Hello everyone! I’m conducting simulations related to the heterogeneity of the lithosphere and the relation with melt in the 2D whole mantle model. I have already employed a viscoplastic model, which includes the viscosity of diffusion creep, plastic yield, and weakening. I am concerned about melt generation and the influence of melt depletion on mantle flow and the lithosphere. But I’m currently using a post-processing melt fraction to calculate melt. I have some confusion about how to implement melt depletion:
I want to implement melt depletion (density change) while maintaining the viscosity using the viscoplastic model (I have noted the conflict between plasticity and the melt transport). I’d like to use the compositing model to combine the two models (viscoplastic model and melt model) to change the density. But when I have more than one composition (like crust, mantle, etc.), how should I set the density for each composition? Which model should I choose for the Density option in the Compositing model (viscoplastic or melt model) to make the depletion-related density change considered?
Given the large time scale of the model, I’m more concerned about the impact of density changes caused by melt products on mantle flow and how it influences future melt distribution, at a relatively larger scale. So I prefer a simpler (rougher) melt extraction process(including melt extraction and depletion). I’ve noticed previous discussions that suggest modifying the code to achieve this. I would like to seek some advice on how to implement this functionality.
Thank you very much for your attention and any insights.
Thank you for posting your questions to the forum, which I’ve posted some initial responses to below.
I’d like to use the compositing model to combine the two models (viscoplastic model and melt model) to change the density.
While you can use a compositing approach, I suggest using the reactive fluid transport material model (see material model documentation).
This material model directly composite a base model (such as visco plastic), with the functionality for handling fluid transport and reactions.
This material model also uses a new reaction module design, which will allow users to more easily develop and implement new reaction modules in a modular fashion.
But when I have more than one composition (like crust, mantle, etc.), how should I set the density for each composition? Which model should I choose for the Density option in the Compositing model (viscoplastic or melt model) to make the depletion-related density change considered?
I think the best approach would be to do this in a new reaction model, where you use the name of the field and field type to determine how the densities (and other properties change).
I’ve noticed previous discussions that suggest modifying the code to achieve this. I would like to seek some advice on how to implement this functionality.
Can you specify what additional information is needed beyond the advice provided in the linked discussions?
I think the first step would be to write out the equations and workflows for a simple analytical case, such as the reactions and change in material properties as P-T conditions change at a single point.
This benchmark then provides a reference case that you can try to reproduce in ASPECT with the new functionality.
Sorry for my late reply, and thank you very much for your response! I have checked the reactive fluid transport material model, and it appears to meet the requirements for the combination of viscosity and density changes due to melting in the existing model. I will further learn how to set up this model.
And sorry for the confusion regarding the second point. My previous explanation was not very clear. Although ASPECT has already implemented a more complex melt migration process, which includes the interaction between melt and solid, it might be too complicated for my model to fully consider all these intricate details. To simplify, I want to create a model that only focuses on melt extraction and density changes, without considering melt migration. Your suggestions are very helpful for me, as I am not quite familiar with the ASPECT code process and the equations it implements. I think I need to understand the equations, workflow, and the sequence of ASPECT’s operations more deeply to know where to make the necessary modifications.
Thank you once again for your reply and assistance!