[aspect-devel] subduction and magmatism

Tue Apr 17 09:02:15 PDT 2018

Dear Juliane,

thank you very much on such a lengthy and detailed response, explanation and suggestions. I do want to model two-phase flow, implement hydrous melting and track the migration of the melt. Incorporating brittle deformation would be preferable. I presumed this would require changing the code. Thank you for clarifying that to me. I am definitely interested and would like to work on this problem. I am glad that your team is working on this now. I certainly will contact you in near future.

Thanks again!

Best regards,

Nikola

________________________________
From: Juliane Dannberg <judannberg at gmail.com>
Sent: Monday, April 16, 2018 11:58 PM
To: aspect-devel at geodynamics.org; Никола Станковић
Subject: Re: [aspect-devel] subduction and magmatism

Dear Nikola,

it is certainly possible to model geodynamic processes in the lithosphere with ASPECT, and a lot of the current development goes in this direction.
I don't have much experience with subduction models, but Anne Glerum's models would certainly be a good starting point.

For melting in subduction zones, the question would be how exactly you want to deal with the magmatism. Do you just want to know how much melt is generated, but without any active influence on the model evolution? Or do you want to model two-phase flow, where the melt flows with a different velocity than the solid? And, if it is the latter, how do you want to deal with fluids/dehydration of the slab (do you want to model water etc. as a separate phase, or composition of the different phases)?

I think all of those models would require modifying the code to a certain degree. While ASPECT includes a number of simple melting parameterizations, at the moment, there is no model for hydrous melting. So depending on how you want to treat the melt, you would have to extend one of the existing melting parameterizations (for example, ASPECT has the anhydrous melting parametrization from Katz et al., 2003, so it should be straightforward to modify it so that it also includes the hydrous melting described in Katz et al., 2003), or add a new one. You could then simply track the water content as a compositional field in the model, and compute the amount of melt that is generated for each given temperature and pressure. So if this is all you want to look at, I feel this should be easy to do.

If you also want to track the migration of melt, I think this would be more difficult, as this would probably require tracking the composition (and water content) of the melt, and you would also need a hydrous melting model that gives you some sort of partitioning for the water content and the rest of the composition (so, for a certain pressure, temperature and bulk composition, what is the equilibrium melt fraction, what is the composition of the solid, what is the composition of the melt). Tracking the melt composition is something that we plan to include in ASPECT in the near future, but it is not in the current development version. However, we're working on that, and if you're interested in something like this and want to help implementing it, we can certainly think about what exactly you need and how to add this to ASPECT together. Finally, if you plan to include brittle deformation in your model, and also want to model two-phase flow at the same time, this would be a very difficult problem (in general, not just in ASPECT). We are working on material descriptions in ASPECT that allow this kind of model, but it needs a lot of testing and there are many numerical difficulties involved.

So I guess what I am saying is, you can certainly use ASPECT to model subduction, magmatism and deformation of the lithosphere. You should just be aware that depending on how complex you want your models to be, it would require modifying the code. And we are of course happy to help with any questions that might come up.

I hope that helps!

Best,
Juliane

----------------------------------------------------------------------
Juliane Dannberg
Project Scientist, UC Davis
jdannberg.github.io<https://jdannberg.github.io/>
Juliane Dannberg's Homepage<https://jdannberg.github.io/>
jdannberg.github.io
Juliane Dannberg Assistant Project Scientist. Modeling and Visualization Forum for Deep Carbon Computational Infrastructure for Geodynamics Department of Earth and Planetary Sciences

On 04/16/2018 07:33 AM, Никола Станковић wrote:

Hello everyone,

I would like to ask if it is possible to model geodynamic processes in the lithosphere with ASPECT. I am trying to model subduction, and the associated magmatism. I am aware that this code is primarily developed for simulating convection. However, I have found and successfully used some plugins developed for this code, namely subduction plugin by Anne Glerum, as well as viscoplastic plugin.

I am also aware that ASPECT incorporates partial melting, however I haven't seen published papers dealing with modeling magmatism on a detailed scale. In Dannberg and Heister (2016) the melting is associated with a plume. In Glerum et al (2017) subduction is modeled mechanically, there is no associated magmatism.

What I am asking is, whether it is a good idea to use ASPECT to model subduction process, in greater detail as well as detailed magmatism and deformation of the lithosphere. Also if anyone has succeeded in this, any information about it would be very beneficial to me.

Best regards,

Nikola Stanković

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