|Quadrangle map, 1:250,000-scale||CH|
|Quadrangle map, 1:63,360-scale||C-3|
|Nearby scientific data||Find additional scientific data near this location|
|Location and accuracy||The Pallasgreen prospect is at an elevation of about 3,000 feet, 0.8 mile northeast of Crystal Peak and about 0.5 mile north-northwest of the center of section 36, T. 32 N., R. 3 W., of the Fairbanks Meridian. The location is accurate.|
The geology of the Chandalar area is dominated by a system of west-northwest-trending regional faults including a prominent thrust fault in the southern part of the district and a series of major high-angle faults through the center of the area (Bundtzen and Laird, 2009a, 2009b). These faults separate the rocks into two principal units, a west-northwest-trending Upper Plate unit about 3 miles wide in the center of the area and a Lower Plate unit to the north and south. The contact of the two units is a thrust fault on the south side of the Upper Plate rocks and a high-angle fault on the north side. Most of the Upper Plate rocks consist of Devonian upper-greenschist-facies metamorphic rocks, mainly carbonaceous schist; quartz-chlorite-muscovite schist, schist and phyllite derived from turbidites that comprise the Mikado Phyllite, metamorphosed calcareous sandstone, and quartz-muscovite schist. The Lower Plate rocks consist of Devonian, upper-greenschist-facies metamorphic rocks, mainly metamorphosed volcanic agglomerate, chlorite-rich tuffaceous schist, quartz-mica schist derived from mudstone, mica-quartz schist, and quartzite. Both the Upper and Lower Plate rocks are cut by irregular masses, dikes and sills of greenstone, metagabbro, and metadiorite of unknown age. Most of the mineral deposits in the Chandalar area are in the Upper Plate rocks and the deposits often are along the regional, steep-to-vertical, west-northwest-trending faults. There is an additional conjugate set of north-northeast-trending faults that offset the Upper Plate rocks and at least some of the mineralization may be localized at the intersections of the regional west-northwest-trending faults and the conjugate faults.
Although the Pallasgreen prospect was discovered in the early 1900s, there was little more than a few bits of old company information about it prior to the work of Little Squaw Mining Company in 2005 (Barker, 2006 and 2007). A prominent, iron-stained quartz hogback about 25 feet wide that strikes 100-105 degrees with a steep south dip is exposed at the prospect. The footwall of the vein is feldspathic schist; the hanging wall is black graphitic schist. As mapped by Bundtzen and Laird (2009a, 2009b) the host rocks are part of the finely laminated, fine grained, quartz-mica schist unit of the Upper Plate.Brecciated quartz-limonite zones and several joint sets cut the vein. Wispy bands of chlorite and arsenopyrite are common along the footwall and hanging wall contacts. Samples showed little gold. However, float quartz rock and a prospect pit about 300 feet west of the hogback suggest one or more parallel bands or zones of quartz-limonite breccia or quartz veins. The float quartz contain clots and grains of arsenopyrite and galena up to 3 cm. Soil samples in the vicinity contained up to 1.91 parts per million (ppm) gold; rock-chip samples contained up to 12.12 ppm gold. Chips of quartz in the tundra that surround the outcrop suggest that the vein and quartz breccia may be extensive. The gold veins in the Chandalar district are considered mesothermal (Barker and Bundtzen, 2004; Barker, 2006, 2007; Barker and others, 2009) by comparison with similar deposits elsewhere and consideration of fluid inclusion and oxygen and lead isotope studies of the Chandalar mineralization (Ashworth, 1984; Rose and others, 1988; Gacetta and Church, 1989).
|Geologic map unit||(-148.118535588413, 67.5616200744951)|
|Mineral deposit model||Low-sulfide Au-quartz veins (Cox and Singer, 1986; model 36a).|
|Mineral deposit model number||36a|
|Age of mineralization||Possibly Middle Cretaceous based on the assertion of Dillon (1982) that the gold-quartz veins of the central Brooks Range are that age. However, there is no definitive data for the age of the veins of the Chandalar area.|
|Alteration of deposit||Quartz vein is heavily oxidized to limonite.|
|Workings or exploration||Only limited surface sampling by industry.|
|Indication of production||None|
Ashworth, (Lamal) Kate, 1984, Fluid inclusion study of the Eneveloe Vein, Chandalar Mining District: Private Report, Chandalar Development Associates, 8 pages (in files of the Goldrich Mining Company.
Barker, J.C., 2006, Chandalar Mining District, a report of findings and recommendations, 2005: Unpublished report for Little Squaw Gold Mining Company, 93 p. (on the Internet at http://www.goldrichmining.com/Files/corporate/2005AnnualReport011906.pdf, as of February 14, 2010).
Barker, J.C., 2007, Chandalar Mining District, Annual Report of findings for 2006; Unpublished report for Little Squaw Gold Mining Company, 124 p. (On the Internet at http://www.goldrichmining.com/Files/chandalar/chandalar_barker_rpt_2007.pdf, as of February 14, 2010).
Barker, J.C., and Bundtzen, T.K., 2004, Gold deposits of the Chandalar Mining District, Northern Alaska: An information review and recommendations: Unpublished report for the Little Squaw Gold Mining Company, 165 p. (in files of the Goldrich Mining Company).
Barker, J.C., Murray, R.B., Keener, J.O., and Martin, P.L., 2009, Evaluation of the Chandalar mining property: Unpublished report prepared for Goldrich Mining Company, 165 p. (on the Internet at http://www.goldrichmining.com/Files/chandalar/Chandalar_tech_rept_4_15_09.pdf, as of February 14, 2010).
Bundtzen, T.K., and Laird, G.M., 2007a, Geologic map of the Chandalar Mining District, Brooks Range, Northern Alaska, 2007: Unpublished map prepared for Little Squaw Gold Mining Company, 1 sheet, scale 1:20,000. (on the Internet at https://www.goldrichmining.com/media/downloads/technical_reports/regional_chandalar_geo_map_final_07.pdf (last accessed March 2018).
Gacetta, J.D., and Church, S.E., 1989, Lead isotope data base for sulfide occurrences in Alaska, December, 1989: U.S. Geological Survey Open File report 89-688, 59 pages.
Rose, S.C., Pickthorn, W.J., and Goldfarb, R.J., 1988, Gold mineralization by metamorphic fluids in the Chandalar Mining District, southern Brooks range-fluid inclusion and oxygen isotopic evidence, in, Galloway, J.P., and Hamilton, T.D., eds., Geologic studies in Alaska by the U.S. Geological Survey during 1987: U.S. Geological Survey Circular 1016, p. 81-84.
|Reporters||D.J. Grybeck (Contractor, U.S. Geological Survey)|
|Last report date||4/2/2010|