石灰土(碳酸盐岩风化壳)形成地球化学过程研究

以选自贵州遵义官坝、安顺天龙和贵阳龙洞堡三个剖面为例,运用ACNK和ACNKFM三角图解、元素对的协变特征及元素质量迁移系数,对石灰土形成的地球化学过程进行了详细讨论。结果显示:石灰土形成地球化学过程遵循碳酸盐岩风化成土之两阶段模式;官坝剖面的风化程度和过渡性具有碳酸盐岩风化成土初级阶段的特征,天龙和龙洞堡剖面与红色风化壳的基本特征相似,体现出所经历的风化作用过程或所处的阶段不同;龙洞堡剖面与天龙剖面的地球化学特征和演化过程存在一些不同,可能指示灰岩和白云岩风化壳的本质差异。

STUDY ON GEOCHEMICAL PROCESSES IN LIMESTONE SOIL PROFILES

In this paper, three typical limestone soil profiles, located at Guanba of Zunyi, Tianlong of Anshun and Longdongbao of Guiyang respectively, are taken for example. The geochemical processes in the profiles were described in detail based on Al_2O_3-CaO~*+Na_2O-K_2O (A-CN-K) and Al_2O_3- CaO~*+Na_2O+K_2O-Fe_2O_(3T)+MgO (A-CNK-FM) triangular diagrams, the ratios of elements including TiO_2/Al_2O_3, TiO_2/Al_2O_3, TiO_2/ SiO_2 and Al_2O_3/K_2O, and the mass transport coefficient. The results showed that chemical weathering of limestone soils can also be divided into two stages namely “leaching trend of carbonate rock-accumulating trend of insoluble residues” and “weathering trend of insoluble residues”. There is a big difference in degree of weathering and transition-layer between the Guanba and Tianlong, Longdongbao profiles, indicating the Guanba profile should be in a lower weathering stage, the other two are partly equal to the red clay crust; the geochemical processes in the Tianlong and Longdongbao profiles are different, which implies essential differences between limestone and dolomite weathering crusts.