Tectonic setting, metallogenesis and deposit types in Sanjiang Tethyan domain, S.W. China

摘要

Tectonically, the Sanjiang Tethyan Metallogenic Region is located within the eastern Himalayan-Tibetan Orogen in the Sanjiang Tethys, Southwestern China. Although this metallogenic region was initiated in the Early Paleozoic, extensive metallogenesis occurred in the Late Paleozoic, Late Triassic and Himalayan (Tertiary) epochs. Corresponding tectonic settings and environments in the region are: an arc-basin system related to the subduction of the Paleo-Tethyan oceanic slabs; a post-collision crustal extension setting caused by the lithospheric delamination or slab breakoff underneath the Sanjiang Tethys during the Late Triassic; and large-scale strike-slip faulting and thrusting systems due to the Indo-Asian continent collision since the Paleocene. In this metallogenic region, important gold, copper, base metals, rare metals and tin ore belts, incorporating a large number of giant deposits, were developed. The main types of deposits include: (1) porphyry copper deposits, controlled by large-scale strike-slip fault system, (2) VHMS deposits, mainly occurring in intra-arc rift basins and in post-collision crustal extensional basins, (3) shear-zone type gold deposits in the ophiolitic melange zone along the thrusting-shearing system, (4) hydrothermal silver-polymetallic deposits in the Triassic intra-continental rift basins and Tertiary strike-slip pull-apart basins, and (5) Himalayan granite-related greisen-type tin and rare-metallic deposits. Within the metallogenic epochs of the late Paleozoic to Cenozoic, the styles and types of the ore deposits changed from VHMS types in the Late Paleozoic through exhalative-sedimentary type deposits in Late Triassic, to porphyry-type copper deposits, shear-zone type gold deposits, hydrothermal vein-type silver-polymetallic deposits, greisen-type tin and rare-metal deposits in the Cenozoic. Correspondingly, ore-forming metals also changed from a Pb-Zn-Cu-Ag association through Ag-Cu-Pb-Zn, Fe-Ag-Pb and Ag-Au-Hg associations, to Ag-Cu-Pb-Zn, Cu-Mo, Au, Sn, and Li-Rb-Cs-Nb-Zr-Hf-Y-Ce-Sc associations.