HighP

High-pressure metamorphic rocks from subduction-zone environments, belonging to the blueschist and eclogite facies.
  • IMG 3752 Sub-blueschist facies. Yellowish lawsonite and quartz in a vein cutting Permian volcanics, Western Alps, France.
  • IMG 3683 Blueschist facies. Graphitic phyllite with porphyroblasts of carpholite (dark prisms). Mg-Fe carpholite (not in DHZ) is a hydrous Mg-Fe-Al-silicate restricted to blueschist-facies conditions in metapelitic rocks.
  • IMG 3714 Blueschist facies metagabbro, Western Alps, France. Coarse-grained gabbros occur as blocks in the blueschist-facies 'schistes lustres' of the Western Alps. Here igneous augite is fractured and rimmed by dark blue glaucophane.
  • IMG 3708 Blueschist facies metagabbro, Western Alps, France. Here green veins of jadeitic pyroxene traverse a gabbro in which igneous pyroxene is partly transformed into blue glaucophane.
  • IMG 3408 Eclogite facies, low T. Metapelitic schist with garnet, chloritoid (dark green), phengitic muscovite (silver flakes) and quartz. Saas valley, Switzerland.
  • 93a-14 Eclogite facies, low T. Metapelitic schist with large garnet porphyroblasts and schistosity comprising greenish phengitic muscovite. These are rocks subducted beneath the Oman ophiolite.
  • IMG 3652 Eclogite facies, ultrahigh pressure division. Schist with pale pink Mg-rich garnet, phengite, kyanite and quartz. The quartz is all recrystallised from coesite, the high-pressure polymorph of SiO2, and coesite relics can be found inside the garnets. Dora Maira massif, Western Alps, Italy.
  • IMG 3488 Blueschist/eclogite facies (transitional). A glaucophane-rich metabasic rock with small garnets and the distinctive rhombic outlines of lawsonite crystals. These have now been pseudomorphed by clinozoisite and white mica, a reaction that occurred during exhumation. Aosta valley, Western Alps.
  • IMG 3493 Blueschist/eclogite facies (transitional). A metabasic rock consisting of blue glaucophane, green omphacite, red garnet porphyroblasts with long included prisms of glaucophane, and rusty-brown carbonate (ankerite). Aosta valley, Western Alps.
  • IMG 3497 Eclogite facies. Metabasic gneiss consisting of interbanded eclogite and glaucophane-bearing eclogite. Aosta valley, Western Alps.
  • IMG 3378 Eclogite facies. Foliation surface of eclogitic schist with garnet, omphacite, mica and white pseudomorphs after lawsonite. Zermatt area, Switzerland.
  • IMG 3527 Eclogite facies. Foliation surface of eclogitic metabasic schist with garnet, omphacite, clinozoisite and needles of dark glaucophane. Lago di Cignana, Western Alps, Italy.
  • IMG 3622 Eclogite facies. Green omphacite prisms in probable calcareous metasediment, Sesia zone, Western Alps, Italy.
  • IMG 3616 Eclogite facies. Thin folded metabasic layer with green omphacite enclosed in high-pressure schist. Sesia Zone, Western Alps, Italy.
  • IMG 3604 Eclogite facies (partly retrogressed). Gneiss probably derived from intermediate igneous rock, with omphacite-bearing assemblage now partly retrogressed to albite and actinolite (greenschist facies). Sesia Zone, Western Alps, Italy.
  • IMG 3632 Eclogite facies. Ophiolitic metagabbro from the Monviso unit, Italian Western Alps. The green mineral is a chromian omphacite (former augite), brownish regions are rich in garnet, white areas rich in clinozoisite.
  • IMG 3636 Eclogite facies. Banded eclogite, possibly derived from ocean-floor basalt, cut by a small shear zone that has allowed fluid to enter and cause retrograde blue (Na-) and green (Ca-Na-) amphibole growth. Monviso unit, Italian Western Alps.
  • IMG 3531 Eclogite facies. Boudin of green omphacite-rich metabasic eclogite immersed in high-pressure metasedimentary schist. Lago di Cignana, Western Alps, Italy.
  • DREC252 Eclogite facies. Contact between metabasic garnet-omphacite eclogite (below) and eclogite-facies metasedimentary rock (garnet kyanite phengite gneiss), with very little retrogression. Western Norway. [photo: A L Wain]
  • eclogite2 Homogeneous bimineralic garnet-omphacite eclogite, Western Norway. [photo: A L Wain]
  • OPXEC 22 Eclogite facies, ultrahigh pressure division. Metabasic garnet-omphacite-orthopyroxene eclogite. Coesite has been recorded as inclusions in minerals from this rock. Western Norway. [photo: A L Wain]
  • FLEC27 Eclogite facies, partly retrogressed. Margin of metabasic eclogite body against amphibolite-facies gneiss. Fresh eclogite on the right grades into darker-coloured rock in which omphacite is replaced by diopside-plagioclase-amphibole intergrowths. Western Norway. [photo: A L Wain]