TECTONO METAMORPHIC STUDY ALONG THE MANICOUAGAN-FERMONT TRANSECT: A JOURNEY IN THE CENTRAL GRENVILLE PROVINCE AND THE CORE OF A LONG HOT OROGEN

The tectonic evolution of the Grenvillian Orogeny is hotly debated. Two main tectono-metamorphic events define this long, hot orogen : the Ottawan and the later Rigolet registered in the Allochtonous (AB) and Parautochtonous (PB) belts, respectively. The study area, in the northeastern part of the central Grenville Province, was targeted for its strategic location straddling both belts in addition to the Allochtonous Boundary Thrust (ABT) and the orogenic lid (OL), which seemingly escaped the effect of the orogeny. In the Fermont area, located in the PB foreland, an orogenic-wedge tectonic model was proposed, whereas farther south in the Manicouagan Reservoir area a channel flow model was proposed for the uppermost part of the belt. Structurally above, within the AB, ductile extrusion of a high-grade metamorphic nappe was suggested for the exhumation of eclogite facies rocks. These contrasting orogenic processes are locally well documented, but tectono-metamorphic data is unavailable to link them in a coherent 3D evolutionary model.

This study aims at gathering and compiling metamorphic and temporal data points along a transect from south of the Manicouagan Reservoir, up to Fermont and the Grenville Front. This transect will cross all major tectonic levels, from the structurally lower PB, the ABT, the Allochtonous high-pressure and medium-pressure belts up to the OL. An innovative quantitative metamorphic and petrochronological study will then be conducted on samples collected from the different levels and bounding shear zones. We aim to couple the recently developed Quartz-in-Garnet geobarometer with Zr-in-rutile thermometry to build a Pressure-Temperature data set. To support these analyses, we will identify ideal garnets with 3D microtomography, execute thin section chemical mapping and study chemical zoning in garnet and generate isochemical phase diagram sections for the chosen samples. Complemented by the petrochronological study, the data set will then be used to elaborate an integral and exhaustive tectonic model for the central Grenville Province, supported by P-T-t-D paths for the different tectonic levels exposed along the Manicouagan-Fermont transect. Here, we present data compilation and preliminary results of new metamorphic data for the Manicouagan-Fermont transect.