扬子板块西缘攀西地区白草矿区黄铁矿标型元素特征及其指示意义

黄铁矿是重要的金属硫化物矿物,在多种矿床中均有产出,其标型特征对矿床成因、矿体空间分布等具有重要的指示意义。以扬子板块西缘攀西地区白草矿区黄铁矿为研究对象,利用矿相学、电子探针等分析方法来对比研究浸染状、致密块状、斑杂状、网脉状矿石中黄铁矿的标型元素特征。结果表明:白草矿区黄铁矿Fe、S平均含量(质量分数,下同)分别为46.030%、52.815%,介于岩浆成因与热液成因之间,根据矿石特征,黄铁矿以岩浆成因为主,并有少量热液作用参与;将白草矿区黄铁矿δFe-δS特征与金川等典型铜镍硫化物矿床黄铁矿对比,表明白草矿区黄铁矿为典型的岩浆熔离型;由于存在钒钛磁铁矿,Co/Ni值多小于5,说明钒钛磁铁矿与硫化物存在共生关系;岩浆内生成因黄铁矿S/Se值小于15000,白草矿区黄铁矿S/Se值为812~10466,显示白草矿区黄铁矿为岩浆内生成因;Se/Te值随温度降低而升高,显示上述4类矿石黄铁矿结晶顺序为浸染状矿石→致密块状矿石→斑杂状矿石→网脉状矿石;原始地幔标准化主量、微量元素蛛网图显示白草矿区黄铁矿兼具岩浆成因与热液成因。综上所述,攀西地区白草矿区黄铁矿成因主要以岩浆熔离作用为主,并含有少量热液作用。

Characteristics of Pyrite Typomorphic Elements in Baicao Mining Area of Panzhihua-Xichang Region,the Western Margin of Yangtze Plate,China and Their Indication

Pyrite is an important metal sulfide mineral,which occurs in many kinds of deposits.Its typomorphic characteristics are of great significance to the genesis of deposit and the spatial distribution of ore bodies.Taking pyrite in Baicao mining area of Panzhihua-Xichang region,the western margin of Yangtze plate as the research object,the typomorphic element characteristics of pyrite in four kinds of ores,such as disseminated,dense massive,taxitic and net vein,were comparatively studied by analytical methods of mineralography and electron probe micro-analyzer(EPMA).The results show that the average contents of Fe and S in pyrite are 46.030%and 52.815%,respectively,which are between magmatic and hydrothermal origins;according to ore characteristics,pyrite is mainly of magmatic origin,and a small amount of hydrothermal process also participate in the formation of pyrite;compared theδFe-δS characteristics of pyrite in Baicao mining area with those in Jinchuan and other typical Cu-Ni sulfide deposits,it is proved that the sulfide minerals in Baicao mining area are typical magmatic liquation type;the ratio of Co/Ni is less than 5 due to the existence of V-Ti magnetite,which indicates the symbiotic relationship between V-Ti magnetite and sulfide;the ratio of S/Se is 812-10466,which is less than that of magmatic endogenetic pyrite(15000),indicating that pyrite is of magmatic endogenetic origin;the ratio of Se/Te increases with the decrease of temperature,indicating that the crystallization order of pyrite is disseminated ore→dense massive ore→taxitic ore→net vein ore;the primitive mantle-normalized major and trace elements spider diagram shows that pyrite in Baicao mining area has both magmatic and hydrothermal origins.Based on the above typomorphic element characteristics,it is considered that pyrite in Baicao mining area is mainly caused by magmatic liquated mineralization and contains a small amount of hydrothermal action.