Mid-Continent rift - South Shore

background

We are exploring a billion year old tear in the Earth that in some ways resembles East Africa. However, the Mid-Continent Rift did not turn into an ocean (as many rifts do). Instead this event left a gash in the North American continent that runs in a horseshore through Lake Superior down through Michigan on one arm, and Iowa on the other. Into this tear in the Earth erupted vast volumes of basaltic magma over a billion years ago.

objectives

Our primary goals in the region is to use the record of lavas erupted to probe what was going on in the crust and mantle during the ancient rifting events. We can collect lavas that stack on top of one another and thereby get a sense as to how the lava composition changes over time. This reveals insights into what melted to form the lavas and where the magmas that eventually became lavas resided in the crust before eruption.

discoveries

We have found that the source of the magmas which formed these rocks was a magma chamber that experienced many different eruption events and well as recharging events. We continue to explore these rocks and hope to have more work presented soon.

ABSTRACTS

1. Rooney, T.O., Brown, E., Moucha, R., Stein, C., Stein, S. The Last Gasp – the Terminal Magmatic Stages of the Keweenaw LIP, Abstract V34B-08. Presented at 2016 Fall Meeting, AGU, San Francisco, Calif., 12-16 December.

2. *Bonessi, J., Rooney, T.O., *Svoboda, C., Girard, G., 2017, Silicic volcanism of the Porcupine Volcanics; implications for magma differentiation during the terminal stages of volcanism within the Midcontinent Rift. Presented at the Annual Meeting for the Institute for Lake Superior Geology, Wawa, Ontario, Canada. May 10-11 2017.

3. Rooney, T.O., *Lavigne, A., *Svoboda, C., *Lv, M., *Bonessi, J., *Eriksen, Z., *Kelly, T., *Noyce, K., Stein, C., Stein, S., Moucha, R., Brown, E., The Lake Shore Traps – A terminal cycle of the Keweenaw Flood Basalt event. Presented at the Annual Meeting for the Institute for Lake Superior Geology, Wawa, Ontario, Canada. May 10-11 2017.

4. Svoboda, C.D.*, Rooney T.O., LaVigne, A.*, Brown, E., Stein, S., Stein, C., Moucha R., Crustal Contamination in the Terminal Stages of the Keweenawan Large Igneous Province: Geochemical Evidence from the Porcupine Mountains. Abstract 16-10. Geological Society of America Abstracts with Programs v. 50 (6).

5. Davis, W.R..*, Collins, M.*, LaVigne A.*, Rooney T.O., Krans, S.R.*, Brown, E., Stein, S., Stein, C., Moucha R., 2018. Implications of geochemical, petrographic and stratigraphic analyses of the upper Portage Lake Volcanics for the Keweenaw flood basalts. Abstract 119-4. Geological Society of America Abstracts with Programs v. 50 (6).

6. Bonessi, J.*, Rooney T.O., LaVigne A.*, Svoboda C.*, Girard, G., Moucha R., Brown, E., Stein, C., Stein, S. 2018. Silicic Volcanism of the Porcupine Volcanics: Implications for magma differentiation during the terminal stages of volcanism within the Midcontinent Rift. Abstract 119-6. Geological Society of America Abstracts with Programs v. 50 (6).

7. Davis, W.R..*, Collins, M.*, LaVigne A.*, Rooney T.O., Krans, S.R.*, Brown, E., Stein, S., Stein, C., Moucha R., 2018. Implications of geochemical, petrographic and stratigraphic analyses of the upper Portage Lake Volcanics for the Keweenaw flood basalts. Presented at the NASA Michigan Space Grant Consortium Conference in Ann Arbor, November 10^th, 2018.

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