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Vertical distribution of elements in regolith over mineral deposits and implications for mapping geochemical weak anomalies in covered areas

Cheng Qiuming
Vertical distribution of elements in regolith over mineral deposits and implications for mapping geochemical weak anomalies in covered areas
Geochemistry - Exploration, Environment, Analysis (February 2014) 14 (3): 277-289

Abstract

Several case studies are presented to demonstrate that significant migration of elements in regolith over mineral deposits can reach the earth surface through thick layers of superimposed regolith. Data obtained from drill-holes in Mo-W and Mo-Ag mineral deposits in Eastern Inner Mongolia, China using portable X-ray fluorescence (pXRF, Niton XL3t 950) and data from other areas reported in the literature have been modeled using power-law decay functions that describe the regolith decay trends with increasing distance from the underlying altered rocks or saprocks. The results demonstrate that the element concentration in the surface media can be very low due to decay and mask effects, even if a thin layer of overburden exists. In order to characterize the decay behaviour of geochemical concentration of an element in a vertical regolith profile caused by complex mechanisms, a new non-linear differential equation was proposed which assumes the decay rate of concentration is negatively proportional to the concentration itself, with a functional coefficient dependent on vertical distance from the underlying surface of mineralised rocks. Applying Taylor series expansion to the coefficient function, the differential equation can be approximated by four simple dynamic systems, each with explicit solutions including Gaussian functions, exponential functions, power-law functions and exponential functions with inverse distance. These functions can be utilized as either separate or combined models to fit observed data by means of simple linear regression or multivariate regression. The combined mode is useful for evaluating the comprehensive effect of element concentration distribution due to various mechanisms.


ISSN: 1467-7873
EISSN: 2041-4943
Serial Title: Geochemistry - Exploration, Environment, Analysis
Serial Volume: 14
Serial Issue: 3
Title: Vertical distribution of elements in regolith over mineral deposits and implications for mapping geochemical weak anomalies in covered areas
Author(s): Cheng Qiuming
Affiliation: China University of Geosciences, Beijing, China
Pages: 277-289
Published: 20140204
Text Language: English
Publisher: Geological Society Publishing House, London, United Kingdom
Number of pages: unpaginated
References: 63
Accession Number: 2014-019766
Categories: General geochemistryEconomic geology, geology of ore deposits
Document Type: Serial
Bibliographic Level: Analytic
Illustration Description: illus. incl. geol. sketch maps
N37°40'00" - N53°30'00", E98°00'00" - E126°00'00"
Country of Publication: United Kingdom
Secondary Affiliation: GeoRef, Copyright 2019, American Geosciences Institute. Reference includes data from GeoScienceWorld, Alexandria, VA, United States. Reference includes data from The Geological Society, London, London, United Kingdom
Update Code: 201413
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