- Tytuł:
- Petrological studies of Neoproterozoic serpentinized ultramafics of the Nubian Shield: spinel compositions as evidence of the tectonic evolution of Egyptian ophiolites
- Autorzy:
- Azer, M. K.
- Powiązania:
- https://bibliotekanauki.pl/articles/139397.pdf
- Data publikacji:
- 2014
- Wydawca:
- Polska Akademia Nauk. Czytelnia Czasopism PAN
- Tematy:
-
Neoproterozoic
Serpentinite
Arabian-Nubian Shield
chromian spinel
fore-arc
neoproterozoik
serpentynit
spinel - Opis:
- 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 TiO2 contents (<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.
- Źródło:
-
Acta Geologica Polonica; 2014, 64, 1; 113-127
0001-5709 - Pojawia się w:
- Acta Geologica Polonica
- Dostawca treści:
- Biblioteka Nauki
Artykuł