Very early Archean crustal-accretion complexes preserved in the North Atlantic craton

Journal Article · Thu Aug 01 00:00:00 EDT 1991 · Geology; (United States)

DOI:https://doi.org/10.1130/0091-7613(1991)019<0791:VEACAC>2.3.CO;2· OSTI ID:5963893

Nutman, A P ^[1]; Collerson, K D ^[2]

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1. Australian National Univ., Canberra (Australia)
2. Univ. of California, Santa Cruz (United States)

The North Atlantic craton contains very early Archean supracrustal rocks, orthogneisses, and massive ultramafic rocks. Most units of supracrustal rocks are dominated by mafic volcanic rocks, layered gabbros, and banded iron formations, bust some also contain abundant felsic volcanic-sedimentary rocks, quartzites, and marbles. Some quartzites contain detrital zircons derived from rocks identical in age to felsic volcanic-sedimentary rocks in these sequences (ca. 3800 Ma) and also from older (ca. 3850 Ma) sources. The presence of the ca. 3850 Ma detrital zircons suggests that the supracrustal units containing them were deposited on, or close to, ca. 3850 Ma sialic crust. The massive ultramafic rocks have chemical affinities to upper mantle rocks. The voluminous suites of tonalitic gneisses are dominated by 3700-3730 Ma bodies that intrude the supracrustal sequences, but they also locally contain components with ages between 3820 and 3920 Ma. The diverse supracrustal units, upper mantle rocks, and {ge} 3820 Ma components in the gneisses were tectonically interleaved in very early Archean convergent plate boundaries, giving rise to accretion complexes. In the period 3700-3730 Ma, voluminous tonalitic magmas produced by partial melting of predominantly mafic rocks in the base of the accretion complexes were emplaced at higher levels, forming juvenile continental crust and leaving behind a refractory lower crustal to upper mantle substrate.

• OSTI ID: 5963893
• Journal Information: Geology; (United States), Vol. 19:8; ISSN 0091-7613
• Country of Publication: United States
• Language: English

Related Subjects

58 GEOSCIENCES
RESERVOIR ROCK
AGE ESTIMATION
BOUNDARY CONDITIONS
CANADA
CONTINENTAL CRUST
GABBROS
GEOLOGIC HISTORY
GREENLAND
MAGMA
MARBLE
NORTH AMERICA
PLATE TECTONICS
PRECAMBRIAN ERA
QUARTZITES
SEDIMENTARY ROCKS
VOLCANIC ROCKS
ZIRCON
DEVELOPED COUNTRIES
EARTH CRUST
GEOLOGIC AGES
IGNEOUS ROCKS
METAMORPHIC ROCKS
MINERALS
PLUTONIC ROCKS
ROCKS
SILICATE MINERALS
TECTONICS
580000* - Geosciences