Publication Type:Book Chapter
Source:A special issue devoted to the mineral deposits of the Sudbury Basin, Economic Geology Publishing Company, Lancaster, PA, United States, Volume 97, p.1577-1606 (2002)
Keywords:absolute age, amphibole group, Ar/Ar, baddeleyite, Canadian Shield, chain silicates, chemical composition, clinoamphibole, copper ores, country rocks, crystallization, cumulates, dates, dike swarms, emplacement, geochemistry, geometry, Grenville Province, hornblende, intrusions, K/Ar, matrix, metal ores, metals, mineral deposits, genesis, nesosilicates, nickel ores, North America, ore-forming fluids, orthosilicates, oxides, platinum ores, Precambrian, proterozoic, rare earths, recrystallization, silicates, Sm/Nd, Southern Province, superior province, textures, U/Pb, upper Precambrian, whole rock, zircon, zircon group
The 2490-2475 m.y. intrusions of the East Bull Lake intrusive suite occur in an ENE-trending discontinuous belt along the presently exposed boundary between the Archaean Superior and the Proterozoic Southern provinces of the Canadian Shield near Sudbury, Ontario. The intrusive suite is part of a regional Palaeoproterozoic magmatic event, extending from 2490 to 2440 m.y. This regional magmatic event is thought to be the result of a mantle plume-driven, intracontinental rifting event that led to the development of a major basin to the S that was subsequently filled by sedimentary rocks of the Huronian supergroup. The East Bull Lake intrusive suite appears to have been emplaced along a major axial-rift fault related to this rifting event. Field and geochemical evidence summarized here indicates that the three largest East Bull Lake suite intrusions, the East Bull Lake, Agnew Lake and River Valley intrusions, crystallized from similar, low Ti, high Al tholeiitic parent magmas that originated in deeper, more basic chambers. It is proposed that the primary magmas for the East Bull Lake suite intrusions were second-stage melts derived from a sublithospheric depleted mantle source that had been modified by Neoarchaean subduction and accretion events. Feeder dykes to the mineralized parts of the intrusions appear to have been saturated in sulphide upon emplacement and had relatively high background PGE contents compared to those for other known magmatic PGE deposits; however, the economic potential of the contact-type mineralization hinges on the efficacy of the physical concentration process, which upgraded the metal content and size of the original sulphide particles inside the magma chambers. Based on the proposed basal accumulation model, the best prospective mineralization is most likely to occur in embayments along the sidewall and floor of the intrusions.
GeoRef, Copyright 2018, American Geological Institute.<br/>2003-014847<br/>Agnew Lake<br/>East Bull Lake Suite<br/>River Valley