Mineralogy and paleoenvironment of associated litofacies to Lake Pellegrini Nabentonite deposit (Neuquén Basin, Argentina)

PETTINARI, GISELA; MUSSO, TELMA BELÉN; GALÁN, ANA BELÉN; POZO, MANUEL

Conferencia; International Conference of European Clay Groups Association; 2023

The Na-bentonites from the Lake Pellegrini deposit occur in the Upper Cretaceous AllenFormation in the Neuquén Basin (Argentina). The bentonites are associated with claystones,mudstones, siltstones and hetherolitic facies that have been previously interpreted asperimarine to continental. In this paper we study the textural features and composition of thefacies associated with the bentonites. The aim is to better understand the sedimentologicalcontext and consequently the conditions involved in the formation of the authigenic Nasmectite. The mineralogical study has been carried out by XRD and the description of thelithofacies by petrography from resin embedded thin sections.The siltstones are dominated by phyllosilicates (40-56%) with subordinate quartz andplagioclase (>10%) and traces of potassium feldspar and gypsum. The presence ofclinoptilolite-heulandite stands out, reaching 7%. Petrographically have been identified:muscovite, biotite, opaques, rutile, monazite, garnet, zircon and volcanic rock fragments. Theclay minerals can be microlaminated, acting as a cement enclosing the skeletal components.The mudstones/claystones are dominated by phyllosilicates (60-82%) with quartz (14-30%) andto a lesser extent (