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Petrogenesis of songshugou dunite body in the Qin{1.ng orogenic belt, Central china: Constraints from geochemistry and melt inclusions

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Science china Earth Sciences 2005年第8期48卷 1146-1157页

作者： su li1,2, song shuguang3 & zhou dingwu1 1. key laboratory of continental dynamics of the ministry of education, department of geology, northwestern university, xi’an 710069, china 2. The Geological Lab Center, china university of Geosciences (Beijing), Beijing 100083, china 3. key laboratory of Orogenic Belts of the ministry of education, department of geology, Peking university, Beijing 100871, china key {1. of continental dynamics of the ministry of education Department of Geology Northwestern University Xi’an China The Geological Lab Center China University of Geosciences (Beijing)Beijing China key {1. of Orogenic Belts of the ministry of education Department of Geology Peking University Beijing China

The songshugou dunite body, which occupies an area of about 20 km2, is the largest ultramafic massif in the eastern Qin{1.ng orogenic belt, Central china. The major compo-nent of this body is dunitic rocks including mylonitic dunite and coarse-grained dunite; they oc-cupy about 95 vol% of the total body. Petrography, mineral composition, major and trace ele-ments and primitive melt inclusions have been investigated in this paper; all revealed that this dunite body is the product of melt-rock interaction by porous percolation flow. In comparison with dunite sills or veins in harzburgite from the basal part of Oman ophio{1.te, this dunite body is characterized by lower contents of Al2O3, CaO and HREE but higher content of highly incom-patible elements and Zr and Hf. The LREE enriched patterns and primitive mantle norma{1.zed spidergrams of trace elements are also different from the Oman dunite. Combining with melt in-clusions observed in o{1.vines, we conclude that this dunite body is the product of large- scale porous percolation flow of high-MgO melts within depleted mantle peridotites. The high-MgO magma, in essence, was most probably produced at the hot head of an upwel{1.ng mantle plume. The occurrence of the songshugou dunite body is closely associated with the activity of mantle super-plume in Neo-Proterozoic era in the Yangtze Craton.

关键词： songshugou dunite body, geochemistry, melt inclusion, mantle plume, Qinling orogenic belt.

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Formation of the Permian basalts and implications of geochemical tracing for paleo-tectonic setting and regional tectonic background in the Turpan-Hami and Santanghu basins,xinjiang

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Science china Earth Sciences 2006年第6期49卷 584-596页

作者： zhou dingwu1,2, liU Yiqun1,2, xiNG xiujuan1, HAO Jianrong1, DONG Yunpeng1 & OUYANG Zhengjian1 1. key laboratory of continental dynamics, ministry of education, Northwest university department of geology, Northwest university, xi’an 710069, china 2. Geoinformation Science & Engineering College, SDUST, Qingdao 266510, china key {1. of continental dynamics Ministry of Education Northwest University Xi’an China Geoinformation Science & Engineering College SDUST Qingdao China department of {1. Northwest University Xi’an China

The Turpan-Hami and Santanghu basins are the late Paleozoic-Mesozoic-Cenozoicreworked intracontinental basins that {1.perposed on the folded basement of the Paleozoic orogenicbelt. ^(40)Ar/^(39)Ar geochronological study of the basalts developed in the basins reveals that theformation period is Permain (293—266 Ma). From geochemical comparison of the basalts, theSantanghu basalts exhibit a strong depletion in Nb and Ta, and a selective enrichment in HFSE,reflecting that the source region is influenced by the {1.bducted components related to {1.bduction ofthe ancient oceanic crust and characterized with ''lagged arc volcanic rocks''. In contrast, theTurpan-Hami basalts show a slight depletion in Nb and Ta, high Th/Ta ratio, similar to the basaltsformed in an intracontinental ex-tensional zone or in an initial rift. Combined with the formationperiod of the ophiolite and ophiolite melange zones and regional magmatic activities occurring onthe post-orogenic extensional background in northern xinjiang, it can be inferred from thesegeochemical characteristics that the tectonic background for forming the Turpan-Hami and Santanghubasins is closely related to the regional extension after the continent-continent collisionalorogeny. The basalts of the two basins came from different sources on the post-orogenic extensionalbackground of the similar basin-forming dynamics. Although the settings are all intracontinentalrift, the source for the Santanghu basalts is obviously {1.bjected to the metasomatism of the{1.bducted components, implying the existence of the previous {1.bduction.

关键词： xinjiang, Tu-Ha basin, Santanghu basin, basalt, postorogeny, tectonic setting, extensional background.

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geology and geochemistry of the Bingdaban ophio{1.tic mélange in the boundary fault zone on the northern Central Tianshan Belt,and its tectonic imp{1.cations

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Science china Earth Sciences 2007年第1期50卷 17-24页

作者： DONG YunPeng ZHANG GuoWei zhou {1. LUO JinHai ZHANG Chengli xiA linQi XU XueYi li xiangMin The key {1. of continental dynamics Ministry of EducationDepartment of GeologyNorthwest UniversityXi’an 710069China Shandong university of Science and Technology Qingdao 266510China xi’an Institute of geology and Mineral Resources China Geological SurveyXi’an 710054China

The properties and tectonic significance of the fault bound zone on the northern margin of the Central Tianshan belt are key is{1.es to understand the tectonic framework and evolutionary history of the Tianshan Orogenic Belt. Based on the geological and geochemical studies in the Tianshan orogenic belt, it is {1.ggested that the ophiolitic slices found in the Bingdaban area represent the remaining oceanic crust of the Early Paleozoic ocean between the Hazakstan and Zhungaer blocks. Mainly com-posed of basalts, gabbros and diabases, the ophiolites were overthrust onto the boundary fault be-tween the Northern Tianshan and Central Tianshan belts. The major element geochemistry is charac-terized by high TiO2 (1.50%-2.25%) and MgO (6.64%-9.35%), low K2O (0.06%-0.41.) and P2O5 (0.1.-0.2%), and Na2O>K2O as well. Low ΣREE and depletion in LREE indicate that the original magma was derived from a depleted mantle source. Compared with a primitive mantle, the geochemistry of the basalts from the Bingdaban area is featureded by depletion in Th, U, Nb, La, Ce and Pr, and unfrac-tionated in HFS elements. The ratios of Zr/Nb, Nb/La, Hf/Ta, Th/Yb and Hf/Th are similar to those of the typical N-MORB. It can be interpreted that the basalts in the Bingdaban area were derived from a de-pleted mantle source, and formed in a matured mid-oceanic ridge setting during the matured evolu-tionary stage of the Northern Tianshan ocean. In comparison with the basalts, the diabases from the Bingdaban area show higher contents of Al2O3, ∑REE and HFS elements as well as unfractionated incompatible elements except Cs, Rb and Ba, and about 1. times the values of the primitive mantle. Thus, the diabases are thought to be derived from a primitive mantle and similar to the typical E-MORB. The diabases also have slight Nb depletion accompanying no apparent Th enrichment compared with N-MORB. From studies of the regional geology and all above evidence, it can be {1.ggested that the diabases from the Bingdaban

关键词： geochemistry ophiolite suture zone Bingdaban Tianshan orogenic belt.

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A new paleoenvironmental index for anoxic events—Mo isotopes in black shales from Upper Yangtze marine sediments

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Science china Earth Sciences 2011年第7期54卷 1024-1033页

作者： zhou {1.an su Jie HUANG JunHua YAN Jiaxing xiE xiNong GAO Shan DAI MengNing Tonger State key {1. of Geological Processes and Mineral Resources China University ofGeosciences Wuhan 430074 China key {1. of Biogeology and Environmental geology of ministry of education China University of Geosciences Wuhan 430074 China key {1. of Tectonics and Petroleum Resources of ministry of education China University of Geosciences Wuhan 430074 China State key {1. of continental dynamics Department of Geology Northwest University Xi'an 710069 China Wuxi Institute of Petroleum geology China Petroleum & Chemical Corporation Wuxi 214151 China

This paper investigates the high-solution of Mo isotopes and uses trace-element analyses for fresh and representative black shales and siliceous shales collected from the transition between the Late Ordovician and the Early Silurian at the Wangjiawan section in Yichang and the Late Permian Dalong Formation in the Shangsi Section of Sichuan. The applicability of different geochemical parameters used as paleo-oxygenation indices are also compared. The preliminary results show that V/（V＋Ni）, Uauth （auth U）, V/Cr, Ceanom and U/Th have a scattered variation range, but most samples plot within the suboxic-anoxic fields. The suboxic-anoxic environment was dominant during the deposition and formation of the two anoxic facies. These redox indicators show little correspondence to the δ98M0 values. The U/Mo ratio can be used as a potential proxy for the paleo-redox conditions due to the possibility that Mo is enriched relative to U at different redox gradients during early diagenesis. This evidence is more significant for the euxinicity condition and corresponds to positive δ98M0 （〉1.5%o） values with low U/Mo ratios. This evidence is likely related to the depositional conditions near the boundary between anoxic and euxinic environ- ments, which are characterised by low bioturbation or water circulation. Other samples reveal a wide scatter of U/Mo ratios and δ98M0 〈1.5%0. These results are likely due to punctuated improvements in oxygenation with intense bioturbation or water circulation, which led to the redistribution of trace element.

关键词： molybdenum isotopes proxy for paleo-redox conditions black shale Upper Yangtze

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Paleomagnetic results from Late Carboniferous to Early Permian rocks in the northern Qiangtang terrane, Tibet,{1., and their tectonic implications

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Science china Earth Sciences 2017年第1期60卷 124-134页

作者： YANG xingFeng CHENG xin zhou YaNan MA Lun ZHANG xiaoDong YAN ZhaoSheng PENG xiMing {1. HaiLun WU HanNing department of {1. and State key laboratory of continental dynamics Northwest University Xi 'an 710069 China

Results of a systematic paleomagnetic study are reported based on Late Carboniferous to Early Permian sedimentary rocks on the north slope of the Tanggula Mountains, in the northern Qiangtang terrane （NQT）, Tibet,{1.. Data revealed that magnetic minerals in limestone samples from the Zarigen Formation （CP^z）are primarily composed of magnetite, while those in sandstone samples from the Nuoribagaribao Formation （Pnr） are dominated by hematite alone, or hematite and magnetite in combination. Progressive thermal, or alternating field, demagnetization allowed us to isolate a stable high temperature component （HTC） in 1.7 specimens from 1. sites which successfully passed the conglomerate test, consistent with primary remnance. The tilt-corrected mean direction for Late Carboniferous to Early Permian rocks in the northern Qiangtang terrane is D°=30.2°, Is=-40.9°, ks=269.0, a95=2.3°, N=1., which yields a corresponding paleomagnetic pole at 25.7°N, 241.5°E （alp/rim=2.8°/1.7°）, and a paleolatitude of 23.4°S. Our results, together with previously reported paleomagnetic data, indicate that：（1. the NQT in Tibet,{1., was located at a low latitude in the southern hemisphere, and may have belonged to the northern margin of Gondwana during the Late Carboniferous to Early Permian; （2） the Paleo-Tethys Ocean was large during the Late Carboniferous to Early Permian, and （3） the NQT subsequently moved rapidly northwards, perhaps related to the fact that the Paleo-Tethys Ocean was rapidly contracting from the Late Permian to Late Triassic while the Bangong Lake-Nujiang Ocean, the northern branch of the Neo-Tethys Ocean, expanded rapidly during this time.

关键词： Northem Qiangtang terrane Late Carboniferous Early Permian Rock magnetism Conglomerate test Paleomagnetic pole

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Paleoenvironmental implications of high-density records in Co-rich seamount crusts from the Pacific Ocean

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Science china Earth Sciences 2008年第10期51卷 1460-1469页

作者： WANG xiaoHong zhou {1.Ping WANG YiMin ZHANG XueHua {1.U xiaoMing FAN xingTao {1.U Kexin zhou Jianxiong ministry of {1. key laboratory for Earth surface Processes Department of GeographyPeking UniversityBeijing 100871China National Research Center for Geoanalysis Beijing 100037China Guangzhou Marine Geological {1.rvey Guangzhou 510760China The key {1. of continental dynamics Northwest UniversityXi’an 710069China The key {1. of Heavy Ion Physics Ministry of EducationPeking UniversityBeijing 100871China Institute of Mineral Resources Chinese Academy of Geological SciencesBeijing 100037China

Co-rich seamount crusts have been shown to possess great potential for providing information on paleoceanographic and paleoclimatic changes. High resolution data are essential to decipher and correctly understand {1.ch high-density records. With the development of modern microprobe techniques, detailed sampling of crusts can be performed and it is possible to retrieve detailed information about envi- ronmental changes recorded in the seamount crusts. We report here geochemical re{1.lts of more than 40 elements (including all rare earth elements) of four Co-rich seamount crust samples, which were collected from seamounts in the central and western Pacific Ocean. These data were obtained with two micro-probe techniques: Electron Probe Micro Analyzer and Laser Ablation Inductively Coupled Plasma Mass Spectrometry. The chronological framework of the seamount crust samples was determined using the cos- mogenic 1.Be and the Co-chronometer. Records of elemental composition, P, and Al/(Fe + Mn) and Y/Ho ratios across the sections of the four samples are used to identify paleoceanographic and paleoclimatic events over the past ~30 Ma. These data show that: (1. Al/(Fe + Mn) in the western Pacific seamount crust is a useful proxy for the assessment of changes of source materials related to the variability of the Asian monsoon; (2) P and Y/Ho can be used as proxies to infer biogenic episodes. Finally we discuss the methodology related to dating and micro-probe analysis used in crust study.

关键词： Co-rich seamount crust micro-probe chronology geochemical record paleo-oceanic environment

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Post-collisional plutonism with adakitic signatures:The Triassic Yangba granodiorite (Bikou terrane,northern Yangtze Block)

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Chinese Journal Of Geochemistry 2008年第1期27卷 72-81页

作者： QIN Jiangfeng LAI Shaocong li Yongfei State key {1. of continental dynamics Department of Geology Northwest University Xi＇ an 710069 China

The post-collisional Yangba granodiorite intruded into the Bikou metasedimentary-volcanic group, southern Mianlue {1.ture, central china. The host granodiorites contain many mafic microgranular enclaves which have acicular apatite, phenocrysts of host granodiorites, implying that the enclaves have been incorporated as magma globules into host granodioritic magma and undergone rapid cooling. The variation trends of major and trace ele- ments between enclaves and host rocks {1.ggest a mixing and mingling process with respect to their petrogenesis. The mafic microgranular enclaves are characterized by shoshonite with SiO2≤63%, σ (4.54–6.1.)>3.3, high K2O content (4.22%–6.04%), K2O/Na2O>1. in the K2O-SiO2 diagram, all the samples plot in the shoshonite field, which are enriched in liLE and LREE, with obvious Nb, Ta negative anomalies, indicating a {1.bducting fluid-metasomatised mantle source. Zircon LA-ICP-MS dating of the granodiorites yielded an age of 21..4±8.3 Ma, indicating they were formed during the late-orogenic or post-collisional stage (≤242±21.Ma) of the South Qinling Mountain Belt. The host granodiorites have many close compositional similarities to high-silica adakites from {1.- pra-{1.bduction zone setting, but tend to have a higher concentration of K2O (3.22%–3.84%) and Mg#. Chon- drite-normalized rare-earth element patterns are characterized by high ratios of (La/Yb)N, the extreme HREE deple- tion and a lack of significant Eu anomalies. In conjunction with the high abundances of Ba and Sr as well as the low abundances of Y and HREE, these patterns {1.ggest a feldspar-poor, garnet ± amphibole-rich fractionation mineral assemblage. High Mg# values demonstrate that the host granodiorites were contaminated by enclave magma. On a whole, integrated geological and geochemical studies {1.ggested the Yangba granodiorites and their mafic micro- granular enclaves re{1.lted from mixing of enriched mantle-derived shoshonitic magma and thickened lower crust-derived felsic ma

关键词：深成现象三叠纪花岗岩岩石

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The northern Qiangtang Block rapid drift during the Triassic Period:Paleomagnetic evidence

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Geoscience Frontiers 2019年第6期10卷 2313-2327页

作者： Yanan zhou xin Cheng Yiying Wu Vadim Kravchinsky Ruiqi Shao Weijie Zhang Bitian Wei Ruiyao Zhang Fanrong Lu Hanning Wu department of {1.&State key laboratory of continental dynamics Northwest UniversityXi’an 710069China department of Physics University of AlbertaABCanada

As one of the pivotal Gondwana-derived blocks,the kinematic history of the northern Qiangtang Block(in the Tibetan Plateau)remains unclear,mainly because quantitative paleomagnetic data to determine the paleoposition are ***,for this study,we collected 226 samples(1. sites)from Triassic sedimentary rocks in the Raggyorcaka and Tuotuohe areas of the northern Qiangtang Block(NQB).Stepwise demagnetization isolated high temperature/field components from the *** Early and Late Triassic datasets passed field tests at a 99%confidence level and were proved to be primary *** were calculated to be at 24.9°N and 21..5°E with A95=8.2°(N=8)for the Early Triassic dataset,and at 68.1.N,1.9.9 E with A(95)=5.6°(N=37)for the Late Triassic,the latter being combined with a coeval volcanic dataset published *** paleopoles correspond to paleolatitudes of1..3°S±8.2°and 29.9 N1..6°,*** previously published results,we reconstructed a three-stage northward drift process for the NQB.(1.The northern Qiangtang Block was located in the subtropical part of the southern hemisphere until the Early Triassic;(2)thereafter,the block rapidly drifted northward from southern to northern hemispheres during the Triassic;and(3)the block converged with the Eurasian continent in the Late ***^4800 km northward movement from the Early to Late Triassic corresponded to an average motion rate of^1..85 cm/*** rapid drift of the NQB after the Early Triassic led to a rapid transformation of the Tethys Ocean.

关键词： Northern Qiangtang block Paleomagnetism Plate tectonics Tethys ocean Tibetan plateau Triassic

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