Monte Cristo

Prospect, Active

Commodities and mineralogy

Main commodities Au
Other commodities Fe
Ore minerals arsenopyrite; pyrite; pyrrhotite
Gangue minerals quartz; sericite

Geographic location

Quadrangle map, 1:250,000-scale TY
Quadrangle map, 1:63,360-scale D-7
Latitude 61.7649
Longitude -152.4617
Nearby scientific data Find additional scientific data near this location
Location and accuracy The center of the Monte Cristo prospect is about 13 miles north of Mount Gerdine in the Tordrillo Mountains. It is about 1.5 miles north of lake 2885 on the 1:63,360-scale topographic map, near the center of section 1, T. 19 N., R. 18 W., of the Seward Meridian. This location is accurate to within 500 feet.

Geologic setting

Geologic description

The Monte Cristo prospect was first identified by Millrock Resources Inc. in 2009 and was optioned to Brixton Metals Corp. in 2010 (Eden, 2010). This prospect is located in the Kahlitna Terrain. There has been little past exploration in this area due to the challenges posed by the mountainous terrain and alpine glaciers. However, the glacial retreat of recent years has improved exposure and access (Millrock Resources Inc., 2014).
The rocks in the vicinity of the Monte Cristo prospect are highly altered Jurassic and Cretaceous volcaniclastic rocks and Tertiary granitic rocks (Wilson and others, 2009). There is little iron-staining, but carbonate alteration covers an area about 3.5 by 4.5 kilometers in size. Eden (2010) suggests that the mineralization is part of a gold porphyry system.
In 2009 and 2010, Millrock did a geochemical survey over the area consisting of 213 soil samples, and collected 80 rock samples. This exploration work showed that the gold mineralization at Monte Cristo is hosted in zones of highly hydrothermally altered volcaniclastic and porphyritic intrusive rocks. Mineralized zones occur on two parallel ridge-backs separated by about 300 m of shallow glacial debris cover. Rock samples assayed up to 4.2 grams per tonne gold and soil samples (talus fines) assayed up to grams per tonne gold. Alteration is dominated by carbonate with quartz-sericite assemblages (Millrock Resources Inc., 2014).
In 2011, Brixton (2011) collected rock samples and carried out soil and stream-sediment geochemical surveys over the area. Samples they collected typically included 1-3 percent pyrite, pyrrhotite, and arsenopyrite that occurs along fractures and disseminated. Brixton terminated their agreement with Millrock in January, 2012.
Geologic map unit (-152.463895026234, 61.7643164780208)
Mineral deposit model Polymetallic vein? (Cox and Singer, 1986; model 22c)
Mineral deposit model number 22c?
Age of mineralization May be related to a nearby Tertiary granitic intrusion (Eden, 2010).
Alteration of deposit Widespread carbonate alteration (Eden, 2010) with quartz and sericite (Millrock Resources Inc., 2014).

Production and reserves

Workings or exploration The Monte Cristo prospect was first identified by Millrock Resources Inc. in 2009 and was optioned to Brixton Metals Corp. in 2010 (Eden, 2010). In 2009 and 2010, Millrock did a geochemical survey over the area and collected numerous rock samples (Millrock Resource Inc., 2012). Brixton Metals sampled the property in 2011 and carried out soil and stream-sediment surveys (Brixton Metals, 2011).
Indication of production None
Reserve estimates None.
Production notes None.

References

References

Eden, Karsten, 2010, Cristo property, Kahiltna region, south-central Alaska: Unpublished technical report for Brixton Metals Corporation, 217 p. (posted on www.sedar.com, Jan 11, 2011).
Millrock Resource Inc., 2014, Cristo: http://www.millrockresources.com/projects/cristo (as of April 28, 2014).
Millrock Resources Inc., 2010, Millrock Finalizes Exploration Agreement With Brixton Metals And Reports On Exploration Results, Cristo Property, Alaska: http://millrock.yourmanagedserver.com/news/millrock-finalizes-exploration-agreement-with-brixton-metals-and-reports-on (News Release, October 29, 2010).
Millrock Resources Inc., 2012, Millrock announces termination of option on Cristo property, Kahiltna region: http://www.millrockresources.com/news/millrock_announces_termination_of_option_on_cristo_property_kahiltna_r/ (News release, January 12, 2012).
Reporters D.J. Grybeck (Contractor, USGS); V.C. Zinno (Alaska Earth Sciences, Inc.)
Last report date 4/28/2014