FAN Chun-xiao1, ZHANG Xiao-ke1, PAN Yu-guan2, CAI Yuan-feng2*
(1. School of Earth Sciences and Engineering, Nanjing University, Nanjing 210023, China;
2. State Key Laboratory of Mineral Deposits Research, Nanjing 210023, China)
Abstract: The brown soil profile of Shandong Province and red soil profile of Guangdong Province have been studied in this paper by using various techniques including X-ray diffraction (XRD), Diffused UV-Vis-NIR reflectance spectroscopy (DSR), and full-pattern fitting quantitative calculation based on Rietveld techniques in order to analyze mineral components of soils, the quantitative variation of distributions of minerals, and the interconversion relationship among clay minerals in profiles, and to reveal the constraint of climate on the forming mechanism of soils. Results show that: 1) Mineral compositions of soils in two profiles are different. The soils of the Shandong brown soil profile contain non-clay minerals, including feldspar, quartz, calcite, and minor iron-aluminum oxides and actinolite, and clay minerals of illite, chlorite, montmorillonite, and kaolinite, with their contents generally decreased in following order of illite> chlorite≈montmorillonite > kaolinite in Shandong profile. The soils of the Guangdong red soil profiles are composed of quartz, hematite, goethite, gibbsite, illite, vermiculite and kaolinite, with their contents decreased in following order of kaolinite > illite > vermiculite. In addition, soils of two profiles contain a little amorphous minerals. 2) Soils of the Shandong brown soil profile contain residual primary silicate minerals, such as actinolite, and calcite, which is easy to be dissolved , due to the weak chemical weathering but strong physical weathering resulted from the dry and cold climate. However, soils of the Guangdong red soil profile are rich in iron-aluminum oxides resulted from the significant desilication and aluminum enrichment due to the strong chemical weathering in hot and humid climate. 3) The weathering indexes calculated based on data using the Rietveld full-pattern fitting model are consistent with the changes of mineral contents in profiles.
Keywords: The Rietveld full-pattern fitting model; brown soil; red soil; climate; clay minerals
ACTA MINERALOGICA SINICA Vol. 40, No.1, 2020, page 16-24
