Country rock (geology)

Country rock is a geological term meaning the rock native to an area. It is similar and in many cases interchangeable with the terms basement and wall rocks.

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The term is used to denote the usual strata of a region in relation to the rock which is being discussed or observed.

The following are areas in geology when the term country rock is used;

• Intrusive settings; when describing a pluton or dike one may describe the igneous rock as intruding the surrounding country rock, the rock into which the pluton has intruded.
• In describing the texture or structure of lit-par-lit intrusion, the intrusive is described in relation to the country rock or wall rock
• Alluvial settings; when describing recent alluvium the material that has arrived through volcanic, glacial or fluvial action can be described as a veneer on the country rock
• In economic geology; country rock is the gangue or unmineralised rocks within which the ore deposit or veins are set. This is, again essentially interchangeable with the term wall rock.