Stratigraphic and Structural Setting of Sediment-Hosted Blackbird Gold–Cobalt–Copper Deposits, East-Central Idaho, U.S.A.

Lund, Karen; Tysdal, R.G.

doi:10.2110/pec.07.86.0129

Cited by 12 publications

(24 citation statements)

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“…1). Early workers mapped these strata as the Yellowjacket Formation, but Tysdal and colleagues (Tysdal, 2003;Tysdal et al, 2003;Lund and Tysdal, 2007) assigned them to the lithologically similar Apple Creek Formation; this report follows the latter, more recent formational assignment. U-Pb detrital zircon data for the Apple Creek Formation obtained by Link et al (2007) suggest a depositional age of 1445 to 1410 Ma; recent sensitive high resolution ion microprobe (SHRIMP) U-Pb data for detrital zircons in metasandstone from the Blackbird district provide a more precise maximum age of 1409 ± 10 Ma (Aleinikoff et al, 2012).…”

Section: Geologic Settingmentioning

confidence: 76%

“…U-Pb detrital zircon data for the Apple Creek Formation obtained by Link et al (2007) suggest a depositional age of 1445 to 1410 Ma; recent sensitive high resolution ion microprobe (SHRIMP) U-Pb data for detrital zircons in metasandstone from the Blackbird district provide a more precise maximum age of 1409 ± 10 Ma (Aleinikoff et al, 2012). Strata that host the mineral deposits are chiefly quartzite, siltite, and argillite, which in some areas display sedimentary features of predominantly turbidite deposition in a rift-related marine basin (Tysdal, 2003;Lund and Tysdal, 2007). The broadly coeval Yellowjacket Formation locally contains scapolite-rich rocks and carbonate strata that record shallow-water, intertidal to supratidal settings including evaporite deposition (Tysdal and Desborough, 1997;Tysdal, 2003).…”

Section: Geologic Settingmentioning

confidence: 99%

“…A felsic alkalic pluton of Late Cambrian age (497 ± 6 Ma) crops out ca. 10 km east of the district (Lund and Tysdal, 2007;Lund et al, 2010).…”

Section: Geologic Settingmentioning

confidence: 99%

“…Simplified regional geology of the Idaho cobalt belt including locations of metallic mineral deposits and occurrences. Geology from Tysdal et al (2003) and Lund and Tysdal (2007). Ages of granitoid rocks (mainly megacrystic granite and augen gneiss) and Apple Creek Formation are from Aleinikoff et al (2012); age of megacrystic granite on north side of the Blackbird district is 1377 ± 4 Ma (see Aleinikoff et al, 2012).…”

Section: Geologic Settingmentioning

confidence: 99%

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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: Geologic Settingmentioning

confidence: 76%

Section: Geologic Settingmentioning

confidence: 99%

“…A felsic alkalic pluton of Late Cambrian age (497 ± 6 Ma) crops out ca. 10 km east of the district (Lund and Tysdal, 2007;Lund et al, 2010).…”

Section: Geologic Settingmentioning

confidence: 99%

Section: Geologic Settingmentioning

confidence: 99%

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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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“…The host rocks originated as thinly interlayered, arkosic coarse-grained siltstone and fine-grained sandstone deposited by turbidity currents. Host rocks are lower greenschist to middle amphibolite facies regional metamorphic rocks in thrust-slivered packages, located beneath a major regional Cretaceous thrust fault (Lund and Tysdal, 2007). Mineralization was introduced into the country rocks as a series of structurally controlled, quartz-rich veins, biotite-rich breccia veins, and minor albite and siderite veinlets that maintain consistent order and sulfide-mineral associations.…”

Section: Deposit Type Descriptionmentioning

confidence: 99%

Geology and mineral resources of the North-Central Idaho Sagebrush Focal Area: Chapter C in <em>Mineral resources of the Sagebrush Focal Areas of Idaho, Montana, Nevada, Oregon, Utah, and Wyoming</em>

Mauk¹,

Zientek²,

Hearn³

et al. 2016

Scientific Investigations Report

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For more information on the USGS-the Federal source for science about the Earth, its natural and living resources, natural hazards, and the environment-visit http://www.usgs.gov or call 1-888 -ASK-USGS.For an overview of USGS information products, including maps, imagery, and publications, visit http://store.usgs.gov.Any use of trade, firm, or product names is for descriptive purposes only and does not imply endorsement by the U.S. Government.Although this information product, for the most part, is in the public domain, it also may contain copyrighted materials as noted in the text. Permission to reproduce copyrighted items must be secured from the copyright owner.Suggested citation: Lund, K., Zürcher, L., Hofstra, A.H., Van Gosen, B.S., Benson, M.E., Box, S.E., Anderson, E.D., Bleiwas, D.I., DeAngelo, J., Drake, R.M., II, Fernette, G.L., Giles, S.A., Glen, J.M.G., Haacke, J.E., Horton, J., John, D.M., Robinson, G.R., Jr., Rockwell, B.W., San Juan, C.A., Shaffer, B.N., Smith, S.M., and Williams, C.F., 2016, Geology and mineral resources of the North-Central Idaho Sagebrush Focal Area (ver. 1.1, October 27, 2016): U.S. Geological Survey Scientific Investigations Report 2016-5089 -C, 147 p., http://dx.doi.org/10.3133/sir20165089C. Supplemental InformationTemperature in degrees Celsius (°C) may be converted to degrees Fahrenheit (°F) as°F = (1.8 × °C) + 32.Temperature in degrees Fahrenheit (°F) may be converted to degrees Celsius (°C) as°C = (°F -32) / 1.8. DatumsVertical coordinate information is referenced to the North American Datum of 1983 (NAD 83). Horizontal coordinate information is referenced to the North American Datum of 1983 (NAD 83).Altitude, as used in this report, refers to distance above the vertical datum. Executive SummaryThe U.S. Department of the Interior has proposed to withdraw approximately 10 million acres of Federal lands from mineral entry (subject to valid existing rights) from 12 million acres of lands defined as Sagebrush Focal Areas (SFAs) in Idaho, Montana, Nevada, Oregon, Utah, and Wyoming (for further discussion on the lands involved see Day and others, 2016).The purpose of the proposed action is to protect the greater sage-grouse (Centrocercus urophasianus) and its habitat from potential adverse affects of locatable mineral exploration and mining. To inform the decision on whether to withdraw the SFAs from mineral entry, the Bureau of Land Management (BLM) requires a mineral-resource assessment be completed to identify mineral resources within the proposed area of withdrawal. The USGS Sagebrush Mineral-Resource Assessment (SaMiRA) project was initiated in November 2015 and supported by the BLM to (1) assess locatable mineral-resource potential and (2) to describe leasable and salable mineral resources for the seven SFAs and Nevada additions. Geologic SettingThe purpose of this chapter is to document the geology and mineral resources of the North-Central Idaho Sagebrush Focal Area ("study area"), which extends from east-central to south-central Idaho. The geologically complex ar...

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Re-Os systematics and geochemistry of cobaltite (CoAsS) in the Idaho cobalt belt, Belt-Purcell Basin, USA: Evidence for middle Mesoproterozoic sediment-hosted Co-Cu sulfide mineralization with Grenvillian and Cretaceous remobilization

Saintilan

Creaser

Bookstrom

2017

Ore Geology Reviews

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We report the first study of the Re-Os systematics of cobaltite (CoAsS) using disseminated grains and massive sulfides from samples of two breccia-type and two stratabound deposits in the Co-Cu-Au Idaho cobalt belt (ICB), Lehmi Sub-basin to the Belt-Purcell Basin, Idaho, USA. Using a 185 Re+ 190 Os spike solution, magnetic and non-magnetic fractions of cobaltite mineral separates give reproducible Re-Os analytical data for aliquot sizes of 150 to 200 mg. Cobaltite from the ICB has highly radiogenic 187 Os/ 188 Os ratios (17-45) and high 187 Re/ 188 Os ratios (600-1800) but low Re and total Os contents (ca. 0.4-4 ppb and 14-64 ppt, respectively). Containing 30 to 74% radiogenic 187 Os, cobaltite from the ICB is amenable to Re-Os age determination using the isochron regression approach.Re-Os data for disseminated cobaltite mineralization in a quartz-tourmaline breccia from the Haynes-Stellite deposit yield a Model 1 isochron age of 1349 ± 76 Ma (2σ, n = 4, mean squared weighted deviation MSWD = 2.1, initial 187 Os/ 188 Os ratio = 4.7 ± 2.2). This middle Mesoproterozoic age is preserved despite a possible metamorphic overprint or a pulse of metamorphic-hydrothermal remobilization of pre-existing cobaltite that formed along fold cleavages during the ca. 1190-1006 Ma Grenvillian orogeny. This phase of remobilization is tentatively identified by a Model 3 isochron age of 1132 ± 240 Ma (2σ, n = 7, MSWD = 9.3, initial 187 Os/ 188 Os ratio of 9.0 ± 2.9) for cobaltite in the quartztourmaline breccia from the Idaho zone.All Mesoproterozoic cobaltite mineralization in the district was affected by greenschist-to lower amphibolites-facies (garnet zone) metamorphism during the Late Jurassic to Late Cretaceous Cordilleran orogeny. However, the fine-to coarse-grained massive cobaltite mineralization from the shear zonehosted Chicago zone is the only studied deposit that has severely disturbed Re-Os systematics with evidence for a linear trend of mixing with (metamorphic?) fluids.The new Re-Os ages and extremely high initial 187 Os/ 188 Os ratios of cobaltite reported here favor a magmatic-hydrothermal genetic model for a multi-stage REE-Y-Co-Cu-Au mineralization occurring at ca. 1370 to 1349 Ma, and related to the emplacement of the Big Deer Creek granite pluton at ca. 1377 Ma. In our model, deposition of paragenetically early xenotime and gadolinite was followed by an influx of Mesoproterozoic evaporitic brines and magmatic-hydrothermal fluids containing metals and reduced sulfur derived from mafic and oceanic island-arc Archean to Paleoproterozoic rocks in the Laurentian basement. Cobaltite mineralization (and the closure of the Re-Os isotopic system in this mineral) occurred upon cooling of these fluids at an inferred temperature of 300ºC or below.

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Stratigraphic and Structural Setting of Sediment-Hosted Blackbird Gold–Cobalt–Copper Deposits, East-Central Idaho, U.S.A.

Cited by 12 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

Geology and mineral resources of the North-Central Idaho Sagebrush Focal Area: Chapter C in <em>Mineral resources of the Sagebrush Focal Areas of Idaho, Montana, Nevada, Oregon, Utah, and Wyoming</em>

Re-Os systematics and geochemistry of cobaltite (CoAsS) in the Idaho cobalt belt, Belt-Purcell Basin, USA: Evidence for middle Mesoproterozoic sediment-hosted Co-Cu sulfide mineralization with Grenvillian and Cretaceous remobilization

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