Mateo Dorado-Troughton HBSc thesis abstract

The Albany deposit is an igneous-hosted, fluid-derived, graphite deposit hosted within two intrusive vertical pipe structures, known as the East and West pipes, and is located near Hearst, Ontario.  The deposit is estimated to contain 24 million tonnes of ore with an average grade of 3.98% graphite.  The deposit is found near the southern margin of the Nagagami River Alkalic Complex (NRAC), but the precise location of the NRAC’s contact with the surrounding country rock is difficult to establish based on geophysics.  Therefore, it was previously unknown whether the deposit was hosted within the NRAC, another alkalic complex, or within the country rock of the Marmion/Eastern Wabigoon terrane.

This study focuses on characterising the rocks of the NRAC and the host rocks to the Albany deposit.  The NRAC is comprised dominantly of amphibole-pyroxene syenites, while the host rocks contain syenites, monzonites, granites, diorites, and granodiorites. Geochemical analysis shows that the host rocks to the Albany deposit are comprised of two geochemically distinct groups.  The igneous rocks that comprise the matrix of the East and West pipes that are coeval and post-date mineralization, show a particular similarity to the syenites of the Nagagami River Alkalic Complex, while the second group displays a distinct geochemistry and tectonic signature.

The distinction between these two groups suggests that the Albany graphite deposit is hosted directly on the Nagagami River Alkalic Complex’s southern margin, the pipes themselves are formed from the NRAC’s parent magma, and the host rocks represent a portion of the NRAC as well as the country rock of the Marmion/Eastern Wabigoon terrane.