Late Archaean terrane accretion in the Godthåb region, southern West Greenland

Friend, C. R. L.; Nutman, Allen P.; McGregor, V. R.

doi:10.1038/335535a0

Cited by 176 publications

(51 citation statements)

References 20 publications

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“…It is tectonically intercalated with terranes of Neoarchaean gneisses devoid of Eoarchaean material and is also intruded by younger bodies of 13/3/2007 Nutman et al 3850 Ma tonalites -7 -crustally-derived granite (Friend et al 1987(Friend et al , 1988McGregor et al 1991;Crowley 2002;Friend and Nutman 2005b). The Complex is now considered to consist of separate tectonic slices -the Faeringehavn terrane in the south (indicated by F's on Fig.…”

Section: Geological Overviewmentioning

confidence: 99%

“…At most localities in the Itsaq Gneiss Complex, detailed field evidence for the Eoarchaean evolution of the rocks has been obliterated by strong polyphase ductile deformation during Neoarchaean terrane assembly events (McGregor, 1973;Friend et al 1987Friend et al , 1988McGregor et al 1991;Nutman et al 1996Nutman et al , 2000Crowley, 2002). During these events the originally cross-cutting Ameralik dykes were mostly transformed into sub-concordant, disrupted tabular amphibolites (McGregor 1973;Chadwick and Nutman 1979;McGregor et al 1991).…”

Section: Heterogeneous Strain and Migmatisationmentioning

confidence: 99%

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∼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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Section: Geological Overviewmentioning

confidence: 99%

Section: Heterogeneous Strain and Migmatisationmentioning

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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“…Friend et al (1987Friend et al ( , 1988 demonstrated that the region contains several unrelated orthogneiss complexes, which are tectono-stratigraphic terranes bounded by folded amphibolite facies Archaean mylonites. These terranes had different early 2/4/2007 Storø gold paper -4 -histories (ages of tonalitic gneisses and intra-terrane metamorphism) prior to tectonic juxtaposition along the mylonites and pan-terrane deformation and metamorphism later in the Archaean (Friend et al, 1987(Friend et al, , 1988Nutman et al, 1989). McGregor et al (1991) used the terrane assembly model to propose that the Nuuk region contains a deeply eroded Archaean continent-continent collision zone comprising mostly pre-collisional basement rocks.…”

Section: Neoarchaean Tectonothermal Evolution Of the Nuuk Region: Assmentioning

confidence: 99%

“…1; Crowley, 2002). Zircon geochronology has indicated several important later Archaean terrane assembly events, from likely first terrane assembly at c. 2950 Ma, through to important 2720-2680 Ma and 2650-2600 Ma terrane assembly and high grade metamorphism events, and finally intrusion of the c. 2560 Ma, late-kinematic Qôrqut Granite Complex (see Schiøtte et al, 1988;Friend et al, 1988Friend et al, , 1996Friend and Nutman, 2005a;Nutman et al, 1989Nutman et al, , 2004Crowley, 2002; Friend in press for data, discussion and interpretations).…”

Section: Neoarchaean Tectonothermal Evolution Of the Nuuk Region: Assmentioning

confidence: 99%

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2635Ma amphibolite facies gold mineralisation near a terrane boundary (suture?) on Storø, Nuuk region, southern West Greenland

Nutman

Christiansen

Friend³

2007

Precambrian Research

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Gold on Storø (in the Nuuk region of southern West Greenland) occurs in a slice of strongly deformed, amphibolite facies, Neoarchaean quartzo-feldspathic metasedimentary rocks and amphibolites in tectonic contact with the Eoarchaean Faeringehavn terrane and the Meso-to Neoarchaean Akia terrane. The gold is associated with either löllingite (FeAs) + arsenopyrite or pyrrhotite, which belong with the amphibolite facies silicate mineral assemblages. Zircons were U/Pb dated by SHRIMP to constrain the timing of mineralisation. The 2700-2830 Ma oscillatory-zoned, high Th/U volcano-sedimentary zircon as whole grains and cores are interpreted to give the maximum depositional age of the rocks hosting the gold. A granite sheet barren of gold that cuts gold mineralised rocks gives an age of ca. 2550 Ma, which is the absolute minimum age of mineralisation. Metamorphic zircons associated with auriferous arsenopyrite (particularly close to secondary löllingite), pyrrhotite and in the coexisting amphibolite facies silicate minerals were dated in situ, in polished thin sections. These have lower average Th/U and yielded dates of ca. 2635 Ma, which is interpreted as the age of the gold-bearing mineral assemblages and hence probably the mineralisation. Supracrustal packages containing abundant quartzo-feldspathic sedimentary rocks with depositional ages of ca. 2800 Ma and metamorphosed at 2650-2600 Ma also occur as folded tectonic intercalations along the western edge of the Faeringehavn terrane south of Storø. Moreover, in the 3080-2960 Ma Kapisilik terrane to the north and east of Storø, high-grade metamorphic events also occurred between 2650 and 2600 Ma. However, the Eoarchaean Faeringehavn terrane to the south and east of Storø shows widespread zircon growth and recrystallisation during 2720-2700 Ma regional metamorphism, but not at 2650-2600 Ma. The Storø gold prospect is thus located near an important tectonic terrane boundary (cryptic suture?) between domains with different Neoarchaean metamorphic history. Storø mineralisation at ca. 2635 Ma probably occurred during deformation of this boundary shortly after it was created, and at Storø maybe was focussed in an area of low strain in a major antiform. The general tectonic frameworks for ca. 2635 Ma gold mineralisation on Storø and in the Yilgarn Craton are similar. These gold provinces are compared and contrasted, and the likely reason why so much less gold occurs in the Nuuk region is discussed.

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Metamorphism, Crustal Evolution and Amalgamation of Meso- to Neo-Archaean Greenstone-Granite Craton and Granulite-Gneiss Terrane in Rajasthan

Guha

2018

Society of Earth Scientists Series

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Late Archaean terrane accretion in the Godthåb region, southern West Greenland

Cited by 176 publications

References 20 publications

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

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

2635Ma amphibolite facies gold mineralisation near a terrane boundary (suture?) on Storø, Nuuk region, southern West Greenland

Metamorphism, Crustal Evolution and Amalgamation of Meso- to Neo-Archaean Greenstone-Granite Craton and Granulite-Gneiss Terrane in Rajasthan

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