Use this geological calculation for a transparent first-pass interpretation of measured rock, soil, fluid, well, stratigraphic, isotopic, geophysical, or seismic data under an explicitly selected model.

SiO2

SiO2 weight percent.

Na2O

Na2O weight percent.

K2O

K2O weight percent.

Prepare total-alkalis versus silica coordinates and the Le Bas silica band for plotting on the IUGS TAS diagram. The tool evaluates the supplied inputs together and returns the named outputs below; it does not infer omitted operating conditions or change the units shown.^[1]

Total alkalis

Na2O + K2O in weight percent.

SiO2

SiO2 weight percent.

K2O/Na2O

K2O divided by Na2O.

Silica band

TAS horizontal axis band at the given silica content.

• Classification diagrams and geochemical ratios require appropriate normalization, oxidation-state treatment, volatile basis, analytical quality, alteration screening, mineral or whole-rock context, and a composition within the method's calibration domain.
• Use finite inputs in the displayed units and preserve more precision than the final presentation requires. Independently verify safety-critical, financial, compliance, or production decisions.

Compare independent measurements and models, retain units and analytical metadata, propagate uncertainty, and validate interpretations against logs, cores, maps, laboratory data, or field observations.

• Harker Diagram Silica Calculator

  Prepare one silica-versus-oxide point pair for a Harker variation diagram.

• QAPF Plot Calculator

  Normalize modal quartz, alkali feldspar, plagioclase and feldspathoid contents to QAPF coordinates and pick the plotting triangle.

• AFM Diagram Calculator

  Convert whole-rock oxides to AFM coordinates with ferric iron recalculated to FeO for the tholeiitic-calc-alkaline AFM triangle.