Iron and magnesium content correlate with color index in s type granites.
Peraluminous s type granite.
Clemens and stevens 2012 patiño douce 1999.
As a consequence of the lower na and ca contents the s type granites are always oversaturated in al or peralu minous and that is the case also for the more felsic i type granites.
The rock formed in this type is called tronjhomite or plagio granite.
Peraluminous granites can be produced either by partial melting of metasedimentary rocks s type or metaigneous rocks i type which has been well documented by experimental petrology e g.
While apatite inclusions are common they are not as abundant or large as apatites in s type granites.
These granites have been called s type chappell white 1974 syn collisional granitoids pearce et al 1984 continental collision granitoids maniar piccoli 1989 and muscovite peraluminous granites barbarin 1999.
S type granite this type is of sedimentary origin paraorigin from anatexis of sedimentary rocks with high al2o3 and low sio2 content ex.
Magma type is usually peraluminous magma al2o3 na2o k2o cao.
With respect to aluminium s type granites are always peraluminous or have a total alkali.
S type granites always contain more al than the amounts of na ca and k in the rock required to form feldspars primarily owing to their derivation from source components that had previously been weathered.
Therefore the presence of muscovite alone.
Primary muscovite can occur in weakly peraluminous fractionated i type granites.
In addition s type granites contain more magnesium than iron.
Those rocks are therefore always saturated in al or peraluminous.
