| Reference Type | Journal (article/letter/editorial) |
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| Title | Solid solution and cation ordering limits in high-temperature sodic pyroxenes from the Nybö eclogite pod, Norway |
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| Journal | Mineralogical Magazine | ISSN | 0026-461X |
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| Authors | Carpenter, M. A. | Author |
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| Smith, D. C. | Author |
| Year | 1981 (March) | Volume | 44 |
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| Issue | 333 |
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| Publisher | Mineralogical Society |
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| Download URL | https://rruff.info/doclib/MinMag/Volume_44/44-333-37.pdf+ |
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| DOI | doi:10.1180/minmag.1981.44.333.04Search in ResearchGate |
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| Generate Citation Formats |
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| Mindat Ref. ID | 3216 | Long-form Identifier | mindat:1:5:3216:6 |
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| GUID | 0 |
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| Full Reference | Carpenter, M. A., Smith, D. C. (1981) Solid solution and cation ordering limits in high-temperature sodic pyroxenes from the Nybö eclogite pod, Norway. Mineralogical Magazine, 44 (333) 37-44 doi:10.1180/minmag.1981.44.333.04 |
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| Plain Text | Carpenter, M. A., Smith, D. C. (1981) Solid solution and cation ordering limits in high-temperature sodic pyroxenes from the Nybö eclogite pod, Norway. Mineralogical Magazine, 44 (333) 37-44 doi:10.1180/minmag.1981.44.333.04 |
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| In | (1981, March) Mineralogical Magazine Vol. 44 (333) Mineralogical Society |
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| Abstract/Notes | AbstractA range of sodic pyroxenes (Jd78Ac2Aug20Jd24Ac9Aug67) from the Nybö eclogite pod, Norway, have been examined by electron-microprobe analysis and by transmission electron microscopy.. Five different microprobes give generally compatible results and new analyses completely fill the natural composition gap in jadeite-rich omphacites with ∼ 3–12% acmite, confirming complete miscibility at high temperatures (⩾ 700 °C). Crystals with omphacite compositions around jadeite: augite = 1:1 contain antiphase domains resulting from the C2/c → P2/n cation ordering transformation. Exsolution microstructures were not observed, from which it is concluded that there are no two-phase regions separating the P2/n and C2/c stability fields at high temperatures (∼ 620–750 °C) and that cooling was too rapid for exsolution to occur in the jadeite/omphacite and omphacite/augite low-temperature solvi. Crystals whose compositions depart significantly from Jd:Aug= 1:1 have weak, diffuse h + k = odd reflections in selected area electron diffraction patterns which are interpreted as being due to short-range ordering outside the true P2/n stability field. The short-range ordering and lack of exsolution are consistent with a previous suggestion that the order/disorder transformation in omphacite is second (or higher) order in character. The average antiphase domain sizes (up to ∼ 3500 Å) are larger than any previously recorded in omphacites and are consistent with available petrological evidence for a long period of annealing at high temperatures before tectonic uplift and cooling. |
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