S Typ Granit

Later contributions chappell and white 1984 chappell and white 1992 provided further details of the i and s type subdivision of granites in the lachlan fold belt lfb of southeastern australia.

S typ granit. It was at an earlier granite symposium in south america santiago chile that chappell and white 1974 first proposed the i and s type granite 1 subdivision. The biotites in i type granites are greener in general than those in s type both in hand sample and in plane polarized light. S type granite this type is of sedimentary origin paraorigin from anatexis of sedimentary rocks with high al2o3 and low sio2 content ex. High amounts of na2o and s type granitoids derived from sedimentary protoliths and containing high amounts of al2o3 and relatively low amounts of na2o.

Petrographic features are representative of the chemical. Magma type is usually peraluminous magma al2o3 na2o k2o cao. They are recognized by a specific set of mineralogical geochemical textural and isotopic characteristics. I type granite formed by the igneous and s type granite formed by melting of metasedimentary rocks.

Amphibole and pyroxene are more common in i type granitoids while s type granitoids may have garnet cordierite and sillimanite. S type granites i type granites a type granitoids m type granitoids s type granites occur in regional metamorphic terranes partial melting of metasediments high al but contain no hornblende biotite muscovite cordierite garnet high rb in source rocks initial sr ratios 0 710 i type granites. Both types of granitoids may also contain biotite. 2001 and frost and frost 2011 have also provided exhaustive analysis and classification of granitic suites based on a range of major element indices.

S type granites are over saturated in aluminium with an asi index greater than 1 1 where asi al 2 o 3 cao na 2 o k 2 o in mol percent. These result in i type granitoids derived from igneous protoliths and containing moderate amounts of al 2 o 3 and high amounts of na 2 o and s type granitoids derived from sedimentary protoliths and containing high amounts of al 2 o 3 and relatively low amounts of na 2 o. If they are generated from different continental settings and from different magma so can we see. More mafic composition granites those with a higher color index contain more hornblende and biotite.

S type granites are a category of granites first proposed by chappell white. Garnet is a very common accessory mineral in this type. Amphibole and pyroxene are more common in i type granitoids. I type granites are thought to have been derived from deep crust formed by underplating and thus are infracrustal in contrast to the supracrustal s type source rocks.

Hornblende is a typical i type granite mineral which never occurs in s type granite. Tectonic setting is arc collision. Crystallisation of feldspars from felsic granite melts leads to distinctive changes in the trace element compositions of more evolved i and s type granites.