Hydrothermal rutile U-Pb dating of gold mineralization in the Jiangnan Orogen: A case study of the Hengjiangchong gold deposit in northeastern Hunan

Abstract

The Jiangnan Orogen is a well-known gold belt in China with a large number of gold deposits. The Jiangnan Orogen has complex geological history, and most gold deposits have not been well dated. Consequently, the regional timing of gold mineralization is still controversial. The Hengjiangchong is a representative gold deposit in the orogen. In this study, syn-ore hydrothermal rutile in quartz-polymetallic sulfides-gold-calcite veins was dated by LA-ICP-MS, yielding a Tera-Wasserburg lower intercept U-Pb date of 416.1 ± 7.3 Ma (2σ, n = 26, MSWD = 2.4). This date represents the age of gold mineralization at Hengjiangchong, and falls within the generally accepted timing of gold mineralization in the Jiangnan Orogen (ca. 425–400 Ma). Combined with the regional kinematics, gold mineralization likely occurred during the extension associated with the Yangtze-Cathaysia post-collisional deformation in the Siluro-Devonian intracontinental orogen. This also indicates that the late Silurian was a major gold mineralization epoch in the Jiangnan Orogen, challenging to some previous claims that late Silurian hydrothermal veins are largely ore barren.