Petrogenesis of Archean (2.7 Ga) Mafic Volcanic Assemblages Near Ely, MN

Abstract

The Vermilion District in northeastern Minnesota contains one of the classic Neoarchean Archean granite-greenstone belt terranes in the United States that formed between 2722 Ma to ~2661 Ma. Crustal development during Archean is controversial. Scientists do not know if the formation of the crust was due to subduction or non-subduction tectonic processes. This study describes the geochemistry of Archean mafic volcanic assemblages near Ely, MN and documents geochemical geospatial/stratigraphic variations. The geochemical variations throughout stratigraphy will test volcanic and tectonic models for Archean crustal development. Compiling data from newly collected samples with existing data will provide a near-complete geochemical transect throughout the Archean mafic volcanic assemblages in northeast Minnesota. The interpretations from this project can improve our understanding of the role of modern, subduction-dominated plate tectonics or plume-dominated mechanisms in the formation of Archean cratons. A comprehensive study of the geochemical characteristics of the rocks in this region can improve scientists understanding of Archean tectonic processes, crust formation, and crustal architecture. The interpretations will not only be important for the study of Minnesota’s geology, but also will allow for more regional geodynamic interpretations and correlations with Archean rocks that extend into Ontario, Canada.