A first national nickel petrogeochemical map of China: Methodology and implications

Abstract

Large-scale petrogeochemical maps are invaluable tools in Earth system science and applied geochemistry. Their creation often requires extensive sampling and careful consideration of how representative a sample's composition is of local chemistry, making them relatively rare. By integrating geochemical data from 39951 rock samples and employing advanced mapping techniques, this study presents the first petrogeochemical map of nickel across China. Sampling across China provides novel insights into spatial variability at large scales and geological controls of nickel within exposed crust. A close relationship between nickel concentration and lithology is observed. Nickel concentration tends to be relatively low in regions dominated by granites, carbonates ($\mathrm{Ni}\lesssim$14.5 μg/g), arenaceous, argillaceous, and intermediate rock ($\mathrm{Ni}\lesssim$34.8 μg/g), and highest in regions dominated by basic and ultrabasic rocks and their eroded products ($\mathrm{Ni}\gtrsim$34.8 μg/g). Concentrations of nickel measured in exposed crust and nearby sediments are highly correlated. Additionally, nickel concentrations are shown to vary systematically between tectonic units. For instance, large-scale geological processes such as continent collision, plume activity, and plate subduction, which generated widespread ophite belt sutures, basaltic igneous provinces, and granitic igneous provinces, have significant influence on nickel concentration. The mapping approach used in this study can be extended to incorporate other elements in future research.