Origin and genesis of the Goldenville iron formations and implications for mineralization, Baie Verte, Newfoundland, Canada

Abstract

The Goldenville iron formation (IF) and associated sedimentary rocks, within the Point Rousse complex of the Baie Verte Peninsula, hosts the Goldenville Au deposit and produced 23 tonnes of ore between 1904-1906 (158 oz gold recovered). The Goldenville IF marks the end of Cambrian-Ordovician (~489-485 Ma) Au-rich VMS activity (i.e., VMS Rambler-Ming district), is considered to be correlative with the Nugget Pond IF with both iron formations believed to form a marker unit between the Mount Misery Formation and the overlying Snooks Arm Group cover sequence (~470 Ma), and captures paleo-oceanic redox conditions during the transition from the Cambrian to Ordovician. Despite economic, stratigraphic, and geological importance of the Goldenville IF, it has received very little textural-mineralogical-geochemical study. The Goldenville horizon is a laterally discontinuous, fine-grained, and laminated unit within argillites, volcaniclastic rocks, and basalt flows. Chemostratigraphy provides evidence of multiple iron formation horizons between the Mount Misery Formation and the overlying Snooks Arm Group cover sequence. In particular, the position of the Goldenville iron formation is lower in stratigraphy and contained within the Mount Misery Formation. In the IF, the lithogeochemical data reflect varying contributions from detrital material, hydrothermal discharge, and hydrogenous elements scavenged from seawater. Samples with the highest hydrothermally sourced Fe and Mn abundance preserve evidence in their REE+Y chemistry for two distinct oxide particle scavenging shuttles that operated in a volcanically active basin with oxygenated bottom waters. Textural evidence of gold in and proximal to the IF suggests that hydrothermal fluids interacted with Fe³⁺-bearing minerals within the IF, resulting in wall rock sulfidation and the co-precipitation of gold and pyrite.