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Neoproterozoic SHRIMP U–Pb zircon ages of silica-rich Dokhan Volcanics in the North Eastern Desert, Egypt [查看] ChristophBreitkreuz、HassanEliwa、IbrahimKhalaf、KhaledElGameel、BenjaminBühler、SergeiSergeev、AlexanderLarionov、MamoruMurata

Chronology of Neoproterozoic volcanosedimentary successions remains controversial for many regions of the Arabian–Nubian Shield, including the Dokhan Volcanics of NE Egypt. New U–Pb zircon SHRIMP ages have been obtained for 10 silica-rich ignimbrites and two subvolcanic dacitic bodies, mapped as Dokhan Volcanics, from the North Eastern Desert of Egypt. Crystallization ages range between 592±5 and 630±6Ma (Early Ediacaran). Apparently, the late consolidation of the Arabian–Nubian Shield was accompanied by the evolution of isolated volcanic centres and basin systems which developed during a period of approx. 40 Ma, independently in space and time and probably under changing tectonic regimes.The obtained age data together with other previously published reliable ages for Dokhan Volcanics suggest two main pulses of volcanic activity: 630–623Ma and 618–592 Ma. Five samples contain inherited zircons, with ages of 669, 715–746, 847 and 1530 Ma, supporting models that North Eastern Desert crust is mainly juvenile Neoproterozoic crust.

Precambrian crustal contribution to the Variscan accretionary prism of the Kaczawa Mountains (Sudetes, SW Poland) evidence from SHRIMP dating of detrital zircons [查看] RyszardKryza、JanZalasiewicz、StanisławMazur、PawełAleksandrowski、SergeySergeev、AlexanderLarionov

SHRIMP dating of detrital zircons from sandstones of the Gackowa Formation (Kaczawa Complex, Sudetes, SW Poland) indicates input from late (550–750 Ma) and early Proterozoic to Archaean sources (~2.0–3.4 Ga, the latter being the oldest recorded age from the Sudetic region). These dates preclude within-terrane derivation from seemingly correlatory acid volcanic rocks of early Palaeozoic age.Rather, they indicate provenance from Cadomian and older rocks that currently form part of other, geographically distant terranes; the most likely source identified to date is the Lusatian Block in the Saxothuringian Zone. Hence, the Gackowa Formation may be late Proterozoic rather than early Palaeozoic in depositional age, possibly coeval with the late Proterozoic (pre-Cadomian) greywackes of Lusatia, being subsequently tectonically interleaved with early Palaeozoic volcanic rocks into the Kaczawa accretionary prism during the Variscan orogeny. However, correlation with the lithologically similar early Ordovician Dubrau Quartzite of Saxothuringia, and so assignation to the early Paleozoic (post-Cadomian) rift succession deposited at the northern margin of Gondwana, cannot yet be precluded.

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