Skip to main content Accessibility help

Formation of granular-textured layers and laminae within the Rhum crystal pile

  • I. M. Young (a1) and C. H. Donaldson (a1)


In the allivalite of cyclic unit 9 in the Eastern Layered Series of the Rhum intrusion there is an undulatory contact between a relatively dense pyroxene-rich rock and a less dense pyroxene-poor rock. The three-dimensional form of this contact resembles that developed between two fluids deforming under the influence of gravity. Minor layers, laminae and lamination in these rocks in places cut across the contact between the pyroxene-rich and pyroxene-poor rock types. They are, therefore, inferred to post-date the formation of the contact and hence to have formed within a porous crystal pile on the chamber floor. Possible mechanisms of formation are discussed but their origin remains unclear. These observations cast doubt on the common assumption that the combination of granular (cumulus) textures and layering structures is sufficient evidence on which to infer equilibrium of granular crystals with a contemporary magma.



Hide All
Allen, J. R. L. 1970. Physical Processes of Sedimentation. London: George Allen & Unwin. 248 pp.
Allen, J. R. L. 1977. The possible mechanics of convolute lamination in graded sand beds. Journal of the Geological Society of London 134, 1931.
Anketell, J. M., Cegla, J. & Dzulynski, S. 1970. On the deformational structures in systems with reversed density gradients. Annals of the Geological Society of Poland 40, 329.
Becke, F. 1903. Uber Mineralbestand und Struktur der Kristallinen Schiefer. International Geological Congress. Report of the 9th Session, Vienna, 353–70.
Berner, H., Ramberg, H. & Stephansson, O. 1972. Diapirism in theory and experiment. Tectonophysics 15, 197218.
Bowen, N. L. 1919. Crystallization-differentiation in magmas. Journal of Geology 27, 393430.
Brothers, R. N. 1964. Petrofabric analyses of Rhum and Skaergaard layered rocks. Journal of Petrology 5, 255–74.
Brown, G. M. 1956. The layered ultrabasic rocks of Rhum, Inner Hebrides. Philosophical Transactions of the Royal Society of London B 240, 153.
Butcher, A. R. 1985. Channelled metasomatism in Rhum layered cumulates – evidence from late-stage veins. Geological Magazine 122, 503–18.
Campbell, I. H. 1978. Some problems with the cumulus theory. Lithos 11, 311–23.
Casey, J. F. & Karson, J. A. 1982. Magma chamber profiles from the Bay of Islands ophiolite complex. Nature 292, 295301.
Collinson, J. D. & Thompson, D. B. 1982. Sedimentary Structures. London: George Allen & Unwin. 194 pp.
Correns, C. W. 1949. Growth and dissolution of crystals under linear pressure. Discussions of the Faraday Society 5, 267–71.
Donaldson, C. H. 1982. Origin of some of the Rhum harrisites by segregation of intercumulus liquid. Mineralogical Magazine 45, 201–9.
Dunham, A. C. 1965. A new type of banding in ultrabasic rocks from central Rhum, Inverness-shire, Scotland. American Mineralogist 50, 1410–20.
Dunham, A. C. & Wadsworth, W. J. 1978. Cryptic variation in the Rhum layered intrusion. Mineralogical Magazine 42, 347–56.
Huppert, H. H. & Sparks, R. S. J. 1980. The fluid dynamics of a basaltic magma chamber replenished by hot, dense ultrabasic magma. Contributions to Mineralogy and Petrology 75, 279–89.
Irvine, T. N. 1980. Magmatic density currents and cumulus processes. American Journal of Science 280, A 158.
Irvine, T. N. 1982. Terminology for layered intrusions. Journal of Petrology 23, 127–62.
Lee, C. A. 1981. Post-deposition structures in the Bushveld Complex mafic sequence. Journal of the Geological Society of London 138, 327–41.
Loney, R. A. & Himmelberg, G. K. 1983. Structure and petrology of the La Perouse gabbro intrusion, Fairweather Range, southeastern Alaska. Journal of Petrology 24, 377423.
McBirney, A. R. & Noyes, R. M. 1979. Crystallization and layering of the Skaergaard intrusion. Journal of Petrology 20, 487554.
Marsh, B. D. 1979. Island arc development: observations, experiments and speculations. Journal of Geology 87, 687713.
Morse, S. A. 1979. Kiglapait geochemistry. I. Systematics, sampling and density. Journal of Petrology 20, 555–90.
Morse, S. A. 1980. Basalts and Phase Diagrams New York: Springer-Verlag. 493 pp.
Morse, S. A. & Nolan, K. M. 1984. Origin of strongly reversed rims on plagioclase in cumulates. Earth and Planetary Science Letters 68, 485–98.
Parsons, I. & Butterfield, A. W. 1981. Sedimentary features of the Nunarssuit and Klokken syenites, S. Greenland. Journal of the Geological Society of London 138, 289306.
Raiswell, R. 1971. The growth of Cambrian and Liassic concretions. Sedimentology 17, 147–71.
Ramberg, H. 1967. Gravity, deformation and the Earth's Crust. London: Academic Press. 214 pp.
Schuiling, R. D. & Wensink, H. 1962. Porphyroblastic and poikiloblastic textures. The growth of large crystals in a solid medium. Neues Jahrbuch für Mineralogie Monatshefte, 247–54.
Shaw, H. R. 1980. The fracture mechanisms of magma transport from the mantle to the surface. In Physics of Magmatic Processes (ed. Hargraves, R. B.), pp. 201–64. Princeton: University Press.
Sparks, R. S. J., Huppert, H. E., Kerr, R. C., McKenzie, D. P. & Tait, S. R. 1985. Postcumulus processes in layered intrusions. Geological Magazine 122, 555–68.
Spry, A. 1969. Metamorphic Textures. Oxford: Pergamos Press. 350 pp.
Thy, P. & Wilson, J. R. 1980. Primary igneous load-cast deformation structures in the Fongen-Hyllingen layered basic intrusion, Trondheim Region, Norway. Geological Magazine 117, 363–71.
Wager, L. R. & Brown, G. M. 1968. Layered Igneous Rocks. Edinburgh: Oliver & Boyd. 588 pp.
Wager, L. R., Brown, G. M. & Wadsworth, W. J. 1960. Types of igneous cumulates. Journal of Petrology 1, 7385.
Whitehead, J. A. & Luther, D. S. 1975. Dynamics of laboratory diapir and plume models. Journal of Geophysical Research 80, 705–17.
Yoder, H. S. 1978.Basic magma generation and aggregation. Bulletin Volcanologique 41, 301–16.
Young, I. M. 1984. Mixing of interstitial and supernatant liquids in Rhum layered intrusion. Mineralogical Magazine 48, 345–50.

Formation of granular-textured layers and laminae within the Rhum crystal pile

  • I. M. Young (a1) and C. H. Donaldson (a1)


Full text views

Total number of HTML views: 0
Total number of PDF views: 0 *
Loading metrics...

Abstract views

Total abstract views: 0 *
Loading metrics...

* Views captured on Cambridge Core between <date>. This data will be updated every 24 hours.

Usage data cannot currently be displayed