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TitleTrace element geochemistry of magnetite and its relationship to mineralization in the Great Bear Magmatic Zone, NWT, Canada - preliminary findings
AuthorAcosta Góngora, P; Ootes, L; Jackson, V A; Samson, I M; Corriveau, L
SourceGeological Association of Canada-Mineralogical Association of Canada, Joint Annual Meeting, Abstracts Volume vol. 36, 2011 p. 1; 1 CD-ROM
Alt SeriesEarth Sciences Sector, Contribution Series 20120007
MeetingGAC/AGC - MAC/AMC - SEG - SGA; Ottawa; CA; May 25-27, 2011
Mediapaper; CD-ROM; digital
ProvinceNorthwest Territories
AreaLou Lake; Cole Lake; Fab Lake
Lat/Long WENS-117.0000 -116.5000 63.7500 63.5000
Subjectseconomic geology; geochemistry; trace element geochemistry; trace element analyses; magnetite; mineral occurrences; mineral deposits; iron oxides; copper; gold; uranium; Great Bear Magmatic Zone
ProgramGEM: Geo-mapping for Energy and Minerals, Uranium
AbstractThe Paleoproterozoic Great Bear magmatic zone is the focus of ongoing exploration for iron oxide copper-gold (IOCG) mineralization. Examples include the Sue-Dianne and NICO deposits. This project aims to characterize the nature and geochemistry of the fluids responsible for the mineralization in these deposits and other similar prospects in the southern part of the region. Petrographic and hand specimen descriptions of 45 samples provides a preliminary paragenetic sequence for the DAMP, FAB, and Nori prospects and the NICO and Sue Dianne advanced exploration projects. Mineralization at DAMP, FAB and Sue Dianne (Cu±Ag, U) are hosted by brecciated felsic volcanic rocks and characterized by an early stage of hematite and magnetite, followed by the deposition of chalcopyrite, bornite, and chalcocite as the main Cu ore minerals. The FAB showing contains two generations of magnetite; an older phase disseminated on the breccia lithoclasts and a younger phase found as the matrix to the breccia and veins. At Nori (Cu-Mo-U), tourmaline-biotite-uraninite veins crosscut the Treasure Lake metasedimentary rocks and also have two generations of magnetite; early phase disseminated in the wall rock and a later phase occurring in veins with K-feldspar coeval with molybdenite, uraninite, and chalcopyrite mineralization. At the NICO (Au-Bi-Co-Cu) deposit, the ore minerals are hosted by hydrothermally altered metasedimentary rocks of the Treasure Lake Group. Several generations of magnetite have been recognized and include pre- (strata bound magnetite replacement), syn- (magnetite in arsenopyrite-bearing veins, vein selvages and breccias, and/or strongly overprinting the host metasedimentary bedding) and post-mineralization (late-stage magnetite veins) episodes. Thus, magnetite is found in all the mineral showings and advanced exploration projects within this area, and it is often closely related to mineralized rocks. We present the results obtained by an electron microprobe
analyses and suggest that the trace elements in magnetite, especially V, have a significant variation between the different prospects and advanced exploration projects. Furthermore, local variations in V and Co, can be used to distinguish between preand syn-mineralization magnetite. This study indicates that the trace element signature of magnetite may be a suitable tool for mineral exploration in the GBmz. Future analytical investigations utilizing ICP-MS will be carried out to constrain the results reported here.