Publication Type:Book Chapter
Source:Targeted Geoscience Initiative 4; contributions to the understanding of Precambrian lode gold deposits and implications for exploration, Geological Survey of Canada, Calgary, AB, Canada, p.139-155 (2015)
Keywords:Abitibi Belt, absolute age, Archean, breccia, brecciation, Canada, Canadian Shield, copper ores, dates, dikes, diorites, eastern canada, gold ores, Hydrothermal alteration, igneous rocks, intrusions, magmatism, metal ores, metasomatism, mineralization, North America, Ontario, plutonic rocks, Precambrian, Re/Os, superior province, Swayze greenstone belt, tonalite, U/Pb
The recently discovered Cote Gold deposit, located in the southeast limb of the Swayze greenstone belt, Abitibi Subprovince, is an Archean low-grade, high-tonnage Au(-Cu) deposit. The deposit is hosted by the 2741 Ma Chester intrusive complex (CIC), a high-level, multi-phase, laccolithic-shaped synvolcanic intrusion composed of several tonalite and diorite phases. Although a close temporal and spatial relationship exists between the phases of the CIC, whole-rock geochemistry on least-altered samples suggests they are petrogenetically unrelated. Notably, the tonalite phases are characterized chemically as low-Al type, which is atypical of the tonalite-trondhjemite-granodiorite suites in the Archean Superior Province and elsewhere, but typical of primitive arc submarine environments. The mineralized system at the Cote Gold deposit is cospatial with a multi-phase, magmatic-hydrothermal breccia body that contains multiple brecciation events and matrices and is overprinted by several alteration types (biotite, sericite, silica-sodic). Whole-rock geochemistry indicates that the deposit is Au(-Cu) only and is relatively depleted in other elements (e.g. As, F, Bi, Te). The overlap of Re-Os dates on syn-gold-deposition molybdenite (2739 + or - 9 Ma) with the 2741 Ma CIC is consistent with field observations that suggest an overlap of magmatic and hydrothermal events. The results of this study have defined a new significant early stage gold metallogenic event in the Abitibi Subprovince at 2740 Ma and the deposit provides a guide for future exploration in other composite, subvolcanic, low-Al intrusions in the Archean.
GeoRef, Copyright 2018, American Geological Institute.<br/>2016-084460<br/>Chester Complex<br/>Cote Gold Deposit