Kelly Creek Prospect, Port Clarence District, Nome Borough, Alaska, USA
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Geology: The Kelly Creek prospect is in metapelitic rocks - mica-quartz shist and graphitic quartz schist - intercalated in a metasedimentary sequence that includes schistose, micaceous, parly dolomitic marble, mica-calcite schist, and minor micaceous quartzite. The metasedimentary sequence is interpreted to represent a limestone-shale assemblage with related facies variations. It is now highly deformed and perhaps isoclinally folded. Schistosity now dips moderately in various directions in the prospect area; steep-dipping marble-schist contacts and other strong linear features may indicate the location of normal faults. A mafic to intermediate (?) metavolcanic and metasedimentary assemblage consisting of various greenschist and amphibolite lithologies intercalated regionally with some calcareous quartzite and marble is present in the headwaters of Fox Creek, 3 miles north of the Kelly Creek prospect. The relation of the metavolcanic assemblage to the pelitic schist/marble assemblage that hosts the Kelly Creek prospect is not known. All of the metavolcanic and metasedimentary rocks in the Kelly Creek and Fox Creek area are of unknown but probable Paleozoic age although Sainsbury (1972) mapped them as Precambrian. The Kelly Creek prospect is primarily within tundra-mantled metapelitic rocks in saddles and slopes between rubble uplands of schistose marble; bedrock outcrops are only locally present within the marble uplands. The metapelitic rocks have lineated quartz segregations along their foliation and disseminated euhedral pyrite crystals are common. Soil geochemical surveys following up gold and arsenic anomalies in stream sediments from the west headwater drainage of Kelly Creek led to discovery of the prospect (Hudson and Wyman, 1983; Hudson, 1984). The soil geochemical surveys defined an irregular but large area (3,000 x 4,000 feet) containing anomalous gold to 1.4 ppm, arsenic to greater than 1,000 ppm, antimony to 62 ppm, mercury to 5,000 ppb, and silver to 0.9 ppm. The gold, arsenic, and antimony values define strong, coherent, multielement anomalies. Mercury is commonly elevated along with these elements but its distribution and concentration is more erratic; it is more widely dispersed at anomalous levels than the other three elements. Rock samples from frost boils and surface pits 3 to 4 feet deep show that the stronger anomalies are associated with silicified breccia and quartz-stockwork veined, sooty, black carbonaceous quartz schist. Quartz stockwork veins are thin, less than 0.5 inches wide, and locally broken and recemented by a fine-grained, dark siliceous matrix. Two small diameter diamond drill holes encountered mineralization at shallow depths (Marrs and Ivey, 1984). These holes were oriented N 45 E, they were inclined 45 and 60 degrees, and they reached 140 and 154 feet total depth. One encountered 77 feet of 0.032 opt gold and the other 44 feet of 0.035 opt gold. The higher gold concentrations seem to be in a zone that dips shallowly west although all the rocks in these two holes had highly anomalous metal contents; gold is commonly present in the several hundred ppb range. Clay is locally present in fractures and as part of the matrix in breccia. Dolomite and calcite are reported to be in veins with quartz in some drill core (Marrs and Ivey, 1984). Pyrite is disseminated in pelitic schist and is present in all mineralized rocks and a part is probably sedimentary in origin. Quartz segregations along the foliation in pelitic shist are recrystallized, sugary textured, and vuggy in mineralized rocks. Arsenopyrite has not been conclusively identified but it is probably present. The controls on mineralization have not been defined, the distribution of grade has not been determined, and large areas of anomalous soil geochemistry have not been evaluated by the previous work.
Workings: Exploration includes: regional stream sediment geochemistry; a soil geochemical survey on a grid covering a 3,000 x 6,000 foot area; several shallow surface pits; and four small-diameter diamond drill holes (Cook Inlet Region, Inc., 1985).
Age: Unknown; probably mid-to Late Cretaceous; mineralization postdates regional deformation.
Alteration: Brecciation, silicification, and quartz stockwork veining is common in pelitic schist. Quartz veins may contain some carbonate minerals. Clay and limonite are present in some mineralized rocks.
Reserves: Not defined
Commodities (Major) - Au
Development Status: None
Deposit Model: Disseminated and stockwork quartz and gold mineralization in metapelitic rocks.
5 entries listed. 4 valid minerals.
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Hudson, T.L., 1984, 1983 Seward Peninsula reconnaissance project: Anchorage, Alaska, Anaconda Minerals Company internal report (Report held by Cook Inlet Region, Inc., Anchorage, Alaska). Hudson, T.L., and Wyman, W. F., 1983, Interim report on areas of Seward Peninsula warranting further prospecting and evaluation: Anchorage, Anaconda Minerals Company internal report, 84 p., 7 plates. (Report held by Cook Inlet Region Inc., Anchorage, Alaska.) Marrs, C.D., and Ivey, J.A., 1984, 1984 Prospect evaluation project; Kelly Creek (Fox claims): Anchorage, Alaska, Anaconda Minerals Company internal report. (Report held by Cook Inlet Region, Inc., Anchorage, Alaska).