Coupling mechanism of basin and orogen in the Tianshan Orogenic Belt since Late Mesozoic: Influence on the source–sink process of sandstone‐type uranium mineralization

Abstract

The coupling mechanism of the Tianshan Orogenic Belt (TOB) and the basins on its sides (Junggar, Turpan–Hami, Tarim, Yili, etc.) since the Late Mesozoic was complex and multi‐levelled. Based on gravity, magnetism, Moho discontinuity, and lithospheric velocity structure of the TOB, together with the structural and sedimentary data of the basins, a model is proposed to reflect the influence of the basin–orogen coupling on the regional source–sink processes of sandstone‐type uranium mineralization since the Late Mesozoic. Generally, there are four main stages of tectonic movements that have changed the coupling mechanism of basin and orogeny: including the Early Yanshanian Movement, the Late Yanshanian Movement, the Middle Himalayan Movement, and the Late Himalayan Movement. These four movements together controlled the mineralization of the sandstone‐type uranium deposits in the TOB together. The mineralization of sandstone‐type uranium deposits in the TOB can be divided into three metallogenic stages: the ore‐bearing formation stage (T‐J2), the tectonic reversal‐related metallogenic stage (J3‐N1), and the epigenetic regenerating ore‐preserving stage (N2‐Q). The tectonic reversal‐related metallogenic stage can be subsequently divided into three sub‐stages: the pre‐metallogenic stage (J3), the sub‐metallogenic stage (K), and the main metallogenic stage (E‐N1). The associated uplift led to the deformation of the mineralized strata in the basins, while the reducing agent migration along faults enhanced the reduction environment within the strata, which affected the enrichment and distribution of the uranium mineralization in the strata. Meanwhile, the recharge and the change of flow state of groundwater also contributed to the later transformation and mineralization. The intra‐continental subduction caused deep lithospheric buckling and depression in the TOB, accompanied by local‐scale mantle convection, which accounts for both tectonic and geodynamic settings for the regional basin–orogen coupling mechanism. In addition, the far‐field effect of the India–Eurasian collision also provided the driving force for the sandstone‐type uranium mineralization in the TOB.