A geological and geophysical synthesis of the Chapais region: eastern part of the Quebec Abitibi Belt

The Chapais region has been extensively studied during the last 40 years. Recent work in this area has provided information that can be used to assess the various models proposed for similar volcano-sedimentary belts. By using the known surface geology and measured rock densities, gravity interpretation can define the structure of the geological formations. Aeromagnetic data have been used to improve surface mapping in areas of few or no outcrop. It is concluded that the Chibougamau syncline has a depth extension of about 4 km. The depth extension of the granitic intrusives cannot be accurately determined because of lack of knowledge of their density variation with depth. Any geological model must satisfy potential field data constraints, especially those given by gravity data. In the present case, it is shown that only those models indicating a limited thickness of volcano-sedimentary rocks are acceptable. -English summary