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shrimp zircon U-Pb geochronology of early Mesozoic felsic igneous rocks from the southern Lancangjiang and its tectonic implications

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Science china Earth sciences 2006年第10期49卷 1032-1042页

作者： PENG Touping1,2, WANG Yuejun1, FAN Weiming1, LIU Dunyi3. SHI Yuruo3.& MIAO Laicheng4 1. Key Laboratory of Isotope Geochronology and Geochemistry, Guangzhou institute of Geochemistry, chinese academy of {3., Guangzhou 510640, china 2. Graduate University of chinese academy of {3., Beijing 10003., china 3. shrimp isotope Laboratory, chinese academy of geological sciences, Beijing 10003., china 4. institute of geology and Geophysics, chinese academy of {3., Beijing 100029, china Key Laboratory of Isotope Geochronology and Geochemistry Guangzhou Institute of Geochemistry Chinese Academy of Sciences Guangzhou China Graduate University of chinese academy of sciences Beijing China shrimp isotope Laboratory Chinese Academy of Geological Sciences Beijing China institute of geology and Geophysics Chinese Academy of Sciences Beijing China

The shrimp zircon U-Pb geochronology of three typical samples, including two monzo nitic granites from the Lincang batholith and a rhyolite from the Manghuai Formation are presented in the southern Lancangjiang, western Yunnan Province. The analyses of zircons for the biotite monzonitic granites from the northern (02DX-13.) and southern (20JH-10) Lincang batholith show the single and tight clusters on the concordia, and yield the weighted mean 206Pb/23.U ages of 229.4 ± 3.0 Ma and 23..4 ± 3.6 Ma, respectively, representing the crystallized ages of these granites. The zircons for the rhyolitic sample (02DX-95) from the Manghuai Formation give a weighted mean 206Pb/23.U age of 23..0 ± 5.0 Ma. These data suggest that the igneous rocks from the Lincang granitic batholith and Manghuai Formation have a similar crystallized age. In combination with other data, it is inferred that both were generated at a narrow age span (~23. Ma) and were originated from the postcollisional tectonic regime. An early Proterozoic 206Pb/23.U apparent age of 1977±44 Ma is additionally obtained from one zircon from the biotite monzonitic granite (southern Lincang batholith), indicative of devel- opment of the early Proterozoic Yangtze basement in the region. These precisely geochronological data provide important constraints on better understanding the Paleozoic tectonic evolution of the Tethys, western Yunnan Province.

关键词： shrimp zircon U-Pb dating, Middle Triassic, Lincang granitic batholith, Manghuai Formation rhyolite, southern Lancangjiang.

Petrogenesis and dating of the Kangding complex,Sichuan Province

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Science china Earth sciences 2005年第5期48卷 622-634页

作者： CHEN Yuelong 1 , LUO Zhaohua 1 , ZHAO Junxiang, LI Zhihong, ZHANG Hongfei & SONG Biao 3.1. Faculty of Earth sciences and Natural Resources, china University of Geosciences, Beijing 100083. china 2. Faculty of Earth sciences, china University of Geosciences, Wuhan 43.074, china 3. Beijing shrimp center, institute of geology, chinese academy of geological sciences, Beijing 10003., china Faculty of Earth sciences and Natural Resources China University of Geosciences Beijing China Faculty of Earth sciences China University of Geosciences Wuhan China Beijing shrimp center Institute of Geology Chinese Academy of Geological Sciences Beijing China

An analysis of major and trace element geochemistry and shrimp U-Pb zircon dating of mafic, intermediate, and felsic rocks from the Mianning metamorphic complex of Si- chuan Province was conducted. One of our conclusions is that a majority of the zircons crystal- lized between 721 and 773.Ma in a magmatic regime. The complexes contain early to late Pa- leo-proterozoic relict zircons from ancient continental crust. The oldest age, 2468 Ma, may rep- resent the basement of the Yangtze block. Overgrowth zircon rims and palingenetic zircons have been observed and dated, and are believed to have formed after crystallization, during Paleozoic and Mesozoic metamorphic-anatexis. We also conclude that depletion of Nb, Ta, HREE, in a spider-diagram normalized to primitive mantle and calc-alkaline association, implies that they formed in island-arc or under-plating settings.

关键词： Kangding complex, zircons, shrimp, tectonic setting.

U-Pb dating of zircon from the bed parallel anatectic granitic intrusion in the Baoban group in Hainan Island and the tectonic implication

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Science china Earth sciences 2005年第12期48卷 2092-2103页

作者： DING Shijiang1, HU Jianmin2, SONG Biao3.4, CHEN Mulun1, XIE Shengzhou1 & FAN Yuan1 1. geological Surveying institute of Hainan, Haikou 570206, china 2. institute of Geomechanics, chinese academy of geological sciences, Beijing 100081, china 3. Beijing center of shrimp, Beijing 10003., china 4. institute of geology, chinese academy of geological sciences, Beijing 10003., china geological Surveying institute of Hainan Haikou China institute of Geomechanics Chinese Academy of Geological Sciences Beijing China Beijing center of shrimp Beijing China institute of geology Chinese Academy of Geological Sciences Beijing China

The petrological and geochemical features of the bed parallel granitic intrusion in the Pre-Cambrian Baoban group in Hainan Island attest to the anatexis origin of the granites. U-Pb dating analyses of zircons from the anatectic granite and the biotite two-feldspar gneiss in the Baoban group, using shrimp II in the Beijing Ion-probe center, acquire 206Pb/23.U ages of 3.8±3.5 Ma (of granite, 95% confidence level, MSDW=1.23. and 3.2.9±6.1 Ma (of gneiss, 95% confidence level, MSDW = 2.04) respectively. The two late Devonian ages indicate consistently a tectonic- thermal event experienced in Hainan Island, and are the first discovered record of the Devonian geological process in the district. This event possibly resulted from the deep ther-mal-dynamic process when the Gondwana continent began to break up in the Devonian period.

关键词： Hainan Island, Devonian period, anatectic granite, zircon shrimp U-Pb dating.

Re-Os(ICP-MS)dating of the massive sulfide ores from the Jinchuan Ni-Cu-PGE deposit

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Science china Earth sciences 2005年第10期48卷 1672-1677页

作者： YANG Gang1,2, DU Andao1, LU Jiren3. QU Wenjun1 & CHEN Jiangfeng2 1. National Research center of Geoanalysis, Beijing 10003., china 2. Laboratory for Earth Material Cycling, School of Earth and Space {3., University of Science and Technology of china, Hefei 23.026, china 3. institute of Mineral Resource, chinese academy of geological sciences, Beijing 10003., china National Research center of Geoanalysis University of Science and Technology of china chinese academy of geological {3.

Massive sulfide ore from the Jinchuan Ni-Cu-PGE deposit was dated by Re-Os technique using Carius Tube digestion, Os distillation, Re extraction by acetone and ICP-MS measurement. An isochron giving an age of 83. ± 3. Ma, initial 187Os/188Os ratio of 0.279 ± 0.018 (MSWD = 1.7) and γOs = 13. ± 15 is obtained. The Re-Os age obtained agrees, within analytical uncertainties, with previous shrimp zircon U-Pb age of 827 ± 8 Ma (n=5, MSWD = 4.3.. The result suggests that the deposit was formed at Neoproterozoic and that the formation of the Jinchuan Ni-Cu-PGE sulfide deposit may be closely related to the plume activity, which were attributed to the breakup of the Rodinia supercontinent. The high γOs of the massive ores sug-gests that crustal material was involved in the formation of the Jinchuan deposit, however, the quantity of the added crustal material is less than 10%.

关键词： Jinchuan Ni-Cu-PGE deposit, Re-Os dating, ICP-MS.

shrimp U-Pb dating and Hf isotopic analyses of Middle Ordovician meta-cumulate gabbro in central Qiangtang, northern Tibetan Plateau

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Science china Earth sciences 2010年第5期53卷 657-664页

作者： ZHAI QingGuo1 WANG Jun1, LI Cai2 & SU Li3.1 institute of geology, chinese academy of geological sciences, Beijing 10003.,{3. 2 College of Earth sciences, Jilin University, Changchun 13.061,{3. 3.The geological Laboratory center and State Key Laboratory of geological Processes and Mineral Resources,{3. University of Geo- sciences, Beijing 100083.{3. institute of geology Chinese Academy of Geological Sciences Beijing China College of Earth sciences Jilin University Changchun China The geological Laboratory center and State Key Laboratory of geological Processes and Mineral Resources China University of Geosciences Beijing China

Metabasites consisting of metamorphic ultra-mafic rocks, cumulate gabbro, gabbro (diabase), basalt, and plagiogranite are exposed at the Taoxinghu area in central Qiangtang, northern Tibetan Plateau. Zircon shrimp U-Pb dating for the cumulate gabbro yields a weighted mean age of 467±4 Ma, which is the oldest and most reliable magmatic age in this area. Zircon 176Hf/177Hf ratios range from 0.282615 to 0.282657, with εHf(t) values of 5.02±0.28, indicating that the cumulate gabbro was mainly derived from the depleted mantle. In addition, geochemical data of metabasites suggest that they have similar characteristics to those in the mid-ocean ridge basalts (MORB). The Taoxinghu metabasites may represent the fragment of Early Paleozoic ophiolite in the "Central Uplift" of the Qiangtang, northern Tibetan Plateau.

关键词： Qiangtang cumulate gabbro shrimp dating Hf isotope

shrimp zircon U-Pb dating in Jingshan "migmatitic granite", Bengbu and its geological significance

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中国科学：地球科学英文版 2005年第2期48卷 185-191页

作者： XU Wenliang, WANG Qinghai, YANG Debin, LIU Xiaochun & GUO Jinghui College of Earth sciences, Jilin University, Changchun 13.061, china institute of Geomechanics,{3., Beijing 100081, china institute of geology & Geophysics, chinese academy of sciences, Beijing 100029, china College of Earth sciences Jilin UniversityChangchun130061China institute of Geomechanics Chinese Academy of Geological SciencesBeijing100081China institute of geology & Geophysics Chinese Academy of SciencesBeijing100029China

The petrographic characteristics of Jingshan "migmatitic granite" and the occurrence of the magmatic zircons indicate that the granite was formed by normal crystallization of felsic melts. All zircons in the granite have inherited cores and fine-scale oscillatory zoning rims of magmatic origin. It is realized that the granite was formed at 160.2±1.3.Ma through dating magmatic zircons. The generation of the granitic magma could be related to the lithospheric mantle and/or lower crust delamination after the ultrahigh pressure metamorphism (UHPM) in Triassic. Most inherited zircons yield the ages of 217.1±6.6 Ma, which is consistent with the peak UHPM in the Dabie-Sulu orogenic belt. Some of the inherited zircons (43.-722 Ma) constitute a discordia line with the upper intercept age of 850+85/-68 Ma and a lower intercept age of 261+100/-140 Ma. These ages imply that the granite could be derived from the partial melting of the crustal materials of the South china Block that was intensively superimposed by the UHPM. The UHPM could be the reason for the major Pb loss at ±220 Ma.

关键词： zircon, U-Pb dating, migmatitic granite, geological significance, Bengbu.

Zircon shrimp U-Pb dating for the Cangshuipu volcanic rocks and its implications for the lower boundary age of the Nanhua strata in South china

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Science Bulletin 2003年第16期48卷 1663-1669页

作者： WANG Jian1, LI Xianhua2, DUAN Taizhong3. LIU Dunyi4, SONG Biao4, LI Zhongxiong1 & GAO Yonghua5 1. Chengdu institute of geology and Mineral Resources, china Geologi-cal Survey, Chengdu 610082, china 2. Guangzhou {3. of Geochemistry, chinese academy of sciences, Guangzhou 510640, china 3. Colorado School of Mines, Golden, CO 80401-1887, USA (Present address: Marathon Oil Company, Houston, TX 77056-2725, USA) 4. institute of geology, chinese academy of geological sciences, Bei-jing 10003., china 5. Graduate School of the chinese academy of geological sciences, Beijing 10003., china Correspondence should be addressed to Wang Jian (e-mail: jianwang@ ***) Chengdu institute of geology and Mineral Resources China Geological Survey Chengdu China Guangzhou institute of Geochemistry Chinese Academy of Sciences Guangzhou China Colorado School of Mines Golden USA institute of geology Chinese Academy of Geological Sciences Beijing China Graduate School of the chinese academy of geological sciences Beijing China

The continental volcanic rocks and volcaniclas-tic sedimentary conglomerates of the Cangshuipu Formation occur well in Yiyang of Hunan Province, consisting of a wedge-shaped succession of Neoproterozoic strata that over-lie with high-angle unconformity the flysch turbidites of the Lengjiaxi Group in the Upper Mesoproterozoic Eonothem. shrimp zircon U-Pb dating gives a weighted mean age of 814 12 Ma for the dacitic volcanic agglomerates from the lowest part of the volcanic rocks in the Cangshuipu Forma-tion. This age is younger than previously reported values of 921—93. Ma for the volcanic rocks from the Cangshuipu Formation. Our new dating represents the lower boundary age of the Neoproterozoic System in the studied area. The younger age for the Cangshuipu volcanic rocks is supported by the following observations: （1） Lower Neoproterozoic strata （814—1000 Ma） are missing in the studied area; （2） the Nanhua rift system was initiated at about 820 Ma; and （3. an age of820 Ma may be taken as the lower boundary tim-ing of the Nanhua System （even Neoproterozoic） in South china.

关键词： Zicon U-Pb dating Neoproterozoic volcanics rift basin Nanhua System.

shrimp zircon U-Pb age and Nd isotopic study on the Nyainqêntanglha Group in Tibet

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Science china Earth sciences 2005年第9期48卷 1377-1386页

作者： HU Daogong1, WU Zhenhan1, JIANG Wan1, SHI Yuruo2, YE Peisheng1 & LIU Qisheng1 1. institute of Geomechanics, chinese academy of geological sciences, Beijing 100081, china 2.{3., chinese academy of geological sciences, Beijing shrimp Centre, Beijing 10003., china institute of Geomechanics Chinese Academy of Geological Sciences Beijing China institute of geology Chinese Academy of Geological Sciences Beijing SHRIMP Centre Beijing China

The Nyainqêntanglha Group is traditionally viewed as the oldest metamorphic basement in the Lhasa block, but its formation age and tectonic setting remain debate. Zircons extracted from the metamorphic sequence of volcanics and intrusions of the Nyainqêntanglha Group, 10 km west of Nam Co in northern Lhasa block, have been investigated by cathodolu- minescence (CL), backscattered (BSE) and dated by ion microprobe (shrimp). We conclude that the U-Pb age of 787±9 Ma of zircons from the trondhjemite imposes a constraint on maxi- mum protolith age, and minimum formation age of the Nyainqêntanglha Group is constrained by U-Pb age of 748±8 Ma of zircons from the granite. The formation age of the Nyainqêntanglha Group is consistent with sedimentary age of Greater Himalayan rocks, showing that they devel- oped coevally in an arc-basin tectonic setting of Neoproterozoic active continental margin along the northern margin of the India shield. The inherited zircons from the tholetiite and granite give older 207Pb/206Pb ages from 947 to 1766 Ma. The positive εNd( t ) value indicates that the mafic rocks were derived from the depleted mantle, but contaminated by the older continental crustal material. Integrated Nd model age and U-Pb age data provide excellent evidence for the exis- tence of Mesoproterozoic basement in the Lhasa block during Neoproterozoic time.

关键词： Nyainqêntanglha Group, shrimp dating, Nd isotope, Neoproterozoic, Tibet.

Zircon shrimp geochronology of the Xinkailing-Kele complex in the northwestern Lesser Xing'an Range,and its geological implications

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Zircon SHRIMP geochronology of the Xinkailing-Kele complex i...