Constellation, le dépôt institutionnel de l'Université du Québec à Chicoutimi

Résumé

The Metal Earth (ME) project aims to understand the underlying geological mechanisms differentiating well endowed and less endowed mineralized zones in Precambrian greenstone belts of the Canadian Shield. ME acquires and collates various geological observations and geophysical data along 13 selected transects within the Superior Craton. The ME objective is to create valid 2D and 3D models of subsurface features, so as to identify components that contribute to mineralization processes. Thus far, the project has acquired gravity readings along 10 transects. The Bouguer reduced data were combined with the existing gravity data provided by the Geological Survey of Canada throughout the areas of interest. In this paper, data along the Chibougamau transect (~†128 line kilometers oriented SW-NE) located in the northeastern part of the Abitibi sub-province is considered. The Chibougamau area is one of the well-endowed transects where the geology consists of volcanic and sedimentary rocks, with tonalitic gneissic cores. Gravity and compiled high-resolution magnetic data along this transect were modelled using an initial petrophysical model constrained by geological observations made at the surface, seismic sections at depth and measured petrophysical properties. Potential field data modelling requires adjusting the shape, densities and magnetic susceptibilities of features at depth and can resolve the geometry of some features which are transparent in seismic sections. For example, the model provides an improvement in estimating the size, shape, and depth of plutonic bodies such as the Barlow and Chibougamau plutons across the Lac DorÈ Complex. The new modified model is consistent with the known structural geology (the synclinorium and anticlinorium of volcanic and sedimentary rocks). The model also helps us to improve the seismic interpretation and identify dykes and faults. The improved understanding of these subsurface features will potentially help to identify components contributing to mineralising processes in the Chibougamau area.