Divide Hill Prospect, Nome Mining District, Nome Census Area, Alaska, USAi

Regional Level Types
Divide Hill Prospect	Prospect
Nome Mining District	Mining District
Nome Census Area	Census Area
Alaska	State
USA	Country

Location: 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.
Geology: 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).
Workings: 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.
Age: Mid-Cretaceous; postdates regional metamorphism and is probably similar in age to other lode gold deposits of Seward Peninsula.
Alteration: Local silicification and more pervasive introduction of pyrite and ankerite in the vicinity of vein systems.

Commodities (Major) - Au
Development Status: None
Deposit Model: Low sulfide, Au-quartz vein (Cox and Singer, 1986; model 36a).

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Link to USGS - Alaska:	NM118

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References