Deep geoelectric structure for mineral resource assessment in the Payette National Forest, Idaho

Rodriquez, B.D.; Stanley, William D.; Heran, William D.

doi:10.3133/ofr96666

Cited by 2 publications

(1 citation statement)

References 9 publications

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“…A magnetotelluric (MT) survey across west-central Idaho by Rodriguez et al (1996) indicated a very conductive zone, which extends from 10 to 30 km deep, east of the Idaho batholith, beneath an area that contains hot springs and mineral deposits in Precambrian metasedimentary rocks, Cretaceous intrusive rocks, and Tertiary volcanic and intrusive rocks. This conductive zone was interpreted to represent a very thick section of sedimentary rocks, containing thermal fluids.…”

Section: Geophysicsmentioning

confidence: 99%

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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Section: Geophysicsmentioning

confidence: 99%

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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Resistivity structure across the Humboldt River basin, north-central Nevada

Rodriguez¹,

Williams²

2002

Open-File Report

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Magnetotelluric data collected along five profiles show deep resistivity structures beneath the Battle Mountain-Eureka and Carlin gold trends in north-central Nevada, which appear consistent with tectonic breaks in the crust that possibly served as channels for hydrothermal fluids. It seems likely that gold deposits along these linear trends were, therefore, controlled by deep regional crustal fault systems.Two-dimensional resistivity modeling of the magnetotelluric data generally show resistive (30 to 1,000 ohm-m) crustal blocks broken by sub-vertical, two-dimensional, conductive (1 to 10 ohmm) zones that are indicative of large-scale crustal fault zones. These inferred fault zones are regional in scale, trend northeast-southwest, north-south, and northwest-southeast, and extend to mid-crustal (20 km) depths. The conductors are about 2-to 15-km wide, extend from about 1 to 4 km below the surface to about 20 km depth, and show two-dimensional electrical structure. By connecting the locations of similar trending conductors together, individual regional crustal fault zones within the upper crust can be inferred that range from about 4to 10-km wide and about 30-to 150-km long. One of these crustal fault zones coincides with the Battle Mountain-Eureka mineral trend. The interpreted electrical property sections also show regional changes in the resistive crust from south to north. Most of the subsurface in the upper 20 km beneath Reese River Valley and southern Boulder Valley are underlain by rock that is generally more conductive than the subsurface beneath Kelly Creek Basin and northern Boulder Valley. This suggests that either elevated-temperature or high-salinity fluids, alteration, or carbonaceous rocks are more pervasive in the more conductive area (Battle Mountain Heat-Flow High), which implies that the crust beneath these valleys is either more fractured or has more carbonaceous rocks than in the area surveyed along the 41st parallel.

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Deep geoelectric structure for mineral resource assessment in the Payette National Forest, Idaho

Cited by 2 publications

References 9 publications

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

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

Resistivity structure across the Humboldt River basin, north-central Nevada

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