Holt

Other Names: Holt McDermott
District: Kirkland Lake
Commodities :   Gold

The Harker Holloway district, which lies to the NNE of Kirkland Lake, is largely defined by the Holloway and Holt McDermott mines which are centred on the major Destor-Porcupine Fault with which the Timmins-Porcupine deposits 120 km to the west, are also associated. These mines are approximately 50 km to the north of the Larder Lake-Cadillac Fault that is the key structure at the Kirkland Lake deposits (see below). In this district the Destor-Porcupine Fault zone is marked by slivers of turbidites and Timiskaming like sediments and separates two contrasting domains of south-dipping volcanic rocks. The Holloway deposit, north of the fault, is within the 2717-2713 Ma mafic and ultramafic flows of the Stoughton-Roquemaure Group, while Holt McDermott, south of the fault is hosted by the 2701 Ma Kinojevis Group Fe-tholeiites.

The rocks adjacent to the Destor-Porcupine Fault are metamorphosed to greenschist facies with a variably developed sub-vertical penetrative foliation and an elongation lineation directed down dip. Volcanics on both sides are cut by a number of steeply south-dipping brittle and/or ductile faults that may be splays of the main structure, while several small syenite dykes are found within the orebody zone at Holt McDermott. The orebodies are typically tabular zones of disseminated, but usually <5%, pyrite and associated micro-veinlet stockworks, all within intensely altered tholeiitic basalt. The localisation of ore is variable, occurring along i). low strain lithological contacts, or ii). shallow dipping discordant zones, while iii). one is spatially coincident with an array of shallowly dipping syenite dykes. Economic gold coincides with intervals of intense albite-ankerite alteration (commonly with disseminated specular hematite), grading out into sericitic halos which in turn become broader surrounding zones of calcite alteration. Sub-horizontal extensional veinlets composed of quartz-calcite±pyrite and scheelite, are found in some orebodies, where they are developed perpendicular to the penetrative foliation. It has been suggested the ore is related to distal hydrothermal activity centred on Timiskaming age (2675-2680 Ma) monzonite-syenite stocks.

The Holt McDermott mine is owned by Barrick Gold Corp who control some 10.67 km of mineralised strike length centred on the McKenna and Ghostmount Faults which are splays of the Destor-Porcupine Fault. The ore is strongly deformed and brecciated and comprises variably silicified, carbonised, albitised and pyritised volcanics bounded by unaltered rock of the same type. Production in 1999 totalled 0.566 mt of ore with an average head grade of 6.4 g/t Au and a metallurgical recovery of 96.1% to produce 3.36 t (0.108 Moz) Au at a total cost of USD234 per oz. Reserves at the end of 1999 were 2.4 mt @ 6.5 g/t Au, amounting to 15.55 t (0.49 Moz) Au.

Holloway is 84.65% owned by the operator, Newmont Canada, the balance being held by Teddy Bear Valley Mines Ltd. Production in 2000 was 3.4 t (0.11 Moz) Au at a total cost of USD 204 per oz. Reserves in 2000 were 4.4 mt @ 6.2 g/t Au plus a resource of 1.4 mt @ 6.2 g/t Au, for a total of approximately 36 t (1.16 Moz) Au. 

(Source: Porter GeoConsultancy, www.portergeo.com.au, 2001)

DM Sample Photographs

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