Hostname: page-component-cd9895bd7-lnqnp Total loading time: 0 Render date: 2024-12-24T16:26:14.023Z Has data issue: false hasContentIssue false
  • English
  • Français

Sulphide droplets-and the Unit 11/12 chromite band, Rhum: a mineralogical study

Published online by Cambridge University Press:  01 May 2009

A. C. Dunham  and
F. C. F. Wilkinson
A. C. Dunham
Affiliation:
Department of Geology, University of Hull, HU6 7RX, U.K.
F. C. F. Wilkinson
Affiliation:
Department of Geology, University of Hull, HU6 7RX, U.K.
Get access Rights & Permissions [Opens in a new window]

Abstract

A microscopic and electron microprobe investigation has been made of six samples of the allivalite–chromitite–peridotite band at the junction of Units 11 and 12, Eastern Layered Series, Rhum. Analyses are presented of olivine, plagioclase and pyroxene, the plagioclase showing reverse zoning in the chromitite. Sulphide droplets occur within and above the chromitite, and contain pyrrhotite, pentlandite, cubanite, bornite, digenite, chalcocite, native copper and electrum, as well as chromite zoned to magnetite, spinel and ilmenite. The variation from aluminous chromite to chromite in the chromitite is confirmed by analyses of five new traverses. The rocks formed during and just after the time when new magma entered the magma chamber. The variation in the chromite compositions is ascribed mainly to magmatic variation in composition due to the mixing process.

Type
Articles
Information
Geological Magazine , Volume 122 , Issue 5 , September 1985 , pp. 539 - 548
Copyright
Copyright © Cambridge University Press 1985

Access options

Get access to the full version of this content by using one of the access options below. (Log in options will check for institutional or personal access. Content may require purchase if you do not have access.)

References

Brown, G. M. 1956. The layered ultrabasic rocks of Rhum, Inner Hebrides. Philosophical Transactions of the Royal Society of London B 240, 1–53.Google Scholar
Buchanan, D. L. & Jones, M. J. (eds) 1984. Sulphide Deposits in Mafic and Ultramafic Rocks. London: The Institution of Mining and Metallurgy, 164 pp.Google Scholar
Craig, J. R. & Scott, S. D. 1974. Sulfide phase equilibria. Chapter 5 in Sulfide Mineralogy (ed. Ribbe, P. H.), pp. CS1–CS110. Mineralogical Society of America Short Course Notes, Volume 1.Google Scholar
Dunham, A. C. 1970. The emplacement of the Tertiary igneous complex of Rhum. In Mechanism of Igneous Intrusion (eds. Newall, G. and Rast, N.), pp. 23–32. Liverpool: The Seel House Press.Google Scholar
Dunham, A. C., Gandy, M. K. & Taylor, A. P. 1976. Experimental investigation of the basalt–pyrite system at 1 atmosphere pressure, and some geological implications. In Progress in Experimental Petrology. Third Progress Report of Research Supported by N.E.R.C. at Edinburgh and Manchester Universities, 1972–1975, (ed. Biggar, G. M.), pp. 83–8. N.E.R.C. Publications Series D, No. 6.Google Scholar
Dunham, A. C. & Wadsworth, W. J. 1978. Cryptic variation in the Rhum layered intrusion. Mineralogical Magazine 42, 347–56.CrossRefGoogle Scholar
Dunham, A. C. & Wilkinson, F. C. F. 1978. Accuracy, precision and detection limits of energy-dispersive electron-microprobe analyses of silicates. X-ray Spectrometry 7, 50–6.CrossRefGoogle Scholar
Gibb, F. G. F. 1976. Ultrabasic rocks of Rhum and Skye: the nature of the parent magma. Journal of the Geological Society of London 132, 209–22.CrossRefGoogle Scholar
Henderson, P. 1975. Reaction trends shown by chrome-spinels of the Rhum layered intrusion. Geochimica el Cosmochimica Acta 39, 1035–44.CrossRefGoogle Scholar
Henderson, P. & Suddaby, P. 1971. The nature and origin of the chrome-spinel of the Rhum layered intrusion. Contributions to Mineralogy and Petrology 33, 21–31.CrossRefGoogle Scholar
Huppert, H. H. & Sparks, R. S. J. 1980. The fluid dynamics of a basaltic magma chamber replenished by influx of hot, dense ultrabasic magma. Contributions to Mineralogy and Petrology 75, 279–89.CrossRefGoogle Scholar
Irvine, T. N. 1974. Formation of chromitite layers. In Annual Report of the Director, Geophysical Laboratory, Carnegie Institution of Washington Yearbook 73, pp. 311–16. Washington.Google Scholar
Misra, K. C. & Fleet, M. E. 1973. The chemical composition of synthetic and natural pentlandite assemblages. Economic Geology 68, 518–39.CrossRefGoogle Scholar
Morimoto, N. & Koto, K. 1970. Phase relations of the Cu–S system at low temperatures: stability of anilite. American Mineralogist 55, 106–17.Google Scholar
Muan, A. 1975. Phase relations in chromium oxide-containing systems at elevated temperatures. Geochimica et Cosmochimica Acta 39, 791–802.CrossRefGoogle Scholar
Osborn, E. F. & Muan, A. 1960. The system MgO–Al2O3–SiO2. Plate 3 in Phase Equilibrium Diagrams of Oxide Systems. Columbus, Ohio: American Ceramic Society and Edward Orton Jr. Ceramic Foundation.Google Scholar
Palacz, Z. A. & Tait, S. R. 1985. Isotopic and geochemical investigation of unit 10 from the Eastern Layered Series of the Rhum Intrusion, Northwest Scotland. Geological Magazine 122, 485–90.CrossRefGoogle Scholar
Putnis, A. & Price, G. D. 1979. The nature and significance of exsolved phases in some chrome spinels from the Rhum layered intrusion. Mineralogical Magazine 43 519–26.CrossRefGoogle Scholar
Skinner, B. J. & Peck, D. L. 1969. An immiscible sulfide melt from Hawaii. In Magmatic Ore Deposits (ed. Wilson, H. D. B.), pp. 310–22. Economic Geology Monographs No. 4.CrossRefGoogle Scholar
Wadsworth, W. J. 1961. The ultrabasic rocks of south-west Rhum. Philosophical Transactions of the Royal Society of London B244, 21–64.Google Scholar
Wager, L. R., Vincent, E. A. & Smales, A. A. 1957. Sulphides in the Skaergaard intrusion, East Greenland. Economic Geology 52, 855–903.CrossRefGoogle Scholar
Young, I. M. 1984. Mixing of supernatant and interstitial fluids in the Rhum layered intrusion. Mineralogical Magazine 48, 345–50.CrossRefGoogle Scholar