John N Aleinikoff
John Aleinikoff is a Scientist Emeritus with the Geology, Geophysics, and Geochemistry Science Center.
Science and Products
Filter Total Items: 109
Petrology and U-PB geochronology of the Robertson River Igneous Suite, Blue Ridge province, Virginia - Evidence for multistage magmatism associated witn an early episode of Laurentian rifting
The Late Neoproterozoic (735-702 Ma) Robertson River Igneous Suite includes at least eight plutons ranging in composition from syenogranite to alkali feldspar granite to alkali feldspar syenite. These plutons intruded Mesoproterozoic (1.2-1.0 Ga) gneissic basement of the Blue Ridge anticlinorium in northern and central Virginia during an early episode of Laurentian rifting. Robertson River plutons
Authors
Richard P. Tollo, John N. Aleinikoff
Metamorphic and structural history of continental crust at a Mesozoic collisional margin, the Ruby terrane, central Alaska
The Ruby terrane is an elongate fragment of continental crustal rocks that is structurally overlain by thrust slices of oceanic crust. Our results from the Kokrines Hills, in the south‐central part of the Ruby terrane, demonstrate that the low‐angle schistose fabric formed under high‐P/low‐T conditions, at peak conditions of 10.8‐13.2 kbar and 425‐550° C, consistent with the rare occurrence of gla
Authors
S. M. Roeske, Cynthia Dusel-Bacon, John N. Aleinikoff, L. W. Snee, Marvin A. Lanphere
U-Pb ages of metarhyolites of the Catoctin and Mount Rogers formations, central and southern Appalachians: Evidence for two pulses of Iapetan rifting
No abstract available.
Authors
John N. Aleinikoff, Robert E. Zartman, Marianne Walter, Douglas W. Rankin, Peter T. Lyttle, William C. Burton
Isotopic tracers of gold deposition in Paleozoic limestones, southern Nevada
Strontium isotopic analyses of barren and mineralized Paleozoic carbonate rocks show that hydrothermal fluids added radiogenic strontium (87Sr) to the mineralized zones. At Bare Mountain, samples collected from mineralized areas have ??87Srt values (per mil deviation from primary marine values) ranging from +3.0 to +23.0 (mean of this log-normal distribution is +7.0), whereas unmineralized carbona
Authors
Z. E. Peterman, B.L. Widmann, B.D. Marshall, J. N. Aleinikoff, K. Futa, S. A. Mahan
Devonian volcanogenic massive sulfide deposits and occurrences, southern Yukon-Tanana Terrace, eastern Alaska Range, Alaska
A belt of volcanogenic massive sulfide deposits extends for over 150 km along the southern margin of the Yukon-Tanana terrane of the eastern Alaska Range. Located north of the Denali fault, the Yukon-Tanana terrane forms a major basement unit in east-central Alaska. The volcanogenic massive sulfide deposits are primarily in the Jarvis Creek Glacier subterrane, one of the highest structural-stratig
Authors
I. M. Lange, W. J. Nokleberg, S.R. Newkirk, J. N. Aleinikoff, S. E. Church, H.R. Krouse
Do ages of authigenic K-feldspar date the formation of Mississippi valley-type Pb-Zn deposits, central and southeastern United States?: Pb isotopic evidence
Pb concentrations and isotopic compositions have been determined for authigenic over-growths and detrital cores of K-feldspar from Cambrian sedimentary rocks in Texas, Tennessee, and Pennsylvania (referred to as group 1) and southeastern Missouri (referred to as group 2). Overgrowths and cores were separated by abrasion and analyzed separately. In three group 1 samples, cores have Pb isotopic rati
Authors
J. N. Aleinikoff, M. Walters, Michael J. Kunk, P.P. Hearn
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 the Arch
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 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, indicate that
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
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 the southern
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
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
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 Mount Holly
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
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 zircon, leav
Authors
J. N. Aleinikoff, D.L. Winegarden, M. Walters
Science and Products
Filter Total Items: 109
Petrology and U-PB geochronology of the Robertson River Igneous Suite, Blue Ridge province, Virginia - Evidence for multistage magmatism associated witn an early episode of Laurentian rifting
The Late Neoproterozoic (735-702 Ma) Robertson River Igneous Suite includes at least eight plutons ranging in composition from syenogranite to alkali feldspar granite to alkali feldspar syenite. These plutons intruded Mesoproterozoic (1.2-1.0 Ga) gneissic basement of the Blue Ridge anticlinorium in northern and central Virginia during an early episode of Laurentian rifting. Robertson River plutons
Authors
Richard P. Tollo, John N. Aleinikoff
Metamorphic and structural history of continental crust at a Mesozoic collisional margin, the Ruby terrane, central Alaska
The Ruby terrane is an elongate fragment of continental crustal rocks that is structurally overlain by thrust slices of oceanic crust. Our results from the Kokrines Hills, in the south‐central part of the Ruby terrane, demonstrate that the low‐angle schistose fabric formed under high‐P/low‐T conditions, at peak conditions of 10.8‐13.2 kbar and 425‐550° C, consistent with the rare occurrence of gla
Authors
S. M. Roeske, Cynthia Dusel-Bacon, John N. Aleinikoff, L. W. Snee, Marvin A. Lanphere
U-Pb ages of metarhyolites of the Catoctin and Mount Rogers formations, central and southern Appalachians: Evidence for two pulses of Iapetan rifting
No abstract available.
Authors
John N. Aleinikoff, Robert E. Zartman, Marianne Walter, Douglas W. Rankin, Peter T. Lyttle, William C. Burton
Isotopic tracers of gold deposition in Paleozoic limestones, southern Nevada
Strontium isotopic analyses of barren and mineralized Paleozoic carbonate rocks show that hydrothermal fluids added radiogenic strontium (87Sr) to the mineralized zones. At Bare Mountain, samples collected from mineralized areas have ??87Srt values (per mil deviation from primary marine values) ranging from +3.0 to +23.0 (mean of this log-normal distribution is +7.0), whereas unmineralized carbona
Authors
Z. E. Peterman, B.L. Widmann, B.D. Marshall, J. N. Aleinikoff, K. Futa, S. A. Mahan
Devonian volcanogenic massive sulfide deposits and occurrences, southern Yukon-Tanana Terrace, eastern Alaska Range, Alaska
A belt of volcanogenic massive sulfide deposits extends for over 150 km along the southern margin of the Yukon-Tanana terrane of the eastern Alaska Range. Located north of the Denali fault, the Yukon-Tanana terrane forms a major basement unit in east-central Alaska. The volcanogenic massive sulfide deposits are primarily in the Jarvis Creek Glacier subterrane, one of the highest structural-stratig
Authors
I. M. Lange, W. J. Nokleberg, S.R. Newkirk, J. N. Aleinikoff, S. E. Church, H.R. Krouse
Do ages of authigenic K-feldspar date the formation of Mississippi valley-type Pb-Zn deposits, central and southeastern United States?: Pb isotopic evidence
Pb concentrations and isotopic compositions have been determined for authigenic over-growths and detrital cores of K-feldspar from Cambrian sedimentary rocks in Texas, Tennessee, and Pennsylvania (referred to as group 1) and southeastern Missouri (referred to as group 2). Overgrowths and cores were separated by abrasion and analyzed separately. In three group 1 samples, cores have Pb isotopic rati
Authors
J. N. Aleinikoff, M. Walters, Michael J. Kunk, P.P. Hearn
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 the Arch
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 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, indicate that
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
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 the southern
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
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
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 Mount Holly
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
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 zircon, leav
Authors
J. N. Aleinikoff, D.L. Winegarden, M. Walters