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Long-lived granite-related molybdenite mineralization at Connemara, western Irish Caledonides

Published online by Cambridge University Press:  22 April 2010

MARTIN FEELY*
Affiliation:
Earth and Ocean Sciences, Quadrangle Building, School of Natural Sciences, National University of Ireland, Galway, Ireland
DAVID SELBY
Affiliation:
Department of Earth Sciences, Durham University, Durham DH1 3LE, UK
JON HUNT
Affiliation:
Earth and Ocean Sciences, Quadrangle Building, School of Natural Sciences, National University of Ireland, Galway, Ireland
JAMES CONLIFFE
Affiliation:
Department of Earth Sciences, Memorial University, St Johns, Newfoundland, Canada
*
Author for correspondence: martin.feely@nuigalway.ie

Abstract

New Re–Os age determinations from the Galway Granite (samples: KMG = 402.2 ± 1.1 Ma, LLG = 399.5 ± 1.7 Ma and GBM = 383.3 ± 1.1 Ma) show that in south Connemara, late Caledonian granite-related molybdenite mineralization extended from c. 423 Ma to c. 380 Ma. These events overlap and are in excellent agreement with the published granite emplacement history determined by U–Pb zircon geochronology. The spatial distribution of the late-Caledonian Connemara granites indicates that initial emplacement and molybdenite mineralization occurred at c. 420 Ma (that is, the Omey Granite and probably the Inish, Leterfrack and Roundstone granites) to the N and NW of the Skird Rocks Fault, an extension of the orogen-parallel Southern Uplands Fault in western Ireland. A generally southern and eastward progression of granite emplacement (and molybdenite mineralization) sited along the Skird Rocks Fault then followed, at c. 410 Ma (Roundstone Murvey and Carna granites), at c. 400 Ma (Errisbeg Townland Granite, Megacrystic Granite, Mingling Mixing Zone Granodiorite, Lough Lurgan Granite and Kilkieran Murvey Granite) and at c. 380 Ma (Costelloe Murvey Granite, Shannapheasteen and Knock granites). The duration of granite magmatism and mineralization in Connemara is similar to other sectors of the Appalachian–Caledonian orogeny and several tectonic processes (e.g. slab-breakoff, asthenospheric flow, transtension and decompression) may account for the duration and variety of granite magmatism of the western Irish Caledonides.

Type
Original Article
Copyright
Copyright © Cambridge University Press 2010

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References

Atherton, M. P. & Ghani, A. A. 2002. Slab breakoff: A model for Caledonian, Late Granite syn-collisional magmatism in the orthotectonic (metamorphic) zone of Scotland and Donegal, Ireland. Lithos 62 (3–4), 6585.CrossRefGoogle Scholar
Baxter, S., Graham, N. T., Feely, M., Reavy, R. J. & Dewey, J. F. 2005. A microstructural and fabric study of the Galway Granite, Connemara, Western Ireland. Geological Magazine 142, 115.CrossRefGoogle Scholar
Buchwaldt, R., Kroner, A., Todt, W., Feely, M. & Toulkerides, T. 1998. Geochemistry, single zircon ages and Sm/Nd isotope analysis of the Galway Granite batholith, western Ireland. Acta Universitatis Carolinae-Geologica 42, 215–16.Google Scholar
Buchwaldt, R., Kroner, A., Toulkerides, T., Todt, W. & Feely, M. 2001. Geochronology and Nd–Sr systematics of Late Caledonian granites in western Ireland: new implications for the Caledonian orogeny. Geological Society of America Abstracts with Programs 33, No. 1, A32.Google Scholar
Bradley, D. C., Tucker, R. D., Lux, D. R., Harris, A. G. & McGregor, D. C. 2000. Migration of the Acadian Orogen and Foreland Basin Across the Northern Appalachians of Maine and Adjacent Areas. U. S. Geological Survey Professional Paper 1624, 49 pp.Google Scholar
Brown, P. E., Ryan, P. D., Soper, N. J. & Woodcock, N. H. 2008. The Newer Granite problem revisited: a transtensional origin for the Early Devonian Trans-Suture Suite. Geological Magazine 145, 235–56.CrossRefGoogle Scholar
Coats, J. S. & Wilson, J. R. 1971. The eastern end of the Galway Granite. Mineralogical Magazine 38, 138–51.CrossRefGoogle Scholar
Condon, D. J., Bowring, S. A., Pitcher, W. S. & Hutton, D. W. H. 2004. Rates and tempo of granitic magmatism; a U–Pb geochronological investigation of the Donegal Batholith (Ireland). Abstracts with Programs, Geological Society of America 36 (5), 406.Google Scholar
Conliffe, J., Selby, D., Porter, S. J. & Feely, M. 2010. Re–Os molybdenite dates from the Ballachulish and Kilmelford Igneous Complexes (Scottish Highlands): age constraints for late Caledonian magmatism. Journal of the Geological Society, London 167, 297302.CrossRefGoogle Scholar
Crowley, Q. & Feely, M. 1997. New perspectives on the order and style of granite emplacement in the Galway Batholith, western Ireland. Geological Magazine 134, 539–48.CrossRefGoogle Scholar
Derham, J. M. 1986. Structural control of sulphide mineralization at Mace Head, Co. Galway. In Geology and genesis of mineral deposits in Ireland (eds Andrews, C. J., Crowe, R. W. A., Finlay, S., Pennell, W. M. & Pyne, J.), pp. 187–93. Irish Association for Economic Geology.CrossRefGoogle Scholar
Derham, J. M. & Feely, M. 1988. A K-feldspar breccia from the Mo–Cu stockwork deposit in the Galway Granite, west of Ireland. Journal of the Geological Society, London 145, 661–7.CrossRefGoogle Scholar
Dewey, J. F. & Strachan, R. A. 2003. Changing Silurian–Devonian relative plate motion in the Caledonides: sinistral transpression to sinistral transtension. Journal of the Geological Society, London 160, 219–29.CrossRefGoogle Scholar
El-Desouky, M., Feely, M. & Mohr, P. 1996. Diorite–granite magma mingling and mixing along the axis of the Galway Granite batholith, Ireland. Journal of the Geological Society, London 153, 361–74.CrossRefGoogle Scholar
Feely, M., Coleman, D., Baxter, S. & Miller, B. 2003. U–Pb zircon geochronology of the Galway Granite, Connemara, Ireland: implications for the timing of late Caledonian tectonic and magmatic events and for correlations with Acadian plutonism in New England. Atlantic Geology 39, 175–84.CrossRefGoogle Scholar
Feely, M., Selby, D., Conliffe, J. & Judge, M. 2007. Re–Os geochronology and fluid inclusion microthermometry of molybdenite mineralization in late-Caledonian Omey Granite, western Ireland. Applied Earth Science 116 (3), 143–9.CrossRefGoogle Scholar
Feely, M., Leake, B. E., Baxter, S., Hunt, J. & Mohr, P. 2006. A geological guide to the Granites of the Galway Batholith, Connemara, western Ireland. Geological Survey of Ireland, 62 pp. ISBN 1-899702-56-3.Google Scholar
Friedrich, A. M., Bowring, S. A., Martin, M. W. & Hodges, K. V. 1999. Short-lived continental magmatic arc at Connemara, western Irish Caledonides: implications for the age of the Grampian orogeny. Geology 27, 2730.2.3.CO;2>CrossRefGoogle Scholar
Gallagher, V., Feely, M., Hoegelsberger, H., Jenkin, G. R. T. & Fallick, A. E. 1992. Geological, fluid inclusion and stable isotope studies of Mo mineralisation, Galway Granite, Ireland. Mineralium Deposita 27, 314–25.CrossRefGoogle Scholar
Jacques, J. M. & Reavy, R. J. 1994. Caledonian plutonism and major lineaments in the SW Scottish Highlands. Journal of the Geological Society, London 151, 955–69.CrossRefGoogle Scholar
Kerr, A. 1997. Space–time composition relationships among Appalachian-cycle plutonic suites in Newfoundland. Geological Society of America Memoirs 191, 193220.Google Scholar
Leake, B. E. 1974. The crystallisation history and mechanism of emplacement of the western part of the Galway Granite, Connemara, western Ireland. Mineralogical Magazine 39, 498513.CrossRefGoogle Scholar
Leake, B. E. 1978. Granite emplacement: the granites of Ireland and their origin. In Crustal evolution in NW Britain and adjacent regions (eds Bowes, D. R. & Leake, B. E.), pp. 221–48. Geological Journal, Special Issue 10.Google Scholar
Leake, B. E. 1989. The metagabbros, orthogneisses and paragneisses of the Connemara complex, western Ireland. Journal of the Geological Society, London 146, 575–96.CrossRefGoogle Scholar
Leake, B. E. 2006. Mechanism of emplacement and crystallisation history of the northern margin and centre of the Galway Granite, western Ireland. Transactions of the Royal Society of Edinburgh, Earth Sciences 97, 123.CrossRefGoogle Scholar
Leake, B. E. & Tanner, P. W. G. 1994. The geology of the Dalradian and associated rocks of Connemara, western Ireland. Royal Irish Academy, ISBN 1-874045-18-6, 96 pp.Google Scholar
Lynch, E. P., Selby, D., Feely, M. & Wilton, D. H. C. 2009. New constraints on the timing of molybdenite mineralization in the Devonian Ackley Granite Suite, southeastern Newfoundland: Preliminary results of Re–Os geochronology Current Research. Newfoundland and Labrador Department of Natural Resources, Geological Survey Report (09-1), 225–34.Google Scholar
Markey, R., Stein, H. & Morgan, J. 1998. Highly precise Re–Os dating for molybdenite using alkaline fusion and NTIMS. Talanta 45, 935–46.CrossRefGoogle ScholarPubMed
Max, M. D., Ryan, P. D. & Inamdar, D. D. 1983. A magnetic deep structural geology interpretation of Ireland. Tectonics 2, 223–33.CrossRefGoogle Scholar
Max, M. D. & Talbot, V. 1986. Molydenum concentrations in the western end of the Galway Granite and their structural setting. In Geology and genesis of mineral deposits in Ireland (eds Andrews, C. J., Crowe, R. W. A., Finlay, S., Pennell, W. M. & Pyne, J.), pp. 177–85. Irish Association for Economic Geology.CrossRefGoogle Scholar
McKie, D. & Burke, K. 1955. The geology of the islands of South Connemara. Geological Magazine 92, 487–98.CrossRefGoogle Scholar
Murphy, T. 1952. Measurements of gravity in Ireland: Gravity survey of central Ireland. Dublin Institute of Advanced Studies, Geophysics Memoirs 2.Google Scholar
Neilsen, J. C., Kokelaar, B. P. & Crowley, Q. G. 2009. Timing, relations and cause of plutonic and volcanic activity of the Siluro-Devonian post-collision magmatic episode in the Grampian Terrane, Scotland. Journal of the Geological Society, London 166, 545–61.CrossRefGoogle Scholar
O'Raghallaigh, C., Feely, M., McArdle, P., MacDermot, C., Geoghegan, M. & Keary, R. 1997. Mineral localities in the Galway Bay Area, Geological Survey of Ireland, Report Series, RS97/1 (Mineral Resources), 70 pp.Google Scholar
O'Reilly, C., Jenkin, G. R. T., Feely, M., Alderton, D. H. M. & Fallick, A. E. 1997. A fluid inclusion and stable isotope study of 200 Ma of fluid evolution in the Galway Granite, Connemara, Ireland. Contributions to Mineralogy and Petrology 129, 120–42.CrossRefGoogle Scholar
Pidgeon, R. T. 1969. Zircon U–Pb ages from the Galway Granite and the Dalradian, Connemara, Ireland. Scottish Journal of Geology 5, 375–92.CrossRefGoogle Scholar
Porter, S. J. & Selby, D. 2010. Rhenium–Osmium (Re–Os) molybdenite geochronology of the Cruachan Granite, Etive Complex, Western Scotland: Implications for the timing of Skarn-type mineralization at Coire Buidhe, emplacement chronology and Re–Os molybdenite systematics. Scottish Journal of Geology 46 (1), 16.CrossRefGoogle Scholar
Pracht, M., Lees, A., Leake, B. E., Feely, M., Long, C. B., Morris, J. & McConnell, B. 2004. Geology of Galway Bay; A geological description to accompany the bedrock geology 1:100,000 scale map series, sheet 14, Galway Bay. Geological Survey of Ireland, 76 pp.Google Scholar
Selby, D. & Creaser, R. A. 2001 Re–Os geochronology and systematics in molybdenum from the Endako porphyry molybdenum deposit, British Columbia, Canada. Economic Geology 96, 197204.CrossRefGoogle Scholar
Selby, D. & Creaser, R. A. 2004. Macroscale NTIMS and microscale LA-MC-ICP-MS Re–Os isotopic analysis of molybdenite: Testing spatial restriction for reliable Re–Os age determinations, and implications for the decoupling of Re and Os within molybdenite. Geochimica et Cosmochimica Acta 68, 3897–908.CrossRefGoogle Scholar
Selby, D., Creaser, R. A. & Feely, M. 2004. Accurate Re–Os molybdenite dates from the Galway Granite, Ireland. A critical comment to: Disturbance of the Re–Os chronometer of molybdenites from the late-Caledonian Galway Granite, Ireland, by hydrothermal fluid circulation. Geochemical Journal 38, 291–4.CrossRefGoogle Scholar
Selby, D., Creaser, R. A., Stein, H. J., Markey, R. J. & Hannah, J. L. 2007. Assessment of the 187Re decay constant accuracy and precision: cross calibration of the 187Re–187Os molybdenite and U–Pb zircon chronometers. Geochimica et Cosmochimica Acta 71, 19992013.CrossRefGoogle Scholar
Smoliar, M. I., Walker, R. J. & Morgan, J. W. 1996. Re–Os isotope constraints on the age of Group IIA, IIIA, IVA and IVB iron meteorites. Science 271, 10991102.CrossRefGoogle Scholar
Stein, H. J., Markey, R. J. & Morgan, J. W. 1997. Highly precise and accurate Re–Os ages for molybdenite from the east Qinling molybdenum, Shaanxi province, China. Economic Geology 92, 827–35.CrossRefGoogle Scholar
Townend, R. 1966. The geology of some granite plutons from western Connemara, Co. Galway. Proceedings of the Royal Irish Academy 65B, 157202.Google Scholar
Watson, J. V. 1984. The ending of the Caledonian orogeny in Scotland. Journal of the Geological Society, London 141, 193214.CrossRefGoogle Scholar
Whalen, J. B., McNicoll, V. J., Van Staal, C. R., Lissenberg, C. J., Longstaffe, F. J., Jenner, G. A. & Van Breeman, O. 2006. Spatial, temporal and geochemical characteristics of Silurian collision-zone magmatism, Newfoundland Appalachians: An example of a rapidly evolving magmatic system related to slab break-off. Lithos 89, 377404.CrossRefGoogle Scholar
Williams, D. M., Armstrong, H. A. & Harper, D. A. T. 1988. The age of the South Connemara Group, Ireland and its relationship to the Southern Uplands Zone of Scotland and Ireland. Scottish Journal of Geology 24, 279–87.CrossRefGoogle Scholar
Wright, P. C. 1964. The petrology, chemistry and structure of the Galway Granite of the Carna area, Co. Galway. Proceedings of the Royal Irish Academy 63B, 239–64.Google Scholar