Carbonate U Pb and illite Rb Sr geochronology of sediment-hosted gold: A case study of Yata gold deposit

Abstract

In situ U–Pb dating of carbonate minerals and Rb–Sr dating of illite was carried out on the Yata sediment-hosted disseminated-type gold deposit in the Youjiang basin, South China. The new study determines the timing of gold mineralization and clarifies the geological conditions required for the successful application of in situ U–Pb dating of alteration-related carbonate minerals. The results suggest that the Yata gold deposit likely formed during two metallogenic episodes. Illite Rb–Sr ages of 178.6 ± 5.8 Ma (MSWD = 1.2) for the 2–0.5 μm fraction and 171.3 ± 3.4 Ma (MSWD = 0.62) for the 0.5–0.2 μm fraction constrain an earlier episode of gold mineralization to >178.6 Ma. Hydrothermal carbonate minerals within the Yata gold deposit are associated with organic matter. In situ U–Pb dating of paragenetically early ankerite and later calcite veins yields ages of 149.0 ± 10.4 Ma (MSWD = 2.0) and 147.3 ± 32.6 Ma (MSWD = 1.8), respectively. These mineral ages and their petrographic relationships provide unequivocal evidence that another episode of gold mineralization occurred in the Early Cretaceous . Importantly, this study demonstrates in situ U–Pb dating is applicable to low-temperature deposits consisting of organic-rich hydrothermal carbonates characteristic of relatively high common Pb. Such deposits potentially include hydrothermal antimony, Carlin-type gold deposits, gold‐uranium, and carbonate-hosted uranium deposits. • Carbonate U–Pb dating constrains the age of late mineralization to ca. 150 Ma. • Illite Rb–Sr ages constrain the early stage of gold mineralization to ca. 178–172 Ma. • U–Pb isotope analysis can provide reliable ages for U-rich hydrothermal carbonates.