Prospect, Inactive

Alternative names


Commodities and mineralogy

Main commodities Au
Ore minerals arsenopyrite; gold
Gangue minerals quartz

Geographic location

Quadrangle map, 1:250,000-scale SV
Quadrangle map, 1:63,360-scale C-2
Latitude 59.51
Longitude -150.48
Nearby scientific data Find additional scientific data near this location
Location and accuracy The Tidewater prospect is on the steep, rocky, east shore of Surprise Bay in the southeast corner of the Seldovia C2 quadrangle. Surprise Bay is in the West Arm of Nuka Bay. A short adit that was at sea level prior to the 1964 earthquake is now almost completely flooded at high tide (Richter, 1970). The adit was 42 feet in length but is less 25 feet long now due to wave action. This is Cobb's (1972, MF-397) location 27 and Richter's (1970) location 10. Cobb (1972, OFR 80-87) summarized the relevant references under the name Tidewater.

Geologic setting

Geologic description

The prospect is in graywacke and interbedded slate of the Cretaceous Valdez Group (Richter, 1970). Prior to 1931, a 41 foot adit was driven on a vein that strikes N80E and dips 72S. The vein consists of a half-foot of sheeted quartz with scattered lens of arsenopyrite along the footwall and as much as four feet of barren quartz stockwork in the hanging wall. The country rock along the hanging wall is a graywacke that was brecciated prior to the introduction of the quartz stockwork. Assay values ranged from $38.90 to $18.00 per ton with gold at $20.67 per ounce (Pilgrim, 1933).
Geologic map unit (-150.482097801563, 59.509420197581)
Mineral deposit model Low-sulfide, Au-quartz vein (Cox and Singer, 1986; model 36a)
Mineral deposit model number 36a
Age of mineralization Tertiary; Boden and others (1991) report other veins in the district are about 55 m.y. old.
Alteration of deposit None reported although, Borden and others (1991) report other veins in the Nuka Bay district show carbonization, sulfidization, sericitization, and silicification of the wall rock adjacent to the veins.

Production and reserves

Workings or exploration A 41 foot adit was driven in the 1930s. Richter (1970) took a single channel sample across the vein in the face of the drift, that assayed 6.5 ppm gold.
Indication of production None
Reserve estimates None.
Production notes Probably none.