Misty Mountain Occurrence, Aleutians District, Aleutians West Borough, Alaska, USA
Location: Locality is southeast of Summer Bay lake and is accurate.
Geology: This occurrence is primarily a very high ( more than 40 colors per pan) gold pan concentrate anomaly. Country rocks are strongly propylitically altered andesitic tuffs and flows capped by unaltered basaltic volcanic rocks. The andesitic rocks host a wide-spaced cockscomb quartz vein system containing rare arsenopyrite. 'The veining appears to be controlled by several shear zones that developed in response to large-scale faulting (Randolph, 1991).' Battle Mountain Exploration considered source of pan concentrate anomaly indeterminate as their fieldwork was unable to delineate a source. A ridge to the north of the occurrence hosts several wide-spaced quartz vein systems; however, sampling did not locate highly anomalous areas.
Workings: Pan concentrate, rock, and soil sampling by BMEC. Rock sampling was of andesitic rocks cut by quartz veins in the stream basin. Highest gold from these rocks was 168 ppb, pan concentrate from the basin yielded 170 ppb Au and 930 ppb Hg.
Age: Late Tertiary or younger
Alteration: Regional propylitic alteration; no apparent wall-rock alteration around vein.
Commodities (Major) - Au; (Minor) - Hg
Development Status: No
Deposit Model: Epithermal gold vein
ReferencesRandolph, D.B., 1991, Unalaska project, 1990 final report: Battle Mountain Exploration Company, Alaska District, 62 p., 5 appendices, 15 plates, various scales. (Report held by the Aleut Corporation, Anchorage, Alaska.)
| Arsenopyrite|| Gold|| Quartz|
3 entries listed. 3 valid minerals.
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