The Barrencs Gallic Mining Network (Aude, France) in its Geological and Mineralogical Context

The ancient mining works of Barrencs, situated in the Orbiel valley on a plateau between the Lastours and Fournes-Cabardes villages (Aude, France), were discovered at the end of the 19(th) c. For more than a century these were thought to be Roman in origin. Between 2009 and 2012, the mining works have been studied as part of a research program carried out by a mining archaeological specialised team of TRACES laboratory of Toulouse 2 Jean-Jaures University. The study identified a vast mining complex that exploited vertical to sub-vertical vein structures, showing perfect organisation and a high technical level of the miners. It also permitted to push back in time the mining activity, to the Iron Age. The geological study, carried out in close relation with the archaeological investigations, shows an excellent mining proficiency, based on a good geologic empirical knowledge that guided the ancient miners, both for ore deposit survey and for its eventual extraction. The mineralogical and elemental analyses conducted via a systematic sampling through out the entire studied mine area, showed that the area under study is rich in copper, silver, and lead epithermal mineralisations. The composition of mineralogical ore deposits is dominated by pyrite, chalcopyrite, silver-bearing gray coppers, galena and silver-bearing galena, sphalerite, and copper sulphides (often argentiferous). Complex silver-copper-lead sulphides and thiosalts are present in smaller proportions. It appears that, for the ancient miners, the mined ore was rich in copper, silver and lead. Theses first results are quite promising and further study will focus on other issues, such as the ore volumes extracted, the ore treatment methods, and the types of production or trading areas; all important for the total comprehension of this ancient mining complex.