Polson & Ickis Prospect (Apex; Hillside; Wano; Adit; Astor; Daly-West; Veda; Thompson Prospects), McLean Arm, Prince of Wales Island, Ketchikan District, Prince of Wales-Outer Ketchikan Borough, Alaska, USA

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Location: This site covers an area about 1,500 feet long and 400 feet wide that trends west-northwest. Within the area, there are numerous claims, pits and trenches, and several adits, many of which date from before World War I. Over the years, these have been described collectively and separately under various names by several workers, and some of the names are probably the names of claims. The best known are the Polson and Ickis prospects, which have a long history under that name and it is the name used by MacKevett (1963). Roehm (1938) and Maas and others (1991, 1995), however, describe them under the name Apex. The Hillside and Wano prospects, which were probably included with the Polson and Ickis in early reports, are described separately by MacKevett (1963) and by Maas and others (1991,1995). In this record they are included with the Polson and Ickis. The Veta prospect has been included with the Polson and Ickis prospects in several early reports but it is described separately in this report (DE040). The site is about at the center of the main workings of the Polson and Ickis/Apex prospects, about 0.2 mile east of the center of section 1, T. 82 S., R. 89 E. The Hillside and Wano prospects are about 800 feet to the northwest. The 1994 edition of the USGS D-1, 1:63,360-scale topographic map outlines a patented claim block(?) that probably includes most of the Polson & Ickis property.
Geology: The rocks in the region consist of various phases of a Silurian or Ordovician batholith and include quartz monzonite, syenite, quartz diorite, and diorite (Gehrels, 1992). (A fine-grained phase of the quartz diorite and diorite apparently was often called 'greenstone' in early reports.) The prospect area is cut by several large faults and by many smaller ones, some of which localize mineralized quartz-calcite-barite veins. The prospects were explored by at least 5 adits that total about 520 feet of underground workings, and by numerous pits and trenches. Exploration in the area began before World War I, but there apparently has been no production (Wright, 1909; Knopf, 1910, 1911; Smith 1914; Chapin, 1916, 1918). The ore deposits consist of quartz-calcite-barite veins a few feet or less thick that commonly are along fault zones (Roehm, 1936; MacKevett, 1963; Maas and others, 1991, 1995). The veins typically contain modest to abundant amounts of pyrite, minor chalcopyrite, hematite, and chrysocolla, and small amounts of bornite and gold. Post-ore faulting is common and there is usually intense argillic alteration for several feet into the granitic wallrock. The veins are well exposed in the three adits of the Polson and Ickis prospects. They are in a series of steep fault zones that strike N to N25E in monzonite that grades into syenite. At the Wano prospect, the principal structure is a fault that strikes N25E and dips 70SE in a salient of monzonite in fine-grained diorite. The monzonite is intensely silicified and sericitized. Work by the U.S. Bureau of Mines (1944) defined a shear zone with copper-gold-silver mineralization that extends for at least 1,000 feet. The Bureau calculated the reserves as 2,263,000 tons of material that contains 0.51 percent copper, 0.01 ounce of gold per ton, and 0.81 ounce of silver per ton. Maas and others (1991, 1995) extensively sampled the deposits. In the lower adit of the Polson and Ickis prospect, a 4-foot-thick quartz-calcite-barite vein contains pyrite, chalcopyrite, bornite, malachite, azurite, and limonite. A 0.3-foot chip sample across the best copper mineralization contained 2.16 percent copper and 212 parts per billion (ppb) gold. Samples from a similar fault zone in the the middle adit contained 0.59 to 0.63 percent copper and 0.330 to 2.312 ppb gold. Samples across 1.9 feet of vein in the highest adit contained 0.28 percent copper and 17 ppb gold. Maas and others (1991) found three adits and 7 open cuts at the Hillside and Wano prospects that expose mineralization along a fault zone. Chip and other representative samples that vary from 1 to 5.6 feet long contained 666 to 12,580 parts per million (ppm) copper and 82 to 435 ppb gold. Selected high-grade samples contained up to 2.79 percent copper, 11.2 ppm silver, and 7.15 ppm gold.
Workings: At least five adits with a total of about 520 feet of underground workings. Numerous trenches and prospect pits.
Age: The veins cut Silurian or Ordovician granitic wall rocks.
Alteration: Post-ore faulting is common and the granitic wallrock commonly is intensely argillized for several feet from the veins. At one location, the monzonite is intensely silicified and sericitized.
Reserves: Work by the U.S. Bureau of Mines in 1944 defined a shear zone with copper-gold-silver mineralization that extends for at least 1,000 feet. It contains indicated reserves of 2,263,000 tons of mineralized rock that average 0.51 percent copper, 0.01 ounce of gold per ton, and 0.81 ounce of silver per ton.

Commodities (Major) - Ag, Au, Cu; (Minor) - Ba
Deposit Model: Polymetallic veins (Cox and Singer, 1986; model 22c).

Mineral List

Azurite Baryte Bornite

Calcite Chalcopyrite Chrysocolla

Gold Hematite Malachite

Pyrite Quartz

11 entries listed. 11 valid minerals.

References