Kako Prospect, Marshall Mining District, Kusilvak Census Area, Alaska, USAi

Regional Level Types
Kako Prospect	Prospect
Marshall Mining District	Mining District
Kusilvak Census Area	Census Area
Alaska	State
USA	Country

Location: The Kako prospect is on the ridge crest at the head of Buster Creek (see RM008). It is on a saddle at an elevation of about 800 feet, 1,200 feet southwest of hill 901. The map site is in the SE1/4 sec. 13, T. 21 N., R. 67 W., of the Seward Meridian.
Geology: The Kako lode gold prospect was discovered in 1974 by Resource Associates of Alaska (RAA) geologists under contract to Calista Corporation. RAA completed surface examination and a grid geochemical survey in 1974 and 1975. Calista Corporation and others continued work on the prospect in 1989 (Hickok and McAtee, 1990), 1996, and 1997 (Enos, 1997; Bull and Schneider, 1997). The principal gold-bearing area that has been identified is centered on a saddle at the head of Buster Creek, where there is a 30- by 300-foot area of rhyolite breccia. The breccia consists of angular sericite/clay-altered rhyolite fragments in a matrix of quartz, iron oxide, sericite/clay, and possibly jarosite (Bull and Schneider, 1997). It is vuggy and variably silicified. Thirty-two rock samples of the breccia range in gold content from 100 ppb to 900 ppb (Hickok and McAtee, 1990). Silver content ranges as much as 9.6 ppm, and arsenic content is commonly several hundred parts per million to greater than 2,000 ppm. A few hundred rock and soil samples have been collected in the general prospect area over several years. These samples show that arsenic is widely distributed at anomalous levels that are commonly a few hundred or more parts per million. Other elements locally occur in anomalous amounts (Hickok and McAtee, 1990). These include silver (to 17.9 ppm), copper (to 562 ppm), lead (to 431 ppm), zinc (to 750 ppm), antimony (to 112 ppm), and mercury (to 100 ppm). Bedrock in the area of the prospect includes a zone about 2,500 feet across in which outcrops of felsic intrusive rocks are common. These rocks consist of aphanitic rhyolite to quartz porphyry that intrude strata that include chert, limestone, siltstone, and shale. The sedimentary rocks are in contact to the north and south with mafic volcanic rocks (Enos, 1997). The sedimentary and mafic volcanic rocks are part of the Paleozoic to Mesozoic Gemuk Group (Hoare and Coonrad, 1959). The bedrock units and several faults strike approximately northwest-southeast and trend toward Buster Creek (RM008), where felsic intrusive rocks have been reported to be bedrock in some areas of previous placer mining (Hickok and McAtee, 1990).
Workings: The Kako prospect has been explored by surface mapping and grid-based soil and rock geochemical surveys. Some of the geochemical surveys used hand and power augers to recover subsurface materials.
Age: Cretaceous or Tertiary. Mineralization is hosted by felsic intrusive rocks that are probably part of a regional suite of Upper Cretaceous and Lower Tertiary igneous rocks that are widespread in southwest Alaska. The sedimentary rocks intruded by the felsic igneous rocks may be as young as Early Cretaceous (Hoare and Coonrad, 1959).
Alteration: Silicification, sericite/clay replacement, and oxidation.

Commodities (Major) - Ag, Au
Development Status: None
Deposit Model: Gold in altered and brecciated rhyolite

Other Databases

Link to USGS - Alaska:	RM007

Other Regions, Features and Areas containing this locality

References