Mineral resource appraisal of the Salmon National Forest, Idaho

Johnson, Rick; Close, T.J.; McHugh, Ed

doi:10.3133/ofr98478

Cited by 8 publications

(9 citation statements)

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“…The Black Pine deposit, ca. 15 km southeast of the district, contains a small high-grade sulfide resource of 1.0 Mt at 4.5 wt % Cu, 0.08 wt % Co, and 1.03 g/t Au (Johnson et al, 1998). A recent compilation by the USGS indicates that past production plus reserves and resources in 14 deposits of the Blackbird district, excluding Black Pine, total 16.8 Mt at an average grade of 0.74 wt % Co, 1.37 wt % Cu, and 1.04 g/t Au.…”

Section: History and Productionmentioning

confidence: 99%

Strata-Bound Fe-Co-Cu-Au-Bi-Y-REE Deposits of the Idaho Cobalt Belt: Multistage Hydrothermal Mineralization in a Magmatic-Related Iron Oxide Copper-Gold System

Slack

2012

Economic Geology

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Mineralogical and geochemical studies of strata-bound Fe-Co-Cu-Au-Bi-Y-rare-earth element (REE) deposits of the Idaho cobalt belt in east-central Idaho provide evidence of multistage epigenetic mineralization by magmatic-hydrothermal processes in an iron oxide copper-gold (IOCG) system. Deposits of the Idaho cobalt belt comprise three types: (1) strata-bound sulfide lenses in the Blackbird district, which are cobaltite and, less commonly, chalcopyrite rich with locally abundant gold, native bismuth, bismuthinite, xenotime, allanite, monazite, and the Be-rich silicate gadolinite-(Y), with sparse uraninite, stannite, and Bi tellurides, in a gangue of quartz, chlorite, biotite, muscovite, garnet, tourmaline, chloritoid, and/or siderite, with locally abundant fluorapatite or magnetite; (2) discordant tourmalinized breccias in the Blackbird district that in places have concentrations of cobaltite, chalcopyrite, gold, and xenotime; and (3) strata-bound magnetite-rich lenses in the Iron Creek area, which contain cobaltiferous pyrite and locally sparse chalcopyrite or xenotime. Most sulfide-rich deposits in the Blackbird district are enclosed by strata-bound lenses composed mainly of Cl-rich Fe biotite; some deposits have quartz-rich envelopes.Whole-rock analyses of 48 Co-and/or Cu-rich samples show high concentrations of Au (up to 26.8 ppm), Bi (up to 9.16 wt %), Y (up to 0.83 wt %), ΣREEs (up to 2.56 wt %), Ni (up to 6,780 ppm), and Be (up to 1,180 ppm), with locally elevated U (up to 124 ppm) and Sn (up to 133 ppm); Zn and Pb contents are uniformly low (≤821 and ≤61 ppm, respectively). Varimax factor analysis of bulk compositions of these samples reveals geochemically distinct element groupings that reflect statistical associations of monazite, allanite, and xenotime; biotite and gold; detrital minerals; chalcopyrite and sparse stannite; quartz; and cobaltite with sparse selenides and tellurides. Significantly, Cu is statistically separate from Co and As, consistent with the general lack of abundant chalcopyrite in cobaltite-rich samples.Paragenetic relations determined by scanning electron microscopy indicate that the earliest Y-REE-Be mineralization preceded deposition of Co, Cu, Au, and Bi. Allanite, xenotime, and gadolinite-(Y) commonly occur as intergrowths with and inclusions in cobaltite; the opposite texture is rare. Monazite, in contrast, forms a poikiloblastic matrix to cobaltite and thin rims on allanite and xenotime, reflecting a later metamorphic paragenesis. Allanite and xenotime also show evidence of late dissolution and reprecipitation, forming discordant rims on older anhedral allanite and xenotime and separate euhedral crystals of each mineral. Textural data suggest extensive deformation of the deposits by folding and shearing, and by pervasive recrystallization, all during Cretaceous metamorphism. Sensitive high resolution ion microprobe U-Pb geochronology by Aleinikoff et al. (2012) supports these paragenetic interpretations, documenting contemporaneous Mesoproterozoic growth of early xenotime and ...

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Section: History and Productionmentioning

confidence: 99%

Strata-Bound Fe-Co-Cu-Au-Bi-Y-REE Deposits of the Idaho Cobalt Belt: Multistage Hydrothermal Mineralization in a Magmatic-Related Iron Oxide Copper-Gold System

Slack

2012

Economic Geology

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“…Other features shown include the Great Divide megashear (GDM;after O'Neill et al, 2007), the Sheep Creek Cu-Co deposit (SC; after Graham et al, 2012), the rifted continental margin (RCM;after O'Neill et al, 2007), and accreted oceanic terranes (Pz-Mz-Paleozoic to Mesozoic). (B) Simplified geologic map of the Salmon River Mountains, after Evans and Green (2003), showing selected Co-Cu ore zones and prospects of the Idaho cobalt belt (after Johnson et al, 1998), all of which are in Mesoproterozoic strata of the Lemhi subbasin within the Poison Creek thrust plate. Stippling represents the southern boundary of the regional garnet zone (after Lewis et al, 2012).…”

Section: Locationmentioning

confidence: 99%

“…Fold sets are numbered from oldest (F 1 ) to youngest (F 4 ). Locations of selected Cu ± Co sites in and around the Idaho cobalt belt are from Johnson et al (1998). Names of most mines and some prospects are spelled fully, but others are abbreviated as follows: HS-Haynes-Stellite (Co), bc-Bonanza Copper (Cu-Co-Au), cnc-Conicu (Co-Cu), ec-Elkhorn Creek (Co-Cu), ma-Mary Ann (Co-Cu), sr-Sweet Repose (Cu-Co), tp-Tinkers Pride (Co-Cu), and ef-East Fork (Co-Cu, ~40 km NE of the Salmon Canyon Copper prospect).…”

Section: Previous Workmentioning

confidence: 99%

“…A description by Johnson et al (1998) of the Mary Ann prospect, which is in the proximal footwall of the Iron Lake thrust plate, did not mention garnets. However, a schistose mafic dike in the Lookout structural block (also in the footwall of the Iron Lake thrust plate) contains large and abundant garnets (dated ca.…”

Section: Gradational Base Of the Garnet Zonementioning

confidence: 99%

“…Diagrammatic geologic map and cross section of the Blackbird mine area and its surroundings: (A) Geologic map, showing the Blackbird, Lookout, and Haynes-Stellite structural blocks, and the southwest margin of the megacrystic granite pluton of Big Deer Creek. Sources of information includeVhay (1948),Evans and Connor (1993),Johnson et al (1998), andTysdal et al (2003). Labeled mines and prospects are the Bonanza Copper prospect (bc), Haynes-Stellite mine (HS), Sweet Repose prospect (sr), and Tinkers Pride prospect (tp).…”

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Geologic history of the Blackbird Co-Cu district in the Lemhi subbasin of the Belt-Purcell Basin

Bookstrom

Box

Cossette

et al.

Geological Society of America Special Papers

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The Blackbird cobalt-copper (Co-Cu) district in the Salmon River Mountains of east-central Idaho occupies the central part of the Idaho cobalt belt-a northwest-elongate, 55-km-long belt of Co-Cu occurrences, hosted in grayish siliciclastic metasedimentary strata of the Lemhi subbasin (of the Mesoproterozoic Belt-Purcell Basin). The Blackbird district contains at least eight stratabound ore zones and many discordant lodes, mostly in the upper part of the banded siltite unit of the Apple Creek Formation of Yellow Lake, which generally consists of interbedded siltite and argillite. In the Blackbird mine area, argillite beds in six stratigraphic intervals are altered to biotitite containing over 75 vol% of greenish hydrothermal biotite, which is preferentially mineralized. Past production and currently estimated resources of the Blackbird district total ~17 Mt of ore, averaging 0.74% Co, 1.4% Cu, and 1.0 ppm Au (not including downdip projections of ore zones that are open downward). A compilation of relative-age relationships and isotopic age determinations indicates that most cobalt mineralization occurred in Mesoproterozoic time, whereas most copper mineralization occurred in Cretaceous time. Mesoproterozoic cobaltite mineralization accompanied and followed dynamothermal metamorphism and bimodal plutonism during the Middle Mesoproterozoic East Kootenay orogeny (ca. 1379-1325 Ma), and also accompanied Grenville-age (Late Mesoproterozoic) thermal metamorphism (ca. 1200-1000 Ma). Stratabound cobaltite-biotite

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Distribution of Cu, Co, As, and Fe in mine waste, sediment, soil, and water in and around mineral deposits and mines of the Idaho Cobalt Belt, USA

Gray

Eppinger

2012

Applied Geochemistry

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Mineral resource appraisal of the Salmon National Forest, Idaho

Cited by 8 publications

References 0 publications

Strata-Bound Fe-Co-Cu-Au-Bi-Y-REE Deposits of the Idaho Cobalt Belt: Multistage Hydrothermal Mineralization in a Magmatic-Related Iron Oxide Copper-Gold System

Strata-Bound Fe-Co-Cu-Au-Bi-Y-REE Deposits of the Idaho Cobalt Belt: Multistage Hydrothermal Mineralization in a Magmatic-Related Iron Oxide Copper-Gold System

Geologic history of the Blackbird Co-Cu district in the Lemhi subbasin of the Belt-Purcell Basin

Distribution of Cu, Co, As, and Fe in mine waste, sediment, soil, and water in and around mineral deposits and mines of the Idaho Cobalt Belt, USA

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