DOI: http://dx.doi.org/10.5027/andgeoV49n1-3387

El Escorial calcitic marbles (Cushamen Metamorphic Complex, Macizo Norpatagónico): 87Sr/86Sr isotopic characterization and age of sedimentation

Juan A. Murra, Edgardo G. Baldo, Sebastián O. Verdecchia, Carlos D. Ramacciotti, †Carmen Galindo

Abstract


The El Escorial marbles (Cushamen Metamorphic Complex) along with amphibolites form metamorphic septa within the permian granitoids of the Mamil Choique Formation (261-286 Ma). The metamorphism, determined in granulite facies migmatic gneisses septa cropping out 120 km southwest of El Escorial, occurs at 311±27 Ma (CHIME method in monazite). The marbles are calcitic (calcite >95%, R.I.: 0.5 to 2.5%) and show 87Sr/86Sr ratios between 0.70768 and 0.70825 (n=10). The data provided in this work, added to previous contributions, allow to constraints the sedimentation age of the silicic-carbonate successions of the Cushamen Metamorphic Complex between ca. 385 and 335 Ma. This suggests the existence of a mixed carbonate-siliciclastic platform at least in the southernmost portion of southwestern Gondwana between Middle Devonian and early Carboniferous (Middle Mississippian).

Keywords


Marble; Sr isotopes; Norpatagonian Massif; Southwest Gondwana

How to cite this article Murra, J.; Baldo, E.; Verdecchia, S.; Ramacciotti, C.; Galindo, †. 2022, El Escorial calcitic marbles (Cushamen Metamorphic Complex, Macizo Norpatagónico): 87Sr/86Sr isotopic characterization and age of sedimentation. Andean Geology 49 (1): 77-93. [doi:http://dx.doi.org/10.5027/andgeoV49n1-3387]