Rosalind Tuthill Helz, Ph.D. (Former Employee)
Science and Products
Filter Total Items: 47
Electron microprobe analyses of glasses from Kīlauea tephra units, Kīlauea Volcano, Hawaii Electron microprobe analyses of glasses from Kīlauea tephra units, Kīlauea Volcano, Hawaii
This report presents approximately 2,100 glass analyses from three tephra units of Kīlauea Volcano: the Keanakākoʻi Tephra, the Kulanaokuaiki Tephra, and the Pāhala Ash. It also includes some new analyses obtained as part of a re-evaluation of the MgO contents of glasses in two of the three original datasets; this re-evaluation was conducted to improve the consistency of glass MgO...
Authors
Rosalind L. Helz, David A. Clague, Larry G. Mastin, Timothy R. Rose
Petrologic insights into basaltic volcanism at historically active Hawaiian volcanoes Petrologic insights into basaltic volcanism at historically active Hawaiian volcanoes
Study of the petrology of Hawaiian volcanoes, in particular the historically active volcanoes on the Island of Hawai‘i, has long been of worldwide scientific interest. When Dr. Thomas A. Jaggar, Jr., established the Hawaiian Volcano Observatory (HVO) in 1912, detailed observations on basaltic activity at Kīlauea and Mauna Loa volcanoes increased dramatically. The period from 1912 to 1958...
Authors
Rosalind T. Helz, David A. Clague, Thomas W. Sisson, Carl R. Thornber
Discerning crystal growth from diffusion profiles in zoned olivine by in situ Mg–Fe isotopic analyses Discerning crystal growth from diffusion profiles in zoned olivine by in situ Mg–Fe isotopic analyses
Mineral zoning is used in diffusion-based geospeedometry to determine magmatic timescales. Progress in this field has been hampered by the challenge to discern mineral zoning produced by diffusion from concentration gradients inherited from crystal growth. A zoned olivine phenocryst from Kilauea Iki lava lake (Hawaii) was selected for this study to evaluate the potential of Mg and Fe...
Authors
Corliss Kin I. Sio, Nicolas Dauphas, Fang-Zhen Teng, Marc Chaussidon, Rosalind T. Helz, Mathieu Roskosz
Zinc isotope fractionation during magmatic differentiation and the isotopic composition of the bulk Earth Zinc isotope fractionation during magmatic differentiation and the isotopic composition of the bulk Earth
he zinc stable isotope system has been successfully applied to many and varied fields in geochemistry, but to date it is still not completely clear how this isotope system is affected by igneous processes. In order to evaluate the potential application of Zn isotopes as a proxy for planetary differentiation and volatile history, it is important to constrain the magnitude of Zn isotopic
Authors
Heng Chen, Paul S. Savage, Fang-Zehn Teng, Rosalind T. Helz, Frederic Moynier
Disequilibrium dihedral angles in dolerite sills Disequilibrium dihedral angles in dolerite sills
The geometry of clinopyroxene-plagioclase-plagioclase junctions in mafic rocks, measured by the median dihedral angle Θcpp, is created during solidification. In the solidifying Kilauea Iki (Hawaii) lava lake, the wider junctions between plagioclase grains are the first to be filled by pyroxene, followed by the narrower junctions. The final Θcpp, attained when all clinopyroxene...
Authors
Marian B. Holness, Chris Richardson, Rosalind T. Helz
Toward an understanding of disequilibrium dihedral angles in mafic rocks Toward an understanding of disequilibrium dihedral angles in mafic rocks
The median dihedral angle at clinopyroxene-plagioclase-plagioclase junctions in mafic rocks, Θcpp, is generally lower than equilibrium (109˚ {plus minus} 2˚). Observation of a wide range of mafic bodies demonstrates that previous work on systematic variations of Θcpp is incorrect in several important respects. Firstly, the spatial distribution of plagioclase compositional zoning...
Authors
Marian B. Holness, Madeleine C.S. Humphreys, Rachel Sides, Rosalind T. Helz, Christian Tegner
Science and Products
Filter Total Items: 47
Electron microprobe analyses of glasses from Kīlauea tephra units, Kīlauea Volcano, Hawaii Electron microprobe analyses of glasses from Kīlauea tephra units, Kīlauea Volcano, Hawaii
This report presents approximately 2,100 glass analyses from three tephra units of Kīlauea Volcano: the Keanakākoʻi Tephra, the Kulanaokuaiki Tephra, and the Pāhala Ash. It also includes some new analyses obtained as part of a re-evaluation of the MgO contents of glasses in two of the three original datasets; this re-evaluation was conducted to improve the consistency of glass MgO...
Authors
Rosalind L. Helz, David A. Clague, Larry G. Mastin, Timothy R. Rose
Petrologic insights into basaltic volcanism at historically active Hawaiian volcanoes Petrologic insights into basaltic volcanism at historically active Hawaiian volcanoes
Study of the petrology of Hawaiian volcanoes, in particular the historically active volcanoes on the Island of Hawai‘i, has long been of worldwide scientific interest. When Dr. Thomas A. Jaggar, Jr., established the Hawaiian Volcano Observatory (HVO) in 1912, detailed observations on basaltic activity at Kīlauea and Mauna Loa volcanoes increased dramatically. The period from 1912 to 1958...
Authors
Rosalind T. Helz, David A. Clague, Thomas W. Sisson, Carl R. Thornber
Discerning crystal growth from diffusion profiles in zoned olivine by in situ Mg–Fe isotopic analyses Discerning crystal growth from diffusion profiles in zoned olivine by in situ Mg–Fe isotopic analyses
Mineral zoning is used in diffusion-based geospeedometry to determine magmatic timescales. Progress in this field has been hampered by the challenge to discern mineral zoning produced by diffusion from concentration gradients inherited from crystal growth. A zoned olivine phenocryst from Kilauea Iki lava lake (Hawaii) was selected for this study to evaluate the potential of Mg and Fe...
Authors
Corliss Kin I. Sio, Nicolas Dauphas, Fang-Zhen Teng, Marc Chaussidon, Rosalind T. Helz, Mathieu Roskosz
Zinc isotope fractionation during magmatic differentiation and the isotopic composition of the bulk Earth Zinc isotope fractionation during magmatic differentiation and the isotopic composition of the bulk Earth
he zinc stable isotope system has been successfully applied to many and varied fields in geochemistry, but to date it is still not completely clear how this isotope system is affected by igneous processes. In order to evaluate the potential application of Zn isotopes as a proxy for planetary differentiation and volatile history, it is important to constrain the magnitude of Zn isotopic
Authors
Heng Chen, Paul S. Savage, Fang-Zehn Teng, Rosalind T. Helz, Frederic Moynier
Disequilibrium dihedral angles in dolerite sills Disequilibrium dihedral angles in dolerite sills
The geometry of clinopyroxene-plagioclase-plagioclase junctions in mafic rocks, measured by the median dihedral angle Θcpp, is created during solidification. In the solidifying Kilauea Iki (Hawaii) lava lake, the wider junctions between plagioclase grains are the first to be filled by pyroxene, followed by the narrower junctions. The final Θcpp, attained when all clinopyroxene...
Authors
Marian B. Holness, Chris Richardson, Rosalind T. Helz
Toward an understanding of disequilibrium dihedral angles in mafic rocks Toward an understanding of disequilibrium dihedral angles in mafic rocks
The median dihedral angle at clinopyroxene-plagioclase-plagioclase junctions in mafic rocks, Θcpp, is generally lower than equilibrium (109˚ {plus minus} 2˚). Observation of a wide range of mafic bodies demonstrates that previous work on systematic variations of Θcpp is incorrect in several important respects. Firstly, the spatial distribution of plagioclase compositional zoning...
Authors
Marian B. Holness, Madeleine C.S. Humphreys, Rachel Sides, Rosalind T. Helz, Christian Tegner