“巫山黄土”元素地球化学特征及成因和物源意义

Elemental Compositions of the "Wushan Loess" : Implications for Origin and Sediment Source

为了探讨"巫山黄土"的成因及物源,对剖面73个样品进行了常量元素测试和分析,并与已知典型的黄土剖面的元素地球化学特征进行了比较.结果表明:(1)"巫山黄土"主要化学成分以SiO2、Al2O3和TFe2O3(TFe2O3=Fe2O3+FeO)为主,三者的平均含量之和为84.84%,与上部陆壳(UCC)(86.2%)、洛川黄土(85.34%)、镇江下蜀土(86.76%)均非常接近。(2)"巫山黄土"常量元素质量百分含量与洛川、甘孜黄土和西风红黏土的均比较接近,显示了具有相同或相近的沉积环境和类型。(3)"巫山黄土"的TiO2/Al2O3—K2O/Al2O3的数据点主要分布区域与镇江下蜀土与川西的甘孜黄土大致相同,经UCC标准化后的"巫山黄土"分布曲线与其它风成黄土也显示了较好的相似性,从而说明"巫山黄土"具有风积成因的特点。(4)元素比值分析显示"巫山黄土"与甘孜黄土、洛川黄土均十分相近,在Mg/Mn、Al/Mg、Fe/K方面与甘孜黄土更为接近,而在Mg/Ca、Si/Al方面与洛川黄土更为一致,可能与两处黄土同源。

73 samples from the typical section of the ＂Wushan Loess＂ were analyzed for elemental compositions in or- der to obtain information about its origin and sediment source. Elemental analysis show that the major elements of the ＂Wushan Loess＂ contain SiO2, Al2O3 and TFe2O3（Fe2O3＋FeO） , average concentration of those is 84.8%. It is simi- lar as the UCC （86.2%）, Luoehuan Loess （85.34%） and Zhenjiang Xiashu Loess （86.76%）. Elemental composi- tions of the ＂Wushan Loess＂ were similar as the Luochuan lmess, Ganzi lmess and Xifeng Red Clay, indicating the similar sediment environment. TiO2/Al2O3 vs.K2O/Al2O3 diagram shows that the ＂Wushan Loess＂ and the Ganzi Lo- ess had almost the same elemental compositions. Besides the UCC-normalized patterns were also similar, indicating the aeolian origin. Elemental ratios show that the ＂Wushan Loess＂ were derived from multi-provenances. Besides, the ＂Wushan Loess＂ were reworked by fluvial process.