Experimental and thermodynamic constraints on mineral equilibrium in pantelleritic magmas
Résumé
In this study we present the results of phase equilibrium experiments performed on two samples of pantellerites differing slightly in composition and mineral assemblages. Phase relationships were established at 1 kbar, for temperatures ranging between 680 °C - 900 °C and redox conditions around the fayalite-magnetite-quartz (FMQ) buffer (equivalent to ΔNNO-0.68 to −0.60). The experimental results are compared with the results of previous experiments carried out on similar material (Di Carlo et al., 2010). We also compare our data with thermobarometric results based on established mineral-mineral equilibria gathered from Pantelleria and other peralkaline localities (Pantelleria: White et al., 2005, White et al., 2009; Liszewska et al., 2018; Eburru, Kenya: Ren et al., 2006; and Menengai, Kenya: Macdonald et al., 2011). We focus our attention on how mineral assemblages are affected by (i) small variations of starting compositions, and (ii) temperature and redox conditions. Our findings shed new light on mineral-liquid and mineral-mineral equilibria governing the occurrence of aenigmatite, olivine, ilmenite and sodian amphibole phases in pantellerites.
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