Geochemical-exploration studies in the Coeur d'Alene district, Idaho and Montana

Gott, Garland Bayard; Cathrall, John B.

doi:10.3133/pp1116

Cited by 13 publications

(7 citation statements)

References 10 publications

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“…10) suggest that 20 to 30 percent of the lead is from the crustal endmember. Using average lead contents of Proterozoic Belt rocks and subduction-related andesite of about 15 to 20 ppm (Harrison and Grimes, 1970;Gott and Cathrall, 1980) and 6 ppm (Gill, 1981), respectively, we infer the plutons could represent "normal" subduction-related melts contaminated by roughly 5 to 15 wt % Proterozoic rock.…”

Section: Crystallization Environment and General Originsupporting

confidence: 55%

Comparative petrologic evolution of the Sn and W granites of the Fairbanks-Circle area, interior Alaska

Newberry¹,

Burns²,

Swanson³

et al. 1990

Geological Society of America Special Papers

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Late Cretaceous to Early Tertiary granitic plutons associated with W skarn or Sn greisen-skarn occur interspersed in a belt 70x 200-km-long just northeast of Fairbanks, Alaska. All plutons intrude the late Precambrian-early Paleozoic Yukon-Tanana terrane and are similar in major-element compositions (dominantly granodiorite to monzogranite), initial Sr isotopic ratios (0.710 to 0.719), and Pb isotopic signatures ( 206 Pb/ 204 Pb = 19.17 to 19.37). Biotite compositions and opaque mineral abundances indicate both types of plutons crystallized along a buffered path intermediate between nickel-nickel oxide and quartz-magnetite-fayalite. Both suites contain multiple igneous units, with younger, usually equigranular, units spatially related to mineralized zones. Isotopic, trace-element, and mineralogical data suggest an "I-type," "ilmenite-series" classification for both pluton suites. Because the W and Sn plutons appear to represent magmas with similar origins and source materials, differences in observed metallogeny are thought to be related to differences in environment of crystallization and vapor loss. Such differences include: age (102 to 87 Ma for W plutons, 73 to 50 Ma for Sn plutons), crystallization pressure (1 to 2 kbar for W plutons, <0.5 kbar for Sn plutons), vapor loss history (late for the W plutons and early + late for the Sn plutons), and fluorine trends (decreasing F with increasing differentiation for the W plutons and increasing F for the Sn plutons). Differences in confining pressure (depth) and vapor loss history are associated with differences in age: the younger (Sn) plutons are shallower, and the older (W) plutons are deeper. Trace-element patterns (e.g., Rb, B, Be, W, Sn, Li) are similar for least differentiated units of both pluton types, increasing modestly with increasing differentiation for the W plutons and increasing strongly for the Sn plutons. Data are most compatible with 80 to 95 percent fractionation (crystal-liquid) followed by vapor loss for the W plutons and 80 to 90 percnt fractionation (crystal-liquid) for the Sn plutons, with early vapor loss followed by (liquid-liquid?) "ultrafractionation." Ultrafractionation and subsequent ore element enrichment occurs in the Sn plutons by early vapor loss and subsequent F enrichment in the residual magma. The data suggest that metallogeny differences for W vs. Sn plutons in our study area are not a function of differences in initial metal contents of the magmas but are more likely due to differences in magmatic evolution.

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Section: Crystallization Environment and General Originsupporting

confidence: 55%

Comparative petrologic evolution of the Sn and W granites of the Fairbanks-Circle area, interior Alaska

Newberry¹,

Burns²,

Swanson³

et al. 1990

Geological Society of America Special Papers

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“…), isotopic evidence that the Pb in stibnite was derived from Belt rocks, and the restricted occurrence of stibnite veins in the Prichard Formation, we surmise that the Sb in the stibnite veins also was derived from the Prichard Formation. Previous geochemical analyses of soil and rock in the Coeur d'Alene district (Gott & Cathrall ) and stream sediment in the Wallace 1 × 2° quadrangle (Leach & Hopkins ) have shown that the background abundance of Sb in the Prichard is about 1 ppm. Together with knowledge of the concentration of Sb in ore fluids (2000 ppm), the amount of Sb in the US Antimony mine (15.4 kt) and the respective densities of the Prichard Formation and hydrothermal fluids (approximately 2.65 and 1 g/cc), it is possible to estimate the minimum volumes of source rock (assuming 100% recovery of Sb) and ore fluid required to generate the deposit.…”

Section: Resultsmentioning

confidence: 99%

Fluid inclusion evidence for a genetic link between simple antimony veins and giant silver veins in the Coeur d'Alene mining district, ID and MT, USA

et al. 2013

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The US Antimony mine in west central Montana is the United States' second largest quartz–stibnite vein deposit with production and reserves of about 15.4 kt of antimony. It is in the Mesoproterozoic Belt Basin on the eastern side of the Coeur d'Alene mining district that is known for its world class Ag, Pb, and Zn veins. To advance understanding of the origin and relation of the simple quartz–stibnite veins in the Prichard Formation to the giant Ag‐rich tetrahedrite veins in the Revett and St. Regis Formations, fluid inclusions in quartz from the US Antimony mine were characterized using a variety of single inclusion and bulk analysis techniques. The measured Sb concentrations in fluid inclusions (approximately 2000 ppm) agree with equilibrium models for stibnite‐saturated fluids at the measured homogenization temperatures (224–263°C), salinities (approximately 5 wt.% NaCl), H2S concentrations (<0.001 mole%), and near neutral pH indicated by sericitic alteration. The aqueous‐carbonic fluid inclusions in quartz from the US Antimony mine have P‐T‐X that are similar to previous results on fluid inclusions from the giant silver veins in the district. The assemblage and abundance of trace elements and ore metals (Sb > As > Fe > Pb > Zn > Cu > Ag) in fluid inclusions from the US Antimony mine support previous interpretations, based upon Pb isotopes, that the quartz–stibnite veins are genetically related to the Ag‐rich tetrahedrite veins. In particular, the measured range of Ag concentrations in US Antimony fluid inclusions brackets that calculated on the basis of equilibrium with tetrahedrite in the silver veins. These data clearly show that hydrothermal fluids in the Prichard Formation contained metals that were fixed at shallower levels in the Revett and St. Regis Formations. We surmise that both the antimony and silver veins formed in response to Cretaceous magmatism, prograde metamorphism of the lower Prichard Formation, and episodic discharge of metamorphic fluids along dilatant faults. Ascending fluids deposited quartz and stibnite in the upper Prichard Formation and siderite, quartz, and tetrahedrite at shallower levels in the Revett and St. Regis Formations in response to cooling, decompression, phase separation, and mixing with external fluids.

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“…Health problems in the basin for humans and wildlife are linked to high concentrations of particulate Pb in surface soils and sediment and to ingestion of those particles. Elevated concentrations of particulate Pb are associated with soils that formed over mineralized rocks in the area (Gott and Cathrall, 1980), tailings from mills that processed the mineralized rock (Long, 1998b), and atmospheric fallout from smelters that operated in the mining district (U.S. Environmental Protection Agency, 1994). There are no new sources of particulate Pb from smelters or tailings today be-cause of closure of the smelters and environmental regulations that prohibit the dumping of tailings into rivers.…”

Section: Particulate Leadmentioning

confidence: 99%

Impacts of historical mining in the Coeur d'Alene River Basin

Balistrieri¹,

Box²,

Bookstrom³

et al. 2010

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Geochemical-exploration studies in the Coeur d'Alene district, Idaho and Montana

Cited by 13 publications

References 10 publications

Comparative petrologic evolution of the Sn and W granites of the Fairbanks-Circle area, interior Alaska

Comparative petrologic evolution of the Sn and W granites of the Fairbanks-Circle area, interior Alaska

Fluid inclusion evidence for a genetic link between simple antimony veins and giant silver veins in the Coeur d'Alene mining district, ID and MT, USA

Impacts of historical mining in the Coeur d'Alene River Basin

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