Exley, R. A., Smith, J. V., Hervig, R. L. (1982) Cr-rich spinel and garnet in two peridotite xenoliths from the Frank Smith mine South Africa: Significance of Al and Cr distribution between spinel and garnet. Mineralogical Magazine, 45 (337) 129-134 doi:10.1180/minmag.1982.045.337.14
| Reference Type | Journal (article/letter/editorial) | ||
|---|---|---|---|
| Title | Cr-rich spinel and garnet in two peridotite xenoliths from the Frank Smith mine South Africa: Significance of Al and Cr distribution between spinel and garnet | ||
| Journal | Mineralogical Magazine | ISSN | 0026-461X |
| Authors | Exley, R. A. | Author | |
| Smith, J. V. | Author | ||
| Hervig, R. L. | Author | ||
| Year | 1982 | Volume | 45 |
| Issue | 337 | ||
| Publisher | Mineralogical Society | ||
| Download URL | https://rruff.info/doclib/MinMag/Volume_45/45-337-129.pdf+ | ||
| DOI | doi:10.1180/minmag.1982.045.337.14Search in ResearchGate | ||
| Generate Citation Formats | |||
| Mindat Ref. ID | 3324 | Long-form Identifier | mindat:1:5:3324:8 |
| GUID | 0 | ||
| Full Reference | Exley, R. A., Smith, J. V., Hervig, R. L. (1982) Cr-rich spinel and garnet in two peridotite xenoliths from the Frank Smith mine South Africa: Significance of Al and Cr distribution between spinel and garnet. Mineralogical Magazine, 45 (337) 129-134 doi:10.1180/minmag.1982.045.337.14 | ||
| Plain Text | Exley, R. A., Smith, J. V., Hervig, R. L. (1982) Cr-rich spinel and garnet in two peridotite xenoliths from the Frank Smith mine South Africa: Significance of Al and Cr distribution between spinel and garnet. Mineralogical Magazine, 45 (337) 129-134 doi:10.1180/minmag.1982.045.337.14 | ||
| In | (1982) Mineralogical Magazine Vol. 45 (337) Mineralogical Society | ||
| Abstract/Notes | AbstractPeridotite xenoliths 73β106 and 73β109 have coarse textures. All minerals in 73β106 are very Ti-rich, and include olivine (Fo 87.6), orthopyroxene (En 90.0), garnet (core TiO2 0.8, Cr2O3 7; rim 1.4, 4 wt. %), spinel (TiO2 5, Cr2O3 38), clinopyroxene (A12O3 1β8) secondary mica (TiO2 6, Cr2O3 2.5 near garnet 0.5 away from garnet), and serpentine (FeO 5β12) enclosing perovskite-rimmed ilmenite and minute apatites. All minerals in peridotite 73β109 are Ti-poor, and include olivine (Fo 92.6), orthopyroxene (En 93.6), garnet (Cr2O3 3.1β3.8), spinel (55), ureyitic diopside, primary mica (TiO2 0.06, Cr2O3 1.0, BaO 0.5, Cl 0.04), and serpentine (FeO 2β23). Various thermometers indicate βΌ 1350K (73β106) and 1100K (73β109). The low Al2O3 in the orthopyroxenes gives 39β47 kb for 73β109 from the Wood-Banno barometer. In 73β106, the spinel lies in secondary mica next to the garnet rim, whereas the spinel of 73β109 occurs in grains enclosed by garnet. The former assemblage indicates diffusion-dependent disequilibrium, whereas the latter is attributed to simultaneous growth of spinel and garnet, perhaps consequent upon exsolution from orthopyroxene. Complex behaviour was found for the Cr/Al distribution in published analyses of garnet and spinel. The 73β109 pair lies near the Thaba Putsoa trend, and the 73β106 assemblages are displaced towards the kelyphite region in which garnet and spinel have similar Cr/Al. Spinel and garnet may coexist over a 30 kb pressure interval ranging from βΌ 16 kb for low bulk Cr to βΌ 40 kb for high Cr. | ||
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