Abstract:

The Ordovician gypsums in Linfen,Shanxi Province,can be divided into four types,namely autochthonous precipited,allochthonous deposited,diagenetic replaced and veinfilledtypes.Theautochthonousgypsum includinglaminated gypsum,banded gypsum and massive gypsum,which were formed by chemical precipitation in saline water depressions of shallow platform.The diagenetic replaced gypsum contains stromatolitic gypsum,oolitic gypsum and nodular gypsum which were formed in the uplift of the shallow platform and occurred in vadose zone during the penecontemporaneous stage.The allochthonous de-posited gypsum includes rudaceous gypsum and edgewise gypsum formed in places be-tween the depressions and the uplifts.The vein-filled gypsum was formed in transforma-tion process of gypsum and anhydrite related to abnormal high pressure resulted from de-hydration and the absorbing expansion.