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Zircon U-Pb-Hf constraints from Gongga Shan granites on young crustal melting in eastern Tibet

Geoscience Frontiers 2019年第3期10卷 885-894页

作者： Nick M.W.Roberts Michael P.Searle NERC Isotope Geosciences Laboratory British Geological Survey Environment Science Centre Department of Earth sciences University of Oxford

The Gongga Shan batholith is a complex granitoid batholith on the eastern margin of the Tibetan Plateau with a long history of magmatism spanning from the Triassic to the Pliocene. Late Miocene-Pliocene units are the youngest exposed crustal melts within the entire Asian plate of the Tibetan ***, we present in-situ zircon Hf isotope constraints on their magmatic source, to aid the understanding of how these young melts were formed and how they were exhumed to the surface. Hf isotope signatures of Eocene to Pliocene zircon rims(ε_(Hf)(t)=-4 to +4), interpreted to have grown during localised crustal melting, are indicative of melting of a Neoproterozoic source region, equivalent to the nearby exposed Kangding Complex. Therefore, we suggest that Neoproterozoic crust underlies this region of the Songpan-Ganze terrane, and sourced the intrusive granites that form the Gongga Shan batholith. Localised young melting of Neoproterozoic lower or middle crust requires localised melt-fertile lithologies. We suggest that such melts may be equivalent to seismic and magnetotelluric low-velocity and high-conductivity zones or "bright spots" imaged across much of the Tibetan Plateau. The lack of widespread exposed melts this age is due either to the lack of melt-fertile rocks in the middle crust, the very low erosion level of the Tibetan plateau, or to a lack of mechanism for exhuming such melts. For Gongga Shan, where some melting is younger than nearby thermochronological ages of low temperature cooling, the exact process and timing of exhumation remains enigmatic, but their location away from the Xianshuihe fault precludes the fault acting as a conduit for the young melts. We suggest that underthrusting of dry granulites of the lower Indian crust(Archaean shield) this far northeast is a plausible mechanism to explain the uplift and exhumation of the eastern Tibetan Plateau.

关键词： Tibet Himalaya Hf isotopes Zircon Crustal melting

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An explosive seismic sounding profile across the transition zone between west Kunlun Mts. and Tarim Basin

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science China Earth sciences 2001年第7期44卷 666-672页

作者：李秋生高锐卢德源李敬卫范景义张之英刘文李英康闫全人李德兴 1. Lithosphere Research Center Chinese Academy of Geological Science 100037 Beijing China 2. Chinese Academy of geological science No. 562 Institute 101601 Sanhe China

The explosive seismic sounding profile across the transition zone from the west Kunlun Mts. to the Tarim Basin revealed the complex deep structure formed by continent-continent collision on the northern margin of the Tibetan Plateau. The profile shows that the attitude of the Moho is in agreement with that of the crystalline basement in the Tarim Basin and the whole crust dips as a thick slate southwards with an angle from 5° to 7°. Meanwhile, the Moho depth increases from 40 km to 57 km within a distance of 150 km in the southern Tarim region, depicting the subduction of the crust of this region towards the west Kunlun Mts. The crust of the northern slope of the west Kunlun Mts. shows an evident compressed and shortened feature, that is, the basement is uplifted, the interface dips northwards and the Moho rises abruptly to become flat, so that the lower crust is as thick as 20 km.

关键词： explosive seismic sounding Tarim Basin west Kunlun Mts crust structure Moho interface

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The Changhsingian Foraminiferal Fauna of the Meishan D Section, Zhejiang, China, and their Ecostratigraphic Implications

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Acta Geologica Sinica(English Edition) 2018年第4期92卷 1299-1323页

作者： KE Xue LUO Liang WEI Yi KOU Xiaohu ZHANG Zongyan HE Weihong institute of geological Survey China University of Geosciences China geological Survey Chengdu Center Safety Engineering College North China Institute of Science & Technology China geological Survey Wuhan Center School of Earth sciences China University of Geosciences

Samples were collected continuously and systematically from Beds 2 to 30 of the Meishan D section, and nearly 4,000 foraminiferal specimens were recognized. In total, 72 species （partially including undetermined species and conformis species） in 34 genera of foraminifers were identified. Twelve foraminiferal community zones were established from Beds 2 to 27 based on the abundance, dominance, diversity, and equitability of the foraminiferal fauna and a functional morphological analysis of the dominant and characteristic species. The habitat type indicated by each community zone and the sedimentary features were used to determine the paleo-water depths and the relative changes in sea level. We generated curves of both the habitat type and the hydrodynamic conditions, which together indicate the relative changes in the paleo-water depth and the substrate features in the studied area during the Changhsingian. This study discusses the possible relationship between the foraminiferal community zones and the sea-level changes based on a statistical analysis of the foraminiferal community zones.

关键词： foraminifera Habitat type Changhsingian ecostratigraphy Meishan D section

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Possible Water and Ice on the Moon Revealed by Discovery of a Congeliturbated Fan

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Acta Geologica Sinica(English Edition) 2016年第4期90卷 1535-1536页

作者： HAN Tonglin YU Changqing CHEN Peng LIN Jingxing institute of Geology Chinese Academy of Geological Science Geophysics College Chengdu University of Technology

The nature of the Moon＇s surface has always been controversial. American scientists first suggested that there has been water and ice on the Moon （Watson et al., 1961）, a hypothesis supported by some but not other researchers （Compiling Committee, 2006; Ouyang, 2005; Wang, 2010）. So whether there has been or is any water on the Moon or not, is a matter of heated debate.

关键词： Possible Water and Ice on the Moon Revealed by Discovery of a Congeliturbated Fan

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A New Oviraptorid Dinosaur (Theropoda: Oviraptorosauria) from the Late Cretaceous of Jiangxi Province, Southern China

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Acta Geologica Sinica(English Edition) 2013年第4期87卷 899-904页

作者： WEI Xuefang PU Hanyong XU Li LIU Di Lü Junchang institute of Geology Chinese Academy of Geological Sciences Henan geological Museum

A new oviraptorid dinosaur Jiangxisaurus ganzhouensis gen. et sp. nov., is erected based on a partial skeleton from the Upper Cretaceous Nanxiong Formation of Ganzhou City, Jiangxi Province. The new taxon differs from other oviraptorids in the weakly downturned rostrum of the lower jaw, much-elongated mandible with a height-to-length ratio being about 20% and the length ratio of radius to humerus of about 0.70. This species not only adds a new member to oviraptorid dinosaurs, but also provides more information about oviraptorid paleogeographical distribution in southern China.

关键词： Oviraptoridae Jiangxisaurus Nanxiong Formation Upper Cretaceous Ganzhou Basin,Jiangxi Province

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Seismic Activity and Fuzzy Comprehensive Evaluation of Crustal Stability in the Beijing Region

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Acta Geologica Sinica(English Edition) 1994年第1期68卷 1-13页

作者： Huang Qinghua, Ma Yinsheng, institute of Geomechanics, C hinese Academy of geological science, Beijingand Song Xinchu Seismological Bureau of Zhejiang Province, Hangzhou, Zhejiang institute of Geomechanics Chinese Academy of Geological Science Beijing China

This paper discusses the seismic activity in Beijing M unicipality and its adjacent areas (which are referred to as the Beijing region in the paper). By using fuzzy mathematics, the factors controlling regional crustal stability are transformed into fuzzy information and then a model of fuzzy diagnosis is established. A fuzzy comprehensive evaluation of regional crustal stability in the Beijing region is made according to the seismic and geological conditions of the region.

关键词： fuzzy mathematics regional stability Beijing

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Neoproterozoic Volcanic Rocks in the Southern Quruqtagh of Northwest China:Geochemistry,Zircon Geochronology and Tectonic Implications

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Acta Geologica Sinica(English Edition) 2013年第1期87卷 118-130页

作者： ZHANG Yingli WANG Zongqi YAN Zhen WANG Tao institute of Mineral Resources Chinese Academy of Geological Sciences institute of Geology Chinese Academy of Geological Sciences

The Early Neoproterozoic Beiyixi Formation volcanic rocks of the southern Quruqtagh comprise mainly of a suite of tholeiitic basalts, alkaline andesites, and calc-alkaline rhyolites. The rhyolites are characterized by variably fractionated enrichment in light rare earth elements （LREE） and fiat in heavy rare earth elements （HREE）, and strongly negative Eu anomalies. Compared to the rhyolites, the andesites also exhibit enrichment in LREE and flat HREE （chondrite-normalized values of La/Yb,and La/Sm are 13.30-41.09, 3.18-6.89 respectively）. Their rare earth element patterns display minor negative Eu anomalies. Both of them exhibit coherent patterns with strongly to moderately negative anomalies of Nb, Zr, Ti, and Hf on spider diagrams. Two rhyolite and one andesite magmatic zircons with defined oscillatory zoning yielded weighted mean 206pb/23Su ages of 743 ± 7 Ma, 741±2 Ma, and 7274 Ma. These ages are interpreted to represent the timing of volcanic eruptions. According to geochemistry and rock type, these volcanic rocks formed within a continental island-arc environment following subduction of the oceanic crust during the Early Neoproterozoic period.

关键词： Quruqtagh Beiyixi Formation volcanic rocks geochemistry zircon geochronology,tectonic setting

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Granular titanite from the Roter Kamm crater in Namibia:Product of regional metamorphism,not meteorite impact

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Geoscience Frontiers 2022年第3期13卷 156-163页

作者： Aaron J.Cavosie Christopher J.Spencer Noreen Evans Kai Rankenburg Robert J.Thomas Paul H.Macey Space science and Technology centre and The institute for Geoscience Research School of Earth and Planetary ScienceCurtin UniversityPerthWA 6102Australia Dept.of geological sciences and geological Engineering Queen’s UniversityOntarioCanada John de Laeter centre Curtin UniversityPerthWA 6102Australia Council for Geoscience BellvilleWestern CapeSouth Africa

Accessory minerals with so-called granular texture have risen in importance as geochronological tools for U-Pb dating of meteorite impact events. Grain-scale recrystallization, typically triggered by a combination of high-strain deformation and post-impact heating, can create a polycrystalline microstructure consisting of neoblasts that expel radiogenic Pb, which are thus ideal for isotopic dating. While granular domains in zircon and monazite from shocked rocks have been demonstrated to preserve impact ages,few U-Pb dating studies have been conducted on granular microstructures in titanite(CaTiSiO;). Here we report the occurrence of granular-textured titanite from ~2020 Ma granite basement rock exposed in the rim of the 4–5 Ma Roter Kamm impact structure in Namibia. Orientation mapping reveals two microstructurally distinct titanite populations: one consisting of strained/deformed grains, and the other consisting of grains that comprise aggregates of strain-free neoblasts. In situ U-Pb geochronology on 37 grains shows that most grains from both titanite populations yield indistinguishable U-Pb dates of ca.1025 Ma, consistent with the observed microstructures forming during the Mesoproterozoic Namaqua Orogeny. Only four grains preserved older age domains, recording ca. 1875 Ma Paleoproterozoic metamorphism. Two significant observations emerge:(1) none of the analyzed titanite grains yield the 2020 Ma igneous crystallization age previously established from zircon in the same sample, and(2) no age-resetting was detected that could be attributed to the 4 to 5 Ma Roter Kamm impact *** the similarity of the neoblastic microstructure to minerals from other sites with an established impact provenance, the granular texture and near-complete Pb-loss in titanite from Roter Kamm granite instead records a Paleo-to Mesoproterozoic polymetamorphic history, rather than Miocene age shockrelated processes. These results highlight the critical importance of grain-scale cont

关键词： Namibia Roter Kamm Titanite EBSD Geochronology

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Lithosphere architecture characterized by crust±mantle decoupling controls the formation of orogenic gold deposits

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National science Review 2023年第3期10卷 77-91页

作者： Zengqian Hou Qingfei Wang Haijiang Zhang Bo Xu Nian Yu Rui Wang David I.Groves Yuanchuan Zheng Shoucheng Han Lei Gao Lin Yang institute of Geology Chinese Academy of Geological Sciences State Key Laboratory of geological Processes and Mineral Resources China University of Geosciences(Beijing) School of Earth and Space sciences University of Science and Technology of China School of Electrical Engineering Chongqing University centre for Exploration Targeting University of Western Australia

This study,via combined analysis of geophysical and geochemical data,reveals a lithospheric architecture characterized by crust-mantle decoupling and vertical heat-flow conduits that control orogenic gold mineralization in the Ailaoshan gold belt on the southeastern margin of *** mantle seismic tomography indicates that the crust-mantle decoupled deformation,defined from previous seismic anisotropy analysis,was formed by upwelling and lateral flow of the asthenosphere,driven by deep sub duction of the Indian continent,Our magnetotelluric and seismic images show both a vertical conductor across the Moho and high Vp/Vs anomalies both in the uppermost mantle and lowest crust,suggesting that crust-mantle decoupling promotes ponding of mantle-derived basic melts at the base of the crust via a heat-flow *** gas isotope and halogen ratios of gold-related ore minerals indicate a mantle source of ore fluid.A rapid decrease in Cl/F ratios of lamprophyres under conditions of 1.2 GPa and1050 ℃ suggests that the ore fluid was derived from degassing of the basic *** lithospheric architecture is recognized in other orogenic gold provinces,implying analogous formational controls.

关键词： crust–mantle decoupling lithosphere architecture orogenic gold deposit seismic tomography magnetotelluric imaging Tibet

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Electro-osmotic flow and heat transfer of a non-Newtonian fluid in a hydrophobic microchannel with Navier slip

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Journal of Hydrodynamics 2015年第5期27卷 647-657页

作者： MISRA J.C. SINHA A. Adjunct Professor Centre for Healthcare Science and Technology Indian Institute of Engineering Science and Technology School of Medical science and Technology Indian Institute of Technology

In this paper, we investigate the implications of electro-osmosis on electrohydrodynamic transport of a non-Newtonian fluid on a hydrophobic micro-channel by developing a suitable analytical method. Velocity-slip and temperature-jump conditions are paid due attention. An attempt has been made to examine the effects of rheological and electro-osmotic parameters on the kinematics of the fluid. The nonlinear Poisson-Boltzmann equation governing the formation of the electrical double layer and the body force that is generated by the applied potential are accounted for in the study. Perturbation solutions are presented. In order to exhibit the applicability of the analysis, the problem of electro-osmotic flow and heat transfer of blood in an arteriole has been taken up as an illustrative example of a real-life problem. An intensive quantitative study has been made through numerical computation of the physical variables involved in the analysis, which are of special interest in the study. The computational results are presented graphically. The study reveals that the temperature of blood can be controlled by increasing/decreasing the Joule heating parameter.

关键词： electro-osmotic flow hydrophobic microchannel electrical double layer viscoelastic fluid velocity-slip temperature-jump

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