ِِِِ Metasomatic Andalusite in Deh Salm metamorphic complex

Category Petrology
Group GSI.IR
Location The 25 Symposium of Geosciences
Author B.Mehrabi-Sh.Mahmodi
Holding Date 01 July 2007


 Andalusite is one of the Al2SiO5 polymorphs, usually formed in high temperature and low pressure metamorphism. Recent studies show that andalusite may be formed directly from magma crystallization and during metasomatic presses. In this research formation and features of metasomatic andalusite in Dehsal metamorphic complex have been studied. This complex situated in east of Iran and mainly consists of different schists, granitic intrusions and pegmatites.  In Dehsalm metamorphic complex, in the contact of granitoids and metamorphic rocks andalusite has been formed as a result of metasomatism. Metasomatic andalusite formed in less than 2kb pressure, 550˚C temperature and in the presence of acidic granitic fluids in low pH condition.  EPMA analyses show Fe, K and REE are different in metasomatic andalusite and metasomatic ones. Fe ranges 0.12-0.97 and 0.11-0.16 in metasomatic and metamorphic andalusites respectively. K is up to 0.79 in metasomatic andalusite, while it is less than 0.02 in metamorphic andalusite. Concentration of other elements is similar in both. Comparing internal structure shows that metamorphic andalusite formed in higher temperature than metasomatic andalusite and in some parts it has been replaced by sillimanite. 



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