Abstract:

The ore genesis model of the Xinqiao Cu-Au deposit in Tongling of Anhui 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 1.2 to 1.22 Ra, 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 favor the submarine exhalative-hydrothermal origin for the stratiform mineralization in Xinqiao Cu-Au deposit.

Key words: He and Ar isotopes, crustal fluid, mantle fluid, Xinqiao Cu-Au deposit, Tongling, Anhui