|
Article |
1 Department of Geology, Imperial College of Science and Technology, London, SW72BP, UK
2 Department of Geology, Memorial University of Newfoundland, St. Johns, Newfoundland, Canada
3 Department of Earth Sciences, The Open University, Milton Keynes, MK76AA, UK
4 Department of Geology, Trinity College, Dublin 2, Republic of Ireland
Bimodal associations of basalt and rhyolite of Upper Ordovician age which were erupted in a submarine environment occur within the Caledonian orogenic belt of South Britain at Parys Mountain (Anglesey), in Snowdonia (North Wales) and at Avoca (SE Ireland). The volcanic rocks have experienced hydrothermal alteration and low-grade metamorphism, and therefore immobile elements (e.g. Ti, Zr, Nb, Y) have been used to identify the original geochemical characteristics. The basalts have characters transitional between volcanic ‘arc’ and ‘within plate’ types consistent with eruption on an extensional part of an active continental margin. Two groups of rhyolites have been identified. A low-Zr group (Zr<500ppm), represented at all three locations, is interpreted as originally of high-K, subalkaline type. A high-Zr group (Zr>500ppm), represented at Snowdonia and Avoca, is interpreted as originally being peralkaline in composition; their high Zr/Nb ratios (>10) are typical of peralkaline rhyolites erupted above subduction zones. The bimodal nature of the associations and the peralkaline character of some rhyolites indicates magma production in a complex tectonic setting, transitional between an active continental margin/island arc and an extensional environment. Associated sulphide mineralization is volcanogenic and probably syn-sedimentary. High-level, rhyolitic magma chambers are thought to have driven convection of the hydrothermal fluids from which the sulphides precipitated.
This article has been cited by other articles:
 |
|
 |
|
  S. J. Piercey, J. M. Peter, J. K. Mortensen, S. Paradis, D. C. Murphy, and T. L. Tucker Petrology and U-Pb Geochronology of Footwall Porphyritic Rhyolites from the Wolverine Volcanogenic Massive Sulfide Deposit, Yukon, Canada: Implications for the Genesis of Massive Sulfide Deposits in Continental Margin Environments Economic Geology, 2008; 103: 5 - 33. [Abstract] [Full Text] [PDF]
|
|
|
|
 |
|
 S. Gursu and M. C. Goncuoglu Petrogenesis and geodynamic evolution of the Late Neoproterozoic post-collisional felsic magmatism in NE Afyon area, western central Turkey Geological Society, London, Special Publications, 2008; 297: 409 - 431. [Abstract] [Full Text] [PDF]
|
|
|
|
 |
|
 C. M. Fanning, C.M. Fanning, R.J. Pankhurst, C.W. Rapela, E.G. Baldo, C. Casquet, and C. Galindo K-bentonites in the Argentine Precordillera contemporaneous with rhyolite volcanism in the Famatinian Arc Journal of the Geological Society, 2004; 161: 747 - 756. [Abstract] [Full Text] [PDF]
|
|
|
|
|
|
C. W. Rapela, C.W. Rapela, R.J. Pankhurst, C.M. Fanning, and L.E. Grecco Basement evolution of the Sierra de la Ventana Fold Belt: new evidence for Cambrian continental rifting along the southern margin of Gondwana Journal of the Geological Society, 2003; 160: 613 - 628. [Abstract] [Full Text] [PDF]
|
|
|
|
 |
|
 S. Koeniger, S. KONIGER, and V. LORENZ Geochemistry, tectonomagmatic origin and chemical correlation of altered Carboniferous-Permian fallout ash tuffs in southwestern Germany Geological Magazine, 2002; 139: 541 - 558. [Abstract] [Full Text] [PDF]
|
|
|
|
 |
|
 N. A. Van Wagoner, M. I. Leybourne, K. A. Dadd, D. K. Baldwin, and W. McNeil Late Silurian bimodal volcanism of southwestern New Brunswick, Canada: Products of continental extension GSA Bulletin, 2002; 114: 400 - 418. [Abstract] [Full Text] [PDF]
|
|
|
|
|
|
S. J. Piercey, S. J. Piercey, S. Paradis, D. C. Murphy, and J. K. Mortensen Geochemistry and Paleotectonic Setting of Felsic Volcanic Rocks in the Finlayson Lake Volcanic-Hosted Massive Sulfide District, Yukon, Canada, Economic Geology, 2001; 96: 1877 - 1905. [Abstract] [Full Text] [PDF]
|
|
|
|
|
|
T. J. Barrett, T. J. Barrett, W. H. MacLean, and S. C. Tennant Volcanic Sequence and Alteration at the Parys Mountain Volcanic-Hosted Massive Sulfide Deposit, Wales, United Kingdom: Applications of Immobile Element Lithogeochemistry Economic Geology, 2001; 96: 1279 - 1305. [Abstract] [Full Text] [PDF]
|
|
|
|
 |
|
 A. Maria and O. D. Hermes Volcanic Rocks in the Narragansett Basin, Southeastern New England: Petrology and Significance to Early Basin Formation Am J Sci, 2001; 301: 286 - 312. [Abstract] [Full Text] [PDF]
|
|
|
|
 |
|
 L. A. KIRSTEIN, D. W. PEATE, C. J. HAWKESWORTH, S. P. TURNER, C. HARRIS, and M. S. M. MANTOVANI Early Cretaceous Basaltic and Rhyolitic Magmatism in Southern Uruguay Associated with the Opening of the South Atlantic J. Petrology, 2000; 41: 1413 - 1438. [Abstract] [Full Text] [PDF]
|
|
|
|
|
|
P. A. Floyd, M. C. Goncuoglu, J. A. Winchester, and M. K. Yaliniz Geochemical Character and Tectonic Environment of Neotethyan Ophiolitic Fragments and Metabasites in the Central Anatolian Crystalline Complex, Turkey Geological Society, London, Special Publications, 2000; 173: 183 - 202. [Abstract] [PDF]
|
|
|
|
|
|
W.E.S. GIBBONS and T. P. YOUNG Mid-Caradoc magmatism in central Llyn, rhyolite petrogenesis, and the evolution of the Snowdonia volcanic corridor in NW Wales Journal of the Geological Society, 1999; 156: 301 - 316. [Abstract] [PDF]
|
|
|
|
|
|
B. BRIAND, M. PIBOULE, D. SANTALLIER, and J. L. BOUCHARDON Geochemistry and tectonic implications of two Ordovician bimodal igneous complexes, southern French Massif Central Journal of the Geological Society, 1991; 148: 959 - 971. [Abstract] [PDF]
|
|
|
|
|
|
B. J. McCONNELL, C. J. STILLMAN, and J. HERTOGEN An Ordovician basalt to peralkaline rhyolite fractionation series from Avoca, Ireland Journal of the Geological Society, 1991; 148: 711 - 718. [Abstract] [PDF]
|
|
|
|
|
|
R. E. BEVINS, G. J. LEES, and R. A. ROACH Ordovician bimodal volcanism in SW Wales: geochemical evidence for petrogenesis of the silicic rocks Journal of the Geological Society, 1991; 148: 719 - 729. [Abstract] [PDF]
|
|
|
|
|
|
M. B. ALLEN, B. F. WINDLEY, Z. CHI, Z. ZHONG-YAN, and W. GUANG-REI Basin evolution within and adjacent to the Tien Shan Range, NW China Journal of the Geological Society, 1991; 148: 369 - 378. [Abstract] [PDF]
|
|
|
|
|
|
P. T. LEAT and R. S. THORPE Snowdon basalts and the cessation of Caledonian subduction by the Longvillian Journal of the Geological Society, 1989; 146: 965 - 970. [Abstract] [PDF]
|
|
|
|
|
|
R. S. THORPE, P. T. LEAT, R. E. BEVINS, and D. J. HUGHES Late-orogenic alkaline/subalkaline Silurian volcanism of the Skomer Volcanic Group in the Caledonides of south Wales Journal of the Geological Society, 1989; 146: 125 - 132. [Abstract] [PDF]
|
|
|
|
|
|
P. KOKELAAR Tectonic controls of Ordovician arc and marginal basin volcanism in Wales Journal of the Geological Society, 1988; 145: 759 - 775. [Abstract] [PDF]
|
|
|
|
|
|
R. D. DALLMEYER and W. GIBBONS The age of blueschist metamorphism in Anglesey, North Wales: evidence from 40Ar/39Ar mineral dates of the Penmynydd schists Journal of the Geological Society, 1987; 144: 843 - 850. [Abstract] [PDF]
|
|
