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The transition between blueschists and lawsonite-bearing eclogites based on observations from Corsican metabasalts |
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| Authors: | Jean-Michel Caron Guy Pquignot |
| Institution: | Laboratoire de Pétrologie - U.A. 726, Université Claude Bernard Lyon I, 27–43 Boulevard du 11 Novembre, 69622, Villeurbanne Cédex, France |
| 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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