Contributions to Mineralogy and Petrology

, Volume 94, Issue 4, pp 452–460 | Cite as

A sapphirine-cordierite-garnet-sillimanite granulite from Enderby Land, Antarctica: implications for FMAS petrogenetic grids in the granulite facies

  • S. L. Harley


A quartz-absent magnesian paragneiss layer from Mount Sones, in the Archaean Napier complex of Enderby Land, Antarctica, contains the stable divariant FMAS assemblage sapphirine (XMg=78) — cordierite (XMg=87) — garnet (XMg=51) — sillimanite. Rare green spinel (XMg=53.5, ZnO=2.65wt%) occurs as inclusions mainly within sapphirine, but also within sillimanite and garnet. Late thin coronas of cordierite (XMg=90.5) mantle sapphirine in contact with extensively exsolved anorthoclase. The mineral textures are interpreted to indicate the former stability of a hypersthene-quartz absent assemblage followed by the development of the FMAS equilibrium assemblage sapphirine-cordierite-garnet-sillimanite (sp, hy, qz) and further divariant reaction involving the consumption of sapphirine. The (sp, hy, qz) assemblage uniquely defines the stable P-T reaction topology appropriate to granulites from the Napier Complex, as this paragenesis is allowed in the grids of Hensen (1971, 1986) but is not possible in other grids which assume the stability of a sapphirine-absent ([sa]) FMAS invariant point involving the phases spinel, garnet, hypersthene, cordierite, sillimanite and quartz. The observed mineral assemblages and textures are consistent with peak metamorphism between the [sp] and [hy] invariant points of Hensen (1971), at temperatures of 930–990° C, followed by cooling on a lower dP/dT trajectory towards the (sp, qz) univariant line. The initial spinel-bearing assemblage was stabilized by Zn and to a lesser extent by Ni and Cr, and hence does not require a marked decrease in temperature and increase in pressure to produce the (sp, hy, qz) assemblage. It is inferred that fO2 conditions substantially lower than those used in the experiments of Annersten and Seifert (1981) prevailed in the high-grade metamorphism in the Napier Complex.


Cordierite Mineral Texture Phase Spinel Sillimanite Invariant Point 
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  1. Annersten H, Seifert F (1981) Stability of the assemblage orthopyroxene-sillimanite-quartz in the system MgO-FeO-Fe2O3-Al2O3-SiO2-H2O. Contrib Mineral Petrol 77:158–165Google Scholar
  2. Caporuscio FA, Morse SA (1978) Occurrence of sapphirine plus quartz at Peekskill, New York. Am J Sci 278:1334–1342Google Scholar
  3. Ellis DJ (1980) Osumilite-sapphirine-quartz granulites from Enderby Land, Antarctica: P-T conditions of metamorphism, implications for garnet-cordierite equilibria and the evolution of the deep crust. Contrib Mineral Petrol 74:201–210Google Scholar
  4. Ellis DJ, Sheraton JW, England RN, Dallwitz WB (1980) Osumilite-sapphirine-quartz granulites from Enderby Land, Antarctica — mineral assemblages and reactions. Contrib Mineral Petrol 72:123–143Google Scholar
  5. Grew ES (1980) Sapphirine+quartz association from Archaean rocks in Enderby Land, Antarctica. Am Mineral 65:821–836Google Scholar
  6. Grew ES (1982) Osumilite in the sapphirine-quartz terrane of Enderby Land, Antarctica: implications for osumilite petrogenesis in the granulite facies. Am Mineral 67:762–787Google Scholar
  7. Harley SL (1983) Regional geobarometry — geothermometry and metamorphic evolution of Enderby Land, Antarctica, pp 25–30. In: Oliver RL, James PR, Jago JB (eds) Antarctic Geoscience. Aust Acad Sci, Canberra, 1983 pp 697Google Scholar
  8. Harley SL (1985) Garnet-orthopyroxene bearing granulites from Enderby Land, Antarctica: metamorphic pressure-temperature-time evolution of the Archaean Napier Complex. J Petrol 26:819–856Google Scholar
  9. Harley SL, Black LP (1986) The Archaean geological evolution of Enderby Land, Antarctica. In: Tarney J, Park R Evolution of the Lewisian and comparable precambrian high-grade terranes. Spec Publ Geol Soc Lond (in press)Google Scholar
  10. Harris NBW, Holland TJB (1984) The significance of cordieritehypersthene assemblages from the Beitbridge region of the Central Limpopo Belt: evidence for rapid decompression in the Archaen? Am Mineral 69:1037–1049Google Scholar
  11. Hensen BJ (1971) Theoretical phase relations involving cordierite and garnet in the system MgO-FeO-Al2O3-SiO2. Contrib Mineral Petrol 33:191–214Google Scholar
  12. Hensen BJ (1986) Theoretical phase relations involving garnet and cordierite revisited: the influence of oxygen fugacity on the stability of sapphirine and spinel in the system Mg-Fe-Al-Si-O. Contrib Mineral Petrol 92:362–367Google Scholar
  13. Hensen BJ, Green DH (1973) Experimental study of the stability of cordierite and garnet in pelitic compositions at high pressures and temperatures. Contrib Mineral Petrol 38:151–166Google Scholar
  14. Parsons I, Brown WL (1983) A TEM and microprobe study of a two-perthite alkali gabbro: Implications for the ternary feldspar system. Contrib Mineral Petrol 82:1–12Google Scholar
  15. Sandiford MA (1985). The metamorphic evolution of granulites at Fyfe Hills: implications for Archaean crustal thickness in Enderby Land, Antarctica. J Metam Geol 3:155–178Google Scholar
  16. Sheraton JW, Black LP (1983) Geochemistry of precambrian gneisses: relevance for the evolution of the East Antarctic shield. Lithos 16:273–296Google Scholar
  17. Sheraton JW, Offe LA, Tingey RJ, Ellis DJ (1980) Enderby Land, Antarctica — and unusual Precambrian high grade metamorphic terrain. J Geol Soc Aust 27:305–317Google Scholar
  18. Vielzeuf D (1983) The spinel and quartz associations in high grade xenoliths from Tallante (N.E. Spain) and their potential use in geothermometry and barometry. Contrib Mineral Petrol 82:301–311Google Scholar
  19. Waters DJ (1986) Metamorphic history of sapphirine-bearing and related magnesian gneisses from Namaqualand, South Africa. J Petrol 27:541–565Google Scholar
  20. Windley BF, Ackermand D, Herd RK (1984) Sapphirine/kornerupine-bearing rocks and crustal uplift history of the Limpopo belt, South Africa. Contrib Mineral Petrol 86:342–358Google Scholar

Copyright information

© Springer-Verlag 1986

Authors and Affiliations

  • S. L. Harley
    • 1
  1. 1.Department of Earth SciencesUniversity of OxfordOxfordUK

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