Multi-parameter comprehensive identification of the genesis of Lower Paleozoic dolomite in Tarim Basin,China

Abstract

Massive dolomites are widely distributed in Lower Palaeozoic of Tarim Basin,northwest China.The genesis of these dolomites can be attributed to four dolomitization models,i.e.,sabkha model,seepage-reflux model,burial model and hydrothermal model.The sabkha dolomites occurred in an evaporitic intertidal-supertidal environment and featured the deposits of gypsum-bearing dolomicrites.The seepage-reflux dolomites occurred in an evaporite platform(lagoon) environment and featured crystal powder dolomites with the original rock structure.The burial dolomites were developed in multi-stage burial environment,characterized by the fine-medium crystalline dolomites.The hydrothermal dolomites featured medium-coarse crystalline dolomites,which were associated with hydrothermal minerals.The dolomites that differed in the genesis were developed in various diagenetic environments and stages,showing different characteristics in terms of petrography,geochemistry and geophysical response.This study summarized the multi-parameter identification of four genesis models of Lower Palaeozoic dolomite in Tarim Basin based on the detailed study of massive cores,thin sections and geochemical data of major elements,carbon and oxygen isotopes,strontium isotopes and rare earth elements,in combination with comprehensive analysis of well logging,seismic response characteristics,paleogeography,paleoclimate and tectonic setting,etc.This methodology overcomes the multiple solutions of dolomite genesis by comprehensive analysis.