Geological Verification of Nonlinear Behavior of Trace Element Migration in Vertical Regolith over Mineral Deposits

Abstract:

Ore element concentration in surface media such as soils, stream sediments, tills, and vegetation has been used by geochemical exploration for mineral resources assessment and mineral deposit prediction. The spatial variability of distribution of ore element caused by cascade mineralization processes can be modeled by multifractal modeling. The singularities observed in the element concentration geochemical maps can be used for delineating target areas for mineral exploration. In this paper we provide a detailed and comprehensive geological investigation of element concentration in regolith over mineralized rocks. Several drill cores from a Mo-W-Ag hydrothermal mineral deposit were selected to study the migration of elements in the regolith. Soils in the top section of these drill cores were systematically analyzed using pXRF on-site and other analytical devices in the lab. About 33 samples from the 10-m section of regolith were analyzed for multiple elements compositions, mineral and clay compositions, grain morphology, grain size distribution, and phase of element occurrence in the rock debris and clay of regolith. Various statistical distribution models have been applied to describe the distributions of the above analytical quantities. These include a two-peak grain size distribution of the regolith indicating multiples formation of the regolith such as deeply weathered rock debris and sands and transported clay sediments. Power-law distributions are observed in vertical concentration distribution of some ore elements in the regolith. Ore element Mo is mainly concentrated on the surface of the fine grain clay but not in the grain of sand and rock debris which implies that the concentration of Mo might be due to element migration process from the altered rocks under the regolith.