| Reference Type | Journal (article/letter/editorial) |
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| Title | Petrogenesis of migmatites in the Huntly-Portsoy area, north-east Scotland |
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| Journal | Mineralogical Magazine |
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| Authors | Ashworth, J. R. | Author |
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| Year | 1976 (September) | Volume | 40 |
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| Issue | 315 |
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| Publisher | Mineralogical Society |
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| Download URL | https://rruff.info/doclib/MinMag/Volume_40/40-315-661.pdf+ |
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| DOI | doi:10.1180/minmag.1976.040.315.01Search in ResearchGate |
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| Generate Citation Formats |
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| Mindat Ref. ID | 6957 | Long-form Identifier | mindat:1:5:6957:5 |
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| GUID | 0 |
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| Full Reference | Ashworth, J. R. (1976) Petrogenesis of migmatites in the Huntly-Portsoy area, north-east Scotland. Mineralogical Magazine, 40 (315) 661-682 doi:10.1180/minmag.1976.040.315.01 |
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| Plain Text | Ashworth, J. R. (1976) Petrogenesis of migmatites in the Huntly-Portsoy area, north-east Scotland. Mineralogical Magazine, 40 (315) 661-682 doi:10.1180/minmag.1976.040.315.01 |
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| In | (1976, September) Mineralogical Magazine Vol. 40 (315) Mineralogical Society |
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| Abstract/Notes | SummaryMigmatites are described from the Sillimanite-potash-feldspar Zone of the aureole around the Newer Basic suite of synorogenic intrusions. The lowest-grade migmatites are trondhjemitoid (characterized by the assemblage quartz-plagioclase-biotite) or muscovite-granitoid (quartz-plagioclase potash-feldspar-muscovite-sillimanite-biotite). With increasing grade, a transition occurs to cordierite-granitoid assemblages (quartz-plagioclase-potash-feldspar-cordierite-garnet-sillimanite-biotite), which persist to the highest grades observed, where there are also noritoid migmatites (quartz-plagioclase-orthopyroxene-cordierite-biotite). The trondhjemitoids are texturally simple because the minerals did not undergo dehydration reactions. Textural immaturity and consistently cotectic modal compositions indicate that their leucosomes originated as melts. Scatter of plagioclase compositions suggests that the partial melting occurred in small closed systems. The other migmatites have more fusible compositions, so it is deduced that they also underwent partial melting. Retrograde reaction textures are used to infer the sequence of reactions, involving muscovite and biotite, by which melting proceeded during prograde evolution. Whereas the fugacity of water probably varied among spatially associated trondhjemitoid leucosomes, in the muscovite-granitoids it was constrained to an approximately constant value, at given pressure and temperature, by the buffering effect of the mineral assemblage. |
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