i-80 Gold Corp. has 100% interest in the Lone Tree Project, which is held through its subsidiary, Goldcorp Dee LLC.
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Summary:
Deposit Type
The Lone Tree deposit is characterized as a pluton-related or distal-disseminated Ag-Au deposit.
As discussed by Peters et al. (in Wallace et al. 2004) the Lone Tree deposit among others in the Battle Mountain district appears to be related genetically to porphyry systems, even though many deposits do not contain obvious near-surface features that would indicate this connection, mainly because the gold-silver mineralization in these deposits may be over one km away from the causative intrusions. This is why the deposit has been characterized as both “distal disseminated” (to intrusive center). Due to complex tectonic and extension in the region, the mineralization in these deposit types may have substantially different geometric relations to the intrusive centers and hosted in different stratigraphic horizons. The mineralization at Lone Tree occurs in intensely fractured three stratigraphic horizons which is similar in other deposits in the region; however, it is not the same in all deposits. Gold is associated with low Ag:Au (<2:1), As, Sb, Hg and Tl as well as elevated Bi, Mo and W. Gold is hosted in arsenopyrite indicating higher temperatures of ore formation in comparison to typical Carlin-type deposits where gold is hosted in arsenian pyrite.
Deposit Geology and Mineralization
Mineralization is hosted within structures which crosscut all three Paleozoic rock sequences present in the mine area. The oldest of these three sequences is the Ordovician Valmy Formation, which is a part of the Roberts Mountain Allochthon.
In the mine area, the Valmy consists primarily of quartzite, with lesser amounts of chert, argillite, and minor basalt. The Valmy rocks are unconformably overlain by rocks of the Pennsylvanian Antler Sequence, which belong to the Battle and Edna Mountain Formations. The Lone Tree Extension Project, Humboldt County, Nevada). The Edna Mountain Formation at Lone Tree is typified by a sandy siltstone unit grading downward into a lithic sandstone unit. The Battle Formation is observed as a poorly sorted cobble conglomerate of varying thickness. A thin calcareous sandstone tentatively identified as a lateral equivalent of the Antler Formation rocks present at the Marigold Mine has been encountered in drill holes on the southeastern margin of the mine area. Rocks of the Pennsylvanian-Permian Havallah sequence were thrust over the Antler Sequence rocks in the mine area during the Sonoma Orogeny. The Havallah Sequence at Lone Tree encompasses several rock types within at least three packages, but is dominated by siltstones, chert, and basalts with lesser sandstones and conglomerates.
Although gold mineralization is present in all three Paleozoic sequences, Antler Sequence rocks appear to have been preferentially mineralized within the structural zones. Alluvial cover over the deposit ranges from a minimum of two feet to a maximum in excess of 400 feet. Bedrock has been sharply down-dropped to the north and to the southeast by postmineral faulting, creating alluvium-filled basins in excess of 1,000 feet deep.
Gold Mineralogy
Gold mineralization occurs as sub-micron sized inclusions within a distinct generation of very fine-grained pyrite and arsenopyrite in the sulfide zone. Evidence gathered to date suggests that the main gold deposition event occurred in a temperature range of 200° to 400° (Holley et al., 2019). The ore mineralogy shows evidence of two overprinted assemblages reflecting at least two hydrothermal episodes at Lone Tree. Partial oxidation of the main stage mineralization occurred prior to a later, epithermal event characterized by open-space filling textures and weakly auriferous pyrite and marcasite. In the oxidized portions of the deposit, and particularly in the Havallah rocks, gold occurs as micron-sized particles in goethite and limonite. Post-mineral oxidation extends as much as 700 feet down major structures such as the Wayne Zone. No supergene effects or gold remobilization have been proven or documented at the Lone Tree Mine.