Isotopic characterization of Jurassic evaporites. Aconcagua-Neuquén Basin, Argentina

Gabriela Lo Forte, F. Ortí Cabo, L. Rosell

Abstract


Isotopic analysis can be used to interpret the origin of evaporitic sediments. A preliminary isotopic study of strontium, oxygen and sulphur has been carried out in Ca-sulphate facies of Jurassic marine evaporates (Tábanos Formation and Auquilco Formation) outcropping in southern Mendoza, Aconcagua-Neuquén Basin (Argentina), as a part of a comprehensive sedimentologic study. The analysed sections are located at arroyo Las Leñitas, Cañada Ancha and arroyo Blanco. Sampled units include laminated, banded, and nodular lithofacies, made up of anhydrite, secondary gypsum and calcite. The mineralogy was studied by conventional petrographic analysis and X-ray diffraction. The 87Sr/86Sr ratio was obtained in six samples, with values ranging from 0.706793 to 0.706839, which match marine calcium-sulphate data of the same age. A similar conclusion may be derived from ten samples analysed for oxygen (δ18O) and sulphur (δ34S) isotopic composition: the obtained values are between +11.55‰ and +14.42‰, and between +17.25‰ and +18.48‰ respectively. The sedimentologic- stratigraphic evidence and the isotopic data both suggest a marine origin for the Tábanos and Auquilco evaporites, without an analytically detectable contribution of continental waters or hydrothermal solutions. The results also suggest that no isotope fractionation occurred during the primary gypsum-to-anhydrite-to-secondary gypsum transformations.

Keywords


Marine evaporites; Isotopic composition; Jurassic; Aconcagua-Neuquén Basin; Argentina.

Full Text:

PDF


DOI: https://doi.org/10.1344/105.000001404

Refbacks

  • There are currently no refbacks.




Creative Commons License
This work is licensed under a Creative Commons Attribution-ShareAlike License.

                                                                                                            
            Facultat de Ciències de la Terra                       Geociències Barcelona                           Institut de Diagnosi Ambiental                    Universitat Autònoma de Barcelona           
                Universitat de Barcelona                                                                                          i Estudis de l'Aigua (CSIC) 
 
 
Geologica Acta (ISSN-1695-6133)
Biblioteca de Ciències de la Terra (UB-CSIC) | Facultat de Ciències de la Terra, Martí i Franquès s/n 08028 Barcelona | Spain
Phone: +34 93 403 19 89 | E-mail: geologica-acta@ictja.csic.es
RCUB RCUB Declaració ètica Avís Legal Centre de Recursos per a l'Aprenentatge i la Investigació Universitat de Barcelona