Steven Therrien's HBSc Thesis Abstract

The Red Lake Mine, located approximately 560 km northwest of Thunder Bay, Ontario, contains three possible iron formation units that reside in the metamorphosed, Archean tholeiitic volcano-sedimentary Balmer assemblage within the Red Lake greenstone belt part of the Uchi Subprovince of the Superior Province.  These three units were investigated to determine if the units are indeed iron formation.  

Forty-three samples were collected in total from 16, 21 and 46 levels of the Red Lake mine's Balmer Complex.  Forty-three thin sections and whole-rock geochemical analysis were used to define the mineralogical and geochemical characteristics of all three units.  X-ray diffraction was used in conjunction with petrography to confirm mineralogy.

Samples consist of sulphide-rich and sulphide-poor bands macroscopically and microscopically.  Sulphide-rich bands consist of mainly pyrite and pyrrhotite while sulphide-poor bands mainly consist of quartz, muscovite and chlorite.  All three units display slight positive Eu anomalies and fractionated LREE<HREE profiles indicative of hydrothermal input and characteristic of ancient Archean iron formations.  All three lithologies contain a large proportion of detrital material with 16 and 21 level containing the highest proportion and 46 the lowest.  46 level has the highest proportion of metalliferous material of all three lithologies.

It was determined that 16 and 21 level samples did not meet the criteria to be called iron formation, but rather these levels correspond to metalliferous sediments.  On the other hand, 46 level samples correspond to sulphide facies Algoma-type iron formation that have been diluted by detrital sediment.  Geochemical data from the surrounding area suggests that the major source of detritus is calc-alkaline in origin with some mixing with an unidentified additional source lithology (ASL) enriched in Th and HFSE elements.