Fluid inclusion and stable isotope studies of the Mesloula Pb-Zn-Ba ore deposit, NE Algeria: Characteristics and origin of the mineralizing fluids

Laouar, R., Salmi-Laouar, S., Sami, L., Boyce, A. J. , Kolli, O., Boutaleb, A. and Fallick, A. E. (2016) Fluid inclusion and stable isotope studies of the Mesloula Pb-Zn-Ba ore deposit, NE Algeria: Characteristics and origin of the mineralizing fluids. Journal of African Earth Sciences, 121, pp. 119-135. (doi:10.1016/j.jafrearsci.2016.06.004)

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Abstract

In the Saharan Atlas (NE Algeria), the Triassic evaporitic formation was brought to the surface through the thick Cretaceous and Tertiary sedimentary cover as diapirs due to the effect of Atlasic tectonic events. The diapir piercing began in the Jurassic and has continued through present day. Many outcrops of several square kilometres are distributed in a large area (approximately 80 km wide) that extends northeasterly over 300 km towards Tunisia. The diapiric evaporitic formation is often accompanied by the emplacement of Pb-Zn-Ba-F mineralization. The Mesloula massif is an example of these deposits. Fluid inclusion and sulphur, carbon and oxygen isotope studies were carried out on Pb-Zn-Ba mineralization and associated gangue carbonates. Gypsum of the Triassic formation was also analysed for its sulphur isotope composition to show the role of evaporates in the generation of this typical peridiapiric deposit. Gypsum from the Triassic formation showed a narrow range of δ34SVCDT values, ranging from +14.6 to +15.5‰ (n = 8). This range is comparable to that of Triassic seawater sulphates. Sulphide minerals yielded δ34SVCDT values between 0 and + 11.7‰ (n = 15), indicating that sulphide sulphur was likely derived from Triassic sulphates through thermochemical sulphate reduction (TSR) because fluid inclusion microthermometric measurements yielded a mean temperature of 150 °C. Residual sulphate in such a system would have been enriched in 34S; this is reflected in the barite δ34SVCDT values, which range from +21.1 to +33.5‰ (n = 5). The δ13CVPDB values of calcite minerals, ranging from +2.1 to +6.3‰ (n = 4), indicate an inorganic carbon origin, likely from the host carbonate rocks. δ18OVSMOW values were between +21.9 and + 24.9‰, indicating that the most likely source of mineralizing fluids was formation water.

Item Type:Articles
Additional Information:AJB is funded by NERC support of the Isotope Community Support Facility at SUERC.
Status:Published
Refereed:Yes
Glasgow Author(s) Enlighten ID:Fallick, Professor Anthony and Boyce, Professor Adrian
Authors: Laouar, R., Salmi-Laouar, S., Sami, L., Boyce, A. J., Kolli, O., Boutaleb, A., and Fallick, A. E.
College/School:College of Science and Engineering > Scottish Universities Environmental Research Centre
Journal Name:Journal of African Earth Sciences
Publisher:Elsevier
ISSN:1464-343X
ISSN (Online):1879-1956
Published Online:03 June 2016

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