Albert H Hofstra
Al Hofstra is a Research Geologist with the Geology, Geophysics, and Geochemistry Science Center.
Science and Products
Filter Total Items: 76
Evidence for Proterozoic and late Cretaceous-early Tertiary ore-forming events in the Coeur d'Alene district, Idaho and Montana
New 40 Ar/ 39 Ar age spectra on sericite and lead isotope data on tetrahedrite, siderite, galena, bournonite, and stibnite, together with previously published isotopic, geochemical, and geologic studies provide evidence for two major vein-forming events in the Coeur d'Alene district and surrounding areas of the Belt basin. The data suggest that the zinc- and lead-rich veins (e.g., Bunker Hill and
Authors
D. L. Leach, A. H. Hofstra, S. E. Church, L.W. Snee, R. B. Vaughn, R. E. Zartman
The composition of fluid inclusions in ore and gangue minerals from the Silesian-Cracow Mississippi Valley-type Zn-Pb deposits Poland: Genetic and environmental implications
The composition of fluids extracted from ore and gangue sulfide minerals that span most of the paragenesis of the Silesian-Cracow district was determined using a newly developed ion chromatographic (IC) technique. Ionic species determined were Na+, NH+4, Ca2+, Mg2+, K+, Rb+, Sr2+, Ba2+, Cl-, Br-, F-, I-, PO3-4, CO2-3, HS-, S2O2-3, SO2-4, NO-3, and acetate. Mineral samples included six from the Pom
Authors
J. G. Viets, A. H. Hofstra, P. Emsbo, A. Kozlowski
Fluid-inclusion gases in sphalerite, galena, and dolomite from the Silesian-Cracow Zn-Pb district, Poland
The gases in fluid inclusions from samples of sphalerite, galena, and sparry dolomite from ore deposits in the Silesian-Cracow zinc-lead district were determined by mass spectrometry. The results show that CO2 is the major gas in the fluid inclusions with lesser amounts of CH4. Samples of galena and sphalerite also commonly contain H2S and short-chain hydrocarbon gases. Gases in sphalerite and gal
Authors
D. L. Leach, L.E. Apodaca, A. Kozlowski, G. P. Landis, A. H. Hofstra
Chemical reaction path modeling of ore deposition in Mississippi Valley-type Pb-Zn deposits of the Ozark region, U.S. Midcontinent: A reply
No abstract available.
Authors
Geoffrey S. Plumlee, David L. Leach, Albert H. Hofstra, Gary P. Landis, Elisabeth L. Rowan, John G. Viets
Chemical reaction path modeling of ore deposition in Mississippi Valley-type Pb-Zn deposits of the Ozark region, US midcontinent
The Ozark region of the U.S. midcontinent is host to a number of Mississippi Valley-type districts, including the world-class Viburnum Trend, Old Lead Belt, and Tri-State districts and the smaller Southeast Missouri barite, Northern Arkansas, and Central Missouri districts. There is increasing evidence that the Ozark Mississippi Valley-type districts formed locally within a large, interconnected h
Authors
G.S. Plumlee, D. L. Leach, A. H. Hofstra, G. P. Landis, E. L. Rowan, J. G. Viets
Reconnaissance stream-sediment geochemistry of Twentynine Palms Marine Corps Base, California
No abstract available.
Authors
Albert H. Hofstra, D. L. Fey, J.M. Motooka, D.A. Hopkins
Geology and mineral resource potential of the Chattanooga 1° x 2° quadrangle, Tennessee and North Carolina — A preliminary assessment
No abstract available.
Authors
Sandra H. Clark, Gregory T Spanski, D. G. Hadley, A. H. Hofstra
Reconnaissance stream-sediment geochemistry of Death Valley National Monument, California
No abstract available.
Authors
Albert H. Hofstra, D. L. Fey, J.M. Motooka, B. H. Roushey, Lee-Ann Bradley
Handbook of geochemical data for the Trona 1 degree x 2 degrees Quadrangle; Southern California Mineral Resource Framework and Assessment Project
No abstract available.
Authors
Albert H. Hofstra
Fluid inclusion gas chemistry as a potential minerals exploration tool: Case studies from Creede, CO, Jerritt Canyon, NV, Coeur d'Alene district, ID and MT, southern Alaska mesothermal veins, and mid-continent MVT's
Recent advances in instrumentation now permit quantitative analysis of gas species from individual fluid inclusions. Fluid inclusion gas data can be applied to minerals exploration empirically to establish chemical (gas composition) signatures of the ore fluids, and conceptually through the development of genetic models of ore formation from a framework of integrated geologic, geochemical, and iso
Authors
G. P. Landis, A. H. Hofstra
Genesis of sediment-hosted disseminated-gold deposits by fluid mixing and sulfidization: chemical-reaction-path modeling of ore- depositional processes documented in the Jerritt Canyon district, Nevada
Integrated geologic, geochemical, fluid-inclusion, and stableisotope studies of the gold deposits in the Jerritt Canyon district, Nevada, provide evidence that gold deposition was a consequence of both fluid mixing and sulfidization of host-rock iron. Chemical-reaction-path models of these ore-depositional processes confirm that the combination of fluid mixing, including simultaneous cooling, dilu
Authors
A. H. Hofstra
Origin of late dolomite cement by CO2-saturated deep basin brines: evidence from the Ozark region, central United States
Studies of fluid inclusions in regionally extensive late dolomite cement (LDC) throughout the Ozark region show that CO2 effervescence was widespread during dolomite precipitation. On the basis of quantitative analyses of inclusion fluids, reaction-path modeling shows that LDC with trace amounts of sulfides can be deposited by effervescence of a CO2-saturated basin brine as it migrates to shallowe
Authors
D. L. Leach, G.S. Plumlee, A. H. Hofstra, G. P. Landis, E. L. Rowan, J. G. Viets
Science and Products
Filter Total Items: 76
Evidence for Proterozoic and late Cretaceous-early Tertiary ore-forming events in the Coeur d'Alene district, Idaho and Montana
New 40 Ar/ 39 Ar age spectra on sericite and lead isotope data on tetrahedrite, siderite, galena, bournonite, and stibnite, together with previously published isotopic, geochemical, and geologic studies provide evidence for two major vein-forming events in the Coeur d'Alene district and surrounding areas of the Belt basin. The data suggest that the zinc- and lead-rich veins (e.g., Bunker Hill and
Authors
D. L. Leach, A. H. Hofstra, S. E. Church, L.W. Snee, R. B. Vaughn, R. E. Zartman
The composition of fluid inclusions in ore and gangue minerals from the Silesian-Cracow Mississippi Valley-type Zn-Pb deposits Poland: Genetic and environmental implications
The composition of fluids extracted from ore and gangue sulfide minerals that span most of the paragenesis of the Silesian-Cracow district was determined using a newly developed ion chromatographic (IC) technique. Ionic species determined were Na+, NH+4, Ca2+, Mg2+, K+, Rb+, Sr2+, Ba2+, Cl-, Br-, F-, I-, PO3-4, CO2-3, HS-, S2O2-3, SO2-4, NO-3, and acetate. Mineral samples included six from the Pom
Authors
J. G. Viets, A. H. Hofstra, P. Emsbo, A. Kozlowski
Fluid-inclusion gases in sphalerite, galena, and dolomite from the Silesian-Cracow Zn-Pb district, Poland
The gases in fluid inclusions from samples of sphalerite, galena, and sparry dolomite from ore deposits in the Silesian-Cracow zinc-lead district were determined by mass spectrometry. The results show that CO2 is the major gas in the fluid inclusions with lesser amounts of CH4. Samples of galena and sphalerite also commonly contain H2S and short-chain hydrocarbon gases. Gases in sphalerite and gal
Authors
D. L. Leach, L.E. Apodaca, A. Kozlowski, G. P. Landis, A. H. Hofstra
Chemical reaction path modeling of ore deposition in Mississippi Valley-type Pb-Zn deposits of the Ozark region, U.S. Midcontinent: A reply
No abstract available.
Authors
Geoffrey S. Plumlee, David L. Leach, Albert H. Hofstra, Gary P. Landis, Elisabeth L. Rowan, John G. Viets
Chemical reaction path modeling of ore deposition in Mississippi Valley-type Pb-Zn deposits of the Ozark region, US midcontinent
The Ozark region of the U.S. midcontinent is host to a number of Mississippi Valley-type districts, including the world-class Viburnum Trend, Old Lead Belt, and Tri-State districts and the smaller Southeast Missouri barite, Northern Arkansas, and Central Missouri districts. There is increasing evidence that the Ozark Mississippi Valley-type districts formed locally within a large, interconnected h
Authors
G.S. Plumlee, D. L. Leach, A. H. Hofstra, G. P. Landis, E. L. Rowan, J. G. Viets
Reconnaissance stream-sediment geochemistry of Twentynine Palms Marine Corps Base, California
No abstract available.
Authors
Albert H. Hofstra, D. L. Fey, J.M. Motooka, D.A. Hopkins
Geology and mineral resource potential of the Chattanooga 1° x 2° quadrangle, Tennessee and North Carolina — A preliminary assessment
No abstract available.
Authors
Sandra H. Clark, Gregory T Spanski, D. G. Hadley, A. H. Hofstra
Reconnaissance stream-sediment geochemistry of Death Valley National Monument, California
No abstract available.
Authors
Albert H. Hofstra, D. L. Fey, J.M. Motooka, B. H. Roushey, Lee-Ann Bradley
Handbook of geochemical data for the Trona 1 degree x 2 degrees Quadrangle; Southern California Mineral Resource Framework and Assessment Project
No abstract available.
Authors
Albert H. Hofstra
Fluid inclusion gas chemistry as a potential minerals exploration tool: Case studies from Creede, CO, Jerritt Canyon, NV, Coeur d'Alene district, ID and MT, southern Alaska mesothermal veins, and mid-continent MVT's
Recent advances in instrumentation now permit quantitative analysis of gas species from individual fluid inclusions. Fluid inclusion gas data can be applied to minerals exploration empirically to establish chemical (gas composition) signatures of the ore fluids, and conceptually through the development of genetic models of ore formation from a framework of integrated geologic, geochemical, and iso
Authors
G. P. Landis, A. H. Hofstra
Genesis of sediment-hosted disseminated-gold deposits by fluid mixing and sulfidization: chemical-reaction-path modeling of ore- depositional processes documented in the Jerritt Canyon district, Nevada
Integrated geologic, geochemical, fluid-inclusion, and stableisotope studies of the gold deposits in the Jerritt Canyon district, Nevada, provide evidence that gold deposition was a consequence of both fluid mixing and sulfidization of host-rock iron. Chemical-reaction-path models of these ore-depositional processes confirm that the combination of fluid mixing, including simultaneous cooling, dilu
Authors
A. H. Hofstra
Origin of late dolomite cement by CO2-saturated deep basin brines: evidence from the Ozark region, central United States
Studies of fluid inclusions in regionally extensive late dolomite cement (LDC) throughout the Ozark region show that CO2 effervescence was widespread during dolomite precipitation. On the basis of quantitative analyses of inclusion fluids, reaction-path modeling shows that LDC with trace amounts of sulfides can be deposited by effervescence of a CO2-saturated basin brine as it migrates to shallowe
Authors
D. L. Leach, G.S. Plumlee, A. H. Hofstra, G. P. Landis, E. L. Rowan, J. G. Viets