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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. Shear-zone systems and melts: feedback relations and self-organization in orogenic belts

    NASA Astrophysics Data System (ADS)

    Brown, Michael; Solar, Gary S.

    1998-03-01

    In orogenic belts, the common spatial and temporal association of granites with crustal-scale shear-zone systems suggests melt transfer from source to upper crust was the result of a feedback relation. In this relation, the presence of melt in the crust profoundly affects the rheology, and induces localization of strain within shear-zone systems. Consequently, melt is moved out of the source preferentially along high-strain zones, which helps the system to accommodate strain. Because actively deforming orogenic belts are non-equilibrium systems, they may generate dissipative structure by self-organization; we interpret crustal-scale shear-zone systems and their associated granites as the manifestation of this self-organization. The architecture and permeability structure are controlled by the type of shear-zone system (transcurrent, normal, reverse or oblique); this is the primary control on melt transfer in orogenic belts. During active deformation, movement of melt is by percolative flow and melt essentially is pumped through the system parallel to the maximum principal finite elongation direction. If a build-up of melt pressure occurs, melt-enhanced embrittlement enables tensile and dilatant shear fracturing, and transfer of melt is by channelized flow. We illustrate feedback relations between migmatites, crustal-scale shear-zone systems and granites using examples from the Cadomian belt of western France and the northern Appalachian orogen of the eastern U.S.A. In orogenic belts dominated by transcurrent shear, where the maximum principal finite elongation direction may have a shallow to subhorizontal plunge, granite arrested during ascent through the system commonly develops C- S fabrics. This suggests percolative flow is not effective in expelling melt from these systems; the resulting build-up of melt pressure enables fracturing and channelized transfer of melt, which crystallizes during persistent deformation (e.g. the St. Malo migmatite belt, Cadomian belt

  3. Accretionary orogens: definition, character, significance

    NASA Astrophysics Data System (ADS)

    Cawood, P. A.; Kroener, A.; Windley, B. F.

    2003-04-01

    Classic models of orogens involve a Wilson cycle of ocean opening and closing with orogenesis related to continent-continent collision. Such models fail to explain the geological history of a significant number of orogenic belts throughout the world in which deformation, metamorphism and crustal growth took place in an environment of on-going plate convergence. These belts are termed accretionary orogens but have also been refereed to as non-collisional orogens, Pacific-type orogens, Turkic-type and exterior orogens. Accretionary orogens evolve in generally curvilinear belts comprising dominantly mafic to silicic igneous rocks and their sedimentary products and accumulated largely in marine settings. They are variably deformed and metamorphosed by tectono-thermal events aligned parallel to, and punctuating, facies trends. Accretionary orogens form at sites of subduction of oceanic lithosphere and consist of magmatic arcs systems along with material accreted from the downgoing plate and eroded from the upper plate. Deformational features include structures formed in extension and compressive environments during steady-state convergence (arc/backarc vs. accretionary prism) that are overprinted by short regional compressive orogenic events. Orogenesis takes place through 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 over-riding the downgoing plate. The Circum-Pacific region provides outstanding examples of accretionary orogens. The Pacific formed during breakup of Rodinia in the Neoproterozoic and has never subsequently closed, resulting in a series of overall ocean-ward younging orogenic systems that have always faced an open ocean, yet have been the sites of repeated tectono-thermal events and

  4. 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.

  5. 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.

  6. Orogen-Parallel and -Normal Extension at the Dinarides-Hellenides Junction during Clockwise Rotation and Radial Expansion of the Retreating Hellenic Arc-Trench System

    NASA Astrophysics Data System (ADS)

    Handy, M.; Fügenschuh, B.; Giese, J.; Le Breton, E.; Muceku, B.; Onuzi, K.; Pleuger, J.; Schmid, S. M.; Ustaszewski, K. M.

    2015-12-01

    Normal faults at the junction of the Dinarides and Hellenides in northern Albania trend both perpendicular and parallel to thrusts and fold axes. Most prominent is the SSE-dipping Skutari-Pec Normal Fault (SPNF), one of a system of normal faults that accommodate NW-SE-directed, orogen-parallel extension. Extensional throw along the SPNF increases from zero in northwestern Albania to at least 2 km near the Albania-Kosovo border, near where the brittle arm of the SPNF bounds the Mio-Pliocene Kosovo Basin. This differential orogen-parallel extension along the SPNF defines a vertical rotational axis in northwestern Albania that is interpreted to have accommodated 20-30° of clockwise motion of internal units on the southeastern (Hellenic) side of the fault with respect to the northwestern (Dinaric) side. Such rotation is in agreement with previously published paleomagnetic data and plate motion studies. The footwall of the SPNF exposes lower units of the Dinaric nappe stack that underwent vertical shortening and non-coaxial shearing during extensional exhumation. In the hangingwall of the SPNF, a system of orogen-parallel trending normal faults accommodate orogen-normal displacement of up to several km. Both orogen-parallel and -perpendicular systems of normal faults cut Late Cretaceous to Oligocene thrusts and folds, and are associated with pronounced Miocene paleo-relief. Most of this normal faulting is Miocene to Pliocene based on syn-extensional deposits in the Kosovo Basins and on thermal modelling of ZHe, AFT and AHe data, which suggest accelerated cooling at 18 Ma and between 4-6 Ma. Both fault systems also cut Holocene deposits, indicating ongoing extension. This corroborates published GPS data and earthquake focal mechanisms indicating active extension of the crust south and southeast of the SPNF. It is proposed that extension and clockwise rotation in this area were coeval and accommodated southwestward retreat and radial expansion of the Hellenic arc during

  7. 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.

  8. 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

  9. Climate Variability and Surface Processes in Tectonically Active Orogens: Insights From the Southern Central Andes and the Northwest Himalaya

    NASA Astrophysics Data System (ADS)

    Strecker, M. R.; Bookhagen, B.

    2008-12-01

    The Southern Central Andes of NW Argentina and the NW Himalaya are important orographic barriers that intercept moisture-bearing winds associated with monsoonal circulation. Changes in both atmospheric circulation systems on decadal to millennial timescales fundamentally influence differences in the amount and location of rainfall in both orogens. In India, the eastern arm of the monsoonal circulation draws moisture from the Bay of Bengal and transports humid air masses along the southern Himalayan front to the northwest. There, at the end of the monsoonal conveyer belt, rainfall is diminished and moisture typically does not reach far into the orogen interior. Similar conditions apply to the NW Argentine Andes, which are located within the precipitation regime of the South American Monsoon. Here, pronounced local relief blocks humid air masses from the Amazon region, resulting in extreme gradients in rainfall that leave the orogen interior dry. However, during negative ENSO years (La Niña) and intensified Indian Summer Monsoon years, moisture penetrates farther into the Andean and Himalayan orogens, respectively. Structurally pre- conditioned valley systems may enhance this process and funnel moisture far into the orogen interior. The greater availability of moisture increases runoff, lateral scouring of mountin streams, and ultimately triggers intensified hillslope processes on decadal to centennial timescales. In both environments, the scenario of intensified present-day surface processes and rates is analogous to protracted episodes of enhanced mass removal from hillslopes via deep-seated landslides during the early Holocene and late Pleistocene. Apparently, these episodes were also associated with transient storage of voluminous conglomerates and lacustrine deposits in narrow intermontane basins. Subsequently, these deposits were incised, partly removed, and the fluvial systems adjusted themselves to the pre-depositional base levels through a readjustment and

  10. Active shortening within the Himalayan orogenic wedge implied by the 2015 Gorkha earthquake

    NASA Astrophysics Data System (ADS)

    Whipple, Kelin X.; Shirzaei, Manoochehr; Hodges, Kip V.; Ramon Arrowsmith, J.

    2016-09-01

    Models of Himalayan neotectonics generally attribute active mountain building to slip on the Himalayan Sole Thrust, also termed the Main Himalayan Thrust, which accommodates underthrusting of the Indian Plate beneath Tibet. However, the geometry of the Himalayan Sole Thrust and thus how slip along it causes uplift of the High Himalaya are unclear. We show that the geodetic record of the 2015 Gorkha earthquake sequence significantly clarifies the architecture of the Himalayan Sole Thrust and suggests the need for revision of the canonical view of how the Himalaya grow. Inversion of Gorkha surface deformation reveals that the Himalayan Sole Thrust extends as a planar gently dipping fault surface at least 20-30 km north of the topographic front of the High Himalaya. This geometry implies that building of the high range cannot be attributed solely to slip along the Himalayan Sole Thrust over a steep ramp; instead, shortening within the Himalayan wedge is required to support the topography and maintain rapid rock uplift. Indeed, the earthquake sequence may have included a moderate rupture (Mw 6.9) on an out-of-sequence thrust fault at the foot of the High Himalaya. Such internal deformation is an expected response to sustained, focused rapid erosion, and may be common to most compressional orogens.

  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. Nature and timing of large landslides within an active orogen, eastern Pamir, China

    NASA Astrophysics Data System (ADS)

    Yuan, Zhaode; Chen, Jie; Owen, Lewis A.; Hedrick, Kathryn A.; Caffee, Marc W.; Li, Wenqiao; Schoenbohm, Lindsay M.; Robinson, Alexander C.

    2013-01-01

    Large-scale landsliding (involving ≫ 106 m3 in volume) is important in landscape development in high mountains. To assess the importance of large landslides in high mountains, four large landslides (Bulunkou, Muztagh, Taheman, and Yimake) were mapped in the NE Chinese Pamir at the westernmost end of the Himalayan-Tibetan orogen and dated using 10Be terrestrial cosmogenic nuclides. The Bulunkou landslide at the southernmost end of Muji Valley is composed of ~ 1.7 × 107 m3 of landslide debris and has an age of 2.0 ± 0.1 ka. The Muztagh landslide, located on the SW side of the massif Muztagh Ata, is composed of ~ 4.7 × 108 m3 of debris, and has an age of 14.3 ± 0.8 ka. The Taheman landslide, located south of Muztagh Ata, is composed of ~ 2.6 × 108 m3 of landslide debris and has an age of 6.8 ± 0.2 ka. The Yimake landslide, on the northern frontal range of the Pamir at the southwestern end of the Tarim basin, is composed of ~ 1.4 × 109 m3 of landslide debris and has an age of 7.1 ± 0.6 ka. Two other large landslides are present in the region, the Aerpa Aigezi (on a tributary of the Gez River) and the Bile Jiyi (on the Yarkand River) landslides, and are composed of ~ 1.6 × 107 m3 and ~ 5.2 × 106 m3 of landslide debris, respectively. However, the Aerpa Aigezi and Bile Jiyi landslides were not studied in as much detail or dated because of their inaccessibility. Given the tectonically active nature of this region, with numerous active faults, and the morphology of the landslides, these landslides were likely triggered by earthquakes. However, other causes — including long-term increased precipitation and geologic bedrock structure — could be important contributing factors in their formation.

  13. 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

  14. Coeval emplacement and orogen-parallel transport of gold in oblique convergent orogens

    NASA Astrophysics Data System (ADS)

    Upton, Phaedra; Craw, Dave

    2016-12-01

    Varying amounts of gold mineralisation is occurring in all young and active collisional mountain belts. Concurrently, these syn-orogenic hydrothermal deposits are being eroded and transported to form placer deposits. Local extension occurs in convergent orogens, especially oblique orogens, and facilitates emplacement of syn-orogenic gold-bearing deposits with or without associated magmatism. Numerical modelling has shown that extension results from directional variations in movement rates along the rock transport trajectory during convergence, and is most pronounced for highly oblique convergence with strong crustal rheology. On-going uplift during orogenesis exposes gold deposits to erosion, transport, and localised placer concentration. Drainage patterns in variably oblique convergent orogenic belts typically have an orogen-parallel or sub-parallel component; the details of which varies with convergence obliquity and the vagaries of underlying geological controls. This leads to lateral transport of eroded syn-orogenic gold on a range of scales, up to > 100 km. The presence of inherited crustal blocks with contrasting rheology in oblique orogenic collision zones can cause perturbations in drainage patterns, but numerical modelling suggests that orogen-parallel drainage is still a persistent and robust feature. The presence of an inherited block of weak crust enhances the orogen-parallel drainage by imposition of localised subsidence zones elongated along a plate boundary. Evolution and reorientation of orogen-parallel drainage can sever links between gold placer deposits and their syn-orogenic sources. Many of these modelled features of syn-orogenic gold emplacement and varying amounts of orogen-parallel detrital gold transport can be recognised in the Miocene to Recent New Zealand oblique convergent orogen. These processes contribute little gold to major placer goldfields, which require more long-term recycling and placer gold concentration. Most eroded syn-orogenic

  15. The Structure of The Lithosphere-asthenosphere System Beneath The Alpine Orogen Derived From High-resolution Teleseismic Tomography

    NASA Astrophysics Data System (ADS)

    Lippitsch, R.; Kissling, E.; Ansorge, J.; Transalp Working Group

    In the tectonically complex Alpine region, three different plates (European, Adriatic, and Ligurian) amalgamated when the orogen was formed. To understand the evolution of this orogen and the interactions between the three lithospheric blocks, knowledge of the actual structure of the lithosphere-asthenosphere system is of great importance. To illuminate the structure of the uppermost mantle we perform high-resolution tele- seismic tomography. Our data set consists of 4200 manually picked first P-arrivals from 220 teleseismic events with even azimuthal distribution recorded at permanent and temporary seismic networks in the greater Alpine area. In the first step of this study corrections are calculated for the contribution of the Alpine crust to travel-times of incoming wave fields that may account for up to 50% of the observed travel-time residuals. The 3D crustal model established from controlled-source seismology data represents the large-scale shallow Alpine structure which clearly reflects the effects of the Africa Europe plate collision. Tests with synthetic data document that the combi- nation of non-linear inversion, high-quality teleseismic data, and usage of an a priori 3D crustal model allows a reliable resolution of cells at 50km*50km*30km with a velocity variation in the order of +/- 3% in the upper mantle. Our tomographic images illuminate the structure of the uppermost mantle to depth of 400 km and reflect the cur- rent status of the complex processes that formed the Alpine orogen. Along strike of the Alps, the inversion reveals a fast, slab-like body beneath the orogen. We interpret this feature as the subducted mainly oceanic lithosphere, which is in many places still attached to continental European lower lithosphere. Down to 250 km depths, this slab seems to be rather thin (less than 80 km) and steeply dipping. It significantly broad- ens at greater depth. Our results are in general agreement with earlier tomographic studies. However, the increase

  16. 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

  17. Active Folding In The Puli Basin, Constraints On Strain Across A Sub-Critical Region Of The Taiwanese Orogen

    NASA Astrophysics Data System (ADS)

    Wilcox, T.; Mueller, K.; Chen, Y.

    2006-12-01

    The Puli topographic embayment in central western Taiwan is interpreted as a region of sub-critical taper (assuming uniform decollement geometry) within the otherwise critically tapered wedge of the Taiwanese orogen. This sub-critical portion of the thrust belt drives the current orogenic architecture and reorganization of strain in and around Puli. Age dating and mapping of fold axis' that deform Late Quaternary terrace deposits in the Puli Basin suggest that at least 380 meters of fault slip (or a minimum of about 350 meters of horizontal shortening) has occurred over the last 50-60 Ka, yielding a minimum slip rate of 8mm/yr for the Shuilikeng blind thrust and fault-related fold. Given our existing age constraints, which only define the oldest Late Quaternary strata in the Puli Basin, the slip rate on this same structure could approach 13mm/yr (i.e. we use strain in younger deposits as a starting point for measuring shortening). Geodetic convergence rates (with respect to Asia) in the northern half of the island average ~10mm/yr or less, while convergence rates in the southwestern part of the orogen average ~40mm/yr. Previous maps of geodetic strain suggest the Puli Basin, corresponds with strain gradients of about 15mm/yr. Identifiable kink bends in terrace deposits were used to define the kinematics of actively growing folds, indicating the sense and magnitude of slip on blind thrusts that currently accommodate strain. This implies that active contraction occurs over a broader area across Puli than in other parts of Taiwan, but within the Basin contraction appears most likely limited to slip on a single fault (in addition to rapidly slipping thrusts in the foreland). Backstepping of thrusts at Puli is due to the first-order decrease in mass of the wedge at this latitude. While decreased mass in the wedge can be initially estimated by its thickness (as measured by the distance between the decollement as mapped at depth by microseismicity and average topography

  18. Modern Strain and Structural Architecture of the Central Taiwanese Orogen - Evidence for Active Backstepping in Response to Erosion?

    NASA Astrophysics Data System (ADS)

    Mueller, K.; Chen, Y.; Powell, L.

    2002-12-01

    The topography and tectonic geomorphology of west-central Taiwan is interpreted to suggest that increased erosion in a region of relatively lower relief is accommodated by backstepping of active thrust faults and folds. Average topography is 1.0-2.0 km lower in the west-central part of the orogen and is defined by a broad, 80 km-wide depression located between the Chelungpu thrust (to the west) and the main drainage divide of the Island (to the east). The area of lower relief is floored by a piggyback basin (the Puli Basin) and a region defined by radially-oriented river channels incised deeply into the slate belt further east. Evidence for stalling of frontal folds and active backstepping of more hindward thrust sheets includes (from west to east): low rates of shortening across the frontal Pakuashan anticline, latest Pleistocene reactivation and rapid slip across the Chelungpu thrust, rapidly uplifted fault-bend folds in the hangingwalls of the Shuangtung and Shuichanglin thrusts, and growth of nascent blind thrusts and folds in the piggyback Puli Basin further east. We argue the region underlain by the Puli Basin has always been an area of relatively lower relief and not been deeply eroded because it is located above a regional decollement which translates but does not uplift rocks in this region as much as in adjacent parts of the fold belt. Restorations of thrust sheets exposed in river valleys incised through the Puli Basin also do not require significant erosion of folds developed in their hangingwalls. Finally, the critical taper of the orogen appears to be maintained by a more steeply-dipping decollement that marks the base of the thin-skinned wedge beneath the Puli Basin. The region incised by radially-oriented river valleys in the slate belt has been more greatly exhumed, based on published thermochronologic data, the amount of river incision and metamorphic grade. Capture of longitudinal valleys incised into the slate belt by west-flowing rivers

  19. Mapping the Structure of the Lithosphere-Asthenosphere System Under the Alpine Orogen with High-Resolution Teleseismic Tomography

    NASA Astrophysics Data System (ADS)

    Lippitsch, R.; Kissling, E.; Ansorge, J.

    2001-12-01

    Understanding the evolution of the Alpine orogen and the interaction between different lithospheric blocks requires precise knowledge of the structure of the lithosphere-asthenosphere system. To assess the gross features of the uppermost mantel we perform high-resolution teleseismic tomography. The data base encompasses 5000 manually picked first P-arrivals from 220 teleseismic events with even azimuthal distribution recorded at permanent and temporary seismic networks in the greater Alpine area. The tomographic study consists of these components: (1) Corrections for the contribution of the Alpine crust to travel-times of incoming wave fields that may account for up to 50% of the observed travel-time residuals. The 3-D crustal model established from controlled-source seismology data represents the large-scale Alpine crustal structure which clearly reflects the effects of the African-European plate collision. (2) Tests with synthetic data document that the combination of non-linear inversions, high-quality teleseismic data, and usage of an a priori 3-D crustal model allows reliable resolution of cells at 50km*50km*30km with a velocity variation in the order of +/- 3% in the upper mantle. (3) Our tomographic images illuminate the structure of the uppermost mantle to depth of 400 km reflecting the complex processes that formed the Alpine orogen when three different plates were amalgamated (European, Adriatic, and Ligurian plates). In the western Alps, the inversion results show a steep W-E dipping high-velocity anomaly which we interpret as the subducting European plate. In the eastern Alps we find high-velocity anomalies in a depth range of 150 km to 300 km beneath the axis of the orogen. At present, the relation of this material with European or Adriatic lithosphere remains unclear. Our results are in general agreement with earlier lithospheric studies. However, the increase in resolution illuminates significantly more complex lithospheric slab geometries, which

  20. 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.

  1. 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.

  2. Sampling Laurentia: Detrital zircon geochronology offers evidence for an extensive Neoproterozoic river system originating from the Grenville orogen

    NASA Astrophysics Data System (ADS)

    Rainbird, Robert H.; Hearnan, Larry M.; Young, Grant

    1992-04-01

    Neoproterozoic fluvial quartzarenites from the Shaler Group on Victoria Island in the western Canadian Arctic yield a diverse suite of detrital zircons. U-Pb ages from single zircons fall into three modes: Archean (3.01-2.62 Ga), Paleoproterozoic (1.97-1.84 Ga), and Meso proterozoic (1.64-1.03 Ga). Particularly intriguing is the unusually high proportion (50%) of the Mesoproterozoic mode, as the nearest exposed source is the Grenville structural province, ˜3000 km southeast of Victoria Island. Unimodal northwest paleocurrents, obtained from cross-bedding, are compatible with a southeasterly provenance. These data, supported by sedimentological evidence from the Shaler Group and from correlative strata in the northwestern Canadian Cordillera, imply the existence of a large, perennial river system flowing north-westward from the Grenville orogen. An analogy with the Llanos drainage basin in Venezuela and Colombia is proposed on the basis of similar geography, climate, and sedimentation. These data also provide a maximum age for the Shaler Group (basal Reynolds Point Formation) of about 1.11 Ga.

  3. 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

  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. 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

  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

    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. Mode of extensional tectonics in the southeastern Betics (SE Spain): Implications for the tectonic evolution of the peri-Alborán orogenic system

    NASA Astrophysics Data System (ADS)

    MartíNez-MartíNez, J. M.; Azañón, J. M.

    1997-04-01

    The Gibraltar arc, which closes the westernmost part of the Mediterranean basin, is a Miocene A-type subduction arc formed by the continental collision of various pre-Miocene terranes in the major zone of collision between the Iberian and African cratons. The hanging-wall block, known as the Alborán domain, has undergone more than 300 km migration from a more easterly position, where it was the continuation of the Alpine Cretaceous-Paleogene orogen. Contemporaneous with thin-skinned thrusting in the footwall, the Alborán domain underwent two episodes of nearly orthogonal extension in which extensional systems developed with directions of extension varying from a NNW-SSE system, orthogonal to the belt axis, in the late Burdigalian-Langhian to a WSW directed orogen-parallel one in the Serravallian. The superposition of these two systems resulted in a chocolate tablet megastructure. This extensional pattern is not satisfactorily explained in previously proposed models for the evolution of the arc. Orthogonal extension is plausible in a process of the gravitational collapse of an overthickened crust; nevertheless, orogen-parallel extension is more difficult to explain in this context. We advocate that the WSW directed low-angle normal faults formed during large-scale extension in connection with important westward arc migration. The driving force of extension in a general context of convergence is controversial and varies between a convective removal model and a delamination model. Constraints on both the timing and the kinematics of extension, as presented in this paper, seem to support the contribution of both mechanisms. Convective removal may have started the process, but continued N-S convergence could have resulted in westward tectonic escape and asymmetric lateral inflow of asthenospheric material accompanying lithospheric delamination.

  8. Flow of ultra-hot Precambrian orogens and the making of crustal layering in Phanerozoic orogenic plateaux

    NASA Astrophysics Data System (ADS)

    Chardon, Dominique; Gapais, Denis; Cagnard, Florence; Jayananda, Mudlappa; Peucat, Jean-Jacques

    2010-05-01

    Reassessment of structural / metamorphic properties of ultra-hot Precambrian orogens and shortening of model weak lithospheres support a syn-convergence flow mode on an orogen scale, with a large component of horizontal finite elongation parallel to the orogen. This orogen-scale flow mode combines distributed shortening, gravity-driven flow, lateral escape, and three-dimensional mass redistribution of buried supracrustal rocks, magmas and migmatites in a thick fluid lower crust. This combination preserves a nearly flat surface and Moho. The upper crust maintains a nearly constant thickness by real-time erosion and near-field clastic sedimentation and by ablation at its base by burial of pop-downs into the lower crust. Steady state regime of these orogens is allowed by activation of an attachment layer that maintains kinematic compatibility between the thin and dominantly plastic upper crust and a thick "water bed" of lower crust. Because very thin lithospheres of orogenic plateaux and Precambrian hot orogens have similar thermomechanical structures, bulk orogenic flow comparable to that governing Precambrian hot orogens should actually operate through today's orogenic plateaux as well. Thus, syn-convergence flow fabrics documented on exposed crustal sections of ancient hot orogens that have not undergone collapse may be used to infer the nature of flow fabrics that are imaged by geophysical techniques beneath orogenic plateaux. We provide a detailed geological perspective on syn-convergence crustal flow in relation to magma emplacement and partial melting on a wide oblique crustal transition of the Neoarchean ultra-hot orogen of Southern India. We document sub-horizontal bulk longitudinal flow of the partially molten lower crust over a protracted period of 60 Ma. Bulk flow results from the interplay of (1) pervasive longitudinal transtensional flow of the partially molten crust, (2) longitudinal coaxial flow on flat fabrics in early plutons, (3) distributed, orogen

  9. Variations in erosional efficiency modulate orogenic growth of the Alborz Mountains (N Iran)

    NASA Astrophysics Data System (ADS)

    Ballato, Paolo; Landgraf, Angela; Stockli, Daniel; Ghasemi, Mohammad; Strecker, Manfred; Kirby, Eric

    2014-05-01

    The recognition that redistribution of mass by erosion governs orogenic evolution has radically changed our perspective on the coupling between climate and mountain building processes. Climate modulates the efficiency of surface processes, which modifies crustal stresses and this is expected to produce the cessation of shortening at the orogenic front, onset of out-of-sequence thrusting, and increased rates of rock -uplift and sediment supply. Unambiguous characterization of these multiple responses through field-based studies, however, has remained challenging. Here, we show that coordinated changes in the rates and patterns of exhumation and deformation during the development of the Alborz Mountains (N Iran) were driven by abrupt, large magnitude (0.6 to 1.5 km) fluctuations in base level in the adjacent Caspian Sea. We argue that sustained regression of the paleoshoreline from ~6 to 3.2 Ma enhanced erosional efficiency of fluvial systems and increased exhumation within the axial orogenic zone and along the northern range flank which, in turn, drove coordinated retreat of the deformation fronts. When base level rose again at 3.2 Ma, exhumation in the orogen interior slowed and range-bounding faults were reactivated. This was associated with the progressive establishment of positive feedbacks loop between orographically-induced precipitation, focused erosion, exhumation, and rock uplift. Overall, these coordinated changes offer compelling evidence that enhanced erosion can indeed trigger a structural reorganization within an actively deforming orogen.

  10. Governing the Himalaya from first collision to orogenic collapse - the long-lasting shear zone that we call the Southern Tibet Detachment System

    NASA Astrophysics Data System (ADS)

    Edwards, M. A.; Kidd, W. S. F.

    2003-04-01

    Major shear zones govern crustal failure and thereby the architecture of major mountain belts. The central layer of the Himalayan orogen is an exhumed, 10-30 km thick, gently N-dipping mid-crustal section of extensively migmatised metamorphic and/or crystalline rock that is geometrically bounded by coeval normal- and thrust-sense shear zones, termed the Southern Tibet Detachment System (STDS) and the Main Central Thrust System (MCT), above and below the layer, respectively. These shear zones have accommodated the exhumation of the mid-crustal layer all along the ~2000 km orogen for the youngest third of the ca. 60 m.y. since collision began. Our work in southern Tibet shows that the STDS is a 100s m to few km thick, normal sense shear zone that has operated at a range of deformation conditions, and has often incorporated coalesced melt products and much fluid. These phases in particular have dynamically interacted with the existing shear zone rocks to alter the STDS constituent properties through time. Exposed today are little- to un-metamorphosed sedimentary rocks of the former Indian passive margin (Tethyan zone) juxtaposed by the STDS above sillimanite grade gneisses or mid-crustal leucogranites. In the eastern Himalaya, the predominant STDS hanging wall rock type in actual contact with the crystallines is a unit of regionally distinctive black phyllite. The STDS thus accounts for 10s or 100s of km of exhumation and represents, in a sense, orogenic "collapse" (but is likely only a "passive" upper boundary of dominantly pure shear accompanying wedge extrusion). The STDS is, however, a contemporary re-utilisation (D2) of a shear zone that developed as a primary thrust detachment during thin-skinned fold &thrust contraction accompanying early collision (D1) in the initial F&T belt convergence, good evidence for which is preserved. Locally, the major shear zone of STDS has been further reworked (D3) as discrete listric detachment horizons for the various N

  11. The anatomy of a deep intracontinental orogen

    NASA Astrophysics Data System (ADS)

    Raimondo, Tom; Collins, Alan S.; Hand, Martin; Walker-Hallam, Althea; Smithies, R. Hugh; Evins, Paul M.; Howard, Heather M.

    2010-08-01

    The crustal architecture of central Australia has been profoundly affected by protracted periods of intracontinental deformation. In the northwestern Musgrave Block, the Ediacaran-Cambrian (600-530 Ma) Petermann Orogeny resulted in pervasive mylonitic reworking of Mesoproterozoic granites and granitic gneisses at deep crustal levels (P = 10-14 kbar and T = 700-800°C). SHRIMP and LA-ICPMS dating of zircon indicate that peak metamorphic conditions were attained at circa 570 Ma, followed by slow cooling to ˜600-660°C at circa 540 Ma driven by exhumation along the Woodroffe Thrust. Strong links between regional kinematic partitioning, pervasive high shear strains and partial melting in the orogenic core, and an anomalous lobate thrust trace geometry suggest that north vergent shortening was accompanied by the gravitational collapse and lateral escape of a broad thrust sheet. Like the present-day Himalayan-Tibetan system, the macroscopic structural, metamorphic, and kinematic architecture of the Petermann Orogen appears to be dominantly shaped by large-scale ductile flow of lower crustal material. We thus argue that the anatomy of this deep intracontinental orogen is comparable to collisional orogens, suggesting that the deformational response of continental crust is remarkably similar in different tectonic settings.

  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. Lateral variations in lithospheric and landscape evolution at both ends of the Himalaya-Tibet orogen

    NASA Astrophysics Data System (ADS)

    Zeitler, P. K.; Schmidt, J. L.; Meltzer, A.

    2015-12-01

    At the broadest scale, like many orogens the Himalaya encompass a range of orogenic features that are remarkably similar along much of the length of the mountain belt and its neighboring terranes. At one scale of consideration, these similarities appear to be a signal that fundamental processes associated with lithospheric collision have been active. However, the vast size of the Himalaya and Tibet, the different climate regimes experienced by the orogen across time and space, and the along-strike variations in the continental and arc margins that faced one another before collision, make it at once remarkable that any similarities exist, and important to more critically evaluate their nature. The eastern and western Himalayan syntaxes confound any attempt to generalize too much about the Himalaya-Tibet orogen. By area these features occupy at least 25% of the orogenic belt, and compared to the "main" portions of the arc they show clear differences in their lithospheric structures, landscapes, and evolution. The boundary and initial conditions that shaped the eastern and western indentor corners were and are different, as is the nature and timing of erosional exhumation. Some of the most active geologic processes on Earth have recently been in play within the syntaxes, and the evolution of landscapes and fluvial systems, important in developing the sedimentary record of the Himalaya-Tibet system, has been complex and variable in space and time. Southeasternmost Tibet and the Lhasa Block in particular exemplify this complexity both in its complex topographic evolution linked to surface processes and climate, and in lateral variability in lithospheric structure. Taking a system viewpoint, an important question to debate is the degree to which there are features in the Himalaya-Tibet system that are robustly emergent, given the broad boundary conditions of the continental collision plus the suite of local and regional geodynamical processes that have operated during

  14. 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

  15. Compressional intracontinental orogens: Ancient and modern perspectives

    NASA Astrophysics Data System (ADS)

    Raimondo, Tom; Hand, Martin; Collins, William J.

    2014-03-01

    Compressional intracontinental orogens are major zones of crustal thickening produced at large distances from active plate boundaries. Consequently, any account of their initiation and subsequent evolution must be framed outside conventional plate tectonics theory, which can only explain the proximal effects of convergent plate-margin interactions. This review considers a range of hypotheses regarding the origins and transmission of compressive stresses in intraplate settings. Both plate-boundary and intraplate stress sources are investigated as potential driving forces, and their relationship to rheological models of the lithosphere is addressed. The controls on strain localisation are then evaluated, focusing on the response of the lithosphere to the weakening effects of structural, thermal and fluid processes. With reference to the characteristic features of intracontinental orogens in central Asia (the Tien Shan) and central Australia (the Petermann and Alice Springs Orogens), it is argued that their formation is largely driven by in-plane stresses generated at plate boundaries, with the lithosphere acting as an effective stress guide. This implies a strong lithospheric mantle rheology, in order to account for far-field stress propagation through the discontinuous upper crust and to enable the support of thick uplifted crustal wedges. Alternative models of intraplate stress generation, primarily involving mantle downwelling, are rejected on the grounds that their predicted temporal and spatial scales for orogenesis are inconsistent with the observed records of deformation. Finally, inherited mechanical weaknesses, thick sedimentary blanketing over a strongly heat-producing crust, and pervasive reaction softening of deep fault networks are identified as important and interrelated controls on the ability of the lithosphere to accommodate rather than transmit stress. These effects ultimately produce orogenic zones with architectural features and evolutionary

  16. Metamorphic complexes in accretionary orogens: Insights from the Beishan collage, southern Central Asian Orogenic Belt

    NASA Astrophysics Data System (ADS)

    Song, Dongfang; Xiao, Wenjiao; Windley, Brian F.; Han, Chunming; Yang, Lei

    2016-10-01

    The sources of ancient zircons and the tectonic attributions and origins of metamorphic complexes in Phanerozoic accretionary orogens have long been difficult issues. Situated between the Tianshan and Inner Mongolia orogens, the Beishan orogenic collage (BOC) plays a pivotal role in understanding the accretionary processes of the southern Central Asian Orogenic Belt (CAOB), particularly the extensive metamorphic and high-strained complexes on the southern margin. Despite their importance in understanding the basic architecture of the southern CAOB, little consensus has been reached on their ages and origins. Our new structural, LA-ICP-MS zircon U-Pb and Hf isotopic data from the Baidunzi, Shibandun, Qiaowan and Wutongjing metamorphic complexes resolve current controversial relations. The metamorphic complexes have varied lithologies and structures. Detrital zircons from five para-metamorphic rocks yield predominantly Phanerozoic ages with single major peaks at ca. 276 Ma, 286 Ma, 427 Ma, 428 Ma and 461 Ma. Two orthogneisses have weighted mean ages of 294 ± 2 Ma and 304 ± 2 Ma with no Precambrian inherited zircons. Most Phanerozoic zircons show positive εHf(t) values indicating significant crustal growth in the Ordovician, Silurian and Permian. The imbricated fold-thrust deformation style combined with diagnostic zircon U-Pb-Hf isotopic data demonstrate that the metamorphic rocks developed in a subduction-accretion setting on an arc or active continental margin. This setting and conclusion are supported by the nearby occurrence of Ordovician-Silurian adakites, Nb-rich basalts, Carboniferous-Permian ophiolitic mélanges, and trench-type turbidites. Current data do not support the presence of a widespread Precambrian basement in the evolution of the BOC; the accretionary processes may have continued to the early Permian in this part of the CAOB. These relationships have meaningful implications for the interpretation of the tectonic attributions and origins of other

  17. Pebble and bedrock abrasion during fluvial transport in active orogenic setting : experimental study and application to natural hydrographic networks.

    NASA Astrophysics Data System (ADS)

    Attal, M.; Lavé, J.

    2003-04-01

    At mountain range scale, rivers play an important role in shaping the landscape : in response to active uplift, they incise into bedrock and ensure base level lowering for hillslopes erosion. At the same time, they ensure evacuation of erosion products out of the range as suspended- or bedload. Incision rates are commonly equated with a stream power law, assuming that river incision depends only on hydrodynamic variables. However, this simplification is not mechanically satisfying : in many settings, river bedload fluxes exert an important control on incision rates, by limiting bedrock exposure or by providing an efficient tool for river mechanical abrasion. It is therefore important to better quantify the abrasion processes during bedload transport both to deduce pebble size reduction that controls carrying capacity and bedrock exposure, and to derive bedrock incision laws. Such characterization can be constrained through experimental studies or field measurements. Experimental studies on pebble and bedrock abrasion have been conducted for a long time [e.g. Daubree, 1879]. They generally provide incision rates around two orders of magnitude below natural downstream fining rates. Previous authors have suggested that this discrepancy could be explained by the fact that experimental device doesn’t reproduce really the abrasion phenomena effective in natural rivers, like saltation and following impacts. In this way, we have built an experimental device in order to reproduce these abrasion phenomena. It consists of a circular flume of 30 cm width and of 60 cm curvature radius. Water is injected tangentially on four points ; it generates a flow that produce sediment motion. Velocity vertical profile is roughly similar to what could be observed in natural rivers. The bottom and the sides of the device are interchangeable, in order to measure distinctly pebble abrasion or the interactions between sediment load and substratum. The aim of this experimental study is to

  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. 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

  20. 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.

  1. The role of inherited subduction asymmetries on the build-up of orogenic wedges: the Dinarides/Carpathians/Balkans and Eastern Alps/Dinarides connections

    NASA Astrophysics Data System (ADS)

    Matenco, L. C.; Cloetingh, S.

    2009-04-01

    The controlling mechanisms of orogenic shortening and collision govern the architecture of the coeval sedimentary infill of foreland and back-arc basins and their subsequent exhumation. Continental collision coincides with the onset of large-scale out-of-sequence deformation, modelling studies indicating that orogenic steady state largely involves exhumation in the core of the orogen, which is recorded in natural examples by hinterland exhumation associated with processes such as crustal-scale backthrusting. High convergence rates will apparently exhume large amounts of crustal material entering the collision zone along bi-vergent orogens defining a "retro-shear" type of collision. However, in "soft" collisional orogens (such as the Carpathians) the lower orogenic plate is not always a "conveyer belt", i.e. transferring and incorporating material into the upper plate. The low convergence rates couple this lower plate distributing crustal exhumation all across the orogen due to the gradual shift of the lower plate accretion, defining a "foreland-coupling" type of collision mechanics. The balance between the two types of collisions is lesss known. In the case of the Alps and the Hellenides-Balkanides systems, the "retro-shear" exhumation can also be alternatively defined as being in the direct continuation of pre-existing asymmetries from inherited subduction zones (such as the Dinarides or the Carpathians). These subduction zones evolved and were gradually closed/collided during Cretaceous and Eocene and are in the prolongation of the Southern Alps (and peri-Adriatic lineament) and the Balkans retro-wedges respectively. The activity of these retro-wedges is recorded during and/or immediately after the foreland-coupling collision of these neighbouring subduction zones with compatible kinematics. A causal relationship is therefore argued by means of structures, large scale profiling and quantitative reconstructions.

  2. 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.

  3. 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.

  4. 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

  5. Topography of the Variscan orogen in Europe: failed-not collapsed

    NASA Astrophysics Data System (ADS)

    Franke, Wolfgang

    2014-07-01

    The Variscan orogenic collage consists of three subduction-collision systems (Rheno-Hercynian, Saxo-Thuringian and Massif Central-Moldanubian). Devonian to early Carboniferous marine strata are widespread not only in the individual foreland fold and thrust belts, but also in post-tectonic basins within these foreland belts and on the Cadomian crust of peri-Gondwanan microcontinental fragments, which represent the upper plates of the subduction/collision zones. These marine basins preclude high elevations in the respective areas and also in their neighbourhood. Widespread late Carboniferous intra-montane basins with their coal-bearing sequences are likewise incompatible with high and dry plateaus. While narrow belts with high elevations remain possible along active margins within the orogen, comparison of the Variscides with the Himalaya/Tibetan plateau is unfounded. Plausible reasons for the scarcity of high Variscan relief include subduction of oceanic and even continental crust, subduction erosion, orogen-parallel extension and—most important—lithospheric thinning accompanied by high heat flow and magmatism. In many areas, timing and areal array of magmatism and HT metamorphism are not compatible with a model of tectonic thickening and subsequent gravitational collapse. It is suggested, instead, that lithospheric thinning and heating are due to mantle activities caused by the Tethys rift. The lower and middle crust were thermally softened and rendered unfit for stacking and isostatic uplift: in terms of topography, the Variscides represent a failed orogen. The HT regime also explains the abundance of granitoids and HT/LP metamorphic rocks typical of the Variscides. Melting in the HT regime extracted mafic components from Variscan and Cadomian crust as well as from Cadomian metasomatized lithospheric mantle, thus mimicking subduction-related magmatism. The onset of the HT regime at c. 340 Ma may also have triggered the final ascent of HP/UHP felsic metamorphic

  6. Collision-Orogen provenance: Modern sands from big Himalayan rivers

    NASA Astrophysics Data System (ADS)

    Garzanti, E.; Vezzoli, G.; Andò, S.; France-Lanord, C.; Singh, S. K.; Clift, P.

    2003-04-01

    The Himalayan orogen represents the most important source of terrigenous detritus on Earth. The Ganga-Brahmaputra river system ranks first in terms of sediment load, and together with the Indus carried to the Indian Ocean ca 2 billion tons of sediments annually. Stored in the Bengal and Indus fans, the world's largest turbiditic cones by far, are ca 15*10^6km^3 of detritus derived from the Himalayas since the Paleogene. Nevertheless, petrographic and mineralogic composition of sediments transported by big Himalayan rivers has been poorly documented so far. This high-resolution actualistic study provides a key to interpret detrital modes of Tertiary foreland basin strata, and sheds light on diagnostic features of collision-orogen provenance. Composition of Himalayan-derived sands indicates dominant contribution from amphibolite-facies rocks exposed both south and north of the Indus-Tsangpo suture, reflecting extreme uplift and widespread exhumation of the deep roots of the orogen. Hornblende-dominated dense-mineral suites of both Indus and Brahmaputra sands are largely derived from Asian active-margin plutons. The Indus sands in particular reflect major supply from arc batholiths, widely exposed in Ladakh, Kohistan, and along the Karakorum and Hindukush belts. The Ganga sands are instead chiefly derived from High-Himalayan nappes with Tertiary metamorphism up to sillimanite-grade. Intermediate composition characterizes the Brahmaputra sands, shed largely from High Himalayan crystalline rocks subject to very rapid erosion around the Namche-Barwa syntaxis, and subordinately from Gangdese batholiths in the Tibetan tract and from plutonic rocks of the Mishmi hills farther downstream. Supply from sedimentary covers and recycling of accreted foreland-basin strata are significant, whereas volcanic and ophiolitic detritus is volumetrically negligible. Carbonate grains, common in the Indus sands and present in the Ganga sands, are negligible in the Brahmaputra sands

  7. The Impact of Partial Melting in the Orogenic Cycle

    NASA Astrophysics Data System (ADS)

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

    2010-12-01

    Open source, community driven numerical codes available at geodynamics.org allow geologists to model orogenic processes including partial melting and its consequences during orogenic cycles. Here we explore the role of partial melting during continental subduction and its impact on the evolution of orogenic plateaux and that of migmatite-cored metamorphic core complexes. Continental subduction and orogenic plateaux: Numerical experiments show that when continental slabs buried into the mantle meet their solidus, crustal melt is confined to the slab during its ascent and ponds at the Moho (Fig. 1a). The displaced overlying crust is extruded horizontally into the weak lower crust of the continent, resulting in Earth’s surface uplift to form an orogenic plateau, and Moho downward motion to accommodate the influx of material into the lower crust. This model suggests a link between continental subduction, melting and the build up of orogenic plateaux, and show that partial melting may be a significant process in exhumation of ultrahigh-pressure (UHP) rocks. Model results are consistent with the common association of UHP rocks and migmatite. Growth and destruction of orogenic plateaux: The lateral growth of orogenic plateaux is often attributed to the flow of the plateau weak partially melted lower crust into its foreland in some cases over a distance > 1500 km in 15 myr. Using pre-thickening temperatures compatible with Tibet’s uplift history, we show that mass redistribution processes are dynamically coupled, and that CFE velocities are limited to less than 1 cm.yr-1 (~150 km in 15 myr) by cooling and crystallization of the melted channel in the foreland and by any upward deviation into metamorphic domes of the melted channel by extension in the plateau (Fig. 1b). Gravitational collapse and metamorphic core complexes: Localization of extension in the upper crust triggers convergent flow in the partially molten deep crust channel. This convergent flow leads to the

  8. 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

  9. Detrital fission-track-compositional signature of an orogenic chain-hinterland basin system: The case of the late Neogene Quaternary Valdelsa basin (Northern Apennines, Italy)

    NASA Astrophysics Data System (ADS)

    Balestrieri, M. L.; Benvenuti, M.; Tangocci, F.

    2013-05-01

    Detrital thermochronological data collected in syn-tectonic basin deposits are a promising tool for deciphering time and processes of the evolution of orogenic belts. Our study deals with the Valdelsa basin, one of the wider basins of central Tuscany, Italy. The Valdelsa basin is located at the rear of the Northern Apennines, a collisional orogen whose late Neogene Quaternary development is alternatively attributed to extensional and compressional regimes. These contrasting interpretations mostly rely on different reconstructions of the tectono-sedimentary evolution of several basins formed at the rear of the chain since the late Tortonian. Here, we explore the detrital thermochronological-compositional signature of tectonic and surface processes during the Valdelsa basin development. For this aim, detrital apatite fission-track analysis of 21 sand samples from the latest Messinian Gelasian fluvial to shallow marine basin deposits, has been accompanied by a clast composition analysis of 7 representative outcrops of the conglomerate facies. The grain-age distributions of the sediment samples are generally characterized by two distinct components, one younger peak (P1) varying between 5.5 ± 2.8 and 9.5 ± 1.0 Ma and one older peak (P2) varying from 15.0 ± 8.0 to 41.0 ± 10 Ma. By comparison with some bedrock ages obtained from the E-NE basin shoulder, we attributed the P2 peak to the Ligurian Units and the P1 peak to the Macigno Formation (Tuscan Units). These units are arranged one upon the other in the complex nappe pile forming the Northern Apennines orogen. While the gravel composition indicates a predominant feeding from the Ligurian units all along the sedimentary succession with a subordinate occurrence of Macigno pebbles slightly increasing upsection, the P1 peak is present even in the oldest collected sandy sediments. The early P1 occurrence reveals that the Macigno was exposed in the E-NE basin shoulder since at least the latest Messinian-early Zanclean

  10. 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.

  11. 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

  12. Collisional melange development: Geologic associations of active melange-forming processes with exhumed melange facies in the western Banda orogen, Indonesia

    NASA Astrophysics Data System (ADS)

    Harris, R. A.; Sawyer, R. K.; Audley-Charles, M. G.

    1998-06-01

    Analysis of block assemblages, matrix clay mineral composition and microfauna, and offshore seismic reflection profiles reveal that the Bobonaro melange in the Timor region is sourced from mud-rich Australian continental margin sequences that are remobilized during accretion and form various facies depending on the structural conditions of emplacement. Melange facies include broken formation, matrix-rich mud injections, and classic mixed block-in-clay facies. Each of these are distinguished by varying degrees of remobilization, mixing, and dispersion at different structural positions across the orogenic wedge. The most important structural control is whether melange was generated beneath or in front of upper plate Banda forearc basement (Banda Terrane). At the present collisional deformation front in the Timor trough, seismic reflection profiles show that melange forms mostly by stratal detachment and fluid-assisted remobilization above a basal decollement propagating laterally along overpressured Jurassic to Cretaceous clay-rich sequences of the distal Australian continental margin. The broken, clay-rich material injects upward through faults to form intrusive bodies at the base of slope cover sediment to form mud ridges at the surface. Similar patterns of stratal disruption are exposed onshore in the Pliocene Kolbano fold and thrust wedge of southern Timor, which is structurally contiguous with the Timor trough deformation front. Melange in the Kolbano Mountains is mostly broken formation and matrix-rich injections of mud from Jurassic and Cretaceous units. Deformation mechanisms include intense layer-parallel extension associated with emplacement by mud diapirs that rise from near the decollement upward to the surface along fault conduits. In the hinterland of the orogenic wedge (East Timor and northern West Timor), melange is dominantly of mixed block-in-clay facies with large blocks derived from roof thrust sheets of intermixed Banda Terrane and Maubisse

  13. Suturing and extensional reactivation in the Grenville orogen, Canada

    NASA Astrophysics Data System (ADS)

    Busch, Jay P.; Mezger, Klaus; van der Pluijm, Ben A.

    1997-06-01

    Sutures are zones of weakness within orogenic belts that have the potential to become reactivated during orogenic evolution. The Robertson Lake shear zone marks a major tectonic boundary in the southeastern Grenville orogen of Canada that has been intermittently active for at least 130 m.y. The shear zone played a major role in the compressional stage of the orogenic cycle as well as during postorogenic collapse. The zone separates the Elzevir terrane to the west and the Frontenac terrane to the east. Sphene ages (U-Pb) indicate that these two terranes have distinct tectonothermal histories and that the shear zone represents a “cryptic suture.” In its current state, the shear zone is a low angle (30°ESE dip) plastic to brittle extensional shear zone that separates the Mazinaw (footwall) and Sharbot Lake (hanging wall) domains. Integration of structural, metamorphic, and chronologic data leads to a model that describes the complete evolution of this fundamental tectonic boundary that evolved from an early compressional zone (ca. 1030 Ma) to a late extensional zone (until at least 900 Ma).

  14. 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

  15. 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

  16. European Variscan orogenic evolution as an analogue of Tibetan-Himalayan orogen: Insights from petrology and numerical modeling

    NASA Astrophysics Data System (ADS)

    Maierová, P.; Schulmann, K.; Lexa, O.; Guillot, S.; Štípská, P.; Janoušek, V.; Čadek, O.

    2016-07-01

    The European Variscan orogeny can be compared to the Tibetan-Himalayan system for three main reasons: (1) The Variscan belt originated through progressive amalgamation of Gondwanan blocks that were subsequently squeezed between the Laurussia and Gondwana continents. Similarly, the Tibetan-Himalayan orogen results from amalgamated Gondwanan blocks squeezed between Asia and India. (2) The duration of the collisional period and the scale of the two orogens are comparable. (3) In both cases the collisional process resulted in formation of a thick crustal root and long lasting high-pressure granulite facies metamorphism. Recent petrological data allow a more detailed comparison pointing to similarities also in the midcrustal re-equilibration of the granulites and their association with specific (ultra)potassic magmatic rocks. In both orogens, the origin of the granulites was attributed to relamination and thermal maturation of lower crustal allochthon below upper plate crust. Subsequent evolution was explained by midcrustal flow eventually leading to extrusion of the high-grade rocks. We propose that the lower and middle crustal processes in hot orogens are connected by gravity overturns. Such laterally forced gravity-driven exchanges of material in the orogenic root were already documented in the Variscides, but the recent data from Tibet and Himalaya show that this process may have occurred also elsewhere. Using numerical models, we demonstrate that the exchange of the lower and middle crust can be efficient even for a minor density inversion and various characteristics of the crustal layers. The modeled pressure-temperature paths are compatible with two-stage metamorphism documented in Tibet and Himalaya.

  17. 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

  18. 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

  19. 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.

  20. 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.

  1. Feeding the "aneurysm": Orogen-parallel mass transport into Nanga Parbat and the western Himalayan syntaxis

    NASA Astrophysics Data System (ADS)

    Whipp, David M.; Beaumont, Christopher; Braun, Jean

    2014-06-01

    The Nanga Parbat-Haramosh massif (NPHM; western Himalayan syntaxis) requires an influx of mass exceeding that in the adjacent Himalayan arc to sustain high topography and rapid erosional exhumation rates. What supplies this mass flux and feeds this "tectonic aneurysm?" We show, using a simple 3-D model of oblique orogen convergence, that velocity/strain partitioning results in horizontal orogen-parallel (OP) crustal transport, and the same behavior is inferred for the Himalaya, with OP transport diverting converging crust toward the syntaxis. Model results also show that the OP flow rate decreases in the syntaxis, thereby thickening the crust and forming a structure like the NPHM. The additional crustal thickening, over and above that elsewhere in the Himalayan arc, sustains the rapid exhumation of this "aneurysm." Normally, velocity/strain partitioning would be minimal for the Himalayan arc where the convergence obliquity is no greater than ~40°. However, we show analytically that the Himalayan system can act both as a critical wedge and exhibit strain partitioning if both the detachment beneath the wedge and the bounding rear shear zone, which accommodates OP transport, are very weak. Corresponding numerical results confirm this requirement and demonstrate that a Nanga Parbat-type shortening structure can develop spontaneously if the orogenic wedge and bounding rear shear zone can strain rate soften while active. These results lead us to question whether the position of NPHM aneurysm is localized by river incision, as previously suggested, or by a priori focused tectonic shortening of the crust in the syntaxis region as demonstrated by our models.

  2. A geophysical model of the Variscan orogenic root (Bohemian Massif): Implications for modern collisional orogens

    NASA Astrophysics Data System (ADS)

    Guy, Alexandra; Edel, Jean-Bernard; Schulmann, Karel; Tomek, Čestmir; Lexa, Ondrej

    2011-05-01

    surface geology are interpreted as a result of Carboniferous partial overturn of low density lower crust and high and intermediate density crust in the area of central root and by viscous extrusion of low density orogenic lower crust over the high density Bruno-Vistulian continent. Comparison of these data with geophysical profiling of the Andean and the Tibetan plateaus suggests that modern orogenic systems reveal comparable deep crustal geophysical pattern. Based on these similarities we propose that the Variscan root represents a deep crustal section of above mentioned plateaus, which may have develop by the same orogenic process.

  3. Orogenic, Ophiolitic, and Abyssal Peridotites

    NASA Astrophysics Data System (ADS)

    Bodinier, J.-L.; Godard, M.

    2003-12-01

    "Tectonically emplaced" mantle rocks include subcontinental, suboceanic, and subarc mantle rocks that were tectonically exhumed from the upper mantle and occur:(i) as dispersed ultramafic bodies, a few meters to kilometers in size, in suture zones and mountain belts (i.e., the "alpine," or "orogenic" peridotite massifs - De Roever (1957), Thayer (1960), Den Tex (1969));(ii) as the lower ultramafic section of large (tens of kilometers) ophiolite or island arc complexes, obducted on continental margins (e.g., the Oman Ophiolite and the Kohistan Arc Complex - Coleman (1971), Boudier and Coleman (1981), Burg et al. (1998));(iii) exhumed above the sea level in ocean basins (e.g., Zabargad Island in the Red Sea, St. Paul's islets in the Atlantic and Macquarie Island in the southwestern Pacific - Tilley (1947), Melson et al. (1967), Varne and Rubenach (1972), Bonatti et al. (1981)).The "abyssal peridotites" are samples from the oceanic mantle that were dredged on the ocean floor, or recovered from drill cores (e.g., Bonatti et al., 1974; Prinz et al., 1976; Hamlyn and Bonatti, 1980).Altogether, tectonically emplaced and abyssal mantle rocks provide insights into upper mantle compositions and processes that are complementary to the information conveyed by mantle xenoliths (See Chapter 2.05). They provide coverage to vast regions of the Earth's upper mantle that are sparsely sampled by mantle xenoliths, particularly in the ocean basins and beneath passive continental margins, back-arc basins, and oceanic island arcs.Compared with mantle xenoliths, a disadvantage of some tectonically emplaced mantle rocks for representing mantle compositions is that their original geodynamic setting is not exactly known and their significance is sometimes a subject of speculation. For instance, the provenance of orogenic lherzolite massifs (subcontinental lithosphere versus upwelling asthenosphere) is still debated (Menzies and Dupuy, 1991, and references herein), as is the original setting

  4. 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

  5. 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 δ15N 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 δ15N values of 1 to 6 per mil. The δ18O 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 δD values of hydrothermal micas are between -110 and -60 per mil. Ore fluids have calculated δ18O values of 8 to 16 per mil and δD values of -65 to -10 per mil at an estimated temperature of 300δC; δD 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 δDH2O 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

  6. Deformation during terrane accretion in the Saint Elias orogen, Alaska

    USGS Publications Warehouse

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

    2004-01-01

    The Saint Elias orogen of southern Alaska and adjacent Canada is a complex belt of mountains formed by collision and accretion of the Yakutat terrane into the transition zone from transform faulting to subduction in the northeast Pacific. The orogen is an active analog for tectonic processes that formed much of the North American Cordillera, and is also an important site to study (1) the relationships between climate and tectonics, and (2) structures that generate large- to great-magnitude earthquakes. The Yakutat terrane is a fragment of the North American plate margin that is partly subducted beneath and partly accreted to the continental margin of southern Alaska. Interaction between the Yakutat terrane and the North American and Pacific plates causes significant differences in the style of deformation within the terrane. Deformation in the eastern part of the terrane is caused by strike-slip faulting along the Fairweather transform fault and by reverse faulting beneath the coastal mountains, but there is little deformation immediately offshore. The central part of the orogen is marked by thrusting of the Yakutat terrane beneath the North American plate along the Chugach-Saint Elias fault and development of a wide, thin-skinned fold-and-thrust belt. Strike-slip faulting in this segment may he localized in the hanging wall of the Chugach-Saint Elias fault, or dissipated by thrust faulting beneath a north-northeast-trending belt of active deformation that cuts obliquely across the eastern end of the fold-and-thrust belt. Superimposed folds with complex shapes and plunging hinge lines accommodate horizontal shortening and extension in the western part of the orogen, where the sedimentary cover of the Yakutat terrane is accreted into the upper plate of the Aleutian subduction zone. These three structural segments are separated by transverse tectonic boundaries that cut across the Yakutat terrane and also coincide with the courses of piedmont glaciers that flow from

  7. 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

  8. 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

  9. Influence of structural setting on sulphur isotopes in Archean orogenic gold deposits, Eastern Goldfields Province, Yilgarn, Western Australia

    NASA Astrophysics Data System (ADS)

    Hodkiewicz, P. F.; Groves, D. I.; Davidson, G. J.; Weinberg, R. F.; Hagemann, S. G.

    2009-02-01

    The published mean δ34S values of ore-related pyrites from orogenic gold deposits of the Eastern Goldfields Province, Yilgarn Craton lie between -4‰ and +4‰. As for orogenic gold deposits worldwide, most deposits have positive means and a restricted range of δ34S values, but some have negative means and wider ranges of δ34S values. Wall-rock carbonation and back-mixing of similar-source fluids with different fluid pathways can explain some of the more negative δ34S signatures. However, structural setting appears to be the most important factor controlling ore-fluid oxidation state and hence the distribution of δ34S values in gold-related pyrites. Shear-hosted deposits appear to have experienced fluid-dominated processes such as phase separation, whereas stockwork, vein-hosted or disseminated deposits formed under conditions of greater rock buffering. At Victory-Defiance, in particular, negative δ34S values are more common in gently dipping dilational structures, compared to more compressional steeply dipping structures. It appears most likely that fluid-pressure fluctuations during fault-valve cycles establish different fluid-flow regimes in structures with different orientations. Rapid fluid-pressure fluctuations in dilational structures during seismic activity can cause partitioning of reduced gas phases from the ore fluid during extreme phase separation and hence are an effective method of ore-fluid oxidation, leading to large, local fluctuations in oxidation state. It is thus not necessary to invoke mixing with oxidised magmatic fluids to explain δ34S signatures indicative of oxidation. In any case, available, robust geochronology in the Eastern Goldfields Province does not support the direct involvement of oxidised magmatic fluids from adjacent granitic intrusions in orogenic gold genesis. Thus, negative mean δ34S values and large variations in δ34S values of ore-related pyrites in world-class orogenic gold deposits are interpreted to result from

  10. Structural insights into the early stages of exhumation along an orogen-scale detachment: The South Tibetan Detachment System, Dzakaa Chu section, Eastern Himalaya

    NASA Astrophysics Data System (ADS)

    Cottle, John M.; Jessup, Micah J.; Newell, Dennis L.; Searle, Michael P.; Law, Richard D.; Horstwood, Matthew S. A.

    2007-11-01

    Structural transects through the South Tibetan Detachment system (STDS) in the Dzakaa Chu valley, Tibet reveal a ˜1000-m thick, low-angle (<35°) zone of distributed ductile shear that displaces Paleozoic sediments over amphibolite facies gneisses, calc-mylonites and leucogranites of the Greater Himalayan Series (GHS). Within the shear zone, grain-size reduction with dynamic recrystallisation of quartz and growth of secondary phyllosilicates accommodated ductile deformation at elevated temperatures. Small-scale brittle normal faults and extensional shear veins overprint ductile features recording deformation at lower temperatures. Our structural data indicate that the Dzakaa Chu STDS records a progression from ductile- to brittle-deformation without development of a discrete detachment fault(s) that is common to many STDS sections. U(-Th)-Pb dating of post-kinematic leucogranites suggest that, in the lower part of the shear zone, mylonitic fabric development occurred prior to ˜20 Ma. By integrating structural and geochronological evidences we propose that the Dzakaa Chu STDS represents a deeper structural position than elsewhere in the Himalaya and provides important insight into the early ductile exhumation of the GHS that was dominated by movement along a 1-km wide shear zone without discrete brittle detachments. These findings are an important step towards understanding the development of low-angle detachment fault systems active during continental collision.

  11. Orogenic gold deposits: a proposed classification in the context of their crustal distribution and relationship to other gold deposit types

    USGS Publications Warehouse

    Groves, D.I.; Goldfarb, R.J.; Gebre-Mariam, M.; Hagemann, S.G.; Robert, F.

    1998-01-01

    The so-called 'mesothermal' gold deposits are associated with reginally metamorphosed terranes of all ages. Ores were formed during compressional to transpressional deformation processes at convergent plate margins in accretionary and collisional orogens. In both types of orogen, hydrated marine sedimentary and volcanic rocks have been added to continental margins during tens to some 100 million years of collision. Subduction-related thermal events, episodically raising geothermal gradients within the hydrated accretionary sequences, initiate and drive long-distance hydrothermal fluid migration. The resulting gold-bearing quartz veins are emplaced over a unique depth range for hydrothermal ore deposits, with gold deposition from 15-20 km to the near surface environment. On the basis of this broad depth range of formation, the term 'mesothermal' is not applicable to this deposit types as a whole. Instead, the unique temporal and spatial association of this deposit type with orogeny means that the vein systems are best termed orogenic gold deposits. Most ores are post-orogenic with respect to to tectonism of their immediate host rocks, but are simultaneously syn-orogenic with respect to ongoing deep-crustal, subduction-related thermal processes and the prefix orogenic satisfies both these conditions. On the basis of their depth of formation, the orogenic deposits are best subdivided into epizonal (12 km) classes.

  12. 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

  13. 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

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

    PubMed

    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 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 resulted in the evolution

  15. 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.

  16. Paleozoic orogens in New England, USA

    USGS Publications Warehouse

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

  17. Magnetotelluric imaging beneath the Taiwan orogen: An arc-continent collision

    NASA Astrophysics Data System (ADS)

    Bertrand, Edward A.; Unsworth, Martyn J.; Chiang, Chih-Wen; Chen, Chow-Son; Chen, Chien-Chih; Wu, Francis T.; TürkoǧLu, Ersan; Hsu, Han-Lun; Hill, Graham J.

    2012-01-01

    The Taiwan orogen has formed since the late Miocene by oblique collision between the Luzon Volcanic Arc on the Philippine Sea Plate, and the Eurasian continental margin. This oblique collision has produced an orogen that decreases in age from north to south, and permits study of the temporal evolution of an arc-continent collision. These factors make Taiwan a favorable location to study the process of arc-continent collision. The first long-period magnetotelluric (MT) measurements were recorded in Taiwan as part of the Taiwan Integrated Geodynamics Research (TAIGER) project in 2006-7. Measurements were made at 82 sites on three transects across south, central and north Taiwan, that span the breadth of the orogen and cross all major tectonic boundaries. Robust, remote reference processing of the MT time series data resulted in high-quality soundings that were modeled in both 2 and 3-dimensions. These MT models support predictions of lithospheric deformation (i.e., thick-skinned tectonics) beneath the Central Ranges in south and central Taiwan, but are inconsistent with predictions of orogen-scale thin-skinned models. The MT resistivity model for northern Taiwan is consistent with dewatering of the subducting Philippine slab, and with deformation described by the subducting-indenter tectonic model. Modeling the TAIGER MT data has definitively shown that conductive, and seismically active crustal structures, exist to 30+ km beneath the orogen. These conductive regions, interpreted as interconnected fluid, map pervasive zones of collisional deformation that are lithospheric in scale.

  18. 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.

  19. 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.

  20. 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.

  1. 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.

  2. Origin and structure of major orogen-scale exhumed strike-slip

    NASA Astrophysics Data System (ADS)

    Cao, Shuyun; Neubauer, Franz

    2016-04-01

    The formation of major exhumed strike-slip faults represents one of the most important dynamic processes affecting the evolution of the Earth's lithosphere and surface. Detailed models of the potential initiation and properties and architecture of orogen-scale exhumed strike-slip faults and how these relate to exhumation are rare. In this study, we deal with key properties controlling the development of major exhumed strike-slip fault systems, which are equivalent to the deep crustal sections of active across fault zones. We also propose two dominant processes for the initiation of orogen-scale exhumed strike-slip faults: (1) pluton-controlled and (2) metamorphic core complex-controlled strike-slip faults. In these tectonic settings, the initiation of faults occurs by rheological weakening along hot-to-cool contacts and guides the overall displacement and ultimate exhumation. These processes result in a specific thermal and structural architecture of such faults. These types of strike-slip dominated 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 during various stages of faulting. The high variety of distinctive fault rocks is a potential evidence for recognition of these types of strike-slip faults. Exhumation of mylonitic rocks is, therefore, a common feature of such reverse oblique-slip strike-slip faults, implying major transtensive and/or transpressive processes accompanying pure strike-slip motion during exhumation. Some orogen-scale strike-slip faults nucleate and initiate along rheologically weak zones, e.g. at granite intrusions, zones of low-strength minerals, thermally weakened crust due to ascending fluids, and lateral borders of hot metamorphic core complexes. A further mechanism is the juxtaposition of mechanically strong mantle lithosphere to hot asthenosphere in continental transform faults (e.g., San

  3. Miocene thrusting in the eastern Sila Massif: Implication for the evolution of the Calabria-Peloritani orogenic wedge (southern Italy)

    NASA Astrophysics Data System (ADS)

    Vignaroli, G.; Minelli, L.; Rossetti, F.; Balestrieri, M. L.; Faccenna, C.

    2012-05-01

    Alpine orogens in the central Mediterranean region have revealed the concomitance of crustal extension in back-arc domain and crustal shortening in frontal domain. Quantitative data of deformation in the frontal orogenic wedges are necessary to understand how the shortening-extension pair evolves in terms of structures, orogenic transport, timing, and exhumation rate. This paper deals with kinematics and ages of the frontal thrust systems of the Calabria-Peloritani Arc (Italy) exposed in the eastern Sila Massif. We first present structural fieldwork, onshore and offshore well log data, and new apatite fission-track (AFT) thermochronology. Then, we describe the structural architecture of the studied area as an ENE-verging stacking of thrust sheets involving basement units and syn-orogenic sediments. The AFT study documents that thrust sheets entered the partial annealing zone from 18 Ma to 13 Ma. This Early-Middle Miocene thrusting phase was coeval with exhumation of high-pressure/low temperature metamorphic rocks in the hinterland of the orogen (Coastal Chain area), mainly driven by top-to-the-W extensional tectonics. Opposite kinematic shear senses (contractional top-to-the-E and extensional top-to-the-W) and different exhumation rates (slow in the frontal, more rapid in the hinterland) are framed in a tectonic scenario of a critically tapered orogenic wedge during the eastward retreating of the Apennine slab.

  4. 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

  5. Short episodes of crust generation during protracted accretionary processes: Evidence from Central Asian Orogenic Belt, NW China

    NASA Astrophysics Data System (ADS)

    Tang, Gong-Jian; Chung, Sun-Lin; Hawkesworth, Chris J.; Cawood, P. A.; Wang, Qiang; Wyman, Derek A.; Xu, Yi-Gang; Zhao, Zhen-Hua

    2017-04-01

    Accretionary orogens are major sites of generation of continental crust but the spatial and temporal distribution of crust generation within individual orogens remains poorly constrained. Paleozoic (∼540-270 Ma) granitic rocks from the Alati, Junggar and Chinese Tianshan segments of the Central Asian Orogenic Belt (CAOB) have markedly bimodal age frequency distributions with peaks of ages at ∼400 Ma and 280 Ma for the Altai segment, and ∼430 Ma and 300 Ma for the Junggar and Chinese Tianshan segments. Most of the magma was generated in short time intervals (∼20-40 Ma), and variations in magma volumes and in Nd-Hf isotope ratios are taken to reflect variable rates of new crust generation within a long-lived convergent plate setting. The Junggar segment is characterized by high and uniform Nd-Hf isotope ratios (εNd (t) = + 5 to + 8; zircon εHf (t) = + 10 to + 16) and it appears to have formed in an intra-oceanic arc system. In the Altai and Chinese Tianshan segments, the Nd-Hf isotope ratios (εNd (t) = - 7 to + 8; zircon εHf (t) = - 16 to + 16) are lower, although they increase with decreasing age of the rock units. The introduction of a juvenile component into the Chinese Tianshan and Altai granitic rocks appears to have occurred in continental arc settings and it reflects a progressive reduction in the contributions from old continental lower crust and lithospheric mantle. Within the long-lived convergent margin setting (over ∼200 Ma), higher volumes of magma, and greater contributions of juvenile material, were typically emplaced over short time intervals of ∼20-40 Ma. These intervals were associated with higher Nb/La ratios, coupled with lower La/Yb ratios, in both the mafic and granitic rocks, and these episodes of increased magmatism from intraplate-like sources are therefore thought to have been in response to lithospheric extension. The trace element and Nd-Hf isotope data, in combination with estimates of granitic magma volumes, highlight

  6. 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.

  7. 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,

  8. An isotopic perspective on growth and differentiation of Proterozoic orogenic crust: From subduction magmatism to cratonization

    NASA Astrophysics Data System (ADS)

    Johnson, Simon P.; Korhonen, Fawna J.; Kirkland, Christopher L.; Cliff, John B.; Belousova, Elena A.; Sheppard, Stephen

    2017-01-01

    The in situ chemical differentiation of continental crust ultimately leads to the long-term stability of the continents. This process, more commonly known as 'cratonization', is driven by deep crustal melting with the transfer of those melts to shallower regions resulting in a strongly chemically stratified crust, with a refractory, dehydrated lower portion overlain by a complementary enriched upper portion. Since the lower to mid portions of continental crust are rarely exposed, investigation of the cratonization process must be through indirect methods. In this study we use in situ Hf and O isotope compositions of both magmatic and inherited zircons from several felsic magmatic suites in the Capricorn Orogen of Western Australia to highlight the differentiation history (i.e. cratonization) of this portion of late Archean to Proterozoic orogenic crust. The Capricorn Orogen shows a distinct tectonomagmatic history that evolves from an active continental margin through to intracratonic reworking, ultimately leading to thermally stable crust that responds similarly to the bounding Archean Pilbara and Yilgarn Cratons. The majority of magmatic zircons from the main magmatic cycles have Hf isotopic compositions that are generally more evolved than CHUR, forming vertical arrays that extend to moderately radiogenic compositions. Complimentary O isotope data, also show a significant variation in composition. However, combined, these data define not only the source components from which the magmas were derived, but also a range of physio-chemical processes that operated during magma transport and emplacement. These data also identify a previously unknown crustal reservoir in the Capricorn Orogen.

  9. Complexities of Lu-Hf geochronology in convergent orogens

    NASA Astrophysics Data System (ADS)

    Mulcahy, S. R.; Vervoort, J. D.

    2015-12-01

    Subduction, terrane accretion, and arc magmatism leave a complex and sometimes incomplete record of metamorphism and deformation. The range of metamorphic temperatures and assemblages produced throughout the tectonic evolution of a single orogen often requires multiple isotopic systems to date distinct events. Lu-Hf geochronology, notably, has proven successful for dating metamorphism from a variety of bulk compositions spanning temperatures <350-850 C. We review the success of applying Lu-Hf geochronology in combination with other isotopic systems to date metamorphism from range of metamorphic conditions within convergent margins. We then discuss some complexities of Lu-Hf geochronology when dating samples with complicated metamorphic histories. Garnet and lawsonite isochrons often exhibit excess scatter (high MSWD's) that can be attributed to a number of factors: secondary mineral inclusions, prolonged garnet growth durations, disequilibrium at low temperatures, and polyphase metamorphic histories. Samples with high-Hf inclusions in isotopic equilibrium host phases can lead to decreased precision, but still produce meaningful ages. At high temperatures Lu-Hf ages may date peak metamorphism, cooling from peak temperatures, or result in spurious ages because of preferential retention of 176Hf over 176Lu in garnet. Despite these complexities, and perhaps because of them, new aspects of the metamorphic history may be revealed that are not readily recorded by other isotopic systems. Minerals other than garnet and lawsonite, particularly apatite, and perhaps epidote, offer exciting new possibilities for Lu-Hf geochronology. Careful fieldwork, detailed petrology and geochemistry, and collaborative efforts using multiple isotopic systems offer the best approach to solving tectonic problems in convergent orogens.

  10. Active optical zoom system.

    PubMed

    Wang, Di; Wang, Qiong-Hua; Shen, Chuan; Zhou, Xin; Liu, Chun-Mei

    2014-11-01

    In this work, we propose an active optical zoom system. The zoom module of the system is formed by a liquid lens and a spatial light modulator (SLM). By controlling the focal lengths of the liquid lens and the encoded digital lens on the SLM panel, we can change the magnification of an image without mechanical moving parts and keep the output plane stationary. The magnification can change from 1/3 to 3/2 as the focal length of the encoded lens on the SLM changes from infinity to 24 cm. The proposed active zoom system is simple and flexible, and has widespread application in optical communications, imaging systems, and displays.

  11. Imaging nervous system activity.

    PubMed

    Fields, Douglas R; Shneider, Neil; Mentis, George Z; O'Donovan, Michael J

    2009-10-01

    This unit describes methods for loading ion- and voltage-sensitive dyes into neurons, with a particular focus on the spinal cord as a model system. In addition, we describe the use of these dyes to visualize neural activity. Although the protocols described here concern spinal networks in culture or an intact in vitro preparation, they can be, and have been, widely used in other parts of the nervous system.

  12. The role of radiogenic heat in prolonged intraplate reworking: The Capricorn Orogen explained?

    NASA Astrophysics Data System (ADS)

    Korhonen, Fawna J.; Johnson, Simon P.

    2015-10-01

    Links between intraplate crustal deformation and the thermal regime of the lithosphere have been investigated using numerical models, but these conceptual models must be tested using well-constrained natural systems. The Proterozoic Capricorn Orogen of Western Australia is ideally suited for such a study; after arc accretion, it records a protracted history of intracrustal differentiation and over one billion years of subsequent tectonic reworking. The early addition of juvenile arc material initially reduced the heat production of the crust, whereas subsequent recycling of the deep crust ultimately produced radiogenic granites in the shallow crust. Using whole rock and magmatic zircon compositions, we show that the shallow crust of the Capricorn Orogen has been progressively enriched in heat-producing elements with time. The high heat production is mainly controlled by thorium, concentrated in LREE-enriched phosphates that grew during the late stages of crystallization of crustally-derived granites. Using a numerical model, we investigate the thermal effects of this evolved crustal stratification and compare them with quantitative data on the pressure-temperature-time evolution of a non-magmatic Mesoproterozoic reworking event. The results provide new information concerning the process by which the thermal conditions necessary for the reworking of orogenic crust are generated and sustained for prolonged timescales (>110 Ma). Furthermore, we demonstrate that perturbations to the radiogenic crust lead to warmer geotherms and consequent lithospheric weakening, which has a fundamental control on intraplate reworking of long-lived orogens.

  13. Young upper crustal chemical composition of the orogenic Japan Arc

    NASA Astrophysics Data System (ADS)

    Togashi, Shigeko; Imai, Noboru; Okuyama-Kusunose, Yasuko; Tanaka, Tsuyoshi; Okai, Takashi; Koma, Takeshi; Murata, Yasuaki

    2000-11-01

    A new geochemical estimate of the young (mainly Paleozoic age to present) upper crust of the Japan Arc shows a dacitic composition in contrast to the idea that andesite is predominant in active orogenic arcs. Temporal changes in composition are not significant from the Paleozoic age to the present for the Japan Arc. The major element composition is similar to previous models of old cratonic upper crusts. The coincidence in the major elements between young and old crusts indicates that essential mechanisms during crust formation have not changed from the Archean era to the present. In trace element compositions the average young upper crust of the Japan Arc has higher Sb and As concentrations and lower concentrations of alkaline, light rare earth, and high field strength elements with respect to previous models of continental upper crusts. The large degree of constancy of trace element composition in marine sedimentary rocks is in contrast to the large variety in igneous rocks. However, the averages for both accretionary and nonaccretionary sedimentary rocks are almost identical to the average for the igneous rocks of the Japan Arc, with the exceptions of high Sb and As concentrations in unmetamorphosed sedimentary rocks. The compositional homogeneity among different types of rocks on an arc scale implies that recycling processes mechanically mix the arc-derived igneous materials to homogenize the chemical composition during erosion, transportation, sedimentation, accretion, and uplifting. Since the contribution of oceanic crust to the composition of arc crust is small, the recycling processes have not changed the bulk upper crustal composition of the active continental margin except increase the Sb and As from sediments. Instead, the influx of differentiated acidic rocks from depth is essential to characterize the orogenic crust formation of the young Japan Arc. The characteristically low incompatible element content of the Japanese upper arc crust appears

  14. Orogen parallel britlle extension in the Inner Northwestern Alps.

    NASA Astrophysics Data System (ADS)

    Champagnac, J. D.; Sue, C.; Delacou, B.; Burkhard, M.

    2003-04-01

    Rising attention has been recently paid to the latest extensional structures in the Alps, which took place under increasingly brittle conditions (e.g. Bistacchi, et al. 2000, Sue and Tricart 2002). Some of these structures seems to be still active . This brittle extension mainly occurs in the core of the arc, in the internal zones and could be linked to the ongoing extension observed under the light of seismotectonics studies (Sue, et al. 1999). Here we analyze the brittle deformation in the internal zone of the Northwestren Alps, from the Simplon fault zone (to the Northeast) to the Vanoise area (to the South). Our analysis is based on systematic mapping of the fault patterns, using remote sensing analysis combined with field work. The fault pattern we studied crosscuts all the ductile compression-related structures and piles of nappes. Thus, this brittle deformation postdates the ductile deformations, and is associated to one of the latter tectonic event in the belt during the recent-alpine history (Neogene times). The determination of paleostress field(s), based on the inversion of a large database of fault/stria measurements constrain the behaviour of this fault pattern: The results indicate a major large scale extensional paleostress field, in the NE-SW direction. In the South Valais, this orogen-parallel extension could be linked to the normal/dextral Simplon-Rhône fault zone dynamics. Further to the South, the paleostress fields also locally indicate NE-SW extension, but the driving forces remains a matter of debate. The orogen-parallel extension observed in this study have to be linked to the orogen-radial extension observed by (Sue and Tricart 2002) in the Briançonnais area, further to the South. We must also determine the relationship between the large scale brittle extension and the seismotectonics radial-to-the-arc extension. The geographic and/or temporal variations of the (paleo)stress fields remain to be constrain to precise the recent geodynamics

  15. Active control system trends

    NASA Technical Reports Server (NTRS)

    Yore, E. E.; Gunderson, D. C.

    1976-01-01

    The active control concepts which achieve the benefit of improved mission performance and lower cost and generate system trends towards improved dynamic performance, more integration, and digital fly by wire mechanization are described. Analytical issues and implementation requirements and tools and approaches developed to address the analytical and implementation issues are briefly discussed.

  16. 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…

  17. 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…

  18. 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).

  19. 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.

  20. Early tectonic evolution of the Thomson Orogen in Queensland inferred from constrained magnetic and gravity data

    NASA Astrophysics Data System (ADS)

    Spampinato, Giovanni P. T.; Betts, Peter G.; Ailleres, Laurent; Armit, Robin J.

    2015-05-01

    The crustal architecture as well as the kinematic evolution of the Thomson Orogen in Queensland is poorly resolved because the region is concealed under thick Phanerozoic sedimentary basins and the basement geology is known from limited drill holes. Combined potential field and seismic interpretation indicates that the Thomson Orogen is characterized by prominent regional NE- and NW-trending structural grain defined by long wavelength and low amplitude geophysical anomalies. The 'smooth' magnetic signature is interpreted to reflect deeply buried source bodies in the mid- to lower crust. Short wavelength positive magnetic features that correlate with negative gravity anomalies are interpreted to represent shallower granitic intrusions. They appear to be focused along major fault zones that might have controlled the locus for magmatism. The eastern Thomson Orogen is characterized by a prominent NE structural grain and orthogonal faults and fold interference patterns resulting in a series of troughs and highs. The western Thomson Orogen consists of a series of NW-trending structures interpreted to reflect reverse faults. Sedimentation and basin development are interpreted to have initiated in the Neoproterozoic to Early Cambrian during E-W- to ENE-WSW extension, possibly related to the Rodinia break-up. This extensional event was followed by Late Cambrian shortening recorded in the Maneroo Platform and the Diamantina River Domain which possibly correlates with the Delamerian Orogeny. Renewed deposition and volcanism occurred during the Ordovician and may have continued until Late Silurian, resulting in thinned Proterozoic basement crust and extensive basin systems that formed in a distal continental back-arc environment. Our interpretation places the Thomson Orogen to the west of the Neoproterozoic passive margin preserved in the Anakie Inlier. The region is likely to represent the internal extensional architecture during the Rodinia break-up that has been

  1. Lateral thinking: 2-D interpretation of thermochronology in convergent orogenic settings

    NASA Astrophysics Data System (ADS)

    Batt, Geoffrey E.; Brandon, Mark T.

    2002-05-01

    Lateral motion of material relative to the regional thermal and kinematic frameworks is important in the interpretation of thermochronology in convergent orogens. Although cooling ages in denuded settings are commonly linked to exhumation, such data are not related to instantaneous behavior but rather to an integration of the exhumation rates experienced between the thermochronological 'closure' at depth and subsequent exposure at the surface. The short spatial wavelength variation of thermal structure and denudation rate typical of orogenic regions thus renders thermochronometers sensitive to lateral motion during exhumation. The significance of this lateral motion varies in proportion with closure temperature, which controls the depth at which isotopic closure occurs, and hence, the range of time and length scales over which such data integrate sample histories. Different chronometers thus vary in the fundamental aspects of the orogenic character to which they are sensitive. Isotopic systems with high closure temperature are more sensitive to exhumation paths and the variation in denudation and thermal structure across a region, while those of lower closure temperature constrain shorter-term behaviour and more local conditions. Discounting lateral motion through an orogenic region and interpreting cooling ages purely in terms of vertical exhumation can produce ambiguous results because variation in the cooling rate can result from either change in kinematics over time or the translation of samples through spatially varying conditions. Resolving this ambiguity requires explicit consideration of the physical and thermal framework experienced by samples during their exhumation. This can be best achieved through numerical simulations coupling kinematic deformation to thermal evolution. Such an approach allows the thermochronological implications of different kinematic scenarios to be tested, and thus provides an important means of assessing the contribution of

  2. Microdiamonds from the European Variscan Orogenic Belt

    NASA Astrophysics Data System (ADS)

    Kotkova, J.; Jakubova, P.; Whitehouse, M.; Fedortchouk, Y.

    2014-12-01

    Diamond, along with coesite, has been discovered recently in the continental crustal rocks of the European Variscan orogenic belt, namely the Bohemian Massif (BM). In addition to the garnet-phengite gneiss in Germany, western BM, microdiamond occurs in major rock forming minerals - garnet, kyanite - and in zircon in ultrahigh-pressure rocks overprinted under high-pressure granulite facies conditions (c. 16-20 kbar, c. 1000°C) in the northern and eastern BM. Well-preserved 10-30 μm-sized microdiamonds from northern BM exhibit diverse morphologies (SEM data) depending upon the host rock type. Octahedral diamond occurs in felsic garnet-kyanite-feldspar-quartz rock (metasediment), whereas intermediate garnet-clinopyroxene-feldspar-quartz rock contains a cubo-octahedral variety. Diamond morphology can be thus controlled by solid impurities available in the medium of crystallization (K- vs. Ca-bearing fluids or melts), as shown by experiments. Pointed-bottom negatively oriented trigonal etch pits on the octahedral diamond faces developed due to diamond resorption at CO2-dominated environment (less than 50 wt % of H2O, experimental data), possibly by action of a residual fluid. SIMS determined δ13C values range from -22 to -21 ‰ for the felsic rock and from - 26 to - 33 for the intermediate one, corresponding to the typical range of organic carbon δ13C and inconsistent with a significant mantle carbon (δ13C ~ - 5 ‰) input. Diamond-bearing domains in zircon, also analysed by SIMS, yielded a Variscan U-Pb age of c. 340 Ma. The present stage of knowledge allows us to conclude that (i) metamorphic diamonds in the BM occur in lithologies of metasedimentary character, and their carbon source was organic; (ii) crustal-derived CO2-rich fluids with impurities played an important role in diamond formation and dissolution; (iii) diamonds formed during the Variscan orogenic cycle and (iv) diamonds are best preserved in the external domain of the Variscan orogenic belt.

  3. Three Dimensional Spatial and Temporal Evolution of Rheology in Orogens: A Field Perspective

    NASA Astrophysics Data System (ADS)

    Brown, M.; Solar, G.

    2001-12-01

    To understand mountain building, we require knowledge of behavior and mechanics of deformation of lithosphere materials. Based on deformation experiments at high-strain-rates, including work by Mervyn Paterson, and data from field studies of rocks inferred to have been melt-bearing during deformation at natural strain rates, melt-bearing rocks generally are weaker than those at subsolidus conditions. Further, we require knowledge of how material behavior changes in 3-d during mountain building as geotherms evolve and rocks melt and melt migrates and ponds at shallower levels. Data to address this issue come from the field, where relations among melt flow (continuous vs. cyclic), rheological transitions [brittle-viscous transition zone (BVTZ) and anatectic front (AF)] and deformation (viscous vs. brittle) yield natural constraints for use in dynamic models of orogenesis. In the Acadian Orogen of New England, based on high-precision ages, Lower Paleozoic rocks were deformed synchronously with greenschist-granulite facies metamorphism and emplacement of plutons. Based on geochemistry, migmatites are residual and peraluminous leucogranite was derived from a similar source, implying a genetic relation. In middle crust, below the BVTZ [in part below the AF (in migmatite)] deformation involved non-coaxial non-plane strain flow in which the inclined vorticity vector was stretched along its length and deformation partitioned into steeply inclined S-L and L>>S tectonite zones. Metamorphic field gradient is of low dP/dT type, P-T paths are clockwise and thermal peak was late syntectonic, reflecting regionally elevated thermal gradients and pluton-driven thermal pulses. In migmatite, leucosome relations with tectonite fabrics and dilatant shear surfaces, and sheets and cylinders of cumulate-dominated granite, suggest cyclic failure and batch melt transport by shear surface and channel flow (conditional open-system behavior). Below the AF, differential stress is low and if melt

  4. 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

  5. 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

  6. Lead isotope study of orogenic lherzolite massifs

    NASA Astrophysics Data System (ADS)

    Hamelin, Bruno; Allègre, Claude J.

    1988-12-01

    Orogenic lherzolites allow for almost "in-situ" observation of mantle isotopic heterogeneities on a restricted geographical scale, in contrast to basalts for which melting processes have averaged original mantle compositions over uncertain scales. Pb isotopes from whole rocks and clinopyroxenes from the massifs of Lherz (Pyrenees), Lanzo (Alps), Beni Bousera (Morocco) and Zabargad (Red Sea) show internal heterogeneities that encompass the entire range of variation observed in oceanic basalts. Some depleted lherzolites have a very unradiogenic composition similar to that of the most depleted ridge tholeiites. Pyroxenites from mafic layers generally have more radiogenic compositions, some of them comparable to the most radiogenic oceanic island results. The isotopic differences between lherzolites and pyroxenites vanish where layers are very closely spaced ( < 2 cm). In this case, the lherzolites may have equilibrated with the more Pb-rich pyroxenites through solid-state diffusion under mantle conditions. These results directly illustrate the smallest scales at which Pb isotopic heterogeneity may survive within the mantle. The genesis of these heterogeneities are discussed within the framework of the "marble cake" mantle model [1], where lherzolites are residues left over after oceanic crust extraction, whereas pyroxenites represent either basaltic or cumulate portions of the oceanic crust, reinjected by subduction and stretched by solid-state mixing during mantle convection. The Pb isotope data suggest that each massif was involved in several cycles of convective overturn, segregation and reinjection of the oceanic crust, during periods well over 1 Ga. If the upper mantle is made of interlayered radiogenic and unradiogenic layers, basalt heterogeneities may result from preferential melt-extraction from different layers depending on the degree of melting, as well as from large-scale, plume-related mantle heterogeneities. Orogenic lherzolites therefore allow direct

  7. Orogenic float of the Venezuelan Andes

    NASA Astrophysics Data System (ADS)

    Monod, Bernard; Dhont, Damien; Hervouët, Yves

    2010-07-01

    The Venezuelan (or Mérida) Andes are a NE-trending intracontinental orogen that started to rise from the Middle Miocene due to the E-W far field convergence between the Maracaibo block to the northwest and the Guyana shield to the southeast. Oblique convergence is responsible for strain partitioning with thrusting along both foreland basins and right-lateral strike-slip faulting along the NE-SW Boconó fault cutting the Venezuelan Andes along-strike. The central part of the belt is also cut by the N-S left-lateral strike-slip Valera fault that connects the Boconó fault, both faults bounding the Trujillo block that escapes towards the NNE. Even though the regional geology of belt is well known, its structure at depth remains a matter of debate. Our work, based on the integration of geological and geophysical data aims to better constrain the deep geometry of faults and the tectonic evolution of the mountain belt. We used the orogenic float model to construct two NW-SE trans-Andean crustal scale balanced sections. The Late Neogene-Quaternary shortening varies from 40 km in the south to 30 km in the north across the Trujillo block, indicating that a quarter of the deformation seems to be absorbed by the tectonic escape process. More importantly, a major reorganization in the crust took place in the Early Pliocene. It is characterized by the imbrication of the Maracaibo crust into the Guyana crust. This resulted in the subduction of the Guyana lower crust and the formation of a NW-vergent basement thrust propagating upwards and surfacing along the Las Virtudes thrust. Rapid uplift of the northern flank of the belt subsequently occurred together with massive deposition of the Plio-Quaternary coarse grained Betijoque formation in the northwestern foreland basin.

  8. An accreted micro-continent in the north of the Dabie Orogen, East China: Evidence from detrital zircon dating

    NASA Astrophysics Data System (ADS)

    Zhu, Guang; Wang, Yongsheng; Wang, Wei; Zhang, Shuai; Liu, Cheng; Gu, Chengchuan; Li, Yunjian

    2017-02-01

    Continent-continent collision between the North China Block (NCB) and South China Block (SCB) took place along the Qinling-Tongbai-Hong'an-Dabie orogens during the Triassic. A micro-continent with Paleozoic arc magmatism has been recognized in the northern Qinling-Tongbai orogens; however, it remains unclear whether the micro-continent extended to the Dabie Orogen to form a ribbon-shaped micro-continent, due to later burial by the Hefei Basin in the north. To solve this problem, we conducted LA-ICP-MS Usbnd Pb dating of zircons from Silurian to Cretaceous sandstones and volcanic rocks from the southern margin of the basin. The age spectra of detrital zircons suggest that the Dabie Orogen and later basin cover were the sources of the analyzed sandstones. The detrital and inherited zircons indicate Neoproterozoic, early and late Paleozoic magmatism in the Beihuaiyang unit in the north of the Dabie Orogen. The zircon and previous geophysical data show that a micro-continent bounded by the Feizhong Suture in the north and the Xiaotian-Mozitang Suture in the south existed between the NCB and the Triassic Dabie Orogen, and its northern half is buried by the Jurassic-Paleogene Hefei Basin. The Beihuaiyang micro-continent experienced early Paleozoic arc magmatism caused by southward subduction of the Erlangping oceanic crust and late Paleozoic magmatism related to northward subduction of the Paleotethyan oceanic crust. The micro-continent was accreted to the southern edge of the NCB at the end of the Early Devonian (ca. 400 Ma) via arc-continent collision. Similarly to the Qinling-Tongbai orogens, the Dabie Orogen contains a Paleozoic accretionary system in the north and a Triassic collisional system in the south; thus, it is suggested that a ribbon-shaped micro-continent, > 900 km long and 50-100 km wide, was present along the entire Qinling-Tongbai-Hong'an-Dabie orogens prior to the middle Paleozoic. This micro-continent might have originated as a result of middle

  9. Sulfur- and lead-isotope signatures of orogenic gold mineralisation associated with the Hill End Trough, Lachlan Orogen, New South Wales, Australia

    NASA Astrophysics Data System (ADS)

    Downes, P. M.; Seccombe, P. K.; Carr, G. R.

    2008-11-01

    The Hill End Trough (HET) is a deformed middle Silurian to Early Devonian sediment-dominated rift within the northeastern Lachlan Orogen. The HET hosts the Hill End, Hargraves, Napoleon Reefs, Stuart Town and Windeyer low-sulfide orogenic gold deposits. Adjacent to the HET are the Bodangora and Gulgong gold deposits. In this study we present 91 new sulfur- and 18 new lead-isotope analyses and collate a further 25 sulfur- and 32 lead-isotopes analyses from unpublished sources for these deposits. Larger gold deposits in the HET have near 0 δ34S‰ values indicating that sulfur in these systems was sourced from a magmatic reservoir. The dominant lead isotope signature for HET-hosted deposits reflects a crustal source however some mantle-derived lead has been introduced into the HET. Sulfur- and lead-isotopic results suggest that gold was sourced from mantle-derived magmatic units beneath the HET. The study supports earlier studies at Hill End by concluding that the majority of orogenic gold mineralisation in and adjacent to the HET formed during the Early Carboniferous period.

  10. Application of electron spin resonance (ESR) dating to ductile shearing: Examples from the Qinling orogenic belt, China

    NASA Astrophysics Data System (ADS)

    Ren, Shenglian; Song, Chuanzhong; Li, Jiahao

    2016-04-01

    Shear zones are common structures in orogenic belts and elucidation of the tectonic evolution of these orogenic belts to a large degree depends on understanding the kinematics and timing of shear deformation. However, there is a lack of an accurate, fast and convenient way to determine the timing of deformation. In this paper, we apply the ESR (electron spin-resonance spectroscopy) dating method to three syntectonic quartz veins from the Funiushan tectonic belt in the Qinling orogenic belt in central China. The results agree well with the available ages of deformation in the area obtained through other dating methods. This demonstrates the accuracy and feasibility of using the ESR method to date quartz crystals formed during deformation. The method is fast and convenient, and satisfies the accuracy requirement. It is an effective means for determining the timing of deformation, especially in areas with intensive fluid activity during deformation.

  11. Imaging nervous system activity.

    PubMed

    Fields, R D; O'Donovan, M J

    2001-05-01

    Optical imaging methods rely upon visualization of three types of signals: (1) intrinsic optical signals, including light scattering and reflectance, birefringence, and spectroscopic changes of intrinsic molecules, such as NADH or oxyhemoglobin; (2) changes in fluorescence or absorbance of voltage-sensitive membrane dyes; and (3) changes in fluorescence or absorbance of calcium-sensitive indicator dyes. Of these, the most widely used approach is fluorescent microscopy of calcium-sensitive dyes. This unit describes protocols for the use of calcium-sensitive dyes and voltage-dependent dyes for studies of neuronal activity in culture, tissue slices, and en-bloc preparations of the central nervous system.

  12. 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)

  13. Intraplate geodynamics and magmatism in the evolution of the Central Asian Orogenic Belt

    NASA Astrophysics Data System (ADS)

    Yarmolyuk, V. V.; Kuzmin, M. I.; Ernst, R. E.

    2014-10-01

    The Central Asian Orogenic Belt (CAOB) was produced as a consequence of the successive closure of the Paleoasian Ocean and the accretion of structures formed within it (island arcs, oceanic islands, and backarc basins) to the Siberian continent. The belt started developing in the latest Late Neoproterozoic, and this process terminated in the latest Permian in response to the collision of the Siberian and North China continents that resulted in closure of the Paleoasian ocean (Metcalfe, 2006; Li et al., 2014; Liu et al., 2009; Xiao et al., 2010; Didenko et al., 2010). Throughout the whole evolutionary history of this Orogenic Belt, a leading role in its evolution was played by convergent processes. Along with these processes, an important contribution to the evolution of the composition and structure of the crust in the belt was made by deep geodynamic processes related to the activity of mantle plumes. Indicator complexes of the activity of mantle plumes are identified, and their major distribution patterns in CAOB structures are determined. A number of epochs and areas of intraplate magmatism are distinguished, including the Neoproterozoic one (Rodinia breakup and the origin of alkaline rock belt in the marginal part of the Siberian craton); Neoproterozoic-Early Cambrian (origin of oceanic islands in the Paleoasian Ocean); Late Cambrian-Early Ordovician (origin of LIP within the region of Early Caledonian structures in CAOB); Middle Paleozoic (origin of LIP in the Altai-Sayan rift system); Late Paleozoic-Early Mesozoic (origin of the Tarim flood-basalt province, Central Asian rift system, and a number of related zonal magmatic areas); Late Mesozoic-Cenozoic (origin of continental volcanic areas in Central Asia). Geochemical and isotopic characteristics are determined for magmatic complexes that are indicator complexes for areas of intraplate magmatism of various age, and their major evolutionary trends are discussed. Available data indicate that mantle plumes

  14. Orogenic superstructure behaviour and mid-crustal plastic flow in the central Nepal Himalaya

    NASA Astrophysics Data System (ADS)

    Godin, L.; Kellett, D. A.; Larson, K. P.

    2007-12-01

    In the central Nepal Himalaya, the Tethyan sedimentary sequence (TSS) forms the superstructure to mid-crustal infrastructure rocks of the Greater Himalayan sequence (GHS); the top-to-the-north South Tibetan detachment system (STDS) defines their contact. North-verging folds, opposite to the main orogenic vergence, structurally dominate the TSS. Although the absolute age of this folding is unknown, structural observations and 40Ar/39Ar thermochronology indicate that it formed between 50-23 Ma, predating the dominant Miocene motion on the STDS. The GHS records a two-stage post-collisional history, marked by ca. 35 Ma burial metamorphism, followed by high-T, low-P, ca. 22 Ma metamorphism. Dominant top-to-the-south shear fabrics developed at peak temperatures at ca. 22 Ma pervasively transpose linear and planar features within the GHS. Vorticity analyses yield kinematic vorticity numbers between 0.29 and 0.80 (81-41% pure shear), with a significant amount of stretch parallel to the flow plane (34-53%). 40Ar/39Ar thermochronological data indicate that southward extrusion of the GHS terminated with cessation of movement on the STDS at 19 Ma. Our data suggest that the orogenic superstructure actively influenced the behaviour of the infrastructure in the early stages of orogenesis through fold-thrust belt formation leading to prograde 35 Ma metamorphism in the GHS. Associated melt weakening in the infrastructure allowed the initiation of southward plastic flow of the GHS, locally modifying the vergence of superstructural folds towards the north. As melt weakening in the middle crust intensified and the rheological contrast between superstructure and infrastructure increased, the upper crust decoupled from the middle crust and deformation in the upper crust temporarily ceased. By 17 Ma the extruded mid-crustal rocks cooled sufficiently to require the upper, brittle component of the STDS to become active. As cooling continued (17-14 Ma), the superstructure and underlying

  15. 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.

  16. Geology of the Byrd Glacier Discontinuity (Ross Orogen): New survey data from the Britannia Range, Antarctica

    USGS Publications Warehouse

    Carosi, R.; Giacomini, F.; Talarico, F.; Stump, E.

    2007-01-01

    Field activities in the Britannia Range (Transantarctic Mountains, Antarctica) highlighted new geological features around the so-called Byrd Glacier discontinuity. Recent field surveys revealed the occurrence of significant amounts of medium- to high-grade metamorphic rocks, intruded by abundant coarse-grained porphyritic granitoids. Most of the granitoids are deformed, with foliation parallel to the regional foliation in the metamorphics. Two main episodes of deformation are observed. Tight to isoclinal folds and penetrative axial plane foliation are related to the D1 phase, open folds to the D2. The main foliation (D1) trends nearly E-W in agreement with the trend in the southern portion of the Byrd Glacier. In most outcrops, granitic dykes are folded and stretched by the D2 deformation, which shows similar characteristics with the D2 deformation south of the Byrd Glacier. This suggests the occurrence in the Ross orogen of an orogen-normal structure south and north of the Byrd Glacier.

  17. 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

  18. An isotopic perspective on growth and differentiation of Proterozoic orogenic crust: From subduction magmatism to cratonization

    SciTech Connect

    Johnson, Simon P.; Korhonen, Fawna J.; Kirkland, Christopher L.; Cliff, John B.; Belousova, Elena A.; Sheppard, Stephen

    2017-01-01

    The in situ chemical differentiation of continental crust ultimately leads to the long-term stability of the continents. This process, more commonly known as ‘cratonization’, is driven by deep crustal melting with the transfer of those melts to shallower regions resulting in a strongly chemically stratified crust, with a refractory, dehydrated lower portion overlain by a complementary enriched upper portion. Since the lower to mid portions of continental crust are rarely exposed, investigation of the cratonization process must be through indirect methods. In this study we use in situ Hf and O isotope compositions of both magmatic and inherited zircons from several felsic magmatic suites in the Capricorn Orogen of Western Australia to highlight the differentiation history (i.e. cratonization) of this portion of late Archean to Proterozoic orogenic crust. The Capricorn Orogen shows a distinct tectonomagmatic history that evolves from an active continental margin through to intracratonic reworking, ultimately leading to thermally stable crust that responds similarly to the bounding Archean Pilbara and Yilgarn Cratons.

  19. Influence of preexisting tectonic trends on geometries of Sevier orogenic belt and its foreland in Utah

    SciTech Connect

    Picha, F.; Gibson, R.I.

    1985-05-01

    The tectonic style of the late Mesozoic Sevier orogenic belt in Utah was greatly affected by preexisting structural trends that date from the late Precambrian rifting and fragmentation of the North American continent. The late Precambrian cratonic margin (Cordilleran hinge line) was marked by a system of prominent faults including the north-south-trending ancestral Wasatch and ancient Ephraim faults and the southwest-northeast-trending Leamington, Scipio, Cove Fort, and Paragonah faults. During the Paleozoic and Mesozoic, renewed activity on these faults affected the geometries of the late Paleozoic Paradox and Oquirrh basins, the boundaries of the Jurassic Arapien Formation, and the sedimentary pattern of the Cretaceous foreland basin. Many of these fault zones were reactivated as tectonic ramps (e.g., the ancient Ephraim fault) and tear faults (e.g., the Leamington fault) during the compressional Sevier tectonism. The Fillmore arch and some other structural highs situated along the edge of the late Precambrian craton caused ramping of the inner Keystone-Pavant-Canyon thrust sheets and telescoping of the frontal thrust sheets. Post-thrust uplift of basement highs led to tectonic denudation and to the development of low-angle, extensional faults, such as the Sevier detachment. Northeast-trending lineaments, such as the Cove Fort and Paragonah lineaments, were reactivated as right-lateral strike-slip faults. They also affected the extent of the Marysvale volcanic field.

  20. 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,…

  1. 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

  2. Tectonometamorphic evolution of the Rhodope orogen

    NASA Astrophysics Data System (ADS)

    Krenn, Kurt; Bauer, Christoph; Proyer, Alexander; KlöTzli, Urs; Hoinkes, Georg

    2010-08-01

    This study combines new data on tectonostratigraphy, macrostructures and microstructures, petrology, and geochronology to propose a comprehensive model for the tectonometamorphic evolution of the Rhodope orogen from the Jurassic to the early Paleogene. Rocks from two study areas in the central and eastern Greek Rhodope represent a continental suture zone (Rhodope Suture Zone), with the included material most likely forming an extensional allochthon south of the European continent during Permo/Triassic times that was subsequently subducted beneath Europe in the Early Jurassic (≥180 Ma). On the basis of comparable metamorphic ages and coherent structures but differences in metamorphic conditions and lithologies, the rocks of the Rhodope Suture Zone are subdivided into an upper and a lower part. The prograde history is linked with subduction-related structures in the lower part (uniaxial stretching, deformation stage D1). In metapelites, the earliest stage of metamorphism recorded at circa 180 Ma occurred at least under ultrahigh-pressure metamorphic conditions. The rocks of the upper part experienced isothermal decompression with partial anatexis. Exhumation paths of both parts differ in temperature because of the relative tectonic position within the exhuming wedge. Exhumation was forced by the Nestos Shear Zone that controlled the early phase of normal displacement by SW shearing at the base (lower part) and NE shearing on top (upper part) from the Late Jurassic to the Late Cretaceous (deformation stage D2). An intervening stage of mineral recrystallization and thermal reequilibration in the upper part was followed by a common exhumation history of both parts at pressures lower than about 12 kbar (35-40 km depth). During this stage, exhumation was controlled by southwest directed shearing and folding (deformation stage D3). Slab retreat to the south led to subsequent extension (deformation stage D4) and final exhumation coeval with the formation of basement domes

  3. Stalled Orogen Linked to East Antarctic Craton Assembly

    NASA Astrophysics Data System (ADS)

    Martos, Y. M.; Ferraccioli, F.; Finn, C.; Bell, R. E.; Jordan, T. A.; Damaske, D.

    2015-12-01

    The interior of East Antarctica is often regarded as a coherent Archean craton surrounded by Paleo to Neoproterozoic orogenic belts. Here we use recent aerogeophysical, satellite magnetic, satellite gravity and passive seismic results in central East Antarctica to challenge this view. Firstly, anomalously thick crust (compared to most other cratons) has been imaged in East Antarctica by both passive seismic and gravity modelling with values up to 60 km (Ferraccioli et al., 2011, Nature; An et al., 2015, JGR). The thick crust underlies both the Gamburtsev Subglacial Mountains and an elevated region between Lake Vostok and Dronning Maud Land, referred to as the East Antarctic Mountain Ranges plateau (An et al., 2015). Second, satellite magnetic data reveal that the Gamburtev Province lies in between the Ruker/Princess Elizabeth Land, Vostok, Nimrod/South Pole and Recovery provinces. The Nimrod/ South Pole province is a Paleo to Meso Proterozoic igneous province formed along the edges of the Archean/Paleoproterozoic Mawson continent (e.g. Goodge and Fanning, 2010 JGR). Our aerogeophysical and sediment provenance data interpretations suggest that the Gamburtsev Province represents a distinct Grenvillian-age orogenic belt. A stalled orogen with thick crust (i.e. an orogen where widespread orogenic collapse and root delamination has not occurred)- is preserved in the interior of East Antarctica resembling e.g. the Paleoproterozoic Trans Hudson Orogen and segments of Grenvillian orogens in Laurentia. The stalled orogen may relate to widespread accretionary and collisional events within Rodinia. However, passive seismic interpretations (An et al., 2015) favour linking crustal thickening to the Pan-African age assembly of Greater India, East Antarctica and Australia within Gondwana (e.g. Aitken et al., 2014 GRL). Further aerogeophysical observations over Princess Elizabeth Land are timely to enable more robust correlations with geological observations and to help dating the

  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. 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

  6. 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

    2016-05-11

    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.

  7. 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.

  8. 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.

  9. Evolution of the Late Mesoproterozoic Cordilleran-Type (not COLLISIONAL!) Sveconorwegian (grenville) Orogen in SW Norway

    NASA Astrophysics Data System (ADS)

    Slagstad, T.; Sauer, S.; Roberts, N. M.; Marker, M. K.; Røhr, T. S.; Schiellerup, H.

    2011-12-01

    The Late Mesoproterozoic Sveconorwegian orogen in SW Baltica is traditionally interpreted as the eastward continuation of the Grenville orogen in Canada, resulting from collision with Amazonia and forming a central part in the assembly of the Rodinia supercontinent. We challenge this conventional view based on results from recent work in SW Norway that demonstrate voluminous subduction-related magmatism from ca. 1070 to 990 Ma, encompassing the period when collision is purported to have taken place. The rocks form a >100 km long and 50 km wide belt referred to as the Sirdal Magmatic Belt, intruding ca. 1500 Ma crust. Coeval granitoid magmatism up to 200 km to the east into the orogen has transitional calc-alkaline/A-type to A-type compositions, which we interpret to reflect continental back-arc magmatism. High-grade metamorphism in the region started at 1035 Ma with a peak at 1000 Ma, indicating that metamorphism may have resulted from plutonic activity, but not the other way around as would be expected in a collision setting. Following Sveconorwegian orogenesis, widespread A-type granite magmatism between 970 and 930 Ma (Hornblende-Biotite Granite Suite), and anorthosite-mangerite-charnockite magmatism (Rogaland Igneous Complex) between 930 and 915 Ma, is recorded in the Sveconorwegian Province. We interpret this evolution to suggest that the cessation of subduction-related magmatism at ca. 990 Ma did not involve continent-continent collision, but instead reflects a period of horizontal subduction between 990 and 930 Ma (or ca. 950 Ma), during which hydration of the overlying lower continental crust induced widespread crustal melting and A-type magmatism. Subsequent foundering of this underthrust oceanic crust and delamination of the arc's mantle root between 950 and 930 Ma may have given rise to the Rogaland Igneous Complex, the youngest massif-type anorthosite complex in the Grenville-Sveconorwegian orogen. Isotope data on the Sirdal Magmatic Belt indicate a

  10. Extensional orogenic collapse captured by strike-slip tectonics: Constraints from structural geology and Usbnd Pb geochronology of the Pinhel shear zone (Variscan orogen, Iberian Massif)

    NASA Astrophysics Data System (ADS)

    Fernández, Rubén Díez; Pereira, Manuel Francisco

    2016-11-01

    The late Paleozoic collision between Gondwana and Laurussia resulted in the polyphase deformation and magmatism that characterizes the Iberian Massif of the Variscan orogen. In the Central Iberian Zone, initial continental thickening (D1; folding and thrusting) was followed by extensional orogenic collapse (D2) responsible for the exhumation of high-grade rocks coeval to the emplacement of granitoids. This study presents a tectonometamorphic analysis of the Trancoso-Pinhel region (Central Iberian Zone) to explain the processes in place during the transition from an extension-dominated state (D2) to a compression-dominated one (D3). We reveal the existence of low-dipping D2 extensional structures later affected by several pulses of subhorizontal shortening, each of them typified by upright folds and strike-slip shearing (D3, D4 and D5, as identified by superimposition of structures). The D2 Pinhel extensional shear zone separates a low-grade domain from an underlying high-grade domain, and it contributed to the thermal reequilibration of the orogen by facilitating heat advection from lower parts of the crust, crustal thinning, decompression melting, and magma intrusion. Progressive lessening of the gravitational disequilibrium carried out by this D2 shear zone led to a switch from subhorizontal extension to compression and the eventual cessation and capture of the Pinhel shear zone by strike-slip tectonics during renewed crustal shortening. High-grade domains of the Pinhel shear zone were folded together with low-grade domains to define the current upright folded structure of the Trancoso-Pinhel region, the D3 Tamames-Marofa-Sátão synform. New dating of syn-orogenic granitoids (SHRIMP Usbnd Pb zircon dating) intruding the Pinhel shear zone, together with the already published ages of early extensional fabrics constrain the functioning of this shear zone to ca. 331-311 Ma, with maximum tectonomagmatic activity at ca. 321-317 Ma. The capture and apparent cessation

  11. 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

  12. 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.

  13. 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

  14. Active Shimmy Control System

    DTIC Science & Technology

    1975-12-01

    reviewed by thoe nformation Offite (01) end Is reslesuabe to the National Technical Wnrdstleftiv Oervico (WI2B). At N13..S it iuil be, avail-able th the...Figure 2, - are used only for the passive system. BH and BL are hydraulic (velocity squared) and linear shimmy damper constants, and KALP in the...NOTES KPH i.63E6 1.403E6 x KrI 11.20 5000 .. X &T, ~ ipl, , x KOC 77270 - X KALP 18000 -X IPH 69.7 83.9 X ITH .68 x "ITI, .03 - x ITII2 3.h9 - xIA .o

  15. Active Tensor Magnetic Gradiometer System

    DTIC Science & Technology

    2007-11-01

    Modify Forward Computer Models .............................................................................................2 Modify TMGS Simulator...active magnetic gradient measurement system are based upon the existing tensor magnetic gradiometer system ( TMGS ) developed under project MM-1328...Magnetic Gradiometer System ( TMGS ) for UXO Detection, Imaging, and Discrimination.” The TMGS developed under MM-1328 was successfully tested at the

  16. 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

  17. The nature of orogenic crust in the central Andes

    NASA Astrophysics Data System (ADS)

    Beck, Susan L.; Zandt, George

    2002-10-01

    The central Andes (16°-22°S) are part of an active continental margin mountain belt and the result of shortening of the weak western edge of South America between the strong lithospheres of the subducting Nazca plate and the underthrusting Brazilian shield. We have combined receiver function and surface wave dispersion results from the BANJO-SEDA project with other geophysical studies to characterize the nature of the continental crust and mantle lithospheric structure. The major results are as follows: (1) The crust supporting the high elevations is thick and has a felsic to intermediate bulk composition. (2) The relatively strong Brazilian lithosphere is underthrusting as far west (65.5°W) as the high elevations of the western part of the Eastern Cordillera (EC) but does not underthrust the entire Altiplano. (3) The subcrustal lithosphere is delaminating piecemeal under the Altiplano-EC boundary but is not completely removed beneath the central Altiplano. The Altiplano crust is characterized by a brittle upper crust decoupled from a very weak lower crust that is dominated by ductile deformation, leading to lower crustal flow and flat topography. In contrast, in the high-relief, inland-sloping regions of the EC and sub-Andean zone, the upper crust is still strongly coupled across the basal thrust of the fold-thrust belt to the underthrusting Brazilian Shield lithosphere. Subcrustal shortening between the Altiplano and Brazilian lithosphere appears to be accommodated by delamination near the Altiplano-EC boundary. Our study suggests that orogenic reworking may be an important part of the "felsification" of continental crust.

  18. Anatexis of mafic and felsic lower crust: Geochemistry and Nd, Sr and Pb isotopes of late-orogenic granodiorites and leucogranites (Damara orogen, Namibia)

    NASA Astrophysics Data System (ADS)

    Osterhus, Lennart; Jung, Stefan

    2010-05-01

    intermediate or felsic lower crust. In a plate-tectonic context, a correlation between lower crustal magmatism and changes in the direction of micro-plate movements between the central and the southern part of the Damara orogen can be suggested, provoking re-activation of lithospheric shear zones. If such reactivation caused a reversal in the sense of movement, the associated faults opened and propagated as tensional faults. This would have allowed fracturing through the continental crust causing pressure release, channeling of volatiles, partial melting and generation of magmas from the lower crust. This suggestion is confirmed by the intrusion of the pluton along a major crustal shear zone, the Okahandja Lineament. The intrusion was probably accompanied by a change in the stress field which renewed transcurrent movements along this lithospheric shear zone.

  19. Modification of the Himalayan Orogenic Wedge by Late Cenozoic Southeastward Flow of Tibet

    NASA Astrophysics Data System (ADS)

    Hodges, K. V.; Whipple, K. X.; Kirby, E.; Arrowsmith, R.; Shirzaei, M.

    2014-12-01

    Continental plateaus are reservoirs of excess gravitational energy that can influence the late-stage geodynamic evolution of adjacent orogenic wedges. In the central Himalaya (80-88˚E), most late Cenozoic deformation has involved roughly N-S shortening within the Himalayan orogenic wedge. Within this region, all 1976-2014 Mw 5 and larger earthquakes had thrust mechanisms associated with slip along major arc-parallel structures within or at the base of the orogenic wedge. In contrast, the segment of the wedge between 88˚E and 91˚E - including easternmost Nepal, the Sikkim region of India, and Bhutan - is characterized by a complex deformation field that includes thrusting on arc-parallel wedge structures but also transcurrent faulting at high angles to the Himalayan arc. In fact, over the same 1976-2014 period, all but one of the Mw 5 and larger earthquakes in this region had transcurrent fault mechanisms, mostly consistent with dextral strike-slip along NW-striking faults. We refer to this region as the central-eastern Himalayan transition zone. Although direct field evidence of the surface breaks of these faults has not been established, the orientations of nodal planes of large earthquakes, as well as alignments of microearthquake arrays, suggest that they may connect northward to a discontinuous family of arc-parallel faults - most showing evidence for oblique slip, with variable normal and dextral-transcurrent components - which we interpret as the long-term structural manifestation of the boundary between the distinctive modern strain fields of Tibet (E-W extension) and the central Himalaya (N-S shortening). In addition, transverse faults of the central-eastern Himalayan transition zone may project southward, beneath sediments near the Ganges and Bhramaputra confluence, as dextral tear faults linking the active thrust front of the central Himalaya to the active thrust front of the Shillong Plateau in northeastern India. We hypothesize that the broadening of

  20. Magnetic signatures related to orogenic gold mineralization, Central Lapland Greenstone Belt, Finland

    NASA Astrophysics Data System (ADS)

    Airo, M.-L.; Mertanen, S.

    2008-03-01

    A number of lode-gold occurrences are hosted by hydrothermally altered greenstones along the southern boundary of the Palaeoproterozoic Central Lapland Greenstone Belt. The hydrothermally altered and mineralised zones are related to a major thrust and shear zone system that extends much across northern Finland. Spatial correlation between mineralized zones, brittle structural features and chemical alteration was explored and identified from high-resolution aeromagnetic data, in combination with airborne electromagnetic and gamma-ray spectrometric data and coupled with petrophysical and palaeomagnetic studies. The most prominent magnetic, ductile signatures formed during the Svecofennian Orogeny (1900-1800 Ma), resulting in elastic, curved, continuous magnetic patterns. These elastic anomaly patterns were disturbed by tectonic stress from S-SW, resulting in parallel, regularly oriented fracture families and thrust faults normal to the main stress direction. According to aeromagnetic, palaeomagnetic and structural evidence, the thrust zone was active during the latest stage of the orogenic event, but was also reactivated at a later date. Airborne gamma-ray data reveals zones of potassic alteration in the ultramafic rock units in the vicinity of cross-sections of these two fault sets. Chemical and mineralogical changes during alteration and metamorphism strongly affected the mafic and ultramafic host rocks throughout the deformation zone. The strong potassium enrichment and coinciding destruction of magnetic minerals resulted in enhanced potassium concentration and reduction of magnetic anomaly amplitudes. Palaeomagnetic results indicate that the remanent magnetization for the altered ultramafic rocks along the thrust zone is of chemical origin (CRM) and was acquired at 1880-1840 Ma, which is presumed also to be the age of the chemical alteration related to gold mineralization.

  1. 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.

  2. 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.

    2017-02-01

    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.

  3. 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

  4. Discriminating fluid source regions in orogenic gold deposits using B-isotopes

    NASA Astrophysics Data System (ADS)

    Lambert-Smith, James S.; Rocholl, Alexander; Treloar, Peter J.; Lawrence, David M.

    2016-12-01

    opposing population in the δ11B data for both tourmaline groups reflects continual tourmaline growth throughout mineralization, which records the process of fluid mixing. A peak in δ11B values at ∼8‰ largely controlled by tourmalines of syn- to post-ore timing represents a mixture of the two isotopically distinct fluids. This paper demonstrates that B-isotopes in tourmaline can be instrumental in interpreting complex and dynamic hydrothermal systems. The importance of B as an integral constituent of orogenic ore forming fluids and as a gangue phase in orogenic gold deposits makes B-isotope analysis a powerful tool for testing the level of source region variability in these fluids, and by extension, that of metal sources.

  5. Asymmetric exhumation across the Pyrenean orogen: implications for the tectonic evolution of a collisional orogen

    NASA Astrophysics Data System (ADS)

    Fitzgerald, P. G.; Muñoz, J. A.; Coney, P. J.; Baldwin, S. L.

    1999-11-01

    The Pyrenees are a collisional mountain belt formed by convergence between the Afro-Iberian and European plates. Apatite fission track thermochronology from three vertical profiles along the ECORS seismic line constrain the exhumation history of the Pyrenean orogen and hence tectonic models for its formation. In the Eocene there is relatively uniform exhumation across the Pyrenees, but significantly more exhumation occurs on the southern flank of the axial zone in the Oligocene. The variation in exhumation patterns is controlled by a change in how convergence is accommodated within the Pyrenean double-wedge. Accommodation of thrusting on relict extensional features that leads to inversion dominated thrust stacking resulted in relatively slow exhumation in the Eocene. However, subsequent crustal wedging and internal deformation in the upper crust under the stacked duplex of antiformal nappes resulted in extremely rapid exhumation on the southern flank in the Oligocene. The Maladeta profile in the southern axial zone records extremely rapid Early Oligocene exhumation followed by dramatic slowing or cessation of exhumation in the middle Oligocene and the formation of an apatite partial annealing zone (PAZ). This PAZ has subsequently been exhumed 2-3 km since the Middle Miocene, supporting the observations of Coney et al. [J. Geol. Soc. London 153 (1996) 9-16] that the southern flank of the range was buried by ≤2-3 km of syntectonic conglomerates in the Oligocene and subsequently re-excavated from Late Miocene to Recent. The present-day topographic form of the Pyrenees is largely a relict of topography that formed in the Eocene and the Oligocene. Comparison with paleoclimatic records indicates that the Eocene-Oligocene exhumation patterns are controlled by tectonic forces rather than resulting from an orographic effect due to uplift of the Pyrenees.

  6. 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

  7. Structural development of an Archean Orogen, Western Point Lake, Northwest Territories

    NASA Astrophysics Data System (ADS)

    Kusky, Timothy M.

    1991-08-01

    The Point Lake orogen in the central Archean Slave Province of northwestern Canada preserves more than 10 km of structural relief through an eroded antiformal thrust stack and deeper anastomosing midcrustal mylonites. Fault restoration along a 25 km long transect requires a minimum of 69 km slip and 53 km horizontal shortening. In the western part of the orogen the basal decollement places mafic plutonic/volcanic rocks over an ancient tonalitic gneiss complex. Ten kilometers to the east in the Keskarrah Bay area, slices of gneiss unroofed on brittle thrusts shed molasse into several submerged basins. Conglomerates and associated thinly bedded sedimentary rocks are interpreted as channel, levee, and overbank facies of this thrust-related sedimentary fan system. The synorogenic erosion surface at the base of the conglomerate truncates premetamorphic or early metamorphic thrust faults formed during foreland propagation, while other thrusts related to hinterland-progressing imbrication displace this unconformity. Tightening of synorogenic depositional troughs resulted in the conglomerates' present localization in synclines to the west of associated thrust faults and steepening of structural dips. Eastern parts of the orogen consist of isoclinally folded graywackes composed largely of Mutti and Ricci-Lucchi turbidite facies B, C, and D, interpreted as submarine fan deposits eroded from a distant volcanic arc. Thrust faults in the metasedimentary terrane include highly disrupted slate horizons with meter-scale duplex structures, and recrystallized calcmylonites exhibiting sheath folds and boudin trains with very large interboudin distances. The sequence of fabric development and the overall geometry of this metasedimentary terrane strongly resembles younger forearc accretionary prisms. Conditions of deformation along the thrusts parallel the regional metamorphic zonation: amphibolite facies in the basal decollement through greenschist facies shear zones to cataclastic

  8. 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.

  9. 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

  10. Orogenic gold and geologic time: A global synthesis

    USGS Publications Warehouse

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

    2001-01-01

    Orogenic gold deposits have formed over more than 3 billion years of Earth's history, episodically during the Middle Archean to younger Precambrian, and continuously throughout the Phanerozoic. This class of gold deposit is characteristically associated with deformed and metamorphosed mid-crustal blocks, particularly in spatial association with major crustal structures. A consistent spatial and temporal association with granitoids of a variety of compositions indicates that melts and fluids were both inherent products of thermal events during orogenesis. Including placer accumulations, which are commonly intimately associated with this mineral deposit type, recognized production and resources from economic Phanerozoic orogenic-gold deposits are estimated at just over one billion ounces gold. Exclusive of the still-controversial Witwatersrand ores, known Precambrian gold concentrations are about half this amount. The recent increased applicability of global paleo-reconstructions, coupled with improved geochronology from most of the world's major gold camps, allows for an improved understanding of the distribution pattern of orogenic gold in space and time.

  11. 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

  12. Identifying glacial influences on sedimentation in tectonically-active, mass flow dominated arc basins with reference to the Neoproterozoic Gaskiers glaciation (c. 580 Ma) of the Avalonian-Cadomian Orogenic Belt

    NASA Astrophysics Data System (ADS)

    Carto, Shannon L.; Eyles, Nick

    2012-06-01

    Neoproterozoic 'Avalonian-Cadomian' volcanic arc basins once lay peripheral to Gondwana and are now found around the North Atlantic Ocean in New England, Atlantic Canada and northwestern Europe as 'peri-Gondwanan terranes.' Their thick (up to 9 km) marine fills are dominated by turbidites, debrites (diamictites and variably graded conglomerates), slumps and olistostromes recording the dominance of mass flow processes in arc basins oversupplied with volcaniclastic sediment. Several diamictite horizons in these basins were identified as glacial tillites more than one hundred years ago on the basis of poor textural sorting, and the lack of any understanding of mass flow processes. An association with thin-bedded turbidite facies, then interpreted as glaciolacustrine varvites, was seen as evidence for widespread glacial conditions which is still the basis today of a near global 'Gaskiers glaciation' at c. 580 Ma, despite classic sedimentological work which shows that the 'tillites' and 'varvites' of these basins are deep marine sediment gravity flow deposits. Only in two basins (Gaskiers Formation, Avalon Peninsula in Newfoundland, and the Konnarock Formation of Virginia) is a distal and regionally-restricted glacial influence on marine sedimentation identified from ice-rafted, striated dropstones in turbidites but terrestrial 'ice-contact' facies are absent. As revealed in this study, terrestrial glacial facies may not have survived frequent volcanic activity such as seen today on glaciated active plate margin volcanoes such as Mount Rainier in Washington USA, and Cotopaxi Volcano in Ecuador where primary glacial sediment is frequently reworked by lahars, pyroclastic flows, debris avalanches and outburst floods. The weight of evidence presented in this study indicates that ice covers during the Gaskiers glaciation were not widespread across the Avalonian-Cadomian back arc basins; the deep marine Grenada Basin (Caribbean Sea) filled with turbidites, debrites (lahars

  13. 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

  14. 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).

  15. 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

  16. 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.

  17. Syn-Convergent Orogen-Parallel Low-Angle Normal-Sense Faults: One Process or Several?

    NASA Astrophysics Data System (ADS)

    Kellett, D. A.; Grujic, D.

    2010-12-01

    Low-angle normal-sense faults (LANFs) form in both extensional and contractional settings. Recent field and experimental studies have demonstrated that exhumed footwall tectonites in extensional LANFs are not necessarily down-dip equivalents of the surface detachment, instead they may deform during distributed flow in the mid- or lower crust. We propose that syn-contractional LANFs also need not result from a single, progressive deformation. The South Tibetan detachment system (STDS) is a network of low-angle normal sense faults and shear zones (LANFs) that formed in the Miocene coevally with and parallel to contractional structures during lithospheric shortening accompanying development of the Himalayan orogen. In the eastern Himalaya, the STDS is exposed multiple times across orogen strike, and each exposure is characterized by differences in: metamorphic grade between the footwall and hanging wall rocks; numbers of individual structures; amounts of ductile versus brittle deformation, and; times of activity. Using new and published geochronologic, geothermometric and structural data, we characterize and distinguish three different types of LANFs within the STDS: 1. Mid-crustal flow LANFs, formed by ductile flow of melt-weakened mid-crust between stronger upper and lower crust that produced a sub-horizontal diffuse, ductile shear zone separating high metamorphic grade mid-crustal anatectite from low metamorphic grade upper-crustal rocks. Such structures do not cut down-section and locally may preserve a reversal in shear sense. 2. Extrusion LANFs, formed during extrusion of a mid-crust slab along focused opposing-sense bounding shear zones. The extruding slab is roofed by discrete ductile-brittle to brittle faults that post-date and partly excise a mid-crustal flow LANF. 3. Destabilization LANFs, formed by local extension of the upper crust accompanying destabilization and doming of the mid-crust, and characterized by single or conjugate ductile-brittle to brittle

  18. Mass elevation and lee effects markedly lift the elevational distribution of ground beetles in the Himalaya-Tibet orogen

    PubMed Central

    Schmidt, Joachim; Böhner, Jürgen; Brandl, Roland; Opgenoorth, Lars

    2017-01-01

    Mass elevation and lee effects markedly influence snow lines and tree lines in high mountain systems. However, their impact on other phenomena or groups of organisms has not yet been quantified. Here we quantitatively studied their influence in the Himalaya–Tibet orogen on the distribution of ground beetles as model organisms, specifically whether the ground beetle distribution increases from the outer to the inner parts of the orogen, against latitudinal effects. We also tested whether July temperature and solar radiation are predictors of the beetle’s elevational distribution ranges. Finally, we discussed the general importance of these effects for the distributional and evolutionary history of the biota of High Asia. We modelled spatially explicit estimates of variables characterizing temperature and solar radiation and correlated the variables with the respective lower elevational range of 118 species of ground beetles from 76 high-alpine locations. Both July temperature and solar radiation significantly positively correlated with the elevational ranges of high-alpine beetles. Against the latitudinal trend, the median elevation of the respective species distributions increased by 800 m from the Himalayan south face north to the Transhimalaya. Our results indicate that an increase in seasonal temperature due to mass elevation and lee effects substantially impact the regional distribution patterns of alpine ground beetles of the Himalaya–Tibet orogen and are likely to affect also other soil biota there and in mountain ranges worldwide. Since these effects must have changed during orogenesis, their potential impact must be considered when biogeographic scenarios based on geological models are derived. As this has not been the practice, we believe that large biases likely exist in many paleoecological and evolutionary studies dealing with the biota from the Himalaya-Tibet orogen and mountain ranges worldwide. PMID:28339461

  19. Mass elevation and lee effects markedly lift the elevational distribution of ground beetles in the Himalaya-Tibet orogen.

    PubMed

    Schmidt, Joachim; Böhner, Jürgen; Brandl, Roland; Opgenoorth, Lars

    2017-01-01

    Mass elevation and lee effects markedly influence snow lines and tree lines in high mountain systems. However, their impact on other phenomena or groups of organisms has not yet been quantified. Here we quantitatively studied their influence in the Himalaya-Tibet orogen on the distribution of ground beetles as model organisms, specifically whether the ground beetle distribution increases from the outer to the inner parts of the orogen, against latitudinal effects. We also tested whether July temperature and solar radiation are predictors of the beetle's elevational distribution ranges. Finally, we discussed the general importance of these effects for the distributional and evolutionary history of the biota of High Asia. We modelled spatially explicit estimates of variables characterizing temperature and solar radiation and correlated the variables with the respective lower elevational range of 118 species of ground beetles from 76 high-alpine locations. Both July temperature and solar radiation significantly positively correlated with the elevational ranges of high-alpine beetles. Against the latitudinal trend, the median elevation of the respective species distributions increased by 800 m from the Himalayan south face north to the Transhimalaya. Our results indicate that an increase in seasonal temperature due to mass elevation and lee effects substantially impact the regional distribution patterns of alpine ground beetles of the Himalaya-Tibet orogen and are likely to affect also other soil biota there and in mountain ranges worldwide. Since these effects must have changed during orogenesis, their potential impact must be considered when biogeographic scenarios based on geological models are derived. As this has not been the practice, we believe that large biases likely exist in many paleoecological and evolutionary studies dealing with the biota from the Himalaya-Tibet orogen and mountain ranges worldwide.

  20. 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.

  1. 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

  2. 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

  3. Solar active region display system

    NASA Astrophysics Data System (ADS)

    Golightly, M.; Raben, V.; Weyland, M.

    2003-04-01

    The Solar Active Region Display System (SARDS) is a client-server application that automatically collects a wide range of solar data and displays it in a format easy for users to assimilate and interpret. Users can rapidly identify active regions of interest or concern from color-coded indicators that visually summarize each region's size, magnetic configuration, recent growth history, and recent flare and CME production. The active region information can be overlaid onto solar maps, multiple solar images, and solar difference images in orthographic, Mercator or cylindrical equidistant projections. Near real-time graphs display the GOES soft and hard x-ray flux, flare events, and daily F10.7 value as a function of time; color-coded indicators show current trends in soft x-ray flux, flare temperature, daily F10.7 flux, and x-ray flare occurrence. Through a separate window up to 4 real-time or static graphs can simultaneously display values of KP, AP, daily F10.7 flux, GOES soft and hard x-ray flux, GOES >10 and >100 MeV proton flux, and Thule neutron monitor count rate. Climatologic displays use color-valued cells to show F10.7 and AP values as a function of Carrington/Bartel's rotation sequences - this format allows users to detect recurrent patterns in solar and geomagnetic activity as well as variations in activity levels over multiple solar cycles. Users can customize many of the display and graph features; all displays can be printed or copied to the system's clipboard for "pasting" into other applications. The system obtains and stores space weather data and images from sources such as the NOAA Space Environment Center, NOAA National Geophysical Data Center, the joint ESA/NASA SOHO spacecraft, and the Kitt Peak National Solar Observatory, and can be extended to include other data series and image sources. Data and images retrieved from the system's database are converted to XML and transported from a central server using HTTP and SOAP protocols, allowing

  4. 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

  5. Tectonic Evolution of Naxos (cyclades): A Record of The Thermal-mechanical Evolution of An Orogenic Wedge

    NASA Astrophysics Data System (ADS)

    Vanderhaeghe, O.; Duchêne, S.; Hibsch, C.; Malartre, F.; Aissa, R.; Martin, L.; Fotiades, .; de St Blanquat, M.; Habert, G.

    A synthesis of published work and preliminary results from a multidisciplinary study of the various crustal levels exposed in the island of Naxos in the Cyclades allows to propose a model for the evolution of the orogenic accretionary wedge in this region. Naxos is characterized by the juxtaposition of metamorphic rocks and Late Oligocene- Early Miocene to Upper Pliocene sedimentary basins along a low-angle detachment. Migmatites, dated at ca. 15 Ma (Keay et al., 2001), appear in the core of a structural dome and are surrounded by a sequence of metasedimentary rocks. From the edge of the island to the core of the dome, the metasedimentary sequence is affected by a metamorphism grading from blue schists to amphibolite facies (Jansen and Schuil- ing, 1976). Ar-Ar ages decrease from ca. 45 in the blue schists to ca. 10 Ma in the migmatites (Andriessen et al., 1979, Wijbrans and McDougall, 1986). The sedimen- tary basins are filled mainly by coarse silicoclastic deposits. Sedimentological and geomorphological features suggest a transition from a shallow marine to a continental environment during Miocene time. Data from the metamorphic rocks indicate that the dynamic evolution of the wedge is marked by a first stage of burial and subsequent exhumation of the metasedimen- tary rocks controlled by the interplay between deformation related to convergence and denudation (erosion and tectonic). The formation of the dome cored by migmatites is interpreted as the result of the development of a gravitational instability associated to the genesis of a partially molten layer at depth in the thickened orogenic wedge. This event is synchronous to the activity of the low-angle detachment and the per- vasive top-to-the-North non-coaxial deformation which affects all rock units above the migmatites. The nature of the link between diapiric upwelling of the dome and the transition from thickening to thinning of the orogenic wedge remains to be estab- lished. Progressive exhumation and

  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. Orogen-scale L tectonite domain in the Tongbai orogenic belt, central China: Geological setting and origin

    NASA Astrophysics Data System (ADS)

    Liu, Huan; Lin, Shoufa; Song, Chuanzhong

    2017-01-01

    L tectonite is well developed and widely distributed in the Tongbai orogenic belt in central China. The orogenic belt as a whole has an antiformal geometry and the hinge of the antiform is subhorizontal and trends NW-SE. The L tectonite occurs in the core of the antiform, in a zone that is 10-30 km wide and over 100 km long. Lineations in the L tectonite are sub-horizontal, parallel to the hinge of the antiform. Sheath folds are also well developed associated with the L tectonite, with the hinges parallel to the lineations. Migmatite occurs in the core and structurally below the L tectonite and has a gradational relationship with the L tectonite. The domain of L tectonite is bounded by three ductile shear zones, on the north, at the top and on the south, respectively. Well-developed shear sense indicators indicate that the southern, the overlying and the northern shear zones have a dextral, top-to-NW and sinistral sense of shear, respectively. These geometrical and kinematic data indicate that the three shear zones are likely part of a single shear zone that wraps around the L-tectonite domain. The L-tectonite zone in the core moves southeast relative to the hanging wall. The development of the tectonite is interpreted to be a result of this special geometry and kinematics and reflects a post-collisional orogen-parallel extension synchronous with migmatization and the continuing convergence between the Yangtze Block and the North China Block in the Early Cretaceous.

  8. Thrust-related, diapiric, and extensional doming in a frontal orogenic wedge: example of the Montagne Noire, Southern French Hercynian Belt

    NASA Astrophysics Data System (ADS)

    Soula, Jean-Claude; Debat, Pierre; Brusset, Stéphane; Bessière, Gilbert; Christophoul, Frédéric; Déramond, Joachim

    2001-11-01

    The Montagne Noire, which is situated at the toe of the orogenic wedge of the French Massif Central South European Variscides, appears to be a well-suited area for studying the origin and evolution of middle to upper crustal domes adjacent to foreland basins. The data reported in the present paper show that the Montagne Noire dome is a particular type of basement-involved frontal culmination in an orogenic wedge and foreland basin system. This frontal culmination is characterized by a syn-contractional HT decompression recorded by clockwise PTt paths and widespread strata overturning in thrust and fold structures, which controlled the sedimentation in the adjacent foreland basin. These unusual characteristics are interpreted to be a result of the succession of thrusting, diapirism and extensional collapse. Antiformal stacking of syn-metamorphic thrust sheets controlled the first stages of the foreland basin development. Diapirism was essentially responsible for the HT decompression and widespread strata overturning. Extensional doming was a result of late- to post-metamorphic collapse acting on the pre-existing high-amplitude dome. Diapirism and associated isothermal decompression metamorphism, which constitute the essential difference between the Montagne Noire and 'ordinary' frontal ridges in orogenic wedges, were probably enhanced by a local partial melting of the upper to middle crust. It is suggested that the occurrence of these phenomena in front of an orogenic wedge was related to local over-thickening due to the superposition of an upper crustal antiformal stack on top of a lower crustal ramp anticline.

  9. 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

  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. Paleo-Mesoproterozoic arc-accretion along the southwestern margin of the Amazonian craton: The Juruena accretionary orogen and possible implications for Columbia supercontinent

    NASA Astrophysics Data System (ADS)

    Scandolara, J. E.; Correa, R. T.; Fuck, R. A.; Souza, V. S.; Rodrigues, J. B.; Ribeiro, P. S. E.; Frasca, A. A. S.; Saboia, A. M.; Lacerda Filho, J. V.

    2017-01-01

    The southwestern portion of the Amazonian craton, between the Ventuari-Tapajós province and the Andean chain, has been ascribed to a succession of orogenic events from 1.81 to 0.95 Ga, culminating with widespread anorogenic magmatism. Southwestward of the Serra do Cachimbo graben occurs the Juruena accretionary orogenic belt (ca. 1.81-1.51 Ga), previously included in the Rio Negro-Juruena and Rondonian/San Ignácio geocronological provinces or Rondônia-Juruena geologic province. The Juruena orogen proposed here includes the Jamari and Juruena tectonostratigraphic terranes, products of convergence which culminated in the soft collision of the Paraguá protocraton and the Tapajós-Parima arc system (Tapajós Province) ca. 1.69-1.63 Ga ago. Geophysical, geochemical, petrological and geochronological data and systematic geological mapping suggest that the convergent event resulted in a single orogenic system with two continental margin arcs, namely the Jamari and Juruena arcs. Modern geological and tectonic approaches, combined with aerogeophysics data, enable to interpreting this wide region of the Amazonian craton as a Paleoproterozoic orogen with well defined petrotectonic units and tectonoestructural framework. The Juruena orogen is an E-W trending belt, about 1100 km long and 350 km wide, inflecting to NW-SE, in Mato Grosso, Amazonas and Rondonia, Brazil. The general direction of the belt, its inflections and internal geometric and kinematic aspects of its macrostructures do not corroborate the general NW-SE trend of the originally proposed geocronological provinces. The Juruena accretionary orogen has been the site of repeated reactivation with renewed basin formation, magmatism and orogeny during the Mesoproterozoic and the early Neoproterozoic. U-Pb and whole-rock Sm-Nd ages, Ar-Ar and Rb-Sr mineral ages suggest that the older high grade tectonometamorphic events in the Juruena accretionary orogen took place between 1.69 and 1.63 Ga, defining the metamorphic

  12. 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.

  13. 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

  14. New assemly model of Jiangnan Orogen: insight from detrital zircon geochronology of pre-Cretaceous strata, South China

    NASA Astrophysics Data System (ADS)

    Su, J.; Dong, S.

    2013-12-01

    The Jiangnan Orogen separates the Yangtze and Cathaysian Blocks in South China and provokes a longstanding debate on the amalgamation history between the two Blocks. The assembly of the two Blocks is termed Sibao orogeny marked by undeformed Late Neoproterozoic strata (Banxi Group) overlying on the deformed Early Neoproterozoic strata (Lengjiaxi Group) in China. Detrital zircons can provide critical links in recognizing the source history of a deposit, sedimentary dispersal systems and tectonic reconstructions. Therefore, fifteen sandstone samples taken from pre-Cretaceous strata of Yangtze Block are analyzed to constrain the evolution of the South China Block (SCB), especially the assembly between Yangtze and Cathaysia Blocks. The results show that the detrital zircons from the Neoproterozoic Lengjiaxi Group (ca. 830 Ma) near the boundary of large detachment fault of Hengshan have similar age populations with that in the other sites of the Jiangnan Orogen, different from that of the Kunyang and Dahongshan Groups (>960 Ma) in the southwestern margin of the Yangtze Block. The detrital zircons from Paleozoic samples have similar age populations with that in the Cathaysia Block. We infer that they originate from the Cathaysia Block, together with paleogeography, paleocurrent and former research. The detrital zircons of middle-late Jurassic sandstones in southwestern and central Yangtze yield dominant populations at 2.0-1.7 Ga and subordinate Groups of 2.6-2.4Ga, 0.7-0.8Ga and 0.6-0.4Ga. The provenance of late Triassic strata may be derived from southern Yangtze and North China Block due to the collisions among the Indosina, South China and North China Blocks, whereas the Jurassic sediments may be partly derived from uplift erosion of Jiangnan Orogen due to intra-continental orogeny induced by pacific subduction towards Eurasia Plate. The tectothermal event occurred at ca. 1.1-0.8 Ga has long been attributed to the assembly or breakup of Yangtze and Cathaysia Blocks

  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. Geodynamic control on orogenic and anorogenic magmatic phases in Sardinia and Southern Spain: Inferences for the Cenozoic evolution of the western Mediterranean

    NASA Astrophysics Data System (ADS)

    Beccaluva, L.; Bianchini, G.; Natali, C.; Siena, F.

    2011-04-01

    The genetic relationships between orogenic (i.e. subduction related) and anorogenic (i.e. intra-plate) Cenozoic igneous phases have been investigated in two regions of the western Mediterranean area: Sardinia and Southern Spain. In Sardinia the 'orogenic' magmatism (38-12 Ma) is followed by the 'anorogenic' volcanism, mostly since about 6 Ma, whereas in Southern Spain the 'anorogenic' volcanism follows the 'orogenic' phase (34-6 Ma) after a gap of 0-4 Ma in the Betic-Calatrava districts. The older orogenic magmatism (tholeiitic, calcalkaline and more potassic products) of both areas is related to the subduction of the Ionian oceanic lithosphere which developed beneath the Paleo-European-Iberian continental margin probably since Middle-Late Eocene. This subduction system migrated southeastwards with time up to its present position in the Eolian-Calabrian Arc and the Betic-Alboran regions along the Apennine-Maghrebide belt. Relics of subducted lithosphere are geophysically recorded as nearly-vertical bodies down to 500-600 km, flattening for several hundreds of kilometres under the Tyrrhenian-Sardinia and Betic-Calatrava areas, respectively. These relics of subducted slabs, which pond over large areas of the mantle transition zone, appear to play a significant role also in the genesis of the younger anorogenic magmas, whose major volcanic fields lie above the frontal part of the subducted slab where convective instabilities and upward mantle flow components are geophysically supported by laboratory and 3D numerical models. This dynamic response to subduction, involving localised mantle upwellings and remobilization of pre-existing mantle components, may have been a fundamental factor in the generation of anorogenic magmas. Due to slab roll-back and inter-arc extension in both Eolian-Tyrrhenian and Betic-Alboran regions, the magma sources of the previous orogenic phases can be completely replaced by "fresh" mantle diapirs from which anorogenic magmas will be generated

  17. Self-consistent orogenic wedge formation and shear zone propagation due to thermal softening

    NASA Astrophysics Data System (ADS)

    Jaquet, Yoann; Duretz, Thibault; Schmalholz, Stefan M.

    2016-04-01

    We present two dimensional numerical simulations of orogenic wedge formation for a viscoelastoplastic lithosphere under compression. The thermo-mechanical model is based on the principle of energy conservation and includes temperature-dependent rheologies. With this approach, shear zones caused by thermal softening develop spontaneously in the absence of strain softening. The initial locus of shear localization is controlled by either lateral temperature variations (100°C) at the model base or by lateral variations in crustal thickness. The first episode of strain localization occurs after 15% bulk shortening. With ongoing strain, a series of shear zones arise and propagate towards the foreland leading to the self-consistent formation of an orogenic wedge. We investigate the impact of bulk shortening rates, erosion and rheology on the dynamics of wedge formation, the associated topography and uplift rates. The maximum topography reaches up to 10 km and the surface morphology evolves according to shear zone activation and deactivation. Uplift rates are transient and peak values are maintained only on very short time scales. A running average of the uplift rate versus time curves with a time-window of 4 My provides average uplift rates in the order of a few millimeters per year. Erosion is an important parameter for the formation and the evolution of the wedge (e.g. can control the spacing of shear zones by modifying crustal thickness). Rheological parameters, such as the friction angle or the upper crustal viscosity, control the occurrence of strain localization. Bulk shortening rates between 10-15 and 10-16 s-1 do not have a major impact on the resulting wedge structure.

  18. Sand petrology and focused erosion in collision orogens: the Brahmaputra case

    NASA Astrophysics Data System (ADS)

    Garzanti, Eduardo; Vezzoli, Giovanni; Andò, Sergio; France-Lanord, Christian; Singh, Sunil K.; Foster, Gavin

    2004-03-01

    The high-relief and tectonically active Himalayan range, characterized by markedly varying climate but relatively homogeneous geology along strike, is a unique natural laboratory in which to investigate several of the factors controlling the composition of orogenic sediments. Coupling of surface and tectonic processes is most evident in the eastern Namche Barwa syntaxis, where the Tsangpo-Siang-Brahmaputra River, draining a large elevated area in south Tibet, plunges down the deepest gorge on Earth. Here composition of river sands changes drastically from lithic to quartzofeldspathic. After confluence with the Lohit River, draining the Transhimalayan-equivalent Mishmi arc batholiths, sediment composition remains remarkably constant across Assam, indicating subordinate contributions from Himalayan tributaries. Independent calculations based on petrographical, mineralogical, and geochemical data indicate that the syntaxis, representing only ∼4% of total basin area, contributes 35±6% to the total Brahmaputra sediment flux, and ∼20% of total detritus reaching the Bay of Bengal. Such huge anomalies in erosion patterns have major effects on composition of orogenic sediments, which are recorded as far as the Bengal Fan. In the Brahmaputra basin, in spite of very fast erosion and detrital evacuation, chemical weathering is not negligible. Sand-sized carbonate grains are dissolved partially in mountain reaches and completely in monsoon-drenched Assam plains, where clinopyroxenes are selectively altered. Plagioclase, instead, is preferentially weathered only in detritus from the Shillong Plateau, which is markedly enriched in microcline. Most difficult to assess is the effect of hydraulic sorting in Bangladesh, where quartz, garnet and epidote tend to be sequestered in the bedload and trapped on the coastal plain, whereas cleavable feldspars and amphiboles are concentrated in the suspended load and eventually deposited in the deep sea. High-resolution petrographic and

  19. Southern Costa Rica: an Island-arc Segment That Behaves Like a Doubly Vergent Orogen

    NASA Astrophysics Data System (ADS)

    Brandes, C.; Winsemann, J.

    2007-12-01

    Southern Central America is a Mesosoic/Cenozoic island-arc that evolved from the subduction of the Farallón Plate below the Caribbean Plate. The southern Costa Rican land-bridge comprises deformed fore-arc and back-arc basins in the west and east, respectively, separated by the up to 3.8 km high Talamanca Range. The structure of the southern Central American island-arc is similar to doubly vergent and asymmetric orogens. The deformed fore-arc basin in the west and the Limon fold-and-thrust belt in the east can be interpreted as pro-wedge and retro-wedge, respectively. The Talamanca Range represents the uplifted block in between. The pro-wedge is wider and has a lower slope angle than the retro-wedge. The uplift of the Talamanca Range is probably related to a system of conjugate shear zones. Precipitation is unevenly distributed, with orographic effects concentrating precipitation in SW Costa Rica, which has caused pro-wedge denudation, leading to exhumation of granitic rocks at in the interior of the mountain range. The large-scale structure of the Central American island-arc in southern Costa Rica can be described using models of continental collision zones. Previous studies attributed the deformation and uplift pattern to the subduction/collision of the Cocos Ridge. Another reasonable driving mechanism for the evolution of such an orogen in an oceanic island-arc setting is the basal traction due to long-term subduction of the Cocos Plate at a very low angle.

  20. 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.

  1. Neoproterozoic and Paleozoic accretionary orogens exposed at different crustal levels

    NASA Astrophysics Data System (ADS)

    Kroener, A.

    2002-12-01

    Accretionary orogens in the upper crust are dominated by trench and forearc deposits, obducted ophiolite fragments, exotic terranes and well defined structural boundaries such as major shear zones. The Neoproterozoic Arabian-Nubian shield (ANS) of western Arabia and NE Africa, the huge terrain of the Neoproterozoic to Palaeozoic Central Asian mobile belt (CAMB) and the present Indonesian Archipelago are prime examples of such orogens. In the ANS and CAMB, field relationships, rock associations, differences in structural style and metamorphic grade, and geochronology have led to the recognition of terrane assemblages that are related to processes of lateral accretion as now observed in the southwest Pacific and lasting for several hundred my. In the ANS, ocean crust and arc formation began about 900 Ma ago, and terrane accretion was completed by ~600 Ma, whereas in the CAMB the oldest oceanic crust formed some 1000 Ma ago, and terrane accretion continued into the late Palaeozoic. Typical rock associations are trench and forearc sediments, island-arc volcanics, calc-alkaline granitoids, dismembered ophiolite suites and gneissic rocks (microcontinents?) constituting exotic terranes and mostly of distinctly older age and more complex tectono-metamorphic history than the surrounding lower grade rocks. Shear zones frequently separate the terranes and in the ANS also constitue seismic discontinuities extending to the lower crust. The middle to lower crustal high grade assemblages of the Neoproterozoic Mozambique belt (MB) of East Africa, Madagascar, southernmost India, Sri Lanka and East Antarctica are considered to be a deep crustal analogue to the upper crustal accretionary belts described above. Typical characteristics are (1) voluminous calc-alkaline granitoid suites, now layered gneisses, and interpreted as root zones of arc terranes, (2) tectonic interdigitation of Archaean to Palaeoproterozoic gneisses with Neoproterozoic rocks, probably brought about during

  2. Vorticity analysis in the Zagros orogen, Shiraz area, Iran

    NASA Astrophysics Data System (ADS)

    Sarkarinejad, Khalil; Heibati, Zahra

    2016-10-01

    Quantitative vorticity analyses in orogenic belts are essential for studying the kinematics of deformation and can be performed using a range of methods. The combination of microstructural analysis for vorticity with other methods creates a more rigorous analysis. In order to determine the degree of non-coaxiality and spatial pattern of vorticity during deformation in the Zagros Orogenic Belt, a study area containing the boundary of the Zagros Folded Belt and the Zagros Fold-and-Thrust Belt is selected. The study area is situated in the Shiraz region of E-Zagros in Iran. The kinematic vorticity analysis is carried out using 4 methods based on: (1) the degree of asymmetry of the calcite c-axis fabric, (2) the assumption that the orientation of the long axes of calcite within an oblique stylolite foliation delineates the direction of the instantaneous stretching axis, (3) the assumption that the tension gash tips determine the direction of the instantaneous stretching axis and (4) stylolite teeth determine the direction of the instantaneous stretching axis. C-axis data from calcite give a kinematic vorticity number between 0.68 and 0.83, and the orientation of the long axes of calcite grains yields a range between 0.5 and 0.84. Stylolites provide a kinematic vorticity number between 0.5 and 0.79, and tension gashes provide a kinematic vorticity number between 0.56 and 0.81. This range of vorticity numbers confirms the contributions of both simple (33-59%) and pure shear (41-67%). Twining of calcite also reveals that the last stage of deformation occurred at a temperature of 170-200 °C. Spatial analysis reveals an increase in the simple shear component from the SW of the Zagros Folded Belt to the NE of the Zagros Fold-and-Thrust Belt.

  3. 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.

  4. 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).

  5. 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

  6. 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.

  7. Final « pop-up » structural reactivation of the internal part of an orogenic wedge: west-central Pyrenees

    NASA Astrophysics Data System (ADS)

    Meresse, F.; Jolivet, M.; Labaume, P.; Teixell, A.

    2009-04-01

    Université Montpellier 2, INSU-CNRS, Laboratoire Géosciences Montpellier, cc060, 34095 Montpellier Cedex 5, France florian.meresse@gm.univ-montp2.fr Tectonics-sedimentation relationships are often used to describe the tectonic evolution of orogenic wedges. However, does the sedimentary record associated to the build-up of the wedge recall the entire tectonic history? Numerous studies based on tectono-stratigraphic and thermochronological data, as well as numerical modeling, have demonstrated that on the large scale the growth of the Pyrenees is characterized by a southward propagation of the deformation (e.g., Muñoz, 1992; Morris et al., 1998; Fitzgerald et al., 1999; Beaumont et al., 2000). However, in the west-central Pyrenees, recent thermochronological data have suggested that the in-sequence propagation of the basement thrust system was followed by out-of-sequence (re)activation of hinterland structures after the South-Pyrenean Frontal Thrust had been sealed (Jolivet et al., 2007). To better describe the structural evolution of the Pyrenean prism, we focused our work on a NNE-SSW transect from the northern piedmont (Bagnères-de-Bigorre), through the Axial Zone and down to the Jaca basin where tectonics-sedimentation relationships have been extensively described (e.g., Teixell, 1996). A crustal scale cross-section combined with detailed apatite fission track analysis are used as a case study to unravel in detail the deformation history. Apatite fission track data from the Bagnères-de-Bigorre Paleozoic massif (central ages: 41-42 Ma) and the Lesponne Hercynian granite (central age: 31 Ma) located in the North-Pyrenean Zone and in the north of the Axial Zone, respectively, reveal Middle Eocene-Early Oligocene denudation ages of the northern part of the wedge. Immediately to the south, central ages around 24-20 Ma attest to a Latest Oligocene-Early Miocene denudation ages of the Chiroulet granite. According to the structural context, these results suggest a

  8. 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.

  9. Content Analysis in Systems Engineering Acquisition Activities

    DTIC Science & Technology

    2016-04-30

    shape requirements definitions for system upgrade or modification contracts and new baseline contracts. Finally, content analysis training and skill...back to the system designers, this information can then be used to shape requirements definition for system upgrade or modification contracts and new...Activity System Requirements Definition Ensuring the system requirements adequately reflect the stakeholder requirements Negotiating modifications to

  10. 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

  11. Mechanisms of doubly-vergent vs. single-sided orogens: insights from numerical modelling

    NASA Astrophysics Data System (ADS)

    Vogt, K.; Matenco, L. C.; Gerya, T.; Cloetingh, S.

    2014-12-01

    Zones of continent collision form mountain ranges with high topographies and complex geometries. Compressional stresses during ongoing convergence result in crustal thickening and localized deformation, where crustal material is transported and redistributed within the orogen. We use numerical high-resolution thermo-mechanical models to investigate the physical processes of continent collision zones and its implications on rock exhumation. We demonstrate that compression of two continental blocks, separated by a rheologically weak suture zone can result in (i) doubly-vergent (Fig. A) or (ii) single-sided orogens (Fig. B), with distinct geometries, deformation and exhumation patterns. The transition between these different modes of collision is strongly controlled by the rheology of the continental lithosphere and therefore its temperature distribution. Doubly-vergent orogens form at relatively high thermal gradients, while single-sided orogens are typical for lower ones. Doubly-vergent orogens (Fig. A) are formed in response to the gradual accretion of crustal material to the upper plate along retro-shears. In these models continental subduction results in upper plate deformation and nested exhumation against retro-shears. Typical examples include the collision recorded by the Swiss Alps and the Pyrenees. In contrast, single-sided orogens are characterized by large-scale lower plate deformation and are accompanied by the subduction of lower crustal material (Fig. B). Modeling infers that shortening and associated exhumation will gradually propagate towards the foreland. In this situation, no significant retro-shear formation is observed, which is in agreement with recent physical modelling studies on deformation of the continental lithosphere [Willingshofer et al., 2013]. Natural examples of such single sided orogens are common in the Mediterranean (Carpathians, Dinarides, Apennines, Betics) or the SE Asia subduction zones. We conclude that deformation and

  12. 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

  13. 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.

  14. 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.

  15. 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

  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. A robust activity marking system for exploring active neuronal ensembles.

    PubMed

    Sørensen, Andreas T; Cooper, Yonatan A; Baratta, Michael V; Weng, Feng-Ju; Zhang, Yuxiang; Ramamoorthi, Kartik; Fropf, Robin; LaVerriere, Emily; Xue, Jian; Young, Andrew; Schneider, Colleen; Gøtzsche, Casper René; Hemberg, Martin; Yin, Jerry Cp; Maier, Steven F; Lin, Yingxi

    2016-09-23

    Understanding how the brain captures transient experience and converts it into long lasting changes in neural circuits requires the identification and investigation of the specific ensembles of neurons that are responsible for the encoding of each experience. We have developed a Robust Activity Marking (RAM) system that allows for the identification and interrogation of ensembles of neurons. The RAM system provides unprecedented high sensitivity and selectivity through the use of an optimized synthetic activity-regulated promoter that is strongly induced by neuronal activity and a modified Tet-Off system that achieves improved temporal control. Due to its compact design, RAM can be packaged into a single adeno-associated virus (AAV), providing great versatility and ease of use, including application to mice, rats, flies, and potentially many other species. Cre-dependent RAM, CRAM, allows for the study of active ensembles of a specific cell type and anatomical connectivity, further expanding the RAM system's versatility.

  18. 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.

  19. 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

  20. Modes of orogen-parallel stretching and extensional exhumation in response to microplate indentation and roll-back subduction (Tauern Window, Eastern Alps)

    NASA Astrophysics Data System (ADS)

    Scharf, A.; Handy, M. R.; Favaro, S.; Schmid, S. M.; Bertrand, A.

    2013-09-01

    The Tauern Window exposes a Paleogene nappe stack consisting of highly metamorphosed oceanic (Alpine Tethys) and continental (distal European margin) thrust sheets. In the eastern part of this window, this nappe stack (Eastern Tauern Subdome, ETD) is bounded by a Neogene system of shear (the Katschberg Shear Zone System, KSZS) that accommodated orogen-parallel stretching, orogen-normal shortening, and exhumation with respect to the structurally overlying Austroalpine units (Adriatic margin). The KSZS comprises a ≤5-km-thick belt of retrograde mylonite, the central segment of which is a southeast-dipping, low-angle extensional shear zone with a brittle overprint (Katschberg Normal Fault, KNF). At the northern and southern ends of this central segment, the KSZS loses its brittle overprint and swings around both corners of the ETD to become subvertical, dextral, and sinistral strike-slip faults. The latter represent stretching faults whose displacements decrease westward to near zero. The kinematic continuity of top-east to top-southeast ductile shearing along the central, low-angle extensional part of the KSZS with strike-slip shearing along its steep ends, combined with maximum tectonic omission of nappes of the ETD in the footwall of the KNF, indicates that north-south shortening, orogen-parallel stretching, and normal faulting were coeval. Stratigraphic and radiometric ages constrain exhumation of the folded nappe complex in the footwall of the KSZS to have begun at 23-21 Ma, leading to rapid cooling between 21 and 16 Ma. This exhumation involved a combination of tectonic unroofing by extensional shearing, upright folding, and erosional denudation. The contribution of tectonic unroofing is greatest along the central segment of the KSZS and decreases westward to the central part of the Tauern Window. The KSZS formed in response to the indentation of wedge-shaped blocks of semi-rigid Austroalpine basement located in front of the South-Alpine indenter that was part

  1. High-temperature metamorphism of the Yushugou ophiolitic slice: Late Devonian subduction of seamount and mid-oceanic ridge in the South Tianshan orogen

    NASA Astrophysics Data System (ADS)

    Zhang, Li; Jin, Zhenmin

    2016-12-01

    The South Tianshan Orogenic Belt (STOB), representing the southern segment of the Central Asian Orogenic Belt (CAOB), underwent a long-lived and subduction-related accretionary orogenic process. Revealing the petrogenesis of high-pressure (HP) metamorphic ophiolitic slices within this orogen is of crucial importance to understanding the geodynamic evolution of the STOB. In this study, we carry out a petrological, geochemical and geochronological study of HP mafic granulites from the Yushugou ophiolitic slice within the South Tianshan Accretionary Complex. Our results combined with previously published data suggest that the Yushugou mafic granulites, including garnet-clinopyroxene granulite, garnet two-pyroxene granulite and garnet-orthopyroxene granulite, are generally subalkaline to alkaline basalts, and show geochemical characteristics of MORB and OIB. The nominally anhydrous minerals of the mafic granulites contain certain but trace amounts of water in the manner of structural OH and sub-microscopic fluid inclusions. The granulites have a possible protolith age of ca. 400 Ma and metamorphic age of 390-360 Ma, and underwent HP and high-temperature (HT) granulite-facies metamorphism under conditions of 12-14 kbar and 840-950 °C and low H2O activity. Our study indicates that the Yushugou ophiolitic slice was probably derived from seamount that formed at mid-oceanic ridge closing to the oceanic trench and subduction zone during the Early Devonian, and then underwent metamorphism and deformation as a result of the subduction of the seamount and associated spreading ridge during the Middle to Late Devonian. Therefore, the Yushugou HP ophiolitic slice provides an important information of the Paleozoic tectonic evolutionary of the STOB.

  2. Magma-assisted strain localization in an orogen-parallel transcurrent shear zone of southern Brazil

    NASA Astrophysics Data System (ADS)

    Tommasi, AndréA.; Vauchez, Alain; Femandes, Luis A. D.; Porcher, Carla C.

    1994-04-01

    . Synkinematic granitoids localize most, if not all, deformation in the studied shear zone. The regional continuity and the pervasive character of the magmatic fabric in the various synkinematic granitic bodies, consistently displaying similar plane and direction of flow, argue for accommodation of large amounts of orogen-parallel movement by viscous deformation of these magmas. Moreover, activation of high-temperature deformation mechanisms probably allowed a much easier deformation of the hot synkinematic granites than of the colder country rock and, consequently, contributed significantly to the localization of deformation. Finally, the small extent of the low-temperature deformation suggests that the strike-slip deformation ended approximately synchronously with the final cooling of the peraluminous granites. The evolution of the deformation reflects the strong influence of synkinematic magma emplacement and subsequent cooling on the thermomechanical evolution of the shear zone. Magma intrusion in an orogen-scale transcurrent shear zone deeply modifies the rheological behavior of the continental crust. It triggers an efficient thermomechanical softening localized within the fault that may subsist long enough for large displacements to be accommodated. Therefore the close association of deformation and synkinematic magmatism probably represents an important factor controlling the mechanical response of continental plates in collisional environments.

  3. An active tactile perception system

    NASA Astrophysics Data System (ADS)

    Petriu, E.; Greenspan, M.; Gelinas, F.; McMath, W. S.; Yeung, S. K.

    System development and application aspects are described for an experimental robotic system for the tactile perception of the global geometric profile of object surfaces which are larger than the dimensions of the tactile sensor. Local cutaneous information provided by a tactile sensor is integrated with the kinesthetic position parameters of a robot arm, resulting in a 3D geometric model of the tactile sensor pose on the explored object surface. Currently available tactile sensors provide poor information on the geometric profile of 3D object surfaces. In order to maximize the information available for 3D analysis, an instrumented passive compliant wrist was used to attach a pressure measuring tactile probe to the robot arm carrier. Data was collected by a noncompliant planar sensing array in direct contact with an object surface. Information recorded includes the following: positional and orientation data on the robot arm manipulator, passive compliance kinesthetic data as measured by the kinematics of the wrist, and cutaneous tactile data represented by the binary image of the sensors pose on the object. The dimensions of the sensor array were found to be a critical factor in system performance. Use of a large array results in fewer touch poses being required to explore an object's surface, on the other hand a large planar array will touch fewer and higher peaks thus missing surface detail. To improve performance, there is a need to design tactile sensors specifically for geometric profile measuring.

  4. Kinematics of the Torcal Shear Zone: transpressional tectonics shaping orogenic curves in the northern Gibraltar Arc.

    NASA Astrophysics Data System (ADS)

    Barcos, Leticia; Balanyá, Juan Carlos; Díaz-Azpiroz, Manuel; Expósito, Inmaculada; Jiménez-Bonilla, Alejandro

    2014-05-01

    zones as well as normal faults accommodating fold axis parallel extension. iiii) The Sierra de las Cabras-Camorolos sector, located at the E-end of the TSZ, is divided into two structural domains: a western domain, dominated by N120ºE dextral strike-slip faults, and an eastern domain structured by a WSW-ENE thrust system and normal faults with extension subparallel to the direction of the shortening structures. TSZ displacement at the lateral tip of this sector seems to be mainly accommodated by NNE trending thrusts in the northern TSZ block. The TSZ induces the near vertical extrusion of paleomargin rock units within the deformation band and the dextral deflection of the structural trend shaping the lateral end of the WGA salient. Our results suggest the TSZ started in the Upper Miocene and is still active. Moreover, the TSZ trends oblique to regional transport direction assessed both by field data and modelling. The estimated WNW-ESE far-field velocity vector in the TAM and the SVA points to the importance of the westward drift of the Internal Zones relative to the external wedge and fits well with the overall WGA kinematic frame. Nor the WGA salient neither the TSZ can be fully explained by the single Europe-Africa plate convergence.

  5. 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

  6. Crustal shortening, exhumation, and strain localization in a collisional orogen: The Bajo Pequeño Shear Zone, Sierra de Pie de Palo, Argentina

    NASA Astrophysics Data System (ADS)

    Garber, Joshua M.; Roeske, Sarah M.; Warren, Jessica; Mulcahy, Sean R.; McClelland, William C.; Austin, Lauren J.; Renne, Paul R.; Vujovich, Graciela I.

    2014-07-01

    The Bajo Pequeño Shear Zone (BPSZ) is a lower-crustal shear zone that records shortening and exhumation associated with the establishment of a new plate boundary, and its placement in a regional structural context suggests that local- to regional-scale strain localization occurred with progressive deformation. A kilometer-scale field and analytical cross section through the ~80 m thick BPSZ and its adjacent rocks indicates an early Devonian (405-400 Ma) phase of deformation on the western margin of Gondwanan continental crust. The earliest stages of the BPSZ, recorded by metamorphic and microstructural data, involved thrusting of a hotter orthogneiss over a relatively cool pelitic unit, which resulted in footwall garnet growth and reset footwall white mica 40Ar/39Ar ages in proximity to the shear zone. Later stages of BPSZ activity, as recorded by additional microstructures and quartz c-axis opening angles, were characterized by strain localization to the center of the shear zone coincident with cooling and exhumation. These and other data suggest that significant regional tectonism persisted in the Famatinian orogenic system for 60-70 million years after one microplate collision (the Precordillera) but ceased 5-10 million years prior to another (Chilenia). A survey of other synchronous structures shows that strain was accommodated on progressively narrower structures with time, indicating a regional pattern of strain localization and broad thermal relaxation as the Precordillera collision evolved.

  7. Deformation processes in orogenic wedges: New methods and application to Northwestern Washington State

    NASA Astrophysics Data System (ADS)

    Thissen, Christopher J.

    Permanent deformation records aspects of how material moves through a tectonic environment. The methods required to measure deformation vary based on rock type, deformation process, and the geological question of interest. In this thesis we develop two new methods for measuring permanent deformation in rocks. The first method uses the autocorrelation function to measure the anisotropy present in two-dimensional photomicrographs and three-dimensional X-ray tomograms of rocks. The method returns very precise estimates for the deformation parameters and works best for materials where the deformation is recorded as a shape change of distinct fabric elements, such as grains. Our method also includes error estimates. Image analysis techniques can focus the method on specific fabric elements, such as quartz grains. The second method develops a statistical technique for measuring the symmetry in a distribution of crystal orientations, called a lattice-preferred orientation (LPO). We show that in many cases the symmetry of the LPO directly constrains the symmetry of the deformation, such axial flattening vs. pure shear vs. simple shear. In addition to quantifying the symmetry, the method uses the full crystal orientation to estimate symmetry rather than pole figures. Pole figure symmetry can often be misleading. This method works best for crystal orientations measured in samples deformed by dislocation creep, but otherwise can be used on any mineral without requiring information about slip systems. In Chapter 4 we show how deformation measurements can be used to inform regional tectonic and orogenic models in the Pacific Northwestern United States. A suite of measurements from the Olympic Mountains shows that uplift and deformation of the range is consistent with an orogenic wedge model driven by subduction of the Juan de Fuca plate, and not northward forearc migration of the Oregon block. The deformation measurements also show that deformation within the Olympic Mountains

  8. The distribution, geochronology and geochemistry of early Paleozoic granitoid plutons in the North Altun orogenic belt, NW China: Implications for the petrogenesis and tectonic evolution

    NASA Astrophysics Data System (ADS)

    Meng, Ling-Tong; Chen, Bai-Lin; Zhao, Ni-Na; Wu, Yu; Zhang, Wen-Gao; He, Jiang-Tao; Wang, Bin; Han, Mei-Mei

    2017-01-01

    Abundant early Paleozoic granitoid plutons are widely distributed in the North Altun orogenic belt. These rocks provide clues to the tectonic evolution of the North Altun orogenic belt and adjacent areas. In this paper, we report an integrated study of petrological features, U-Pb zircon dating, in situ zircon Hf isotope and whole-rock geochemical compositions for the Abei, 4337 Highland and Kaladawan Plutons from north to south in the North Altun orogenic belt. The dating yielded magma crystallization ages of 514 Ma for the Abei Pluton, 494 Ma for the 4337 Highland Pluton and 480-460 Ma for the Kaladawan Pluton, suggesting that they are all products of oceanic slab subduction because of the age constraint. The Abei monzogranites derived from the recycle of Paleoproterozoic continental crust under low-pressure and high-temperature conditions are products of subduction initiation. The 4337 Highland granodiorites have some adakitic geochemical signatures and are sourced from partial melting of thickened mafic lower continental crust. The Kaladawan quartz diorites are produced by partial melting of mantle wedge according to the positive εHf(t) values, and the Kaladawan monzogranite-syenogranite are derived from partial melting of Neoproterozoic continental crust mixing the juvenile underplated mafic material from the depleted mantle. These results, together with existing data, provide significant information about the evolution history of oceanic crust subduction during the 520-460 Ma. The initiation of subduction occurred during 520-500 Ma with formation of Abei Pluton; subsequent transition from steep-angle to flat-slab subduction at ca.500 Ma due to the arrival of buoyant oceanic plateaus, which induces the formation of 4337 Highland Pluton. With ongoing subduction, the steep-angle subduction system is reestablished to cause the formation of 480-460 Ma Kaladawan Pluton. Meanwhile, it is this model that account for the temporal-spatial distribution of these early

  9. Orogenic gold mineralisation hosted by Archaean basement rocks at Sortekap, Kangerlussuaq area, East Greenland

    NASA Astrophysics Data System (ADS)

    Holwell, D. A.; Jenkin, G. R. T.; Butterworth, K. G.; Abraham-James, T.; Boyce, A. J.

    2013-04-01

    A gold-bearing quartz vein system has been identified in Archaean basement rocks at Sortekap in the Kangerlussuaq region of east Greenland, 35 km north-northeast of the Skaergaard Intrusion. This constitutes the first recorded occurrence of Au mineralisation in the metamorphic basement rocks of east Greenland. The mineralisation can be classified as orogenic style, quartz vein-hosted Au mineralisation. Two vein types have been identified based on their alteration styles and the presence of Au mineralisation. Mineralised type 1 veins occur within sheared supracrustal units and are hosted by garnet-bearing amphibolites, with associated felsic and ultramafic intrusions. Gold is present as native Au and Au-rich electrum together with arsenopyrite and minor pyrite and chalcopyrite in thin alteration selvages in the immediate wall rocks. The alteration assemblage of actinolite-clinozoisite-muscovite-titanite-scheelite-arsenopyrite-pyrite is considered to be a greenschist facies assemblage. The timing of mineralisation is therefore interpreted as being later and separate event to the peak amphibolite facies metamorphism of the host rocks. Type 2 quartz veins are barren of mineralisation, lack significant alteration of the wall rocks and are considered to be later stage. Fluid inclusion microthermometry of the quartz reveals three separate fluids, including a high temperature ( T h = 300-350 °C), H2O-CO2-CH4 fluid present only in type 1 veins that in interpreted to be responsible for the main stage of Au deposition and sulphidic wall rock alteration. It is likely that the carbonic fluids were actually trapped at temperatures closer to 400 °C. Two other fluids were identified within both vein types, which comprise low temperature (100-200 °C) brines, with salinities of 13-25 wt% eq. NaCl and at least one generation of low salinity aqueous fluids. The sources and timings of the secondary fluids are currently equivocal but they may be related to the emplacement of

  10. 40 Ma years of hydrothermal W mineralization during the Variscan orogenic evolution of the French Massif Central revealed by U-Pb dating of wolframite

    NASA Astrophysics Data System (ADS)

    Harlaux, Matthieu; Romer, Rolf L.; Mercadier, Julien; Morlot, Christophe; Marignac, Christian; Cuney, Michel

    2017-03-01

    We present U-Pb thermal ionization mass spectrometer (TIMS) ages of wolframite from several granite-related hydrothermal W±Sn deposits in the French Massif Central (FMC) located in the internal zone of the Variscan belt. The studied wolframite samples are characterized by variable U and Pb contents (typically <10 ppm) and show significant variations in their radiogenic Pb isotopic compositions. The obtained U-Pb ages define three distinct geochronological groups related to three contrasting geodynamic settings: (i) Visean to Namurian mineralization (333-327 Ma) coeval with syn-orogenic compression and emplacement of large peraluminous leucogranites (ca. 335-325 Ma), (ii) Namurian to Westphalian mineralization (317-315 Ma) synchronous with the onset of late-orogenic extension and emplacement of syn-tectonic granites (ca. 315-310 Ma) and (iii) Stephanian to Permian mineralization (298-274 Ma) formed during post-orogenic extension contemporaneous with the Permian volcanism in the entire Variscan belt. The youngest ages (276-274 Ma) likely reflect the reopening of the U-Pb isotopic system after wolframite crystallization and may correspond to late hydrothermal alteration (e.g. ferberitization). Our results demonstrate that W(±Sn) mineralization in the FMC formed during at least three distinct hydrothermal events in different tectono-metamorphic settings over a time range of 40 Ma.

  11. 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.

  12. 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.

  13. 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.

  14. 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.

  15. 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.

  16. 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.

  17. 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.

  18. Orogen-perpendicular structures in the central Tasmanides and implications for the Paleozoic tectonic evolution of eastern Australia

    NASA Astrophysics Data System (ADS)

    Abdullah, Rashed; Rosenbaum, Gideon

    2017-01-01

    The curvilinear E-W structures of the southern Thomson Orogen are approximately orthogonal to the general N-S structural trend of the Tasmanides of eastern Australia. The origin of these orogen-perpendicular structures and their implications to tectonic reconstructions of eastern Gondwana are not fully understood. Here we use geophysical data to unravel the geometry, kinematics and possible timing of major structures along the boundary between the Thomson Orogen and the southern Tasmanides (Delamerian and Lachlan orogens). Aeromagnetic data from the southern Thomson Orogen show WNW, E-W and/or ENE trending structural grains, corresponding to relatively long wavelength linear geophysical anomalies. Kinematic analyses indicate strike-slip and transpressional deformation along these geophysically defined faults. Structural relationships indicate that faulting took place during the Benambran (Late Ordovician to Middle Silurian) and Tabberabberan (late Early to Middle Devonian) orogenies. However, some of the described crustal-scale structures may have developed in the Cambrian during the Delamerian Orogeny. Interpretation of deep seismic data shows that the crust of the southern Thomson Orogen is substantially thicker than the Lachlan Orogen crust, which is separated from the Thomson Orogen by the north-dipping Olepoloko Fault. A major lithospheric-scale change across this boundary is also indicated by a contrast in seismic velocities. Together with evidence for the occurrence of Delamerian deformation in both the Koonenberry Belt and northeastern Thomson Orogen, and a significant contrast in the width of the northern Tasmanides versus the southern Tasmanides, it appears that the southern Thomson Orogen may represent the locus of orogen-perpendicular segmentation, which may have occurred in response to along-strike plate boundary variations.

  19. 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.

  20. 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…

  1. 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.

  2. Metals distributions in activated sludge systems

    SciTech Connect

    Patterson, J.W.; Kodukula, P.S.

    1984-05-01

    Despite extensive laboratory and field studies over the past 25 years, little advance has been made in prediction of metals distribution and removal in activated sludge treatment systems. This paper reports the results of carefully controlled pilot studies, from which empirical metals distribution models were developed. The models accurately predict the distribution of process stream metals at each point in the activated sludge process between the soluble and solids phases. The distribution models together with data on primary and secondary clarifier suspended solids removal efficiencies, are easily applied to predict the removals of influent metals in activated sludge systems. 36 references, 2 figures.

  3. 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.

  4. 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.

  5. 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

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

    NASA Astrophysics Data System (ADS)

    Rosenberg, Claudio; Berger, Alfons; Bellahsen, Nicolas; Bousquet, Romain

    2014-05-01

    The width of orogens may change through time depending on the amount of shortening, on the efficiency of erosion, on the strength and thickness of the plates, or on the occurrence of pre-existing and newly formed weaknesses within the plates. The effect of erosion rates on the width of the Alps was controversially discussed, based on estimates of paleo-erosion rates and paleo-widths of the orogen. However, both parameters are difficult to reconstruct. In this contribution we investigate the causes of present-day, along-strike changes of width of the Eastern and the Central Alps to understand its width changes through time. Based on a series of 6 orogen-scale cross-sections and their retro-deformation we set the width of the thickened accreted lower plate in relation to the amount of collisional shortening and exhumation. We conclude that higher amounts of shortening systematically coincide with smaller widths of the thickened, accreted lower plate, i.e. the width of the mountain chain north of the South-Alpine indenters. Changes of width by a factor 2 along orogen segments of less than 200 km length cannot result from long-term climatic differences and sedimentary or paleontological evidences suggesting such differences are lacking. Therefore, erosional processes did not directly control the width of the orogen, which did not behave as a critical taper. Higher amounts of shortening coincide with larger amplitudes of orogen-scale, upright folds, with larger amounts of exhumation, and with higher exhumation rates. Hence, erosion did play a major role in reducing by up to 35 km the vertical crustal thickness in order to accommodate and allow shortening by folding, but along-strike changes of erosion rates were governed by different amounts of shortening, not by different climate.

  7. 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.; 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

  8. The plasminogen activator system: biology and regulation.

    PubMed

    Irigoyen, J P; Muñoz-Cánoves, P; Montero, L; Koziczak, M; Nagamine, Y

    1999-10-01

    The regulation of plasminogen activation involves genes for two plasminogen activators (tissue type and urokinase type), two specific inhibitors (type 1 and type 2), and a membrane-anchored urokinase-type plasminogen-activator-specific receptor. This system plays an important role in various biological processes involving extracellular proteolysis. Recent studies have revealed that the system, through interplay with integrins and the extracellular matrix protein vitronectin, is also involved in the regulation of cell migration and proliferation in a manner independent of proteolytic activity. The genes are expressed in many different cell types and their expression is under the control of diverse extracellular signals. Gene expression reflects the levels of the corresponding mRNA, which should be the net result of synthesis and degradation. Thus, modulation of mRNA stability is an important factor in overall regulation. This review summarizes current understanding of the biology and regulation of genes involved in plasminogen activation at different levels.

  9. 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.

  10. 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

  11. Cooling and inferred uplift/erosion history of the Grenville Orogen, Ontario: Constraints from 40Ar/39Ar thermochronology

    NASA Astrophysics Data System (ADS)

    Cosca, Michael A.; Sutter, John F.; Essene, Eric J.

    1991-10-01

    Stepwise 40Ar/39Ar degassing experiments of 57 mineral separates of hornblende, muscovite, biotite, and perthitic microcline have been used in conjunction with petrologic observations to place regional constraints on the postmetamorphic cooling and the inferred uplift and erosion history of the Grenville Orogen in Ontario. The 40Ar/39Ar data support an interpretation of slow, nearly uniform cooling (1°-4°C/m.y.) from temperatures of ˜500°C to below ˜150°C. In the Central Gneiss Belt (CGB) hornblendes cooled through Ar closure between 930 and 1025 Ma, whereas in the Central Metasedimentary Belt (CMB) hornblendes record the following range in 40Ar/39Ar cooling ages: 1104 Ma in the Frontenac terrane, 1007-1067 Ma in the Sharbot Lake terrane, 919-1026 Ma in the Elzevir terrane, and 972 Ma in the Central Metasedimentary Belt Boundary Zone. Regional uplift/erosion rates of 0.03-0.14 km/m.y. have been estimated for the Grenville Orogen in Ontario based on the 40Ar/39Ar data, a model retrograde P-T path for rocks of the CGB, and an upper time constraint provided by flat, overlying Cambrian and Ordovician sediments. These erosion rates are consistent with rates estimated for other Proterozoic or Archean granulite terranes but are an order of magnitude slower than active orogens such as the Alps and Himalayas. A regular variation in hornblende 40Ar/39Ar cooling ages is observed in rocks that traverse highly strained often mylonitic shear zones that separate the four major terranes of the CMB. The pattern of 40Ar/39Ar ages is interpreted to reflect late-tectonic extension, consistent with field observations in the Central Metasedimentary Belt Boundary Zone and elsewhere in the CMB. Up to 13 km of vertical displacement is inferred for some rocks in the CMB between the time they cooled below closure to argon diffusion in hornblende (˜500°C) and their exposure at the surface (˜25°C).

  12. 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.

  13. A robust activity marking system for exploring active neuronal ensembles

    PubMed Central

    Sørensen, Andreas T; Cooper, Yonatan A; Baratta, Michael V; Weng, Feng-Ju; Zhang, Yuxiang; Ramamoorthi, Kartik; Fropf, Robin; LaVerriere, Emily; Xue, Jian; Young, Andrew; Schneider, Colleen; Gøtzsche, Casper René; Hemberg, Martin; Yin, Jerry CP; Maier, Steven F; Lin, Yingxi

    2016-01-01

    Understanding how the brain captures transient experience and converts it into long lasting changes in neural circuits requires the identification and investigation of the specific ensembles of neurons that are responsible for the encoding of each experience. We have developed a Robust Activity Marking (RAM) system that allows for the identification and interrogation of ensembles of neurons. The RAM system provides unprecedented high sensitivity and selectivity through the use of an optimized synthetic activity-regulated promoter that is strongly induced by neuronal activity and a modified Tet-Off system that achieves improved temporal control. Due to its compact design, RAM can be packaged into a single adeno-associated virus (AAV), providing great versatility and ease of use, including application to mice, rats, flies, and potentially many other species. Cre-dependent RAM, CRAM, allows for the study of active ensembles of a specific cell type and anatomical connectivity, further expanding the RAM system’s versatility. DOI: http://dx.doi.org/10.7554/eLife.13918.001 PMID:27661450

  14. Crustal structures from the Wuyi-Yunkai orogen to the Taiwan orogen: The onshore-offshore wide-angle seismic experiments of the TAIGER and ATSEE projects

    NASA Astrophysics Data System (ADS)

    Kuo, Yao-Wen; Wang, Chien-Ying; Kuo-Chen, Hao; Jin, Xin; Cai, Hui-Teng; Lin, Jing-Yi; Wu, Francis T.; Yen, Horng-Yuan; Huang, Bor-Shouh; Liang, Wen-Tzong; Okaya, David; Brown, Larry

    2016-12-01

    Knowledge of the crustal structure is important for understanding the tectonic framework and geological evolution of southeastern China and adjacent areas. In this study, we integrated the datasets from the TAIGER (TAiwan Integrated GEodynamic Research) and ATSEE (Across Taiwan Strait Explosion Experiment) projects to resolve onshore-offshore deep crustal seismic profiles from the Wuyi-Yunkai orogen to the Taiwan orogen in southeastern China. Three seismic profiles were resolved, and the longest profile was 850 km. Unlike 2D and 3D first arrival travel-time tomography from previous studies, we used both refracted and reflected phases (Pg, Pn, PcP, and PmP) to model the crustal structures and the crustal reflectors. In total, data from 40 shots, 2 earthquakes, and approximately 1,950 stations were used; 15,612 arrivals were selected among three transects. Using these data, we determined the complex crustal evolution since the Paleozoic era , involving the closed Paleozoic rift basin in central Fujian, the Cenozoic extension due to the South China Sea opening beneath the coastline of southern Fujian, and the on-going collision of the Taiwan orogen. The shape of the Moho, which also reflects the crustal evolution, can be summarized as follows: 30 km deep to the west of Fujian, deepening toward central Fujian ( 35 km), becoming shallower toward the Taiwan Strait ( 28 km), deepening again toward the mountain belt of Taiwan ( 42 km), and becoming shallower toward the Pacific Ocean ( 10 km).

  15. 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.

  16. 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.

  17. A geophysical model of lower crustal structure of the Palaezoic crustal root (Bohemian Massif): implications for modern collisional orogens

    NASA Astrophysics Data System (ADS)

    Guy, Alexandra; Edel, Jean Bernard; Schulmann, Karel; Tomek, Cestmir; Lexa, Ondrej

    2010-05-01

    overturn of low density lower crust and high and intermediate density crust in the area of central root. The crustal structure in the east is interpreted as a result of viscous extrusion of low density orogenic lower crust over the high density Brunia continent. Comparison of these data with geophysical profiling of the Andean and the Tibetan plateaus suggests that modern orogenic systems reveal comparable but thicker deep crustal pattern. Based on these similarities we propose that the Variscan root represents a deep crustal section of above mentioned plateaus which may have develop by the same orogenic process.

  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 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.

  20. Active Materials for Photonic Systems (AMPS)

    DTIC Science & Technology

    2007-11-02

    market . Overall Program Summary The overall objective of the Active Materials for Photonic Systems (AMPS) program was to develop and demonstrate...mode fiber, with alignment tolerances of several microns functions well for data communications , single mode fiber is required for several significant...in the laser/optics community . Boeing and MCNC have signed a memorandum of agreement for commercialization and are actively seeking partners for

  1. 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.

  2. 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

  3. Gamma band activity in the reticular activating system.

    PubMed

    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 pre

  4. Active imaging system with Faraday filter

    SciTech Connect

    Snyder, J.J.

    1992-12-31

    This invention is comprised of an active imaging system which has a low to medium powered laser transmitter and a 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 wile eliminating solar background.

  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. Evidence of Early Cretaceous transpression in the Sulu orogenic belt, eastern China

    NASA Astrophysics Data System (ADS)

    Wang, Jun; Chang, Su-Chin; Lin, Peijun; Zhu, Xiaoqing; Fu, Yongtao; Zhang, Haichun

    2016-09-01

    Recent studies have documented marine turbidites with syn-sedimentary deformation features in the central Sulu orogenic belt of eastern China. These units preserve essential information on the Late Mesozoic evolution of the Sulu orogenic belt. Referred to as the Baxiandun Formation, the turbidites exhibit similar lithologic characteristics to nearby units such as the Lingshandao Formation that have been well studied even though precise geochronologic constraints are lacking for a more precise correlation. This study reports detrital zircon Usbnd Pb age data that correlate the Baxiandun Formation turbidites of the central Sulu orogenic belt to the Early Cretaceous Lingshandao Formation. We also report Al-in-hornblende emplacement depth estimates for granitic intrusions of the Sulu orogenic belt's Laoshan mountain. A sharp contact between the Laoshan granites and the marine Baxiandun Formation indicates that the Baxiandun basin rapidly subsided to the emplacement depth of the Laoshan plutons. Lateral correlation among the marine turbidites, the Lingshandao and Baxiandun Formations, combined with information established by previous studies indicates initiation of transpressional tectonics at 122-121 Ma. Transpression ceased with the emplacement of the Laoshan granites, whose A1-type composition indicates a return to extensional tectonics at ca. 111 Ma.

  7. 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.

  8. Orogen-parallel deformation of the Himalayan midcrust: Insights from structural and magnetic fabric analyses of the Greater Himalayan Sequence, Annapurna-Dhaulagiri Himalaya, central Nepal

    NASA Astrophysics Data System (ADS)

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

    2016-11-01

    The metamorphic core of the Himalaya (Greater Himalayan Sequence, GHS), in the Annapurna-Dhaulagiri region, central Nepal, recorded orogen-parallel stretching during midcrustal evolution. Anisotropy of magnetic susceptibility and field-based structural analyses suggest that midcrustal deformation of the amphibolite facies core of the GHS occurred under an oblate/suboblate strain regime with associated formation of low-angle northward dipping foliation. Magnetic and mineral stretching lineations lying within this foliation from the top of the GHS record right-lateral orogen-parallel stretching. We propose that oblate strain within a midcrustal flow accommodated oblique convergence between India and the arcuate orogenic front without the need for strain partitioning in the upper crust. Oblate flattening may have also promoted orogen-parallel melt migration and development of melt-depleted regions between km3 scale leucogranite culminations at 50-100 km intervals along orogen strike. Following the cessation of flow, continued oblique convergence led to upper crustal strain partitioning between orogen-perpendicular convergence on thrust faults and orogen-parallel extension on normal and strike-slip faults. In the Annapurna-Dhaulagiri Himalaya, orogen-parallel stretching lineations are interpreted as a record of transition from midcrustal orogen-perpendicular extrusion to upper crustal orogen-parallel stretching. Our findings suggest that midcrustal flow and upper crustal extension could not be maintained simultaneously and support other studies from across the Himalaya, which propose an orogen-wide transition from midcrustal orogen-perpendicular extrusion to upper crustal orogen-parallel extension during the mid-Miocene. The 3-D nature of oblate strain and orogen-parallel stretching cannot be replicated by 2-D numerical simulations of the Himalayan orogen.

  9. 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

  10. Transport in active systems crowded by obstacles

    NASA Astrophysics Data System (ADS)

    Huang, Mu-Jie; Schofield, Jeremy; Kapral, Raymond

    2017-02-01

    The reactive and diffusive dynamics of a single chemically powered Janus motor in a crowded medium of moving but passive obstacles is investigated using molecular simulation. It is found that the reaction rate of the catalytic motor reaction decreases in a crowded medium as the volume fraction of obstacles increases as a result of a reduction in the Smoluchowski diffusion-controlled reaction rate coefficient that contributes to the overall reaction rate. A continuum model is constructed and analyzed to interpret the dependence of the steady-state reaction rate observed in simulations on the volume fraction of obstacles in the system. The steady-state concentration fields of reactant and product are shown to be sensitive to the local structure of obstacles around the Janus motor. It is demonstrated that the active motor exhibits enhanced diffusive motion at long times with a diffusion constant that decreases as the volume fraction of crowding species increases. In addition, the dynamical properties of a passive tracer particle in a system containing many active Janus motors is studied to investigate how an active environment influences the transport of non-active species. The diffusivity of a passive tracer particle in an active medium is found to be enhanced in systems with forward-moving Janus motors due to the cooperative dynamics of these motors.

  11. 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…

  12. 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.

  13. 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.

  14. Crustal Fluid Evolution and Changes in Deformation Conditions during Regional Syn- to Post-Orogenic Exhumation: Southeastern Piedmont, Southern Appalachians

    SciTech Connect

    Evans, M.A.

    2000-07-05

    Fluid inclusion microthermometric data from veins in the southeastern Piedmont province record the changes in fluid composition and deformation conditions during regional exhumation and cooling related to Late Paleozoic syn- to post-orogenic processes and early Mesozoic rifting. In general, the composition of post-metamorphic fluids that were trapped late during the Alleghanian orogeny and during post-orogenic exhumation are remarkably consistent across the southeastern Piedmont, indicating regional fracture connectivity. The first fluids were trapped in veins that formed during the last phases of the Alleghanian. These syn-deformational fluids are CO2-saturated low salinity brines (salinities of 2.6 to 5.7 wt. percent NaCl equivalent) with homogenization temperatures in the range of 200 degrees to 365 degrees C. They were trapped under lithostatic pressures between 240 and 280 MPa, indicating burial depths of 11.2 to 12.7 km. These depths are similar to emplacement depths of post-kinematic plutons, suggesting a period of rapid isobaric cooling. Low-salinity H2O inclusions and rare CO2-rich inclusions are evidence for Early Mesozoic regional decompression as fracturing above the brittle-to-ductile transition allowed regional pore-fluid pressure to drop to hydrostatic levels. Convective circulation of meteoric water resulted in the dilution of 'in-situ' fluids, and ultimately to a system saturated with meteoric water. These fluids continued to be trapped in vein minerals through much of the Mesozoic as rift basins formed during the opening of the Atlantic Ocean. Late Paleozoic through Mesozoic exhumation rates for the eastern Piedmont province average 0.063 km m.y.-1 and cooling rates average approximately 1.9 degrees C m.y.-1. These low rates may be directly related to thinned crust and lithosphere resulting from delamination processes during the late Alleghanian orogeny.

  15. Broad band and long period magnetotellurics for imaging the onshore portion of Santos basin and orogenic belts of southeast Brazil

    NASA Astrophysics Data System (ADS)

    Solon, F. F.; Fontes, S. L.; Miquelutti, L. G.; La Terra, E. F.

    2012-12-01

    Between October 2011 and April 2012, we carried out 81 broad band and 40 long period magnetotelluric soundings covering the frequency range 1000 Hz - 0.0001 Hz. These soundings are distributed into two parallel 210km long profiles, approximately 50 km apart, spaced 5 km with EM field components oriented to the magnetic north and east directions. Both ADU07 (Metronix) and LEMI 417 (Lviv) systems were used. Typically, three to four MT soundings were measured simultaneously for this study. Both profiles initiate at the coast and continues to the continent direction. These profiles crossed two major Neoproterozoic Orogenic Belts, Brasilia and Ribeira, as well as several geosutures in the basement of the marginal basins of southeastern Brazil. The geophysical survey associated with the available geological information brought important contributions to the understanding of the main geosutures presents in the area. One located at the southeast end of the MT profiles, separating the tectonic domains of Ribeira Belt from the Pre-cambrian lands of Santos Basin. The other one situated in the extreme northwest of the MT profiles, limiting the Ribeira and Brasilia Belts. Data were processed using a robust remote-reference technique. Strike and dimensionality analysis along with G-B decomposition support a general 2-D regional character of the conductivity distribution in the area, allowing us to create a 2-D inversion model. Good misfit can be observed between the measured and calculated transfer functions projected onto the profile direction. Very preliminary results imaged the two main suture zones between the orogenics belts and allow inferences about the geographic position of their lateral limits.

  16. Out-of-sequence deformation and expansion of the Himalayan orogenic wedge: insight from the Changgo culmination, south central Tibet

    NASA Astrophysics Data System (ADS)

    Larson, Kyle P.; Godin, Laurent; Davis, William J.; Davis, Don W.

    2010-08-01

    The Changgo culmination, one of the North Himalayan domes in south central Tibet, consists of a multiphase granite core surrounded by a deformed metasedimentary carapace. The granitic core records general non-coaxial shear with a top-to-the-south sense shear component. The contact between the core and the carapace is a shear zone, characterized by general non-coaxial shear with a top-to-the-north shear sense, interpreted to be the northern continuation of the South Tibetan detachment system (STDS). The shear zone contains lenses of leucogranite dated at 35.4 Ma. This is interpreted to reflect Eocene crustal thickening, coeval with the earliest shortening event recorded in the carapace. The main phase of the Changgo granite crystallized at 23.5 Ma, while undeformed aplite dikes, the youngest phase observed in the granite, were intruded at 22.1 Ma. Aplite dikes crosscut the main deformation fabric within the Changgo granite; therefore, that deformation and associated south directed shearing must have ended between 23.5 Ma and 22.1 Ma. The dikes are strained within the STDS, indicating that final displacement along the STDS must post-date 22 Ma, yet be older than 18.4 Ma, the cooling age of muscovite in the shear zone. It is proposed that the exhumation of the Changgo culmination is related to tectonically driven erosion in response to crustal thickening and rebuilding of the orogenic critical taper wedge. Subsequently, deformation in the wedge migrated toward the foreland, expanding the orogenic wedge laterally and moving the locus of displacement from the Main Central thrust structurally downward to the Main Boundary thrust.

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

    NASA Astrophysics Data System (ADS)

    Porwal, Alok; Yu, Le

    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.

  18. Closed-loop active optical system control

    NASA Astrophysics Data System (ADS)

    Sparks, T. E.

    1980-01-01

    A control system, based on a real-time lateral shear interferometer has been developed for use in control during thermal tests and static error compensation experiments. The minicomputer which controls the interferometer and provides its service functions also controls the active system, thereby giving flexibility to the algorithm. The minicomputer system contains 288 K bytes of memory and 15 M bytes of disk storage. The interferometer system employed is composed of the measuring head and its support electronics, a video display on which wavefront contour maps are generated, and a DECwriter operator console. The versatility provided by the use of a general purpose interferometer system allows for interactive control of the closed-loop process. Various arithmetic capabilities such as the addition of wavefronts, division by a constant, and fitting of wavefront data with Zernike polynomials, allow for measurements to be averaged and for removal of alignment errors before correction is performed.

  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. 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.

  1. 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.

  2. Upper mantle structure beneath the Alpine orogen from high-resolution teleseismic tomography

    NASA Astrophysics Data System (ADS)

    Lippitsch, Regina; Kissling, Edi; Ansorge, JöRg

    2003-08-01

    To understand the evolution of the Alpine orogen, knowledge of the actual structure of the lithosphere-asthenosphere system is important. We perform high-resolution teleseismic tomography with manually picked P wave arrival times from seismograms recorded in the greater Alpine region. The resulting data set consists of 4199 relative P wave arrivals and 499 absolute P wave arrivals from 76 teleseismic events, corrected for the contribution of the Alpine crust to the travel times. The three-dimensional (3-D) crustal model established from controlled-source seismology data for that purpose represents the large-scale Alpine crustal structure. Absolute P wave arrival times are used to compute an initial reference model for the inversion. Tests with synthetic data document that the combination of nonlinear inversion, high-quality teleseismic data, and usage of an a priori 3-D crustal model allows a reliable resolution of cells at 50 km × 50 km × 30 km. Hence structures as small as two cells can be resolved in the upper mantle. Our tomographic images illuminate the structure of the uppermost mantle to depth of 400 km. Along strike of the Alps, the inversion reveals a high-velocity structure that dips toward the SE beneath the Adriatic microplate in the western and central Alps. In the eastern Alps we observe a northeastward dipping feature, subducting beneath the European plate. We interpret this feature in the western and central Alps as subducted, mainly continental European lower lithosphere. For the east, we propose that parts of the Vardar oceanic basin were subducted toward the NE, forcing continental Adriatic lower lithosphere to subduct northeastward beneath the European plate.

  3. Doming in compressional orogenic settings: New geochronological constraints from the NW Himalaya

    NASA Astrophysics Data System (ADS)

    Robyr, Martin; Hacker, Bradley R.; Mattinson, James M.

    2006-04-01

    In the central and southeastern parts of the Himalayas, the High Himalayan Crystalline (HHC) high-grade rocks are mainly exhumed in the frontal part of the range, as a consequence of a tectonic exhumation controlled by combined thrusting along the Main Central Thrust (MCT) and extension along the South Tibetan Detachment System (STDS). In the NW Himalaya, however, the hanging wall of the MCT in the frontal part of the range consists mainly of low- to medium-grade metasediments (Chamba zone), whereas most of the amphibolite facies to migmatitic gneisses of the HHC of Zanskar are exposed in a more internal part of the orogen as a large-scale dome structure referred to as the Gianbul dome. This Gianbul dome is cored by migmatitic paragneisses formed at peak conditions of 800°C and 8 kbar. This migmatitic core is symmetrically surrounded by rocks of the sillimanite, kyanite ± staurolite, garnet, biotite, and chlorite mineral zones. The structural data from the Miyar-Gianbul Valley section reveal that the Gianbul dome is bounded by two major converging thrust zones, the Miyar Thrust Zone and the Zanskar Thrust Zone, which were reactivated as ductile zones of extension referred to as the Khanjar Shear Zone (KSZ) and the Zanskar Shear Zone (ZSZ), respectively. Geochronological dating of monazites from various migmatites and leucogranite in the core of the Gianbul dome indicates ages between 26.6 and 19.8 Ma. These results likely reflect a high-temperature stage of the exhumation history of the HHC of Zanskar and consequently constrain the onset of extension along both the ZSZ and the KSZ to start shortly before 26.6 Ma. Several recent models interpret that ductile extrusion of the high-grade, low-viscosity migmatites of HHC reflects combined extension along the ZSZ and thrusting along the MCT. Hence our new data constrain the onset of the thrusting along the MCT to start shortly before 26.6 Ma.

  4. 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

  5. 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.

  6. 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.

  7. 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.

  8. 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.

  9. 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.

  10. Active magnetic bearings give systems a lift

    NASA Astrophysics Data System (ADS)

    O'Connor, Leo

    1992-07-01

    While the active magnetic bearings currently being used in such specialized applications as centrifugal compressors for natural gas pumps are more expensive than conventional bearings, they furnish improved machine service life, controlled damping of high-speed rotors to eliminate critical-speed vibrations, and the obviation of lubrication systems. Attention is presently given to magnetic bearings used by the electric power industry, homopolar magnetic radial and thrust bearings, weapon-system and gas turbine engine applications of magnetic bearings, and the benefits of magnetic bearings for energy-storage flywheels.

  11. 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.

  12. Bacteriophage: A Model System for Active Learning

    PubMed Central

    LUCIANO, CARL S.; YOUNG, MATTHEW W.; PATTERSON, ROBIN R.

    2002-01-01

    Although bacteriophage provided a useful model system for the development of molecular biology, its simplicity, accessibility, and familiarity have not been fully exploited in the classroom. We describe a student-centered laboratory course in which student teams selected phage from sewage samples and characterized the phage in a semester-long project that modeled real-life scientific research. The course used an instructional approach that included active learning, collaboration, and learning by inquiry. Cooperative student teams had primary responsibility for organizing the content of the course, writing to learn using a journal article format, involving the entire group in shared laboratory responsibilities, and applying knowledge to the choice of new experiments. The results of student evaluations indicated a high level of satisfaction with the course. Our positive experience with this course suggests that phage provides an attractive model system for an active-learning classroom. PMID:23653543

  13. 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

  14. A Photoacoustic Study of Chemically Active Systems.

    DTIC Science & Technology

    1983-09-01

    unless so designated by other documentation IS. KEY WORDS (Continue w reverse aide If neceeairy wd Identify by block nmber) Photoacoustic, Spectroscopy ...CwcAhnm i, pwo If w M Idntitty by block nin1b9) -,xThe method of gas-microphone photoacoustic spectroscopy and the related photothermal deflection... spectroscopy have been developed for application to chemically active systems. Fourier Transform Infrared Photoacoustic Spectros- copy has been used to study

  15. 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.

  16. Laser-probe 40Ar/39Ar dating of strain fringes: Mid-Cretaceous synconvergent orogen-parallel extension in the interior of the Sevier orogen

    NASA Astrophysics Data System (ADS)

    Wells, Michael L.; Spell, Terry L.; Hoisch, Thomas D.; Arriola, Tonia; Zanetti, Kathleen A.

    2008-06-01

    UV and CO2 laser-probe 40Ar/39Ar in situ analyses of phlogopite and muscovite in fibrous strain fringes from greenschist-facies metamorphic rocks document mica growth ages at temperatures lower than their closure temperatures, and therefore directly date deformation. The new dates resolve the age of the earliest ductile fabric recorded in the Raft River-Albion-Grouse Creek metamorphic core complex of Utah and Idaho. Phlogopite was dated in quartz-calcite-phlogopite strain fringes around pyrite in Pennsylvanian-Permian rocks from the Grouse Creek Mountains (Utah) using both the UV and CO2 laser probe; muscovite was dated in quartz-muscovite strain fringes around pyrite in deformed Jurassic sills from the Black Pine Mountains (Idaho) using the CO2 laser probe. Phlogopite 40Ar/39Ar ages for individual strain fringes (Grouse Creek Mountains) range from 92 Ma to 110 Ma, with the most reliable ages ranging from 101 Ma to 110 Ma (mean age, 105.0 ± 5.8 Ma). Muscovite 40Ar/39Ar ages for individual strain fringes (Black Pine Mountains) range from 97 Ma to 112 Ma (mean age, 104.7 ± 5.8 Ma). Strain fringes are associated with a subhorizontal foliation and a generally N-trending elongation lineation exhibiting components of top-to-the-north simple shear and coaxial strain accommodating N-S extension and subvertical shortening. Midcrustal northward flow at 105 (±6) Ma within the interior of the Sevier orogen, coeval with east-directed shortening in the foreland and with plate convergence, records orogen-parallel synconvergent extension. We favor gravitational relaxation of structural culminations resulting from focused crustal shortening as a driving mechanism for orogen-parallel flow.

  17. Crustal Structure And Magmatism, Coast Mountains Orogen, Latitude 52-53 degrees North, British Columbia, Canada

    NASA Astrophysics Data System (ADS)

    Rusmore, M. E.; Gehrels, G.; Woodsworth, G. J.

    2007-12-01

    New geologic data and U-Pb ages reveal complex history of arc accretion, crustal thickening and migration of magmatic fronts during deformation. Plutonic ages define distinct western and eastern Jurassic - mid Cretaceous arcs that share a common history after ~90 Ma. Juxtaposition of these arcs occurred during mid- Cretaceous crustal shortening in a dominantly SW-vergent crustal-scale thrust belt. Significant crustal thickening buried 151 Ma granitic clasts to pressures > 6 kb, and mid-Cretaceous plutons were emplaced at this depth along the axis of the orogen. Thrusting continued after establishment of the 90 Ma arc; a regional SW-verging thrust emplaced high-grade metamorphic rocks of the Yukon-Tanana terrane and deep-seated plutons over low- grade rocks of the Alexander and Wrangellia terranes. The shear zone is coincident with the western boundary of 82-89 Ma plutons and a regionally extensive, late-kinematic, sill-like pluton. Dextral shear zones preserved on the flanks of the orogen suggest a component of Late Cretaceous transpression. By 75 Ma, metamorphism, deformation, and magmatism had migrated central portions of the orogen and there is no evidence of ductile deformation and syn-kinematic metarmorphism younger than ~70 - 65 along the western flank of the orogen. The Coast shear zone localized 62-58 Ma synkinematic plutons during NE-side up displacement, creating a sharp western magmatic front. Sparse cooling ages suggest plutons and metamorphic rocks adjacent to the CSZ cooled through 500-600 deg between 54-58 Ma during exhumation along the shear zone. Voluminous granitic plutons were emplaced from ~55-50 Ma, but significant crustal extension that affected the eastern side of the orogen farther north is not evident along this transect. This history supports previous models of crustal subcretion and the generation of arc magmas in thickened crust. Definition of two pre-90 Ma arcs negates models calling for simple Andean-style orogen prior to mid

  18. 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.

  19. 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

  20. 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.

  1. 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.

  2. 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.

  3. Processing abstract language modulates motor system activity.

    PubMed

    Glenberg, Arthur M; Sato, Marc; Cattaneo, Luigi; Riggio, Lucia; Palumbo, Daniele; Buccino, Giovanni

    2008-06-01

    Embodiment theory proposes that neural systems for perception and action are also engaged during language comprehension. Previous neuroimaging and neurophysiological studies have only been able to demonstrate modulation of action systems during comprehension of concrete language. We provide neurophysiological evidence for modulation of motor system activity during the comprehension of both concrete and abstract language. In Experiment 1, when the described direction of object transfer or information transfer (e.g., away from the reader to another) matched the literal direction of a hand movement used to make a response, speed of responding was faster than when the two directions mismatched (an action-sentence compatibility effect). In Experiment 2, we used single-pulse transcranial magnetic stimulation to study changes in the corticospinal motor pathways to hand muscles while reading the same sentences. Relative to sentences that do not describe transfer, there is greater modulation of activity in the hand muscles when reading sentences describing transfer of both concrete objects and abstract information. These findings are discussed in relation to the human mirror neuron system.

  4. 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.

  5. Cardiac autonomic nervous system activity in obesity.

    PubMed

    Liatis, Stavros; Tentolouris, Nikolaos; Katsilambros, Nikolaos

    2004-08-01

    The development of obesity is caused by a disturbance of energy balance, with energy intake exceeding energy expenditure. As the autonomic nervous system (ANS) has a role in the regulation of both these variables, it has become a major focus of investigation in the fields of obesity pathogenesis. The enhanced cardiac sympathetic drive shown in most of the studies in obese persons might be due to an increase in their levels of circulating insulin. The role of leptin needs further investigation with studies in humans. There is a blunted response of the cardiac sympathetic nervous system (SNS) activity in obese subjects after consumption of a carbohydrate-rich meal as well as after insulin administration. This might be due to insulin resistance. It is speculated that increased SNS activity in obesity may contribute to the development of hypertension in genetically susceptible individuals. It is also speculated that the increase in cardiac SNS activity under fasting conditions in obesity may be associated with high cardiovascular morbidity and mortality.

  6. 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.

  7. 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.

  8. LSST active optics system software architecture

    NASA Astrophysics Data System (ADS)

    Thomas, Sandrine J.; Chandrasekharan, Srinivasan; Lotz, Paul; Xin, Bo; Claver, Charles; Angeli, George; Sebag, Jacques; Dubois-Felsmann, Gregory P.

    2016-08-01

    The Large Synoptic Survey Telescope (LSST) is an 8-meter class wide-field telescope now under construction on Cerro Pachon, near La Serena, Chile. This ground-based telescope is designed to conduct a decade-long time domain survey of the optical sky. In order to achieve the LSST scientific goals, the telescope requires delivering seeing limited image quality over the 3.5 degree field-of-view. Like many telescopes, LSST will use an Active Optics System (AOS) to correct in near real-time the system aberrations primarily introduced by gravity and temperature gradients. The LSST AOS uses a combination of 4 curvature wavefront sensors (CWS) located on the outside of the LSST field-of-view. The information coming from the 4 CWS is combined to calculate the appropriate corrections to be sent to the 3 different mirrors composing LSST. The AOS software incorporates a wavefront sensor estimation pipeline (WEP) and an active optics control system (AOCS). The WEP estimates the wavefront residual error from the CWS images. The AOCS determines the correction to be sent to the different degrees of freedom every 30 seconds. In this paper, we describe the design and implementation of the AOS. More particularly, we will focus on the software architecture as well as the AOS interactions with the various subsystems within LSST.

  9. Tectonic implications of U-Pb zircon ages of the himalayan orogenic belt in nepal

    PubMed

    DeCelles; Gehrels; Quade; LaReau; Spurlin

    2000-04-21

    Metasedimentary rocks of the Greater Himalaya are traditionally viewed as Indian shield basement that has been thrust southward onto Lesser Himalayan sedimentary rocks during the Cenozoic collision of India and Eurasia. Ages determined from radioactive decay of uranium to lead in zircon grains from Nepal suggest that Greater Himalayan protoliths were shed from the northern end of the East African orogen during the late Proterozoic pan-African orogenic event. These rocks were accreted onto northern Gondwana and intruded by crustal melts during Cambrian-Ordovician time. Our data suggest that the Main Central thrust may have a large amount of pre-Tertiary displacement, that structural restorations placing Greater Himalayan rocks below Lesser Himalayan rocks at the onset of Cenozoic orogenesis are flawed, and that some metamorphism of Greater Himalayan rocks may have occurred during early Paleozoic time.

  10. 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

  11. 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

  12. Scuba diving activates vascular antioxidant system.

    PubMed

    Sureda, A; Batle, J M; Ferrer, M D; Mestre-Alfaro, A; Tur, J A; Pons, A

    2012-07-01

    The aim was to study the effects of scuba diving immersion on plasma antioxidant defenses, nitric oxide production, endothelin-1 and vascular endothelial growth factor levels. 9 male divers performed an immersion at 50 m depth for a total time of 35 min. Blood samples were obtained before diving at rest, immediately after diving, and 3 h after the diving session. Leukocyte counts, plasma 8oxoHG, malondialdehyde and nitrite levels significantly increased after recovery. Activities of lactate dehydrogenase, creatine kinase, catalase and superoxide significantly increased immediately after diving and these activities remained high after recovery. Plasma myeloperoxidase activity and protein levels and extracellular superoxide dismutase protein levels increased after 3 h. Endothelin-1 concentration significantly decreased after diving and after recovery. Vascular endothelial growth factor concentration significantly increased after diving when compared to pre-diving values, returning to initial values after recovery. Scuba diving at great depth activated the plasma antioxidant system against the oxidative stress induced by elevated pO₂ oxygen associated with hyperbaria. The decrease in endothelin-1 levels and the increase in nitric oxide synthesis could be factors that contribute to post-diving vasodilation. Diving increases vascular endothelial growth factor plasma levels which can contribute to the stimulation of tissue resistance to diving-derived oxidative damage.

  13. Tectonically active sediment dispersal system in SW Taiwan margin with emphasis on the Gaoping (Kaoping) Submarine Canyon

    NASA Astrophysics Data System (ADS)

    Yu, Ho-Shing; Chiang, Cheng-Shing; Shen, Su-Min

    2009-03-01

    The sediment dispersal system in southwestern Taiwan margin consists of two main parts: the subaerial drainage basin and the offshore receiving marine basin. In plan view, this sediment dispersal system can be further divided into five geomorphic units: (1) the Gaoping (formerly spelled Kaoping) River drainage basin, (2) the Gaoping (Kaoping) Shelf, (3) the Gaoping (Kaoping) Slope, (4) the Gaoping (Kaoping) Submarine Canyon and (5) the Manila Trench in the northernmost South China Sea. The Gaoping River drainage basin is a small (3250 km 2), tectonically active and overfilled foreland basin, receiving sediments derived from the uprising Central Range of Taiwan with a maximum elevation of 3952 m. The Gaoping Submarine Canyon begins at the mouth of the Gaoping River, crosses the narrow Gaoping Shelf (~ 10 km) and the Gaoping Slope, and finally merges into the northern termination of the Manila Trench over a distance of ~ 260 km. The SW Taiwan margin dispersal system is characterized by a direct river-canyon connection with a narrow shelf and frequent episodic sediment discharge events in the canyon head. In a regional source to sink scheme, the Gaoping River drainage basin is the primary source area, the Gaoping Shelf being the sediment bypass zone and the Gaoping Slope being the temporary sink and the Manila Trench being the ultimate sink of the sediment from the Taiwan orogen. It is inferred from seismic data that the outer shelf and upper slope region can be considered as a line source for mass wasting deposits delivered to the lower Gaoping Slope where small depressions between diapiric ridges are partially filled with sediment or are empty. At present, recurrent hyperpycnal flows during the flood seasons are temporarily depositing sediments mainly derived from the Gaoping River in the head of the Gaoping Submarine Canyon. On the decadal and century timescales, sediments temporarily stored in the upper reach are removed over longer timescales probably by

  14. 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

  15. 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.

  16. 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.

  17. Forearc basin correlations from around the Texas Orocline, New England Orogen, east Australia

    NASA Astrophysics Data System (ADS)

    Hoy, Derek; Rosenbaum, Gideon; Shaanan, Uri; Wormald, Richard

    2014-05-01

    The late Paleozoic to early Mesozoic New England Orogen occupies much of the eastern seaboard of Australia. The orogen formed by west-dipping subduction (present-day coordinates) of the paleo-Pacific plate beneath eastern Gondwana. The southern part of the orogen exhibits a series of tight bends (oroclines) that are evident in the curvature of a Devonian-Carboniferous subduction complex, in particular the forearc basin and accretionary complex. The Emu Creek Block is thought to be part of the forearc basin that is exposed in the eastern limb of the Texas Orocline, but until now the tectonostratigraphic origin of the Emu Creek Block has only been inferred from limited geological data. Here we present detrital zircon geochronology (U/Pb ICP-MS ages), a new geological map of the block, and a revised stratigraphic section. Lithological investigation of strata within the block and the age distribution of detrital zircons indicate that the sediments in the Emu Creek Block were derived from a Carboniferous magmatic arc and were most likely deposited in a forearc basin. Our new geochronological constraints indicate deposition during the late Carboniferous. We therefore propose that rocks in the Emu Creek Block are arc-distal correlatives of the forearc basin in the opposing (western) limb of the Texas Orocline, specifically the Willuri and Currabubula formations. Extensive orocline-parallel structures in the forearc basin indicate that the eastern limb of the Texas Orocline was rotated in the course of oroclinal bending by approximately 135 degrees relative to the western limb. The correlation of the forearc basin blocks on opposite limbs of the Texas Orocline provides an independent constraint on its geometry and further improves our understanding of New England Orogen tectonostratigraphy and the crustal structure of eastern Australia.

  18. Application of the Orogenic Float Model for the Structural Evolution of the Venezuelan Andes

    NASA Astrophysics Data System (ADS)

    Dhont, D.; Monod, B.; Hervouet, Y.; Klarica, S.

    2010-12-01

    The Venezuelan (or Mérida) Andes form a NE-SW-striking intracontinental orogen that started to uplift in the Middle Miocene due to E-W convergence between the Maracaibo block to the northwest and the Guyana shield to the southeast. Oblique collision resulted in strain partitioning accommodated by (1) transverse shortening along thrust faults bounding the belt on both flanks, (2) right-lateral slip along the Bocono fault running more or less along the chain axis and (3) tectonic escape of the Trujillo block moving towards the NE in between the Bocono and the N-S-striking sinistral Valera faults. Even though the surface geology of the Venezuelan Andes is well known, its structure at depth remains a matter of debate. Among the mechanisms that have proposed to account for the crustal architecture and evolution of the mountain belt, we develop the idea that the deformation process in this orogen is consistent with a model of orogenic float where the upper crust is decoupled from its underlying lithosphere above a large-scale mid-crustal detachment zone. According to this model, all the major faults involved in the strain partitioning sole into the detachment horizon and may therefore be considered as upper crustal faults. The integration of the orogenic float into a coherent evolutionary model provides further insight on both the crustal structure of the Venezuelan Andes and on the tectonic history of the region. A major reorganization in the crust occurred in the Early Pliocene when the Maracaibo block penetrated as a wedge into the Guyana crust. This event was accompanied by a rapid uplift of the Venezuelan Andes in association with the NE-ward crustal escape of the Trujillo block whose motion is accompanied by the lateral spreading of the upper crust.

  19. Topography and subduction geometry in the central Andes: Clues to the mechanics of a noncollisional orogen

    NASA Technical Reports Server (NTRS)

    Gephart, John W.

    1994-01-01

    The central Andeean orogen between 12 deg and 32 deg S latitude exhibits a high degree of spatial order: principally an extraordinary bilateral symmetry that is common to the Earth's surface, the underlying Wadati-Benioff zone, and the Nazca/South America plate kinematics, which has been stable since the mid-Tertiary. This spatial order must reflect the physical mechanisms of mountain building in this noncollisional orogen. The shapes of the topography and subduction zone can be reduced to symmetric and antisummeric components relative to any verical symmetry plane; the particular plaen which minimizes the antisymmetry (and maximizes the symmetry) is well resolved and is essentially coincident with the stable Euler equator of Nacza/South America relative motion since the mid-Tertiary. That the topography, subduction geometry, and persistent mid-Tertiary plate kinematics share common spatial and geometric elements suggests that he distribution of topography in this orogen depends strongly on the dynamics of subduction. Other factors that might affect the topography and underlying tectonics, such as climate and inherited strutura fabric, which have different spatial characterisitcs, must be of less significance at a continental scale. Furthermore, the small components of asymmetry among the various elements of the orogen appear to be mutually relate in a simple way; it is possible that this coupled asymmetry is associated with a late Teriary change in plate kinematics. These observations suggest that there is a close connection between plate tectonics and the form of the Earth's surface in this noncollisional setting. It follows hta the distribution of topography near convergent plate boundaries may provide a powerful constraing for understanding the dynamics of subduction.

  20. 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.

  1. 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.

  2. 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.

  3. 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.

  4. Electromechanical Modelling of an Active Isolation System

    DTIC Science & Technology

    1991-04-01

    Department of Mechanical Engineering, Auburn University, Auburn , AL 36849, U.S.A. Active Control of Automobile Two-Stage Suspension System-Half Car Model...element model ..... one d.imensnional modelo -ilo0- S-120 1 L 0 0.05 0.1 0.15 0.2 0.25 0.3 0.35 0.4 0.45 0.5 Frequency(f/fO) 6(b) Sensor Voltage S20 10 16

  5. 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.

  6. 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.

  7. 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.

  8. 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.

  9. 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.

  10. Actively controlled vibration welding system and method

    DOEpatents

    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.

  11. Orogen-parallel mass transport along the arcuate Himalayan front into Nanga Parbat and the western Himalayan syntaxis

    NASA Astrophysics Data System (ADS)

    Whipp, David; Beaumont, Christopher

    2016-04-01

    Along the length of the Himalayan arc, Quaternary rock exhumation rates are highest in the Himalayan syntaxes at the lateral ends of the arc. In the western Himalayan syntaxis, these rates may exceed 10 mm/a over the past 2 Ma, requiring an additional source of crustal mass into this region to maintain the high-elevation topography. We have previously demonstrated that strain partitioning of oblique convergence can produce a significant orogen-parallel mass flux into the syntaxis of a Himalaya-like orogen and balance the rapid rates of surface denudation. However, the magnitude of this orogen parallel mass flux and whether strain is partitioned across the Himalayan thrust front is affected by the strength of the material bounding and within the Himalayan orogenic wedge, the dip angle of the basal detachment and the convergence obliquity angle γ. Strain partitioning is expected for a finite-length Himalaya-like segmented linear orogen with an obliquity of γ = 30 - 40°, but the obliquity angle in the Himalayan arc varies from 0 at the center of the arc to ˜ 40° in the western Himalayan syntaxis region. Thus, the conditions in which strain partitioning will occur may not be met along much of the length of the arc. Though there is clear evidence of strain partitioning in the Himalaya, preliminary results from 3D numerical geodynamic models of an orogen with an arcuate geometry based on the Himalaya suggest strain partitioning does not occur for the same conditions observed in earlier models of segmented linear orogens or orogens with a smaller arc radius. In those models, the proportion of the orogen length with a high obliquity angle was greater, which favors strain partitioning. In numerical experiments of an arcuate Himalayan orogen with weak material (friction angle φ ≤ 5°) at the back of the orogenic wedge, strain partitioning is only observed in the toe of the orogenic wedge (10-15 km from the thrust front) at the western end of the arc, rather than for

  12. Active pulse synchronization for OPCPA systems

    NASA Astrophysics Data System (ADS)

    Ueffing, Moritz; Metzger, Thomas; Deng, Yunpei; Schwarz, Alexander; Krausz, Ferenc; Kienberger, Reinhard

    2011-05-01

    The parametric amplification in nonlinear crystals requires both spacial and temporal stability of pump and seed pulses to attain stability of the amplified pulse. Especially the development of thin disk pump sources with pulse lengths down to 2 ps requires a temporal stability well beyond 100 fs . To reduce the timing shifts between pump and seed pulses in OPCPA systems we introduce a novel, active pulse synchronization system combining a high precision translation stage and a piezo-electric driven mirror. The timing jitter reduction of OPCPAs with kHz repetition rate demands a fast detection system allowing nearly shot to shot correction. Therefore the spectrum of a cross-correlation between the 1030 nm , 1 nm bandwidth pump and a broad bandwidth Ti:Sa seed pulse stretched to 10 ps in a BBO crystal is directly and in real time measured using a position sensitive detector. This method can easily be adopted to other OPA/OPCPA systems giving the chance to correct not only for slow drifts but also for fluctuations up to 300 Hz .

  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. Horizontal motions, bedrock incision, and the structure of relief in growing folds and orogens

    NASA Astrophysics Data System (ADS)

    Seixas, G.; Alejandre, J.; Hilley, G. E.

    2013-12-01

    Topographic divide asymmetry may arise from gradients in rock erodibility and orographic precipitation across a mountain belt, and/or tectonic displacement fields that uplift and translate rock horizontally during orogenesis. While simple models exploring relief in active orogens typically consider tectonic motions that are uniform and vertical, the displacement field at Earth's surface generated by slip on finite-length faults is inherently inhomogeneous and contains vertical and horizontal components, which may play an important role in divide asymmetry. In this study, we consider channel profiles that evolve according to the shear stress rule for bedrock fluvial erosion and that experience inhomogeneous horizontal and vertical components of tectonic motion. Dimensional analysis of our revised shear stress rule reveals a dimensionless coefficient that relates bedrock erodibility and basin geometry to slip rate on the underlying fault. We implement our model in a series of 1D non-dimensional numerical experiments that calculate river profile geometry on either side of a topographic divide that is free to advect through the model domain in response to horizontal motion. We drive the models with displacements calculated over a dipping, buried edge dislocation, and examine non-dimensional relief and divide asymmetry resulting from variations in fault dip, non-dimensional fault tip location and non-dimensional model extent. We find that asymmetry results from the full displacement field and from the vertical displacement field alone. Fault dip plays a strong role in the magnitude and direction of divide asymmetry, both in models that include the horizontal motions and those that neglect them. The greatest divide asymmetry resulting from the full displacement field is achieved over dislocations with shallow non-dimensional upper tip depths and small dip angles, although steeply-dipping faults produce asymmetry in the opposite direction. By setting the horizontal

  15. 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.

  16. An Automatic Tremor Activity Monitoring System (TAMS)

    NASA Astrophysics Data System (ADS)

    Kao, H.; Thompson, P. J.; Rogers, G.; Dragert, H.; Spence, G.

    2006-12-01

    We have developed an algorithm that quantitatively characterizes the level of seismic tremors from recorded seismic waveforms. For each hour of waveform at a given station, the process begins with the calculation of scintillation index and moving average with various time lengths. The scintillation index (essentially the `normalized variance of intensity of the signal') is adapted from the studies of pulses in radio waves and is an efficient tool to identify the energy bursts of tremor signals. Both scintillation index and moving average values are fed into a series of logic gates to determine if tremor activity exists. This algorithm is implemented in the Tremor Activity Monitoring System (TAMS) to provide automatic early alerts for episodic tremor and slip (ETS) events in the northern Cascadia margin. Currently, TAMS retrieves the digital waveforms recorded during the previous day from the Canadian National Seismographic Network (CNSN) archive server at 1 AM every morning. The detecting process is repeated for all stations and hours to determine the level of tremor activity of the previous day. If a sufficient number of stations within a radius of 100 km are determined to have tremor patterns and coherent tremor arrivals can be found at more than 3 stations, TAMS automatically sends out alert emails to a list of subscribers with a figure summarizing the hours and locations of coherent tremors. TAMS outputs are very consistent with the work done by visual inspection, especially for major ETS events. It is straightforward to configure TAMS into a near-real-time system that can send out hourly (or shorter) reports if necessary.

  17. 49 CFR 234.225 - Activation of warning system.

    Code of Federal Regulations, 2014 CFR

    2014-10-01

    ... 49 Transportation 4 2014-10-01 2014-10-01 false Activation of warning system. 234.225 Section 234....225 Activation of warning system. A highway-rail grade crossing warning system shall be maintained to activate in accordance with the design of the warning system, but in no event shall it provide less than...

  18. 49 CFR 234.225 - Activation of warning system.

    Code of Federal Regulations, 2012 CFR

    2012-10-01

    ... 49 Transportation 4 2012-10-01 2012-10-01 false Activation of warning system. 234.225 Section 234....225 Activation of warning system. A highway-rail grade crossing warning system shall be maintained to activate in accordance with the design of the warning system, but in no event shall it provide less than...

  19. 49 CFR 234.225 - Activation of warning system.

    Code of Federal Regulations, 2013 CFR

    2013-10-01

    ... 49 Transportation 4 2013-10-01 2013-10-01 false Activation of warning system. 234.225 Section 234....225 Activation of warning system. A highway-rail grade crossing warning system shall be maintained to activate in accordance with the design of the warning system, but in no event shall it provide less than...

  20. 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.

  1. 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

  2. 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

  3. 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

  4. 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

  5. From microscope to mountain belt: 150 years of petrology and its contribution to understanding geodynamics, particularly the tectonics of orogens

    NASA Astrophysics Data System (ADS)

    Brown, M.

    2001-09-01

    tectonic processes that may operate during exhumation, although these are less well understood. The expanding database of key information, combined with predictions from modelling, has allowed the identification of characteristic P-T-t evolutions expected for rocks that have undergone distinct tectono-metamorphic histories. However, relating structural events recorded by rocks to specific points along the P-T evolution remains problematic, particularly regarding complex overprinting patterns of inclusion trails in porphyroblasts. These advances have improved our understanding of the tectonic evolution of orogens. At the extreme of conditions for crustal metamorphism are the recently discovered ultra-high pressure (UHP) and ultra-high temperature (UHT) facies of metamorphism. Both are problematic given our limited knowledge of processes at these conditions, particularly the return of UHP rocks from peak- P conditions and the mechanism for extreme heat in the crust in UHT metamorphism. The extreme depth inferred for metamorphism in some UHP terranes raises the issue of whether theoretically plausible tectonic overpressures can be dynamically maintained to affect metamorphic reactions. If the pressure gradient recorded by UHP rocks is greater than lithostatic, the UHP metamorphism may have occurred at depths shallower than currently believed. These studies have provided a reliable first-order framework for the comparison of rocks of ancient suture zones where the plate tectonics situation is less certain. However, orogens are spatially and temporally extended nonlinear systems with feedback relations. Such complex systems generate apparently simple behavior by self-organization, and the influence of unique histories must be respected.

  6. 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.

  7. Deep structures and surface boundaries among Proto-Tethyan micro-blocks: Constraints from seismic tomography and aeromagnetic anomalies in the Central China Orogen

    NASA Astrophysics Data System (ADS)

    Sun, Wenjun; Li, Sanzhong; Liu, Xin; Santosh, M.; Zhao, Shujuan; Guo, Lingli; Cao, Huahua; Yu, Shan; Dai, Liming; Zhang, Yong

    2015-09-01

    The Qinling-Qilian orogen preserves the records of Early Paleozoic convergence among the Proto-Tethyan micro-blocks. In this study, we analyze the seismic velocity structure and the aeromagnetic anomalies in the Qinling-Qilian orogen and its adjacent areas, showing that the northernmost boundaries of these Proto-Tethyan micro-blocks are defined by the Guyuan-Longshoushan Fault in the Qilian orogen and by the Luonan-Luanchuan Fault in the Qinling orogen, respectively. The lithosphere north of the Qinling-Qilian orogen subducted southward under the Qinling-Qilian orogen. The boundaries of the micro-blocks in the Qinling-Qilian orogen of the Proto-Tethys domain are mostly EW- or NE-trending. Combined with Early Paleozoic geological records, our results indicate that the south-dipping low-velocity anomaly under the Alxa block and the south-dipping high-velocity ones under the North Qilian orogen and the North China block might indicate that the Alxa block, the North Qilian Oceanic slab and the North China block subducted southward. The south-dipping high-velocity anomaly under the North Qilian orogen is interpreted as the remnant of the Proto-Tethys Ocean in that area. However, the north-dipping low-velocity anomaly under the South Qinling and the North Qinling orogens, the Qaidam block and the north-dipping high-velocity one under the Yangtze and the Bikou blocks suggest that the South Qinling and the North Qinling orogens, the Qaidam, the Yangtze and the Bikou blocks subducted northward. The present spatial framework of the Qinling-Qilian orogen is related to Early Paleozoic convergence among the Proto-Tethyan micro-blocks.

  8. 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.

  9. Space Station Active Thermal Control System modeling

    NASA Technical Reports Server (NTRS)

    Hye, Abdul; Lin, Chin H.

    1988-01-01

    The Space Station Active Thermal Control System (ATCS) has been modeled using modified SINDA/SINFLO programs to solve two-phase Thermo-fluid problems. The modifications include changes in several subroutines to incorporate implicit solution which allows larger time step as compared to that for explicit solutions. Larger time step saves computer time but involves larger computational error. Several runs were made using various time steps for the ATCS model. It has been found that for a reasonable approach, three times larger time step as compared to that used in explicit method is a good value which will reduce the computer time by approximately 50 percent and still maintain the accuracy of the output data to within 90 percent of the explicit values.

  10. New resorbable polymeric systems with antithrombogenic activity.

    PubMed

    Rodríguez, G; Gallardo, A; San Román, J; Rebuelta, M; Bermejo, P; Buján, J; Bellón, J M; Honduvilla, N G; Escudero, C

    1999-12-01

    The synthesis and application as resorbable coatings of vascular grafts of a new polyacrylic derivative of Triflusal (2-acetyloxy-4-trifluoromethyl)benzoic acid, a commercial drug with antithrombogenic properties, are described. The high-molecular-weight polyacrylic system is rather stable in physiological conditions and provides a chemical support for the slow release of the pharmacologically active compound, Triflusal, or its main metabolite (2-hydroxy-4-trifluoromethyl)benzoic acid (HTB). Experiments of deposition and retention of platelets in static basal conditions using plasma-rich medium from blood of sheep, seem to indicate that the polymeric coating of the polyacrylic derivative of Triflusal improves the antiaggregating character for platelets of the surface of small-diameter vascular grafts without the application of other antithrombogenic drugs.

  11. 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.

  12. Hercynian post-collisional magmatism in the context of Paleozoic magmatic evolution of the Tien Shan orogenic belt

    NASA Astrophysics Data System (ADS)

    Seltmann, Reimar; Konopelko, Dmitry; Biske, Georgy; Divaev, Farid; Sergeev, Sergei

    2011-10-01

    for ascending asthenospheric material and heat influx in the crust. This produced both granitoid magmas and hydrothermal fluid flow. As a result post-collisional intrusions and orogenic Au deposits, known in the region, formed coevally and were tectonically controlled; (4) between 240 and 220 Ma a Triassic thermal event affected the region resulting in resetting and growth of new zircon grains which is detected on a regional scale. Probably the influx of heat into the crust during the Triassic was tectonically focused and varied significantly in different terranes. In the region under investigation the Triassic thermal event was not accompanied by any significant magmatic activity. Thus, after cessation of Hercynian post-collisional magmatism ca. 280 Ma ago there was a long magmatically quiet period in the Tien Shan.

  13. 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.

  14. 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

  15. 49 CFR 234.225 - Activation of warning system.

    Code of Federal Regulations, 2011 CFR

    2011-10-01

    ... 49 Transportation 4 2011-10-01 2011-10-01 false Activation of warning system. 234.225 Section 234... Maintenance, Inspection, and Testing Maintenance Standards § 234.225 Activation of warning system. A highway-rail grade crossing warning system shall be maintained to activate in accordance with the design of...

  16. 49 CFR 234.225 - Activation of warning system.

    Code of Federal Regulations, 2010 CFR

    2010-10-01

    ... 49 Transportation 4 2010-10-01 2010-10-01 false Activation of warning system. 234.225 Section 234... Maintenance, Inspection, and Testing Maintenance Standards § 234.225 Activation of warning system. A highway-rail grade crossing warning system shall be maintained to activate in accordance with the design of...

  17. Short-lived polyphase deformation during crustal thickening and exhumation of a collisional orogen (Ribeira Belt, Brazil)

    NASA Astrophysics Data System (ADS)

    Faleiros, F. M.; Campanha, G. A. C.; Pavan, M.; Almeida, V. V.; Rodrigues, S. W. O.; Araújo, B. P.

    2016-12-01

    The Ribeira Belt (Brazil) is a Neoproterozoic collisional-related feature that was located in a south-central position in West Gondwana. We present quantitative data on finite strain, flow vorticity and deformation temperatures for the Curitiba Terrane, a major segment of the southern Ribeira Belt. Six deformation phases (D1-D6) related with crustal thickening and exhumation were recognized. D1 and D2-related microstructures are preserved exclusively within porphyroblasts, in part grown during stages of high-pressure (∼9-12 kbar) isobaric heating after crustal thickening. D3 phase was active from peak metamorphism attained in contrasting crustal levels (810-400 °C), to the early stage of exhumation (500-400 °C), as indicated by petrological, microstructural and quartz c-axis fabric evidence. Kinematic vorticity results indicate that the SL3 mylonitic fabric resulted from a simple shear-dominated deformation related with westward thrusting. North-verging overturned D4 folds with E-W-trending subhorizontal axes derived from a pure shear-dominated deformation. Regional D5 open folds with subvertical axes and NNE-SSW-trending traces were produced by indentation tectonics. D6 phase comprises retrograde orogen-parallel transcurrent shear zones related with scape tectonics. Geochronological data indicate that D3-D6 phases occurred between 584 and 580 Ma, suggesting a fast exhumation rate of ∼8 mm/year for the deepest rocks from the southern Ribeira Belt.

  18. 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.

  19. Spatially Concentrated Erosion Focuses Deformation Within the Himalayan Orogenic Wedge: Sutlej Valley, NW Himalaya, India

    NASA Astrophysics Data System (ADS)

    Thiede, R. C.; Arrowsmith, J.; Bookhagen, B.; McWilliams, M.; Sobel, E. R.; Strecker, M. R.

    2004-12-01

    Long-term erosion processes in the NW-Himalaya have not only shaped the distribution of topography and relief, but may also exert a regional control on the kinematic history of the Himalayan orogenic wedge. The topographic front of the orogenic wedge forms the southern margin of the High Himalaya and may be related to subsurface structures such as a crustal ramp or a blind thrust. Drastic along- and across-strike erosional gradients characterize the modern Himalaya and range from high-erosion regions along the southern High Himalayan front where monsoonal precipitation is able to penetrate far into the range, to low-erosion sectors across the moderately elevated Lesser Himalaya to the south and the high-elevation, arid sectors to the north. Published paleo-elevation estimates from the Thakkhola Graben (Nepal) suggest that by ~11 Ma the southern Tibetan Plateau and probably the High Himalaya had been uplifted to elevations comparable to the recent conditions. Thus, the presently observed pronounced erosional gradients have likely existed across the orogen since then. However, the cause of high rock-uplift and exhumation rates along distinct segments of the southern front of the High Himalaya are still a matter of debate. New apatite fission track (AFT) and 40Ar/39Ar data sampled along an orogen-perpendicular transect following the Sutlej Valley, approximately perpendicular to the Himalayan orogen, constrain the distribution patterns of rapid cooling related to rock uplift and exhumation. Combined with published thermochronologic data, this comprehensive AFT dataset from south of the High Himalaya mountain front to the interior of the Tethyan Himalaya allows us to derive a regional uplift and exhumation scenario. Our new 40Ar/39Ar ages ranging between 17 and 4 Ma reveal diachronous exhumation of two crystalline nappes (Higher and Lesser Himalayan crystalline) during Miocene-Pliocene time. In contrast, the AFT data ranging from 1.3 to 4.6 Ma indicate synchronous, fast

  20. Subduction-related magmatism and crustal role in the early stage of the Damara Orogen, Namibia: new constraints from combined U-Pb and Lu-Hf isotopes from the Goas Magmatic Complex

    NASA Astrophysics Data System (ADS)

    Milani, L.; Kinnaird, J.; Lehmann, J.; Naydenov, K.; Saalmann, K.; Frei, D.; Gerdes, A.

    2013-12-01

    Based on new U-Pb ages on zircons, the tholeiitic to calcalkaline Goas intrusive Complex marks the first magmatic Pan-African event in the inland branch of the Damara Orogen at ca. 575 Ma. The Goas orogenic event reflects the Pan-African collision between the Congo and Kalahari Cratons. The new ages provide a better constraint on the evolution of the orogenic suite, indicating that the Goas Complex has been emplaced in a relatively short time, not exceeding 25-30 Ma, with continuous magmatic activity from early tholeiitic metagabbro/hornblendite to main bodies with calcalkaline affinity. The absence of a time gap between the tholeiitic metagabbro/hornblendites and the calcalkaline products is documented. Our new geochemical and geochronological data concur with previous tectono-stratigraphic models by supporting the existence of an orogenic event with subduction of the Kalahari Craton below the Congo Craton, closure of the interposed ocean between the two cratons and subsequent continent-continent collision. Hf isotopes resulted in invariably negative ɛHft values (-34.4 to -3.8). This is indicative of relevant crustal contribution also within the early calcalkaline magmatism. A prolonged crustal residence time and the apparent lack of a substantial juvenile contribution imply that the mantle-derived magmas below the former active margin were unable to pass through the lithosphere, but managed to heat-up sections of the lower crust sufficiently to invoke large-scale melting and reworking processes in the upper crust. A notable mixing between different crustal components is apparent from the wide range of ɛHft distribution, although the values of single intrusions usually cluster within relatively small ranges. This suggests that the different intrusions reflect heterogeneous feeding crustal portions, but that each single event formed by melting of a rather uniform crustal material, which would indicate storage in a proper magmatic chamber, contamination with

  1. 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.

  2. 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

  3. Geomorphological-thermo-mechanical modeling: Application to orogenic wedge dynamics

    NASA Astrophysics Data System (ADS)

    Ueda, K.; Willett, S. D.; Gerya, T.; Ruh, J.

    2015-09-01

    Coupled geomorphological-thermo-mechanical modeling is presented in a new implementation that combines two established thermo-mechanical and landscape evolution models. A finite-difference marker-in-cell technique is used to solve for the thermo-mechanical problem including complex visco-plastic rheologies in high resolution. Each timestep is synchronously solved with a fluvial landscape evolution model that includes numerical solution of fluvial incision and analytical hillslope processes for both diffusive and slope-limited processes on an adaptive grid. The implementation is successful in modeling large deformation at different scales. We demonstrate high degrees of coupling through processes such as exhumation of rocks with different erodibilities. Sensitivity of the coupled system evolution to surface parameters, and mechanical parameters, is explored for the established case of development of compressive wedges. The evolution of wedge models proves to be primarily sensitive to erodibility and the degree of river network integration. Relief follows deformation in propagating forward with wedge growth. We apply the method to a large-scale model of continental collision, in which a close relationship between deep tectonics, fluvial network evolution, and uplift and erosion can be demonstrated.

  4. Role of Lithosphere structural inheritance in the localization of intraplate deformation: the example of the Tien Shan (Central Asian Orogenic Belt)

    NASA Astrophysics Data System (ADS)

    Jourdon, Anthony; Le Pourhiet, Laetitia; Petit, Carole; Rolland, Yann

    2016-04-01

    Due to the India-Asia collision, the deformation of the Eurasian continent extends over several thousand kilometers, far away from the Himalayan belt. However, some areas like the Tarim craton are poorly deformed while others, as the Tien Shan belt or Tibet plateau, display large deformation rates. These actively deforming areas correspond to ancient plate boundaries which were previously involved in the construction of large orogenic belts. The Tien Shan is a relevant example to study the role of structural inheritance in the localization of recent deformation because of its Paleozoic tectonic history. Indeed, the Tien Shan has been built during two consecutive orogenies (Caledonian and Variscan) which formed large scale structures (as suture zones) clearly identifiable on the field. These structures are now reworked as active deformation zones where large earthquakes can occur. In order to improve our understanding of the role of this strong structural inheritance on the Cenozoic deformation, this study couples two approaches: 1-A field study which allowed us to identify the major Paleozoic structures, their geometry and the main lithologies involved. Our new findings include the reconnaissance of a transcurrent system in Middle Tien Shan, and a south-dipping structure of the major suture zone of the South Tien Shan/ North Tarim. 2-Based on a reconstruction of the pre-Cenozoic structure geometries, we use the thermomechanical modeling code Ptatin to simulate the lithospheric deformation of the belt depending on the geometry and rheology of inherited structures. Our results show that inherited structures first localize the deformation before that antithetic neoformed structures develop on the outer parts of the belt. This result is consistent with seismologic, seismic and GPS data, which show that the deformation is now localized on the borders of the belt, and especially propagates in the South Tien Shan/ North Tarim boundary along a N-dipping top-to-the South

  5. 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.

  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. Orogenic Float Model: an Explanation for the Dynamics of the Venezuelan Andes

    NASA Astrophysics Data System (ADS)

    Monod, B.; Dhont, D.; Hervouet, Y.

    2008-12-01

    The Venezuelan (or Merida) Andes are a NE-trending intracontinental orogen that started to rise from the late Miocene due to the E-W far field convergence between the Maracaibo block to the northwest and the Guyana shield to the southeast. Oblique convergence is responsible for strain partitioning with thrusting along both foreland basins and right-lateral strike-slip faulting along the NE-SW Bocono fault cutting the Venezuelan Andes along-strike. The central part of the belt is also cut by the N-S left-lateral strike-slip Valera fault that branches the Bocono fault in the triple junction geometry, favoring the crustal escape of the Trujillo triangular block towards the NE. Onset of strike-slip motion along major faults and their geometry at depth remains a matter of debate. Our work, based on the integration of geologic and geophysical data aims to better constrain both the geometry and the tectonic evolution of the major tectonic structures. We use the orogenic float model (Oldow et al., 1990) as a first hypothesis to construct two NW-SE trans-Andean crustal scale balanced sections. The late Neogene-Quaternary shortening varies from 40 km in the south to 30 km in the north across the Trujillo block, indicating that a quarter of the deformation seems to be absorbed by the tectonic escape process. The cross-sections served also as the basis for the building of a 3-D geologic model of the Venezuelan Andes, permitting to clearly understand the link and geometry of the faults at depth. The decollement level used for the orogenic float model, located at 20 km depth, is crucial for the motion of the Trujillo block. Both the Bocono and Valera faults have listric shapes connecting to the decollement level. The connexion of the two fault surfaces forms a hinge line dipping towards the north in a geometry favoring the escape of the Trujillo block and allowing the gravity forces to play an important role in the process. Oldow J. S., Bally A. W., Ave Lallemant H. G., 1990

  8. Carbonatitic metasomatism in orogenic dunites from Lijiatun in the Sulu UHP terrane, eastern China

    NASA Astrophysics Data System (ADS)

    Su, Bin; Chen, Yi; Guo, Shun; Chu, Zhu-Yin; Liu, Jing-Bo; Gao, Yi-Jie

    2016-10-01

    Among orogenic peridotites, dunites suffer the weakest crustal metasomatism at the slab-mantle interface and are the best lithology to trace the origins of orogenic peridotites and their initial geodynamic processes. Petrological and geochemical investigations of the Lijiatun dunites from the Sulu ultrahigh-pressure (UHP) terrane indicate a complex petrogenetic history involving melt extraction and multistage metasomatism (carbonatitic melt and slab-derived fluid). The Lijiatun dunites consist mainly of olivine (Fo = 92.0-92.6, Ca = 42-115 ppm), porphyroblastic orthopyroxene (En = 91.8-92.8), Cr-spinel (Cr# = 50.4-73.0, TiO2 < 0.2 wt.%) and serpentine. They are characterized by refractory bulk-rock compositions with high MgO (45.31-47.07 wt.%) and Mg# (91.5-91.9), and low Al2O3 (0.48-0.70 wt.%), CaO (0.25-0.44 wt.%) and TiO2 (< 0.03 wt.%) contents. Whole-rock platinum group elements (PGE) are similar to those of cratonic mantle peridotites and Re-Os isotopic data suggest that dunites formed in the early Proterozoic ( 2.2 Ga). These data indicate that the Lijiatun dunites were the residues of 30% partial melting and were derived from the subcontinental lithospheric mantle (SCLM) beneath the North China craton (NCC). Subsequent carbonatitic metasomatism is characterized by the formation of olivine-rich (Fo = 91.6-92.6, Ca = 233-311 ppm), clinopyroxene-bearing (Mg# = 95.9-96.7, Ti/Eu = 104-838) veins cutting orthopyroxene porphyroblasts. Based on the occurrence of dolomite, mass-balance calculation and thermodynamic modeling, carbonatitic metasomatism had occurred within the shallow SCLM (low-P and high-T conditions) before dunites were incorporated into the continental subduction channel. These dunites then suffered weak metasomatism by slab-derived fluids, forming pargasitic amphibole after pyroxene. This work indicates that modification of the SCLM beneath the eastern margin of the NCC had already taken place before the Triassic continental subduction. Orogenic

  9. Vehicle Systems Engineering and Integration Activities

    DTIC Science & Technology

    2012-08-31

    procedural and subjective (see Program Managers Guide: A Modular Open Systems Approach to Acquisition Version 2, Open Systems Joint Task Force, http...a sensor pod for the Man- Transportable Robotic System (MTRS) PoR. The acquisition agent for the MTRS PoR is the Robotic System Joint Program...subjective (see Program Managers Guide: A Modular Open Systems Approach to Acquisition Version 2, Open Systems Joint Task Force, http://www.acq.osd.mil

  10. 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…

  11. Active dc filter for HVDC systems

    SciTech Connect

    Zhang, W. ); Asplund, G.

    1994-01-01

    This article is a case history of the installation of active dc filters for high-performance, low-cost harmonics filtering at the Lindome converter station in the Konti-Skan 2 HVDC transmission link between Denmark and Sweden. The topics of the article include harmonics, interference, and filters, Lindome active dc filter, active dc filter design, digital signal processor, control scheme, protection and fault monitoring, and future applications.

  12. The importance of late- and post-orogenic crustal growth in the early Proterozoic: Evidence from Sm-Nd isotopic studies of igneous rocks in the Makkovik Province, Canada

    NASA Astrophysics Data System (ADS)

    Kerr, Andrew; Fryer, Brian J.

    1994-07-01

    Sm-Nd isotopic studies suggest that large tracts of 1900-1700 Ma old crust in Laurentia-Baltica is of 'juvenile' origin. This crust has generally been ascribed to arc magmatism, sustained over long periods, and most conceptual models for crustal growth emphasize this process. The late- to post-orogenic granitoid rocks that areally dominate many ancient orogenic belts are commonly viewed as anatectic derivatives of the earlier arc-type crust. However, in regions of short crustal residence, the time resolution of isotopic tracers, such as the Sm-Nd system, does not permit discrimination between this model and continued growth of the crust during post-orogenic magmatism. The relative contributions of recycled crust and new, mantle-derived material in late- to post-orogenic magmas can only be assessed where they also transect much older crustal blocks. The Nd isotopic signatures of 1800-1720 Ma igneous suites in the Makkovik Province define such a boundary between an Archean craton and a juvenile Proterozoic domain. In the juvenile domain, the Nd signatures of most igneous suites are equivocal (initial epsilon(sub Nd) = 0 to +2), and they could be anatectic derivatives of slightly older orthogneisses; however, addition of new, mantle-derived material is documented by 'A-type' granites with initial epsilon(sub Nd) up to +4. In the cratonic domain, temporally and compositionally equivalent igneous suites mostly have initial epsilon(sub Nd) of -7 to -3, significantly above local Archean basement, which has epsilon(sub Nd) of -15 at 1800 Ma. Conservative calculations suggest that most of these suites contain more than 50% new, mantle-derived material. These results suggest significant crustal growth via late-stage magmatism, and direct interaction of mantle-derived magmas and lower crustal rocks. In contrast, 1650 Ma igneous suites lack clear systematic variation in epsilon(sub Nd), and are interpreted as representing crustal growth via later, distal, arc-type magmatism

  13. Process of activation of a palladium catalyst system

    SciTech Connect

    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.

  14. 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.

  15. 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

    2014-10-16

    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.

  16. 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.

  17. Origin of unusual HREE-Mo-rich carbonatites in the Qinling orogen, China

    PubMed Central

    Song, Wenlei; Xu, Cheng; Smith, Martin P.; Kynicky, Jindrich; Huang, Kangjun; Wei, Chunwan; Zhou, Li; Shu, Qihai

    2016-01-01

    Carbonatites, usually occurring within intra-continental rift-related settings, have strong light rare earth element (LREE) enrichment; they rarely contain economic heavy REE (HREE). Here, we report the identification of Late Triassic HREE-Mo-rich carbonatites in the northernmost Qinling orogen. The rocks contain abundant primary HREE minerals and molybdenite. Calcite-hosted fluid inclusions, inferred to represent a magmatic-derived aqueous fluid phase, contain significant concentrations of Mo (~17 ppm), reinforcing the inference that these carbonatitic magmas had high Mo concentrations. By contrast, Late Triassic carbonatites in southernmost Qinling have economic LREE concentrations, but are depleted in HREE and Mo. Both of these carbonatite types have low δ26Mg values (−1.89 to −1.07‰), similar to sedimentary carbonates, suggesting a recycled sediment contribution for REE enrichment in their mantle sources. We propose that the carbonatites in the Qinling orogen were formed, at least in part, by the melting of a subducted carbonate-bearing slab, and that 10 Ma younger carbonatite magmas in the northernmost Qinling metasomatized the thickened eclogitic lower crust to produce high levels of HREE and Mo. PMID:27857170

  18. Origin of unusual HREE-Mo-rich carbonatites in the Qinling orogen, China

    NASA Astrophysics Data System (ADS)

    Song, Wenlei; Xu, Cheng; Smith, Martin P.; Kynicky, Jindrich; Huang, Kangjun; Wei, Chunwan; Zhou, Li; Shu, Qihai

    2016-11-01

    Carbonatites, usually occurring within intra-continental rift-related settings, have strong light rare earth element (LREE) enrichment; they rarely contain economic heavy REE (HREE). Here, we report the identification of Late Triassic HREE-Mo-rich carbonatites in the northernmost Qinling orogen. The rocks contain abundant primary HREE minerals and molybdenite. Calcite-hosted fluid inclusions, inferred to represent a magmatic-derived aqueous fluid phase, contain significant concentrations of Mo (~17 ppm), reinforcing the inference that these carbonatitic magmas had high Mo concentrations. By contrast, Late Triassic carbonatites in southernmost Qinling have economic LREE concentrations, but are depleted in HREE and Mo. Both of these carbonatite types have low δ26Mg values (‑1.89 to ‑1.07‰), similar to sedimentary carbonates, suggesting a recycled sediment contribution for REE enrichment in their mantle sources. We propose that the carbonatites in the Qinling orogen were formed, at least in part, by the melting of a subducted carbonate-bearing slab, and that 10 Ma younger carbonatite magmas in the northernmost Qinling metasomatized the thickened eclogitic lower crust to produce high levels of HREE and Mo.

  19. Sequential kinetic modelling: A new tool decodes pulsed tectonic patterns in early hot orogens of Earth

    NASA Astrophysics Data System (ADS)

    Bhowmik, Santanu Kumar; Chakraborty, Sumit

    2017-02-01

    Tectonic styles in an early hot Earth were different from the present-day situation governed by plate tectonics. Processes in such hot settings remain poorly understood because they often occur on timescales that are below the resolution of conventional isotopic clocks, the rock records are fragmentary, and these have been superposed by later high-temperature events. We have developed a tool based on diffusion kinetics to overcome these difficulties and reconstruct sequences of short-lived episodes. Application of the method to a rock from the ultra-hot c.1.6 Ga orogenic domain of the Central Indian Tectonic Zone, where additional data are available to verify the results, shows that pulses of approach and roll-back of colliding plates preceded the final closure and collision. We demonstrate that cooling from ultra-high temperature metamorphic conditions in the orogen took place in multiple pulses that occurred with a periodicity of about 10 Myr at rates that vary between 100's to 10's °C/Myr, and burial-/exhumation-rates that vary between 30 and 2 km/Myr, respectively. Such details of tectonic processes in the Precambrian, with quantification of variable heating-, cooling-, burial-, and exhumation-rates of individual stages, have not been accessible until now. Application of this method to other regions would provide a means of exploring the thermal viability of the inferred long durations (>100 Myr) for some ultra-high temperature orogenies.

  20. Origin of unusual HREE-Mo-rich carbonatites in the Qinling orogen, China.

    PubMed

    Song, Wenlei; Xu, Cheng; Smith, Martin P; Kynicky, Jindrich; Huang, Kangjun; Wei, Chunwan; Zhou, Li; Shu, Qihai

    2016-11-18

    Carbonatites, usually occurring within intra-continental rift-related settings, have strong light rare earth element (LREE) enrichment; they rarely contain economic heavy REE (HREE). Here, we report the identification of Late Triassic HREE-Mo-rich carbonatites in the northernmost Qinling orogen. The rocks contain abundant primary HREE minerals and molybdenite. Calcite-hosted fluid inclusions, inferred to represent a magmatic-derived aqueous fluid phase, contain significant concentrations of Mo (~17 ppm), reinforcing the inference that these carbonatitic magmas had high Mo concentrations. By contrast, Late Triassic carbonatites in southernmost Qinling have economic LREE concentrations, but are depleted in HREE and Mo. Both of these carbonatite types have low δ(26)Mg values (-1.89 to -1.07‰), similar to sedimentary carbonates, suggesting a recycled sediment contribution for REE enrichment in their mantle sources. We propose that the carbonatites in the Qinling orogen were formed, at least in part, by the melting of a subducted carbonate-bearing slab, and that 10 Ma younger carbonatite magmas in the northernmost Qinling metasomatized the thickened eclogitic lower crust to produce high levels of HREE and Mo.

  1. 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.

  2. Limited Investigation of Active Feel Control Stick System (Active Stick)

    DTIC Science & Technology

    2009-06-01

    at VCORNER .............. 15 Figure 12: Pitch Rate Response to 1.5 g Commanded Force PTI at VHI ......................... 16 Figure 13: Pitch Angle...Response to 1.5 g Commanded Force PTI at VHI ...................... 17 Figure 14: Flight Control System Stick Attributes at VLO...23 Figure 19: Cooper-Harper Ratings for Head Down Display Task ( VHI ) ......................... 24 Figure 20: Fine

  3. Cenozoic landforms and post-orogenic landscape evolution of the Balkanide orogen: Evidence for alternatives to the tectonic denudation narrative in southern Bulgaria

    NASA Astrophysics Data System (ADS)

    Gunnell, Y.; Calvet, M.; Meyer, B.; Pinna-Jamme, R.; Bour, I.; Gautheron, C.; Carter, A.; Dimitrov, D.

    2017-01-01

    Continental denudation is the mass transfer of rock from source areas to sedimentary depocentres, and is typically the result of Earth surface processes. However, a process known as tectonic denudation is also understood to expose deep-seated rocks in short periods of geological time by displacing large masses of continental crust along shallow-angle faults, and without requiring major contributions from surface erosion. Some parts of the world, such as the Basin and Range in the USA or the Aegean province in Europe, have been showcased for their Cenozoic tectonic denudation features, commonly described as metamorphic core-complexes or as supradetachment faults. Based on 22 new apatite fission-track (AFT) and 21 helium (AHe) cooling ages among rock samples collected widely from plateau summits and their adjacent valley floors, and elaborating on inconsistencies between the regional stratigraphic, topographic and denudational records, this study frames a revised perspective on the prevailing tectonic denudation narrative for southern Bulgaria. We conclude that conspicuous landforms in this region, such as erosion surfaces on basement-cored mountain ranges, are not primarily the result of Paleogene to Neogene core-complex formation. They result instead from "ordinary" erosion-driven, subaerial denudation. Rock cooling, each time suggesting at least 2 km of crustal denudation, has exposed shallow Paleogene granitic plutons and documents a 3-stage wave of erosional denudation which progressed from north to south during the Middle Eocene, Oligocene, Early to Middle Miocene, and Late Miocene. Denudation initially prevailed during the Paleogene under a syn-orogenic compressional regime involving piggyback extensional basins (Phase 1), but subsequently migrated southward in response to post-orogenic upper-plate extension driven by trench rollback of the Hellenic subduction slab (Phase 2). Rare insight given by the denudation pattern indicates that trench rollback

  4. Tools for active control system design

    NASA Technical Reports Server (NTRS)

    Adams, W. M., Jr.; Tiffany, S. H.; Newsom, J. R.

    1984-01-01

    Efficient control law analysis and design tools which properly account for the interaction of flexible structures, unsteady aerodynamics and active controls are developed. Development, application, validation and documentation of efficient multidisciplinary computer programs for analysis and design of active control laws are also discussed.

  5. A Hybrid Activity System as Educational Innovation

    ERIC Educational Resources Information Center

    Yamazumi, Katsuhiro

    2008-01-01

    This article analyzes a hybrid after-school learning activity for children called "New School" (NS). NS is an inter-institutional, collaborative project based on a partnership between a university and local elementary schools that also involves other social actors and institutions. Using a framework of third generation activity theory, the article…

  6. 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

  7. Climate and Orogenic Evolution of the Sierra Nevada and Westernmost Basin and Range as Recorded in the Pliocene-Pleistocene Waucobi Lake Beds

    NASA Astrophysics Data System (ADS)

    De Masi, C. L.; Castillo, C. M.; Deino, A. L.; Scott, G. R.; Klemperer, S. L.; Knott, J.

    2015-12-01

    The interplay between climate and orogenic evolution is archived in lacustrine basins as changes in basin geometry, sedimentary input, water level, and lacustrine chemistry. The Pliocene-Pleistocene Waucobi Lake Beds in the Owens Valley east of Big Pine, CA and Sierra Nevada Mountains are uplifted onto the western White-Inyo Mountain piedmont with a tephrochronology age of 2.2-2 Ma. We present 40Ar/39Ar and paleomagnetic chronology, isotopic analysis of clays and seismic data to evaluate the climate and tectonic controls on the Waucobi basin. Within the 130-m-thick lake beds, we determined ages of 2.6-2 Ma on sanidine from intercalated tuff beds by 40Ar/39Ar single-crystal laser step-heating method. A paleomagnetic reversal identifies the Gauss/Matuyama boundary at 2.5-2.6 Ma. Clay mineral analysis shows phillipsite, an alkaline clay, dominating the lower section of Waucobi whereas the upper section contains montmorillonite, a fresh water clay. Deuterium isotopic analyses were performed on clay showing δD values for phillipsite increasing between 2.6-2.5 Ma from -105 ‰ to -60 ‰ indicating a wet climate, whereas δD values in montmorillonite decrease between 2.3-2.2 Ma from -70 ‰ to -90 ‰ implying a drier climate. Shallow active seismic studies suggest a basement depth of 300 m near the locality Duchess canyon. Clay mineral and isotopic analyses indicate that Waucobi records an environment that does not reflect climate change represented by other lake systems in the eastern Sierra. This suggests that Waucobi records tectonic changes occurring between the Sierra Nevada and White-Inyo Mountains. Assuming a constant sedimentation rate calculated from the Duchess canyon exposure of 91 m and ages of 2.6-2.3 Ma, the seismic data indicates that the base of the lake section may be as old as 3.5 Ma. We suggest that lake formation coincides with extension-strike slip tectonics along the western Basin and Range, and uplift of the Sierra from the mid-Pliocene to

  8. Cretaceous Exhumation of the North American Cordillera Measured through Mineral Multi-Dating: Insights into Basin Filling Models and Orogenic Architecture

    NASA Astrophysics Data System (ADS)

    Painter, C. S.; Carrapa, B.; DeCelles, P. G.; Gehrels, G. E.; Thomson, S. N.

    2015-12-01

    Apatite fission track (AFT) thermochronology is an effective thermochronometer to measure source exhumation in the North American Cordillera, western U.S.A. We use a combination of thermochronology and geochronology to measure lag times, i.e., the difference in time between the cooling and depositional ages of a mineral crystal. These lag-time measurements using source exhumation ages, measured with AFT thermochronology, and depositional ages, measured with biostratigraphy and detrital zircon U-Pb geochronology, indicate constant to decreasing lag times of 0-5 m.y. throughout the Cretaceous. These lag times are consistent with rapid exhumation rates of ~0.9->1 km/m.y. One pitfall of using detrital thermochronology to measure source exhumation is assuring that the apatite crystals are exhumed apatites and not volcanic apatites introduced into the system from the volcanic arc. To do this we use U-Pb geochronology to remove samples contaminated with young arc derived apatites and keep those with old exhumed apatites. Five of the seven detrital AFT samples were significantly contaminated with young volcanic apatites, showing that U-Pb geochronology should be a routine step in measuring lag times. Our findings demonstrate that coarse-grained foreland basin deposits in the Cretaceous Western Interior, in both the proximal and distal settings, were deposited during times of active tectonism and exhumation and that sediments are not stored in wedge-top and proximal foredeep settings for long periods of time, i.e. >5 m.y., and then subsequently reworked distally. Exhumation rates of ~0.9->1 km/m.y. are not sustainable over the entire orogenic belt for the duration of the Sevier orogeny, indicated by the lack of deep-crustal material exhumed in the North American Cordillera. High exhumation rates were likely concentrated over the eastward-propagating Sevier fold-thrust belt, whereas the Nevadaplano and hinterland experienced much slower rates of exhumation. This variation in

  9. 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.

  10. Comparison of garnet-biotite, calcite-graphite, and calcite-dolomite thermometry in the Grenville Orogen; Ontario, Canada

    NASA Astrophysics Data System (ADS)

    Rathmell, Mark A.; Streepey, Margaret M.; Essene, Eric J.; van der Pluijm, Ben A.

    The Elzevir Terrane of the Grenville Orogen in southern Ontario contains metapelites and abundant graphitic marbles that were regionally metamorphosed from the upper greenschist to upper amphibolite facies. Comparative thermometry was undertaken with widely used calibrations for the systems garnet-biotite, calcite-dolomite, and calcite-graphite. Temperatures that are obtained from matrix biotites paired with prograde garnet near-rim analyses are usually consistent with those determined using calcite-graphite thermometry. However, calcite-graphite thermometry occasionally yields low temperatures due to lack of equilibration of anomalously light graphite. Application of calcite-graphite and garnet-biotite systems may yield temperatures up to 70°C higher than calcite-dolomite in amphibolite facies rocks. Calcite-dolomite temperatures most closely approach those from calcite-graphite and garnet-biotite when the samples contain a single generation of dolomite and calcite grains contain no visible dolomite exsolution lamellae. However, some of these samples yield temperatures considerably lower than temperatures calculated from calcite-graphite and garnet-biotite thermometry, indicating that the calcite-dolomite thermometer may have been partially reset during retrogression. Estimated peak metamorphic temperatures of regional metamorphism between Madoc (upper greenschist facies) and Bancroft (upper amphibolite facies) range from 500 to 650°C. These results place the chlorite-staurolite isograd at 540°C, the kyanite-sillimanite isograd at 590°C, and the sillimanite-K-feldspar isograd at 650°C. Although each thermometer may have an absolute uncertainty of as much as +/-50°C, the 50 to 60°C temperature differences between the isograds are probably accurate to 10 to 20°C. An incomplete picture of the thermal gradients can result from the application of only one thermometer in a given area. Simultaneous application of several systems allows one to recognize and

  11. Active Control of Complex Physical Systems: An Overview

    DTIC Science & Technology

    1992-09-01

    release; distribution is unlimited. 13. ABSTRACT (Maxtmum 200 words) Active control of complex systems imposes unique requirements for physical models and...months after the meeting, SPrinte In USA. Acceslon For NTIS CRA&W DTIC TAB Unlannounced ] Active Control of Complex Physical Systems Justificatton An...control strategies. Physical models This work on the active control of which are adequate to predict the influence of specific physical systems has been

  12. 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.

  13. Bigelow Expandable Activity Module (BEAM) Monitoring System

    NASA Technical Reports Server (NTRS)

    Wells, Nathan

    2017-01-01

    What is Bigelow Expandable Activity Module (BEAM)? The Bigelow Expandable Activity Module (BEAM) is an expandable habitat technology demonstration on ISS; increase human-rated inflatable structure Technology Readiness Level (TRL) to level 9. NASA managed ISS payload project in partnership with Bigelow Aerospace. Launched to ISS on Space X 8 (April 8th, 2016). Fully expanded on May 28th, 2016. Jeff Williams/Exp. 48 Commander first entered BEAM on June 5th, 2016.

  14. 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

  15. 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.

  16. Hybrid energy storage systems utilizing redox active organic compounds

    SciTech Connect

    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.

  17. A summary of systems definition project activities

    NASA Technical Reports Server (NTRS)

    Jones, G. J.; Biringer, K. L.

    1978-01-01

    Design information and subsystem requirement definition to the overall program is presented. Application analysis and conceptual design for the wide variety of systems, system tradeoff studies and engineering design for the more promising application types, and the identification of the technology status and requirements for major subsystems and components are described. The residential design and analysis contracts, hybrid photovoltaic/solar thermal electric conversion contract, and development of prototype combined photovoltaic/thermal flat-plate collectors were studied.

  18. 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

  19. 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

  20. Alpine-type tectonics in the Paleoproterozoic Lapland-Kola Orogen

    NASA Astrophysics Data System (ADS)

    Mudruk, S. V.; Balagansky, V. V.; Gorbunov, I. A.; Raevsky, A. B.

    2013-07-01

    The Kola region in the northeastern Baltic Shield is characterized by diverse Paleoproterozoic collision processes. The Keivy Terrane is one of the major tectonic units in the northeastern foreland of the Paleoproterozoic Lapland-Kola Collisional Orogen, which markedly differs in a number of parameters from other tectonic units of the Kola region. The study of the Keivy Terrane allowed us to unravel one more basic difference: the large Paleoproterozoic sheath synform of the Serpovidny (Crescentic) Range localized in this terrane. Its core is occupied by volcanic and sedimentary rocks, which correlate with the fill of the Imandra-Varzuga Rift; the limbs are composed of metamorphosed mature sedimentary rocks known as Keivy paraschists of Neoarchean or Paleoproterozoic age. The lower limb of the Serpovidny Synform is strongly squeezed, whereas the upper limb consists of almost undeformed rocks. The deformed rocks underwent ductile flow under conditions of simple or general shear. In the degree of its asymmetry and main parameters, the Serpovidny Synform is similar to the plunging and recumbent anticlines in the Helvetic nappes of the Alps. It is concluded that the Paleoproterozoic core of the Serpovidny Sheath Synform, or plunging anticline, is a fragment of the almost completely eroded deep Serpovidny Nappe of the Helvetic type. During the collision related to the Lapland-Kola Orogeny (1.9-2.0 Ga), this nappe was pushed out northward from the Paleoproterozoic Imandra-Varzuga Rift, which is situated 50 km south of the Serpovidny structure, and thrust over the Keivy paraschists. The latter, together with underlying the Lebyazhka Gneiss, were folded in the process of thrusting and were involved in the structure of the Serpovidny Synform. The Keivy paraschists make up a para-autochthon or a separate nappe of the Pennine type. The Archean Lebyazhka metafelsic volcanics underlie the Keivy paraschists and overlie granitoids of the Archean basement that remained undeformed

  1. Lateral flow in the middle crust - Analogue experiments from the Svecofennian orogen

    NASA Astrophysics Data System (ADS)

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

    2013-04-01

    The exposed Svecofennian crust (50-65 km) has been suggested to have thickened in continental accretion between Archean and Paleoproterozoic terranes, probably at a high convergence rate. It is likely that this thickened orogen experienced lateral spreading during its final stages. This post-orogenic event has reshaped the collisional framework and modified its bulk appearance. In this study, we have used scaled analogue centrifuge modeling to simulate extensional lateral flow at the Archean- Paleoproterozoic boundary zone during final stages of the Svecofennian orogeny. The analogue models simulate both the evolution of a mechanical boundary between two rheologically different tectonic blocks, and the role of pre-existing weaknesses at moderate angles (representing the old stacking structures). In models the upper layer is brittle, the middle layer is ductile, and the lower layer is more viscous. The layers represent upper, middle and lower crust, respectively. The Proterozoic layers have lower viscosity values than the Archean layers at similar depths. The materials are based on the plastilina modelling putty, which is mixed with acid oil, silicone, sweetener and/or barium sulphate to get the appropriate composition for each layer. Both the Archean and the Paleoproterozoic blocks have a low-viscous middle crust. The three layered models are extended unilaterally. The model results show that during extension the rheologically different layers deform and spread at different rates during the tectonic collapse. This results in 1) vertical rotation of the Archean and Proterozoic boundary; 2) the pre-existed faults become listric and discontinuous; and 3) the upward flow of the low viscosity middle layer to fill the newly-formed gaps between the upper layer blocks. The experiments show geometrically similar crustal-scale structures to those observed in the deep seismic reflection profiles (FIRE). Thus it is possible that lateral flow has taken place in the core of the

  2. Origin of allanite in gneiss and granite in the Dabie orogenic belt, Central East China

    NASA Astrophysics Data System (ADS)

    Guo, Haihao; Xiao, Yilin; Xu, Lijuan; Sun, He; Huang, Jian; Hou, Zhenhui

    2017-03-01

    Allanite is a common accessory mineral phase, representing an important carrier of rare earth elements, Th, U, Sr and other trace elements in most continental rocks. As Th and U can be incorporated into the allanite lattice, the mineral is a good geochronological tool for constraining geological events. Moreover, the trace element features δEu, Th/U ratio and common lead content of allanite are indicators of the forming conditions. Allanite and coexisting epidote-group minerals are abundant in ultrahigh-pressure (UHP) metamorphic rocks from the Dabie-Sulu orogen in central East China. However, if these minerals formed in the Neoproterozoic as magmatic phases, or in the Triassic as metamorphic phases is a matter of long-standing controversy. We report major and trace element analyses of whole rocks, allanite and coexisting epidote-group minerals, together with U-Th-Pb isotopic compositions of allanite in UHP gneiss from the Dabie-Sulu orogen, and allanite in the adjacent Jingshan granite. The granite is emplaced along the southeastern margin of the North China Craton and considered a product of partial melting of the subducted Dabie-Sulu gneiss. Trace elements (low Th/U and La/Sm, high δEu and high Sr) and high common lead concentrations indicate a metamorphic origin of allanite-epidote in the UHP gneiss. On the other hand, coarse-grained allanite from the Jingshan granite shows a corrosion core and a magmatic rim with common 208Pb up to 70% in the core and less than 30% in the rim. The allanite cores are of peritectic and the rims of magmatic origin with ages of ∼160 Ma, consistent with the granite crystallization age. In combination with previous studies, we conclude that the allanite of the Jingshan granite has form from the subducted and remolten Dabie-Sulu gneiss. Allanite records Triassic UHP metamorphic ages as well as Jurassic peritectic-magmatic ages as a part of the evolution of the Dabie-Sulu orogen.

  3. Sympathoadrenal system and activation of glycogenolysis during muscular activity.

    PubMed

    Cartier, L J; Gollnick, P D

    1985-04-01

    Comparisons were made of the appearance of phosphorylase (PHOS) a and lactate (LA) during electrical stimulation of the gastrocnemius (GM) and soleus (SM) muscles of normal and sympathectomized (SYMPX) rats. Ten-second stimulation at 3 Hz increased PHOS a approximately fourfold in the GM of normal rats, whereafter it declined during stimulation until at 60 s it was similar to rest. The increase in PHOS a of GM from SYMPX rats after 10 s of stimulation was approximately 50% that of normal rats. Stimulation of the SM produced smaller and slower increases in PHOS a with the peak occurring after 60 s, which remained constant to 90 s. SYMPX did not alter this effect in the SM. LA production and creatine phosphate depletion in the GM were continuous throughout stimulation and uninfluenced by SYMPX. This was true for the SM with the exception of LA production being greater after SYMPX. [ATP] was unchanged by electrical stimulation. The rate and magnitude of the PHOS a appearance was a function of stimulation frequency. Reversion of PHOS to the b form after stimulation was rapid, with approximately 50% of the peak value being attained in 2.5 s, and at 5 s the values were those of rest. These data demonstrate that an intact sympathoadrenal system is not obligatory for the initiation of glycogenolysis in skeletal muscle.

  4. 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

  5. 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

  6. 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…

  7. [Increased fibrinolytic activity during cardiopulmonary bypass is caused by activated protein C system].

    PubMed

    Gando, S; Tedo, I; Masio, H; Goda, Y; Kawahigashi, H

    1994-06-01

    To examine the hypothesis that activated protein C system during cardiopulmonary bypass surgery may increase fibrinolytic activity during cardiopulmonary bypass, protein C activity, protein C antigen and thrombomodulin of sixteen patients undergoing elective cardiopulmonary bypass surgery were investigated after induction of anesthesia, before and after cardiopulmonary bypass, and at the end of operation. Protein C activity decreased and thrombomodulin increased significantly after the cardiopulmonary bypass. There were no significant correlations of thrombomodulin with protein C activity and protein C antigen. In conclusion, we have demonstrated that protein C system is activated and circulating thrombomodulin appears in the systemic circulation during cardiopulmonary bypass surgery and this enhanced activation of protein C system is possibly related to the reported increase of fibrinolytic activity during cardiopulmonary bypass.

  8. Petrology and geochemistry of Abyssal Peridotites from the Manipur Ophiolite Complex, Indo-Myanmar Orogenic Belt, Northeast India: Implication for melt generation in mid-oceanic ridge environment

    NASA Astrophysics Data System (ADS)

    Krishnakanta Singh, A.

    2013-04-01

    The Manipur Ophiolite Complex (MOC) located in the Indo-Myanmar Orogenic Belt (IMOB) of Northeast India forms a section of the Tethyan Ophiolite Belt of the Alpine-Himalayan orogenic system. Whole rock compositions and mineral chemistry of mantle peridotites from the MOC show an affinity to the abyssal peridotites, characterized by high contents of Al2O3 (1.28-3.30 anhydrous wt.%); low Cr# of Cr-spinel (0.11-0.27); low Mg# of olivine (˜Fo90) and high Al2O3 in pyroxenes (3.71-6.35 wt.%). They have very low REE concentrations (∑REE = 0.48-2.14 ppb). Lherzolites display LREE-depleted patterns (LaN/SmN = 0.14-0.45) with a flat to slightly fractionated HREE segments (SmN/YbN = 0.30-0.65) whereas Cpx-harburgites have flat to upward-inflected LREE patterns (LaN/SmN = 0.13-1.23) with more fractionated HREE patterns (SmN/YbN = 0.13-0.65) than the lherzolite samples. Their platinum group elements (PGE) contents (<50 ppb) and distinct mantle-normalised PGE patterns with the Pd/Ir values (1.8-11.9) and Pt/Pt* values (0.2-1.1) show an affinity to the characteristic of the residual mantle material. Evaluation of mineralogical and petrological characteristics of these peridotites suggests that they represent the residues remaining after low degree of partial melting (˜2-12%) in the spinel stability field of a mid-oceanic ridge environment. The well-preserved mid-oceanic ridge characteristics of these peridotites further suggest that the mantle section was subsequently trapped in the forearc region of the subduction zone without undergoing significant modification in their chemistry by later subduction-related tectonic and petrological processes before its emplacement to the present crustal level.

  9. 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.

  10. 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.

  11. 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.…

  12. 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…

  13. 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.

  14. 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

  15. Carboniferous rifted arcs leading to an archipelago of multiple arcs in the Beishan-Tianshan orogenic collages (NW China)

    NASA Astrophysics Data System (ADS)

    Tian, Zhonghua; Xiao, Wenjiao; Windley, Brian F.; Zhang, Ji'en; Zhang, Zhiyong; Song, Dongfang

    2016-12-01

    The Beishan and East Tianshan Orogenic Collages in the southernmost Central Asian Orogenic Belt (CAOB) record the final stages of evolution of the Paleo-Asian Ocean. These collages and their constituent arcs have an important significance for resolving current controversies regarding their tectonic setting and age, consequent accretionary history of the southern CAOB, and the closure time of the Paleo-Asian Ocean. In this paper, we present our work on the southern Mazongshan arc and the northern Hongyanjing Basin in the Beishan Orogenic Collage (BOC), and our comparison with the Bogda arc and associated basins in the East Tianshan Orogenic Collage. Field relationships indicate that the Pochengshan fault defines the boundary between the arc and basin in the BOC. Volcanic rocks including basalts and rhyolites in the Mazongshan arc have bimodal calc-alkaline characteristics, an enrichment in large ion lithophile elements such as Rb, Ba, and Pb and depletion in high field-strength elements (e.g., Nb and Ta), which were probably developed in a subduction-related tectonic setting. We suggest that these bimodal calc-alkaline volcanic rocks formed in rifted arcs instead of post-orogenic rifts with mantle plume inputs. By making detailed geochemical comparisons between the Mazongshan arc and the Bogda arc to the west, we further propose that they are similar and both formed in arc rifts, and helped generate a Carboniferous archipelago of multiple arcs in the southern Paleo-Asian Ocean. These data and ideas enable us to postulate a new model for the tectonic evolution of the southern CAOB.

  16. 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.

  17. 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.

  18. 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

  19. 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…

  20. Fused-Ring Oxazolopyrrolopyridopyrimidine Systems with Gram-Negative Activity

    PubMed Central

    Chen, Yiyuan; Moloney, Jonathan G.; Christensen, Kirsten E.; Moloney, Mark G.

    2017-01-01

    Fused polyheterocyclic derivatives are available by annulation of a tetramate scaffold, and been shown to have antibacterial activity against a Gram-negative, but not a Gram-positive, bacterial strain. While the activity is not potent, these systems are structurally novel showing, in particular, a high level of polarity, and offer potential for the optimization of antibacterial activity. PMID:28098784

  1. A System for Monitoring Posture and Physical Activity Using Accelerometers

    DTIC Science & Technology

    2007-11-02

    Abstract- Accelerometers can be used to monitor physical activity in the home over prolonged periods. We describe a novel system for...processing schema in which these parameters are extracted is described. Keywords - physical activity , accelerometers, congestive heart failure, chronic...When monitoring the condition of patients with neurodegenerative or chronic diseases, a knowledge of their body movement and physical activity

  2. Activities for endoscopy information systems standardization in Japan.

    PubMed

    Yokoi, Hideto; Fujino, Masayuki A

    2006-01-01

    There are two activities for Japanese endoscopy information system. One is for a standard terminology (Minimal Standard Terminology: MST) for endoscopy reporting. Other is Integrating Healthcare Enterprise Japan (IHE-J) for an integration of hospital information system. In IHE-J activity, the members revealed specificities of an endoscopy workflow by making a comparison with a radiology workflow. The authors will propose a scheme for systematic standardization based on our experiences in the standardization activities.

  3. Iberseis: A Deep Seismic Reflection Image of A Variscan Transpresive Orogen

    NASA Astrophysics Data System (ADS)

    Carbonell, R.; Simancas, F.; Juhlin, C.; Ayarza, P.; Gonzalez-Loderio, F.; Perez-Estaun, A.; Plata, J.; Iberseis Group

    As part of EUROPROBE's SW Iberia project a 303 km long deep seismic reflection profile was acquired along one of the most complete transects of the Variscan Oro- gen providing key knowledge on fundamental questions about the dynamics of the southwestern European lithosphere. The seismic profile (IBERSEIS) crosses two su- tures that separate three main tectonic terranes which are: South Portuguese Zone, Ossa-Morena Zone and Central Iberian Zone. A prominent mid- lower crustal seismic fabric is observed along the involved terranes. The geometry of the most prominent surface sutures such as the Beja-Acebuches ophiolite and the Badajoz-Córdoba shear zone are clearly identified. A well defined horizontal Moho reveals an approximately constant crustal thikness of 30-33 km along the entire profile. The South Portuguese Zone features a typical geometry of a thrust and fold belt architecture. The high res- olution achieved by the relatively close receiver and shot spacing has imaged very detailed structures within this thin skinned tectonic unit, including thust staks and du- plexes which implying a realtively large crustal shortning. Good structural detail has also been obtained in the Ossa-Morena Zone, which is characterized by the presence of folded recumbent folds and thrusts. At mid-crutal level a high 2-3 s thick band of high reflectivity has been identified across the Ossa-Morena and Central Iberian Zones which is a unique feature among tanspresive orogens. This seismic image provably re- veals the strain partitioning during the oblique transpression tectonics that build up the orogen.

  4. Retrodeformable cross sections for 3-dimensional structural analysis, Ouachita orogen, Arkansas

    NASA Astrophysics Data System (ADS)

    Johnson, H. E.; Wiltschko, D. V.

    2010-12-01

    A fundamental tectonic problem is how deformation proceeds from hinterland to foreland in a fold and thrust belt (FTB). Wedge models explain many of the first-order observations found in most FTBs such as the internal deformation of material, thickening of hinterland, presence of a basal décollement, and an overall wedge shape that tapers to the foreland. These models currently have not been tested at the scale of the individual folds and faults. Moreover, most of the data available on, for instance, the sequence of events is best dated in the syntectonic sediments. Timing of uplift and motion of interior structures are not clear when using dates from these syntectonic sediments to some extent because an absolute connection between them is lacking. The purpose of this project is to develop a model for the evolution of the Ouachita orogen through the construction of a series of retrodeformable cross sections. A novel aspect of these cross sections is the combination of new and published thermal (i.e., illite ‘crystallinity’) and thermochronologic (i.e., zircon fission track) data collected at a variety of stratigraphic depths along the lines of section. These data will help to determine the cessation of thrust motion as well as the initial depth from which the thrust sheet emerged. An Ordovician Mazarn sample in the eastern exposed orogenic core has zircon grains with 55% reset fission track ages, whereas an overlying Ordovician Blakely sample about ~30 km to the southwest along strike has 15% being reset. Illite ‘crystallinity’ (IC) values indicate maximum burial metamorphism temperatures of anchizone (~250-350°C) coinciding with the location of the Ordovician Mazarn sample. Regionally, IC decreases from the culmination of the Benton Uplift and to the southwest along regional strike for samples that have similar stratigraphic age. These new timing and thermal constraints on an improved kinematic model are the necessary first steps in testing wedge models

  5. 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.

  6. Pb isotopic composition of Paleozoic sediments derived from the Appalachian orogen

    SciTech Connect

    Krogstad, E.J. . Dept. of Geology)

    1993-03-01

    Differences in [sup 207]Pb/[sup 204]Pb at restricted ranges of [sup 206]Pb/[sup 204]Pb are robust indicators of differences in the earliest history of crust or mantle reservoirs, surviving later changes in U/Pb that may be due to melting, metamorphism, or sedimentary reworking. Ayuso and Bevier (1991) have used the [sup 207]Pb/[sup 204]Pb differences between Late Paleozoic granites in the N. Appalachians to trace their sources in either Laurentian (Grenville) lithosphere, or docked (Avalonian) lithosphere. If the Pb isotopic composition of Avalonian lithosphere is unique to that source among all lithospheric reservoirs in the Appalachian orogeny, the sediments shed off the orogen should record the first appearance of rocks with this extraneous Pb isotopic composition as they become accreted. The high [sup 207]Pb/[sup 204]Pb at similar [sup 206]Pb/[sup 204]Pb that may be indicative of all outboard terranes occurs in sedimentary rocks younger than middle Ordovician in New York and Maine, and younger than Ordovician in Virginia. Older sediments (Hadrynian, Cambrian), as well as autochthonous basement and paraautochonous basement slices, have lower [sup 207]Pb/[sup 204]Pb at similar [sup 206]Pb/[sup 204]Pb. The low [sup 207]Pb/[sup 204]Pb at similar [sup 206]Pb/[sup 204]Pb shown by these rocks may be a locally diagnostic signature of Late Proterozoic Laurentian lithosphere. The high [sup 207]Pb/[sup 204]Pb at similar [sup 206]Pb/[sup 204]Pb may be a locally diagnostic signature of Late Proterozoic accreted terranes. Rocks with accreted terrane Pb isotopic composition became dominant in the provenance of sediments along the strike of the Appalachian orogen by middle Ordovician time.

  7. 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

  8. Relative strength of lithospheric mantle compared to granulite lower crust in orogenic roots: insight from field laboratory.

    NASA Astrophysics Data System (ADS)

    Kusbach, V.; Ulrich, S.; Schulmann, K.

    2009-04-01

    filled shear zones S3 oriented at high angle to the megafold axial plane. The mineral zoning of coarse-grained peridotite pre-mylonitic microstructure reflects probably metamorphic processes deep in the mantle and is not connected with variations in observed olivine LPO patterns in fine-grained mylonite. The LPO of olivine most likely results from strain partitioning in the intra-mantle transpressive shear zone, along which the mantle sheet was emplaced into orogenic lower crust. At this stage the granulites responded by development of mylonitic fabric S1-2 and the coherency of fabrics may indicate at least partial mechanical coupling and low rheological contrast between lower crust and mantle. The whole sequence was subsequently exhumed, folded and re-deformed at mid-crustal levels during almost orthogonal D3 event. Folding mechanism of peridotite sheet is governed by active amplification, while the flow in retrogressed and partially molten granulites was entirely passive. The folds in front of fold hinge are probably related to propagation of fold head in frontally constrained space, while shear zones in the core of megafold reflect post-buckle flattening. Our observations suggest transient evolution of the rheological contrast between mantle and crust lithologies marked by decrease of competence of partially molten crustal material in mid-crustal levels.

  9. Some comparisons of the structure and evolution of the southern Appalachian Ouachita orogen and portions of the Trans-European Suture Zone region

    NASA Astrophysics Data System (ADS)

    Keller, G. Randy; Hatcher, Robert D.

    1999-12-01

    Many aspects of the tectonic history of the Appalachian-Ouachita orogen and the Trans-European suture region are similar. In a tectonic sense, they are geographically linked, because at the end of the Paleozoic, one could travel from Texas to Poland following a continuous orogenic belt. Much of each of these orogenic belts is, however, buried by younger strata, and thus geophysical studies are a key element of efforts to better understand them. Many more geophysical data are needed to provide a comprehensive picture of the deep structure, but in several areas new models of the lithospheric structure are emerging. In this paper, we review some of these models and introduce two new ones for the southern Appalachians. In addition, we explore the implications of these models for the evolution of these orogenic belts, drawing attention to similarities and differences in their structure and evolution. The Appalachian and Caledonian orogens represent temporally parallel development along irregular Late Proterozoic continental margins, but the crustal structure is different because of different accretionary elements and complications in the geometry of the original margins. Lateral transport via thrusting can confuse efforts to tie geologic structures identified on the surface with deep structures. For example, in the Appalachian-Ouachita orogen, the thrust-related transport distance for major features such as the Blue Ridge-Piedmont sheet and the Benton uplift is at least 200 km. On a crustal scale, deformation in the Appalachian-Ouachita orogen varies greatly in style and intensity. In the Ouachita orogen, the Late Proterozoic continental margin seems to be preserved, while in the northern Appalachians crustal-scale deformation is intense. Along the US Appalachians, the major crustal structure variation is the thin, dense crust of Avalonia abutting the relatively thick crust of Laurentia. Along the Ouachita orogen, several large crustal blocks can be identified that are

  10. 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.

  11. 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.

  12. 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.

  13. Collaborative Point Paper on Active Protection Systems

    DTIC Science & Technology

    2006-10-01

    construction, the silicone immediately becomes soft and flexible again; fabric uses spacer yarns to create 3D structure designed for optimal...absorption of impacting force; fabric’s surface coating and spacer yarns in immediate impact area instantly become rigid and transmit energy to adjacent... spacer yarns , thus absorbing and distributing energy away from impact site; micro- engineering provides maximum protection & leaves system lightweight

  14. 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.

  15. Activation of the methylreductase system from Methanobacterium bryantii by corrins.

    PubMed Central

    Whitman, W B; Wolfe, R S

    1985-01-01

    Corrins activated the methylreductase system from Methanobacterium bryantii three- to fivefold in extracts resolved from low-molecular-weight factors. Corrins did not substitute for ATP and component B, which were also required for maximal activity. The concentration of diaquacobinamides required for one-half maximal activity was 1 microM. The concentrations of cyanocobalamin, methylcobalamin, Co alpha-(5-hydroxybenzimidazoyl)-Co beta-cyanocobamide, and 5'-deoxyadenosylcobinamide required for one-half maximal activity were between 4 and 7 microM. Deoxyadenosylcobalamin was nearly inactive. Activation was independent of thiols, coenzyme M, and ATP. Activation was also observed after partial purification of the methylreductase system by agarose column chromatography. Corrins were required in catalytic concentrations, methylcobalamin was not required, and methanogenesis was enzymatic. Corrin activation of the methylreductase is a novel effect on methanogenesis. However, the physiological significance of the corrin activation is uncertain. PMID:3930464

  16. European Cenozoic rift system

    NASA Astrophysics Data System (ADS)

    Ziegler, Peter A.

    1992-07-01

    The European Cenozoic rift system extends from the coast of the North Sea to the Mediterranean over a distance of some 1100 km; it finds its southern prolongation in the Valencia Trough and a Plio-Pleistocene volcanic chain crossing the Atlas ranges. Development of this mega-rift was paralleled by orogenic activity in the Alps and Pyrenees. Major rift domes, accompanied by subsidence reversal of their axial grabens, developed 20-40 Ma after beginning of rifting. Uplift of the Rhenish Shield is related to progressive thermal lithospheric thinning; the Vosges-Black Forest and the Massif Central domes are probably underlain by asthenoliths emplaced at the crust/mantle boundary. Evolution of this rift system, is thought to be governed by the interaction of the Eurasian and African plates and by early phases of a plate-boundary reorganization that may lead to the break-up of the present continent assembly.

  17. 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.

  18. Synchronization of two different systems by using generalized active control

    NASA Astrophysics Data System (ADS)

    Ho, Ming-Chung; Hung, Yao-Chen

    2002-09-01

    We have already generalized the techniques from active control theory, and applied them to synchronize two different systems. In this Letter, we demonstrate these techniques by period-system, Lorenz and Rossler systems. Moreover, the effect of external noise is also included in our discussion.

  19. 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.

  20. 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

  1. 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

  2. Retinal waves coordinate patterned activity throughout the developing visual system.

    PubMed

    Ackman, James B; Burbridge, Timothy J; Crair, Michael C

    2012-10-11

    The morphological 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 show 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.

  3. 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.

  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. Global positioning system: a new opportunity in physical activity measurement.

    PubMed

    Maddison, Ralph; Ni Mhurchu, Cliona

    2009-11-04

    Accurate measurement of physical activity is a pre-requisite to monitor population physical activity levels and design effective interventions. Global Positioning System (GPS) technology offers potential to improve the measurement of physical activity. This paper 1) reviews the extant literature on the application of GPS to monitor human movement, with a particular emphasis on free-living physical activity, 2) discusses issues associated with GPS use, and 3) provides recommendations for future research. Overall findings show that GPS is a useful tool to augment our understanding of physical activity by providing the context (location) of the activity and used together with Geographical Information Systems can provide some insight into how people interact with the environment. However, no studies have shown that GPS alone is a reliable and valid measure of physical activity.

  6. Global positioning system: a new opportunity in physical activity measurement

    PubMed Central

    Maddison, Ralph; Ni Mhurchu, Cliona

    2009-01-01

    Accurate measurement of physical activity is a pre-requisite to monitor population physical activity levels and design effective interventions. Global Positioning System (GPS) technology offers potential to improve the measurement of physical activity. This paper 1) reviews the extant literature on the application of GPS to monitor human movement, with a particular emphasis on free-living physical activity, 2) discusses issues associated with GPS use, and 3) provides recommendations for future research. Overall findings show that GPS is a useful tool to augment our understanding of physical activity by providing the context (location) of the activity and used together with Geographical Information Systems can provide some insight into how people interact with the environment. However, no studies have shown that GPS alone is a reliable and valid measure of physical activity. PMID:19887012

  7. 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.

  8. 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.

  9. [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.

  10. International Collaboration Activities on Engineered Barrier Systems

    SciTech Connect

    Jove-Colon, Carlos F.

    2016-08-31

    The Used Fuel Disposition Campaign (UFDC) within the DOE Fuel Cycle Technologies (FCT) program has been engaging in international collaborations between repository R&D programs for high-level waste (HLW) disposal to leverage on gathered knowledge and laboratory/field data of near- and far-field processes from experiments at underground research laboratories (URL). Heater test experiments at URLs provide a unique opportunity to mimetically study the thermal effects of heat-generating nuclear waste in subsurface repository environments. Various configurations of these experiments have been carried out at various URLs according to the disposal design concepts of the hosting country repository program. The FEBEX (Full-scale Engineered Barrier Experiment in Crystalline Host Rock) project is a large-scale heater test experiment originated by the Spanish radioactive waste management agency (Empresa Nacional de Residuos Radiactivos S.A. – ENRESA) at the Grimsel Test Site (GTS) URL in Switzerland. The project was subsequently managed by CIEMAT. FEBEX-DP is a concerted effort of various international partners working on the evaluation of sensor data and characterization of samples obtained during the course of this field test and subsequent dismantling. The main purpose of these field-scale experiments is to evaluate feasibility for creation of an engineered barrier system (EBS) with a horizontal configuration according to the Spanish concept of deep geological disposal of high-level radioactive waste in crystalline rock. Another key aspect of this project is to improve the knowledge of coupled processes such as thermal-hydro-mechanical (THM) and thermal-hydro-chemical (THC) operating in the near-field environment. The focus of these is on model development and validation of predictions through model implementation in computational tools to simulate coupled THM and THC processes.

  11. 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.

  12. The function of the earth observing system - Data information system Distributed Active Archive Centers

    NASA Technical Reports Server (NTRS)

    Lapenta, C. C.

    1992-01-01

    The functionality of the Distributed Active Archive Centers (DAACs) which are significant elements of the Earth Observing System Data and Information System (EOSDIS) is discussed. Each DAAC encompasses the information management system, the data archival and distribution system, and the product generation system. The EOSDIS DAACs are expected to improve the access to earth science data set needed for global change research.

  13. A hybrid electromagnetic shock absorber for active vehicle suspension systems

    NASA Astrophysics Data System (ADS)

    Ebrahimi, Babak; Bolandhemmat, Hamidreza; Behrad Khamesee, Mir; Golnaraghi, Farid

    2011-02-01

    The use of electromagnetic dampers (ED) in vehicle active suspension systems has drawn considerable attention in the past few years, attributed to the fact that active suspension systems have shown superior performance in improving ride comfort and road handling of terrain vehicles, compared with their passive and semi-active counterparts. Although demonstrating superb performance, active suspensions still have some shortcomings that must be overcome. They have high energy consumption, weight, and cost and are not fail-safe in case of a power breakdown. The novel hybrid ED, which is proposed in this paper, is a potential solution to the above-mentioned drawbacks of conventional active suspension systems. The proposed hybrid ED is designed to inherit the high-performance characteristics of an active ED with the reliability of a passive damper in a single package. The eddy current damping effect is utilised as a source of the passive damping. First, a prototype ED is designed and fabricated. The prototype ED is then utilised to experimentally establish the design requirements for a real-size active ED. This is accomplished by comparing its vibration isolation performance in a 1-DOF quarter-car test rig with that of a same-class semi-active damper. Then, after a real-size active ED is designed, the concept of hybrid damper is introduced to the damper design to address the drawbacks of the active ED. Finally, the finite-element method is used to accurately model and analyse the designed hybrid damper. It is demonstrated that by introducing the eddy current damping effect to the active part, a passive damping of approximately 1570 Ns/m is achieved. This amount of passive damping guarantees that the damper is fail-safe and reduces the power consumption more than 70%, compared with an active ED in an automotive active suspension system.

  14. 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).

  15. 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.

  16. 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)

  17. Disorder-mediated crowd control in an active matter system

    PubMed Central

    Pinçe, Erçağ; Velu, Sabareesh K. P.; Callegari, Agnese; Elahi, Parviz; Gigan, Sylvain; Volpe, Giovanni; Volpe, Giorgio

    2016-01-01

    Living active matter systems such as bacterial colonies, schools of fish and human crowds, display a wealth of emerging collective and dynamic behaviours as a result of far-from-equilibrium interactions. The dynamics of these systems are better understood and controlled considering their interaction with the environment, which for realistic systems is often highly heterogeneous and disordered. Here, we demonstrate that the presence of spatial disorder can alter the long-term dynamics in a colloidal active matter system, making it switch between gathering and dispersal of individuals. At equilibrium, colloidal particles always gather at the bottom of any attractive potential; however, under non-equilibrium driving forces in a bacterial bath, the colloids disperse if disorder is added to the potential. The depth of the local roughness in the environment regulates the transition between gathering and dispersal of individuals in the active matter system, thus inspiring novel routes for controlling emerging behaviours far from equilibrium. PMID:26956085

  18. Disorder-mediated crowd control in an active matter system

    NASA Astrophysics Data System (ADS)

    Pinçe, Erçağ; Velu, Sabareesh K. P.; Callegari, Agnese; Elahi, Parviz; Gigan, Sylvain; Volpe, Giovanni; Volpe, Giorgio

    2016-03-01

    Living active matter systems such as bacterial colonies, schools of fish and human crowds, display a wealth of emerging collective and dynamic behaviours as a result of far-from-equilibrium interactions. The dynamics of these systems are better understood and controlled considering their interaction with the environment, which for realistic systems is often highly heterogeneous and disordered. Here, we demonstrate that the presence of spatial disorder can alter the long-term dynamics in a colloidal active matter system, making it switch between gathering and dispersal of individuals. At equilibrium, colloidal particles always gather at the bottom of any attractive potential; however, under non-equilibrium driving forces in a bacterial bath, the colloids disperse if disorder is added to the potential. The depth of the local roughness in the environment regulates the transition between gathering and dispersal of individuals in the active matter system, thus inspiring novel routes for controlling emerging behaviours far from equilibrium.

  19. Global vision systems regulatory and standard setting activities

    NASA Astrophysics Data System (ADS)

    Tiana, Carlo; Münsterer, Thomas

    2016-05-01

    A number of committees globally, and the Regulatory Agencies they support, are active delivering and updating performance standards for vision system: Enhanced, Synthetic and Combined, as they apply to both Fixed Wing and, more recently, Rotorcraft operations in low visibility. We provide an overview of each committee's present and past work, as well as an update of recent activities and future goals.

  20. Understanding Tensions: Activity Systems Analysis of Cross-Continental Collaboration

    ERIC Educational Resources Information Center

    Ryder, LanHui Zhang; Yamagata-Lynch, Lisa

    2014-01-01

    Using the lens of Vygotsky's sociocultural theory, activity theory, and Engeström's activity systems analysis, this qualitative study explores students' experiences in the context of a sixteen-week transpacific collaboration between seven students at Northern Illinois University (NIU) and seven students from Shandong Normal University (SDNU),…

  1. Metamorphic evolution and geochronology of the Dunhuang orogenic belt in the Hongliuxia area, northwestern China

    NASA Astrophysics Data System (ADS)

    Wang, Hao Y. C.; Wang, Juan; Wang, Guo-Dong; Lu, Jun-Sheng; Chen, Hong-Xu; Peng, Tao; Zhang, Hui C. G.; Zhang, Qian W. L.; Xiao, Wen-Jiao; Hou, Quan-Lin; Yan, Quan-Ren; Zhang, Qing; Wu, Chun-Ming

    2017-03-01

    Garnet-bearing mafic granulites and amphibolites from the Hongliuxia area of the southern Dunhuang orogenic belt, northwestern China, commonly occur as lenses or boudinages enclosed within metapelite or marble, which represent the block-in-matrix feature typical of orogenic mélange. Three to four generations of metamorphic mineral assemblages are preserved in these rocks. In the high-pressure amphibolites, prograde mineral assemblages (M1) occur as inclusions (hornblende + plagioclase + quartz ± chlorite ± epidote ± ilmenite) preserved within garnet porphyroblasts, and formed at 550-590 °C and 7.7-9.2 kbar based on geothermobarometry. The metamorphic peak mineral assemblages (M2) are composed of garnet + hornblende + plagioclase + quartz + clinopyroxene, as well as titanite + zircon + rutile + apatite as accessory minerals in the matrix, and are estimated to have formed at 640-720 °C and 14.1-16.0 kbar. The first retrograde assemblages (M3) are characterized by "white-eye socket" symplectites (hornblende + plagioclase + quartz ± biotite ± epidote ± magnetite) rimming garnet porphyroblasts, which formed at the expense of the garnet rims and adjacent matrix minerals during the decompression stage under P-T conditions of 610-630 °C and 5.6-11.8 kbar. The second retrograde assemblages (M4) are intergrowths of actinolite and worm-like quartz produced by the breakdown of the matrix hornblendes, and formed under P-T conditions of ∼490 °C and ∼2.8 kbar. For the high-pressure mafic granulites,