Daniel Lafontaine's Honours Thesis Abstract
The Gunflint and Biwabik Formations form the middle unit of the sedimentary- metasedimentary Animikie group. In an attempt to further understanding of the history of the Gunflint Formation a series of samples for chemical analysis were taken from five drill-holes (MC-1-89, ON-06, MGS-02, MGS-08, and 18279) throughout the formation. Special attention was given to the siliciclastic–volcaniclastic material that mixes with the chemical sediment at some horizons in the formation. Two areas of siliciclastics were defined through graphing Al2O3 vs depth, TiO2 vs Depth and Na2O/TiO2 vs Depth.
The first, middle, area rich in volcaniclastics–siliciclastics was observed in drill-hole MC-1-89 at 103.2 meters from the top of the formation, ON-06 at 103.6 meters from the top of the formation, MGS-02 at 95.7 meters from the top of the formation, and MGS-08 at 64.1 meters from the top of the formation. The relationship between Zr/TiO2 was analyzed through the use of a scatter point graph. It revealed a slope with an average of 166. The relationship between zirconium and titanium oxide was compared to possible volcanics to define a source. The most likely source, the Gunflint volcanics analyzed at Mink Mountain, revealed no correlation with the volcaniclastics - siliciclastics. However, the slope revealed the Zr/TiO2 ratio of the siliciclastics – volcaniclastics had some similarities with the dacitic volcanic flows from the Emperor volcanics. A similar study of the relationship between V/TiO2 revealed similar results in comparison with the Gunflint volcanics from Mink Mountain, However, it could not be compared successfully to the Emperor volcanics.
The top unit containing volcaniclastics - siliciclastics was observed in drill-hole MC-1-89 at 22.7 meters from the top of the formation, ON-06 at 26.7 meters from the top of the formation, and MGS-02 at 24.6 meters from the top of the formation. The volcaniclastics – siliciclastics do not appear in drill-hole MGS-08. The material continues to the top of the formation. The material was isolated and the relationship between Zr/TiO2 was analyzed through the use of scatter point graphs. They revealed a slope with an average of 317.8. This slope differed from the ratio of the middle siliciclastics – volcaniclastics. The relationship between zirconium and titanium oxide was compared to possible volcanics for a source. It was found the most likely source for the siliciclastics is eroded average continental crust.
Lapilli tuffs were also analyzed and a comparison of Zr/TiO2 and V/TiO2 to the Gunflint volcanics indicated that it is likely that the Mink Mountain Gunflint volcanics were deposited in the area surrounding the flows as reworked Lapilli tuffs. These are interlayered with the middle siliciclastic-rich unit.
Two periods of alteration were observed in the vertical bar graphs of K2O/Na2O vs depth and vertical bar graphs of Al2O3/Fe2O3 vs Depth. In drill-hole MC-1-89 there is an area of alteration from 95.1 to 86.6 meters from the top of the formation and in ON-06 it occurs at 91.5 meters to 87.2 meters from the top of the formation. This period of alteration ended there in the north. This probably indicates a regression and drop in sealevel not exposing sediment in the offshore to the south. A second area of alteration was observed in MC-1-89 from 4.6 to 2.5 meters from the top of the formation, in ON-06 at 19.5 meters to 4.5 meters from the top of the formation, in MGS-02 there is only one noticeable region of alteration at 7.4 meters to 2.2 meters from the top of the formation, and in MGS-08 the upper area of alteration is at 3.4 meters to the top of the formation. Using Al2O3/Fe2O3 vs depth of depletion in iron is only seen in this top region of alteration. This depletion might exist because of dissolution and hydrolysis caused by infiltrating of rain water, probable due to a period of subaerial exposure.