The Temagami geophysical anomaly (Ontario, Canada): geological cause and relationship to the 1.85 Ga Sudbury impact event
Final Report Abstract
The Temagami Anomaly immediately to the northeast of the 1850 Ma asteroid impactgenerated Sudbury Igneous Complex (SIC), Ontario, is one of the largest unexplained geophysical anomalies in North America. Principal goal of the project was the investigation of the geology above this hitherto poorly studied anomaly, which covers, on surface, an area of 1200 km2, with the aim of possibly finding indications as to its geological cause. To this effect, rock exposures in the field and recent as well as historic drill core (reaching depths of >2 km) were mapped and sampled. This was followed by a petrological and geochemical characterization, qualitative and semi-quantitative mineral identification, whole rock geochemical analysis, Nd, Sr, and Pb isotope analyse as well as U-Pb age dating of titanite and apatite. The results obtained testify the existence of impact melt rocks at a hitherto unknown distance from the SIC within the geographic area of the Temagami Anomaly, but also the presence of numerous dykes, which can be attributed to several magmatic events at ca. 2.22 Ga, 2.17 Ga and 1.87 Ga. The latter, known elsewhere as the Circum-Superior Large Igneous Province (CSLIP), could be documented for the study area for the first time. This finding now offers a potential explanation for the Temagami Anomaly, which could be due to a combination of shallow, locally exposed, Archaean banded iron formation and a larger, deep-seated (>5 km) layered ultramafic intrusive body as part of the CSLIP. The exploration potential for nickel, copper and platinum-group-elements to the northeast of the SIC could be significantly increased. At the same time, the new results confirm the model of a large multi-ring structure for the Sudbury impact and help to better understand the emplacement of impact melts.
Publications
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Rathbun Lake revisited: a magmatic-hydrothermal Pd-Pt-Cu occurrence possibly related to the Sudbury impact. Proceedings of the 15th Biennial SGA Meeting, Glasgow, Volume 2, pp. 605-608.
Kawohl, A., Frimmel, H.E., Whymark, W. & Bite, A.
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Very distant Sudbury impact dykes revealed by drilling the Temagami geophysical anomaly. Precambrian Research, 324, 220-235.
Kawohl, Alexander; Frimmel, Hartwig E.; Bite, Andrejs; Whymark, Wesley & Debaille, Vinciane
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High-Grade Magmatic Platinum Group Element-Cu(-Ni) Sulfide Mineralization Associated with the Rathbun Offset Dike of the Sudbury Igneous Complex (Ontario, Canada). Economic Geology, 115(3), 505-525.
Kawohl, Alexander; Whymark, Wesley E.; Bite, Andrejs & Frimmel, Hartwig E.
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On the depth of crater excavation and melting during the Sudbury impact: geochemical evidence from chilled impact melt dykes. European Geosciences Union General Assembly, Vienna, Austria,
Kawohl, A., Frimmel, H.E., Whymark, W. & Bite, A.
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Hornblende Thermobarometry of Impact Melt Rocks: A Case Study from the Rathbun Offset Dike, Sudbury Impact Structure, Canada. 53rd Lunar and Planetary Science Conference, The Woodlands, Texas, LPI Contribution No. 2678, id.1369.
Kawohl, A.
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Geology, geochemistry, and apatite/titanite U–Pb geochronology of ca. 1.88 Ga alkaline ultrabasic dykes in the Southern Province near Sudbury, Ontario. Canadian Journal of Earth Sciences, 60(1), 62-77.
Kawohl, Alexander; Frimmel, Hartwig E.; Whymark, Wesley E.; Millonig, Leo J. & Gerdes, Axel
