Hostname: page-component-745bb68f8f-s22k5 Total loading time: 0 Render date: 2025-01-28T09:51:40.875Z Has data issue: false hasContentIssue false
  • English
  • Français

K—Ar ages of alkaline igneous rocks in the northern Oman mountains, NE Arabia, and their relations to rifting, passive margin development and destruction of the Oman Tethys

Published online by Cambridge University Press:  01 May 2009

S. J. Lippard  and
D. C. Rex
S. J. Lippard
Affiliation:
Department of Earth Sciences, Open University, Milton Keynes, MK7 6AA, U.K.
D. C. Rex
Affiliation:
Department of Earth Sciences, The University, Leeds, LS2 9JT, U.K.
Get access Rights & Permissions [Opens in a new window]

Summary

K–Ar ages of biotites from a variety of alkaline volcanics and minor intrusive rocks in the nothern Oman mountains allochthon give a range of ages from Triassic (230 Ma) to mid Cretaceous (92 Ma) and represent igneous activity on the Oman continental margin throughout the Mesozoic. This was a passive margin destroyed by the emplacement across it of a pile of nappes in the late Cretaceous, including a largely intact thrust sheet of Upper Cretaceous oceanic lithosphere (the Semail ophiolite). Biotite ankaramite dykes, cutting compositionally similar volcanics, in the thrust complex immediately beneath the ophiolite, give Triassic ages and are related to the rifting and break-up of the northeast Arabian margin at the beginning of formation of the Oman Tethys. Mid Cretaceous (Cenomanian–Turonian) ages are mostly recorded from the northern part of the mountains where there are alkaline tuffs in a sedimentary melange. They are approximately the same age as the ophiolite and may be related to tectonic instability of the Oman margin immediately prior to ophiolite emplacement. Alkaline sills, intrusive into a variety of rocks, including Triassic volcanics, give Jurassic and Cretaceous ages and are interpreted as periodic alkaline activity on the Oman margin throughout passive margin development.

Type
Articles
Information
Geological Magazine , Volume 119 , Issue 5 , September 1982 , pp. 497 - 503
Copyright
Copyright © Cambridge University Press 1982

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

Allemann, F. & Peters, T. 1972. The ophiolite-radiolarite belt of the northern Oman mountains. Eclog. geol. Helv. 65, 659–97.Google Scholar
Brunn, J., Gracianski, P., Gutnic, M., Juteau, T., Lefevre, R., Marcoux, J., Monod, O. & Poisson, A. 1970. Structures majeures et corrélations stratigraphiques dans les Taurides occidentales. Bull. Soc. geol. Fr. 12, 515–56.CrossRefGoogle Scholar
Glennie, K. W., Boeuf, M., Hughes Clark, M. W., Moody-Stuart, M., Pilaar, W. F. H. & Reinhardt, B. M. 1973. Late Cretaceous nappes in the Oman mountains and their geologic evolution. Bull. Am. Ass. Petrol. Geol. 57, 5–27.Google Scholar
Glennie, K. W., Boeuf, M., Hughes Clark, M. W., Moody-Stuart, M., Pilaar, W. F. H. & Reinhardt, B. M. 1974. Geology of the Oman mountains. Vehr. K. ned. geol-mijnb. Genoot. 1–423.Google Scholar
Graham, G. M. 1980. Evolution of a passive margin and nappe emplacement in the Oman mountains. In Ophiolites. Proc. Int. Ophiolite Symp. (ed. Panayioutou, A.), pp. 414–23. Republic of Cyprus, Ministry of Agriculture and Natural Resources Geological Survey Department.Google Scholar
Hynes, A. 1974. Igneous activity at the birth of an ocean basin in eastern Greece. Can. J. Earth Sci. 11, 842–53.CrossRefGoogle Scholar
Lanphere, M. A. 1981. K-Ar ages of metamorphic rocks at the base of the Samail ophiolite, Oman. J. geophys. Res. 86, 2777–82.CrossRefGoogle Scholar
Lees, G. M. 1928. The geology and tectonics of Oman and parts of southeast Arabia. Q. Jl. geol. Soc. Lond. 84, 585–670.CrossRefGoogle Scholar
Parrot, J. F. 1977. Ophiolites du nord-ouest syrien et évolution de la croûte océnique tethysienne au cours de mésozoïque. Tectonophys. 41, 251–68.CrossRefGoogle Scholar
Pearce, J. A. 1975. Basalt geochemistry used to investigate past tectonic environments on Cyprus. Techtonophys. 25, 41–67.CrossRefGoogle Scholar
Rex, D. C. & Dodson, M. H. 1970. Improved resolution and precision of argon analyses using an MS10 mass spectrometer. Eclog. geol. Helv. 63, 257–80.Google Scholar
Rocci, G. & Lapierre, H. 1969. Etude comparative des diverses manifestations du volcanisme préorogenique au sud de Chypre. Schweiz. miner. petrogr. Mitt. 49, 31–46.Google Scholar
Searle, M. P., Lippard, S. J., Smewing, J. D. & Rex, D. C. 1980. Volcanic rocks beneath the Semail nappe in the northern Oman mountains and their significance in the Mesozoic evolution of Tethys. J. geol. Soc. 137, 589–604.CrossRefGoogle Scholar
Searle, M. P. & Malpas, J. 1980. Structure and metamorphism of rocks beneath the Semail ophiolite of Oman and their significance in ophiolite obduction. Trans. R. Soc. Edinb. 71, 247–62.CrossRefGoogle Scholar
Tilton, G. R., Hopson, C. A. & Wright, J. E. 1981. Uranium–lead isotopic ages of the Samail ophiolite, Oman, with applications of Tethyan ocean ridge tectonics. J. geophys. Res 86, 2763–76.CrossRefGoogle Scholar
Tippit, P. R., Pessagno, E. A. & Smewing, J. D. 1981. The biostratigraphy of sediments in the volcanic unit of the Samail ophiolite. J. geophys. Res. 86, 2756–62.CrossRefGoogle Scholar