Speciation problem with multiple minerals in phase diagram using Act2

[Qingping1]

 

Hello,

       I hope you're doing well. I've been working on creating a pH-log with a SiO2(aq) phase diagram using the conditions specified in Figure 1 (P=1000 bars, T=250°C, a(Mg++)=0.1, a(Fe++)=0.001, a(Ca++)=0.001, a(k+)=0.001, a(O2(aq))=0.001). I've referred to the input parameters shown in Figure 2, but it seems that when using GWB, I'm not able to generate the same minerals as depicted in Figure 1. I'm wondering if there are any important details that I might have overlooked. I would be immensely grateful if you could kindly assist me in reproducing the phase diagram accurately. Your guidance would be highly appreciated. Thank you very much.

Best regards,

Qingping 

Fig 1

 

 

 

 

 

Fig2

 

 

 

 

 

 

Fig.3

chlorite,mica,and epidote.ac2

[Jia Wang]

Hello Qingping,

Thank you for providing the example and input file. A couple of suggestions to help you get started with troubleshooting.

You should check if the dataset you are using to generate the diagram is the same as the one used to generate the published figure. For example, I see that the diagram includes the species HAlO2(aq). The default thermodynamic dataset, thermo.tdat, does not include this species. You may want to check in the paper for more information regarding the thermodynamic data used to generate the diagram. You should also check that the equilibrium constants for the reactions in the dataset you are using are also the same as the ones used in Figure 1. The GWB program installs a set of default thermo datasets that you can find in your Gtdata folder or download again from our webpage.

Also note that the GWB programs consider all reactions in the dataset. The mineral fields that appear shows the most stable minerals. If minerals that appear are not considered in your system, you set the program to exclude those minerals in the Suppress dialog (Config menu -> Suppress…).

Hope this helps,
Jia Wang
Aqueous Solutions LLC

[Qingping1]

9 hours ago, Jia Wang said:

Hello Qingping,

Thank you for providing the example and input file. A couple of suggestions to help you get started with troubleshooting.

You should check if the dataset you are using to generate the diagram is the same as the one used to generate the published figure. For example, I see that the diagram includes the species HAlO2(aq). The default thermodynamic dataset, thermo.tdat, does not include this species. You may want to check in the paper for more information regarding the thermodynamic data used to generate the diagram. You should also check that the equilibrium constants for the reactions in the dataset you are using are also the same as the ones used in Figure 1. The GWB program installs a set of default thermo datasets that you can find in your Gtdata folder or download again from our webpage.

Also note that the GWB programs consider all reactions in the dataset. The mineral fields that appear shows the most stable minerals. If minerals that appear are not considered in your system, you set the program to exclude those minerals in the Suppress dialog (Config menu -> Suppress…).

Hope this helps,
Jia Wang
Aqueous Solutions LLC

Hi Jia,

         Thank you for your helpful suggestions. I'll review the dataset and equilibrium constants to ensure they match the published figure. Your advice on using the Suppress dialog is also noted. Your assistance is greatly appreciated.

[John Washington]

Hello,

I was wondering if you could answer my question on plotting in ACT2.  I recently plotted log Al3+ vs pH to show the stability field for gibbsite.  Then I added to the default thermodynamic dataset the equilibrium constants reported by Kirk Nordstrom for 'microcrystalline gibbsite' and 'amorphous Al(OH)3'.  What I want to do is show all three mineral stability fields, each contained in the more stable field of the next.  I am just returning to GWB after about 10 years; I did this with an earlier version of GWB I think but I don't see how to do this now.  For the time being, I copy-pasted graphs in PowerPoint to achieve my end primitively -- I am pasting this below to show you what I want.

Is there a more elegant way to generate this graph in GWB, showing all three solid phases, gibbsite, microcrystalline gibbsite, and amorphous Al(OH)3? 

Thanks very much for any advice,

John

 

[Brian Farrell]

Hi John,

No, there is no way to combine the diagrams in Act2. PowerPoint is the way to go.

Regards,

Brian Farrell
Aqueous Solutions LLC

[John Washington]

Thank you Brian.  I must have used PowerPoint to generate my figure 10 years ago as well then.  Time fogs the memory. --John