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

中国科学院地质与地球物理研究所第11届（2011年度）学术年会

作者： Laicheng Miao~(a*),Fuqin Zhang~a,Weiming Fan~a and Dunyi Liu~b a institute of geology and Geophysics,chinese academy of sciences,beijing,china b beijing shrimp centre,institute of geology, chinese academy of geological sciences,beijing,china

We propose that inherited Neoproterozoic zircons in Mesozoic igneous rocks from the eastern portion of the North china craton(NCC) were initially derived from the Yangtze/South china block,rather than from the NCC *** mechanism that introduced these zircons into the NCC was likely tectonic underplating during Triassic continental subduction/collision of the Yangtze block beneath the *** addition of abundant crustal materials represented by the exotic zircons,probably along the Moho or weak interfaces within the NCC crust,led to the crustal thickening of the *** sialic materials contributed significantly to the Mesozoic igneous rocks, either as source rocks or as contaminants of magmas generated during an extensional environment following crustal *** thickening was spatially linked to lithospheric thinning,with both occurring mainly in the eastern segment of the NCC, suggestive of an intrinsic relationship between thickening and thinning events during Mesozoic evolution of the NCC.

关键词： inherited zircons felsic igneous rocks underplating of the NCC Mesozoic magmatism North china craton

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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. institute of geology, chinese academy of geological sciences, beijing shrimp centre, beijing 100037, china 1. institute of Geomechanics Chinese Academy of Geological Sciences 100081 Beijing China 2. institute of geology Chinese Academy of Geological Sciences Beijing SHRIMP Centre 100037 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.

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 sciences, Guangzhou 510640, china 2. Graduate University of chinese academy of sciences, beijing 100039, china 3. shrimp isotope Laboratory, chinese academy of geological sciences, beijing 100037, china 4. institute of geology and Geophysics, chinese academy of sciences, 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-137) and southern (20JH-10) Lincang batholith show the single and tight clusters on the concordia, and yield the weighted mean 206Pb/238U ages of 229.4 ± 3.0 Ma and 230.4 ± 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/238U age of 231.0 ± 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 (~230 Ma) and were originated from the postcollisional tectonic regime. An early Proterozoic 206Pb/238U 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.

Characteristics of the Middle-Late Triassic sedimentary facies assemblages in the Songpan-Ruoergai area

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Progress in Natural Science:Materials International 2007年第3期17卷 305-313页

作者： YAN Zhen, YU Liangjun, LI Jiliang, bIAN Qiantao, WANG Zongqi and YANG Yongcheng ( institute of geology, chinese academy of geological sciences, beijing 100037, china State Key Laboratory of Lithospheric Evolution, institute of geology and Geophysics, chinese academy of sciences, beijing 100029, china Shaanxi Insititute of geology Survey, Xianyang 712000, china) [a]institute of geology Chinese Academy of Geological Sciences Beijing China [b]State Key Laboratory of Lithospheric Evolution Institute of Geology and Geophysics Chinese Academy of Sciences Beijing China [c]Shaanxi Insititute of geology Survey Xianyang China

The Middle-Late Triassic sedimentary rocks in the Songpan-Ruoergai area mainly consist of calcareous siltstone, muddy limestone, lithic arkose, feldspathic litharenite, mudstone, wormkalk, oolithic limestone, and conglomerate. Except for limestone bed increasing eastward longitudinally and vertically, the calcareous component of the sandstones increases obviously. Abundant benthic and plant fossils and their clasts occur within these rocks. The sedimentary structures predominately contain flaser, parallel, tabular, wavy, and herringbone cross beddings. These data coevally imply that the Middle-Late Triassic sediments deposited in the fluvial, lake and tide environments. Additionally, the rocks display graded, parallel, hummocky beddings, and sandy lamination, a feature characteristic of storm deposits.

关键词： Middle-Upper Triassic fluvial-lake environments tide environment tempestite Songpan-Ruoergai

Geochronology of Yanshanian Magmatism and Metamorphism in the Hinterland of the Dabie Mountains and Their Geologic Implications

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Acta Geologica Sinica(English Edition) 1992年第2期66卷 155-163,222页

作者： Chen Tingyu Niu baogui Liu Zhigang Fu Yunlian Ren Jishun institute of geology, chinese academy of geological sciences, beijing institute of geology Chinese Academy of Geological Sciences Beijing

A strong tectono-magmatic thermal event has been revealed by field observations of granitic, migmatiticand metamorphic rocks in the hinterland of the Dabie Mountains. K-Ar, Ar-Ar and Rb-Sr determinationsshow that the event took place 133-117 Ma ago (Yanshanian). Contemporaneously, a southwestwardthrust-type ductile shearing at multiple levels occurred in the lower crust or at even deeper levels, suggestingthat the Dabie Mountains region was still under the influence ot strong continent-continent overlappingtectonism of the Yangtze block under the Sino-Korean block at depth. Metamorphic rocks of amphibolitefacies, migmatites and deep structural deformations resulting from this tectonothermal event are now exposedto the surface. The present features of the Dabie Mountains thus have appeared only since ca. 100 Ma b.P. Theblock composed of the Dabie Group is not an uplift or shield which would have undergone a long-continuederosion.

关键词： Geochronology of Yanshanian Magmatism and Metamorphism in the Hinterland of the Dabie Mountains and Their Geologic Implications

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 100037, china 4. institute of geology, chinese academy of geological sciences, beijing 100037, china 1. geological Surveying institute of Hainan 570206 Haikou China 2. institute of Geomechanics Chinese Academy of Geological Sciences 100081 Beijing China 3. beijing Center of shrimp 100037 Beijing China 4. institute of geology Chinese Academy of Geological Sciences 100037 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/238U ages of 368±3.5 Ma (of granite, 95% confidence level, MSDW=1.23) and 362.9±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.

Mesozoic thrusts and extensional structures in the Daqingshan orogen, Inner Mongolia, and their temporal and spatial relationship

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Progress in Natural Science:Materials International 2007年第2期17卷 177-186页

作者： QI Guowei, ZHANG Jinjiang , WANG Xinshe and GUO Lei ( Key Laboratory of Orogenic belts and Crustal Evolution, Ministry of Education, china School of Earth and Space sciences, Peking University, beijing 100871, china institute of geology, chinese academy of geological sciences, beijing 100037, china) [a]Key Laboratory of Orogenic belts and Crustal Evolution Ministry of Education China [b]School of Earth and Space sciences Peking University Beijing China [c]chinese academy of geological sciences Institute of Geology Beijing China

Three large-scale thrusts developed in the Daqingshan orogen, Inner Mongolia, with a northeast-east trending from Louhuashan to Suletu are described in this paper. These northwest-directed thrusts, together with the four tectonic belts (or tectonic sheets) separated by these faults, formed a typical thrusting system. The originally defined Hohhot metamorphic core complex may be a tectonic sheet, making the uppermost tectonic unit of the thrusting system and truncated by the Daqingshan detachment fault on top. The existing tectono-chronological studies showed that the thrusting of this region possibly happened at the same time as the extension along the top detachment fault. This presents that the contraction and extension in Daqingshan orogen were probably simultaneous. The structural pattern of the Daqingshan orogen can be correlated to the Himalayan orogen, and models for simultaneous thrusting and detachment in Himalaya may give a hint for explaining the development of the Daqingshan orogen.

关键词： Daqingshan thrust metamorphic core complex detachment fault contraction-extension transform Himalaya.

Experimental Study on the Mechanism for the Formation of Sn- bearing Granite in Northern Guangxi

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Acta Geologica Sinica(English Edition) 1994年第2期68卷 169-182,228页

作者： Liang Xiangji, Qiao Li, Wang Fusheng and Yang Chonghui institute of geology, chinese academy of geological sciences, beijing institute of geology Chinese Academy of Geological Sciences Beijing

Experimental results have proved that the Xuefengian Sn-bearing biotite granites were formed by remelting and recrystallization of the Proterozoic metamorphic rocks of the Sibao Group at 500× 105-2000× 105 Pa and 750-570℃ and further testified that the F- and b-bear-ing aqueous solution played an important part in decreasing the formation temperature of the rocks. The results tally with the reality of the field geology. The authors have thus brought to light the mechanism for the formation of the Sn-bearing biotite granites and expounded the significance of their formation in the crust dynamics of South china.

关键词： experimental study Sn-bearing biotite granites formation mechanism northern Guangxi

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 430074, china 3. beijing shrimp Center, institute of geology, chinese academy of geological sciences, beijing 100037, china 1. Faculty of Earth sciences and Natural Resources China University of Geosciences 100083 Beijing China 2. Faculty of Earth sciences China University of Geosciences 430074 Wuhan China 3. beijing shrimp Center Institute of Geology Chinese Academy of Geological Sciences 100037 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.

MELT AND FLUID INCLUSIONS IN IGNEOUS ROCKS IN CENTRAL XIZANG (TIbET)

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Science in china,Ser.b 1986年第7期29卷 771-784页

作者：王碧香 institute of geology chinese academy of geological sciences beijing

Through a study of the characteristics and composition of melt and fluid inclusions in volcanic rocks and their associated granites in the subduction zone of the Tibetan plate, it has been found that the characteristics of the inclusions in quite a few minerals of various rock types are closely related to the nature of molten magmas, thickness of strata and cooling speed. Therefore, their characteristics may be used to discriminate different lithofacies types. In this paper the evolution and crystallization of magmas are discussed on the basis of the glass composition of the inclusions measured using the electron probe, and the gas composition and its parameters are used in elucidating the physico-chemical conditions of rock and ore formation.

关键词： TIbET MELT AND FLUID INCLUSIONS IN IGNEOUS ROCKS IN CENTRAL XIZANG