Rifting and

Continental Volcanism

✦ Ropy pahoehoe lava flow-top texture in 1100 million year old Keweenawan volcanic rocks at Mamainse Point, ON, Canada (photo: Steve Shirey)

A fundamental part of the Wilson cycle of plate tectonics is the break-up of continents by rifting. In this setting, there is a unique interplay between magmatic sources that may reside in the passively upwelling asthenospheric mantle, the dynamically rising plume mantle and the rigid subcontinental lithospheric mantle. Although not all rifts go to completion as is evident in the 1100 million year old Midcontinent Rift System of the United States (left), they can still illuminate the architecture of the deep continent.

Relevant Publications

Smith, J. M., Ripley, E. M., Li, C., Shirey, S. B. & Benson, E. K. (2022) Magmatic origin for the massive sulfide ores in the sedimentary country rocks of mafic–ultramafic intrusions in the Midcontinent Rift System. Mineralium Deposita 1–22. https://doi.org/10.1007/s00126-022-01095-2 Supplemental File 1 Supplemental File 2

Nelson, W., Hanan, B., Graham, D., Shirey, S., Yirgu, G., Ayalew, D., Furman, T. (2019). Distinguishing Plume and Metasomatized Lithospheric Mantle Contributions to Post-Flood Basalt Volcanism on the Southeastern Ethiopian Plateau. Journal of Petrology 60(5), 1063-1094. https://dx.doi.org/10.1093/petrology/egz024

Taranovic, V., Ripley, E. M., Li, C., & Shirey, S. B. (2018). S, O, and Re-Os Isotope Studies of the Tamarack Igneous Complex: Melt-Rock Interaction During the Early Stage of Midcontinent Rift Development. Economic Geology, 113(5), 1161–1179. http://doi.org/10.5382/econgeo.2018.4585

Nelson, W. R., Furman, T., van Keken, P. E., Shirey, S. B., & Hanan, B. B. (2012). Os-Hf isotopic insight into mantle plume dynamics beneath the East African Rift System. Chemical Geology, 320-321, 66–79. http://doi.org/10.1016/j.chemgeo.2012.05.020

Ding, X., Ripley, E. M., Shirey, S. B., & Li, C. (2012). Os, Nd, O and S isotope constraints on country rock contamination in the conduit-related Eagle Cu–Ni–(PGE) deposit, Midcontinent Rift System, Upper Michigan. Geochimica Et Cosmochimica Acta, 89, 10–30. http://doi.org/10.1016/j.gca.2012.04.029

Shirey, S.B., 1997, Re-Os isotopic compositions of Midcontinent Rift System picrites; implications for plume-lithosphere interaction and enriched mantle sources: Canadian Journal of Earth Sciences, v. 34, p. 489-503.

Nicholson, S.W., Shirey, S.B., Schulz, K.J., and Green, J.C., 1997, Rift-wide correlation of 1.1 Ga Midcontinent Rift System basalts; implications for multiple mantle sources during rift development: Canadian Journal of Earth Sciences, v. 34, p. 504-520.

Hart, W.K., Carlson, R.W., and Shirey, S.B., 1997, Radiogenic Os in primitive basalts from the northwestern U.S.A.; implications for petrogenesis: Earth and Planetary Science Letters, v. 150, p. 103-116.

Nicholson, S.W., and Shirey, S.B., 1992, Nd and Pb isotopic evolution of basalts of the 1.1 Ga Midcontinent Rift; evidence for a region-wide model for plume-lithosphere-asthenosphere interaction, in Ayuso Robert, A., and Schultz Klaus, J., eds., Informal notes; workshop on the Application of isotope systems to geological problems.: Open-File Report - U. S. Geological Survey: Reston, VA, United States, U. S. Geological Survey, p. 155-161.

Klewin, K.W., and Shirey, S.B., 1992, The igneous petrology and magmatic evolution of the Midcontinent Rift system: Tectonophysics, v. 213, p. 33-40.

Ellam, R.M., Carlson, R.W., and Shirey, S.B., 1992, Evidence from Re-Os isotopes for plume-lithosphere mixing in Karoo flood basalt genesis: Nature, v. 359, p. 718-721.

Klewin, K.W., Berg, J.H., Shirey, S.B., Carlson, R.W., and Anonymous, 1991, Isotopic and trace element evidence for time progressive changes in the source region of flood basalts: Eos, Transactions, American Geophysical Union, v. 72, p. 280.

Nicholson, S.W., and Shirey, S.B., 1990, Midcontinent Rift volcanism in the Lake Superior region; Sr, Nd, and Pb isotopic evidence for a mantle plume origin: Journal of Geophysical Research, v. 95, p. 10,851-10,868.