桂阳台子上蚀变岩体型锡矿床地质特征及找矿意义

该矿床赋存于大义山复式岩体中侏罗纪三江口序列花岗岩最晚期次的介头单元中心部位。矿体呈似层状，中心部位隐伏，NE端长约500m，宽400m，平均厚15．30m，Sn平均品位0．5%；南西段长400m，宽240m，厚4－25m，Sn平均品位0．7％。矿区有蚀为细粒花岗岩型和云英岩型两类锡矿。矿石矿物主要是锡石，次有黑钨矿、辉钼矿、铌钽铁锰矿等，脉石矿物 主要是长石、云母、石英等。围岩蚀变发育、类型多样，其中云英岩化、黄玉化、萤石化和褐铁矿化是重要的找矿标志，岩浆上的前锋位置且多组节理，裂隙的交 汇处，是有利的储矿空间。介头单元等晚期岩体的顶盖及其前锋部位，是寻找该类型锡矿的有利地段。

GEOLOGIC CHARACTERISTICS AND THE SIGNIFICANCE OF EXPLOITING Sn-DEPOSIT OF ALTERNATION ROCK IN GUIYANG ESTRADE

The deposit exists in the Jietou unit center of multifold rock in the afternoon of Sanjiangkou sequence granite of Dafu Mountain, Middle Jurassic period. The mine-body, layer-shaped, center part lying blind, is 500m long, 400m wide and 15.3m thick at NE end with average content Sn 0.5%; the segment at SW trend is 400m long, 240m wide and 4-25m thick with average content Sn 0.7%. There are two types of Sn ores (including alteration granite and Greisen types). Oreminerals largely are cassiterite, secondly wolframite, molybdenite, Nb-Ta-Fe-Mn ore etc., gangue minerals are mainly feldspar, mica, quarz etc. Greisen-lithify, topaz-lithify, fluorite-lithify, and limonite-lithify are important mark in seeking mine with alteration wall rock development and type variety. The vanguard position of intruding magma and intersects of several Joints and fractures are the ore-contained space. The coping and vanguard of Jietou unit etc. afternoon rock are the advantageous place for seeking the type of Sn-ore.