CONSTRAINTS OF THE SEDIMENTARY ENVIRONMENT AND PROVENANCE AREA ON THE MINERALOGY AND GEOCHEMISTRY OF CRETACEOUS NA-BENTONITES FROM THE NEUQUÉN BASIN (ARGENTINA)

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

Conferencia; International Joint Conference Clays Application & Valorisation Minerals & Materials Sciences; 2022

In the North Patagonian region of Argentina the Neuquén Basin is among the largest bentonite producing areas in the country. Especially relevant are the Cretaceous bentonites which are sodic and with excellent deposits in Lake Pellegrini (Allen Formation) and Justina área (Anacleto Formation) (Musso et al. 2022). This work compares the mineralogy and geochemistry of bentonite samples from the Lake Pellegrini and Justina deposits. The aim is to determine the possible influence of the sedimentary environment in which the bentonite originated and the role of the pyroclastic precursor component on dioctahedral smectite formation. For this purpose, 66 samples of bentonites and associated lithofacies have been studied mineralogically by XRD, FTIR and optical and electron microscopy. In a selection of 11 bentonites, chemical analysis of major and traceelements has been carried out. In the Justina deposit, three mineralogical associations have been differentiated, two of them linked to bentonites in which the predominance of sodium dioctahedral smectite is observed, but with variations in “crystallinity”. The third association is detrital, linked to sandstones and mudstones, and presents an irregular illite-smectite mixed layer with a Predominance of smectite. In the studied lithofacies, the presence of zeolites of the analcime type (up to 5%) stand out. In the Lake Pellegrini deposit, two associations can be distinguished in which sodium dioctahedral smectite predominates, with the best “crystallinity” in thetwo bentonite beds. Zeolites of the clinoptilolite-heulandite series have also been identified (