Sb-Deposits in the Variscan Armorican Belt (France) - Potential Relationships with Basic Intrusions and High-Density Magnetic Lithologies at Depth

Abstract : Sb-deposits in the Variscan Armorican belt constitute a large part of this resource in France notably with the La Lucette deposit (42000 tons of Sb). Although these mineralizations are known since the 19th century, relationships between geological features and antimony deposits remain unclear. Here we perform a spatial statistical analysis using Geographic Information System software (GIS), geophysical and geological data (Ripley's function, spatial distribution analysis of geophysical values, and distance to the nearest neighbour) in order to identify particular geophysical zones where Sb-deposits are potentially clustering and to assess affinity with different geological objects. We show that there are specific ranges of gravity and magnetic values associated to Sb-deposits. These characteristic ranges outline several zones of high density and relatively high magnetic susceptibility that cover only 17.6 % of the surface of the Armorican Massif and contain or are close to more than 50 % of Sb-deposits. Moreover, Sb-deposits far from these zones are related with major faults. Our results reveal spatial relationships between Sb-deposits, major faults and high-density and magnetic zones that are interpreted as reflecting the occurrence of basic rocks at depth. The use of such a statistical approach enables to highlight geological controls of the mineralization