Author Topic: Display compositions for fractional crystallization for multiple temperatures  (Read 185 times)

dufourfrederic

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Hello,

I am contacting you because I am having trouble to find out how rhyolite MELTS works for extracting compositions for a temperature range by fractional crystallization.

First, is this action is possible to do ?

Here is the composition for my basalt:

Initial Composition: SiO2 49.2
Initial Composition: TiO2 0.901
Initial Composition: Al2O3 14.13
Initial Composition: Fe2O3 8.65
Initial Composition: Cr2O3 0.00
Initial Composition: FeO 7.78
Initial Composition: MnO 0.076
Initial Composition: MgO 8.63
Initial Composition: CaO 4.57
Initial Composition: Na2O 0.57
Initial Composition: K2O 3.88
Initial Composition: P2O5 0.12
Initial Composition: H2O 0.5
Initial Temperature: 1220.00
Final Temperature: 700.00
Increment Temperature: 10.00
Initial Pressure: 1000.00
Final Pressure: 1000.00
Increment Pressure: 0.00
dp/dt: 0.00
log fo2 Path: None

I would like to compute rhyolite MELTS from 1220 celsius to 700 celsius, with an increment of 10 degrees celsius, and obtain the composition every 10 degrees.

The result of this would be next, to calculate the M value from the melt composition at each step (from Boenhke et al., 2013), determine the partition coefficient, and then work out the Zircon saturation temperature. 
After that, I would have to use Zr of my WR data between the available melt and trace the evolution of the Zr concentration of the melt during fractional crystallization. Finally I should find out the zircon saturation point in the melt by plotting the Zr concentration vs Temperature.

I hope it is clear and understanding.
Thank you very much for your help !

Frederic Dufour

Paula

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Hi,

Yes, it's possible, though I haven't tried it on as Fe-rich a composition as this. What you are trying to do is pretty similar to the "getting started" example, so I suggest you try working through that first:

https://magmasource.caltech.edu/forum/index.php/topic,133.0.html

For displaying the results, especially on Windows, the best option is MELTS for Excel's "Combine tbl" function:

https://magmasource.caltech.edu/forum/index.php/topic,828.0.html

Are you running this in the Windows Subsystem for Linux? If you haven't already, it's worth setting up some links so that the input and output files are stored with your regular Windows files and not inside Ubuntu (see towards the bottom of this post):

https://magmasource.caltech.edu/forum/index.php/topic,841.0.html

Paula

dufourfrederic

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Dear Paula,

Thank you very much for your answer and your help.

Yes, I have been running rMELTS for Windows under Linux and set up my links in my windows files previously.

However, I still can't figure out the problems for running my sample. If I run with Fe2O3 and FeO, the program is aborted and it states that the liquid component Fe2O3 has a negative mole fraction. But if I run without FeO, the program fails and states that the quadratic minimization algorithm has failed to converge (I 've put fractionate liquids in both cases).

I don't know how to solve the problem and finally get a composition after fractional crystallization.

Would you have an idea about that ?

Thank you very much,
Frederic

Paula

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Hi Frederic,

I take it you meant "fractionate solids"? You could try running it with the fO2 buffer on e.g. your starting composition is roughly QFM+3 (if you put this into the .melts file it needs to be "+3FMQ"). Even without the fO2 buffer it almost gets there (fails at ~720oC) so you may have enough to work out the zircon saturation.

Paula

dufourfrederic

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Hi Paula,

thank you very much for your help it was very helpful !

Best,
Frederic