Assessment Of Deep Gold Resources And 3D Metallogenic Prediction In Northwest Jiaodong,Shandong Province

The metallogenic conditions in the northwest area of Jiaodong are superior,the gold resources arc rich,and the proven resource reserves account for more than 90%of the entire Jiaodong area.The types of gold deposits are mainly altered rock type(Jiaojia type)and quartz vein type(Linglong type)in the fracture zone.The deposits are controlled by Mesozoic magmatic rocks and NE-NNE trending fault structures.Most of the deposits are distributed on the edge of the rock.The main metallogenic belt is composed of the Sanshandao gold belt,Jiaojia gold belt,and Zhaoyuan-Pingdu gold belt in the main fault zone of NE-NNE and the secondary faults in the lower wall.In recent years,with the increase in mining depth and the depletion of the main ore body resources,the demand for finding replacement resources and deep prospecting is increasing.In the deep prospecting work,due to economic constraints,breaking through the traditional drilling-based prospecting methods is difficult;however,the applications of new deep prospecting technologies represented by 3D geological modeling and 3D metallogenic prediction to find mineral deposits have begun.The 3D prospecting prediction is based on a comprehensive analysis of metallogenic geological conditions and ore-controlling rules,relying on the continuous improvement of comprehensive multi-element prospecting information,such as geological deposit exploration data and geophysical and geochemical data.Prospecting research is carried out using the ore body.The application of this technology will greatly promote the"positioning," "quantitative prediction," and "fixed probability" prospecting research and the evaluation of the deep gold deposits in gold mining concentration areas.In this study,the Jiaojia gold ore belt and Zhaoyuan-Pingdu gold ore belt were selected as the key areas.The southern extension of the Jiaojia belt was measured by a controlled-source audio-frequency magnetotelluric sounding profile and a polarization measurement profile.The location of the southern extension of the Jiaojia belt was verified,and the ore belt was extended further south by about 3 km.In the central and southern sections of the Zhaoyuan-Pingdu gold ore belt,a 1:50000 gravity measurement and a 1:50000 magnetic method measurement were carried out.Based on the results of geological interpretation,studies were conducted in the Dayingezhuang-Xiadian gold ore field using the methods of controlled-source audio-frequency magnetotelluric sounding and tectonic superimposed halos;the Zhaoyuan-Pingdu gold ore belt was under the Quaternary coverage area of the south extension.In the Jiaojia metallogenic belt,the deepest sailing mining area;Zhaoxian mining area;and the Zhaoyuan-Pingdu metallogenic belt,Dayin'gezhuang,Xiadian,and other gold deposits were selected,and borehole samples were collected to analyze trace pyrite deposits.The analyses included rare earth element analysis,inclusion composition analysis,inclusion temperature measurement,multi-isotope analysis,through fluid inclusions,S and He-Ar isotopes,and gold-bearing mineral pyrite.The fluid inclusions in the main ore-forming period of the gold deposits in the study area are believed to be H2O-CO2 mixed fluids,containing a small amount of CH4,and are medium-temperature,medium--salinity,and low-density fluids.The salinity is reduced in the late stage of mineralization,and the metallogenic environment is the reducing environment.The magmatic-hydrothermal fluid formation is the main part in the early metallogenic process,and the mantle fluid is involved in the main metallogenic stage,and more atmospheric precipitation is added in the later stage.The metallogenic process is related to the hydrothermal metamorphic alteration of huge scale and depth after the magmatic period,andand this alteration leads to the formation of the hydrothermal metamorphic gold deposit after the magmatic period.Based on the analysis of the ore body's occurrence rule,lateral rule,and other factors affecting the control of gold mineralization enrichment,the "cubic prediction model method"was used to carry out 3D modeling,and the "3D evidence weight method" and "3D information amount.”Using this method—which involved a 3D prediction of the integration of positioning,quantitative data,and the fixed probability of deep ore bodies—the 3D geological models of the Jiaojia metallogenic belt and Dayingezhuang-Xiadian area were established.This 3D modeling helped in realizing the 3D visualization of the Northwest Jiaodong gold deposit concentration area,which is a new breakthrough from the traditional 2D prospecting to the 3D prospecting prediction.Using the 3D prediction model,six ore prospecting target areas were delineated,and"target" and"quantitative" predictions were realized at two target areas deep in the Jiaojia gold metallogenic belt.A total of 27 orebodies were drilled in this study,and the newly added resource was x t,reaching the scale of a super-large gold mine.The successful application of the 3D metallogenic prediction of the Jiaojia metallogenic belt and Dayingezhuang-Xiadian area provides a reference and a replicable and marketable technical method for deep prospecting research in the entire northwest Jiaodong area.