Publication Details

Ali, S. A. & Aswad, K. J. (2013). SHRIMP U-Pb dating of zircon inheritance in Walash arc volcanic rocks ( Paleogene age) , Zagros suture zone, NE Iraq: new insights into crustal contributions to trachytic andesite generation. Iraqi National Journal of Earth Sciences, 13 (1), 45-58.

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Iraqi National Journal of Earth Sciences


SHRIMP U-Pb ages were determined on single zircon grains separated fromcombined samples (i.e. GA8-GA9) belonging to a trachytic andesite, Galalaharea,Walash arc volcanic rocks, Northwestern Zagros Suture Zone, NE Iraq. Therock suite in the studied area ranges from calc-alkaline to alkaline (i.e., Ga8-Ga9).The New reconnaissance SHRIMP U-Pb zircon ages of GA8 - GA9 reveal twoepisodes of Palaeoproterozoic inherited zircon growth:1- 1953±39 Ma cores.2- ca. 1777±28 Ma rims. This provides evidence for the ancestry of terrane(i.e. crystalline basement).which had been pervasively overprinted by Mesoproterozoic thermal eventsthat facilitate the growth of zircon rims.The cathodoluminescence (CL) imagesshow no evidence of the zircon growth during Tertiary magmatism. The rims arewide and darker in CL compared to the cores. The oscillatory zoned cores probablygrew from magma of probably dioritic to gabbroic in composition, due to the highzircon Th/U ratio of ~1. The lower Th/U and high-U zircon rims could have grownin a superimposed migmatitic event with the growth of new zircon in localisedmelting. The core-rim pair of analyses is interpreted as indicating that the zirconsare inherited / recycled Paleogene magma due to crustal contamination. ThePalaeoproterozoic U-Pb zircon age may be correlated with the Khida terrane(1800-1650 Ma), in the north-westernmost portion of the ''Arabian Craton'' inSaudi Arabia. Here, a thinned Palaeoproterozoic continental basement fragment in Neo-Tethys might have contaminated the upwelling calc-alkaline magma beforeerupting. Keywords: SHRIMP U-P, Zagros, Iraq, Walash, Naopurdan.