|Quadrangle map, 1:250,000-scale||NM|
|Quadrangle map, 1:63,360-scale||D-1|
|Nearby scientific data||Find additional scientific data near this location|
|Location and accuracy||The Divide Hill prospect, developed by Cominco American in 1995 and 1996, is the northeast extension of the Divide prospect (NM058). Divide Hill is the north-trending ridge between Boer Creek and Nome River. Its crest is shown as elevation 1546 feet. The prospect is mostly in the E1/2NE 1/4 section 26, T. 7 S., R. 33 W., Kateel River Meridian. The location is the approximate center of four drill hole locations; it is accurate to within 500 feet.|
The Divide Hill prospect is part of a large auriferous area that includes Boer Creek (NM049) and the Divide prospect (NM058). The prospect at Divide Hill was explored by four drill holes (Div-10, -11, -12, -13), all in the E1/2NE 1/4 section 26, T. 7 S., R. 33 W. Significant gold-bearing intercepts were found in holes Div-10 and -12. Hole Div-10 had 25 feet of 0.028 ounce of gold per ton and hole Div-12 contained 52 feet of 0.092 ounce of gold per ton. This appears to be the best drill hole in the Divide-Divide Hill area (Cominco American, written communication, August 22, 1996). The Divide Hill area does not appear to have been trenched.
On the basis of descriptions of mineralization at the Divide prospect (NM058) to the south, mineralization here is expected to be gold-bearing, quartz veins along steeply dipping joints and fractures. The veins have albite and local silicified selvages, and larger veins have several feet of selvage with ankerite. In general, pyritization appears to be a favorable indication of nearby gold mineralization. In decreasing order of abundance, the ore minerals in the veins are pyrite, arsenopyrite, pyrrhotite, galena, stibnite, sphalerite, and jamesonite.
The host rocks at the Divide Hill prospect are metasedimentary rocks of retrograde greenschist or lower amphibolite facies, including graphitic and calcareous schist, blue-gray, gray, and black marble, and black quartz schist and quartzite (Hummel, 1962 [MF 248]). Hummel (1962 [MF 248]) mapped less graphitic rocks west and northwest of Quartz Gulch, including most of the canyon of Boer Creek. Projection of mapped bedrock geology from the west suggests that some of these metamorphic rocks could be biotite-bearing (Sainsbury, Hummel, and Hudson, 1972; Bundzten and others, 1994). The schistose rocks are mostly phyllonites with slip schistosity approximately parallel to lithologic contacts and original bedding. Schistosity strikes northeast to east-northeast and dips about 30 degrees southeast.The metamorphic rocks here are probably part of the Nome Group derived from Proterozoic to early Paleozoic protoliths (Till and Dumoulin, 1994). The Nome Group underwent regional blueschist facies metamorphism in the Late Jurassic or Early Cretaceous (Sainsbury, Coleman, and Kachadoorian, 1970; Forbes and others, 1984; Thurston, 1985; Armstrong and others, 1986; Hannula and McWilliams, 1995). The blueschist facies rocks were recrystallized to greenschist facies or higher metamorphic grades in conjunction with regional extension, crustal melting, and magmatism in the mid-Cretaceous (Hudson and Arth, 1983; Miller and Hudson, 1991; Miller and others, 1992; Dumitru and others, 1995; Hannula and others, 1995; Hudson, 1994; Amato and others, 1994; Amato and Wright, 1997, 1998). Lode gold mineralization on Seward Peninsula is related to the higher temperature metamorphism in the mid-Cretaceous (Apodoca, 1994; Ford, 1993 [thesis]; Ford and Snee, 1996; Goldfarb and others, 1997).
|Geologic map unit||(-165.288525716278, 64.8559421300626)|
|Mineral deposit model||Low sulfide, Au-quartz vein (Cox and Singer, 1986; model 36a).|
|Mineral deposit model number||36a|
|Age of mineralization||Mid-Cretaceous; postdates regional metamorphism and is probably similar in age to other lode gold deposits of Seward Peninsula.|
|Alteration of deposit||Local silicification and more pervasive introduction of pyrite and ankerite in the vicinity of vein systems.|
|Workings or exploration||Four reverse circulation holes were drilled in 1996 in conjunction with the Cominco American evaluation of the general area between Divide Creek (NM057) and Boer Creek (NM049), both long recognized as placer gold sources in the north Nome River area.|
|Indication of production||None|
Amato, J.M., and Wright, J.E., 1997, Potassic mafic magmatism in the Kigluaik gneiss dome, northern Alaska--A geochemical study of arc magmatism in an extensional tectonic setting: Journal of Geophysical Research, v. B102, no. 4, p. 8065-8084.
Amato, J.M., and Wright, J.E., 1998, Geochronologic investigations of magmatism and metamorphism within the Kigluaik Mountains gneiss dome, Seward Peninsula, Alaska, in Clough, J.G., and Larson, Frank, eds., Short Notes on Alaskan Geology 1997: Alaska Division of Geological and Geophysical Surveys Professional Report 118a, p. 1-21.
Apodoca, L.E., 1994, Genesis of lode gold deposits of the Rock Creek area, Nome mining district, Seward Peninsula, Alaska: Boulder, Colorado, University of Colorado, Ph.D. dissertation, 208 p.
Armstrong, R.L., Harakal, J.E., Forbes, R.B., Evans, B.W., and Thurston, S.P., 1986, Rb-Sr and K-Ar study of metamorphic rocks of the Seward Peninsula and southern Brooks Range, Alaska, in Evans, B.W., and Brown, E.H., eds., Blueschists and eclogites: Geological Society of America Memoir 164, p. 184-203.
Bundtzen, T.K., Reger, R.D., Laird, G.M., Pinney, D.S., Clautice, K.H., Liss, S.A., and Cruse, G.R., 1994, Progress report on the geology and mineral resources of the Nome mining district: Alaska Division of Geological and Geophysical Surveys, Public Data-File 94-39, 21 p., 2 sheets, scale 1:63,360.
Dumitru, T.A., Miller, E.L., O'Sullivan, P.B., Amato, J.M., Hannula, K.A., Calvert, A.T., and Gans, P.B., 1995, Cretaceous to Recent extension in the Bering Strait region, Alaska: Tectonics, v. 14, p. 549-563.
Forbes, R.B., Evans, B.W., and Thurston, S.P., 1984, Regional progressive high-pressure metamorphism, Seward Peninsula, Alaska: Journal of Metamorphic Geology, v. 2, p. 43-54.
Ford, R.C., 1993, Geology, geochemistry, and age of gold lodes at Bluff and Mt. Distin, Seward Peninsula, Alaska: Golden, Colorado School of Mines, Ph.D. dissertation, 302 p.
Ford, R.C., and Snee, L.W., 1996, 40Ar/39Ar thermochronology of white mica from the Nome district, Alaska--The first ages of lode sources to placer gold deposits in the Seward Peninsula: Economic Geology, v. 91, p. 213-220.
Goldfarb, R.J., Miller, L.D., Leach, D.L., and Snee, L.W, 1997, Gold deposits in metamorphic rocks in Alaska, in Goldfarb, R.J., and Miller, L.D., eds., Mineral Deposits of Alaska: Economic Geology Monograph 9, p. 151-190.
Hannula, K.A., and McWilliams, M.O., 1995, Reconsideration of the age of blueschist facies metamorphism on the Seward Peninusla, Alaska, based on phengite 40Ar/39Ar results: Journal of Metamorphic Geology, v. 13, p. 125-139.
Hannula, K.A., Miller, E.L., Dumitru, T.A., Lee, Jeffrey, and Rubin, C.M., 1995, Structural and metamorphic relations in the southwest Seward Peninsula, Alaska; Crustal extension and the unroofing of blueschists: Geological Society of America Bulletin, v. 107, p. 536-553.
Hudson, T.L., 1994, Crustal melting events in Alaska, in Plafker, G., and Berg, H. C., eds., The Geology of Alaska: Geological Society of America, DNAG, The Geology of North America, Vol. G-1, p. 657-670.
Hudson, T.L., and Arth, J. G., 1983, Tin granites of Seward Peninsula, Alaska: Geological Society of America Bulletin, v. 94, p. 768-790.
Hummel, C.L., 1962, Preliminary geologic map of the Nome D-1 quadrangle, Seward Peninsula, Alaska: U.S. Geological Survey Miscellaneous Field Studies Map MF-248, 1 sheet, scale 1:63,360.
Miller, E.L., and Hudson, T.L., 1991, Mid-Cretaceous extensional fragmentation of a Jurassic-Early Cretaceous compressional orogen, Alaska: Tectonics, v. 10, p. 781-796.
Miller, E.L., Calvert, A.T., and Little, T.A., 1992, Strain-collapsed metamorphic isograds in a sillimanite gneiss dome, Seward Peninsula, Alaska: Geology, v. 20, p. 487-490.
Sainsbury, C.L., Coleman, R.G., and Kachadoorian, Reuben, 1970, Blueschist and related greenschist faces rocks of the Seward Peninsula, Alaska, in Geological Survey research 1970: U.S. Geological Survey Professional Paper 700-B, p. B33-B42.
Sainsbury, C.L., Hummel, C.L., and Hudson, Travis, 1972, Reconnaissance geologic map of the Nome quadrangle, Seward Peninsula, Alaska: U.S. Geological Survey Open-File Report 72-326, 28 p., 1 sheet, scale 1:250,000.
Thurston, S.P., 1985, Structure, petrology, and metamorphic history of the Nome Group blueschist terrane, Salmon Lake area, Seward Peninsula, Alaska: Geological Society of America Bulletin, v. 96, p. 600-617.
Till, A.B., and Dumoulin, J.A, 1994, Geology of Seward Peninsula and St. Lawrence Island, in Plafker, G., and Berg, H.C., eds., The Geology of Alaska: Geological Society of America, DNAG, The Geology of North America, v. G-1, p. 141-152.
|Reporters||C.C. Hawley and Travis L. Hudson|
|Last report date||10/22/1999|