What is the meaning of anorthosite?
What is the meaning of anorthosite?
Anorthosite (/ænˈɔːrθəˌsaɪt/) is a phaneritic, intrusive igneous rock characterized by its composition: mostly plagioclase feldspar (90–100%), with a minimal mafic component (0–10%). Pyroxene, ilmenite, magnetite, and olivine are the mafic minerals most commonly present.
What texture is anorthosite?
Anorthosite is usually a coarse-grained intrusive igneous rock with color varies between white, yellowish to brown, shades of gray, blush and smoky pigment.
How is anorthosite formed?
Anorthosite can form by floatation of low-density plagioclase in the magma due to the density difference between plagioclase and melt (Wood et al., 1970). The extensive occurrence of anorthosite on the Moon requires a global magma body, referred to as the lunar magma ocean (LMO) (Yamamoto et al., 2012).
Where would you find anorthosite?
Anorthosite is also found on the lunar surface. Although these large masses are generally supposed to provide the best sample of the deep lithosphere (the outer shell of the Earth), they often appear to be floored over most of their outcrop area.
Is anorthosite found on the moon?
From Earth, lunar anorthosite is visible as the light-colored, highly reflective parts of the Moon’s surface known as the lunar highlands. These are the Moon’s oldest rocks—more than 4 billion years old—and covered the young Moon’s entire surface before its crust was pummeled and broken up by asteroids and comets.
What is anorthosite used for?
Anorthosite is an almost monomineralic, feldspathic rock with a great variety of industrial applications (Table 1). Anorthosite massifs are known to host important ore depos- its such as ilmenite and are, in many cases, excellent sources for high-quality rock aggregate and also for dimension- stone.
Is anorthosite a volcanic?
Anorthosite is usually considered to be a cumulate rock. One more interesting aspect is that most plutonic igneous rocks have extrusive equivalents. These pairs are gabbro-basalt, granite-rhyolite, etc. But there is absolutely no volcanic equivalent of anorthosite.
Where is carbonatite found?
Carbonatites usually occur as small plugs within zoned alkalic intrusive complexes, or as dikes, sills, breccias, and veins. They are almost exclusively associated with continental rift-related tectonic settings.
What are the oldest rocks on the Moon?
Anorthosites, rocks composed almost entirely of plagioclase feldspar, are the oldest rocks on the Moon. They appear to have formed when feldspar crystallized and floated to the top of a global magma ocean that surrounded the Moon soon after it formed.
What destroyed the oldest rocks of the Moon?
Weathering and plate tectonics destroyed Earth’s oldest rocks. The Moon has rocks older than any that have been found on Earth, and they record a valuable early piece of the Earth and Moon’s shared history.
What destroyed the oldest rocks on the moon?
What minerals are in carbonatite?
Carbonatites are a relatively rare type of igneous rock composed of greater than 50 vol % primary carbonate minerals, primarily calcite and/or dolomite, and contain the highest concentrations of REEs of any igneous rocks.
What kind of rock is an anorthosite made of?
5.1 Formation. Anorthosite is a phaneritic, intrusive igneous rock which is characterized by a predominance of plagioclase feldspar which is almost 90–100%, and a minimal mafic component.
What kind of iridescence does an anorthosite have?
Polished slab; blue color is labradorescence. Since they are primarily composed of plagioclase feldspar, most of Proterozoic anorthosites appear, in outcrop, to be grey or bluish. Individual plagioclase crystals may be black, white, blue, or grey, and may exhibit an iridescence known as labradorescence on fresh surfaces.
Where does the metasomatism of anorthosite come from?
• They are originated from early crystallisation and accumulation of anorthite-rich plagioclase and their staining off by filter pressing process. Metasomatism: • Process of metasomatic replacement attendant with higher grades of metamorphism is also an originating way of anorthosite.
What is the plagioclase composition of an anorthosite?
Such layering clearly has origins with a rheologically liquid-state magma . Proterozoic anorthosites are typically >90% plagioclase, and the plagioclase composition is commonly between An 40 and An 60 (40–60% anorthite ).