John N Aleinikoff
John Aleinikoff is a Scientist Emeritus with the Geology, Geophysics, and Geochemistry Science Center.
Science and Products
Filter Total Items: 109
SHRIMP U-Pb and 40Ar/39Ar age constraints for relating plutonism and mineralization in the Boulder batholith region, Montana SHRIMP U-Pb and 40Ar/39Ar age constraints for relating plutonism and mineralization in the Boulder batholith region, Montana
The composite Boulder batholith, Montana, hosts a variety of mineral deposit types, including important silver-rich polymetallic quartz vein districts in the northern part of the batholith and the giant Butte porphyry copper-molybdenum pre-Main Stage system and crosscutting copper-rich Main Stage vein system in the southern part of the batholith. Previous dating studies have identified...
Authors
Karen Lund, John N. Aleinikoff, Michael J. Kunk, Daniel M. Unruh, G. D. Zeihen, W. C. Hodges, Edward A. du Bray, J. Michael O’Neill
U-Th-Pb dating of hydrothermal minerals from Carlin-type gold deposits, Nevada- Results and evaluation 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
SHRIMP U-Pb geochronology of volcanic rocks, Belt Supergroup, western Montana: Evidence for rapid deposition of sedimentary strata SHRIMP U-Pb geochronology of volcanic rocks, Belt Supergroup, western Montana: Evidence for rapid deposition of sedimentary strata
New sensitive high resolution ion microprobe (SHRIMP) U–Pb zircon analyses from two tuffs and a felsic flow in the middle and upper Belt Supergroup of northwestern Montana significantly refine the age of sedimentation for this very thick (15-20 km) Middle Proterozoic stratigraphic sequence. In ascending stratigraphic order, the results are (1) 1454 ± 9 Ma for a tuff in the upper part of...
Authors
K. V. Evans, J. N. Aleinikoff, J. D. Obradovich, C.M. Fanning
Isotopic evidence for the sources of Cretaceous and tertiary granitic rocks, east-central Alaska: Implications for the tectonic evolution of the Yukon-Tanana terrane Isotopic evidence for the sources of Cretaceous and tertiary granitic rocks, east-central Alaska: Implications for the tectonic evolution of the Yukon-Tanana terrane
Magnetotelluric traverses across the southern Yukon-Tanana terrane (YTT) reveal the presence of a thick conductive layer (or layers) beneath Paleozoic crystalline rocks. These rocks have been interpreted to be flysch of probable Mesozoic age, on the basis of the occurrence of Jurassic-Cretaceous flysch in the Kahiltna assemblage and Gravina-Nutzotin belt flanking the YTT to the southwest...
Authors
J. N. Aleinikoff, G. L. Farmer, R. O. Rye, W. J. Nokleberg
U-Pb geochronology of zircon and monazite from Mesoproterozoic granitic gneisses of the northern Blue Ridge, Virginia and Maryland, USA U-Pb geochronology of zircon and monazite from Mesoproterozoic granitic gneisses of the northern Blue Ridge, Virginia and Maryland, USA
Mesoproterozoic granitic gneisses comprise most of the basement of the northern Blue Ridge geologic province in Virginia and Maryland. Lithology, structure, and U-Pb geochronology have been used to subdivide the gneisses into three groups. The oldest rocks, Group 1, are layered granitic gneiss (1153 ?? 6 Ma), hornblende monzonite gneiss (1149 ?? 19 Ma), porphyroblastic granite gneiss...
Authors
J. N. Aleinikoff, W.C. Burton, P. T. Lyttle, A. E. Nelson, C.S. Southworth
200,000 years of climate change recorded in eolian sediments of the High Plains of eastern Colorado and western Nebraska 200,000 years of climate change recorded in eolian sediments of the High Plains of eastern Colorado and western Nebraska
Loess and eolian sand cover vast areas of the western Great Plains of Nebraska, Kansas and Colorado (Fig. 1). In recent studies of Quaternary climate change, there has been a renewed interest in loess and eolian sand. Much of the attention now given to loess stems from new studies of long loess sequences that contain detailed records of Quaternary glacial-interglacial cycles, thought to...
Authors
Daniel R. Muhs, James B. Swinehart, David B. Loope, John N. Aleinikoff, Josh Been
Science and Products
Filter Total Items: 109
SHRIMP U-Pb and 40Ar/39Ar age constraints for relating plutonism and mineralization in the Boulder batholith region, Montana SHRIMP U-Pb and 40Ar/39Ar age constraints for relating plutonism and mineralization in the Boulder batholith region, Montana
The composite Boulder batholith, Montana, hosts a variety of mineral deposit types, including important silver-rich polymetallic quartz vein districts in the northern part of the batholith and the giant Butte porphyry copper-molybdenum pre-Main Stage system and crosscutting copper-rich Main Stage vein system in the southern part of the batholith. Previous dating studies have identified...
Authors
Karen Lund, John N. Aleinikoff, Michael J. Kunk, Daniel M. Unruh, G. D. Zeihen, W. C. Hodges, Edward A. du Bray, J. Michael O’Neill
U-Th-Pb dating of hydrothermal minerals from Carlin-type gold deposits, Nevada- Results and evaluation 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
SHRIMP U-Pb geochronology of volcanic rocks, Belt Supergroup, western Montana: Evidence for rapid deposition of sedimentary strata SHRIMP U-Pb geochronology of volcanic rocks, Belt Supergroup, western Montana: Evidence for rapid deposition of sedimentary strata
New sensitive high resolution ion microprobe (SHRIMP) U–Pb zircon analyses from two tuffs and a felsic flow in the middle and upper Belt Supergroup of northwestern Montana significantly refine the age of sedimentation for this very thick (15-20 km) Middle Proterozoic stratigraphic sequence. In ascending stratigraphic order, the results are (1) 1454 ± 9 Ma for a tuff in the upper part of...
Authors
K. V. Evans, J. N. Aleinikoff, J. D. Obradovich, C.M. Fanning
Isotopic evidence for the sources of Cretaceous and tertiary granitic rocks, east-central Alaska: Implications for the tectonic evolution of the Yukon-Tanana terrane Isotopic evidence for the sources of Cretaceous and tertiary granitic rocks, east-central Alaska: Implications for the tectonic evolution of the Yukon-Tanana terrane
Magnetotelluric traverses across the southern Yukon-Tanana terrane (YTT) reveal the presence of a thick conductive layer (or layers) beneath Paleozoic crystalline rocks. These rocks have been interpreted to be flysch of probable Mesozoic age, on the basis of the occurrence of Jurassic-Cretaceous flysch in the Kahiltna assemblage and Gravina-Nutzotin belt flanking the YTT to the southwest...
Authors
J. N. Aleinikoff, G. L. Farmer, R. O. Rye, W. J. Nokleberg
U-Pb geochronology of zircon and monazite from Mesoproterozoic granitic gneisses of the northern Blue Ridge, Virginia and Maryland, USA U-Pb geochronology of zircon and monazite from Mesoproterozoic granitic gneisses of the northern Blue Ridge, Virginia and Maryland, USA
Mesoproterozoic granitic gneisses comprise most of the basement of the northern Blue Ridge geologic province in Virginia and Maryland. Lithology, structure, and U-Pb geochronology have been used to subdivide the gneisses into three groups. The oldest rocks, Group 1, are layered granitic gneiss (1153 ?? 6 Ma), hornblende monzonite gneiss (1149 ?? 19 Ma), porphyroblastic granite gneiss...
Authors
J. N. Aleinikoff, W.C. Burton, P. T. Lyttle, A. E. Nelson, C.S. Southworth
200,000 years of climate change recorded in eolian sediments of the High Plains of eastern Colorado and western Nebraska 200,000 years of climate change recorded in eolian sediments of the High Plains of eastern Colorado and western Nebraska
Loess and eolian sand cover vast areas of the western Great Plains of Nebraska, Kansas and Colorado (Fig. 1). In recent studies of Quaternary climate change, there has been a renewed interest in loess and eolian sand. Much of the attention now given to loess stems from new studies of long loess sequences that contain detailed records of Quaternary glacial-interglacial cycles, thought to...
Authors
Daniel R. Muhs, James B. Swinehart, David B. Loope, John N. Aleinikoff, Josh Been