Test and application of the geochemical lithogene on weathering profiles developed over granitic and basaltic rocks in China

Abstract

Geochemical gene is a new technique presented recently and its property needs to be tested. Two weathering profiles developed over granitic and basaltic rocks were sampled and analyzed in Dunhua area in Northeast China with a cool temperate monsoon climate. Based on their major and trace elemental compositions, the geochemical lithogene numbered as LG01 was coded and samples' gene similarities were calculated relative to their parent rocks and top soils respectively. According to the similar gene criterion of ≥80% on gene similarity, the geochemical lithogene LG01 shows not only good heredity (on similar gene from parent rock to top soil) but also good inheritance (on similar gene from top soil to parent rock) in each weathering profile. That is to say, the geochemical lithogene LG01 illustrates good stability during weathering. According to the composition classification method based on the acidic similarity (a gene similarity relative to the acidic rock with the LG01 gene of 10202020202), the weathered products of the profile developed over granite are acidic-like composition (with acidic similarity of ≥80%) and those formed on basalt are basic-like composition (with acidic similarity of ≤20%). These indicate the validity of the composition classification method based on the geochemical lithogene LG01. In order to test the property and application of LG01 in a wider range, four newly reported weathering profiles (a granitic profile and a basaltic profile located in a warm temperate monsoon climate zone, another granitic profile in a subtropical monsoon climate zone, and another basaltic profile in a tropical monsoon climate zone) were also discussed. Their results verify the conclusion that the geochemical lithogene LG01 not only illustrates good stability among samples due to rock weathering but also is a potential tool on classification of rocks and their weathered products.