John McBride HBSc thesis abstract

Thesis Title: 
Investigation of the Magnetite Olivine Coarse Grained Gabbro Units of the Eastern Gabbro, Marathon, Ontario

The investigation of the Magnetite-Olivine Gabbro unit within the Eastern Gabbro of the Coldwell Alkaline Complex was carried out in order to determine whether the Magnetite-Olivine Gabbro unit was petrogenetically related to the EG.  Petrographic analysis of the mineral phases and textures of the newly defined magnetite-olivine coarse grained gabbro was undertaken to determine if it is a subunit of the Easter Gabbro or petrogenetically a separate unit similar to other gabbro units in the area, such as the Geordie Lake Intrusion or the Two Duck Lake Intrusion.  Petrographicly the Magnetite-Olivine Gabrro is a distinct unit showing an increases grain size, magnetite banding, plagioclase alignment and mineral components which are not seen in the Eastern Gabbro such as biotite, apatite and chalcopyrite.  Using SEM-EDX, both the Eastern Gabbro and the Magenetite-Oliving Gabbro were analyzed revealing that all major components were compositionally similar suggesting the same parent magma.  Relative to the other gabbroic intrusions into the Eastern Gabbro the Magnetite-Olivine Gabbro shows little to no correlation to that of the Geordie Lake Intrusion however, it is similar in some respects to that of the Two Duck Lake Intrusion, but is more evolved.  In reference to mineralization in the Magnetite-Olivine Gabbro there was no visible PGM, however, there was an increase in chalcopyrite.