magnetic fabrics of granitic plutons and gneisses, northwestern ontario
abstract
specimens of plutonic granitic gneisses have been collected from different
locations of the superior province. the study of their koenigsberger ratio (related to
natural remanent magnetization) and the theoretical koenigsberger ratio (related to
maximum artificial remanent magnetization) shows that the theoretical koenigsberger
ratio of the specimens is less dispersed than the koenigsberger ratio. there is a power
law relation between the remanent magnetization and induced magnetization for the
koenigsberger ratio and the theoretical koenigsberger ratio and this power law relation is
due to variation of amount of ferromagnetic minerals in the specimens.
a structural study of the mckenzie granite (ne of thunder bay), the rice bay
dome and the sawhill dome (ne of fort frances) have also been performed. the
mckenzie granite magnetic fabrics cannot be used as kinematic indicators because of the
non-coaxiality of the direction of the magnetic ellipsoid axes and also because a primary
fabric has been overprinted by a secondary one. the rice bay dome fabrics are noncoaxial
but are clearly related to the regional strain and mineral lineation: they may be
related to the diapiric emplacement of the dome. sawhill dome fabrics are not related to
the diapiric emplacement of the dome but to a later event related to the southern border of
the dome adjacent to the quetico fault.
collections
- retrospective theses [1604]