Differentiation of an upper crustal magma reservoir via crystalmelt separation recorded in the San Gabriel pluton, central Chile

I. Payacán*, F. Gutiérrez, O. Bachmann, M. Parada

*Autor correspondiente de este trabajo

Producción científica: Contribución a una revistaArtículorevisión exhaustiva

9 Citas (Scopus)

Resumen

Crystal-melt separation has been invoked as a mechanism that generates compositional variabilities in magma reservoirs hosted within the Earth’s crust. However, the way phase separation occurs within such reservoirs is still debated. The San Gabriel pluton of central Chile is a composite pluton (12.82 ± 0.19 Ma) with wide textural/compositional variation (52– 67 wt% SiO2) and presents a great natural laboratory for studying processes that occur in upper crustal magma reservoirs. Geochemical and geochronological data supported by numerical models reveals that shallow magma differentiation via crystal-melt separation occurred in magma with intermediate composition and generated high-silica magmas and cumulate residues that were redistributed within the reservoir. The pluton is composed of three units: (1) quartz-monzonites representing the main hosting unit, (2) a porphyritic monzogranite located at the lowest exposed levels, and (3) coarse-grained quartzmonzodiorites with cumulate textures at the middle level of the intrusive. Calculations of mass balance and thermodynamic modeling of major and trace elements indicate that <40 vol% of haplogranitic residual melt was extracted from the parental magma to generate quartz-monzonites, and 50– 80 vol% was extracted to generate quartz-monzodiorites, which implies that both units represent crystal-rich residues. By contrast, the monzogranites are interpreted as a concentration of remobilized residual melts that followed 30–70 vol% fractionation from a mush with 0.4–0.55 of crystal fraction. The monzogranites represent the upper level of a pulse that stopped under a crystal-rich mush zone, probably leaving a mafic cumulate zone beneath the exposed pluton.

Idioma originalInglés
Páginas (desde-hasta)348-369
Número de páginas22
PublicaciónGeosphere
Volumen19
N.º2
DOI
EstadoPublicada - 2023
Publicado de forma externa

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© 2023 The Authors

Áreas temáticas de ASJC Scopus

  • Geología
  • Estratigrafía

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