Journal : Acta Geologica Polonica
Article : Petrological studies of Neoproterozoic serpentinized ultramafics of the Nubian Shield: spinel compositions as evidence of the tectonic evolution of Egyptian ophiolites

Authors :
Muszer, J.
Institute of Geological Sciences, University of Wrocław, Cybulskiego 30, PL-50-204 Wrocław, Poland,,
Fedorowski, J.
Institute of Geology, Adam Mickiewicz University, Maków Polnych 16, Pl-61-606 Poznań, Poland,,
Machłajewska, I.
Institute of Applied Geology, Silesian University of Technology, Akademicka 2, PL-41-200 Gliwice, Poland,,
Kennedy, W. J.
Oxford University Museum of Natural History, Parks Road, Oxford OX1 3W and Department of Earth Sciences, Parks Road, Oxford OX1 3AN, United Kingdom,,
Fatim, A. N.
Geological Survey of Pakistan, Quetta, Pakistan,
Brachaniec, T.
Department of Geochemistry, Mineralogy and Petrography; Faculty of Earth Science; University of Silesia; Będzińska Str. 60, PL-41-200 Sosnowiec, Poland,,
Karwowski, Ł.
Department of Geochemistry, Mineralogy and Petrography; Faculty of Earth Science; University of Silesia; Będzińska Str. 60, PL-41-200 Sosnowiec, Poland.,,
Szopa, K.
Department of Geochemistry, Mineralogy and Petrography; Faculty of Earth Science; University of Silesia; Będzińska Str. 60, PL-41-200 Sosnowiec, Poland,,
Kennedy, W. J.
Oxford University Museum of Natural History, Parks Road, Oxford OX1 3W,,
Azer, M. K.
Geology Department, National Research Centre, 12622-Dokki, Cairo, Egypt,,
Abstract : The mafic-ultramafic rocks of the Gabal El-Degheimi area, Central Eastern Desert of Egypt, are parts of an ophiolitic section. The ophiolitic rocks are dismembered and tectonically enclosed within, or thrust over, island arc assemblages. Serpentinites, altered slices of the upper mantle, represent a distinctive lithology of the dismembered ophiolites. Some portions of the serpentinized rocks contain fresh relicts of primary minerals such as chromian spinel and olivine. The abundance of bastite and mesh textures suggests harzburgite and dunite protoliths, respectively, for these serpentinites. Some fresh cores of chromian spinel are rimmed by ferritchromite and Cr-magnetite. The development of alteration rims around chromian spinel cores indicates their formation during prograde alteration and under oxidizing conditions during lower amphibolite facies metamorphism. Fresh chromian spinels are characterized by high contents of Cr2O3(48.92–56.74 wt. %), Al2O3(10.29–20.08wt. %), FeO (16.24–28.46 wt. %) and MgO (4.89–14.02 wt. %), and very low TiO2contents (<0.16 wt. %). The analyzed fresh chromian spinels have high Cr# (0.62–0.79) characteristic of spinels in mantle peridotite that has undergone some degree of partial melting. The data presented here suggest that the mantle peridotites of the Gabal El-Degheimi area are similar to forearc peridotites of suprasubduction zone environments.
Keywords : neoproterozoik, serpentynit, spinel, Neoproterozoic, Serpentinite, Arabian-Nubian Shield, Chromian spinel, fore-arc,
Publishing house : Faculty of Geology of the University of Warsaw
Publication date : 2014
Number : Vol. 64, no. 1
Page : 113 – 127

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Qute : Muszer, J. ,Fedorowski, J. ,Machłajewska, I. ,Kennedy, W. J. ,Fatim, A. N. ,Brachaniec, T. ,Karwowski, Ł. ,Szopa, K. ,Kennedy, W. J. ,Azer, M. K. ,Azer, M. K. , Petrological studies of Neoproterozoic serpentinized ultramafics of the Nubian Shield: spinel compositions as evidence of the tectonic evolution of Egyptian ophiolites. Acta Geologica Polonica Vol. 64, no. 1/2014