Basement influence on the supracrustal and plutonic evolution and deformation of an Archean greenstone belt

Abstract

The 10-14 km thick Archean volcano-sedimentary sequence in the Chibougamau region is composed of two mafic to felsic cycles, and of two thick, predominantly epiclastic, sedimentary sequences. The supracrustal suite is isoclinally folded along east-west axes, and punctuated by syn-volcanic, syn-kinematic and post-kinematic plutons. Tonalitic basement occurs along the northern margin, in a central horst, and as large rafts in later batholiths. Events affecting the supracrustal rocks are recorded in the tectono-magnetic history of the basement gneiss superimposed on the events related to basement formation. A tentative model favors a continent margin with periodic rifting controlling the development of the supracrustal sequence. A basement fracture pattern established at the outset has influenced every stage in the deposition, intrusion, and deformation of the belt. -from Authors