Unnamed Occurrences (ARDF - TN057; Miller Gulch; Mynook Creek), Rampart Mining District, Yukon-Koyukuk Census Area, Alaska, USAi

Regional Level Types
Unnamed Occurrences (ARDF - TN057; Miller Gulch; Mynook Creek)	- not defined -
Rampart Mining District	Mining District
Yukon-Koyukuk Census Area	Census Area
Alaska	State
USA	Country

Location: These mineral occurrences are described by Spurr (1898) as being on Miller Gulch, half a mile above Little Mynook (Minook) Creek, and near the mouth of the (Miller) gulch on the main Mynook (Minook) Creek. Miller Gulch in the Minook Creek area is not named on the topographic map, and it probably was renamed at a later date, possibly as Little Minook Jr. Creek. For this record, the site is assumed to be on Minook Creek approximately half a mile upstream from its junction with Little Minook Creek, in the southwest quarter of section 6, T. 7 N., R. 12 W., of the Fairbanks Meridian. The location, although uncertain, probably is accurate within 3,000 feet.
Geology: Bedrock in the area of Little Minook Jr. Creek consists of gabbro, mafic volcanic and volcaniclastic rocks, argillite, chert, and limestone of the Triassic Rampart Group (Chapman and others, 1982; Reifenstuhl and others, 1997 [RI 97-15a]). The drainage area of the creek includes the Tertiary gravel-covered California and Idaho bars. Minook Creek generally follows the trace of a high-angle normal fault (Reifenstuhl and others, 1997 [RI 97-15a]). Spurr (1898) describes many shear zones in massive rock on Miller Gulch and Mynook Creek. On Miller Gulch, half a mile above Little Mynook (Minook) Creek, and near the mouth of Miller Gulch on the main Mynook (Minook) Creek are many shear zones impregnated with sulfides (Spurr, 1898). An outcrop of hard, aphanitic, green slate on Minook Creek is altered up to 17 feet wide and sheared along joint and stratification surfaces. The outcrop is stained yellow by iron oxides and green by a mixture of calcite and copper silicate (Spurr, 1898). The outcrop also contain calcareous sandstone, described as a vein, containing occasional broken bits of mica. Abundant chalcopyrite and pyrite, possibly replacing calcite, fill interstices between quartz grains. Small clumps of siderite are also present. An assay of a rock sample from the outcrop contained a trace of gold and 0.2 ounce of silver per ton (Spurr, 1898). It is claimed that previous samples have shown considerable quantities of precious metals, with one assay up to $296 to the ton (gold at $20.67 per ounce, and silver at $0.60 per ounce) (Spurr, 1898). A sample of one of the deposits in Miller Gulch contained 0.01 ounce of gold to the ton and a trace of silver (Spurr, 1898).
Workings: On Miller Gulch, half a mile above Little Mynook (Minook) Creek, and near the mouth of Miller Gulch on the main Mynook (Minook) Creek are many silicified shear zones impregnated with sulfides (Spurr, 1898). An outcrop of hard, aphanitic, green slate on Minook Creek is altered up to 17 feet wide and sheared along joint and stratification surfaces. The outcrop is stained yellow by iron oxides and green by a mixture of calcite and copper silicate (Spurr, 1898). The outcrop also contain calcareous sandstone, described as a vein, containing occasional broken bits of mica. Abundant chalcopyrite and pyrite, possibly replacing calcite, fill interstices between quartz grains. Small clumps of siderite are also present. An assay of a rock sample from the outcrop contained a trace of gold and 0.2 ounce of silver per ton (Spurr, 1898). It is claimed that previous samples have shown considerable quantities of precious metals, with one assay up to $296 to the ton (gold at $20.67 per ounce, and silver at $0.60 per ounce) (Spurr, 1898). A sample of one of the deposits in Miller Gulch contained 0.01 ounce of gold to the ton and a trace of silver (Spurr, 1898).
Alteration: Silicification.

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

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Link to USGS - Alaska:	TN057

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References