河南土门萤石脉型钼矿床流体包裹体研究及成因探讨

Study of fluid inclusions and ore genesis of the Tumen Mo-fluorite vein deposit, Henan province.

河南方城土门萤石脉型钼矿床位于栾川断裂北侧的华熊地块东南部。矿体呈断续的脉状、似层状、透镜状产于花岗斑岩外接触带,赋矿构造为大理岩与片岩之间的层间断层。矿石主要由萤石、硫化物和碳酸盐等矿物组成。矿脉穿插关系、矿石组构和矿物组合显示了4阶段矿化:分别以白色萤石(Ⅰ阶段)、紫色萤石-辉钼矿(Ⅱ阶段)、辉钼矿多金属硫化物(Ⅲ阶段)以及碳酸盐(Ⅳ阶段)为标志。各阶段萤石中流体包裹体可分为4类:NaCl-H_2O型(W类)、CO_2-H_2O-NaCl型(C类)、纯CO_2型(PC类)及含子晶包裹体(S类)。冷热台测试显示,Ⅰ阶段均一温度为300～420℃,峰值为360～410℃,Ⅱ阶段均一温度180～380℃,峰值为220～300℃;Ⅰ阶段流体盐度高达49.68 wt%NaCl eqv.,Ⅱ阶段则不高于13.07 wt%NaCl eqv.。从早到晚,W类包裹体平均密度由0.88g/cm^3减小到0.84g/cm^3,C类包裹体CO_2的平均密度由0.66g/cm^3增高到0.82g/cm^3。总体来说,土门萤石-钼矿床形成于中高温、高盐度、富CO_2和F的流体系统,成因上归属于大陆背景的浆控脉状热液成矿系统。

The Tumen fluorite-Mo deposit, Fangcheng County, Henan province, occurs in southeastern Huaxiong Terrane which is north of the regional Luanchuan fault. Hosted by inter-bed fractures between marble and schist, orebodies are strata-bound lodes and lens occurred in the outer contact zone of granite porphyry and host-rocks of reversal wing of a geosyncline. Main minerals of ores include luorite, sulfides and carbonate. According to the crosscutting relations of veins and ore textures and structures, hydrothermal ore-form ng process are divided into four stages characterized by mineral assemblages of (I) white fluorite, (II) Mo-bearing purple fluorite, III) polymetallic sulfides, and (IV) carbonates, respectively. Fluid inclusions include four compositional types: NaCl-H(2)O (W-type), (CO(2)-H(2)O-NaCl (C-type), pure CO(2) (PC-type) and daughter crystal bearing (S-type). Microthermometry in fluid inclusions in fluories shows that the homogeneous temperatures of stage I range from 300 similar to 420 degrees C, with majority of 360 similar to 410 degrees C; and those of stage II, range from 180 similar to 380 degrees C with majority of 220 similar to 300 degrees C. In correspondence, The fluid inclusion salinities of stage I are up to 49.68 wt% NaCl eqv., whereas those of stage II are no higher than 13.07 wt% NaCl eqv.,. From early to late stages, the densities of W-type inclusions decrease from 0.88 to 0.84g/cm(3), and the densities of CO(2) in C-type inclusions increase from 0.66 to 0.82 g/cm(3). In general the Tuman Mo deposit has been formed by a medima-to-high temperature, high salinity and high-contents of CO(2) and F fluid-system, and is genetically attributed to intrusion-related vein type hydrothermal system developed in intra-continental setting.