作　　者： ; ; ; ; ; ; ; ;

机构地区： 中国科学院广州地球化学研究所有机地球化学国家重点实验室

出　　处： 《地质论评》 2006年第4期477-485,i0002-i0003,共11页

摘　　要： 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 organic type, characteristic and its relationship with copper mineralization in the Keweenaw-like-type copper ore deposit, Yunnan-Guzhou boundary, were investigated using Organic petrology and organic geochemistry methods. The results showed that there are two types of organic matter. One is from humic organic matter and was detected as vitrinite and fusinite, which deposited during the intermittence of volcanic effusion of the late Emeishan basalt. Another is filling bitumen that originated from sapropel organic matter. Maturation of organic matter from ore deposit had reached VRo 1. 6% ～ 1.9% stage, much higher than those from the outside of the ore deposit （VRo 1. 08% ～ 1.35%）. Maturities of the late filling bitumen are within ERo = 1. 32% ～ 1. 56%, slightly lower than that of the humic organic matter. Total carbon isotope composition of these two types of organic matter varies significantly. The δ^13C of vitrinite and carbonaceous wood ranges from -21.29‰ to -22.5‰, whereas δ^13C of filling bitumen fails in the range of -32.2‰～-33.14‰. Biomarkers in the filling bitumen are characterized by high concentrations of tricyclic terpenoids, gamaceranes and 4-methylsteranes, no predominance of C27-C28-C29 steranes distribution, indicating a typical characteristic of aquatic organic matter input. Based on the regional geological background, it is postulated that the bitumen was originated from Paleozoic marine strata （Devonian or lower Permian sediments）. Raman laser spectroscopic analysis showed that there is high methane content in liquid fluid inclusions, which is benefit to the reduction of copper oxide to natural copper. According to the assemblage of altered minerals, maturity of organic matter and the homogeneous temperature of the fluid inclusions in the vein minerals, the copper element in basalt experienced separation and enrichment at early stages with high temperature, but the massive formation of natural copper took place at late stages with moderate pressure and temperature

关 键 词： 自然铜矿床 固体沥青 镜质体 流体包裹体 碳同位素 生物标志化合物

领　　域： [天文地球] [天文地球] [天文地球] [天文地球]