THE ABUNDANCE AND DISTRIBUTION OF CRITICAL MINERALS IN VARIOUS MINERAL DEPOSITS OF CLIMAX-TYPE MAGMATIC-HYDROTHERMAL SYSTEMS OF THE UNITED STATES

Climax-type systems (N~50) in the western Unites States are mostly Eocene to Pliocene in age and are best known for their enormous porphyry molybdenum deposits (N=12). They occur in post-subduction, extensional tectonic settings and are associated with A-type granites contemporaneous with bimodal volcanism that produced trachybasalt and silicic rhyolite. Porphyry stocks in these systems emanate from highly evolved silica (>75% SiO₂)- and fluorine (>1%)- rich plutons that often contain niobium-yttrium-fluorine (NYF) pegmatites containing niobium, beryllium, and rare earth elements (REE). These porphyry intrusions are enriched in molybdenum, lithium, rubidium (>500 ppm), tungsten, tin, niobium (>50 ppm) and tantalum (≳2ppm). Associated porphyry molybdenum deposits are relatively high grade (typically 0.1−0.3 percent Mo), can be very large (100−1,000 million tons), and consist of quartz-molybdenite stockworks with silicic and potassic alteration that lie above and around the apex of cupolas. Small amounts of tungsten, tin, and REE (as wolframite, cassiterite, monazite) were produced from the Climax mine in CO. Climax-type systems also generate peripheral, zinc-rich polymetallic skarn, vein and replacement deposits, distal disseminated silver-gold deposits, as well as high sulfidation (HS) and intermediate sulfidation (IS) epithermal deposits that contain a diverse suite of critical minerals such as manganese, tellurium, tungsten, bismuth, indium, fluorspar, barite, germanium, gallium, antimony and arsenic (e.g. Deer Trail deposit, UT; Bare Mountain District, NV; and several deposits in the San Juan Mountains, CO). They also generate lithocap alunite deposits, such as Blawn Mountain and Alunite Ridge in UT that contain significant amounts of potash (K₂SO₄), aluminum, and gallium. Climax-type systems include topaz rhyolites associated with the world’s largest volcanogenic beryllium deposit and smaller uranium, tin, and fluorspar deposits. Climax-type systems are therefore an important past, current, and potential future source of several critical minerals.