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    SHRIMP U-Pb zircon geochronology of Yangfang aefiriteaugite syenite in Wuyi Mountains of South China and its tectonic implications [查看] WANGQiang、ZHAOZhenhua、JIANPing、BAOZhiwei、XIONGXiaolin、MAJinlong
    Abstract In addition to the wide spread peraluminous granites, some alkaline or alkali-rich intrusive rocks were recently observed in the Wuyi Mountains. The Yangfang aegiriteaugite syenites in the Wuyi Mountains are strongly enriched in light rare earth elements (LREE), K, Ba, Ga, Zr and Y. What is more, differentiations of REE are obvious. In addition, the Yangfang aegiriteaugite syenites have also some characteristics similar to A-type granite. Zircons are selected from the Yangfang aegiriteaugite syenites for Sensitive High-Resolution Ion Microprobe (SHRIMP- Ⅱ ) U-Pb geochronology study. 15 analyses give concordant 206Pb/238U ages in a narrow range of 233—249 Ma, which correspond to a single age population with a weighted mean 206Pb/238U age of 242 ± 4 Ma, which records the crystallization time of the aegiriteaugite syenites. It is suggested that: (1) there were early Triassic peralkaline intrusive rocks in South China; (2) the early Indosinian extension event was probably active in local area, South China. This discovery provides a new insight for farther understanding of “Indosinian orogeny” in South China.
    SHRIMP U-Pb zircon geochronology and its implications on the Xilin Gol Complex，Inner Mongolia,China [查看] SHIGuanghai、LIUDunyi、ZHANGFuqin、JIANPing、MIAOLaicheng、SHIYuruo、
    Abstract The Xilin Gol Complex, consisting of deformed and metamorphosed rocks, was exposed as a large geological unit within the Central Asian Orogenic Belt, but its forming and subsequent deformed and metamorphic time has been an issue of little consensus. Petrographic analyses and SHRIMP dating on biotite-plagioclase gneiss, one of the major rocks within the Xilin Gol Complex, in southeast Xilinhot City, Inner Mongolia, China, where the Xilin Gol Complex was identified and named, yield its lower limit age of 437 ± 3 Ma (2s ) by its magmatic zircon SHRIMP U-Pb dating, and an upper limit age of 316 ± 3Ma (2s ), which was constrained by SHRIMP dating of magmatic zircons from adjacent undeformed garnet-bearing granite which intruded the Complex.The Complex was thus determined to be formed and subsequently deformed/metamorphosed from the late Ordovician-early Silurian to the mid-Carboniferous. Consequently, it is not the Precambrian terrane as previously considered by most geologists. More or less, the major rock —— biotiteplagioclase gneiss within the Complex is more likely to be Paleozoic fore-arc turbidite formation before metamorphism and intensive deformation, in which the detrital zircons gave sporadic Precambrian ages as old as up to 3.1 Ga. The source of the turbidite formation is multiple, which may be derived either from the North China Craton, or from the South-Mongolia Micro-continent, or probably came from a potential and undiscovered in situ terranes aged 600—800 Ma or even up to ca 3.1 Ga near the Complex.
    SHRIMP dating of volcanic rocks from Ningwu area and its geological implications [查看] ZHANGQI、JIANPING、LIUDunyi、WANGYanglong、QIANQing、WANGYan、XUEHuaimin
    Abstract The SHRIMP U-Pb ages are reported for the volacnic rocks from the Longwangshan and the Dawangshan formations respectively,Ningwu area,Jiangsu Province,The Dawagnshan formation(NB-01) is dated at(127±3）Ma，and the Longwangshan formation(NL-01),(131±4）Ma，besides,a few Archean zircons are also found in the Longwangshan formation,which suggests a possible Archean basement in the region.
    Paleoproterozoic lower crust beneath Nushan in Anhui Province Evidence from zircon SHRIMP U-Pb dating on granulite xenoliths in Cenozoic alkali basalt [查看] HUANGXiaolong、XUYigang、LIUDunyi、JIANPing
    Abstract Zircon SHRIMP U-Pb dating was carried out for an intermediate granulite xenolith in Cenozoic alkali basalt from Nushan. The results suggest that the lower crust beneath Nushan may have formed at about 2400—2200 Ma,and have been subjected to granulite-facies metamorphism at 1915±27 Ma. The old age of the Nushan lower crust is consistent with the geochemical similarities between Nushan granulite xenoliths and Archean-Paleoproterozoic granulite terrains in the North China craton, but it is not distinguishable from high-grade metamorphic rocks in the Yangtze craton where such old ages were also reported.Significant Pb-loss occurs in the Nushan zircons, implying important influence of widespread Mesozoic to Cenozoic underplating in East China on the lower crust beneath Nushan.
    Zircon U-Pb SHRIMP ages of high-pressure granulite in Yushugou ophiolitic terrane in southern Tianshan and their tectonic implications [查看] ZHOUDingwu、SULi、JIANPing、WANGRunsan、LIUXiaoming、LUGuanxiang、WANGJuli
    Abstract Zircons from two high-pressure granulite samples from the Yushugou ophiolitic terrane, southern Tianshan have been investigated by cathodoluminescence, LAICPMS and ion microprobe (SHRIMP) for their internal textures, trace elemental compositions and in situ dating. The weighted mean ages of these two samples are 392±7 and 390±11 Ma, respectively, representing the granulite-facies metamorphic age of the ophiolitic terrane, and indicating that the southern Tianshan ocean initiated its northward subduction since the early Devonian.
    Emplacement age and tectonic implications of the Xilinhot A-type granite in Inner Mongolia,China [查看] SHIGuanghai、MIAOLaicheng、ZHANGFuqing、JIANPing、FANWeiming、LIUDunyi
    Abstract A new rock type of granite, approximate 45km2 in area and located about 10 km south of Xilinhot, Inner Mongolia, was found in the Sunitezuoqi (or called Suzuoqi)-Xilinhot tectonic belt and identified as an A-type miarolitic intrusion. The pluton has miarolitic structure and is composed chiefly of perthite, quartz, euhedral albite and potassium feldspar. Various types of textures occur in the pluton, such as perthitie, graphic and myrmekite textures.Only quartz is found in miarolitic cavity. This A-type granite with seagull-shaped REE patterns and obvious negative Eu anomaly (d Eu = 0.24—0.28) is high in SiO2 (76%—77%), K and Na (Na2O + K2O = 7.75%—8.15%) and low in Ca (CaO= 0.20%—0.22%), Fe and Mg. Both petrographical observations and chemical compositions indicate that it is an A-type granite. Zircon SHRIMP U-Pb analyses indicate that this A-type granite was emplaced at 276 ± 2 Ma and coeval with the same type of granites in the adjacent areas. Therefore, it suggests that this pluton was likely formed in a post-orogenic extensional setting and probably related to break-off of subducted slabs in Central Asian Orogenic Belt (CAOB), which indicate that the Sunitezuoqi-Xilinhot belt was tectonically evolved into post-orogenic stage since early Permian.
    Opening of the Tethys in southwest China and its significance to the breakup of East Gondwanalang in late PaleozoicEvidence from SHRIMP U-Pb zircon analyses for the Garze ophiolite block [查看] YANQuanren、WANGZongqi、LIUShuwen、LIQiugen、ZHANGHongyuan、WANGTao、LIUDunyi、SHIYuruo、JIANPing、WANGJianguo、ZHANGDehui、ZHAOJian
    Abstract SHRIMP U-Pb zircon analyses for a gabbro sample from the Garzê ophiolite block yielded a mean 206Pb/238U age of 292±4 Ma, which indicated that the spreading time of the Garzê-Litang Tethys was most likely at the earliest Permian. Combined with previous studies, we suggest that the opening of the Tethys in southwest China was derived from breakup of the East Gondwanaland in the late Paleozoic.
    High-pressure granulite from Western Kunlun,northwestern China Its metamorphic evolution,zircon SHRIMP U-Pb ages and tectonic implication [查看] QUJunFeng、ZHANGLiFei、AIYongLiang、LÜZeng、WANGJianPing、ZHOUHui、WANGShiYan
    High-pressure mafic granulites occurring as lenticular bodies within garnet-amphibolites in Kangxiwar Fault have been first reported in this paper. The P-T conditions of two metamorphic stages were obtained using calibrated geothermal barometers and ThermoCalc Program. The peak metamorphic condition of these high-pressure granulites is about 760―820℃, 1.0―1.2 GPa and the retrograde metamorphic condition is about 620―720℃, 0.7―0.8 GPa. The petrological studies show that they have a near-isobaric cooling P-T path which suggests that the Western Kunlun underwent initial crustal thickening, subsequent exhumation and cooling. The SHRIMP zircon U-Pb dating gives two groups of ages for high-pressure granulites. One is 177±6 Ma which is obtained from the rim of the zircon. We consider this age should be the metamorphic age. And the other is 456±30 Ma which is obtained from the core of the zircon and should be the protolith age. The formation of these high-pressure granulites in western Kunlun is closely correlated with the evolution of the Paleo-Tethys and has important implications for the research on Tethys and Paleo-Asian tectonic zone.
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