The proposed Big Frog Wilderness is comprised of approximately 1820 hectares (18.2 km 2 ) of mountainous terrain in the Cherokee and Chattahoochee National Forests south of the Ocoee River in Polk County, Tennessee, and Fannin County, Georgia. Rocks of the study area are greenschist-facies metasandstone, meta-arkose, metagraywacke, and dark slate of the Ocoee Supergroup of late Precambrian age. A major thrust fault, correlated with the Greenbrier Fault, separates fine-grained slaty rocks of the Snowbird Group on the northwest side, from coarse clastic sediments and interbedded slates of the Great Smoky Group on the southeast. North- and northeast-trending folds are common in the map area. Minor deposits of Quaternary sand and gravel occur locally in the lower parts of large streams. Semiquantitative spectrographic, atomic absorption, and selected fire assay analyses were done on more than 200 samples of rock, soil, and stream sediment. No significant metal anomalies were found for 31 major, minor, and trace elements. In many places, metasiltstone and metasandstone contain trace amounts of chalcopyrite and sphalerite as microscopic intergrowths with the chief sulfide minerals, pyrite and pyrrhotite. Sulfides make up as much as 5 to 10 percent of some rocks and provide concentrations of Cu, Zn, and As slightly higher than background in samples of rock and soil. Rocks containing these disseminated base-metal sulfides are of insufficient grade to have current economic potential, however. No metallic mineral resources are known within the proposed Big Frog Wilderness. Nonmetallic resources, including slate and phyllite, stone, and sand and gravel are present locally, but are not presently a value because similar resources exist closer to markets outside the study area. These deposits therefore would have only marginal use in the region.

Georgia, Tennessee↗

USGS1979

Map showing lithostratigraphic and structural setting of stratabound (massive) sulfide deposits in the U.S. Appalachians

No abstract available.

Appalachians↗

USGS1979

K-Ar age of alunite alteration at Red Mountain, Lake City area, western San Juan Mountains, Colorado

The San Juan Mountains of southwestern Colorado are famous for rich vein deposits of base and precious metals and for patterns of conspicuous hydrothermal alteration. Areas of acid-sulfate alteration, characterized by extensive base leaching of volcanic rocks or hypabyssal plutons, are of current interest because of their local association with Au, Ag, and, in some cases, U mineralization (Lipman and others, 1976; Cunningham and others, 1978; Steven and others, 1979). Potential may also exist for recovery of aluminum from altered rocks rich in alunite (Hall, 1978). Alunite has been shown to be suitable for K-Ar dating in other mining districts (Mehnert and others, 1973b; Ashley and Silberman, 1976). We report here two concordant K-Ar ages determined on hydrothermal alunite from Red Mountain, in the Lake City area of the western San Juan Mountains.

Colorado↗

USGS1979

Mineral resources of the Citico Creek Wilderness Study Area, Monroe County, Tennessee

The proposed Citico Creek Wilderness comprises about 5,670 hectares (56.7 km2) in the Cherokee National Forest south of the Little Tennessee River in easternmost Monroe County, Tennessee. Principal drainages are Citico Creek and Doublecamp Creek. Rocks of the study area include greenschist-facies arkosic metasandstone, metagraywacke, slate, and metaconglomerate of the Great Smoky Group of late Precambrian age. Minor deposits of unconsolidated Quaternary alluvium locally mantle the bedrock. Deformation is shown by asymmetric and overturned folds and by several major faults. More than 500 sample s of soil, rock, and stream sediment were collected and analyzed for 31 major, minor, and trace elements by semiquantitative spectrographic, atomic absorption, and fire assay methods No significant metal anomalies were detected. Concentrations of Cu, Co, As, Pb, and Zn slightly higher than background are found within sulfidic parts of a distinctive stratigraphic unit composed of graphitic slate and metagraywacke. Pyrite and pyrrhotite are the chief sulfide minerals, with traces o f accessory sphalerite, chalcopyrite, galena, and arsenopyrite occurring as microscopic intergrowths. A reconnaissance ground radiometric survey and subsequent neutron activation analyses of selected radioactive rock samples show that the sulfidic parts of the graphitic slate unit have a relatively high content of Th and U, but are not potentially economic. No metallic mineral resources appear to exist within the Citico Creek Wilderness Study Area. Resources of slate, silica, and stone are present, but they display no special qualities to differentiate them from other such material throughout the region. Ceramic evaluation tests on selected samples of slate indicate that the slate would have only marginal use for structural clay products such as brick and tile. Minor sand and gravel deposits occur along a few streams but are present in larger quantities and are more easily recovered in other areas.

Tennessee↗

USGS1979

Geochemical analyses of rock, soil, and stream sediment samples from the Big Frog Wilderness Study Area, Polk County, Tennessee and Fannin County, Georgia

Semiquantitative spectrographic analyses for 31 elements and atomic absorption analyses for gold and zinc on 43 stream sediments, 5 panned concentrates, 65 soils, and 81 rock samples from the Big Frog Wilderness Study Area and vicinity, Polk County, Tennessee, and Fannin County, Georgia, are reported here in detail. Locations for all 194 samples are given in Universal Transverse Mercator (UTM) coordinates. Rocks analyzed include metasiltstone, metasandstone, metaconglomerate, slate, and vein quartz. The data contain no obviously anomalous values that might be related to economically recoverable mineralization.

Georgia, Tennessee↗

USGS1979

The Yellow Dog peridotite and a possible buried igneous complex of lower Keweenawan age in the northern peninsula of Michigan

Partly serpentinized peridotite of early Keweenawan age crops out in two places along a 20-kilometer-long zone of positive aeromagnetic anomalies in northern Marquette County, Michigan. Most of the area is mantled by Pleistocene drift with few bedrock exposures. Petrographic and electron microprobe studies show that the peridotite was originally a plagioclase lherzolite containing 40 to 50 percent olivine (Fo8 0 ) and approximately 10 to 15 percent each of enstatite (En 78 Wo 04 Fs 18 ) and diopsidic augite (En 47 Wo 42 Fs 11 ). The plagioclase varies from 5 to 10 percent, and according to Morris (1977) is labradorite with a composition of An 57-65 . Major oxide minerals (4 to 6 percent) are ilmenite and magnetite. Sulfides comprise 1 to 2 percent of the peridotite and are chiefly pyrrhotite, pentlandite, and chalcopyrite. Ground magnetic, gravity, and very low frequency electro-magnetic (VLF-EM) surveys have refined the location and magnitude of anomalies previously known only from aeromagnetic studies. These surveys together with soil geochemical studies suggest that peridotite, and possibly other mafic rocks forming a differentiated igneous complex, may occur throughout a belt 20 kilometers long (east-west) and 1 to 2 kilometers wide (north-south). Differentiated igneous complexes in many parts of the world are hosts for copper, nickel, chromium, or precious-metal deposits. The peridotite in the area of this study is anomalously rich in copper and sulfur compared to world-wide averages for peridotite. Positive electro-magnetic anomalies found near the peridotite outcrops may be caused by sulfide-rich zones in the igneous rocks and should be explored further for copper-nickel mineralization.

Michigan↗

USGS1978

Premetamorphic hydrothermal origin of the Tungsten Queen vein, Hamme District, North Carolina, as indicated by mineral textures and minor structures

The Hamme Tungsten district is a 13-km long, 2-km wide, northeast-trending belt located in northern Vance County, North Carolina and southern Mecklenburg County, Virginia (Fig. 1). The district contains the largest quartz-wolframite-type vein deposits in the United States. Over 50 tungsten-bearing veins occur in this area (Espenshade, 1947), from which more than 1 million short ton units of WO 3 have been produced since World War II Mining terminated in 1971 after a sharp drop in the price of tungsten; currently, the district is inactive.

North Carolina, Virginia↗

USGS1978

Occurrence and formation of avicennite, Tl2O3 , as a secondary mineral at the Carlin gold deposit, Nevada

Avicennite, Tl 2 O 3 , occurs as grains disseminated in silicified limestones in the upper part of the East ore zone of the Carlin gold deposit, Nevada. The avicennite is formed by the oxidation of carlinite, Tl 2 S, found in primary unoxidized carbonaceous ore immediately below the avicennite. The grains of avicennite closely resemble carlinite in size and shape. Some avicennite occurs as thin coatings on carlinite, but the time of its formation is unclear. Avicennite grains are polycrystalline, porous, dark gray to black, with a hackly fracture but no discernible cleavage. The Mohs hardness is 2.0±0.5; Vickers hardness ranges from 46.0 to 80.5 kg mm -2 . Measured density is distinctly low, 8.9 g cm -3 (or Mg m -3 ), relative to the calculated density, 10.34 g cm -3 . The mineral is isometric, space group Ia 3. a =10.5468±0.0003 angstroms or 1.05468±0.00003 nm, Z =16, and the volume of the unit cell is 1173.17±0.04 Ǻ 3 or 1.17317±0.00004 nm 3 . The most intense X-ray diffraction peaks are 3.044 (100), 1.864 (38), 2.637 (37), and 1.590 (30). In reflected light, avicennite is pale to medium gray and isotropic and lacks discernible bireflectance. Reflectance in air ranges from 10.6 to 13.0 percent. Avicennite is nearly pure Tl 2 O 3 , containing 89.6 weight percent Tl and 10.5 weight percent O by microprobe analysis. Other elements present, detected by emission spectrographic analysis, are: Pb, 300 ppm; Ca, 100 ppm; and Si, Al, Fe, Mg, Ag, Cr, Cu, Ni, and Ti, all <50 ppm.

Nevada↗

USGS1977

The Yellow Dog peridotite and a possible buried igneous complex of Lower Keweenawan Age in the northern peninsula of Michigan

Partly serpentinized peridotite of early Keweenawan age crops out in two places along a 20-km-long zone of positive aeromagnetic anomalies in northern Marquette County, Michigan. Most of the area is mantled by Pleistocene drift and the bedrock is not exposed. Petrographic and electron microprobe studies show that the peridotite was originally a plagioclase lherzolite containing 40-50% olivine (Fo8 0 ) and approximately 10-15% each of enstatite (En 78 Wo 04 Fs 18 ) and diopsidic augite (En 47 Wo 42 Fs 11 ), with 5-10% calcic labradorite (~An 70 ). Major oxide minerals (4-6%) are ilmenite and magnetite. Sulfides comprise 1 to 2 percent of the peridotite and are chiefly pyrrhotite, pentlandite, and chalcopyrite. Ground magnetic, gravity, and very low frequency electro-magnetic surveys have refined the location and magnitude of anomalies previously known only from aeromagnetic studies. These surveys together with soil geochemical studies suggest that peridotite, and possibly other mafic rocks forming a differentiated igneous complex, may occur throughout a belt 20 km long (E-W) and 1-2 km wide (N-S). Differentiated igneous complexes in many parts of the world are hosts for Cu, Ni, Cr, or precious metal deposits. The peridotite in the area of this study is anomalously rich in Cu and S compared to world-wide averages for peridotite. Positive electro-magnetic anomalies found near the peridotite outcrops may be caused by sulfide-rich zones in the igneous rocks and should be explored further for Cu-Ni mineralization.

Michigan↗