Experimental calibration of the partitioning of Fe and Mg between biotite and garnet

✍ Scribed by J. M. Ferry; F. S. Spear

• Publisher: Springer
• Year: 1978
• Tongue: English
• Weight: 445 KB
• Volume: 66
• Category: Article
• ISSN: 0010-7999
• DOI: 10.1007/bf00372150

✦ Synopsis

The cation exchange reaction Fe3A12Si30 a 2 + KMg3A1Si3Olo(OH)2 = Mg3AlzSi30 m + KFe3-A1Si3Olo(OH)/ has been investigated by determining the partitioning of Fe and Mg between synthetic garnet, (Fe, Mg)3A11Si3012, and synthetic biotite, K(Fe, Mg)3A1Si3Olo(OH) 2. Experimental results at 2.07 kbar and 550~ ~ C are consistent with in [(Mg/Fe) garnet/(Mg/Fe) biotite] =-2109/T(~ +0.782. The preferred estimates for AI~ and AS of the exchange reaction are 12,454cal and 4.662 e.u., respectively. Mixtures of garnet and biotite in which the ratio garnet/biotite = 49/1 were used in the cation exchange experiments. Consequently the composition of garnet-biotite pairs could approach equilibrium values in the experiments with minimal change in garnet composition (few tenths of a mole percent).

Equilibrium was demonstrated at each temperature by reversal of the exchange reaction. Numerical analysis of the experimental data yields a geothermometer for rocks containing biotite and garnet that are close to binary Fe--Mg compounds.