Density/area power-law models for separating multi-scale anomalies of ore and toxic elements in stream sediments in Gejiu mineral district, Yunnan Province, China

Abstract

Abstract. This contribution introduces a fractal filtering technique newly developed on the basis of a spectral energy density vs. area power-law model in the context of multifractal theory. It can be used to map anisotropic singularities of geochemical landscapes created from geochemical concentration values in various surface media such as soils, stream sediments, tills and water. A geochemical landscape can be converted into a Fourier domain in which the spectral energy density is plotted against the area (in wave number units), and the relationship between the spectrum energy density (S) and the area (A) enclosed by the above-threshold spectrum energy density can be fitted by power-law models. Mixed geochemical landscape patterns can be fitted with different S-A power-law models in the frequency domain. Fractal filters can be defined according to these different S-A models and used to decompose the geochemical patterns into components with different self-similarities. The fractal filtering method was applied to a geochemical dataset from 7,349 stream sediment samples collected from Gejiu mineral district, which is famous for its word-class tin and copper production. Anomalies in three different scales were decomposed from total values of the trace elements As, Sn, Cu, Zn, Pb, and Cd. These anomalies generally correspond to various geological features and geological processes such as sedimentary rocks, intrusions, fault intersections and mineralization.

Identifying Geochemical Anomalies Associated with Gold Mineralization Using Factor Analysis and Spectrum–Area Multifractal Model in Laowan District, Qinling-Dabie Metallogenic Belt, Central China

“…According to the anisotropic scale characteristics in the frequency domain, the S-A multifractal model decomposes the spatial model into several components. After lots of practice, it has proved to be useful for breaking down complex geochemical patterns: e.g., [7,40,[79][80][81].…”

“…The second group of models considers not only frequency but also spatial distributions of data. Since Mandelbrot [34] first proposed the concept of fractals, fractal technology has been widely used in geosciences and has become a powerful tool for separating different geochemical populations: e.g., [23,[35][36][37][38][39][40][41][42][43][44][45][46][47]. Geochemical exploration data generally don't conform to a normal distribution, but rather a lognormal distribution [48], and the enrichment and distribution of trace elements are characterized by multifractals [49].…”

Identifying Hydrothermal Alterations Using Singularity Mapping of PCA Images Based on ASTER Data

“…The mineralized areas are outlined by boxes: (1) Kader, (2) Godekolvari, (3) Iju, (4) Serenu, (5) Chahfiroozeh, (6) Parkam and Meiduk, and (7) Abdar and other elements to identify local anomalies. Cheng et al [17] highlighted the anomalies of trace elements using a fractal method in three different scales. Shahriari et al [18] determined the threshold angles of Spectral Angle Mapper analysis with a fractal technique to map hydrothermal alterations.…”

Identifying gravity anomalies caused by granitic intrusions in Nanling mineral district, China: a multifractal perspective

“…Cheng and his colleagues proposed the singularity theory (Cheng et al 2010;Cheng 2012b) based on the C-A fractal model to quantify geo-anomalies according to the invariant properties between fractal measure and scale. A number of case studies have demonstrated that the singularity index is a powerful tool to identify geochemical anomalies, to process remote sensing information, and to analyze the spatial distribution of mineral deposits Cheng 2007;Wang, Zhao, and Cheng 2011;Zuo 2011).…”