Lithospheric Material Structure Of The Sanjiang Tethys Orogenic Belt And Its Constraints On Porphyry Metallogenesis

The Sanjiang Tethyan Orogen(SJTO)records a complex tectonic evolution of Proto-Tethys.Paleo-Tethys,Meso-Tethys,Neo-Tethys and the Cenozoic Indian-Eurasian continental collision.The lithospheric structure is very impotant to understand regional regularity and deep metallogenic dynamic mechanism of porphyry Cu-(Mo-Au)deposits in different tectonic setting.In this paper,combining the mineralogy,geochemistry and isotopic mapping,we gain better insights into the lithospheric structure and its constraints on the porphyry deposits in the SJTO.(1)By studying the geochemistry of the Late Triassic,Late Cretaceous and Paleogene rocks in the SJTO,we suggest that the diagenesis and mineralization in the late Triassic are related to the westward subduction of the Ganzi-Litang Ocean.The diagenesis and mineralization in the Late Cretaceous are related to the post-collision and extension of Zhongzan Block.The Paleogene diagenesis and metallogenesis in the post-collision and extension environment are related to the delamination of continental lithospheric mantle.It is proposed that the relationship between subduction and accretion of oceanic crust,post-collision extension,delamination of continental lithospheric mantle and the metallogenic mechanism of porphyry Cu-(Mo-Au)deposits.Those results provide adequate theoretical supports for the exploration of the porphyry Cu-(Mo-Au)deposits.(2)Hf-Nd isotopic and whole-rock geochemical mappings of the SJTO reveal the compositions and properties of different blocks.We suggest that the formation and modification of the juvenile crust in the collisional orogen are of great significance in the Earth's material cycle and the formation of the continent.(3)Based on the study of regional lithospheric architecture,we suggest that the porphyry Cu-(Mo-Au)deposits are located in the juvenile crust of the Jinshajiang-Ailaoshan Suture and the surrounding areas.We suggest that the lithospheric architecture and its crustal type control the genesis and localization of distinct ore deposits,and should form a key component to screen out strategic perspectives for mineral exploration.(4)The comparative research of Hf isotopic mapping in the Tibet and SJTO indicates that the formation of porphyry Cu-(Mo-Au)deposits is related to the growth of juvenile crust.It is likely to form large-scale porphyry Cu-(Mo-Au)deposits in the juvenile crust with the larger occupancy or contribution rate of mantle-derived components.Those results provide great theoretical significance for the study of the formation of porphyry deposits in orogenic belt.