Eos, Transactions American Geophysical Union, May 3, 2017
A leading geochemist who became well known for creating the first high-precision mass spectromete... more A leading geochemist who became well known for creating the first high-precision mass spectrometer, called Lunatic I, that measured isotope ratios in lunar samples from the Apollo missions.
Introduction: Isotopic studies have demonstrated that the Earth and Moon are remarkably similar i... more Introduction: Isotopic studies have demonstrated that the Earth and Moon are remarkably similar in their isotopic compositions for many elements (e.g., O, Ti, Cr and W isotopic anomalies and Mg and Si stable isotopes). This similarity between the Earth and Moon is unique in our Solar System when compared to other planetary bodies (such as Mars, Vesta 4 and other asteroids represented by the various classes of meteorites). However, in contrast to the isotopic composition of many elements, the Fe isotopic compositions of all lunar samples are significantly different from those of the bulk silicate Earth. This difference is well resolved within the current analytical uncertainties and has been repeatedly reported in samples ranging from mare basalts, highland anorthosites, Mg-suite plutonic rocks, to lunar regolith [1–7]. It has been debated whether such a global Fe isotopic difference represents a primary signature of the Giant Impact due to the evaporative Fe loss [1], or of an unide...
Proceedings of the National Academy of Sciences, 2019
Significance The discovery of numerous exoplanet systems containing diverse populations of planet... more Significance The discovery of numerous exoplanet systems containing diverse populations of planets orbiting very close to their host stars challenges the planet formation theories based on the solar system. Here, we focus on the planets with radii of 2–4 R ⊕ , whose compositions are debated. They are thought to be either gas dwarfs consisting of rocky cores embedded in H 2 -rich gas envelopes or water worlds containing significant amounts of H 2 O-dominated fluid/ice in addition to rock and gas. We argue that these planets are water worlds.
Carbonate-rich sedimentary rocks of the western Anabar region, northern Siberia, preserve an exce... more Carbonate-rich sedimentary rocks of the western Anabar region, northern Siberia, preserve an exceptional record of evolutionary and biogeochemical events near the Proterozoic/Cambrian boundary. Sedimentologically, the boundary succession can be divided into three sequences representing successive episodes of late transgressive to early highstand deposition; four parasequences are recognized in the sequence corresponding lithostratigraphically to the Manykai Formation. Small shelly fossils are abundant and include many taxa that also occur in standard sections of southeastern Siberia. Despite this coincidence of faunal elements, biostratigraphic correlations between the two regions have been controversial because numerous species that first appear at or immediately above the basal Tommotian boundary in southeastern sections have first appearances scattered through more than thirty metres of section in the western Anabar. Carbon- and Sr-isotopic data on petrographically and geochemica...
Proceedings of the National Academy of Sciences of the United States of America, Feb 21, 2017
At ocean spreading ridges, circulation of seawater through rock at elevated temperatures alters t... more At ocean spreading ridges, circulation of seawater through rock at elevated temperatures alters the chemical and isotopic composition of oceanic crust. Samples obtained from drilling into ocean floor and from ophiolites have demonstrated that certain isotope systems, such as (18)O/(16)O and (87)Sr/(86)Sr, are systematically modified in hydrothermally altered oceanic crust. Although K is known to be mobile during hydrothermal alteration, there have not yet been any K-isotope analyses of altered oceanic crustal materials. Moreover, the (41)K/(39)K of seawater was recently found to be significantly higher than that of igneous rocks, so the addition of seawater K to oceanic crust would be expected to generate (41)K/(39)K variations in affected rocks. Here, we report high-precision (41)K/(39)K measurements for samples from the Bay of Islands ophiolite, and we document large variations in (41)K/(39)K, covarying with previous determinations of (87)Sr/(86)Sr. Our data indicate that analytic...
The Earth-Moon system has unique chemical and isotopic signatures compared with other planetary b... more The Earth-Moon system has unique chemical and isotopic signatures compared with other planetary bodies; any successful model for the origin of this system therefore has to satisfy these chemical and isotopic constraints. The Moon is substantially depleted in volatile elements such as potassium compared with the Earth and the bulk solar composition, and it has long been thought to be the result of a catastrophic Moon-forming giant impact event. Volatile-element-depleted bodies such as the Moon were expected to be enriched in heavy potassium isotopes during the loss of volatiles; however such enrichment was never found. Here we report new high-precision potassium isotope data for the Earth, the Moon and chondritic meteorites. We found that the lunar rocks are significantly (>2σ) enriched in the heavy isotopes of potassium compared to the Earth and chondrites (by around 0.4 parts per thousand). The enrichment of the heavy isotope of potassium in lunar rocks compared with those of th...
Eos, Transactions American Geophysical Union, May 3, 2017
A leading geochemist who became well known for creating the first high-precision mass spectromete... more A leading geochemist who became well known for creating the first high-precision mass spectrometer, called Lunatic I, that measured isotope ratios in lunar samples from the Apollo missions.
Introduction: Isotopic studies have demonstrated that the Earth and Moon are remarkably similar i... more Introduction: Isotopic studies have demonstrated that the Earth and Moon are remarkably similar in their isotopic compositions for many elements (e.g., O, Ti, Cr and W isotopic anomalies and Mg and Si stable isotopes). This similarity between the Earth and Moon is unique in our Solar System when compared to other planetary bodies (such as Mars, Vesta 4 and other asteroids represented by the various classes of meteorites). However, in contrast to the isotopic composition of many elements, the Fe isotopic compositions of all lunar samples are significantly different from those of the bulk silicate Earth. This difference is well resolved within the current analytical uncertainties and has been repeatedly reported in samples ranging from mare basalts, highland anorthosites, Mg-suite plutonic rocks, to lunar regolith [1–7]. It has been debated whether such a global Fe isotopic difference represents a primary signature of the Giant Impact due to the evaporative Fe loss [1], or of an unide...
Proceedings of the National Academy of Sciences, 2019
Significance The discovery of numerous exoplanet systems containing diverse populations of planet... more Significance The discovery of numerous exoplanet systems containing diverse populations of planets orbiting very close to their host stars challenges the planet formation theories based on the solar system. Here, we focus on the planets with radii of 2–4 R ⊕ , whose compositions are debated. They are thought to be either gas dwarfs consisting of rocky cores embedded in H 2 -rich gas envelopes or water worlds containing significant amounts of H 2 O-dominated fluid/ice in addition to rock and gas. We argue that these planets are water worlds.
Carbonate-rich sedimentary rocks of the western Anabar region, northern Siberia, preserve an exce... more Carbonate-rich sedimentary rocks of the western Anabar region, northern Siberia, preserve an exceptional record of evolutionary and biogeochemical events near the Proterozoic/Cambrian boundary. Sedimentologically, the boundary succession can be divided into three sequences representing successive episodes of late transgressive to early highstand deposition; four parasequences are recognized in the sequence corresponding lithostratigraphically to the Manykai Formation. Small shelly fossils are abundant and include many taxa that also occur in standard sections of southeastern Siberia. Despite this coincidence of faunal elements, biostratigraphic correlations between the two regions have been controversial because numerous species that first appear at or immediately above the basal Tommotian boundary in southeastern sections have first appearances scattered through more than thirty metres of section in the western Anabar. Carbon- and Sr-isotopic data on petrographically and geochemica...
Proceedings of the National Academy of Sciences of the United States of America, Feb 21, 2017
At ocean spreading ridges, circulation of seawater through rock at elevated temperatures alters t... more At ocean spreading ridges, circulation of seawater through rock at elevated temperatures alters the chemical and isotopic composition of oceanic crust. Samples obtained from drilling into ocean floor and from ophiolites have demonstrated that certain isotope systems, such as (18)O/(16)O and (87)Sr/(86)Sr, are systematically modified in hydrothermally altered oceanic crust. Although K is known to be mobile during hydrothermal alteration, there have not yet been any K-isotope analyses of altered oceanic crustal materials. Moreover, the (41)K/(39)K of seawater was recently found to be significantly higher than that of igneous rocks, so the addition of seawater K to oceanic crust would be expected to generate (41)K/(39)K variations in affected rocks. Here, we report high-precision (41)K/(39)K measurements for samples from the Bay of Islands ophiolite, and we document large variations in (41)K/(39)K, covarying with previous determinations of (87)Sr/(86)Sr. Our data indicate that analytic...
The Earth-Moon system has unique chemical and isotopic signatures compared with other planetary b... more The Earth-Moon system has unique chemical and isotopic signatures compared with other planetary bodies; any successful model for the origin of this system therefore has to satisfy these chemical and isotopic constraints. The Moon is substantially depleted in volatile elements such as potassium compared with the Earth and the bulk solar composition, and it has long been thought to be the result of a catastrophic Moon-forming giant impact event. Volatile-element-depleted bodies such as the Moon were expected to be enriched in heavy potassium isotopes during the loss of volatiles; however such enrichment was never found. Here we report new high-precision potassium isotope data for the Earth, the Moon and chondritic meteorites. We found that the lunar rocks are significantly (>2σ) enriched in the heavy isotopes of potassium compared to the Earth and chondrites (by around 0.4 parts per thousand). The enrichment of the heavy isotope of potassium in lunar rocks compared with those of th...
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