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Unnamed Occurrence (ARDF - MH363; on lower Alteration Creek), Chistochina District, Valdez-Cordova Borough, Alaska, USA

Latitude: 63°0'53"N
Longitude: 144°14'49"W
Location: This occurrence is on the east side of Alteration Creek. It is near the north edge of the NW1/4NE1/4 section 10, T. 14 N., R. 6 E., Copper River Meridian, at an elevation of about 3,900 feet. The occurrence corresponds to locality 15 of Richter (1967).
Geology: The rocks at this occurrence are highly altered Tetelna Volcanics of Pennsylvanian age (Richter and others, 1977). Earlier Richter [1967] mapped the rocks as Slana basalt. The Tetelna Volcanics are largely composed of flows, avalanche deposits, and tuff with lesser amounts of fine-grained volcaniclastic rocks. An extensive area extending easterly has been silicified and pyritized. Subsequent oxidation, acid leaching, and formation of secondary limonite has nearly obliterated primary volcanic textures in the rocks. Richter (1967) found a trace of gold in two of three samples collected at or near this site. Two stream-sediment samples collected from Alteration Creek below the occurrence were weakly anomalous in copper (Richter, 1967). Extensive oxidation of pyrite at the site possibly resulted in acidic surface waters that mobilized copper and minimized the copper values in the stream-sediment samples.
Workings: Only limited surface sampling.
Age: Pennsylvanian to Permian on the basis of the age of the host rocks; may be related to and synchronous with a Cretaceous (?) intrusion about a mile to the east.
Alteration: Intense silicification and pyritization of original volcanic rocks.

Commodities (Major) - Au; (Minor) - Cu (?)
Development Status: None
Deposit Model: Porphyry Cu, distal (Cox and Singer, 1986; model 20c).

References

Richter, D.H., 1967, Geology of the upper Slana-Mentasta Pass area, southcentral Alaska: Alaska Division of Geological and Geophysical Surveys Geological Report 30, 27 p., 2 sheets, scale 1:63,360. Richter, D.H., Sharp, W.N., Dutro, J.T., Jr., and Hamilton, W.B., 1977, Geologic map of parts of the Mount Hayes A-1 and A-2 quadrangles, Alaska: U.S. Geological Survey Miscellaneous Investigations Series Map I-1031, 1 sheet, scale 1:63,360.

Mineral List

Limonite
Pyrite
Quartz


3 entries listed. 2 valid minerals.

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Copyright © Jolyon Ralph and Ida Chau 1993-2011. Jobs in Alaska, USA Site Map. Locality, mineral & photograph data are the copyright of the individuals who submitted them.Further information contact the Site hosted & developed by Jolyon Ralph. Mindat.org is an online information resource dedicated to providing free mineralogical information to all. Mindat relies on the contributions of hundreds of members and supporters. Mindat does not offer minerals for sale. If you would like to add information to improve the quality of our database, then click here to register. Current server date and time: 2nd Jul 2011 19:51:41
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