Arc Magma Crystallization

[Bhuvan]

Hello all!

I am trying to model crystallization of arc magmas at pressures (1GPa - 0.1GPa) using MELTS v1.2.0 with two objectives:

1. Effect of P and initial H2O on the amphibole crystallization and composition
2. Crystallization of An rich (An98) plagioclase

However, amphibole is never found as a crystallizing phase no matter the initial H2O content or the pressure. Increasing H2O content would lead to water being present as a separate fluid phase, and hence never triggers amphibole due to a decrease in magma's water contents or An rich plagioclase crystallization.

Any leads on solving this?

The primary magma composition is as follows:

Initial Composition: SiO2 49.0555
Initial Composition: TiO2 0.4904
Initial Composition: Al2O3 16.3157
Initial Composition: Fe2O3 1.3472
Initial Composition: Cr2O3: 0.033
Initial Composition: FeO 8.4557
Initial Composition: MgO 9.7423
Initial Composition: CaO 10.2108
Initial Composition: Na2O 1.3813
Initial Composition: K2O 0.0100
Initial Composition: H2O 2.9910
Initial Temperature: 1383
Increment Temperature: -10.00
Mode: Fractionate Solids

Thanks in advance!

[Paula]

See here - https://magmasource.caltech.edu/forum/index.php/topic,833.msg1420.html#msg1420

The amphibole project did not turn out as planned, due to Covid. But we are still chipping away at it. And interesting things are coming out of Mark Ghiorso and co-workers MELTS+DEW model, which includes F and Cl that could be key to stabilizing amphibole. E.g:

https://conf.goldschmidt.info/goldschmidt/2023/meetingapp.cgi/Paper/13890

So I guess the advice to watch this space (or spaces) still applies.

Paula