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Sample records for eastern kunlun orogenic

  1. Sulfur and lead isotope geochemistry of the orogenic gold deposits in the eastern Kunlun area, Qinghai province

    International Nuclear Information System (INIS)

    Feng Chengyou; Zhang Dequan; Li Daxin; She Hongquan; Zhu Huaping

    2003-01-01

    Based on researches on the basic geological characteristics and sulfur and lead isotopic geochemistry of four typical gold deposits, it is considered that they have many similar geo-geochemical characteristics and are all related genetically to orogenic process. Therefore, they should belong to a type of orogenic gold deposits according to the newest classification of gold deposits provided by Kerrich et al. (2000). There is a big change in the average 34 S values of the sulfides selected from different deposits, varying from -3.7‰-4.4‰ and tower-shape distribution is apparent. The lead isotope in four gold deposits is characterized by high compositions and minor changes, with 206 Pb/ 204 Pb > 18.3380, 207 Pb/ 204 Pb > 15.5555, 208 Pb/ 204 Pb >38.1796 in ores and wall-rocks, it can be concluded that the ore-forming material consisting of sulfur and lead are mainly derived from wall-rocks. Intensive subduction and collision during late Paleozoic and early Mesozoic not only formed deep faults, large-scale shear belt, and low-order folds and faults but also induced fluidization and mineralization, and resulted in formation and zonal distribution of several large or medium gold deposits in this area. (authors)

  2. Apatite fission track evidence on the uplifting of eastern Kunlun mountains

    International Nuclear Information System (INIS)

    Yuang Wanming; Dong Jinquan; Tang Yunhui; Wang Shicheng

    2004-01-01

    A series of samples were collected from about south-north section through Buqingshan and Dulan, eastern Kunlun mountains, China. The 41 apatite fission track ages (FTA) of these samples lie between 25.2 and 130.4 Ma, all of the apatite fission track ages are significantly younger than the host rocks. There are similar evolution trends for Middle-Kunlun zone and North-Kunlun zone, i.e. the FTA becomes less with slow increase of elevations and their uplifting rates are about 2.22 m/Ma. Differently, the FTA in South-Kunlun zone positively correlates to elevation, decreasing 11 m/Ma. It may be shown that South-Kunlun fault play a different and/or more important role on incontinent evolution than Middle-Kunlun fault. (author)

  3. A new vision of the intracontinental evolution of the eastern Kunlun Mountains, Northern Qinghai-Tibet plateau, China

    International Nuclear Information System (INIS)

    Yuan, W.-M.; Zhang, X.-T.; Dong, J.-Q.; Tang, Y.-H.; Yu, F.-S.; Wang, S.-C.

    2003-01-01

    Based on apatite fission track ages (FTA) of 41 samples collected from a south-north transect of the eastern Kunlun mountains, Qinghai-Tibet Plateau, China, this paper shows that (1) the FTA in different blocks increases with the distance from the South-Kunlun fault and Mid-Kunlun faults, respectively, indicating the control of the main faults on the tectonic evolution of this region; and (2) the thermal histories are characterized by slow cooling from ∼160 deg. C to ∼80 deg. C at ∼240 to ∼20 Ma, followed by rather rapid cooling to surface temperatures

  4. Origin of the Bashierxi monzogranite, Qiman Tagh, East Kunlun Orogen, NW China: A magmatic response to the evolution of the Proto-Tethys Ocean

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    Zheng, Zhen; Chen, Yan-Jing; Deng, Xiao-Hua; Yue, Su-Wei; Chen, Hong-Jin; Wang, Qing-Fei

    2018-01-01

    The Qiman Tagh of the East Kunlun Orogen, NW China, lies within the Tethysides and hosts a large W-Sn belt associated with the Bashierxi monzogranite. To constrain the origin of the granitic magmatism and its relationship with W-Sn mineralization and the tectonic evolution of the East Kunlun Orogen and the Tethys, we present zircon U-Pb ages and Hf isotopic data, and whole-rock compositional and Sr-Nd-Pb isotopic data of the Bashierxi monzogranite. The granite comprises quartz, K-feldspar, plagioclase, and minor muscovite, tourmaline, biotite, and garnet. It contains high concentrations of SiO2, K2O, and Al2O3, and low concentrations of TiO2 and MgO, indicating a peraluminous high-K calc-alkaline affinity. The rocks are enriched in Rb, U, Pb, and light rare earth elements, and relatively depleted in Eu, Ba, Nb, Sr, P, and Ti, and are classified as S-type granites. Twenty zircon grains yield a weighted mean 238U/206Pb age of 432 ± 2.6 Ma (mean square weighted deviation = 1.3), indicating the occurrence of a middle Silurian magmatic event in the region. Magmatic zircons yield εHf(t) values of -6.7 to 0.7 and corresponding two-stage Hf model ages of 1663-1250 Ma, suggesting that the granite was derived from Mesoproterozoic crust, as also indicated by 207Pb/206Pb ages of 1621-1609 Ma obtained from inherited zircon cores. The inherited zircon cores yield εHf(t) values of 8.3-9.6, which indicate the generation of juvenile crust in the late Paleoproterozoic. Samples of the Bashierxi granite yield high initial 87Sr/86Sr ratios and radiogenic Pb concentrations, and negative εNd(t) values. Isotopic data from the Bashierxi granite indicate that it was derived from partial melting of ancient (early Paleozoic to Mesoproterozoic) sediments, possibly representing recycled Proterozoic juvenile crust. Middle Silurian granitic magmatism resulted from continental collision following closure of the Proto-Tethys Ocean. The Qiman Tagh represents a Caledonian orogenic belt containing

  5. Apatite fission track analysis for revealing tectonic events of the Bayinguole area in the west section of Eastern Kunlun Mountains, northern Qinghai-Tibet Plateau

    International Nuclear Information System (INIS)

    Chen Xiaoning; Yuan Wanming; Hao Nana; Duan Hongwei; Feng Yunlei; Zhang Aikui

    2014-01-01

    Background: Qimantage is an important tectonic metallogenic belt in western part of East Kunlun Mountain. It has experienced complex geological evolution, and significant mineralization. However, because of the plateau climate and inaccessibility, fewer research works have been done on this area, especially after Indo-sinian epoch. Purpose: Our work is to research tectonic activity, thermal history and uplifting around Bayinguole river in Qimantage belt. Methods: The apatite fission-track method was applied to research the tectonic setting, simulate the thermal history and calculate the uplift size and uplift speed. Results: A series of apatite fission track ages from granitoid samples in Bayinguole area of Eastern Kunlun Mountain were obtained, ranging from 120 Ma to 47 Ma that might be divided into three groups': 120-100 Ma, 67 Ma and 54-47 Ma. These ages reflected tectonic events in this area very well. Conclusions: The 120-100 Ma and 67 Ma ages present collision-convergences of Gangdese terrane and Himalayan terrane with their north-side terranes in Early Cretaceous and Late Cretaceous respectively. The ages of 54-47 Ma reflect post-orogenic stretching events in Eocene. Three stages of thermal evolution history are revealed by apatite fission track modeling in this area. Stage one 180-140 Ma is in the bottom temperature of apatite fission track anneal zone. Stage two 140-13 Ma records slow cooling. The last stage after 13 Ma records rapid cooling with temperature dropped 50℃. The uplifting ranges for these three stages are 1.0 km, 0.6 km and 1.4 km, respectively. The cumulative amount of uplift is about 3.0 km. The formula calculations for the 3 samples have their rock uplifts of 3623 m, 3317 m and 3769 m, respectively, averaging 3570 m, in accordance with the results based on the 3 stage thermal history. (authors)

  6. Shoshonitic- and adakitic magmatism of the Early Paleozoic age in the Western Kunlun orogenic belt, NW China: Implications for the early evolution of the northwestern Tibetan plateau

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    Wang, Jian; Hattori, Keiko; Liu, Jianguo; Song, Yue; Gao, Yongbao; Zhang, Han

    2017-08-01

    The Western Kunlun orogenic belt in the northwestern margin of the Tibetan plateau contains two magmatic belts; early Paleozoic belt in the northern part of Western Kunlun Terrane (WKT), and early Mesozoic belt in the southern part of WKT. Both formed from northward subduction of the Paleo-Tethys. The early Paleozoic belt contains large Datong and Qiukesu igneous complexes and many smaller plutons. The Datong complex is mainly composed of dark-colored porphyritic syenite and monzonite with minor light-colored dykes of granite and monzonite. The dark-colored rocks are characterized by moderate SiO2 (58.2-69.3 wt.%), and high Al2O3 (15.3-17.1 wt.%), total alkali (Na2O + K2O = 8.07-10.2 wt.%) and ratios of K2O/Na2O (0.77-1.83). They plot in "shoshonite" field, and show high abundances of LILE including LREE ((La/Yb)n = 15.4-26.2; mean 20.2) with pronounced negative anomalies of Nb-Ta-P-Ti in normalized trace elemental patterns and weak negative anomalies of Eu (δEu = 2Eun/(Smn + Gdn) = 0.68-0.80). The light-colored rocks contain slightly higher concentrations of SiO2 (60.3-72.0 wt.%), similar Al2O3 (14.7-17.6 wt.%), and slightly lower total alkalis (6.57-9.14 wt.%) than dark-colored rocks. They show adakitic geochemical signatures with low Y (5.80-17.2 ppm) and Yb (0.63-1.59 ppm), and high Sr/Y (> 40). U-Pb zircon dating indicates that shoshonitic rocks and adakitic dykes formed at 444 Ma to 443 Ma, and a separate small adakitic plug at 462 Ma. The mean εHf(t) values of zircon range from - 1.6 to - 0.94 (n = 14) with TDM2 of 1.5 Ga for shoshonitic rocks and εHf(t) values from - 1.8 to + 0.72 (n = 12) with TDM2 of 1.4 to 1.5 Ga for adakitic rocks. Shoshonitic rocks show initial 87Sr/86Sr and εNd(t) of 0.7092-0.7100 and - 3.9 to - 3.2, respectively, and adakitic rocks yield initial 87Sr/86Sr and εNd(t) of 0.7099-0.7134 and - 3.6 to - 3.1, respectively. Similar Sr, Nd, and Hf isotope compositions for the shoshonitic and adakitic rocks suggest similar ancient rocks

  7. Provenance and tectonic setting of siliciclastic rocks associated with the Neoproterozoic Dahongliutan BIF: Implications for the Precambrian crustal evolution of the Western Kunlun orogenic belt, NW China

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    Hu, Jun; Wang, He; Wang, Min

    2017-10-01

    The Late Neoproterozoic Dahongliutan BIF is associated with siliciclastic rocks in the Tianshuihai terrane of the Western Kunlun orogenic belt (WKO), NW China. The sedimentary rocks have various weathering indices (e.g., CIA = 57-87, PIA = 61-96 and Th/U = 4.85-12.45), indicative of varying degrees of weathering in the source area. The rocks have trace element ratios, such as Th/Sc = 0.60-1.21 and Co/Th = 0.29-1.67, and light rare earth element (LREE) enriched chondrite-normalized REE patterns, suggesting that they were mainly sourced from intermediate and felsic rocks. Available U-Pb ages of detrital zircon from these rocks reveal that the detrital sources may have been igneous and metamorphic rocks from the WKO and the Tarim Block. Our study suggests that the Dahongliutan BIF and hosting siliciclastic rocks may have deposited in a setting transitional from a passive to active continental margin, probably related to the Late Neoproterozoic-Early Cambrian seafloor spreading and subduction of the Proto-Tethys Ocean. U-Pb dating of 163 detrital zircons defines five major age populations at 2561-2329 Ma, 2076-1644 Ma, 1164-899 Ma, 869-722 Ma and 696-593 Ma. These age groups broadly correspond to the major stages of supercontinent assembly and breakup events widely accepted for Columbia, Rodinia and Gondwana. Some zircons have TDM2 model ages of 3.9-1.8 Ga and negative εHf(t) values, suggesting that the Archean to Paleoproterozoic (as old as Eoarchean) crustal materials were episodically reworked and incorporated into the late magmatic process in the WKO. Some Neoproterozoic zircons have TDM2 model ages of 1.47-1.07 Ga and 1.81-1.53 Ga and positive εHf(t) values, indicating juvenile crustal growth during the Mesoproterozoic. Our new results, combined with published data, imply that both the Tianshuihai terrane in the WKO and the Tarim Block share the same Precambrian tectonic evolution history.

  8. Orogen-transverse tectonic window in the Eastern Himalayan fold belt: A superposed buckling model

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    Bose, Santanu; Mandal, Nibir; Acharyya, S. K.; Ghosh, Subhajit; Saha, Puspendu

    2014-09-01

    The Eastern Lesser Himalayan fold-thrust belt is punctuated by a row of orogen-transverse domal tectonic windows. To evaluate their origin, a variety of thrust-stack models have been proposed, assuming that the crustal shortening occurred dominantly by brittle deformations. However, the Rangit Window (RW) in the Darjeeling-Sikkim Himalaya (DSH) shows unequivocal structural imprints of ductile deformations of multiple episodes. Based on new structural maps, coupled with outcrop-scale field observations, we recognize at least four major episodes of folding in the litho-tectonic units of DSH. The last episode has produced regionally orogen-transverse upright folds (F4), the interference of which with the third-generation (F3) orogen-parallel folds has shaped the large-scale structural patterns in DSH. We propose a new genetic model for the RW, invoking the mechanics of superposed buckling in the mechanically stratified litho-tectonic systems. We substantiate this superposed buckling model with results obtained from analogue experiments. The model explains contrasting F3-F4 interferences in the Lesser Himalayan Sequence (LHS). The lower-order (terrain-scale) folds have undergone superposed buckling in Mode 1, producing large-scale domes and basins, whereas the RW occurs as a relatively higher-order dome nested in the first-order Tista Dome. The Gondwana and the Proterozoic rocks within the RW underwent superposed buckling in Modes 3 and 4, leading to Type 2 fold interferences, as evident from their structural patterns.

  9. Geothermal constraints on enrichment of boron and lithium in salt lakes: An example from a river-salt lake system on the northern slope of the eastern Kunlun Mountains, China

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    Tan, Hongbing; Chen, Jun; Rao, Wenbo; Zhang, Wenjie; Zhou, Huifang

    2012-06-01

    Some rivers on the northern slope of the eastern Kunlun Mountains in the Qaidam Basin, China, show very high concentrations of boron and lithium. Correspondingly, the salt lakes fed by these rivers show an unusual enrichment of boron and lithium, and become an important economic resource. The origin of boron and lithium has long been debated. The aim of this study is to analyze the water chemistry and hydrogen and oxygen isotopic composition of river water to understand the unusual enrichment of boron and lithium in the salt lakes of the Qaidam Basin. Oxygen and hydrogen isotope data show that the source of river water in the winter and summer originates from the Kunlun Mountain ice and snow melt water, respectively. The water chemistry shows that boron and lithium contents are high but little variable with seasons in the Nalenggele River and Wutumeiren River waters. By contrast, other rivers have much lower lithium and boron contents. Moreover, the contents of B3+ and Li+ in the river loads or bed sands show little difference amongst the rivers. This indicates that removal by adsorption or input by surface rock weathering is not the main controlling factor of the B3+ and Li+ variation in the rivers. Rivers with high B3+ and Li+ content are chemically similar to geothermal waters in the Tibetan Plateau. In addition, the source area of the Nalenggele River is located in a collision zone of the Kunlun Mountains and Altun Mountains. Large and deep faults can serve as conduits for geothermal fluids. Thus, deep geothermal waters in the source area can easily migrate to the surface and discharge as springs feeding the rivers. They are an important source of B3+ and Li+ to the rivers. The abnormally high contents of B3+ and Li+ in the Nalenggele and Wutumeiren Rivers also suggest that the geothermal source area may be a future target for boron and lithium resources.

  10. Geothermal structure of the eastern Black Sea basin and the eastern Pontides orogenic belt: Implications for subduction polarity of Tethys oceanic lithosphere

    Directory of Open Access Journals (Sweden)

    Nafiz Maden

    2013-07-01

    Full Text Available The numerical results of thermal modeling studies indicate that the lithosphere is cold and strong beneath the Black Sea basin. The thermal lithospheric thickness increases southward from the eastern Pontides orogenic belt (49.4 km to Black Sea basin (152.2 km. The Moho temperature increases from 367 °C in the trench to 978 °C in the arc region. The heat flow values for the Moho surface change between 16.4 mW m−2 in the Black Sea basin and 56.9 mW m−2 in the eastern Pontides orogenic belt. Along the southern Black Sea coast, the trench region has a relatively low geothermal potential with respect to the arc and back-arc region. The numerical studies support the existence of southward subduction beneath the Pontides during the late Mesozoic–Cenozoic.

  11. Eastern Turkish high plateau as a small Turkic-type orogen: Implications for post-collisional crust-forming processes in Turkic-type orogens

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    Şengör, A. M. Celâl; Özeren, Mehmet Sinan; Keskin, Mehmet; Sakınç, Mehmet; Özbakır, Ali Değer; Kayan, İlhan

    Post-collisional magmatism may be generated by extensive crustal melting in Tibet-type collisional environments or by falling out of slabs from under giant subduction-accretion complexes in Turkic-type collisional orogens giving rise to decompression melting of the asthenospheric mantle replacing the removed oceanic lithosphere. In Turkic-type post-collisional magmatism, the magmatic products are dominantly alkalic to peralkalic and greatly resemble those of extensional regions giving rise to much confusion especially in interpreting old collisional orogenic belts. Such magmatic regions are also host to a variety of economically valuable ore deposits, including gold. One place in the world where today active, Turkic-type post-collisional magmatism is present is the eastern Anatolian high plateau, produced after the terminal Arabia/Eurasia collision in the late Miocene. The plateau is mostly underlain by the late Cretaceous to Oligocene East Anatolian Accretionary Complex, which formed south of the Rhodope-Pontide magmatic arc. This subduction-accretion complex has been further shortening since the collision, but it has also since been domed and became almost entirely covered by at least 15,000 km 3 of volcanic rocks. The volcanic rocks are calc-alkalic in the north, transitional in the middle, and alkalic in the south of the plateau. Where the crust is thinnest today (less than 38 km), the volcanics are derived almost entirely from an enriched mantle. The ages of the volcanics also become younger from north to south, from about 11 Ma to possibly 17th century AD. We interpret the origin of the magmatic rocks as the result of decompression melting of the asthenospheric mantle sucked towards the exposed base of the East Anatolian Accretionary Complex as the oceanic lithosphere beneath it fell out. The lower density of the hot asthospheric material was the cause of the doming. We believe that similar processes dominated the post-collisional tectonics of such vast

  12. Seismic evidence for multiple-stage exhumation of high/ultrahigh pressure metamorphic rocks in the eastern Dabie orogenic belt

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    Luo, Yinhe; Zhao, Kaifeng; Tang, Chi-Chia; Xu, Yixian

    2018-05-01

    The Dabie-Sulu orogenic belt in China contains one of the largest exposures of high and ultrahigh pressure (HP and UHP) metamorphic rocks in the world. The origin of HP/UHP metamorphic rocks and their exhumation to the surface in this belt have attracted great interest in the geologic community because the study of exhumation history of HP/UHP rocks helps to understand the process of continental-continental collision and the tectonic evolution of post-collision. However, the exhumation mechanism of the HP-UHP rocks to the surface is still contentious. In this study, by deploying 28 broadband seismic stations in the eastern Dabie orogenic belt and combining seismic data from 40 stations of the China National Seismic Network (CNSN), we image the high-resolution crustal isotropic shear velocity and radial anisotropy structure using ambient noise tomography. Our high-resolution 3D models provide new information about the exhumation mechanism of HP/UHP rocks and the origin of two dome structures.

  13. Strain histories from the eastern Central Range of Taiwan: A record of advection through a collisional orogen

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    Mondro, Claire A.; Fisher, Donald; Yeh, En-Chao

    2017-05-01

    In the eastern Central Range of Taiwan there is a regional variation in the orientation of maximum finite stretch across the slate belt, with down-dip maximum stretch found in the western Central Range and along-strike maximum stretch in the eastern Central Range. Incremental strain histories from syntectonic fibers in pyrite pressure shadows indicate a progressive change in extension direction from down dip to along strike during deformation, there is a corresponding temporal variation in stretching direction shown in samples from the eastern edge of the Central Range, a pattern that mimics the regional west-to-east spatial variation. These observed temporal and spatial strain distributions are used to evaluate the kinematics associated with slaty cleavage development during advection through the Taiwan orogenic system. The subduction zone beneath the island of Taiwan is influenced by two types of obliquity that have the potential to generate the observed along-strike stretching. First, the plate motion vector of the Philippine Sea plate relative to the Eurasian plate is slightly oblique to the regional strike of the mountain range, which could result in partitioning of strike slip shearing into the interior of the collision. Second, the north-south Luzon volcanic arc on the Philippine Sea Plate is obliquely oriented relative to the northeast-southwest edge of the Eurasian continental margin, which could result in lateral extrusion of the ductile core of the range. Incremental strain histories in cleavage-parallel samples represent a time-for-space equivalence where the stretching direction is fixed relative to the position within the mountain belt architecture (e.g., the topographic divide), and temporal variations in the eastern central Range reflect lateral advection through the strain field in response to accretionary and erosional fluxes. Incremental strain histories in cleavage perpendicular samples show both clockwise and counter-clockwise rotation of

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

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

    2015-10-01

    high Hg content (up to 11 mass %). The Cu-Au deposits in the Flatschach area show similarities with meso- to epizonal orogenic lode gold deposits regarding the geological setting, the structural control of mineralization, the type of alteration, the early (stage 1) sulfide assemblage and composition of gold. Unique about the Flatschach district is the lower-temperature overprint of copper arsenides (domeykite and koutekite) and copper sulfides (djurleite, yarrowite/spionkopite) on earlier formed sulfide mineralization. Based on mineralogical considerations temperature of stage 2 mineralization was between about 70 °C and 160 °C. Gold was locally mobilized during this low-temperature hydrothermal overprint as well as during stage 3 supergene oxidation and cementation processes.

  15. Kanfenggou UHP Metamorphic Fragment in Eastern Qinling Orogen and Its Relationship to Dabie-Sulu UHP and HP Metamorphic Belts, Central China

    Institute of Scientific and Technical Information of China (English)

    Suo Shutian; Zhong Zengqiu; Zhou Hanwen; You Zhendong

    2003-01-01

    In the Central Orogenic Belt, China, two UHP metamorphic belts are discriminated mainly based on a detailed structural analysis of the Kanfenggou UHP metamorphic fragment exposed in the eastern Qinling orogen, and together with previous regional structural, petrological and geochronological data at the scale of the orogenic domain. The first one corresponds to the South Altun-North QaidamNorth Qinling UHP metamorphic belt. The other is the Dabie-Sulu UHP and HP metamorphic belts. The two UHP metamorphic belts are separated by a series of tectonic slices composed by the Qinling rock group, Danfeng rock group and Liuling or Foziling rock group etc. respectively, and are different in age of the peak UHP metamorphism and geodynamic implications for continental deep subduction and collision. Regional field and petrological relationships suggest that the Kanfenggou UHP metamorphic fragment that contains a large volume of the coesite- and microdiamond-bearing eclogite lenses is compatible with the structures recognized in the South Altun and North Qaidam UHP metamorphic fragments exposed in the western part of China, thereby forming a large UHP metamorphic belt up to 1 000 km long along the orogen strike. This UHP metamorphic belt represents an intercontinental deep subduction and collision belt between the Yangtze and Sino-Korean cratons, occurred during the Paleozoic. On the other hand, the well-constrained Dabie-Sulu UHP and HP metamorphic belts occurred mainly during Triassic time (250-220 Ma), and were produced by the intrucontinental deep subduction and collision within the Yangtze craton. The Kanfenggou UHP metamorphic fragment does not appear to link with the Dabie-Sulu UHP and HP metamorphic belts along the orogen. There is no reason to assume the two UHP metamorphic belts us a single giant deep subduction and collision zone in the Central Orogenic Belt situated between the Yangtze and Sino-Korean cratons. Therefore, any dynamic model for the orogen must account

  16. Comparison of the November 2002 Denali and November 2001 Kunlun Earthquakes

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    Bufe, C. G.

    2002-12-01

    Major earthquakes occurred in Tibet on the central Kunlun fault (M 7.8) on November 14, 2001 (Lin and others, 2002) and in Alaska on the central Denali fault (M 7.9) on November 3, 2002. Both earthquakes generated large surface waves (Kunlun Ms 8.0 (USGS) and Denali Ms 8.5). Each event occurred on east-west-trending strike-slip faults and exhibited nearly unilateral rupture propagating several hundred kilometers from west to east. Surface rupture length estimates were about 400 km for Kunlun, 300 km for Denali. Maximum surface faulting and moment release were observed far to the east of the points of rupture initiation. Harvard moment centroids were located east of USGS epicenters by 182 km (Kunlun) and by 126 km (Denali). Maximum surface faulting was observed near 240 km (Kunlun, 16 m left lateral) and near 175 km (Denali, 9 m right lateral) east of the USGS epicenters. Significant thrust components were observed in the initiation of the Denali event (ERI analysis and mapped thrust) and in the termination of the Kunlun rupture, as evidenced by thrust mechanisms of the largest aftershocks which occurred near the eastern part of the Kunlun rupture. In each sequence the largest aftershock was about 2 orders of magnitude smaller than the mainshock. Moment release along the ruptured segments was examined for the 25-year periods preceding the main shocks. The Denali zone shows precursory accelerating moment release with the dominant events occurring on October 22, 1996 (M 5.8) and October 23, 2002 (M 6.7). The Kunlun zone shows nearly constant moment release over time with the last significant event before the main shock occurring on November 26, 2000 (M 5.4). Moment release data are consistent with previous observations of annual periodicity preceding major earthquakes, possibly due to the evolution of a critical state with seasonal and tidal triggering (Varnes and Bufe, 2001). Annual periodicity is also evident for the larger events in the greater San Francisco Bay

  17. Discovery of Latest Cretaceous OIB-type alkaline gabbros in the Eastern Pontides Orogenic Belt, NE Turkey: Evidence for tectonic emplacement of seamounts

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    Eyuboglu, Yener; Dudas, Francis O.; Chatterjee, Nilanjan; Liu, Ze; Yılmaz-Değerli, Sedanur

    2018-06-01

    The Meso-Cenozoic geodynamic evolution of the Eastern Pontides Orogenic Belt, a mountain chain extending parallel to the southeastern margin of the Black Sea, has been controversial for the last forty years. Here we present data for a newly discovered alkaline gabbro body and its surrounding basaltic rocks in the northern part of the Eastern Pontides Orogenic Belt. We also provide a comprehensive assessment of the Late Mesozoic-Cenozoic geodynamic evolution of the Eastern Mediterranean region. The gabbroic body is bounded by reverse faults along its northern and southern borders and is surrounded by vesicular, pillow-fragment breccias and pillow basalts. Mineral compositions suggest that crystallization of the gabbros began at about 1170 °C, and the lowest preserved crystallization T is near 1000 °C. Estimated pressure at the beginning of crystallization is 5.7-7.4 kb. The 40Ar/39Ar dating of kaersutite and plagioclase and Usbnd Pb dating of titanite indicated that the Hayrat gabbro crystallized at 67 Ma (Late Maastrichtian). Whole rock major-trace-rare earth element and Sr-Nd-Pb isotope data indicate that the gabbros and basalts have different origins. The gabbros are alkaline and exhibit the geochemical features of OIB, whereas the basalts are tholeiitic and reveal depletions of HFSE that are similar to those of arc rocks. The gabbros are strongly fractionated, and derive from an enriched, lithospheric mantle source, with partial melting occurring in a garnet-stable environment. The basalts are less fractionated, and probably derive from a shallower source in which spinel peridotite was the predominant lithology. Considering all new and old geological, geochemical, geochronological and geophysical data from the Black Sea Basin and the Eastern Pontides-Lesser Caucasus-Alborz Orogenic Belt, we suggest that the alkaline Hayrat gabbro formed in an oceanic intraplate setting, and was accreted to the forearc region of the Eastern Pontides Orogenic Belt during

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

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    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

  19. 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

    Science.gov (United States)

    Doebrich, J.L.; Al-Jehani, A. M.; Siddiqui, A.A.; Hayes, T.S.; Wooden, J.L.; Johnson, P.R.

    2007-01-01

    The Neoproterozoic Ar Rayn terrane is exposed along the eastern margin of the Arabian shield. The terrane is bounded on the west by the Ad Dawadimi terrane across the Al Amar fault zone (AAF), and is nonconformably overlain on the east by Phanerozoic sedimentary rocks. The terrane is composed of a magmatic arc complex and syn- to post-orogenic intrusions. The layered rocks of the arc, the Al Amar group (>689 Ma to ???625 Ma), consist of tholeiitic to calc-alkaline basaltic to rhyolitic volcanic and volcaniclastic rocks with subordinate tuffaceous sedimentary rocks and carbonates, and are divided into an eastern and western sequence. Plutonic rocks of the terrane form three distinct lithogeochemical groups: (1) low-Al trondhjemite-tonalite-granodiorite (TTG) of arc affinity (632-616 Ma) in the western part of the terrane, (2) high-Al TTG/adakite of arc affinity (689-617 Ma) in the central and eastern part of the terrane, and (3) syn- to post-orogenic alkali granite (607-583 Ma). West-dipping subduction along a trench east of the terrane is inferred from high-Al TTG/adakite emplaced east of low-Al TTG. The Ar Rayn terrane contains significant resources in epithermal Au-Ag-Zn-Cu-barite, enigmatic stratiform volcanic-hosted Khnaiguiyah-type Zn-Cu-Fe-Mn, and orogenic Au vein deposits, and the potential for significant resources in Fe-oxide Cu-Au (IOCG), and porphyry Cu deposits. Khnaiguiyah-type deposits formed before or during early deformation of the Al Amar group eastern sequence. Epithermal and porphyry deposits formed proximal to volcanic centers in Al Amar group western sequence. IOCG deposits are largely structurally controlled and hosted by group-1 intrusions and Al Amar group volcanic rocks in the western part of the terrane. Orogenic gold veins are largely associated with north-striking faults, particularly in and near the AAF, and are presumably related to amalgamation of the Ar Rayn and Ad Dawadimi terranes. Geologic, structural, and metallogenic

  20. An evolving tectonic environment of Late Carboniferous to Early Permian granitic plutons in the Chinese Altai and Eastern Junggar terranes, Central Asian Orogenic Belt, NW China

    Science.gov (United States)

    Zhang, Chen; Liu, Dongdong; Luo, Qun; Liu, Luofu; Zhang, Yunzhao; Zhu, Deyu; Wang, Pengfei; Dai, Quanqi

    2018-06-01

    The Central Asian Orogenic Belt (CAOB) represents one of the most important sites of juvenile crustal growth during the Phanerozoic. Located in the central part of the CAOB, the Chinese Altai and Eastern Junggar terranes record the collisional processes between the peri-Siberian and Kazakhstan orogenic systems. However, the precise timing of collision between the two terranes remains controversial. The Wukuli and Kadelat plutons in the Chinese Altai belt are dated at ∼305 and ∼280 Ma respectively, whereas the Aketas pluton in the Eastern Junggar terrane is dated at ∼308 Ma. Granites from the Wukuli and Kadelat plutons are strongly peraluminous (A/CNK > 1.1), and are characterized by low Al2O3, Na2O, MnO, MgO, CaO and heavy rare earth element (HREE) contents, but with high SiO2, K2O and Rb contents as well as high Rb/Sr ratios. Granites from the Wukuli pluton have low εNd(t) and εHf(t) values of -3.7 to -3.4 and -9.7 to +4.9, whereas those from the Kadelat pluton have values of -3.6 to -3.4 and -8.0 to +2.6. These features suggest S-type affinity for the Wukuli and Kadelat plutons with magma derivation through partial melting of Mesoproterozoic metasediments. The Aketas pluton is composed of weakly peraluminous quartz monzonites that have A/CNK values ranging from 0.92 to 1.08, with high Na2O, Sr, and Sr/Y, and low Y, Yb, Nb, and Ta. These rocks display positive εNd(t) (+4.8 to +6.4) and εHf(t) (+9.7 to +14.6) values, and low initial 87Sr/86Sr ratios (0.703357-0.703868), similar to modern adakites, suggesting that the quartz monzonites were derived from the partial melting of lower crustal material. The geochemical characteristics suggest that the Aketas pluton was formed in a subduction-related setting, the Wukuli pluton in a syn-collisional setting, and the Kadelat pluton in the subsequent post-orogenic strike-slip-related setting. In combination with data from other granitoids in these two terranes, the Aketas pluton represents the youngest record of

  1. Extensional collapse in the Neoproterozoic Araçuaí orogen, eastern Brazil: a setting for reactivation of asymmetric crenulation cleavage

    Science.gov (United States)

    Marshak, Stephen; Alkmim, Fernando F.; Whittington, Alan; Pedrosa-Soares, Antônio Carlos

    2006-01-01

    The Araçuaí orogen of eastern Brazil is one of many Brasiliano/Pan African orogens formed during the Neoproterozoic assembly of Gondwana. Its western edge, bordering the São Francisco craton, is the Serra do Espinhaço fold-thrust belt, in which top-up-to-the-west (reverse-sense) faults, west-verging folds (F 1), and east-dipping spaced to phyllitic cleavage (S 1) developed. We have found that the kinematics of deformation changes markedly at the hinterland margin of this fold-thrust belt. Here, beneath a plateau known as the Chapada Acauã, metadiamictite and fine-grained pelitic schist comprise an east-dipping belt that contains an assemblage of structures indicative of top-down-to-the-east (normal-sense) shear. This assemblage includes a cascade of F 2 folds that refold F 1 folds and verge down the dip of the belt's enveloping surfaces, vertical tension gashes, and top-down-to-the-east rotated clasts. Based on the presence of these structures, we propose that the plateau exposes a regional-scale normal-sense shear zone, here called the Chapada Acauã shear zone (CASZ). Because F 2 folds refold F 1 folds, normal-sense shear in the CASZ occurred subsequent to initial west-verging thrusting. Considering this timing of motion in the CASZ, we suggest that the zone accommodated displacement of the internal zone of the Araçuaí orogen down, relative to its foreland fold-thrust belt, and thus played a role in extensional collapse of the orogen. The CASZ trends parallel to preserved thrusts to the west, and thus may represent an inverted thrust fault. Notably, throughout the CASZ, S 1 schistosity has been overprinted by a pervasive, west-dipping asymmetric crenulation cleavage (S 2). The sigmoid shape of S 1 surfaces in S 2 microlithons require that slip on each S 2 surface was top-down-to-the-west. S 2 cleavage is axial-planar to the down-dip verging F 2 folds. Based on its geometry, we suggest that S 2 cleavage initiated either as an antithetic extensional

  2. Records of Mesoproterozoic taphrogenic events in the eastern basement of the Araçuaí Orogen, southeast Brazil

    Directory of Open Access Journals (Sweden)

    Tobias Maia Rabelo Fonte-Boa

    Full Text Available ABSTRACT: The history of palaeocontinents alternates long fragmentation to drift periods with relatively short agglutination intervals. One of the products of a Rhyacian-Orosirian orogeny was a palaeocontinent that brought together the basement of the Araçuaí-West Congo orogen (AWCO with regions now located in the São Francisco and Congo cratons. From ca. 2 Ga to ca. 0.7 Ga, this large region of the São Francisco-Congo palaeocontinent was spared of orogenic events, but underwent at least five taphrogenic events recorded by anorogenic magmatism and/or sedimentation. The taphrogenic events are well documented in the AWCO proximal portions and neighboring cratonic regions, but lack evidence in the AWCO high-grade core. Our studies on amphibolites intercalated in the Rhyacian Pocrane complex, basement of the Rio Doce magmatic arc, allowed to the recognition of two Mesoproterozoic taphrogenic episodes. The oldest one, a Calymmian episode, is recorded by amphibolites with a zircon magmatic crystallization age at 1529 ± 37 Ma (U-Pb SHRIMP, and lithochemical signature of basaltic magmatism related to continental intraplate settings. Another set of amphibolite bodies records the youngest taphrogenic episode, a Stenian event, with a zircon magmatic crystallization age at 1096 ± 20 Ma (U-Pb SHRIMP, and lithochemical signature similar to mature magmatism of continental rift setting. The Calymmian episode (ca. 1.5 Ga correlates to the Espinhaço II basin stage and mafic dikes of the northern Espinhaço, Chapada Diamantina and Curaçá domains, while the Stenian episode (ca. 1.1 Ga correlates to the Espinhaço III basin stage. We also present U-Pb data for 87 detrital zircon grains from a quartzite lens intercalated in the Pocrane complex, the Córrego Ubá quartzite. Its age spectrum shows main peaks at 1176 ± 21 Ma (35%, 1371 ± 30 Ma (18%, 1536 ± 22 Ma (19%, 1803 ± 36 Ma (17% and 1977 ± 38 Ma (12%, suggesting a Stenian (ca. 1176 Ma maximum

  3. Sulfur isotope composition of orogenic spinel lherzolite massifs from Ariege (north-eastern pyrenees, France): An ion microprobe study

    Energy Technology Data Exchange (ETDEWEB)

    Chaussidon, M. (Centre de Recherches Petrographiques et Geochimiques, Vandoeuvre-les-Nancy (France)); Lorand, J. (Unite associee au CNRS, Paris (France))

    1990-10-01

    The orogenic spinel lherzolite massifs from Ariege, which represent tectonically emplaced fragments of the sub-continental upper mantle, are composed mainly of variously depleted peridotites. These rocks are crosscut by two generations of pyroxenites. The first is made up of layered pyroxenites, which are interpreted either as crystal segregates from Triassic continental tholeiites or as subducted parts of the oceanic crust re-injected within the upper mantle. The second consists of amphibole-rich dikes separated from Cretaceous alkali basalts. Forty sulfide grains, occurring either as inclusions within silicates or as interstitial grains, were investigated by ion microprobe for their sulfur isotopic compositions. Comparison between sulfide inclusions in silicates and interstitial sulfide grains strongly suggests that serpentinization and pyrenean metamorphism had no significant effect don the {delta}{sup 34}S values. Likewise, these values are broadly independent of the degree of partial melting. The negative {delta}{sup 34}S values of the massive peridotites could represent an ancient depletion event in the upper mantle. By contrast, the positive {delta}{sup 34}S values observed in the layered pryoxenites and the amphibole-rich dikes indicate that the two parent magmas had in common a mantle source variously enriched in {sup 34}S. Therefore, the present study reveals two extreme reservoirs characterized by different {delta}{sup 34}S values in the upper mantle. This range of variations can explain most {delta}{sup 34}S values found in MORB, continental tholeiites, and alkali basalts.

  4. Early Paleozoic dioritic and granitic plutons in the Eastern Tianshan Orogenic Belt, NW China: Constraints on the initiation of a magmatic arc in the southern Central Asian Orogenic Belt

    Science.gov (United States)

    Du, Long; Long, Xiaoping; Yuan, Chao; Zhang, Yunying; Huang, Zongying; Sun, Min; Zhao, Guochun; Xiao, Wenjiao

    2018-03-01

    Early Paleozoic dioritic and granitic plutons in the Eastern Tianshan Orogenic Belt (ETOB) have been studied in order to constraint the initiation of a magmatic arc formed in this region. Zircon U-Pb dating indicates that two dioritic plutons in the northern ETOB were generated in the Late Ordovician (452 ± 4 Ma) and the Early Silurian (442 ± 3 Ma), respectively. Diorites from the two plutons are characterized by enrichments in large ion lithophile elements (LILE) and highly incompatible elements, with depletions in high field strength elements (HSFE) displaying typical geochemical features of a subduction-related origin. They have positive εNd(t) values (+5.08-+6.58), relatively young Nd model ages (TDM = 0.71-1.08 Ga), with Ta/Yb (0.05-0.09) and Nb/Ta ratios (12.06-15.19) similar to those of depleted mantle, suggesting a juvenile mantle origin. Their high Ba/La (13.3-35.9), low Th/Yb (0.72-2.02), and relatively low Ce/Th (4.57-14.7) and Ba/Th (47.8-235) ratios indicate that these diorites were probably produced by partial melting of a depleted mantle wedge metasomatized by both subducted sediment-derived melts and slab-derived aqueous fluids. Zircon U-Pb dating of a granitic pluton in the northern ETOB yielded a Late Ordovician intrusion age of 447 ± 5 Ma. Granites from this pluton show calc-alkaline compositions with geochemical characteristics of I-type granites. They also show positive εNd(t) values (+6.49-+6.95) and young Nd model ages (TDM = 0.69-0.87 Ga), indicating that the granites were most likely derived from juvenile lower crust. Our new dating results on the dioritic and granitic plutons suggest that arc-type magmatism in the northern ETOB began prior to or at the Late Ordovician (452-442 Ma). In addition, north-dipping subduction of the Kangguertage oceanic lithosphere may account for the arc-type magmatism and the geodynamic process of the ETOB in the Early Paleozoic.

  5. The Wenquan ultramafic rocks in the Central East Kunlun Fault zone, Qinghai-Tibet Plateau—crustal relics of the Paleo-Tethys ocean

    Science.gov (United States)

    Jia, Lihui; Meng, Fancong; Feng, Huibin

    2018-06-01

    The Wenquan ultramafic rocks, located in the East Kunlun Orogenic belt in the northeastern part of the Qinghai-Tibet Plateau, consist of dunite, wehrlite, olivine-clinopyroxenite and clinopyroxenite, and exhibit cumulate textures. Olivine from dunite has high Fo (forsterite, 90.0-91.8 wt%) and NiO content (0.15-0.42 wt%). Cr-spinels from all of the rocks in this suite are characterized by high Cr# (100×[Cr/(Cr + Al)], 67-91), low Mg# (100×[Mg/(Mg + Fe2+)], 17-35) and low TiO2 contents (mostly rocks show enrichment of LILE, Sr, and Ba, and depletion of Nb and Th. High-Mg# (mostly > 80) and low-CaO (evolution along the Central East Kunlun Fault zone.

  6. 2.5D seismic velocity modelling in the south-eastern Romanian Carpathians Orogen and its foreland

    Science.gov (United States)

    Bocin, Andrei; Stephenson, Randell; Tryggvason, Ari; Panea, Ionelia; Mocanu, Victor; Hauser, Franz; Matenco, Liviu

    2005-12-01

    The DACIA-PLAN (Danube and Carpathian Integrated Action on Processes in the Lithosphere and Neotectonics) deep seismic reflection survey was performed in August-September 2001, with the objective of obtaining new information on the deep structure of the external Carpathians nappe system and the architecture of the Tertiary/Quaternary basins developed within and adjacent to the Vrancea zone, including the rapidly subsiding Focsani Basin. The DACIA-PLAN profile is about 140 km long, having a roughly WNW-ESE direction, from near the southeast Transylvanian Basin, across the mountainous south-eastern Carpathians and their foreland to near the Danube River. A high resolution 2.5D velocity model of the upper crust along the seismic profile has been determined from a tomographic inversion of the DACIA-PLAN first arrival data. The results show that the data fairly accurately resolve the transition from sediment to crystalline basement beneath the Focsani Basin, where industry seismic data are available for correlation, at depths up to about 10 km. Beneath the external Carpathians nappes, apparent basement (material with velocities above 5.8 km/s) lies at depths as shallow as 3-4 km, which is less than previously surmised on the basis of geological observations. The first arrival travel-time data suggest that there is significant lateral structural heterogeneity on the apparent basement surface in this area, suggesting that the high velocity material may be involved in Carpathian thrusting.

  7. Uplifting of the Jiamusi Block in the eastern Central Asian Orogenic Belt, NE China: evidence from basin provenance and geochronology

    Science.gov (United States)

    Liu, Yongjiang; Wen, Quanbo; Han, Guoqing; Li, Wei

    2010-05-01

    the Paleo-Asian Ocean the Jiamusi Block underwent a very rapid exhumation in the late Permian. In the early Mesozoic the area went into a basin developing stage and formed a large basin as a whole during the Early Cretaceous. In the Late Cretaceous the Jiamusi Block started uplifting and the basin was broken into isolate small basins. References: Bureau of Geology and Mineral Resources of Heilongjiang Province. Regional geology of Heilongjiang Province. Beijing: Geological Publishing House, 1993.578-581. Cao Chengrun, Zheng Qingdao. Structural evolution feature and its significance of hydrocarbon exploration in relict basin formation, Eastern Heilongjiang province. Journal of Jilin university (Earth Science Edition), 2003, 33(2):167-172. Lang Xiansheng. Biologic Assemblage features of Coal-bearing Strata in Shuangyashan-Jixian coal-field. Coal geology of China, 2002, 14(2):7-12. Piao Taiyuan , Cai Huawei , Jiang Baoyu. On the Cretaceous coal-bearing Strata in Eastern Heilongjiang. Journal Of Stratigraphy, 2005, 29:489-496. Wang Jie , He Zhonghua , Liu Zhaojun , Du Jiangfeng , Wang Weitao. Geochemical characteristics of Cretaceous detrital rocks and their constraint on provenance in Jixi Basin. Global Geology,2006, 25(4):341-348. DickinsonW R and Christopher A. Suczek. Plate Tectonics and Sandstone Composition. AAPG B. 1979,63(12 ):2164-2182. DickinsonW R, Beard L S, Brakenridge G R, et al. Provenance of North American Phanerozoic sandstones in relation to tectonic setting. Bull Geo-Soc Amer, 1983, 94: 222-235. Maruyama S, Seno T. Orogeny and relative plate motions: Example of the Japanese Islands. Tectonophysics, 1986,127(3-4):305-329. Maruyama S, Isozaki Y, Kimura Gand Terabayashi M C.Paleogeographic maps of the Japanese Islands: plate tectonic systhesis from 750 Ma to the present. Island Arc, 1997,6:121-142.

  8. The final pulse of the Early Cenozoic adakitic activity in the Eastern Pontides Orogenic Belt (NE Turkey): An integrated study on the nature of transition from adakitic to non-adakitic magmatism in a slab window setting

    Science.gov (United States)

    Eyuboglu, Yener; Dudas, Francis O.; Santosh, M.; Eroğlu-Gümrük, Tuğba; Akbulut, Kübra; Yi, Keewook; Chatterjee, Nilanjan

    2018-05-01

    The Eastern Pontides Orogenic Belt, one of the best examples of a fossil continental arc in the Alpine-Himalayan system, is characterized by adakitic magmatism during the Early Cenozoic. Popular models correlate the adakitic magmatism to syn- or post-collisional processes occurring after the collision between the Eastern Pontides Orogenic Belt and the Tauride Platform at the end of Late Mesozoic and/or beginning of the Cenozoic. We present new geological, petrological and chronological data from andesites and felsic tuffs exposed in the Bayburt area, in the southern part of the Eastern Pontides Orogenic Belt, and discuss the nature of the transition from adakitic to non-adakitic activities in a continental arc. Major, trace and rare earth element concentrations of both andesites and felsic tuffs clearly suggest that they are related to arc magmatism in a continental arc with adakitic composition. The isotopic compositions are permissive of mixing between a component similar to depleted mantle and a second component that is either mafic lower crust or subducted oceanic crust. 39Ar/40Ar hornblende and U/Pb zircon dating indicate that this adakitic magmatism in the Bayburt area ended by about 47 Ma, and transformed into non-adakitic, granitoid arc magmatism in the area immediately north of Bayburt in the Lutetian (∼46 Ma). Based on our new results in conjunction with available data, we propose that the beginning of northward rollback of a south-directed subducting slab, and simultaneous opening of a slab window related to ridge subduction, triggered both adakitic magmatism for approximately a 10 Myr period between 57.6 and 47 Ma and arc-parallel extension that caused the opening of the Early Cenozoic sedimentary basins. We also suggest that the shallow marine environment, in which Nummulite-bearing sandy limestones accumulated in the Early Cenozoic, was transformed into a saline-lake environment during the pyroclastic activity that produced the studied felsic tuffs

  9. In-situ U-Pb, Hf and Re-Os isotopic analyses of the Xiangshan Ni-Cu-Co deposit in Eastern Tianshan (Xinjiang), Central Asia Orogenic Belt: Constraints on the timing and genesis of the mineralization

    Science.gov (United States)

    Han, Chunming; Xiao, Wenjiao; Zhao, Guochun; Ao, Songjian; Zhang, Jien; Qu, Wenjun; Du, Andao

    2010-12-01

    The timing and genesis of the major Ni-Cu-Co sulfide deposit in the Xiangshan intrusion have been studied based on newly obtained in-situ U-Pb, Hf and Re-Os isotopic analyses. The SIMS U-Pb zircon ages of the gabbro hosting the Ni-Cu-Co sulfide deposit indicate that the Xiangshan intrusion was emplaced at 279.6 ± 1.1 Ma (95% confidence level, MSWD = 1.30, n = 15). On the basis of combined geological and geochronological evidence, we suggest that the Xiangshan and other adjacent Ni-Cu deposits were formed in the same period. Sulphides have low common Os concentrations and high Re/Os ratios, similar to sulphide ores from the Duluth, Sally Malay and Voisey Bay complexes. The Re-Os isotopic data from the disseminated and massive ores from the Xiangshan intrusion do not form a single isochron, as they have different initial Os ratios. The Hf and Os isotopic data suggest that the Xiangshan intrusion and associated Ni-Cu-Co mineralization were derived from crustally contaminated mantle melts. The geochemical data show a tholeiitic affinity and a strong suprasubduction zone signature with negative Nb, Sr, and Ti anomalies similar to N-MORB and E-MORB. We suggest that the mafic-ultramafic rocks and associated Ni-Cu mineralization of the Eastern Tianshan orogen formed in an Alaska-type subduction zone-arc setting. Some diagnostic features of ridge-trench interaction are present in the Chinese East Tianshan orogen (e.g. granites, adakites, high-Mg andesites, near-trench magmatism, Alaskan-type mafic-ultramafic complexes, high-temperature metamorphic belts that prograde rapidly from low-grade belts, and orogenic gold deposits). The above distinctive rock groups are probably related to the same thermal event, ridge subduction, as in the Cenozoic orogen of Alaska. We suggest that ridge subduction is the most plausible mechanism to provide the necessary heat. Ridge subduction provides an important promising model for understanding many aspects of the evolution of the Chinese

  10. Petrogenesis of the Yaochong granite and Mo deposit, Western Dabie orogen, eastern-central China: Constraints from zircon U-Pb and molybdenite Re-Os ages, whole-rock geochemistry and Sr-Nd-Pb-Hf isotopes

    Science.gov (United States)

    Chen, Wei; Xu, Zhaowen; Qiu, Wenhong; Li, Chao; Yu, Yang; Wang, Hao; Su, Yang

    2015-05-01

    The Dabie orogen is among the most famous continent-continent collisional orogenic belts in the world, and is characterized by intensive post-collisional extension, magmatism and Mo mineralization. However, the genetic links between the mineralization and the geodynamic evolution of the orogen remain unresolved. In this paper, the Yaochong Mo deposit and its associated granitic stocks were investigated to elucidate this issue. Our new zircon U-Pb ages yielded an Early Cretaceous age (133.3 ± 1.3 Ma) for the Yaochong granite, and our molybdenite Re-Os dating gave a similar age (135 ± 1 Ma) for the Mo deposit. The Yaochong stock is characterized by high silica and alkali but low Mg, Fe and Ca. It is enriched in light rare earth elements (LREEs) and large ion lithophile elements (LILEs: Rb, K, Th and U), but strongly depleted in heavy REEs, and high field strength elements (HFSEs: Nb, Ta, Ti and Y). The Yaochong granite has initial 87Sr/86Sr ratios of 0.7087-0.7096, and Pb isotopic ratios of (206Pb/204Pb)i = 16.599-16.704, (207Pb/204Pb)i = 15.170-15.618 and (208Pb/204Pb)i = 36.376-38.248. The granite has εNd(t) of -18.0 to -16.3 and εHf(t) values of -26.5 to -20.0. All these data indicate that the Yaochong granite is a high-K calc-alkaline fractionated I-type granite, and may have originated from partial melting of the thickened Yangtze continental crust. The Mo ores also show low radiogenic Pb isotopes similar to the Yaochong stock. Medium Re content in molybdenite (21.8-74.8 ppm) also suggests that the ore-forming materials were derived from the thickened lower crust with possibly minor mixing with the mantle. Similar to the Eastern Dabie orogen, the thickened crust beneath the Western Dabie orogen may also have experienced tectonic collapse, which may have exerted fundamental geodynamic controls on the two-stage Mo mineralization in the region.

  11. Metamorphic rock-hosted orogenic gold deposit style at Bombana (Southeast Sulawesi and Buru Island (Maluku: Their key features and significances for gold exploration in Eastern Indonesia

    Directory of Open Access Journals (Sweden)

    Arifudin Idrus

    2017-06-01

    are identified. Early quartz veins are segmented, sigmoidal discontinuous and parallel to the foliation of the host rock. This generation of quartz veins is characterized by crystalline relatively clear quartz, and weakly mineralized with low sulfide and gold contents. The second type of quartz veins occurs within the ‘mineralized zone’ of about 100 m in width and ~1,000 m in length. Gold mineralization is intensely overprinted by argillic alteration. The mineralization-alteration zone is probably parallel to the mica schist foliation and strongly controlled by N-S or NE-SW-trending structures. Gold-bearing quartz veins are characterized by banded texture particularly following host rock foliation and sulphide banding, brecciated and rare bladed-like texture. Alteration types consist of propylitic (chlorite, calcite, sericite, argillic and carbonation represented by graphite banding and carbon flakes. Ore mineral comprises pyrite, native gold, pyrrhotite, and arsenopyrite. Cinnabar and stibnite are present in association with gold. Ore chemistry indicates that 11 out of 15 samples yielded more than 1 g/t Au, in which 6 of them graded in excess of 3 g/t Au. All high-grade samples are composed of limonite or partly contain limonitic material. This suggests the process of supergene enrichment. Interestingly, most of the high-grade samples contain also high concentrations of As (up to 991ppm, Sb (up to 885ppm, and Hg (up to 75ppm. Fluid inclusions in both quartz vein types consist of 4 phases including L-rich, V-rich, L-V-rich and L1-L2-V (CO2-rich phases. The mineralizing hydrothermal fluid typically is CO2-rich, of moderate temperature (300-400 ºC, and low salinity (0.36 to 0.54 wt.% NaCl eq. Based on those key features, gold mineralization in Bombana and Buru Island tends to meet the characteristics of orogenic, mesothermal types of gold deposit. Metamorphic rock-hosted gold deposits could represent the new targets for gold exploration particularly in Eastern

  12. Kinematics of active deformation across the Western Kunlun mountain range (Xinjiang, China), and potential seismic hazards within the southern Tarim Basin

    DEFF Research Database (Denmark)

    Guilbaud, Christelle; Simoes, Martine; Barrier, Laurie

    2017-01-01

    remains seismic. To quantify the rate of active deformation and the potential for major earthquakes in this region, we combine a structural and quantitative morphological analysis of the Yecheng-Pishan fold, along the topographic mountain front in the epicentral area. Using a seismic profile, we derive......The Western Kunlun mountain range is a slowly converging intra-continental orogen where deformation rates are too low to be properly quantified from geodetic techniques. This region has recorded little seismicity, but the recent July 2015 (Mw 6.4) Pishan earthquake shows that this mountain range...... a structural cross-section in which we identify the fault that broke during the Pishan earthquake, an 8-12 km deep blind ramp beneath the Yecheng-Pishan fold. Combining satellite images and DEMs, we achieve a detailed morphological analysis of the Yecheng-Pishan fold, where we find nine levels of incised...

  13. Earthquake activity along the Himalayan orogenic belt

    Science.gov (United States)

    Bai, L.; Mori, J. J.

    2017-12-01

    The collision between the Indian and Eurasian plates formed the Himalayas, the largest orogenic belt on the Earth. The entire region accommodates shallow earthquakes, while intermediate-depth earthquakes are concentrated at the eastern and western Himalayan syntaxis. Here we investigate the focal depths, fault plane solutions, and source rupture process for three earthquake sequences, which are located at the western, central and eastern regions of the Himalayan orogenic belt. The Pamir-Hindu Kush region is located at the western Himalayan syntaxis and is characterized by extreme shortening of the upper crust and strong interaction of various layers of the lithosphere. Many shallow earthquakes occur on the Main Pamir Thrust at focal depths shallower than 20 km, while intermediate-deep earthquakes are mostly located below 75 km. Large intermediate-depth earthquakes occur frequently at the western Himalayan syntaxis about every 10 years on average. The 2015 Nepal earthquake is located in the central Himalayas. It is a typical megathrust earthquake that occurred on the shallow portion of the Main Himalayan Thrust (MHT). Many of the aftershocks are located above the MHT and illuminate faulting structures in the hanging wall with dip angles that are steeper than the MHT. These observations provide new constraints on the collision and uplift processes for the Himalaya orogenic belt. The Indo-Burma region is located south of the eastern Himalayan syntaxis, where the strike of the plate boundary suddenly changes from nearly east-west at the Himalayas to nearly north-south at the Burma Arc. The Burma arc subduction zone is a typical oblique plate convergence zone. The eastern boundary is the north-south striking dextral Sagaing fault, which hosts many shallow earthquakes with focal depth less than 25 km. In contrast, intermediate-depth earthquakes along the subduction zone reflect east-west trending reverse faulting.

  14. Mesozoic-Cenozoic evolution of the Zoige depression in the Songpan-Ganzi flysch basin, eastern Tibetan Plateau: Constraints from detrital zircon U-Pb ages and fission-track ages of the Triassic sedimentary sequence

    Science.gov (United States)

    Tang, Yan; Zhang, Yunpeng; Tong, Lili

    2018-01-01

    The Zoige depression is an important depocenter within the northeast Songpan-Ganzi flysch basin, which is bounded by the South China, North China and Qiangtang Blocks and forms the northeastern margin of the Tibetan Plateau. This paper discusses the sediment provenance and Mesozoic-Cenozoic evolution of the Zoige depression in the Songpan-Ganzi flysch basin, eastern Tibetan Plateau, using the detrital zircon U-Pb ages and apatite fission-track data from the Middle to Late Triassic sedimentary rocks in the area. The U-Pb ages of the Middle to Late Triassic zircons range from 260-280 Ma, 429-480 Ma, 792-974 Ma and 1800-2500 Ma and represent distinct source region. Our new results demonstrate that the detritus deposited during the Middle Triassic (Ladinian, T2zg) primarily originated from the Eastern Kunlun and North Qinling Orogens, with lesser contributions from the North China Block. By the Late Triassic (early Carnian, T3z), the materials at the southern margin of the North China Block were generally transported westward to the basin along a river network that flowed through the Qinling region between the North China and South China Blocks: this interpretation is supported by the predominance of the bimodal distribution of 1.8 Ga and 2.5 Ga age peaks and a lack of significant Neoproterozoic zircon. Since the Late Triassic (middle Carnian, T3zh), considerable changes have occurred in the source terranes, such as the cessation of the Eastern Kunlun Orogen and North China Block sources and the rise of the northwestern margin of the Yangtze Block and South Qinling Orogen. These drastic changes are compatible with a model of a sustained westward collision between the South China and North China Blocks during the late Triassic and the clockwise rotation of the South China Block progressively closed the basin. Subsequently, orogeny-associated folds have formed in the basin since the Late Triassic (late Carnian), and the study area was generally subjected to uplifting and

  15. Age constraints on deformation of the eastern Hodgkinson Province, north Queensland: new perspectives on the evolution of the northern Tasman Orogenic Zone

    International Nuclear Information System (INIS)

    Zucchetto, R.G.; Henderson, R.A.; Davis, B.K.; Wysoczanski, R.

    1999-01-01

    Granitic plutons of the Wangetti and Mt Formartine Supersuites intrude the Hodgkinson Formation of the Macalister Range district of the eastern Hodgkinson Province, north Queensland, Australia. Field and microstructural analyses of country-rock fabrics and those of the granites show four deformational events (D 1 -D 4 ) for the district, in common with other sectors of the Hodgkinson Province. Structural relationships show that plutons of the two supersuites were emplaced at different times. The Wangetti Granite lacks fabric development, but the deflection of country-rock cleavage trends around it and the microscale crenulation of S 2 on the rims of D 4 porphyroblasts within its aureole indicate syn-D 4 emplacement, consistent with the Early Permian crystallisation age attributed to this pluton from isotopic evidence. Plutons of the Mt Formartine Supersuite show the effects of multiple (D 2 -D 4 ) deformation. An emplacement age of 357 ± 6 Ma (latest Devonian) was obtained for this granite by SHRIMP U-Pb analyses of zircon. This identifies an early episode of plutonism for the Hodgkinson Province, most granites from which are of Permian age. The new date constrains the age of D 2 for the Macalister Range district and the age of the protolith of the Hodgkinson Formation as pre-Carboniferous. It matches the age previously determined for one of several small, related granitic stocks in the southeastern Camel Creek Subprovince of the Broken River Province. Structural relationships for granites of this age suggest that their emplacement was broadly associated with the first episode of regional-scale orogenesis and the development of penetrative fabrics in the Hodgkinson - Broken River Fold Belt. Copyright (1999) Blackwell Science Pty Ltd

  16. Origin of ore-forming fluids of the Haigou gold deposit in the eastern Central Asian Orogenic belt, NE China: Constraints from H-O-He-Ar isotopes

    Science.gov (United States)

    Zeng, Qingdong; He, Huaiyu; Zhu, Rixiang; Zhang, Song; Wang, Yongbin; Su, Fei

    2017-08-01

    The Haigou lode deposit contains 40 t of gold at an average grade of 3.5 g/t, and is one of the largest deposits in the Jiapigou gold belt located along the eastern segment of the northern margin of the North China Craton. The deposit comprises 15 gold-bearing quartz veins hosted in a Carboniferous monzonite-monzogranite stock. Cretaceous dikes consisting of diorite, diabase, and granodiorite porphyries are well developed in the deposit. The diorite porphyry dikes (130.4 ± 6.3 Ma) occur together with gold-bearing quartz veins in NNE- and NE-striking faults. Gold-bearing quartz veins crosscut the diorite porphyry dikes, and the veins are in turn crosscut by E-W-striking 124.6 ± 2.2 Ma granodiorite porphyry dikes. The mineralization mainly occurs as auriferous quartz veins with minor amounts of sulfide minerals, including pyrite, galena, chalcopyrite, and molybdenite. Gold occurs as either native gold or calaverite. Common gangue minerals in the deposit include quartz, sericite, and calcite. The deposit is characterized by various types of hydrothermal alteration, including silicification, sericitization, chloritization, potassic alteration, and carbonatization. Three stages of hydrothermal activity have been recognized in the deposit: (1) a barren quartz stage; (2) a polymetallic sulfide (gold) stage; (3) a calcite stage. Fluid inclusions in hydrothermal pyrites have 3He/4He ratios of 0.3 to 3.3 Ra and 40Ar/36Ar ratios of 351 to 1353, indicating mixing of fluids of mantle and crustal origin. Hydrothermal quartz yielded δ18O values of -1.3‰ to +7.2‰ and δD values of fluid inclusions in the quartz vary between -80‰ and -104‰. These stable isotope data also suggest mixing of magmatic and meteoric fluids. Noble gas and stable isotopic data suggest that the ore fluids have a predominant mantle source with a significant crustal component. Based on the spatial association of gold-bearing quartz veins with early Cretaceous intrusions, and the H-O-He-Ar isotopic

  17. Mineral chemistry and geochemistry of the Late Neoproterozoic Gabal Abu Diab granitoids, Central Eastern Dessert, Egypt: Implications for the origin of rare metal post-orogenic A-type granites

    Science.gov (United States)

    Sami, Mabrouk; Ntaflos, Theodoros; Farahat, Esam S.; Ahmed, Awaad F.; Mohamed, Haroun A.

    2015-04-01

    The Neoproterozoic Gabal Abu Diab pluton is a part of the Arabian Nubian shield (ANS) continental crust and located in the Central Eastern Desert (CED) of Egypt. It constitutes multiphase granitic pluton intruded into granodiorite and metagabbro-diorite rocks with sharp and nonreactive contacts. Based on field observations, colors, structural variations and petrographic investigations, this granitic outcrop consists of an inner core of two-mica granite (TMG) followed outward by garnet bearing muscovite granite (GBMG) and albite granite (AG). Petrographical study indicated that medium to coarse-grained TMG is dominated by K-feldspar (Or88-98), quartz, plagioclase (albite, An0-7), muscovite and biotite with hypidiomorphic texture. With exception the appearance of garnet and the disappearance of biotite the GBMG resembles the TGM, while AG is leucocratic without any mafic mineral. The main accessories are zircon, Nb and Ta-bearing rutile, columbite, ilmenorutile, ilmenite, magnetite and apatite. This mineralogical similarity and the existence of columbite group minerals (CGM) in all granitoids, indicates a cogenetic relationship. Microprobe analyses reveal that, besides the CGM, rutile and ilmenite are the main repository phases for Nb-Ta-Ti. Columbite-(Mn) exists as individual subhedral crystals (up to 100μm in size) or intimate intergrowth with Nb-bearing rutile and/or ilmenite. The CGM are represented mostly by columbite-(Mn) with Ta/(Ta+Nb) and Mn/(Mn+Fe) ratio ranging from 0.02-0.08 and 0.4-0.9, respectively suggesting extreme degree of magmatic fractionation. Rutile contains significant amounts of Ta (up to 4 wt.% Ta2O5) and Nb (up to 22 wt.% Nb2O5). Biotites are phlogopite-annite in composition (Ann47-60Phlog40-53,on average) and are enriched with AlIV that characterize peraluminous granites. Garnets contain 60-69 mol.% spessartine and 28-36 mol.% almandine where, the ratio of spessartine and almandine together exceeds 95 mole percent, similar to garnet occur

  18. Shallow seismic structure of Kunlun fault zone in northern Tibetan Plateau, China: Implications for the 2001 M s8.1 Kunlun earthquake

    Science.gov (United States)

    Wang, Chun-Yong; Mooney, W.D.; Ding, Z.; Yang, J.; Yao, Z.; Lou, H.

    2009-01-01

    The shallow seismic velocity structure of the Kunlun fault zone (KLFZ) was jointly deduced from seismic refraction profiling and the records of trapped waves that were excited by five explosions. The data were collected after the 2001 Kunlun M s8.1 earthquake in the northern Tibetan Plateau. Seismic phases for the in-line record sections (26 records up to a distance of 15 km) along the fault zone were analysed, and 1-D P- and S-wave velocity models of shallow crust within the fault zone were determined by using the seismic refraction method. Sixteen seismic stations were deployed along the off-line profile perpendicular to the fault zone. Fault-zone trapped waves appear clearly on the record sections, which were simulated with a 3-D finite difference algorithm. Quantitative analysis of the correlation coefficients of the synthetic and observed trapped waveforms indicates that the Kunlun fault-zone width is 300 m, and S-wave quality factor Q within the fault zone is 15. Significantly, S-wave velocities within the fault zone are reduced by 30-45 per cent from surrounding rocks to a depth of at least 1-2 km, while P-wave velocities are reduced by 7-20 per cent. A fault-zone with such P- and S-low velocities is an indication of high fluid pressure because Vs is affected more than Vp. The low-velocity and low-Q zone in the KLFZ model is the effect of multiple ruptures along the fault trace of the 2001 M s8.1 Kunlun earthquake. ?? 2009 The Authors Journal compilation ?? 2009 RAS.

  19. Paleomagnetic constraints on the Cenozoic kinematic evolution of the Pamir plateau from the Western Kunlun Shan foreland

    Science.gov (United States)

    Li, Zhenyu; Ding, Lin; Lippert, Peter C.; Wei, Honghong

    2013-09-01

    Thick Cenozoic marine and terrestrial sediments are widely distributed along the perimeter of the Pamir plateau and provide valuable information on the kinematic evolution of the region. Here, we report new biostratigraphic and paleomagnetic results from the piedmont of the Western Kunlun Shan to constrain the magnitude and timing of vertical-axis rotations along the eastern margin of the Pamir. Sampling sites were selected by rock formations and ages, which are based on previous field mapping and on litholostratigraphic and biostratigraphic work presented here. Thermomagnetic analysis, step-wise thermal demagnetization behavior, and positive field tests all suggest that the characteristic remanent magnetization (ChRM) directions most probably have a primary detrital and chemical origin. Our results indicate variable, minor, but in some intervals significant vertical axis rotations with respect to a stable Asian reference frame. This pattern of rotations is similar to paleomagnetic data reported in previously published studies from the Eastern Pamir foreland. In contrast, published paleomagnetic data from the Western Pamir foreland consistently indicate significant CCW rotations within that region. Collectively, these results challenge simple oroclinal bending models for the origin of the Pamir salient, and instead are more consistent with an asymmetric "half-orocline" kinematic model in which the curvature of the Western Pamir is the product of a combination of lithospheric bending of an originally quasi-linear mountain belt and radial thrusting, and the subdued curvature of the eastern edge of the plateau is the result of lateral translation of the Pamir plateau northward past Tibet and Tarim along the Kashgar-Yecheng transfer system. Our results are consistent with activity on the Kashgar-Yecheng transfer system in the Early Miocene.

  20. Devonian post-orogenic extension-related volcano-sedimentary rocks in the northern margin of the Tibetan Plateau, NW China: Implications for the Paleozoic tectonic transition in the North Qaidam Orogen

    Science.gov (United States)

    Qin, Yu; Feng, Qiao; Chen, Gang; Chen, Yan; Zou, Kaizhen; Liu, Qian; Jiao, Qianqian; Zhou, Dingwu; Pan, Lihui; Gao, Jindong

    2018-05-01

    The Maoniushan Formation in the northern part of the North Qaidam Orogen (NQO), NW China, contains key information on a Paleozoic change in tectonic setting of the NQO from compression to extension. Here, new zircon U-Pb, petrological, and sedimentological data for the lower molasse sequence of the Maoniushan Formation are used to constrain the timing of this tectonic transition. Detrital zircons yield U-Pb ages of 3.3-0.4 Ga with major populations at 0.53-0.4, 1.0-0.56, 2.5-1.0, and 3.3-2.5 Ga. The maximum depositional age of the Maoniushan Formation is well constrained by a youngest detrital zircon age of ∼409 Ma. Comparing these dates with geochronological data for the region indicates that Proterozoic-Paleozoic zircons were derived mainly from the NQO as well as the Oulongbuluk and Qaidam blocks, whereas Archean zircons were probably derived from the Oulongbuluk Block and the Tarim Craton. The ∼924, ∼463, and ∼439 Ma tectonothermal events recorded in this region indicate that the NQO was involved in the early Neoproterozoic assembly of Rodinia and early Paleozoic microcontinental convergence. A regional angular unconformity between Devonian and pre-Devonian strata within the NQO suggests a period of strong mountain building between the Oulongbuluk and Qaidam blocks during the Silurian, whereas an Early Devonian post-orogenic molasse, evidence of extensional collapse, and Middle to Late Devonian bimodal volcanic rocks and Carboniferous marine carbonate rocks clearly reflect long-lived tectonic extension. Based on these results and the regional geology, we suggest that the Devonian volcano-sedimentary rocks within the NQO were formed in a post-orogenic extensional setting similar to that of the East Kunlun Orogen, indicating that a major tectonic transition from compression to extension in these two orogens probably commenced in the Early Devonian.

  1. Reworked crustal of early Paleozoic WuYi Orogen revealed by receiver function data

    Science.gov (United States)

    Wei, Y.; Duan, Y.; Tian, X.; Zhao, Y.

    2017-12-01

    Intraplate orogenic belt, which occurs at the rigid and undeformable plate interiors, is a distinct new type of orogen rather than an interplate or plate marginal orogenic belt, whose deformation occurs exclusively at plate margins. Therefore, intraplate orogenic belts are the most obvious exception to the plate-tectonic paradigm, they are uncommon in Earth's history. The early Paleozoic Wuyi orogen in South China is one of the few examples of intraplate orogen, and is a key to understanding the process of intraplate orogenesis and global early Paleozoic geodynamics. In this study, we select teleseismic records from 45 mobile linear seismic stations deployed in Wuyi Mountain and 58 permanent stations setting in Jiangxi and Fujian provinces, from January 2011 to December 2012, and calculate the crustal thickness and average crustal Vp/Vs ratio using the H-κ stacking method. The main results include the following: 1) the crustal average Poission's ratio shows an increase tendency from land to sea, the interior of Wuyi orogen belt with an low ration less than 0.23, and the coastline with high ration which is up to 0.28, which indicate a very heterogeneous crustal structure and composition in Wuyi orogen and coast belt. 2) the crustal thickness ranges 28-34 km and shows a tendency of thinning from inland to coast in the region of SE China margin, which maight mean the eastern Eurasia lithospheric is extension and thinning induced by the subducted paleo-Pacific slab. To conclusion, we assume that Wuyi orogen experienced upper crustal thickening, lower crust and lithosphere delamination during the early Paleozoic orogeny, and lithosphere extension in Mesozoic. This research is founded by the Natural Science Foundation of China (41174052 and 41604048).

  2. 40Ar/39Ar thermo-chronology and lithospheric mechanisms. Methodological and applied approach: the Kunlun range (Asia) and the Afar triple junction area (East Africa)

    International Nuclear Information System (INIS)

    Mock, C.

    1998-01-01

    A 40 Ar/ 39 Ar thermo-chronological study has been carried out for two contrasted geodynamic settings: - the Eastern Kunlun range (Northern Tibet), in order to characterize the lithospheric deformation mechanisms related to the India-Asia collision; - the Afar triple junction area (East Africa), in order to constrain the timing of mantle plume-related basement uplift in Ethiopia and Yemen, which will indicate whether rifting was active or passive. In the Kunlun, the cooling event (9-15 deg.C/Ma) outlined at 30 Ma for the granitoids (Bt = 128-138 Ma; Kf = 102-147 Ma) reflects a denudation event (0.2-0.3 km/Ma), related to ramp stacking and normal faulting with associated uplift. This unroofing period is coeval with the great Asian strike-slip faults. This suggests that 30 Ma ago, the India-Asia collision was accommodated by lateral extrusion along great strike-slip faults, which might have led to local crustal thickening because of the formation of anticlines from major thrusts 'branching' from the Kunlun fault. In the Afar area the Panafrican basement (granitoids = 462-678 Ma;metamorphic rocks 505-750 Ma) has undergone a reheating event during the Cenozoic; its temperature is estimated around 138-177 deg.C over the last 50 Ma for a depth of 2 km, implying a thermal gradient of 69-88 deg./km. This reheating event results from both heat conduction, related to the mantle plume. and heat advection. because of magma transfer. However, it was not possible to define the timing of the mantle plume-related basement uplift. This study outlines the important thermal effect of continental flood basalts on the crust and suggests that the 40 Ar/ 39 Ar thermo-chronology does not allow to characterize the denudation of the lithosphere for an extension-type geodynamic setting. Finally, some of the results suggest that diffusion in the laboratory and in nature may be different. 40 Ar/ 39 Ar thermo-chronological analysis thus might be tricky, especially in investigating geologic

  3. The Paleozoic metamorphic history of the Central Orogenic Belt of China from 40Ar/39Ar geochronology of eclogite garnet fluid inclusions

    NARCIS (Netherlands)

    Qiu, H.N.; Wijbrans, J.R.

    2008-01-01

    The pressure-temperature-time evolution of the UHP eclogites of Dabie-Sulu, in the eastern sector of the Central Orogenic Belt of China shows a complex pattern of predominantly Triassic, and to a lesser extent Early Paleozoic ages.

  4. South China provenance of the lower-grade Penglai Group north of the Sulu UHP orogenic belt, eastern China. Evidence from detrital zircon ages and Nd-Hf isotopic composition

    International Nuclear Information System (INIS)

    Li Xianghui; Chen Fukun; Guo Jinghui; Xie Liewen; Siebel, Wolfgang

    2007-01-01

    The Dabie-Sulu ultrahigh-pressure orogenic belt resulted from the early Mesozoic collision of the North China block and South China block (comprising the Yangtze and the Cathaysia) and subsequent exhumation of the subducted South China continental slabs. This belt consists of tectonically juxtaposed rock units of different metamorphic grade. Provenance of the low-grade metamorphic terranes exposed along the northern part of the belt can offer useful information about the location of the boundary between these two continental blocks. This study reports detrital zircon ages and Nd-Hf isotopic composition of sedimentary rocks of the low-grade Penglai Group, situated north of the Sulu UHP terrane. Results show that detrital zircon grains mostly crystallized during Mesoproterozoic time, clustering at 1.7 Ga to 1.6 Ga and 1.2 Ga. Nd isotopic composition (T DM value) of the Penglai Group suggests that sedimentary sources are similar to average crustal material of the Yangtze block and mostly formed in Paleo- to Mesoproterozoic. Late Mesoproterozoic detrital zircons probably demonstrate the sedimentary material was derived from the boundary of the Yangtze and Cathaysia blocks, which was formed by the late Mesoproterozoic convergence. Absence of Neoproterozoic detrital zircons from the Penglai sediments probably suggests a late Mesoproterozoic to early Neoproterozoic deposition age (about 1.1 Ga to 0.8 Ga). The age and isotopic evidence implies that the Penglai Group originated from the South China block and probably was thrust onto the basement of the North China block during the early Mesozoic continental collision. (author)

  5. Seismic investigation of the Kunlun Fault: Analysis of the INDEPTH IV 2-D active-source seismic dataset

    Science.gov (United States)

    Seelig, William George

    The Tibetan Plateau has experienced significant crustal thickening and deformation since the continental subduction and collision of the Asian and Indian plates in the Eocene. Deformation of the northern Tibetan Plateau is largely accommodated by strike-slip faulting. The Kunlun Fault is a 1000-km long strike-slip fault near the northern boundary of the Plateau that has experienced five magnitude 7.0 or greater earthquakes in the past 100 years and represents a major rheological boundary. Active-source, 2-D seismic reflection/refraction data, collected as part of project INDEPTH IV (International Deep Profiling of Tibet and the Himalaya, phase IV) in 2007, was used to examine the structure and the dip of the Kunlun fault. The INDEPTH IV data was acquired to better understand the tectonic evolution of the northeastern Tibetan Plateau, such as the far-field deformation associated with the continent-continent collision and the potential subduction of the Asian continent beneath northern Tibet. Seismic reflection common depth point (CDP) stacks were examined to look for reflectivity patterns that may be associated with faulting. A possible reflection from the buried North Kunlun Thrust (NKT) is identified at 18-21 km underneath the East Kunlun Mountains, with an estimated apparent dip of 15°S and thrusting to the north. Minimally-processed shot gathers were also inspected for reflections off near-vertical structures such as faults and information on first-order velocity structure. Shot offset and nearest receiver number to reflection was catalogued to increase confidence of picks. Reflections off the North Kunlun (NKF) and South Kunlun Faults (SKF) were identified and analyzed for apparent dip and subsurface geometry. Fault reflection analysis found that the North Kunlun Fault had an apparent dip of approximately 68ºS to an estimated depth of 5 km, while the South Kunlun Fault dipped at approximately 78ºN to an estimated 3.5 km depth. Constraints on apparent dip and

  6. Continental Growth and Recycling in Convergent Orogens with Large Turbidite Fans on Oceanic Crust

    Directory of Open Access Journals (Sweden)

    Ben D. Goscombe

    2013-07-01

    Full Text Available Convergent plate margins where large turbidite fans with slivers of oceanic basement are accreted to continents represent important sites of continental crustal growth and recycling. Crust accreted in these settings is dominated by an upper layer of recycled crustal and arc detritus (turbidites underlain by a layer of tectonically imbricated upper oceanic crust and/or thinned continental crust. When oceanic crust is converted to lower continental crust it represents a juvenile addition to the continental growth budget. This two-tiered accreted crust is often the same thickness as average continental crustal and is isostatically balanced near sea level. The Paleozoic Lachlan Orogen of eastern Australia is the archetypical example of a tubidite-dominated accretionary orogeny. The Neoproterozoic-Cambrian Damaran Orogen of SW Africa is similar to the Lachlan Orogen except that it was incorporated into Gondwana via a continent-continent collision. The Mesozoic Rangitatan Orogen of New Zealand illustrates the transition of convergent margin from a Lachlan-type to more typical accretionary wedge type orogen. The spatial and temporal variations in deformation, metamorphism, and magmatism across these orogens illustrate how large volumes of turbidite and their relict oceanic basement eventually become stable continental crust. The timing of deformation and metamorphism recorded in these rocks reflects the crustal thickening phase, whereas post-tectonic magmatism constrains the timing of chemical maturation and cratonization. Cratonization of continental crust is fostered because turbidites represent fertile sources for felsic magmatism. Recognition of similar orogens in the Proterozoic and Archean is important for the evaluation of crustal growth models, particularly for those based on detrital zircon age patterns, because crustal growth by accretion of upper oceanic crust or mafic underplating does not readily result in the addition of voluminous zircon

  7. Mineral mapping in the western Kunlun Mountains using Tiangong-1 hyperspectral imagery

    Science.gov (United States)

    Ge, W.; Cheng, Q.; Jing, L.; Chen, Y.; Guo, X.; Ding, H.; Liu, Q.

    2016-04-01

    The unmanned Chinese space module Tiangong-1 was launched in September 2011 with a hyperspectral sensor on board. The sensor combines high spatial and spectral resolution suitable for mineral mapping. In this study, Tiangong-1 hyperspectral data were employed for mineral mapping in the western Kunlun Mountains, an important metallogenic belt in China. A Spectral Hourglass Wizard method was applied to detect common minerals from the Tiangong- 1 shortwave infrared data with reference to a set of spectral libraries. Spectral information on minerals, such as zoisite, mica, quartz, sodalite, dolomite, and actinolite, was extracted from the data. The resulting mineral interpretation maps were highly correlated with the reference geological maps and information from ASTER satellite imagery, suggesting that the hyperspectral data are suitable for mineral mapping.

  8. Orogenic, Ophiolitic, and Abyssal Peridotites

    Science.gov (United States)

    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

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

    Science.gov (United States)

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

    2015-05-01

    Carboniferous back-arc basin formed as a result of slab rollback ascribed to northward subduction of the Niujuanzi oceanic lithosphere. Subduction of this back-arc basin probably took place in the early Carboniferous, generating the widespread arc-related granitoids including adakitic plutons, and overlapping earlier arc assemblages. The Beishan orogenic collage is not the eastern extension of the Chinese Central Tianshan, but it was generated by the same north-dipping subduction system separated by the Xingxingxia transform fault, as revealed by available regional data. This contribution implies that in addition to fore-arc accretion, back-arc accretion ascribed to opening and closure of a back-arc basin may also have been a common process in the construction of the CAOB, resembling that of the Mesozoic-Cenozoic subduction-accretion system in the SW pacific.

  10. Geological characters and petrological characters of metamorphosed medium-acidic intrusive complexes in Ludong Orogenic Belt,China

    Institute of Scientific and Technical Information of China (English)

    凌贤长; 胡庆立; 王丽霞

    2002-01-01

    Ludong orogenic belt in China is an importantal continent collision orogenic belt in eastern Asia, between Sino-Korean landmass and Yangtze landmass. The host rock of the orogenic belt is metamorphosed medium-acidic intrusive complexes, which can be divided into four types, that's, quartz dioritz, granite dioritz, monzonitic granite and undertint monzonitic granite, principal minerals are plagioclases, potassium feldspars and quartzs, minor minerals are hornblendes, biotites, clinopyxenes and garnets, accessory mineral types and assemblages are very similar, specially, various rocks are mainly fine-grained textures. They have the history of regional amphibolite facies metamorphism and deep-middle-shallow structural layer deformation, and are changed into various gneiss and tectonic system. There are many xenolithes of middle Proterozoic eclogite-host rock extrahigh-high pressure metamorphic complexes, a small xenolithes of early Proterozoic layered metamorphite system and granulites, and ultrabasic-basic rocks of various epoches in the metamorphosed medium-acidic intrusive complexes.

  11. Antioxidant Activity, Antitumor Effect, and Antiaging Property of Proanthocyanidins Extracted from Kunlun Chrysanthemum Flowers

    Directory of Open Access Journals (Sweden)

    Siqun Jing

    2015-01-01

    Full Text Available The objective of the present study was to evaluate the antioxidant activity, antitumor effect, and antiaging property of proanthocyanidins from Kunlun Chrysanthemum flowers (PKCF grown in Xinjiang. In vitro antioxidant experiments results showed that the total antioxidant activity and the scavenging capacity of hydroxyl radicals (•OH and 1,1-diphenyl-2-picrylhydrazyl (DPPH• radicals increased in a concentration-dependent manner and were stronger than those of vitamin C. To investigate the antioxidant activity of PKCF in vivo, we used serum, liver, and kidney from mouse for the measurement of superoxide dismutase (SOD, malondialdehyde (MDA, and total antioxidant capacity (T-AOC. Results indicated that PKCF had antioxidative effect in vivo which significantly improved the activity of SOD and T-AOC and decreased MDA content. To investigate the antitumor activity of PKCF, we used H22 cells, HeLa cells, and Eca-109 cells with Vero cells as control. Inhibition ratio and IC50 values were measured by 3-(4,5-dimethylthiazol-2-yl-2,5-diphenyltetrazolium bromide (MTT assay; PKCF showed great inhibitory activity on H22 cells and HeLa cells. We also used fruit flies as a model for analyzing the anti-aging property of PKCF. Results showed that PKCF has antiaging effect on Drosophila. Results of the present study demonstrated that PKCF could be a promising agent that may find applications in health care, medicine, and cosmetics.

  12. AN EARLY PERMIAN GARNET-BEATING PERALUMINOUS GRANITIC PLUTON IN THE SOUTH TIANSHAN OROGENIC BELT, NW CHINA: PETROLOGICAL, MINERALOGICAL AND GEOCHEMICAL CONSTRAINTS

    Directory of Open Access Journals (Sweden)

    Qie Qin

    2017-01-01

    Full Text Available The Ku’erchu granitic pluton (283±4 Ma was exposed in the eastern part of the South Tianshan Orogenic Belt. The granites from the intrusion are mainly composed of orthoclase (~45 vol. %, plagioclase (~15 vol. %, quartz (~20 vol. %, muscovite (~10 vol. % and biotite (~5 vol. %, with accessory minerals including garnet, zircon and Fe-Ti oxide.

  13. Structure of the Kaoko Belt, Namibia: progressive evolution of a classic transpressional orogen

    Science.gov (United States)

    Goscombe, Ben; Hand, Martin; Gray, David

    2003-07-01

    The Kaoko Belt portion of the Damara Orogen, Namibia, is the deeply eroded core of a sinistral transpressional orogen that has half-flower structure geometry centred on the major, 4-5-km-wide Purros Mylonite Zone. Formed between the Congo Craton in the east and Rio De La Plata Craton in Brazil, the Kaoko Belt represents the northern coastal arm of a triple junction within the Pan-African Orogenic System. Consisting of reworked Archaean, Palaeoproterozoic and Mesoproterozoic basement and a cover of Neoproterozoic Damara Sequence, the Kaoko Belt can be sub-divided structurally into three parallel NNW-trending zones. The Eastern Kaoko Zone comprises sub-greenschist facies shelf carbonates that have been uprightly folded. The Central Kaoko Zone contains a slope and deep basin facies succession that has experienced intense deformation, including pervasive reworking of basement into large-scale east-vergent nappes. The Western Kaoko Zone is predominantly deep basin facies of high metamorphic grade intruded by numerous granites. It has experienced intense wrench-style deformation with formation of upright isoclines and steep, crustal-scale shear zones. The Kaoko Belt evolved through three distinct phases of a protracted Pan-African Orogeny in the late Neoproterozoic to Cambrian. (1) An early Thermal Phase (M 1) was responsible for pervasive partial melting and granite emplacement in the Western Kaoko Zone from 656 Ma. (2) The Transpressional Phase produced the geometry of the belt by progressive sinistral shearing between 580 and 550 Ma. Deformation was continuously progressive through two stages and involved both temporal and spatial migration of deformation outwards towards the margin. The early strike-slip Wrench-Stage produced a high-strain L-S fabric by sub-horizontal transport. Deformation became progressively more transpressive, with high-angle convergence and flattening strains during the Convergent-Stage. In this stage, strike-slip movements evolved through

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

    Science.gov (United States)

    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

  15. Evolving lithospheric flexure and paleotopography of the Pyrenean Orogen from 3D flexural modeling and basin analysis

    Science.gov (United States)

    Curry, M. E.; van der Beek, P.; Huismans, R. S.; Muñoz, J. A.

    2017-12-01

    The Pyrenees are an asymmetric, doubly-vergent orogen with retro- and pro- foreland basins that preserve a record of deformation since the Mesozoic. The extensive research and exploration efforts on the mountain belt and flanking foreland basins provide an exceptional dataset for investigating geodynamics and surface processes over large spatial and temporal scales in western Europe. We present the results of a numerical modeling study investigating the spatio-temporal variation in lithospheric flexure in response to the developing orogen. We employ a finite element method to model the 3D flexural deformation of the lithosphere beneath the Pyrenean orogen since the onset of convergence in the late Cretaceous. Using subsurface, geophysical, and structural data, we describe the evolving geometry of both the French Aquitaine and Spanish Ebro foreland basins at the present (post-orogenic), the mid-Eocene (peak orogenic), the Paleocene (early orogenic), and the end of the Cretaceous (pre- to early orogenic). The flexural modeling provides insight into how both the rigidity of the lithosphere and the paleotopographic load have varied over the course of orogenesis to shape the basin geometry. We find that the overriding European plate has higher rigidity than the subducting Iberian plate, with modern Effective Elastic Thickness (EET) values of 20 ± 2 and 12 ± 2 km, respectively. Modeling indicates that the modern rigidity of both plates decreases westward towards the Bay of Biscay. The lithospheric rigidity has increased by 50% since the Mesozoic with early Cenozoic EET values of 13 ± 2 and 8 ± 1 km for the European and Iberian plates, respectively. The topographic load began increasing with convergence in the late Cretaceous, reaching modern levels in the central and eastern Pyrenees by the Eocene. In contrast, the topographic load in the western Pyrenees was 70% of the modern value in the Eocene, and experienced topographic growth through the Oligo-Miocene. The

  16. Late-orogenic mantle garnet pyroxenites evidence mantle refertilization during exhumation of orogenic belt

    Science.gov (United States)

    Chazot, G.; France, L.; Kornprobst, J.; Dallai, L.; Vannucci, R.

    2008-12-01

    The petrological and geochemical study of garnet bearing pyroxenites from four localities (FMC, Morocco, Jordan, Cameroon) demonstrates that these rocks are cumulates crystallised in the lithospheric mantle domain. Metamorphic reactions, exsolutions and trace elements WR analysis demonstrate that their crystallisation pressure ranges between 1 and 2GPa (30 to 60km). The elaboration of the PTt paths for the studied samples attests of important movements in the respective lithospheres. Replaced in the geodynamical contexts, the samples are interpreted to represent the crystallisation of melts formed during exhumation of orogenic domains. Radiogenic isotopes (Sr-Nd) show that in a very same region, the samples are isotopicaly heterogeneous but are similar to the respective regional lithosphere. Initial isotopic ratios lead to propose that the FMC samples have crystallised at the end of the Hercynian orogen and that the samples from the other localities (Morocco, Jordan and Cameroon) have crystallised at the end of the Pan-African orogen. After recalculation at the crystallisation time, the isotopic compositions are in good agreement with the respective regional lithosphere ones and so samples of this study could represent the product of the melting of these lithospheres. The analyses of oxygen stable isotopes allow to precise the model; they show that twelve of the samples come from the melting of a lherzolitic mantle and that the four others come from the melting of a heterogeneous mantle formed of lherzolites and eclogites. The presence of some hydrous minerals such as amphiboles and micas and the trace elements WR analyses show that some of the samples were affected by a late metasomatic event. Results of our study show that thermal relaxation following orogenic events lead to the crystallisation of pyroxenites in the lithosphere. The presence of lage amounts of mantle pyroxenites in old orogenic regions confers physical and chemical particularities to these

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

    Science.gov (United States)

    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.

  18. Estimates of late Cenozoic climate change relevant to Earth surface processes in tectonically active orogens

    Science.gov (United States)

    Mutz, Sebastian G.; Ehlers, Todd A.; Werner, Martin; Lohmann, Gerrit; Stepanek, Christian; Li, Jingmin

    2018-04-01

    The denudation history of active orogens is often interpreted in the context of modern climate gradients. Here we address the validity of this approach and ask what are the spatial and temporal variations in palaeoclimate for a latitudinally diverse range of active orogens? We do this using high-resolution (T159, ca. 80 × 80 km at the Equator) palaeoclimate simulations from the ECHAM5 global atmospheric general circulation model and a statistical cluster analysis of climate over different orogens (Andes, Himalayas, SE Alaska, Pacific NW USA). Time periods and boundary conditions considered include the Pliocene (PLIO, ˜ 3 Ma), the Last Glacial Maximum (LGM, ˜ 21 ka), mid-Holocene (MH, ˜ 6 ka), and pre-industrial (PI, reference year 1850). The regional simulated climates of each orogen are described by means of cluster analyses based on the variability in precipitation, 2 m air temperature, the intra-annual amplitude of these values, and monsoonal wind speeds where appropriate. Results indicate the largest differences in the PI climate existed for the LGM and PLIO climates in the form of widespread cooling and reduced precipitation in the LGM and warming and enhanced precipitation during the PLIO. The LGM climate shows the largest deviation in annual precipitation from the PI climate and shows enhanced precipitation in the temperate Andes and coastal regions for both SE Alaska and the US Pacific Northwest. Furthermore, LGM precipitation is reduced in the western Himalayas and enhanced in the eastern Himalayas, resulting in a shift of the wettest regional climates eastward along the orogen. The cluster-analysis results also suggest more climatic variability across latitudes east of the Andes in the PLIO climate than in other time slice experiments conducted here. Taken together, these results highlight significant changes in late Cenozoic regional climatology over the last ˜ 3 Myr. Comparison of simulated climate with proxy-based reconstructions for the MH and

  19. Tectonic controls of Holocene erosion in a glaciated orogen

    OpenAIRE

    Adams, Byron A.; Ehlers, Todd A.

    2018-01-01

    Recent work has highlighted a strong, worldwide, glacial impact of orogen erosion rates over the last 2 Ma. While it may be assumed that glaciers increased erosion rates when active, the degree to which past glaciations influence Holocene erosion rates through the adjustment of topography is not known. In this study, we investigate the influence of long-term tectonic and post-glacial topographic controls on erosion in a glaciated orogen, the Olympic Mountains, USA. We present 14 new 10Be and ...

  20. THE APPLICATION OF REMOTE SENSING AND AERO-GEOPHYSICS DATA FUSION ON METALLOGENIC PROGNOSIS IN QIMANTAGE OF EAST KUNLUN MONTAIN AREA

    OpenAIRE

    Jia, W.; Zhang, H.; Lin, J.; Zhao, H.

    2013-01-01

    Based on west of Qimantage of East Kunlun mountain area, takes advantage of ASTER data, according to the altered mineral spectral characteristics, remote sensing alteration information is extracted. Incorporation the anomaly extraction results with high-precision aero geophysical data processing results, a multiple resource information fusion model is proposed. The fusion model of two totally different type of data which is a special attention in geospatial academia now, which can im...

  1. Metallogenic relationships to tectonic evolution - the Lachlan Orogen, Australia

    Science.gov (United States)

    Bierlein, Frank P.; Gray, David R.; Foster, David A.

    2002-08-01

    Placing ore formation within the overall tectonic framework of an evolving orogenic system provides important constraints for the development of plate tectonic models. Distinct metallogenic associations across the Palaeozoic Lachlan Orogen in SE Australia are interpreted to be the manifestation of interactions between several microplates and three accretionary complexes in an oceanic back-arc setting. In the Ordovician, significant orogenic gold deposits formed within a developing accretionary wedge along the Pacific margin of Gondwana. At the same time, major porphyry Cu-Au systems formed in an oceanic island arc outboard of an evolved magmatic arc that, in turn, gave rise to granite-related Sn-W deposits in the Early Silurian. During the ongoing evolution of the orogen in the Late Silurian to Early Devonian, sediment-hosted Cu-Au and Pb-Zn deposits formed in short-lived intra-arc basins, whereas a developing fore-arc system provided the conditions for the formation of several volcanogenic massive sulphide deposits. Inversion of these basins and accretion to the Australian continental margin triggered another pulse of orogenic gold mineralisation during the final consolidation of the orogenic belt in the Middle to Late Devonian.

  2. Spatial and temporal distribution of the orogenic gold deposits in the Late Palaeozoic Variscides and Southern Tianshan: How orogenic are they?

    NARCIS (Netherlands)

    Boorder, H. de

    2012-01-01

    A principal uncertainty in models of orogenic ore deposits concerns their ages relative to orogenic processes. The yardstick of the relation has resided, loosely, in the peak of metamorphism. Age estimates in the Variscides and Tianshan indicate that most orogenic ore deposits were formed in the

  3. What Can Modern River Profiles Tell Us about Orogenic Processes and Orogen Evolution?

    Science.gov (United States)

    Whipple, K. X.

    2008-12-01

    Numerous lines of evidence from theory, numerical simulations, and physical experiments suggest that orogen evolution is strongly coupled to atmospheric processes through the interrelationships among climate, topography, and erosion rate. In terms of orogenic processes and orogen evolution, these relationships are most important at the regional scale (mean topographic gradient, mean relief above surrounding plains) largely because crustal deformation is most sensitive to erosional unloading averaged over sufficiently long wavelengths. For this reason, and because above moderate erosion rates (> 0.2 mm/yr) hillslope form becomes decoupled from erosion rate, attention has focused on the river network, and even on particularly large rivers. We now have data that demonstrates a monotonic relationship between erosion rate and the channel steepness index (slope normalized for differences in drainage area) in a variety of field settings. Consequently, study of modern river profiles can yield useful information on recent and on-going patterns of rock uplift. It is not yet possible, however, to quantitatively isolate expected climatic and lithologic influences on this relationship. A combination of field studies and theoretical analyses are beginning to reveal the timescale of landscape response, and thus the topographic memory of past conditions. At orogen scale, river profile response to a change in rock uplift rate is on the order of 1-10 Myr. Because of these long response times, the modern profiles of large rivers and their major tributaries can potentially preserve an interpretable record of rock uplift rates since the Miocene and are insensitive to short-term climatic fluctuations. Only significant increases in rock uplift rate, however, are likely to leave a clear topographic signature. Strategies have been developed to differentiate between temporal and spatial (tectonic, climatic, or lithologic) influences on channel profile form, especially where spatially

  4. Architecture and mineral deposit settings of the Altaid orogenic collage: a revised model

    Science.gov (United States)

    Yakubchuk, Alexander

    2004-09-01

    The Altaids are an orogenic collage of Neoproterozoic-Paleozoic rocks located in the center of Eurasia. This collage consists of only three oroclinally bent Neoproterozoic-Early Paleozoic magmatic arcs (Kipchak, Tuva-Mongol, and Mugodzhar-Rudny Altai), separated by sutures of their former backarc basins, which were stitched by new generations of overlapping magmatic arcs. In addition, the Altaids host accreted fragments of the Neoproterozoic to Early Paleozoic oceanic island chains and Neoproterozoic to Cenozoic plume-related magmatic rocks superimposed on the accreted fragments. All these assemblages host important, many world-class, Late Proterozoic to Early Mesozoic gold, copper-molybdenum, lead-zinc, nickel and other deposits of various types. In the Late Proterozoic, during breakup of the supercontinent Rodinia, the Kipchak and Tuva-Mongol magmatic arcs were rifted off Eastern Europe-Siberia and Laurentia to produce oceanic backarc basins. In the Late Ordovician, the Siberian craton began its clockwise rotation with respect to Eastern Europe and this coincides with the beginning of formation of the Mugodzhar-Rudny Altai arc behind the Kipchak arc. These earlier arcs produced mostly Cu-Pb-Zn VMS deposits, although some important intrusion-related orogenic Au deposits formed during arc-arc collision events in the Middle Cambrian and Late Ordovician. The clockwise rotation of Siberia continued through the Paleozoic until the Early Permian producing several episodes of oroclinal bending, strike-slip duplication and reorganization of the magmatic arcs to produce the overlapping Kazakh-Mongol and Zharma-Saur-Valerianov-Beltau-Kurama arcs that welded the extinct Kipchak and Tuva-Mongol arcs. This resulted in amalgamation of the western portion of the Altaid orogenic collage in the Late Paleozoic. Its eastern portion amalgamated only in the early Mesozoic and was overlapped by the Transbaikal magmatic arc, which developed in response to subduction of the oceanic crust

  5. Stable isotopes in fossil mammals, fish and shells from Kunlun Pass Basin, Tibetan Plateau: Paleo-climatic and paleo-elevation implications

    Science.gov (United States)

    Wang, Yang; Wang, Xiaoming; Xu, Yingfeng; Zhang, Chunfu; Li, Qiang; Tseng, Zhijie Jack; Takeuchi, Gary; Deng, Tao

    2008-06-01

    We report the results of a stable isotope study of a late Pliocene fauna recently discovered in the Kunlun Mountain Pass area (˜ 4700 m above sea level) on the northern Tibetan Plateau. The δ13C values of enamel samples from modern herbivores from the Kunlun Pass Basin range from - 14.8 to - 10.6‰, with a mean of - 12.0 ± 0.7‰, indicating pure C3 diets consistent with the current dominance of C3 vegetation in the area. In contrast, enamel samples from fossil herbivores yielded δ13C values of - 5.4‰ to - 10.2‰ (with a mean of - 7.9 ± 1.3‰), significantly higher than those of modern herbivores in the area. The higher δ13C values indicate that these ancient herbivores, unlike their modern counterparts, had a variety of diets ranging from pure C3 to mixed C3/C4 vegetation. The local ecosystems in the Kunlun Pass area in the late Pliocene likely included grasslands that had small amounts of C4 grasses. The δ18O values of enamel from large herbivores shifted to higher values after the late Pliocene, indicating a significant change in the δ18O of local meteoric water. We estimate that there has been approximately 3.2‰ increase in annual δ18O values of meteoric water since ˜ 2-3 Ma, most likely driven by changes in the regional hydrological cycle possibly as a result of tectonic and climate change. The δ18O values of fossil fish teeth/bones and gastropod shells, along with abundance of aquatic plants and other invertebrate fossils, clearly indicate that the Kunlun Pass Basin once had plenty of water and was occupied by a freshwater lake in the late Pliocene. Our isotope data from both terrestrial and aquatic fossils suggest that the Kunlun Pass Basin was a hospitable place with a much warmer and wetter climate in the late Pliocene, very different from today's rock desert and cold steppe environments. The mean annual temperature in the late Pliocene estimated from the δ18O of fossil bone carbonate and paleo-water was about 10 ± 8 °C, much higher

  6. Ice core records of climate variability on the Third Pole with emphasis on the Guliya ice cap, western Kunlun Mountains

    Science.gov (United States)

    Thompson, Lonnie G.; Yao, Tandong; Davis, Mary E.; Mosley-Thompson, Ellen; Wu, Guangjian; Porter, Stacy E.; Xu, Baiqing; Lin, Ping-Nan; Wang, Ninglian; Beaudon, Emilie; Duan, Keqin; Sierra-Hernández, M. Roxana; Kenny, Donald V.

    2018-05-01

    Records of recent climate from ice cores drilled in 2015 on the Guliya ice cap in the western Kunlun Mountains of the Tibetan Plateau, which with the Himalaya comprises the Third Pole (TP), demonstrate that this region has become warmer and moister since at least the middle of the 19th century. Decadal-scale linkages are suggested between ice core temperature and snowfall proxies, North Atlantic oceanic and atmospheric processes, Arctic temperatures, and Indian summer monsoon intensity. Correlations between annual-scale oxygen isotopic ratios (δ18O) and tropical western Pacific and Indian Ocean sea surface temperatures are also demonstrated. Comparisons of climate records during the last millennium from ice cores acquired throughout the TP illustrate centennial-scale differences between monsoon and westerlies dominated regions. Among these records, Guliya shows the highest rate of warming since the end of the Little Ice Age, but δ18O data over the last millennium from TP ice cores support findings that elevation-dependent warming is most pronounced in the Himalaya. This, along with the decreasing precipitation rates in the Himalaya region, is having detrimental effects on the cryosphere. Although satellite monitoring of glaciers on the TP indicates changes in surface area, only a few have been directly monitored for mass balance and ablation from the surface. This type of ground-based study is essential to obtain a better understanding of the rate of ice shrinkage on the TP.

  7. Linking orogen and peripheral foreland basin: conceptual model and application to the Southalpine-Dinaric (Friuli) orocline

    Science.gov (United States)

    Heberer, Bianca; Neubauer, Franz

    2010-05-01

    Surface uplift and rock exhumation within an orogen are generally a consequence of convergence, and can often be linked with subsidence in a peripheral foreland. Since vertical loads act on the entire lithosphere, these processes can, therefore, be considered as plate-scale processes. Here, we propose a conceptual model for this linkage for the Friuli orocline and its surrounding units. The Friuli orocline stretches from the ENE-trending Southern Alps to the SE-trending Dinarides. There, two Neogene stages of convergence and associated deformation can be differentiated: (1) a Mid-Late Miocene phase of increased surface uplift and intra-orogenic subsidence of sedimentary basins reflecting intra-orogenic crustal-scale folding. Depocentres are e.g. the flexural Belluno, Ljubljana and Klagenfurt basins. (2) A second stage of convergence during Late Pliocene-Pleistocene times led to overall surface uplift in the orogen and contemporaneous pronounced subsidence in the peripheral foreland basin (Venetian platform and the northern Adriatic Sea). We propose, that the spatially variable extent of subsidence originates in variably strong orogen-basin coupling, i.e. weak coupling during stage 1 vs. strong coupling during stage 2. This interpretation is based on the apatite fission track age pattern, the distribution of intra-orogenic Neogene sediment basins and subsidence analyses in the foreland basin (Barbieri et al., 2007). Available low-temperature thermochronological data for the Southern Alps and the NW Dinarides are sparse, in contrast to a dense network of primarily apatite fission track ages north of the Periadriatic lineament (e.g. summarized by Luth & Willingshofer, 2008). AFT ages adjacent to the eastern Periadriatic Lineament mainly range from 15 to 25 Ma (Hejl, 1997; Fodor et al., 2008). Detrital studies on Oligocene to Miocene sediments from the Venetian foreland basin yielded dominant age groups clustering roughly around 20 and 30 Ma (Stefani et al., 2008

  8. What happens along the flank and corner of a continental indenter? Insights from the easternmost Himalayan orogen and constraints on the models of the India-Asia collision

    Science.gov (United States)

    Haproff, P. J.; Yin, A.; Zuza, A. V.

    2017-12-01

    Investigations of continental collisions often focus on thrust belts oriented perpendicular to the plate-convergence direction and exclude belts that bound the flanks of a continental indenter despite being crucial to understanding the collisional process. Research of the Himalayan orogen, for example, has mostly centered on the east-trending thrust belt between the eastern and western syntaxes, resulting in inadequate examination of the north-trending Indo-Burma Ranges located along the eastern margin of India. To better understand the development of the entire Himalayan orogenic system, we conducted field mapping across the Northern Indo-Burma Range (NIBR), situated at the intersection of the eastern Himalaya and Indo-Burma Ranges. Our research shows that major lithologic units and thrust faults of the Himalaya extend to the NIBR, suggesting a shared geologic evolution. The structural framework of the NIBR consists of a southwest-directed thrust belt cored by a hinterland-dipping duplex, like the Himalaya. However, the Northern Indo-Burma orogen is distinct based on (1) the absence of the Tethyan Himalayan Sequence and southern Gangdese batholith, (2) the absence of the South Tibetan detachment, (3) crustal shortening greater than 80%, (4) an incredibly narrow orogen width of 7-33 km, (5) exposure of an ophiolitic mélange complex as a klippe, (6) and right-slip shear along the active range-bounding thrust fault. Furthermore, lithospheric deformation along the flank and northeast corner of India is characterized by right-slip transpression partitioned between the thrust belt and right-slip faults. Such a regime is interpreted to accommodate both contraction and clockwise rotation of Tibetan lithosphere around India, consistent with existing continuum deformation and rotation models.

  9. Seismological Constraints on Lithospheric Evolution in the Appalachian Orogen

    Science.gov (United States)

    Fischer, K. M.; Hopper, E.; Hawman, R. B.; Wagner, L. S.

    2017-12-01

    Crust and mantle structures beneath the Appalachian orogen, recently resolved by seismic data from the EarthScope SESAME Flexible Array and Transportable Array, provide new constraints on the scale and style of the Appalachian collision and subsequent lithospheric evolution. In the southern Appalachians, imaging with Sp and Ps phases reveals the final (Alleghanian) suture between the crusts of Laurentia and the Gondwanan Suwannee terrane as a low angle (Kellogg, 2017) isostatic arguments indicate crustal thicknesses were 15-25 km larger at the end of the orogeny, indicating a thick crustal root across the region. The present-day residual crustal root beneath the Blue Ridge mountains is estimated to have a density contrast with the mantle of only 104±20 kg/m3. This value is comparable to other old orogens but lower than values typical of young or active orogens, indicating a loss of lower crustal buoyancy over time. At mantle depths, the negative shear velocity gradient that marks the transition from lithosphere to asthenosphere, as illuminated by Sp phases, varies across the Appalachian orogen. This boundary is shallow beneath the northeastern U.S. and in the zone of Eocene volcanism in Virginia, where low velocity anomalies occur in the upper mantle. These correlations suggest recent active lithosphere-asthenosphere interaction.

  10. Evaluation of the Orogenic Belt Hypothesis for the Formation of Thaumasia, Mars

    Science.gov (United States)

    Nahm, A. L.; Schultz, R. A.

    2008-12-01

    The Thaumasia Highlands (TH) and Solis Planum are two of the best-known examples of compressional tectonics on Mars. The TH is a region of high topography located in the southern portion of the Tharsis Province, Mars. Solis Planum is located in eastern Thaumasia. Two hypotheses for the formation of this region have been suggested: sliding on a weak horizon or thrusting analogous to orogenic wedges on Earth. Both hypotheses require a shallowly dipping to sub-horizontal weak horizon below Thaumasia. Wrinkle ridges in Solis Planum are also inferred to sole into a décollement. If Thaumasia formed by thrusting related to sliding on a décollement, then certain conditions must be met as in critical taper wedge mechanics (CTWM) theory. If the angle between the surface slope and the basal décollement is less than predicted by the critical taper equation, the 'subcritical' wedge will deform internally until critical taper is achieved. Once the critical taper has been achieved, internal deformation ceases and the wedge will slide along its base. Formation of orogenic belts on Earth (such as the Central Mountains in Taiwan) can be described using CTWM. This method is applied here to the Thaumasia region on Mars. The surface slope (alpha) was measured in three locations: Syria Planum-Thaumasia margin, Solis Planum, and the TH. Topographic slopes were compared to the results from the critical taper equation. Because the dip of the basal décollement (beta) cannot be measured directly as on Earth, the dip angle was varied at 0 - 10 degrees; these values span the range of likely values based on terrestrial wedges. Pore fluid pressure (lambda) was varied between 0 (dry) and 0.9 (overpressured); these values span the full range of this important unknown parameter. Material properties, such as the coefficients of internal friction and of the basal décollement, were varied using reasonable values. Preliminary results show that for both reasonable (such as lambda = 0, mu b = 0

  11. Geochronology, geochemical and Sr-Nd-Hf-Pb isotopic compositions of the granitoids in the Yemaquan orefield, East Kunlun orogenic belt, northern Qinghai-Tibet Plateau: Implications for magmatic fractional crystallization and sub-solidus hydrothermal alteration

    Science.gov (United States)

    Yin, Shuo; Ma, Changqian; Xu, Jiannan

    2017-12-01

    A general consensus has emerged that high field strength elements (HFSE) can mobile to some extent in a hydrothermal fluid. However, there are hot debates on whether sub-solidus hydrothermal alteration can lower the Nb/Ta ratio in evolved melts. In this study, we present petrography, geochronology and geochemistry of the barren and mineralized rocks in the Yemaquan skarn iron deposit, northern Qinghai-Tibet Plateau, to probe magmatic-hydrothermal transition. The barren rocks consist of diorites, granodiorites, granites and syenogranites, whereas the porphyritic granodiorites are associated with mineralization for an excellent consistency between the magmatic zircon U-Pb age (225 ± 2 Ma) and the hydrothermal phlogopite 40Ar-39Ar age (225 ± 1.5 Ma). The Sr-Nd-Hf-Pb isotopic data demonstrate that the Yemaquan granitoids are originated from a relatively homogenous enriched mantle with different degrees of crust contamination (assimilation fractional crystallization, AFC). Trace elements signatures indicate that the porphyritic granodiorites related to mineralization display amphibole crystallization for high water contents, whereas the barren granites have gone through biotite crystallization due to potassium enrichment by continuous upper crust contamination, both of which are responsible for their Nb/Ta ratios, respectively. Modeling results suggest that a basaltic melt with Nb/Ta ratio of 15.3 can reach a minimum Nb/Ta ratio of 12 in the producing granodioritic melt by amphibole fractional crystallization based on partition coefficients of Nb and Ta between amphibole and melts from previous experiments. This may explain the average Nb/Ta ratio (13.7) of the barren granodiorites, while it cannot account for the average Nb/Ta ratio (8.4) of the mineralized porphyritic granodiorites, and it is even lower than that of the granites (10.3) with biotite fractional crystallization. Exsolution of a magmatic-hydrothermal fluid is inevitable when a water saturated magma emplaced in shallow crust, leading to a transportation of certain chemical components from the magmatic melts to exsolved fluids. Because Nb seems more mobile than Ta in fluorine-bearing fluids, we contend that a preferentially transport Nb over Ta by sub-solidus hydrothermal alteration can further lower the Nb/Ta ratios of the mineralized porphyritic granodiorites, which may also result in a broad range of HFSE contents and their ratios in the altered porphyritic granodiorites formed in a post-magmatic process.

  12. Assessment of BRDF effect of Kunlun Mountain glacier on Tibetan Plateau as a potential pseudo-invariant calibration site

    Science.gov (United States)

    Wang, Ling; Hu, Xiuqing; Chen, Lin

    2017-09-01

    Calibration is a critical step to ensure data quality and to meet the requirement of quantitative remote sensing in a broad range of scientific applications. One of the least expensive and increasingly popular methods of on-orbit calibration is the use of pseudo invariant calibration sites (PICS). A spatial homogenous and temporally stable area of 34 km2 in size around the center of Kunlun Mountain (KLM) over Tibetan Plateau (TP) was identified by our previous study. The spatial and temporal coefficient of variation (CV) this region was better than 4% for the reflective solar bands. In this study, the BRDF impacts of KLM glacier on MODIS observed TOA reflectance in band 1 (659 nm) are examined. The BRDF impact of KLM glacier with respect to the view zenith angle is studied through using the observations at a fixed solar zenith angle, and the effect with respect to the sun zenith angle is studied based on the observations collected at the same view angle. Then, the two widely used BRDF models are applied to our test data to simulate the variations of TOA reflectance due to the changes in viewing geometry. The first one is Ross-Li model, which has been used to produce the MODIS global BRDF albedo data product. The second one is snow surface BRDF model, which has been used to characterize the bidirectional reflectance of Antarctic snow. Finally, the accuracy and effectiveness of these two different BRDF models are tested through comparing the model of simulated TOA reflectance with the observed one. The results show that variations of the reflectances at a fixed solar zenith angle are close to the lambertian pattern, while those at a fixed sensor zenith angle are strongly anisotropic. A decrease in solar zenith angle from 50º to 20º causes an increase in reflectance by the level of approximated 50%. The snow surface BRDF model performs much better than the Ross-Li BRDF model to re-produce the Bi-Directional Reflectance of KLM glacier. The RMSE of snow surface BRDF

  13. Orogenic structural inheritance and rifted passive margin formation

    Science.gov (United States)

    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. Dynamic Settings and Interactions between Basin Subsidence and Orogeny in Zhoukou Depression and Dabie Orogenic Belt

    Institute of Scientific and Technical Information of China (English)

    2000-01-01

    This paper presents a study of the geo-dynamic setting and the relation between orogenic uplift and basin subsidence in the inland Zhoukou depression and Dabie orogenic belt. Since the Mesozoic the evolution of Zhoukou depression can be divided into three stages: (1) foreland basin, (2) transitional stage, (3) fault depression. Formation and variations of basin were not only related to the orogenesis, but also consistent with the orogenic uplift.

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

    Science.gov (United States)

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

    2015-11-01

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

  16. Occurrence and significance of blueschist in the southern Lachlan Orogen

    International Nuclear Information System (INIS)

    Spaggiari, C.V.; Gray, D.R.; Foster, D.A.; Fanning, C.M.

    2002-01-01

    Serpentinite/talc-matrix melanges, bearing blocks of blueschist metavolcanics, occur within the Heathcote and Governor Fault Zones of the southern Lachlan Orogen. In the Heathcote Fault Zone, serpentinite-matrix melange consists of blocks or small pods of boninite, andesite, ultramafic rocks, chert and volcanogenic sandstone variably metamorphosed to prehnite-pumpellyite, greenschist, or greenschist to blueschist facies. In the Governor Fault Zone, blueschist metavolcanics occur as blocks within serpentinite/talc matrix that is interleaved with prehnite-pumpellyite to greenschist facies, intermediate pressure slate and phyllite. Ar/Ar dating of white mica from slaty mud-matrix (broken formation) indicates that the main fabric development occurred at 446 ± 2 Ma. U-Pb (SHRIMP) dating of titanite from blueschists in the Governor Fault Zone indicates that metamorphism occurred at approximately 450 Ma, close to the time of melange formation. Previously published, Ar/Ar dating of white mica from phyllite and biotite from metadiorite in the Heathcote Fault Zone suggest that blueschist metamorphism occurred at a similar time. These ages are supported by field relationships. Illite crystallinity and b 0 data from white mica, and the preservation of blueschist blocks indicate that these fault zones maintained low temperatures both during and after intermediate- to high-pressure metamorphism. Occurrences of blueschists in the Arthur Lineament of the Tyennan (Delamerian) Orogen in Tasmania, and in the New England Orogen, have different ages, and in conjunction with the occurrences described here, suggest that subduction-accretion processes contributed significantly to the development of the Tasmanides from Cambrian through to Carboniferous times. Copyright (2002) Geological Society of Australia

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

    Science.gov (United States)

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

    2015-04-01

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

  18. Geochemical evidence for Paleozoic crustal growth and tectonic conversion in the Northern Beishan Orogenic Belt, southern Central Asian Orogenic Belt

    Science.gov (United States)

    Yuan, Yu; Zong, Keqing; He, Zhenyu; Klemd, Reiner; Jiang, Hongying; Zhang, Wen; Liu, Yongsheng; Hu, Zhaochu; Zhang, Zeming

    2018-03-01

    The Beishan Orogenic Belt is located in the central southernmost part of the Central Asian Orogenic Belt (CAOB), which plays a key role in understanding the formation and evolution of the CAOB. Granitoids are the documents of crustal and tectonic evolution in orogenic belts. However, little is known regarding the petrogenesis and geodynamic setting of the widely distributed Paleozoic granitoids in the Northern Beishan Orogenic Belt (NBOB). The present study reveals significant differences concerning the petrogenesis and tectonic setting of early and late Paleozoic granitoids from the NBOB. The early Paleozoic granitoids from the 446-430 Ma Hongliuxia granite complex of the Mazongshan unit and the 466-428 Ma Shibanjing complex of the Hanshan unit show classic I-type granite affinities as revealed by the relative enrichment of LILEs and LREEs, pronounced depletions of Nb, Ta and Ti and the abundant presence of hornblende. Furthermore, they are characterized by strongly variable zircon εHf(t) values between - 16.7 and + 12.8 and evolved plagioclase Sr isotopic compositions of 0.7145-0.7253, indicating the involvement of both juvenile and ancient continental crust in the magma source. Thus, we propose that the early Paleozoic granitoids in the NBOB were generated in a subduction-related continental arc setting. In contrast, the late Paleozoic 330-281 Ma granitoids from the Shuangjingzi complex of the Hanshan unit exhibit positive zircon εHf(t) values between + 5.8 and + 13.2 and relatively depleted plagioclase Sr isotopic compositions of 0.7037-0.7072, indicating that they were mainly formed by remelting of juvenile crust. Thus, an intra-plate extensional setting is proposed to have occurred during formation of the late Paleozoic granitoids. Therefore, between the early and late Paleozoic, the magma sources of the NBOB granitoids converted from the reworking of both juvenile and ancient crusts during a subduction-induced compressional setting to the remelting of

  19. Granite ascent and emplacement during contractional deformation in convergent orogens

    Science.gov (United States)

    Brown, Michael; Solar, Gary S.

    1998-09-01

    Based on a case study in the Central Maine Belt of west-central Maine, U.S.A., it is proposed that crustal-scale shear zone systems provide an effective focussing mechanism for transfer of granite melt through the crust in convergent orogens. During contractional deformation, flow of melt in crustal materials at depths below the brittle-plastic transition is coupled with plastic deformation of these materials. The flow is driven by pressure gradients generated by buoyancy forces and tectonic stresses. Within the oblique-reverse Central Maine Belt shear zone system, stromatic migmatite and concordant to weakly discordant irregular granite sheets occur in zones of higher strain, which suggests percolative flow of melt to form the migmatite leucosomes and viscous flow of melt channelized in sheet-like bodies, possibly along fractures. Cyclic fluctuations of melt pressure may cause instantaneous changes in the effective permeability of the flow network if self-propagating melt-filled tensile and/or dilatant shear fractures are produced due to melt-enhanced embrittlement. Inhomogeneous migmatite and schlieric granite occur in zones of lower strain, which suggests migration of partially-molten material through these zones en masse by granular flow, and channelized flow of melt carrying entrained residue. Founded on the Central Maine Belt case study, we develop a model of melt extraction and ascent using the driving forces, stress conditions and crustal rheologies in convergent, especially transpressive orogens. Ascent of melt becomes inhibited with decreasing depth as the solidus is approached. For intermediate a(H 2O) muscovite-dehydration melting, the water-saturated solidus occurs between 400 and 200 MPa, near the brittle-plastic transition during high- T-low- P metamorphism, where the balance of forces favors (sub-) horizontal fracture propagation. Emplacement of melt may be accommodated by ductile flow and/or stoping of wall rock, and inflation may be accommodated

  20. Critical elements in Carlin, epithermal, and orogenic gold deposits

    Science.gov (United States)

    Goldfarb, Richard J.; Hofstra, Albert H.; Simmons, Stuart F.

    2016-01-01

    Carlin, epithermal, and orogenic gold deposits, today mined almost exclusively for their gold content, have similar suites of anomalous trace elements that reflect similar low-salinity ore fluids and thermal conditions of metal transport and deposition. Many of these trace elements are commonly referred to as critical or near-critical elements or metals and have been locally recovered, although typically in small amounts, by historic mining activities. These elements include As, Bi, Hg, In, Sb, Se, Te, Tl, and W. Most of these elements are now solely recovered as by-products from the milling of large-tonnage, base metal-rich ore deposits, such as porphyry and volcanogenic massive sulfide deposits.A combination of dominance of the world market by a single country for a single commodity and a growing demand for many of the critical to near-critical elements could lead to future recovery of such elements from select epithermal, orogenic, or Carlin-type gold deposits. Antimony continues to be recovered from some orogenic gold deposits and tellurium could potentially be a primary commodity from some such deposits. Tellurium and indium in sphalerite-rich ores have been recovered in the past and could be future commodities recovered from epithermal ores. Carlin-type gold deposits in Nevada are enriched in and may be a future source for As, Hg, Sb, and/or Tl. Some of the Devonian carbonaceous host rocks in the Carlin districts are sufficiently enriched in many trace elements, including Hg, Se, and V, such that they also could become resources. Thallium may be locally enriched to economic levels in Carlin-type deposits and it has been produced from Carlin-like deposits elsewhere in the world (e.g., Alsar, southern Macedonia; Lanmuchang, Guizhou province, China). Mercury continues to be recovered from shallow-level epithermal deposits, as well as a by-product of many Carlin-type deposits where refractory ore is roasted to oxidize carbon and pyrite, and mercury is then

  1. Role of mantle dynamics in rebuilding the Tianshan Orogenic Belt in NW China: A seismic tomographic investigation

    Science.gov (United States)

    He, Chuansong; Santosh, M.

    2018-05-01

    The Tianshan orogenic belt, Junggar terrane and Altai terrane are located at the southwestern part of the Central Asian Orogenic Belt (CAOB). Here, we investigate the velocity structure beneath the Xinjiang region in NW China, which includes the Tarim terrane, Tianshan orogenic belt, Junggar terrane and Altai terrane with a view to evaluate the mantle dynamics based on teleseismic data recorded by 103 seismic stations. Our tomographic results show both high and low velocity perturbations beneath the Tianshan orogenic belt. We suggest that the high velocity perturbations beneath this orogenic belt might represent the northward subducted lithosphere of the Tarim Basin and the southward subducted lithosphere of the Junggar Basin. The low velocity structure beneath the Tianshan orogenic belt might represent asthenosphere upwelling that triggered the extensive magmatism which contributed to rebuilding of the Tianshan orogenic belt.

  2. Juvenile crustal recycling in an accretionary orogen: Insights from contrasting Early Permian granites from central Inner Mongolia, North China

    Science.gov (United States)

    Yuan, Lingling; Zhang, Xiaohui; Xue, Fuhong; Liu, Fulin

    2016-11-01

    Coeval high-K calc-alkaline to alkaline granites constitute important components of post-collisional to post-orogenic igneous suites in most orogenic belts of various ages on Earth and their genesis harbors a key to ascertaining critical geodynamic controls on continental crustal formation and differentiation. This zircon U-Pb dating and geochemical study documents three contrasting Early Permian granites from Erenhot of central Inner Mongolia, eastern Central Asian Orogenic Belt (CAOB) and reveals concurrent high-K calc-alkaline to alkaline granite association derived from successive partial melting of distinct protoliths. The ca. 280 Ma Gancihuduge (GCG) pluton shows a calc-alkaline I-type character, with initial 87Sr/86Sr ratios of 0.7035 to 0.7039, εNd(t) of + 1.87 to + 4.70, zircon εHf(t) of + 8.0 to + 13.2 and δ18O from 7.4 to 8.7‰. The ca. 276 Ma Cailiwusu (CLS) pluton is magnesian and peraluminous, with initial 87Sr/86Sr ratios of 0.7036 to 0.7040, εNd(t) of + 1.9 to + 2.4, zircon εHf(t) of + 6.5 to + 12.1 and δ18O from 9.7 to 10.9‰. These features are consistent with partial melts of mixed sources composed of newly underplated meta-basaltic to -andesitic protoliths and variable supracrustal components, with distinctively higher proportion of the latter in the CLS pluton. By contrast, the ca. 279 Ma Kunduleng (KDL) suite exhibits an A-type magmatic affinity, with typical enrichment in alkalis, Ga, Zr, Nb and Y, εNd(t) of + 2.39 to + 3.55, zircon εHf(t) from + 8.3 to + 12.3 and δ18O values from 6.8 to 7.5‰. These features suggest that they stem from high-temperature fusion of dehydrated K-rich mafic to intermediate protoliths. Besides presenting a snapshot into a stratified crustal architecture in δ18O, these contrasting granites could not only serve as a temporal marker for monitoring post-collisional extension in the aftermath of a retreating subduction zone, but also present spatial magmatic proxy for tracing crustal formation and

  3. SPECIFIC VELOCITY STRUCTURE OF THE UPPER MANTLE IN THE TRANSBAIKALIA SEGMENT OF THE MONGOLIA-OKHOTSK OROGENIC BELT

    Directory of Open Access Journals (Sweden)

    V. M. Soloviev

    2017-01-01

    Full Text Available The paper presents the results of deep seismic studies on Geophysical Reference Profile 1-SB (Sredneargunsk – Ust-Karenga – Taksimo – Vitim in East Transbaikalia,Russia. The1200 kmlong profile crosses the major tectonic structures of the Central Asian fold belt: the Argun median massif, the Selenga-Stanovoy and Transbaikalia folded regions, and the Baikal rift zone. Its northwestern fragment extends into the Angara-Lena monocline of the Siberian platform. The southeastern (Transbaikalia and northwestern (Baikal-Patom fragments of the profile are based on the spot (differential seismic sounding technique using explosions and 40-tonne vibrators. The south­eastern (Transbaikalia fragment shows small crustal thickness values (~40 km, an almost horizontal position of the Moho, and high velocities of longitudinal waves (~8.4 km/sec beneath the Moho. The analysis of parallelism graphs and the dynamic expression of the wave refracted from the Moho suggests a less than 5–10 km thick layer of high velocities and low gradients below Moho. The database on theterritoryofTransbaikaliaincludes ~200 wave arrival times from large earthquakes, which were refracted at the Moho at distances of ~200–1400 km. As part of the tomographic interpretation, using additional DSS data on the Moho, theterritoryofTransbaikaliahas been mapped to show the patterns of the threshold velocity values at the Moho. The seismic data was used to contour an area with high velocity values in the mantle in the central part of the Mongolia-Okhotsk orogenic belt and the neighboring fold structures of Transbaikalia. According to the analysis of the seismic and geologic data on the study area, the mantle layer with high velocity values in the Mongolian-Okhotsk orogenic belt may be represented by the eclogitic rock plates.

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

    Science.gov (United States)

    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.

  5. Metal mobility during metamorphism and formation of orogenic gold deposits: Insights from the Dalradian of Scotland

    OpenAIRE

    Engström, Adam

    2013-01-01

    Orogenic gold deposits occur within metamorphic belts throughout the world and have through time represented the source for over 25% of the world’s gold production. Although orogenic gold deposits are of great economic importance, controversies exist on the subject of fluid and metal sources and there have been few studies of gold´s distribution and mobility outside of large economic deposits. Research made by Pitcairn et al. (2006), on the Mesozoic Otago and Alpine schists of New Zealand, ob...

  6. Eastern Europe

    International Nuclear Information System (INIS)

    Baret, J.P.; Corcuff, A.; Jousten, M.; Cherie, J.B.; Gorge, X.; Augustin, X.; Belime, F.

    1999-01-01

    By its economical and political impact, nuclear energy has an important contribution the countries of Eastern Europe that goes beyond simple energy source. The most important challenge is to gain a safety culture. Improvements have been noted but the reactors safety must stay a priority of the international cooperation in Eastern Europe. The plan for the completion and improvement of Mochovce nuclear plant is described, the situation of Chernobyl and how to make the sarcophagus in safe is discussed, the experience of a french P.M.E. ( small and medium size firm) called Corys Tess that has chosen to position itself on the Eastern Europe nuclear market is related. (N.C.)

  7. Temporal evolution of granitic magmas in the Luanchuan metallogenic belt, east Qinling Orogen, central China: Implications for Mo metallogenesis

    Science.gov (United States)

    Li, Dong; Han, Jiangwei; Zhang, Shouting; Yan, Changhai; Cao, Huawen; Song, Yaowu

    2015-11-01

    The Luanchuan metallogenic belt, located within the eastern part of the Qinling Orogen, central China, hosts a number of world-class Mo deposits that are closely related to small late Mesozoic granitic plutons. Zircon U-Pb dating of distinct plutons in the Luanchuan metallogenic belt has yielded ages of 153 ± 1, 154 ± 2, 152 ± 2, and 148 ± 1 Ma. Molybdenite Re-Os isotopic compositions of Yuku ore district in the southern part of Luanchuan metallogenic belt has yielded an isochron age of 146 ± 1 Ma, which is consistent with the large-scale mineralization ages in the northern part of the Luanchuan metallogenic belt. A combination of previous studies and new geochronological and isotopic data show a concordant temporal and genetic link between granitic magmatism and Mo mineralization in the Luanchuan metallogenic belt, suggesting that this mineralization episode formed the most extensive Mo mineralization belt in the east Qinling Orogen. Zircon grains from Mo-related granitic plutons show similar trace element distributions. High-precision Multi Collector-Inductively Coupled Plasma-Mass Spectrometry (MC-ICP-MS) Pb isotope analysis of K-feldspar megacrysts from mineralization-related granites suggest that they were derived from the lower crust. Similarly, the Pb isotopic compositions of pyrite coprecipitated with molybdenite also suggest that the metals were derived form the lower crust, with probably minor mantle contribution. A continuum mineralization model that describes the sourcing of Mo from an evolving granitic magma over successive differentiation events, possibly in separate but connected magma chambers, could explain the remarkable Mo enrichment in the Luanchuan metallogenic belt. The volatile- and Mo-bearing granitic magmas ascended as diapirs from the deep crust, and were emplaced as dikes in the upper crust. Lithological differences between these Mo-bearing granites may relate to different stages in the evolution of individual magmas. Finally, ore

  8. Looking at the roots of the highest mountains: the lithospheric structure of the Himalaya-Tibet and the Zagros orogens. Results from a geophysical-petrological study

    Science.gov (United States)

    Tunini, L.; Jimenez-Munt, I.; Fernandez, M.; Villasenor, A.; Afonso, J. C.; Verges, J.

    2013-12-01

    The Himalaya-Tibet and Zagros orogens are the two most prominent mountain belts built by continental collision. They are part of a huge belt of Cenozoic age which runs from the Pyrenees to Burma. In its central sector, the collision with the southern margin of the Eurasian plate has resulted not only in the building of mountain ranges over the north-eastern edges of the Arabian and Indian plates but also in widespread deformation 1000-3000 km from the suture zones. Zagros and Himalaya-Tibet orogens share many geodynamic processes but at different rates, amount of convergence and stage of development. The study of their present-day structures provides new insights into their quasi coeval collisional event pointing out differences and similarities in the mountain building processes. We present 2D crust and upper mantle cross-sections down to 400 km depth, along four SW-NE trending profiles. Two profiles cross the Zagros Mountains, running from the Mesopotamian Foreland Basin up to the Alborz and Central Iran. Two other profiles run through the Himalaya-Tibetan orogen: the western transect crosses the western Himalaya, Tarim Basin, Tian Shan Mountains and Junggar Basin; the eastern transect runs from the Indian shield to the Beishan Basin, crossing the eastern Himalaya, Tibetan Plateau, Qaidam Basin and Qilian Mountains. We apply the LitMod-2D code which integrates potential fields (gravity and geoid), isostasy (elevation) and thermal (heat flow and temperature distribution) equations, and mantle petrology. The resulting crust and upper mantle structure is constrained by available data on elevation, Bouguer anomaly, geoid height, surface heat flow and seismic data including P- and S-wave tomography models. Our results show distinct deformation patterns between the crust and the lithospheric mantle beneath the Zagros and Himalaya-Tibetan orogens, indicating a strong strain partitioning in both areas. At crustal level, we found a thickening beneath the Zagros and the

  9. The asymmetric evolution of the Colombian Eastern Cordillera. Tectonic inheritance or climatic forcing? New evidence from thermochronology and sedimentology

    Science.gov (United States)

    Ramirez-Arias, Juan Carlos; Mora, Andrés; Rubiano, Jorge; Duddy, Ian; Parra, Mauricio; Moreno, Nestor; Stockli, Daniel; Casallas, Wilson

    2012-11-01

    New thermochronological data, facies, paleocurrents and provenance allow us to refine the chronology of deformation in the central segment of the Colombian Eastern Cordillera. Based on a new extensive AFT dataset, we document the spatial evolution of active deformation, from the axial zone of the Eastern Cordillera at about 50 Ma in to active growth of the frontal thin skinned structures in Late Miocene time. Paleocurrents allow us to push backwards into the Middle to Early Late-Miocene the emergence of the easternmost frontal thrust; whereas careful assessment of exposure gates tied to AFT data enable to refine the unroofing history for Eocene to Miocene times. Based on that, we produced a kinematically restored cross section with higher resolution than previous assessments. Using these datasets, we compare the evolution of the central segment of the Eastern Cordillera in this region with the evolution of adjacent areas in the context of climatic forcing of orogenic evolution. We find that in this region and, in the Eastern Cordillera in general, tectonic inheritance and transpression exert an initial dominant control on the initial orogen asymmetry, which is later enhanced due to an orographically-focused erosion. We therefore suggest that it is not climate alone the factor controlling orogenic asymmetry in the Eastern Cordillera of Colombia.

  10. Temporal constraints on the kinematics of the destabilization of an orogen : syn- to post-orogenic extensional collapse of the Northern Aegean region

    NARCIS (Netherlands)

    Lips, A.L.W.

    1998-01-01

    The Mediterranean region is situated at the interface of the African and Eurasian plates and has been shaped by the Alpine Orogeny and the subsequent post-orogenic extension during the convergence and collision of the African and Eurasian plates. Numerous tectonic studies have focussed on the role

  11. Temporal constraints on the kinematics of the destabilization of an orogen : syn- to post-orogenic extensional collapse of the Northern Aegean region

    NARCIS (Netherlands)

    Lips, A.L.W.

    1998-01-01

    The Mediterranean region is situated at the interface of the African and Eurasian plates and has been shaped by the Alpine Orogeny and the subsequent post-orogenic extension during the convergence and collision of the African and Eurasian plates. Numerous tectonic studies have focussed on the

  12. Deformation of the Songshugou ophiolite in the Qinling orogen

    Science.gov (United States)

    Sun, Shengsi; Dong, Yunpeng

    2017-04-01

    The Qinling orogen, middle part of the China Central Orogenic Belt, is well documented that was constructed by multiple convergences and subsequent collisions between the North China and South China Blocks mainly based on geochemistry and geochronology of ophiolites, magmatic rocks as well as sedimentary reconstruction. However, this model is lack of constraints from deformation of subduction/collision. The Songshugou ophiolite outcropped to the north of the Shangdan suture zone represents fragments of oceanic crust and upper mantle. Previous works have revealed that the ophiolite was formed at an ocean ridge and then emplaced in the northern Qinling belt. Hence, deformation of the ophiolite would provide constraints for the rifting and subduction processes. The ophiolite consists chiefly of metamorphosed mafic and ultramafic rocks. The ultramafic rocks contain coarse dunite, dunitic mylonite and harzburgite, with minor diopsidite veins. The mafic rocks are mainly amphibolite, garnet amphibolite and amphibole schist, which are considered to be eclogite facies and retrograde metamorphosed oceanic crust. Amphibole grains in the mafic rocks exhibit a strong shape-preferred orientation parallel to the foliation, which is also parallel to the lithologic contacts between mafic and ultramafic rocks. Electron backscattered diffraction (EBSD) analyses show strong olivine crystallographic preferred orientations (CPO) in dunite including A-, B-, and C-types formed by (010)[100], (010)[001] and (100)[001] dislocation slip systems, respectively. A-type CPO suggests high temperature plastic deformation in the upper mantle. In comparison, B-type may be restricted to regions with significantly high water content and high differential stress, and C-type may also be formed in wet condition with lower differential stress. Additionally, the dunite evolved into amphibolite facies metamorphism with mineral assemblages of olivine + talc + anthophyllite. Assuming a pressure of 1.5 GPa

  13. Some aspects of the role of rift inheritance on Alpine-type orogens

    Science.gov (United States)

    Tugend, Julie; Manatschal, Gianreto; Mohn, Geoffroy; Chevrot, Sébastien

    2017-04-01

    Processes commonly recognized as fundamental for the formation of collisional orogens include oceanic subduction, arc-continent and continent-continent collision. As collisional belts result from the closure of oceanic basins and subsequent inversion of former rifted margins, their formation and evolution may also in theory be closely interlinked with the initial architecture of the former rifted margins. This assumption is indeed more likely to be applicable in the case of Alpine-type orogens, mainly controlled by mechanical processes and mostly devoid of arc-related magmatism. More and more studies from present-day magma-poor rifted margins illustrate the complex evolution of hyperextended domains (i.e. severely thinned continental crust (images across the Pyrenees (PYROPE) and the Alps (CIFALPS) reveal a surprisingly comparable present-day overall crustal and lithospheric structure. Based on the comparison between the two orogens we discuss: (1) the nature and depth of decoupling levels inherited from hyperextension; (2) the implications for restorations and interpretations of orogenic roots (former hyperextended domains vs. lower crust only); and (3) the nature and major role of buttresses in controlling the final stage of collisional processes. Eventually, we discuss the variability of the role of rift-inheritance in building Alpine-type orogens. The Pyrenees seem to represent one extreme, where rift-inheritance is important at different stages of collisional processes. In contrast, in the Alps the role of rift-inheritance is subtler, likely because of its more complex and polyphase compressional deformation history.

  14. Post-20 Ma Motion of the Adriatic Plate: New Constraints From Surrounding Orogens and Implications for Crust-Mantle Decoupling

    Science.gov (United States)

    Le Breton, Eline; Handy, Mark R.; Molli, Giancarlo; Ustaszewski, Kamil

    2017-12-01

    A new kinematic reconstruction that incorporates estimates of post-20 Ma shortening and extension in the Apennines, Alps, Dinarides, and Sicily Channel Rift Zone (SCRZ) reveals that the Adriatic microplate (Adria) rotated counterclockwise as it subducted beneath the European Plate to the west and to the east, while indenting the Alps to the north. Minimum and maximum amounts of rotation are derived by using, respectively, estimates of crustal extension along the SCRZ (minimum of 30 km) combined with crustal shortening in the Eastern Alps (minimum of 115 km) and a maximum amount (140 km) of convergence between Adria and Moesia across the southern Dinarides and Carpatho-Balkan orogens. When combined with Neogene convergence in the Western Alps, the best fit of available structural data constrains Adria to have moved 113 km to the NW (azimuth 325°) while rotating 5 ± 3° counterclockwise relative to Europe since 20 Ma. Amounts of plate convergence predicted by our new model exceed Neogene shortening estimates of several tens of kilometers in both the Apennines and Dinarides. We attribute this difference to crust-mantle decoupling (delamination) during rollback in the Apennines and to distributed deformation related to the northward motion of the Dacia Unit between the southern Dinarides and Europe (Moesia). Neogene motion of Adria resulted from a combination of Africa pushing from the south, the Adriatic-Hellenides slab pulling to the northeast, and crustal wedging in the Western Alps, which acted as a pivot and stopped farther northwestward motion of Adria relative to Europe.

  15. Palaeozoic synorogenic sedimentation in central and northern Australia: a review of distribution and timing with implications for the evolution of intracontinental orogens

    International Nuclear Information System (INIS)

    Haines, P.W.; Hand, M.; Sandiford, M.

    2001-01-01

    The Palaeozoic Alice Springs Orogeny was a major intraplate tectonic event in central and northern Australia. The sedimentological, structural and isotopic effects of the Alice Springs Orogeny have been well documented in the northern Amadeus Basin and adjacent exhumed Arunta lnlier, although the full regional extent of the event, as well as lateral variations in timing and intensity are less well known. Because of the lack of regional isotopic data, we take a sedimentological approach towards constraining these parameters, compiling the location and age constraints of inferred synorogenic sedimentation across a number of central and northern Australian basins. Such deposits are recorded from the Amadeus, Ngalia, Georgina, Wiso, Eastern Officer and, possibly, Warburton Basins. Deposits are commonly located adjacent to areas of significant basement uplift related to north-south shortening. In addition, similar aged orogenic deposits occur in association with strike-slip tectonism in the Ord and southern Bonaparte Basins of northwest Australia. From a combination of sedimentological and isotopic evidence it appears that localised convergent deformation started in the Late Ordovician in the eastern Arunta lnlier and adjacent Amadeus Basin. Synorogenic style sedimentation becomes synchronously widespread in the late Early Devonian and in most areas the record terminates abruptly close to the end of the Devonian. A notable exception is the Ngalia Basin in which such sedimentation continued until the mid-Carboniferous. In the Ord and Bonaparte Basins there is evidence of two discrete pulses of transcurrent activity in the Late Devonian and Carboniferous. The sedimentological story contrasts with the isotopic record from the southern Arunta lnlier, which has generally been interpreted in terms of continuous convergent orogenic activity spanning most of the Devonian and Carboniferous, with a suggestion that rates of deformation increased in the mid-Carboniferous. Either

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

    Science.gov (United States)

    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

  17. Multiple sulfur isotopes monitor fluid evolution of an Archean orogenic gold deposit

    Science.gov (United States)

    LaFlamme, Crystal; Sugiono, Dennis; Thébaud, Nicolas; Caruso, Stefano; Fiorentini, Marco; Selvaraja, Vikraman; Jeon, Heejin; Voute, François; Martin, Laure

    2018-02-01

    The evolution of a gold-bearing hydrothermal fluid from its source to the locus of gold deposition is complex as it experiences rapid changes in thermochemical conditions during ascent through the crust. Although it is well established that orogenic gold deposits are generated during time periods of abundant crustal growth and/or reworking, the source of fluid and the thermochemical processes that control gold precipitation remain poorly understood. In situ analyses of multiple sulfur isotopes offer a new window into the relationship between source reservoirs of Au-bearing fluids and the thermochemical processes that occur along their pathway to the final site of mineralisation. Whereas δ34S is able to track changes in the evolution of the thermodynamic conditions of ore-forming fluids, Δ33S is virtually indelible and can uniquely fingerprint an Archean sedimentary reservoir that has undergone mass independent fractionation of sulfur (MIF-S). We combine these two tracers (δ34S and Δ33S) to characterise a gold-bearing laminated quartz breccia ore zone and its sulfide-bearing alteration halo in the (+6 Moz Au) structurally-controlled Archean Waroonga deposit located in the Eastern Goldfields Superterrane of the Yilgarn Craton, Western Australia. Over 250 analyses of gold-associated sulfides yield a δ34S shift from what is interpreted as an early pre-mineralisation phase, with chalcopyrite-pyrrhotite (δ34S = +0.7‰ to +2.9‰) and arsenopyrite cores (δ34S = ∼-0.5‰), to a syn-mineralisation stage, reflected in Au-bearing arsenopyrite rims (δ34S = -7.6‰ to +1.5‰). This shift coincides with an unchanging Δ33S value (Δ33S = +0.3‰), both temporally throughout the Au-hosting hydrothermal sulfide paragenesis and spatially across the Au ore zone. These results indicate that sulfur is at least partially recycled from MIF-S-bearing Archean sediments. Further, the invariant nature of the observed MIF-S signature demonstrates that sulfur is derived from a

  18. Neodymium and strontium isotope study of ophiolite and orogenic lherzolite petrogenesis

    International Nuclear Information System (INIS)

    Richard, P.; Allegre, C.J.; Paris-7 Univ., 75

    1980-01-01

    Neodymium isotopic analyses have been measured on nine ophiolites and four orogenic lherzolites. Epsilonsub(Nd) varies from +12 to +3 in the ophiolites and from +18 to +2 in the orogenic lherzolites. The majority of the analyses plot on a epsilonsub(Nd)-epsilonsub(Sr) correlation line as defined by Nd and Sr isotopic analyses of oceanic basalts. However, certain ophiolitic and lherzolitic samples exhibit high 87 Sr/ 86 Sr ratios and as such lie to the right of the correlation line towards seawater compositions. From these data one can postulate several origins for ophiolites including that of mid-ocean ridges and ocean islands. If the orogenic lherzolites are interpreted as representative of the mantle occurring below active ridges a more complex model is required involving mantle heterogeneity and multi-episodic chemical fractionation starting prior to 2 Ga ago. (orig.)

  19. Accretionary and collisional orogenesis in the south domain of the western Central Asian Orogenic Belt (CAOB)

    Science.gov (United States)

    Cai, Keda; Long, Xiaoping; Chen, Huayong; Sun, Min; Xiao, Wenjiao

    2018-03-01

    The Central Asian Orogenic Belt (CAOB) was the result of long-lived multi-stage tectonic evolution, including Proterozoic to Paleozoic accretion and collision, Mesozoic intracontinental modification, and Cenozoic rapid deformation and uplift. The accretionary and collisional orogenesis of its early history generated a huge orogenic collage consisting of diverse tectonic units including island arcs, ophiolites, accretionary prisms, seamounts, oceanic plateaus and micro-continents. These incorporated orogenic components preserved valuable detailed information on orogenic process and continental crust growth, which make the CAOB a key region to understanding of continental evolution, mantle-crust interaction and associated mineralization. The western CAOB refers to the west region in North Xinjiang of China and circum-Balkash of Kazakhstan, with occurrences of the spectacular Kazakhstan orocline and its surrounding mountain belts. Because orogenic fabrics of this part mostly preserve their original features caused by the interactions among the southern Siberian active margin in the north and the Tarim Craton in the south, the western CAOB can be regarded as an ideal region to study the processes of the accretionary and collisional orogenesis and associated mineralization. Since a large number of researchers have been working on this region, research advances bloom strikingly in a short-time period. Therefore, we, in this special issue, focus on these new study advances on the south domain of the western CAOB, including the Kazakhstan collage system, Tianshan orogenic belt and Beishan region, and it is anticipated that this issue can draw more attention from the international research groups to be interested in the studies on orogenesis of the CAOB.

  20. The giant Jiaodong gold province: The key to a unified model for orogenic gold deposits?

    Directory of Open Access Journals (Sweden)

    David I. Groves

    2016-05-01

    Full Text Available Although the term orogenic gold deposit has been widely accepted for all gold-only lode-gold deposits, with the exception of Carlin-type deposits and rare intrusion-related gold systems, there has been continuing debate on their genesis. Early syngenetic models and hydrothermal models dominated by meteoric fluids are now clearly unacceptable. Magmatic-hydrothermal models fail to explain the genesis of orogenic gold deposits because of the lack of consistent spatially – associated granitic intrusions and inconsistent temporal relationships. The most plausible, and widely accepted, models involve metamorphic fluids, but the source of these fluids is hotly debated. Sources within deeper segments of the supracrustal successions hosting the deposits, the underlying continental crust, and subducted oceanic lithosphere and its overlying sediment wedge all have their proponents. The orogenic gold deposits of the giant Jiaodong gold province of China, in the delaminated North China Craton, contain ca. 120 Ma gold deposits in Precambrian crust that was metamorphosed over 2000 million years prior to gold mineralization. The only realistic source of fluid and gold is a subducted oceanic slab with its overlying sulfide-rich sedimentary package, or the associated mantle wedge. This could be viewed as an exception to a general metamorphic model where orogenic gold has been derived during greenschist- to amphibolite-facies metamorphism of supracrustal rocks: basaltic rocks in the Precambrian and sedimentary rocks in the Phanerozoic. Alternatively, if a holistic view is taken, Jiaodong can be considered the key orogenic gold province for a unified model in which gold is derived from late-orogenic metamorphic devolatilization of stalled subduction slabs and oceanic sediments throughout Earth history. The latter model satisfies all geological, geochronological, isotopic and geochemical constraints but the precise mechanisms of auriferous fluid release, like many

  1. Climate Changes Documented in Ice Core Records from Third Pole Glaciers, with Emphasis on the Guliya Ice Cap in the Western Kunlun Mountains over the Last 100 Years

    Science.gov (United States)

    Thompson, L. G.; Yao, T.; Beaudon, E.; Mosley-Thompson, E.; Davis, M. E.; Kenny, D. V.; Lin, P. N.

    2016-12-01

    The Third Pole (TP) is a rapidly warming region containing 100,000 km2 of ice cover that collectively holds one of Earth's largest stores of freshwater that feeds Asia's largest rivers and helps sustain 1.5 billion people. Information on the accelerating warming in the region, its impact on the glaciers and subsequently on future water resources is urgently needed to guide mitigation and adaptation policies. Ice core histories collected over the last three decades across the TP demonstrate its climatic complexity and diversity. Here we present preliminary results from the flagship project of the Third Pole Environment Program, the 2015 Sino-American cooperative ice core drilling of the Guliya ice cap in the Kunlun Mountains in the western TP near the northern limit of the region influenced by the southwest monsoon. Three ice cores, each 51 meters in length, were recovered from the summit ( 6700 masl) while two deeper cores, one to bedrock ( 310 meters), were recovered from the plateau ( 6200 masl). Across the ice cap the net balance (accumulation) has increased annually by 2.3 cm of water equivalent from 1963-1992 to 1992-2015, and average oxygen isotopic ratios (δ18O) have enriched by 2‰. This contrasts with the recent ablation on the Naimona'nyi glacier located 540 km south of Guliya in the western Himalaya. Borehole temperatures in 2015 on the Guliya plateau have warmed substantially in the upper 30 meters of the ice compared to temperatures in 1992, when the first deep-drilling of the Guliya plateau was conducted. Compared with glaciers in the northern and western TP, the Himalayan ice fields are more sensitive to both fluctuations in the South Asian Monsoon and rising temperatures in the region. We examine the climatic changes of the last century preserved in ice core records from sites throughout the TP and compare them with those reconstructed for earlier warm epochs, such as the Medieval Climate Anomaly ( 950-1250 AD), the early Holocene "Hypsithermal

  2. The crustal structures from Wuyi-Yunkai orogen to Taiwan orogen: the onshore-offshore wide-angle seismic experiment of TAIGER and ATSEE projects

    Science.gov (United States)

    Kuochen, H.; Kuo, N. Y. W.; Wang, C. Y.; Jin, X.; Cai, H. T.; Lin, J. Y.; Wu, F. T.; Yen, H. Y.; Huang, B. S.; Liang, W. T.; Okaya, D. A.; Brown, L. D.

    2015-12-01

    The crustal structure is key information for understanding the tectonic framework and geological evolution in the southeastern China and its adjacent area. In this study, we integrated the data sets from the TAIGER and ATSEE projects to resolve onshore-offshore deep crustal seismic profiles from the Wuyi-Yunkai orogen to the Taiwan orogen in southeastern China. Totally, there are three seismic profiles resolved and the longest profile is 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. 40 shots, 2 earthquakes, and about 1,950 stations were used and 15,319 arrivals were picked among three transects. As a result, the complex crustal evolution since Paleozoic era are shown, which involved the closed Paleozoic rifted basin in central Fujian, the Cenozoic extension due to South China sea opening beneath the coastline of southern Fujian, and the on-going collision of the Taiwan orogen.

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

    Science.gov (United States)

    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

  4. Reassessment of the geologic evolution of selected precambrian terranes in Brazil, based on SHRIMP U-Pb data, part 2: mineiro and Aracuai orogens and Southern Sao Francisco craton

    International Nuclear Information System (INIS)

    Silva, Luiz Carlos da; Pimentel, Marcio; Armstrong, Richard; Noce, Carlos Mauricio; Pedrosa-Soares, Antonio Carlos; Carneiro, Mauricio Antonio

    2002-01-01

    This paper discusses new zircon SHRIMP (Sensitive High Resolution Ion Microprobe) U-Pb geochronological data for 19 key-exposures of several geological units exposed at the eastern border of the Southern Sao Francisco Craton and at the adjacent Proterozoic Mineiro and Aracuai orogens. Samples were collected along several E-W tran sects, aiming at tracing the precise limit of the Sao Francisco Craton Archean basement, as well as assessing the extension of the successive proterozoic orogenic collages. Due to the complex geologic history and/or high grade metamorphism which most of the rock units investigated have undergone, zircon morphology and the U-Pb analytical data exhibit very complex patterns. These are characterized by a combination of inheritance, partial resetting and new zircon growth during high-grade metamorphism. As a consequence, very careful and detailed analyses of cathodoluminescence imagery were required to allow distinction between inheritance, newly melt-precipitated zircon and partially reset zircons, as well as between the ages of magmatic and metamorphic events. In the southeastern border of the craton 5 units yielded Archean crystallization ages ranging from ca. 3000-2700 Ma, with poorly constrained metamorphic ages ranging from ca. 2850 to 550 Ma. The TTG gneissic complex exposed to the east and south of the Quadrilatero Ferrifero, formerly ascribed to the Archean basement, have crystallization ages from ca. 2210 Ma to 2050 Ma, and can now be interpreted as representing pre- to syn-collisional magmatic phases of the Mineiro Belt. Metamorphic ages of ca. 2100 Ma and 560 Ma are also well constrained in zircon populations from these gneisses. The crystallization age of ca 1740 Ma observed for an alkaline granite of the Borrachudos Suite (intrusive into the Archean basement east of the Southern Espinhaco Range) confirmed previous conventional U-Pb data for this Paleoproterozoic rift-related magmatism. One of the major basement inliers within the

  5. Variability of orogenic magmatism during Mediterranean-style continental collisions : A numerical modelling approach

    NARCIS (Netherlands)

    Andrić, N.; Vogt, K.; Matenco, L.; Cvetković, V.; Cloetingh, S.; Gerya, T.

    The relationship between magma generation and the tectonic evolution of orogens during subduction and subsequent collision requires self-consistent numerical modelling approaches predicting volumes and compositions of the produced magmatic rocks. Here, we use a 2D magmatic-thermomechanical numerical

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

    NARCIS (Netherlands)

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

    2016-01-01

    Abstract 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

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

    Science.gov (United States)

    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. The Alpine-Carpathian-Dinaridic orogenic system: correlation and evolution of tectonic units

    NARCIS (Netherlands)

    Schmid, S.M.; Bernoulli, D.; Fügenschuh, B.; Matenco, L.C.; Schefer, S.; Schuster, R.; Tischler, M.; Ustaszewski, K.

    2008-01-01

    A correlation of tectonic units of the Alpine-Carpathian-Dinaridic system of orogens, including the substrate of the Pannonian and Transylvanian basins, is presented in the form of a map. Combined with a series of crustal-scale cross sections this correlation of tectonic units yields a clearer

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

    Science.gov (United States)

    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.

  10. Magnetic fabric transposition in folded granite sills in Variscan orogenic wedge

    Czech Academy of Sciences Publication Activity Database

    Závada, Prokop; Calassou, T.; Schulmann, K.; Hrouda, F.; Štípská, P.; Hasalová, Pavlína; Míková, J.; Magna, T.; Mixa, P.

    2017-01-01

    Roč. 94, January (2017), s. 166-183 ISSN 0191-8141 R&D Projects: GA ČR GA14-15632S Institutional support: RVO:67985530 Keywords : orogenic sill * AMS fabric * folding Subject RIV: DB - Geology ; Mineralogy OBOR OECD: Geology Impact factor: 2.408, year: 2016

  11. Deformation correlations, stress field switches and evolution of an orogenic intersection: The Pan-African Kaoko-Damara orogenic junction, Namibia

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    Ben Goscombe

    2017-11-01

    Full Text Available Age calibrated deformation histories established by detailed mapping and dating of key magmatic time markers are correlated across all tectono-metamorphic provinces in the Damara Orogenic System. Correlations across structural belts result in an internally consistent deformation framework with evidence of stress field rotations with similar timing, and switches between different deformation events. Horizontal principle compressive stress rotated clockwise ∼180° in total during Kaoko Belt evolution, and ∼135° during Damara Belt evolution. At most stages, stress field variation is progressive and can be attributed to events within the Damara Orogenic System, caused by changes in relative trajectories of the interacting Rio De La Plata, Congo, and Kalahari Cratons. Kaokoan orogenesis occurred earliest and evolved from collision and obduction at ∼590 Ma, involving E–W directed shortening, progressing through different transpressional states with ∼45° rotation of the stress field to strike-slip shear under NW–SE shortening at ∼550–530 Ma. Damaran orogenesis evolved from collision at ∼555–550 Ma with NW–SE directed shortening in common with the Kaoko Belt, and subsequently evolved through ∼90° rotation of the stress field to NE–SW shortening at ∼512–508 Ma. Both Kaoko and Damara orogenic fronts were operating at the same time, with all three cratons being coaxially convergent during the 550–530 Ma period; Rio De La Plata directed SE against the Congo Craton margin, and both together over-riding the Kalahari Craton margin also towards the SE. Progressive stress field rotation was punctuated by rapid and significant switches at ∼530–525 Ma, ∼508 Ma and ∼505 Ma. These three events included: (1 Culmination of main phase orogenesis in the Damara Belt, coinciding with maximum burial and peak metamorphism at 530–525 Ma. This occurred at the same time as termination of transpression and initiation of

  12. Arc magmatism as a window to plate kinematics and subduction polarity: Example from the eastern Pontides belt, NE Turkey

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    Yener Eyuboglu

    2011-01-01

    Full Text Available The Eastern Pontides orogenic belt in the Black Sea region of Turkey offers a critical window to plate kinematics and subduction polarity during the closure of the Paleotethys. Here we provide a brief synthesis on recent information from this belt. We infer a southward subduction for the origin of the Eastern Pontides orogenic belt and its associated late Mesozoic–Cenozoic magmatism based on clear spatial and temporal variations in Late Cretaceous and Cenozoic arc magmatism, together with the existence of a prominent south-dipping reverse fault system along the entire southern coast of the Black Sea. Our model is at variance with some recent proposals favoring a northward subduction polarity, and illustrates the importance of arc magmatism in evaluating the geodynamic milieu associated with convergent margin processes.

  13. The Russian-Kazakh Altai orogen: An overview and main debatable issues

    Directory of Open Access Journals (Sweden)

    Inna Safonova

    2014-07-01

    Full Text Available The paper reviews previous and recently obtained geological, stratigraphic and geochronological data on the Russian-Kazakh Altai orogen, which is located in the western Central Asian Orogenic Belt (CAOB, between the Kazakhstan and Siberian continental blocks. The Russian-Kazakh Altai is a typical Pacific-type orogen, which represents a collage of oceanic, accretionary, fore-arc, island-arc and continental margin terranes of different ages separated by strike-slip faults and thrusts. Evidence for this comes from key indicative rock associations, such as boninite- and turbidite (graywacke-bearing volcanogenic-sedimentary units, accreted pelagic chert, oceanic islands and plateaus, MORB-OIB-protolith blueschists. The three major tectonic domains of the Russian-Kazakh Altai are: (1 Altai-Mongolian terrane (AMT; (2 subduction-accretionary (Rudny Altai, Gorny Altai and collisional (Kalba-Narym terranes; (3 Kurai, Charysh-Terekta, North-East, Irtysh and Char suture-shear zones (SSZ. The evolution of this orogen proceeded in five major stages: (i late Neoproterozoic–early Paleozoic subduction-accretion in the Paleo-Asian Ocean; (ii Ordovician–Silurian passive margin; (iii Devonian–Carboniferous active margin and collision of AMT with the Siberian continent; (iv late Paleozoic closure of the PAO and coeval collisional magmatism; (v Mesozoic post-collisional deformation and anarogenic magmatism, which created the modern structural collage of the Russian-Kazakh Altai orogen. The major still unsolved problem of Altai geology is origin of the Altai-Mongolian terrane (continental versus active margin, age of Altai basement, proportion of juvenile and recycled crust and origin of the middle Paleozoic units of the Gorny Altai and Rudny Altai terranes.

  14. Erosion rates across space and timescales from a multi-proxy study of rivers of eastern Taiwan

    Science.gov (United States)

    Fellin, Maria Giuditta; Chen, Chia-Yu; Willett, Sean D.; Christl, Marcus; Chen, Yue-Gau

    2017-10-01

    We derive erosion rates from detrital zircon fission-track ages and cosmogenic nuclide concentrations from sediments from the modern rivers of eastern Taiwan in order to investigate how surface erosional processes vary in space and time across the young arc-continent collisional orogen of Taiwan. Taiwan is characterized by rapid rates of exhumation, a fluvial and landslide-dominated landscape, high seismicity, high relief and frequent typhoons. The obliquity between the convergence direction and the trend of the plate boundary provides a gradient in uplift and variations in longevity of orogenic activity with a young, immature orogen in the south, a mature orogen in central and northern Taiwan, and perhaps even the cessation of orogeny in the far north. The modern zircon fission-track detrital record is consistent with basement ages that show that much of the orogen is eroding at high rates with basin-wide mean zircon fission-track cooling ages as young as 0.9 Ma. The erosion rates derived from concentrations of cosmogenic nuclides (10Be) provide erosion rates averaged over much shorter timescales, but these two proxies provide estimates of erosion rates that are within error of each other across most of the collisional belt. Erosion rates are lowest in the immature zone of the orogen (Taiwan, and increase to values ≥ 4 km/Ma in central Taiwan. Geomorphic indices, in particular channel steepness, are also correlated with erosion rates, suggesting that fluvial erosion is the dominant exhumation process and that landscape evolution is reacting primarily to tectonic forcing, fast enough to keep the landscape in a state of quasi-equilibrium where erosion rates and rock uplift rates are nearly equal. We find no measurable effects due to rock erodibility or precipitation rate, but if these parameters co-vary with tectonic uplift rate, our data could not resolve the influence of each.

  15. A prolonged Cenozoic erosional period in East Kunlun (Western China): Constraints of detrital apatite (U-Th)/He ages on the onset of mountain building along the northern margin of the Tibetan Plateau

    Science.gov (United States)

    Shi, Wenbei; Wang, Fei; Wu, Lin; Yang, Liekun; Zhang, Weibin; Wang, Yinzhi

    2018-01-01

    The timing of the development of the highland topography along the northern margin of the Tibetan Plateau is the key to understanding the manner of Tibetan growth and the far-field effects of the collision between India and Eurasia. Although various studies have investigated the exhumation and uplift of the basement rocks, thermochronological studies on the detritus from a continuous depositional sequence inan intermontane basin are lacking but might shed light on this issue. In this study, a set of detrital apatites from an upper Eocene to Pliocene depositional sequence in the Kumukol Basin, the largest intermontane basin in the East Kunlun, were dated by using the (U-Th)/He technique. The detrital apatites had consistent ages of ∼40 Ma for all deposit formations from bottom to top, which were older than the depositional ages. The ages and their consistency suggested that these detrital apatites were not reset and that the ages represented the original ages in the provenance region. These detrital apatite ages from the upper Eocene to Pliocene formations strongly suggested that the high mountains surrounding the Kumukol Basin formed at or before ∼40 Ma and have remained high since then. The process of mountain building resulted in a prolonged period of erosion from ∼40 to 2.6 Ma. The coupling of mountain and basin at ∼40 Ma was widespread along the East Kunlun. Our present results constrain the time of onset of the mountain building along the northern margin of the Tibetan Plateau, which may represent a rapid response to the India-Eurasian collision.

  16. Is the HP-UHP Hong'an-Dabie-Sulu orogen a piercing point for offset on the Tan-Lu fault?

    Science.gov (United States)

    Leech, Mary L.; Webb, Laura E.

    2013-02-01

    The Tan-Lu fault is a major strike-slip fault in eastern China that appears to offset the high-grade rocks of the Hong'an-Dabie-Sulu orogen left-laterally ˜540 km. We evaluate models for the collision between the South and North China blocks, published radiometric dates recording HP-UHP metamorphism and exhumation in the Hong'an-Dabie and Sulu terranes, and the timing of sinistral motion on the Tan-Lu fault to evaluate whether UHP rocks provide a piercing point for offset on the Tan-Lu fault. UHP metamorphism in Hong'an-Dabie was concurrent with Sulu based on U-Pb dating of coesite-bearing domains of zircon at 244 ± 5-226 ± 2 Ma for Hong'an-Dabie and 243 ± 4-225 ± 2 Ma for Sulu. Retrograde metamorphism began c. 220 Ma for both Hong'an-Dabie and Sulu, but retrograde zircon growth ended c. 214 Ma in Hong'an-Dabie and continued until c. 202 Ma in Sulu based on U-Pb dating of zircon domains external to coesite-bearing domains. Structures in Sulu are rotated 25° counter-clockwise from, but are broadly similar to, Hong'an-Dabie suggesting the two areas have a common Triassic orogenic history that pre-dates motion on the Tan-Lu fault, and that is consistent with paleomagnetic studies. We constructed a pre-Cretaceous restoration of the Hong'an-Dabie-Sulu belt that moves the Sulu terrane south, aligning the suture and the eclogite-facies isograd, and rotates Sulu c. 25° clockwise to re-align structures with Hong'an-Dabie. Our restoration is supported by published data and shows that the Hong'an-Dabie-Sulu orogen is a piercing point for post-collisional offset on the Tan-Lu fault and that these regions shared a common subduction-exhumation history. The Tan-Lu fault did not play a significant role in the Hong'an-Dabie-Sulu collision and likely developed later, in the Early Cretaceous.

  17. Analogue modeling of rotational orogenic wedges: implications for the Neogene structural evolution of the Southern Central Andes (33°-35°S)

    Science.gov (United States)

    Herrera, S. S.; Farías, M.; Pinto, L.; Yagupsky, D. L.; Guzman, C.; Charrier, R.

    2017-12-01

    Structural evolution of the southernmost Central Andes is a major subject of debate. Overall vergence within the range and how intra-continental subduction prompts Andean orogeny are controversial topics. Between 33°-35° S, strike of the western slope main structures shifts southwards, from N-S to NNE-SSW, defining the Maipo Orocline. Likely, width of the Principal Cordillera increases southwards. Despite, a progressive southward decrease in orogenic volume has been determined for the segment. To understand such latitudinal variations, and to provide explanations for overall vergence, we carry out analogue models of contractional wedges to explore upper-crustal thrust system development with a progressive variation of the convergence vector. The model setup consisted of a fixed plate on which a mobile plate generated a velocity discontinuity. The upper-crust was simulated using low-cohesive quartz sand. The mobile plate was fixed at its northern end to a pivot, thus progressively incrementing shortening and the obliquity of convergence southwards. PIV photogrammetry recorded wedge evolution. A classical doubly-vergent wedge was formed, consisting of a steep 35° dipping, static thrust on the retro-side, an uplifted core, and an incipient forward-breaking, 25° critically tapered imbricated thrust fan on the pro-side, wider (in plan-view) where the imposed shortening reached the maximum. The resulting wedge is reminiscent of: the steep western Andean slope, in which the bordering thrust has maintained its present position during the Neogene; and the east-vergent fold-and-thrust belt of the eastern slope. The asymmetrical doubly vergence of the model suggests west-directed subduction of the South American continent beneath the orogen. The southward width increase is geometrically comparable to the natural analogue, yet we observe a flat contrast with orogenic shortening and volume estimates for the region. This can be attributed to the fact that uplift and erosion

  18. Unraveling the tectonic evolution of a Neoproterozoic-Cambrian active margin in the Ribeira Orogen (Se Brazil): U-Pb and Lu-Hf provenance data

    Energy Technology Data Exchange (ETDEWEB)

    Fernandes, Gabriel Lamounier de F. [Servico Geologico do Estado do Rio de Janeiro (DRM-RJ), Niteroi, RJ (Brazil); Schmitt, Renata; Bongiolo, Everton M.; Mendes, Julio [Universidade Federal do Rio de Janeiro (UFRJ), RJ (Brazil); Basei, Miguel S. [Universidade de Sao Paulo (USP), SP (Brazil)

    2015-07-01

    Full text: The Neoproterozoic-Ordovician Central Ribeira Orogen, in SE Brazil, presents two contrasting tectonic domains in its southern portion: (a) The Arc Domain constituted of Neoproterozoic to Paleozoic magmatic rocks and low P-high T metamorphic para (Sao Fidelis Group) - and ortho- derived units (in Oriental Terrane); and (b) The Basement Domain, constituted of a Paleoproterozoic and Neoproterozoic medium P-high T metamorphic para (Palmital-Buzios Succession)- and ortho-derived units (in Cabo Frio Tectonic Domain). Our work focuses on paraderived rocks sequences from both domains. The provenance analysis using U-Pb and Lu-Hf in zircon grains is presented here as an effective tool to unravel the paleogeography and nature of the pre-collisional sedimentary basins. We performed 505 analyses (U-Pb) on detrital zircon grains and some metamorphic overgrowths from six paragneiss samples. Besides, 141 analyses (Lu-Hf) in six samples only on the detrital zircon grains domains. All samples present a main peak from Neoproterozoic sources (750-570 Ma) and the other minor peak in the Stenian/Tonian periods (1200-850Ma), this indicate an orogenic contribution for this basin. Scarce register from the Mesoproterozoic and two peaks in the Archean/Paleoproterozoic (2.6 and 1.9 Ga) are recognized as a contribution from an ancient continent. The Lu-Hf data reveals a juvenile source for the detrital zircon grains from Buzios Succession while Palmital and Sao Fidelis Group units show a main crustal signature for their detrital zircon population. Based on the U-Pb and Lu-Hf data presented here, plus petrological data, geological correlations, and compilation of data from literature, we propose a tectonic model for the origin of para-derived rocks from the eastern part of the Ribeira Orogen. Starting with an extensional environment of ca. 600 Ma in a back-arc basin (Buzios succession deposition) and continuing as an active margin between 570 and 550 Ma in the fore-arc and prism

  19. Formation of Cretaceous Cordilleran and post-orogenic granites and their microgranular enclaves from the Dalat zone, southern Vietnam: Tectonic implications for the evolution of Southeast Asia

    Science.gov (United States)

    Shellnutt, J. Gregory; Lan, Ching-Ying; Van Long, Trinh; Usuki, Tadashi; Yang, Huai-Jen; Mertzman, Stanley A.; Iizuka, Yoshi; Chung, Sun-Lin; Wang, Kuo-Lung; Hsu, Wen-Yu

    2013-12-01

    Cordilleran-type batholiths are useful in understanding the duration, cyclicity and tectonic evolution of continental margins. The Dalat zone of southern Vietnam preserves evidence of Late Mesozoic convergent zone magmatism superimposed on Precambrian rocks of the Indochina Block. The Dinhquan, Deoca and Ankroet plutons and their enclaves indicate that the Dalat zone transitioned from an active continental margin producing Cordilleran-type batholiths to highly extended crust producing within-plate plutons. The Deoca and Dinhquan plutons are compositionally similar to Cordilleran I-type granitic rocks and yield mean zircon U/Pb ages between 118 ± 1.4 Ma and 115 ± 1.2 Ma. Their Sr-Nd whole rock isotopes (ISr = 0.7044 to 0.7062; εNd(T) = - 2.4 to + 0.2) and zircon Hf isotopes (εHf(T) = + 8.2 ± 1.2 and + 6.4 ± 0.9) indicate that they were derived by mixing between a mantle component and an enriched component (i.e. GLOSS). The Ankroet pluton is chemically similar to post-orogenic/within-plate granitic rocks and has a zircon U/Pb age of 87 ± 1.6 Ma. Geobarometric calculations indicate that amphibole within the Ankroet pluton crystallized at a depth of ~ 6 kbar which is consistent with the somewhat more depleted Sr-Nd isotope (ISr = 0.7017 to 0.7111; εNd(T) = - 2.8 to + 0.6) and variable εHf(T) compositions suggesting a stronger influence of crustal material in the parental magma. The compositional change of the Dalat zone granitic rocks during the middle to late Cretaceous indicates that the tectonic regime evolved from a continental arc environment to one of post-orogenic extension. The appearance of sporadic post-90 Ma magmatism in the Dalat zone and along the eastern margin of Eurasian indicates that there was no subsequent orogenic event and the region was likely one of highly extended crust that facilitated the opening of the South China Sea during the latter half of the Cenozoic.

  20. Proterozoic orogenic belts and rifting of Indian cratons: Geophysical constraints

    Directory of Open Access Journals (Sweden)

    D.C. Mishra

    2014-01-01

    Full Text Available The Aravalli–Delhi and Satpura Mobile Belts (ADMB and SMB and the Eastern Ghat Mobile Belt (EGMB in India form major Proterozoic mobile belts with adjoining cratons and contemporary basins. The most convincing features of the ADMB and the SMB have been the crustal layers dipping from both sides in opposite directions, crustal thickening (∼45 km and high density and high conductivity rocks in upper/lower crust associated with faults/thrusts. These observations indicate convergence while domal type reflectors in the lower crust suggest an extensional rifting phase. In case of the SMB, even the remnant of the subducting slab characterized by high conductive and low density slab in lithospheric mantle up to ∼120 km across the Purna–Godavari river faults has been traced which may be caused by fluids due to metamorphism. Subduction related intrusives of the SMB south of it and the ADMB west of it suggest N–S and E–W directed convergence and subduction during Meso–Neoproterozoic convergence. The simultaneous E–W convergence between the Bundelkhand craton and Marwar craton (Western Rajasthan across the ADMB and the N–S convergence between the Bundelkhand craton and the Bhandara and Dharwar cratons across the SMB suggest that the forces of convergence might have been in a NE–SW direction with E–W and N–S components in the two cases, respectively. This explains the arcuate shaped collision zone of the ADMB and the SMB which are connected in their western part. The Eastern Ghat Mobile Belt (EGMB also shows signatures of E–W directed Meso–Neoproterozoic convergence with East Antarctica similar to ADMB in north India. Foreland basins such as Vindhyan (ADMB–SMB, and Kurnool (EGMB Supergroups of rocks were formed during this convergence. Older rocks such as Aravalli (ADMB, Mahakoshal–Bijawar (SMB, and Cuddapah (EGMB Supergroups of rocks with several basic/ultrabasic intrusives along these mobile belts, plausibly formed during

  1. Deformation Partitioning: The Missing Link Between Outcrop-Scale Observations And Orogen-Scale Processes

    Science.gov (United States)

    Attia, S.; Paterson, S. R.; Jiang, D.; Miller, R. B.

    2017-12-01

    Structural studies of orogenic deformation fields are mostly based on small-scale structures ubiquitous in field exposures, hand samples, and under microscopes. Relating deformation histories derived from such structures to changing lithospheric-scale deformation and boundary conditions is not trivial due to vast scale separation (10-6 107 m) between characteristic lengths of small-scale structures and lithospheric plates. Rheological heterogeneity over the range of orogenic scales will lead to deformation partitioning throughout intervening scales of structural development. Spectacular examples of structures documenting deformation partitioning are widespread within hot (i.e., magma-rich) orogens such as the well-studied central Sierra Nevada and Cascades core of western North America: (1) deformation partitioned into localized, narrow, triclinic shear zones separated by broad domains of distributed pure shear at micro- to 10 km scales; (2) deformation partitioned between plutons and surrounding metamorphic host rocks as shown by pluton-wide magmatic fabrics consistently oriented differently than coeval host rock fabrics; (3) partitioning recorded by different fabric intensities, styles, and orientations established from meter-scale grid mapping to 100 km scale domainal analyses; and (4) variations in the causes of strain and kinematics within fold-dominated domains. These complex, partitioned histories require synthesized mapping, geochronology, and structural data at all scales to evaluate partitioning and in the absence of correct scaling can lead to incorrect interpretations of histories. Forward modeling capable of addressing deformation partitioning in materials containing multiple scales of rheologically heterogeneous elements of varying characteristic lengths provides the ability to upscale the large synthesized datasets described above to plate-scale tectonic processes and boundary conditions. By comparing modeling predictions from the recently developed

  2. The susceptibility of large river basins to orogenic and climatic drivers

    Science.gov (United States)

    Haedke, Hanna; Wittmann, Hella; von Blanckenburg, Friedhelm

    2017-04-01

    Large rivers are known to buffer pulses in sediment production driven by changes in climate as sediment is transported through lowlands. Our new dataset of in situ cosmogenic nuclide concentration and chemical composition of 62 sandy bedload samples from the world largest rivers integrates over 25% of Earth's terrestrial surface, distributed over a variety of climatic zones across all continents, and represents the millennial-scale denudation rate of the sediment's source area. We can show that these denudation rates do not respond to climatic forcing, but faithfully record orogenic forcing, when analyzed with respective variables representing orogeny (strain rate, relief, bouguer anomaly, free-air anomaly), and climate (runoff, temperature, precipitation) and basin properties (floodplain response time, drainage area). In contrast to this orogenic forcing of denudation rates, elemental bedload chemistry from the fine-grained portion of the same samples correlates with climate-related variables (precipitation, runoff) and floodplain response times. It is also well-known from previous compilations of river-gauged sediment loads that the short-term basin-integrated sediment export is also climatically controlled. The chemical composition of detrital sediment shows a climate control that can originate in the rivers source area, but this signal is likely overprinted during transfer through the lowlands because we also find correlation with floodplain response times. At the same time, cosmogenic nuclides robustly preserve the orogenic forcing of the source area denudation signal through of the floodplain buffer. Conversely, previous global compilations of cosmogenic nuclides in small river basins show the preservation of climate drivers in their analysis, but these are buffered in large lowland rivers. Hence, we can confirm the assumption that cosmogenic nuclides in large rivers are poorly susceptible to climate changes, but are at the same time highly suited to detect

  3. Nature and provenance of the Beishan Complex, southernmost Central Asian Orogenic Belt

    Science.gov (United States)

    Zheng, Rongguo; Li, Jinyi; Xiao, Wenjiao; Zhang, Jin

    2018-03-01

    The ages and origins of metasedimentary rocks, which were previously mapped as Precambrian, are critical in rebuilding the orogenic process and better understanding the Phanerozoic continental growth in the Central Asian Orogenic Belt (CAOB). The Beishan Complex was widely distributed in the southern Beishan Orogenic Collage, southernmost CAOB, and their ages and tectonic affinities are still in controversy. The Beishan Complex was previously proposed as fragments drifted from the Tarim Craton, Neoproterozoic Block or Phanerozoic accretionary complex. In this study, we employ detrital zircon age spectra to constrain ages and provenances of metasedimentary sequences of the Beishan Complex in the Chuanshanxun area. The metasedimentary rocks here are dominated by zircons with Paleoproterozoic-Mesoproterozoic age ( 1160-2070 Ma), and yield two peak ages at 1454 and 1760 Ma. One sample yielded a middle Permian peak age (269 Ma), which suggests that the metasedimentary sequences were deposited in the late Paleozoic. The granitoid and dioritic dykes, intruding into the metasedimentary sequences, exhibit zircon U-Pb ages of 268 and 261 Ma, respectively, which constrain the minimum deposit age of the metasedimentary sequences. Zircon U-Pb ages of amphibolite (274 and 216 Ma) indicate that they might be affected by multi-stage metamorphic events. The Beishan Complex was not a fragment drifted from the Tarim Block or Dunhuang Block, and none of cratons or blocks surrounding Beishan Orogenic Collage was the sole material source of the Beishan Complex due to obviously different age spectra. Instead, 1.4 Ga marginal accretionary zones of the Columbia supercontinent might have existed in the southern CAOB, and may provide the main source materials for the sedimentary sequences in the Beishan Complex.

  4. Seismic anisotropies of the Songshugou peridotites (Qinling orogen, central China) and their seismic implications

    Science.gov (United States)

    Cao, Yi; Jung, Haemyeong; Song, Shuguang

    2018-01-01

    Though extensively studied, the roles of olivine crystal preferred orientations (CPOs or fabrics) in affecting the seismic anisotropies in the Earth's upper mantle are rather complicated and still not fully known. In this study, we attempted to address this issue by analyzing the seismic anisotropies [e.g., P-wave anisotropy (AVp), S-wave polarization anisotropy (AVs), radial anisotropy (ξ), and Rayleigh wave anisotropy (G)] of the Songshugou peridotites (dunite dominated) in the Qinling orogen in central China, based on our previously reported olivine CPOs. The seismic anisotropy patterns of olivine aggregates in our studied samples are well consistent with the prediction for their olivine CPO types; and the magnitude of seismic anisotropies shows a striking positive correlation with equilibrium pressure and temperature (P-T) conditions. Significant reductions of seismic anisotropies (AVp, max. AVs, and G) are observed in porphyroclastic dunite compared to coarse- and fine-grained dunites, as the results of olivine CPO transition (from A-/D-type in coarse-grained dunite, through AG-type-like in porphyroclastic dunite, to B-type-like in fine-grained dunite) and strength variation (weakening: A-/D-type → AG-type-like; strengthening: AG-type-like → B-type-like) during dynamic recrystallization. The transition of olivine CPOs from A-/D-type to B-/AG-type-like in the forearc mantle may weaken the seismic anisotropies and deviate the fast velocity direction and the fast S-wave polarization direction from trench-perpendicular to trench-oblique direction with the cooling and aging of forearc mantle. Depending on the size and distribution of the peridotite body such as the Songshugou peridotites, B- and AG-type-like olivine CPOs can be an additional (despite minor) local contributor to the orogen-parallel fast velocity direction and fast shear-wave polarization direction in the orogenic crust such as in the Songshugou area in Qinling orogen.

  5. Recent advances about of the orogenic modern belt (1000-500 M.A.) in Uruguay

    International Nuclear Information System (INIS)

    Bossi, J.

    1989-01-01

    Progress in lithologic, structural, tectonic and geo tectonic data about a 1000-500 m.y.orogenic belt developed at the East of Uruguay, arrived in the 80, are here described. Conclusions are mainly based on the 1/100.000 scale geologic map of a 6000 sq. km comprised between Sierra Ballena, Sierra de Animas, Pan de Azucar and Mariscala. These new data clearly states the lithological distribution and contribute to guide strategic prospect ion.

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

    Energy Technology Data Exchange (ETDEWEB)

    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.

  7. A Comparative Study of the Electrical Structure of Circum Tibetan Plateau Orogenic Belts and its Tectonic Implications

    Science.gov (United States)

    Jin, Sheng; Zhang, Letian; Wei, Wenbo; Ye, Gaofeng; Jing, Jianen; Dong, Hao; Xie, Chengliang; Yin, Yaotian

    2017-04-01

    The Tibetan Plateau, as known as "roof of the world", was created through the on-going continent-continent collision between the Indian and Eurasian plates since 55 Ma. As the process continues, the plateau is growing both vertically and horizontally. The horizontal expansion of the plateau is blocked by the Yangtze block in the east, the Tarim block in the north, and the Ordos block in the northeast, and consequently lead to the formation of the circum Tibetan plateau orogenic belts. To better understand the mechanism behind this process, we conducted a comparative study by collecting 7 magnetotelluric (MT) profiles over the margins of the Tibetan plateau, namely, the INDEPTH 100, 700 and 800 lines in the southern Tibet, the INDEPTH 4000 and 5000 lines across the Altyn Tagh fault on the northern margin of the plateau, as well as other two profiles across the Haiyuan fault and the Longmenshan fault on the northeastern and eastern margins of the plateau deployed under the framework of project SinoProbe. The electrical features of the stable blocks surrounding the Tibetan plateau are generally resistive, while crustal conductive layers are found to be wide spread within the plateau. The southern margin of the Tibetan plateau is characterized by large scale underthrust of the Indian lithosphere beneath the plateau. This intense converging process created the thrust fault system distributed along the southern margin of the Tibetan plateau over 1000 km. Crustal conductive layers discovered in southern Tibet are generally associated with the southward crustal flow that originated from the lower crust within the plateau and exhumed along the thrust belts in the Himalayas. On the eastern margin of the Tibetan plateau, the electrical structures suggest that the Yangtze block wedged into the Tibetan lithosphere and caused decoupling between the crust and upper mantel. Large scale conductors discovered beneath the Songpan-Ganze block reflect that the eastward crustal flow was

  8. 2.5D seismic velocity modelling in the south-eastern Romanian Carpathians Orogen and its foreland.

    NARCIS (Netherlands)

    Bocin, A.; Stephenson, R.A.; Tryggvason, A.; Panea, I; Mocanu, V.I.; Hauser, F

    2005-01-01

    The DACIA-PLAN (Danube and Carpathian Integrated Action on Processes in the Lithosphere and Neotectonics) deep seismic reflection survey was performed in August-September 2001, with the objective of obtaining new information on the deep structure of the external Carpathians nappe system and the

  9. The effect of flexural isostasy on the response time of orogenic systems

    Science.gov (United States)

    Braun, J.; Margirier, A.; Guerit, L.

    2017-12-01

    The concept of orogenic steady-state implies that mountain belts can reach a dynamic balance between uplift and erosion in order to maintain a quasi-constant shape. The final morphology of the mountain will be a function of the relative efficiency between uplift and erosion and is therefore likely to be modulated by climate. However, reaching such a steady-state cannot be instantaneous and there must exist a time lag between the onset of convergence and the full development of the mountain topography. Similarly, when an orogenic system is subject to a marked change in convergence rate or in climatic conditions, it takes a certain time for it to adapt to such a change and develop a new steady-state morphology. It is during these transient phases that the nature and efficiency of the interactions between tectonics and climate are most likely to be constrained by observations and understood. The duration of this transient stage remains, however, poorly constrained and understood. As shown by many authors (Whipple and Tucker, 1999, for example) the rate at which tectonic systems evolve to reach steady-state is likely controlled by climate and rock strength, which both determine the efficiency of erosional processes, and the rate of uplift. Here we show that isostasy also plays a very important role in determining the length of the transient phase and that, depending on the level of isostatic adjustment, which in turn depends on the flexural strength of the underlying lithosphere, isostasy can change the time it takes for an orogenic system to reach steady-state by an order of magnitude, i.,e. from a few millions to a few tens of millions of years. This has very important implications. It may explain why many young orogenic systems display an increase in uplift and erosion rate millions of years after the onset of collision and that, in these situations, such an increase does not require a steady change in tectonic and/or climate conditions/forcing. We also show that

  10. Paleozoic magmatism and porphyry Cu-mineralization in an evolving tectonic setting in the North Qilian Orogenic Belt, NW China

    Science.gov (United States)

    Qiu, Kun-Feng; Deng, Jun; Taylor, Ryan D.; Song, Kai-Rui; Song, Yao-Hui; Li, Quan-Zhong; Goldfarb, Richard J.

    2016-05-01

    The NWW-striking North Qilian Orogenic Belt records the Paleozoic accretion-collision processes in NW China, and hosts Paleozoic Cu-Pb-Zn mineralization that was temporally and spatially related to the closure of the Paleo Qilian-Qinling Ocean. The Wangdian Cu deposit is located in the eastern part of the North Qilian Orogenic Belt, NW China. Copper mineralization is spatially associated with an altered early Paleozoic porphyritic granodiorite, which intruded tonalites and volcaniclastic rocks. Alteration zones surrounding the mineralization progress outward from a potassic to a feldspar-destructive phyllic assemblage. Mineralization consists mainly of quartz-sulfide stockworks and disseminated sulfides, with ore minerals chalcopyrite, pyrite, molybdenite, and minor galena and sphalerite. Gangue minerals include quartz, orthoclase, biotite, sericite, and K-feldspar. Zircon LA-ICPMS U-Pb dating of the ore-bearing porphyritic granodiorite yielded a mean 206Pb/238U age of 444.6 ± 7.8 Ma, with a group of inherited zircons yielding a mean U-Pb age of 485 ± 12 Ma, consistent with the emplacement age (485.3 ± 6.2 Ma) of the barren precursor tonalite. Rhenium and osmium analyses of molybdenite grains returned model ages of 442.9 ± 6.8 Ma and 443.3 ± 6.2 Ma, indicating mineralization was coeval with the emplacement of the host porphyritic granodiorite. Rhenium concentrations in molybdenite (208.9-213.2 ppm) suggest a mantle Re source. The tonalities are medium-K calc-alkaline. They are characterized by enrichment of light rare-earth elements (LREEs) and large-ion lithophile elements (LILEs), depletion of heavy rare-earth elements (HREEs) and high-field-strength elements (HFSEs), and minor negative Eu anomalies. They have εHf(t) values in the range of +3.6 to +11.1, with two-stage Hf model ages of 0.67-1.13 Ga, suggesting that the ca. 485 Ma barren tonalites were products of arc magmatism incorporating melts from the mantle wedge and the lithosphere. In contrast, the

  11. Paleozoic magmatism and porphyry Cu-mineralization in an evolving tectonic setting in the North Qilian Orogenic Belt, NW China

    Science.gov (United States)

    Qiu, Kun-Feng; Deng, Jun; Taylor, Ryan D.; Song, Kai-Rui; Song, Yao-Hui; Li, Quan-Zhong; Goldfarb, Richard J.

    2016-01-01

    The NWW-striking North Qilian Orogenic Belt records the Paleozoic accretion–collision processes in NW China, and hosts Paleozoic Cu–Pb–Zn mineralization that was temporally and spatially related to the closure of the Paleo Qilian-Qinling Ocean. The Wangdian Cu deposit is located in the eastern part of the North Qilian Orogenic Belt, NW China. Copper mineralization is spatially associated with an altered early Paleozoic porphyritic granodiorite, which intruded tonalites and volcaniclastic rocks. Alteration zones surrounding the mineralization progress outward from a potassic to a feldspar-destructive phyllic assemblage. Mineralization consists mainly of quartz-sulfide stockworks and disseminated sulfides, with ore minerals chalcopyrite, pyrite, molybdenite, and minor galena and sphalerite. Gangue minerals include quartz, orthoclase, biotite, sericite, and K-feldspar. Zircon LA-ICPMS U–Pb dating of the ore-bearing porphyritic granodiorite yielded a mean 206Pb/238U age of 444.6 ± 7.8 Ma, with a group of inherited zircons yielding a mean U–Pb age of 485 ± 12 Ma, consistent with the emplacement age (485.3 ± 6.2 Ma) of the barren precursor tonalite. Rhenium and osmium analyses of molybdenite grains returned model ages of 442.9 ± 6.8 Ma and 443.3 ± 6.2 Ma, indicating mineralization was coeval with the emplacement of the host porphyritic granodiorite. Rhenium concentrations in molybdenite (208.9–213.2 ppm) suggest a mantle Re source. The tonalities are medium-K calc-alkaline. They are characterized by enrichment of light rare-earth elements (LREEs) and large-ion lithophile elements (LILEs), depletion of heavy rare-earth elements (HREEs) and high-field-strength elements (HFSEs), and minor negative Eu anomalies. They have εHf(t) values in the range of +3.6 to +11.1, with two-stage Hf model ages of 0.67–1.13 Ga, suggesting that the ca. 485 Ma barren tonalites were products of arc magmatism incorporating melts from the mantle wedge and

  12. The Rio Pardo salient, northern Araçuaí orogen: an example of a complex basin-controlled fold-thrust belt curve

    Directory of Open Access Journals (Sweden)

    Eliza Peixoto

    Full Text Available ABSTRACT: The Rio Pardo salient, the large antitaxial curve described by the Araçuaí fold-and-thrust belt along the southeastern edge of the São Francisco craton, is one of the most prominent and one of the least studied features of the Brasiliano Araçuaí-West Congo orogenic system (AWCO. In addition to the Archean/Paleoproterozoic basement, the salient is comprised of metasedimentary rocks mainly from the Neoproterozoic Macaúbas Group and the Salinas Formation. Its western limb occupies a portion of the Espinhaço ridge, where the NS-trending structures of the Araçuaí belt progressively curve NE and E, thereby defining the hinge zone along the Serra Geral on the Minas-Bahia boundary. The eastern limb is NW-trending and marked by a major shear zone. In models postulated to generate the AWCO through the closure of the Neoproterozoic Macaúbas basin, this large curve plays a critical kinematic role. Yet, in spite of this, its development is still not fully understood. How did this curve originate? Which factors controlled its generation? Our field study performed in the northern Araçuaí orogen characterized the kinematic picture of the salient, and led to a model that addresses these questions. The results we obtained indicate that the Rio Pardo salient developed in response to four deformation phases. The contractional D1 and D2 phases are coaxial and responsible for a craton-directed tectonic transport along the salient’s outer arc, which is coupled with an overall southward motion of the inner arc, thereby giving rise to a rather complex kinematic picture. Furthermore, structures of the D1/D2 phases define a zigzag pattern with alternating NE- and NW-trending segments along the salient’s leading edge. Along the NE-trending segments, the metasedimentary rocks are thrust northwestwards on top of the craton basement, while along the NW-trending segments, the supracrustal rocks are displaced along dextral to reverse

  13. Fault Dating in the US Rockies and Large Regional Extent of Deformation Pulses Along the Sevier Orogen of North America.

    Science.gov (United States)

    van der Pluijm, B.; Lynch, E. A.; Pana, D.; Yonkee, A.

    2017-12-01

    Recent Ar dating of clay-rich fault rock in the Canadian Rockies identified multiple orogenic pulses: Late Jurassic (163-146 Ma), Mid-Cretaceous (103-99 Ma), Late Cretaceous (76-72 Ma) and Eocene (54-52 Ma; Pana and van der Pluijm, GSAB 2015). New dating in the US Rockies combined with ages in the most frontal section along an Idaho-Wyoming transect show a remarkably similar age pattern: Meade Thrust, 108-102 Ma; (S)Absaroka Thrust, 73 Ma; Darby-Bear Thrust, 56-50 Ma. These radiometric fault ages in the US Rockies match field and tectono-stratigraphic predictions, analogues to those in the Canadian Rockies. Thus, a remarkably long (>1500km) lateral tract along the North American Sevier orogen is characterized by at least three major orogenic pulses that are structurally contiguous. These orogenic pulses are progressively younger in the direction of easterly thrust fault motion (toward cratonic interior) and are separated by long periods of relative tectonic quiescence. We interpret the extensive regional continuity of deformation pulses and tectonic quiescence along the Sevier Orogen as the result of three plate reorganization events in western North America since the Late Jurassic.

  14. The tectono-magmatic evolution of the occidental terrane and the Paraiba do Sul Klippe within the Neoproterozoic Ribeira orogenic Belt, Southeastern Brazil

    International Nuclear Information System (INIS)

    Valladares, Claudia Sayao; Duarte, Beatriz Paschoal; Heilbron, Monica; Ragatky, Diana

    2000-01-01

    The occidental Terrane is envisaged as the eastern/southeastern reworked margin of the Sao Francisco/Rio de la Plata plate associated with and E-trending subduction under the Congo plate. The Paraiba do Sul Klippe is part of the Oriental Terrane, envisaged as a portion of the Congo plate. A collisional-stage resulted in intense westward deformation of the Occidental Terrane under intermediate pressure metamorphism (syn-D1+D2 events). A late-collisional stage resulted in subvertical folding and steep shear zones (D3 event). Both stages were associated with voluminous crustal-derived granites. U-Pb and Sm-Nd geochronology as well as geochemical and structural data point to three magmatic episodes: a syn-collisional stage 1; a syn-collisional stage 2; and a late-collisional stage. This paper presents a magmatic evolutionary model for this crustal segment of the Ribeira orogenic belt based on new geological data of Brasiliano granites and data available in the literature. (author)

  15. Geometry, kinematics and tectonic models of the Kazakhstan Orocline, Central Asian Orogenic Belt

    Science.gov (United States)

    Li, Pengfei; Sun, Min; Rosenbaum, Gideon; Yuan, Chao; Safonova, Inna; Cai, Keda; Jiang, Yingde; Zhang, Yunying

    2018-03-01

    The Central Asian Orogenic Belt (CAOB) is one of the largest accretionary orogens on Earth and is characterized by the occurrence of tight oroclines (Kazakhstan and Tuva-Mongolian oroclines). The origin of these large-scale orogenic curvatures is not quite understood, but is fundamentally important for understanding crustal growth and tectonic evolution of the CAOB. Here we provide an outline of available geological and paleomagnetic data around the Kazakhstan Orocline, with an aim of clarifying the geometry, kinematics and geodynamic origin of the orocline. The Kazakhstan Orocline is evident in a total magmatic image, and can be traced by the continuation of high magnetic anomalies associated with the Devonian Volcanic Belt and the Late Devonian to Carboniferous Balkhash-Yili arc. Paleomagnetic data show ∼112-126° clockwise rotation of the northern limb relative to the southern limb in the Late Devonian to Early Carboniferous, as well as ∼15-28° clockwise rotation of the northern limb and ∼39-40° anticlockwise rotation of the southern limb relative to the hinge of the orocline during the Late Carboniferous to Permian. We argue that the Kazakhstan Orocline experienced two-stage bending with the early stage of bending (Late Devonian to Early Carboniferous; ∼112-126°) driven by slab rollback, and the later stage (Late Carboniferous to Permian; 54-68°) possibly associated with the amalgamation of the Siberian, Tarim and Baltic cratons. This new tectonic model is compatible with the occurrence of rift basins, the spatial migration of magmatic arc, and the development of large-scale strike-slip fault systems during oroclinal bending.

  16. Continental Delamination of the Romanian Eastern Carpathians: A Lower Crustal Origin of the Vrancea Seismogenic Zone?

    Science.gov (United States)

    Fillerup, M. A.; Knapp, J. H.; Knapp, C. C.

    2006-12-01

    Two lithosphere-scale, explosive-source seismic reflection profiles (DRACULA I and DACIA PLAN), inclusive of the hinterland and foreland of the Romanian Eastern Carpathians, provide new evidence for the geodynamic origin of the Vrancea Seismogenic Zone (VSZ) of Romania. These data, collected to evaluate existing subduction-related and delamination geodynamic models proposed to explain the intermediate depth seismicity associated with the Vrancea zone, show evidence of continental crust extending continuously above the VSZ from the Carpathian foreland well into the Transylvanian hinterland. Crustal thicknesses inferred from these data based on reflectivity show a 40-45 km crust below the Transylvanian basin abruptly shallowing to 32 km for ~120 km beneath the fold and thrust belt of the main Carpathian orogen and thickening again to 38-42 km crust in the foreland. This thinned crust outlines an apparent lower crustal sub-orogenic cavity that is overlain by a relatively subhorizontal reflective fabric absent of dipping reflectivity. The northwest dipping Vrancea seismogenic body, a 30x70x200 km volume of intermediate depth earthquakes, is located on the eastern flank of the apparently thin crust beneath the Carpathian orogen. Amplitude decay curves show penetration of seismic energy to a depth of ~60 km in the vicinity of the sub-orogenic cavity, implying this non- reflective zone is a geologic signature. Rotation of the VSZ about a hinge beneath the foreland basin at a depth of ~50 km restores to fill the lower-crustal cavity under the orogen, suggesting the VSZ represents a portion of brittle lower crust delaminated during continental lithospheric delamination which may have caused regional uplift of the Transylvanian basin. The lack of through-going, dipping crustal-scale boundaries along this composite lithospheric transect would appear to preclude subduction as an explanation for seismicity in the VSZ, consistent with abundant surface geologic data. These

  17. Orogenic inheritance and continental breakup: Wilson Cycle-control on rift and passive margin evolution

    Science.gov (United States)

    Schiffer, C.; Petersen, K. D.

    2016-12-01

    Rifts often develop along suture zones between previously collided continents, as part of the Wilson cycle. The North Atlantic is such an example, formed where Pangaea broke apart along Caledonian and Variscan sutures. Dipping upper mantle structures in E. Greenland and Scotland, have been interpreted as fossil subduction zones and the seismic signature indicates the presence of eclogite and serpentinite. We speculate that this orogenic material may impose a rheological control upon post-orogenic extension and we use thermo-mechanical modelling to explore such effects. Our model includes the following features: 1) Crustal thickness anomalies, 2) Eclogitised mafic crust emplaced in the mantle lithosphere, and 3) Hydrated mantle peridotite (serpentinite) formed in a pre-rift subduction setting. Our models indicate that the inherited structures control the location and the structural and magmatic evolution of the rift. Rifting of thin initial crust allows for relatively large amounts of serpentinite to be preserved within the uppermost mantle. This facilitates rapid continental breakup and serpentinite exhumation. Magmatism does not occur before continental breakup. Rifts in thicker crust preserve little or no serpentinite and thinning is more focused in the mantle lithosphere, rather than in the crust. Continental breakup is therefore preceded by magmatism. This implies that pre-rift orogenic properties may determine whether magma-poor or magma-rich conjugate margins are formed. Our models show that inherited orogenic eclogite and serpentinite are deformed and partially emplaced either as dipping structures within the lithospheric mantle or at the base of the thinned continental crust. The former is consistent with dipping sub-Moho reflectors often observed in passive margins. The latter provides an alternative interpretation of `lower crustal bodies' which are often regarded as igneous bodies. An additional implication of our models is that serpentinite, often

  18. Antecedence of the Yarlung-Siang-Brahmaputra River, eastern Himalaya

    Science.gov (United States)

    Lang, Karl A.; Huntington, Katharine W.

    2014-07-01

    At the eastern terminus of the Himalayan orogen, distortion and capture of southeast Asian drainage basins reflects regional patterns of crustal strain due to the indentation of the Indian Plate into Eurasia. After flowing eastward >1000 km along the southern margin of Tibet, the Yarlung-Siang-Brahmaputra River turns abruptly southward through the eastern Himalayan syntaxis rapidly exhuming a crustal scale antiform in an impressive >2 km knickpoint. This conspicuous drainage pattern and coincidence of focused fluvial incision and rapid rock exhumation has been explained by the capture of an ancestral, high-elevation Yarlung River by headward erosion of a Himalayan tributary. However, recent observation of Tibetan detritus in Neogene foreland basin units complicates this explanation, requiring a connection from Tibet to the foreland prior to the estimated onset of rapid rock exhumation. We constrain the sedimentary provenance of foreland basin units deposited near the Brahmaputra River confluence in the eastern Himalayan foreland basin using detrital zircon U-Pb geochronology. We interpret the significant presence of Gangdese-age detritus in each foreland basin unit to indicate that connection of the Yarlung-Siang-Brahmaputra River was established during, or prior to foreland deposition in the Early Miocene. Our results indicate that connection of the Yarlung-Siang-Brahmaputra River precedes exhumation of the syntaxis, demonstrating the potential for the progressive coevolution of rock uplift and rapid erosion of the Namche Barwa massif.

  19. Molybdenum mineralization related to the Yangtze's lower crust and differentiation in the Dabie Orogen: Evidence from the geochemical features of the Yaochong porphyry Mo deposit

    Science.gov (United States)

    Liu, Qing-Quan; Li, Bin; Shao, Yong-Jun; Lu, An-Huai; Lai, Jian-Qing; Li, Yong-Feng; Luo, Zheng-Zhuan

    2017-06-01

    The Dabie Orogen is a world-class case for large amounts of Mo mineralization in that it contains at least 10 porphyry Mo deposits with Mo metal reserves over 3 Mt from the time period of 156-110 Ma. However, the principal mechanism for the Mo mineralization remains controversial due to the lack of a precise definition of its source and shallow ore-forming process, which is essential to understand these rare large Mo deposits. Detailed geochronology, geochemistry, and isotopic data for ore-related granites and minerals were analyzed in order to place constraints on the massive Mo mineralization in the Dabie Orogen in eastern China. The Yaochong molybdenum orebodies were hosted in the transition belt and alteration zone between the granitic stocks and the Dabie Complex and were characterized as numerous veinlets with potassic, phyllic and propylitic alterations. The buried Yaochong granitic intrusions and associated molybdenum mineralization yield Early Cretaceous ages of magmatic activities at ca. 138 Ma and extremely similar Re-Os isotope ages for the corresponding Mo metallogenic event at ca. 137 Ma. The Yaochong monzogranite and granite porphyry belong to the highly fractionated I-type granites, which are believed to be derived from the dominantly Yangtze's lower crust mixed with the Northern Dabie Complex due to their geochemical and isotope features. The elemental diversity and isotopic homogeneity suggest that the formation of the Yaochong monzogranite involved the fractionation of biotite, garnet and minor feldspar and accessory minerals combined with a weak crustal assimilation process. In contrast, the granite porphyry was possibly generated by the partial melting of the same mixed lower continental crust via the differentiation process involving the fractionation of feldspar, apatite, and/or titanite. Fractional crystallization processes can significantly elevate the molybdenum concentration in the residual melts. The biotite fractional crystallization

  20. Geochemistry of Gneisses from Dabie Complex and Tongbai Complex in Qinling-Tongbai-Dabie Orogenic Belt: Implications for Location of Yangtze-Sino-Korean Suture

    Institute of Scientific and Technical Information of China (English)

    2000-01-01

    The Dabie complex (DC) and the Tongbai complex (TBC) are separately distributed in the middle and eastern parts of the Qinling-Tongbai-Dabie orogenic belt. In this study, the Dabie complex can be divided into two units: one is the complex with no high pressure and ultrahigh pressure metamorphic rocks (DC1), and the other is the complex containing coesite-bearing eclogite lenses or boudins (DC2). Gneisses are predominant in the TBC, DC1 and DC2. Major and trace element data of gneisses in the TBC, DC1 and DC2 show them to be the orthogneisses. The gneisses in the DC1 have higher incompatible element contents and higher ratios of w(K2O)/w(Na2O) and w(La)n/w(Yb)n than those in the DC2. However, no obvious differences arise in other element contents and the ratios of w(La)/w( Nb), w(Nb)/w(Th), w(Nb)/w(Hf), w(Ba)/w(La), w(Sm)/w(Nd) and w(Th)/w(U) between the gneisses in the DC2 and those in the DC1. These observations suggest that the protoliths of the gneisses in the DC2 have affinities to those in the DC1. The difference between the DC1 and DC2 gneisses in incompat- ible element contents could reflect the difference in their partial melting extent. The TBC gneisses are geochemically similar to the DC1 gneisses, suggesting that the TBC and DC1 gneisses are the same lithologic unit in the Qinling-Tongbai-Dabie orogenic belt and that they have experienced similar formations and evolution histories. In the Qinling-Tongbai area, the TBC is part of the northern blocks of the Yangtze craton. Given the similarity of geochemical characteristics, the rock assemblage and the ages between the TBC and DC1 gneisses, we can infer that the Dabie complex also belongs to the northern blocks of the Yangtze craton. In terms of the distribution of eciogites and metamorphic facies, we propose that the collisionai suture in the Dabie area is distributed along the Xiaotian-Mozitan fault, at the contact with the Shang-Dan-Tongbai fault to the west.

  1. Magnetotelluric Imaging of the Lithosphere Across the Variscan Orogen (Iberian Autochthonous Domain, NW Iberia)

    Science.gov (United States)

    Alves Ribeiro, J.; Monteiro-Santos, F. A.; Pereira, M. F.; Díez Fernández, R.; Dias da Silva, Í.; Nascimento, C.; Silva, J. B.

    2017-12-01

    A new magnetotelluric (MT) survey comprising 17 MT soundings throughout a 30 km long N30°W transect in the Iberian autochthons domain of NW Iberia (Central Iberian Zone) is presented. The 2-D inversion model shows the resistivity structure of the continental crust up to 10 km depth, heretofore unavailable for this region of the Variscan Orogen. The MT model reveals a wavy structure separating a conductive upper layer underlain by a resistive layer, thus picturing the two main tectonic blocks of a large-scale D2 extensional shear zone (i.e., Pinhel shear zone). The upper layer represents a lower grade metamorphic domain that includes graphite-rich rocks. The lower layer consists of high-grade metamorphic rocks that experienced partial melting and are associated with granites (more resistive) emplaced during crustal thinning. The wavy structure is the result of superimposed crustal shortening responsible for the development of large-scale D3 folds (e.g., Marofa synform), later deflected and refolded by a D4 strike-slip shear zone (i.e., Juzbado-Penalva do Castelo shear zone). The later contribution to the final structure of the crust is marked by the intrusion of postkinematic granitic rocks and the propagation of steeply dipping brittle fault zones. Our study demonstrates that MT imaging is a powerful tool to understand complex crustal structures of ancient orogens in order to design future prospecting surveys for mineral deposits of economic interest.

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

    Science.gov (United States)

    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.

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

    Science.gov (United States)

    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. Differential growth of the northern Tibetan margin: evidence for oblique stepwise rise of the Tibetan Plateau

    Science.gov (United States)

    Wang, Fei; Shi, Wenbei; Zhang, Weibin; Wu, Lin; Yang, Liekun; Wang, Yinzhi; Zhu, Rixiang

    2017-01-01

    Models of how high elevations formed across Tibet predict: (a) the continuous thickening of a “viscous sheet”; (b) time-dependent, oblique stepwise growth; and (c) synchronous deformation across Tibet that accompanied collision. Our new observations may shed light on this issue. Here, we use 40Ar/39Ar and (U-Th)/He thermochronology from massifs in the hanging walls of thrust structures along the Kunlun Belt, the first-order orogenic range at the northern Tibetan margin, to elucidate the exhumation history. The results show that these massifs, and hence the plateau margin, were subject to slow, steady exhumation during the Early Cenozoic, followed by a pulse of accelerated exhumation during 40–35 Ma. The exhumation rate increases westward (from ~0.22 to 0.34 and 0.5 mm/yr). The two-fold increase in exhumation in the western part (0.5 mm/yr) compared to the eastern part suggests westward increases in exhumation and compressional stress along the Kunlun Belt. We relate these observations to the mechanisms responsible for the oblique stepwise rise of Tibet. After collision, oblique subduction beneath Kunlun caused stronger compressional deformation in the western part than in the eastern part, resulting in differential growth and lateral extrusion. PMID:28117351

  5. Reassessment of the geologic evolution of selected precambrian terranes in Brazil, based on SHRIMP U-Pb data, part 2: mineiro and Aracuai orogens and Southern Sao Francisco craton; Reavaliacao da evolucao geologica em terrenos pre-cambrianos brasileiros com base em novos dados U-Pb SHRIMP, parte 2: orogeno Aracuai, cinturao mineiro e craton Sao Francisco Meridional

    Energy Technology Data Exchange (ETDEWEB)

    Silva, Luiz Carlos da; Pimentel, Marcio [Brasilia Univ., DF (Brazil). Inst. de Geociencias]. E-mail: luizcarlos@aneel.gov.br; Leite, Carlos Augusto; Vieira, Valter Salino; Silva, Marcio Antonio da; Paes, Vinicius Jose de Castro; Cardoso Filho, Joao Moraes [Companhia de Pesquisas de Recursos Minerais (CPRM), Belo Horizonte, MG (Brazil); Armstrong, Richard [Australian National Univ., Canberra (Australia). Research School of Earth Sciences; Noce, Carlos Mauricio; Pedrosa-Soares, Antonio Carlos [Minas Gerais Univ., Belo Horizonte (Brazil). Inst. de Geociencias. Centro de Pesquisa Manuel Teixeira da Costa; Carneiro, Mauricio Antonio [Ouro Preto Univ., MG (Brazil). Dept. de Geologia

    2002-12-15

    This paper discusses new zircon SHRIMP (Sensitive High Resolution Ion Microprobe) U-Pb geochronological data for 19 key-exposures of several geological units exposed at the eastern border of the Southern Sao Francisco Craton and at the adjacent Proterozoic Mineiro and Aracuai orogens. Samples were collected along several E-W tran sects, aiming at tracing the precise limit of the Sao Francisco Craton Archean basement, as well as assessing the extension of the successive proterozoic orogenic collages. Due to the complex geologic history and/or high grade metamorphism which most of the rock units investigated have undergone, zircon morphology and the U-Pb analytical data exhibit very complex patterns. These are characterized by a combination of inheritance, partial resetting and new zircon growth during high-grade metamorphism. As a consequence, very careful and detailed analyses of cathodoluminescence imagery were required to allow distinction between inheritance, newly melt-precipitated zircon and partially reset zircons, as well as between the ages of magmatic and metamorphic events. In the southeastern border of the craton 5 units yielded Archean crystallization ages ranging from ca. 3000-2700 Ma, with poorly constrained metamorphic ages ranging from ca. 2850 to 550 Ma. The TTG gneissic complex exposed to the east and south of the Quadrilatero Ferrifero, formerly ascribed to the Archean basement, have crystallization ages from ca. 2210 Ma to 2050 Ma, and can now be interpreted as representing pre- to syn-collisional magmatic phases of the Mineiro Belt. Metamorphic ages of ca. 2100 Ma and 560 Ma are also well constrained in zircon populations from these gneisses. The crystallization age of ca 1740 Ma observed for an alkaline granite of the Borrachudos Suite (intrusive into the Archean basement east of the Southern Espinhaco Range) confirmed previous conventional U-Pb data for this Paleoproterozoic rift-related magmatism. One of the major basement inliers within the

  6. Hydrothermal alteration styles in ancient and modern orogenic gold deposits, New Zealand

    International Nuclear Information System (INIS)

    Craw, D.; Upton, P.; MacKenzie, D.J.

    2009-01-01

    Orogenic hydrothermal systems in the South Island of New Zealand were active during Mesozoic and late Cenozoic collisional deformation and metamorphism of greywacke/schist terranes. Observations on the currently active mountain-building environment yield insights on processes occurring in the upper 5-15 km of the crust, and observations on an adjacent lithologically identical exhumed ancient mountain belt provide information on processes at 10-20 km in the crust. Hydrothermal fluids were mainly derived from metamorphic dehydration reactions and/or circulating topographically driven meteoric water in these mountain belts. Three geochemically and mineralogically different types of hydrothermal alteration and vein mineralisation occurred in these orogenic belts, and gold enrichment (locally economic) occurred in some examples of each of these three types. The first type of alteration involved fluids that were in or near chemical equilibrium with their greenschist facies host rocks. Fluid flow was controlled by discontinuous fractures, and by microshears and grain boundaries in host rocks, in zones from metres to hundreds of metres thick. Vein and alteration mineralogy was similar to that of the host rocks, and included calcite and chlorite. The second type of alteration occurred where the fluids were in distinct disequilibrium with the host rocks. Fracture permeability was important for fluid flow, but abundant host rock alteration occurred as well. The alteration zones were characterised by decomposition of chlorite and replacement by ankeritic carbonate in zones up to tens of metres thick. The mineralising fluid was deep-sourced and initially rock-equilibrated, with some meteoric input. The third type of mineralisation was controlled almost exclusively by fracture permeability, and host rock alteration was minor (centimetre scale). This mineralisation type commonly involved calcite and chlorite as vein and alteration minerals, and mineralisation fluids had a major

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

    Science.gov (United States)

    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

  8. Eastern Redcedar Seedling Assessment

    Data.gov (United States)

    U.S. Environmental Protection Agency — Eastern redcedar tree seedling growth in response to various soil, nitrogen, and photosynthetic radiation characteristics. This dataset is associated with the...

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

    Science.gov (United States)

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

    2017-10-01

    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.

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

    Science.gov (United States)

    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

  11. EARLY STAGE OF THE CENTRAL ASIAN OROGENIC BELT BUILDING: EVIDENCES FROM THE SOUTHERN SIBERIAN CRATON

    Directory of Open Access Journals (Sweden)

    D. P. Gladkochub

    2017-01-01

    Full Text Available The origin of the Central-Asian Orogenic Belt (CAOB, especially of its northern segment nearby the southern margin of the Siberian craton (SC is directly related to development and closure of the Paleo-Asian Ocean (PAO. Signatures of early stages of the PAO evolution are recorded in the Late Precambrian sedimentary successions of the Sayan-Baikal-Patom Belt (SBPB on the southern edge of SC. These successions are spread over 2000 km and can be traced along this edge from north-west (Sayan area to south-east (Baikal area and further to north-east (Patom area. Here we present the synthesis of all available and reliable LA-ICP-MS U-Pb geochronological studies of detrital zircons from these sedimentary successions.

  12. 40Ar-39Ar method for age estimation: principles, technique and application in orogenic regions

    International Nuclear Information System (INIS)

    Dalmejer, R.

    1984-01-01

    A variety of the K-Ar method for age estimation by 40 Ar/ 39 Ar recently developed is described. This method doesn't require direct analysis of potassium, its content is calculated as a function of 39 Ar, which is formed from 39 K under neutron activation. Errors resulted from interactions between potassium and calcium nuclei with neutrons are considered. The attention is paid to the technique of gradual heating, used in 40 Ar- 39 Ar method, and of obtaining age spectrum. Aplicabilities of isochronous diagram is discussed for the case of presence of excessive argon in a sample. Examples of 40 Ar- 39 Ar method application for dating events in orogenic regions are presented

  13. The Pan-African Damara Orogen of South West Africa/Namibia

    International Nuclear Information System (INIS)

    Miller, R.McG.

    1983-01-01

    The structural grain of the Damara orogen points to a reversal of spreading and to north-westward subduction of the African cratons below a South American craton and of the Kalahari Craton below the Congo Craton. D 1 recumbent folding was followed by intrusion of 650 m.y.-old granitic rocks, uplift and erosion and deposition of a northern molasse. D 2 deformation in the coastal arm marked the continental collision phase in this region. The final, large-scale deformational event in this region caused westward-vergent back folding which was followed by intrusion of 570 m.y.-old post-tectonic granites. In the Central Zone, widespread intrusion of 550 m.y.-old, syntectonic granites and extrusion of their volcanic equivalents in a 150 km-wide, high-temperature-low-pressure zone along the leading edge of the Congo Craton was accompanied by uplift, erosion and the deposition of K-rich greywackes as a fore-arc sequence above the earlier, spreading-phase deposits in the closing Southern Zone ocean. Sedimentological aspects of the Damara along the southern margin of the orogen suggest that the lower Nama Group, which contains a unique Ediacara fauna and was derived from easterly sources, was deposited between about 650 and 550 m.y. ago during deformation north of the Southern Zone ocean. During the final major deformation event in the Central Zone (D 3 doming), the fore-arc deposits and the underlying passive-margin sediments to the south were deformed. The Damaran granitic rocks are Hercynotype; granites make up 96 per cent of the more than 200 plutons. Average compositions have a slightly less calc-alkaline character than typical compressional margin granitic suites. Early granites have I-type chemistries and appear to have been derived from deep crustal sources, whereas most of the young granites have intermediate to S-type compositions and were generated at various crustal levels

  14. Isolating active orogenic wedge deformation in the southern Subandes of Bolivia

    Science.gov (United States)

    Weiss, Jonathan R.; Brooks, Benjamin A.; Foster, James H.; Bevis, Michael; Echalar, Arturo; Caccamise, Dana; Heck, Jacob; Kendrick, Eric; Ahlgren, Kevin; Raleigh, David; Smalley, Robert; Vergani, Gustavo

    2016-08-01

    A new GPS-derived surface velocity field for the central Andean backarc permits an assessment of orogenic wedge deformation across the southern Subandes of Bolivia, where recent studies suggest that great earthquakes (>Mw 8) are possible. We find that the backarc is not isolated from the main plate boundary seismic cycle. Rather, signals from subduction zone earthquakes contaminate the velocity field at distances greater than 800 km from the Chile trench. Two new wedge-crossing velocity profiles, corrected for seasonal and earthquake affects, reveal distinct regions that reflect (1) locking of the main plate boundary across the high Andes, (2) the location of and loading rate at the back of orogenic wedge, and (3) an east flank velocity gradient indicative of décollement locking beneath the Subandes. Modeling of the Subandean portions of the profiles indicates along-strike variations in the décollement locked width (WL) and wedge loading rate; the northern wedge décollement has a WL of ~100 km while accumulating slip at a rate of ~14 mm/yr, whereas the southern wedge has a WL of ~61 km and a slip rate of ~7 mm/yr. When compared to Quaternary estimates of geologic shortening and evidence for Holocene internal wedge deformation, the new GPS-derived wedge loading rates may indicate that the southern wedge is experiencing a phase of thickening via reactivation of preexisting internal structures. In contrast, we suspect that the northern wedge is undergoing an accretion or widening phase primarily via slip on relatively young thrust-front faults.

  15. Magmatism in the Shapinggou district of the Dabie orogen, China: Implications for the formation of porphyry Mo deposits in a collisional orogenic belt

    Science.gov (United States)

    Ren, Zhi; Zhou, Taofa; Hollings, Pete; White, Noel C.

    2018-05-01

    The Shapinggou molybdenum deposit is located in the Qinling-Dabie Orogen, which hosts the world's largest molybdenum belt. The igneous rocks at Shapinggou can be divided into two stages (136-127 Ma and 118-114 Ma), the early suite of felsic (136-127 Ma, SiO2 = 58.0 to 72.9 wt%) and mafic rocks (133-128 Ma, SiO2 = 45.2 to 57.0 wt%), and a later suite comprising syenite (117 Ma, SiO2 = 64.2 to 65.0 wt%), quartz syenite porphyry (116 Ma, 62.5 to 70.0 wt%), granite porphyry (112 Ma, SiO2 = 75.5 to 77.6 wt%) and diorite porphyry (111 Ma, SiO2 = 56.6 to 59.7 wt%). The early-stage felsic rocks display high SiO2, Al2O3, Na2O, K2O, Sr, LREE contents, and Sr/Y, (La/Yb)N ratios, initial Sr isotope ratios of 0.7076 to 0.7089, but low MgO, FeOT, Y, Yb contents and negative εNd(t) values, consistent with partial melting of the lower continental crust. The early-stage mafic rocks exhibit low SiO2, high MgO, Ni and Cr contents, consistent with an upper mantle source, but trace element and isotope data suggest a role for crustal contamination. The late-stage syenite and quartz syenite porphyry show high abundances of Na2O, K2O, Al2O3, HFSEs (e.g., Th, U, Zr, Hf) and significant negative Eu anomalies. The late-stage granite porphyry displays high SiO2 contents, and depletions in Ba, Sr, Eu and Ti. The geochemical features of the late-stage intrusions are similar to A-type granites. Crystal fractionation of plagioclase, K-feldspar, biotite/ muscovite, amphibole/ garnet and Fe-Ti oxides controlled the evolution of the magma. The geochemical and isotopic data suggest that the rocks at Shapinggou were likely derived from a mixed source of lithospheric mantle, subducted continental crust of the Yangtze Block (Kongling Group) and partial melts of the Dabie Complex. Early stage rocks represent melts of the source with a lower proportion of Dabie Complex materials, whereas late stage rocks were derived from a source with a higher proportion Dabie Complex component. The geochemical and

  16. Reactivation of inherited structures during the opening of the South Atlantic: a low-temperature thermochronology study on the Araçuaí orogenic belt (east Brazilian margin)

    Science.gov (United States)

    Van Ranst, Gerben; De Grave, Johan; Pedrosa-Soares, Antonio Carlos; Tack, Luc; Baudet, Daniel; Novo, Tiago

    2017-04-01

    A subject that has historically been regarded with increasing interest in geology are the supercontinent-cycles. This still poses questions about tectonic evolution on a regional scale, more precisely on the role of reactivation of older, pre-existing structures (inheritance), in which the same faults or weak zones are reactivated rather than the emergence of new systems. A region that is ideally suited for this research is the Araçuaí-West Congo Orogenic belt (AWCO), which is situated partly in eastern Brazil (Gonçalves et al., 2014) and partly in western Africa (D.R. Congo, Congo Brazza, Gabon and Angola; Frimmel et al., 2006; Tack et al., 2001). This orogenic belt was formed during the Cambrian as a result of a series of extension and compression events, of which the final phase is known as the Braziliano-Pan-African orogenesis (e.g. Pedrosa-Soares & Alkmim, 2011). During the break-up of Gondwana and the opening of the South Atlantic, the AWCO became separated. The main part is situated in east Brazil, known as the Araçuaí orogeny, while on the west African margin, the West Congo Belt is a witness to this event. In order to gain a better understanding, the tectonic movements should be placed in an absolute timeframe. Multi-method low-temperature thermochronology lends itself as an ideal tool for this purpose. In this study samples from N-S and E-W profiles in east Brazil (Caparáo-Vitória-Gov. Valadares) have been acquired. These samples are investigated using the apatite fission track (AFT) and apatite (U-Th-Sm)/He (AHe) methods. In a later phase the samples which were taken on profiles in the D.R. Congo (Lower Congo) will be analysed by the same methods. Preliminary results for the Brazilian margin indicate cooling ages ranging between 55 Ma and c. 80 Ma.

  17. Gas in Eastern Europe

    International Nuclear Information System (INIS)

    Anon.

    1994-01-01

    West European gas companies have long recognised the potential for lucrative business within eastern Europe. But they recognise that the region's integration into the west European system will be far from straightforward, with deals between east European gas companies and their western counterparts invariably containing financial mechanisms, such as barter trade, that are designed to cope with the easterners' shortage of hard currency. (author)

  18. Middle Eastern rhinoplasty.

    Science.gov (United States)

    Azizzadeh, Babak; Mashkevich, Grigoriy

    2010-02-01

    The ethnic appearance of the Middle Eastern nose is defined by several unique visual features, particularly a high radix, wide overprojecting dorsum, and an amorphous hanging nasal tip. These external characteristics reflect distinct structural properties of the osseo-cartilaginous nasal framework and skin-soft tissue envelope in patients of Middle Eastern extraction. The goal, and the ultimate challenge, of rhinoplasty on Middle Eastern patients is to achieve balanced aesthetic refinement, while avoiding surgical westernization. Detailed understanding of the ethnic visual harmony in a Middle Eastern nose greatly assists in preserving native nasal-facial relationships during rhinoplasty on Middle Eastern patients. Esthetic alteration of a Middle Eastern nose follows a different set of goals and principles compared with rhinoplasties on white or other ethnic patients. This article highlights the inherent nasal features of the Middle Eastern nose and reviews pertinent concepts of rhinoplasty on Middle Eastern patients. Essential considerations in the process spanning the consultation and surgery are reviewed. Reliable operative techniques that achieve a successful aesthetic outcome are discussed in detail. Copyright 2010 Elsevier Inc. All rights reserved.

  19. Folded Basinal Compartments of the Southern Mongolian Borderland: A Structural Archive of the Final Consolidation of the Central Asian Orogenic Belt

    Directory of Open Access Journals (Sweden)

    Dickson Cunningham

    2017-01-01

    Full Text Available The Central Asian Orogenic Belt (CAOB records multiple Phanerozoic tectonic events involving consolidation of disparate terranes and cratonic blocks and subsequent reactivation of Eurasia’s continental interior. The final amalgamation of the CAOB terrane collage involved diachronous closure of the Permian-Triassic Solonker suture in northernmost China and the Jurassic Mongol-Okhotsk suture in northeast Mongolia and eastern Siberia. The distribution, style, and kinematics of deformation associated with these two terminal collision events is poorly documented in southern Mongolia and northernmost China because these regions were later tectonically overprinted by widespread Cretaceous basin and range-style crustal extension and Miocene-recent sinistral transpressional mountain building. These younger events structurally compartmentalized the crust into uplifted crystalline basement blocks and intermontane basins. Consequently, widespread Cretaceous and Late Cenozoic clastic sedimentary deposits overlie older Permian-Jurassic sedimentary rocks in most basinal areas and obscure the deformation record associated with Permian-Triassic Solonker and Jurassic Mongol-Okhotsk collisional suturing. In this report, satellite image mapping of basinal compartments that expose folded Permian-Jurassic sedimentary successions that are unconformably overlapped by Cretaceous-Quaternary clastic sediments is presented for remote and poorly studied regions of southern Mongolia and two areas of the Beishan. The largest folds are tens of kilometers in strike length, east-west trending, and reveal north-south Late Jurassic shortening (present coordinates. Late Jurassic fold vergence is dominantly northerly in the southern Gobi Altai within a regional-scale fold-and-thrust belt. Local refolding of older Permian north-south trending folds is also evident in some areas. The folds identified and mapped in this study provide new evidence for the regional distribution and

  20. Petrological and zircon evidence for the Early Cretaceous granulite-facies metamorphism in the Dabie orogen, China

    Science.gov (United States)

    Gao, Xiao-Ying; Zhang, Qiang-Qiang; Zheng, Yong-Fei; Chen, Yi-Xiang

    2017-07-01

    An integrated study of petrology, mineralogy, geochemistry, and geochronology was carried out for contemporaneous mafic granulite and diorite from the Dabie orogen. The results provide evidence for granulite-facies reworking of the ultrahigh-pressure (UHP) metamorphic rock in the collisional orogen. Most zircons from the granulite are new growth, and their U-Pb ages are clearly categorized into two groups at 122-127 Ma and 188 ± 2 Ma. Although these two groups of zircons show similarly steep HREE patterns and variably negative Eu anomalies, the younger group has much higher U, Th and REE contents and Th/U ratios, much lower εHf(t) values than the older group. This suggests their growth is associated with different types of dehydration reactions. The older zircon domains contain mineral inclusions of garnet + clinopyroxene ± quartz, indicating their growth through metamorphic reactions at high pressures. In contrast, the young zircon domains only contain a few quartz inclusions and the garnet-clinopyroxene-plagioclase-quartz barometry yields pressures of 4.9 to 12.5 kb. In addition, the clinopyroxene-garnet Fe-Mg exchange thermometry gives temperatures of 738-951 °C. Therefore, the young zircon domains would have grown through peritectic reaction at low to medium pressures. The younger granulite-facies metamorphic age is in agreement not only with the adjacent diorite at 125 ± 1 Ma in this study but also the voluminous emplacement of coeval mafic and felsic magmas in the Dabie orogen. Mineral separates from both mafic granulite and its adjacent diorite show uniformly lower δ18O values than normal mantle, similar to those for UHP eclogite-facies metaigneous rocks in the Dabie orogen. In combination with major-trace elements and zircon Lu-Hf isotope compositions, it is inferred that the protolith of mafic granulites shares with the source rock of diorites, both being a kind of mafic metasomatites at the slab-mantle interface in the continental subduction channel

  1. A discussion on the tectonic implications of Ediacaran late- to post-orogenic A-type granite in the northeastern Arabian Shield, Saudi Arabia

    Science.gov (United States)

    Robinson, F. A.; Bonin, B.; Pease, V.; Anderson, J. L.

    2017-03-01

    The transition from late-orogenic to post-orogenic magmatism following major orogenic episodes such as the Neoproterozoic to Cambrian East African Orogen (EAO) is an important, yet not well-understood geological event marking the cessation of subduction-controlled magmatism between buoyant lithospheric fragments. Forming the northern part of the EAO in the Arabian-Nubian Shield are three granitic suites that successively intruded the same northeastern area and post-date the 640 Ma major orogenic episode: (1) 620-600 Ma alkali feldspar (hypersolvous) granite with alkaline/ferroan/A-type geochemistry, (2) 599 Ma granite cumulates (some garnet-bearing) with calc-alkaline/magnesian affinities, and (3) 584-566 Ma alkali feldspar (hypersolvous) granite (aegirine-bearing) with a distinctive peralkaline/ferroan/A-type signature. Combining whole-rock geochemistry from the southern and northern Arabian Shield, suites 1 and 2 are suggested to be products of late-orogenic slab tear/rollback inducing asthenospheric mantle injection and lower crustal melting/fractionation toward A-type/ferroan geochemistry. Suite 3, however, is suggested to be produced by post-orogenic lithospheric delamination, which replaced the older mantle with new asthenospheric (rare earth element-enriched) mantle that ultimately becomes the thermal boundary layer of the new lithosphere. Major shear zones, such as the 620-540 Ma Najd Fault System (NFS), are some of the last tectonic events recorded across the Arabian Shield. Data presented here suggest that the NFS is directly related to the late-orogenic (620-600 Ma) slab tear/rollback in the northeastern Shield as it met with opposing subduction polarity in the southern Shield. Furthermore, this study infers that east and west Gondwana amalgamation interacted with opposing convergence reflected by the NFS.

  2. Geochronology, geochemistry and Hf–Sr–Nd isotopes of the ore-bearing syenite from the Shapinggou porphyry Mo deposit, East Qinling-Dabie orogenic belt

    Directory of Open Access Journals (Sweden)

    Tao He

    2016-12-01

    Full Text Available The Shapinggou Mo deposit is located in the western Dabie mountains, the eastern part of the Qinling-Dabie molybdenum orogenic belt. Shapinggou Mo deposit is a concealed deposit with the ore body mainly hosted by explosive breccia of Gaijing and the granite porphyry as well as the syenite of Shapinggou. Geochemistry study show that the SiO2 contents of Shapinggou syenite range from 61.74 to 69.93%, and the A/CNK from 0.95 to 1.06, classified as metaluminous to weak peraluminous, belonging to alkalic to shoshonitic series. The Mo deposits in Qinling Mo belt formed in two main periods, i.e., the first period occurred in to the Early Cretaceous (145–130 Ma, the second period in the late Early Cretaceous (130–110 Ma. Most of the Mo deposits in Dabie region formed in the second period. The results of zircon U–Pb show that the age of the Shapinggou syenite is 111.3 ± 1.2 Ma, which belongs to the second period. Proterozoic-Archean inherited zircons suggest that it may include some more ancient crustal material like Kongling group. The ɛHf(t values of Shapinggou syenite range from −15.6 to −8.0, TDM2(Hf from 1.7 to 2.16 Ga, respectively. The ɛNd(t values of the Shapinggou syenite range from −12.29 to −11.76, TDM2(Nd from 1.85 to 1.89 Ga, the 87Sr/86Sr from 0.709 to 0.710, respectively. Results of zircon Hf isotope and whole rock Sr–Nd isotope of Shapinggou syenite indicate that the Mo ore-forming materials were mainly generated from old Yangtze craton, e.g., gneiss from Dabie orogeny, mixed with some juvenal mantle materials. The geodynamics of the Shapinggou Mo deposit corresponded to an extension period in Eastern China, which caused by large scale lithospheric thinning. The delamination caused asthenosphere upwelling and crust-mantle interaction, which provided the ore-forming material and heat.

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

    Science.gov (United States)

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

    1994-04-01

    In a lithospheric-scale, orogen-parallel transcurrent shear zone of the Pan-African Dom Feliciano belt of southern Brazil, two successive generations of magmas, an early calc-alkaline and a late peraluminous, have been emplaced during deformation. Microstructures show that these granitoids experienced a progressive deformation from magmatic to solid state under decreasing temperature conditions. Magmatic deformation is indicated by the coexistence of aligned K-feldspar, plagioclase, micas, and/or tourmaline with undeformed quartz. Submagmatic deformation is characterized by strain features, such as fractures, lattice bending, or replacement reactions affecting only the early crystallized phases. High-temperature solid-state deformation is characterized by extensive grain boundary migration in quartz, myrmekitic K-feldspar replacement, and dynamic recrystallization of both K-feldspar and plagioclase. Decreasing temperature during solid-state deformation is inferred from changes in quartz crystallographic fabrics, decrease in grain size of recrystallized feldspars, and lower Ti amount in recrystallized biotites. Final low-temperature deformation is characterized by feldspar replacement by micas. The geochemical evolution of the synkinematic magmatism, from calc-alkaline metaluminous granodiorites with intermediate 87Sr/86Sr initial ratio to peraluminous granites with very high 87Sr/86Sr initial ratio, suggests an early lower crustal source or a mixed mantle/crustal source, followed by a middle to upper crustal source for the melts. Shearing in lithospheric faults may induce partial melting in the lower crust by shear heating in the upper mantle, but, whatever the process initiating partial melting, lithospheric transcurrent shear zones may collect melt at different depths. Because they enhance the vertical permeability of the crust, these zones may then act as heat conductors (by advection), promoting an upward propagation of partial melting in the crust

  4. Superposed orogenic collision and core-complex formation at the present contact between the Dinarides and the Pannonian basin: The Bukulja and Cer Mountains in central and western Serbia

    Science.gov (United States)

    Matenco, Liviu; Toljic, Marinko; Ducea, Mihai; Stojadinovic, Uros

    2010-05-01

    Formation of large extensional detachments during orogenic collapse can follow inherited weakness zones such as major asymmetries given by pre-existing subduction zones active during mountain building processes. This is valid in particular in low-topography foreland coupling orogens of Mediterranean type where large amounts of deformation is concentrated in their lower plates, favoring weakness zones activated during a subsequent phase of extensional collapse. One good place to study the orogenic collapse post-dating major collision is the NE margin of the Dinarides in central and western Serbia, where Cretaceous-Eocene shortening and collision was recorded in the Alpine Tethys Sava zone between the European-derived Dacia and Tisza mega-units and the lower Adriatic plate. This is the same place where the Pannonian basin formed as a Miocene back-arc basin in response to a different subduction and roll-back taking place along the external Carpathians. A lineament of Paleogene and Miocene plutons is observed at the northern and eastern margin of the Dinarides, interpreted to be the product of both syn- to post-orogenic subduction magmatism and of decompressional melting during the Pannonian extension. Two of these plutons, Cer and Bukulja, located in western and respectively central Serbia, are intruded in the Jadar-Kopaonik composite thrust sheet, part of the lower Adriatic plate, near the contact with the main suture formed during the Cretaceous-Eocene subduction of the Sava zone. The Lower Miocene age (19-17Ma) Bukulja intrusion is a S-type granite with rare aplitic veins (Cvetkovic et al., 2007). The Cer intrusive complex is a S type two mica granite of around 16Ma in age with an older I-type quartz monzonite component (Koroneos et al. in press). Both granitoids are intruded into the Jadar-Kopaonik metamorphic series, which are in direct contact along the northern, eastern and southern flank with non-metamorphosed, mainly clastic sediments of Cretaceous-Miocene in

  5. Uranium cycle and tectono-metamorphic evolution of the Lufilian Pan-African orogenic belt (Zambia)

    International Nuclear Information System (INIS)

    Eglinger, Aurelien

    2013-01-01

    Uranium is an incompatible and lithophile element, and thus more concentrated in silicate melt produced by the partial melting of the mantle related to continental crust formation. Uranium can be used as a geochemical tracer to discuss the generation and the evolution of continental crust. This thesis, focused on the Pan-African Lufilian belt in Zambia, combines structural geology, metamorphic petrology and thermos-barometry, fluid inclusions, geochemistry and geochronology in order to characterize the uranium cycle for this crustal segment. Silici-clastic and evaporitic sediments have been deposited within an intra-continental rift during the dislocation of the Rodinia super-continent during the early Neo-proterozoic. U-Pb ages on detrital zircon grains in these units indicate a dominant Paleo-proterozoic provenance. The same zircon grains show sub-chondritic εHf (between 0 and -15) and yield Hf model ages between ∼2.9 and 2.5 Ga. These data suggest that the continental crust was generated before the end of the Archean (< 2.5 Ga) associated with uranium extraction from the mantle. This old crust has been reworked by deformation and metamorphism during the Proterozoic. Uranium has been re-mobilized and reconcentrated during several orogenic cycles until the Pan-African orogeny. During this Pan-African cycle, U-Pb and REY (REE and Yttrium) signatures of uranium oxides indicate a first mineralizing event at ca. 650 Ma during the continental rifting. This event is related to late diagenesis hydrothermal processes at the basement/cover interface with the circulation of basinal brines linked to evaporites of the Roan. The second stage, dated at 530 Ma, is connected to metamorphic highly saline fluid circulations, synchronous to the metamorphic peak of the Lufilian orogeny (P=9±3 kbar; T=610±30 deg. C). These fluids are derived from the Roan evaporite dissolution. Some late uranium re-mobilizations are described during exhumation of metamorphic rocks and their

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

    Science.gov (United States)

    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

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

    Science.gov (United States)

    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.

  8. Crustal surface wave velocity structure of the east Albany-Fraser Orogen, Western Australia, from ambient noise recordings

    Science.gov (United States)

    Sippl, C.; Kennett, B. L. N.; Tkalčić, H.; Gessner, K.; Spaggiari, C. V.

    2017-09-01

    Group and phase velocity maps in the period range 2-20 s for the Proterozoic east Albany-Fraser Orogen, Western Australia, are extracted from ambient seismic noise recorded with the 70-station ALFREX array. This 2 yr temporary installation provided detailed coverage across the orogen and the edge of the Neoarchean Yilgarn Craton, a region where no passive seismic studies of this scale have occurred to date. The surface wave velocities are rather high overall (>3 km s-1 nearly everywhere), as expected for exposed Proterozoic basement rocks. No clear signature of the transition between Yilgarn Craton and Albany-Fraser Orogen is observed, but several strong anomalies corresponding to more local geological features were obtained. A prominent, NE-elongated high-velocity anomaly in the northern part of the array is coincident with a Bouguer gravity high caused by the upper crustal metamorphic rocks of the Fraser Zone. This feature disappears towards longer periods, which hints at an exclusively upper crustal origin for this anomaly. Further east, the limestones of the Cenozoic Eucla Basin are clearly imaged as a pronounced low-velocity zone at short periods, but the prevalence of low velocities to periods of ≥5 s implies that the uppermost basement in this area is likewise slow. At longer periods, slightly above-average surface wave velocities are imaged below the Eucla Basin.

  9. Magnitude of crustal shortening and structural framework of the easternmost Himalayan orogen, northern Indo-Burma Ranges of northeastern India

    Science.gov (United States)

    Haproff, P. J.; Yin, A.

    2016-12-01

    Along-strike variation in crustal shortening throughout the Himalayan orogen has been attributed to (1) diachronous, eastward-increasing convergence, or (2) localized controls including pre-collisional stratigraphic configuration and climate. In this study, we present new geologic maps and balanced cross-sections across the easternmost segment of the Himalayan orogen, the N-S-trending N. Indo-Burma Ranges of northeastern India. First order structures are NE-dipping, km-wide ductile thrust shear zones with mylonitic fabrics indicating top-to-the SW motion. Major structures include the Mayodia klippe and Hunli window, generated during folding of the SW-directed Tidding thrust and duplexing of Lesser Himalayan rocks (LHS) at depth. Reconstruction of two balanced cross-sections yields minimum shortening estimates of 70% (48 km) and 71% (133 km), respectively. The widths of the orogen for each transect are 21 km and 54 km, respectively. Our percent strain values are comparable to that of western Arunachal Himalaya, reflecting eastward-increasing strain due to counterclockwise rotation of India during convergence or along-strike variation in India's subduction angle. However, shortening magnitudes much less than that of the Sikkim (641 km), Bhutan (414-615 km), and western Arunachal Himalaya (515-775 km) could signal eastward increasing shortening of a unique Himalayan stratigraphic framework, evidenced by few GHC rocks, absence of Tethyan strata, and an extensive subduction mélange and forearc complex.

  10. Timing of Mississippi Valley-type mineralization: Relation to Appalachian orogenic events

    Energy Technology Data Exchange (ETDEWEB)

    Kesler, S.E.; van der Pluijm, B.A. (Univ. of Michigan, Ann Arbor (USA))

    1990-11-01

    Although Mississippi Valley-type deposits in Lower Ordovician carbonate rocks of the Appalachian orogen are commonly interpreted to have been precipitated by basinal brines, the timing of brine migration remains poorly known. Late Paleozoic K-Ar isotopic ages on authigenic K-feldspar, which is widespread in Appalachian carbonate rocks, as well as evidence of paleomagnetic overprints of similar age, have focused attention on the possibility that these Mississippi Valley-type deposits formed as a result of late Paleozoic deformation. Geologic and geochemical similarities among most of these deposits, from Georgia to Newfoundland, including unusually high sphalerite/galena ratios, isotopically heavy sulfur, and relatively nonradiogenic lead, suggest that they are coeval. Sphalerite sand that parallels host-rock layering in many of the deposits indicates that mineralization occurred before regional deformation. Although the late Paleozoic age of deformation in the southern Appalachians provides little constraint on the age of Mississippi Valley-type mineralization, deformation of these deposits in the Newfoundland Appalachians is early to middle Paleozoic in age. Thus, if Ordovician-hosted, Appalachian Mississippi Valley-type deposits are coeval, they must have formed by middle Paleozoic time and cannot be the product of a late Paleozoic fluid-expulsion event. This hypothesis has important implications for basin evolution, fluid events, and remagnetization in the Appalachians.

  11. Organic molecular paleohypsometry: A new approach to reconstructing the paleoelevation history of an orogen

    Science.gov (United States)

    Hren, M. T.; Ouimet, W. B.

    2017-12-01

    Paleoelevation data is critical to understanding the links and feedbacks between rock-uplift and erosion yet few approaches have proved successful in quantifying changes in paleoelevation rapidly eroding, tropical landscapes. In addition, quantitative methods of reconstructing paleoelevation from marine sedimentary archives are lacking. Here we present a new approach to quantifying changes in paleoelevation that is based on the geochemical signature of organic matter exported via the main river networks of an orogen. This new approach builds on fundamentals of stable isotope paleoaltimetry and is akin to the theory behind cosmogenic isotope records of catchment-integrated erosion. Specifically, we utilize predictable patterns of precipitation and organic molecular biomarker stable isotopes to relate the hypsometry of organic matter in a catchment to the geochemical signal in exported organic carbon. We present data from two sites (the cold temperate White Mountains of New Hampshire, USA and the tropical, rapidly eroding landscape of Taiwan) to demonstrate this relationship between exported carbon geochemistry and catchment hypsometry and the validity of this approach.

  12. Devonian magmatism in the Timan Range, Arctic Russia - subduction, post-orogenic extension, or rifting?

    Science.gov (United States)

    Pease, V.; Scarrow, J. H.; Silva, I. G. Nobre; Cambeses, A.

    2016-11-01

    Devonian mafic magmatism of the northern East European Craton (EEC) has been variously linked to Uralian subduction, post-orogenic extension associated with Caledonian collision, and rifting. New elemental and isotopic analyses of Devonian basalts from the Timan Range and Kanin Peninsula, Russia, in the northern EEC constrain magma genesis, mantle source(s) and the tectonic process(es) associated with this Devonian volcanism to a rift-related context. Two compositional groups of low-K2O tholeiitic basalts are recognized. On the basis of Th concentrations, LREE concentrations, and (LREE/HREE)N, the data suggest two distinct magma batches. Incompatible trace elements ratios (e.g., Th/Yb, Nb/Th, Nb/La) together with Nd and Pb isotopes indicate involvement of an NMORB to EMORB 'transitional' mantle component mixed with variable amounts of a continental component. The magmas were derived from a source that developed high (U,Th)/Pb, U/Th and Sm/Nd over time. The geochemistry of Timan-Kanin basalts supports the hypothesis that the genesis of Devonian basaltic magmatism in the region resulted from local melting of transitional mantle and lower crust during rifting of a mainly non-volcanic continental rifted margin.

  13. Three-dimensional thermoluminescence spectra of different origin quartz from Altay Orogenic belt, Xinjiang, China

    International Nuclear Information System (INIS)

    Tan Kaixuan; Liu Zehua; Zeng Sheng; Liu Yan; Xie Yanshi; Rieser, Uwe

    2009-01-01

    Three-dimensional thermoluminescence spectra are measured for different types of geological origin quartz from the Altay orogenic belt, northern Xinjiang, China. The results show striking differences which appear to be characteristic of their geological origin. Granitic quartz is dominated by emission bands at 420-430 nm, 550-560 nm, at a temperature of 170 deg. C. Pegmatite quartz is characterized by an intense 480 nm emission band at 170 deg. C. Volcanic quartz has exclusive UV (340-360 nm) and violet (410-430 nm) emission bands. Hydrothermal quartz exhibits very different TL spectral characteristics because of different hydrothermal activity and mineralization. Only one TL peaks at 485 nm/170 deg. C was observed in sedimentary quartz. An intense 730 nm emission band observed at 170 deg. C considered generally to be characteristics of feldspar was observed in quartz from granite and hydrothermal Au-bearing quartz. This TL peak is probably related to the centre of [FeO 4 ] 0 on an Si site. All samples show an intense 990-1000 nm emission band at 330 deg. C. Identical types of quartz formed in different regions or different geological and tectonic settings can also exhibit striking differences in TL spectra.

  14. Polyphase Neoproterozoic orogenesis within the east Africa- Antarctica orogenic belt in central and northern Madagascar

    Science.gov (United States)

    Key, R.M.; Pitfield, P.E.J.; Thomas, Ronald J.; Goodenough, K.M.; Waele, D.; Schofield, D.I.; Bauer, W.; Horstwood, M.S.A.; Styles, M.T.; Conrad, J.; Encarnacion, J.; Lidke, D.J.; O'connor, E. A.; Potter, C.; Smith, R.A.; Walsh, G.J.; Ralison, A.V.; Randriamananjara, T.; Rafahatelo, J.-M.; Rabarimanana, M.

    2011-01-01

    Our recent geological survey of the basement of central and northern Madagascar allowed us to re-evaluate the evolution of this part of the East Africa-Antarctica Orogen (EAAO). Five crustal domains are recognized, characterized by distinctive lithologies and histories of sedimentation, magmatism, deformation and metamorphism, and separated by tectonic and/or unconformable contacts. Four consist largely of Archaean metamorphic rocks (Antongil, Masora and Antananarivo Cratons, Tsaratanana Complex). The fifth (Bemarivo Belt) comprises Proterozoic meta-igneous rocks. The older rocks were intruded by plutonic suites at c. 1000 Ma, 820-760 Ma, 630-595 Ma and 560-520 Ma. The evolution of the four Archaean domains and their boundaries remains contentious, with two end-member interpretations evaluated: (1) all five crustal domains are separate tectonic elements, juxtaposed along Neoproterozoic sutures and (2) the four Archaean domains are segments of an older Archaean craton, which was sutured against the Bemarivo Belt in the Neoproterozoic. Rodinia fragmented during the early Neoproterozoic with intracratonic rifts that sometimes developed into oceanic basins. Subsequent Mid- Neoproterozoic collision of smaller cratonic blocks was followed by renewed extension and magmatism. The global 'Terminal Pan-African' event (560-490 Ma) finally stitched together the Mid-Neoproterozoic cratons to form Gondwana. ?? The Geological Society of London 2011.

  15. Uraniferous alaskitic granites with special reference to the Damara Orogenic Belt

    International Nuclear Information System (INIS)

    Toens, P.D.; Corner, B.

    1980-10-01

    The control and patterns of uranium mineralisation in the alaskitic granites of the Damara Orogenic Belt are discussed. The polyphase Damara metamorphism produced high-grade metamorphic assemblages, migmatites and syn-, late-, and post-tectonic anatectic granites through reactivation of the basement and overlying Damara rocks. During anatexis the incompatible elements, particularly the uranium derived from these formations, were incorporated into the melts which then rose, in an attempt to attain gravitational equilibrium, by varying distances depending on the depth of origin of the melts, on their water content and on the availability of tensional environments. Fractional crystallisation during ascent and increased water content concentrated the uranium into residual melts which finally crystallised as alaskitic pegmatitic granite. Structural episodes played an important part in the emplacement of the uraniferous granites and the presence of marble bands was an important factor in not only providing a structural trap for the alaskitic melts and associated uranium-rich volatiles, but also by leading to the boiling of the magma and the subsequent deposition of uranium. The present-day level of erosion is considered to be an important factor contributing to the preservation of many of the uraniferous granite bodies. In addition it is suggested that secondary enrichment occurring above the water-table in the prevailing desert environment is an important criterion in enriching the tenor of mineralisation to ore grades. The exploration techniques necessary for the location of uraniferous granite bodies are briefly outlined [af

  16. Geological and geochemical implications of the genesis of the Qolqoleh orogenic gold mineralisation, Kurdistan Province (Iran

    Directory of Open Access Journals (Sweden)

    Taghipour Batoul

    2015-03-01

    Full Text Available The Qolqoleh gold deposit is located in the northwestern part of the Sanandaj-Sirjan Zone (SSZ, within the NE-SW trending Qolqoleh shear zone. Oligocene granitoids, Cretaceous meta-limestones, schists and metavolcanics are the main lithological units. Chondrite-normalised REE patterns of the ore-hosting metavolcanics indicate REE enrichment relative to hanging wall (chlorite-sericite schist and footwall (meta-limestone rocks. The pattern also reflects an enrichment in LREE relative to HREE. It seems that the LREE enrichment is related to the circulation of SO42- and CO2-bearing fluids and regional metamorphism in the Qolqoleh shear zone. Both positive and negative Eu anomalies are observed in shear-zone metavolcanics. These anomalies are related to the degree of plagioclase alteration during gold mineralisation and hydrothermal alteration. In progressing from a metavolcanic protomylonite to an ultramylonite, significant changes occurred in the major/trace element and REE concentration. Utilising an Al-Fe-Ti isocon for the ore-hosting metavolcanics shows that Sc, Y, K, U, P, and M-HREE (except Eu are relatively unchanged; S, As, Ag, Au, Ca, LOI, Rb and LREE are enriched, and Sr, Ba, Eu, Cr, Co and Ni decrease with an increasing degree of deformation. Based on geochemical features and comparison with other well-known shear zones in the world, the study area is best classified as an Isovolume-Gain (IVG type shear zone and orogenic type gold mineralisation.

  17. The Evolution of Eastern Himalayan Syntaxis of Tibetan Plateau

    Science.gov (United States)

    Zhang, S.; Wu, T.; Li, M.; Zhang, Y.; Hua, Y.; Zhang, B.

    2017-12-01

    Indian plate has been colliding with Eurasian plate since 50Ma years ago, resulting in the Tethys extinction, crust shortening and Tibetan plateau uplift. But it is still a debate how the Tibetan Plateau material escaped. This study tries to invert the distributions of dispersion phase velocity and anisotropy in Eastern Himalayan Syntaxis (EHS) based on the seismic data. We focused on the seven sub-blocks around EHS region. Sub-block "EHS" represents EHS corner with high velocity anomalies, significantly compressed in the axle and strike directions. Sub-blocks "LSD", "QTB" and "SP-GZB" are located at its northern areas with compressions also, and connected with low-velocity anomalies in both crustal and upper mantle rocks. Sub-block "ICB" is located at its southern area with low velocity anomaly, and connected with Tengchong volcano. Sub-blocks "SYDB" and "YZB" are located at its eastern areas with high velocity anomalies in both crustal and upper mantle rocks. Our results demonstrated that significant azimuthal anisotropy of crust (t£30s) and upper mantle (30s£t£60s). Crustal anisotropy indicates the orogenic belt matched well with the direction of fast propagation, and upper mantle anisotropy represents the lattic-preferred orientation (LPO) of mantle minerals (e.g. olivine and basalt), indicating the features of subducting Indian plate. Besides, Red River fault is a dextral strike fault, controlling the crustal and mantle migration. There is a narrow zone to be the channel flow of Tibetan crustal materials escaping toward Yunnan area. The evolution of EHS seems constrained by gravity isostatic mechanism. Keywords: Tibetan Plateau; Eastern Himalayan Syntaxis; Red River fault; crustal flow; surface wave; anisotropy

  18. Calcite twinning strain variations across the Proterozoic Grenville orogen and Keweenaw-Kapuskasing inverted foreland, USA and Canada

    Directory of Open Access Journals (Sweden)

    John P. Craddock

    2017-11-01

    Full Text Available We report the calcite twinning strain results of a traverse across the Grenville orogen from Parry Sound, Ontario (NW to Ft. Ann, New York (SE, including the younger, adjacent Ordovician Taconic allochthon. Fifty four carbonates (marbles, calcite veins, Ordovician limestone were collected resulting in 68 strain analyses on mechanically twinned calcite (n = 2337 grains across the Central Gneiss Belt (CGB; 3 samples, the Central Metasedimentary Belt (CMB; 27 samples, the Central Granulite Terrane (CGT; Adirondack's; 13 samples and the Ottawan Orogenic Lid (OOL; 11 samples. Twinning strains in the greenschist-grade OOL marbles preserve N–S shortening and U-Pb titanite ages (∼1150 Ma; n = 4 document these marbles formed during the Shawinigan (1190–1140 Ma part of the Grenville orogen. From northwest to southeast, the Ottawan (1095–1020 Ma twinning strain is dominantly a layer-parallel shortening fabric oriented N–S (Parry Sound, then becomes parallel to the Grenville thrust direction (NW–SE across the CMB to the Adirondack Highlands where the sub-horizontal shortening strain becomes margin-parallel (SW–NE. Within the regional sample suite there are two areas studied in detail, the Bancroft shear zone (n = 11 and a roadcut on the southeast side of the Adirondack Mountains (Ft. Ann, NY; n = 8. Marbles from the Bancroft shear zone contain calcite grains with 2 sets of twin lamellae (e1 and e2. The better-developed e1 sets (n = 406 record a horizontal fabric oriented NW–SE whereas the younger e2 lamellae (n = 146 preserve a margin-parallel (SW–NE horizontal fabric. Both the e1 and e2 strains record an overprint vertical shortening strain (NEV, perhaps related to extensional orogenic collapse. We also report an Ottawan orogen-aged granoblastic mylonite (1093 Ma, U-Pb zircon; 1102 Ma Ar-Ar biotite in the Keweenaw thrust hanging wall 500 km inboard of the Grenville front and interpret the relations of Grenville

  19. On protolith-, metamorphic overprint, microstructure and rheology of mineral assemblages in orogenic peridotites of the central Scandinavian Caledonides

    Science.gov (United States)

    Gilio, Mattia; Clos, Frediano; Van Roermund, Herman L. M.

    2013-04-01

    The Scandinavian Caledonides (SC) are a deeply eroded Alpine-type orogenic belt formed by closure of the Iapetus ocean and collision between Baltica and Laurentia (500-380 Ma). The SC consists of a stack of Nappe Complexes (from bottom to top called Lower, Middle, Upper and Uppermost Allochthons) thrusted to the east over the Baltic Shield (Brueckner and Van Roermund, 2004; Gee et al., 2008). Fossil lithospheric mantle fragments, called orogenic peridotites, have been found within the (upper part of) middle, upper and uppermost Allochthons, as well as in the reworked basement gneisses (a.o Western Gneiss Complex (WGC)) along the Norwegian west coast. They occur as isolated lenses that contain diverse mineral parageneses and/or bulk rock compositions. Crustal incorporation of orogenic peridotite is classically interpreted to be the result of plate collisional processes related to orogeny (Brueckner and Medaris, 2000). The WGC and parts of the upper part of the Middle Allochthon (a.o. Seve Nappe Complex (SNC) in N Jämtland/S Västerbotten, central Sweden), are well known for the occurrence of high (HP) and ultrahigh pressure (UHP) metamorphic terranes (of Caledonian age). The (U)HPM evidence clearly demonstrates the deep metamorphic origin of these rocks interpreted to be caused by continental subduction and/or collision. Other metamorphic rocks (of Caledonian age) exposed in allochthonous nappes are solely characterised by greenschist-, amphibolite- and/or MP granulite "facies" mineral assemblages that can be interpreted, in the absence of retrogression, to have formed in less deeply subducted (and/or metamorphic) environments. This duality in metamorphic "facies" allows for a discrimination (at least theoretically) between "deep" versus "shallow" rooted nappes (in central parts of the Scandinavian Caledonides). Conform this reasoning, this duality should also be present within the Caledonian mineral assemblages (= metamorphic overprint) of orogenic peridotites (in

  20. Generation of post-collisional normal calc-alkaline and adakitic granites in the Tongbai orogen, central China

    Science.gov (United States)

    Zhang, Wen-Xiang; Zhu, Liu-Qin; Wang, Hao; Wu, Yuan-Bao

    2018-01-01

    Post-collisional granites are generally generated by partial melting of continental crust during orogenic extension. The occurrence of normal calc-alkaline granites following adakitic granites in a collisional orogen is frequently supposed as a sign of tectonic regime transition from compression to extension, which has been debated yet. In this paper, we present a comprehensive study of zircon U-Pb ages, Hf-O isotopes, as well as whole-rock major and trace elements and Sr-Nd isotopes, for Tongbai and Jigongshan post-collisional granitic plutons in the Tongbai orogen. Zircon U-Pb dating yields intrusion ages of ca. 140 and 135 Ma for the Tongbai and Jigongshan plutons, respectively, suggesting they are post-collisional granites. These granites are high-K calc-alkaline series, metaluminous to weakly peraluminous with A/CNK ratios of 0.85-1.08. The Tongbai gneissic granites are normal calc-alkaline granite, having variable SiO2 (61.93-76.74 wt%) and Sr/Y (2.9-38.9) and (La/Yb)N (1.7-30.1) ratios with variably negative Eu anomalies (0.41-0.92). They have relatively high initial Sr isotope ratios of 0.707571 to 0.710317, and low εNd(t) (- 15.74 to - 11.09) and εHf(t) (- 17.6 to - 16.9) values. Their Nd and Hf model ages range from 2.2 to 1.8 Ga and 2.3 to 2.2 Ga. On the contrary, the Jigongshan granites show higher SiO2 (66.56-72.11 wt%) and Sr/Y (30.1-182.0) and (La/Yb)N (27.4-91.4) ratios with insignificant Eu anomalies (0.73-1.00), belonging to adakitic granite. They have Isr = 0.707843-0.708366, εNd(t) = - 19.83 to - 17.59, and εHf(t) = - 26.0 to - 23.5. Their Nd and Hf model ages vary from ca. 2.5 to 2.4 Ga and ca. 2.8 to 2.6 Ga. The Tongbai and Jigongshan granites are characterized by mantle-like zircon δ18O values (5.17-5.46‰). These geochemical features suggest that the Tongbai and Jigongshan granites were derived from partial melting of Paleoproterozoic and Archean continental crust, respectively. Fractional crystallization affected the geochemical

  1. Origin of the Blue Ridge escarpment along the passive margin of Eastern North America

    Science.gov (United States)

    Spotila, J.A.; Bank, G.C.; Reiners, P.W.; Naeser, C.W.; Naeser, N.D.; Henika, B.S.

    2004-01-01

    The Blue Ridge escarpment is a rugged landform situated within the ancient Appalachian orogen. While similar in some respects to the great escarpments along other passive margins, which have evolved by erosion following rifting, its youthful topographic expression has inspired proposals of Cenozoic tectonic rejuvenation in eastern North America. To better understand the post-orogenic and post-rift geomorphic evolution of passive margins, we have examined the origin of this landform using low-temperature thermochronometry and manipulation of topographic indices. Apatite (U-Th)/He and fission-track analyses along transects across the escarpment reveal a younging trend towards the coast. This pattern is consistent with other great escarpments and fits with an interpretation of having evolved by prolonged erosion, without the requirement of tectonic rejuvenation. Measured ages are also comparable specifically to those measured along other great escarpments that are as much as 100 Myr younger. This suggests that erosional mechanisms that maintain rugged escarpments in the early post-rift stages may remain active on ancient passive margins for prolonged periods. The precise erosional evolution of the escarpment is less clear, however, and several end-member models can explain the data. Our preferred model, which fits with all data, involves a significant degree of erosional escarpment retreat in the Cenozoic. Although this suggests that early onset of topographic stability is not required of passive margin evolution, more data are required to better constrain the details of the escarpment's development. ?? 2003 Blackwell Publishing Ltd.

  2. The nature of transition from adakitic to non-adakitic magmatism in a slab window setting: A synthesis from the eastern Pontides, NE Turkey

    Directory of Open Access Journals (Sweden)

    Yener Eyuboglu

    2013-07-01

    Full Text Available The eastern Pontides orogenic belt provides a window into continental arc magmatism in the Alpine–Himalayan belt. The late Mesozoic–Cenozoic geodynamic evolution of this belt remains controversial. Here we focus on the nature of the transition from the adakitic to non-adakitic magmatism in the Kale area of Gumushane region in NE Turkey where this transition is best preserved. The adakitic lithologies comprise porphyries and hyaloclastites. The porphyries are represented by biotite-rich andesites, hornblende-rich andesite and dacite. The hayaloclastites represent the final stage of adakitic activity and they were generated by eruption/intrusion of adakitic andesitic magma into soft carbonate mud. The non-adakitic lithologies include basaltic-andesitic volcanic and associated pyroclastic rocks. Both rock groups are cutting by basaltic dikes representing the final stage of the Cenozoic magmatism in the study area. We report zircon U-Pb ages of 48.71 ± 0.74 Ma for the adakitic rocks, and 44.68 ± 0.84 Ma for the non-adakitic type, suggesting that there is no significant time gap during the transition from adakitic to non-adakitic magmatism. We evaluate the origin, magma processes and tectonic setting of the magmatism in the southern part of the eastern Pontides orogenic belt. Our results have important bearing on the late Mesozoic–Cenozoic geodynamic evolution of the eastern Mediterranean region.

  3. The Eastern Partnership

    DEFF Research Database (Denmark)

    Nielsen, Kristian L.; Vilson, Maili

    2014-01-01

    When the EU launched the Eastern Partnership (EaP) in 2009, it did so with much rhetoric about projecting its soft power into Eastern Europe. Yet today, the EU's soft power project seems to have stalled, with developments in the region being less than favourable. This article argues that the EaP...... essentially replicated the main weaknesses of the European Neighbourhood Policy, by offering too little incentive and support to the partners, rendering both conditionality and soft power ineffective as tools for milieu shaping. In promoting the EaP as a policy of soft power, the EU has once again forgotten...

  4. Timing and nature of Holocene glacier advances at the northwestern end of the Himalayan-Tibetan orogen

    Science.gov (United States)

    Saha, Sourav; Owen, Lewis A.; Orr, Elizabeth N.; Caffee, Marc W.

    2018-05-01

    Holocene glacial chronostratigraphies are developed for four glaciated valleys at the northwestern end of the Himalayan-Tibetan orogen using geomorphic mapping and cosmogenic 10Be surface exposure dating. The study areas include the Hamtah valley in the Lahul Himalaya, and the Karzok, Lato and upper Stok valleys in Zanskar. Five local glacial stages are dated to ∼10.4, ∼6.1-3.3, ∼2.1-0.9, ∼0.7-0.4, and ∼0.3-0.2 ka based on 49 new moraine boulder ages. Large age dispersions are evident for each of the local glacial stages. This is especially the case for ∼6.1-3.3 and ∼2.1-0.9 ka, which is likely a result of prior and/or incomplete exposures in very young moraine boulders. An additional compilation of 187 published 10Be moraine boulder ages help define seven Himalayan Holocene regional glacial stages (HHs) for the northwestern end of the Himalayan-Tibetan orogen. These HHs date to ∼10.9-9.3, ∼8.2-7.4, ∼6.9-4.3, ∼4.5-2.8, ∼2.7-1.8, ∼1.8-0.9, and forced northerly migration of the Intertropical Convergence Zone and enhanced summer monsoon. The timing of the majority of HHs during mid- and late Holocene corresponds well with the North Atlantic cooling that is likely teleconnected via mid-latitude westerlies, particularly during ∼8 ka and after ∼5 ka. These chronostratigraphies suggest that Holocene glaciation in the northwestern part of the Himalayan-Tibetan orogen is largely influenced by long-term orbital forcing amplified by large-scale migration of the Earth's thermal equator and the associated hemispheric oceanic-atmospheric systems.

  5. Characteristics and significance of uranium bearing pan african younger granite in the eastern desert, Egypt

    International Nuclear Information System (INIS)

    Hassan, M.A.; Dabbour, G.A.; Mohammden, T.F.

    1998-01-01

    Surficial uranium mineralization was discovered in four pan african younger granite plutons in the eastern desert of egypt. The present study revealed great similarity between these plutons both in petrography and geochemistry. They are two-feldspar, two-mica peraluminous granites which have been formed by melting of crustal materials and emplaced during the late stage stage of a late proterozoic orogenic cycle. Radiometric and geochemical investigations indicate that these granites are fertile with respect to U and form a potential target for primary uranium deposits. Four models are suggested to explain the source and mechanism of the surficial uranium mineralization in these granites. The most applicable model is the oxidation of U +4 found in minute disseminated uraninite grains and its subsequent mobilization. This is supported by petrographic and autoradiographic studies. The bearings of the present study on further exploration for uranium deposits in granites of the arabian- Nubian shield in general are discussed

  6. Eastern Frequency Response Study

    Energy Technology Data Exchange (ETDEWEB)

    Miller, N.W.; Shao, M.; Pajic, S.; D' Aquila, R.

    2013-05-01

    This study was specifically designed to investigate the frequency response of the Eastern Interconnection that results from large loss-of-generation events of the type targeted by the North American Electric Reliability Corp. Standard BAL-003 Frequency Response and Frequency Bias Setting (NERC 2012a), under possible future system conditions with high levels of wind generation.

  7. Origin and geodynamic significance of the early Mesozoic Weiya LP and HT granulites from the Chinese Eastern Tianshan

    Science.gov (United States)

    Mao, Ling-Juan; He, Zhen-Yu; Zhang, Ze-Ming; Klemd, Reiner; Xiang, Hua; Tian, Zuo-Lin; Zong, Ke-Qing

    2015-12-01

    The Chinese Tianshan in the southwestern part of the Central Asian Orogenic Belt (CAOB) is characterized by a variety of high-grade metamorphic rocks, which provide critical constraints for understanding the geodynamic evolution of the CAOB. In this paper, we present detailed petrological and zircon U-Pb geochronological studies of the Weiya low-pressure and high-temperature (LP-HT) granulites of the Chinese Eastern Tianshan. These granulites were previously considered to be a product of a regional metamorphic orogenic event. Due to different bulk-rock chemistries the Weiya granulites, which occur as lenses within the contact metamorphic aureole of the Weiya granitic ring complex, have a variety of felsic-pelitic and mafic granulites with different textural equilibrium mineral assemblages including garnet-cordierite-sillimanite-bearing granulites, cordierite-sillimanite-bearing granulites, cordierite-orthopyroxene-bearing granulites, and orthopyroxene-clinopyroxene-bearing granulites. Average P-T thermobarometric calculations and conventional geothermobarometry indicates that the Weiya granulites underwent early prograde metamorphism under conditions of 600-650 °C at 3.2-4.2 kbar and peak metamorphism of 750-840 °C at 2.9-6.3 kbar, indicating a rather high geothermal gradient of ca. 60 °C/km. Zircon U-Pb LA-ICP-MS dating revealed metamorphic ages between 244 ± 1 to 237 ± 3 Ma, which are in accordance with the crystallization age of the Weiya granitic ring complex. We suggest that the formation of the Weiya granulites was related to contemporaneous granitic magmatism instead of a regional metamorphic orogenic event. In addition, a Late Devonian metamorphic age of ca. 380 Ma was recorded in zircon mantle domains from two pelitic samples which is consistent with the metamorphic age of the Xingxingxia metamorphic complex in the Chinese Eastern Tianshan. This suggests that the mantle domains of the zircon grains of the Weiya granulites probably formed during the

  8. Active shortening, intermontane basin formation, and geomorphic evolution in an orogenic plateau: Central Puna Plateau, NW Argentina (24°37'S, 67°03'W)

    Science.gov (United States)

    Strecker, Manfred R.; Alonso, Ricardo N.; Bookhagen, Bodo; Freymark, Jessica; Pingel, Heiko

    2017-04-01

    The high-elevation Andean Plateau (Altiplano-Puna; 4km) is a first-order morphotectonic province of the Central Andes and constitutes the world's second largest orogenic plateau. While there are many unifying basin characteristics in this region, including internal drainage, semi-arid to arid climate and associated deposition of evaporites, there are notable differences between the northern and southern parts of the plateau. In contrast to the vast basins of the Altiplano (north) and incipient establishment of fluvial connectivity and sediment transport to the foreland, the Puna (south) comprises numerous smaller basins, bordered by reverse-fault bounded ranges up to 6 km high. The plateau is internally drained and fluvial connectivity with the foreland does not exist leading to thick sedimentary basin fills that comprise continental evaporites, volcanic and clastic deposits, typically between 3 and 5 km thick. However, repeated impacts of climate change and superposed tectonic activity in the southern plateau have resulted in further basin differentiation, abandonment or re-arrangement of fluvial networks and impacts on sediment transport. Here we report evidence for sustained contractional tectonic activity in the Pocitos Basin in the southern plateau. On the western margin of the basin fanning of dipping strata and regraded, steeply inclined gravel-covered pediment surfaces and wind gaps associated with gravel derived from distant sources in the west document late Tertiary to Pleistocene growth of an approximately N-S oriented and N plunging anticline. The growth of the eastern limb of this anticline has caused the isolation of a formerly more extensive basin. In addition, Late Pleistocene and Holocene lake shorelines and lacustrine deposits are tilted eastward along the same structure and InSAR measurements of deformed lake terraces document that the fold is growing. Despite widely reported extensional faulting in the southern Puna, we conclude (1) that the

  9. Geophysical modeling across Inner and Outer Western Carpathians in Eastern Slovakia

    Science.gov (United States)

    Vozar, J.; Bezak, V.; Bielik, M.; Majcin, D.; Vajda, P.; Bilcik, D.

    2017-12-01

    We present a multidimensional geophysical modelling of Central and Eastern Slovakia in the area of contact zone between the Inner and Outer Western Carpathians, and the East Slovakian Basin. Our crustal and lithospheric studies are based on geophysical data collected during CELEBRATION 2000 project and project THERMES. The new magnetotelluric (MT) multidimensional modelling is combined with seismic 2D wide angle refraction profiles and gravimetric modelling. Together with thermal information gathered from the area we constructed new integrated geophysical models of structures included in the evolution of the Carpathian orogen. Preliminary results of MT modelling in Eastern Slovakia suggest more electrically conductive structures in the middle and lower crustal depths in comparison with Central Slovakia, where we observed structures dominated by resistive complexes overlaid by conductive sedimentary formations. The higher conductivities below the East Slovakian Basin restrict penetration depth of the geoelectrical images. The electrically conductive structures are connected with tectono-thermal development in Neogene and presence of volcanic activity. Another significant conductive anomaly is imaged along the contact zone between Inner and Outer Western Carpathians in depths of about 10 - 20km, which is known as the Carpathian Conductivity Anomaly (CCA). In order to improve the depth resolution of MT models we decided to combine geoelectrical images with density and velocity models of the area. We used integrated petrological and geophysical modeling code to obtain thermally consistent lithospheric scale models of the area. A possible preliminary geological interpretation of the northern segment of investigated area suggests a resistive European platform below conductive flysch sediments. The boundary between Inner and Outer Carpthians represented by the Klippen Belt on the surface is changed to the CCA in higher depths. In the direction to the south there are

  10. Tectonic evolution of a part of the Tethyside orogenic collage: The Kargi Massif, northern Turkey

    Science.gov (United States)

    Tüysüz, Okan

    1990-02-01

    The central part of the Rhodope-Pontide fragment, one of the major tectonic units in Turkey, provides critical data for evaluating the Cimmeride and Alpide evolution of the Mediterranean Tethysides. Tectonic events that affected the central part of the Rhodope-Pontide fragment since the end of the Paleozoic, generated east-west trending belts with the event of every episode redeforming and partly obliterating the structures of previous episodes. This evolution may be conveniently described in terms of three major episodes: (1) Two different realms of pre-Dogger oceanic rocks are present in the area. The northern realm coincided with main branch of Paleo-Tethys that was being actively destroyed by south dipping subduction. The southern realm, the Karakaya ocean, a back arc basin related to this subduction, began opening by rifting of a retroarc carbonate platform during the Permo-Triassic. To the west a continental domain with sparse magmatism seperated the two oceanic areas. Toward the east the two oceans become united by the wedging out of the continental domain. These two pre-Dogger oceans closed during the Lias, and their remnants were emplaced between the southern margin of Laurasia and the fragments of the Cimmerian continent. (2) The second episode partly overlapped the first with rifting south of the Cimmerian continent fragment during the Lias. This rifting was followed by a transgression which covered the ruins of the Cimmeride orogenic belt by the Malm. This rifting concurrently led to the development of the northern branch of the Neo-Tethys and a south facing Atlantic-type continental margin. A southerly thickening sedimentary prism developed on this margin during the Lias to early Cretaceous interval. (3) The floor of the northern branch of Neo-Tethys began to be consumed along the north dipping subduction zone beneath the previosly constructed continental margin. This convergent margin generated a magmatic arc to the north and to the south a subduction

  11. Two modes of orogenic collapse of the Pamir plateau recorded by titanite

    Science.gov (United States)

    Stearns, M. A.; Hacker, B. R.; Ratschbacher, L.; Rutte, D.; Kylander-Clark, A. R.

    2013-12-01

    Processes that operate in the mid- to lower crust during and following continent-continent collision are important for understanding how orogenic plateaux transition from thickening to collapse. In the central and southern Pamir, mid- to lower crustal rocks crop out in two belts of extensional domes. The central Pamir domes were exhumed by symmetrical N-S extension. In contrast, the southern Pamir domes were exhumed by asymmetrical top to the south (NNW-SSE) extension via a rolling-hinge detachment. To investigate the high-temperature exhumation history, titanites were dated using LASS (laser ablation split stream-ICP-MS). A multi-collector ICP was used to collect U-Pb isotopic ratios and a single collector ICP-MS was used to measure trace-element abundances. The data indicate that the central Pamir domes began exhumation synchronously at ~17 Ma. Titanite from the southern Pamir record two periods of protracted (re)crystallization: older metamorphic dates ranging from ~35-18 Ma and younger igneous and metamorphic dates from ~15-7 Ma. Samples with single populations of titanite dates are present throughout both groups. Samples with more-complex date populations typically have distinct trace-element (e.g., Sr, Y, Zr, and Nb) groups that can be used to distinguish different date populations (e.g., older dates may have higher Zr and younger dates lower Zr). The distinct early exhumation histories of the north and south Pamir require either a diachronous single process or two semi-independent processes. The N to S sequence of exhumation, ranges of dates, and overall extension directions may be related to two important plate-tectonic events inferred from seismic data: 1) breakoff of the northward subducting Indian slab around ~20 Ma, and 2) southward subduction and northwestward rollback of the Asian lithosphere between ~15-10 Ma based on geodetic convergence rates and Benioff zone length. We interpret these two lithospheric-detachment events to have driven the

  12. Geochemical modeling of orogenic gold deposit using PCANN hybrid method in the Alut, Kurdistan province, Iran

    Science.gov (United States)

    Mohammadzadeh, Mohammadjafar; Nasseri, Aynur

    2018-03-01

    In this paper stream sediments based geochemical exploration program with the aim of delineating potentially promising areas by a comprehensive stepwise optimization approach from univariate statistics, PCA, ANN, and fusion method PCANN were under taken for an orogenic gold deposit located in the Alut, Kurdistan province, NW of Iran. At first the data were preprocessed and then PCA were applied to determine the maximum variability directions of elements in the area. Subsequently the artificial neural network (ANN) was used for quick estimation of elemental concentration, as well as discriminating anomalous populations and intelligent determination of internal structure among the data. However, both the methods revealed constraints for modeling. To overcome the deficiency and shortcoming of each individual method a new methodology is presented by integration of both "PCA & ANN" referred as PCANN method. For integrating purpose, the detected PCs pertinent to ore mineralization selected and intruded to neural network structure, as a result different MLPs with various algorithms and structures were produced. The resulting PCANN maps suggest that the gold mineralization and its pathfinder elements (Au, Mo, W, Bi, Sb, Cu, Pb, Ag & As) are associated with metamorphic host rocks intruded by granite bodies in the Alut area. In addition, more concealed and distinct Au anomalies with higher intensity were detected, confirming the privileges of the method in evaluating susceptibility of the area in delineating new hidden potential zones. The proposed method demonstrates simpler network architecture, easy computational implementation, faster training speed, as well as no need to consider any primary assumption about the behavior of data and their probability distribution type, with more satisfactory predicting performance for generating gold potential map of the area. Comparing the results of three methods (PCA, ANN and PCANN), representing the higher efficiency and more

  13. Fluid-driven normal faulting earthquake sequences in the Taiwan orogen

    Science.gov (United States)

    Wang, Ling-hua; Rau, Ruey-Juin; Lee, En-Jui

    2017-04-01

    Seismicity in the Central Range of Taiwan shows normal faulting mechanisms with T-axes directing NE, subparallel to the strike of the mountain belt. We analyze earthquake sequences occurred within 2012-2015 in the Nanshan area of northern Taiwan which indicating swarm behavior and migration characteristics. We select events larger than 2.0 from Central Weather Bureau catalog and use the double-difference relocation program hypoDD with waveform cross-correlation in the Nanshan area. We obtained a final count of 1406 (95%) relocated earthquakes. Moreover, we compute focal mechanisms using USGS program HASH by P-wave first motion and S/P ratio picking and 114 fault plane solutions with M 3.0-5.87 were determined. To test for fluid diffusion, we model seismicity using the equation of Shapiro et al. (1997) by fitting earthquake diffusing rate D during the migration period. According to the relocation result, seismicity in the Taiwan orogenic belt present mostly N25E orientation parallel to the mountain belt with the same direction of the tension axis. In addition, another seismic fracture depicted by seismicity rotated 35 degree counterclockwise to the NW direction. Nearly all focal mechanisms are normal fault type. In the Nanshan area, events show N10W distribution with a focal depth range from 5-12 km and illustrate fault plane dipping about 45-60 degree to SW. Three months before the M 5.87 mainshock which occurred in March, 2013, there were some foreshock events occurred in the shallow part of the fault plane of the mainshock. Half a year following the mainshock, earthquakes migrated to the north and south, respectively with processes matched the diffusion model at a rate of 0.2-0.6 m2/s. This migration pattern and diffusion rate offer an evidence of 'fluid-driven' process in the fault zone. We also find the upward migration of earthquakes in the mainshock source region. These phenomena are likely caused by the opening of the permeable conduit due to the M 5

  14. Relationship between deep structure and oil-gas in the eastern Tarim Basin

    Science.gov (United States)

    Yu, Changqing; Qu, Chen; Han, Jianguang

    2017-04-01

    The Tarim Basin is a large composite superimposed basin which developed in the Presinian continental basement. It is an important area for oil and gas replacement in China. In the eastern part of Tarim Basin, the exploration and research degree is very low and less system, especially in the study of tectonic evolution and physical property change. Basing on the study of geophysics, drilling and regional geological data in this area, analysis of comprehensive geophysical, geological and geophysical analysis comparison are lunched by new methods and new technology of geophysical exploration. Fault, tectonic evolution and change of deep character in the eastern Tarim Basin are analyzed in system. Through in-depth study and understanding of the deep structure and physical changes of the eastern region, we obtain the fault characteristics in the study area and the deep structure and physical change maps to better guide the oil and gas exploration in this area. The east area is located in the eastern Tarim Basin, west from the Garr Man depression, Well Kunan 1 - Well Gucheng 4 line to the East, north to Kuruketage uplift group near Qunke 1 wells, south to Cherchen fault zone, east to Lop Nor depression, an area of about 9 * 104 square kilometres, Including the East of Garr Man sag, Yingjisu depression, Kongquehe slope, Tadong low uplift and the Lop Nor uplift, five two grade tectonic units. The east area of Tarim is belonging to Tarim plate. It changes with the evolution of the Tarim plate. The Tarim plate is closely related to the collision between the Yining - the Junggar plate, the Siberia plate and the southern Qiangtang - the central Kunlun plate. Therefore, it creates a complex tectonic pattern in the eastern Tarim basin. Earth electromagnetic, gravity, deep seismic and other geophysical data are processed by a new generation of geophysical information theory and method, including multi-scale inversion of potential field inversion (Hou and Yang, 2011), 3D

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

    Science.gov (United States)

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

    2013-12-01

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

  16. Eastern Europe's market role

    International Nuclear Information System (INIS)

    Schreiber, K.F.

    1991-01-01

    Until the late 1980s, trade in nuclear fuel between market economy countries and those with planned economies was limited. The exception to this was in the enrichment market across Western Europe during the 1970s. Most of the nuclear generating plants in the Soviet Union and Eastern Europe are light water reactors needing enriched uranium. Under the fuel supply agreements with Eastern Europe, the Soviet Union has provided all of the regions' enrichment services, and therefore it has developed the only enrichment facilities. Techsnabexport (TENEX), the USSR foreign trade organization for the nuclear fuel cycle, first appeared in the early 1970s. It was as an alternative supplier to the US government, which had a monopoly in the West regarding enrichment. In 1986 the USSR entered and soon dominated the spot market for enrichment. Political changes in Eastern Europe at the end of 1989 and throughout 1990 opened the nuclear fuel market even wider. In 1990 the USSR began allowing exports of concentrates, as well as enriched product, and a free flow of trade to the Western market is now developing for both enrichment and uranium. (author)

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

    Science.gov (United States)

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

    2014-07-01

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

  18. Natural and mining-related mercury in an orogenic greywacke terrane, South Island, New Zealand

    International Nuclear Information System (INIS)

    Holley, E.A.; Craw, D.; Kim, J.P.

    2010-01-01

    Mercury (Hg) is naturally present in warm springs and mesothermal (orogenic) gold-bearing quartz vein systems in the South Island of New Zealand. Mercury amalgamation was used historically in ore processing at gold (Au) mines, resulting in composite natural and anthropogenic Hg signatures at these sites. This study compares natural Hg enrichment of the Au vein systems, residual anthropogenic Hg added for amalgamation, and enrichment of naturally present Hg during ore processing. Mercury concentration data are presented for solids and water at historic mine sites, the modern Macraes mine, fault-related warm springs, and zones of naturally occurring cinnabar and Hg-bearing Au. Arsenic (As) concentrations are also presented, as As is the most environmentally significant element in this tectonic setting. Tailings and processing residues at historic mine sites (Blackwater mine, West Coast; Golden Point and Golden Bar, Hyde-Macraes shear zone) contain up to 1000 mg/kg Hg, and in adjacent surface waters Hg is at or slightly above background from 0.6 to 0.8 ng/L. Relative to South Island Hg, As is more environmentally significant: solid wastes at some historic mine and mineral processing sites contain up to 30.5 wt% As due to enrichment of natural As in mineralised rocks. Shallow groundwater and processing waters at the modern Macraes mine are up to 0.01 mg/L Hg due to natural Hg in mineralised rocks, and no significant Hg elevation is evident in nearby surface waters, which are 3 to 10 4 times higher than primary ore, and Hg is disproportionally increased relative to As, indicating that much of the Hg was added during the amalgamation process. Natural cinnabar deposition from warm springs results in localised, strongly elevated Hg, equal to or less than the Hg contents in historic mine processing residues. Warm spring precipitates are up to 111 mg/kg Hg and waters are 0.3 μg/L Hg, comparable to data reported for active North Island geothermal (epithermal-style) systems

  19. Geological and geochemical implications of the genesis of the Qolqoleh orogenic gold mineralisation, Kurdistan Province (Iran)

    Science.gov (United States)

    Taghipour, Batoul; Ahmadnejad, Farhad

    2015-03-01

    The Qolqoleh gold deposit is located in the northwestern part of the Sanandaj-Sirjan Zone (SSZ), within the NE-SW trending Qolqoleh shear zone. Oligocene granitoids, Cretaceous meta-limestones, schists and metavolcanics are the main lithological units. Chondrite-normalised REE patterns of the ore-hosting metavolcanics indicate REE enrichment relative to hanging wall (chlorite-sericite schist) and footwall (meta-limestone) rocks. The pattern also reflects an enrichment in LREE relative to HREE. It seems that the LREE enrichment is related to the circulation of SO42- and CO2-bearing fluids and regional metamorphism in the Qolqoleh shear zone. Both positive and negative Eu anomalies are observed in shear-zone metavolcanics. These anomalies are related to the degree of plagioclase alteration during gold mineralisation and hydrothermal alteration. In progressing from a metavolcanic protomylonite to an ultramylonite, significant changes occurred in the major/trace element and REE concentration. Utilising an Al-Fe-Ti isocon for the ore-hosting metavolcanics shows that Sc, Y, K, U, P, and M-HREE (except Eu) are relatively unchanged; S, As, Ag, Au, Ca, LOI, Rb and LREE are enriched, and Sr, Ba, Eu, Cr, Co and Ni decrease with an increasing degree of deformation. Based on geochemical features and comparison with other well-known shear zones in the world, the study area is best classified as an Isovolume-Gain (IVG) type shear zone and orogenic type gold mineralisation. Based on the number of phases observed at room temperature and their microthermometric behaviour, three fluid inclusion types have been recognised in quartz-sulphide and quartz-calcite veins: Type I monophase aqueous inclusions, Type II two-phase liquid-vapour (L-V) inclusions which are subdivided into two groups based on the homogenisation temperature (Th): a) L-V inclusions with Th from 205 to 255°C and melting temperature of last ice (Tm) from -3 to -9°C. b) L-V inclusions with higher Th from 335 to 385

  20. Topographic evolution of a continental indenter: The eastern Southern Alps

    Science.gov (United States)

    Robl, Jörg; Heberer, Bianca; Prasicek, Günther; Neubauer, Franz; Hergarten, Stefan

    2017-04-01

    The topographic evolution of the eastern Southern Alps (ESA) is controlled by the Late Oligocene - Early Miocene indentation of the Adriatic microplate into an overthickened orogenic wedge emplaced on top of the European plate. Rivers follow topographic gradients that evolve during continental collision and in turn incise into bedrock counteracting the formation of topography. In principle, erosional surface processes tend to establish a topographic steady state so that an interpretation of topographic metrics in terms of the latest tectonic history should be straightforward. However, a series of complications impede deciphering the topographic record of the ESA. The Pleistocene glaciations locally excavated alpine valleys and perturbed fluvial drainages. The Late Miocene desiccation of the Mediterranean Sea and the uplift of the northern Molasse Basin led to significant base level changes in the far field of the ESA and the Eastern Alps (EA), respectively. Among this multitude of mechanisms, the processes that dominate the current topographic evolution of the ESA and the ESA-EA drainage divide have not been identified and a number of questions regarding the interaction of crustal deformation, erosion and climate in shaping the present-day topography remain. We demonstrate the expected topographic effects of each mechanism in a 1-dimensional model and compare them with observed channel metrics. Modern uplift rates are largely consistent with long-term exhumation in the ESA and with variations in the normalized steepness index (ksn) indicating a stable uplift and erosion pattern since Miocene times. We find that ksn increases with uplift rate and declines from the indenter tip in the northwest to the foreland basin in the southeast. The number and magnitude of knickpoints and the distortion in longitudinal channel profiles similarly decrease towards the east. Most knickpoints probably evolved during Pleistocene glaciation cycles, but may represent the incrementally

  1. Multiple fluid sources/pathways and severe thermal gradients during formation of the Jílové orogenic gold deposit, Bohemian Massif, Czech Republic

    Czech Academy of Sciences Publication Activity Database

    Zachariáš, J.; Žák, Karel; Pudilová, M.; Snee, L. W.

    2013-01-01

    Roč. 54, October (2013), s. 81-109 ISSN 0169-1368 Institutional research plan: CEZ:AV0Z30130516 Institutional support: RVO:67985831 Keywords : Orogenic gold deposits * Carbon isotopes * Oxygen isotopes * Bismuth * Age * Bohemian Massif Subject RIV: DB - Geology ; Mineralogy Impact factor: 3.383, year: 2013

  2. Bicarbonate-rich fluid inclusions and hydrogen diffusion in quartz from the Libčice orogenic gold deposit, Bohemian Massif

    Czech Academy of Sciences Publication Activity Database

    Hrstka, Tomáš; Dubessy, J.; Zachariáš, J.

    2011-01-01

    Roč. 281, 3-4 (2011), s. 317-332 ISSN 0009-2541 Institutional research plan: CEZ:AV0Z30130516 Keywords : bicarbonate * fluid inclusions * hydrogen diffusion * orogenic gold deposits * raman spectroscopy Subject RIV: DB - Geology ; Mineralogy Impact factor: 3.518, year: 2011

  3. Palaeozoic polymetamorphism in the North Qinling orogenic belt, Central China: Insights from petrology and in situ titanite and zircon U-Pb geochronology

    NARCIS (Netherlands)

    Li, Y.; Zhou, H.; Li, Q.L.; Xiang, H.; Zhong, Z.Q.; Brouwer, F.M.

    2014-01-01

    The Qinling orogenic belt experienced multiple phases of orogenesis during the Palaeozoic. Unraveling the timing and P- T conditions of these events is the key to understanding the convergence processes between the South China and the North China Blocks. The Songshugou Complex, located in the

  4. Nature and timing of the final collision of Central Asian Orogenic Belt: insights from basic intrusion in the Xilin Gol Complex, Inner Mongolia, China

    NARCIS (Netherlands)

    Li, Y.; Zhou, H.; Brouwer, F.M.; Xiao, W.; Wijbrans, J.R.; Zhao, J.; Zhong, Z.; Liu, H.

    2014-01-01

    The Solonker suture zone of the Central Asian Orogenic Belt (CAOB) records the final closure of the Paleo-Asian Ocean. The nature and timing of final collision along the Solonker suture has long been controversial, partly because of an incomplete record of isotopic ages and differing interpretations

  5. Climate instability and tipping points in the Late Devonian: Detection of the Hangenberg Event in an open oceanic island arc in the Central Asian Orogenic Belt

    Czech Academy of Sciences Publication Activity Database

    Carmichael, A.; Waters, J. A.; Batchelor, C. J.; Coleman, D. M.; Suttner, T. J.; Kido, E.; Moore, L. M.; Chadimová, Leona

    2016-01-01

    Roč. 32, 1 April (2016), s. 213-231 ISSN 1342-937X Institutional support: RVO:67985831 Keywords : Central Asian Orogenic Belt * chemostratigraphy * Devonian-Carboniferous * Hangenberg Event * West Junggar Subject RIV: DB - Geology ; Mineralogy Impact factor: 6.959, year: 2016

  6. 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

    NARCIS (Netherlands)

    Wang, H.; Wu, Y.B.; Qin, Z.W.; Zhu, L.Q.; Liu, Q.; Liu, X.C.; Gao, J.; Wijbrans, J.R.; Gong, H.J.; Yuan, H.L.

    2013-01-01

    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

  7. Geodynamics of oceanic plateau and plume head accretion and their role in Phanerozoic orogenic systems of China

    Directory of Open Access Journals (Sweden)

    Peter G. Betts

    2015-01-01

    Full Text Available We present three 3D numerical models of deep subduction where buoyant material from an oceanic plateau and a plume interact with the overriding plate to assess the influence on subduction dynamics, trench geometry, and mechanisms for plateau accretion and continental growth. Transient instabilities of the convergent margin are produced, resulting in: contorted trench geometry; trench migration parallel with the plate margin; folding of the subducting slab and orocline development at the convergent margin; and transfer of the plateau to the overriding plate. The presence of plume material beneath the oceanic plateau causes flat subduction above the plume, resulting in a “bowed” shaped subducting slab. In plateau-only models, plateau accretion at the edge of the overriding plate results in trench migration around the edge of the plateau before subduction is re-established directly behind the trailing edge of the plateau. The plateau shortens and some plateau material subducts. The presence of buoyant plume material beneath the oceanic plateau has a profound influence on the behaviour of the convergent margin. In the plateau + plume model, plateau accretion causes rapid trench advance. Plate convergence is accommodated by shearing at the base of the plateau and shortening in the overriding plate. The trench migrates around the edge of the plateau and subduction is re-established well behind the trailing edge of the plateau, effectively embedding the plateau into the overriding plate. A slab window forms beneath the accreted plateau and plume material is transferred from the subducting plate to the overriding plate through the window. In all of the models, the subduction zone maintains a relatively stable configuration away from the buoyancy anomalies within the downgoing plate. The models provide a dynamic context for plateau and plume accretion in Phanerozoic accretionary orogenic systems such as the East China Orogen and the Central Asian

  8. Paleotsunamis in Eastern Taiwan

    Science.gov (United States)

    Yen, Jiun-Yee; Yu, Neng-Ti; Hirakawa, Kazuomi; Chyi, Shyh-Jeng; Huang, Shao-Yi

    2017-04-01

    Although Taiwan is located in the active collision zone between Eurasian and the Philippine Sea plate with very high seismicity in and surrounding the island, and supposedly highly susceptible to tsunami hazard. However, there is no record of tsunami hazard in the past one hundred years, and only very few historical records show some possible extreme event occurred. Therefore study of tsunami was scarce in Taiwan. Although historical records do show possible tsunami events, the records were too sparse and incomplete to confidently reconstruct the paleotsunami events. In the past few years, numerical simulations based on possible tsunami-genic zones near Taiwan show that the island could be affected by the correctly directed tsunami. Nevertheless, there is no detail, scientific research of paleotsunami records yet in Taiwan. Our field survey in eastern Taiwan (facing the western Pacific Ocean) along the coast uncovered several outcrops contain gravels embedded in well-developed soil layers. The rounded meta-sandstone gravels are clearly beach-origin and were brought to their current location upon extreme wave events, which is composed of either volcanic-clastic deposits from nearby hills or organic soil layers formed locally. Our investigation indicates that there are at least 3 events in the northern half of eastern Taiwan and at least 2 events in southern part of eastern Taiwan. Although these outcrops are next to the shoreline and Taiwan is susceptible from typhoons, these gravels could be farther away from the beach at the time of their deposition due to current high retreat rate of the sea cliff. Further investigations are needed to delineate possible sources of tsunamis that caused the deposits.

  9. West-directed thrusting south of the eastern Himalayan syntaxis indicates clockwise crustal flow at the indenter corner during the India-Asia collision

    Science.gov (United States)

    Haproff, Peter J.; Zuza, Andrew V.; Yin, An

    2018-01-01

    Whether continental deformation is accommodated by microplate motion or continuum flow is a central issue regarding the nature of Cenozoic deformation surrounding the eastern Himalayan syntaxis. The microplate model predicts southeastward extrusion of rigid blocks along widely-spaced strike-slip faults, whereas the crustal-flow model requires clockwise crustal rotation along closely-spaced, semi-circular right-slip faults around the eastern Himalayan syntaxis. Although global positioning system (GPS) data support the crustal-flow model, the surface velocity field provides no information on the evolution of the India-Asia orogenic system at million-year scales. In this work, we present the results of systematic geologic mapping across the northernmost segment of the Indo-Burma Ranges, located directly southeast of the eastern Himalayan syntaxis. Early research inferred the area to have experienced either right-slip faulting accommodating northward indentation of India or thrusting due to the eastward continuation of the Himalayan orogen in the Cenozoic. Our mapping supports the presence of dip-slip thrust faults, rather than strike-slip faults. Specifically, the northern Indo-Burma Ranges exposes south- to west-directed ductile thrust shear zones in the hinterland and brittle fault zones in the foreland. The trends of ductile stretching lineations within thrust shear zones and thrust sheets rotate clockwise from the northeast direction in the northern part of the study area to the east direction in the southern part of the study area. This clockwise deflection pattern of lineations around the eastern Himalayan syntaxis mirrors the clockwise crustal-rotation pattern as suggested by the crustal-flow model and contemporary GPS velocity field. However, our finding is inconsistent with discrete strike-slip deformation in the area and the microplate model.

  10. Dating emplacement and evolution of the orogenic magmatism in the internal Western Alps

    DEFF Research Database (Denmark)

    Berger, Alfons; Thomsen, Tonny B.; Ovtcharova, Maria

    2012-01-01

    The Canavese Line in the Western Alps represents the position in the Alpine chain, where alkaline and calc-alkaline magmatism occur in close spatial and temporal association. In addition to available data on the alkaline Valle del Cervo Pluton, we present petrological and geochemical data...... on the Miagliano tonalite. The latter is of special interest, because it is located in the south-eastern side of the Canavese Line, in contrast to most Periadriatic Plutons. The dioritic to tonalitic rocks of the Miagliano Pluton represent an intermediate stage of a calc-alkaline differentiation, demonstrated...... by relics of two different pyroxenes as well as the texture of allanite. Hornblende barometry indicates pressures of similar to 0.46 GPa consistent with the presence of magmatic epidote. Field relationships between the two Plutons, the volcanic and volcaniclastic rocks of the Biella Volcanic Suite...

  11. An overview of the regional, geological and structural setting of the uraniferous granites in the Damara Orogen, Namibia

    International Nuclear Information System (INIS)

    Brynard, H.J.; Andreoli, M.A.G.

    1988-01-01

    Uranium-bearing granites, comprising both potentially economic deposits and source rocks for uranium deposits in duricrustal and sedimentary sequences, occur in the Damara Orogen of Namibia. The economically important uraniferous granites are mainly confined to the Central Zone, delimited by the Omaruru and Okahandja lineaments, which demarcate the boundary between two markedly different magnetic and hence depositional and/or tectonic regimes. Various models to explain the origin and evolution of the uranium-enriched granites have been proposed to date, none of which are found to explain the observed petrological phenomena adequately. The paper critically reviews the existing literature on the origin of the granites and some criteria for exploration are discussed. (author). 24 refs, 6 figs, 2 tabs

  12. Constraining a Precambrian Wilson Cycle lifespan: An example from the ca. 1.8 Ga Nagssugtoqidian Orogen, Southeastern Greenland

    Science.gov (United States)

    Nicoli, Gautier; Thomassot, Emilie; Schannor, Mathias; Vezinet, Adrien; Jovovic, Ivan

    2018-01-01

    In the Phanerozoic, plate tectonic processes involve the fragmentation of the continental mass, extension and spreading of oceanic domains, subduction of the oceanic lithosphere and lateral shortening that culminate with continental collision (i.e. Wilson cycle). Unlike modern orogenic settings and despite the collection of evidence in the geological record, we lack information to identify such a sequence of events in the Precambrian. This is why it is particularly difficult to track plate tectonics back to 2.0 Ga and beyond. In this study, we aim to show that a multidisciplinary approach on a selected set of samples from a given orogeny can be used to place constraints on crustal evolution within a P-T-t-d-X space. We combine field geology, petrological observations, thermodynamic modelling (Theriak-Domino) and radiogenic (U-Pb, Lu-Hf) and stable isotopes (δ18O) to quantify the duration of the different steps of a Wilson cycle. For the purpose of this study, we focus on the Proterozoic Nagssugtoqidian Orogenic Belt (NOB), in the Tasiilaq area, South-East Greenland. Our study reveals that the Nagssugtoqidian Orogen was the result of a complete three stages juvenile crust production (Xjuv) - recycling/reworking sequence: (I) During the 2.60-2.95 Ga period, the Neoarchean Skjoldungen Orogen remobilised basement lithologies formed at TDM 2.91 Ga with progressive increase of the discharge of reworked material (Xjuv from 75% to 50%; δ18O: 4-8.5‰). (II) After a period of crustal stabilization (2.35-2.60 Ga), discrete juvenile material inputs (δ18O: 5-6‰) at TDM 2.35 Ga argue for the formation of an oceanic lithosphere and seafloor spreading over a period of 0.2 Ga (Xjuv from < 25% to 70%). Lateral shortening is set to have started at ca. 2.05 Ga with the accretion of volcanic/magmatic arcs (i.e. Ammassalik Intrusive Complex) and by subduction of small oceanic domains (M1: 520 ± 60 °C at 6.6 ± 1.4 kbar). (III) Continental collision between the North Atlantic

  13. Earthquake hazard assessment in the Zagros Orogenic Belt of Iran using a fuzzy rule-based model

    Science.gov (United States)

    Farahi Ghasre Aboonasr, Sedigheh; Zamani, Ahmad; Razavipour, Fatemeh; Boostani, Reza

    2017-08-01

    Producing accurate seismic hazard map and predicting hazardous areas is necessary for risk mitigation strategies. In this paper, a fuzzy logic inference system is utilized to estimate the earthquake potential and seismic zoning of Zagros Orogenic Belt. In addition to the interpretability, fuzzy predictors can capture both nonlinearity and chaotic behavior of data, where the number of data is limited. In this paper, earthquake pattern in the Zagros has been assessed for the intervals of 10 and 50 years using fuzzy rule-based model. The Molchan statistical procedure has been used to show that our forecasting model is reliable. The earthquake hazard maps for this area reveal some remarkable features that cannot be observed on the conventional maps. Regarding our achievements, some areas in the southern (Bandar Abbas), southwestern (Bandar Kangan) and western (Kermanshah) parts of Iran display high earthquake severity even though they are geographically far apart.

  14. Expansion of the granitic post-orogenic magmatism in the formation of Serrinha (Northeastern Bahia, B R), Sao Francisco craton

    International Nuclear Information System (INIS)

    Rios, Debora Correia; Conceicao, Herbet; Rosa, Maria de Lourdes da Silva; Marinho, Moacyr Moura; Davis, Donaldo Wayne

    2005-01-01

    The Pedra Vermelha Granitic Massif, located at the North area of Serrinha Nucleus, presents a circular shape, being intrusive at the Archaean geoscience-magmatic basement rocks and the Paleoproterozoic volcano sedimentary sequences. The single zircon U-Pb dating yield a crystallization age of 2080 ± 8 Ma. The geological, petrographic al and litogeochemical characteristics of the studied rocks are similar to those of the Morro do Lopes granitic magmatism (2076 ± 6 a 2071 ± 6 Ma), which is located at the South area of this nucleus. These allow us to infer that those post-orogenic alkaline bodies are widespread throughout the Serrinha Nucleus and constitute its last Paleoproterozoic magmatic expression. (author)

  15. Energy in Eastern Europe

    International Nuclear Information System (INIS)

    Bouma, J.W.J.

    1993-01-01

    The present energy market in Central and Eastern Europe differs strongly from the energy situation in open market economies. Compared to the European Communities, the energy market in Central and eastern Europe is characterized by its high energy intensity, high quantity of imported oil and gas from a one country (the ex-Soviet Union), the dominant role of solid fossil fuels in some countries, and environmental pollution. Expected future developments are the reduction of the energy intensity and the total energy consumption, the reduction of the industrial energy consumption, the reduction of the solid fossil fuels as well as the geographic distribution of energy import. The restructuring of the energy industry has been started by introducing a market orientated policy including privatisation and the promotion of the free play of price-making forces, accompanied by relatively small-scale investments. Recent data indicate a decrease of energy consumption due to the economic decline and the shut-down of companies in the heavy industries. (A.S.) 4 figs. 5 tabs

  16. Pipelines to eastern Canada

    International Nuclear Information System (INIS)

    Otsason, J.

    1998-01-01

    This presentation focused on four main topics: (1) the existing path of pipelines to eastern Canada, (2) the Chicago hub, (3) transport alternatives, and (4) the Vector Pipeline' expansion plans. In the eastern Canadian market, TransCanada Pipelines dominates 96 per cent of the market share and is effectively immune to expansion costs. Issues regarding the attractiveness of the Chicago hub were addressed. One attractive feature is that the Chicago hub has access to multiple supply basins including western Canada, the Gulf Coast, the mid-continent, and the Rockies. Regarding Vector Pipelines' future plans, the company proposes to construct 343 miles of pipeline from Joliet, Illinois to Dawn, Ontario. Project description included discussion of some of the perceived advantages of this route, namely, extensive storage in Michigan and south-western Ontario, the fact that the proposed pipeline traverses major markets which would mitigate excess capacity concerns, arbitrage opportunities, cost effective expansion capability reducing tolls, and likely lower landed costs in Ontario. Project schedule, costs, rates and tariffs are also discussed. tabs., figs

  17. The Sanfengshan copper deposit and early Carboniferous volcanogenic massive sulfide mineralization in the Beishan orogenic belt, Northwestern China

    Science.gov (United States)

    Wang, Jialin; Gu, Xuexiang; Zhang, Yongmei; Zhou, Chao; He, Ge; Liu, Ruiping

    2018-03-01

    The Sanfengshan copper deposit, located in the Beishan orogenic belt, Northwestern China, is hosted in the lower member of the Hongliuyuan Formation, an early Carboniferous metavolcanic-sedimentary sequence. Mineralization occurs as stratiform, stratiform-like and lenticular orebodies, and comprises of laminated, brecciated, banded, massive, and disseminated ores. The mineralogy is dominated by pyrite, chalcopyrite and sphalerite. Fe-Mn chert is widely distributed and generally occurs as massive, laminated, bands or lenses, which are consistent with the orebody. Alteration at Sanfengshan displays a clear concentric zoning pattern and the footwall alteration is more intense and somewhat thicker than the hanging-wall alteration. Systematic geochemical investigation on the volcanic rocks in this area shows that the basalts of the Hongliuyuan Formation (HLY) are predominantly tholeiites with nearly flat rare earth element (REE) pattern, insignificant negative anomalies of high field strength elements (HFSEs), and low Ti/V and Th/Nb ratios. They were most likely derived from partial melting of depleted asthenospheric mantle and formed in a fore-arc setting during initiation of the southward subduction of the Paleo-Asian Ocean. The basalts of the Maotoushan Formation (MTS) display a calc-alkaline nature and are enriched in large ion lithophile elements (LILEs) and depleted in HFSEs, suggesting an active continental margin setting. Sulfur isotope (δ34S) values of the sulfide and sulfate minerals vary between 0‰ and 5.4‰, which are consistent with sulfur derivation from leaching of the host volcanic rocks, although a direct magmatic contribution cannot be ruled out. The Re-Os isotope data of pyrite yield an isochron age of 353 ± 35 Ma, consistent with the age of the host HLY basalts. Thus, a syngenetic (volcanogenic massive sulfide) model is proposed and it is concluded that the Sanfengshan copper deposit is a typical Cyprus-type VMS deposit that formed in an early

  18. Metamorphic Rock-Hosted Orogenic Gold Deposit Type as a Source of Langkowala Placer Gold, Bombana, Southeast Sulawesi

    Directory of Open Access Journals (Sweden)

    Arifudin Idrus

    2014-06-01

    Full Text Available DOI: 10.17014/ijog.v6i1.114In 2008, placer gold was discovered in Langkowala area (Bombana Regency, Southeast Sulawesi, Indonesia, and more than 60,000 traditional gold miners in the early 2009 have been operating by digging vertical pits and panning active stream sediments. The grade of placer gold ranges from 50 to 140 g/t. Local geological framework indicates that the placer gold is not related to volcanic rock-related hydrothermal gold deposit, e.g. epithermal, skarn or porphyry. This paper describes a preliminary study on possible primary deposit type as a source of the Langkowala (Bombana secondary placer gold. A field study indicates that the Langkowala (Bombana placer/paleoplacer gold is possibly related to gold-bearing quartz veins/veinlets hosted by metamorphic rocks particularly mica schist and metasediments in the area. These quartz veins/veinlets are currently recognized in metamorphic rocks at Wumbubangka Mountains, a northern flank of Rumbia Mountain Range. Sheared, segmented quartz veins/veinlets are of 2 cm to 2 m in width and contain gold in a grade varying between 2 and 61 g/t. At least, there are two generations of the quartz veins. The first generation of quartz vein is parallel to foliation of mica schist and metasediments with general orientation of N 300oE/60o; the second quartz vein generation crosscut the first quartz vein and the foliation of the wallrock. The first quartz veins are mostly sheared/deformed, brecciated, and occasionally sigmoidal, whereas the second quartz veins are relatively massive. The similar quartz veins/veinlets types are also probably present in Mendoke Mountain Range, in the northern side of Langkowala area. This primary gold deposit is called as ‘orogenic gold type’. The orogenic gold deposit could be a new target of gold exploration in Indonesia in the future.

  19. The deep structure of the Sichuan basin and adjacent orogenic zones revealed by the aggregated deep seismic profiling datum

    Science.gov (United States)

    Xiong, X.; Gao, R.; Li, Q.; Wang, H.

    2012-12-01

    The sedimentary basin and the orogenic belt are the basic two tectonic units of the continental lithosphere, and form the basin-mountain coupling system, The research of which is the key element to the oil and gas exploration, the global tectonic theory and models and the development of the geological theory. The Sichuan basin and adjacent orogenic belts is one of the most ideal sites to research the issues above, in particular by the recent deep seismic profiling datum. From the 1980s to now, there are 11 deep seismic sounding profiles and 6 deep seismic reflection profiles and massive seismic broadband observation stations deployed around and crossed the Sichuan basin, which provide us a big opportunity to research the deep structure and other forward issues in this region. Supported by the National Natural Science Foundation of China (Grant No. 41104056) and the Fundamental Research Funds of the Institute of Geological Sciences, CAGS (No. J1119), we sampled the Moho depth and low-velocity zone depth and the Pn velocity of these datum, then formed the contour map of the Moho depth and Pn velocity by the interpolation of the sampled datum. The result shows the Moho depth beneath Sichuan basin ranges from 40 to 44 km, the sharp Moho offset appears in the western margin of the Sichuan basin, and there is a subtle Moho depression in the central southern part of the Sichuan basin; the P wave velocity can be 6.0 km/s at ca. 10 km deep, and increases gradually deeper, the average P wave velocity in this region is ca. 6.3 km/s; the Pn velocity is ca. 8.0-8.02 km/s in Sichuan basin, and 7.70-7.76 km/s in Chuan-Dian region; the low velocity zone appears in the western margin of the Sichuan basin, which maybe cause the cause of the earthquake.

  20. The structural style of foot wall shortcuts along the eastern foothills of the Colombian eastern cordillera. Differences with other inversion related structures

    International Nuclear Information System (INIS)

    Mora, Andres; Parra, Mauricio

    2008-01-01

    For the first time we show geological evidence of unambiguously documented foot wall shortcuts adjacent to the trace of inverted master normal faults, in the Eastern Cordillera of Colombia. The Eastern Cordillera is an orogen whose width and location are traced by a Mesozoic Graben. However, few structures related with the Graben have been documented up to the date. In this study we propose the Ariari-Guatiquia region as a type location for a unique observation of foot wall shortcuts. The master normal faults in the Ariari-Guatiquia region, and documented in this manuscript, were active during the Lower Cretaceous, partially inverted during the Andean orogenesis (since the Oligocene at least) and active still nowadays. In the hanging wall basins of those master normal faults, like the Servita fault, all the Cretaceous syn-rift sequence has been deposited and maximum paleo-temperatures in the lowermost Cretaceous rocks are higher than those for the Zircon FT partial annealing zone (250 Celsius degrade; 23,15 K). In contraction, the inverted master normal faults are high angle basement involved features that generated the main topographic contrast and exposing Lower Cretaceous units or older. In contrast, in the adjacent foot wall shortcuts only part of the syn-rift Lower Cretaceous sequence was deposited or more commonly was not deposited at all. Maximum paleo-temperatures reached by the basal Cretaceous units exposed in the hanging wall blocks of the foot wall shortcuts are always less than those of the Zircon FT partial annealing zone (250 Celsius degrade; 23,15 K). Finally we use AFT data to document that the foot wall shortcuts originated during the Late Miocene and later as shallowly dipping faults generating low elevation hanging wall areas. All the described features are present in the Ariari-Guatiquia region. However, northwards and along strike in the Eastern foothills there is a lot of partially analogue scenarios with respect to those described in the

  1. Eastern Sources of Invitational Education.

    Science.gov (United States)

    Ryback, David

    1993-01-01

    Presents historical perspective suggesting that invitational theory shares many beliefs with ancient Eastern philosophies. Submits that teachers and other educators who embrace the invitational perspective may benefit from an understanding of Eastern principles. Briefly describes Buddhism, Confucianism, Taoism, Zen Buddhism, and their relevance to…

  2. Rhinoplasty in Middle Eastern Patients.

    Science.gov (United States)

    Sajjadian, Ali

    2016-01-01

    Rhinoplasty in patients of Middle Eastern origin requires complete understanding of nasal morphology and an individualized approach to create a racially congruent and aesthetically pleasing outcome. In this article, common anatomic features and characteristics and detailed steps, surgical techniques, and operative maneuvers that can lead to predictable outcome in rhinoplasty of Middle Eastern patients are discussed. Copyright © 2016 Elsevier Inc. All rights reserved.

  3. Subduction and exhumation of a continental margin in the Scandinavian Caledonides: Insights from ultrahigh pressure metamorphism, late orogenic basins and 3D numerical modelling

    Science.gov (United States)

    Cuthbert, Simon

    2017-04-01

    The Scandinavian Caledonides (SC) represents a plate collision zone of Himalayan style and scale. Three fundamental characteristics of this orogen are: (1) early foreland-directed, tectonic transport and stacking of nappes; (2) late, wholesale reversal of tectonic transport; (3) ultrahigh pressure metamorphism of felsic crust derived from the underthrusting plate at several levels in the orogenic wedge and below the main thrust surface, indicating subduction of continental crust into the mantle. The significance of this for crustal evolution is the profound remodeling of continental crust, direct geochemical interaction of such crust and the mantle and the opening of accommodation space trapping large volumes of clastic detritus within the orogen. The orogenic wedge of the SC was derived from the upper crust of the Baltica continental margin (a hyper-extended passive margin), plus terranes derived from an assemblage of outboard arcs and intra-oceanic basins and, at the highest structural level, elements of the Laurentian margin. Nappe emplacement was driven by Scandian ( 430Ma) collision of Baltica with Laurentia, but emerging Middle Ordovician ages for diamond-facies metamorphism for the most outboard (or rifted) elements of Baltica suggest prior collision with an arc or microcontinent. Nappes derived from Baltica continental crust were subducted, in some cases to depths sufficient to form diamond. These then detached from the upper part of the down-going plate along major thrust faults, at which time they ceased to descend and possibly rose along the subduction channel. Subduction of the remaining continental margin continued below these nappes, possibly driven by slab-pull of the previously subducted Iapetus oceanic lithosphere and metamorphic densification of subducted felsic continental margin. 3D numerical modelling based upon a Caledonide-like plate scenario shows that if a continental corner or promontory enters the subduction zone, the continental margin

  4. Geochemical Consequences of Lithospheric Delamination in the Eastern Mediterranean: Evidence From Young Turkish Basalts

    Science.gov (United States)

    Furman, T.; Kurkcuoglu, B.; Plummer, C.

    2007-12-01

    Magmatism associated with continental collision is increasingly attributed to major disturbance of or within the lithosphere. Geochemical and isotopic data on post-collisional primitive mafic lavas from across the Anatolian plate enable us to assess the effects of lithospheric delamination (slab rollback and breakoff) as indicated by geophysical studies. The Anatolian province displays geodynamically complex manifestations of the closure of neo-Tethys and the collision between Africa and Europe that commenced circa 30 Ma. The current south- southwestward motion of Anatolia, a.k.a. "Turkish escape", is accommodated by slab rollback along the Hellenic trench and orogenic collapse along both the eastern and western margins of the microplate. Volcanism occurs primarily along the fault zones that border and cross-cut Anatolia, and major element characteristics of the lavas vary with both space and time. In Western Anatolia, early Miocene collisional calc- alkaline magmatism was followed by Quaternary alkaline volcanism (Alici et al. 1998, 2002; Aldanmaz et al. 2000, 2006) related to orogenic collapse, presumably resulting from slab rollback. Orogenic collapse in Eastern Anatolia is facilitated by slab breakoff as determined by geophysical studies (Zor et al. 2003; Angus et al. 2006; Lei & Zhao 2007). This transition was accompanied a change from mid-Miocene calc-alkaline to Quaternary alkaline volcanism (e.g., Yilmaz 1990; Pearce et al. 1990). Central Anatolia displays calc-alkaline and tholeiitic volcanism, including alkali olivine basalts; plate tectonic reconstructions (Lyberis et al. 1992) indicate that the African slab did not reach Central Anatolia. Sr-Nd isotope values from each volcanic province define linear arrays that converge upon a common unradiogenic value typical of global depleted mantle. We suggest that mafic volcanism throughout Anatolia is supported by a common asthenospheric component, modified by identifiable, location-specific additions. In areas

  5. Eastern Equine Encephalitis Virus

    Energy Technology Data Exchange (ETDEWEB)

    Borucki, M. [Lawrence Livermore National Lab. (LLNL), Livermore, CA (United States)

    2010-08-05

    Eastern equine encephalitis virus (EEEV) is a mosquito-borne virus capable of causing large outbreaks of encephalitis in humans and horses. In North America, EEEV infection has a very high mortality rate in humans, and survivors often suffer severe neurological sequelae. Interestingly, EEEV infections from South American isolates are generally subclinical. Although EEEV is divided into two antigenic varieties and four lineages, only eleven isolates have been sequenced and eight of these are from the North American variety (Lineage I). Most sequenced strains were collected from mosquitoes and only one human isolate has been sequenced. EEEV isolates exist from a variety of hosts, vectors, years, and geographical locations and efforts should focus on sequencing strains that represent this diversity.

  6. Middle Eastern power systems

    International Nuclear Information System (INIS)

    Anon.

    1992-01-01

    Middle Eastern Power systems have evolved independently of each other over many decades. The region covers a wide geographical area of over 4 million square kilometers with an estimated population in 1990 of over 120 million people. This paper discusses the present status and future power system developments in the Middle East with emphasis on the Mashrequ Arab Countries (MAC). MAC consists of Egypt, Iraq, Jordan, Lebanon, Syria, Yemen, and the six Gulf Cooperation Council (GCC) countries, namely, Bahrain, Kuwait, Qatar, Saudi Arabia, Oman, and the United Arab Emirates (UAE). Interconnections within MAC and possible extensions to Turkey, Europe, and Central Africa are discussed. A common characteristic of the MAC power systems is that they are all operated by government or semi-government bodies. The energy resources in the region are varied. Countries such as Iraq, Egypt, and Syria have significant hydro power resources. On the other hand, the GCC countries and Iraq have abundant fossil fuel reserves

  7. Skarn-mineralized porphyry adakites in the Harlik arc at Kalatage, E. Tianshan (NW China): Slab melting in the Devonian-early Carboniferous in the southern Central Asian Orogenic Belt

    Science.gov (United States)

    Mao, Qigui; Yu, Mingjie; Xiao, Wenjiao; Windley, Brian F.; Li, Yuechen; Wei, Xiaofeng; Zhu, Jiangjian; Lü, Xiaoqiang

    2018-03-01

    The geodynamic control of mineralization in the accretionary evolution of the Central Asian Orogenic Belt (CAOB) has long been controversial. Here we report new field, geochemical and geochronological data on recently defined porphyry and skarn-type ore deposits (Devonian-Early Carboniferous) in the Kalatage area in the middle of the Harlik-Dananhu arc, Eastern Tianshan, NW China in the southern CAOB, with the aim of better understanding the accretionary tectonics and genesis of porphyry and skarn-type mineralization. The Yudai porphyry Cu-(Au) deposits and the Xierqu skarn Cu-Fe-(Au) deposits are closely associated with Middle Devonian adakitic diorite porphyries (382-390 Ma), which are calc-alkaline and characterized by high Na2O/K2O ratios and Sr contents (310-1020 ppm), strong depletion of HREE (e.g., Yb = 0.80-1.44 ppm) and Y (7.68-14.50 ppm), and all enriched in Rb, Sr, Ba, K and depleted in Nb and Ti. They are characterized by distinctive Eu positive anomalies, high Na2O contents and MORB-like Sr and Nd isotope signatures (high εNd(t) = +6.1 to +7.0 and low (87Sr/86Sr)i = 0.70412-0.70462). These adakites most likely formed by melting of a young/hot subducted oceanic slab, and adakites in general are important carriers of porphyry Cu ± (Au) deposits. Early Carboniferous adakites in the Tuwu area south of Kalatage are known to have similar features. Therefore, skarn-mineralized porphyry adakites get younger from north to south, suggesting southward migration of the Harlik-Dananhu arc from 390 Ma to 322 Ma. These data indicate that partial melting of hot (and/or young) oceanic crustal slabs were an important mechanism of accretionary crustal growth and mineralization in the southern CAOB.

  8. Seismic Anisotropy Beneath Eastern North America: Results from Multi-Event Inversion

    Science.gov (United States)

    Li, Y.; Levin, V. L.; Chen, X.

    2017-12-01

    Seismic anisotropy observed from the split core-refracted shear phases reflects upper mantle deformation. To characterize anisotropic signatures beneath eastern North America, we collected observations along a 1300 km long array from James Bay to the Fundy Basin. The averaged splitting parameters of individual sites show uniform fast polarization orientation of 80° and delay times linearly decreasing from 1.0 s in the Appalachians to 0.5 s in the Superior Province. We also see directional variation of fast polarizations at most sites, which is a likely effect of vertical changes in anisotropic properties. For sites with 10 or more observations, we used a multi-event inversion technique to solve for the underlying anisotropic structure. The technique considers the NULL observations from single-event analysis that are excluded from the averaged splitting parameters. For models with a single 100 km thick anisotropic layer with a horizontal fast axis, we find up to 6% of anisotropy in the Appalachian Orogen, equivalent to a splitting delay time of 1.5 s. Anisotropy strength reduces to 1.8% in the Superior Province, equivalent to delay times under 0.5 s. The overall decrease in anisotropic strength is modified by local changes of up to 2%, suggesting small-scale local variations near the surface. Orientations of the fast axes change from 60° in the Appalachian Orogen to 90° in the Superior Province, and are also modulated by local deviations. In the Appalachian Orogen the fast axes are close to the absolute plate motion in a hot-spot reference frame, while those in the Superior Province differ from it by almost 30°. Average values of splitting delays agree well with results of inversions in the Superior Province, and diverge in the Appalachians. Conversely, averaged fast polarizations match inversion results in the Appalachians, and are systematically different in the Superior Province. For an set of sites with recording periods exceeding 5 years, we will test more

  9. Gravity characteristics of the panafrican orogen in Ghana, Togo and Benin (West Africa)

    International Nuclear Information System (INIS)

    El-Hadji Tidjani, M.; Affaton, P.; Louis, P.; Socohou, A.

    1993-06-01

    The studied area is straddling the West-African Craton and Nigerian-Beninian panafrican mobile plate. From west to east, it is composed of three large petrostructural sets which show specific gravity characteristics: the Volta Basin domain, constituted of sedimentary formations lying in a major discordance on the West-African Craton crystalline basement; it exhibits positive gravity anomalies probably linked with basic magmatic intrusions met in the basin. Next, one medial set, corresponding to the external structural unit domain of the Dahomeyid range; composed of epi- to mesozonal rocks, it shows large negative anomaly panels very likely in close relation with the tectonic overload. Finally, one eastern set, comprising gneisso-migmatitic internal units of the Nigerian-Beninian plate western border; it mainly outlines positive anomalies which seem to be in connection with granulitic and basic complexes encountered in places inside this area. This set includes the suture zone. We mention in these three sets numerous gravity discontinuities which testify to the great structural complexity of the region. However, this complexity is frequently concealed or attenuated by counterbalance and smoothing phenomena. This gravity complexity increases from north to south, and is interpreted as the sign of a rise of the southern part deep zones of this sector during the panafrican event. Moreover, this complexity also might testify to an aggregation of panafrican mobile plate compartments. (author). 33 refs, 12 figs

  10. Reassessment of the geologic evolution of selected precambrian terranes in Brazil, based on new SHRIMP U-Pb data, part 1: central-eastern border of Sao Francisco Craton in Bahia state, Brazil

    International Nuclear Information System (INIS)

    Silva, Luiz Carlos da; Pimentel, Marcio; Jost, Hardy; Armstrong, Richard

    2002-01-01

    This paper discusses new U-Pb SHRIMP zircon data for 12 key-exposures of several geological units exposed at the eastern border of the Sao Francisco Craton. The samples represent mostly Archean basement units within the Paleoproterozoic Eastern Bahia Belt (Orogen). Samples were collected along several E-W tran sects trying to more accurately assess the areal distribution of the Archean polycyclic basement of the Sao Francisco Craton and to identify the limits of Paleoproterozoic metamorphic overprint resulting from the development of the Eastern Bahia Orogen. Owing to the polycyclic evolution and/or high grade metamorphic conditions which most of the rock units investigated have undergone, zircon morphology and the U-Pb analytical data exhibit very complex patterns. These are characterized by a combination of inheritance, partial resetting and new zircon growth during high grade metamorphism. As a consequence, very careful and detailed analyses of cathodoluminescence imagery were required to allow distinction between inheritance, newly melt-precipitated zircon and partially reset zircons, as well as between the ages of magmatic and metamorphic events. Except for one unit (sample LH 44), which present crystallization age of ca 3000 Ma - interpreted, therefore, as the eastern extension of the Serrinha Craton - the others are ascribed to two major age groups at ca. 2870-2500 Ma and ca. 2200?-2030 Ma. The former group includes ortho gneisses with crystallization ages between ca. 2870-2500 Ma, which have been mapped and interpreted, in its major extension, as juvenile Paleoproterozoic arc (Itabuna and Salvador-Curaca belts/domains). The new data presented in this study, however, indicate that these ortho gneisses represent a multi-episodic collage of primitive Archean orogenic arcs, which gave rise to the Archean basement of that part of the Sao Francisco Craton. All the investigated zircon populations were extensively recrystallized at ca. 2080-2050 Ma as a result of

  11. Discovery of Miocene adakitic dacite from the Eastern Pontides Belt (NE Turkey) and a revised geodynamic model for the late Cenozoic evolution of the Eastern Mediterranean region

    Science.gov (United States)

    Eyuboglu, Yener; Santosh, M.; Yi, Keewook; Bektaş, Osman; Kwon, Sanghoon

    2012-08-01

    The Cenozoic magmatic record within the ca. 500 km long eastern Pontides orogen, located within the Alpine metallogenic belt, is critical to evaluate the tectonic history and geodynamic evolution of the eastern Mediterranean region. In this paper we report for the first time late Miocene adakitic rocks from the southeastern part of the eastern Pontides belt and present results from geochemical and Sr-Nd isotopic studies as well as zircon U-Pb geochronology. The Tavdagi dacite that we investigate in this study is exposed as round or ellipsoidal shaped bodies, sills, and dikes in the southeastern part of the belt. Zircons in the dacite show euhedral crystal morphology with oscillatory zoning and high Th/U values (up to 1.69) typical of magmatic origin. Zircon LA-ICPMS analysis yielded a weighted mean 206Pb/238U age of 7.86 ± 0.15 Ma. SHRIMP analyses of zircons with typical magmatic zoning from another sample yielded a weighted mean 206Pb/238U age of 8.79 ± 0.19 Ma. Both ages are identical and constrain the timing of dacitic magmatism as late Miocene. The Miocene Tavdagi dacite shows adakitic affinity with high SiO2 (68.95-71.41 wt.%), Al2O3 (14.88-16.02 wt.%), Na2O (3.27-4.12 wt.%), Sr (331.4-462.1 ppm), Sr/Y (85-103.7), LaN/YbN (34.3-50.9) and low Y (3.2-5 ppm) values. Their initial 143Nd/144Nd (0.512723-0.512736) and 87Sr/86Sr (0.70484-0.70494) ratios are, respectively, lower and higher than those of normal oceanic crust. The geological, geochemical and isotopic data suggest that the adakitic magmatism was generated by partial melting of the mafic lower crust in the southeastern part of the eastern Pontide belt during the late Miocene. Based on the results presented in this study and a synthesis of the geological and tectonic information on the region, we propose that the entire northern edge of the eastern Pontides-Lesser Caucasus-Elbruz magmatic arc was an active continental margin during the Cenozoic. We identify a migration of the Cenozoic magmatism towards

  12. Evidences for an orogenic-induced global cooling at the Frasnian-Famennian boundary (ca 376 Ma BP)

    Science.gov (United States)

    Averbuch, O.; Tribovillard, N.; Devleeschouwer, X.; Riquier, L.

    2003-04-01

    Late Devonian time (Famennian, 376--362 Ma BP) is a period of both intense orogenic activity and drastic climatic variations with the onset of a major glaciation event upon parts of the Gondwanian Southern America and Africa situated in high southern latitudes. This global cooling event is coeval with a significant fall in the atmospheric CO_2 content as suggested both by stomatal data and modelling. In the stratigraphic record, the Frasnian-Famennian transition is characterized by a great loss of biotic diversity and pronounced environmental changes with the demise of reefal carbonate platforms and the deposition of extensive organic-rich levels (Kellwasser levels) in Late Frasnian times followed by a rapid global scale sea-level fall and an increase in detrital input in the basal Famennian. We propose to relate the Famennian global cooling and the associated environnmental changes to the development of major mountain cordilleras extending on one hand from the Urals to South America (including the Central Asian, the European, the Northern African, the Appalachian belts) and on the other hand from the western American Antler to the Arctic Ellesmerian belt. Extensive high pressure metamorphic rocks dated between ca 380 and 360 Ma BP, pervasive deformations distributed along the belt (Eo-Variscan phase) and synorogenic molassic rocks trapped within the flexural foreland basins indicate a major collisional event in Late Frasnian-Famennian times inducing an important crustal thickening and associated high continental relief. The major drop in the atmospheric CO2 content would be driven by the conjunction of two orogenic-induced mechanisms : (1) the intensification of silicate weathering on the continental areas as attested by a major rise in the 87Sr/86Sr composition of sea water at the Frasnian-Famennian boundary ; the coeval development of vascular plants on emerged lands is also probably an important factor in enhanced chemical weathering of continental soils (2

  13. Origins of two types of serpentinites from the Qinling orogenic belt, central China and associated fluid/melt-rock interactions

    Science.gov (United States)

    Wu, Kai; Ding, Xing; Ling, Ming-Xing; Sun, Wei-dong; Zhang, Li-Peng; Hu, Yong-Bin; Huang, Rui-Fang

    2018-03-01

    Serpentinites are important volatile and fluid mobile element repositories in oceanic lithosphere and subduction zones, and thus provide significant constraints on global geochemical cycles and tectonic evolution at convergent margins. In this contribution, two types of serpentinites from the Mianlue suture zone in the Qinling orogenic belt, central China, are identified on the basis of detailed mineralogical and geochemical study. Serpentinites from the Jianchaling region (Group 1) are composed of lizardite/chrysotile + magnesite + magnetite. Most of these serpentinites (Group 1a), consist of pseudomorphic orthopyroxene and olivine, and are characterized by low Al2O3/SiO2, high MgO/SiO2 and Ir-type PGEs to Pt ratios, suggesting a residual mantle origin. Meanwhile, the U-shape REE pattern and positive Eu, Sr and Ba anomalies of these serpentinites indicate that serpentinization fluids have interacted with gabbroic cumulates at moderately high temperatures or associate with the chlorinity and redox conditions of the fluid. Considering the limited mobility of U in the hydrating fluids for the Group 1a serpentinites, hydrating fluids for these serpentinites are most likely derived from the dehydrated slab, and have been in equilibrium with subducting sediments. There are also some serpentinites with low-grade metamorphic recrystallization from the Jianchaling region (Group 1b), represented by recrystallized serpentine minerals (antigorite). The trace element compositions of these Group 1b serpentinites suggest that partial dehydration of serpentinites associated with the transformation from lizardite to antigorite in subduction zone is also likely to affect the geochemistry of serpentinites. Serpentinites from the Liangyazi region (Group 2) are composed of antigorite + dolomite + spinel + magnetite. The high Cr number (0.65-0.80) and low Ti concentrations of spinels in Group 2 serpentinites indicate a refractory mantle wedge origin. Fertile major element compositions

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

    Science.gov (United States)

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

    2011-01-01

    The Kharapeh gold deposit is located along the northwestern margin of the Sanandaj–Sirjan Zone (SSZ) in the West Azerbaijan province, Iran. It is an epizonal orogenic gold deposit formed within the deformed zone between central Iran and the Arabian plate during the Cretaceous–Tertiary Zagros orogeny. The deposit area is underlain by Cretaceous schist and marble, as well as altered andesite and dacite dikes. Structural analysis indicates that the rocks underwent tight to isoclinal recumbent folding and were subsequently co-axially refolded to upright open folds during a second deformation. Late- to post-tectonic Cenozoic granites and granodiorites occur northeast of the deposit area. Mineralization mainly is recognized within NW-trending extensional structures as veins and breccia zones. Normal faults, intermediate dikes, and quartz veins, oriented subparallel to the axial surface of the Kharapeh antiform, indicate synchronous extension perpendicular to the fold axis during the second folding event. The gold-bearing quartz veins are >1 km in length and average about 6 m in width; breccia zones are 10–50 m in length and ≤1 m in width. Hydrothermal alteration mainly consists of silicification, sulfidation, chloritization, sericitization, and carbonatization. Paragenetic relationships indicate three distinct stages—replacement and silicification, brecciation and fracture filling, and cataclastic brecciation—with the latter two being gold-rich. Fluid inclusion data suggest mineral deposition at temperatures of at least 220–255°C and depths of at least 1.4–1.8 km, from a H2O–CO2±CH4 fluid of relatively high salinity (12–14 wt.% NaCl equiv.), which may reflect metamorphism of passive margin carbonate sequences. Ore fluid δ18O values between about 7‰ and 9‰ suggest no significant meteoric water input, despite gold deposition in a relatively shallow epizonal environment. Similarities to other deposits in the SSZ suggest that the deposit formed as

  15. 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

    Science.gov (United States)

    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

  16. Survey report: Eastern Caribbean.

    Science.gov (United States)

    Yinger, N

    1991-01-01

    Over 1 million people live on 8 small islands in the Eastern Caribbean: St. Kitts-Nevis, Montserrat, Grenada, St. Vincent, Antigua, Barbados, St. Lucia, and Dominica. Starting in 1985 the International Planned Parenthood Federation, Western Hemisphere Region has carried out a series of contraceptive prevalence surveys in these countries. Current information is provided by these surveys in the areas of fertility levels and preferences, contraceptive knowledge and use. Also, socioeconomic, historical and demographic background and analysis such as fertility patterns, desire for additional children, and breastfeeding data; contraceptive awareness including family planning methods and sources; contraceptive use by method, source, and timing, satisfaction, and male attitudes are provided in the surveys, but not in the report abstracted here. The total fertility rate (TFR) and the contraceptive prevalence rate (CPR) for the 8 islands are as follows: St. Kitts-Nevis (1984) 2.9 TFR, 40.6 CPR; St. Vincent (1988) 2.9 TFR, 58.3 CPR; Antigua (1988) 1.8 TFR, 52.6 CPR; Barbados (1988) not given, 55.0 CPR; St. Lucia (1988) 3.2 TFR, 47.3 CPR; Dominica (1987) 3.2 TFR, 49.8 CPR. The islands have unusual demographic patterns related to extensive out-migration.

  17. Middle Eastern Christians in Europe

    DEFF Research Database (Denmark)

    Sparre, Sara Cathrine Lei; Hunter, Alistair; Jørgensen, Anne Rosenlund

    This booklet, published in English, Danish, Swedish and Arabic, has the aim to present overall findings of the research project Defining and Identifying Middle Eastern Christians in Europe (DIMECCE) to a broader audience.......This booklet, published in English, Danish, Swedish and Arabic, has the aim to present overall findings of the research project Defining and Identifying Middle Eastern Christians in Europe (DIMECCE) to a broader audience....

  18. The Heart of China revisited: II Early Paleozoic (ultra)high-pressure and (ultra)high-temperature metamorphic Qinling orogenic collage

    Science.gov (United States)

    Bader, Thomas; Franz, Leander; Ratschbacher, Lothar; de Capitani, Christian; Webb, A. Alexander G.; Yang, Zhao; Pfänder, Jörg A.; Hofmann, Mandy; Linnemann, Ulf

    2013-07-01

    Orogens with multiple (ultra)high-pressure ((U)HP) and (ultra)high-temperature ((U)HT) metamorphic events provide a complex but telling record of oceanic and continental interaction. The Early Paleozoic history of the "Heart of China," the Qinling orogenic collage, offers snapshots of at least three (U)HP and two (U)HT metamorphic events. The preservation of remnants of both oceanic and continental domains together with a ≥110 Myr record of magmatism allows the reconstruction of the processes that resulted in this disparate metamorphism. Herein, we first illuminate the pressure-temperature-time (P-T-t) evolution of the Early Paleozoic (U)HP and (U)HT events by refining the petrographic descriptions and P-T estimates, assess published, and employ new U/Th-Pb zircon, monazite, and titanite, and 40Ar-39Ar phengite geochronology to date the magmatic and metamorphic events. Then we explore how the metamorphic and magmatic events are related tectonically and how they elucidate the affinities among the various complexes in the Qinling orogenic collage. We argue that a Meso-Neoproterozoic crustal fragment—the Qinling complex—localized subduction-accretion events that involved subduction, oceanic-arc formation, and back-arc spreading along its northern margin, and mtantle-wedge exhumation and spreading-ridge subduction along its southern margin.

  19. Unfolding the arc: The use of pre-orogenic constraints to assess the evolution of the Variscan belt in Western Europe

    Science.gov (United States)

    Casas, Josep M.; Brendan Murphy, J.

    2018-06-01

    We present a pre-orogenic, early Paleozoic, palinspastic reconstruction of the northern Gondwana margin that was subsequently involved in the Late Paleozoic Variscan orogeny in central and Western Europe. Our reconstruction is based on two pre-orogenic data sets, the age and distribution of Cambrian-Ordovician magmatism and the detrital zircon age signature of late Neoproterozoic-early Paleozoic clastic rocks. We obtain this reconstruction by unfolding the Ibero-Armorican arc and by restoring the movement of the large-scale dextral strike-slip faults that transect the different tectono-stratigraphic units. Our results favour an irregular shape for this part of the northern Gondwana margin with a N-S central segment linking two E-W oriented segments. The proposed reconstruction and the structural restoration of the main features of Variscan deformation is in accordance with some aspects of previously proposed structural models, such as the curved geometry of the Gondwanan margin required by the indentor model for continental collision, the role played by the large strike-slip faults in dispersing formerly juxtaposed units, and the regional-scale oroclinal folding of part of this margin during late Carboniferous-Early Permian times. The combined use of the pre-orogenic geological constraints and palinspastic restoration is a useful approach that may provide a foundation for continual refinement of reconstructions as more data become available.

  20. Timing of sediment-hosted Cu-Ag mineralization in the Trans-Hudson orogen at Janice Lake, Wollaston Domain, Saskatchewan, Canada

    Science.gov (United States)

    Perelló, José; Valencia, Víctor A.; Cornejo, Paula; Clifford, John; Wilson, Alan J.; Collins, Greg

    2018-04-01

    The Janice Lake Cu-Ag mineralization in the Wollaston Domain of northern Saskatchewan is hosted by a metasedimentary sequence in the upper part of the Wollaston Supergroup of the Trans-Hudson orogen. The Wollaston Supergroup was deposited between 2070 and 1865 Ma in a foreland basin setting constructed over Archean basement of the Hearne craton. The Trans-Hudson orogen underwent final collision and peak metamorphism at 1810 Ma, during consolidation of Laurentia and its amalgamation with the Columbia supercontinent. Titanite is a common constituent of the post-peak metamorphic assemblages of Trans-Hudson lithotectonic units and accompanied disseminated sediment-hosted Cu sulfide mineralization at Janice Lake. Titanite crystals, intergrown with chalcocite over a strike-length of 2 km of Cu-bearing stratigraphy, were dated by the ID-TIMS and LA-ICP-MS U-Pb methods, returning an age range from 1780 to 1760 Ma and a weighted average age of 1775 ± 10 Ma. The titanite ages effectively date the associated chalcocite-dominated sediment-hosted Cu-Ag mineralization and its formation during initial post-orogenic uplift and cooling, 30 myr after peak metamorphism. The age-range and tectonic setting of the Janice Lake mineralization confirms that sediment-hosted Cu mineralization was an integral part of the metallogenic endowment of Columbia and that its emplacement coincided with the continental-scale Trans-Hudson orogeny rather than with diagenesis and extensional basin development 100 myr earlier.

  1. The AlpArray Seismic Network: A Large-Scale European Experiment to Image the Alpine Orogen

    Science.gov (United States)

    Hetényi, György; Molinari, Irene; Clinton, John; Bokelmann, Götz; Bondár, István; Crawford, Wayne C.; Dessa, Jean-Xavier; Doubre, Cécile; Friederich, Wolfgang; Fuchs, Florian; Giardini, Domenico; Gráczer, Zoltán; Handy, Mark R.; Herak, Marijan; Jia, Yan; Kissling, Edi; Kopp, Heidrun; Korn, Michael; Margheriti, Lucia; Meier, Thomas; Mucciarelli, Marco; Paul, Anne; Pesaresi, Damiano; Piromallo, Claudia; Plenefisch, Thomas; Plomerová, Jaroslava; Ritter, Joachim; Rümpker, Georg; Šipka, Vesna; Spallarossa, Daniele; Thomas, Christine; Tilmann, Frederik; Wassermann, Joachim; Weber, Michael; Wéber, Zoltán; Wesztergom, Viktor; Živčić, Mladen

    2018-04-01

    The AlpArray programme is a multinational, European consortium to advance our understanding of orogenesis and its relationship to mantle dynamics, plate reorganizations, surface processes and seismic hazard in the Alps-Apennines-Carpathians-Dinarides orogenic system. The AlpArray Seismic Network has been deployed with contributions from 36 institutions from 11 countries to map physical properties of the lithosphere and asthenosphere in 3D and thus to obtain new, high-resolution geophysical images of structures from the surface down to the base of the mantle transition zone. With over 600 broadband stations operated for 2 years, this seismic experiment is one of the largest simultaneously operated seismological networks in the academic domain, employing hexagonal coverage with station spacing at less than 52 km. This dense and regularly spaced experiment is made possible by the coordinated coeval deployment of temporary stations from numerous national pools, including ocean-bottom seismometers, which were funded by different national agencies. They combine with permanent networks, which also required the cooperation of many different operators. Together these stations ultimately fill coverage gaps. Following a short overview of previous large-scale seismological experiments in the Alpine region, we here present the goals, construction, deployment, characteristics and data management of the AlpArray Seismic Network, which will provide data that is expected to be unprecedented in quality to image the complex Alpine mountains at depth.

  2. Chemical and spectroscopic characteristics of potassium white micas related to polystage evolution of the Central Western Carpathians orogenic wedge

    Science.gov (United States)

    Sulák, Marián; Kaindl, Reinhard; Putiš, Marián; Sitek, Jozef; Krenn, Kurt; Tóth, Ignác

    2009-12-01

    Potassium white micas in sheared basement and cover rocks from the Central Western Carpathians (CWC) were investigated by PL microscopy, electron microprobe (EMP) analysis, Mössbauer and micro-Raman spectroscopy. We specified chemical and spectroscopic characteristics, which allow distinction between celadonite-poor (muscovitic) and celadonite-rich (phengitic) white mica (Wmca). Wmca generations formed during a polystage evolution in changing P- T conditions ranging from the very low to medium temperatures at medium pressure within the Alpidic CWC orogenic wedge. BSE imaging, EMP analyses and X-ray element maps indicate chemical differences between muscovite and phengite, mainly in Al, Fe and Si contents. Mössbauer spectroscopy revealed their contrasting spectra, related to different hyperfine parameters, mainly of quadrupole splitting (QS of Ms: 2.6-2.7 mm/s, or 2.9-3.0 mm/s for Phg), corresponding to Fe 2+ and Fe 3+ contents. Blastomylonitic samples with a single dominating Wmca generation and finite-strain XZ sections were suitable for micro-Raman study. These data corroborate correlation between the frequencies of two vibrational modes of Wmca and Si content. The investigated Wmca generations indicate an enhanced transformation between Wmca phases in shear zones.

  3. Comparison of the orogenic displacement of sodium caseinate with the caseins from the air-water interface by nonionic surfactants.

    Science.gov (United States)

    Woodward, N C; Gunning, A P; Mackie, A R; Wilde, P J; Morris, V J

    2009-06-16

    Displacement of sodium caseinate from the air-water interface by nonionic surfactants Tween 20 and Tween 60 was observed by atomic force microscopy (AFM). The interfacial structure was sampled by Langmuir-Blodgett deposition onto freshly cleaved mica substrates. Protein displacement occurred through an orogenic mechanism: it involved the nucleation and growth of surfactant domains within the protein network, followed by failure of the protein network. The surface pressure at which failure of the protein network occurred was essentially independent of the type of surfactant. The major component of sodium caseinate is beta-casein, and previous studies at the air-water interface have shown that beta-casein networks are weak, failing at surface pressures below that observed for sodium caseinate. The other components of sodium caseinate are alpha(s)- and kappa-caseins. Studies of the displacement of alpha(s)-caseins from air-water interfaces show that these proteins also form weak networks that fail at surface pressures below that observed for sodium caseinate. However, kappa-casein was found to form strong networks that resisted displacement and failed at surface pressures comparable to those observed for sodium caseinate. The AFM images of the displacement suggest that, despite kappa-casein being a minor component, it dominates the failure of sodium caseinate networks: alpha(s)-casein and beta-casein are preferentially desorbed at lower surface pressures, allowing the residual kappa-casein to control the breakdown of the sodium caseinate network at higher surface pressures.

  4. Greisen deposits associated to carboniferous post-orogenic granites with mineralization potential, Sierra de Fiambala, Catamarca, Argentina

    International Nuclear Information System (INIS)

    Fogliata, A. S.; Rubinstein, N. R.; Avila, J. C.; Baez, M.

    2008-01-01

    The Fiambala range is located in the central south part of the province of Catamarca, Western Sierras Pampeanas, Argentina. It is largely conformed by Precambrian metamorphic rocks, a Cambrian granitic intrusive, Ordovician basic and ultra basic rocks and epi zonal Carboniferous granites (Los Ratones, El Salto and Ayacucho Granites). The Carboniferous granites are sub alkaline, weakly peraluminous, high silica (except for the porphyritic facies of Los Ratones granite) and moderately enriched in K. Contents of trace elements and REE indicate that El S alto and Ayacucho granites and the granular facies of Los Ratones granite have characteristics of evolved and differentiated granite associated with hydrothermal systems. The variations of trace elements, particularly Sn, W, U, Rb, Ba, Zr and Sr suggest that they correspond to granites with mineralization potential. Genetically linked to these granites there are Sn, W, U and minor base metals greisen deposits. The hydrothermal process that yield to these deposits involved two main alteration stages, beginning with alkali metasomatism follow by greissenization. According to the isotopic ages the hydrothermal processes postdate about 1 Ma the magmatic activity. The analyses of the granites and the associated greisen deposits confirm that the post orogenic carboniferous magmatism is the major metallogenetic control of the ore deposits from the studied area. This metallogenetic control could be a useful tool in prospecting similar deposits in the rest of the Western Sierras Pampeanas. (Author)

  5. Late Archaean-early Proterozoic source ages of zircons in rocks from the Paleozoic orogen of western Galicia, NW Spain

    Energy Technology Data Exchange (ETDEWEB)

    Kuijper, R P; Priem, H N.A. [Laboratorium voor Isotopen-Geologie, Amsterdam (Netherlands); Den Tex, E [Rijksuniversiteit Utrecht (Netherlands). Inst. voor Aardwetenschappen

    1982-08-01

    U-Pb data are reported for nine suites of zircons and three monazites from the Paleozoic orogen in western Galicia: one paragneiss and six orthogneisses from the early Paleozoic basement, and two Carboniferous (ca. 310 Ma old) intrusions of two-mica granite. New whole-rock Rb-Sr analyses, along with earlier data, indicate an age of ca. 470-440 Ma (Ordovician) for the emplacement of the granitic precursors of the orthogneisses. Monazite from the paragneiss also yields an U-Pb age of ca. 470 Ma. From the high initial /sup 87/Sr//sup 86/Sr ratios an involvement of Precambrian continental crust material is evident in the generation of the early Paleozoic suite of granites, while the zircon U-Pb data give evidence of the presence of about 3.0-2.0 Ga old (late Archaean-early Proterozoic) components in the source material. Zircons from the oldest sedimentary rocks in the area, now present as catazonal paragneisses and a likely source for the granites, likewise reveal a provenance age of 3.0-2.0 Ga.

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

    Directory of Open Access Journals (Sweden)

    Hongzhong Li

    2014-01-01

    Full Text Available 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/YbN, and (La/CeN 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.

  7. Pre- and syn-Ross orogenic granitoids at Drake Head and Kartografov Island, Oates Coast, northern Victoria Land, East Antarctica

    International Nuclear Information System (INIS)

    Adams, C.J.; Roland, N.W.

    2002-01-01

    The majority of the Oates Coast, northern Victoria Land granitoids, typified by those at Drake Head and Kartografov Island (Harald Bay), are monzogranites with lesser granodiorites and minor quartz-monzodiorite and syenogranite. All are plagioclase-K-feldspar-biotite granitoids with additional muscovite, garnet and/or hornblende, and are subalkaline and peraluminous. Berg Granite typifies the early Ordovician, Granite Harbour Instrusive (GHI) suite of the Ross Orogen at the Oates Coast. Granitoids from Kartografov Island have higher amounts of Fe+Mg+Ti and an ambiguous Rb-Sr geochronology: they could be either pre-Ross Orogeny in age, or syn-Ross Orogeny and representing a lower structural level of GHI. The Drake Head granite gneiss has a fractionated leuco-granite composition similar to Berg Granite, and is intruded by granite and granodiorite. Rb-Sr ages indicate that all are Neoproterozoic, although the granite gneiss result is probably an errorchron age, reflecting its less uniform nature (granodiorite:649 ± 30 Ma, initial ratio 0.7065 +/- 6; granite gneiss: 682 ± 140 Ma, initial ratio 0.7107 ± 50). These late Neoproterozoic granitoids provide a source for distinctive detrital zircon age components in extensive early Paleozoic turbidites of Australia-New Zealand-Antarctica. (author). 24 refs., 5 figs., 1 tab

  8. Melting of subducted continental crust: Geochemical evidence from Mesozoic granitoids in the Dabie-Sulu orogenic belt, east-central China

    Science.gov (United States)

    Zhao, Zi-Fu; Liu, Zhi-Bin; Chen, Qi

    2017-09-01

    Syn-collisional and postcollisional granitoids are common in collisional orogens, and they were primarily produced by partial melting of subducted continental crust. This is exemplified by Mesozoic granitoids from the Dabie-Sulu orogenic belt in east-central China. These granitoids were emplaced in small volumes in the Late Triassic (200-206 Ma) and the Late Jurassic (146-167 Ma) but massively in the Early Cretaceous (111-143 Ma). Nevertheless, all of them exhibit arc-like trace element distribution patterns and are enriched in Sr-Nd-Hf isotope compositions, indicating their origination from the ancient continental crust. They commonly contain relict zircons with Neoproterozoic and Triassic U-Pb ages, respectively, consistent with the protolith and metamorphic ages for ultrahigh-pressure (UHP) metaigneous rocks in the Dabie-Sulu orogenic belt. Some granitoids show low zircon δ18O values, and SIMS in-situ O isotope analysis reveals that the relict zircons with Neoproterozoic and Triassic U-Pb ages also commonly exhibit low δ18O values. Neoproterozoic U-Pb ages and low δ18O values are the two diagnostic features that distinguish the subducted South China Block from the obducted North China Block. Thus, the magma source of these Mesozoic granitoids has a genetic link to the subducted continental crust of the South China Block. On the other hand, these granitoids contain relict zircons with Paleoproterozoic and Archean U-Pb ages, which are present in both the South and North China Blocks. Taken together, the Mesozoic granitoids in the Dabie-Sulu orogenic belt and its hanging wall have their magma sources that are predominated by the continental crust of the South China Block with minor contributions from the continental crust of the North China Block. The Triassic continental collision between the South and North China Blocks brought the continental crust into the thickened orogen, where they underwent the three episodes of partial melting in the Late Triassic, Late

  9. Area Studies and Eastern Europe: How Eastern Europe Collapsed

    Directory of Open Access Journals (Sweden)

    Mirjana Kasapović

    2007-01-01

    Full Text Available In the first part, the author outlines the development of area studies in contemporary comparative politics, and points to their importance for the development of political science. In the second part, she examines the methodology – research design and methods – of regional comparatistics, paying particular attention to the problem of defining the region as a central category in this field of comparative politics. The third and central part is focused on the emergence of Eastern Europe as a historical-political and socio-cultural region in the course of history, especially after World War II, and on its dissolution in the processes of democratic transformation of communist regimes in the last two decades. The dissolution of Eastern Europe has resulted in restoration of a tripartite political geography in the area which it used to take up, made up of Central Europe, Southeast Europe and the proper Eastern Europe.

  10. Environmental protection in Eastern Europe

    International Nuclear Information System (INIS)

    Kabala, S.

    1990-01-01

    There is a need for the development of institutional structures to make the transfer of technology work to improve the ability of Eastern Europe to find solutions to its environmental problems. Envisioned is technical assistance: U.S. experts who will work on-site with Eastern European experts. The idea is to technically train individuals in pollution-prevention methods. Trained experts could then upgrade processes to save input, energy, and materials. In the exchange of environmental information, discussions have led to four issues: it is expensive to transfer equipment and make qualified personnel available for a long period; information is comparatively inexpensive to convey; in Eastern Europe there are trained and competent personnel; the theoretical knowledge, academic knowledge, and education are at a very high level but little of this knowledge has been put into practice. The technology transfer goal is to develop a response to needs identified by partner institutions and counterpart professionals that will enable Eastern Europe to tap resources that do exist- scientific, managerial, and economic resources and tap information resources in the US in order to address the environmental problems that exist in Eastern Europe

  11. Structurally controlled 'teleconnection' of large-scale mass wasting (Eastern Alps)

    Science.gov (United States)

    Ostermann, Marc; Sanders, Diethard

    2015-04-01

    In the Brenner Pass area (Eastern Alps) , closely ahead of the most northward outlier ('nose') of the Southern-Alpine continental indenter, abundant deep-seated gravitational slope deformations and a cluster of five post-glacial rockslides are present. The indenter of roughly triangular shape formed during Neogene collision of the Southern-Alpine basement with the Eastern-Alpine nappe stack. Compression by the indenter activated a N-S striking, roughly W-E extensional fault northward of the nose of the indenter (Brenner-normal fault; BNF), and lengthened the Eastern-Alpine edifice along a set of major strike-slip faults. These fault zones display high seismicity, and are the preferred locus of catastrophic rapid slope failures (rockslides, rock avalanches) and deep-seated gravitational slope deformations. The seismotectonic stress field, earthquake activity, and structural data all indicate that the South-Alpine indenter still - or again - exerts compression; in consequence, the northward adjacent Eastern Alps are subject mainly to extension and strike-slip. For the rockslides in the Brenner Pass area, and for the deep-seated gravitational slope deformations, the fault zones combined with high seismic activity predispose massive slope failures. Structural data and earthquakes mainly record ~W-E extension within an Eastern Alpine basement block (Oetztal-Stubai basement complex) in the hangingwall of the BNF. In the Northern Calcareous Alps NW of the Oetztal-Stubai basement complex, dextral faults provide defacement scars for large rockfalls and rockslides. Towards the West, these dextral faults merge into a NNW-SSE striking sinistral fault zone that, in turn, displays high seismic activity and is the locus of another rockslide cluster (Fern Pass cluster; Prager et al., 2008). By its kinematics dictated by the South-Alpine indenter, the relatively rigid Oetztal-Stubai basement block relays faulting and associated mass-wasting over a N-S distance of more than 60

  12. Nuclear power in Eastern Europe

    Energy Technology Data Exchange (ETDEWEB)

    Thomas, S. (Sussex Univ., Brighton (UK). Science Policy Research Unit)

    1991-01-01

    The main aim of this article is that of illustrating the experience of the use of nuclear power in Eastern Europe in order to estimate the degree of adequacy or inadequacy of COMECON's nuclear technology. The author examines four areas of interest concerning: the feasibility of new orders for nuclear plants in Eastern Europe; the pros and cons of completing half-built nuclear power plants; current policy towards existing nuclear power plants; and a review of the available evidence on the operating performance of plants in Eastern Europe. The common belief that the nuclear power experience had by old COMECON countries is uniformly bad does not seem to be fully supported by the limited evidence available. In the author's opinion, the prospects for a successful nuclear power industry in these countries depends on a series on interdependent factors among which, human skills hold a prominent position.

  13. Strategy Formation in Eastern Jutland

    DEFF Research Database (Denmark)

    Olesen, Kristian

    2008-01-01

      In Eastern Jutland a strategy formation process has been initiated with the aim of developing a strategic spatial plan for the city region.  An organisation has been set up to deal with the first phase of the process, which is to carry out three functional analyses and prepare a common vision...... in the area.   The municipalities acknowledge the articulation of the city region and the initiated planning process.  However, the municipalities might see the arena as means to lobby for infrastructure investments in Eastern Jutland, as it is doubtful whether the municipalities will feel encouraged to enter...... a process, which is aiming at increasing the national regulation within their territory.    The result might very well be that the discussion about future infrastructure investments is not linked to discussions about future urban development in Eastern Jutland.  These aspects raises serious questions about...

  14. Eastern Orthodox perspectives on violence

    DEFF Research Database (Denmark)

    Hilton Saggau, Emil

    2017-01-01

    Abstract: In the post-communist era, the contemporary national Eastern Orthodox churches have often been accused of taking either direct or ideological part in violence across Eastern Europe. In several scholarly analyses, the churches have been linked with ethnic and national violence. They have...... thus been identified as an ideological root for a distinctive ethno-religious nationalism either blocking the way for a pluralistic society or simply defying it. These cases of violence and conflicts, as well as their subsequent analysis, only point to a practical and visible manifestation of conflicts......, and they therefore don’t answer a broader theological question, namely the question of the general position of the Eastern Orthodox churches regarding violence. This article will address this broader question of what the Orthodox churches’ position is on violence and discuss the co-relation and intersection between...

  15. Geochemistry and chronology of the early Paleozoic diorites and granites in the Huangtupo volcanogenic massive sulfide (VMS) deposit, Eastern Tianshan, NW China: Implications for petrogenesis and geodynamic setting

    Science.gov (United States)

    Zheng, Jiahao; Chai, Fengmei; Feng, Wanyi; Yang, Fuquan; Shen, Ping

    2018-03-01

    The Eastern Tianshan orogen contains many late Paleozoic porphyry Cu and magmatic Cu-Ni deposits. Recent studies demonstrate that several early Paleozoic volcanogenic massive sulfide (VMS) Cu-polymetallic and porphyry Cu deposits were discovered in the northern part of Eastern Tianshan. This study presents zircon U-Pb, whole-rock geochemical, and Sr-Nd isotopic data for granites and diorites from the Huangtupo VMS Cu-Zn deposit, northern part of the Eastern Tianshan. Our results can provide constraints on the genesis of intermediate and felsic intrusions as well as early Paleozoic geodynamic setting of the northern part of Eastern Tianshan. LA-ICP-MS zircon U-Pb analyses suggest that the granites and diorites were formed at 435 ± 2 Ma and 440 ± 2 Ma, respectively. Geochemical characteristics suggest that the Huangtupo granites and diorites are metaluminous rocks, exhibiting typical subduction-related features such as enrichment in LILE and LREE and depletion in HFSE. The diorites have moderate Mg#, positive εNd(t) values (+6.4 to +7.3), and young Nd model ages, indicative of a depleted mantle origin. The granites exhibit mineral assemblages and geochemical characteristics of I-type granites, and they have positive εNd(t) values (+6.7 to +10.2) and young Nd model ages, suggesting a juvenile crust origin. The early Paleozoic VMS Cu-polymetallic and porphyry Cu deposits in the northern part of Eastern Tianshan were genetically related. The formation of the early Paleozoic magmatic rocks as well as VMS and porphyry Cu deposits in the northern part of Eastern Tianshan was due to a southward subduction of the Junggar oceanic plate.

  16. Regional Development of Eastern Slovakia

    Directory of Open Access Journals (Sweden)

    Monika Hergezelová

    2017-08-01

    Full Text Available Purpose and Originality: The aim of the work is to provide an overview of regional development in Eastern Slovakia, where are Košice and Prešov Region. The originality of the work lies in the work of enriching the SWOT analysis from the author Eve Rajčáková, which is given in the book deals with the issue of Regional development and regional policy of the European Union and Slovakia. Research question: The conditions of life of people in eastern Slovakia. Method: For writing this contribution will be used method of analysis and statistics. Knowledge on this subject have been looking on the internet and in books and sources of information publicly available. Using the data collected, we dealt with the issue of regional development in the Košice and Prešov regions. Results: The topic was the beginning focused on the overall characteristics of eastern Slovakia. Furthermore, we are at work we dealt with social and economic phenomena in both regions of eastern Slovakia. We focused on GDP, unemployment and tourism, which is in the region is widespread. Society: It is well known that there are obviously different living conditions in eastern Slovakia as in other parts of Slovakia. People are forced to, mainly because of employment, leave their region to move or commute to work to the west. The paper point out the right of this negative phenomenon that is quite visible - high unemployment. Limitations: The limits of work are limited by problems of regional development in eastern Slovakia, mainly focusing on economic and social phenomena in the society.

  17. Orogenic plateau growth: Expansion of the Turkish-Iranian Plateau across the Zagros fold-and-thrust belt

    Science.gov (United States)

    Allen, M. B.; Saville, C.; Blanc, E. J.-P.; Talebian, M.; Nissen, E.

    2013-03-01

    This paper shows how the Turkish-Iranian Plateau grows laterally by incrementally incorporating adjacent parts of the Zagros fold-and-thrust belt. The limit of significant, seismogenic, thrusting in the Zagros (Mw > 5) occurs close to the regional 1250 m elevation contour. The seismicity cutoff is not a significant bedrock geology boundary. Elevations increase northward, toward regional plateau elevations of 2 km, implying that another process produced the extra elevation. Between the seismogenic limit of thrusting and the suture, this process is a plausibly ductile thickening of the basement, suggesting depth-dependent strain during compression. Similar depth-dependant crustal strain may explain why the Tibetan plateau has regional elevations 1500 m greater than the elevation limit of seismogenic thrusting at its margins. We estimate 68 km shortening across the Zagros Simply Folded Belt in the Fars region, and 120 km total shortening of the Arabian plate. The Dezful Embayment is a low strain zone in the western Zagros. Deformation is more intense to its northeast, in the Bakhtyari Culmination. The orogenic taper (across strike topographic gradient) across the Dezful Embayment is 0.0004, and across the Bakhtyari Culmination, 0.022. Lateral plateau growth is more pronounced farther east (Fars), where a more uniform structure has a taper of 0.010 up to elevations of 1750 m. A >100 km wide region of the Zagros further northeast has a taper of 0.002 and is effectively part of the Turkish-Iranian Plateau. Internal drainage enhances plateau development but is not a pre-requisite. Aspects of the seismicity, structure, and geomorphology of the Zagros do not support critical taper models for fold-and-thrust belts.

  18. Cenozoic Deformation of the Tarim Basin (Xinjiang, China): a Record of the Deformation Propagation through the Asian Orogenic System

    Science.gov (United States)

    Laborde, A.; Barrier, L.; Simoes, M.; Li, H.

    2016-12-01

    During the Cenozoic, the ongoing India-Eurasia collision resulted in the formation of the Himalayan-Tibetan plateau and reactivated the Tian Shan and Altai ranges located thousands of kilometers further north. Despite numerous studies carried out on the geology and tectonics of this large convergent orogenic system, several mechanisms remain controversial such as the stress propagation through the Asia Continent or the strain partitioning between crustal thickening and lateral extruding of its lithosphere. Located between the Tibetan Plateau and the Tian Shan Range, the Tarim Basin and its several kilometres thick Cenozoic sediments derived from the surrounding mountain belts are key recorders to reconstruct the evolution of the latters. Moreover, this basin is often considered as a relatively rigid block, which behaved as a secondary ``indenter'' transmitting collisional stresses to the Tian Shan. However, due to the size of the Tarim and its thick Cenozoic sedimentary series hiding most of its structures, the constraints on the spatial distribution and timing of the its Cenozoic deformation remain fragmentary. Therefore, the main objective of our study was to produce a synthetic view of this deformation at the scale of the whole basin. Based on numerous surface and subsurface data (satellite images, field surveys, seismic profiles, and well data), we established a tectonic map of the Cenozoic structures in the region and built balanced geological cross-sections across the basin. Our surface and subsurface observations confirm that, contrary to what had been proposed, the Tarim block has also undergone a major deformation during the Cenozoic. The quantification and history of this deformation provide useful insights into the modalities of the crustal shortening in the area and the problems of stress propagation and strain partitioning following the Indo-Asian collision.

  19. Accreted seamounts in North Tianshan, NW China: Implications for the evolution of the Central Asian Orogenic Belt

    Science.gov (United States)

    Yang, Gaoxue; Li, Yongjun; Kerr, Andrew C.; Tong, Lili

    2018-03-01

    The Carboniferous Bayingou ophiolitic mélange is exposed in the North Tianshan accretionary complex in the southwestern part of the Central Asian Orogenic Belt (CAOB). The mélange is mainly composed of serpentinised ultramafic rocks (including harzburgite, lherzolite, pyroxenite, dunite and peridotite), pillowed and massive basalts, layered gabbros, radiolarian cherts, pelagic limestones, breccias and tuffs, and displays block-in-matrix structures. The blocks of ultramafic rocks, gabbros, basalts, cherts, and limestones are set in a matrix of serpentinised ultramafic rocks, massive basalts and tuffs. The basaltic rocks in the mélange show significant geochemical heterogeneity, and two compositional groups, one ocean island basalt-like, and the other mid-ocean ridge-like, can be distinguished on the basis of their isotopic compositions and immobile trace element contents (such as light rare earth element enrichment in the former, but depletion in the latter). The more-enriched basaltic rocks are interpreted as remnants/fragments of seamounts, derived from a deep mantle reservoir with low degrees (2-3%) of garnet lherzolite mantle melting. The depleted basalts most likely formed by melting of a shallower spinel lherzolite mantle source with ∼15% partial melting. It is probable that both groups owe their origin to melting of a mixture between plume and depleted MORB mantle. The results from this study, when integrated with previous work, indicate that the Junggar Ocean crust (comprising a significant number of seamounts) was likely to have been subducted southward beneath the Yili-Central Tianshan block in the Late Devonian-Early Carboniferous. The seamounts were scraped-off and accreted along with the oceanic crust in an accretionary wedge to form the Bayingou ophiolitic mélange. We present a model for the tectonomagmatic evolution of this portion of the CAOB involving prolonged intra-oceanic subduction with seamount accretion.

  20. Eastern European retailers and wholesalers' buying behaviour

    DEFF Research Database (Denmark)

    Esbjerg, Lars; Stacey, Julia

    1999-01-01

    During the last ten years, retailing in Eastern Europe has undergone considerable changes. The entry of Western European retail chains into Eastern Europe has helped accelerate the distributive trade of Eastern Europe. But what does it take to sell fish and cheese to retailers and wholesalers...... in Eastern Europe compared to Western Europe? Eastern European buyers attach great importance to other aspects when they list new suppliers and products than does Western European retailing. These are the results of a MAPP study of Eastern European retail and wholesale buying behaviour for fish and cheese....... Low prices and favourable terms of payment are most important when retailers in Eastern Europe buy fish and cheese. Then follows the supplier's range of products, trustworthiness of the supplier and product quality. Eastern European wholesalers also rank price and financial conditions as most...

  1. Eastern Africa Social Science Research Review: Contact

    African Journals Online (AJOL)

    Eastern Africa Social Science Research Review: Contact. Journal Home > About the Journal > Eastern Africa Social Science Research Review: Contact. Log in or Register to get access to full text downloads.

  2. Common Pb isotope mapping of UHP metamorphic zones in Dabie orogen, Central China: Implication for Pb isotopic structure of subducted continental crust

    Science.gov (United States)

    Shen, Ji; Wang, Ying; Li, Shu-Guang

    2014-10-01

    We report Pb isotopic compositions for feldspars separated from 57 orthogneisses and 2 paragneisses from three exhumed UHPM slices representing the North Dabie zone, the Central Dabie zone and the South Dabie zone of the Dabie orogen, central-east China. The feldspars from the gneisses were recrystallized during Triassic continental subduction and UHP metamorphism. Precursors of the orthogneisses are products of Neoproterozoic bimodal magmatic events, those in north Dabie zone emplaced into the lower crust and those in central and south Dabie zones into middle or upper crust, respectively. On a 207Pb/204Pb vs. 206Pb/204Pb diagram, almost all orthogneisses data lie to the left of the 0.23 Ga paleogeochron and plot along the model mantle evolution curve with the major portion of the data plotting below it. On a 208Pb/204Pb vs. 206Pb/204Pb diagram the most of data of north Dabie zone extend in elongate arrays along the lower crustal curve and others extend between the lower crustal curve to near the mantle evolution curve for the plumbotectonics model. This pattern demonstrates that the Pb isotopic evolution of the feldspars essentially ended at 0.23 Ga and the orthogneiss protoliths were principally dominated by reworking of ancient lower crust with some addition of juvenile mantle in the Neoproterozoic rifting tectonic zone. According to geological evolution history of the locally Dabie orogen, a four-stage Pb isotope evolution model including a long time evolution between 2.0 and 0.8 Ga with a lower crust type U/Pb ratio (μ = 5-6) suggests that magmatic emplacement levels of the protoliths of the orthogneisses in the Dabie orogen at 0.8 Ga also play an important role in the Pb evolution of the exhumed UHPM slices, corresponding to their respective Pb characters at ca. 0.8-0.23 Ga. For example, north Dabie zone requires low μ values (3.4-9.6), while central and south Dabie zones require high μ values (10.9-17.2). On the other hand, Pb isotopic mixing between

  3. Petrogenesis of granitoids and associated xenoliths in the early Paleozoic Baoxu and Enping plutons, South China: Implications for the evolution of the Wuyi-Yunkai intracontinental orogen

    Science.gov (United States)

    Yu, Yang; Huang, Xiao-Long; Sun, Min; He, Peng-Li

    2018-05-01

    The early Paleozoic Wuyi-Yunkai orogen was associated with extensive felsic magmatic activities and the orogenic core was mainly distributed in the Yunkai and Wugong domains located in the western Cathaysia block and in the Wuyi domain located in the central part of the Cathaysia block. In order to investigate the evolution of the Wuyi-Yunkai orogen, elemental and Sr-Nd isotopic analyses were performed for granites from the Baoxu pluton in the Yunkai domain and from the Enping pluton in the central part of the Cathaysia block. The Baoxu pluton consists of biotite granite with abundant xenoliths of gneissic granite, granodiorite and diorite, and the Enping pluton is mainly composed of massive granodiorite. Biotite granites (441 ± 5 Ma) and gneissic granite xenolith (443 ± 4 Ma) of the Baoxu pluton are all weakly peraluminous (A/CNK = 1.05-1.10). They show high Sr/Y and La/Yb ratios and have negative bulk-rock εNd(t) values (-7.0 to -4.4), which are similar to coeval gneissic S-type granites in the Yunkai domain and were probably derived from dehydration melting of a sedimentary source with garnet residue in the source. Granodiorites (429 ± 3 Ma) from Enping and granodiorite xenolith (442 ± 4 Ma) from Baoxu are metaluminous and have REE patterns with enriched light REE and flat middle to heavy REE, possibly generated by the dehydration melting of an igneous basement at middle to lower crustal level. Diorite xenolith from Baoxu is ultrapotassic (K2O = 4.9 wt%), has high contents of MgO (7.0 wt%), Cr (379 ppm) and Ni (171 ppm) and shows pronounced negative Nb, Ta and Ti anomalies. This xenolith also has negative εNd(t) value (-3.6) and low Rb/Ba and high Ba/Sr ratios, and is thus interpreted to be derived from an enriched lithospheric mantle with the breakdown of phlogopite. Early Paleozoic I- and S-type granites in the Wuyi-Yunkai orogen mostly have negative εNd(t) values and do not have juvenile components, consistent with genesis by an intracontinental

  4. THE FIELD OF RECENT TECTONIC STRESSES IN CENTRAL AND SOUTH-EASTERN ASIA

    Directory of Open Access Journals (Sweden)

    Yu. L. Rebetsky

    2014-01-01

    Global CMT Database, reconstructions based on the first catalog are mapped. In the maps showing consolidated patterns of the state of stresses, spacious areas of horizontal extension of the crust in Tibet are clearly identified. In the south, such areas are bordered by regions of horizontal compression of the crust in Himalaya; in the north and north-east, they are bordered by regions of horizontal shear of the crust in East Kunlun. According to results of calculations at stage 2 of the method of cataclastic analyses, the crust in the central part of Tibet is subject to intensive confining pressure and lateral compression that is reduced in the neighboring regions. The crust in the southern and northern parts of Pamir is also subject to horizontal extension and shear. Regions of horizontal compression are located to the north, west and south of Pamir. Regulations of the field of recent tectonic stresses of Tibet and Pamir, which are revealed in this study, can be explained by the concept of ‘tectonic spreading’ of these regions due to gravity, which causes intensive horizontal spreading of the crust in Himalaya when the southern boundary of Tibet bends outwards and spreads over the Indian ‘indenter’ moving in the north–north-eastern direction. It is suggested by the data on horizontal extension of the crust in Tibet and underthrusting shear stresses over the horizontal zones that the impact Indian ‘indenter’ does not go beyond the crust of Pamir and the crust of the central parts of Tibet which is located above the long-term active mantle plume.  

  5. Currency substitution in Eastern Europe

    NARCIS (Netherlands)

    van Aarle, B.; Budina, N.

    1995-01-01

    Monetary instability during the transition process from a command economy to a market economy has induced a considerable increase in currency substitution in Eastern Europe. Currency substitution itself affects monetary stability since it reduces the stability of velocity. This paper investigates

  6. Anthracnose Diseases of Eastern Hardwoods

    Science.gov (United States)

    Frederick H. Berry

    1985-01-01

    Anthracnose diseases of hardwood trees are widespread throughout the Eastern United States. The most common symptom of these diseases is dead areas or blotches on the leaves. Because of the brown and black, scorched appearance of the leaves, the diseases are sometimes called leaf blight.

  7. Citizenship norms in Eastern Europe

    NARCIS (Netherlands)

    Coffé, H.R.; Lippe, T. van der

    2010-01-01

    Research on Eastern Europe stresses the weakness of its civil society and the lack of political and social involvement, neglecting the question: What do people themselves think it means to be a good citizen? This study looks at citizens’ definitions of good citizenship in Poland, Slovenia, the Czech

  8. Uranium mining in Eastern Germany

    International Nuclear Information System (INIS)

    Sauer, H.D.

    1990-01-01

    A problem which simply does not exist in Western Germany is the uranium mining in the South of Eastern Germany (SDAG Wismuth). The cleaning up and control measure which are urgently needed will be a task for more than one generation. (orig./HP) [de

  9. An analogue of long-term stability of flow-path structure in crystalline rocks distributed in the orogenic belt, Japan

    Energy Technology Data Exchange (ETDEWEB)

    Yoshida, H. [Nagoya University, University Museum Material Research Section, 464-8601, Chikusa, Nagoya, 464-8601 (Japan)]. E-mail: dora@num.nagoya-u.ac.jp; Takeuchi, M. E-mail: takeuchi@eps.nagoya-u.ac.jp

    2004-07-01

    In the orogenic belt, in the Japanese islands, crystalline rocks from the youngest to older ages and of different orders have been identified which have formed massive areas. The fracture system observed within these rock masses implies that the groundwater and solute can be conducted through the fracture's network. It is expected that the nuclides can be retarded due to chemical sorption and/or physical retardation by the fracture fillings and fracture open pore geometry. Most of the evaluation framework of the nuclides retardation process in the geological disposal of high level radioactive waste (HLW) is, however, basically taken into account in the present geological state, without changes of structural and mineralogical features, and in its influence on the groundwater flow system over a long period of time. This paper seeks analogous evidence that can provide the confidence of such evaluation methodology and its long-term applicability. Here, we describe the fracture system developed in the crystalline rock with the different ages intruded in the orogenic belt in order to build the long-term fracturing and its 'stability' model. In particular, comparisons with the rock of 1.9-0.8 Ma Takidani Granodiorite (the youngest pluton in the world), ca. 67 Ma of Toki Granite and ca. 117 Ma Kurihashi Granodiorite located in central to northwest Japan suggest a unique characteristic of the fracture forming process and their relatively stable geometrical changing. This analogue enables us to provide a model to build the confidence of a safety context applicable for the geological setting under the orogenic field with a long-term scale. The model may also be useful for other stable tectonic settings as well as for a site characterisation methodology of crystalline rock for HLW geological disposal. (author)

  10. A Mesozoic orogenic cycle from post-collision to subduction in the southwestern Korean Peninsula: New structural, geochemical, and chronological evidence

    Science.gov (United States)

    Park, Seung-Ik; Kwon, Sanghoon; Kim, Sung Won; Hong, Paul S.; Santosh, M.

    2018-05-01

    The Early to Middle Mesozoic basins, distributed sporadically over the Korean Peninsula, preserve important records of the tectonic history of some of the major orogenic belts in East Asia. Here we present a comprehensive study of the structural, geochemical, geochronological, and paleontological features of a volcano-sedimentary package, belonging to the Oseosan Volcanic Complex of the Early to Middle Mesozoic Chungnam Basin, within the Mesozoic subduction-collision orogen in the southwestern Korean Peninsula. The zircon U-Pb data from rhyolitic volcanic rocks of the complex suggest Early to Middle Jurassic emplacement age of ca. 178-172 Ma, harmonious with plant fossil taxa found from the overlying tuffaceous sedimentary rock. The geochemical data for the rhyolitic volcanic rocks are indicative of volcanic arc setting, implying that the Chungnam Basin has experienced an intra-arc subsidence during the basin-expanding stage by subduction of the Paleo-Pacific (Izanagi) Plate. The Jurassic arc-related Oseosan Volcanic Complex was structurally stacked by the older Late Triassic to Early Jurassic post-collisional basin-fill of the Nampo Group by the Jangsan fault during basin inversion. The Late Jurassic to Early Cretaceous K-feldspar and illite K-Ar ages marked the timing of inversion tectonics, contemporaneous with the magmatic quiescence in the southern Korean Peninsula, likely due to flat-lying or low-angle subduction. The basin evolution history preserved in the Mesozoic Chungnam Basin reflects a Mesozoic orogenic cycle from post-collision to subduction in the southwestern Korean Peninsula. This, in turn, provides a better understanding of the spatial and temporal changes in Mesozoic tectonic environments along the East Asian continental margin.

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

    Science.gov (United States)

    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

  12. An interpretation of the aeromagnetic data covering portion of the Damara orogenic belt, with special reference to the occurrence of uraniferous granite

    International Nuclear Information System (INIS)

    Corner, B.

    1982-12-01

    This thesis comprises primarily palaeomagnetic studies within the Damara orogenic belt of South West Africa (Namibia), as well as an interpretation of the regional structure, utilizing published aeromagnetic data. The prime objectives of the study were to aid uranium exploration programmes in this area by establishing any possible magnetic relationships associated with the uraniferous granites in the area, and to interpret regional structure from the aeromagnetic data. Cursory interpretation of the airborne radiometric data is also undertaken. Gravity traverses, conducted across three dome structures with which uranium mineralisation is intimately associated, are interpreted in order to determine the origin of these structures

  13. A mass-wasting dominated Quaternary mountain range, the Coastal Range in eastern Taiwan

    Science.gov (United States)

    Hsieh, Meng-Long; Hogg, Alan; Song, Sheng-Rong; Kang, Su-Chen; Chou, Chun-Yen

    2017-12-01

    Fluvial bedrock incision, which creates topographic relief and controls hillslope development, has been considered the key medium linking denudation and tectonic uplift of unglaciated mountains. This article, however, shows a different scenario from the Coastal Range in eastern Taiwan. This range, with the steepness inherited from pre-orogenic volcanoes, has been subject to mass wasting even before its emergence above sea level no earlier than Middle Pleistocene. Numerous terraced alluvial fans/fan deltas record the ancient mass movements of the range, including rock avalanches. Multiple radiocarbon dates sequences not clearly related to the known climate-change events, and are believed to have been triggered mainly by severe rainfall events, large earthquakes, or their combinations. The resulting fluctuation of sediment yield has episodically changed river behavior, forming river terraces in catchments >1 km2. Alluvial terraces are typically exhibited close to the source ridges of mass movements, and strath terraces along the downstream parts of rivers. Both were created when enormous sediment supply had exceeded or matched the prevailing river transport capacity. This process, along with the protection by giant boulders from mass movement, disturbed the long-term incision trend of rivers in response to tectonic uplift. As a result, the observed Holocene bedrock incision at most sites has not kept pace with the tectonic uplift. The spatial contrast in mass-wasting histories further accounts for the great diversity of the terrace sequences, even in areas with similar tectonic and base-level conditions.

  14. Tectonic setting and strain analysis of Halaban Area, Eastern Arabian Shield, Saudi Arabia

    Science.gov (United States)

    Alamri, Y. A., II; Kassem, O. M. K.

    2016-12-01

    Finite strain technique was applied for Abt schist, sheared granitoids and volcanosedimentary rocks exposed at Halaban area, Eastern Arabian Shield. This study aims to attempt to decipher the relationship of these lithologies to nappe contacts and to clarify the nature of subhorizontal foliation pervasively recorded in the Halaban area. The Rf/φ and Fry methods are utilized on quartz and feldspar porphyroclasts, as well as on mafic crystals, such as hornblende and biotite, in eighteen samples. The X/Z axial ratios range from 1.12 to 4.99 for Rf/φ method and from 1.65 to 4.00 for Fry method. The direction of finite strain for the long axes displays clustering along the WNW trend (occasionally N) with slight plunging. The Z axes are subvertical and associated with a subhorizontal foliation. The data reveal oblate strain symmetry (flattening) and the strain magnitudes show no considerable increase towards the tectonic contacts. The obtained finite-strain data demonstrate that the sheared granitoids are mildly to moderately deformed. It is suggested that the accumulation of finite strain was not associated with any significant volume change. The penetrative subhorizontal foliation was concurrent with thrusting and shows nearly the same attitudes of tectonic contacts with the overlying nappes. Field relations and observations, together with finite stain data, are inconsistent with the proposed idea that nappes in orogens resulted from simple-shear deformation.

  15. Petroleum prospectivity of the onshore Gaspe and offshore Anticosti Basins, eastern Canada

    International Nuclear Information System (INIS)

    Durling, P.; Martel, T.; Waldron, J.W.F.

    1998-01-01

    The development of oil and gas reserves on the Scotian Shelf and the Grand Banks of Newfoundland has sparked a renewed interest in the onshore Gaspe-Connecticut Valley Synclinorium (GCVS) and the offshore Anticosti Basin. The geologic history of each basin was described and some of the geological relationships that suggest the presence of hydrocarbon resources in the area were reviewed. The Anticosti Basin developed in a rift and open marine shelf environment during the early Cambrian period. Petroleum exploration in the Basin began in the early 1960s when Imperial Oil collected 435 km of single channel seismic reflection data - enough to identify several drilling locations. Eight wells were drilled on the island which resulted in a number of shows of oil and gas. The GCVS was developed within the Appalachian Orogen and is comprised of fine grained siliciclastic turbidites. The structural geology of the GCVS is more complicated than the Anticosti Basin. Petroleum exploration in the GCVS has, for the most part, been in the eastern part of the Gaspe Peninsula where one producing well is located. The central part is mainly unexplored for petroleum resources

  16. S-type granite from the Gongpoquan arc in the Beishan Orogenic Collage, southern Altaids: Implications for the tectonic transition

    Science.gov (United States)

    Wang, Xinyu; Yuan, Chao; Zhang, Yunying; Long, Xiaoping; Sun, Min; Wang, Lixing; Soldner, Jeremie; Lin, Zhengfan

    2018-03-01

    Voluminous Paleozoic intrusions occur in the Beishan Orogenic Collage (BOC) and their genesis and tectonic background are important to reconstruct the accretion-collision processes in the southernmost Altaids. Paleozoic is an important period for arc development in the BOC, where the Gongpoquan and Huaniushan arcs are located. There are two pulses of magmatism in the Huaniushan and Gongpoquan arcs, i.e., the ca. 470-423 Ma I-type and ca. 424-395 Ma S- and A-type granitoids. In this study, we focus on two peraluminous granitic plutons in the Gongpoquan arc, i.e., the Baitoushan muscovite granite and Haergen two-mica granite, aiming at unraveling their petrogenesis and tectonic background. Zircon LA-ICP-MS U-Pb dating yields emplacement ages of ca. 409-395 Ma and ca. 409 Ma for the Baitoushan and Haergen plutons, respectively. Both the granitic plutons are strongly peraluminous with A/CNK ratios of 1.10-1.20, indicative of S-type affinities. The rocks are characterized by high SiO2 and K2O contents with high CaO/Na2O ratios. Moreover, the rocks possess low MgO contents, Rb/Sr and Rb/Ba ratios, together with their relatively high initial 87Sr/86Sr ratios (0.7139-0.7152) and less radiogenic εNd(t) values (-3.15 to -5.17), implying a clay-poor and plagioclase-rich crustal source. Compared with earlier pulse of arc-related magmatism (ca. 470-423 Ma), the latter pulse of magmatism (ca. 424-395 Ma) consists mainly of "normal granite" characterized by higher SiO2 (>66%) and K2O contents, weaker fractionated REE patterns and lower δEu values, and gabbroic to dioritic intrusions are only sporadic. Moreover, the granitoids of the latter pulse show variable but more crust-like Sr-Nd isotopic compositions ((87Sr/86Sr)0 = 0.7038-0.7327; εNd(t) = -6.70 to +0.33) than the earlier ones ((87Sr/86Sr)0 = 0.7024-0.7080; εNd(t) = -2.56 to +8.86), indicating that the Early Devonian (ca. 424-395 Ma) experienced extensive crustal melting with minor involvement of mantle materials

  17. The Origin of the Chinese Central Tianshan Block in the Southern Central Asian Orogenic Belt: Evidence from Detrital Zircon Study

    Science.gov (United States)

    Huang, Z.; Long, X.; Yuan, C.

    2016-12-01

    The Chinese Central Tianshan Block (CTB) is one of the oldest continental fragments in the southern Central Asian Orogenic Belt (CAOB). Although it is vital for understanding the evolution of the CAOB, its origin has been poorly studied. The CTB was previously suggested to have been originated from the North China, the South China, the Tarim cratons or the East European Craton (Baltica). A total of 165 concordant U-Pb and Hf isotopic analyses of detrital zircon are obtained from three meta-sediments in the CTB, including one meta-sandstone from Xingxingxia formation and one meta-sandstone as well as one quartzite from Kawabulake formation. Detrital zircon grains from the Xingxingxia and Kawabulake formations are dominated by respective youngest age populations at 1002 Ma and 930-960 Ma, providing constraints on the maximum depositional ages for these two formations. Zircon grains from the meta-sediments have very similar age distributions, with two dominant peaks at 0.93-1.0 Ga and 1.0-1.6 Ga and a minor peak at 2.3-2.7 Ga. They have similar Hf isotopic signatures, suggesting that the meta-sediments in the CTB share similar sedimentary provenance. The early Neoproterozoic detrital zircon grains are mainly local-derived, whereas the Paleo-Mesoproterozoic grains are both autochthonous and allochthonous. The occurrence of these Mesoproterozoic and Neoproterozoic zircon grains are coincident with the Nuna breakup and the Rodinia assembly. This suggests that the CTB might experience the tectonic switching of the Nuna to the Rodinia. The distinct Meso-Neoproterozoic age patterns and Hf isotopic compositions of these detrital grains from the CTB and the surrounding blocks indicate that the CTB was not located close to the North China, the South China or the Tarim cratons in Precambrian. Our new data suggest that the CTB was most likely once a part of the East European Craton before the Neoproterozoic. This study was supported by National Basic Research Program of China

  18. Nature and source of the ore-forming fluids associated with orogenic gold deposits in the Dharwar Craton

    Directory of Open Access Journals (Sweden)

    Biswajit Mishra

    2018-05-01

    Full Text Available Neoarchean orogenic gold deposits, associated with the greenstone-granite milieus in the Dharwar Craton include (1 the famous Kolar mine and the world class Hutti deposit; (2 small mines at Hira-Buddini, Uti, Ajjanahalli, and Guddadarangavanahalli; (3 prospects at Jonnagiri; and (4 old mining camps in the Gadag and Ramagiri-Penakacherla belts. The existing diametric views on the source of ore fluid for formation of these deposits include fluids exsolved from granitic melts and extracted by metamorphic devolatilization of the greenstone sequences. Lode gold mineralization occurs in structurally controlled higher order splays in variety of host rocks such as mafic/felsic greenstones, banded iron formations, volcaniclastic rocks and granitoids. Estimated metamorphic conditions of the greenstones vary from lower greenschist facies to mid-amphibolite facies and mineralizations in all the camps are associated with distinct hydrothermal alterations. Fluid inclusion microthermometric and Raman spectroscopic studies document low salinity aqueous-gaseous (H2O + CO2 ± CH4 + NaCl ore fluids, which precipitated gold and altered the host rocks in a narrow P–T window of 0.7–2.5 kbar and 215–320 °C. While the calculated fluid O- and C-isotopic values are ambiguous, S-isotopic compositions of pyrite-precipitating fluid show distinct craton-scale uniformity in terms of its reduced nature and a suggested crustal sulfur source.Available ages on greenstone metamorphism, granitoid plutonism and mineralization in the Hutti Belt are tantamount, making a geochronology-based resolution of the existing debate on the metamorphic vs. magmatic fluid source impossible. In contrast, tourmaline geochemistry suggests involvement of single fluid in formation of gold mineralization, primarily derived by metamorphic devolatilization of mafic greenstones and interlayered sedimentary rocks, with minor magmatic contributions. Similarly, compositions of scheelite

  19. Central and eastern European activities

    International Nuclear Information System (INIS)

    Rea, J.L.

    1993-01-01

    The Florida State University/Technical University of Budapest environmental research center, Center for Hungarian/American Environmental Research, Studies and Exchanges (CHAERSE), provides a resource base for information and technologies that is used to address near- and long-term environmental problems within the Department of Energy (DOE) complex and in Central and Eastern Europe. The CHAERSE is used as a technology transfer conduit for environmental restoration and waste management (ER/WM) problems and solutions. The International Technology Exchange Division (ITED) used the CHAERSE as one source of information for the identification of international ER/WM technologies being developed in Central and Eastern Europe. This was accomplished by matching high-priority problems in that region to high-priority problems in the DOE Complex; conducting symposia, meetings and workshops with international environmental experts; and identifying innovative technologies

  20. Nuclear power in Eastern Europe

    International Nuclear Information System (INIS)

    Sturm, R.

    1993-01-01

    This paper analyses the operating experience of nuclear power plants in Eastern and Western Europe, the former Soviet Union and the United States to investigate differences in the effects of learning, technical change and the effect of recent political developments. The performance of Soviet-designed reactors compares favourably with Western reactors on the standard performance measures. However, learning curve estimates reveal a disturbing trend: the former Soviet Union and all countries in Eastern Europe experience increasing unplanned losses as plants age, whereas all Western countries reduce their unplanned losses. A similar ''forgetting'' phenomenon is observable for plant availability and there is some evidence that the recent political and economic reorganization have exacerbated this trend. (Author)

  1. Petrogenesis and tectonic implications of Late Devonian arc volcanic rocks in southern Beishan orogen, NW China: Geochemical and Nd-Sr-Hf isotopic constraints

    Science.gov (United States)

    Guo, Qian-Qian; Chung, Sun-Lin; Xiao, Wen-Jiao; Hou, Quan-Lin; Li, Shan

    2017-05-01

    Late Devonian (ca. 370 Ma) volcanic rocks provide important information about the nature of magmatism during the tectonic transition between the Early and Late Paleozoic in the Beishan orogen, southern Central Asian Orogenic Belt. They are predominantly an andesitic-dacitic-rhyolitic assemblage, characterized by alkali contents ranging from slightly calcic to slightly alkaline. The rhyolitic rocks are generally ferroan, whereas the andesitic rocks are magnesian. These volcanic rocks exhibit similar trace element characteristics to those of continental arcs. Strongly negative εNd(t) values (- 2.8 to - 3.6) and high Sr isotopic compositions (initial 87Sr/86Sr = 0.7036-0.7108) suggest that they are mainly derived from an ancient crust. However, the positive zircon εHf(t) values (+ 1.4 to + 16.4) support the role of juvenile components in their genesis, indicating the significant input of new mantle-derived magmas. These characteristics imply a hybrid derivation, from an ancient crustal source with the addition of juvenile materials during magma genesis, or perhaps heterogeneous contamination or hybridization during magma emplacement. Combined with the regional geology, our results indicate that the Late Devonian magmatism resulted from a southward retreat of the subduction zone, which records significant continental crustal growth in a transitional arc or an accretionary arc setting. The distinct geochemical compositions, especially the Nd-Hf isotope decoupling of the Dundunshan volcanic rocks, imply a significant change in the geodynamic setting in the Late Paleozoic.

  2. Changes in dip and frictional properties of the basal detachment controlling orogenic wedge propagation and frontal collapse: The external central Betics case

    Science.gov (United States)

    Jimenez-Bonilla, A.; Torvela, T.; Balanyá, J. C.; Expósito, I.; Díaz-Azpiroz, M.

    2016-12-01

    Thin-skinned fold-and-thrust belts (FTBs) have been extensively studied through both field examples and modeling. The overall dynamics of FTBs are, therefore, well understood. One less understood aspect is the combined influence of across-strike changes in the detachment properties and the basement topography on the behavior of an orogenic wedge. In this paper, we use field data together with reflection seismic interpretation from the external zones of the central Betics FTB, southern Spain, to identify a significant increase in the wedge basal dip (a basement "threshold") coinciding with the pinch-out of a weak substrate. This induced both changes to the wedge geometry and to the basal friction, which in turn influenced the wedge dynamics. The changing dynamics led to a transient "stagnation" of the FTB propagation, topographic buildup, and subsequent collapse of the FTB front. This in turn fed an important Langhian depocenter made up of mass transport deposits. Coevally with the FTB propagation, extension took place both parallel and perpendicular to the orogenic trend. This case study illustrates how across-strike changes in wedge basal properties can control the detailed behavior of a developing FTB front, but questions remain regarding the time-space interaction and relative importance of the basal parameters.

  3. Thermobarometry and electron-microprobe Th-U-Pb monazite dating in garnet metapelites from the Capelinha Formation, Aracuai Orogen, Brazil

    Energy Technology Data Exchange (ETDEWEB)

    Queiroga, Glaucia Nascimento; Martins, Maximiliano de Souza; Castro, Marco Paulo de; Jordt-Evangelista, Hanna; Silva, Ana Lucia da, E-mail: glauciaqueiroga@yahoo.com.br, E-mail: maximilianomartins@yahoo.com.br, E-mail: marco_pcastro@yahoo.com, E-mail: hanna@degeo.ufop.br, E-mail: alucia.silva@hotmail.com [Universidade Federal de Ouro Preto (UFOP), Ouro Preto, MG (Brazil). Escola de Minas. Departamento de Geologia; Pedrosa-Soares, Antonio Carlos, E-mail: pedrosa@igc.ufmg.br [Universidade Federal de Minas Gerais (UFMG), Belo Horizonte, MG (Brazil). Instituto de Geociencias. Departamento de Geologia; Schulz, Bernhard, E-mail: bernhard.schulz@mineral.tu-freiberg.de [TU Bergakademie - Institute of Mineralogy, Freiberg - Saxony (Germany)

    2016-01-15

    The Capelinha Formation (Macaubas Group) consists of a lower quartzitic unit with metamafic intercalations and an upper metapelitic sequence. It occurs in a complex tectono-metamorphic sector of the Aracuai orogen, where post-collisional collapse-related structures superimposed collisional structures. The garnet-bearing assemblages started crystallization in the collisional deformation stage that formed the main regional foliation around 570 Ma. Garnet porphyroblasts display a well developed growth zonation of Fe-Mg-Ca-Mn and show, from core to rim, increasing almandine and pyrope contents in contrast with decreasing grossular and spessartine contents. Mineral relations and microstructures provide criteria for local equilibria and a structurally controlled application of geothermobarometry based on cation exchange and net transfer reactions. The P-T values calculated from cores to rims of garnets, aligned along clockwise trends, resulted in increasing temperatures (from 500 deg C up to 620 deg C) under decompression conditions (from 8.0 kbar to 4.5 kbar). The Th-UPb dating of homogeneous monazites by electron microprobe revealed a recrystallization period at around 490 - 480 Ma. These ages can be related to the tectono-thermal event associated with the gravitational collapse, constraining the youngest time limit for metamorphic processes in the Aracuai orogen. (author)

  4. Museology History of Eastern Siberia

    Directory of Open Access Journals (Sweden)

    Natalia D. Firer

    2012-08-01

    Full Text Available The article is focused on the aspects of the establishment of the first museums and libraries in Eastern Siberia. The author considers the role of the museum in development of culture and public education in Minusinsk, Yeniseysk, notes the valuable contribution of the activities of merchants and intelligentsia to the museum business, as well as the reflection of the present and past of museums in Siberia.

  5. Eastern Africa Coastal Forest Programme

    OpenAIRE

    Younge, A.

    2002-01-01

    The eastern African coastal forest ecoregion is recognised as one of Africa’s centres of species endemism, and is distributed over six countries (Somalia, Kenya, Tanzania, Mozambique, Zimbabwe and Malawi). Most is found in Kenya, Tanzania and Mozambique, which form our focal region. The coastal forests are fragmented, small and surrounded by poor communities that have a high demand for land and forest resources. Although coastal forests have significant cultural and traditional...

  6. CIS/Eastern countries. A curtain raising on eastern Europe

    International Nuclear Information System (INIS)

    Anon.

    1998-01-01

    Slowly and laboriously a new russian petroleum industry is setting in. To illustrate this new scenery, statistical data and maps, giving the production and consumption rates are presented. Two big companies (Shell and B.P.) stand for the privatization of Rosneft, the russian petroleum group. The legal and financial petroleum aspects of Russian are changing but very slowly, attracting the western companies around the petroleum industry. But this interest remains careful. The european bank of investment (BEI) decided to take a financial share in the eastern energy. (A.L.B.)

  7. Paleozoic–early Mesozoic gold deposits of the Xinjiang Autonomous Region, northwestern China

    Science.gov (United States)

    Rui, Zongyao; Goldfarb, Richard J.; Qiu, Yumin; Zhou, T.; Chen, R.; Pirajno, Franco; Yun, Grace

    2002-01-01

    The late Paleozoic–early Mesozoic tectonic evolution of Xinjiang Autonomous Region, northwestern China provided a favorable geological setting for the formation of lode gold deposits along the sutures between a number of the major Eastern Asia cratonic blocks. These sutures are now represented by the Altay Shan, Tian Shan, and Kunlun Shan ranges, with the former two separated by the Junggar basin and the latter two by the immense Tarim basin. In northernmost Xinjiang, final growth of the Altaid orogen, southward from the Angara craton, is now recorded in the remote mid- to late Paleozoic Altay Shan. Accreted Early to Middle Devonian oceanic rock sequences contain typically small, precious-metal bearing Fe–Cu–Zn VMS deposits (e.g. Ashele). Orogenic gold deposits are widespread along the major Irtysh (e.g. Duyolanasayi, Saidi, Taerde, Kabenbulake, Akexike, Shaerbulake) and Tuergen–Hongshanzui (e.g. Hongshanzui) fault systems, as well as in structurally displaced terrane slivers of the western Junggar (e.g. Hatu) and eastern Junggar areas. Geological and geochronological constraints indicate a generally Late Carboniferous to Early Permian episode of gold deposition, which was coeval with the final stages of Altaid magmatism and large-scale, right-lateral translation along older terrane-bounding faults. The Tian Shan, an exceptionally gold-rich mountain range to the west in the Central Asian republics, is only beginning to be recognized for its gold potential in Xinjiang. In this easternmost part to the range, northerly- and southerly-directed subduction/accretion of early to mid-Paleozoic and mid- to late Paleozoic oceanic terranes, respectively, to the Precambrian Yili block (central Tian Shan) was associated with 400 to 250 Ma arc magmatism and Carboniferous through Early Permian gold-forming hydrothermal events. The more significant resulting deposits in the terranes of the southern Tian Shan include the Sawayaerdun orogenic deposit along the Kyrgyzstan

  8. Sedimentary records on the subduction-accretion history of the Russian Altai, northwestern Central Asian Orogenic Belt

    Science.gov (United States)

    Chen, Ming; Sun, Min

    2017-04-01

    The Russian Altai, comprising the northern segment of the Altai-Mongolian terrane (AM) in the south, the Gorny Altai terrane (GA) in the north and the intervening Charysh-Terekta-Ulagan-Sayan suture zone, is a key area of the northwestern Central Asian Orogenic Belt (CAOB). A combined geochemical and detrital zircon study was conducted on the (meta-)sedimentary sequences from the Russian Altai to reveal the tectono-magmatic history of these two terranes and their amalgamation history, which in turn place constraints on the accretionary orogenesis and crustal growth in the CAOB. The Cambrian-Ordovician meta-sedimentary rocks from the northern AM are dominated by immature sediments possibly sourced from intermediate-felsic igneous rocks. Geochemical data show that the sediments were likely deposited in a continental arc-related setting. Zircons separated from these rocks are mainly 566-475 Ma and 1015-600 Ma old, comparable to the magmatic records of the Tuva-Mongolian terrane and surrounding island arcs in the western Mongolia. The similar source nature, provenance and depositional setting of these rocks to the counterparts from the Chinese Altai (i.e., the southern AM) imply that the whole AM possibly represents a coherent accretionary prism of the western Mongolia in the early Paleozoic rather than a Precambrian continental block with passive marginal deposition as previously thought. In contrast, the Cambrian to Silurian (meta-)sedimentary rocks from the GA are characterized by a unitary zircon population with ages of 640-470 Ma, which were potentially sourced from the Kuznetsk-Altai intra-oceanic island arc in the east of this terrane. The low abundance of 640-540 Ma zircons (5%) may attest that this arc was under a primitive stage in the late Neoproterozoic, when mafic igneous rocks dominated. However, the voluminous 530-470 Ma zircons (95%) suggest that this arc possibly evolved toward a mature one in the Cambrian to early Ordovician with increasing amount of

  9. The Kalatongke magmatic Ni-Cu deposits in the Central Asian Orogenic Belt, NW China: product of slab window magmatism?

    Science.gov (United States)

    Li, Chusi; Zhang, Mingjie; Fu, Piaoer; Qian, Zhuangzhi; Hu, Peiqing; Ripley, Edward M.

    2012-01-01

    The Permian Kalatongke Ni-Cu deposits in the Central Asian Orogenic Belt are among the most important Ni-Cu deposits in northern Xinjiang, western China. The deposits are hosted by three small mafic intrusions comprising mainly norite and diorite. Its tectonic context, petrogenesis, and ore genesis have been highly contested. In this paper, we present a new model involving slab window magmatism for the Kalatongke intrusions. The origin of the associated sulfide ores is explained in the context of this new model. Minor amounts of olivine in the intrusions have Fo contents varying between 71 and 81.5 mol%, which are similar to the predicted values for olivine crystallizing from coeval basalts in the region. Analytic modeling based on major element concentrations suggests that the parental magma of the Kalatongke intrusions and the coeval basalts represent fractionated liquids produced by ˜15% of olivine crystallization from a primary magma, itself produced by 7-8% partial melting of depleted mantle peridotite. Positive ɛ Nd values (+4 to +10) and significant negative Nb anomalies for both intrusive and extrusive rocks can be explained by the mixing of magma derived from depleted mantle with 6-18% of a partial melt derived from the lower part of a juvenile arc crust with a composition similar to coeval A-type granites in the region, plus up to 10% contamination with the upper continental crust. Our model suggests that a slab window was created due to slab break-off during a transition from oceanic subduction to arc-arc or arc-continent collision in the region in the Early Permian. Decompression melting in the upwelling oceanic asthenosphere produced the primary magma. When this magma ascended to pond in the lower parts of a juvenile arc crust, it underwent olivine crystallization and at the same time triggered partial melting of the arc crust. Mixing between these two magmas followed by contamination with the upper crust after the magma ascended to higher crustal

  10. 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

    Science.gov (United States)

    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

  11. Reconstruction of multiple P-T-t stages from retrogressed mafic rocks: Subduction versus collision in the Southern Brasília orogen (SE Brazil)

    Science.gov (United States)

    Tedeschi, Mahyra; Lanari, Pierre; Rubatto, Daniela; Pedrosa-Soares, Antônio; Hermann, Jörg; Dussin, Ivo; Pinheiro, Marco Aurélio P.; Bouvier, Anne-Sophie; Baumgartner, Lukas

    2017-12-01

    The identification of markers of subduction zones in orogenic belts requires the estimation of paleo-geothermal gradients through pressure-temperature-time (P-T-t) estimates in mafic rocks that potentially derive from former oceanic units once. However, such markers are rare in supracrustal sequences specially in deeply eroded and weathered Precambrian orogens, and reconstructing their metamorphic history is challenging because they are commonly retrogressed and only preserve a few mineral relicts of high-pressure metamorphism. Metamorphosed mafic rocks from Pouso Alegre region of the Neoproterozoic Southern Brasília Orogen outcrop as rare lenses within continental gneisses. They have previously been classified as retrograde eclogites, based on the presence of garnet and the characteristic symplectitic texture replacing omphacite. These rocks were interpreted to mark the suture zone between the Paranapanema and São Francisco cratons. To test the possible record of eclogitic conditions in the Pouso Alegre mafic rocks, samples including the surrounding felsic rocks have been investigated using quantitative compositional mapping, forward thermodynamic modeling and in-situ dating of accessory minerals to refine their P-T-t history. In the metamorphosed mafic rocks, the peak pressure assemblage of garnet and omphacite (Jd20, reconstructed composition) formed at 690 ± 35 °C and 13.5 ± 3.0 kbar, whereas local retrogression into symplectite or corona occurred at 595 ± 25 °C and 4.8 ± 1.5 kbar. The two reactions were coupled and thus took place at the same time. A zircon U-Pb age of 603 ± 7 Ma was obtained for metamorphic rims and linked to the retrogression stage. Monazite and metamorphic zircon U-Th-Pb ages for the surrounding rocks are at ca. 630 Ma and linked to peak pressure conditions similar to the one recorded by the mafic rocks. The low maximal pressure of 14 kbar and the high geothermal gradient do not necessarily support subduction process

  12. Cultural Clues to the Middle Eastern Student

    Science.gov (United States)

    Parker, Orin D.; And Others

    1976-01-01

    Cultural patterns and characteristics of Middle Eastern students indicate their adaptability ease or difficulty in American society. Manners, paternalistic patterns, religion, and social relationships are discussed. (LBH)

  13. Re-membering Eastern Europe

    DEFF Research Database (Denmark)

    Wilken, Lisanne

    2016-01-01

    -Soviet states into the “Eurovision” has been represented and discussed in Britain and Denmark, two countries with their own complex and complicated relationship to "Europe". Taking the cue from a growing scholarly production that argues for the importance of pop culture in the construction of social...... for analysing (political) memory. It then discusses the ways that the “Eastern enlargement” of the Contest in the 1990s triggered discussions of borders and belonging in both a historical and contemporary perspective. Finally the paper zooms in on British and Danish debates of three post-Soviet states; Estonia...

  14. HOMED-Homicides Eastern Denmark

    DEFF Research Database (Denmark)

    Colville-Ebeling, Bonnie; Frisch, Morten; Lynnerup, Niels

    2014-01-01

    Background:An introduction to a forensic medical homicide database established at the Department of Forensic Medicine in Copenhagen. Content: The database contains substantial clinical and demographic data obtained in conjunction with medico-legal autopsies of victims and forensic clinical...... examinations of perpetrators in homicide cases in eastern Denmark. Validity and coverage: The database contains information on all homicide cases investigated at the Department of Forensic Medicine in Copenhagen since 1971. Coverage for the catchment area of the department is assumed to be very good because...

  15. Petrography, geochemistry and tectonic setting of Salmabad Tertiary volcanic rocks, southeast of Sarbisheh, eastern Iran

    Directory of Open Access Journals (Sweden)

    Masoumeh Goodarzi

    2014-10-01

    Full Text Available Introduction The area reviewed and studied in this paper is located 5 km southeast of Sarbisheh city at eastern border of the Lut block (Jung et al., 1983; Karimpour et al., 2011; Richards et al., 2012 in eastern Iran between 59° 47′ and 59° 53′ E longitude and 32°30′ and 32°34′ N latitude. The magmatic activity in the Lut block began in middle Jurassic (165-162 Ma and reached its peak in Tertiary (Jung et al., 1983. Volcanic and subvolcanic rocks of Tertiary age cover over half of Lut block with up to 2000 m thickness and formed due to subduction prior to the collision of the Arabian and Asian plates (Camp and Griffis, 1982; Tirrul et al., 1983; Berberianet et al., 1982. Most of magmatic activity in the Lut block formed in middle Eocene (Karimpour et al., 2011 The andesitic volcanics were erupted together with the dacites and rhyodacites during a time interval of some 50 Ma from early Cretaceous to early Neogene. It can be assumed that the intensity of the volcanic activity was varying significantly during this time span (Jung et al., 1983.Tertiary volcanic rocks (Eocene-Oligocene to Pliocene with intermediate composition associated with pyroclastic rocks cropped out in eastern parts of Salmabad village, southeast of Sarbisheh. The main purpose of this paper is better understand the tectono-magmatic setting of the Tertiary volcanic rocks in southeast of Sarbisheh, eastern Iran based on geochemical characteristics. Materials and methods Eleven samples were analyzed for major elements by inductively coupled plasma (ICP technologies and trace elements were analyzed using inductively coupled plasma mass spectrometry (ICP-MS, following a lithium metaborate/tetraborate fusion and nitric acid total digestion, at the SGS Laboratories, Toronto, Canada. Results In the Salmabad area, Tertiary volcanic rocks with mainly intermediate (andesitic composition are exposed associated with pyroclastic deposits such as tuff, breccia and agglomerate

  16. Fission-track evidence of tectonic evolution in the northwestern ...

    Indian Academy of Sciences (India)

    Guo-Qiang Sun

    2018-02-14

    Feb 14, 2018 ... from further collision of the Indian and Eurasian plates along the Yarlung Tsangpo suture zone. Strata ... Kunlun orogenic belt system using fission-track analysis of ... which had a decisive role in the development and ... boundary of the basin (Yue et al. ... Tagh fault commenced strike-slip movement (Yue.

  17. Project finance in Eastern Europe

    International Nuclear Information System (INIS)

    Hart, R.C.

    1993-01-01

    A dysfunctional system of commercial, legal, and financial institutions is the primary problem facing the energy sectors in Eastern Europe. Generally, a major systemic transformation is well underway in the area and is already showing signs of success. The empty promise of export credit financing exerts a significant negative influence on this reform process. The discipline of project finance provides the best, if not the only, basis for financing the modernization of the Eastern European energy sector. An example is given of the Cracow Environmental Project, a modernization project. The power plant is a combined heat and power facility with 460 MW of electric capacity and 1450 MW of thermal energy capacity. Located near the center of Cracow, the plant burns hard coal and provides more than seventy percent of the central district heat consumed in the city. The scope of proposed improvements has changed from the addition of capacity to a combination of modernization and environmental retrofit of the existing plant. The total estimated cost of the improvements program is 150 million dollars. The project consists of three major elements. First, it has proposed and is in the process of restructuring the ownership of the power plant. Second, it is engaged in a major restructuring of the commercial arrangements that govern the operation of the plant. Finally, it is in the late stages of selecting an engineering, procurement, and construction consortium with which it will contract to design and make major improvements to the existing plant

  18. Natural gas in Eastern Europe

    Energy Technology Data Exchange (ETDEWEB)

    Grabarczyk, Ewa; McCallum, Robert; Wergeland, Tor H

    1994-12-31

    The paper is based on Ewa Grabarczyk`s thesis ``The European Gas Market and the Former East Block Countries`` in the Master of International Business Programme at the Norwegian School of Economics and Business Administration. The material of Grabarczyk`s work has been split into two parts; SNF Working Papers Nos. 97/93 and 98/93. Working Paper 97/93 ``The European Gas Markets`` contains an equilibrium model of the European Gas Market employed to investigate some scenarios to the consequences of an integration of the former Soviet Union. Working Paper 98/93 ``Natural Gas in Eastern Europe`` contains descriptions of the energy sectors of former Eastern European countries and an evaluation of the potential future demand for natural gas in these nations. The paper has chapters on each country and sections on reserves, production, exports and markets, transport possibilities and technology, demand and development as well as evaluation of the present situation. 11 figs., 37 tabs., 33 refs

  19. Shear wave anisotropy in the Eastern Himalaya, Burmese arc and adjoining regions

    Science.gov (United States)

    Mangalampally, R. K.; Saikia, D.; Singh, A.; Roy, S.; Panuganti, S. R.; Lyngdoh, A. C.

    2017-12-01

    This study presents new results of 231 shear wave splitting and 395 "Null" measurements at 58 broadband seismic stations installed in the hitherto less investigated eastern Himalaya, Burmese arc and adjoining regions. The analysis reveals complex patterns of anisotropy, with significant variations in delay times. The fast polarisation directions (FPD) at stations within the Himalaya, Burmese Arc and the foredeep are coherent, parallel to the strike of the orogens. Measurements within the eastern and central Arunachal Himalaya are predominantly "Null''. However, in the western and central parts, these are relatively small, centered at 0.7s. The FPDs follow the trends of major tectonic features like the Main Boundary Thrust and the Main Central Thrust in the central segment of Arunachal Himalaya. In the Burmese arc region, the delay times show a large variability (0.4-2.1s). The Assam foredeep exhibits splitting delays in the range 0.5 to 1.2 s, with the FPDs trending nearly EW to NE. The FPDs parallel to the strike of the mountain belts can be best explained in terms of a coherently deformed lithospheric mantle under the compressional effects ensuing from the collision between India and Asia. Null measurements in regions like the Siang window may be due to a complex anisotropic pattern due to Indian plate interaction with Eurasia and Burma plates, causing different layers of anisotropic fabric with completely different orientations. Another possibility is the coincidence of source polarisation direction with the fast axis, since most of the waveforms analysed are from a narrow back azimuthal range of 100-125°. E-W oriented FPDs may coincide with the backazimuth of the source, resulting in smaller delays. Null measurements in eastern Himalaya may reflect cancellation of anisotropy caused by APM related flow (NE) and compressional effects of the Himalaya (EW). In the Bengal Basin, the Nulls could be due to two different mechanisms, namely, frozen anisotropic fabric

  20. Mafic dykes at the southwestern margin of Eastern Ghats belt ...

    Indian Academy of Sciences (India)

    Ghats belt: Evidence of rifting and collision. S Bhattacharya. 1,∗ ... 1.3 Ga, which may have been initiated by intra-plate volcanism. 1. Introduction ... tively, is described as a compressional orogen. Keywords. ... charnockite gneiss, around Naraseraopet, AP (b) Thin mafic ... Sometimes orthopyroxene also occurs at margin of.

  1. Orogen migration and tectonic setting of the Andrelândia Nappe system: An Ediacaran western Gondwana collage, south of São Francisco craton

    Science.gov (United States)

    Campos Neto, Mario da Costa; Basei, Miguel Angelo Stipp; Assis Janasi, Valdecir de; Moraes, Renato

    2011-12-01

    The southern Brasília Orogen is organized in a pile of nappes that records the Neoproterozoic history of the subduction and collision between passive and active margins, respectively belonging to the São Francisco and Paranapanema Plates. The whole pile of allochthons comprises the rootless Andrelândia Nappe System (the upper kyanite-bearing granulite of Três Pontas-Varginha Nappe, the intermediate high-pressure amphibolite-to eclogite facies of Liberdade Nappe and the lower Andrelândia Nappe) that is located below an Andean-type magmatic arc (Socorro-Guaxupé Nappe) and overrides the Lima Duarte Nappe and the Carrancas Nappe System. The tectonic units of the Andrelândia Nappe System seem to be exotic to the São Francisco Plate. The retroeclogite of the Liberdade Nappe yielded a 670 Ma SHRIMP U-Pb age in zircon, that is interpreted as the age of N-MORB-type basic magmatism. Detrital zircon grains of proximal flysh deposits of wackes in the Andrelândia Nappe present similar ages that reflect the crystallization in its source area. Both, rocks present Nd isotopic juvenile signatures with T DM in the range of 1.4 to 1.1 Ga. Rhyacian orthogneisses occur as slices in the Liberdade Nappe and have Nd isotope signature of juvenile source. The building of the collision pile of the whole system of nappes was diachronic and records a continuous outward migration of the orogen. The main structure is a middle crust-level duplex. The propagation of the structure and the metamorphism advanced progressively from the upper to the lower nappes, as is shown by U-Pb monazite ages in the range of 618-595 Ma for the Andrelândia Nappe System and 590-575 Ma for the Carrancas and Lima Duarte nappes.

  2. Transpressional folding and associated cross-fold jointing controlling the geometry of post-orogenic vein-type W-Sn mineralization: examples from Minas da Panasqueira, Portugal

    Science.gov (United States)

    Jacques, Dominique; Vieira, Romeu; Muchez, Philippe; Sintubin, Manuel

    2018-02-01

    The world-class W-Sn Panasqueira deposit consists of an extensive, subhorizontal vein swarm, peripheral to a late-orogenic greisen cupola. The vein swarm consists of hundreds of co-planar quartz veins that are overlapping and connected laterally over large distances. Various segmentation structures, a local zigzag geometry, and the occurrence of straight propagation paths indicate that they exploited a regional joint system. A detailed orientation analysis of the systematic joints reveals a geometrical relationship with the subvertical F2 fold generation, reflecting late-Variscan transpression. The joints are consistently orthogonal to the steeply plunging S0-S2 intersection lineation, both on the regional and the outcrop scale, and are thus defined as cross-fold or ac-joints. The joint system developed during the waning stages of the Variscan orogeny, when already uplifted to an upper-crustal level. Veining reactivated these cross-fold joints under the conditions of hydraulic overpressures and low differential stress. The consistent subperpendicular orientation of the veins relative to the non-cylindrical F2 hinge lines, also when having an inclined attitude, demonstrates that veining did not occur during far-field horizontal compression. Vein orientation is determined by local stress states variable on a meter-scale but with the minimum principal stress consistently subparallel to fold hinge lines. The conspicuous subhorizontal attitude of the Panasqueira vein swarm is thus dictated by the geometry of late-orogenic folds, which developed synchronous with oroclinal buckling of the Ibero-Armorican arc.

  3. Age and kinematics of ductile deformation in the Cerro Durazno area, NW Argentina: Significance for orogenic processes operating at the western margin of Gondwana during Ordovician - Silurian times

    Science.gov (United States)

    Wegmann, Maja I.; Riller, Ulrich; Hongn, Fernando D.; Glodny, Johannes; Oncken, Onno

    2008-07-01

    The Cerro Durazno Pluton belongs to a suite of Paleozoic granitoid intrusions in NW-Argentina, that are central for understanding the tectonic setting of the western margin of Gondwana in Ordovician and Silurian times. The pluton and its host rocks were tectonically overprinted by metamorphic mineral shape fabrics formed under middle greenschist-facies metamorphic conditions and associated with the nearby Agua Rosada Shear Zone. Kinematic analysis of the shear zone based on the geometric relationship between individual segments of the shear plane and principal axes of mineral fabric ellipsoids indicates reverse-sense of shear with a minor component of left-lateral displacement. This is compatible with the kinematics of other ductile deformation zones in this area, collectively forming a network, which accomplished orogen-parallel extension in addition to vertical thickening. Using the Rb-Sr isotopic system, an undeformed pegmatite dike of the Cerro Durazno Pluton was dated at 455.8 ± 3.6 Ma and mineral fabrics of the Agua Rosada Shear Zone formed at middle greenschist-facies metamorphism gave deformation ages of 437.0 ± 3.8 Ma and ⩽428.4 ± 4.5 Ma. Thus, tectonic overprint at low metamorphic grade occurred about 20-30 Ma after terminal magmatism in the Cerro Durazno area. Our data from the Cerro Durazno area and regional considerations suggest that the western margin of Gondwana was characterized by orogen-parallel extension in addition to crustal thickening as well as episodes of magmatism and ductile deformation that varied greatly in time and space.

  4. The Chinese North Tianshan Orogen was a rear-arc (or back-arc) environment in the Late Carboniferous: constraint from the volcanic rocks in the Bogda Mountains

    Science.gov (United States)

    Xie, W.

    2017-12-01

    The Tianshan Orogen is a key area for understanding the Paleozoic tectonics and long-lasting evolution of the Central Asian Orogenic Belt (CAOB). However, considerable debate persists as to its tectonic setting during the late Paleozoic, with active subduction system and intraplate large igneous provinces as two dominant schools (Ma et al., 1997; Gu et al., 2000; Xiao et al., 2004; Han et al., 2010; Shu et al., 2011; Chen et al., 2011; Xia et al., 2012). With aims of providing constraints on this issue, petrology, mineralogy, geochronological and geochemistry for the Late Carboniferous volcanics from the Bogda Mountains have been carried out. We find two suits of high-Al basalt (HAB, 315-319 Ma) and a suit of submarine pillow basalt ( 311 Ma) in this region. Both of the two basalts belong to the tholeiitic magma (the tholeiitic index THI > 1) and contain low pre-eruptive magmatic H2O (coexisted with the Bogda HABs is I-type intermediate ignimbrites and rhyolite lavas. The rhyolites are formed by partial melting of a hydrated and juvenile arc crust and the ignimbrites are affected by magma mingling and feldspar fractionation (Xie et al., 2016c). The two basalts both have the MORB-like Sr-Nd-Hf-Pb isotopes and arc-like trace element compositions. We discuss that they may have been generated from a dry and depleted mantle source metasomatized by coexisted felsic volcanics were likely formed in a rear-arc or back-arc environment, probably related to southward subduction of the Paleo-Tianshan Ocean (Xie et al., 2016a, b, c).

  5. 76 FR 28210 - Eastern Arizona Counties Resource Advisory Committee

    Science.gov (United States)

    2011-05-16

    ... DEPARTMENT OF AGRICULTURE Forest Service Eastern Arizona Counties Resource Advisory Committee AGENCY: Forest Service, USDA. ACTION: Notice of meeting. SUMMARY: The Eastern Arizona Counties will meet...: Julia Faith Rivera, RAC Program Manager, Eastern Arizona Counties Resource Advisory Committee, Apache...

  6. 76 FR 41755 - Eastern Arizona Counties Resource Advisory; Meeting

    Science.gov (United States)

    2011-07-15

    ... DEPARTMENT OF AGRICULTURE Forest Service Eastern Arizona Counties Resource Advisory; Meeting AGENCY: Forest Service, USDA. ACTION: Notice of meeting. SUMMARY: The Eastern Arizona Counties Resource... FURTHER INFORMATION CONTACT: Julia Faith Rivera, RAC Program Manager, Eastern Arizona Counties Resource...

  7. Old age mortality in Eastern and South-Eastern Asia

    Directory of Open Access Journals (Sweden)

    Danan Gu

    2013-11-01

    Full Text Available Background: Eastern and South-Eastern Asian countries have witnessed a marked decline in old age mortality in recent decades. Yet no studies have investigated the trends and patterns in old age morality and cause-of-death in the region. Objective: We reviewed the trends and patterns of old age mortality and cause-of-death for countries in the region. Methods: We examined data on old age mortality in terms of life expectancy at age 65 and age-specific death rates from the 2012 Revision of the World Population Prospects for 14 countries in the region (China, Hong Kong, Democratic People's Republic of Korea, Indonesia, Japan, Lao People's Democratic Republic, Myanmar, Malaysia, Mongolia, Philippines, Republic of Korea, Singapore, Thailand, and Viet Nam and data on cause-of-death from the WHO for five countries (China, Hong Kong, Japan, Republic of Korea, and Singapore from 1980 to 2010. Results: While mortality transitions in these populations took place in different times, and at different levels of socioeconomic development and living environment, changes in their age patterns and sex differentials in mortality showed certain similarities: women witnessed a similar decline to men in spite of their lower mortality, and young elders had a larger decline than the oldest-old. In all five countries examined for cause-of-death, most of the increases in life expectancy at age 65 in both men and women were attributable to declines in mortality from stroke and heart disease. GDP per capita, educational level, and urbanization explained much of the variations in life expectancy and cause-specific mortality, indicating critical contributions of these basic socioeconomic development indicators to the mortality decline over time in the region. Conclusions: These findings shed light on the relationship between epidemiological transition, changing age patterns of mortality, and improving life expectancy in these populations.

  8. Babesia microti infection, eastern Pennsylvania, USA.

    Science.gov (United States)

    Acosta, Marcela E Perez; Ender, Peter T; Smith, Erin M; Jahre, Jeffrey A

    2013-07-01

    Infection with Babesia microti has not been well-described in eastern Pennsylvania, USA, despite the vector of this organism being prevalent. We report 3 cases of babesiosis in eastern Pennsylvania in persons without recent travel outside the region or history of blood transfusions, suggesting emergence of this infection.

  9. Eastern Africa Social Science Research Review

    African Journals Online (AJOL)

    The Eastern Africa Social Science Research Review (EASSRR) is a bi-annual journal published by the Organization for Social Science Research in Eastern Africa (OSSREA). Since the publication of its maiden ... Emerging regions in Ethiopia: are they catching up with the rest of Ethiopia? EMAIL FULL TEXT EMAIL FULL ...

  10. tive conflict resolution mechanism in eastern Ethiopia

    African Journals Online (AJOL)

    eastern Ethiopia: The case of the Ittu ... The study was conducted in eastern Ethiopia where the Somali and ... Zigale Tamir Tenaw is assistant professor in the Department of Gender and Development ..... regional state in collaboration with the local people – aggravate the already ..... Resource Based Conflict Network,.

  11. Cenozoic Structural and Stratigraphic Evolution of the Ulukışla and Sivas Basins (Central and Eastern Turkey)

    Science.gov (United States)

    Gürer, Derya; Darin, Michael H.; van Hinsbergen, Douwe J. J.; Umhoefer, Paul J.

    2017-04-01

    Because subduction is a destructive process, the surface record of subduction-dominated systems is naturally incomplete. Sedimentary basins may hold the most complete record of processes related to subduction, accretion, collision, and ocean closure, and thus provide key information for understanding the kinematic evolution of orogens. In central and eastern Anatolia, the Late Cretaceous-Paleogene stratigraphic record of the Ulukışla and Sivas basins supports the hypothesis that these once formed a contiguous basin. Importantly, their age and geographic positions relative to their very similar basement units and ahead of the Arabian indenter provide a critical record of pre-, syn- and post-collisional processes in the Anatolian Orogen. The Ulukışla-Sivas basin was dissected and translated along the major left-lateral Ecemiş fault zone. Since then, the basins on either side of the fault evolved independently, with considerably more plate convergence accommodated to the east in the Sivas region (eastern Anatolia) than in the Ulukışla region (central Anatolia). This led to the deformation of marine sediments and underlying ophiolites and structural growth of the Sivas Fold-and-Thrust Belt (SSFTB) since latest Eocene time, which played a major role in marine basin isolation and disconnection, along with a regionally important transition to continental conditions with evaporite deposition starting in the early Oligocene. We use geologic mapping, fault kinematic analysis, paleomagnetism, apatite fission track (AFT) thermochronology, and 40Ar/39Ar geochronology to characterize the architecture, deformation style, and structural evolution of the region. In the Ulukışla basin, dominantly E-W trending normal faults became folded or inverted due to N-S contraction since the Lutetian (middle Eocene). This was accompanied by significant counter-clockwise rotations, and post-Lutetian burial of the Niǧde Massif along the transpressional Ecemiş fault zone. Since Miocene

  12. Evidence of Variscan and Alpine tectonics in the structural and thermochronological record of the central Serbo-Macedonian Massif (south-eastern Serbia)

    Science.gov (United States)

    Antić, Milorad D.; Kounov, Alexandre; Trivić, Branislav; Spikings, Richard; Wetzel, Andreas

    2017-07-01

    The Serbo-Macedonian Massif (SMM) represents a composite crystalline belt within the Eastern European Alpine orogen, outcropping from the Pannonian basin in the north to the Aegean Sea in the south. The central parts of this massif (south-eastern Serbia) consist of the medium- to high-grade Lower Complex and the low-grade Vlasina Unit. Outcrop- and micro-scale ductile structures in this area document three major stages of ductile deformation. The earliest stage D1 is related to isoclinal folding, commonly preserved as up to decimetre-scale quartz-feldspar rootless fold hinges. D2 is associated with general south-eastward tectonic transport and refolding of earlier structures into recumbent metre- to kilometre-scale tight to isoclinal folds. Stages D1 and D2 could not be temporally separated and probably took place in close sequence. The age of these two ductile deformation stages was constrained to the Variscan orogeny based on indirect geological evidence (i.e. ca. 408-ca. 328). During this period, the SMM was involved in a transpressional amalgamation of the western and eastern parts of the Galatian super-terrane and subsequent collision with Laurussia. Outcrop-scale evidence of the final stage D3 is limited to spaced and crenulation cleavage, which are probably related to formation of large-scale open upright folds as reported previously. 40Ar/39Ar thermochronology was applied on hornblende, muscovite, and biotite samples in order to constrain the age of tectonothermal events and activity along major shear zones. These 40Ar/39Ar data reveal three major cooling episodes affecting the central SMM. Cooling below greenschist facies conditions in the western part of the Vlasina Unit took place in a post-orogenic setting (extensional or transtensional) in the early Permian (284 ± 1 Ma). The age of activity along the top-to-the-west shear zone formed within the orthogneiss in the Božica area of the Vlasina Unit was constrained to Middle Triassic (246 ± 1 Ma). This

  13. 77 FR 51966 - Eastern Arizona Resource Advisory Committee

    Science.gov (United States)

    2012-08-28

    ... DEPARTMENT OF AGRICULTURE Forest Service Eastern Arizona Resource Advisory Committee AGENCY: Forest Service, USDA. ACTION: Notice of meeting. SUMMARY: The Eastern Arizona Resource Advisory Committee...

  14. Ozone modelling in Eastern Austria

    Energy Technology Data Exchange (ETDEWEB)

    Stohl, A.; Wotawa, G.; Kromp-Kolb, H. [Univ. of Agriculture, Vienna (Austria). Inst. of Meteorology and Physics; Winiwater, W. [Austrian Research Centre, Seibersdorf (Austria); Baumann, R.; Spangl, W. [Federal Environmental Agency, Vienna (Austria)

    1995-12-31

    High ozone concentrations are frequently observed in Eastern Austria, often exceeding local as well as international health standards, both for short-term as well as for long-term exposures. The maximum concentrations are produced in urban plumes, e.g. of the city of Vienna, whereas regional-scale transport and production of ozone is more important for the long-term concentrations. The Pannonian Ozone Project (POP) is an Austrian research initiative to model photochemical processes on a regional as well as on a local scale with a Lagrangian model to better understand the mechanisms leading to the high ozone concentrations and to develop abatement strategies. Up to now, focus has been on the regional scale. Aircraft, tethered balloon, tetroon and intensified ground measurements are carried out to validate the model. Although the major measurement campaign will be held in summer 1995, first results from a measurement campaign in summer 1994 are already available

  15. Erosion Associated with Seismically-Induced Landslides in the Middle Longmen Shan Region, Eastern Tibetan Plateau, China

    Directory of Open Access Journals (Sweden)

    Zhikun Ren

    2017-08-01

    Full Text Available The 2008 Wenchuan earthquake and associated co-seismic landslide was the most recent expression of the rapid deformation and erosion occurring in the eastern Tibetan Plateau. The erosion associated with co-seismic landslides balances the long-term tectonic uplift in the topographic evolution of the region; however, the quantitative relationship between earthquakes, uplift, and erosion is still unknown. In order to quantitatively distinguish the seismically-induced erosion in the total erosion, here, we quantify the Wenchuan earthquake-induced erosion using the digital elevation model (DEM differential method and previously-reported landslide volumes. Our results show that the seismically-induced erosion is comparable with the pre-earthquake short-term erosion. The seismically-induced erosion rate contributes ~50% of the total erosion rate, which suggests that the local topographic evolution of the middle Longmen Shan region may be closely related to tectonic events, such as the 2008 Wenchuan earthquake. We propose that seismically-induced erosion is a very important component of the total erosion, particularly in active orogenic regions. Our results demonstrate that the remote sensing technique of differential DEM provides a powerful tool for evaluating the volume of co-seismic landslides produced in intermountain regions by strong earthquakes.

  16. The genesis of the slab window-related Arzular low-sulfidation epithermal gold mineralization (eastern Pontides, NE Turkey

    Directory of Open Access Journals (Sweden)

    Enver Akaryalı

    2013-07-01

    Full Text Available The Arzular mineralization is one of the best examples of epithermal gold deposits in the eastern Pontides orogenic belt. The mineralization is hosted by the subduction-related basaltic andesites and is mainly controlled by E–W and NE–SW trending fracture zones. The main ore minerals are galena, sphalerite, pyrite, chalcopyrite, tetrahedrite and gold. Homogenization temperatures of fluid inclusions are between 130 and 295 °C for quartz and between 90 and 133 °C for sphalerite. Sulphur isotope values obtained from pyrite, galena and sphalerite vary between −1.2‰ and 3‰, indicating that sulphur belongs to magmatic origin and was derived from the Lutetian non-adakitic granitic intrusions in the region. Oxygen isotope values are between 15.0‰ and 16.7‰, and hydrogen isotope values are between −87‰ and −91‰. The sulphur isotope thermometer yielded temperatures in the range of 244–291 °C for the ore formation. Our results support the hypothesis that the Arzular mineralization is a low-sulfidation epithermal gold deposit associated with non-adakitic subduction-related granitic magmas that were generated by slab window-related processes in a south-dipping subduction zone during the Lutetian.

  17. Magmatic context of Bou Skour copper deposit (Eastern Anti-Atlas, Morocco): Petrogrography, geochemistry and alterations

    Science.gov (United States)

    EL Azmi, Daoud; Aissa, M.; Ouguir, H.; Mahdoudi, M. L.; El Azmi, M.; Ouadjo, A.; Zouhair, M.

    2014-09-01

    The Bou Skour copper deposit is located in the western part of the Saghro massif (Eastern Anti-Atlas), about 50 km East of the city of Ouarzazate. It is subdivided into several areas that are, from North to South: “Panthère”, “Chaigne”, “Anne Marie”, “Chapeau de fer” and “Patte d'Oie”. The latter is economically the most important and is the object of this study. The “Patte d'Oie” district consists mainly of extrusive and intrusive igneous rocks. The extrusive rocks are represented by andesites spatially associated with pyroclastic terms (ignimbrites and pyroclastic breccias). This volcanic unit is intruded by a pink granite pluton and a I-type granodiorite with equigranular texture (Bou Skour granodiorite) showing to the border a microgranular facies (microgranodiorite). All these magmatic formations are intersected by rhyolitic dykes (NNE-SSW) and doleritic dykes (WNW-ESE to NW-SE). The granodiorite and andesite have undergone a polyphase hydrothermal alteration: (i) potassic alteration, (ii) phyllitic alteration, (iii) silicification, (iv) argillic alteration and (v) propylitic alteration. The analysis of geochemical data of granodiorite, granite, andesite and dolerite confirmed: (i) their petrographic natures, (ii) the medium-K calc-alkaline affiliation of andesite and granodiorite, which would have been set up into an active geotectonic environment, probably of island arc or collision, during the Pan-African orogeny, (iii) The high-K calc-alkaline character of granite indicating a post-collision development during the Pan-African orogeny and (iv) The alkaline affinity of the dolerite which is linked to an extensive post-orogenic setting (post-Pan-African). The copper mineralization of “Patte d'Oie” area is hosted, exclusively, in the andesitic and granodioritic facies. It is represented, essentially, by chalcopyrite and bornite minerals and is, probably, related to a porphyry system (disseminated and stockwork mineralization

  18. Surface Wave Analysis of Regional Earthquakes in the Eastern Rift System (Africa)

    Science.gov (United States)

    Oliva, S. J. C.; Guidarelli, M.; Ebinger, C. J.; Roecker, S. W.; Tiberi, C.

    2015-12-01

    The Northern Tanzania Divergence (NTD), the youngest part of the East African Rift System, presents the opportunity to obtain insights about the birth and early stages of rifting before it progresses to mature rifting and seafloor spreading. This region is particularly interesting because the Eastern rift splits into three arms in this area and develops in a region of thick and cold lithosphere, amid the Archaean Tanzanian craton and the Proterozoic orogenic belt (the Masai block). We analyzed about two thousand seismic events recorded by the 39 broadband stations of the CRAFTI network during its two-year deployment in the NTD area in 2013 to 2014. We present the results of surface wave tomographic inversion obtained from fundamental-mode Rayleigh waves for short periods (between 4 to 14 seconds). Group velocity dispersion curves obtained via multiple filter analysis are path-averaged and inverted to produce 0.1º x 0.1º nodal grid tomographic maps for discrete periods using a 2D generalization of the Backus and Gilbert method. To quantify our results in terms of S-wave velocity structure the average group velocity dispersion curves are then inverted, using a linearized least-squares inversion scheme, in order to obtain the shear wave velocity structure for the upper 20 km of the crust. Low velocity anomalies are observed in the region 50 km south of Lake Natron, as well as in the area of the Ngorongoro crater. The implications of our results for the local tectonics and the development of the rifting system will be discussed in light of the growing geophysical database from this region.

  19. Earthquake focal mechanisms and stress orientations in the eastern Swiss Alps

    International Nuclear Information System (INIS)

    Marschall, I.; Deichmann, N.; Marone, F.

    2013-01-01

    This study presents an updated set of earthquake focal mechanisms in the Helvetic and Penninic/Austroalpine domains of the eastern Swiss Alps. In eight cases, based on high-precision relative hypocentre locations of events within individual earthquake sequences, it was possible to identify the active fault plane. Whereas the focal mechanisms in the Helvetic domain are mostly strike-slip, the Penninic/Austroalpine domain is dominated by normal-faulting mechanisms. Given this systematic difference in faulting style, an inversion for the stress field was performed separately for the two regions. The stress field in the Penninic/Austroalpine domain is characterized by extension oriented obliquely to the E-W strike of the orogen. Hence, the Penninic nappes, which were emplaced as large-scale compressional structures during the Alpine orogenesis, are now deforming in an extensional mode. This contrasts with the more compressional strike-slip regime in the Helvetic domain towards the northern Alpine front. Relative to the regional stress field seen in the northern Alpine foreland with a NNW-SSE compression and an ENE-WSW extension, the orientation of the least compressive stress in the Penninic/Austroalpine domain is rotated counter-clockwise by about 40 °C. Following earlier studies, the observed rotation of the orientation of the least compressive stress in the Penninic/Austroalpine region can be explained as the superposition of the regional stress field of the northern foreland and a uniaxial extensional stress perpendicular to the local trend of the Alpine mountain belt. (authors)

  20. Ethnographies of Grey Zones in Eastern Europe

    DEFF Research Database (Denmark)

    Over the last two decades, Eastern Europe has experienced extensive changes in geo-political relocations and relations leading to everyday uncertainty. Attempts to establish liberal democracies, re-orientations from planned to market economics, and a desire to create ‘new states’ and internationa......Over the last two decades, Eastern Europe has experienced extensive changes in geo-political relocations and relations leading to everyday uncertainty. Attempts to establish liberal democracies, re-orientations from planned to market economics, and a desire to create ‘new states...... contemporary Eastern Europe....

  1. Ethnographies of Grey Zones in Eastern Europe:

    DEFF Research Database (Denmark)

    Over the last two decades, Eastern Europe has experienced extensive changes in geo-political relocations and relations leading to everyday uncertainty. Attempts to establish liberal democracies, re-orientations from planned to market economics, and a desire to create ‘new states’ and internationa......Over the last two decades, Eastern Europe has experienced extensive changes in geo-political relocations and relations leading to everyday uncertainty. Attempts to establish liberal democracies, re-orientations from planned to market economics, and a desire to create ‘new states...... contemporary Eastern Europe....

  2. Cenozoic deformation from the Yakutat-North American collision to the eastern margin of the Northern Canadian Cordillera

    Science.gov (United States)

    Enkelmann, E.

    2017-12-01

    The western margin of the Northern Cordillera of North America is dominated by transform motion of the Yakutat microplate along the Fairweather fault system. In southeast Alaska the transform boundary changes to convergence and the oblique collision of the buoyant Yakutat microplate formed the St. Elias Mountains. One of the outstanding questions in understanding the St. Elias orogeny is how stress from the plate boundary has been transferred inboard and distributed strain in the North American plate. The timing, amount, and spatial pattern of deformation and rock exhumation have been studied using multiple thermochronology methods. Together the data reveal that Late Cenozoic deformation inboard of the Fairweather Fault and the colliding Yakutat plate corner at the St. Elias syntaxis was spatially very limited, resulting in rock exhumation within a cooling associated with Cordilleran deformation, and Paleocene-Eocene cooling due to spreading-ridge subduction. In contrast, the region west of the St. Elias syntaxis is dominated by convergence, which resulted in significant Cenozoic deformation in southeastern and southern Alaska. In the St. Elias orogen itself, most of the Late Cenozoic deformation and exhumation occurs within the Yakutat microplate and its Cenozoic sedimentary cover that composes the fold-thrust belt. The efficient interaction between tectonic uplift and glacial erosion resulted in rapid exhumation (>1 km/Myr) and extreme rates (4 km/Myr) that are localized at the syntaxis region and have shifted southward over the past 10 Myr. Far-field deformation reaches more than 500 km to the northwest of the convergent margin and caused mountain building in south-central Alaska. Deformation to the northeast is unclear. New thermochronology data from the eastern margin of the Northern Canadian Cordillera (Northwest Territory) reveal exhumation during the Oligocene to early Miocene. At this time, transform motion was already dominating the plate margin in the

  3. Lesser Himalayan sequences in Eastern Himalaya and their deformation: Implications for Paleoproterozoic tectonic activity along the northern margin of India

    Directory of Open Access Journals (Sweden)

    Dilip Saha

    2013-05-01

    Full Text Available Substantial part of the northern margin of Indian plate is subducted beneath the Eurasian plate during the Caenozoic Himalayan orogeny, obscuring older tectonic events in the Lesser Himalaya known to host Proterozoic sedimentary successions and granitic bodies. Tectonostratigraphic units of the Proterozoic Lesser Himalayan sequence (LHS of Eastern Himalaya, namely the Daling Group in Sikkim and the Bomdila Group in Arunachal Pradesh, provide clues to the nature and extent of Proterozoic passive margin sedimentation, their involvement in pre-Himalayan orogeny and implications for supercontinent reconstruction. The Daling Group, consisting of flaggy quartzite, meta-greywacke and metapelite with minor mafic dyke and sill, and the overlying Buxa Formation with stromatolitic carbonate-quartzite-slate, represent shallow marine, passive margin platformal association. Similar lithostratigraphy and broad depositional framework, and available geochronological data from intrusive granites in Eastern Himalaya indicate strikewise continuity of a shallow marine Paleoproterozoic platformal sequence up to Arunachal Pradesh through Bhutan. Multiple fold sets and tectonic foliations in LHS formed during partial or complete closure of the sea/ocean along the northern margin of Paleoproterozoic India. Such deformation fabrics are absent in the upper Palaeozoic–Mesozoic Gondwana formations in the Lesser Himalaya of Darjeeling-Sikkim indicating influence of older orogeny. Kinematic analysis based on microstructure, and garnet composition suggest Paleoproterozoic deformation and metamorphism of LHS to be distinct from those associated with the foreland propagating thrust systems of the Caenozoic Himalayan collisional belt. Two possibilities are argued here: (1 the low greenschist facies domain in the LHS enveloped the amphibolite to granulite facies domains, which were later tectonically severed; (2 the older deformation and metamorphism relate to a Pacific type

  4. Eastern Renewable Generation Integration Study

    Energy Technology Data Exchange (ETDEWEB)

    Bloom, Aaron [National Renewable Energy Lab. (NREL), Golden, CO (United States); Townsend, Aaron [National Renewable Energy Lab. (NREL), Golden, CO (United States); Palchak, David [National Renewable Energy Lab. (NREL), Golden, CO (United States); Novacheck, Joshua [National Renewable Energy Lab. (NREL), Golden, CO (United States); King, Jack [RePPAE LLC, Wexford, PA (United States); Barrows, Clayton [National Renewable Energy Lab. (NREL), Golden, CO (United States); Ibanez, Eduardo [GE Energy, Denver, CO (United States); O' Connell, Matthew [National Renewable Energy Lab. (NREL), Golden, CO (United States); Jordan, Gary [GE Energy, Denver, CO (United States); Roberts, Billy [National Renewable Energy Lab. (NREL), Golden, CO (United States); Draxl, Caroline [National Renewable Energy Lab. (NREL), Golden, CO (United States); Gruchalla, Kenny [National Renewable Energy Lab. (NREL), Golden, CO (United States)

    2016-08-01

    The Eastern Interconnection (EI) is one of the largest power systems in the world, and its size and complexity have historically made it difficult to study in high levels of detail in a modeling environment. In order to understand how this system might be impacted by high penetrations (30% of total annual generation) of wind and solar photovoltaic (PV) during steady state operations, the National Renewable Energy Laboratory (NREL) and the U.S. Department of Energy (DOE) conducted the Eastern Renewable Generation Integration Study (ERGIS). This study investigates certain aspects of the reliability and economic efficiency problem faced by power system operators and planners. Specifically, the study models the ability to meet electricity demand at a 5-minute time interval by scheduling resources for known ramping events, while maintaining adequate reserves to meet random variation in supply and demand, and contingency events. To measure the ability to meet these requirements, a unit commitment and economic dispatch (UC&ED) model is employed to simulate power system operations. The economic costs of managing this system are presented using production costs, a traditional UC&ED metric that does not include any consideration of long-term fixed costs. ERGIS simulated one year of power system operations to understand regional and sub-hourly impacts of wind and PV by developing a comprehensive UC&ED model of the EI. In the analysis, it is shown that, under the study assumptions, generation from approximately 400 GW of combined wind and PV capacity can be balanced on the transmission system at a 5-minute level. In order to address the significant computational burdens associated with a model of this detail we apply novel computing techniques to dramatically reduce simulation solve time while simultaneously increasing the resolution and fidelity of the analysis. Our results also indicate that high penetrations of wind and PV (collectively variable generation (VG

  5. Orogenic potassic mafic magmatism, a product of alkaline-peraluminous mixing ? Variscan 'calc-alkaline' rocks from the Central Iberian and Ossa Morena Zones, Central Spain.

    Science.gov (United States)

    Scarrow, Jane H.; Cambeses, Aitor; Bea, Fernando; Montero, Pilar; Molina, José F.; Moreno, Juan Antonio

    2013-04-01

    Orogenic magmatic rocks provide information about mantle and crust melt-generation and -interaction processes. In this context, minor potassic mafic stocks which are formed of enriched mantle and crustal components and are common as late-orogenic intrusions in granitic plutons give insight into the timing of new crust formation and crustal recycling. Potassic mafic stocks are prevalent, albeit low volume, constituents of granite batholiths all through the European Variscan (350-280 Ma). In the Central Iberia Zone, Spanish Central System, crustal-melt, S-type, granitoid plutons are intruded by minor concomitant ultramafic-intermediate appinitic-vaugneritic stocks. Notwithstanding their whole-rock calc-alkaline composition, the stocks apparently did not have a subduction-related origin. Recent studies have attributed their genesis to mixing of alkaline mantle and peraluminous crustal melts. Their primary alkaline character, as indicated by amphibole and biotite mineral chemistry data, points, rather, towards an extension-related genesis. In the Ossa Morena Zone, south of the Central Iberian Zone, the igneous rocks also have a whole-rock calc-alkaline composition which has been considered to be the result of northward subduction of the South Portuguese Zone. Nevertheless, identification of a 'sill' of significant volume of mafic magma in the middle crust, the ´IBERSEIS reflective body', in a seismic profile across the Ossa Morena and South Portuguese Zones has cast doubt upon the calc-alkaline magmatism-subduction model; leading, instead, to the magmatism being attributed to intra-orogenic extension related to a mantle plume active from 340 Ma to 330 Ma. The aim here, then, is to reinvestigate the petrogenesis and age of the calc-alkaline rocks of the Ossa Morena Zone to determine their tectonomagmatic context be it subduction-, plume- or extension-related, and establish what they may reveal about mantle-crust interactions. Focussing, initially, on the Valencia del

  6. 78 FR 43874 - Texas Eastern Transmission, LP; Notice of Application

    Science.gov (United States)

    2013-07-22

    ... DEPARTMENT OF ENERGY Federal Energy Regulatory Commission [Docket No. CP13-514-000] Texas Eastern Transmission, LP; Notice of Application On July 2, 2013, Texas Eastern Transmission, LP (Texas Eastern) filed... natural gas facilities no longer in service. As described more fully in the Application, Texas Eastern...

  7. 76 FR 7833 - Texas Eastern Transmission, LP; Notice of Application

    Science.gov (United States)

    2011-02-11

    ...] Texas Eastern Transmission, LP; Notice of Application Take notice that on January 25, 2011, Texas Eastern Transmission, LP (Texas Eastern), 5400 Westheimer Court, Houston, Texas 77056, filed in the above... TEAM 2012 Project. Specifically, Texas Eastern requests: (i) Authorization under NGA sections 7(b) and...

  8. Transcultural Memory in Eastern European Migrant Literature

    DEFF Research Database (Denmark)

    Ortner, Jessica

    of the major processes that circulate memories across cultural and national borderlines. This paper will investigate the circulation of memories in Eastern Europe migrant-literature that since 2000 has become an increasingly influential literary tendency in Germany. Articulating an eastern perspective...... consciously follow the mission to “enlighten and inform Western readers about their eastern neighbours” (Haines 2008). Causing an “eastern enlargement” of German literature (Bürger-Koftis 2008), the wave of migrant authors broadens Germany’s cultural memory by supplementing it with “new” memories. Furthermore......The “transcultural turn” of memory studies focuses on the fluid and dynamic aspects of cultural memory. This paper is concerned with the traveling of memories along the paths of migration. As migrants carry along “collective images and narratives of the past” (Erll 2011), migration is one...

  9. Eastern and Southern Africa Seismological Working Group

    International Nuclear Information System (INIS)

    Ogubazghi, G.

    2002-01-01

    Member countries of the Eastern and Southern Africa Seismologica Working Group are listed. The presentation also gives the objectives, activities, date of birth and sponsors of the said ESARSWG. Areas of possible cooperation with CTBTO are indicated

  10. Eastern Canada natural gas developments

    International Nuclear Information System (INIS)

    Wall, A.

    2001-01-01

    This power point presentation addressed the following topics regarding development of natural gas in eastern Canada: (1) the 18 Tcf of proven natural gas reserves at Sable Island, (2) Canadian markets benefiting from the Maritimes and Northeast Pipeline (M and NP), (3) a 20 year franchise agreement between Enbridge Gas and the government of New Brunswick, (4) the 25 year provincial franchise agreement by Sempra Atlantic Gas, and (5) Sable Island's influence on central Canada. The Sable Offshore Energy Project (SOEP) is now producing about 540,000 MMBtu/day from 6 fields. Plans for Tier 2 expansion are underway. Firm contracts for the M and NP are scheduled to transport gas from the SOEP to markets in Nova Scotia, New Brunswick, Maine and New Hampshire. Sable gas is also a potential supply for the Quebec market. Gaz Metropolitain and Enbridge have proposed to build the Cartier Pipeline from the Quebec/New Brunswick border to Quebec City. It is unlikely that Sable Island supply will directly serve the Ontario market. Canadian customers for Sable gas and M and NP service include pulp and paper companies, oil refineries, power generators and local distribution companies (LDC), with the majority of demand coming form the electric power industry. tabs., figs

  11. Eastern countries - WIN activity review

    International Nuclear Information System (INIS)

    Stiopol, Mihaela

    1998-01-01

    Women can play this important role in informing people about nuclear energy. WIN is a world-wide association of women working professionally in the fields of nuclear energy and radiation application who want to devote their time to public information. The main goal of the WIN is to establish an objective and effective communication with the public through educational programmes, information exchange and arranging study visits. The membership includes women working in medicine and health care, in regulatory authorities, in industry and as independent researches at Universities. They want to contribute to objectively informing the public by making presentation, discussing and giving information materials on subjects such as; radiation, radioactivity and health effects medical applications nuclear energy nuclear power plants and their safety nuclear and environment uranium mining radiation protection energy sustainable development WIN is also open to men, supporting the goals of WIN. The intention of this paper was to underline the main aspects which reflect WIN activity in some Eastern and Central countries. There are common features and also specific elements for each country. But the goal is the same: to assure an effective and a real information of the public related to the nuclear field

  12. Fold superimposition in the Permian groups in the central Beishan orogenic collage (northwestern China): highlights for the late evolution of the Altaids

    Science.gov (United States)

    Zhonghua, Tian; Wenjiao, Xiao; Yehua, Shan

    2013-04-01

    The southernmost part of the Central Asian Orogenic Belt (CAOB) or Altaids (Sengör and Burtman, 1993; Xiao et al., 2009), a rare and magnificent example of mesoscopic fold superimposition, involving the Permian sandstone, slightly to mildly metamorphosed clastic rocks, is well exposed in the central Beishan Orogenic Collage (BOC). We provide a detailed description of the morphological features of this phenomenon, based on an enormous amount of structural data collected during recent twice field mapping in the study area. Two phases of folds are readily distinguishable both in satellite image (Fig.la) and our own field map (Fig.1b). Fold is tight to close, N-S-trending in the first phase (F1), and open and E-W-trending in the second phase (F2). The first phase upright folds were refolded into a smaller number of (F2), whose axial planes and axes are vertical or subvertical. They plunge gentle to moderately in the former and moderately to steeply in the latter. Their interference is in general categorized as Ramsay's (Ramsay, 1967) type 2 or Ghosh's third/fourth mode based on the value of initial tightness. However, from east to west there exists a slight variation of a zigzag to crescent to mushroom interference pattern. This subtle variation corresponds with the westward increases of the F2 interlimb angle and of the percentage of coarse-grain clastic rocks, suggesting its dependence upon the F2 deformation and the lithology. Axial slaty cleavages (S1) and associated dip-slip slickensides are more abundant in the first phase. Cleavages and strike-slip slickensides related to the seconding refolding are also occurred in the area. Finally, according to the petrological, geochemical and geochronological data, we conclude that the deformation history of the superposed folds were associated with the late evolution in the BOC. In the late Permian, the fold superimposition occurred in sedimentary rocks deposited in a Permian back-arc basin. The basin was intensely

  13. Geochronological and sedimentological evidences of Panyangshan foreland basin for tectonic control on the Late Paleozoic plate marginal orogenic belt along the northern margin of the North China Craton

    Science.gov (United States)

    Li, Jialiang; Zhou, Zhiguang; He, Yingfu; Wang, Guosheng; Wu, Chen; Liu, Changfeng; Yao, Guang; Xu, Wentao; Zhao, Xiaoqi; Dai, Pengfei

    2017-08-01

    There is a wide support that the Inner Mongolia Palaeo-uplift on the northern margin of the North China Craton has undergone an uplifting history. However, when and how did the uplift occurred keeps controversial. Extensive field-based structural, metamorphic, geochemical, geochronological and geophysical investigations on the Inner Mongolia Palaeo-uplift, which suggested that the Inner Mongolia Palaeo-uplift was an uplifted region since the Early Precambrian or range from Late Carboniferous-Early Jurassic. The geochemical characteristics of the Late Paleozoic to Early Mesozoic intrusive rocks indicated that the Inner Mongolia Palaeo-uplift was an Andean-type continental margin that is the extensional tectonic setting. To address the spatial and temporal development of the Inner Mongolia Palaeo-uplift, we have carried out provenance analysis of Permian sedimentary rocks which collected from the Panyangshan basin along the northern margin of the North China Craton. The QFL diagram revealed a dissected arc-recycled orogenic tectonic setting. Moreover, the framework grains are abundant with feldspar (36-50%), indicating the short transport distance and unstable tectonic setting. Detrital zircon U-Pb analysis ascertained possible provenance information: the Precambrian basement ( 2490 and 1840 Ma) and continental arc magmatic action ( 279 and 295 Ma) along the northern margin of the North China Craton. The projection in rose diagrams of the mean palaeocurrent direction, revealing the SSW and SSE palaeoflow direction, also shows the provenance of the Panyangshan basin sources mainly from the Inner Mongolia Palaeo-uplift. The andesite overlying the Naobaogou Formation has yielded U-Pb age of 277.3 ± 1.4 Ma. The additional dioritic porphyry dike intruded the Naobaogou and Laowopu Formations, which has an emplacement age of 236 ± 1 Ma. The above data identify that the basin formed ranges from Early Permian to Middle Triassic (277-236 Ma). Accordingly, the Inner Mongolia

  14. The energy question in Eastern Europe

    International Nuclear Information System (INIS)

    Locatelli, C.

    1992-01-01

    In a first part, this book describes the energetic schemes, energy consumption and centralized economy in Eastern Europe countries. In the second part, the relationships between energy supply and macro-economic disequilibria in USSR is studied: Petroleum and power generation are chosen as example. In the third part, the book shows the energetic stakes in Central and Eastern Europe: the end of the exchange model (imports, exports) and the energetic schemes facing economical reforms

  15. Midwifery education in Central-Eastern Europe.

    Science.gov (United States)

    Mivšek, Polona; Baškova, Martina; Wilhelmova, Radka

    2016-02-01

    Problems in midwifery in many Central-Eastern European countries are very similar; it is possible to speak about the evolving Central-Eastern model of midwifery care. The educational models of this region have a relatively strong theoretical part; however, there is an insufficient practical dimension. Theoretical part of midwifery education in the universities is relatively autonomous and is slowly changing the professional identity of graduates. Copyright © 2015 Elsevier Ltd. All rights reserved.

  16. 75 FR 68397 - DeQueen and Eastern Railroad, LLC-Acquisition and Operation Exemption-DeQueen and Eastern...

    Science.gov (United States)

    2010-11-05

    ... Eastern Railroad, LLC--Acquisition and Operation Exemption--DeQueen and Eastern Railroad Company DeQueen and Eastern Railroad, LLC (DQE), a noncarrier, has filed a verified notice of exemption under 49 CFR 1150.31 to acquire from DeQueen and Eastern Railroad Company and to operate approximately 47 miles of...

  17. Timing and implications for the late Mesozoic geodynamic settings of eastern North China Craton: Evidences from K-Ar dating age and sedimentary-structural characteristics records of Lingshan Island, Shandong Province

    Science.gov (United States)

    Li, Jie; Jin, Aiwen; Hou, Guiting

    2017-12-01

    The Lingshan Island in Shandong Province in the eastern North China Craton, well known for the Late Mesozoic multi-scale slide-slump structures is related to paleo-earthquake. Terrigenous clastic rocks, volcanic clastic rocks and volcanic lavas are extensively exposed in the Lingshan Island and its adjacent regions of the Shandong Province, which led to fierce debates on their ages, sedimentary characteristics and tectono-sedimentary evolution. In this contribution, we present the characteristics of the Late Mesozoic stratigraphy in the Lingshan Island. Whole-rock K-Ar dating of dyke at Beilaishi and rhyolites at Laohuzui of the Lingshan Island yielded ages of 159 Ma and 106-92 Ma which coincides with the Laiyang Period rifting and the Qingshan Period rifting in the Jiaolai Basin, respectively. On the basis of the analysis to the Late Mesozoic sedimentary environment of `flysch' and `molasse'-like formations as well as tectonic stress fields reconstruction, four episodes of the tectono-sedimentary evolution were established in the Lingshan Island and its adjacent regions in the eastern North China Craton. They consist of two episodes of extensional events for the syn-rift, and two episodes of compression events for the inversion of the post-rift. The entire episodes can be summarized as follows: (1) the first syn-rift NW-SE extension in Laiyang Period can be identified by the `flysch' formation (Unit 1) and by emplacement of the NE-trending dyke in the Laiyang Group. This syn-rift episode can be related to the NW-SE post-orogenic extension resulted from the gravity collapse of the thickened lithosphere along the Sulu Orogen. (2) The first post-rift NW-SE inversion, which was caused by the NW-directed subduction of Izanaqi Plate, can be well documented by the `X' type conjugate joints as well as slide slump folds in Unit 1. (3) The second syn-rift NW-SE extension in Qingshan Period is characterized by rhyolite rocks (Unit 2). This syn-rift episode can be considered

  18. Comment on "Timing and nature of the Xinlin-Xiguitu Ocean: constraints from ophiolitic gabbros in the northern Great Xing'an Range, eastern Central Asian Orogenic Belt" by Feng et al. (2016)

    Science.gov (United States)

    Ni, Dong-Hong

    2017-09-01

    We disagree the transitional supra-subduction zone model of Feng et al. (Int J Earth Sci (Geol Rundsch) 105:491-505, 2016) for the tectonic setting of Jifeng ophiolite suite in NE China. Existence of the komatiite in the Jifeng ophiolite indicates an oceanic plateau environment for this ophiolite suite within the so-called Xinlin-Xiguitu ocean.

  19. Eastern slopes grizzly bear project

    Energy Technology Data Exchange (ETDEWEB)

    NONE

    2001-01-01

    The cumulative effects of human activities on the grizzly bears in the central Canadian Rockies are not well known. As a result, a project was initiated in 1994 to address the urgent requirement for accurate scientific information on the habitat and populations of grizzly bears in the area of the Banff National Park and Kananaskis Country. This area is probably the most heavily used and developed area where the grizzly still survives. The information gathered throughout the course of this study will be used to better protect and manage the bears and other sensitive carnivores in the region. Using telemetry, researchers are monitoring 25 grizzly bears which were radio-collared in a 22,000 square-kilometer area in the upper Bow Valley drainage of the eastern Alberta slopes. The researchers involved in the project are working with representatives from Husky Oil and Talisman Energy on the sound development of the Moose Mountain oil and gas field without adversely affecting the grizzly bear population. Information collected over seven years indicated that the grizzly bears have few and infrequent offspring. Using the information gathered so far, the location of the Moose Mountain to Jumping Pound pipeline was carefully selected, since the bears recover very slowly from high mortality, and also considering that the food and cover had already been compromised by the high number of roads, trails and other human activities in the area. The status of the population and habitat of the grizzly bear will be assessed upon the conclusion of the field research phase in 2001. Models will be updated using the data obtained during eight years and will assist in the understanding of complex variables that affect grizzly bears.

  20. Controls of structural inheritance on orogenic curvature and foreland basin sedimentation: Insights from the Przemyśl area, Western Carpathians

    Science.gov (United States)

    Szaniawski, Rafał; Mazzoli, Stefano; Jankowski, Leszek

    2017-10-01

    Orogenic curvatures can have various origins and are widely debated worldwide. In the Poland-Ukraine border area, the Outer Western Carpathians are characterized by a marked curvature. The origin of this curvature was analysed by integrating stratigraphic information with structural constraints and anisotropy of the magnetic susceptibility (AMS) data. Hangingwall frontal ramp domains are characterized by a relatively simple deformation dominated by layer-parallel shortening and folding around a regional NW-SE trending axis, recorded by an AMS lineation with a similar trend. On the other hand, the N-S trending hangingwall oblique ramp domain is characterized by maximum AMS axes recording transpressional strain either dominated by simple shear (sub-horizontal AMS lineation) or pure shear (steeply plunging AMS lineation) components. Early Miocene basin inversion with two distinct depocentres created a number of different detachment surfaces and thickness variations for the sedimentary successions involved in thrusting. The main depocentre of the Lower-Middle Miocene foredeep was originally located in the recess area of the curved Carpathian front. On the other hand, the occurrence of a salient to the west resulted in the axial zone of the foreland flexure being filled with allochthonous units, thereby dramatically reducing the accommodation space for foredeep sediments in this area. Our results suggest that thrust-belt geometry was controlled by the inherited Mesozoic extensional basin architecture.

  1. Thermochronometry across the Austroalpine-Pennine boundary, Central Alps, Switzerland: Orogen-perpendicular normal fault slip on a major ‘overthrust’ and its implications for orogenesis

    Science.gov (United States)

    Price, Jason B.; Wernicke, Brian P.; Cosca, Michael A.; Farley, Kenneth A.

    2018-01-01

    Fifty‐one new and 309 published thermochronometric ages (nine systems with closure temperatures ranging from ~450 to 70°C) from the Graubünden region of the Central Alps demonstrate that a pronounced thermal mismatch between the Austroalpine allochthon (Alpine “orogenic lid”) and the Pennine zone persisted until at least 29 Ma and, allowably, until circa 18 Ma. The observed mismatch supports previous suggestions that the famous “overthrust” between the Austroalpine allochthon and the Pennine zone, historically regarded as primarily an Eocene top‐north thrust fault, is in fact primarily an Oligocene‐Miocene normal fault that has a minimum of 60 km of displacement with top‐south or top‐southeast sense of shear. Two hallmarks of Alpine geology, deposition of the foredeep Molasse and emplacement of the Helvetic nappes, appear to be coeval, peripheral manifestations of crustal thickening via the interposition of the Pennine zone as a northward intruding wedge between the Austroalpine “lid” and the European cratonic margin, with the Helvetic system (European margin) acting as the “floor” of the wedge. We presume the Penninic wedge is driven by the buoyant rise of subducted crust no longer able to remain attached to the descending slab. If so, emplacement of the Pennine wedge could have occurred mainly after Adria was juxtaposed against cratonic Europe.

  2. Thermochronometry Across the Austroalpine-Pennine Boundary, Central Alps, Switzerland: Orogen-Perpendicular Normal Fault Slip on a Major "Overthrust" and Its Implications for Orogenesis

    Science.gov (United States)

    Price, Jason B.; Wernicke, Brian P.; Cosca, Michael A.; Farley, Kenneth A.

    2018-03-01

    Fifty-one new and 309 published thermochronometric ages (nine systems with closure temperatures ranging from 450 to 70°C) from the Graubünden region of the Central Alps demonstrate that a pronounced thermal mismatch between the Austroalpine allochthon (Alpine "orogenic lid") and the Pennine zone persisted until at least 29 Ma and, allowably, until circa 18 Ma. The observed mismatch supports previous suggestions that the famous "overthrust" between the Austroalpine allochthon and the Pennine zone, historically regarded as primarily an Eocene top-north thrust fault, is in fact primarily an Oligocene-Miocene normal fault that has a minimum of 60 km of displacement with top-south or top-southeast sense of shear. Two hallmarks of Alpine geology, deposition of the foredeep Molasse and emplacement of the Helvetic nappes, appear to be coeval, peripheral manifestations of crustal thickening via the interposition of the Pennine zone as a northward intruding wedge between the Austroalpine "lid" and the European cratonic margin, with the Helvetic system (European margin) acting as the "floor" of the wedge. We presume the Penninic wedge is driven by the buoyant rise of subducted crust no longer able to remain attached to the descending slab. If so, emplacement of the Pennine wedge could have occurred mainly after Adria was juxtaposed against cratonic Europe.

  3. Gold and trace element zonation in pyrite using a laser imaging technique: Implications for the timing of gold in orogenic and carlin-style sediment-hosted deposits

    Science.gov (United States)

    Large, R.R.; Danyushevsky, L.; Hollit, C.; Maslennikov, V.; Meffre, S.; Gilbert, S.; Bull, S.; Scott, R.; Emsbo, P.; Thomas, H.; Singh, B.; Foster, J.

    2009-01-01

    Laser ablation ICP-MS imaging of gold and other trace elements in pyrite from four different sediment- hosted gold-arsenic deposits has revealed two distinct episodes of gold enrichment in each deposit: an early synsedimentary stage where invisible gold is concentrated in arsenian diagenetic pyrite along with other trace elements, in particular, As, Ni, Pb, Zn, Ag, Mo, Te, V, and Se; and a later hydrothermal stage where gold forms as either free gold grains in cracks in overgrowth metamorphic and/or hydrothermal pyrite or as narrow gold- arsenic rims on the outermost parts of the overgrowth hydrothermal pyrite. Compared to the diagenetic pyrites, the hydrothermal pyrites are commonly depleted in Ni, V, Zn, Pb, and Ag with cyclic zones of Co, Ni, and As concentration. The outermost hydrothermal pyrite rims are either As-Au rich, as in moderate- to high- grade deposits such as Carlin and Bendigo, or Co-Ni rich and As-Au poor as in moderate- to low-grade deposits such as Sukhoi Log and Spanish Mountain. The early enrichment of gold in arsenic-bearing syngenetic to diagenetic pyrite, within black shale facies of sedimentary basins, is proposed as a critical requirement for the later development of Carlin-style and orogenic gold deposits in sedimentary environments. The best grade sediment-hosted deposits appear to have the gold climax event, toward the final stages of deformation-related hydrothermal pyrite growth and fluid flow. ?? 2009 Society of Economic Geologists, Inc.

  4. Teleseismic P-wave tomography and the upper mantle structure of the Sulu orogenic belt (China): implications for Triassic collision and exhumation mechanism

    Science.gov (United States)

    Peng, Miao; Tan, Handong; Jiang, Mei; Xu, Zhiqin; Li, Zhonghai; Xu, Lehong

    2016-12-01

    As the largest ultrahigh-pressure (UHP) metamorphic tectonic unit outcropping in the world, the Dabie-Sulu UHP metamorphic belt is considered to be one of the best areas for studying the continental dynamics. However, their continental collision and exhumation mechanism are still debated. We performed a 3D teleseismic P-wave tomography beneath the Sulu orogen for the purpose of understanding the deep structure. The tomographic results show that there is a prominently near-SN-trending low-velocity zone (LVZ) close to the Tanlu fault (TLF), indicating a slab tear of the subducted Yangtze plate (YZP) during the initial Early Triassic collision. Our results also suggest that both the Yangze crustal slab and the North China lithospheric slab were dragged downwards by the subducted oceanic slab, which constituted a ‘two-sided’ subduction mode. A conceptual geodynamic model is proposed to explain the exhumation of Sulu high- to UHP rocks and imply a polyphase exhumation driven by buoyancy of continental materials at different depth and upward extrusion of crustal partial melting rocks to the surface at the later stage.

  5. Syn-collisional felsic magmatism and continental crust growth: A case study from the North Qilian Orogenic Belt at the northern margin of the Tibetan Plateau

    Science.gov (United States)

    Chen, Shuo; Niu, Yaoling; Xue, Qiqi

    2018-05-01

    The abundant syn-collisional granitoids produced and preserved at the northern Tibetan Plateau margin provide a prime case for studying the felsic magmatism as well as continental crust growth in response to continental collision. Here we present the results from a systematic study of the syn-collisional granitoids and their mafic magmatic enclaves (MMEs) in the Laohushan (LHS) and Machangshan (MCS) plutons from the North Qilian Orogenic Belt (NQOB). Two types of MMEs from the LHS pluton exhibit identical crystallization age ( 430 Ma) and bulk-rock isotopic compositions to their host granitoids, indicating their genetic link. The phase equilibrium constraints and pressure estimates for amphiboles from the LHS pluton together with the whole rock data suggest that the two types of MMEs represent two evolution products of the same hydrous andesitic magmas. In combination with the data on NQOB syn-collisional granitoids elsewhere, we suggest that the syn-collisional granitoids in the NQOB are material evidence of melting of ocean crust and sediment. The remarkable compositional similarity between the LHS granitoids and the model bulk continental crust in terms of major elements, trace elements, and some key element ratios indicates that the syn-collisional magmatism in the NQOB contributes to net continental crust growth, and that the way of continental crust growth in the Phanerozoic through syn-collisional felsic magmatism (production and preservation) is a straightforward process without the need of petrologically and physically complex processes.

  6. Eclogites and garnet clinopyroxenites in the Anrakhai complex, Central Asian Orogenic Belt, Southern Kazakhstan: P-T evolution, protoliths and some geodynamic implications

    Science.gov (United States)

    Pilitsyna, Anfisa V.; Tretyakov, Andrey A.; Degtyarev, Kirill E.; Cuthbert, Simon J.; Batanova, Valentina G.; Kovalchuk, Elena V.

    2018-03-01

    The Anrakhai Metamorphic Complex (AMC), located in the SE part of the Chu-Ili Mountains of Southern Kazakhstan in the western part of Central Asian Orogenic Belt, exhibits occurrences of HP metamorphic rocks in the form of eclogites and garnet clinopyroxenites with peak metamorphic conditions of 750-850° and 15-19 kbar estimated with both conventional geothermobarometric methods and phase diagram modeling. P-T estimates as well as intimate field relations evidently imply a common metamorphic history for eclogites and garnet clinopyroxenites of the AMC. These high-pressure, medium temperature eclogite facies P-T conditions are indicative of a collision or subduction tectonic setting. Major and trace element geochemistry suggests that they probably had a common magmatic origin as part of a suite of differentiated tholeiitic intrusions. Furthermore, distinctive mineral and chemical compositions of these eclogites and garnet clinopyroxenites correspond to the Fe-Ti type of ultramafic rocks suggesting that they may have been derivatives of intraplate tholeiitic melts, introduced into continental crust before HP metamorphism.

  7. IAEA/WHO postal dose audits for radiotherapy hospitals in Eastern and South-Eastern Europe

    International Nuclear Information System (INIS)

    Izewska, J.; Vatnitsky, S.; Shortt, K.R.

    2004-01-01

    The IAEA/WHO TLD programme has been in operation for 34 years. In this period the calibration of approximately 5200 high-energy photon beams in over 1300 radiotherapy hospitals in 115 countries worldwide was checked. Of these, 18% of the audits were performed in Eastern and South-Eastern Europe. There are large contrasts in the region; while the results are very good for most countries, a few countries struggle with basic problems in dosimetry. The hospitals operating radiotherapy services without qualified medical physicists or dosimetry equipment have poorer results than those properly equipped and staffed. Only about 2/3 of TLD audit participants in Eastern Europe have the appropriate dosimetry equipment. To achieve consistency of the audit results within Eastern and South-Eastern Europe, strengthening of radiotherapy infrastructure in a few countries would be necessary. (authors)

  8. Paleomagnetic Results of Permo-Carboniferous Volcanic-sedimentary Strata in Mid-eastern Inner Mongolia, China: Implications for Tectonic Evolution of the Eastern CAOB

    Science.gov (United States)

    Zhang, D.; Huang, B.; Zhao, J.; Bai, Q.; Zhang, Y.; Zhou, T.

    2015-12-01

    There has been hotly debating over the closure time of the eastern Paleo-Asian Ocean and the tectonic evolution of the eastern CAOB (Central Asian Orogenic Belt) for decades. To better puzzle out this controversy, we carried out a detailed paleomagnetic study on the Permo-Carboniferous volcanic-sedimentary strata in mid-eastern Inner Mongolia, northeast of China. More than 820 samples were collected from 81 sites and titanium-poor magnetite and hematite are proved as the principal magnetic carriers. (1)In Kingan Block, 9 sites of volcanic rocks from Dashizhai Formation (P1) were calculated to get a mean magnetic direction Dg/Ig = 285.5°/77.4°, kg = 68.2, α95 = 6.8° before and Ds/Is = 206.5°/48.2°, ks = 100.8, α95 = 5.5°, N = 9 after bedding correction, which suggests a paleolatitude of 34.5°±5°N. Both the positive fold test and reversal test suggest a pre-folding magnetization and thus may indicate a primary remanence. (2)Three volcanic sections of Baoligaomiao Formation (C3-P1) from Uliastai Passive Margin were sampled and a mean magnetic direction derived from 16 sites is Dg/Ig = 30.1°/31.8°, kg = 16.3, α95 = 9.8° before and Ds/Is = 65.6°/58.1°, ks = 39.8, α95 = 6.1°, N = 16 after bedding correction. The corresponding paleomagnetic pole Plat. /Plong = 43.1° N/186.7°E, A95=8° suggests a paleolatitude of 38.7°±6.3°N. A primary remanence is confirmed by positive fold test. (3) In the northern margin of NCB (North China Block), a ChRM is successfully isolated from 6 sites of basaltic rocks in Elitu Formation (P2) as Dg/Ig = 351.1°/67.2°, kg = 2.1, α95 = 71.8° before and Ds/Is = 351.1°/29.1°, ks = 32.7, α95 = 71.8°, N = 16 after bedding correction, and thus yielded a paleomagnetic pole as Plat. /Plong = 63.1° N/313.5°E, A95=9.5°, which suggests a paleolatitude of 17.2°±7.2°N. A positive fold test and reversal test indicate that the remanence should be primary. The paleomagetic pole of Kingan Block and Uliastai Passive Margin are

  9. Late Paleozoic closure of the Ob-Zaisan Ocean along the Irtysh/Chara shear zone and implications for arc amalgamation and oroclinal bending in the western Central Asian Orogenic Belt

    Science.gov (United States)

    Li, Pengfei; Sun, Min; Rosenbaum, Gideon

    2016-04-01

    The Irtysh/Chara Shear Zone is one of the largest strike-slip systems in the Central Asian Orogenic Belt (CAOB). It records collisional processes of the peri-Siberian orogenic system with the West Junggar-Kazakhstan-Tianshan orogenic system following the closure of the Ob-Zaisan Ocean, but the exact timing of these events remains enigmatic. We conducted detailed structural analysis along the Irtysh Shear Zone (NW China), which together with new geochronological data allows us to reconstruct the tectonic evolution during the final closure of the Ob-Zaisan Ocean. Our results showed that subduction-accretion processes lasted at least until the Late Carboniferous in the Chinese Altai and the East/West Junggar. The subsequent arc amalgamation is characterized by a cycle of crustal thickening, orogenic collapse and transpressional thickening. On a larger scale, the West Junggar- Kazakhstan -Tianshan orogenic system defines a U-shape oroclinal structure (e.g. Xiao et al., 2010). A major phase of oroclinal bending that involved ~110° rotation may have occurred during the Late Devonian to Early Carboniferous (Levashova et al., 2012). Previous authors have linked oroclinal bending with the late Paleozoic amalgamation of the western CAOB, and proposed that a quasi-linear West Junggar- Kazakhstan -Tianshan orogenic system was buckled during the convergence of the Siberian and Tarim cratons following the closure of the Ob-Zaisan Ocean (in the north) and the South Tianshan Ocean (in the south) (e.g. Abrajevitch et al., 2008). This model, however, is not supported by our new data that constrain the closure of the Ob-Zaisan Ocean to the Late Carboniferous. Alternatively, we propose that oroclinal bending may have involved two phases of bending, with the ~110° rotation in the Late Devonian to Early Carboniferous possibly associated with trench retreat. Further tightening may have occurred in response to the convergence of the Siberian and Tarim cratons during the Late

  10. Cenozoic basin thermal history reconstruction and petroleum systems in the eastern Colombian Andes

    Science.gov (United States)

    Parra, Mauricio; Mora, Andres; Ketcham, Richard A.; Stockli, Daniel F.; Almendral, Ariel

    2017-04-01

    Late Mesozoic-Cenozoic retro-arc foreland basins along the eastern margin of the Andes in South America host the world's best detrital record for the study of subduction orogenesis. There, the world's most prolific petroleum system occur in the northernmost of these foreland basin systems, in Ecuador, Colombia and Venezuela, yet over 90% of the discovered hydrocarbons there occur in one single province in norteastern Venezuela. A successful industry-academy collaboration applied a multidisciplinary approach to the study of the north Andes with the aim of investigating both, the driving mechanisms of orogenesis, and its impact on hydrocarbon accumulation in eastern Colombia. The Eastern Cordillera is an inversion orogen located at the leading edge of the northern Andes. Syn-rift subsidence favored the accumulation of km-thick organic matter rich shales in a back-arc basin in the early Cretaceous. Subsequent late Cretaceous thermal subsidence prompted the accumulation of shallow marine sandstones and shales, the latter including the Turonian-Cenomanian main hydrocarbon source-rock. Early Andean uplift since the Paleocene led to development of a flexural basin, filled with mainly non-marine strata. We have studied the Meso-Cenozoic thermal evolution of these basins through modeling of a large thermochronometric database including hundreds of apatite and zircon fission-track and (U-Th)/He data, as well as paleothermometric information based on vitrinite reflectance and present-day temperatures measured in boreholes. The detrital record of Andean construction was also investigated through detrital zircon U-Pb geochronometry in outcrop and borehole samples. A comprehensive burial/exhumation history has been accomplished through three main modeling strategies. First, one-dimensional subsidence was used to invert the pre-extensional lithospheric thicknesses, the magnitude of stretching, and the resulting heat flow associated to extension. The amount of eroded section and

  11. Experience in implementing projects in Eastern Europe

    International Nuclear Information System (INIS)

    Weichard, A.; Bauer, I.; Rieck, R.; Ziehm, R.

    2007-01-01

    The article covers the present projects and activities in Eastern Europe of Nukem Technologies GmbH. The company's East European business began in 1973 in the field of uranium trading. After difficult negotiations in the period of the ''cold war'' it became possible to enter into an agreement with the Soviet foreign trade organization, Techsnabexport, about purchases of uranium for Western nuclear power plants. In the course of Nukem's realignment in the late 1980s, the focus was shifted more and more to the possibility of exporting into other countries the technologies developed and proven in Germany. This included countries in Eastern Europe. The situation changed abruptly with the political opening of Eastern Europe. A large potential market opened to Nukem as a supplier of technologies and plants for waste treatment and, later, the wider area of decommissioning. The partners in Eastern Europe were interested in proven, modern solutions. The ensuing success was also due to the fact that Nukem, in the early nineties, hired specialists from the new German federal states who had studied in the Soviet Union and were familiar with Russian technology, language, and culture. Soliciting analogous projects in the countries of Eastern Europe other than the former Soviet Union was begun in a parallel process. Very soon it turned out that also the interim storage of spent fuel elements constituted a potential market. (orig.)

  12. Foggy Diaspora: Romanian Women in Eastern Serbia

    Directory of Open Access Journals (Sweden)

    Sorescu-Marinković Annemarie

    2016-06-01

    Full Text Available Drawing on ethnographic and anthropological research on the Romanian communities in Eastern Serbia, this article seeks to contribute to the global scholarship on diaspora and migration. It reveals interesting differences between the well defined and intensely studied notion of “diaspora” on the one hand, and the understudied, but useful concept of “near diaspora” on the other. First, the presence of Romanians in Eastern Serbia is looked at from a gender perspective, in the wider context of feminization of international migration. Second, the paper argues that the Romanian women in Eastern Serbia adopt the strategy of living in the “social fog”, thus becoming what can be termed “foggy diaspora”.

  13. Uterine prolapse prevention in Eastern Nepal

    DEFF Research Database (Denmark)

    Radl, Christina Mathilde; Rajwar, Ranjita; Aro, Arja R.

    2012-01-01

    are working well or the attitudes toward them. This paper presents the findings of a qualitative study on primary and secondary prevention of uterine prolapse in Eastern Nepal. Method: The study involved eight focus group discussions with 71 women in six villages of the eastern districts of Siraha and Saptari......: It was found that patriarchy, gender discrimination, and cultural traditions such as early marriage and pregnancy make it difficult for people to discontinue uterine prolapse risk behaviors. Women are aware of risk factors, prevention, and treatment, but are powerless to change their situations. Health...

  14. Mycoplasma gallopavonis in eastern wild turkeys.

    Science.gov (United States)

    Luttrell, M P; Eleazer, T H; Kleven, S H

    1992-04-01

    Serum samples and tracheal cultures were collected from eastern wild turkeys (Meleagris gallopavo sylvestris) trapped for relocation in South Carolina (USA) during 1985 to 1990. Sera were tested for Mycoplasma gallisepticum and M. synoviae by the rapid plate agglutination and hemagglutination inhibition tests and were found to be negative. Tracheal cultures were negative for all pathogenic Mycoplasma spp., including M. gallisepticum, M. synoviae, M. meleagridis, and M. iowae. However, M. gallopavonis was isolated from every group of wild turkeys tested in 1986 to 1990. These data suggest that M. gallopavonis, which is generally considered nonpathogenic, may be a common microorganism in eastern wild turkeys.

  15. Eastern Germany Ahead in Employment of Women

    OpenAIRE

    Elke Holst; Anna Wieber

    2014-01-01

    Almost a quarter of a century after the fall of the Wall, there are still more women in employment in eastern Germany than in the west. Although the disparity is marginal now, the two regions started from dramatically different levels. In 1991, immediately after reunification, the employment rate for women in western Germany was 54.6 percent, but since then it has increased year on year, reaching 67.5 percent in 2012. In eastern Germany, female employment initially plummeted after the fall of...

  16. Fission track geochronology of Eastern Ghats

    Energy Technology Data Exchange (ETDEWEB)

    Virk, H S; Koul, S L; Singh, S [Punjabi Univ., Patiala (India). Dept. of Physics

    1978-12-01

    Fission track geochronology of Eastern Ghats has been established by using fission track technique in dating micaceous and accessory minerals occurring in the region. Annealing studies confirm that radiation damage fossil tracks can be erased in minerals under intense metamorphic episodes thus resetting the geological clock. The fission track ages of the minerals range between 450 +- 5 m.y. to 622 +- 148 m.y. It is concluded that f.t. ages of the minerals date the last metamorphic event of the Eastern Ghats, known as the Indian Ocean Cycle.

  17. Middle Eastern Christian spaces in Europe

    DEFF Research Database (Denmark)

    Galal, Lise Paulsen; Hunter, Alistair; McCallum, Fiona

    2016-01-01

    Despite little scholarly attention, Middle Eastern Christian Churches are a well-established element of the European religious landscape. Based on collaborative research, this article examines how three mutual field visits facilitated a deeper understanding of the complexity that characterises...... church establishment and activities among Iraqi, Assyrian/Syriac and Coptic Orthodox Christians in the UK, Sweden and Denmark. Exploring analytical dimensions of space, diversity, size, and minority position we identify three positions of Middle Eastern Christians: in London as the epitome of super...

  18. Basalts and picrites from a plume-type ophiolite in the South Qilian Accretionary Belt, Qilian Orogen: Accretion of a Cambrian Oceanic Plateau?

    Science.gov (United States)

    Zhang, Yuqi; Song, Shuguang; Yang, Liming; Su, Li; Niu, Yaoling; Allen, Mark B.; Xu, Xin

    2017-05-01

    Oceanic plateaus with high-Mg rocks in the present-day oceanic crust have attracted much attention for their proposed mantle-plume origins and abnormally high mantle potential temperatures (Tp). However, equivalent rocks in ancient oceanic environments are usually poorly preserved because of deformation and metamorphism. Here we present petrological, geochronological and geochemical data for pillow lavas from Cambrian ophiolites in the Lajishan and Yongjing regions of the South Qilian Accretionary Belt (SQAB), from the southern part of the Qilian Orogen, northern China. Three rock groups can be identified geochemically: (1) sub-alkaline basalts with enriched mid- ocean ridge basalt (E-MORB) affinity; (2) alkaline basalts with oceanic island basalt (OIB) features, probably derived from partial melting of an enriched mantle source; and (3) picrites with MgO (18-22 wt%). Cr-numbers [Cr# = Cr/(Cr + Al)] of spinels from the picrites suggest 18-21% degree of partial melting at the estimated mantle potential temperature (Tp) of 1489-1600 °C, equivalent to values of Cenozoic Hawaiian picrites (1500-1600 °C). Zircons from one gabbro sample yielded a U-Pb Concordia age of 525 ± 3 Ma, suggesting the oceanic crust formed in the Cambrian. Available evidence suggests that Cambrian mantle plume activity is preserved in the South Qilian Accretionary Belt, and influenced the regional tectonics: "jamming" of the trench by thick oceanic crust explains the emplacement and preservation of the oceanic plateau, and gave rise to the generation of concomitant Ordovician inner-oceanic island arc basalts via re-organisation of the subduction zones in the region.

  19. Elucidating tectonic events and processes from variably tectonized conglomerate clast detrital geochronology: examples from the Hongliuhe Formation in the southern Central Asian Orogenic Belt, NW China

    Science.gov (United States)

    Cleven, Nathan; Lin, Shoufa; Davis, Donald; Xiao, Wenjiao; Guilmette, Carl

    2017-04-01

    This work expands upon detrital zircon geochronology with a sampling and analysis strategy dating granitoid conglomerate clasts that exhibit differing degrees of internal ductile deformation. As deformation textures within clastic material reflect the variation and history of tectonization in the source region of a deposit, we outline a dating methodology that can provide details of the provenance's tectonomagmatic history from deformation-relative age distributions. The method involves bulk samples of solely granitoid clasts, as they are representative of the magmatic framework within the provenance. The clasts are classified and sorted into three subsets: undeformed, slightly deformed, and deformed. LA-ICPMS U-Pb geochronology is performed on zircon separates of each subset. Our case study, involving the Permian Hongliuhe Formation in the southern Central Asian Orogenic Belt, analyzes each of the three clast subsets, as well as sandstone detrital samples, at three stratigraphic levels to yield a profile of the unroofed provenance. The age spectra of the clast samples exhibit different, wider distributions than sandstone samples, considered an effect of proximity to the respective provenance. Comparisons of clast data to sandstone data, as well as comparisons between stratigraphic levels, yield indications of key tectonic processes, in addition to the typical characteristics provided by detrital geochronology. The clast data indicates a minimal lag time, implying rapid exhumation rates, whereas sandstone data alone would indicate a 90 m.y. lag time. Early Paleozoic arc building episodes appear as Ordovician peaks in sandstone data, and Silurian-Devonian peaks in clast data, indicating a younging of magmatism towards the proximal provenance. A magmatic hiatus starts in the Devonian, correlating with the latest age of deformed clasts, interpreted as timing of collisional tectonics. Provenance interpretation using the correlations seen between the clast and sandstone

  20. Orogen-parallel variation in exhumation and its influence on critical taper evolution: The case of the Emilia-Romagna Apennine (Italy)

    Science.gov (United States)

    Bonini, Marco

    2018-03-01

    The Northern Apennine prowedge exposes two adjacent sectors showing a marked along-strike change in erosion intensity, namely the Emilia Apennine to the northwest and the Romagna Apennine to the southeast. This setting has resulted from Pliocene erosion (≤5 Ma) and exhumation, which have affected the whole Romagna sector and mostly the watershed ridge in Emilia. Such an evolution has conceivably influenced the equilibrium of this fold-and-thrust belt, which can be evaluated in terms of critical Coulomb wedge theory. The present state of the thrust wedge has been assessed by crosschecking wedge tapers measured along transverse profiles with fluid pressure values inferred from deep wellbores. The interpretation of available data suggests that both Emilia and Romagna are currently overcritical. This condition is compatible with the presence in both sectors of active NE-dipping normal faults, which would work to decrease the surface slope of the orogenic wedge. However, the presence of Late Miocene-Pliocene passive-roof and out-of-sequence thrusts in Romagna may reveal a past undercritical wedge state ensuing during the regional erosion phase, thereby implying that the current overcritical condition would be a recent feature. The setting of the Emilia Apennine (i.e., strong axial exhumation and limited erosion of the prowedge) suggests instead a long lasting overcritical wedge, which was probably contemporaneous with the Pliocene undercritical wedge in Romagna. The reasons for this evolution are still unclear, although they may be linked to lithosphere-scale processes that have promoted the uplift of Romagna relative to Emilia. The lessons from the Northern Apennine thus suggest that erosion and exhumation have the ability to produce marked along-strike changes in the equilibrium of a fold-and-thrust belt.

  1. Inferred Early Permian Arc Rifting in Bogda Mountain, Southernmost of the Central Asia Orogenic Belt: Evidence from a Peperite Bearing Volcano-Sedimentary Succession

    Science.gov (United States)

    Memtimin, M.; Guo, Z.

    2017-12-01

    Late Paleozoic tectonic history, especially Carboniferous-Permian periods, of the Central Asia Orogenic Belt (CAOB) is considered to be the turning point for the termination of terrane amalgamation and closure of the Paleoasian Ocean. However, the debate about the paleoenvironment and tectonic setting of the region during the period is still not resolved. In this study, we report a set of volcano-sedimentary sequence in the Bogda Mountain of the southernmost of CAOB, which is associated with contemporaneous subaqueous emplacement of and interaction between mafic lava and carbonate sediments. The succession contains four distinct facies including closely packed pillow basalts, pillow basalts with interstitial materials, hyaloclastites and peperites. We discuss their formation and emplacement mechanism, interaction between hot magma-water/unconsolidated sediments and thermal metamorphism during the interaction. Textural features of the sequence, especially hyaloclastites and peperites, provide clear evidence for in situ autofragmentation of lava flows, synvolcanic sedimentation of carbonates, fuel coolant interaction when hot magma bulldozed into wet unconsolidated sediments, and represent autochthonous origin of the succession. Lateral transition of the lithofacies indicate a progressively deepening subaqueous environment, resembling a stepwise evolution from early stage of volcanic intrusion with lower lava flux in shallower water level to increasingly subsiding basin with more lava flux in greater depth. Previous studies determined that the mafic magma was intruded around the Carboniferous-Permian boundary ( 300Ma), and geochemical studies showed the magma was originated from dry depleted mantle with little crustal contamination. Nevertheless, the succession was thought to be fault related allochthones formation which was transferred in as part of a Carboniferous intraplate arc. Combining our findings with the previous study results, we propose a new model to

  2. The tectonometamorphic evolution of the Apuseni Mountains (Romania): Geodynamic constraints for the evolution of the Alps-Carpathians-Dinaride system of orogens

    Science.gov (United States)

    Reiser, Martin; Schuster, Ralf; Fügenschuh, Bernhard

    2015-04-01

    New structural, thermobarometric and geochronological data allow integrating kinematics, timing and intensity of tectonic phases into a geodynamic model of the Apuseni Mountain, which provides new constraints for the evolution of the Alps-Carpathians-Dinaride system of orogens. Strong differences in terms of deformation directions between Early and Late Cretaceous events provide new constraints on the regional geodynamic evolution during the Cretaceous. Geochronological and structural data evidence a Late Jurassic emplacement of the South Apuseni Ophiolites on top of the Biharia Nappe System (Dacia Mega-Unit), situated in an external position at the European margin. Following the emplacement of the ophiolites, three compressive deformation phases affected the Apuseni Mountains during Alpine orogeny: a) NE-directed in-sequence nappe stacking and regional metamorphic overprinting under amphibolite-facies conditions during the Early Cretaceous ("Austrian Phase"), b) NW-directed thrusting and folding, associated with greenschist-facies overprinting, during the early Late Cretaceous ("Turonian Phase") and c) E-W internal folding together with brittle thrusting during the latest Cretaceous ("Laramian Phase"). Major tectonic unroofing and exhumation at the transition from Early to Late Cretaceous times is documented through new Sm-Nd Grt, Ar-Ar Ms and Rb-Sr Bt ages from the study area and resulted in a complex thermal structure with strong lateral and vertical thermal gradients. Nappe stacking and medium-grade metamorphic overprinting during the Early Cretaceous exhibits striking parallels between the evolution of the Tisza-Dacia Mega-Units and the Austroalpine Nappes (ALCAPA Mega-Unit) and evidences a close connection. However, Late Cretaceous tectonic events in the study area exhibit strong similarities with the Dinarides. Thus, the Apuseni Mountains represent the "missing link" between the Early Cretaceous Meliata subduction (associated with obduction of ophiolites

  3. Effects of lateral variations of crustal rheology on the occurrence of post-orogenic normal faults: The Alto Tiberina Fault (Northern Apennines, Central Italy)

    Science.gov (United States)

    Pauselli, Cristina; Ranalli, Giorgio

    2017-11-01

    The Northern Apennines (NA) are characterized by formerly compressive structures partly overprinted by subsequent extensional structures. The area of extensional tectonics migrated eastward since the Miocene. The youngest and easternmost major expression of extension is the Alto Tiberina Fault (ATF). We estimate 2D rheological profiles across the NA, and conclude that lateral rheological crustal variations have played an important role in the formation of the ATF and similar previously active faults to the west. Lithospheric delamination and mantle degassing resulted in an easterly-migrating extension-compression boundary, coinciding at present with the ATF, where (i) the thickness of the upper crust brittle layer reaches a maximum; (ii) the critical stress difference required to initiate faulting at the base of the brittle layer is at a minimum; and (iii) the total strengths of both the brittle layer and the whole lithosphere are at a minimum. Although the location of the fault is correlated with lithospheric rheological properties, the rheology by itself does not account for the low dip ( 20°) of the ATF. Two hypotheses are considered: (a) the low dip of the ATF is related to a rotation of the stress tensor at the time of initiation of the fault, caused by a basal shear stress ( 100 MPa) possibly related to corner flow associated with delamination; or (b) the low dip is associated to low values of the friction coefficient (≤ 0.5) coupled with high pore pressures related to mantle degassing. Our results establishing the correlation between crustal rheology and the location of the ATF are relatively robust, as we have examined various possible compositions and rheological parameters. They also provide possible general indications on the mechanisms of localized extension in post-orogenic extensional setting. The hypotheses to account for the low dip of the ATF, on the other hand, are intended simply to suggest possible solutions worthy of further study.

  4. Carboniferous - Early Permian magmatic evolution of the Bogda Range (Xinjiang, NW China): Implications for the Late Paleozoic accretionary tectonics of the SW Central Asian Orogenic Belt

    Science.gov (United States)

    Wali, Guzalnur; Wang, Bo; Cluzel, Dominique; Zhong, Linglin

    2018-03-01

    The Late Paleozoic magmatic evolution of the Bogda Range (Chinese North Tianshan) is important for understanding the accretionary history of the Central Asian Orogenic Belt. We investigated the Carboniferous and Lower Permian volcanic and sedimentary sequences of the Daheyan section, southern Bogda Range, and present new zircon U-Pb ages and whole-rock geochemical data for the volcanic rocks. One Carboniferous rhyolite is dated at 298 ± 8 Ma; a Permian basalt yielded many Proterozoic zircon xenocrysts, and its maximum age (∼297 Ma) is constrained by the detrital zircon ages of the sandstone that stratigraphically underlies it. These volcanic rocks belong to calc-alkaline series. We further synthesize previous geochronological, geochemical and isotopic data of magmatic and sedimentary rocks in the Bogda Range. The available data indicate that the magmatism occurred continuously from 350 Ma to 280 Ma. A comprehensive analysis allows us to propose that: (1) the Carboniferous to Early Permian magmatic rocks of the Bogda Range generally show consistent arc-type features; (2) increasing mantle input through time suggests intra-arc extension in a supra-subduction zone; (3) the localized occurrence of Early Permian alkaline pillow basalts and deep water sediments close to the major shear zone advocate a transtensional crustal thinning during the transition from Carboniferous convergence to Early Permian transcurrent tectonics; (4) occurrence of a large number of Proterozoic zircon xenocrysts in the Late Paleozoic magmatic rocks, and Proterozoic detrital zircons in the coeval clastic sediments suggest a continental or transitional basement of the Bogda Arc; (5) subduction in the Bogda area terminated prior to the deposition of Middle Permian terrestrial sediments.

  5. Crustal nature and origin of the Russian Altai: Implications for the continental evolution and growth of the Central Asian Orogenic Belt (CAOB)

    Science.gov (United States)

    Cai, Keda; Sun, Min; Buslov, M. M.; Jahn, Bor-ming; Xiao, Wenjiao; Long, Xiaoping; Chen, Huayong; Wan, Bo; Chen, Ming; Rubanova, E. S.; Kulikova, A. V.; Voytishek, E. E.

    2016-04-01

    The Central Asian Orogenic Belt is a gigantic tectonic collage of numerous accreted terranes. However, its geodynamic evolution has been hotly debated primarily due to incomplete knowledge on the nature of these enigmatic terranes. This work presents new detrital zircon U-Pb and Hf isotopic data to constrain the crustal nature and origin of the Russian Altai, a critical segment of Altai-Mongolian terrane. The youngest zircon 206Pb/238U ages of 470 Ma constrain that the Terekta Formation, previously envisaged as Precambrian basement, was actually deposited after the Middle Ordovician. As for the three more sedimentary sequences above the Terekta Formation, they have youngest zircon 206Pb/238U ages of 425 Ma, 440 Ma and 380 Ma, respectively, indicating their depositions likely in the Late Silurian to Devonian. From all analyses, it is noted that many zircon U-Pb ages cluster at ca. 520 Ma and ca. 800 Ma, and these zircons display oscillatory zoning and have subhedral to euhedral morphology, which, collectively, suggests that adjacent Neoproterozoic to Paleozoic igneous rocks were possibly dominant in the sedimentary provenance. Additionally, a few rounded Archean to Mesoproterozoic zircon grains are characterized by complex texture, which are interpreted as recycling materials probably derived from the Tuva-Mongolian microcontinent. Precambrian rocks have not been identified in the Russian Altai, Chinese Altai and Mongolian Altai so far, therefore, Precambrian basement may not exist in the Altai-Mongolian terrane, but this terrane probably represents a large subduction-accretion complex built on the margin of the Tuva-Mongolian microcontinent in the Early Paleozoic. Multiple episodes of ridge-trench interaction may have caused inputs of mantle-derived magmas to trigger partial melting of the newly accreted crustal materials, which contributed to the accretionary complex. During accretionary orogenesis of the CAOB, formation of such subduction-accretion complex is

  6. Eastern Africa Social Science Research Review: About this journal

    African Journals Online (AJOL)

    Eastern Africa Social Science Research Review: About this journal. Journal Home > Eastern Africa Social Science Research Review: About this journal. Log in or Register to get access to full text downloads.

  7. Eastern Africa Social Science Research Review: Site Map

    African Journals Online (AJOL)

    Eastern Africa Social Science Research Review: Site Map. Journal Home > About the Journal > Eastern Africa Social Science Research Review: Site Map. Log in or Register to get access to full text downloads.

  8. Petrogenesis of late Paleozoic-to-early Mesozoic granitoids and metagabbroic rocks of the Tengchong Block, SW China: implications for the evolution of the eastern Paleo-Tethys

    Science.gov (United States)

    Zhu, Ren-Zhi; Lai, Shao-Cong; Qin, Jiang-Feng; Zhao, Shao-Wei

    2018-03-01

    This paper presents precise zircon U-Pb, bulk-rock geochemical, and Sr-Nd-Pb isotopic data for metagabbro, quartz diorite, and granite units within the Tengchong Block of SW China, which forms the southeastern extension of the Himalayan orogeny and the southwestern section of the Sanjiang orogenic belt, a key region for furthering our understanding of the evolution of the eastern Paleo-Tethys. These data reveal four groups of zircon U-Pb ages that range from the late Paleozoic to the early Mesozoic, including a 263.6 ± 3.6 Ma quartz diorite, a 218.5 ± 5.4 Ma two-mica granite, a 205.7 ± 3.1 Ma metagabbroic unit, and a 195.5 ± 2.2 Ma biotite granite. The quartz diorite in this area contains low concentrations of SiO2 (60.71-64.32 wt%), is sodium-rich, and is metaluminous, indicating formation from magmas generated by a mixed source of metamafic rocks with a significant metapelitic sedimentary material within lower arc crust. The two-mica granites contain high concentrations of SiO2 (73.2-74.3 wt%), are strongly peraluminous, and have evolved Sr-Nd-Pb isotopic compositions, all of which are indicative of a crustal source, most probably from the partial melting of felsic pelite and metagreywacke/psammite material. The metagabbros contain low concentrations of SiO2 (50.17-50.96 wt%), are sodium-rich, contain high concentrations of Fe2O3T (9.79-10.06 wt%) and CaO (6.88-7.12 wt%), and are significantly enriched in the Sr (869-894 ppm) and LREE (198.14-464.60 ppm), indicative of derivation from magmas generated by a metasomatized mantle wedge modified by the sedimentary-derived component. The biotite granites are weakly peraluminous and formed from magmas generated by melting of metasedimentary sources dominated by metagreywacke/psammite material. Combining the petrology and geochemistry of these units with the regional geology of the Indosinian orogenic belt provides evidence for two stages of magmatism: an initial stage that generated magmas during partial melting of

  9. 78 FR 6319 - Eastern Hydroelectric Corporation; Notice Rejecting Request for Rehearing

    Science.gov (United States)

    2013-01-30

    ... DEPARTMENT OF ENERGY Federal Energy Regulatory Commission [Project No. 7019-068] Eastern... an order amending license Article 401 for Eastern Hydroelectric Corporation's (Eastern Hydroelectric....\\1\\ On January 11, 2013, Eastern Hydroelectric filed a request for rehearing of Commission staff's...

  10. Gluing of Eastern Hardwoods: A Review

    Science.gov (United States)

    Terry Sellers; James R. McSween; William T. Nearn

    1988-01-01

    Over a period of years, inrreasing demand for softwoods in the Eastern United States has led to an increase in the growth of hardwoods on cut-over softwood sites. Unfortunately these hardwood trees are often of a size and shape unsuitable for the production of high-grade lumber and veneer. They do, however, represent a viable, economic soures of raw material for...

  11. Diagnosing injury to eastern forest trees

    Science.gov (United States)

    John M. Skelly; Donald D. Davis; William Merrill; E. Alan Cameron; H. Daniel Brown; David B. Drummond; Leon S., eds. Dochinger

    1987-01-01

    The purpose of this manual is to assist members of the National Vegetation Survey in recognizing air pollutant-induced injury and in identifying disease and insect damage that may be confused with air pollutant-induced injury to forest vegetation in the eastern United States. Ozone, sulfur dioxide, and, to a limited geographic extent, hydrogen fluoride, are all...

  12. Fragmentation of eastern United States forest types

    Science.gov (United States)

    Kurt H. Riitters; John W. Coulston

    2013-01-01

    Fragmentation is a continuing threat to the sustainability of forests in the Eastern United States, where land use changes supporting a growing human population are the primary driver of forest fragmentation (Stein and others 2009). While once mostly forested, approximately 40 percent of the original forest area has been converted to other land uses, and most of the...

  13. Trends in Employee Ownership in Eastern Europe

    DEFF Research Database (Denmark)

    Mygind, Niels

    2012-01-01

    are tested using the new members of the EU in Eastern Europe and the candidate country of Croatia as cases. There is no coherent panel data, but by categorizing specific trends in each country and then combining the different trend variables it is possible to identify the most important factors influencing...

  14. The "New Politics" of EU's Eastern Enlargement

    DEFF Research Database (Denmark)

    Zank, Wolfgang

    The paper gives an overview of EU's eastern enlargement and draws some theoretical conclusions. In particular, it stresses the point that the EU member states in the process of enlargement have entered a phase of "new politics", characterised by multilateralism, conditionality, help and binding...

  15. INORGANIC ELEMENTS AND DISTRIBUTION OF EASTERN OYSTERS.

    Science.gov (United States)

    Fisher, William S. In press. Inorganic Elements and Distribution of Eastern Oysters (Abstract). To be presented at the 96th Annual Meeting (Aquaculture 2004) of the National Shellfisheries Association, 1-5 March 2004, Honolulu, HI. 1 p. (ERL,GB R962). For over a century w...

  16. Faulting in eastern New Mexico: Revision 1

    International Nuclear Information System (INIS)

    Murphy, P.J.

    1987-08-01

    This area in eastern New Mexico is being studied because of its proximity to a proposed high-level nuclear waste repository site in Deaf Smith County, Texas. Regional and local tectonics must be thoroughly understood in order to be able to predict future tectonic activities in the site region. Hydrogeologic studies indicate that ground-water recharge, for regional deep and shallow aquifer systems, occurs primarily within the study area. Regional, easterly ground-water flow may be significantly affected by the spacing, orientation, and character of faults identified in this report. The tectonic history of eastern New Mexico is developed from information from 660 exploratory wells. A history of recurrent tectonic movements is evident, beginning possibly in the late Precambrian and extending into the late Cenozoic. The nature of the evidence includes the lateral and vertical distribution and the lithology of these deposits. The results are presented mainly as isopach and structure contour maps and as structural cross sections. The Paleozoic tectonic history of eastern New Mexico is similar and related to the history of the Texas Panhandle. Differences occur primarily in the Mesozoic and Cenozoic histories; tectonic uplift persisted for longer periods and faults show evidence of repeated movements in eastern New Mexico. This is probably a result of the proximity of the area to the Laramide and Basin and Range deformational events. 442 refs., 35 figs

  17. Eastern forest environmental threat assessment center

    Science.gov (United States)

    Southern Research Station. USDA Forest Service

    2010-01-01

    The Eastern Forest Environmental Threat Assessment Center (EFETAC) provides the latest research and expertise concerning threats to healthy forests – such as insects and disease, wildland loss, invasive species, wildland fire, and climate change – to assist forest landowners, managers and scientists throughout the East. Established in 2005, EFETAC is a joint effort of...

  18. Efficient silvicultural practices for eastern hardwood management

    Science.gov (United States)

    Gary W. Miller; John E. Baumgras

    1994-01-01

    Eastern hardwood forests are now managed to meet a wide range of objectives, resulting in the need for silvicultural alternatives that provide timber, wildlife, aesthetics, recreation, and other benefits. However, forest management practices must continue to be efficient in terms of profiting from current harvests, protecting the environment, and sustaining production...

  19. Is Eastern Hardwood Sawtimber Becoming Scarcer?

    Science.gov (United States)

    William G. Luppold; Gilbert P. Dempsey; Gilbert P. Dempsey

    1996-01-01

    In recent years the hardwood lumber industry has become increasingly concerned about the availability and quality of hardwood sawtimber. However, these concerns seem to contradict USDA Forest Service estimates of increased volume and quality of hardwood sawtimber. This paper examines changes in eastern hardwood sawtimber inventories and the apparent contradiction...

  20. What's known about managing eastern white pine

    Science.gov (United States)

    Charles R. Lockard

    1959-01-01

    At the 1957 meeting of the Northeastern Forest Research Advisory Council the comment was made that although Eastern white pine has been the most studied forest tree species in the Northeast, the only literature on the management of the species was in reports on isolated and uncoordinated studies. There was no comprehensive compendium of knowledge.

  1. Biomass productivity improvement for eastern cottonwood

    Science.gov (United States)

    Terry L. Robison; Randy J. Rousseau; Jianwei Zhang

    2006-01-01

    Eastern cottonwood ( Populus deltoides Marsh.) is grown in plantations by MeadWestvaco for use at its Wickliffe Kentucky Fine Papers Mill1. Genetic and productivity research over the past two decades have led to significant increases in biomass yield while reducing production costs.Initially, genetic research identified fast growing...

  2. Eastern national forests: managing for nontimber products

    Science.gov (United States)

    James L. Chamberlain; Robert J. Bush; A.L. Hammett; Philip A. Araman

    2002-01-01

    Many products are harvested from the forests of the eastern United States that are not timber-based but originate from plant materials. Over the past decade, concern has grown about the sustainability of the forest resources from which these products originate, and an associated interest in managing for these products has materialized. A content analysis of the...

  3. Lifting the curtain in Eastern Europe

    International Nuclear Information System (INIS)

    Rodgers, L.M.

    1991-01-01

    This article discusses the opportunities for engineering and technical services and investment in Eastern Bloc nations. Topics include political stability, capital and currency, economies, municipal waste processing plants, power generation equipment, nuclear and fossil power, technology, environmental protection, and construction and operation practices

  4. Rhinoplasty in the Middle Eastern nose.

    Science.gov (United States)

    Apaydin, Fazil

    2014-08-01

    In this article, the main characteristics of Middle Eastern patients seeking rhinoplasty are reported. Besides the preoperative preparation, surgical techniques that can be used to obtain good results are discussed. The pitfalls of profile alignment, tip procedures and skin have been noted as well. Copyright © 2014 Elsevier Inc. All rights reserved.

  5. Eastern Africa Journal of Rural Development

    African Journals Online (AJOL)

    The Eastern Africa Journal of Rural Development (EAJRD) is now going to be jointly published by the Ugandan Agricultural Economics Association - a professional body for Agricultural Economists and those interested in agricultural economics and rural development issues - and the Department of Agricultural Economics ...

  6. Culture and Language Learning: Middle Eastern Students.

    Science.gov (United States)

    Magrath, Douglas

    Middle Eastern students face cultural conflicts in adapting to the western value system. While feeling obligated to maintain their native culture they also need to feel comfortable with the culture of their target language. In attempting to identify with a new group, ESL students may sense a loss of membership in their native group. Culture stress…

  7. Astroparticle physics at the Eastern Colombia region

    Science.gov (United States)

    Asorey, Hernán; Núñez, Luis A.

    2015-12-01

    We present the emerging panorama of Astroparticle Physics at the Eastern Colombia region, and describe several ongoing projects, most of them related to the Latin American Giant Observatory (LAGO) Project. This research work is carried out at the Grupo de Investigaciones en Relatividad y Gravitacin of Universidad Industrial de Santander.

  8. Environmental Factors Influencing Artisanal Fishing in Eastern ...

    African Journals Online (AJOL)

    user

    The study identified the environmental factors affecting artisanal fishing in. Eastern Obolo local government area of Akwa ... colonial administration (Anko &Eyo, 2003). According to Olomola (1998), artisanal ... The problems faced by artisanal fishers in Nigeria are not far from what is experienced by artisanal fishermen in ...

  9. 78 FR 70573 - Eastern States: Filing of Plats of Survey

    Science.gov (United States)

    2013-11-26

    ... DEPARTMENT OF THE INTERIOR Bureau of Land Management [LLES956000 L14200000.BJ0000 14X] Eastern... BLM-Eastern States office in Springfield, Virginia, 30 calendar days from the date of publication in the Federal Register. FOR FURTHER INFORMATION CONTACT: Bureau of Land Management-Eastern States, 7450...

  10. 75 FR 4412 - Eastern States: Filing of Plats of Survey

    Science.gov (United States)

    2010-01-27

    ... DEPARTMENT OF THE INTERIOR Bureau of Land Management [LLES956000-L14200000-BJ0000] Eastern States... survey of the lands described below in the BLM-Eastern States office in Springfield, Virginia, 30... of Land Management-Eastern States, 7450 Boston Boulevard, Springfield, Virginia 22153. Attn...

  11. 76 FR 49760 - Texas Eastern Transmission, LP; Notice of Application

    Science.gov (United States)

    2011-08-11

    ... DEPARTMENT OF ENERGY Federal Energy Regulatory Commission [Docket No. CP11-524-000] Texas Eastern Transmission, LP; Notice of Application Take notice that on July 29, 2011, Texas Eastern Transmission, LP (Texas Eastern), 5400 Westheimer Court, Houston, Texas 77056-5310, filed with the Federal Energy...

  12. 75 FR 45611 - Texas Eastern Transmission LP; Notice of Application

    Science.gov (United States)

    2010-08-03

    ... DEPARTMENT OF ENERGY Federal Energy Regulatory Commission [Docket No. CP10-471-000] Texas Eastern Transmission LP; Notice of Application July 27, 2010. Take notice that on July 15, 2010, Texas Eastern Transmission (Texas Eastern), P.O. Box 1642, Houston, Texas 77251-1642, filed in Docket No. CP10-471-000, an...

  13. 75 FR 39579 - Eastern States: Filing of Plats of Survey

    Science.gov (United States)

    2010-07-09

    ...] Eastern States: Filing of Plats of Survey AGENCY: Bureau of Land Management, Interior. ACTION: Notice of... file the plats of survey of the lands described below in the BLM-Eastern States office in Springfield... CONTACT: Bureau of Land Management-Eastern States, 7450 Boston Boulevard, Springfield, Virginia 22153...

  14. 78 FR 66352 - Texas Eastern Transmission, LP; Notice of Application

    Science.gov (United States)

    2013-11-05

    ... DEPARTMENT OF ENERGY Federal Energy Regulatory Commission [Docket No. CP14-9-000] Texas Eastern Transmission, LP; Notice of Application Take notice that on October 17, 2013, Texas Eastern Transmission, LP (Texas Eastern), 5400 Westheimer Court, Houston, Texas 77056, filed an application in Docket No. CP14-9...

  15. 75 FR 65028 - Eastern States: Filing of Plat of Survey

    Science.gov (United States)

    2010-10-21

    ...] Eastern States: Filing of Plat of Survey AGENCY: Bureau of Land Management, Interior. ACTION: Notice of... of survey of the lands described below in the BLM-Eastern States office in Springfield, Virginia, 30... of Land Management-Eastern States, 7450 Boston Boulevard, Springfield, Virginia 22153. Attn...

  16. 78 FR 54482 - Eastern States: Filing of Plats of Survey

    Science.gov (United States)

    2013-09-04

    ... DEPARTMENT OF THE INTERIOR Bureau of Land Management [LLES956000-L14200000-BK0000] Eastern States... the Federal Register, Volume 78, Number 2, on pages 318-319 a notice entitled ``Eastern States: Filing... resurvey of a portion of the Qualla Indian Boundary, land held in trust for the Eastern Band of Cherokee...

  17. 76 FR 77846 - Eastern States: Filing of Plat of Survey

    Science.gov (United States)

    2011-12-14

    ...] Eastern States: Filing of Plat of Survey AGENCY: Bureau of Land Management, Interior. ACTION: Notice of... survey of the lands described below in the BLM-Eastern States office in Springfield, Virginia, 30... of Land Management-Eastern States, 7450 Boston Boulevard, Springfield, Virginia 22153. Attn...

  18. 75 FR 72837 - Eastern States: Filing of Plats of Survey

    Science.gov (United States)

    2010-11-26

    ...] Eastern States: Filing of Plats of Survey AGENCY: Bureau of Land Management, Interior. ACTION: Notice of... (BLM) will file the plats of survey of the lands described below in the BLM-Eastern States office in... INFORMATION CONTACT: Bureau of Land Management-Eastern States, 7450 Boston Boulevard, Springfield, Virginia...

  19. 76 FR 55700 - Eastern States: Filing of Plat of Survey

    Science.gov (United States)

    2011-09-08

    ...] Eastern States: Filing of Plat of Survey AGENCY: Bureau of Land Management, Interior. ACTION: Notice of... survey of the lands described below in the BLM-Eastern States office in Springfield, Virginia, 30... of Land Management-Eastern States, 7450 Boston Boulevard, Springfield, Virginia 22153. Attn...

  20. 75 FR 18234 - Eastern States: Filing of Plat of Survey

    Science.gov (United States)

    2010-04-09

    ...] Eastern States: Filing of Plat of Survey AGENCY: Bureau of Land Management, Interior. ACTION: Notice of...) will file the plats of survey of the lands described below in the BLM-Eastern States office in... INFORMATION CONTACT: Bureau of Land Management--Eastern States, 7450 Boston Boulevard, Springfield, Virginia...

  1. 78 FR 48900 - Eastern States: Filing of Plat of Survey

    Science.gov (United States)

    2013-08-12

    ...] Eastern States: Filing of Plat of Survey AGENCY: Bureau of Land Management, Interior. ACTION: Notice of... survey of the lands described below in the BLM-Eastern States office in Springfield, Virginia, 30... of Land Management-Eastern States, 7450 Boston Boulevard, Springfield, Virginia 22153. Attn...

  2. 76 FR 45293 - Eastern States: Filing of Plat of Survey

    Science.gov (United States)

    2011-07-28

    ...] Eastern States: Filing of Plat of Survey AGENCY: Bureau of Land Management, Interior. ACTION: Notice of... survey of the lands described below in the BLM-Eastern States office in Springfield, Virginia, 30... of Land Management-Eastern States, 7450 Boston Boulevard, Springfield, Virginia 22153. Attn...

  3. 76 FR 48882 - Eastern States: Filing of Plat of Survey

    Science.gov (United States)

    2011-08-09

    ...] Eastern States: Filing of Plat of Survey AGENCY: Bureau of Land Management, Interior. ACTION: Notice Of... survey of the lands described below in the BLM-Eastern States office in Springfield, Virginia, 30... of Land Management--Eastern States, 7450 Boston Boulevard, Springfield, Virginia 22153. Attn...

  4. 76 FR 3651 - Eastern States: Filing of Plat of Survey

    Science.gov (United States)

    2011-01-20

    ... DEPARTMENT OF THE INTERIOR Bureau of Land Management [LLES956000-L14200000-BJ0000] Eastern States... described below in the BLM-Eastern States office in Springfield, Virginia, 30 calendar days from the date of publication in the Federal Register. FOR FURTHER INFORMATION CONTACT: Bureau of Land Management-Eastern States...

  5. 75 FR 13302 - Eastern States: Filing of Plat of Survey

    Science.gov (United States)

    2010-03-19

    ...] Eastern States: Filing of Plat of Survey AGENCY: Bureau of Land Management, Interior. ACTION: Notice of...) will file the plat of survey of the lands described below in the BLM-Eastern States office in... INFORMATION CONTACT: Bureau of Land Management--Eastern States, 7450 Boston Boulevard, Springfield, Virginia...

  6. 77 FR 30314 - Eastern States: Filing of Plat of Survey

    Science.gov (United States)

    2012-05-22

    ...] Eastern States: Filing of Plat of Survey AGENCY: Bureau of Land Management, Interior ACTION: Notice... the BLM-Eastern States office in Springfield, Virginia, 30 calendar days from the date of publication in the Federal Register. FOR FURTHER INFORMATION CONTACT: Bureau of Land Management-Eastern States...

  7. 78 FR 16294 - Eastern States: Filing of Plat of Survey

    Science.gov (United States)

    2013-03-14

    ... DEPARTMENT OF THE INTERIOR Bureau of Land Management [LLES956000-L14100000-BX0000] Eastern States... of Land Management (BLM) will file the plat of survey of the lands described below in the BLM-Eastern... Register. FOR FURTHER INFORMATION CONTACT: Bureau of Land Management-Eastern States, 7450 Boston Boulevard...

  8. 77 FR 63856 - Eastern States: Filing of Plats of Survey

    Science.gov (United States)

    2012-10-17

    ...] Eastern States: Filing of Plats of Survey AGENCY: Bureau of Land Management, Interior. ACTION: Notice of... plats of survey of the lands described below in the BLM-Eastern States office in Springfield, Virginia... CONTACT: Bureau of Land Management-Eastern States, 7450 Boston Boulevard, Springfield, Virginia 22153...

  9. 76 FR 16444 - Eastern States: Filing of Plat of Survey

    Science.gov (United States)

    2011-03-23

    ... DEPARTMENT OF THE INTERIOR Bureau of Land Management [LLES956000-L14200000-BJ0000] Eastern States... described below in the BLM-Eastern States office in Springfield, Virginia. DATES: BLM will file the plat of survey on April 22, 2011. FOR FURTHER INFORMATION CONTACT: Bureau of Land Management-Eastern States, 7450...

  10. 75 FR 33635 - Eastern States: Filing of Plat of Survey

    Science.gov (United States)

    2010-06-14

    ... DEPARTMENT OF THE INTERIOR Bureau of Land Management [LLES956000-L14200000-BJ0000] Eastern States... described below in the BLM--Eastern States office in Springfield, Virginia, 30 calendar days from the date...--Eastern States, 7450 Boston Boulevard, Springfield, Virginia 22153. Attn: Cadastral Survey. SUPPLEMENTARY...

  11. 78 FR 23952 - Eastern States: Filing of Plats of Survey

    Science.gov (United States)

    2013-04-23

    ...] Eastern States: Filing of Plats of Survey AGENCY: Bureau of Land Management, Interior. ACTION: Notice of... file the plats of survey of the lands described below in the BLM-Eastern States office in Springfield... CONTACT: Bureau of Land Management-Eastern States, 7450 Boston Boulevard, Springfield, Virginia 22153...

  12. 75 FR 42459 - Eastern States: Filing of Plat of Survey

    Science.gov (United States)

    2010-07-21

    ...] Eastern States: Filing of Plat of Survey AGENCY: Bureau of Land Management, Interior. ACTION: Notice of... survey of the lands described below in the BLM-Eastern States office in Springfield, Virginia, 30... of Land Management-Eastern States, 7450 Boston Boulevard, Springfield, Virginia 22153. Attn...

  13. 76 FR 45292 - Eastern States: Filing of Plats of Survey

    Science.gov (United States)

    2011-07-28

    ...] Eastern States: Filing of Plats of Survey AGENCY: Bureau of Land Management, Interior. ACTION: Notice of... the plats of survey of the lands described below in the BLM-Eastern States office in Springfield... CONTACT: Bureau of Land Management--Eastern States, 7450 Boston Boulevard, Springfield, Virginia 22153...

  14. 75 FR 80069 - Eastern States: Filing of Plat of Survey

    Science.gov (United States)

    2010-12-21

    ...] Eastern States: Filing of Plat of Survey AGENCY: Bureau of Land Management, Interior. ACTION: Notice of... survey of the lands described below in the BLM-Eastern States office in Springfield, Virginia, 30... of Land Management-Eastern States, 7450 Boston Boulevard, Springfield, Virginia 22153. Attn...

  15. 78 FR 64933 - Texas Eastern Transmission, LP; Notice of Application

    Science.gov (United States)

    2013-10-30

    ... DEPARTMENT OF ENERGY Federal Energy Regulatory Commission [Docket No. CP14-4-000] Texas Eastern Transmission, LP; Notice of Application Take notice that on October 10, 2013, Texas Eastern Transmission, (Texas Eastern), having its principal place of business at 5400 Westheimer Court, Houston, Texas, 77056...

  16. 76 FR 38381 - Texas Eastern Transmission, LP; Notice of Amendment

    Science.gov (United States)

    2011-06-30

    ... DEPARTMENT OF ENERGY Federal Energy Regulatory Commission [Docket No. CP11-67-001] Texas Eastern Transmission, LP; Notice of Amendment Take notice that on June 13, 2011, Texas Eastern Transmission, LP (Texas Eastern), 5400 Westheimer Court, Houston, Texas 77056, filed in the above referenced docket an amendment...

  17. 77 FR 37919 - Eastern States: Filing of Plat of Survey

    Science.gov (United States)

    2012-06-25

    ... DEPARTMENT OF THE INTERIOR Bureau of Land Management [LLES956000-L19100000-Bk0000] Eastern States... of Land Management (BLM) will file the plat of survey of the lands described below in the BLM-Eastern... Register. FOR FURTHER INFORMATION CONTACT: Bureau of Land Management-Eastern States, 7450 Boston Boulevard...

  18. 76 FR 2133 - Eastern States: Filing of Plat of Survey

    Science.gov (United States)

    2011-01-12

    ... DEPARTMENT OF THE INTERIOR Bureau of Land Management [LLES956000-L14200000-BJ0000] Eastern States... described below in the BLM-Eastern States office in Springfield, Virginia, 30 calendar days from the date of publication in the Federal Register. FOR FURTHER INFORMATION CONTACT: Bureau of Land Management-Eastern States...

  19. 76 FR 6816 - Eastern States: Filing of Plat of Survey

    Science.gov (United States)

    2011-02-08

    ...] Eastern States: Filing of Plat of Survey AGENCY: Bureau of Land Management, Interior. ACTION: Notice of... survey of the lands described below in the BLM-Eastern States office in Springfield, Virginia, 30... of Land Management--Eastern States, 7450 Boston Boulevard, Springfield, Virginia 22153. Attn...

  20. 76 FR 26767 - Eastern States: Filing of Plat of Survey

    Science.gov (United States)

    2011-05-09

    ... DEPARTMENT OF THE INTERIOR Bureau of Land Management [LLES956000-L14200000-BJ0000] Eastern States... described below in the BLM-Eastern States office in Springfield, Virginia, 30 calendar days from the date of publication in the Federal Register. FOR FURTHER INFORMATION CONTACT: Bureau of Land Management-Eastern States...

  1. 78 FR 79687 - Texas Eastern Transmission, LP; Notice of Application

    Science.gov (United States)

    2013-12-31

    ... DEPARTMENT OF ENERGY Federal Energy Regulatory Commission [Docket No. CP14-29-000] Texas Eastern Transmission, LP; Notice of Application Take notice that on December 10, 2013 Texas Eastern Transmission, LP (Texas Eastern), at 5400 Westheimer Court, Houston, Texas 77056, filed an application in Docket No. CP14...

  2. 77 FR 26534 - Texas Eastern Transmission, LP; Notice of Application

    Science.gov (United States)

    2012-05-04

    ... DEPARTMENT OF ENERGY Federal Energy Regulatory Commission [Docket No. CP12-164-000] Texas Eastern Transmission, LP; Notice of Application Take notice that on April 19, 2012, Texas Eastern Transmission, LP (Texas Eastern), 5400 Westheimer Court, Houston, Texas 77056, filed in Docket No. CP12-164-000, a request...

  3. 77 FR 20015 - Texas Eastern Transmission, LP; Notice of Application

    Science.gov (United States)

    2012-04-03

    ... DEPARTMENT OF ENERGY Federal Energy Regulatory Commission [Docket No. CP12-88-000] Texas Eastern Transmission, LP; Notice of Application Take notice that on March 19, 2012, Texas Eastern Transmission, LP (Texas Eastern), 5400 Westheimer Court, Houston, Texas 77056-5310, filed an application in Docket No...

  4. 76 FR 33342 - Eastern States; Filing of Plats of Survey

    Science.gov (United States)

    2011-06-08

    ...] Eastern States; Filing of Plats of Survey AGENCY: Bureau of Land Management, Interior. ACTION: Notice of... published in the Federal Register, Volume 75, Number 174, on page 54910 a notice entitled ``Eastern States..., 2011 and the plat of survey accepted June 22, 2010, was officially filed in Eastern States Office...

  5. 75 FR 4412 - Eastern States: Filing of Plat of Survey

    Science.gov (United States)

    2010-01-27

    ...] Eastern States: Filing of Plat of Survey AGENCY: Bureau of Land Management, Interior. ACTION: Notice of... file the plat of survey of the lands described below in the BLM-Eastern States office in Springfield... CONTACT: Bureau of Land Management-Eastern States, 7450 Boston Boulevard, Springfield, Virginia 22153...

  6. 77 FR 12045 - Texas Eastern Transmission, LP; Notice of Application

    Science.gov (United States)

    2012-02-28

    ... DEPARTMENT OF ENERGY Federal Energy Regulatory Commission [Docket No. CP12-68-000] Texas Eastern Transmission, LP; Notice of Application Take notice that on February 16, 2012, Texas Eastern Transmission, LP (Texas Eastern), PO Box 1642, Houston, Texas 77056 filed an application in the above referenced docket...

  7. 76 FR 18210 - Texas Eastern Transmission, LP; Notice of Application

    Science.gov (United States)

    2011-04-01

    ... DEPARTMENT OF ENERGY Federal Energy Regulatory Commission [Docket No. CP11-138-000] Texas Eastern Transmission, LP; Notice of Application On March 15, 2011, Texas Eastern Transmission Corporation (Texas Eastern), 5400 Westheimer Court, Houston, Texas 77056-5310, filed with the Federal Energy Regulatory...

  8. 77 FR 58575 - Eastern States: Filing of Plat of Survey

    Science.gov (United States)

    2012-09-21

    ...] Eastern States: Filing of Plat of Survey AGENCY: Bureau of Land Management, Interior. ACTION: Notice... the BLM-Eastern States office in Springfield, Virginia, 30 calendar days from the date of publication in the Federal Register. FOR FURTHER INFORMATION CONTACT: Bureau of Land Management-Eastern States...

  9. 76 FR 65533 - Eastern States: Filing of Plat of Survey

    Science.gov (United States)

    2011-10-21

    ...] Eastern States: Filing of Plat of Survey AGENCY: Bureau of Land Management, Interior. ACTION: Notice of... of survey of the land described below in the BLM-Eastern States office in Springfield, Virginia, 30... of Land Management--Eastern States, 7450 Boston Boulevard, Springfield, Virginia 22153. Attn...

  10. 75 FR 18145 - Eastern Arizona Counties Resource Advisory Committee

    Science.gov (United States)

    2010-04-09

    ... DEPARTMENT OF AGRICULTURE Forest Service Eastern Arizona Counties Resource Advisory Committee AGENCY: Forest Service, USDA. ACTION: Notice of meeting. SUMMARY: The Eastern Arizona Counties Resource... Rivera, Coordinator, Eastern Arizona Counties Resource Advisory Committee, c/o Forest Service, USDA, P.O...

  11. 75 FR 54910 - Eastern States: Filing of Plat of Survey

    Science.gov (United States)

    2010-09-09

    ...] Eastern States: Filing of Plat of Survey AGENCY: Bureau of Land Management, Interior. ACTION: Notice of... survey of the lands described below in the BLM-Eastern States office in Springfield, Virginia, 30... of Land Management-Eastern States, 7450 Boston Boulevard, Springfield, Virginia 22153. Attn...

  12. Assessing health literacy in the eastern and middle-eastern cultures

    OpenAIRE

    Nair, Satish Chandrasekhar; Satish, Karthyayani Priya; Sreedharan, Jayadevan; Ibrahim, Halah

    2016-01-01

    Abstract Background Health literacy is a term employed to assess the ability of people to meet the increasing demands related to health in a rapidly evolving society. Low health literacy can affect the social determinants of health, health outcomes and the use of healthcare services. The purpose of the study was to develop a survey construct to assess health literacy within the context of regional culture. Different socioeconomic status among the Eastern and Middle Eastern countries may restr...

  13. Assessing health literacy in the eastern and middle-eastern cultures.

    Science.gov (United States)

    Nair, Satish Chandrasekhar; Satish, Karthyayani Priya; Sreedharan, Jayadevan; Ibrahim, Halah

    2016-08-19

    Health literacy is a term employed to assess the ability of people to meet the increasing demands related to health in a rapidly evolving society. Low health literacy can affect the social determinants of health, health outcomes and the use of healthcare services. The purpose of the study was to develop a survey construct to assess health literacy within the context of regional culture. Different socioeconomic status among the Eastern and Middle Eastern countries may restrict, health information access and utilization for those with low literacy. By employing expert panel, Delphi technique, focus group methodologies, and pre-testing using participants (N = 900) from the UAE and India, a survey construct to the Eastern-Middle Eastern cultures was developed. Reliability was assessed using Cronbach's α and validity using Factor analysis. Kiaser-Meyer-Olkin (KMO) sampling adequacy and Bartlett's tests were used to assess the strength of the relationship among the variables. Inclusion of non-health related items were found to be critical in the authentic assessment of health literacy in the Eastern and Middle Eastern population given the influence of social desirability. Thirty-two percentage of the original 19-item construct was eliminated by the focus group for reasons of relevance and impact for the local culture. Field pretesting participants from two countries, indicated overall construct reliability (Cronbach's α =0.85), validity and consistency (KMO value of 0.92 and Bartlett's test of sphericity was significant). The Eastern-Middle Eastern Adult Health Literacy (EMAHL13), screening instrument is brief, simple, a useful indicator of whether or not a patient can read. It assessespatients' ability to comprehend by distinguishing between health and non-health related items. The EMAHL13 will be a useful too for the reliable assessment of health literacy in countries, where culture plays a significant impact. This will be the first steptowards providing

  14. Pachybrachis (Coleoptera, Chrysomelidae, Cryptocephalinae) of Eastern Canada

    Science.gov (United States)

    Barney, Robert J.; LeSage, Laurent; Savard, Karine

    2013-01-01

    Abstract Seventeen Pachybrachis species occurring in eastern Canada [Ontario (ON), Québec (QC), New Brunswick (NB), Nova Scotia (NS), and Prince Edward Island (PE)] are treated by the authors. Two new national records were discovered, both from southernmost Ontario: P. cephalicus Fall and P. luctuosus Suffrian. Four species were new provincial records: P. cephalicus (ON), P. luctuosus (ON, QC), P. obsoletus Suffrian (NB), P. peccans (PE). A fully illustrated key to the Pachybrachis of eastern Canada is provided and supported with extensive photographs, distribution maps, and plant associations. Three species were distributed from southern Ontario into at least one province in the Maritimes (P. nigricornis (Say), P. obsoletus Suffrianand P. peccans Suffrian). Six species were distributed along the shores of the Great Lakes (Erie, Michigan, and Ontario) and rivers (Ottawa, Saguenay and St. Lawrence), but unknown from central and northern ON and QC (P. bivittatus (Say), P. hepaticus hepaticus (F. E. Melsheimer), P. othonus othonus (Say), P. pectoralis (F. E. Melsheimer), P. spumarius Suffrianand P. trinotatus (F. E. Melsheimer)). Seven species were rare, five being found exclusively from southern ON (P. calcaratus Fall, P. cephalicus, P. luridus (Fabricius), P. subfasciatus (J. E. LeConte)and P. tridens (F. E. Melsheimer)), with two having, in addition, a disjunct population in QC (P. atomarius (F. E. Melsheimer)and P. luctuosus). One species was found to be the northern most extension of an eastern United States (US) distribution into the eastern townships of QC (P. m-nigrum (F. E. Melsheimer)). There were no Pachybrachis that could be considered arctic, subarctic, or boreal species; no specimens were found from Labrador and Newfoundland, and all species had southern affinities. Pachybrachis atomarius, P. calcaratus, P. luridus, P. subfaciatus, and P. tridens, not seen over the last 30–70 years, may be extirpated from eastern Canada. PMID:24163583

  15. Phylogeography of Eastern Grey Kangaroos, Macropus giganteus, Suggests a Mesic Refugium in Eastern Australia.

    Directory of Open Access Journals (Sweden)

    Brett A Coghlan

    Full Text Available Phylogeographic studies around the world have identified refugia where fauna were able to persist during unsuitable climatic periods, particularly during times of glaciation. In Australia the effects of Pleistocene climate oscillations on rainforest taxa have been well studied but less is known about the effects on mesic-habitat fauna, such as the eastern grey kangaroo (Macropus giganteus. The eastern grey kangaroo is a large mammal that is common and widespread throughout eastern Australia, preferring dry mesic habitat, rather than rainforest. As pollen evidence suggests that the central-eastern part of Australia (southeast Queensland and northern New South Wales experienced cycles of expansion in mesic habitat with contraction in rainforests, and vice versa during glacial and interglacial periods, respectively, we hypothesise that the distribution of the eastern grey kangaroo was affected by these climate oscillations and may have contracted to mesic habitat refugia. From 375 mitochondrial DNA control region sequences from across the distribution of eastern grey kangaroos we obtained 108 unique haplotypes. Phylogenetic analysis identified two clades in Queensland, one of which is newly identified and restricted to a small coastal region in southern Queensland north of Brisbane, known as the Sunshine Coast. The relatively limited geographic range of this genetically isolated clade suggests the possibility of a mesic habitat refugium forming during rainforest expansion during wetter climate cycles. Other potential, although less likely, reasons for the genetic isolation of the highly distinct clade include geographic barriers, separate northward expansions, and strong local adaptation.

  16. Phylogeography of Eastern Grey Kangaroos, Macropus giganteus, Suggests a Mesic Refugium in Eastern Australia.

    Science.gov (United States)

    Coghlan, Brett A; Goldizen, Anne W; Thomson, Vicki A; Seddon, Jennifer M

    2015-01-01

    Phylogeographic studies around the world have identified refugia where fauna were able to persist during unsuitable climatic periods, particularly during times of glaciation. In Australia the effects of Pleistocene climate oscillations on rainforest taxa have been well studied but less is known about the effects on mesic-habitat fauna, such as the eastern grey kangaroo (Macropus giganteus). The eastern grey kangaroo is a large mammal that is common and widespread throughout eastern Australia, preferring dry mesic habitat, rather than rainforest. As pollen evidence suggests that the central-eastern part of Australia (southeast Queensland and northern New South Wales) experienced cycles of expansion in mesic habitat with contraction in rainforests, and vice versa during glacial and interglacial periods, respectively, we hypothesise that the distribution of the eastern grey kangaroo was affected by these climate oscillations and may have contracted to mesic habitat refugia. From 375 mitochondrial DNA control region sequences from across the distribution of eastern grey kangaroos we obtained 108 unique haplotypes. Phylogenetic analysis identified two clades in Queensland, one of which is newly identified and restricted to a small coastal region in southern Queensland north of Brisbane, known as the Sunshine Coast. The relatively limited geographic range of this genetically isolated clade suggests the possibility of a mesic habitat refugium forming during rainforest expansion during wetter climate cycles. Other potential, although less likely, reasons for the genetic isolation of the highly distinct clade include geographic barriers, separate northward expansions, and strong local adaptation.

  17. Elemental and Sr-Nd isotopic geochemistry of Cretaceous to Early Paleogene granites and volcanic rocks in the Sikhote-Alin Orogenic Belt (Russian Far East): implications for the regional tectonic evolution

    Science.gov (United States)

    Zhao, Pan; Jahn, Bor-ming; Xu, Bei

    2017-09-01

    The Sikhote-Alin Orogenic Belt in Russian Far East is an important Late Mesozoic to Early Cenozoic accretionary orogen related to the subduction of the Paleo-Pacific Plate. This belt was generated by successive accretion of terranes made of accretionary prisms, turbidite basins and island arcs to the continental margin of northeastern Asia (represented by the Bureya-Jiamusi-Khanka Block) from Jurassic to Late Cretaceous. In order to study the tectonic and crustal evolution of this orogenic belt, we carried out zircon U-Pb dating, and whole-rock elemental and Sr-Nd isotopic analyses on granites and volcanic rocks from the Primorye region of southern Sikhote-Alin. Zircon dating revealed three episodes of granitoid emplacement: Permian, Early Cretaceous and Late Cretaceous to Early Paleogene. Felsic volcanic rocks (mainly rhyolite, dacite and ignimbrite) that overlay all tectonostratigraphic terranes were erupted during 80-57 Ma, postdating the accretionary process in the Sikhote-Alin belt. The Cretaceous-Paleogene magmatism represents the most intense tectonothermal event in the Sikhote-Alin belt. Whole-rock major and trace elemental data show arc-like affinity for granitoids and volcanic rocks, indicating that they were likely generated in a supra-subduction setting. Their initial 87Sr/86Sr ratios range from 0.7048 to 0.7114, and εNd(t) values vary from +1.7 to -3.8 (mostly < 0). Thus, the elemental and Sr-Nd isotopic data suggest that the felsic magmas were generated by partial melting of source rocks comprising mantle-derived juvenile component and recycled crustal component. In addition to the occurrence in the Sikhote-Alin orogenic belt, Cretaceous to Early Paleogene magmatic rocks are also widespread in NE China, southern Korean peninsula, Japanese islands and other areas of Russian Far East, particularly along the coastal regions of the Okhotsk and Bering Seas. These rocks constitute an extended magmatic belt along the continental margin of NE Asia. The

  18. Testing the effects of topography, geometry, and kinematics on modeled thermochronometer cooling ages in the eastern Bhutan Himalaya

    Science.gov (United States)

    Gilmore, Michelle E.; McQuarrie, Nadine; Eizenhöfer, Paul R.; Ehlers, Todd A.

    2018-05-01

    In this study, reconstructions of a balanced geologic cross section in the Himalayan fold-thrust belt of eastern Bhutan are used in flexural-kinematic and thermokinematic models to understand the sensitivity of predicted cooling ages to changes in fault kinematics, geometry, topography, and radiogenic heat production. The kinematics for each scenario are created by sequentially deforming the cross section with ˜ 10 km deformation steps while applying flexural loading and erosional unloading at each step to develop a high-resolution evolution of deformation, erosion, and burial over time. By assigning ages to each increment of displacement, we create a suite of modeled scenarios that are input into a 2-D thermokinematic model to predict cooling ages. Comparison of model-predicted cooling ages to published thermochronometer data reveals that cooling ages are most sensitive to (1) the location and size of fault ramps, (2) the variable shortening rates between 68 and 6.4 mm yr-1, and (3) the timing and magnitude of out-of-sequence faulting. The predicted ages are less sensitive to (4) radiogenic heat production and (5) estimates of topographic evolution. We used the observed misfit of predicted to measured cooling ages to revise the cross section geometry and separate one large ramp previously proposed for the modern décollement into two smaller ramps. The revised geometry results in an improved fit to observed ages, particularly young AFT ages (2-6 Ma) located north of the Main Central Thrust. This study presents a successful approach for using thermochronometer data to test the viability of a proposed cross section geometry and kinematics and describes a viable approach to estimating the first-order topographic evolution of a compressional orogen.

  19. Thrusting and multiple folding in the Neoproterozoic Pan-African basement of Wadi Hodein area, south Eastern Desert, Egypt

    Science.gov (United States)

    Abdeen, M. M.; Sadek, M. F.; Greiling, R. O.

    2008-09-01

    Detailed field mapping and structural studies of the area around the mouth of Wadi Hodein, some 20 km west of Shalatein at the Red Sea coast in the south Eastern Desert of Egypt, revealed four phases of structural deformation (D1-D4) affecting the Neoproterozoic Pan-African basement rocks. D1 is related to arc-arc collision and is represented by ENE-WSW oriented megascopic upright open folds associated with low angle thrusts and mesoscopic tight, overturned and recumbent F1 folds. Kinematic indicators indicate thrusting towards the SSE. D2 is represented by NNW-SSE oriented megascopic and mesoscopic folds, which are tight, verge towards the WSW and display a left-stepping en echelon pattern. D3 includes major NNW-SSE trending sinistral shear zones that show subordinate reverse fault components and dip steeply towards the ENE. These sinistral shear zones are comparable with the Najd Fault System, as they display a similar sense of movement and relationships to earlier structures. Therefore, they are interpreted to be the continuation of the Najd Shear System in southern Egypt. D2 and D3 are related to accretion of east and west Gondwana. D4 is represented by E-W oriented dextral faults with left-stepping segments. The first three deformation events are in agreement with the general evolutionary model for the East African Orogen in the Arabian-Nubian Shield that begins with NNW-SSE shortening, followed by ENE-WSW compression and subsequent deformation by the NNW-SSE striking Najd Fault System. The E-W dextral faults may be the conjugate shear fractures to the D3 NNW-SSE oriented sinistral wrench faults or are related to a subsequent event, D4. NW-SE oriented gold-bearing quartz veins originated during D1 and were subsequently deformed by D2-D4 events.

  20. Microstructural finite strain analysis and 40Ar/39Ar evidence for the origin of the Mizil gneiss dome, eastern Arabian Shield, Saudi Arabia

    Science.gov (United States)

    Al-Saleh, Ahmad M.; Kassem, Osama M. K.

    2012-07-01

    The Mizil antiform is a gneiss-cored culmination situated near the northern end of the Ar Rayn island arc terrane, which is the easternmost exposed tectonic unit of the Arabian Shield. This domal structure has a mantle of metamorphosed volcanosedimentary rocks belonging to the Al-Amar Group, and an igneous interior made up of foliated granodiorite-tonalite with adakitic affinity. The gneissic core has a SHRIMP U-Pb zircon age of 689 ± 10 Ma making it the oldest rock unit in the Ar Rayn terrane. An adakite diapir, formed by the melting of the subducted crust of a young marginal basin, and rising through the volcanosedimentary succession of the Ar Rayn island arc is thought to have caused the observed doming. Relatively uniform strain throughout the dome combined with strong vertical shortening and the roughly radial pattern of stretching lineation is consistent with diapirism; the absence of strain localization rules out detachment faulting as a causative mechanism. Amphibolites from the metamorphic envelope have an 40Ar/39Ar age of 615 ± 2 Ma; the age gap between core and cover is thought to reflect the resetting of metamorphic ages during the final suturing event, a phenomenon that is often observed throughout the eastern shield. Aeromagnetic anomalies beneath the Phanerozoic sedimentary cover indicate the presence of a collage of accreted terranes east of the Ar Rayn terrane that were probably amalgamated onto the Arabian margin during the latest stages of the closure of the Mozambique ocean; culminant orogeny is believed to have taken place between 620 and 600 Ma as these terrane collided with a major continental mass to the east referred to here as the eastern Arabian block (EAB). The Mizil gneiss dome is therefore considered to have formed in a convergent contractional setting rather than being the outcome of extensional post-orogenic collapse.

  1. The topography of a continental indenter: The interplay between crustal deformation, erosion, and base level changes in the eastern Southern Alps

    Science.gov (United States)

    Heberer, B.; Prasicek, G.; Neubauer, F.; Hergarten, S.

    2017-01-01

    Abstract The topography of the eastern Southern Alps (ESA) reflects indenter tectonics causing crustal shortening, surface uplift, and erosional response. Fluvial drainages were perturbed by Pleistocene glaciations that locally excavated alpine valleys. The Late Miocene desiccation of the Mediterranean Sea and the uplift of the northern Molasse Basin led to significant base level changes in the far field of the ESA and the Eastern Alps (EA), respectively. Among this multitude of mechanisms, the processes that dominate the current topographic evolution of the ESA and the ESA‐EA drainage divide have not been identified. We demonstrate the expected topographic effects of each mechanism in a one‐dimensional model and compare them with observed channel metrics. We find that the normalized steepness index increases with uplift rate and declines from the indenter tip in the northwest to the foreland basin in the southeast. The number and amplitude of knickpoints and the distortion in longitudinal channel profiles similarly decrease toward the east. Changes in slope of χ‐transformed channel profiles coincide spatially with the Valsugana‐Fella fault linking crustal stacking and uplift induced by indenter tectonics with topographic evolution. Gradients in χ across the ESA‐EA drainage divide imply an ongoing, north directed shift of the Danube‐ESA watershed that is most likely driven by a base level rise in the northern Molasse basin. We conclude that the regional uplift pattern controls the geometry of ESA‐EA channels, while base level changes in the far field control the overall architecture of the orogen by drainage divide migration. PMID:28344912

  2. Prevalence of blood parasites in eastern versus Western house finches: are eastern birds resistant to infection?

    Science.gov (United States)

    Davis, Andrew K; Hood, Wendy R; Hill, Geoffrey E

    2013-09-01

    The rapid spread of the bacterial disease, Mycoplasma gallisepticum (MG), throughout the introduced range of house finches (Carpodacus mexicanus) in eastern North America, compared to its slower spread through the native western range, has puzzled researchers and highlights the need to understand the relative differences in health state of finches from both populations. We conducted a light-microscope survey of hemoparasites in populations of finches from Arizona (within the western range) and from Alabama (within the eastern range), and compared our estimates of prevalence to published reports from house finches sampled in both ranges. Of the 33 Arizona birds examined, we recorded hematozoan infections in 16 (48.5%) individuals, compared to 1 infected Alabama bird out of 30 birds examined (3.3%). Based on independent surveys of seven western North American and five eastern North American populations of house finches the average prevalence of blood parasites in western populations is 38.8% (±17.9 SD), while the average prevalence within the eastern range is only 5.9% (±6.1 SD). The average rate of infection among all songbirds sampled in the east is 34.2% (±4.8 SD). Thus, our surveys of wild birds as well as previously published observations point to eastern house finches having a much lower prevalence of blood parasite infections than their western counterparts. Combined with the fact that eastern finches also tend to have lower rates of avian pox infections than do western birds (based on a literature review), these observations suggest that eastern birds have either strong resistance to these infections or high susceptibility and associated mortality.

  3. Leucogranites in Lhozag, southern Tibet: Implications for the tectonic evolution of the eastern Himalaya

    Science.gov (United States)

    Huang, Chunmei; Zhao, Zhidan; Li, Guangming; Zhu, Di-Cheng; Liu, Dong; Shi, Qingshang

    2017-12-01

    Petrogenesis of the Himalayan leucogranite is strongly influenced by conditions which are associated with the tectonic evolution of Himalayan orogen. In this article, we present petrological, geochronological and geochemical results of the Lhozag leucogranites that crop out alongside the South Tibetan Detachment System (STDS) in the east of Himalaya. Zircon U-Pb dating revealed three episodes of leucogranitic magmatism in Lhozag at 17.8 ± 0.1 Ma, 15.1 ± 0.1 Ma, and 12.0 ± 0.1 Ma, respectively. The Lhozag leucogranites show relatively low εNd(t), low zircon εHf(t) and high initial 87Sr/86Sr ratios, which are similar to the High Himalayan Crystalline Series (HHCS), indicating that they were derived from the HHCS. The characteristics of relatively high Na2O and Rb contents, high Rb/Sr ratios and low CaO, MgO, TFe2O3, TiO2, and Sr contents indicate that both the ca. 18 Ma Lhozag tourmaline leucogranites and the ca. 15 Ma Lhozag two-mica granites were derived from fluid-absent muscovite-dehydration melting of metasediments. The opposite geochemistry characteristics of the ca. 12 Ma Khula Kangri two-mica granites imply that these granites are derived from fluid-present melting of metasediments. Four Khula Kangri two-mica granite samples with relatively lower TiO2, TFe2O3, MgO, and CaO contents, higher Rb concentrations and Rb/Sr ratios could be evolved from the Khula Kangri two-mica granites with relatively lower Rb/Sr ratios. The melting behaviors of the Lhozag leucogranites varied from fluid-absent melting to fluid-present melting, implying that there were P-T-XH2O variations in the deep crust. The tectonic evolution would give rise to variation of P-T-XH2O variation, and subsequent transformation of melting behavior. Our new results display the transformation of melting behavior of the Lhozag leucogranites, which implies the tectonic evolution from earlier N-S extension to later E-W extension in the eastern Himalaya at ca. 12 Ma.

  4. Geochronology and geochemistry of the Niujuanzi ophiolitic mélange, Gansu Province, NW China: implications for tectonic evolution of the Beishan Orogenic Collage

    Science.gov (United States)

    Wang, Shengdong; Zhang, Kexin; Song, Bowen; Li, Shucai; Li, Ming; Zhou, Jie

    2018-01-01

    The Niujuanzi ophiolitic mélange (NOM), located in the Beishan Orogenic Collage, marks the termination between the Huaniushan arc and Mingshui-Hanshan Massifs. The NOM is mainly composed of gabbros, diabases, plagiogranites, basalts, and greywacke. Two gabbros have ages of 433.8 ± 3.1 and 354.0 ± 3.3 Ma, two plagiogranites have ages of 429.8 ± 2 and 448.7 ± 2.0 Ma, and a diabase has an age of 433.4 ± 3.2 Ma. The gabbros and diabases are calc-alkaline and tholeiitic, with high Al2O3, CaO, and TiO2 contents and low FeOT contents. The gabbros have high Mg# values (49-82), while the diabases have relatively low Mg# values (46-61). The plagiogranites are calc-alkaline and metaluminous, with high SiO2 and Na2O contents and low Al2O3 and K2O contents. The gabbros and diabases are enriched in large iron lithophile elements and slightly depleted in high field strength elements relative to N-MORB and their trace element characteristics are similar to E-MORB. With respect to rare earth element (REE), they have slightly enriched LREEs relative to HREEs. The majority of the plagiogranite trace elements approximate those of the volcanic arc granite. The plagiogranites have obviously enriched LREEs relative to HREEs, with a slightly to strongly negative Eu anomaly, which is similar to ORG but distinct from volcanic arc and within plate granite. The NOM was formed from the Ordovician to the Carboniferous, representing the expansion period of the Niujuanzi Ocean. The gabbros, diabases, and plagiogranites were formed in a mid-ocean ridge environment. The gabbros and diabases were generated by different degrees of partial melting of the mantle, and the plagiogranites derived from both the crystallization differentiation of basaltic magma and the partial melting of amphibolites in the crust.

  5. Age and composition of the UHP garnet peridotites in the Dabie orogenic belt (central China) record complex crust-mantle interaction in continental margin

    Science.gov (United States)

    Zhao, Y.; Zheng, J.; Wang, B.

    2017-12-01

    The Dabie-Sulu UHP belt was created by the collision between the North and South China cratons in Middle Triassic time (240-225 Ma). There are lots of garnet-bearing ultramafic body occurs as a lens in the belt. Age and composition of the Maowu garnet peridotites in the Dabie orogenic belt are reported. The garnet harzburgites are main moderately refractory (Mg#Ol=92) and minor fertile (Mg#Ol=88) with high Ni (2344-2603 ppm) and low Al2O3 (0.35-0.54 wt.%), CaO (0.76-2.19 wt.%) and TiO2 (˜0.01 wt.%). Zircons in the harzburgites mainly document metamorphism at 230 ± 2 Ma, 275 ± 5 Ma, 357 ± 4 Ma, and complex minor populations of ages including: 1.8 Ga, 1.3 Ga, and Neoproterozic-early Paleozoic ages (901-420 Ma). The early Meszosic and late Paleozoic zircons have similar trace-element patterns and ranges in ɛHf(t) (+0.6 to +3.4), Th/U ratio (0.2-0.7) and Hf depleted-mantle model ages (TDM ) mainly cluster in the interval 1.2-0.9 Ga. In contrast, the Paleo-Mesoproterozoic zircons have negative ɛHf(t) (-24.9 to -2.7) and oldest Hf TDM = 3.4Ga. Zircons of Neoproterozic-early Paleozoic have a wide range of Hf depleted-mantle model ages (2.4-0.7Ga) and ɛHf(t) (-15.3 to +9.5). Above of the all, we suggest that the Maowu garnet harzburgites are interpreted as a fragment of the metasomatized ancient lithospheric mantle beneath the southern margin of the North China Craton. They experienced the Proterozoic thermal event (1.9-1.8Ga), which is coeval with the assembly of the supercontinent Columbia. And then 1.3Ga mantle metasomatism with asthenospheric materials resulted in the final breakup of the Columbia supercontinent. Neoproterozic-early Paleozoic (901-420 Ma), deep parts of the south margin of the craton were metasomatized during the assembly and breakup of the Rodinia supercontinent. Then, the southern margin of the craton occurred oceanic crust subduction ( 357 Ma), subsequent continental deep subduction and final continent-continent collision in Triassic.

  6. On the formation and evolution of the Pannonian basin: constraints derived from the orogenic collapse recorded at the junction between Carpathians and Dinarides

    Science.gov (United States)

    Matenco, L. C.; Radivojevic, D.

    2012-04-01

    -ward prolongation of the large scale extension in an area that is adjacent across Carpathians to the Moesian platform suggests that the roll-back of the Carpathians is not the only mechanism that is responsible for the formation of the Pannonian basin. The correlation with similar extensional structures superposed over the orogenic chain located S-wards strongly points towards a component of Pannonian collapse driven by a Middle Miocene roll-back of a Dinaridic slab. The study provides critical constraints for the pre-Neogene evolution of an area where there major crustal blocks (i.e. Tisza, Dacia and Dinarides) are juxtaposed together with their partly overlying obducted ophiolitic sequences against the major oceanic suture of Dinarides, the Sava zone.

  7. Peeking out of the basins: looking for the Late Devonian Kellwasser Event in the open ocean in the Central Asian Orogenic Belt, southwestern Mongolia

    Science.gov (United States)

    Thomas, R. M., Jr.; Carmichael, S. K.; Waters, J. A.; Batchelor, C. J.

    2017-12-01

    Two of the top five most devastating mass extinctions in Earth's history occurred during the Late Devonian (419.2 Ma - 358.9 Ma), and are commonly associated with the black shale deposits of the Kellwasser and Hangenberg ocean anoxia events. Our understanding of these extinction events is incomplete partly due to sample bias, as 95% of the field sites studying the Late Devonian are limited to continental shelves and continental marine basins, and 77% of these sites are derived from the Euramerican paleocontinent. The Samnuuruul Formation at the Hoshoot Shiveetiin Gol locality (HSG), located in southwestern Mongolia, offers a unique opportunity to better understand global oceanic conditions during the Late Devonian. The HSG locality shows a continuous sequence of terrestrial to marine sediments on the East Junggar arc; an isolated, open-ocean island arc within the Central Asian Orogenic Belt (CAOB). Samples from this near shore locality consist of volcanogenic silts, sands and immature conglomerates as well as calc-alkalic basalt lava flows. Offshore sections contain numerous limestones with Late Devonian fossil assemblages. Preliminary biostratigraphy of the associated marine and terrestrial sequences can only constrain the section to a general Late Devonian age, but TIMS analysis of detrital zircons from volcanogenic sediments from the Samnuuruul Formation in localities 8-50 km from the site suggests a late Frasnian age (375, 376 Ma). To provide a more precise radiometric age of the HSG locality, zircon geochronology using laser ablation inductively coupled plasma mass spectrometry (LA-ICPMS) will be performed at UNC-Chapel Hill. If the HSG section crosses the Frasnian-Famennian boundary, geochemical, mineralogical, and ichnological signatures of the Kellwasser Event are expected to be preserved, if the Kellwasser Event was indeed global in scope (as suggested by Carmichael et al. (2014) for analogous sites on the West Junggar arc in the CAOB). Black shale

  8. Petrography, geochemistry, and U-Pb geochronology of pegmatites and aplites associated with the Alvand intrusive complex in the Hamedan region, Sanandaj-Sirjan zone, Zagros orogen (Iran)

    Science.gov (United States)

    Sepahi, Ali Asghar; Salami, Sedigheh; Lentz, David; McFarlane, Christopher; Maanijou, Mohammad

    2018-04-01

    The Alvand intrusive complex in the Hamedan area in Iran is in the Sanandaj-Sirjan zone of the Zagros orogen. It consists of a wide range of plutonic rocks, mainly gabbro, diorite, granodiorite, granite, and leucogranites that were intruded by aplitic and pegmatitic dykes. At least three successive magmatic episodes generated an older gabbro-diorite-tonalite assemblage, followed by a voluminous granodiorite-granite association, which was then followed by minor leucocratic granitoids. Aplitic and pegmatitic dykes and bodies have truncated both plutonic rocks of the Alvand intrusive complex and its metamorphic aureole. Chemically they belong to peraluminous LCT (Li-, Cs-, and Ta-bearing) family of pegmatites. Mineralogically, they resemble Muscovite (MS) and Muscovite Rare Element (MSREL) classes of pegmatites. High amounts of some elements, such as Sn (up to 10,000 ppm), Rb (up to 936 ppm), Ba (up to 706 ppm), and LREE (up to 404 ppm) indicate the highly fractionated nature of some of these aplites and pegmatites. U-Pb dating of monazite, zircon, and allanite by LA-ICPMS indicate the following ages: monazite-bearing aplites of Heydareh-e-Poshteshahr and Barfejin areas, southwest of Hamedan, give an age range of 162-172 Ma; zircon in Heydareh-e-Poshteshar gives an average age of 165 Ma and for allanite-bearing pegmatites of Artiman area, north of Tuyserkan, an age of 154.1 ± 3.7 Ma was determined. These overlap with previously reported ages (ca. 167-153 Ma) for the plutonic rocks of the Alvand complex. Therefore, these data reveal that the Jurassic was a period of magmatism in the Hamedan region and adjacent areas in the Sanandaj-Sirjan zone, which was situated at the southern edge of the central Iranian micro-plate (southern Eurasian plate) at this time. Our results also suggest that advective heating in a continental arc setting has caused melting of fertile supracrustal lithologies, such as meta-pelites. These partial melts were then emplaced at much higher

  9. Fuel shortage hits eastern Siberia region

    International Nuclear Information System (INIS)

    Land, R.

    1992-01-01

    Moscow's loss of absolute authority over the Russian economy has contributed to growing chaos in the supply of oil and gas to the former U.S.S.R.'s far eastern territories. This paper reports that Sakhalin Island, which has provided a substantial portion of the area's hydrocarbon fuels, has shown increasing reluctance to sell oil and gas for nearly worthless rubles to its eastern Siberian neighbors. Instead, it is bartering as much as possible of its surplus petroleum for foreign food and consumer goods. Moscow's Izvestia newspaper strongly criticized Sakhalin authorities for placing the island's interests ahead of the welfare of the Russian republic as a whole. It the Sakhalin's selfish attitude resulted in near disaster last winter for the economy and populace of neighboring Khabarovsk territory on the Siberian mainland. Only milder than normal winter weather prevented a catastrophe, Izvestia reported. Even so, some old people died from the cold in Khabarovsk, a city of 600,000 population

  10. International uranium production. An eastern Canadian perspective

    International Nuclear Information System (INIS)

    Albino, G.R.

    1984-01-01

    The Eastern Canadian perspective on uranium production is based on 30 years of continuous mining at Elliot Lake and on the experience of selling uranium over the same time period, mainly to export markets. In Ontario the orebodies are basically contiguous, being part of the same large formation. All the mining is underground. Ore grades are low, but economic extraction is improved by continuity and uniformity of grades, stable ground conditions, and the ability to mine and mill on a large scale. Mining is being carried out by two companies, Denison and Rio Algom. It is unlikely that mine capacity will be increased. Government policies have significant effects on the Eastern Canadian uranium industry in particular, as to U.S. import policies. (L.L.)

  11. Late Ordovician brachiopods from eastern North Greenland

    DEFF Research Database (Denmark)

    Mac Ørum Rasmussen, Christian

    2013-01-01

    Late Ordovician rhynchonelliformean brachiopods, typical of the North American Red River fauna, are found sporadically in the BOrglum River Formation of the Centrum SO area, Kronprins Christian Land, eastern North Greenland. The geographical distribution of this characteristic brachiopod fauna......) to younger strata exclusively yielding specimens of H.gigas. As H.gigas occurs in the upper part of the Cape Calhoun Formation in Washington Land, it indicates that the upper boundary of the Cape Calhoun Formation is considerably younger than previous estimates, reaching into the uppermost Katian (middle...... (Richmondian), it possesses a strong provincial signal during the later Ordovician. The new occurrences indicate that this fauna extended to the north-eastern margin of the Laurentian Craton. It lived in close association with cosmopolitan faunal elements that may have been the earliest sign of the succeeding...

  12. Nuclear insurance in Central and Eastern Europe

    International Nuclear Information System (INIS)

    Warren, G.

    1998-01-01

    In the world outside the former Soviet Union, insurance industries in their respective domestic markets have pooled their resources so as to provide a secure and cost-effective conduit for the transaction of insurance business on behalf of the nuclear industry. These are the so-called nuclear pools. This paper explains the four main principles behind nuclear liability insurance and discusses their application to Central Europe and in particular to the problems facing the nuclear industry in Eastern Europe. (author)

  13. Phytoremediation of Excavation in Eastern Siberia

    Science.gov (United States)

    Timofeeva, S. S.; Zhmurova, T. M.

    2017-04-01

    The paper deals with prospects and applicability of phytoremediation technology in the conditions of Eastern Siberia as applied to gypsum stone extraction of Zalarinsky deposit in Irkutsk region. It analyses dust intensity for different technological processes of the deposit and evaluates the dust loading on the workers of the deposit. The selection of plantings that have potential to neutralize the dust loading produced by the plot “Severniy” is carried out.

  14. Drained Triaxial Tests on Eastern Scheldt Sand

    DEFF Research Database (Denmark)

    Praastrup, U.; Jakobsen, Kim Parsberg

    In the process of understanding and developing models for geomaterials, the stress-strain behaviour is commonly studied by performing triaxial tests. In the present study static triaxial tests have been performed to gain knowledge of the stress-strain behaviour of frictional materials during...... monotonic loading. The tests reported herein are all drained tests, starting from different initial states of stress and following various stress paths. AIl the tests are performed on reconstituted medium dense specimens of Eastern Scheldt Sand....

  15. Cancer Control in Central and Eastern Europe

    OpenAIRE

    La Vecchia, Carlo; Conte, Pierfranco

    2016-01-01

    In Central and Western Europe, cancer mortality is declining at slower rates as compared with rates in the rest of the world. More than a generation has now passed since the end of nonmarket economies in Central and Eastern Europe. It is time for this area of the continent to close the gap in cancer incidence and mortality rates between it and Western Europe and other high-income areas of the world.

  16. U-Pb SHRIMP and {sup 40}Ar/{sup 39}Ar constraints on the timing of mineralization in the Paleoproterozoic Caxias orogenic gold deposit, Sao Luis cratonic fragment, Brazil

    Energy Technology Data Exchange (ETDEWEB)

    Klein, Evandro Luiz, E-mail: evandro.klein@cprm.gov.br [Servico Geologico do Brasil (CPRM), Belem, PA (Brazil); Tassinari, Colombo Celso Gaeta, E-mail: ccgtassi@usp.br [Universidade de Sao Paulo (USP), SP (Brazil). Instituto de Geociencias. Centro de Pesquisas Geocronologicas; Vasconcelos, Paulo Marcos, E-mail: paulo@earth.uq.edu.au [University of Queensland, School of Earth Sciences, Brisbane (Australia)

    2014-07-01

    Caxias is an orogenic gold deposit in the Sao Luis cratonic fragment, which is correlated with the Rhyacian terranes of the West-African Craton. The deposit postdates peak metamorphism (estimated at 2100 ± 15 Ma) and is hosted in a shear zone that cuts across schists of the Aurizona Group (2240 ± 5 Ma) and the Caxias Microtonalite. The emplacement age of the microtonalite, as determined in this work by SHRIMP U-Pb zircon dating, is 2009 ± 11 Ma and represents a latest age magmatic event in the Sao Luis cratonic fragment. Older zircon age of 2139 ± 10 Ma is interpreted as due to inheritance from the older granitoid or volcanic suites (magmatic sources?) or to contamination during emplacement. Lead isotope compositions indicate that the Pb incorporated in ore-related pyrite was probably sourced from regional, orogenic calc-alkaline granitoids of ca. 2160 Ma. Hydrothermal sericite from Caxias yielded a {sup 40}Ar/{sup 39}Ar plateau age of 1990 ± 30 Ma, which combined with the emplacement age of the Caxias Microtonalite brackets the age of gold mineralization between 2009 ± 11 and 1990 ± 30 Ma. (author)

  17. EU, Eastern Europe and Values Imperialism

    Directory of Open Access Journals (Sweden)

    Stephen White

    2014-01-01

    Full Text Available This paper proposes an idea of'values imperialism'as a helpful way of conceptualising the relationship between the EU and the states that came within its sphere of influence after the end of the Cold War, particularly its 'neighbours' in Eastern Europe. Values imperialism places its emphasis on the 'superstructure', including norms, laws and social practices. EU larger objective was that the assumptions about government and ownership that were favoured by the dominant powers (EU and the West in the broad term should be absorbed and recapitulated by those countries that were subordinate. The broad framework ofsubordination was established by the Partnership and Cooperation Agreements that began to be concluded from 1994 onwards. Patterns of'values imperialism'could also be discovered in the EU Common Strategies on Russia and Ukraine that were adopted in 1999. Article also points out several cases when the EU intervened directly in the domestic affairs of the Eastern Europe countries in a manner that was not always compatible with the provisions on state sovereignty: a 'European Instrument for Democracy and Human Rights', launched in 2006, interventions ofEU representatives in the work of local courts and organisation of exit polls, which could be used to discredit the official election results and in this way to undermine the position of local governments. Finally, the author concludes that the EU used 'values imperialism'practices in order to extend its influence, particularly in the Eastern Europe.

  18. SO2 emission scenarios of eastern China

    International Nuclear Information System (INIS)

    Qi, L.; Hao, J.; Lu, M.

    1995-01-01

    Under the National Key Project in Eighth Five-year Plan, a study was carried out on forecasting SO 2 emission from coal combustion in China, with a special emphasis on the eastern area. 3 scenarios, i.e. 'Optimistic', 'Pessimistic' and 'Business as Usual' scenarios were developed trying to cover changing scale of coal consumption and SO 2 emission from 1990 to 2020. A 'Top-down' approach was employed, and coal consumption elasticity was defined to project future economic growth and coal consumption. SO 2 emission scenarios were outlined, based on coal consumption, estimated sulfur content level and prospective SO 2 control situation. Emission level for each 1 degree longitude x 1 degree latitude grid cell within eastern China was also estimated to show geographical distribution of SO 2 sources. The results show that SO 2 emission in China will increase rapidly, if the current situation for energy saving and SO 2 control is maintained without improvement; measures enhanced reasonably with economic growth could stop further increase of emission by 2010. Realization of more encouraging objective to keep emission at even below 1990 level needs, however, more stringent options. The share of eastern China in the country's total emission would increase until 2000, while the general changing tendency would principally follow the scenarios of the whole country. 4 refs., 5 figs., 1 tab

  19. Human paleoecological integration in subarctic eastern Beringia

    Science.gov (United States)

    Lanoë, François B.; Reuther, Joshua D.; Holmes, Charles E.; Hodgins, Gregory W. L.

    2017-11-01

    We contribute to the understanding of megafauna extinction and human dispersal in subarctic eastern Beringia by focusing on changes in the trophic dynamics of the large mammal community as well as the ecological role of humans as a predator and competitor. We reconstruct habitat use by megafauna and humans throughout the Pleistocene-Holocene boundary based on zooarchaeological data and stable isotope ratios of collagen. Our results are consistent with habitat heterogeneity and availability being important factors in the changing abundance of large herbivores. We argue that an increase in herbivore diversity and biomass at the beginning of the Bølling-Allerød interstadial and a relative lack of competitors favored the initial human colonization of subarctic eastern Beringia. As herbivore resources dwindled later in the Late Glacial, people increasingly relied on bison and wapiti. By efficiently extracting some of the highest-ranked resources in the landscape, people are likely to have contributed to the trophic displacement or regional extirpation of other large predators. The ecological patterns that we observe in subarctic eastern Beringia are consistent with a mixture of both top-down and bottom-up controls over biotic turnover.

  20. Crisis of the EU Eastern Policy

    Directory of Open Access Journals (Sweden)

    Irina V. Bolgova

    2014-01-01

    Full Text Available The results of the Vilnius summit of the EaP project and the consequent Ukrainian crisis with major international effects make possible questioning about the eventual scenarios of the EU eastern politics and possible configurations ofinternational interactions. The article elaborates on the key elements and trends of the EU activities at the post-soviet space that are likely to frame the context of its further developments. The most visible trends analysed here are the extreme differentiation of bilateral relations within the EaP project alongside with the growing symbolism of official rhetoric and program practices of the European Union. As a result, we see the EU's intention to narrow the geographical and qualitative field of its activities on the eastern directionwith saving the shell of the EaP for nominal functioning. Such tactics is not likely to result in a drastic change of the model of conflict dependencies in the "shared neighbourhood". The article analyses key misperceptions of the actors involved in the complex of interactions in the region. The structure is complicated by the deepening and widening of Russia-lead Eurasian integration project. Current crisis of the EU eastern policy is considered to derive from the exaggeration of the value-based, normative aspect of the common foreign policy in general and will have the systemic consequences both for the European external actions and for its internal developments.

  1. Seismic hazard in the eastern United States

    Science.gov (United States)

    Mueller, Charles; Boyd, Oliver; Petersen, Mark D.; Moschetti, Morgan P.; Rezaeian, Sanaz; Shumway, Allison

    2015-01-01

    The U.S. Geological Survey seismic hazard maps for the central and eastern United States were updated in 2014. We analyze results and changes for the eastern part of the region. Ratio maps are presented, along with tables of ground motions and deaggregations for selected cities. The Charleston fault model was revised, and a new fault source for Charlevoix was added. Background seismicity sources utilized an updated catalog, revised completeness and recurrence models, and a new adaptive smoothing procedure. Maximum-magnitude models and ground motion models were also updated. Broad, regional hazard reductions of 5%–20% are mostly attributed to new ground motion models with stronger near-source attenuation. The revised Charleston fault geometry redistributes local hazard, and the new Charlevoix source increases hazard in northern New England. Strong increases in mid- to high-frequency hazard at some locations—for example, southern New Hampshire, central Virginia, and eastern Tennessee—are attributed to updated catalogs and/or smoothing.

  2. Petrography, geochemistry and Sm-Nd isotopes of the granites from eastern of the Tapajós Domain, Pará state

    Directory of Open Access Journals (Sweden)

    Flávio Robson Dias Semblano

    Full Text Available ABSTRACT: The Tapajós Domain, located in the southern portion of the Amazonian Craton, is a tectonic domain of the Tapajós-Parima Province, a Paleoproterozoic orogenic belt adjacent to a reworked Archean crust, the Central Amazonian Province. This domain has been interpreted as the product of an assemblage of successive magmatic arcs followed by post-orogenic A-type magmatism formed ca. 1880 Ma-old granites of the Maloquinha Intrusive Suite. The study presented here was carried out in four granitic bodies of this suite (Igarapé Tabuleiro, Dalpaiz, Mamoal and Serra Alta from the eastern part of the Tapajós Domain, as well as an I-type granite (Igarapé Salustiano related to the Parauari Intrusive Suite. The A-type granites are syenogranites and monzogranites, and alkali feldspar granites and quartz syenites occur subordinately. These rocks are ferroan, alkalic-calcic to alkalic and dominantly peraluminous, with negative anomalies of Ba, Sr, P and Ti and high rare earth elements (REE contents with pronounced negative Eu anomaly. This set of features is typical of A-type granites. The Igarapé Salustiano granite encompasses monzogranites and quartz monzonites, which are magnesian, calcic to calc-alkalic, high-K and mainly metaluminous, with high Ba and Sr contents and depleted pattern in high field strength elements (HFSE and heavy rare earth elements (HREE, characteristic of I-type granites. The source of magma of these A-type granites is similar to post-collisional granites, while the I-type granite keeps syn-collisional signature. Most of the studied granites have εNd (-3.85 to -0.76 and Nd TDM model ages (2.22 to 2.46 Ga compatible with the Paleoproterozoic crust of the Tapajós Domain. We conclude that the Archean crust source (εNd of -5.01 and Nd TDM of 2.6 Ga was local for these A-type granites.

  3. Assessing health literacy in the eastern and middle-eastern cultures

    Directory of Open Access Journals (Sweden)

    Satish Chandrasekhar Nair

    2016-08-01

    Full Text Available Abstract Background Health literacy is a term employed to assess the ability of people to meet the increasing demands related to health in a rapidly evolving society. Low health literacy can affect the social determinants of health, health outcomes and the use of healthcare services. The purpose of the study was to develop a survey construct to assess health literacy within the context of regional culture. Different socioeconomic status among the Eastern and Middle Eastern countries may restrict, health information access and utilization for those with low literacy. Methods By employing expert panel, Delphi technique, focus group methodologies, and pre-testing using participants (N = 900 from the UAE and India, a survey construct to the Eastern-Middle Eastern cultures was developed. Reliability was assessed using Cronbach’s α and validity using Factor analysis. Kiaser-Meyer-Olkin (KMO sampling adequacy and Bartlett’s tests were used to assess the strength of the relationship among the variables. Results Inclusion of non-health related items were found to be critical in the authentic assessment of health literacy in the Eastern and Middle Eastern population given the influence of social desirability. Thirty-two percentage of the original 19-item construct was eliminated by the focus group for reasons of relevance and impact for the local culture. Field pretesting participants from two countries, indicated overall construct reliability (Cronbach’s α =0.85, validity and consistency (KMO value of 0.92 and Bartlett’s test of sphericity was significant. Conclusion The Eastern-Middle Eastern Adult Health Literacy (EMAHL13, screening instrument is brief, simple, a useful indicator of whether or not a patient can read. It assessespatients’ ability to comprehend by distinguishing between health and non-health related items. The EMAHL13 will be a useful too for the reliable assessment of health literacy in countries, where culture plays a

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

    Science.gov (United States)

    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

  5. Fragments of deeper parts of the hanging wall mantle preserved as orogenic peridotites in the central belt of the Seve Nappe Complex, Sweden

    Science.gov (United States)

    Clos, Frediano; Gilio, Mattia; van Roermund, Herman L. M.

    2014-04-01

    Formation conditions of olivine microstructures are investigated in the Kittelfjäll spinel peridotite (KSP), a fragment of lithospheric mantle which occurs as an isolated body within high grade metamorphic crustal rocks of the Seve Nappe Complex (SNC), southern Västerbotten, central Sweden. The KSP is an orogenic peridotite containing a well developed penetrative compositional layering, defined by highly depleted dunite with olivine Mg# (100 × Mg/Mg + Fe) of 92.0-93.5 and harzburgite with lower Mg# (91.0-92.5). Dunite is characterized by three contrasting olivine microstructures formed in response to different tectonometamorphic events: Coarse-grained, highly strained olivine porphyroclasts (M1) up to 20 cm long are surrounded by dynamically recrystallized olivine grains (M2) defining a characteristic olivine "foam" microstructure (grain size: 200-2000 μm). An olivine "mortar" (M3) microstructure (10-50 μm) forms a penetrative fabric element only in strongly localized, cm-to-m sized shear zones that crosscut earlier structures/foliations. Olivine fabric analysis in synergy, with mineralogical and chemical analyses, reveals that the KSP body represents old, possibly Archean, sub-continental lithospheric mantle that was crustally emplaced into the Caledonian tectonic edifice from the hanging wall mantle during exhumation of the subducted Seve Nappe Complex (Jämtlandian orogeny ~ 454 Ma). Olivine porphyroclasts (M1) grew at high temperature during dominant isobaric cooling after extensive polybaric melt extraction (> 40%) and subsequent refertilization. The onset of the early Caledonian deformation is interpreted to be related to the crustal emplacement of the KSP during eduction of the SNC. This phase is characterized by the development of the olivine M2 foam microstructure, formed at 650-830 °C/1-2 GPa by dislocation creep processes producing an E-type CPO's by the operation of the [100](001) and subordinate [001](100) slip systems with operating flow stress

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

    Science.gov (United States)

    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

  7. 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

    Science.gov (United States)

    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

  8. Devonian granitoids and their hosted mafic enclaves in the Gorny Altai terrane, northwestern Central Asian Orogenic Belt: crust-mantle interaction in a continental arc setting

    Science.gov (United States)

    Chen, Ming; Sun, Min

    2016-04-01

    Granitoids are a major component in the upper continental crust and hold key information on how did the continental crust grow and differentiate. This study focuses on the Yaloman intrusive complex from the Gorny Altai terrane, northwestern Central Asian Orogenic Belt (CAOB). The association of granitoids and mafic enclaves can provide important clues on the source nature, petrogenetic processes and geodynamic setting of the Yaloman intrusive complex, which in turn will shed light on the crustal evolution in the northwestern CAOB. Zircon U-Pb dating shows that the granitoids, including quartz diorites and granodiorites, were emplaced in ca. 389-387 Ma. The moderate Na2O + K2O contents and low A/CNK values indicate that these rocks belong to the sub-alkaline series with metaluminous to weakly peraluminous compositions. The granitoids yield two-stage zircon Hf model ages of ca. 0.79-1.07 Ga and whole-rock Nd model ages of ca. 0.90-0.99 Ga, respectively, implying that they were mainly sourced from Neoproterozoic juvenile crustal materials. The mafic enclaves show an almost identical crystallization age of ca. 389 Ma. The identification of coarse-grained xenocrysts and acicular apatites, together with the fine-grained texture, makes us infer that these enclaves are likely to represent magmatic globules commingled with the host magmas. The low SiO2 and high MgO contents of the mafic enclaves further suggest that substantial mantle-derived mafic melts were probably involved in their formation. Importantly, the SiO2 contents of the granitoids and mafic enclaves are well correlated with other major elements and most of the trace elements. Also a broadly negative correlation exists between the SiO2 contents and whole-rock epsilon Nd (390 Ma) values of the granitoids. Given the observation of reversely zoned plagioclases within the granitoids and the common occurrence of igneous mafic enclaves, we propose that magma mixing probably played an important role in the formation

  9. What can the Cretaceous-to-present latitude history of the Lhasa terrane tell us about plate-scale deformation in the Tibetan-Himalayan orogen? (Invited)

    Science.gov (United States)

    Lippert, P. C.; Van Hinsbergen, D. J.; Dupont-Nivet, G.; Huang, W.

    2013-12-01

    Published paleomagnetic data from well-dated sedimentary and volcanic rocks from the Lhasa terrane have been re-evaluated in a statistically consistent framework to assess the latitude history of southern Tibet from ~110 Ma to the present. We apply a methodology similar to the one used by the Time-Averaged geomagnetic Field Initiative to each paleomagnetic data set to establish coherency within and between paleomagnetic data from Tibet (see Session T023 for more details). Moreover, we use only sedimentary data that have been evaluated for and, where necessary, corrected for sedimentary inclination shallowing. The resulting apparent polar wander path (APWP) shows that the southern margin of the Lhasa terrane at the longitudes of Nepal remained at 20×4°N latitude from ~110 to at least 50 Ma and subsequently drifted northward to its present latitude of 29°N. This latitude history provides a paleomagnetically-determined collision age between the Tibetan Himalaya and the southern margin of Asia that is 49.5×4.5 Ma at 21×4° N latitude. The paleomagnetic age and latitude of this collision may be a few millions of years earlier and ~2° lower if estimates for shortening within the suture zone are considered. When compared to the global APWP of Torsvik et al. (2012) in Eurasian coordinates, the Lhasa APWP indicates that at most 1100×560 km of post-50 Ma India-Asia convergence was partitioned into Asian lithosphere. The lower bound of these paleomagnetic estimates is consistent with the magnitude of upper crustal shortening within Asia calculated from orogen-scale geological reconstructions. An implication is that 1700×560 km or more post-50 Ma India-Asia convergence was partitioned into Greater India. Paleomagnetic data from the Tibetan Himalaya are consistent with >2000 km of extension of Greater Indian lithosphere after break-up from Gondwana but prior to collision with the southern margin of Asia. Cenozoic subduction of this Cretaceous extensional basin following

  10. Postobductional extension along and within the Frontal Range of the Eastern Oman Mountains

    Science.gov (United States)

    Mattern, Frank; Scharf, Andreas

    2018-04-01

    The Oman Mountains formed by late Cretaceous obduction of the Tethys-derived Semail Ophiolite. This study concerns the postobductional extension on the northern flank of the mountain belt. Nine sites at the northern margins of the Jabal Akhdar/Nakhl and Saih Hatat domes of the Eastern Oman ("Hajar") Mountains were investigated. The northern margins are marked by a system of major interconnected extensional faults, the "Frontal Range Fault". While the vertical displacements along the Saih Hatat and westerly located Jabal Nakhl domes measure 2.25-6.25 km, 0.5-4.5 km and 4-7 km, respectively, it amounts to 1-5 km along the Jabal Akhdar Dome. Extension had started during the late Cretaceous, towards the end of ophiolite emplacement. Two stages of extension can be ascertained (late Cretaceous to early Eocene and probably Oligocene) at the eastern part of the Frontal Range Fault System (Wadi Kabir and Fanja Graben faults of similar strike). Along the intervening and differently striking fault segments at Sad and Sunub the same two stages of deformation are deduced. The first stage is characterized again by extension. The second stage is marked by dextral motion, including local transtension. Probable Oligocene extension affected the Batinah Coast Fault while it also affected the Wadi Kabir Fault and the Fanja Graben. It is unclear whether the western portion of the Frontal Range Fault also went through two stages of deformation. Bedding-parallel ductile and brittle deformation is a common phenomenon. Hot springs and listwaenite are associated with dextral releasing bends within the fault system, as well as a basalt intrusion of probable Oligocene age. A structural transect through the Frontal Range along the superbly exposed Wadi Bani Kharous (Jabal Akhdar Dome) revealed that extension affected the Frontal Range at least 2.5 km south of the Frontal Range Fault. Also here, bedding-parallel shearing is important, but not exclusive. A late Cretaceous thrust was

  11. Eastern Canadian Gastrointestinal Cancer Consensus Conference 2016.

    Science.gov (United States)

    Bossé, D; Ng, T; Ahmad, C; Alfakeeh, A; Alruzug, I; Biagi, J; Brierley, J; Chaudhury, P; Cleary, S; Colwell, B; Cripps, C; Dawson, L A; Dorreen, M; Ferland, E; Galiatsatos, P; Girard, S; Gray, S; Halwani, F; Kopek, N; Mahmud, A; Martel, G; Robillard, L; Samson, B; Seal, M; Siddiqui, J; Sideris, L; Snow, S; Thirwell, M; Vickers, M; Goodwin, R; Goel, R; Hsu, T; Tsvetkova, E; Ward, B; Asmis, T

    2016-12-01

    The annual Eastern Canadian Gastrointestinal Cancer Consensus Conference 2016 was held in Montreal, Quebec, 5-7 February. Experts in radiation oncology, medical oncology, surgical oncology, and infectious diseases involved in the management of patients with gastrointestinal malignancies participated in presentations and discussion sessions for the purpose of developing the recommendations presented here. This consensus statement addresses multiple topics: ■ Follow-up and survivorship of patients with resected colorectal cancer■ Indications for liver metastasectomy■ Treatment of oligometastases by stereotactic body radiation therapy■ Treatment of borderline resectable and unresectable pancreatic cancer■ Transarterial chemoembolization in hepatocellular carcinoma■ Infectious complications of antineoplastic agents.

  12. A vegetation map for eastern Africa

    DEFF Research Database (Denmark)

    Lillesø, Jens-Peter Barnekow; van Breugel, Paulo; Graudal, Lars

    2015-01-01

    The potential natural vegetation (PNV) map of eastern and southern Africa covers the countries Burundi, Ethiopia, Kenya, Uganda, Rwanda, Tanzania, and Zambia. The first version of the map was developed by various partners in East Africa and Europe in 2010 and has now reached version 2. The map...... is available in different formats and is accompanied by an extensive documentation of the floristic, physiognomic and other characteristics of the different vegetation types and useful woody species in the 8 countries. It is complemented by a species selection tool, which can be used to 'find the right tree...

  13. Dakota, Minnesota and Eastern Railroad: 1997

    OpenAIRE

    Paul R. Reed; Carol J. Cumber

    1998-01-01

    Approximately twenty-five years ago, a majority of the railroads in the industry were either in or near bankruptcy. As a partial cure, a series of federal and state legislation was enacted which freed the industry from archaic laws passed in the days railroads enjoyed a virtual monopoly in U.S. transportation. One of the outcomes of this new legislation was the freedom granted major railroads to abandon or sell off excess trackage to entrepreneurs. The Dakota Minnesota & Eastern (DM&E) is a r...

  14. Diatoms in Liyu Lake, Eastern Taiwan

    Directory of Open Access Journals (Sweden)

    Liang-Chi Wang

    2010-09-01

    Full Text Available This study described the diatoms appeared in the sediments of Liyu Lake, a lowland natural lake situated at Hualen, eastern Taiwan. A total of 50 species was found in the sediments of this eutrophic lake. In them, 8 species were reported for the first time in Taiwan. They are: Cymbella thienemannii, Navicula absoluta, Navicula bacillum, Frustulia rhomboides var. crassinervia, Gyrosigma procerum, Nitzschia paleacea Epithemia smithii and Eunotia subarcuatioides. The ultrastructures of each species were described on the basis of observations under a scanning electron microscope. The ecological implications of the occurrence of these diatom species in this lake were inferred.

  15. Eastern and western happiness in work behavior

    Directory of Open Access Journals (Sweden)

    Jaroslava Kubátová

    2017-10-01

    Full Text Available The purpose of this article is to clarify what motivates East Asian work behavior. The research question is: How can a Western manager better understand work behavior and motivation in East Asian cultures? Knowledge about national culture, motivation and the concept of happiness are connected via deductive and comparative methods, while pointing out their new connections and relations. We argue that work motivation in East Asian cultures can be explained using the self-concept-based motivation meta-theory as it corresponds to the East Asian concept of face and that the East Asian self-concept originates with the Eastern concept of happiness.

  16. Environmental Regulation Impacts on Eastern Interconnection Performance

    Energy Technology Data Exchange (ETDEWEB)

    Markham, Penn N [ORNL; Liu, Yilu [ORNL; Young II, Marcus Aaron [ORNL

    2013-07-01

    In the United States, recent environmental regulations will likely result in the removal of nearly 30 GW of oil and coal-fired generation from the power grid, mostly in the Eastern Interconnection (EI). The effects of this transition on voltage stability and transmission line flows have previously not been studied from a system-wide perspective. This report discusses the results of power flow studies designed to simulate the evolution of the EI over the next few years as traditional generation sources are replaced with environmentally friendlier ones such as natural gas and wind.

  17. Permeability Tests on Eastern Scheldt Sand

    DEFF Research Database (Denmark)

    Jakobsen, Kim Parsberg

    on the characteristics of the soil matrix, the permeability is determined for different void ratios. All tests are performed on reconstituted specimens of Eastern Scheldt Sand. The permeability is determined by use of a falling head apparatus. Finally the test results are briefly summarised and a relationship between......The flow through porous media plays an important role in various engineering disciplines, as for example in ground water hydrology and soil mechanics. In the present study the permeability is determined for a fine, saturated sand. As the flow through a porous media strongly depends...

  18. Wooden Calendar Sticks in Eastern Europe

    Science.gov (United States)

    Koleva, Vesselina; Koleva, Svetlana

    Wooden calendar sticks have preserved an archaic time-keeping tradition, which, during the Middle Ages, was one of the tools for establishing and disseminating Christian chronology and the liturgical calendars of the Western and Eastern Churches. The calendars vary in size and shape, type of signs, and structure of the record. Christian symbols interwoven with signs and pictograms mark days of importance in the ritual and economic year cycle. The wooden calendars are considered one of the proofs of the syncretism between the pagan tradition and Christian rites in folk cultures.

  19. The Trading Potential of Eastern Europe

    OpenAIRE

    Wang, Zhen Kun; Winters, L. Alan

    1991-01-01

    This paper fits a gravity model to the trade of 76 market economies. It then applies the model to data on East European economies to estimate what their trading potential might have been, had behaved like market economies in the mid-1980s. At existing levels of national income, the liberalization of Eastern Europe and the Soviet Union is unlikely to affect their mutual trade and trade with developing countries, but it will increase trade with industrial counties by factors of three to thirty....

  20. A Silurian-early Devonian slab window in the southern Central Asian Orogenic Belt: Evidence from high-Mg diorites, adakites and granitoids in the western Central Beishan region, NW China

    Science.gov (United States)

    Zheng, Rongguo; Xiao, Wenjiao; Li, Jinyi; Wu, Tairan; Zhang, Wen

    2018-03-01

    The Beishan orogenic belt is a key region for deciphering the accretionary processes of the southern Central Asian Orogenic Belt. Here in this paper we present new zircon U-Pb ages, bulk-rock major and trace element, and zircon Hf isotopic data for the Baitoushan, and Bagelengtai plutons in the western Central Beishan region to address the accretionary processes. The Baitoushan pluton consists of quartz diorites, monzonites and K-feldspar granites, with zircon LA-ICP-MS U-Pb ages of 435 Ma, 421 Ma and 401 Ma, respectively. The Baitoushan quartz diorites and quartz monzonites exhibit relatively high MgO contents and Mg# values (63-72), display enrichments in LILEs and LREEs, and exhibit high Ba (585-1415 ppm), Sr (416-570 ppm) and compatible element (such as Cr and Ni) abundances, which make them akin to typical high-Mg andesites. The Baitoushan quartz diorites and quartz monzonites were probably generated by the interaction of subducted oceanic sediment-derived melts and mantle peridotites. The Baitoushan K-feldspar granites are ascribed to fractionated I-type granites with peraluminous and high-K calc-alkaline characteristics. They exhibit positive εHf(t) values (2.43-7.63) and Mesoproterozoic-Neoproterozoic zircon Hf model ages (0.92-1.60 Ga). Those early Devonian granites, including Baitoushan K-feldspar granite and Gongpoquan leucogranites (402 Ma), are derived from melting of the mafic lower crust and/or sediments by upwelling of hot asthenospheric mantle. The Bagelengtai granodiorites exhibit similar geochemical signatures with that of typical adakites, with a zircon SHRIMP U-Pb age of 435 Ma. They exhibit relatively high Sr (502-628 ppm) and Al2O3 (16.40-17.40 wt.%) contents, and low MgO (1.02-1.29 wt.%), Y (3.37-6.94 ppm) and HREEs contents, with relatively high Sr/Y and (La/Yb)N ratios. The Bagelengtai granodiorites were derived from partial melting of subducted young oceanic crust, with significant contributions of subducted sediments, subsequently

  1. Intercontinental and intracontinental biogeography of the eastern Asian - Eastern North American disjunct Panax (the ginseng genus, Araliaceae), emphasizing its diversification processes in eastern Asia.

    Science.gov (United States)

    Zuo, Yun-Juan; Wen, Jun; Zhou, Shi-Liang

    2017-12-01

    The intercontinental biogeography between eastern Asia and eastern North America has attracted much attention from evolutionary biologists. Further insights into understanding the evolution of the intercontinental disjunctions have been hampered by the lack of studies on the intracontinental biogeography in eastern Asia, a region with complex geology, geography, climates and habitats. Herein we studied the biogeographic history of the eastern Asian-eastern North American disjunct genus Panax with special emphasis on the investigation of its uneven diversification in Asia. This study reconstructs the diversification history of Panax and also emphasizes a large clade of Panax taxa, which has a wide distribution in eastern Asia, but was unresolved in previous studies. We examined the noncoding plastid DNA fragments of trnH-psbA, rps16, and psbM-trnD, the mitochondrial b/c intron of NAD1, and the nuclear ribosomal internal transcribed spacer (ITS) region of 356 samples from 47 populations. The results revealed the subtropical Northern Hemisphere origin (Asia or Asia and North America) of Panax in the Paleocene. Intercontinental disjunctions between eastern Asia and eastern North America formed twice in Panax, once estimated in early Eocene for the split of P. trifolius and another in mid-Miocene for the divergence of P. quinquefolius. Intercontinental diversifications in Panax showed temporal correlation with the increase of global temperature. The evolutionary radiation of the P. bipinnatifidus species complex occurred around the boundary of Oligocene and Miocene. Strong genetic structure among populations of the species complex was detected and the populations may be isolated by distance. The backbone network and the Bayesian clustering analysis revealed a major evolutionary radiation centered in the Hengduan Mountains of western China. Our results suggested that the evolutionary radiation of Panax was promoted by geographic barriers, including mountain ranges

  2. Preferred nasolabial angle in Middle Eastern population.

    Science.gov (United States)

    Alharethy, Sami

    2017-05-01

    To define the preferred nasolabial angle measurement in Middle Eastern population. An observational study was conducted from January 2012 to January 2016 at the Department of Otolaryngology, Head and Neck Surgery, King Abdulaziz University Hospital, King Saud University, Riyadh, Kingdom of Saudi Arabia. A total of 1027 raters, 506 males, and 521 females were asked to choose the most ideal nasolabial angle for 5 males and 5 females lateral photographs whose nasolabial angle were modified with Photoshop into the following angles (85°, 90°, 95°, 100°, 105°, and 110°). Male raters preferred the angle of 89.5° ± 3.5° (mean ± SD) for males and 90.8° ± 5.6° for females. While female raters preferred the angle of 89.3° ± 3.8° for males and 90.5° ± 4.8° for females. ANOVA test compare means among groups: p: 0.342, and there is no statistically significant difference between groups. The results of our study showed an even more acute angles than degrees found in the literature. It shows that what young generation in our region prefers and clearly reflects that what could be explained as under rotation of the nasal tip in other cultures is just the ideal for some Middle Eastern population.

  3. Origin and evolution of multi-stage felsic melts in eastern Gangdese belt: Constraints from U-Pb zircon dating and Hf isotopic composition

    Science.gov (United States)

    Guo, Liang; Zhang, Hong-Fei; Harris, Nigel; Pan, Fa-Bin; Xu, Wang-Chun

    2011-11-01

    This integrated study of whole rock geochemistry, zircon U-Pb dating and Hf isotope composition for seven felsic rocks from the Nyingchi Complex in eastern Himalayan syntaxis has revealed a complex magmatic history for the eastern Gangdese belt. This involves multiple melt sources and mechanisms that uniquely identify the tectonic evolution of this part of the Himalayan orogen. Our U-Pb zircon dating reveals five stages of magmatic or anatectic events: 165, 81, 61, 50 and 25 Ma. The Jurassic granitic gneiss (165 Ma) exhibits εHf(t) values of + 1.4 to + 3.5. The late Cretaceous granite (81 Ma) shows variable εHf(t) values from - 0.9 to + 6.2, indicating a binary mixing between juvenile and old crustal materials. The Paleocene granodioritic gneiss (61 Ma) has εHf(t) values of + 5.4 to + 8.0, suggesting that it originated from partial melting of a juvenile crustal material. The Eocene anatexis is recorded in the leucosome, which has Hf isotopic composition similar to that of the Jurassic granite, indicating that the leucosome could be derived from partial melting of the Jurassic granite. The late Oligocene biotite granite (25 Ma) shows adakitic geochemical characteristics, with Sr/Y = 49.3-56.6. The presence of a large number of inherited zircons and negative εHf(t) values suggest that it sourced from anatexis of crustal materials. In contrast to the Gangdese batholiths that are mainly derived from juvenile crustal source in central Tibet, the old crustal materials play an important role for the magma generation of the felsic rocks, suggesting the existence of a crustal basement in the eastern Gangdese belt. These correspond to specific magmatic evolution stages during the convergence between India and Asia. The middle Jurassic granitic gneiss resulted from the northward subduction of the Neo-Tethyan oceanic slab. The late Cretaceous magmatism is probably related to the ocean ridge subduction. The Paleocene-Eocene magmatism, metamorphism and anatexis are

  4. Tracking the multi-stage exhumation history of the western Chinese Tianshan by Apatite Fission Track (AFT) dating - Implications for the preservation of epithermal deposits in ancient orogenic belt

    Science.gov (United States)

    Wang, Yannan; Cai, Keda

    2017-04-01

    The western Chinese Tianshan, located in the southern domain of the Central Asian Orogenic Belt (CAOB), was originally constructed by multiple accretion-collision processes in the Paleozoic, and was superimposed by complex intracontinental tectonic evolution in the Mesozoic-Cenozoic. Understanding the timing and mechanism of the latter geological processes is critical to unravel the preservation conditions of the epithermal deposits in the western Chinese Tianshan. This work presents new apatite fission track (AFT) data for three mountain ranges of the western Chinese Tianshan to track their exhumation history. Our AFT data gave a wide range of ages from 76.8 ±