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.
Peraluminous s type granite.
The plutons here named peraluminous a type granites pags differs from other peraluminous ferroan granites as classified by frost and frost 2011 in that the latter ones are commonly associated with the metaluminous variety.
With respect to aluminium s type granites are always peraluminous or have a total alkali.
In addition s type granites contain more magnesium than iron.
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.
The rock formed in this type is called tronjhomite or plagio granite.
Those rocks are therefore always saturated in al or peraluminous.
Primary muscovite can occur in weakly peraluminous fractionated i type granites.
Therefore the presence of muscovite alone.
Iron and magnesium content correlate with color index in s type granites.
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.
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.
S type granite this type is of sedimentary origin paraorigin from anatexis of sedimentary rocks with high al2o3 and low sio2 content ex.
Peralumino us granite s can be produce d either by pa rtial melti ng of metasedime ntary rocks s t ype or metaigne ous rocks i ty pe which has been well documented by expe rimental petrology.
Magma type is usually peraluminous magma al2o3 na2o k2o cao.
