Petrographic, rare earth elements and isotope constraints on the dolomite origin of Ordovician Majiagou Formation (Jizhong Depression, North China)

Abstract Dolomites from the Ordovician Majiagou Formation are considered major hydrocarbon reservoir rocks in the Yangshuiwu area, Jizhong Depression. However, the origin of the dolomites remains unclear. This study utilizes the composite analysis of seawater-normalized rare earth elements (REEs), petrography and isotopes (C, O and Sr) to trace dolomitizing fluids and processes. Three types of dolomite are identified: planar-s to nonplanar microcrystalline (type D1) dolomite (