| Ultrapotassic Igneous Rocks |
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Information AboutUltrapotassic Igneous Rocks |
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Ultrapotassic rocks are defined by molar K2O/Na2O >3. The definition of what is an ultrapotassic rock and what is not is defined by a set of geochemical eutectics defined by the origination of certain types of magmas. In order to produce a molar K2O/Na2O ratio in excess of three, a rock must be produced by
Melting must favor liberating potassium as opposed to sodium; generally this may be achieved by partial melting of a plagioclase-poor source rock, or by melting of a potassium-enriched source rock, such as subducted sediments. Ultrapotassic granites are uncommon but are usually produced by melting of the continental crust above upwelling mafic magma, such as at Rift zones. Types of ultrapotassic rocks
Economic importance The economic importance of ultrapotassic rocks is wide and varied; : Leucite , Nepheline and other feldspathoids make excellent refractories, hence nepheline syenite is mined in Norway for use in manufacture of kiln glasses and furnace tiles. : Kimberlite s, Lamproite s and perhaps even Lamprophyre s are known to contain Diamond . These rocks are all produced at depths in excess of 120km and thus can bring diamond to the surface as xenocrysts. :Ultrapotassic granites are a known host for much granite-hosted Gold mineralisation. Significant Porphyry -style mineralisation is won from highly potassic to ultrapotassic granites. :Ultrapotassic A-type intracontinental granites may be associated with Fluorite , Niobium and Tantalite |
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