The pan gold project, being developed by Midway Gold, is located around 35km west of Eureka in the western region of White Pine County, Nevada. It is the US’s biggest gold producing state and home to two of the top ten biggest gold mines in the world.
Pan will be a low-cost shallow open-pit mining operation extracting oxidised gold ore to be treated using heap-leaching technology. The feasibility study for the $99m Pan project was completed in November 2011, and the ground-breaking ceremony was held in January 2014 after receiving final permission in December 2013. Mining activities at the pan project began in September 2014 and the first gold was poured in March 2015.
The average annual gold production is estimated at 81,000oz over nine years of mine life. When operational, the Pan project is expected to create 145 full-time jobs.
Pan gold deposit geology and reserves
The Pan gold deposit, situated at the northern end of the Pancake mountain range in east-central Nevada, is a Carlin-type epithermal and disseminated gold deposit hosted by carbonate and clastic sedimentary rocks of Devonian to Permian age. The gold resource outcropping at the surface is associated with oxide mineralisation in elongate breccias along the north-south trending pan fault.
The Pan deposit was discovered in 1978 and explored by a number of companies before being acquired by Midway in 2007. Midway completed 209 drill holes for a total length of 95,394ft by September 2011.
As of November 2011, the mine was estimated to hold 25.24million tonnes (Mt) of ore (grading 0.6g/t Au) in proven and 23.06Mt of ore (grading 0.51g/t Au) in probable reserves. The contained gold reserve at the mine was estimated to be 864,000oz.
Mining and processing at pan gold mine
The Pan gold mining operation will comprise two open-pits (south pan and north pan) and a central leach pad to process the extracted ore. The South Pan pit is planned to be mined first in the initial phase of mining operation.
Open-pit mining method involving drill, blast, load and haul is employed to extract the ore from the shallow gold deposit. The mining fleet will comprise of a Bucyrus RH120E front shovel, a Cat 992 front end loader, and Cat 785D 150t haul trucks, along with other support equipment.
During the initial years of mining, the run-of-mine ore is stacked directly onto the heap leach pad. The The company plans to implement run-of-mine methods avoiding the initially planned two-stage crushing circuit. The primary ore, crushed near the pit, will be transported by haul trucks to the crushing facility housing secondary and tertiary cone crushers. The waste material will be directly hauled to the waste dump. The crushed and screened ore will be conveyed to the heap leach pad which can handle up to 6.2mt of ore per year.
The ore leached with conventional heap leaching methods will be processed at an adsorption, desorption and recovery (ADR) plant with an average estimated recovery of 75%.
Infrastructure facilities and construction details
An 11km long main access road connecting the mine with the US Highway 50 is being constructed. A 24.9kV line is also being constructed to connect the mine with a new 69kV substation being built near the US Highway 50. The mine site will also use a generator as a backup in case of a main power supply failure.
The water supply system at the mine will comprise of two production wells, an 180,000gal storage tank, a small water treatment system to deliver potable water, and diesel-driven pumps to supply fire water to various facilities.
Other infrastructure facilities at the mine area include two waste rock disposal sites, a 9,600ft2 two-storey office building, a 13,050ft2 building housing warehouse and laboratory, and a 10,800ft2 process building.
Contractors/consultants involved with the development of Midway’s gold project in Nevada
Midway awarded the engineering, procurement, construction and management (EPCM) contract for the pan project to Jacobs Engineering in November 2013.
Gustavson Associates was commissioned to conduct the primary feasibility study for the project and to update the mineral resource estimation of the mine.
Summit Valley Technologies, a subsidiary of FLSmidth, is the supplier of gold recovery equipment for the processing plant.
Engineering study for the heap leach pad was conducted by SRK Consulting.
Ledcor was selected as the mining contractor for the Pan Project in May 2014. It will provide all mining-related services including manpower and equipment during the initial years of open-pit operation.