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单词 anorthosite
释义
anorthosite

Astronomy
  • A medium- to coarse-grained igneous rock, grey to white in colour. It is composed almost entirely of calcium-rich plagioclase feldspar (95%), one of the most common rock-forming minerals, together with minor amounts of pyroxene (4%), olivine, and iron oxides. Anorthosite is thought to comprise a significant fraction of the lunar crust, and is present at all the Apollo and Luna landing sites. Samples of anorthosites 4.4–4.5 billion years old were among the oldest lunar rocks returned by spacecraft.


Geology and Earth Sciences
  • Plutonic rock composed almost entirely of plagioclase feldspar (90% or more) which may be oligoclase, andesine, labradorite, or bytownite. These rocks occur most frequently in Precambrian shield areas as non-stratiform intrusions or in layered complexes. Anorthosite also constitutes the Lunar Highlands where it is largely composed of the calcium end-member anorthite.


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