New publications: Open File 2010-09 and Geoscience Map 2011-2

Notice: Canadian Journal of Earth Sciences Special Issue released

BCGS Open File 2010-09: Geochemical Pathfinders to Drift Covered Copper-gold Sulphide Mineralization in central British Columbia

R. Lett

Open File 2010-9 describes soil geochemical orientation surveys over the Mouse Mountain and Shiko Lake porphyry Cu-Au mineral occurrences and two other areas near Soda Creek and Alexandria. Bedrock in this part of British Columbia between Williams Lake and Quesnel is mainly glacial sediment covered and consists of Mesozoic-age rocks overlain by younger plateau basalts. The primary aim of the soil sampling was to examine the soil geochemical expression of porphyry Cu-Au and related sulphide mineralization in drift and barren bedrock covered areas. In each survey area samples from different soil horizons were analysed for multi-elements by a range of techniques including instrumental neutron activation (INAA), aqua regia-inductively coupled mass spectrometry (aqua regia-ICPMS), Mobile Metal Ion leach (MMI) TM, Enzyme LeachSM, BioLeachSM and Soil Gas Hydrocarbons (SGH) and for soil pH and loss on ignition (LOI). Gold and other mineral grains were also identified and counted in the heavy mineral concentrate of C soil horizon samples.

Gold, Cu, Mo and V soil anomalies outlined by soil sampling over the Mouse Mountain and Shiko Lake mineral properties are most likely caused by minerals entrained in a till deposited down-ice from bedrock hosted sulphide mineralization. Copper, Au, Ni and V by aqua regia-ICPMS show greatest anomaly contrast in the C soil horizon compared to the B and F-H horizons whereas Ag and Mo are more elevated in the F-H organic horizon. The number and relative shape of Au grains in the C soil sample heavy mineral concentrates complements the soil geochemistry in locating a buried bedrock source for the minerals. Comparison of SGH, multi element and pH patterns in the soil at Mouse Mountain and Shiko Lake suggest that the geochemistry may have been modified by a reduced chimney induced by oxidizing sulphides in bedrock. A model developed by interpreting all of the geochemical data displays the most likely relationship between the bedrock, drainage and soil geochemistry in areas where bedrock is concealed beneath a till veneer.

Geoscience Map 2011-02: Geology, Geochronology, Lithogeochemistry and Metamorphism of theQuatsino-Port McNeill Area, Northern Vancouver Island (NTS 092L/11, and parts of 092L/05, 12 and13)

G.T. Nixon, J.L. Hammack, V.M. Koyanagi, G.J. Payie, A.J. Orr, J.W. Haggart, M.J. Orchard, E.T.Tozer, R.M. Friedman, D.A. Archibald, J. Palfy and F. Cordey

Geoscience Map 2011-2 (1:50 000-scale) is the second in a series of five new geological maps (Geoscience Maps 2011-1 to 2011-5) of northern Vancouver Island which together provide a revised Early Mesozoic stratigraphic framework and Mesozoic-Tertiary plutonic history for southern Wrangellia. Geoscience Map 2011-2 describes the geology, geochronology, lithogeochemistry and metamorphism of the Quatsino – Port McNeill area (NTS 092L/11 and parts of 092L/05, 12 and 13). The map area is underlain by a folded and faulted sequence of Late Triassic to Middle Jurassic volcanic and sedimentary rocks of the Vancouver and Bonanza groups intruded by granitoids of the Early to Middle Jurassic Island Plutonic Suite. The deformed Triassic-Jurassic rocks are unconformably overlain by Cretaceous marine clastics and cut locally by Tertiary dikes and minor intrusions. Middle Jurassic intrusions of the Island Plutonic Suite (e.g. Rupert Inlet Pluton) are spatially and genetically associated with important calc-alkaline Cu-Au-Mo porphyry-style mineralization at the former Island Copper mine, as well as coeval high-sulphidation, base- and precious-metal epithermal prospects hosted by rhyolitic flows and pyroclastic rocks in the Pemberton Hills – Mount McIntosh area to the west (Geoscience Map 2011-1). Intriguingly, a dyke similar to the one associated with mineralization at Island Copper extends over 5 km east of the Rupert Inlet Pluton beneath a thick cover of glacial drift, as inferred from geophysical surveys, and remains to be drill-tested. A major, westerly-trending fault zone, the Holberg Fault, exposed in cliffs on the headland between Rupert and Holberg inlets, separates well-mineralized, Middle Jurassic intrusions and the largely coeval Holberg volcanic unit of the Bonanza Group from their Early Jurassic counterparts to the south. Radical changes in lowermost Jurassic stratigraphy are also evident across this structural corridor: a thick, predominantly subaerial, volcanic-volcaniclastic sequence (Le Mare Lake volcanic unit) south of the Holberg Fault largely correlates with a more condensed succession of intercalated, marine sedimentary and volcaniclastic strata north of the fault zone (Nahwitti River siltstone-wacke unit and lower part of the overlying Holberg volcanic unit). In the eastern part of the area, outliers of Neogene Alert Bay volcanic rocks rest unconformably on a downdropped block of Upper Cretaceous sedimentary strata of the Nanaimo Group. Regional metamorphism is generally characterized by very low-grade mineral assemblages (prehnite-pumpellyite to zeolite facies) except in the vicinity of faults and intrusive contacts where the rocks may reach upper greenschist to amphibolite grade, respectively.

Canadian Journal of Earth Sciences Special Issue on “New Insights in Cordilleran Intermontaine Geoscience: Reducing Exploration Risk in the Mountain Pine Beetle-Affected Area of British Columbia

The June issue of Canadian Journal of Earth Sciences is a Special Issue which presents a summary of geoscience research and investigations designed to address the negative economic impacts of the current mountain pine beetle infestation by attracting mineral and oil and gas exploration.

The Geoscience for Mountain Pine Beetle programs were cooperatively led by Geological Survey of Canada, Geoscience BC, and the British Columbia Ministry of Energy and Mines, each drawing on their area of experience and expertise. Geoscience program components included using geophysics to see through the locally extensive cover of volcanic and glacial deposits, as well as augmenting the existing regional geoscience knowledge base with new baseline geology, mineral deposits, and geochemistry data.

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Release Notification 2011-11

July 28, 2011