Mespelt

Prospect, Undetermined

Commodities and mineralogy

Main commodities Ag; Pb; U
Other commodities Au; Sn; W; Zn
Ore minerals galena; metazeunerite; pyrite; sphalerite; zeunerite
Gangue minerals calcite; limonite; quartz; siderite

Geographic location

Quadrangle map, 1:250,000-scale TL
Quadrangle map, 1:63,360-scale D-5
Latitude 62.89
Longitude -152.21
Nearby scientific data Find additional scientific data near this location
Location and accuracy The Mespelt prospect is located at the end of the trail shown in the east half of Section 2, T. 32 N., R. 16 W., of the Seward Meridian. C.C. Hawley and Associates, Inc. (1978, Fig. 4.2-C) locate this prospect approximately 800 feet east-southeast of Little Mountain at about 4300 feet. Also shown by Reed and others (1978) as locality 5.

Geologic setting

Geologic description

The Mespelt prospect consists of two bulldozer cuts, several prospect pits, and a 40 foot shaft (now caved) constructed to evaluate a 7-foot-wide, 1,000-foot-long quartz-carbonate vein that cuts the Tertiary-age Tonzona granitic pluton (Tmt), part of the McKinley sequence mapped by Reed and Nelson (1980). The vein, comprised of argentiferous galena, low-grade uranium, and tin mineralization, occurs beneath a gossan cap. High grade grab samples collected in 1959 contained 0.18 to 32.91 oz/ton Ag; trace Au, up to 46.4 percent Pb, 0.037 to 0.14 percent eU, up to 2.52 percent Sb, up to 0.06 percent Sn, and 0.01 to 0.04 percent W. A chip sample collected in 1956 assayed 56.3 percent WO3 (Maloney and Thomas, 1966, Table 3; Reed and others, 1978). Greisen assemblages of quartz-tourmaline-muscovite are developed adjacent to the vein. Tin in excess of 1,500 ppm in the nonmagnetic heavy-mineral concentrates from stream silt samples collected from the Camp Creek drainage to the west of this prospect is reported by Curtin, Karlson, Tripp, and Day (1978).
The geologic setting of the Mespelt silver-lead-tin-tungsten vein is described, as follows, by C.C. Hawley and Associates, Inc., (1978) and Reed and Nelson (1980). Blocky slate, argillite, thin-bedded siliceous limestone and chert define a belt of lower Paleozoic sedimentary and metavolcanic rocks (possibly Keevy Peak, Totalanika series, or equivalents) bordered by the Tonzona granitic pluton. The granite has three phases: a coarse-grained, locally porphyritic biotite granite; a medium-grained biotite granite; and a late fine-grained, leucocratic, locally aplitic, muscovite - tourmaline granite in which ovoid clusters of small black tourmaline crystals give the rock a 'dalmatian' appearance. Muscovite may exceed biotite and accessory minerals include tourmaline with lesser amounts of topaz, fluorite, garnet, zircon, and apatite. Late-stage greisen veinlets, like those at the Mespelt prospect, contain muscovite, topaz, tourmaline, locally abundant beryl, and occasionally, cassiterite. Lead, silver and tin mineralization occurs in Paleozoic metasediments and metavolcanic rocks along the north and northeast contact of the pluton. The Tonzona pluton has metamorphosed the country rocks to skarn assemblages along the contact and has formed skarn hosted polymetallic mineralization such as at the Jiles-Knudson (TL 004), Boulder Creek (TL073) and the nearby Hogback prospect (TL006).
In much of the literature, the Jiles-Knudson, Mespelt, Hogback and Boulder Creek are included as the Purkeypile group of lode claims.
Geologic map unit (-152.212232173524, 62.8894446455772)
Mineral deposit model Fringe zone of Pb, Zn, and Ag sulfide mineralization to tin veins (generally related to the tin vein model of Cox and Singer, 1986; model 15b).
Mineral deposit model number 15b
Age of mineralization Tertiary; mineralization in the Boulder Creek, Jiles-Knudson, Hogback and Mespelt areas is interpreted to be linked to the Tonzona granite (Tmt), part of the McKinley Sequence, that has been determined to range from 52.3 to 56.2 m.y. in age (Reed and Lanphere, 1972; Reed and Nelson, 1980).
Alteration of deposit Greisen assemblages of quartz-tourmaline-muscovite-chlorite are developed locally (C.C. Hawley and Associates, Inc. 1978).

Production and reserves

Workings or exploration Workings consist of two bulldozer cuts, prospect pits, and a 40-foot shaft (now caved) (C.C. Hawley and Associates, Inc., 1978).
Indication of production None
Production notes No published information available.

Additional comments

High grade samples were taken by the U.S. Bureau of Mines in 1959 and by the Alaska Division of Geological and Geophysical Surveys (C.C. Hawley and Associates, Inc., 1978). In much of the literature, the Jiles-Knudson, Mespelt, Hogback and Boulder Creek are included as the Purkeypile group of lode claims.
High grade grab samples collected in 1959 contained 0.18 to 32.91 oz/ton Ag; trace Au, up to 46.4% Pb, 0.037 to 0.14% eU, up to 2.52% Sb, up to 0.06% Sn, and 0.01 to 0.04% W. A chip sample collected in 1956 assayed 56.3% WO3 (Maloney and Thomas, 1966, Table 3; Reed and others, 1978). Greisen assemblages of quartz-tourmaline-muscovite are developed adjacent to the vein. Tin in excess of 1,500 ppm in the nonmagnetic heavy-mineral concentrates from stream silt samples collected from the Camp Creek drainage to the west of this prospect is reported by Curtin, Karlson, Tripp, and Day (1978).

References

MRDS Number A011561

References

Reporters Madelyn A. Millholland (Millholland & Associates)
Last report date 8/10/1998