Abstract:
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) SiO
2,Fe
2O
3 and Al
2O
3 are dominated chemical components for all samples, the average content of SiO
2 is lower than that of UCC, those of Fe
2O
3 and Al
2O
3 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, SiO
2/Al
2O
3, and SiO
2/R
2O
3. 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) SiO
2/Al
2O
3 and SiO
2/R
2O
3 indicate the trend of chemical weathering of TX-section:the degree of weathering increasing down-section, and being further confirmed by TiO
2-Al
2O
3,TiO
2-Fe
2O
3,TiO
2-SiO
2, and Al
2O
3-K
2O 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
τj,w coefficient also responded to the trend of weathering weakening upward.