IDEAN   23403
INSTITUTO DE ESTUDIOS ANDINOS "DON PABLO GROEBER"
Unidad Ejecutora - UE
congresos y reuniones científicas
Título:
Evolution of Middle to Late Miocene Arc-Related Magmatism Between 35° and 38°S, Southern Central Andes, Argentina
Autor/es:
LITVAK VANESA; SPAGNUOLO, M. G; FOLGUERA A.; RAMOS, V.A.
Lugar:
Foz do Iguaçu
Reunión:
Congreso; The Meeting of the Americas; 2010
Resumen:
Middle to Late mesosilicic volcanism is broadly distributed in a series of volcanic complexes along a NE trend in southern Central Andes (35°-38° S). Kay et al. (2006) pointed out that lavas from Middle Miocene age located in a back arc position show chemical signature that reflects a variable slab geometry that corresponds to a shallow subduction period that began at ~ 20 Ma. Volcanic units can be grouped in two stages according to their age and geochemical characteristics: the first includes lavas form 10 to 14 Ma (Nullo et al. 2002, Kay et al. 2006), of basaltic andesitic to dacitic composition which erupted in the backarc, and has relatively weak arc signatures (Kay et al. 2006). The second stage includes lavas from 8 to 3.5 Ma (Nullo et al. 2002, Kay et al. 2006), which shows an increase of typical arc-related chemical signature that evidences a subducted slab component.New insights from Miocene Charilehue volcanic sequences, which are located in the south-westernmost area, and San Rafael block volcanism, that correspond to the north-easternmost outcrops of the region, show contrasting arc-related signature. Charilehue volcanics can be related to the first stage mentioned before showing an arc-related chemical signature weaker when compared to younger volcanism (Spagnuolo et al. 2009). On the contrary, San Rafael volcanism shows strong evidence of slab derived components and arc influence (Litvak et al. 2008). Moreover, younger San Rafael volcanics show an increase in pressure conditions of magma source given by its rare element signature when compared to the younger stage previously mentioned, reflecting a more evolved volcanic arc and an increase in crustal thickness due to tectonic shortening during subducted slab flattening.The contrasting spatial distribution, age and chemical signature of Charilehue and San Rafael block volcanism allow understanding the beginning of the slab influence, the real dimensions of arc-expansion, and the evolution of the shallow subduction in southern Central Andes at 35°-38°S.