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Holt Mine

The Holt Mine is a reliable producer with a long history of reserve replacement

Quick Facts

Holt Shaft

Location Matheson, Ontario
Mine type Underground, access by shaft
2018 Production 67,770 ounces
Deposit type Sulphide replacement - Mafic Volcanic
Process Ore is processed at the Holt Mill
End product Gold doré
Infrastructure Holt Mill, 3,000 tpd capacity; Holt Shaft, 1,500 tpd hoisting plant capacity
Commenced Operation August 1988
Resources & Reserves

Holt Mine Overview

The Holt Mine was originally built and operated by Barrick in the late 1980’s. The mine has a long history of reserve replacement. Approximately 85% of the current reserves are situated in three zones: Zone 4, Zone 6 and Zone 7.

Kirkland Lake Gold completed the acquisition of St Andrew Goldfields Ltd. in January of 2016, which included the Taylor, Holloway, Holt and Hislop mines and a milling facility on the Holt property.

Operating Data

Empty 2018  2017 20161
Gold produced (oz) 67,770
66,677 57,086
Ore processed (tonnes) 471,819
462,987 416,048
Gold grade (g/t) 4.7
4.7 4.52
Recovery (%) 94.6
94.8 94.5

(1) - Represents operating data for the entire 12-month period ended December 31, 2016, including the period of January 1, 2016 to January 25, 2016 prior to the acquisition of St Andrew Goldfields Ltd. (“SAS”) by KLG on January 26, 2016

Mining Method & Processing

Mining at Holt is primarily conducted using Long Hole Stoping with cemented rock fill. A 1.2 km deep shaft provides skipping capacity of 1,500 tpd. Currently, approximately 85% of the mining activities takes place in Zone 4 and 6, with development towards Zone 7, in anticipation of starting production in 2018. Ore hoisted from the Holt Mine is conveyed directly to the Holt Mill via a series of 1,000 tonnes to 3,000 tonnes storage bins.

The Holt Mill is one of the most efficient gold mills in the region with a capacity of 3,000 tpd, of which approximately 1,500 tpd are supplied from the Holt Mine and a little under 700 tpd from the Taylor Mine, representing a 75% utilization rate.

The Holt Mill was constructed in 1988, originally designed for a throughput of 1,360 tpd. Expansions in 1988 and 2001 increased the throughput to 2,500 tpd and 3,000 tpd respectively.

Surface ore storage totals 4,900 tonnes in three bins. There is a grinding circuit, two cyclone cluster circuits, a thickener, and a Carbon-in-Leach (CIL) circuit within the plant facilities.

Precious metal stripping is performed in batch. Carbon is transferred to an adsorption column where a Zadra process is utilized as the gold elution method. Barren solution is circulated through two shell and tube heat exchangers and a 360 kW electric inline heater. The resulting pregnant solution is pumped from the solution tank to an electrowinning cell. The gold precipitate is further refined using a 125 kW inductotherm furnace.

Geology & Mineralization

The Holt Mine Complex is a mafic volcanic, sulphide replacement hosted gold deposit. The mineralized zones are structurally controlled by both the McDermott Fault and the Ghostmount Fault Zone, which are splays off of the Porcupine-Destor Fault (PDF). Unlike other quartz vein hosted deposits in the region, native gold at the Holt Mine occurs as very fine grains spatially associated with pyrite, typically located in fractures, on grain boundaries, or encapsulated in pyrite grains. Zone thickness can widen from less than 10 metres to locally more than 50 metres. Historically, mined zones include the South (Zone 4), C-104, McDermott, Worvest/Three Star, Mattawasaga, and C-97 zones, which occur over a strike length of three kilometres and have been mined to depths of over one kilometre below surface. More recently, the bulk of the existing gold mineralization is located within Zone 4, Zone 6, Zone 7 and C zones.

The mineralized zones at the Holt Mine display two pronounced shoot plunges: (a) moderate to steep east plunges that outline the major zones, and (b) alignment of zones and small mineralized shoots along shallow west plunging axes.

Exploration at Holt

Underground exploration at Holt is focused on two primary areas: above Zone 4 to the west in an area known as V93 and NBS as well to the East between Zone 6 and Zone 7. In 2017, drilling is targeting Zone 4 to the east, and between the Mattawasaga Zone (east of Zone 6) and Zone 7. Drill results to date indicate that Zone 7 will be a major driver of future production at the Holt Mine, contributing approximately 500 tpd to Holt Mine mill feed. Zone 7, which is accessed from the 435 Level, is located approximately 400 m east of the Holt Mine workings along the Ghostmount Fault Zone and two km southeast of the Holloway production shaft.