Talk:Ultramafic rock
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Ultramafic and ultrabasic are actually different terms. Ultramafic is an igneous rock which is composed of greater than 90% mafic minerals, but ultrabasic is an igneous rock which has silica content lower than 45% (weight%). First is mineralogic and second is chemical classification and they should be different articles. Rock can be ultrabasic but it doesn't mean that it should be automatically ultramafic. Siim 20:09, 5 September 2005 (UTC)
That's fairly pedantic at best. Its like saying a highly mafic-mineral rich granitoid isn't felsic because it has >10% mafic minerals. Anorthosite; since it's got >45% silica due to being >90% plagioclase, and isn't ultramafic because it's >90% 'felsic' minerals...? But it's formed by accumulation from ultramafic magmas? So I disagree with you. Ultramafic rocks are ultrabasic rocks, and arguing specifics ignores the fact that they are all hot, fairly primitive (in a fractional crystallisation sense) rocks.Rolinator 09:48, 24 December 2005 (UTC)
