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用有机岩石学和有机地球化学方法研究了铜矿中有机质的类型、特征及其与自然铜矿化的关系。观测结果表明:矿床中有机质的类型比较复杂,有峨眉山玄武岩晚期火山喷发间歇沉积的腐殖型有机质转变的镜质组、丝质组和由腐泥型有机质成因的充填状沥青。铜矿区原生沉积有机质经受的热演化程度达到VRo1.6%～1.9%,远比矿区外围VRo1.08%～1.35%高,说明矿区受热程度高。后期进入的充填沥青热演化程度为ERo=1.32%～1.56%,略比原生沉积有机质低。镜质体和炭化木的总碳同位素介于-21.29‰～-22.5‰之间,充填沥青总碳同位素介于-32.2‰～-33.14‰之间,两类有机质的碳同位素组成差别很大。充填沥青生物标志化合物组合表现为:高三环萜化合物、高伽玛蜡烷、C27-C28-C29甾烷均势分布、丰富四甲基甾烷等,反映出低等水生生源输入特征,综合区域地质背景资料,初步推测其可能来源于古生代海相沉积有机质(泥盆系或下二叠统源岩)。流体包裹体组成的激光拉曼测定结果表明,流体中CH4含量较高,表明成矿体系富含甲烷,有利于氧化铜还原为自然铜的反应。据矿区蚀变矿物组合与有机的热演化程度,以及矿区脉石矿物的流体包裹体均一温度测定结果,玄武岩中的铜具有早期高温分异富集特征,但是大量自然铜是在晚期温度、压力不太高的流体中受多种有机质还原作用形成的。
The types and characteristics of organic matter in copper deposits and its relationship with natural copper mineralization were studied by using organic petrology and organic geochemical methods. The results show that the type of organic matter in the deposit is rather complicated. There are vitrinite, siliceous group and filling bitumen formed by sapropel organic matter in intermittent deposition of volcanic Emeishan basalt volcano. The thermal evolution of the primary sedimentary organic matter in the copper mines reaches VRo1.6% ~ 1.9%, which is far higher than the VRo1.08% -1.35% in the periphery of the ore district, indicating that the thermal degree in the mining area is high. The thermal evolution of filling asphalt entering later stage is ERo = 1.32% ~ 1.56%, which is slightly lower than that of primary sedimentary organic matter. The total carbon isotope of vitrinite and carbonized wood is between -21.29 ‰ and -22.5 ‰, and the total carbon isotope of filled bitumen is between -32.2 ‰ and -33.14 ‰. The carbon isotopic composition of the two types of organic matter varies greatly. The combination of biomarker compounds in packed bitumen showed high tricyclic terpene compounds, high gamma wax, C27-C28-C29 sterane biodistribution and rich tetramethylstannane, which reflected the input characteristics of lower aquatic biotic sources. The comprehensive regional According to the geological background data, it is preliminarily supposed that it may come from Paleozoic marine sedimentary organic matter (Devonian or Lower Permian source rocks). Laser Raman measurements of fluid inclusions show that the higher CH4 content in the fluid indicates that the metallogenic system is rich in methane, which is favorable for the reduction of copper oxide to natural copper. According to the alteration of mineral assemblages in the mining area and the degree of organic thermal evolution, as well as the homogenization temperature measurement of the fluid inclusions in the gangue minerals, the basalts have the characteristics of early high temperature enrichment and enrichment, but a large amount of natural copper is formed during the late temperature and pressure Not too high fluid by a variety of organic reduction formed.