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    Zircon SHRIMP U-Pb dating for the Cangshuipu volvanic rocks and its implications for the lower boundary age of the Nanhua strata in South China [查看] WANGJian、LIXianhua、DUANTaizhong、LIUDunyi、SONGBiao、LIZhongxiong、GAOYonghua
    Abstract The continental volcanic rocks and volcaniclastic sedimentary conglomerates of the Cangshuipu Formation occur well in Yiyang of Hunan Province, consisting of a wedge-shaped succession of Neoproterozoic strata that overlie 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 Formation.This age is younger than previously reported values of 921—933 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 of ~820 Ma may be taken as the lower boundary timing of the Nanhua System (even Neoproterozoic) in South China.
    SHRIMP U-Pb zircon dating of the uppermost Cretaceous Furao Formation near the Heilong River：An age chosest to the KT boundary [查看] LIXianhua、LIWuxian、CHENPeiji、WANXiaoqiao、LIGang、SONGBiao、JIANGJianhong、LIUJicai、YINDeshun、YANWei
    SHRIMP U-Pb zircon age of the Jinchuan ultramafic intrusion and its geological significance [查看] LIXianhua、SULi、SONGBiao、LIUDunyi
    U-Pb dating of zircon from the bed parallel anatectic graniteic intrusion in the Baban group in Hainan Island and the tectonic implication [查看] DINGShijiang、HUJianmin、SONGBiao、CHENMulun、XIEShengzhou、FANYuan
    Abstract 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 thermal-dynamic process when the Gondwana continent began to break up in the Devonian period.
    SHRIMP U-Pb zircon Geochronology of the Xiaotongguanshan and Shatanjiao Intrusions and Its Petrological Implications in the Tongling Aear,Anhui [查看] DIYongjun、WUGanguo、ZHANGDa、SONGBiao、ZANGWenshuan、ZHANGZhongyi、LIJinwen
    Abstract This paper determines the crystallization ages of the Xiaotongguanshan quartz monzodiorite and Shatanjiao quartz monzonite porphyry from the Tongling area using the SHRIMP zircon U-Pb method. The crystallization age of the former is 142.8±1.8 Ma; that of the latter is 151.8±2.6 Ma. These data indicate that they were formed during the Late Jurassic (142.8 to 151.8 Ma). Zoned magma chamber was formed because of double diffusive convection. Therefore, the intrusive sequence of magma is generally from quartz monzonite through quartz monzodiorite to pyroxene monzodiorite, i.e. an inverted sequence.
    Petrogenesis and dating of the Kangding complex,Sichuan Province [查看] CHENYuelong、LUOZhaohua、ZHAOJunxiang、LIZhihong、ZHANGHongfei、SONGBiao
    Abstract 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 Sichuan Province was conducted. One of our conclusions is that a majority of the zircons crystallized between 721 and 773 Ma in a magmatic regime. The complexes contain early to late Paleo- proterozoic relict zircons from ancient continental crust. The oldest age, 2468 Ma, may represent 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.
    Detrital Zircon Dating of Meso-and Neoproterozoic Rocks in North China and Its Implications [查看] GAOLinzhi、LIUPengju、YINChongyu、ZHANGChuanheng、DINGXiaozhong、LIUYanxue、SONGBiao
    New dates from Meso-and Neoproterozoic strata contribute to the recently defined Orecambrian stratigraphical timescale of China agreed by the Subcommission on the Precambrian System,and the National Commission on Stratigraphy of CHina on Nov.24,2009.First,the age range of the Chingcheng System,including the Changzhougou,Chuanlinggou,Tuanshanzi and Dahongyu formations has been constrained to 1.8-1.6Ga.second,the Jinxian System including the Gaoyuzhuang,Yangzhuang,Wumishan,HOngshuizhuang and Tieling formations has been constrained to 1.6-1.4Ga.Third,an as-yet unnamed(undefined)system(1.4-1.0Ga)is only developed in the Xiamaling Formation at JIxian section,Tianjing.OFrth,the Qingbaikou System,including the Luotuoling and jing'eryu formationshas been constrained to 1.0-0.78Ga.Fifth,the Nanhuan System ranges betwwen 780-635Ma，and the Sinian System is within 635-542Ma,However,according to a series of SHRIMP U-Pb dates from the late Precambrian in the JIangnan Orogen Belt in South China Platform,the constrained strata will be redefined as in the upper part of the Qingkaikou SYstem.To aid global geodynamics,it is useful to denote a late Precambrain section with unified,precise and high-precision chronological dating;this is here defined in North China Block and Jiaoliao-Korean Block. However,the Neoproterozoic Qingkaikou study in North China will be influence in whole Meso-and Neoproterozoic in the Jiangnan Orogenic Belt in betwwen the Yangtze Block and the Cathaysia Block in South China.
    Occurrence of Neoproterozoic low-grade metagranite in the western Beihuaiyang zone, the Dabie orogen [查看] LIUYiCan、LIULiXiang、GUXiaoFeng、LIShuGuang、LIUJia1、SONGBiao
    Based on detailed field investigations and petrographic observations, we discovered Neoproterozoic-emplaced granite from the metavolcanics of the Dingyuan Formation in the western Beihuaiyang zone, the Dabie orogen. This study reports the results of zircon U-Pb dating and preliminary petrographic observations on two metagranite samples. The studied rocks experienced epidote-amphibolite facies metamorphism and strong structural deformation. Their U-Pb ages are 726 ± 6 and 758 ± 12 Ma, respectively, similar to those for the Luzhenguan complex in the eastern segment of the Beihuaiyang zone. In combination with previously determined 635 ± 5 Ma low-grade metagabbro, this study suggests the occurrence of at least two types of Neoproterozoic intrusive rocks in the Beihuaiyang zone, the northern margin of the South China Block (SCB): 726−758 Ma metagranite and 635 Ma metagabbro. These rocks occur within the metamorphosed Ordovician volcanic zone (originally named the Dingyuan Formation) and are in tectonic contact to each other, but they formed in different tectonic settings. The protolith ages for the Neoproterozoic low-grade metaigneous rocks are in good agreement not only with ages for two episodes of mid- and late-Neoproterozoic mafic and felsic magmatism in the Suizhou and Zaoyang area, Hubei Province, but also agree with protolith ages of ultrahigh-pressure metaigneous rocks in the Dabie-Sulu orogenic belt. In view of their tectonic relationships to country rocks, it appears that these Neoproterozoic low-grade rocks are exotic and they may have been detached and scraped from subducting SCB crust in the early Triassic during the initial continental subduction, and thrusted over Paleozoic metamorphosed rocks in the southern margin of the North China Block during continental collision.
    Reclassification of the Meso- and NeoproterozoicChronostratigraphy of North China by SHRIMP Zircon Ages [查看] GAOLinzhi、ZHANGChuanheng、LIUPengju、TANGFeng、SONGBiao、DINGXiaozhong
    High-quality zircon U-Pb ages acquried from Meso-and Neoproterozoic strata in North China in recent years has provided a hig-resolution chronostratigraphic famework for dating.A basis of this hig-level chronostratigraphic system provides the foundation for a global Precambrian study and stratigraphic correlation and so recent geological studies have focused attention on systemic SHRIMP zircon dating.A chronology of Meso-and Neoproterozoic strata and the time of origin of the overlying Changcheng System is given on the basis of new SHRIMP zircon dating from the Qianxi Complex and diabase of the Chuanlinggou Formation.A new tectonostratigraphy for a Neoproterozoic chronostratigraphic framework in the southeastern margin of the North CHina continent is underpinned by the new SHRIMP zircon dating of Neoproterozoic mafic magma diabase in the Jiao-LIao-Xu-Huai Sub-Province.
    SHRIMP zircon U-Pb dating from K-bentonite in the top of Ordovician of Wangjiawan Section, Yichang, Hubei, China [查看] HUYanHua、ZHOUJiBin、SONGBiao、LIWei1、SUNWeiDong
    The Global boundary Stratotype Section and Point (GSSP) for the base of the Hirnantian Stage (the latest stage of the Ordovician System) is defined at a point 0.39m below the base of the Kuanyinchiao Bed in the Wangjiawan North Section, which is the upper most “golden spike” of the Ordovician.However, this “golden spike” is lack of reliable geochronology data. This article gives a sensitive high resolution ion microprobe (SHRIMPII) zircon U-Pb dating for a K-bentonite sample from the Kuanyinchiao Bed in the Wangjiawan North Section. The age of the K-bentonite sample is 443.2±1.6 Ma, that is to say, the isotopic age of the uppermost of Hirnantian Stage, the point of Ordovician-Silurian boundary, should be near to, but slightly younger than 443.2±1.6 Ma. This age is identical to the Ordovician- Silurian boundary age 443.7±1.5 Ma as declared by International Commission on Stratigraphy (ICS). So, this research provides some good geochronlogical data for the Hirnantian Stage and the Ordovician-Silurian boundary as well as the global correlation.
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