The first great geologic expeditions of the United States set off in the mid-1800s, equipped with mules, rifles, and early scientific instruments. Their goal: to uncover the great mineral wealth of the United States and learn about its earliest geologic history.
Understanding the Mineral Resources of the Midcontinent Rift
USGS Publishes Story Map of the Midcontinent Rift
Now, you too can learn some of that history and see a small part of the mineral potential of the United States without leaving your comfortable chair! The USGS has just released a new interactive Story Map describing the Mineral Deposits of the Midcontinent Rift System.
The Midcontinent Rift System, which curves for more than 2000 km across the Upper Midwest, is one of the world’s great continental rifts. Rifting began about 1.1 billion years ago, when the Earth’s crust began to split along the margin of the Superior craton. Rifting ended before the crust completely opened to form a new ocean, and as time passed rift rocks were buried beneath younger rocks. With erosion and glaciation, the ancient rocks of the Midcontinent Rift were exposed in the Lake Superior region, creating much of its spectacular shoreline.
In the Lake Superior region, rocks of the rift contain a wealth of mineral resources that formed by magmatic and hydrothermal processes during the ~30 million year course of rift development. Rift rocks are host to Michigan’s storied native copper deposits, and contain significant copper and nickel that were deposited during various stages of rift development.
In this Story Map, mineral deposit locations and descriptions, compiled from the USGS Mineral Resource Data System and the Ontario Geological Survey Mineral Deposit Inventory, are categorized by mineral commodity, mineral deposit type, and the relative time frame of mineralization.
This Story Map also describes a new comprehensive digital Geographic Information System for the Midcontinent Rift System recently compiled by the USGS from numerous regional studies conducted over the last several decades.
Characterizing the mineral resources of the Midcontinent Rift System is a priority of the USGS Mineral Resources Program, and we hope you enjoy this Story Map that tells just part of the amazing story of this important geologic feature.