Structural evolution of the Archean rocks in Ivisârtoq and the neighboring inner Godthåbsfjord region, southern West Greenland

Hall, R. P.; Friend, C. R. L.

doi:10.1130/0091-7613(1979)7<311:seotar>2.0.co;2

Cited by 41 publications

(29 citation statements)

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“…The axial trace of the later stage of deformation can be mapped throughout most of the area. This interpretation is consistent with that of Hall & Friend (1979), the two stages equating with their second and third stages. No trace has been recorded of their first stage.…”

Section: Structuresupporting

confidence: 89%

“…Only rarely do the dykes in Ivisartoq occur in swarms; even less frequently do they have distinctive plagioclase crystals or clusters of crystals which are the C type dykes in Chadwick's (1981) classification. In north-east Ivisartoq Amitsoq gneisses, classified by the presence of Ameralik dykes (Hall & Friend, 1979;fig. 14 this report), have extensive outcrop.…”

Section: Comments On the Classification Of Gneissesmentioning

confidence: 99%

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Continuation of the mapping of Archaean rocks in the southern part of the Ivisârtoq map sheet

Brewer¹,

Coe²,

Robertson³

1983

rapggu

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Field work was resumed in the southern part of the Ivisartoq map sheet in the 1982 field season. S.R. completed an area in Kangiussap nuna and undertook special investigations including detailed sampling for isotope studies in selected areas in more northern parts. K.c. was joined by M.B. for mapping in Nunatarssuaq so that by the end of the field season more than three quarters of the southern part had been mapped and the work is well up to schedule (fig. 12). The ground covered in 1982 presented problems similar to those of 1981, the main difficulty being that of assigning quartzo-feldspathic gneisses to one of the established groups. The well tried criteria have again proved to be fallible and Ouf conviction that a large scale isotope programme is essential is strengthened. This programme is already in hand.

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Section: Structuresupporting

confidence: 89%

Section: Comments On the Classification Of Gneissesmentioning

confidence: 99%

Continuation of the mapping of Archaean rocks in the southern part of the Ivisârtoq map sheet

Brewer¹,

Coe²,

Robertson³

1983

rapggu

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“…In the fjord Itilleq and on the semi-nunatak Ivisaartoq (Fig. 1), reconnaissance geological mapping has long recognised the presence of Eoarchaean gneisses (Allaart et al 1977;Hall and Friend, 1979). These have been scientifically neglected compared with the gneisses of Akilia and surrounding islands in the southwest, and the Isua area in the north.…”

Section: Migmatites and Inheritance-bearing Neosomementioning

confidence: 99%

∼3,850 Ma tonalites in the Nuuk region, Greenland: geochemistry and their reworking within an Eoarchaean gneiss complex

Nutman

Bennett

Friend

et al. 2007

Contrib Mineral Petrol

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Hidaka, H. (2007). ~3,850 Ma tonalites in the Nuuk region, Greenland: geochemistry and their reworking within an Eoarchaean gneiss complex. Contributions to Mineralogy and Petrology, 154 (4), 385-408. ~3,850 Ma tonalites in the Nuuk region, Greenland: geochemistry and their reworking within an Eoarchaean gneiss complex AbstractThe Eoarchaean (>3,600 Ma) Itsaq Gneiss Complex of southern West Greenland is dominated by polyphase orthogneisses with a complex Archaean tectonothermal history. Some of the orthogneisses have c. 3,850 Ma zircons, and they vary from rare single phase metatonalites to more common complexly banded migmatites. This is due to heterogeneous strain, in situ anatexis and granitic veining superimposed during younger tectonothermal events. In the single-phase tonalites with c. 3,850 Ma zircon, oscillatory-zoned prismatic zircon is all 3,850 Ma old, but shows patchy ancient loss of radiogenic Pb. SHRIMP spot analyses and laser ablation ICP-MS depth profiling show that thin (usually < 10 μm) younger (3,590 Ma and Neoarchaean) shells of lower Th/U metamorphic zircon are present on these 3,850 Ma zircons. Several samples with this simple zircon population occur on islands near Akilia. In contrast, migmatites usually contain more complex zircon populations, with often more than one generation of igneous zircon present. Additional zircon dating of banded gneisses across the Complex shows that samples with c. 3,850 Ma igneous zircon are not just a phenomenon restricted to Akilia and adjacent islands. For example, migmatites from Itilleq (c. 65 km from Akilia) contain variable amounts of oscillatory-zoned 3,850 Ma and 3,650 Ma zircon, interpreted, respectively, as the rock age and the time of crustal melting under Eoarchaean metamorphism. With only 110-140 ppm Zr in the tonalites and likely magmatic temperatures of >850°C, zircon solubilitymelt composition relationships show that they were only one-third saturated in zircon. Any zircon entrained in the precursor magmas would thus have been highly soluble. Combined with the cathodoluminesence imaging, this demonstrates that the c. 3,850 Ma oscillatory zoned zircon crystallised out of the melt and hence gives a magmatic age. Thus the rare well-preserved tonalites and palaeosome in migmatites testify that c. 3,850 Ma quartzo -feldspathic rocks are a widespread (but probably minor) component in the Itsaq Gneiss Complex. C. 3,850 Ma zircon with negative Eu anomalies (showing growth in felsic systems) also occurs as detrital grains in rare c. 3,800 Ma metaquartzites and as inherited grains in some 3,660 Ma granites (sensu stricto). These demonstrate that still more c. 3,850 Ma rocks were present, but were recycled into Eoarchaean sediments and crustally derived granites. The major and trace element characteristics (e.g. LREE enrichment, HREE depletion, low MgO) of the best-preserved c. 3,850 Ma rocks are typical of Archaean TTG suites, and thus argue for crust formation processes involving important contributions from melting of hydrated mafic crust to the...

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“…Eoarchaean rocks of the Isukasia terrane lie to the north and east of Mesoarchaean 85 rocks of the Kapisilik terrane (Hall and Friend, 1979;Chadwick, 1985Chadwick, , 1990Friend 86 and Nutman, 2005). Mapping, structural studies, metamorphic petrology and zircon 87 U-Th-Pb-Hf isotopic data reveal a history of Mesoarchaean collision between the 88 Isukasia terrane (an old continental massif) and >3000 Ma components of the 89 Kapisilik terrane (a juvenile arc).…”

mentioning

confidence: 99%

Mesoarchaean collision of Kapisilik terrane 3070Ma juvenile arc rocks and >3600Ma Isukasia terrane continental crust (Greenland)

Nutman

Bennett

Friend

et al. 2015

Precambrian Research

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Structural evolution of the Archean rocks in Ivisârtoq and the neighboring inner Godthåbsfjord region, southern West Greenland

Cited by 41 publications

References 0 publications

Continuation of the mapping of Archaean rocks in the southern part of the Ivisârtoq map sheet

Continuation of the mapping of Archaean rocks in the southern part of the Ivisârtoq map sheet

∼3,850 Ma tonalites in the Nuuk region, Greenland: geochemistry and their reworking within an Eoarchaean gneiss complex

Mesoarchaean collision of Kapisilik terrane 3070Ma juvenile arc rocks and >3600Ma Isukasia terrane continental crust (Greenland)

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