ROLE OF THE JUVENILE VERSES REWORKED CONTINENTAL CRUST IN THE GENERATION OF THE ARABIAN-NUBIAN SHIELD: INSIGHTS FROM U-PB GEOCHRONOLOGY, HF ISOTOPIC AND TRACE ELEMENT COMPOSITION OF DETRITAL ZIRCONS FROM THE EASTERN COAST OF THE RED SEA, KINGDOM OF SAUDI ARABIA

This study reports the U-Pb ages, Hf isotopic composition and trace element chemistry of detrital zircons extracted from four composite beach sand samples from the eastern coast of the Red Sea. U-Pb data identified three age populations, including Ediacaran (540 - 635 Ma), Cryogenian (640-720 Ma) and Tonian (720 - 1000 Ma). Inherited and xenocrystic zircons yielded Neoproterozoic dates ranging from 1400 - 1000 Ma and much older Paleoproterozoic and Archean dates ranging from 3.1 -1.8 Ga. The Ediacaran zircons ranging in age from 629 to 587 Ma yielded individual radiogenic but enriched εHf (t) values (i.e., below the depleted mantle curve) vary from +6 to +10.9. The εHf (t) of the depleted mantle during the Ediacaran is +14 ± 1. While Cryogenian zircons (725-663 Ma) yielded elevated and depleted εHf (t) values range from +10.1 to +13.7. Few Tonian zircons yielded near-chondritic εHf (t) composition of 0 ± 2.5. Neoproterozoic zircons (1048-1012Ma) generally yielded chondritic to nonradiogenic εHf (t) composition with a maximum of -13.8. Two Paleoproterozoic zircons dated at 2.03 and 1.8 Ga yielded εHf (t) composition of -0.9 and -10.7, respectively. Zircon trace element chemistry coupled with age data and Hf isotopic composition suggest that the Cryogenian zircons are related to the intra-oceanic subduction-related magmatic rocks produced by the fractionation of the sublithospheric mantle-derived sources. In contrast, the enriched Ediacaran zircons can be related to the post-collision magmatic rocks produced by the partial melting of a distinct and enriched mantle reservoir formed during the earlier Crygenian-Tonian arc development. However, the presence of Neo- as well as Paleoproterozoic with some Archean zircons suggest that in addition to the mantle-derived sources, contribution of older crustal sources may not be ruled out.