4th International Conference of Palaeogeography

260 / 2019-06-30 23:47:27

Characteristics and genetic mechanism of the dolomite in the Middle Permian Maokou Formation, southeast Sichuan Basin

Maokou Formation; southeast Sichuan Basin; genetic mechanism; geochemical characteristics

The dolomites in Maokou Formation, southeast Sichuan basin are mainly developed in the mid-upper Member 3 of Maokou Formation, which can be dividied ino fine-medium crystalline dolomite, coarse-grained dolostones and brecciaous dolomite according to petrological characteristics. As viewed from the contrast in geochemical characteristics between micritic limestone and other types of dolomite samples, saddle dolomite and matrix dolomite have higher 87Sr/86Sr ratios than primitive limestone, and obviously lower δ18O values than primitive limestone. The difference between the weak positive anomaly of Eu in dolomite and the limestone isotopes may be caused by the participation of high temperature geo-bydrotherm during the dolomitization process．The dolomitization of Maokou Formation is dominated by multiple factors as follows: (1)the limestone with grain beach facies possesses favorable porosity and permeability, and thus have a higher possibility of dolomitization than micritic limestone with beach interact sea and middle slope facies;(2) )the thermal effect of Emeishan large igneous province provides abnormally high paleo-geothermal context for dolomitization;(3)hydrotherm associated with magmatism are the major sources of Mg in dolomitization;(4)according to the seismic interpretation, the fault systems along the northeast offer rapid migration channels for dolomitization fluid.