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 iri the Onaping Formation
includes silicification, albitization, chloritization, calcitization,
and complex feldspathization, which directly underlies Zn-Cu-Pb ore de
posits. Geochronologic data demonstrate a middle to lower crustal sour
ce for the crater-fill deposit that was subsequently affected by the h
ydrothermal event at 1848.4 + 3.8/-1.8 Ma. These and other data confir
m that the crater-fill breccia, hydrothermal system, Sudbury igneous c
omplex, and its sublayer Ni-ore-bearing units were emplaced as a resul
t of impact. The ages of events associated with the Sudbury structure
are now more closely constrained than in any other meteorite impact st
ructure.