Metamorphism of different Rocks
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This document summarizes the metamorphism of different rock types including ultramafic, mafic, pelitic, and calcareous rocks. Ultramafic rocks like peridotite and serpentinite can transform into serpentine, anthophyllite, olivine, and pyroxene minerals. Mafic rocks like basalt metamorphose into amphiboles and chlorite at low grades and amphibolite at intermediate grades, and granulite at highest grades. Pelitic rocks contain chlorite, muscovite, quartz and albite. Calcareous rocks like limestone coarsen but change little, while impure limestone forms diverse calcium-magnesium-sil
Metamorphism of different Rocks
- 1. METAMORPHISM OF 1.ULTRAMAFIC AND MAFIC 2. PELITIC AND CALCAREOUS ROCKS
- 2. MAFIC ROCK : - MAgnesium and FerrIC - Examples : Basalt and gabb ro - A large percentage of dark-colored minerals such as amphibole ULTRAMAFIC ROCK. - Examples :peridotite, kimberlite, lamprophyre, lamproite, dunite, and komatiite.
- 3. Metamorphosed ultramafics rocks contain the following mineral assemblage: Serpentine Olivine + H2O = serpentine Mg2SiO4 + H2O = Mg3Si2O5(OH)4 Anthophyllite Olivine Pyroxene 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
- 4. Olivine, pyroxene, and plagioclase in an original basalt change to amphiboles and chlorite (both commonly green) as water in the pore spaces reacts with the original minerals at temperatures and pressures of low grade metamorphism. Amphibolite - As pressure and temperature increase to intermediate grades of metamorphism, only dark colored amphiboles and plagioclase survive and the resulting rock is called an amphibolite. Granulite - At the highest grade of metamorphism the amphiboles are replaced by pyroxenes and garnets, the foliation is lost and a granulite that has a granulitic texture is produced.
- 5. Calcareous rocks are formed from a variety of chemical and detrital sediments such as limestone, dolostone, or marl and are largely composed of calcium oxide (CaO), magnesium oxide (MgO), and carbon dioxide (CO2), with varying amounts of aluminum, silicon, iron, and water. Pelitic rocks are derived from mudstone (shale) protoliths and are rich in potassium (K), aluminum (Al), silicon (Si), iron (Fe), magnesium (Mg), and water (H2O), with lesser amounts of manganese (Mn), titanium (Ti), calcium (Ca), and other constituents. Pelitic rocks are slates or phyllites and typically contain chlorite, muscovite, quartz and albite; Biotite zone
- 6. As calcite has broad P-T stability range, the metamorphism of pure limestone to marble results in coarsening , but little change in mineralogy. Metamorphism of impure limestone and dolostone (containing minor amount of other minerals like Quartz, feldspar create a far more diverse assemblage of Ca-Mg-Si bearing minerals contained in metacarbonates
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