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TitreSeismic properties of rocks affected by hydrothermal alteration: a case study from the Lalor Lake VMS mining camp
AuteurMiah, K; Bellefleur, G; Schetselaar, E
SourceAmerican Geophysical Union (AGU) Fall Meeting 2013, abstracts; MR13A-2228, 2013 p. 1
LiensOnline - En ligne
Séries alt.Secteur des sciences de la Terre, Contribution externe 20140412
RéunionAGU 2013 Fall Meeting; San Francisco; US; décembre 9-13, 2013
Mediaen ligne; numérique
Lat/Long OENS-100.5000 -100.0000 56.0000 55.7500
Sujetsétablissement de modèles; gîtes sulfureux; gîtes volcanogènes; minéralisation; altération; interprétations géophysiques; interpretations sismiques; gisements minéraux hydrothermaux; altération hydrothermale; géophysique; minéraux métalliques; Précambrien
ProgrammeÉtude des gîtes de sulfures massifs volcaniques, Initiative géoscientifique ciblée (IGC-4)
Résumé(disponible en anglais seulement)
Global demand of base metals, uranium, diamonds, and precious metals has been pushing technological barrier to find and extract minerals at higher depth, which was not feasible in just a few decades ago. Seismic properties of rocks containing and surrounding ore bodies have been useful in characterizing and modeling geologic structures, and mapping high-resolution images of ore bodies. Although seismic surveys and drill hole sonic and density logs are essential for mineral exploration at depth, limited availability of seismic logs to link rock properties of different ore forming geologic structure is a hindrance to seismic interpretations. Volcanogenic Massive Sulphides (VMS) are rich in minerals and of primary interests among geologists and mining industries alike. VMS deposits occur due to focused discharge of metal-enriched fluids associated in the hydrothermal alteration process, and are rich in Zn, Cu, Pb, Ag, Au, etc. Alteration halos surrounding ore deposits can be widespread, and their locations are easier to determine than the deposits within them. Physical rock properties affected by alteration can provide clues on type and potentially size of ore deposits in the surrounding area. In this context, variations in seismic properties of rocks due to hydrothermal alteration near the deposits can help in improving modeling accuracy, and better interpretation of seismic data for economic mineral exploration. While reflection seismic techniques can resolve ore bodies at higher depths than other conventional geophysical techniques, they are relatively expensive both in terms of field data acquisition and post-processing, especially for high-resolution 3D surveys. Acoustic impedance contrasts of ore lenses with their hosting rock environment; geometry, size and spatial location relative to the surface affect their detection with seismic data. Therefore, apriori knowledge of seismic rock properties from drill hole logs and core samples in the potential survey area are essential to determine whether any 2D/3D active survey would be worth conducting. In situ density and velocity logs, and thus, acoustic impedance provide first order control on reflectivity of various lithologies. In this abstract, we analyzed well logs from 12 drill holes geographically located in the northern Manitoba, Canada, in an attempt to characterize lithologies based on their seismic properties. Velocities, density, acoustic impedance and Poisson's ratio of major lithologies were compared among each other. Massive sulphide and Diorite have higher average acoustic impedance than the others. Our quantitative analysis suggests that alteration has considerable effect on overall acoustic impedance of Argillite, Felsic Volcanic and Stringer Sulphide rocks. This can be useful in selecting values of model parameters for seismic wave propagation simulation, which can be used to compare with seismic survey data. In addition, core sample analysis from the same drill holes aided our understanding of mineralization, alteration, and overall composition of different rocks under consideration.