豫西小秦岭太华群变质岩蚀变与金成矿

发布时间：2018-05-29 17:45

本文选题：太华群变质岩 + 蚀变　；参考：《中国地质大学(北京)》2017年硕士论文

【摘要】：小秦岭地区位于华北克拉通南缘,是我国造山型金矿的主要产地之一。本文对小秦岭地区太华群远、近矿体两条剖面上的黑云斜长片麻岩和斜长角闪片麻岩进行了岩相学、矿物学及岩石地球化学研究,旨在查明变质岩蚀变与金成矿的关系。野外调研和镜下观察结果显示,从远离矿体到靠近矿体,各类变质岩的主要矿物组合无明显差异,但蚀变(以绢云母化、绿泥石化和绿帘石化为主)强度显著增强,黄铁矿、黄铜矿和磁铁矿等金属矿物含量明显升高。矿物学分析结果显示,从远离矿体到靠近矿体,黑云母和角闪石蚀变显著增强,使其中的铁和金等成矿元素活化,为之后大量磁铁矿和黄铁矿的形成以及金的沉淀富集提供了物质基础。后生黄铁矿较原生黄铁矿Ag、As、Cu等与金成矿关系密切的元素含量更高,与金矿化关系更密切。岩石地球化学研究显示,小秦岭地区太华群变质岩的原岩为岩浆岩。从远离矿体到靠近矿体,变质岩Au、Ag、Cu、Pb和Zn等成矿元素的丰度明显升高,表明岩石的蚀变作用使成矿元素明显富集。黑云斜长片麻岩和斜长角闪片麻岩与含金矿石具有相似的REE分布模式,表明金的富集与成矿可能主要与此类变质岩中金的活化、迁移及富集有关。综合已经获得的地质地球化学资料,认为太华群中的斜长角闪片麻岩和黑云斜长片麻岩为金矿化提供了物质来源,燕山期花岗质岩浆活动为金矿的形成提供了热动力。蚀变作用使变质岩中的金发生活化,并随带出的K+、Na~+和Fe~(2+)等以络合物的形式在热液流体中向低压处运移。经过一系列强烈的水岩反应,含金络合物分解使金在合适的构造部位沉淀成矿。
[Abstract]:Located in the southern margin of North China Craton, Xiaoqinling area is one of the main origin of orogenic gold deposits in China. In this paper, the petrographic, mineralogical and petrogeochemical studies of the black cloud plagiocline gneiss and the obliquity diorite gneiss in Taihua Group, near the orebody, in Xiaoqinling area, are carried out in order to find out the relationship between metamorphic alteration and gold mineralization. The results of field investigation and microscopic observation show that there is no significant difference in the main mineral assemblages of various metamorphic rocks from far away from orebodies to near orebodies, but the intensity of alteration (sericite, green mud and green curtain) is significantly enhanced, and pyrite, etc. The content of chalcopyrite and magnetite and other metal minerals increased obviously. The results of mineralogical analysis show that the alteration of biotite and hornblende is significantly enhanced from the distance from orebody to near orebody, so that the metallogenic elements such as iron and gold are activated. It provides a material basis for the formation of a large number of magnetite and pyrite and the precipitation and enrichment of gold. Compared with primary pyrite, epigenetic pyrite has higher content of elements such as Agn, As-Cu, which are closely related to gold mineralization, and is more closely related to gold mineralization. The petrogeochemical study shows that the primary rock of Taihua Group metamorphic rock in Xiaoqinling area is magmatic rock. From the distance from orebody to near orebody, the abundance of ore-forming elements such as Au-Ag-Cu-Pb and Zn in metamorphic rocks is obviously increased, which indicates that the alteration of rocks makes the ore-forming elements obviously enriched. There is a similar REE distribution pattern between the gneiss and amphibole gneiss and the gold-bearing ore, indicating that the enrichment and mineralization of gold may be mainly related to the activation, migration and enrichment of gold in these metamorphic rocks. Based on the obtained geological and geochemical data, it is considered that the plagioclase diornesian gneiss and the black cloud plagioclase gneiss in Taihua Group provide the material source for gold mineralization, and the Yanshanian granitic magmatic activity provides the thermal power for the formation of the gold deposit. The alteration makes blond hair in metamorphic rocks alive, and the K ~ + Na ~ and Fe~(2) are transported in the form of complex compounds in hydrothermal fluid to low pressure. After a series of strong water-rock reactions, the gold complex decomposes to precipitate gold in a suitable structure.
【学位授予单位】：中国地质大学(北京)
【学位级别】：硕士
【学位授予年份】：2017
【分类号】：P618.51

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