Sr, C and O isotope composition of marbles from the Sierra de de Ancasti, Eastern Sierras Pampeanas, Argentina : age and constraints for the Neoproterozoic-Lower Paleozoic evolution of the proto-Gondwana margin
Murra, Juan Alberto (Universidad Nacional de Córdoba. Centro de Investigaciones en Ciencias de la Tierra)
Baldo, Edgardo G. A. (Universidad Nacional de Córdoba. Centro de Investigaciones en Ciencias de la Tierra)
Galindo, Carmen (Universidad Complutense de Madrid. Departamento de Petrología y Geoquímica)
Casquet Martín, Cesar (Universidad Complutense de Madrid. Departamento de Petrología y Geoquímica)
Pankhrust, Robert John (British Geological Survey)
Rapela, Carlos Washington (Universidad de La Plata. Centro de Investigaciones Geológicas)
Dahlquist, Juan Andrés (Universidad Nacional de Córdoba. Centro de Investigaciones en Ciencias de la Tierra)
Consejo Nacional de Investigaciones Científicas y Técnicas (Argentina)

Data:	2011
Resum:	The Sierra Brava Complex on the eastern flank of the Sierra de Ancasti consists of marbles, metabasites, calc-silicate rocks, psammo-pelitic schists and gneisses. In the central part of this sierra a thick succession of banded schists (Ancasti Formation) crops out. Regional metamorphism of these rocks is attributed to the Famatinian orogeny (Ordovician), metamorphic grade increasing westwards and southwards and culminating in a migmatite complex on the western side of the Sierra. The meta-carbonate rocks are subdivided into a northeastern group (low-grade calcite marbles), and a southeastern group (high-grade calcite and calcite-dolomite marbles). Twenty-three marble samples were analysed for Sr isotope composition and Rb, Mn, Mg and Ca contents, and six for C and O isotope composition. An Ediacaran depositional age of 570 -590Ma is inferred by reference to the trend of 87Sr/86Sr in Neoproterozoic seawater. Thus the metacarbonates are probably slightly older than the Ancasti Formation (equivalent to the Puncoviscana Formation of northern Argentina), which has a maximum sedimentation age of ca. 570Ma. Ediacaran depositional ages have also been reported for metacarbonates elsewhere in Argentina, Uruguay and Brazil. We propose that the Sierra de Ancasti carbonates on one hand, and those in the Western Sierras Pampeanas (Difunta Correa Sequence) and -tentativelythe Corumbá Group of Brazil on the other, represent platforms on opposite margins of the extinct Clymene Ocean, whereas Neoproterozoic carbonate successions such as the Loma Negra Formation (Tandilia, southern Argentina) and the Arroyo del Soldado Group (Uruguay) were deposited on the eastern side (present coordinates) of the Rio de la Plata craton, which at the time occupied a position farther to the north.
Drets:	Aquest document està subjecte a una llicència d'ús Creative Commons. Es permet la reproducció total o parcial, la distribució, la comunicació pública de l'obra i la creació d'obres derivades, fins i tot amb finalitats comercials, sempre i quan aquestes es distribueixin sota la mateixa llicència que regula l'obra original i es reconegui l'autoria de l'obra original.
Llengua:	Anglès
Document:	Article ; recerca ; Versió publicada
Matèria:	Isotope stratigraphy ; Neoproterozoic ; Gondwana ; Ancasti ; Sierras Pampeanas
Publicat a:	Geologica acta, Vol. 9, Núm. 1 (Març 2011) , p. 79-92, ISSN 1696-5728

Adreça alternativa: https://raco.cat/index.php/GeologicaActa/article/view/240543
Adreça alternativa: https://revistes.ub.edu/index.php/GEOACTA/article/view/105.000001645
DOI: 10.1344/105.000001645

14 p, 3.3 MB

El registre apareix a les col·leccions:
Articles > Articles publicats > Geologica acta
Articles > Articles de recerca