| Quadrangle map, 1:250,000-scale | CG |
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| Quadrangle map, 1:63,360-scale | B-2 |
| Latitude | 56.2647 |
| Longitude | -158.5109 |
| Nearby scientific data | Find additional scientific data near this location |
| Location and accuracy | The Marshinlak prospect is located near the peak of a north-northwest trending ridge about 1.8 miles from where Marshinlak Creek enters Mallard Duck Bay; 0.3 mile southwest from the center of section 21, T. 45 S., R. 59 W., of the Seward Meridian. This location is accurate to within 1/4 mile of the center of the prospect. |
Geologic descriptionThe Marshinlak Creek precious metal vein prospect is located on Chignik Lagoon Native Corp. (CLNC) lands approximately 4 kilometers north of the porphyry center at the Mallard Duck Bay prospect (CG002). The area was visited briefly by Resource Associates of Alaska (RAA) in 1982. Their efforts were focused on a subparallel set of poorly-exposed silver-gold bearing quartz veins located south of Marshinlak Creek. They collected a total of 25 vein samples, 23 of which contained gold with an average of 0.5 gram per tonne (parts per million (ppm)). The area is prospective for epithermal-style vein mineralization and/or a deep-seated porphyry target (Lipske and Rotert, 2008).
Rock types include diorite stocks up to 2000 feet in diameter and a system of northeast-trending quartz-diorite dikes, which are up to a half mile in length and up to several hundred feet in thickness. A system of andesite dikes trends N 30 to 40 W and dips vertically across a 4000-foot wide zone. All of these intrusives cut Eocene-Oligocene volcanics of the Meshik Formation, which consists of andesite and basalt flows, volcaniclastic breccias, volcaniclastic sediments, and tuffaceous units (Anderson and others, 1979).
South of Marshinlak Creek, a swarm of discontinuous and poorly-exposed quartz ± calcite ± pyrite ± arsenopyrite veins are exposed in subcrops and frost boils. The host andesites bear weak propylitic alteration but are strongly hydrolytized along veins. It is inferred that two or three west-northwest-trending veins are exposed over a zone measuring one kilometer in width by approximately 1.5 kilometers along strike, and at least 300 meters vertically. Subcrops were typically no wider than two meters, though RAA reported vein widths of up to five meters (15 feet). Vein mineralogy consists of white sugary to clear drusy quartz plus accessory calcite, pyrite, and local arsenopyrite. Uppermost vein exposures were dominated by calcite. A 3 kilometer by 1 kilometer area of bleached and oxidized andesite is located immediately north of Marshinlak Creek and comprises variable quartz-sericite-pyrite alteration with a widespread argillic overprint. Minor amounts of high-level advanced argillic alteration characterized by vuggy residual quartz and coarse white mica with local jarosite was recognized via handlens at uppermost levels. The sericitic-argillic alteration zone is haloed by weakly propylitized andesite (Lipske and Rotert, 2008).
A suite of 35 hand samples were submitted for supplemental portable infrared mineral analyzer (PIMA) testing. Through PIMA analyses from 2008 work, mineral species including smectite, illite, kaolinite, dickite, chlorite, and epidote were positively identified. Possible accessory carbonate, silica, and amphibole were reported in several samples. Based on these results, the hydrothermal alteration at Marshinlak Creek consists of propylitic, argillic, and advanced argillic assemblages (Lipske and Rotert, 2008). The rock chip and vein sampling completed at Marshinlak Creek in 2008 confirms the high grade results reported from previous workers. A total of 25 vein samples were collected and returned results of up to 84.7 ppm gold, 745 ppm silver, 853 ppm copper, 1490 ppm arsenic, and 155 ppm antimony. The upper range of each is defined by the results of sample 314182, a quartz vein in float that contained 1 to 2 volume percent visible chalcopyrite, arsenopyrite, and an unidentified black sooty sulfide or sulfosalt. The float was observed downslope from a sample location that RAA reported as a 15-foot wide quartz vein. Excluding sample 314182, vein samples averaged 0.511 ppm gold, 0.4 ppm silver, 78.6 ppm copper, and 261 ppm arsenic, which are consistent with the results reported by RAA in Moller et al., 1982 (Lipske and Rotert, 2008). | |
| Geologic map unit | (, ) |
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| Mineral deposit model | Porphyry copper; porphyry copper-molybdenum; polymetallic veins (Cox and Singer, 1986; models 17, 21a, 22c). |
| Mineral deposit model number | 17, 21a, 22c |
| Age of mineralization | The probable age of mineralization is estimated at 21 to 27 million years (Wilson, 1980). |
| Alteration of deposit | Propylitic, argillic, sericitic, and silica alteration (Lipske and Rotert, 2008). |
| Workings or exploration |
A field program was performed in by Metallica Resource Inc. with a joint venture agreement with Full Metal Minerals (USA) Inc., on behalf of Bristol Bay Native Corporation (BBNC). This 2008 program entailed preliminary reconnaissance mapping and sampling at Marshinlak (Lipkse and Rotert, 2008). A total of 31 vein samples and two lines of ground magnetics were collected south of Marshinlak Creek. North of Marshinlak Creek, approximately forty samples were collected on 50 meter centers and four lines of ground magnetics were completed. A suite of 35 hand samples were submitted for supplemental portable infrared mineral analyzer (PIMA) testing (Lipkse and Rotert, 2008). |
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| Indication of production | None |
Additional commentsThis record was created in 2014 to separate Marshinlak from Mallard Duck Bay (CG002), in which this site was previously combined with. The geology, location, and reports all separated these prospects. | |
ReferencesLipske, Joanna, and Rotert, Joel, 2008, Southwest Alaska Peninsula Report, 2008 Annual Report, Prepared for Bristol Bay Native Corporation, Metallica Resources Alaska Inc., Full Metal Minerals (USA) Inc., Alaska Earth Sciences, Inc., 41 p. (Unpublished report held by Alaska Earth Sciences, Inc., Anchorage, Alaska).
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| Reporters | V.C. Zinno (Alaska Earth Sciences, Inc.) |
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| Last report date | 12/17/2014 |