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Mount Hinton: Overview
The Mount Hinton property is located in the Mayo mining district of central Yukon and in the southeast part of the world-famous Keno Hill silver mining camp. The Keno Hill Camp is situated in the central part of the 550 km long Tombstone Gold Belt, a region of silver and gold mineralization in Alaska and Yukon related to mid-Cretaceous intrusions called the Tombstone Plutonic Suite.
The Mount Hinton property is situated within the eastern part of the Keno Hill mining camp, a district that hosts more than 35 individual mines and is historically Canada's second largest primary silver producer. Although silver mineralization is found in veins on the Mount Hinton property, gold is the most significant component in many of the 72 bedrock showings and float occurrences that have been discovered on the property by previous operators. Creeks draining the property have yielded significant placer gold production and are still being mined.
The Mount Hinton property is directly accessible by a 10 km all-weather road from Keno City and consists of two claim blocks that total 400 mineral claims and cover 82 sq km. The Yukon's hydroelectric power grid extends to Alexco Resource Corp.'s Bellekeno deposit, which is located 3 km north of the Mount Hinton claim block and lies along a road system that accesses the northern part of the Mount Hinton property.
Rockhaven acquired an option to purchase a 100% interest in the Mount Hinton property (News Release dated March 8th, 2010) by making cash payments totaling $500,000 over a three year period to an arm's length syndicate.
Mount Hinton: Geology
Simplified geological map of the western Selwyn Basin showing the main tectonic features, location of Tombstone intrusions important gold prospects (boxes) and Mount Hinton gold vein property (modified after Stephens et al., 2004).
The Mount Hinton property lies along the southwest margin of Selwyn Basin, a region of deep water, off shelf sedimentation that persisted from late Precambrian to Middle Devonian time. The property is largely underlain by interbedded Mississippian phyllitic quartzite, chloritic and carbonaceous phyllite and massive to well foliated quartzite with lesser limestone (Figure 3) of the informally named Keno Hill Quartzite or "Central Quartzite" (Roots, 1997).
Both the Robert Service Thrust Fault and enclosing rocks are intruded by the Roop Lakes Pluton, a 100 km2 elliptical stock that lies about 10 km east of the main area of vein mineralization on the Mount Hinton property. Igneous petrology is dominated by medium grained granodiorite with lesser quartz monzonite.
The Mount Hinton area lies in the southeast part of the Keno Hill mining camp, part of the 550 km long Tombstone Gold Belt. Between 1913 and 1990, 6,657 tonnes (214 million ounces) of silver, 35,000 tonnes of lead and 21,000 tonnes of zinc were extracted from the extensive and numerous vein faults in the Keno Hill area. Average recovered grade was 1373 g/t (40.1 oz/ton) Silver, 6.7% lead and 4.1% zinc (Cathro, 2006).
The Tombstone Gold Belt is coincident with, and genetically related to, mid-Cretaceous plutonism of the 92 Ma Tombstone Plutonic Suite (Hart and Burke, 2002). A 92.8+0.5 Ma age for the Roop Lakes quartz monzonite pluton has been determined by isotopic dating. This age as well as its petrology places the intrusion within the Tombstone Plutonic Suite.
Tombstone Gold Belt proximal mineralization occurs within or adjacent to the mineralizing pluton as replacements, disseminations, stockworks, skarns and discrete veins with a gold-bismuth or tungsten-copper association (Hart and Burke, 2002). Distal mineralization occurs at some distance from the associated pluton either as disseminations or veins that are dominated by a gold-arsenic-antimony-mercury association or a lead-zinc-silver association. Precious metal bearing veins on the Mount Hinton property probably belong to the distal suite.
Mount Hinton: Mineralization
The geological setting and style of mineralization defined to date on the Mount Hinton property are the same as those for the vein faults that supplied silver-lead-zinc ore to a number of successful underground and surface mines in the nearby Keno Hill mining camp.
Two types of vein mineralization are represented in the district (Boyle, 1965). The earliest stage was characterized by deposition of hydrothermal silica, which precipitated as quartz lenses in dilatent zones within northeast trending faults. In addition to this constituent, considerable amounts of sulphur, arsenic, and iron with lesser antimony, lead, copper, gold and silver were introduced. This is the most common type of precious metal mineralization on the Mount Hinton property.
The second type of vein mineralization in the Keno Hill mining camp is a later stage of iron, manganese, sulphur, antimony, lead, zinc, silver and cadmium enrichment hosted by siderite rather than quartz gangue. This style of vein fault is responsible for the bulk of the historical silver-lead-zinc production from the Keno Hill area. Ore shoots comprise less than 2% of the vein faults but this density locally increases to 20% within productive areas. The #1 Vein and the newly discovered 67 Vein are the only showings of this type that have been discovered to date on the Mount Hinton property.
Boyle (1965) notes that the most favourable host rocks for vein formation are thick bedded quartzites and greenstones. The principal economic lodes are located in four structural settings:
- at the junction of two or more vein faults,
- at the junction of a vein fault and offsetting bedding plane fault,
- within or immediately below massive quartzites and greenstones, or
- where the vein faults pass into phyllite or thin bedded quartzite.
As many as 72 mineralized veins, vein segments or discrete mineralized vein float trains have been discovered to date on the Mount Hinton that are believed to belong to the distal suite surrounding the Roop Lakes stock. The known Mt. Hinton veins as well as the Keno Hill silver deposits occur within the Keno Hill Quartzite where brittle failure created major fracture zones for hydrothermal fluids migration and mineral deposition. The Mount Hinton veins consist of fractured milky quartz hosting and (in order of abundance) arsenopyrite, galena, jamesonite, pyrite, sphalerite, siderite and gold as well as weathering products scorodite (after arsenopyrite), limonite (after pyrite) and anglesite (after galena). Mineralized shoots on the veins typically range between 0.2 and 3.0 m wide and grade between 1 and 30 g/t gold, 50 and 1500 g/t silver and 0.5 to 2.5% lead. Maximum grades of 127.5 g/t gold, 30,822 g/t silver, and 75% lead have been returned from rock samples.
Most of the historical work on the Mount Hinton property has been done near ridge crests where steep topography and permafrost have complicated exploration. The broad valleys between ridges have seen little exploration, even though strong soil geochemical anomalies and favourable host rocks are found within those areas. Previous operators identified numerous soil geochemical anomalies and geophysical targets that have not yet been drilled or trenched. Creeks draining Mount Hinton contain anomalous placer gold concentrations. For over 100 years, Duncan Creek and its tributaries Lightning Creek (with its tributary Thunder Gulch) and Upper Duncan Creek draining northern and western parts of the Gustavus Range with Mt. Hinton remain primary placer-producing locations in Yukon indicating the strong possibility of a lode deposit in this area. Both lithologic and structural controls of gold vein occurrences identified for TPS intrusions in general and locally for the Mount Hinton property have to be carefully considered during future exploration. Quartz veins hosted by ENE-trending steeply-dipping transverse fault systems remain the principal target for further investigation. Recent exploration programs of soil sampling, trenching, mapping and detailed prospecting identified several areas of interest that will be the focus of Rockhaven's future exploration programs.
Mount Hinton: 2010 Exploration Results
The 2010 exploration program included the collection of approximately 1600 auger soil samples from three areas on the property: #5 Vein, Granite Creek Basin and #1 Vein.
The #5 Vein is located in the south-central part of the property. Historical work included percussion drilling and excavator trenching within a 100 by 600 m area at the top of a ridge where the vein is exposed at surface. This work identified a 20 m wide structural zone hosting anomalous gold and silver mineralization. The 2010 work outlined a soil geochemical anomaly that extends 1080 m south along strike from the vein exposure in a previously unexplored part of the property. This anomaly is 25 to 100 m wide and features strongly elevated gold (10 to 171 ppb), arsenic (31 to 681 ppm), silver (0.2 to 4.1 ppm), and antimony (4 to 61 ppm) values. Geological mapping and prospecting indicate that the anomaly is associated with brittle rock units, which are particularly favourable for vein development.
The Granite Creek Basin target is situated in a valley immediately northeast of the #5 Vein. This target was originally identified in 1965 when silt samples taken from the valley during a district-wide geochemistry program conducted by the Geological Survey of Canada returned the strongest gold-in-silt anomalies within the Keno Hill mining camp. Despite these very encouraging results, no systematic exploration has been conducted at this target. Auger soil sampling conducted by Rockhaven in 2010 identified a 500 by 600 m soil geochemical anomaly within which 40% of the samples yielded strongly anomalous values between 50 and 3310 ppb (0.05 to 3.31 g/t) gold.
The #1 Vein is located in the eastern part of the property about 4 km northeast of the #5 Vein. Historical work at the #1 Vein consisted of four excavator trenches and two diamond drill holes. Reinterpretation of the geology indicates the holes tested a bedding plane fault, not one of the transverse vein structures which are known to host the most significant vein occurrences in the Keno Hill mining camp. Prospecting by United Keno Hill Mines in 1966 at the #1 Vein discovered galena float boulders grading 30,822 g/t (or 899 oz/ton) silver and 14,400 g/t (or 420 oz/ton) silver. The source of this material has never been located. The best soil sample from 2010 work on this target was collected 600 m northeast of the drill area along the projected trace of the vein structure. It returned 93.2 ppm silver and 1185 ppm lead.
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