Geology of the Mount Brenner stock near Dawson City, Yukon Territory

The Mount Brenner stock has intruded folded sedimentary and meta sedimentary rock that lie 40 miles northeast of Dawson City, Yukon Territory. The stock consists of four major concentric zones: (l) an outer zone of fine to medium-grained augite-biotite monzonite; (2) a zone of very coarse-grained monzonite porphyry; (3) an intermediate zone of porphyritic horn blende monzonite; and (4) a central zone of coarse-grained pink quartz monzonite porphyry. Except for the outer zone, all rock types are porphyritic and the alignment of feldspar phenocrysts gives the rocks a primary flow structure which conforms to steeply outward dipping gradational internal contacts. All external contacts are sharp. The regional structural trend is modified in the vicinity of the stock so that beds are generally conformable with the intrusive contact. From structural evidence, it is concluded that at the present level of erosion, the stock was emplaced by forceful injection. The different rock zones of the stock can be accounted for by differentiation of an augite-biotite monzonite magma by a combination of crystal fractionation , volatile and alkali diffusion, and multiple intrusion.Science, Faculty ofEarth, Ocean and Atmospheric Sciences, Department ofGraduat