Calculation of fluid activity within Hamadan migmatite using cordierite minerals

Document Type : علمی -پژوهشی

Abstract

Intrusion of the Alvand complex (intrusions formed during Jurassic) in to the host metapelitic rocks (schistes) created pelitic hornfelses and anatectic migmatitesReactions Sil/And +‏ Bt = Crd +‏ Spl+‏ Kfs + melt and Bt+Als+Pl+Qtz = Grt+Kfs+melt, are the most reactions for the development of melt in the metapelitic rocks of Alvand aureole, and is commonly attributed to the process of fluid-absent partial melting. Using multiple equilibria, temperature (~750 ºC) and pressure (~4-5 kbar), have been calculated for the formation of the anatectic migmatites rocks. The volatile saturation surfaces and saturation isopleths for both H2O and CO2 in cordierite are strongly pressure dependent. In contrast, the uptake of H2O by cordierite in equilibrium with melts formed through biotite dehydration melting, controlled by the distribution of H2O between granitic melt and cordierite, DW[DW=wtH2O(melt)/ wtH2O (Crd), is mainly temperature dependent. The cordierite from a mesosome from this region yields a calculated total aH2O (0.62) + aCO2 (0.15) of < 0.77 at these P-T conditions. Melt H2O contents (3.7 wt percentage) and cordierite H2O contents (1.1 wt percentage) yields DW=3.36, compatible with model dehydration melting reactions. This range in DW cause a 15-30 relative decrease in the total wt of melt produced from pelites

Keywords

References

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Researches in Earth Sciences
Volume 7, Issue 3 - Serial Number 27
October 2016
Pages 108-125

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