地质学报2017，Vol.91Issue(9)：1985-2003,19.
西藏雄村铜金矿区侏罗系砂岩地球化学特征:对构造背景的约束
Geochemical Characteristics of the Jurassic Sandstones in the Xiongcun Copper-Gold Deposit, Tibet: Constraints on Tectonic Setting
摘要
Abstract
Xiongcun copper-gold deposit is located in the middle of the southern margin ofthe Gangdise orogenic belt.Its southern margin is near to the Yarlung Zangbo suture zone (IYS) and Xigaze forearc basin, and the north is Xietongmen Eocene biotite granodiorite batholith.Based on the comprehensive microscopical identification and the analytical contents of major elements and trace elements (including REE) from the Xiongcun sandstones, the tectonic settings and provenance were studied.The result of study indicates that the content of SiO2 varies from 53.27％ to 66.13％ (average 58.27％) and is similar to that (66.1％) of Paleozoic greywackes.The high content of Al2O3 varies from 14.53％ to 24.04％ (average 20.12％), this may suggest that there are some feldspar in sandstones and with strong clayization.Combined with the microscopic characteristics, the Xiongcun sandstone may belong to feldspathic lithic sandstone.The special major element assemblages Fe2O3 + MgO (7.3 ％ ～ 17.6 ％), TiO2 (0.68 ％ ～ 1.25 ％) and Al2O3/SiO2(0.22％～0.45％) of the Xiongcun sandstones are similar to those of Oceanic Island Arc.It can be seen from the spider diagram that the Xiongcun sandstones are depleted in HFSE elements such as Ta, Nb, P,Ti and HREE, and enriched with LILE elements such as K, Rb, U and REE.The chondrite standard curve of REEs has rightward trend which reveals an enrichment of LREEs and an indifference of HREEs.The contents of standard trace elementsTh (2.5×10-6), Zr (114×10-6), Hf (3.6×10-6), Ce (27.95×10-6), Ti (0.54×10-6) and the ratios of trace elements Th/U (2.9), Zr/Th (46), La/Sc (0.72), Th/Sc(0.11) show that the genesis of the Xiongcun sandstones is Oceanic Island Arc.The discriminatory diagrams of La-Th-Sc, Th-Sc-Zr/10 and Th-Co Zr/10 were the same result.There are weak negative Ce anomalies and positive Eu anomalies in the PAAS-normalized rare element plots, which show the same conclusion with these from major elements and trace elements, indicating that the sandstones are influenced by both seawater and the fluids from deep.Diagrams of Co/Th-La/Sc and La/Th-Hf show that the provenance of Xiongcun sandstones is mixed with intermediate acidic felsic volcanic rocks and andesitic volcanic rocks.Combined with the detrital zircon ages of the sandstones (studied by other researcher), it is considered that the detrital zircon ages are not early in Late Triassic, and the provenance is of island arc volcanics features.关键词
雄村/岛弧/砂岩/构造背景/物源/岩石地球化学Key words
Xiongcun/island arc/sandstones/tectonic settings/provenance/petrogeochemistry引用本文复制引用
杨宗耀,王勇,郎兴海,唐菊兴,张忠,张金树,高一鸣,黄勇,谢富伟,付燕刚..西藏雄村铜金矿区侏罗系砂岩地球化学特征:对构造背景的约束[J].地质学报,2017,91(9):1985-2003,19.基金项目
本文为大陆构造与动力学国家重点实验室开放基金重点项目(编号K201401)、国家自然科学基金项目(编号41502079、41172077)、四川省青年基金项目(编号2014JQ0047)、四川省教育厅自然科学重点项目(编号15ZA0073)和地调项目(编号12120114068401)联合资助成果. （编号K201401）
