How can the parent rock help identify a metamorphic rock?
Published by admin on October 30, 2010
Because they generally (unless there’s a lot of metasomatism) have the same overall chemistry.
Sandstones are dominated by quartz so will result in its metamorphic equivalent being a meta-quartzite. The texture changes, the chemistry doesn’t.
Limestones are dominated by calcite so will result in its metamorphic equivalent being also dominated by calcite as a marble. The texture changes, the chemistry doesn’t.
Shales are dominates by clay minerals. This results in their metamorphic equivalents making use of the same potassium, aluminium & silicate radicles / ions & transforming them into new metamorphic minerals; the very fine particle size of the clay minerals helps this process. The texture AND the chemistry changes but the chemical changes are simply a rearrangement of the ingredients available resulting in schists, phyllites or slates.
Finally, moving on to igneous rocks, similar things can be said about a granite that is transformed into a gneiss or a basalt transformed into an amphibolite (possibly with the addition of only water).
Because they generally (unless there’s a lot of metasomatism) have the same overall chemistry.
Sandstones are dominated by quartz so will result in its metamorphic equivalent being a meta-quartzite. The texture changes, the chemistry doesn’t.
Limestones are dominated by calcite so will result in its metamorphic equivalent being also dominated by calcite as a marble. The texture changes, the chemistry doesn’t.
Shales are dominates by clay minerals. This results in their metamorphic equivalents making use of the same potassium, aluminium & silicate radicles / ions & transforming them into new metamorphic minerals; the very fine particle size of the clay minerals helps this process. The texture AND the chemistry changes but the chemical changes are simply a rearrangement of the ingredients available resulting in schists, phyllites or slates.
Finally, moving on to igneous rocks, similar things can be said about a granite that is transformed into a gneiss or a basalt transformed into an amphibolite (possibly with the addition of only water).
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