On the geology of the country around ivigtut, SW-Greenland

Berthelsen, A.

doi:10.1007/bf01840080

Cited by 21 publications

(15 citation statements)

References 3 publications

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“…Lamprophyres are abundant in the craton margin section of the Gardar, and on the basis of cross-cutting relations are considered to largely predate all other Gardar dykes in the area (Berthelsen, 1962;Berthelsen and Henriksen, 1975), although they cut the Grønnedal-Íka complex. Individual lamprophyres have been dat ed at 1227±29 Ma and 1249±29 M a (Patchett, 1977).…”

Section: Craton Marginmentioning

confidence: 99%

“…Individual lamprophyres have been dat ed at 1227±29 Ma and 1249±29 M a (Patchett, 1977). The lamprophyre dykes are generally 1 -5 m wide, trending NE to east, and are particularly abundant in an ENE trending, mineralized zone on the Ivittuut peninsula (Berthelsen, 1962). The lamprophyres are variable, including camptonites, spessartites, kersantites and ultrama c aillikites.…”

Section: Craton Marginmentioning

confidence: 99%

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Carbonatites and lamprophyres of the Gardar Province – a ‘window’ to the sub-Gardar mantle?

Coulson¹,

Goodenough²,

Pearce³

et al. 2003

Mineral. mag.

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Carbonatite magmas are considered to be ultimately derived from mantle sources, which may include lithospheric and asthenospheric reservoirs. Isotopic studies of carbonatite magmatism around the globe have typically suggested that more than one source needs to be invoked for generation of the parental melts to carbonatites, often involving the interaction of asthenosphere and lithosphere.In the rift-related, Proterozoic Gardar Igneous Province of SW Greenland, carbonatite occurs as dykes within the Igaliko Nepheline Syenite Complex, as eruptive rocks and diatremes at Qassiarsuk, as a late plug associated with nepheline syenite at Grønnedal-Íka, and as small bodies associated with ultramafic lamprophyre dykes. The well-known cryolite deposit at Ivittuut was also rich in magmatic carbonate. The carbonatites are derived from the mantle with relatively little crustal contamination, and therefore should provide important information about the mantle sources of Gardar magmas. In particular, they are found intruded both into Archaean and Proterozoic crust, and hence provide a test for the involvement of lithospheric mantle.A synthesis of new and previously published major and trace element, Sr, Nd, C and O isotope data for carbonatites and associated lamprophyres from the Gardar Province is presented. The majority of Gardar carbonatites and lamprophyres have consistent geochemical and isotopic signatures that are similar to those typically found in ocean island basalts. The geochemical characteristics of the two suites of magmas are similar enough to suggest that they were derived from the same mantle source. C and O isotope data are also consistent with a mantle derivation for the carbonatite magmas, and support the theory of a cogenetic origin for the carbonatites and the lamprophyres. The differences between the carbonatites and lamprophyres are considered to represent differing degrees of partial melting of a similar source.We suggest that the ultimate source of these magmas is the asthenospheric mantle, since there is no geochemical or isotopic evidence for their having been derived directly from ancient, enriched sub-continental lithospheric mantle. However, it is likely that the magmas actually formed through a two-stage process, with small-degree volatile-rich partial melts rising from the asthenospheric mantle and being ‘frozen in’ as metasomites, which were then rapidly remobilized during Gardar rifting.

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Section: Craton Marginmentioning

confidence: 99%

Section: Craton Marginmentioning

confidence: 99%

Carbonatites and lamprophyres of the Gardar Province – a ‘window’ to the sub-Gardar mantle?

Coulson¹,

Goodenough²,

Pearce³

et al. 2003

Mineral. mag.

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“…The oldest Gardar intrusions in the Border Zone are NE-easttrending lamprophyric dykes, which are most abundant in a zone of mineralization and faulting on the Ivittuut peninsula (Berthelsen 1962). These lamprophyres are typically porphyritic, with phenocrysts of hornblende, biotite, augite or sericitized plagioclase in a fine-grained groundmass composed principally of biotite, hornblende, opaque oxides, chlorite and carbonate.…”

Section: Geology Of the Ivittuut Areamentioning

confidence: 99%

“…The trend of the oldest dykes is roughly east-west, with younger dykes trending progressively more northeastwards (Berthelsen 1962). They typically comprise early olivine and plagioclase, ophitically enclosed by augite, with opaque oxides and apatite.…”

Section: Geology Of the Ivittuut Areamentioning

confidence: 99%

Long-term memory of subduction processes in the lithospheric mantle: evidence from the geochemistry of basic dykes in the Gardar Province of South Greenland

Goodenough

Upton

Ellam

2002

JGS

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The rift-related magmas of the Proterozoic Gardar Igneous Province were emplaced across the contact between the South Greenland Archaean craton and the Palaeoproterozoic Ketilidian mobile belt. It has been suggested that the geochemistry of Gardar intrusive rocks in the two areas varies across the craton margin and that this reflects a lithospheric control. However, comparison of the geochemical and isotopic signatures of basic and ultrabasic dykes from across the area shows that there is no systematic variation related to the age of the country rock. All the Gardar basic rocks are inferred to have been derived from the mantle, with relatively little crustal contamination. We suggest that the lithospheric mantle beneath the Gardar Province was enriched by slab-derived fluids during the Ketilidian orogeny (c. 1800 Ma). Subsequent melting of this mantle source was promoted during Gardar rifting when volatile-rich, small-degree melts from the asthenosphere were introduced into the lithospheric mantle, forming enriched metasomites. Ultrabasic lamprophyre dykes in the Gardar Province represent melts derived largely from these metasomites, whereas basaltic magmas were formed by larger-scale melting of the lithospheric mantle, inheriting a subductionrelated signature. There is no evidence that the Gardar magmas were derived from a highly enriched lithospheric keel that had existed since craton formation.

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“…Based on extensive teamwork A. BERTHELSEN (1960BERTHELSEN ( , 1962 has compiled the results of the geological mapping in the Ivigtut region, SW Greenland. This work is a further and more refined development of the c1assical investigations of C. E. WEGMANN (1938) in which the Ketilidian orogenic cycle, together with the Gardar period of cratogenic events, were established.…”

Section: General Geologymentioning

confidence: 99%

On some pre-Cambrian metadolerites from the central Ivigtut region SW Greenland

Bondesen¹,

Henriksen²

1965

bullggu

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After their consolidation, the Ketilidian gneisses were transversed by several generations of tensional, doleritic dykes-the Kuánitic dykes. During a later episode (the Sánerutian) these dykes were metamorphosed to varying degrees of alteration which increase in the described area from west to east. Along a specific metadolerite, which can be traced approx. 40 km, the metamorphic grade changes from greenschist to amphibolite facies. In the western parts static conditions and in the eastern parts dynamic conditions, prevailed during the alteration. Sánerutian shear zones in the eastern parts depict the dynamic conditions found here.

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On the geology of the country around ivigtut, SW-Greenland

Cited by 21 publications

References 3 publications

Carbonatites and lamprophyres of the Gardar Province – a ‘window’ to the sub-Gardar mantle?

Carbonatites and lamprophyres of the Gardar Province – a ‘window’ to the sub-Gardar mantle?

Long-term memory of subduction processes in the lithospheric mantle: evidence from the geochemistry of basic dykes in the Gardar Province of South Greenland

On some pre-Cambrian metadolerites from the central Ivigtut region SW Greenland

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