个旧花岗岩的成因、演化及其找矿意义

个旧地区的花岗岩,从其时空分布和矿物学,岩石化学、微量地素、稀土元素、以及同位素特征看,具有一定的继承和演化关系.研究表明,本区花岗岩的形成经历了两次岩浆活动.其中龙岔河岩体是燕山早期岩浆活动的产物.而马松岩体.神仙水岩体、白沙冲岩体以及老卡岩体则为燕山晚期岩浆活动不同阶段的产物.从成因上看,上述各岩体可能皆属陆壳改造型(S型)花岗岩.但是早期龙岔河岩体在一定程度上又表现出同熔型(Ⅰ型)花岗岩的特征,各种地质和地球化学特征的对比表明.这些岩体可能具有相似的源岩物质(组成).从晚期各岩体表现的特征看,它们可能都属于含锡花岗岩体.由此,个旧地区大面积分布砂锡矿的成因和来源问题便可以得到较为圆满的解释.通过对神仙水、白冲岩体为含锅花岗岩的认定,结合本区原生锅矿的分布规律.笔者认为.神仙水岩体东南以及白沙冲岩体周围.可能与马松岩体和老卡岩体周围一样,是一个潜在的找矿远景区.

ORIGIN,EVOLUTION AND PROSPECTING SIGNIFICANCE OF GRANITES IN THE GEJIU TIN FIELD,YUNNAN PROVINCE

Based on the distribution, mineralogy, petrochemistry, trace and rare earth elements, Rb-Sr, Sm-Nd and oxygen isotopic characteristics of the granites in Gejiu, it can be concluded that the granites are the products of two stages of magmas: the Longchahe granite is product of the melted earth crust, in the, early Yanshanian; the Mashong, Shenxianshui, Baishachong and Laoka granites are differentiated products of the late Yanshanian magma. They display certain inheritance and evolutional relations from early to late stages. This may indicate that they have the similar source rocks and the products of the selected melting of these rocks. The late Yanshanian granites are all tin-bearing granites compared with the known tin-bering granite. This may give a good explanation to existence of large quantity of stream tin distribution in the eastern Gejiu fault. Tt may also have some significance to find tin deposits at the southern (or southcastern) area of the Shenxianshui and Baishachong granite bodies.