北祁连清水沟——白柳沟Fe-S和Pb-Zn-Cu型块状硫化物矿床形成环境探讨

摘要

青海祁连县清水沟—白柳沟新元古代寒武纪大陆裂谷双峰式海相火山岩中产有Fe-S和Pb-Zn-Cu型块状硫化物矿床.这两类矿床除受所在火山岩陆壳幔源区的部分熔融程度和火山作用旋回性不同影响外,主要受产生构造位置和火山岩浆源区物性条件所控制.其中产Fe-S型矿床的石头沟-香子沟穹窿火山作用,相对形成于近裂谷扩张中心的深海环境,以低K2O钙碱性的拉斑玄武质或英安质下地壳为物源区环境;郭米寺-白柳沟穹窿的Pb-Zn-Cu型火山作用形成于远离扩张中心的陆缘弧环境,源区为一种由地幔源和壳源共同构成的混合源.在矿床成因类型方面,前者近似塞浦路斯的铜黄铁矿,后者为较典型的日本黑矿型.%Fe-S type and Pb-Zn-Cu type massive sulfide deposits occur in the Neoproterozoic-Cambrian continental rift bimodal marine volcanic rocks in Qingshuigou-Bailiugou of Qilian County Qinghai Province.The ore deposits of this two types are not only influenced to some extent by partial melting of the volcanic rocks in crust-mantle source region and volcanism,but controlled by tectonic positions and physical conditions of magmatic source.Volcanism in the Shitougou-Xiangzigou dome hosting Fe-S type deposits happened correspondingly in the deep sea environment near to the center of rift expansion,with dacite in lower crust or the K2 O-low calc-alkali basalt lower crust as the provenance.In comparison,volcanism in the Guomisi-Bailiugou dome hosting Pb-Zn-Cu type deposits happened correspondingly in the continental margin arc environment away from the center of rift expansion and took mixture of the mantle source and crust source.In regard to metallogenic type,the former is similar to the Cyprus-type and the latter is Kuroko-type.