| Acasta Gneiss Complex | |
|---|---|
| Stratigraphic range: Archean ~ | |
| Type | Complex |
| Sub-units | Idiwhaa tonalitic gneiss[1] |
| Underlies | Central Slave Cover Group |
| Area | > 13,000 km (8,100 mi) |
| Thickness | unknown |
| Lithology | |
| Primary | tonalitic and granodioritic orthogneisses |
| Other | mafic and ultramafic gneisses |
| Location | |
| Region | Slave Craton, Northwest Territories |
| Country | Canada |
| Type section | |
| Named for | Acasta River |
| Named by | J. E. King[2] |
| Year defined | 1985 |
The Acasta Gneiss Complex, also called the Acasta Gneiss, is a body of felsic to ultramafic Archean basement rocks, gneisses, that form the northwestern edge of the Slave Craton in the Northwest Territories, Canada, about 300 km (190 mi) north of Yellowknife, Canada. This geologic complex consists largely of tonalitic and granodioritic gneisses and lesser amounts of mafic and ultramafic gneisses. It underlies and is largely concealed by thin, patchy cover of Quaternary glacial sediments over an area of about 13,000 km2 (5,000 sq mi). The Acasta Gneiss Complex contains fragments of the oldest known crust and record of more than a billion years (>4.0–2.9 Ga) of magmatism and metamorphism.[1][3][4] The Acasta Gneiss Complex is exposed in a set of anticlinoriums within the foreland fold and thrust belt of the Paleoproterozoic Wopmay Orogen.[5][6]
- ^ a b Reimink, J.R., Chacko, T., Stern, R.A. and Heaman, L.M., 2016b. The birth of a cratonic nucleus: lithogeochemical evolution of the 4.02–2.94 Ga Acasta Gneiss Complex. Precambrian Research, 281, pp.453-472.
- ^ King, J. E., 1985. Structure of the Metamorphic Internal Zone, Northern Wopmay Orogen, Northwest Territories, Canada, Ph.D. dissertation, Queen's University, Kingston, Ontario. 208 pp.
- ^ Reimink, J.R., Chacko, T., Carlson, R.W., Shirey, S.B., Liu, J., Stern, R.A., Bauer, A.M., Pearson, D.G. and Heaman, L.M., 2018. Petrogenesis and tectonics of the Acasta Gneiss Complex derived from integrated petrology and 142Nd and 182W extinct nuclide-geochemistry. Earth and Planetary Science Letters, 494, pp.12-22.
- ^ Reimink, J.R., Baue, A.M., and Chacko, T., 2019. The Acasta Gneiss Complex. In Van Kranekdonk, M.J., Smithies, R.H., and Bennett, V.C., eds., pp. 329-347. Earth's Oldest Rocks. Amsterdam, Elsevier. 1112 pp. ISBN 978-0-444-63901-1
- ^ King, J.E., 1986. The metamorphic internal zone of Wopmay Orogen (Early Proterozoic), Canada: 30 km of structural relief in a composite section based on plunge projection. Tectonics, v. 5, pp. 973-994.
- ^ St-Onge, M.R., King, J.E., and Lalonde, A.E., 1988. Geology, east-central Wopmay Orogen, District of Mackenzie, Northwest Territories. Geological Survey of Canada, Open File Report, 1923, 3 sheets, scale 1:125,000.