澧阳平原黑褐色土壤剖面常量元素地球化学特征

MAJOR-ELEMENTAL CHARACTERISTICS OF DARK BROWN SOIL IN LIYANG PLAIN,THE MIDDLE REACHES OF YANGTZE RIVER

对澧阳平原典型土壤剖面——玉成(YC)剖面进行常量元素地球化学分析,结果表明,YC剖面沉积物中SiO2,Al2O3和TFe2O3(包括Fe2O3和FeO)三者的含量总和达到80%—85%,其中SiO2的含量占60%—65%,Al2O3含量在12%—15%之间,而TFe2O3的含量占5.5%—7%;其它常量元素的含量相对较低,表现为K2O(2.5%—2.8%)>TiO2(1.2%—1.5%)>MgO(0.7%—1.2%)>CaO(0.5%—0.8%)>Na2O(0.4%—0.6%)>MnO(0.1%—0.5%)>P2O5(0.1%—0.15%).黑褐色土壤剖面CIA值(74.82)远高于上地壳(UCC)的平均值47.96,明显高于黄土高原黄土(63.73)和古土壤(67.36),略高于镇江下蜀黄土(70.45).表明黑褐色土壤剖面经历了比黄土高原黄土和古土壤更强烈的化学风化.CIA指数的垂向变化表明黑褐色土壤剖面经历了风化相对较弱、风化相对较强、风化相对较弱、风化相对较强4个阶段.

Based on the field investigation, sampling and major-elemental analysis at the YC profile in the Liyang plain, discussed the major-elemental geochemistry characteristics of dark brown soil, and revealed environmental significance. The results show that the content of major elements is mainly made of SiO2, Al2O3 and TFe2O3 The total content of SiO2, Al2O3 and TFe2O3 is more than 80%. among them, the content of SiO2 varies between 60% and 65%. The contents of other major elements indicate the sequence, in decreasing order, follows： SiO2 （60%--65%） 〉Al2O3 （ 12%-15% ） 〉 TFe2O3 （5.5%-7%） 〉 K2O（2. 5%-2. 8% ） 〉 TiO2（1.2%-1.5%） 〉 MGO（0.7%-1.2%） 〉 CAO（0.5%-0.8%） 〉Na2O（0.4%-0.6%） 〉 MnO （0. 1%-0.5% ） 〉 P2O5 （0. 1%-0. 15% ）. The CIA index of dark brown soil profile （74. 82） is much higher than it of UCC （47.96）, and higher than loess （63.73） and paleosol （ 67.36 ） in Loess Plateau. Those show the sediments have experimented more intensive weathering process than those in the loess and paleosol in Loess Plateau. The vertical change of CIA index indicates four stages of relatively stronger weathering, relatively weaker weathering, relatively stronger weathering and relatively weaker weathering.