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Ballygowan, United Kingdom

Hollis S.P.,UK National Oceanography Center | Hollis S.P.,CSIRO | Cooper M.R.,Geological Survey of Ireland | Roberts S.,UK National Oceanography Center | And 3 more authors.
Journal of the Geological Society | Year: 2013

Recent Ar-Ar and U-Pb zircon geochronology from across the British and Irish Caledonides has revealed a prolonged period of arc-ophiolite formation (c. 514-464 Ma) and accretion (c. 490-470 Ma) to the Laurentian margin during the Grampian orogeny. The Slieve Gallion Inlier of Northern Ireland, an isolated occurrence of the Tyrone Volcanic Group, records the development of a peri-Laurentian island arc-backarc and its obduction to an outboard microcontinental block. Although a previous biostratigraphic age constraint provides a firm correlation of at least part of the volcanic succession to the Ca1 Stage of the Arenig (c. 475- 474 Ma), there is uncertainty on its exact statigraphic position in the Tyrone Volcanic Group. Earliest magmatism is characterized by light rare earth element (LREE) depleted island-arc tholeiite. Overlying deposits are dominated by large ion lithophile and LREE-enriched, hornblende-phyric and feldspathic calc-alkaline basaltic andesites and andesitic tuffs with strongly negative εNdt values. Previously published biostratigraphic age constraints, combined with recent U-Pb zircon geochronology and new petrochemical correlations, suggest that the Slieve Gallion Inlier is equivalent to the lower Tyrone Volcanic Group. Temporal and geochemical correlations between the Slieve Gallion Inlier and Charlestown Group of Ireland suggest that they may be part of the same arc system, which was accreted at a late stage (c. 470 Ma) in the Grampian orogeny. A switch from tholeiitic volcanism to calc-alkaline dominated activity within the Lough Nafooey Group of western Ireland occurred prior to c. 490 Ma, some 15-20 Myr earlier than at Tyrone and Charlestown. © 2013 The Geological Society of London.

Hollis S.P.,UK National Oceanography Center | Hollis S.P.,CSIRO | Roberts S.,UK National Oceanography Center | Cooper M.R.,Geological Survey of Ireland | And 6 more authors.
Bulletin of the Geological Society of America | Year: 2012

In order to understand the progressive growth of continental margins and the evolution of continental crust, we must first understand the formation of allochthonous ophiolitic and island-arc terranes within ancient orogens and the nature of their accretion. During the early Paleozoic closure of the Iapetus Ocean, diverse sets of arc terranes, oceanic tracts, and ribbon-shaped micro conti nental blocks were accreted to the passive continental margin of Laurentia during the Grampian-Taconic orogeny. In the northern Appalachians in central Newfoundland, Canada, three distinct phases of arc-ophiolite accretion have been recognized. New field mapping, high-resolution airborne geo physics, whole-rock and Nd-isotope geochemistry, and U-Pb zircon geochronology within the Tyrone Volcanic Group of Northern Ireland have allowed all three episodes to now be correlated into the British and Irish Caledonides. The Tyrone Volcanic Group (ca. 475-469 Ma) is characterized by mafic to intermediate lavas, tuffs, rhyolite, banded chert, ferruginous jasperoid, and argillaceous sedimentary rocks cut by numerous high-level intrusive rocks. Geochemical signatures are consistent with formation within an evolving peri-Laurentian island-arc/backarc, which underwent several episodes of intra-arc rifting prior to its accretion at ca. 470 Ma to an outboard peri-Laurentian microcontinental block. Outriding microcontinental blocks played a fundamental role within the orogen, explaining the range of ages for Iapetan ophiolites and the timing of their accretion, as well as discrepancies between the timing of ophiolite emplacement and the termination of the Laurentian Cambrian-Ordovician shelf sequences. Accretion of the Tyrone arc and its associated suprasubduction-zone ophiolite represents the third stage of arc-ophiolite emplacement to the Laurentian margin during the Grampian-Taconic orogeny in the British and Irish Caledonides. © 2012 Geological Society of America.

Taylor W.,16 Mill Road
Tropical Animal Health and Production | Year: 2016

Gordon Scott did much to inspire the eradication of rinderpest, probably the most outstanding veterinary achievement of the twentieth century, and one currently inspiring is the proposed eradication of peste des petits ruminants (PPR), a disease of sheep and goats caused by a closely related Morbillivirus. The evolution and geographic spread of PPR along with its epidemiological characteristics are discussed and related to ways in which its spread can be reduced through the provision of diagnostic aids to sanitary livestock movement at local level. Taking a historical look at rinderpest eradication, it was shown that much could be achieved using a legislation-backed zoosanitary approach or, once developed, the build up of herd immunities in isolated populations. As the final cap to this (circa), two hundred-year-long process, major national and internationally funded vaccination programmes falling within the informal coordinatorship of the OIE and FAO showed that final eradication could be achieved with remarkable rapidity if the seat of infection was known and if appropriate national and international interventions were aimed at ending virus transmission. Were such international cooperation to be forthcoming once more, the understanding, tools and experiences now on offer suggest that PPR could be controlled and eradicated far more rapidly than rinderpest. © 2016 Springer Science+Business Media Dordrecht

Hollis S.P.,UK National Oceanography Center | Hollis S.P.,CSIRO | Cooper M.R.,Geological Survey of Ireland | Roberts S.,UK National Oceanography Center | And 4 more authors.
Journal of the Geological Society | Year: 2013

The Tyrone Plutonic Group of Northern Ireland represents the upper portions of a tectonically dissected suprasubduction-zone ophiolite accreted to the composite Laurentian margin during the Middle Ordovician. Understanding its development and relationship to the Tyrone Central Inlier, an outboard fragment of relatively high-grade, peri-Laurentian continental crust, is essential for reconstructing the closure of the Iapetus Ocean. The Tyrone Plutonic Group is composed of tectonized layered, isotropic and pegmatitic gabbros, sheeted dolerite dykes and rare pillow lavas. New U-Pb zircon thermal ionization mass spectrometry geochronology has yielded an age of 483.68 ± 0.81 Ma from pegmatitic gabbro. Geochemical characteristics, Nd and Sr isotope systematics, and zircon inheritance indicate that the Tyrone Plutonic Group formed above a north-dipping subduction zone, by the propagation of a spreading centre into a microcontinental block. Synkinematic, calc-alkaline tonalitic to granitic material preserved in the contact zone between the Tyrone Plutonic Group and the Tyrone Central Inlier has produced pressure estimates of 2.3-4.0 ± 0.6 kbar and temperatures of 525-610 °C. Coeval arc-ophiolite accretion at c. 470 Ma may explain how sillimanite-grade metamorphic conditions were reached locally in the underlying Tyrone Central Inlier. Strong temporal, geochemical and lithological similarities exist to the Annieopsquotch Ophiolite Belt of Newfoundland. © 2013 The Geological Society of London.

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