Archean felsic volcanic rocks

Fig. 1. A schematic diagram showing the formation environment of Archean felsic volcanic rocks. Modified from Giles (1980).[1] Felsic eruption forms felsic volcanic rocks near the volcano and a spectrum of volcano-sedimentary sequence in the sea in Archean.[1]

Archean felsic volcanic rocks are felsic volcanic rocks that were formed in the Archean Eon (4 to 2.5 billion years ago).[2] The term "felsic" means that the rocks have silica content of 62–78%.[3] Given that the Earth formed at ~4.5 billion year ago,[4] Archean felsic volcanic rocks provide clues on the Earth's first volcanic activities on the Earth's surface started 500 million years after the Earth's formation.[5]

As the Archean Earth was hotter than the present, formation of felsic volcanic rocks may differ from the modern plate tectonics.[5][6][7]

Archean felsic volcanic rocks are distributed only in the preserved Archean greenstone belts, where deformed sequences of volcanic-sedimentary rocks are common.[5][6][8] Felsic volcanic rocks are rare in the early Earth and only contribute to less 20% of rocks in the Archean greenstone belts worldwide.[6] In contrast, mafic volcanic rocks (such as basalt and komatiite, silicate content <52%[3]) occupy about 50% in the greenstone belts.[6] Thus, felsic volcanic rocks are rare members in the Archean terranes.

Archean felsic volcanic activities commonly occur in submarine environments.[7] The composition of Archean felsic volcanic rocks are equivalent to a spectrum between dacite and rhyolite.[5] They can be distinguished by their mineral assemblages, rock chemistry and rock layer relationship in the sequences.[7]

Archean felsic volcanic rocks are utilised to date the timing of geological events and match distant rock units in separated Archean cratons.[9] They are important to reconstruct Archean geological environments.[10][11]

Felsic granitoids are the most prevalent rock type in Archean terranes.[6] These intrusive felsic igneous rocks include TTG suites (Tonalite-trondhjemite-granodiorite) that contributes over half the portion of Archean cratons.[6] They have implications in finding how the felsic volcanic rocks were formed and related to the granitoids.[9][12]

  1. ^ a b Giles, Christopher William (1980). A comparative study of Archaean and Proterozoic felsic volcanic associations in Southern Australia / by Chris W. Giles (Thesis).
  2. ^ Cohen, K.M., Finney, S.M., Gibbard, P.L., Fan, J.-X. (2013). The ICS International Chronostratigraphic Chart. Episodes 36, 199-204.
  3. ^ a b Cite error: The named reference :15 was invoked but never defined (see the help page).
  4. ^ Braterman, Paul S. "How Science Figured Out the Age of Earth". Scientific American. Retrieved 2018-12-02.
  5. ^ a b c d Halla, J; Whitehouse, M. J.; Ahmad, T.; Bagai, Z. (2017). "Archaean granitoids: an overview and significance from a tectonic perspective". Geological Society, London, Special Publications. 449 (1): 1–18. Bibcode:2017GSLSP.449....1H. doi:10.1144/SP449.10. ISSN 0305-8719.
  6. ^ a b c d e f Condie, Kent C. (1993). "Chemical composition and evolution of the upper continental crust: Contrasting results from surface samples and shales". Chemical Geology. 104 (1–4): 1–37. Bibcode:1993ChGeo.104....1C. doi:10.1016/0009-2541(93)90140-e. hdl:10068/310317. ISSN 0009-2541.
  7. ^ a b c Cite error: The named reference :18 was invoked but never defined (see the help page).
  8. ^ Szilas, Kristoffer (2018). "A Geochemical Overview of Mid-Archaean Metavolcanic Rocks from Southwest Greenland". Geosciences. 8 (7): 266. Bibcode:2018Geosc...8..266S. doi:10.3390/geosciences8070266. ISSN 2076-3263.
  9. ^ a b Agangi, Andrea; Hofmann, Axel; Elburg, Marlina A. (2018). "A review of Palaeoarchaean felsic volcanism in the eastern Kaapvaal craton: Linking plutonic and volcanic records". Geoscience Frontiers. 9 (3): 667–688. doi:10.1016/j.gsf.2017.08.003. ISSN 1674-9871.
  10. ^ Van Kranendonk, Martin J.; Hugh Smithies, R.; Hickman, Arthur H.; Wingate, Michael T.D.; Bodorkos, Simon (2010). "Evidence for Mesoarchean (≈3.2Ga) rifting of the Pilbara Craton: The missing link in an early Precambrian Wilson cycle". Precambrian Research. 177 (1–2): 145–161. Bibcode:2010PreR..177..145V. doi:10.1016/j.precamres.2009.11.007. ISSN 0301-9268.
  11. ^ Thorpe, R.I.; Hickman, A.H.; Davis, D.W.; Mortensen, J.K.; Trendall, A.F. (1992). "U-Pb zircon geochronology of Archaean felsic units in the Marble Bar region, Pilbara Craton, Western Australia". Precambrian Research. 56 (3–4): 169–189. Bibcode:1992PreR...56..169T. doi:10.1016/0301-9268(92)90100-3. ISSN 0301-9268.
  12. ^ Paradis, Suzanne; Ludden, John; Gélinas, Léopold (1988). "Evidence for contrasting compositional spectra in comagmatic intrusive and extrusive rocks of the late Archean Blake River Group, Abitibi, Quebec". Canadian Journal of Earth Sciences. 25 (1): 134–144. Bibcode:1988CaJES..25..134P. doi:10.1139/e88-013. ISSN 0008-4077.