granite intrusions. Despite the differences in relative timing, metal association and the size of these deposits, fluid inclusion microthermometry indicates that all deposits are genetically associated with similar low-salinity aqueous, CO2-bearing fluids. The majority of these fluid inclusions also have similar 40Ar/36Ar values of less than 1500 and 36Ar concentrations of 2.6-58 ppb (by mass) that are equal to or much greater than air-saturation levels (1.3-2.7 ppb). Limited amounts of nitrogen-rich fluids are present at a local scale and have the highest measured 40Ar/36Ar values of up to 5,700, suggesting an external or distinct source compared to the aqueous fluids. The predominance of low-salinity aqueous-carbonic fluids with low 40Ar/36Ar values, in both `orogenic' and `intrusion-related' gold deposits, is attributed to fluid production from common basement volcano-sedimentary sequences and fluid interaction with sedimentary cover rocks (turbidites). Aqueous fluid inclusions in the Stawell-Magdala deposit of western Victoria (including those associated with N2) preserve mantle-like Br/Cl and I/Cl values. In contrast, fluid inclusions in deposits in the eastern structural zones, which contain more abundant shales, have elevated molar I/Cl ratios with maximum values of 5,170 × 10-6 in the Melbourne Zone. Br/I ratios in this zone range from 0.5 to 3.0 that are characteristic of fluid interaction with organic-rich sediments. The maximum I/Cl and characteristic

  9. South Tien Shan orogenic belt: structure, magmatism and gold mineralization (Uzbekistan)

    NASA Astrophysics Data System (ADS)

    Koneev, Rustam; Seltmann, Reimer

    2014-05-01

    The Southern Tien Shan represents one of the key units of the Central Asian orogenic belt in Uzbekistan. Together with the Beltau-Kurama volcano-plutonic arc it formed as a result of subduction of the crust under the Turkistan paleoocean and the Kazakhstan continent, followed by collision and post-collisional strike-slip processes. The Southern Tien Shan is of particular interest due to its gold mineralisation. It hosts the giant Muruntau gold deposit and the large gold deposits of Amantaitau, Daugyztau, Myutenbay (Kyzylkum ore district) and Charmitan, Guzhumsay, Urtalik (Nurata ore district). The Middle Tienshan hosts within the Beltau-Kurama volcano-plutonic arc the Kurama ore district with the giant Kalmakyr Cu-Au porphyry and large epithermal Au-Ag deposits of Kochbulak and Kyzylalma. Yakubchuk et al. (2005) and others stress that the largest ore clusters are confined by the intersections of volcano-plutonic belts and transform faults in result of sinistral strike slip dislocations during the Permo-Carboniferous. Others believe that the ore giants are in addition controlled by hot spots - a mantle plume, superimposed on the crust architecture shaped by the subduction processes. Zircon U-Pb geochronology of main intrusive massifs of Uzbekistan (CERCAMS data) showed that granitoid magmatism is predominantly of postcollisional age, manifested in the accretionary units at 270-290 Ma, whereas subduction magmatism prevails as characteristic in the volcano-plutonic arc at 300-320 Ma. Determination of sulphide mineralization ages using Os-Re method (CERCAMS data), are respectively 283-289 Ma and 298-314 Ma. The studies were performed in the framework of IGCP- 592. References 1. Yakubchuk A.S., Shatov V.V., Kirwin D. et al., (2005) Gold and base metal metallogeny of the Central Asian Orogenic supercollage: Society of Economic Geologists, Inc. Economic Geology, 100th, Anniversary Volume, 1035-1068. 2. Groves, D.I., Goldfarb, R.J., Gebre-Mariam, M., Hagemann, S.G. and

  10. Orogenic development of the Adrar des Iforas (Tuareg Shield, NE Mali): new geochemical and geochronological data and geodynamic implications

    NASA Astrophysics Data System (ADS)

    Bosch, Delphine; Bruguier, Olivier; Caby, Renaud; Buscail, Francois; Hammor, Dalila

    2016-04-01

    Laser-ablation U-Th-Pb analyses of zircon and allanite from magmatic and metamorphic rocks of the Adrar des Iforas (Northern Mali) allow re-examining the relationships between the different crustal units constituting the western part of the Tuareg Shield, as well as the timing of magmatic and metamorphic events in the West Gondwana Orogen. Granulite-facies metamorphism in the Iforas Granulitic Unit (IGU) and at In Bezzeg occurred at 1986 ± 7 Ma and 1988 ± 5 Ma respectively. This age is slightly younger, but consistent with that of the HT granulite facies event characterizing the In Ouzzal granulitic unit (IOGU), thereby substantiating the view that these units once formed a single granulitic belt of c. 800 km long. High-grade metamorphic basement units of the Kidal terrane surrounding the IGU contain Paleoproterozoic magmatic rocks crystallized between 1982 ± 8 Ma and 1966 ± 9 Ma. Inherited components in these rocks (2.1 Ga and 2.3-2.5 Ga) have ages similar to that of detrital zircons at In Bezzeg and to that of basement rocks from the IGU. This is taken as evidence that the Kidal terrane and the IGU formed a single crustal block at least until 1.9 Ga. East of the Adrar fault, the Tin Essako orthogneiss is dated at 2020 ± 5 Ma, but escaped granulite facies metamorphism. During the Neoproterozoic, the Kidal terrane underwent a long-lived continental margin magmatism. To the west, this terrane is bounded by the Tilemsi intra-oceanic island arc, for which a gneissic sub-alkali granite was dated at 716 ± 6 Ma. A synkinematic diorite extends the magmatic activity of the arc down to 643 ± 4 Ma, and, along with litterature data, indicates that the Tilemsi arc had a life span of about 90 Ma. Backward docking to the western margin of the Kidal terrane is documented by migmatites dated at 628 ± 6 Ma. Subduction related processes and the development of the Kidal active margin was responsible for the development of a back-arc basin in the Tafeliant area, with

  11. Orogenic development of the Adrar des Iforas (Tuareg Shield, NE Mali): New geochemical and geochronological data and geodynamic implications

    NASA Astrophysics Data System (ADS)

    Bosch, Delphine; Bruguier, Olivier; Caby, Renaud; Buscail, François; Hammor, Dalila

    2016-05-01

    Laser-ablation U-Th-Pb analyses of zircon and allanite from magmatic and metamorphic rocks of the Adrar des Iforas in Northern Mali allow re-examining the relationships between the different crustal units constituting the western part of the Tuareg Shield, as well as the timing of magmatic and metamorphic events in the West Gondwana Orogen. Granulite-facies metamorphism in the Iforas Granulitic Unit (IGU) and at In Bezzeg occurred at 1986 ± 7 Ma and 1988 ± 5 Ma respectively. This age is slightly younger, but consistent with that of the HT granulite facies event characterizing the In Ouzzal granulitic unit (IOGU), thereby substantiating the view that these units once formed a single granulitic belt of c. 800 km long. High-grade metamorphic basement units of the Kidal terrane surrounding the IGU contain Paleoproterozoic magmatic rocks crystallized between 1982 ± 8 Ma and 1966 ± 9 Ma. Inherited components in these rocks (2.1 Ga and 2.3-2.5 Ga) have ages similar to that of detrital zircons at In Bezzeg and to that of basement rocks from the IGU. This is taken as evidence that the Kidal terrane and the IGU formed a single crustal block at least until 1.9 Ga. East of the Adrar fault, the Tin Essako orthogneiss is dated at 2020 ± 5 Ma, but escaped granulite facies metamorphism. During the Neoproterozoic, the Kidal terrane underwent a long-lived continental margin magmatism. To the west, this terrane is bounded by the Tilemsi intra-oceanic island arc, for which a gneissic sub-alkali granite was dated at 716 ± 6 Ma. A synkinematic diorite extends the magmatic activity of the arc down to 643 ± 4 Ma, and, along with literature data, indicates that the Tilemsi arc has a life span of about 90 Ma. Backward docking to the western margin of the Kidal terrane is documented by migmatites dated at 628 ± 6 Ma. Subduction related processes and the development of the Kidal active margin was responsible for the development of a back-arc basin in the Tafeliant area, with

  12. Segmentation and kinematics of the Kazerun fault system (southern Iran): Implications for active deformation partitioning within the Zagros fold-and-thrust belt

    NASA Astrophysics Data System (ADS)

    Authemayou, C. A.; Bellier, O. B.; Chardon, D. C.; Malekzade, Z. M.; Abbassi, M. A.

    2003-04-01

    Iran is located within the interaction zone between the Arabian and Eurasian plates that currently converge at 30 mm/yr. Since the Miocene, continental collision resulted in the formation of the NW-trending Zagros fold-and-thrust belt that accommodates c.a. 10 mm/yr of NNE-trending shortening. The southeastern part of the thrust belt is affected by the north-trending, right lateral Kazerun Fault System (KFS) stretching from the Main Reverse Fault (i.e., the back-stop of the fold-and-thrust belt) in the vicinity of Borujen, in the North, to the Persian Gulf coast near Kormuj, in the south. Reconnaissance tectonic and geomorphic observations, combined with SPOT satellite image analyses allows characterising the KFS active trace geometry and kinematics as well as its relations with the folds and the thrust faults. This further allows evaluating the transfer process from right-lateral slip along the KSF to the fold-and-thrust system. The KFS consists in three North-trending fault zones of equivalent lengths (100 km) that show evidence for a northward increasing activity. The southern terminations of the fault zones are bent towards SE strikes and are generally connected westward with WNW-trending thrusts and ramp anticlines. Those terminations display a horsetail splay fault geometry associated with an eastward decrease of both the strike-slip and dip-slip component of finite offsets. Fault slip-vectors analyses indicate a consistent right-lateral strike-slip tectonic regime all along the KFS associated with a regionally homogeneous NNE-trending 1 direction. The central and northern fault zones show evidence for systematic Quaternary right-lateral offsets of geomorphic features such as stream beds and alluvial fans, as well as shutter ridges and faceted spurs. The northern termination of the KFS shows the most obvious criteria for active slip and the highest geomorphic offsets. This fault zone connects the southeastern tip of the Main Recent Fault, the major active

  13. Tectonic evolution of the Montagne Noire and a possible orogenic model for syncollisional exhumation of deep rocks, Variscan belt, France

    NASA Astrophysics Data System (ADS)

    Aerden, Domingo G. A. M.

    1998-02-01

    Structural analysis in the Montagne Noire, including a study of inclusion trail patterns in andalusite, garnet, and staurolite porphyroblasts, reveals a succession of five foliations in alternately steep and flat-lying orientations. This is inferred to reflect multiple gravitational collapse phases that intervened during continuous plate convergence. Initial crustal thickening by foliation development and folding (D1) was responsible for eclogite-facies metamorphism in the gneissic basement. Subsequent thrusting and recumbent folding (D2) generated a subhorizontal crenulation cleavage during Namuro-Westphalian times, while previous steep structures became rotated. Petrological and microstructural evidence indicate that thrust nappes were emplaced by a gravitational spreading mechanism, while undergoing internal thinning. An important amount of basement exhumation took place synchronously. These observations form the basis for a new orogenic model in which thermal reequilibration of a previously thickened orogen induces gravitational instability in the upper crust. Collapse of the upper crust causes it to spreadout horizontally over continuously converging relatively cool plates thereby creating low-angle thrust nappes. The upper crustal thinning facilitates simultaneous extrusion of lower crust in vertical root zones at the orogen center, which on reaching the higher part of the orogen can be incorporated in the nappes and displaced horizontally. Following such a mechanism of nappe tectonics, renewed horizontal shortening (D3) produced the Montagne Noire gneissic dome by upright folding of nappe-related foliations with orogen-parallel stretching. Previous crustal thinning had led to an increased heat flux between basement and cover so that during D3, cover sequences were still rising in temerature, while basement rocks had already commenced their retrograde path during D2. Peak-metamorphic conditions in the cover triggered a second gravitational collapse during

  14. Active and intelligent packaging systems for a modern society.

    PubMed

    Realini, Carolina E; Marcos, Begonya

    2014-11-01

    Active and intelligent packaging systems are continuously evolving in response to growing challenges from a modern society. This article reviews: (1) the different categories of active and intelligent packaging concepts and currently available commercial applications, (2) latest packaging research trends and innovations, and (3) the growth perspectives of the active and intelligent packaging market. Active packaging aiming at extending shelf life or improving safety while maintaining quality is progressing towards the incorporation of natural active agents into more sustainable packaging materials. Intelligent packaging systems which monitor the condition of the packed food or its environment are progressing towards more cost-effective, convenient and integrated systems to provide innovative packaging solutions. Market growth is expected for active packaging with leading shares for moisture absorbers, oxygen scavengers, microwave susceptors and antimicrobial packaging. The market for intelligent packaging is also promising with strong gains for time-temperature indicator labels and advancements in the integration of intelligent concepts into packaging materials. PMID:25034453

  15. Active synchronization between two different chaotic dynamical system

    SciTech Connect

    Maheri, M.; Arifin, N. Md; Ismail, F.

    2015-05-15

    In this paper we investigate on the synchronization problem between two different chaotic dynamical system based on the Lyapunov stability theorem by using nonlinear control functions. Active control schemes are used for synchronization Liu system as drive and Rossler system as response. Numerical simulation by using Maple software are used to show effectiveness of the proposed schemes.

  16. Active synchronization between two different chaotic dynamical system

    NASA Astrophysics Data System (ADS)

    Maheri, M.; Arifin, N. Md; Ismail, F.

    2015-05-01

    In this paper we investigate on the synchronization problem between two different chaotic dynamical system based on the Lyapunov stability theorem by using nonlinear control functions. Active control schemes are used for synchronization Liu system as drive and Rossler system as response. Numerical simulation by using Maple software are used to show effectiveness of the proposed schemes.

  17. NASA's UAS [Unmanned Aircraft Systems] Related Activities

    NASA Technical Reports Server (NTRS)

    Bauer, Jeffrey

    2012-01-01

    NASA continues to operate all sizes of UAS in all classes of airspace both domestically and internationally. Missions range from highly complex operations in coordination with piloted aircraft, ground, and space systems in support of science objectives to single aircraft operations in support of aeronautics research. One such example is a scaled commercial transport aircraft being used to study recovery techniques due to large upsets. NASA's efforts to support routine UAS operations continued on several fronts last year. At the national level in the United States (U.S.), NASA continued its support of the UAS Executive Committee (ExCom) comprised of the Federal Aviation Administration (FAA), Department of Defense (DoD), Department of Homeland Security (DHS), and NASA. The committee was formed in recognition of the need of UAS operated by these agencies to access to the National Airspace System (NAS) to support operational, training, development and research requirements. Recommendations were received on how to operate both manned and unmanned aircraft in class D airspace and plans are being developed to validate and implement those recommendations. In addition the UAS ExCom has begun developing recommendations for how to achieve routine operations in remote areas as well as for small UAS operations in class G airspace. As well as supporting the UAS ExCom, NASA is a participant in the recently formed Aviation Rule Making Committee for UAS. This committee, established by the FAA, is intended to propose regulatory guidance which would enable routine civil UAS operations. As that effort matures NASA stands ready to supply the necessary technical expertise to help that committee achieve its objectives. By supporting both the UAS ExCom and UAS ARC, NASA is positioned to provide its technical expertise across the full spectrum of UAS airspace access related topic areas. The UAS NAS Access Project got underway this past year under the leadership of NASA s Aeronautics

  18. Stable isotope and Ar/Ar evidence of prolonged multi-scale fluid flow during exhumation of orogenic crust: example from the Mont Blanc and Aar massifs (NW Alps)

    NASA Astrophysics Data System (ADS)

    Rolland, Yann; Rossi, Magali

    2015-04-01

    The spatial and temporal scales and the geometry of fluid pathways in a collisional orogen are investigated using stable isotope analysis (O, C, H) and 40Ar/39Ar dating of vein minerals formed at c. 11-16 Ma in the Mont Blanc and the Aar External Crystalline Massifs. In both massifs 40Ar/39Ar dating of veins adularia provides evidence for progressive crystallization from 16 to 9 Ma, and mainly at 11-12 Ma following veins opening during shear zone activity. The fluid flow duration thus ranges from 4 to 5 Ma in the two massifs. The δ18O values of vein quartz and calcite are similar to those of undeformed crystalline and sedimentary host-rocks, suggesting rock buffering, while carbon isotope ratios of vein calcites fall into three compositional groups. A-type veins have δ13C values that are buffered by the Helvetic metasediments, which suggests that these veins formed in a closed-system from a locally-derived CO2-rich fluid. The fluid in equilibrium with C-type veins has depleted δ13C values similar to mantle-CO2, while the intermediate δ13C values of B-type veins suggest mixing between the A-type and C-type fluids. These results are in agreement with crustal- to lithosphere-scale upward vertical fluid flow along vertical shear zones related to the strike-slip system bounding the Adriatic block since 16-20 Ma, connecting a deep-seated fluid to some downward flow in the sedimentary cover of External Crystalline Massifs.

  19. Late Mesozoic and Cenozoic thermotectonic evolution along a transect from the north China craton through the Qinling orogen into the Yangtze craton, central China

    NASA Astrophysics Data System (ADS)

    Hu, Shengbiao; Raza, Asaf; Min, Kyoungwon; Kohn, Barry P.; Reiners, Peter W.; Ketcham, Richard A.; Wang, Jiyang; Gleadow, Andrew J. W.

    2006-12-01

    Cretaceous and Cenozoic reactivation of the Triassic Qinling-Dabie orogen between the north China and Yangtze cratons resulted from the combined effects of Pacific subduction-back-arc extension in east China and collisions in west China. We report new apatite fission track and apatite and zircon (U-Th)/He data from east Qinling along a >400-km-long N-S transect from Huashan through the Qinling orogen to Huangling. The ages show a general pattern of younging northward. Three major cooling phases are defined by modeling the multiple thermochronologic data sets. The first phase occurred locally in the North and South Qinling during the late Triassic to early Jurassic, following heating associated with the Triassic Yangtze subduction and exhumation of the Wudang metamorphic core complex on the cratonal edge. A second phase represents regional exhumation between 100 and 60 Ma, coeval with rifting marked by the Late Cretaceous-Eocene (K2-E) red bed deposition in eastern China and possibly indicating a link with Pacific subduction-back-arc extension in eastern China; however, it may also have been superimposed by eastward tectonic escape resulting from the Lhasa-West Burma-Qiangtang-Indochina collision. The third cooling phase was initiated at ˜45 Ma exclusively in the north Qinling and in the footwall of the graben-bounding normal fault of the Weihe graben in the Lesser Qinling. We suggest the third phase was related to reactivation of the Qinling fault system as a result of eastward tectonic escape imposed by the India-Asia collision at ˜50 Ma.

  20. Retinal waves coordinate patterned activity throughout the developing visual system

    PubMed Central

    Ackman, James B.; Burbridge, Timothy J.; Crair, Michael C.

    2014-01-01

    Summary The morphologic and functional development of the vertebrate nervous system is initially governed by genetic factors and subsequently refined by neuronal activity. However, fundamental features of the nervous system emerge before sensory experience is possible. Thus, activity-dependent development occurring before the onset of experience must be driven by spontaneous activity, but the origin and nature of activity in vivo remains largely untested. Here we use optical methods to demonstrate in live neonatal mice that waves of spontaneous retinal activity are present and propagate throughout the entire visual system before eye opening. This patterned activity encompassed the visual field, relied on cholinergic neurotransmission, preferentially initiated in the binocular retina, and exhibited spatiotemporal correlations between the two hemispheres. Retinal waves were the primary source of activity in the midbrain and primary visual cortex, but only modulated ongoing activity in secondary visual areas. Thus, spontaneous retinal activity is transmitted through the entire visual system and carries patterned information capable of guiding the activity-dependent development of complex intra- and inter- hemispheric circuits before the onset of vision. PMID:23060192

  1. Paleozoic accretionary orogenesis in the eastern Beishan orogen: constraints from zircon U-Pb and 40Ar/39Ar geochronology

    NASA Astrophysics Data System (ADS)

    Ao, Songjian; Xiao, Wenjiao; Windley, Brian; Mao, Qigui

    2016-04-01

    The continental growth mechanism of the Altaids in Central Asia is still in controversy between models of continuous subduction-accretion versus punctuated accretion by closure of multiple oceanic basins. The Beishan orogenic belt, located in the southern Altaids, is a natural laboratory to address this controversy. Key questions that are heavily debated are: the closure time and subduction polarity of former oceans, the emplacement time of ophiolites, and the styles of accretion and collision. This paper reports new structural data, zircon ages and Ar-Ar dates from the eastern Beishan Orogen that provide information on the accretion process and tectonic affiliation of various terranes. Our geochronological and structural results show that the younging direction of accretion was northwards and the subduction zone dipped southwards under the northern margin of the Shuangyingshan micro-continent. This long-lived and continuous accretion process formed the Hanshan accretionary prism. Our field investigations show that the emplacement of the Xiaohuangshan ophiolite was controlled by oceanic crust subduction beneath the forearc accretionary prism of the Shuangyingshan-Mazongshan composite arc to the south. Moreover, we address the age and terrane affiliation of lithologies in the eastern Beishan orogen through detrital zircon geochronology of meta-sedimentary rocks. We provide new information on the ages, subduction polarities, and affiliation of constituent structural units, as well as a new model of tectonic evolution of the eastern Beishan orogen. The accretionary processes and crustal growth of Central Asia were the result of multiple sequences of accretion and collision of manifold terranes. Reference: Ao, S.J., Xiao, W., Windley, B.F., Mao, Q., Han, C., Zhang, J.e., Yang, L., Geng, J., Paleozoic accretionary orogenesis in the eastern Beishan orogen: Constraints from zircon U-Pb and 40Ar/39Ar geochronology. Gondwana Research, doi: http://dx.doi.org/10.1016/j

  2. Active Venting System Offshore Northern Norway

    NASA Astrophysics Data System (ADS)

    Chand, Shyam; Rise, Leif; Bellec, Valérie; Dolan, Margaret; Bøe, Reidulv; Thorsnes, Terje; Buhl-Mortensen, Pål; Buhl-Mortensen, Lene

    2008-07-01

    A combined sediment-sampling, high-resolution seismic, multiple echo sounder, and video survey was conducted offshore Vesterålen, northern Norway, in October 2007 as part of the ongoing Marine Area Database for Norwegian Coast and Oceanic Regions (MAREANO) program. MAREANO is a multidisciplinary seabed mapping program conducting physical, biological, and environmental mapping in the Lofoten/southern Barents Sea area. Data and analysis arising from this program will provide the basis for ecosystem-based management of Norway's coastal and offshore regions. The survey used multicorer, box corer, and grab samplers; a TOPAS parametric subbottom profiler; 18-, 38-, 70-, 120-, 200-, and 400-kilohertz echo sounders; and a CAMPOD camera system with two video cameras and lights mounted on an aluminum frame.

  3. Correlated Rotational Noise in Active Brownian Systems

    NASA Astrophysics Data System (ADS)

    Wagner, Caleb; Baskaran, Aparna

    We consider a system of self-propelled particles in a viscous medium for which the angle parametrizing the direction of particle propulsion is subject to correlated noise. The physics involved in the correlated noise is explored by deriving a modified Smoluchowski equation that governs the evolution of the probability distribution for particle positions and orientations. More precisely, given noise correlations that decay exponentially in time with decay constant ν, we give the modified Smoluchowski equation as a perturbative expansion in ν. While the physical origins of correlated noise may be diverse, we give one interpretation of the resulting dynamics in terms of inertial effects that are absent from the usual overdamped description of self-propelled particles in a viscous medium.

  4. Active control system for high speed windmills

    DOEpatents

    Avery, D.E.

    1988-01-12

    A pump stroke is matched to the operating speed of a high speed windmill. The windmill drives a hydraulic pump for a control. Changes in speed of a wind driven shaft open supply and exhaust valves to opposite ends of a hydraulic actuator to lengthen and shorten an oscillating arm thereby lengthening and shortening the stroke of an output pump. Diminishing wind to a stall speed causes the valves to operate the hydraulic cylinder to shorten the oscillating arm to zero. A pressure accumulator in the hydraulic system provides the force necessary to supply the hydraulic fluid under pressure to drive the actuator into and out of the zero position in response to the windmill shaft speed approaching and exceeding windmill stall speed. 4 figs.

  5. Active control system for high speed windmills

    DOEpatents

    Avery, Don E.

    1988-01-01

    A pump stroke is matched to the operating speed of a high speed windmill. The windmill drives a hydraulic pump for a control. Changes in speed of a wind driven shaft open supply and exhaust valves to opposite ends of a hydraulic actuator to lengthen and shorten an oscillating arm thereby lengthening and shortening the stroke of an output pump. Diminishing wind to a stall speed causes the valves to operate the hydraulic cylinder to shorten the oscillating arm to zero. A pressure accumulator in the hydraulic system provides the force necessary to supply the hydraulic fluid under pressure to drive the actuator into and out of the zero position in response to the windmill shaft speed approaching and exceeding windmill stall speed.

  6. Deep crustal structure and seismic expression of the central Appalachian orogenic belt

    SciTech Connect

    Herman, G.C. Rutgers Univ., New Brunswick, NJ )

    1992-03-01

    Deep-seismic reflection profiles across parts of the Central Appalachian orogenic belt indicate that the crust here includes an exposed Paleozoic fold-and-thrust belt that is mainly soled in Proterozoic Grenville basement. Translation strain in the foreland and Highlands resulting from Paleozoic orogenesis is as much as 25 km, exclusive of layer-parallel-shortening penetrative strains. This estimate is limited by the slight structural relief beneath the Pocono plateau and by the lack of extensive Cambrian-Ordovician cover beneath the sole thrust. Earlier estimates of translation strain are much higher. To the southwest, this parautochthonous region is separated by an unrecognized structural transition from the more allochthonous parts of the central and southern Appalachian overthrust belt, marked by significantly larger translation strains. Crustal architecture in the hinterland part of the region is poorly understood due to data gaps.

  7. Drainage Pattern, Along-Strike Topography and Three-Dimensional Construction of the Himalayan orogen

    NASA Astrophysics Data System (ADS)

    Yin, A.

    2005-12-01

    Past studies on the Himalayan orogen have mostly emphasized its 2-D evolution in cross-section view. As a result, how the orogen has grown in 3-D remains poorly understood. For example, it is not clear if the >1500-km long Main Central Thrust (MCT) and Main Boundary Thrust (MBT) were initiated synchronously along the whole orogen or started at one segment and then propagated laterally during subsequent fault motion. To clarify this issue, I examined the Himalayan drainage pattern, along-strike topography, and geometry and kinematics of growing contractional structures across both the Himalayan front and the Shillong Plateau. The main observations may be summarized as follows. (1) The five rivers that cut across the Himalaya are arranged approximately symmetric with respect to the Himalayan-arc axis (~85° E): the Arun River (87° E) is in the middle with the Sutlej (77° E) and Indus (72° E) Rivers in the west and the Subansiri (93° E) and Yalu-Brahmaputra (96° E) Rivers in the east. (2) Between the eastern and western syntaxes, south-flowing drainages east of 85.5° E are consistently deflected to the east by east-growing anticlines and thrusts, whereas drainages west of 85.5°E are deflected systematically to the west by west-growing anticlines and thrusts along the Himalayan front. The only region where no drainage deflection is observed is the Bhutan Himalaya. There all rivers flow straight across the Himalayan front. (3) The deflected drainage pattern indicates that the Shillong Plateau south of the eastern Himalaya has been growing westward. (4) The along-crest Himalayan topographic profile concaves downward, starting from ~5200 m just inside the two syntaxes and reaching 8848 m at Mt. Everest (~87° E). (5) There are a total of 17 major growing contractional structures in the Main Frontal Thrust Zone (MFTZ), with 10 in the west and 7 in the east. Each structure has a length between ~20 km and >150 km, but the west-growing structures in the west are

  8. Fault dating in the Canadian Rocky Mountains: Evidence for late Cretaceous and early Eocene orogenic pulses

    USGS Publications Warehouse

    van der Pluijm, B.A.; Vrolijk, P.J.; Pevear, D.R.; Hall, C.M.; Solum, J.

    2006-01-01

    Fault rocks from the classic Rocky Mountain foreland fold-and-thrust belt in south-western Canada were dated by Ar analysis of clay grain-size fractions. Using X-ray diffraction quantification of the detrital and authigenic component of each fraction, these determinations give ages for individual faults in the area (illite age analysis). The resulting ages cluster around 72 and 52 Ma (here called the Rundle and McConnell pulses, respectively), challenging the traditional view of gradual forward progression of faulting and thrust-belt history of the area. The recognition of spatially and temporally restricted deformation episodes offers field support for theoretical models of critically stressed wedges, which result in geologically reasonable strain rates for the area. In addition to regional considerations, this study highlights the potential of direct dating of shallow fault rocks for our understanding of upper-crustal kinematics and regional tectonic analysis of ancient orogens. ?? 2006 Geological Society of America.

  9. Flood magnitude frequency and lithologic control on bedrock river incision in post-orogenic terrain

    NASA Astrophysics Data System (ADS)

    Jansen, John D.

    2006-12-01

    Mixed bedrock-alluvial rivers-bedrock channels lined with a discontinuous alluvial cover-are key agents in the shaping of mountain belt topography by bedrock fluvial incision. Whereas much research focuses upon the erosional dynamics of such rivers in the context of rapidly uplifting orogenic landscapes, the present study investigates river incision processes in a post-orogenic (cratonic) landscape undergoing extremely low rates of incision (< 5 m/Ma). River incision processes are examined as a function of substrate lithology and the magnitude and frequency of formative flows along Sandy Creek gorge, a mixed bedrock-alluvial stream in arid SE-central Australia. Incision is focused along a bedrock channel with a partial alluvial cover arranged into riffle-pool macrobedforms that reflect interactions between rock structure and large-flood hydraulics. Variations in channel width and gradient determine longitudinal trends in mean shear stress ( τb) and therefore also patterns of sediment transport and deposition. A steep and narrow, non-propagating knickzone (with 5% alluvial cover) coincides with a resistant quartzite unit that subdivides the gorge into three reaches according to different rock erodibility and channel morphology. The three reaches also separate distinct erosional styles: bedrock plucking (i.e. detachment-limited erosion) prevails along the knickzone, whereas along the upper and lower gorge rock incision is dependent upon large formative floods exceeding critical erosion thresholds ( τc) for coarse boulder deposits that line 70% of the channel thalweg (i.e. transport-limited erosion). The mobility of coarse bed materials (up to 2 m diameter) during late Holocene palaeofloods of known magnitude and age is evaluated using step-backwater flow modelling in conjunction with two selective entrainment equations. A new approach for quantifying the formative flood magnitude in mixed bedrock-alluvial rivers is described here based on the mobility of a key

  10. Deep origin and hot melting of an Archaean orogenic peridotite massif in Norway.

    PubMed

    Spengler, Dirk; van Roermund, Herman L M; Drury, Martyn R; Ottolini, Luisa; Mason, Paul R D; Davies, Gareth R

    2006-04-13

    The buoyancy and strength of sub-continental lithospheric mantle is thought to protect the oldest continental crust (cratons) from destruction by plate tectonic processes. The exact origin of the lithosphere below cratons is controversial, but seems clearly to be a residue remaining after the extraction of large amounts of melt. Models to explain highly melt-depleted but garnet-bearing rock compositions require multi-stage processes with garnet and clinopyroxene possibly of secondary origin. Here we report on orogenic peridotites (fragments of cratonic mantle incorporated into the crust during continent-continent plate collision) from Otrøy, western Norway. We show that the peridotites underwent extensive melting during upwelling from depths of 350 kilometres or more, forming a garnet-bearing cratonic root in a single melting event. These peridotites appear to be the residue after Archaean aluminium depleted komatiite magmatism. PMID:16612379

  11. An Active RFID Accountability System (RAS) for Constrained Wireless Environments

    SciTech Connect

    Barker, Alan M; Hanson, Gregory R; Sexton, Angela Kay; Jones Jr, J P; Freer, Eva B; Sjoreen, Andrea L

    2011-01-01

    A team from Oak Ridge National Laboratory (ORNL) has developed an RFID Accountability System (RAS) that allows items with active RFID tags to be tracked in environments where tags may not be able to transmit their location continuously. The system uses activators that transmit a short range signal. Active RFID tags are in a sleep state until they encounter an activator. Then they transmit a signal that is picked up by the antennas installed throughout the building. This paper presents the theory of operation, application areas, lessons learned, and key features developed over the course of seven years of development and use.

  12. Cross-sectional anatomy and geodynamic evolution of the Central Pontide orogenic belt (northern Turkey)

    NASA Astrophysics Data System (ADS)

    Hippolyte, J.-C.; Espurt, N.; Kaymakci, N.; Sangu, E.; Müller, C.

    2016-01-01

    Geophysical data allowed the construction of a ~250-km-long lithospheric-scale balanced cross section of the southern Black Sea margin (Espurt et al. in Lithosphere 6:26-34, 2014). In this paper, we combine structural field data, stratigraphic data, and fault kinematics analyses with the 70-km-long onshore part of the section to reconstruct the geodynamic evolution of the Central Pontide orogen. These data reveal new aspects of the structural evolution of the Pontides since the Early Cretaceous. The Central Pontides is a doubly vergent orogenic wedge that results from the inversion of normal faults. Extensional subsidence occurred with an ENE-trend from Aptian to Paleocene. We infer that the Black Sea back-arc basin also opened during this period, which was also the period of subduction of the Tethys Ocean below the Pontides. As in the Western Pontides, the Cretaceous-Paleocene subsidence was interrupted from Latest Albian to Coniacian time by uplift and erosion that was probably related to a block collision and accretion in the subduction zone. The restoration of the section to its pre-shortening state (Paleocene) shows that fault-related subsidence locally reached 3600 m within the forearc basin. Structural inversion occurred from Early Eocene to Mid-Miocene as a result of collision and indentation of the Pontides by the Kırşehir continental block to the south, with 27.5 km (~28 %) shortening along the section studied. The inversion was characterized by NNE-trending shortening that predated the Late Neogene dextral escape of Anatolia along the North Anatolian Fault and the modern stress field characterized by NW-trending compression within the Eocene Boyabat basin.

  13. Seismological structure of the 1.8 Ga Trans-Hudson Orogen of North America

    NASA Astrophysics Data System (ADS)

    Gilligan, Amy; Bastow, Ian D.; Darbyshire, Fiona A.

    2016-06-01

    Precambrian tectonic processes are debated: what was the nature and scale of orogenic events on the younger, hotter, and more ductile Earth? Northern Hudson Bay records the Paleoproterozoic collision between the Western Churchill and Superior plates—the ˜1.8 Ga Trans-Hudson Orogeny (THO)—and is an ideal locality to study Precambrian tectonic structure. Integrated field, geochronological, and thermobarometric studies suggest that the THO was comparable to the present-day Himalayan-Karakoram-Tibet Orogen (HKTO). However, detailed understanding of the deep crustal architecture of the THO, and how it compares to that of the evolving HKTO, is lacking. The joint inversion of receiver functions and surface wave data provides new Moho depth estimates and shear velocity models for the crust and uppermost mantle of the THO. Most of the Archean crust is relatively thin (˜39 km) and structurally simple, with a sharp Moho; upper-crustal wave speed variations are attributed to postformation events. However, the Quebec-Baffin segment of the THO has a deeper Moho (˜45 km) and a more complex crustal structure. Observations show some similarity to recent models, computed using the same methods, of the HKTO crust. Based on Moho character, present-day crustal thickness, and metamorphic grade, we support the view that southern Baffin Island experienced thickening during the THO of a similar magnitude and width to present-day Tibet. Fast seismic velocities at >10 km below southern Baffin Island may be the result of partial eclogitization of the lower crust during the THO, as is currently thought to be happening in Tibet.

  14. 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.

  15. 3-D ore body modeling and structural settings of syn-to late orogenic Variscan hydrothermal mineralization, Siegerland district, Rhenish Massif, NW Germany

    NASA Astrophysics Data System (ADS)

    Peters, Meike; Hellmann, André; Meyer, Franz Michael

    2013-04-01

    The Siegerland district is located in the fold-and thrust-belt of the Rhenish Massif and hosts diverse syn-to late orogenic mineralization styles. Peak-metamorphism and deformation occurred at 312-316±10 Ma (Ahrendt et al., 1978) at temperature-pressure conditions of 280-320°C and 0.7-1.4 kbar (Hein, 1993). In addition to syn-orogenic siderite-quartz mineralization at least four different syn-to late orogenic mineralization stages are identified comprising Co-Ni-Cu-Au, Pb-Zn-Cu, Sb-Au, and hematite-digenite-bornite ores (Hellmann et al., 2012). The earliest type of syn-orogenic ore mineralization is formed by siderite-quartz veins, trending N-S, E-W and NE-SW. The vein systems are closely related to fold and reverse fault geometries (Hellmann et al., 2012). The most important structural feature is the first-order Siegen main reverse fault showing an offset into three major faults (Peters et al., 2012). The structural control on ore formation is demonstrated by the Co-Ni-Cu-Au mineralization generally hosted by NE-ENE trending reverse faults and associated imbrication zones that have reactivated the older siderite-quartz veins. In this study, we developed a 3-D model of the Alte Buntekuh ore bodies in the Siegerland district, using Datamine Studio3 to investigate the structural setting of Co-Ni-Cu-Au mineralization. The salient structural and spatial data for the 3-D model were taken from old mine level plans as well as from geological and topographical maps. The ore bodies are located immediately in the hanging wall of the southern branch of the Siegen main reverse fault (Peters et al., 2012). From the model it becomes obvious, that the earlier siderite-quartz veins, dipping steeply to the NW, are cross-cut and segmented by oppositely dipping oblique reverse faults. Individual ore body segments are rotated and displaced, showing a plunge direction to the SW. The 3-D model further reveals the presence of hook-like, folded vein arrays, highly enriched in cobalt

  16. [Activities of System Studies and Simulation, Inc.

    NASA Technical Reports Server (NTRS)

    2004-01-01

    Contents include the following: 1. Launch Vehicle Interface Work Performed: a. S3 provided to KSC the new launch inclination targets needed for the April '04 launch date. 2. Prelaunch operations work performed: a. S3 updated the staffing plan for MSFC on-console personnel\\during the Final Countdown prior to launch. 3. Software Assessment Work Performed: a. S3 evaluated and recommended approval for Program Control Board (PCB) proposed change 649 for ground software changes, as well as change 650 and 650A for Stored Program Commands. 4. Education and Public Outreach Work Performed: a. S3 continues to coordinate the effort for the design and fabrication of scale models of the GP-3 for use at the launch site, education forums, and management/technical briefings. S3 also prepared a Change Request for additional funds needed for fabrication of additional scale models. S3 drafted the planned uses of these models, including the possibility of participation in the Boston, MA showings of the traveling Einstein Exhibit. 5. Program Management Support Work Performed: a. S3 prepared the input for and closed three MSFC Centerwide Action Item Tracking Systems (CAITS) actions during this period.

  17. Zircon dating of Neoproterozoic and Cambrian ophiolites in West Mongolia and implications for the timing of orogenic processes in the central part of the Central Asian Orogenic Belt

    NASA Astrophysics Data System (ADS)

    Jian, Ping; Kröner, Alfred; Jahn, Bor-ming; Windley, Brian F.; Shi, Yuruo; Zhang, Wei; Zhang, Fuqin; Miao, Laicheng; Tomurhuu, Dondov; Liu, Dunyi

    2014-06-01

    We present new isotopic and trace element data to review the geochronological/geochemical/geological evolution of the central part of the Central Asian Orogenic Belt (CAOB), and find a fundamental geological problem in West Mongolia, which has traditionally been subdivided into northwestern early Paleozoic (formerly Caledonian) and southerly late Paleozoic (formerly Hercynian) belts by the Main Mongolian Lineament (MML). We resolve this problem with SHRIMP zircon dating of ophiolites and re-evaluation of much published literature. In Northwest Mongolia the Dariv-Khantaishir ophiolite marks the boundary between the Lake arc in the west and the Dzabkhan-Baydrag microcontinent in the east. Zircons from a microgabbro and four plagiogranites yielded weighted mean 206Pb/238U ages of 568 ± 5 Ma, 567 ± 4 Ma, 560 ± 8 Ma (Dariv), 573 ± 8 Ma and 566 ± 7 Ma (Khantaishir) that we interpret as reflecting the time of ophiolite formation (ca. 573-560 Ma). Metamorphic zircons from an amphibolite on a thrust boundary between the Khantaishir ophiolite and the Dzabkhan-Baydrag microcontinent formed at 514 ± 8 Ma, which we interpret as the time of overthrusting. In South Mongolia the Gobi Altai ophiolite and the Trans-Altai Gurvan Sayhan-Zoolen forearc with an ophiolite basement were investigated. Zircons of a layered gabbro (lower ophiolite crust) and a leucogabbro (mid-upper crust) of the Gobi Altai ophiolite yielded crystallization ages of 523 ± 5 Ma and 518 ± 6 Ma. The age data constrain the formation time of ophiolite within ca. 523-518 Ma. Zircons from four samples of the Gurvan Sayhan-Zoolen forearc, with similar hybrid adakite-boninite affinities, yielded 519 ± 4 Ma for an anorthosite, ≥ 512 ± 4 Ma for a hornblendite and 520 ± 5 and 511 ± 5 Ma for two diorites. The ophiolite basement has an upper age limit of 494 ± 6 Ma, determined by dating a tonalite dike cutting the Zoolen ophiolite. Integrating available zircon ages as well as geochemical and geological data

  18. Comparative study between two different active flutter suppression systems

    NASA Technical Reports Server (NTRS)

    Nissim, E.

    1978-01-01

    An activated leading-edge (LE)-tailing-edge (TE) control system is applied to a drone aircraft with the objective of enabling the drone to fly subsonically at dynamic pressures which are 44% above the open-loop flutter dynamic pressure. The control synthesis approach is based on the aerodynamic energy concept and it incorporates recent developments in this area. A comparison is made between the performance of the activated LE-TE control system and the performance of a TE control system, analyzed in a previous work. The results obtained indicate that although all the control systems achieve the flutter suppression objectives, the TE control system appears to be somewhat superior to the LE-TE control system, in this specific application. This superiority is manifested through reduced values of control surface activity over a wide range of flight conditions.

  19. Space Activism as an Epiphanic Belief System

    NASA Technical Reports Server (NTRS)

    Mendell, Wendell

    2006-01-01

    Years of interaction with young people in the space industry and in space activists groups led to my observation that many such individuals can cite a quite specific life event that triggered a life-long interest in or commitment to creating a space future. I am particularly intrigued by parallels between such experiences and the phenomenon of epiphanic experiences among committed Christians. I see analogies between the puzzlement among space activists and among Christian groups as to the reasons for so many people being "unbelievers." At a small international meeting on lunar exploration in 2003, I heard two separate lunch speakers cite such personal experiences. At the beginning of a break in that meeting, I grabbed the microphone from the chairman and asked each person to write down on a pad by his chair whether or not he (or she) had experienced a specific event that led to their involvement in space. If the answer was positive, I asked for a brief narrative, for their age at the time, and for their current age. I received 53 submissions, 20% of which simply stated that their involvement in space exploration was happenstance. (Apollo astronaut John Young was among these.) The other 80% of the submissions had specific stories. The ages at the time of the epiphany ranged from 4 to 47; and their current ages ranged from 22 to 78. I will present a high-level characterization of these inputs. Interest in space exploration as a form of belief system is consistent with choosing NASA goals for the purpose of inspiration and with phenomena such as the "Overview Effect". More research might explore what form the transcendent experience takes and whether it might be associated with feelings of universal connection such as the noosphere or "The Force". From a pragmatic point of view, outreach strategies for exploration should focus on giving individuals access to personal, potentially transformational experiences as opposed to astronaut talks at civic clubs.

  20. Active Storage Processing in a Parallel File System

    SciTech Connect

    Felix, Evan J.; Fox, Kevin M.; Regimbal, Kevin M.; Nieplocha, Jarek

    2006-01-01

    By creating a processing system within a parallel file system one can harness the power of unused processing power on servers that have very fast access to the disks they are serving. By inserting a module the Lustre file system the Active Storage Concept is able to perform processing with the file system architecture. Results of using this technology are presented as the results of the Supercomputing StorCloud Challenge Application are reviewed.

  1. Bactericidal activity of metal-mediated peroxide-ascorbate systems.

    PubMed

    Drath, D B; Karnovsky, M L

    1974-11-01

    Model systems containing ascorbate, hydrogen peroxide, and divalent copper or cobalt have been shown to possess marked bactericidal activity. At equivalent concentrations, copper-containing systems were more bactericidal than the corresponding mixtures containing cobalt. Cobalt at concentrations below 10(-4) M did not appreciably augment microbicidal activity, whereas systems containing copper at concentrations as low as 5 x 10(-6) M were still capable of causing some bacterial death. Manganese was inactive. None of these systems was as potent as the well known myeloperoxidase-peroxide-halide system. The mechanisms of action of these systems are not as yet clear. The possibility that they function through the generation of superoxide (O(2) (-)), hydroxyl radical (OH.), or other free radicals was explored through the use of superoxide dismutase and several free radical scavengers. It seems likely at present that the two active metal-mediated systems function via separate mechanisms. The copper system acts with dehydroascorbate, whereas the cobalt system does not. Activity in the cobalt system appears to depend upon the generation of free radicals. PMID:16558093

  2. Complement profile and activation mechanisms by different LDL apheresis systems.

    PubMed

    Hovland, Anders; Hardersen, Randolf; Nielsen, Erik Waage; Enebakk, Terje; Christiansen, Dorte; Ludviksen, Judith Krey; Mollnes, Tom Eirik; Lappegård, Knut Tore

    2012-07-01

    Extracorporeal removal of low-density lipoprotein (LDL) cholesterol by means of selective LDL apheresis is indicated in otherwise uncontrolled familial hypercholesterolemia. During blood-biomaterial interaction other constituents than the LDL particles are affected, including the complement system. We set up an ex vivo model in which human whole blood was passed through an LDL apheresis system with one of three different apheresis columns: whole blood adsorption, plasma adsorption and plasma filtration. The concentrations of complement activation products revealed distinctly different patterns of activation and adsorption by the different systems. Evaluated as the final common terminal complement complex (TCC) the whole blood system was inert, in contrast to the plasma systems, which generated substantial and equal amounts of TCC. Initial classical pathway activation was revealed equally for both plasma systems as increases in the C1rs-C1inh complex and C4d. Alternative pathway activation (Bb) was most pronounced for the plasma adsorption system. Although the anaphylatoxins (C3a and C5a) were equally generated by the two plasma separation systems, they were efficiently adsorbed to the plasma adsorption column before the "outlet", whereas they were left free in the plasma in the filtration system. Consequently, during blood-biomaterial interaction in LDL apheresis the complement system is modulated in different manners depending on the device composition. PMID:22373816

  3. Dual-Actuator Active Vibration-Control System

    NASA Technical Reports Server (NTRS)

    Kascak, Albert F.; Kiraly, Louis J.; Montague, Gerald T.; Palazzolo, Alan B.; Manchala, Daniel

    1994-01-01

    Dual-actuator active vibration-control (DAAVC) system is developmental system of type described in "Active Vibration Dampers for Rotating Machinery" (LEW-15427). System features sensors and actuators positioned and oriented at bearings to measure and counteract vibrations of shaft along either of two axes perpendicular to axis of rotation. Effective in damping vibrations of helicopter-engine test stand, making it safer to operate engine at speeds near and above first resonance of engine/test-stand system. Opens new opportunities for engine designers to draw more power from engine, and concept applicable to other rotating machines.

  4. Activity-Based Costing Systems for Higher Education.

    ERIC Educational Resources Information Center

    Day, Dennis H.

    1993-01-01

    Examines traditional costing models utilized in higher education and pinpoints shortcomings related to proper identification of costs. Describes activity-based costing systems as a superior alternative for cost identification, measurement, and allocation. (MLF)

  5. Active mirror alignment control system for the MACE telescope

    NASA Astrophysics Data System (ADS)

    Kulgod, S. V.; Pious, Lizy; Chadda, V. K.; Kaul, S. R.; Yadav, K. K.; Koul, R.

    2002-03-01

    The conceptual design of an active mirror contol system for the MACE telescope, being set up by the Bhabha Atomic Research Centre at Mt. Abu, is described. Preliminary results obtained from recent laboratory trials are also described.

  6. A Survey of Active Vibration Isolation Systems for Microgravity Applications

    NASA Technical Reports Server (NTRS)

    Grodsinsky, Carlos M.; Whorton, Mark S.

    2000-01-01

    In view of the utility of space vehicles as orbiting science laboratories, the need for vibration isolation systems for acceleration sensitive experiments has gained increasing visibility. To date, three active microgravity vibration isolation systems have successfully been demonstrated in flight. This paper provides a tutorial discussion of the microgravity vibration isolation problem including a description of the acceleration environment of the International Space Station and attenuation requirements as well as a comparison of the dynamics of passive isolation, active rack-level isolation, and active payload-level isolation. This paper also surveys the flight test results of the three demonstrated systems: Suppression of Transient Accelerations By Levitation (STABLE); the Microgravity Vibration Isolation Mount (MIM); and the Active Rack Isolation System (ARIS).

  7. Survey of Active Vibration Isolation Systems for Microgravity Applications

    NASA Technical Reports Server (NTRS)

    Grodsinsky, Carlos M.; Whorton, Mark S.

    2000-01-01

    In view of the utility of space vehicles as orbiting science laboratories, the need for vibration isolation systems for acceleration-sensitive experiments has gained increasing visibility. To date, three active microgravity vibration isolation systems have successfully been demonstrated in flight. A tutorial discussion of the microgravity vibration isolation problem, including a description of the acceleration environment of the International Space Station and attenuation requirements, as well as a comparison or the dynamics of passive isolation, active rack-level isolation, and active payload-level isolation is provided. The flight test results of the three demonstrated systems: suppression of transient accelerations by levitation, the microgravity vibration isolation mount, and the active rack isolation system are surveyed.

  8. Activity Theory in Information Systems Research and Practice: Theoretical Underpinnings for an Information Systems Development Model

    ERIC Educational Resources Information Center

    Mursu, Anja; Luukkonen, Irmeli; Toivanen, Marika; Korpela, Mikko

    2007-01-01

    Introduction: The purpose of information systems is to facilitate work activities: here we consider how Activity Theory can be applied in information systems development. Method. The requirements for an analytical model for emancipatory, work-oriented information systems research and practice are specified. Previous research work in Activity…

  9. Overview of coupled bunch active damper systems at FNAL

    SciTech Connect

    Steimel, J.; Crisp, J.; Ma, Hengjie; Marriner, J.; McGinnis, D.

    1996-05-01

    Beam intensities in all of the accelerators at Fermilab will increase significantly when the Main Injector becomes operational and will cause unstable oscillations in transverse position and energy. Places where the coupled bunch oscillations could dilute emittances include the Booster, Main Injector, and Tevatron. This paper provides an overview of the active feedback system upgrades which will be used to counteract the problem. It will explain the similarities between all the systems and will also explain design differences between longitudinal and transverse systems, fast sweeping systems, and systems for partially filled machines. Results from operational systems will also be shown. 7 refs., 4 figs., 1 tab.

  10. Overview of coupled-bunch active damper systems at FNAL

    SciTech Connect

    Steimel, J.; Crisp, J.; Ma, H.; Marriner, J.; McGinnis, D.

    1997-01-01

    Beam intensities in all of the accelerators at Fermilab will increase significantly when the Main Injector becomes operational and will cause unstable oscillations in transverse position and energy. Places where the coupled bunch oscillations could dilute emittances include the Booster, Main Injector, and Tevatron. This paper provides an overview of the active feedback system upgrades which will be used to counteract the problem. It will explain the similarities between all the systems and will also explain design differences between longitudinal and transverse systems, fast sweeping systems, and systems for partially filled machines. Results from operational systems will also be shown. {copyright} {ital 1997 American Institute of Physics.}

  11. On protolith-, metamorphic overprint, microstructure and rheology of mineral assemblages in orogenic peridotites of the central Scandinavian Caledonides

    NASA Astrophysics Data System (ADS)

    Gilio, Mattia; Clos, Frediano; Van Roermund, Herman L. M.

    2013-04-01

    The Scandinavian Caledonides (SC) are a deeply eroded Alpine-type orogenic belt formed by closure of the Iapetus ocean and collision between Baltica and Laurentia (500-380 Ma). The SC consists of a stack of Nappe Complexes (from bottom to top called Lower, Middle, Upper and Uppermost Allochthons) thrusted to the east over the Baltic Shield (Brueckner and Van Roermund, 2004; Gee et al., 2008). Fossil lithospheric mantle fragments, called orogenic peridotites, have been found within the (upper part of) middle, upper and uppermost Allochthons, as well as in the reworked basement gneisses (a.o Western Gneiss Complex (WGC)) along the Norwegian west coast. They occur as isolated lenses that contain diverse mineral parageneses and/or bulk rock compositions. Crustal incorporation of orogenic peridotite is classically interpreted to be the result of plate collisional processes related to orogeny (Brueckner and Medaris, 2000). The WGC and parts of the upper part of the Middle Allochthon (a.o. Seve Nappe Complex (SNC) in N Jämtland/S Västerbotten, central Sweden), are well known for the occurrence of high (HP) and ultrahigh pressure (UHP) metamorphic terranes (of Caledonian age). The (U)HPM evidence clearly demonstrates the deep metamorphic origin of these rocks interpreted to be caused by continental subduction and/or collision. Other metamorphic rocks (of Caledonian age) exposed in allochthonous nappes are solely characterised by greenschist-, amphibolite- and/or MP granulite "facies" mineral assemblages that can be interpreted, in the absence of retrogression, to have formed in less deeply subducted (and/or metamorphic) environments. This duality in metamorphic "facies" allows for a discrimination (at least theoretically) between "deep" versus "shallow" rooted nappes (in central parts of the Scandinavian Caledonides). Conform this reasoning, this duality should also be present within the Cal