摘要
黑牛洞铜矿床是近年来国内发现的富铜矿床之一。磁黄铁矿是该矿床中含量最高的金属矿物,且与该矿床最重要的矿石矿物黄铜矿共生。本文试图通过研究磁黄铁矿的矿物学特征,为揭示黑牛洞铜矿床的成因提供重要参考信息。本文运用电子探针、扫描电镜、X 射线衍射分析和矿相显微镜观测等方法,对黑牛洞不同产状磁黄铁矿进行了形貌、化学组成和结构分析。研究表明不同矿石类型的磁黄铁矿均为六方晶系,其 Fe 原子含量的百分比变化范围是42.43%～45.58%。在 Fe-S 相图中,黑牛洞矿床的磁黄铁矿位于磁黄铁矿和黄铁矿共生相区。据研究,黑牛洞矿床中磁黄铁矿的成分、结构和矿物组合中罕见黄铁矿等信息寓示磁黄铁矿的峰期变质温度高于450℃。该矿床中磁黄铁矿至少有两种成因,即主要从流体中沉淀并受变质的磁黄铁矿和少量由黄铁矿变质脱硫而成的磁黄铁矿。黑牛洞矿床矿体和蚀变围岩中石墨广泛发育表明,变质过程处于强还原环境,而还原环境中s在流体中的溶解度较小且易于沉淀。矿床中黑色电气石的普遍产出表明中高温热液存在。这与磁黄铁矿的标型特征相对应。中高温流体存在、强还原环境和碳质的催化作用等为黄铁矿变质形成磁黄铁矿提供了有利的条件,也为黑牛洞铜矿床铜元素在韧性剪切带形成的有利容矿空间中沉淀、再富集提供了必要的物理化学条件。
The contents of iron in pyrrhotite in the Heiniudong copper deposits are in a range of 42.43 - 45.58 atom% detected by using the technique of X-ray energy dispersive spectrometry. The compositions of pyrrhotite are plotted onto ＂pyrrhotite ＋ pyrite＂ area in the diagram of Fe-S system. All pyrrhotite samples selected from different types of ores are of hexagonal structure determined by X-ray energy dispersive spectrometry. According to typomorphic structural characteristics that the presence of annealing texture in pyrrhotite and the corresponding absence of pyrite take place over the temperature range 550℃ to 450℃, the structure and composition of pyrrhotite in the deposit, combined with the characteristic of seldom occurrence of pyrite in ores, indicate that the peak metamorphic temperature should be higher than 450℃. Pyrrhotite may be generated either by precipitating from metal bearing fluid or/and by the reduction of pyrite. The presence of graphite in the ores and wallrocks implies an intensively reductive circumstance in metamorphism, and sulfur has low solubility in reductive circumstance. The association of tourmaline with pyrrhotite and chalcopyrite indicates the existence of middle-high temperature fluid in metamorphism. The existence of fluid, carbonaceous material catalyses reaction and the intensively reductive circumstance are favourable for the generation of pyrrhotite, and for remobilized copper to precipitate in favourable settings which are provided by ductile shear zones.
出处
《岩石学报》
SCIE
EI
CAS
CSCD
北大核心
2008年第3期562-568,共7页
Acta Petrologica Sinica
基金
矿产资源补偿费矿产勘查项目"四川省九龙县里伍铜矿外围普查"
成都地质矿产研究所青年基金项目联合资助
关键词
磁黄铁矿
黑牛洞矿床
富铜矿
受变质矿床
成矿机制
Pyrrhotite
Heiniudong copper deposit
Cu-rich deposit
Metamorphosed deposit
Ore-forming mechanism
