Hostname: page-component-76fb5796d-2lccl Total loading time: 0 Render date: 2024-04-28T01:52:04.533Z Has data issue: false hasContentIssue false
  • English
  • Français

Terrane amalgamation in the Clew Bay region, west of Ireland

Published online by Cambridge University Press:  01 May 2009

J. D. Johnston  and
W. E. A. Phillips
J. D. Johnston
Affiliation:
Department of Geology, Trinity College, Dublin 2, Ireland
W. E. A. Phillips
Affiliation:
Department of Geology, Trinity College, Dublin 2, Ireland
Get access Rights & Permissions [Opens in a new window]

Abstract

The Caledonides of the west of Ireland provide a well-exposed and well-mapped example of an oblique collision zone. The east-northeast trending Deer Park and Achill Beg Fault system is a crustal scale ductile sinistral strike-slip duplex of late Ordovician age, imbricating late Precambrian granulite facies lower crustal rocks, near eclogite facies supracrustal rocks, up to amphibolite facies Dalradian metasedimentary rocks and greenschist facies Cambro-Ordovician rocks. This fault system is correlated with a pre-Devonian component of the Highland Boundary Fault system in southern Scotland. In the Clew Bay area, the high pressure-low temperature facies metamorphic rocks, in tectonic contact with greenschist facies Cambro-Ordovician rocks, are together interpreted as an accretionary prism complex related to northwestward directed subduction. Both of these are allocthonous terrains with respect to the Dalradian terrane to the north (North West Mayo). To the south, the Cambro-Ordovician rocks docked with a probable Dalradian block containing ultramafic intrusives (Deer Park Complex) during the late Ordovician. The Deer Park Complex and South Mayo Trough linked earlier, during the Arenig.

Silurian and Lower-Middle Devonian redbed successions sit unconformably on the metamorphic rocks. Deposition and deformation of these cover rocks was controlled by oblique strike-slip movements on the Leek Fault whose strike swings from west-northwest to north-northeast, following earlier basement trends, as it is traced eastwards from Clew Bay. The Leek Fault System may be correlated with the Leannan Fault of northwest Donegal, a splay of the Great Glen Fault system of central Scotland. East of Clew Bay, this sinistral shear generated local dilation on the more northerly trending bend of the Leek Fault. Lower and Middle Old Red Sandstone redbeds were developed here. The west-northwest trend of the Leek Fault in Clew Bay acted as a compressional bend during these sinistral movements and transpressional southwest directed thrusting developed in Silurian rocks. Post-Middle Old Red Sandstone pre-late Tournaisian dextral displacement on the Leek Fault reversed this pattern with transtension in Clew Bay allowing intrusion of small carbonated peridotite bodies into Silurian rocks and easterly directed thrusting of Middle Old Red Sandstone rocks east of the Bay on the transpressional north-south bend.

A tectonic model for the region is presented here. This model involves a northwestward directed subduction system, 150 to 750 km of Arenig sinistral strike slip movement, and eastwards insertion of the Connemara block with formation of the Ordovician South Mayo Trough as a pull-apart basin. Subsequently, a further 130 to 650 km eastward displacement of rocks took place south of the Deer Park Fault in later Ordovician times. The magnitudes of these estimates are directly proportional to an assumed maximum wavelength of 1500 km for promontories on the original Laurentian margin, and using the current juxtaposition of terranes, a minimum wavelength of 300 km is inferred.

Type
Articles
Information
Geological Magazine , Volume 132 , Issue 5 , September 1995 , pp. 485 - 501
Copyright
Copyright © Cambridge University Press 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

Aftalion, M., & Max, M. D., 1987. U-Pb geochronology from the Precambrian Annagh Division gneisses and the Termon Granite, N. W. Co. Mayo, Ireland. Journal of the Geological Society of London 144, 401–6.CrossRefGoogle Scholar
Alsop, G. I., & Hutton, D. H. W., 1990. A review and revision of Dalradian stratigraphy in central and southern Donegal, Ireland. Irish Journal of Earth Sciences 10, 181–98.Google Scholar
Alsop, G. I., & Jones, C. S., 1991. A review and correlation of Dalradian stratigraphy in the SW/central Ox Mountains and southern Donegal, Ireland. Irish Journal of Earth Sciences 11, 99–112.Google Scholar
Andrews, J. R., Phillips, W. E. A., & Molloy, M. A., 1978. The metamorphic rocks of the north central Ox Mountains inlier of Counties Sligo and Mayo. Journal of Earth Sciences, Royal Dublin Society, 1, 173–94.Google Scholar
Archer, J. B., 1977. Llanvirn stratigraphy of the Galway-Mayo border area, western Ireland. Geological Journal 12, 77–98.Google Scholar
Bickle, M. J., Kidd, R. G. W., & Nisbet, E., 1972. The Silurian of the Croagh Patrick Range, Co. Mayo. Scientific Proceedings of the Royal Dublin Society 4A, 231–49.Google Scholar
Bluck, B. J., 1985. The Scottish Paratectonic Caledonides. Scottish Journal of Geology 21, 437–64.CrossRefGoogle Scholar
Briden, J. C., Robertson, D. J., & Smethurst, M. A., 1989. Terrane rotations in the Irish Caledonides. Journal of the Geological Society of London 146, 909–11.Google Scholar
Clift, P. D., & Ryan, P. D., 1994. Geochemical evolution of an Ordovician island arc, South Mayo, Ireland. Journal of the Geological Society of London 151, 329–2.Google Scholar
Dewey, J. F., 1962. The provenance and emplacement of Upper Arenigian turbidites in Co. Mayo, Eire. Geological Magazine 98, 399–405.Google Scholar
Dewey, J. F., 1963. The Lower Palaeozoic stratigraphy of central Murrisk, Co., Mayo, Ireland, and the evolution of the South Mayo trough. Quarterly Journal of the Geological Society of London 119, 313–44.Google Scholar
Dewey, J. F., 1967. The structural and metamorphic history of the Lower Palaeozoic rocks of central Murrisk, County Mayo, Eire. Quarterly Journal of the Geological Society of London 123, 125–55.Google Scholar
Dewey, J. F., 1990. The Ordovician evolution of the south Mayo trough, western Ireland. Tectonics 9, 887–901.CrossRefGoogle Scholar
Dewey, J. F., & Phillips, W. E. A., 1963. A tectonic profile across the Caledonides of South Mayo. Liverpool and Manchester Geological Journal 4, 61–76.CrossRefGoogle Scholar
Dewey, J. F., & Ryan, P. D., 1990. The Ordovician evolution of the South Mayo Trough, western Ireland. Tectonics 9, 887–901.Google Scholar
Dewey, J. F., & Shackleton, R. M., 1984. A model for the evolution of the Grampian tract in the early Caledonides and Appalachians. Nature 312, 115–21.Google Scholar
Graham, J. R., 1981. The “Old Red Sandstone” of County Mayo, Northwest Ireland. Geological Journal 16, 157–73.CrossRefGoogle Scholar
Graham, J. R., 1987. The nature and field relations of the Ordovician Maumtrasna Formation, Co. Mayo, Ireland. Geological Journal 22, 347–70.Google Scholar
Graham, J. R., Leake, B. E., & Ryan, P. D., 1985. The Geology of South Mayo, University of Glasgow (map).Google Scholar
Graham, J. R., & Smith, D. G., 1981. The age and significance of a small lower Palaeozoic inlier in county Mayo. Journal of Earth Sciences, Royal Dublin Society 4, 1–6.Google Scholar
Gray, J. R., & Yardley, B. W. D., 1979. A Caledonian blueschist from the Irish Dalradian. Nature 315, 210–12.Google Scholar
Halliday, A. N., Graham, C. R., Aftalion, M., & Dymore, P., 1989. The depositional age of the Dalradian Supergroup: U-Pb and Sm-Nd isotopic studies of the Tayvallich Volcanics, Scotland. Journal of the Geological Society, London 146, 3–6.Google Scholar
Harper, D. A. T., Williams, D. M., & Armstrong, H. A., 1989. Stratigraphical correlations adjacent to the Highland Boundary Fault in the west of Ireland. Journal of the Geological Society, London 146, 381–4.Google Scholar
Harris, A. L., 1969. The relationships of the Leny Limestone to the Dalradian. Scottish Journal of Geology 5, 187–90.Google Scholar
Harris, D. H. M., 1993. The Caledonian evolution of the Laurentian margin in western Ireland. Journal of the Geological Society, London 150, 669–72.CrossRefGoogle Scholar
Henderson, W. G., & Robertson, A. H. F., 1982. The Highland Border rocks and their relation to marginal basin development in the Scottish Caledonides. Journal of the Geological Society, London 139, 433–50.Google Scholar
Hutton, D. H. W., 1987. Strike-slip terranes and a model for the evolution of the British and Irish Caledonides. Geological Magazine 124, 405–25.Google Scholar
Hutton, D. H. W., & Dewey, J. F., 1986. Palaeozoic terrane accretion in the western Irish Caledonides. Tectonics 5, 1115–24.Google Scholar
Johnston, J. D., 1992. The fractal geometry of vein systems: the potential for ore reserve calculation. In The Irish Minerals Industry 1980–1990 (eds Bowden, A. A., Earls, G., O’Connor, P. G. and Pyne, J.), pp. 105–17. Dublin: Irish Association for Economic Geology.Google Scholar
Johnston, J. D., 1995. Major Caledonian thrusting and folding in Precambrian rocks, NorthWest Mayo, Ireland. Geological Magazine 132, 91–112.Google Scholar
Kennedy, M. J., 1980. Serpentinite-bearing melange in the Dalradian of county Mayo and its significance in the development of the Dalradian basement. Irish Journal of Earth Sciences 3, 117–26.Google Scholar
Kirwan, P. J., Daly, J. S., & Menuge, J. F., 1989. A minimum age for the deposition of the Dalradian Supergroup sediments in Ireland. Terra Abstracts 1, 16.Google Scholar
Klemperer, S. L., Ryan, P. D., & Snyder, D. B., 1991. A deep seismic reflection transect across the Irish Caledonides. Journal of the Geological Society, London 148, 167–70.Google Scholar
Leake, B. E., & Tanner, P. W. G., 1994. The geology of the Dalradian and associated rocks of Connemara, Western Ireland. A report to accompany the 1:63, 360 geological map and cross-sections of Connemara. Dublin: Royal Irish Academy, 96 pp.Google Scholar
Leake, B. E., Tanner, P. W., Singh, D., & Halliday, A. N., 1983. Major southward thrusting of the Dalradian rocks of Connemara, western Ireland. Nature 305, 219–23.Google Scholar
Max, M. D., 1989. The Clew Bay Group: A displaced terrane of Highland Border Group Rocks (Cambro-Ordovician) in northwest Ireland. Geological Journal 24, 1–17.Google Scholar
Max, M. D., Long, C. B., & MacDermot, C. N., 1992. The geology of North West Mayo. Sheet 6. 1:1 000000. Map with accompanying notes. Dublin: Geological Survey of Ireland.Google Scholar
Max, M. D., O’Connor, P. J., & Long, C. B., 1984. PreCaledonian basement of the NE Ox Mountains and Lough Derg inliers, Ireland. Geological Survey of Ireland Bulletin 3, 203–9.Google Scholar
Max, M. D., Ryan, P. D., & Inamdar, D. D., 1983. A magnetic deep structural geology interpretation of Ireland. Tectonics 2, 431–51.CrossRefGoogle Scholar
McCaffrey, K. J. W., 1992. Igneous emplacement in the transpressive shear zone: Ox Mountains igneous complex. Journal of the Geological Society, London 149, 221–36.Google Scholar
McCaffrey, K. J. W., 1994. Magmatic and solid state deformation partitioning in the Ox Mountains granodiorite. Geological Magazine 131, 639–52.CrossRefGoogle Scholar
McKerrow, W. S., & Campbell, C. J., 1960. The stratigraphy and structure of the Lower Palaeozoic rocks of north-west Galway. Scientific Proceedings of the Royal Dublin Society 27A, 27–52.Google Scholar
Menuge, J. F., & Daly, S. R., 1990. Proterozoic evolution of the Erris Complex, NW Mayo, Ireland: Neodymium isotope evidence. In Mid-Proterozoic geology of the southern margin of proto Laurentia-Baltica (eds Gower, C. F., Rivers, T. and Ryan, B.), pp. 41–51. Geological Association of Canada Special Paper no. 38.Google Scholar
Menuge, J. F., Williams, D. M., & O’Connor, P. D., 1995. Silurian turbidites used to reconstruct a volcanic terrain and its Mesoproterozoic basement in the Irish Caledonides. Journal of the Geological Society, London 152, 269–78.Google Scholar
Morris, W. A., 1976. Palaeomagnetic results from the Lower Palaeozoic of Ireland. Canadian Journal of Earth Sciences 13, 294–304.Google Scholar
Murphy, F. C., Anderson, T. B., DALY, J. S., Gallagher, V., Graham, J. R., Harper, D. A. T., Johnston, J. D., Kennan, P. S., Kennedy, M. J., Long, C. B., Morris, J. H., O’Keeffe, W. G., Parkes, M., Ryan, P. D., Sloan, R. J., Stillman, C. J., Tietzsch-Tyler, D., Todd, S. P., & Wrafter, J. P., 1990. An appraisal of Caledonian suspect terranes in Ireland. Irish Journal of Earth Sciences 11, 11–42.Google Scholar
Murphy, T., 1974. Gravity Anomaly Map of Ireland. Communications of the Dublin Institute for Advanced Studies, Bulletin no. 32.Google Scholar
Palmer, D., Johnston, J. D., Dooley, T., & Maguire, K., 1989. The Silurian of Clew Bay, Ireland: part of the Midland valley of Scotland. Journal of the Geological Society, London 146, 385–8.Google Scholar
Pankhurst, R. J., Andrews, J. R., Phillips, W. E. A., & Sanders, I. S., 1976. Age and structural setting of the Slieve Gamph igneous complex, Co. Mayo, Eire. Journal of the Geological Society, London 132, 327–36.Google Scholar
Phillips, W. E. A., 1973. The pre-Silurian rocks of Clare Island, Co. Mayo, Ireland and the age of the metamorphism of the Dalradian. Journal of the Geological Society of London 129, 585–606.Google Scholar
Phillips, W. E. A., 1974. The stratigraphy, sedimentary environments and palaeogeography of the Silurian strata of Clare Island, Co. Mayo, Ireland. Journal of the Geological Society, London 130, 19–41.Google Scholar
Phillips, W. E. A., 1981. The orthotectonic Caledonides. In A Geology of Ireland (ed. Holland, C. H.), pp. 17–40. Edinburgh: Scottish Academic Press.Google Scholar
Phillips, W. E. A., Rickards, R. B., & Dewey, J. F., 1970. The Lower Palaeozoic rocks of the Louisburgh area, Co. Mayo. Proceedings of the Royal Irish Academy 70A, 195–209.Google Scholar
Phillips, W. E. A., Stillman, C. J., & Murphy, T., 1976. A Caledonian plate tectonic model. Journal of the Geological Society, London 32, 579–609.CrossRefGoogle Scholar
Riddihough, R. P., & Max, M. D., 1976. Continuation of the Highland Boundary Fault in Ireland. Geological Journal 11, 109–20.Google Scholar
Rogers, G., Dempster, T. J., Bluck, B. J., & Tanner, P. W. G., 1989. A high precision U-Pb age for the Ben Vuirich granite: implications for the evolution of the Scottish Dalradian Supergroup. Journal of the Geological Society, London 146, 789–98.Google Scholar
Rushton, A., & Phillips, W. E. A., 1973. A specimen of Protospongia Hicksi from the Dalradian of Clare Island, Co. Mayo, Ireland. Palaeontology 16, 231–7.Google Scholar
Ryan, P. D. R., & Archer, J. B., 1977. The South Mayo Trough: a possible Ordovician Gulf of California-type marginal basin in the West of Ireland. Canadian Journal of Earth Sciences 14, 2453–61.Google Scholar
Ryan, P. D., & Dewey, J. F., 1991, A geological and tectonic cross-section of the Caledonides of western Ireland. Journal of the Geological Society, London 148, 173–80.Google Scholar
Ryan, P. D., Floyd, P. A., & Archer, J. B., 1980. The stratigraphy and petrochemistry of the Lough Nafooey Group (Tremadocian), western Ireland. Journal of the Geological Society, London 137, 443–58.Google Scholar
Ryan, P. D. R., Sawal, V., & Rowlands, A. S., 1983. Ophiolitic melange separates the ortho- and paratectonic Caledonides of in western Ireland. Nature 301, 50–2.Google Scholar
Sanders, I. S., Daly, J. S., & Davies, G. R., 1987. Late Proterozoic high-pressure granulite facies metamorphism in the north-east Ox inlier, north-west Ireland. Journal of Metamorphic Geology 5, 69–86.CrossRefGoogle Scholar
Smethurst, M. A., & Briden, J. C., 1988. Palaeomagnetism of Silurian sediments in W. Ireland: evidence for block rotation in the Caledonides. Geophysical Journal 95, 327–46.CrossRefGoogle Scholar
Smethurst, M. A., MacNiocaill, C., & Ryan, P. D., 1994. Oroclinal bending in the Caledonides of western Ireland. Journal of the Geological Society of London 151, 315–28.Google Scholar
Tanner, P. W. G., 1995. Is there an exotic terrene at the Highland Border in Scotland? Geological Magazine 132, 000–000.Google Scholar
Tanner, P. W. G., & Lesley, A. G., 1994. A pre-D2 age for the 590 Ma Ben Vuirich Granite in the Dalradian of Scotland. Journal of the Geological Society of London 151, 209–12.Google Scholar
Thomas, W. A., 1977. Evolution of Appalachian—Ouachita salients and recesses from reentrants and promontories in the continental margin. American Journal of Science 277, 1233–78.Google Scholar
Thompson, S. J., Shine, C. H., Cooper, C., Halls, C., & Zhao, R., 1992. Shear-hosted gold mineralization in Co. Mayo, Ireland. In The Irish Minerals Industry 1980–1990 (eds Bowden, A. A., Earls, G., O’Connor, P. G. and Pyne, J.), pp. 21–38. Dublin: Irish Association for Economic Geology.Google Scholar
Williams, D. M., 1990. Evolution of Ordovician terranes in western Ireland and their possible Scottish equivalents. Transactions of the Royal Society of Edinburgh, Earth Sciences 81, 23–9.Google Scholar
Williams, D. M., Harkin, J., Armstrong, H. A., & Higgs, K. T., 1994. A late Caledonian melange in Ireland: implications for tectonic models. Journal of Geological Society of London 151, 307–14.Google Scholar
Williams, D. M., & Harper, D. A. T., 1991. End-Silurian modifications of Ordovician terranes in western Ireland. Journal of the Geological Society, London 149, 159–62.Google Scholar
Williams, D. M., & Rice, A. H. N., 1989. Low-angle extensional faulting and the emplacement of the Connemara Dalradian, Ireland. Tectonics 8, 417–28.Google Scholar
Williams, H., 1978. 1:1 000000 scale Tectonic and Lithofacies map of the Appalachians. Map. Memorial University of Newfoundland, St. Johns, Canada.Google Scholar
Williams, S. H., & Harper, D. A. T., 1994. Late Tremadoc graptolites from the Lough Nafooey Group, South Mayo, western Ireland. Irish Journal of Earth Sciences 13, 107–11.Google Scholar
Winchester, J. A., & Max, M. D., 1987 a. A displaced and metamorphosed peralkali granite related to late Proterozoic Labrador and Gadar Suites: the Doo Lough granite of County Mayo, N. W. Ireland. Canadian Journal of Earth Sciences 24, 631–42.Google Scholar
Winchester, J. A., & Max, M. D., 1987 b. The pre-Caledonian Iniskea Division of Northwest Co. Mayo, Ireland: its geochemistry and probable stratigraphic position. Geological Journal 22, 309–32.CrossRefGoogle Scholar
Wrafter, J. P., & Graham, J. R., 1989. Ophiolitic detritus in the Ordovician sediments of South Mayo, Ireland. Journal of the Geological Society of London 146, 213–15.Google Scholar
Yardley, B. W. D., 1980. Metamorphism and orogeny in the Irish Dalradian. Journal of the Geological Society, London 137, 303–9.Google Scholar
Yardley, B. W. D., Barber, J. P., & Gray, J. R., 1987. The metamorphism of the Dalradian rocks of western Ireland and its relation to tectonic setting. Philosophical Transactions of the Royal Society of London A321, 243–70.Google Scholar
Yardley, B. W. D., Vine, F. J., & Baldwin, C. T., 1982. The plate tectonic setting of NW Britain and Ireland in late Cambrian and early Ordovician times. Journal of the Geological Society, London 139, 455–63.Google Scholar