云南会泽HZT 型铅锌矿床蚀变白云岩特征及岩石-地球化学找矿标志

蚀变白云岩是会泽超大型铅锌矿床的赋矿围岩。通过矿区调研和近矿围岩典型剖面精细测量,矿区蚀变中-粗晶白云岩从颜色上可分为4种类型:肉红中粗晶白云岩、米黄色针孔状粗晶白云岩、灰白孔洞状粗晶白云岩、纯白色粗晶白云岩;前三者与矿体产出关系密切,从远矿到近矿依次为:肉红中粗晶白云岩→米黄色针孔状粗晶白云岩→灰白孔洞状粗晶白云岩→铅锌矿石;总结了3个带主要矿物组合、组构特征,认为3个带在白云石重结晶程度、显微构造、黄铁矿、晶洞充填物及裂隙等具明显差异,据此可作为辨识赋矿白云岩的重要标志。同时,对比了摆佐组白云岩(矿化粗晶白云岩、粗晶白云岩、白云石化灰岩)主量元素变化特征,分析了近矿蚀变白云岩主量元素及其比值与矿体距离的相关性,以及CaO与其他主量元素相关性,确定了热液蚀变参数有SiO2、MgO/CaO、K2O/CaO、Al2O3/TFe等,为找矿预测提供理论依据。

Altered dolomite features and petro-geochemical prospecting indicators in the Huize lead-zinc deposit

Dolomite is a host rock in the Huize superlarge lead-zinc deposit. The near-ore dolomite shows zonation in space and can be divided into three types, namely grayish white-white coarse-grained (pinhole) dolomite, beige (local miarolitic cavitiy) coarsegrained dolomite and pale red-red coarse grained crystalline dolomite. The authors analyzed the mineral assemblage zonation and fabric characteristics, and reached the conclusion that there exist significant differences between these types of dolomite in such aspects as the degree of recrystallization in dolomite, microstructure of dolomite, crystalline form of pyrite, vuggy fillings and fissures, and these differences can serve as important indicators for identifying ore- bearing dolomite. The authors also studied element geochemistry of near-ore dolomite and other three types of dolomites in Baizuo Formation (mineralized dolomite, coarsegrained dolomite, and dolomitic limestone). According to the relationships between major element content of dolomites and the distance from the ore body and between major element content of dolomites and CaO content, the authors investigated the alteration of rocks and determined the hydrothermal alteration parameters of the coarse-grained dolomites, which are SiO2, MgO /CaO, K2O / CaO and Al2O3/TFe2O3.