地质学报2018，Vol.92Issue(6)：1297-1312,16.
北祁连银灿铜锌矿床有关火山岩年代学及地球化学研究
Geochronological and Geochemical Study of Volcanic Rocks from the Yincan Cu-Zn Deposit in North Qilian
摘要
Abstract
The Yincan deposit,located in the middle part of North Qilian Mountains,is a small-sized Cu-Zn ore deposit occurring in the Lenglonglin volcanic rock belt.Ore-bearing rocks consist of basalt-rhyolite association of the Yingou Group,with mineralization occurring in bimodal rhyolitic volcanic rocks.Spatially,orebodies show well developed zonation,from the lower part upward,gradual change from Zn→Cu-Zn→Cu→Fe orebody.Zircon LA-ICP-MS dating yielded concordant ages of 454.0±2.0 Ma and 417.7 ±1.7 Ma for basalt and rhyolite,respectively,indicating that the Yincan deposit formed in Middle Ordovician.Geochemical data show that the basalt belongs to sub-alkaline tholeiite because of low TiO2 (0.22％～0.25％),high MgO (10.83％～14.17％,Mg# =68～73),Cr (974×10-6～1110×10 6),Ni (219 × 10-6 ～291 × 10-6).Trace element primitive mantle-normalized spidergram shows a distinct loss of Nb,and REE chondrite-normalized diagram shows a left-dipping pattern.The rhyolite belongs to the low-K tholeiitic series and is depleted in Th,Nb,Ta,Sr and Ti,probably generated by partial melting of the crust rocks.The both volcanic rocks show characteristic of bimodal volcanic rocks and formed in the island arc rifting environment triggered by slab subduction of North Qilian ocean.The δ34S compositions (+4.3‰～+8.7‰) of the ore deposit show the mixing features of mantle-driven magmatic sulfur and seawater reduced sulfur.The weak water-rock reaction in the Yincan deposit led to a less amount of metal materials leached from volcanic rocks.This may be one important reason for the small size of the Yincan deposit.关键词
双峰式火山岩/年代学与地球化学/银灿铜锌矿床/冷龙岭火山岩带/北祁连Key words
bimodal volcanic rocks/geochronology and geochemistry/Yincan Cu-Zn deposit/Lenglongling volcanic belt/North Qilian引用本文复制引用
郭周平,赵辛敏,王育习,白赟,张江伟,高永伟,张海松..北祁连银灿铜锌矿床有关火山岩年代学及地球化学研究[J].地质学报,2018,92(6):1297-1312,16.基金项目
本文为中国地质调查局项目(编号:DD20160012)资助成果. （编号:DD20160012）
