滇西锡矿带地质特征与成矿构造背景

Geologic characteristics and tectonic settings of tin deposits in West Yunnan,China

通过对滇西锡矿带矿床的野外地质特征、区域地质演化、时空分布、地球化学特征、成因、物质来源与成矿地球动力学背景等方面的研究,综合探讨滇西锡矿带的成矿地质特征与区域成矿构造背景,并浅析其找矿前景。结果表明滇西主要锡矿床类型为云英岩型、热液脉型和矽卡岩型;燕山晚期—喜马拉雅早期花岗岩体与锡矿关系最为密切;含锡岩浆岩主要是富硅、富碱、基性组分低及高分异的深层重熔型花岗岩;同位素年龄资料显示,锡矿床主要形成于110～50Ma B.P.,与中—新特提斯封闭碰撞时期吻合。结合三江多岛弧盆-碰撞造山构造演化分析,认为滇西地区锡矿床及成矿花岗岩主要形成于陆-陆碰撞体制。

Through the researches on the field geological characteristics,the regional geological evolution,the space-time distribution,the geochemical characteristics,the genesis,the material sources and the metallogenic geodynamic background.This paper synthetically discusses the ore-forming geological characteristics and regional metallogenic tectonic background of the West Yunnan tin ore belt and makes a simple analysis of its prospecting future.The results show that most of the tin deposits in West Yunnan belong to the types of greisen,hydrothermal veins and skarn.One of the strongest associations with tin deposits is the late Yanshanian-early Himalayan high differentiation granite.It is rich in K and Si and poor in Mg,Fe and comes from the deep remelt.Isotopic age determinations show that the granite-associated tin deposits formed during 110～50 Ma B.P.which is approximately same as the time of medium-new Tethys collisions.Considering the tectonic evolution of the ＂poly-island-ocean and basin system＂,it can be concluded that the West Yunnan tin deposits and their related granites were formed by the continental collision regimes.