Agnico Eagle Mines Ltd owns 100% of the Holt Complex, which includes three mines, the Taylor mine, Holt mine and Holloway mine, as well as the Holt mill.
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Summary:
At Holt-Holloway, the deposit is a mafic volcanic hosted where the gold mineralization is quite unlike the classical Superior province auriferous quartz vein systems resulting from deformed, extensional fracture arrays. Rather, it is associated with disseminated sulphides in altered rock, sometimes described as replacement mineralization. Mineralization typically consists of moderately to steeply dipping tabular zones of disseminated pyrite (generally less than 5 per cent per volume) and gold in intensely altered tholeiitic basalt, with variably developed microveinlet stockworks. The ore is gold rich (Au:Ag is greater than 5) and contains concentrations of arsenic. The mineralized zones occur in a variety of geological settings reflecting a variety of controls on the localization of the mineralization: along low-strain lithological contacts (Lightning, Blacktop and Lightning Deep zones at Holloway), along brittle and/or ductile faults (McDermott, Worvest and Mattawasaga zones), and as shallowly dipping discordant zones (Tousignant, South Zone and Zone 4) of which the South Zone (Holt) is spatially coincident with an array of shallowly dipping syenitic dykes.
Mineralized zones are coincident with zones of intense albite-ankerite alteration of the host basalt, which, in turn, are partly fringed by sericite alteration haloes at Holloway and fringed by broader zones of calcite alteration. Disseminated specular hematite can be present within or outboard of mineralized zones.
Gold mineralization at the Holt and Holloway Mines is associated with replacement carbonate pyrite-albite-quartz alteration that overprints mafic volcanic rocks in, and adjacent to, D3-D4 high strain zones. The overprinting of multiple mineralization phases in the same area suggests that mineralization was long lived and spanned syntectonic deformation during exploitation of the same fluid channel ways.
The deposit types vary within the Taylor Mine Complex. The Shaft Deposit furthest east is identified as a Felsic intrusive related model, with a contemporaneous green carbonate association. Feldspar porphyritic intrusions are the host to high grade gold veins and high concentrations of disseminated sulphides (generally pyrite).
Within the West Porphyry Deposit, free gold is found within quartz dominant extension veins and veinlets, cross-cutting the foliation present within the chrome-mica and chloritic altered ultramafic rock. This unit can be up to 20 m thick as the true extent of the veins are not fully understood. Additionally, the main shear (interpreted to be the contact of the PDF between the mafic and sediment contact, is host to a quartz brecciated shear vein, which can be up to 2m thick. Altered mafic units consisting of high concentrations of disseminated sulphides are also host to gold mineralization.
The Taylor Mineralization is in close proximity, within the hanging wall, to the PDF. Over a strike length of 2.3 kilometres there are three mineralization zones that have been identified. From east to west these are:
- The Shaft Deposit, with gold mineralization associated with felsic intrusive rocks.
- The West Porphyry Deposit (WPZ), a system of stacked lenses, with the gold mineralization associated with felsic intrusive and altered mafic-ultramafic rocks (Green Quartz Carbonate).
- The Shoot Deposit, with gold mineralization hosted by argillaceous metasedimentary rocks within a package of green quartz carbonate. Gold commonly occurs as relatively coarse-sized free gold in quartz, but also occurs as fine particles, which may be intimately associated with sulphides (particularly pyrite and locally, arsenopyrite) both in quartz-carbonate veins or in surrounding altered host rocks.