Spatial patterns of geochemical elements measured on rock surfaces by portable X-ray fluorescence: application to hand specimens and rock outcrops

Abstract

Spatial distribution of geochemical elements at hand-specimen and outcrop scale provides significant evidence for the processes of formation and alteration of rocks. Portable X-ray fluorescence (pXRF) analyses is a non-destructive and cost-effective methodology to rapidly measure multi-elemental concentrations in-situ , and its application makes the study of the distribution of geochemical elements efficient. In this paper two pXRF instruments, the Tianrui EDX-P730S and the Niton XL3t 950, were employed for measuring geochemical data for two samples of Pb and Zn ore hand specimens and at outcrop scale in an area of skarn formation. The data are processed by GIS and principal component analysis (PCA) for interpreting element associations involved in mineralization processes. The first three principal components obtained by PCA for the data measured on the rock surface of the two hand specimens may represent early stage Zn-dominated mineralization, superimposed Zn and Pb mineralization and late stage Pb-dominated mineralization. These three zones of mineralization can be delineated by the scores of multiple elements on the first three principal components. The first four principal components obtained from the outcrop surface data were found to be related to the marble, diorite, and two stages of skarn-type mineralization (Cu and Zn mineralization and Pb, Zn and Fe mineralization).