Synthesis of the Tectonic, Magmatic, and Metallogenic Evolution of the Midcontinent Rift System

Science Center Objects

The overall project objective is to develop a comprehensive synthesis of the tectonic, magmatic, and metallogenic evolution of the Midcontinent Rift System (MRS) through time by integrating geophysical, magmatic, and geochemical data and to create 3-D models of the rift over its evolution.

Image shows two scientists in hard hats standing in a quarry

The Midcontinent region is the focus of active mineral exploration, including for mineral deposit types previously unrecognized there.  Here, USGS scientists Laurel Woodruff and Suzanne Nicholson visit an anorthosite quarry, Duluth Complex, MN. (Credit: Klaus, Schulz, USGS. Public domain.)

Science Issue and Relevance

The Midcontinent region is the focus of active mineral exploration, including for mineral deposit types previously unrecognized there. This is an opportune time to re-evaluate models for the development of the tectonic, magmatic, and metallogenic evolution of the Midcontinent Rift System. Using the USGS's new geographic information system (GIS) compilation for the entire Lake Superior region (including the Canadian side) and new tools for analyzing large amounts of spatial data, we can now integrate and evaluate data in a larger regional and 3-D context. This new regional data compilation (as yet unpublished) will help determine:

  1. How the crust and lithosphere responded to the upwelling of the proposed mantle plume and their subsequent interactions from about 1120 Ma to 1085 Ma, and
  2. How the architecture of the rift (evolving from plateau basalts to the formation of central grabens, with subsequent development of sedimentary basins and horsts) influenced formation and distribution of a wide variety of mineral deposit types.
Image shows a map if minerals near Lake Superior

Much of the Great Lakes' mineral wealth can be traced to the Mid-Continent Rift. Here is a generalized geologic map of the Midcontinent Rift System. Modified from Dean Peterson, Duluth Metals.(Public domain.)

Methodology to Address Issue

The goals of this project are:

  1. To develop a comprehensive synthesis of the tectonic, magmatic, and mineral deposit evolution of the Midcontinent Rift System by integrating geophysical, magmatic, and geochemical data
  2. To illustrate the results with a series of conceptual 3-D models of the rift over its ~35 Ma evolution.

Architecture of the Midcontinent Rift System: We'll collaborate with geophysicists working on the Midcontinent Rift System to develop a series of conceptual 3-D models of the magmatic evolution of the rift event. These results will provide details of the upper crustal structure and stratigraphy of buried parts of the rift, and deeper structures within the lower crust and lithosphere, to evaluate the potential for undiscovered mineralization in unexposed rift segments.

Magmatic Evolution and Metallogeny of the Midcontinent Rift System: We will use the rift-wide GIS compilation of geochemical, isotopic, and age data for volcanic and intrusive rocks to synthesize the magmatic evolution of the rift. New geochemical and isotopic analyses, along with limited additional age dating, will be done to fill in key gaps. This task will also use the GIS compilation, as well as new deposit model information and outcomes of recent assessments for conduit- and contact-type nickel-copper-platinum group elements (Ni-Cu-PGE) mineralization in the Lake Superior region, to update the metallogeny of the Midcontinent Rift System (Nicholson and others, 1992).

Dynamic GIS Archive of Midcontinent Rift System Data: Having compiled the initial GIS for the Midcontinent Rift System, we will continue to update the GIS, adding new datasets where appropriate, updating existing geochemical and isotopic datasets as time and funding allow, and responding to other uses for these data.

scientists standing near lake

2013 Institute on Lake Superior Geology field trip.(Credit: William Cannon, USGS. Public domain.)

View of lake shore from woods

Shovel Point North Shore, Minnesota. (Credit: Klaus Schulz, USGS. Public domain.)

view of mountain lake

Panoramic view of Lake of the Clouds, Porcupine Mountains Wilderness State park, MI (from Woodruff and others, 2013). (Credit: William Cannon, USGS. Public domain.)