Mercury vapour haloes in near-surface air above ore deposits and faults on Vancouver Island, British Columbia, Canada

Volatile geogenic components, such as CO2, He, Rn, and Hg0, form haloes in soil gas and near-surface air directly above mineral deposits. This contrasts with lithochemical, hydrochemical, and biochemical dispersion haloes that can be laterally displaced or obscured by transported overburden. Mercury vapour surveys have been used in exploration, because Hg occurs in most types of enogenic ore deposit types and is highly mobile. Low background concentrations in the atmosphere (1.2 to 1.5 ng/m3) enable detecting even weak Hg emissions directly above buried ore deposits. In this study, we measured Hg vapour in air 1-50 cm above ground at 15 sites on Vancouver Island, British Columbia, Canada. To evaluate the effectiveness of the method across a range of settings, these sites include different types of known mineralized zones, barren rocks, and faults, both buried and exposed. The direct and continuous analysis via a portable RA-915M mercury analyzer reveals Hg vapour concentrations ranging from 0.5 to 54.4 ng/m3. The highest Hg concentration was observed above tailings at the Bentley Au occurrence, possibly due to the amalgamation technique used for fine gold extraction between late 1800s and early 1900s. Prominent Hg vapour haloes mark shear-hosted Cu-Ag-Au sulphides at Mount Skirt (13.4x background Hg), epithermal Au-Ag-Cu at Mount Washington (8.9x background Hg), and sediment-covered polymetallic volcanogenic massive sulphides at the Lara-Coronation occurrence (4.2 to 6.6x background Hg). Basalt-hosted Cu-Ag-Au sulphide zones at the Sunro past producer are marked by weak Hg vapour anomalies relative to local background. Faults, including the Leech River fault, which was active in the Quaternary, are also marked by weak Hg vapour anomalies. The study confirms that, although the Hg level is influenced by weather, the real-time Hg vapour measurement of near-surface air can instantly delineate mineralized zones and fault structures that are buried under overburden 10s of m thick. In contrast to soil gas sampling, this simple and rapid technique can be applied to mineral exploration and geological mapping under overburden above any type of surface, including outcrops, talus, bogs, water bodies, snow, and permafrost.

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New geoscientific constraints on the hydrocarbon potential of the Nechako–Chilcotin plateau of central British Columbia

Canadian Journal of Earth Sciences ◽

10.1139/cjes-2014-0054 ◽

2014 ◽

Vol 51 (4) ◽

pp. v-ix ◽

Cited By ~ 2

Author(s):

Andrew J. Calvert ◽

Graham D.M. Andrews

Keyword(s):

British Columbia ◽

Large Scale ◽

Mountain Pine Beetle ◽

Geological Mapping ◽

Hydrocarbon Exploration ◽

Special Issue ◽

Near Surface ◽

Mountain Pine ◽

Geophysical Surveys ◽

Pine Beetle

Infestation by the mountain pine beetle, Dendroctonus ponderosae, decimated the forests of central British Columbia from 1999 to 2012, severely impacting the forest industry of the Nechako–Chilcotin plateau. In response, all levels of government recognized the value in developing other areas of economic activity, such as hydrocarbon and mineral exploitation, to support local economies. Exploration for resources beneath the Nechako–Chilcotin plateau has historically been constrained by Tertiary volcanic sequences and Quaternary glacial deposits that obscure the underlying geology and limit geophysical imaging. Thus, a coordinated program comprising additional geological mapping, borehole data analysis, and modern geophysical surveys of the area was initiated in 2006, with the objective of better defining the subsurface geology, solving problems of imaging through the complex near-surface, and developing improved regional geological and tectonic models. An initial set of papers arising from this fieldwork, which focused on issues relevant to mineral and hydrocarbon exploration, was published in June 2011 in a Special Issue of the Canadian Journal of Earth Sciences. This Introduction to the second “Mountain Pine Beetle” Special Issue summarizes a set of scientific papers that focus on topics more related to hydrocarbon exploration and the large-scale structure of the crust. The papers deal with the development, thickness, and present distribution of the most prospective Cretaceous sedimentary rocks, as well as characterizing the physical properties of the near-surface volcanic units.

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Some Characteristics of Nitinat Lake, An Inlet on Vancouver Island, British Columbia

Journal of the Fisheries Research Board of Canada ◽

10.1139/f64-097 ◽

1964 ◽

Vol 21 (5) ◽

pp. 1069-1081 ◽

Cited By ~ 17

Author(s):

T. G. Northcote ◽

Mildred S. Wilson ◽

D. R. Hurn

Keyword(s):

British Columbia ◽

Surface Water ◽

Vancouver Island ◽

Near Surface

The morphometry, temperature, salinity, and oxygen characteristics are described for an inlet on the southwestern coast of Vancouver Island. Although the inlet is over 200 m deep, only the upper 20–30 m (about [Formula: see text] of its total volume) appears to be oxygenated. There are marked changes, both vertically and horizontally, in salinity of near-surface water. All components of the biota observed are either marine, brackish or euryhaline forms.

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Inverse modeling constrained by potential field data, petrophysics, and improved geologic mapping: A case study from prospective northwest Tasmania

Geophysics ◽

10.1190/geo2019-0636.1 ◽

2020 ◽

Vol 85 (5) ◽

pp. K13-K26 ◽

Cited By ~ 1

Author(s):

Esmaeil Eshaghi ◽

Anya M. Reading ◽

Michael Roach ◽

Mark Duffett ◽

Daniel Bombardieri ◽

...

Keyword(s):

Potential Field ◽

Mineral Exploration ◽

Physical Property ◽

Gravity Anomalies ◽

Ore Deposits ◽

Magnetic Data ◽

Contact Aureole ◽

Variable Degree ◽

Near Surface ◽

Potential Field Data

The Heazlewood-Luina-Waratah area is a prospective region for minerals in northwest Tasmania, Australia, associated with historically important ore deposits related to the emplacement of granite intrusions and/or ultramafic complexes. The geology of the area is poorly understood due to the difficult terrain and dense vegetation. We have constructed an initial high-resolution 3D geologic model of this area using constraints from geologic maps and geologic and geophysical cross sections. This initial model is improved upon by integrating results from 3D geometry and physical property inversion of potential field (gravity and magnetic) data, petrophysical measurements, and updated field mapping. Geometry inversion reveals that the Devonian granites in the south are thicker than previously thought, possibly connecting to deep sources of mineralization. In addition, we identified gravity anomalies to the northeast that could be caused by near-surface granite cupolas. A newly discovered ultramafic complex linking the Heazlewood and Mount Stewart Ultramafic Complexes in the southwest also has been modeled. This implies a greater volume of ultramafic material in the Cambrian successions and points to a larger obducted component than previously thought. The newly inferred granite cupolas and ultramafic complexes are targets for future mineral exploration. Petrophysical property inversion reveals a high degree of variation in these properties within the ultramafic complexes indicating a variable degree of serpentinization. Sensitivity tests suggest maximum depths of 2–3 km for the contact aureole that surrounds major granitic intrusions in the southeast, whereas the Heazlewood River complex is likely to have a deeper source up to 4 km. We have demonstrated the value of adding geologic and petrophysical constraints to 3D modeling for the purpose of guiding mineral exploration. This is particularly important for the refinement of geologic structures in tectonically complex areas that have lithology units with contrasting magnetic and density characteristics.

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The plainfin midshipman’s soundscape at two sites around Vancouver Island, British Columbia

Marine Ecology Progress Series ◽

10.3354/meps12730 ◽

2018 ◽

Vol 603 ◽

pp. 189-200 ◽

Cited By ~ 4

Author(s):

WD Halliday ◽

MK Pine ◽

APH Bose ◽

S Balshine ◽

F Juanes

Keyword(s):

British Columbia ◽

Vancouver Island

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Diurnal effects on the helium concentration in soil-gas and near-surface atmosphere

Open-File Report ◽

10.3133/ofr76715 ◽

1976 ◽

Cited By ~ 3

Author(s):

G. Michael Reimer ◽

Alan A. Roberts ◽

E.H. Denton

Keyword(s):

Soil Gas ◽

Near Surface ◽

Helium Concentration ◽

Surface Atmosphere

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Airborne geophysical surveys in Greenland – 1996 update

Geological Survey of Denmark and Greenland Bulletin ◽

10.34194/ggub.v176.5069 ◽

1997 ◽

pp. 75-79

Author(s):

Robert W. Stemp

Keyword(s):

Mineral Exploration ◽

Geological Mapping ◽

Digital Data ◽

Magnetic Survey ◽

Aeromagnetic Survey ◽

West Greenland ◽

South West ◽

Geophysical Surveys ◽

The Government ◽

Airborne Geophysical Data

NOTE: This article was published in a former series of GEUS Bulletin. Please use the original series name when citing this article, for example: Stemp, R. W. (1997). Airborne geophysical surveys in Greenland – 1996 update. Geology of Greenland Survey Bulletin, 176, 75-79. https://doi.org/10.34194/ggub.v176.5069 _______________ Two major airborne geophysical surveys were carried out in 1996, the third year of a planned five-year electromagnetic and magnetic survey programme (project AEM Greenland 1994–1998) financed by the Government of Greenland, and the second year of an aeromagnetic survey programme (project Aeromag) jointly financed by the governments of Denmark and Greenland; both projects are managed by the Geological Survey of Denmark and Greenland (GEUS). The two 1996 surveys were: 1) Project Aeromag 1996 in South-West and southern West Greenland;2) Project AEM Greenland 1996 in South-West Greenland. All areas surveyed and planned for future surveys as of March 1997 are shown in Figure 1. Results of both the 1996 surveys were released in March 1997, as a continuation of a major effort to make high quality airborne geophysical data available for both mineral exploration and geological mapping purposes. The data acquired are included in geoscientific databases at GEUS for public use; digital data and maps may be purchased from the Survey. The main results from the 1996 surveys are described in Thorning & Stemp (1997) and Stemp (1997). Two further new airborne surveys have already been approved for data acquisition during the 1997 field season, with subsequent data release in March 1998. A summary of all surveys completed, in progress or planned since the formal inception of project AEM Greenland 1994–1998 is given in Table 1. The programme was expanded to include a separate regional aeromagnetic survey in 1995, provisionally for 1995–1996, with extension subject to annual confirmation and funding.

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Mineral Physicochemistry Underlying Feature-Based Extraction of Mineral Abundance and Composition from Shortwave, Mid and Thermal Infrared Reflectance Spectra

Minerals ◽

10.3390/min11040347 ◽

2021 ◽

Vol 11 (4) ◽

pp. 347

Author(s):

Carsten Laukamp ◽

Andrew Rodger ◽

Monica LeGras ◽

Heta Lampinen ◽

Ian C. Lau ◽

...

Keyword(s):

Mineral Exploration ◽

Relevant Information ◽

Ore Deposits ◽

Reflectance Spectra ◽

Full Potential ◽

Infrared Reflectance ◽

Vibrational Modes ◽

Diagnostic Features ◽

Wide Range ◽

Mineral Assemblages

Reflectance spectroscopy allows cost-effective and rapid mineral characterisation, addressing mineral exploration and mining challenges. Shortwave (SWIR), mid (MIR) and thermal (TIR) infrared reflectance spectra are collected in a wide range of environments and scales, with instrumentation ranging from spaceborne, airborne, field and drill core sensors to IR microscopy. However, interpretation of reflectance spectra is, due to the abundance of potential vibrational modes in mineral assemblages, non-trivial and requires a thorough understanding of the potential factors contributing to the reflectance spectra. In order to close the gap between understanding mineral-diagnostic absorption features and efficient interpretation of reflectance spectra, an up-to-date overview of major vibrational modes of rock-forming minerals in the SWIR, MIR and TIR is provided. A series of scripts are proposed that allow the extraction of the relative intensity or wavelength position of single absorption and other mineral-diagnostic features. Binary discrimination diagrams can assist in rapidly evaluating mineral assemblages, and relative abundance and chemical composition of key vector minerals, in hydrothermal ore deposits. The aim of this contribution is to make geologically relevant information more easily extractable from reflectance spectra, enabling the mineral resources and geoscience communities to realise the full potential of hyperspectral sensing technologies.

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