Isograd
Sign in to saveAlso known as isogradient, isogradients, isogrades, isograde
__NOTOC__ An isograd is a concept used in the study of metamorphic rocks. The metamorphic grade of such a rock is a rough measure of the degree of metamorphism it has undergone, as characterised by the presence of certain index minerals. An isograd is a theoretical surface comprising points all at the same metamorphic grade, and thus separates metamorphic zones whose rocks contain different index minerals.
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__NOTOC__ An isograd is a concept used in the study of metamorphic rocks. The metamorphic grade of such a rock is a rough measure of the degree of metamorphism it has undergone, as characterised by the presence of certain index minerals. An isograd is a theoretical surface comprising points all at the same metamorphic grade, and thus separates metamorphic zones whose rocks contain different index minerals.
On geological maps focusing on metamorphic terranes (or landscapes underlain by metamorphic rocks), the boundaries between rocks of different metamorphic grade are commonly demarcated by isograd lines. The garnet isograd, for example, would separate regions containing garnet from those without.
Excerpted from Wikipedia’s “Isograd” article, available under the CC BY-SA 4.0 licence.