Mafic rocks vs. Sbmineralisation: a role in the early metal distribution processes? Insights from the Variscan Armorican belt (France)
Abstract
The Armorican belt is part of the western
European Variscan belt. Although the region was one
of the world leader producers of antimony at the
beginning of the 20th century, the geological controls
behind these deposits remain badly constrained. Here
we present a spatial statistical analysis of the Sbmineralisation,
together with geophysical and
geological data [1]. Results show that the Sbmineralisation
is spatially associated with strong
positive gravity and magnetic anomalies which must
be linked to the presence of mafic/ultramafic bodies
at depth. This spatial link is further supported by the
numerous outcropping occurrences of dolerite dykes
and sills close to the Sb-deposits and sometimes
hosting the mineralisation. This mafic magmatism,
dated by in-situ U-Pb analyses on apatite at ca. 360
Ma, appears as a regional-scale event at the
Devonian-Carboniferous boundary. In addition, new
data suggests that mafic magmatism may have
probably played a role in the early distribution or
redistribution processes of metal stock in the
subsequent history of the antimony in the Variscan
Armorican belt.
[1] Pochon et al. (2016). Terra Nova, doi:
10.1111/ter.12201