Weathering Mechanism of Rock-Soil Interface in Weathering Profile Derived from Carbonate Rocks: Preliminary Study of Leaching Simulation in Rock Powder Layer
详细信息
- 责任者：Feng Zhigang (School of Nuclear Resource and Nuclear Fuel Engineering ; University of South China ; Hengyang 421001 ; China) ; Ma Qiang
- 刊名：Acta Geologica Sinica
- 出版年：2012
- 卷期：87(1)
- 关键词：碳酸盐岩 ; carbonate rocks ; 风化作用 ; weathering
- 页码：p.119-132
- 图表：illus., 2 tables, 60 refs.
- 分类号：0803
- issnNo：ISSN0001-5717
- isbnNo：CN11-1951/P
摘要
The feature that rock-soil interface shows distinct change on weathering profiles of carbonate rocks is an obstacle to exploring weathering mechanism of carbonate rocks by directly using the development characteristics of field geological cross-sections.This study selected rock-soil interfaces from four typical in-situ weathering profiles of carbonate rocks in central Guizhou Province and western Hunan Province,China as an example.Under the temperature of 24～29.5℃,leaching trial experiment was carried out on the samples column from each profile by simulating dry-hot weathering condition,i.e.warm or hot weather and well-drained weathering state,and using water saturated with CO2,with leaching end marked by complete dissolution of carbonate.Dynamic analyses on major rock-forming elements from leachate and leaching residues reveal the weathering mechanism of rock-soil interface in weathering profiles of carbonate rocks.The research result is as follows.① During weathering of rock-soil interface in carbonate rocks,carbonate dissolution is synchronous with decomposition of acid-insoluble material,and acid-insoluble fractions have shown a clear weathering tendency at the beginning of carbonate dissolution.② In a well-drained weathering environment,base cations and Si stemming from decomposition of acid-insoluble residues including silicates are more inclined to migrate with leaching solution,which makes it difficult to form authigenic clay minerals such as smectite,illite,kaolinite,etc.during weathering.Among other rock-forming elements in acid-insoluble phase,both Ti and Al are inert elements,Fe is weak migrated,and Mn and P show significant activity.③ During water-rock interaction process,due to the fact that carbonate is excessive to water-rock interaction,dissolution intensity of carbonate is mainly constrained by the texture of rock powder layer.Coarser grains lead to well penetrability,resulting in fast water-rock interaction and low dissolution of carbonate,and vice versa.However,for water-rock interaction,acid-insoluble fraction is inadequate throughout the leaching cycle,and its volume is a main factor constraining water-rock interaction intensity.