安徽宁国大坞尖钨矿床成矿流体及成矿物质来源——来自氢、氧和硫同位素证据

Sources of ore-forming fluids and materials of Dawujian tungsten deposit in Ningguo, Anhui Province:Constraints from hydrogen-oxygen-sulfur isotope geochemistry

大坞尖钨矿床位于扬子陆块南缘与华夏古陆块的接合部位,是皖南地区典型的层控矽卡岩型矿床,近年来在该区域内钨多金属矿的找矿取得很大的突破。成矿流体及成矿物质来源的确定对矿床成因研究、找矿方向及区域成矿规律认识具有重要意义。文章对主成矿期的石英和黄铁矿进行了氢、氧和硫同位素测试。数据显示,主成矿期石英的流体包裹体中水的δD_(SMOW)值为-98.2‰^-70.1‰,δ18O_(SMOW)值为11.5‰~13.9‰之间,成矿流体主要来自岩浆水,有大气降水的混合;黄铁矿的δ34SV-CDT值为4.6‰~5.2‰,硫源单一,主要为岩浆来源,可能有少量地层S混入。矿床氢、氧和硫稳定同位素研究表明,燕山期大钨尖地区大规模的构造-岩浆活动不仅带来了大量的成矿物质,而且使地层中的成矿物质活化迁移,并在有利的构造部位沉淀富集,从而形成钨多金属矿床。

Located in the junction of the Cathaysia Block and the southern margin of the Yangtze block the Dawujian deposit is a typical stratabound skarn tungsten deposit in the south of Anhui Province. There have been great breakthroughs in ore prospecting and exploration for tungsten-molybdenum polymetallic deposits recently. The determination of the sources of ore-forming fluids and materials of the Dawujian deposit is very important for the study of deposit genesis and regional metallogenic regularities. This paper reports the analytical results of the hydrogen-oxygen-sulfur isotopes of the Dawujian deposit. The results show that the δDSMOW values of quartz vein range from -98.2‰ to -70.1‰ and the δ^18OSMOW values range from 11.5‰ to 13.9‰. The combined isotopic data suggest that the ore-forming fluids were derived from magmatic water and mixed with meteoric water. The δ^34SV-CDT values of sulfide range from 4.6‰ to 5.2‰, indicating that the sulfur in the fluid was derived mainly from magma, probably with the addition of a small amount of sulfur from the strata. Based on the present study of hydrogen-oxygen-sulfur isotope geochemistry, the authors have concluded that the large-scale Yanshanian tectonic-magmatic activity not only brought a large amount of metallogenic materials to the deposit but also promoted the activation and migration of metallogenic materials from the strata. These materials were precipitated and concentrated in some favorable structures and formed the W-polymetallic deposit.