Geological And Geophysical Interpretation And Metallogenic Prospective Analysis In Heyuanbei District Xiangshan Ore Field

In this paper,based on the CNNC"Long Chan high-precision geophysical and geochemical exploration project",the study of rock physical properties,faults between the two groups,metamorphic basement and deep structural framework had been carried out in Heyuanbei district in Xiangshan.Combined with transmagmatic fluid theory and three-dimensional geological-geophysical model,the favorable position for uranium mineralization had been predicted.More than 1400 pieces of typical rock physical samples in Xiangshan volcanic basin had been tested in density,magnetic susceptibility and resistivity.Four broad categories of typical rock(porphyroclastic lava,rhyolite dacite,metamorphic and granitic porphyry)of the physical parameters in the frequency histogram,depth-properties scatter plot and a typical drilling depth-properties images had been drawn.From those images,it was founded that there were obvious differences in density overlying volcanic cover and basement rocks,a difference of 0.1-0.2g/cm~3,while differences in density between volcanic layers was smaller,which was 0.02-0.04g/cm~3,the density difference between cover and basement volcanic rocks might be the basis of gravity data inversion for detecting the substrate interface undulating shape,basement structures.On the magnetic characteristics,porphyroclastic lava showed high magnetic characteristic while rhyolite dacite and metamorphic basement rocks reflected relatively low magnetic susceptibility,so there was an obvious interface which between Goose Lake Ridge group porphyroclastic lava layer and rhyolite dacite layer,metamorphic basement layers.On the electrical characteristics,overall rock resistivity changes from top to bottom is such as Goose Lake Ridge group porphyroclastic lava high resistivity layer-the drumming group rhyolite dacite low resistivity layer-metamorphic basement high resistivity layer,showed a typical"high resistance-low resistance-high resistance"mode.For 1:10000 high precision ground magnetic survey data,processing methods such as reduction to magnetic pole,continuation,derivation were applied in inferring faults interpretation,magnetic substrate interface inversion.4 deep fracture zones and17 normal faults were detected and magnetic inversion results showed that the lowest basement of research area located in the east,which the altitudes was approximately-805m,while the deepest was about-1500m in the central of research area.For the1:10000 AMT profiles in the research area,nonlinear conjugate gradient inversion algorithm was used to calculate AMT data,and combined with drilling,geological data,and TE+TM joint resistivity inversion mode as background to constraint iterative calculation.With the results of several two-dimensional cross-sectional images,faults,interfaces between layers,the shape of basement could be inferred.Three-dimensional model was established by the interpretation of magnetic and AMT methods.In that way,Topography,geology and fracture interfaces were displayed in three-dimensional space.According to the three-dimensional model,drilling and geological information,the interpretation results of deep structure in heyuanbei district were formed.Finally,favorable uranium mineralization area was predicted,instructed by transmagmetic fluids theory.