Why the intensive variables options doesn't work?

[Zou]

I am trying the example "Using MELTS to calculate an Isobaric, Isenthalpic Assimilation Model" in "Rhyolite-melts v1.2.0". But I can't type the temperature increment as undefined (n.a.) and the same as the dP/dT and any Enthalpy settings. Why this? Is the version problem or something? Please help me.  ;D

[Paula]

The graphical user interface was rewritten since those tutorials were made (and even the 'new' interface is best part of twenty years old, though the underlying models have been updated since). For explanations of some of the differences, see the [EX] Rhyolite-MELTS (GUI) version of tutorial: 'Quick start using MELTS' post.

Anyway, you don't need to type in 'n.a.'. Once you have selected "isenthalpic" mode, the program will know that the temperature increment does not need to be defined. The first calculation will be isothermal, which gives the initial enthalpy for the subsequent calculations. The enthalpy increment is defined by how much material you are assimilating and its temperature/composition.

Paula

[Zou]

The graphical user interface was rewritten since those tutorials were made (and even the 'new' interface is best part of twenty years old, though the underlying models have been updated since). For explanations of some of the differences, see the [EX] Rhyolite-MELTS (GUI) version of tutorial: 'Quick start using MELTS' post.

Anyway, you don't need to type in 'n.a.'. Once you have selected "isenthalpic" mode, the program will know that the temperature increment does not need to be defined. The first calculation will be isothermal, which gives the initial enthalpy for the subsequent calculations. The enthalpy increment is defined by how much material you are assimilating and its temperature/composition.

Paula

Thanks so much! That problem has been solved now. And do I need to stop this Assimilation Model manually? I find that this calculation does not stop automatically.
Also, when I try fractionation Model, there is a problem http://melts.ofm-research.org/Manual/UnixManGifs/Quadratic-Failure.GIF . I try to perturb the system a bit by changing T, P or bulk composition slightly and start the calculation again using the Execute/Halt entry on the Commands menu. But it doesn't work. What should I do in this case？ Thank you in advance.

Zou

[Paula]

Hi Zou,

The problem with the assimilation not stopping in isenthalpic mode is a bug. It should be fixed on the 'alphaMELTS branch' of the code hosted at the ENKI Code repository (the relevant project is called 'xMelts', although it's really rhyolite-MELTS/pMELTS; you would need to ask Mark Ghiorso for access).

However, none of the executables on the OFM site - Mac or Linux - reflect this edit. The Linux executables that I posted on the alphaMELTS links page, to deal with a different issue do have the isenthalpic assimilation bug fix. I will add Mac versions there when I get a chance.

For the fractionation model, you need to give a bit more information - what was the starting composition and conditions?

Cheers,
Paula

[Zou]

Hi Zou,

The problem with the assimilation not stopping in isenthalpic mode is a bug. It should be fixed on the 'alphaMELTS branch' of the code hosted at the ENKI Code repository (the relevant project is called 'xMelts', although it's really rhyolite-MELTS/pMELTS; you would need to ask Mark Ghiorso for access).

However, none of the executables on the OFM site - Mac or Linux - reflect this edit. The Linux executables that I posted on the alphaMELTS links page, to deal with a different issue do have the isenthalpic assimilation bug fix. I will add Mac versions there when I get a chance.

For the fractionation model, you need to give a bit more information - what was the starting composition and conditions?

Cheers,
Paula

Hi Paula,

Thanks for reply! I can't find "xMetls" at the ENKI Code repository. Maybe I must to ask Mark Ghiorso for access to find it? Also, I hope you can add Mac latest versions at the OFM site or alphaMELTS as soon as possible! 

For the fractionation model, I just tried the given example Using MELTS to calculate an Isobaric Crystal Fractionation Model.

Looking forward to your kind reply.

All the best,
Zou

[Paula]

Hi Zou,

Yes, for access to the xMelts code you will need to as Mark Ghiorso to add you to the ENKI group (or if you PM me your GitLab username I can ask him for you).

Mac executables with the bug fix are now available on the alphaMELTS links page. Hope that fixes things.

For the fractionation calculation, I haven't tried running it recently but I can't see why it would fail unless a step was missed. Did "Compute Redox State" work?

Cheers,
Paula

[Zou]

Hi Zou,

Yes, for access to the xMelts code you will need to as Mark Ghiorso to add you to the ENKI group (or if you PM me your GitLab username I can ask him for you).

Mac executables with the bug fix are now available on the alphaMELTS links page. Hope that fixes things.

For the fractionation calculation, I haven't tried running it recently but I can't see why it would fail unless a step was missed. Did "Compute Redox State" work?

Cheers,
Paula

Hi Paula,

First, thanks for the latest version. The Assimilation calculation can be finished and stopped automatically.

For the fractionation calculation, "Compute Redox State" worked. I just followed every step of the Using MELTS to calculate an Isobaric Crystal Fractionation Model exactly. And I also choose the "Fractionation Solid" entry in options menu. You could try to run this mode.

Cheers,
Zou 

[Paula]

Hi Zou,

It's been a long time but I finally did try that FC example in rhyolite-MELTS 1.0.2. It fails right as MgO is exhausted from the system. As rhyolite-MELTS makes adjustments to the (solid) quartz and sanidine end members to match the water-saturated ternary granite minimum, I'm not all that surprised that it affects the behavior in other very evolved compositions. To check, I also ran it in alphaMELTS 1.9 (which has MELTS rather than rhyolite-MELTS); clinopyroxene is dropped from the assemblage and the calculation continues down to 800 ^oC.

It's possible that one of the usual "what to do when MELTS fails" strategies e.g. reducing the temperature increment could help. But the point is that it's a change in the underlying model, and not anything you are doing that is different from the original example.

Paula