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Ultramafic rocks (also referred to as ultrabasic rocks, although the terms are not wholly equivalent) are igneous and meta -igneous rocks with a very low silica content (less than 45%), generally >18% MgO, high FeO, low potassium, and are composed of usually greater than 90% mafic minerals (dark colored, high magnesium and iron content).
These accumulations typically occur on the floor of the magma chamber, although they are possible on the roofs if anorthite plagioclase is able to float free of a denser mafic melt. [ 1 ] Cumulates are typically found in ultramafic intrusions , in the base of large ultramafic lava tubes in komatiite and magnesium rich basalt flows and also in ...
A mafic mineral or rock is a silicate mineral or igneous rock rich in magnesium and iron. Most mafic minerals are dark in color, and common rock-forming mafic minerals include olivine, pyroxene, amphibole, and biotite. Common mafic rocks include basalt, diabase and gabbro. Mafic rocks often also contain calcium -rich varieties of plagioclase ...
Magmatism. Geological map showing the Gangdese batholith, which is a product of magmatic activity about 100 million years ago. Magmatism is the emplacement of magma within and at the surface of the outer layers of a terrestrial planet, which solidifies as igneous rocks. It does so through magmatic activity or igneous activity, the production ...
Closeup view about 30 cm × 20 cm (12 in × 8 in). Serpentinite is a metamorphic rock composed predominantly of one or more serpentine group minerals formed by near to complete serpentinization of mafic to ultramafic rocks. Its name originated from the similarity of the texture of the rock to that of the skin of a snake. [1]
Rare ultramafic rocks, which contain more than 90% mafic minerals, and carbonatite rocks, containing over 50% carbonate minerals, have their own special classifications. [5] [6] Hypabyssal rocks resemble volcanic rocks more than they resemble plutonic rocks, being nearly as fine-grained, and are usually assigned volcanic rock names.
In 2016, the International Astronomical Union (IAU) organized a Working Group on Star Names (WGSN) [2] to catalog and standardize proper names for stars. The WGSN's first bulletin, dated July 2016, [3] included a table of 125 stars comprising the first two batches of names approved by the WGSN (on 30 June and 20 July 2016) together with names of stars adopted by the IAU Executive Committee ...
Ultrapotassic igneous rocks. Ultrapotassic igneous rocks are a class of rare, volumetrically minor, generally ultramafic or mafic silica-depleted igneous rocks. While there are debates on the exact classifications of ultrapotassic rocks, they are defined by using the chemical screens K 2 O/Na 2 O > 3 in much of the scientific literature. [1]