The Ouarzazate Supergroup and its plutonic keel: the relics of an Ediacaran silicic large igneous province in North Africa
Posted on 13.04.2022 - 12:10
Abstract: Ouarzazate igneous rocks from Sidi Ifni, southwest Morocco, define a >3 km thick pile of mostly pyroclastic falls and flows of rhyolitic and dacitic ignimbrite and tuff, underpinned by comagmatic granitoid plutons. These rocks formed during two closely spaced periods of magmatism dated to c. 595–585 Ma and c. 575–560 Ma, with the majority of rocks comprised of ferroan alkali-feldspar rhyolite, syenorhyolite or monzorhyolite. These rocks divide into high-HREE and low-HREE types that discriminate as both volcanic-arc and within-plate magma types. Coeval, but less common, mafic rocks are comprised of olivine-normative, trachybasalt and basaltic trachyandesite. Temporal and compositional equivalents of Ouarzazate volcanic and intrusive rocks crop out widely across North Africa and extend into the previously contiguous regions of northeast North America. Collectively these erupted/shallowly-emplaced Ouarzazate-like rocks represent asthenospheric partial melts that are variably hybridized by additions from the lithospheric mantle and crust. The root cause of asthenospheric upwelling remains unknown, although the foundering of pre-collision subducted oceanic lithosphere may provide a plausible explanation. The vast geographic extent over which Ouarzazate-like igneous rocks are found, together with their composition and intra-plate setting, support the conclusion that these rocks represent the remnants of a late Ediacaran silicic large igneous province.
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Schulte, B.; Boger, S. D.; Benziane, F.; Yazidi, A.; Fanning, C. M. (2022): The Ouarzazate Supergroup and its plutonic keel: the relics of an Ediacaran silicic large igneous province in North Africa. Geological Society of London. Collection. https://doi.org/10.6084/m9.figshare.c.5945756.v1
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S. D. Boger
C. M. Fanning
vast geographic extentpreviously contiguous regionsnortheast north americanorth africa abstractmostly pyroclastic fallscomagmatic granitoid plutons595 – 585575 – 560like igneous rocksintrusive rocks cropplate magma typesouarzazate igneous rocksplate settingrocks representrocks formedrocks dividemafic rocksvariably hybridizedsouthwest moroccosidi ifniroot causeplutonic keelplausible explanationouarzazate supergroupmagmatism datedlithospheric mantleless commonhree typesferroan alkalifeldspar rhyoliteemplaced ouarzazatedacitic ignimbritecompositional equivalentsc .</basaltic trachyandesite