Ore-forming processes and mineralization of complex tectonic system during the Mesozoic: A case from Xilamulun Cu-Mo metallogenic belt

The Xilamulun metallogenic belt, located between Central Asian Orogenic Belt and North China Craton, is situated at the junction between the Paleo-Asian Ocean and the west Circum-Pacific tectonic regime. The ore belt was controlled by some tectonic systems, such as post-collisional extension of the Central Asian Orogenic Belt, Mongolia-Okhosk orogen, west Circum-Pacific tectonic and lithosphere large-scale thinning. Molybdenite Re-Os and zircon U-Pb dating of the Xilamulun ore belt show three periods of mineralizations which occurred at 260 similar to 220Ma, 180 similar to 150Ma and 140 similar to 120Ma, respectively. Combined with the regional geology and geochemical study, we suggest that the mineralizations in the belt were formed during multiple geodynamic settings. The mineralization in 260 similar to 220Ma is probably related to a post-collisional extension stage with the generation of the porphyry molybdenum-copper deposits; The stage of 180 similar to 150Ma is related to a tectonic stress transformation from NS to EW; The large-scale mineralization occurred at 140 similar to 120Ma is related to the lithosphere thinning due to the upwelling of asthenosphere under the intra-continent extension. Based on geology and geochemistry of Mo-Cu deposits, authors suggest three ore-forming modes; i.e . "Chehugou","Jiguanshan" and "Aolunhua"-types. Study data show that ore-forming specialization are restricted by acid-alkali degree of host rock, magma source, oxygen fugacity of rock, evolvement fashion of magma and tectonic setting.