Heckla; Greenpoint Prospect, Hyder Mining District, Prince of Wales-Hyder Census Area, Alaska, USAi

Regional Level Types
Heckla; Greenpoint Prospect	Prospect
Hyder Mining District	Mining District
Prince of Wales-Hyder Census Area	Census Area
Alaska	State
USA	Country

Five claims staked in 1925. Prospect covered by 12-claim Greenpoint group staked in 1970. Site is in Misty Fiords National Monument.
Location: The Heckla prospect, in the southern part of the 12-claim Greenpoint group staked in 1970, is in Section 31 at an elevation of about 4000 feet on the northwest slope of a mountain about 1 mile south-southwest of the confluence of Through and Greenpoint glaciers (Berg and others, 1977, p. 96; Elliott and Koch, 1981, p. 10, loc. 24).
Geology: The country rocks in the area of the Heckla prospect are mainly pelitic hornfels of the Jurassic or older Mesozoic Hazelton Group. Near the prospect, graywacke hornfels is cut by dikes of diorite or andesite that may be apophyses of Triassic Texas Creek Granodiorite, and by felsic dikes that may be apophyses of Eocene Hyder Quartz Monzonite (Berg and others, 1977, p. 15-18, 22-23, 96-97; Smith, 1977; Koch, 1996). The mineral deposit (Berg, and others, 1977, p. 96-100) consists of five principal quartz fissure veins up to about 4 feet thick. The veins cut graywacke hornfels and minor calcareous schist and contain pyrite, galena, and molybdenite, locally abundant sphalerite and pyrrhotite, sporadic chalcopyrite and a little malachite, and microscopic traces of covellite and digenite. Small amounts of anglesite are in some of the more oxidized zones. Some of the quartz is vuggy and locally iron stained. The wallrock adjacent to the main (Heckla) vein is sheared, altered, and impregnated with sulfides over a width of about 3 feet. Channel samples of the veins collected in 1972 by the U.S. Bureau of Mines (Berg, 1977, p. 98-99) contain up to 9% Pb, 8.5% Zn, 1% Cu, and 15% Mo; assays also show up to 20 oz of Ag and 0.23 oz of Au per ton. Moffit (1927, p. 30) reports that a one-ton test shipment was made in 1925 by 'Hummel, Blasher, and Moss,' which Buddington (1929, p. 102) indicates came from the Heckla prospect. Buddington (p. 101-102) also reports that a picked sample yielded 0.08 oz of Au and 54.3 oz of Ag per ton, 21.6% Pb, 32.1% Zn, and 4.1% Cu. Lead-isotope studies of the galena at the Heckla prospect (Maas, 1995, p. 229-248) indicate that the deposit is Eocene in age, contemporaneous with emplacement of the Hyder Quartz Monzonite.
Workings: Early exploration consisted of a small amount of stripping and excavation of several small, shallow opencuts. Locator of Greenpoint group staked in 1970 explored property by geologic mapping, sampling, some ground geophysics, and shallow diamond drilling. Early reports describe a picked sample that yielded 0.08 oz of Au and 54.3 oz of Ag per ton, 21.6% Pb, 32.1% Zn, and 4.1% Cu. Channel samples collected by U.S. Bureau of Mines in 1972 contained up to 9% Pb, 8.5% Zn, 1% Cu, and 15% Mo; assays also showed up to 20 oz of Ag and 0.23 oz Au per ton.
Age: Lead-isotope studies of the galena at the Heckla prospect (Maas, 1995, p. 229-248) indicate that the deposit is Eocene in age, contemporaneous with emplacement of the Hyder Quartz Monzonite.
Alteration: Wallrocks adjacent to veins are impregnated with sulfide minerals. Local iron staining. Local oxidation and formation of secondary copper and lead minerals.
Production: One-ton test shipment made in 1925.

Commodities (Major) - Ag, Cu, Mo, Pb, Zn; (Minor) - Au
Development Status: Yes; small
Deposit Model: Polymetallic veins

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Link to USGS - Alaska:	BC024

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References