Carissa Isaac MSc thesis abstract

Thesis Title: 
Stable isotope (N, O, H) geochemistry, petrology and compositions of biotite of the Musselwhite Mine, Ontario: implications for mineralisation

Musselwhite Mine is located on the south shore of Opapimiskan Lake, approximately 480 km north of Thunder Bay. Hosted in the  ~2.8Ga North Caribou Lake greenstone belt of the North Caribou Terrane, Superior Province, Musselwhite is currently classified as a shear hosted orogenic gold deposit. The deposit is hosted in an iron formation within a volcanic pile of intermediate to felsic metavolcanic rocks, metabasalts and komatiitic metabasalts and has been metamorphosed to amphibolite grade.

Twenty biotite and 30 quartz samples have been analyzed for δ15N, δ18O and δD from Musselwhite Mine as well as 12 biotite samples from the granitoid rocks surrounding the North Caribou Lake Greenstone Belt. Nitrogen isotopes in biotite from Musselwhite Mine are characterized by a δ15N range from -1.3 to 11.1 per mil. Oxygen and hydrogen isotopes of biotite samples from the mine range from +7.1 to +10.1 per mil for δ18O and -55 to -100 per mil for δD.

Oxygen isotope signatures from quartz samples from Musselwhite range from +12.4 to +17.1 per mil. Values for the silicate facies iron formation and mineralized zones are consistent with previous work by Otto (2002) and indicate fluid compositions that fall within both the magmatic and metamorphic range.

Biotite samples from granites and metasedimentary rocks adjacent to the deposit have a δ15N range of -6.9 to +6.1 per mil. Oxygen and hydrogen isotopic ranges for the granitoid plutonic rocks are +2.0 to +4.0 per mil and -59 to -80 per mil respectively; values are typical of felsic plutonic rocks.

The δ15N, δ18O and δD stable isotopic data generated for Musselwhite Mine suggest that magmatic fluids played a role in the formation of the deposit.  

Carissa is working on her PhD at the University of Western Australia in Perth

A copy of the thesis can be downloaded here