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Differences of granitic weathering at the northern and southern feet of Dabie Mountains,Central China: Implication for tectonic and climatic environments |
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| Authors: | Haijin?Xu |
| Institution: | 1. Graduate School, China University of Geosciences, Wuhan 430074, China 2. Faculty of Earth Sciences, China University of Geosciences, Wuhan 430074, China 3. Department of Resource, Environment and Agricultural Chemistry, Huazhong Agricultural University, Wuhan 430070, China |
| Abstract: | Two weathering profiles of Yanshanian granites on the southern and northern feet of the Dabie Mountains were investigated. The results showed that, on the southern foot of the Dabie Mountains, the weathering profile of the Sikongshan biotite monzonitic granite was eroded with remarkable loss of alkila, calcium and silicon, and richness of aluminium during hydrolysis process and in acidic mediums. Feldspar and biotite, major rock-forming minerals, were altered to illite→(vermiculite→1.4 nm transition minerals) →kaolinite→halloysite. However, on the northern foot of the Dabie Mountains, the Hepeng biotite orthogranite weathering profile was stable, without silicon depletion, but with remarkably enriched iron and noncrystalline during oxidizing process and in feebly acidic-neutral mediums. The major rock-forming minerals such as feldspar and biotite in the Hepeng weathering profile were weathered to smectites and halloysite→noncrystalline. The above results reveal that weathering differences of the granites between southern and northern feet of the Dabie Mountains may be related to climatic environments and tectonic movements. The southern foot, in hot and rainy environments, was uplifted by tectonics and was intensively leached. The soils in the southern slope were under acidic conditions. In contrast, the northern foot was slightly leached in hot and droughty environments, and the soils were under feebly acidic-neutral conditions. |
| Keywords: | Dabie Mountains granite weathering process mineralogy geochemistry |
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