High-precision U–Pb dating of complex zircon from the Lewisian Gneiss Complex of Scotland using an incremental CA-ID-TIMS approach

Crowley, Quentin; Key, R.M.; Noble, Stephen R.

doi:10.1016/j.gr.2014.04.001

Cited by 30 publications

(18 citation statements)

References 69 publications

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“…1.8-1.7 Ga (e.g. Whitehouse 1993;Kinny and Friend 1997;Friend and Kinny 2001;Whitehouse and Bridgewater 2001;Kinny et al 2005;Park 2005;Wheeler et al 2010;Mason 2012Mason , 2016Goodenough et al 2013;Davies and Heaman 2014;Crowley et al 2015). This geological history has strong similarities to the Nagssugtoqidian belt of SE Greenland, and the two segments of crust are thought to have been contiguous prior to opening of the North Atlantic (Kalsbeek et al 1993;Friend and Kinny 2001;Park 2005).…”

Section: Location and Regional Settingmentioning

confidence: 99%

The nature and significance of the Faroe-Shetland Terrane: Linking Archaean basement blocks across the North Atlantic

Holdsworth

Morton

Frei

et al. 2019

Precambrian Research

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Additional information: Use policyThe full-text may be used and/or reproduced, and given to third parties in any format or medium, without prior permission or charge, for personal research or study, educational, or not-for-prot purposes provided that:• a full bibliographic reference is made to the original source • a link is made to the metadata record in DRO • the full-text is not changed in any way The full-text must not be sold in any format or medium without the formal permission of the copyright holders.Please consult the full DRO policy for further details.Abstract: Core samples of the continental basement rocks that underlie the eastern Faroe-Shetland Basin (FSB) and its inshore margins west of Shetland reveal a suite of predominantly granodioritic to granitic orthogneisses (including TTG), together with lesser volumes of foliated granitoids and subordinate dioritic to mafic gneisses and amphibolites. A small area of lithologically similar gneisses also crops out onshore at North Roe/Uyea west of the Caledonian front in Shetland. In the core samples, coarse grained gneissose textures and mineralogies consistent with upper amphibolite facies metamorphism are overprinted by a weak, but ubiquitous, static greenschist facies retrogression. Later structures include widespread epidote-quartz veining, and local developments of mylonite, cataclasite, pseudotachylite and phyllonite. Regions associated with the Rona Ridge oil fields (e.g. Clair, Lancaster) also preserve extensive brittle fracturing and associated low temperature hydrothermal mineralization (quartz, adularia, calcite, pyrite/chalcopyrite) with significant fracture-hosted hydrocarbons. New and published U-Pb zircon analyses from the gneisses offshore give a relatively narrow range of Neoarchaean protolith ages (ca 2.7-2.8 Ga) spread over a geographic area of 60,000 km 2 west of Shetland. Detrital zircon data from overlying Triassic-Cretaceous sedimentary sequences in the FSB suggest an equivalent limited range of Neoarchaean source materials. Hf isotopic data indicate involvement of Palaeo-to Mesoarchaean crustal sources. Overall, our findings suggest that a major phase of Neoarchaean crustal formation and associated high grade metamorphism dominates basement rocks in the region. They are similar in age and lithology to the protoliths of the nearest onshore Lewisian Complex of NW Scotland (Rhiconich Terrane). However, they lack geochronological or textural evidence for the widespread Proterozoic Laxfordian events (ca 1.7-1.8 Ga) which are widespread in Scotland. This suggests that the Precambrian rocks west of Shetland -the Faroe-Shetland Terrane -can be correlated with the Archaean rocks of the Central Greenland-Rae Craton and that a northern limit of Proterozoic reworking lies just offshore from the north coast of Scotland. Sample HM11705 comes from 13.00 m depth in BGS borehole 88/02. The succession encountered in this borehole was described by Chambers et al. (2005) as comprising quartzo-feldspathic schist cut by cataclasite bands. The analysed sa...

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Section: Location and Regional Settingmentioning

confidence: 99%

The nature and significance of the Faroe-Shetland Terrane: Linking Archaean basement blocks across the North Atlantic

Holdsworth

Morton

Frei

et al. 2019

Precambrian Research

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“…Although evidence of a metamorphic overprint of the KIC above greenschist grade is absent in the Tarfala Valley, radiogenic lead loss due to Caledonian orogenesis, which would results in a shift of SIMS age analyses down the concordia, cannot be discounted. CA-TIMS, employed in the study by Baird et al (2014), is designed to remove (surficial) domains of zircon grains that may have suffered Pb loss (Mattinson, 2005;Crowley et al, 2015;Schaltegger et al, 2015). Geochronological methods using CA-treated zircon have been documented to yield less data scatter, and 4 -6% higher ages than methods that do not (von Quadt et al, 2014).…”

Section: Age Of the Kicmentioning

confidence: 99%

“…800 Ma. When dealing with complex zircon exhibiting multi-age domains, single-crystal TIMS ages, although precise, are often difficult to interpret (Crowley et al, 2015). Micro-beam methods such as SIMS, on the other hand, have a higher spatial resolution, thus allowing the analysis of individual zircon domains.…”

Section: Age Of the Kicmentioning

confidence: 99%

Root zone of a continental rift: the Neoproterozoic Kebnekaise Intrusive Complex, northern Swedish Caledonides

Kirsch

Svenningsen²

2015

GFF

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Mafic magmatic rocks formed between ca. 615 and 560 Ma along the Neoproterozoic margins of Baltica and Laurentia are classically attributed to continental rifting heralding the opening of the Iapetus Ocean. We report new data for the Kebnekaise Intrusive Complex (KIC) exposed in the Seve Nappes in northern Sweden. The KIC consists of sheeted dolerite dykes and gabbroic bodies with mutually intrusive relations. Major and trace element data exhibit a transitional-to normal-mid-ocean-ridge basalt-type geochemical signature. Differentiation processes and late-stage liquid immiscibility of a tholeiitic melt are considered to account for the compositional range exhibited by the KIC igneous rocks. U/Pb SIMS geochronological data from zircon rims yield an emplacement age of 578^9 Ma. The KIC is thus younger and more depleted than coeval mafic rocks found in the Seve Nappe, and is interpreted to represent a highlevel magma plumbing system in a late-stage continental rift. The composition and volume of rift-related igneous rocks in the Seve Nappes are inconsistent with a mantle plume origin, but are thought to record progressive lithospheric thinning and increasing involvement of an asthenospheric mantle component.

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“…Chemical abrasion has been adapted for incrementally dissolving complex single grains to produce high-precision TIMS ages not discernible using micro-beam techniques [21]. It has also been demonstrated to be effective for SIMS U-Pb zircon geochronology [22].…”

Section: +mentioning

confidence: 99%

Chemical Abrasion Applied to LA-ICP-MS U–Pb Zircon Geochronology

et al. 2014

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Zircon (ZrSiO 4 ) is the most commonly used mineral in U-Pb geochronology. Although it has proven to be a robust chronometer, it can suffer from Pb-loss or elevated common Pb, both of which impede precision and accuracy of age determinations. Chemical abrasion of zircon involves thermal annealing followed by relatively low temperature partial dissolution in HF acid. It was specifically developed to minimize or eliminate the effects of Pb-loss prior to analysis using Thermal Ionization Mass Spectrometry (TIMS). Here we test the application of chemical abrasion to Laser Ablation Inductively Coupled Plasma Mass Spectrometry (LA-ICP-MS) by analyzing zircons from both untreated and chemically abraded samples. Rates of ablation for high alpha-dose non-treated zircons are up to 25% faster than chemically abraded equivalents. Ablation of 91500 zircon reference material demonstrates a ca. 3% greater down-hole fractionation of 206 Pb/ 238 U for non-treated zircons. These disparities necessitate using chemical abrasion for both primary reference material and unknowns to avoid applying an incorrect laser induced fractionation correction. All treated samples display a marked increase in the degree of concordance and/or lowering of common Pb, thereby illustrating the effectiveness of chemical abrasion to LA-ICP-MS U-Pb zircon geochronology. OPEN ACCESSMinerals 2014, 4 504

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High-precision U–Pb dating of complex zircon from the Lewisian Gneiss Complex of Scotland using an incremental CA-ID-TIMS approach

Cited by 30 publications

References 69 publications

The nature and significance of the Faroe-Shetland Terrane: Linking Archaean basement blocks across the North Atlantic

The nature and significance of the Faroe-Shetland Terrane: Linking Archaean basement blocks across the North Atlantic

Root zone of a continental rift: the Neoproterozoic Kebnekaise Intrusive Complex, northern Swedish Caledonides

Chemical Abrasion Applied to LA-ICP-MS U–Pb Zircon Geochronology

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