Diagenesis of Paleozoic playa-lake and ephemeral-stream deposits from the Pimenta Bueno Formation, Siluro–Devonian (?) of the Parecis Basin, central Brazil

摘要: Abstract The Parecis Basin is a large intracratonic rift located in central Brazil and filled with Paleozoic carbonate, evaporite siliciclastic sediments. occurrence of gas seeps has recently attracted significant exploration interest by the Brazilian petroleum agency Petrobras. continuously cored PB-01-RO well provided first opportunity to study depositional environments, diagenetic evolution hydrocarbon potential largely unknown sedimentary successions Basin. lithologies, belonging Siluro–Devonian (?) Pimenta Bueno Formation, are interpreted as deposited playa-lake ephemeral-stream environments. deposits display strong facies control on mineral assemblages evolution. Diagenetic minerals include eogenetic hematite smectitic clay coats quartz cement, mesogenetic process includes precipitation sulfates (anhydrite barite) carbonates (calcite, dolomite kutnahorite–ankerite–huntite), followed partial dissolution these sulfates, feldspar grains. Telogenetic processes kaolinite within secondary pores, replacement anhydrite gypsum. A second burial phase mesodiagenesis indicated discrete K-feldspar crystals moldic pores after dissolved feldspars, illitization etched, telogenetic kaolinite. show early dolomitization lime mud, nodules extensive silicification. were replaced gypsum chalcedony during telodiagenesis. Potential source rocks locally represented organic shales. fluvial sandstones fair reservoir quality limited compaction, their intergranular volume, suggesting that succession undergone moderate burial. seals for accumulations evaporites mudstones. presence an active system basin, seeps, suggests good Basin, stresses importance studying its successions.