3d Geochemical Modeling Of Jiaodong Gold Deposits ——A Case Study Of The Qujia Gold Deposit,Laizhou

The distribution patterns of primary halos and secondary halos are described individually in traditional geochemical exploration.How to construct the spatial correspondence between primary halos and secondary halos,and establish an integrated geochemical exploration model from primary to secondary halos is an urgent scientific problem that need to be solved.In the past,the geochemical exploration models were all two-dimensional models,including the profile model of the primary halo and the curve model of the secondary halo.The establishment of a three-dimensional model is a technical problem that needs to be solved to accurately describe the spatial geometry of geochemical anomalies.Based on the above scientific and technical problems,this paper takes the Qujia gold deposit discovered in the Jiaojia metallogenic belt coverage area in Jiaodong as an example,and conducts an integrated three-dimensional geochemical exploration model combining the primary halo based on the borehole data and the surface secondary halo based on the fine-grained soil geochemical data,to provide a technical and theoretical support for the geochemical exploration in coverage areas.The Jiaodong gold ore deposit cluster is the biggest one in China and the third-biggest one in the world,respectively.In this study,three-dimensional(3D)geochemical modeling were formulated by integrating geochemical data from 1130 rock samples of 38 borehole cores and652 fine-grained surface soil samples using Micromine software.The goal is to discuss and determine dominant factors of 3D geochemical patterns and explore dispersion process of mineralized and pathfinder elements during ore-forming and weathering processes,construct a complete evidence chain of primary halo formation with fluid transport during ore-forming process to secondary anomalies during the weathering process to provide strong theoretical support for deep-penetrating geochemical exploration methods.Based on a 3D geochemical model of the continuous spatial distribution of ore-forming elements and indicator elements,the complete geometric characteristics are as follows:Au,Ag,TFe₂O₃,S,and Bi in the primary halo are distributed in stable and continuous high contents along the ore-controlling structural fault zone;Hg in the primary halo is distributed in discontinuous lenticular along the ore-controlling structure,and in discontinuous beaded or funnel-like distribution in the vertical direction,accompanied by weak Au anomalies;high contents of Cl and Pb appear above the Jiaojia fault;the composite anomalies of Au,Ag and Hg exist in the surface fine-grained soil above the ore bodies and the Jiaojia fault zone,which suggests Au,Ag,and Hg migrated axially along the ore-controlling structure and vertically though the cover(rock and transported cover).This model provides a strong empirical basis for the genesis of surface geochemical anomalies and their inheritance relationship from deep concealed deposits.In addition,elemental 3D geochemical patterns,ore body distribution characteristics,and low iron content of Linglong monzogranite indicate that phase separation is the potential mechanism of gold precipitation and mineralization.The correlation between the ore bodies,primary halos and secondary halos indicates that ore-related and pathfinder elements in the deep concealed ore bodies and primary halos migrate vertically due to various mechanisms and form geochemical anomalies in the above fined-grained soil due to the adsorption of clay minerals and iron-manganese oxides.Compared with the underlying primary halo,soil fine-grained Au and Ag anomalies were significantly enhanced.However,the weathering of exposed mineralization in the eastern higher-altitude area led to the activation,migration of Au and Ag to form secondary anomalies in the mid-west higher-altitude area,which seriously interferes with the geochemical exploration.As a semi-volatile metal,Hg tends to form strong anomalies above the concealed ore bodies.And Hg is in the form of adsorption state and insoluble inorganic matter in the soil and hard to migrate laterally.Based on the factor analysis based alr-transformed soil fine-grained geochemical data,the results presented that F4(Au-Ag association)is an ore-related element association,and F2(Hg-Br-I-S-Se-Sn association)is the product of the migration of deep ore-forming fluids to the shallow surface,and can be used as indicator elements.Consequently,the composite anomaly of fine-grained soil Au-Ag-Hg is used as an indicator of geochemical exploration of deep concealed ore bodies.The high coincidence between fine-grained soil geochemical anomalies and ore bodies proves that fine-grained soil prospecting method is an effective deep-penetrating geochemical exploration method for the coverage area in the warm temperate humid climate zone.