The Chisna Project covers an area of approximately 965 km2 in the Chistochina Mining District of south-central Alaska consisting of 1,106 State of Alaska claims and 65,900 acres of land leased from the Ahtna Corporation. The project targets Cretaceous copper-gold porphyry-style mineralization of a similar age to the Pebble deposit located approximately 600 km to the southwest. The target area is a belt 65 km long and 15 km wide extending from Slate Creek, 30 km northeast of Paxson, to Slana on the Tok Cutoff Highway. Access is via aircraft, or winter roads from the Tok Highway near the power corridor.
Originally acquired from AngloGold
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The area has been subject to extensive historical placer gold mining operations and modest historical bedrock exploration efforts. The region has historically produced a total of approximately 200,000 ounces of placer gold, mostly from the Slate Creek area (a Chisna Block target)*. A large number of gold and copper occurrences are known in the area. However, little modern exploration has been done and the lode potential is considered high. Partial historic data indicates that some work was done in the northeast part of the belt (POW target) during the 1980s and in the southeast part of the belt (Grubstake target) during the 1990s.
* This information is not indicative of the mineralization on the Chisna property or the potential production from or any future mining of the Chisna property.
Stream sediment surveying and geological mapping in the Chisna Project area have successfully identified several areas with alteration and mineralization styles that are typical of high level porphyry-type alteration including potassic alteration with biotite and magnetite veining. Mineralization is generally hosted in Permian-Triassic volcanic rocks which have been intruded by Jurassic and Cretaceous mafic and felsic intrusions. The Grubstake Prospect, in the Southeast Claim Block, has concentric zoned alteration with outer propylitic and inner potassic zones. Surface assays at Grubstake returned values as high as 7.11% copper and 11.45 g/t gold. Fault-hosted mineralization at the POW Prospect, in the northwest Chisna claim block, has returned surface samples with values as high as 12.0 g/t gold and 3% copper.
For more information, please click here for the Chisna June 2010 Technical Report.
International Tower Hill (ITH) staked the Chisna Block in 2006 and conducted regional stream sediment surveys and prospecting. Based on the favorable results of that work, additional claims were staked and in 2007 an airborne magnetic and EM survey was flown over the Chisna Block. Later in 2007, based on favorable results in the southeast end of the belt, a helicopter magnetic survey was flown over the Grubstake target. In addition, an analysis of satellite imagery was undertaken in 2007 which produced an iron oxide and clay alteration map of the region outlining a number of new target areas which have yet to be explored.
In 2008 and 2009, ITH covered the bulk of the claim blocks with a stream sediment survey which identified multiple targets in the SE extension of the main Chisna claim block. In addition, a number of magnetic anomalies were investigated in the area southwest of the main claim blocks which returned copper mineralization from follow up prospecting and additional claims were staked.
Corvus took over the project from ITH in 2010 and will be managing the joint venture with Ocean Park (OCP). The Corvus-OCP joint venture is focused on testing the porphyry and precious metal potential of the Chisna belt using detailed airborne and ground geophysics to define drill targets which will be aggressively tested. A 2010 summer exploration program was carried out and included 2,926 metres (9600 feet) of diamond drilling, soil and rock sampling, airborne ZTEM surveying, and ground-based magnetotelluric (MT) with three-dimensional induced polarization chargeability-resistivity surveying and inversion modeling over selected target areas.
Surface exploration results from the 2010 program identified two new targets of mineralization which will be further explored in 2011. These include the Golden Range target where bedrock values of up to 50.4g/t gold and soil values of up to 6.5g/t gold have been found along a 9- kilometre - long zone of extensive gossanous iron carbonate alteration. Another target, known as Southwest Grubstake, was discovered as a series of parallel quartz-dolomite-barite veins up to 2 metres wide defined over a 600-metre-long trend containing metal values from rock chip sampling of up to 46.5 g/t gold, 17.9 g/t silver, 1.3% lead and 0.19% zinc. These new targets will be further exp
The summer 2011 drill program at the Golden Range target is a follow-up to the 769 grab samples that yielded results as high as 79.8 g/t gold. Samples from quartz-gelena-barite veins at the Southwest Grubstake target have produced high grades.
Results from six drill holes and four surface trenches from the Notch target at Golden Range were completed and results reported on November 8, 2011. Highlights of the results include the following drill results:
Surface mapping and trench sampling at the Notch has shown that mineralization is hosted in a shear zone 40-60 metres thick which dips 40-50 degrees to the south. The entire zone is altered and mineralized with higher grade zones of quartz-arsenopyrite hosted in specific intervals within the larger structural zone. Surface trenching at the Notch target include the following:
Significant Intercepts* from Trenching/Drilling at the Corazon target and drilling
at the City and Matador targets
*Intercepts calculated using a cut off of 0.1g/t gold with a maximum of 3 metres of internal waste. These intercepts are not true widths. At this time, there is insufficient data with respect to the shape of the mineralization to calculate its true orientation in space.
Significant rock sample assay results from the Jolly Green prospect.
2012 Exploration Results
During the 2011 exploration season, the Jolly Green target in the Southwestern portion of the Grubstake zone, north of the Golden Range area emerged as a priority follow-up target where initial ridge and spur soil sampling revealed a significant copper, gold, silver, molybdenum and tungsten anomaly. In the summer 2012 exploration season, Corvus continued with surface prospecting and mapping. High-grade structurally controlled copper mineralization was found at the Jolly Green target and continues for 700 metres of strike in a NNW trend (image 11). Mineralization in a typical copper porphyry style mineralization was found to the west of Jolly Green at the West Green target (image 12). The 2013 season will look to further target this emerging area of interest.
None has been defined to date.