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黔西南地区是世界第二大卡林型金矿床集中区,同时也发育有大量古油藏,二者空间关系密切,但是否具有成因联系目前尚不清楚且存在较大争议。本文报道该区典型金矿床与成矿有关的热液矿物中流体包裹体的气相组成和高品位金矿石中沥青的激光拉曼光谱分析结果,以探讨含有机质流体与金成矿作用之间的关系。研究表明,虽然含砷富金黄铁矿、石英、方解石、萤石和雄黄等热液矿物形成于不同的成矿阶段,但其中流体包裹体的有机气相组分种类、含量及相对比例整体较为一致,表明成矿流体中的有机络离子团在成矿作用过程中没有发生明显的分解或重组,进而说明黔西南卡林型金矿成矿作用过程中有机质并未以有机络离子团的形式对金进行有效搬运或其搬运金的能力非常有限。在N2/Ar-CO2/CH4流体来源判别图解中,各蚀变矿物中的流体包裹体气相组成主要落在循环的大气降水区域,经大气水区域向岩浆流体区域延伸,整体上构成一条非常好的线性分布趋势,暗示成矿流体可能起源于深部岩浆但在演化过程中有大量循环大气水的加入。水银洞金矿床的1件石英样品偏离上述趋势线并向有机流体方向偏移,可能反映了流体迁移过程中有机质的加入。该区金矿床的矿石中均不同程度地发育浸染状沥青,不同矿床中沥青的激光拉曼光谱特征基本一致,说明该区金矿床中的沥青具有相同成因。根据沥青激光拉曼光谱特征地质温度计反演计算的成矿早阶段流体温度为317~336℃,明显高于区域古地温温度(160~250℃)以及区域古油藏的流体包裹体均一温度(73~175℃),说明该区卡林型金矿床的成矿热源与区域古地温无关。对区域地质及近年来地球物理与地球化学最新成果的综合分析表明,该区卡林型金矿床可能是叠加在区域古地温场之上的深部岩浆活动远端低温热液成矿作用的产物,与金矿床空间关系密切的有机质可能为来自先存古油藏并沿控矿构造发生逃逸的油气物质裂解产物,金成矿与区域古油藏之间不存在成因联系。
Southwestern Guizhou Province is the second largest Carlin-type gold deposit in the world. At the same time, a large number of paleo-oil reservoirs are also developed. The two are closely related in space. However, it is unclear and there is much controversy over the existence of causal relationship. This paper reports the gas phase composition of fluid inclusions and hydrothermal Raman spectra of high-grade gold ore in hydrothermal minerals related to ore-forming in the typical gold deposits in this area to investigate the relationship between organic fluid and gold mineralization . The results show that hydrothermal minerals such as arsenic, auriferous pyrite, quartz, calcite, fluorite and realgar formed in different stages of mineralization. However, the types, contents and relative proportions of the organic gas components in the fluid inclusions are generally consistent. Indicating that the organic ion clusters in the ore-forming fluids did not decompose or reorganize obviously during the mineralization process, thus indicating that the organic matter in the Carlin-type gold deposits in the southwestern Guizhou Province did not react with gold ions in the form of organic network ions There is very limited capacity to effectively carry or transfer gold. In the source discrimination diagram of N2 / Ar-CO2 / CH4 fluids, the gas-phase composition of the fluid inclusions in the altered minerals mainly falls in the recirculating atmospheric precipitation area and extends to the magma fluid area through the atmospheric water area, forming a very good overall Linear distribution trend, suggesting that the ore-forming fluid may originate in the deep magma but there is a large amount of circulating atmospheric water in the evolutionary process. A quartz sample from the Shuiyindong gold deposit deviated from the above trendline and shifted to the direction of organic fluid, probably reflecting the addition of organic matter during fluid migration. In the gold deposits of the area, dip-like bitumen is developed to varying degrees in different ore deposits. The laser Raman spectra of the bitumen in different deposits are basically the same, indicating that the bitumen in the gold deposits in the area has the same genesis. The temperature of the fluid in the early stage of mineralization calculated from the inversion of the characteristic laser thermogram of the laser Raman spectroscopy is 317 ~ 336 ℃, which is obviously higher than the palaeotropical temperature (160 ~ 250 ℃) and the homogenization temperature of the fluid inclusions 73 ~ 175 ℃), indicating that the metallogenic heat source of Carlin-type gold deposit in the area has nothing to do with the paleo-geothermal temperature in the region. The comprehensive analysis of the regional geology and recent achievements in geophysics and geochemistry shows that the Carlin-type gold deposit in this area may be the product of the remote low-temperature hydrothermal mineralization superimposed on the deep magmatic activity over the regional paleo-geothermal field, The organic matter closely related to the gold deposit may be the pyrolysis product of hydrocarbons from the preexisting reservoirs and escaping along the ore-controlling structures. There is no genetic relationship between the gold mineralization and the regional paleo-oil reservoirs.