Albert H Hofstra
Al Hofstra is a Research Geologist with the Geology, Geophysics, and Geochemistry Science Center.
Science and Products
Filter Total Items: 76
Noble gas data from Goldfield and Tonopah epithermal Au-Ag deposits, ancestral Cascades Arc, USA: Evidence for a primitive mantle volatile source
The He, Ne, and Ar isotopic composition of fluid inclusions in ore and gangue minerals were analyzed to determine the source of volatiles in the high-grade Goldfield and Tonopah epithermal Au-Ag deposits in southwestern Nevada, USA. Ar and Ne are mainly atmospheric, whereas He has only a minor atmospheric component. Corrected 3He/4He ratios (with atmospheric He removed) range widely from 0.05 to 3
Authors
Andrew H. Manning, Albert H. Hofstra
The Valmy thrust sheet: A regional structure formed during the protracted assembly of the Roberts Mountains allochthon, Nevada, USA
A synthesis of field, biostratigraphic, detrital zircon geochronologic, and remote sensing data across north-central Nevada, United States, defines a thick, regionally extensive sheet of Middle–Upper Ordovician Valmy Formation quartzite that structurally overlies deformed early Paleozoic units of the Roberts Mountains allochthon. Late Paleozoic regional unconformities that record tectonic disrupti
Authors
Christopher S. Holm-Denoma, Albert H. Hofstra, Barnaby W. Rockwell, Paula J. Noble
Isotopic data for Late Cretaceous intrusions and associated altered and mineralized rocks in the Big Belt Mountains, Montana
The quartz monzodiorite of Mount Edith and the concentrically zoned intrusive suite of Boulder Baldy constitute the principal Late Cretaceous igneous intrusions hosted by Mesoproterozoic sedimentary rocks of the Newland Formation in the Big Belt Mountains, Montana. These calc-alkaline plutonic masses are manifestations of subduction-related magmatism that prevailed along the western edge of North
Authors
Edward A. du Bray, Daniel M. Unruh, Albert H. Hofstra
Mineral thermometry and fluid inclusion studies of the Pea Ridge iron oxide-apatite–rare earth element deposit, Mesoproterozoic St. Francois Mountains Terrane, southeast Missouri, USA
Mineral thermometry and fluid inclusion studies were conducted on variably altered and mineralized samples from the Mesoproterozoic Pea Ridge iron oxide-apatite (IOA)-rare earth element (REE) deposit in order to constrain P-T conditions, fluid chemistry, and the source of salt and volatiles during early magnetite and later REE mineralization.Scanning electron microscopy (SEM)-cathodoluminescence a
Authors
Albert H. Hofstra, Corey J. Meighan, Xinyu Song, Iain Samson, Erin E. Marsh, Heather A. Lowers, Poul Emsbo, Andrew G. Hunt
Critical elements in Carlin, epithermal, and orogenic gold deposits
Carlin, epithermal, and orogenic gold deposits, today mined almost exclusively for their gold content, have similar suites of anomalous trace elements that reflect similar low-salinity ore fluids and thermal conditions of metal transport and deposition. Many of these trace elements are commonly referred to as critical or near-critical elements or metals and have been locally recovered, although ty
Authors
Richard J. Goldfarb, Albert H. Hofstra, Stuart F. Simmons
Geology and mineral resources of the North-Central Idaho Sagebrush Focal Area: Chapter C in Mineral resources of the Sagebrush Focal Areas of Idaho, Montana, Nevada, Oregon, Utah, and Wyoming
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 Scientific Investigations Report 2016–5089–A). The purpo
Authors
Karen Lund, Lukas Zürcher, Albert H. Hofstra, Bradley S. Van Gosen, Mary Ellen Benson, Stephen E. Box, Eric D. Anderson, Donald I. Bleiwas, Jacob DeAngelo, Ronald M. Drake, Gregory L. Fernette, Stuart A. Giles, Jonathan M. G. Glen, Jon E. Haacke, John D. Horton, David John, Gilpin R. Robinson, Barnaby W. Rockwell, Carma A. San Juan, Brian N. Shaffer, Steven M. Smith, Colin F. Williams
By
Energy and Minerals Mission Area, Energy Resources Program, Mineral Resources Program, National Laboratories Program, Science and Decisions Center, Geology, Energy & Minerals Science Center, Geology, Minerals, Energy, and Geophysics Science Center, Geology, Geophysics, and Geochemistry Science Center, National Minerals Information Center
Geology and mineral resources of the Sheldon-Hart Mountain National Wildlife Refuge Complex (Oregon and Nevada), the Southeastern Oregon and North-Central Nevada, and the Southern Idaho and Northern Nevada (and Utah) Sagebrush Focal Areas: Chapter B in
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 Scientific Investigations Report 2016–5089–A). The purpo
Authors
Peter G. Vikre, Mary Ellen Benson, Donald I. Bleiwas, Joseph Colgan, Pamela M. Cossette, Jacob DeAngelo, Connie L. Dicken, Ronald M. Drake, Edward A. du Bray, Gregory L. Fernette, Jonathan M. G. Glen, Jon E. Haacke, Susan M. Hall, Albert H. Hofstra, David John, Stephen Ludington, Mark J. Mihalasky, James J. Rytuba, Brian N. Shaffer, Lisa L. Stillings, John C. Wallis, Colin F. Williams, Douglas B. Yager, Lukas Zürcher
Extreme variation of sulfur isotopic compositions in pyrite from the Qiuling sediment-hosted gold deposit, West Qinling orogen, central China: An in situ SIMS study with implications for the source of sulfur
High spatial resolution textural (scanning electron microscope (SEM)), chemical (electron microprobe (EMP)) and laser ablation-inductively coupled plasma-mass spec- trometry (LA-ICP-MS)), and sulfur isotopic (secondary ion mass spectrometry (SIMS)) analyses of pyrite from the Qiuling sediment-hosted gold deposit (232±4 Ma) in the West Qinling orogen, central China were conducted to distinguish pyr
Authors
Lei Chen, Xian-hua Li, Jian-wei Li, Albert H. Hofstra, Yu Liu, Alan E. Koenig
Pre-eruptive conditions of the Hideaway Park topaz rhyolite: Insights into metal source and evolution of magma parental to the Henderson porphyry molybdenum deposit, Colorado
The Hideaway Park tuff is the only preserved extrusive volcanic unit related to the Red Mountain intrusive complex, which produced the world-class Henderson porphyry Mo deposit. Located within the Colorado Mineral Belt, USA, Henderson is the second largest Climax-type Mo deposit in the world, and is therefore an excellent location to investigate magmatic processes leading to Climax-type Mo mineral
Authors
Celestine N. Mercer, Albert H. Hofstra, Todor I. Todorov, Julie Roberge, Alain Burgisser, David T. Adams, Michael A. Cosca
Silicate melt inclusion evidence for extreme pre-eruptive enrichment and post-eruptive depletion of lithium in silicic volcanic rocks of the western United States: implications for the origin of lithium-rich brines
To evaluate whether anatectic and/or highly fractionated lithophile element-enriched rhyolite tuffs deposited in arid lacustrine basins lose enough lithium during eruption, lithification, and weathering to generate significant Li brine resources, pre-eruptive melt compositions, preserved in inclusions, and the magnitude of post-eruptive Li depletions, evident in host rhyolites, were documented at
Authors
Albert H. Hofstra, T.I. Todorov, C.N. Mercer, D.T. Adams, E.E. Marsh
Ore genesis constraints on the Idaho cobalt belt from fluid inclusion gas, noble gas isotope, and ion ratio analyses--a reply
Burlinson (2013) questions the veracity of the H2 concentrations reported for fluid inclusion extracts from minerals in the Idaho cobalt belt (Table 2; Landis and Hofstra, 2012) and suggests that they are an analytical artifact of electron-impact mass spectrometry. He also declares that H2 should not be present in fluid inclusions because it is invariably lost by diffusion and is never detected in
Authors
Albert H. Hofstra, Gary P. Landis
Analyzing legacy U.S. Geological Survey geochemical databases using GIS: applications for a national mineral resource assessment
This report emphasizes geographic information system analysis and the display of data stored in the legacy U.S. Geological Survey National Geochemical Database for use in mineral resource investigations. Geochemical analyses of soils, stream sediments, and rocks that are archived in the National Geochemical Database provide an extensive data source for investigating geochemical anomalies. A study
Authors
Douglas B. Yager, Albert H. Hofstra, Matthew Granitto
Science and Products
Filter Total Items: 76
Noble gas data from Goldfield and Tonopah epithermal Au-Ag deposits, ancestral Cascades Arc, USA: Evidence for a primitive mantle volatile source
The He, Ne, and Ar isotopic composition of fluid inclusions in ore and gangue minerals were analyzed to determine the source of volatiles in the high-grade Goldfield and Tonopah epithermal Au-Ag deposits in southwestern Nevada, USA. Ar and Ne are mainly atmospheric, whereas He has only a minor atmospheric component. Corrected 3He/4He ratios (with atmospheric He removed) range widely from 0.05 to 3
Authors
Andrew H. Manning, Albert H. Hofstra
The Valmy thrust sheet: A regional structure formed during the protracted assembly of the Roberts Mountains allochthon, Nevada, USA
A synthesis of field, biostratigraphic, detrital zircon geochronologic, and remote sensing data across north-central Nevada, United States, defines a thick, regionally extensive sheet of Middle–Upper Ordovician Valmy Formation quartzite that structurally overlies deformed early Paleozoic units of the Roberts Mountains allochthon. Late Paleozoic regional unconformities that record tectonic disrupti
Authors
Christopher S. Holm-Denoma, Albert H. Hofstra, Barnaby W. Rockwell, Paula J. Noble
Isotopic data for Late Cretaceous intrusions and associated altered and mineralized rocks in the Big Belt Mountains, Montana
The quartz monzodiorite of Mount Edith and the concentrically zoned intrusive suite of Boulder Baldy constitute the principal Late Cretaceous igneous intrusions hosted by Mesoproterozoic sedimentary rocks of the Newland Formation in the Big Belt Mountains, Montana. These calc-alkaline plutonic masses are manifestations of subduction-related magmatism that prevailed along the western edge of North
Authors
Edward A. du Bray, Daniel M. Unruh, Albert H. Hofstra
Mineral thermometry and fluid inclusion studies of the Pea Ridge iron oxide-apatite–rare earth element deposit, Mesoproterozoic St. Francois Mountains Terrane, southeast Missouri, USA
Mineral thermometry and fluid inclusion studies were conducted on variably altered and mineralized samples from the Mesoproterozoic Pea Ridge iron oxide-apatite (IOA)-rare earth element (REE) deposit in order to constrain P-T conditions, fluid chemistry, and the source of salt and volatiles during early magnetite and later REE mineralization.Scanning electron microscopy (SEM)-cathodoluminescence a
Authors
Albert H. Hofstra, Corey J. Meighan, Xinyu Song, Iain Samson, Erin E. Marsh, Heather A. Lowers, Poul Emsbo, Andrew G. Hunt
Critical elements in Carlin, epithermal, and orogenic gold deposits
Carlin, epithermal, and orogenic gold deposits, today mined almost exclusively for their gold content, have similar suites of anomalous trace elements that reflect similar low-salinity ore fluids and thermal conditions of metal transport and deposition. Many of these trace elements are commonly referred to as critical or near-critical elements or metals and have been locally recovered, although ty
Authors
Richard J. Goldfarb, Albert H. Hofstra, Stuart F. Simmons
Geology and mineral resources of the North-Central Idaho Sagebrush Focal Area: Chapter C in Mineral resources of the Sagebrush Focal Areas of Idaho, Montana, Nevada, Oregon, Utah, and Wyoming
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 Scientific Investigations Report 2016–5089–A). The purpo
Authors
Karen Lund, Lukas Zürcher, Albert H. Hofstra, Bradley S. Van Gosen, Mary Ellen Benson, Stephen E. Box, Eric D. Anderson, Donald I. Bleiwas, Jacob DeAngelo, Ronald M. Drake, Gregory L. Fernette, Stuart A. Giles, Jonathan M. G. Glen, Jon E. Haacke, John D. Horton, David John, Gilpin R. Robinson, Barnaby W. Rockwell, Carma A. San Juan, Brian N. Shaffer, Steven M. Smith, Colin F. Williams
By
Energy and Minerals Mission Area, Energy Resources Program, Mineral Resources Program, National Laboratories Program, Science and Decisions Center, Geology, Energy & Minerals Science Center, Geology, Minerals, Energy, and Geophysics Science Center, Geology, Geophysics, and Geochemistry Science Center, National Minerals Information Center
Geology and mineral resources of the Sheldon-Hart Mountain National Wildlife Refuge Complex (Oregon and Nevada), the Southeastern Oregon and North-Central Nevada, and the Southern Idaho and Northern Nevada (and Utah) Sagebrush Focal Areas: Chapter B in
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 Scientific Investigations Report 2016–5089–A). The purpo
Authors
Peter G. Vikre, Mary Ellen Benson, Donald I. Bleiwas, Joseph Colgan, Pamela M. Cossette, Jacob DeAngelo, Connie L. Dicken, Ronald M. Drake, Edward A. du Bray, Gregory L. Fernette, Jonathan M. G. Glen, Jon E. Haacke, Susan M. Hall, Albert H. Hofstra, David John, Stephen Ludington, Mark J. Mihalasky, James J. Rytuba, Brian N. Shaffer, Lisa L. Stillings, John C. Wallis, Colin F. Williams, Douglas B. Yager, Lukas Zürcher
Extreme variation of sulfur isotopic compositions in pyrite from the Qiuling sediment-hosted gold deposit, West Qinling orogen, central China: An in situ SIMS study with implications for the source of sulfur
High spatial resolution textural (scanning electron microscope (SEM)), chemical (electron microprobe (EMP)) and laser ablation-inductively coupled plasma-mass spec- trometry (LA-ICP-MS)), and sulfur isotopic (secondary ion mass spectrometry (SIMS)) analyses of pyrite from the Qiuling sediment-hosted gold deposit (232±4 Ma) in the West Qinling orogen, central China were conducted to distinguish pyr
Authors
Lei Chen, Xian-hua Li, Jian-wei Li, Albert H. Hofstra, Yu Liu, Alan E. Koenig
Pre-eruptive conditions of the Hideaway Park topaz rhyolite: Insights into metal source and evolution of magma parental to the Henderson porphyry molybdenum deposit, Colorado
The Hideaway Park tuff is the only preserved extrusive volcanic unit related to the Red Mountain intrusive complex, which produced the world-class Henderson porphyry Mo deposit. Located within the Colorado Mineral Belt, USA, Henderson is the second largest Climax-type Mo deposit in the world, and is therefore an excellent location to investigate magmatic processes leading to Climax-type Mo mineral
Authors
Celestine N. Mercer, Albert H. Hofstra, Todor I. Todorov, Julie Roberge, Alain Burgisser, David T. Adams, Michael A. Cosca
Silicate melt inclusion evidence for extreme pre-eruptive enrichment and post-eruptive depletion of lithium in silicic volcanic rocks of the western United States: implications for the origin of lithium-rich brines
To evaluate whether anatectic and/or highly fractionated lithophile element-enriched rhyolite tuffs deposited in arid lacustrine basins lose enough lithium during eruption, lithification, and weathering to generate significant Li brine resources, pre-eruptive melt compositions, preserved in inclusions, and the magnitude of post-eruptive Li depletions, evident in host rhyolites, were documented at
Authors
Albert H. Hofstra, T.I. Todorov, C.N. Mercer, D.T. Adams, E.E. Marsh
Ore genesis constraints on the Idaho cobalt belt from fluid inclusion gas, noble gas isotope, and ion ratio analyses--a reply
Burlinson (2013) questions the veracity of the H2 concentrations reported for fluid inclusion extracts from minerals in the Idaho cobalt belt (Table 2; Landis and Hofstra, 2012) and suggests that they are an analytical artifact of electron-impact mass spectrometry. He also declares that H2 should not be present in fluid inclusions because it is invariably lost by diffusion and is never detected in
Authors
Albert H. Hofstra, Gary P. Landis
Analyzing legacy U.S. Geological Survey geochemical databases using GIS: applications for a national mineral resource assessment
This report emphasizes geographic information system analysis and the display of data stored in the legacy U.S. Geological Survey National Geochemical Database for use in mineral resource investigations. Geochemical analyses of soils, stream sediments, and rocks that are archived in the National Geochemical Database provide an extensive data source for investigating geochemical anomalies. A study
Authors
Douglas B. Yager, Albert H. Hofstra, Matthew Granitto