El-Mahallawi M. M.

Árva-Sós Erzsébet

English

Radiometric ages of some metagabbros using amphiboles were determined with the conventional K-Ar method. The ages ofpargasitic hornblende from the Meatiq metagabbro gave 599±32 Ma, 544±21 Ma and 539±21 Ma. Tlie latter two ages reflect some K incorporation after crystallization. The age of 599±32 is the time of total resetting and metamorphism of this rock. This age is slightly below the age of the Abu Ziran Orogeny (613 ±2 Ma) which cause the obduction of ophioRtic melange onto the iniracrustal basement (HABIB et al. 1985); culmination of metamorphism and deformation (STRUCHIO et al. 1982) or emplacement of Abu Ziran pluton and timing of major crustal movement (STERN an d HEDGE 1985). The age of tremolitic hornblende from El-Sid pluton gave 421±76 Ma, 440+18 Ma and 543±75 Ma. These ages are too young and their scatter is great due to the very low K content. Moreover, the tremolitic hornblende is strongly strained and sometimes occurred as aggregates of fibrous crystals, raising the possibility of continuous Ar loss. So, the given ages suggest either the termination of Ar diffusion at that time or partial loss during later events subsequent to the pluton's emplacement. A relationship to local tectonic movement might be suggested but is not well documented

University of Szeged

Petrography, geochemistry and K-Ar dating of some metagabbros from the Central Eastern Desert, Egypt

http://acta.bibl.u-szeged.hu/24811/1/mineralogica_034_071-078.pdf

Petrography, geochemistry and K-Ar dating of some metagabbros from the Central Easern Desert, Egypt

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University of Szeged