Abstract

New U-Pb geochronologic data from the Sudbury structure directly link extensive hydrothermal activity in crater-fill breccias with the 1850 Ma impact event, and constrain complex impact-induced processes to <4 m.y. Semiconformable alteration of breccias in the Onaping Formation includes silicification, albitization, chloritization, calcitization, and complex feldspathization, which directly underlies Zn-Cu-Pb ore deposits. Geochronologic data demonstrate a middle to lower crustal source for the crater-fill deposit that was subsequently affected by the hydrothermal event at 1848.4 +3.8/−1.8 Ma. These and other data confirm that the crater-fill breccia, hydrothermal system, Sudbury igneous complex, and its sublayer Ni-ore-bearing units were emplaced as a result of impact. The ages of events associated with the Sudbury structure are now more closely constrained than in any other meteorite impact structure.

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