湖南清水塘铅锌矿斑点板岩的成因

Ogrigin of spotted slates of Qingshuitang Pb-Zn deposit in Hunan Province

湖南清水塘铅锌矿位于湖南省祁东县内,斑点板岩为矿床的主要赋矿地层,该斑点板岩为多期变质叠加形成。文章主要通过研究显微镜下斑点板岩的岩相学特征确定斑点板岩矿物共生组合,厘定3期变质,分别为早期区域变质、中期热接触变质、后期热液蚀变。还借助绿泥石电子探针分析和Mg元素扫面,确定了斑点板岩中绿泥石为斜绿泥石,应用绿泥石成分分析厘清了绿泥石形成期次,划分了早期区域变质绿泥石和晚期热液变质绿泥石。应用绿泥石成分温度计确定了绿泥石形成温度条件,区域变质绿泥石形成温度为100～115℃,热液成因绿泥石形成温度为125℃左右,绿泥石化学特征验证了岩相学观察中确定的3期变质。

Qingshuitang Pb-Zn deposit is located inQidong, Hunan Province. Spotted slates are considered as a mineralized stratum of the deposit, which is formed by multistage metamorphism. This study used polarizing microscope to identify the mineral assemblages of spotted slates, and the study has determined 3 stage of metamorphism:firstly, regional metamorphism;secondly, contact metamorphism;and the third, hydrothermal liquid alteration. This study, by utilizing EMPA analysis and Mg-element scan, determined mineralization stages of chlorite and classification of chlorite, which manifested that the chlorite is clinochlore, no matter the chlorite is located in spots or in bulk material. The EPMA analysis distinguished 2 phases of chlorite:early-stage regional metamorphic chlorite, late-stage hydrothermal chlorite. Forming temperature of regional metamorphic chlorite is approximately 125℃, and forming temperature of hydrothermal chlorite is approximately 115℃. Chemical composition of chlorite has justified the result of petrography study as well.