Stibnite - La Lucette mine

Research program - Oct. 2019 - Mar. 2023


AUREOLE aims to produce 3D predictive modelling of ore deposits locations and their subsequent environmental impacts. To reach this goal, the methodology developed in the project is based on the interdisciplinary of its consortium.
Indeed, a first crucial step is the application of up-to-date approaches to constrain geological and metallogenic features related to ore deposits, including occurrences evidenced by spatial statistical analyses and 3D modelling of geological infrastructures. For this purpose, a focus on the geological controls on Sb-W-Hg mineralizing systems and their location  understanding will be led by: structural geology study, from microscale to regional scale, mineral chemistry (with a strong input from trace-elements analyses by LA-ICP-MS), fluid characterisation, stable isotopes analyses (H, O, C), geochronological analyses using modern methods such as U-Pb on apatite, calcite, rutile; Ar-Ar on phengite-illite; and when possible Re-Os on sulphides.
In order to identify the potential Sb and associated metals source’s , powerful tools (i.e. LA-ICP-MS, EPMA, SIMS) will be use to evaluate metal carriers in the different studied rocks and quantify elemental redistribution from metals-bearing source rocks to ore deposit. Depending on metal carriers assessment, innovative experiments (i) of hydrothermal leaching of metals-bearing source rocks (magmatic and/ or metasedimentary) and at (ii) magmatic conditions will be performed, in order to appraise the metals partitioning (i.e. Sb, W, Hg, As) between fluids, silicate melts and crystals.

A specific task will quantify the mineral occurences spatial distribution with respect to mafic intrusion through numerical fluid flow modelling using Comsol Multiphysics software,based on 3D geological models built with GeoModeller software. 3D models on selected key areas will be constrained by geological and structural datasets, gravimetric forward and/or reverse modelling.

In order to predict environmental signatures of Sb-W-Hg deposits, AUREOLE will analyse the processes contributing and conditioning the mobilisation and transport of metals from ore deposits and enriched geological formations. It will assess the physical processes and related parameters, namely: (i) the geomorphology, which have a strong impact on the change from stable to unstable conditions, and (ii) the supergene weathering, which promote the sequestration or the release of metals in natural waters. Study of the organic processes driving the cycle and mobility of metals will evaluate effects of plants, land uses and organic matter, as well as the risks related with the transfer of metals to biota. A specific task will focus on effects of bacterial processes involved in the solubilisation of metal(oid)s from rocks, their transfer in soils compatments, and the bacterial biodiversity associated to these processes.

All the collected knowledge will be showcased by mineral resources prospectivity and associated environmental risk assessment. Spatial statistical analyses will allow evidencing and quantifying the deposits spatial distribution characteristics (e.g. random, cluster) and their spatial links along with lithologies and structures. As far as possible, neighbourhood computations will be performed in 3D based on the 3D geological/geophysical models built in the project. AUREOLE will carry out mineral prospectivity approaches using most of available and innovative techniques including that developed at BRGM (i.e. Cell-based Association). Original approach corresponding to weighting prospectivity maps by spatial datasets (DTM, weathering, rainfall, land-use, etc), which represent surface processes that control metalloids mobilisation and transport, will produce environmental risk assessment large-scale map. The computational clusters, the techniques and the algorithms of spatial data crossing of ANTEA group will be used to compute these maps on a large scale.