Keith David Peden HBSc thesis abstract

In this study, a traverse is taken across the boundary between the Quetico gneiss belt and the Shebandowan - Wawa volcano-plutonic belt as established by previous workers.  The detailed mapping was carried out at Shabaqua, Ontario, approximately 55 kilometers west of the City of Thunder Bay.

Three different rock types are recognized at the outcrop scale.  They are:  1/  conglomerates,  2/  metapelites and interbedded arenites, and 3/  biotite schists.

Towards the south end of the map area is a polymict conglomerate with clasts up to 25 centimeters in length.  The matrix is a coarse lithic greywacke.

A metasediemntary sequence of metapelites with minor interbedded arenites occupies the central portion of the map area.  The metapelites are fine grained, dark grey foliated rocks.  The arenite are light coloured and display relict sedimentary textures.

The biotite schists, in the northern end of the map area, are foliated, porphyroblastic rocks.  Sedimentary textures are not observed.

Microscopically, seven mineral assemblages are identified, defining three metamorphic facies.  In the conglomerate and part of the metapelites, lower greenschist facies is represented by the assemblage; quartz-plagioclase-chlorite.  The upper greenschistfacies is outlined within the metapelites by the diagnostic mineral assemblages of; quartz-plagioclase-biotite and quartz-plagioclase-biotite-garnet.  Four assemblages define the lower amphibolite facies in the metapelites and biotite schists.  They are:  quartz-biotite-cordierite, quartz-biotite-cordierite-garnet, quartz-biotite-muscovite-garnet, and quartz-biotite-muscovite-staurolite.

Based on textural and mineralogical work, the metamorphism across the boundary appears to be gradational and continuous.  The boundary is not a discrete line but rather, a transition zone.