THE ARABO-NUBIAN SHIELD AND SINAI WERE WELD AT HIGH SUB-ANTARCTIC LATITUDES IN THE LATE PROTEROZOIC:A PALEOMAGNETIC STUDY ON THE DIKE SWARMS (CA 590MA) IN THE NORTH EASTERN DESERT AND SINAI, EGYPT

The Late Proterozoic NW-SE bimodal dyke swarms were collected from the North Eastern Desert of Egypt [Dokhan-Gattar range and Esh Mellaha range] and Sinai [Wadi Feiran and Durba/Araba range]. Sampling was done after removing weathered rocks. A solar compass was exclusively used for orientation.

Thermal demagnetization of the progressively acquired Isothermal remanence categorized the collection into Goethite, Goethite/Hematite (G/H), Goethite/Magnetite (G/M) and Goethite/Hematite/magnetite dominated sites. After the decay of the thermally soft PDF carried by Goethite, the five G/H-dominated sites decay toward the origin (T>680°C) yielding a tilt-corrected paleomagnetic pole at 37°S/ 49°E (Dec/Inc=166.5°/41°). This pole is close to the Late Paleozoic poles of Africa and thus considered as pre-tilting remagnetization during the Hercynean orogeny. On the other hand, after the removal of the soft PDF, the G/M-dominated sites (18 sites from the Eastern Desert and 20 sites from Sinai) were characterized by the decay of a stable component (T<590°C). The paleomagnetic poles for the Eastern Desert and Sinai 47°N/359°E (Dp/Dm=11°/12.7°) and 28°N/345°E (8°/10°) respectively in the in situ coordinates becoming 34°N/349°E (7°/8°) and 37°/351°E (6°/7°)after tilt-correction. The Site-means of the Eastern Desert and Sinai separately passed the classical fold test. Based on the reasonable freshness of the samples reflected in their minerals, dissimilarity with the younger Late Paleozoic remagnetization and the positive fold test, the characteristic paleomagnetic directions and poles of the present study could be considered as representing the northern part of the Arabo-Nubian in the Late Proterozoic (Ca 590Ma).

Based on the close similarity of the paleomagnetic poles obtained from the synchronous dyke swarms, the North Eastern Desert and Sinai could have been weld together in the Arabo-Nubian Shield since Late Precambrian time. It seems also that the Arabo-Nubian Shield was at a respectively high southern (sub- Antarctic) latitudes at ca 590 ago.