Research progress on the flat subduction and its metallogenic effect, two cases analysis and some prospects

Abstract

Flat subduction is a type of subduction in which the oceanic crust under overlying plate subducted horizontally or shallowly (usually with the subduction angle < 10°) , occurring in ~ 10% of the world' s convergent margins. Many studies indicate that there is genetic relationship between plenty of large-giant porphyry Cu deposits or epithermal Au deposits and flat subduction, especially those deposits developed at Andes. Meanwhile, flat subduction may bring about a large amount of impacts on orogeny, earthquake, crust deformation, crust-mantle interaction. Therefore, research on flat subduction is of great significance. Basing on absorbing and summarizing previous research fruits, this paper gave a comprehensive introduction on flat subduction from the following aspects: the main expression of flat subduction, the transition of subduction type in geologic time, the evolution of flat subduction, the possible mechanisms causing flat subduction. Then we analyzed and discussed the possible connection between flat subduction and accretionary orogeny, and the relationship between flat subduction and porphyry Cu deposits, and also the difference between flat subduction and mid-oceanic ridge subduction ( slab window). And then we introduced two possible flat subduction examples, which are Laramide orogeny and Mesozoic granite belt of Southeast China. Finally we summarized several conclusions of flat subduction, and proposed our thoughts and prospects on flat subduction in future, which are Central Asian Orogenic Belt especially the Balkash porphyry copper belt in Kazakhstan and adjacent area and the Bangonghu-Nujiang Au-rich porphyry copper belt in Tibet as the two potential areas of developing ancient flat subduction.