Albert H Hofstra
Al Hofstra is a Research Geologist with the Geology, Geophysics, and Geochemistry Science Center.
Science and Products
Filter Total Items: 76
A special issue devoted to gold deposits in Northern Nevada: Part 1. Regional studies and epitherrmal deposits
No abstract available.
Authors
D. A. John, A. H. Hofstra, T. G. Theodore
Geologic setting and genesis of the Mule Canyon low-sulfidation epithermal gold-silver deposit, north-central Nevada
The Mule Canyon mine exploited shallow, low-sulfidation, epithermal Au-Ag deposits that lie near the west side of the Northern Nevada rift in northern Lander County, Nevada. Mule Canyon consists of six small deposits that contained premining reserves of about 8.2 Mt at an average grade of 3.81 g Au/tonne. It is an uncommon mafic end member of low-sulfidation Au-Ag deposits associated with tholeiit
Authors
D. A. John, A. H. Hofstra, R. J. Fleck, J.E. Brummer, E.C. Saderholm
The Tuscarora Au-Ag district: Eocene volcanic-hosted epithermal deposits in the Carlin gold region, Nevada
The Tuscarora mining district contains the oldest and the only productive Eocene epithermal deposits in Nevada. The district is a particularly clear example of association of low-sulfidation deposits with igneous activity and structure, and it is unusual in that it consists of two adjoining but physically and chemically distinct types of low-sulfidation deposits. Moreover, Tuscarora deposits are o
Authors
S.B. Castor, D.R. Boden, C.D. Henry, J. S. Cline, A. H. Hofstra, W. C. McIntosh, R. M. Tosdal, J.P. Wooden
Lithogeochemistry of Carlin-type gold mineralization in the Gold Bar district, Battle Mountain-Eureka trend, Nevada
The Gold Bar district contains five Carlin-type gold deposits and four resources for a combined gold endowment of 1.6 M oz [50 t]. The gold deposits are hosted in Devonian carbonate rocks below parautochthonous and allochthonous Paleozoic siliciclastic rocks emplaced during the Early Mississippian Antler orogeny. The district is in the Battle Mountain-Eureka trend, a long-lived structural feature
Authors
O. Yigit, A. H. Hofstra
Structural controls on Carlin-type gold mineralization in the gold bar district, Eureka County, Nevada
The Gold Bar district in the southern Roberts Mountains, 48 km northwest of Eureka, Nevada, contains one main deposit (Gold Bar), five satellite deposits, and other resources. Approximately 0.5 Moz of gold have been recovered from a resource of 1,639,000 oz of gold in Carlin-type gold deposits in lower plate, miogeoclinal carbonate rocks below the Roberts Mountains thrust. Host rocks are unit 2 of
Authors
O. Yigit, E.P. Nelson, M.W. Hitzman, A. H. Hofstra
Origin and significance of postore dissolution collapse breccias cemented with calcite and barite at the Meikle gold deposit, Northern Carlin trend, Nevada
The final event in a complicated hydrothermal history at the Meikle gold deposit was gold deficient but caused extensive postore dissolution of carbonate, collapse brecciation, and precipitation of calcite and barite crystals in the resulting cavities. Although previously interpreted to be part of the Carlin-type hydrothermal system, crosscutting relationships and U-Th-Pb geochronology constrain t
Authors
P. Emsbo, A. H. Hofstra
Alligator ridge district, East-Central Nevada: Carlin-type gold mineralization at shallow depths
Carlin-type deposits in the Alligator Ridge mining district are present sporadically for 40 km along the north-striking Mooney Basin fault system but are restricted to a 250-m interval of Devonian to Mississippian strata. Their age is bracketed between silicified ca. 45 Ma sedimentary rocks and unaltered 36.5 to 34 Ma volcanic rocks. The silicification is linked to the deposits by its continuity w
Authors
C.J. Nutt, A. H. Hofstra
Geology and geochemistry of Carlin-type gold deposits in China
The Carlin-type gold deposits in China lie mostly near the margins of the Proterozoic Yangtze and Aba cratons. Submicron-sized gold in micron-sized arsenian pyrite is disseminated in fractured Cambrian through Triassic carbonaceous shale and carbonate rocks, and is associated with anomalous Hg, Sb, As, U, and Tl. Alteration typically includes silicification, argilization, and sulfidation. Aqueous
Authors
H. Rui-Zhong, S. Wen-Chao, B. Xian-Wu, T. Guang-Zhi, A. H. Hofstra
U-Th-Pb dating of hydrothermal minerals from Carlin-type gold deposits, Nevada- Results and evaluation
No abstract available.
Authors
A. H. Hofstra, Wayne R. Premo, Poul Emsbo, J. S. Cline, John N. Aleinikoff
Ore-fluid evolution at the Getchell Carlin-type gold deposit, Nevada, USA
Minerals and fluid-inclusion populations were examined using petrography, microthermometry, quadrupole mass-spectrometer gas analyses and stable-isotope studies to characterize fluids responsible for gold mineralization at the Getchell Carlin-type gold deposit. The gold-ore assemblage at Getchell is superimposed on quartz-pyrite vein mineralization associated with a Late-Cretaceous granodiorite st
Authors
Jean S. Cline, Albert H. Hofstra
Syngenetic Au on the Carlin trend: Implications for Carlin-type deposits
A new type of gold occurrence recently discovered in the Carlin trend, north-central Nevada, is clearly distinct from classic Carlin-type gold ore. These occurrences are interpreted to be of sedimentary exhalative (sedex) origin because they are stratiform and predate compaction and lithification of their unaltered Devonian host rocks. They contain barite that exhibits δ34S and δ180 values identic
Authors
P. Emsbo, R.W. Hutchinson, A. H. Hofstra, J.A. Volk, K. H. Bettles, G.J. Baschuk, C.A. Johnson
Age constraints on Jerritt Canyon and other Carlin-type gold deposits in the western United States-relationship to mid-Tertiary extension and magmatism
Carlin-type gold deposits are difficult to date and a wide range of ages has been reported for individual deposits. Therefore, several methods were employed to constrain the age of the gold deposits in the Jerritt Canyon district. Dated igneous rocks with well-documented crosscutting relationships to ore provided the most reliable constraints. K/Ar and 40 Ar/ 39 Ar dates on igneous rocks are as fo
Authors
A. H. Hofstra, L. W. Snee, R. O. Rye, H. W. Folger, J.D. Phinisey, R.J. Loranger, A.R. Dahl, C.W. Naeser, H. J. Stein, M. Lewchuk
Science and Products
Filter Total Items: 76
A special issue devoted to gold deposits in Northern Nevada: Part 1. Regional studies and epitherrmal deposits
No abstract available.
Authors
D. A. John, A. H. Hofstra, T. G. Theodore
Geologic setting and genesis of the Mule Canyon low-sulfidation epithermal gold-silver deposit, north-central Nevada
The Mule Canyon mine exploited shallow, low-sulfidation, epithermal Au-Ag deposits that lie near the west side of the Northern Nevada rift in northern Lander County, Nevada. Mule Canyon consists of six small deposits that contained premining reserves of about 8.2 Mt at an average grade of 3.81 g Au/tonne. It is an uncommon mafic end member of low-sulfidation Au-Ag deposits associated with tholeiit
Authors
D. A. John, A. H. Hofstra, R. J. Fleck, J.E. Brummer, E.C. Saderholm
The Tuscarora Au-Ag district: Eocene volcanic-hosted epithermal deposits in the Carlin gold region, Nevada
The Tuscarora mining district contains the oldest and the only productive Eocene epithermal deposits in Nevada. The district is a particularly clear example of association of low-sulfidation deposits with igneous activity and structure, and it is unusual in that it consists of two adjoining but physically and chemically distinct types of low-sulfidation deposits. Moreover, Tuscarora deposits are o
Authors
S.B. Castor, D.R. Boden, C.D. Henry, J. S. Cline, A. H. Hofstra, W. C. McIntosh, R. M. Tosdal, J.P. Wooden
Lithogeochemistry of Carlin-type gold mineralization in the Gold Bar district, Battle Mountain-Eureka trend, Nevada
The Gold Bar district contains five Carlin-type gold deposits and four resources for a combined gold endowment of 1.6 M oz [50 t]. The gold deposits are hosted in Devonian carbonate rocks below parautochthonous and allochthonous Paleozoic siliciclastic rocks emplaced during the Early Mississippian Antler orogeny. The district is in the Battle Mountain-Eureka trend, a long-lived structural feature
Authors
O. Yigit, A. H. Hofstra
Structural controls on Carlin-type gold mineralization in the gold bar district, Eureka County, Nevada
The Gold Bar district in the southern Roberts Mountains, 48 km northwest of Eureka, Nevada, contains one main deposit (Gold Bar), five satellite deposits, and other resources. Approximately 0.5 Moz of gold have been recovered from a resource of 1,639,000 oz of gold in Carlin-type gold deposits in lower plate, miogeoclinal carbonate rocks below the Roberts Mountains thrust. Host rocks are unit 2 of
Authors
O. Yigit, E.P. Nelson, M.W. Hitzman, A. H. Hofstra
Origin and significance of postore dissolution collapse breccias cemented with calcite and barite at the Meikle gold deposit, Northern Carlin trend, Nevada
The final event in a complicated hydrothermal history at the Meikle gold deposit was gold deficient but caused extensive postore dissolution of carbonate, collapse brecciation, and precipitation of calcite and barite crystals in the resulting cavities. Although previously interpreted to be part of the Carlin-type hydrothermal system, crosscutting relationships and U-Th-Pb geochronology constrain t
Authors
P. Emsbo, A. H. Hofstra
Alligator ridge district, East-Central Nevada: Carlin-type gold mineralization at shallow depths
Carlin-type deposits in the Alligator Ridge mining district are present sporadically for 40 km along the north-striking Mooney Basin fault system but are restricted to a 250-m interval of Devonian to Mississippian strata. Their age is bracketed between silicified ca. 45 Ma sedimentary rocks and unaltered 36.5 to 34 Ma volcanic rocks. The silicification is linked to the deposits by its continuity w
Authors
C.J. Nutt, A. H. Hofstra
Geology and geochemistry of Carlin-type gold deposits in China
The Carlin-type gold deposits in China lie mostly near the margins of the Proterozoic Yangtze and Aba cratons. Submicron-sized gold in micron-sized arsenian pyrite is disseminated in fractured Cambrian through Triassic carbonaceous shale and carbonate rocks, and is associated with anomalous Hg, Sb, As, U, and Tl. Alteration typically includes silicification, argilization, and sulfidation. Aqueous
Authors
H. Rui-Zhong, S. Wen-Chao, B. Xian-Wu, T. Guang-Zhi, A. H. Hofstra
U-Th-Pb dating of hydrothermal minerals from Carlin-type gold deposits, Nevada- Results and evaluation
No abstract available.
Authors
A. H. Hofstra, Wayne R. Premo, Poul Emsbo, J. S. Cline, John N. Aleinikoff
Ore-fluid evolution at the Getchell Carlin-type gold deposit, Nevada, USA
Minerals and fluid-inclusion populations were examined using petrography, microthermometry, quadrupole mass-spectrometer gas analyses and stable-isotope studies to characterize fluids responsible for gold mineralization at the Getchell Carlin-type gold deposit. The gold-ore assemblage at Getchell is superimposed on quartz-pyrite vein mineralization associated with a Late-Cretaceous granodiorite st
Authors
Jean S. Cline, Albert H. Hofstra
Syngenetic Au on the Carlin trend: Implications for Carlin-type deposits
A new type of gold occurrence recently discovered in the Carlin trend, north-central Nevada, is clearly distinct from classic Carlin-type gold ore. These occurrences are interpreted to be of sedimentary exhalative (sedex) origin because they are stratiform and predate compaction and lithification of their unaltered Devonian host rocks. They contain barite that exhibits δ34S and δ180 values identic
Authors
P. Emsbo, R.W. Hutchinson, A. H. Hofstra, J.A. Volk, K. H. Bettles, G.J. Baschuk, C.A. Johnson
Age constraints on Jerritt Canyon and other Carlin-type gold deposits in the western United States-relationship to mid-Tertiary extension and magmatism
Carlin-type gold deposits are difficult to date and a wide range of ages has been reported for individual deposits. Therefore, several methods were employed to constrain the age of the gold deposits in the Jerritt Canyon district. Dated igneous rocks with well-documented crosscutting relationships to ore provided the most reliable constraints. K/Ar and 40 Ar/ 39 Ar dates on igneous rocks are as fo
Authors
A. H. Hofstra, L. W. Snee, R. O. Rye, H. W. Folger, J.D. Phinisey, R.J. Loranger, A.R. Dahl, C.W. Naeser, H. J. Stein, M. Lewchuk