Insights on the crustal evolution of the West African Craton from Hf isotopes in detrital zircons from the Anti-Atlas belt



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Abati Gómez, Jacobo and Aghzer, Abdel Mouhsine and Gerdes, Axel and Ennih, Nasser (2012) Insights on the crustal evolution of the West African Craton from Hf isotopes in detrital zircons from the Anti-Atlas belt. Precambrian research, 212-13 . pp. 263-274. ISSN 0301-9268

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The Lu-Hf isotopic composition of detrital zircons has been used to investigate the crustal evolution of
the northern part of the West African Craton (WAC). The zircons were separated from six samples of
siliciclastic sedimentary rocks from the main Neoproterozic stratigraphic units of the Anti-Atlas belt,
from the Sirwa and Zenaga inliers. The data suggest that the north part of the WAC formed during three
cycles of juvenile crust formation with variable amount of reworking of older crust. The younger group
of zircons, with a main population clustering around 610 Ma, has a predominant juvenile character and
evidences of moderate mixing with Paleoproterozoic and Neoarchean crust, which supports that most
igneous and metamorphic rocks where zircons originally crystallized were formed in an ensialic magmatic
arc environment. The group of zircons in the age range 1.79–2.3 Ga corresponds to the major crust
forming event in the WAC: the Eburnian orogeny. The isotopic data indicate that the provenance area
should represent a crustal domain that was separated from a mantle reservoir at ∼2050–2300 Ma, and
further evolved with a time-integrated 176Lu/177Hf of ∼0.01, characteristic of continental crust. The evolution
of the Eburnian orogeny is, consequently, compatible with new crust formation in an island arc
environment, the transition to a continental arc setting and a final continent–continent collision. The
Lower Paleoproterozoic and Neoarchean evolution (2.3–2.75 Ga) includes a group of detrital zircon ages
that has not been identified up to now in the igneous or metamorphic rocks of the north WAC basement.
Their Hf isotopic signature points to reworking of mainly juvenile Neoarchean crust with some Meso- to
Palaearchean contributions. The significance of these ages is uncertain: they can represent a tectonothermal
event not discovered yet in the Reguibat Shield or the zircons can be far traveled from an unknown

Item Type:Article
Uncontrolled Keywords:Anti-Atlas belt, Morocco, Hf isotopes, Detrital zircon, Crustal evolution
Subjects:Sciences > Geology > Petrology
ID Code:25385
Deposited On:12 May 2014 11:18
Last Modified:12 May 2014 11:18

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