Mineralization and fluid inclusion studies of the Aptian carbonate-hosted PbZnBa ore deposits at Jebel Hamra, Central Tunisia

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• 作者：Jaloul Bejaoui^a ; ^b ; ^{bjaoui_geo@yahoo.fr} ; Salah Bouhlel^b ; Esteve Cardellach^c ; À ; ngels Canals^d ; Joaquim Perona^c ; À ; ngels Piqué ; ^d
• 关键词：Jebel Hamra ; Upper Aptian ; Fluid inclusion ; Thermochemical ; Basinal brines ; Tunisia
• 刊名：Journal of Geochemical Exploration
• 出版年：2013
• 出版时间：May, 2013
• 年：2013
• 卷：128
• 期：Complete
• 页码：136-146
• 全文大小：3558 K

文摘

The Jebel Hamra, which is hosted in the Graben Zone of central Tunisia, is an epigenetic dolomite-hosted PbZnBa deposit that replaces platform carbonates of Lower Cretaceous age (Upper Aptian). Mineralization occurs as stratiform lenses, and breccia- and paleokarst-fillings. Ore reserves are around 0.5 Mt and grades are 7 % Zn and 3 % Pb. Sulphide mineralization occurs as local replacement of dolomitized and silicified carbonate strata. Primary inclusion fluids in sphalerite have homogenization temperatures ranging from 110 to 152 ¡ãC with a mode at 137 ¡ãC. Final ice-melting temperatures range from ? 15 to ? 10 ¡ãC, corresponding to salinities of 13.5-18.5 wt. % NaCl equiv. Fluid inclusions in saddle dolomite homogenize to the liquid phase between 175¡ãC and 193 ¡ãC, with a mode at 187 ¡ãC. Final ice-melting temperatures range from ? 23 to ? 15 ¡ãC corresponding to salinities between 18 and 24 wt. % NaCl equiv. ¦Ä³⁴S values of sphalerite and galena vary between ? 3 and + 6.3¡ë, compatible with a thermochemical reduction of sulfate from Triassic evaporites (¦Ä³⁴S = + 15¡ë). PbZnBa mineralization is spatially and possibly genetically related to E-W-trending fractures, which acted as conduits and/or depositional sites for circulating hydrothermal fluids. Fluid inclusion and sulfur isotope data suggest the contribution of basinal brines in ore formation. Combined field, sedimentological, mineralogical, isotopic and geochemical data of the Lower Cretaceous mineralization in Jebel Hamra is compatible with Mississippi-Valley-type mineralization.