Comparison of datasets obtained by global-scale geochemical sampling in Australia, China and Europe

Catchment/floodplain sediment geochemical datasets from three continental-scale geochemical projects in Australia (AU), China (CH) and Europe (EU) were studied by comparing sample media, sample preparation, elements determined, analytical methods, detection limits and proportions of reportable values, and certified reference materials used. Twenty six elements (Ba, Ce, Co, Cr, Cu, Mo, Nb, Ni, Pb, Rb, Sr, Th, V, Y, Zn, Zr, Al2O3, CaO, K2O, MgO, MnO, Na2O, P2O5, SiO2, Fe2O3 (total), TiO2) were considered comparable among the 35 determined by all three projects, according to the criteria for global comparability of elements proposed in this paper. The median concentrations of all elements (except Co, Y, Zr, SiO2 and TiO2) in the three datasets increase in the following order: AU < EU <= CH, and the median CH/EU ratios for all elements range from 0.98 to 1.94, while the median CH/AU and EU/AU ratios for elements, such as CaO, Na2O, MgO and Zn are generally greater than 2 (and up to 7), which could be explained partly by protracted weathering in Australia, and partly by the smaller grain size fraction analysed of the CH dataset (<1 mm) compared to AU and EU (<2 mm). In conclusion, a unified sample medium should be collected and unified sample preparation techniques should be followed. Key elements related to mineral resources and the environment should be determined and international or exchanged internal standard materials inserted in new national or global geochemical mapping projects in order to generate globally comparable datasets for establishing global geochemical baselines. (C) 2013 Elsevier B.V. All rights reserved.