滇东北与二叠纪玄武岩有关的铜矿床

【作者】 唐冬梅；

【导师】 钱壮志；

【作者基本信息】 长安大学 ， 矿物学、岩石学、矿床学， 2006， 硕士

【摘要】 滇东北地区位于扬子准地台西缘，大面积出露晚二叠纪峨眉山大陆溢流玄武岩，前人对这一区域峨眉山玄武岩的岩浆活动、地层层序、大地构造环境，以及岩石地球化学和矿床地球化学的研究积累了大量资料。但在矿床类型、成矿物源、成矿过程及时代研究等方面还有待进一步深入。研究区的峨眉山玄武岩分为四个岩性段，铜矿化主要发育于峨眉山玄武岩组第四岩性段和其沉积间断面之上的二叠纪宣威组底部。依据容矿主岩，铜矿化可分为三种类型：1．玄武岩型；2．玄武岩中含碳沉积岩夹层型；3．沉积间断面上铝土质泥岩型。矿化在成矿物质来源和空间分布上均与本区二叠纪玄武岩密切相关，同时又不同程度的受后期地质作用影响，最终成矿明显晚于二叠纪玄武岩的形成。 本文主要选择滇东北鲁甸—会泽等地区不同类型的铜矿，在总结前人研究成果的基础上，针对容矿主岩和矿石的微量、稀土元素、稳定同位素有机地球化学、流体包裹体特征等进行了较系统的研究。初步探讨了这类铜矿的成矿过程。 通过研究，本文取得的主要进展如下： 1．在对新近发现的大黑山铜矿系统研究基础上，确立了一种新的铜矿类型—铝土质泥岩铜矿。该类型铜矿发育于二叠纪宣威组底部与峨眉山玄武岩接触的灰色、灰绿色铝土质泥岩或紫斑—褐红色铝土质泥岩中，矿体呈层状或似层状，铜矿物以斑铜矿、辉铜矿为主，局部地段含较多的黄铁矿，个别地区矿石见钛铁氧化物，次生矿物为孔雀石、黑铜矿、铜蓝；脉石矿物主要有高岭石、蒙脱石硅质水铝石。 2．研究区三种类型铜矿的铅同位素示踪研究，成矿物质主要来自于邻近的二叠纪玄武岩；硫同位素研究结果显示，玄武岩型铜矿和含碳沉积岩夹层型铜矿中的硫有两种来源：二叠纪玄武岩和蒸发岩中的硫（有有机质硫的参与）；而铝土质泥岩铜矿中的硫主要来源于沉积地层中蒸发岩的硫。 3．依据野外观察，铜矿体主要产出于层间滑动带／破碎带及其邻近，由此限定了成矿的时间不应早于致使地层褶皱、破碎的构造事件（燕山期）的时限。 4．矿石主要元素分析显示，铝土质泥岩型铜矿的Cu含量为0.022～2.71×10^-2，Ga为60～87×10^-6、Co为134～197×10^-6，后两者的含量达到了铜矿更多还原

【Abstract】 The northeast of Yunnan province laid on the west part of Yangtze Platform. This region cropped out very large areas of Emeishan continental flood basalt （CFB）. Previous study contained much information about this region such as magma action, section, structure background, mineral geochemistry and deposit geochemistry related to the continental flood basalt, but there is little study about deposits types, metallogenetic material, metallogenetic process and metallogenetic time. Our research region’s Emeishan Basalt has divided into four part of mineral, Most of the copper mineral occurred in the fourth layer of Emeishan Basalt and bottom of Permian Xuanwei formation which on the top of sedimentary discontinuity. According to the host rock controlled mineral, it can be classified to three types, the first one is basalt-type copper deposits, the second one is carbonaceous sedimentary interlayers-type, and the last one is bauxitic mudstone-type on the sedimentary discontinuity. Themineralization has significant related to the basalt in the deviate of mineral material and space distribution. At the same time, geological structure had affected mineralization in various degrees; metallogenetic function is later than the form of Permian basalt conspicuously.This article has selected several deposits of the three types of Cu deposits in the Ludian-Huize region. Based on the previous study, this article discusses host-rock, trace-elements, REE, stable isotopic, organic geochemistry and fluid inclusions of copper deposits systemically, and the metallogenetic process was discussed simply. The main conclusions are as follows:1. Base on the recent system study of Daheishan copper deposits, we built a new type of copper deposits- bauxitic mudstone-type. This type of copper deposits appeared in the gray, celadon bauxitic mudstone or purple and maroon bauxitic mudstone which laid in bottom of Permian Xuanwei formation. The ore body is stratiform or stratoid structure. Ore mineral is bornite and chalcocite, some part contain higher pyrite, secondary ore mineral is malachite, melaconis and covellite, gangue mineral is kaolinite, ascanite and so on..2.According to the research of Pb isotopic, the metallogenetic material mainly originated from the Permian basalts; the study of sulfur isotopic find that the sulfur of the basalt-type copper deposits and carbonaceous sedimentary interlayers-type copper deposits originated from both Permian basalts and evaporate of sedimentary section, S in bauxitic mudstone-type copper deposits originated from evaporate of sedimentary layers.3.The ore body of the copper deposits mainly occurred in the interlayer sliding belt/fracture belt, so the time of metallogenet is not before the structure of Yanshanian, in the stage caused the sliding of the sections.4.The copper value of bauxitic mudstone-type deposits on the sedimentary discontinuity is 0.022～2.71×10^-2, the value of Ga is 60～87×10^-6 and Co is 134～ 197×10^-6, both reach the standard of industrial utilization grade.更多还原