John N Aleinikoff
John Aleinikoff is a Scientist Emeritus with the Geology, Geophysics, and Geochemistry Science Center.
Science and Products
Filter Total Items: 109
Lead isotopic evidence for the origin of Paleo- and Mesoproterozoic rocks of the Colorado Province, U.S.A. Lead isotopic evidence for the origin of Paleo- and Mesoproterozoic rocks of the Colorado Province, U.S.A.
Lead isotopic ratios of K-feldspars and whole-rocks from 1.7- and 1.4-Ga plutonic rocks of the Colorado Province are relatively non-radiogenic for 207Pb 204Pb, plotting below the average crust model curve of Stacey and Kramers (1975), indicating that the terrane was derived primarily from juvenile, mantle material. Slightly more radiogenic ratios in the northern part of the terrane, near...
Authors
J. N. Aleinikoff, J. C. Reed, J. L. Wooden
The Mount Evans batholith in the Colorado Front Range: Revision of its age and reinterpretation of its structure The Mount Evans batholith in the Colorado Front Range: Revision of its age and reinterpretation of its structure
The Mount Evans batholith, in the central Front Range of Colorado, is composed of a main phase of massive to conspicuously foliated monzogranite and granodiorite and undeformed aplite and pegmatite. The Mount Evans batholith was previously considered to be part of the 1.7 Ga Routt Plutonic Suite. New U-Pb zircon ages on four samples (granodiorite, monzogranite, and granite), however...
Authors
J. N. Aleinikoff, J. C. Reed, E. Dewitt
Contrasting P‐T‐t paths: Thermochronologic evidence for a Late Paleozoic final assembly of the Avalon Composite Terrane in the New England Appalachians Contrasting P‐T‐t paths: Thermochronologic evidence for a Late Paleozoic final assembly of the Avalon Composite Terrane in the New England Appalachians
Strongly contrasting pressure‐temperature‐time paths for the Avalon composite terrane and the structurally overlying Putnam‐Nashoba zone in eastern New England obtained from thermochronologic and thermobarometric data are best explained by a late Paleozoic underthrusting of cover rocks by the Avalon composite terrane. We present new Ar and U‐Pb thermochronologic data that show that in...
Authors
R. P. Wintsch, J. F. Sutter, Michael J. Kunk, John N. Aleinikoff, Michael J. Dorais
Preliminary geologic map of the Mount Hayes quadrangle, eastern Alaska Range, Alaska Preliminary geologic map of the Mount Hayes quadrangle, eastern Alaska Range, Alaska
No abstract available.
Authors
W. J. Nokleberg, J. N. Aleinikoff, I. M. Lange, S. R. Silva, R. T. Miyaoka, C. E. Schwab, R. E. Zehner, G. C. Bond, D.H. Richter, T. E. Smith, J. H. Stout
Trondhjemitic, 1.35-1.31 Ga gneisses of the Mount Holly Complex of Vermont: evidence for an Elzevirian event in the Grenville Basement of the United States Appalachians Trondhjemitic, 1.35-1.31 Ga gneisses of the Mount Holly Complex of Vermont: evidence for an Elzevirian event in the Grenville Basement of the United States Appalachians
A newly recognized suite of trondhjemite–tonalite and dacitic gneiss forms a 10 km wide belt of rocks within the Mount Holly Complex in the central part of the Green Mountain massif of Vermont. Field relationships and chemistry indicate that these gneisses are calc-alkaline, volcanic, and hypabyssal plutonic rocks older than the Middle Proterozoic regional deformation that affected the...
Authors
N. M. Ratcliffe, J. N. Aleinikoff, W.C. Burton, P. Karabinos
UPb ages of zircon rims: A new analytical method using the air-abrasion technique UPb ages of zircon rims: A new analytical method using the air-abrasion technique
We present a new technique for directly dating, by conventional techniques, the rims of zircons. Several circumstances, such as a xenocrystic or inherited component in igneous zircon and metamorphic overgrowths on igneous cores, can result in grains with physically distinct age components. Pneumatic abrasion has been previously shown by Krogh to remove overgrowths and damaged areas of...
Authors
J. N. Aleinikoff, D.L. Winegarden, M. Walters
Science and Products
Filter Total Items: 109
Lead isotopic evidence for the origin of Paleo- and Mesoproterozoic rocks of the Colorado Province, U.S.A. Lead isotopic evidence for the origin of Paleo- and Mesoproterozoic rocks of the Colorado Province, U.S.A.
Lead isotopic ratios of K-feldspars and whole-rocks from 1.7- and 1.4-Ga plutonic rocks of the Colorado Province are relatively non-radiogenic for 207Pb 204Pb, plotting below the average crust model curve of Stacey and Kramers (1975), indicating that the terrane was derived primarily from juvenile, mantle material. Slightly more radiogenic ratios in the northern part of the terrane, near...
Authors
J. N. Aleinikoff, J. C. Reed, J. L. Wooden
The Mount Evans batholith in the Colorado Front Range: Revision of its age and reinterpretation of its structure The Mount Evans batholith in the Colorado Front Range: Revision of its age and reinterpretation of its structure
The Mount Evans batholith, in the central Front Range of Colorado, is composed of a main phase of massive to conspicuously foliated monzogranite and granodiorite and undeformed aplite and pegmatite. The Mount Evans batholith was previously considered to be part of the 1.7 Ga Routt Plutonic Suite. New U-Pb zircon ages on four samples (granodiorite, monzogranite, and granite), however...
Authors
J. N. Aleinikoff, J. C. Reed, E. Dewitt
Contrasting P‐T‐t paths: Thermochronologic evidence for a Late Paleozoic final assembly of the Avalon Composite Terrane in the New England Appalachians Contrasting P‐T‐t paths: Thermochronologic evidence for a Late Paleozoic final assembly of the Avalon Composite Terrane in the New England Appalachians
Strongly contrasting pressure‐temperature‐time paths for the Avalon composite terrane and the structurally overlying Putnam‐Nashoba zone in eastern New England obtained from thermochronologic and thermobarometric data are best explained by a late Paleozoic underthrusting of cover rocks by the Avalon composite terrane. We present new Ar and U‐Pb thermochronologic data that show that in...
Authors
R. P. Wintsch, J. F. Sutter, Michael J. Kunk, John N. Aleinikoff, Michael J. Dorais
Preliminary geologic map of the Mount Hayes quadrangle, eastern Alaska Range, Alaska Preliminary geologic map of the Mount Hayes quadrangle, eastern Alaska Range, Alaska
No abstract available.
Authors
W. J. Nokleberg, J. N. Aleinikoff, I. M. Lange, S. R. Silva, R. T. Miyaoka, C. E. Schwab, R. E. Zehner, G. C. Bond, D.H. Richter, T. E. Smith, J. H. Stout
Trondhjemitic, 1.35-1.31 Ga gneisses of the Mount Holly Complex of Vermont: evidence for an Elzevirian event in the Grenville Basement of the United States Appalachians Trondhjemitic, 1.35-1.31 Ga gneisses of the Mount Holly Complex of Vermont: evidence for an Elzevirian event in the Grenville Basement of the United States Appalachians
A newly recognized suite of trondhjemite–tonalite and dacitic gneiss forms a 10 km wide belt of rocks within the Mount Holly Complex in the central part of the Green Mountain massif of Vermont. Field relationships and chemistry indicate that these gneisses are calc-alkaline, volcanic, and hypabyssal plutonic rocks older than the Middle Proterozoic regional deformation that affected the...
Authors
N. M. Ratcliffe, J. N. Aleinikoff, W.C. Burton, P. Karabinos
UPb ages of zircon rims: A new analytical method using the air-abrasion technique UPb ages of zircon rims: A new analytical method using the air-abrasion technique
We present a new technique for directly dating, by conventional techniques, the rims of zircons. Several circumstances, such as a xenocrystic or inherited component in igneous zircon and metamorphic overgrowths on igneous cores, can result in grains with physically distinct age components. Pneumatic abrasion has been previously shown by Krogh to remove overgrowths and damaged areas of...
Authors
J. N. Aleinikoff, D.L. Winegarden, M. Walters