Origin of granitic magma by crustal remobilisation: Rb-Sr and Pb/Pb geochronology and isotope geochemistry of the late Archaean Qôrqut Granite Complex of southern West Greenland

Moorbath, S.; Taylor, Paul N.; Goodwin, Roy

doi:10.1016/0016-7037(81)90131-9

Cited by 95 publications

(20 citation statements)

References 15 publications

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“…The age is in agreement with previously published Rb-Sr ages on the Q6rqut Granite Complex (Moorbath et al, 1981). However, the initial 87Sr/ 86 Sr ratio is somewhat lower than that of 0.7081 ± 0.0008 reported by Moorbath et al (1981), but it is still consistent with crustal partial melting to produce the Q6rqut granite of Kangiussap nuna. This last group indudes samples that were provisionally assigned to Niik 4 on field criteria by Coe & Robertson (1982).…”

Section: Rb/86srsupporting

confidence: 91%

Provisional results of isotope investigations into quartzo-feldspathic rocks from Kangiussap nunâ, Ivisârtoq sheet, southern West Greenland

Robertson¹

1983

rapggu

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The geology of Kangiussap nuna has been described by Walton (1976), Allaart et al., (1977) and more recently, folIowing 1:20000 mapping, by Coe & Robertson (1982) (see also Brewer et al., this report). A heterogeneous banded gneiss believed to be Amitsoq is intruded by multiphase Nl1k gneiss. Coe & Robertson (1982) recognised five phases of Nl1k gneiss (Nl1k 1-5). These are cut by undeformed to weakly foliated granites and pegmatites which were judged to be of Qorqut age (Coe & Robertson, 1982). This report presents the results of Rb-Sr whole rock-analyses and provisional Pb isotope results on representative samples of Nl1k 1 to 4 and Qorqut granite (terminology of Coe & Robertson, 1982). These samples were collected during field mapping in 1981 as part of the Ivisiirtoq project for the Geological Survey of Greenland at the University of Exeter. Rb-Sr ratios were determined by X-ray fluorescence spectrometry at the University of Oxford. Sr and Pb isotopes were measured in the same laboratories on VG Micromass 30 and Isomass 54E mass spectrometers, respectively. The generous assistance of P. N. Taylor and S. Moorbath is gratefully acknowledged.

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Section: Rb/86srsupporting

confidence: 91%

Provisional results of isotope investigations into quartzo-feldspathic rocks from Kangiussap nunâ, Ivisârtoq sheet, southern West Greenland

Robertson¹

1983

rapggu

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“… a The isotopic signatures of the regional sources were defined from literature data: MAR [ O'Nions et al , 1977; Carter et al , 1979; Zindler et al , 1979; Cohen et al , 1980; Gariépy et al , 1983] (see full references in the work by Fagel et al [1999]), EVC [ Michard et al , 1985; Liew and Hofmann , 1988] (see full references in the work by Fagel et al [1999]), EPC, GPC and SPC [ O'Nions et al , 1983; Miller and O'Nions , 1984; Michard et al , 1985; André et al , 1986] (see full references in the work by Fagel et al [1999]), SSB [ Andersen et al , 1994; Knudsen et al , 1997], GKB [ Patchett and Bridgewater , 1984; Kalsbeek and Taylor , 1985], GNB [ Taylor et al , 1980; Kalsbeek et al , 1984, 1988, 1993], GAC [ Moorbath et al , 1981; Taylor et al , 1992], LNP [ Baadsgaard et al , 1979], GP [ Schärer , 1991], SP [ Gariépy and Allègre , 1985; Shirey and Hanson , 1986; Barrie and Shirey , 1991; Vervoort et al , 1993; Henry et al , 1998], and WGR [ Goldstein and Jacobsen , 1987, 1988; Asmerom and Jacobsen , 1993] (see full references in the work by Fagel et al , 2002]). Mean and median values were calculated in order to take into account the uncertainty of the end‐member composition [see Fagel et al , 2002].…”

Section: Discussionmentioning

confidence: 99%

Holocene evolution of deep circulation in the northern North Atlantic traced by Sm, Nd and Pb isotopes and bulk sediment mineralogy

Fagel

Mattielli

2011

Paleoceanography

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Bulk mineralogy, Sm, Nd and Pb elemental and isotopic compositions of the clay‐size fraction of Holocene sediments were analyzed in three deep North Atlantic cores to trace the particle provenance. The aims of the present paper are to identify the origin of the particles driven by deep currents and to reconstruct deep circulation changes over the Holocene in the North Atlantic. The three cores are retrieved in fracture zones; two of them are located in the Island Basin along the gyre of North Atlantic Deep Water, and the third core is located off the present deep circulation gyre in the Labrador Sea. Whereas sedimentary supplies in the Labrador Sea were constantly derived from proximal sources, the geochemical mixing trends in the Iceland Basin samples indicate pronounced changes in the relative contribution of continental margin inputs over the past 6 kyr. Supplies from western European margin that sharply increased at 6 kyr were progressively diluted by a larger contribution of Scandinavian margins over the last 3 kyr. Changes in composition of the particles imply significant reorganization of paleocirculation of the deep North Atlantic components in the eastern basins: mainly reorganizations for both Iceland‐Scotland Overflow Water and Norwegian Sea Overflow Water. Moreover the unusual Pb isotopic composition of the oldest sediments from the southern Iceland Basin indicates that distal supplies from Greenland margin were driven into the Iceland Basin, supporting a deep connection between Labrador Sea and Iceland Basin through the Charlie Gibbs Fracture Zone prior the Holocene Transition period.

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“…For this purpose, zircon was analysed from the Neoarchaean Qôrqut Granite Complex, SW Greenland. This granite has long been known to contain a large component of Palaeo‐ and Mesoarchaean source material on account of the very juvenile whole‐rock Pb‐ and evolved Sr‐isotope composition (Moorbath et al. 1981).…”

Section: Applicationsmentioning

confidence: 99%

“…For this purpose, zircon was analysed from the Neoarcha-ean Qôrqut Granite Complex, SW Greenland. This granite has long been known to contain a large component of Palaeo-and Mesoarchaean source material on account of the very juvenile whole-rock Pb-and evolved Sr-isotope composition (Moorbath et al 1981). Accordingly, it is not surprising that xenocrystic zircons from 2900 to 3600 Ma have been documented in addition to major high-grade metamorphic and partial melting events from 2500 to 2700 Ma (Nutman et al 2010).…”

Section: Finding Different Ages In Composite Signalsmentioning

confidence: 99%

VizualAge: A Novel Approach to Laser Ablation ICP‐MS U‐Pb Geochronology Data Reduction

Petrus¹,

Kamber²

2012

Geostandard Geoanalytic Res

760

294

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VizualAge, a new computer software tool for analysing U‐Pb data obtained by laser ablation‐inductively coupled plasma‐mass spectrometry, was developed. It consists of a data reduction scheme (DRS) for Iolite (a general mass spectrometry data analysis tool) as well as visualisation routines. In addition to the U/Pb and Th/Pb ages calculated by Iolite’s U‐Pb geochronology DRS, VizualAge also calculates 207Pb/206Pb ages and common Pb corrections for each time‐slice of raw data. Importantly, VizualAge allows one to display a live concordia diagram for visualising data on such a diagram as an integration interval is being adjusted. This provides instantaneous feedback regarding discordance, uncertainty, error correlation and common Pb. Several zircon data sets were used to illustrate how the live concordia could be used as a powerful inspection tool, revealing a single analysis to consist of zones of concordance, metamict areas, as well as inherited cores or younger overgrowths. VizualAge also constructs histograms, conventional and Tera‐Wasserburg type concordia diagrams, as well as 3D U‐Th‐Pb and total U‐Pb concordia diagrams. The precision and accuracy of data reduced with VizualAge are demonstrated with examples of the Plešovice, Temora‐2 and Penglai zircon reference materials. Data for zircon from the Long Lake Batholith (Wyoming craton) were used to illustrate how VizualAge calculated common Pb corrections and helped to expose as yet unexplained difficulties with accurately determining 204Pb.

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Origin of granitic magma by crustal remobilisation: Rb-Sr and Pb/Pb geochronology and isotope geochemistry of the late Archaean Qôrqut Granite Complex of southern West Greenland

Cited by 95 publications

References 15 publications

Provisional results of isotope investigations into quartzo-feldspathic rocks from Kangiussap nunâ, Ivisârtoq sheet, southern West Greenland

Provisional results of isotope investigations into quartzo-feldspathic rocks from Kangiussap nunâ, Ivisârtoq sheet, southern West Greenland

Holocene evolution of deep circulation in the northern North Atlantic traced by Sm, Nd and Pb isotopes and bulk sediment mineralogy

VizualAge: A Novel Approach to Laser Ablation ICP‐MS U‐Pb Geochronology Data Reduction

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