地质通报Issue(1)：71-90,20.
藏南冈底斯南缘程巴岩体高Sr/Y花岗闪长岩和包体形成机制及Sr-Nd-Hf同位素制约
摘要
Abstract
The Chengba Complex on the southern margin of the Gangdise batholiths in southern Tibet comprises mainly granodio⁃rite and subordinately dioritic enclaves and leucogabbro. Zircon U-Pb analytical results demonstrate that the granodiorites formed at 29.40±0.18Ma to 29.42±0.25Ma, whereas the fine-grained dioritic enclaves formed at 30.02±0.15Ma. Bulk-rock major and trace el⁃ement and isotope (Sr-Nd-Hf) analyses indicate that the granodiorites are characterized by relatively high SiO 2 (65.2%~66.2%) and K2O (3.2%~4.0%) but low FeO and MgO, and high Sr (774×10-6~813×10-6), low Y (9.9×10-6~11.2×10-6), and hence high Sr/Y ra⁃tios (>60 and up to 82). In contrast, the dioritic enclaves are relatively low in SiO2 (53%~56.1%) and K2O (1.5%~3.2%), but high in MgO and FeO with relatively high Na/K ratios (≥2). Both are enriched in LREE and LILE and depleted in HREE and HFSE and have similar relatively high zirconεHf(t) values(+1.1~+6.2)as well as negative whole-rockεNd (t) values(-2.9~-5.9). Combined with data available, the new results obtained by the authors suggest that the Chengba granodiorite and dioritic enclaves were formed within a time span of ca.1Ma. Similar isotopic characteristics imply that they were derived from similar sources. The high Sr/Y ratios in Chengba granodiorite, in contrast to low Sr/Y ratios in the mafic enclaves, possibly do not represent primary magma composition. Instead, the high Sr/Y and high Ba characteristics of the Chengba granodiorite might have resulted from fractional crystallization of parent magmas with low Sr/Y ratios and low Ba content like those mafic enclaves.关键词
冈底斯岩基/程巴岩体/花岗闪长岩/高Sr/Y/闪长质包体/LA-ICP-MS锆石U-Pb年龄Key words
Gangdise batholith/Chengba rock mass/granodiorite/high Sr/Y/dioritic enclaves/LA-ICP-MS zircon U-Pb ages分类
天文与地球科学引用本文复制引用
尚振,曾令森,高利娥,高家昊,陈福坤,侯可军,王倩,郭春丽..藏南冈底斯南缘程巴岩体高Sr/Y花岗闪长岩和包体形成机制及Sr-Nd-Hf同位素制约[J].地质通报,2016,(1):71-90,20.基金项目
国家自然科学基金项目(批准号41425010、41273034)和中国地质调查局项目 （批准号41425010、41273034）
