| 其他摘要 | 在峨眉山玄武岩广泛分布的川滇黔地区分布着三种与峨眉山玄武岩相关的铜矿类型：①玄武岩之上宣威组中的沉积型铜矿；②玄武岩中的热液型铜矿；③玄武岩底部与茅口灰岩接触面上的风化淋滤型铜矿。其中的热液型铜矿由于被发现与基韦诺超大型铜矿相似而引起广泛关注，本文研究的杏仁状玄武岩中的自然铜矿就是该类型铜矿中的主要组成部分之一，本文称其为“杏仁体式”自然铜矿。本文通过显微镜镜下鉴定、场发射扫描电子显微镜分析（FE-SEM）、电子探针分析（EPMA）、X射线衍射分析（XRD）、激光拉曼光谱分析、X射线荧光光谱分析（XRF）、电感耦合等离子体质谱分析（ICP-MS）等多种手段对研究区样品中矿石矿物标型特征、矿物组合特征、固溶体分离结构特征、主微量元素特征以及同位素特征等进行了分析研究，认为川南滇北“杏仁体式”自然铜矿为火山热液矿床，形成于低温还原环境，成矿作用发生在岩浆作用结束期及间歇期热液阶段，成矿经历过热液蚀变改造。铜矿物生成顺序为：自然铜→斑铜矿、辉铜矿、黄铜矿→赤铜矿、黑铜矿、孔雀石等。玄武岩中广泛分布的沥青与自然铜同时形成，并为自然铜及铜的硫化物的形成提供了强还原环境。沥青形成温度和斑铜矿-辉铜矿的固溶体分解温度将自然铜形成温度区间限定为290~225℃。研究区几个矿化点的杏仁状玄武岩性质、来源相同，均为碱性亚碱性玄武岩，原始岩浆来自成分均一的地幔，经历过轻微地壳混染，成岩过程为一个充分的结晶分异过程，成岩后经历过强烈的热液蚀变改造（如碳酸盐化、绿泥石化等）。峨眉山玄武岩具有高的Cu背景值（平均170ppm），为自然铜矿床的形成提供了必要的物质基础。矿石的铅同位素特征指示成矿物质来源于峨眉山玄武岩。有机质中的碳同位素指示沥青为异地来源的腐泥型，来自下伏古油气藏。最后通过与美国基韦诺铜矿对比，研究认为，杏仁状玄武岩中的自然铜矿可以是一种有开发价值的铜矿类型，在铜背景值高的玄武岩分布区应注意加强对这种类型铜矿的找矿工作。; There are three types of copper deposits associated with Emeishan basalts in the Sichuan-Yunnan-Guizhou region, which are widely distributed with the Emeishan basalts: (1) sedimentary copper deposits in Xuanwei Formation overlying the basalt; (2) hydrothermal copper deposits in basalt;(3) the weathering-cracked copper deposits on the contact surface between the bottom of Emeishan basalt and Maokou limestone. The hydrothermal type copper deposits are noticed extensively. Beacause they were found similar to Keweenaw copper deposits. The native copper deposit in amygdaloidal basalt researched in this paper , which we called the “Amygdule -type” native copper deposit, is one of the important components of hydrothermal copper deposits. In this paper, ore minerals typomorphic characteristics, mineral assemblage, exsolution texture, major-trace element characteristics and isotopic characteristics were studied by microscopic microscopy, Scanning Electron Microscope(SEM), Electron Probe Micro Analysis(EPMA), X Ray Diffraction(XRD), Laser Raman Spectroscopy, X Ray Fluorescence(XRF), Inductively Coupled Plasma Mass Spectrometry(ICP-MS) and so on, show that the “Amygdule -type” native copper deposits are volcanic hydrothermal ore deposits that formed in low-temperature reducing environment, Significantly, the mineralization occurs in the hydrothermal stage, the dormant period or the terminal period of magmatism. The mineral sequence are as follows: copper→ bornite，chalcocite，chalcopyrite→cuprite，tenorite，malachite. Bitumen is generated almost simultaneously as the native copper，and provides a kind of strong reducing environment for the deposition of the native copper and copper sulfides. The temperature range of copper is defined as 290 ~ 225℃ by the forming temperature of bitumen and the exsolution temperature of bornite-chalcocite. In the study area, several mineralized almond-shaped basalts are of the same origin, both alkaline and alkaline basalts. The original magma comes from the homogeneous mantle, which expriences mild crustal contamination and the diagenetic process is a sufficient process of crystallization, which experiences strong hydrothermal alterations (such as carbonatization, chloritization, etc.)later. Emeishan basalts have a high Cu background value (average 170 ppm), providing the necessary material basis for the formation of natural copper deposits. The lead isotopic character of the ore indicates that the ore-forming material is derived from the Emeishan basalt. The carbon isotopes in organic matter indicate that the bitumen is from the off-site source of saprolite, from the underlying paleo-oil reservoirs. Finally, compared with the United States Keweenaw copper deposits, studies suggest that the native copper deposit in amygdaloidal basalt can be a kind of valueble copper type for developing，we should strengthen prospecting for this type of copper in basalt area with high copper background value. |
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