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Continuous fractional crystallization fugacity problem

Started by jakemoore, January 29, 2009, 12:11:07 PM

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jakemoore

Anyone,

I'm trying to run a simple fractional exercise, trying to get a handle on the LLOD for a "parental" magma, which is basaltic.  I've run into a fugacity problem, and I'm tearing my hair out trying to solve it.

environment variables
ADIABAT_VERSION MELTS
ADIABAT_MODE isobaric
ADIABAT_MAXT 1600
ADIABAT_MINT 900
ADIABAT_DELTAT -10
ADIABAT_CRASH_FILE adiabat.out
ADIABAT_CELSIUS_OUTPUT true
ADIABAT_CONTINUOUS true
ADIABAT_MINF 0.005

.melts file (my "parental" melt)
Initial Composition: SiO2 46.85
Initial Composition: TiO2 2.54
Initial Composition: MgO 10.48
Initial Composition: MnO 0.16
Initial Composition: CaO 10.01
Initial Composition: Na2O 2.59
Initial Composition: Al2O3 12.75
Initial Composition: P2O5 0.4
Initial Composition: K2O 0.95
Initial Composition: FeO 11.5
Initial Temperature: 1600
Initial Pressure: 8000
log fo2 Path: NONE

batch file
1
baxter.melts
5
3
+2
0
4
1
11
adiabat.out
0

The calculation fails on the first attempt and is as follows:
Initial Adiabat_1ph calculation at: P 8000.000000, T 1600.000000
liquid: 98.531 g 47.55 2.58 12.94 3.05 8.92 0.16 10.64 10.16 2.63 0.96 0.41
Activity of H2O = 0  Melt fraction = 1
Can't compute fO2 without FEO and FE2O3
Can't compute fO2 without FEO and FE2O3


This batch file sets the fugacity buffer at QFM+2 and leaves it set throughout the entire run, but I also tried turning the buffer off after a single, buffered (option 3) calculation as well.  No luck.  To make sure the problem wasn't in my batch file, I tried running with some of the standard .melts files that came with the program using my batch file, each of which ran okay.

I'm sure it's a really simple solution, but I'm not seeing it.  Can anyone point me in the right direction?

Thanks,
Jacob


pluffi

Jacob,

First, let's see if I understand you problem correctly. You want to run an isobaric fractional crystallization of the composition given in the .melts file; the process should start at 1600 C / 8000 bar and proceed in -10 C steps. If so, and you're still looking for the solution, here you go (the solution is trivial indeed, and has nothing to do with fugacity).

The error hides in your environment file. If you want to run fractional crystallization, you should unset "ADIABAT_CONTINUOUS true", which is dedicated to fractional melting, and set "ADIABAT_FRACTIONATE_SOLIDS true" instead. You've imposed a superliquidus starting PT condition for your system, case in which removing the melt is not okay - this is what generates the error message. I suspect that your runs with the standard .melts compositions didn't crash because their initial T,P happened to be set below their liquidus. But that wasn't fractional crystallization either.

Peter

jakemoore

Peter,

Yes, that's the solution.  Some stray variables must have made it into my file.  I knew it was something simple (and dumb) like that!

Much appreciated,
Jacob

Paula

El3m3nt's post is spam.  I guess posting random links on forums is a good method for search engine optimisation...  Shame to have to ban him / her - the El3m3nt name was rather appropriate here!