Hostname: page-component-669899f699-cf6xr Total loading time: 0 Render date: 2025-04-29T05:26:03.863Z Has data issue: false hasContentIssue false
  • English
  • Français

Structure and metamorphism of rocks beneath the Semail ophiolite of Oman and their significance in ophiolite obduction

Published online by Cambridge University Press:  03 November 2011

M. P. Searle  and
J. Malpas
M. P. Searle
Affiliation:
Department of Geology, Memorial University of Newfoundland, St John's, Newfoundland, Canada, A1B 3X5.
J. Malpas
Affiliation:
Department of Geology, Memorial University of Newfoundland, St John's, Newfoundland, Canada, A1B 3X5.
Get access Rights & Permissions [Opens in a new window]

Abstract

Metamorphic rocks showing an inverted metamorphic zonation from upper amphibolite fades immediately beneath the peridotite to greenschist fades at lower levels, crop out discontinuously along the base of the Semail ophiolite thrust sheet in the Oman Mountains of eastern Arabia. These metamorphic rocks show polyphase deformation, mylonitic fabrics, and have been disrupted, folded and imbricated, and in places form tectonic inclusions in a serpentinite melange. In the more intact sequences, garnet-clinopyroxene amphibolites, with rare hornblende-bearing marbles and banded quartzites, occur at the higher levels, whilst a wide range of metasedimentary and metabasaltic rocks occur in the greenschist fades. Low glaucophane content of amphiboles and low jadeite content of clinopyroxenes suggest relatively low pressures of crystallisation. The distribution coefficient KD for co-existing garnet and clinopyroxene suggests a temperature range of 670 to 750°C. Residual heat from the recently formed ophiolite probably provided the dominant heat source for metamorphism, although frictional heating could have supplemented this. The metamorphic rocks were produced during Cenomanian-Turonian (late Cretaceous) times.

The sub-ophiolite metamorphic rocks, together with basal serpentinite, Triassic alkaline and tholeiitic basalts (Haybi volcanic group), mountain-sized ‘exotic’ limestones and an upper Cretaceous sedimentary melange, comprise a distinct thrust slice termed the Haybi complex, which always overlies marine sediments of the allochthonous Hawasina complex and underlies the Semail ophiolite. The rocks of the Haybi complex are bounded by major thrust planes, the Semail thrust above and the Haybi thrust beneath, which truncate all schistosities, fold axes, imbricate thrusts and associated features. A model for ophiolite obducton is presented based on a palinspastic reconstruction of the allochthonous rocks on the Oman continental margin.

Keywords

allochthonousbasaltCenomaniandistribution coefficient KDfoldfrictional heatlimestonemelangeoceanic lithosphereresidual heatserpentinitethrustTuronian24°N56°E
Type
Research Article
Information
Earth and Environmental Science Transactions of The Royal Society of Edinburgh , Volume 71 , Issue 4 , 1980 , pp. 247 - 262
Copyright
Copyright © Royal Society of Edinburgh 1980

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.)

Article purchase

Temporarily unavailable

References

Alabaster, T., Pearce, J. A. & Elboushi, I. 1979. Geological setting of massive sulphide deposits in part of the Oman ophiolite. Abstracts International Ophiolite Symposium, Cyprus, 127–8. Geological Survey Department, Nicosia, Cyprus.Google Scholar
Alleman, F. & Peters, T. 1972. The ophiolite-radiolarite belt of the north Oman Mountains. ECLOGAE GEOL HELV 65, 657–97.Google Scholar
Armstrong, R. L. & Dick, H. 1974. A model for the development of thin overthrust sheets of crystalline rock. GEOLOGY 2, 35–40.2.0.CO;2>CrossRefGoogle Scholar
Banno, S. 1970. Classification of eclogites in terms of physical conditions of their origin. PHYS EARTH PLANET INTERIORS 3, 405–21.CrossRefGoogle Scholar
Brookfield, M. E. 1977. The emplacement of giant ophiolite nappes 1. Mesozoic-Cenozoic examples. TECTONOPHYSICS 37, 247–303.CrossRefGoogle Scholar
Brown, M. A. 1979. Cryptic layering in mantle rocks from Oman. Abstracts International Ophiolite Symposium, Cyprus, 19. Geological Survey Department, Nicosia, Cyprus.Google Scholar
Coleman, R. G. 1967. Glaucophane schists from California and New Caledonia. TECTONOPHYSICS 4, 479–98.CrossRefGoogle Scholar
Coleman, R. G. 1971. Plate tectonic emplacement of upper mantle peridotites along continental edges. J GEOPHYS RES 76, 1212–22.CrossRefGoogle Scholar
Coleman, R. G. 1977. Ophiolites — Ancient Oceanic Lithosphere? Berlin: Springer-Verlag.CrossRefGoogle Scholar
Coleman, R. G. & Lanphere, M. A. 1971. Distribution and age of high-grade blueschists, associated eclogites, and amphibolites from Oregon and California. BULL GEOL SOC AM 82, 2396–412.CrossRefGoogle Scholar
Dewey, J. F. 1976. Ophiolite obduction. TECTONOPHYSICS 31, 93–120.CrossRefGoogle Scholar
Elliott, D. 1976. The motion of thrust sheets. J GEOPHYS RES 81, 949–63.CrossRefGoogle Scholar
Gass, I. G. 1968. Is the Troodos massif of Cyprus a fragment of Mesozoic ocean floor? NATURE LONDON 220, 39–12.CrossRefGoogle Scholar
Gealey, W. K. 1977. Ophiolite obduction and geologic evolution of the Oman Mountains and adjacent areas. BULL GEOL SOC AM 88, 1183–91.2.0.CO;2>CrossRefGoogle Scholar
Glennie, K. W., Boeuf, M. G. A., Clarke, M. W. H., Moody-Stuart, M., Pilaar, W. F. H. & Reinhardt, B. M. 1973. Late Cretaceous nappes in the Oman Mountains and their geologic evolution. BULL AM ASSOC PET GEOL 57, 5–27.Google Scholar
Glennie, K. W., Boeuf, M. G. A., Clarke, M. W. H., Moody-Stuart, M., Pilaar, W. F. H. & Reinhardt, B. M. 1974. Geology of the Oman Mountains. NED GEOL-MIJNBOUWKD GENOOT 31, 1–423.Google Scholar
Graham, G. M. & England, P. C. 1976. Thermal Regimes and Regional Metamorphism in the vicinity of overthrust faults: an example of shear heating and inverted metamorphic zonation from Southern California. EARTH PLANET SCI LETT 31, 142–52.CrossRefGoogle Scholar
Jamieson, R. A. 1977. The first metamorphic sodic amphibole identified from the Newfoundland Appalachians — its occurrence, composition and possible tectonic implications. NATURE LONDON 265, 428.CrossRefGoogle Scholar
Jamieson, R. A. 1979. Ophiolite emplacement as recorded in the dynamothermal aureole of the St. Anthony complex Northwestern Newfoundland. Abstracts International Ophiolite Symposium, Cyprus, 92. Geological Survey Department, Nicosia, Cyprus.Google Scholar
Lanphere, M. A. 1979. K-Ar ages of metamorphic rocks at the base of the Semail ophiolite, Oman. EOS TRANS AM GEOPHYS UNION 60, 963.Google Scholar
Lees, G. M. 1928. Geology and tectonics of Oman and parts of south-east Arabia. Q J GEOL SOC LONDON 84, 585–670.CrossRefGoogle Scholar
Lemoine, M. 1973. About gravity gliding in the western Alps. In De Jong, K. A. & Scholten, R. (eds) Gravity and Tectonics, 201–6. New York: Wiley Interscience.Google Scholar
Malpas, J. 1978. Magma generation in the upper mantle, field evidence from ophiolite suites, and application to the generation of oceanic lithosphere. PHILOS TRANS R SOC LONDON A288, 527–46.Google Scholar
Malpas, J. 1979. Dynamothermal aureole beneath the Bay of Islands ophiolite in western Newfoundland. CAN J EARTH SCI 16, 2086–101.CrossRefGoogle Scholar
Malpas, J. & Stevens, R. K. 1977. The origin and emplacement of the ophiolite suite with examples from western Newfoundland. GEOTECTONICS ACAD SCI USSR 11, 453–66.Google Scholar
Malpas, J., Stevens, R. K. & Strong, D. F. 1973. Amphibolite associated with the Newfoundland ophiolite. Its classification and tectonic significance. GEOLOGY 1, 45–7.2.0.CO;2>CrossRefGoogle Scholar
Mitchell, A. H. & Reading, H. G. 1971. The evolution of Island Arcs. J GEOL 79, 253–84.CrossRefGoogle Scholar
Moores, E. M. & Vine, F. J. 1971. The Troodos Massif of Cyprus and other ophiolites as oceanic crust: evaluation and implication. PHILOS TRANS R SOC LONDON A268, 443–66.Google Scholar
Oxburgh, E. R. 1972. Flake tectonics and continental collision. NATURE LONDON 239, 202–4.CrossRefGoogle Scholar
Pearce, J. A. 1979. Genesis and eruptive setting of lavas from Tethyan ophiolites. Abstracts International Ophiolite Symposium, Cyprus, 59–60. Geological Survey Department, Nicosia, Cyprus.Google Scholar
Pearce, J. A., Alabaster, T., Shelton, A. W. & Searle, M. P. 1980. The Oman ophiolite as a Cretaceous arc-basin complex: evidence and implications. PHILOS TRANS R SOC LONDON in press.Google Scholar
Raheim, A. & Green, D. H. 1974. Experimental determination of the temperature and pressure dependence of the Fe-Mg partition coefficient for coexisting garnet and clinopyroxene. CONTRIB MINERAL PETROL 48, 179–203.CrossRefGoogle Scholar
Raheim, A. & Green, D. H. 1975. P, T paths of natural eclogites during metamorphism — a record of subduction. LITHOS 10, 317–28.CrossRefGoogle Scholar
Reinhardt, B. M. 1969. On the genesis and emplacement of ophiolites in the Oman Mountains geosyncline. SCHWEIZ MINERAL PETROL 49, 1–30.Google Scholar
Searle, M. P. 1980. The Metamorphic sheet and underlying volcanic rocks beneath the Semail ophiolite in the northern Oman Mountains of Arabia. Unpublished Ph.D. Thesis, Open University.CrossRefGoogle Scholar
Searle, M. P., Lippard, S. J., Smewing, J. D. & Rex, D. C. 1980. Distribution age and tectonic significance of volcanic rocks beneath the Semail ophiolite in northern Oman. J GEOL SOC LONDON in press.Google Scholar
Seely, D. R., Vail, P. R. & Walton, G. C 1974. Trench-slope model. In Burk, C. A. & Drake, C. L. (eds) The Geology of continental margins, 249–60. New York: Springer-Verlag.CrossRefGoogle Scholar
Smewing, J. D., Simonian, K., Elboushi, I. & Gass, I. G. 1977. Mineralised fault zone on the Oman ophiolite spreading axis. GEOLOGY 5, 534–8.2.0.CO;2>CrossRefGoogle Scholar
Smith, A. G. 1971. Alpine Deformation and the Oceanic areas of the Tethys Mediterranean and Atlantic. BULL GEOL SOC AM 82, 2039–70.CrossRefGoogle Scholar
Smith, A. G. & Woodcock, N. H. 1976. Emplacement model for some Tethyan ophiolites. GEOLOGY 4, 653–6.2.0.CO;2>CrossRefGoogle Scholar
Stoneley, R. 1975. On the origin of ophiolite complexes in the southern Tethys region. TECTONOPHYSICS 25, 303–22.CrossRefGoogle Scholar
Tilton, G. R., Wright, J. E. & Hopson, C. A. 1979. Uranium–lead isotopie ages of the. Samail ophiolite, Sultanate of Oman. EOS TRANS AM GEOPHYS UNION 60, 962.Google Scholar
Tippit, P. R. & Pessagno, E. A. 1979. Age of the Samail ophiolite based on radiolarian biostratigraphy. EOS TRANS AM GEOPHYS UNION 60, 962.Google Scholar
Tippit, P. R., Pessagno, E. A. & Smewing, J. D. In press. The biostratigraphy of sediments in the volcanic unit of the Oman ophiolite. J GEOPHYS RES.Google Scholar
Weiland, M. J. & Mitchell, A. H. 1977. Emplacenent of the Oman ophiolite: a mechanism related to subduction and collision. BULL GEOL SOC AM 88, 1081–8.2.0.CO;2>CrossRefGoogle Scholar
Williams, H. & Smyth, W. R. 1973. Metamorphic aureoles beneath ophiolite suites and Alpine peridotites: tectonic implications with west Newfoundland examples. AM J SCI 273, 594–621.CrossRefGoogle Scholar
Wilson, H. H. 1969. Late Cretaceous eugeosynclinal sedimentation, gravity tectonics and ophiolite emplacement in Oman Mountains, southeast Arabia. BULL AM ASSOC PET GEOL 53, 626–71.Google Scholar
Woodcock, N. H. & Robertson, A. H. F. 1977. Origins of some ophiolite-related metamorphic rocks of the ‘Tethyan’ belt. GEOLOGY 5, 373–6.Google Scholar