The Eau Claire Volcanic Complex (ECVC) was thought to have formed on an Archean crustal block (~2.6-3.0 Ga) called the Marshfield Terrane during the Penokean Orogen along the southern margin of the Superior craton. The other volcanic terrane within the Penokean Orogen, the Pembine-Wausau terrane, is interpreted to have formed without older crust and hosts about 150 million tonnes of metallic sulfide ores. The ‘continental’ setting of the Marshfield Terrane assumes this region is not prospective for the same ores. However, U/Pb isotopic and other geochemical data from the ECVC challenges this current model. The ECVC is challenging to study because of a lack of mineral exploration (and drilling) coupled with rare outcrop exposure due to glacial/fluvial sediment and Paleozoic rock cover. This project studies remote, inaccessible outcrops along the Eau Claire River to refine the tectonic model and terrane boundaries. Samples were collected from the limited outcrop exposure along the North Fork of the Eau Claire River. These samples were then processed in order to isolate zircon grains. Zircons are a common mineral used for U/Pb radiometric dating. The zircons were then analyzed at Laurentian University (Sudbury, Ontario, Canada) via Laser Ablation Inductively Coupled Plasma Mass Spectrometer (LA-ICP-MS). This type of laser ablation allows us to collect U/Pb and trace element geochemistry from each individual grain that was analyzed. This data combined with petrology and geochemistry data from the previous year can provide a deeper understanding of the formation conditions, metamorphic history, and potential alteration processes that formed the bedrock.
