Kinawa Granite - an Archean-aged migmatite from Brazil. It formed about 2.72-2.75 billion years ago by metamorphism of an older precursor rock (protolith) that dates to about 3.00-3.38 billion years. This migmatite is quarried in the southern São Francisco Craton of southeastern Brazil. It consists of quartz (gray), feldspar (white), and mafic minerals (black).
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Migmatites are very high grade metamorphic rocks that form by partial melting of gneisses. The felsic minerals have melted, cooled, and recrystallized - they form the light-colored, crystalline-textured bands in the rock. The mafic minerals have higher melting temperatures and still retain their metamorphic foliated character.
Tags: kinawa granite migmatite Precambrian sao francisco craton brazil
Iguana Green Granite - faulted and sheared gneiss (or migmatite) from Brazil.
Gneiss is a common high-grade, foliated metamorphic rock characterized by alternating bands of light- and dark-colored minerals. It forms by metamorphism of schists or felsic-to-intermediate intrusive igneous rocks (e.g., granite).
Locality: attributed to a quarry near the town of Messias Targino, Rio Grande do Norte State, eastern Brazil
Tags: Iguana Green Granite gneiss migmatite Messias Targino Rio Grande do Norte State Brazil
Migmatite is a very high grade metamorphic rock that has been subjected to partial melting. It has both crystalline and foliated texture. The crystalline portions have melted, cooled, and solidified - usually to bands of pinkish-colored granite. The foliated portions resemble gneiss and have not melted. Migmatite is essentially ~half-igneous and ~half-metamorphic.
Locality: loose boulder along the lower stretches of Hellroaring Road (= Forest Service Road 2004), northwestern side of Rock Creek Canyon, southwest of the town of Red Lodge, Beartooth Mountains, Montana, USA
Tags: migmatite metamorphic rock rocks metamorphics Hellroaring Road Creek Canyon Beartooth Mountains Montana
Migmatite in the Precambrian of Colorado, USA.
Migmatites are very high grade metamorphic rocks that form by partial melting of gneisses. The felsic minerals have melted, cooled, and recrystallized - they form the light-colored, crystalline-textured bands in the rock. The mafic minerals have higher melting temperatures and still retain their metamorphic foliated character.
The outcrop seen here is an Paleoproterozoic-aged migmatite at the Rocky Mountain Front in Colorado. This is part of the local Precambrian basement. Upper Paleozoic redbeds are nonconformably overlying the basement in the area.
Stratigraphy: "Idaho Springs Formation", late Paleoproterozoic, ~1.7 Ga
Locality: Red Rocks Park, west of Denver, north-central Colorado, USA
Tags: migmatite Idaho Springs Formation Precambrian Proterozoic Paleoproterozoic Rocky Mountain Front Red Rocks Park Denver Colorado
Iguana Green Granite - convoluted gneiss (or migmatite) from Brazil.
Gneiss is a common high-grade, foliated metamorphic rock characterized by alternating bands of light- and dark-colored minerals. It forms by metamorphism of schists or felsic-to-intermediate intrusive igneous rocks (e.g., granite).
Locality: attributed to a quarry near the town of Messias Targino, Rio Grande do Norte State, eastern Brazil
Tags: Iguana Green Granite gneiss migmatite Messias Targino Rio Grande do Norte State Brazil