System type: Sediment-hosted Carlin-type
Target: Fault-controlled and disseminated gold
The Baker Spring Project covers an area of strong silicification twelve miles north of Newmont Mining Corporation’s Long Canyon mine, which is slated for production by early 2017. It lies along the eastern range front of the Pequop Mountains, the same setting as Long Canyon, which is a sediment-hosted (Carlin-type) gold system containing a resrve of 1.2 million ounces of gold at a 2.31 g/t gold.
Baker Spring is a Carlin-type gold target containing multiple structurally-controlled zones of silicification (jasperoid) along north-northwest trending faults, an orientation similar to many of the productive gold deposits of northern Nevada. Extensive replacement-style silicification in Paleozoic carbonate rocks occurs marginal to the fault-controlled jasperoids. Although sampling to date has not detected elevated gold contents, the jasperoids contain strongly-elevated mercury and other trace metals and locally contain disseminated pyrite and hydrothermal barite, features characterisitic of productive Carlin-type gold deposits. Individual silicified fault zones are at least 4,000 feet long and project into or are surrounded by valley-fill gravel (alluvium) along the northeast corner of the Pequop Range. Alluvial cover in the area appears to be thin, with jasperoids in some areas surrounded by more than 3,000 feet of cover between outcrops.
The range-front setting is very prospective; the majority of the large gold systems in Nevada are developed in these settings. Also, the strong silicification along steep faults indicates that there is a local, deep-seated fluid source. The elevated mercury contents are increasing outboard into the alluvial-covered valley, a possible vector to concealed gold mineralization, as mercury is elevated at Long Canyon to the south.
Newmont Mining completed the first drilling at Baker Spring in 2012, but the program was limited to six shallow (< 600 feet) widely-spaced holes. Only two of the six holes crossed silicified fault zones, and these holes crossed the structures at depths of only 250-300 feet. The holes were too shallow to adequately test different stratigraphic units or the multiple silicified fault zones given the presence of anomalous Hg, regarded as indicative of the shallower parts of a hydrothermal system.