Using zircon geochronology to resolve the Archaean geology of southern West Greenland

Hollis, Julie; Frei, Dirk; Gool, Jeroen A.M. van; Garde, Adam A.; Persson, Mac

doi:10.34194/geusb.v10.4908

Cited by 16 publications

(12 citation statements)

References 4 publications

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“…Supracrustal rocks are scattered throughout the 1000 km length of the Archean complex of southern West Greenland. Many clastic-sediment samples have been given maximum depositional ages by dates of detrital zircons, or minimum ages by dates of crosscutting dikes, and all of these ages are <3.1 Ga, despite the widespread occurrence of polymetamorphic gneisses that include Mesoarchean and Paleoarchean zircons (Hollis et al, 2005(Hollis et al, , 2006Nutman et al, 2004a). Many of these young dated rocks are close to Isua, as noted previously.…”

Section: Isua Dome and Greenstone Beltmentioning

confidence: 83%

“…(Polat et al, 2007, nevertheless argued, with chemotectonics, that the volcanic rocks in one of those successions were ensimatic oceanic rocks.) Zircon U-Pb age determinations of ages of hundreds of detrital igneous grains in many of the sandstones show numerous detrital grains to be younger than 3.1 Ga in all samples, and felsic volcanic rocks in the successions also to be younger than 3.1 Ga (Hollis et al, 2005(Hollis et al, , 2006Nutman et al, 2004a.…”

Section: Southwest Greenland-early Supracrustals Foundered Late Suprmentioning

confidence: 97%

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Earth's first two billion years—The era of internally mobile crust

Hamilton¹

2007

Geological Society of America Memoirs

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The magmatic and tectonic processes of the pre-2.5 Ga hot, young Earth differed profoundly from those of the modern planet. The ancient rocks differ strikingly in individual and collective composition, occurrence, association, and structure from modern rocks. Widespread forcing of Archean geology into plate-tectonic frameworks refl ects unwarranted faith in uniformitarianism and in inappropriate chemical discriminants, and disregard for the lack of features that characterize plate interactions. Archean crust records extreme and prolonged internal mobility and was far too weak and mobile to behave as rigid plates, required, by defi nition, for plate tectonics. None of the geologic indicators of subduction, arc magmatism, and continental sundering, separation, and convergence have been documented. No Archean oceanic crust or mantle has been recognized, and the only known basement to supracrustal rocks, including the thick basalts, high-Mg basalts, and ultramafi c lavas that typify greenstone successions, consists of tonalite-trondhjemite-granodiorite (TTG) migmatites and gneisses. A thick global melabasaltic protocrust likely formed by ca. 4.45 Ga, and from it TTG suites were extracted by partial melting over the next 2 b.y. Delamination of the increasingly dense restitic protocrust enabled rise of lighter and hotter depleted mantle and hence more melting. The oldest known crustal materials are zircons, which scatter in age back to 4.4 Ga and are recycled in migmatites whose fi nal crystallization was after 3.8 Ga, and in ancient sediments. Earth may have had a dense greenhouse atmosphere, not a hydrosphere, before 3.6 Ga, for the oldest proved supracrustal rocks are of that age, and older felsic crust may have been too hot to permit rise of dense melts. Rigid plates of lithosphere did not stabilize until a billion years after that and then were mostly small and local. Dense lavas erupted atop mobile felsic crust after 3.6 Ga produced a density inversion that was partly righted by sinking of the volcanic rocks and rising of the subjacent TTG. In some places, the early dense rocks retained cohesion and sank as synclinal keels between rising domiform diapiric batholiths. In others, the early dense rocks sank deep into mobile TTG crust, and only later in Archean time was the felsic substrate strong enough to enable dome-and-keel style. The TTG substrate rose slowly, with variable amounts of partial melting to generate more-fractionated melts

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Section: Isua Dome and Greenstone Beltmentioning

confidence: 83%

Section: Southwest Greenland-early Supracrustals Foundered Late Suprmentioning

confidence: 97%

Earth's first two billion years—The era of internally mobile crust

Hamilton¹

2007

Geological Society of America Memoirs

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“…The Summit in central Greenland is 3231 m above sea level (asl); in southern Greenland, the highest elevation is 2873 m asl (Figure S1 in the supporting information) [ Bamber , ]. The geology of the current ice‐free margin has been extensively studied [e.g., Baadsgaard , ; Friend and Nutman , ; Hollis et al ., ; Dawes , ]. Most of the bedrock is Precambrian shield and is mainly composed of granitic gneiss and granitoids [ Dawes , ].…”

Section: Geology Glaciology and Climatementioning

confidence: 99%

Noble gas signatures in Greenland: Tracing glacial meltwater sources

Niu

Castro

Aciego

et al. 2015

Geophysical Research Letters

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This study represents the first comprehensive noble gas study in glacial meltwater from the Greenland Ice Sheet. It shows that most samples are in disequilibrium with surface collection conditions. A preliminary Ne and Xe analysis suggests that about half of the samples equilibrated at a temperature of ~0°C and altitudes between 1000 m and 2000 m, with a few samples pointing to lower equilibration altitudes and temperatures between 2°C and 5°C. Two samples suggest an origin as melted ice and complete lack of equilibration with surface conditions. A helium component analysis suggests that this glacial meltwater was isolated from the atmosphere prior to the 1950s, with most samples yielding residence times ≤ 420 years. Most samples represent a mixture between a dominant atmospheric component originating as precipitation and basal meltwater or groundwater, which has accumulated crustal 4He over time.

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“…The Kapisilik terrane's southern contact with the Tre Brødre and Tasiusarsuaq terranes is poorly defined (Friend and Nutman, 2005b;Nutman and Friend, 2007). The Kapisilik terrane consists of 3080À2950 Ma tonalitic to monzogranitic orthogneiss and lenses of amphibolite, aluminous gneiss and meta-anorthosite (Friend and Nutman, 2005b;Hollis et al, 2006;Nutman and Friend, 2007). The~3080À3070 Ma Ivisaartoq and Ujarassuit greenstone belts constitute larger belts in the terrane (Friend and Nutman, 2005b).…”

Section: Kapisilik Terranementioning

confidence: 99%

“…The~3080À3070 Ma Ivisaartoq and Ujarassuit greenstone belts constitute larger belts in the terrane (Friend and Nutman, 2005b). Monzogranite and pegmatite were emplaced at 2820À2800 Ma (Hollis et al, 2006). The~3075 Ma Ivisaartoq greenstone belt consists of a tectonostratigraphic sequence of meta-anorthosite, meta-leucogabbro, pyrite-quartz rock, serpentinite, amphibolite, calc-silicate rocks (locally magnetite-bearing), felsic schist, metagabbro and meta-diorite ( Fig.…”

Section: Kapisilik Terranementioning

confidence: 99%

Metallogeny of the North Atlantic Craton in Greenland

2015

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The North Atlantic Craton (NAC) extends along the coasts of southern Greenland. At its northern and southern margins, Archaean rocks are overprinted by Palaeoproterozoic orogeny or overlain by younger rocks. Typical granite-greenstone and granite-gneiss complexes represent the entire Archaean, with a hiatus from ∼3.55–3.20 Ga. In the granulite- and amphibolite-facies terranes, the metallogeny comprises hypozonal orogenic gold and Ni-PGE-Cr-Ti-V in mafic-ultramafic magmatic systems. Gold occurrences are widespread around and south of the capital, Nuuk. Nickel mineralization in the Maniitsoq Ni project is hosted in the Norite belt; Cr and PGE in Qeqertarssuatsiaq, and Ti-V in Sinarsuk in the Fiskenæsset complex. The lower-grade metamorphic Isua greenstone belt hosts the >1000 Mt Isua iron deposit in an Eoarchaean banded iron formation. Major Neoarchaean shear zones host mesozonal orogenic gold mineralization over considerable strike length in South-West Greenland. The current metallogenic model of the NAC is based on low-resolution data and variable geological understanding, and prospecting has been the main exploration method. In order to generate a robust understanding of the metal endowment, it is necessary to apply an integrated and collective approach. The NAC is similar to other well-endowed Archaean terranes but is underexplored, and is therefore likely to host numerous targets for greenfields exploration.

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Using zircon geochronology to resolve the Archaean geology of southern West Greenland

Cited by 16 publications

References 4 publications

Earth's first two billion years—The era of internally mobile crust

Earth's first two billion years—The era of internally mobile crust

Noble gas signatures in Greenland: Tracing glacial meltwater sources

Metallogeny of the North Atlantic Craton in Greenland

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