Abstract

This paper reports initial research on a quantitative methodology for the delineation of consistent geologic areas as exploration target areas or favorable resource areas for epithermal gold-silver deposits. Important features of the methodology include (1) the use of a genetic model to structure information and to guide the analyses of geodata; (2) the identification of recognition criteria for heat source, the critical genetic factor selected for epithermal gold-silver deposits; (3) the enhancement of geodata using sample and variable weighting in selected multivariate statistical analyses and using two-dimensional Fourier transformations, filtering, and coherency analysis in the frequency domain for selected data; (4) the use of a control area to develop relationships useful in synthesizing information variables from the basic geodata (geochemistry, hydrothermal alteration, magnetism, gravity, structure, and lithology) that capture jointness effects; (5) the optimum cutting of each information variable to yield anomalies; and (6) the resolution of multiple information anomalies to probability anomalies for heat source by a two-stage multivariate logistic analysis. The methodology is demonstrated on the Walker Lake quadrangle of Nevada and California, a region known to have gold-silver deposits. This demonstration produced a map showing the consistent geologic areas. Thirty-two of these consistent geologic areas were selected as exploration target areas for epithermal gold-silver deposits. One of these target areas, located at Windmill, is shown in greater detail, revealing its magnetic, gravitational, geochemical, and structural anomalies.

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