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
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Filter Total Items: 47
A catalogue of drill core recovered from Kilauea Iki lava lake, from 1967 to 1979
The purpose of this report is to serve as a descriptive catalogue for drill core recovered from Kilauea Iki lava lake, from 1967 to 1979. Kilauea Iki lava lake was formed when lavas of the 1959 summit eruption were ponded in Kilauea Iki pit crater, a large pit crater at the extreme upper end of Kilauea's east rift zone (Fig. 1). This eruption is one of the best documented of Kilauean eruptions: Mu
Major oxide, trace element, and glass chemistry of Columbia River basalt samples collected between 1971 and 1977
In this report we are making available all chemical analyses of whole rocks and selected glasses for samples of Columbia River Basalt that we collected between 1971 and 1977 during reconnaissance geologic mapping of the Columbia Plateau.
Differentiation and magma mixing on Kilauea's east rift zone - A further look at the eruptions of 1955 and 1960. Part I. The late 1955 lavas
The lavas of the 1955 east rift eruption of Kilauea Volcano have been the object of considerable petrologic interest for two reasons. First, the early 1955 lavas are among the most differentiated ever erupted at Kilauea, and second, the petrographic character and chemical composition of the lava being erupted changed significantly during the eruption. This shift, from more differentiated (MgO=5.0-
Reequilibration of chromite within Kilauea Iki lava lake, Hawaii
Chromite mainly occurs as tiny inclusions within or at the edges of olivine phenocrysts in the 1959 Kilauea Iki lava lake. Liquilus chromite compositions are only preserved in scoria that was rapidly quenched from eruption temperatures. Analyses of drill core taken from the lava lake in 1960, 1961, 1975, 1979, and 1981 show that chromite becomes richer in Fe+2, Fe+3, Ti and poorer in Mg, Al, Cr th
U-Pb and Sm-Nd ages for the Stillwater Complex and its associated sills and dikes, Beartooth Mountains, Montana: identification of a parent magma?
Seven analyses from two samples of the Lower Banded series of the Stillwater Complex, Montana, yielded a U-Pb zircon-baddeleyite age of 2705??4 Ma. A more precise age of 2704??1 Ma is obtained if we regress only five of seven analyses. In either case, the age is in very good agreement with the previously reported Sm-Nd mineral isochron age of 2701??8 Ma for a gabbro from the Lower Banded series. N
Diapiric transfer of melt in Kilauea Iki lava lake, Hawaii: a quick, efficient process of igneous differentiation
Kilauea Iki lava lake, formed in 1959, is a large pond of picritic basalt (average MgO content = 15.34% by weight), which has cooled and crystallized as a small, self-roofed magma chamber. Differentiation processes recognized as active in the lake include rather inefficient settling of the larger (2-10 mm) olivine phenocrysts, formation of segregation veins, and formation of diapir-like vertical o
Geothermometry of Kilauea Iki lava lake, Hawaii
Data on the variation of temperature with time and in space are essential to a complete understanding of the crystallization history of basaltic magma in Kilauea Iki lava lake. Methods used to determine temperatures in the lake have included direct, downhole thermocouple measurements and Fe-Ti oxide geothermometry. In addition, the temperature variations of MgO and CaO contents of glasses, as dete
The 1977 eruption of Kilauea volcano, Hawaii
Kilauea volcano began to erupt on September 13, 1977, after a 21.5-month period of quiescence. Harmonic tremor in the upper and central east rift zone and rapid deflation of the summit area occurred for 22 hours before the outbreak of surface activity. On the first night, spatter ramparts formed along a discontinuous, en-echelon, 5.5-km-long fissure system that trends N70??E between two prehistori
Crystallization history of Kilauea Iki lava lake as seen in drill core recovered in 1967-1979
Kilauea Iki lava lake formed during the 1959 summit eruption, one of the most picritic eruptions of Kilauea Volcano in the twentieth century. Since 1959 the 110 to 122 m thick lake has cooled slowly, developing steadily thickening upper and lower crusts, with a lens of more molten lava in between. Recent coring dates, with maximum depths reached in the center of the lake, are: 1967 (26.5 m). 1975
Phase relations of basalts in their melting range at PH2O = 5 kb as a function of oxygen fugacity: Part I. Mafic phases
The phase relations of three basalts, the Picture Gorge tholeiite, the 1921 Kilauea olivine tholeiite, and the 1801 Hualalai alkali basalt, were studied at 5 kb water pressure, 680–1000°C, at the oxygen fugacities of the quartz-fayalite-magnetite (QFM) and hematite-magnetite (HM) buffers.In the range 680–850 °C, the crystalline assemblage on the QFM buffer is dominantly hornblende+ plagioclase, ±
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Filter Total Items: 47
A catalogue of drill core recovered from Kilauea Iki lava lake, from 1967 to 1979
The purpose of this report is to serve as a descriptive catalogue for drill core recovered from Kilauea Iki lava lake, from 1967 to 1979. Kilauea Iki lava lake was formed when lavas of the 1959 summit eruption were ponded in Kilauea Iki pit crater, a large pit crater at the extreme upper end of Kilauea's east rift zone (Fig. 1). This eruption is one of the best documented of Kilauean eruptions: MuMajor oxide, trace element, and glass chemistry of Columbia River basalt samples collected between 1971 and 1977
In this report we are making available all chemical analyses of whole rocks and selected glasses for samples of Columbia River Basalt that we collected between 1971 and 1977 during reconnaissance geologic mapping of the Columbia Plateau.Differentiation and magma mixing on Kilauea's east rift zone - A further look at the eruptions of 1955 and 1960. Part I. The late 1955 lavas
The lavas of the 1955 east rift eruption of Kilauea Volcano have been the object of considerable petrologic interest for two reasons. First, the early 1955 lavas are among the most differentiated ever erupted at Kilauea, and second, the petrographic character and chemical composition of the lava being erupted changed significantly during the eruption. This shift, from more differentiated (MgO=5.0-Reequilibration of chromite within Kilauea Iki lava lake, Hawaii
Chromite mainly occurs as tiny inclusions within or at the edges of olivine phenocrysts in the 1959 Kilauea Iki lava lake. Liquilus chromite compositions are only preserved in scoria that was rapidly quenched from eruption temperatures. Analyses of drill core taken from the lava lake in 1960, 1961, 1975, 1979, and 1981 show that chromite becomes richer in Fe+2, Fe+3, Ti and poorer in Mg, Al, Cr thU-Pb and Sm-Nd ages for the Stillwater Complex and its associated sills and dikes, Beartooth Mountains, Montana: identification of a parent magma?
Seven analyses from two samples of the Lower Banded series of the Stillwater Complex, Montana, yielded a U-Pb zircon-baddeleyite age of 2705??4 Ma. A more precise age of 2704??1 Ma is obtained if we regress only five of seven analyses. In either case, the age is in very good agreement with the previously reported Sm-Nd mineral isochron age of 2701??8 Ma for a gabbro from the Lower Banded series. NDiapiric transfer of melt in Kilauea Iki lava lake, Hawaii: a quick, efficient process of igneous differentiation
Kilauea Iki lava lake, formed in 1959, is a large pond of picritic basalt (average MgO content = 15.34% by weight), which has cooled and crystallized as a small, self-roofed magma chamber. Differentiation processes recognized as active in the lake include rather inefficient settling of the larger (2-10 mm) olivine phenocrysts, formation of segregation veins, and formation of diapir-like vertical oGeothermometry of Kilauea Iki lava lake, Hawaii
Data on the variation of temperature with time and in space are essential to a complete understanding of the crystallization history of basaltic magma in Kilauea Iki lava lake. Methods used to determine temperatures in the lake have included direct, downhole thermocouple measurements and Fe-Ti oxide geothermometry. In addition, the temperature variations of MgO and CaO contents of glasses, as deteThe 1977 eruption of Kilauea volcano, Hawaii
Kilauea volcano began to erupt on September 13, 1977, after a 21.5-month period of quiescence. Harmonic tremor in the upper and central east rift zone and rapid deflation of the summit area occurred for 22 hours before the outbreak of surface activity. On the first night, spatter ramparts formed along a discontinuous, en-echelon, 5.5-km-long fissure system that trends N70??E between two prehistoriCrystallization history of Kilauea Iki lava lake as seen in drill core recovered in 1967-1979
Kilauea Iki lava lake formed during the 1959 summit eruption, one of the most picritic eruptions of Kilauea Volcano in the twentieth century. Since 1959 the 110 to 122 m thick lake has cooled slowly, developing steadily thickening upper and lower crusts, with a lens of more molten lava in between. Recent coring dates, with maximum depths reached in the center of the lake, are: 1967 (26.5 m). 1975Phase relations of basalts in their melting range at PH2O = 5 kb as a function of oxygen fugacity: Part I. Mafic phases
The phase relations of three basalts, the Picture Gorge tholeiite, the 1921 Kilauea olivine tholeiite, and the 1801 Hualalai alkali basalt, were studied at 5 kb water pressure, 680–1000°C, at the oxygen fugacities of the quartz-fayalite-magnetite (QFM) and hematite-magnetite (HM) buffers.In the range 680–850 °C, the crystalline assemblage on the QFM buffer is dominantly hornblende+ plagioclase, ±