碳酸盐岩风化壳母岩的不均一性: 来自粒度分析的证据

Since the content of acidic insoluble matter of carbonate rock very low, the volume of weathering crust is hugely reduced in comparison with the basement carbonate rock and to form one-meter deep weathering crust needs to consume more than deca meter to n×10 meters deep basement carbonate rock, so the identification of the homogeneity of the basement carbonate rock is necessary and is the basis of the research on weathering crust concerning thick red weathering crust as well as weathering crust in karst areas. This paper discusses the grain size distribution characteristics of three typical residual weathering crusts from the Huaxi, Huchao and Xinpu profiles in the karst area of Guizhou. The result shows that the Inhomogeneity of the basement carbonate rock is objective reality. The grain size distribution feature of these profiles well indicates the inhomogeneity of the basement carbonate rock. The geochemical behaviour of the weathering crust derived from the inhomogenous basement carbonate rock will certainly deviates from the common evolving direction of the weathering crust developed on the homogenous basement carbonate rock. In addition, the inertia element ratios, such as Ti/Zr, Ti/Al, Sm/Nd, Zr/Hf, Nb/Ta, Th/Sc, Zr/Nb and so on, often using for tracing material origin in the supergene zone, may not be suitable for indicating the basement carbonate rock of weathering crust. These ratios greatly vary from bedrock to weathering crust or cannot apparently differentiate the discrepancy from the weathering crust of different bedrocks, this perhaps bear a relation to special weathering process of carbonate rock.