A multivariate model for mineral endowment.

Abstract

This study proposes a multivariate statistical model for mineral endowment and estimates the model parameters for epithermal precious metal deposits in the Walker Lake 1° x 2° quadrangle of Nevada and California. The multiple regression model developed in this study is utilized to describe mineral endowment as a function of quantified geology. Geology and mineral endowment are quantified on consistent geological areas or intrinsic samples, which represent a homogenous multivariate population whose members are statistically independent. A new, geologically-defined mineral endowment descriptor, volume of mineralized rock (VMR), is proposed, which is defined as the total volume of rock exhibiting anomalous concentrations of metallic and non-metallic minerals occurring within a particular type of mineral deposit present above a specified maximum depth in the crust of a region. The proposed model incorporates an externally-defined measure of mineral exploration completeness in an exploration model to mitigate problems of information completeness inherent in regression models applied under the principle of analogy. The geodata variables employed as dependent variables in the regression model include primary geodata and synthesized information variables representing lithology, geochemistry, geological structure, and geophysics. A variable representing alteration mineralogy is developed using remote sensing satellite data. A radiometric correction is applied to Thematic Mapper (TM) data, and image processing techniques are employed to construct color ratio composite images, which are input into a maximum likelihood classifier to produce a map of mineral alteration. A regression model having a linear form is estimated for epithermal precious metal deposits in the Walker Lake 1° x 2° quadrangle and employed to predict volumes of mineralized rock. These estimates are useful for mineral exploration and mineral resource assessment. The model predictions in the study area indicate that the best exploration potential for deposits of the epithermal environment in the Walker Lake 1° x 2° quadrangle is in the south-central and southeast portions of the quadrangle. For resource assessment, the estimated volumes of mineralized rock, as descriptions of the physical entities of mineralization, provide inputs to an approach which would model the economics and technology necessary to transform this mineralization into mineral resources.