THE TECTONIC, MAGMATIC AND MINERALIZATION HISTORY OF THE SUDBURY STRUCTURE

The Sudbury Structure consists of three major components: 1) the Sudbu ry Basin; 2) the Sudbury Igneous Complex which surrounds the basin as an elliptical collar; and 3) an outer zone of shatter-coned and intens ely brecciated footwall rocks. Although the Sudbury Event which formed the structure may be unique, the area has, in fact, been shaped by a series of tectonic, magmatic and mineralization events which can be co nsidered in terms of two Wilson cycles of continental extension and cl osure. The first cycle, from 2500 to 1700 Ma, included the following e vents: doming (uplift of Levack Gneiss Complex); NE-SW extension (Mata chewan dikes); N-S to NW-SE rifting (faults, mafic intrusions, sedimen tation, and Ni-Cu-PGE and U mineralization); NW-SE extension (Nipissin g diabase, and Ni-Cu-PGE, Ag, Co mineralization); and NW-SE and NE-SW closure (Penokean Orogeny, 1900 to 1700 Ma) with superimposed meteorit e impact (1850 Ma, Ni-Cu-PGE, Zn-Cu-Pb deposits). The second cycle, fr om 1700 to 1000 Ma, included: N-S extension (alkali metasomatism, Au); N-S extension (hornblende diabase dikes along the Murray fault set); NNE-SSW extension (olivine diabase dikes); NE-SW extension (Fecunis La ke fault set); and NW-SE closure (Grenvillian Orogeny). The rich and d iverse Ni-Cu-PGE and subordinate Zn-Pb-Cu and Au mineralization of the Sudbury region is related to endogenic and impact-triggered crustal e xtension and magmatism. The Sudbury Structure apparently was the site of a triple junction or hot-spot. The Sudbury ores, although located w ithin an impact structure, are analogous in terms of age and tectonic setting to Ni-Cu-PGE and Zn-Pb-Cu ores elsewhere in the world. Meteori te impact accentuated on-going ore forming processes and magmatism at Sudbury. (C) 1997 Canadian Institute of Mining, Metallurgy and Petrole um.