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Geochronology and palaeomagnetism of a late Proterozoic island arc terrane from the Red Sea Hills, northeast Sudan

Abstract:

Size fractions and single grains of zircon, hornblende and biotite have been dated to define the formation age and thermal history of the northern Haya Terrane (NHT), a late Proterozoic island arc terrane of the Red Sea Hills (RSH), northeast Sudan. UPb and 207Pb 206Pb zircon data for acidic volcanics and granitoid rocks bracket the time of formation of the NHT between 887 ± 20 and 854 ± 9 Ma. 40Ar 39Ar hornblende and biotite ages of a gabbro near Suakin suggest passage through the argon closing temperature for hornblende at about 841 ± 4 Ma and 782 ± 6 Ma for biotite. The hornblende age is considered to be representative of the age of magnetic blocking and, hence, the age of the characteristic magnetization of the Suakin Gabbro. The direction of magnetization obtained from these rocks is Dec 244.2; Inc -3.9; α95 = 8.0; k = 41.9, based on nine sites, which corresponds to a palaeopole position at 25.3°S, 313.7°E (dp = 4.0, dm = 8.0). This pole is significantly different from other palaeopole positions of comparable age from Eastern Africa and indicates a separation between the NHT and the ancient eastern margin of Africa of approximately 3000 km at the time of magnetization. © 1992.