CARBONIFEROUS RETRO-ARC, NW ARGENTINA: ASYMMETRICAL HOT LITHOSPHERE CONTROLLED BY A CRUSTAL DISCONTINUITY?

ALASINO, P.H.L; CASQUET , C.; PANKHUSRT, R.J.; RAPELA, C.W.; GALINDO, C.; DAHLQUIST, J.A.

Ávila

Simposio; Seventh Hutton Symposium on Granites and Related Rocks.; 2011

Universidad de Salamanca. Universidad de Granada. Escuela Politécnica Superior de Ávila.

Carboniferous magmatism in the western Gondwana margin (28°–32° S.) exhibits a compositional progression in space and time that is interpreted as reflecting different juxtaposed basement blocks. (1) Over more than 1000 km in the Eastern Sierras Pampeanas (ESP) minor but widespread anorogenic A-type magmatism (355–335 Ma) produced mainly mid-alkaline K-feldspar porphyritic granite and coeval alkaline mafic dykes (the latter geochemically classified as back-arc basin basalt). These granites occur as scattered plutons (at least 15 have been identified), usually with sub-circular forms, intruding Early Palaeozoic metamorphic and plutonic belts. (2) In the Western Sierras Pampeanas (WSP), where the basement is of Grenville age, the Carboniferous magmatism is represented by a calc-alkaline magmatic arc (2000 thick alluvial conglomerates and shallow-marine strata of Mississippian age (Martina et al., 2011 and reference therein). Carboniferous A-type magmatism in the ESP was probably controlled by an asymmetrical stretched lithosphere with continental crust thickening eastwards to the foreland.