Andrew Graba HBSc thesis abstract

The Chipman Lake carbonatite is located NW of Marathon, Ontario, within the Wabigoon Subprovince of the Superior Province.  The dikes are generally less than one meter thick and outcrop along the glaciated shores of Chipman Lake.  The spatial localization of multiple alkaline and carbonatite complexes along the Thiel Fault supports a relationship to Midcontinent rift related events.  Recent exploration in the area has revealed some new outcropping thin dikes, which had not been previously identified.  The focus of this study was to classify these new occurrences of Chipman Lake carbonatite dikes, based on their mineralogy and petrology, and compare with other previously investigated carbonatites.  Minerals identified include dolomite, calcite, ferroan dolomite, phlogopite, biotite, fluoromagnesio- arfvedsonite, apatite, albite, K-feldspar, aegirine, pyrochlore, pyrite, synchysite, cerrusite and burbankite.  The Chipman Lake dikes were determined to represent carbonatites without associated silicate rocks and are interpreted to be the late stage fluids derived from a nearby or buried carbonatitic parent.  The presence of Ca-bearing niobium pyrochlore and the REE-fluorocarbonate synchysite are strong indications of a primary carbonatite parent.  Detailed analysis of pyrochlore indicated that these pyrochlore were calcium-bearing niobium pyrochlore with enrichment in U and Ce.