Stable isotope study of the igneous, metamorphic and mineralized rocks of the Edough complex, Annaba, Northeast Algeria

Laouar, R., Boyce, A.J., Ahmed-Said, Y., Ouabadi, A., Fallick, A.E. and Toubal, A. (2002) Stable isotope study of the igneous, metamorphic and mineralized rocks of the Edough complex, Annaba, Northeast Algeria. Journal of African Earth Sciences, 35(2), pp. 271-283. (doi:10.1016/S0899-5362(02)00037-4)

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Publisher's URL: http://dx.doi.org/10.1016/S0899-5362(02)00037-4

Abstract

The petrogenesis of igneous, metamorphic and mineralized rocks in the Edough massif, NE Algeria, indicates an interplay between crustal and magmatic sources, and magmatic and surface fluids, as determined by sulphur and oxygen isotopic analyses. The Tertiary igneous rocks (microgranites and rhyolites) show a tendency towards I-type granitoids with delta(34)S values of +5.4 +/- 2.2parts per thousand (1sigma) and delta(18)O between +5.6parts per thousand and +6.9parts per thousand, with the most hydrothermally altered rocks having the lowest delta(18)O values. This is indicative of seawater being a major component of the hydrothermal fluids. Seawater interaction with the granitoids produced enrichment in S-34 of sulphide-sulphur in both the microgranites and associated skarn mineralization. However, in the Beleleita WSn-(Au) deposit, magmatic fluids dominated the mineralization, reflected by delta(34)S values of +1.7parts per thousand and + 1.8parts per thousand. The basement amphibolites of Kef Lakhal indicate derivation from a basaltic magma with delta(18)O ranging from +4.9parts per thousand to +8.6parts per thousand. Locally altered amphibolite has the lowest delta(18)O values suggestive of meteoric water interaction, whereas the highest delta(18)O indicate the incorporation of crustal material during the genesis of the amphibolites. Crustal contamination is also reflected in their delta(34)S of -18parts per thousand to +2.1parts per thousand, with the most contaminated rocks having the lowest delta(34)S. Host Palaeozoic mica schists with delta(18)O of +12.7parts per thousand, and delta(34)S of -13.2parts per thousand and associated marbles (delta(34)S -9.9parts per thousand to - 17.4parts per thousand) are thought to be the most likely contaminants. At the Ain Barbar Fe-Cu-Pb-Zn deposit, delta(34)S values range between -9.6parts per thousand and -10.8parts per thousand, indicating that the sulphide-sulphur and base-metals were likely leached from the host Cretaceous flysch and/or the underlying mica schists, with local Tertiary magmatic rocks providing the heat for local convection cells. At Boumaiza Fe- deposit, delta(34)S values of the sulphide-sulphur extend from -1.2parts per thousand to -8.1parts per thousand indicative of magmatic sulphur with the incorporation of substantial amounts of sulphur derived from the host mica schists.

Item Type:Articles
Status:Published
Refereed:Yes
Glasgow Author(s) Enlighten ID:Fallick, Professor Anthony and Boyce, Professor Adrian
Authors: Laouar, R., Boyce, A.J., Ahmed-Said, Y., Ouabadi, A., Fallick, A.E., and Toubal, A.
Subjects:Q Science > QE Geology
College/School:College of Science and Engineering > Scottish Universities Environmental Research Centre
Journal Name:Journal of African Earth Sciences
ISSN:0899-5362

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