云南个旧卡房锡-铜矿床碱长花岗岩厘定及意义

Charateristics of Alkali Feldspar Granite in Kafang Sn-Cu Deposit,Gejiu,Yunnan Province,China

卡房矿床位于个旧矿田东南部,矿区花岗岩为致矿岩体,以往对花岗岩的研究也较多,对花岗岩的定名为:黑云母花岗岩、黑云母二长花岗岩或者黑云母斜长花岗岩等等。通过对卡房花岗岩进行系统的岩矿鉴定和电子探针分析,发现长石为碱性长石(钾长石和钠长石),钠长石的An值均小于等于5。因此最终确定卡房岩体花岗岩为碱长花岗岩。而这种碱长花岗岩由富挥发分的岩浆形成,液态不混溶作用广泛发育于岩体顶部附近,是锡多金属矿富集成矿的主要分异方式,钠长石的An值可部分作为花岗岩成矿属性的评价标识之一。

Kafang deposit is located in the Southeast of Gejiu ore field. The granite of the deposit is the mineralization rock. Anciently, the granite was also named by different researchers as biotite granite, biotite-monzogranite or biotite plagioclase granite and so on. However, microscope and electron microprobe analysis of the granite show that all the feldspars are K-feldspar and albite （An〈5）, suggesting that the granite should be named as alkali feldspar granite. This kind of granite is usually formed from rich-volatile （Li-F） magma, with the extensive development of liquid immiscibility at the top of it. The effect of liquid immiscibility is the main differentiation way for forming the Sn-polymetallic deposit. The albite＇s An value could be used as an indicator for evaluating granite in searching for Sn polymetallic mieralization.