Hostname: page-component-586b7cd67f-dsjbd Total loading time: 0 Render date: 2024-11-25T08:16:36.874Z Has data issue: false hasContentIssue false
  • English
  • Français

The gabbro–dyke transition zone demonstrated on Tviberg, Solund–Stavfjord Ophiolite Complex

Published online by Cambridge University Press:  01 May 2009

K. P. Skjerlie  and
H. Furnes
K. P. Skjerlie
Affiliation:
Geologisk Institutet, Allegaten 41,5007 Bergen-Universitetet, Norway
H. Furnes
Affiliation:
Geologisk Institutet, Allegaten 41,5007 Bergen-Universitetet, Norway
Get access Rights & Permissions [Opens in a new window]

Abstract

The transition zone between 100 % dykes and high-level plutonic rocks of the Solund-Stavfjord Ophiolite Complex is complex due to the existence of many lithologies with different and variable contact relationships. The rocks of the plutonic complex vary in composition from FeTi basaltic to quartz dioritic, and the grain sizes vary from fine to pegmatitic. Felsic varieties are produced by fractional crystallization of basaltic magma as demonstrated by geochemical evolution and by gradual transition from gabbro to quartz diorite. Patches of fractionated dioritic rocks may show both gradual and intrusive relationships with the surrounding host gabbro. This demonstrates that late-stage liquids commonly left the source region and locally intruded the surrounding parent rocks. The high-level plutonic rocks are thoroughly epidotized and are cut by dykes consisting of granoblastic epidote and quartz. The high-level plutonic complex is associated with irregular bodies of fine- to medium-grained plagioclase-porphyritic diabase of high MgO content. These diabase bodies are intruded by dykes that become progressively more regular in shape. The plutonic complex locally shows intrusive relationships with the overlying 100% dyke complex, but is itself cut by two dyke swarms. The dykes of the first swarm formed while the plutonic complex experienced sinistral shear strain, and the dykes are generally less regular and thinner than the dykes of the second swarm. This indicates that the dykes of the first swarm intruded while the rocks of the plutonic complex were still hot, while the next dyke swarm intruded later when the rock complex was colder. Dykes of both swarms range in composition from slightly to strongly fractionated, suggesting that the magma chambers they were expelled from underwent significant fractionation in between magma replenishment. Numerous dykes of both swarms carry large quantities of glomeroporphyritic aggregates of plagioclase and altered clinopyroxene, indicating that the source area to the dykes very often was a crystal mush.

Type
Articles
Information
Geological Magazine , Volume 133 , Issue 5 , September 1996 , pp. 573 - 582
Copyright
Copyright © Cambridge University Press 1996

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

Alsaker, E., & Furnes, H. 1994. Geochemistry of the Sunnfjord Melange: sediment mixing from different sources during obduction of the Solund-Stavfjord Ophiolite Complex, Norwegian Caledonides. Geological Magazine 131, 105–21.CrossRefGoogle Scholar
Andersen, T. B., Skjerlie, K. P., & Furnes, H. 1990. The Sunnfjord Melange, evidence of Silurian ophiolite accretion in the west Norwegian Caledonides. Journal of the Geological Society, London 147, 59–68.Google Scholar
Anderson, R. N., Honnorez, J., Becker, K., Adamson, A. C, Alt, J. C, Emmermann, R., Kempton, P. D., Kinoshita, H., Laverne, C, Mottl, M. J., & Newmark, R. L. 1982. DSDP Hole 504B, the first reference section over 1 km through layer 2 of the oceanic crust. Nature 300, 589–94.CrossRefGoogle Scholar
Auzende, J.-M., Bldeau, D., Bonatti, E., Cannat, M., Honnorez, J., LagabrielleY, Malavielle J. Y, Malavielle J., Mamaloukas-Frangoulis, V., & Mevel, C. 1990. The MAR-Vema Fracture Zone intersection surveyed by deep submersible, Nautile. Terra Nova 2, 68.CrossRefGoogle Scholar
Ballard, R. D., & Van Andel, Tj. H. 1977. Morphology and tectonics of the inner rift valley at lat 36050’N on the Mid- Atlantic Ridge. Geological Society of America Bulletin 88, 507–30.Google Scholar
Coleman, R. G. 1977. Ophiolites: Ancient Oceanic Lithosphere? Springer-Verlag, 229 pp.Google Scholar
Dunning, G. R., & Pedersen, R. B. 1988. U/Pb ages of ophiolites and arc-related plutons of the Norwegian Caledonides: implications for the development of Iapetus. Contributions to Mineralogy and Petrology 98, 13–23.Google Scholar
Francheteau, J., Armijo, R., Cheminée, J., Hekinian, R., Lonsdale, P., & Blum, N. 1990. I Ma East Pacific Rise oceanic crust and uppermost mantle exposed by rifting in Hess Deep (equatorial Pacific Ocean). Earth and Planetary Science Letters 101, 281–95.CrossRefGoogle Scholar
Furnes, H., Skjerlie, K. P., Pedersen, R. B., Andersen, T. B., Stillman, C. J., Suthren, R. J., Tysseland, M., & Garmann, L. B. 1990. The Solund—Stavfjord Ophiolite Complex and associated rocks, west Norwegian Caledonides: geology, geochemistry and tectonic environment. Geological Magazine 127, 209–24.Google Scholar
Furnes, H., Johansen, R. J., & Skjerlie, K. P. 1992. FeTi-poor and FeTi-rich basalts in the Solund-Stavfjord Ophiolite Complex, west Norwegian Caledonides: relationships and genesis. Neues Jahrbuchfiir Mineralogie, MonatsheftH. 4, 153–68.Google Scholar
Hibbard, M. J., & Waiters, R. J. 1985. Fracturing and diking in incompletely crystallized granitic plutons. Lithos 18, 1–12.Google Scholar
Knapp, R. B., & Knight, J. E. 1977. Differential thermal expansion of pore fluids: Fracture propagation and microearthquake production in hot pluton environments. Journal of Geophysical Research 82, 2515–22.CrossRefGoogle Scholar
Nicolas, A. 1989. Structures of ophiolites and dynamics of oceanic lithosphere. Kluwer Academic Publishers, 367 pp.Google Scholar
Nicolas, A., & Boudier, F. 1991. Rooting of the sheeted dike complex in the Oman ophiolite. In Ophiolite and Evolution of the Oceanic Lithosphere (eds Tj. Peters et al.), pp. 39–54. Ministry of Petroleum and Minerals, Sultanate of Oman.Google Scholar
Pedersen, R. B. 1986. The nature and significance of magma chamber margins in ophiolites: examples from the Norwegian Caledonides. Earth and Planetary Science Letters 11, 100–12.Google Scholar
Pedersen, R. B., & Malpas, J. 1984. The origin of oceanic plagiogranites from the Karmφy ophiolite, Western Norway, Contributions to Mineralogy and Petrology 88, 36–52.Google Scholar
Pedersen, R. B., Furnes, H., & Dunning, G. R. 1991. A U/Pb age for the Sulitjelma Gabbro, North Norway: further evidence for the development of a Caledonian marginal basin in Ashgill—Llandovery time. Geological Magazine 128, 141–53.CrossRefGoogle Scholar
Richardson, C. J., Cann, J. R., Richards, H. G., & Cowan, J. G., 1987. Metal depleted root zones of the Troodos oreforming hydrothermal systems, Cyprus. Earth and Planetary Science Letters 84, 243–53.CrossRefGoogle Scholar
Rosencrantz, E. 1983. The structure of sheeted dikes and associated rocks in North Arm massif, bay of Islands ophiolite complex, and the intrusive process at oceanic spreading centers. Canadian Journal of Earth Science 20, 787–801.Google Scholar
Schiffman, P., Smith, B. M., Varga, R. J., & Moores, E. M. 1987. Geometry, conditions, and timing of off-axis hydrothermal metamorphism and ore deposition in the Solea graben, N. Troodos, Cyprus. Nature 325, 423–5.CrossRefGoogle Scholar
Skjerlie, K. P., Furnes, H., & Johansen, R. J. 1989. Magmatic development and tectonomagmatic models for the Solund—Stavfjord Ophiolite Complex: West Norwegian Caledonides. Lithos 23, 137–51.CrossRefGoogle Scholar
Skjerlie, K. P., & Furnes, H. 1990. Evidence for a fossil transform fault in the Solund—Stavfjord Ophiolite Complex: west Norwegian Caledonides. Tectonics 9, 1631–48.Google Scholar
Smith, D. K., & Cann, J. R. 1993. Building the crust at the Mid- Atlantic Ridge. Nature 365, 707–15.Google Scholar