[Objective]Dolostones are widely developed in the mid-Permian rocks in eastern Yunnan and western Guizhou(China).A series of studies have previously been conducted on their genesis,and various formation mecha-nisms have been proposed.However,the source of Mg ions and the main controlling influences of the dolomitization process remain controversial.These problems severely hinder further exploration for oil and gas in the region.[Methods]This study analyzed in detail the regularity of the distribution of dolostone and its petrographic and geochemical characteristics,using outcrop and core observation as well as drilling data.[Results and Conclusions](1)The formation mechanism of dolostone in the study area is the open thermal convection dolomitization.Mg2+ in dolomitizing fluids originates mostly from seawater,with a minor component coming from deep hydrothermal fluids.(2)The dolomitizing fluid mainly migrates through pores in bioclastic grainstone and faults and fracture systems.Driven by spatial variations in temperature,the fluid migrates along the circulation flow pathways,resulting in fast and pervasive dolomitization of Middle Permian limestone.(3)The main controlling factors of dolostone development are shoal facies and Emei mantle plume(active area).
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