Significance of SHRIMP U-Pb dating of the Imperial Porphyry and associated Dokhan Volcanics, Gebel Dokhan, north Eastern Desert, Egypt

SHRIMP U-Pb zircon dating was undertaken on two samples of Dokhan Volcanics from the type area at Gebel Dokhan, north Eastern Desert, Egypt. A quartz andesite from the Imperial Porphyry unit has a weighted 206Pb/238U age of 593 f 13 Ma (20). A sample of grey andesite, from 450 m lower in the succession, has a weighted 206Pb/23*U age of 602 + 9 Ma (20). These ages are interpreted to record the time of eruption of the Dokhan Volcanics. Two concordant zircon cores in the upper sample define a weighted *06Pb/238U age of 685 f 16 Ma (2o), indicating inheritance from an older source. These cores have oscillatory zoning and may be derived from the ‘older’ granite basement or even an earlier volcanic sequence in the area. Care should, therefore, be taken in correlating all volcanic rocks in the Eastern Desert of Egypt with the Dokhan Volcanic Formation, as defined at the type locality. Q 2000 Elsevier Science Limited. All