地质学报2017，Vol.91Issue(1)：94-110,17.
柴达木盆地北缘果可山石英闪长岩LA-ICP-MS锆石U-Pb定年及其成因
LA-ICP-MS Zircon U-Pb Dating and Petrogenesis of the Quartz-Diorites from the Guokeshan Area in the Northern Margin of the Qaidam Basin
摘要
Abstract
LA-ICP-MS zircon U-Pb dating yields a weighed mean age of 247 ± 3 Ma for quartz-diorite at Guokeshan area.These rocks consist of plagioclase (55％ to 60％),quartz (15％ to 20％),hornblende (10％ to 15％) and biotite (5％ to 10％) and belong to metaluminous to weakly peraluminous with A/CNK values varing from 0.95 to 1.02,indicating I-type granite affinity.They are characterized by enrichment of LREEs and LILEs (eg.,K,Rb,Cs,Ba,Th) and depletion of HREEs and HFSEs (eg.,Nb,Ta,P,Ti),which are consistent with typical features of arc-magmatite.In addition to the presence of abundance mafic microgranular enclaves in samps,they exhibit higher MgO contents (ranging from 2.04％ to 2.44％) and Mg# values (ranging from 48.9 to 51.9) than experimental melts generated by partial melting of metabasalts/pelites at 1 to 4 GPa,suggesting that they were derived from by magmas mixing between magma produced by partial melting of amphiboite in lower crust and magma derived from enrich mantle.The low Ti-in-zircon temperatures and high zircon Ce4+/Ce3+ ratios indicate zircons were crystallized from low temperature and high oxygen fugacity magmas,and the involvement of water-bearing melts/fluids during the formation of the magmas.All samples fall into the fields of volcanic arc granite in the granite tectonic environment discrimination diagrams,and show high La/Nb ratios (ranging from 2.27 to 2.64),which are consistent with active continental margin area (＞2.0).Combined with regionally geological setting,we suggest that the Guokeshan quartz-diorites are formed as a continental margin arc by the northern subduction of Palaeo-Tethys ocean.关键词
果可山/石英闪长岩/锆石U-Pb定年/岩石成因/构造环境Key words
Guokeshan/quartz-diorites/zircon U-Pb dating/petrogenesis/tectonic environment引用本文复制引用
王玉松,牛漫兰,李秀财,吴齐,韩雨,赵齐齐,笪梁超..柴达木盆地北缘果可山石英闪长岩LA-ICP-MS锆石U-Pb定年及其成因[J].地质学报,2017,91(1):94-110,17.基金项目
本文为国家自然科学基金项目(编号:41272221,41372207)和中国地质调查局地质调查项目(编号:12120115069401,1212011120159)资助的成果. （编号:41272221,41372207）
