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This work aims to understand the distribution and migration mechanisms of U and Mo between surface sediment and water in acid mine drainage (AMD) regions near a molybdenum mining region. A series of river sediment and water samples near the Jinduicheng mining area, one of the largest deposits of molybdenite ore in Asia, were collected and analyzed. Our results indicate that: (1) The pH value of river water samples increases with distance from upstream to downstream, while the pH has poor correlation with Mo and U; (2) The content of Mo and U in the sediment are significantly higher than the background value, which suggests potential pollution; (3) The content of Mo and U in the water and sediments in the lower reaches of the Wenyu river is significantly linearly related with the distance from the mining area, suggesting that AMD is a potential source; (4) BCR analysis shows that Mo in river sediments mainly existed as the residual, while U mainly existed as the non-residual; (5) The distribution coefficient Kd(Mo) exceeds Kd(U), indicating that Mo is enriched in sediments while U is more prone to porewater. [ABSTRACT FROM AUTHOR]

• Three episodes of magmatism and mineralization occurred at 317–263, 262–235, and 233–202 Ma. • Subduction and collision-related felsic plutonism and volcanism as well as associated mineralization are well defined. • An improved Paleo-Tethyan tectonomagmatic model has been established for TSOB. The Truong Son orogenic belt (TSOB) is part of the eastern Tethyan mineral deposit domain, and preserves a near-complete record of Paleo-Tethyan orogeny-related magmatism and mineralization. By compiling and evaluating the data of plutonic and (sub)volcanic rocks and associated deposits on a regional scale, and combining with new data of typical igneous rocks and mineral deposits, we establish a unified Paleo-Tethyan evolutionary model to help understanding the metallogeny in the TSOB. The geochronological data reveal the felsic magmatism and associated mineralization occurred in Carboniferous–Triassic (ca. 317–202 Ma) with a magmatic lull at ca. 270–263 Ma. Before the lull, most igneous rocks are high-Mg#, sodic, metaluminous I-type granitoids (or volcanic equivalents) with depleted Hf isotopes, which were derived from a juvenile crustal source with significant mantle contribution. After the lull, the igneous rocks (ca. 262–235 Ma) consist of metaluminous I-type granitoids and abundant S-type granitoids with geochemical features of low-Mg#, potassic, peraluminous and enriched Hf isotopes, suggesting their derivation from ancient continental crust without obvious mantle contribution. This magmatic lull corresponds to the tectonic transition from subduction to initial collision, which reasonably accounts for the changing of petrogenetic types and magma sources of the associated igneous rocks in the TSOB. The slightly depleted Hf isotopes of the ca. 234–202 Ma rocks possibly suggest another episode of tectonic transition in Late Triassic. The distinct mineralization styles and S isotopes of ore deposits of each episode indicate that mineralization was related to the tectonic evolution and magmatism in each stage. Here, we propose an evolutionary model for the Paleo-Tethys orogeny in the TSOB, as follows: (1) low-angle subduction beneath the TSOB during Late Carboniferous-Late Permian, favored the formation of juvenile crust-derived adakitic rocks and high-Mg# I-type felsic rocks as well as associated porphyry Cu ± Au, skarn Fe ± Cu ± Au and epithermal Au–Ag mineralization; (2) subsequent collision during Late Permian-Middle Triassic not only accounted for the generation of Precambrian crust-derived I-type granitoids and intrusion-related Au ± Ag deposits, but also resulted in the formation of low-Mg# S-type rocks, minor volcanic rocks and associated porphyry and/or skarn Sn ± Zn ± Pb deposits; (3) possible post-collisional extension during Late Triassic may be favorable for the formation of metaluminous, high-K (±high Mg#) I-type granitoids and volcanic rocks, and Carlin Au, porphyry and/or skarn mineralization. [ABSTRACT FROM AUTHOR]