赣中良山钼矿床流体包裹体特征及其地质意义

良山钼矿是近年来赣中地区新发现的钼矿，浅部矿体主要赋存于南华系浅变质岩系的构造裂隙中，矿石类型以含辉钼矿石英脉为主。流体包裹体岩相学和显微测温结果表明：含辉钼矿石英脉中的流体包裹体主要呈星散状随机或成群分布，其形态多样，大小集中在2~15 μm，包裹体的类型主要有纯液相包裹体、富气相两相包裹体、富液相两相包裹体和含液体CO₂三相包裹体4类，其中以富液相两相包裹体最为发育；包裹体的均一温度为136~298 ℃，盐度为1.22%~10.11%NaCleqv，密度为0.78~0.99 g/cm3，成矿流体属中-低温、低盐度、较低密度流体；成矿压力估算为13~70 MPa，形成深度为0.5~2.6 km。流体包裹体激光拉曼光谱分析表明：包裹体中气液相成分以H₂O为主，气相中还有少量的CO₂和CO。H、O、S同位素组成显示：成矿流体的δD值介于-61‰~-57.9‰，δ¹⁸OH₂O值介于-3.32‰~-0.52‰，具有岩浆水和大气降水混合的特征；成矿热液中的δ³⁴S值介于-1.8‰~+1.9‰，具有岩浆硫的特征。综合成矿地质特征及相关分析，认为成矿流体可能与燕山期的岩浆活动有关，属于岩浆热液流体，混合作用及钾化作用是促进金属富集沉淀成矿的主要因素，推测矿床属于岩浆热液充填石英脉型钼矿。

Characteristics of Fluid Inclusions of the Liangshan Molybdenum Deposit in Central Jiangxi Province and Their Geological Implications

The Liangshan molybdenum is one of molybdenum deposits recently discovered in central Jiangxi Province. Its major molybdenite ore bodies are situated within the tectonic fissures of Nanhua system low-grade metamorphic rocks, and molybdenite-quartz veins are the main mineralization types.Fluid inclusions in quartz veins suggest that these inclusions are distributed in groups or scattered stars randomly with long axes of 2-15 microns.There are four types of fluid inclusions, including pure liquid inclusions, gas-rich two-phase inclusions, liquid-rich two-phase inclusions and liquid phase CO₂-bearing three-phase inclusions. Liquid-rich two-phase inclusions are the main type of fluid inclusions.The homogenization temperatures range from 136 to 298 ℃, the salinities range from 1.22% to 10.11% NaCleqv and the density range from 0.78 to 0.99 g/cm³, indicating medium-low temperature, low salinity and lower density.The ore-forming pressure is estimated at 13 to 70 MPa, and the depth is about 0.5 to 2.6 km. The inclusions in gas and liquid ingredients all are mainly composed of H₂O with a small amount of CO₂ and CO in gases by the test of Laser Raman spectroscopy. The hydrogen and oxygen isotopic compositions of the ore-forming fluids show that δD values of the ore-forming fluid are between -61‰ and -57.9‰, and δ¹⁸OH₂O are between -3.32‰ and -0.52‰, which indicates that the ore-forming fluids were derived from the mixing of magmatic water and meteoric water.The sulfur isotope compositions of ore-forming fluid show that δ³⁴S values of the ore-forming fluid are between -1.8‰ and +1.9‰, which indicates that the sulfur of ore-forming fluid has the characteristics of the sulfur of magma source. Our comprehensive studies suggest that the ore-forming fluid of the Liangshan molybdenum deposit is related with the Yanshannian magmatic activities, the mixing of magma fluid with the meteoric water and later potassic alternation are two main factors to ore-forming material enrichment and precipitation. Therefore, it is proposed that the Liangshan molybdenum deposit is a typical hydrothermal filling quartz vein type deposit related with magmatic activities.