Generation of crystal-poor rhyolites from a shallow plutonic reservoir in the Famatinian arc (Argentina)

CAMILLETTI, GIULIANO C.; CRISTOFOLINI, EBER A.; CORNET, JULIEN; ARMAS, PAULA; ESCRIBANO, FACUNDO A.; OTAMENDI, JUAN E.; BACHMANN, OLIVIER

JOURNAL OF VOLCANOLOGY AND GEOTHERMAL RESEARCH

ELSEVIER SCIENCE BV

Año: 2022 vol. 431 p. 1 - 17

0377-0273

The Ordovician rocks of Sierra Las Planchadas are an exceptionally preserved natural example of a plutonic-volcanic connection. Located in northwestern Argentina, the Las Planchadas Formation consists of a monzogranitic batholith that displays a window into the source of large subvolcanic rhyolitic rocks, cryptodomes and volcanic feeder-dykes. Mafic intrusions and felsic dykes occur cutting the plutonic rocks. Grain-scale relationships, whole-rock compositions and mineral chemistry indicate that monzogranites and rhyolites are two comagmatic members which differentiated within upper crust magma reservoirs. Monzogranites accumulated some plagioclase and trapped a large volume of melt, denoted by a high modal percentage (~64–71%) of near-solidus minerals, comprised of alkali feldspar, albite-rich plagioclase (An