Chapter 10 Geology and Metallogeny of Tungsten and Tin Deposits in China

Abstract Tungsten and Sn deposits in China are widely distributed in the South China block (i.e., Yangtze craton-Cathaysian block), Himalaya, Tibetan, Sanjiang, Kunlun, Qilian, Qinling, Dabie, and Sulu orogens, and Central Asian orogenic belt. Among these, the South China block hosts the majority of the mineralization with about 73% (9.943 million tonnes WO3) and 85% (6.561 million tonnes Sn) of the country’s total W and Sn resources, respectively. The W resource mainly occurs as skarn (63%), quartz-vein (17%), porphyry (17%), and greisen (3%) Sulu deposits, whereas Sn is present in skarn (81%), quartz veins that are typically tourmaline-bearing (6%), sulfide-rich veins or mantos (5%), greisen (5%), and porphyry (3%) Sulu deposits. The W and Sn mineralization formed during numerous events from Neoproterozoic to Paleocene with a peak in the period from the Middle Jurassic to Early Cretaceous, and with an uneven spatial and temporal distribution pattern. The Neoproterozoic Sn (W) deposits (850–790 Ma) occur on the southern and western margins of the Yangtze craton, the early Paleozoic W(Sn) deposits (450–410 Ma) are mainly distributed in the northern Qilian and the westernmost part of the eastern Kunlun orogens, the late Paleozoic Sn and W deposits (310–280 Ma) are mainly developed in the western part of the Central Asian orogenic belt, the Triassic W and Sn deposits (250–210 Ma) are widely scattered over the whole country, the Early Jurassic to Cretaceous W and Sn deposits (198–80 Ma) mainly occur in eastern China, and the late Early Cretaceous to Cenozoic Sn and W deposits (121–56 Ma) are exposed in the Himalaya-Tibetan-Sanjiang orogen. The petrologic characteristics of W- and Sn-related granitoids in China vary with the associated ore elements and can be divided into the Sn-dominant, W-dominant, W-Cu, and Mo-W (or W-Mo) groups. The granitoids associated with the Sn- and W-dominant magmatic-hydrothermal systems are highly fractionated S- and I-type, high-K calc-alkaline and (or) shoshonitic intrusions that show a metaluminous to peraluminous nature. They exhibit enrichments in F, B, Be, Rb, Nb, and Ta, depletions in Ti, Ca, Sr, Eu, Ba, and Zr, and strongly negative Eu anomalies. The granitoids associated with W-Cu and W-Mo deposits are of a high-K calc-alkaline to shoshonitic nature, metaluminous, depleted in Nb and Ta, and display weakly negative Eu anomalies. Granitoids associated with Sn- and W-dominant deposits are reduced, whereas those linked to W-Cu and Mo-W deposits are relatively more oxidized. The magma sources of W-dominant granitoids are ancient crust, whereas those connected with Sn, Mo-W, and W-Cu deposits are from variable mixing of ancient and juvenile crustal components. The spatial and temporal distribution pattern of W and Sn deposits in China is intimately related to the regional geodynamic evolution. The Neoproterozoic Sn deposits are associated with peraluminous, highly fractionated, and volatile-enriched (boron and fluorine) S-type granites sourced from the melting of an ancient crust in a postcollisional setting related to the assembly of the Rodinia supercontinent. The early Paleozoic W deposits are genetically associated with highly fractionated S-type granites formed during postcollisional events and were derived from the partial melting of a thickened continental crust in the context of Proto-Tethyan assembly. Granitoids associated with late Paleozoic Sn and W deposits were derived from the melting of an ancient and juvenile crust with I-type affinity associated with the closure of the Paleo-Asian Ocean. Although the Triassic W and Sn deposits are related to the assembly of Asian blocks within the Pangea supercontinent, their geologic settings are variable. Those in the South China block and the Himalaya-Tibetan-Sanjiang belt are associated with collision and magma derivation through the partial melting of a thickened continental crust, whereas in the Kunlun-Qilian-Qinling-Dabie-Sulu orogen and the Central Asian orogenic belt, a postcollisional extensional setting dominates. The Early Jurassic (198–176 Ma) W deposits, located in the northern part of northeast China, are associated with highly fractionated I-type granites derived from melting of juvenile crust and emplaced during the subduction of the Mongol-Okhotsk oceanic plate. The extensive group of Middle Jurassic to Cretaceous W and Sn deposits formed at two stages at 170 to 135 and 135 to 80 Ma. The former stage is associated with highly fractionated S- and I-type granites that are the products of partial melting of thickened crust with heat input possibly derived from a slab window associated with the Paleo-Pacific oceanic plate subduction beneath the Eurasian continent. The later stage is closely associated with NNE-trending strike-slip faults along the Eurasian continental margin and is coeval with the formation of rift basins, metamorphic core complexes, and porphyry-epithermal Cu-Au-Ag deposits. These processes, which were instrumental for the formation of a wide range of mineral deposits, can be ascribed to the regional lithospheric thinning and delamination of a thickened lithosphere and thermal erosion in a postsubduction extensional setting. The 121 to 56 Ma Sn deposits in the Himalaya-Tibetan-Sanjiang orogen are associated with S-type granite or I-type granodiorite emplacement in a back-arc extensional setting during Neo-Tethys plate subduction.