Genesis of gold mineralization in southwestern Hunan, South China: Evidence from ore-hosted zircon geochronology and geochemistry

The southwestern Hunan province (SHP) is an important gold mineralization province in the Xuefengshan Uplift (South China) and is represented by quartz vein-type gold deposits. Gold deposits and occurrences in this district are geologically similar and can be regarded as specific manifestations of the same extensive gold mineralization in different spatial locations. In this study, the metal sources and mineralization processes of gold mineralization in the SHP have been discussed based on zircon geochronology and geochemistry from six gold deposits. The zircon age distribution is similar in most of the samples, mainly plotted in a narrow range: 900 to 600 Ma, with the major peak around 800 ± 50 Ma. It overlaps with the detrital zircon age distributions of the Lengjiaxi Group, Banxi Group, and Jiangkou Formation. The trace elements and Lu-Hf compositions of these zircons further prove an original relationship between the gold mineralization and strata. In addition, the Indosinian magmatic activities might also be potential sources for the zircons in these deposits, as 7 of 349 analyzed zircons with ages of approximately ∼240 Ma were observed. The differences in trace, as well as rare elements, have been widely seen in zircons suggesting that the gold mineralization has been modified to different degrees by post-mineralization hydrothermal fluids which are considered as related to Indosinian magmatic activities. Combined with the geological characteristics of gold mineralization, the gold deposits in the SHP are typical orogenic gold deposits forming during the Caledonian movement and modified by Indosinian magmatic-hydrothermal fluids. The highlights of this study are using zircon geochronology and geochemistry to clarify the genesis of gold mineralization in the SHP and providing a new method to understand the genesis of similar vein-type gold mineralization worldwide.