Marigold mine, Battle Mountain Mining District, Humboldt County, Nevada, USAi

Regional Level Types
Marigold mine	Mine
Battle Mountain Mining District	Mining District
Humboldt County	County
Nevada	State
USA	Country

Sec 18 T33N R43E. Gold.
Carlin type.
Marigold is the second largest sedimentary rock-hosted disseminated gold deposit in the Battle Mountain mining district, with 3.7 million mined ounces of gold at an average grade of 0.67 g/t.


Structure: Golconda Thrust Fault North- and northwest-striking Basin and Range normal faulting are evident inthe mine area.

Alteration: Host rocks have been subjected to decarbonation, argillization, silicification, and supergene oxidation. Partial removal of carbonate from originally calcareous rocks preceded gold mineralization and resulted in increased porosity and permeability. In some ore zones, intensely argillized rocks above and below mineralization may have served as impermeable seals to confine later gold-bearing hydrothermal fluids. Silicification may be coeval with gold deposition and is represented by local replacement of favorable lithologies and jasperoid development in fault zones. Oxidation is thought to be supergene, but the possibility of hypogene oxidation is not ruled out.

Commodity: Ore Materials: gold Gangue Materials: barite, calcite, jarosite, hematite, limonite

Deposit: Most of the gold occurs as very fine (<5 micron) blebs in iron oxide pseudomorphs after pyrite, or as similar sized grains in carbonate veins or jarosite-stained quartz matrix material. In the 8 south orebody, gold mineralization correlates well with the intensity of iron oxide staining in the matrix, dark red iron oxide and jarosite usually indicate high gold content, whereas yellow iron oxide is associated with lower grade mineralization.

Deposit type: Distal disseminated Ag-Au

Development: Details of the original discovery are unknown. Historic production was confined to underground workings in the immediate vicinity of the old Marigold Mine. Several thousand tons were shipped in the 1930s by Frank Horton. In 1982, Marigold Development Co. mined, crushed, and heap leached approximately 3200 tons of ore from an open pit on the site of the abandoned underground workings. This effort produced 271 ounces of gold at an estimated recovery rate of 75%. Exploration work within the mine area, prior to the involvement of Cordex in 1985, included extensive rock sampling, grid soil geochemistry, VLF-EM surveys, drilling, and geologic mapping by numerous companies. Most of the work was concentrated near the underground workings. Approximately 200 holes were drilled prior to 1985. In 1985, VEK/Andrus Associates drilled three holes on claims 1 mile NE of the underground workings in an area of alluvial cover. These holes intersected shallow bedrock, deep oxidation, anomalous trace element concentrations, and a gold-bearing interval of 0.017 opt gold from 720-765 ft. Depth (VEK hole #2). Cordex leased the VEK claims in September 1985 on the basis of these drill results. A drilling program was initiated in November 1985. The third and fourth holes of the program intersected ore grade intervals near the center of the 8 South ore zone. In 1986, consolidation of the land position was achieved by forming a joint venture between Cordex and Santa Fe Pacific Mining Corp. and leasing the claim block, which included the historic Marigold Mine. A 1250 ton/day carbon-in-leach mill was built to process ore grading over 0.04 opt gold. Recovery grade material was to be heap leached at a rate of approximately 1500 tons/day. The life of the mine was expected to exceed nine years. In 2003 Glamis Gold and Barrick Gold received permits for their Millennium Expansion project at the Marigold Mine, which will develop four new open pits at the site and two new heap leach facilities. The four new pits will be called Target I, Target II, Basalt and Antler. Once Millennium is in full swing, Glamis expects to produce 180,000 ounces of gold per year. In conjunction with the expansion program, Glamis has continued its in-fill and step-out drilling programs. By early 2006, Glamis Gold and joint venture Barrick Gold began their Millennium Expansion at the Marigold Mine in Humboldt County that will approximately triple the mine?s production.

Ore(s): North- and northwest-striking Basin and Range normal faults, with minor or no offset, are the most important structural controls. The Golconda Thrust is not thought to be important as an ore control. Beds of calcareous conglomerate in the upper portions of the antler sequence host a majority of the ore, but parts of the Valmy Formation and lower Antler Sequence also host ore.

Other Databases

Link to USGS MRDS:	10310301
Link to USGS MRDS:	10125353

Other Regions, Features and Areas containing this locality

References