Middle Devonian magmatism of the Sierra de San Luis

LÓPEZ DE LUCHI, M. G.,; IANNIZZOTTO, N.; GEUNA, S.; RAPALINI, A.E.; SIEGESMUND ,S; WEMMER, K.,

Avila

Simposio; Seven Hutton Symposium; 2011

Universidad Salamanca/Universidad de Granada

Middle Devonian Achalian granitoids intruded the Eastern Sierras Pampeanas (ESP) basement ca. 600 km east of the inferred proto-Pacific margin of Gondwana margin in which a coeval crustal thickening event was recognized (López de Luchi et al, 2007 and references therein). In Sierra de San Luis voluminous Middle Devonian batholiths are made up by an I- to A-type hybrid monzonite–granite suite with metaluminous magnesian alkali-calcic (393-385 Ma) porphyritic to equigranular monzonite- quartz monzonite– granodiorite±calc-alkalic monzogranite and mildly peraluminous magnesian to ferroan alkali-calcic equigranular monzogranites. SiO2 (50–62%), high Mg# (50–60), Cr, Ni, V, LILE, LREE, Th, Zr and Ba, Sr, Sr/Y, (La/Yb)N (50-20), smooth Eu/Eu*, moderate Na2O (ca 3.5) and troughs at Nb and Ta for monzonitic rocks suggest that garnet was a major residual phase with a minor role of plagioclase and a relatively deep seated lithospheric mantle source which underwent subduction-related metasomatism