THE ROLE OF TELOGENETIC INJECTION OF MAGMATICALLY DERIVED CO₂IN THE FORMATION OF DAWSONITE FROM THE CASTILLO FORMATION, CHUBUT GROUP, PATAGONIA, ARGENTINA

Abstract

We report the occurrence of dawsonite, NaAlCO 3 (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 δ 13 C PDB (-0.1 to 1.5‰) are consistent with a magmatic source of CO 2 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.

Dawsonite and ankerite formation in the LDX-1 structure, Yinggehai basin, South China sea: An analogy for carbon mineralization in subsurface sandstone aquifers

“…The formation of dawsonite from feldspar has been observed in numerous systems. For example, feldspars were observed to be altered to dawsonite in the Lam Formation of Shabwa basin Yemen (Worden, 2006), in the reservoirs of the Castillo structure of the Golfo San Jorge basin (Comerio et al, 2014), and in the Songliao basin, the Hailaer basin, and the East Sea basin in China (Gao et al, 2009;Liu et al, 2011;Zhao et al, 2018;Zhou et al, 2014). The reaction forming dawsonite from albite can be written (Bénézeth et al, 2007;Hellevang et al, 2005;Ryzhenko, 2006;Xi et al, 2016):…”