Geologic description
The Marty adit is part of a group of 35 claims and properties that were consolidated under the name Marty Group in the 1920s and fell under the control of the Alaska Windham Gold Mining Company in 1930 (Kimble and others, 1984). As defined in this data base, the properties in the claim block include the Fries and Falls Quartz prospects (SD040); the Marty adit; the Yates and nearby unnamed prospects (SD042); the Yellow Jacket prospect (SD043); and the Jackson prospect, Keith prospect, and the Jensen Mine (SD044). These properties are often referred to collectively as the Second Zone as defined by Spencer (1906). The early history of these properties is described in detail by Redman (1988). A small stamp mill was erected on on the south side of Spruce Creek in 1900 and fed by a 3,000-foot aerial tram to the Yellow Jacket prospect; in 1927, a Lane mill, the Marty mill, was erected on the north side of Spruce Creek and tied to the Jensen adit by a 4,400-foot aerial tram. There may have been small test runs of ore through the early stamp mill from one or more of the prospects but the only significant production in the Second Zone is apparently from the Jensen Mine which produced 18 tons of hand sorted ore in 1927 that contained about 50 ounces of gold. In general, the deposits in the Second Zone are gold-quartz veins with few sulfides; the best values are in veins that crosscut muscovite schist of Cretaceous age that generally trends about N30W (Brew and Grybeck, 1984). Although the mines at the head of Windham Bay were examined by various companies from the 1930s to the establishment of the Chuck River Wilderness Area, there has been little substantial work and no new underground workings. The underground workings here consist of a 540-foot adit with a 490-foot crosscut, and 3 raises (Kimble and others, 1984). Several quartz veins are exposed in the adit and the crosscut was systematically sampled. But few of the samples contained significant amounts of gold and the best sample, a 10-foot channel sample, contained about 0.4 part per million gold. The prospect was active from 1904 to 1936 but apparently produced no ore. Kimble and others (1984) mapped the geology and located their sampling on their Figure 36. The deposit at the Marty prospect has been dated at 55.8 million years by Goldfarb and others (1997); like others in the Juneau Gold Belt, they thought it was formed from fluids generated by Cretaceous metamorphism and then forced to the site of deposition by the emplacement of the Coast Range Batholith. |