Petrogenesis of cordierite-bearing S-type granitoids in Sierra de Chepes, Famatinian orogen, Argentina

Andalusite and Na- and Li-rich cordierite in the La Costa pluton, Sierras Pampeanas, Argentina: textural and chemical evidence for a magmatic origin

“…This however contradicts growing evidence for late magmatic muscovite in many moderate-depth ('" 1-2 kbar) intrusions (e.g. Dahlquist et al 2005 and references therein). Moreover, textural and chemical evidence presented here points to a primary origin for sorne of the muscovites in the Santa Cruz igneous facies.…”

“…Textural evidence, along with whole-rock and mineral chemical compositions, suggests that Na-and Li-rich cormerite of the Santa Cruz igneous facies crystallized from a peralurninous magma, and that it was at sorne stage in equilibrium with andalusite (see also Clarke 1995 ;Erdrnann et al 2004;Clarke et al 2005 ;Dahlquist et al 2005). The chernical composition of the Na-and Li-rich cormerite is consistent with the whole-rock chemistry of the Santa Cruz monzogranite.…”

“…The high ASI values (1.27-1.42; Table 2) of the Santa Cruz igneous facies suggest that the granitic magma was saturated in alurnina, making Gordillo et al 1985 ;Clarke 1995 ;Dahlquist et al 2005;Clarke et al 2005 and references therein). In addition, Patiño Douce (1992) has shown that the activity coefficient of Al in silicic melts is a function of the alkali content of the melt, whereby alkali-rich a Mg Na Fig.…”

“…Muscovite "a" and "b, c" (subscripts) correspond to primary and secondary muscovite, respectively (see text). Abbreviations mineral after KIetz (1983 ) bdl below detection limit et al 199 1;Villaseca and Barbero 1994;Cerny et al 1997 ;Rapela et al 2002;Erdmann et al 2004;Dahlquist et al 2005). Trace elements provide complementary information on the origin of the minerals, particularly for the case of cormerite (e.g.…”

“…whether they crystallized from the magma or were trapped as xenocrysts (e.g. Flood and Shaw 1975 ;Clarke et al 1976Clarke et al , 2005Bellido and Barrera 1979;Phillips et al 198 1;Allen and Barr 1983 ;Weber et al 1985 ;Dimer and Dupraz 1986;Georget and Fourcade 1988 ;Clarke 1995 ;Erdrnann et al 2004;Gottesmann and Forster 2004;Dahlquist et al 2005). We have focused here on the petrography, mineral chemistry, and the bulk major and trace element composition of the Santa Cruz igneous facies of the La Costa peraluminous granite pluton in the province of La Rioja, NW Argentina, which contains Na-and Li-rich cormerite, andalusite and muscovite.…”