You cannot use the caliper log and
GR spectrometry RATIOS (Thorium/Uranium, Thorium/Potassium and Potassium/Uranium) to compute mineral voumes in the mineral models using Mineral Solver in Interactive Petrophysics.
The input logs must be functions of the properties of the minerals in the model.
Caliper log is a mechanical measurement of the hole size and is not a function of mineral properties, meaning it is independent of mineral properties.
The hole size can be anything inside clays, quartz, calcite, dolomite etc.
Likewise, the spectral GR RATIOS are also not direct functions of minerals in the formation. They are just ratios of the three components of the spectral GR log.
Therefore, they should not be used as input curves to solve for mineral volumes.
You can use the actual Potassium, Thorium and Uranium curves as input for your mineral models if you want.
However, you need to know the specific values of K, Th and U for each of the minerals in your model.