Rosalind Tuthill Helz, Ph.D.
Rosalind Tuthill Helz is a Scientist Emeritus at the Florence Bascom Geoscience Center.
Rosalind Helz is a Scientist Emeritus at the Frances Bascom Center. She received her undergraduate degree in Geology from Stanford University in 1965, and graduate degrees in Geochemistry and Mineralogy from Penn State University in 1968 (M.S.) and 1978 (Ph.D). Since joining the USGS in March 1968, she has devoted her career to studying the behavior of mafic magmas, specializing in the use of petrology and chemistry to elucidate differentiation processes in mafic magmatic systems. Ongoing work includes completion of reports on the long-term study of Kilauea Iki lava lake, Hawaii and completion of reports on studies of the basal sill swarm associated with the Stillwater Complex, Montana.
Professional Experience
Smithsonian Museum of Natural History (Research Associate)
Education and Certifications
Ph.D, Mineralogy and Petrology, The Pennsylvania State University, 1978
M.Sc., Mineralogy and Petrology, The Pennsylvania State University, 1968
B.S., Geology, Stanford University, 1965
Science and Products
Filter Total Items: 47
Magma storage and transport timescales for the 1959 Kīlauea Iki eruption and implications for diffusion chronometry studies using time-series samples versus tephra deposits
Complex crystal cargo in basaltic eruptions has the potential to yield diverse insights on pre- and syn-eruptive timescales of magma storage and transport. Research on eruption products from the 1959 eruption from Kīlauea Iki Crater at Kīlauea volcano (Hawai‘i) demonstrates that time-series samples collected during an eruption can yield a wealth of information not accessible by studying the fall d
Authors
Kendra J. Lynn, Rosalind L. Helz
Melt surges, flow differentiation, and remobilization of crystal-rich mushes in response to unloading: Observations from Kīlauea Iki lava lake, Hawaii
Field and laboratory studies of the 1959 Kīlauea Iki lava lake have provided insight into differentiation processes in mafic magma chambers. This paper explores how partially molten basaltic mushes responded to unloading as a consequence of drilling. Most holes drilled from 1967 to 1979 terminated in a melt-rich internal differentiate with a sharp crust-melt interface. These interfaces were not st
Authors
Rosalind L. Helz
Proportions, timing, and re-equilibration progress during the 1959 Summit Eruption of Kīlauea: An example of magma mixing processes operating during OIB petrogenesis
Petrographic and chemical analysis of scoria samples collected during the 1959 Kīlauea summit eruption illustrates the progress of thermal and chemical homogenization of the melts, and the gradual growth and/or re-equilibration of olivine phenocrysts, over the course of the eruption. Glass compositions show that thermal equilibration was largely complete within the span of the eruption, whereas ch
Authors
Rosalind L. Helz
Major-element compositional data and thermal data for drill core from Kīlauea Iki lava lake, plus analyses of glasses from scoria of the 1959 summit eruption of Kīlauea Volcano, Hawaii
This report presents electron microprobe data on glasses and selected crystalline phases from Kīlauea Iki lava lake and glasses from the 1959 summit eruption of Kīlauea Volcano, Hawaii. Some of these data have been published previously, but the complete set has not been published before. In addition, this report includes electron microprobe data for phases in melting experiments reported earlier,
Authors
Rosalind Tuthill Helz
Olivine-melt relationships and syneruptive redox variations in the 1959 eruption of Kīlauea Volcano as revealed by XANES
The 1959 summit eruption of Kīlauea Volcano exhibited high lava fountains of gas-rich, primitive magma, containing olivine + chromian spinel in highly vesicular brown glass. Microprobe analysis of these samples shows that euhedral rims on olivine phenocrysts, in direct contact with glass, vary significantly in forsterite (Fo) content, at constant major-element melt composition, as do unzoned groun
Authors
Rosalind L. Helz, Elizabeth Cottrell, Maryjo N. Brounce, Katherine A. Kelley
Evidence for large compositional ranges in coeval melts erupted from Kīlauea's summit reservoir
Petrologic observations on Kīlauea's lavas include abundant microprobe analyses of glasses, which show the range of melts available in Kīlauea's summit reservoir over time. During the past two centuries, compositions of melts erupted within the caldera have been limited to MgO = 6.3–7.5 wt%. Extracaldera lavas of the 1959, 1971, and 1974 eruptions contain melts with up to 10.2, 8.9, and 9.2 wt% Mg
Authors
Rosalind T. Helz, David A. Clague, Larry G. Mastin, Timothy R. Rose
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 contents among t
Authors
Rosalind L. Helz, David A. Clague, Larry G. Mastin, Timothy R. Rose
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 saw a gra
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
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 isotopes for
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
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 fractionati
Authors
Heng Chen, Paul S. Savage, Fang-Zehn Teng, Rosalind T. Helz, Frédéric Moynier
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-plagioclase-plagiocl
Authors
Marian B. Holness, Chris Richardson, Rosalind T. Helz
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 demonstrates that
Authors
Marian B. Holness, Madeleine C.S. Humphreys, Rachel Sides, Rosalind T. Helz, Christian Tegner
Science and Products
Filter Total Items: 47
Magma storage and transport timescales for the 1959 Kīlauea Iki eruption and implications for diffusion chronometry studies using time-series samples versus tephra deposits
Complex crystal cargo in basaltic eruptions has the potential to yield diverse insights on pre- and syn-eruptive timescales of magma storage and transport. Research on eruption products from the 1959 eruption from Kīlauea Iki Crater at Kīlauea volcano (Hawai‘i) demonstrates that time-series samples collected during an eruption can yield a wealth of information not accessible by studying the fall d
Authors
Kendra J. Lynn, Rosalind L. Helz
Melt surges, flow differentiation, and remobilization of crystal-rich mushes in response to unloading: Observations from Kīlauea Iki lava lake, Hawaii
Field and laboratory studies of the 1959 Kīlauea Iki lava lake have provided insight into differentiation processes in mafic magma chambers. This paper explores how partially molten basaltic mushes responded to unloading as a consequence of drilling. Most holes drilled from 1967 to 1979 terminated in a melt-rich internal differentiate with a sharp crust-melt interface. These interfaces were not st
Authors
Rosalind L. Helz
Proportions, timing, and re-equilibration progress during the 1959 Summit Eruption of Kīlauea: An example of magma mixing processes operating during OIB petrogenesis
Petrographic and chemical analysis of scoria samples collected during the 1959 Kīlauea summit eruption illustrates the progress of thermal and chemical homogenization of the melts, and the gradual growth and/or re-equilibration of olivine phenocrysts, over the course of the eruption. Glass compositions show that thermal equilibration was largely complete within the span of the eruption, whereas ch
Authors
Rosalind L. Helz
Major-element compositional data and thermal data for drill core from Kīlauea Iki lava lake, plus analyses of glasses from scoria of the 1959 summit eruption of Kīlauea Volcano, Hawaii
This report presents electron microprobe data on glasses and selected crystalline phases from Kīlauea Iki lava lake and glasses from the 1959 summit eruption of Kīlauea Volcano, Hawaii. Some of these data have been published previously, but the complete set has not been published before. In addition, this report includes electron microprobe data for phases in melting experiments reported earlier,
Authors
Rosalind Tuthill Helz
Olivine-melt relationships and syneruptive redox variations in the 1959 eruption of Kīlauea Volcano as revealed by XANES
The 1959 summit eruption of Kīlauea Volcano exhibited high lava fountains of gas-rich, primitive magma, containing olivine + chromian spinel in highly vesicular brown glass. Microprobe analysis of these samples shows that euhedral rims on olivine phenocrysts, in direct contact with glass, vary significantly in forsterite (Fo) content, at constant major-element melt composition, as do unzoned groun
Authors
Rosalind L. Helz, Elizabeth Cottrell, Maryjo N. Brounce, Katherine A. Kelley
Evidence for large compositional ranges in coeval melts erupted from Kīlauea's summit reservoir
Petrologic observations on Kīlauea's lavas include abundant microprobe analyses of glasses, which show the range of melts available in Kīlauea's summit reservoir over time. During the past two centuries, compositions of melts erupted within the caldera have been limited to MgO = 6.3–7.5 wt%. Extracaldera lavas of the 1959, 1971, and 1974 eruptions contain melts with up to 10.2, 8.9, and 9.2 wt% Mg
Authors
Rosalind T. Helz, David A. Clague, Larry G. Mastin, Timothy R. Rose
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 contents among t
Authors
Rosalind L. Helz, David A. Clague, Larry G. Mastin, Timothy R. Rose
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 saw a gra
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
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 isotopes for
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
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 fractionati
Authors
Heng Chen, Paul S. Savage, Fang-Zehn Teng, Rosalind T. Helz, Frédéric Moynier
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-plagioclase-plagiocl
Authors
Marian B. Holness, Chris Richardson, Rosalind T. Helz
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 demonstrates that
Authors
Marian B. Holness, Madeleine C.S. Humphreys, Rachel Sides, Rosalind T. Helz, Christian Tegner