Abstract:

The Permian System in Sichuan basin is composed of shallow water carbonate rocks deposited on a platform in a warm and humid climate with very flourishing biota.Dolomitization occurred under the following circumstances:(1)replcement by large coarse-grained dolomites along the fractures and pores;(2)replacement by small rhombohedral dolomites along the suture lines and(3)replacement by large coarse-grained dolomites of fresh-saline water origin.The last mentioned dolomites predominate the other two,with the ancient carbonate rock upland of biolith origin in neighboring provinces playing the controlling role.