The role of Telogenetic Injection of Magmatically Derived CO2 in the formation of Dawsonite from the Castillo Formation, Chubut Group, Patagonia Argentina

We report the occurrence of dawsonite, NaAlCO3(OH)2, in volcaniclastic rocks of the Albian hydrocarbon reservoir Castillo Formation, Golfo San Jorge Basin, neighboring the Cañadón Asfalto Basin in Patagonia; this is the first known occurrence in Argentina. Dawsonite replaces crystals pseudomorphically, and can also be found as a cement together with other carbonates, which induced a loss in the porosity of the host rock. Previous studies reported incomplete chemical reactions which suggested that oligoclase and analcime were dawsonite precursors. In the present work we document either totally achieved or incomplete chemical reactions which led to the transformation of analcime into kaolinite and dawsonite into kaolinite, respectively. These facts allowed us to deduce that the transformation of analcime into kaolinite was via dawsonite, minerals formed during different stages under a telogenetic regime. Dawsonite values of δ13C PDB (−0.1 to 1.5‰) are consistent with a magmatic source of CO2 provided by hypabyssal, basic alkaline igneous rocks of regional importance starting in the Eocene. We identify both internal and external sources of Na and Al used in the formation of dawsonite.Fil: Comerio, Marcos. FCEN UBA, Instituto de Estudios Andinos “Don Pablo Groeber”; Argentina. Provincia de Buenos Aires. Gobernación. Comision de Invest.científicas. Centro de Tecnología de Recursos Minerales y Ceramica. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - la Plata. Centro de Tecnología de Recursos Minerales y Ceramica; ArgentinaFil: Morosi, Martin Eduardo. Provincia de Buenos Aires. Gobernación. Comision de Invest.científicas. Centro de Tecnología de Recursos Minerales y Ceramica. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - la Plata. Centro de Tecnología de Recursos Minerales y Ceramica; ArgentinaFil: Tunik, Maisa Andrea. Universidad Nacional de Río Negro. Sede Alto Valle. Instituto de Investigaciones en Paleobiología y Geología; ArgentinaFil: Paredes, José Matildo. Universidad Nacional de la Patagonia "San Juan Bosco". Facultad de Ciencias Naturales - Sede Comodoro. Departamento de Geología; ArgentinaFil: Zalba, Patricia Eugenia. Provincia de Buenos Aires. Gobernación. Comision de Invest.científicas. Centro de Tecnología de Recursos Minerales y Ceramica. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - la Plata. Centro de Tecnología de Recursos Minerales y Ceramica; Argentina. Monash University; Australi