湖南湘东钨矿区花岗岩地质地球化学特征及意义

Geological and geochemical characteristics and significance of granites in Xiangdong tungsten mining area of Hunan

通过对湖南湘东钨矿三类花岗岩系统的岩矿鉴定和探针分析,确定燕山早期花岗岩中的长石为碱性长石,钠长石 An〈5,大多数样品 An〈3；而印支期花岗岩的斜长石 An=10～15,为更长石。因此,确定邓阜仙复式岩体的岩性,分别为印支期的粗粒斑状黑云母二长花岗岩、燕山早期的中粒斑状白云母碱长花岗岩和细粒碱长花岗岩。系统的常量、微量元素地球化学研究也显示出燕山早期岩浆作用明显不同于印支期花岗岩,具有富硅、偏铝、富钙碱等特点,燕山早期花岗岩为碱长花岗岩,和南岭地区与脉型钨矿有关碱长花岗岩一致。成矿与燕山早期花岗岩浆活动有关。

Based on rock-mineral identification and electron probing analysis of three types of granite systems in Xiangdong tungsten mining area of Hunan,it is verified that the feldspar in early Yanshanian granites is alkali feldspar,in albite An〈5,and in most samples An〈3.The anorthose in Indosinian granites has An=10～15,and it is oligoclase.Hence,the lithology of Denghuxian complex massif is coarse grained porphyritic biotite monzonitic granite,early Yanshanian medium grained porphyritic muscovite alkali-feldspar granite and fine grained alkali-feldspar granite.The systematic geochemical research on macro-elements and trace el-ements shows that early Yanshanian magmatism is characterized by silica-rich,meta-aluminic and calc-alka-line-rich which is apparently different from Indosinian granites.Early Yanshanian granite is alkali-feldspar granite,and it is consistent with alkali-feldspar granite related to vein type tungsten deposit in Nanling area. The mineralization is related to magmation of early Yanshanian granites.