• journal_title：Geology
• Contributor：G. Stevens ; J. D. Clemens ; G. T. R. Droop
• Publisher：Geological Society of America
• Date：1995-
• Format：text/html
• Language：en
• Identifier：10.1130/0091-7613(1995)023<0925:HCIGAC>2.3.CO;2
• journal_abbrev：Geology
• issn：0091-7613
• volume：23
• issue：10
• firstpage：925

Huge volumes of S-type granitic and volcanic rocks, as well as many migmatites, are the products of fluid-absent partial melting in metasedimentary protoliths at granulite-facies conditions. Thus, it is essential to know the controls on the fertility of metasedimentary rocks as magma sources. In the present experiments on fluid-absent partial melting of biotite in metasedimentary rocks, cordierite proportion is inversely correlated with melt fraction. At constant pressure (P) and temperature (T), this variation in melt proportion is a function of bulk-rock Mg number [100 Mg/(Mg + Fe)] and activity of alumina ((alpha)_Al(subscript)2_O(subscript)3). However, melt compositions are essentially unaffected. At 0.5 GPa, the calculated H₂O contents of cordierite decrease as T increases from 850 to 1000 ° C. In aluminous metasedimentary rocks, the cordierite stability field considerably overlaps with the conditions of fluid-absent melting in the middle to lower crust, severely restricting melt productivity. Consequently, metapelites may be much less fertile sources of granitic magma than metagraywackes.