Study Of The Comprehensive Geophysical And Geochemical Prospecting Methods In Loess Covered Area Of Luoning County,Henan Province

The silver-polymetallic ore metallogenic belt in Luoning County,Henan Province,is located in the Xiaoshan Mountains uplift fault area of the Huaxiong Taelung,and is part of the gold-silver-molybdenum-tungsten polymetallic belt of the Little Qinling-Xiaoshan Mountains-Wai Fang Shan in western Henan Province.The area has complex geological structure and strong magmatic activity,and has good geological conditions for mineralization,which is one of the important and highly potential mineralization areas in Henan Province.The Cenozoic fault basin in the region is built up with red sand and gravel of the Neoproterozoic Luoyang Group,which is covered by a large area of Quaternary loess.Due to the special topography,the traditional geological survey methods cannot achieve the expected results in the process of regional survey carried out in the area.To address this situation,this paper selects the silver-polymetallic mineralization zone in the loess-covered area of Luoning County,Henan Province,as the study area,extracts comprehensive information based on geological,geophysical and geochemical techniques and methods,and circles the mineralization target area on this basis,with the aim of providing a scientific basis for the subsequent guidance of mineralization search.This work carried out the following aspects of research:1.Analyze and summarize the geological data of Luoning Loess Covered Area,and initially identify the basic geological features such as stratigraphy,magmatic rocks and tectonics of the study area;clarify the distribution range and distribution pattern of known mining sites.2.The 1:50,000 ground-based high precision magnetic data in the study area are processed by using analytic extension,interpolation cutting and two-dimensional wavelet multi-scale decomposition.The two-dimensional wavelet multiscale decomposition is considered to be effective in separating the magnetic survey data in this area and can better reflect the magnetic field characteristics of geological bodies at different depths.And using two-dimensional wavelet fracture analysis,fracture identification at different depths was carried out,and the fracture inference map of the study area was drawn.Based on the difference of magnetic characteristics of regional geological units,the geological units under the coverage area were initially classified using the method of dynamic clustering.3.The 1:50,000 aqueous sediment data of Ag,Au,As,Bi,Co,Cu,Mo,Ni,Pb,Sb,W,Zn and other elements were processed using descriptive statistics,correlation analysis,factor analysis and other multivariate statistical analysis methods to determine the distribution characteristics and elemental combination patterns of each element,and the geochemical maps of each element were drawn.4.In order to eliminate the differences in geochemical element distribution caused by different geological backgrounds,which led to the problem that high geochemical background values were misclassified as anomalies while low background values were ignored.The multiple fractal(S-A fractal)method is used for geochemical anomaly circling.By comparing with the traditional method of anomaly circling,the S-A fractal method can suppress the high background values and extract the weak geochemcal anomalies.The area of geochemical anomalies traced by this method is smaller,the concentration centers are more concentrated,and the traced geochemical anomalies are better overlapped with the mineral occurrences,which can more effectively reduce the extent of non-mineral-induced anomalies.This study also uses the S-A fractal method to circle the combined elemental anomalies determined by factor analysis.5.Based on the MORPAS system,the target area is circled using the weights-ofevidence method for the study area.Through the comprehensive study of regional geological,geophysical and geochemical mineral control elements and the quantitative analysis of the relationship between each mineral control element and the spatial distribution of mineral resources,eight evidence factors,including favorable stratigraphy,stratigraphic combination entropy,magnetic anomaly,F1 anomaly,number of bars,average orientation,equal density and superiority,were selected as the geological variables for this prediction,and 5 A-grade targets,6 B-grade targets and 14 C-grade targets were circled.Most of the occurrences in the area fall within the target areas,which indicates that the prediction is highly accurate and can provide a certain basis for guiding the mineral search work.