Biogeochemistry for critical mineral resources exploration: examples from the Beauvoir (Li-Ta-Sn-Be) and La Bosse (W) deposits (France).

Abstract:

For a big part of the planet, the majority of economic deposits located near the surface have been targeted. Then, new exploration projects must aim to discover “hidden" deposits for which "traditional" methods of exploration like stream sediments or classic soil geochemical prospecting are unfortunately less efficient.

Biogeochemistry have been tested for a large range of deposits and commodities around the World. Within the framework of the UpDeep project (EIT Raw Materials), which aimed at developing the geochemical expertise on deep buried exploration into Europe, we performed biogeochemistry survey on the vicinity of the Beauvoir rare-metals (Li-Ta-Sn-Be) granite and La Bosse stockwerck (W) located in the Variscan French Massif Central.

One of the challenging questions of exploration geochemistry in Western Europe is the long-term anthropogenic contamination related to past mining activities but also agriculture and forestry, which can strongly affect primary geochemical anomalies. In the studied area, mining activities extended from Antiquity to the middle of the last century, and forestry is actually a well-developed activity.

We collected 84 samples of fern, 80 samples of bramble and 64 samples of Douglas fir in order to compare their geochemical signal. In this Western European context, identification of a homogenously distributed vegetation media represents a complex issue. However, the approach seems valuable to target this type of critical metals ore deposits.