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Orbicular Igneous Rocks

Igneous rocks + Hornblende-hornfels facies

Required Geological Setting

Accretionary complexes + Plutonic rocks


Igneous rocks having orbicular structures. The boundaries between orbicules and a massive matrix is clear. Mineral assemblages in orbicules change concentrically. In some cases, hornfels fragments originated from sedimentary rocks are observed at the center of orbicules. Orbicular igneous rocks distribute tabular at the upper part of stocks of igneous rocks. Orbicular igneous rocks are reported from S-type granites, granodiorites, diorites, gabbroes, andesites, and stratiform magmatic deposits. Origin of igneous rocks is not known well.

Orbicular igneous rocks

Distribution of obicular igneous rocks described in this site. Red is ilmenite-series granites corresponding to S-type granites, and blue is magnetite-series granites corresponding to I-type granites.

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