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.

Peraluminous s type granite. 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. 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. While apatite inclusions are common they are not as abundant or large as apatites in s type granites. Those rocks are therefore always saturated in al or peraluminous.

In addition s type granites contain more magnesium than iron. Clemens and stevens 2012 patiño douce 1999. Primary muscovite can occur in weakly peraluminous fractionated i type granites. 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. 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. Iron and magnesium content correlate with color index in s type granites. Therefore the presence of muscovite alone.

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. 3 i type granites show a gradual change from metaluminous to peraluminous composition with increasing sio 2 whereas s type granites display either constant values or slight decrease with increasing sio 2 ascribed to.