Geochronological constraints on the magmatic, metamorphic and thermal evolution of the Connemara Caledonides, western Ireland

Friedrich, Anke; Hodges, Kip; Bowring, Samuel A.; Martin, Mark W.

doi:10.1144/gsjgs.156.6.1217

Cited by 89 publications

(84 citation statements)

References 47 publications

Supporting

Mentioning

Contrasting

Order By: Relevance

“…In Newfoundland, volcanism in the continentward-facing arc lasted until Ϸ460 Ma in contrast to 467 Ma in western Ireland. The postflip, continental margin arc in Newfoundland is manifest as a granodiorite͞tonalite ''sea'' of plutons [25][26][27]; possibly, some of the bodies classified above as precollisional arc plutons may be syn-collisional or postflip.…”

Section: The Western Irish and Scottish Caledonides: The Grampian Orogenmentioning

confidence: 99%

“…Kennedy (25) recognized that the Grampian Orogeny must have been an Ordovician (26) rather than a Precambrian or pre-Ordovician event. Dewey and Mange (10) recognized that the Orogeny must have occurred during a very short time interval during the deposition of the conformable stratigraphic sequence of the South Mayo Trough (SMT), supported by geochronology (27) and geology (28). Orogeny is, perhaps, best understood by studying the facies and detrital mineralogy of coeval sedimentary basins; the Grampian Orogen permits the integration of these data with metamorphic͞geochronologic data.…”

mentioning

confidence: 99%

See 1 more Smart Citation

Orogeny can be very short

Dewey

2005

Proc. Natl. Acad. Sci. U.S.A.

202

139

View full text Add to dashboard Cite

In contrast to continent͞continent collision, arc-continent collision generates very short-lived orogeny because the buoyancy-driven impedance of the subduction of continental lithosphere, accompanied by arc͞suprasubduction-zone ophiolite obduction, is relieved by subduction polarity reversal (flip). This tectonic principle is illustrated by the early Ordovician Grampian Orogeny in the British and Irish Caledonides, in which a wealth of detailed sedimentologic, heavy mineral, and geochronologic data pin the Orogeny to a very short Arenig͞Llanvirn event. The Orogeny, from the initial subduction of continental margin sediments to the end of postflip shortening, lasted Ϸ18 million years (my). The collisional shortening, prograde-metamorphic phase of the Orogeny lasted 8 my, extensional collapse and exhumation of midcrustal rocks lasted 1.5 my, and postflip shortening lasted 4.5 my. Strain rates were a typical plate-boundary-zone 10 ؊15 . Metamorphism, to the second sillimanite isograd, with extensive partial melting, occurred within a few my after initial collision, indicating that conductive models for metamorphic heat transfer in Barrovian terrains are incorrect and must be replaced by advective models in which large volumes of mafic͞ultramafic magma are emplaced, syn-tectonically, below and into evolving nappe stacks. Arc͞continent collision generates fast and very short orogeny, regional metamorphism, and exhumation.8 million year orogeny ͉ continent͞arc collision ͉ orogenic mechanisms

show abstract

Section: The Western Irish and Scottish Caledonides: The Grampian Orogenmentioning

confidence: 99%

mentioning

confidence: 99%

Orogeny can be very short

Dewey

2005

Proc. Natl. Acad. Sci. U.S.A.

202

139

View full text Add to dashboard Cite

show abstract

“…Indeed, Caledonian basement rocks north of the Iapetus suture in the British Isles contain numerous important orogenic gold prospects extending from the Mayo-Curlew Basin of western Ireland (Croagh Patrick and the mineralization of the Sheeffry Hills insuccession of Ordovician volcanic and sedimentary rocks (Clift and Ryan, 1994;Friedrich et al, 1999a). The obscured contact between the Connermara terrane and the South Mayo Trough is inferred to be a strike-slip terrane boundary (Friedrich et al, 1999b). The Connemara Dalradian and rocks of the South Mayo Trough are unconformably overlain by Silurian (Llandovery <443 Ma) sedimentary rocks (Friedrich et al, 1999b: Fig.…”

Section: Introductionmentioning

confidence: 99%

Atypical Gold Mineralization in an Orogenic Setting--The Bohaun Deposit, Western Irish Caledonides

et al. 2011

View full text Add to dashboard Cite

The Bohaun gold deposit in County Galway, western Ireland is located in the Caledonian orogenic belt, proximal to a major accretionary boundary. The mineralization is hosted in a normal extensional fault, representing a zone of repeated extension and vein infilling of open cavities, within clastic sedimentary rocks, which have only reached the late diagenetic zone of low-grade metamorphism.The mineralization consists of undeformed veins, stockworks and breccias. Quartz dominates all the veins and commonly displays multiple growth stages and a variety of classic epithermal textures, including comb, plumose and banded, indicative of low confining pressures. The veins have a simple mineralogy comprising quartz-sericite-chlorite with minor sulfides, hematite, rare visible gold, with a high silver content (up to 41 wt %), and late barite and dolomite.Vein quartz is associated with two fluids compositions: Type I with moderate to high salinity (8.0-23.6 wt % NaCl equiv) and Type II with low to moderate salinity (0.0-7.8 wt % NaCl equiv). CO 2 contents in both fluid types are <3.5 wt percent. The majority of fluid inclusion homogenization temperatures range from 126 to 257 o C and geologically constrained depth estimates (≤5 km) indicate maximum fluid inclusion trapping temperatures between 175 and 245°C.The geodynamic setting of Bohaun, which comprises a deformed continental margin of an allochthonous terrane, is typical of orogenic gold deposits. However, an orogenic association for the Bohaun mineralization is discounted on the basis of fluid inclusion evidence, atypical vein textures, gold grain composition and undeformed veins. While vein textures locally resemble those found in epithermal quartz-adularia mineralization, there is no obvious magmatic association and alteration is restricted to the veins and immediate host rocks. The origin of the gold at Bohaun remains enigmatic. However, we favor an association with widespread Carboniferous or later mineralizing fluids and a model which involves transport and deposition of gold from a basinal brine type fluid, in a similar fashion to red-bed Au-Pd mineralization. Bohaun provides further evidence that low temperature brines may be capable of generating economic grade gold mineralization, independent of other fluids.3

show abstract

“…Barr et al 1995) and western Ireland (e.g. Friedrich et al 1999aFriedrich et al , 1999b. In contrast, the geochronological database available for Caledonian metamorphic events in northern Scotland still largely comprises a relatively small number of Rb-Sr whole-rock isochron determinations together with scattered Rb-Sr, U-Pb and K-Ar mineral analyses (e.g.…”

mentioning

confidence: 99%

U–Pb geochronology of deformed metagranites in central Sutherland, Scotland: evidence for widespread late Silurian metamorphism and ductile deformation of the Moine Supergroup during the Caledonian orogeny

Kinny

Strachan

Friend

et al. 2003

JGS

View full text Add to dashboard Cite

Within the Caledonides of central Sutherland, Scotland, the Neoproterozoic metasedimentary rocks of the Moine Supergroup record NW-directed D 2 ductile thrusting and nappe assembly, accompanied by widespread tight-to-isoclinal folding and amphibolite-facies metamorphism. A series of metagranite sheets which were emplaced and penetratively deformed during D 2 have been dated using SHRIMP U-Pb geochronology. Zircon ages of 424 AE 8 Ma (Vagastie Bridge granite), 420 AE 6 Ma (Klibreck granite) and 429 AE 11 Ma (Strathnaver granite) are interpreted to date emplacement, and hence regional D 2 deformation, during mid-to late Silurian time. Titanite ages of 413 AE 3 Ma (Vagastie Bridge granite) and 416 AE 3 Ma (Klibreck granite) are thought to date post-metamorphic cooling through a blocking temperature of c. 550-500 8C. A mid-to late Silurian age for D 2 deformation supports published models that have viewed the internal ductile thrusts of this part of the orogen as part of the same kinematically linked system of forelandpropagating thrusts as the marginal Moine Thrust Zone. The new data contrast with previous interpretations that have viewed the dominant structures and metamorphic assemblages within the Moine Supergroup as having formed during the early to mid-Ordovician Grampian arc-continent orogeny. The mid-to late Silurian D 2 nappe stacking event in Sutherland is probably a result of the collision of Baltica with the Scottish segment of Laurentia.

show abstract

Geochronological constraints on the magmatic, metamorphic and thermal evolution of the Connemara Caledonides, western Ireland

Cited by 89 publications

References 47 publications

Orogeny can be very short

Orogeny can be very short

Atypical Gold Mineralization in an Orogenic Setting--The Bohaun Deposit, Western Irish Caledonides

U–Pb geochronology of deformed metagranites in central Sutherland, Scotland: evidence for widespread late Silurian metamorphism and ductile deformation of the Moine Supergroup during the Caledonian orogeny

Contact Info

Product

Resources

About