Geologic description
The bedded rocks in the vicinity of the Venus prospect are Silurian: they include conglomerate with chert, rhyolite, and diorite clasts; and volcanic graywacke, tuff, agglomerate, and andesite. A Cretaceous gabbro pluton is south of the prospect (Sainsbury, 1961).
As described by Roehm (1938 [PE 119-12]), Warner and others (1961), and Maas and others (1995), the prospect is in greenstone (andesite?) cut by a diorite dike. The deposit is a vein that strikes N85E, dips steeply south, and is exposed for about 200 feet. The vein varies from a few inches thick at its eastern end to about 6 feet thick at its western end. Figure 35 of Warner and others (1961) is a map of the deposit. The vein locally is almost entirely pyrrhotite, with minor pyrite, sphalerite, chalcopyrite. The gangue is quartz and calcite. Three samples contained 0.01 ounce of gold per ton, up to 1 ounce of silver per ton, 0.91 to 1.78 percent copper, 33.1 to 52.4 percent iron, and 0.13 to 1.01 percent zinc (Warner and others, 1961). A sample across 6 feet of the vein contained 1.7 percent copper, 0.2 percent zinc, and 40.2 parts per million silver (Maas and others, 1995). The volcanic rocks up to several meters from the vein have been pyritized and intensely altered to chlorite and epidote. The deposit was found in 1904 by a magnetic survey. The workings consist of more than 800 feet of trenches and at least one short adit. Maas and others (1995) estimate that the deposit has an inferred resource of about 7,200 metric tons of material of variable grade. |