Geologic history of the Saguenay region, Quebec (Central Granulite Terrain of the Grenville Province): a working hypothesis
The Saguenay region is divided into three lithostructural units, namely (1) a gneiss complex; (2) batholithic anorthosite and mangerite complexes; and (3) late- to post-kinematic plutons. Three age groups of rocks in the gneiss complex are defined by increasing complexity of structure and mobilizates. Rocks of age group I (paragneiss, granite I) show extremely complex structure and contain three generations of mobilizates. Structures in rocks of age group II (granite II, amphibolite II dykes) are less complex and two generations of mobilizates are present. Rocks of age group III (granite III, amphibolite III dykes) contain one foliation and one generation of mobilizates. Metamorphosed mafic dykes are stratigraphic markers permitting correlation of age groups over vast tracts of terrain.Well-preserved igneous structures (cumulate layering) and textures (cumulate textures, ophitic textures) prove that anorthosite and mangerite crystallized from magmas. Anorthosite has been granulated and foliated, metamorph...