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Holloway-Holt (Holt McDermott) |
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Ontario, Canada |
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Au
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Super Porphyry Cu and Au
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IOCG Deposits - 70 papers
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All papers now Open Access.
Available as Full Text for direct download or on request. |
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The Harker Holloway district, which lies to the NNE of Kirkland Lake, is largely defined by the Holloway and Holt McDermott mines, subsequently amalgamated as the Holloway-Holt operation, which are centred on the major Destor-Porcupine Fault with which the Timmins-Porcupine deposits 120 km to the west, are also associated (#Location: 48° 31' 8"N, 79° 44' 31"W).
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 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 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 orebodies at the two deposits 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 Holloway deposit is hosted by the 30 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. Mineralisation occurs where a 200 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 ENE trends from east to WNW trends that are more typical at the property scale. Mineralisation in the Holloway Mine comprises the Lightning, Middle, and Blacktop zones, which are replacement carbonate-quartz-albite-pyrite zones developed adjacent to and within the high strain zones that overprint earlier formed albite-hematite alteration that preferentially replaces variolitic flow units (from St Andrews Goldfields Limited website).
The Holt McDermott mine to 2004, this mine was owned by Barrick Gold Corp who controlled 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 to 2006, the mine was 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.
In 2004, Newmont acquired Holt McDermott, and in 2006 sold both mines to St Andrews Goldfields Limited (SAS)
Remaining resources at the Holloway-Holt project at December 31, 2013 were (SAS, 2014):
Measured + indicated resource 3.460 Mt @ 4.07 g/t Au
Inferred resource - 3.279 Mt @ 4.59 g/t Au.
The most recent source geological information used to prepare this decription was dated: 2001.
This description is a summary from published sources, the chief of which are listed below.
© Copyright Porter GeoConsultancy Pty Ltd. Unauthorised copying, reproduction, storage or dissemination prohibited.
Holloway
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Ropchan J R, Luinstra B, Benn K, Ayer J, Berger B, Dahn R, Labine R, Amelin Y, Fowler A D 2002 - Host rock and structural controls on the nature and timing of Gold mineralization at the Holloway Mine, Abitibi Subprovince, Ontario: in Econ. Geol. v97 pp 291-309
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Porter GeoConsultancy Pty Ltd (PorterGeo) provides access to this database at no charge. It is largely based on scientific papers and reports in the public domain, and was current when the sources consulted were published. While PorterGeo endeavour to ensure the information was accurate at the time of compilation and subsequent updating, PorterGeo, its employees and servants: i). do not warrant, or make any representation regarding the use, or results of the use of the information contained herein as to its correctness, accuracy, currency, or otherwise; and ii). expressly disclaim all liability or responsibility to any person using the information or conclusions contained herein.
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