Project and job offers

PhD project in co-tutorship at U. Avignon/UQAM: Modeling of processes leading to isotopic record of behavior of continental hydrosystems by limestone concretions.

This thesis aims to establish the control factors and mechanisms at the origin of the recording of isotopic signatures during the precipitation of calcareous concretions at the level of the sources. From targeted laboratory experiments, a numerical modeling of the coupled behavior of the chemistry of major elements (Ca, Mg) and isotopologues (13C-12C, 18O-16O) will be proposed (a modeling of the behavior of trace elements (Sr, Ba, Ra) and stable isotopes of strontium may also be considered if the opportunity arises). It aims to transcribe the variations of chemical and isotopic compositions of calcareous concretions into variations of hydrological factors (flow of sources and recharge rate). This modeling approach will be extended to data from travertine deposits (Turkey, Spain, France, Poland) to reconstruct the response of sources to recent climate changes and groundwater abstraction. (13C-12C, 18O-16O) sera proposée (une modélisation du comportement des éléments traces (Sr, Ba, Ra) et des isotopes stables du strontium pourra également être envisagée si l’opportunité se présente). Elle vise à transcrire les variations de compositions chimiques et isotopiques des concrétions calcaires en des variations de facteurs hydrologiques (débit des sources et taux de recharge). Cette approche de modélisation sera étendue à des données issues de dépôts de travertins (Turquie, Espagne, France, Pologne) pour reconstituer la réponse des sources aux changements récents du climat et aux prélèvements d’eau souterraine.

Ph.D. project: Stable strontium (88 / 86Sr) isotope systematics in quartz-carbonate veins from orogenic gold deposits in the Val d´Or region, Quebec

Carbonate precipitation and decarbonation reactions are frequently associated with hydrothermal fluids and gold mineralization. The Val-D'Or vein field (Louvicourt to Malartic) in the Abitibi subprovince is a typical example of this association. The vein field and associated orogenic gold deposits in this zone are characterized by the association of gold with sulphide-quartz-carbonate veins (+/- tourmaline and other accessory minerals). The stable isotopes (C, O, H) and the radiogenic isotopes of strontium (87/86Sr) of the different phases in the veins (quartz, carbonate, tourmaline) indicate that gold was deposited due to mixing between hydrothermal (metamorphic) fluids and shallow crustal waters. The metamorphic fluids are the product of the dehydration and decarbonation reactions of the Archean crust. We propose an innovative use of the stable isotopes of strontium (88/86Sr) to constrain the role of carbonation and decarbonation reactions associated with the formation of veins and gold precipitation. The main objective of this study is to build better exploration models and to better understand the origin of gold in orogenic gold deposits.