| 1: crystallizes; 2: olivine and crystallize; 3: pyroxene and crystallize; 4: plagioclase crystallizes | Plutonic rock in North America |
|---|---|
| Le Maitre editor 2002 Igneous Rocks: A Classification and Glossary of Terms, Recommendations of the International Union of Geological Sciences, Subcommission of the Systematics of Igneous Rocks | examples and Chemical classification also extends to differentiating rocks that are chemically similar according to the TAS diagram, for instance;• While cooling, the magma evolves in composition because different minerals crystallize from the melt |
At the bottom of the magma reservoir, a forms.
24| While cooling, the magma evolves in composition because different minerals crystallize from the melt | At the bottom of the magma reservoir, a forms |
|---|---|
| examples and Chemical classification also extends to differentiating rocks that are chemically similar according to the TAS diagram, for instance;• | Chemical: total alkali-silica content for classification used when modal or mineralogic data is unavailable:• Close-up of granite an intrusive igneous rock exposed in , India |
This is not an exact method, because the classification of igneous rocks also depends on other components than silica, yet in most cases it is a good first guess.
14| If the approximate volume fractions of minerals in the rock are known, the rock name and silica content can be read off the diagram | Basic classification scheme for igneous rocks on their |
|---|---|
| 1: crystallizes; 2: olivine and crystallize; 3: pyroxene and crystallize; 4: plagioclase crystallizes |
.