河南省洛宁县寨凹钼矿床流体包裹体研究及矿床成因

Fluid inclusion constraints on the origin of the Zhaiwa Mo deposit,Luoning county,Henan Province

寨凹钼矿床位于华北克拉通南缘的熊耳地体,矿床定位受马超营断裂带的次级断裂控制,矿体呈脉状赋存于太华超群石板沟组黑云角闪斜长片麻岩中。成矿过程包括3个阶段:石英-辉钼矿阶段(Ⅰ)、石英-多金属硫化物阶段(Ⅱ)、石英-碳酸盐阶段(Ⅲ),其中,Ⅰ阶段为主成矿阶段。寨凹钼矿床可见2类流体包裹体,即水溶液型和含子晶包裹体;激光拉曼指示包裹体成分主要为H2O。从早到晚,流体包裹体均一温度从Ⅰ阶段100～260℃,经Ⅱ阶段110～160℃,变化为Ⅲ阶段120～180℃,矿床总体属于低温热液矿床;流体包裹体盐度从Ⅰ阶段的2～25wt%NaCl.eqv演化至Ⅱ阶段的6～30wt%NaCl.eqv,然后降为Ⅲ阶段的7～25wt%NaCl.eqv。Ⅰ阶段均一温度范围宽广、流体包裹体盐度由双峰式演化为单峰式以及包裹体温度-盐度双变图的负相关性指示了流体混合是主要的成矿机制。寨凹钼矿流体包裹体以高密度、高盐度的低温低压流体为特征,是含CaCl2流体参与成矿的结果,热的岩浆流体与冷的含CaCl2的卤水的混合,导致了辉钼矿的沉淀。寨凹钼矿床地质和流体包裹体特征与侵入岩相关的成矿系统一致,指示其成因类型为与侵入岩有关的钼矿床。

The Zhaiwa Mo deposit, in Luoning county, Henan province, is located in the Xiong＇er Terrane in southern margin of North China Craton. Its ore bodies, occurring as lode, are hosted in biotite-amphibole-plagiogneiss of the Taihua Group and controlled by subsidiary faults of the Machaying fault which is the south boundary fault of the Xiong＇er terrane. Three stages of hydrothermal ore-forming process are recognized, Quartz-molybdenite （ I ）, which is the main metaUogenic stage, Quartz-polymetallic sulfide （Ⅱ） and Quartz- carbonate （Ⅲ）. Two types of fluid inclusions, i.e. H2O-NaCl, daughter mineral-bearing, are observed. Laser- lkaman spectrum showing that the most important component of fluid inclusion is water. From early to late stages, homogeneous temperatures of fluid inclusions change from 100-260 ℃ （ I ）, through 110-160℃ （Ⅱ）, to 120-180℃ （Ⅲ）, this showing that the Zhaiwa Mo deposit belongs to low-temperature hydrothermal deposit; salinities change from 2-25 wt%NaCl.eqv（ I ）, through 6-30 wt%NaCl.eqv （Ⅱ）, and to 7-25 wt%NaCl.eqv（Ⅲ）. The broad range of homogeneous temperatures of stage I , the evolution of salinities from bimodal to unimodal, and negative correlation between homogeneous temperatures and salinities indicate that fluid mixing is the most important metallogenic mechanism in Zhaiwa Mo deposit. The characteristic of fluid inclusion in Zhaiwa Mo deposit are high density, high salinities and low temperature, which is the result of CaCl2-bearing fluid involved in ore forming process, the mixing of hot magmatic fluid and cold CaCl2-bearing brine result to precipitation of molyhdenite. In summary, The geological and fluid inclusions features of the Zhaiwa Mo deposit are similar to intrusion-related deposit, we affirm that the Zhaiwa Mo deposit is a intrusion-related Mo deposit.