Evolution of the Sudbury igneous complex contact metamorphic aureole and controls on anatexis

THE ISSUE:

Much of the Ni-Cu-PGE mineralization in the Sudbury Structure was generated and modified within the anatectic and contact metamorphic aureole of the Sudbury Igneous Complex (SIC). To increase our chances of exploration success in this complex environment, new and novel exploration techniques are needed, yet few studies have been conducted that show how to identify the presence of a contact metamorphic aureole around the SIC. This is critical for a deeper understanding of the thermal architecture during the development of some types of contact and footwall ore deposits.

THE SOLUTION:

Defining field, microscopic and geochemical criteria to establish the nature and extent of partial melting, metamorphic devolatilization, and fluid interaction within the SIC contact metamorphic aureole and the overprint of the aureole by regional metamorphism will provide the context to understand the thermal structure and evolution around the SIC.

THE RESULTS:

Field observations indicate that large portions of the South Range metamorphic aureole surrounding the SIC can be resolved despite complications due to post-metamorphic events, primary lithologic heterogeneities, and the geometry of the SIC contact. Geochemical data has proven useful in establishing fingerprints to distinguish rocks that are highly affected by contact metamorphism compared to similar rocks in the more distal part of the metamorphic aureole. This is extremely useful as new and existing geochemistry databases can now be studied to see if similar rocks outside the study area show the same characteristics. Finding rocks with matching characteristics would indicate their proximity to the SIC during cooling and solidification of the SIC melt sheet.