滇西来利山锡矿自然重砂矿物组合及其成矿响应

INDICATION OF HEAVY MINERALS COMBINATION OF LAILISHAN TIN DEPOSIT IN WESTERN YUNNAN

自然重砂矿物通常被用来解释沉积物的产生、搬运、物源特征以及地球化学等性质,然而即使是化学成分较稳定的锡石,也很少有人研究其矿物组合在锡矿找矿中的指示作用,特别是对中国重要的锡矿富集区——滇西锡成矿带而言。锡矿中自然重砂矿物的组合可指示出源区原生矿床的种类及矿床成因等信息,为新矿床的发现界定相关靶区位置。研究结果显示,来利山锡矿重砂矿物组合中不仅有锆石、磷灰石、绿帘石、金红石、锐钛矿等大多数花岗岩常见的重砂矿物,亦报出了含锡花岗岩特有的一种气成矿物——电气石,来自含锡花岗岩的重砂矿物百分含量均不高(<3%)。同时,在短距离搬运过程中,重砂矿物组合以锡石+黄铁矿+磁铁矿为主,伴随有独居石、赤铁矿、褐铁矿等。重砂矿物组合中黄铁矿的大量报出表明其成矿源区主体为锡石—硫化物型锡矿体而非云英岩型锡矿体。

Heavy minerals are commonly used to explain sediments, transportation, source and geochemistry. Cassiterite, stable as its chemical components, is seldom used as an indicator of tin deposit in western Yunnan tin zone, China＇s vital tin concentrating area. Heavy minerals combination of tin deposits can indicate the deposit types and genesis, helps locate the new discovery. Heavy minerals of Lailishan tin deposit are composed of zicon, apatite, epidote, rutile and anatase, commonly found in granites, and tourmaline, a specific tin-bearing granite mineral, totally less than 3% in weight. In a short transportation, heavy minerals combination includes cassiterite, pyrite and magnetite, also associated with monazite, hematite and limonite. Large quantity of pyrites implies a cassiterite-sulfides ore body rather than Greisen type.