|Quadrangle map, 1:250,000-scale||SP|
|Quadrangle map, 1:63,360-scale||A-6|
|Nearby scientific data||Find additional scientific data near this location|
|Location and accuracy||This prospect is at an elevation of about 3600 feet on a ridge 5 miles north of Avaraart Lake. It is in section 23, T. 20. N., R. 14 E., of the Kateel River Meridian. The location is and accurate to within 1000 ft. The site corresponds to locality 61 of Grybeck and Nelson (1981).|
This prospect explores a silver-base metal volcanogenic massive sulfide deposits in a sequence of low to medium grade metamorphosed basaltic and rhyolitic rocks, submarine ash flow tuffs, and pelitic and carbonaceous sedimentary rocks known as the Ambler schist belt. The deposit is Devonian or Mississippian in age, based on fossil evidence and U-Pb radiometric dating (Hitzman and others, 1986). Numerous copper-stained zones in the schists have been explored by prospect pits and several diamond drill holes. The deposit is similar to, and probably an extension of, the deposits at SP032 (Grybeck and Nelson, 1981).
Two distinct mineralized zones were noted, separated stratigraphically by approximately 1,500 feet, which are referred to as the north and south mineral zones (Ellis, 1983).
The south mineral zone lies within a white schist unit about 150 feet thick overlying country rock schist and underlying a thick metasediment unit. Along the ridge an upper horizon 5 feet thick of disseminated and banded sulfide along with another lower zone of approximately 30 feet thick of banded and disseminated sulfides is present as outcrop and subcrop. The south mineral zone can be traced approximately 3,500 feet from the ridge to the east by gossan float and outcrop (Ellis, 1983).The north mineral zone lies within a black schist unit approximately 100 feet thick overlying a country rock schist and underlying a siliceous rock unit approximately 100 feet thick. This unit is mineralized for at least 3000 feet where the zone is covered to the east by a large rock slide. To the east gossan boulder samples collected indicate massive sulfides of ore grade with a minimum thickness of 1 foot. Many boulders of mineralized black schist were noted in the rock slide. Along the 3000 feet strike of the black schist outcropping or sub-outcropping, mineralization of banded sulfides up to 1/4 inch to 7 inches thick along with disseminated sphalerite, galena, and pyrite. Rock chip samples collected from a massive sulfide lens contained from 2 to 14 percent lead, 1.6 to 5.5 ounces silver, 6 to 10 percent zinc, and 1.5 to 3.4 percent copper (Ellis, 1983).
|Geologic map unit||(-155.736725416759, 67.1174724512065)|
|Mineral deposit model||Kuroko massive sulfide (Cox and Singer, 1986; model 28a)|
|Mineral deposit model number||28a|
|Age of mineralization||Syngenetic massive sulfide deposit in Devonian or Mississippian host rocks (Grybeck and Nelson, 1981).|
|Alteration of deposit||Locally prominent copper-staining (Grybeck and Nelson, 1981).|
|Workings or exploration||
The deposit has been explored by a number of prospect pits and several diamond drill holes (Grybeck and Nelson, 1981).Approximately 110 soil samples were collected during the early 1980’s over a previously discovered magnetic/geochemical anomalous zone. Results of this work showed an anomalous copper and lead trend, which is open ended to the north. This open-end anomaly is believed to be caused by a metal bearing meta-chert unit contained in rocks of the 'Middle Felsic Belt'. Rock chip samples collected from a massive sulfide lens contained from 2 to 14 percent lead, 1.6 to 5.5 ounces silver, 6 to 10 percent zinc, and 1.5 to 3.4 percent copper (Ellis, 1983).
|Indication of production||None|
Additional commentsPrior to being named Cymbad (in 2014), this site was known as 'Unnamed (north of Avaraat Lake)'.
Cox, D.P., and Singer, D.A., eds., 1986, Mineral deposit models: U.S. Geological Survey Bulletin 1693, 379 p.
Ellis, W.T., 1983, Ambler River Project, Alaska, Project Memorandum No. 10, 1983 Field Investigations, Sunshine Mining Company, 49 p. (Report held at Alaska Earth Sciences, Inc., Anchorage, AK).
Grybeck, D.J., and Nelson, S.W., 1981, Mineral deposit map of the Survey Pass quadrangle, Brooks Range, Alaska: U.S. Geological Survey Miscellaneous Field Studies Map MF-1176-F, 1 sheet, scale 1:250,000.
Hitzman, M.W., Profett, J.M., Jr., Schmidt, J.M., and Smith, T.E., 1986, Geology and mineralization of the Ambler district, northwestern Alaska: Economic Geology, v. 81, p. 1592-1618.
|Reporters||S.W. Nelson (Anchorage, Alaska); A. Angel and V.C. Zinno (Alaska Earth Sciences, Inc.)|
|Last report date||12/4/2014|