Elsevier

Lithos

Volume 19, Issues 3–4, October 1986, Pages 205-218
Lithos

The transition between blueschists and lawsonite-bearing eclogites based on observations from Corsican metabasalts

https://doi.org/10.1016/0024-4937(86)90023-XGet rights and content

Abstract

Syntectonic eclogites, associated with blueschist parageneses, have recrystallized in metabasalts from eastern Corsica under very low temperatures (420°C). The evolution of these eclogites is recorded by the order of development of metamorphic minerals, as demonstrated by helicitic inclusions of lawsonite and actinolite in Fe-rich garnets, and the occurrence of fibrous Na-pyroxenes in the pressure shadows and cracks of boudinaged garnets, within a foliated matrix composed of glaucophane, CaFe garnets and lawsonite.

A Schreinemakers analysis has been completed on the lawsonite-ferroglaucophane-actinolite-almandine-grossular-ferro-omphacite-chlorite system in a (T,P,μH2O)-space. The resulting three-dimensional relationships are applied to the studied samples. They are consistent with a prograde increase in temperature at low μH2O, producing eclogites from blueschists, and with a subsequent retrogressive decrease in pressure.

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