Multi-field Coupled Numerical Simulation Of Ore-Bearing Hydrothermal Migration Process

The Jiaojia gold deposit is one of the most typical altered-type gold deposits in the northwestern Jiaodong gold province,with a clear alteration zonation.However,it is still unclear for the influence of fault structure occurrence on ore-bearing hydrothermal migration,the formation conditions of hydrothermal alteration zonation and the spatial location of chemical reaction associated with gold precipitation.Firstly,this paper constructed the geological model of the mining area and the dynamic model of the hydrothermal mineralization process by combining with the geological facts of the deposit and the existing metallogenic theories.Subsequently,this paper used the multi-field coupled numerical simulation method to carry out numerical simulation research on the ore-bearing hydrothermal migration and alteration mineralization process of the Jiaojia gold deposit.The main research work and results are as follows:（1）The regional geological background and geological characteristics of Jiaojia gold deposit were analyzed.And the control effect of fault structure occurrence on the ore bodies and the alteration and mineralization characteristics of the deposit were studied.The metallogenic model of Jiaojia gold deposit was summarized,and the geological conceptual model of numerical simulation of ore-bearing hydrothermal migration process was established.（2）Based on the dynamic mechanism of hydrothermal mineralization and the geological characteristics of Jiaojia gold deposit,the coupling mathematical model of multi-physical and chemical fields in FLAC3D and TOUGHREACT software was discussed,and the dynamic model of ore-bearing hydrothermal migration and alteration mineralization of the Jiaojia gold deposit were constructed.（3）The FLAC3D software was used to simulate the force heat flow multi field coupling numerical simulation of ore bearing hydrothermal migration process under different fault structure occurrence.The simulation results show that the change of fracture width has a great influence on the temperature field,but has unobvious influence on the strain and fluid fields.The change of fault dip angle has unobvious influence on the temperature distribution,but has a great influence on the strain and fluid seepage fields.The above research results show that the fault zone has an obvious control on the evolution of metallogenic temperature and fluid pressure.From the perspective of numerical simulation,it is verified that the fault zone is a favorable ore-conducting structure and ore-controlling structure,and the smaller fault dip angle is relatively favorable for the formation of altered rock type ore body.（4）The TOUGHREACT software was used to simulate the hydrothermal alteration and mineralization process of the deposit.The volume fraction of altered minerals,the chemical equilibrium concentration of ore-forming material migration form and the spatial distribution of p H value were obtained.The simulation results show that potassic alteration has occurred near the fault zone,and gold mainly migrates in the form of[Au（HS）₂]^-.Then pyrite-sericite-quartz alteration was overprinted,and the precipitation of pyrite promoted the replacement of gold from the complex,and the increase of p H value may be the factor causing gold precipitation.It indicates that the superposition of alteration and the change of physical and chemical conditions form the existing alteration variation zoning.The footwall close to the fault zone is a favorable position for gold precipitation and enrichment.The above simulation results deepen the understanding of ore-controlling by fault structures and hydrothermal alteration in the Jiaojia gold deposit,and provide valuable reference and basis for the exploration of hidden orebodies in the deep margin.