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S-type Granite
S-type granites are a category of granites first proposed in 1974. They are recognized by a specific set of Mineralogy, mineralogical, Geochemistry, geochemical, textural, and Isotope, isotopic characteristics. S-type granites are over-saturated in aluminium, with an ASI index greater than 1.1 where ASI = Al2O3 / (CaO + Na2O +K2O) in mol percent; Petrography, petrographic features are representative of the chemical composition of the initial magma as originally put forth by Chappell and White are summarized in their table 1. Mineralogy Major minerals (present in amounts > 5 volume%) Like all Granite, granites, the modal mineralogy of S-type granites are dominated by Alkali feldspar, alkali- and plagioclase feldspars and quartz. Thus, S-type granites are silica over-saturated (contain quartz), and do not contain feldspathoids. An interesting feature of S-type granites, at the hand sample scale, is that alkali-feldspars are typically white in color (rather than pink) excluding sa ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] [Amazon] |
Granite
Granite ( ) is a coarse-grained (phanerite, phaneritic) intrusive rock, intrusive igneous rock composed mostly of quartz, alkali feldspar, and plagioclase. It forms from magma with a high content of silica and alkali metal oxides that slowly cools and solidifies underground. It is common in the continental crust of Earth, where it is found in igneous intrusions. These range in size from dike (geology), dikes only a few centimeters across to batholiths exposed over hundreds of square kilometers. Granite is typical of a larger family of ''granitic rocks'', or ''granitoids'', that are composed mostly of coarse-grained quartz and feldspars in varying proportions. These rocks are classified by the relative percentages of quartz, alkali feldspar, and plagioclase (the QAPF diagram, QAPF classification), with true granite representing granitic rocks rich in quartz and alkali feldspar. Most granitic rocks also contain mica or amphibole minerals, though a few (known as leucogranites) conta ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] [Amazon] |
