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Pyroxene-hornfels facies

Chemical Process (Solid-phase growth) - Contact metamorphic facies series

Index Minerals

Orthopyroxene, Garnet

Required Geological Setting

Contact metamorphic rocks, low-P metamorphic rocks


Metamorphic rocks formed by contact metamorphism or regional metamorphism in the following condition: 650-800 degree and less than 0.2 GPa (shallower than 5 km depth). A metamorphic facies formed by heat of magma. Pyroxene-hornfels facies metamorphic rocks are observed as contact metamorphic rocks aroud intrusions of plutonic rocks, in subduction zones as Ryoke-type low-P metamorphic rocks, accidental lithic fragments in pyroclastics, or xenoliths (xenocrysts) in igneous rocks.

Pyroxene-hornfels facies

Distribution of metamorphic rocks subjected to Pyroxene-hornfels facies contact metamorphism described in this site. Protolith of blue dots is bedded Mn deposit, and protoliths of green dots are igneous rocks and sedimentary rocks. Yellow zones are sedimentary rocks, pink parts are S-type (Ilmenite series) plutonic rocks, and blue parts are I-type (Magnetite series) plutonic rocks.

Change of mineral assemblages

  • [ Extinct ] Muscovite, Hornblende, Microcline
  • [ Appear ] Orthopyroxene, Garnet, Orthoclase

Mineral Assemblages

  • [ Felsic Rocks ] Orthoclase, Quartz, Plagioclase, Biotite
  • [ Mafic Rocks ] Orthopyroxene (Enstatite), Clinopyroxene, Plagioclase, (Olivine)
  • [ Ultramafic Rocks ] Enstatite, Serpentine
  • [ Mudstone ] Cordierite, Quartz, Sillimanite/Andalusite, Orthoclase, (Biotite, Garnet)
  • [ Laterite ]
  • [ Bedded Mn ] Bustamite, Rhodonite, Spessartine, Manganocummingtonite, K-feldspar
  • [ Carbonate Rocks ] Diopside, Grossular, Wollastonite, (Vesuvianite, Forsterite, Periclase, Clinohumite, Spinel, Biotite)
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