Country rock (geology)
Country rock is a geological term meaning the rock native to an area, in which there is an intrusion of viscous geologic material, commonly magma, or perhaps rock salt (in salt domes) or unconsolidated sediments.
Country rock can denote the widespread lithology of a region in relation to the rock which is being discussed or observed.
Settings in geology when the term country rock is used include:
Most intrusions into country rock are via magma. Usually, country rock is intruded by an igneous body of rock which formed when magma forced upward through fractures, or melted through overlying rock. Magma then cooled into solid rock, different from the surrounding country rock. Sometimes, a fragment of country rock will break off and become incorporated into the intrusion, and is called a xenolith, from Greek, ξένος, xenos, "strange,", and λίθος, lithos, the ancient Greek word for "stone."
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