Welcome! This project uses the olivine-spinel geothermometer (Jianping et al., 1995) and olivine-orthopyroxene-spinel geo-oxybarometer (Sack and Ghiorso, 1991a,b; Wood, 1990). The calculators in the Jupyter notebook are built upon the ThermoEngine package from the ENKI project.
To use the geothermo-barometer app, click the 'launch binder' tab under this paragraph, which will take you to repository interface. The interface is still under developement, however the geothermo-barometer is operational. Once you hit the 'lauch binder' tab it will take you to the ENKI-portal interface, where you can dismiss any pop-ups and click the green button at the bottom of the screen to access the Jupyter Notebook of interest which is called "Ol-Opx-SplV14.ipynb". Double click the orange tab on the left hand side with that name, and then hit the 'Run' button that appears at the top of the notebook (it is a triangle symbol - like a 'play' button). Once you have done that, scroll to the bottom of the screen where you can input your mineral data and the notebook will output the associated temperature and oxygen fugacity.
If you use the results derived from this app in publications, please cite it using the DOI badge [in development].
The equations used in this notebook include:
Olivine-Spinel geothermometer (Jianping et al., 1995)
T°K=((4250×Y_Cr^Spl )+1343)/((ln_Kd^0)+(1.825×Y_Cr^Spl)+0.571) (Eq. 10)
Where:
T°K = Temperature in Kelvin
Y_Cr^Spl = mole fraction of Cr in spinel [Cr/Cr+Al+Fe^3+]
ln_Kd^0 = ln_Kd - 2(Y_Fe3+^Spl) (Eq. 9)
Where:
ln_Kd = ln(((X_Mg^Ol)(X_Fe^Spl))/((X_Fe^Ol)(X_Mg^Spl))) (Eq. 2 from Fabries, 1979)
X_Mg^Ol = mole fraction of Mg in olivine [Mg/Mg+Fe]
X_Fe^Ol = mole fraction of Fe in olivine [Fe/Mg+Fe]
X_Mg^Spl = mole fraction of Mg in spinel [Mg/Mg+Fe]
X_Fe^Spl = mole fraction of Fe in spinel [Fe/Mg+Fe]
Y_Fe3+^Spl = mole fraction of Fe3+ in spinel [Fe3+/Cr+Al+Fe3+]
Olivine-Orthopyroxene-Spinel oxybarometer (Wood, 1990)
log(fO2)=[logfO2 (QFM)_(P,T)+220/T+0.35-0.0369P/T] - [12(log(X_Fe^Ol))-(2620/T)((X_Mg^Ol)^2)] + [3(log(X_Fe^M1*X_Fe^M2 )^opx]+ [2(log(a_Fe3O4^spl))]
Where:
P = pressure in bars --> inputted by the user
log(fO2)= -2441.9/T°K+8.29
[12(log(X_Fe^Ol))-(2620/T)((X_Mg^Ol)^2)] --> X_Mg^Ol = mole fraction of forsterite, and X_Fe^Ol = mole fraction of fayalite
[3(log(X_Fe^M1*X_Fe^M2 )^opx]
where... after the code calculates the individual cation values, including Al(IV), Al(VI), Cr, and Ti are placed into the M1 position of the opx formula, while Ca and Mn cations are placed in M2. After this, Fe and Mg cations are evenly distributed between the M1 and M2 postions, and thus X_Fe^M1 and X_Fe^M2 can be calculated, where they represent the atomic fractions of Fe in the M1 and M2 positions.
[2(log(a_Fe3O4^spl))]
where... a_Fe3O4^spl represents the activity of magnetite in spinel, which is calculated using the quinary model for cubic oxides from Sack and Ghioso (1991a, b)