摘要
东北寨金矿床是我国迄今为止发现的规模最大的浅成热液形成的微细浸染型金矿床。对矿床的同位素组成的研究表明,成矿溶液主要来自大气降水,矿化和蚀变作用是在水/岩比值较低的体系中进行的;硫来自围岩中的还原硫;碳酸盐岩地层是提供金属组分的主源层。地下热液在环流过程中,从围岩中萃取金属矿质,并迁移到黑色岩系地层的破碎带中成矿。
The Dongbeizhai gold deposit recently discovered in the northwestern area of Sichuan Province has its fine-disseminted ore bodies occurred in sedimentary carbonate-clastic formation. The ore bodies are strictly confined to the black rock layer of the sedimentary clastic formation by a major fault in this area. The ore-forming process in the deposit may be divided into three stages: (1) sedimentary-metamorphic, (2) percolation-hydrothermal(including two epoches, the main and the late epoches), and (3) superficial oxidation-leaching. Gold was concentrated mainly in super-microgr-ains in the hydrothermal stage. The hydrothermal mineralization is characterized by appearances of realgar, quartz, calcite, pyrite, with a minor amount of stibnite, arse-nopyrite and arsenic, etc.. Temperature of the hydrothermal fluids was in a range 220?to 120℃, and the mineralization depth is less 2km.The hydrothermal minerals in the Dongbeizhai gold deposit have their δ534S values - 5.8-6.3 (sulfides), δ18O values 15.1-27.2‰(quartz and calcite), and δ13C values -4.7-2.7‰ (calcite); hydrothermal fluids have δ18O values 12.8-16.7‰ (obtainedfrom isotope fractionation equation of calcite-water), δD values-66.6--75.5‰(fluidinclusions); initial ratio 87Sr/86Sr in the hydrothermal calcite is similar to that in the carbonate. Lead isotopic composition shows that the ore lead has its genetic relation with that in the carbonate rock.The above-described isotopic study shows that most of the ore-forming solutions was mainly derived from the ancient meteoric water; the amount of the hydrothermal fluids in mineralizing and altering systems was relatively small, sulfur in the fluids from the reduced sulfur in the country rocks, and the carbon predominantly from the carbonate layer and less from organic carbon in the black layer. The sedimentary carbonate rock was a main source for the metallogenic materials in ore. The hydrothermal mineralization took place in Yenshanian period. In the light of its geological features and genesis the Dongbeizhai gold deposit is believed to be the Carlin-type gold deposits
出处
《地质科学》
CAS
CSCD
北大核心
1991年第2期159-173,共15页
Chinese Journal of Geology(Scientia Geologica Sinica)
关键词
金
矿床
同位素
地球化学
浸染型
gold deposit, isotopic geochemistry, fine-disseminated ore, Carlin-type, Dongbeizhai, Sichuan
