Application of comprehensive prospecting method in deep covered area: taking the Dazhang skarn type magnetic-rich deposit in Western Shandong as an example

Deep prospecting is an important direction for mineral resources exploration in the future in China. However, it is difficult to prospect in deep covered areas. How to explore and accurately locate ore bodies in deep covered areas is a key challenge that needs to be overcome in prospecting work. This paper takes the Dazhang skarn type magnetic-rich deposit in Western Shandong Province as an example, and summarizes a comprehensive prospecting method for iron ore in deep covered areas. Firstly, through the results of regional area gravity and magnetic surveys and secondary development and utilization, the fault structure is inferred, local anomalies are delineated, and the exploration and selection areas are completed; secondly, high-precision gravity and magnetic scanning is carried out in the exploration area to narrow the planar distribution range of the target body and delineate the prospecting target area; finally, re-conduct large-scale comprehensive geophysical prospecting combined with gravity, magnetic and electrical surveys on the prospecting target area, dissect and qualitatively analyze local anomalies, and locate favorable occurrence spaces for target bodies. Through drilling and deep verification, four of the five drill holes in the target area delineated shows mineral deposits, and one showed mineralization. The exploration process of “systematically collecting data-redeveloping and utilizing regional geophysical data-high-precision area gravity and magnetic surveys-comprehensive geophysical profile surveys-deep verification of anomalies in key areas through drilling” and the comprehensive prospecting method of “ground-magnetic-gravity-electric-drilling-survey” have achieved significant results that discovered the magnetite-rich body with an average grade of total iron of 55.59%, of which the magnetic iron grade is 52.25%. The comprehensive prospecting method has been hoped can provide a reference for deep prospecting of skarn type iron ore deposits in similar deep and thick covered areas.