Low-temperature thermochronology of the Carlin-type gold deposits in southwestern Guizhou, China: Implications for mineralization age and geological thermal events

Abstract

The Dian-Qian-Gui area in southwestern China is the second-largest concentration of the Carlin-type gold deposits in the world, and the southwestern Guizhou is the most important gold-producing district of the Dian-Qian-Gui area. Dating of the Carlin-type gold deposits is always a challenge due to the lack of ore-stage minerals which are suitable for conventional radiometric dating. Low-temperature thermochronometers, including fission track and (U-Th)/He, are temperature-sensitive radiometric dating techniques and have been successfully applied to elucidate many aspects of ore deposits, including the timing and duration of mineralization processes.In this study, zircon fission track, zircon (U-Th)/He and apatite fission track dating techniques were applied to the Carlin-type gold deposits in southwestern Guizhou. Samples for zircon and apatite analyses were collected from mineralized or altered sedimentary rocks in Shuiyindong, Taipingdong, Bojitian, Yata and Getang gold deposits. Four groups of thermochronological ages were obtained, i.e., 192–216 Ma, 132–160 Ma, 88 Ma, and 19–40 Ma, which are considered to be the records of four geological thermal events. Of them, most zircon fission track ages and all zircon (U-Th)/He ages concentrate in 132–160 Ma. Thermochronological constraints, combined with field relationships, suggest that the mineralization of the Carlin-type gold deposits in southwestern Guizhou most likely occurred in this period. Partial zircon fission track ages are in 192–216 Ma. They may record the cooling timing of a pre-ore thermal event caused by the Indosinian orogeny, which is supported by the paleogeotemperature restoration. A few zircon grains with high U content yield fission track age of 88 Ma, which may record a post-ore thermal event associated with the intrusion of local mafic dykes. All apatite fission track ages range in 19–40 Ma, which may record a lower temperature but extensive hydrothermal superimposition in the Cenozoic. Additionally, a corresponding relationship between zircon fission track ages and stratigraphic sequences was identified in the Huijiabao anticline, which is considered to reflect the decrease of temperature and duration of ore-forming hydrothermal activity from lower to upper stratigraphic sequences.