|Quadrangle map, 1:250,000-scale||CG|
|Quadrangle map, 1:63,360-scale||C-2|
|Nearby scientific data||Find additional scientific data near this location|
|Location and accuracy||This prospect is in T. 42 S., R. 58 W., of the Seward Meridian, located in a northeast facing valley near the headwaters of an unnamed creek entering Dry Creek approximately 1 mile north of Chignik Bay. The location is accurate to 1 mile.|
At this prospect sandstone, siltstone, argillite, and conglomerate of the Jurassic Naknek Formation have been intruded by a small dacite stock, which is surrounded by a sulfide system and alteration halo covering approximately 2 square miles (Fields, 1977). The intrusive is mainly dacite, but quartz diorite, andesite, and quartz porphyry have also been reported. The intrusive is part of a nearly east-west trending linear belt extending from Weasel Mountain (CG008) on the east to Cathedral Creek (CG001) on the west. The Bee Creek prospect was explored by Bear Creek Mining Company in 1975 and 1976 and by Resource Associates of Alaska in 1979 and 1981.
The prospect is marked by geochemical and color anomalies. Clusters of arsenic, copper, gold, lead, silver, and zinc anomalies surround the deposit. The main mineralized area is in a steep cirque basin that varies from 500 to 1,500 feet in elevation. Work by Resource Associates of Alaska (Anderson and others, 1979) suggests that mineralization may extend southwest into the McKinsey Valley.
The mineralization is mainly at the border of the dacite stock in arkose, conglomerate, and quartzite. Resource Associates of Alaska (Anderson and others, 1979) state that the hornfelsed sediments near the contact contain the best mineralization and that the mineralization decreases towards the core of the intrusive. The age of the mineralization is between 3.2 and 3.8 million years (Wilson, 1980; Wilson and Cox, 1983).
Chalcopyrite and pyrite occur in a stockwork of hairline fractures containing quartz-sulfide veinlets throughout an area about 2,000 feet in diameter. Disseminated chalcopyrite and pyrite occur in biotitized hornfels and these sulfides replace mafic minerals in the dacite. Molybdenite is finely disseminated in quartz veinlets, in gypsum veinlets, and in clots of chalcopyrite. Pyrite forms a halo on the periphery of the system. Some magnetite veins have been reported; they appear to be early in the mineralization sequence and contain no sulfides. Veins containing lead and zinc values are peripheral to the copper zone. Within the copper zone, richer surface samples contained 500 to 2,000 parts per million (ppm) copper, 0.04 to 0.18 ppm gold, 20 to 220 ppm molybdenum, and 0.4 to 0.18 ppm silver (Fields, 1977).
Secondary biotite is widely distributed both within and beyond the chalcopyrite zone. It replaces mafic minerals and forms fine-grained aggregates both in the pluton and in the surrounding sediments. The biotite zone centers on the stock and extends irregularly southward over an area of 1,500 by 3,400 feet. Discontinuous zones of sericitic alteration are peripheral to the biotite zone and are locally superimposed on the potassic and propylitic alteration. Propylitic alteration of chlorite and epidote forms an outer alteration zone. A strong zone of argillic alteration located between the phyllic and propylitic zones also has been reported (Butherus and others, 1981).After drilling at Bee Creek in 2006, Full Metal Minerals and Metallica Resources interpreted the deposit as a multiphase dioritic intrusion within a coincident copper-gold-molybdenum anomaly centered on a magnetic high about 2 kilometers in diameter (Full Metal Minerals, 2008; Metallica Resources, 2008).
|Geologic map unit||(-158.386647881026, 56.5109226512296)|
|Mineral deposit model||Porphyry copper; porphyry copper-molybdenum (Cox and Singer, 1986; models 17, 21a).|
|Mineral deposit model number||17, 21a|
|Age of mineralization||Pliocene (Fields, 1977), between 3.2 and 3.8 Ma (Wilson, 1980).|
|Alteration of deposit||The alteration at this prospect appears to be the classic porphyry type with a potassic core grading outward through phyllic, argillic, and propylitic alteration zones although these may not all be developed fully. The best copper mineralization is in the potassic zone (Fields, 1977).|
|Workings or exploration||
Bear Creek Mining Company drilled 5 holes in the copper zone in 1975 and 1976. Four holes averaged 500-1200 ppm copper and 5-28 ppm molybdenum. The best hole averaged 0.25 percent copper, 0.01 percent molybdenum, and 0.06 ppm gold over 500 feet. In 1979 Resource Associates of Alaska discovered two areas of polymetallic quartz veins. Samples of this material contained up to 5700 ppm copper, 4.4 ppm gold, 1.18 percent lead, 530 ppm molybdenum, 4.2 ounces silver per ton, and 1.62 percent zinc (Anderson and others, 1979). A resource of 4.5 to 9 million tonnes grading 0.25 percent copper and 0.01 percent molybdenum has been estimated (Young and others, 1997).
Along with geological mapping, geochemical sampling, and ground-based geophysics, Full Metal Minerals (FMM) and Metallica Resources (Metallica) drilled 2 holes on the Bee Creek porphyry in 2006. Notable intercepts in the two holes were: 1) 34 meters that contained 0.26 percent copper and 0.085 gram of gold per ton, 2) 118 meters that contained 0.31 percent copper and 0.126 gram of gold per ton, including 40 meters that contained 0.51 percent copper and 0.212 gram of gold per ton. The holes were mostly in sedimentary rocks cut by numerous intermediate to felsic dikes (Full Metal Minerals, 2008; Metallica Resources, 2008).
FMM and Metallica conducted field work in 2008, which included vein sampling and an orientation drainage survey employing bulk leach extractable gold (BLEG) analysis and drilled two holes. One grab sample of a quartz-sphalerite-galena vein float in one of the eastern secondary drainages (314322) contained 5.180 parts per million (ppm) gold, 251 ppm silver, 1050 ppm copper, 3.8 percent lead, and 5.9 percent zinc. Results from BLEG analysis were up to 0.232 ppm gold (Lipske and Rotert, 2008).
In 2013, a regional aeromagnetic survey was completed. There appears to be good correlation between magnetic highs and known porphyry occurrences (Gregory Beischer, Millrock Resources, Inc., oral communication, 2013). In 2014, Millrock Resources Inc. completed a high-resolution airborne magnetic survey, which indicated that known mineralization may continue to the southwest below a ridge in that area (Millrock Resources Inc., 2014).Mineralization, alteration and anomalous copper values in soils and rocks extend over a broad area at the Dry Creek prospect indicating the potential for a significant porphyry Cu-Mo-Au deposit near surface and potentially at depth. Although several holes have been drilled at the property, few of the geochemical or geophysical anomalies have been tested (Millrock Resources, Inc., 2015).
|Indication of production||None|
|Reserve estimates||The prospect contains an estimated resource of 4.5 to 9 million tonnes grading 0.25 percent copper, 0.01 percent molybdenum, and trace gold (Young and others, 1997).|
This prospect is located on land conveyed to or patented by the Bristol Bay Native Corporation. In August 2005, Metallica Resources entered into a joint venture agreement with Full Metal Minerals to explore on BBNC lands.In 2013, Millrock Resources Inc. made an agreement with the BBNC to explore for minerals (Millrock Resources Inc., 2014).
|MRDS Number||A010659; A012444|
|Reporters||S.H. Pilcher (Anchorage); D.J. Grybeck (Port Ludlow, WA); V.C. Zinno (Alaska Earth Sciences, Inc.); F.H. Wilson, USGS|
|Last report date||2/25/2016|