地质通报2017，Vol.36Issue(9)：1542-1552,11.
欧龙布鲁克地块西北缘青海冷湖北片麻状花岗闪长岩锆石U-Pb年龄、地球化学特征及地质意义
Zircon U-Pb ages, geochemistry and geologi-cal significance of gneissic granodiorite in northern Lenghu, Qinghai Province
摘要
Abstract
The gneissic granodiorite in northern Lenghu of Qinghai Province is characterized by low SiO2 and MgO,and high Al2O3, Na2O and CaO, with alumina saturation index A/CNK of 0.92~0.797. These features suggest that this gneissic granodiorite belongs to the high-K calci-alkaline peraluminous rocks and metaluminous rocks. The chondrite-normalized REE values show right-in-clined patterns with slightly negative Eu anomaly. The primitive mantle normalized trace element spidergrams are characterized by en-riched LILE(such as Rb, Th and U)and depleted HFSE(such as Nb,Ta and Zr), which is comparable with the characteristics of oro-genic magmatic rocks,suggesting a volcanic arc tectonic setting associated with subduction. Moreover, the gneissic granodiorite is characterized by rich Na2O and A12O3, high Sr, Sr/Yb and LREE, and inconspicuous differentiation of HREE. These features imply that the rocks in northern Lenghu of Qinghai were probably formed by the melting of basaltic rocks with amphibole as a residual phase. With the U-Pb isotopic age of 470.2±1.2Ma(n=19,MSWD=0.68)of granodiorite,the authors believe that north Al-tun oceanic crust subducted toward Oulongbuluke block in Early Ordovician.关键词
片麻状花岗闪长岩/LA-ICP-MS锆石U-Pb测年/地球化学/青海冷湖北Key words
gneissic granodiorite/LA-ICP-MS zircon U-Pb dating/substance records/geochemistry/northern Lenghu of Qinghai Province分类
天文与地球科学引用本文复制引用
辜平阳,查显锋,陈锐明,董增产,庄玉军,查方勇,胡朝斌,李培庆..欧龙布鲁克地块西北缘青海冷湖北片麻状花岗闪长岩锆石U-Pb年龄、地球化学特征及地质意义[J].地质通报,2017,36(9):1542-1552,11.基金项目
陕西自然科学基金项目《青海阿尔金东段新太古代米兰岩群中麻粒岩成因及变质作用过程研究》(编号:2017JM4001)、中国地质调查局项目《青海阿尔金1:5万打柴沟等6幅区调》(编号:1212011121193)和国家自然科学基金项目《青藏高原羌塘地区地壳早期物质探索研究》(批准号:41002063) （编号:2017JM4001）
