The Cuyano proto-ocean between the Chilenia and Cuyania terranes: Rifting and plume interaction during the Neoproterozoic-early Paleozoic evolution of the SW Gondwana margin

BOEDO, F.L.; ALVARADO, P.; ARIZA, J.P.; KAY, S.M.; PEREZ, S.B.; VUJOVICH, G.I.

GEOLOGICAL MAGAZINE

CAMBRIDGE UNIV PRESS

Lugar: Cambridge; Año: 2021

0016-7568

The Precordillera Mafic-Ultramafic Belt (PMUB), located in central-western Argentina, comprises mafic and ultramafic bodies interlayered or in tectonic contact with marine siliciclastic rocks. Nd-Sr isotope, whole-rock and mineral geochemical data performed in magmatic units suggest a relatively different spatial and temporal evolution through the belt. The southern PMUB (south of 32°S) evolved as an intra-continental rifted margin with E-MORB-like tholeiitic to alkaline magmatism, to a proto-narrow ocean basin (Cuyano proto-ocean), and tholeiitic N-MORB geochemical signature. The magmatism is this region spread out from the Neoproterozoic to the Early Paleozoic. The northern PMUB (28-32°S) instead evolved as an intra-continental rifted margin with dominant tholeiitic E-MORB-like magmatism during the Early Paleozoic. REE trends and HFSE systematics in conjunction with estimated potential mantle temperature of ~50-100°C over ambient mantle suggest the presence of a mantle plume in the production of the PMUB magmatism. We proposed that the magmatism in the southern PMUB was linked with the opening episode of the Iapetus Ocean due to a rising mantle plume. In this context, the Neoproterozoic Catoctin Formation and the Southern Oklahoma Aulacogen in the conjugated Laurentian margin seems to be not only contemporaneous but also share a similar plume-enriched mantle source. The crustal thinning and magmatism in northern PMUB could have been more like related to the effect of a tensional field due to a subduction margin in western Gondwana. In both cases, the E-MORB geochemical signature identified along the whole extension of the PMUB could be more like described as a plume-distal ridge tectonic setting. The closure of the Cuyano proto-ocean and the collision of the Chilenia terrane against Cuyania terrane took place at 390-365 Ma, without any trusty evidence of arc-type magmatic activity in the northern section of the PMUB.