安徽铜陵冬瓜山铜矿床的叠加改造成矿机制：来自矿石结构的证据  

The Superimposed Mineralization of the Dongguashan Cu Deposit in Tongling Area,Anhui Province: Evidence from the Ore Texture

作　　者：郭维民[1] 陆建军[1] 章荣清[1] 招湛杰[1] 徐兆文[1] 

机构地区：[1]南京大学成矿作用国家重点实验室,南京大学地球科学与工程学院,南京210093

出　　处：《地质学报》2011年第7期1223-1232,共10页Acta Geologica Sinica

基　　金：高等学校博士科学点专项科研基金(编号1999028435)资助的成果

摘　　要：长江中、下游地区块状硫化物矿床普遍受到燕山期岩浆及其热液的改造与叠加。本文以铜陵冬瓜山矿床为例,探讨这类矿床的成矿机制。该矿床主要由层状硫化物矿体组成,伴有矽卡岩型和斑岩型矿体。野外地质观察及室内矿相学的研究表明,冬瓜山层状矿体中矿石遭受了强烈的热变质作用及热液交代作用。进变质过程中形成的结构主要为黄铁矿受燕山期岩浆侵入所引起的热变质作用转变为磁黄铁矿、磁铁矿时所形成的交代结构。退变质过程则以磁黄铁矿的退火结构、黄铁矿变斑晶生长和六方磁黄铁矿的形成为特征。热液交代结构主要表现为单斜与六方磁黄铁矿的交生结构以及黄铜矿对磁黄铁矿、黄铁矿的交代结构。黄铜矿普遍交代经历过热变质作用的磁黄铁矿、黄铁矿,表明层状矿体中的铜可能主要来自于燕山期岩浆热液的叠加。磁黄铁矿、黄铁矿的存在对于黄铜矿从岩浆热液中沉淀具有重要意义。上述矿石结构特征表明冬瓜山铜矿床的形成可能经历了三个阶段:①石炭纪海底喷流和热水沉积作用形成了以硫、铁为主的块状硫化物矿床;②燕山期岩浆侵入所引起的热变质作用使层状硫化物矿体中的黄铁矿转变为磁黄铁矿以及磁铁矿,并经历了一个缓慢的冷却过程;③岩浆热液叠加致使层状硫化物矿体富集铜,并形成新的矽卡岩型和斑岩型矿体。The massive sulfide deposits in the Middle-Lower region of Yangtze River have undergone extensive superimposition and reformation by Yanshanian magma.Taking the Dongguashan Cu deposit in Tongling as a study case,this paper discusses the metallogenic mechanism of these Cu deposits.Dongguashan deposit comprises mainly of a large stratiform sulfide orebody with some subordinate skarn and porphyry type orebodies.Field and microscopic investigation show that the sulfide ores at Dongguashan deposit underwent intensive thermal metamorphism and hydrothermal replacement.The prograde ore textures were formed through the phase conversions from pyrite to pyrrhotite and magnetite by the heating of Yanshanian granite magma.Retrograde metamorphism is characterized by presence of annealing textures in pyrrhotite,porphyroblastic growth of pyrite and formation of pure hexagonal pyrrhotite.The hydrothermal replacement textures were represented by the intergrowths of hexagonal and monoclinic pyrrhotites and replacement of pyrrhotites and pyrite by chalcopyrite.The chalcopyrite in the stratiform orebody was formed by replacement of pyrite and pyrrhotite,which have experienced contact metamorphism related to the Yanshanian intrusions.This suggests that chalcopyrite in the stratiform orebody was mainly overprinted from the Yanshanian magmatic fluids.The pre-existing pyrrhotite and pyrite have important significance for the precipitation of chalcopyrite from magmatic fluids.Base on the characteristics of ore textures,the formation of Dongguashan Cu deposit can be described as three stages： 1） During the Carboniferous period,the massive sulfide deposit was formed by the submarine exhalative and sedimentation,the compositions of which were dominantly S and Fe;2） The heat from Yanshanian granite intrusions has resulted in phase changes from the pyrite to pyrrhotites and magnetite,and then the stratiform sulfide orebody has underwent a slow cooling process;3） The overprinting of magmatic hydrothermal fluids lead to enrichment of lar

关 键 词：矿石结构 冬瓜山铜矿床 叠加改造 铜陵 

分 类 号：P618.41[天文地球—矿床学]