Genesis of Dolomite Reservoir in Ediacaran Chigbrak Formation of Tarim Basin, NW China: Evidence from U–Pb Dating, Isotope and Element Geochemistry

The Chigbrak Formation in the Upper Ediacaran is one of important exploration targets Tarim Basin, NW China. However, no significant discoveries have been made this field, and unclear reservoir genesis factors restricting breakthrough. This study examined outcrops Aksu area northwestern Basin by using systematic descriptions petrologic features Formation. Samples were selected for tests stable carbon oxygen isotopic compositions, strontium rare earth elements, LA–ICP–MS element mapping U–Pb dating. It was found that (1) mainly composed dolomitic microbialite, with average values δ13C (PDB), δ18O (PDB) 87Sr/86Sr 3.50‰, 2.95‰ 0.709457, has similar geochemical characteristics to coeval seawater. dolomites also characterized a medium degree cation ordering (avg. 0.68), low content ΣREEs 9.03 ppm) chondrite standardized curve REEs showing enrichment LREE depletion HREE. ages range from 538 618 Ma, corresponding age period. (2) Dolomitization occurred marine diagenetic environment during penecontemporaneous period, seawater as dolomitization fluid. (3) Vugs are dominant pore type Formation, they products dissolution meteoric water (4) main controlling lithofacies, controlled fourth– or fifth–order sequences tectonic movement, early dolomitization. research results great significance dolomite prediction Basin.