Sample records for sulu uhp terrane

  1. An exotic terrane in the Sulu UHP region, China (United States)

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


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

  2. Thermochronology of the Sulu ultrahigh-pressure metamorphic terrane: Implications for continental collision and lithospheric thinning (United States)

    Liu, Li-Ping; Li, Zheng-Xiang; Danišík, Martin; Li, Sanzhong; Evans, Noreen; Jourdan, Fred; Tao, Ni


    The thermal history of the Dabie-Sulu orogenic belt provides important constraints on the collision process between the South China and North China blocks during the Mesozoic, and possible lithospheric thinning event(s) in the eastern North China Block. This study reports on the thermal evolution of the Sulu ultrahigh-pressure metamorphic (UHP) terrane using zircon U-Pb geochronology and multiple thermochronology methods such as mica and hornblende 40Ar/39Ar, zircon and apatite fission track, and zircon and apatite (U-Th)/He dating. 40Ar/39Ar and zircon (U-Th)/He data show that the UHP terrane experienced accelerated cooling during 180-160 Ma. This cooling event could be interpreted to have resulted from extensional unroofing of an earlier southward thrusting nappe, or, more likely, an episode of northward thrusting of the UHP rocks as a hanging wall. A subsequent episode of exhumation took place between ca. 125 Ma and 90 Ma as recorded by zircon (U-Th)/He data. This event was more pronounced in the northwest section of the UHP terrane, whereas in the southeast section, the zircon (U-Th)/He system retained Jurassic cooling ages of ca. 180-160 Ma. The mid-Cretaceous episode of exhumation is interpreted to have resulted from crustal extension due to the removal of thickened, enriched mantle. A younger episode of exhumation was recorded by apatite fission track and apatite (U-Th)/He ages at ca. 65-40 Ma. Both latter events were linked to episodic thinning of lithosphere along the Sulu UHP terrane in an extensional environment, likely caused by the roll-back of the Western Pacific subduction system.

  3. Is the HP-UHP Hong'an-Dabie-Sulu orogen a piercing point for offset on the Tan-Lu fault? (United States)

    Leech, Mary L.; Webb, Laura E.


    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.

  4. 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


    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

  5. On the Preservation of Intergranular Coesite in UHP Eclogite at Yangkou Bay, Sulu belt of eastern China (United States)

    Wang, L.; Wang, S.; Brown, M.


    In contrast to coesite that occurs as inclusions in zircon and rock-forming minerals, intergranular coesite is preserved in UHP eclogite at Yangkou in the Sulu belt. The survival of intergranular coesite is intriguing because the eclogite experienced phengite growth and partial melting during exhumation. The coesite eclogite occurs as rootless isoclinal fold noses within quartz-rich schist which contains 10-20 vol% phengite, whereas phengite is absent from coesite eclogite in the fold noses. To evaluate the factors that control preservation of intergranular coesite, four samples representative of different stages along the retrograde P-T path were selected for study. For each sample we determined the number of intergranular coesite grains per cm2 and the OH content of garnet and omphacite. As the number of coesite grains decreases, the bulk rock OH content increases from transformation to quartz of intergranular coesite outside of the fold noses. The fluid is inferred to have been a supercritical fluid probably residual from prograde dehydration but also derived by dissolution of nominally anhydrous minerals. Post-metamorphic-peak deformation combined with fluid percolation along sheared fold limbs induced phengite growth during initial exhumation and then facilitated partial melting. In contrast, fold hinges in competent layers are unfavourable sites for fluid penetration. At Yangkou, the intergranular coesite is preserved in the fold noses where it was protected from both penetrative deformation and fluid ingress. Therefore, the fold noses maintained a relatively dry environment that allowed preservation of the intergranular coesite. Thus, deformation partitioning and strain localization impose local controls on fluid distribution and migration in UHP eclogite. This study informs our understanding of variations in fluid regime during exhumation of deeply subducted continental crust.

  6. 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


    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)

  7. Age and duration of eclogite-facies metamorphism, North Qaidam HP/UHP terrane, Western China (United States)

    Mattinson, C.G.; Wooden, J.L.; Liou, J.G.; Bird, D.K.; Wu, C.L.


    Amphibolite-facies para-and orthogneisses near Dulan, at the southeast end of the North Qaidam terrane, enclose minor eclogite and peridotite which record ultra-high pressure (UHP) metamorphism associated with the Early Paleozoic continental collision of the Qilian and Qaidam microplates. Field relations and coesite inclusions in zircons from paragneiss suggest that felsic, mafic, and ultramafic rocks all experienced UHP metamorphism and a common amphibolite-facies retrogression. SHRIMP-RG U-Pb and REE analyses of zircons from four eclogites yield weighted mean ages of 449 to 422 Ma, and REE patterns (flat HREE, no Eu anomaly) and inclusions of garnet, omphacite, and rutile indicate these ages record eclogite-facies metamorphism. The coherent field relations of these samples, and the similar range of individual ages in each sample suggests that the ???25 m.y. age range reflects the duration of eclogite-facies conditions in the studied samples. Analyses from zircon cores in one sample yield scattered 433 to 474 Ma ages, reflecting partial overlap on rims, and constrain the minimum age of eclogite protolith crystallization. Inclusions of Th + REE-rich epidote, and zircon REE patterns are consistent with prograde metamorphic growth. In the Lu??liang Shan, approximately 350 km northwest in the North Qaidam terrane, ages interpreted to record eclogite-facies metamorphism of eclogite and garnet peridotite are as old as 495 Ma and as young as 414 Ma, which suggests that processes responsible for extended high-pressure residence are not restricted to the Dulan region. Evidence of prolonged eclogite-facies metamorphism in HP/UHP localities in the Northeast Greenland eclogite province, the Western Gneiss Region of Norway, and the western Alps suggests that long eclogite-facies residence may be globally significant in continental subduction/collision zones.

  8. Comparison of Conventional, Trace Element, and Pseudosection Thermobarometry in UHP Eclogite, North Qaidam Terrane, Western China (United States)

    Mattinson, C. G.; Regel, M. E.; Zhang, J.


    In the southeastern North Qaidam terrane, near Dulan, felsic host gneisses enclose minor eclogite lenses. A small (~3°C/km) increase in temperatures to the west based on Zr-in-Rt thermometry is supported by a textural trend of zoned garnet with prograde mineral inclusions in the west to unzoned garnet with only peak-stage inclusions in the east. A western eclogite sample contains minor Ep and trace Phe in addition to Grt-Omp-Qtz-Rt; a strong foliation is defined by banding of Grt and Omp. Garnet Ca falls significantly from core (Alm44Prp23Grs32) to rim (Alm48Prp27Grs23). Phengite contains 3.34-3.36 Si pfu. Conventional Grt-Omp-Phe thermobarometry yields 23-27 kbar, 660-730°C, and Zr-in-Rt thermometry yields 671 ± 9°C (n = 37). An isochemical phase diagram (pseudosection) for the system NCKFMASHO calculated with PerpleX indicates that garnet Xgrs decreases with increasing P and T, suggesting that observed garnet zoning reflects prograde growth. Garnet rim compositional isopleths intersect at 23-27 kbar, 580-620°C, depending on choice of effective bulk composition and assumed Fe3+/Fetotal. Garnet rims help define the foliation, suggesting that these P-T conditions apply to this deformation. An eastern eclogite sample contains minor Ep and abundant, coarse-grained Phe in addition to Grt-Omp-Qtz-Rt; foliation is weak. Garnet zoning is weak; compositions are Alm41-43Prp26-28Grs29-32. Phengite cores contain 3.48-3.56 Si pfu. Conventional Grt-Omp-Phe thermobarometry yields 32-36 kbar, 700-750°C, and Zr-in-Rt thermometry yields 691 ± 12°C (n = 34). Conventional thermobarometry and pseudosections yield similar peak P-T conditions, but from different mineral compositions: thermobarometry yields peak P from high-Ca Grt, but the pseudosection yields peak P from intermediate-Ca Grt; maximum Ca in Grt is predicted at lower P and T. Pseudosection-based peak Ts are significantly lower than those from Zr-in-Rt and conventional thermometry. Wide isopleth spacing in the

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

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


    To constrain the origin and flow behavior of amphibolite-facies retrograde fluids during slab exhumation, we investigate the textures, trace element contents, and in situ strontium (Sr) isotopic compositions (using LA-MC-ICP-MS) of multiple types of epidote and apatite in the UHP eclogite and amphibolites from the Hualiangting area (Dabie terrane, China). The UHP epidote porphyroblasts in the eclogite (Ep-E), which formed at 28-30 kbar and 660-720 °C, contain high amounts of Sr, Pb, Th, Ba, and light rare earth elements (LREEs) and have a narrow range of initial 87Sr/86Sr ratios (0.70431 ± 0.00012 to 0.70454 ± 0.00010). Two types of amphibolite-facies epidote were recognized in the amphibolites. The first type of epidote (Ep-AI) developed in all the amphibolites and has slightly lower trace element contents than Ep-E. The Ep-AI has a same initial 87Sr/86Sr ratio range as the Ep-E and represents the primary amphibolite-facies retrograde product that is associated with an internally buffered fluid at 8.0-10.3 kbar and 646-674 °C. The other type of epidote (Ep-AII) occurs as irregular fragments, veins/veinlets, or reaction rims on the Ep-AI in certain amphibolites. Elemental X-ray maps reveal the presence of Ep-AI relics in the Ep-AII domains (appearing as a patchy texture), which indicates that Ep-AII most likely formed by the partial replacement of the Ep-AI in the presence of an infiltrating fluid. The distinctly lower trace element contents of Ep-AII are ascribed to element scavenging by a mechanism of dissolution-transport-precipitation during replacement. The Ep-AII in an individual amphibolite exhibits large intra- and inter-grain variations in the initial 87Sr/86Sr ratios (0.70493 ± 0.00030 to 0.70907 ± 0.00022), which are between those of the Ep-AI and granitic gneisses (wall rock of the amphibolites, 0.7097-0.7108). These results verify that the infiltrating fluid was externally derived from granitic gneisses. The matrix apatite in the amphibolites has

  10. Terrane-Scale Metastability in Subducted Himalayan Continental Crust as Revealed by Integrated Petrological and Geodynamic Modeling (United States)

    Palin, R. M.; Reuber, G. S.; White, R. W.; Kaus, B. J. P.; Weller, O. M.


    The Tso Morari massif, northwest India, is one of only two regions in the Himalayan Range that exposes subduction-related ultrahigh-pressure (UHP) metamorphic rocks. The tectonic evolution of the massif is strongly debated, however, as reported pressure estimates for peak metamorphism range between 2.4 GPa and 4.8 GPa. Such ambiguity hinders effective lithospheric-scale modeling of the early stages of the orogen's evolution. We present the results of integrated petrological and geodynamic modeling (Palin et al., 2017, EPSL) that provide new quantitative constraints on the prograde-to-peak pressure-temperature-time (P-T-t) path, and predict the parageneses that felsic and mafic components of the massif crust should have formed under equilibrium conditions. Our model shows that peak P-T conditions of 2.6-2.8 GPa and 600-620 °C, representative of subduction to 90-100 km depth (assuming lithostatic pressure), were reached just 3 Myr after the onset of collision. These P-T-t constraints correlate well with those reported for similar UHP eclogite in the along-strike Kaghan Valley, Pakistan, suggesting that the northwest Himalaya contains dismembered remnants of a 400-km long UHP terrane comparable in size to the Western Gneiss Region, Norway, and the Dabie-Sulu belt, China. The extremely high pressures (up to 4.8 GPa) for peak metamorphism reported by some workers are likely to be unreliable due to thermobarometry having been performed on minerals that did not represent equilibrium assemblages. Furthermore, key high-P minerals predicted to form in subducted Tso Morari continental crust (e.g. jadeite, Mg-rich garnet) are absent from natural samples in the region, reflecting the widespread metastable preservation of lower-pressure protolith assemblages during subduction and exhumation. This result questions the reliability of geodynamic simulations of orogenesis that are commonly predicated on equilibrium metamorphism operating continuously throughout tectonic cycles.

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

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


    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.

  12. Primary production in the Sulu Sea

    Indian Academy of Sciences (India)

    R. Narasimhan (Krishtel eMaging) 1461 1996 Oct 15 13:05:22

    its remotely sensed values from OCTS (Ocean Colour Temperature Scanner) are found to be in ... Although the Sulu Sea is more productive than the adjacent South China Sea, the central area ... surrounding ocean by a chain of islands.

  13. UHP lamp systems for projection applications

    International Nuclear Information System (INIS)

    Derra, Guenther; Moench, Holger; Fischer, Ernst; Giese, Hermann; Hechtfischer, Ulrich; Heusler, Gero; Koerber, Achim; Niemann, Ulrich; Noertemann, Folke-Charlotte; Pekarski, Pavel; Pollmann-Retsch, Jens; Ritz, Arnd; Weichmann, Ulrich


    Projection systems have found widespread use in conference rooms and other professional applications during the last decade and are now entering the home TV market at a considerable pace. Projectors as small as about one litre are able to deliver several thousand screen lumens and are, with a system efficacy of over 10 lm W -1 , the most efficient display systems realized today. Short arc lamps are a key component for projection systems of the highest efficiency for small-size projection displays. The introduction of the ultra high performance (UHP) lamp system by Philips in 1995 can be identified as one of the key enablers of the commercial success of projection systems. The UHP lamp concept features outstanding arc luminance, a well suited spectrum, long life and excellent lumen maintenance. For the first time it combines a very high pressure mercury discharge lamp with extremely short and stable arc gap with a regenerative chemical cycle keeping the discharge walls free from blackening, leading to lifetimes of over 10 000 h. Since the introduction of the UHP lamp system, many important new technology improvements have been realized: burner designs for higher lamp power, advanced ignition systems, miniaturized electronic drivers and innovative reflector concepts. These achievements enabled the impressive increase of projector light output, a remarkable reduction in projector size and even higher optical efficiency in projection systems during the last years. In this paper the concept of the UHP lamp system is described, followed by a discussion of the technological evolution the UHP lamp has undergone so far. Last, but not least, the important improvements of the UHP lamp system including the electronic driver and the reflector are discussed. (review article)

  14. Evolution of supercritical fluid in deeply subducted continental crust: a case study of composite granite-quartz veins in the Sulu belt, China (United States)

    Wang, S.; Wang, L.; Brown, M.


    Although fluid plays a key role in element transport and rock strength during subduction to and exhumation from ultrahigh pressure (UHP) metamorphic conditions, the source of supercritical fluid at P above the second critical endpoints (SCE) and the subsequent evolution are not well constrained. To provide insight into the evolution of supercritical fluid in continental subduction zones, we undertook an integrated study of composite granite-quartz veins in retrogressed and migmatitic UHP eclogite at General's Hill, N of Qingdao, in the central Sulu belt. The composite veins are irregularly distributed in the eclogite, which occurs as blocks within gneiss. The granite component is enriched in large ion lithophile elements and light rare earth elements but depleted in high field strength elements and heavy rare earth elements, indicating crystallization from a melt phase of crustal origin. Additionally, the granite contains high modal phengite (22-30 vol%) and clinozoisite/epidote (3-10 vol%), implying precipitation from a H2O-rich silicate melt. By contrast, the quartz component is dominated by SiO2 (99.10 wt%), and contains low total rare earth elements (ΣREE = 0.46 ppm), indicating precipitation from an aqueous fluid. The crystallization age of the composite veins is 221 ± 2 Ma, which is younger than the UHP metamorphism in the Sulu belt at ca 230 Ma, consistent with formation during exhumation. Initial 176Hf/177Hf ratios and δ18O values of metamorphic zircons from the composite veins, and Sr-Nd isotope compositions of the granites all lie between values for eclogite and gneiss, indicating a mixed source. Accordingly, we propose that a supercritical fluid generated from the gneiss and the included blocks of eclogite at P-T conditions above the SCE for both compositions became trapped in the eclogite during exhumation. At P below the SCE for the hydrous granite system, the mixed supercritical fluid separated into immiscible aqueous melt and aqueous fluid and

  15. Application of ultra high pressure (UHP) in starch chemistry. (United States)

    Kim, Hyun-Seok; Kim, Byung-Yong; Baik, Moo-Yeol


    Ultra high pressure (UHP) processing is an attractive non-thermal technique for food treatment and preservation at room temperature, with the potential to achieve interesting functional effects. The majority of UHP process applications in food systems have focused on shelf-life extension associated with non-thermal sterilization and a reduction or increase in enzymatic activity. Only a few studies have investigated modifications of structural characteristics and/or protein functionalities. Despite the rapid expansion of UHP applications in food systems, limited information is available on the effects of UHP on the structural and physicochemical properties of starch and/or its chemical derivatives included in most processed foods as major ingredients or minor additives. Starch and its chemical derivatives are responsible for textural and physical properties of food systems, impacting their end-use quality and/or shelf-life. This article reviews UHP processes for native (unmodified) starch granules and their effects on the physicochemical properties of UHP-treated starch. Furthermore, functional roles of UHP in acid-hydrolysis, hydroxypropylation, acetylation, and cross-linking reactions of starch granules, as well as the physicochemical properties of UHP-assisted starch chemical derivatives, are discussed.

  16. Melting of subducted continental crust: Geochemical evidence from Mesozoic granitoids in the Dabie-Sulu orogenic belt, east-central China (United States)

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


    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

  17. The extremely high 137Cs inventory in the Sulu Sea: a possible mechanism

    International Nuclear Information System (INIS)

    Yamada, Masatoshi; Wang Zhongliang; Zheng Jian


    Large-volume seawater samples were collected in the Sulu and South China Seas and their 137 Cs activities were determined by γ-ray spectrometry using a low background type high-purity Ge detector. Vertical distributions of 137 Cs activity showed an exponential decrease in the South China Sea, whereas a subsurface maximum at 200 m depth and monotonic decrease below 300 m were observed in the Sulu Sea. A significant difference in intermediate water 137 Cs activities in the 500-2000 m depth was observed between the Sulu and South China Seas, i.e., the 137 Cs activities in the Sulu Sea were remarkably higher than those in the South China Sea. The difference in the 137 Cs inventory below 500 m was ∼1200 Bq m -2 between the Sulu and South China Seas. The 137 Cs total inventory of 3200 Bq m -2 in the Sulu Sea was 5.7 times higher than that expected from global fallout. A possible mechanism controlling this extremely high 137 Cs total inventory may be inflows of the 137 Cs rich water masses through the Luzon Strait, lateral transport across the Mindoro Strait into the Sulu Sea, and then subduction into the deep layer in the basin

  18. Variation of Rare Earth Elements (REEs) in the Sulu and Celebes ...

    African Journals Online (AJOL)

    This study provides a dataset of rare earth elements (REEs) in the seawater of Sulu and Celebes Seas of Malaysian waters during the PMSE 09' expedition, which was conducted to define the pattern of REEs in both seas. Samples were collected, filtered and pre-concentrated on-board ship then analyzed by using ICP-MS.

  19. Gravity signatures of terrane accretion (United States)

    Franco, Heather; Abbott, Dallas


    In modern collisional environments, accreted terranes are bracketed by forearc gravity lows, a gravitational feature which results from the abandonment of the original trench and the initiation of a new trench seaward of the accreted terrane. The size and shape of the gravity low depends on the type of accreted feature and the strength of the formerly subducting plate. Along the Central American trench, the accretion of Gorgona Island caused a seaward trench jump of 48 to 66 km. The relict trench axes show up as gravity lows behind the trench with minimum values of -78 mgal (N of Gorgona) and -49 mgal (S of Gorgona) respectively. These forearc gravity lows have little or no topographic expression. The active trench immediately seaward of these forearc gravity lows has minimum gravity values of -59 mgal (N of Gorgona) and -58 mgal (S of Gorgona), respectively. In the north, the active trench has a less pronounced gravity low than the sediment covered forearc. In the Mariana arc, two Cretaceous seamounts have been accreted to the Eocene arc. The northern seamount is most likely a large block, the southern seamount may be a thrust slice. These more recent accretion events have produced modest forearc topographic and gravity lows in comparison with the topographic and gravity lows within the active trench. However, the minimum values of the Mariana forearc gravity lows are modest only by comparison to the Mariana Trench (-216 mgal); their absolute values are more negative than at Gorgona Island (-145 to -146 mgal). We speculate that the forearc gravity lows and seaward trench jumps near Gorgona Island were produced by the accretion of a hotspot island from a strong plate. The Mariana gravity lows and seaward trench jumps (or thrust slices) were the result of breaking a relatively weak plate close to the seamount edifice. These gravity lows resulting from accretion events should be preserved in older accreted terranes.

  20. Coconuts and the emergence of violence in Sulu: Beyond resource competition paradigms

    Directory of Open Access Journals (Sweden)

    Yancey Orr


    Full Text Available Agricultural differentiation can lead to cultural differentiation. Among the Sulu Archipelago’s Tausug in south Philippines, increased coconut production has resulted in more violence and banditry among individuals and communities than among other Tausug populations engaged in other economic activities. Although resource competition in social theory has been used to explicate the connections between agriculture and violence (Vayda, Rappaport, Homer-Dixon, Stinchcombe, Peluso, Watts, this is not the case in Sulu. Coconut production influences violence through its low labour requirement which allows the intensification of culturally valued male violence (rites of passage, feuding; the low level of skills entailed in its cultivation and harvesting which limits the roles men can play in Tausug society; and the lack of ‘nurturing’ (as an activity inherent in its cultivation.

  1. Distribution of 137Cs in surface seawater and sediment around Sabahs Sulu-Sulawesi Sea

    International Nuclear Information System (INIS)

    Mohd Izwan Abdul Aziz; Ahmad Sanadi Abu Bakar; Yii, Mei Wo; Nurrul Assyikeen Jaffary; Zaharudin Ahmad


    The studies on distribution of 137 Cs in surface seawater and sediment around Sabahs Sulu-Sulawesi Sea were carried out during Ekspedisi Pelayaran Saintifik Perdana (EPSP) in July 2009. About sixteen and twenty five sampling locations were identified for surface seawater and sediment respectively in Sabahs Sulu-Sulawesi Sea. Large volumes of seawater samples are collected and co-precipitation technique was employed to concentrate cesium content before known amounts of 134 Cs tracer were added as yield determinant. Grab sampler were used to collect surface sediment sample. The caesium precipitate and sediment were dried and finely ground before counted using gamma-ray spectrometry system at 661 keV. The activity of 137 Cs was found in surface seawater and sediment to be in the range 1.73 Bq/ m 3 to 5.50 Bq/ m 3 and 1.15 Bq/ kg to 4.53 Bq/ kg respectively. (author)

  2. UHP metamorphism recorded by kyanite-bearing eclogite in the Seve Nappe Complex of northern Jämtland, Swedish Caledonides

    NARCIS (Netherlands)

    Janák, M.; Van Roermund, H.; Majka, J.; Gee, D.

    The first evidence for ultrahigh-pressure (UHP) metamorphism in the Seve Nappe Complex of the Scandinavian Caledonides is recorded by kyanite-bearing eclogite, found in a basic dyke within a garnet peridotite body exposed close to the lake Friningen in northern Jämtland (central Sweden). UHP

  3. The Sulu-Sulawesi Sea: environmental and socioeconomic status, future prognosis and ameliorative policy options. (United States)

    DeVantier, Lyndon; Alcala, Angel; Wilkinson, Clive


    The Sulu-Sulawesi Sea, with neighboring Indonesian Seas and South China Sea, lies at the center of the world's tropical marine biodiversity. Encircled by 3 populous, developing nations, the Philippines, Indonesia and Malaysia, the Sea and its adjacent coastal and terrestrial ecosystems, supports ca. 33 million people, most with subsistence livelihoods heavily reliant on its renewable natural resources. These resources are being impacted severely by rapid population growth (> 2% yr-1, with expected doubling by 2035) and widespread poverty, coupled with increasing international market demand and rapid technological changes, compounded by inefficiencies in governance and a lack of awareness and/or acceptance of some laws among local populations, particularly in parts of the Philippines and Indonesia. These key root causes all contribute to illegal practices and corruption, and are resulting in severe resource depletion and degradation of water catchments, river, lacustrine, estuarine, coastal, and marine ecosystems. The Sulu-Sulawesi Sea forms a major geopolitical focus, with porous borders, transmigration, separatist movements, piracy, and illegal fishing all contributing to environmental degradation, human suffering and political instability, and inhibiting strong trilateral support for interventions. This review analyzes these multifarious environmental and socioeconomic impacts and their root causes, provides a future prognosis of status by 2020, and recommends policy options aimed at amelioration through sustainable management and development.

  4. Geochemical Constraints for Mercury's PCA-Derived Geochemical Terranes (United States)

    Stockstill-Cahill, K. R.; Peplowski, P. N.


    PCA-derived geochemical terranes provide a robust, analytical means of defining these terranes using strictly geochemical inputs. Using the end members derived in this way, we are able to assess the geochemical implications for Mercury.

  5. Circum-North Pacific tectonostratigraphic terrane map (United States)

    Nokleberg, Warren J.; Parfenov, Leonid M.; Monger, James W.H.; Baranov, Boris B.; Byalobzhesky, Stanislav G.; Bundtzen, Thomas K.; Feeney, Tracey D.; Fujita, Kazuya; Gordey, Steven P.; Grantz, Arthur; Khanchuk, Alexander I.; Natal'in, Boris A.; Natapov, Lev M.; Norton, Ian O.; Patton, William W.; Plafker, George; Scholl, David W.; Sokolov, Sergei D.; Sosunov, Gleb M.; Stone, David B.; Tabor, Rowland W.; Tsukanov, Nickolai V.; Vallier, Tracy L.; Wakita, Koji


    The companion tectonostratigraphic terrane and overlap assemblage of map the Circum-North Pacific presents a modern description of the major geologic and tectonic units of the region. The map illustrates both the onshore terranes and overlap volcanic assemblages of the region, and the major offshore geologic features. The map is the first collaborative compilation of the geology of the region at a scale of 1:5,000,000 by geologists of the Russian Far East, Japanese, Alaskan, Canadian, and U.S.A. Pacific Northwest. The map is designed to be a source of geologic information for all scientists interested in the region, and is designed to be used for several purposes, including regional tectonic analyses, mineral resource and metallogenic analyses (Nokleberg and others, 1993, 1994a), petroleum analyses, neotectonic analyses, and analyses of seismic hazards and volcanic hazards. This text contains an introduction, tectonic definitions, acknowledgments, descriptions of postaccretion stratified rock units, descriptions and stratigraphic columns for tectonostratigraphic terranes in onshore areas, and references for the companion map (Sheets 1 to 5). This map is the result of extensive geologic mapping and associated tectonic studies in the Russian Far East, Hokkaido Island of Japan, Alaska, the Canadian Cordillera, and the U.S.A. Pacific Northwest in the last few decades. Geologic mapping suggests that most of this region can be interpreted as a collage of fault-bounded tectonostratigraphic terranes that were accreted onto continental margins around the Circum-

  6. Mechanisms of continental subduction and exhumation of HP and UHP rocks

    NARCIS (Netherlands)

    Burov, Evgene; Francois, Thomas; Yamato, Philippe; Wolf, Sylvie

    We discuss possible scenarios of continental collision, and their relation to mechanisms of exhumation of HP and UHP rocks, inferred from thermo-mechanical numerical models accounting for thermo-rheological complexity of the continental lithosphere. Due to this complexity, mechanisms of continental

  7. Age and composition of the UHP garnet peridotites in the Dabie orogenic belt (central China) record complex crust-mantle interaction in continental margin (United States)

    Zhao, Y.; Zheng, J.; Wang, B.


    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.

  8. Mutations of the Transporter Proteins GlpT and UhpT Confer Fosfomycin Resistance in Staphylococcus aureus

    Directory of Open Access Journals (Sweden)

    Su Xu


    Full Text Available With the increasing spread of methicillin-resistant Staphylococcus aureus worldwide, fosfomycin has begun to be used more often, either alone or in combination with other antibiotics, for treating methicillin-resistant S. aureus infections, resulting in the emergence of fosfomycin-resistant strains. Fosfomycin resistance is reported to be mediated by fosfomycin-modifying enzymes (FosA, FosB, FosC, and FosX and mutations of the target enzyme MurA or the membrane transporter proteins UhpT and GlpT. Our previous studies indicated that the fos genes might not the major fosfomycin resistance mechanism in S. aureus, whereas mutations of glpT and uhpT seemed to be more related to fosfomycin resistance. However, the precise role of these two genes in S. aureus fosfomycin resistance remains unclear. The aim of the present study was to investigate the role of glpT and uhpT in S. aureus fosfomycin resistance. Homologous recombination was used to knockout the uhpT and glpT genes in S. aureus Newman. Gene complementation was generated by the plasmid pRB473 carrying these two genes. The fosfomycin minimal inhibitory concentration (MIC of the strains was measured by the E-test to observe the influence of gene deletion on antibiotic susceptibility. In addition, growth curves were constructed to determine whether the mutations have a significant influence on bacterial growth. Deletion of uhpT, glpT, and both of them led to increased fosfomycin MIC 0.5 μg/ml to 32 μg/ml, 4 μg/ml, and >1024 μg/ml, respectively. By complementing uhpT and glpT into the deletion mutants, the fosfomycin MIC decreased from 32 to 0.5 μg/ml and from 4 to 0.25 μg/ml, respectively. Moreover, the transporter gene-deleted strains showed no obvious difference in growth curves compared to the parental strain. In summary, our study strongly suggests that mutations of uhpT and glpT lead to fosfomycin resistance in S. aureus, and that uhpT mutation may play a more important role. The high

  9. Urea- Hydrogen Peroxide (UHP Oxidation of Thiols to the Corresponding Disulfides Promoted by Maleic Anhydride as Mediator

    Directory of Open Access Journals (Sweden)

    M. H. Habibi


    Full Text Available Urea-hydrogen peroxide (UHP was used in the presence of maleic anhydride as mediator in a simple and convenient method for the oxidation in high yield of some thiols to the corresponding disulfides. Peroxymaleic acid formed in situ from the reaction of UHP with maleic anhydride has a key role in this oxidation. Performance of the reaction in various solvents showed that methanol was the solvent of choice at 0 oC. The products were isolated by simple filtration on silica gel.

  10. Linking Tengchong Terrane in SW Yunnan with Lhasa Terrane in southern Tibet through magmatic correlation (United States)

    Xie, Jincheng; Zhu, Dicheng; Dong, Guochen; Zhao, Zhidan; Wang, Qing


    New zircon U-Pb data, along with the data reported in the literature, reveal five phases of magmatic activity in the Tengchong Terrane since the Early Paleozoic with spatial and temporal variations summarized as: Cambrian-Ordovician (500-460 Ma) to the eastern, minor Triassic (245-206 Ma) in the eastern and western, abundant Early Cretaceous (131-114 Ma) in the eastern, extensive Late Cretaceous (77-65 Ma) in the central, and Paleocene-Eocene (65-49 Ma) in the central and western Tengchong Terrane, in which the Cretaceous-Eocene magmatism was migrated from east to west (Xu et al., 2012). The increased zircon eHf(t) of the Early Cretaceous granitoids from -12.3 to -1.4 at ca. 131-122 Ma to -4.6 to +7.1 at ca. 122-114 Ma identified for the first time in this study and the magmatic flare-up at ca. 53 Ma in the central and western Tengchong Terrane (Wang et al., 2014, Ma et al., 2015) indicate the increased contributions from mantle- or juvenile crust-derived components. The spatial and temporal variations and changing magmatic compositions with time in the Tengchong Terrane closely resemble the Lhasa Terrane in southern Tibet. Such similarities, together with the data of stratigraphy and paleobiogeography (Zhang et al., 2013), enable us to propose that the Tengchong Terrane in SW Yunnan is most likely linked with the Lhasa Terrane in southern Tibet, both of which experience similar tectonomagmatic histories since the Early Paleozoic. References Ma, L.Y., Wang, Y.J., Fan, W.M., Geng, H.Y., Cai, Y.F., Zhong, H., Liu, H.C., Xing, X.W., 2014. Petrogenesis of the early Eocene I-type granites in west Yingjiang (SW Yunnan) and its implication for the eastern extension of the Gangdese batholiths. Gondwana Research 25, 401-419. Wang, Y.J., Zhang, L.M., Cawood, P.A., Ma, L.Y., Fan, W.M., Zhang, A.M., Zhang, Y.Z., Bi, X.W., 2014. Eocene supra-subduction zone mafic magmatism in the Sibumasu Block of SW Yunnan: Implications for Neotethyan subduction and India-Asia collision

  11. Common Pb isotope mapping of UHP metamorphic zones in Dabie orogen, Central China: Implication for Pb isotopic structure of subducted continental crust (United States)

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


    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

  12. Tectonostratigraphic terranes of the frontier circum-Pacific region

    Energy Technology Data Exchange (ETDEWEB)

    Howell, D.G.; Jones, D.L.; Schermer, E.R.


    Many major exploration frontiers around the Pacific are in regions where complex geologic relations reflect plate-tectonic processes, crustal mobility, and accretion of exotic terranes. The destruction of the proto-Pacific ocean (Panthalassa) involved accretion of terranes to cratonal regions such as Gondwana and Laurasia. Terranes in southwestern New Zealand and eastern Antarctica were also probably accreted during the Paleozoic. The southern margin of Siberia, extending into China, underwent a protracted period of accretion from the late Precambrian through the early Mesozoic. Mid-Paleozoic accretion is reflected in the Innuitian foldbelt of the Arctic Ocean, the Black Clastic unit of the northern Rocky Mountains, and the Antler orogeny of the western US cordillera. The Mesozoic breakup of Pangaea and the acceleration of subduction aided in the rifting and dispersal of terranes from equatorial paleolatitudes. Fragments of these terranes now compose much of the continental margins of the Pacific basin, including New Zealand, Indochina, southern China, southeast Siberia, the North American cordillera, and South America. Some terranes are presently being further fragmented by post-accretionary dispersion processes such as strike-slip faulting in western North America and Japan. Although the character and distribution of terranes in the western US are fairly well documented, details are needed for other terranes around the Pacific basin. Interpretation of structure and stratigraphy at depth will be aided by more data on the timing of accretion and the nature of deformation associated with accretion and dispersion. Such data are needed for further define specific exploration targets in the circum-Pacific region.


    Directory of Open Access Journals (Sweden)

    Wenjiao Xiao


    Full Text Available The exhumation and tectonic emplacement of eclogites and blueschists take place in forearc accretionary complexes by either forearc- or backarc-directed extrusion, but few examples have been well analysed in detail. Here we present an example of oblique wedge extrusion of UHP/HP rocks in the Atbashi accretionary complex of the Kyrgyz South Tianshan.

  14. Commercial-Industrial Cleaning, by Pressure-Washing, Hydro-Blasting and UHP-Jetting The Business Operating Model and How-To Manual for 450 Specific Applications

    CERN Document Server

    Maasberg, Wolfgang


    Commercial-Industrial Cleaning, by Pressure-Washing, Hydro-Blasting and UHP-Jetting is the first proprietary manual for cleaning and rehabilitation through pressure-washing, hydro-blasting and ultra high pressure water jetting (UHP).   It examines the cleaning, restoration and rehabilitation of statuary and historical structures; manufacturing hardware; and application technologies for residential, commercial and industrial areas, structures and buildings. Commercial-Industrial Cleaning, by Pressure-Washing, Hydro-Blasting and UHP-Jetting contains over 450 applications from agricultural, marine, municipal, food processing, paper-pulp, pharmaceutical and cosmetic, industrial and power generating maintenance areas. It includes gear lists to help readers easily identify the appropriate tooling and equipment for each specific application and industry.   Commercial-Industrial Cleaning, by Pressure-Washing, Hydro-Blasting and UHP-Jetting supplies readers with the tools to create a successful business model for re...

  15. Partial melting of UHP calc-gneiss from the Dabie Mountains (United States)

    Liu, Penglei; Wu, Yao; Liu, Qiang; Zhang, Junfeng; Zhang, Li; Jin, Zhenmin


    Exhumation melting has been proposed for the ultra-high pressure (UHP) metamorphic rocks in the Dabie Mountains based on melting experiments. We document here the first petrological and mineralogical evidence demonstrating that the UHP calc-gneisses from the Ganjialing area in the Dabie Mountains experienced partial melting during early exhumation. The assemblage of garnet, phengite (Si = 3.65 pfu), coesite, rutile and carbonate preserved in the calc-gneisses indicates a peak metamorphic condition of 692-757 °C and 4.0-4.8 GPa. Partial melting is indicated by several lines of evidence: the melting textures of phengite, the feldspar-dominated films, bands, branches, blebs and veins, the euhedral K-feldspars, the intergrowth film of plagioclase and K-feldspar, the plagioclase + biotite intergrowth after garnet and the epidote poikiloblasts. Polyphase inclusions in garnet are characterized with wedge-like offshoots and serrate outlines whereas those in epidote display negative crystal shapes, which can be best interpreted by entrapment of former melts. We propose a wet melting reaction of Phn + Q ± Na-Cpx + H2O = Bt + Pl + Grt + felsic melts, which likely took place at ca.650-800 °C and ca.1.0-2.0 GPa, to interpret the melting event in the calc-gneisses. Chemical exchanges between garnet and melts produced new garnet domains with higher almandine, spessartine, MREE, HREE and Y but lower grossular, pyrope, P, Sc, Ti, V and Zr contents. Zr-in-rutile thermometer reveals a low temperature of 620-643 °C at 5 GPa, indicating a later reset for Zr in rutile. Healed fractures are suggested to be responsible for the formation of some polyphase inclusions in garnet.

  16. Trace elements and stable isotope ratios (δ13C and δ15N) in fish from deep-waters of the Sulu Sea and the Celebes Sea

    International Nuclear Information System (INIS)

    Asante, Kwadwo Ansong; Agusa, Tetsuro; Kubota, Reiji; Mochizuki, Hiroko; Ramu, Karri; Nishida, Shuhei; Ohta, Suguru; Yeh, Hsin-ming; Subramanian, Annamalai; Tanabe, Shinsuke


    Trace elements (TEs) and stable isotope ratios (δ 15 N and δ 13 C) were analyzed in fish from deep-water of the Sulu Sea, the Celebes Sea and the Philippine Sea. Concentrations of V and Pb in pelagic fish from the Sulu Sea were higher than those from the Celebes Sea, whereas the opposite trend was observed for δ 13 C. High concentrations of Zn, Cu and Ag were found in non-migrant fish in deep-water, while Rb level was high in fish which migrate up to the epipelagic zone, probably resulting from differences in background levels of these TEs in each water environment or function of adaptation to deep-water by migrant and non-migrant species. Arsenic level in the Sulu Sea fish was positively correlated with δ 15 N, indicating biomagnification of arsenic. To our knowledge, this is the first study on relationship between diel vertical migration and TE accumulation in deep-water fish.

  17. Remelting of nanogranitoids in UHP felsic granulites from Erzgebirge (Bohemian Massif, Germany) (United States)

    Acosta-vigil, A.; Stöckhert, B.; Hermann, J.; Yaxley, G.; Cesare, B.; Bartoli, O.


    Crustal melting commonly takes place at pressures ≤ 1.5 GPa. Anatexis at UHP conditions, however, can occur during subduction of continental crust down to mantle depths. Understanding the timing, mechanisms and nature of this process is important as it has major mechanical and geochemical implications. One way to address this problem is through the novel studies of nanogranitoids in migmatites and granulites (Cesare et al. 2015). We have remelted crystallized former melt inclusions (nanogranitoids) trapped in garnets of diamond-bearing UHP felsic granulites from Erzgebirge, Bohemian Massif. These rocks are made of Qtz+Phe+Pl+Grt+Ky+Bt+Dia, and their peak conditions have been estimated at P≥4.5 GPa and T≥1000 ºC. Nanogranitoids appear homogeneously distributed throughout the entire garnet crystals, are 5-50 µm across and often isometric, with partially developed negative crystal shape, and were trapped during garnet growth in the presence of melt. The mineral assemblage within nanogranites consists of Qtz+Pl+Phe+Pg+Phl±Ky±Dia±Gr±Ap±Rt (Stöckhert et al. 2009). Fragments of nanogranitoids-bearing garnets were loaded inside gold capsules, enclosed in SiO2 or C powders that acted as cushion, either dry or with H2O in excess, and subjected to conditions between 975-1100 ºC and 2.5-4.5 GPa for 2-24 hrs. Re-homogenization has not been completely achieved. Nanogranitoids partially melt, melt often coexists with Als, diamond or Gr, and Grt grows into the melt to form a higher #Mg and Ti, ≈5 µm fringe. Preliminary EMP analyses indicate that melts are granitic sensu stricto, with low FeOt+MgO (≈2 wt%), moderate to high in ASI, and high in TiO2 (≈0.4-0.8 wt%), P2O5 (up to 1 wt%) and volatiles (100-EMP totals ≈ 10-15 wt%). These preliminary results suggest that (i) anatexis started in the presence of a H2O-rich fluid phase, (ii) melt was present and equilibrated at quite high T (>850-950 ºC, Hayden & Watson 2007) at or close to peak conditions, (iii) Als

  18. Cooperative Actions of CRP-cAMP and FNR Increase the Fosfomycin Susceptibility of Enterohaemorrhagic Escherichia coli (EHEC) by Elevating the Expression of glpT and uhpT under Anaerobic Conditions. (United States)

    Kurabayashi, Kumiko; Tanimoto, Koichi; Tomita, Haruyoshi; Hirakawa, Hidetada


    Bacterial infections to anaerobic site are often hard to be treated because the activity of most of antimicrobials decreases under anaerobic conditions. However, fosfomycin rather provides a greater activity under anaerobic conditions than aerobic conditions. Previously, we found that expression of glpT and uhpT , fosfomycin symporters in enterohaemorrhagic Escherichia coli (EHEC) was upregulated by FNR, a global regulator during the anaerobiosis of the bacterium, which led to increased uptake and susceptibility to this drug. In this study, we showed that expression of glpT and uhpT is induced by CRP-cAMP, the regulator complex under both aerobic and anaerobic conditions. The activity of CRP-cAMP in EHEC was elevated under anaerobic conditions because levels of both CRP and cAMP were higher in the cells when grown anaerobically than those when grown aerobically. Results of expression study using mutants indicated that CRP-cAMP is indispensable for expression of glpT but not uhpT -whereas that of uhpT requires UhpA that is the response regulator composing of two-component system with the sensor kinase, UhpB. The CRP-cAMP protein bound to a region that overlaps RNA polymerase binding site for glpT and region upstream of UhpA binding site for uhpT . FNR bound to a region further upstream of CRP-cAMP binding site on region upstream of the glpT gene. These combined results suggested that increased antibacterial activity of fosfomycin to EHEC under anaerobic conditions is due to activation of FNR and increment of CRP-cAMP activity. Then, FNR enhances the expression of glpT activated by CRP-cAMP while CRP-cAMP and FNR cooperatively aids the action of UhpA to express uhpT to maximum level.

  19. Gondwanan/peri-Gondwanan origin for the Uchee terrane, Alabama and georgia: Carolina zone or Suwannee terrane(?) and its suture with Grenvillian basement of the Pine Mountain window (United States)

    Steltenpohl, M.G.; Mueller, P.M.; Heatherington, A.L.; Hanley, T.B.; Wooden, J.L.


    The poorly known, suspect, Uchee terrane occupies a critical tectonic position with regard to how and when peri-Gondwanan (Carolina) and Gondwanan (Suwannee) terranes were sutured to Laurentia. It lies sandwiched between Laurentian(?) continental basement exposed in the Pine Mountain window and adjacent buried Gondwanan crust of the Suwannee terrane. The Uchee terrane has been proposed as both a septum of Piedmont rocks that once was continuous across the erosionally breached Pine Mountain window or part of the Carolina zone. To help resolve this issue, we conducted U-Pb (SHRIMP-RG) (sensitive high-resolution ion microprobe-reverse geometry) zircon studies and whole-rock isotopic analyses of principal metasedimentary and metaplutonic units. U-Pb ages for zircons from the Phenix City Gneiss suggest igneous crystallization at ca. 620 Ma, inheritance ca. 1000 to ca. 1700 Ma, and a ca. 300 Ma (Alleghanian) overprint recorded by zircon rims. Zircons from the metasedimentary/metavolcaniclastic Moffits Mill Schist yield bimodal dates at ca. 620 and 640 Ma. The 620 to 640 Ma dates make these rocks age-equivalent to the oldest parts of the Carolina slate belt (Virgilina and Savannah River) and strongly suggest a Gondwanan (Pan-African and/or Trans-Brasiliano) origin for the Uchee terrane. Alternatively, the Uchee terrane may be correlative with metamorphic basement of the Suwannee terrane. The ca. 300 Ma overgrowths on zircons are compatible with previously reported 295 to 288 Ma 40Ar/39Ar hornblende dates on Uchee terrane rocks, which were interpreted to indicate deep tectonic burial of the Uchee terrane contemporaneous with the Alleghanian orogeny recorded in the foreland. Temperature-time paths for the Uchee terrane are similar to that of the Pine Mountain terrane, indicating a minimum age of ca. 295 Ma for docking. In terms of tectono-metamorphic history of the Uchee terrane, it is important to note that no evidence for intermediate "Appalachian" dates (e.g, Acadian or

  20. Serpentinite-driven Exhumation of the UHP Lago di Cignana Unit in the Fossil Alpine Plate Interface (United States)

    Scambelluri, M.; Gilio, M.; Angiboust, S.; Godard, M.; Pettke, T.


    The Lago di Cignana Unit (LCU) is a coesite- [1] and diamond-bearing [2] slice of oceanic-derived eclogites and metasediments recording Alpine UHP metamorphism at 600 °C-3.2 GPa (~110 km depth) [3]. The LCU is tectonically sandwiched between the eclogitic Zermatt-Saas Zone (ZSZ; 540 °C-3.2 GPa) [4] and the blueschist Combin Zone (400 °C-0.9 GPa) [5] along a tectonic structure joining HP units recording a ~1.2 GPa (40 km) pressure difference. So far, the ZSZ has been attributed to normal HP conditions and the mechanism driving exhumation and accretion of the LCU in its present structural position is not fully understood.We performed petrography and bulk-rock trace element analyses of rocks from LCU and ZSZ serpentinites. We observed that, while serpentinites in the core of the ZSZ show normal subduction zone trace elements and REE's patterns, the Ol+Ti-chu+Chl veins and host serpentinites enveloping the LCU are strongly enriched in sediment-derived fluid-mobile elements (U, Th, Nb, Ta, Ce, Y, As, Sb) and REE's: their patterns well match those of the closely associated LCU-UHP rocks.The presence of extremely enriched Ol+Ti-chu+Chl veins in the serpentinites at direct contact with the UHP Lago di Cignana Unit suggests that fluid exchange between serpentinite and LCU crustal rocks occurred at peak metamorphic conditions. Their coupling therefore occurred during subduction burial and/or peak UHP conditions. As such, the buoyancy force originating from the relatively light serpentinites fuelled the exhumation of the Lago di Cignana Unit. In this contest, the tectonic contact between the Zermatt-Saas Zone and the Combin Zone evolved into a true tectonic plate interface surface.1. Reinecke (1998). Lithos 42(3), 147-189; 2. Frezzotti et al. (2011). Nat. Geosci. 4(10), 703-706; 3. Groppo et al. (2009). J. Metam. Geol. 27(3), 207-231; 4. Angiboust et al. (2009). Terra Nova 21(3), 171-180; 5. Reddy et al. (1999). J. Metam. Geol. 17, 573-590.

  1. Microwave-Accelerated Iodination of Some Aromatic Amines, Using Urea-Hydrogen Peroxide Addition Compound (UHP as the Oxidant

    Directory of Open Access Journals (Sweden)

    Lech Skulski


    Full Text Available A fast and simple method for the oxidative iodination of some aromatic amines, under microwave irradiation, is reported, using diiodine and the the strongly Hbonded urea-hydrogen peroxide addition compound (H2NCONH2···H2O2, UHP as the oxidant. The reactions were carried out in boiling CHCl3 under a reflux condenser to afford, within 10 minutes, the purified monoiodinated products in 40-80% yields.

  2. Quartz exsolution topotaxy in clinopyroxene from the UHP eclogite of Weihai, China (United States)

    Xu, Haijun; Zhang, Junfeng; Zong, Keqing; Liu, Liang


    Abundant oriented silica precipitates of α-quartz (4.0 ± 1.0 vol.%), in part coexisting with calcic amphiboles (topotactic relationships with their host clinopyroxenes. Three types of crystallographic topotactic relationship have been identified between quartz and host clinopyroxene: (1) 52% quartz precipitates share the same orientation for the c-axes with [0001]qz//[001]cpx; (2) 34% quartz precipitates share the same orientation for the a-axes with [11 2 bar0]qz//[001]cpx; and (3) 11% quartz precipitates share the same orientation for the s-planes with (11 2 bar1)qz//(100)cpx. Other quartz axes and planes disperse in large or small girdles around the shared axes or planes. Many quartz rods/needles are elongated parallel to the [001]cpx with the long axes of quartz being either [0001]qz or [11 2 bar0]qz. Amphibole precipitates have also a strong crystallographic relationship with host clinopyroxene, i.e., (100)amp//(100)cpx, [010]amp//[010]cpx, and [001]amp//[001]cpx. These results provide quantitative microstructural evidence supporting an exsolution origin for oriented quartz needles/rods in clinopyroxene and demonstrate that the exsolution of quartz from clinopyroxene occurred within the stability field of α-quartz rather than coesite. The oriented precipitates of α-quartz, in part coexisting with calcic amphiboles, in host clinopyroxene are probably promoted by supercritical fluid or partial melting during the early exhumation of eclogites. Our results suggest that oriented quartz precipitates in clinopyroxene cannot be used as an indisputable UHP-indicator.


    Directory of Open Access Journals (Sweden)



    Full Text Available Astrozone Red'in sulu çözeltilerinden aktif kömür üzerine adsorpsiyonu incelendi. Adsorpsiyon prosesi Lagergren birinci mertebe kinetik eşitliğine uydu. Adsorbent konsantrasyonu Astrozone Red adsorpsiyonunu önemli ölçüde etkiledi. Denge değerleri Langmuir modeline uydu ve isoterm sabitleri hesaplandı. Astrozon Red adsorpsiyonu çözeltilerin pH'larının artması ile arttı. Adsorpsiyon termodinamiği prosesin ekzotermik ve kendiliğinden olduğunu gösterdi.

  4. Geophysical constraints for terrane boundaries in southern Mongolia (United States)

    Guy, Alexandra; Schulmann, Karel; Munschy, Marc; Miehe, Jean-Marc; Edel, Jean-Bernard; Lexa, Ondrej; Fairhead, Derek


    The Central Asian Orogenic Belt (CAOB) is a typical accretionary orogen divided into numerous lithostratigraphic terranes corresponding to magmatic arcs, back arcs, continental basement blocks, accretionary wedges and metamorphic blocks. These terranes should be in theory characterized by contrasting magnetic and gravity signatures thanks to their different petrophysical properties. To test this hypothesis, the stratigraphically defined terranes in southern Mongolia were compared with potential field data to constrain their boundaries and extent. The existence of terranes in southern Mongolia cannot be attested by the uniform geophysical fabrics due to the lack of systematic correspondence between the high/low amplitude and high/low frequency geophysical domains and major terranes. Processed magnetic and gravity grids show that both gravity and magnetic lineaments are E-W trending in the west and correlate with direction of some geological units. In the east, both magnetic and gravity lineaments are disrupted by NE-SW trending heterogeneities resulting in complete blurring of the geophysical pattern. Correlation of magnetic signal with geological map shows that the magnetic highs coincide with late Carboniferous-early Permian volcanic and plutonic belts. The matched-filtering shows good continuity of signal to the depth located along the boundaries of these high magnetic anomalies which may imply presence of deeply rooted tectono-magmatic zones. The axes of high density bodies in the western and central part of the studied CAOB are characterized by periodic alternations of NW-SE trending high frequency and high amplitude gravity anomalies corresponding to late Permian to Triassic cleavage fronts up to 20 km wide. The matched-filtering analysis shows that the largest deformation zones are deeply rooted down to 20 km depth. Such a gravity signal is explained by the verticalization of high density mantle and lower crustal rocks due to localized vertical shearing

  5. The distribution and diversity of sea cucumbers in the coral reefs of the South China Sea, Sulu Sea and Sulawesi Sea (United States)

    Woo, Sau Pinn; Yasin, Zulfigar; Ismail, Siti Hasmah; Tan, Shau Hwai


    A study on the distribution and diversity of sea cucumbers in the coral reefs of the South China Sea, Sulu Sea and Sulawesi Sea was carried out in July 2009. The survey was done using wandering transect underwater with SCUBA. Twelve species of sea cucumber were found from four different families and nine genera. The most dominant family was Holothuriidae (five species), followed by Stichopodidae (three species), Synaptidae (three species) and Cucumariidae with only one species. The most dominant species found around the island was Pearsonothuria graffei, which can be found abundantly on substrate of dead corals in a wide range of depth (6-15 m). The Sulawesi Sea showed a higher diversity of sea cucumber with seven different species compared to the South China Sea with only six different species and Sulu Sea with only two species. Ordination by multidimensional scaling of Bray-Curtis similarities clustered the sampling locations to three main clusters with two outgroups. Previous studies done indicated a higher diversity of sea cucumber as compared to this study. This can be indication that the population and diversity of sea cucumbers in the reef is under threat.

  6. Fate of Subducting Organic Carbon: Evidence from HP/UHP Metasedimentary Suites (United States)

    Kraft, K.; Bebout, G. E.


    Community interest in deep-Earth C cycling has focused attention on extents of C release from subducting oceanic lithosphere and sediment and the fate of this released C. Many have suggested that, based on isotopic and other arguments, 20% of the C subducted into the deeper mantle is in reduced form (organic); however, individual margins show large variation in carbonate to organic C ratios. Despite the size of the potentially deeply subducted organic C reservoir, its fate in subducting sections remains largely unexplored, with most attention paid to release of carbonate C. To characterize the forearc behavior of organic C, metamorphosed to P-T as high as that beneath volcanic fronts, we evaluated records of reduced C (RC) contents and isotope compositions in HP/UHP metasediments: 1) Schistes Lustres/Cignana (SLC) suite (Alps; Cook-Kollars et al., 2014, Chem Geol) with abundant carbonate and resembling sediment entering the East Sunda trench; and (2) Franciscan Complex (FC), W. Baja Terrain (WBT), Catalina Schist (CS) metasediments (Sadofsky and Bebout, 2003, G3), largely sandstone-shale sequences containing very little carbonate. In general, more Al-rich samples (shaley) in the terrigenous metasedimentary suites have higher concentrations of RC, which in low-grade units preserves δ13C of its organic protoliths. Carbonate-poor rocks in the SLC suite, and at ODP Site 765, show correlated major element (Al, Mg, Mn, Ti, P) and RC contents (up to 1.2 wt.%) reflecting sandstone-shale mixture. In the FC, WBT, and CS, the more Al-rich samples contain up to 2 wt. % RC. In high-grade Catalina Schist, RC has elevated δ13C due to C loss in CH4 and high-grade Alps rocks show reduced RC wt. % normalized to Al content. We consider processes that could alter contents and isotopic compositions of RC in sediment, e.g., devolatilization, closed-system exchange with carbonate, redox reactions, isotopic exchange with C in externally-derived fluids. It appears that, on modern Earth

  7. Siberia, the wandering northern terrane, and its changing geography through the Palaeozoic (United States)

    Cocks, L. Robin M.; Torsvik, Trond H.


    The old terrane of Siberia occupied a very substantial area in the centre of today's political Siberia and also adjacent areas of Mongolia, eastern Kazakhstan, and northwestern China. Siberia's location within the Early Neoproterozoic Rodinia Superterrane is contentious (since few if any reliable palaeomagnetic data exist between about 1.0 Ga and 540 Ma), but Siberia probably became independent during the breakup of Rodinia soon after 800 Ma and continued to be so until very near the end of the Palaeozoic, when it became an integral part of the Pangea Supercontinent. The boundaries of the cratonic core of the Siberian Terrane (including the Patom area) are briefly described, together with summaries of some of the geologically complex surrounding areas, and it is concluded that all of the Palaeozoic underlying the West Siberian Basin (including the Ob-Saisan Surgut area), Tomsk Terrane, Altai-Sayan Terranes (including Salair, Kuznetsk Alatau, Batenov, Kobdin and West Sayan), Ertix Terrane, Barguzin Terrane, Tuva-Mongol Terrane, Central Mongolia Terrane Assemblage, Gobi Altai and Mandalovoo Terranes, Okhotsk Terrane and much of the Verkhoyansk-Kolyma region all formed parts of peri-Siberia, and thus rotated with the main Siberian Craton as those areas were progressively accreted to the main Siberian Terrane at various times during the latest Neoproterozoic and Palaeozoic. The Ertix Terrane is a new term combining what has been termed the "Altay Terrane" or "NE Xinjiang" area of China, and the Baytag, Baaran and Bidz terranes of Mongolia. The Silurian Tuvaella brachiopod fauna is restricted only to today's southern parts of peri-Siberia. Thus, allowing for subsequent rotation, the fauna occurs only in the N of the Siberian Terrane, and, as well as being a helpful indicator of what marginal terranes made up peri-Siberia, is distinctive as being the only Silurian fauna known from northern higher latitudes globally. In contrast, the other terranes adjacent to peri

  8. Minor elements, HREE and d18O distribution in UHP garnets from the Dora-Maira massif (western Alps) (United States)

    Brunet, F.; Chazot, G.; Vielzeuf, D.; Chopin, C.


    preferentially incorporated into garnet. Garnet growth leads to progressive depletion of these elements in the matrix. There is no significant influx of HREE during UHP garnet growth. The homogeneity of the δ18O ratio within garnet crystals is also an indication of UHP growth in a close metamorphic system. Jadeite-quartzite veins have geochemical characteristics close to that of the country-rock gneiss from which they could originate. They would then represent an evidence of Mg-quartzite and country gneiss interaction at UHP.

  9. Preferential rifting of continents - A source of displaced terranes (United States)

    Vink, G. E.; Morgan, W. J.; Zhao, W.-L.


    Lithospheric rifting, while prevalent in the continents, rarely occurs in oceanic regions. To explain this preferential rifting of continents, the total strength of different lithospheres is compared by integrating the limits of lithospheric stress with depth. Comparisons of total strength indicate that continental lithosphere is weaker than oceanic lithosphere by about a factor of three. Also, a thickened crust can halve the total strength of normal continental lithosphere. Because the weakest area acts as a stress guide, any rifting close to an ocean-continent boundary would prefer a continental pathway. This results in the formation of small continental fragments or microplates that, once accreted back to a continent during subduction, are seen as displaced terranes. In addition, the large crustal thicknesses associated with suture zones would make such areas likely locations for future rifting episodes. This results in the tendency of new oceans to open along the suture where a former ocean had closed.

  10. Elevated Expression of GlpT and UhpT via FNR Activation Contributes to Increased Fosfomycin Susceptibility in Escherichia coli under Anaerobic Conditions (United States)

    Kurabayashi, Kumiko; Tanimoto, Koichi; Fueki, Shinobu; Tomita, Haruyoshi


    Because a shortage of new antimicrobial agents is a critical issue at present, and with the spread of multidrug-resistant (MDR) pathogens, the use of fosfomycin to treat infections is being revisited as a “last-resort option.” This drug offers a particular benefit in that it is more effective against bacteria growing under oxygen-limited conditions, unlike other commonly used antimicrobials, such as fluoroquinolones and aminoglycosides. In this study, we showed that Escherichia coli strains, including enterohemorrhagic E. coli (EHEC), were more susceptible to fosfomycin when grown anaerobically than when grown aerobically, and we investigated how the activity of this drug was enhanced during anaerobic growth of E. coli. Our quantitative PCR analysis and a transport assay showed that E. coli cells grown under anaerobic conditions had higher levels of expression of glpT and uhpT, encoding proteins that transport fosfomycin into cells with their native substrates, i.e., glycerol-3-phosphate and glucose-6-phosphate, and led to increased intracellular accumulation of the drug. Elevation of expression of these genes during anaerobic growth requires FNR, a global transcriptional regulator that is activated under anaerobic conditions. Purified FNR bound to DNA fragments from regions upstream of glpT and uhpT, suggesting that it is an activator of expression of glpT and uhpT during anaerobic growth. We concluded that the increased antibacterial activity of fosfomycin toward E. coli under anaerobic conditions can be attributed to elevated expression of GlpT and UhpT following activation of FNR, leading to increased uptake of the drug. PMID:26248376

  11. Some contrasting biostratigraphic links between the Baker and Olds Ferry Terranes, eastern Oregon (United States)

    Nestell, Merlynd K.; Blome, Charles D.


    New stratigraphic and paleontologic data indicate that ophiolitic melange windows in the Olds Ferry terrane of eastern Oregon contain limestone blocks and chert that are somewhat different in age than those present in the adjacent Baker terrane melange. The melange windows in the Olds Ferry terrane occur as inliers in the flyschoid Early and Middle Jurassic age Weatherby Formation, which depositionally overlies the contact between the melange-rich Devonian to Upper Triassic rocks of the Baker terrane on the north, and Upper Triassic and Early Jurassic volcanic arc rocks of the Huntington Formation on the south. The Baker terrane and Huntington Formation represent fragments of a subduction complex and related volcanic island arc, whereas the Weatherby Formation consists of forearc basin sedimentary deposits. The tectonic blocks in the melange windows of the Weatherby Formation (in the Olds Ferry terrane) are dated by scarce biostratigraphic evidence as Upper Pennsylvanian to Lower Permian and Upper Triassic. In contrast, tectonic blocks of limestone in theBaker terrane yield mostly fusulinids and small foraminifers of Middle Pennsylvanian Moscovian age at one locality.Middle Permian (Guadalupian) Tethyan fusulinids and smaller foraminifers (neoschwagerinids and other Middle Permian genera) are present at a few other localities. Late Triassic conodonts and bryozoans are also present in a few of the Baker terrane tectonic blocks. These limestone blocks are generally embedded in Permian and Triassic radiolarian bearing chert or argillite. Based on conodont, radiolarian and fusulinid data, the age limits of the meange blocks in the Weatherby Formation range from Pennsylvanian to Late Triassic.

  12. Cenozoic extensional tectonics of the Western Anatolia Extended Terrane, Turkey

    International Nuclear Information System (INIS)

    Cemen, I; Catlos, E J; Gogus, O; Diniz, E; Hancer, M


    The Western Anatolia Extended Terrane in Turkey is located on the eastern side of the Aegean Extended Terrane and contains one of the largest metamorphic core complexes in the world, the Menderes massif. It has experienced a series of continental collisions from the Late Cretaceous to the Eocene during the formation of the Izmir-Ankara-Erzincan suture zone. Based our field work and monazite ages, we suggest that the north-directed postcollisional Cenozoic extension in the region is the product of three consecutive stages, triggered by three different mechanisms. The first stage was initiated about 30 Ma ago, in the Oligocene by the Orogenic Collapse the thermally weakened continental crust along the north-dipping Southwest Anatolian shear zone. The shear zone was formed as an extensional simple-shear zone with listric geometry at depth and exhibits predominantly normal-slip along its southwestern end. But, it becomes a high-angle oblique-slip shear zone along its northeastern termination. Evidence for the presence of the shear zone includes (1) the dominant top to the north-northeast shear sense indicators throughout the Menderes massif, such as stretching lineations trending N10E to N30E; and (2) a series of Oligocene extensional basins located adjacent to the shear zone that contain only carbonate and ophiolitic rock fragments, but no high grade metamorphic rock fragments. During this stage, erosion and extensional unroofing brought high-grade metamorphic rocks of the Central Menderes massif to the surface by the early Miocene. The second stage of the extension was triggered by subduction roll-back and associated back-arc extension in the early Miocene and produced the north-dipping Alasehir and the south-dipping Bueyuek Menderes detachments of the central Menderes massif and the north-dipping Simav detachment of the northern Menderes massif. The detachments control the Miocene sedimentation in the Alasehir, Bueyuek Menderes, and Simav grabens, containing high

  13. Far-travelled permian chert of the North Fork terrane, Klamath mountains, California (United States)

    Mankinen, E.A.; Irwin, W.P.; Blome, C.D.


    Permian chert in the North Fork terrane and correlative rocks of the Klamath Mountains province has a remanent magnetization that is prefolding and presumably primary. Paleomagnetic results indicate that the chert formed at a paleolatitude of 8.6?? ?? 2.5?? but in which hemisphere remains uncertain. This finding requires that these rocks have undergone at least 8.6?? ?? 4.4?? of northward transport relative to Permian North America since their deposition. Paleontological evidence suggests that the Permian limestone of the Eastern Klamath terrane originated thousands of kilometers distant from North America. The limestone of the North Fork terrane may have formed at a similar or even greater distance as suggested by its faunal affinity to the Eastern Klamath terrane and more westerly position. Available evidence indicates that convergence of the North Fork and composite Central Metamorphic-Eastern Klamath terranes occurred during Triassic or Early Jurassic time and that their joining together was a Middle Jurassic event. Primary and secondary magnetizations indicate that the new composite terrane containing these and other rocks of the Western Paleozoic and Triassic belt behaved as a single rigid block that has been latitudinally concordant with the North American craton since Middle Jurassic time.

  14. 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.


    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.

  15. Cebollati group, Nico Perez terrane: Definition and age

    International Nuclear Information System (INIS)

    Gaucher, C; Chemale, F.; Bossi, J.; Castiglioni, E.; Castiglioni, E.


    The Cebollati Group (Nico Perez Terrane) is formally erected in this work to include a meta sedimentary succession informally known as L as Teta s Complex . It is shown that the stratigraphy of the unit can be reconstructed at a number of sections between Minas and Zapicìn, using sedimentary structures and stromatolites as geo petal indicators. The basement of the group is represented by metamorphic rocks and granitoids of the La China Complex, for which a new U-Pb zircon age of 3.029 ± 54 Ma is presented. The Cebollatií Group comprises, from base to top, three formations: the Arroyo Ma lo Formation (sandstones and petites), Cerro de Valuable Formation (dolostones, partly stromatolitic, and p elites) and the Cerro del Diamant e Formation (p elites, BIF, quartz-pebble conglomerates and sandstones). The mean thickness of the Cebollatií Group is ca. 2 km, being greatest in the south and diminishing to the north. Available ages for the unit suggested a Neoarchean depositional age of 2.75 Ga. However, in this work 12 Nd model ages are presented for sedimentary rocks of the Cebollatí Group, which are mostly younger than 2.75 Ga, the youngest being 1.64 Ga. These ages call into question the Neoarchean age accepted for the unit, suggesting a Meso proterozoic depositional age. The evidence supporting both views is discussed in view of the new data. The minimum age of the Cebollatí Group is 1.3 Ga on the basis of carbon isotope ratios of dolostones and deformational ages consistently around 1.25 Ga

  16. Grenvillean sutures zones in the northern portion of the Cuyania terrane, Republica Argentina. geophysical evidence

    International Nuclear Information System (INIS)

    Chernicoff, C.; Vujovich, G.


    In the northern portion of the Cuyania terrane there is geophysical evidence for the ocurrence of two ancient WNW suture zones, corresponding to the Guandacol and Vinchina lineaments. The location of these sutures is consistent with analogous structures in Laurentia, in the Ouachita embayment region, where the Grenvillean orogen trends WNW. It is argued that the WNW transform faults pertaining to the Ouachita rift would have developed as a result of a reactivation of compressional structures of identical orientation associated to the accretion of Grenvillean terranes. The Guandacol and Vinchina lineaments would have been in physical continuity with analogous megastructures in the Ouachita embayment region, and they both would have originated as compressional structures, later reactivated as transcurrent fault zones during the late Proterozoic early Paleozoic. The interpretation of the Guandacol and Vinchina lineaments as Grenvillean suture zones would add more complexity to the Cuyania terrane, with respect to what has been described up to now; they could precede the amalgamation of the Pie de Palo and Precordillera terranes (constituents of the Cuyania composite terrane) [es

  17. The Khida terrane - Geology of Paleoproterozoic rocks in the Muhayil area, eastern Arabian Shield, Saudi Arabia (United States)

    Stoeser, D.B.; Whitehouse, M.J.; Stacey, J.S.


    The bulk of the Arabian Shield of Saudi Arabia is underlain by Neoproterozoic terranes of oceanic affinity that were accreted during Pan-African time (about 680- 640Ma). Geologicalmappingandisotopicinvestigations during the 1980’s,however, provided the first evidence for Paleoproterozoic continental crust within the east- central part of the shield in Saudi Arabia. These studies delineated an older basement domain, herein referred to as the Khida terrane (Fig. l), which is defined as that part of the southern Afif composite terrane underlain by Paleoproterozoicto Archean continental crust (Stoeser and Stacey, 1988). The isotopic and geochronologic work to support our current studies within the Khida terrane are discussed in a companion abstract (Whitehouse et al., this volume). The regional geology and geochronology of the region has been summarized in detail by Johnson (1996). The current study is based on the continued use of samples previously collected in the Khida area by the authors and others as well as new field work conducted by us in 1999. This work further defines the occurrence of late Paleoproterozoic rocks at Jabal Muhayil, which is located at the eastern margin of the exposed terrane (Fig. 1). Our isotopic work is at an early stage and this abstract partly relates geologic problems that remain to be resolved. 

  18. The Athabasca Granulite Terrane and Evidence for Dynamic Behavior of Lower Continental Crust (United States)

    Dumond, Gregory; Williams, Michael L.; Regan, Sean P.


    Deeply exhumed granulite terranes have long been considered nonrepresentative of lower continental crust largely because their bulk compositions do not match the lower crustal xenolith record. A paradigm shift in our understanding of deep crust has since occurred with new evidence for a more felsic and compositionally heterogeneous lower crust than previously recognized. The >20,000-km2 Athabasca granulite terrane locally provides a >700-Myr-old window into this type of lower crust, prior to being exhumed and uplifted to the surface between 1.9 and 1.7 Ga. We review over 20 years of research on this terrane with an emphasis on what these findings may tell us about the origin and behavior of lower continental crust, in general, in addition to placing constraints on the tectonic evolution of the western Canadian Shield between 2.6 and 1.7 Ga. The results reveal a dynamic lower continental crust that evolved compositionally and rheologically with time.

  19. Relationships between the Brook Street Terrane and Median Tectonic Zone (Median Batholith) : evidence from Jurassic conglomerates

    International Nuclear Information System (INIS)

    Tulloch, A.J.; Kimbrough, D.L.; Landis, C.A.; Mortimer, N.; Johnston, M.R.


    U-Pb zircon ages of 237-180 Ma and c. 280 Ma of seven granitoid clasts from the Rainy River Conglomerate which lies within the eastern Median Tectonic Zone (Median Batholith) in Nelson, and the Barretts Formation of the Brook Street Terrane in Southland, constrain the depositional ages of both units to be no older than c. 180-200 Ma (Early Jurassic). The minimum age of the Rainy River Conglomerate is constrained by the 147 +2 -1 Ma (Latest Jurassic) emplacement age of the One Mile Gabbronorite (new name: previously western Buller Diorite). The ages and chemistry of five of the granitoid clasts are broadly compatible with derivation from rocks that are now represented by Triassic plutons of the Median Tectonic Zone (Median Batholith), although ages as young as 180 Ma are slightly outside the range of the latter as currently exposed in New Zealand. The age (273-290 Ma, 237 +/- 3 Ma) and chemistry of the other two clasts (one each from Rainy River Conglomerate and Barretts Formation) suggest derivation from the Brook Street Terrane. Similarity in stratigraphic age, depositional characteristics, granitoid clast ages and composition between Rainy River Conglomerate and Barretts Formation suggests that they are broadly correlative and collectively overlapped a combined Brook Street Terrane - Median Batholith (MTZ) before the Late Jurassic (147 +2 -1 Ma). Sedimentary overlap may also have continued across to Middle Jurassic conglomeratic strata in the Murihiku Terrane to the east of the Brook Street Terrane. A U-Pb zircon age of 261 +/- 2 Ma is reported for Pourakino Trondhjemite of the Brook Street Terrane. (author). 56 refs., 10 figs., 4 tabs

  20. Chronologic constraints on the tectonic evolution of the Wilson Lake terrane of the Grenville Province, Canada

    DEFF Research Database (Denmark)

    Reno II, Barry Len; Korhonen, F.J.; Stout, J.H.

    the Grenville Orogen in North America. Many of these terranes record evidence of two orogenies: the Labradorian Orogeny at ca. 1710-1600 Ma, and the Grenville Orogeny at ca. 1080-980 Ma. The rocks in the Wilson Lake terrane are interpreted to have been subjected to peak pressures of ~0.95 GPa......) monazite exhibits distinct core and rim zoning in yttrium X-ray compositional maps, and occurs predominately in the melanosome of the rocks, and 2) a population of smaller (up to ~50 µm) unzoned monazite rarely occurs in quartz-rich layers of the rocks. In a majority of the melanosome-hosted monazite, (U...

  1. The Paleozoic-Mesozoic recycling of the Rakaia Terrane, South Island, New Zealand : sandstone clast and sandstone petrology, geochemistry, and geochronology

    International Nuclear Information System (INIS)

    Wandres, A.M.; Bradshaw, J.D.; Ireland, T.


    The Torlesse terranes - part of the New Zealand Eastern Province - are accretionary complexes that comprise an enormous volume of quartzofeldspathic sandstones and mudstones with subsidiary conglomerates plus minor oceanic assemblages. Two terranes are recognised in the South Island - the Permian to Late Triassic Rakaia Terrane and the Late Jurassic to Early Cretaceous Pahau Terrane. Sandstone clasts from two Rakaia Terrane and two Pahau Terrane conglomerates were collected. We present the first combined detailed information on petrography and geochemistry of Torlesse conglomerate sandstone clasts and use our own and published U-Pb SHRIMP detrital zircon age data to demonstrate the recycling of the Rakaia Terrane into Rakaia strata itself and into Pahau Terrane strata. Sandstone clast major and trace element chemical data largely support petrographic observations derived from thin-section analysis. The similarities of petrographic and geochemical data between sandstone clasts from the Rakaia Terrane and Rakaia sandstones suggest that clasts in the Permian Te Moana and Late Triassic Lake Hill Conglomerates were derived by autocannibalistic reworking of older, consolidated, Rakaia sediments. Data from sandstone clasts from the Pahau Terrane suggest that uplift of the Rakaia Terrane continued into the Cretaceous. These Pahau Terrane clasts indicate that at the time of the Pahau sedimentation Permian to early Late Triassic Rakaia rocks were exposed and recycled into the Pahau Basin. (author). 57 refs., 8 figs., 3 tables

  2. Metamorphic P-T-t-d evolution of (U)HP metabasites from the South Tianshan accretionary complex (NW China) - Implications for rock deformation during exhumation in a subduction channel

    Czech Academy of Sciences Publication Activity Database

    Soldner, J.; Oliot, E.; Schulmann, K.; Štípská, P.; Kusbach, Vladimír; Anczkiewicz, R.


    Roč. 47, July (2017), s. 161-187 ISSN 1342-937X Institutional support: RVO:67985530 Keywords : eclogite * Tianshan massif * (U)HP metamorphic belt Subject RIV: DB - Geology ; Mineralogy OBOR OECD: Geology Impact factor: 6.959, year: 2016

  3. A tectonic reconstruction of accreted terranes along the paleo-Pacific margin of Gondwana (United States)

    Bammel, Brandon

    The southern oceanic margin of Gondwana was nearly 40,000 km long or 24,854.8 miles. The southern margin was the result of the Terra Australis orogen. Spanning 18,000 km or 11,184.7 miles and is proposed as one of the largest and longest lived orogens in Earth history. The paleo-Pacific margin of Gondwana consisted of segments of the Australian-Antarctic craton, southern South America (modern Argentina and Chile), southern South Africa, Marie Byrdland, New Zealand and its adjacent continental shelf, the Ellsworth Mountains, and the Transantarctic Mountains. The process of terrane accretion has played a substantial part in the assembly of the continents as they look today. The paleo-Pacific margin of Gondwana was an active region of terrane accretion from the Neoproterozoic to the Late Mesozoic. This research study examines the accretion of terranes across the paleo-Pacific Gondwana margin to provide a comprehensive reconstruction. A paleogeographic basemap was created using PALEOMAP Project maps and the geology data was provided by the School of Geoscience from the University of Witwatersrand of South Africa. Location and data analyzed for terranes were collected building a PDF library of journal articles across numerous geological publications.

  4. Basic hypabissal, gondwanic magmatism: a new contribution for tecto no-stratigraphic terranes recognition in Uruguay

    International Nuclear Information System (INIS)

    Bossi, J.


    The possibility of having sufficient structural, geochronologic and geochemical data about the dykes and sills of Cuaro formation and the Corral de Piedra dyke swarm allowed to suggest the nature of the Mantle source and the injection process of each filonian set. Three units injected in the Gondwana continent were recognized: not outcropping Cuaro formation, at Piedra Alta Terrane; outcropping Cuaro Fm. in the Nico Perez Terrane, and the Corral de Piedra dyke swarm in the Cuchilla Dionisio terrane It was found different behavior in several important parameters in each one of them: mantelic source , melting percentage and crustal contamination. It may be concluded that Mantle nature and crust thickness and composition are different in each block, what supports. the idea that continental socle was constructed by amalgamation of different units of allocton provenence. When heat loss became difficult by the mega-continent consolidation, each fragment acted of different way. This represents a very strong argument favoring terrane Cuchilla Dionisio alloctony leaned to 525 Ma as regional geological mapping indicated

  5. Late Ordovician palaeogeography and the positions of the Kazakh terranes through analysis of their brachiopod faunas (United States)

    Popov, Leonid E.; Cocks, Robin M.


    Detailed biogeographical and biofacies analyses of the Late Ordovician brachiopod faunas with 160 genera, grouped into 94 faunas from individual lithotectonic units within the Kazakh Orogen strongly support an archipelago model for that time in that area. The Kazakh island arcs and microcontinents within several separate clusters were located in the tropics on both sides of the Equator. Key units, from which the Late Ordovician faunas are now well known, include the Boshchekul, Chingiz-Tarbagatai, and Chu-Ili terranes. The development of brachiopod biogeography within the nearly ten million year time span of the Late Ordovician from about 458 to 443 Ma (Sandbian, Katian, and Hirnantian), is supported by much new data, including our revised identifications from the Kazakh Orogen and elsewhere. The Kazakh archipelago was west of the Australasian segment of the Gondwana Supercontinent, and relatively near the Tarim, South China and North China continents, apart from the Atashu-Zhamshi Microcontinent, which probably occupied a relatively isolated position on the south-western margin of the archipelago. Distinct faunal signatures indicate that the Kazakh terranes were far away from Baltica and Siberia throughout the Ordovician. Although some earlier terranes had joined each other before the Middle Ordovician, the amalgamation of Kazakh terranes into the single continent of Kazakhstania by the end of the Ordovician is very unlikely. The Late Ordovician brachiopods from the other continents are also compared with the Kazakh faunas and global provincialisation statistically determined.

  6. The ophiolitic North Fork terrane in the Salmon River region, central Klamath Mountains, California (United States)

    Ando, C.J.; Irwin, W.P.; Jones, D.L.; Saleeby, J.B.


    The North Fork terrane is an assemblage of ophiolitic and other oceanic volcanic and sedimentary rocks that has been internally imbricated and folded. The ophiolitic rocks form a north-trending belt through the central part of the region and consist of a disrupted sequence of homogeneous gabbro, diabase, massive to pillowed basalt, and interleaved tectonitic harzburgite. U-Pb zircon age data on a plagiogranite pod from the gabbroic unit indicate that at least this part of the igneous sequence is late Paleozoic in age.The ophiolitic belt is flanked on either side by mafic volcanic and volcaniclastic rocks, limestone, bedded chert, and argillite. Most of the chert is Triassic, including much of Late Triassic age, but chert with uncertain stratigraphic relations at one locality is Permian. The strata flanking the east side of the ophiolitic belt face eastward, and depositional contacts between units are for the most part preserved. The strata on the west side of the ophiolitic belt are more highly disrupted than those on the east side, contain chert-argillite melange, and have unproven stratigraphic relation to either the ophiolitic rocks or the eastern strata.Rocks of the North Fork terrane do not show widespread evidence of penetrative deformation at elevated temperatures, except an early tectonitic fabric in the harzburgite. Slip-fiber foliation in serpentinite, phacoidal foliation in chert and mafic rocks, scaly foliation in argillite, and mesoscopic folds in bedded chert are consistent with an interpretation of large-scale anti-formal folding of the terrane about a north-south hinge found along the ophiolitic belt, but other structural interpretations are tenable. The age of folding of North Fork rocks is constrained by the involvement of Triassic and younger cherts and crosscutting Late Jurassic plutons. Deformation in the North Fork terrane must have spanned a short period of time because the terrane is bounded structurally above and below by Middle or Late

  7. Lithospheric electrical structure of the middle Lhasa terrane in the south Tibetan plateau (United States)

    Liang, Hongda; Jin, Sheng; Wei, Wenbo; Gao, Rui; Ye, Gaofeng; Zhang, Letian; Yin, Yaotian; Lu, Zhanwu


    The Lhasa terrane in southern Tibetan plateau is a huge tectono-magmatic belt and an important metallogenic belt. Its formation evolution process and mineralization are affected by the subduction of oceanic plate and subsequent continental collision. However, the evolution of Lhasa terrane has been a subject of much debate for a long time. The Lithospheric structure records the deep processes of the subduction of oceanic plate and continental collision. The magnetotelluric (MT) method can probe the sub-surface electrical conductivity, newly dense broadband and long period magnetotelluric data were collected along a south-north trending profile that across the Lhasa terrane at 88°-89°E. Dimensionality analyses demonstrated that the MT data can be interpreted using two-dimensional approaches, and the regional strike direction was determined as N110°E.Based on data analysis results, a two-dimensional (2-D) resistivity model of crust and upper mantle was derived from inversion of the transverse electric mode, transverse magnetic mode and vertical magnetic field data. Inversion model shows a large north-dipping resistor that extended from the upper crust to upper mantle beneath the Himalaya and the south of Lhasa Terrane, which may represent the subducting Indian continental lithosphere. The 31°N may be an important boundary in the Lhasa Terrane, the south performs a prominent high-conductivity anomaly from the lower crust to upper mantle which indicates the existence of asthenosphere upwelling, while the north performs a higher resistivity and may have a reworking ancient basement. The formation of the ore deposits in the study area may be related to the upwelling of the mantle material triggered by slab tearing and/or breaking off of the Indian lithosphere, and the mantle material input also contributed the total thickness of the present-day Tibetan crust. The results provide helpful constrains to understand the mechanism of the continent-continent collision and

  8. Origin and tectonic evolution of early Paleozoic arc terranes abutting the northern margin of North China Craton (United States)

    Zhou, Hao; Pei, Fu-Ping; Zhang, Ying; Zhou, Zhong-Biao; Xu, Wen-Liang; Wang, Zhi-Wei; Cao, Hua-Hua; Yang, Chuan


    The origin and tectonic evolution of the early Paleozoic arc terranes abutting the northern margin of the North China Craton (NCC) are widely debated. This paper presents detrital zircon U-Pb and Hf isotopic data of early Paleozoic strata in the Zhangjiatun arc terrane of central Jilin Province, northeast (NE) China, and compares them with the Bainaimiao and Jiangyu arc terranes abutting the northern margin of the NCC. Detrital zircons from early Paleozoic strata in three arc terranes exhibit comparable age groupings of 539-430, 1250-577, and 2800-1600 Ma. The Paleoproterozoic to Neoarchean ages and Hf isotopic composition of the detrital zircons imply the existence of the Precambrian fragments beneath the arc terranes. Given the evidences from geology, igneous rocks, and detrital zircons, we proposed that the early Paleozoic arc terranes abutting the northern margin of the NCC are a united arc terrane including the exotic Precambrian fragments, and these fragments shared a common evolutionary history from Neoproterozoic to early-middle Paleozoic.

  9. Crustal structure of norther Oaxaca terrane; The Oaxaca and caltepec faults, and the Tehuacan Valley. A gravity study. (United States)

    Campos-Enriquez, J. O.; Alatorre-Zamora, M. A.; Ramón, V. M.; Belmonte, S.


    Northern Oaxaca terrane, southern Mexico, is bound by the Caltepec and Oaxaca faults to the west and east, respectively. These faults juxtapose the Oaxaca terrane against the Mixteca and Juarez terranes, respectively. The Oaxaca Fault also forms the eastern boundary of the Cenozoic Tehuacan depression. Several gravity profiles across these faults and the Oaxaca terrane (including the Tehuacan Valley) enables us to establish the upper crustal structure of this region. Accordingly, the Oaxaca terrane is downward displaced to the east in two steps. First the Santa Lucia Fault puts into contact the granulitic basamental rocks with Phanerozoic volcanic and sedimentary rocks. Finally, the Gavilan Fault puts into contact the Oaxaca terrane basement (Oaxaca Complex) into contact with the volcano-sedimentary infill of the valley. This gravity study reveals that the Oaxaca Fault system gives rise to a series of east tilted basamental blocks (Oaxaca Complex?). A structural high at the western Tehuacan depression accomadates the east dipping faults (Santa Lucia and Gavilan faults) and the west dipping faults of the Oaxaca Fault System. To the west of this high structural we have the depper depocenters. The Oaxaca Complex, the Caltepec and Santa Lucia faults continue northwestwards beneath Phanerozoic rocks. The faults are regional tectonic structures. They seem to continue northwards below the Trans-Mexican Volcanic Belt. A major E-W to NE-SW discontinuity on the Oaxaca terrane is inferred to exist between profiles 1 and 2. The Tehuacan Valley posses a large groundwater potential.

  10. Unusual central Nevada geologic terranes produced by Late Devonian Antler orogeny and Alamo impact (United States)

    Poole, Forrest G.; Sandberg, Charles


    This Special Paper is the product of nearly 25 years of geologic investigations. It is an exposition of two small areas, both less than 25 km east of the Mississippian Roberts Mountains allochthon, but each displaying a different, unique geologic terrane, previously undocumented in Nevada and perhaps in North America. One area, the Bisoni-McKay, at the south end of the Fish Creek Range, displays an olistostrome, shed eastward during the late Late Devonian (early Famennian) from a migrating Antler orogenic forebulge. The other, the Warm Springs–Milk Spring, at the south end of the Hot Creek Range, displays a deeper marine terrane affected by the early Late Devonian (middle Frasnian) Alamo impact.

  11. Zircon U-Pb ages of Guyana greenstone-gneiss terrane

    Energy Technology Data Exchange (ETDEWEB)

    Gibbs, A.K. (Cornell Univ., Ithaca, NY (USA)); Olszewski, W.J. Jr. (New Hampshire Univ., Durham (USA))


    Isotopic U-Pb studies of zircons collected from weathered metagreywackes of the Barama-Mazaruni Supergroup of northern Guyana, South America, demonstrate an age of origin of ca. 2250 Ma. This is the best estimate for the age of the associated metavolcanic rocks. Zircons from weathered gneiss of the Bartica complex, adjacent to the volcanic-sedimentary belts, yield a similar age. The contiguous greenstone-gneiss terrane of eastern Venezuela is also of similar age and comparable greenstone-gneiss terranes of eastern Suriname and French Guiana are probably also of this age. Continental crust formation of a style closely comparable to that of the Canadian Archean occurred on a very widespread scale in the Lower Proterozoic of the Guiana shield. The lead losses from the weathered zircons are comparable to those from zircons from fresh rock from the adjacent terrane of Venezuela, and the advantages of field concentration from numerous saprolite exposures warrant use of such material in future geochronological studies of the region.

  12. Detrital zircon ages in Buller and Takaka terranes, New Zealand : constraints on early Zealandia history

    International Nuclear Information System (INIS)

    Adams, C.J.; Mortimer, N.; Campbell, H.J.; Griffin, W.L.


    Detrital zircon ages are presented for 34 early Palaeozoic sandstones from Buller and Takaka terranes, New Zealand, and formerly adjacent parts of Australia-Antarctica. The Buller-Takaka datasets always have two major groups: Ordovician-late Neoproterozoic, 444-700 Ma (but mainly 540-700 Ma), termed 'Gondwana Assembly' (GA), and early Neoproterozoic-Mesoproterozoic, 700-1600 Ma (but mainly 900-1200 Ma), termed 'Rodinia Assembly' (RA). In both terranes, significant age components within these groups are strikingly similar and also have RA/GA ratios, 0.6-1.8. The Cambrian volcanic arc of the Takaka Terrane has contributed little to the zircon patterns. Proportions of Late Cambrian-Early Ordovician zircons, characteristic of granitoid sources in the Ross-Delamerian Orogen are low. The zircons are predominantly reworked with contemporary zircons only evident in a few Buller datasets. The zircon patterns suggest that two major sources (late Mesoproterozoic and late Neoproterozoic), enduring over 120 Ma, were widely distributed and it is postulated they form Precambrian basement beneath southern Zealandia. (author).

  13. Precambrian terranes of African affinities in the southeastern part of Brazil and Uruguay

    International Nuclear Information System (INIS)

    Basei, M.A.S; Junior, Siga; Harara, O.M; Preciozzi, F; Sato, K; Kaufuss, G


    The interest in correlating terranes at opposite margins of the South Atlantic Ocean reflects a natural curiosity of both researchers who work in the eastern South-America and who study southwestern Africa. On a large scale scenario the geology of this region is characterized by a central portion composed of Neo proterozoic-Cambrian belts (Dom Feliciano, Kaoko, Damara, Gariep, Saldania) having on each side old gneissic-migmatitic terrains on both continents (Luis Alves, Rio de La Plata, Kalahari and Congo). In South America the Neoproterozoic Dom Feliciano Belt (DFB) predominates in the eastern part of the region and is internally organized according to three different crustal segments characterized, from southeast to northwest, by a Granite belt (deformed I-type medium to high calc-alkaline granites and alkaline granitoid rocks; a Schist belt (volcano-sedimentary rocks metamorphosed from greenschist to amphibolite facies and intrusive granitoids), and a Foreland basin (anchimetamorphic sedimentary and volcanic rocks), the latter situated between the Schist belt and the Archean-Paleoproterozoic foreland. Despite discontinuously covered by younger sediments, the NS continuity of these three crustal segments is suggested by similar lithotypes, structural characteristics, ages and isotopic signature, as well as by the gravimetric data. The Major Gercino, Cordilheira, and Sierra Ballena shear zones are part of the major NE-SW lineaments that affect all southern Brazilian and Uruguayan Precambrian terrains. They separate the Dom Feliciano Schist Belt (supracrustal rocks of the Brusque-Porongos and Lavalleja groups), to the West, from the granitoids of the Granite belt, to the East. The shear zones are characterized by a regional NE trend and a resultant oblique direction of movement where ductile-brittle structures predominate. It is here postulated, as discussed later on, that this lineament separates terranes that are geologically, geo chronologically and isotopically

  14. Isotopic provenance analysis and terrane tectonics: a warning about sediment transport distances

    International Nuclear Information System (INIS)

    Bassett, K.N.


    Full text: In the last 10 years the field of provenance analysis has undergone a revolution with the development of single-crystal isotopic dating techniques, the most common being U/Pb zircon and 40Ar/39Ar techniques. These have allowed age determination of single crystals thus providing more detail about probable provenance of each individual grain rather than an averaged population of grains. The usefulness for resolving complex terrane accretion and translation histories was immediately obvious and there have been many studies in many different regions aimed at tracking terrane motions by provenance of individual grains upward through the stratigraphy of a basin. Recent research in the North American Cordilleran terranes and in the New Zealand Torlesse Superterrane show how widely used and powerful these provenance analysis techniques are. However, isotopic provenance analysis has often been presented as key information to resolve controversies around terrane translation histories with very little discussion of the context of sedimentary facies and sediment transport mechanisms. An example is the recent use of U/Pb detrital zircon ages as the supposedly controversy-ending evidence for the amount of lateral translation of the Insular Superterrane in British Columbia (Baja BC) (Mahoney et al., 1999). The zircon grains were separated from fine-grained turbidite deposits and could easily have been transported over very large distances by a variety of mechanisms; yet they were presented as definitively resolving the Baja BC controversy. Modern examples illustrate the problem of using the provenance of fine grained sediment to constrain terrane tectonics. Sediment in the tip of the Bengal submarine fan was transported ∼3000 km from source, first by fluvial processes then by sediment gravity flow in the submarine fan. The detrital isotopic ages of single grains are the same as the depositional ages indicating a very rapid unroofing and transport rate with minimal



    KILIÇ, Murat; ÇEPELİOĞULLAR, Özge; ÖZSİN, Gamzenur; UZUN, Başak Burcu; E. PÜTÜN, Ayşe


    Yapılan bu çalışmada tarımsal bir atık olan nohut samanı, sulu çözeltilerden boyar madde gideriminde biyosorbent olarak değerlendirilmiştir. Çözelti pH’ı, biyosorbent miktarı, başlangıç boyar madde derişimi, temas süresi ve çözelti sıcaklığının biyosorpsiyon işlemine olan etkileri incelenmiştir. Ayrıca, metilen mavisi biyosorpsiyonuna ait denge izoterm, termodinamik ve kinetik çalışmalar gerçekleştirilmiştir. Biyosorpsiyon denge verilerinin Freundlich izotermi ile uyumlu olduğu belirlenmiş, b...

  16. The Svalbard Caledonides - a collage of Laurentian, Timanian and exotic terranes assembled by Silurian - Late (?) Devonian transcurrent faulting. (United States)

    Andresen, Arild; Gasser, Deta


    New field and geochronological data from NE Greenland and Svalbard indicate that most of the sub-terranes making up the Svalbard Caledonides (Eastern, Northwestern and Southwestern Terranes) are derived from Laurentias eastern margin. The Neoproterozoic deposits of the Eastern Terrane (Nordaustlandet) show an almost one to one correlation with the Late Neoproterozoic Eleonore Bay Supergroup in NE Greenland. Great similarities also exist between the substratum to the Neoproterozoic deposits in the two areas. The "Barentsian plate/continent" is interpreted to be derived from Laurentias eastern margin Lithologic similarities also exist between parts of the Northwestern Terrane and NE Greenland. The geologic evolution of Svalbard`s Southwestern Terrane, with subduction complexes and Late Neoproterozoic intrusives (Timanian ?) is poorly understood. It will, however, be argued that there is no need to invoke considerable right lateral strike-slip movement of the Motalefjellet subduction complex and related rocks from a position in Arctic Canada to their present position within the Southwestern Terrane, as proposed by some authors. The structural grain of the Svalbard Caledonides, oblique to East Greenland and Scandinavian Caledonides, as well as the Ellesmerian Orogen, is interpreted to be due to counter-clockwise rotation (c. 45o) of the Caledonian trend. A counter-clockwise rotation is to be expected when the northward moving terranes reached the E-W trending Franklinian Basin north of Greenland/Laurentia, which in Early Devonian time had not yet started to close. The model predicts that there should be a dramatic change in the Caledonian structural grain somewhere south of Bjørnøya. It is furthermore speculated that the fan-shaped orientation of Late Paleozoic rift basins in the Western Barents Sea is controlled by reactivation of the rotated structural trend (e.g. Billefjorden Fault Zone and Billefjorden Trough).

  17. Distribution and Diversity of Carboniferous and Permian Colonial Rugose Coral Faunas in Western North America: Clues for Placement of Allochthonous Terranes

    Directory of Open Access Journals (Sweden)

    Calvin H. Stevens


    Full Text Available Colonial rugose corals are common in western cratonal North America and in some of the allochthonous terranes, now amalgamated against its western margin. Throughout the Late Paleozoic, the coral faunas in these two different settings were significantly different. Comparisons of these faunas suggest that during the Mississippian the Alexander terrane probably was southwest of Arctic Alaska and the Stikine terrane probably lay west of the southern part of the North American craton. The Cache Creek terrane lay far out in the Paleopacific Ocean. The Pennsylvanian faunas suggest that the Quesnellia and Eastern Klamath terranes were situated southwest of Arctic Alaska and the Alexander terrane was somewhat farther southwest and farther from cratonal North America. The Stikine terrane continued to be positioned west of the southern part of the North American craton. During the Early Permian, terranes with a cratonal faunal aspect may have lain 2000–3000 km west of cratonal North America and latitudinally generally southwest of their present positions. In the Middle Permian these terranes were carried southward relative to the North American craton. Simultaneously the Tethyan Realm expanded eastward.

  18. Lower precambrian of the Keivy Terrane, Northeastern Baltic Shield: A stratigraphic succession or a collage of tectonic sheets? (United States)

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


    The Keivy Terrane in the northeastern Baltic Shield appreciably differs from the adjacent tectonic blocks. In the northwestern part of this terrane (the Serpovidny Range), an outlier of Paleoproterozoic supracrustal rocks called the Serpovidny structure is surrounded by Archean (?) Keivy high-alumina paraschists. As follows from structural and magnetic data, the Paleoproterozoic rocks are deformed into a tight sheath fold 8 × 2 km in size at the surface and 5 km in length along the sheath axis. Faults parallel to the boundaries of the layers and locally cutting them off at an acute angle are involved in folding as well. The outer boundaries of the Serpovidny structure are tectonic. This structure is complementary to a larger tectonic lens composed of the Keivy mica schists. It is concluded that all of the supracrustal rocks of the Serpovidny Range are in fact tectonic sheets and lenses deformed into sheath folds. The literature data show that kilometer-scale sheath folds occur throughout the Keivy paraschist belt and most likely were formed owing to thrusting of the Murmansk Craton onto the Keivy Terrane in the south-southwestern direction. Foliation and lineation related to thrusting have been established in the Archean silicic metavolcanics and peralkaline granites occupying the most part of the terrane. In contrast, the granitoids and gabbroanorthosites of the Archean basement, which form a block 90 × 20 km in the southwestern Keivy Terrane, were not affected by Paleoproterozoic deformation. In other words, a detached assembly of tectonic sheets composed of the upper and middle crustal rocks that underwent deformation at the initial stage of the Paleoproterozoic Lapland-Kola Orogeny and the Archean basement, which is free of this deformation, are distinguished. The depth of detachment is estimated at 20-25 km. The detachment of the upper and middle crust in the Keivy Terrane and its position in the structure of the Baltic Shield are consistent with a

  19. Two possibilities for New Siberian Islands terrane tectonic history during the Early Paleozoic based on paleomagnetic data (United States)

    Metelkin, Dmitry V.; Chernova, Anna I.; Vernikovsky, Valery A.; Matushkin, Nikolay Yu.


    The New Siberian Islands (NSI), located in the East Siberian Sea in the junction region of various structural elements, are a key target for deciphering the tectonic evolution of the Eastern Arctic. In recent years, we went on several expeditions and gathered an extensive geological material for this territory. Among other things, we could prove that the basement of the De Long and Anjou archipelagos structures is Precambrian and the overlying Paleozoic sections formed within the same terrane. The form of the boundaries of the NSI terrane are actively debated and are probably continued from the Lyakhovsky islands in the south-west to the southern parts of the submerged Mendeleev Ridge, for which there is increasing evidence of continental crust. Today there are several models that interpret the Paleozoic-Mesozoic tectonic history and structural affiliation of the NSI terrane. Some propose that the Paleozoic sedimentary section formed in a passive margin setting of the Siberian paleocontinent. Others compare its history with marginal basins of the Baltica and Laurentia continents or consider the NSI terrane as an element of the Chukotka-Alaska microplate. These models are mainly based on results of paleobiogeographical and lithological-facies analyses, including explanations of probable sources for detrital zircons. Our paleomagnetic research on sedimentary, volcanogenic-sedimentary and igneous rocks of the Anjou (Kotelny and Bel'kovsky islands) and De Long (Bennett, Jeannette and Henrietta islands) archipelagos let us calculate an apparent polar wander path for the early Paleozoic interval of geological history, which allows us to conclude that the NSI terrane could not have been a part of the continental plates listed above, but rather had active tectonic boundaries with them. Our paleomagnetic data indicate that the NSI terrane drifted slowly and steadily in the tropical and subtropical regions no higher than 40 degrees. However, the main uncertainty for the

  20. Modification of an ancient subcontinental lithospheric mantle by continental subduction: Insight from the Maowu garnet peridotites in the Dabie UHP belt, eastern China (United States)

    Chen, Yi; Su, Bin; Chu, Zhuyin


    Orogenic mantle-derived peridotites commonly originate from the subcontinental lithospheric mantle (SCLM) and thus provide a key target to investigate the modification of the SCLM by a subducting slab. The Maowu ultramafic rocks from the Dabie ultrahigh-pressure (UHP) metamorphic belt have formerly been debated as representing cumulates or mantle-derived peridotites. Detailed petrological and geochemical data presented in this study provide new constraints on the origin and formation of the peridotites involving melt depletion in the ancient SCLM and deep crustal metasomatism. The Maowu garnet dunites have refractory bulk compositions characterized by high Mg# (91.9-92.0) and Ni (2537-2892 ppm) values and low Al2O3 (0.26-0.76 wt.%), CaO (0.05-0.32 wt.%), TiO2 (China craton. Many garnet orthopyroxenite veins crosscutting the Maowu dunites preserve abundant metasomatic textures and show variable enrichment in incompatible elements. Mineral and whole-rock chemistry indicate that these veins represent metasomatic products between the wall dunites and silica-rich hydrous melts under UHP conditions. The veins show large variations in platinum-group element (PGE) signatures and Re-Os isotopes. The garnet-poor orthopyroxenite veins are characterized by low Al2O3 ( 6 wt.%) and S (99-306 ppm) contents and show melt-like PGE patterns and high 187Os/188Os ratios (up to 0.36910). These features, combined with the occurrence of interstitial sulfides in the garnet-rich orthopyroxenite veins, suggest that crust-derived sulfur-saturated silicate melts may have significantly modified the PGE signature and destroyed the Re-Os systematics of the SCLM. However, when the crust-derived silicate melts became sulfur-depleted, such melts would not significantly modify the PGE patterns, radiogenic Os-isotope compositions or the Re-depletion model ages of the SCLM. Consequently, deep crust-mantle interactions in continental subduction zones could induce high degrees of Os isotopic

  1. Low palaeoelevation of the northern Lhasa terrane during late Eocene: Fossil foraminifera and stable isotope evidence from the Gerze Basin. (United States)

    Wei, Yi; Zhang, Kexin; Garzione, Carmala N; Xu, Yadong; Song, Bowen; Ji, Junliang


    The Lhasa terrane is a key region for understanding the paleoelevation of the southern Tibetan Plateau after India-Asia collision. The Gerze Basin, located in the northern part of the Lhasa terrane, is a shortening-related basin. We discovered Lagena laevis (Bandy) fossils in upper Eocene strata of the Gerze Basin. This type of foraminifera is associated with lagoon and estuarine environments, indicating that the northern part of the Lhasa terrane was near sea level during the late Eocene. We speculate that these foraminifera were transported inland by storm surges to low elevation freshwater lakes during times of marine transgressions. This inference is consistent with the relatively positive δ(18)O values in carbonate from the same deposits that indicate low palaeoelevations close to sea level. Considering the palaeoelevation results from the nearby Oligocene basins at a similar latitude and the volcanic history of the Lhasa terrane, we infer that large-magnitude surface uplift of the northern Lhasa terrane occurred between late Eocene and late Oligocene time.

  2. The Apuseni Mountains, Romania, a Variscan Collage of Ordovician Gondwanan Terranes (United States)

    Balintoni, I. C.; Balica, C.; Zaharia, L.; Chen, F.; Cliveti, M.; Hann, H. P.; Ghergari, L.


    The basement of the Apuseni Mountains, Romania, consists of three pre-Variscan terranes, sutured during an Early Variscan amalgamation around 351 Ma (Balintoni et al., this volume). The northern Someş Terrane (ST) is predominantly gneissic, while the southern Baia de Arieş Terrane (BAT) is dominated by the presence of large carbonate lenses, although metagranites and other types of orthogneisses can be found. These two terranes are sutured through the Biharia terrane, probably an accreted island arc. LA-ICP-MS datings on zircons extracted from orthogneisses and metagranites were performed in order to constrain the age of ST and BAT. A number of previously CL-imaged crystals were ablated at the China's University of Geosciences, Wuhan. From ST we dated an orthogneiss occurring in structurally lowermost position, a metatuff situated in the upper strongly retrogressed part and a twenty detrital crystal population sampled from a metasandstone. The 206Pb/238U apparent ages were projected using the weighted average plots.A magmatic crystallization age of 472.8±5.0 Ma (Upper Early Ordovician) resulted for one of the orthogneiss samples, besides several older ages at 505.7, 566.3 and 708.2 Ma corresponding to inherited cores. Another sample from the same rock appeared strongly affected by lead loss during a later thermotectonic event, most of the apparent ages grouping around 352±14 Ma. This age is similar with the age of the suture between ST and BT (Balintoni et al., this volume). The main zircon population of one metatuff sample furnished an averaged age of 423±7.2 Ma, also found in two additional samples, but their significance is obscure for the moment. Two primary magmatic ages arise at 464.2 and 473.8 Ma, an older value of 758.7 Ma corresponding to an inherited core. Detrital zircon ages range between 534.8 and 2596.8 Ma. The younger value represents an upper age constraint for the protolith age of ST-rocks. From BAT we dated the Lupşa metaporphyroid and the

  3. Seismic signatures of the Pan-African orogeny: implications for southern Indian high-grade terranes (United States)

    Rai, Abhishek; Gaur, V. K.; Rai, S. S.; Priestley, K.


    We present the results of a study designed to investigate and compare the seismic characteristics of the once contiguous terranes of eastern Gondwanaland, now incorporated in five separated continental masses, which, during the Neoproterozoic (~600Ma) Pan-African orogeny, suffered a high degree of thermal stress and deformation. Receiver functions and surface wave data from stations located in East Antarctica, Sri Lanka, the southern-Indian high-grade terranes, Madagascar and the Tanzania-Mozambique belt, were used to determine the shear-wave velocity structure, Moho depth and VP/VS values of the respective crustal segments. This study provides an additional dimension to the otherwise well-documented characteristic petrology of their surface exposures and other geological signatures such as their extensive granulitization and gem formation during the Pan-African event. Analysis of the receiver functions and surface wave data for these seismic stations located on their present day widely distributed continental fragments have been made. It is observed that with the exception of KOD (at Kodaikanal hill), situated on the southern Indian granulites having the thickest crust (~43.5 km), most of the Pan-African granulitic terranes have a crustal thicknesses of ~37 +/- 0.8km, with a transition to higher velocity at mid-crustal depths, and that their bulk composition is felsic. Average crustal VP/VS values (1.704 +/- 0.03) and thicknesses (37.8 +/- 0.8km), for four stations (SYO, PALK, TRV and ABPO), now located in East Antarctica, Sri Lanka, India and Madagascar, respectively, show remarkable similarity, indicating that the Pan-African orogeny was extensive enough to reorder the crustal structure of a wide region with a broadly similar stamp.

  4. Paleomagnetic Constraints on the Tectonic History of the Mesozoic Ophiolite and Arc Terranes of Western Mexico (United States)

    Boschman, L.; Van Hinsbergen, D. J. J.; Langereis, C. G.; Molina-Garza, R. S.; Kimbrough, D. L.


    The North American Cordillera has been shaped by a long history of accretion of arcs and other buoyant crustal fragments to the western margin of the North American Plate since the Early Mesozoic. Accretion of these terranes resulted from a complex tectonic history interpreted to include episodes of both intra-oceanic subduction within the Panthalassa/Pacific Ocean, as well as continental margin subduction along the western margin of North America. Western Mexico, at the southern end of the Cordillera, contains a Late Cretaceous-present day long-lived continental margin arc, as well as Mesozoic arc and SSZ ophiolite assemblages of which the origin is under debate. Interpretations of the origin of these subduction-related rock assemblages vary from far-travelled exotic intra-oceanic island arc character to autochthonous or parautochthonous extended continental margin origin. We present new paleomagnetic data from four localities: (1) the Norian SSZ Vizcaíno peninsula Ophiolite; (2) its Lower Jurassic sedimentary cover; and (3) Barremian and (4) Aptian sediments derived from the Guerrero arc. The data show that the Mexican ophiolite and arc terranes have a paleolatitudinal plate motion history that is equal to that of the North American continent. This suggests that these rock assemblages were part of the overriding plate and were perhaps only separated from the North American continent by temporal fore- or back-arc spreading. These spreading phases resulted in the temporal existence of tectonic plates between the North American and Farallon Plates, and upon closure of the basins, in the growth of the North American continent without addition of any far-travelled exotic terranes.

  5. Piedra lata terrane of Uruguay: Rb-Sr geochronological data of two new paleoproterozoic (transamazonian) granitoids

    International Nuclear Information System (INIS)

    Cingolani, C; Bossi, J; Varela, R; Maldonado, S.; Pineyro, D.; Schipilov, A


    The Precambrian basement of Uruguay consists of three major terranes separated and crosscut by wide NE-striking subvertical transcurrent shear zones. The western terrane as a part of the Rio de la Plata Craton is known as the Piedra Alta Terrane (PAT). This is separated from the Nico Perez Terrane by the Sarandi del Yi-Piri olis subvertical shear zone (Bossi et al., 1993). A mafic dykes complex intruded the PAT at 1.8 Ga and was not later deformed. The PAT has equivalent rocks in the igneous-metamorphic basement of Tandilia region and the Martin Garcia Island, Buenos Aires Province, Argentina (Dalla Salda et al., 1988; Cingolani and Dalla Salda, 2000). The PAT shows no evidence of the Neoproterozoic orogenies and is considered a best preserved Paleoproterozoic block (Transamazonian Cycle). It contains three E-W trending belts of volcano-sedimentary rocks with low grade metamorphism. These are from south to north: Pando, San Jose and Andresito belts (Bossi et al., 1996). Associated with them, three granitic-gneissic zones he Ecilda Paullier, Florida and Feliciano- were recognized with magmatic intrusives emplaced at different crustal levels. The San Jose belt is the largest supracrustal unit and contains abundant volcanic and volcaniclastic rocks of low grade metamorphic (Paso Severino Fm.) with sheets of granitic rocks intercalated (Mutti et al., 1996; Bossi et al., 1996). The associated granitic rocks are of large areal extension, mostly granodiorites and tonalites, and minor monzogranite and gabbro (e.g. Cerro Rospide region), including xenoliths from Paso Severino Fm. Towards the north of the San Jose belt an important Florida granitized zone is developed in the central part of the PAT, where the Pintos massif was recognized. The main purpose of this contribution is to offer new Rb-Sr geochronological data from two granitoid units, The Cerro Rospide intrusive in Paso Severino Fm. and Pintos massif included in medium grade migmatic-metamorphic complex and its

  6. Interpretation of gravity profiles across the northern Oaxaca terrane, its boundaries and the Tehuacán Valley, southern Mexico (United States)

    Campos-Enríquez, J. O.; Alatorre-Zamora, M. A.; Keppie, J. D.; Belmonte-Jiménez, S. I.; Ramón-Márquez, V. M.


    A gravity study was conducted across the northern Oaxaca terrane and its bounding faults: the Caltepec and Oaxaca Faults to the west and east, respectively. These faults juxtapose the Oaxaca terrane against the Mixteca and Juarez terranes, respectively. The Oaxaca Fault also forms the eastern boundary of the Cenozoic Tehuacán depression. On the west, at depth, the Tehuacán valley is limited by the normal buried Tehuacán Fault. This gravity study reveals that the Oaxaca Fault system gives rise to a series of east tilted basamental blocks (Oaxaca Complex). The tectonic depression is filled with Phanerozoic rocks and has a deeper depocenter to the west. The gravity data also indicate that on the west, the Oaxaca Complex, the Caltepec and Santa Lucia faults continue northwestwards beneath Phanerozoic rocks. A major E-W to NE-SW discontinuity is inferred to exist between profiles 1 and 2.

  7. Development of Ultra-high Purity (UHP) Fe-Based Alloys with High Creep and Oxidation Resistance for A-USC Technology (United States)

    Hamdani, Fethi; Das, Nishith K.; Shoji, Tetsuo


    The design of ultra-high purity (UHP) Fe-based model alloys for advanced ultra-supercritical (A-USC) technology is attempted in this work. Creep testing has been performed in air at 700 °C and a stress level of 150 MPa. Analysis of the fracture surface and cross section of the crept specimen was performed. To evaluate the oxidation resistance in A-USC conditions, oxidation testing was performed in supercritical water (SCW) at 700 °C and 25 MPa. Weight gain (WG) measurements and meticulous characterization of the oxide scale were carried out. Based on thermodynamics and density functional theory calculations, some reactive elements in the Fe-Cr-Ni system were designated to promote precipitation strengthening and to improve the hydrogen-accelerated oxidation resistance. The addition of a 2 wt pct Mo into Fe-22Cr-22Ni-0.6Nb wt pct-based matrix did not significantly improve the creep resistance. The addition of 0.26 wt pct Zr coupled with cold working was effective for improving creep properties. The Mo-modified model alloy showed almost the same WG value as SUS310, while the Zr-modified alloy showed a higher WG value. Meanwhile, a Cr-enriched continuous oxide layer was formed at the oxidation front of the Zr-modified alloy and SUS310S after exposure to SCW conditions.

  8. Development of Ultra-high Purity (UHP) Fe-Based Alloys with High Creep and Oxidation Resistance for A-USC Technology (United States)

    Hamdani, Fethi; Das, Nishith K.; Shoji, Tetsuo


    The design of ultra-high purity (UHP) Fe-based model alloys for advanced ultra-supercritical (A-USC) technology is attempted in this work. Creep testing has been performed in air at 700 °C and a stress level of 150 MPa. Analysis of the fracture surface and cross section of the crept specimen was performed. To evaluate the oxidation resistance in A-USC conditions, oxidation testing was performed in supercritical water (SCW) at 700 °C and 25 MPa. Weight gain (WG) measurements and meticulous characterization of the oxide scale were carried out. Based on thermodynamics and density functional theory calculations, some reactive elements in the Fe-Cr-Ni system were designated to promote precipitation strengthening and to improve the hydrogen-accelerated oxidation resistance. The addition of a 2 wt pct Mo into Fe-22Cr-22Ni-0.6Nb wt pct-based matrix did not significantly improve the creep resistance. The addition of 0.26 wt pct Zr coupled with cold working was effective for improving creep properties. The Mo-modified model alloy showed almost the same WG value as SUS310, while the Zr-modified alloy showed a higher WG value. Meanwhile, a Cr-enriched continuous oxide layer was formed at the oxidation front of the Zr-modified alloy and SUS310S after exposure to SCW conditions.

  9. Shallow magnetic inclinations in the Cretaceous Valle Group, Baja California: remagnetization, compaction, or terrane translation? (United States)

    Smith, Douglas P.; Busby, Cathy J.


    Paleomagnetic data from Albian to Turonian sedimentary rocks on Cedros Island, Mexico (28.2° N, 115.2° W) support the interpretation that Cretaceous rocks of western Baja California have moved farther northward than the 3° of latitude assignable to Neogene oblique rifting in the Gulf of California. Averaged Cretaceous paleomagnetic results from Cedros Island support 20 ± 10° of northward displacement and 14 ± 7° of clockwise rotation with respect to cratonic North America. Positive field stability tests from the Vizcaino terrane substantiate a mid-Cretaceous age for the high-temperature characteristic remanent magnetization in mid-Cretaceous strata. Therefore coincidence of characteristic magnetization directions and the expected Quaternary axial dipole direction is not due to post mid-Cretaceous remagnetization. A slump test performed on internally coherent, intrabasinal slump blocks within a paleontologically dated olistostrome demonstrates a mid-Cretaceous age of magnetization in the Valle Group. The in situ high-temperature natural remanent magnetization directions markedly diverge from the expected Quaternary axial dipole, indicating that the characteristic, high-temperature magnetization was acquired prior to intrabasinal slumping. Early acquisition of the characteristic magnetization is also supported by a regional attitude test involving three localities in coherent mid-Cretaceous Valle Group strata. Paleomagnetic inclinations in mudstone are not different from those in sandstone, indicating that burial compaction did not bias the results toward shallow inclinations in the Vizcaino terrane.

  10. Terrane accumulation and collapse in central Europe: seismic and rheological constraints (United States)

    Meissner, R.


    An attempt is made to compare the tectonic units and their evolution in central Europe with the deep seismic velocity structure and patterns of reflectivity. Caledonian and Variscan terrane accretion and orogenic collapse dominate the tectonic development in central and western Europe and have left their marks in a distinct velocity structure and crustal thickness as well as in the various reflectivity patterns. Whereas the memory of old collisional structures is still preserved in the rigid upper crust, collapse processes have formed and modified the lower crust. They have generally created rejuvenated, thin crusts with shallow Mohos. In the Variscan internides, the center of collision and post-orogenic heat pulses, the lower crust developed strong and thick seismic lamellae, the (cooler) externides show a thrust and shear pattern in the whole crust, and the North German Basin experienced large mafic intrusions in the lower crust and developed a high-velocity structure with only very thin lamellae on top of the Moho. The various kinds of reflectivity patterns in the lithosphere can be explained by a thermo-rheological model from terrane collision, with crustal thickening to collapse in a hot, post-orogenic setting.

  11. Tectonic superposition of the Kurosegawa Terrane upon the Sanbagawa metamorphic belt in eastern Shikoku, southwest Japan

    International Nuclear Information System (INIS)

    Suzuki, Hisashi; Isozaki, Yukio; Itaya, Tetsumaru.


    Weakly metamorphosed pre-Cenozoic accretionary complex in the northern part of the Chichibu Belt in Kamikatsu Town, eastern Shikoku, consists of two distinct geologic units; the Northern Unit and Southern Unit. The Northern Unit is composed mainly of phyllitic pelites and basic tuff with allochthonous blocks of chert and limestone, and possesses mineral paragenesis of the glaucophane schist facies. The Southern Unit is composed mainly of phyllitic pelites with allochthonous blocks of sandstone, limestone, massive green rocks, and chert, and possesses mineral paragenesis of the pumpellyite-actinolite facies. The Southern Unit tectonically overlies the Northern Univ by the south-dipping Jiganji Fault. K-Ar ages were dated for the recrystallized white micas from 11 samples of pelites and basic tuff in the Northern Unit, and from 6 samples of pelites in the Southern Unit. The K-Ar ages of the samples from the Northern Unit range in 129-112 Ma, and those from the Southern Unit in 225-194 Ma. In terms of metamorphic ages, the Northern Unit and Southern Unit are referred to the constituents of the Sanbagawa Metamorphic Belt, and to those of the Kurosegawa Terrane, respectively. Thus, tectonic superposition of these two units in the study area suggests that the Kurosegawa Terrane occurs in a higher structural position over the Sanbagawa Metamorphic Belt in eastern Shikoku. (author)

  12. Is Absence of Evidence of UHPM Evidence of Absence: Did Conditions on Earth Before the Ediacaran Period Allow Formation of UHP Rocks but Only Rarely Their Exhumation? (United States)

    Brown, M.


    UHPM provides petrologic evidence of transport of continental lithosphere to asthenospheric depth and return of some of these materials to crustal depth. The rock record registers UHPM since the Ediacaran Period, and studies of inclusion assemblages in zircon have increased the evidence of UHPM in Phanerozoic orogens and enabled an assessment of the real estate involved. Plots of apparent thermal gradient vs. age of metamorphism and P vs. age of metamorphism reveal two dramatic changes in inferred thermal environment and inferred depth of metamorphism from which continental lithosphere has been recovered during Earth evolution. First, from the Mesoarchean Era to the Neoproterozoic Era, sutures in subduction-to- collision orogens are marked by eclogite and high-pressure granulite metamorphism (characterized by apparent thermal gradients of 750-350 C/GPa). The P of metamorphism in sutures jumped from the Eoarchean-Paleoarchean up to 2 GPa during the Paleoproterozoic. Second, from the Cryogenian- Ediacaran to the present, many sutures in subduction-to-collision orogens, and sometimes intracratonic sutures in the overriding plate, are marked by UHPM (characterized by apparent thermal gradients of 2.7GPa. Given this pattern of secular change to colder apparent thermal gradients in sutures, the recent discovery of diamonds in zircons of crustal paragenesis in Neoarchean sedimentary rocks is surprising. Maybe UHPM has been possible since the Neoarchean but the evidence was rarely exhumed or if exhumed maybe the evidence was rarely preserved? The Appalachian/Caledonian-Variscide-Altaid and the Cimmerian-Himalayan-Alpine orogenic systems were formed by successive closure of short-lived oceans by transfer and suturing of ribbon-continent terranes derived from the Gondwanan side. Subduction of young ocean lithosphere followed by choking of the subduction channel by arc or terrane collision limited transport of water to the mantle wedge, and suppressed development of small

  13. Contrasting styles of sedimentation and deformation in the Chugach Terrane accretionary complex, south-central Alaska (United States)

    Amato, J. M.; Pavlis, T. L.; Worthman, C.; Kochelek, E.; Day, E. M.; Clift, P. D.; Hecker, J.


    In southeast Alaska the Chugach terrane represents an accretionary complex associated with several arcs active at 200-65 Ma. This lithostratigraphic unit consists of blueschists with Early Jurassic metamorphic ages and uncertain depositional ages; the Jurassic-Cretaceous McHugh Complex; and the Late Cretaceous Valdez Group. Detrital zircon ages from densely sampled transects reveals patterns in the assembly of the complex. Blueschists are almost totally barren of zircon, suggesting protoliths derived from mafic-intermediate volcanic protoliths far from a continental source. There is an age gap between the blueschists and the McHugh complex interpreted to be caused by an episode of tectonic erosion. The McHugh Complex is two separate units that are lithologically and geochronologically distinct. The older McHugh is a melange is dominated by stratally disrupted volcanic rocks, chert, and argillite. The oldest McHugh rocks have maximum depositional ages (MDA) of 177-150 Ma at Seldovia and 157-145 Ma at Turnagain Arm; the lack of older rocks at Turnagain Arm suggests removal of structural section by faulting. The MDAs of the older McHugh rocks do not decrease progressively away from the arc. There is a 45 m.y. gap in MDA between the older McHugh and the Late Cretaceous McHugh rocks. The younger McHugh rocks are dominated by volcanogenic sandstone and coarse conglomerate and MDA decreases from 100 Ma near the boundary with the older McHugh mesomelange to 85 Ma near the Valdez Group. The Valdez Group consists of coherently bedded turbidites with a MDA range of 85-60 Ma that decreases progressively outboard of the arc source. A sample from the Orca Group of the Prince William terrane is lithologically similar to the Valdez Group and there is no gap in MDA between Valdez and Orca Groups. 55 Ma dikes cut the McHugh and Valdez Groups in the western Chugach and Kenai Mountains. The oldest units of the Chugach terrane are the most deformed, with deformation and metamorphism

  14. Gamma-ray spectrometry of granitic suites of the Paranaguá Terrane, Southern Brazil (United States)

    Weihermann, Jessica Derkacz; Ferreira, Francisco José Fonseca; Cury, Leonardo Fadel; da Silveira, Claudinei Taborda


    The Paranaguá Terrane, located in the coastal portion of the states of Santa Catarina, Paraná and São Paulo in Southern Brazil is a crustal segment constituted mainly by an igneous complex, with a variety of granitic rocks inserted into the Serra do Mar ridge. The average altitude is approximately 1200 m above sea level, with peaks of up to 1800 m. Due to the difficulty of accessing the area, a shortage of outcrops and the thick weathering mantle, this terrane is understudied. This research aims to evaluate the gamma-ray spectrometry data of the granitic suites of the Paranaguá Terrane, in correspondence with the geological, petrographical, lithogeochemical, relief and mass movement information available in the literature. Aerogeophysical data were acquired along north-south lines spaced at 500 m, with a mean terrain clearance of 100 m. These data cover potassium (K, %), equivalent in thorium (eTh, ppm) and equivalent in uranium (eU, ppm). After performing a critical analysis of the data, basic (K, eU, eTh) and ternary (R-K/G-eTh/B-eU) maps were generated and then superimposed on the digital elevation model (DEM). The investigation of the radionuclide mobility across the relief and weathering mantle consisted of an analysis of the schematic profiles of elevation related with each radionuclide; a comparison of the K, eU and eTh maps with their 3D correspondents; and the study of mass movements registered in the region. A statistical comparison of lithogeochemical (K, U, Th) and geophysical (K, eU, eTh) data showed consistency in all the granitic suites studied (Morro Inglês, Rio do Poço and Canavieiras-Estrela). Through gamma-ray spectrometry, it was possible to establish relationships between scars (from mass movements) and the gamma-ray responses as well as the radionuclide mobility and the relief and to map the granitic bodies.

  15. Cretaceous–Eocene provenance connections between the Palawan Continental Terrane and the northern South China Sea margin

    NARCIS (Netherlands)

    Shao, Lei; Cao, Licheng; Qiao, Peijun; Zhang, Xiangtao; Li, Qianyu; van Hinsbergen, Douwe J.J.


    The plate kinematic history of the South China Sea opening is key to reconstructing how the Mesozoic configuration of Panthalassa and Tethyan subduction systems evolved into today's complex Southeast Asian tectonic collage. The South China Sea is currently flanked by the Palawan Continental Terrane

  16. Paleozoic subduction complex and Paleozoic-Mesozoic island-arc volcano-plutonic assemblages in the northern Sierra terrane (United States)

    Hanson, Richard E.; Girty, Gary H.; Harwood, David S.; Schweickert, Richard A.


    This field trip provides an overview of the stratigraphic and structural evolution of the northern Sierra terrane, which forms a significant part of the wall rocks on the western side of the later Mesozoic Sierra Nevada batholith in California. The terrane consists of a pre-Late Devonian subduction complex (Shoo Fly Complex) overlain by submarine arc-related deposits that record the evolution of three separate island-arc systems in the Late Sevonian-Early Mississippian, Permian, and Late Triassic-Jurassic. The two Paleozoic are packages and the underlying Shoo Fly Complex have an important bearing on plate-tectonic processes affecting the convergent margin outboard of the Paleozoic Cordilleran miogeocline, although their original paleogeographic relations to North America are controversial. The third arc package represents an overlap assemblage that ties the terrane to North America by the Late Triassic and helps constrain the nature and timing of Mesozoic orogenesis. Several of the field-trip stops examine the record of pre-Late Devonian subduction contained in the Shoo Fly Complex, as well as the paleovolcanology of the overlying Devonian to Jurassic arc rocks. Excellent glaciated exposures provide the opportunity to study a cross section through a tilted Devonian volcano-plutonic association. Additional stops focus on plutonic rocks emplaced during the Middle Jurassic arc magmatism in the terrane, and during the main pulse of Cretaceous magmatism in the Sierra Nevada batholith to the east.

  17. The UHP metamorphic Seve Nappe Complex of the Swedish Caledonides - a new occurrence of the microdiamond-bearing gneisses and their exhumation (United States)

    Klonowska, Iwona; Janák, Marian; Majka, Jarosław; ‎ Froitzheim, Nikolaus; Gee, David G.


    The ultra-high pressure metamorphism (UHPM) in the Seve Nappe Complex of the Swedish Caledonides has been recently recognized within several lithologies including gneisses, eclogites and garnet pyroxenites (e.g. Janák et al. 2013, Klonowska et al. 2014a, Majka et al. 2014). Thermodynamic modelling and thermobarometric calculations indicate peak pressure conditions of >3GPa at c. 800-900°C (reaching the diamond stability field) for eclogites and garnet pyroxenites from northern Jämtland (e.g. Klonowska et al. 2014b). In addition to this, the first microdiamonds were found in paragneisses from the Snasahögarna Mt. in central Jämtland (Majka et al. 2014). Here we report a new discovery of microdiamond together with moissanite (SiC) from one of the world's most famous localities for thrusting, Mount Åreskutan, where long transport distances were recognized already in the 19th century (Törnebohm 1888). Garnet porphyroblasts in gneisses from the Åreskutan Mt. contain abundant mineral inclusions, mainly graphite, carbonates and quartz, together with fluid inclusions of CO2 concentrated in swarms. Among these inclusions three microdiamonds were found in two gneiss samples. In one of the samples moissanite was also discovered. Both minerals were identified by micro-Raman spectroscopy. In addition to these 'swarm' inclusions, biotite, kyanite, rutile, feldspars, zircon, monazite, ±phengite, ±muscovite, ±spinel, ±ilmenite, ±apatite occur in garnets. Phase equilibrium modelling for the phengite-bearing gneiss confirms its UHP history at temperatures of c. 800°C. Recent discoveries of UHP metamorphism within the Seve Nappe Complex derived from the Baltican outer margin (part of the Middle Allochthon) challenged us to present a new tectonic model incorporating exhumation of the deeply subducted continental rocks together with mantle lithosphere peridotites. Majka et al. (2014) introduced a new "under-pressure"-driven exhumation mechanism of rocks buried in

  18. Microprobe monazite constraints for and early (ca. 790 Ma) Braziliano orogeny: The Embu Terrane, southeastern Brazil

    International Nuclear Information System (INIS)

    Vlach, Silvio R.F


    The evolution of the Mantiqueira Orogenetic System, Southeastern Brazil, comprises discrete episodes of tectonic collage and docking of remnants of Rodinia break-up in the borders of the Sao Francisco Craton. This system is related to the closure of the Adamastor ocean and assemblage of the western Gondwana super-continent during Neoproterozoic times (ca. 610-530 Ma, Brito Neves et al., 1999; Campos Neto, 2000). This report presents monazite microprobe dating results for metassediments from the Embu Complex, an important lithological unit from the Ribeira Belt, currently included in the Juiz de Fora terrane, a unit added to the Sao Francisco Craton at ca. 600-580 Ma. (Campos Neto, 2000). The age results unravel a main metamorphic episode and related orogeny at ca. 790 Ma and bring new insights concerning the agglutination of Gondwana in this region during the Neoproterozoic (au)

  19. Paleointensity determination on Neoarchaean dikes within the Vodlozerskii terrane of the Karelian craton (United States)

    Shcherbakova, V. V.; Lubnina, N. V.; Shcherbakov, V. P.; Zhidkov, G. V.; Tsel'movich, V. A.


    The results of paleomagnetic studies and paleointensity determinations from two Neoarchaean Shala dikes with an age of 2504 Ma, located within the Vodlozerskii terrane of the Karelian craton, are presented. The characteristic components of primary magnetization with shallow inclinations I = -5.7 and 1.9 are revealed; the reliability of the determinations is supported by two contact tests. High paleointensity values are obtained by the Thellier-Coe and Wilson techniques. The calculated values of the virtual dipole moment (11.5 and 13.8) × 1022 A m2 are noticeably higher than the present value of 7.8 × 1022 A m2. Our results, in combination with the previous data presented in the world database, support the hypothesized existence of a period of high paleointensity in the Late Archaean-Early Proterozoic.

  20. kepler's dark worlds: A low albedo for an ensemble of Neptunian and Terran exoplanets (United States)

    Jansen, Tiffany; Kipping, David


    Photometric phase curves provide an important window onto exoplanetary atmospheres and potentially even their surfaces. With similar amplitudes to occultations but far longer baselines, they have a higher sensitivity to planetary photons at the expense of a more challenging data reduction in terms of long-term stability. In this work, we introduce a novel non-parametric algorithm dubbed phasma to produce clean, robust exoplanet phase curves and apply it to 115 Neptunian and 50 Terran exoplanets observed by kepler. We stack the signals to further improve signal-to-noise, and measure an average Neptunian albedo of Ag greenhouse effect, our work implies that kepler's solid planets are unlikely to resemble cloudy Venusian analogs, but rather dark Mercurian rocks.

  1. Are turtleback fault surfaces common structural elements of highly extended terranes? (United States)

    Çemen, Ibrahim; Tekeli, Okan; Seyitoğlu, Gűrol; Isik, Veysel


    The Death Valley region of the U.S.A. contains three topographic surfaces resembling the carapace of a turtle. These three surfaces are well exposed along the Black Mountain front and are named the Badwater, Copper Canyon, and Mormon Point Turtlebacks. It is widely accepted that the turtlebacks are also detachment surfaces that separate brittlely deformed Cenozoic volcanic and sedimentary rocks of the hanging wall from the strongly mylonitic, ductilely deformed pre-Cenozoic rocks of the footwall. We have found a turtleback-like detachment surface along the southern margin of the Alasehir (Gediz) Graben in western Anatolia, Turkey. This surface qualifies as a turtleback fault surface because it (a) is overall convex-upward and (b) separates brittlely deformed hanging wall Cenozoic sedimentary rocks from the ductilely to brittlely deformed, strongly mylonitic pre-Cenozoic footwall rocks. The surface, named here Horzum Turtleback, contains striations that overprint mylonitic stretching lineations indicating top to the NE sense of shear. This suggests that the northeasterly directed Cenozoic extension in the region resulted in a ductile deformation at depth and as the crust isostatically adjusted to the removal of the rocks in the hanging wall of the detachment fault, the ductilely deformed mylonitic rocks of the footwall were brought to shallower depths where they were brittlely deformed. The turtleback surfaces have been considered unique to the Death Valley region, although detachment surfaces, rollover folds, and other extensional structures have been well observed in other extended terranes of the world. The presence of a turtleback fault surface in western Anatolia, Turkey, suggests that the turtleback faults may be common structural features of highly extended terranes.

  2. Effects of silicate weathering on water chemistry in forested, upland, felsic terrane of the USA

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    Stauffer, R.E.; Wittchen, B.D.


    The authors use data from the US EPA National Surface Water Survey (NSWS), the USGS Bench-Mark Station monitoring program, and the National Acid Deposition Program (NADP) to evaluate the role of weathering in supplying base cations to surface waters in forested, upland, felsic terrane of the northeastern, northcentral, and northwestern (Idaho batholith) US. Multivariate regression reveals differential effects of discharge on individual base cations and silica, but no secular trend in the Ca/Na denudation rate over 24 yr (1965-1988) for the Wild River catchment in the White Mountains. Because the turn-over time for Na in the soil-exchange complex is only ca. 1.5 yr, the long-term behavior of the ratios Ca/Na and Si/Na in waters leaving this catchment indicates that weathering is compensating for base cation export. In every subregion, Ca and Mg concentrations in lakes are statistically linked to nonmarine Na, but the median Ca/Na ratio is greater than the ratio in local plagioclase. The authors attribute this inequality to nonstoichiometric weathering of calcium in juvenile (formerly glaciated) terrane, not to leaching of exchangeable cations by So 4 because intraregional and cross-regional statistical analysis reveals no effect of atmospherically derived sulfate ion. The median base cation denudation rates (meq m -2 yr -1 ) for these American lake regions are: Maine granites (108); western Adirondack felsic gneiss (85); Vermilion batholith (42); Idaho batholith (52). The regional rates are high enough to compensate for present wet deposition of acidifying anions except in some vulnerable lake watersheds in the western Adirondacks


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    Full Text Available Ağaçlı Linyit kömürlerinden elde edilen aktif kömür, sulu çözeltilerden Cr(VI uzaklaştırmak için kullanılmıştır. Cr(VI adsorpsiyonu başlangıç konsantrasyonu, zaman, pH, adsorbent konsantrasyonu ve sıcaklığın fonksiyonu olarak çalışılmıştır. Adsorpsiyon verileri Langmuir ve Freundlich izotermlerine uydurulmuştur. Adsorpsiyon hız sabitini hesaplamak için Lagergren eşitliği kullanıldı. Adsorbe edilen Cr(VI miktarı pH değerinin azalması ile artmış, sıcaklığın artması ile azalmıştır.

  4. Geophysical modeling of the northern Appalachian Brompton-Cameron, Central Maine, and Avalon terranes under the New Jersey Coastal Plain (United States)

    Maguire, T.J.; Sheridan, R.E.; Volkert, R.A.


    A regional terrane map of the New Jersey Coastal Plain basement was constructed using seismic, drilling, gravity and magnetic data. The Brompton-Cameron and Central Maine terranes were coalesced as one volcanic island arc terrane before obducting onto Laurentian, Grenville age, continental crust in the Taconian orogeny [Rankin, D.W., 1994. Continental margin of the eastern United States: past and present. In: Speed, R.C., (Ed.), Phanerozoic Evolution of North American Continent-Ocean Transitions. DNAG Continent-Ocean Transect Volume. Geological Society of America, Boulder, Colorado, pp. 129-218]. Volcanic island-arc rocks of the Avalon terrane are in contact with Central Maine terrane rocks in southern Connecticut where the latter are overthrust onto the Brompton-Cameron terrane, which is thrust over Laurentian basement. Similarities of these allochthonous island arc terranes (Brompton-Cameron, Central Maine, Avalon) in lithology, fauna and age suggest that they are faulted segments of the margin of one major late Precambrian to early Paleozoic, high latitude peri-Gondwana island arc designated as "Avalonia", which collided with Laurentia in the early to middle Paleozoic. The Brompton Cameron, Central Maine, and Avalon terranes are projected as the basement under the eastern New Jersey Coastal Plain based on drill core samples of metamorphic rocks of active margin/magmatic arc origin. A seismic reflection profile across the New York Bight traces the gentle dipping (approximately 20 degrees) Cameron's Line Taconian suture southeast beneath allochthonous Avalon and other terranes to a 4 sec TWTT depth (approximately 9 km) where the Avalonian rocks are over Laurentian crust. Gentle up-plunge (approximately 5 degrees) projections to the southwest bring the Laurentian Grenville age basement and the drift-stage early Paleozoic cover rocks to windows in Burlington Co. at approximately 1 km depth and Cape May Co. at approximately 2 km depths. The antiformal Shellburne

  5. 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 (United States)

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


    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

  6. Elemental and isotopic (C, O, Sr, Nd) compositions of Late Paleozoic carbonated eclogite and marble from the SW Tianshan UHP belt, NW China: Implications for deep carbon cycle (United States)

    Zhu, Jianjiang; Zhang, Lifei; Lü, Zeng; Bader, Thomas


    Subduction zones are important for understanding of the global carbon cycle from the surface to deep part of the mantle. The processes involved the metamorphism of carbonate-bearing rocks largely control the fate of carbon and contribute to local carbon isotopic heterogeneities of the mantle. In this study, we present petrological and geochemical results for marbles and carbonated eclogites in the Southwestern Tianshan UHP belt, NW China. Marbles are interlayered with coesite-bearing pelitic schists, and have Sr-Nd isotopic values (εNd (T=320Ma) = -3.7 to -8.9, 87Sr/86Sr (i) = 0.7084-0.7089), typical of marine carbonates. The marbles have dispersed low δ18OVSMOW values (ranging from 14 to 29‰) and unaffected carbon isotope (δ13CVPDB = -0.2-3.6‰), possibly due to infiltration of external H2O-rich fluids. Recycling of these marbles into mantle may play a key role in the carbon budget and contributed to the mantle carbon isotope heterogeneity. The carbonated eclogites have high Sr isotopic compositions (87Sr/86Sr (i) = 0.7077-0.7082) and positive εNd (T = 320 Ma) values (from 7.6 to 8.2), indicative of strong seafloor alteration of their protolith. The carbonates in the carbonated eclogites are mainly dolomite (Fe# = 12-43, Fe# = Fe2+/(Fe2+ + Mg)) that were added into oceanic basalts during seafloor alteration and experienced calcite - dolomite - magnesite transformation during the subduction metamorphic process. The uniformly low δ18O values (∼11.44‰) of carbonates in the carbontaed eclogites can be explained by closed-system equilibrium between carbonate and silicate minerals. The low δ13C values (from -3.3 to -7.7‰) of the carbonated eclogites most likely reflect contribution from organic carbon. Recycling of these carbonated eclogites with C isotope similar to typical mantle reservoirs into mantle may have little effect on the mantle carbon isotope heterogeneity.

  7. Paleomagnetic contributions to the Klamath Mountains terrane puzzle-a new piece from the Ironside Mountain batholith, northern California (United States)

    Mankinen, Edward A.; Gromme, C. Sherman; Irwin, W. Porter


    We obtained paleomagnetic samples from six sites within the Middle Jurassic Ironside Mountain batholith (~170 Ma), which constitutes the structurally lowest part of the Western Hayfork terrane, in the Klamath Mountains province of northern California and southern Oregon. Structural attitudes measured in the coeval Hayfork Bally Meta-andesite were used to correct paleomagnetic data from the batholith. Comparing the corrected paleomagnetic pole with a 170-Ma reference pole for North America indicates 73.5° ± 10.6° of clockwise rotation relative to the craton. Nearly one-half of this rotation may have occurred before the terrane accreted to the composite Klamath province at ~168 Ma. No latitudinal displacement of the batholith was detected.

  8. Punta del este terrane: meso proterozoic basement and neo proterozoic cover

    International Nuclear Information System (INIS)

    Preciozzi, F.; Sanchez Bettucci, L.; Basei, M.; Peel, E.; Oyhantcabal, P.; Cordani, U.


    Full text: Eastern basement of Uruguay consists of Meso and Neoproterozoic rocks. Mesoproterozoic basement had been deformed by pre-Brasiliano and Brasiliano events. Regional variations in this basement and in the Neoproterozoic cover show equivalent deformation styles and intensities. Models proposed for tectonic evolution have been scarce and confusing. Specially, the ones that concern the moment of collision and/or juxtaposition of blocks. The Punta del Este Terrane (PET) is composed of gneisses and migmatites formed between 1000 Ma to 900 Ma (Preciozzi et al., 2001). These rocks had been strongly reworked during Brasiliano and Rio Doce orogenesis (ca. 900-500 Ma). This crustal segment represents a high grade metamorphic terrane, which is correlated to some gneissic complexes southwest of Africa. Particularly, it is correlated to Kibaran-Namaqua Belt in Namibia. U-Pb ages between 1000 Ma and 900 Ma, obtained in zircons from tonalitic granitoids, are interpreted as indicative of their crystallization (Fig. 1). Besides, anatectic fluids related to migmatites leucosomes yielded ages of ca. 520 to 540 Ma. This denotes that superimposed metamorphic conditions during Brasiliano orogenesis reached, at least, lower amphibolite facies. PET basement gneisses present Sm-Nd model ages (TDM) between 2.4 to 1.8 Ga, showing long crustal residence, corroborated by the very negative εNd values of –1.3 and –14.3. During Brazilian orogenesy they were affected by deformation processes and anatexis. Metasedimentary PET cover occurs near La Paloma and Rocha towns. It is represented by a siliciclastic metasedimentary succession corresponding to the Rocha formation. In La Pedrera town recognized three sedimentary facies were (1-3): (1) sandstones and pelites; (2) green pelites; and (3) rhytmites. The transition from facies (1) to facies (3) shows the passage from fluvial environment with tidal influence to tidal flat with predominance of sub tidal deposits (Pazos and S

  9. Lithospheric discontinuities beneath the U.S. Midcontinent - signatures of Proterozoic terrane accretion and failed rifting (United States)

    Chen, Chen; Gilbert, Hersh; Fischer, Karen M.; Andronicos, Christopher L.; Pavlis, Gary L.; Hamburger, Michael W.; Marshak, Stephen; Larson, Timothy; Yang, Xiaotao


    Seismic discontinuities between the Moho and the inferred lithosphere-asthenosphere boundary (LAB) are known as mid-lithospheric discontinuities (MLDs) and have been ascribed to a variety of phenomena that are critical to understanding lithospheric growth and evolution. In this study, we used S-to-P converted waves recorded by the USArray Transportable Array and the OIINK (Ozarks-Illinois-Indiana-Kentucky) Flexible Array to investigate lithospheric structure beneath the central U.S. This region, a portion of North America's cratonic platform, provides an opportunity to explore how terrane accretion, cratonization, and subsequent rifting may have influenced lithospheric structure. The 3D common conversion point (CCP) volume produced by stacking back-projected Sp receiver functions reveals a general absence of negative converted phases at the depths of the LAB across much of the central U.S. This observation suggests a gradual velocity decrease between the lithosphere and asthenosphere. Within the lithosphere, the CCP stacks display negative arrivals at depths between 65 km and 125 km. We interpret these as MLDs resulting from the top of a layer of crystallized melts (sill-like igneous intrusions) or otherwise chemically modified lithosphere that is enriched in water and/or hydrous minerals. Chemical modification in this manner would cause a weak layer in the lithosphere that marks the MLDs. The depth and amplitude of negative MLD phases vary significantly both within and between the physiographic provinces of the midcontinent. Double, or overlapping, MLDs can be seen along Precambrian terrane boundaries and appear to result from stacked or imbricated lithospheric blocks. A prominent negative Sp phase can be clearly identified at 80 km depth within the Reelfoot Rift. This arrival aligns with the top of a zone of low shear-wave velocities, which suggests that it marks an unusually shallow seismic LAB for the midcontinent. This boundary would correspond to the top of a

  10. North America as an exotic terrane'' and the origin of the Appalachian--Andean Mountain system

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    Dalziel, I.W.D; Gahagan, L.M. (Univ. of Texas, Austin, TX (United States). Inst. for Geophysics); Dalla Salda, L.H. (Univ. Nacional de La Plata, La Plata (Argentina). Centro de Investigaciones Geologicas)


    North America was sutured to Gondwana in the terminal Alleghanian event of Appalachian orogenesis, thus completing the late Paleozoic assembly of Pangea. The suggestion that the Pacific margins of East Antarctica-Australia and Laurentia may have been juxtaposed during the Neoproterozoic prompts reevaluation of the widely held assumptions that the ancestral Appalachian margin rifted from northwestern Africa during the earliest Paleozoic opening of Iapetus, and remained juxtaposed to that margin, even though widely separated from it at times, until the assembly of Pangea. The lower Paleozoic carbonate platform of northwestern Argentina has been known for a long time to contain Olenellid trilobites of the Pacific or Columbian realm. Although normally regarded as some kind of far-travelled terrane that originated along the Appalachian margin of Laurentia, it has recently been interpreted as a fragment detached from the Ouachita embayment of Laurentia following Taconic-Famatinian collision with Gondwana during the Ordovician. The Oaxaca terrane of Mexico, on the other hand, contains a Tremadocian trilobite fauna of Argentine-Bolivian affinities, and appears to have been detached from Gondwana following the same collision. The Wilson cycle'' of Iapetus ocean basin opening and closing along the Appalachian and Andean orogens may have involved more than one such continental collision during clockwise drift of Laurentia around South America following late Neoproterozoic to earliest Cambrian separation. Together with the collisions of baltic and smaller terranes with Laurentia, this could explain the protracted Paleozoic orogenic history of both the Appalachian and proto-Andean orogens.

  11. Terrane Boundary Geophysical Signatures in Northwest Panay, Philippines: Results from Gravity, Seismic Refraction and Electrical Resistivity Investigations

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    Jillian Aira S. Gabo


    Full Text Available Northwest Panay consists of two terranes that form part of the Central Philippine collision zone: Buruanga Peninsula and Antique Range. The Buruanga Peninsula consists of a Jurassic chert-clastic-limestone sequence, typical of oceanic plate stratigraphy of the Palawan Micro-continental Block. The Antique Range is characterized by Antique Ophiolite Complex peridotites and Miocene volcanic and clastic rocks, representing obducted oceanic crust that serves as the oceanic leading edge of the collision with the Philippine Mobile Belt. The Nabas Fault is identified as the boundary between the two terranes. This study employed the gravity method to characterize the Northwest Panay subsurface structure. Results indicate higher Bouguer anomaly values for Buruanga Peninsula than those for Antique Range, separated by a sudden decrease in gravity values toward the east-southeast (ESE direction. Forward gravity data modeling indicates the presence of an underlying basaltic subducted slab in the Buruanga Peninsula. Furthermore, the Nabas Fault is characterized as an east-dipping thrust structure formed by Buruanga Peninsula basement leading edge subduction beneath Antique Range. Additional geophysical constraints were provided by shallow seismic refraction and electrical resistivity surveys. Results from both methods delineated the shallow subsurface signature of the Nabas Fault buried beneath alluvium deposits. The gravity, seismic refraction and electrical resistivity methods were consistent in identifying the Nabas Fault as the terrane boundary between the Buruanga Peninsula and the Antique Range. The three geophysical methods helped constrain the subsurface configuration in Northwest Panay.

  12. Post-peak metamorphic evolution of the Sumdo eclogite from the Lhasa terrane of southeast Tibet (United States)

    Cao, Dadi; Cheng, Hao; Zhang, Lingmin; Wang, Ke


    A reconstruction of the pressure-temperature-time (P-T-t) path of high-pressure eclogite-facies rocks in subduction zones may reveal important information about the tectono-metamorphic processes that occur at great depths along the plate interface. The majority of studies have focused on prograde to peak metamorphism of these rocks, whereas after-peak metamorphism has received less attention. Herein, we present a detailed petrological, pseudosection modeling and radiometric dating study of a retrograded eclogite sample from the Sumdo ultrahigh pressure belt of the Lhasa terrane, Tibet. Mineral chemical variations, textural discontinuities and thermodynamic modeling suggest that the eclogite underwent an exhumation-heating period. Petrographic observations and phase equilibria modeling suggest that the garnet cores formed at the pressure peak (∼2.5 GPa and ∼520 °C) within the lawsonite eclogite-facies and garnet rims (∼1.5 GPa and spans an interval of ∼7 million years, which is a minimum estimate of the duration of the eclogite-facies metamorphism of the Sumdo eclogite.

  13. UTE park group and other meso proterozoic units of the Nico Perez terrane: Rodina connecting

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    Gaucher, C; Chemale, F.; Bossi, J.; Sial, A.; Chiglino, L.


    The Parque UTE Group is a volcano sedimentary succession metamorphosed in green schist facies, comprising (from base to top): the Canada Espinillo Formation (prasinites, pelites, andesite s), the Mina Valencia Formation (dolostones, limestones, marls) and the Cerro del Mast il Formation (black pelites, limestones, acid tuffs). Thickness of the GPU exceeds 2.5 km; base and top are not exposed. U-Pb zircon ages for basic magmatic rocks at the base and rhyolites at the top yielded 1492±4 and 1429±21 Ma, respectively. 13C values of carbonates of the Pug are characterized by a plateau at +1‰ VPDB, bracketed between two negative excursions.These values are consistent with an early Mesoproterozoic depositional age. Detrital zircon age spectra show that the source area of the GPU was the Nico Perez Terrane, being thus native to the Rio de la Plata Craton (Rpc). A Mesoproterozoic tectonic event at 1.25 Ga, recorded at both sides of the Sarandi del Yi mega shear, is discussed. New U-Pb zircon ages are presented for the La China Complex at its type area, where a schistosity N60W cuts the metamorphic banding and is parallel to thrusts dated K-Ar at 1253±32 Ma. The ages obtained are: 3096±45 Ma (main metamorphic event) and 1252 Ma (lower intercept). These data confirm the occurrence of a Grenvillian-aged tectonic event in Uruguay, suggesting that the RPC was part of the super continent Rodinia

  14. Combined U-Pb SHRIMP and Hf isotope study of the Late Paleozoic Yaminué Complex, Rio Negro Province, Argentina: Implications for the origin and evolution of the Patagonia composite terrane

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    Carlos J. Chernicoff


    Combining geological and isotope data, as well as geophysical models, we identify the Yaminué Complex within the La Esperanza-Yaminué crustal block flanked by two other, distinct crustal blocks: the Eastern block which forms part of the Patagonia terrane sensu stricto, located in the eastern Patagonian region, and the Western block forming part of the Southern Patagonia terrane. Their origins and timing of amalgamation to form the Patagonia composite terrane are also discussed.

  15. Recognition of the Kaweka Terrane in northern South Island, New Zealand : preliminary evidence from Rb-Sr metamorphic and U-Pb detrital zircon ages

    International Nuclear Information System (INIS)

    Adams, C.J.; Mortimer, N.; Campbell, H.J.; Griffin, W.L.


    Detrital zircon U-Pb ages and Rb-Sr metamorphic ages from low-grade Torlesse Supergroup metasedimentary rocks from North Canterbury and Marlborough provide preliminary evidence for a continuation of the Kaweka Terrane of the central North Island into the Torlesse Composite Terrane of the South Island. This would extend from the south side of the Wairau Fault in the upper Wairau River valley southwards to the Lake Tennyson and Lake Sumner areas, and as far as Hawarden. Rb-Sr ages indicate Jurassic metamorphism, 170±24 Ma, with initial 87 Sr/ 86 Sr ratios at that time 0.7073 ± 0.0007 i.e. similar to their North Island counterparts. These Kaweka Terrane rocks have detrital zircon ages that follow the distinctive pattern of the Torlesse rocks in general, i.e. substantial (>30%) Permian-Triassic and Precambrian-Early Palaeozoic groupings, but they also have minor youngest age components c. 175-165 Ma which constrain a maximum Early-Middle Jurassic depositional age. In detail, significant, older zircon components are Late Permian-Early Triassic (260-240 Ma) and Late Triassic (220-210 Ma), but the Precambrian-Early Palaeozoic detrital zircon ages are more scattered. The Kaweka Terrane thus forms a linear belt (c. 500 km) along the length of the Torlesse Composite Terrane in both North and South Islands. In the South Island it coincides with the Esk Head Belt, i.e. east of the Rakaia Terrane (Triassic-Late Permian) and west of the Pahau Terrane (Early Cretaceous-Late Jurassic). (author). 61 refs., 4 figs., 2 tabs.

  16. Park Volcanics, Murihiku Terrane, New Zealand : petrology, petrochemistry, and tectonic significance

    International Nuclear Information System (INIS)

    Coombs, D.S.; Cook, N.D.J.; Kawachi, Y.; Johnstone, R.D.; Gibson, I.L.


    The Late Triassic to Early Jurassic Park Volcanics Group comprises minor shallow intrusive and extrusive bodies emplaced during mainly marine sedimentation of the Murihiku Terrane, southern New Zealand. Gowan Andesite in western Southland and Glenham Porphyry andesites in eastern Southland are high-K andesites. Glassy examples have commonly lost K during alteration. Orthoclase contents of Or 3.6-3.7 in plagioclase phenocrysts at An 50 confirm the high-K nature of the melts at the time of phenocryst crystallisation. The Gowan andesites have higher Fe/Mg than the Glenham and related differences in minor element chemistry suggesting lower ∫O 2 during fractionation of the parent magma. Pinney Volcanics in western Southland are mostly high-K trachydacites but, like Glenham Porphyry, include minor rhyolite. Barnicoat Andesite in the Nelson area is medium-K olivine andesite, marginally tholeiitic in terms of its FeO*/MgO versus SiO 2 behaviour, but otherwise is typically calc-alkaline, as are the Gowan, Glenham, and Pinney. Analyses of pyroxenes (augites, orthopyroxenes, reaction rim and groundmass pigeonites) reveal xenocrysts recording an early stage of magma fractionation, slight iron enrichment in the andesite stage, and lowered Fe/Mg and increased Ca contents in augites of the most felsic rocks. Titanian tschermakite and titanian magnesio-tschermakite of deep-seated origin participated in fractionation leading to the Pinney Volcanics, and magnesio-hornblende, edenite, and biotite crystallised as minor late stage minerals following high-level emplacement of Gowan Andesite and siliceous Glenham Porphyry members. Low 87 Sr/ 86 Sr ratios (c. 0.7034-0.7037), REE and multi-element distribution patterns, and the mineralogical features collectively suggest fractionation of the andesites from parental basalt originating in an enriched mantle wedge above a subduction zone, with minimal contamination by continental crust. High-K andesites appear to be unknown in clearly

  17. Precambrian Terranes of African affinities in the southeastern part of Brazil and Uruguay

    International Nuclear Information System (INIS)

    Preciozzi, F.; Basei, M.; Siga Junior, H.; Sato, K.; Kaufuss, G.


    The interest in correlating terranes at opposite margins of the South Atlantic Ocean reflects a natural curiosity of both researchers who work in the eastern South-America and who study southwestern Africa. On a large scale scenario the geology of this region is characterized by a central portion composed of Neoproterozoic-Cambrian belts (Dom Feliciano, Kao ko, Damara, Gariep, Saldania) having on each side old gneissic-migmatitic terrains on both continents (Luis Alves, Rio de La Plata, Kalahari and Congo). In South America the Neoproterozoic Dom Feliciano Belt (DFB) predominates in the eastern part of the region and is internally organized according to three different crustal segments characterized, from southeast to northwest, by a Granite belt (deformed I-type medium to high calc-alkaline granites and alkaline granitoid rocks; a Schist belt (volcano-sedimentary rocks metamorphosed from green schist to amphibolite facies and intrusive granitoids), and a Fore land basin (anchimetamorphic sedimentary and volcanic rocks), the latter situated between the Schist belt and the Archean-Paleoproterozoic fore land. Despite discontinuously covered by younger sediments, the NS continuity of these three crustal segments is suggested by similar lithotypes, structural characteristics, ages and isotopic signature, as well as by the gravimetric data. The Major Gercino, Cordilheira, and Sierra Ballena shear zones are part of the major NE-SW lineaments that affect all southern Brazilian and Uruguayan Precambrian terrains. They separate the Dom Feliciano Schist Belt (supra crustal rocks of the Brusque-Porongos and Lavalleja groups), to the West, from the granitoids of the Granite belt, to the East. The shear zones are characterized by a regional NE trend and a resultant oblique direction of movement where ductile-brittle structures predominate

  18. Identification of thermotectonics events by 40Ar/39Ar methodology, in Jauru, Pontes e Lacerda and Rio Alegre Terrane - southwest portion of Amazon Craton

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    Paulo, Valeria Guimaraes de


    The southwest portion of Amazon Craton, subject of these work, correspond to the southwest region of Mato Grosso State and is inserted on Rio Negro-Juruena, Rondoniana-San Ignacio and Sunsas-Aguapei geochronologic Provinces. This region is surrounded by three big terranes: Jauru, Pontes e Lacerda and Rio Alegre. The main aim of this study is to use the ages of termochronologic events obtained by 40 Ar/ 39 Ar methodology, including data of literature, to contribute with the study of the geotectonic evolution on this region. Twenty samples were analyzed and 40 Ar/ 39 Ar ages found for the Jauru Terrane vary of 1539 ± 3 Ma to 1338 ± 3 Ma, for the Pontes e Lacerda Terrane the interval obtained was of 946,1 ± 0,8 Ma to 890 ± 2 Ma and for Rio Alegre Terrane the ages are between 1407 ± 3 Ma to 1321 ± 2 Ma. U/Pb, Rb/Sr and Sm/Nd data from previous works, together with 40 Ar/ 39 Ar results allowed to obtain cooling average rates to each terrane. The Jauru Terrane units cooling age is equivalent to 1,52 Ga. The cooling average rates found to Alto Jauru Greenstone belt rocks is 2,4 deg C - 1,0 Ma and to Magmatic Arc Cachoeirinha is 10,8 deg C - 1,0 Ma. Stabilization age obtained for Pontes and Lacerda Terrane is about 900 Ma coherent with the cooling age of the Sunsas Aguapei Event (1,0 - 0,9 Ga) and cooling average rates calculate were the lower, equivalent to 1,0 deg C - 1,0 Ma. Cooling age found in Rio Alegre Terrane was 1,35 Ga, possibility correspond to collision age these terrane with Amazonian protoCraton and cooling average rates of 5,0 deg C - 1,0 Ma. Finally, younger age found of 900 Ma, coherent to the Sunsas - Aguapei Event, probably represent the last regional event that affected these rocks, characterizing the stabilization period of the southwest portion of Amazon Craton. (author)

  19. A geologic guide to Wrangell-Saint Elias National Park and Preserve, Alaska; a tectonic collage of northbound terranes (United States)

    Winkler, Gary R.; with contributions by MacKevett, E. M.; Plafker, George; Richter, D.H.; Rosenkrans, D.S.; Schmoll, H.R.


    Wrangell-Saint Elias National Park and Preserve, the largest unit in the U.S. National Park System, encompasses near 13.2 million acres of geological wonderments. This geologic guide presents history of exploration and Earth-science investigation; describes the complex geologic makeup; characterizes the vast college of accretion geologic terranes in this area of Alaska's continental margin; recapitulates the effects of earthquakes, volcanoes, and glaciers; characterizes the copper and gold resources of the parklands; and describes outstanding locales within the park and preserve area. A glossary of geologic terms and a categorized list of additional sources of information complete this report.

  20. Late Cretaceous tectonothermal evolution of the southern Lhasa terrane, South Tibet: Consequence of a Mesozoic Andean-type orogeny (United States)

    Dong, Xin; Zhang, Ze-ming; Klemd, Reiner; He, Zhen-yu; Tian, Zuo-lin


    The Lhasa terrane of the southern Tibetan Plateau participated in a Mesozoic Andean-type orogeny caused by the northward subduction of the Neo-Tethyan oceanic lithosphere. However, metamorphic rocks, which can unravel details of the geodynamic evolution, are rare and only exposed in the south-eastern part of the Lhasa terrane. Therefore, we conducted a detailed petrological, geochemical and U-Pb zircon geochronological study of the late Cretaceous metamorphic rocks and associated gabbros from the Nyemo inlier of the southern Lhasa terrane. The Nyemo metamorphic rocks including gneisses, schists, marbles and calc-silicate rocks, experienced peak amphibolite-facies contact metamorphism under P-T conditions of 3.5-4.0 kbar and 642-657 °C with a very high geothermal gradient of 45-50 °C/km, revealing a distinct deflection from the steady-state geotherm during low-pressure metamorphism. Inherited magmatic zircon cores from the metamorphic rocks yielded protolith ages of 197-194 Ma, while overgrowth zircon rims yielded metamorphic ages of ca. 86 Ma. Whole-rock chemistry and zircon Hf isotopes suggest that the protoliths of the gneisses and schists are andesites and tuffs of the early Jurassic Sangri Group, which were derived from a depleted mantle source of a continental arc affinity. The coeval intimately-associated gabbro (ca. 86 Ma) crystallized under P-T conditions of 3.5-5.3 kbar and 914-970 °C, supplying the heat flux high enough to cause the contact metamorphism of the Sangri Group rock types. We propose that the intrusion of the gabbro and a simultaneous pressure increase of up to 4.0 kbar, which is related to crustal thickening due to crustal overthrusting and the intrusion of mafic material, resulted in the late Cretaceous metamorphism of the early Jurassic Sangri Group during an Andean-type orogeny. Furthermore the Nyemo metamorphic rocks, which have previously been considered to represent slivers of the Precambrian metamorphic basement of the Lhasa terrane

  1. Accretionary history of the Altai-Mongolian terrane: perspectives from granitic zircon U-Pb and Hf-isotope data (United States)

    Cai, Keda; Sun, Min; Xiao, Wenjiao


    The Central Asian Orogenic Belt (CAOB) consists of many tectonic terranes with distinct origin and complicated evolutionary history. Understanding of individual block is crucial to reconstruct the geodynamic history of the gigantic accetionary collage. This study presents zircon U-Pb ages and Hf isotopes for the granitoid rocks in the Russian Altai mountain range (including Gorny Altai, Altai-Mongolian terrane and CTUS suture zone between them), in order to clarify the timing of granitic magmatism, source nature, continental crustal growth and tectonic evolution. Our dating results suggest that granitic magmatism of the Russian Altai mountain range occurred in three major episodes including 445~429 Ma, 410~360 Ma and ~241 Ma. Most of the zircons within the Paleozoic granitoids present comparable positive ɛHf(t) values and Neoproterozoic crustal model ages, which favor the interpretation that the juvenile crustal materials produced in the early stage of CAOB were probably dominant sources for the Paleozoic magmatism in the region. The inference is also supported by widespread occurrence of short-lived juvenile materials including ophiolites, seamount relics and arc assemblages in the north CAOB. Consequently, the Paleozoic massive granitic rocks maybe not represent continental crustal growth at the time when they were emplaced, but rather record reworking of relatively juvenile Proterozoic crustal rocks although mantle-derived mafic magma was possibly involved to sever as heat engine during granitic magma generation. The Early Triassic granitic intrusion may be product in an intra-plate environment, as the case of same type rocks in the adjacent areas. The positive ɛHf(t) values (1.81~7.47) and corresponding Hf model ages (0.80~1.16 Ga) together with evidence of petrology are consistent with the interpretation that the parental magma of the Triassic granitic intrusion was produced from enriched mantle-derived sources under an usually high temperature condition

  2. Subduction metamorphism in the Himalayan ultrahigh-pressure Tso Morari massif: An integrated geodynamic and petrological modelling approach (United States)

    Palin, Richard M.; Reuber, Georg S.; White, Richard W.; Kaus, Boris J. P.; Weller, Owen M.


    The Tso Morari massif is one of only two regions where ultrahigh-pressure (UHP) metamorphism of subducted crust has been documented in the Himalayan Range. The tectonic evolution of the massif is enigmatic, as reported pressure estimates for peak metamorphism vary from ∼2.4 GPa to ∼4.8 GPa. This uncertainty is problematic for constructing large-scale numerical models of the early stages of India-Asia collision. To address this, we provide new constraints on the tectonothermal evolution of the massif via a combined geodynamic and petrological forward-modelling approach. A prograde-to-peak pressure-temperature-time (P-T-t) path has been derived from thermomechanical simulations tailored for Eocene subduction in the northwestern Himalaya. Phase equilibrium modelling performed along this P-T path has described the petrological evolution of felsic and mafic components of the massif crust, and shows that differences in their fluid contents would have controlled the degree of metamorphic phase transformation in each during subduction. Our model predicts that peak P-T conditions of ∼2.6-2.8 GPa and ∼600-620 ∘C, representative of 90-100 km depth (assuming lithostatic pressure), could have been reached just ∼3 Myr after the onset of subduction of continental crust. This P-T path and subduction duration correlate well with constraints reported for similar UHP eclogite in the Kaghan Valley, Pakistan Himalaya, suggesting that the northwest Himalaya contains dismembered remnants of what may have been a ∼400-km-long UHP terrane comparable in size to the Western Gneiss Region, Norway, and the Dabie-Sulu belt, China. A maximum overpressure of ∼0.5 GPa was calculated in our simulations for a homogeneous crust, although small-scale mechanical heterogeneities may produce overpressures that are larger in magnitude. Nonetheless, the extremely high pressures for peak metamorphism reported by some workers (up to 4.8 GPa) are unreliable owing to conventional thermobarometry

  3. Continuation, south of Oaxaca City (southern Mexico) of the Oaxaca-Juarez terrane boundary and of the Oaxaca Fault. Based in MT, gravity and magnetic studies (United States)

    Campos-Enriquez, J. O.; Corbo, F.; Arzate-Flores, J.; Belmonte-Jimenez, S.; Arango-Galván, C.


    The Oaxaca Fault represents Tertiary extensional reactivation of the Juarez shear zone constituting the boundary-suture between the Oaxaca and Juarez terranes (southern Mexico). South of Oaxaca City, the fault trace disappears and there are not clear evidences for its southward continuation at depth. The crust in southern México has been studied through seismic refraction, and seismological and magnetotelluric (MT) studies. The refraction studies did not image the Oaxaca Fault. However, previous regional MT studies suggest that the Oaxaca-Juarez terrane boundary lies to the east of the Zaachila and Mitla sub-basins, which implies sinistral displacement along the Donaji Fault. Campos-Enriquez et al. (2009) established the shallow structure of the Oaxaca-Juarez terrane boundary based in detailed gravity and magnetic studies. This study enabled: 1) to establish the shallow structure of the composite depression comprising three N-S sub-basins: the northern Etla and southern Zaachila sub-basins separated by the Atzompa sub-basin. According to the Oaxaca-Juarez terrane boundary is displaced sinistrally ca. 20 km along the E-W Donají Fault, which defines the northern boundary of the Zaachila sub-basin. At the same time,, the Oaxaca Fault may either continue unbroken southwards along the western margin of a horst in the Zaachila sub-basin or be offset along with the terrane boundary. This model implies that originally the suture was continuous south of the Donaji Fault. A constraint for the accreation of the Oaxaca and Juarez terranes. Thirty MT soundings were done in the area of the Central Valleys, Oaxaca City (southern Mexico). In particular we wanted to image the possible southward continuation of the Oaxaca Fault. 22 Mt sounding are located along two NE-SW profiles to the northern and to the south of the City of Oaxaca. To the north of Oaxaca City, the electrical resistivity distribution obtained show a clear discontinuity across the superficial trace of the Oaxaca

  4. Geology of the Severnaya Zemlya Archipelago and the North Kara Terrane in the Russian high Arctic (United States)

    Lorenz, Henning; Männik, Peep; Gee, David; Proskurnin, Vasilij


    The Severnaya Zemlya Archipelago is located at 80°N near the continental shelf break, between the Kara and Laptev seas. Sedimentary successions of Neoproterozoic and Palaeozoic age dominate the bedrock geology. Together with Northern Tajmyr, Severnaya Zemlya constitutes the main land areas of the North Kara Terrane (NKT), which is inferred here to have been a part of the Timanide margin of Baltica, i.e. an integral part of Baltica at least since the Vendian. Vendian turbidites derived from the Timanide Orogen are inferred to have been deposited on Neoproterozoic greenschist facies, granite-intruded basement. Shallow-water siliclastic deposition in the Early to Mid-Cambrian was followed by highly organic-rich shales in the Late Cambrian and influx of more turbidites. An episode of folding, the Kan’on River deformation, separates these formations from the overlying Tremadocian conglomerates and sandstones. In the Early Ordovician, rift-related magmatic rocks accompanied the deposition of variegated marls, sandstones, carbonates and evaporites. Dark shales and gypsiferous limestones characterise the Mid-Ordovician. Late Ordovician quartz-sandstones mark a hiatus, followed by carbonate rocks that extend up into and through most of the Silurian. The latter give way upwards into Old Red Sandstones, which are inferred to have been deposited in a Caledonian foreland basin. Deformation, reaching the area in the latest Devonian or earliest Carboniferous and referred to as the Severnaya Zemlya episode, is thought to be Caledonian-related. The dominating E-vergent structure was controlled by décollement zones in Ordovician evaporite-bearing strata; detachment folds and thrusts developed in the west and were apparently impeded by a barrier of Ordovician igneous rocks in the east. Below the décollement zones, the Neoproterozoic to Early Ordovician succession was deformed into open to close folds. The exposed strata in the lower structural level have been juxtaposed with

  5. Constraints of detrital zircon U-Pb ages and Hf isotopes on the provenance of the Triassic Yidun Group and tectonic evolution of the Yidun Terrane, Eastern Tibet (United States)

    Wang, Bai-Qiu; Wang, Wei; Chen, Wei Terry; Gao, Jian-Feng; Zhao, Xin-Fu; Yan, Dan-Ping; Zhou, Mei-Fu


    Eastern Tibet to the west of the Yangtze Block consists of the Yidun and Songpan-Ganzi Terranes, separated by the Ganzi-Litang suture zone. The Yidun Terrane includes the Zhongza Massif to the west, but the eastern part of the Yidun terrane is covered by the Yidun Group extending from the south (Shangri-La region) to the north (Changtai region). The Yidun Group, from the base upward, includes the Lieyi, Qugasi, Tumugou and Lanashan formations, which are mainly composed of volcanic-flysch successions. Based on the ages of volcanic interlayers and plutonic intrusions, depositional ages of the Qugasi and Tumugou formations are considered to be slightly older than 230 Ma and ca. 220-230 Ma respectively, which are prominently older than the previous estimates. The Yidun Group in the Changtai region has two prominent detrital zircon age peaks at 400-480 and 880-980 Ma and a minor peak at 2.45-2.50 Ga. This pattern suggests a detritus source from the Zhongza Massif, which was a micro-continent separated from the western Yangtze Block. In contrast, the Yidun Group in the Shangri-La region has various zircon age spectra among different formations. The Qugasi Formation in this region has detrital zircon age patterns similar to the Yidun Group in the Changtai region. However, the overlying Tumugou Formation shows distinct age peaks at Triassic (220-240 Ma), Neoproterozoic (~ 720-880 Ma), and Paleoproterozoic (~ 1.75-1.90 Ga). This age pattern is similar to that of the Xikang Group of the Songpan-Ganzi Terrane to the east. The detrital zircon age difference between the Qugasi and Tumugou formations in this region indicates a transition of sedimentary sources from the Zhongza Massif to locally distributed Triassic magmatic rocks at ~ 230 Ma. It is thus suggested that the Songpan-Ganzi Terrane may have been connected to or collided with the southern part of the Yidun Terrane during the Late Triassic, whereas the Songpan-Ganzi Terrane and the northern part of the Yidun Terrane

  6. 40Ar/39Ar incremental-release ages of biotite from a progressively remetamorphosed Archean basement terrane in southwestern Labrador

    International Nuclear Information System (INIS)

    Dallmeyer, R.D.


    Gneisses within Archean basement terrane adjacent to the southwestern portion of the Labrador Trough were variably retrograded during a regional metamorphism of Grenville age (ca. 1000 Ma). Bioties from non-retrograded segments of the gneiss terrane record 40 Ar/ 39 Ar plateau and isochron ages which date times of cooling following an episode of the Kenoran orogeny (2376-2391 Ma). A suite of gneiss samples displaying varying degrees of retrograde alteration was collected across the Grenville metamorphic gradient. Bioties in these samples show no petrographic evidence of retrograde alteration, however they do record internally discordant 40 Ar/ 39 Ar age spectra. Although the extent of internal discordance is variable, the overall character of the release patterns is similar with younger apparent ages recorded in intermediate-temperature gas fractions. The total-gas dates range from 2257+-27 Ma (northwest) to 1751+-23 Ma (southeast), suggesting that variable quantities of radiogenic argon were lost from the Archean biotites during Grenville metamorphism. The 'saddle-shaped' nature of the discordant spectra indicates that argon loss was not accomplished through single-stage, volume diffusion processes. (orig./ME)

  7. Geophysical interpretation of the gneiss terrane of northern Washington and southern British Columbia, and its implications for uranium exploration (United States)

    Cady, John W.; Fox, Kenneth F.


    The Omineca crystalline belt of northeastern Washington and southern British Columbia has a regional Bouguer gravity high, and individual gneiss domes within the terrane are marked by local gravity highs. Models of crustal structure that satisfy the limited available seismic-refraction data and explain the gravity high over the gneiss terrane permit the hypothesis that the core metamorphic complexes are the surface expression of a zone of dense infrastructure that makes up the upper 20 km (kilometers) of the crust within the crystalline belt. The Omineca crystalline belt is characterized regionally by low aeromagnetic relief. The gneiss domes and biotite- and biotite-muscovite granites are generally marked by low magnetic relief, whereas hornblende-biotite granites often cause magnetic highs. Exceptional magnetic highs mark zones of magnetic rock within the biotite- and biotite-muscovite granites and the gneiss domes; these areas are worthy of study, both to determine the origin and disposition of the magnetite and to explore the possible existence of uraniferous magnetite deposits.

  8. The Ellsworth terrane, coastal Maine: Geochronology, geochemistry, and Nd-Pb isotopic composition - Implications for the rifting of Ganderia (United States)

    Schulz, K.J.; Stewart, D.B.; Tucker, R.D.; Pollock, J.C.; Ayuso, R.A.


    The Ellsworth terrane is one of a number of fault-bounded blocks that occur along the eastern margin of Ganderia, the western-most of the peri-Gondwanan domains in the northern Appalachians that were accreted to Laurentia in the Paleozoic. Geologic relations, detrital zircon ages, and basalt geochemistry suggest that the Ellsworth terrane is part of Ganderia and not an exotic terrane. In the Penobscot Bay area of coastal Maine, the Ellsworth terrane is dominantly composed of bimodal basalt-rhyolite volcanic sequences of the Ellsworth Schist and unconformably overlying Castine Volcanics. We use new U-Pb zircon geochronology, geochemistry, and Nd and Pb isotopes for these volcanic sequences to constrain the petrogenetic history and paleotectonic setting of the Ellsworth terrane and its relationship with Ganderia. U-Pb zircon geochronology for rhyolites indicates that both the Ellsworth Schist (508.6 ?? 0.8 Ma) and overlying Castine Volcanics (503.5 ?? 2.5 Ma) are Middle Cambrian in age. Two tholefitic basalt types are recognized. Type Tb-1 basalt, present as pillowed and massive lava flows and as sills in both units, has depleted La and Ce ([La/Nd]N = 0.53-0.87) values, flat heavy rare earth element (REE) values, and no positive Th or negative Ta anomalies on primitive mantle-normalized diagrams. In contrast, type Th-2 basalt, present only in the Castine Volcanics, has stightly enriched LREE ([La/Yb]N = 1.42-2.92) values and no Th or Th anomalies. Both basalt types have strongly positive ??Nd (500) values (Th-1 = +7.9-+8.6; Th-2 = +5.6-+7.0) and relatively enriched Pb isotopic compositions (206Ph/204Pb = 18.037-19.784; 207/204Pb = 15.531-15.660; 2088Pb/204Pb = 37.810-38.817). The basalts have compositions transitional between recent normal and enriched mid-ocean-ridge basalt, and they were probably derived by partial melting of compositionatly heterogeneous asthenosphenc mantle. Two types of rhyolite also are present. Type R-1 rhyolite, which mostly occurs as tuffs

  9. GPR Imaging of Fault Related Folds in a Gold-Bearing Metasedimentary Sequence, Carolina Terrane, Southern Appalachian Mountains (United States)

    Diemer, J. A.; Bobyarchick, A. R.


    The Carolina terrane comprises Ediacaran to earliest Paleozoic mixed magmatic and sedimentary assemblages in the central and eastern Piedmont of the Southern Appalachian Mountains. The terrane was primarily deformed during the Late Ordovician Cherokee orogeny, that reached greenschist facies metamorphism. The Albemarle arc, a younger component of the Carolina terrane, contains volcanogenic metasedimentary rocks with intercalated mainly rhyolitic volcanic rocks. Regional inclined to overturned folds with axial planar cleavage verge southeast. At mesoscopic scales (exposures of a few square meters), folds sympathetic with regional folds are attenuated or truncated by ductile shear zones or contractional faults. Shear and fault zones are most abundant near highly silicified strataform zones in metagraywacke of the Tillery Formation; these zones are also auriferous. GPR profiles were collected across strike of two silicified, gold-bearing zones and enclosing metagraywacke to characterize the scale and extent of folding in the vicinity of ore horizons. Several GSSI SIR-3000 / 100 MHz monostatic GPR profiles were collected in profiles up to 260 meters long. In pre-migration lines processed for time zero and background removal, several clusters of shallow, rolling sigmoidal reflectors appeared separated by sets of parallel, northwest-dipping reflective discontinuities. These features are inferred to be reverse faults carrying contractional folds. After migration with an average velocity of 0.105 m/ns, vertical heights of the inferred folds became attenuated but not removed, and contractional fault reflections remained prominent. After migration, a highly convex-up cluster of reflections initially assumed to be a fold culmination resolved to an elliptical patch of high amplitudes. The patch is likely an undisclosed shaft or covered trench left by earlier gold prospecting. In this survey, useful detail appeared to a depth of 7.5 meters, and only a few gently inclined

  10. Cenozoic mantle composition evolution of southern Tibet indicated by Paleocene ( 64 Ma) pseudoleucite phonolitic rocks in central Lhasa terrane (United States)

    Qi, Yue; Gou, Guo-Ning; Wang, Qiang; Wyman, Derek A.; Jiang, Zi-Qi; Li, Qiu-Li; Zhang, Le


    The question of whether continental subduction processes in collisional orogenic belts can trigger wide-spread mantle metesomatism and crustal material recycling remains unresolved. Miocene (25-8 Ma) ultrapotassic rocks in southern Tibet are the only mantle-derived magmatic rocks emplaced after the collision between India and Asia and they have been linked to the onset of east-west extensional stresses as the surface uplift of the Tibetan Plateau reached near-maximum elevation. However, their petrogenesis remains highly controversial, particularly the issue of whether their extremely enriched Sr-Nd isotopic characteristics were related to metasomatism derived from subducted Indian continental materials during the Cenozoic. Here we report on a Paleocene silicate-unsaturated, pseudoleucite phonolitic dike, in the Rongniduo area of central Lhasa terrane. In-situ SIMS (secondary ion mass spectrometry) apatite U-Pb age indicates the dike was generated at 64.1 ± 4.2 Ma, which slightly predates the age of initial India and Asia collision (about 55-50 Ma). This is the oldest age yet reported for ultrapotassic rocks in southern Tibet. Samples from this dike have distinctly more depleted Sr-Nd (whole rock: (87Sr/86Sr)i = 0.7064 to 0.7062, εNd(t) = - 1.5 to 0.4; in situ apitite: (87Sr/86Sr)i = 0.7059 to 0.7060, εNd(t) = - 2.0 to 0.4) isotopic compositions, than those of Miocene (25-8 Ma) ultrapotassic rocks in the central Lhasa terrane ((87Sr/86Sr)i = 0.7106 to 0.7399, εNd(t) = - 10.6 to - 18.5). Our new data provides important constraints on pre-collisional mantle characteristics beneath the Lhasa terrane. We suggest that these 64 Ma pseudoleucite phonolitic rocks were derived from the enriched lithospheric mantle metasomatized by subducted Tethyan oceanic materials in response to Neo-Tethyan slab roll-back. As a consequence, the younger Miocene ultrapotassic rocks, which display different geochemical compositions from the pre-collisional ultrapotassic rocks, were most

  11. Geochronological and geochemical constraints on the origin of the Yunzhug ophiolite in the Shiquanhe-Yunzhug-Namu Tso ophiolite belt, Lhasa Terrane, Tibetan Plateau (United States)

    Zeng, Yun-Chuan; Xu, Ji-Feng; Chen, Jian-Lin; Wang, Bao-Di; Kang, Zhi-Qiang; Huang, Feng


    The formation of the Shiquanhe-Yunzhug-Namu Tso ophiolite mélange zone (SNMZ) within the Lhasa Terrane, Tibetan Plateau, is key to understanding the Mesozoic tectonic evolution of this terrane, which remains controversial. We show that the Yunzhug ophiolite in the central segment of the SNMZ formed at 150 Ma, based on U-Pb dating of zircons from a gabbroic sample in a well-developed sheeted dike complex. Geochemically, these mafic rocks are dominated by E-MORB-type compositions, along with minor amounts of rocks with P-MORB-type compositions. The samples also exhibit high εNd(t) values and lack negative Nb and Ta anomalies. Data for all the samples plot within the MORB array on a Th/Yb-Nb/Yb diagram. Therefore, these mafic rocks most likely formed in either a slow spreading oceanic setting or an embryonic ocean, and not in a back-arc basin as has been previously assumed. Taking into account the regional geology, we propose that the Yunzhug ophiolite is part of a distinct ophiolitic belt and represents material formed in an embryonic ocean within the Lhasa Terrane, which provides new insights into the Jurassic tectonic evolution of the Lhasa Terrane.

  12. Grenville age of basement rocks in Cape May NJ well: New evidence for Laurentian crust in U.S. Atlantic Coastal Plain basement Chesapeake terrane (United States)

    Sheridan, R.E.; Maguire, T.J.; Feigenson, M.D.; Patino, L.C.; Volkert, R.A.


    The Chesapeake terrane of the U.S. mid-Atlantic Coastal Plain basement is bounded on the northwest by the Salisbury positive gravity and magnetic anomaly and extends to the southeast as far as the Atlantic coast. It underlies the Coastal Plain of Virginia, Maryland, Delaware and southern New Jersey. Rubidium/Strontium dating of the Chesapeake terrane basement yields an age of 1.025 ?? 0.036 Ga. This age is typical of Grenville province rocks of the Middle to Late Proterozoic Laurentian continent. The basement lithologies are similar to some exposed Grenville-age rocks of the Appalachians. The TiO2 and Zr/P2O5 composition of the metagabbro from the Chesapeake terrane basement is overlapped by those of the Proterozoic mafic dikes in the New Jersey Highlands. These new findings support the interpretation that Laurentian basement extends southeast as far as the continental shelf in the U.S. mid-Atlantic region. The subcrop of Laurentian crust under the mid-Atlantic Coastal Plain implies unroofing by erosion of the younger Carolina (Avalon) supracrustal terrane. Dextral-transpression fault duplexes may have caused excessive uplift in the Salisbury Embayment area during the Alleghanian orogeny. This extra uplift in the Salisbury area may have caused the subsequent greater subsidence of the Coastal Plain basement in the embayment.

  13. U-Pb detrital zircon geochronology from the basement of the Central Qilian Terrane: implications for tectonic evolution of northeastern Tibetan Plateau (United States)

    Liu, Changfeng; Wu, Chen; Zhou, Zhiguang; Yan, Zhu; Jiang, Tian; Song, Zhijie; Liu, Wencan; Yang, Xin; Zhang, Hongyuan


    The Tuolai Group dominates the Central Qilian Terrane, and there are different opinions on the age and tectonic attribute of the Tuolai Group. Based on large-scale geologic mapping and zircon dating, the Tuolai Group is divided into four parts: metamorphic supracrustal rocks, Neoproterozoic acid intrusive rocks, early-middle Ordovician acid intrusive rocks and middle Ordovician basic intrusive rocks. The metamorphic supracrustal rocks are the redefined Tuolai complex-group and include gneiss and schist assemblage by faulting contact. Zircon U-Pb LA-MC-ICP-MS dating was conducted on these samples of gneiss and migmatite from the gneiss assemblage, quartzite, two-mica schist and slate from the schist assemblage. The five detrital samples possess similar age spectra; have detrital zircon U-Pb main peak ages of 1.7 Ga with youngest U-Pb ages of 1150 Ma. They are intruded by Neoproterozoic acid intrusive rocks. Therefore, the Tuolai Group belonging to late Mesoproterozoic and early Neoproterozoic. With this caveat in mind, we believe that U-Pb detrital zircon dating, together with the geologic constraints obtained from this study and early work in the neighboring regions. We suggest that the formation age of the entire crystalline basement rocks of metasedimentary sequence from the Central Qilian Terrane should be constrained between the Late Mesoproterozoic and the Late Neoproterozoic, but not the previous Paleoproterozoic. The basement of the Central Qilian Terrane contains the typical Grenville ages, which indicates the Centre Qilian Terrane have been experienced the Grenville orogeny event.

  14. Geochronology and geochemistry of the Early Jurassic Yeba Formation volcanic rocks in southern Tibet: Initiation of back-arc rifting and crustal accretion in the southern Lhasa Terrane (United States)

    Wei, Youqing; Zhao, Zhidan; Niu, Yaoling; Zhu, Di-Cheng; Liu, Dong; Wang, Qing; Hou, Zengqian; Mo, Xuanxue; Wei, Jiuchuan


    Understanding the geological history of the Lhasa Terrane prior to the India-Asia collision ( 55 ± 10 Ma) is essential for improved models of syn-collisional and post-collisional processes in the southern Lhasa Terrane. The Miocene ( 18-10 Ma) adakitic magmatism with economically significant porphyry-type mineralization has been interpreted as resulting from partial melting of the Jurassic juvenile crust, but how this juvenile crust was accreted remains poorly known. For this reason, we carried out a detailed study on the volcanic rocks of the Yeba Formation (YF) with the results offering insights into the ways in which the juvenile crust may be accreted in the southern Lhasa Terrane in the Jurassic. The YF volcanic rocks are compositionally bimodal, comprising basalt/basaltic andesite and dacite/rhyolite dated at 183-174 Ma. All these rocks have an arc-like signature with enriched large ion lithophile elements (LILEs; e.g., Rb, Ba and U) and light rare earth elements (LREEs) and depleted high field strength elements (HFSEs; e.g., Nb, Ta, Ti). They also have depleted whole-rock Sr-Nd and zircon Hf isotopic compositions, pointing to significant mantle isotopic contributions. Modeling results of trace elements and isotopes are most consistent with the basalts being derived from a mantle source metasomatized by varying enrichment of subduction components. The silicic volcanic rocks show the characteristics of transitional I-S type granites, and are best interpreted as resulting from re-melting of a mixed source of juvenile amphibole-rich lower crust with reworked crustal materials resembling metagraywackes. Importantly, our results indicate northward Neo-Tethyan seafloor subduction beneath the Lhasa Terrane with the YF volcanism being caused by the initiation of back-arc rifting. The back-arc setting is a likely site for juvenile crustal accretion in the southern Lhasa Terrane.

  15. Linking the southern West Junggar terrane to the Yili Block: Insights from the oldest accretionary complexes in West Junggar, NW China (United States)

    Ren, Rong; Han, Bao-Fu; Guan, Shu-Wei; Liu, Bo; Wang, Zeng-Zhen


    West Junggar is known to tectonically correlate with East Kazakhstan; however, the tectonic link of the southern West Junggar terrane to adjacent regions still remains uncertain. Here, we examined the oldest accretionary complexes, thus constraining its tectonic evolution and link during the Early-Middle Paleozoic. They have contrasting lithologic, geochemical, and geochronological features and thus, provenances and tectonic settings. The Laba Unit was derived from the Late Ordovician-Early Devonian continental arc system (peaking at 450-420 Ma) with Precambrian substrate, which formed as early as the Early Devonian and metamorphosed during the Permian; however, the Kekeshayi Unit was accumulated in an intra-oceanic arc setting, and includes the pre-Late Silurian and Late Silurian subunits with or without Precambrian sources. Integrated with the regional data, the southern West Junggar terrane revealed a tectonic link to the northern Yili Block during the Late Silurian to Early Devonian, as suggested by the comparable Precambrian zircon age spectra between the southern West Junggar terrane and the micro-continents in the southern Kazakhstan Orocline, the proximal accumulation of the Laba Unit in the continental arc atop the Yili Block, and the sudden appearance of Precambrian zircons in the Kekeshayi Unit during the Late Silurian. This link rejects the proposals of the southern West Junggar terrane as an extension of the northern Kazakhstan Orocline and the Middle Paleozoic amalgamation of West Junggar. A new linking model is thus proposed, in which the southern West Junggar terrane first evolved individually, and then collided with the Yili Block to constitute the Kazakhstan continent during the Late Silurian. The independent and contrasting intra-oceanic and continental arcs also support the Paleozoic archipelago-type evolution of the Central Asian Orogenic Belt.

  16. Precambrian Field Camp at the University of Minnesota Duluth - Teaching Skills Applicable to Mapping Glaciated Terranes of the Canadian Shield (United States)

    Miller, J. D.; Hudak, G. J.; Peterson, D.


    Since 2007, the central program of the Precambrian Research Center (PRC) at the University of Minnesota Duluth has been a six-week geology field camp focused on the Precambrian geology of the Canadian Shield. This field camp has two main purposes. First and foremost is to teach students specialized field skills and field mapping techniques that can be utilized to map and interpret Precambrian shield terranes characterized by sparse outcrop and abundant glacial cover. In addition to teaching basic outcrop mapping technique , students are introduced to geophysical surveying (gravity, magnetics), glacial drift prospecting, and drill core logging techniques in several of our geological mapping exercises. These mapping methodologies are particularly applicable to minerals exploration in shield terranes. The second and equally important goal of the PRC field camp is to teach students modern map-making and map production skills. During the fifth and sixth weeks of field camp, students conduct "capstone" mapping projects. These projects encompass one week of detailed bedrock mapping in remote regions of northern Minnesota that have not been mapped in detail (e.g. scales greater than 1:24,000) and a second week of map-making and map generation utilizing geographic information systems (currently ArcGIS10), graphics software packages (Adobe Illustrator CS4), and various imaging software for geophysical and topographic data. Over the past five years, PRC students and faculty have collaboratively published 21 geologic maps through the Precambrian Research Center Map Series. These maps are currently being utilized in a variety of ways by industry, academia, and government for mineral exploration programs, development of undergraduate, graduate, and faculty research projects, and for planning, archeological studies, and public education programs in Minnesota's state parks. Acquisition of specialized Precambrian geological mapping skills and geologic map-making proficiencies has

  17. Petrography and geochemistry of five granitic plutons from south central Uruguay: contribution to the knowledge of the Piedra Alta terrane

    International Nuclear Information System (INIS)

    Preciozzi, F.


    Granitoid rocks in south-central Uruguay are largely concentrated in three east-west trending metamorphic belts, known as (from south to north) the Montevideo Belt, the San José Belt and the Arroyo Grande Belt. These belts are separated from one another by intervening bands of gneisses of granitic composition. The whole assemblage, the gneisses as well as the metamorphic belts and their associated granites, collectively constitute the Piedra Alta Terrane. Five of these granite plutons, two from the San José Belt and three from the Arroyo Grande Belt, have been studied in some detail and the chemical composition of 86 samples (major elements as well as a selected suite of trace elements) have been determined. These data, as well as Rb-Sr isotopic data, show that these plutons are typically composite in nature, and that the various units range in age from 1900 Ma to 2500 Ma. The older ages were obtained from the main units of the plutons themselves whereas the younger ages are from late dykes which were emplaced into the plutons and which are clearly not related to them. The plutons are predominantly, but not exclusively, of calc-alkaline affinity and are typically synorogenic whereas the dykes are post-orogenic and are either calc-alkaline or alkaline in composition. These data have been incorporated into a tectonic model for the Piedra Alta Terrane which is considerably different from that heretofore proposed. The essential features of the geological history of the area are: 1) development of an older ''basement'' of granitic gneisses 2) deposition, upon or adjacent to this gneisses basement, of a typical Archean greenstone belt assemblage (no komatiites so far reported) 3) Paleo-proterozoic metamorphism, followed by syn-tectonic to post-tectonic intrusion of the plutonic rocks 4) major tectonic dislocation(s) associated with the Transamazonian orogeny 5) dyke emplacement (post-orogenic to anorogenic) following the Transamazonian orogeny

  18. Integration of potential and quasipotential geophysical fields and GPR data for delineation of buried karst terranes in complex environments (United States)

    Eppelbaum, L. V.; Alperovich, L. S.; Zheludev, V.; Ezersky, M.; Al-Zoubi, A.; Levi, E.


    Karst is found on particularly soluble rocks, especially limestone, marble, and dolomite (carbonate rocks), but is also developed on gypsum and rock salt. Subsurface carbonate rocks involved in karst groundwater circulation considerably extend the active karst realm, to perhaps 14% of the world's land area (Price, 2009). The phenomenon of the solution weathering of limestone is the most widely known in the world. Active sinkholes growth appears under different industrial constructions, roads, railways, bridges, airports, buildings, etc. Regions with arid and semi-arid climate occupy about 30% of the Earth's land. Subsurface in arid regions is characterized by high variability of physical properties both on lateral and vertical that complicates geophysical survey analysis. Therefore for localization and monitoring of karst terranes effective and reliable geophysical methodologies should be applied. Such advanced methods were developed in microgravity (Eppelbaum et al., 2008; Eppelbaum, 2011b), magnetic (Khesin et al., 1996; Eppelbaum et al., 2000, 2004; Eppelbaum, 2011a), induced polarization (Khesin et al., 1997; Eppelbaum and Khesin, 2002), VLF (Eppelbaum and Khesin, 1992; Eppelbaum and Mishne, 2012), near-surface temperature (Eppelbaum, 2009), self-potential (Khesin et al., 1996; Eppelbaum and Khesin, 2002), and resistivity (Eppelbaum, 1999, 2007a) surveys. Application of some of these methodologies in the western and eastern shores of the Dead Sea area (e.g., Eppelbaum et al., 2008; Ezersky et al., 2010; Al-Zoubi et al., 2011) and in other regions of the world (Eppelbaum, 2007a) has shown their effectiveness. The common procedures for ring structure identification against the noise background and probabilistic-deterministic methods for recognizing the desired targets in complex media are presented in Khesin and Eppelbaum (1997), Eppelbaum et al. (2003), and Eppelbaum (2007b). For integrated analysis of different geophysical fields (including GPR images) intended

  19. The Cannery Formation--Devonian to Early Permian arc-marginal deposits within the Alexander Terrane, Southeastern Alaska (United States)

    Karl, Susan M.; Layer, Paul W.; Harris, Anita G.; Haeussler, Peter J.; Murchey, Benita L.


    cherts on both Admiralty and Kupreanof Islands contain radiolarians as young as Permian, the age of the Cannery Formation is herein extended to Late Devonian through early Permian, to include the early Permian rocks exposed in its type locality. The Cannery Formation is folded and faulted, and its stratigraphic thickness is unknown but inferred to be several hundred meters. The Cannery Formation represents an extended period of marine deposition in moderately deep water, with slow rates of deposition and limited clastic input during Devonian through Pennsylvanian time and increasing argillaceous, volcaniclastic, and bioclastic input during the Permian. The Cannery Formation comprises upper Paleozoic rocks in the Alexander terrane of southeastern Alaska. In the pre-Permian upper Paleozoic, the tectonic setting of the Alexander terrane consisted of two or more evolved oceanic arcs. The lower Permian section is represented by a distinctive suite of rocks in the Alexander terrane, which includes sedimentary and volcanic rocks containing early Permian fossils, metamorphosed rocks with early Permian cooling ages, and intrusive rocks with early Permian cooling ages, that form discrete northwest-trending belts. After restoration of 180 km of dextral displacement of the Chilkat-Chichagof block on the Chatham Strait Fault, these belts consist, from northeast to southwest, of (1) bedded chert, siliceous argillite, volcaniclastic turbidites, pillow basalt, and limestone of the Cannery Formation and the Porcupine Slate of Gilbert and others (1987); (2) greenschist-facies Paleozoic metasedimentary and metavolcanic rocks that have Permian cooling ages; (3) silty limestone and calcareous argillite interbedded with pillow basalt and volcaniclastic rocks of the Halleck Formation and the William Henry Bay area; and (4) intermediate-composition and syenitic plutons. These belts correspond to components of an accretionary complex, contemporary metamorphic rocks, forearc-basin deposits,

  20. On the metamorphic history of an Archaean granitoid greenstone terrane, East Pilbara, Western Australia, using the 40Ar/39Ar age spectrum technique

    International Nuclear Information System (INIS)

    Wijbrans, J.R.; McDougall, I.


    Age spectrum analyses of blue-green hornblendes from amphibolites from the Western Shaw Belt, East Pilbara, Western Australia, indicate an age of at least 3200 Ma for early regional metamorphism. Ages on hornblende and muscovite from the narrow contact zone with the adjacent Yule Batholith probably data updoming of the granitoid gneiss terranes at 2950 Ma. Hornblendes from within the Shaw Batholith and from a contact zone of a post-tectonic granitoid yield ages of 2840-2900 Ma, indicating either prolonged high temperatures within the granitoid gneiss terranes or a separate thermal pulse associated with the intrusion of post-tectonic granitoids. The preservation of very old hornblendes in a narrow greenstone belt surrounded by massive granitoid gneiss domes indicates that remarkable contrasts in metamorphic geotherms existed over short distances during the Late Archaean, suggesting that updoming occurred during a period of rapid tectonism. (orig.)

  1. On the metamorphic history of an Archaean granitoid greenstone terrane, East Pilbara, Western Australia, using the /sup 40/Ar//sup 39/Ar age spectrum technique

    Energy Technology Data Exchange (ETDEWEB)

    Wijbrans, J.R.; McDougall, I.


    Age spectrum analyses of blue-green hornblendes from amphibolites from the Western Shaw Belt, East Pilbara, Western Australia, indicate an age of at least 3200 Ma for early regional metamorphism. Ages on hornblende and muscovite from the narrow contact zone with the adjacent Yule Batholith probably data updoming of the granitoid gneiss terranes at 2950 Ma. Hornblendes from within the Shaw Batholith and from a contact zone of a post-tectonic granitoid yield ages of 2840-2900 Ma, indicating either prolonged high temperatures within the granitoid gneiss terranes or a separate thermal pulse associated with the intrusion of post-tectonic granitoids. The preservation of very old hornblendes in a narrow greenstone belt surrounded by massive granitoid gneiss domes indicates that remarkable contrasts in metamorphic geotherms existed over short distances during the Late Archaean, suggesting that updoming occurred during a period of rapid tectonism.

  2. Paleomagnetism of Early Paleozoic Rocks from the de Long Archipelago and Tectonics of the New Siberian Islands Terrane (United States)

    Metelkin, D. V.; Chernova, A. I.; Matushkin, N. Y.; Vernikovskiy, V. A.


    The De Long archipelago is located to the north of the Anjou archipelago as a part of a large group between the Laptev Sea and the East Siberian Sea - the New Siberian Islands and consists of Jeannette Island, Bennett Island and Henrietta Island. These islands have been shown to be part of a single continental terrane, whose tectonic history was independent of other continental masses at least since the Ordovician. Paleomagnetic and precise geological data for the De Long archipelago were absent until recently. Only in 2013 special international field trips to the De Long Islands could be organized and geological, isotope-geochronological and paleomagnetic studies were carried out.On Jeannette Island a volcanic-sedimentary sequence intruded by mafic dikes was described. The age of these dikes is more likely Early Ordovician, close to 480 Ma, as evidenced by the results of our 40Ar/39Ar and paleomagnetic investigations of the dolerites as well as the result from detrital zircons in the host rocks published before. On Bennett Island, there are widespread Cambrian-Ordovician mainly terrigenous rocks. Paleomagnetic results from these rocks characterize the paleogeographic position of the De Long archipelago at 465 Ma and perhaps at 530 Ma, although there is no evidence for the primary origin of magnetization for the latter. On Henrietta Island the Early Cambrian volcanic-sedimentary section was investigated. A paleomagnetic pole for 520 Ma was obtained and confirmed by new 40Ar/39Ar results. Adding to our previous paleomagnetic data for the Anjou archipelago the extended variant of the apparent polar wander path for the New Siberian Island terrane was created. The established paleolatitudes define its location in the equatorial and subtropical zone no higher than 40 degrees during the Early Paleozoic. Because there are no good confirmations for true polarity and related geographic hemisphere we present two possibilities for tectonic reconstruction. But both these

  3. Paleomagnetic data from the Caborca terrane, Mexico: Implications for Cordilleran tectonics and the Mojave-Sonora megashear hypothesis (United States)

    Molina Garza, Roberto S.; Geissman, John W.


    Two ancient magnetizations have been isolated in rocks of the Caborca terrane, northwest Mexico. The characteristic magnetizations of Neoproterozoic and Paleozoic miogeoclinal shelf-strata, arc-derived Lower Jurassic marine strata, and Jurassic volcanic and volcaniclastic rocks are of dual polarity and east-northeast declination (or south-southwest) and shallow inclination. Magnetizations in Neoproterozoic and Paleozoic miogeoclinal strata are interpreted as secondary (J*) and to be of similar age to those observed in Lower and Middle Jurassic rocks. Remanence acquisition is bracketed between about 190 and 160 Ma. The overall mean (D=15.0°, I=8.5° n=38 sites; six localities; k=19.1, α95=5.5°) suggests a moderate to large clockwise rotation of 12 to 50° (depending on reference direction assumed) of the Caborca terrane, and rocks of the Sonoran segment of the Cordilleran volcanic arc, with respect to the North America craton. When compared with expected inclinations, observed values are not anomalously steep, arguing against statistically significant southward latitudinal displacement of the Caborca block after remanence acquisition. Late Cretaceous intrusions yield primary, dual-polarity steep inclination ``K'' magnetizations (D=341.4°, I=52.3° n=10 sites; five localities; k=38.3, α95=7.9°) and have locally remagnetized Neoproterozoic and Jurassic strata. When present, secondary (K*) magnetizations in Neoproterozoic strata are of higher coercivity and higher unblocking temperature than the characteristic (J*) magnetization. Importantly, the regional internal consistency of data for Late Cretaceous intrusions suggests that effects of Tertiary tilt or rotation about a vertical axis over the broad region sampled (~5000 km2) are not substantial. Late Cretaceous primary (K) magnetizations and secondary (K*) magnetizations yield a combined mean of D=348.1°, I=50.7° (N=10 localities; 47 sites; k=53.5, α95=6.7°), indicating at most small (displacement is near

  4. Gravity and magnetic survey of the Oaxaca city region: Cenozoic horst-and-graben structure superimposed on the Oaxaca-Juarez terrane boundary, southern Mexico (United States)

    Campos-Enríquez, J. O.; Belmonte-Jiménez, S. I.; Keppie, J. D.; Ortega-Gutiérrez, F.; Arzate, J. A.; Martínez-Silva, J.; Martínez-Serrano, R. G.


    A geophysical survey of the Oaxaca Fault along the north-trending Etla and Zaachila valleys area, southern Mexico, shows a series of NNW-SSE Bouguer and magnetic anomalies with steeper gradients towards the east. The Oaxaca Fault represents Tertiary extensional reactivation of the Juarez shear zone that constitutes the boundary between the Oaxaca and Juárez terranes. Cooperative interpretation of six combined gravity and magnetic NE-SW profiles perpendicular to the valleys indicates the presence of a composite depression comprising three N-S sub-basins: the northern Etla and southern Zaachila sub-basins separated by the Atzompa sub-basin. The Etla sub-basin is bounded by the moderately E-dipping, Etla Fault and the more steeply W-dipping Oaxaca Fault, which together constitute a graben that continues southwards into the Atzompa graben. The deeper Zaachila sub-basin, south of Oaxaca city, is a wide V-shaped graben with a horst in the middle. The new geophysical data suggest that the Oaxaca-Juarez terrane boundary is displaced sinistrally ca. 20 km along the E-W Donají Fault, which defines the northern boundary of the Zaachila sub-basin. On the other hand, the Oaxaca Fault may either continue unbroken southwards along the western margin of the horst in the Zaachila sub-basin or be offset along with the terrane boundary. The sinistral movement may have taken place either during the Late Mesozoic-Early Cenozoic, Laramide Orogeny as a lateral ramp in the thrust plane or under Miocene-Pliocene, NE-SW extension. The former suggests that the Donají Fault is a transcurrent fault, whereas the latter implies that it is a transfer fault. The models imply that originally the suture was continuous south of the Donaji Fault and provide a constraint for the accretion of the Oaxaca and Juarez terranes.

  5. Early Cretaceous I-type granites in the Tengchong terrane: New constraints on the late Mesozoic tectonic evolution of southwestern China

    Directory of Open Access Journals (Sweden)

    Yi Fang


    Full Text Available The Early Cretaceous granitoids that are widespread in the Tengchong terrane of Southwest China play a critical role in understanding the tectonic framework associated with the Tethyan oceans. In this study, we present a detailed description of zircon U–Pb ages, whole-rock geochemistry and Hf isotopes for the Laoxiangkeng pluton in the eastern Tengchong terrane and elucidate their petrogenesis and geodynamic implications. Zircon U–Pb dating of the Laoxiangkeng pluton yields ages of 114 ± 1 Ma and 115 ± 1 Ma, which imply an Early Cretaceous magmatic event. The Laoxiangkeng pluton enriched in Si and Na, is calc-alkaline and metaluminous, and has the characteristics of highly fractionated I-type granites. Zircons from the pluton have calculated εHf(t values of −12.7 to −3.7 and two-stage model ages of 1327–1974 Ma, respectively, indicating a mixed source of partial melting of Paleo-Neoproterozoic crust-derived compositions with some inputs of mantle-derived magmas. By integrating all available data for the regional tectonic evolution of the eastern Tethys tectonic domain, we conclude that the Early Cretaceous magmatism in the Tengchong terrane was produced by the northeastward subduction of the Meso-Tethyan Bangong–Nujiang Ocean.

  6. 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


    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)

  7. Petrography and geochronology (U/Pb-Sm/Nd) the Passagem Granite, Pensamiento Granitoid Complex, Paragua Terrane, SW Amazon Craton, Mato Grosso, Brazil

    International Nuclear Information System (INIS)

    Jesus, Gisely Carmo de; Sousa, Maria Zelia Aguiar de; Ruiz, Amarildo Salina; Matos, Joao Batista de


    The Passagem granite includes stocks, plugs and dikes located in the Ricardo Franco hill - Vila Bela da Santissima Trindade region - state of Mato Grosso, central Brazil. The Passagem Granite is included in the Paragua terrane - SW Amazonian Craton. It consists of isotropic monzogranite, sienogranite and more rarely granodiorites with leucocratic dark gray to white color. These rocks range from hypidomorphic inequigranular to xenomorphic texture, fine to medium grained. Biotite is the only primary mafic present as essential phase and characterize an expanded slightly acid sequence formed by a sub-alkaline magmatism of high-potassium calc-alkaline, slightly peraluminous composition from arc magmatic tectonic environment during a post-collisional period. Mechanism of fractional crystallization of plagioclase, biotite, titanite, apatite and zircon associated with simultaneous crustal assimilation are suggested for the evolution of these rocks. The results support the hypothesis of a post-collisional magmatism in the Paragua terrane at 1284 +- 20 Ma corresponding to the crystallization age of the Passagem granite. This paper propose that Passagem Granite represents as an extension in Brazilian terrane of the Pensamiento Granitoid Complex. (author)

  8. Ancient terrane boundaries as probable seismic hazards: A case study from the northern boundary of the Eastern Ghats Belt, India

    Directory of Open Access Journals (Sweden)

    Saibal Gupta


    Full Text Available In the eastern part of the Indian shield, late Paleozoic–Mesozoic sedimentary rocks of the Talchir Basin lie precisely along a contact of Neoproterozoic age between granulites of the Eastern Ghats Mobile Belt (EGMB and amphibolite facies rocks of the Rengali Province. At present, the northern part of the basin experiences periodic seismicity by reactivation of faults located both within the basin, and in the Rengali Province to the north. Detailed gravity data collected across the basin show that Bouguer anomalies decrease from the EGMB (∼+15 mGal, through the basin (∼−10 mGal, into the Rengali Province (∼−15 mGal. The data are consistent with the reportedly uncompensated nature of the EGMB, and indicate that the crust below the Rengali Province has a cratonic gravity signature. The contact between the two domains with distinct sub-surface structure, inferred from gravity data, coincides with the North Orissa Boundary Fault (NOBF that defines the northern boundary of the Talchir Basin. Post-Gondwana faults are also localized along the northern margin of the basin, and present-day seismic tremors also have epicenters close to the NOBF. This indicates that the NOBF was formed by reactivation of a Neoproterozoic terrane boundary, and continues to be susceptible to seismic activity even at the present-day.

  9. 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 (United States)

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


    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

  10. Evidence From Detrital Zircon U-Pb Analysis for Suturing of Pre-Mississippian Terranes in Arctic Alaska (United States)

    Moore, T. E.; Potter, C. J.; O'Sullivan, P. B.; Aleinikoff, J. N.


    Detrital zircon U-Pb ages of pre-Mississippian sandstones were determined using SHRIMP and LA-ICPMS techniques for four key geographic parts of the Arctic Alaska terrane, northern Alaska. In the northeastern Brooks Range, a sample of quartz-rich turbidites from the Proterozoic Neroukpuk Quartzite yielded zircon ages ranging from 980 Ma to 2.9 Ga with clusters at 980-1100 Ma, 1680-1850 Ma and 2220-2660 Ma. Quartz and chert-bearing sandstone in the Tulageak well from Ordovician-Silurian argillite in basement beneath the North Slope yielded a broad spectrum of ages between 1.0 to 2.1 Ga and 2.8 Ga, including peaks at 1.0-1.2 and 1.5-1.7 Ga. Paleozoic zircons cluster at 390 and 440 Ma in this sample, indicating it is Devonian. Lithic sandstone from the Silurian Iviagik Group at Cape Dyer on the Lisburne Peninsula yielded a variety of ages from 450 to 1600 Ma, with a large peak at 475-600 Ma and several grains between 1.9 and 2.5 Ga. In contrast to the broad distributions of the latter two samples, zircons in metamorphosed Proterozoic-Cambrian(?) lithic sandstone from the an unnamed metagraywacke unit near Mt. Snowden on the Dalton Highway in the southern Brooks Range are largely 600-650 Ma with lesser clusters at 1050-1200 Ma and 1600-1900 Ga. Samples of quartz-rich Mississippian sandstone at the base of the unconformably overlying Mississippian to Triassic Ellesmerian sequence near three of the pre-Mississippian sample locations were also analyzed. Mississippian sandstones from the West Dease well (near the Tulageak well) and at Cape Dyer on the Lisburne Peninsula display zircon distributions similar to those found in the underlying pre-Mississippian samples, indicating the Mississippian clastic strata are locally derived and that the observed zircon distributions are representative of a broad area. However, the Mississippian Kekiktuk Conglomerate, which rests on the Neroukpuk Quartzite in the northeastern Brooks Range, also contains a variety of ages between 560 and

  11. The metallogeny of Late Triassic rifting of the Alexander terrane in southeastern Alaska and northwestern British Columbia (United States)

    Taylor, C.D.; Premo, W.R.; Meier, A.L.; Taggart, J.E.


    A belt of unusual volcanogenic massive sulfide (VMS) occurrences is located along the eastern margin of the Alexander terrane throughout southeastern Alaska and northwestern British Columbia and exhibits a range of characteristics consistent with a variety of syngenetic to epigenetic deposit types. Deposits within this belt include Greens Creek and Windy Craggy, the economically most significant VMS deposit in Alaska and the largest in North America, respectively. The occurrences are hosted by a discontinuously exposed, 800-km-long belt of rocks that consist of a 200- to 800-m-thick sequence of conglomerate, limestone, marine elastic sedimentary rocks, and tuff intercalated with and overlain by a distinctive unit of mafic pyroclastic rocks and pillowed flows. Faunal data bracket the age of the host rocks between Anisian (Middle Triassic) and late Norian (late Late Triassic). This metallogenic belt is herein referred to as the Alexander Triassic metallogenic belt. The VMS occurrences show systematic differences in degree of structural control, chemistry, and stratigraphic setting along the Alexander Triassic metallogenic belt that suggest important spatial or temporal changes in the tectonic environment of formation. At the southern end of the belt, felsic volcanic rocks overlain by shallow-water limestones characterize the lower part of the sequence. In the southern and middle portion of the belt, a distinctive pebble conglomerate marks the base of the section and is indicative of high-energy deposition in a near slope or basin margin setting. At the northern end of the belt the conglomerates, limestones, and felsic volcanic rocks are absent and the belt is composed of deep-water sedimentary and mafic volcanic rocks. This northward change in depositional environment and lithofacies is accompanied by a northward transition from epithermal-like structurally controlled, discontinuous, vein- and pod-shaped, Pb-Zn-Ag-Ba-(Cu) occurrences with relatively simple mineralogy

  12. Detrital rutile geochemistry and thermometry from the Dabie orogen: Implications for source-sediment links in a UHPM terrane (United States)

    Liu, Lei; Xiao, Yilin; Wörner, G.; Kronz, A.; Simon, K.; Hou, Zhenhui


    This study explores the potential of detrital rutile geochemistry and thermometry as a provenance tracer in rocks from the Central Dabie ultrahigh-pressure metamorphic (UHPM) zone in east-central China that formed during Triassic continental collision. Trace element data of 176 detrital rutile grains selected from local river sediments and 91 rutile grains from distinct bedrocks in the Shuanghe and Bixiling areas, obtained by both electron microprobe (EMP) and in situ LA-ICP-MS analyses, suggest that geochemical compositions and thermometry of detrital rutiles are comparable to those from their potential source rocks. After certification of the Cr-Nb discrimination method for the Central Dabie UHPM zone, we show that 29% of the detrital rutiles in the Shuanghe area were derived from metamafic sources whereas in the Bixiling area that it is up to 76%. Furthermore, the proportion of distinct types of detrital rutiles combined with modal abundances of rutile in metapelites and metamafic bedrocks can be used to estimate the proportion of different source lithologies. Based on this method the proportion of mafic source rocks was estimated to ∼10% at Shuanghe and >60% at Bixiling, respectively, which is consistent with the proportions of eclogite (the major rutile-bearing metamafic rock) distribution in the field. Therefore, the investigation of detrital rutiles is a potential way to evaluate the proportion of metamafic rocks and even to prospect for metamafic bodies in UHPM terranes. Zr-in-rutile temperatures were calculated at different pressures and compared with temperatures derived from rock-in rutiles and garnet-clinopyroxene Fe-Mg thermometers. Temperatures calculated for detrital rutiles range from 606 °C to 707 °C and 566 °C to 752 °C in Shuanghe and Bixiling, respectively, at P = 3 GPa with an average temperatures of ca. 630 °C for both areas. These temperature averages and ranges are similar to those calculated for rutiles from surrounding source rocks

  13. Silicate-Oxide Equilibria in the Wilson Lake Terrane, Labrador - Evidence for a Pre- Metamorphic Oxidizing Event (United States)

    Korhonen, F. J.; Stout, J. H.


    The presence of Fe3+ and Ti in silicates and their presumed equilibration with Fe2+-Fe3+-Ti oxide minerals has long been recognized as an important factor in metamorphic phase equilibria. The Red Wine Mountains massif is a granulite facies unit in the Wilson Lake terrane of central Labrador, where this equilibration is especially important for estimating both temperature and fO2 during peak metamorphism. Peak assemblages are sapphirine + quartz, and orthopyroxene + sillimanite + quartz. The coexisting oxides, which are largely responsible for the pronounced aeromagnetic high of the massif, consist of nearly pure magnetite and an exsolved titanohematite. Estimates of fO2 based on magnetite + integrated titanohematite compositions are slightly below that defined by the pure magnetite-hematite buffer. This assemblage is also responsible for the magnetic signature of metagabbro and metanorite dikes, a fact which challenges the conventional wisdom that the high Fe3+ content of the host paragneisses was inherited from a highly oxidized ferruginous shale. We suggest here that prior to granulite facies metamorphism, an oxidizing hydrothermal event either coeval or following the emplacement of mafic dikes into the paragneiss host was responsible for the highly oxidized nature of the massif as a whole. Subsequent metamorphism then produced the observed assemblages. This scenario is supported by recent U-Pb zircon and monazite ages of ca. 1626 ± 10 Ma, which indicate that both metagabbro dikes and host paragneiss were metamorphosed at the same time. Dike emplacement and the oxidizing event must have preceded 1626 Ma. The implications of this pre-metamorphic oxidizing event is that Fe3+ becomes an inherent and fixed component in the chemical system during metamorphism. Phase relationships, preliminary thermodynamic modeling, and geothermobarometric constraints indicate that peak temperatures are lower than those previously determined for Fe3+-absent systems. More appropriate

  14. Early Jurassic Volcanism in the South Lhasa Terrane, Southern Tibet: Record of Back-arc Extension in the Active Continental Margin (United States)

    Wei, Y.; Zhao, Z.; Zhu, D. C.; Wang, Z.; Liu, D.; Mo, X.


    Indus-Yarlung Zangbo Suture Zone (IYZSZ) represents the Mesozoic remnants of the Neo-Tethyan Ocean lithosphere after its northward subduction beneath the Lhasa Terrane. The evolution of the Neo-Tethyan Ocean prior to India-Asia collision remains unclear. To explore this period of history, we investigate zircon U-Pb geochronology, geochemistry and Nd-Hf isotopes of the Early Jurassic bimodal-like volcanic sequence around Dagze area, south Tibet. The volcanic sequence comprises calc-alkaline basalts to rhyolites whereas intermediate components are volumetrically restricted. Zircons from a basaltic andesite yielded crystallization age of 178Ma whereas those from 5 silicic rocks were dated at 183-174Ma, which suggest that both the basaltic and the silicic rocks are coeval. The basaltic rocks are enriched in LREE and LILE, and depleted in HFSE, with Epsilon Nd(t) of 1.6-4.0 and zircon Epsilon Hf(t) of 0.7-11.8, which implies that they were derived from a heterogenetic mantle source metasomatized by subduction components. Trace element geochemistry shows that the basaltic rocks are compositionally transitional from normal mid-ocean ridge basalts (N-MORB) to island arc basalts (IAB, e.g. Zedong arc basalts of ~160-155Ma in the south margin of Lhasa Terrane), with the signature of immature back-arc basin basalts. The silicic rocks display similar Nd-Hf isotopic features of the Gangdese batholith with Epsilon Nd(t) of 0.9-3.4 and zircon Epsilon Hf(t) of 2.4-17.7, indicating that they were possibly generated by anatexis of basaltic juvenile lower crust, instead of derived from the basaltic magma. These results support an Early to Middle Jurassic (183-155Ma) model that the back-arc extension tectonic setting were existing in the active continental margin in the south Lhasa Terrane.

  15. Sedimentology of Hirnantian glaciomarine deposits in the Balkan Terrane, western Bulgaria: Fixing a piece of the north peri-Gondwana jigsaw puzzle (United States)

    Chatalov, Athanas


    Glaciomarine deposits of late Hirnantian age in the western part of the Palaeozoic Balkan Terrane have persistent thickness ( 7 m) and lateral uniformity in rock colour, bedding pattern, lithology, and sedimentary structures. Four lithofacies are distinguished from base to top: lonestone-bearing diamictites, interbedded structureless mudstones, crudely laminated diamictites, and finely laminated mudstones. The diamictites are clast-poor to clast-rich comprising muddy to sandy varieties. Their compositional maturity is evidenced by the very high amount of detrital quartz compared to the paucity of feldspar and unstable lithic grains. Other textural components include extraclasts derived from the local Ordovician basement, mudstone intraclasts, and sediment aggregates. Turbate structures, grain lineations, and soft sediment deformation of the matrix below larger grains are locally observed. Sedimentological analysis reveals that deposition occurred in an ice-intermediate to ice-distal, poorly agitated shelf environment by material supplied from meltwater buoyant plumes and rain-out from ice-rafted debris. Remobilization by mass-flow processes (cohesive debris flows and slumps) was an important mechanism particularly for the formation of massive diamictites. The glaciomarine deposits represent a typical deglaciation sequence reflecting retreat of the ice front (grounded or floating ice sheet), relative sea-level rise and gradually reduced sedimentation rate with increasing contribution from suspension fallout. This sequence was deposited on the non-glaciated shelf of the intracratonic North Gondwana platform along the southern margin of the Rheic Ocean. The Hirnantian strata of the Balkan Terrane can be correlated with similar glaciomarine deposits known from peri-Gondwana terranes elsewhere in Europe showing clear 'Armorican affinity'. Several lines of evidence suggest that the provenance of siliciclastic material was associated mainly with sedimentary recycling of

  16. The Dom Feliciano belt (Brazil-Uruguay)and its fore land (Rio de la Plata Craton): framework, tectonic evolution and correlations with similar terranes of southwestern Africa

    International Nuclear Information System (INIS)

    Basei, M.; Siga, O.; Masquelin, H.; Harara, O.; Reis Neto, J.; Preciozzi, F.


    The Dom Feliciano Belt (DFB) stretches for ca. 1,200 km along southeastern Brazil and eastern Uruguay, with an average width of 150 km. From its northern limit in Santa Catarina to its termination m Uruguay, DFB is internally organized according three crustal segments characterized, from southeast to northwest, by a Granitoid belt (calci-alkaline to alkaline granitoid rocks deformed to different degrees); a Schist belt (volcano-sedimentary rocks metamorphosed from green schist to amphibolite facies), and a Fore land belt (sedimentary and anchimetamorphic volcanic rocks), the latter situated between the Schist belt and the old western terranes. Despite discontinuously covered by younger sediments, the continuity of these three segments is suggested by the similar lithotypes and structural characteristics, as well as by the gravimetric geophysical signature.In this work, DBF is interpreted as the product of successive subduction s and collisions related to the agglutination of different terranes generated or intensely reworked from the Neoproterozoic to the Cambrian, during the Brasiliano and Rio Doce orogenesis, with maximum time starting at 900 Ma (opening of the Adamastor Ocean) and ending at 530 Ma (deformation of the fore land basins) related to the tecto no-magmatic events associated with the formation of the Western Gondwana.Besides the Neoproterozoic DFB and its fore land, the Rio de la Plata Craton and the Luis Alves Microplate, constituted by Paleoproterozoic gneissic-migmatitic rocks, two other tectonic units can be recognized in southeastern Brazil and eastern Uruguay: the Sao Gabriel Block (RS) where Neoproterozoic juvenile material can be characterized in regional scale (in great part associated with an island are), and the Punta del Este Terrane, which presents, in southern Uruguay, an ortho gneiss basement with ages around 1,000 Ma and a meta sedimentary cover (Rocha Group), which can correspond in the South-American portion, to the Namaqua and Gariep

  17. Late Triassic Porphyritic Intrusions And Associated Volcanic Rocks From The Shangri-La Region, Yidun Terrane, Eastern Tibetan Plateau: Implications For Adakitic Magmatism And Porphyry Copper Mineralization (United States)

    Wang, B.; Zhou, M.; Li, J.; Yan, D.


    The Yidun terrane, located on the eastern margin of the Tibetan plateau, has been commonly considered to be a Triassic volcanic arc produced by subduction of the Ganzi-Litang oceanic lithosphere. The Yidun terrane is characterized by numerous arc-affinity granitic intrusions located along a 500-km-long, north-south-trending belt. Among these granitic bodies, several small porphyritic intrusions in the southern segment of the terrane (Shangri-La region) are associated with large porphyry copper deposits. These porphyritc intrusions are composed of diorite and quartz diorite, and spatially associated with andesites and dacites. LA-ICP-MS zircon U-Pb ages of the intrusions range from 230 to 215 Ma. The andesites and dacites are intercalated with slates and sandstones and have ages of around 220 Ma. The intrusive and volcanic rocks have SiO2 contents from 56.6 to 67.1 wt.%, Al2O3 from 14.2 to 17.4 wt.% and MgO from 1.9 to 4.2 wt.%. They show significant negative Nb-Ta anomalies on primitive mantle-normalized spidergrams. They have high La/Yb (13-49) ratios with no prominent Eu anomalies. All the rocks have high Sr (258-1980 ppm), and low Y (13-21 ppm) with high Sr/Y ratios (29-102). The geochemical features indicate that both the volcanic rocks and porphyritic intrusions were derived from adakitic magmas. They have similar initial 87Sr/86Sr ratios (0.7058 to 0.7077) and ɛNd (-1.88 to -4.93) values, but can be further divided into two groups: high silica (HSA) and low silica adakitic rocks (LSA). The HSA, representing an early stage of magmatism (230 to 215 Ma), were derived from oceanic slab melts with limited interaction with the overlying mantle wedge. At 215 Ma, more extensive interaction resulted in the formation of LSA. We propose that HSA were produced by flat subduction leading to melting of oceanic slab, whereas subsequent slab break-off caused the significant interaction between slab melts and the mantle wedge and thus the generation of the LSA. Compared with

  18. Draa Sfar, Morocco: A Visean (331 Ma) pyrrhotite-rich, polymetallic volcanogenic massive sulphide deposit in a Hercynian sediment-dominant terrane


    Marcoux , Eric; Belkabir , Abdelhay; Gibson , Harold L.; Lentz , David; Ruffet , Gilles


    International audience; Draa Sfar is a Visean, stratabound, volcanogenic massive sulphide ore deposit hosted by a Hercynian carbonaceous, black shale-rich succession of the Jebilet terrane, Morocco. The ore deposit contains 10 Mt grading 5.3 wt.% Zn, 2 wt.% Pb, and 0.3 wt.% Cu within two main massive sulphides orebodies, Tazakourt (Zn-rich) and Sidi M'Barek (Zn–Cu rich). Pyrrhotite is by far the dominant sulphide (70 to 95% of total sulphides), sphalerite is fairly abundant, chalcopyrite and ...

  19. Stable Isotope Evidence for a Complex Fluid Evolution of the Northwestern British Columbia Coast Ranges Related to Terrane Accretion (United States)

    Moertle, J.; Holk, G. J.


    Stable isotope geochemistry reveals a complex fluid evolution for the Western Metamorphic Belt (WMB), Coast Ranges Batholith (CRB), Central Gneiss Complex (CGC) and Coast Ranges Megalineament (CRM). These fluids are a product of a complex tectonic history related to terrane accretion that includes oblique convergence, metamorphism, magmatism, and orogenic collapse. From W-to-E, these fluid systems are as follows. High-pressure greenschist-to-amphibolite facies metasedimentary rocks of the WMB record variable mineral δD (-61 to -104‰) and δ18O (e.g., quartz +9.6 to +13.4‰) values with multiple minerals in apparent isotopic equilibrium (T ~ 450-550°C) suggest a low W/R system dominated by metamorphic fluids. Variable and non-equilibrium δD (-53 to -143‰) and δ18O (e.g., biotite +2.3 to +5.3‰) values from diorites of the Quottoon pluton affected by the ductile CRM suggest a complex evolution that involved both metamorphic and meteoric-hydrothermal fluids in this dextral shear zone; these results differ from those 300 km along strike to the north that documented only metamorphic fluids in the CRM (Goldfarb et al., 1988). Our data and those of Magaritz and Taylor (1976) from granulite facies metasediments of the CGC and plutons of the western CRB reveal homogeneous δD values (-62 to -78‰) and a restricted range of δ18O values (e.g., quartz +8.5 to +11.5‰) with all minerals in equilibrium at T > 570°C indicate a system dominated by magmatic fluids. Calculated whole-rock δ18O values (~ +7‰) for the Quottoon pluton and CRB intrusive rocks suggest a mantle origin for these magmas. Reinterpretation of very low δD (< -150‰) and quartz-feldspar δ18O pairs that display extreme disequilibrium (feldspar δ18O values as low as -5‰) from the Ponder pluton, eastern CRB, and Hazelton Group point reveals that the major meteoric-hydrothermal system that affected these rocks was related to Eocene detachment faulting along the Shames Lake fault system, a

  20. Age/isotopic characterisation of the Waipapa Group in Northland and Auckland, New Zealand, and implications for the status of the Waipapa Terrane

    International Nuclear Information System (INIS)

    Adams, C.J.; Maas, R.


    Rb-Sr ages of low-grade metasediments of the Waipapa Group (probable Permian-Jurassic) of Northland and Auckland range from Late Triassic (c. 209-217 Ma) to Middle Jurassic (c. 164-174 Ma), reflecting deformation and metamorphism during the Rangitata Orogeny. K-Ar ages indicate Middle Jurassic (c. 165-175 Ma) uplift and cooling of the western Omahuta-Puketi Forest block, and later, Middle-Late Jurassic (c. 150-160 Ma) cooling of the Helena Bay to Hunua Ranges eastern coastal block. In the intervening Western Bay of Islands block, there is evidence of local Early Cretaceous (c. 135 Ma) metamorphism. Rb-Sr whole-rock isochron age (t) and initial 87 Sr/ 86 Sr ratio (i) data support the assignment of Waipapa Group of the westernmost, Omahuta-Puketi block to the Caples Terrane. The remaining data have a consistent (t)-(i) signature, with (i) values 0.7039-0.7049, unlike Permian-Cretaceous Torlesse Supergroup metasediments with more radiogenic (i) values, typically >0.7060. They thus support the retention of a separate, Waipapa Terrane which continues southwards through central North Island to the Kaimanawa Ranges, and probably to Kapiti Island, and schist equivalents in eastern Marlborough. (author). 62 refs., 5 figs., 3 tabs

  1. The basement of the Punta de Este Terrane: A meso proterozoic heritage at the eastern border of Rio de La Plata craton

    International Nuclear Information System (INIS)

    Preciozzi, F.; Peel, E.; Sanchez, L.; Basei, M.


    U-Pb zircon ages between 1000 and 900 Ma corresponding to the nuclei of zircon crystals extracted from the basement of the Punta del Este Terrane (Eastern Uruguay) allowed the correlation of the protoliths of this domain with rocks attributed to the Namaqua Belt in Southwestern Africa. SHRIMP ages obtained for the ortho gneissic rocks allowed to place at ca. 750 Ma the generations of gneisses and migmatites. Differently from what occurred in Africa, reworking of this crustal segment during the Brasiliano-Pan african orogenesis was very intense, reaching the granulite facies around 640Ma. Acid volcanic and volcaniclastic rocks (Sierra de Aguirre Formation) with ages around 570 Ma, late sedimentary basins (San Carlos Formation) and post-tectonic granitoids (Santa Teresa and José Ignacio batholith s) mark the end of the events related with the Brasiliano/Pan-African orogenesis. The final collision between the Punta del Este Terrane and the western domains represented by the Dom Feliciano Belt and the Río de La Plata Craton may have occurred at around 535 Ma

  2. Circum-Pacific accretion of oceanic terranes to continental blocks: accretion of the Early Permian Dun Mountain ophiolite to the E Gondwana continental margin, South Island, New Zealand (United States)

    Robertson, Alastair


    Accretionary orogens, in part, grow as a result of the accretion of oceanic terranes to pre-existing continental blocks, as in the circum-Pacific and central Asian regions. However, the accretionary processes involved remain poorly understood. Here, we consider settings in which oceanic crust formed in a supra-subduction zone setting and later accreted to continental terranes (some, themselves of accretionary origin). Good examples include some Late Cretaceous ophiolites in SE Turkey, the Jurassic Coast Range ophiolite, W USA and the Early Permian Dun Mountain ophiolite of South Island, New Zealand. In the last two cases, the ophiolites are depositionally overlain by coarse clastic sedimentary rocks (e.g. Permian Upukerora Formation of South Island, NZ) that then pass upwards into very thick continental margin fore-arc basin sequences (Great Valley sequence, California; Matai sequence, South Island, NZ). Field observations, together with petrographical and geochemical studies in South Island, NZ, summarised here, provide evidence of terrane accretion processes. In a proposed tectonic model, the Early Permian Dun Mountain ophiolite was created by supra-subduction zone spreading above a W-dipping subduction zone (comparable to the present-day Izu-Bonin arc and fore arc, W Pacific). The SSZ oceanic crust in the New Zealand example is inferred to have included an intra-oceanic magmatic arc, which is no longer exposed (other than within a melange unit in Southland), but which is documented by petrographic and geochemical evidence. An additional subduction zone is likely to have dipped westwards beneath the E Gondwana margin during the Permian. As a result, relatively buoyant Early Permian supra-subduction zone oceanic crust was able to dock with the E Gondwana continental margin, terminating intra-oceanic subduction (although the exact timing is debatable). The amalgamation ('soft collision') was accompanied by crustal extension of the newly accreted oceanic slab, and

  3. Triassic arc-derived detritus in the Triassic Karakaya accretionary complex was not derived from either the S Eurasian margin (Istanbul terrane) or the N Gondwana margin (Taurides) (United States)

    Ustaömer, Timur; Ayda Ustaömer, Petek; Robertson, Alastair H. F.; Gerdes, Axel; Zulauf, Gernold


    We present new U-Pb zircon source age data for Upper Triassic sandstones of the Istanbul Terrane (S Eurasian margin) and also for Triassic sandstones of the Taurides (N Gondwana margin). The main aim is to detect and quantify the contribution of Triassic magmatism as detritus to either of these crustal blocks. This follows the recent discovery of a Triassic magmatic arc source for the Triassic sandstones of the Palaeotethyan Karakaya subduction-accretion complex (Ustaömer et al. 2013; this meeting). Carboniferous (Variscan) zircon grains also form a significant detrital population, plus several more minor populations. Six sandstone samples were studied, two from the İstanbul Terrane (Bakırlıkıran Formation of the Kocaeli Triassic Basin) and four from the Tauride Autochthon (latest Triassic Üzümdere Formation and Mid-Triassic Kasımlar Formations; Beyşehir region). Detrital zircon grains were dated by the laser ablation-inductively coupled plasma-mass spectrometer (LA-ICP-MS) U-Pb method at Goethe University, Frankfurt. Our results do not reveal Triassic detritus in the Üzümdere Formation. The U-Pb age of the analysed zircon grains ranges from 267 Ma to 3.2 Ga. A small fraction of Palaeozoic zircons are Permian (267 to 296 Ma), whereas the remainder are Early Palaeozoic. Ordovician grains (4%) form two age clusters, one at ca. 450 Ma and the other at ca. 474 Ma. Cambrian-aged grains dominate the zircon population, while the second largest population is Ediacaran (576 to 642 Ma). Smaller populations occur at 909-997 Ma, 827-839 Ma, 1.8-2.0 Ga and 2.4-2.6 Ga. The sandstones of the Kasımlar Formation have similar zircon age cluster to those of the somewhat younger Üzümdere Formation, ranging from 239 Ma to 2.9 Ga. A few grains gave Anisian ages. Cambrian zircon grains are less pronounced than in the Kasımlar Formation compared to the Üzümdere Formation. The detrital zircon record of Tauride sandstones, therefore, not indicates significant contribution

  4. Uncertainty in 14C model ages of groundwater: The influence of soil gas in terranes dominated by C3 plants (United States)

    Nelson, S.; Hart, R.; Eggett, D.


    Groundwater is the largest source of fresh water readily available to humanity and aquifers with long residence times are particularly susceptible to overuse. Thus, it is important to have quantitative estimates of the residence time of water in such aquifers. Many models used to calculate 14C ages of groundwater depend on an estimate of the δ13C value of carbon dioxide in soil at the time of recharge, a value that must be estimated. Other work has suggested that for terranes dominated by C3 plants, -23‰ is an appropriate value, and sensitivity calculations show that the apparent age of a groundwater is strongly dependent on the choice of this parameter. This is especially true where the measured values of δ13C of dissolved inorganic carbon (DIC) are used to estimate the contribution of “dead” carbon to the DIC load via the dissolution of calcite in the aquifer and soil zones. To better understand the temporal and spatial isotopic and abundance variability of soil carbon dioxide, we established soil gas sampling sites that encompassed a wide variety of settings in terms of season, elevation, climate, and plant community that were sampled monthly throughout regions of the state of Utah where C3 flora dominate. Direct measurements of soil gas suggest a value of -21.8 ± 1.4‰ (1σ) is a good input variable as long as: a) C3 vegetation dominates, and b) extreme aridity does not prevail such that plant densities and soil microbial activities are minimized. If recharge is envisaged to occur during spring and early summer in highly vegetated uplands, a value of -24.0 ± 0.6‰ may be more appropriate as statistical analysis reveals that seasonality and plant density are most clearly correlated to the carbon isotope composition of carbon dioxide in soil gas. Although the two values and ranges cited above values do not diverge strongly from other published estimates, they place fairly narrow limits on the uncertainty of ±500 and ±200 yr., respectively, in

  5. The Punta del Este Suspect Terrane: a possible counterpart in Eastern Uruguay of the Namaqua Complex and Gariep Belt in Western Africa

    International Nuclear Information System (INIS)

    Preciozzi, F.; Basei, M.; Peel, E.


    The geology of the southwestern extreme of the African continent is characterised by a series of mobile belts that delimit the western margin of the block constituted by the Kalahari-Kapvaal cratons. In this context, Panafrican belts predominate, represented in the north-northwestern portion by the Damara, in the western region by the Gariep and, in the southern region by the Saldania. These belts, of Neoproterozoic-Eopaleozoic ages predominantly expose sedimentary covers metamorphosed in the greenschist facies. In the northwestern portion of South Africa and south of Namibia, of major interest for the correlation intended in this work. The basement of the Panafrican cover, in this case the Gariep Group, is largely constituted by medium- to high-grade terranes generated during the Kibarian event (1.2-1.1Ga) responsible for the formation of igneous and metamorphic rocks and attributed to the Metamorphic Namaqua-Natal Complex (Frimmel, 1995). This Complex presents low-pressure granulite facies conditions (Clifford et al., 1981) with polymetamorphic evolution, where old nuclei of Paleoproterozoic age (1800-2000Ma) occur within the terranes generated during the Kibarian orogeny. U-Pb studies in zircons by SHRIMP (Robb et al., 1998) confirmed for Namaqua two rock-generating events with pulses between 1220-1170 Ma (Kibarian) and 1060-1030Ma (Namaqua); with the latter the third regional deformation and important magmatism phases would be associated. In this period granulitic metamorphism and intrusion of granitoids 2 occurred and are presently represented by the Nababeep and Modderfontein gneisses that are cut by the Concordia and Rietberg granitoids. The Panafrican superposition is registered predominantly along the coastal region. The Gariep Group occurs along the coastal region tectonically covering the terranes associated with the Namaqua Metamorphic Complex. It is characterised by a group constituted mainly by rocks of very low to low metamorphic grade distributed in

  6. Shaping the Australian crust over the last 300 million years: insights from fission track thermotectonic imaging and denudation studies of key terranes

    International Nuclear Information System (INIS)

    Kohn, B.P.; Gleadow, A.J.W.; Brown, R.W.; O'Sullivan, P.B.; Foster, D.A.; Gallagher, K.


    Apatite fission track thermochronology is a well-established tool for reconstructing the low-temperature thermal and tectonic evolution of continental crust. The variation of fission track ages and distribution of fission track lengths are primarily controlled by cooling, which may be initiated by earth movements and consequent denudation at the Earth's surface and/or by changes in the thermal regime. Using numerical forward-modelling procedures these parameters can be matched with time-temperature paths that enable thermal and tectonic processes to be mapped out in considerable detail. This study describes extensive Australian regional fission track datasets that have been modelled sequentially and inverted into time-temperature solutions for visualisation as a series of time-slice images depicting the cooling history of present-day surface rocks during their passage through the upper crust. The data have also been combined with other datasets, including digital elevation and heat flow, to image the denudation history and the evolution of palaeo-topography. These images provide an important new perspective on crustal processes and landscape evolution and show how important tectonic and denudation events over the last 300 million years can be visualised in time and space. The application of spatially integrated denudation-rate chronology is also demonstrated for some key Australian terranes including the Lachlan and southern New England Orogens of southeastern Australia, Tasmania, the Gawler Craton, the Mt lsa lnlier, southwestern Australian crystalline terranes (including the Yilgarn Craton) and the Kimberley Block. This approach provides a readily accessible framework for quantifying the otherwise undetectable, timing and magnitude of long-term crustal denudation in these terranes, for a part of the geological record previously largely unconstrained. Discrete episodes of enhanced denudation occurred principally in response to changes in drainage, base

  7. Map Showing Geologic Terranes of the Hailey 1°x2° Quadrangle and the western part of the Idaho Falls 1°x2° Quadrangle, south-central Idaho (United States)

    Department of the Interior — The paper version of Map Showing Geologic Terranes of the Hailey 1°x2° Quadrangle and the western part of the Idaho Falls 1°x2° Quadrangle, south-central Idaho was...

  8. Mantle accretion evidence during the neoproterozoic of the Pernambuco-Alagoas terrane, and its significance to the evolution of the Borborema Province, NE Brazil

    International Nuclear Information System (INIS)

    Silva Filho, A.F.; Guimaraes, I.P; Van Schmus, W.R


    The Borborema Province is located in NE Brazil, corresponding to the western part of a major fold belt, which extends from Brazil to West Africa. According to paleogeographic reconstruction, it is located between the Congo, Sao Francisco and West Africa cratons. The Pernambuco-Alagoas Terrane is a major tectonic unit of the Borborema Province and comprises high-grade metamorphic sequences and the greatest granitic batholiths of this province. The granitic batholiths Maribondo-Correntes, Buique-Paulo Afonso and Aguas Belas-Caninde and their ortho derived country rocks show metaluminous and peraluminous compositions, and εNd(0,60 Ga) between +3,2 and -2,0 and T DM between 0,90 Ga and 1,20 Ga. These Nd isotope data favour a crustal evolution hypothesis involving accretion of juvenile material at least during the Brasiliano orogenesis collision and perhaps the formation of a juvenile lithosphere during the end of the Mesoproterozoic (au)

  9. Regional framework and geology of iron oxide-apatite-rare earth element and iron oxide-copper-gold deposits of the Mesoproterozoic St. Francois Mountains Terrane, southeast Missouri (United States)

    Day, Warren C.; Slack, John F.; Ayuso, Robert A.; Seeger, Cheryl M.


    This paper provides an overview on the genesis of Mesoproterozoic igneous rocks and associated iron oxide ± apatite (IOA) ± rare earth element, iron oxide-copper-gold (IOCG), and iron-rich sedimentary deposits in the St. Francois Mountains terrane of southeast Missouri, USA. The St. Francois Mountains terrane lies along the southeastern margin of Laurentia as part of the eastern granite-rhyolite province. The province formed during two major pulses of igneous activity: (1) an older early Mesoproterozoic (ca. 1.50–1.44 Ga) episode of volcanism and granite plutonism, and (2) a younger middle Mesoproterozoic (ca. 1.33–1.30 Ga) episode of bimodal gabbro and granite plutonism. The volcanic rocks are predominantly high-silica rhyolite pyroclastic flows, volcanogenic breccias, and associated volcanogenic sediments with lesser amounts of basaltic to andesitic volcanic and associated subvolcanic intrusive rocks. The iron oxide deposits are all hosted in the early Mesoproterozoic volcanic and volcaniclastic sequences. Previous studies have characterized the St. Francois Mountains terrane as a classic, A-type within-plate granitic terrane. However, our new whole-rock geochemical data indicate that the felsic volcanic rocks are effusive derivatives from multicomponent source types, having compositional similarities to A-type within-plate granites as well as to S- and I-type granites generated in an arc setting. In addition, the volcanic-hosted IOA and IOCG deposits occur within bimodal volcanic sequences, some of which have volcanic arc geochemical affinities, suggesting an extensional tectonic setting during volcanism prior to emplacement of the ore-forming systems.The Missouri iron orebodies are magmatic-related hydrothermal deposits that, when considered in aggregate, display a vertical zonation from high-temperature, magmatic ± hydrothermal IOA deposits emplaced at moderate depths (~1–2 km), to magnetite-dominant IOA veins and IOCG deposits emplaced at shallow

  10. Advanced Land Observing Satellite (ALOS) Phased Array Type L-Band Synthetic Aperture Radar (PALSAR) mosaic for the Kahiltna terrane, Alaska, 2007-2010 (United States)

    Cole, Christopher J.; Johnson, Michaela R.; Graham, Garth E.


    The U.S. Geological Survey (USGS) has initiated a multi-disciplinary study investigating the applicability of remote sensing technologies for geologic mapping and identification of prospective areas for base and precious metal deposits in remote parts of Alaska. The Kahiltna terrane in southwestern Alaska was selected for investigation because of its known mineral deposits and potential for additional mineral resources. An assortment of technologies is being investigated to aid in remote analysis of terrain, and includes imaging spectroscopy (hyperspectral remote sensing), high spatial resolution electro-optical imagery, and Synthetic Aperture Radar (SAR). However, there are significant challenges to applying imaging spectroscopy and electro-optical imagery technologies in this area because of the low solar angle for parts of the year, seasonal periods of darkness and snow cover, and the frequently cloudy weather that characterizes Alaska. Synthetic Aperture Radar (SAR) was selected because this technology does not rely on solar illumination and has all-weather capability.

  11. An autochthonous Avalonian basement source for the latest Ordovician Brenton Pluton in the Meguma terrane of Nova Scotia: U-Pb-Hf isotopic constraints and paleogeographic implications (United States)

    Duncan Keppie, J.; Gregory Shellnutt, J.; Dostal, Jaroslav; Fraser Keppie, D.


    The Ediacaran-Ordovician Meguma Supergroup was thrust over Avalonia basement prior to the intrusion of post-Acadian, ca. 370 Ma, S-type granitic batholiths. This has led to two main hypotheses regarding the original location of the Meguma terrane, a continental rise prism bordering either NW Africa or Avalonia. On the other hand, the pre-Acadian, ca. 440 Ma Brenton pluton has yielded the following U/Pb LA-ICP-MS zircon data: (1) 448 ± 3 Ma population peak inferred to be the intrusive age and (2) ca. 550 and 700 Ma inherited ages common to both Avalonia and NW Africa. In contrast, Hf isotopic analyses of zircon yielded model ages ranging from 814 to 1127 Ma with most between 940 and 1040 Ma: such ages are typical of Avalonia and not NW Africa. The ages of the inherited zircons found within the Brenton pluton suggest that it was probably derived by partial melting of sub-Meguma, mid-crustal Avalonian rocks, upon which the Meguma Supergroup was deposited. Although Avalonia is commonly included in the peri-Gondwanan terranes off NW Africa or Amazonia, paleomagnetic data, faunal provinciality, and Hf data suggest that, during the Ediacaran-Early Cambrian, it was an island chain lying near the tropics (ca. 20-30 °S) and was possibly a continuation of the Bolshezemel volcanic arc accreted to northern Baltica during the Ediacaran Timanide orogenesis. This is consistent with the similar derital zircon population in the Ediacaran-Cambrian Meguma Supergroup and the Dividal Group in northeastern Baltica.

  12. What was the Paleogene latitude of the Lhasa terrane? A reassessment of the geochronology and paleomagnetism of Linzizong volcanic rocks (Linzhou basin, Tibet) (United States)

    Huang, Wentao; Dupont-Nivet, Guillaume; Lippert, Peter C.; van Hinsbergen, Douwe J. J.; Dekkers, Mark J.; Waldrip, Ross; Ganerød, Morgan; Li, Xiaochun; Guo, Zhaojie; Kapp, Paul


    The Paleogene latitude of the Lhasa terrane (southern Tibet) can constrain the age of the onset of the India-Asia collision. Estimates for this latitude, however, vary from 5°N to 30°N, and thus, here, we reassess the geochronology and paleomagnetism of Paleogene volcanic rocks from the Linzizong Group in the Linzhou basin. The lower and upper parts of the section previously yielded particularly conflicting ages and paleolatitudes. We report consistent 40Ar/39Ar and U-Pb zircon dates of 52 Ma for the upper Linzizong, and 40Ar/39Ar dates ( 51 Ma) from the lower Linzizong are significantly younger than U-Pb zircon dates (64-63 Ma), suggesting that the lower Linzizong was thermally and/or chemically reset. Paleomagnetic results from 24 sites in lower Linzizong confirm a low apparent paleolatitude of 5°N, compared to the upper part ( 20°N) and to underlying Cretaceous strata ( 20°N). Detailed rock magnetic analyses, end-member modeling of magnetic components, and petrography from the lower and upper Linzizong indicate widespread secondary hematite in the lower Linzizong, whereas hematite is rare in upper Linzizong. Volcanic rocks of the lower Linzizong have been hydrothermally chemically remagnetized, whereas the upper Linzizong retains a primary remanence. We suggest that remagnetization was induced by acquisition of chemical and thermoviscous remanent magnetizations such that the shallow inclinations are an artifact of a tilt correction applied to a secondary remanence in lower Linzizong. We estimate that the Paleogene latitude of Lhasa terrane was 20 ± 4°N, consistent with previous results suggesting that India-Asia collision likely took place by 52 Ma at 20°N.

  13. Petrogenesis, U-Pb and Sm-Nd geochronology of the Furna Azul Migmatite: partial melting evidence during the San Ignacio Orogeny, Paragua Terrane, SW Amazon Craton

    Energy Technology Data Exchange (ETDEWEB)

    Nascimento, Newton Diego Couto do; Ruiz, Amarildo Salina; Pierosan, Ronaldo; Lima, Gabrielle Aparecida de; Matos, Joao Batista; Lafon, Jean-Michel; Moura, Candido Augusto Veloso, E-mail:, E-mail:, E-mail:, E-mail:, E-mail:, E-mail:, E-mail: [Universidade Federal do Para (GEOCIAM/UFPA), Belem, PA (Brazil). Instituto Nacional de Ciencia e Tecnologia de Geociencias da Amazonia


    The Furna Azul Migmatite is a ∼10 km{sup 2} complex located in Pontes e Lacerda city, Mato Grosso, Brazil. It belongs to Paragua Terrane, limit with Rio Alegre Terrane, southeast of San Ignacio Province, in Amazon Craton. It consists of transitional metatexites with amphibolite enclaves and dioritic injections. The rocks were divided in residuum rich and leucosome rich; both have three deformation phases marked by folded stromatic layers affected by spaced foliation and metamorphosed in amphibolite facies, represented by garnet, biotite, sillimanite, and by the clinopyroxene in the enclaves. The metamorphic retrograde to greenschist is marked by formation of chlorite, muscovite and prehnite. Residuum-rich metatexites show higher CaO and Na{sub 2}O contents, separating them from K{sub 2}O, Ba and Rb enriched transitional metatexites. U-Pb on zircon and Sm-Nd whole-rocks dating indicates that the residuum-rich metatexite crystallized at 1436 ± 11 Ma, with a T{sub DM} age of 1.90 Ga and ε{sub Nd(1.43)} of -0.54, whereas the dioritic injection crystallized at 1341,7 ± 17 Ma with a T{sub DM} age of 1.47 Ga and ε{sub Nd(1.34)} of 3.39. These results indicate that the Furna Azul Migmatite protolith was formed during the San Ignacio Orogeny and was reworked during the same orogeny, as basement for collisional to post-magmatic granites from Pensamiento Intrusive Suite. (author)

  14. Garnet peridotite found in the Greater Antilles (United States)

    Abbott, Richard N., Jr.; Draper, Grenville; Keshav, Shantanu

    Although Alpine peridotites are relatively common in collisional orogenic zones, garnet-bearing peridotites are rare and only associated with high pressure/ultra-high pressure or temperature (HP/UHP or T) terranes [Brueckner and Medaris, 2000; Medaris, 1999]. Until recently all reported occurrences of Alpine-type garnet peridotites and HP/UHP terranes were in Eurasia and Africa, with one occurrence in the Seward Peninsula, Alaska [Till, 1981;Lieberman and Till, 1987]. Now a new Alpine-type garnet peridotite locality has been discovered in the Caribbean island of Hispaniola. This discovery is the second of its kind in the Americas.

  15. New evidence for Oligocene to Recent slip along the San Juan fault, a terrane-bounding structure within the Cascadia forearc of southern British Columbia, Canada (United States)

    Harrichhausen, N.; Morell, K. D.; Regalla, C.; Lynch, E. M.


    Active forearc deformation in the southern Cascadia subduction zone is partially accommodated by faults in the upper crust in both Washington state and Oregon, but until recently, these types of active forearc faults have not been documented in the northern part of the Cascadia forearc on Vancouver Island, British Columbia. Here we present new evidence for Quaternary slip on the San Juan fault that indicates that this terrane-bounding structure has been reactivated since its last documented slip in the Eocene. Field work targeted by newly acquired hi-resolution lidar topography reveals a deformed debris flow channel network developed within colluvium along the central portion of the San Juan fault, consistent with a surface-rupturing earthquake with 1-2 m of offset since deglaciation 13 ka. Near the western extent of the San Juan fault, marine sediments are in fault contact with mélange of the Pandora Peak Unit. These marine sediments are likely Oligocene or younger in age, given their similarity in facies and fossil assemblages to nearby outcrops of the Carmanah Group sediments, but new dating using strontium isotope stratigraphy will confirm this hypothesis. If these sediments are part of the Carmanah Group, they occur further east and at a higher elevation than previously documented. The presence of Oligocene or younger marine sediments, more than 400 meters above current sea level, requires a substantial amount of Neogene rock uplift that could have been accommodated by slip on the San Juan fault. A preliminary analysis of fault slickensides indicates a change in slip sense from left-lateral to normal along the strike of the fault. Until further mapping and analysis is completed, however, it remains unclear whether this kinematic change reflects spatial and/or temporal variability. These observations suggest that the San Juan fault is likely part of a network of active faults accommodating forearc strain on Vancouver Island. With the recent discovery of

  16. Rb-Sr whole-rock and mineral ages, K-Ar, 40Ar/39Ar, and U-Pb mineral ages, and strontium, lead, neodymium, and oxygen isotopic compositions for granitic rocks from the Salinian Composite Terrane, California: (United States)

    Kistler, R.W.; Champion, D.E.


    This report summarizes new and published age and isotopic data for whole-rocks and minerals from granitic rocks in the Salinian composite terrane, California. Rubidium-strontium whole-rock ages of plutons are in two groups, Early Cretaceous (122 to 100 Ma) and Late Cretaceous (95 to 82 Ma). Early Cretaceous plutons occur in all granitic rock exposures from Bodega Head in the north to those from the Santa Lucia and Gabilan Ranges in the central part of the terrane. Late Cretaceous plutons have been identified in the Point Reyes Peninsula, the Santa Lucia and the Gabilan Ranges, and in the La Panza Range in the southern part of the terrane. Ranges of initial values of isotopic compositions are 87Sr/86Sr, 0.7046-0.7147, δ18O, +8.5 to +12.5 per mil, 206Pb/204Pb, 18.901-19.860, 207Pb/204Pb, 15.618-15.814, 208Pb/204Pb, 38.569- 39.493, and εNd, +0.9 to -8.6. The initial 87Sr/86Sr=0.706 isopleth is identified in the northern Gabilan Range and in the Ben Lomond area of the Santa Cruz Mountains, in Montara Mountain, in Bodega Head, and to the west of the Farallon Islands on the Cordell Bank. This isotopic boundary is offset about 95 miles (160km) by right-lateral displacements along the San Gregorio-Hosgri and San Andreas fault systems.

  17. The Park Volcanics Group : field relations of an igneous suite emplaced in the Triassic-Jurassic Murihiku Terrane, South Island, New Zealand

    International Nuclear Information System (INIS)

    Coombs, D.S.; Cook, N.D.J.; Campbell, J.D.


    Park Volcanics Group is proposed for igneous rocks, either shallow intrusive or extrusive, emplaced in the Murihiku Terrane during Triassic-Jurassic times. The term replaces Park Intrusives of Mutch, some members of which are shown to be extrusive rather than intrusive. Formation status within the group is given to Gowan Andesite and Pinney Volcanics (new names) in western Southland, Glenham Porphyry in eastern Southland, and Barnicoat Andesite (new) in the Richmond area, Nelson. Gowan Andesite is a porphyritic feldspar two-pyroxene andesite with a glassy or microcrystalline groundmass. A suite of low-grade metavolcanic rocks which forms the main mass of Malakoff Hill and which has formerly been included in the 'Park Intrusives' is here excluded and ascribed to the Takitimu Group; representative chemical data are given. Glenham Porphyry is typically a porphyritic feldspar two-pyroxene andesite texturally similar to the Gowan Andesite but with significant geochemical differences. Two volumetrically minor members are recognised, Habukinini Trachydacite and Kenilworth Rhyolite. In the north of its outcrop area, Glenham Porphyry is emplaced on or into Late Triassic terrestrial beds; in the middle it overlies Kaihikuan (Middle Triassic) and is overlain by Otapirian (latest Triassic) marine beds; and in the southeast it is directly overlain by Ururoan (late Early to early Middle Jurassic) conglomerates and marine sandstones. Pinney Volcanics are restricted to a very few, probably one, massive conglomeratic horizon in the Oretian Stage. The commonest rock type is a two-pyroxene trachydacite, modified by very-low-grade burial metamorphism. Auto-brecciation is characteristic and rock types change over short distances. Hornblende-rich variants occur as well as more felsic varieties including rhyolite ignimbrite. These may have been erupted onto a bouldery floodplain or shallow-marine surface, but alternatively may have been mass-emplaced by debris avalanche resulting from

  18. Paleoproterozoic (ca. 1.8 Ga) arc magmatism in the Lützow-Holm Complex, East Antarctica: Implications for crustal growth and terrane assembly in erstwhile Gondwana fragments (United States)

    Takahashi, Kazuki; Tsunogae, Toshiaki; Santosh, M.; Takamura, Yusuke; Tsutsumi, Yukiyasu


    The Lützow-Holm Complex (LHC) of East Antarctica forms a part of the latest Neoproterozoic-Cambrian high-grade metamorphic segment of the East African-Antarctic Orogen. Here we present new petrological, geochemical, and zircon U-Pb geochronological data on meta-igneous rocks from four localities (Austhovde, Telen, Skallevikshalsen, and Skallen) in the LHC, and evaluate the regional Paleoproterozoic (ca. 1.8 Ga) arc magmatism in this terrane for the first time. The geochemical features reveal a volcanic-arc affinity for most of the meta-igneous rocks from Austhovde and Telen, suggesting that the protoliths of these rocks were derived from felsic to mafic arc magmatic rocks. The protoliths of two mafic granulites from Austhovde are inferred as non-volcanic-arc basalt such as E-MORB, suggesting the accretion of remnant oceanic lithosphere together with the volcanic-arc components during the subduction-collision events. The weighted mean 206Pb/238U ages of the dominant population of magmatic zircons in felsic orthogneisses from Austhovde and Telen show 1819 ± 19 Ma and 1830 ± 10 Ma, respectively, corresponding to Paleoproterozoic magmatic event. The magmatic zircons in orthogneisses from other two localities yield upper intercept ages of 1837 ± 54 Ma (Skallevikshalsen), and 1856 ± 37 Ma and 1854 ± 45 Ma (Skallen), which also support Paleoproterozoic magmatism. The earlier thermal events during Neoarchean to Early Paleoproterozoic are also traced by 206Pb/238U ages of xenocrystic zircons in the felsic orthogneisses from Austhovde (2517 ± 17 Ma and 2495 ± 15 Ma) and Telen (2126 ± 16 Ma), suggesting partial reworking of the basement of a 2.5 Ga microcontinent during ca. 1.8 Ga continental-arc magmatism. The timing of peak metamorphism is inferred to be in the range of 645.6 ± 10.4 to 521.4 ± 12.0 Ma based on 206Pb/238U weighted mean ages of metamorphic zircon grains. The results of this study, together with the available magmatic ages as well as geophysical and

  19. 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 (United States)

    Chen, Ming; Sun, Min


    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

  20. What can the Cretaceous-to-present latitude history of the Lhasa terrane tell us about plate-scale deformation in the Tibetan-Himalayan orogen? (Invited) (United States)

    Lippert, P. C.; Van Hinsbergen, D. J.; Dupont-Nivet, G.; Huang, W.


    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

  1. Late Triassic porphyritic intrusions and associated volcanic rocks from the Shangri-La region, Yidun terrane, Eastern Tibetan Plateau: Adakitic magmatism and porphyry copper mineralization (United States)

    Wang, Bai-Qiu; Zhou, Mei-Fu; Li, Jian-Wei; Yan, Dan-Ping


    Early Mesozoic porphyritic intrusions in the Shangri-La region, southern Yidun terrane, SW China, are spatially associated with andesites and dacites. These intrusions are composed of diorite and quartz diorite, and are closely related to copper mineralization. LA-ICP-MS zircon U-Pb ages of the intrusions range from 230 to 215 Ma. The associated andesites and dacites are interlayered with slates and sandstones and have ages of around 220 Ma. All of the intrusive and extrusive rocks have similar, highly fractionated REE patterns and high La/Yb (13-49) ratios with no prominent Eu anomalies. They display pronounced negative Nb-Ta and Ti anomalies on primitive mantle-normalized spidergrams. Their SiO2 contents range from 56.6 to 67.1 wt.%, Al2O3 from 14.2 to 17.4 wt.% and MgO from1.9 to 4.2 wt.%. All the rocks have high Sr (258-1980 ppm), and low Y (13-21 ppm) with high Sr/Y ratios (29-102). These features suggest that both the volcanic rocks and porphyritic intrusions were derived from adakitic magmas. They have similar initial 87Sr/86Sr ratios (0.7058 to 0.7077) and εNd (- 1.88 to - 4.93) values, but belong to high silica (HSA) and low silica adakitic rocks (LSA). The HSA represent an early stage of magmatism (230 to 215 Ma) and were derived from oceanic slab melts with limited interaction with the overlying mantle wedge during ascent. At 215 Ma, more extensive interaction produced the LSA. We propose that the early adakitic magmas (HSA) formed by flat subduction leading to melting of oceanic slab, whereas subsequent slab break-off caused the significant interaction between slab melts and the mantle wedge and thus the generation of the later adakitic magmas (LSA).

  2. Geology, petrology, U-Pb (SHRIMP) geochronology of the Morrinhos granite - Paragua terrane, SW Amazonian craton: implications for the magmatic evolution of the San Ignacio orogeny

    Energy Technology Data Exchange (ETDEWEB)

    Franca, Ohana; Ruiz, Amarildo Salina; Sousa, Maria Zelia Aguiar de, E-mail:, E-mail:, E-mail: [Universidade Federal de Mato Grosso (UFMT), Cuiaba, MT (Brazil). Instituto de Ciencias Exatas e da Terra. Dept. de Geologia Geral; Batata, Maria Elisa Froes, E-mail: [Universidade Federal de Mato Grosso (UFMT), Cuiaba, MT (Brazil). Grupo de Pesquisa em Evolucao Crustal e Tectonica; Lafon, Jean-Michel [Universidade Federal do Para (GEOCIAM/UFPA), Belem, PR (Brazil). Inst. Nacional de Cencia e Tecnologia de Geociencias da Amazonia


    Morrinhos granite is a batholith body that is slightly elongated in the NNW direction and approximately 1,140 km{sup 2} long; it is located in the municipality of Vila Bela da Santissima Trindade of the state of Mato Grosso, Brazil, in the Paragua Terrane, Rondonian-San Ignacio Province, in the SW portion of the Amazonian Craton. This intrusion displays a compositional variation from tonalite to monzogranite, has a medium to coarse inequigranular texture and is locally porphyritic; biotite is the predominant mafic in one of the facies, and hornblende is predominant in the other, with both metamorphosed into the green schist facies. The studied rocks characterize an intermediate to acidic sequence that was formed by a subalkaline magmatism; the series is alkali-calcic to metaluminous to slightly peraluminous, and the rocks evolved through fractioned crystallization mechanisms. The structural data show two deformation phases represented by penetrative foliation (S{sub 1}) and open folds (D{sub 2}), and both phases were most likely related to the San Ignacio Orogeny. The geochronological (U-Pb SHRIMP) and isotopic (Sm-Nd) investigations of these rocks indicated a crystallization age of 1350±12Ma, T{sub DM} of approximately 1.77 Ga and εNd{sub (1.35}) with a negative value of -2.57, suggesting that their generation was related to a partial melting process of a Paleoproterozoic (Statherian) continental crust. The results herein indicate that the Morrinhos granite was generated in a continental magmatic arc in a late- to post-orogenic stage of the San Ignacio Orogeny, and it can be recognized as belonging to the Pensamiento Intrusive Suite. (author)

  3. Seismic evidence for multiple-stage exhumation of high/ultrahigh pressure metamorphic rocks in the eastern Dabie orogenic belt (United States)

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


    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.

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

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


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

  5. Brittle deformation in Southern Granulite Terrane (SGT): A study of pseudotachylyte bearing fractures along Gangavalli Shear Zone (GSZ), Tamil Nadu, India. (United States)

    mohan Behera, Bhuban; Thirukumaran, Venugopal; Biswal, Tapas kumar


    High grade metamorphism and intense deformation have given a well recognition to the Southern Granulite Terrane (SGT) in India. TTG-Charnockite and basic granulites constitute the dominant lithoassociation of the area. Dunite-peridotite-anorthosite-shonkinite and syenites are the intrusives. TTG-charnockite-basic granulite have undergone F1 (isoclinal recumbent), F2 (NE-SW) and F3 (NW-SE) folds producing several interference pattern. E-W trending Neoarchean and Palaeoproterozoic Salem-Attur Shear Zone exhibits a low angle ductile thrust as well as some foot print of late stage brittle deformation near Gangavalli area of Tamil Nadu. The thrust causes exhumation of basic granulites to upper crust. Thrusting along the decollement has retrograded the granulite into amphibolite rock. Subsequently, deformation pattern of Gangavalli area has distinctly marked by numerous vertical to sub-vertical fractures mostly dominating along 0-15 and 270-300 degree within charnockite hills that creates a maximum stress (σ1) along NNW and minimum stress (σ3) along ENE. However, emplacement of pseudotachylyte vein along N-S dominating fracture indicates a post deformational seismic event. Extensive fractures produce anastomose vein with varying thickness from few millimeters to 10 centimeters on the outcrop. ICP-AES study results an isochemical composition of pseudotachylyte vein that derived from the host charnockitic rock where it occurs. But still some noticeable variation in FeO-MgO and Na2O-CaO are obtained from different parts within the single vein showing heterogeneity melt. Electron probe micro analysis of thin sections reveals the existence of melt immiscibility during its solidification. Under dry melting condition, albitic rich melts are considered to be the most favorable composition for microlites (e.g. sheaf and acicular micro crystal) re-crystallization. Especially, acicular microlites preserved tachylite texture that suggest its formation before the final coagulation

  6. New Geochronology and Radiometric Age Dates Improve the Definition and Continuity of Accreted Tectonic Terranes of Northern Venezuela and the Lesser Antilles (United States)

    Baquero, M.; Mann, P.; Audemard, F. A.


    We use new and compiled geochronology and radiometric dates from the area of Venezuela to Tobago to define the following crustal provinces: 1) Guyana shield forms a sub-circular area of Pan-African rocks against which all younger terranes have collided and partially assumed its rounded shape: ages for the Guyana Shield range from >3.4 Ga to 1.8 Ga; 2) accreted Paleozoic rocks form a sub-circular, largely buried province that surround the Guiana Shield to the north and west; the El Pilar strike-slip fault forms the abrupt, northern limit of the Precambrian-Paleozoic craton in Venezuela characterized by crustal thicknesses of 40-50 km; 3) the Early to Late Cretaceous Great Arc of the Caribbean forms a continuous basement high that can be traced from northern Colombia, through the ABC Islands to La Blanquilla Island, and north along the Aves Ridge to the Greater Antilles; ages of the GAC generally are in the range of Late Cretaceous to early Eocene and have geochemistry consistent with intra-oceanic island arcs or oceanic plateau rocks with the exception of La Orchila Island with a Paleozoic intrusive age; the GAC collided from west to east with the passive margin of South America from Paleocene in western Venezuela to Plio-Pleistocene in the Trinidad area and marks the west to east passage of the Caribbean plate past the South American plate; 4) a post-GAC rifting event affected the GAC-South America suture from late Eocene to middle Miocene time in the Falcón Basin of western Venezuela with ages on intrusive and volcanic from 34 to 15.4 Ma; these ages are coeval with intrusive ages from the southernmost Lesser Antilles on Los Frailes and Los Testigos Islands and range from 35.7±2.6 to 36.4±0.5 Ma; the age of the intervening basin, the Bonaire basin, is poorly known but may be coeval with the Oligocene-Miocene extension that extended the suture zone in western Venezuela and extended the Lesser Antilles arc in early Middle Miocene time to form the Lesser Antilles

  7. High resolution crustal structure for the region between the Chilenia and Cuyania terrane above the Pampean flat slab of Argentina from local receiver function and petrological analyses (United States)

    Ammirati, J. B.; Alvarado, P. M.; Pérez, S. B.; Beck, S. L.; Porter, R. C.; Zandt, G.


    Jean-Baptiste Ammirati 1,Sofía Perez 1, Patricia Alvarado 1, Susan L. Beck 2, Ryan Porter 3 and George Zandt 2(1) CIGEOBIO-CONICET, Universidad Nacional de San Juan, Argentina (2) The University of Arizona, USA (3) Northern Arizona University, USA At ~31ºS, The subduction of the Nazca plate under the South American plate presents along-strike variations of its dip angle referred to the Chilean-Pampean flat slab. Geological observations suggest that the regional crustal structure is inherited from the accretion of different terranes at Ordovician times and later reactivated during Andean compression since Miocene. Geophysical observations confirmed that the structure is extending in depth with décollement levels that accommodate crustal shortening in the region. In order to get a better insight on the shallow tectonics we computed high frequency local receiver functions from slab seismicity (~100 km depth). Local earthquakes present a higher frequency content that permits a better vertical resolution. Using a common conversion point (CCP) stacking method we obtained cross sections showing high-resolution crustal structure in the western part of the Pampean flat slab region, at the transition between the Precordillera and the Frontal Cordillera. Our results show a well-defined structure and their lateral extent for both units down to 80 km depth. In good agreement with previous studies, our higher resolution images better identify very shallow discontinuities putting more constraints on the relationships with the regional structural geology. Recent petrological analyses combined with RF high-resolution structure also allow us to better understand the regional crustal composition. Interestingly, we are able to observe a shifting structure beneath the Uspallata-Calingasta Valley, highlighting the differences in terms of crustal structure between the Precordillera and the Frontal Cordillera. Previously determined focal mechanisms in the region match well this

  8. Using remote sensing techniques and field-based structural analysis to explore new gold and associated mineral sites around Al-Hajar mine, Asir terrane, Arabian Shield (United States)

    Sonbul, Abdullah R.; El-Shafei, Mohamed K.; Bishta, Adel Z.


    Modern earth resource satellites provide huge amounts of digital imagery at different resolutions. These satellite imageries are considered one of the most significant sources of data for mineral exploration. Image processing techniques were applied to the exposed rocks around the Al-Aqiq area of the Asir terrane in the southern part of the Arabian Shield. The area under study has two sub-parallel N-S trending metamorphic belts of green-schist facies. The first belt is located southeast of Al-Aqiq, where the Al-Hajar Gold Mine is situated. It is essentially composed of metavolcanics and metasedimentary rocks, and it is intruded by different plutonic rocks of primarily diorite, syenite and porphyritic granite. The second belt is located northwest of Al-Aqiq, and it is composed of metavolcanics and metasedimentary rocks and is intruded by granite bodies. The current study aimed to distinguish the lithological units, detect and map the alteration zones, and extract the major fault lineaments around the Al-Hajar gold prospect. Digital satellite imageries, including Landsat 7 ETM + multispectral and panchromatic and SPOT-5 were used in addition to field verification. Areas with similar spectral signatures to the prospect were identified in the nearby metamorphic belt; it was considered as a target area and was inspected in the field. The relationships between the alteration zones, the mineral deposits and the structural elements were used to locate the ore-bearing zones in the subsurface. The metasedimentary units of the target area showed a dextral-ductile shearing top-to-the-north and the presence of dominant mineralized quartz vein-system. The area to the north of the Al-Hajar prospect showed also sub-parallel shear zones along which different types of alterations were detected. Field-based criteria such as hydrothermal breccia, jasper, iron gossans and porphyritic granite strongly indicate the presence of porphyry-type ore deposits in Al-Hajar metamorphic belt that

  9. Origin of the mafic microgranular enclaves (MMEs) and their host granitoids from the Tagong pluton in Songpan-Ganze terrane: An igneous response to the closure of the Paleo-Tethys ocean (United States)

    Chen, Qiong; Sun, Min; Zhao, Guochun; Yang, Fengli; Long, Xiaoping; Li, Jianhua; Wang, Jun; Yu, Yang


    The Songpan-Ganze terrane is mainly composed of a Triassic sedimentary sequence and late Triassic-Jurassic igneous rocks. A large number of plutons were emplaced as a result of tectono-magmatic activity related to the late stages of Paleo-Tethys ocean closure and ensuing collision. Granitoids and their hosted mafic enclaves can provide important constraints on the crust-mantle interaction and continental crustal growth. Mesozoic magmatism of Songpan-Ganze remains enigmatic with regard to their magma generation and geodynamic evolution. The Tagong pluton (209 Ma), in the eastern part of the Songpan-Ganze terrane, consists mainly of monzogranite and granodiorite with abundant coeval mafic microgranular enclaves (MMEs) (ca. 208-209 Ma). The pluton comprises I-type granitoid that possesses intermediate to acidic compositions (SiO2 = 61.6-65.8 wt.%), high potassium (K2O = 3.2-4.1 wt.%), and high Mg# (51-54). They are also characterized by arc-type enrichment of LREEs and LILEs, depletion of HFSEs (e.g. Nb, Ta, Ti) and moderate Eu depletions (Eu/Eu* = 0.46-0.63). Their evolved zircon Hf and whole-rock Nd isotopic compositions indicate that their precursor magmas were likely generated by melting of old lower continental crust. Comparatively, the MMEs have lower SiO2 (53.4-58.2 wt.%), higher Mg# (54-67) and show covariation of major and trace elements, coupled with field and petrographic observations, such as the disequilibrium textures of plagioclase and amphibole, indicating that the MMEs and host granitoids were originated from different magma sources but underwent mafic-felsic magma mixing process. Geochemical and isotopic data further suggest that the precursor magma of the MMEs was formed in the continental arc setting, mainly derived from an ancient metasomatized lithospheric mantle wedge. The Triassic granitoids from the Songpan-Ganze terrane show remarkable temporal-spatial-petrogenetic affinities to the counterparts of subduction zones in the Yidun and Kunlun arc

  10. Survival of the Lhasa Terrane during its collision with Asia due to crust-mantle coupling revealed by ca. 114 Ma intrusive rocks in western Tibet (United States)

    Wang, Qing; Zhu, Di-Cheng; Liu, An-Lin; Cawood, Peter A.; Liu, Sheng-Ao; Xia, Ying; Chen, Yue; Wang, Hao; Zhang, Liang-Liang; Zhao, Zhi-Dan


    Survival of the Lhasa Terrane during its drift across the Tethyan Ocean and subsequent collision with Asia was likely maintained by mechanical coupling between its ancient lithospheric mantle and the overlying crust. Evidence for this coupling is provided by geochronological and geochemical data from high-Mg dioritic porphyrite dikes that intruded into granodiorites with dioritic enclaves within the Nixiong Batholith in the western segment of the central Lhasa subterrane, southern Tibet. Zircon LA-ICP-MS U-Pb dating indicates synchronous emplacement of dioritic porphyrite dikes (113.9 ± 2 Ma), dioritic enclaves (113.9 ± 1 Ma), and host granodiorites (113.1 ± 2 Ma). The hornblende-bearing granodiorites are metaluminous to weakly peraluminous (A/CNK = 0.95-1.05) and belong to high-K calc-alkaline I-type granite. These rocks are characterized by low Mg# (37-43), negative zircon εHf(t) values (-6.8 to -1.2), and negative whole-rock εNd(t) values (-8.1 to -5.4), suggestive of derivation through anatexis of ancient lower crust. The two least-mixed or contaminated dioritic porphyrite dike samples have high MgO (8.46-8.74 wt%), high Mg# (69-70), and high abundances of compatible elements (e.g., Cr = 673-646 ppm, Ni = 177-189 ppm), which are close to those of primitive magma. They are high-K calc-alkaline and show negative whole-rock εNd(t) values (-1.9 to -1.2), indicating that these samples are most likely derived from the partial melting of ancient lithospheric mantle that was metasomatized by slab-derived fluids. The dioritic enclave samples are metaluminous high-K calc-alkaline and have varying negative whole-rock εNd(t) values (-7.8 to -3.7), which are interpreted as the result of magma mixing between the ancient lower crust-derived melts and asthenospheric mantle- (rather than lithospheric mantle-) derived melts. The Nd isotope mantle model ages of the least-mixed or contaminated high-Mg dioritic porphyrite dike samples (1.1-1.4 Ga) are close to the Nd isotope

  11. Cryogenian alkaline magmatism in the Southern Granulite Terrane, India: Petrology, geochemistry, zircon U-Pb ages and Lu-Hf isotopes (United States)

    Santosh, M.; Yang, Qiong-Yan; Ram Mohan, M.; Tsunogae, T.; Shaji, E.; Satyanarayanan, M.


    The Southern Granulite Terrane (SGT) in India preserves the records of the formation and recycling of continental crust from Mesoarchean through Paleoproterozoic to Neoproterozoic and Cambrian, involving multiple subduction-accretion-collision associated with major orogenic cycles. A chain of unmetamorphosed and undeformed alkaline magmatic intrusions occurs along the northern margin of the SGT aligned along paleo-suture zones. Here we investigate two representative plutons from this suite, the Angadimogar syenite (AM) and the Peralimala alkali granite (PM) through field, petrological, geochemical, zircon U-Pb and Lu-Hf studies. Magma mixing and mingling textures and mineral assemblages typical of alkaline rocks are displayed by these plutons. The whole-rock major and trace element data characterize their alkaline nature. In trace element discrimination diagrams, the AM rocks straddle between the VAG (volcanic-arc granites) and WPG (within plate granites) fields with most of the samples confined to the VAG field, whereas the PM rocks are essentially confined to the WPG field. The diversity in some of the geochemical features between the two plutons is interpreted to be the reflection of source heterogeneities. Most zircon grains from the AM and PM plutons display oscillatory zoning typical of magmatic crystallization although some grains, particularly those from the PM pluton, show core-rim structures with dark patchy zoned cores surrounded by irregular thin rims resulting from fluid alteration. The weighted mean 206Pb/238U ages of the magmatic zircons from three samples of the AM syenite are in the range of 781.8 ± 3.8 Ma to 798 ± 3.6 Ma and those from two samples of the PM alkali granite yield ages of 797.5 ± 3.7 Ma and 799 ± 6.2 Ma. A mafic magmatic enclave from the AM pluton shows weighted mean 206Pb/238U age of 795 ± 3.3 Ma. The AM and PM plutons also carry rare xeneocrystic zircons which define upper intercept concordia ages of 3293 ± 13 Ma and 2530

  12. Paleomagnetic constraints on early collisional deformation along the eastern margin of the Qiantang terrane (Tibetan plateau) at 50 and 37 Ma. (United States)

    Roperch, Pierrick; Dupont-Nivet, Guillaume; Guillot, Stéphane; Goussin, Fanny; Huang, Wentao; Replumaz, Anne; Yang, Zhang; Guo, Zhaojie; Song, Bowen


    Ongoing controversies on the timing and latitude of the India-Asia collision with associated formation of the Tibetan plateau have major implications on geodynamic, climatic and biotic models. Rock paleomagnetic inclinations and declinations enable in principle to quantify respectively paleolatitudes and tectonic rotations. However, shallow paleomagnetic inclinations observed for most of the Cenozoic rocks across the active belts of Central Asia have been controversially interpreted as resulting from non dipolar geomagnetic fields, inclination flattening in the sedimentary data or large scale continental deformation. In addition tectonic rotations from the Eastern margin of Tibet may result from extrusion or dextral shear associated with implication on the early collision. We present new paleomagnetic results from two Cenozoic basins of the Eastern part of the Qiantang block characterized by two short-lived volcanic fields at 37-38Ma (Nangqian area) and 49-51Ma (Xialaxiu area). In the Xialaxiu area, we sampled the volcanic field near the town of Xialaxiu and red beds filling the Sangalaxiu basin 10 to 20km farther north. Results from the red beds after tilt correction (D=328.3°, I=34.3°, α95=7.6°) confirm the result (D=322.0°, I=32.3°, α95=9.5°) previously obtained by Cogne et al., (1999) but the age and nature of the characteristic magnetization are uncertain. The mean direction calculated from 21 sites in volcanic rocks provides a more reliable paleofield (D=11.9°, I=41.6°, α95=8.0°). Comparison with the expected direction for stable Eurasia suggest no rotation but significant post 50 Ma shortening north of the Qiantang block in agreement with results from the Lhasa terrane at the same age (56-47 Ma) (van Hinsbergen et al., 2012). In the Nangqian basin, paleomagnetic sites have been collected in red beds sediments, sills and dikes intruding the red bed sequence and in extrusive volcanic rocks mainly found on top of the sedimentary sequence. A well

  13. Recycling of Amazonian detrital zircons in the Mixteco terrane, southern Mexico: Paleogeographic implications during Jurassic-Early Cretaceous and Paleogene times (United States)

    Silva-Romo, Gilberto; Mendoza-Rosales, Claudia Cristina; Campos-Madrigal, Emiliano; Morales-Yáñez, Axél; de la Torre-González, Alam Israel; Nápoles-Valenzuela, Juan Ivan


    In the northeastern Mixteco terrane of southern Mexico, in the Ixcaquixtla-Atzumba region, the recycling of Amazonian detrital zircons records the paleogeography during the Mesozoic period in the context of the breakup of Pangea, a phenomenon that disarticulated the Sanozama-La Mora paleo-river. The clastic units of southern Mexico in the Ayuquila, Otlaltepec and Zapotitlán Mesozoic basins, as well as in the Atzumba Cenozoic basin, are characterized by detrital zircon contents with ages specific to the Amazonian craton, ranging between 3040 and 1278 Ma. The presence of zircons of Amazonian affinity suggests a provenance by recycling from carrier units such as the La Mora Formation or the Ayú Complex. In the area, the Ayú and Acatlán complexes form the Cosoltepec block, a paleogeographic element that during Early Cretaceous time acted as the divide between the slopes of the paleo-Gulf of Mexico and the paleo-Pacific Ocean. The sedimentological characteristics of the Jurassic-Cenozoic clastic successions in the Ixcaquixtla-Atzumba region denote relatively short transport in braided fluvial systems and alluvial fans. In this way, several basins are recognized around the Cosoltepec block. At the southeastern edge of the Cosoltepec block, the Ayuquila and Tecomazúchil formations accumulated in the Ayuquila continental basin on the paleo-Pacific Ocean slope. On the other hand, within the paleo-Gulf of Mexico slope, in the Otlaltepec continental basin, the Piedra Hueca and the Otlaltepec formations accumulated. The upper member of the Santa Lucía Formation accumulated in a transitional environment on the southwestern shoulder of the Zapotitlán basin, as well as on the paleo-Gulf of Mexico slope. In the Ayuquila basin, a marine transgression is recognized that advanced from south to north during the Late Jurassic. At the northeastern edge of the Cosoltepec block, we propose that the Santa Lucía formation attests to a transgression from the paleo-Gulf of Mexico

  14. Geochemistry, petrography, and zircon U-Pb geochronology of Paleozoic metaigneous rocks in the Mount Veta area of east-central Alaska: implications for the evolution of the westernmost part of the Yukon-Tanana terrane (United States)

    Dusel-Bacon, Cynthia; Day, Warren C.; Aleinikoff, John N.


    We report the results of new mapping, whole-rock major, minor, and trace-element geochemistry, and petrography for metaigneous rocks from the Mount Veta area in the westernmost part of the allochthonous Yukon–Tanana terrane (YTT) in east-central Alaska. These rocks include tonalitic mylonite gneiss and mafic metaigneous rocks from the Chicken metamorphic complex and the Nasina and Fortymile River assemblages. Whole-rock trace-element data from the tonalitic gneiss, whose igneous protolith was dated by SHRIMP U–Pb zircon geochronology at 332.6 ± 5.6 Ma, indicate derivation from tholeiitic arc basalt. Whole-rock analyses of the mafic rocks suggest that greenschist-facies rocks from the Chicken metamorphic complex, a mafic metavolcanic rock from the Nasina assemblage, and an amphibolite from the Fortymile River assemblage formed as island-arc tholeiite in a back-arc setting; another Nasina assemblage greenschist has MORB geochemical characteristics, and another mafic metaigneous rock from the Fortymile River assemblage has geochemical characteristics of calc-alkaline basalt. Our geochemical results imply derivation in an arc and back-arc spreading region within the allochthonous YTT crustal fragment, as previously proposed for correlative units in other parts of the terrane. We also describe the petrography and geochemistry of a newly discovered tectonic lens of Alpine-type metaharzburgite. The metaharzburgite is interpreted to be a sliver of lithospheric mantle from beneath the Seventymile ocean basin or from sub-continental mantle lithosphere of the allochthonous YTT or the western margin of Laurentia that was tectonically emplaced within crustal rocks during closure of the Seventymile ocean basin and subsequently displaced and fragmented by faults.

  15. Flux and genesis of CO2 degassing from volcanic-geothermal fields of Gulu-Yadong rift in the Lhasa terrane, South Tibet: Constraints on characteristics of deep carbon cycle in the India-Asia continent subduction zone (United States)

    Zhang, Lihong; Guo, Zhengfu; Sano, Yuji; Zhang, Maoliang; Sun, Yutao; Cheng, Zhihui; Yang, Tsanyao Frank


    Gulu-Yadong rift (GYR) is the longest extensional, NE-SW-trending rift in the Himalayas and Lhasa terrane of South Tibet. Many volcanic-geothermal fields (VGFs), which comprise intense hot springs, steaming fissures, geysers and soil micro-seepage, are distributed in the GYR, making it ideal area for studying deep carbon emissions in the India-Asia continent subduction zone. As for the northern segment of GYR in the Lhasa terrane, its total flux and genesis of CO2 emissions are poorly understood. Following accumulation chamber method, soil CO2 flux survey has been carried out in VGFs (i.e., Jidaguo, Ningzhong, Sanglai, Tuoma and Yuzhai from south to north) of the northern segment of GYR. Total soil CO2 output of the northern GYR is about 1.50 × 107 t a-1, which is attributed to biogenic and volcanic-geothermal source. Geochemical characteristics of the volcanic-geothermal gases (including CO2 and He) of the northern GYR indicate their significant mantle-derived affinities. Combined with previous petrogeochemical and geophysical data, our He-C isotope modeling calculation results show that (1) excess mantle-derived 3He reflects degassing of volatiles related with partial melts from enriched mantle wedge induced by northward subduction of the Indian lithosphere, and (2) the crust-mantle interaction can provide continuous heat and materials for the overlying volcanic-geothermal system, in which magma-derived volatiles are inferred to experience significant crustal contamination during their migration to the surface.

  16. Divergent plate motion drives rapid exhumation of (ultra)high pressure rocks (United States)

    Liao, Jie; Malusà, Marco G.; Zhao, Liang; Baldwin, Suzanne L.; Fitzgerald, Paul G.; Gerya, Taras


    Exhumation of (ultra)high pressure [(U)HP] rocks by upper-plate divergent motion above an unbroken slab, first proposed in the Western Alps, has never been tested by numerical methods. We present 2D thermo-mechanical models incorporating subduction of a thinned continental margin beneath either a continental or oceanic upper plate, followed by upper-plate divergent motion away from the lower plate. Results demonstrate how divergent plate motion may trigger rapid exhumation of large volumes of (U)HP rocks directly to the Earth's surface, without the need for significant overburden removal by erosion. Model exhumation paths are fully consistent with natural examples for a wide range of upper-plate divergence rates. Exhumation rates are systematically higher than the divergent rate imposed to the upper plate, and the modeled size of exhumed (U)HP domes is invariant for different rates of upper-plate divergence. Major variations are instead predicted at depth for differing model scenarios, as larger amounts of divergent motion may allow mantle-wedge exhumation to shallow depth under the exhuming domes. The transient temperature increase, due to ascent of mantle-wedge material in the subduction channel, has a limited effect on exhumed continental (U)HP rocks already at the surface. We test two examples, the Cenozoic (U)HP terranes of the Western Alps (continental upper plate) and eastern Papua New Guinea (oceanic upper plate). The good fit between model predictions and the geologic record in these terranes encourages the application of these models globally to pre-Cenozoic (U)HP terranes where the geologic record of exhumation is only partly preserved.

  17. Lost Terranes of Zealandia: possible development of late Paleozoic and early Mesozoic sedimentary basins at the southwest Pacific margin of Gondwanaland, and their destination as terranes in southern South America Terrenos perdidos de Zealandia: posible desarrollo de cuencas sedimentarias del Paleozoico tardío y Mesozoico temprano en el margen suroccidental del Pacífico de Gondwana y su destino como terrenos en el sur de América del Sur

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    Christopher J Adams


    Full Text Available Latest Precambrian to Ordovician metasedimentary successions and Cambrian-Ordovician and Devonian-Carboniferous granitoids form the major part of the basement of southern Zealandia and adjacent sectors of Antarctica and southeast Australia. Uplift/cooling ages of these rocks, and local Devonian shallow-water cover sequences suggest that final consolidation of the basement occurred through Late Paleozoic time. A necessary consequence of this process would have been contemporaneous erosion and the substantial development of marine sedimentary basins at the Pacific margin of Zealandia. These are found nowhere at the present day, suggesting that the basins have been lost by tectonic erosion, perhaps in a margin-parallel dextral translation similar to late Paleozoic-Mesozoic suspect terranes of New Zealand. Aprobable detrital zircon age pattern is assembled for these lost Zealandia sediments, and then compared with those of pre-Jurassic (probable Triassic to Devonian metasedimentary rocks in the Chilean archipelago. Significant Mesoproterozoic, latest Neoproterozoic-Cambrian and Devonian-Carboniferous detrital zircon age components are common to both, thus supporting a possible Chilean terrane destination for these 'lost terranes of Zealandia'.Las sucesiones metasedimentarias del Precámbrico tardío al Ordovícico y granitoides del Cámbrico-Ordovícico y Devónico-Carbonífero constituyen la mayor parte del basamento del sur de Zealandia y sectores adyacentes de la Antartica y el sudeste de Australia. Las edades de enfriamiento/alzamiento de estas rocas y la cobertura local de secuencias de aguas someras del Devónico, sugieren que la consolidación definitiva del basamento se produjo durante el Paleozoico tardío. Una consecuencia necesaria de este proceso habría sido la erosion contemporánea y el desarrollo sustancial de cuencas sedimentarias marinas en el margen del Pacífico de Zealandia. Estas no se encuentran en ninguna parte en la

  18. Petrography and geochronology (U/Pb-Sm/Nd) the Passagem Granite, Pensamiento Granitoid Complex, Paragua Terrane, SW Amazon Craton, Mato Grosso, Brazil; Petrologia e geocronologia (U/Pb-Sm/Nd) do Granito Passagem, Complexo Granitoide Pensamiento, SW do Craton Amazonico (MT)

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    Jesus, Gisely Carmo de, E-mail: [Universidade Federal de Mato Grosso (ICET/UFMT), Cuiaba, MT (Brazil). Inst. de Ciencias Exatas e da Terra. Programa de Pos-Graduacao em Geociencias; Sousa, Maria Zelia Aguiar de, E-mail: [Universidade Federal de Mato Grosso(ICET/UFMT), Cuiaba, MT (Brazil). Inst. de Ciencias Exatas e da Terra. Dept. de Recursos Minerais; Ruiz, Amarildo Salina; Matos, Joao Batista de, E-mail:, E-mail: jmatos@cpd.ufmt.b [Universidade Federal de Mato Grosso (ICET/UFMT), Cuiaba, MT (Brazil). Inst. de Ciencias Exatas e da Terra. Dept. de Geologia Geral


    The Passagem granite includes stocks, plugs and dikes located in the Ricardo Franco hill - Vila Bela da Santissima Trindade region - state of Mato Grosso, central Brazil. The Passagem Granite is included in the Paragua terrane - SW Amazonian Craton. It consists of isotropic monzogranite, sienogranite and more rarely granodiorites with leucocratic dark gray to white color. These rocks range from hypidomorphic inequigranular to xenomorphic texture, fine to medium grained. Biotite is the only primary mafic present as essential phase and characterize an expanded slightly acid sequence formed by a sub-alkaline magmatism of high-potassium calc-alkaline, slightly peraluminous composition from arc magmatic tectonic environment during a post-collisional period. Mechanism of fractional crystallization of plagioclase, biotite, titanite, apatite and zircon associated with simultaneous crustal assimilation are suggested for the evolution of these rocks. The results support the hypothesis of a post-collisional magmatism in the Paragua terrane at 1284 +- 20 Ma corresponding to the crystallization age of the Passagem granite. This paper propose that Passagem Granite represents as an extension in Brazilian terrane of the Pensamiento Granitoid Complex. (author)

  19. Archean crustal evolution of the Narryer Gneiss Terrane, Western Australia, as revealed by the U-Pb age and Hf-isotope compositions of zircon from the granitic gneisses (United States)

    Sylvester, P.; Souders, K.; Crowley, J. L.; Myers, J.


    The Narryer Gneiss Terrane of the Yilgarn Craton, Western Australia, is an important area for studies of early crustal evolution because of the preservation of (1) detrital zircons of Hadean to Archean age in the Jack Hills and Mt. Narryer metasedimentary belts, and (2) several widespread units of granitic gneisses emplaced between ca. 3.7 and 2.6 Ga. We have analyzed the U-Pb geochronology and Hf-isotope geochemistry of magmatic zircons from 38 samples of the granitic gneisses using laser ablation - (multicollector) - ICPMS. The sample suite is dominated by the Meeberrie gneiss, a banded quartz-microcline-oligoclase-biotite gneiss of monzogranite to granodiorite composition, and the Dugel gneiss, a leucocratic, pegmatite-layered syenogranite gneiss, but gneisses of dioritic to tonalitic composition, as well as less deformed granite sheets, are also represented. Magmatic zircons were identified on the basis of the preservation of oscillatory zoning in BSE and CL images, igneous Th/U ratios (>0.2), and concordant U-Pb isotopic systematics with low common Pb contents. The results indicate many of the gneisses are composed of the products of multiple magmatic events, as has been reported previously for samples of the Meeberrie gneiss (Kinny & Nutman, 1996, Precambrian Res. 78, 165-178). Major ages of magmatism preserved in the gneisses occurred at ca. 3685-3665 Ma, 3620-3565 Ma, 3495-3440 Ma, 3375-3330 Ma, and 3300-3260 Ma. The late granite sheets crystallized at 2710-2645 Ma. Hf-isotope compositions of the zircons trend to less radiogenic values with decreasing age, with ɛHf values of ca. 0 to -5 for 3.7-3.4 Ga gneisses, ca. -1 to -9 for 3.4-3.2 Ga gneisses and ca. -5 to -20 for the late granite sheets. The array of the Hf isotopic compositions with time for the entire sample set are fit well by a regression indicating a source reservoir with a 176Lu/177Hf of 0.022 extracted from the depleted mantle at 3.9 Ga. This suggests that the Narryer gneisses and late granite

  20. Geology, petrology, U-Pb (shrimp geochronology of the Morrinhos granite -Paraguá terrane, SW Amazonian craton: implications for the magmatic evolution of the San Ignácio orogeny

    Directory of Open Access Journals (Sweden)

    Ohana França

    Full Text Available Morrinhos granite is a batholith body that is slightly elongated in the NNW direction and approximately 1,140 km2 long; it is located in the municipality of Vila Bela da Santíssima Trindade of the state of Mato Grosso, Brazil, in the Paraguá Terrane, Rondonian-San Ignácio Province, in the SW portion of the Amazonian Craton. This intrusion displays a compositional variation from tonalite to monzogranite, has a medium to coarse inequigranular texture and is locally porphyritic; biotite is the predominant mafic in one of the facies, and hornblende is predominant in the other, with both metamorphosed into the greenschist facies. The studied rocks characterize an intermediate to acidic sequence that was formed by a subalkaline magmatism; the series is alkali-calcic to metaluminous to slightly peraluminous, and the rocks evolved through fractioned crystallization mechanisms. The structural data show two deformation phases represented by penetrative foliation (S1 and open folds (D2, and both phases were most likely related to the San Ignácio Orogeny. The geochronological (U-Pb SHRIMP and isotopic (Sm-Nd investigations of these rocks indicated a crystallization age of 1350 ± 12 Ma, TDMof approximately 1.77 Ga and εNd(1.35with a negative value of -2.57, suggesting that their generation was related to a partial melting process of a Paleoproterozoic (Statherian continental crust. The results herein indicate that the Morrinhos granite was generated in a continental magmatic arc in a late- to post-orogenic stage of the San Ignácio Orogeny, and it can be recognized as belonging to the Pensamiento Intrusive Suite.

  1. Evolution of the Archean continental crust in the nucleus of the Yangtze block: Evidence from geochemistry of 3.0 Ga TTG gneisses in the Kongling high-grade metamorphic terrane, South China (United States)

    Qiu, Xiao-Fei; Ling, Wen-Li; Liu, Xiao-Ming; Lu, Shan-Song; Jiang, Tuo; Wei, Yun-Xu; Peng, Lian-Hong; Tan, Juan-Juan


    Archean Tonalite-Trondhjemite-Granodiorite (TTG) rocks are scattered within the Kongling high-grade metamorphic terrane (KHMT) in the northern South China block. A comprehensive geochronological and geochemical study is carried out on the Taoyuan granitic gneisses, a newly recognized TTG suite in the northwestern KHMT. This suite has long been regarded as a Mesoproterozoic magmatic pluton, but U-Pb zircon ages of 2994 ± 22 Ma and 2970 ± 15 Ma are obtained by LA-ICP-MS method in this study. The Taoyuan gneiss suite is trondhjemitic in composition, and has high SiO2 (67.80-74.93 wt.%), Na2O (5.11-5.81 wt.%) contents with Na2O/K2O ratios greater than unity, and low Ni (2.56-7.61 ppm), Cr (1.26-7.67 ppm), Yb (0.32-0.82 ppm) and Y (4.48-11.5 ppm) contents. Plots show large variation in La/Yb and Sr/Y ratios and pronounced depletion in Nb, Ta and Ti in the primitive mantle-normalized spiderdiagram. The gneiss suite also displays two-stage Nd model ages close to its crystallization age with corresponding εNd(t) values of -2.5 to +3.5. It is thus suggested that the Taoyuan gneisses, in fact, is part of the Archean Kongling basement complex. Geochemical evidence implies that the TTG rocks may be derived from partial melting of subducted oceanic crust from a garnetiferous amphibolite source with residual assemblage of garnet + amphibole + plagioclase. Our study further indicates that the nucleus of the Yangtze block might experience a juvenile continental crustal growth during Mesoarchean. We also suggest that the Yangtze block may have its own crustal evolutionary history independent from the North China craton and the Tarim block before Paleoproterozoic.

  2. Lithology and mineralogy recognition from geochemical logging tool data using multivariate statistical analysis. (United States)

    Konaté, Ahmed Amara; Ma, Huolin; Pan, Heping; Qin, Zhen; Ahmed, Hafizullah Abba; Dembele, N'dji Dit Jacques


    The availability of a deep well that penetrates deep into the Ultra High Pressure (UHP) metamorphic rocks is unusual and consequently offers a unique chance to study the metamorphic rocks. One such borehole is located in the southern part of Donghai County in the Sulu UHP metamorphic belt of Eastern China, from the Chinese Continental Scientific Drilling Main hole. This study reports the results obtained from the analysis of oxide log data. A geochemical logging tool provides in situ, gamma ray spectroscopy measurements of major and trace elements in the borehole. Dry weight percent oxide concentration logs obtained for this study were SiO 2 , K 2 O, TiO 2 , H 2 O, CO 2 , Na 2 O, Fe 2 O 3 , FeO, CaO, MnO, MgO, P 2 O 5 and Al 2 O 3 . Cross plot and Principal Component Analysis methods were applied for lithology characterization and mineralogy description respectively. Cross plot analysis allows lithological variations to be characterized. Principal Component Analysis shows that the oxide logs can be summarized by two components related to the feldspar and hydrous minerals. This study has shown that geochemical logging tool data is accurate and adequate to be tremendously useful in UHP metamorphic rocks analysis. Copyright © 2017 Elsevier Ltd. All rights reserved.

  3. Rare earth element and strontium isotopic study of seamount-type limestones in Mesozoic accretionary complex of Southern Chichibu Terrane, central Japan. Implication for incorporation process of seawater REE into limestones

    International Nuclear Information System (INIS)

    Tanaka, Kazuya; Miura, Noriko; Asahara, Yoshihiro; Kawabe, Iwao


    Ishimaki and Tahara limestones occur as exotic blocks juxtaposed in the Mesozoic (Jurassic) accretionary complex of Southern Chichibu Terrane in eastern Aichi Prefecture, central Japan. They are supposed to be of the seamount-type limestone, since they have no terrigenous materials and are intimately associated with greenstones. REE (rare earth elements) and Sr isotopic studies for the limestones have been made in order to know their geochemical characteristics, ages and origins. Their 87 Sr/ 86 Sr ratios, when referred to the seawater 87 Sr/ 86 Sr curve and relevant geological data, suggest that Ishimaki and Tahara limestones are the late Permian and the Carboniferous to the Early Permian, respectively. Two greenstone fragments found inside the Ishimaki limestone block and one greenstone sample associated with Tahara limestone block, resemble the Hawaiian alkali basalt in the their REE and Y patterns. This is supporting the idea that the limestone blocks may be parts of reef limestones on ancient volcanic seamounts. All the limestone samples, except three unusual Tahara ones, show seawater REE and Y signatures in their chondrite-normalized patterns. Their REE/Ca ratios, however, are 10 2 -10 4 times as high as those ratios of modern biogenic carbonates like corals and the seawater. Accordingly, seawater REE and Y were incorporated into the limestones, when originally biogenic carbonates transformed into inorganic calcite and its secondary growths occurred in diagenesis in contact with sufficient seawater. This view is favored by the reported REE partition experiment between calcite overgrowths and seawater solution. The seawater Ce anomaly as a function of water depth in the modern ocean is a key to infer the water depth of the REE and Y incorporation. The Ce anomalies given by log (Ce/Ce*) for about a half of Ishimaki samples and most of Tahara ones are between -0.5 and -0.2, which are compatible with the shallow water origin. Another half of Ishimaki samples

  4. Chapter 2 Western dominance Piedra Alta terrane

    International Nuclear Information System (INIS)


    Piedra Alta Stone includes: geo chemical and geochronology of the granitic complex is located in the SW portion of the crystalline basement of Uruguay. It consists of four thin metamorphic belts separated by a granitic complex - gneissic - migmatítico (CGG) and associated with an important granite, granodiorite, basic or ultrabasic magmatic. Belts north to south are called Arroyo Grande Andresito by renowned Bossi et al. (2000); San Jose (Preciozzi et al., 1991), San Juan (Preciozzi et al, 2005) and Montevideo (Bossi et al., 1993) Pando by renowned Bossi et al. (2000). They are composed of volcano-sedimentary units of different degrees of metamorphism and a set of associated intrusions

  5. Punta del Este terrane : a better knowledge

    International Nuclear Information System (INIS)

    Preciozzi, F.; Sanchez Bettucci, L; Basei, M.


    Field Punta del Este (TPE) is constituted by a series of gneisses and migmatites formed in the range of 1000 and 900 Ma, and have been intensely reworked during Rio Doce orogeny (ca. 600-500 Ma). This cortical segment represents high-grade metamorphic terrain, correlatable with complex gneiss Southwest Africa, particularly with Kibariáno Belt - Namaqualanos recognized in the southwestern portion of Africa (Namibia). U-Pb zircon ages in tonalite granitoids indicate values ​​between 1000 and 900 Ma and were interpreted as indicating the time of generation of these rocks. This should also be the age of high-grade metamorphism that affected a large part of the gneissic rocks of the region. Moreover, the anatectic related mobilized leucosomes ages of migmatites gave ca. 520-540 Ma, indicating that the metamorphic conditions (overlapping) during the Rio Doce orogeny reached at least the amphibolite facies. The metasedimentary cover TPE occurs in the vicinity of the towns of La Paloma Rocha. These are represented by a siliciclastic metasedimentary sequence represented by Rocha Formation. Despite the poly phase deformation and low grade metamorphism affecting this training, primary structures are common such as stratification plano-parallel, cross-bedding, hummock y and massive levels with gradational stratification

  6. 西藏拉萨地块过铝质花岗岩中继承锆石的物源区示踪及其古地理意义%Tracing the provenance of inheritedzircons from peraluminous granites in the Lhasa Terrane and its paleogeographic implications

    Institute of Scientific and Technical Information of China (English)

    朱弟成; 赵志丹; 牛耀龄; 王青; DILEK Yildirim; 管琪; 刘勇胜; 莫宣学


    rocks (and their metamorphosed equivalents). This paper reports the whole-rock geochemical and zircon U-Pb geochronological data (95 analyses) of the Early Jurassic peraluminous granites in the central Lhasa subterrane. These data, in combination with the existing data of inherited zircons (104 analyses) from the Permian and Late Triassic peraluminous granites currently available in the central Lhasa subterrane, are used to characterize the inherited zircon signature of the Lhasa Terrane. These granites belong to strongly peraluminous S-type granites, which contain abundant inherited zircons that define two main age populations of 1250 ~ ll00Ma (peak at 1181 ± 14Ma) and 550 ~450Ma (peak at 494 ±7Ma), comparable to the ca. 1170 Ma age population defined by detrital zircons from Paleozoic sedimentary rocks and the emplacement timing of Cambrian volcanic rocks in the Lhasa Terrane, respectively. The ca. 1170Ma age population defined by inherited and detrital zircons in the Lhasa Terrane differs significantly from the age distributions ( peak at ca. 960Ma) defined by detrital zircons from Neoproterozoic-Paleozoic sedimentary rocks in the western Qiangtang, Amdo, and Tethyan Hiamalaya in southern Tibet We propose that the ca 1181 Ma inherited zircons from peraluminous granites in the central Lhasa subterrane were most likely derived from the Albany-Fraser orogenic belt in southwestern Australia and Wilkes Province in East Antarctica, as do the coeval detrital zircons from Paleozoic sedimentary rocks in the Lhasa Terrane, and that the ca, 494 Ma inherited zircons might have been sourced from both the Western Australia and Lhasa Terrane itself. This paper provides evidence of U-Pb dating on inherited zircons from peraluminous granites for the paleogeographic connection between the Lhasa Terrane and northern Australia. Our studies on the geology of the Lhasa Terrane indicate that a combined in-situ U-Pb dating on inherited zircons from peraluminous granites and detrital

  7. Civil Society Engagement in the Sulu Archipelago: Mobilizing Vibrant Networks to Win the Peace (United States)


    The revolutions of 1989 in Eastern Europe revitalized the idea of civil society. In the collapse of communist states, civil society played a...Security 26, no. 1 (Summer): 93-128. Arrow, Ruaridh. 2011. How to start a revolution. iTunes APP and Documentary. Produced by The Project Factory and

  8. Tekstil boyar maddesinin sulu çözeltilerinden elektrokimyasal yöntemler ile giderimi


    Yamaç, Duygu


    Bu çalışmada bir azo boya olan Deep Red içeren model atıksuyun arıtımı için mikroelektroliz, elektrokoagülasyon ve elektro-Fenton yöntemleri kullanıldı. Mikroelektroliz deneylerinde boya giderimi üzerinde dolgu maddesi, çözelti derişimi, pH, elektriksel iletkenlik ve besleme hızının etkileri incelenmiştir. Mikroelektroliz için en yüksek giderim olan %99,5 değerine toz demir talaşı-aktif karbon dolgu maddesi ile, 150 mg/L çözelti derişiminde, pH değeri 3, elektriksel iletkenlik ...

  9. Evaluation of Ultra High Pressure (UHP) Firefighting in a Room-and-Contents Fire (United States)


    legal liability or responsibility for the accuracy, completeness, or usefulness of any information, apparatus, product, or process disclosed, or...venomous insects. Abort Criteria and Procedures If a fire has already been lit and an abort is necessary, the firefighter(s) will attempt to put

  10. Formation of Atoll Garnets in the UHP Eclogites of the Tso Morari ...

    Indian Academy of Sciences (India)


    across the studied atoll grains show elemental variations with higher concentrations of Ca and. 10 ...... from a single eclogite outcrop in the complex and probably represent a case of accidental. 28 ... Textural and compositional relations in the.

  11. Formation of atoll garnets in the UHP eclogites of the Tso Morari Complex, Ladakh, Himalaya (United States)

    Jonnalagadda, Mallika K.; Karmalkar, Nitin R.; Duraiswami, Raymond A.; Harshe, Shivani; Gain, Sarah; Griffin, William L.


    The eclogites of the Tso Morari Complex, Ladakh, NW Himalayas preserve both garnets with spectacular atoll textures, as well as whole porphyroblastic garnets. Whole garnets are euhedral, idiomorphic and enclose inclusions of amphibole, phengite and zoisite within the cores, and omphacite and quartz/coesite towards the rims. Detailed electron microprobe analyses and back-scattered electron images show well-preserved prograde zoning in the whole garnets with an increase in Mg and decrease in Ca and Mn contents from the core to the rim. The atoll garnets commonly consist of euhedral ring over island/peninsular core containing inclusions of phengite, omphacite and rarely amphibole between the core and ring. Compositional profiles across the studied atoll grains show elemental variations with higher concentrations of Ca and Mn with low Mg at the peninsula/island cores; contrary to this low Ca, Mn and high Mg is observed at the outer rings. Temperature estimates yield higher values at the Mg-rich atoll garnet outer rings compared to the atoll cores. Atoll garnet formation was favoured by infiltration of fluid formed due to breakdown of hydrous phases, and/or the release of structurally bounded OH from nominally anhydrous minerals at the onset of exhumation. Infiltration of fluids along pre-existing fracture pathways and along mineral inclusion boundaries triggered breakdown of the original garnet cores and released elements which were subsequently incorporated into the newly-grown garnet rings. This breakdown of garnet cores and inward re-growth at the outer ring produced the atoll structure. Calibrated geo-thermobarometers and mineral equilibria reflect that the Tso Morari eclogites attain peak pressures prior to peak temperatures representing a clockwise path of evolution.

  12. Formation of atoll garnets in the UHP eclogites of the Tso Morari ...

    Indian Academy of Sciences (India)

    Mallika K Jonnalagadda


    Nov 22, 2017 ... Shivani Harshe1, Sarah Gain2 and William L Griffin2. 1. Department of ..... M orari complex. L1. -. N ormal. G arnet. T rav erse. Mineral. G arnet. A mp. Garnet. Cp x. G ...... along with white mica occur as shear bands (0.5. GPa and 500 ..... erals in the crust; Treatise on Geochemistry, Amsterdam. Elsevier 3 ...

  13. Lithium Behavior during Growth of Metasedimentary Garnets from the Cignana UHP Locality, Italy (United States)

    Bebout, G. E.; Tsujimori, T.; Ota, T.; Shimaki, Y.; Kunihiro, T.; Carlson, W. D.; Nakamura, E.


    We investigated major and trace element concentrations and δ7Li in garnets in Lago di Cignana metasedimentary rocks (peak conditions ~550˚C, 2.5-3.0 GPa), following the EPMA-SIMS approach of Tsujimori et al. (2014; IMA conference abstract). Previous work on the devolatilization history of these rocks (Bebout et al., 2013; Cook-Kollars et al., 2014; both in Chemical Geology) provides a petrologic and geochemical context for this study. Lithium is of interest as a tracer of fluid-rock interactions and because of its potential to isotopically fractionate during diffusional processes. All garnets are almandine-rich with strongly decreasing MnO and increasing MgO toward rims. HREEs, Y, and Li also show strong zoning, with elevated concentrations in cores (15-50 ppm Li) and marked high-concentration anomalies (up to 117 ppm Li, 5500 ppm Y), with little or no major element shift, as growth annuli at which some garnets have elevated δ7Li. In all garnets, rutile inclusions appear abruptly at annuli and outward toward rims, accompanied by inclusions of a Ca- and LREE-rich phase and decreased Nb concentrations in garnet. These relationships appear to reflect prograde garnet-forming reaction(s) that in part involved titanite breakdown to stabilize rutile, which resulted in delivery of more abundant Y and HREEs at surfaces of growing garnets to produce growth annuli. The co-enrichment of Li and Y+REEs is attributed to their mutual incorporation via a charge-coupled substitution (Carlson et al., 2014; American Mineralogist); thus the increased Li uptake is a passive consequence of the elevated concentrations of Y+REEs. Distributions of δ7Li are complex, with most garnets showing only subtle core-to-rim variation other than at Y+REE annuli. At annuli, some garnets display elevated δ7Li (by up to 8‰), while others in the same rock do not. Small-scale fluctuations in δ7Li may correlate with abrupt shifts in major and trace element concentrations, suggesting that changes in the minerals involved as reactants exert some control on the evolution of δ7Li.

  14. Application of Waste Heat Recovery Energy Saving Technology in Reform of UHP-EAF (United States)

    Zhao, J. H.; Zhang, S. X.; Yang, W.; Yu, T.


    The furnace waste heat of a company’s existing 4 × 100t ultra-high-power electric arc furnaces is not used and discharged directly of the situation has been unable to meet the national energy-saving emission reduction requirements, and also affected their own competitiveness and sustainable development. In order to make full use of the waste heat of the electric arc furnace, this paper presents an the energy-saving transformation program of using the new heat pipe boiler on the existing ultra-high-power electric arc furnaces for recovering the waste heat of flue gas. The results show that after the implementation of the project can save energy equivalent to 42,349 tons of standard coal. The flue gas waste heat is fully utilized and dust emission concentration is accorded with the standard of Chinese invironmental protection, which have achieved good results.

  15. Mafic rocks from Erinpura gneiss terrane in the Sirohi region ...

    Indian Academy of Sciences (India)

    1Department of Geology, University of Rajasthan, Jaipur 302 004, India. 2GeoZentrum .... from massive to foliated types wherein the gener- ally steep foliations show ... ered for kinematic analyses of the shear movement. These features are ...

  16. Geochronologic synthesis of the Piedra Alta Terrane, Uruguay

    International Nuclear Information System (INIS)

    Preciozzi, F.; Peel, E.


    In the Pre cordillera of Córdoba there are sixteen bands of ductile deformation, which allows tectonic significance assign them to four groups. One of them, which belongs to Deformation Gaza Tunnels, consists of post metamorphic strips uprooting of Orogen Pampeano Cambrian reverse nature, produced by convergent general shear (transpressional), related to collisional stages terrain Posthumous Pampa against Gondwana margin, and famatinian subduction. New radiometric data obtained by the K / Ar method amphiboles and micas allow better narrow activity tectonics of the strip, which would have nucleated after the M2 metamorphic peak (ca. 534 Ma), uprooted the Orogen Cambrian and Ordovician exhumándolo up early (onset of subduction Famatinian), when located the Charquina (474 ​​Ma) granodiorite. The period of tectonic activity FDLT (ca. 64 Ma), coincide with the approach of land Cuyania the Gondwana margin, prior to placement and final collision in the Middle to Late Ordovician. At the same time, in the field Pampeano they would be producing con tractional stages end collision with terrain Pampa the western margin of Gondwana. Subsequently, the FDLT would have cooled to the middle Silurian, when the Sierras de Cordoba and San Luis They continued their exhumation through isotherm muscovite. After cooling this generalized, deformation occurs and Devonian magmatism that penetrativamente affected the Pre cordillera eastern

  17. Tectonics of suspect terranes mountain building and continental growth

    CERN Document Server

    Howell, David G


    Year by year the Earth sciences grow more diverse, with an inevitable increase in the degree to which rampant specialization isolates the practitioners of an ever larger number of sub fields. An increasing emphasis on sophisticated mathematics, physics and chemistry as well as the use of advanced technology have. set up barriers often impenetrable to the uninitiated. Ironically, the potential value of many specialities for other, often non-contiguous once has also increased. What is at the present time quiet, unseen work in a remote corner of our discipline, may tomorrow enhance, even revitalize some entirely different area. The rising flood of research reports has drastically cut the time we have available for free reading. The enormous proliferation of journals expressly aimed at small, select audiences has raised the threshold of access to a large part of the literature so much that many of us are unable to cross it. This, most would agree, is not only unfortunate but downright dangerous, limiting by sheer...

  18. Emplacement kinematics of nepheline syenites from the Terrane ...

    Indian Academy of Sciences (India)

    R. Narasimhan (Krishtel eMaging) 1461 1996 Oct 15 13:05:22

    tiled up in an imbricate fashion (figure 3b). The majority of the minerals in nepheline syenite show uniform extinction, feldspars show straight twin lamellae and hornblende and biotite flakes lack any kind of kink on their cleavage. Thus it has been inferred that the minerals are predominantly of magmatic origin and have not ...

  19. Eclogite-facies metamorphism in impure marble from north Qaidam orogenic belt: Geodynamic implications for early Paleozoic continental-arc collision (United States)

    Chen, Xin; Xu, Rongke; Schertl, Hans-Peter; Zheng, Youye


    In the North Qaidam ultrahigh-pressure (UHP) metamorphic belt, impure marble and interbedded eclogite represent a particular sedimentary provenance and tectonic setting, which have important implications for a controversial problem - the dynamic evolution of early Paleozoic subduction-collision complexes. In this contribution, detailed field work, mineral chemistry, and whole-rock geochemistry are presented for impure marble to provide the first direct evidence for the recycling of carbonate sediments under ultrahigh-pressures during subduction and collision in the Yuka terrane, in the North Qaidam UHP metamorphic belt. According to conventional geothermobarometry, pre-peak subduction to 0.8-1.3 GPa/485-569 °C was followed by peak UHP metamorphism at 2.5-3.3 GPa/567-754 °C and cooling to amphibolite facies conditions at 0.6-0.7 GPa/571-589 °C. U-Pb dating of zircons from impure marble reveals a large group with ages ranging from 441 to 458 Ma (peak at 450 Ma), a smaller group ranging from 770 to 1000 Ma (peak at 780 Ma), and minor >1.8 Ga zircon aged ca. 430 Ma UHP metamorphism. The youngest detrital zircons suggest a maximum depositional age of ca. 442 Ma and a burial rate of ca. 1.0-1.1 cm/yr when combined with P-T conditions and UHP metamorphic age. The REE and trace element patterns of impure marble with positive Sr and U anomalies, negative high field strength elements (Nb, Ta, Zr, Hf, and Ti), and Ce anomalies imply that the marble had a marine limestone precursor. Impure marble intercalated with micaschist and eclogite was similar to limestone and siltstone protoliths deposited in continental fore-arc or arc setting with basic volcanic activity. Therefore, the Yuka terrane most likely evolved in a continental island arc setting during the Paleozoic. These data suggest that metasediments were derived from a mixture of Proterozoic continental crust and juvenile early Paleozoic oceanic and/or island arc crust. In addition, their protoliths were likely

  20. Detrital zircon provenance from three turbidite depocenters of the Middle-Upper Triassic Songpan-Ganzi complex, central China: Record of collisional tectonics, erosional exhumation, and sediment production (United States)

    Weislogel, A.L.; Graham, S.A.; Chang, E.Z.; Wooden, J.L.; Gehrels, G.E.


    To test the idea that the voluminous upper Middle to Upper Triassic turbidite strata in the Songpan-Ganzi complex of central China archive a detrital record of Dabie ultrahigh-pressure (UHP) terrane unroofing, we report 2080 single detrital U-Pb zircon ages by sensitive high-resolution ion microprobe-reverse geometry (SHRIMP-RG) and laser ablation-inductively coupled plasma-mass spectrometry (LA-ICP-MS) analysis from 29 eastern Songpan-Ganzi complex sandstone samples. Low (Th/U zircons, consistent with crystallization under UHP conditions, are rare in eastern Songpan-Ganzi complex zircon, and U-Pb ages of low Th/U zircons are incompatible with a Dabie terrane source. An unweighted pair group method with arithmetic mean nearest-neighbor analysis of Kolmogorov-Smirnov two-sample test results reveals that the eastern Songpan-Ganzi complex is not a single contiguous turbidite system but is instead composed of three subsidiary depocenters, each associated with distinct sediment sources. The northeastern depocenter contains zircon ages characterized by Paleozoic and bimodally distributed Precambrian zircon populations, which, together with south-to southeast-directed paleocurrent data, indicate derivation from the retro-side of the Qinling-Dabie (Q-D) collisional orogen wedge. In the central depocenter, the dominantly Paleozoic detrital zircon signature and south-to southwest-oriented paleocurrent indicators reflect a profusion of Paleozoic zircon grains. These data are interpreted to reflect an influx of material derived from erosion of Paleozoic supra-UHP rocks of the Dabie terrane in the eastern Qinling-Dabie orogen, which we speculate may have been enhanced by development of a monsoonal climate. This suggests that erosional unroofing played a significant role in the initial phase of UHP exhumation and likely influenced the petrotectonic and structural evolution of the Qinling-Dabie orogen, as evidenced by compressed Triassic isotherms/grads reported in the Huwan

  1. Maruyamaite, a new K-dominant tourmaline coexisting with diamond -an important accessory mineral in UHP rocks (United States)

    Stock, M. J.; Humphreys, M.; Smith, V.; Pyle, D. M.; Isaia, R.


    The apatite crystal structure is capable of incorporating H2O, F and Cl, as well as trace CO2 and sulphur. These can be related to parental magma compositions through application of a series of pressure and temperature-dependent exchange reactions (Piccoli and Candela, 1994), permitting apatite crystals to preserve a record of all major volatile species in the melt. Furthermore, due to the general incompatibility of P in other rock-forming minerals, apatite is ubiquitous in igneous systems and often begins crystallising early, such that apatite inclusions within phenocrysts record melt volatile contents throughout magmatic differentiation. In this work, we compare the compositions of apatite inclusions and microphenocrysts with pyroxene-hosted melt inclusions from the Astroni 1 eruption of Campi Flegrei, Italy. These data are coupled with magmatic differentiation models (Gualda et al., 2012), experimental volatile solubility data (Webster et al., 2014) and thermodynamic models of apatite compositional variations (Piccoli and Candela, 1994) to determine a time-series of magmatic volatile evolution in the build-up to eruption. We find that apatite halogen/OH ratios decreased through magmatic differentiation, while melt inclusion F and Cl concentrations increased. Melt inclusion H2O contents are constant at ~2.5 wt%. These data are best explained by volatile-undersaturated differentiation over most of the crystallisation history of the Astroni 1 melt, with melt inclusion H2O contents reset during ascent, due to rapid H diffusion through the phenocryst hosts (Woods et al., 2000). Given the rapid diffusivity of volatiles in apatite (Brenan, 1993), preservation of undersaturated compositions in microphenocrysts suggests that saturation was only achieved a few days to months before eruption and that it may have been the transition into a volatile-saturated state that ultimately triggered eruption. Piccoli and Candela, 1994. Am. J. of Sc., 294, 92-135. Gualda et al., 2012. J. Pet., 53, 875-890. Webster et al., 2014. J. Pet., 55, 2217-2248. Woods et al., 2000. Am. Min., 85, 480-487. Brenan, 1993. Chem. Geol., 110, 195-210.

  2. A young multilayered terrane of the northern Mare Imbrium revealed by Chang’E-3 mission (United States)

    Xiao, Long; Zhu, Peimin; Fang, Guangyou; Xiao, Zhiyong; Zou, Yongliao; Zhao, Jiannan; Zhao, Na; Yuan, Yuefeng; Qiao, Le; Zhang, Xiaoping; Zhang, Hao; Wang, Jiang; Huang, Jun; Huang, Qian; He, Qi; Zhou, Bin; Ji, Yicai; Zhang, Qunying; Shen, Shaoxiang; Li, Yuxi; Gao, Yunze


    China’s Chang’E-3 (CE-3) spacecraft touched down on the northern Mare Imbrium of the lunar nearside (340.49°E, 44.12°N), a region not directly sampled before. We report preliminary results with data from the CE-3 lander descent camera and from the Yutu rover’s camera and penetrating radar. After the landing at a young 450-meter crater rim, the Yutu rover drove 114 meters on the ejecta blanket and photographed the rough surface and the excavated boulders. The boulder contains a substantial amount of crystals, which are most likely plagioclase and/or other mafic silicate mineral aggregates similar to terrestrial dolerite. The Lunar Penetrating Radar detection and integrated geological interpretation have identified more than nine subsurface layers, suggesting that this region has experienced complex geological processes since the Imbrian and is compositionally distinct from the Apollo and Luna landing sites.

  3. A young multilayered terrane of the northern Mare Imbrium revealed by Chang'E-3 mission. (United States)

    Xiao, Long; Zhu, Peimin; Fang, Guangyou; Xiao, Zhiyong; Zou, Yongliao; Zhao, Jiannan; Zhao, Na; Yuan, Yuefeng; Qiao, Le; Zhang, Xiaoping; Zhang, Hao; Wang, Jiang; Huang, Jun; Huang, Qian; He, Qi; Zhou, Bin; Ji, Yicai; Zhang, Qunying; Shen, Shaoxiang; Li, Yuxi; Gao, Yunze


    China's Chang'E-3 (CE-3) spacecraft touched down on the northern Mare Imbrium of the lunar nearside (340.49°E, 44.12°N), a region not directly sampled before. We report preliminary results with data from the CE-3 lander descent camera and from the Yutu rover's camera and penetrating radar. After the landing at a young 450-meter crater rim, the Yutu rover drove 114 meters on the ejecta blanket and photographed the rough surface and the excavated boulders. The boulder contains a substantial amount of crystals, which are most likely plagioclase and/or other mafic silicate mineral aggregates similar to terrestrial dolerite. The Lunar Penetrating Radar detection and integrated geological interpretation have identified more than nine subsurface layers, suggesting that this region has experienced complex geological processes since the Imbrian and is compositionally distinct from the Apollo and Luna landing sites. Copyright © 2015, American Association for the Advancement of Science.

  4. Dry Stream Reaches in Carbonate Terranes: Surface Indicators of Ground-Water Reservoirs (United States)

    Brahana, J.V.; Hollyday, E.F.


    In areas where dry stream reaches occur, subsurface drainage successfully competes with surface drainage, and sheet-like dissolution openings have developed parallel to bedding creating the ground-water reservoir. Union Hollow in south-central Tennessee is the setting for a case study that illustrates the application of the dry stream reach technique. In this technique, dry stream reach identification is based on two types of readily acquired information: remotely sensed black and white infrared aerial photography; and surface reconnaissance of stream channel characteristics. Test drilling in Union Hollow subsequent to identification of the dry reach proved that a localized ground-water reservoir was present.

  5. 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.


    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. Natural Hg content in the Au-bearing vein systems results in minor elevation of dissolved Hg in some catchments. South Island Au occurs as an Au-Ag-Hg alloy, up to 8.4 wt% Hg. Cinnabar (HgS) occurs in mesothermal-style veins and as detrital grains in Quaternary gravels hosting Au-Ag-Hg alloy. The Nevis River catchment water, which locally flows through gravels containing cinnabar and Hg-bearing alluvial gold, contains up to 7 ng/L dissolved Hg. This is rapidly diluted to near 3 ng/L by low-Hg waters, and no effects of anthropogenic Hg addition near alluvial mining areas were detected; the dissolved Hg is likely derived from Hg-bearing gold. Mobilisation of Hg from study sites to downstream environments is at least partially controlled by solubility of cinnabar and elemental mercury. (author). 47 refs., 9 figs.

  6. A transect through the base of the Bronson Hill Terrane in western New Hampshire (United States)

    Walsh, Gregory J.; Valley, Peter M.; Sicard, Karri R.; Thompson, Thelma Barton; Thompson, Peter J.


    This trip will present the preliminary results of ongoing bedrock mapping in the North Hartland and Claremont North 7.5-minute quadrangles in western New Hampshire. The trip will travel from the Lebanon pluton to just north of the Sugar River pluton (Fig. 1) with the aim of examining the lower structural levels of the Bronson Hill anticlinorium (BHA), and the nature of the boundary with the rocks of the Connecticut Valley trough (CVT). Spear and others (2002, 2003, 2008) proposed that western New Hampshire was characterized by five major faults bounding five structural levels including, from lowest to highest, the “chicken yard line”, Western New Hampshire Boundary Thrust, Skitchewaug nappe, Fall Mountain nappe, and Chesham Pond nappe. Lyons and others (1996, 1997) showed the lowest level cored by the Cornish nappe and floored by the Monroe fault. Thompson and others (1968) explained the geometry of units by folding without major thrust faults, and described the second level as the Skitchewaug nappe. This trip will focus on the two lowest levels which we have revised to call the Monroe and Skitchewaug Mountain thrust sheets. Despite decades of geologic mapping in the northeastern United States at various scales, little 1:24,000-scale (or larger scale) modern bedrock mapping has been published for the state of New Hampshire. In fact, of the New England states, New Hampshire contains the fewest published, modern bedrock geologic maps. Conversely, adjacent Vermont has a relatively high percentage of modern bedrock maps due to focused efforts to create a new state-wide bedrock geologic map over the last few decades. The new Vermont map (Ratcliffe and others, 2011) has identified considerable gaps in our knowledge of the bedrock geology in adjacent New Hampshire where published maps are, in places, more than 50 years old and at scales ranging from 1:62,500 to 1:250,000. Fundamental questions remain concerning the geology across the Connecticut River, especially in regards to the stratigraphy of the BHA and CVT, and the distribution, or even existence, of faults ranging in age from Devonian to Mesozoic (e.g., Spear and others, 2008; McWilliams and others, 2010; Walsh and others, 2010). Questions to ponder on this trip include, but are not limited to: 1) Is the Bronson Hill anticlinorium allochthonous? 2) What is the crust beneath the Bronson Hill anticlinorium? 3) Is there a “Big Staurolite nappe” as proposed by Spear and others (2002, 2003, 2008)? 4) What is the role of Taconic, Acadian, and Alleghanian orogenesis in the tectonic development of the region? Modern 1:24,000-scale mapping is the first step towards answering these questions. Mapping will be supplemented by modern geochronology and geochemistry as this project develops. We plan to share some of our provisional results during this field trip.

  7. Provenance and tectonic setting of the Triassic Yidun Group, the Yidun Terrane, Tibet

    Directory of Open Access Journals (Sweden)

    Bai-Qiu Wang


    Prominently high Zr/Sc ratio or Hf concentration and Paleoproterozoic Nd modal ages (1.94–2.21 Ga point to input of recycling components derived from old sedimentary source in a relatively stable tectonic setting.

  8. A history of Proterozoic terranes in southern South America: From Rodinia to Gondwana

    Directory of Open Access Journals (Sweden)

    C. Casquet


    Full Text Available The role played by Paleoproterozoic cratons in southern South America from the Mesoproterozoic to the Early Cambrian is reconsidered here. This period involved protracted continental amalgamation that led to formation of the supercontinent Rodinia, followed by Neoproterozoic continental break-up, with the consequent opening of Clymene and Iapetus oceans, and finally continental re-assembly as Gondwana through complex oblique collisions in the Late Neoproterozoic to Early Cambrian. The evidence for this is based mainly on a combination of precise U-Pb SHRMP dating and radiogenic isotope data for igneous and metamorphic rocks from a large area extending from the Rio de la Plata craton in the east to the Argentine Precordillera in the west and as far north as Arequipa in Peru. Our interpretation of the paleogeographical and geodynamic evolution invokes a hypothetical Paleoproterozoic block (MARA embracing basement ultimately older than 1.7 Ga in the Western Sierras Pampeanas (Argentina, the Arequipa block (Peru, the Rio Apa block (Brazil, and probably also the Paraguaia block (Bolivia.

  9. Interesting insights into instability of slopes and rock fall in the morphodynamic Himalayan terrane (United States)

    Singh, T. N.; Vishal, V.; Pradhan, S. P.


    Himalayan mountain ranges are tectonically and seismically very active and experience many disastrous events with time due to slope failure. Frequent failures of rock cut slopes cause obstruction in traffic and often lead to fatalities. In recent years, the number of tragedies has increased when associated with regional phenomena such at the Kedarnath tragedy of 2013 and the Gorkha earthquake of 2015. The influence of such phenomena on the stability of slopes along important national highways and key settlement areas only raise the risk to lives and property. We conducted a multi-approach investigation for some key slopes along the National Highway 58 in Uttarakhand Himalaya, India. A very detailed field work was conducted to identify the unstable slopes and those with some history of failure. The pertinent geomechanical characteristics of the representative rock samples were determined in the laboratory. Based on the structural data, kinematic analysis was carried out. Finally the slopes were simulated using FDM based simulator, Flac/Slope for analysing the health of the slopes and Rockfall 4.0 to investigate the phenomenon of rockfall along the Highway. It was found that few slopes were weak due to the inherent weak rock materials while few slopes made up of high strength rocks were effectively weak due to prone-to-failure orientation of the joints. Quantification of bounce-height of rock blocks during fall, their energy, velocity and displacement along the slope was also done. Using 3-D simulations, few critically-stable slopes that appear to be stable, were identified. Little ground movement could be capable of triggering a large scale failure in the area. Slopes in the studied region are under threat to failure and need immediate proper planning using the suggested remedial measures.

  10. An oxygen isotope study of quartz veins within eclogites from the Dabie terrane

    Institute of Scientific and Technical Information of China (English)

    LI; Yiliang


    [1]Liu, T. S., Loess and the Environment, Beijing: China Ocean Press, 1985, 1-251.[2]Chen, L. X., Zhu, Q. G., Luo, H. B. et al., East Asian Monsoon, Beijing: China Meteorology Press, 1991, 28-61.[3]An, Z. S., Liu, T. S., Lu, Y. C. et al., The long-term palaeomonsoon variation recorded by the loess-palaeosol sequence in central China, Quaternary International, 1990, (7/8): 91-95.[4]Guo, Z. T., Liu, T. S., Fedoroff, N. et al., Shift of the monsoon intensity on the Loess Plateau at ca. 0.85 MaBP, Chinese Science Bulletin, 1993, 38(2): 586-591.[5]Chen, J., An, Z. S., Wang, Y. J. et al., Distributions of Rb and Sr in the Luochuan loess-paleosol sequence of China during the last 800 ka: Implications for paleomonsoon variations, Science in China, Ser. D, 1999, 42(3): 225-232.[6]Chen, J., Wang, Y. J., Ji, J. F. et al., Rb/Sr variations and its climatic stratigraphical significance of a loess-paleosol profile from Luochuan, Shaanxi Province, Quaternary Sciences (in Chinese), 1999, 19(4): 350-356.[7]Guo, Z. T.,Liu, T. S., Fedoroff, N. et al., Climate extremes in loess of China coupled with the strength of deep-water for-mation in the North Atlantic, Global and Planetary Change, 1998, 18: 113-128.[8]Guo, Z. T., Liu, T. S., An, Z. S., Paleosols of the last 0.15 Ma in the Weinan loess section and their paleoclimate signifi-cance, Quaternary Sciences (in Chinese), 1994, 14(3): 256-269.[9]Guo, Z, T,, Fedoroff, N., Liu, T. S., Micromorphology of the loess-paleosol sequence of the last 130 ka in China and pa-leoclimatic event, Science in China (in Chinese), Ser. D, 1996, 26(3): 392-398.[10]Guo, Z., Liu, T., Guiot, J., et al., High frequency pulses of East Asian monsoon climate in the last two glaciations: Link with the North Atlantic, Climate Dynamics, 1996, 12: 701-709.[11]Guo, Z. T., Peng, S. Z., Wei, L. Y. et al., Weathering signals of Millennial-Scale oscillations of the East Asian Summer monsoon over the last 220 ka, Chinese Science Bulletin, 1999, 44 (supplement 1): 20-25.[12]Ding, Z. L., Yu, Z. W., Rutter, N. W. et al., Towards an orbital time scale for Chinese loess deposits, Quaternary Science Review, 1994,13: 39-70.[13]Duchaufour, Ph., Pedologie, Tome 1: Pedogenese et Classification, Paris-New York-Barcelone-Milan: Masson, 1983, 1-477.[14]Singer, M. J., Bowen, L. H., Verosub, K. L. et al., Mossbauer spectroscopic evidence for citrate-bicarbonate-dithionite ex-traction of maghemite from soils, Clays and Clay Minerals,1995, 43: 1-7.[15]Hunt, C. P., Singer, M. J., Kletetschka, G. et al., Effect of citrate-bicarbonate-dithionite treatment on fine-grained mag-netite and maghemite, Earth Planet. Sci. Lett., 1995, 130: 87-94.[16]Mehra, O., Jackson, M. L., Iron oxide removal from soil and clay by a dithionite-citrate system buffered with sodium bi-carbonate, Clay and Clay Minerals, 1960, 7: 317-327.[17]McKeague, J. A., Manual on soil sampling and methods of analysis, Toronto: Canadian Society of Soil Science, 1981, 1-212.[18]Kukla, G., An, Z. S., Melice, J. L. et al., Magnetic susceptibility record of Chinese loess, Transaction of Royal Society of Edinburgh, Earth Sciences, 1990, 81: 263-288.[19]Guo, Z. T., Wei, L. Y., Lu, H. Y. et al., Changes in the composition of Late Pleistocene aeolian dust and the environmental significance, Quaternary Sciences (in Chinese), 1999, 19(1): 41-48.[20]Heller, F., Liu, X. M., Liu, T. S. et al., Magnetic susceptibility of loess in China, Earth and Planetary Science Letters, 1991,103: 301-310.[21]Yang, J. D., Chen, J., An, Z. S. et al., Variations in 87Sr/86Sr Ratios of calcites in Chinese loess: A proxy for chemical weathering associated with the East Asian Summer monsoon, Palaeogeography Palaeoclimatology Palaeoecology, 2000,157: 151-159.[22]Verosub, K. L., Fine, P., Singer, M. J. et al., Pedogenesis and paleoclimate: Interpretation of the magnetic susceptibility record of Chinese loess-paleosol sequences, Geology, 1993, 21: 1011-1014.[23]Banerjee, S. K., Hunt, C. P., Liu, X., Separation of local signals from the regional paleomonsoon record of the Chinese loess plateau: A rock magnetic approach, Geophys. Res. Lett., 1993, 20: 843-846.[24]Vidic, N. J., TenPas, J. D., Verosub, K. L. et al., Separation of pedogenic and lithogenic components of magnetic suscepti-bility in the Chinese loess/paleosol sequence as determined by the CBD procedure and a mixing analysis, Geophys. J. Int., 2000, 142: 551-562.[25]Deng, C. L., Yuan, B. Y., Zhu, R. X. et al., Magnetic susceptibility of Holocene loess-black loam sequence from Jiaodao, Shanxi, before and after citrate-bicarbonate-dithionite extraction, Chinese Journal of Geophysics (in Chinese), 2000, 43(4): 514-520.[26]Hunt, C. P., Banerjee, S. K., Han, J. M. et al., Rock-magnetic proxies of climate change in the loess-palaeosol sequences of the western Loess Plateau of China, 1995, Geophys. J. Int., 1995, 123: 232-244.[27]Liu, X. M., Liu, T. S., Heller, F. et al., The grain size of magnetic minerals in Chinese loess and its implications for paleo-climate, Science in China (in Chinese), Ser. B, 1991, 21(6): 639-644.[28]Chen, F. H., Bloemendal, J., Feng, Z. D. et al., East Asian monsoon variations during oxygen isotope stage 5: Evidence from the northwestern margin of the Chinese Loess Plateau, Quaternary Science Reviews, 1999, 18: 1127-1135.[29]Pan, B. T., Wang, J. M., Loess record of Qinghai-Xizang Plateau monsoon variations in the eastern part of the plateau since the Last Interglacial, Quaternary Sciences (in Chinese), 1999, 19(4): 330-335.[30]Imbrie, J., Imbrie, J. Z., Modeling the climate response to orbital variation, Science, 1980, 207: 943-953.[31]Liu, T. S., Quaternary Environment (in Chinese), Beijing: Science Press, 1997, 189-239.

  11. Guides to Some Volcanic Terranes in Washington, Idaho, Oregon, and Northern California (United States)

    Johnston, David A.; Donnelly-Nolan, Julie M.


    This guidebook arose out of a series of field trips held in conjunction with the Pacific Northwest American Geophysical Union meeting held in Bend, Oregon, September 1979. The PNAGU meeting included special volcanology sessions planned by William I. Rose, Jr., Bruce A. Nolf, amd David A. Johnston. Publication of the guidebook volume was originally planned for early 1980 by the Oregon Department of Geology and Mineral Industries (DOGAMI). Inevitable delays, subsequent scheduling problems, and the death of Dave Johnston in the May 18 eruption of Mount St. Helens led to this publication as a USGS Circular. This circular differs from typical U.S. Geological Survey compilations in that not all these papers have been examined by the Geologic Names Committee of the Survey. This Committee is charged with ensuring consistent usage of formational and other stratigraphic names in U.S. Geological Survey publications. Because many of the contributions are from workers outside the Survey, review by the Geologic Names Committee would have been inappropriate. Each author provided camera-ready pages, and the articles have not been edited for uniformity of style or usage. The contributions are generally ordered so as to describe the areas from north to south. Typically, the roadlog comes after the descriptive article except in the case of the Medicine Lake Highland articles, for which the road log is first and several topical contributions follow.

  12. The Rooiwater complex and associated rocks, Murchison granitoid-greenstone terrane, Kaapvaal Craton

    International Nuclear Information System (INIS)

    Vearncombe, J.R.; Walsh, K.L.


    The greater than 2625 Ma Rooiwater Complex is a thick, on-end differentiated basic igneous body exposed along the northern margin of the Murchison schist belt. It is metamorphosed to amphibolite facies and regionally retrograded and hydrothermally altered. Metamorphosed anorthosite, gabbro, pyroxenite, sulphide-bearing gabbros, thick magnetite layers, and granites are compatible with the hypothesis that the Complex is a layered intrusion, tectonically rotated and intruded by younger, genetically unrelated granites. Increasing TiO 2 and decreasing V 2 O 3 contents southwards in the magnetites layers combined with a general southern disposition of differentiated hornblende granite suggest that the Rooiwater Complex faces south. Although the Rubbervale Formation is pervasively deformed and metamorphosed at the greenschist facies, field relations and isotopic and rare earth element data tentatively suggest that a genetic relationship exists, the Rubbervale Formation being a possible roof to the Rooiwater intrusion, being derived from the same or a similar undepleted magmatic source. A paucity of ultramafic cumulates and up to 1,5 km of hornblende granites may relate to a source magma more felsic than that of other layered intrusions. In order to determine model ages for the Eden pluton, the Free State hornblende granite, the Quagga quartz amphibolite, the Rubbervale formation, and the Novengilla gabbro-anorthosite series. Rb-Sr and Pb isotopic analyses were undertaken

  13. Dynamics Of Karstification: A Model Applied To Hydraulic Structures In Karst Terranes (United States)

    Dreybrodt, W.


    To model the development of karst channels from primary fissures in limestone, a computer simulation of solutional widening of a fracture by calcite agressive water is proposed. The parameters defining the problem are the initial width a0 of the fracture, its length l, and the hydraulic gradient i driving water through it. The dissolution rates limestone determine how fast enlargement of the fractures proceeds. At a calcite concentration, c, far from equilibrium, the dissolution follows a first-order rate law, F(1)=α0(ceq-c); close to the equilibrium concentration, ceq, a slow fourth-order rate law F(4)=β0(ceq-c)4 is valid. The results show that, at the time of initiation, the water flow through the karst channels increases slowly in time until an abrupt increase occurs. After this moment of breakthrough, the channel enlarges rapidly and evenly over its entire length by first-order kinetics. Breakthrough times have been calculated for karstification under natural conditions for low hydraulic gradients as functions of a0, l, and i. Special attention is given to karstification in the vicinity of hydraulic structures where hydraulic gradients are high (>0.5) and channel lengths are below 200 m. We find that the breakthrough event will occur in less than 100 years, if: (i/l) > (5.3·10-8a0 -2.63PCO2 -0.77) where l is in m and a0 is in cm, (i/l) is given in m-1, and PCO2[atm] is the CO2 pressure of the water entering the fracture. After this event, the channels will widen to a width of about 1 cm within only 10 years, which can cause considerable leakage near or through hydraulic structures. Finally, critical values of the parameters i, l, a0, which give the conditions of failure in various types of hydraulic structures are discussed.

  14. Porfiroblastic hornblendites: lithological, guide of arch root plutonism in Piedra Alta Terrane. (Paleoproterozoic, Uruguay)

    International Nuclear Information System (INIS)

    Bossi, J.; Pineyro, D.


    Petrographic and geochemical features of porphyroblastic hornblendites in Piedra Alta Terrene of Uruguay are described. Their spatial and genetic relationships whith hornblendic gabbros and other basic plutonic rocks is also stablished. Their association with low grade metamorphic supracrustals inmagmatic mingling structures and late development, suggests an origin related to high vapour pressure that take off stability to gabbro paragenesis and favours Deer's reaction:pyroxene+ plagioclase +water= hornblende + SIO2. The silica produced is expressed as quartz dikes frequently mineralized with gold and platinum group elements. San Carlos gabbro is an uruguayan exemple of such proposed model.

  15. Crystallization Age and Impact Resetting of Ancient Lunar Crust from the Descartes Terrane (United States)

    Norman, M. D.; Borg, L. E.; Nyquist, L. E.; Bogard, D. D.


    Lunar ferroan anorthosites (FANs) are relics of an ancient, primary feldspathic crust that is widely believed to have crystallized from a global magma ocean. Compositions and ages of FANs provide fundamental information about the origin and magmatic evolution of the Moon, while the petrology and thermal history of lunar FANs illustrate the structure and impact history of the lunar crust. Here we report petrologic, geochemical, and isotopic (Nd-Sr-Ar) studies of a ferroan noritic anorthosite clast from lunar breccia 67215 to improve our understanding of the composition, age, and thermal history of the Moon.

  16. A numerical study on the flow upstream of a wind turbine on complex terran

    DEFF Research Database (Denmark)

    Meyer Forsting, Alexander Raul; Bechmann, Andreas; Troldborg, Niels


    The interaction of a wind turbine with the upstream flow-field in complex and flat terrain is studied using Reynolds-averaged Navier-Stokes (RANS) simulations with a two equation turbulence closure. The complex site modelled is Perdigao (Portugal), where a turbine is located on one of two parallel...... the wind turbine wake trajectory which in turn governs the orientation of the induction zone...

  17. Geologic framework of the Alaska Peninsula, southwest Alaska, and the Alaska Peninsula terrane (United States)

    Wilson, Frederic H.; Detterman, Robert L.; DuBois, Gregory D.


    The Alaska Peninsula is composed of the late Paleozoic to Quaternary sedimentary, igneous, and minor metamorphic rocks that record the history of a number of magmatic arcs. These magmatic arcs include an unnamed Late Triassic(?) and Early Jurassic island arc, the early Cenozoic Meshik arc, and the late Cenozoic Aleutian arc. Also found on the Alaska Peninsula is one of the most complete nonmetamorphosed, fossiliferous, marine Jurassic sedimentary sections known. As much as 8,500 m of section of Mesozoic sedimentary rocks record the growth and erosion of the Early Jurassic island arc.

  18. Mineral dissolution and precipitation in carbonate dominated terranes assessed using Mg isotopes (United States)

    Tipper, E.; Calmels, D.; Gaillardet, J.; Galy, A.


    Carbonate weathering by carbonic acid consumes atmospheric CO2 during mineral dissolution, fixing it as aqueous bicarbonate over millennial time-scales. Ocean acidification has increased the solubility of CO2 in seawater by changing the balance of pH to alkalinity (the oceanic reservoir of carbon). This has lengthened the time-scale for CO2 sequestration by carbonate weathering to tens of thousands of years. At a global scale, the net consumption of CO2 is at least equal to that from silicate weathering, but there is far less work on carbonate weathering compared to silicate weathering because it has generally been assumed to be CO2 neutral on geological time-scales. Carbonate rocks are more readily dissolved than silicate rocks, meaning that their dissolution will likely respond much more rapidly to global environmental change when compared with the dissolution of silicate minerals. Although far less concentrated than Ca in many carbonates, Mg substitutes for Ca and is more concentrated than any other metal ion. Tracing the behavior of Mg in river waters, using Mg stable isotopes (26Mg/24Mg ratio expressed as delta26Mg in per mil units) is therefore a novel way to understand the complex series of dissolution/precipitation reactions that govern solute concentrations of Ca and Mg, and hence CO2 transfer by carbonate weathering. We present new Mg isotope data on a series of river and spring waters from the Jura mountains in North-East France. The stratigraphic column is relatively uniform throughout the Jura mountains and is dominated by limestones. As the limestone of the Jura Mountains were deposited in high-energy shallow water environments (shore line, lagoon and coral reefs), they are usually clay and organic poor. The delta26Mg of the local rocks is very constant at circa -4permil. The delta26Mg of the river waters is also fairly constant, but offset from the rock at -2.5permil. This is an intriguing observation because the dissolution of limestones is expected to be congruent, meaning that the Mg released to solutes during mineral dissolution should have the same composition as the host rock. Some of this difference is likely accounted for by atmospheric deposition or cyclic inputs, but this cannot account for all of the 1.5permil shift between rock and water. It is plausible that some of the difference is explained by trace levels of Mg-silicate dissolution (with a delta26Mg of circa 0permil), but equally carbonate precipitation and attendant Mg isotope fractionation could theoretically account for the difference between rock and water. The various plausible explications will be discussed, as well as the implications of the data for better understanding carbonate weathering.

  19. Northward subduction-related orogenesis of the southern Altaids: Constraints from structural and metamorphic analysis of the HP/UHP accretionary complex in Chinese southwestern Tianshan, NW China

    Directory of Open Access Journals (Sweden)

    Mark Scheltens


    Full Text Available The Chinese Tianshan belt of the southern Altaids has undergone a complicated geological evolution. Different theories have been proposed to explain its evolution and these are still hotly debated. The major subduction polarity and the way of accretion are the main problems. Southward, northward subduction and multiple subduction models have been proposed. This study focuses on the structural geology of two of the main faults in the region, the South Tianshan Fault and the Nikolaev Line. The dip direction in the Muzhaerte valley is southward and lineations all point towards the NW. Two shear sense motions have been observed within both of these fault zones, a sinistral one, and a dextral one, the latter with an age of 236–251 Ma. Structural analyses on the fault zones show that subduction has been northward rather than southward. The two shear sense directions indicate that the Yili block was first dragged along towards the east due to the clockwise rotation of the Tarim block. After the Tarim block stopped rotating, the Yili block still kept going eastward, inducing the dextral shear senses within the fault zones.

  20. Implication of corona formation in a metatroctolite to the granulite facies overprint of HP-UHP rocks in the Moldanubian Zone (Bohemian Massif)

    Czech Academy of Sciences Publication Activity Database

    Faryad, S. W.; Kachlík, V.; Sláma, Jiří; Hoinkes, G.


    Roč. 33, č. 3 (2015), s. 295-310 ISSN 0263-4929 Institutional support: RVO:67985831 Keywords : coronitic metatroctolite * granulite facies * Moldanubian Zone * sapphirine * spinel * Variscan orogeny Subject RIV: DB - Geology ; Mineralogy Impact factor: 3.673, year: 2015

  1. Rheological and geodynamic controls on the mechanisms of subduction and HP/UHP exhumation of crustal rocks during continental collision : Insights from numerical models

    NARCIS (Netherlands)

    Burov, Evgene; Francois, Thomas; Agard, Philippe; Le Pourhiet, Laetitia; Meyer, Bertrand; Tirel, C.; Lebedev, Sergei; Yamato, Philippe; Brun, Jean Pierre


    While subduction of crustal rocks is increasingly accepted as a common scenario inherent to convergent processes involving continental plates and micro-continents, its occurrence in each particular context, as well as its specific mechanisms and conditions is still debated. The presence of

  2. Enzimatik, asidik ve sulu ekstraksiyon metotları ile çiriş (Asphodelus aestivus Brot. yumrularının HPLC ile şeker kompozisyonları

    Directory of Open Access Journals (Sweden)

    Dr. Eyyüp KARAOĞUL


    Full Text Available Çalışmanın amacı çiriş otu (Asphodelus aestivus Brot. yumrularının ekstraksiyon verimlerini ve çözünebilir şeker kompozisyonlarını incelemektir. Çiriş yumrularının ekstraksiyon işlemleri; 150 µL, 300 µL ve 450 µL hacimlerinde Gluko-Amilaz, α-Amilaz ve eşit oranlarda α-Amilaz&Gluko-Amilaz enzim takviyeleri 60 dk, 90 dk, 120 dk ve 180 dk sürelerinde saf su ve 0,8 M ve 1,6 M konsantrasyonunda asetik ve sülfürik asit takviyeleri ile yapılmıştır. Bu yumrularda şeker kompozisyonlarının tespiti için yüksek performanslı sıvı kromatografisi ve refraktif-indeks dedektörü (HPLC-RID cihazı kullanılmıştır. Çiriş otu yumrularının ekstraksiyon verimleri gravimetrik yöntemle tespit edilmiştir. Çiriş otu yumrularında şeker kompozisyonlarının belirlenmesi için glukoz, galaktoz, ksiloz, fruktoz ve sukroz referans olarak kullanılmış ve bunların kalibrasyon grafikleri çizilmiştir. Elde edilen sonuçlara göre uygulanan farklı ekstraksiyon türleri, hem verimlerin hem de şeker birimlerinin farklı oranlarda çıkmasına sebep olmuş; genellikle ekstraksiyon verimleri % 81-96 arasında seyretmiştir. Ancak en yüksek ekstraksiyon verimi(% 96, enzim veya asit takviyeleri ile yapılan metotların aksine, bir katkının olmadığı saf su ekstraksiyonunda tespit edilmiştir. Çiriş otu yumruları içerisinde glukoz, galaktoz, ksiloz, fruktoz ve sükroz şeker kompozisyonları belirlenmiştir. Çiriş yumrularından elde edilen şekerlerin ana bileşimleri, sükroz için enzimatik metotta 2.510 µg/ml, asidik metotlarda ksiloz için 1.043 µg/ml ve galaktoz için 2.180 µg/ml olarak tespit edilmiştir. Bazı şeker birimleri ise ekstraksiyon metoduna bağlı olarak hidroliz edilememiştir. Elde edilen sonuçlardan ekstraksiyon metotları oligomer veya polimer formunda olan karbonhidratları hidroliz ederek sükroz oranının daha yüksek çıkmasına sebep olduğu anlaşılmıştır. Ekstraksiyona uygulanan takviyeler, sükrozu hidroliz ederek hem glukoz, hem de fruktoz miktarının daha fazla çıkmasını sağlamıştır. Ekstraksiyon koşullarının daha ekstrem olduğu şartlarda ise şekerlerin hidroksimetilfurfurala dönüşmesi şekerlerin tükendiğini göstermiştir.


    Directory of Open Access Journals (Sweden)

    Vahti Aladağlı


    Full Text Available Bu çalışma yeni polimerik kaliksaren türevinin hazırlanması ve p-nitrofenolün (PNF adsorpsiyonunda sorbent malzemesi olarak uygulanmasını içermektedir. Kaliksaren türevleri 1-5'in hazırlanmasından sonra, 5 no'lu moleküle aminopropil silika jel destek maddesi tutturularak polimerik kaliksaren 6 türevi elde edildi. Bütün bileşikler, FTIR, 1H NMR, elemental analizi, TGA ve SEM gibi metotlar kullanılarak karakterize edildi. Aminopropil silika jel immobilize kaliks[4]aren (K[4]APS 6, PNF adsorpsiyonu çalışmalarında sorbent olarak kullanılmış ve pH, etkileşim süresi, konsantrasyon, proses sıcaklığı ve sorbent dozajı gibi parametreler çalışıldı. Sonuçlara göre, 6 no'lu molekülün PNF adsorpsiyonu için optimum koşullar pH 6, etkileşim süresi 1 saat, PNF konsantrasyonu 5.0x10-5 M, sorbent dozajı 0.025g ve proses sıcaklığı 25oC olarak bulundu. PNF adsorpsiyon mekanizması, Langmuir ve Freundlich izotermleri ile değerlendirildi

  4. On protolith-, metamorphic overprint, microstructure and rheology of mineral assemblages in orogenic peridotites of the central Scandinavian Caledonides (United States)

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


    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

  5. The Strontium Isotope Record of Zavkhan Terrane Carbonates: Strontium Isotope Stability Through the Ediacaran-Cambrian Transition


    Petach, Tanya N.


    First order trends in the strontium isotopic (87Sr/86Sr) composition of seawater are controlled by radiogenic inputs from the continent and non-radiogenic inputs from exchange at mid-ocean ridges. Carbonates precipitated in seawater preserve trace amounts of strontium that record this isotope ratio and therefore record the relative importance of mid-ocean ridge and weathering chemical inputs to sea water composition. It has been proposed that environmental changes during the Ediacaran-Cambria...

  6. B-DNA model systems in non-terran bio-solvents : Implications for structure, stability and replication

    NARCIS (Netherlands)

    Hamlin, Trevor A.; Poater, Jordi; Fonseca Guerra, Célia; Bickelhaupt, F. Matthias


    We have computationally analyzed a comprehensive series of Watson-Crick and mismatched B-DNA base pairs, in the gas phase and in several solvents, including toluene, chloroform, ammonia, methanol and water, using dispersion-corrected density functional theory and implicit solvation. Our analyses

  7. Stitching the western Piedmont of Virginia: Early Paleozoic tectonic history of the Ellisville Pluton and the Potomac and Chopawamsic Terranes (United States)

    Hughes, K. S.; Hibbard, J. P.; Sauer, R.T.; Burton, William C.


    The theme of the 2014 Virginia Geological Field Conference is the tectonic development, economic geology, and seismicity of the western Piedmont of Louisa County, Virginia. It is timely for the conference to turn its attention here, for during the past decade these aspects of western Piedmont geology have garnered the renewed attention of researchers. In terms of regional tectonics, it has been hypothesized that the major structure in the region, the Chopawamsic fault system, represents the most significant boundary in the Appalachian orogen, the main Iapetan suture (Hibbard et al., 2014). Economically, recent elevated market values of metals— particularly that of gold—has spurred reconsideration of the economic geology of the western Piedmont. Finally, the August 23, 2011, M5.8 earthquake, with its epicenter in our field area, startled the North American east coast and has revived awareness of the seismic potential of the region. This renewed interest in the geology of the western Piedmont of north-central Virginia has led to new detailed bedrock mapping, detailed surficial mapping, high-resolution UPb TIMS zircon geochronology, U-Pb LA-ICPMS detrital zircon geochronology, radiogenic isotope geochemistry, major/minor/REE geochemistry, and geophysical studies (e.g. Bailey et al., 2005, 2008; Bailey and Owens, 2012: Berti et al., 2012; Burton et al., 2014; Burton, in progress; Harrison, 2012; Horton et al., 2010, in press; Hughes, 2010, 2014; Hughes et al., 2013a, 2013b, 2014, in press a, in press b; Malenda, in progress; Owens et al., 2013; Spears and Gilmer 2012; Spears et al. 2013, Terblanche, 2013; Terblanche and Nance, 2012). A host of institutions have taken part in the research, including North Carolina State University, the Virginia Department of Mines, Minerals, and Energy, the U.S. Geological Survey, Virginia Tech, Lehigh University, and the College of William and Mary. Many of these investigations remain active. The majority of the data presented herein is the product of research conducted from 2010 to 2014 by geologists at North Carolina State University. This field trip guide is intended to complement a Geological Society of America field guide (Hughes et al., 2014) that covers the western Piedmont geology along strike to the northeast in the vicinity of Fredericksburg. Geologic mapping and geochronologic and geochemical sampling were coordinated between these two areas as part of a study funded in part by the National Science Foundation and the USGS EDMAP program. Some of the stops in this guide have previously been written up in past field guides (Hughes, 2010; Burton et al., 2014) and are reused here because of their ease of access for large groups and because of new data that update the context and our understanding of the outcrops.

  8. Mineral chemical and petrographic occurrences os iron of the south east of Uruguay (Nico Pere z terrane)

    International Nuclear Information System (INIS)

    Oyhantcabal, P.; Sanchez Bettucci, L.; Siegesmund, S.; Pineyro, D.


    Two iron-formation deposits from S E Uruguay were petrographic ally and mineralogically investigated (including microprobe mineral chemistry). The deposit from Piedra de Gigante (ANCAP) quarry is related to tectonic slivers of a platform succession in ortho gneiss of ca. 1750 Ma. Data of detrital zircon in this platform succession point to Meso- to Neo proterozoic age.The iron deposit of Piedra del Gigante (ANCAP) quarry belongs to a succession of mica schists, quartz-muscovite schists, marbles and basic rocks. Magnetite rich layers alternate with banded rocks rich in hematite, carbonate and amphibole. Carbonate is dolomite (Mg0.7Ca1.08Mn0.05Fe0.11(CO3)2) and the amphibole is a pale green tremolite (Na0,18Ca1,68Mn0,07Mg4,16Fe+++0,2Fe++0,55Al0,03(Si7,86Al0,13)O22(OH)2). This iron deposit shows strong deformation associated with martitization of magnetite and formation of specularite rich layers where relicts of magnetite (partly martitized) are occasionally observed. Available data are not conclusive about the genesis. The low iron-content of the amphibole together with dolomite in the mineral association cast doubts on a BIF-type origin, but low contents of Al2O3, V2O3, MnO and ZnO in magnetite do not indicate an igneous origin. High oxygen fugacity during martitization in medium-T metamorphic conditions could have determined that iron rich amphiboles were not formed as is normally expected in iron-formations. In the outcrop of Cerro la Higuerita (Grupo Arroyo del Soldado; Ediacaran) a succession of metapelites (bottom), iron rich pelites and iron formations (top) is observed. The metapelites contain evidences of volcanic contribution (phenochrysts of quartz and alkali feldspar as well as shards in the matrix) suggesting a volcanic source for the iron. This iron-formation contains magnetite pheno blasts (partly martitized) and fine disseminated laths of hematite in the matrix, together with grunerite (Na0,04Ca0,17 Mn0,02Mg1,36Fe5,35Al0,07(Si7,97Al0,03)O22(OH)2 ) and chlorite (diabantite; K0,84Na0,85Ca0,10Mg6,22 Fe+22,21Al1,93Fe+30,17Mn0,05 [Si6,97 Al1,03 O20] (OH)16). The characteristics are consistent with a Rapitan-type for this Neoproterozoic BIF. (author)

  9. Metamorphosed carbonates of Krkonoše Mountains and Paleozoic evolution of Sudetic terranes (NE Bohemia, Czech Republic)

    Czech Academy of Sciences Publication Activity Database

    Hladil, Jindřich; Patočka, František; Kachlík, V.; Melichar, R.; Hubačík, M.


    Roč. 54, č. 5 (2003), s. 281-297 ISSN 1335-0552 R&D Projects: GA AV ČR IAA3111102 Institutional research plan: CEZ:AV0Z3013912 Keywords : Cambrium * carbonates * Krkonoše Subject RIV: DB - Geology ; Mineralogy Impact factor: 0.397, year: 2003

  10. Paleomagnetic Constraints From the Baoshan Area on the Deformation of the Qiangtang-Sibumasu Terrane Around the Eastern Himalayan Syntaxis

    NARCIS (Netherlands)

    Li, Shihu|info:eu-repo/dai/nl/411296248; van Hinsbergen, Douwe J.J.|info:eu-repo/dai/nl/269263624; Deng, Chenglong; Advokaat, Eldert L.; Zhu, Rixiang

    The Sibumasu Block in SE Asia represents the eastward continuation of the Qiangtang Block. Here we report a detailed rock magnetic and paleomagnetic study on the Middle Jurassic and Paleocene rocks from northern Sibumasu, to document the crustal deformation during the India-Asia collision since the

  11. Alakit and Daldyn kimberlite fields, Siberia, Russia: Two types of mantle sub-terranes beneath central Yakutia?

    Directory of Open Access Journals (Sweden)

    I.V. Ashchepkov


    Full Text Available Mineral data from Yakutian kimberlites allow reconstruction of the history of lithospheric mantle. Differences occur in compositions of mantle pyropes and clinopyroxenes from large kimberlite pipes in the Alakit and Daldyn fields. In the Alakit field, Cr-diopsides are alkaline, and Stykanskaya and some other pipes contain more sub-calcic pyropes and dunitic-type diamond inclusions, while in the Daldyn field harzburgitic pyropes are frequent. The eclogitic diamond inclusions in the Alakit field are sharply divided in types and conditions, while in the Daldyn field they show varying compositions and often continuous Pressure–Temperature (P–T ranges with increasing Fe# with decreasing pressures. In Alakit, Cr-pargasites to richterites were found in all pipes, while in Daldyn, pargasites are rare Dalnyaya and Zarnitsa pipes. Cr-diopsides from the Alakit region show higher levels of light Rare Earth Elements (LREE and stronger REE-slopes, and enrichment in light Rare Earth Elements (LREE, sometimes Th-U, and small troughs in Nb-Ta-Zr. In the Daldyn field, the High Field Strength Elements HFSE troughs are more common in clinopyroxenes with low REE abundances, while those from sheared and refertilized peridotites have smooth patterns. Garnets from Alakit show HREE minima, but those from Daldyn often have a trough at Y and high U and Pb. PTXfO2 diagrams from both regions show similarities, suggesting similar layering and structures. The degree of metasomatism is often higher for pipes which show dispersion in P–Fe# trends for garnets. In the mantle beneath Udachnaya and Aykhal, pipes show 6–7 linear arrays of P–Fe# in the lower part of the mantle section at 7.5–3.0 GPa, probably reflecting primary subduction horizons. Beneath the Sytykanskaya pipe, there are several horizons with opposite inclinations which reflect metasomatic processes. The high dispersion of the P–Fe# trend indicating widespread metasomatism is associated with decreased diamond grades. Possible explanation of the differences in mineralogy and geochemistry of the mantle sections may relate to their tectonic positions during growth of the lithospheric keel. Enrichment in volatiles and alkalis possibly corresponds to interaction with subduction-related fluids and melts in the craton margins. Incorporation of island arc peridotites from an eroded arc is a possible scenario.

  12. Investigating high zircon concentrations in the fine fraction of stream sediments draining the Pan-African Dahomeyan Terrane in Nigeria

    International Nuclear Information System (INIS)

    Key, Roger M.; Johnson, Christopher C.; Horstwood, Matthew S.A.; Lapworth, Dan J.; Knights, Katherine V.; Kemp, Simon J.; Watts, Michael; Gillespie, Martin; Adekanmi, Michael; Arisekola, Tunde


    Sixteen hundred stream sediments (<150 μm fraction) collected during regional geochemical surveys in central and SW Nigeria have high median and maximum concentrations of Zr that exceed corresponding Zr concentrations found in stream sediments collected from elsewhere in the World with similar bedrock geology. X-ray diffraction studies on a sub-set of the analysed stream sediments showed that Zr is predominantly found in detrital zircon grains. However, the main proximal source rocks (Pan-African ‘Older Granites’ of Nigeria and their Proterozoic migmatitic gneiss country rocks) are not enriched in zircon (or Zr). Nevertheless, U–Pb LA-ICP-MS dating with cathodoluminescence imaging on detrital zircons, both from stream sediment samples and underlying Pan-African ‘Older Granites’ confirms a local bedrock source for the stream sediment zircons. A combination of tropical/chemical weathering and continuous physical weathering, both by ‘wet season’ flash flooding and ‘dry season’ unidirectional winds are interpreted to have effectively broken down bedrock silicate minerals and removed much of the resultant clay phases, thereby increasing the Zr contents in stream sediments. The strong correlation between winnowing index (Th/Al) and Zr concentration across the study area support this interpretation. Therefore, ‘anomalous’ high values of Zr, as well as other elements concentrated in resistant ‘heavy’ minerals in Nigeria’s streams may not reflect proximal bedrock concentrations of these elements. This conclusion has important implications for using stream sediment chemistry as an exploration tool in Nigeria for primary metal deposits associated with heavy minerals.

  13. Tracing the depositional history of Kalimantan diamonds by zircon provenance and diamond morphology studies (United States)

    Kueter, Nico; Soesilo, Joko; Fedortchouk, Yana; Nestola, Fabrizio; Belluco, Lorenzo; Troch, Juliana; Wälle, Markus; Guillong, Marcel; Von Quadt, Albrecht; Driesner, Thomas


    Diamonds in alluvial deposits in Southeast Asia are not accompanied by indicator minerals suggesting primary kimberlite or lamproite sources. The Meratus Mountains in Southeast Borneo (Province Kalimantan Selatan, Indonesia) provide the largest known deposit of these so-called "headless" diamond deposits. Proposals for the origin of Kalimantan diamonds include the adjacent Meratus ophiolite complex, ultra-high pressure (UHP) metamorphic terranes, obducted subcontinental lithospheric mantle and undiscovered kimberlite-type sources. Here we report results from detailed sediment provenance analysis of diamond-bearing Quaternary river channel material and from representative outcrops of the oldest known formations within the Alino Group, including the diamond-bearing Campanian-Maastrichtian Manunggul Formation. Optical examination of surfaces of diamonds collected from artisanal miners in the Meratus area (247 stones) and in West Borneo (Sanggau Area, Province Kalimantan Barat; 85 stones) points toward a classical kimberlite-type source for the majority of these diamonds. Some of the diamonds host mineral inclusions suitable for deep single-crystal X-ray diffraction investigation. We determined the depth of formation of two olivines, one coesite and one peridotitic garnet inclusion. Pressure of formation estimates for the peridotitic garnet at independently derived temperatures of 930-1250 °C are between 4.8 and 6.0 GPa. Sediment provenance analysis includes petrography coupled to analyses of detrital garnet and glaucophane. The compositions of these key minerals do not indicate kimberlite-derived material. By analyzing almost 1400 zircons for trace element concentrations with laser ablation ICP-MS (LA-ICP-MS) we tested the mineral's potential as an alternative kimberlite indicator. The screening ultimately resulted in a small subset of ten zircons with a kimberlitic affinity. Subsequent U-Pb dating resulting in Cretaceous ages plus a detailed chemical reflection make

  14. 137Cs inventories in the water column collected from the South and South China Seas

    International Nuclear Information System (INIS)

    Yamada, M.; Wang, Z.-L.; Zheng, J.


    Seawater samples were collected in the Sulu and South China Seas and their 137 Cs activities were determined by γ spectrometry. A significant difference in intermediate water 137 Cs activities in the 750-1500 m depth was observed between the Sulu and South China Seas. The 137 Cs inventories in the Sulu Sea was 5.7 times higher than that of the integrated deposition density of atmospheric global fallout at the same latitude of 0-10degN. A possible mechanism controlling this extremely high 137 Cs inventories may be inflows of 137 Cs rich North Pacific Tropical Water and upper North Pacific Intermediate Water through the Luzon Straight from the West Philippine Sea, and lateral transport across the Mindoro Strait into the Sulu Sea, then conveyance into the deep layer in the Sulu Sea basin. (author)

  15. Amélioration des méthodes de protection anticorrosion des structures métalliques : Sous-sujet : Application des systèmes dits de "maintenance" sur préparation de surface UHP




    Le problème actuel de l'entretien de la protection anticorrosion des structures métalliques est l'augmentation du coût découlant des contraintes règlementaires récentes sur l'évacuation et le traitement des déchets. Lors d'un chantier d'entretien, le principal poste générateur de déchets est le décapage. Toutes les solutions techniques permettant de diminuer la quantité et/ou la nocivité des déchets de décapage sont donc intéressantes aussi bien du point de vue économique que de celui de la p...

  16. The lower-temperature-pressure stability of pyrope in the presence of quartz in the system MgO-Al2O3-SiO2 (United States)

    Cheng, N.; Jenkins, D. M.


    Pyrope (Mg3Al2Si3O12) is the dominant component in garnets from type A eclogites. Determining the lower-pressure-temperature (P-T) stability of pyrope in the presence of quartz helps put constraints on the stability of quartz-bearing eclogites and therefore the depths to which crustal rocks in high pressure/ultra-high pressure (HP/UHP) terranes can be transferred. It also defines the lower-pressure stability of the nearly pure pyrope-bearing quartzites of the Dora Maira massif of the Western Alps (Chopin, 1984, Contrib. Min. Pet.). Aside from the approximate boundary proposed by Hensen & Essene (1971, Contrib. Min. Pet.), there has been no detailed study of the lower P-T stability of pyrope + quartz. A reversed determination of the reaction 3 enstatite + 2 kyanite = 2 pyrope + 2 quartz has been done in the system MgO-Al2O3-SiO2 over the P-T range of 900-1100 °C and 1.6-2.5 GPa for durations of 24 hours. Double capsules, one using pure enstatite and the other Al-rich (10 wt% Al2O3) enstatite in the starting mixtures, were used to obtain reversals on the Al content in the orthopyroxene (Opx). Experiments were done using a ½-inch diameter piston-cylinder press and NaCl-pyrex-MgO pressure media. Run products were analyzed using powder XRD and electron microprobe. Reaction direction was readily determined from peak height changes on XRD patterns. The reaction has been bracketed at 1.65 GPa at 1100 °C with > 12 wt% Al2O3 in Opx; 2.05 GPa at 1000 °C with 10 wt% Al2O3 in Opx; and 2.4 GPa at 930 °C with 5 wt% Al2O3 in Opx. The reaction boundary is slightly curved to higher P with increasing T caused by increasing Al in Opx. The boundary observed in this study is about 100 °C or 0.4 GPa higher than previously proposed by Hensen & Essene (1971) and 70-170 °C or 0.6-0.7 GPa higher than the boundary calculated in this system using THERMOCALC ds6.22 (Holland & Powell, 2011, J. Meta. Geol.) and about 1-4 wt% higher Al2O3 contents in Opx. Higher pressure runs in the field

  17. Geochronology of Zircon in Eclogite Reveals Imbrication of the Ultrahigh-Pressure Western Gneiss Region of Norway. (United States)

    Young, D. J.; Kylander-Clark, A. R.; Root, D. B.


    Eclogite provides the only record of kinematic events at the deepest levels of orogens. Integrating the U-Pb geochronology and trace element chemistry of zircon in eclogite reveals the most complete view of the PTt history, yet low concentrations of uranium and zirconium and drier compositions that hinder zircon growth at peak conditions render it a challenging rocktype for this approach. The iconic Western Gneiss Region (WGR) in Norway is one of the largest terranes of deeply subducted continental rocks in the world, and contains many indicators of ultrahigh-pressure metamorphic conditions (P>2.8 GPa) that developed during the Siluro-Devonian Caledonian Orogeny. A metamorphic transition from amphibolite-facies to ultrahigh-pressure eclogite facies broadly coincides with a km-scale shear zone that underlies the majority of the WGR. A critical unknown is the timing of movement on this feature, which emplaced allochthonous units above the Baltica basement, but might also have accommodated late-orogenic exhumation of the WGR from mantle depths. We carried out laser ablation split-stream ICPMS (LASS) and selected multigrain TIMS analyses of zircons from eleven eclogites across the southern WGR, of which eight are located within or above the shear zone. LASS spots on polished grains mostly yield weakly discordant Proterozoic intrusive ages, and often minimal indication of a Caledonian (U)HP metamorphic overprint. Direct ablation into unpolished zircon reveals thin rims of Caledonian age in some cases. Overall, the dataset shows that all samples began zircon growth at approximately the same time (ca. 430-420 Ma). Eclogite from lower levels of the shear zone does not contain any dates younger than ca. 410 Ma, however, while eclogite from higher levels continued growth until ca. 400 Ma. We interpret this to result from thrusting of the WGR above cooler basement after 410 Ma, terminating new zircon crystallization within the shear zone but allowing limited further growth in

  18. NCBI nr-aa BLAST: CBRC-DSIM-02-0033 [SEVENS

    Lifescience Database Archive (English)

    Full Text Available CBRC-DSIM-02-0033 ref|YP_001141368.1| regulator of uhpT [Aeromonas salmonicida subsp. salmon...icida A449] gb|ABO89620.1| regulator of uhpT [Aeromonas salmonicida subsp. salmonicida A449] YP_001141368.1 3.1 20% ...

  19. NCBI nr-aa BLAST: CBRC-TNIG-22-0321 [SEVENS

    Lifescience Database Archive (English)

    Full Text Available CBRC-TNIG-22-0321 ref|ZP_01866313.1| sensory histidine kinase UhpB [Vibrio shilonii... AK1] gb|EDL54948.1| sensory histidine kinase UhpB [Vibrio shilonii AK1] ZP_01866313.1 1.4 27% ...

  20. Mass-production of Cambro-Ordovician quartz-rich sandstone as a consequence of chemical weathering of Pan-African terranes: Environmental implications [rapid communication (United States)

    Avigad, D.; Sandler, A.; Kolodner, K.; Stern, R. J.; McWilliams, M.; Miller, N.; Beyth, M.


    A vast sheet of mature quartz sand blanketed north Africa and Arabia from the Atlantic coast to the Persian Gulf in Cambro-Ordovician times. U-Pb geochronology of a representative section of Cambrian sandstone in southern Israel shows that these sediments are dominated by 550-650 Ma detrital zircons derived from Neoproterozoic Pan-African basement. The short time lag between magmatic consolidation of a Pan-African source and deposition of its erosional products indicates that, despite their significant mineralogical maturity, the voluminous quartz-rich sandstones on the northern margin of Gondwana are essentially first-cycle sediments. Mass production of these voluminous first-cycle quartz-rich sandstones resulted from widespread chemical weathering of the Pan-African continental basement. We suggest that conditions favoring silicate weathering, particularly a warm and humid climate, low relief and low sedimentation rates prevailed over large tracts of Gondwana in the aftermath of the Pan-African orogeny. An unusually corrosive Cambro-Ordovician atmosphere and humid climate enhanced chemical weathering on the vegetation-free landscape. We infer that late Neoproterozoic-Cambro-Ordovician atmospheric pCO 2 rose as a consequence of widespread late Neoproterozoic volcanism, followed by an uptake of CO 2 by chemical weathering to produce the Cambro-Ordovician sandstone as a negative feedback.

  1. Recovery act. Characterizing structural controls of EGS-candidate and conventional geothermal reservoirs in the Great Basin. Developing successful exploration strategies in extended terranes

    Energy Technology Data Exchange (ETDEWEB)

    Faulds, James [Univ. of Nevada, Reno, NV (United States)


    We conducted a comprehensive analysis of the structural controls of geothermal systems within the Great Basin and adjacent regions. Our main objectives were to: 1) Produce a catalogue of favorable structural environments and models for geothermal systems. 2) Improve site-specific targeting of geothermal resources through detailed studies of representative sites, which included innovative techniques of slip tendency analysis of faults and 3D modeling. 3) Compare and contrast the structural controls and models in different tectonic settings. 4) Synthesize data and develop methodologies for enhancement of exploration strategies for conventional and EGS systems, reduction in the risk of drilling non-productive wells, and selecting the best EGS sites.

  2. Assessment of subsidence in karst terranes at selected areas in East Tennessee and comparison with a candidate site at Oak Ridge, Tennessee: Phase 2

    International Nuclear Information System (INIS)

    Newton, J.G.; Tanner, J.M.


    Work in the respective areas included assessment of conditions related to sinkhole development. Information collected and assessed involved geology, hydrogeology, land use, lineaments and linear trends, identification of karst features and zones, and inventory of historical sinkhole development and type. Karstification of the candidate, Rhea County, and Morristown study areas, in comparison to other karst areas in Tennessee, can be classified informally as youthful, submature, and mature, respectively. Historical sinkhole development in the more karstified areas is attributed to the greater degree of structural deformation by faulting and fracturing, subsequent solutioning of bedrock, thinness of residuum, and degree of development by man. Sinkhole triggering mechanisms identified are progressive solution of bedrock, water-level fluctuations, piping, and loading. 68 refs., 18 figs., 11 tabs

  3. Geology, geochemistry, and geochronology (U-Pb) of the Rio Fortuna Gneiss - Serra do Bau intrusive Suite - Paragua Terrane SW Amazonian Craton

    Energy Technology Data Exchange (ETDEWEB)

    Faria, Debora Almeida; Ruiz, Amarildo Salina; Matos, Joao Batista; Sousa, Maria Zelia Aguiar de; Lima, Gabrielle Aparecida de [Research Group on Crustal and Tectonic Evolution, Guapore, RS (Brazil); Universidade Federal de Mato Grosso (ICET/UFMT), Cuiaba, MT (Brazil). Instituto de Ciencias Exatas e da Terra; Inst. Nacional de Ciencia e Tecnologia de Geociencias da Amazonia (GEOCIAM), Belem, PA (Brazil); Moacir Jose Buenano Macambira, E-mail:, E-mail:, E-mail:, E-mail:, E-mail:, E-mail: [Research Group on Crustal and Tectonic Evolution, Guapore, RS (Brazil); Universidade Federal do Para (UFPA), Belem, PA (Brazil)


    The Rio Fortuna Gneiss crops out in the Serra Santa Barbara, near the Fortuna military headquarters, on the Brazil-Bolivia border. These orthogneisses are located in a portion of the Paragua terrain affected by the Sunsas Orogeny (1.0-0.9 Ga.). They are classified as monzo to granodiorite orthogneisses and underwent at least three episodes of deformation. The U-Pb zircon age of 1,711 ± 13 Ma obtained by laser ablation MC-ICP-MS is interpreted as the crystallization age of this orthogneiss. Geochemically, these rocks form a sequence comprising acidic subalkaline magmatism, calc-alkalic-type high-K, and metaluminous to peraluminous. (author)

  4. Geochemical discrimination of metasedimentary sequences in the Krkonoše-Jizera Terrane (West Sudetes, Bohemian Massif): paleotectonic and stratigraphic constraints

    Czech Academy of Sciences Publication Activity Database

    Winchester, J. A.; Patočka, František; Kachlík, V.; Melzer, M.; Nawakowski, C.; Crowley, Q. G.; Floyd, P. A.


    Roč. 54, č. 5 (2003), s. 267-280 ISSN 1335-0552 R&D Projects: GA AV ČR IAA3111102 Grant - others:CZ-XE(XE) PACE TMR Network ERBFMRXCT97-0136 Institutional research plan: CEZ:AV0Z3013912 Keywords : geochemistry * metasediments * tectonic setting Subject RIV: DD - Geochemistry Impact factor: 0.397, year: 2003

  5. Sediment-infill volcanic breccia from the Neoarchean Shimoga greenstone terrane, western Dharwar Craton: Implications on pyroclastic volcanism and sedimentation in an active continental margin (United States)

    Manikyamba, C.; Saha, Abhishek; Ganguly, Sohini; Santosh, M.; Lingadevaru, M.; Rajanikanta Singh, M.; Subba Rao, D. V.


    We report sediment-infill volcanic breccia from the Neoarchean Shimoga greenstone belt of western Dharwar Craton which is associated with rhyolites, chlorite schists and pyroclastic rocks. The pyroclastic rocks of Yalavadahalli area of Shimoga greenstone belt host volcanogenic Pb-Cu-Zn mineralization. The sediment-infill volcanic breccia is clast-supported and comprises angular to sub-angular felsic volcanic clasts embedded in a dolomitic matrix that infilled the spaces in between the framework of volcanic clasts. The volcanic clasts are essentially composed of alkali feldspar and quartz with accessory biotite and opaques. These clasts have geochemical characteristics consistent with that of the associated potassic rhyolites from Daginkatte Formation. The rare earth elements (REE) and high field strength element (HFSE) compositions of the sediment-infill volcanic breccia and associated mafic and felsic volcanic rocks suggest an active continental margin setting for their generation. Origin, transport and deposition of these rhyolitic clasts and their aggregation with infiltrated carbonate sediments may be attributed to pyroclastic volcanism, short distance transportation of felsic volcanic clasts and their deposition in a shallow marine shelf in an active continental margin tectonic setting where the rhyolitic clasts were cemented by carbonate material. This unique rock type, marked by close association of pyroclastic volcanic rocks and shallow marine shelf sediments, suggest shorter distance between the ridge and shelf in the Neoarchean plate tectonic scenario.

  6. How far did the Cadomian ʽterranesʼ travel from Gondwana during early Palaeozoic? A critical reappraisal based on detrital zircon geochronology

    Czech Academy of Sciences Publication Activity Database

    Žák, J.; Sláma, Jiří


    Roč. 60, č. 3 (2018), s. 319-338 ISSN 0020-6814 Institutional support: RVO:67985831 Keywords : Avalonian-Cadomian belt * Bohemian Massif * laser ablation ICP-MS * Moldanubian unit * Rheic Ocean * Tepla-Barrandian unit Subject RIV: DB - Geology ; Mineralogy OBOR OECD: Geology Impact factor: 2.262, year: 2016

  7. Microstructural and seismic properties of the upper mantle underneath a rifted continental terrane (Baja California): An example of sub-crustal mechanical asthenosphere?

    NARCIS (Netherlands)

    Palasse, L.N.; Vissers, R.L.M.; Paulssen, H.; Basu, A.R.; Drury, M.R.


    The Gulf of California rift is a young and active plate boundary that links the San Andreas strike-slip fault system in California to the oceanic spreading system of the East Pacific Rise. The xenolith bearing lavas of the San Quintin volcanic area provide lower crust and upper mantle samples from

  8. Research Article Special Issue

    African Journals Online (AJOL)


    Aug 8, 2017 ... both seas are affected by local river drainage from Borneo ... marine water column system of Sulu Sea on the vertical profile of physical, chemical ..... in rainwater from Guiyang, an acid rain impacted zone of Southwest China.

  9. Western cratonic domain in Uruguay: geochronology

    International Nuclear Information System (INIS)

    Preciozzi, F.; Peel, F.; Muzio, R.; Ledesma, J.; Guerequiz, R.


    In this article has been studied the Western cratonic in Uruguay are divided into three major units: Piedra Alta Terrane, Valentines Block and Pavas Terrane. Piedra Alta Terrane has of evidence of Neo proterozoic orogenesis . Sarandi del Yi -Arroyo Solis Grande shear zone separate, it from Valentine block . Valentine Block separate it from Pavas terrane by Cueva del Tigre shear zone

  10. Coupling of Oceanic and Continental Crust During Eocene Eclogite-Facies Metamorphism: Evidence From the Monte Rosa Nappe, Western Alps, Italy (United States)

    Lapen, T. J.; Johnson, C. M.; Baumgartner, L. P.; Skora, S.; Mahlen, N. J.; Beard, B. L.


    Subduction of continental crust to HP-UHP metamorphic conditions requires overcoming density contrasts that are unfavorable to deep burial, whereas exhumation of these rocks can be reasonably explained through buoyancy-assisted transport in the subduction channel to more shallow depths. In the western Alps, both continental and oceanic lithosphere has been subducted to eclogite-facies metamorphic conditions. The burial and exhumation histories of these sections of lithosphere bear directly on the dynamics of subduction and the stacking of units within the subduction channel. We address the burial history of the continental crust with high precision U-Pb rutile and Lu-Hf garnet geochronology of the eclogite-facies Monte Rosa nappe (MR), western Alps, Italy. U-Pb rutile ages from quartz-carbonate-white mica-rutile veins that are hosted within eclogite and schist of the MR, Gressoney Valley, Italy, indicate that it was at eclogite-facies metamorphic conditions at 42.6 +/- 0.6 Ma. The sample area (Indren glacier, Furgg zone; Dal Piaz, 2001) consists of eclogite boudins that are surrounded by micaceous schist. Associated with the eclogite and schist are quartz-carbonate-white mica-rutile veins that formed in tension cracks in the eclogite and along the contact between eclogite and surrounding schist. Intrusion of the veins occurred at eclogite-facies metamorphic conditions (480-570°C, >1.3-1.4 GPa) based on textural relations, oxygen isotope thermometry, and geothermobarometry. Lu-Hf geochronology of garnet from a chloritoid-talc-garnet-phengite-quartz-calcite-pyrite - chalcopyrite bearing boudin within talc-chloritoid whiteschists of the MR, Val d'Ayas, Italy (Chopin and Monie, 1984; Pawlig, 2001) yields an age of 40.54 +/- 0.36 Ma. The talc-chloritoid whiteschists from the area record pressures and temperatures of 1.6-2.4 GPa and 500-530°C (Chopin and Monie, 1984; Le Bayon et al., 2006) indicating near UHP metamorphic conditions. Based on the age, P-T, and textural

  11. Hard Coat Layers by PE-CVD Process for the Top Surface of Touch Panel

    International Nuclear Information System (INIS)

    Okunishi, T; Sato, N; Yazawa, K


    In order to protect surface from damages, the high pencil hardness and the high abrasion resistance are required for the hard coat layers on polyethylene telephthalate (PET) films for the application of touch panel surface. We have already found that the UV-curing-hard-coat-polymer (UHP) coated PET films show the poor abrasion resistance, while they have the high pencil hardness. It reveals that the abrasion resistance of hard coat layers of the UHP is not simply dependent on the pencil hardness. In this work, we have studied to improve the abrasion resistance of SiOC films as hard coat layers, which were formed by PE-CVD process on UHP coated PET. The abrasion resistance was evaluated by Taber abrasion test. PE-CVD hard coat layers which formed on UHP coater PET films have showed the better abrasion resistance and have the possibility of substitution to the thin glass sheets for touch panel application.

  12. The Development and Design of a Prototype Ultra High Pressure P-19 Firefighting Vehicle

    National Research Council Canada - National Science Library

    Menchini, Christopher P; Dierdorf, Douglas; Kalberer, Jennifer L; McDonald, Michael J; Cozart, Kristofor S; Casarez, Adriana; Carr, Jr, Virgil J


    ...) and combined agent firefighting using compressed air foam (CAF) and dry chemical. The latest demonstrator uniquely incorporating both UHP and combined agent firefighting capability is a retrofitted P-19...

  13. 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


    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 Aracuai Orogen, the Caparao charnockitic granulite, revealed magmatic crystallization age of ca. 2195 Ma. Zircons from an amphibolite of the Pocrane Complex, also a basement inlier within the Aracuai Orogen, yielded an age of ca. 1500 Ma. Both inliers furnished well-constrained neo proterozoic metamorphic overprint at ca. 590 Ma. The sub alkaline gneissic granite from the Salto da Divisa Suite yielded a magmatic crystallization age of ca. 870 Ma, close to U-Pb ages of the continental rift magmatism found in the African counterpart of the Aracuai Orogen. Four gneissic granites from the Aracuai Orogen (three of them previously interpreted as part of the Archean/Paleoproterozoic basement) were dated in the range of ca. 560-570 Ma, and were correlated to the γ2 2 syn-collisional magmatism. Borders of some zircon grains from the older (ca. 570 Ma) dated unit (Nanuque Granite) yielded ages around 500 Ma, similar to U-Pb ages obtained from titanite, monazite and zircon in other localities from the Aracuai Orogen. This youngest ages could be related to heating effects caused by melting of country rocks and ascent of magmas formed during the collapse of the orogen. (author)

  14. Protracted deformation during cooling of the Paleoproterozoic arc system as constrained by {sup 40}Ar/{sup 39}Ar ages of muscovite from brittle faults: the Transamazonan Bacajá Terrane, Brazil

    Energy Technology Data Exchange (ETDEWEB)

    Perico, Edimar; Barros, Carlos Eduardo de Mesquita; Mancini, Fernando [Universidade Federal do Paraná – UFPR, Curitiba, PR (Brazil); Rostirolla, Sidnei Pires, E-mail: [Rosneft, Rio de Janeiro, RJ (Brazil)


    In the Paleoproterozoic Transamazonas Province, synkinematic granitogenesis has taken place synchronously with compressive tectonic stress. The synkinematic character of the granites is marked by their WNW elongate shape, and by the presence of pervasive and concordant synmagmatic foliation. Ductile shear zones are concordant to the previous regional WNW structures, and tend to be accommodated along contacts between Rhyacian synkinematic granitoids and both Archean orthogneisses and Siderian metabasites. Locally phyllonitic shear zones and brittle-ductile shear zones with cataclasites are oriented subparallel to the preexisting ductile foliation. Late orogenic brittle faults N30E-trending strike-slip faults are either sinistral or destral. {sup 40}Ar/{sup 39}Ar dating of muscovite developed on fault planes gave ages of 1977 ± 8 Ma and 1968 ± 11 Ma. Structural and geochronological data from rocks of the Transamazonas Province permit to conclude that most mylonites and brittle structures were controlled by preexisting structures such as geological contacts and petrographic facies boundaries. Compressive tectonic stress would have initiated at ca. 2100 Ma, since the former magmatic arc (Bacajaí complex), still present at 2070 Ma when syntectonic granites were emplaced and remained until 1975 Ma after granite plutonism and regional cooling. (author)

  15. Ecosystem health in mineralized terrane: Data from podiform chromite (Chinese Camp mining district, California), quartz alunite (Castle Peak and Masonic mining districts, Nevada/California), and Mo/Cu porphyry (Battle Mountain mining district, Nevada) deposits (United States)

    Steve W. Blecker; Lisa L. Stillings; Michael C. Amacher; James A. Ippolito; Nicole M. DeCrappeo


    The myriad definitions of soil/ecosystem quality or health are often driven by ecosystem and management concerns, and they typically focus on the ability of the soil to provide functions relating to biological productivity and/or environmental quality (Doran and Parkin, 1994; Karlen and others, 1997). A variety of attempts have been made to create indices that quantify...

  16. U-Pb zircon and 40Ar/39Ar geochronology of sericite from hydrothermal alteration zones: new constraints for the timing of Ediacaran gold mineralization in the Sukhaybarat area, western Afif terrane, Saudi Arabia (United States)

    Harbi, Hesham M.; Ali, Kamal A.; McNaughton, Neal J.; Andresen, Arild


    The Sukhaybarat East and Red Hill deposits, in the northeastern part of the Arabian Shield, are mesothermal vein-type gold deposits hosted by late Cryogenian-Ediacaran intrusive rocks of the Idah suites (diorite, tonalite, granodiorite) and, at Sukhaybarat East, also by Ediacaran metasedimentary rocks. Gold mineralization comprises quartz-arsenopyrite veins (Sukhaybarat East), quartz-carbonate-pyrite veins (Red Hill), and subordinate gold-base metal sulfide veins. In the Red Hill deposit, alteration is complicated due to multiple overprinting hydrothermal events and is characteristically affected by pervasive, pink quartz-K-feldspar-hematite alteration which is overprinted by potassic alteration characterized by a quartz-biotite-carbonate-muscovite/sericite-rutile-apatite assemblage. This assemblage is associated with molybdenite veins which appear to form late in the paragenetic sequence and may represent either evolution of the ore fluid composition, or a later, unrelated mineralized fluids. Hydrothermal alteration at the Sukhaybarat East deposit is dominated by quartz-carbonate-sericite-arsenopyrite assemblages. Zircon from ore-hosting tonalite at Sukhaybarat East yields a U-Pb age of 629 ± 6 Ma, and biotite from the same rock gives an 40Ar/39Ar age of 622 ± 23 Ma. The 40Ar/39Ar age is within the uncertainty range for the U-Pb age of the host intrusion and is interpreted as a minimally disturbed cooling age for the tonalite. In the Red Hill area, granodiorite was emplaced at 615 ± 5 Ma, whereas muscovite/sericite separated from a mineralized sample of a quartz-carbonate-pyrite vein, that was overprinted by molybdenite-bearing veinlets, yields an 40Ar/39Ar age of 597 ± 8 Ma. We interpreted this age to represent the maximum age of the molybdenite mineralization and the probable minimum age of gold mineralization in the Red Hill deposit.

  17. 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


    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 the Eastern Bahia Belt collision. The isotopic signature and the metamorphic assemblage are suggestive of recrystallization in very deep crustal levels, under high P and T conditions. A similar metamorphic regime is recorded in the western Jequie Block (sample LC 61), so far interpreted as a craton area which has been stable since the Archean. Accordingly, the Eastern Bahia Belt was characterized as the deep roots of a collisional orogeny, with discrete newly accreted magmas between ca. 2200? and ca. 2090 Ma - herein ascribed to the Western Bahia Orogeny which was formerly referred to as the Itabuna, Salvador-Curaca and Salvador-Esplanada belts. (author)

  18. Geochemistry of granitoid rocks from the western Superior Province: Evidence for 2- and 3-stage crustal evolution models (United States)

    Beakhouse, G. P.; errane) are discussed.


    The Superior Province is divisible into subprovinces that can be classified as greenstone-tonalite, paragneiss, or batholitic terranes and are distinguished by differences in lithologic proportions, metamorphic grade, and structural style. The origin and significance of contrasting geochemical characteristics of plutonic rocks from the Winnipeg River subprovince (a batholithic terrane) and the Wabigoon subprovince (a greenstone-tonalite terrane) are discussed.

  19. Review of past and present geotectonic concepts of eastern indonesia (United States)

    Katili, John A.

    equatorial Indo-Pacific region, for example, has recently been compared to the terrane map of the North American Cordillera. The position of eastern Indonesia within the plate-tectonic framework is the key to resolving contradictory views on the tectonics of the Banda Sea. For example, did the Indonesian orogeny take place at the Gondwana margin or the Asian margin, are Timor and Seram a tectonic melange and thus part of the Tertiary Indonesian island arcs, or are these two islands a part of the passive Australian margin? Oceanic magnetic stripes from the Sulu, Celebes and Banda Seas all trend NE-SW. These new data suggest that the Sulu, Celebes and probably the Banda Sea represent areas of trapped Indian Ocean crust. Deep sea drilling in the Banda Sea can resolve much controversy. The Banda Sea occupies a critical position in the complex convergent zone between Australia, Southeast Asia and the Philippine Sea Plate. The determination of the stratigraphy and basement ages of the Banda Sea will constrain evolutionary models which have been proposed. Another unsolved question of key importance in our understanding of the evolution of Sulawesi and the Moluccas is the function and timing of events of the Birdhead 'bacon slicer', or the tectonic shaving in Irian Jaya. Once this mechanism is understood, the development and timing of the various structural features of Sulawesi, Halmahera and the Banda Arc will be classified. Opinions still differ regarding the 'birthplace' of the micro-continents in the Banda Sea. Some regard them as a result of Jurassic rifting of Gondwana in northwestern Australia while others consider them displaced westward from northern Irian Jaya along the Sorong transform fault. Several authors suggested that the eastern parts of Sulawesi, Buru and Seram represent micro-continents which originated from Irian Jaya, while others considered East Sulawesi and north Sulawesi remnants of ophiolite belts or fragments of island arcs that originate from the Pacific

  20. Optimized ultra-high-pressure-assisted extraction of procyanidins from lychee pericarp improves the antioxidant activity of extracts. (United States)

    Zhang, Ruifen; Su, Dongxiao; Hou, Fangli; Liu, Lei; Huang, Fei; Dong, Lihong; Deng, Yuanyuan; Zhang, Yan; Wei, Zhencheng; Zhang, Mingwei


    To establish optimal ultra-high-pressure (UHP)-assisted extraction conditions for procyanidins from lychee pericarp, a response surface analysis method with four factors and three levels was adopted. The optimum conditions were as follows: 295 MPa pressure, 13 min pressure holding time, 16.0 mL/g liquid-to-solid ratio, and 70% ethanol concentration. Compared with conventional ethanol extraction and ultrasonic-assisted extraction methods, the yields of the total procyanidins, flavonoids, and phenolics extracted using the UHP process were significantly increased; consequently, the oxygen radical absorbance capacity and cellular antioxidant activity of UHP-assisted lychee pericarp extracts were substantially enhanced. LC-MS/MS and high-performance liquid chromatography quantification results for individual phenolic compounds revealed that the yield of procyanidin compounds, including epicatechin, procyanidin A2, and procyanidin B2, from lychee pericarp could be significantly improved by the UHP-assisted extraction process. This UHP-assisted extraction process is thus a practical method for the extraction of procyanidins from lychee pericarp.

  1. Fulltext PDF

    Indian Academy of Sciences (India)

    R.Narasimhan(krishtel emaging) 1461 1996 Oct 15 13:05:22

    Primary production in the Sulu Sea. 209. Joshi P C see Singh Randhir. 413. Kalra R see Rajaram Girija. 51 ... ton pigment in the Laccadive (Lakshadweep) Sea as observed by the Coastal Zone Colour Scanner 163 ... Seasonal and interannual variations in pigments in the Adriatic Sea. 215. Mujumdar V R see Bawiskar S M.

  2. Journal of Earth System Science | Indian Academy of Sciences

    Indian Academy of Sciences (India)

    ... and the Philippines, is separated from the surrounding ocean by two chains of islands. ... its remotely sensed values from OCTS (Ocean Colour Temperature Scanner) ... The greater primary productivity may provide the explanation for the higher ... Although the Sulu Sea is more productive than the adjacent South China ...

  3. Strategies for Countering Terrorist Safe Havens (United States)


    Sea and the Sulu Archipelago [which include the countries of Indonesia, Malaysia , and the Philippines] make it a difficult region for authorities to...prison massacre in May 1992. Meanwhile, the effect of the censorship laws was, naturally, to muzzle the opposition, the media and reports of human

  4. Land Ownership and Migration: Impact on the Muslim Secessionist Conflict in the Southern Philippines (United States)


    provinces (provinces of of Tawi-Tawi, Sulu, Basilan, Lanao del Sur and Maguindanao), and some municipalities of Zamboanga del Sur, Zamboanga Sibugay...Muslim Filipinos, edited by Peter G. Gowing and Robert D. McAmis. Manila: Solidaridad Publishing House, 1974. 72 Mercado , Elesio. as cited in Lawrence

  5. Application of Ultra High Pressure Cavitation Peening to Prevent PWSCC on Primary Plant Components

    Energy Technology Data Exchange (ETDEWEB)

    Poling, G.R.


    Primary Water Stress Corrosion Cracking (PWSCC) on Alloy 600/82/182 susceptible materials can lead to increased costs for maintenance and repair/replacement activities on nuclear power plant primary components. A process called Ultra High Pressure (UHP) cavitation peening can be safely and cost effectively applied to the susceptible materials to generate compressive stresses on the surface and prevent PWSCC initiation. AREVA has developed the tooling systems to apply the UHP cavitation peening process on reactor vessel head penetration nozzles, bottom mounted nozzles and primary nozzles. Applying the UHP cavitation peening process before PWSCC initiation will prevent future repairs/replacements, reduce maintenance costs, and provide more effective on-time for the reactor. (Author)

  6. Evaluation of ultra-high-performance-fiber reinforced concrete binder content using the response surface method

    International Nuclear Information System (INIS)

    Aldahdooh, M.A.A.; Muhamad Bunnori, N.; Megat Johari, M.A.


    Highlights: • We develop a practical method for adjusting the binder content of UHP-FRC. • We adjust the binder content of UHP-FRC mixtures using RSM. • Increasing the cement content does not contribute to enhance strength. • Increasing the content of cement will increase the flow of UHP-FRC mixtures. - Abstract: One of the major disadvantages in ultra-high-performance-fiber reinforced concrete (UHP-FRC) is its high ordinary Portland cement (OPC) content, which directly translates into an increase in OPC production. More OPC production results in increased emission of greenhouse gases, as well increased electrical energy consumption and concrete price. This study is aimed at adjusting the binder content (OPC and silica fume (SF) contents) of UHP-FRC using the response surface method. The present investigation shows that, for a given water/binder and superplasticizer/OPC, the compressive strength is independent of the binder content, whereas the flow depends on the binder content. Increasing the binder content does not enhance the strength compared with the required design strength because the capillary porosity increases with increasing OPC content; however, the workability increases. The final result is the production of a UHP-FRC with an OPC content of 720.49 kg/m 3 , an SF content of 214.25 kg/m 3 , a compressive strength of 181.41 MPa, a direct tensile strength of 12.49 MPa, a bending tensile strength of 30.31 MPa, and a flow of 167 mm

  7. Acoustic emission from a solidifying aluminum-lithium alloy (United States)

    Henkel, D. P.; Wood, J. D.


    Physical phenomena associated with the solidification of an AA2090 Al-Li alloy have been characterized by AE methods. Repeatable patterns of AE activity as a function of solidification time are recorded and explained for ultrahigh-purity (UHP) aluminum and an Al-4.7 wt pct Cu binary alloy, in addition to the AA2090 Al-Li alloy, by the complementary utilization of thermal, AE, and metallographic methods. One result shows that the solidification of UHP aluminum produces one discrete period of high AE activity as the last 10 percent of solid forms.

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

    Cuthbert, Simon


    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

  9. A new garnet-orthopyroxene thermometer developed: method, results and applications (United States)

    Olivotos, Spyros-Christos; Kostopoulos, Dimitrios


    The Fe-Mg exchange reaction between garnet and orthopyroxene is a robust geothermometer that has extensively been used to retrieve metamorphic temperatures from granulitic and peridotitic/pyroxenitic lithologies with important implications on the thermal state of the continental lithosphere. More than 800 experimental mineral pairs from both simple and complex systems were gleaned from the literature covering the P-T range 0.5-15 GPa / 800-1800°C. Grt was treated as a senary (Py, Alm, Grs, Sps, Kno and Uv), whereas Opx as a septenary (En, Fs, Di, Hd, FeTs, MgTs and MgCrTs) solid solution. For Opx, Al in the M1 site was calculated following Carswell (1991) and Fe/Mg equipartitioning between sites was assumed. A mixing on sites model was employed to calculate mole fractions of components for both minerals. With regard to the excess free energy of solution and activity coefficients the formalism of Mukhopadhyay et al. (1993) was adopted treating both minerals as symmetric regular solutions. Calibration was achieved in multiple steps; in each step ΔS was allowed to vary until the standard deviation of the differences between experimental and calculated temperature for all experiments was minimised. The experiment with the largest absolute relative deviation in temperature was then eliminated and the process was repeated. The new thermometer reproduces the experimental data to within 50°C and is independent of P-T-X variations within the bounds of the calibrant data set. Application of our new calibration to metamorphosed crustal and mantle rocks that occur both as massifs and xenoliths in volcanics suggested the following results. Granulite terranes have recorded differences in temperature between peak and re-equilibration conditions in the range 100-340°C, primarily depending on the mechanism and rate of exhumation. Several provinces retain memory of discrete cooling pulses (e.g. Palni Hills, South Harris, Adirondacks, E. Antarctic Belt, Aldan Shield) whereas

  10. The dehydration, rehydration and tectonic setting of greenstone belts in a portion of the northern Kaapvaal Craton, South Africa (United States)

    Vanreenen, D. D.; Barton, J. M., Jr.; Roering, C.; Vanschalkwyk, J. C.; Smit, C. A.; Debeer, J. D.; Stettler, E. H.


    High-grade gneiss terranes and low-grade granite-greenstone terranes are well known in several Archaean domains. The geological relationship between these different crustal regions, however, is still controversial. One school of thought favors fundamental genetic differences between high-grade and low-grade terranes while others argue for a depth-controlled crustal evolution. The detailed examination of well-exposed Archaean terranes at different metamorphic grades, therefore, is not only an important source of information about the crustal levels exposed, but also is critical to the understanding of the possible tectonic and metamorphic evolution of greenstone belts with time. Three South African greenstone belts are compared.

  11. Oxigen isotope compositions as indicators of epidote granite genesis in the Borborema Provinces, NE Brazil

    International Nuclear Information System (INIS)

    Ferreira, V.P.; Valley, J.W; Sial, A.N; Spicuzza, M.J


    Neoproterozoic magmatic epidote-bearing granitoids intrude low-grade metapelites in the Cachoeirinha-Salgueiro terrane (CST), and gneisses and migmatites in the Serido terrane (ST), in the Borborema structural province, northeastern Brazil. Granitoids in both terranes contain biotite and hornblende, and are metaluminous, calc-alkalic, and oxidized I-type granites according to White's (1992) classification. However, in spite of these similarities, this work shows that mineral oxygen isotope data from plutons of the two terranes indicate different magma sources, and that magmatic epidote besides crystallizing at different pressure conditions, can have variable isotopic composition (au)

  12. Interaction force and motion estimators facilitating impedance control of the upper limb rehabilitation robot. (United States)

    Mancisidor, Aitziber; Zubizarreta, Asier; Cabanes, Itziar; Bengoa, Pablo; Jung, Je Hyung


    In order to enhance the performance of rehabilitation robots, it is imperative to know both force and motion caused by the interaction between user and robot. However, common direct measurement of both signals through force and motion sensors not only increases the complexity of the system but also impedes affordability of the system. As an alternative of the direct measurement, in this work, we present new force and motion estimators for the proper control of the upper-limb rehabilitation Universal Haptic Pantograph (UHP) robot. The estimators are based on the kinematic and dynamic model of the UHP and the use of signals measured by means of common low-cost sensors. In order to demonstrate the effectiveness of the estimators, several experimental tests were carried out. The force and impedance control of the UHP was implemented first by directly measuring the interaction force using accurate extra sensors and the robot performance was compared to the case where the proposed estimators replace the direct measured values. The experimental results reveal that the controller based on the estimators has similar performance to that using direct measurement (less than 1 N difference in root mean square error between two cases), indicating that the proposed force and motion estimators can facilitate implementation of interactive controller for the UHP in robotmediated rehabilitation trainings.

  13. Irradiation-assisted stress corrosion cracking of austenitic alloys

    International Nuclear Information System (INIS)

    Was, G.S.; Atzmon, M.


    An experimental program has been conducted to determine the mechanism of irradiation-assisted stress-corrosion cracking (IASCC) in austenitic stainless steel. High-energy protons have been used to produce grain boundary segregation and microstructural damage in samples of controlled impurity content. The densities of network dislocations and dislocation loops were determined by transmission electron microscopy and found to resemble those for neutron irradiation under LWR conditions. Grain boundary compositions were determined by in situ fracture and Auger spectroscopy, as well as by scanning transmission electron microscopy. Cr depletion and Ni segregation were observed in all irradiated samples, with the degree of segregation depending on the type and amount of impurities present. P, and to a lesser extent P, impurities were observed to segregate to the grain boundaries. Irradiation was found to increase the susceptibility of ultra-high-purity (UHP), and to a much lesser extent of UHP+P and UHP+S, alloys to intergranular SCC in 288 degree C water at 2 ppm O 2 and 0.5 μS/cm. No intergranular fracture was observed in arcon atmosphere, indicating the important role of corrosion in the embrittlement of irradiated samples. The absence of intergranular fracture in 288 degree C argon and room temperature tests also suggest that the embrittlement is not caused by hydrogen introduced by irradiation. Contrary to common belief, the presence of P impurities led to a significant improvement in IASCC over the ultrahigh purity alloy

  14. Increasing the graduation rates of minority medical students. (United States)

    Payne, J L; Nowacki, C M; Girotti, J A; Townsel, J; Plagge, J C; Beckham, T W


    The University of Illinois College of Medicine has operated a program since 1969 to recruit minority students into the college and to increase the graduation rates of these students once they enroll. Known as the Medical Opportunities Program (MOP) until 1978, the program was expanded in 1978 and renamed the Urban Health Program (UHP). The authors of the present paper discuss the results of these programs, particularly the effect of granting minority students delays in completing graduation requirements. The MOP (1969 through 1978) increased graduation rates for minority students from 55 percent for those who graduated on time to 81 percent for both on-time and delayed graduates. Under the first seven years of the UHP (1979 through 1985), more minority students have been offered places, and more have enrolled than in the 10 years of the MOP. The retention rate under the UHP, if it holds, will be higher than that under the MOP. For the combined MOP-UHP period, the retention rate for minority students was 88 percent; 69.8 percent of the graduates were on time, and 30.2 were delayed.

  15. 76 FR 71434 - Continental Tire North America, Inc., Grant of Petition for Decision of Inconsequential... (United States)


    ... petition and all supporting documents log onto the Federal Docket Management System Web site at: http://www...) 366-7002. Affected are approximately 28,169 size 235/55R18 100V SL Continental brand CrossContact UHP...

  16. Immiscible melt droplets in garnet, as represented by ilmenite-magnetite-spinel spheroids in an eclogite-garnet peridotite association, Blanský les Granulite Massif, Czech Republic

    Czech Academy of Sciences Publication Activity Database

    Vrána, S.; Ackerman, Lukáš; Erban, V.; Halodová, P.


    Roč. 101, č. 1 (2016), s. 82-92 ISSN 0003-004X Institutional support: RVO:67985831 Keywords : eclogite * Fe-Ti-rich melt * garnet peridotite * garnetite * Ilmenite-magnetite-spinel * Invited Centennial article * Moldanubian Zone * UHP crystallization Subject RIV: DD - Geochemistry Impact factor: 2.021, year: 2016

  17. Kinetic and thermodynamic analysis of ultra-high pressure and heat ...

    African Journals Online (AJOL)

    Purpose: To undertake comparative kinetic and thermodynamic analyses of the interaction of bovine serum albumin (BSA) with IgG pre-treated with ultra-high pressure (UHP) and moderate heat. Methods: BSA solutions were processed at 100 – 600 MPa and 25 – 40 °C. We applied an optical biosensor based on surface ...

  18. Impact of He and Cr on defect accumulation in ion-irradiated ultrahigh-purity Fe(Cr) alloys

    DEFF Research Database (Denmark)

    Prokhodtseva, A.; Décamps, B.; Ramar, Amuthan


    The effect of He on the primary damage induced by irradiation in ultrahigh-purity (UHP) Fe and Fe(Cr) alloys was investigated by transmission electron microscopy (TEM). Materials were irradiated at room temperature in situ by TEM in a microscope coupled to two ion accelerators, simultaneously pro...

  19. Mesozoic monazite in Neoproterozoic metasediments. Evidence for low-grade metamorphism of Sinian sediments during Triassic continental collision, Liaodong Peninsula, NE China

    International Nuclear Information System (INIS)

    Wan Yusheng; Song Tianrui; Liu Dunyi; Yang Tiannan; Yin Xiaoyan; Zhang Qiaoda; Chen Zhenyu


    Sericite phyllite from the Sinian Shisanlitai Formation, Dalian area, Liaodong Peninsula, NE China, contains an assemblage of newly-formed lower-greenschist facies minerals (sericite, chlorite, Fe minerals and Ti minerals) plus aggregates of fine-grained monazite. The texture of the monazite, its mineral inclusions, and its close association with Fe oxide minerals show that it is not detrital or diagenetic, but a product of the low-grade metamorphism. SHRIMP U-Th-Pb dating of the monazite at 217±15 Ma shows that the metamorphism, and associated regional deformation and fluid flow, occurred in the Late Triassic, coeval with the waning stages of the Dabie-Sulu orogeny. The Dabie-Sulu tectonothermal event has produced both deformation and metamorphism in rocks of the eastern North China Block at least up to ∼200 km north of the main continent-continent collision zone. (author)

  20. CTC Sentinel. Volume 2, Issue 6, June 2009 (United States)


    establish a leather - tanning works in Mumbai’s Kurla area.37 Like Sheikh, though, Shahbandri dropped out of high school and became a full-time SIMI...173 Cr.P.C.) in the Court of Additional Chief Metropoli- tan Magistrate, 37th Court, Esplanade, Mumbai,” Mum- bai Police Headquarters, February 25...attempt. – AFP, May 13 May 13, 2009 (PHILIPPINES): A roadside bomb targeted the governor of Sulu Province, Abdusakur Tan . The governor survived the

  1. Simplifying Decision Making: A Practical Framework (United States)


    philosophy so interesting for students ; it was always a pleasure to be in his class. We also owe our gratitude to Dr. William Fox who graciously...basically labourer in the palm oil industry. Among the social fallout of this crisis could be their forced deportation, as many of them are poor and... Inclusion in Bangsamoro Framework Agreement. Sultan was very concerned that the authority over the ancestral kingdom of Sulu and North Borneo was to be

  2. Studies in Intelligence. Volume 58, Number 3 (Unclassified Articles from September 2014) (United States)


    boarded two Catalina fl ying boats for Tawi Tawi, an island province separating the Sulu Sea and Celebes Sea between Sabah, Malaysia and Zamboanga...Operations and Campaigns Exposed Throughout the Civil War, the northern press, which fi ercely op- posed censorship and had among its core more than...which fi ercely opposed censorship , was responsible for several serious disclosures. The “Unfettered Press” 23Studies in Intelligence Vol 58, No. 3

  3. The U.S.-China Military Scorecard: Forces, Geography, and the Evolving Balance of Power, 1996-2017 (United States)


    the Philippines and Vietnam, efforts should also be made with the states of Southeast Asia’s “southern tier,” including Indonesia and Malaysia . This...Hanoi THAILAND CAMBODIA VIETNAM LAOS MALAYSIA MALAYSIA BRUNEI PHILIPPINES TAIWAN INDONESIA South China Sea PhilippineSea Sulu Sea Palawan uzon Hainan...blocked pages hosted on U.S. cloud computing services, and simple proxy serv- ers, to circumvent censorship .83 Recently, however, China has become more

  4. U.S. Special Operations Forces in the Philippines, 2001-2014 (United States)


    brother-in-law and senior AQ finan- cier Mohammed Jamal Khalifa used Philippine front companies and charities to support the Bojinka plots, as well...adversaries. The population ideally becomes less hospitable to the enemy forces, which shrinks their sup- port base, resources, and room for maneuver. Local...the entire Sulu archipelago, of which Jolo was the capital, to be a hospitable environment indeed, permitting freedom of movement from island to

  5. Geological and Geophysical Integration Regarding a Structural Evolution Modelling of a Suture Zone Controlled by a Cratonic Buttress - The Case of Dom Feliciano Orogenic Belt, SSE Brazil, Implications for Western Gondwana Assembly (United States)

    Bruno, H.; Almeida, J.; Heilbron, M. C. P. L.; Salomão, M.


    The matters surrounding the amalgamation of tectonic blocks during the Brasiliano / Pan-African orogeny have been the main subject of study of several works in recent years. The main objective of this work is the hierarchy and discrimination of the boundaries between the known tectonic blocks, integrating geological and geophysical data. The geology of the study area is dominated by Precambrian terranes; Luís Alves Terrane, the vulcanosedimentary sequences of the Itajaí and Campo Alegre Basins, the metasedimentary sequences of the Brusque and Paranaguá Terranes and their granitic suites besides the granitoids of the Florianópolis Terrane. The shear zones and faults that separate these crustal blocks were developed during the Brasiliano / Pan-African orogenic cycle that led to the formation of the supercontinent Gondwana. These tectonic boundaries generally separate blocks of different rheology and crustal thickness. The integration of geological and geophysical data allowed the identification of important structural lineaments and crustal boundaries. The presented geodynamic model suggests that the suture between the block composed of the Brusque, Paranaguá and Florianópolis Terranes and the block composed by the Luís Alves Terrane is the Itajaí Perimbó Shear Zone, and not the Major Gercino Shear Zone as previously suggested. Considering the Itajaí Perimbó Shear Zone as the suture zone, the metassediments of the Brusque Terrane were deposited on the basement of the Florianópolis Terrane, hereby declared as part of the Angola Craton, and are correlated to the metassediments of the Paranaguá Terrane as a passive margin that in approximately ca. 650 My became active margin, functioning as a forearc basin. The oblique collision between the blocks would have occurred with the development of a dextral transpression in the Itajaí Perimbó Shear Zone, separating the Luís Alves Terrane from the Brusque Terrane, a sinistral transcurrence represented by the

  6. Comment on “The role of interbasin groundwater transfers in geologically complex terranes, demonstrated by the Great Basin in the western United States”: report published in Hydrogeology Journal (2014) 22:807–828, by Stephen T. Nelson and Alan L. Mayo (United States)

    Masbruch, Melissa D.; Brooks, Lynette E.; Heilweil, Victor M.; Sweetkind, Donald S.


    The subject article (Nelson and Mayo 2014) presents an overview of previous reports of interbasin flow in the Great Basin of the western United States. This Comment is presented by authors of a cited study (comprising chapters in one large report) on the Great Basin carbonate and alluvial aquifer system (GBCAAS; Heilweil and Brooks 2011; Masbruch et al. 2011; Sweetkind et al. 2011a, b), who agree that water budget imbalances alone are not enough to accurately quantify interbasin flow; however, it is proposed that statements made in the subject article about the GBCAAS report are inaccurate. The Comment authors appreciate the opportunity to clarify some statements made about the work.

  7. 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:; 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


    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 Aracuai Orogen, the Caparao charnockitic granulite, revealed magmatic crystallization age of ca. 2195 Ma. Zircons from an amphibolite of the Pocrane Complex, also a basement inlier within the Aracuai Orogen, yielded an age of ca. 1500 Ma. Both inliers furnished well-constrained neo proterozoic metamorphic overprint at ca. 590 Ma. The sub alkaline gneissic granite from the Salto da Divisa Suite yielded a magmatic crystallization age of ca. 870 Ma, close to U-Pb ages of the continental rift magmatism found in the African counterpart of the Aracuai Orogen. Four gneissic granites from the Aracuai Orogen (three of them previously interpreted as part of the Archean/Paleoproterozoic basement) were dated in the range of ca. 560-570 Ma, and were correlated to the {gamma}2{sub 2} syn-collisional magmatism. Borders of some zircon grains from the older (ca. 570 Ma) dated unit (Nanuque Granite) yielded ages around 500 Ma, similar to U-Pb ages obtained from titanite, monazite and zircon in other localities from the Aracuai Orogen. This youngest ages could be related to heating effects caused by melting of country rocks and ascent of magmas formed during the collapse of the orogen. (author)

  8. Reassessment of the geologic evolution of selected precambrian terranes in Brazil, based on new SHRIMP U-Pb data, part 3: Borborema, Southern Mantiqueira and Rio Negro-Juruena provinces; Reavaliacao da evolucao geologica em terrenos pre-cambrianos brasileiros com base em novos dados U-Pb SHRIMP, parte 3: Provincias Borborema, Mantiqueira Meridional e Rio Negro-Juruena

    Energy Technology Data Exchange (ETDEWEB)

    Silva, Luiz Carlos da; Pimentel, Marcio [Brasilia Univ., DF (Brazil). Inst. de Geociencias]. E-mail:; Scandolara, Jaime; Ramgrab, Gilberto [Centro de Pesquisas e Recursos Minerais, Brasilia, DF (Brazil); Wildner, Wilson; Sander, Andrea [Centro de Pesquisas e Recursos Minerais, Porto Alegre, RS (Brazil); Angelim, Luiz Alberto de Aquino [Centro de Pesquisas e Recursos Minerais, Recife, PE (Brazil); Vasconcelos, Antonio Maurilio [Centro de Pesquisas e Recursos Minerais, Fortaleza, CE (Brazil); Rizzoto, Gilmar; Quadros, Marcio Luiz do Espirito Santo [Centro de Pesquisas e Recursos Minerais, Porto Veolho, RO (Brazil); Armstrong, Richard [Australian National Univ., Canberra (Australia). Research School of Earth Sciences; Rosa, Ana Lucia Zucatti da [PETROBRAS, Rio de Janeiro, RJ (Brazil). Centro de Pesquisas


    This paper discusses new SHRIMP U-Pb data for 17 key-exposures (mostly granites and ortho gneisses) from the Borborema, Southern Mantiqueira (Pelotas Orogen) and Rio Negro-Juruena provinces. In the Borborema Province (Ceara state) two samples from the Cruzeta Complex TTG ortho gneisses, ascribed to the Paleoproterozoic basement, were studied. One revealed Paleoarchean crystallization minimum age of ca. 3270 Ma. Accordingly, the gneiss is interpreted as the oldest continental crustal remnant already recognised in Ceara. The other sample, from the Saboeiro-Aiuaba Granite gave a crystallization age of ca. 625 Ma, suggesting the correlation of this syn-orogenic pluton with the Brasiliano II orogenic system (climax at 630 Ma). In the Paraiba state the granodioritic gneiss pluton ascribed to the Mesoproterozoic Sume Complex showed a crystallization age of ca. 640 Ma, also indicating that its evolution is associated with the Brasiliano II orogenic system. In the Pernambuco state one widespread ortho gneissic unit within the Pernambuco-Alagoas Massif (Belem do Sao Francisco Complex), mapped as a component of the Meso proterozoic Cariris Velho Orogen, yielded a crystallization age of ca. 2079 Ma and metamorphic overprinting at ca. 655 Ma (1{sigma}), without evidence of a Mesoproterozoic (Cariris Velhos) reworking. In the southern part of the province, near the northern margin of the Sao Francisco Craton, the Santa Maria da Boa Vista (S-type) orthogneiss yielded a crystallisation age of ca. 3070 Ma. In the southern Mantiqueira Province/Pelotas Orogen a foliated granitic pluton (mylonitic) from the Florianopolis Batholith showed Paleoproterozoic protolithic age of ca. 2175 Ma and imprecise Brasiliano age on reprecipitated overgrowths. Both results match previous ages obtained on the orthogneisses protoliths from the Aguas Mornas complex, the main exposure of reworked basement within the batholith. The large, zoned calc-alkaline pluton of the Maruim Suite, confirmed its complex post-collisional history relatively to the ca. 650-630 Ma Pelotas Orogen. Two tonalitic rocks yielded crystallization ages of ca. 611 Ma and ca. 608 Ma, whereas a granitic end member a crystallisation age of ca. 580 Ma. An attempt to determine the age of rifting that originated the post-collisional foreland Itajai Basin, a resedimented volcaniclastic felsic layer was investigated. The CL imagery revealed a very heterogeneous zircon population with a dominant detrital group ranging in age between ca. 1730-1800 Ma. One euhedral volcanic crystal, yielded an apparent age of ca. 608 Ma, interpreted as the best estimate age for the onset of the Itajai volcanic-sedimentary basin, and a minimum age for the volcanogenic episode. In the SW domain of the Rio Negro- Juruena Province in Mato Grosso state, a pluton related to the Aripuana Granitic Suite, revealed a crystallization age of ca. 1540 Ma. As the granite is related to Au and Cu-Zn hydrothermal mineralization, this precise geochronologic constraint on its emplacement age is also an important clue for exploratory purposes. In the central domain of the province, in Rondonia state, two orthogneissic units exposed in the vicinities of Ariquemes and Mutum-Parana were dated at ca. 1660 Ma and ca. 1728 Ma respectively, and attributed to the Jamari Complex. In the same domain, two mylonitic leucogranites exposed close to Cacoal and Espigao do Oeste, belonging to the Serra da Providencia Intrusive Suite yielded crystallisation ages of ca. 1522 Ma and ca. 1545 Ma, respectively. The former, showed also solid-state external overgrowths dated at ca. 1400 Ma, owing to recrystallizing processes at the roots of deep seated mylonitic shear zones. Finally, two orthogneissic units with crystallization ages of ca. 1555 Ma and ca. 1545 Ma - coeval with the crystallization age of the Serra da Providencia Intrusive Suite - showed metamorphic overgrowths aged at ca. 1325 Ma, suggestive of overprinting by a regional metamorphic event, not reported in previous works on the suite, but already recognised in other associations in the region. (author)

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

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


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

  10. Geochronology of Hydrothermal Processes Leading to the Formation of the Au–U Mineralization at the Rompas Prospect, Peräpohja Belt, Northern Finland: Application of Paired U–Pb Dating of Uraninite and Re–Os Dating of Molybdenite to the Identification of Multiple Hydrothermal Events in a Metamorphic Terrane

    Directory of Open Access Journals (Sweden)

    Ferenc Molnár


    Full Text Available The Peräpohja belt comprises a greenschist to amphibolite facies; multiply-folded supracrustal sequence of quartzites; mafic volcanics; carbonate rocks; black shales; mica schists and greywackes deposited from ca. 2.44 Ga to 1.92 Ga; during protracted rifting of the Archaean basement. Metamorphism and multiple folding of the basin fill occurred during the Svecofennian orogeny (1.92–1.80 Ga. The Rompas Au–U mineralization is hosted within deformed and metamorphosed calcsilicate veins in mafic volcanics. Textural evidence suggests that deposition and periods of uraninite re-mobilization were followed by localized hydrocarbon-bearing fluid flow which produced pyrobitumen crusts around grains of uraninite. Gold precipitated during the latest hydrothermal event at around 1.75 Ga. In situ U–Pb dating of uraninite by laser ablation inductively coupled mass spectroscopy (LA-ICP-MS, and Re–Os dating of molybdenite, indicate that primary hydrothermal uranium mineralization forms two age clusters; about 2.03–2.01 and 1.95–1.94 Ga. Resetting of the U–Pb system and precipitation of new generations of uraninite are associated with major deformation and metamorphic stages of the Svecofennian orogeny at 1.91–1.89 Ga, 1.85 Ga, and 1.80 Ga. Gold deposition was synchronous with the emplacement of the 1.75–1.78 Ga late/post-orogenic granitoids. The gold-producing hydrothermal event is also recorded by Re–Os dating of molybdenite from the gold-bearing Mg-metasomatized metasedimentary and metavolcanic units at the Palokas prospect; a few kilometres from Rompas. Results of this study confirm that some domains in the structure of uraninite may preserve the original crystallization age, despite an overprinting amphibolite facies metamorphic and other hydrothermal events. The study supports the utility of in situ U–Pb dating of uraninite and the ability of Re–Os dating to assist in sorting out different hydrothermal events in areas with complex tectonic; magmatic and metamorphic histories.

  11. Role of mantle dynamics in rebuilding the Tianshan Orogenic Belt in NW China: A seismic tomographic investigation (United States)

    He, Chuansong; Santosh, M.


    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.

  12. Reconnaissance Geologic Map of the Hayfork 15' Quadrangle, Trinity County, California (United States)

    Irwin, William P.


    The Hayfork 15' quadrangle is located just west of the Weaverville 15' quadrangle in the southern part of the Klamath Mountains geologic province of northern California. It spans parts of six generally north-northwest-trending tectonostratigraphic terranes that are, from east to west, the Eastern Klamath, Central Metamorphic, North Fork, Eastern Hayfork, Western Hayfork, and Rattlesnake Creek terranes. Remnants of a once-widespread postaccretionary overlap assemblage, the Cretaceous Great Valley sequence, crop out at three localities in the southern part of the Hayfork quadrangle. The Tertiary fluvial and lacustrine Weaverville Formation occupies a large, shallow, east-northeast-trending graben in the south half of the quadrangle. The small area of Eastern Klamath terrane is part of the Oregon Mountain outlier, which is more widely exposed to the east in the Weaverville 15' quadrangle. It was originally mapped as a thrust plate of Bragdon(?) Formation, but it is now thought by some to be part of an outlier of Yreka terrane that has been dislocated 60 km southward by the La Grange Fault. The Central Metamorphic terrane, which forms the footwall of the La Grange Fault, was formed by the eastward subduction of oceanic crustal basalt (the Salmon Hornblende Schist) and its overlying siliceous sediments with interbedded limestone (the Abrams Mica Schist) beneath the Eastern Klamath terrane. Rb-Sr analysis of the Abrams Mica Schist indicates a Middle Devonian metamorphic age of approximately 380 Ma, which probably represents the age of subduction. The North Fork terrane, which is faulted against the western boundary of the Central Metamorphic terrane, consists of the Permian(?) North Fork ophiolite and overlying broken formation and melange of Permian to Early Jurassic (Pliensbachian) marine metasedimentary and metavolcanic rocks. The ophiolite, which crops out along the western border of the terrane, is thrust westward over the Eastern Hayfork terrane. The Eastern

  13. MURI: An Integrated Multi-Scale Approach for Understanding Ion Transport in Complex Heterogeneous Organic Materials (United States)


    small membrane samples. Mechanical properties were tested at 30 and 60°C under dry or water saturated gas conditions. Water in the membrane has a...hydroxide conductivity (Figure 3) of the films was measured under a CO2 free environment, using UHP nitrogen gas . We noticed PCMS-PCOE-PCMS-TTMPP gave a...movement of anions is not confined, thus showing a higher degree of freedom for diffusion. This kind of behaviour can tell us about lack of defined

  14. Turvalisus kõigepealt / Jukka Antila

    Index Scriptorium Estoniae

    Antila, Jukka


    TM võrdleb suverehve. Testiauto: Volkswagen Golf. Rehvimõõt: 205/55 R 16. Rehvid: Apollo Alnac 4G, Barum Bravuris 3 HM, Continental ContiPremiumContact 5, Dunlop Sport Blu Response, Firestone Firehawk TZ300, Goodride Sport SA-37, Goodyear Efficient Grip Performance, Hankook Ventus Prime 2, Kumho Solus HS51, Landsail LS 588 UHP, Michelin Primacy 3, Nankang Econex NA-1, Nokian Hakka Blue, Pirelli Cinturato P7 Blue, Vredestein Sportrac 5 Giugiaro

  15. Unraveling P-T-t-D Evolution of Zermatt-Saas Ophiolites from Valtournanche: from Ocean Opening to Mountain Building (United States)

    Rebay, G.; Tiepolo, M.; Zanoni, D.; Langone, A.; Spalla, M. I.


    The Zermatt-Saas (ZS) Zone, formerly part of Tethyan oceanic crust and variously affected by oceanic metamorphism, is now part of the orogenic suture that developed in the Western European Alps during the Alpine subduction and collision. The ZS rocks preserve a dominant HP to UHP metamorphic imprint overprinted by greenschist facies metamorphism. The age of the oceanic protoliths is considered to be middle to upper Jurassic whereas the HP metamorphism is mostly considered to be Eocene. In upper Valtournanche ZS ophiolites, the dominant regional S2 foliation is mapped with spatial continuity in serpentinite, metarodingite and eclogite and is defined by HP/UHP parageneses in all lithotypes. It developed at 2.5 ± 0.3 GPa and 600 ± 20°C during Alpine subduction. S2 foliation of serpentinites wraps rare clinopyroxene and zircon relics. Trace element composition of clinopyroxene suggests that they crystallised from a melt in equilibrium with plagioclase: they most likely represent relicts of gabbroic assemblages. The clinopyroxene porphyroclasts have rims indented within S2 and compositions similar to fine-grained clinopyroxeneII defining S2, suggesting that they recrystallised during Alpine subduction. Zircon cores show, under CL, sector zoning typical of magmatic growth. U-Pb dates suggest their crystallisation during Middle Jurassic. Magmatic cores have thin fringe overgrowths parallel to the S2 foliation. U-Pb concordant analyses on these domains reveal an Upper Cretaceous-Paleocene crystallization most likely representing the HP to UHP Alpine re-equilibration. This suggests that some sections of the ZS have experienced HP to UHP metamorphism earlier than previously thought, opening new interpretative geodynamic scenarios. Remarkably, these new dates are similar to those recorded for the HP re-equilibration in the continental crust of the adjacent Austroalpine units (upper plate of the Alpine subduction system) and to those recorded for prograde metamorphism in

  16. Integrated smart bearings for next generation aero-engines Part 1: Development of a sensor suite for automatic bearing health monitoring


    Bashir, Imran; Wang, Ling; Harvey, Terence; Zaghari, Bahareh; Weddell, Alexander; White, Neil


    The development of smart bearing solutions will contribute to increased aircraft engine reliability, allowing the early detection of bearing failure through robust health monitoring. This project aims to develop intelligent bearing systems for an Ultra High Propulsion Efficiency (UHPE) ground test demonstrator, where a fully integrated self-powered wireless sensing system will be developed for future aircraft. This paper provides a comprehensive review of the state-of-the-art smart bearing te...

  17. Influence of mid-crustal rheology on the deformation behavior of continental crust in the continental subduction zone (United States)

    Li, Fucheng; Sun, Zhen; Zhang, Jiangyang


    Although the presence of low-viscosity middle crustal layer in the continental crust has been detected by both geophysical and geochemical studies, its influence on the deformation behavior of continental crust during subduction remains poorly investigated. To illustrate the crustal deformation associated with layered crust during continental subduction, we conducted a suite of 2-D thermo-mechanical numerical studies with visco-brittle/plastic rheology based on finite-differences and marker-in-cell techniques. In the experiments, we established a three-layer crustal model with a quartz-rich middle crustal layer embedded between the upper and lower continental crust. Results show that the middle crustal layer determines the amount of the accreted upper crust, maximum subduction depth, and exhumation path of the subducted upper crust. By varying the initial effective viscosity and thickness of the middle crustal layer, the further effects can be summarized as: (1) a rheologically weaker and/or thicker middle crustal layer results in a larger percentage of the upper crust detaching from the underlying slab and accreting at the trench zone, thereby leading to more serious crustal deformation. The rest of the upper crust only subducts into the depths of high pressure (HP) conditions, causing the absence of ultra-high pressure (UHP) metamorphic rocks; (2) a rheologically stronger and/or thinner middle crustal layer favors the stable subduction of the continental crust, dragging the upper crust to a maximum depth of ∼100 km and forming UHP rocks; (3) the middle crustal layer flows in a ductile way and acts as an exhumation channel for the HP-UHP rocks in both situations. In addition, the higher convergence velocity decreases the amount of subducted upper crust. A detailed comparison of our modeling results with the Himalayan collisional belt are conducted. Our work suggests that the presence of low-viscosity middle crustal layer may be another possible mechanism for

  18. Plutons and accretionary episodes of the Klamath Mountains, California and Oregon (United States)

    Irwin, William P.; Wooden, Joseph L.


    The Klamath Mountains consist of various accreted terranes and include many plutons that range in composition from gabbro to granodiorite. Some of the plutons (preaccretionary plutons) were parts of terranes before the terranes accreted; others (accretionary plutons) intruded during or after the accretion of their host terrane(s). This report attempts to (1) graphically illustrate how the Klamath Mountains grew by the accretion of allochthonous oceanic terranes during early Paleozoic to Cretaceous times, (2) identify the plutons as either preaccretionary or accretionary, and (3) genetically relate the plutonic intrusions to specific accretionary episodes. The eight accretionary episodes portrayed in this report are similar to those shown by Irwin and Mankinen (1998) who briefly described the basis for the timing of the episodes and who illustrated the ~110 degrees of clockwise rotation of the Klamath Mountains since Early Devonian time. Each episode is named for the accreting terrane. In all episodes (Figs. 1-8), the heavy black line represents a fault that separates the accreting oceanic rocks on the left from earlier accreted terranes on the right. The preaccretionary plutons are shown within the accreting oceanic crustal rocks to the left of the heavy black line, and the accretionary plutons in most instances are shown intruding previously accreted terranes to the right. Episodes earlier than the Central Metamorphic episode (Fig. 1), and that may have been important in the formation of the early Paleozoic nucleous of the province (the Eastern Klamath terrane), are not known. The 'Present Time' distribution of the accreted terranes and plutons is shown at a large scale in Figure 9. The schematic vertical section (Fig. 10) depicts the terranes as a stack of horizontal slabs that include or are intruded by vertical plutons. Note that at their base the ~170 Ma preaccretionary plutons of the Western Hayfork subterrane are truncated by the ~164 Ma Salt Creek

  19. Derivation of P-T paths from high-pressure metagranites - Examples from the Gran Paradiso Massif, western Alps (United States)

    Massonne, Hans-Joachim


    Metamorphosed granites (SiO2 ≥ 70 wt.%) are, in fact, a common rock type in high pressure (HP) and ultrahigh pressure (UHP) terrains, but these rocks were rarely used to derive metamorphic P-T paths. To test the suitability of HP metagranites for such derivations, two metagranites from the Gran Paradiso Massif were studied applying elemental mapping of phengite and garnet and calculated P-T pseudosections contoured by various chemical and modal parameters. Both rocks contain phengite with maximum Si contents of about 3.42 Si per formula unit (pfu) and 3.55 Si pfu in cores, and accessory garnet which is compositionally zoned. Garnet core compositions are rich in grossular component (XCa up to 0.72). Only a rough P-T path could be derived with peak pressures below 2 GPa because, for instance, Si contents in phengite become geobarometrically insensitive at HP conditions, when biotite is not anymore stable. A test of the pseudosection approach to a metagranite from the North Qaidam UHP metamorphic belt resulted in an ambiguous finding. In fact, compositions of garnet and phengite in this rock are indicative of both UHP and specific HP conditions ( 1.3 GPa, 530 °C), but the latter conditions fit the entire mineralogical observations better.

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

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


    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.

  1. Image analysis method to quantify the effect of different treatments on the visual meat/shell ratio of half-shelled green lipped mussels (Perna canaliculus). (United States)

    Kim, Min Geun; Alçiçek, Zayde; Balaban, Murat O; Atar, Hasan Huseyin


    Aquacultured green lipped mussel (Perna canaliculus) is the New Zealand export leader of seafood in terms of weight. Different treatments shrink mussel meat differently and affect the consumer perception of half-shelled mussels. In order to quantify this, digital images of half-shelled green lipped mussels subjected to two postharvest treatments (ultrahigh pressure (UHP) and heat treatment (HT)) and raw controls were taken. The ratio of the view area of the meat to that of the shell (labelled as 'visual condition index' (VCI)) was measured using image analysis. A polygonal region of interest was defined on the image to depict the boundary of the meat and to calculate the view area. Raw mussels had a VCI of 85%. HT mussels had a much reduced VCI of 41%, indicating shrinkage of the meat due to heat. UHP treatment used as a shucking method resulted in a VCI of 83%. Since VCI is one measure of quality for the consumer, this quantitative method can be used in the optimization of shucking treatment (HT or UHP). VCI can be used to optimize postharvest treatments to minimize meat shrinkage. This method can also be applied to other shellfish such as oysters and clams. © 2013 Society of Chemical Industry.

  2. The Utrecht Health Project: Optimization of routine healthcare data for research

    International Nuclear Information System (INIS)

    Grobbee, Diederick E.; Hoes, Arno W.; Verheij, Theo J. M.; Schrijvers, Augustinus J. P.; Ameijden, Erik J. C. van; Numans, Mattijs E.


    Background. Research on the impact of changes in healthcare policy, developments in community and public health and determinants of health and disease during lifetime may effectively make use of routine healthcare data. These data, however, need to meet minimal criteria for quality and completeness. Research opportunities are further improved when routine data are supplemented with a standardized 'baseline' assessment of the full population. This formed the basis for a new study initiated in a newly developed large residential area in Leidsche Rijn, part of the city of Utrecht, the Netherlands.Methods. All new inhabitants are invited by their general practitioner to participate in the Utrecht Health Project (UHP). Informed consent is obtained and an individual health profile (IHP) is made by dedicated research nurses. The IHP is the starting point for the UHP research database as well as for the primary care electronic medical records. Follow-up data are collected through continuous linkage with the computerized medical files recorded by the general practitioners. UHP staff in each practice takes care of quality management of registration as well as data handling.Results. Currently, over 60 of invited new residents in the area have given informed consent with participation steadily increasing. Discussion. The Utrecht Health Project combines key elements of traditional epidemiologic cohort studies with the current power of routine electronic medical record keeping in primary care. The research approach optimizes routine health care data for use in scientific research

  3. Geologic Map of the Weaverville 15' Quadrangle, Trinity County, California (United States)

    Irwin, William P.


    The Weaverville 15' quadrangle spans parts of five generally north-northwest-trending accreted terranes. From east to west, these are the Eastern Klamath, Central Metamorphic, North Fork, Eastern Hayfork, and Western Hayfork terranes. The Eastern Klamath terrane was thrust westward over the Central Metamorphic terrane during early Paleozoic (Devonian?) time and, in Early Cretaceous time (approx. 136 Ma), was intruded along its length by the massive Shasta Bally batholith. Remnants of overlap assemblages of the Early Cretaceous (Hauterivian) Great Valley sequence and the Tertiary Weaverville Formation cover nearly 10 percent of the quadrangle. The base of the Eastern Klamath terrane in the Weaverville quadrangle is a peridotite-gabbro complex that probably is correlative to the Trinity ophiolite (Ordovician), which is widely exposed farther north beyond the quadrangle. In the northeast part of the Weaverville quadrangle, the peridotite-gabbro complex is overlain by the Devonian Copley Greenstone and the Mississippian Bragdon Formation. Where these formations were intruded by the Shasta Bally batholith, they formed an aureole of gneissic and other metamorphic rocks around the batholith. Westward thrusting of the Eastern Klamath terrane over an adjacent body of mafic volcanic and overlying quartzose sedimentary rocks during Devonian time formed the Salmon Hornblende Schist and the Abrams Mica Schist of the Central Metamorphic terrane. Substantial beds of limestone in the quartzose sedimentary unit, generally found near the underlying volcanic rock, are too metamorphosed for fossils to have survived. Rb-Sr analysis of the Abrams Mica Schist indicates a metamorphic age of approx. 380 Ma. West of Weavervillle, the Oregon Mountain outlier of the Eastern Klamath terrane consists mainly of Bragdon Formation(?) and is largely separated from the underlying Central Metamorphic terrane by serpentinized peridotite that may be a remnant of the Trinity ophiolite. The North Fork

  4. Reconnaissance geologic map of the Hyampom 15' quadrangle, Trinity County, California (United States)

    Irwin, William P.


    The Hyampom 15' quadrangle lies west of the Hayfork 15' quadrangle in the southern part of the Klamath Mountains geologic province of northern California. It spans parts of four generally northwest-trending tectono- stratigraphic terranes of the Klamath Mountains, the Eastern Hayfork, Western Hayfork, Rattlesnake Creek, and Western Jurassic terranes, as well as, in the southwest corner of the quadrangle, a small part of the Pickett Peak terrane of the Coast Range province. Remnants of the Cretaceous Great Valley overlap sequence that once covered much of the pre-Cretaceous bedrock of the quadrangle are now found only as a few small patches in the northeast corner of the quadrangle. Fluvial and lacustrine deposits of the mid-Tertiary Weaverville Formation crop out in the vicinity of the village of Hyampom. The Eastern Hayfork terrane is a broken formation and m-lange of volcanic and sedimentary rocks that include blocks of chert and limestone. The chert has not been sampled; however, chert from the same terrane in the Hayfork quadrangle contains radiolarians of Permian and Triassic ages, but none clearly of Jurassic age. Limestone at two localities contains late Paleozoic foraminifers. Some of the limestone from the Eastern Klamath terrane in the Hayfork quadrangle contains faunas of Tethyan affinity. The Western Hayfork terrane is part of an andesitic volcanic arc that was accreted to the western edge of the Eastern Hayfork terrane. It consists mainly of metavolcaniclastic andesitic agglomerate and tuff, as well as argillite and chert, and it includes the dioritic Ironside Mountain batholith that intruded during Middle Jurassic time (about 170 Ma). This intrusive body provides the principal constraint on the age of the terrane. The Rattlesnake Creek terrane is a melange consisting mostly of highly dismembered ophiolite. It includes slabs of serpentinized ultramafic rock, basaltic volcanic rocks, radiolarian chert of Triassic and Jurassic ages, limestone containing

  5. 137Cs, 239+24Pu and 24Pu/239Pu atom ratios in the surface waters of the western North Pacific Ocean, eastern Indian Ocean and their adjacent seas

    International Nuclear Information System (INIS)

    Yamada, Masatoshi; Zheng Jian; Wang Zhongliang


    Surface seawater samples were collected along the track of the R/V Hakuho-Maru cruise (KH-96-5) from Tokyo to the Southern Ocean. The 137 Cs activities were determined for the surface waters in the western North Pacific Ocean, the Sulu and Indonesian Seas, the eastern Indian Ocean, the Bay of Bengal, the Andaman Sea, and the South China Sea. The 137 Cs activities showed a wide variation with values ranging from 1.1 Bq m -3 in the Antarctic Circumpolar Region of the Southern Ocean to 3 Bq m -3 in the western North Pacific Ocean and the South China Sea. The latitudinal distributions of 137 Cs activity were not reflective of that of the integrated deposition density of atmospheric global fallout. The removal rates of 137 Cs from the surface waters were roughly estimated from the two data sets of Miyake et al. [Miyake Y, Saruhashi K, Sugimura Y, Kanazawa T, Hirose K. Contents of 137 Cs, plutonium and americium isotopes in the Southern Ocean waters. Pap Meteorol Geophys 1988;39:95-113] and this study to be 0.016 yr -1 in the Sulu and Indonesian Seas, 0.033 yr -1 in the Bay of Bengal and Andaman Sea, and 0.029 yr -1 in the South China Sea. These values were much lower than that in the coastal surface water of the western Northwest Pacific Ocean. This was likely due to less horizontal and vertical mixing of water masses and less scavenging. 239+24 Pu activities and 24 Pu/ 239 Pu atom ratios were also determined for the surface waters in the western North Pacific Ocean, the Sulu and Indonesian Seas and the South China Sea. The 24 Pu / 239 Pu atom ratios ranged from 0.199 ± 0.026 to 0.248 ± 0.027 on average, and were significantly higher than the global stratospheric fallout ratio of 0.18. The contributions of the North Pacific Proving Grounds close-in fallout Pu were estimated to be 20% for the western North Pacific Ocean, 39% for the Sulu and Indonesian Seas and 42% for the South China Sea by using the two end-member mixing model. The higher 24 Pu / 239 Pu atom ratios

  6. Strategi Najib Razak Dalam Upaya Pemenangan Pemilihan Raya Malaysia 2013


    Pakpahan, Saiman; Permadi, Arya Luthfi


    This research is aimed to see how Najib Razak uses his foreign policy attacking Sabah as his winning strategy on Malaysia Election €œPemilihan Raya€ in 2013. Najib Razak and his party, UMNO (United Malay National Organization) is not in good condition where it has lost many votes in 2008 election. Toward this situation, Najib Razak also faced Sulu€™s Attack that is commited by MNLF.This research uses pluralism perspective and idiosincratic theory where stuffs related to personal life of the ...

  7. Hydrogeochemical and stream sediment sampling for uranium in the sandstone environment

    International Nuclear Information System (INIS)

    Wenrich, K.J.


    Sandstone terranes commonly host uranium occurrences in the western United States. In addition, because sedimentary terranes, particularly shales and immature, not well cemented sandstone, contribute more sediment and soluble material than do plutonic, volcanic, or metamorphic terranes they are an excellent regime for hydrogeochemical and stream-sediment prospecting. Because of higher conductivity, and hence higher uranium content, of waters draining such environments the sampling need not be as precise nor the analytical detection limit as low as in other terranes to yield a successful survey. Nevertheless, reasonable preparation and care of the samples is recommended: (1) The water samples should be filtered through 0.45 μm membranes and acidified to a pH of less than 1. (2) Because the adsorption of uranium by organic material is so significant it is recommended that the reasonable finest stream-sediment fraction, 4 , conductivity, etc.) are useful in the data reduction towards the elimination of false anomalies. (author)

  8. Into the Abyss: The Case of the Collapsing Sinkhole. (United States)

    Ozsvath, David L.


    Presents a case study to teach about the relationship between sinkhole development and groundwater levels in Orlando, Florida. Discusses the relationship between groundwater levels and sinkhole formation in a karst terrane. Includes discussion questions. (YDS)

  9. The Rhyacian El Cortijo suture zone: Aeromagnetic signature and insights for the geodynamic evolution of the southwestern Rio de la Plata craton, Argentina

    Directory of Open Access Journals (Sweden)

    Carlos J. Chernicoff


    We envisage the pre-Neoproterozoic evolution of the Tandilia belt to have been initiated by the extension of Neoarchean (∼2650 Ma crust occurred during Siderian times (2500–2300 Ma, causing the separation between the Balcarce, Tandilia and Buenos Aires terranes, and the development of narrow oceans at both north and south sides of the Tandilia terrane, accompanied by ∼2300–2200 Ma sedimentation over transitional –continental to oceanic– crust, and arc magmatism developed in the Tandilia terrane. The island arc represented by the El Cortijo Formation was also developed at this time. At late Rhyacian times, it occurred in both the closure of the narrow oceans developed previously, the entrapment of the El Cortijo island arc, as well as anatectic magmatism in the Balcarce terrane.

  10. Reconnaissance geologic map of the Dubakella Mountain 15 quadrangle, Trinity, Shasta, and Tehama Counties, California (United States)

    Irwin, William P.; Yule, J. Douglas; Court, Bradford L.; Snoke, Arthur W.; Stern, Laura A.; Copeland, William B.


    The Dubakella Mountain 15' quadrangle is located just south of the Hayfork quadrangle and just east of the Pickett Peak quadrangle. It spans a sequence of four northwest-trending tectonostratigraphic terranes of the Klamath Mountains geologic province that includes, from east to west, the Eastern Hayfork, Western Hayfork, Rattlesnake Creek, and Western Jurassic terranes, as well as, in the southwest corner of the quadrangle, part of a fifth terrane, the Pickett Peak terrane of the Coast Ranges geologic province. The Eastern Hayfork terrane is a broken formation and melange of volcanic and sedimentary rocks that include blocks of limestone and chert. The limestone contains late Permian microfossils of Tethyan faunal affinity. The chert contains radiolarians of Mesozoic age, mostly Triassic, but none clearly Jurassic. The Western Hayfork terrane is an andesitic volcanic arc that consists mainly of agglomerate, tuff, argillite, and chert, and includes the Wildwood pluton. That pluton is related to the Middle Jurassic (about 170 Ma) Ironside Mountain batholith that is widely exposed farther north beyond the Dubakella Mountain quadrangle. The Rattlesnake Creek terrane is a highly disrupted ophiolitic melange of probable Late Triassic or Early Jurassic age. Although mainly ophiolitic, the melange includes blocks of plutonic rocks (about 200 Ma) of uncertain genetic relation. Some scattered areas of well-bedded mildly slaty detrital rocks of the melange appear similar to Galice Formation (unit Jg) and may be inliers of the nearby Western Jurassic terrane. The Western Jurassic terrane consists mainly of slaty to phyllitic argillite, graywacke, and stretched-pebble conglomerate and is correlative with the Late Jurassic Galice Formation of southwestern Oregon. The Pickett Peak terrane, the most westerly of the succession of terranes of the Dubakella Mountain quadrangle, is mostly fine-grained schist that includes the blueschist facies mineral lawsonite and is of Early

  11. The Alto Moxoto Terrain in Eastern Paraiba ('Caldas Brandao Massif')

    International Nuclear Information System (INIS)

    Neves, Benjamim Bley de Brito; Campos Neto, Mario da Costa; Souza, Solange Lucena de; Schmus, William Randall Van; Fernandes, Tania Maria Gomes


    The Alto Moxoto Terrane (TAM), at the east of Paraiba State is mostly composed of sheared ortho gneisses, porphyritic granodioritic gneisses and it bears an imbricated sheet of Al-rich (garnet-biotite-sillimanite) gneisses, deeply affected by migmatization phenomena. This litho-structural assemblage is drawing a regional asymmetric anti formal structure, with its axial zone running parallel to the B R-230 highway (E-W trending). It is limited in both, north (Alto Pajeu terrane) and south (Rio Capibaribe terrane) sides by important shear zones, which are feather faults connected with the development of the Pernambuco lineament, to the southwest. The adopted designation of 'terrane' is based upon its singular geological features, in terms of lithological and structural characteristics, Paleoproterozoic in age and sharp limits with the different confining terranes. TAM is here considered as a mega-fragment of the Atlantica Super continent, that was built up by the Paleoproterozoic Collage ('Transamazonian') and that was preserved in the framework of West Gondwana (Brasiliano/Pan African Collage) as a 'terrane'. This terrane shows conspicuous continuity to the far interior of the province, to the southwestern part of Pernambuco State, and so doing, it demonstrates that the former designation of 'Caldas Brandao Massif must be ruled out, as obsolete for many reasons. Geochronological determinations using Rb-Sr, Sm-Nd and U-Pb methods confirm the Paleoproterozoic age of this terrane, with the presence of some Archean protoliths as well as the various degrees of structural reworking and isotopic reseting promoted by the Brasiliano Cycle. This cycle was responsible for some intrusive granites, for most of the general geological features, like usual informal limits and even the present shape of the TAM, a typical reworked 'basement inlier'. (author)

  12. Detrital Zircons Split Sibumasu in East Gondwana (United States)

    Zhang, X.; Chung, S. L.


    It is widely accepted that Sibumasu developed as a united terrane and originated from NW Australian margin in East Gondwana. Here we report new detrital zircon U-Pb-Hf isotopic data from Sumatra that, in combination with literature data, challenge and refute the above long-held view. In particular, the East and West Sumatra terranes share nearly identical Precambrian to Paleozoic detrital zircon age distributions and Hf isotopes, indicating a common provenance/origin for them. The Sumatra detrital zircons exhibit a prominent population of ca. 1170-1070 Ma, indistinguishable from those of the Lhasa and West Burma terranes, with detritus most probably sourcing from western Australia. By contrast, Sibuma (Sibumasu excluding Sumatra) detrital zircons display a prevailing population of ca. 980-935 Ma, strongly resembling those of the western Qiangtang terrane, with detrital materials most likely derived from Greater India and Himalayas. Such markedly distinct detrital zircon age profiles between Sumatra and Sibuma require disparate sources/origin for them, provoking disintegration of the widely-adopted, but outdated, term Sibumasu and thus inviting a new configuration of East Gondwana in the early Paleozoic, with Sumatra and West Burma lying outboard the Lhasa terrane in the NW Australian margin and Sibuma situated in the northern Greater Indian margin. More future investigations are needed to establish the precise rifting and drifting histories of Sumatra and Sibuma, as two separated terranes, during the breakup of Gondwana.

  13. Lithosphere evolution during the pre devonian of Uruguay: Prevalence of strike slip faults

    International Nuclear Information System (INIS)

    Bossi, J.


    The available data about mega shear zones were analyzed. Also the geo chronological trusty data about pre devonian rocks from Uruguay were overlapped. Emphasizing in the basic rocks, four tecto no-stratigraphy c terranes might be recognized. The approximate age of those rocks is known as well as the displacement trend. It can be concluded that the transmazonian age Piedra Alta Terrane (transmazonian age 2000 ± 100 My) is the most ancient block followed by the Tandilla Terrane (ages 2200 ± 100 My) which was joined through 1700 Ma. The Nico Perez Terrane displaced itself towards South generating the continental N10W mega shear fault Sarandi del Yi- Piriapolis towards 1250 My. Finally, the Arachania called continent made tangential collision from SE towards 525 Ma generating the ultramylonites band of the Sierra Ballena share zone. Each one of these terranes have totally different stratigraphy and lithological associations, and the chronological ages did not agree with the arrival of each one of the identified terranes

  14. Geologic map of the Strawberry Butte 7.5’ quadrangle, Meagher County, Montana (United States)

    Reynolds, Mitchell W.; Brandt, Theodore R.


    The 7.5′ Strawberry Butte quadrangle in Meagher County, Montana near the southwest margin of the Little Belt Mountains, encompasses two sharply different geologic terranes.  The northern three-quarters of the quadrangle are underlain mainly by Paleoproterozoic granite gneiss, across which Middle Cambrian sedimentary rocks rest unconformably.  An ancestral valley of probable late Eocene age, eroded northwest across the granite gneiss terrane, is filled with Oligocene basalt and overlying Miocene and Oligocene sandstone, siltstone, tuffaceous siltstone, and conglomerate.  The southern quarter of the quadrangle is underlain principally by deformed Mesoproterozoic sedimentary rocks of the Newland Formation, which are intruded by Eocene biotite hornblende dacite dikes.  In this southern terrane, Tertiary strata are exposed only in a limited area near the southeast margin of the quadrangle.  The distinct terranes are juxtaposed along the Volcano Valley fault zone—a zone of recurrent crustal movement beginning possibly in Mesoproterozoic time and certainly established from Neoproterozoic–Early Cambrian to late Tertiary time.  Movement along the fault zone has included normal faulting, the southern terrane faulted down relative to the northern terrane, some reverse faulting as the southern terrane later moved up against the northern terrane, and lateral movement during which the southern terrane likely moved west relative to the northern terrane.  Near the eastern margin of the quadrangle, the Newland Formation is locally the host of stratabound sulfide mineralization adjacent to the fault zone; west along the fault zone across the remainder of the quadrangle are significant areas and bands of hematite and iron-silicate mineral concentrations related to apparent alteration of iron sulfides.  The map defines the distribution of a variety of surficial deposits, including the distribution of hematite-rich colluvium and iron-silicate boulders.  The southeast

  15. Genetic stock compositions and natal origin of green turtle (Chelonia mydas foraging at Brunei Bay

    Directory of Open Access Journals (Sweden)

    Juanita Joseph


    Full Text Available Knowledge of genetics composition and growth stages of endangered green turtles, as well as the connectivity between nesting and foraging grounds is important for effective conservation. A total of 42 green turtles were captured at Brunei Bay with curved carapace length ranging from 43.8 to 102.0 cm, and most sampled individuals were adults and large juveniles. Twelve haplotypes were revealed in mitochondrial DNA control region sequences. Most haplotypes contained identical sequences to haplotypes previously found in rookeries in the Western Pacific, Southeast Asia, and the Indian Ocean. Haplotype and nucleotide diversity indices of the Brunei Bay were 0.8444±0.0390 and 0.009350±0.004964, respectively. Mixed-stock analysis (for both uninformative and informative prior weighting by population size estimated the main contribution from the Southeast Asian rookeries of the Sulu Sea (mean ≥45.31%, Peninsular Malaysia (mean ≥17.42%, and Sarawak (mean ≥12.46%. Particularly, contribution from the Sulu Sea rookery was estimated to be the highest and lower confidence intervals were more than zero (≥24.36%. When estimating contributions by region rather than individual rookeries, results showed that Brunei Bay was sourced mainly from the Southeast Asian rookeries. The results suggest an ontogenetic shift in foraging grounds and provide conservation implications for Southeast Asian green turtles.

  16. Geometries of geoelectrical structures in central Tibetan Plateau from INDEPTH magnetotelluric data (United States)

    Vozar, Jan; Jones, Alan G.; Le Pape, Florian


    Magnetotelluric (MT) data collected on N-S profiles crossing the Banggong-Nujiang Suture, which separates the Qiangtang and Lhasa Terranes in central Tibet, as a part of InterNational DEep Profiling of Tibet and the Himalaya project (INDEPTH) are modeled by 2D and 3D inversion codes. The 2D deep MT model of line 500 confirms previous observations concluding that the region is characterized to first-order by a resistive upper crust and a conductive, partially melted, middle to lower crust that extends from the Lhasa Terrane to the Qiangtang Terrane with varying depth. The same conductive structure setting, but in shallower depths is also present on the eastern 400 line. From deep electromagnetic sounding, supported by independent 1D integrated petro-physical investigation, we can estimate the next upper-mantle conductive layer at depths from 200 km to 250 km below the Lhasa Terrane and less resistive Tibetan lithosphere below the Qiangtang Terrane with conductive upper-mantle in depths about 120 km. The anisotropic 2D modeling reveals lower crustal anisotropy in Lhasa Terrane, which can interpreted as crustal channel flow. The 3D inversion models of all MT data from central Tibet show dominant 2D regional strike of mid and lower crustal structures equal N110E. This orientation is parallel to Shuanghu suture, BengCo Jiali strike-slip fault system and perpendicular to convergence direction. The lower crust conductor in central Lhasa Terrane can be interpreted more likely as 3D lower Indian crust structure, located to the east from line 500, than geoelectrical anisotropic crustal flow.

  17. Metamorphic Perspectives of Subduction Zone Volatiles Cycling (United States)

    Bebout, G. E.


    Field study of HP/UHP metamorphic rocks provides "ground-truthing" for experimental and theoretical petrologic studies estimating extents of deep volatiles subduction, and provides information regarding devolatilization and deep subduction-zone fluid flow that can be used to reconcile estimates of subduction inputs and arc volcanic outputs for volatiles such as H2O, N, and C. Considerable attention has been paid to H2O subduction in various bulk compositions, and, based on calculated phase assemblages, it is thought that a large fraction of the initially structurally bound H2O is subducted to, and beyond, subarc regions in most modern subduction zones (Hacker, 2008, G-cubed). Field studies of HP/UHP mafic and sedimentary rocks demonstrate the impressive retention of volatiles (and fluid-mobile elements) to depths approaching those beneath arcs. At the slab-mantle interface, high-variance lithologies containing hydrous phases such as mica, amphibole, talc, and chlorite could further stabilize H2O to great depth. Trench hydration in sub-crustal parts of oceanic lithosphere could profoundly increase subduction inputs of particularly H2O, and massive flux of H2O-rich fluids from these regions into the slab-mantle interface could lead to extensive metasomatism. Consideration of sedimentary N concentrations and δ15N at ODP Site 1039 (Li and Bebout, 2005, JGR), together with estimates of the N concentration of subducting altered oceanic crust (AOC), indicates that ~42% of the N subducting beneath Nicaragua is returned in the corresponding volcanic arc (Elkins et al., 2006, GCA). Study of N in HP/UHP sedimentary and basaltic rocks indicates that much of the N initially subducted in these lithologies would be retained to depths approaching 100 km and thus available for addition to arcs. The more altered upper part of subducting oceanic crust most likely to contribute to arcs has sediment-like δ15NAir (0 to +10 per mil; Li et al., 2007, GCA), and study of HP/UHP eclogites

  18. Magnitude of long-term non-lithostatic pressure variations in lithospheric processes: insight from thermo-mechanical subduction/collision models (United States)

    Gerya, Taras


    On the one hand, the principle of lithostatic pressure is habitually used in metamorphic geology to calculate paleo-depths of metamorphism from mineralogical pressure estimates given by geobarometry. On the other hand, it is obvious that this lithostatic (hydrostatic) pressure principle should only be valid for an ideal case of negligible deviatoric stresses during the long-term development of the entire tectono-metamorphic system - the situation, which newer comes to existence in natural lithospheric processes. The question is therefore not "Do non-lithostatic pressure variations exist?" but " What is the magnitude of long-term non-lithostatic pressure variations in various lithospheric processes, which can be recorded by mineral equilibria of respective metamorphic rocks?". The later question is, in particular, relevant for various types of high-pressure (HP) and ultrahigh-pressure (UHP) rocks, which are often produced in convergent plate boundary settings (e.g., Hacker and Gerya, 2013). This question, can, in particular, be answered with the use of thermo-mechanical models of subduction/collision processes employing realistic P-T-stress-dependent visco-elasto-brittle/plastic rheology of rocks. These models suggest that magnitudes of pressure deviations from lithostatic values can range >50% underpressure to >100% overpressure, mainly in the regions of bending of rheologically strong mantle lithosphere (Burg and Gerya, 2005; Li et al., 2010). In particular, strong undepresures along normal faults forming within outer rise regions of subducting plates can be responsible for downward water suction and deep hydration of oceanic slabs (Faccenda et al., 2009). Weaker HP and UHP rocks of subduction/collision channels are typically subjected to lesser non-lithostatic pressure variations with characteristic magnitudes ranging within 10-20% from the lithostatic values (Burg and Gerya, 2005; Li et al., 2010). The strength of subducted crustal rocks and the degree of

  19. Timing of metamorphism and exhumation in the Nordøyane ultra-high-pressure domain, Western Gneiss Region, Norway: New constraints from complementary CA-ID-TIMS and LA-MC-ICP-MS geochronology (United States)

    Butler, J. P.; Jamieson, R. A.; Dunning, G. R.; Pecha, M. E.; Robinson, P.; Steenkamp, H. M.


    We present the results of a combined CA-ID-TIMS and LA-MC-ICP-MS U-Pb geochronology study of zircon and associated rutile and titanite from the Nordøyane ultra-high-pressure (UHP) domain in the Western Gneiss Region (WGR) of Norway. The dated samples include 4 eclogite bodies, 2 host-rock migmatites, and 2 cross-cutting pegmatites and leucosomes, all from the island of Harøya. Zircon from a coesite eclogite yielded an age of ca. 413 Ma, interpreted as the time of UHP metamorphism in this sample. Zircon data from the other eclogite bodies yielded metamorphic ages of ca. 413 Ma, 407 Ma, and 406 Ma; zircon trace-element data associated with 413 Ma and 407 Ma ages are consistent with eclogite-facies crystallization. In all of the eclogites, U-Pb dates from zircon cores, interpreted as the times of protolith crystallization, range from ca. 1680-1586 Ma, consistent with Gothian ages from orthogneisses in Nordøyane and elsewhere in the WGR. A zircon core age of ca. 943 Ma from one sample agrees with Sveconorwegian ages of felsic gneisses and pegmatites in the western part of the area. Migmatites hosting the eclogite bodies yielded zircon core ages of ca. 1657-1591 Ma and rim ages of ca. 395-392 Ma, interpreted as the times of Gothian protolith formation and Scandian partial melt crystallization, respectively. Pegmatite in an eclogite boudin neck yielded a crystallization age of ca. 388 Ma, interpreted as the time of melt crystallization. Rutile and titanite from 3 samples (an eclogite and two migmatites) yielded concordant ID-TIMS ages of 378-376 Ma. The results are similar to existing U-Pb data from other Nordøyane eclogites (415-405 Ma). In combination with previous pressure-temperature data from the coesite eclogite, these ages indicate that peak metamorphic conditions of 3 GPa/760 °C were reached ca. 413 Ma, followed by decompression to 1 GPa/810 °C by ca. 397 Ma and cooling below ca. 600 °C by ca. 375 Ma. The results are compatible with protracted UHP

  20. Strontium and oxygen isotopic variations in mesozoic and tertiary plutons of central Idaho

    International Nuclear Information System (INIS)

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


    Regional variations in initial 87 Sr/ 86 Sr ratios (rsub(i)) of Mesozoic plutons in central Idaho locate the edge of Precambrian continental crust at the boundary between the late Paleozoic-Mesozoic accreted terranes and Precambrian sialic crust in western Idaho. The rsub(i) values increase abruptly but continuously from less than 0.704 in the accreted terranes to greater than 0.708 across a narrow, 5 to 15 km zone, characterized by elongate, lens-shaped, highly deformed plutons and schistose metasedimentary and metavolcanic units. The chemical and petrologic character of the plutons changes concomitantly from ocean-arc-type units to a weakly peraluminous, calcit to calcalkalic suite. Plutons in both suites yield Late Cretaceous ages, but Permian through Early Cretaceous bodies are confined to the accreted terranes and early Tertiary intrusions are restricted to areas underlain by Precambrian crust. The two major terranes were juxtaposed between 75 and 130 m.y. ago, probably between 80 and 95 m.y. Oxygen and strontium isotopic ratios and Rb and Sr concentrations of the plutonic rocks document a significant upper-crustal contribution to the magmas that intrude Precambrian crust. Magmas intruding the arc terranes were derived from the upper mantle/subducted oceanic lithosphere and may have been modified by anatexis of earlier island-arc volcanic and sedimentary units. (orig./PW)

  1. Tectonics of the Philippines and ambient regions from geophysical inversions (United States)

    Liu, W.; Li, C.; Zhou, Z.; Fairhead, J. D.


    The geological study in the Philippines and ambient regions is relatively low so far for the rather scanty data and complex geological structure. Therefore it is a challenge to do the research with limited data. In this paper, an investigation of the Philippines and surrounding area has been carried out using regional magnetic and gravity anomalies. Owing to the difficulties and limitations in reduction to the pole at the low latitudes, analytical signal amplitudes of magnetic anomalies are calculated as the equivalent substitute. Application of the Parker-Oldenburg algorithm to Bouguer gravity anomalies yields a 3D Moho topography. Curie-point depths are estimated from the magnetic anomalies using a windowed wavenumber-domain algorithm. This paper aims to reveal the structure of the Manila subduction zone accurately, and moreover, to clarify the interplay between the magmatism and subduction in the Manila Trench and East Luzon Trough. On the basis of Bouguer gravity anomaly and AS(analytical signal) of magnetic anomaly, the positions of hydrated mantle wedge in the subduction zones of this area are identified in the areas charicterizd by the distribution of high-and low value of Bouguer gravity anomaly or the paralell high value of Bouguer gravity anomaly and AS. Using our inversion results together with some other published information, the boundaries of Palawan Block, Philippine Mobile Belt and Sulu-Celebes Block are defined and the collision history of PCB(Palawan continental block)-PMB (Philippine mobile belt) and PCB-Sulu Sea is also discussed. A "seismic gap" near the 14 degree north latitude on Manila Trench, mentioned in previous studies, is thought to be induced by the slab melting and plastic behavior due to the relatively high geothermal gradient. In the central Philippines, it is likely that an incipient collision-related rifting is proceeding. Furthermore, a possible new evolution model of Sulu Sea, in which the Cagayan Ridge area is thought to be the

  2. Lithostratigraphy, sedimentology and paleography from The Arroyo del Soldado group

    International Nuclear Information System (INIS)

    Gaucher, C.; Sprechmann, P.; Montana, J.; Martinez, S.


    The lithostratigraphy of the Vendian to Lower Cambrian Arroyo del Soldado Group of the Nico Perez Terrane is presented. The Yerbal Formation is defined and the Barriga Negra Formation is included in the Group. The Arroyo del Soldado Group represents a transgressive - regressive sequence developed on a passive continental margin, reaching a thickness of 5000m. The lithofacies succession is mainly explained by the combination of tectonic processes, global climatic - and sea level changes. Its geographic extension allows the determination of the eastern and southern boundaries of the Nico Perez Terrane. The known surface of this Terrane is therefore considerably increased. Several outcroups previously assigned to the Lavalleja Group are in this paper included in the Arroyo del Soldado Group, using sedimentalogical and paleontological criteria

  3. Western cratonic domains in Uruguay: geochronology

    International Nuclear Information System (INIS)

    Preciozzi, F.; Peel, E.; Muzio, E.; Ledesma, R.; Guerequiz, R.


    The western cratonic domains in Uruguay are divided into three major units: Piedra Alta Terrane, Valentines Block and Pavas Block. Piedra Alta Terrane lacks of evidence of Neoproterozoic orogenesis (deformation, metamorphism or magmatism). Sarandí del Yi - Arroyo Solís Grande shear zone, separates it from Valentines Block. Valentines Block is separated from Pavas Block by Cueva del Tigre shear zone. Magmatic rocks with different ages, compositions and emplacements occur all over the Piedra Alta Terrane distributed in three metamorphic belts (Arroyo Grande, San José and Montevideo) as well as in the Central Gneissic-Migmatitic Complex (Figure 1). Samples from the Gneissic-Migmatitic complex, late tectonic granitoids and basic rocks associated to the metamorphic belts were analyzed using Rb/Sr, U/Pb, K/Ar and Sm/Nd methodologies. The age ranges obtained for granitoids

  4. (U-Th)/He thermochronometric constraints on the late Miocene-Pliocene northern Cordillera Real, tectonic development of the northern Cordillera Real, tectonic development of the Interandean Depression, the Spikings, Ecuador. (United States)

    Spikings, R. A.; Crowhurst, P. V.


    The low sensitivity of apatite fission track (AFT) thermochronometry at temperatures less than ˜60 °C suggests that AFT data sets from the Andean Cordilleras may have frequently failed to identify specific periods after 9 Ma when cooling rates were high. Forward modeling of (U-Th)/He apatite age data obtained from the juxtaposed Paleozoic-Mesozoic Alao, Loja, and Salado terranes in the northern Cordillera Real, Ecuador, has improved the resolution of previous AFT thermal histories for the past 9 My. The Alao and Loja terranes form a coherent, structural block that resided at temperatures greater than 70-80 °C until ˜3.3-2.8 Ma and then cooled rapidly to less than 40 °C at rates of >15 °C/My. Intraterrane variations in the cooling and exhumation histories in the Salado terrane suggest that nonterrane-bounding faults played a significant role during its Pliocene-Recent evolution. The Salado terrane preserves an older history that reveals elevated cooling rates during 22-19 and 18-15 Ma. Subsequently, the terrane cooled rapidly from greater than 90 °C to less than 40 °C during 11-8 and 5.5-3.5 Ma at rates of >8 °C/My. Vertical reactivation of the Llanganates fault, which separates the Salado and Loja terranes, during the Pliocene-Recent coincides with the main stages of formation of the juxtaposed Interandean Depression, which provides further constraints on the growth phases of the depression and the Cordillera.

  5. Geological evolution of the Neoproterozoic Bemarivo Belt, northern Madagascar (United States)

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


    The broadly east-west trending, Late Neoproterozoic Bemarivo Belt in northern Madagascar has been re-surveyed at 1:100 000 scale as part of a large multi-disciplinary World Bank-sponsored project. The work included acquisition of 14 U-Pb zircon dates and whole-rock major and trace element geochemical data of representative rocks. The belt has previously been modelled as a juvenile Neoproterozoic arc and our findings broadly support that model. The integrated datasets indicate that the Bemarivo Belt is separated by a major ductile shear zone into northern and southern "terranes", each with different lithostratigraphy and ages. However, both formed as Neoproterozoic arc/marginal basin assemblages that were translated southwards over the north-south trending domains of "cratonic" Madagascar, during the main collisional phase of the East African Orogeny at ca. 540 Ma. The older, southern terrane consists of a sequence of high-grade paragneisses (Sahantaha Group), which were derived from a Palaeoproterozoic source and formed a marginal sequence to the Archaean cratons to the south. These rocks are intruded by an extensive suite of arc-generated metamorphosed plutonic rocks, known as the Antsirabe Nord Suite. Four samples from this suite yielded U-Pb SHRIMP ages at ca. 750 Ma. The northern terrane consists of three groups of metamorphosed supracrustal rocks, including a possible Archaean sequence (Betsiaka Group: maximum depositional age approximately 2477 Ma) and two volcano-sedimentary sequences (high-grade Milanoa Group: maximum depositional age approximately 750 Ma; low grade Daraina Group: extrusive age = 720-740 Ma). These supracrustal rocks are intruded by another suite of arc-generated metamorphosed plutonic rocks, known as the Manambato Suite, 4 samples of which gave U-Pb SHRIMP ages between 705 and 718 Ma. Whole-rock geochemical data confirm the calc-alkaline, arc-related nature of the plutonic rocks. The volcanic rocks of the Daraina and Milanoa groups also

  6. Piedmont seismic reflection study: A program integrated with tectonics to probe the cause of eastern seismicity

    Energy Technology Data Exchange (ETDEWEB)

    Glover, L. III; Coruh, C.; Costain, J.K.; Bollinger, G.A. (Virginia Polytechnic Inst. and State Univ., Blacksburg, VA (United States). Dept. of Geological Sciences)


    A new tectonic model of the Appalachian orogen indicates that one, not two or more, terrane boundaries is present in the Piedmont and Blue Ridge of the central and southern Appalachians. This terrane boundary is the Taconic suture, it has been transported in the allochthonous Blue Ridge/Piedmont crystalline thrust nappe, and it is repeated at the surface by faulting and folding associated with later Paleozoic orogenies. The suture passes through the lower crust and lithosphere somewhere east of Richmond. It is spatially associated with seismicity in the central Virginia seismic zone, but is not conformable with earthquake focal planes and appears to have little causal relation to their localization.

  7. Structural analysis south of the malakand and adjoining areas, northern pakistan

    International Nuclear Information System (INIS)

    Ahmad, I.; Jehan, N.


    Two major faults the Kishora thrust and a back thrust. dominate the structure of the study area. The Kishora thrust divide the study area into two tectonic terranes, the Indus melanges including Dargai ultramafic complex, and the Indian shelf terrane, whereas the back thrust brings higher grade almandine zone rocks in contact with low grade chlorite zone rocks near Bar Bazdara and Zormandai village. An important aspect of this study is the relationship of the structures of Swat with the Peshawar basin. The structures and stratigraphy in Swat extends into the Peshawar basin. (author)

  8. Permian Tethyan Fusulinina from the Kenai Peninsula, Alaska (United States)

    Stevens, C.H.; Davydov, V.I.; Bradley, D.


    Two samples from a large, allochthonous limestone block in the McHugh Complex of the Chugach terrane on the Kenai Peninsula, Alaska, contain species of 12 genera of Permian Fusulinina including Abadehella, Kahlerina, Pseudokahlerina?, Nankinella, Codonofusiella, Dunbarula, Parafusulina?, Chusenella, Verbeekina, Pseudodoliolina, Metadoliolina?, Sumatrina?, and Yabeina, as well as several other foraminiferans and one alga. The assemblage of fusulinids is characteristically Tethyan, belonging to the Yabeina archaica zone of early Midian (late Wordian) age. Similar faunas are known from the Pamirs, Transcaucasia, and Japan, as well as from allochthonous terranes in British Columbia, northwestern Washington, and Koryakia in eastern Siberia.

  9. Dynamics of mineral crystallization from precipitated slab-derived fluid phase: first in situ synchrotron X-ray measurements (United States)

    Malaspina, Nadia; Alvaro, Matteo; Campione, Marcello; Wilhelm, Heribert; Nestola, Fabrizio


    Remnants of the fluid phase at ultrahigh pressure (UHP) in subduction environments may be preserved as primary multiphase inclusions in UHP minerals. The mode of crystallization of daughter minerals during precipitation within the inclusion and/or the mechanism of interaction between the fluid at supercritical conditions and the host mineral are still poorly understood from a crystallographic point of view. A case study is represented by garnet-orthopyroxenites from the Maowu Ultramafic Complex (China) deriving from harzburgite precursors metasomatized at ~4 GPa, 750 °C by a silica- and incompatible trace element-rich fluid phase. This metasomatism produced poikilitic orthopyroxene and inclusion-rich garnet porphyroblasts. Solid multiphase primary inclusions in garnet display a size within a few tens of micrometres and negative crystal shapes. Infilling minerals (spinel: 10-20 vol%; amphibole, chlorite, talc, mica: 80-90 vol%) occur with constant volume proportions and derive from trapped solute-rich aqueous fluids. To constrain the possible mode of precipitation of daughter minerals, we performed for the first time a single-crystal X-ray diffraction experiment by synchrotron radiation at Diamond Light Source. In combination with electron probe microanalyses, this measurement allowed the unique identification of each mineral phase and reciprocal orientations. We demonstrated the epitaxial relationship between spinel and garnet and between some hydrous minerals. Such information is discussed in relation to the physico-chemical aspects of nucleation and growth, shedding light on the mode of mineral crystallization from a fluid phase trapped at supercritical conditions.

  10. Dispositivo Robótico Multifuncional para la Rehabilitación de las Extremidades Superiores

    Directory of Open Access Journals (Sweden)

    Aitziber Mancisidor


    Full Text Available En este trabajo se presenta un dispositivo de rehabilitación innovador por su flexibilidad y eficiencia denominado Universal Haptic Pantograph (UHP. Este robot, gracias a su estructura multi-configurable permite la rehabilitación del miembro superior con un único dispositivo. Además, se ha diseñado con la habilidad de realizar diferentes tareas asistivas y resistivas, pudiendo así adaptarse al estado de recuperación del paciente. Finalmente, el software Telereha genera un entorno de realidad virtual que facilita la ejecución del ejercicio y aumenta la motivación del paciente. El sistema de control del robot se ha implementado entiempo real con el fin de garantizar la correcta ejecución de las tareas de rehabilitación. Usando este sistema, se han realizado diferentes ensayos experimentales.  Los resultados demuestran que el robot de rehabilitación UHP funciona  correctamente  con diferentes tareas de rehabilitación, realizando movimientos suaves y seguros que garantizan la seguridad del usuario.

  11. Virtual Sensors for Advanced Controllers in Rehabilitation Robotics. (United States)

    Mancisidor, Aitziber; Zubizarreta, Asier; Cabanes, Itziar; Portillo, Eva; Jung, Je Hyung


    In order to properly control rehabilitation robotic devices, the measurement of interaction force and motion between patient and robot is an essential part. Usually, however, this is a complex task that requires the use of accurate sensors which increase the cost and the complexity of the robotic device. In this work, we address the development of virtual sensors that can be used as an alternative of actual force and motion sensors for the Universal Haptic Pantograph (UHP) rehabilitation robot for upper limbs training. These virtual sensors estimate the force and motion at the contact point where the patient interacts with the robot using the mathematical model of the robotic device and measurement through low cost position sensors. To demonstrate the performance of the proposed virtual sensors, they have been implemented in an advanced position/force controller of the UHP rehabilitation robot and experimentally evaluated. The experimental results reveal that the controller based on the virtual sensors has similar performance to the one using direct measurement (less than 0.005 m and 1.5 N difference in mean error). Hence, the developed virtual sensors to estimate interaction force and motion can be adopted to replace actual precise but normally high-priced sensors which are fundamental components for advanced control of rehabilitation robotic devices.

  12. Native oxidation of ultra high purity Cu bulk and thin films

    International Nuclear Information System (INIS)

    Iijima, J.; Lim, J.-W.; Hong, S.-H.; Suzuki, S.; Mimura, K.; Isshiki, M.


    The effect of microstructure and purity on the native oxidation of Cu was studied by using angle-resolved X-ray photoelectron spectroscopy (AR-XPS) and spectroscopic ellipsometry (SE). A high quality copper film prepared by ion beam deposition under a substrate bias voltage of -50 V (IBD Cu film at V s = -50 V) showed an oxidation resistance as high as an ultra high purity copper (UHP Cu) bulk, whereas a Cu film deposited without substrate bias voltage (IBD Cu film at V s = 0 V) showed lower oxidation resistance. The growth of Cu 2 O layer on the UHP Cu bulk and both types of the films obeyed in principle a logarithmic rate law. However, the growth of oxide layer on the IBD Cu films at V s = 0 and -50 V deviated upward from the logarithmic rate law after the exposure time of 320 and 800 h, respectively. The deviation from the logarithmic law is due to the formation of CuO on the Cu 2 O layer after a critical time

  13. Novel PVA-DNA nanoparticles prepared by ultra high pressure technology for gene delivery

    International Nuclear Information System (INIS)

    Kimura, Tsuyoshi; Okuno, Akira; Miyazaki, Kozo; Furuzono, Tsutomu; Ohya, Yuichi; Ouchi, Tatsuro; Mutsuo, Shingo; Yoshizawa, Hidekazu; Kitamura, Yoshiro; Fujisato, Toshiyta; Kishida, Akio


    Polyvinyl alcohol (PVA)-DNA nanoparticles have been developed by ultra high pressure (UHP) technology. Mixture solutions of DNA and PVA having various molecular weights (Mw) and degree of saponifications (DS) were treated under 10,000 atmospheres (981 MPa) condition at 40 deg. C for 10 min. Agarose gel electrophoresis and scanning electron microscope observation revealed that the PVA-DNA nanoparticles with average diameter of about 200 nm were formed. Using PVA of higher Mw and degree of saponifications, the amount of nanoparticles formed increased. The driving force of nanoparticle formation was the hydrogen bonding between DNA and PVA. In order to apply the PVA-DNA nanoparticles for gene delivery, the cytotoxicity and the cellular uptake of them were investigated using Raw264 cell lines. The cell viability was not influenced whether the presence of the PVA-DNA nanoparticles. Further, the nanoparticles internalized into cells were observed by fluorescent microscope. These results indicates that the PVA-DNA nanoparticles prepared by UHP technology showed be useful as drug carrier, especially for gene delivery

  14. Virtual Sensors for Advanced Controllers in Rehabilitation Robotics

    Directory of Open Access Journals (Sweden)

    Aitziber Mancisidor


    Full Text Available In order to properly control rehabilitation robotic devices, the measurement of interaction force and motion between patient and robot is an essential part. Usually, however, this is a complex task that requires the use of accurate sensors which increase the cost and the complexity of the robotic device. In this work, we address the development of virtual sensors that can be used as an alternative of actual force and motion sensors for the Universal Haptic Pantograph (UHP rehabilitation robot for upper limbs training. These virtual sensors estimate the force and motion at the contact point where the patient interacts with the robot using the mathematical model of the robotic device and measurement through low cost position sensors. To demonstrate the performance of the proposed virtual sensors, they have been implemented in an advanced position/force controller of the UHP rehabilitation robot and experimentally evaluated. The experimental results reveal that the controller based on the virtual sensors has similar performance to the one using direct measurement (less than 0.005 m and 1.5 N difference in mean error. Hence, the developed virtual sensors to estimate interaction force and motion can be adopted to replace actual precise but normally high-priced sensors which are fundamental components for advanced control of rehabilitation robotic devices.

  15. Sediment Biogeochemistry After the Entrance of Cable Bacteria

    DEFF Research Database (Denmark)

    Risgaard-Petersen, Nils

    fields which may strongly modify ionic transports. They form pH extremes, and accelerate the dissolution of iron sulfides, and carbonates in subsurface sediment. They further promote the formation of iron oxides and carbonates at the sediment surface and stimulate the removal of sulfides......, sulfide-rich coastal sediments, salt marshes seasonally hypoxic basins, subtidal coastal mud plains, as well as freshwater sediments and waterlogged soils. In this talk I will review our current knowledge on how cable bacteria influence the biogeochemistry of sediments. The cable bacteria form electric...... and the formation of sulfate[3] Field studies conducted in the marine environment indicate that some of these effects are expressed in a way that marine systems with active cable bacteria populations have elevated phosphorus-retention{Sulu-Gambari, 2016 #1501} and acts as strong buffers against adverse stage...

  16. Pamuklu örme kumaşların reaktif boya ile boyanması esnasında tuz ve boyarmadde miktarına bağlı olarak boyama kinetiğinin incelenmesi


    ÖZDEMİR, Agah Oktay; TUTAK, Mustafa


    Yüksek yaş haslıkları, geniş renk paletleri ve çok sayıdaki boyama yöntemine uygunluk gibi avantajları nedeniyle reaktif boyarmaddeler, selülozik esaslı kumaşların boyanmasında önemli bir boyarmadde sınıfını oluşturmaktadırlar. Reaktif boyalar ve pamuk lifleri sulu ortamda çözünerek anyonik karaktere sahip olurlar. Boya ve pamuk lifi arasındaki negatif yükü ortadan kaldırıp boyarmaddelerin lifler tarafından çekilmesini sağlamak için boya banyosuna tuz eklenir. Bu çalışmada ticari olarak kulla...



    KILIÇ, Murat; ÇEPELİOĞULLAR, Özge; KIRBIYIK, Çisem; PÜTÜN, Ayşe Eren; PÜTÜN, Ersan


    Bu çalışmada, kömür uçucu külü sulu çözeltilerden nikel(II) iyonlarının gideriminde düşük maliyetli adsorban olarak değerlendirilmiştir. pH, adsorban miktarı, temas süresi ve başlangıç ağır metal derişimi gibi adsorpsiyon işlemini etkileyen deneysel parametrelerin optimizasyonu gerçekleştirilmiştir. Elde edilen deneysel veriler Langmuir, Freundlich ve Dubinin-Radushkevich (D-R) izotermleri kullanılarak modellenmiştir. Langmuir modelinin adsorpsiyon verilerine daha iyi uyduğu belirlenmiştir. U...

  18. Dipturus amphispinus sp. nov., a new longsnout skate (Rajoidei: Rajidae) from the Philippines. (United States)

    Last, Peter R; Alava, Moonyeen


    A new long-snouted skate, Dipturus amphispinus sp. nov., is formally described based on material caught in the Sulu Sea and later acquired from fish markets of the central and southern Philippines. It differs from its congeners in the western North Pacific, apart from D. wuhanlingi (East and South China Seas), in having a variably-defined, parallel row of posterolaterally directed lumbar thorns, and well-developed scapular thorns on each side of the disc. However, the paired rows of lumbar thorns are better defined in Dipturus amphispinus sp. nov. than in D. wuhanlingi, and these species also differ in some aspects of their morphometrics, meristics and squamation. Dipturus amphispinus sp. nov. displays marked sexual dimorphism with adult males having a relatively broader mouth, much longer teeth, a relatively shorter snout, head and disc, a taller first dorsal fin, and a proportionally longer posterior pelvic-fin lobe and tail, than adult-sized females.

  19. First record of Parelasmopus setiger Chevreux, 1901 from Singapore, including synonymization of Parelasmopus siamensis Wongkamhaeng, Coleman & Pholpunthin, 2013 with Parelasmopus setiger (Crustacea, Amphipoda, Maeridae

    Directory of Open Access Journals (Sweden)

    Azman Abdul Rahim


    Full Text Available Parelasmopus setiger has been widely described from tropical to subtropical regions from Philippine Islands, Sulu Sea, Indonesia, Australia, north Indian Ocean and the Seychelles by several authors. The present study provides detailed descriptions of Parelasmopus setiger Chevreux, 1901 (Crustacea: Amphipoda based on newly collected specimens from Pulau Hantu, Singapore. Morphological characters of the specimens closely resemble those of Parelasmopus setiger and Parelasmopus siamensis Wongkamhaeng, Coleman & Pholpunthin, 2013. The specimens of both the species were quite similar to the Singapore specimens, although the shapes of appendages vary with growth and locality; therefore, P. siamensis is synonymized with P. setiger. The following species characteristics for P. setiger are indicated: 1 antenna 1 peduncle with 2 setae; 2 male gnathopod 2 propodus palm transverse; 3 Pereopods 5 to 7 posterior margins with long slender setae; and 4 dorsal carina pattern for pereonite 7 and pleonites 1 to 3.

  20. Sympatric occurrence and population dynamics of Scylla spp. in equatorial climate: Effects of rainfall, temperature and lunar phase (United States)

    Fazhan, Hanafiah; Waiho, Khor; Darin Azri, Mohammad Farhan; Al-Hafiz, Ismail; Norfaizza, Wan Ibrahim Wan; Megat, Fadhlul Hazmi; Jasmani, Safiah; Ma, Hongyu; Ikhwanuddin, Mhd


    Mud crabs (Scylla spp.) are known to exist sympatrically in the wild. However, information on their population dynamics and the influence of climate parameters and lunar phase, especially along the equatorial region, are limited. Four sampling stations representing three seas (the Strait of Malacca, South China Sea and Sulu Sea) along the equator were selected. Mud crabs were collected using baited traps during spring tides from April 2012 to July 2013. All three Scylla species, S. olivacea, S. tranquebarica and S. paramamosain live in sympatry in the three seas. Scylla olivacea is the most prevalent species in the Strait of Malacca and South China Sea, whereas S. paramamosain dominates the Sulu Sea. The total crab abundance was not affected by rainfall or temperature. The abundance of S. tranquebarica in Strait of Malacca was negatively correlated with temperature and positively correlated with rainfall whereas the abundance of S. paramamosain positively correlated with temperature only at South China Sea. Scylla tranquebarica was the largest in terms of body size and it showed interchanging abundance trends with S. paramamosain. The average body size of S. paramamosain did not differ significantly with that of S. tranquebarica and S. olivacea. This decrease is most likely attributed to overfishing. Significant seasonal fluctuations in mean carapace width were detected in S. tranquebarica and S. paramamosain, but not in S. olivacea. The monthly sex ratio of all three species occasionally fluctuates above the equal sex ratio value. Lunar phase did not affect species abundance, but males and females were significantly heavier during full moon. These findings serve as a baseline of seasonal variation in crab population dynamics that are useful in mud crab fisheries and resource management.

  1. PVC esaslı CTP kesme atığı dolgulu malzemelerin termal özelliklerinin incelenmesi

    Directory of Open Access Journals (Sweden)

    Arzu Özüyağlı


    Full Text Available Bu çalışmada, PVC üretiminde kullanılan CaCO3 dolgu malzemesi yerine, sanayi atığı kullanılması sonucu termal özelliklerdeki değişim araştırılmıştır. Kullanılan sanayi atığı CTP boru üretiminden sulu kesim sırasında çıkmakta ve SiO2, cam elyaf ve polyester reçine içermektedir. Sulu çamur halinde filtre presten çıkan atık fabrikadan alındıktan sonra kurutma ve eleme işlemleri uygulanarak toz formuna getirilmiştir. Numuneler PVC, CTP atık tozu ve prosese yardımcı maddeler mikserde karıştırılarak ekstrüzyon yöntemi ile profil şeklinde üretilmiştir. Atık toz PVC’ye oranla ağırlıkça %5-%70 oranlarında dolgu malzemesi olarak kullanılmıştır. Kalsit (CaCO3 katkılı ve katkısız PVC numuneleri de benzer proses parametreleri kullanılarak üretilmiştir. Üretilen numuneler, seramik krozeler kullanılarak DTA-TG analizleri yapılmıştır.

  2. Oxygenated volatile organic carbon in the western Pacific convective center: ocean cycling, air-sea gas exchange and atmospheric transport (United States)

    Schlundt, Cathleen; Tegtmeier, Susann; Lennartz, Sinikka T.; Bracher, Astrid; Cheah, Wee; Krüger, Kirstin; Quack, Birgit; Marandino, Christa A.


    A suite of oxygenated volatile organic compounds (OVOCs - acetaldehyde, acetone, propanal, butanal and butanone) were measured concurrently in the surface water and atmosphere of the South China Sea and Sulu Sea in November 2011. A strong correlation was observed between all OVOC concentrations in the surface seawater along the entire cruise track, except for acetaldehyde, suggesting similar sources and sinks in the surface ocean. Additionally, several phytoplankton groups, such as haptophytes or pelagophytes, were also correlated to all OVOCs, indicating that phytoplankton may be an important source of marine OVOCs in the South China and Sulu seas. Humic- and protein-like fluorescent dissolved organic matter (FDOM) components seemed to be additional precursors for butanone and acetaldehyde. The measurement-inferred OVOC fluxes generally showed an uptake of atmospheric OVOCs by the ocean for all gases, except for butanal. A few important exceptions were found along the Borneo coast, where OVOC fluxes from the ocean to the atmosphere were inferred. The atmospheric OVOC mixing ratios over the northern coast of Borneo were relatively high compared with literature values, suggesting that this coastal region is a local hotspot for atmospheric OVOCs. The calculated amount of OVOCs entrained into the ocean seemed to be an important source of OVOCs to the surface ocean. When the fluxes were out of the ocean, marine OVOCs were found to be enough to control the locally measured OVOC distribution in the atmosphere. Based on our model calculations, at least 0.4 ppb of marine-derived acetone and butanone can reach the upper troposphere, where they may have an important influence on hydrogen oxide radical formation over the western Pacific Ocean.

  3. The Dependency of Probabilistic Tsunami Hazard Assessment on Magnitude Limits of Seismic Sources in the South China Sea and Adjoining Basins (United States)

    Li, Hongwei; Yuan, Ye; Xu, Zhiguo; Wang, Zongchen; Wang, Juncheng; Wang, Peitao; Gao, Yi; Hou, Jingming; Shan, Di


    The South China Sea (SCS) and its adjacent small basins including Sulu Sea and Celebes Sea are commonly identified as tsunami-prone region by its historical records on seismicity and tsunamis. However, quantification of tsunami hazard in the SCS region remained an intractable issue due to highly complex tectonic setting and multiple seismic sources within and surrounding this area. Probabilistic Tsunami Hazard Assessment (PTHA) is performed in the present study to evaluate tsunami hazard in the SCS region based on a brief review on seismological and tsunami records. 5 regional and local potential tsunami sources are tentatively identified, and earthquake catalogs are generated using Monte Carlo simulation following the Tapered Gutenberg-Richter relationship for each zone. Considering a lack of consensus on magnitude upper bound on each seismic source, as well as its critical role in PTHA, the major concern of the present study is to define the upper and lower limits of tsunami hazard in the SCS region comprehensively by adopting different corner magnitudes that could be derived by multiple principles and approaches, including TGR regression of historical catalog, fault-length scaling, tectonic and seismic moment balance, and repetition of historical largest event. The results show that tsunami hazard in the SCS and adjoining basins is subject to large variations when adopting different corner magnitudes, with the upper bounds 2-6 times of the lower. The probabilistic tsunami hazard maps for specified return periods reveal much higher threat from Cotabato Trench and Sulawesi Trench in the Celebes Sea, whereas tsunami hazard received by the coasts of the SCS and Sulu Sea is relatively moderate, yet non-negligible. By combining empirical method with numerical study of historical tsunami events, the present PTHA results are tentatively validated. The correspondence lends confidence to our study. Considering the proximity of major sources to population-laden cities

  4. Convective removal of the Tibetan Plateau mantle lithosphere by 26 Ma (United States)

    Lu, Haijian; Tian, Xiaobo; Yun, Kun; Li, Haibing


    During the late Oligocene-early Miocene there were several major geological events in and around the Tibetan Plateau (TP). First, crustal shortening deformation ceased completely within the TP before 25 Ma and instead adakitic rocks and potassic-ultrapotassic volcanics were emplaced in the Lhasa terrane since 26-25 Ma. Several recent paleoelevation reconstructions suggest an Oligocene-early Miocene uplift of 1500-3000 m for the Qiangtang (QT) and Songpan-Ganzi (SG) terranes, although the exact timing is unclear. As a possible response to this uplift, significant desertification occurred in the vicinity of the TP at 26-22 Ma, and convergence between India and Eurasia slowed considerably at 26-20 Ma. Subsequently, E-W extension was initiated no later than 18 Ma in the Lhasa and QT terranes. In contrast, the tectonic deformation around the TP was dominated by radial expansion of shortening deformation since 25-22 Ma. The plateau-wide near-synchroneity of these events calls for an internally consistent model which can be best described as convective removal of the lower mantle lithosphere. Geophysical and petrochemical evidence further confirms that this extensive removal occurred beneath the QT and SG terranes. The present review concludes that, other than plate boundary stress, the internal stress within the TP lithosphere could have contributed to rapid wholesale uplift and a series of concomitant tectonic events, accompanied by major aridification, since 26 Ma.

  5. Database for Regional Geology, Phase 1: A Tool for Informing Regional Evaluations of Alternative Geologic Media and Decision Making

    Energy Technology Data Exchange (ETDEWEB)

    Perry, Frank Vinton [Los Alamos National Lab. (LANL), Los Alamos, NM (United States); Kelley, Richard E. [Los Alamos National Lab. (LANL), Los Alamos, NM (United States); Birdsell, Suzanne M. [Clark Univ., Worcester, MA (United States); Lugo, Alexander Bryan [Los Alamos National Lab. (LANL), Los Alamos, NM (United States); Dobson, Patrick [Lawrence Berkeley National Lab. (LBNL), Berkeley, CA (United States); Houseworth, James [Lawrence Berkeley National Lab. (LBNL), Berkeley, CA (United States)


    Reported is progress in the following areas: Phase 1 and 2 websites for the regional geology GIS database; terrane maps of crystalline basement rocks; inventory of shale formations in the US; and rock properties and in-situ conditions for shale estimated from sonic velocity measurements.

  6. Heat production in an Archean crustal profile and implications for heat flow and mobilization of heat-producing elements

    Energy Technology Data Exchange (ETDEWEB)

    Ashwal, L.D.; Morgan, P.; Kelley, S.A.; Percival, J.A.


    We have measured concentrations of heat producing elements (Th, U, and K) in 58 samples representative of the main lithologies in a 100 km transect of the Superior Province of the Canadian Shield, from the Michipicoten (Wawa) greenstone belt, near Wawa, Ontario, through a domal gneiss terrane of amphibolite grade, to the granulite belt of the Kapuskasing Structural Zone, near Foleyet. (orig./SHOE).

  7. Hydrothermal flake graphite mineralisation in Paleoproterozoic rocks of south-east Greenland

    DEFF Research Database (Denmark)

    Rosing-Schow, Nanna; Bagas, Leon; Kolb, Jochen


    Flake graphite mineralisation is hosted in the Kuummiut Terrane of the Paleoproterozoic Nagssugtoqidian Orogen, south-east Greenland. Eclogite-facies peak-metamorphic assemblages record temperatures of 640–830 °C and pressures of 22–25 kbar, and are retrogressed in the high-pressure amphibolite-f...

  8. Erosion in southern Tibet shut down at ∼10 Ma due to enhanced rock uplift within the Himalaya. (United States)

    Tremblay, Marissa M; Fox, Matthew; Schmidt, Jennifer L; Tripathy-Lang, Alka; Wielicki, Matthew M; Harrison, T Mark; Zeitler, Peter K; Shuster, David L


    Exhumation of the southern Tibetan plateau margin reflects interplay between surface and lithospheric dynamics within the Himalaya-Tibet orogen. We report thermochronometric data from a 1.2-km elevation transect within granitoids of the eastern Lhasa terrane, southern Tibet, which indicate rapid exhumation exceeding 1 km/Ma from 17-16 to 12-11 Ma followed by very slow exhumation to the present. We hypothesize that these changes in exhumation occurred in response to changes in the loci and rate of rock uplift and the resulting southward shift of the main topographic and drainage divides from within the Lhasa terrane to their current positions within the Himalaya. At ∼17 Ma, steep erosive drainage networks would have flowed across the Himalaya and greater amounts of moisture would have advected into the Lhasa terrane to drive large-scale erosional exhumation. As convergence thickened and widened the Himalaya, the orographic barrier to precipitation in southern Tibet terrane would have strengthened. Previously documented midcrustal duplexing around 10 Ma generated a zone of high rock uplift within the Himalaya. We use numerical simulations as a conceptual tool to highlight how a zone of high rock uplift could have defeated transverse drainage networks, resulting in substantial drainage reorganization. When combined with a strengthening orographic barrier to precipitation, this drainage reorganization would have driven the sharp reduction in exhumation rate we observe in southern Tibet.

  9. Basement to surface expressions and critical factors in the genesis of unconformity-related deposits

    International Nuclear Information System (INIS)

    Potter, Eric


    Two subprojects: 1) Basement to surface expressions of deep mineralization and refinement of critical factors leading to the genesis of unconformity-related uranium deposits; and 2) Recognition of uranium ore system alteration signatures in complex terranes: IOCG vs albite-hosted uranium vs volcanic-hosted uranium.

  10. Analog Experiment for rootless cone eruption (United States)

    Noguchi, R.; Hamada, A.; Suzuki, A.; Kurita, K.


    Rootless cone is a unique geomorphological landmark to specify igneous origin of investigated terrane, which is formed by magma-water interaction. To understand its formation mechanism we conducted analog experiment for heat-induced vesiculation by using hot syrup and sodium bicarbonate solution.

  11. Low crustal velocities and mantle lithospheric variations in southern Tibet from regional Pnl waveforms (United States)

    Rodgers, Arthur J.; Schwartz, Susan Y.

    We report low average crustal P-wave velocities (5.9-6.1 km/s, Poisson's ratio 0.23-0.27, thickness 68-76 km) in southern Tibet from modelling regional Pnl waveforms recorded by the 1991-1992 Tibetan Plateau Experiment. We also find that the mantle lithosphere beneath the Indus-Tsangpo Suture and the Lhasa Terrane is shield-like (Pn velocity 8.20-8.25 km/s, lid thickness 80-140 km, positive velocity gradient 0.0015-0.0025 s-1). Analysis of relative Pn travel time residuals requires a decrease in the mantle velocities beneath the northern Lhasa Terrane, the Banggong-Nujiang Suture and the southern Qiangtang Terrane. Tectonic and petrologic considerations suggest that low bulk crustal velocities could result from a thick (50-60 km) felsic upper crust with vertically limited and laterally pervasive partial melt. These results are consistent with underthrusting of Indian Shield lithosphere beneath the Tibetan Plateau to at least the central Lhasa Terrane.

  12. Bedrock Geologic Map of the Old Lyme Quadrangle, New London and Middlesex Counties, Connecticut (United States)

    Walsh, Gregory J.; Scott, Robert B.; Aleinikoff, John N.; Armstrong, Thomas R.


    The bedrock geology of the Old Lyme quadrangle consists of Neoproterozoic and Permian gneisses and granites of the Gander and Avalon terranes, Silurian metasedimentary rocks of the Merrimack terrane, and Silurian to Devonian metasedimentary rocks of uncertain origin. The Avalon terrane rocks crop out within the Selden Neck block, and the Gander terrane rocks crop out within the Lyme dome. The Silurian to Devonian rocks crop out between these two massifs. Previous mapping in the Old Lyme quadrangle includes the work by Lawrence Lundgren, Jr. Lundgren's work provides an excellent resource for rock descriptions and detailed modal analyses of rock units that will not be duplicated in this current report. New research that was not covered in detail by Lundgren is the focus of this report and includes (1) evaluation of the rocks in the core of the Lyme dome in an effort to subdivide units in this area; (2) structural analysis of foliations and folds in and around the Lyme dome; (3) geochronology of selected units within the Lyme dome; and (4) analysis of joints and the fracture properties of the rocks.

  13. Hydrothermal Processes in the Archean - New Insights from Imaging Spectroscopy

    NARCIS (Netherlands)

    Ruitenbeek, F.J.A. van


    The aim of this research was to gain new insights in fossil hydrothermal systems using airborne imaging spectroscopy. Fossil submarine hydrothermal systems in Archean greenstone belts and other geologic terranes are important because of their relationship with volcanic massive sulfide (VMS) mineral

  14. Geology of the Prince William Sound and Kenai Peninsula region, Alaska (United States)

    Wilson, Frederic H.; Hults, Chad P.


    The Prince William Sound and Kenai Peninsula region includes a significant part of one of the world’s largest accretionary complexes and a small part of the classic magmatic arc geology of the Alaska Peninsula. Physiographically, the map area ranges from the high glaciated mountains of the Alaska and Aleutian Ranges and the Chugach Mountains to the coastal lowlands of Cook Inlet and the Copper River delta. Structurally, the map area is cut by a number of major faults and postulated faults, the most important of which are the Border Ranges, Contact, and Bruin Bay Fault systems. The rocks of the map area belong to the Southern Margin composite terrane, a Tertiary and Cretaceous or older subduction-related accretionary complex, and the Alaska Peninsula terrane. Mesozoic rocks between these two terranes have been variously assigned to the Peninsular or the Hidden terranes. The oldest rocks in the map area are blocks of Paleozoic age within the mélange of the McHugh Complex; however, the protolith age of the greenschist and blueschist within the Border Ranges Fault zone is not known. Extensive glacial deposits mantle the Kenai Peninsula and the lowlands on the west side of Cook Inlet and are locally found elsewhere in the map area. This map was compiled from existing mapping, without generalization, and new or revised data was added where available.

  15. The South India Precambrian crust and shallow lithospheric mantle ...

    Indian Academy of Sciences (India)

    Regional geothermal-barometry in the granulite facies terrane of South India; Contrib. Mineral. Petrol. 73. 221–244. Raith M, Karmakar S and Brown M 1997 Ultra high temparature metamorphism and multi-stage decom- pressional of saphirrine granulite from the Palni-. Hill ranges, southern India; J. Metamorph. Geol. 15.

  16. Peak metamorphic temperatures from cation diffusion zoning in garnet

    DEFF Research Database (Denmark)

    Smit, Matthijs Arjen; Scherer, Erik; Mezger, Klaus


    ) to develop a tool that uses the diffusion zoning of these cations in garnet to constrain peak temperature conditions for garnet-bearing rocks. The thermometric approach was externally tested by applying it to garnet crystals from various metamorphic terranes worldwide and comparing the results to published...

  17. Preliminary Evidence for a Second -525-545 Ma old Event of ...

    African Journals Online (AJOL)

    (1995), the 630-700 Ma old event that produced the Eastern Granulites may record regional crustal thickening arising out of collision of India, Madagascar, parts of Easten Antarctica and the Kalahari craton (IMSLEK terranes) with the Congo craton and the Arabian Nubian Shield (ANS). The younger granulite event recorded ...

  18. Transition from island-arc to passive setting on the continental margin of Gondwana: U-Pb zircon dating of Neoproterozoic metaconglomerates from the SE margin of the Teplá-Barrandian Unit, Bohemian Massif

    Czech Academy of Sciences Publication Activity Database

    Sláma, Jiří; Dunkley, D. J.; Kachlík, V.; Kusiak, M. A.


    Roč. 461, 1-4 (2008), s. 44-59 ISSN 0040-1951 Institutional research plan: CEZ:AV0Z30130516 Keywords : Bohemian Massif * Teplá–Barrandian Unit * Neoproterozoic * Armorican Terrane Assemblage * Gondwana * zircon dating Subject RIV: DB - Geology ; Mineralogy Impact factor: 1.677, year: 2008

  19. Metallogenic epoch of the Jiapigou gold belt, Jilin Province, China ...

    Indian Academy of Sciences (India)

    29, Xueyuan Road, Beijing 100083, People's Republic of China. 2Beijing Research .... terrane, which is separated from the central Asian orogenic belt .... Stage I formed the main body of quartz veins ...... size (20–25 μm) fluid inclusions can be observed, although most ..... Canada and Western Australia (Goldfarb et al. 2001 ...

  20. Fulltext PDF

    Indian Academy of Sciences (India)

    Data were arranged according to the Mexican geological provinces, indicating for each province .... geochronologic studies and a unified plate tectonic Grenvillian age), the Xolapa terrane (XO ..... component to explain the relatively high Sr and Nd .... value (see figure 6) and apparently enlarge the Pac0c ..... Zacatecas, Zac.

  1. Origin of giant Martian polygons (United States)

    Mcgill, George E.; Hills, L. S.


    Extensive areas of the Martian northern plains in Utopia and Acidalia planitiae are characterized by 'polygonal terrane'. Polygonal terrane consists of material cut by complex troughs defining a pattern resembling mudcracks, columnar joints, or frost-wedge polygons on earth. However, the Martian polygons are orders of magnitude larger than these potential earth analogues, leading to severe mechanical difficulties for genetic models based on simple analogy arguments. Plate-bending and finite element models indicate that shrinkage of desiccating sediment or cooling volcanics accompanied by differential compaction over buried topography can account for the stresses responsible for polygon troughs as well as the large size of the polygons. Although trough widths and depths relate primarily to shrinkage, the large scale of the polygonl pattern relates to the spacing between topographic elevations on the surface buried beneath polygonal terrane material. Geological relationships favor a sedimentary origin for polygonal terrane material, but our model is not dependent on the specific genesis. Our analysis also suggests that the polygons must have formed at a geologically rapid rate.

  2. Rocks age and metamorphic occurrence from the southeastern part of Sao Paulo State and their crustal evaluation

    International Nuclear Information System (INIS)

    Tassinari, C.C.G.


    Pb-Pb and Rb-Sr whole rock isotope systematics and U-Pb on zircons method analyses are reported for rocks from the southeastern part of Sao Paulo state Brazil. The isotopic studies on granitic intrusions, orthogneissic rocks and migmatitic terranes, in this area, provides an important indication of the age and nature of the continental crust. (author) [pt

  3. A compilation of Sr and Nd isotope data on Mexico

    International Nuclear Information System (INIS)

    Verma, S.P.; Verma, M.P.


    A compilation is given of the available Sr and Nd isotope data on Mexican volcanic-plutonic terranes which cover about one-third of Mexico's territory. The available data are arranged according to a subdivision of the Mexican territory in terms of geological provinces. Furthermore, site and province averages and standard deviations are calculated and their petrogenetic implications are pointed out. (author)

  4. Lithospheric structure of southern Indian shield and adjoining oceans: integrated modelling of topography, gravity, geoid and heat flow data (United States)

    Kumar, Niraj; Zeyen, H.; Singh, A. P.; Singh, B.


    For the present 2-D lithospheric density modelling, we selected three geotransects of more than 1000 km in length each crossing the southern Indian shield, south of 16°N, in N-S and E-W directions. The model is based on the assumption of local isostatic equilibrium and is constrained by the topography, gravity and geoid anomalies, by geothermal data, and where available by seismic data. Our integrated modelling approach reveals a crustal configuration with the Moho depth varying from ˜40 km beneath the Dharwar Craton, and ˜39 km beneath the Southern Granulite Terrane to about 15-20 km beneath the adjoining oceans. The lithospheric thickness varies significantly along the three profiles from ˜70-100 km under the adjoining oceans to ˜130-135 km under the southern block of Southern Granulite Terrane including Sri Lanka and increasing gradually to ˜165-180 km beneath the northern block of Southern Granulite Terrane and the Dharwar Craton. This step-like lithosphere-asthenosphere boundary (LAB) structure indicates a normal lithospheric thickness beneath the adjoining oceans, the northern block of Southern Granulite Terrane and the Dharwar Craton. The thin lithosphere below the southern block of Southern Granulite Terrane including Sri Lanka is, however, atypical considering its age. Our results suggest that the southern Indian shield as a whole cannot be supported isostatically only by thickened crust; a thin and hot lithosphere beneath the southern block of Southern Granulite Terrane including Sri Lanka is required to explain the high topography, gravity, geoid and crustal temperatures. The widespread thermal perturbation during Pan-African (550 Ma) metamorphism and the breakup of Gondwana during late Cretaceous are proposed as twin cause mechanism for the stretching and/or convective removal of the lower part of lithospheric mantle and its replacement by hotter and lighter asthenosphere in the southern block of Southern Granulite Terrane including Sri Lanka

  5. Source constraints on the genesis of Danubian granites in the South Carpathians Alpine Belt (Romania) (United States)

    Duchesne, Jean-Clair; Laurent, Oscar; Gerdes, Axel; Bonin, Bernard; Liégeois, Jean-Paul; Tatu, Mihai; Berza, Tudor


    The pre-Alpine basement of the Lower Danubian nappes in the South Carpathians is made up of two Precambrian terranes (Drăgşan and Lainici-Păiuş) that were intruded by Pan-African/Cadomian and Variscan granitoid massifs. We focus on the major and trace element geochemistry (1) in the Drăgşan terrane, of the Variscan Retezat and Parâng intrusions; (2) in the Lainici-Păiuş terrane, of the Variscan Furcǎtura, Petreanu and Frumosu intrusions and of the Pan-African Vârful Pietrii, Şuşiţa and Olteţ granites and granitic leucosomes of migmatites; and (3) in the Upper Danubian nappes basement, of the Variscan Muntele Mic, Sfârdin, Cherbelezu and Ogradena intrusions. For each intrusion, in which a range of composition is observed, we decipher the differentiation mechanisms (fractional crystallization, hybridization, melt laden with restite minerals, etc.) in order to define the parental liquid compositions. The latter are calc-alkaline to alkali-calcic (except Olteţ that is calcic) and medium to high-K in composition. With [La/Yb]N > 10 and Sr/Y > 15, most melts display the so-called "continental adakite" affinities. The parental melt compositions are compared with experimental data to determine the melting conditions and the nature of the source rock. When the P-T conditions can be estimated, the temperatures range between 850 °C and 875 °C and the pressure between 5 and 15 kbar regardless of the ages of the granites and the terrane in which they have intruded. The source rock composition is dominated by a variety of mafic igneous compositions or metasediments rich in volcanic components. Clay-rich (pelitic) protoliths have not been identified. We confirm a Variscan age (c. 300 Ma) for the Frumosu intrusion granite and inherited Precambrian ages (c. 1.7-1.9 and 2.6-2.9 Ga) for the Motru dyke swarm. Thus, both Drăgşan and Lainici-Păiuş together with the Upper Danubian basement terranes were affected by Variscan post-collisional granitic plutonism. In

  6. U-Pb age constraints for the La Tuna Granite and Montevideo Formation (Paleoproterozoic, Uruguay): Unravelling the structure of the Río de la Plata Craton (United States)

    Pamoukaghlián, Karina; Gaucher, Claudio; Frei, Robert; Poiré, Daniel G.; Chemale, Farid; Frei, Dirk; Will, Thomas M.


    The Río de la Plata Craton is a continental block that crops out in Uruguay, eastern Argentina, southernmost Brazil and Paraguay. It comprises in Uruguay the Piedra Alta, Tandilia and Nico Pérez terranes, separated by the Colonia and the Sarandí del Yí megashears. The La Tuna Granite, which intrudes the Araminda metasandstones in the Tandilia Terrane, was considered Cambrian in age and the intruded sandstones were assigned to the Neoproterozoic Piedras de Afilar Formation. We show that the granite is Paleoproterozoic in age and that the host metasandstones do not belong to the Piedras de Afilar Formation, but to the Paleoproterozoic Montevideo Formation. U-Pb LA ICP-MS of zircon ages for the La Tuna Granite yielded a concordant crystallization age of 2156 ± 26 Ma. Furthermore a metamorphic event at 2010 ± 9 Ma is revealed by Pb stepwise leaching dating of monazites. U-Pb detrital zircon ages of the host Araminda metasandstone yield an upper intercept discordia age of 2152 ± 29 Ma, which marks the intrusion of the La Tuna pluton, and which is in accordance with the zircon U-Pb LA ICP MS constraints. A concordant U-Pb detrital zircon age of 2465 ± 40 Ma provides a maximum depositional age constraint for the metapsammites. Comparing quartz arenites of the Ediacaran Piedras de Afilar Formation with the Araminda metaquartzites, we conclude that they are very similar regarding petrology but they differ in age and metamorphic overprint. Detrital zircons in quartz arenites of the Piedras de Afilar Formation show youngest ages of 1.0 Ga. On the other hand, detrital zircons recovered from the Araminda metasandstones and the age of the intruding granite allow interpreting a depositional age between 2465 and 2150 Ma. Nd model ages show crustal residence times in average more than 200 myr older for the Tandilia Terrane both in Uruguay and Argentina, with a significant Neoarchean component, which is lacking in the Piedra Alta Terrane. Whereas the Piedra Alta Terrane was

  7. Lower Paleozoic deep-water facies of the Medfra area, central Alaska: A section in Geologic studies in Alaska by the U.S. Geological Survey, 1997 (United States)

    Dumoulin, Julie A.; Bradley, Dwight C.; Harris, Anita G.; Repetski, John E.


    Deep-water facies, chiefly hemipelagic deposits and turbidites, of Cambrian through Devonian age are widely exposed in the Medfra and Mt. McKinley quadrangles. These strata include the upper part of the Telsitna Formation (Middle-Upper Ordovician) and the Paradise Fork Formation (Lower Silurian-Lower Devonian) in the Nixon Fork terrane, the East Fork Hills Formation (Upper Cambrian-Lower Devonian) in the East Fork subterrane of the Minchumina terrane, and the chert and argillite unit (Ordovician) and the argillite and quartzite unit (Silurian- Devonian? and possibly older) in the Telida subterrane of the Minchumina terrane.In the western part of the study area (Medfra quadrangle), both hemipelagic deposits and turbidites are largely calcareous and were derived from the Nixon Fork carbonate platform. East- ern exposures (Mt. McKinley quadrangle; eastern part of the Telida subterrane) contain much less carbonate; hemipelagic strata are mostly chert, and turbidites contain abundant rounded quartz and lesser plagioclase and potassium feldspar. Deep-water facies in the Medfra quadrangle correlate well with rocks of the Dillinger terrane exposed to the south (McGrath quadrangle), but coeval strata in the Mt. McKinley quadrangle are compositionally similar to rocks to the northeast (Livengood quadrangle). Petrographic data thus suggest that the Telida subterranes presently defined is an artificial construct made up of two distinct sequences of disparate provenance.Restoration of 90 and 150 km of dextral strike-slip on the Iditarod and Farewell faults, respectively, aligns the deep-water strata of the Minchumina and Dillinger terranes in a position east of the Nixon Fork carbonate platform. This restoration supports the interpretation that lower Paleozoic rocks in the Nixon Fork and Dillinger terranes, and in the western part of the Minchumina terrane (East Fork subterrane and western part of the Telida subterrane), formed along a single continental margin. Rocks in the

  8. Pan-African deformations in the basement of the Negele area, southern Ethiopia (United States)

    Yihunie, Tadesse


    Polydeformed and metamorphosed Neoproterozoic rocks of the East African Orogen in the Negele area constituted three lithostructurally distinct and thrust-bounded terranes. These are, from west to east, the Kenticha, Alghe and Bulbul terranes. The Kenticha and Bulbul terranes are metavolcano-sedimentary and ultramafic sequences, representing parts of the Arabian-Nubian Shield (ANS), which are welded to the central Alghe gneissic terrane of the Mozambique Belt affinity along N-S-trending sheared thrust contacts. Structural data suggest that the Negele basement had evolved through three phases of deformation. During D1 (folding) deformation, north-south upright and inclined folds with north-trending axes were developed. East and west-verging thrusts, right-lateral shearing along the north-oriented Kenticha and Bulbul thrust contacts and related structural elements were developed during D2 (thrusting) deformation. The pervasive D1 event is interpreted to have occurred at 620-610 Ma and the D2 event ended prior to 554 Ma. Right-lateral strike-slips along thrust contacts are interpreted to have been initiated during late D2. During D3, left-lateral strike-slip along the Wadera Shear Zone and respective strike-slip movements along conjugate set of shear zones were developed in the Alghe terrane, and are interpreted to have occurred later than 557 Ma. The structural data suggest that eastward thrusting of the Kenticha and westward tectonic transport of the Bulbul sequences over the Alghe gneissic terrane of the Mozambique Belt, during D2, were accompanied by right-lateral strike-slip displacements along thrust contacts. Right-lateral strike-slip movements along the Kenticha thrust contact, further suggest northward movement of the Kenticha sequence during the Pan-African orogeny in the Neoproterozoic. Left-lateral strike-slip along the orogen-parallel NNE-SSW Wadera Shear Zone and strike-slip movements along a conjugate set of shear zones completed final terrane

  9. The Largs high-latitude oxygen isotope anomaly (New Zealand) and climatic controls of oxygen isotopes in magma

    International Nuclear Information System (INIS)

    Blattner, P.; Williams, J.G.


    In northern Fiordland the Brook Street terrane of New Zealand consists of two units - the predominantly basaltic Plato and the predominantly andesitic Largs terrane. The Permian Plato terrane has normal to slightly enriched δ 18 O values, whereas the Largs terrane, which is of similar pre-early Triassic age, has not yielded a single normal δ 18 O SMOW result, with all of 17 total rocks showing less than 3.2per mille, seven less than -4per mille, and two less than -9per mille. These strongly anomalous data confirm an earlier suggested terrestrial character of Largs deposition, and demand the presence of Permo-Triassic geothermal systems running on subAntarctic to Antarctic meteoric water. The skewed data spectrum suggests a relatively immature flow system and likely values for the recharge water are -20per mille δ 18 O or less. For a climate distribution similar to the present one, inlcuding polar ice caps, this would indicate over 70deg of southern latitude. Rafts and xenoliths of Largs rocks have been entrained within Mackay Intrusives in the early Triassic. On field evidence the Mackay magmas have also intruded an early Darran Complex, but this complex has been substantially reactivated in the Cretaceous. It has δ 18 O values near 5.0per mille, which is distinctly low for island arc magmas. Since the complex is isotopically homogenous, its δ 18 O is unlikely to be a direct effect of the relatively shallow Largs terrane. More probable is a climate related slight depression of the δ 18 O of magma sources, in which other high-latitude, low-δ 18 O sediments and geothermal systems have been involved. (orig.)

  10. Middle to Late Jurassic Tectonic Evolution of the Klamath Mountains, California-Oregon (United States)

    Harper, Gregory D.; Wright, James E.


    The geochronology, stratigraphy, and spatial relationships of Middle and Late Jurassic terranes of the Klamath Mountains strongly suggest that they were formed in a single west-facing magmatic arc built upon older accreted terranes. A Middle Jurassic arc complex is represented by the volcanic rocks of the western Hayfork terrane and consanguineous dioritic to peridotitic plutons. New U/Pb zircon dates indicate that the Middle Jurassic plutonic belt was active from 159 to 174 Ma and is much more extensive than previously thought. This plutonic belt became inactive just as the 157 Ma Josephine ophiolite, which lies west and structurally below the Middle Jurassic arc, was generated. Late Jurassic volcanic and plutonic arc rocks (Rogue Formation and Chetco intrusive complex) lie outboard and structurally beneath the Josephine ophiolite; U/Pb and K/Ar age data indicate that this arc complex is coeval with the Josephine ophiolite. Both the Late Jurassic arc complex and the Josephine ophiolite are overlain by the "Galice Formation," a Late Jurassic flysch sequence, and are intruded by 150 Ma dikes and sills. The following tectonic model is presented that accounts for the age and distribution of these terranes: a Middle Jurassic arc built on older accreted terranes undergoes rifting at 160 Ma, resulting in formation of a remnant arc/back-arc basin/island arc triad. This system collapsed during the Late Jurassic Nevadan Orogeny (150 Ma) and was strongly deformed and stacked into a series of east-dipping thrust sheets. Arc magmatism was active both before and after the Nevadan Orogeny, but virtually ceased at 140 Ma.

  11. Microstructural finite strain analysis and 40Ar/39Ar evidence for the origin of the Mizil gneiss dome, eastern Arabian Shield, Saudi Arabia (United States)

    Al-Saleh, Ahmad M.; Kassem, Osama M. K.


    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.

  12. Crustal nature and origin of the Russian Altai: Implications for the continental evolution and growth of the Central Asian Orogenic Belt (CAOB) (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.


    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

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

    Directory of Open Access Journals (Sweden)

    Inna Safonova


    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. Dynamics of subduction, accretion, exhumation and slab roll-back: Mediterranean scenarios (United States)

    Tirel, C.; Brun, J.; Burov, E. B.; Wortel, M. J.; Lebedev, S.


    A dynamic orogen reveals various tectonic processes brought about by subduction: accretion of oceanic and continental crust, exhumation of UHP-HP rocks, and often, back-arc extension. In the Mediterranean, orogeny is strongly affected by slab retreat, as in the Aegean and Tyrrhenian Seas. In order to examine the different dynamic processes in a self-consistent manner, we perform a parametric study using the fully coupled thermo-mechanical numerical code PARAFLAM. The experiments reproduce a subduction zone in a slab pull mode, with accretion of one (the Tyrrhenian case) and two continental blocks (the Aegean case) that undergo, in sequence, thrusting, burial and exhumation. The modeling shows that despite differences in structure between the two cases, the deformation mechanisms are fundamentally similar and can be described as follows. The accretion of a continental block at the trench beneath the suture zone begins with its burial to UHP-HP conditions and thrusting. Then the continental block is delaminated from its subducting lithosphere. During the subduction-accretion process, the angle of the subducting slab increases due to the buoyancy of the continental block. When the oceanic subduction resumes, the angle of the slab decreases to reach a steady-state position. The Aegean and Tyrrhenian scenarios diverge at this stage, due naturally to the differences of their accretion history. When continental accretion is followed by oceanic subduction only, the continental block that has been accreted and detached stays at close to the trench and does not undergo further deformation, despite the continuing rollback. The extensional deformation is located further within the overriding plate, resulting in continental breakup and the development of an oceanic basin, as in the Tyrrhenian domain. When the continental accretion is followed first by oceanic subduction and then by accretion of another continental block, however, the evolution of the subduction zone is

  15. Dynamics of mineral crystallization at inclusion-garnet interface from precipitated slab-derived fluid phase: first in-situ synchrotron x-ray measurements (United States)

    Malaspina, Nadia; Alvaro, Matteo; Campione, Marcello; Nestola, Fabrizio


    Remnants of the fluid phase at ultrahigh pressure (UHP) in subduction environments may be preserved as primary multiphase inclusions in UHP minerals. These inclusions are frequently hosted by minerals stable at mantle depths, such as garnet, and show the same textural features as fluid inclusions. The mineral infillings of the solid multiphase inclusions are generally assumed to have crystallized by precipitation from the solute load of dense supercritical fluids equilibrating with the host rock. Notwithstanding the validity of this assumption, the mode of crystallization of daughter minerals during precipitation within the inclusion and/or the mechanism of interaction between the fluid at supercritical conditions and the host mineral are still poorly understood from a crystallographic point of view. A case study is represented by garnet orthopyroxenites from the Maowu Ultramafic Complex (China) deriving from harzburgite precursors metasomatised at ~ 4 GPa, 750 °C by a silica- and incompatible trace element-rich fluid phase. This metasomatism produced poikilitic orthopyroxene and inclusion-rich garnet porphyroblasts. Solid multiphase primary inclusions in garnet display a size within a few tens of micrometers and negative crystal shapes. Infilling minerals (spinel: 10-20 vol.%; amphibole, chlorite, talc, mica: 80- 90 vol.%) occur with constant volume ratios and derive from trapped solute-rich aqueous fluids. To constrain the possible mode of precipitation of daughter minerals, we performed for the first time a single-crystal X-ray diffraction experiment by means of Synchrotron Radiation at DLS-Diamond Light Source. In combination with electron probe microanalyses, this measurement allowed the unique identification of each mineral phase and their reciprocal orientations. We demonstrated the epitaxial relationship between spinel and garnet and between some hydrous minerals. Epitaxy drives a first-stage nucleation of spinel under near-to-equilibrium conditions

  16. Study of the recrystallization mechanisms of ultra-high purity iron doped with carbon, manganese and phosphorus; Etude des mecanismes de recristallisation dans le fer de ultra-haute purete dope en carbone, manganese et phosphore

    Energy Technology Data Exchange (ETDEWEB)

    Lesne, L.


    High purity steels have the potential to improve deep drawing properties for automotive applications. Understanding the influence of the chemical composition on the recrystallization mechanisms and on texture development should help to improve their properties. We have studied the influence of 10 ppm of carbon, 1000 ppm of manganese and 120 ppm of phosphorus on the recrystallization mechanisms of ultra-high purity iron (UHP iron > 99.997%). For this purpose we used 4 materials: one undoped (UHP), one doped with C, one doped with C, Mn and one doped With C, Mn, P. In order to restrict grain coarsening in the hot strips, hot rolling was performed in the ferritic region, in one pass of 80% thickness reduction. The hot bands were then fully recrystallized but exhibited non-isotropic textures, with in particular an intense Goss [110]<001> component for the doped materials. The hot-bands were subsequently cold rolled down to a thickness of 0.8 mm corresponding to a thickness reduction of 80%, and then continuously annealed at 10 deg. C/s. The recrystallization kinetics are delayed with the addition of doping elements. In particular, the incubation time for nucleation is shifted towards higher temperatures while the recrystallization velocity increases. The textures of the fully recrystallized materials exhibit a strong Goss component prejudicial for deep drawing properties. We have established that this component can only appear if coarse grains and carbon in solid solution were simultaneously present in the material before deformation. Characterisation of the cold deformed state enabled us to evaluate the energy stored during deformation as a function of the material composition and the grain orientation: - the overall stored energy increases with the doping elements content. - the stored energy in the {gamma} fibre grains is greater than in the {alpha} fibre grains: 30 J/mol for the {gamma} fibre instead of 5 J/mol for the {alpha} fibre, in the undoped UHP iron. In the

  17. Regional metamorphism at extreme conditions: Implications for orogeny at convergent plate margins (United States)

    Zheng, Yong-Fei; Chen, Ren-Xu


    Regional metamorphism at extreme conditions refers either to Alpine-type metamorphism at low geothermal gradients of geothermal gradients of >30 °C/km. Extreme pressures refer to those above the polymorphic transition of quartz to coesite, so that ultrahigh-pressure (UHP) eclogite-facies metamorphism occurs at mantle depths of >80 km. Extreme temperatures refer to those higher than 900 °C at crustal depths of ≤80 km, so that ultrahigh-temperature (UHT) granulite-facies metamorphism occurs at medium to high pressures. While crustal subduction at the low geothermal gradients results in blueschist-eclogite facies series without arc volcanism, heating of the thinned orogenic lithosphere brings about the high geothermal gradients for amphibolite-granulite facies series with abundant magmatism. Therefore, UHP metamorphic rocks result from cold lithospheric subduction to the mantle depths, whereas UHT metamorphic rocks are produced by hot underplating of the asthenospheric mantle at the crustal depths. Active continental rifting is developed on the thinned lithosphere in response to asthenospheric upwelling, and this tectonism is suggested as a feasible mechanism for regional granulite-facies metamorphism, with the maximum temperature depending on the extent to which the mantle lithosphere is thinned prior to the rifting. While lithospheric compression is associated with subduction metamorphism in accretionary and collisional orogens, the thinned orogenic lithosphere undergoes extension due to the asthenospheric upwelling to result in orogen-parallel rifting metamorphism and magmatism. Thus, the rifting metamorphism provides a complement to the subduction metamorphism and its operation marks the asthenospheric heating of the orogenic lithosphere. Because of the partial melting and melt extraction of the lower continental crust, contemporaneous granite-migmatite-granulite associations may serve as a petrological indicator of rifting orogeny that is superimposed on

  18. Geochronologic Constraints on the Location of the Sino-Korean/Yangtze Suture and Evolution of the Northern Dabie Shan (United States)

    Bryant, D. L.; Ayers, J. C.; Gao, S.; Miller, C. F.; Zhang, H.


    The Northern Dabie Complex (NDC) has been proposed to be either a Paleozoic magmatic arc, an exhumed piece of subducted continental crust, or young crust produced almost entirely by Cretaceous extensional magmatism. Ion microprobe zircon 238U-206Pb ages of separates from NDC gneisses center around 689Ma (+/- 31(95%CL)), consistent with the characteristic zircon dates of the Yangtze Craton [1]. Field observations also show that these gneisses, ranging from granitic to dioritic composition, make up a sizeable area ( ~30%) of the NDC. Zircon separates from the Baimajian granitoid, the largest of the widespread Cretaceous intrusions in the NDC, have yielded ages clustered around 677Ma (+/- 79), and 120Ma (+/- 3.4), the latter of which agrees with ion probe Th-Pb monazite ages. The ~700Ma age indicates that this intrusion may be linked with partial melting of underlying Yangtze crust, while the 120Ma age is the age of its crystallization. Granitic intrusions from Sanzushi and Yerenshai in the Dabie ultrahigh-pressure (UHP) region also show clusters of ages at 714Ma (+/- 55) from zircon cores, as well as rims around 250Ma (+/- 38), which is interpreted as the time of collision of the two continental blocks. These age data support the hypothesis set forth by Zhang et al. [2] using Sm-Nd and Pb isotopic data, that the Yangtze block lies beneath the exhumed UHP belt and outcrops as the NDC, which lies between the UHP belt and the Sino-Korean/Yangtze suture. The Baimajian granitoid, however, also shows a range of older zircon core ages from 1.4-2.0Ga, which may represent the early stages of formation of the Yangtze craton. Zhang et al. [2] suggested craton formation at 1.6-2.4Ga but few such ages have been reported for rocks of the Yangtze or Sino-Korean cratons. 1. Hacker, et al. (2000) Journal of Geophysical Research. Vol. 105. p. 13,339. 2. Zhang, et al. (In press) Chemical Geology.

  19. The influence of upper-crust lithology on topographic development in the central Coast Ranges of California (United States)

    Garcia, A.F.; Mahan, S.A.


    A fundamental geological tenet is that as landscapes evolve over graded to geologic time, geologic structures control patterns of topographic distribution in mountainous areas such that terrain underlain by competent rock will be higher than terrain underlain by incompetent rock. This paper shows that in active orogens where markedly weak and markedly strong rocks are juxtaposed along contacts that parallel regional structures, relatively high topography can form where strain is localized in the weak rock. Such a relationship is illustrated by the topography of the central Coast Ranges between the Pacific coastline and the San Andreas fault zone (SAFZ), and along the length of the Gabilan Mesa (the "Gabilan Mesa segment" of the central Coast Ranges). Within the Gabilan Mesa segment, the granitic upper crust of the Salinian terrane is in contact with the accretionary-prism m??lange upper crust of the Nacimiento terrane along the inactive Nacimiento fault zone. A prominent topographic lineament is present along most of this lithologic boundary, approximately 50 to 65. km southwest of the SAFZ, with the higher topography formed in the m??lange on the southwest side of the Nacimiento fault. This paper investigates factors influencing the pattern of topographic development in the Gabilan Mesa segment of the central Coast Ranges by correlating shortening magnitude with the upper-crust compositions of the Salinian and Nacimiento terranes. The fluvial geomorphology of two valleys in the Gabilan Mesa, which is within the Salinian terrane, and alluvial geochronology based on optically-stimulated luminescence (OSL) age estimates, reveal that the magnitude of shortening accommodated by down-to-the-southwest tilting of the mesa since 400ka is less than 1 to 2m. Our results, combined with those of previous studies, indicate that at least 63% to 78% of late-Cenozoic, northeast-southwest directed, upper-crustal shortening across the Gabilan Mesa segment has been accommodated

  20. Oxidative Esterification of Aldehydes with Urea Hydrogen Peroxide Catalyzed by Aluminum Chloride Hexahydrate

    Energy Technology Data Exchange (ETDEWEB)

    Lee, Sin-Ae; Kim, Yoon Mi; Lee, Jong Chan [Chung-Ang University, Seoul (Korea, Republic of)


    We have developed a new, environmentally benign and highly efficient oxidative preparation of methyl esters by the reaction of various aldehydes with UHP in methanol catalyzed by readily accessible aluminum(III) chloride hexahydrate. This new greener and cost effective direct esterification method can serve as a useful alternative to existing protocols. Esters are some of the most important functional groups in organic chemistry and have been found in the sub-structure of a variety of natural products, industrial chemicals, and pharmaceuticals. Numerous methods have been reported for the preparation of various esters. In particular, this method gives low yields for both aldehydes containing electron donating substituents in aromatic rings and heterocyclic aldehydes. Therefore, development of a more general, efficient, and greener protocol for the esterification of aldehydes with readily available catalyst is still desirable.

  1. Comparison of the thermal shock performance of different tungsten grades and the influence of microstructure on the damage behaviour

    International Nuclear Information System (INIS)

    Wirtz, M; Linke, J; Pintsuk, G; Singheiser, L; Uytdenhouwen, I


    The thermal shock performances of two new tungsten grades with 1 and 5 wt% of tantalum were characterized with the electron beam facility JUDITH 1. As a reference material, ultra-high-purity tungsten (W-UHP) with a purity of 99.9999 wt% was used. The induced thermal shock crack networks and surface modifications were analysed by a scanning electron microscope, light microscopy and laser profilometry. Damage and cracking thresholds were defined for all materials as a function of absorbed power density and base temperature. The materials showed significantly different thermal shock behaviour, which is, among others, expressed by differences in cracking patterns, i.e. crack distance and depth. These results allow us to quantify the influence of the materials' mechanical and thermal properties on the thermal shock performance. Furthermore, the specific grain structure of the materials has a significant influence on crack propagation towards the bulk material.

  2. Tracing high-pressure metamorphism in marbles: Phase relations in high-grade aluminous calcite-dolomite marbles from the Greek Rhodope massif in the system CaO-MgO-Al 2O 3-SiO 2-CO 2 and indications of prior aragonite (United States)

    Proyer, A.; Mposkos, E.; Baziotis, I.; Hoinkes, G.


    Four different types of parageneses of the minerals calcite, dolomite, diopside, forsterite, spinel, amphibole (pargasite), (Ti-)clinohumite and phlogopite were observed in calcite-dolomite marbles collected in the Kimi-Complex of the Rhodope Metamorphic Province (RMP). The presence of former aragonite can be inferred from carbonate inclusions, which, in combination with an analysis of phase relations in the simplified system CaO-MgO-Al 2O 3-SiO 2-CO 2 (CMAS-CO 2) show that the mineral assemblages preserved in these marbles most likely equilibrated at the aragonite-calcite transition, slightly below the coesite stability field, at ca. 720 °C, 25 kbar and aCO 2 ~ 0.01. The thermodynamic model predicts that no matter what activity of CO 2, garnet has to be present in aluminous calcite-dolomite-marble at UHP conditions.

  3. The importance of system band broadening in modern size exclusion chromatography. (United States)

    Goyon, Alexandre; Guillarme, Davy; Fekete, Szabolcs


    In the last few years, highly efficient UHP-SEC columns packed with sub-3μm particles were commercialized by several providers. Besides the particle size reduction, the dimensions of modern SEC stationary phases (150×4.6mm) was also modified compared to regular SEC columns (300×6 or 300×8mm). Because the analytes are excluded from the pores in SEC, the retention factors are very low, ranging from -1 UHP-SEC conditions. The goal of this study was to evaluate the loss of efficiency observed with three different instruments (regular HPLC, non-optimized UHPLC and fully optimized UHPLC) offering different system variances. It appears that the new 150×4.6mm, sub-3μm SEC columns cannot be employed on a regular HPLC instrument, since the efficiency loss was equal to 60-85%, when analyzing mAb sample. Optimized UHPLC systems having very low extra-column volumes (typicallyV ec <10μL) have therefore to be used to properly operate these columns. Due to the instrument contribution to band broadening, the apparent efficiency of SEC columns packed with sub-2μm particles can indeed be hampered when using inappropriate system. Considering the extra-column band broadening contribution of current UHPLC instruments, a further decrease of SEC column dimension is therefore not desired. Copyright © 2016 Elsevier B.V. All rights reserved.

  4. Kinetics of the coesite to quartz transformation (United States)

    Mosenfelder, J.L.; Bohlen, S.R.


    The survival of coesite in ultrahigh-pressure (UHP) rocks has important implications for the exhumation of subducted crustal rocks. We have conducted experiments to study the mechanism and rate of the coesite ??? quartz transformation using polycrystalline coesite aggregates, fabricated by devitrifying silica glass cylinders containing 2850H/106 Si at 1000??C and 3.6 GPa for 24h. Conditions were adjusted following synthesis to transform the samples at 700-1000??C at pressures 190-410 MPa below the quartz-coesite equilibrium boundary. Reaction proceeds via grain-boundary nucleation and interface-controlled growth, with characteristic reaction textures remarkably similar to those seen in natural UHP rocks. We infer that the experimental reaction mechanism is identical to that in nature, a prerequisite for reliable extrapolation of the rate data. Growth rates obtained by direct measurement differ by up to two orders of magnitude from those estimated by fitting a rate equation to the transformation-time data. Fitting the rates to Turnbull's equation for growth therefore yields two distinct sets of parameters with similar activation energies (242 or 269 kJ/mol) but significantly different pre-exponential constants. Extrapolation based on either set of growth rates suggests that coesite should not be preserved on geologic time scales if it reaches the quartz stability field at temperatures above 375-400??C. The survival of coesite has previously been linked to its inclusion in strong phases, such as garnet, that can sustain a high internal pressure during decompression. Other factors that may play a crucial role in preservation are low fluid availability - possibly even less than that of our nominally "dry" experiments - and the development of transformation stress, which inhibits nucleation and growth. These issues are discussed in the context of our experiments as well as recent observations from natural rocks. ?? 1997 Elsevier Science B.V.

  5. Advanced analysis techniques for X-ray reflectivities. Theory and application

    International Nuclear Information System (INIS)

    Zimmermann, Klaus Martin


    The first part of this thesis adresses the phase problem in X-ray reflectivity. The analytical properties of the reflection coefficient imply that the phase is completely determined by the Hilbert transform of the logarithm of the modulus and the zeros in the upper half complex plane (UHP). To account in addition for interfacial roughness, a new formula for the Hilbert-phase is derived.In the following, the conditions for which the reflection coefficient has zeros in the UHP is discussed and the existing sufficient condition is extended to rough multi-layer systems. Procedures for locating these zeros are developed. The second part of this thesis introduces a new iterative inversion method for X-ray reflectivity. It expands the profile in a set of eigenfunctions, which are discrete approximations of the eigenfunction of the classical reconstruction problem of a compact supported function from its partially known Fourier-transform. In this work, piecewise constant functions, polygons and second-order B-splines are used to expand the density profile. The eigenvalue problems for the calculation of the above mentioned approximations are stated and solved. The formalism for the calculation of the reflection coefficient for these profiles is developed in dynamical and single-scattering theory. In the experimental part of this work iterative inverse schemes are applied to the analysis of X-ray reflectivity. Different sample systems are investigated: For two titanium-carbon samples tiny details at the Ti/C interface such as the formation of a thin TiC layer can be observed.The density profiles obtained from the reflectivities taken from nickel-carbon samples show the formation of SiC inside the Si sub strate. Finally, the new inversion scheme is applied to a series of reflectivities from a 700 AaSiGe film on a substrate.

  6. Advanced analysis techniques for X-ray reflectivities. Theory and application

    Energy Technology Data Exchange (ETDEWEB)

    Zimmermann, Klaus Martin


    The first part of this thesis adresses the phase problem in X-ray reflectivity. The analytical properties of the reflection coefficient imply that the phase is completely determined by the Hilbert transform of the logarithm of the modulus and the zeros in the upper half complex plane (UHP). To account in addition for interfacial roughness, a new formula for the Hilbert-phase is derived.In the following, the conditions for which the reflection coefficient has zeros in the UHP is discussed and the existing sufficient condition is extended to rough multi-layer systems. Procedures for locating these zeros are developed. The second part of this thesis introduces a new iterative inversion method for X-ray reflectivity. It expands the profile in a set of eigenfunctions, which are discrete approximations of the eigenfunction of the classical reconstruction problem of a compact supported function from its partially known Fourier-transform. In this work, piecewise constant functions, polygons and second-order B-splines are used to expand the density profile. The eigenvalue problems for the calculation of the above mentioned approximations are stated and solved. The formalism for the calculation of the reflection coefficient for these profiles is developed in dynamical and single-scattering theory. In the experimental part of this work iterative inverse schemes are applied to the analysis of X-ray reflectivity. Different sample systems are investigated: For two titanium-carbon samples tiny details at the Ti/C interface such as the formation of a thin TiC layer can be observed.The density profiles obtained from the reflectivities taken from nickel-carbon samples show the formation of SiC inside the Si sub strate. Finally, the new inversion scheme is applied to a series of reflectivities from a 700 AaSiGe film on a substrate.

  7. Structural styles and zircon ages of the South Tianshan accretionary complex, Atbashi Ridge, Kyrgyzstan: Insights for the anatomy of ocean plate stratigraphy and accretionary processes (United States)

    Sang, Miao; Xiao, Wenjiao; Orozbaev, Rustam; Bakirov, Apas; Sakiev, Kadyrbek; Pak, Nikolay; Ivleva, Elena; Zhou, Kefa; Ao, Songjian; Qiao, Qingqing; Zhang, Zhixin


    The anatomy of an ancient accretionary complex has a significance for a better understanding of the tectonic processes of accretionary orogens and complex because of its complicated compositions and strong deformation. With a thorough structural and geochronological study of a fossil accretionary complex in the Atbashi Ridge, South Tianshan (Kyrgyzstan), we analyze the structure and architecture of ocean plate stratigraphy in the western Central Asian Orogenic Belt. The architecture of the Atbashi accretionary complex is subdivisible into four lithotectonic assemblages, some of which are mélanges with "block-in-matrix" structure: (1) North Ophiolitic Mélange; (2) High-pressure (HP)/Ultra-high-pressure (UHP) Metamorphic Assemblage; (3) Coherent & Mélange Assemblage; and (4) South Ophiolitic Mélange. Relationships between main units are tectonic contacts presented by faults. The major structures and lithostratigraphy of these units are thrust-fold nappes, thrusted duplexes, and imbricated ocean plate stratigraphy. All these rock units are complicatedly stacked in 3-D with the HP/UHP rocks being obliquely southwestward extruded. Detrital zircon ages of meta-sediments provide robust constraints on their provenance from the Ili-Central Tianshan Arc. The isotopic ages of the youngest components of the four units are Late Permian, Early-Middle Triassic, Early Carboniferous, and Early Triassic, respectively. We present a new tectonic model of the South Tianshan; a general northward subduction polarity led to final closure of the South Tianshan Ocean in the End-Permian to Late Triassic. These results help to resolve the long-standing controversy regarding the subduction polarity and the timing of the final closure of the South Tianshan Ocean. Finally, our work sheds lights on the use of ocean plate stratigraphy in the analysis of the tectonic evolution of accretionary orogens.

  8. Estimation of Water Within the Lithospheric Mantle of Central Tibet from Petrological-Geophysical Investigations (United States)

    Vozar, J.; Fullea, J.; Jones, A. G.


    Investigations of the lithosphere and sub-lithospheric upper mantle by integrated petrological-geophysical modeling of magnetotelluric (MT) and seismic surface-wave data, which are differently sensitive to temperature and composition, allows us to reduce the uncertainties associated with modeling these two data sets independently, as commonly undertaken. We use selected INDEPTH MT data, which have appropriate dimensionality and large penetration depths, across central Tibet for 1D modeling. Our deep resistivity models from the data can be classified into two different and distinct groups: (i) the Lhasa Terrane and (ii) the Qiangtang Terrane. For the Lhasa Terrane group, the models show the existence of upper mantle conductive layer localized at depths of 200 km, whereas for the Qiangtang Terrane, this conductive layer is shallower at depths of 120 km. We perform the integrated geophysical-petrological modeling of the MT and surface-wave data using the software package LitMod. The program facilitates definition of realistic temperature and pressure distributions within the upper mantle for given thermal structure and oxide chemistry in the CFMAS system. This allows us to define a bulk geoelectric and seismic model of the upper mantle based on laboratory and xenolith data for the most relevant mantle minerals, and to compute synthetic geophysical observables. Our results suggest an 80-120 km-thick, dry lithosphere in the central part of the Qiangtang Terrane. In contrast, in the central Lhasa Terrane the predicted MT responses are too resistive for a dry lithosphere regardless its thickness; according to seismic and topography data the expected lithospheric thickness is about 200 km. The presence of small amounts of water significantly decreases the electrical resistivity of mantle rocks and is required to fit the MT responses. We test the hypothesis of small amounts of water (ppm scale) in the nominally anhydrous minerals of the lithospheric mantle. Such a small

  9. S-N profile of Receive function image across Qiangtang, Northern Tibet (United States)

    He, R.; Gao, R.; Deng, G.; Li, W.; Hou, H.; Lu, Z.; Xiong, X.


    Huge thicken Triassic and Jurassic sediments widely outcorp within Qiangtang, tens of oilstones outcorped within Qiangtang showed that Qiangtang have a good advantage in exploring oil and gas. So, the basement beneath Qiangtang and its structures have become the key for us to look for oil and gas accumulations. Within tectonic settings of Qiangtang, the center uplift of Qiangtang (abbr. CUQT) and its developments have become the great barrier to understand the basement and its structures within the basin. Because of complicated structure relief and blueschist and ophiolite outcorps within the CUQT, there was the paradox for lots of geologist to understand how the CUQT developed. One was that it formed under the extension environment. On the contrary, CUQT was ever paleo-Tethys suture zone, because CUQT had the belt of blueschists and ophiolite. So, different opinions to CUQT resulted in the different viewpoints in the basin beneath Qiangtang terrane. Surveying deep structure beneath the CUQT was the key to understand the basement under Qiangtang. In past two years, we have deployed 40 portable broadband seismic stations along E88°to across the whole Qiangtang from Bangong-Nujiang Suture, southern side of Qiangtang terrane, to northern margin of Qiangtang terrane. The temporary network collected a lot of farm waveform data, which is helpful to know about the more finest deep structure beneath the CUQT and its two sides basin. We used P-to-S receiver functions methods to get deep structure image beneath the profile. The preliminary results showed: (1) Within the crust, the velocity structure beneath southern Qiangtang basin is higher than beneath northern Qiangtang basin. (2) Sedimental layer within southern Qiangtang basin is thichen than within northern Qiangtang basin. Combined with other geophysical information, CUQT is an important lithosphere-level boundary fault belts, and southern Qiangtang basin have great difference with northern Qiangtang basin, in

  10. Transport process of Pu isotope in marginal seas of the western North Pacific Ocean

    Energy Technology Data Exchange (ETDEWEB)

    Yamada, Masatoshi [Department of Radiation Chemistry, Institute of Radiation Emergency Medicine, Hirosaki University, Hirosaki, 036-8564, Aomori (Japan); Zheng, Jian [Research Center for Radiation Protection, National Institute of Radiological Sciences, 4-9-1 Anagawa, Inage, 263-8555, Chiba (Japan)


    Significant quantities of Pu isotopes have been released into the marine environment as the result of atmospheric nuclear weapons testing. Most radionuclides globally dispersed in atmospheric nuclear weapons testing were released into the environment during the 1950's and 1960's. In the western North Pacific Ocean, the principal source can be further distinguished as two distinct sources of Pu: close-in tropospheric fallout from nuclear weapons testing at the Pacific Proving Grounds (PPG) in the Marshall Islands and global stratospheric fallout. Since the {sup 240}Pu/{sup 239}Pu atom ratio is characteristic for the Pu emission source, information on Pu isotopic signature is very useful to better understand the transport process in the oceans and to identify the sources of Pu. The mean atom ratio of {sup 240}Pu/{sup 239}Pu from the global stratospheric fallout is 0.180 ±0.014 based on soil sample data, whereas that from close-in tropospheric fallout from the PPG is 0.33 - 0.36. The {sup 240}Pu/{sup 239}Pu atom ratios in seawater samples collected in marginal seas of the western North Pacific Ocean will provide important and useful data for understanding the process controlling Pu transport and for distinguishing future Pu sources. The objectives of this study were to measure the {sup 239+240}Pu concentrations and {sup 240}Pu/{sup 239}Pu atom ratios in seawater from the Sea of Okhotsk, Japan Sea, South China Sea and Sulu Sea and to discuss the transport process of Pu. Large-volume seawater samples (250 L each) were collected from the surface to the bottom in marginal seas of the western North Pacific Ocean with acoustically triggered quadruple PVC sampling bottles during the R/V Hakuho-Maru cruise. The {sup 239}Pu and {sup 240}Pu concentrations and {sup 240}Pu/{sup 239}Pu atom ratios were measured with a double-focusing SF-ICP-MS, which was equipped with a guard electrode to eliminate secondary discharge in the plasma and to enhance overall sensitivity. In

  11. Mesoscale modeling of smoke transport from equatorial Southeast Asian Maritime Continent to the Philippines: First comparison of ensemble analysis with in situ observations (United States)

    Ge, Cui; Wang, Jun; Reid, Jeffrey S.; Posselt, Derek J.; Xian, Peng; Hyer, Edward


    Atmospheric transport of smoke from equatorial Southeast Asian Maritime Continent (Indonesia, Singapore, and Malaysia) to the Philippines was recently verified by the first-ever measurement of aerosol composition in the region of the Sulu Sea from a research vessel named Vasco. However, numerical modeling of such transport can have large uncertainties due to the lack of observations for parameterization schemes and for describing fire emission and meteorology in this region. These uncertainties are analyzed here, for the first time, with an ensemble of 24 Weather Research and Forecasting model with Chemistry (WRF-Chem) simulations. The ensemble reproduces the time series of observed surface nonsea-salt PM2.5 concentrations observed from the Vasco vessel during 17-30 September 2011 and overall agrees with satellite (Cloud-Aerosol Lidar and Infrared Pathfinder Satellite Observation (CALIPSO) and Moderate Resolution Imaging Spectroradiometer (MODIS)) and Aerosol Robotic Network (AERONET) data. The difference of meteorology between National Centers for Environmental Prediction (NCEP's) Final (FNL) and European Center for Medium range Weather Forecasting (ECMWF's) ERA renders the biggest spread in the ensemble (up to 20 μg m-3 or 200% in surface PM2.5), with FNL showing systematically superior results. The second biggest uncertainty is from fire emissions; the 2 day maximum Fire Locating and Modelling of Burning Emissions (FLAMBE) emission is superior than the instantaneous one. While Grell-Devenyi (G3) and Betts-Miller-Janjić cumulus schemes only produce a difference of 3 μg m-3 of surface PM2.5 over the Sulu Sea, the ensemble mean agrees best with Climate Prediction Center (CPC) MORPHing (CMORPH)'s spatial distribution of precipitation. Simulation with FNL-G3, 2 day maximum FLAMBE, and 800 m injection height outperforms other ensemble members. Finally, the global transport model (Navy Aerosol Analysis and Prediction System (NAAPS)) outperforms all WRF

  12. Surprising discovery of high-grade pelitic schist on Cavalli Seamount, offshore Northland

    International Nuclear Information System (INIS)

    Mortimer, N.; Walker, N.H.; Herzer, R.H.; Calvert, A.; Seward, D.


    Serendipity waits in the world's unexplored places. In March 1999, GNS's ONSIDE expedition to the South Fiji Basin made two dredge hauls on Cavalli seamount expecting to recover Miocene oceanic volcanic rocks. Instead dredge DIA recored 1 kg of 10 cm slickensided and chloritised schist pieces and dredge DIB, which was 1.1 km distant, 100 kg of well-foliated biotite schist, mainly in the form of two large subangular boulders. The presence of calsilicate bands initially suggested a correlation with Buller or Takaka Terranes, but whole rock chemical composition of the schist is more consistent with Murihiku, Waipapa or Pahau Terranes. U-Pb TIMS gheochronometry of individual detrital zircons indicates a maximum 170Ma depositional age for the schist protolith, thus clearly ruling out a Buller or Takaka correlation. Rb-Sr whole rock data suggest a young (Cenozoic?) metamorphic age. (author)

  13. Mesozoic to Cenozoic magmatic history of the Pamir (United States)

    Chapman, James B.; Scoggin, Shane H.; Kapp, Paul; Carrapa, Barbara; Ducea, Mihai N.; Worthington, James; Oimahmadov, Ilhomjon; Gadoev, Mustafo


    New geochronologic, geochemical, and isotopic data for Mesozoic to Cenozoic igneous rocks and detrital minerals from the Pamir Mountains help to distinguish major regional magmatic episodes and constrain the tectonic evolution of the Pamir orogenic system. After final accretion of the Central and South Pamir terranes during the Late Triassic to Early Jurassic, the Pamir was largely amagmatic until the emplacement of the intermediate (SiO2 > 60 wt.%), calc-alkaline, and isotopically evolved (-13 to -5 zircon εHf(t)) South Pamir batholith between 120-100 Ma, which is the most volumetrically significant magmatic complex in the Pamir and includes a high flux magmatic event at ∼105 Ma. The South Pamir batholith is interpreted as the northern (inboard) equivalent of the Cretaceous Karakoram batholith and the along-strike equivalent of an Early Cretaceous magmatic belt in the northern Lhasa terrane in Tibet. The northern Lhasa terrane is characterized by a similar high-flux event at ∼110 Ma. Migration of continental arc magmatism into the South Pamir terrane during the mid-Cretaceous is interpreted to reflect northward directed, low-angle to flat-slab subduction of the Neo-Tethyan oceanic lithosphere. Late Cretaceous magmatism (80-70 Ma) in the Pamir is scarce, but concentrated in the Central and northern South Pamir terranes where it is comparatively more mafic (SiO2 roll-back of the Neotethyan oceanic slab, which is consistent with similarly aged extension-related magmatism in the Karakoram terrane and Kohistan. There is an additional pulse of magmatism in the Pamir at 42-36 Ma that is geographically restricted (∼150 km diameter ellipsoidal area) and referred to as the Vanj magmatic complex. The Vanj complex comprises metaluminous, high-K calc-alkaline to shoshonitic monzonite, syenite, and granite that is adakitic (La/YbN = 13 to 57) with low Mg# (35-41). The Vanj complex displays a range of SiO2 (54-75 wt.%) and isotopic compositions (-7 to -3 εNd(i), 0.706 to

  14. Histoire de la dénudation dans le corridor du loch Ness (Écosse) : mouvements verticaux différentiels le long de la Great Glen Fault (United States)

    Jolivet, Marc


    The Great Glen Fault (GGF) is a major lithospheric strike-slip fault system that cuts across the Caledonian orogenic belt of Scotland. It separates the Northern Highlands terrane from the Grampian terrane. Movement history along the fault extends at least into the Early Palaeozoic. The low-temperature history of the Scottish Highlands covers a significant period from the Late Palaeozoic to the Present, but the magnitude of vertical movements that affected the GGF area during that time is still a matter of debate. Fission track analysis on detailed vertical profiles in the Ballachulish and Strontian complexes, as well as on a profile oriented northeastwards across the GGF, reveals distributed differential vertical movements along the fault during the Late Palaeozoic. The Mesozoic denudation is estimated at a maximum of 2 km before a more recent widespread exhumation event that started at around 40-25 Ma, leading to 1.6 to 2 km of erosion.

  15. Pluton emplacement and magmatic arc construction: A model from the Patagonian batholith (United States)

    Bruce, Robert; Nelson, Eric; Weaver, Stephen


    A model of batholithic construction in Andean arcs and its applicability to possibly similar environments in the past is described. Age and compositional data from the Patagonian batholith of southern Chile show a long history of magmatism in any given area (total age range is 15 to 157 Ma), but different regions appear to have different magmatic starting ages. Furthermore, mafic rocks seem to be the oldest components of any given region. An assembly line model involving semicontinuous magmatism and uplift was outlined, which has implications for other terranes: uplift rates will be proportional to observed ranges in age, and total uplift will be proportional to the age of the oldest pluton in any given area. It is suggested that misleading results would be obtained if only small areas of similar terranes in the Archean were available for study.

  16. Archaean wrench-fault tectonics in the Abitibi greenstone belt of Canada (United States)

    Hubert, C.


    A tectonic model is proposed in which the southern Abitibi belt formed in a series of rift basins which dissected an earlier formed volcanic arc. Comparisons can be made with Phanerozoic areas such as, the Hokuroko basin of Japan, the Taupo volcanic zone of new Zealand and the Sumatra and Nicaragua volcanic arcs. In addition the identification of the major E - W thrust shears make it possible to speculate that the southern Abitibi belt comprises a collage of blocks of terrane which have been accreted against a more stable continental margin or microcontinent. If this interpretation is correct analogies can be made with the SW margin of the U.S.A. in which recently formed blocks of volcanic terrane are being accreted against its western margin.

  17. The prospect of alien life in exotic forms on other worlds. (United States)

    Schulze-Makuch, Dirk; Irwin, Louis N


    The nature of life on Earth provides a singular example of carbon-based, water-borne, photosynthesis-driven biology. Within our understanding of chemistry and the physical laws governing the universe, however, lies the possibility that alien life could be based on different chemistries, solvents, and energy sources from the one example provided by Terran biology. In this paper, we review some of these possibilities. Silanes may be used as functional analogs to carbon molecules in environments very different from Earth; solvents other than water may be compatible for life-supporting processes, especially in cold environments, and a variety of energy sources may be utilized, some of which have no Terran analog. We provide a detailed discussion of two possible habitats for alien life which are generally not considered as such: the lower cloud level of the Venusian atmosphere and Titan's surface environment.

  18. Correlation of basement rocks from Waka Nui-1 and Awhitu-1, and the Jurassic regional geology of Zealandia

    International Nuclear Information System (INIS)

    Mortimer, N.; Raine, J.I.; Cook, R.A.


    Core and cuttings of sandstone and mudstone from Waka Nui-1, an offshore oil exploration well west of Northland, and from Awhitu-1, a water bore in western Auckland, add to the growing number of samples retrieved from otherwise inaccessible basement of the Zealandia continent. On the basis of pollen and spores, the sedimentary rocks at the bottom of Waka Nui-1 are dated as Early-Middle Jurassic, and rocks from Awhitu-1 are Late Jurassic. On the basis of age, sandstone petrology, and geographic position, a correlation of rocks in both wells with Murihiku Terrane is probable. In New Zealand, Jurassic sedimentary rocks have usually been interpreted in a tectonostratigraphic terrane context. An alternative way to look at the New Zealand Late Jurassic to Early Cretaceous sedimentary rocks is as potentially interconnected forearc, intra-arc, back-arc, and intracontinental basins that evolved adjacent to an active margin. (author). 47 refs., 6 figs., 3 tabs

  19. Global map of lithosphere thermal thickness on a 1 deg x 1 deg grid - digitally available

    DEFF Research Database (Denmark)

    Artemieva, Irina


    with no or low quality heat flow data. This analysis requires knowledge oflithosphere age globally.A compilation of tectono-thermal ages of lithospheric terranes on a 1 deg 1 deg grid forms the basis forthe statistical analysis. It shows that, statistically, lithospheric thermal thickness z (in km) depends......This presentation reports a 1 deg 1 deg global thermal model for the continental lithosphere (TC1). The modelis digitally available from the author’s web-site: for continental terranes of different ages (early Archean to present) are constrained by reliabledata...... on borehole heat flow measurements (Artemieva and Mooney, 2001), checked with the original publicationsfor data quality, and corrected for paleo-temperature effects where needed. These data are supplemented bycratonic geotherms based on xenolith data.Since heat flow measurements cover not more than half...

  20. C, Sr and Pb isotopic chemostratigraphy in precambrian carbonate sequences in the eastern transversal domain of the Borborema Province, northastern Brazil

    International Nuclear Information System (INIS)

    Santos, V. H.; Ferreira, V.P.; Sial, A.N; Babinski, M; Pimentel, M.M


    The Transversal Domain, in the Borborema Structural Province, northeastern Brazil, is characterized by a system of NE-trending, left-lateral, transcurrent mega-structure and dextral E-W trending fault zones (Jardim de Sa, 1994). This domain is formed by supracrustal metasedimentary and metavolcansedimentary sequences overlying a gneissic-migmatitic basement. Geological sequences of this domain exhibit distinct lithotectono-stratigraphy that characterize different terranes, separated by shear zones developed during the Cariris Velhos cycle (1.1-0.95 Ga), and that have been reworked during the Brasiliano orogen at the end of the Neoproterozoic (Brito Neves et al., 1995). The objective of this work is to show the results of C, Sr and Pb isotope studies performed in marble lens located near (and in both sides) the proposed boundary between two tectono-stratigraphic terranes (Alto Moxoto and Rio Capibaribe) in the Transversal Domain (au)

  1. Metal sources in Jurassic to miocene ore deposits of Ecuador

    International Nuclear Information System (INIS)

    Chiaradia, M.; Fontbote, L


    The Ecuadorian crust is a mosaic of NNE-SSW-trending terranes representing different geotectonic domains. These terranes, composed by oceanic and continental crust, were formed during the Triassic separation of the North and South American continents and were accreted to the Amazon craton during subduction of the Farallon/Nazca plate, from Early Cretaceous to Early Tertiary (Litherland et al., 1994). In the southwestern part of Ecuador, EW-striking crustal-scale faults, related to the Huancabamba deflection, mark the transition between the Central and Northern Andes. In this study we discuss more than 200 lead isotope compositions of ores as well as magmatic and metamorphic rocks of Ecuador. The interest of carrying out a large-scale isotope survey in the Northern Andes derives from a geotectonic evolution characterized by multi-accretionary episodes which is not recognized in the Central Andes (au)

  2. Phanerozoic tectonic evolution of the Circum-North Pacific (United States)

    Nokleberg, Warren J.; Parfenov, Leonid M.; Monger, James W.H.; Norton, Ian O.; Khanchuk, Alexander I.; Stone, David B.; Scotese, Christopher R.; Scholl, David W.; Fujita, Kazuya


    The Phanerozoic tectonic evolution of the Circum-North Pacific is recorded mainly in the orogenic collages of the Circum-North Pacific mountain belts that separate the North Pacific from the eastern part of the North Asian Craton and the western part of the North American Craton. These collages consist of tectonostratigraphic terranes that are composed of fragments of igneous arcs, accretionary-wedge and subduction-zone complexes, passive continental margins, and cratons; they are overlapped by continental-margin-arc and sedimentary-basin assemblages. The geologic history of the terranes and overlap assemblages is highly complex because of postaccretionary dismemberment and translation during strike-slip faulting that occurred subparallel to continental margins.We analyze the complex tectonics of this region by the following steps. (1) We assign tectonic environments for the orogenic collages from regional compilation and synthesis of stratigraphic and faunal data. The types of tectonic environments include cratonal, passive continental margin, metamorphosed continental margin, continental-margin arc, island arc, oceanic crust, seamount, ophiolite, accretionary wedge, subduction zone, turbidite basin, and metamorphic. (2) We make correlations between terranes. (3) We group coeval terranes into a single tectonic origin, for example, a single island arc or subduction zone. (4) We group igneous-arc and subduction- zone terranes, which are interpreted as being tectonically linked, into coeval, curvilinear arc/subduction-zone complexes. (5) We interpret the original positions of terranes, using geologic, faunal, and paleomagnetic data. (6) We construct the paths of tectonic migration. Six processes overlapping in time were responsible for most of the complexities of the collage of terranes and overlap assemblages around the Circum-North Pacific, as follows. (1) During the Late Proterozoic, Late Devonian, and Early Carboniferous, major periods of rifting occurred along

  3. Geochemistry of reduced gas related to serpentinization of the Zambales ophiolite, Philippines (United States)

    Abrajano, T.A.; Sturchio, N.C.; Kennedy, B.M.; Lyon, G.L.; Muehlenbachs, K.; Böhlke, J.K.


    Methane-hydrogen gas seeps with mantle-like C and noble gas isotopic characteristics issue from partially serpentinized ultramafic rocks in the Zambales ophiolite, Philippines. New measurements of noble gas and 14C isotope abundances, rock/mixed-volatile equilibrium calculations, and previous chemical and isotopic data suggest that these reduced gases are products of periodotite hydration. The gas seeps are produced in rock-dominated zones of serpentinization, and similar gases may be ubiquitous in ultramafic terranes undergoing serpentinization.

  4. Detailed Configuration of the Underthrusting Indian Lithosphere Beneath Western Tibet Revealed by Receiver Function Images (United States)

    Xu, Qiang; Zhao, Junmeng; Yuan, Xiaohui; Liu, Hongbing; Pei, Shunping


    We analyze the teleseismic waveform data recorded by 42 temporary stations from the Y2 and ANTILOPE-1 arrays using the P and S receiver function techniques to investigate the lithospheric structure beneath western Tibet. The Moho is reliably identified as a prominent feature at depths of 55-82 km in the stacked traces and in depth migrated images. It has a concave shape and reaches the deepest location at about 80 km north of the Indus-Yarlung suture (IYS). An intracrustal discontinuity is observed at 55 km depth below the southern Lhasa terrane, which could represent the upper border of the eclogitized underthrusting Indian lower crust. Underthrusting of the Indian crust has been widely observed beneath the Lhasa terrane and correlates well with the Bouguer gravity low, suggesting that the gravity anomalies in the Lhasa terrane are induced by topography of the Moho. At 20 km depth, a midcrustal low-velocity zone (LVZ) is observed beneath the Tethyan Himalaya and southern Lhasa terrane, suggesting a layer of partial melts that decouples the thrust/fold deformation of the upper crust from the shortening and underthrusting in the lower crust. The Sp conversions at the lithosphere-asthenosphere boundary (LAB) can be recognized at depths of 130-200 km, showing that the Indian lithospheric mantle is underthrusting with a ramp-flat shape beneath southern Tibet and probably is detached from the lower crust immediately under the IYS. Our observations reconstruct the configuration of the underthrusting Indian lithosphere and indicate significant along strike variations.

  5. Petrogenesis of the NE Gondwanan uppermost Ediacaran-Lower Cretaceous siliciclastic sequence of Jordan: Provenance, tectonic, and climatic implications (United States)

    Amireh, Belal S.


    Detrital framework modes of the NE Gondwanan uppermost Ediacaran-Lower Cretaceous siliciclastic sequence of Jordan are determined employing the routine polarized light microscope. The lower part of this sequence constitutes a segment of the vast lower Paleozoic siliciclastic sheet flanking the northern Gondwana margin that was deposited over a regional unconformity truncating the outskirts of the East African orogen in the aftermath of the Neoproterozoic amalgamation of Gondwana. The research aims to evaluate the factors governing the detrital light mineral composition of this sandstone. The provenance terranes of the Arabian craton controlled by plate tectonics appear to be the primary factor in most of the formations, which could be either directly inferred employing Dickinson's compositional triangles or implied utilizing the petrographic data achieved and the available tectonic and geological data. The Arabian-Nubian Shield constitutes invariably the craton interior or the transitional provenance terrane within the NE Gondwana continental block that consistently supplied sandy detritus through northward-flowing braided rivers to all the lower Paleozoic formations. On the other hand, the Lower Cretaceous Series received siliciclastic debris, through braided-meandering rivers having same northward dispersal direction, additionally from the lower Paleozoic and lower-middle Mesozoic platform strata in the Arabian Craton. The formations making about 50% of the siliciclastic sequence represent a success for Dickinson's plate tectonics-provenance approach in attributing the detrital framework components primarily to the plate tectonic setting of the provenance terranes. However, even under this success, the varying effects of the other secondary sedimentological and paleoclimatological factors are important and could be crucial. The inapplicability of this approach to infer the appropriate provenance terranes of the remaining formations could be ascribed either to the

  6. Evidence for a western extension of the Angaran phytogeographic province in the Early Permian

    Energy Technology Data Exchange (ETDEWEB)

    Sunderlin, David [Department of the Geophysical Sciences, University of Chicago, Chicago, IL, 60637 (United States)


    A newly described Early Permian fossil plant assemblage in the Mt. Dall conglomerate in the Farewell terrane (Alaska Range, USA) is analyzed from a paleobiogeographic perspective. These data constitute the youngest paleontological dataset yet discovered in this terrane, represent the terrane's only predominantly terrestrial fossil assemblage, and are the only plant macrofossil remains of Early Permian age within a > 1500 km radius today. A suite of multivariate statistical analyses comparing the Mt. Dall paleoflora to similar age (Asselian-Artinskian) collections from the Angaran, Euramerican, and Cathaysian Permian phytogeographic provinces reveals that the Mt. Dall paleoflora has a paleobiogeographic affinity with Sub-Angaran plant fossil assemblages collected from Mongolia and the Primorye region of southeastern Russia. The paleoflora has dual importance in the construction and testing of hypotheses for which there are geographically and temporally few controls. First, these data may be used in association with other faunal and floral remains to test models of the assembly of Alaska, which seek, in part, an understanding of the paleogeographic and lithological origins of accreted terranes. That the Mt. Dall paleoflora indicates mixed Eurasia-North America paleobiogeographic affinity among individual taxa and plots in multivariate space with mid-latitude assemblages on northern Pangea may suggest deposition in that latitudinal belt. Second, contrary to the well-sampled fossil plant-bearing Permo-Carboniferous of the paleotropics and the northeastern temperate Pangean regions (Angaraland), terrestrial biome structure and vegetation type of northwestern Pangea are poorly known. This lack of understanding is due to the paucity of paleofloral collections from this region in this time period and the paleogeographic uncertainty of their position along the ancient active margin of Laurentia. The Mt. Dall paleoflora's phytogeographic affinity to paleobotanical

  7. Mineral parageneses, regional architecture, and tectonic evolution of Franciscan metagraywackes, Cape Mendocino-Garberville-Covelo 30' x 60' quadrangles, northwest California (United States)

    Ernst, W.G.; McLaughlin, Robert J.


    The Franciscan Complex is a classic subduction-zone assemblage. In northwest California, it comprises a stack of west vergent thrust sheets: westernmost Eastern Belt outliers; Central Belt mélange; Coastal Belt Yager terrane; Coastal Belt Coastal terrane; Coastal Belt King Range/False Cape terranes. We collected samples and determined P-T conditions of recrystallization for 88 medium-fine-grained metasandstones to assess their subduction-exhumation histories and assembly of the host allochthons. Feebly recrystallized Yager, Coastal, and King Range strata retain clear detrital features. Scattered neoblastic prehnite occurs in several Coastal terrane metasandstones; traces of possible pumpellyite are present in three Yager metaclastic rocks. Pumpellyite ± lawsonite ± aragonite-bearing Central Belt metasandstones are moderately deformed and reconstituted. Intensely contorted, thoroughly recrystallized Eastern Belt affinity quartzose metagraywackes contain lawsonite + jadeitic pyroxene ± aragonite ± glaucophane. We microprobed neoblastic phases in 23 rocks, documenting mineral parageneses that constrain the tectonic accretion and metamorphic P-T evolution of these sheets. Quasi-stable mineral assemblages typify Eastern Belt metasandstones, but mm-sized domains in the Central and Coastal belt rocks failed to achieve chemical equilibrium. Eastern Belt slabs rose from subduction depths approaching 25–30 km, whereas structurally lower Central Belt mélanges returned from ∼15–18 km. Coastal Belt assemblages suggest burial depths less than 5–8 km. Eastern and Central belt allochthons sequentially decoupled from the downgoing oceanic lithosphere and ascended into the accretionary margin; K-feldspar-rich Coastal Belt rocks were stranded along the continental edge without undergoing appreciable subduction, probably during Paleogene unroofing of the older, deeply subducted units of the Franciscan Complex in east-vergent crustal wedges.

  8. The Middlesex Fells Volcanic Complex: A Revised Tectonic Model based on Geochronology, Geochemistry, and Field Data (United States)

    Hampton, R.


    The Boston Bay area is composed of several terranes originating on the paleocontinent of Avalonia, an arc terrane that accreted onto the continent of Laurentia during the Devonian. Included in these terranes is the Middlesex Fells Volcanic Complex, a bimodal complex composed of both intrusive and extrusive igneous rocks. Initial studies suggested that this volcanic complex formed during a rift event as the Avalonian continent separated from its parent continent 700-900 Ma. New geochemical and geochronological data and field relationships observed in this study establishes a new tectonic model. U-Pb laser ablation zircon data on four samples from different units within the complex reveal that the complex erupted 600 Ma. ICP-MS geochemical analysis of the metabasalt member of the complex yield a trace element signature enriched in Rb, Pb, and Sr and depleted in Th, indicating a subduction component to the melt and interpreted as an eruption into a back-arc basin. The felsic units similarly have an arc related signature when plotted on trace element spider diagrams and tectonic discrimination diagrams. Combined with the field relationships, including an erosional unconformity, stratigraphic and intrusional relationships and large faults from episodic extension events, this data suggests that the Middlesex Fells Volcanic Complex was erupted as part of the arc-sequence of Avalonia and as part of the formation of a back-arc basin well after Avalonia separated from its parent continent. This model presents a significantly younger eruption scenario for the Middlesex Fells Volcanics than previously hypothesized and may be used to study and compare to other volcanics from Avalon terranes in localities such as Newfoundland and the greater Boston area.

  9. The Black Mountain tectonic zone--a reactivated northeast-trending crustal shear zone in the Yukon-Tanana Upland of east-central Alaska: Chapter D in Recent U.S. Geological Survey studies in the Tintina Gold Province, Alaska, United States, and Yukon, Canada--results of a 5-year project (United States)

    O'Neill, J. Michael; Day, Warren C.; Alienikoff, John N.; Saltus, Richard W.; Gough, Larry P.; Day, Warren C.


    The Black Mountain tectonic zone in the YukonTanana terrane of east-central Alaska is a belt of diverse northeast-trending geologic features that can been traced across Black Mountain in the southeast corner of the Big Delta 1°×3° degree quadrangle. Geologic mapping in the larger scale B1 quadrangle of the Big Delta quadrangle, in which Black Mountain is the principal physiographic feature, has revealed a continuous zone of normal and left-lateral strikeslip high-angle faults and shear zones, some of which have late Tertiary to Quaternary displacement histories. The tectonic zone includes complexly intruded wall rocks and intermingled apophyses of the contiguous mid-Cretaceous Goodpaster and Mount Harper granodioritic plutons, mafic to intermediate composite dike swarms, precious metal mineralization, early Tertiary volcanic activity and Quaternary fault scarps. These structures define a zone as much as 6 to 13 kilometers (km) wide and more than 40 km long that can be traced diagonally across the B1 quadrangle into the adjacent Eagle 1°×3° quadrangle to the east. Recurrent activity along the tectonic zone, from at least mid-Cretaceous to Quaternary, suggests the presence of a buried, fundamental tectonic feature beneath the zone that has influenced the tectonic development of this part of the Yukon-Tanana terrane. The tectonic zone, centered on Black Mountain, lies directly above a profound northeast-trending aeromagnetic anomaly between the Denali and Tintina fault systems. The anomaly separates moderate to strongly magnetic terrane on the northwest from a huge, weakly magnetic terrane on the southeast. The tectonic zone is parallel to the similarly oriented left-lateral, strike-slip Shaw Creek fault zone 85 km to the west.

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

    Energy Technology Data Exchange (ETDEWEB)

    Maryak, M.


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

  11. Provenance of Permian-Triassic Gondwana Sequence Units Accreted to the Banda Arc: Constraints from U/Pb and Hf Analysis of Zircons and Igneous Geochemistry (United States)

    Flores, J. A.; Spencer, C. J.; Harris, R. A.; Hoiland, C.


    Analysis of zircons from Australian affinity Permo-Triassic units of the Timor region yield age distributions with large peaks at 230-400 Ma and 1750-1900 Ma (n=435). Similar zircon age peaks are also found in rocks from NE Australia and the eastern Cimmerian block. It is likely that these terranes, which are now widely separated, were once part of the northern edge of Gondwana near what is now the NW margin of Australia. The Cimmerian Block was removed from Gondwana during Early Permian rifting and initiation of the Neo-Tethys Ocean. Hf analysis of zircon from the Aileu Complex in Timor and Kisar shows bimodal (juvenial and evolved) magmatism in the Gondwana Sequence of NW Australia at ~300 Ma. The magmatic event produced basalt with rift valley and ocean floor geochemical affinities, and rhyolite. Similar rock types and isotopic signatures are also found in Permo-Triassic igneous units throughout the Cimmerian continental block. The part of the Cimmerian Block with zircon distributions most like the Gondwana Sequence of NW Australia is the terranes of northern Tibet and Malaysia. The large 1750-1900 Ma zircon peak is much more wide spread, and appears in terranes from Baoshan (SW China) to Borneo. The Permo-Triassic rocks of the Timor region fill syn-rift intracratonic basins that successfully rifted in the Jurassic to form the NW margin of Australia. This passive continental margin first entered the Sunda Trench in the Timor region at around 8 Ma causing the Permo-Triassic rocks to accrete to the edge of the Asian Plate and emerge as a series of mountainous islands in the young collision zone. Eventually, the Australian continental margin will collide with the southern edge of the Asian plate and these Gondwana terranes will rejoin. However, it may be difficult to reconstruct the various ventures of they made over the past 300 Ma.

  12. Crustal structure across the NE Tibetan Plateau and Ordos Block from the joint inversion of receiver functions and Rayleigh-wave dispersions (United States)

    Li, Yonghua; Wang, Xingchen; Zhang, Ruiqing; Wu, Qingju; Ding, Zhifeng


    We investigated the crustal structure at 34 stations using the H-κ stacking method and jointly inverting receiver functions with Rayleigh-wave phase and group velocities. These seismic stations are distributed along a profile extending across the Songpan-Ganzi Terrane, Qinling-Qilian terranes and southwestern Ordos Basin. Our results reveal the variation in crustal thickness across this profile. We found thick crust beneath the Songpan-Ganzi Terrane (47-59 km) that decreases to 45-47 km in the west Qinling and Qilian terranes, and reaches its local minimum beneath the southwestern Ordos Block (43-51 km) at an average crustal thickness of 46.7 ± 2.5 km. A low-velocity zone in the upper crust was found beneath most of the stations in NE Tibet, which may be indicative of partial melt or a weak detachment layer. Our observations of low to moderate Vp/Vs (1.67-1.79) represent a felsic to intermediate crustal composition. The shear velocity models estimated from joint inversions also reveal substantial lateral variations in velocity beneath the profile, which is mainly reflected in the lower crustal velocities. For the Ordos Block, the average shear wave velocities below 20 km are 3.8 km/s, indicating an intermediate-to-felsic lower crust. The thick NE Tibet crust is characterized by slow shear wave velocities (3.3-3.6 km/s) below 20 km and lacks high-velocity material (Vs ≥ 4.0 km/s) in the lower crust, which may be attributed to mafic lower crustal delamination or/and the thickening of the upper and middle crust.

  13. The role of farfield tectonic stress in oceanic intraplate deformation, Gulf of Alaska (United States)

    Reece, Robert S.; Gulick, Sean P. S.; Christesen, Gail L.; Horton, Brian K.; VanAvendonk, Harm J.; Barth, Ginger


    An integration of geophysical data from the Pacific Plate reveals plate bending anomalies, massive intraplate shearing and deformation, and a lack of oceanic crust magnetic lineaments in different regions across the Gulf of Alaska. We argue that farfield stress from the Yakutat Terrane collision with North America is the major driver for these unusual features. Similar plate motion vectors indicate that the Pacific plate and Yakutat Terrane are largely coupled along their boundary, the Transition Fault, with minimal translation. Our study shows that the Pacific Plate subduction angle shallows toward the Yakutat Terrane and supports the theory that the Pacific Plate and Yakutat Terranemaintain coupling along the subducted region of the Transition Fault. We argue that the outboard transfer of collisional stress to the Pacific Plate could have resulted in significant strain in the NE corner of the Pacific Plate, which created pathways for igneous sill formation just above the Pacific Plate crust in the Surveyor Fan. A shift in Pacific Plate motion during the late Miocene altered the Yakutat collision with North America, changing the stress transfer regime and potentially terminating associated strain in the NE corner of the Pacific Plate. The collision further intensified as the thickest portion of the Yakutat Terrane began to subduct during the Pleistocene, possibly providing the impetus for the creation of the Gulf of Alaska Shear Zone, a>200 km zone of intraplate strike-slip faults that extend from the Transition Fault out into the Pacific Plate. This study highlights the importance of farfield stress from complex tectonic regimes in consideration of large-scale oceanic intraplate deformation.

  14. Polyphase deformation history and strain analyses of the post-amalgamation depositional basins in the Arabian-Nubian Shield: Evidence from Fatima, Ablah and Hammamat Basins (United States)

    Hamimi, Zakaria; El-Fakharani, Abdelhamid; Abdeen, Mamdouh M.


    Post-amalgamation depositional basins Asir tectonic terrane. The Hammamat PADB is investigated in Wadi Umm Gheig, Wadi Allaqi and Wadi Hodein in the Egyptian Eastern Desert tectonic terrane. It is supposed that the Fatima is a basin controlled by dextral transcurrent shearing occurred along the NE-oriented Wadi Fatima Shear Zone and the Ablah is a strike-slip pull-apart basin, and both basins were believed to be deposited during and soon after the Nabitah Orogeny (680-640 Ma) that marked suturing of the Afif terrane with the oceanic ANS terranes to the west. They were affected by at least three Neoproterozoic deformation phases and show geometric and kinematic relationships between folding and thrusting. The Hammamat PADB is a fault-bounded basin affected by a NW-SE- to NNW-SSE-oriented shortening phase just after the deposition of the molasse sediments, proved by NW- to NNW-verging folds and SE- to SSE-dipping thrusts that were refolded and thrusted in the same direction. The shortening phase in the Hammamat was followed by a transpressional wrenching phase related to the Najd Shear System, which resulted in the formation of NW-SE sinistral-slip faults associated with positive flower structures that comprise NE-verging folds and SW-dipping thrusts. Strain results in the three studied PADBs are nearly consistent, indicating that they are correlated and underwent the same history of deformation. The ANOVA test indicates that there is no significant difference for the Vector mean and ISYM for the three PADBs. There is only a significant difference for the Harmonic mean (P-value < 0.05). A Post Hoc test (Shefee) shows that the difference exists between the Allaqi and the Umm Gheig's deformed polymictic conglomeratic pebbles of the Hammamat PADB.

  15. Accessory minerals and subduction zone metasomatism: a geochemical comparison of two mélanges (Washington and California, U.S.A.) (United States)

    Sorensen, Sorena S.; Grossman, Jeffrey N.


    The ability of a subducted slab or subducted sediment to contribute many incompatible trace elements to arc source regions may depend on the stabilities of accessory minerals within these rocks, which can only be studied indirectly. In contrast, the role of accessory minerals in lower-T and -P metasomatic processes within paleo-subduction zones can be studied directly in subduction-zone metamorphic terranes.

  16. Are oceanic plateaus sites of komatiite formation? (United States)

    Storey, M.; Mahoney, J. J.; Kroenke, L. W.; Saunders, A. D.


    During Cretaceous and Tertiary time a series of oceanic terranes were accreted onto the Pacific continental margin of Colombia. The island of Gorgona is thought to represent part of the most recent, early Eocene, terrane-forming event. Gorgona is remarkable for the occurrence of komatiites of middle Cretaceous age, having MgO contents up to 24%. The geochemistry of spatially and temporally associated tholeiites suggests that Gorgona is an obducted fragment of the oceanic Caribbean Plateau, postulated by Duncan and Hargraves (1984) to have formed at 100 to 75 Ma over the Galapagos hotspot. Further examples of high-MgO oceanic lavas that may represent fragments of the Caribbean Plateau occur in allochthonous terranes on the island of Curaçao in the Netherlands Antilles and in the Romeral zone ophiolites in the southwestern Colombian Andes. These and other examples suggest that the formation of high-MgO liquids may be a feature of oceanic-plateau settings. The association of Phanerozoic komatiites with oceanic plateaus, coupled with thermal considerations, provides a plausible analogue for the origin of some komatiite-tholeiite sequences in Archean greenstone belts.

  17. Geochronological and mineralogical constraints on depth of emplacement and ascencion rates of epidote-bearing magmas from northeastern Brazil (United States)

    Sial, Alcides N.; Vasconcelos, Paulo M.; Ferreira, Valderez P.; Pessoa, Ricardo R.; Brasilino, Roberta G.; Morais Neto, João M.


    Calc-alkalic to high-K calc-alkalic granitoid plutons in the Borborema province, northeastern Brazil, have been studied to constrain depth of emplacement by mineralogical and geological methods and to estimate upward magma transport rate based on partial dissolution of magmatic epidote. Laser-probe incremental heating 40Ar/ 39Ar dating of biotite and hornblende single crystals from the Neoproterozoic Tavares and Brejinho high-K calc-alkalic magmatic epidote (mEp)-bearing plutons reveals age differences of around 60 M.y. between these two minerals in each of these two intrusions. These data suggest solidification at relatively great depth followed by prolonged cooling interval between the closure temperatures of biotite and hornblende. Al-in-hornblende barometry indicates that hornblende in several mEp-bearing plutons in the Transversal Domain of the Borborema province solidified at 5 to 7 kbar, whereas in the Seridó and Macururé terranes, solidification pressures range from 3 to 4 kbar. Partial dissolution of epidote indicates very rapid upward transport. Partial corrosion occurred during 15-35 years (Cachoerinha-Salgueiro terrane), 10-30 years (Alto Pajeú), 15 years (Seridó), and 10 years (Macururé) corresponding to upward transport rates of 450-1300, 650-1050, 1200, and 1800 m/year respectively in these four terranes. Rapid upward magma migration in most cases was probably facilitated by diking simultaneous with regional shearing.

  18. Observation of the lunar surface by GRS in KAGUYA (SELENE). To solve mystery of moon and manned landing

    International Nuclear Information System (INIS)

    Hasebe, Nobuyuki; Kobayashi, Shingo


    The researches, resources and environment of the moon are reported. The main results such as the magma ocean hypothesis by the Apollo program, the lunar map by Clementine probe and the concentration of Th in the moon by Lunar Prospector probe are explained. B.L. Jolliff et al. proposed the moon consisted of three areas such as the Procellarum KREEP Terrane (PKT), South-Pole Aitken Terrane (SPAT) and Feldspathic Highland Terrane (FHT). The radiations on the lunar surface contain the galactic cosmic ray, solar particle event, second particles produced by interaction between the high energy particles and the materials on the lunar surface, and natural radioactivity from U, Th and K. The gamma ray spectrum on the lunar surface observed by Kaguya gamma ray spectrometer (KGRS) showed the very sharp spectrum of O, Mg, Al, Si, Ca, K, Ti, Fe, Th and U. The distribution of Th in PKT, SPAT and FHT was shown. The outline of KGRS, the energy resolutions of many kinds of gamma ray spectrometers, and the gamma ray energies of main elements are illustrated. (S.Y.)

  19. U-Pb and Hf isotope analysis of detrital zircons from Mesozoic strata of the Gravina belt, southeast Alaska (United States)

    Yokelson, Intan; Gehrels, George E.; Pecha, Mark; Giesler, Dominique; White, Chelsi; McClelland, William C.


    The Gravina belt consists of Upper Jurassic through Lower Cretaceous marine clastic strata and mafic-intermediate volcanic rocks that occur along the western flank of the Coast Mountains in southeast Alaska and coastal British Columbia. This report presents U-Pb ages and Hf isotope determinations of detrital zircons that have been recovered from samples collected from various stratigraphic levels and from along the length of the belt. The results support previous interpretations that strata in the western portion of the Gravina belt accumulated along the inboard margin of the Alexander-Wrangellia terrane and in a back-arc position with respect to the western Coast Mountains batholith. Our results are also consistent with previous suggestions that eastern strata accumulated along the western margin of the inboard Stikine, Yukon-Tanana, and Taku terranes and in a fore-arc position with respect to the eastern Coast Mountains batholith. The history of juxtaposition of western and eastern assemblages is obscured by subsequent plutonism, deformation, and metamorphism within the Coast Mountains orogen, but may have occurred along an Early Cretaceous sinistral transform system. Our results are inconsistent with models in which an east-facing subduction zone existed along the inboard margin of the Alexander-Wrangellia terrane during Late Jurassic-Early Cretaceous time.

  20. Comparison through fission-track analysis of portions of Australia and Antarctica adjacent prior to continental drift

    International Nuclear Information System (INIS)

    Stump, E.; Fitzgerald, P.G.


    Australia and Antarctica have been reconstructed by the matching of three terranes in western Victoria with three terranes in northern Victoria Land. Apparent fission-track ages from granitic rocks of these matched regions are compared. In western Victoria, Australia, data reflect a history of slow cooling following intrusion in early to middle Paleozoic time. In northern Victoria Land, Antarctica, a complex history of cooling and uplift is indicated, with uplift of the present-day mountains commencing approximately 50 Ma. Fission tracks in apatites from most samples from northern Victoria Land were completely re-set to zero by the thermal effects of Jurassic tholeiitic magmatism. Apatite in three samples however, predate the Jurassic and were only partially re-set by this event. Apparent sphene fission-track ages indicate that the three terranes in northern Victoria Land have shared a common thermal history since the Devonian. With the exception of one small area in western Victoria, neither western Victoria nor northern Victoria Land data show a clear influence of rifting and breakup in the late Cretaceous. Overall, the data indicate that once the breakup of Australia and Antarctica had occurred, their thermal and tectonic histories evolved independently along differing paths. (author)

  1. The Cambrian cavalcades in the Cuchilla Dionisio sub ground. Uruguay

    International Nuclear Information System (INIS)

    Bossi, J.


    Most tratadistes consider that Sierra Ballena shear zone (SBSZ) is the western limit of an all octon block after the paper of Boss i and Gauche r (2004) showing a detailed geological map. The same method was applied to sporulation block in the Ne of Treinta y Tres city. It was obtained a 1/100.000 geological map with photo geology and 140 field data in an area of 3500 k m2. This document allowed to discover two kinds of mega - faults put in action at the same time (about 525 Ma): a mega shear zone N30E80E with proto - to ultramylonites similar to SBSZ and a regional thrust fault with vergence to NNW. The thrust fault has different features according to the affected type of rocks. At La Micaela, the mica schists are thrust ed by gneisses and migmatites. To the N W the gneisses became firstly sharply laminated and then, horizontal ultramylonites. Both kind of faulting produced at the same time may not be explained by an orthogonal collision and instead of it, is a naturalist proof of tangential collision and alcoholisation nature of the crustal block. In order to easily understand the new proposal it is necessary to change Paso del Dragón fm by Micaela fm, Cuchilla Dionisio Terrane by Treinta y Tres; Punta del Este Terrane by Punta del Este sub - terrane

  2. Basement geology of Taranaki and Wanganui basins, New Zealand

    International Nuclear Information System (INIS)

    Mortimer, N.; Tulloch, A.J.; Ireland, T.R.


    We present a revised interpretation of the basement geology beneath Late Cretaceous to Cenozoic Taranaki and Wanganui basins of central New Zealand, based on new petrographic, geochemical, and geochronological data from 30 oil exploration wells. Recently published structural and magnetic interpretations of the area assist in the interpolation and extrapolation of geological boundaries. Torlesse and Waipapa terranes have been identified in Wanganui Basin, and Murihiku Terrane in eastern Taranaki Basin, but Maitai and Brook Street terrane rocks have not been recognised. Separation Point Suite, Karamea Suite, and Median Tectonic Zone igneous rocks are all identified on the basis of characteristic petrography, geochemistry, and/or age. SHRIMP U-Pb zircon measurements on igneous samples from western Taranaki wells do not give precise ages but do provide useful constraints: Motueka-1 granite is latest Devonian - earliest Carboniferous; Tangaroa-1 and Toropuihi-1 are Carboniferous; and Surville-1 is Cretaceous (cf. Separation Point Suite). Our interpretation of sub-basin geology is compatible with previously observed onland relationships in the North and South Islands. (author). 47 refs., 6 figs

  3. A Comparative Analysis of Seismological and Gravimetric Crustal Thicknesses below the Andean Region with Flat Subduction of the Nazca Plate

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    Mario E. Gimenez


    Full Text Available A gravimetric study was carried out in a region of the Central Andean Range between 28∘ and 32∘ south latitudes and from 72∘ and 66∘ west longitudes. The seismological and gravimetrical Moho models were compared in a sector which coincides with the seismological stations of the CHARGE project. The comparison reveals discrepancies between the gravity Moho depths and those obtained from seismological investigations (CHARGE project, the latter giving deeper values than those resulting from the gravimetric inversion. These discrepancies are attenuated when the positive gravimetric effect of the Nazca plate is considered. Nonetheless, a small residuum of about 5 km remains beneath the Cuyania terrane region, to the east of the main Andean chain. This residuum could be gravimetrically justified if the existence of a high density or eclogitized portion of the lower crust is considered. This result differed from the interpretations from Project “CHARGE” which revealed that the entire inferior crust extending from the Precordillera to the occidental “Sierras Pampeanas” could be “eclogitized”. In this same sector, we calculated the effective elastic thickness (Te of the crust. These results indicated an anomalous value of Te = 30 km below the Cuyania terrane. This is further conclusive evidence of the fact that the Cuyania terrane is allochthonous, for which also geological evidences exist.

  4. Correlation of Crustal Structures and Seismicity Patterns in Northern Appalachians (United States)

    Yang, X.; Gao, H.


    The earthquake distributions in northern Appalachians are bounded by major geologically-defined terrane boundaries. There is a distinct seismic gap within Taconic Belt between the Western Quebec Seismic Zone (WQSZ) to the west and the seismically active Ganderia terrane to the east. It is not clear, however, what crustal structures control the characteristics of earthquake clustering in this region. Here we present a newly constructed crustal shear velocity model for the northern Appalachians using Rayleigh wave data extracted from ambient noises. Our tomographic model reveals strongly heterogeneous seismic structures in the crust. We observe multiple NW-dipping patches of high-velocity anomalies in the upper crust beneath the southeastern WQSZ. The upper crust shear velocities in the Ganderia and Avalonia region are generally lower than those beneath the WQSZ. The middle crust has relatively lower velocities in the study area. The earthquakes in the study area are constrained within the upper crust. Most of the earthquake hypocenters within the WQSZ are concentrated along the NW-dipping boundaries separating the high-velocity anomalies. In contrast, most of the earthquake hypocenters in the Ganderia and Avalonia region are diffusely distributed without clear vertical lineaments. The orientations of maximum compressive stresses change from W-E in the Ganderia and Avalonia region to SW-NE in the WQSZ. The contrasts in seismicity, velocity, and stress field across the Taconic Belt indicate that the Taconic Belt terrane may act as a seismically inactive buffer zone in northern Appalachians.

  5. The Atuba complex: a paleoproterozoic belt intensively reworked in the neoproterozoic era

    International Nuclear Information System (INIS)

    Siga Junior, O.; Basei, M.A.S.; Machiavelli, A.; Harara, O.M.; Reis Neto, J.M.


    Studies of terranes between the northern Ribeira and southern Dom Feliciano Belts allow the characterization of three geotectonic domains with different evolutions: the Luis Alves, Curitiba and Paranagua terranes. The Atuba complex occurs in Curitiba Domain, which has a northwestern limit with metasediments of the Acungui and Setuva Groups and a southwestern limit with the granulitic gneisses of the Luis Alves domains. The contacts are expressive shear zones. The predominant rocks of the Curitiba Domain are banded, migmatitic gneisses in amphibolite grade with biotite-amphibolite gneissic mesosomes and tonalitic/graodioritic leucosomes, here called the Atuba complex. The migmatites are Paleoproterozoic (2.000±200 Ma) and remigmatized in Neoproterozoic (600±20 Ma). During the latter period temperatures reached more than 500 0 C. The structural pattern indicated shear-controlled tectonics with an important lateral component, and low-angle, south-southeastward transport direction. The terranes of the Atuba complex appear to represent deep-level rocks which were migmatized, granitized and then added to the border of the Luis Alves Microplate during the Neoproterozoic. This late Neoproterozoic tectonic scheme which continued to the Cambro-Ordoviciano seems to be the result of larger scale processes of continental agglutination which ended with the formation of western Gondwanaland. (author). 17 figs., 2 tabs

  6. The Atuba complex: a paleoproterozoic belt intensively reworked in the neoproterozoic era; O complexo Atuba: um cinturao paleoproterozoico intensamente retrabalhado no neoproterozoico

    Energy Technology Data Exchange (ETDEWEB)

    Siga Junior, O.; Basei, M.A.S.; Machiavelli, A.; Harara, O.M. [Sao Paulo Univ., SP (Brazil). Inst. de Geociencias; Reis Neto, J.M. [Parana Univ., Curitiba, PR (Brazil). Dept. de Geologia


    Studies of terranes between the northern Ribeira and southern Dom Feliciano Belts allow the characterization of three geotectonic domains with different evolutions: the Luis Alves, Curitiba and Paranagua terranes. The Atuba complex occurs in Curitiba Domain, which has a northwestern limit with metasediments of the Acungui and Setuva Groups and a southwestern limit with the granulitic gneisses of the Luis Alves domains. The contacts are expressive shear zones. The predominant rocks of the Curitiba Domain are banded, migmatitic gneisses in amphibolite grade with biotite-amphibolite gneissic mesosomes and tonalitic/graodioritic leucosomes, here called the Atuba complex. The migmatites are Paleoproterozoic (2.000{+-}200 Ma) and remigmatized in Neoproterozoic (600{+-}20 Ma). During the latter period temperatures reached more than 500{sup 0} C. The structural pattern indicated shear-controlled tectonics with an important lateral component, and low-angle, south-southeastward transport direction. The terranes of the Atuba complex appear to represent deep-level rocks which were migmatized, granitized and then added to the border of the Luis Alves Microplate during the Neoproterozoic. This late Neoproterozoic tectonic scheme which continued to the Cambro-Ordoviciano seems to be the result of larger scale processes of continental agglutination which ended with the formation of western Gondwanaland. (author). 17 figs., 2 tabs.

  7. Neoproterozoic collision tectonics in the Mozambique Belt of East Africa: evidence from the Uluguru mountains, Tanzania (United States)

    Muhongo, Sospeter


    The fault-bounded Proterozoic metamorphic terranes lying to the E of the Tanzanian craton make up the Usagara tectonic domain and are a part of the transcontinental Mozambique Orogenic Belt (MB). The lithotectonic units in the MB of the East Africa consist of comparable rock assembles which underwent the same complex deformational history and are thought to represent large thrust sheets or nappes. Their shelf- and fore-deep terranes border the Tanzanian craton and make up the foreland terranes of the Pan-African Mozambique Belt. Granulite-gneiss nappes are ubiquitous in the orogen. Granulite-facies metamorphism, associated with recumbent folds, was due to crustal thickening, which took place during the collision between Gondwana fragments. Isotope data suggest a collision (and concomitant granulite-facies metamorphism) age of between 700 and 550 Ma. The orientations of planar and linear fabrics in the granulite-facies rocks of the Uluguru mountains are used to infer the relative crustal block motions during this collisional event. This Pan-African collisional event was characterized by NW-directed movements, oblique to the N-S trend of the orogen, and involved SE-directed backthrusting. The Ubendian Belt of Tanzania and the Aswa Shear Zone in Uganda and Kenya, which both bifurcate around the Tanzania craton, accommodated the tectonically thickened crust, created by the collisional event, through NW-SE sinistral strike-slip movements.

  8. Using SHRIMP zircon dating to unravel tectonothermal events in arc environments. The early Palaeozoic arc of NW Iberia revisited (United States)

    Abati, J.; Castineiras, P.G.; Arenas, R.; Fernandez-Suarez, J.; Barreiro, J.G.; Wooden, J.L.


    Dating of zircon cores and rims from granulites developed in a shear zone provides insights into the complex relationship between magmatism and metamorphism in the deep roots of arc environments. The granulites belong to the uppermost allochthonous terrane of the NW Iberian Massif, which forms part of a Cambro-Ordovician magmatic arc developed in the peri-Gondwanan realm. The obtained zircon ages confirm that voluminous calc-alkaline magmatism peaked around 500Ma and was shortly followed by granulite facies metamorphism accompanied by deformation at c. 480Ma, giving a time framework for crustal heating, regional metamorphism, deformation and partial melting, the main processes that control the tectonothermal evolution of arc systems. Traces of this arc can be discontinuously followed in different massifs throughout the European Variscan Belt, and we propose that the uppermost allochthonous units of the NW Iberian Massif, together with the related terranes in Europe, constitute an independent and coherent terrane that drifted away from northern Gondwana prior to the Variscan collisional orogenesis. ?? 2007 Blackwell Publishing Ltd.

  9. From a collage of microplates to stable continental crust - an example from Precambrian Europe (United States)

    Korja, Annakaisa


    Svecofennian orogen (2.0-1.7 Ga) comprises the oldest undispersed orogenic belt on Baltica and Eurasian plate. Svecofennian orogenic belt evolved from a series of short-lived terrane accretions around Baltica's Archean nucleus during the formation of the Precambrian Nuna supercontinent. Geological and geophysical datasets indicate W-SW growth of Baltica with NE-ward dipping subduction zones. The data suggest a long-lived retreating subduction system in the southwestern parts whereas in the northern and central parts the northeasterly transport of continental fragments or microplates towards the continental nucleus is also documented. The geotectonic environment resembles that of the early stages of the Alpine-Himalayan or Indonesian orogenic system, in which dispersed continental fragments, arcs and microplates have been attached to the Eurasian plate margin. Thus the Svecofennian orogeny can be viewed as proxy for the initial stages of an internal orogenic system. Svecofennian orogeny is a Paleoproterozoic analogue of an evolved orogenic system where terrane accretion is followed by lateral spreading or collapse induced by change in the plate architecture. The exposed parts are composed of granitoid intrusions as well as highly deformed supracrustal units. Supracrustal rocks have been metamorphosed in LP-HT conditions in either paleo-lower-upper crust or paleo-upper-middle crust. Large scale seismic reflection profiles (BABEL and FIRE) across Baltica image the crust as a collage of terranes suggesting that the bedrock has been formed and thickened in sequential accretions. The profiles also image three fold layering of the thickened crust (>55 km) to transect old terrane boundaries, suggesting that the over-thickened bedrock structures have been rearranged in post-collisional spreading and/or collapse processes. The middle crust displays typical large scale flow structures: herringbone and anticlinal ramps, rooted onto large scale listric surfaces also suggestive

  10. The Thermal Structure and Strength of Cratons and their Margins (United States)

    Jaupart, C. P.; Mareschal, J. C.


    The large cratons of today are made of younger terranes that wrap around older cores. Deformation due to accretion did not proceed in homogeneous fashion and was concentrated in the younger belts. This is illustrated clearly in the Archean Superior Province, Canada. In this area, one observes little imbrication of accreted crust and craton core, in contrast to the laterally extensive thrusting that has affected the younger terranes to the South. The boundary between the craton core and accreted belts is a nearly vertical interface delineated by steeply dipping electrical and seismic anomalies extending to the base of the lithosphere. These steeply dipping structures have been interpreted as relicts of the subduction that drove accretion. By contrast, the sub-crustal subduction remnant that is imaged beneath younger terranes to the south shows up as a moderately dipping (≈30°) structure. These observations suggest a stiff craton surrounded by weaker belts. This strength contrast may have affected later events, such as the Keweenawan rifing, which propagated northward through the accreted terranes but stopped short of impinging the craton core. In the Superior Province, crustal heat production is much higher in the accreted terranes than in the craton core, implying higher temperatures and lower mechanical strength. Such a remarkable dichotomy also exists in South Africa, where the Limpopo and Namaqua belts are characterized by higher heat flux and crustal heat production than the adjacent Archean Kaapvaal and Zimbabwe cratons. The generality of this cannot be assessed on the basis of heat flow and heat production data which are scarce in most other cratons. These cratons, however, are characterized by post-orogenic high temperature metamorphism which is best explained by high crustal heat production. This is true, for example, for the Jimperding metamorphic belt at the edge of the Yilgarn craton, Western Australia. Thus, cratons appear to be surrounded, and

  11. Syn- and Post-Accretionary Structures in the Neoproterozoic Central Allaqi-Heiani Suture Zone, Southeastern Egypt (United States)

    Abdeen, M. M.; Abdelghaffar, A. A.


    The Allaqi-Heiani suture (AHS) is the western part of the main Allaqi-Heiani-Gerf-Onib-Sol Hamed-Yanbu suture and represents one of the Neoproterozoic, arc-arc sutures in the Arabian-Nubian Shield (ANS). It separates the ca. 750 Ma South Eastern Desert terrane in the north from the ca. 830-720 Ma Gabgaba terrane in the south. The AHS is a deformed belt of ophiolitic rocks, syn-tectonic granitoids and metasediments. The central AHS zone is divided into three structural domains. The western domain (Ι) is characterized by NNE low thrusts and SSW-vergent folds. The central domain (ΙΙ) includes upright tight to isoclinal NNW-SSE oriented folds and transpressional faults. The eastern domain (ΙΙΙ) shows NNW-SSE oriented open folds. Structural analysis indicates that the area has a poly-phase deformation history involving at least two events. Event D1 was an N-S to NNE-SSW regional shortening generating the SSW-verging folds and the NNE dipping thrusts. Event D2 was an ENE-WSW shortening producing NNW-SSE oriented folds in the central and eastern parts of the study area and reactivating older thrusts with oblique-slip reverse fault movement. The tectonic evolution of the area involves two episodes of collision: an early collision between the South Eastern Desert terrane and the Gabgaba terrane along the AHS after the consumption of a basin floored by oceanic crust above a north-dipping subduction zone; and a later collision between East- and West-Gondwanas at ca. 750-650 Ma, leading to the closure of the Mozambique Ocean. This collision deformed the AHS along N-S trending shortening zones and produced NW-SE and NE-SW oriented sinistral and dextral transpressional faults, respectively. The early collision episode is related to the terrane accretion during the early Pan-African orogen, while the later phase is related to a late Pan-African or Najd orogen.

  12. Differential preservation in the geologic record of intraoceanic arc sedimentary and tectonic processes (United States)

    Draut, Amy; Clift, Peter D.


    Records of ancient intraoceanic arc activity, now preserved in continental suture zones, are commonly used to reconstruct paleogeography and plate motion, and to understand how continental crust is formed, recycled, and maintained through time. However, interpreting tectonic and sedimentary records from ancient terranes after arc–continent collision is complicated by preferential preservation of evidence for some arc processes and loss of evidence for others. In this synthesis we examine what is lost, and what is preserved, in the translation from modern processes to the ancient record of intraoceanic arcs. Composition of accreted arc terranes differs as a function of arc–continent collision geometry. ‘Forward-facing’ collision can accrete an oceanic arc on to either a passive or an active continental margin, with the arc facing the continent and colliding trench- and forearc-side first. In a ‘backward-facing’ collision, involving two subduction zones with similar polarity, the arc collides backarc-first with an active continental margin. The preservation of evidence for contemporary sedimentary and tectonic arc processes in the geologic record depends greatly on how well the various parts of the arc survive collision and orogeny in each case. Preservation of arc terranes likely is biased towards those that were in a state of tectonic accretion for tens of millions of years before collision, rather than tectonic erosion. The prevalence of tectonic erosion in modern intraoceanic arcs implies that valuable records of arc processes are commonly destroyed even before the arc collides with a continent. Arc systems are most likely to undergo tectonic accretion shortly before forward-facing collision with a continent, and thus most forearc and accretionary-prism material in ancient arc terranes likely is temporally biased toward the final stages of arc activity, when sediment flux to the trench was greatest and tectonic accretion prevailed. Collision geometry

  13. Cryptic genetic diversity in the mottled rabbitfish Siganus fuscescens with mitochondrial introgression at a contact zone in the South China Sea. (United States)

    Ravago-Gotanco, Rachel; de la Cruz, Talna Lorena; Pante, Ma Josefa; Borsa, Philippe


    The taxonomy of the mottled rabbitfish Siganus fuscescens species complex has long been challenging. In this study, we analyzed microsatellite genotypes, mitochondrial lineages, and morphometric data from 373 S. fuscescens individuals sampled from the northern Philippines and Hong Kong (South China Sea, Philippine Sea and Sulu Sea basins), to examine putative species boundaries in samples comprising three co-occurring mitochondrial lineages previously reported to characterize S. fuscescens (Clade A and Clade B) or S. canaliculatus (Clade C). We report the existence of two cryptic species within S. fuscescens in the northeast region of the South China Sea and northern Philippine Sea, supported by genetic and morphological differences. Individual-based assignment methods recovered concordant groupings of individuals into two nuclear genotype clusters (Cluster 1, Cluster 2) with (1) limited gene flow, if any, between them (FST = 0.241; P South China Sea. Mitonuclear discordance due to introgression obscures phylogenetic relationships for recently-diverged lineages, and cautions against the use of mitochondrial markers alone for species identification within the mottled rabbitfish species complex in the South China Sea region.

  14. Slow Warming of the Northern South China Sea during the Last Deglaciation

    Directory of Open Access Journals (Sweden)

    Tomoya Shintani


    Full Text Available We have generated a record of alkenone sea surface temperatures (SSTs during the last 28000 years from Core MD97-2146 for the northern South China Sea (SCS. The SST record showed a typical pattern for change in the northern SCS SST. The SST during the LGM was ~25 C, this decreased to ~24 C to 17 ka, increased to ~25.5 C to 14.5 ka, decreased again to ~24.5 C to 11.8 ka, increased gradually to ~27 C to 6 ka, and then increased more gradually to reach ~27.5 C at present. The SST difference ( SSTNSCS = SSTMD97-2146 - SSTMD97-2141 between Cores MD97-2146 (the northern SCS; this study and MD97-2141 (the Sulu Sea; Rosenthal et al. 2003 was used to characterize the SST changes in the northern SCS relative to changes in the adjacent WTPregion. The SSTNSCS decreased from 21 to 11.8 ka and increased after 11.8 ka, indicating slower warming of the northern SCS during the last deglaciation than that of the adjacent western tropical Pacific region.We infer that the slow warming of the northern SCS was principally a result of stronger winter monsoon during the last deglaciation and early Holocene. In addition, the cool water inflow through the Taiwan Strait after 13 ka and the warm water inflow through the Sunda Shelf after 11 ka could influence the SST in the northern SCS.


    Directory of Open Access Journals (Sweden)

    Duto Nugroho


    Full Text Available North Kalimantan Province, notably Tarakan City marine waters, is one of the important fishing ground in boundary area among Sulu Sulawesi Marine Ecoregion. It produces approximately 100 mt/annum of Bombay duck (Harpadon nehereus with valued of US$ 750,000. The sustainability of this fishery is a crucially concern given the following: substantial economic contribution, significant dependence of small-scale fishers on this species for their livelihoods. The fishing intensities considerable and growing threats to their habitats. To evaluate the vulnerability of individual species to over exploitation, the spawning potential ratio (SPR approach applied to describe the status of its existing fisheries. This approach provides the ability to determine fishing mortality as reference points to enhance its sustainability. The objective of this study is to understand this fish biomass resilience to harvesting. The calculated SPR based on the value of estimated length of first capture or Lc at 208 mm is equivalent to the SPR of 28%. With a base line of stocks are generally thought to risk recruitment declining when SPR <20%, recent finding indicated that the existing fishery can be generally described as nearly fully exploited. In recognition of this sector’s has an ecological importance and socio-economic significance, the sustainable development of Bombay duck fisheries should be initiated through developing local fishery committee to provide a their local fishery management plan.

  16. Kabartma Tozları ve Unlu Mamullerde Kullanımları

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    Halef Dizlek


    Full Text Available Kabartma tozları unlu mamullerin üretiminde yaygın bir kullanım alanına sahiptir. Özellikle kek, bisküvi gibi yumuşak buğday unu ile üretilen ürünlerin karakteristik iç yapılarının oluşmasında kullanılırlar. Genellikle bileşimlerinde tek alkali bileşen (sodyum bikarbonat, bir ya da daha fazla sayıda asidik tuz ve dolgu maddesi (mısır nişastası bulunur. Sulu ortamda bikarbonatın asitle reaksiyona girmesi sonucu oluşan CO2 gazı ürünün kabarmasını sağlar, bunun yanı sıra hazmını kolaylaştırır ve albenisini arttırır.

  17. Identifying finite-time coherent sets from limited quantities of Lagrangian data

    Energy Technology Data Exchange (ETDEWEB)

    Williams, Matthew O. [Program in Applied and Computational Mathematics, Princeton University, New Jersey 08544 (United States); Rypina, Irina I. [Department of Physical Oceanography, Woods Hole Oceanographic Institute, Massachusetts 02543 (United States); Rowley, Clarence W. [Department of Mechanical and Aerospace Engineering, Princeton University, New Jersey 08544 (United States)


    A data-driven procedure for identifying the dominant transport barriers in a time-varying flow from limited quantities of Lagrangian data is presented. Our approach partitions state space into coherent pairs, which are sets of initial conditions chosen to minimize the number of trajectories that “leak” from one set to the other under the influence of a stochastic flow field during a pre-specified interval in time. In practice, this partition is computed by solving an optimization problem to obtain a pair of functions whose signs determine set membership. From prior experience with synthetic, “data rich” test problems, and conceptually related methods based on approximations of the Perron-Frobenius operator, we observe that the functions of interest typically appear to be smooth. We exploit this property by using the basis sets associated with spectral or “mesh-free” methods, and as a result, our approach has the potential to more accurately approximate these functions given a fixed amount of data. In practice, this could enable better approximations of the coherent pairs in problems with relatively limited quantities of Lagrangian data, which is usually the case with experimental geophysical data. We apply this method to three examples of increasing complexity: The first is the double gyre, the second is the Bickley Jet, and the third is data from numerically simulated drifters in the Sulu Sea.

  18. Tanikala at Talinhaga: Ang Manunulat na Bilanggong Politikal (Chain and Metaphor: The Writer-Political Prisoner

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    Rommel B. Rodriguez


    Full Text Available In the discourse of Philippine national history, the ethnolinguistic groups in the marginalized islands of Visayas and Mindanao play an important role in the construction of the nation. For instance, the parang sabil of the Tausug may be considered as a form of resistance against the colonizers vis-à-vis the 1896 revolution of the Katipuneros in Luzon. The term parang sabil comes from parang, meaning war or sword, and sabil, meaning killed in the way of God. It is a traditional Tausug practice by which the Tausugs defend their religion Islam against the threatening infidels. This paper will make use of an ethnic narrative song of the Tausug of Sulu entitled “The Parang Sabil of Abdulla and Putli’ Isara,” as a tool to understand how the group fought based on their cultural beliefs, from the armed struggle against a country who treats them as outsiders up to the battles invoked in the name of religion.

  19. Ang Himig at Dalumat ng Pagtutol sa “Parang Sabil nina Abdulla at Putli’ Isara” ng mga Tausug (The Melody and Concept of Resistance in “The Parang Sabil of Abdulla and Putli’ Isara” of the Tausug

    Directory of Open Access Journals (Sweden)

    Jay Jomar F. Quintos


    Full Text Available In the discourse of Philippine national history, the ethnolinguistic groups in the marginalized islands of Visayas and Mindanao play an important role in the construction of the nation. For instance, the parang sabil of the Tausug may be considered as a form of resistance against the colonizers vis-à-vis the 1896 revolution of the Katipuneros in Luzon. The term parang sabil comes from parang, meaning war or sword, and sabil, meaning killed in the way of God. It is a traditional Tausug practice by which the Tausugs defend their religion Islam against the threatening infidels. This paper will make use of an ethnic narrative song of the Tausug of Sulu entitled “The Parang Sabil of Abdulla and Putli’ Isara,” as a tool to understand how the group fought based on their cultural beliefs, from the armed struggle against a country who treats them as outsiders up to the battles invoked in the name of religion.

  20. Identifying finite-time coherent sets from limited quantities of Lagrangian data

    International Nuclear Information System (INIS)

    Williams, Matthew O.; Rypina, Irina I.; Rowley, Clarence W.


    A data-driven procedure for identifying the dominant transport barriers in a time-varying flow from limited quantities of Lagrangian data is presented. Our approach partitions state space into coherent pairs, which are sets of initial conditions chosen to minimize the number of trajectories that “leak” from one set to the other under the influence of a stochastic flow field during a pre-specified interval in time. In practice, this partition is computed by solving an optimization problem to obtain a pair of functions whose signs determine set membership. From prior experience with synthetic, “data rich” test problems, and conceptually related methods based on approximations of the Perron-Frobenius operator, we observe that the functions of interest typically appear to be smooth. We exploit this property by using the basis sets associated with spectral or “mesh-free” methods, and as a result, our approach has the potential to more accurately approximate these functions given a fixed amount of data. In practice, this could enable better approximations of the coherent pairs in problems with relatively limited quantities of Lagrangian data, which is usually the case with experimental geophysical data. We apply this method to three examples of increasing complexity: The first is the double gyre, the second is the Bickley Jet, and the third is data from numerically simulated drifters in the Sulu Sea

  1. Origin of marginal basins of the NW Pacific and their plate tectonic reconstructions (United States)

    Xu, Junyuan; Ben-Avraham, Zvi; Kelty, Tom; Yu, Ho-Shing


    Geometry of basins can indicate their tectonic origin whether they are small or large. The basins of Bohai Gulf, South China Sea, East China Sea, Japan Sea, Andaman Sea, Okhotsk Sea and Bering Sea have typical geometry of dextral pull-apart. The Java, Makassar, Celebes and Sulu Seas basins together with grabens in Borneo also comprise a local dextral, transform-margin type basin system similar to the central and southern parts of the Shanxi Basin in geometry. The overall configuration of the Philippine Sea resembles a typical sinistral transpressional "pop-up" structure. These marginal basins except the Philippine Sea basin generally have similar (or compatible) rift history in the Cenozoic, but there do be some differences in the rifting history between major basins or their sub-basins due to local differences in tectonic settings. Rifting kinematics of each of these marginal basins can be explained by dextral pull-apart or transtension. These marginal basins except the