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TitleElectrical anisotropic characteristics of mineralized and nonmineralized rocks in the Bathurst Mining Camp: implications for airborne conductivity interpretation
AuthorKatsube, T J; Keating, P B; Connell, S; Best, M E; Mwenifumbo, C J
SourceMassive sulfide deposits of the Bathurst Mining Camp, New Brunswick, and northern Maine; by Goodfellow, W D (ed.); McCutcheon, S R (ed.); Peter, J MORCID logo (ed.); Economic Geology Monograph vol. 11, 2003 p. 861-877
LinksOnline - En ligne
Alt SeriesGeological Survey of Canada, Contribution Series 2000141
PublisherSociety of Economic Geologists (Littleton, CO)
Mediapaper; on-line; digital
File formatdoc
ProvinceNew Brunswick
NTS21G; 21H; 21I; 21J; 21O; 21P
Lat/Long WENS -68.0000 -64.0000 48.0000 45.0000
Subjectseconomic geology; general geology; geophysics; igneous and metamorphic petrology; metallic minerals; conductivity; conductivity surveys; e m surveys; resistivity; resistivity surveys; electrical resistivity; mineralization; magnetic surveys, airborne
Illustrationsgeological sketch maps; magnetic maps; magnetic anomaly maps; tables; cross-sections, stratigraphic; photographs; schematic diagrams; stratigraphic columns
ProgramCanada-New Brunswick Exploration Science and Technology (EXTECH II) Initiative, 1994-1999, Bathurst Mining Camp
AbstractMany linear conductivity anomalies have been identified by airborne electromagnetic surveys in the Bathurst Mining Camp, New Brunswick, Canada. In addition, significant electrical anisotropies (>1,000/1) were reported for rock samples from the Bathurst Mining Camp, with conductive directions displaying low electrical resistivities (pr) well within the detection limit (<10 m) of airborne electromagnetic survey systems and directions displaying high pr values exceeding those limits (>1,000 omegam). A study has been carried out to determine the electrical resistivity characteristics of mineralized and nonmineralized rocks from the Bathurst Mining Camp and their implication on airborne electromagnetic interpretation. This study consists of laboratory three-dimensional electrical resistivity measurements and scanning electron microscope analysis. The results are then extrapolated to downhole resistivity logging and airborne electromagnetic survey scales of investigation.
Results indicate that the Bathurst Mining Camp rocks consist of thin layers of electrically resistive to conductive minerals, resulting in high and low pr values in directions parallel and perpendicular to bedding or foliation, respectively. The low pr layers are divided into three categories: good conductors (category I: <10 omegam), with a clear indication that the conductivity is due to thin sulfide layers; conductive rocks (category II: 10-100 omegam), with an indirect indication that the conductivity is due to graphitic layers; and moderate conductors (category III: 100-1,000 omegam), with strong indications that the conductivity is due to good pore-fluid connection in fine-grained material. An analysis, using a multiple equivalent circuit method for extrapolating laboratory results, concluded that the low resistivity zones (<10 omegam) seen in the downhole electrical resistivity logs and the many significant (>10 mS/m) and moderate (1-10 mS/m) airborne electromagnetic linear conductive features could be explained by the category I conductors. However, resistivities of the category II (graphitic layers) rocks were low enough to also be a source of airborne electromagnetic linear conductors. Since the thin sulfide layers are likely to be associated with horizons of ancient hydrothermal activity, the airborne electromagnetic linear features due to category I rocks may not be exploration targets in themselves, but they delineate horizons in which massive sulfide bodies may exist. The airborne electromagnetic linear conductors due to category II rocks, on the other hand, are not expected to be closely associated with massive sulfides although many deposits are hosted by carbonaceous sedimentary rocks.

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