The ophiolitic serpentinites of Neoproterozoic age in the Eastern Desert of Egypt show different types of contact against the country rocks. At the Fawakhir and Gabal Ghadir localities, the contact with the anorogenic granites is distinctly intrusive, with the formation of a limited-scale thermal aureole (up to ~3.15 and ~5.30 m at the two localities, respectively). The metasomatic alterations of the serpentinites caused by flow of hot fluids from the granite led to the formation of meta-ultramafic rocks with abundant dolomite, talc and free silica displaying proximal and distal varieties with respect to the intrusive granite. Combined field, petrographic, whole-rock and microanalytical data help to construct phase equilibria and mineral stabilities along the serpentinite–granite interface based on the μSiO2 and XCO2 variables. Phase diagrams for the thermal assemblages at the Ghadir and Fawakhir aureoles were constructed assuming a pressure of 1–3 kbar. The replacement of antigorite by talc becomes more independent on temperature at XCO2 ≤ 0.2 and the crystallization of dolomite and calcite predominates in the proximal varieties. The upper stability limit of antigorite lies at ~425 °C and ~500 °C at 1 and 3 kbar, respectively. Thus, the granites were emplaced into shallow levels so that they were not able to dehydrate the serpentinites at the two studied localities. Accordingly, the formation of forsterite was not possible at the investigated contact aureoles as the condition to form metamorphic olivine (0.05 < XCO2 < 0.55) was not attained.
Skip Nav Destination
Close
Article navigation
Research Article|
September 01, 2019
Metasomatised serpentinite at the contact with anorogenic granite from the Neoproterozoic ophiolites in the Eastern Desert of Egypt
Adel A. Surour
1
Department of Geology, Faculty of Science, Cairo University
, 12613Giza, Egypt
Corresponding author, e-mail: adelsurour@hotmail.com
Search for other works by this author on:
European Journal of Mineralogy (2019) 31 (5-6): 963–972.
Article history
received:
15 Mar 2019
rev-recd:
28 Aug 2019
accepted:
29 Aug 2019
first online:
14 Sep 2019
Citation
Adel A. Surour; Metasomatised serpentinite at the contact with anorogenic granite from the Neoproterozoic ophiolites in the Eastern Desert of Egypt. European Journal of Mineralogy 2019;; 31 (5-6): 963–972. doi: https://doi.org/10.1127/ejm/2019/0031-2889
Download citation file:
Close
You could not be signed in. Please check your email address / username and password and try again.
Index Terms/Descriptors
- A-type granites
- Africa
- aureoles
- contact metamorphism
- Eastern Desert
- Egypt
- granites
- igneous rocks
- major elements
- metaigneous rocks
- metamorphic rocks
- metamorphism
- metasomatic rocks
- metasomatism
- mineral assemblages
- Neoproterozoic
- North Africa
- ophiolite
- petrography
- phase equilibria
- plutonic rocks
- Precambrian
- Proterozoic
- serpentinite
- spectra
- trace elements
- upper Precambrian
- X-ray diffraction data
- X-ray fluorescence spectra
- Gabal Ghadir
- Fawakhir Granite
Latitude & Longitude