Abstract
The partitioning of sodium between pairs of coexisting potassium and plagioclase feldspars extracted from metamorphic rocks is examined to test its suitability for use as a geothermometer. Rocks from eight different areas were studied in detail, most areas including two zones of metamorphism; in this way a range of metamorphic grade from middle amphibolite facies to various grades of granulite facies was investigated. Data from the metamorphic areas indicate that the distribution of sodium between coexisting feldspar phases cannot give any indications of relative metamorphic grades. Some factors are suggested to account for the different behavior of sodium partitioning between natural and experimental systems. The results for sodium distribution contrast with the temperature-dependent distribution of trace quantities of strontium between the same feldspar pairs.
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