Tianshan, Junggar and Altay Orogens (NW China), the Alpine-Himalayan Fold Belts (Tethyan Orogens), Kunlun and Songpan-Ganzi Terranes

Abstract

The Tianshan, Junggar and Altay orogenic belts in northwest China (Xinjiang) are part of the huge Central Asian Orogenic Belt (CAOB), which extends from the Uralides in the west to the Pacific Ocean margin of eastern Asia. The CAOB is a complex collage of fragments of ancient microcontinents and subduction-related island arc terranes, fragments of oceanic crust volcanic islands and plateaux and successions formed at passive continental margins. The amalgamation of these terranes occurred at various times from the Neoproterozoic to the Mesozoic and was accompanied by several episodes of magmatism. The CAOB is endowed with a large variety and number of mineral deposits, including: epithermal, porphyry and skarn systems, volcanogenic massive sulphides (VMS), lode style Au deposits, orthomagmatic Ni-Cu-PGE, rare metals in pegmatites and sandstone-hosted U deposits. There is abundant literature on various aspects of the geodynamic evolution of the Tianshan, Altay and Junggra belts and selected mineral deposits, both in Chinese and English. A review of the Tuwu, Baogutu porphyry deposits and those of the western Tianshan is provided. Epithermal precious metal deposits of high-sulphidation and low-sulphidation type are numerous in NW China and examples presented are Kuoerzhenkuola, Jinxi-Yelmand, Axi, Kuruer, Shuanffengshan, Jinshangou, Shiyingtan and Mazhaungshan. Similarly, precious metal lodes are abundant in the Tianshan, Junggar and Altay orogenic belts. Typically these lode deposits, commonly labeled as orogenic, occur within high strain zones in brittle (lower greenschist facies), brittle-ductile structures (mid-upper greenschist facies) to ductile (amphibolite facies). Many of the orogenic deposits have a spatial relationship to igneous rocks, while for others there is no clear connection with igneous activity. Therefore, these mineral systems are referred to as Au lodes, avoiding the orogenic or intrusion-related qualifiers.