Bedrock geochemistry, Dickinson County, Michigan

The southern margin of the Archean Superior Province in the central Upper Peninsula of Michigan records Paleoproterozoic tectonic events involved in the ~2.1 Ga rifting of the proposed Archean supercraton Superia and the subsequent assembly of Laurentia. Within a small area of Dickinson County, Michigan, there are many distinctive geologic units with confounding structural and stratigraphic relationships that are key to understanding the geologic and tectonic evolution of the region. The samples included in this data release were collected for geochemistry to complement recent geochronological (Vallini and others, 2006; Ayuso and others, 2018) and geophysical research (Drenth and others, 2021) in the region. The geochemical data encompass the diverse geologic units that crop out mainly in Dickinson County. These eighteen samples include rocks from the Dickinson Group (Solberg schist, Six Mile amphibolite, and East Branch arkose), as well as samples of the Bell Creek gneiss, Hardwood gneiss, porphyritic red granite, gray gneiss, and several of the mafic dikes that cut through the region. Samples were analyzed by ActLabs for major and trace elements.

Ayuso, R.A., Schulz, K.J., Cannon, W.F., Woodruff, L.G., Vasquez, J.A., Foley, N.K., and Jackson, J., 2018, New U-Pb zircon ages for rocks from the granite-gneiss terrane in northern Michigan: evidence for events at ~3750, 2750, and 1850 Ma: 64th Annual Institute on Lake Superior Geology Proceedings, Part 1—Program and Abstracts, p. 7-8.

Drenth, B.J., Cannon, W.F., Schulz, K.J., and Ayuso, R.A., 2021, Geophysical insights into Paleoproterozoic tectonics along the southern margin of the Superior Province, central Upper Peninsula, Michigan, USA: Precambrian Research, v. 359, 106205.

Vallini, D.A., Cannon, W.F., and Schulz, K.J., 2006, Age constraints for Paleoproterozoic glaciation in the Lake Superior region: detrital zircon and hydrothermal xenotime ages for the Chocolay Group, Marquette Range Supergroup: Canadian Journal of Earth Science, v. 43, p. 571-591.