Ophiolite-mantle

Ultrabasic metamorphic rocks that derive from the Earth's mantle, found in ophiolite sequences, orogenic peridotites, or as nodules in volcanic pipes.
  • 114-1408 IMG Lherzolite from the Ronda peridotite massif, southern Spain. Olivine weathers tan-colured, soft. Orthopyroxene forms the larger prominent brown crystals. Clinopyroxene forms the finer-grained greener crystals with a little dark spinel.
  • IMG 5919 Foliated peridotite from the Lizard ophiolite, Cornwall. Olivine weathers orange-brown. Pyroxene (mostly othopyroxene), stands out in narrow bands.
  • IMG 5939 Fully recrystallised and serpentinised peridotite from the Lizard ophiolite, Cornwall. The red veins also consist of serpentine.
  • ign3a Phlogopite-garnet peridotite, Kimberley, South Africa. This rock comes from the subcontinental lithospheric mantle of the Archaean Kaapvaal craton, and was brought up as a xenolith in a kimberlite pipe. The phlogopite (shiny mineral seen around the garnets) is the product of metasomatism from small amounts of percolating alkaline melt or fluid near the base of the lithosphere.
  • IMG 6335 Veined and altered serpentinite derived by hydration and carbonation of mantle harzburgite. From a slab in a stone merchant's yard.
  • IMG 3495 Serpentinite breccia: fragments of serpentinite cemented by a carbonate matrix. Zermatt-Saas ophiolite, Val d'Aosta, Italy.