The Sudbury basin was formed by a 10-15 km wide asteroid or comet impacting a shallow sea in what is now central Ontario, Canada 1.85 billion years ago. The resulting ~200-250 km wide crater is the second largest known in the world, being much larger than the 150 km Chicxulub crater formed by the asteroid that wiped out the dinosaurs. If such as impact were to occur today it would certainly spell the end of life as we know it.
The basin is one of the oldest craters still in existence and has been deformed and eroded into its’ present oval shape and 60 km size. Although the basin itself is not easily recognizable as a crater, smaller scale features such as shatter cones are well known in the area, and a layer of rock fragments blasted out of the crater have been mapped as far away as Minnesota, some 800 km distant. A layer of ash and debris likely encircled the entire planet at the time.
The basin is filled by impact breccias and later sedimentary rocks of the Whitewater Group, and igneous rocks of the Sudbury Igneous Complex (SIC). The SIC forms a ring around the Whitewater Group and is dominated by a melt sheet of norite and gabbro formed by the heat of impact.
Deposits in the Sudbury Basin occur mainly at the base of the SIC and in surrounding dykes, with most being concentrated into two clusters: the South Range near the city of Sudbury and the North Range along the basin’s northern margin. Deposits are often associated with a layer of breccia and are generally graded from massive to disseminated iron, nickel (Ni) and copper (Cu) sulfides moving upwards.
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