Electrical characteristics of rocks and ores in Yadu Pb-Zn deposit,northwest Guizhou Province and practices for deposit discovery by induced polarization
The research area is located in the central part of the northwest trending Yadu-Mangdong tectonic belt.Multiple sporadic Pb-Zn oxide,Pb-Zn sulfide,pyrite,and limonite deposits have been discovered in the Tongkuangshan,Haiba,and Meijiangchong ore sections within the area.Among them,the Haibei ore section has previously discovered a larger Pb-Zn oxide deposit through TEM method,and its mineralization conditions are similar to the giant Pb-Zn deposit in the nearby Zhugongtang area.Analysis shows that there is huge potential for deep exploration.However,due to limitations in terrain,signal interference,and the depth of current geophysical exploration method,the progress of exploration in the later stage is slow.This paper summarizes and analyzes the difficulties existing in the previous mineral exploration in this area.It systematically collects and measures the physical properties of rocks(ores)by combining the geological background characteristics of the exploration area,and finds that the sulfide ores in frequency 0.1-10 Hz band show high phase and high polarization anomalies,with large anomaly intensity,and the differences with the strata are highlighted,which can effectively suppress the interference anomalies brought by the strata;on this basis,we designed an IP exploration with long-cycle current sources and large pole distance,and introduced a parameter η/ρ to plot contour map for anomaly delineation,effectively suppressed the high-resistivity high-polarization anomalies,and discovered 13 low-resistivity high-polarization anomalies with different intensities,and verified the low-resistivity high-polarization anomalies in strip No.6 with forward and inverse pole-dipole sounding of the spread-spectrum induced polarization method,which showed that the high-polarization anomaly of the deep YC74-1 plate was obvious,and the anomaly was located in the dense high-and low-resistivity contact zone,and the intensity of polarization rate anomaly was high,with obvi-ous difference from the surrounding rocks,and it is assumed that the anomaly is caused by sulfide ore in the deep part.The drill holes verified the hidden sulfide ore body in the depth,the ore body is directly produced in the F0 fault fracture zone,and the surrounding rocks are limestone of Permian Qixia Formation to dolomitic graywacke of the Devonian Gaopaoba Formation,the true thickness of the ore body is 3.33-12.47 m,the average thickness is 7.65 m,the Ts is 17.32%-42.57%,and the average Ts is 28.54%,and the burial depth of the ore body is 310.50 m-472.18 m.There is fine vein-like lead-zinc sulfide ore at the drill hole depth of 692.38 m of ZK74-2,the true thickness ore body is 4.00 m.The practice of discovering ore bodies proves that,according to the electri-cal test results of the rock and ore samples,the reasonable design of the induced polarization method with different array combination for prospecting can have better effect of finding deposits in the exploration of sulfide ores in this area.
Yadusulfide iron depositlead-zinc depositspread-spectrum induced polarizationforward and inverse pole-dipole
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