Sulfur isotope and trace element constraints on the conditions of pyrite formation from the Diantou-Shuanglong sandstone-hosted uranium deposit, Ordos Basin, China: Implications for uranium mineralization

• DOI: 10.1016/j.oregeorev.2024.105921
• Publication Date: 2024-02-02T00:03:33Z
• Authors: Yuhan Sun; Yangquan Jiao; Michel Cuney; Liqun Wu; Julien Mercadier; Hui Rong; Yang Liu; Zhenpeng Tao
• Keywords: Trace element

Combined microstructural, isotopic and chemical analysis of pyrite reveals the complexity its genesis from Jurassic Zhiluo Formation in Diantou-Shuanglong sandstone-hosted uranium deposit, southern Ordos Basin. Framboidal, euhedral-subhedral cement are identified by optical microscope scanning electron (SEM). Among them, occurs two forms, either as an independent mineral or wrapped another phase pyrite, where euhedral core is designated Py1, named Py2 rims Py1. Sulfur isotope secondary ion mass spectrometry (SIMS) shows that each has a distinct composition (−30.64 ‰ to −17.94 for −25.19 +19.55 −4.79 +3.73 −24.27 −10.15 Py2). Laser ablation-inductively coupled plasma-mass (LA-ICP-MS) was used reveal considerable range trace element compositions different types pyrite. The concentrated distribution sulfur values enrichment (Co, Tl, Sb, etc.) Py1 indicate it formed thermochemical sulfate reduction (TSR) suffered fractionation. with relatively stable structures absence magmatic hydrothermal activity Basin, we propose rapid subsidence Basin Early Cretaceous led increase basinal fluids temperature which reached threshold TSR formation abiogenic negative depletion other they were bacterial (BSR). Some pyrites show positive δ34S due Rayleigh Although indicates biogenesis, contains high compared biogenic At end subsequent Cretaceous, uplift denudation basin decrease geothermal gradient. Simultaneously, exposed surface received uranium-bearing oxidized fluids, indicating beginning mineralization. pre-ore dissolved form growth textures release during infiltration BSR precipitated enriched resulting moderately content lighter values. Therefore, minerals precipitate around between Py2. We suggest redox processes activities involved mineralization, together promote precipitation. This proposition helpful further understanding mechanism pyritization provides valuable guidance thermogenic interpretation sedimentary basins similar structures.