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News:
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Recent posts
#51
The MELTS family of algorithms, and scientific discussion / Re: Changes to Rhyolite-MELTS ...
Last post by Paula - February 20, 2025, 08:50:57 AMHi Felix,
alphaMELTS corrects the melting point of rutile (see Borisov & Aranovich, 2020), which becomes important for mafic pyroxenites. As the error existed when all the liquid calibrations were done, fixing the pure rutile point can mean rutile appears where you are not expecting it (put another way the "phase absent" constraints on rutile at the time of calibration were too loose). If this is a problem just suppress it - it was virtually impossible to crystalize rutile before so you're not going to miss anything!
As you mention, rhyolite-MELTS adjusts quartz properties to better model the granite ternary minimum and in alphaMELTS we also adjust tridymite and cristobalite to model explosive silicic magmatism on Mars. It's described in the supplementary materials of Payré et al., 2022. You may get tridymite or cristobalite crystallizing where you do not expect it but in this case it is likely down to kinetics in the real system. Again if needed just suppress those phases.
Borisov, A., & Aranovich, L., 2020. Rutile solubility and TiO2 activity in silicate melts: An experimental study. Chemical Geology, 556, 119817. https://www.sciencedirect.com/science/article/pii/S0009254120303569
Payré, V., Siebach, K. L., Thorpe, M. T., Antoshechkina, P., & Rampe, E. B., 2022. Tridymite in a lacustrine mudstone in Gale Crater, Mars: Evidence for an explosive silicic eruption during the Hesperian. Earth and Planetary Science Letters, 594, 117694. https://www.sciencedirect.com/science/article/pii/S0012821X22003302
The feldspar in alphaMELTS was split into plagioclase and alkali-feldspar to simplify bookkeeping. That has a small effect on the modeled sanidine content but well within analytical uncertainty for EMP. If you want something even closer to the original feldspar model e.g. to model the granite ternary minimum, then suppress plagioclase.
The standard state volume of apatite was corrected in alphaMELTS recently, but the difference is negligible.
I believe those are the only model changes versus the ENKI/xMELTS codebase. There are many changes replacing Numerical Recipes code with Gnu Science Library etc. but they should not change the results. If I think of anything else I'll update the post.
Best wishes,
Paula
alphaMELTS corrects the melting point of rutile (see Borisov & Aranovich, 2020), which becomes important for mafic pyroxenites. As the error existed when all the liquid calibrations were done, fixing the pure rutile point can mean rutile appears where you are not expecting it (put another way the "phase absent" constraints on rutile at the time of calibration were too loose). If this is a problem just suppress it - it was virtually impossible to crystalize rutile before so you're not going to miss anything!
As you mention, rhyolite-MELTS adjusts quartz properties to better model the granite ternary minimum and in alphaMELTS we also adjust tridymite and cristobalite to model explosive silicic magmatism on Mars. It's described in the supplementary materials of Payré et al., 2022. You may get tridymite or cristobalite crystallizing where you do not expect it but in this case it is likely down to kinetics in the real system. Again if needed just suppress those phases.
Borisov, A., & Aranovich, L., 2020. Rutile solubility and TiO2 activity in silicate melts: An experimental study. Chemical Geology, 556, 119817. https://www.sciencedirect.com/science/article/pii/S0009254120303569
Payré, V., Siebach, K. L., Thorpe, M. T., Antoshechkina, P., & Rampe, E. B., 2022. Tridymite in a lacustrine mudstone in Gale Crater, Mars: Evidence for an explosive silicic eruption during the Hesperian. Earth and Planetary Science Letters, 594, 117694. https://www.sciencedirect.com/science/article/pii/S0012821X22003302
The feldspar in alphaMELTS was split into plagioclase and alkali-feldspar to simplify bookkeeping. That has a small effect on the modeled sanidine content but well within analytical uncertainty for EMP. If you want something even closer to the original feldspar model e.g. to model the granite ternary minimum, then suppress plagioclase.
The standard state volume of apatite was corrected in alphaMELTS recently, but the difference is negligible.
I believe those are the only model changes versus the ENKI/xMELTS codebase. There are many changes replacing Numerical Recipes code with Gnu Science Library etc. but they should not change the results. If I think of anything else I'll update the post.
Best wishes,
Paula
#52
alphaMELTS for MATLAB/Python / Re: Suppressing liquid and cal...
Last post by Paula - February 20, 2025, 08:16:46 AMI haven't tried that particular example but you should be able to pass a "Suppress: liquid" string to setSystemProperties to turn off liquid and then a "Limit number: liquid 1" to turn it on again.
Garnet is the version with the corrected expressions, which I guess it what you mean by 'new', as that is what is in Mark Ghiorso's codebase. (Biotite on the other hand is the 'old' model, again to match Mark's codebase where possible.) Assumption was that if users need other models, including original MELTS, that they'll have to use alphaMELTS 1.X for backwards compatibility.
The methods should all have docstrings so you can do something like "help(meltsengine)". The possible inputs and outputs are described in the .py files - I don't think there's a more efficient way to examine those than opening the file.
Garnet is the version with the corrected expressions, which I guess it what you mean by 'new', as that is what is in Mark Ghiorso's codebase. (Biotite on the other hand is the 'old' model, again to match Mark's codebase where possible.) Assumption was that if users need other models, including original MELTS, that they'll have to use alphaMELTS 1.X for backwards compatibility.
The methods should all have docstrings so you can do something like "help(meltsengine)". The possible inputs and outputs are described in the .py files - I don't think there's a more efficient way to examine those than opening the file.
#53
alphaMELTS 2 text-menu interface / Re: Question about Equilibrium...
Last post by Paula - February 20, 2025, 07:47:25 AMIt sounds like you have one or more "Mode: fractionate" line(s) in your .melts file. Just delete them all and you'll get perfectly equilibrium crystallization.
#54
easyMelts / Re: [EX] easyMelts version of ...
Last post by Paula - February 20, 2025, 07:43:37 AMQFM P1 - the P stands for 'plus' and M for 'minus'.
#55
alphaMELTS for MATLAB/Python / Re: Suppressing liquid and cal...
Last post by lelkins - February 19, 2025, 06:55:39 AMFollow up -- I know the python version may not have all of this functionality, which is of course okay. Is there possibly a way to specify the garnet calibration (new vs old) yet, though?
#56
The MELTS family of algorithms, and scientific discussion / Changes to Rhyolite-MELTS ± Fl...
Last post by fboschetty - February 19, 2025, 03:34:33 AMDear Paul and Paula,
I'm hoping to test the Rhyolite-MELTS family of compositions against some evolved experimental compositions from LEPR.
I've read Gualda+ 2012 (10.1093/petrology/egr080) and Ghiorso & Gualda 2015 (10.1007/s00410-015-1141-8) to get a handle on how Rhyolite-MELTS was calibrated for evolved compositions.
I have also had a look through the GitHub and GitLab change logs for alphaMELTS for relevant changes since these two papers were published. The only relevant change I can find is that the Tridymite and Cristabolite pure phase models have been adjusted (https://github.com/magmasource/alphaMELTS?tab=readme-ov-file). Could you give me more detail on these changes and any others that I might have missed?
Best wishes,
Felix Boschetty
I'm hoping to test the Rhyolite-MELTS family of compositions against some evolved experimental compositions from LEPR.
I've read Gualda+ 2012 (10.1093/petrology/egr080) and Ghiorso & Gualda 2015 (10.1007/s00410-015-1141-8) to get a handle on how Rhyolite-MELTS was calibrated for evolved compositions.
I have also had a look through the GitHub and GitLab change logs for alphaMELTS for relevant changes since these two papers were published. The only relevant change I can find is that the Tridymite and Cristabolite pure phase models have been adjusted (https://github.com/magmasource/alphaMELTS?tab=readme-ov-file). Could you give me more detail on these changes and any others that I might have missed?
Best wishes,
Felix Boschetty
#57
easyMelts / Re: [EX] easyMelts version of ...
Last post by liushanke - February 17, 2025, 04:47:45 PMHi, I have known the answer: "P" stands for "+" and "M" for "-". Sorry for interrupting the thread.
Quote from: liushanke on February 17, 2025, 12:05:35 AMHi everyone,
I'm using eastMelts and have a question regarding setting the oxygen fugacity. I need to constrain my simulation to QFM+1, but I'm unsure which option to choose from the "Oxygen Fugacity" tab.
I see several options related to QFM, such as QFM P1~P3 and QFM M1~M7. Which of these options corresponds most closely to QFM+1? I've checked the manual and done some online searching, but haven't been able to find a definitive answer.
Any help or clarification would be greatly appreciated!
Thanks,
Shanke
#58
alphaMELTS for MATLAB/Python / Suppressing liquid and calcula...
Last post by lelkins - February 17, 2025, 03:12:47 PMHi Paula! I'm doing some initial testing with alphaMELTS 2 for python, and I would like to do a similar adiabatic/isentropic decompression melting calculation to the old alphaMELTS approach, with a suppressed liquid phase to determine entropy for a given Tp and bulk composition, and then calculating a melting path with the liquid turned back on. So far, I haven't been able to figure out all the necessary commands for python functions and calculations from the available tutorials, though. I know the python versions have been in beta and might not have all of this set up, but I'm finding it hard to tell what functions are possible. Is there an example, or just a list of the python tools and where they are in the package? or maybe some tips on suppressing phases and defining entropy, to get started?
Thanks!
Thanks!
#59
alphaMELTS 2 text-menu interface / Question about Equilibrium vs....
Last post by liushanke - February 17, 2025, 02:32:16 AMHello everyone,
I'm working with alphaMELTS (via alphamelts_win64.exe on Windows) and I'm having a bit of trouble understanding how to properly run equilibrium crystallization simulations.
With easyMelts, I can easily switch between fractional and equilibrium modes by choosing whether or not to fractionate solid phases (if my understanding is correct). However, I'm unsure how to achieve a true equilibrium mode within the alphamelts_win64.exe interface.
When I select option 8 in the main menu ("Solid phase(s) to change settings for"), I'm presented with options that seem to be primarily related to fractional crystallization:
Suppress all solid phases
Allow all standard solid phases; optionally limit maximum number
Do not fractionate any solid phases
Fractionate all standard solid phases (current)
Change whether residual solid is measured...
Adjust amount of solid fractionated during fractionation...
My understanding is that these options are primarily concerned with controlling fractional crystallization. Is it actually possible to perform a strict equilibrium crystallization simulation using alphamelts_win64.exe on Windows?
While the difference between the two modes may be minor for some magma systems, I'm concerned about the potential for significant discrepancies in certain situations, especially at higher pressures and water contents.
Any guidance on this would be greatly appreciated.
Thanks in advance,
Shanke
I'm working with alphaMELTS (via alphamelts_win64.exe on Windows) and I'm having a bit of trouble understanding how to properly run equilibrium crystallization simulations.
With easyMelts, I can easily switch between fractional and equilibrium modes by choosing whether or not to fractionate solid phases (if my understanding is correct). However, I'm unsure how to achieve a true equilibrium mode within the alphamelts_win64.exe interface.
When I select option 8 in the main menu ("Solid phase(s) to change settings for"), I'm presented with options that seem to be primarily related to fractional crystallization:
Suppress all solid phases
Allow all standard solid phases; optionally limit maximum number
Do not fractionate any solid phases
Fractionate all standard solid phases (current)
Change whether residual solid is measured...
Adjust amount of solid fractionated during fractionation...
My understanding is that these options are primarily concerned with controlling fractional crystallization. Is it actually possible to perform a strict equilibrium crystallization simulation using alphamelts_win64.exe on Windows?
While the difference between the two modes may be minor for some magma systems, I'm concerned about the potential for significant discrepancies in certain situations, especially at higher pressures and water contents.
Any guidance on this would be greatly appreciated.
Thanks in advance,
Shanke
#60
easyMelts / Re: [EX] easyMelts version of ...
Last post by liushanke - February 17, 2025, 12:05:35 AMHi everyone,
I'm using eastMelts and have a question regarding setting the oxygen fugacity. I need to constrain my simulation to QFM+1, but I'm unsure which option to choose from the "Oxygen Fugacity" tab.
I see several options related to QFM, such as QFM P1~P3 and QFM M1~M7. Which of these options corresponds most closely to QFM+1? I've checked the manual and done some online searching, but haven't been able to find a definitive answer.
Any help or clarification would be greatly appreciated!
Thanks,
Shanke
I'm using eastMelts and have a question regarding setting the oxygen fugacity. I need to constrain my simulation to QFM+1, but I'm unsure which option to choose from the "Oxygen Fugacity" tab.
I see several options related to QFM, such as QFM P1~P3 and QFM M1~M7. Which of these options corresponds most closely to QFM+1? I've checked the manual and done some online searching, but haven't been able to find a definitive answer.
Any help or clarification would be greatly appreciated!
Thanks,
Shanke