The Fluid-absent Partial Melting of a Zoisite-bearing Quartz Eclogite from 1{middle dot}0 to 3{middle dot}2 GPa; Implications for Melting in Thickened Continental Crust and for Subduction-zone Processes |
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Authors: | SKJERLIE KJELL P; PATINO DOUCE ALBERTO E |
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Institution: | 1DEPARTMENT OF GEOLOGY, UNIVERSITY OF TROMSØ, 9037 TROMSØ, NORWAY
2DEPARTMENT OF GEOLOGY, UNIVERSITY OF GEORGIA, ATHENS, GA 30602, USA |
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Abstract: | Fluid-absent melting experiments on a zoisite- and phengite-bearingeclogite (omphacite, garnet, quartz, kyanite, zoisite, phengiteand rutile) were performed to constrain the melting relationsof these hydrous phases in natural assemblages, as well as themelt and mineral compositions produced by their breakdown. From1·0 to 3·2 GPa the solidus slopes positively from1·5 GPa at 850°C to 2·7 GPa at 1025°C,but bends back at higher pressures to 975°C at 3·2GPa. The melt fraction is always low and the melt compositionsalways felsic and become increasingly so with increasing pressure.The normative AbAnOr compositions of the initialmelts vary from tonalites at 1·0 GPa to tonalitetrondhjemitesat 1·5 GPa, adamellites at 2·1 and 2·7GPa, and to true granites at 3·2 GPa. At pressures < |
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