Temperatures of Neoproterozoic Regional Carbonate Alteration in the Eastern Desert of Egypt
- 1Geosciences Department, the University of Texas at Dallas, Richardson, USA, (arman.boskabadi@utdallas.edu)
- 2Department of Geological Sciences, Stockholm University, Stockholm, Sweden
- 3Institute of Environmental Physics, Heidelberg University, Heidelberg, Germany
- 4Geology Department, Faculty of Science, Beni-Suef University, Beni-Suef, Egypt
- 5Geological Sciences Department, National Research Centre, Cairo, Egypt
- 6Geology Department, Faculty of Science, Helwan University, Cairo, Egypt
- 7Department of Geology, Faculty of Science, Benha University, Benha, Egypt
- 8Institute of Geosciences, University of Kiel, Kiel, Germany
Neoproterozoic ophiolites in the Eastern Desert (ED) of Egypt are pervasively carbonated and listvenitized. Two types of carbonation are recognized: 1) intergrown magnesite (and to lesser extent dolomite) with serpentine and talc that in cases form pure carbonate veins, and 2) cryptocrystalline magnesite veins filling the fractures crosscutting other ophiolitic host rocks. Few studies address the conditions of carbonate alteration of ultramafic rocks, especially the temperature of altering fluids. We employ clumped isotope thermometry on natural dolomite and magnesite from 17 variably carbonated ophiolitic rocks and veins in the ED. Five samples of antigorite-bearing serpentinite, talc-carbonate, and associated carbonate veins yield wide range temperatures of magnesite and dolomite between 213 to 426°C (285±73°C). These temperatures are comparable with previous fluid inclusion thermometry carried out on some of the vein samples (homogenization temperature between 225 to 383°C; Boskabadi et al. 2017). Ten samples of fully quartz-carbonate altered peridotites (i.e. listvenites) record even a wider range of clumped isotope carbonation temperatures between 90 and 452°C (227±112°C). In contrast, two samples of late-stage veins of cryptocrystalline magnesite record lower temperatures of 19 and 28°C. While the constraints on the pressure of carbonation are lacking, the wide range of temperatures for the carbonates in antigorite-bearing serpentinite, talc-carbonate, and listvenite lithologies suggest that carbonation probably occurred at variable depths, whereas the low temperature of cryptocrystalline magnesite veins points to conditions nearer the surface most likely associated with post-obduction processes. Therefore, different sources of carbon and CO2-bearing fluids should have been responsible for the formation of high- and low-temperature carbonates in the region.
Boskabadi et al. 2017. International Geology Review 59, 391–419.
How to cite: Boskabadi, A., Kluge, T., Pitcairn, I., Ali, R., Azer, M., Maurice, A., Stern, R., Bakhit, B., Shahien, M., and Zoheir, B.: Temperatures of Neoproterozoic Regional Carbonate Alteration in the Eastern Desert of Egypt, EGU General Assembly 2020, Online, 4–8 May 2020, EGU2020-18336, https://doi.org/10.5194/egusphere-egu2020-18336, 2020.
