Florida Canyon Gold Inc. (FCGI) is a newly listed company formed pursuant to the spin-out of the United States and Mexican operations of Argonaut Gold Inc. ("Argonaut"), including the Florida Canyon mine in Nevada, U.S.A. and the San Agustin mine in Mexico. The Canadian operations of Argonaut, including the Magino mine, were acquired by Alamos Gold Inc. ("Alamos") on July 12, 2024.
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Summary:
Three types of mineralization are present at Florida Canyon. The primary type is disseminated gold mineralization within siltstone and silty sandstone. In addition, gold mineralization occurs along brecciated contacts and karsted areas of the Natchez Pass limestone. The third type of gold mineralization occurs as epithermal hot springs type vein mineralization.
Florida Canyon was a large tonnage low grade Neogene aged epithermal gold system adjacent to an active geothermal system. The close spatial association with the geothermal system has led to a general belief that Florida Canyon is a hot springs-type epithermal gold deposit. Hydrothermal alteration assemblages and the mineralogy of both oxidized and unoxidized gold mineralization at Florida Canyon have been characterized as having formed in a low-sulfidation epithermal environment.
Mineralization
Three types of mineralization are present at Florida Canyon. The primary type is disseminated gold mineralization within siltstone and silty sandstone. In addition, gold mineralization occurs along brecciated contacts and karsted areas of the Natchez Pass limestone. The third type of gold mineralization occurs as epithermal hot springs type vein mineralization.
The location and geometry of the mineralized bodies at Florida Canyon are a result of structure; the presence of favorable silty argillite, quartzite, and limestone host rocks; and the position of the host rocks relative to structural conduits. The higher-grade zones of mineralization tend, in general, to follow the high-angle, northeast- and northwest-trending fault and shear zones. The more moderate- or lower-grade zones are controlled by favorable host rocks more distal to feeder structures.
Rock units that are more favorable hosts to mineralization include silty argillite, hornfels contact zones with mafic sills, karsted limestone, and platy, silty limestone with interbeds of calcareous shale. Local factors that influence the occurrence and geometry of mineralized bodies include variations in folds, foliation, and bedding in favorable units, intersecting structural fabrics, and proximity to low-angle structures (Taylor 2001). Hypogene mineralization at Florida Canyon consists of native gold and electrum associated with quartz, iron oxides, pyrite, marcasite, and arsenopyrite (Hastings et al., 1987). Quartz is the major gangue material. Secondary minerals identified in the Florida Canyon deposits to date include gypsum (likely remobilized from the Grass Valley Formation), alunite, barite, native sulfur, calcite, dolomite, fluorite, anhydrite, pyrargyrite, pyrrhotite, and stibnite. There are two types of hydrothermal, epithermal quartz veins at Florida Canyon (Hastings et al., 1987). The most important are vein swarms and stockworks that contain most of the gold mineralization. These veins generally follow a north-northeast trend (Hastings et al., 1987) and are characterized by colorless, euhedral to subhedral quartz, or banded chalcedonic white to colorless quartz that contains limonite after pyrite (Taylor, 2001).
The second type of hydrothermal quartz veining occurs as large, through-going, banded fissure veins that follow the original north-northeast structural fabric (Hastings et al., 1987). These veins are interpreted to represent a late hydrothermal event that overprinted the earlier episode of gold-bearing quartz veining and stockworks. These veins are characterized by bands of coarse, prismatic quartz alternating with bands of cherty chalcedony and only occasionally contain economic gold grades. Milky white bull-quartz veins, considered to be metamorphic in origin, may also be present in the mineralized zones, but they are not gold bearing (Taylor, 2001). Locally, pervasive silicification is generally associated with areas of high-density quartz veining and/or intense hydrothermal brecciation (Taylor, 2001). Sericite, adularia, clay, and chlorite occur locally in quartz veins, breccia matrix, and on fracture surfaces. There is extensive argillization and bleaching throughout the deposit area, with pervasive hematization that is largely confined to silty units marginal to the bleached areas (Hastings et al., 1987).
A different style of mineralization has been recognized in the more recently discovered deposits east of the original Florida Canyon Main. At Radio Tower, karsted surfaces in Natchez Pass Limestone are replaced by cryptocrystalline silica forming jasperoid and hornfelsed contact zones between mafic sill and limestone are strongly quartz-veined and pyritized. These ore zones represent a likely older event relative to the younger, hot-spring style mineralization in the Main Pit and Madre areas.