Metallogenic Geodynamics of the Shangri‐la Area Large Mo‐Polymetallic Ore Deposit in Southwest China

in a NW trend along Xiangcheng in Sicuan to Luoji in Yunnan, and we thus call it Xiangcheng-Luoji Yanshanian granite zone in this paper(Fig. 1). In northern part, the wall rock of intrusions is mainly Lamaya Formation (T3lm), and in southern part, the wall rock is Tumugou Formation (T3t). At present, we have discovered more than 10 outcropped or buried intrusions in various sizes, including Cilincuo batholite, Sandaoqiao stock, Rirongcuo stock, Zhujiding stock, Xiuwacu and Relinlin batholite, Hongshan and Tongchanggou intrusions, from north to south of this intrusive zone. They are largely outcropped at high altitude, and mostly buried or semi-buried at low altitute. Typically disseminated molybdenite is found in granite intrusions, and molybdenite veins and quartzmolybdenite veins are developed along fissures. Chalcopyrite veinlets and nodular molybdenite are found in hornfels near intrusions. In southern part, Honshan and Tongchanggou intrusion (apophyse) host Au, Cu mineralization in addition to Mo mineralization in intrusions. In past studies, the Geza Indosinian volcano-magmatic arc in the southern section of the Yidun island arc is called Geza island arc, and the associated Cu-Mo, Pb-Zn, and Au-polymetallic ore deposits are characteristics of the porphyry mineralization systems (Li et al., 2013). East of the Yidun island arc, the Ganzi-Litang suture zone hosts Fe, Cr, orogenic Au deposits and occurrences, which are related to ultramafic and mafic rocks in ophiolitemelanges. These deposits represent tectonics-magmametallogenesis related to closure-orogenic evolution of Indosinian Ganzi-Litang ocean. Eastward, the YanyuanLijiang continental depression zone along the western margin of Yangzi land block is typified by the occurrences of Cu-Ni sulfide and PGE deposit related with Permian Emeishan basalts, which is thought to have produced from the mantle plume activity, and those deposits represent the Late Variscan magma-metallogenesis. Following the closure of the Ganzi-Litang Tethyan ocean, the tectonic terrains, i.e., the southern section of Yidun island arc, Ganzi-Litang suture zone and Yanyuan-Lijiang continental depression zone of the western Yangtze land block, were matched and succeeded by the collisional and inland orogeny. In Late Yanshanian, the S-type granites in this area were formed from the inland collisional orogeny with partial melting of thickened continental crust. The granodiorite, monzonitic granite outcrops are found in northern part of Xiuwacu and Relin between Yunnan and Sichuan, and southward in Yunnan, the buried porphyries are found mainly in Hongshan, Tongchanggou, where the outcropped granodiorite porphyries (dikes) are associated with porphyry-skarn Mo-Cu polymetallic deposits. Since 65 Ma, the large scale strike-slip, shear and napping are typical for the Sanjiang orogenic belt and the western margin of the Yangzi land block, and as a result, the Himalayan alkalic porphyries were emplaced, which were associated with a number of Au-Cu deposits, such as the large scale Beiya Au (Cu) deposit in Yanyuan-Lijiang continental depression zone, Changan Au deposit in Ailaoshan shear zone and Machangqing Cu-Au deposit. Those deposits are included in the “Jinshajiang alkalic porphyry mineralization belt”. The northern part of GanziLitang suture zone extends from NNW at Muli in Sichuan to south at Luoji area in Yunnan, and then to westward. Chlorite glaucophane schist and ophiolitic mélange zone are found in Luoji area, along the Geza regional fault at Tuguancun in Yunnan, where Yidun island arc belt was matched with Yangtze land block. Yanshanian porphyry Mo-polymetallic deposits and Himalayan alkalic porphyry Au(Cu, Mo) deposits are found in all tectonic units (Fig. 1). In brief, the Yanshanian intrusive rocks typically vary from monzonitic granite, granodiorite, to granite aplite and granite porphyry, with the assemblage indices σ varying from high to low, and the alkali contents decreasing as well. Their σ values of <3.3 indicate the normal calcYU Haijun, LI Wenchang and YIN Guanghou, 2014. Metallogenic Geodynamics of the Shangri-la Area Large Mo-Polymetallic Ore Deposit in Southwest China. Acta Geologica Sinica (English Edition), 88(supp. 2): 891-892.