Premium
Production of metaluminous melt during fluid‐present anatexis: an example from the Maghrebian basement, La Galite Archipelago, central Mediterranean
Author(s) -
Ferrero S.,
Braga R.,
Berkesi M.,
Cesare B.,
Laridhi Ouazaa N.
Publication year - 2014
Publication title -
journal of metamorphic geology
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 2.639
H-Index - 114
eISSN - 1525-1314
pISSN - 0263-4929
DOI - 10.1111/jmg.12068
Subject(s) - anatexis , peralkaline rock , geology , fluid inclusions , geochemistry , partial melting , quartz , mantle (geology) , paleontology , volcano
Abstract Garnet brought to the surface by late Miocene granitoids at La Galite Archipelago (Central Mediterranean, Tunisia) contains abundant primary melt and fluid inclusions. Microstructural observations and mineral chemistry define the host garnet as a peritectic phase produced by biotite incongruent melting at ~800 °C and 0.5 GP a, under fluid‐present conditions. The trapped melt is leucogranitic with an unexpected metaluminous and almost peralkaline character. Fluid inclusions are one phase at room temperature, and contain a CO 2 ‐dominated fluid, with minor H 2 O, N 2 and CH 4 . Siderite and an OH ‐bearing phase were identified by Raman and IR spectroscopy within every analysed inclusion, and are interpreted as products of a post‐entrapment carbonation/hydration reaction between the fluid and the host during cooling. The fluid present during anatexis is therefore inferred to have been originally richer in both H 2 O and CO 2 . The production of anatectic melt with a metaluminous signature can be explained as the result of partial melting of relatively Al‐poor protoliths assisted by CO 2 ‐rich fluids.