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TitleElucidating the effects of hydrothermal alteration on seismic reflectivity in the footwall of the Lalor volcanogenic massive sulfide deposit, Snow Lake, Manitoba, Canada
AuthorSchetselaar, E; Bellefleur, G; Hunt, P
SourceMinerals vol. 9, no. 6, 384, 2019 p. 1-23, https://doi.org/10.3390/min9060384 (Open Access)
Year2019
Alt SeriesNatural Resources Canada, Contribution Series 20190160
PublisherMDPI AG
Documentserial
Lang.English
Mediapaper; on-line; digital
File formatpdf (Adobe® Reader®); html
ProvinceManitoba
NTS63K/16
AreaSnow Lake
Lat/Long WENS-101.0000 -99.5000 55.0000 54.5000
Subjectseconomic geology; geophysics; mineralogy; geochemistry; Science and Technology; mineral exploration; mineral deposits; volcanogenic deposits; sulphide deposits; hydrothermal alteration; geophysical surveys; seismic reflection surveys; seismic waves; p waves; seismic velocities; geophysical logging; host rocks; bedrock geology; structural features; faults; lithology; igneous rocks; volcanic rocks; felsic volcanic rocks; mafic volcanic rocks; metamorphic rocks; metamorphic facies; almandine amphibolite facies; greenschist facies; lithogeochemistry; mineralogical analyses; mineral assemblages; cordierite; x-ray emission spectroscopy; scanning electron microscope analyses; modelling; core samples; Lalor Deposit; Paleoproterozoic; Trans-Hudson Orogen; Chisel Basin; volcanogenic massive sulphide deposits (VMS); acoustic impedance; seismic wireline logs; Precambrian; Proterozoic
Illustrationslocation maps; geoscientific sketch maps; tables; schematic diagrams; plots; photomicrographs; bar graphs; models; seismic profiles
ProgramVolcanic and sedimentary systems - volcanogenic massive sulphide ore systems, Targeted Geoscience Initiative (TGI-5)
Released2019 06 25
AbstractThe integrated analysis of seismic rock properties, lithogeochemical data, and mineral compositional data, estimated via scanning electron microscopy-energy dispersive X-ray spectroscopy (SEM-EDS), provides insight into the effects of hydrothermal alteration on seismic reflectivity in the footwall of the Lalor volcanogenic massive sulfide (VMS) deposit, Manitoba, Canada. The effects of hydrothermal alteration on variations in acoustic impedance are secondary in magnitude and superimposed on the dominant acoustic impedance contrast between felsic and mafic volcanic protoliths. This secondary effect is due to an increase in P-wave velocity with increasing intensity of hydrothermal alteration, as measured by the Ishikawa and Carbonate-Chlorite-Pyrite alteration indices. Mixture modeling of the seismic rock properties and mineral percentages suggests that the increase in seismic velocity is due to an increase in abundance of cordierite, which is one of the diagnostic aluminum silicates for hydrothermally-altered volcanic rocks metamorphosed in the upper almandine amphibolite facies. The synthetic seismic data of a simple VMS model consisting of mafic-felsic host rock contacts, a sulfide ore lens, and a discordant hydrothermal conduit, consisting of the amphibolite-facies mineral assemblage (600 ºC, 6 kbar) encountered at Lalor, show enhanced seismic reflections at conduit-host rock contacts, in comparison to its greenschist facies equivalent (350 ºC, 2.5 kbar). This zone of enhanced seismic reflectivity in the footwall of the massive sulfide ore zone is also recognized on the Lalor seismic data suggesting that high-grade terrains hosting VMS deposits possess enhanced potential for the seismic detection of their footwall hydrothermal alteration zones.
Summary(Plain Language Summary, not published)
This paper presents integrated analyses of seismic, geochemical and physical rock property data that provides evidence for the seismic detection of hydrothermally-altered rocks in the footwall of the Lalor volcanogenic massive sulphide deposit.
GEOSCAN ID315051