甘肃白银厂矿田早中寒武世酸性火山岩成因及源区特征的地球化学制约  

Geochemical constraint on the origin and sources of early-middle Cambrain acidic volcanic rocks from Baiyin Ore Deposit

作　　者：郭原生[1] 王金荣[1] 付善明[1] 邱红英[1] 胡沛青[1] 陈建林[1] 秦秀峰[1] 

机构地区：[1]兰州大学资源环境学院,甘肃兰州730000

出　　处：《兰州大学学报（自然科学版）》2003年第5期95-100,共6页Journal of Lanzhou University(Natural Sciences)

基　　金：甘肃省自然科学基金资助项目 ( ZS0 0 1 -A2 5 -0 0 6-Z)

摘　　要：从白银厂矿田早中寒武世酸性火山岩的地球化学研究入手 ,对其成因和源区特征进行了比较深入的探讨 .认为本区酸性火山岩的源岩应是玄武岩和含水辉长质岩石的部分熔融形成的安山岩 ,源岩安山岩部分熔融形成该区流纹岩 ,而英安岩主要由流纹岩浆或与玄武岩浆混合或发生不明显的分离结晶形成 .早—中寒武世 ,该区酸性火山岩的成岩环境为火山弧环境 ,当洋壳俯冲进入深处时 ,由于俯冲板片的脱水导致上地幔楔部分熔融形成源岩玄武岩 ,同时富水的流体萃取洋壳中的大离子亲石元素、轻稀土元素向上进入楔形地幔 ,使地幔橄榄岩富集大离子亲石元素 .地幔中流体的增加导致下地壳中辉长质岩石的部分熔融形成了该区流纹岩的源岩—安山岩 .熔融地幔底辟上升 ,由于高热流而引起下地壳局部熔融和混染 ,使该区酸性火山岩又具有陆壳混染的特征 .The origin and sources of the Early Middle Cambrain acidic volcanic rocks from Baiyin Ore Deposit are completely discussed in this paper in terms of the geochemical characteristics of the rocks. The studied results show that the source rocks of the rhyolites are andecite that had previously formed from the partial melting of the basaltic and water-bearing gabbro rocks which generated from the partial melting of the mantle wedge affected by dehydration of subduction plate in volcanic arc, and that the dacite resulted from the mixing of rhyolitic and basalticmagmas or the fractional crystallization of the latter. Water-enriched fluids extracting LILEs and LREE from the subduction plate made the mantle wedge enriched in these elements. The partial melting and contamination of the lower crust resulted from the affection of diapirism of the high heat mantle melt and made the studied volcanic rocks to acquire the characteristics of continental contamination.

关 键 词：白银厂矿田 酸性火山岩 地球化学 源区特征 

分 类 号：P588.14[天文地球—岩石学] P534.41[天文地球—地质学]