Yerington Copper Project is wholly-owned by Lion Copper and Gold Corp. through its subsidiary, Singatse Peak Services, LLC.
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Summary:
The Project includes the Yerington Copper Deposit, MacArthur Copper Deposit and a portion of the Bear Property which represents three of four known porphyry copper deposits in the Yerington district. All of these deposits lie in Middle Jurassic intrusive rocks of the Yerington batholith.
Copper mineralization on the Property occurs in all three phases of the Yerington Batholith. Intrusive phases, from oldest to youngest, are known as the McLeod Hill Quartz Monzodiorite (field name granodiorite), the Bear Quartz Monzonite, and the Luhr Hill Granite, the source of quartz monzonitic (i.e. granite) porphyry dikes related to copper mineralization.
Following uplift and erosion, a thick Tertiary volcanic section was deposited, circa 18-17 Ma. This entire rock package was then extended along northerly striking, down-to-the-east normal faults that flatten at depth, creating an estimated 2.5 miles of west to east dilation-displacement (Proffett and Dilles, 1984). The extension rotated the section such that the near vertically emplaced batholiths were tilted 60° to 90° westerly. Pre-tilt, flat-lying Tertiary volcanics now crop out as steeply west dipping units in the Singatse Range west of the Property. The easterly extension thus created a present-day surface such that a plan map view represents a cross-section of the geology.
Deposit Types
The Yerington deposit represents a porphyry copper deposit hosted in porphyry dikes that formed in stocks of the upper Yerington batholith. The Yerington porphyry system has been tilted westerly so that the plan view of the deposit is a cross-sectional exposure.
Mining at the Yerington deposit has revealed an alteration geometry displaying the original pyrite-rich cap (present-day leached sericite-limonite on the west end of the Yerington pit) grading downward easterly to quartz-sericite-pyrite alteration and to potassic alteration in the central portion of the pit and then continuing to a soda-flooded root zone at the eastern end.
The MacArthur deposit is a supergene enriched, oxidized porphyry copper system. Within the MacArthur deposit, phyllic alteration from the upper portion of the porphyry system dominates to the west. The alteration grades to potassic in the central MacArthur pit area and pervasive sodic-calcic alteration dominates in the eastern portions of the MacArthur pit and in the far eastern portion of the property.
Mineralization
Yerington Porphyry Copper Deposit
The general geometry of copper mineralization below the Yerington pit is an elongate body extending 6,600 feet along a strike of S62ºE. The modeled mineralization has an average width of 2,000 feet and has been defined by drilling to an average depth of 400-500 feet below the pit bottom at the 3,500-foot elevation.
The copper mineralization and alteration throughout the Yerington district and at the Yerington Property are unusual for porphyry copper camps in that the mineralization is “stripey”, occurring in WNW striking bands or stripes between materials of lesser grade. Clearly, much of this geometry is influenced by the strong, district-wide WNW structural grain observed in fault, fracture and, especially, porphyry dike orientations. Altered, mineralized bands range in width from tens of feet to 200-foot-wide mineralized porphyry dikes mined in the Yerington pit by Anaconda.
Greenish, greenish blue chrysocolla (CuSiO3.2H20) was the dominant copper oxide mineral, occurring as fracture coatings and fillings, easily amenable to an acid leach solution. Historic Anaconda drill logs note lesser neotocite, aka black copper wad (Cu, Fe, Mn), SiO2 and rare tenorite (CuO) and cuprite (Cu2O). Oxide copper also occurs in iron oxide/limonite fracture coatings and selvages.
Chalcopyrite (CuFeS2) was the dominant copper sulfide mineral occurring with minor bornite (Cu5FeS4) primarily hosted in A-type quartz veins in the older porphyry dikes and in quartz monzonite and granodiorite, as well as disseminated between veins in host rock at lesser grade. The unmined mineralized material below the pit bottom consists primarily of chalcopyrite.
MacArthur Deposit
The MacArthur deposit is a large copper mineralized system containing near-surface acid soluble copper mineralization.
The MacArthur Deposit consists of a 50 to 150-ft thick, tabular zone of secondary copper (oxides and/or chalcocite) covering an area of approximately two square miles.
Oxide copper mineralization is most abundant and particularly well exposed in the walls of the legacy MacArthur pit. The most common copper mineral is chrysocolla; also present is black copper wad (neotocite) and trace cuprite and tenorite. The flat-lying zones of oxide copper mirror topography, exhibit strong fracture control and range in thickness from 50 to 100 feet. Secondary chalcocite mineralization forms a blanket up to 50 feet or more in thickness that is mixed with and underlies the oxide copper. Primary chalcopyrite mineralization has been intersected in several locations mixed with and below the chalcocite. The extent of the primary copper is unknown as many of the holes bottomed at 400 feet or less.