Hostname: page-component-586b7cd67f-rcrh6 Total loading time: 0 Render date: 2024-11-20T19:17:56.840Z Has data issue: false hasContentIssue false
  • English
  • Français

Variations in magnetic properties of Unit 10, Eastern Layered Intrusion, Isle of Rum, Scotland: implications for patterns of high temperature hydrothermal alteration

Published online by Cambridge University Press:  03 November 2011

J. Housden ,
W. O'Reilly  and
S. J. Day
J. Housden
Affiliation:
Department of Physics, University of Newcastle upon Tyne, Newcastle upon Tyne, NE1 7RU
W. O'Reilly
Affiliation:
Department of Physics, University of Newcastle upon Tyne, Newcastle upon Tyne, NE1 7RU
S. J. Day
Affiliation:
Department of Geography & Geology, Cheltenham and Gloucester College of Higher Education, Cheltenham, GL50 4AZ
Get access Rights & Permissions [Opens in a new window]

Abstract

An in situ magnetic susceptibility survey of Unit 10 of the Eastern Layered Intrusion of the Isle of Rum, in a line perpendicular to the strike, was carried out as a guide to selecting sampling sites for subsequent laboratory magnetic studies. These laboratory studies indicate that the dominant magnetic phase is magnetite. An effective particle size of the magnetite was derived from the magnetic data: it was found that high concentrations (∼0·3%) of magnetite in the perioditites were achieved by the presence of fewer but larger particles. The regions of lower magnetite concentration (∼0·01%), which are mainly in the plagioclase-rich rocks, contain more abundant but smaller particles.

The variations in magnetic properties correlate with the abundance and inferred temperatures of formation of hydrothermal alteration minerals in the rocks. Petrographic observations indicate temperatures of alteration of 500–800°C in the olivine-rich peridodites in the lower part of the Unit, but of the order of 300°C in the plagioclase-rich rocks at the top of the Unit.

These relationships between magnetic mineralogy and hydrothermal alteration suggest that the magnetite was produced by olivine oxidation during hydrothermal alteration. It is proposed that variations in the magnetic properties of layered cumulate rocks may be used to map out variations in the temperature and intensity of hydrothermal fluid flow. The variations in the Unit 10 rocks studied are interpreted as indicating control of high-temperature hydrothermal fluid flow through them by contrast in permeability between brittle peridotites and quasiplastic plagioclase-rich rocks.

Keywords

magnetic propertieslayered intrusionhydrothermal alteration
Type
Research Article
Information
Earth and Environmental Science Transactions of The Royal Society of Edinburgh , Volume 86 , Issue 2 , 1995 , pp. 91 - 112
Copyright
Copyright © Royal Society of Edinburgh 1995

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

Barton, M. & Van Gaans, C. 1988. Formation of orthopyroxene–FeTi oxide symplectites in PreCambrian intrusives, Rogaland. southern Norway. AM MINERAL 73, 1046–59.Google Scholar
Bedard, J. H., Sparks, R. S. J., Renner, R., Cheadle, M. J. & Hallworth, M. A. 1988. Peridotite sills and metasomatic gabbros in the Eastern Layered Series of the Rhum Complex. J GEOL SOC LONDON 145, 207–24.CrossRefGoogle Scholar
Bird, D. K. & Helgeson, H. C. 1981. Chemical interaction of aqueous solutions with epidote-feldspar mineral assemblages in geologic systems. II. Equilibrium constraints in metamorphic/geothermal processes. AM J SCI 281, 576–614.CrossRefGoogle Scholar
Bird, D. K., Manning, C. E. & Rose, N. M. 1988. Hydrothermal alteration of Tertiary layered gabbros, East Greenland. AM J SCI 288, 405–57.CrossRefGoogle Scholar
Brewster, D. & O'Reilly, W. 1988. Magnetic properties of synthetic analogues of the altered olivines of igneous rocks. GEOPHYS J 95, 421–32.CrossRefGoogle Scholar
Brewster, D. & O'Reilly, W. 1989. Thermoremanent magnetization carried by synthetic analogues of the altered olivines of igneous rocks. EARTH PLANET SCI LETT 93, 123–32.CrossRefGoogle Scholar
Brown, G. M. 1956. The layered ultrabasic rocks of Rhum. Inner Hebrides. PHIL TRANS R SOC LONDON A240, 1–53.Google Scholar
Coppin, R. 1982. A geophysical investigation of the Tertiary igneous complex of Rhum, Inner Hebrides. MSc thesis. University of Durham.Google Scholar
Day, S. J. 1989. The geology of the Hypersthene Gabbro of Ardnamurchan Point and implications for its evolution as a subvolcanic basic magma chamber. PhD thesis, University of Durham.Google Scholar
Donaldson, C. H. 1975. Ultrabasic breccias in layered intrusions—the Rhum complex. J GEOL 83, 33–45.CrossRefGoogle Scholar
Dunham, A. C. & Wadsworth, W. J. 1978. Cryptic variation in the Rhum layered intrusion. MINERAL MAG 22, 347–56.CrossRefGoogle Scholar
Emeleus, C. H. 1987. The Rhum layered complex. Inner Hebrides, Scotland. In: Parsons, I. (ed.) Origins of igneous layering, 263–86. Dordrecht: Reidel.CrossRefGoogle Scholar
Emeleus, C. H. 1991. Tertiary igneous activity. In Craig, G.Y. (ed.) Geology of Scotland, 3rd edn, 455–502London: The Geological Society.Google Scholar
Faithfull, J. W. 1985. The Lower Eastern Layered Series of Rhum. GEOL MAG 122, 459–68.CrossRefGoogle Scholar
Ferry, J. M. 1985. Hydrothermal alteration of Tertiary igneous rocks from the Isle of Skye, N. W. Scotland. Part I: Gabbros. CONTRIB MINERAL PETROL 91, 264–82.CrossRefGoogle Scholar
Forester, R. W. & Harmon, R. S. 1983. Stable isotope evidence for deep meteoric/hydrothermal circulation: Island of Rhum. Inner Hebrides, Scotland. PROC 4TH INT SYMP ON WATER/ROCK INTERACTION, Misasa, Japan.Google Scholar
Frost, B. R. 1991. Magnetic petrology: The factors that control the occurrence of magnetite in crustal rocks. In Lindsley, D.H. (ed.) Oxide minerals: petrologic and magnetic significance. REV MINERAL 25, 489–509.Google Scholar
Greenwood, R. C. 1987. Geology and petrology of the margin of the Rhum ultrabasic intrusion, Inner Hebrides, Scotland. PhD thesis. University of St. Andrews.Google Scholar
Handy, M. R. 1989. Deformation regimes and the rheological evolution of fault zones in the lithospere: the effects of pressure, temperature, grainsize and time. TECTONOPHYS 163, 119–52.CrossRefGoogle Scholar
Harry, D. L., Sawyer, D. S. & Leeman, W. P. 1993. The mechanics of continental extension in western North America: implications for the magmatic and structural evolution of the Great Basin. EARTH PLANET SCI LETT 117, 59–72.CrossRefGoogle Scholar
Hellwege, K.-H. & Hellwege, A. M. (eds) 1970. Magnetic and other properties of oxides and related compounds. Vol. 4 of Landolt-Bornstein numerical data and functional relationships in science and technology (New Series), Group III: Crystal & Solid State Physics. Berlin: Springer-Verlag.Google Scholar
Henderson, P. & Suddaby, P. 1971. The nature and origin of the chrome-spinel of the Rhum layered intrusion. CONTRIB MINERAL PETROL 33, 21–31.CrossRefGoogle Scholar
Housden, J. 1986. A magneto-mineralogical study of igneous rocks from the Rhum Layered Intrusion and the oceanic basements. PhD thesis, University of Newcastle upon Tyne.Google Scholar
Housden, J., de Sa, A. & O'Reilly, W. 1988. The magnetic balance and its application in studying the magnetic mineralogy in igneous rocks. J GEOMAGN GEOELECTR 40, 63–75.CrossRefGoogle Scholar
Huppert, H. E. & Sparks, R. S. J. 1980. The fluid dynamics of a basaltic magma chamber replenished by influx of hot, dense, ultrabasic magma. CONTRIB MINERAL PETROL 75, 279–89.CrossRefGoogle Scholar
Irvine, T. N. 1982. Terminology for layered intrusions. J PETROL 23, 127–62.CrossRefGoogle Scholar
Kusznir, N. J. & Park, R. G. 1987. The extensional strength of the continental lithospere: its dependence upon geothermal gradient, and crustal composition and thickness. In Coward, M. P., Dewey, J. F. & Hancock, P. L. (eds) Continental extensional tectonics, SPEC PUBL GEOL SOC LONDON 28, 35–52.CrossRefGoogle Scholar
Lindsley, D. H. & Frost, B. R. 1992. Equilibria amongst Fe-Ti oxides, pyroxenes, olivine and quartz. Part I: theory. AM MINERAL 77, 987–1003.Google Scholar
Lynch, H. D. & Morgan, P. 1987. The tensile strength of the lithospere and the localisation of extension. In, Dewey, J. F. & Hancock, P. L. (eds) Continental extensional tectonics, SPEC PUBL GEOL SOC LONDON 28, 53–66.CrossRefGoogle Scholar
McQuillin, J. & Tuson, J. 1963. Gravity measurements over the Rhum Tertiary plutonic complex. NATURE 199, 1276–7.CrossRefGoogle Scholar
Moseley, D. 1984. Symplectic exsolution in olivine. AM MINERAL 69, 139–53.Google Scholar
Muir, I. D., Tilley, C. E. & Scoon, J. H. 1957. Contributions to the petrology of Hawaiian basalts. I: The picrite basalts of Kilauea. AM J SCI 255, 241–53.CrossRefGoogle Scholar
Nitsan, U. 1974. Stability field of olivine with respect to oxidation and reduction. J GEOPHYS RES 79, 706–11.CrossRefGoogle Scholar
Norton, D. L. 1988. Metasomatism and permeability. AM J SCI 288, 604–18.CrossRefGoogle Scholar
Norton, D. L., Taylor, H. P. & Bird, D. K. 1984. The geometry and high temperature brittle deformation of the Skaergaard intrusion. J GEOPHYS RES 89, 10178–92.CrossRefGoogle Scholar
O'Reilly, W. 1984. Rock and mineral magnetism. Glasgow: Blackie; New York: Chapman and Hall/Methuen.CrossRefGoogle 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. GEOL MAG 122, 485–90.CrossRefGoogle Scholar
Putnis, A. 1979. Electron petrography of high temperature oxidation in olivine from the Rhum layered intrusion. MINER MAG 43, 293–6.CrossRefGoogle Scholar
Robbins, M., Wertheim, G. K., Sherwood, R. C. and Buchanan, D. N. E. 1971. Magnetic properties and site distributions in the system J PHYS CHEM SOLIDS 32, 717–29.CrossRefGoogle Scholar
Rutter, E. H. & Brodie, K. H. 1991. Lithosphere rheology—a note of caution. J STRUCT GEOL 13, 363–7.CrossRefGoogle Scholar
Schmidbauer, E. 1971. Magnetization and lattice parameters of Ti-substituted Fe–Cr spinels. J PHYS CHEM SOLIDS 32, 71–6.CrossRefGoogle Scholar
Scholz, C. H. 1990. The mechanism of earthquakes and faulting. Cambridge: Cambridge University Press.Google Scholar
Smith, R. B. & Bruhn, R. L. 1984. Intraplate extensional tectonics of the eastern Basin Range; inferences on structural style from seismic reflection data, regional tectonics, and thermal-mechanical models of brittle/ductile deformation. J GEOPHYS RES 89, 5733–62.CrossRefGoogle Scholar
Spear, F. S. 1981. An experimental study of hornblende stability and compositional variability in amphibolite. AM J SCI 281, 697–734.CrossRefGoogle Scholar
Taylor, H. P. & Forester, R. W. 1971. Low-O18 igneous rocks from the intrusive complexes of Skye, Mull and Ardnamurchan, Western Scotland. J PETROL 12, 465–97.CrossRefGoogle Scholar
Volker, J. A. 1983. The geology of the Trallval area, Rhum. Inner Hebrides. PhD thesis, University of Edinburgh.Google Scholar
Wager, L. R., Brown, G. M. & Wadsworth, W. J. 1960. Types of igneous cumulates. J PETROL 1, 73–85.CrossRefGoogle Scholar
Wager, L. R. & Brown, G. M. 1968. Layered igneous rocks. Edinburgh & London: Oliver & Boyd.Google Scholar
Young, I. M., Greenwood, R. C. & Donaldson, C. H. 1988. Formation of the Eastern Layered Series of the Rhum complex, northwest Scotland. CAN MINERAL 26, 225–33.Google Scholar