Известия Томского политехнического университета: Инжиниринг георесурсов (May 2022)
GEOELECTRIC ATTRIBUTES OF RECLAIMED POST-MINING PLACER GOLD DEPOSITS
Abstract
The relevance of the study is determined by the need to identify post-mining placers among the original and delineate untouched areas within the reclaimed landfills during prospecting and exploration for placer gold. The task of determining such boundaries in licensed areas arises when subsoil users, starting to develop a field, open up already washed loose deposits left over from predatory mining or unaccounted for production of previous years. The aim: to determine the specific geoelectric features of post-mining and unworked gold placers. Objects: alluvial post-mining placer gold deposits and in natural occurrence. Methods: electrotomography, numerical simulation, field experiment. Results. On the basis of literature data, a geological model of an alluvial placer in natural occurrence was compiled. It includes deposits of spits facies and coastal shallows with nested paleochannel and bedrock. The model of the reclaimed polygon is distinguished by the absence of boulder-pebble deposits of the paleochannel. On the basis of geological models, geoelectric models were compiled. The absence of a high-resistance inclusion in the model of the exhausted polygon is the main difference from the geoelectric model of the original placer. Numerical modeling of electrical tomography data showed that in the electrical resistivity sections, according to the results of 2-D inversion, a sign of a solid placer is the presence of a local high-resistivity anomaly from a paleochannel, and in the case of a reclaimed polygon, a layer in the upper part of the section, consistent in thickness and electrical resistivity. The established signs were revealed during field studies on alluvial placers in Siberia and the Far East. Geoelectric criteria for identifying original and post-mining placers are universal regardless of the study area and geological situation.
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