Jeffrey Keith - Academia.edu (original) (raw)
Papers by Jeffrey Keith
Economic geology and the bulletin of the Society of Economic Geologists, May 1, 1986
The Pine Grove porphyry molybdenum deposit in the Wah Wah Mountains, southwestern Utah, occurs in... more The Pine Grove porphyry molybdenum deposit in the Wah Wah Mountains, southwestern Utah, occurs in the eroded vent of a lower Miocene ash flow (23-22 m.y. old). The vent, located in a tilted basin-and-range fault block, has been eroded about 1.7 km below the pre-eruption surface; consequently, the closest outcrops of related ash-flow tuff are 10 km away from the vent. Correlation of comagmatic ash-flow tuff and intrusive porphyry is made possible by the presence of accessory almandine-spessartine garnet of unique composition in both extrusive and intrusive units.Several lines of evidence suggest the presence of a parental magma chamber roughly 100 km 3 in size and compositionally zoned from rhyolite to dacite. Each eruptive episode began with a high silica content, rhyolitic magma containing quartz, sanidine, plagioclase, biotite, garnet, titanomagnetite, monazite, xenotime, ilmenorutile (?), and zircon. Presumably in response to continued rapid eruption and deeper drawdown in the parent chamber, some ash-flow eruptions also vented dacitic magma containing quartz, plagioclase, sanidine, biotite, hornblende, augite, titanomagnetite, ilmenite, sphene, apatite, and zircon.The dominant ore-related intrusion was emplaced immediately following concurrent intrusion of rhyolitic and dacitic magma into the vent. Multiple injections of trachyandesitic magma into the base of the chamber may have initiated convection or magma fracturing, surging of dacitic magma, and exsolution of volatiles that resulted, first, in ash-flow eruptions and, later, in episodes of mineralization. Therefore, an unusual combination of eruption mechanics and chamber volume and geometry allowed sampling of possibly the entire compositional range of the chamber during eruption but prohibited the complete loss of rhyolitic magma. Magmatic processes, such as late-stage convection, magma fracturing, and volatile fluxing may have been critical in the development of porphyry Mo mineralization.
GSA Annual Meeting in Phoenix, Arizona, USA - 2019, 2019
GSA Annual Meeting in Indianapolis, Indiana, USA - 2018, 2018
Abstract Large bodies of fibrous orange calcite, up to 400 m long and up to 20 m wide, are hosted... more Abstract Large bodies of fibrous orange calcite, up to 400 m long and up to 20 m wide, are hosted by Mississippian carbonate units in the Uinta Mountains, Utah. Subjacent to the carbonate rocks, emerald mineralization has recently been recognized in the Neoproterozoic Red Pine Shale. Fibrous orange calcite is translucent, and is being mined and used as architectural stone, in carvings, and for other decorative purposes. Calcite veins are located a few km south of the South Flank fault zone (SFFZ) in the vicinity of a swarm of north-trending faults. Portions of the Red Pine Shale along the SFFZ contain abundant secondary pyrite, and altered shale also contains quartz and calcite veins as well as albitization of some arkosic units, and is variably enriched in Cu and Zn. At least three emeralds have been discovered in altered Red Pine Shale. Our work suggests that brines from the Uinta Basin may have migrated upward along the SFFZ and interacted with the organic shale, producing emerald and a CO2–rich fluid that dissolved portions of the overlying Mississippian carbonates. The fluid experienced intermittent loss of aqueous CO2, causing fibrous calcite to rapidly precipitate. This model and setting has similarities to both Mississippi Valley and Colombian emerald deposits.
U.S. Geological Survey professional paper, 1987
Chart showing Stratigraphic relations and nomenclature of the Oligocene Needles Range Group .... ... more Chart showing Stratigraphic relations and nomenclature of the Oligocene Needles Range Group .... Geologic map and idealized cross section of the northeastern segment of the Indian Peak caldera ... Maps showing distribution and thickness of units in the Needles Range Group: A4. Marsden Tuff Member of Escalante Desert Formation and location of Pine Valley caldera
Abstracts with programs, 2018
Gems & Gemology, 2003
wo decades ago, Shigley and Foord (1984) described the spectacular gem-quality red beryl (figure ... more wo decades ago, Shigley and Foord (1984) described the spectacular gem-quality red beryl (figure 1) found at the Ruby Violet mine in the Wah Wah Mountains of southwestern Utah (see also Ream, 1979; Sinkankas, 1976, 1997). Since that time, this material has remained one of the rarest color varieties of gem beryl, with its increased recognition and acceptance in the marketplace being offset by the continued limited scale of production. Although gem beryls are common in granitic pegmatites (i.e., aquamarine, morganite, heliodor, and goshenite) and in certain metamorphic and metasedimentary rocks (emerald), their occurrence in rhyolites is unusual. Conversely, rhyolites occasionally contain crystals of quartz, topaz, and garnet in lithophysal (gas) cavities, or opal as veins or cavity fillings. Besides the Ruby Violet mine, several other occurrences of red beryl (all in rhyolites) are known, but none has produced significant quantities of facet-grade material. These include: Utah
Open-file report /, 1992
Hill-slope deposits Boulder to sand-sized rock fragments that have weathered out from bedrock or ... more Hill-slope deposits Boulder to sand-sized rock fragments that have weathered out from bedrock or alluvium, moved downslope through creep and slopewash, and accumulated on hill slopes. Two types of hill-slope deposits have been mapped, but the hill-slope deposits in most areas have not been distinguished from the underlying bedrock. Qt Talus (Holocene)-Hill-slope deposits of angular fragments of rhyolite derived from the rhyolite lava-flows member of the Blawn Formation (Tbr) in south-central part of map area and from andesite lava flows (Ta) along western edge. Rock fragments range from sand-size to boulders 1 m in diameter. Matrix is generally coarse sand, but locally there is no matrix. Thickness less than 5 m Qc Gravelly colluvium (Holocene and late and middle Pleistocene)~Hill-slope deposits of unsorted, unstratified, subrounded to subangular, light-gray to reddish-brown volcanic pebbles, cobbles and boulders as large as 50 cm in a matrix of reddish-brown angular sand. Consists of a thin mantle of debris eroded from older alluvial deposits (QTf, Qpl, Qp2, Qsl, Qs2) and transported down hill slopes chiefly by creep. Generally overlies early Pleistocene and Pliocene fan alluvium (QTf) and Tertiary lacustrine basin-fill deposits (Te). Older deposits have a calcic soil horizon with laminated calcium carbonate in the upper part. The laminations parallel the hill slope. Calcium carbonate cements the oldest colluvium and completely fills interstices to 1 m depth. Thickness less than 5 m Stream deposits Silt, sand, and gravel that fill channels and form floodplains and terraces along Meadow Valley Wash and minor streams Qal Alluvium of ephemeral streams (Holocene) Channel and floodplain alluvium of small, ephemeral streams. Very pale brown (10YR 7/3) pebbly sand, moderately bedded and poorly sorted, intercalated with lenticular beds of channel-cross-bedded, sandy, pebbly, cobble gravel. Unit also includes alluvium and colluvium in small fans along valley sides. Maximum thickness about 3 m Qsa Floodplain and channel alluvium of Meadow Wash (Holocene)-Floodplain deposits are interbedded very pale brown (10YR 7/3) pebbly sand, gray
Geol. Soc. Am., Abstr. Programs; (United States), 1985
Field characteristics, petrography, and geochemistry of granitoids associated with major W skarn ... more Field characteristics, petrography, and geochemistry of granitoids associated with major W skarn deposits in the Cordillera have been examined to determine magmatic processes or parameters critical for mineralization. Approximately 30 W-bearing systems were examined as well some barren or Mo-related granitoids of similar age. Granitoids which are nearly devoid of Ti-bearing phases such as sphene, ilmenite, and titanomagnetite and exhibit a low Fe/sup +3//Fe/sup +2/ ratio in biotite appear to be correlated with higher grade deposits. Incorporation of W in Ti sites in these minerals may occur early in the crystallization sequence and reduce the amount of W available for incorporation into a magmatic aqueous phase and subsequent ore fluid. Mesozoic granitoids west of the Sr/sub i/ = .708 line in Nevada and California are also correlated with larger W deposits compared to granitoids east of that line. Possibly, assimilation or melting of some pelitic sediment versus assimilation of Precambrian crust during petrogenesis may alter fO/sub 2/ and volatile fugacities sufficient to account for these differences in granitoid mineralogy and W mineralization. Two end-member processes of fluid transport were noted in the granitoids examined. First, moderate albitization and myrmekite development may mark the path of interstial transport of the magmaticmore » component of the ore fluid through proximal ore-related granitoids. Alternatively, transport occurs via quartz veins through a proximal granitoid with magmatic ore fluids originating from a younger source intrusion removed some distance from the skarn.« less
Rocky Mountain Geology, May 1, 2008
Large bodies of fibrous calcite, up to 400 m long and up to 20 m wide, are hosted by Mississippia... more Large bodies of fibrous calcite, up to 400 m long and up to 20 m wide, are hosted by Mississippian carbonate units in the Uinta Mountains, Utah. Subjacent to the carbonate rocks, emerald mineralization has been recognized recently in the Neoproterozoic Red Pine Shale. Two types of fibrous calcites are recognized on the basis of appearance and geochemical characteristics. Fibrous orange calcite is translucent, similar to “Mexican calcite” commonly sold at gem-and-mineral shows, and is being mined and used in carvings and for other decorative purposes. Recently recognized fibrous brown calcite is also present in the same general vicinity. Calcite veins hosted with Mississippian carbonate rocks are located a few kilometers south of the South Flank fault zone (SFFZ) in the vicinity of a swarm of north-trending faults. Parts of the Red Pine Shale along the SFFZ contain abundant secondary pyrite. Altered shale also contains quartz and calcite veins as well as albitized feldspar in some arkosic units and is variably enriched in Cu and Zn. At least three emeralds have been discovered in altered Red Pine Shale. b 18 O VSMOW values of calcite (-10 to -13‰) would be in equilibrium with basin brines (assumed to be –3 to +5‰), suggesting precipitation in the range of 100°–300° C. Our work suggests that sulfate-bearing basinal brines from the Uinta Basin may have migrated upward along the SFFZ and interacted with the carbon-rich shale. As sulfate was reduced by organic carbon to form sulfides, emerald was produced and a CO 2 -rich fluid migrated upward and dissolved parts of the Mississippian carbonates. The fluid experienced intermittent loss of CO 2 gas, which allowed fibrous calcite with cone-in-cone textures to precipitate rapidly. This model and geologic setting have broad similarities to both Mississippi Valley and Colombian emerald deposits. The genesis of fibrous brown calcite, however, is less certain. These calcites lack critical geochemical characteristics that tie orange calcite to precipitation from hot brines; rather stable isotope data are permissive of origin from low-temperature ground water.
Open-file report /, 1979
Unconsolldated, poorly sorted stream, fan, slope-wash, and talus deposits. The unit includes detr... more Unconsolldated, poorly sorted stream, fan, slope-wash, and talus deposits. The unit includes detritus of the unit Tbrt as talus aprons around The Tetons and as a mantle on a pediment between The Tetons and Jockey Road. Total thickness probably does not exceed 40 m FORMATION OF BLAWN WASH (MIOCENE) Rhyolite member of the Tetons Light-gray, pink, lavender, or brown porphyritic rhyolite flows and shallow intrusions with only a few small (<1 mm) phenocrysts of smokey quartz, sanidine, and plagioclase in a microcrystalline matrix. Generally flow layered and locally spherulitic and lithophysal with topaz and rare fluorite in vugs. Sanidine from the intrusive rhyolite south of the Staats mine has a K-Ar age of 20 m.y. (Lindsey and Osmonson, 1978) Rhyolite member of Pink Knolls Flows and shallow intrusive plugs and dikes of gray to brown strongly porphyritic rhyolite; locally vitrophyric. Phenocrysts of quartz, sanidine, plagioclase, and lesser biotite comprise as much as one-third of the rock. Phenocrysts range widely in size, and within individual outcrops, sanidine and quartz range from small crystals to prominent phenocrysts as much as 3 cm and 1 cm across, respectively Tuff member A sequence of light-colored, generally loosely consolidated, vitric-lithic ash-flow and minor air-fall tuffs with intervening beds of stratified water-lain tuffs, volcanic sandstones, and conglomerates. The topaz rhyolite at The Tetons is underlain by a strongly welded ash-flow tuff with collapsed pumice lenses of black or brown glass. Tuffs in the unit contain less than 10 percent phenocrysts of quartz, plagioclase, sanidine, and biotite and have abundant pumice lapilli. Fragments of the Lund Tuff Member as much as 25 cm across are typically present, and are especially common in the epiclastic beds. Scattered fragments of Lund are commonly the only indication of the unit beneath poorly exposed slopes. The unit appears to be comprised of locally derived material, in part representing the precursory explosive facies of younger rhyolite flows and intrusions. Possibly as much as 300 m of this unit is exposed in Blawn Wash Mafic flow member Gray lava flow with phenocrysts of augite and labradorite; weathers brown with red liesegang bands; zeolite amygdules. In these and adjacent quadrangles the unit ranges from 55 to 60 weight percent Si02 and 2.4 to 4.0 K 0 0. Thickness 200 m
GeoResJ, Mar 1, 2015
Remote thermal monitoring of active volcanoes has many important applications for terrestrial and... more Remote thermal monitoring of active volcanoes has many important applications for terrestrial and planetary volcanic systems. In this study, we describe observations of active eruptions on Kilauea and Erta Ale volcanoes using a short-wavelength, high-resolution, consumer digital camcorder and other non-imaging thermal detectors. These systems revealed brightness temperatures close to the eruption temperatures and temperature distributions, morphologies and thermal structures of flow features, tube systems and lava fountains. Lava flows observed by the camcorder through a skylight on Kilauea had a peak in maximum brightness temperatures at 1230°C and showed brightness temperature distributions consistent with most rapid flow at the center. Surface brightness temperatures of cooling lava flows on Kilauea were close to 850°C. Centimeter-scale thermal features are evident around pahoehoe ropes and inflated flows and stalactites in lava tubes. Observations of the fountaining Erta Ale lava lake in February 2011 extend the baseline of observations of the eruptive episode begun in late 2010. We observed a fountain using the camcorder and found a peak in maximum brightness temperatures at 1164°C, consistent with previous studies. Steep temperature gradients were observed across centimeter-scale distances between the highly exposed fountain and cracks and the much cooler lava lake surface and crater walls. The instrument and methods described here lead to robust pictures of the temperatures and temperature distributions at these volcanoes and reveal desired characteristics of planetary remote sensing platforms for the study of volcanically active bodies such as Io.
Geological Society of America Special Papers, 1990
Abstracts with programs, 2021
Economic geology and the bulletin of the Society of Economic Geologists, May 1, 1986
The Pine Grove porphyry molybdenum deposit in the Wah Wah Mountains, southwestern Utah, occurs in... more The Pine Grove porphyry molybdenum deposit in the Wah Wah Mountains, southwestern Utah, occurs in the eroded vent of a lower Miocene ash flow (23-22 m.y. old). The vent, located in a tilted basin-and-range fault block, has been eroded about 1.7 km below the pre-eruption surface; consequently, the closest outcrops of related ash-flow tuff are 10 km away from the vent. Correlation of comagmatic ash-flow tuff and intrusive porphyry is made possible by the presence of accessory almandine-spessartine garnet of unique composition in both extrusive and intrusive units.Several lines of evidence suggest the presence of a parental magma chamber roughly 100 km 3 in size and compositionally zoned from rhyolite to dacite. Each eruptive episode began with a high silica content, rhyolitic magma containing quartz, sanidine, plagioclase, biotite, garnet, titanomagnetite, monazite, xenotime, ilmenorutile (?), and zircon. Presumably in response to continued rapid eruption and deeper drawdown in the parent chamber, some ash-flow eruptions also vented dacitic magma containing quartz, plagioclase, sanidine, biotite, hornblende, augite, titanomagnetite, ilmenite, sphene, apatite, and zircon.The dominant ore-related intrusion was emplaced immediately following concurrent intrusion of rhyolitic and dacitic magma into the vent. Multiple injections of trachyandesitic magma into the base of the chamber may have initiated convection or magma fracturing, surging of dacitic magma, and exsolution of volatiles that resulted, first, in ash-flow eruptions and, later, in episodes of mineralization. Therefore, an unusual combination of eruption mechanics and chamber volume and geometry allowed sampling of possibly the entire compositional range of the chamber during eruption but prohibited the complete loss of rhyolitic magma. Magmatic processes, such as late-stage convection, magma fracturing, and volatile fluxing may have been critical in the development of porphyry Mo mineralization.
GSA Annual Meeting in Phoenix, Arizona, USA - 2019, 2019
GSA Annual Meeting in Indianapolis, Indiana, USA - 2018, 2018
Abstract Large bodies of fibrous orange calcite, up to 400 m long and up to 20 m wide, are hosted... more Abstract Large bodies of fibrous orange calcite, up to 400 m long and up to 20 m wide, are hosted by Mississippian carbonate units in the Uinta Mountains, Utah. Subjacent to the carbonate rocks, emerald mineralization has recently been recognized in the Neoproterozoic Red Pine Shale. Fibrous orange calcite is translucent, and is being mined and used as architectural stone, in carvings, and for other decorative purposes. Calcite veins are located a few km south of the South Flank fault zone (SFFZ) in the vicinity of a swarm of north-trending faults. Portions of the Red Pine Shale along the SFFZ contain abundant secondary pyrite, and altered shale also contains quartz and calcite veins as well as albitization of some arkosic units, and is variably enriched in Cu and Zn. At least three emeralds have been discovered in altered Red Pine Shale. Our work suggests that brines from the Uinta Basin may have migrated upward along the SFFZ and interacted with the organic shale, producing emerald and a CO2–rich fluid that dissolved portions of the overlying Mississippian carbonates. The fluid experienced intermittent loss of aqueous CO2, causing fibrous calcite to rapidly precipitate. This model and setting has similarities to both Mississippi Valley and Colombian emerald deposits.
U.S. Geological Survey professional paper, 1987
Chart showing Stratigraphic relations and nomenclature of the Oligocene Needles Range Group .... ... more Chart showing Stratigraphic relations and nomenclature of the Oligocene Needles Range Group .... Geologic map and idealized cross section of the northeastern segment of the Indian Peak caldera ... Maps showing distribution and thickness of units in the Needles Range Group: A4. Marsden Tuff Member of Escalante Desert Formation and location of Pine Valley caldera
Abstracts with programs, 2018
Gems & Gemology, 2003
wo decades ago, Shigley and Foord (1984) described the spectacular gem-quality red beryl (figure ... more wo decades ago, Shigley and Foord (1984) described the spectacular gem-quality red beryl (figure 1) found at the Ruby Violet mine in the Wah Wah Mountains of southwestern Utah (see also Ream, 1979; Sinkankas, 1976, 1997). Since that time, this material has remained one of the rarest color varieties of gem beryl, with its increased recognition and acceptance in the marketplace being offset by the continued limited scale of production. Although gem beryls are common in granitic pegmatites (i.e., aquamarine, morganite, heliodor, and goshenite) and in certain metamorphic and metasedimentary rocks (emerald), their occurrence in rhyolites is unusual. Conversely, rhyolites occasionally contain crystals of quartz, topaz, and garnet in lithophysal (gas) cavities, or opal as veins or cavity fillings. Besides the Ruby Violet mine, several other occurrences of red beryl (all in rhyolites) are known, but none has produced significant quantities of facet-grade material. These include: Utah
Open-file report /, 1992
Hill-slope deposits Boulder to sand-sized rock fragments that have weathered out from bedrock or ... more Hill-slope deposits Boulder to sand-sized rock fragments that have weathered out from bedrock or alluvium, moved downslope through creep and slopewash, and accumulated on hill slopes. Two types of hill-slope deposits have been mapped, but the hill-slope deposits in most areas have not been distinguished from the underlying bedrock. Qt Talus (Holocene)-Hill-slope deposits of angular fragments of rhyolite derived from the rhyolite lava-flows member of the Blawn Formation (Tbr) in south-central part of map area and from andesite lava flows (Ta) along western edge. Rock fragments range from sand-size to boulders 1 m in diameter. Matrix is generally coarse sand, but locally there is no matrix. Thickness less than 5 m Qc Gravelly colluvium (Holocene and late and middle Pleistocene)~Hill-slope deposits of unsorted, unstratified, subrounded to subangular, light-gray to reddish-brown volcanic pebbles, cobbles and boulders as large as 50 cm in a matrix of reddish-brown angular sand. Consists of a thin mantle of debris eroded from older alluvial deposits (QTf, Qpl, Qp2, Qsl, Qs2) and transported down hill slopes chiefly by creep. Generally overlies early Pleistocene and Pliocene fan alluvium (QTf) and Tertiary lacustrine basin-fill deposits (Te). Older deposits have a calcic soil horizon with laminated calcium carbonate in the upper part. The laminations parallel the hill slope. Calcium carbonate cements the oldest colluvium and completely fills interstices to 1 m depth. Thickness less than 5 m Stream deposits Silt, sand, and gravel that fill channels and form floodplains and terraces along Meadow Valley Wash and minor streams Qal Alluvium of ephemeral streams (Holocene) Channel and floodplain alluvium of small, ephemeral streams. Very pale brown (10YR 7/3) pebbly sand, moderately bedded and poorly sorted, intercalated with lenticular beds of channel-cross-bedded, sandy, pebbly, cobble gravel. Unit also includes alluvium and colluvium in small fans along valley sides. Maximum thickness about 3 m Qsa Floodplain and channel alluvium of Meadow Wash (Holocene)-Floodplain deposits are interbedded very pale brown (10YR 7/3) pebbly sand, gray
Geol. Soc. Am., Abstr. Programs; (United States), 1985
Field characteristics, petrography, and geochemistry of granitoids associated with major W skarn ... more Field characteristics, petrography, and geochemistry of granitoids associated with major W skarn deposits in the Cordillera have been examined to determine magmatic processes or parameters critical for mineralization. Approximately 30 W-bearing systems were examined as well some barren or Mo-related granitoids of similar age. Granitoids which are nearly devoid of Ti-bearing phases such as sphene, ilmenite, and titanomagnetite and exhibit a low Fe/sup +3//Fe/sup +2/ ratio in biotite appear to be correlated with higher grade deposits. Incorporation of W in Ti sites in these minerals may occur early in the crystallization sequence and reduce the amount of W available for incorporation into a magmatic aqueous phase and subsequent ore fluid. Mesozoic granitoids west of the Sr/sub i/ = .708 line in Nevada and California are also correlated with larger W deposits compared to granitoids east of that line. Possibly, assimilation or melting of some pelitic sediment versus assimilation of Precambrian crust during petrogenesis may alter fO/sub 2/ and volatile fugacities sufficient to account for these differences in granitoid mineralogy and W mineralization. Two end-member processes of fluid transport were noted in the granitoids examined. First, moderate albitization and myrmekite development may mark the path of interstial transport of the magmaticmore » component of the ore fluid through proximal ore-related granitoids. Alternatively, transport occurs via quartz veins through a proximal granitoid with magmatic ore fluids originating from a younger source intrusion removed some distance from the skarn.« less
Rocky Mountain Geology, May 1, 2008
Large bodies of fibrous calcite, up to 400 m long and up to 20 m wide, are hosted by Mississippia... more Large bodies of fibrous calcite, up to 400 m long and up to 20 m wide, are hosted by Mississippian carbonate units in the Uinta Mountains, Utah. Subjacent to the carbonate rocks, emerald mineralization has been recognized recently in the Neoproterozoic Red Pine Shale. Two types of fibrous calcites are recognized on the basis of appearance and geochemical characteristics. Fibrous orange calcite is translucent, similar to “Mexican calcite” commonly sold at gem-and-mineral shows, and is being mined and used in carvings and for other decorative purposes. Recently recognized fibrous brown calcite is also present in the same general vicinity. Calcite veins hosted with Mississippian carbonate rocks are located a few kilometers south of the South Flank fault zone (SFFZ) in the vicinity of a swarm of north-trending faults. Parts of the Red Pine Shale along the SFFZ contain abundant secondary pyrite. Altered shale also contains quartz and calcite veins as well as albitized feldspar in some arkosic units and is variably enriched in Cu and Zn. At least three emeralds have been discovered in altered Red Pine Shale. b 18 O VSMOW values of calcite (-10 to -13‰) would be in equilibrium with basin brines (assumed to be –3 to +5‰), suggesting precipitation in the range of 100°–300° C. Our work suggests that sulfate-bearing basinal brines from the Uinta Basin may have migrated upward along the SFFZ and interacted with the carbon-rich shale. As sulfate was reduced by organic carbon to form sulfides, emerald was produced and a CO 2 -rich fluid migrated upward and dissolved parts of the Mississippian carbonates. The fluid experienced intermittent loss of CO 2 gas, which allowed fibrous calcite with cone-in-cone textures to precipitate rapidly. This model and geologic setting have broad similarities to both Mississippi Valley and Colombian emerald deposits. The genesis of fibrous brown calcite, however, is less certain. These calcites lack critical geochemical characteristics that tie orange calcite to precipitation from hot brines; rather stable isotope data are permissive of origin from low-temperature ground water.
Open-file report /, 1979
Unconsolldated, poorly sorted stream, fan, slope-wash, and talus deposits. The unit includes detr... more Unconsolldated, poorly sorted stream, fan, slope-wash, and talus deposits. The unit includes detritus of the unit Tbrt as talus aprons around The Tetons and as a mantle on a pediment between The Tetons and Jockey Road. Total thickness probably does not exceed 40 m FORMATION OF BLAWN WASH (MIOCENE) Rhyolite member of the Tetons Light-gray, pink, lavender, or brown porphyritic rhyolite flows and shallow intrusions with only a few small (<1 mm) phenocrysts of smokey quartz, sanidine, and plagioclase in a microcrystalline matrix. Generally flow layered and locally spherulitic and lithophysal with topaz and rare fluorite in vugs. Sanidine from the intrusive rhyolite south of the Staats mine has a K-Ar age of 20 m.y. (Lindsey and Osmonson, 1978) Rhyolite member of Pink Knolls Flows and shallow intrusive plugs and dikes of gray to brown strongly porphyritic rhyolite; locally vitrophyric. Phenocrysts of quartz, sanidine, plagioclase, and lesser biotite comprise as much as one-third of the rock. Phenocrysts range widely in size, and within individual outcrops, sanidine and quartz range from small crystals to prominent phenocrysts as much as 3 cm and 1 cm across, respectively Tuff member A sequence of light-colored, generally loosely consolidated, vitric-lithic ash-flow and minor air-fall tuffs with intervening beds of stratified water-lain tuffs, volcanic sandstones, and conglomerates. The topaz rhyolite at The Tetons is underlain by a strongly welded ash-flow tuff with collapsed pumice lenses of black or brown glass. Tuffs in the unit contain less than 10 percent phenocrysts of quartz, plagioclase, sanidine, and biotite and have abundant pumice lapilli. Fragments of the Lund Tuff Member as much as 25 cm across are typically present, and are especially common in the epiclastic beds. Scattered fragments of Lund are commonly the only indication of the unit beneath poorly exposed slopes. The unit appears to be comprised of locally derived material, in part representing the precursory explosive facies of younger rhyolite flows and intrusions. Possibly as much as 300 m of this unit is exposed in Blawn Wash Mafic flow member Gray lava flow with phenocrysts of augite and labradorite; weathers brown with red liesegang bands; zeolite amygdules. In these and adjacent quadrangles the unit ranges from 55 to 60 weight percent Si02 and 2.4 to 4.0 K 0 0. Thickness 200 m
GeoResJ, Mar 1, 2015
Remote thermal monitoring of active volcanoes has many important applications for terrestrial and... more Remote thermal monitoring of active volcanoes has many important applications for terrestrial and planetary volcanic systems. In this study, we describe observations of active eruptions on Kilauea and Erta Ale volcanoes using a short-wavelength, high-resolution, consumer digital camcorder and other non-imaging thermal detectors. These systems revealed brightness temperatures close to the eruption temperatures and temperature distributions, morphologies and thermal structures of flow features, tube systems and lava fountains. Lava flows observed by the camcorder through a skylight on Kilauea had a peak in maximum brightness temperatures at 1230°C and showed brightness temperature distributions consistent with most rapid flow at the center. Surface brightness temperatures of cooling lava flows on Kilauea were close to 850°C. Centimeter-scale thermal features are evident around pahoehoe ropes and inflated flows and stalactites in lava tubes. Observations of the fountaining Erta Ale lava lake in February 2011 extend the baseline of observations of the eruptive episode begun in late 2010. We observed a fountain using the camcorder and found a peak in maximum brightness temperatures at 1164°C, consistent with previous studies. Steep temperature gradients were observed across centimeter-scale distances between the highly exposed fountain and cracks and the much cooler lava lake surface and crater walls. The instrument and methods described here lead to robust pictures of the temperatures and temperature distributions at these volcanoes and reveal desired characteristics of planetary remote sensing platforms for the study of volcanically active bodies such as Io.
Geological Society of America Special Papers, 1990
Abstracts with programs, 2021