古岩溶的形成条件及其特征

The Forming Conditions and Characteristics of Palaeokarst

岩溶是大气淡水溶解作用形成的自然构造．古岩溶是地质历史时间产生的岩溶．岩溶的形成需要两个基本条件：（１）相对于围岩来说，流体是未饱和的；（２）不饱和碳酸盐的流体能有效地将溶解产物搬运至远离反应的地方．在岩溶地区以潜水面为标准，把岩溶作用带分为渗流带和潜流带．岩溶的物质基础，碳酸盐岩建造主要形成于南北纬４０°之间的温暖的、清洁的、浅水海洋环境．不整合面，溶蚀孔洞缝，岩溶砾岩和岩溶角砾岩，岩溶地貌是古岩溶的宏观特征．岩溶地区碳酸盐岩的微量元素含量，碳氧稳定同位素值均表现淡水作用的特点．

Karst refers to the physical structures formed by the dissolution of meteoric waters. Palaokarst is a karst formed during geological history. Two conditions are necessary for forming the karst:the fluid must be unsaturated with respect to the country rock,and the fluid of unsaturated carbonate must be able to transport the products of dissolution far away from the site of reaction. In karst areas,karst system is divided into a vadose zone and a phreatic zone on the basis of water table. The material foundation of karst carbonate,mainly formed between 40 degrees north and south latitude. Disconformities,denudation pores,caves,fissures and fractures,karst breccias and conglomerates,and karst geomorphic features are macroscopic characteristics of karst.Both trace elements content of carbonate rocks and the isotopic value for the stabilization of oxygen and hydrogen in karst areas reflect the characteristics of meteoric water.