Alteration zones in the Flin Flon area, Manitoba

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Mare, Marius P. H.
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Five zones of alteration were studied in the Flin Flon area; the Mill-Rock Hill area, the Lakeview prospect, the Trout Portage zone, the Schist Lake-Mandy mine area, and the Cliff Lake fault zone. The alteration zones are small (<1 sq. km), patchy, and did not extend for long distances. The hydrothermal activity formed at least three types of alteration; silicification, sericitization and chloritization. The alteration products (quartz, chlorite, sericite and epidote) were foliated during metamorphism, and are therefore premetamorphic. Electron microprobe analysis of chlorites from altered zones indicate that hydrothermal alteration resulted in Mg-rich (Fe/Fe+Mg < 0.55) chlorite. Areas affected by metamorphic degassing/dewatering and dynamic metamorphism were more Fe-rich (Fe/Fe+Mg > 0.55) as a result of remobilization of iron. Mg-rich chlorites are interpreted to have formed as the result of interaction of Mg-bearing fluids with the host rock. Silicification is identified as the initial episode of hydrothermal alteration at the Trout Portage and Schist Lake-Mandy zones and is associated with the development of silica network veining. The second alteration phase was the development of sericite which resulted in an increase of K, Rb and Ba and a decrease of Ca and Sr. Sericitization was followed by chloritization which resulted in an enrichment of Mg > Fe, Zn, and H20 and depletion of K, Ba and Rb relative to less altered rocks.