Sulfur Recycling at Subduction Zones
Sulfur is a critical element in Earth’s environment. When volcanoes erupt, sulfur is ejected into the atmosphere with cooling effects. Sulfur is also the transport agent and host of economic metals such as lead and zinc. The cluster of factors that control how much sulfur is available to volcanoes and metal deposits is still a major question in science, one that this project seeks to answer. One possible source of sulfur includes the sediments on the seafloor, which are subducted into the Earth to the depths where magmas form. This project is testing this hypothesis by measuring for the first time the sulfur forms and fluxes that feed volcanic systems at different subduction zones. A team of scientists from the US (Prof. Terry Plank - Columbia University), the UK (Prof. Tamsin Mather - Oxford University) and Italy (Prof. Alessandro Aiuppa - University of Palermo) will partner with the Ocean Drilling Program at Texas A&M University and the NERC Ion Microprobe Facility at the University of Edinburgh to make novel measurements of sulfur and its isotopes in sediments and volcanic material. This project, aimed at the very origins of sulfur in magmatic systems, may lead to novel connections between the sulfur supply to ore deposits and volcanic emissions at convergent margins.
This international project targets major unknowns in the sulfur cycle at subduction zones. The US-NSF focus of this project will fill a key knowledge gap in terms of S inputs to the mantle at subduction zones. It will involve extensive analysis of sedimentary sections at the Tonga, Marianas, Aleutians, Alaska and Central America trenches, chosen to represent end-member oceanic environments for sulfur deposition and diagenesis and extreme isotopic variations. Ocean Drilling Programs cores will be analyzed by XRF core scanning, a strategic approach to quantify heterogeneously disseminated pyrite and barite, major hosts of sulfur in sediment. Core scanning results will guide discrete sampling for bulk sulfur and sulfur isotope analyses at the University of Palermo by coupled Elemental Analyzer-Mass Spectrometry with a focus on the sulfide- vs. sulfate-dominated regimes that may occur in a single sedimentary section. The outcome will be the first comprehensive estimates (with uncertainties) for the fluxes and isotopic compositions of S into end-member trenches and improved global estimates. The UK-NERC part of this project will take a novel approach to understanding volcanic arc S outputs. It will measure for the first time the sulfur isotopic composition in undegassed olivine-hosted arc melt inclusions. Planned work will include well-studied melt inclusions suites from the same subducting systems as the sediment targets above. This will ensure close collaboration between the US, UK and Italian parts of this project, and allow for the first-time direct tracing of sulfur isotopes from sediment input to arc output. This project will not only provide the first comprehensive sediment input sulfur fluxes and arc isotopic compositions for any subduction zone, but also test the competing hypotheses that the concentrations and isotopic compositions of arc volcanic sulfur reflect a) the subducted inputs or b) the fractionation of sulfur species and isotopes in the subduction zone.
Publications
Taracsák, Z., Mather, T.A., Ding, S., Plank, T., Brounce, M., Pyle, D.M.
and Aiuppa, A., 2023. Sulfur from the subducted slab dominates the
sulfur budget of the mantle wedge under volcanic arcs. Earth and
Planetary Science Letters, 602, p.117948.
Link to Article
de Moor, J.M., Fischer, T.P. and Plank, T., 2021. Constraints on the sulfur subduction cycle in Central America from sulfur isotope compositions of volcanic gases. Chemical Geology, p.120627.
Link to Article
Ding, S., Plank, T., Wallace, P.J. and Rasmussen, D.J., 2023. Sulfur_X:
A model of sulfur degassing during magma ascent. Geochemistry,
Geophysics, Geosystems, 24(4), p.e2022GC010552.
Link to Article
This international project targets major unknowns in the sulfur cycle at subduction zones. The US-NSF focus of this project will fill a key knowledge gap in terms of S inputs to the mantle at subduction zones. It will involve extensive analysis of sedimentary sections at the Tonga, Marianas, Aleutians, Alaska and Central America trenches, chosen to represent end-member oceanic environments for sulfur deposition and diagenesis and extreme isotopic variations. Ocean Drilling Programs cores will be analyzed by XRF core scanning, a strategic approach to quantify heterogeneously disseminated pyrite and barite, major hosts of sulfur in sediment. Core scanning results will guide discrete sampling for bulk sulfur and sulfur isotope analyses at the University of Palermo by coupled Elemental Analyzer-Mass Spectrometry with a focus on the sulfide- vs. sulfate-dominated regimes that may occur in a single sedimentary section. The outcome will be the first comprehensive estimates (with uncertainties) for the fluxes and isotopic compositions of S into end-member trenches and improved global estimates. The UK-NERC part of this project will take a novel approach to understanding volcanic arc S outputs. It will measure for the first time the sulfur isotopic composition in undegassed olivine-hosted arc melt inclusions. Planned work will include well-studied melt inclusions suites from the same subducting systems as the sediment targets above. This will ensure close collaboration between the US, UK and Italian parts of this project, and allow for the first-time direct tracing of sulfur isotopes from sediment input to arc output. This project will not only provide the first comprehensive sediment input sulfur fluxes and arc isotopic compositions for any subduction zone, but also test the competing hypotheses that the concentrations and isotopic compositions of arc volcanic sulfur reflect a) the subducted inputs or b) the fractionation of sulfur species and isotopes in the subduction zone.
Publications
Taracsák, Z., Mather, T.A., Ding, S., Plank, T., Brounce, M., Pyle, D.M.
and Aiuppa, A., 2023. Sulfur from the subducted slab dominates the
sulfur budget of the mantle wedge under volcanic arcs. Earth and
Planetary Science Letters, 602, p.117948.
Link to Article
de Moor, J.M., Fischer, T.P. and Plank, T., 2021. Constraints on the sulfur subduction cycle in Central America from sulfur isotope compositions of volcanic gases. Chemical Geology, p.120627.
Link to Article
Ding, S., Plank, T., Wallace, P.J. and Rasmussen, D.J., 2023. Sulfur_X:
A model of sulfur degassing during magma ascent. Geochemistry,
Geophysics, Geosystems, 24(4), p.e2022GC010552.
Link to Article
Research Overview
Volatile Cycling
 X-ray tomography image of melt inclusions (orange) inside olivine (green). Image credit: Henry Towbin
Water, CO2 and S are critical volatile components that drive melting in the earth and explosive eruptions, that affect climate and planetary redox, and that presage magma ascent and eruption and form ore deposits. Our work in this area focuses on both seafloor volatile inputs to subduction zones and volcanic volatile outputs. Research areas include the budgets of volatile elements that feed different deep sea trenches – the carbon stored in carbonate vs. organic carbon, and the sulfur stored in sulfide vs. sulfate. C and S isotopes are potential tracers of the fate of these different volatile species, and the extent to whether they return to the earth’s surface as volcanic gases or continue to subduct into the deep mantle. The study of volcanic volatiles relies on melt inclusions trapped inside crystals, as they may be isolated from the effects of degassing. We mine melt inclusions in well-quenched tephra to obtain first-order information on the volatile contents of magmas and their evolution during degassing.
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Volcanism
 Fuego Volcano, 2018:
Credit: Photo: Matt Tumas
Volcanoes are clearly a hazard when they erupt explosively, but they are also portals to melting regions inside Earth. We study both aspects of volcanism. Our work on volatiles links to eruption, and diffusion profiles clock magma ascent prior to eruption. Our work on volatile barometry and magma ascent leads to a new understanding of where magmas stall and assemble and why some eruptions are more explosive than others. We also study volcanic eruptions that bring pieces of the mantle to the surface, and primitive magmas that encode in their chemical composition the pressures and temperatures of their origin. We are establishing real-time multi-sensor arrays on volcanoes to link signals of unrest to petrological constraints on the P-T-X evolution of magma in the run-up to eruption, necessary for developing physics-based eruption forecasts. Projects have taken us to Kilauea, Central America, the Basin and Range and the Aleutian Islands of Alaska.
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AVERT: Anticipating Volcanic Eruptions in Real-Time
Cleveland Volcano, one of the most active volcanoes in the US, sits in the Islands of Four Mountains group of the Aleutian chain. In this image of its summit vent, Carlile Island volcano lies in the background. Credit: Max Kaufman/Alaska Volcano Observatory/University of Alaska Fairbanks, Geophysical Institute
This project, funded by the Gordon and Betty Moore Foundation, will establish the first open-data, real-time, multi-sensor community experiment on active volcanoes. This project is novel not only because it will provide an array of different data streams (seismic, GPS, gas, infrasound and magnetic) but because data will be openly available in near-real time. New high-bandwidth communication satellite constellations now provide the capabilities necessary for real-time monitoring even in the most remote locations. Open, continuous data-streams in place before volcanic eruptions promise to revolutionize the field of volcanology by first increasing scientific understanding of eruptions and then driving the development of forecasts that are timely within the hours to months of “run-up” to eruptions, and improving forecasts as real-time data streams in. This project serves as the first community experiment focused on anticipating eruptions, with open invitations to partners providing support of instrumentation, expertise or analysis.
Fundamental volcano-science questions center around the different roles of magma vs. gas flux in fueling and triggering eruptions. It is currently impossible to answer these questions without contemporary pre-eruption time-series from seismometers sensitive to magma movement, gas instruments that measure the degassing process as magma evolves toward eruption, and geodetic measurements of the rate of volume change in the magma reservoir. Such data have individually shown precursory signals prior to recent eruptions, but are rarely collected in concert and used in real-time to build forecasts.
The targets for AVERT are two neighboring volcanoes, Okmok and Cleveland in Alaska, which both erupt frequently and explosively and are currently displaying different signs of unrest. Okmok is a “closed” volcano; the ground surface has been uplifting for years, a signal that has been hindcast to reveal stress-driven triggering weeks prior to the 2008 eruption. We will augment the existing Okmok network to a total of 8 continuous GPS instruments to inform real-time forecast models. Cleveland is an “open” volcano, currently extruding a lava dome and commonly emitting a gas plume, and yet these gases are not measured in real-time. AVERT will bring both new GPS and gas data streams to Cleveland, and create a robust seismic array to augment the single existing instrument. The multi-sensor arrays on Okmok and Cleveland will serve as testbeds for the developing capabilities of satellite telemetry.
Website
Fundamental volcano-science questions center around the different roles of magma vs. gas flux in fueling and triggering eruptions. It is currently impossible to answer these questions without contemporary pre-eruption time-series from seismometers sensitive to magma movement, gas instruments that measure the degassing process as magma evolves toward eruption, and geodetic measurements of the rate of volume change in the magma reservoir. Such data have individually shown precursory signals prior to recent eruptions, but are rarely collected in concert and used in real-time to build forecasts.
The targets for AVERT are two neighboring volcanoes, Okmok and Cleveland in Alaska, which both erupt frequently and explosively and are currently displaying different signs of unrest. Okmok is a “closed” volcano; the ground surface has been uplifting for years, a signal that has been hindcast to reveal stress-driven triggering weeks prior to the 2008 eruption. We will augment the existing Okmok network to a total of 8 continuous GPS instruments to inform real-time forecast models. Cleveland is an “open” volcano, currently extruding a lava dome and commonly emitting a gas plume, and yet these gases are not measured in real-time. AVERT will bring both new GPS and gas data streams to Cleveland, and create a robust seismic array to augment the single existing instrument. The multi-sensor arrays on Okmok and Cleveland will serve as testbeds for the developing capabilities of satellite telemetry.
Website
Carbon Recycling at Subduction Zones
Map of subduction systems that isolate different carbon inputs.
Carb, carbonate; OrgC, organic carbon; Sed, sediment; Serp, serpentinite; C/S, CO2/S ratio. Credit: Plank & Manning (2019)
In addition to its familiar cycling between the terrestrial biosphere and atmosphere, carbon moves from microfossils on the seafloor to erupting volcanoes and deep diamonds, in a cycle driven by plate tectonics. Subduction links surface biological processes with the deep Earth, creating a planet suffused with the signature of life. The fate and flux of carbon vary from trench to trench, as every subducting slab delivers to the mantle a singular mix of organic and inorganic carbon that heats and pressurizes at a particular rate determined by its age and convergence speed. The study of carbon is challenging due to its heterogeneous distribution on the seafloor as carbonate and organic carbon, and due to its deep exsolution into a gas phase during arc magmatism.
The subduction of sedimentary carbonate is rare today, due to the small fraction of subducting seafloor that has ever been above the calcite compensation depth. Recent in situ measurements of volcanic gas CO2 and S, combined with decades of campaign measurements, have revealed higher CO2/S gases emitted from volcanoes where carbonate sediment subducts, notably Central America, Columbia and New Zealand. Such gas signals represent among the first strong evidence for carbonate recycling at subduction zones. Seafloor sediments approach subduction zones with small amounts (generally < 1 wt%) of organic carbon (OC), but this small concentration nonetheless constitutes a significant flux over geological time with respect to the size, isotopic composition and electron balance of the exosphere. Sites with the greatest concentration of OC include those that receive terrigenous turbidites (e.g., Bengal Fan, Gulf of Alaska, etc.). We are using the mass balance of carbonate and OC to predict the isotopic composition of carbon subducting beneath each volcano along arc segments. Some regions will be dominated by subducting OC, and thus light carbon isotopes relative to the mantle. New carbon isotope data on volcanic gases will provide a new test for recycling of organic carbon at subduction zones. Project Collaborators: Alberto Malinverno (LDEO), Alessandro Aiuppa (Palermo) and Craig Manning (UCLA).
Publications
Lopez, T., Fischer, T.P., Plank, T., Malinverno, A., Rizzo, A.L., Rasmussen, D.J., Cottrell, E., Werner, C., Kern, C., Bergfeld, D. and Ilanko, T., 2023. Tracking carbon from subduction to outgassing along the Aleutian-Alaska Volcanic Arc. Science Advances, 9(26), p.eadf3024.
Link to Article
Plank, T., & Manning, C. E. Subducting carbon. Nature, 574(7778), 343-352.
Link to Article
Plank, T., Malinverno, A. and Manning, C.E. Subducting Carbon: Heterogeneity Rules. In AGU Fall Meeting 2021. AGU.
Link to Abstract
The subduction of sedimentary carbonate is rare today, due to the small fraction of subducting seafloor that has ever been above the calcite compensation depth. Recent in situ measurements of volcanic gas CO2 and S, combined with decades of campaign measurements, have revealed higher CO2/S gases emitted from volcanoes where carbonate sediment subducts, notably Central America, Columbia and New Zealand. Such gas signals represent among the first strong evidence for carbonate recycling at subduction zones. Seafloor sediments approach subduction zones with small amounts (generally < 1 wt%) of organic carbon (OC), but this small concentration nonetheless constitutes a significant flux over geological time with respect to the size, isotopic composition and electron balance of the exosphere. Sites with the greatest concentration of OC include those that receive terrigenous turbidites (e.g., Bengal Fan, Gulf of Alaska, etc.). We are using the mass balance of carbonate and OC to predict the isotopic composition of carbon subducting beneath each volcano along arc segments. Some regions will be dominated by subducting OC, and thus light carbon isotopes relative to the mantle. New carbon isotope data on volcanic gases will provide a new test for recycling of organic carbon at subduction zones. Project Collaborators: Alberto Malinverno (LDEO), Alessandro Aiuppa (Palermo) and Craig Manning (UCLA).
Publications
Lopez, T., Fischer, T.P., Plank, T., Malinverno, A., Rizzo, A.L., Rasmussen, D.J., Cottrell, E., Werner, C., Kern, C., Bergfeld, D. and Ilanko, T., 2023. Tracking carbon from subduction to outgassing along the Aleutian-Alaska Volcanic Arc. Science Advances, 9(26), p.eadf3024.
Link to Article
Plank, T., & Manning, C. E. Subducting carbon. Nature, 574(7778), 343-352.
Link to Article
Plank, T., Malinverno, A. and Manning, C.E. Subducting Carbon: Heterogeneity Rules. In AGU Fall Meeting 2021. AGU.
Link to Abstract
Rapid Magma Ascent Recorded in Volatile Diffusion Profiles
Field crew on Etna. Front row left to right: Rosanna Corsaro, Terry Plank, Daniele Andronico.
Back row: Tom McNeill, Anna Barth, Bruce Houghton
What makes some eruptions more explosive than others? This fundamental questions is still largely unanswered, even after a given eruption has occurred. Theories link eruptive vigor to the amount of gas and stiffness of the magma, but magmas that have similar stiffness and gas-forming species can still erupt in a wide range of styles, some highly explosive, some quiescent. This project explores another fundamental parameter – the rate at which magma rises in the volcanic conduit prior to eruption. The magma ascent rate will affect eruptive volume and vigor and also how bubbles form, grow and coalesce. In general, slow magma rise leads to more efficient bubble separation and less explosive eruption. This project aims to test the control of magma rise speed by extracting timescale information from erupted crystals and glass for several eruptions that span a range of exlosive magnitudes.
This project takes advantage of new developments in using the zonation of volatile species in glass and crystals to obtain diffusive timescales that reflect ascent on the order of minutes to days prior to eruption. Four different chronometers are used: 1) multi-species volatile diffusion through melt embayments, 2) water loss through olivine from melt inclusions of different sizes, 3) water zonation in olivine and clinopyroxene, and 4) zonation inside melt inclusions. Data are obtained from different microbeam techniques (NanoSIMS, FTIR, electron probe, laser ablation ICPMS) that record chemical zonation at the resolution of 5-25 microns. The proposed targets are a pair of well-documented eruptions from each of three volcanoes: Etna (2001 and 3930BP), Cerro Negro (1992 and 1995) and Paricutin (1943 and 1948), which span the range in mass eruption rates that characterize the transition from strombolian to subplinian styles. The eruptions targeted are specifically designed to test ideas as to the relationship between ascent rate and eruption rate in hydrous mafic magmas, among the most common but least well understood eruptions.
Publications
Rasmussen, D.J., Plank, T.A., Roman, D.C. and Zimmer, M.M., 2022. Magmatic water content controls the pre-eruptive depth of arc magmas. Science, 375(6585), pp.1169-1172.
Link to Article
Barth, A., Plank, T. and Towbin, H., 2023. Rates of dehydration in hydrous, high-Fo, magmatic olivines. Geochimica et Cosmochimica Acta, 342, pp.62-73.
Link to Article
Barth, Anna, Megan Newcombe, Terry Plank, Helge Gonnermann, Sahand Hajimirza, Gerardo Soto, Armando Saballos, and Erik Hauri. "Magma decompression rate correlates with explosivity at basaltic volcanoes—Constraints from water diffusion in olivine." Journal of Volcanology and Geothermal Research (2019): 106664.
Link to Article
Barth, A. and Plank, T., 2021. The ins and outs of water in olivine-hosted melt inclusions: hygrometer vs. speedometer. Frontiers in Earth Science, 9, p.343.
Link to Article
This project takes advantage of new developments in using the zonation of volatile species in glass and crystals to obtain diffusive timescales that reflect ascent on the order of minutes to days prior to eruption. Four different chronometers are used: 1) multi-species volatile diffusion through melt embayments, 2) water loss through olivine from melt inclusions of different sizes, 3) water zonation in olivine and clinopyroxene, and 4) zonation inside melt inclusions. Data are obtained from different microbeam techniques (NanoSIMS, FTIR, electron probe, laser ablation ICPMS) that record chemical zonation at the resolution of 5-25 microns. The proposed targets are a pair of well-documented eruptions from each of three volcanoes: Etna (2001 and 3930BP), Cerro Negro (1992 and 1995) and Paricutin (1943 and 1948), which span the range in mass eruption rates that characterize the transition from strombolian to subplinian styles. The eruptions targeted are specifically designed to test ideas as to the relationship between ascent rate and eruption rate in hydrous mafic magmas, among the most common but least well understood eruptions.
Publications
Rasmussen, D.J., Plank, T.A., Roman, D.C. and Zimmer, M.M., 2022. Magmatic water content controls the pre-eruptive depth of arc magmas. Science, 375(6585), pp.1169-1172.
Link to Article
Barth, A., Plank, T. and Towbin, H., 2023. Rates of dehydration in hydrous, high-Fo, magmatic olivines. Geochimica et Cosmochimica Acta, 342, pp.62-73.
Link to Article
Barth, Anna, Megan Newcombe, Terry Plank, Helge Gonnermann, Sahand Hajimirza, Gerardo Soto, Armando Saballos, and Erik Hauri. "Magma decompression rate correlates with explosivity at basaltic volcanoes—Constraints from water diffusion in olivine." Journal of Volcanology and Geothermal Research (2019): 106664.
Link to Article
Barth, A. and Plank, T., 2021. The ins and outs of water in olivine-hosted melt inclusions: hygrometer vs. speedometer. Frontiers in Earth Science, 9, p.343.
Link to Article
Water in the Lithosphere: The Fidelity of Mantle Xenoliths
Mantle xenolith (green) within basaltic bomb (black). Henry Towbin's hand for scale.
The tectonic plates, formed from the outer rigid shell of Earth (termed lithosphere), have a long term strength and evolution that depends on the amount of water contained in mantle minerals. Water inserts itself into mineral defects, in places where Mg or Si are missing from the lattice, and in so doing, weakens the mineral structure. The primary way the water content of the mantle lithosphere is known is through study of xenoliths, pieces of the mantle that get accidently entrained in ascending magma and erupted out volcanoes. Recent research, however, has shown that water can sometimes be gained or lost from minerals at magmatic temperatures (>1000°C) in a matter of minutes. If this is true, then the fidelity of mantle xenoliths is questioned. Xenoliths would not necessarily preserve the concentrations they had in the mantle (> 40 km depth), but be reset to the concentration in the magma that conveyed them to the surface. Additionally, water may be lost during degassing, eruption and cooling in lava flows. If this is true, then most of the existing measurements of water in mantle xenoliths would have to be reinterpreted, and many notions about the strength of the lithosphere reconsidered. This projects aims to determine the fidelity of the water record in mantle xenoliths by intensive study of xenoliths in their context – their size and the water content of their host magma.
This project proposes three different approaches. 1) Study of xenolith-host magma pairs. Most xenoliths studies are carried out in the absence of data on the H2O content of the host magma and thus without constraints on the boundary conditions for H2O exchange. The simple test is whether xenolith minerals and host magma phenocrysts and melt inclusions reflect H2O equilibration. Pilot data on xenolith clinopyroxene and host magma melt inclusions are consistent with H2O equilibration. 2) Study of diffusive lengthscale relationships as a function of grain size, position within the xenolith, and xenolith size. If there is diffusive exchange, then small grains should reflect greater equilibration than large ones. Large xenolith clasts will cool more slowly post-eruption, and may reflect greater extents of dehydration. 3) Study of site-specific zonation patterns in xenolithic olivines and pyroxenes. H is associated with several point defects in both olivine and pyroxene, as identified by specific infrared (IR) absorption bands, and some may diffuse slowly enough to survive hours of transport in hot magma, while others will record degassing and H2O-loss. We address each of these tests with an IR study of olivines and pyroxenes in variably-sized peridotite xenoliths erupted in alkali basalt cinder cones from the western US (Cima and Grand Canyon volcanic fields).
Publications
Towbin et al. (2018) Testing the Fidelity of Peridotite Xenoliths as Records of Water in the Lithospheric Mantle. AGU Fall Meeting.
Link to Article
Towbin, W.H. and Plank, T.A., 2019, December. Origin of Melt Veins in Peridotite Xenoliths. In AGU Fall Meeting Abstracts (Vol. 2019, pp. V11A-01).
Link to Abstract
This project proposes three different approaches. 1) Study of xenolith-host magma pairs. Most xenoliths studies are carried out in the absence of data on the H2O content of the host magma and thus without constraints on the boundary conditions for H2O exchange. The simple test is whether xenolith minerals and host magma phenocrysts and melt inclusions reflect H2O equilibration. Pilot data on xenolith clinopyroxene and host magma melt inclusions are consistent with H2O equilibration. 2) Study of diffusive lengthscale relationships as a function of grain size, position within the xenolith, and xenolith size. If there is diffusive exchange, then small grains should reflect greater equilibration than large ones. Large xenolith clasts will cool more slowly post-eruption, and may reflect greater extents of dehydration. 3) Study of site-specific zonation patterns in xenolithic olivines and pyroxenes. H is associated with several point defects in both olivine and pyroxene, as identified by specific infrared (IR) absorption bands, and some may diffuse slowly enough to survive hours of transport in hot magma, while others will record degassing and H2O-loss. We address each of these tests with an IR study of olivines and pyroxenes in variably-sized peridotite xenoliths erupted in alkali basalt cinder cones from the western US (Cima and Grand Canyon volcanic fields).
Publications
Towbin et al. (2018) Testing the Fidelity of Peridotite Xenoliths as Records of Water in the Lithospheric Mantle. AGU Fall Meeting.
Link to Article
Towbin, W.H. and Plank, T.A., 2019, December. Origin of Melt Veins in Peridotite Xenoliths. In AGU Fall Meeting Abstracts (Vol. 2019, pp. V11A-01).
Link to Abstract
