Arsenic (As) is a highly toxic element for human beings. Groundwater consumption represents one of the main routes of As human intake and the leading cause of poisoning worldwide. High concentrations of As in groundwater are mostly the result of mobilization under natural conditions related to water-rock interactions. In the Abitibi-Témiscamingue region (Province of Québec, Canada), As concentrations have been measured above the government and the World Health Organization guideline value of 10 µg/l. Private wells used for drinking water are often the first affected. These As concentrations seem to be associated with As-bearing sulfides and sulfosalts occurring in the fractured Archean bedrock from the Canadian Shield. However, no detailed studies have confirmed this hypothesis and highlighted the mechanisms for As mobilization in these areas. Geochemical processes controlling As release and mobility in groundwater are governed by complex chemical mechanisms, especially in fractured aquifers. This Ph.D. research work first aims to identify the geological origin of As (i.e. occurrences, abundance and reactivity of most frequent As-bearing minerals) and to characterize the mechanisms controlling its mobility (i.e. oxidation/reduction, sorption/desorption). Hydrochemical and mineral analyses, on both water and rock samples, as well as leaching tests will be carried out in order to answer these issues. This work is part of a general approach to increase knowledge regarding arsenic mobilization in fractured aquifers which still remains an under-studied and poorly understood topic.