滇西永平青羊厂脉状Cu-Co多金属矿床地质特征与成因探讨  

Geological characteristics and metallogeny of the Qingyangchang vein type Cu-Co polymetallic deposit in Yongping County, Western Yunnan, China

作　　者：苏岩 刘凤祥 李余华 邓明国[1] SU Yan;LIU Feng-xiang;LI Yu-hua;DENG Ming-guo(School of Land and Resources Engineering,Kunming University of Science and Technology,Kunming 650093,China;No.209 Geological Team of Yunnan Nuclear Industry,Kunming 650032,China)

机构地区：[1]昆明理工大学,云南昆明650093 [2]云南省核工业二〇九地质大队,云南昆明650032

出　　处：《矿物学报》2020年第5期615-627,共13页Acta Mineralogica Sinica

基　　金：国家自然科学基金项目(编号:41762009,41363001)。

摘　　要：青羊厂脉状Cu-Co多金属矿床是兰坪盆地西南部近年来突破的最新勘查成果,矿体赋存于中生代上侏罗统坝注路组(J3b)暗紫红色砂岩中,但其诸多地质特征明显有别于已知的砂岩型(SSC)Cu矿床。矿区断裂构造发育,主要由NW和NE向两组断裂相互交织成格架状分布。矿体主要呈脉状、透镜状产于NE向张性断裂破碎带中。矿体数量多(16条)、厚度大(最厚14.87 m)、走向延伸长(KT1达652 m)、倾角较陡(60°~80°),矿石Cu品位高(平均2.01%),并伴生Co(0.036%)、Ag(38.60×10-6)。矿床的形成过程可划分为沉积成岩期、热液成矿期和表生期,其中热液成矿期分为阶段Ⅰ(菱铁矿-黄铜矿-重晶石)、阶段Ⅱ(砷黝铜矿-黄铜矿-菱铁矿)、阶段Ⅲ(砷黝铜矿-菱铁矿)和阶段Ⅳ(重晶石-菱铁矿-砷黝铜矿)。主要形成砷黝铜矿、重晶石、菱铁矿、黄铜矿、黄铁矿以及少量辉铜矿、方铅矿、辉铋矿、毒砂、石英和碳酸盐矿物组合。矿石结构以半自形-它形交代结构、出溶结构、骸晶结构以及交代反应边结构为特征,普遍见角砾状、块状、脉状、网脉状、条带状及晶洞构造等典型的热液构造类型。矿体产于区内明显褪色蚀变的构造破碎带内,围岩蚀变发育重晶石化、菱铁矿化及微弱硅化。矿床地质特征研究表明,矿体产出形态、矿石结构、构造、矿化富集特征等无不与本区的断裂、节理、裂隙等有着密切的关系。稀土元素分析表明,不同成矿阶段的重晶石具有稀土总量低且变化小的特征,均为中稀土元素富集的"W"型,显示正Eu异常(δEu=18.99~24.32)和负Ce异常(δCe=0.1~0.14),暗示成矿流体来自于盆地热卤水,成矿物质主要来源于地层(尤其是含膏盐地层)。本文在分析区域成矿地质背景的基础上,通过对矿区地质、矿床(体)特征、矿石组构、围岩蚀变及稀土元素地球化学等特征的详细研究,认为青羊厂矿床的形成与兰坪盆The Qingyangchang vein type Cu-Co polymetallic deposit is the latest achievement of the exploration in the southwestern Lanping basin in recent years. The ore bodies occurred in the dark purple sandstone of the Mesozoic Upper Jurassic Bazhulu Formation(J3 b). However, many geological characteristics of this deposit are obviously different from those of the typical sandstone type(SSC) Cu deposits. The fault structures are developed in the deposit. h Two groups of faults, NW-and NE-trending, are distributed in form of interweaved framework in the deposit area. The ore bodies occurred mainly in forms of veins and lens in NE-trending tensile fracture zones. The deposit has a large number of ore bodies(up to16), which are characterized with relatively large thickness(up to 14.87 m), large extension length(up to 652 m for the KT1 orebody), steep angle(60°-80°), high Cu grade(average 2.01%), and associated Co(0.027%) and Ag(36.29 g/t) of ores. The geological process of deposit can be divided into sedimentary diagenetic stage, hydrothermal ore-forming stage, and supergene stage. The hydrothermal mineralization stage is further divided into four phases including PhaseⅠ(siderite-chalcopyrite-barite), Phase Ⅱ(te nnantite-chalcopyrite-siderite), Phase Ⅲ(tennantite-siderite), and Phase Ⅳ(barite-siderite-tennantite), with hydrothermal mineral assemblages of major tennantite, barite, siderite, chalcopyrite, pyrite and minor chalcocite, galena, bismuthinite, arsenopyrite, quartz, and carbonates. The ores are characterized with subhedral-anhedral replacement, exsolution, skeletal, and replacement rim textures and commonly typical hydrothermal structures such as brecciated, massive, veining, stockwork veining, banded, and miarolitic structures. The ore bodies occurred in the obvious discoloration altered structural fractured zone, with the wall rock alterations of baritization, sideritization, and weak silicification. Geological characteristics of the deposit show that shapes of ore bodies, textures and structures of ore

关 键 词：兰坪盆地 青羊厂脉状Cu-Co矿床 地质特征 稀土元素 矿床成因 找矿标志 

分 类 号：P597[天文地球—地球化学] P618[天文地球—地质学]