Abstract

The Myra Falls Price deposit is a zinc-rich volcanogenic massive-sulphide ore-body located in a mountainous region of central Vancouver Island, British Columbia. High rainfall and steep hydraulic gradients limit the water–mineral contact, which results in a low solute load in the oxygenated groundwater. Despite this, significant element contrasts exist that permit the development of groundwater geochemical methods for exploration. Zinc displays the strongest and most reliable anomaly contrasts in groundwaters associated with mineralization related to the Price deposit. Statistical procedures are used to differentiate two overlapping subpopulations of Zn concentrations, which are partitioned into two constituent populations. A threshold value of 20 μg/l was established, which includes an uncertainty that allows up to 10% of the background population being defined as anomalous. Zn anomalies can be further enhanced with a suite of pathfinder elements associated with primary mineralization and hydrothermal alteration, including Cu, Pb, Cd, Mn, As, Sb, Ba and U.

In addition to massive-sulphide mineralization, sulphides also exist as clasts within a breccia unit designated as the ore-clast breccia (OCB). Effective discrimination is possible between anomalies in groundwaters associated with massive-sulphide mineralization and groundwaters associated with OCB through the use of elements associated with primary mineralization and hydrothermal alteration such as K, Rb, B, Ba, Cd, Sb, U and barite saturation, which are elevated in groundwaters associated with massive-sulphide mineralization but not the OCB.

Groundwater geochemical exploration methods offer a supplemental tool to exploration of Zn-rich massive-sulphide deposits where existing infrastructure, exploration drifts and drill holes are present.

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