|Quadrangle map, 1:250,000-scale||TN|
|Quadrangle map, 1:63,360-scale||C-3|
|Nearby scientific data||Find additional scientific data near this location|
|Location and accuracy||This occurrence is about 2.7 miles south-southwest of the top of Mount Fairplay; it is at an elevation of about 4,000 feet, about 0.4 mile southwest of the center of section 35, T. 22 N., R. 16 E. The location is accurate.|
Various companies explored in the Mount Fairplay area from the 1970s to the 1990s, apparently with indifferent results. The Section 35 prospect dates from work begun in 2006, when Anglo Alaska Gold Corporation staked 6 claims known as the Draken project; the claims included the nearby Silver Lining prospect (TC026). Fire River Gold Corporation acquired the Draken claims in 2009. The Section 35 occurrence (which is just outside the Draken claims) was identified in their sampling.
The Section 35 prospect is in the outer portion of the Mount Fairplay pluton whose outcrop area is about 4 miles in diameter (Foster, 1970; Kerin, 1976; Adams, 2009). The pluton is a Late Cretaceous to early Tertiary alkaline complex with well-developed ring structures. It intrudes biotite schist and gneiss, probably of Mississippian and older age and bimodal felsic and mafic volcanic rocks, probably of Late Cretaceous age. The Mount Fairplay complex was emplaced in three phases between 59 and 67 Ma: 1) an early alkaline ring phase that consists of diorite and several syenite units on the north side of the complex; 2) a later alkaline ring phase that consists of several syenite units and perthosite on the south side of the complex; and 3) a calc-alkaline core phase that consists of hornblende-biotite quartz monzonite. The Section 35 occurrence is in a protoclastic hornblende-biotite syenite on the south side of the complex.A sample of fine-grained syenite contained 16 parts per million beryllium, 172 ppm lanthanum, 145 ppm niobium, 235 ppm thorium, 157 ppm uranium, 33 ppm yttrium, and 291 ppm zirconium (Adams, 2009). The syenite is part of a ring dike complex with accessory apatite, fluorite, and monazite. Adams (2009) noted that some samples from the Silver Lining prospect (TC026), about a mile to the northwest, also contained anomalous uranium, thorium, and rare-earth elements.
|Geologic map unit||(-142.266446658984, 63.6394668763845)|
|Mineral deposit model||REE in syenitic plutonic rocks.|
|Age of mineralization||Late Cretaceous or early Tertiary based on the age of the plutonic host rock.|
|Alteration of deposit||None noted.|
|Workings or exploration||Only surface sampling and mapping.|
|Indication of production||None|
Adams, David, 2009, Geologic report on the Drakan project, Fortymile Mining District, Alaska: Technical Report DK08 43-101 for Fire River Gold Corporation, 49 p. (posted on www.sedar.com, Feb 23, 2009).
Foster, H.L., 1970, Reconnaissance geologic map of the Tanacross quadrangle, Alaska: U.S. Geological Survey Miscellaneous Geological Investigations Map I-593, 1 sheet, scale 1:250,000.
Kerin, L.J., 1976, The reconnaissance petrology of the Mount Fairplay igneous complex: Fairbanks, University of Alaska, M.Sc. thesis, 95 p
Wilson, F.H., Smith, J.G., and Shew, Nora, 1985, Review of radiometric data from the Yukon crystalline terrane, Alaska and Yukon Territory: Canadian Journal of Earth Sciences, v. 22, p. 525-537.
|Reporters||D.J. Grybeck (Contractor, U.S. Geological Survey)|
|Last report date||4/2/2010|