Craton reactivation on the Labrador Sea margins: 40Ar/39Ar age and Sr–Nd–Hf–Pb isotope constraints from alkaline and carbonatite intrusives

Tappe, Sebastian; Foley, Stephen F.; Stracke, Andreas; Romer, Rolf L.; Kjarsgaard, Bruce A.; Heaman, Larry M.; Joyce, Nancy

doi:10.1016/j.epsl.2007.01.036

Cited by 254 publications

(182 citation statements)

References 63 publications

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“…Menzies and Halliday, 1988). A similar apparent loss of deep cratonic keel is described for the Labrador portion of the NAC, for which a cratonic rifting model was proposed (see Tappe et al, 2007). However, while a deep (garnet-or diamond-bearing) cratonic lithospheric mantle keel may be lacking in Scotland, the spinel lherzolites xenoliths from terranes north of the GGF represent the shallow regions of this cratonic SCLM (see Upton et al, 2011 and references therein).…”

Section: The Scottish Portion Of the North Atlantic Craton And Neighbmentioning

confidence: 91%

“…The western part of the NAC in Greenland hosts abundant late Proterozoic ultramafic lamprophyre dykes and sills and kimberlites, which contain mantle xenoliths (c.f., Bizzarro and Stevenson, 2003;Tappe et al, 2006;Bernstein et al, 2007;Tappe et al, 2007;Wittig et al, 2010 and references therein). Xenolith/xenocryst suites comprise (variably) serpentinized ultra-refractory dunites, harzburgites, eclogites, wehrlites and minor lherzolites (e.g.…”

Section: Overview Of the North Atlantic Craton à Formation Amalgamatmentioning

confidence: 99%

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Trace-element abundances in the shallow lithospheric mantle of the North Atlantic Craton margin: Implications for melting and metasomatism beneath Northern Scotland

et al. 2015

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Bulk rock geochemistry and major-and trace-element compositions of clinopyroxene have been determined for three suites of peridotitic mantle xenoliths from the North Atlantic Craton (NAC) in northern Scotland, to establish the magmatic and metasomatic history of subcontinental lithospheric mantle (SCLM) below this region. Spinel lherzolites from the southernmost locality (Streap Com'laidh) have non-NAC mantle compositions, while the two northern xenolith suites (Loch Roag and Rinibar) are derived from the thinned NAC marginal keel. Clinopyroxene compositions have characteristic trace-element signatures which show both 'primary' and 'metasomatic' origins. We use Zr and Hf abundances to identify ancient cryptic refertilization in 'primary' clinopyroxenes. We suggest that Loch Roag and Rinibar peridotite xenoliths represent an ancient ArchaeanPalaeoproterozoic SCLM with original depleted cratonic signatures which were overprinted by metasomatism around the time of intrusion of the Scourie Dyke Swarm (~2.4 Ga). This SCLM keel was preserved during Caledonian orogenesis, although some addition of material and/or metasomatism probably also occurred, as recorded by Rinibar xenoliths. Rinibar and Streap xenoliths were entrained in Permo-Carboniferous magmas and thus were isolated from the SCLM~200 Ma before Loch Roag xenoliths (in an Eocene dyke). Crucially, despite their geographical location, lithospheric mantle peridotite samples from Loch Roag show no evidence of recent melting or refertilization during the Palaeogene opening of the Atlantic.

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Section: The Scottish Portion Of the North Atlantic Craton And Neighbmentioning

confidence: 91%

Section: Overview Of the North Atlantic Craton à Formation Amalgamatmentioning

confidence: 99%

Trace-element abundances in the shallow lithospheric mantle of the North Atlantic Craton margin: Implications for melting and metasomatism beneath Northern Scotland

et al. 2015

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“…5). They resemble the carbonate-rich type aillikites from Aillik Bay, central Labrador (Tappe et al, 2006(Tappe et al, , 2007. However, a few subtle but petrogenetically important differences in the incompatible element distribution exist between Torngat aillikites and mela-aillikites on the one hand, and between the Torngat UML and the type rocks from Aillik Bay on the other hand (Fig.…”

Section: Incompatible Elementsmentioning

confidence: 99%

“…610 to 550 Ma) occurrences in the vicinity of the Labrador Sea are also shown. Note that the position of Greenland is restored for Cenozoic continental drift due to now extinct sea-floor spreading in the Labrador Sea (modified from Tappe et al, 2007). Tectonic features and alkaline rock occurrences mentioned in the text are abbreviated as follows: ASZ, Abloviak shear zone; KSZ, Komaktorvik shear zone; N, Napoleon Bay; S, Saglek block; SSM, Sisimiut-Sarfartoq-Maniitsoq areas; T, Torngat Mountains.…”

Section: Aillikite/carbonatite and Mela-aillikite Compositional Contimentioning

confidence: 99%

“…The Saglek block mela-aillikites fall along the Torngat Sr-Nd-Hf isotope array. Mela-aillikites Table 2 Major (wt%) and trace element (ppm) concentrations of Neoproterozoic carbonatite, aillikite, and mela-aillikite dykes from the Torngat Mountains and the Saglek block, North Atlantic craton, Labrador (Tappe et al, 2006(Tappe et al, , 2007. Pale grey field displays a typical 'Enriched Mantle' derived ocean island basalt trace element pattern for comparison (Eisele et al, 2002).…”

Section: Sr-nd-hf-pb Isotope Compositionmentioning

confidence: 99%

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Between carbonatite and lamproite—Diamondiferous Torngat ultramafic lamprophyres formed by carbonate-fluxed melting of cratonic MARID-type metasomes

Tappe

Foley

Kjarsgaard

et al. 2008

Geochimica et Cosmochimica Acta

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256

104

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New U-Pb perovskite ages reveal that diamondiferous ultramafic lamprophyre magmas erupted through the Archean crust of northern Labrador and Quebec (eastern Canada) .2). These contrasting isotopic characteristics of aillikites/carbonatites and mela-aillikites, along with subtle differences in their modal carbonate, SiO 2 , Al 2 O 3 , Na 2 O, Cs-Rb, and Zr-Hf contents, are consistent with two distinctive metasomatic assemblages of different age in the mantle magma source region.Integration of petrologic, geochemical, and isotopic information leads us to propose that the isotopically enriched component originated from a reduced phlogopite-richterite-Ti-oxide dominated source assemblage that is reminiscent of MARID suite xenoliths. In contrast, the isotopically depleted component was derived from a more oxidized phlogopite-carbonate dominated source assemblage. We argue that low-degree CO 2 -rich potassic silicate melts from the convective upper mantle were preferentially channelled into an older, pre-existing MARID-type vein network at the base of the North Atlantic craton lithosphere, where they froze to form new phlogopite-carbonate dominated veins. Continued stretching and thinning of the cratonic lithosphere during the Late Neoproterozoic remobilized the carbonate-rich vein material and induced volatile-fluxed fusion of the MARID-type veins and the cold peridotite substrate. Isotopic modelling suggests that only 5-12% trace element contribution from such geochemically extreme MARID-type material is required to produce the observed compositional shift from the isotopically most depleted aillikites/carbonatites towards enriched mela-aillikites.We conclude that cold cratonic mantle lithosphere can host several generations of contrasting vein assemblages, and that each may have formed during past tectonic and magmatic events under distinctively different physicochemical conditions. Although cratonic MARID-type and carbonate-bearing veins in peridotite can be the respective sources for lamproite and carbonatite magmas when present as the sole metasome, their concomitant fusion in a complex source region may give rise to a whole new variety of deep volatile-rich magmas and we suggest that orangeites (formerly Group 2 kimberlites), kamafugites, and certain types of ultramafic lamprophyre are formed in this manner.

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The thinning of subcontinental lithosphere: The roles of plume impact and metasomatic weakening

Wang

Hunen

Pearson

2015

Geochem Geophys Geosyst

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Geologically rapid (tens of Myr) partial removal of thick continental lithosphere is evident beneath Precambrian terranes, such as North China Craton, southern Africa, and the North Atlantic Craton, and has been linked with thermomechanical erosion by mantle plumes. We performed numerical experiments with realistic viscosities to test this hypothesis and constrain the most important parameters that influence cratonic lithosphere erosion. Our models indicate that the thermomechanical erosion by a plume impact on typical Archean lithospheric mantle is unlikely to be more effective than long-term erosion from normal plate-mantle interaction. Therefore, unmodified cratonic roots that have been stable for billions of years will not be significantly disrupted by the erosion of a plume event. However, the buoyancy and strength of highly depleted continental roots can be modified by fluid-melt metasomatism, and our models show that this is essential for the thinning of originally stable continental roots. The long-term but punctuated history of metasomatic enrichment beneath ancient continents makes this mode of weakening very likely. The effect of the plume impact is to speed up the erosion significantly and help the removal of the lithospheric root to occur within tens of Myr if affected by metasomatic weakening.

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Craton reactivation on the Labrador Sea margins: 40Ar/39Ar age and Sr–Nd–Hf–Pb isotope constraints from alkaline and carbonatite intrusives

Cited by 254 publications

References 63 publications

Trace-element abundances in the shallow lithospheric mantle of the North Atlantic Craton margin: Implications for melting and metasomatism beneath Northern Scotland

Trace-element abundances in the shallow lithospheric mantle of the North Atlantic Craton margin: Implications for melting and metasomatism beneath Northern Scotland

Between carbonatite and lamproite—Diamondiferous Torngat ultramafic lamprophyres formed by carbonate-fluxed melting of cratonic MARID-type metasomes

The thinning of subcontinental lithosphere: The roles of plume impact and metasomatic weakening

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