碳酸盐岩风化壳及喀斯特成土作用研究

Weathering Crust of Carbonate Rocks and Process of Karst Soil Formation

作者通过大量的野外剖面调查和室内系统分析测试工作，发现碳酸盐岩风化壳具有独特的剖面结构特征；在风化壳剖面中，发现宏观上保留着其下母岩残留结构和构造。微观上见到碳酸盐矿物被溶蚀一交代现象。据此，作者提出喀斯特成土作用学说，认为风化壳的特定结构和粘土层是地下水溶蚀一交代可溶岩作用的结果和产物，地下水是碳酸盐可溶性矿物的溶出和新的粘土矿物组分携人的载体。

Weathering crust on carbonate rocks means the one that was formed from limestones and dolomites and their transitional rocks. It is mainly composed of red clay and has a widespread distribution in tropical and subtropical areas around the world. This type of weathering crust, with thickness of 7 to 8 meters and the maximum, up to 20 is common both in Guizhou and other areas of South China. It is obvious that it has a great influence on agriculture, envirnment, and engineering, especially in Guizhou province, but no attention has been paid to it for a long time. Most of geoscientists speculate that the weathering crust may have been formed of residual unsoluable materials in carbonate rocks during karstification. If so, however, dissolution of carbonate rocks tens of meters in thickness is necessary to form a meter of weatering crust. In fact, it is not truth. For this reason,the authors carried out a special study on it, firstly by the detailed investigation of various laterite profiles in places, then by systematical division and sampling of the representative laterite profile selected out. The works done include chemical bulk-analysis, analyses for rare and rare earth elements, infrared absorption spectroscope,differential thermal analysis, X-ray diffraction analysis and X-ray energy spectroscope,pretrographic microscope,and scanning electron microscope and transmission electron microscope. This study reveals the vertical variations of laterite profile extending deeply down to bedrocks in mineral constituent, chemical composition, RE and REE contents,texture and structure.The theories and views on the origin of weathering crust have been successively discussed and illustrated in the eight concerning papers published in the recent years. The authors found that weathering crust was vertically characterized by a specific structure of carbonate bed rock through solubleleaching layer upward to laterite, within which the original textures and structures of the carbonate rocks such as bedding and lamination are residually kept on the whole, and the disolution and replacement of carbonate minerals by clay minerals were observed in microscope, e. g. SEM. So,the theory of karst soil formation is proposed here that the specific structure of the werthering crust is attributed to the bed rock disolution and replacement of soluble materials in carbonate rocks by underground-Water,this causes the isometric conversion of to laterite,and the underground water plays a role of carrying agent removing soluble materials of carbonate rocks and introducing components into neogenic clay minerals during karst soil formation.