2021, 40(5): 835-848.
doi: 10.11932/karst20210510
Abstract:
The chemical weathering of carbonate rocks is the main form of interaction between the layers in the karst key zone. The weathering crust contains important information about the climate， environment and material circulation. Based on the study of the chemical weathering intensity and element migration characteristics of the karst weathering crust in Guilin， Guangxi， and the comparison of karst weathering crusts of Yunnan， Guizhou and Hunan and the Qinghai-Tibet Plateau， the following conclusions are drawn， （1） The average value of the crust Chemical Alteration Index（CIA）of limestone in Huixian， Guangxi is 92.14， equivalent to the karst weathering crust in Xingyi， Guizhou， which reflects the intense chemical weathering in the hot and humid climate. The CIA of the dolomite weathering crust is equivalent to that of the limestone weathering crust， and is mainly affected by the "insoluble matter"； in terms of topography——from uphill to downhill， from slope to valley， from shallow to deep section——the CIA value of the weathering crust of carbonate rock shows a decreasing trend； （2） The CIA value in southern China， including the Huixian weathering crust in Guangxi，is negatively correlated with latitude. The carbonate weathering crusts in the Qinghai-Tibet Plateau and northern areas are paleoweathering ones， and their CIA values are not correlated with latitude， which may be affected by the subduction and pushing of the Indian plate since the late Tertiary， the uplift of the Qinghai-Tibet Plateau and the deformation of the planation plane； （3） Unlike silicate weathering crust and loess profile， there is no correlation between CIA and Na/K （molar ratio） of carbonate weathering crust，but there is a significant negative correlation between CIA and K/Al （molar ratio）. K/Al can be used to characterize the weathering degree of carbonate profiles， which is mainly affected by the rapid leaching of soluble components. The Chinese carbonate weathering crust has completed the dissolution and leaching of soluble components， and is in the stage of potassium feldspar weathering and clay mineral generation. The weathering crusts of Huixian in Guangxi and Xingyi in Guizhou are closer to the Al end than other weathering crusts，and the degree of chemical weathering is higher； （4） The chemical composition of the Huixian carbonate weathering crust in Guangxi is basically the same as that of the carbonate weathering crust in other parts of China， and an even distribution can be seen on the profile. Compared with UCC， Na， K， Ca and Mg are depleted， but other elements are enriched. Compared with the stable element Ti of the underlying carbonate rock， except that Cr， Fe， P and Al are enriched or unchanged，other elements have undergone significant migration and leaching. The migration order of the elements in the weathering crust of Huixian is，Ca ˃ Mg ˃ B ˃ Na ˃ N ˃ Cd ˃ Zn ˃ As ˃ K ˃ Pb ˃ Si ˃ Mn ˃ Al ˃ Cr ˃ Fe ˃ P. The rapid dissolution loss of high content of Ca and Mg is of an important influence on the mobility of other elements.
WU Huaying,HUANG Chenhui,LI Tengfang,et al.Characteristics of element migration and influencing factors of lime soil in Guilin, Guangxi：A case study of lime soil in Huixian peak-cluster valley[J].Carsologica Sinica,2021,40(05):835-848.. doi: 10.11932/karst20210510.
