四川省九龙县黑牛洞铜锌矿的矿床地质特征、成因及其成矿时代

Geological Characteristics, Genesis and Metallogenic Time of the Heiniudong Copper-Zinc Deposit in Jiulong County, Sichuan Province

通过野外填图、坑探和钻探以及室内测试、研究认为:黑牛洞铜锌矿床原来可能是一个形成于中元古代大陆被动边缘裂谷的大型甚至特大型海相火山块状硫化物矿床;含矿围岩是糜棱岩、千糜岩、糜棱片岩、变晶糜棱岩、变粒岩、浅粒岩和构造蚀变岩,剪切型矿化和蚀变带包裹了矿体,原岩是石英砂岩、泥质石英粉砂岩、泥质岩和硅质岩夹基性火山岩、少量中—酸性、酸性火山岩,经过变质达到高绿片岩相—低角闪岩相。以块状、角砾状和准块状矿石为主的矿床是富铜矿,矿石的铜平均品位为1.68%,锌品位平均为1.53%;矿化与褪色带、硅化关系密切。矿化类型以广泛发育韧性剪切带型浸染状矿化岩或矿石(分别简称剪切型矿化岩或矿石)为特色,具有与糜棱岩、千糜岩相同的变形特征,可见两期以上的金属矿物透镜体、变形条带和不协调微褶皱。矿床具有原地韧性变形改造、变质再生矿床的特点;矿石、矿体的围岩和氢、氧、硫、铅、硅同位素特征显示,块状、准块状和角砾状矿石的矿质基本来源于剪切型矿化岩或矿石,是变质生成矿床,也是原矿石的再生矿床,而剪切型矿化岩或矿石可能是中元古代海底火山-裂谷作用形成的火山块状硫化物矿床经过多期韧性变形、变质改造形成的,是溶解为主的化学再活化的残余。构造改造、再生矿床的成矿时代为134.26±0.5Ma.,形成于燕山晚期。

Through geological mapping, trenching, drilling, and indoor analyses, the Heiniudong Copper-Zinc Deposit was a large or even super-large marine volcanic-associated massive sulifide deposit （VMSD） in the passive continental margin rift during the middle Proterozoic. The 0re-bearing country rocks contain mylonites, phyllonite, mylonitic shists, quartz-blastic mylonites, and tectonites, with orebodies hosted in shear-type mineralization and alteration zones. The primary rocks are quartz sandstones, mud-quartz siltstones, argillites, and siliceous rocks, intercalated with mafic rock and minor intermediate-acidic, acidic volcanic rocks, and are characteristic of high greenschist - low amphibolite facies by metamorphism. The deposit dominated by massive, para-massive and brecciated ores is enriched in copper, with an average Cu grade of 1. 680//oo and an average Zn grade of 1.53o//00. Mineralization is closely related to bleached zone and silicification. Mineralization is characterized by extensively-developed ductile shear-type disseminated rock or ores and is of the same deformation features as mylonite and phyllonite. Multiple mineralized metallic lens, deformation bands and microfolds can be found in the ores. Texture and structure of the ores, and their spatial and temporal distribution, and H, O, S, Pb and Si isotopic features show that massive, para- massive and breccias ores are shear-type minei＇alized rocks or ores, suggesting that the deposit is a metamorphosed deposit, i.e. a reactivated deposit from primary ores. The shear-type mineralized rock or ores are likely a dissolution-dominated reactivated residual of the VMSD deposit which underwent multiple ductile deformation and metamorphic deformation due to middle Proterozoic submarine volcano and rifting. The deposit is characterized by in-site ductile deformation and metamorphic regeneration, with the mineralization age in late Yanshanian epoch （134.26±0.5Ma）.