A preliminary study on numerical simulation of the Jiama porphyry metallogenic system, Tibet, China

Abstract:

Porphyry metallogenic system is a typical hydrothermal metallogenic system. Its metallogenic process is a complex geological process in which mechanical-temperature-fluid flow-chemical migration and reactions are mutually coupled and influenced. At present, there is a lack of numerical simulation of the mineralization process and its mechanism. Based on Jiama porphyry metallogenic system in Tibet, China, we developed and built a two-dimensional finite element multi-field coupling numerical model to research the evolution of stress, strain, temperature, fluid pore pressure and the migration of ore-forming element concentration, and the influence between them. The model results show that the interlayer detachment zone is mainly developed in the area where the ratio of shear stress to horizontal stress is high, which is consistent with the location of skarn deposit; In the early stage of high temperature intrusion cooling, the surrounding rocks at the top boundary of the intrusion produce strain concentration (fracture zone) and overpressure of pore fluid, pore fluid and metallogenic elements are transported outward from the intrusion, and the distribution of metallogenic elements is consistent with that of porphyry potassic alteration and proximal skarn deposit. In the late stage of intrusion cooling, due to the contraction of cooling, several fracture zones appear and cut the carbonate formation, ore-forming elements migrated to the area far from the intrusion in carbonate stratum, fluid overpressure dissipation causes the backflow of pore fluid, which enhances the participation of the crust fluid, and this is advantageous to the formation of distal skarn deposits and epithermal deposits in low temperature. The results of our numerical simulation study are of great significance to further understand the metallogenic process and mechanism of porphyry metallogenic system, and provide guidance for the exploration work such as deposit location and deep prospecting.