Exhumation history and preservation of the Changjiang uranium ore field, South China, revealed by (U-Th)/He and fission track thermochronology

• Published in: Ore geology reviews Vol. 133; p. 104101
• Main Authors: Sun, Yue, Chen, Zhengle, Boone, Samuel C., Zhong, Fujun, Tao, Wei
• Format: Journal Article
• Language: English
• Published: Elsevier B.V 01.06.2021
• Subjects: Changjiang uranium ore field; Exhumation; Low-temperature thermochronology; Ore deposit preservation; South China; Low-temperature thermochronology; Exhumation; Ore deposit preservation; South China; Changjiang uranium ore field
• ISSN: 0169-1368; 1872-7360
• DOI: 10.1016/j.oregeorev.2021.104101

Inverse thermal history modelling results for all samples generated with the QTQt software. Each of the colored lines are the best-fit time-temperature paths for each of the samples. The order of the samples is based on their elevations, with lowest sample best-fit in red and the highest in blue. The light pink and green envelopes are the 95% confidence interval for the uppermost and lowermost samples in the model. The data fit for thermal history model is illustrated by panel inserts showing observed versus predicted ages. Predicted versus observed confined track distributions are displayed in the Supplementary Data. AFT = apatite fission track; PAZ = partial annealing zone; MTL = mean track length. [Display omitted] •ZHe, AFT and AHe data were used to elucidate the tectono-thermal evolution of the Changjiang uranium ore field (CUOF).•Late Cretaceous-Early Paleocene cooling due to Pacific subduction-related transpression.•Slight Middle Paleocene to Middle-Late Eocene reheating due to extension and burial.•Late Eocene-Quaternary tectonic exhumation due to India-Asia collision and eastward extrusion of Tibetan Plateau.•Large uranium ore reserves in the CUOF could remain at depth. The Changjiang uranium ore field (CUOF) is one of the most important and representative granite-type uranium ore fields in South China. Previous work on the CUOF has primarily concerned uranium ore genesis, focusing on aspects such as timing of metallogenesis and uranium mineralization mechanisms. However, the exhumation history and preservation of the ore deposits in the CUOF are poorly constrained. This study reports multi-system low-temperature thermochronology data that constrain the thermal history of the CUOF in the south-central Zhuguangshan complex, providing important insights into its tectonic evolution and the degree of ore preservation. Zircon (U-Th)/He (ZHe) ages of the mineralized and non-mineralized samples from fault-bounded Triassic-Jurassic granitic basement blocks range from 123 to 24 Ma and negatively correlate to effective uranium (eU) content (335–6611 ppm). Apatite fission track (AFT) ages of granite samples vary from 63 to 58 Ma with relatively short to moderate track lengths, and apatite (U-Th-Sm)/He (AHe) ages range from 39 to 24 Ma. Inverse thermal history models from individual and grouped samples produce similar time–temperature reconstructions exhibiting a Cretaceous-Cenozoic three-stage thermal history involving an initial Late Cretaceous-Early Paleocene exhumation phase (~80–60 Ma) and subsequent Middle Paleocene to Middle-Late Eocene burial phase (~60–40 Ma), interpreted to be primarily controlled by temporal, spatial and velocity variabilities in Pacific Plate subduction dynamics. A final Late Eocene-Quaternary stage (~40–0 Ma) of exhumation was likely caused by the uplift associated with India-Asia collision and the eastward extrusion of the Tibetan Plateau. The ~ 1.5–3.6 km of post-mineralization regional exhumation estimated from thermal history reconstructions, combined with existing uranium mineralization data (timing, temperature and pressure conditions) consistent with an ore-forming depth of ~ 3.2–5.6 km, suggest that the bulk of CUOF uranium ore bodies may still be preserved at depth.