THE ELEMENTAL TRANSPORT FEATURES OF RED EARTH FROM TX-SECTION AND ITS PALEO-CLIMATIC IMPLICATIONS

Red earth is an important carrier to record paleo-climatic and paleo-environmental evolution. The major element compositions from TX red earth section in Jinhua-Quzhou basin show that (1) SiO₂,Fe₂O₃ and Al₂O₃ are dominated chemical components for all samples, the average content of SiO₂ is lower than that of UCC, those of Fe₂O₃ and Al₂O₃ are both higher than that of UCC, and K, Na, Ca, Mg, and P are very low. So, TX-section has typical desilica-allitization features. (2) High CIA value and low Ba value both indicated stronger chemical weathering of TX-section, and its loss ignition(LOI) is linear related to CIA, Ba, SiO₂/Al₂O₃, and SiO₂/R₂O₃. To some degree, LOI may be regarded as an indicator for desilica-allitization of TX red earth. The higher LOI is, the stronger desilica-allitization. (3) SiO₂/Al₂O₃ and SiO₂/R₂O₃ indicate the trend of chemical weathering of TX-section:the degree of weathering increasing down-section, and being further confirmed by TiO₂-Al₂O₃,TiO₂-Fe₂O₃,TiO₂-SiO₂, and Al₂O₃-K₂O distributions, from which we can see that chemical weathering degree of plinthitic red earth was stronger than that of typical red earth. (4) Using Zr as calculation strain, mass-balance equations were applied to geochemical analyses to show that Si moves out and Fe and Al are enriched in the plinthitic red earth unit. The τ_j,w coefficient also responded to the trend of weathering weakening upward.