Highly refractory Archaean peridotite cumulates: Petrology and geochemistry of the Seqi Ultramafic Complex, SW Greenland

Hdl Handle:
http://hdl.handle.net/10545/621658
Title:
Highly refractory Archaean peridotite cumulates: Petrology and geochemistry of the Seqi Ultramafic Complex, SW Greenland
Authors:
Szilas, Kristoffer ( 0000-0002-5541-306X ) ; van Hinsberg, Vincent J.; McDonald, Iain; Næraa, Tomas; Rollinson, Hugh ( 0000-0002-6553-8472 ) ; Adetunji, Jacob ( 0000-0002-8491-6440 ) ; Bird, Dennis
Abstract:
This paper investigates the petrogenesis of the Seqi Ultramafic Complex, which covers a total area of approximately 0.5 km2. The ultramafic rocks are hosted by tonalitic orthogneiss of the ca. 3000 Ma Akia terrane with crosscutting granitoid sheets providing an absolute minimum age of 2978 ± 8 Ma for the Seqi Ultramafic Complex. The Seqi rocks represent a broad range of olivine-dominated plutonic rocks with varying modal amounts of chromite, orthopyroxene and amphibole, i.e. various types of dunite (s.s.), peridotite (s.l.), as well as chromitite. The Seqi Ultramafic Complex is characterised primarily by refractory dunite, with highly forsteritic olivine with core compositions having Mg# ranging from about 91 to 93. The overall high modal contents, as well as the specific compositions, of chromite rule out that these rocks represent a fragment of Earth’s mantle. The occurrence of stratiform chromitite bands in peridotite, thin chromite layers in dunite and poikilitic orthopyroxene in peridotite instead supports the interpretation that the Seqi Ultramafic Complex represents the remnant of a fragmented layered complex or a magma conduit, which was subsequently broken up and entrained during the formation of the regional continental crust. Integrating all of the characteristics of the Seqi Ultramafic Complex points to formation of these highly refractory peridotites from an extremely magnesian (Mg# ~ 80), near-anhydrous magma, as olivine-dominated cumulates with high modal contents of chromite. It is noted that the Seqi cumulates were derived from a mantle source by extreme degrees of partial melting (>40%). This mantle source could potentially represent the precursor for the sub-continental lithospheric mantle (SCLM) in this region, which has previously been shown to be ultra-depleted. The Seqi Ultramafic Complex, as well as similar peridotite bodies in the Fiskefjord region, may thus constitute the earliest cumulates that formed during the large-scale melting event(s), which resulted in the ultra depleted cratonic keel under the North Atlantic Craton. Hence, a better understanding of such Archaean ultramafic complexes may provide constraints on the geodynamic setting of Earth’s first continents and the corresponding SCLM.
Affiliation:
Stanford University; McGill University; Lund University; Cardiff University; University of Derby
Citation:
Szilas, K. et al (2017) 'Highly refractory Archaean peridotite cumulates: Petrology and geochemistry of the Seqi Ultramafic Complex, SW Greenland' Geoscience Frontiers, DOI: 10.1016/j.gsf.2017.05.003
Publisher:
Elsevier
Journal:
Geoscience Frontiers
Issue Date:
6-Jun-2017
URI:
http://hdl.handle.net/10545/621658
DOI:
10.1016/j.gsf.2017.05.003
Additional Links:
http://linkinghub.elsevier.com/retrieve/pii/S1674987117300993
Type:
Article
Language:
en
ISSN:
16749871
Sponsors:
Department of Geological Sciences, Stanford University, 450 Serra Mall, Stanford, CA 94305, USA Department of Earth & Planetary Sciences, McGill University, Quebec, Canada Department of Geology, Lund University, Sölvegatan 12, 223 62 Lund, Sweden School of Earth and Ocean Sciences, Cardiff University, Main Building, Cardiff CF10 3AT, United Kingdom College of Science, University of Derby, Derby, DE22 1GB, UK
Appears in Collections:
Environmental Sustainability Research Centre

Full metadata record

DC FieldValue Language
dc.contributor.authorSzilas, Kristofferen
dc.contributor.authorvan Hinsberg, Vincent J.en
dc.contributor.authorMcDonald, Iainen
dc.contributor.authorNæraa, Tomasen
dc.contributor.authorRollinson, Hughen
dc.contributor.authorAdetunji, Jacoben
dc.contributor.authorBird, Dennisen
dc.date.accessioned2017-06-21T15:42:44Z-
dc.date.available2017-06-21T15:42:44Z-
dc.date.issued2017-06-06-
dc.identifier.citationSzilas, K. et al (2017) 'Highly refractory Archaean peridotite cumulates: Petrology and geochemistry of the Seqi Ultramafic Complex, SW Greenland' Geoscience Frontiers, DOI: 10.1016/j.gsf.2017.05.003en
dc.identifier.issn16749871-
dc.identifier.doi10.1016/j.gsf.2017.05.003-
dc.identifier.urihttp://hdl.handle.net/10545/621658-
dc.description.abstractThis paper investigates the petrogenesis of the Seqi Ultramafic Complex, which covers a total area of approximately 0.5 km2. The ultramafic rocks are hosted by tonalitic orthogneiss of the ca. 3000 Ma Akia terrane with crosscutting granitoid sheets providing an absolute minimum age of 2978 ± 8 Ma for the Seqi Ultramafic Complex. The Seqi rocks represent a broad range of olivine-dominated plutonic rocks with varying modal amounts of chromite, orthopyroxene and amphibole, i.e. various types of dunite (s.s.), peridotite (s.l.), as well as chromitite. The Seqi Ultramafic Complex is characterised primarily by refractory dunite, with highly forsteritic olivine with core compositions having Mg# ranging from about 91 to 93. The overall high modal contents, as well as the specific compositions, of chromite rule out that these rocks represent a fragment of Earth’s mantle. The occurrence of stratiform chromitite bands in peridotite, thin chromite layers in dunite and poikilitic orthopyroxene in peridotite instead supports the interpretation that the Seqi Ultramafic Complex represents the remnant of a fragmented layered complex or a magma conduit, which was subsequently broken up and entrained during the formation of the regional continental crust. Integrating all of the characteristics of the Seqi Ultramafic Complex points to formation of these highly refractory peridotites from an extremely magnesian (Mg# ~ 80), near-anhydrous magma, as olivine-dominated cumulates with high modal contents of chromite. It is noted that the Seqi cumulates were derived from a mantle source by extreme degrees of partial melting (>40%). This mantle source could potentially represent the precursor for the sub-continental lithospheric mantle (SCLM) in this region, which has previously been shown to be ultra-depleted. The Seqi Ultramafic Complex, as well as similar peridotite bodies in the Fiskefjord region, may thus constitute the earliest cumulates that formed during the large-scale melting event(s), which resulted in the ultra depleted cratonic keel under the North Atlantic Craton. Hence, a better understanding of such Archaean ultramafic complexes may provide constraints on the geodynamic setting of Earth’s first continents and the corresponding SCLM.en
dc.description.sponsorshipDepartment of Geological Sciences, Stanford University, 450 Serra Mall, Stanford, CA 94305, USA Department of Earth & Planetary Sciences, McGill University, Quebec, Canada Department of Geology, Lund University, Sölvegatan 12, 223 62 Lund, Sweden School of Earth and Ocean Sciences, Cardiff University, Main Building, Cardiff CF10 3AT, United Kingdom College of Science, University of Derby, Derby, DE22 1GB, UKen
dc.language.isoenen
dc.publisherElsevieren
dc.relation.urlhttp://linkinghub.elsevier.com/retrieve/pii/S1674987117300993en
dc.rightsArchived with thanks to Geoscience Frontiersen
dc.subjectArchaeanen
dc.subjectUltramaficen
dc.subjectNorth Atlantic cratonen
dc.subjectDuniteen
dc.subjectPlatinum-group elementsen
dc.subjectUltra-depleted mantleen
dc.subjectFiskefjorden
dc.titleHighly refractory Archaean peridotite cumulates: Petrology and geochemistry of the Seqi Ultramafic Complex, SW Greenlanden
dc.typeArticleen
dc.contributor.departmentStanford Universityen
dc.contributor.departmentMcGill Universityen
dc.contributor.departmentLund Universityen
dc.contributor.departmentCardiff Universityen
dc.contributor.departmentUniversity of Derbyen
dc.identifier.journalGeoscience Frontiersen
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