Isotope and trace-element geochemistry of Proterozoic Natkusiak flood basalts from the northwestern Canadian Shield

Dupuy, C.; Michard, A.; Dostál, J.; Dautel, D.; Baragar, W R A

doi:10.1016/0009-2541(94)00128-u

Cited by 18 publications

(16 citation statements)

References 24 publications

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“…480 Ma). The degree of differentiation of the HP mafic granulites, their trace element patterns and largely variable isotopic composition suggest that they could have been derived either from partial melting of a heterogeneous subcontinental mantle (Hergt et al 1989;Pegram 1990;Hooper and Hawkesworth 1993;Turner and Hawkesworth 1995) or from contamination of basic magmas with continental rocks during their ascent (Dupuy and Dostal 1984;Campbell 1985;Arndt et al 1993;Dupuy et al 1995). Consecutively, injection of less-differentiated and more-depleted basic magmas into this progressively thinner crust occurred and overlay the layered gabbros (Fig.…”

Section: Discussionmentioning

confidence: 94%

Geochemical evolution of high-pressure mafic granulites from the Bacariza formation (Cabo Ortegal complex, NW Spain): an example of a heterogeneous lower crust

Galán¹,

Marcos²

1997

Geologische Rundschau

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The Cabo Ortegal complex (northwestern Iberian massif ) is a klippen formed of several structural units stacked during the Hercynian collision. All these units include ultramafic rocks, metabasites and quartzfeldspathic gneisses affected by different metamorphic conditions. The Bacariza formation is heterogeneous showing a conspicuous layering mainly defined by alternate high-pressure ultrabasic-to-basic granulites, retrogressed garnet amphibolites of intermediate composition and rare acid rocks forming garnet trondhjemitic gneisses. This layering is inherited from a gabbroic protolith showing a composition rich in Fe and Ti. Major and trace elements of these rocks can be correlated to continental tholeiitic series of extensional settings. These high-pressure granulites are situated in normal contact between$serpentinised ultramafic rocks and other high-grade metabasites with lessevolved and more-depleted composition comparable to T-type and N-type MORB. It is suggested that the layered gabbro-type protolith was part of a continuous mafic crust. This crust was initially formed during Early Ordovician in a continental extensional setting and progressively evolved to oceanic spreading.

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Section: Discussionmentioning

confidence: 94%

Geochemical evolution of high-pressure mafic granulites from the Bacariza formation (Cabo Ortegal complex, NW Spain): an example of a heterogeneous lower crust

Galán¹,

Marcos²

1997

Geologische Rundschau

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“…Camiré, La Fléche & Jenner, 1995;Dupuy et al 1995). Such a hypothesis cannot be excluded for the Pb isotope composition of the Greek Triassic subalkaline basalts, but does require special pleading.…”

Section: C Was Triassic Extension Associated With Subduction?mentioning

confidence: 90%

The nature of Triassic extension-related magmatism in Greece: evidence from Nd and Pb isotope geochemistry

Pe‐Piper

1998

Geol. Mag.

115

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The widespread Triassic volcanic rocks of Greece, dismembered during the Hellenide orogeny, are used to interpret the nature of Triassic rifting. Four assemblages of volcanic rocks are distinguished on geochemical criteria: (1) a predominant subalkaline basalt-andesite-dacite series with a high proportion of pyroclastic rocks; (2) minor shoshonites; (3) alkali basalt and (4) MORB. The stratigraphic and palaeogeographic distribution of these rock types is synthesized. New Pb and Nd isotopic data are used to discriminate between hypotheses suggesting that either subduction or extension was responsible for the Triassic volcanism. In the subalkaline basalt assemblage, ε Nd is negative with depleted mantle model ages > 1.5 Ga. Pb isotopic compositions are mostly close to the very distinctive compositional field of Cenozoic extensional rocks of the Aegean area, with very high 207 Pb/ 204 Pb for relatively low 206 Pb/ 204 Pb ratios. These isotopic data confirm interpretations based on trace elements that subalkaline basalts were predominantly derived from melt-depleted peridotite in the sub-continental lithospheric mantle as a result of extension. Small areas of enriched hydrous mantle partially melted to yield shoshonitic magmas. Nd and Pb isotopic compositions of the alkali basalts are quite different from those in other rock types and suggest a HIMU mantle source component derived from a small plume, which also influenced MORB compositions. Distribution of these various rock types is used to constrain palaeogeographic reconstruction of Triassic micro-continental blocks.

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“…Archean granites and Paleoproterozoic sedimentary rocks underlie the Neoproterozoic strata . The Natkusiak fl ood basalts (Baragar 1976;Jefferson, 1985;Jefferson et al, 1985;Dostal et al, 1986;Dupuy et al, 1995) are the uppermost formation of the Shaler Supergroup. The Natkusiak Formation has a thin, heterogeneous basal unit (fl ows, volcaniclastics, and lahars), succeeded by sheet fl ows defi ning two geochemical volcanic cycles (each ~500 m thick; Dostal et al, 1986).…”

Section: Victoria Island Geologymentioning

confidence: 99%

Fault-mediated melt ascent in a Neoproterozoic continental flood basalt province, the Franklin sills, Victoria Island, Canada

Bédard

Naslund

Nábělek

et al. 2012

Geological Society of America Bulletin

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The Neoproterozoic Franklin large igneous province on Victoria Island, Canada, is characterized by continental fl ood basalts and a sill-dominated feeder system. Field relationships indicate that fault-guided transfer zones allowed magma to jump up-section to form higher-level intrusions. Where sills connect to dikes and magmas moved upsection , roof and wall rocks are characterized by wide and intense contact-metamorphic haloes , consistent with throughfl ow of magma. The geometric constraints suggest that conduits may have opened episodically and then closed when magma pressure waned. The episodic nature of conduit opening events can explain the pulsed ascent of crystal slurries, and may also play a role in the deposition of Ni-sulfi des.

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Isotope and trace-element geochemistry of Proterozoic Natkusiak flood basalts from the northwestern Canadian Shield

Cited by 18 publications

References 24 publications

Geochemical evolution of high-pressure mafic granulites from the Bacariza formation (Cabo Ortegal complex, NW Spain): an example of a heterogeneous lower crust

Geochemical evolution of high-pressure mafic granulites from the Bacariza formation (Cabo Ortegal complex, NW Spain): an example of a heterogeneous lower crust

The nature of Triassic extension-related magmatism in Greece: evidence from Nd and Pb isotope geochemistry

Fault-mediated melt ascent in a Neoproterozoic continental flood basalt province, the Franklin sills, Victoria Island, Canada

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