Geochemical evidence for the tectonic setting of early Proterozoic metavolcanic sequences in southern Lake Superior region.
Samples of metabasaltic dikes and lavas from early Proterozoic rock units in the southcentral Lake Superior region were analyzed for major and selected trace elements in order to compare their chemical composition with those of rocks from modern, known tectonic environments. The rocks exhibit a relatively wide compositional range in which the least evolved samples show a chemical composition similar to that of T-type MORB. Based on geochemical characteristics and tectonic discrimination diagrams, I conclude that the rock suites were emplaced in an extensional regime. The geochemical patterns of these rocks are similar to those of British Tertiary Volcanic Province and continental tholeiitic basalts from Rdendeka. which ernnted in more recent rift environments.