The Charnockite Geotherm

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Science  11 Nov 1977:
Vol. 198, Issue 4317, pp. 614-617
DOI: 10.1126/science.198.4317.614


Charnockite, a hypersthene-bearing granite, and other associated rocks of the charnockite series have a global distribution. These rocks, according to evidence from mineral-chemical and experimental phase equilibrium relations, formed or recrystallized at temperatures between 800° and 900°C and at relatively shallow depths of 6 to 12 kilometers. This evidence indicates the existence of geothermal gradients of 70° to 100°C per kilometer probably at various times, the latest being around 1300 x 106 years ago.