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A fluid inclusion and stable isotope study of the world class imiter silver deposit (Morocco)

Abstract : The Imiter silver mine is a world-class deposit located in the Eastern part of the Anti-Atlas (Morocco). The deposit is hosted by Cryogenian black shales and Ediacaran volcanics, and unconformablyoverlain by Paleozoic sedimentary rocks. The paragenetic sequence for the gangue mineral is composedby amacroscopically white quartz (Qz1) associated with the deposition of galena and scarce silver mineralsas matrix of hydraulic breccias, followed by a grey quartz (Qz2) associated with the main silver deposition event and a first generation of scarcedolomite (Dol1). A third episode is characterized by massive pink dolomite precipitation (Dol2) with minor quartz (Qz3) and base metals. Finally, a surficial event affects the mineralisation and is responsible for a secondary ore enrichment. Microthermometry study coupled with Raman analyses reveals that fluid inclusions are CaCl2-dominated. The general trend is a decrease of temperature from Qz1 (250°C) to Dol1 (80°C) then Dol 2 (probably below 70°C) depositions. Fluid salinity increases from Qz1 (6.3 to 19.0 wt % NaCleq) to Dol1 (27.2 % wt NaCleq), and decreases with the precipitation of Dol2 associated with quartz 3 (15 %wt NaCleq). The 18O isotopic composition of fluids in equilibrium with quartz and dolomitesuggestsamagmatic, metamorphic and/or basinal origin for the fluid at the origin of Qz1, and that meteoric / surficial basinal brinesmay be at the origin of Dol2. The proposed model to explain the ore forming processes in Imiter is a mixing of Ca-brines, probably providing chloride complexes, with a hot NaCl fluid of lower salinity, leading to the precipitation of silver.The results favour the important role of calcic brines, whose origin remains matter to debate in such a giant depositand for whom age of emplacement is strongly discussed.
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Conference papers
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https://hal-insu.archives-ouvertes.fr/insu-01080858
Contributor : Isabelle Dubigeon <>
Submitted on : Thursday, November 6, 2014 - 1:53:57 PM
Last modification on : Friday, June 12, 2020 - 3:22:08 PM

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  • HAL Id : insu-01080858, version 1

Citation

Claudie Hulin, Michel Dubois, Johann Tuduri, Alain Chauvet, Philippe Boulvais, et al.. A fluid inclusion and stable isotope study of the world class imiter silver deposit (Morocco). 24 ème Réunion des sciences de la Terre 2014, Oct 2014, Pau, France. pp.373. ⟨insu-01080858⟩

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