Artículos de revistas
A Neoproterozoic age for the chromitite and gabbro of the Tapo ultramafic Massif, Eastern Cordillera, Central Peru and its tectonic implications
Fecha
2011-12Registro en:
Tassinari, C. C. G.; Castroviejo, R.; Rodrigues, J. F.; Acosta, J., & Pereira, E. (2011) - A Neoproterozoic age for the chromitite and gabbro of the Tapo ultramafic Massif, Eastern Cordillera, Central Peru and its tectonic implications. Journal of South American Earth Sciences, 32(4), 429–437. Doi: 10.1016/j.jsames.2011.03.008
Journal of South American Earth Sciences
Journal of South American Earth Sciences, vol. 32, n° 4, 2011.
Autor
Tassinari, Colombo Celso Gaeta
Castroviejo Bolibar, Ricardo
Rodrigues, José Feliciano
Acosta Ale, Jorge Gilberto
Pereira, Eurico
Institución
Resumen
The ultramafic–mafic rocks of the Tapo Complex are exposed in the Eastern Cordillera of the Central Peruvian Andes. This complex is composed of serpentinised peridotites and metabasites with some podiform chromitite lenses and chromite disseminations and overlies the sandstones, conglomerates, and tuffs of the Carboniferous Ambo Group. The metagabbros and amphibolites show a tholeiitic affiliation and a flat REE spider diagram, with a slight LREE depletion and a positive Eu anomaly suggesting magmatic accumulation of plagioclase, in an ocean ridge or ocean island environment. Sm–Nd isotopic analyses were performed on chromite as well as on whole rock from the gabbro. All samples yielded an Sm–Nd isochrone age of 718 ± 47 Ma with an initial 143Nd/144Nd of 0.51213 ± 0.00005. The ¿Nd (718 Ma) values calculated for both chromite and gabbro are in close agreement, around 8.0, implying that they were formed at the same time from the same mantelic magma source. Furthermore a K–Ar age on amphibole of 448 ± 26 Ma was obtained, interpreted as the cooling age of a younger orogenic event. These rocks represent slices of oceanic crust (from a dismembered ophiolitic complex), metamorphosed and later overthrust on upper Palaeozoic continental formations.