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:
Regional Geology
The Holloway and Holt mines lie within the Southern Abitibi Greenstone Belt (SAGB) of the Superior Province in north-eastern Ontario. The 40 km long, mostly contiguous HoltHolloway property package is a grouping of strategically located claims straddling the Porcupine-Destor Fault Zone (“PDF”) midway along its 260 km length.
Local Geology
The deformation history of the area is defined by five events. The earliest episode of regional D1 deformation (compression and extension) predated the Porcupine angular unconformity at 2,690 Ma. The D2 event (compression and extension) post-dated the Porcupine assemblage and resulted in localized folding and thrusting and early southside up, dip-slip, ductile deformation on regional deformation zones. Broadly synchronous with the syntectonic opening of the Timiskaming basins in dilatational jogs was D3 folding that resulted in significant left lateral slip movement along the PDF. The D4 folding event created synclines within the Timiskaming assemblage rocks and rightlateral strike-slip displacement along the PDF. The D4-D5 event represents the final stage of transpressional deformation along the PDF. Gold mineralization in the HoltHolloway area is interpreted to be early D3 in age. Lightning Zone replacement mineralization is cut by an inter-mineral dike with an age of 2672 ± 1.9Ma, which is overprinted by a later auriferous quartz-carbonate veining event. The bulk of the gold in the Timmins area was related to late D3 events.
Holloway Property Geology
The Holloway deposit is hosted by the 30 m to 150 m wide Holloway unit, a south dipping band of Fe-tholeiitic mafic volcanic rocks that is bounded to the south and north by south facing turbiditic sedimentary rocks and komatiitic ultramafic volcanic rocks, respectively. Mineralization occurs where a 200 m to 300 m wide corridor of east-northeast trending D2-D3 high strain zones obliquely crosses the Holloway unit, resulting in a deflection in its strike to east-northeast trends, from east to westnorthwest trends that are more typical at the property scale.
DEPOSIT TYPE
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 syn-tectonic deformation during exploitation of the same fluid channel ways.
Holloway
The Holloway deposit is hosted by the 30 m to 150 m wide Holloway unit, a south dipping band of Fe-tholeiitic mafic volcanic rocks which is bounded to the north and south by south facing turbiditic sedimentary rocks and komatiitic ultramafic volcanic rocks, respectively. Mineralization occurs where a 200 m to 300 m wide corridor of east-northeast trending D2-D3 high strain zones obliquely crosses the Holloway unit, resulting in a deflection in its strike to east-northeast trends from east to westnorthwest trends that are more typical at the property scale (Rhys, 2005a). Mineralization in the Holloway Mine comprises the Lightning, Middle, and Blacktop zones.
Lightning Zone
The Lightning Zone is host to by far the largest zone at the Holloway Mine. It comprises a series of generally interconnected lenses of pyritic replacement mineralization localized at and near the northern portions of the Holloway Unit, frequently within variolitic units. Two stages of alteration are evident: pre-mineralization albite-hematite-quartz and syn-mineralization pyrite-quartz-albite-carbonate-sericite. Gold mineralization occurs as native grains associated with fine-grained clustered pyrite occurring as stringers and veinlets, irregular clumps, and dense vein haloes. Quartz veins are generally not mineralized. “Typical” ore contains on average 10 % to 55% clustered pyrite. Gold most often occurs along the pyrite grain boundaries or, less often, along fractures in pyrite grains. Accessory arsenopyrite, chalcopyrite, sphalerite, and scheelite are very minor constituents overall. Gold grain sizes average 5 µm to 9 µm and visible gold is rare.
Middle Zone
Middle Zone In addition to the quartz vein related mineralization associated with the flat faults, a series of north-trending, moderate to steep east-dipping quartz-tourmaline shear veins occurs in the Middle Zone, west of the main Lightning Zone mineralized body. The veins are developed in narrow reverse shear zones and are probably intermediate in age between the Lighting Zone and flat fault related quartz veining episodes. These veins are quartz dominated and contain variable quantities of black tourmaline as ribbons and stylolites. They have auriferous pyritic envelopes and outer sericitecarbonate alteration. The veins are cut by the shallow quartz extension veins associated with the flat faults, and their local development in areas of the Lightning Zone style disseminated mineralization suggests that they overprint it, forming an intermediate mineralizing phase. The veins are affected by open and ptygmatic F3/F4 folds, and by F5 folds, consistent with the earlier timing than the less strained quartz extension veins that cut them. At their northern end at least, the quartz-tourmaline veins penetrate into Lightning Zone style replacement mineralization and split up or dissipate as they enter it.
Blacktop Zone
Located 2.4 km due east of the Holloway shaft, the Blacktop Zone is developed in an east-northeast trending high strain zone, or network of high strain zones, associated with intense S3-S4 development and sericite-carbonate-chlorite alteration of mafic volcanic rocks. As is the case at the Lightning Zone, the area of high strain at Blacktop is associated with an east-northeast trending deflection in the otherwise dominantly east-west to west-northwest trend of lithologies. The Blacktop Zone is a tabular (typically two metres to seven metres thick) and shallow southerly dipping zone which is hosted by and cuts obliquely across the Holloway Unit. The zone may be at least 100 m in strike length. The mineralization coincides with an apparent 20 m to 80 m top to the north (reverse) displacement of the northern contact of the Holloway Unit with ultramafic volcanic rocks, and of subunits internal to the Holloway Unit.