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Lecture TWELVE Metamorphism of Ultramafic rocks (Metaultramafics)

Lecture TWELVE Metamorphism of Ultramafic rocks (Metaultramafics). What is the Metaultramafics?. Metaultramafics , are metamorphosed ultramafic igneous rocks. Ultramafic rocks are generated in the upper mantle and composed of <90% mafic minerals , which include:

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Lecture TWELVE Metamorphism of Ultramafic rocks (Metaultramafics)

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  1. Lecture TWELVE Metamorphism of Ultramafic rocks(Metaultramafics)

  2. What is the Metaultramafics? • Metaultramafics,are metamorphosed ultramafic igneous rocks. • Ultramafic rocks are generated in the upper mantle and composed of <90% mafic minerals, which include: • Olivine (Ol) (Mg,Fe)2SiO4, • Orthopyroxene (Opx) (Mg,Fe)SiO3 and • Clinopyroxene (Cpx) Ca(Mg,Fe)Si2O6 • and comprises rocks such as: • - Dunite (Ol), Pyroxenite (Cpx+Opx), Peridotite (Cpx+Opx+Ol) include harzburgite (Ol+Opx) and lherzolite (Ol+Cpx). • Chemically, the Utramafic chemical system of the ultramafic is simple (SiO2, MgO, FeO, CaO)

  3. Mineralogy of Metaultramafics • Metaultramafics contain the following mineral assemblage: • Talc • Serpentine • Olivine + H2O = serpentine • Mg2SiO4 + H2O = Mg3Si2O5(OH)4 • Anthophyllite • Olivine • Pyroxene

  4. 1- Rock types of the metamorphosed ultramafic rocks • The rock types of the metamorphosed ultramafic rocks are usually mono-mineralic and include: - Serpentintes: a massive to schistose rock with abundant serpentine minerals. - Talc fels / talc schist: Talc rich foliated/non-foliated rocks - Ophicalcites: serpentine + carbonate calcite - Anthophyllite schist. - Peridotites: Olivine bearing ultrmafics

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