Publication: Andalusite and Na- and Li-rich cordierite in the La Costa pluton,
Sierras Pampeanas, Argentina: textural and chemical evidence
for a magmatic origin
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2010
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Springer Science Business Media
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Abstract
The La Costa pluton in the Sierra de Velasco
(NW Argentina) consists of S-type granitoids that can be
grouped into three igneous facies: the alkali-rich Santa
Cruz facies (SCF, SiO2 *67 wt%) distinguished by the
presence of andalusite and Na- and Li-rich cordierite
(Na2O = 1.55–1.77 wt% and Li2O = 0.14–0.66 wt%), the
Anillaco facies (SiO2 *74 wt%) with a significant proportion
of Mn-rich garnet, and the Anjullo´n facies (SiO2
*75 wt%) with abundant albitic plagioclase. The petrography,
mineral chemistry and whole-rock geochemistry of
the SCF are compatible with magmatic crystallization of
Na- and Li-rich cordierite, andalusite and muscovite from
the peraluminous magma under moderate P–T conditions
(*1.9 kbar and ca. 735C). The high Li content of cordierite
in the SCF is unusual for granitic rocks of intermediate
composition.
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The original publication is available at www.springerlink.com