Fieldwork developed within the framework of multi- and interdisciplinary research activities (in the fields of mineral deposits and archaeology) recently led to the discovery of mineralisations and mining workings so far unreported, within a calcschist sequence cropping out in the lower part of the Servìn and Masòc valleys. Both field and lab data, although preliminary, indicate that they represent two different types of mineralisation; moreover, both of them show significant differences compared with those cropping out at higher elevation in the same valleys. The mineralisation of the Servìn valley is made of thin layers extremely rich in sulfides of iron, copper and zinc (pyrite, chalcopyrite and sphalerite with minor bornite and pyrrhotite) parallel to the foliation of the host calcschists. It represents a concentration of Fe-Cu-Zn massive sulfides related to exhalative-sedimentary processes at bottom of the Jurassic ocean. The mineralisation crops out in two small excavations, probably made for copper exploitation and/or prospecting. The age of these workings is unknown; at least part of them should post-date the XVII century. In the lower Masòc valley a several tens of metres long mining gallery was found along a fault plane, driven for exploiting a mineralisation related to the circulation of hydrothermal fluids. The filling material, almost completely removed, consisted of iron-rich carbonate (likely ankerite rather than siderite), now strongly weathered to limonitic products. The available data, and especially the strong similarities with the descriptions from historical sources, suggest that the gallery is part of the underground workings of the «Masòc mine», exploited for silver between the sixteenth and the eighteenth century and never been identified in the field before. Recherches de terrain dans le cadre d’études multi- et interdisciplinaires (dans le domaine de la géologie et de l’archéologie) conduit à la découverte, dans les schistes lustrés de la partie inférieure des vallées du Servìn et du Masòc, de minéralisations et excavations minières pas signalées auparavant. Les données de terrain et de laboratoire, bien que préliminaires, montrent qu’il s’agit de deux types différents de minéralisation, trahissant des différences significatives même par rapport à celles connues à plus haute altitude dans les mêmes vallées. La minéralisation de la vallée du Servìn est constituée de couches minces très riches en sulfures de fer, de cuivre et de zinc (pyrite, chalcopyrite et sphalérite avec subordonnées bornite et pyrrhotite) parallèlement à la schistosité des schistes lustrés. Cela représente une concentration de sulfures massifs de fer-cuivre-zinc liée aux processus exhalatifs sur le fond de l’océan jurassique. La minéralisation se trouve dans deux excavations de faible longueur, probablement faites pour l’exploitation et/ou la recherche de concentrations de cuivre. L’âge de ces excavations est inconnu, mais au moins en partie postérieur au XVIIe siècle).

Nuovi ritrovamenti di mineralizzazioni e di lavori minerari nei valloni di Servìn e del Masòc (Usseglio, valli di Lanzo): primi dati geologico-petrografici e microanalitici

ROSSETTI, Piergiorgio;CASTELLI, Daniele Carlo Cesare;
2013-01-01

Abstract

Fieldwork developed within the framework of multi- and interdisciplinary research activities (in the fields of mineral deposits and archaeology) recently led to the discovery of mineralisations and mining workings so far unreported, within a calcschist sequence cropping out in the lower part of the Servìn and Masòc valleys. Both field and lab data, although preliminary, indicate that they represent two different types of mineralisation; moreover, both of them show significant differences compared with those cropping out at higher elevation in the same valleys. The mineralisation of the Servìn valley is made of thin layers extremely rich in sulfides of iron, copper and zinc (pyrite, chalcopyrite and sphalerite with minor bornite and pyrrhotite) parallel to the foliation of the host calcschists. It represents a concentration of Fe-Cu-Zn massive sulfides related to exhalative-sedimentary processes at bottom of the Jurassic ocean. The mineralisation crops out in two small excavations, probably made for copper exploitation and/or prospecting. The age of these workings is unknown; at least part of them should post-date the XVII century. In the lower Masòc valley a several tens of metres long mining gallery was found along a fault plane, driven for exploiting a mineralisation related to the circulation of hydrothermal fluids. The filling material, almost completely removed, consisted of iron-rich carbonate (likely ankerite rather than siderite), now strongly weathered to limonitic products. The available data, and especially the strong similarities with the descriptions from historical sources, suggest that the gallery is part of the underground workings of the «Masòc mine», exploited for silver between the sixteenth and the eighteenth century and never been identified in the field before. Recherches de terrain dans le cadre d’études multi- et interdisciplinaires (dans le domaine de la géologie et de l’archéologie) conduit à la découverte, dans les schistes lustrés de la partie inférieure des vallées du Servìn et du Masòc, de minéralisations et excavations minières pas signalées auparavant. Les données de terrain et de laboratoire, bien que préliminaires, montrent qu’il s’agit de deux types différents de minéralisation, trahissant des différences significatives même par rapport à celles connues à plus haute altitude dans les mêmes vallées. La minéralisation de la vallée du Servìn est constituée de couches minces très riches en sulfures de fer, de cuivre et de zinc (pyrite, chalcopyrite et sphalérite avec subordonnées bornite et pyrrhotite) parallèlement à la schistosité des schistes lustrés. Cela représente une concentration de sulfures massifs de fer-cuivre-zinc liée aux processus exhalatifs sur le fond de l’océan jurassique. La minéralisation se trouve dans deux excavations de faible longueur, probablement faites pour l’exploitation et/ou la recherche de concentrations de cuivre. L’âge de ces excavations est inconnu, mais au moins en partie postérieur au XVIIe siècle).
2013
Terre rosse, pietre verdi e blu cobalto Miniere a Usseglio. Seconda raccolta di studi
Museo Civico Alpino «Arnaldo Tazzetti»
215
228
9788890507649
Rossetti P.; Castelli D.; Gattiglia A.; Rossi M.
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Utilizza questo identificativo per citare o creare un link a questo documento: https://hdl.handle.net/2318/142395
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