安徽铜陵新桥铜-金矿床的He、Ar同位素组成及其意义

ORIGIN OF ORE-FORMING FLUIDS OF THE XINQIAO Cu-Au DEPOSIT IN THE TONGLING MINERAL DISTRICT,ANHUI: EVIDENCE FROM He AND Ar ISOTOPES

对安徽铜陵新桥铜 金矿床层状矿体和块状矿体的黄铁矿进行了流体包裹体的He、Ar同位素研究。结果表明,成矿流体的N(40Ar)/N(36Ar)≈238～293,N(3He)/N(4He)≈1 03～1 23Ra,与大气饱和水(包括大气降水和海水)的特征值N(3He)/N(4He)=1Ra,N(40Ar)/N(36Ar)=295 5非常接近,表明成矿流体含大气降水和海水,这与野外地质特征也相符合,反映了成矿流体来自海底喷流(热水)沉积作用过程,这一认识为该区铜 金矿床可能的海底热液喷流成因提供了新的证据。

The ore genesis model of the Xinqiao Cu-Au deposit in Tongling of Auhui Province has long been in dispute, and the major debate focuses on whether the stratiform orebodies formed during the Yanshanian magmatic-hydrothermal event or they were products of carbonferious syn-sedimentary exhalative-hydrothermal event. The paper presents helium isotope data from fluid inclusions of five pyrites. The pyrites were collected from the stratiform orebodies in the deposit, and their ()~3He/()~4He ratios are significantly higher than 1, range from 1.02 to 1.22Ra, which indicateds a mantle component in the responsible hydrothermal fluids. It is suggested that the ore-forming fluids were a mixture of deep circulating seawater and a mantle-derived fluids, which are similar to many of those modern submarine hydrothermal fluids.The data provide a new evidence that favour the submarine exhalative-hydrothermal origin for the stratiform mineralization in Xinqiao Cu-Au deposit.