Borehole geophysical logs and physical property table for massive sulphide deposits in the Cordillera, British Columbia, including logs from the Buttle Lake, Chu chua, Equity Silver, Goldstream, Highland Valley, Lara and Sullivan deposits

Killeen, P G; Mwenifumbo, C J; Elliott, B E

doi:10.4095/204900

Cited by 2 publications

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“…Three Geological Survey of Canada geotechnical boreholes described in Open File 2610 (Killeen et al 1995)…”

Section: Geotechnical Boreholesmentioning

confidence: 99%

“…The associated GSC report attributes these low resistance values to conductive minerals such as sulphides, oxides, and graphite. In the case that these minerals are absent or less abundant, the low resistances are attributed to porosity, degree of fracturing, and pore water salinity and saturation (Killeen et al 1995). It is likely that bedrock with a lower resistivity exists within the survey site that is indistinguishable from overburden and vice versa, such as a porous limestone and tuff, see table 2.2.…”

Section: Discrimination Between Overburden and Bedrock Resistivitymentioning

confidence: 99%

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Correcting airborne gravity data for overburden thickness using airborne transient electromagnetic data

Caron¹

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A new methodology is presented that corrects gravity data for lateral changes in overburden thickness through the creation of a bedrock topography (BedTopo) map. The methodology results in a Bouguer anomaly map where bathymetry, overburden thickness, and bedrock are reduced to a reference datum. This methodology applies to airborne, ground, and gravity gradiometry surveying. Also presented is a working methodology for inverting helicopter transient electromagnetic (HTEM) survey data to resolve the overburden-bedrock contact using discrete layered-earth modelling in a highland terrain for the purpose of creating a BedTopo map. A study site with a glacial overburden within the Nechako Plateau of British Colombia, Canada is used as a case study. AeroTEM III HTEM survey data is inverted using BC Wells water well data, which provides ground-truth to guide inversion. Water well inversions show that the HTEM methodology can estimate the depth of bedrock with an sRMS % error of 61% of the total thickness indicated by the water wells. The HTEM methodology was found to be inaccurate in areas where 3D topography effects are prominent and over areas where a conductive anomaly is hosted within the bedrock. AeroTEM III HTEM survey data is inverted in order to create a BedTopo map. AIRGrav gravity data is reduced using digital elevation model, BedTopo, and bathymetry data in order to create a BedTopo corrected Bouguer anomaly map of the study site. Inversion results of the study site used 4-and 5-layer models with results showing that overburden varies in thickness from 0 to 265 m, with an average of 35 m, and an inverted i resistivity that ranges from 3 to ~680 Ω•m. Bedrock resistivity ranged from 0.5 to over 10,000 Ω•m. An analysis and comparison of Bouguer anomaly maps with and without a BedTopo correction was conducted. Results show that variations in overburden thickness that are < 30 m may not be detectable by an airborne gravimeter system due to GPS noise, and that overburden thickness variations >100 m, which create anomalies larger than 3 mGal, if not considered may contribute to interpretation errors on a Bouguer anomaly map. This dissertation would not have been possible without the guidance and the help of several individuals, and group of individuals, who in one way or another contributed and

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“…Three Geological Survey of Canada geotechnical boreholes described in Open File 2610 (Killeen et al 1995)…”

Section: Geotechnical Boreholesmentioning

confidence: 99%

Section: Discrimination Between Overburden and Bedrock Resistivitymentioning

confidence: 99%

Correcting airborne gravity data for overburden thickness using airborne transient electromagnetic data

Caron¹

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Correcting airborne gravity data for overburden thickness: a case study from the Nechako interior plateau, British Columbia

et al. 2019

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Large areas of bedrock in Canada, such as in the interior plateau of British Columbia, are covered by a thick glacial overburden. Lateral variations in overburden thickness can create spurious anomalies in gravity data. These anomalies can be of a size and amplitude similar to those associated with mineral bodies and can be mistaken for them. A methodology is introduced that corrects gravity data for changes in overburden thickness through the use of a bedrock topography map created by integrating information from a helicopter transient electromagnetic survey with geological survey data, well water data, and gravel pit locations. The approach is tested for a 68 km × 38 km area in the prospective Nechako interior plateau of British Columbia, Canada. The methodology extends the traditional Bouguer corrections by taking into account the gravitational contribution of the overburden. Results show that the capability of an airborne survey to detect a change in overburden thickness depends primarily on survey line spacing and to a lesser extent on the level of random noise in the gravity data. The bedrock topography correction has the capability of removing the gravitational attraction of overburden for the purpose of revealing, through interpretation, geological structures in the gravity data that originate from the bedrock and are otherwise concealed.

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Borehole geophysical logs and physical property table for massive sulphide deposits in the Cordillera, British Columbia, including logs from the Buttle Lake, Chu chua, Equity Silver, Goldstream, Highland Valley, Lara and Sullivan deposits

Cited by 2 publications

References 0 publications

Correcting airborne gravity data for overburden thickness using airborne transient electromagnetic data

Correcting airborne gravity data for overburden thickness using airborne transient electromagnetic data

Correcting airborne gravity data for overburden thickness: a case study from the Nechako interior plateau, British Columbia

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