|Quadrangle map, 1:250,000-scale||KC|
|Quadrangle map, 1:63,360-scale||C-6|
|Nearby scientific data||Find additional scientific data near this location|
|Location and accuracy||
The New Adit prospect is at an elevation of about 350 feet, 0.3 mile east of Falls Creek and and about 0.7 mile north-northwest of the mouth of Falls Creek. The site is in section 19, T. 72 S., R. 88 E., of the Copper River Meridian. It corresponds to loc. 256 in Maas and others (1995, fig. 46). The location is accurate within 0.1 mile.Also see Additional comments.
Maas and others (1995, p. 183 and fig 46) describe the country rocks in the area of this site as felsic schist and metavolcanic rocks (greenstone). Berg and others (1988, p. 17-19) describe them as gray and green phyllite and semischist derived from intertonguing flysch and andesitic and basaltic volcanic rocks. The strata were regionally metamorphosed to greenschist grade in Late Cretaceous time (Brew, 1996, p. 27). Their premetamorphic age is uncertain. Berg and others (1988, p. 17) note that they closely resemble Upper Jurassic to mid-Cretaceous marine flysch and volcanic rocks nearby on Gravina Island.
The deposit is a 1.8-foot-thick auriferous quartz fissure vein in felsic schist (Maas and others, 1995, p. 183, table 26, and fig. 46). The mineralization is not described, but it probably consists of pyrite, which may also occur in bleached wallrock adjacent to the vein. The vein was explored, probably in the early 1900s, by an adit of unknown length. Assays of samples taken across the vein show up to 26.9 ppm Au (Maas and others, 1995, table 26).Maas and others (1995, p. 184 and fig. 46) describe a unit of bleached, chlorite-sericite schist containing varying amounts of pyrite that crops out along the northeast shore of Smugglers Cove. An adjacent schist unit contains more chlorite than sericite. The cumulative width of the two units is up to 90 feet and they have been traced northward along strike for nearly 4200 feet. A gold-bearing horizon that includes the New Adit prospect occurs near the contact between these two units. Maas and others suggest that this gold-bearing pyritic belt of schists is of volcanic-exhalative origin. The age of the postulated exhalative deposits is unknown. The quartz fissure vein at the New Adit, which presumably crosscuts the foliation in the schist, probably is Late Cretaceous (also see KC028).
|Geologic map unit||(-131.982683048978, 55.6076371703046)|
|Mineral deposit model||Low-sulfide gold-quartz vein (Cox and Singer, 1986; model 36a); Distal disseminated Ag-Au? (Bliss, 1992; model 19c)|
|Mineral deposit model number||36a, 19c?|
|Age of mineralization||The quartz fissure vein probably is Late Cretaceous.|
|Alteration of deposit||The wallrock adjacent to the vein is bleached and pyritic.|
|Workings or exploration||The vein was explored, probably in the early 1900s, by an adit of unknown length. Assays of samples taken across the vein show up to 26.9 ppm Au (Maas and others, 1995, table 26).|
|Indication of production||None|
Additional commentsThis record is based mainly on a description of the New Adit prospect by Maas and others (1995, loc. 256 on fig. 46). Earlier reports (Brooks, 1902, p. 57: summarized in Elliott and others, 1978, loc. 35; and in Cobb and Elliott, 1980, p. 64) place the Last Chance prospect (KC033) at approximately the same location at the New Adit, but Maas and others indicate that the Last Chance instead is adjacent to the Old Glory mine (KC033).
Berg, H.C., Elliott, R.L., and Koch, R.D., 1988, Geologic map of the Ketchikan and Prince Rupert quadrangles, southeastern Alaska: U.S. Geological Survey Mineral Investigations Series Map I-1807, 27 p., scale 1:250,000.
Brew, D.A., 1996, Geologic map of the Craig, Dixon Entrance, and parts of the Ketchikan and Prince Rupert quadrangles, southeastern Alaska: U.S. Geological Survey Miscellaneous Field Studies Map MF-2319, 53 p., 1 sheet, scale 1:250,000.
Brooks, A.H., 1902, Preliminary report on the Ketchikan mining district, Alaska, with an introductory sketch of the geology of southeastern Alaska: U.S. Geological Survey Professional Paper 1, 120 p.
Cobb, E.H., and Elliott, R.L., 1980, Summaries of data on and lists of references to metallic and selected nonmetallic mineral deposits in the Ketchikan and Prince Rupert quadrangles, Alaska: U.S. Geological Survey Open-File Report 80-1053, 157 p.
Elliott, R.L., Berg, H.C., and Karl, S.M., 1978, map and table describing metalliferous and selected non-metalliferous mineral deposits, Ketchikan and Prince Rupert quadrangles, Alaska: U.S. Geological Survey Open-File Report 78-73-B, 17 p., 1 sheet, scale 1:250,000.
|Reporters||H.C. Berg, USGS|
|Last report date||6/30/1999|