Glaucophanites and eclogites from Val Chiusella,Sesia-Lanzo zone (Italian Alps) |
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| Authors: | Dietmar Reinsch |
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| Institution: | (1) Mineralogisch-Petrographisches Institut der Technischen Universität, Gauss-Straße 29, D-3300 Braunschweig, Federal Republic of Germany |
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| Abstract: | In the metabasites of Val Chiusella, metamorphic assemblages are present, corresponding to the glaucophane schist facies, i.e. garnet glaucophanites to omphacite-garnet glaucophanites, as well as to the eclogite facies, i.e., glaucophane eclogites, eclogites, and omphacite felses. Both groups of assemblages are divided by the critical reaction 1 zoisite +1 glaucophane  1.2 omphacite+0.8 garnet+0.7 paragonite +1.4 quartz+0.8 H2O. From textural evidence it is clear that in the investigated area this reaction proceeded to the right according to a prograde metamorphism. Correspondingly, K
garn-cpx
D(Fe/Mg) values of coexisting garnet-omphacite pairs in the glaucophane schist facies assemblages are higher than in the eclogite facies assemblages and reflect a temperature increase from about 450 ° C to about 550 ° C at minimum water vapour pressures of 12 to 16 kb. |
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