关键词: 风尘, 玄武岩, 土壤, 化学风化, Nd同位素

Abstract: It is great significance to the identification and contribution of dust in pedogenesis，because the dust affect the global biogeochemical cycle. In this study, two typical weathering profiles (Meihua village, Mingguang County, Anhui Province and Baota village, Xuyi county, Jiangsu Province) and some surface and stream sediment samples were selected from the basaltic platform of Jiangsu Anhui Province. The main minerals, clay minerals, major and trace elements, Sr and Nd isotopic compositions of the samples were analyzed systematically. The results show that the basalt is mainly composed of plagioclase and pyroxene, and the weathered bedrock is mainly composed of montmorillonite, while the soil is characterized composed of dust minerals such as quartz and illite, which are not found in bedrock and weathered bedrock. The bedrock and weathered basalt are characterized by high Mg, low Si, K and no Eu anomaly, while the soil is characterized by high Si, K, low Mg and negative Eu anomaly. Relative to soil, the bedrock and weathered bedrock have a much higher εNd and much lower ⁸⁶Sr/⁸⁷Sr value. All mineral, element and isotope evidences show that the dust can serviced as important component of soil. Calculated by the Nd isotope mixing model, it can been foundthat the contribution of dust to the soil is more than 60%. The weathering of basalt is characterized by complete montmorillonization and significant removal of Ca and Mg. In Meihuacun section, Ce negative anomaly appears in the surface soil, while Ce positive anomaly appears in the lower layer. It is also found that the content of Si and K in the soil increases due to the accretion of wind dust. Affected by relatively large elevation difference, basalt weathering products and settled wind dust are easily eroded by precipitation, resulting in thinner weathering profile, which makes basalt weathering in “supply limited” mode. This work provides new geological evidence for the weathering mechanism of basalt and the role of wind dust in the element geochemical cycle.

Key words: dust, basalt, soil, chemical weathering, Nd isotope