John N Aleinikoff
John Aleinikoff is a Scientist Emeritus with the Geology, Geophysics, and Geochemistry Science Center.
Science and Products
Filter Total Items: 109
Deciphering multiple Mesoproterozoic and Paleozoic events recorded in zircon and titanite from the Baltimore Gneiss, Maryland: SEM imaging, SHRIMP U-Pb geochronology, and EMP analysis
The Baltimore Gneiss, exposed in antiforms in the eastern Maryland Piedmont, consists of a suite of felsic and mafic gneisses of Mesoproterozoic age. Zircons from the felsic gneisses are complexly zoned, as shown in cathodoluminescence imaging; most zircon grains have multiple overgrowth zones, some of which are adjacent and parallel to elongate cores. Sensitive high-resolution ion microprobe (SHR
Authors
John N. Aleinikoff, J. Wright Horton,, Avery A. Drake, R. P. Wintsch, C.M. Fanning, K. Yi
U-Pb geochronology and evolution of Mesoproterozoic basement rocks, western Connecticut
Geologic mapping and U-Pb geochronology by ion microprobe on zircon, titanite, and monazite in the New Milford quadrangle, western Connecticut indicate Meso-proterozoic events at ca. 1.3, 1.05, and 0.99 Ga in the Laurentian basement rocks. Pink granite gneiss (1311 ± 7 Ma) intruded a paragneiss sequence during the early stages of the Elzevirian orogeny. During the Ottawan orogeny, syn-tectonic ana
Authors
Gregory J. Walsh, John N. Aleinikoff, C. Mark Fanning
Improved 206Pb/238U microprobe geochronology by the monitoring of a trace-element-related matrix effect; SHRIMP, ID-TIMS, ELA-ICP-MS and oxygen isotope documentation for a series of zircon standards
Precise isotope dilution-thermal ionisation mass spectrometry (ID-TIMS) documentation is given for two new Palaeozoic zircon standards (TEMORA 2 and R33). These data, in combination with results for previously documented standards (AS3, SL13, QGNG and TEMORA 1), provide the basis for a detailed investigation of inconsistencies in 206Pb/238U ages measured by microprobe. Although these ages are norm
Authors
L.P. Black, S.L. Kamo, C. M. Allen, D.W. Davis, J. N. Aleinikoff, J.W. Valley, R. Mundil, I.H. Campbell, R.J. Korsch, I.S. Williams, C. Foudoulis
Neoproterozoic A-type granitoids of the central and southern Appalachians: Intraplate magmatism associated with episodic rifting of the Rodinian supercontinent
Emplacement of compositionally distinctive granitic plutons accompanied two pulses (765-680 and 620-550Ma) of crustal extension that affected the Rodinian craton at the present location of the central Appalachians during the Neoproterozoic. The dominantly metaluminous plutons display mineralogical and geochemical characteristics of A-type granites including high FeO t/MgO ratios, high abundances o
Authors
R.P. Tollo, J. N. Aleinikoff, M. J. Bartholomew, D.W. Rankin
SHRIMP U-Pb geochronology of Neoproterozoic Windermere Supergroup, central Idaho: Implications for rifting of western Laurentia and synchroneity of Sturtian glacial deposits
In central Idaho roof pendants, a northwest-trending belt of metamorphosed strata, correlative with the Windermere Supergroup, links northern and southern segments of the western Laurentia Neoproterozoic rift belt. Nine newly named formations within the Gospel Peaks sequence-A through Gospel Peaks sequence-D record Cryogenian preglacial, rift-glacial, and postglacial events as well as Neoproterozo
Authors
K. Lund, J. N. Aleinikoff, K. V. Evans, C.M. Fanning
Stratigraphy, geochronology, and accretionary terrane settings of two Bronson Hill arc sequences, northern New England
The Ammonoosuc Volcanics, Partridge Formation, and the Oliverian and Highlandcroft Plutonic Suites of the Bronson Hill anticlinorium (BHA) in axial New England are widely accepted as a single Middle to Late Ordovician magmatic arc that was active during closure of Iapetus. Mapping and U–Pb dating indicate, however, that the BHA contains two volcano-sedimentary-intrusive sequences of probable oppos
Authors
R. H. Moench, J. N. Aleinikoff
P-T-t paths and differential Alleghanian loading and uplift of the Bronson Hill terrane south central New England
Late Paleozoic U-Pb ages of sphene and 40Ar/39Ar cooling ages of amphibole and muscovite from rocks of the Bronson Hill terrane in Connecticut and central Massachusetts reflect a late Paleozoic (Alleghanian) overprint on Acadian metamorphic rocks. Prograde Alleghanian sphenes crystallized during the Late Pennsylvanian, and eliminate the possibility that amphibole ages reflect delayed Permian cooli
Authors
R. P. Wintsch, Michael J. Kunk, J.L. Boyd, J. N. Aleinikoff
TEMORA 1: A new zircon standard for Phanerozoic U-Pb geochronology
The role of the standard is critical to the derivation of reliable U-Pb zircon ages by micro-beam analysis. For maximum reliability, it is critically important that the utilised standard be homogeneous at all scales of analysis. It is equally important that the standard has been precisely and accurately dated by an independent technique. This study reports the emergence of a new zircon standard th
Authors
L.P. Black, S.L. Kamo, C. M. Allen, J. N. Aleinikoff, D.W. Davis, R.J. Korsch, C. Foudoulis
SHRIMP and Conventional UPb ages of Ordovician granites and tonalites in the central Appalachian Piedmont: Implications for Paleozoic tectonic events
Discordant Cambrian U-Pb ages of questionable reliability for metamor-phosed plutonic rocks in the central Appalachian Piedmont of northern Virginia, Maryland, and the District of Columbia have led to different regional geologic interpretations and controversies. In this study, we use the sensitive high resolution ion microprobe (SHRIMP) for dating 25-m diameter areas on individual zircons from Pi
Authors
John N. Aleinikoff, J. Wright Horton,, Avery Ala Drake
U-Pb zircon geochronology of the Paleoproterozoic Tagragra de Tata inlier and its Neoproterozoic cover, western Anti-Atlas, Morocco
New U-Pb zircon data obtained by sensitive high resolution ion microprobe (SHRIMP) from the Tagragra de Tata inlier in the western Anti-Atlas, Morocco establish Paleoproterozoic ages for the basement schists, granites, and metadolerites, and a Neoproterozoic age for an ignimbrite of the Ouarzazate Series in the cover sequence. The age of interbedded felsic metatuff in the metasedimentary and metav
Authors
G. J. Walsh, J. N. Aleinikoff, F. Benziane, A. Yazidi, T. R. Armstrong
U-Pb geochronology of zircon and polygenetic titanite from the Glastonbury Complex, Connecticut, USA: An integrated SEM, EMPA, TIMS, and SHRIMP study
U-Pb ages for zircon and titanite from a granodioritic gneiss in the Glastonbury Complex, Connecticut, have been determined using both isotope dilution thermal ionization mass spectrometry (TIMS) and the sensitive high resolution ion microprobe (SHRIMP). Zircons occur in three morphologic populations: (1) equant to stubby, multifaceted, colorless, (2) prismatic, dark brown, with numerous cracks, a
Authors
J. N. Aleinikoff, R. P. Wintsch, C.M. Fanning, M. J. Dorais
Stratigraphy, geochronology, and accretionary terrane settings of two Bronson Hill arc sequences, northern New England
The Ammonoosuc Volcanics, Partridge Formation, and the Oliverian and Highlandcroft Plutonic Suites of the Bronson Hill anticlinorium (BHA) in axial New England are widely accepted as a single Middle to Late Ordovician magmatic arc that was active during closure of Iapetus. Mapping and U–Pb dating indicate, however, that the BHA contains two volcano-sedimentary-intrusive sequences of probable oppos
Authors
R. H. Moench, J. N. Aleinikoff
Science and Products
Filter Total Items: 109
Deciphering multiple Mesoproterozoic and Paleozoic events recorded in zircon and titanite from the Baltimore Gneiss, Maryland: SEM imaging, SHRIMP U-Pb geochronology, and EMP analysis
The Baltimore Gneiss, exposed in antiforms in the eastern Maryland Piedmont, consists of a suite of felsic and mafic gneisses of Mesoproterozoic age. Zircons from the felsic gneisses are complexly zoned, as shown in cathodoluminescence imaging; most zircon grains have multiple overgrowth zones, some of which are adjacent and parallel to elongate cores. Sensitive high-resolution ion microprobe (SHR
Authors
John N. Aleinikoff, J. Wright Horton,, Avery A. Drake, R. P. Wintsch, C.M. Fanning, K. Yi
U-Pb geochronology and evolution of Mesoproterozoic basement rocks, western Connecticut
Geologic mapping and U-Pb geochronology by ion microprobe on zircon, titanite, and monazite in the New Milford quadrangle, western Connecticut indicate Meso-proterozoic events at ca. 1.3, 1.05, and 0.99 Ga in the Laurentian basement rocks. Pink granite gneiss (1311 ± 7 Ma) intruded a paragneiss sequence during the early stages of the Elzevirian orogeny. During the Ottawan orogeny, syn-tectonic ana
Authors
Gregory J. Walsh, John N. Aleinikoff, C. Mark Fanning
Improved 206Pb/238U microprobe geochronology by the monitoring of a trace-element-related matrix effect; SHRIMP, ID-TIMS, ELA-ICP-MS and oxygen isotope documentation for a series of zircon standards
Precise isotope dilution-thermal ionisation mass spectrometry (ID-TIMS) documentation is given for two new Palaeozoic zircon standards (TEMORA 2 and R33). These data, in combination with results for previously documented standards (AS3, SL13, QGNG and TEMORA 1), provide the basis for a detailed investigation of inconsistencies in 206Pb/238U ages measured by microprobe. Although these ages are norm
Authors
L.P. Black, S.L. Kamo, C. M. Allen, D.W. Davis, J. N. Aleinikoff, J.W. Valley, R. Mundil, I.H. Campbell, R.J. Korsch, I.S. Williams, C. Foudoulis
Neoproterozoic A-type granitoids of the central and southern Appalachians: Intraplate magmatism associated with episodic rifting of the Rodinian supercontinent
Emplacement of compositionally distinctive granitic plutons accompanied two pulses (765-680 and 620-550Ma) of crustal extension that affected the Rodinian craton at the present location of the central Appalachians during the Neoproterozoic. The dominantly metaluminous plutons display mineralogical and geochemical characteristics of A-type granites including high FeO t/MgO ratios, high abundances o
Authors
R.P. Tollo, J. N. Aleinikoff, M. J. Bartholomew, D.W. Rankin
SHRIMP U-Pb geochronology of Neoproterozoic Windermere Supergroup, central Idaho: Implications for rifting of western Laurentia and synchroneity of Sturtian glacial deposits
In central Idaho roof pendants, a northwest-trending belt of metamorphosed strata, correlative with the Windermere Supergroup, links northern and southern segments of the western Laurentia Neoproterozoic rift belt. Nine newly named formations within the Gospel Peaks sequence-A through Gospel Peaks sequence-D record Cryogenian preglacial, rift-glacial, and postglacial events as well as Neoproterozo
Authors
K. Lund, J. N. Aleinikoff, K. V. Evans, C.M. Fanning
Stratigraphy, geochronology, and accretionary terrane settings of two Bronson Hill arc sequences, northern New England
The Ammonoosuc Volcanics, Partridge Formation, and the Oliverian and Highlandcroft Plutonic Suites of the Bronson Hill anticlinorium (BHA) in axial New England are widely accepted as a single Middle to Late Ordovician magmatic arc that was active during closure of Iapetus. Mapping and U–Pb dating indicate, however, that the BHA contains two volcano-sedimentary-intrusive sequences of probable oppos
Authors
R. H. Moench, J. N. Aleinikoff
P-T-t paths and differential Alleghanian loading and uplift of the Bronson Hill terrane south central New England
Late Paleozoic U-Pb ages of sphene and 40Ar/39Ar cooling ages of amphibole and muscovite from rocks of the Bronson Hill terrane in Connecticut and central Massachusetts reflect a late Paleozoic (Alleghanian) overprint on Acadian metamorphic rocks. Prograde Alleghanian sphenes crystallized during the Late Pennsylvanian, and eliminate the possibility that amphibole ages reflect delayed Permian cooli
Authors
R. P. Wintsch, Michael J. Kunk, J.L. Boyd, J. N. Aleinikoff
TEMORA 1: A new zircon standard for Phanerozoic U-Pb geochronology
The role of the standard is critical to the derivation of reliable U-Pb zircon ages by micro-beam analysis. For maximum reliability, it is critically important that the utilised standard be homogeneous at all scales of analysis. It is equally important that the standard has been precisely and accurately dated by an independent technique. This study reports the emergence of a new zircon standard th
Authors
L.P. Black, S.L. Kamo, C. M. Allen, J. N. Aleinikoff, D.W. Davis, R.J. Korsch, C. Foudoulis
SHRIMP and Conventional UPb ages of Ordovician granites and tonalites in the central Appalachian Piedmont: Implications for Paleozoic tectonic events
Discordant Cambrian U-Pb ages of questionable reliability for metamor-phosed plutonic rocks in the central Appalachian Piedmont of northern Virginia, Maryland, and the District of Columbia have led to different regional geologic interpretations and controversies. In this study, we use the sensitive high resolution ion microprobe (SHRIMP) for dating 25-m diameter areas on individual zircons from Pi
Authors
John N. Aleinikoff, J. Wright Horton,, Avery Ala Drake
U-Pb zircon geochronology of the Paleoproterozoic Tagragra de Tata inlier and its Neoproterozoic cover, western Anti-Atlas, Morocco
New U-Pb zircon data obtained by sensitive high resolution ion microprobe (SHRIMP) from the Tagragra de Tata inlier in the western Anti-Atlas, Morocco establish Paleoproterozoic ages for the basement schists, granites, and metadolerites, and a Neoproterozoic age for an ignimbrite of the Ouarzazate Series in the cover sequence. The age of interbedded felsic metatuff in the metasedimentary and metav
Authors
G. J. Walsh, J. N. Aleinikoff, F. Benziane, A. Yazidi, T. R. Armstrong
U-Pb geochronology of zircon and polygenetic titanite from the Glastonbury Complex, Connecticut, USA: An integrated SEM, EMPA, TIMS, and SHRIMP study
U-Pb ages for zircon and titanite from a granodioritic gneiss in the Glastonbury Complex, Connecticut, have been determined using both isotope dilution thermal ionization mass spectrometry (TIMS) and the sensitive high resolution ion microprobe (SHRIMP). Zircons occur in three morphologic populations: (1) equant to stubby, multifaceted, colorless, (2) prismatic, dark brown, with numerous cracks, a
Authors
J. N. Aleinikoff, R. P. Wintsch, C.M. Fanning, M. J. Dorais
Stratigraphy, geochronology, and accretionary terrane settings of two Bronson Hill arc sequences, northern New England
The Ammonoosuc Volcanics, Partridge Formation, and the Oliverian and Highlandcroft Plutonic Suites of the Bronson Hill anticlinorium (BHA) in axial New England are widely accepted as a single Middle to Late Ordovician magmatic arc that was active during closure of Iapetus. Mapping and U–Pb dating indicate, however, that the BHA contains two volcano-sedimentary-intrusive sequences of probable oppos
Authors
R. H. Moench, J. N. Aleinikoff