Carlin is a sediment-hosted disseminated gold deposit.

Gold Quarry is one of the largest gold deposits in North America. It is comprised of two stacked orebodies: an upper structural stockwork and a lower stratabound replacement. Overall strike of the main (upper) ore zone is N45E. It is bounded on the west by the Gold Quarry Fault and on the east by the Grey/Challenger fault systems. Mineralization is continuous over 6000 feet of strike. The Deep West orebody is a silica replacement zone at the contact of footwall carbonate rocks and hanging wall siliciclastic rocks. It averages 250 feet in thickness, strikes N20E, dips 30-35 SE, and as known strike length of 2500 feet. Gold grade is double that of the Main (upper) ore zone. The Deep West ore zone is the down dip extension of the Maggie Creek South ore zone. Gold Quarry is one example of a Carlin trend gold deposit that exhibits primary northwest structural control. Mineralization is localized where the N45W Good Hope fault intersects the NE-trending Chukar-Alunite faults.

Gold grains range from <0.1 to 10.0 microns in size and usually occur associated with microfractures or disseminated in microcrystalline cherty matrix. Au:Ag ratio ranges from about 2:1 in mill grade ores to 1:3 in leach grade ores.

Gangue Materials: silica, iron oxides, kaolinite, barite, alunite, pyrite, illite, montmorillonite.

A portal within the Gold Quarry pit provides access to workings. Gold mineralization is hosted in decalcified, silty limestone units of the Siluro- Devonian Roberts Mountains Formation, which are folded into a northeast-trending anticline. Northeast-striking faults allowed gold mineralization to deposit along the hinge and limbs of the anticline. Unique to Chukar is the occurrence of visible gold along fractures.

Ore in the Leeville Project area occurs in two strata-bound zones located in the upper 350 feet of the Roberts Mountains Formation. Ore grade mineralization is located in the footwall of the West Bounding Fault, which trends northeast, dips 60 degrees west, and has approximately 150 feet of apparent normal displacement. The thickest and highest-grade portion of the deposit is located where the northwest-striking Rodeo Creek Fault intersects the footwall of the West Bounding Fault. Ore occurs in grey to black, decalcified (calcite removed) and weakly to moderately silicified rocks composed of 60 to 70 percent quartz, 10 to 30 percent dolomite, 7 to 16 percent kaolinite and illite, and 2 to 4 percent pyrite (Jackson et al. 1997). Mineralized zones of the ore body occur at depths of 1,500 to 2,000 feet below ground surface.

The Genesis Project is located within the Basin and Range Province, a region that extends over most of Nevada and portions of adjoining states. Range-front faulting has created north-south trending fault-block mountain ranges separated by broad valley fill with unconsolidated sediment. The Carlin Trend is a north-northwest alignment of predominantly carbonatehosted gold deposits. Regional folding and thrusting placed siliceous (upper plate) rocks over carbonate (lower plate) rocks. The primary thrust surface in the area is referred to as the Roberts Mountain Thrust. The Gen Fault bisects the Genesis Project area and separates the eastern carbonate assemblage from the western siliceous assemblage.

Lower plate rocks are exposed by a combination of folding and high-angle faulting. The Genesis deposit is located within the hinge zone of the Tuscarora anticline, while the Bluestar and Bobcat deposits occur in the west and the Beast/Sold deposits on the east limb of the same anticline. Numerous dikes and sills are emplaced along bedding planes, low-angle faults, and high-angle faults. The northern portion of the Genesis deposit was intruded by the Goldstrike diorite-granodiorite sill complex.

The western part of the Project area consists primarily of eastern assemblage carbonate rocks from the Roberts Mountains, Popovich, and Rodeo Creek formations. Siliceous rocks from the Vinini Formation comprise most of the eastern part of the Project area. Sedimentary rocks in the Genesis Pit have been cut by the Gen Fault, with siliceous Vinini Formation on the east side of the fault, and carbonate Popovich and Roberts Mountains formations on the west side.

Dominant alteration associated with mineralization within the carbonates is decalcification with accompanying minor silicification, clay alteration, and quartz-sericite-pyrite alteration. Sulfide deposition accompanied these alteration events.

Emigrant gold deposits are contained primarily within the Lower Mississippian-age Webb siltstone and Devonian-age Devils Gate limestone.

Gold occurs in shallow west-dipping tabular bodies at or near the contact of the Webb siltstone and underlying Devils Gate limestone (unconformity), with secondary occurrence of gold along the Emigrant Fault. Gold mineralization is present near the surface. A small percentage of ore occurs in the Mississippian-age Chainman siltstone and Fresh Webb siltstone.

The Emigrant Fault occurs along the western margin of the Emigrant gold deposit. The fault strikes north-I0 degrees-east and dips 80 to 85 degrees west. The fault separates the Chainman siltstone in the hanging-wall (above fault plane) with the Webb siltstone and Devils Gate limestone in the foot-wall (below fault plane) (Figure 3-3) (Thoreson I99I; Lapointe et at al. 1991). Although mineralization commonly occurs adjacent to the Emigrant Fault, elsewhere mineralization lies as much as 3,000 feet east of the fault. The Emigrant Fault is a localizing structure for hydrothermal fluids that migrated up the fault, and outward into adjacent sediment to form disseminated low grade gold deposits. Mineralization extends l2,000 feet along a north-south trend parallel to the fault, and thins away from the fault.

The Carlin complex consists of four open pits and four underground mines. The open pits include the Emigrant and the Gold Quarry pits in the South end of the Carlin Trend and the Silverstar and Goldstar pits in the North end of the Carlin Trend. The Emigrant open pit ceased mining operations in December 2018 while residual leaching of gold continues. The underground mines include Leeville, which is a shaft mine, along with Chukar, Pete Bajo and Exodus, which are portal mines.

Carlin’s an available mining fleet consisting of six shovels and 47 haul trucks, which range from 150 to 250 tons.

The Chukar Footwall Underground mine workings are collared in the southwest corner of the Gold Quarry Pit; three portals are being driven into the walls of the open pit mine. Ore is mined using longhole-stope and cut-and-fill methods.

Approximately 450 million tons (Mt) of waste rock would be removed to extract 60Mt of ore over a twelve-year operational life. Approximately 48.3Mt of oxide leach ore would be placed on the existing North Area Leach Facility and 11.7Mt of mill and refractory ore would be hauled to Mill 5/6 in the South Operations Area.

The Genesis project consists of Beast, Bluestar Ridge, Bobcat, Genesis, Payraise, and West Genesis. The plan is to re-start open pit mining in the area. The Genesis pit, now called Silverstar, is permitted for 650 million tons to be mined. The expansion will start in the old Genesis pit, which has a reserve of 3,000,000 ounces, and progress to West Genesis (now Goldstar) in 2014 or 2015, then to Bobcat (now Bobstar), and finally to Bluestar Ridge. The project also involves back-filling the Blue Star and Beast pits.

The Emigrant operation was mining in three pits and will eventually mine a series of eight small open pits that will be backfilled as they are mined out. The deepest pit will be 283 feet deep.

Approximately 83Mt of waste rock and 92Mt of ore would be mined in the Emigrant Project area (see Proposed Action in Chapter 2). Based on site geology, waste rock that would be excavated has been divided into three general classifications: oxidized Webb siltstone; oxidized Devils Gate limestone (oxide carbonate); and unoxidized Chainman/Fresh Webb siltstone (carbon sulfur refractory). Most rock to be removed from the mine pit would be Webb siltstone (67% of waste rock and 76% of ore) and Devils Gate limestone (32% of waste rock and 2l% of ore). The Chainman/Fresh Webb siltstone accounts for the remainder of the rock to be mined (l% of waste rock and 3% of ore).

For comparison, the nearby Rain Mine has the following percentages of waste rock types: oxidized Webb siltstone = 75 percent; oxidized Devils Gate limestone = I0 percent; and unoxidized Chainman/Fresh Webb siltstone = I5 percent (Harris 2005). The amount of unoxidized Chainmanl/Fresh Webb siltstone waste rock at the Rain Mine (I5%) is greater than that expected for the Emigrant Mine (l%); the amount of Devils Gate limestone waste rock at Rain Mine (l0%) is less than expected at Emigrant (32%). Overall mineralogical composition of the rock types at Rain Mine is similar to Emigrant, with the exception of higher barite content at Rain (Harris 2005).

The majority of the underground ore as well as higher-grade surface refractory ores are processed through the roaster at Mill 6, which consists of a grinding circuit, roasting circuit and a conventional carbon-in leach circuit. Mill 6 processed approximately 3.3 million tons of ore in 2018. Higher-grade surface oxide ores are processed by conventional milling and cyanide leaching at Mill 5. Additionally, Mill 5 operates as a flotation mill treating lower grade, non-carbonaceous, sulfidic refractory ore to produce a gold/pyrite concentrate. Mill 5 processed approximately 4.9 million tons of ore in 2018. Lower-grade surface material with suitable cyanide solubility is treated on one of four heap leach pads.

Mill 5 is a pyrite floatation plant that processes sulfide and oxide ores that are ground in a sag mill and ball mills. The material is then sent to the floatation circuit where the sulfides are floated and dried for later processing in the autoclave or roaster. The oxide material remaining after floatation is sent to a set of carbon-in-leach (CIL) tanks for gold recovery. Mill 6 consists of a double rotating mill and a roaster; sulfide material is fed to the roaster where the sulfides are volatilized. Material leaving the roaster is sent to a set of CIL tanks at Mill 5 for processing. Tailings from both CIL circuits is combined and sent through a Caro’s Acid cyanide destruction circuit before disposal in the Mill 5/6 TSF. Gold-bearing solution from the SAL (i.e., Property and Non-Property Pads) drains to a series of pregnant ponds. Solutions from the pregnant ponds are pumped via pipeline to carbon-in column (CIC) circuits at South Area plant. Loaded carbon is transferred to the carbon handling facility and refinery for further processing.

The circuits at the North Area include a heap leach pad and plant. The gold-bearing solution from the North Area Leach drains to a series of pregnant ponds. Solutions from the pregnant ponds are pumped via pipeline to CIC circuits at the North Area plant. Loaded carbon is transferred to the carbon handling facility at the South Area and refinery for further processing.