Early Archaean granulite-facies metamorphism south of Ameralik, West Greenland

Griffin, William L.; McGregor, V. R.; Nutman, Allen P.; Taylor, Paul N.; Bridgwater, D.

doi:10.1016/0012-821x(80)90119-3

Cited by 146 publications

(60 citation statements)

References 35 publications

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“…This Eoarchaean in situ incipient partial melting and migmatisation is correlated with textural and rare mineralogical observations such as pre-Ameralik dyke relict metamorphic orthopyroxene (metamorphic orthopyroxene in the Itsaq Gneiss Complex rocks variably replaced by amphibole + quartz ± biotite; criteria in McGregor and Friend, 1997) interpreted to reflect Eoarchaean granulite facies metamorphism (McGregor and Mason, 1977;Griffin et al 1980;McGregor, 2000;Friend and Nutman, 2005a). This migmatisation and higher-grade metamorphism compounds the difficulties in the interpretation of geochemical and isotopic data for the Eoarchaean rocks.…”

Section: Heterogeneous Strain and Migmatisationsupporting

confidence: 59%

∼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: Heterogeneous Strain and Migmatisationsupporting

confidence: 59%

∼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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“…Withinplate granite chemistry has been established for the augen gneiss suite (~3.64 Ga). Multiple episodes of amphibolite to granulite facies metamorphism (630-700 °C at 8-10 kb) were also noted [Griffin et al, 1980]. Inclusions of metavolcanic and metasedimentary rocks in the Itsaq Gneiss are dominated by banded and commonly skarn-bearing amphibolites; lesser amounts of BIF, marble, siliceous rocks and calc-silicate rocks have been identified as well.…”

Section: Evidence Of Plume-tectonicsmentioning

confidence: 92%

Age and isotopic geochemical characteristics of Archean carbonatites and alkaline rocks of the Baltic shield

2007

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Paradoxically, the lists of "proxies" of both plate-and plume-related settings are devoid of even a mention of the high-grade metamorphic rocks (granulite, amphibolite and high-temperature eclogite facies). However, the granulite-gneiss belts and areas which contain these rocks, have a regional distribution in both the Precambrian and the Phanerozoic records. The origin and evolution of the granulite-gneiss belts correspond to the activity of plumes expressed in vigorous heating of the continental crust; intraplate magmatism; formation of rift depressions filled with sediments, juvenile lavas, and pyroclastic flow deposits; and metamorphism of lower and middle crustal complexes under conditions of granulite and high-temperature amphibolite facies that spreads over the fill of rift depressions also. Granulite-gneiss complexes of the East European Craton form one of the main components of the large oval intracontinental tectonic terranes of regional or continental rank. Inclusion of the granulite-gneiss complexes from Eastern Europe, North and South America, Africa, India, China and Australia in discussion of the problem indicated in the title to this paper, suggests consideration of a significant change in existing views on the relations between the plate-and plume-tectonic processes in geological history, as well as in supercontinent assembly and decay. The East European and North American cratons are fragments of the long-lived supercontinent Lauroscandia. After its appearance at ~2.8 Ga, the crust of this supercontinent evolved under the influence of the sequence of powerful mantle plumes (superplumes) up to ~0.85 Ga. During this time Lauroscandia was subjected to rifting, partial breakup and the following reconstruction of the continent. The processes of plate-tectonic type (rifting with the transition to spreading and closing of the short-lived ocean with subduction) within Lauroscandia were controlled by the superplumes. Revision of the nature of the granulite-gneiss complexes has led to a fundamental new understanding of: a more important role than envisaged previously for mantle-plume processes in the juvenile additions to the continental crust, especially during the Neoarchaean-Proterozoic; the existence of the supercontinent Lauroscandia from ~2.80 to 0.85 Ga; the leading role of mantle plumes in the interaction of plate-and plume-tectonics in the Neoarchaean-Proterozoic history of Lauroscandia and perhaps of the continental crust as a whole. We propose that the evolution of the geodynamic settings of the Earth's crust origin can be represented as a spiral sequence: the interaction of mantle-plume processes and embryonic microplate tectonics during the Palaeo-Mezoarchaean (~3.8-2.8 Ga) → plume-tectonics and local plume-driven plate-tectonics (~2.80-0.55 Ga) → Phanerozoic plate tectonics along with a reduced role of mantle plumes.Key words: Precambrian; plate-tectonics; plume-tectonics; granulite-gneiss belts; supercontinent; intracontinent oval orogenRecommended by E.V. Sklyarov Аннотация: Ка...

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“…Grenville basement data are from McDaniel and McLennan (1997), Wareham et al (1998), Miller and Barr (2000) and Bell (1982). Lower crust data are from Griffin et al (1980a); ; ; Zhang (2002), and crust data is from Vervoort and Blichert-Toft (1999b). Archean mantle data are from Bell and Blenkinsop (1987); Griffin et al (2000); Pearson (2004); .…”

Section: Figurementioning

confidence: 99%

“…13) within the SCLM (Hoernle et al, 1995;Lustrino and Sharkov, 2006; as well as associated with a Low Velocity Component (LVC) in the underlying mantle (Hoernle et al, 1995). In the event that the parental magmas to the Monteregian Hills interacted with an Archean lower crust during their ascent from the mantle, the average isotopic compositions of an Archean lower crust are depicted in figure 14 (Griffin et al, 1980b;Rudnick and Goldstein, 1990b;Zhang, 2002). The second possibility is the incorporation of an Archean mantle component in the SCLM of the Monteregian Hills.…”

Section: Depth and Degree Of Partial Melting Of Monteregian Magmasmentioning

confidence: 99%

Tracages isotopiques de l'origine et de l'évolution des magmas en milieu continental :

Roulleau¹

2010

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Early Archaean granulite-facies metamorphism south of Ameralik, West Greenland

Cited by 146 publications

References 35 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

Age and isotopic geochemical characteristics of Archean carbonatites and alkaline rocks of the Baltic shield

Tracages isotopiques de l'origine et de l'évolution des magmas en milieu continental :

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