Akia terrane

The Akia terrane is a tectonostratigraphic terrane located in the North Atlantic Craton in southern West Greenland. ^[1] The Akia terrane is bounded to the Southeast by the Eo- to Neo-archaean tectonostratigraphic terranes of the Nuuk region, ^[2] and to the North by the recently recognised Alanngua Complex, which separates the Akia terrane from the Neoarchaean Tuno terrane. ^[3] The crust in the Akia terrane formed in two major pulses. The first at ~3.2 Ga, predominantly comprises dioritic gneisses, whereas the second, at ~3.0 Ga comprises a more diverse mix of TTG and dioritic gneisses with enclaves of supracrustal rocks and mafic-ultramafic intrusions. ^{[3] [4] [5] [6]} Supracrustal rocks are largely tholeiitic and calc-alkaline amphibolites formed at ~3.07 Ga. ^[7] The mafic-ultramafic intrusions include peridotite cumulates ^[8] and a belt of noritic intrusions formed at the same time as the TTG gneisses, the Maniitsoq Norite Belt. ^[9] Various tectonic settings have been proposed for the 3.0 Ga crust forming event, including subduction related magmatism, ^[4] stagnant lid tectonic processes, ^[10] and crust and mantle melting in an ultra-hot orogeny. ^[9]

The terrane underwent high grade granulite facies metamorphism at ~3.0 Ga, immediately after or simultaneous with the second major crust forming event. ^{[9] [10]} Further high temperature metamorphism followed at ~2.7 Ga and ~2.5 Ga. ^{[3] [11]} The earlier event is marked by widespread formation of pegmatite granite dykes ^[6] and may be associated with the juxtaposition of the Akia and Tuno terranes. ^{[3] [11]}

References

1. C. R. L. Friend, A. P. Nutman, V. R. McGregor (1988). "Late Archaean terrane accretion in the Godthåb region, southern West Greenland" . Nature . 335 (6190): 535–538. Bibcode:1988Natur.335..535F. doi:10.1038/335535a0. S2CID   4254354.
2. C. R. L. Friend, A. P. Nutman (2005). "New pieces to the Archaean terrane jigsaw puzzle in the Nuuk region, southern West Greenland: steps in transforming a simple insight into a complex regional tectonothermal model" . Journal of the Geological Society . 162 (1): 147–162. Bibcode:2005JGSoc.162..147F. doi:10.1144/0016-764903-161. S2CID   52855189 – via Lyell Collection.
3. A. Steenfelt, J. Hollis, C. L. Kirkland, A. Sandrin, N. J. Gardiner, H. K. H. Olierook, K. Szilas, P. Waterton, C. Yakymchuk (2021). "The Mesoarchaean Akia terrane, West Greenland, revisited: New insights based on spatial integration of geophysics, field observation, geochemistry and geochronology". Precambrian Research . 352: 105958. Bibcode:2021PreR..352j5958S. doi:10.1016/j.precamres.2020.105958. hdl: 10023/21175 . S2CID   225111824 – via Elsevier Science Direct.
4. A. A. Garde, C. R. L. Friend, A. P. Nutman, M. Marker (2000). "Rapid maturation and stabilisation of middle Archaean continental crust: the Akia terrane, southern West Greenland". Bulletin of the Geological Society of Denmark. 47: 1–27. doi: 10.37570/bgsd-2000-47-01 .
5. A. A. Garde (1997). "Accretion and evolution of an Archaean high-grade grey gneiss – amphibolite complex: the Fiskefjord area, southern West Greenland". Geology of Greenland Survey Bulletin . 177: 1–115. doi: 10.34194/ggub.v179.5075 .
6. N. J. Gardiner, C. L. Kirkland, J. Hollis, K. Szilas, A. Steenfelt, C. Yakymchuk, H. Heide‑Jørgensen (2019). "Building Mesoarchaean crust upon Eoarchaean roots: the Akia Terrane, West Greenland". Contributions to Mineralogy and Petrology . 174 (3): 20. Bibcode:2019CoMP..174...20G. doi: 10.1007/s00410-019-1554-x . hdl: 10023/18486 . S2CID   134027320.
7. K. Szilas, J. Tusch, J. E. Hoffmann, A. A. Garde, C. Münker (2017). "Hafnium isotope constraints on the origin of Mesoarchaean andesites in southern West Greenland, North Atlantic Craton" . Geological Society, London, Special Publications . 449 (1): 19–38. Bibcode:2017GSLSP.449...19S. doi:10.1144/SP449.2. S2CID   132614766 – via Lyell Collection.
8. K. Szilas, V. van Hinsberg, I. McDonald, T.Næraa, H. Rollinson, J. Adetunjie, D. Bird (2018). "Highly refractory Archaean peridotite cumulates: Petrology and geochemistry of the Seqi Ultramafic Complex, SW Greenland". Geoscience Frontiers. 9 (3): 689–714. doi: 10.1016/j.gsf.2017.05.003 . ISSN   1674-9871.
9. Waterton, Pedro; Hyde, William R.; Tusch, Jonas; Hollis, Julie A.; Kirkland, Christopher L.; Kinney, Carson; Yakymchuk, Chris; Gardiner, Nicholas J.; Zakharov, David; Olierook, Hugo K. H.; Münker, Carsten (2020). "Geodynamic Implications of Synchronous Norite and TTG Formation in the 3 Ga Maniitsoq Norite Belt, West Greenland". Frontiers in Earth Science . 8: 406. Bibcode:2020FrEaS...8..406W. doi: 10.3389/feart.2020.562062 . hdl: 10023/20744 . ISSN   2296-6463.
10. C. Yakymchuk, C. L. Kirkland, J. A. Hollis, J. Kendrick, N. J. Gardiner, K. Szilas (2020-04-01). "Mesoarchean partial melting of mafic crust and tonalite production during high-T–low-P stagnant tectonism, Akia Terrane, West Greenland". Precambrian Research. 339: 105615. Bibcode:2020PreR..339j5615Y. doi: 10.1016/j.precamres.2020.105615 . hdl: 10023/19439 . ISSN   0301-9268.
11. C. L. Kirkland, C. Yakymchuk, J. Hollisd, H. Heide-Jørgensen, M. Danišík (2018-09-01). "Mesoarchean exhumation of the Akia terrane and a common Neoarchean tectonothermal history for West Greenland". Precambrian Research. 314: 129–144. Bibcode:2018PreR..314..129K. doi: 10.1016/j.precamres.2018.06.004 . ISSN   0301-9268.