Doug Nikkila HBSc Thesis Abstract

Thesis Title: 
The mineralogy and petrology of a newly-discovered REE occurrence within the Coldwell Complex near Marathon, Ontario

The Coldwell Complex is situated within the Archean Schreiber-White River metavolcanic-metasediment of the Superior Province, and spanning over 25 km in diameter, is the largest alkaline intrusion in North America. There are three magmatic centers of the Coldwell Complex, which in order of intrusion are Center I, Center II and Center III. The focus of this study was to classify syenite rocks related to the three intrusive centers, and identify any REE-bearing minerals present. Fieldwork was completed along HW-17 roadcuts, and North of the highway on Canada Rare Earth claim blocks, termed the ‘Radio Hill’ occurrence. The syenites of the Radio Hill occurrence had not previously been identified due to limited access to the area. Through petrography, Highway-17 samples were classified as Center II Nepheline syenites, where the textures of amphibole, biotite, pyroxene and natrolite compared well to the nepheline syenites previously described by Mitchell and Platt (1982). Syenites of the Radio Hill occurrence were classified as Center III, specifically, ferroedenite syenites. The Radio Hill syenites show an increase in the modal abundance of quartz, and a decrease in natrolite. Compositions of the amphiboles from the Radio Hill syenites compare well with the silicic ferroedenite and hastingsitic hornblende compositions, with sample DN7b showing a trend to Na, Si, and Fe enrichment with Ca and Al depletion. Radio Hill mica have molecular end-member compositions of biotite, with Mg # ranging from 0.082 to 0.294. Radio Hill plagioclase feldspar compositions show An % from 0 to 12.04 %, representing albite to oligioclase end-members. Rare earth element minerals were described and identified from the Radio Hill occurrence using qualitative identification methods with the scanning electron microscope (SEM) at Lakehead University. Minerals found occurring in the Radio Hill syenites, in order of abundance, include Apatite (elevated La, Ce, Nd, and Th), Plumbopyrochlore ((Pb, Y, U, Ca)2-xNb2O6(OH)), Ceriopyrochlore ((Ce, Ca, Y)2(Nb, Ta)2O6(OH, F)), Monazite ((La, Ce, Nd)PO4), and Fluorite.