John N Aleinikoff
John Aleinikoff is a Scientist Emeritus with the Geology, Geophysics, and Geochemistry Science Center.
Science and Products
Filter Total Items: 109
Ordovician volcanic-arc terrane in the Central Appalachian Piedmont of Maryland and Virginia: SHRIMP U-Pb geochronology, field relations, and tectonic significance
U-Pb zircon geochronology and field relations provide insights into metavolcanic and associated rocks in the Central Appalachian Piedmont of Maryland and northern Virginia. Ordovician ages were determined for volcanic-arc rocks of the James Run Formation (Churchville Gneiss Member, 458 ± 4 Ma; Carroll Gneiss Member, 462 ± 4 Ma), Relay Felsite (458 ± 4 Ma), Chopawamsic Formation (453 ± 4 Ma), and a
Authors
J. Wright Horton,, John N. Aleinikoff, Avery A. Drake, C. Mark Fanning
SHRIMP U-Pb dating of recurrent Cryogenian and Late Cambrian-Early Ordovician alkalic magmatism in central Idaho: Implications for Rodinian rift tectonics
Composite alkalic plutonic suites and tuffaceous diamictite, although discontinuously exposed across central Idaho in roof pendants and inliers within the Idaho batholith and Challis volcanic-plutonic complex, define the >200-km-long northwest-aligned Big Creek-Beaverhead belt. Sensitive highresolution ion microprobe (SHRIMP) U-Pb zircon dates on these igneous rocks provide direct evidence for the
Authors
K. Lund, J. N. Aleinikoff, K. V. Evans, E. A. duBray, E.H. deWitt, D.M. Unruh
Thermomagmatic evolution of Mesoproterozoic crust in the Blue Ridge of SW Virginia and NW North Carolina: Evidence from U-Pb geochronology and zircon geothermometry
New geologic mapping, petrology, and U-Pb geochronology indicate that Mesoproterozoic crust near Mount Rogers consists of felsic to mafic meta-igneous rocks emplaced over 260 m.y. The oldest rocks are compositionally diverse and migmatitic, whereas younger granitoids are porphyritic to porphyroclastic. Cathodoluminescence imaging indicates that zircon from four representative units preserves textu
Authors
Richard P. Tollo, John N. Aleinikoff, Joseph L. Wooden, Frank K. Mazdab, Scott Southworth, Mark C. Fanning
Tectonic, magmatic, and metamorphic history of the New Jersey Highlands: New insights from SHRIMP U-Pb geochronology
No abstract available.
Authors
Richard A. Volkert, John N. Aleinikoff, C. Mark Fanning
Geologic Map of the Shenandoah National Park Region, Virginia
The geology of the Shenandoah National Park region of Virginia was studied from 1995 to 2008. The focus of the study was the park and surrounding areas to provide the National Park Service with modern geologic data for resource management. Additional geologic data of the adjacent areas are included to provide regional context. The geologic map can be used to support activities such as ecosystem de
Authors
Scott Southworth, John N. Aleinikoff, Christopher M. Bailey, William C. Burton, E.A. Crider, Paul C. Hackley, Joseph P. Smoot, Richard P. Tollo
Mesozoic magmatism and base-metal mineralization in the Fortymile mining district, eastern Alaska — Initial results of petrographic, geochemical, and isotopic studies in the Mount Veta area
We present here the initial results of a petrographic, geochemical, and isotopic study of Mesozoic intrusive rocks and spatially associated Zn-Pb-Ag-Cu-Au prospects in the Fortymile mining district in the southern Eagle quadrangle, Alaska. Analyzed samples include mineralized and unmineralized drill core from 2006 and 2007 exploration by Full Metal Minerals, USA, Inc., at the Little Whiteman (LWM)
Authors
Cynthia Dusel-Bacon, John F. Slack, John N. Aleinikoff, James K. Mortensen
Geologic and Geochronologic Studies of the Early Proterozoic Kanektok Metamorphic Complex of Southwestern Alaska
The Kanektok complex of southwestern Alaska appears to be a rootless terrane of early Proterozoic sedimentary, volcanic, and intrusive rocks which were metamorphosed to amphibolite and granulite facies and later underwent a pervasive late Mesozoic thermal event accompanied by granitic plutonism and greenschist facies metamorphism of overlying sediments. The terrane is structurally complex and exhi
Authors
Donald L. Turner, Robert B. Forbes, John N. Aleinikoff, Ian McDougall, Carl E. Hedge, Frederic H. Wilson, Paul W. Layer, Chad P. Hults
Evolution of crystalline target rocks and impactites in the chesapeake bay impact structure, ICDP-USGS eyreville B core
The 1766-m-deep Eyreville B core from the late Eocene Chesapeake Bay impact structure includes, in ascending order, a lower basement-derived section of schist and pegmatitic granite with impact breccia dikes, polymict impact breccias, and cataclas tic gneiss blocks overlain by suevites and clast-rich impact melt rocks, sand with an amphibolite block and lithic boulders, and a 275-m-thick granite s
Authors
J. Wright Horton, Michael J. Kunk, Harvey E. Belkin, John N. Aleinikoff, John C. Jackson, I.-Ming Chou
Mineral chemistry and shrimp U-Pb Geochronology of mesoproterozoic polycrase-titanite veins in the sullivan Pb-Zn-Ag Deposit, British Columbia
Small polycrase-titanite veins 0.1-2 mm thick cut the tourmalinite feeder zone in the deep footwall of the Sullivan Pb-Zn-Ag deposit, southeastern British Columbia. Unaltered, euhedral crystals of polycrase and titanite 50-100 ??m in diameter are variably replaced by a finer-grained alteration-induced assemblage composed of anhedral polycrase and titanite with local calcite, albite, epidote, allan
Authors
J. F. Slack, J. N. Aleinikoff, H. E. Belkin, C.M. Fanning, P.W. Ransom
Combined EPMA and SHRIMP analyses of xenotime to interpret the geochronological record
[No abstract available]
Authors
H.A. Lowers, J. N. Aleinikoff, F.K. Mazdab
On the origin and age of the Great Sand Dunes, Colorado
Over the past 100??yr, several hypotheses have been proposed for the origin and age of the Great Sand Dunes. These hypotheses differ widely in the descriptions of dune morphometry, the immediate source of eolian sand, and when sand transport occurred. The primary purpose of this paper is to evaluate these hypotheses and, where warranted, to present new ideas about the origin and age of the Great S
Authors
R.F. Madole, J.H. Romig, J. N. Aleinikoff, D.P. VanSistine, E.Y. Yacob
Isotopic evidence for the diversity of late Quaternary loess in Nebraska: Glaciogenic and nonglaciogenic sources
Pb isotope compositions of detrital K-feldspars and U-Pb ages of detrital zircons are used as indicators for determining the sources of Peoria Loess deposited during the last glacial period (late Wisconsin, ca. 25–14 ka) in Nebraska and western Iowa. Our new data indicate that only loess adjacent to the Platte River has Pb isotopic characteristics suggesting derivation from this river. Most Peoria
Authors
John N. Aleinikoff, Daniel R. Muhs, E. Arthur Bettis, William C. Johnson, C. Mark Fanning, Rachel Benton
Science and Products
Filter Total Items: 109
Ordovician volcanic-arc terrane in the Central Appalachian Piedmont of Maryland and Virginia: SHRIMP U-Pb geochronology, field relations, and tectonic significance
U-Pb zircon geochronology and field relations provide insights into metavolcanic and associated rocks in the Central Appalachian Piedmont of Maryland and northern Virginia. Ordovician ages were determined for volcanic-arc rocks of the James Run Formation (Churchville Gneiss Member, 458 ± 4 Ma; Carroll Gneiss Member, 462 ± 4 Ma), Relay Felsite (458 ± 4 Ma), Chopawamsic Formation (453 ± 4 Ma), and a
Authors
J. Wright Horton,, John N. Aleinikoff, Avery A. Drake, C. Mark Fanning
SHRIMP U-Pb dating of recurrent Cryogenian and Late Cambrian-Early Ordovician alkalic magmatism in central Idaho: Implications for Rodinian rift tectonics
Composite alkalic plutonic suites and tuffaceous diamictite, although discontinuously exposed across central Idaho in roof pendants and inliers within the Idaho batholith and Challis volcanic-plutonic complex, define the >200-km-long northwest-aligned Big Creek-Beaverhead belt. Sensitive highresolution ion microprobe (SHRIMP) U-Pb zircon dates on these igneous rocks provide direct evidence for the
Authors
K. Lund, J. N. Aleinikoff, K. V. Evans, E. A. duBray, E.H. deWitt, D.M. Unruh
Thermomagmatic evolution of Mesoproterozoic crust in the Blue Ridge of SW Virginia and NW North Carolina: Evidence from U-Pb geochronology and zircon geothermometry
New geologic mapping, petrology, and U-Pb geochronology indicate that Mesoproterozoic crust near Mount Rogers consists of felsic to mafic meta-igneous rocks emplaced over 260 m.y. The oldest rocks are compositionally diverse and migmatitic, whereas younger granitoids are porphyritic to porphyroclastic. Cathodoluminescence imaging indicates that zircon from four representative units preserves textu
Authors
Richard P. Tollo, John N. Aleinikoff, Joseph L. Wooden, Frank K. Mazdab, Scott Southworth, Mark C. Fanning
Tectonic, magmatic, and metamorphic history of the New Jersey Highlands: New insights from SHRIMP U-Pb geochronology
No abstract available.
Authors
Richard A. Volkert, John N. Aleinikoff, C. Mark Fanning
Geologic Map of the Shenandoah National Park Region, Virginia
The geology of the Shenandoah National Park region of Virginia was studied from 1995 to 2008. The focus of the study was the park and surrounding areas to provide the National Park Service with modern geologic data for resource management. Additional geologic data of the adjacent areas are included to provide regional context. The geologic map can be used to support activities such as ecosystem de
Authors
Scott Southworth, John N. Aleinikoff, Christopher M. Bailey, William C. Burton, E.A. Crider, Paul C. Hackley, Joseph P. Smoot, Richard P. Tollo
Mesozoic magmatism and base-metal mineralization in the Fortymile mining district, eastern Alaska — Initial results of petrographic, geochemical, and isotopic studies in the Mount Veta area
We present here the initial results of a petrographic, geochemical, and isotopic study of Mesozoic intrusive rocks and spatially associated Zn-Pb-Ag-Cu-Au prospects in the Fortymile mining district in the southern Eagle quadrangle, Alaska. Analyzed samples include mineralized and unmineralized drill core from 2006 and 2007 exploration by Full Metal Minerals, USA, Inc., at the Little Whiteman (LWM)
Authors
Cynthia Dusel-Bacon, John F. Slack, John N. Aleinikoff, James K. Mortensen
Geologic and Geochronologic Studies of the Early Proterozoic Kanektok Metamorphic Complex of Southwestern Alaska
The Kanektok complex of southwestern Alaska appears to be a rootless terrane of early Proterozoic sedimentary, volcanic, and intrusive rocks which were metamorphosed to amphibolite and granulite facies and later underwent a pervasive late Mesozoic thermal event accompanied by granitic plutonism and greenschist facies metamorphism of overlying sediments. The terrane is structurally complex and exhi
Authors
Donald L. Turner, Robert B. Forbes, John N. Aleinikoff, Ian McDougall, Carl E. Hedge, Frederic H. Wilson, Paul W. Layer, Chad P. Hults
Evolution of crystalline target rocks and impactites in the chesapeake bay impact structure, ICDP-USGS eyreville B core
The 1766-m-deep Eyreville B core from the late Eocene Chesapeake Bay impact structure includes, in ascending order, a lower basement-derived section of schist and pegmatitic granite with impact breccia dikes, polymict impact breccias, and cataclas tic gneiss blocks overlain by suevites and clast-rich impact melt rocks, sand with an amphibolite block and lithic boulders, and a 275-m-thick granite s
Authors
J. Wright Horton, Michael J. Kunk, Harvey E. Belkin, John N. Aleinikoff, John C. Jackson, I.-Ming Chou
Mineral chemistry and shrimp U-Pb Geochronology of mesoproterozoic polycrase-titanite veins in the sullivan Pb-Zn-Ag Deposit, British Columbia
Small polycrase-titanite veins 0.1-2 mm thick cut the tourmalinite feeder zone in the deep footwall of the Sullivan Pb-Zn-Ag deposit, southeastern British Columbia. Unaltered, euhedral crystals of polycrase and titanite 50-100 ??m in diameter are variably replaced by a finer-grained alteration-induced assemblage composed of anhedral polycrase and titanite with local calcite, albite, epidote, allan
Authors
J. F. Slack, J. N. Aleinikoff, H. E. Belkin, C.M. Fanning, P.W. Ransom
Combined EPMA and SHRIMP analyses of xenotime to interpret the geochronological record
[No abstract available]
Authors
H.A. Lowers, J. N. Aleinikoff, F.K. Mazdab
On the origin and age of the Great Sand Dunes, Colorado
Over the past 100??yr, several hypotheses have been proposed for the origin and age of the Great Sand Dunes. These hypotheses differ widely in the descriptions of dune morphometry, the immediate source of eolian sand, and when sand transport occurred. The primary purpose of this paper is to evaluate these hypotheses and, where warranted, to present new ideas about the origin and age of the Great S
Authors
R.F. Madole, J.H. Romig, J. N. Aleinikoff, D.P. VanSistine, E.Y. Yacob
Isotopic evidence for the diversity of late Quaternary loess in Nebraska: Glaciogenic and nonglaciogenic sources
Pb isotope compositions of detrital K-feldspars and U-Pb ages of detrital zircons are used as indicators for determining the sources of Peoria Loess deposited during the last glacial period (late Wisconsin, ca. 25–14 ka) in Nebraska and western Iowa. Our new data indicate that only loess adjacent to the Platte River has Pb isotopic characteristics suggesting derivation from this river. Most Peoria
Authors
John N. Aleinikoff, Daniel R. Muhs, E. Arthur Bettis, William C. Johnson, C. Mark Fanning, Rachel Benton