|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 prospect is northwest of the junction of the Nome River and Divide Creek (NM049). It is bounded on the west by Quartz Creek (NM111) and Boer Creek; on the south by Divide Creek (NM057), and on the west by the Campion Ditch. The prospect area extends north for nearly 1 mile and is more than one-half mile wide. The coordinates are approximately at the center of this large mineralized area that extends north across a low hill (locally called Boer Mountain). The prospect is in the upper part of section 35 and in the center of section 26, T. 7 S., R. 33 W. The location is accurate. Stevens (2010) provides numerous detailed maps of the prospect.|
Work on the Divide prospect began in the 1990s (Chris Gierymski, Cominco American, written communication, December 1995; Stevens, 2010). In 1994, David and Daniel Lajack sampled the southeast flank of Boer Mountain (the hill between Boer Creek and the Nome River) on a 2,000- by 2,500 foot grid Seventeen of 57 soil samples contained 100 parts per billion (ppb) or more of gold; the highest was 370 ppb gold. In 1995, Cominco expanded the grid to a 1 mile by 1.5 mile area elongated to the north; they collected almost 700 soil samples, and ran VLF and ground magnetics. A series of 21 trenches with a total length of 5,822 feet. was also dug at that time. About 1,000 samples were collected from the trenches.
At least two major northeast-trending vein zones were found as a result of Cominco's exploration. Trench 1 trends east; it starts about 1,300 feet east of Quartz Creek approximately on the section line between sections 26 and 35 on the southeast flank of Boer Mountain. Several 1- to 3-foot-wide gold-bearing quartz veins that strike northeast and dip nearly vertically were mapped and sampled near trench 1. The channel samples along a 50-foot interval in trench 1 assayed 0.663 ounce of gold per ton. The trench was partly frozen; strong 'muck' anomalies were found along the trench in three sections that aggregated 250 feet in length. Trench D-12 cut approximately the same zone as trench 1, and it was also well mineralized. Trenches D-10 and D-11 were cut nearly on the divide between Quartz Creek and Boer Creek; these trenches also exposed quartz veins that strike northeast and dip steeply to gently. Trench 10 exposed a section 8-feet long that contained 0.047 ounce of gold per ton; trench D-11 exposed 55 feet with 0.437 ounce of gold per ton; 40 feet contained 0.044 ounce of gold per ton; it included an interval of 20 feet long hat contained 0.080 ounce of gold per ton. Trench D-9, north of trenches 10 and 11 and on trend with upper Boer Creek, had a 70-foot interval with 0.024 ounce of gold per ton; it included a section 20 feet long with 0.067 ounce of gold per ton.
The prospect was drilled by Cominco American in 1996 (written communication, August 22, 1996; Stevens, 2010). In general, the drill results were not as good as the trench results. Five holes were drilled at the head of the divide between Quartz Creek and Boer Creek. The best drill hole, D-6, intersected 28 feet with 0.011 ounce of gold per ton. Three holes were drilled southeast of Boer Mountain; hole Div-9 intersected 10 feet with 0.235 ounce of gold per ton. About 2,000 feet east of Boer Mountain, hole Div-3 had 37 feet with 0.055 ounce of gold per ton,; it included 24.7 feet with 0.091 ounce of gold per ton.
In 2002, Rio Fortuna Exploration Corp. drilled 18 holes that totaled 1,357 meters (Stevens, 2010). Lajack Minerals explored the property from 2003 to 2006 and drilled 9 holes that totaled 273 meters.
In 2007, Millrock Resources Inc. and their partner Alix Resources Corp. (2008) drilled 5 holes and cut intervals with significant gold values in each (Stevens,2010). The intervals vary from 0.30 to 8.99 meters thick and contain 1.0 to 10.0 grams of gold per ton.
In 2008, Millrock drilled 22 holes that totaled 2,656 meters and dug 1244 meters of trenches (Stevens, 2010). Some notable intercepts in the drilling were 15.24 meters with 0.09 ounce of gold per ton, 1.52 meters with 0.29 ounces of gold per ton, 10.67 meters with 0.035 ounce of gold per ton, and 6.10 meters with 0.04 ounce of gold per ton. On Dec. 2, 2009, Millrock terminated their agreement with Alix.
In summary, a total of 68 holes totaling 5,848 meters have been drilled on the Divide prospect to 2010 and 45 trenches have been dug that total 3,018 meters (Stevens, 2010).
The gold-bearing quartz veins occur along joints and fractures (Stevens, 2010). The veins have albite and local silicified selvages; larger veins have several feet of selvage with iron-bearing carbonate (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 prospect are metasedimentary rocks of retrograde greenschist or lower amphibolite facies; these include graphitic and calcareous schist; blue-gray, gray, and black marble; and black quartz schist and quartzite (Hummel, 1962). Strata west and northwest of Quartz Gulch, including most of the canyon of Boer Creek, are less graphitic. Projection of 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 phyllonite with slip schistosity approximately parallel to lithologic contacts and original bedding. The schistosity strikes northeast to east-northeast and dips about 30 degrees southeast.The metamorphic rocks 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 mostly related to the higher temperature metamorphism in the mid-Cretaceous (Apodoca, 1994; Ford, 1993, Ford and Snee, 1996; Goldfarb and others, 1997).
|Geologic map unit||(-165.298025141778, 64.8443418147752)|
|Mineral deposit model||Low sulfide Au-quartz vein (Cox and Singer, 1986; model 36a).|
|Mineral deposit model number||36a|
|Age of mineralization||Mid-Cretaceous; the veins postdate regional metamorphism and are probably similar in age to other lode gold deposits of Seward Peninsula.|
|Alteration of deposit||Local silicification and pervasive introduction of pyrite and ankerite near vein systems.|
|Workings or exploration||Work on the Divide prospect began in the 1990s after its discovery by David and Daniel Lajack (Stevens, 2010). Cominco American dug 21 trenches that totaled 1,775 meters and drilled 14 holes that totaled 1,000 meters in 1996. In 2002, Rio Fortuna Exploration Corp. drilled 18 holes that totaled 1,357 meters (Stevens, 2010). Lajack Minerals explored the property from 2003 to 2006 and drilled 9 holes that totaled 273 meters. In 2007, Millrock Resources Inc. and their partner Alix Resources Corp. (2008) drilled 5 holes. In 2008, Millrock drilled 22 holes that totaled 2,656 meters and dug 1,744 meters of trenches (Stevens, 2010). On Dec. 2, 2009, Millrock terminated their agreement with Alix. In summary, a total of 68 holes totaling 5,848 meters have been drilled on the Divide prospect to 2010 and 45 trenches have been dug that total 3,018 meters (Stevens, 2010).|
|Indication of production||None|
Alix Resources Corp., 2008, The Divide property: http://www.alixresources.com/index.php?page=divide (as of May 20, 2008).
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, The geology, geochemistry, and age for lode sources of placer gold deposits in the Seward Peninsula: Technical Presentation, Denver Region Exploration Geologists' Society, November 6, 1993, Denver, Colo., unpaginated.
Ford, R.C., and Snee, L.W., 1996, 40Ar/39Ar geochronology 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 Peninsula, 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 gossans in a sillimanite gneiss dome, Seward Peninsula, Alaska: Geology, v. 20, p. 487-490.
Millrock Resources Inc., 2008, Divide: http://millrockresources.com/index.php/projects/divide/ (as of April 30, 2008).
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.
Stevens, D.L., 2010, Divide prospect, Nome Mining district, Seward Peninsula, Alaska; Unpublished 43-101 report for Millrock Resources Inc., 254 p. (posted on www.sedar.com, Feb. 22, 2010)
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 (Hawley Resources Group); D.J. Grybeck (Contractor, USGS)|
|Last report date||2/28/2011|