Please use this identifier to cite or link to this item: http://hdl.handle.net/1959.14/124054
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- Title
- Mesoarchean subduction processes : 2.87 Ga eclogites from the Kola Peninsula, Russia
- Related
- Geology, Vol. 38, No. 8 (2010), p.739-742
- DOI
- 10.1130/G31219.1
- Publisher
- Geological Society of America
- Date
- 2010
- FoR/RFCD Code(s)
-
040100 Atmospheric Sciences
040300 Geology
040200 Geochemistry
- Author/Creator
- Mints, M. V
- Author/Creator
- Belousova, E. A
- Author/Creator
- Konilov, A. N
- Author/Creator
- Natapov, L. M
- Author/Creator
- Shchipansky, A. A
- Author/Creator
- Griffin, W. L
- Author/Creator
- O'Reilly, S. Y
- Author/Creator
- Dokukina, K. A
- Author/Creator
- Kaulina, T. V
- Description
- The nature of tectonic processes on the early Earth is still controversial. The scarcity of high-pressure metamorphic rocks such as eclogite (the high-pressure equivalent of basalt) in Archean cratons has been used to argue that plate tectonics did not operate until Earth had cooled to a critical point, perhaps around the 2.5 Ga Archean-Proterozoic transition. However, eclogites occur as meter- to kilometer-sized lenses enclosed in Archean gneisses of the Belomorian Province of the Fennoscandian shield. Geochemistry and internal features suggest that the protoliths of the eclogites were interlayered olivine gabbros, troctolites, and Fe-Ti oxide gabbros. Greenschist facies mineral parageneses are enclosed in prograde-zoned eclogite garnets, and peak metamorphic conditions define an apparent thermal gradient (12–15 °C/km), consistent with metamorphism in a warm Archean subduction zone. We show here that these eclogites represent the oldest known high-pressure metamorphic rocks. U-Pb dating and Hf isotope analyses of zircons from the eclogites and a crosscutting felsic vein define a minimum age of 2.87 Ga for the Uzkaya Salma eclogite; a 2.70 Ga age for the Shirokaya Salma eclogite is interpreted as the age of a granulite facies overprint. Thermal overprinting and growth of new zircon also occurred during the Svecofennian (1.9–1.8 Ga) orogeny. These new data imply that plate tectonic processes operated at least locally in late Mesoarchean time. The adakitic nature of the felsic vein suggests that partial melting of hydrated eclogites could produce Archean tonalite-trondhjemite-granodiorite–type magmas.
- Description
- 4 page(s)
- Subject Keyword
- 040100 Atmospheric Sciences
- Subject Keyword
- 040300 Geology
- Subject Keyword
- 040200 Geochemistry
- Resource Type
- journal article
- Organisation
- Macquarie University. National Key Centre for Geochemical Evolution and Metallogeny of Continents (GEMOC)
- Identifier
- http://hdl.handle.net/1959.14/124054
- Identifier
- ISSN:0091-7613
- Identifier
- mq-rm-2010004138
- Language
- eng
- Reviewed
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