Contact metamorphic rocks

Synonym

Heat metamorphic rocks

Overview

Metamorphic rocks formed by contacting sedimentary rocks with high temperature magma. There are two types of contact metamorphic rocks: Contact metamorphic rocks formed by intrusion of magma in sedimentary rocks, and contact metamorphic rocks formed as accidental lithic fragments in magma chamber. Sedimentary rocks suffer re-crystallization by high temperature and supply of materials from magma. Contact metamorphic rocks show granular texture as they were formed under hydrostatic pressure condition, whereas other metamorphic rocks show shistose texture. Degree of metamorphism is higher near the heat source, plutonic rock block formed from magma. It may be difficult to distinguish contact metamorphic rocks from low-P metamorphic rocks because contact metamorphic rocks gradually change to low-P metamorphic rocks in some cases.

Contact metamorphic facies series

Albite-Epidote-hornfels facies > Hornblende-hornfels facies > Pyroxene-hornfels facies > Sanidinite facies