陇东新近纪红粘土与第四纪黄土地球化学特征及其物源和风化指示意义

甘肃省平凉市灵台县邵寨镇剖面风尘堆积底界年龄大约为5.23 Ma B.P.,通过对该剖面新近纪红粘土与第四纪黄土-古土壤序列的常量元素、 微量元素、Nd同位素的测试,分析其在物源和风化方面的指示意义,发现新近纪红粘土与第四纪黄土具有相似的常量、 微量元素UCC标准化曲线和稀土元素球粒陨石标准化曲线,指示二者皆来自广阔的...

Geochemical characteristics of the Tertiary and Quaternary eolian deposits in eastern Gansu province: Implications for provenance and weathering intensity

An eolian deposit section named Shaozhai, which has been developed since the Tertiary in eastern Gansu province, was analyzed for major-trace elements and Sm-Nd isotopic compositions to explore the relationship for the provenance and weathering intensity between the Tertiary red clay and Quaternary loess. The magnetostratigraphy data indicates that the basal age of the typical eolian deposits is about 5.23 Ma B.P.. We observed both similarities and obvious differences in the Tertiary red clay and Quaternary loess. Specifically, the Tertiary red clay has similar UCC-normalized major-trace element abundances and chondrite-normalized rare earth element abundances as the Quaternary loess, demonstrating that dust materials making up these sediments likely have experienced similar and numerous recycling processes prior to deposition. The Tertiary red clay has relatively high abundances of MgO, Li, Cs, Bi and low abundances of Na₂O, La-Lu, Y. In comparison with the Quaternary loess, chemical weathering parameters such as Na₂O/Al₂O₃, CIA, combined with the A-CN-K diagram suggest that the Tertiary Red clay has experienced a stronger weathering intensity. There is not much difference in the TiO₂/Al₂O₃, SiO₂/Al₂O₃, SiO₂/TiO₂, Zr/Hf, Nb/Ta, Lu/Hf, Y/Ho, Th/Nb, Hf/Nb, total rare earth elements, differentiation degree between the light and heavy rare earth element, internal differentiation degree of the light rare earth element, abnormal degree of Ce and Eu, ε_Nd(0) of the Tertiary red clay and Quaternary loess, demonstrating a similar provenance for them. The finer grain size and stronger weathering of the Tertiary red clay may be responsible for the difference in major and trace element content for the Tertiary red clay and Quaternary loess.