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    Prograde and retrograde evolution of eclogite from Adrar Izzilatène (Egéré-Aleksod terrane, Hoggar, Algeria) determined from chemical zoning and pseudosections, with geodynamic implications

    Authors
    Doukkari, S.A.
    Godard, G.
    Diener, J.F.A
    Kienast, J.R.
    Liégeois, J.P.
    Arab, A.
    Drareni, A.
    Ouzegane, K.
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    Discipline
    Earth and related Environmental sciences
    Subject
    Geodynamics and mineral resources
    Audience
    Scientific
    Date
    2015
    Publisher
    Elsevier
    Metadata
    Show full item record
    Description
    Adrar Izzilatène in the Egéré-Aleksod terrane of the LATEA metacraton (Hoggar, Algeria) exposes one of the best preserved examples of eclogite facies metamorphism in Hoggar. Three distinct stages of metamorphic development are recognised, namely, the pre-peak stage (M1), characterised by garnet, amphibole, epidote, quartz and rutile, the peak eclogite facies stage (M2), consisting of omphacite, garnet, edenite, epidote, quartz and rutile, and the retrograde stage (M3), where initial decompression resulted in the appearance of plagioclase, the development of pargasite + plagioclase kelyphites and finally the formation of anhydrous plagioclase + diopside coronas. Porphyroblastic omphacite has a jadeite content of up to XJd = 0.36, which is the highest yet observed for eclogite facies rocks from the Tuareg Shield. Garnet growth zoning patterns are characterised by flat profiles in the cores (XAlm = 0.55 0.60; XPrp = 0.12 0.16; XGrs = 0.26 0.30) before showing a decrease in almandine to XAlm = 0.45, coupled to an increase in pyrope to XPrp = 0.29 and decrease in grossular to XGrs = 0.26 at the rims. Calculated P T MH2O pseudosections show that the prograde M1 assemblage equilibrated at 13 14 kbar and 580 °C, before pressure and temperature increased to 19 kbar and 650 700 °C at fluid-saturated conditions during peak metamorphism. Retrogression involved near-isothermal decompression to 8 9 kbar and 700 750 °C at fluid-undersaturated conditions. Prograde-to-peak metamorphism of the Izzilatène eclogite could have involved either oceanic or continental subduction, followed by exhumation as the area was obducted towards the LATEA metacraton during the Pan-African orogeny and the assembly of Western Gondwana.
    Citation
    Doukkari, S.A.; Godard, G.; Diener, J.F.A; Kienast, J.R.; Liégeois, J.P.; Arab, A.; Drareni, A.; Ouzegane, K. (2015). Prograde and retrograde evolution of eclogite from Adrar Izzilatène (Egéré-Aleksod terrane, Hoggar, Algeria) determined from chemical zoning and pseudosections, with geodynamic implications. , Lithos, Vol. 226, 217-232, Elsevier, DOI: 10.1016/j.lithos.2014.12.007.
    Identifiers
    uri: https://orfeo.belnet.be/handle/internal/2446
    doi: http://dx.doi.org/10.1016/j.lithos.2014.12.007
    Type
    Article
    Peer-Review
    Yes
    Language
    eng
    Links
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