Geology, geochemistry and tectonic settings of molybdenum deposits in Southwest China: A review

Southwest (SW) China hosts more than 26 Mo (Mo-only, Mo-dominated and Mo-bearing) deposits with a total reserve of > 2.5 Mt Mo metal. The region has become one of the most important Mo mineral provinces in China. These Mo deposits are usually fault-controlled, and are located mainly in: (1) Lhasa Terrane, characterized by widely distributed Yanshanian-Himalayan igneous rocks; (2) Qiangtang Terrane, composed by Proterozoic and Early-Paleozoic crystalline basement and Devonian to Jurassic cover rocks; (3) East Kunlun Terrane, comprising Precambrian metamorphic rocks intruded by Paleozoic and Mesozoic granitoid plutons; (4) West Kunlun Terrane, characterized by Precambrian metamorphic basement, Paleozoic metasedimentary rocks, and Early-Paleozoic and Carboniferous-Triassic arc-type plutons; and (5) Yidun arc, composed by Middle and Upper Triassic volcanicsedimentary successions. The Mo mineralization styles are dominated by porphyry-type, but also contain porphyry-skarn, skarn and porphyry-quartz vein types. Orebodies are vein-type or lensoidal, and are hosted by a variety of metamorphic, volcanic, granitic and sedimentary rocks of different ages. Fluid-rock interactions are exemplified by alteration zonation, which usually grades from an innermost potassic alteration zone, via a silicic/sericite alteration zone, to an outermost propylitic alteration zone. The initial high-temperature ore-forming fluids are magmatic in origin, and contain CO2-bearing fluid inclusions. The initial ore-forming fluids would have then evolved to low-temperature, low-pressure, low-salinity and CO2-poor (with meteoric water input) at the late alteration/mineralization stage. Causative granitoids for these Mo deposits have relatively high SiO2, K2O and Al2O3, and low TiO2 and MgO, showing a metaluminous to peraluminous high-K calc-alkaline to shoshonitic affinity. These granitoids exhibit significant depletions in Ba, Nb, Ta, P and Ti, and enrichments in Rb, Th, U and K. It is suggested that they were originated from partial melting of a lower rejuvenated crust, as evidenced by their Sr-Nd-Pb isotopic signatures. The Mo deposits in East and West Kunlun were formed in the Triassic (ca. 258-214 Ma), related to the Paleo-Tethys Ocean subduction and the subsequent continental collision. Major Mo mineralization in the Qiangtang and Lhasa terranes mainly occurred during the syn-collisional compression to post-collisional extension transition of the Qiangtang-Lhasa (ca. 4335 Ma) and India-Asia (ca. 3014 Ma) collisions, respectively. The Late-Cretaceous Mo mineralization (ca. 8873 Ma) in the Yidun arc was formed during the late- or post- Lhasa-Qiangtang collision setting, or the intraplate extension led by the post-Himalayan escape tectonics. The wide range of molybdenite Re contents in these major SW Chinese Mo deposits indicates remarkable differences in metal, fluid sources and ages. (C) 2016 Elsevier B.V. All rights reserved.Excellent Ph.D. Thesis Program of Beijing [20131000104]; 973-Projects [2006CB403508, 2012CB416602]; National Natural Science Foundation of China [40730421, 40425006]SCI(E)ARTICLE,SI965-9958