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Augen gneiss, from the German: Augen, meaning "eyes", is a gneiss resulting from metamorphism of granite, which contains characteristic elliptic or lenticular shear-bound grains (porphyroclasts), normally feldspar, surrounded by finer grained material. The finer grained material deforms around the more resistant feldspar grains to produce this ...
Granite (/ ˈ ɡ r æ n ɪ t / GRAN-it) is a coarse-grained intrusive igneous rock composed mostly of quartz, alkali feldspar, and plagioclase.It forms from magma with a high content of silica and alkali metal oxides that slowly cools and solidifies underground.
Unakite – Multicoloured metamorphic rock – An altered granite; Variolite – Igneous rocks which contain varioles; Vogesite – Type of ultrapotassic igneous rock – A variety of lamprophyre; Wad (mineral) – Porous secondary manganese oxyhydroxide – A rock rich in manganese oxide or manganese hydroxide
Morton gneiss, also known as rainbow gneiss, is an Archean-age gneiss found in the Minnesota River Valley of southwestern Minnesota, United States. It is one of the oldest stones on Earth, at about 3.5 billion years old. Along with the nearby Montevideo Gneiss, it is the oldest intact continental crust rock in the United States. [1]
The original name for this phenomenon was defined by Sederholm (1923) [24] as a rock with "fragments of older rock cemented by granite", and was regarded by him to be a type of migmatite. There is a close connection between migmatites and the occurrence of ‘explosion breccias’ in schists and phyllites adjacent to diorite and granite intrusions.
Gneiss, a foliated metamorphic rock. Quartzite, a non-foliated metamorphic rock. Foliation in geology refers to repetitive layering in metamorphic rocks. [1] Each layer can be as thin as a sheet of paper, or over a meter in thickness. [1] The word comes from the Latin folium, meaning "leaf", and refers to the sheet-like planar structure. [1]
This rock is dominated by pebbles & granules of granite, gneiss, and mafic igneous rocks. Some clasts have been partially epidotized. The matrix is dominated by epidote (green), quartz, and tremolite. Metaconglomerate is a rock type which originated from conglomerate after undergoing metamorphism.
The composition of a parent rock has a direct effect on the composition of the resulting melt. [2] Granitic melts are commonly classified based on the nature of their source rock. [2] One of the more popular classification schemes for granites was first introduced by White and Chappell in 1974. [2]