magnetic fabrics and boundary structure at the quetico - shebandowan subprovince boundary, near kashabowie, nw ontario
abstract
the quetico metasedimentary subprovince and the volcanic-plutonic
shebandowan belt to the south meet along an east-west
steeply dipping boundary that is believed to have been affected
by dextral transpressional deformation. it is also parallel to a
steep metamorphic gradient from greenschist facies rocks to the
north.
macroscopic petrofabrlcs are difficult to observe along
the belt to the west of thunder bay but magnetic susceptibility
fabrics (low-field) are quite consistent. these define a gently
plunging extenslonal fabric parallel to the belt boundary.
within the kashabowle area, general field observations of
subhorizontal stretching (and intersection) lineations, and
cleavage directions are in agreement with magnetic susceptibility
axis directions. mineral separation reveals that all samples
have multiple sources of magnetic susceptibility, dominated by
metamorphic phyllosilicates. consequently it is not possible to
simply quantitatively relate the magnetic fabrics to strain
magnitudes although the magnetic fabrics accurately monitor
significant kinematic directions. analyses of strain of
low-grade detrital quartz grains, magnetic fabrics and general
field observations recognize flattened oblate fabrics. moreover
oblique, subhorizontal lineations favour a transpresslve
kinematic model with compression normal to the belt boundary.
the obliquity between mineral and magnetic lineations seem to
indicate dextral transpresslve deformation.
collections
- retrospective theses [1604]