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Earth and Space Sciences · Glossary

What is Activity diagram?

Also known as: activity diagram (mineral stability)

Definition 15.8 University Earth and Space Sciences — Year 3 · Chapter 15 — Water–Rock Interaction

An activity diagram (mineral stability) divides a plane of activity ratios of a water, such as log⁡(aKX+/aHX+)\log(a_{\ce{K+}}/a_{\ce{H+}}) against log⁡aHX4SiOX4\log a_{\ce{H4SiO4}}, into the fields where each mineral of a chemical system is the stable one.

Stability fields in the system K2O–Al2O3–SiO2–H2O at 25\, C, with the saturation of quartz (dashed) and amorphous silica (dotted). Three invented waters: A, a dilute tropical stream; B, a stream on granite; C, a deep ground water in granite.
Stability fields in the system KX2O\ce{K2O}–AlX2OX3\ce{Al2O3}–SiOX2\ce{SiO2}–HX2O\ce{H2O} at 25 ∘C25\,{}^{\circ}\mathrm{C}, with the saturation of quartz (dashed) and amorphous silica (dotted). Three invented waters: A, a dilute tropical stream; B, a stream on granite; C, a deep ground water in granite.
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