The Grum deposit is one of eight stratiform shale-hosted massive zinc-lead-barite mineral deposits located in the Anvil Range, Yukon. Host sediments were deposited in a Lower Cambrian extensional basin within a trailing margin miogeoclinal wedge. During the Mesozoic, the ore deposits and their host sediments underwent lower greenschist grade metamorphism and complex deformation related to intrusion of the Cretaceous anvil batholith.

The Grum deposit consists of two sulfide horizons which were isoclinally folded into a first phase fold closure that was subsequently refolded into recumbent S-shaped second phase folds plunging to the northwest. The southeastern section of the deposit is disrupted by both steep and low angle faults.

Sulfide deposits occur at a stratigraphic transition between non-calcareous

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phyllites of the Hadrynian to Lower Cambrian Mt. Mye Formation and the Lower Cambrian to Lower Ordovician calcareous phyllites of the Vangorda Formation.

The Grum deposit is similar to other Anvil deposits and can be divided into four major ore facies. These occur in stratigraphic succession from a basal and marginal "ribbon-banded" graphitic quartzite (representing both sedimentary and hydrothermal inputs) upward through pyritic quartzites, massive pyritic sulfides, and finally baritic massive sulfides and sulfates. This zonation is well developed in one of the sulfide horizons at Grum, and could be caused by increasing ^florinO₂ and pH or by decreasing temperature. A sericitized alteration envelope incompletely surrounds the ore horizons and is related to ore fluid influx. Deposition most likely occurred in localized sea-floor deeps from anoxic hydrothermal brines.

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