Grenville events in Moine rocks of the Northern Highlands, Scotland

Brook, M.; Brewer, Martin; Powell, Derek

doi:10.1144/gsjgs.133.5.0489

Cited by 64 publications

(24 citation statements)

References 15 publications

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“…Together with Rb-Sr isochrons yielding c. 1000 Ma ages from the country rocks, these results were interpreted as evidence that the Grenville orogeny had affected the Moine rocks (Brook et al 1977;Brewer et al 1979;Roberts et al 1987). However, recent U-Pb studies on single zircon grains from the granite gneiss have yielded a consistent age of c. 873 Ma for the igneous protolith at Glenfinnan (location C, Fig.…”

Section: West Highland Granite Gneissmentioning

confidence: 86%

Late Precambrian U–Pb titanite age for peak regional metamorphism and deformation (Knoydartian orogeny) in the western Moine, Scotland

Tanner

Evans²

2003

JGS

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There has been controversy over the number and timing of orogenies in the Precambrian Moine block in the Scottish Caledonides since the earliest radiometric dating in the 1960s. This work challenges a recent hypothesis, that this sector of the Laurentian margin was subjected to continuous crustal extension between .900 and 470 Ma. U-Pb dating (thermal ionization mass spectrometry) of titanite from a calcsilicate pod in the Moine (Morar Group) of the western Highlands gives an age of 737 AE 5 Ma. The titanite grew from Fe-Ti-bearing detrital minerals during the main progressive, syn-D 2 , amphibolite-facies (sillimanite zone) regional metamorphism, thus demonstrating that a Neoproterozoic contractional tectonothermal event (Knoydartian orogeny) affected the Moine block following the rift-related emplacement of the West Highland granite gneiss at 873 Ma. We conclude that the Sgurr Beag Thrust, a major tectonic break separating the Morar and Glenfinnan groups of the Moine, is mainly of Neoproterozoic, not Caledonian, age. The early tectonothermal event was succeeded by the Grampian Phase (Caledonian orogeny) at 460-470 Ma.

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Section: West Highland Granite Gneissmentioning

confidence: 86%

Late Precambrian U–Pb titanite age for peak regional metamorphism and deformation (Knoydartian orogeny) in the western Moine, Scotland

Tanner

Evans²

2003

JGS

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“…Rb -Sr isochron of metaconglomerate. Analytical methods are describedin Brook et al (1977). Error is two standard deviations.central Chile between 100 and 250 km to the south of this area indicated that no major rotation or translation of crustal blocks has taken place since Middle Jurassic time(Irwin et al 1987), consistent with an "autochthonous" post-Paleozoic history of this area.…”

mentioning

confidence: 86%

“…Rb-Sr isochron of metavolcanics. Analytical methods are described in Brook et al (1977). Error is two standard deviations.…”

Section: Intrusionsmentioning

confidence: 99%

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Geology of part of a long-lived dynamic plate margin: the coastal cordillera of north-central Chile, latitude 30°51′–31°S

Irwin¹,

García²,

Hervé³

et al. 1988

Can. J. Earth Sci.

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A complex composed of ultrabasic and basaltic lavas, chert, arkose, and conglomerate was assembled in the coast of north-central Chile (lat. 30°30′–31°S) prior to 200 Ma. The character of, and relationships between, the rock formations exposed here are consistent with an autochthonous evolution of this part of Chile in the last 200 Ma. Three major episodes of deformation and metamorphism have been observed in this area. The first episode (F1) produced a compositional layering (S1) and amphibolite-facies metamorphism coeval with the intrusion of an extensive igneous complex between 220 and 200 Ma. A second episode of deformation (F2) locally formed reverse faults and tight, recumbent folds in S1. Units in which F2 folds are well developed yield K–Ar and Rb–Sr ages between 163 and 140 Ma. At between 140 and 126 Ma, upright, open to tight folds (F3) formed with sharp hinges and axial planes that strike north and dip steeply east. Structures of similar age, style, and orientation have been reported as far south as Tierra del Fuego. The timing of the F3 deformation appears to correspond to the opening of the South Atlantic Ocean and accelerated westward motion of South America.

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“…The Strontian Granodiorite intrudes Moinian metasediments, mainly pelites and semipelites of the Glenfinnan Division, which probably underwent metamorphism in the Grenville Orogeny about 1.0 Ga ago (Brook et al, 1976) but have suffered further, Caledonian regional metamorphism (Brook et al, 1977, Table 3). The area studied ( fig.…”

Section: Copyright the Mineralogical Societymentioning

confidence: 99%

Garnet zoning and re-equilibration in the Strontian area, Scotland

Tyler

Ashworth

1981

Mineral. mag.

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ABSTRACT. In Moinian metasediments regionally metamorphosed to sillimanite grade, garnet has subsequently been re-equilibrated in the inner (cordierite-potash feldspar) zone of the aureole of the Strontian Granodiorite. Zoning profiles of garnet from the aureole, and from surrounding regional assemblages, show retrograde Mnrich rims. Some regional garnets are also internally zoned. In the aureole as a whole, the partition measure for Fe and Mg between garnet and biotite shows a correlation with that for Ca between garnet and plagioclase. If interpreted in terms of a simple equilibrium model, this might suggest that pressure decreased with increasing temperature towards the granodiorite, but the trend can more plausibly be attributed to deviation from ideal solidsolution behaviour of Ca in garnet and plagioclase, with incomplete homogenization of garnet as a complicating factor in the outer parts of the aureole. From the difference in the temperature thresholds for garnet core equilibration, the timescale t2 of the thermal event relative to the regional t I is estimated as t2/t 1 ~-10 -1"1-+0"7, consistent with emplacement of the intrusion at an early stage of regional cooling.

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Grenville events in Moine rocks of the Northern Highlands, Scotland

Cited by 64 publications

References 15 publications

Late Precambrian U–Pb titanite age for peak regional metamorphism and deformation (Knoydartian orogeny) in the western Moine, Scotland

Late Precambrian U–Pb titanite age for peak regional metamorphism and deformation (Knoydartian orogeny) in the western Moine, Scotland

Geology of part of a long-lived dynamic plate margin: the coastal cordillera of north-central Chile, latitude 30°51′–31°S

Garnet zoning and re-equilibration in the Strontian area, Scotland

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