Periodic Report Summary 1 - ISOVOLC (Novel isotopic constraints on the environmental impact of continental flood basalt eruptions)
•Project objectives
The project ‘Isovolc’ aims at furthering our understanding of the effect that continental flood basalt eruptions have on the environment. Continental flood basalt (CFB) volcanism is characterised by the repeated eruption of huge batches of magma over relatively brief intervals of time, and delivering large masses of volcanic gas to the atmosphere. Such eruptions appear to precede many of the mass extinction events that punctuate the history of life on Earth.
The overall objective of this study is to use a multi-isotopic approach to assess the environmental impact of a single CFB eruption, as a result of atmospheric loading. Specifically, the novel stable isotope systems zinc (Zn) and copper (Cu), and the radiogenic rhenium-osmium (Re-Os) system are the geochemical tools proposed to accomplish this research, applied to individual flood basalt flows from the Columbia River Basalt lavas, NW USA. Copper and zinc isotopes will be used to distinguish between the gaseous release of S (as SO2, H2SO4, H2S) versus crystalline or aerosol forms, and Re-Os isotopes will be used to fingerprint the source of magmatic volatiles and the timescales of volatile release during eruption. Ultimately, we want to assess whether single flood basalt eruptions are enough to cause deleterious environmental upset.
• Work performed since the project started
The majority of the work performed since the start of the project has centred on constraining the behaviour of Zn and Cu isotopes during igneous processes (i.e. partial melting, fractional crystallisation) and volatile loss from a magma (degassing), and to providing a global isotopic datum for each system, the ‘bulk silicate Earth’ composition. This began with the analysis of a vast number of well-characterised samples from various geological settings, coupled with geochemical modelling techniques to further constrain processes and reservoirs. Much of these findings have been published, or are being written up for publication: these are listed in the ‘Main results’ section.
This initial work revealed a number of new research questions, in particular relating to the differentiation of Earth, and the processes relating to volatile redistribution of elements in the cooling solar nebula. Following up on these questions has involved the analysis of meteorites and experimental samples, provided in collaboration with the Institut de Physique du Globe, Paris. Finally, the most recent component of the project has been the analysis of samples from individual Colombia River flood basalt eruption flows (Roza and Frenchman Springs); this is almost complete and the data are being interpreted; these results will be presented at conferences over the next 6 months.
• Main results
As part of the run up to the project (before the funding officially started) the researcher investigated how Zn isotopes vary during igneous processes and also to provide a Bulk Earth isotopic reference value. This also involved supervision of a PhD student. This work was published as:
Zinc isotope fractionation during magmatic differentiation and the isotopic composition of the bulk Earth. H Chen, PS Savage, FZ Teng, RT Helz, F Moynier; Earth and Planetary Science Letters 369, 34-42 (2013)
Another key part of the project is investigating how Cu isotopes behave during igneous processes, and also to provide a bulk silicate Earth isotope reference value; again, this work is now published in a high impact factor journal:
Copper isotope evidence for large-scale sulphide fractionation during Earth’s differentiation. PS Savage, F Moynier, H Chen, G Shofner, J Siebert, J Badro, I Puchtel; Geochemical Perspectives Letters 1, 53-64 (2015)
Here, it was discovered that the Cu isotope composition of the mantle is distinct from that of the bulk Earth, as defined by meteorites. This has important significance in terms of the physiochemical conditions that existed when Earth’s core formed and the research was featured in number of popular science and national newspaper websites e.g.:
http://www.livescience.com/51249-earth-core-contains-brimstone.html
Further research on the behaviour of Cu isotopes during igneous processes revealed large variations in the mantle; this has been presented at a number of international conferences, e.g.:
Copper isotope heterogeneity in the lithospheric mantle, PS Savage, J Harvey, F Moynier. Invited oral presentation, V.M. Goldschmidt conference, Sacramento, California, USA, (2014) and is in the process of being written up for submission.
As part of the work towards understanding the volatile behaviour of Zn and Cu, the researcher has collaborated with a group from Charles University, Prague, Czech Republic, looking at how these isotope systems are affected during impact events. This work showed extremely large positive isotope fractionations, especially for Cu, and the results have specific bearing on our understanding of volatile depletion during planetary accretion and differentiation (this work is currently under review in Geochimica et Cosmochimica Acta).
Finally, the researcher has been looking at the mass-independent Zn isotope compositions of primitive meteorites, as a tool to assess volatile redistribution of material in the very early stages of the solar system; this work has been presented at conferences and to be submitted to Geochimica et Cosmochimica Acta shortly.
Zinc isotope anomalies in bulk chondrites, PS Savage, F Moynier, M Boyet. Oral presentation, V.M. Goldschmidt conference, Prague, Czech Republic (2015)
• Final results/potential impact
Understanding the effect of volcanic eruptions on the atmosphere, no matter what type or magnitude, is important in the challenge of quantifying the environmental consequences of such eruptions. These could be geologically significant, such as the example of CFBs and their role in the cause of mass extinction events. Or, they could be much smaller, where the atmospheric effect is less extreme but recordable, for instance the 1883 eruption of Krakatoa volcano. This project aims to provide the scientific community with new isotopic tools to constrain the mechanisms and flux of volatile addition to the atmosphere during CFB eruptions. If CFB eruptions are the cause of mass extinction events, it is likely that atmosphere loading is the most damaging process resulting from these events. Hence, all studies which reveal insights into how eruption of these lavas impacts the atmosphere are important for society.
• Main researcher contact details
Paul Savage, Department of Earth Science, Durham University; email: p.s.savage@dur.ac.uk
The project ‘Isovolc’ aims at furthering our understanding of the effect that continental flood basalt eruptions have on the environment. Continental flood basalt (CFB) volcanism is characterised by the repeated eruption of huge batches of magma over relatively brief intervals of time, and delivering large masses of volcanic gas to the atmosphere. Such eruptions appear to precede many of the mass extinction events that punctuate the history of life on Earth.
The overall objective of this study is to use a multi-isotopic approach to assess the environmental impact of a single CFB eruption, as a result of atmospheric loading. Specifically, the novel stable isotope systems zinc (Zn) and copper (Cu), and the radiogenic rhenium-osmium (Re-Os) system are the geochemical tools proposed to accomplish this research, applied to individual flood basalt flows from the Columbia River Basalt lavas, NW USA. Copper and zinc isotopes will be used to distinguish between the gaseous release of S (as SO2, H2SO4, H2S) versus crystalline or aerosol forms, and Re-Os isotopes will be used to fingerprint the source of magmatic volatiles and the timescales of volatile release during eruption. Ultimately, we want to assess whether single flood basalt eruptions are enough to cause deleterious environmental upset.
• Work performed since the project started
The majority of the work performed since the start of the project has centred on constraining the behaviour of Zn and Cu isotopes during igneous processes (i.e. partial melting, fractional crystallisation) and volatile loss from a magma (degassing), and to providing a global isotopic datum for each system, the ‘bulk silicate Earth’ composition. This began with the analysis of a vast number of well-characterised samples from various geological settings, coupled with geochemical modelling techniques to further constrain processes and reservoirs. Much of these findings have been published, or are being written up for publication: these are listed in the ‘Main results’ section.
This initial work revealed a number of new research questions, in particular relating to the differentiation of Earth, and the processes relating to volatile redistribution of elements in the cooling solar nebula. Following up on these questions has involved the analysis of meteorites and experimental samples, provided in collaboration with the Institut de Physique du Globe, Paris. Finally, the most recent component of the project has been the analysis of samples from individual Colombia River flood basalt eruption flows (Roza and Frenchman Springs); this is almost complete and the data are being interpreted; these results will be presented at conferences over the next 6 months.
• Main results
As part of the run up to the project (before the funding officially started) the researcher investigated how Zn isotopes vary during igneous processes and also to provide a Bulk Earth isotopic reference value. This also involved supervision of a PhD student. This work was published as:
Zinc isotope fractionation during magmatic differentiation and the isotopic composition of the bulk Earth. H Chen, PS Savage, FZ Teng, RT Helz, F Moynier; Earth and Planetary Science Letters 369, 34-42 (2013)
Another key part of the project is investigating how Cu isotopes behave during igneous processes, and also to provide a bulk silicate Earth isotope reference value; again, this work is now published in a high impact factor journal:
Copper isotope evidence for large-scale sulphide fractionation during Earth’s differentiation. PS Savage, F Moynier, H Chen, G Shofner, J Siebert, J Badro, I Puchtel; Geochemical Perspectives Letters 1, 53-64 (2015)
Here, it was discovered that the Cu isotope composition of the mantle is distinct from that of the bulk Earth, as defined by meteorites. This has important significance in terms of the physiochemical conditions that existed when Earth’s core formed and the research was featured in number of popular science and national newspaper websites e.g.:
http://www.livescience.com/51249-earth-core-contains-brimstone.html
Further research on the behaviour of Cu isotopes during igneous processes revealed large variations in the mantle; this has been presented at a number of international conferences, e.g.:
Copper isotope heterogeneity in the lithospheric mantle, PS Savage, J Harvey, F Moynier. Invited oral presentation, V.M. Goldschmidt conference, Sacramento, California, USA, (2014) and is in the process of being written up for submission.
As part of the work towards understanding the volatile behaviour of Zn and Cu, the researcher has collaborated with a group from Charles University, Prague, Czech Republic, looking at how these isotope systems are affected during impact events. This work showed extremely large positive isotope fractionations, especially for Cu, and the results have specific bearing on our understanding of volatile depletion during planetary accretion and differentiation (this work is currently under review in Geochimica et Cosmochimica Acta).
Finally, the researcher has been looking at the mass-independent Zn isotope compositions of primitive meteorites, as a tool to assess volatile redistribution of material in the very early stages of the solar system; this work has been presented at conferences and to be submitted to Geochimica et Cosmochimica Acta shortly.
Zinc isotope anomalies in bulk chondrites, PS Savage, F Moynier, M Boyet. Oral presentation, V.M. Goldschmidt conference, Prague, Czech Republic (2015)
• Final results/potential impact
Understanding the effect of volcanic eruptions on the atmosphere, no matter what type or magnitude, is important in the challenge of quantifying the environmental consequences of such eruptions. These could be geologically significant, such as the example of CFBs and their role in the cause of mass extinction events. Or, they could be much smaller, where the atmospheric effect is less extreme but recordable, for instance the 1883 eruption of Krakatoa volcano. This project aims to provide the scientific community with new isotopic tools to constrain the mechanisms and flux of volatile addition to the atmosphere during CFB eruptions. If CFB eruptions are the cause of mass extinction events, it is likely that atmosphere loading is the most damaging process resulting from these events. Hence, all studies which reveal insights into how eruption of these lavas impacts the atmosphere are important for society.
• Main researcher contact details
Paul Savage, Department of Earth Science, Durham University; email: p.s.savage@dur.ac.uk