A Planning Meeting of the Metal Earth Project in Canada Brings Together Both Current and Former DTM Scientists

Metal Earth
Steve Shirey looking at tectonic indicators of intense strain such as rolled feldspar porphyroblasts in orthogneiss of the Central Gneiss Belt, Grenville Province. Photo by Jesse Reimink, DTM.

From June 14 to 17, 2017, postdoctoral associate Jesse Reimink and staff scientist Steve Shirey joined former postdoc Graham Pearson (now at the University of Alberta) and former predoctoral fellow Michael Hamilton (now at the Jack Satterly Geochronology Lab of the Royal Ontario Museum in Sudbury, Ontario) for a planning meeting for the 'Metal Earth' project.

Jesse Reimink and Mike Hamilton looking at Proterozoic gneiss in the Central Gneiss Belt of the Grenville Province. Photo by Steve Shirey, DTM.

The 'Metal Earth' project is a multi-million dollar interdisciplinary project housed at the Harquail School of Economic Geology of Laurentian University in Sudbury and funded chiefly by the Canada-wide Canada First Research Excellence Fund (CFREF). The goal of ‘Metal Earth’ is to explain why some tracts of Archean continental crust are well-endowed with mineral deposits such as gold, platinum group metals, and base metals and others are poorly endowed.

Sudbury Breccia is a distinctive rock known as pseudotachylite composed of local country rock blocks in a black fine-grained matrix created by the intense heat and shock of a meteorite impact. It occurs just below the Sudbury Intrusive Complex and is a distinctive indicator of a meteorite impact. Photo by Steve Shirey, DTM.

Along with Rick Carlson, director of DTM, and former postdoc Richard Walker (now chair of the UMD College Park Geology Department), these six scientists comprise the ‘mantle team' for the project. This team will try to directly link endowment to mantle geodynamic processes.

Steve Shirey exclaiming his surprise at the excellent and large shattercones formed by Earth’s second largest meteorite impact 1850±1 million years ago in Sudbury. The shattercones are classical indicators of meteorite impact and here occur in sandstone of the Hough Lake Group (Huronian Supergroup) at the famous outcrop just south of Ramsey Lake, Sudbury, Ontario. Photo by Jesse Reimink, DTM.

The visit to Sudbury was also an excellent chance to do some rapid and exciting field work. Hamilton, Reimink, and Shirey completed a transect through the middle-crust of the Grenville Province -a well-exposed middle-Proterozoic continental collision zone. They also looked at the second largest bolide impact on Earth, the Sudbury Intrusive Complex. They examined giant pseudotachylite breccia at the base of the complex in three different rock types, looked at shattercones, and traversed the igneous stratigraphy into post-impact fallback pyroclastic rock.

This figure shows the major tectonic provinces of eastern Canada which basically get younger toward the southeast: Superior Craton (Archean; >2500 million years old), Grenville Province (Proterozoic or 542 to 2500 million years old), and Appalachian Province (Phanerozoic <542 million years old). The field excursion described above follows the dashed yellow line in the Grenville Province . Figure taken from Fig. 1a of Petrescu, L., Darbyshire, F., Bastow, I., Totten, E., & Gilligan, A. (2017) Journal of Geophysical Research-Solid Earth, 115, http://doi.org/10.1002/2016JB013599.

Written by Steve Shirey // June 27, 2017

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