不整合研究中的化学风化指标

APPLICATION OF CHEMICAL WEATHERING INDICES IN THE STUDY ON UNCONFORMITY

通过研究不整合结构发现,不整合面下风化岩石同风化壳一样在元素含量上具有富Fe、Al、Ti,贫Ca、Mg、Na的变化规律,因此用于研究风化壳的化学风化指标(IWP、V、ICA、ICW、IPA等),同样适用于研究不整合面下风化岩石。由于母岩成分的差异,风化指标的适用性和界限值不同,V、ICA、ICW、IPA指标可用于碳酸盐岩不整合结构划分,其中风化粘土层其他:ICA>90,ICW>95,V>10,IPA>95,半风化岩石:ICA介于50～90,ICW介于50～95,V介于1～10,IPA介于50～95;V、ICW指标也可用于碎屑岩不整合结构划分,风化粘土层其他:V>5,ICW>90,半风化岩石:V介于1～5,ICW介于50～90。利用化学风化指标可以定量地进行不整合结构划分,提高了不整合结构研究的精度。

According to the studies on unconformity structures,it can be concluded that the rocks in unconformity structural layer are rich in Fe,Al and Ti while poor in Ca,Mg and Na,so the chemical weathering indices(IWP、V、ICA、ICW、IPA,etc.) that can be used to study the weathering crust is also applicable in unconformity structure.Because the applicability and the threshold value of the indices change as the elements of mother rocks,the V,ICA,ICW,IPA is suitable for carbonate rocks in weathered clay rocks,ICA>90,ICW>95,V>10,IPA>95,in semi-weathered rocks,ICA=50～90,ICW=50～95,V=1～10,IPA=50～95),and the V,ICW is suitable for clastic rock(semi-weathered rock:V>5,ICW>90;semi-weathered rocks,V=1～5,ICW=50～95.The unconformity in the Jiyang depression is quantitatively classified with the chemical weathering index,which can further improve the accuracy of the structure research on the unconformity.