Lower Com

Prospect, Active

Commodities and mineralogy

Main commodities Ag; As; Au; Cu; Pb; Sb; Zn
Ore minerals arsenopyrite; chalcopyrite; galena; gold; pyrite; sphalerite; stibnite
Gangue minerals carbonates; quartz

Geographic location

Quadrangle map, 1:250,000-scale TC
Quadrangle map, 1:63,360-scale B-6
Latitude 63.25
Longitude -143.804
Nearby scientific data Find additional scientific data near this location
Location and accuracy The Lower Com prospect is about 1.5 miles northeast of the junction of the Tok River and Stibnite Creek. It is at an elevation of about 3,500 feet about 0.5 mile southwest of the center of section 13, T. 17 N., R. 8 E., of the Copper River Meridian. The location is accurate.

Geologic setting

Geologic description

The Lower Com prospect prospect is one of several similar deposits in a mineral belt about 4 miles long that is called the Tushtena project by the current (2010) operator, Triton Gold Ltd. (Newkirk and others, 1986; DiMarchi and others, 1987; Fonseca, 2009). Work along the belt began in 1976 when Resource Associates of Alaska began geochemical sampling in the area. They soon staked claims over the Discovery Zone prospect (TC034) what then was classified as massive-sulfide mineralization. Their work continued through 1987 in conjunction with several partners and consisted of geologic mapping, rock and soil sampling, and geophysical surveys along what became a belt of deposits. They drilled 17 holes along the belt in 1986 and 8 holes in 1987, totaling 3,390 meters. From 1998 to 2001, Inmet Mining Corporation and Pacific Northwest Resources Company did addition mapping, rock and soil surveys, and they drilled 8 more diamond drill holes totaling 1,489 meters. Eight holes were drilled at the Lower Com prospect. The property was idle until 2007 when James DeMarchi staked 40 claims over the belt and transferred them to Tushtena Resources Ltd. In 2008, they entered into a joint agreement with Triton Gold.
The rocks along the belt consist of two main units: the Devonian to Precambrian, Macomb Belt unit to the east and the Devonian Tushtena Pass unit to the west. They are separated by the Itra Fault, a regional scale, shallowly to moderately dipping thrust fault (Newkirk and others, 1986; DiMarchi and others, 1987; Fonseca, 2009). The Macomb Belt rocks consist mainly of felsic metatuff and volcaniclastic rocks, and sericite-carbonate-quartz phyllonite. The Tushtena Pass unit consists of schist and phyllite, metadiorite, and lithic tuff.
There are two main styles of mineralization along the belt: 1) hanging-wall, bonanza-style vein systems; and 2) footwall, sulfide stockwork and breccia vein systems. The hanging-wall, vein-type mineralization has an arsenic-lead-zinc association with narrow or no alteration envelopes and is characterized by quartz-carbonate-sulfide-gold-mica veins. The footwall, stockwork-breccia zones have a gold-rich core and peripheral antimony-rich mineralization. The deposits are correlative with others along the Tintina gold belt; the key characteristics are the low angle faults that trap the mineralization and the carbonaceous rocks that provide the right chemistry for deposition.
The Lower Com prospect is in the immediate footwall of the Itra Fault (Newkirk and others, 1986; DiMarchi and others, 1987; Fonseca, 2009). The host rock is quartz-mica schist, gneiss, and mylonite of the Macomb Belt rocks that outcrop along the creek at the prospect. The hanging wall above the fault is altered meta-diorite. Mineralized, altered mylonite crops out for more than 240 meters along the creek. The mineralization and alteration consist of: 1) pre-mineral quartz stockworks; 2) synmineralization argillic alteration; 3) synmineralization quartz-dominated stockworks and breccias with up to 50 percent arsenopyrite, pyrite, stibnite; 4) post-mineral quartz stockworks; and 5) post-mineral iron-magnesium-carbonate veinlets. The mineralization is associated with brittle fracturing and faulting along the Itra fault. Drilling indicates that the gold, arsenic, and silver content increases down the dip of the mineralization.
Geologic map unit (-143.806242776145, 63.2496322123439)
Mineral deposit model Tintina Belt-style, gold-arsenopyrite-quartz vein.
Age of mineralization About 70 to 105 Ma by analogy if Tintina Belt-style mineralization.
Alteration of deposit Argillic alteration, silicification, carbonate alteration.

Production and reserves

Workings or exploration The Lower Com prospect prospect is one of several similar deposits in a mineral belt about 4 miles long that is called the Tushtena project by the current (2010) operator, Triton Gold Ltd. (Newkirk and others, 1986; DiMarchi and others, 1987; Fonseca, 2009). Work along the belt began in 1976 when Resource Associates of Alaska began geochemical sampling in the area. They soon staked claims over the Discovery Zone prospect (TC034) what then was classified as massive-sulfide mineralization. Their work continued through 1987 in conjunction with several partners and consisted of geologic mapping, rock and soil sampling, and geophysical surveys along what became a belt of deposits. They drilled 17 holes along the belt in 1986 and 8 holes in 1987, totaling 3,390 meters. From 1998 to 2001, Inmet Mining Corporation and Pacific Northwest Resources Company did addition mapping, rock and soil surveys, and they drilled 8 more diamond drill holes totaling 1,489 meters. Eight holes were drilled at the Lower Com prospect. The property was idle until 2007 when James DeMarchi staked 40 claims over the belt and transferred them to Tushtena Resources Ltd. In 2008, they entered into a joint agreement with Triton Gold.
Indication of production None
Reserve estimates None.
Production notes None.

References

References

1986 Annual Report - Volume 1. Resource Associates of Alaska Inc. Internal Report, 141 p
DiMarchi, J.J., Oreskes, N., Newkirk, S.R. and Hanneman, N.L., 1987. AR/TRIO 1987 Annual Report.
Fonseca, Anna, 2009, Technical report on the Tushtena gold property, Delta Mineral District, Alaska: Technical Report for Triton Gold Limited, 67 p. (as of Feb 1, 2010, posted on the Internet at: http://www.tritongold.com.au/docs/Alaskan_Project_Independent_Geologists_Report.pdf).
Newkirk, S. R., Muntzert, J. K., Puchner, C. C., Hanneman, N. L., and Flanders, R. W., 1986, AR JV
Resource Associates of Alaska Inc. Internal Report, 111 p.
Reporters D.J. Grybeck (Contractor, U.S. Geological Survey)
Last report date 4/2/2010