Volatile Elements

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Frederic Moynier - One of the best experts on this subject based on the ideXlab platform.

  • Evaporation of moderately Volatile Elements from silicate melts: experiments and theory
    Geochimica et Cosmochimica Acta, 2019
    Co-Authors: Paolo A. Sossi, Jasper Berndt, Stephan Klemme, Hugh St. C. O'neill, Frederic Moynier
    Abstract:

    Abstract Moderately Volatile Elements (MVEs) are sensitive tracers of vaporisation in geological and cosmochemical processes owing to their balanced partitioning between vapour and condensed phases. Differences in their volatilities allows the thermodynamic conditions, particularly temperature and oxygen fugacity ( f O 2 ), at which vaporisation occurred to be quantified. However, this exercise is hindered by a lack of experimental data relevant to the evaporation of MVEs from silicate melts. We report a series of experiments in which silicate liquids are evaporated in one-atmosphere (1-atm) gas-mixing furnaces under controlled f O 2 s, from the Fe-“FeO” buffer (iron-wustite, IW) to air (10 -0.68 bars), bracketing the range of most magmatic rocks. Time- ( t ) and temperature ( T) series were conducted from 15 to 930 minutes and 1300-1550°C, at or above the liquidus for a synthetic ferrobasalt, to which 20 Elements, each at 1000 ppm, were added. Refractory Elements ( e.g. , Ca, Sc, V, Zr, REE) are quantitatively retained in the melt under all conditions. The MVEs show highly redox-dependent volatilities, where the extent of element loss as a function of f O 2 depends on the stoichiometry of the evaporation reaction(s), each of which has the general form M x+ n O (x+ n )/2 = M x O x/2 + n /4O 2 . Where n is positive (as in most cases), the oxidation state of the element in the gas is more reduced than in the liquid, meaning lower oxygen fugacity promotes evaporation. We develop a general framework, by integrating element vaporisation stoichiometries with Hertz-Knudsen-Langmuir (HKL) theory, to quantify evaporative loss as a function of t , T and f O 2 . Element volatilities from silicate melts differ from those during solar nebular condensation, and can thus constrain the conditions of Volatile loss in post-nebular processes. Evaporation in a single event strongly discriminates between MVEs, producing a step-like abundance pattern in the residuum, similar to that observed in the Moon or Vesta. Contrastingly, the gradual depletion of MVEs according to their volatility in the Earth is inconsistent with their loss in a single evaporation event, and instead likely reflects accretion from many smaller bodies that had each experienced different degrees of volatilisation.

  • gallium isotopic evidence for the fate of moderately Volatile Elements in planetary bodies and refractory inclusions
    Earth and Planetary Science Letters, 2017
    Co-Authors: Chizu Kato, Frederic Moynier
    Abstract:

    Abstract The abundance of moderately Volatile Elements, such as Zn and Ga, show variable depletion relative to CI between the Earth and primitive meteorite (chondrites) parent bodies. Furthermore, the first solar system solids, the calcium–aluminum-rich inclusions (CAIs), are surprisingly rich in Volatile element considering that they formed under high temperatures. Here, we report the Ga elemental and isotopic composition of a wide variety of chondrites along with five individual CAIs to understand the origin of the Volatile Elements and to further characterize the enrichment of the Volatile Elements in high temperature condensates. The δ 71 Ga (permil deviation of the 71Ga/69Ga ratio from the Ga IPGP standard) of carbonaceous chondrites decreases in the order of CI > CM > CO > CV and is inversely correlated with the Al/Ga ratio. This implies that the Ga budget of the carbonaceous chondrites parent bodies were inherited from a two component mixing of a Volatile rich reservoir enriched in heavy isotope of Ga and a Volatile poor reservoir enriched in light isotope of Ga. Calcium–aluminum-rich inclusions are enriched in Ga and Zn compared to the bulk meteorite and are both highly isotopically fractionated with δ 71 Ga down to −3.56‰ and δ 66 Zn down to −0.74‰. The large enrichment in the light isotopes of Ga and Zn in the CAIs implies that the moderately Volatile Elements were introduced in the CAIs during condensation in the solar nebula as opposed to secondary processing in the meteorite parent body and supports a change in gas composition in which CAIs were formed.

  • gallium isotopic evidence for extensive Volatile loss from the moon during its formation
    Science Advances, 2017
    Co-Authors: Chizu Kato, Frederic Moynier
    Abstract:

    The distribution and isotopic composition of Volatile Elements in planetary materials holds a key to the characterization of the early solar system and the Moon’s formation. The Moon and Earth are chemically and isotopically very similar. However, the Moon is highly depleted in Volatile Elements and the origin of this depletion is still debated. We present gallium isotopic and elemental measurements in a large set of lunar samples to constrain the origin of this Volatile depletion. We show that while Ga has a geochemical behavior different from zinc, both Elements show a systematic enrichment in the heavier isotopes in lunar mare basalts and Mg-suite rocks compared to the silicate Earth, pointing to a global-scale depletion event. On the other hand, the ferroan anorthosites are isotopically heterogeneous, suggesting a secondary distribution of Ga at the surface of the Moon by volatilization and condensation. The isotopic difference of Ga between Earth and the Moon and the isotopic heterogeneity of the crustal ferroan anorthosites suggest that the Volatile depletion occurred following the giant impact and during the lunar magma ocean phase. These results point toward a Moon that has lost its Volatile Elements during a whole-scale evaporation event and that is now relatively dry compared to Earth.

  • Silicon isotopes in angrites and Volatile loss in planetesimals
    Proceedings of the National Academy of Sciences of the United States of America, 2014
    Co-Authors: Emily A. Pringle, Frederic Moynier, Paul S. Savage, J. Badro, Jean-alix Barrat
    Abstract:

    Inner solar system bodies, including the Earth, Moon, and asteroids, are depleted in Volatile Elements relative to chondrites. Hypotheses for this Volatile element depletion include incomplete condensation fromthe solar nebula and Volatile loss during energetic impacts. These processes are expected to each produce characteristic stable isotope signatures. However, processes of planetary differentiation may also modify the isotopic composition of geochemical reservoirs. Angrites are rare meteorites that crystallized only a few million years after calcium - aluminum-rich inclusions and exhibit extreme depletions in Volatile Elements relative to chondrites, making them ideal samples with which to study Volatile element depletion in the early solar system. Here we present high-precision Si isotope data that show angrites are enriched in the heavy isotopes of Si relative to chondritic meteorites by 50-100 ppm/amu. Silicon is sufficiently Volatile such that it may be isotopically fractionated during incomplete condensation or evaporative mass loss, but theoretical calculations and experimental results also predict isotope fractionation under specific conditions of metal-silicate differentiation. We show that the Si isotope composition of angrites cannot be explained by any plausible core formation scenario, but rather reflects isotope fractionation during impact-induced evaporation. Our results indicate planetesimals initially formed from Volatile-rich material and were subsequently depleted in Volatile Elements during accretion.

  • Evaporative fractionation of Volatile stable isotopes and their bearing on the origin of the Moon
    Philosophical transactions. Series A Mathematical physical and engineering sciences, 2014
    Co-Authors: James M.d. Day, Frederic Moynier
    Abstract:

    The Moon is depleted in Volatile Elements relative to the Earth and Mars. Low abundances of Volatile Elements, fractionated stable isotope ratios of S, Cl, K and Zn, high μ (238U/204Pb) and long-term Rb/Sr depletion are distinguishing features of the Moon, relative to the Earth. These geochemical characteristics indicate both inheritance of Volatile-depleted materials that formed the Moon and planets and subsequent evaporative loss of Volatile Elements that occurred during lunar formation and differentiation. Models of Volatile loss through localized eruptive degassing are not consistent with the available S, Cl, Zn and K isotopes and abundance data for the Moon. The most probable cause of Volatile depletion is global-scale evaporation resulting from a giant impact or a magma ocean phase where inefficient Volatile loss during magmatic convection led to the present distribution of Volatile Elements within mantle and crustal reservoirs. Problems exist for models of planetary Volatile depletion following giant impact. Most critically, in this model, the Volatile loss requires preferential delivery and retention of late-accreted Volatiles to the Earth compared with the Moon. Different proportions of late-accreted mass are computed to explain present-day distributions of Volatile and moderately Volatile Elements (e.g. Pb, Zn; 5 to >10%) relative to highly siderophile Elements (approx. 0.5%) for the Earth. Models of early magma ocean phases may be more effective in explaining the Volatile loss. Basaltic materials (e.g. eucrites and angrites) from highly differentiated airless asteroids are Volatile-depleted, like the Moon, whereas the Earth and Mars have proportionally greater Volatile contents. Parent-body size and the existence of early atmospheres are therefore likely to represent fundamental controls on planetary Volatile retention or loss.

Jasper Berndt - One of the best experts on this subject based on the ideXlab platform.

  • Trace element partitioning between sulfide-, metal- and silicate melts at highly reduced conditions : Insights into the distribution of Volatile Elements during core formation in reduced bodies
    Icarus, 2020
    Co-Authors: E. S. Steenstra, Jasper Berndt, Stephan Klemme, V.t. Trautner, W. Van Westrenen
    Abstract:

    Abstract Chalcophile and siderophile element abundances are used to provide important constraints on the interior compositions of planetary bodies as well as the pressure (P) - temperature (T) conditions that prevailed during core formation. The oxygen fugacity (fO2) during core formation varied considerably between the various terrestrial planets and asteroidal bodies in our solar system. Mercury, the aubrite parent body (AuPB) and some terrestrial precursor bodies may have differentiated at highly reduced conditions. At present knowledge about how the metal liquid-silicate melt and sulfide liquid-silicate melt partitioning behavior of major and trace Elements are affected by high S concentrations in the silicate melt at highly reducing conditions is incomplete. Here, we experimentally study the metal-silicate and sulfide-silicate partitioning behavior of trace Elements in reduced silicate melts over a wide range of S contents as a function of redox state at 1 GPa and 1833–1883 K. Silicate melt S contents ranged between ~0.5 and ~20 wt%, with a corresponding silicate FeO range of ~0.4 to ~17.5 wt%, in a fO2 range between 1 and 9 log units below the iron-wustite buffer. Our results reproduce the decrease of the S concentration at sulfide saturation (SCSS) with decreasing FeO contents down to ~3 wt%, as well as its strong increase at 6–9 wt% S, the FeO contents increase again. Results show that most Elements (Mg, Ti, V, Cr, Mn, Cu, Zn, Se, Nb, Cd, Sb, Te, Ta, Tl, Pb and Bi) are more chalcophile than siderophile at reducing conditions, whereas Si, Co, Ni, Ga, Ge, Mo and W preferentially partition into Fe-rich melts instead of sulfide liquids. Silicon, Ti, Se, and Te preferentially partition into Fe-S over (Fe,Mg,Ca)-S liquids, whereas Mn, Zn and Cd are more compatible in the latter. As proposed by Wood and Kiseeva (2015), chalcophile Elements such as Cu, Se and Te behave less chalcophile with increasing S concentrations of the silicate melt, whereas the opposite is observed for nominally lithophile Elements such as Mg, Ca and Ti. The results can be used to improve interpretations of the observed trace element systematics of aubrites and other reduced achondrites. All of the Volatile Elements considered here behave chalcophile at the reducing conditions inferred for differentiation of the AuPB. A significant degree of the observed Volatile element depletions in aubrites may therefore reflect their preferential partitioning into sulfide liquids, rather than degassing during or after differentiation of the AuPB. These results suggest that, depending of the extent of core merging, precursor body differentiation and the efficiency of sulfide liquid segregation, reduced precursor bodies that were incorporated in the early Earth were likely more rich in Volatile Elements than currently assumed.

  • Evaporation of moderately Volatile Elements from silicate melts: experiments and theory
    Geochimica et Cosmochimica Acta, 2019
    Co-Authors: Paolo A. Sossi, Jasper Berndt, Stephan Klemme, Hugh St. C. O'neill, Frederic Moynier
    Abstract:

    Abstract Moderately Volatile Elements (MVEs) are sensitive tracers of vaporisation in geological and cosmochemical processes owing to their balanced partitioning between vapour and condensed phases. Differences in their volatilities allows the thermodynamic conditions, particularly temperature and oxygen fugacity ( f O 2 ), at which vaporisation occurred to be quantified. However, this exercise is hindered by a lack of experimental data relevant to the evaporation of MVEs from silicate melts. We report a series of experiments in which silicate liquids are evaporated in one-atmosphere (1-atm) gas-mixing furnaces under controlled f O 2 s, from the Fe-“FeO” buffer (iron-wustite, IW) to air (10 -0.68 bars), bracketing the range of most magmatic rocks. Time- ( t ) and temperature ( T) series were conducted from 15 to 930 minutes and 1300-1550°C, at or above the liquidus for a synthetic ferrobasalt, to which 20 Elements, each at 1000 ppm, were added. Refractory Elements ( e.g. , Ca, Sc, V, Zr, REE) are quantitatively retained in the melt under all conditions. The MVEs show highly redox-dependent volatilities, where the extent of element loss as a function of f O 2 depends on the stoichiometry of the evaporation reaction(s), each of which has the general form M x+ n O (x+ n )/2 = M x O x/2 + n /4O 2 . Where n is positive (as in most cases), the oxidation state of the element in the gas is more reduced than in the liquid, meaning lower oxygen fugacity promotes evaporation. We develop a general framework, by integrating element vaporisation stoichiometries with Hertz-Knudsen-Langmuir (HKL) theory, to quantify evaporative loss as a function of t , T and f O 2 . Element volatilities from silicate melts differ from those during solar nebular condensation, and can thus constrain the conditions of Volatile loss in post-nebular processes. Evaporation in a single event strongly discriminates between MVEs, producing a step-like abundance pattern in the residuum, similar to that observed in the Moon or Vesta. Contrastingly, the gradual depletion of MVEs according to their volatility in the Earth is inconsistent with their loss in a single evaporation event, and instead likely reflects accretion from many smaller bodies that had each experienced different degrees of volatilisation.

  • The lunar core can be a major reservoir for Volatile Elements S, Se, Te and Sb.
    Scientific reports, 2017
    Co-Authors: E. S. Steenstra, Yanhao Lin, Dian Dankers, N. Rai, Jasper Berndt, S. Matveev, Wim Van Westrenen
    Abstract:

    The Moon bears a striking compositional and isotopic resemblance to the bulk silicate Earth (BSE) for many Elements, but is considered highly depleted in many Volatile Elements compared to BSE due to high-temperature Volatile loss from Moon-forming materials in the Moon-forming giant impact and/or due to evaporative loss during subsequent magmatism on the Moon. Here, we use high-pressure metal-silicate partitioning experiments to show that the observed low concentrations of Volatile Elements sulfur (S), selenium (Se), tellurium (Te), and antimony (Sb) in the silicate Moon can instead reflect core-mantle equilibration in a largely to fully molten Moon. When incorporating the core as a reservoir for these Elements, their bulk Moon concentrations are similar to those in the present-day bulk silicate Earth. This suggests that Moon formation was not accompanied by major loss of S, Se, Te, Sb from Moon-forming materials, consistent with recent indications from lunar carbon and S isotopic compositions of primitive lunar materials. This is in marked contrast with the losses of other Volatile Elements (e.g., K, Zn) during the Moon-forming event. This discrepancy may be related to distinctly different cosmochemical behavior of S, Se, Te and Sb within the proto-lunar disk, which is as of yet virtually unconstrained.

E. S. Steenstra - One of the best experts on this subject based on the ideXlab platform.

  • Trace element partitioning between sulfide-, metal- and silicate melts at highly reduced conditions : Insights into the distribution of Volatile Elements during core formation in reduced bodies
    Icarus, 2020
    Co-Authors: E. S. Steenstra, Jasper Berndt, Stephan Klemme, V.t. Trautner, W. Van Westrenen
    Abstract:

    Abstract Chalcophile and siderophile element abundances are used to provide important constraints on the interior compositions of planetary bodies as well as the pressure (P) - temperature (T) conditions that prevailed during core formation. The oxygen fugacity (fO2) during core formation varied considerably between the various terrestrial planets and asteroidal bodies in our solar system. Mercury, the aubrite parent body (AuPB) and some terrestrial precursor bodies may have differentiated at highly reduced conditions. At present knowledge about how the metal liquid-silicate melt and sulfide liquid-silicate melt partitioning behavior of major and trace Elements are affected by high S concentrations in the silicate melt at highly reducing conditions is incomplete. Here, we experimentally study the metal-silicate and sulfide-silicate partitioning behavior of trace Elements in reduced silicate melts over a wide range of S contents as a function of redox state at 1 GPa and 1833–1883 K. Silicate melt S contents ranged between ~0.5 and ~20 wt%, with a corresponding silicate FeO range of ~0.4 to ~17.5 wt%, in a fO2 range between 1 and 9 log units below the iron-wustite buffer. Our results reproduce the decrease of the S concentration at sulfide saturation (SCSS) with decreasing FeO contents down to ~3 wt%, as well as its strong increase at 6–9 wt% S, the FeO contents increase again. Results show that most Elements (Mg, Ti, V, Cr, Mn, Cu, Zn, Se, Nb, Cd, Sb, Te, Ta, Tl, Pb and Bi) are more chalcophile than siderophile at reducing conditions, whereas Si, Co, Ni, Ga, Ge, Mo and W preferentially partition into Fe-rich melts instead of sulfide liquids. Silicon, Ti, Se, and Te preferentially partition into Fe-S over (Fe,Mg,Ca)-S liquids, whereas Mn, Zn and Cd are more compatible in the latter. As proposed by Wood and Kiseeva (2015), chalcophile Elements such as Cu, Se and Te behave less chalcophile with increasing S concentrations of the silicate melt, whereas the opposite is observed for nominally lithophile Elements such as Mg, Ca and Ti. The results can be used to improve interpretations of the observed trace element systematics of aubrites and other reduced achondrites. All of the Volatile Elements considered here behave chalcophile at the reducing conditions inferred for differentiation of the AuPB. A significant degree of the observed Volatile element depletions in aubrites may therefore reflect their preferential partitioning into sulfide liquids, rather than degassing during or after differentiation of the AuPB. These results suggest that, depending of the extent of core merging, precursor body differentiation and the efficiency of sulfide liquid segregation, reduced precursor bodies that were incorporated in the early Earth were likely more rich in Volatile Elements than currently assumed.

  • The lunar core can be a major reservoir for Volatile Elements S, Se, Te and Sb.
    Scientific reports, 2017
    Co-Authors: E. S. Steenstra, Yanhao Lin, Dian Dankers, N. Rai, Jasper Berndt, S. Matveev, Wim Van Westrenen
    Abstract:

    The Moon bears a striking compositional and isotopic resemblance to the bulk silicate Earth (BSE) for many Elements, but is considered highly depleted in many Volatile Elements compared to BSE due to high-temperature Volatile loss from Moon-forming materials in the Moon-forming giant impact and/or due to evaporative loss during subsequent magmatism on the Moon. Here, we use high-pressure metal-silicate partitioning experiments to show that the observed low concentrations of Volatile Elements sulfur (S), selenium (Se), tellurium (Te), and antimony (Sb) in the silicate Moon can instead reflect core-mantle equilibration in a largely to fully molten Moon. When incorporating the core as a reservoir for these Elements, their bulk Moon concentrations are similar to those in the present-day bulk silicate Earth. This suggests that Moon formation was not accompanied by major loss of S, Se, Te, Sb from Moon-forming materials, consistent with recent indications from lunar carbon and S isotopic compositions of primitive lunar materials. This is in marked contrast with the losses of other Volatile Elements (e.g., K, Zn) during the Moon-forming event. This discrepancy may be related to distinctly different cosmochemical behavior of S, Se, Te and Sb within the proto-lunar disk, which is as of yet virtually unconstrained.

Stephan Klemme - One of the best experts on this subject based on the ideXlab platform.

  • Trace element partitioning between sulfide-, metal- and silicate melts at highly reduced conditions : Insights into the distribution of Volatile Elements during core formation in reduced bodies
    Icarus, 2020
    Co-Authors: E. S. Steenstra, Jasper Berndt, Stephan Klemme, V.t. Trautner, W. Van Westrenen
    Abstract:

    Abstract Chalcophile and siderophile element abundances are used to provide important constraints on the interior compositions of planetary bodies as well as the pressure (P) - temperature (T) conditions that prevailed during core formation. The oxygen fugacity (fO2) during core formation varied considerably between the various terrestrial planets and asteroidal bodies in our solar system. Mercury, the aubrite parent body (AuPB) and some terrestrial precursor bodies may have differentiated at highly reduced conditions. At present knowledge about how the metal liquid-silicate melt and sulfide liquid-silicate melt partitioning behavior of major and trace Elements are affected by high S concentrations in the silicate melt at highly reducing conditions is incomplete. Here, we experimentally study the metal-silicate and sulfide-silicate partitioning behavior of trace Elements in reduced silicate melts over a wide range of S contents as a function of redox state at 1 GPa and 1833–1883 K. Silicate melt S contents ranged between ~0.5 and ~20 wt%, with a corresponding silicate FeO range of ~0.4 to ~17.5 wt%, in a fO2 range between 1 and 9 log units below the iron-wustite buffer. Our results reproduce the decrease of the S concentration at sulfide saturation (SCSS) with decreasing FeO contents down to ~3 wt%, as well as its strong increase at 6–9 wt% S, the FeO contents increase again. Results show that most Elements (Mg, Ti, V, Cr, Mn, Cu, Zn, Se, Nb, Cd, Sb, Te, Ta, Tl, Pb and Bi) are more chalcophile than siderophile at reducing conditions, whereas Si, Co, Ni, Ga, Ge, Mo and W preferentially partition into Fe-rich melts instead of sulfide liquids. Silicon, Ti, Se, and Te preferentially partition into Fe-S over (Fe,Mg,Ca)-S liquids, whereas Mn, Zn and Cd are more compatible in the latter. As proposed by Wood and Kiseeva (2015), chalcophile Elements such as Cu, Se and Te behave less chalcophile with increasing S concentrations of the silicate melt, whereas the opposite is observed for nominally lithophile Elements such as Mg, Ca and Ti. The results can be used to improve interpretations of the observed trace element systematics of aubrites and other reduced achondrites. All of the Volatile Elements considered here behave chalcophile at the reducing conditions inferred for differentiation of the AuPB. A significant degree of the observed Volatile element depletions in aubrites may therefore reflect their preferential partitioning into sulfide liquids, rather than degassing during or after differentiation of the AuPB. These results suggest that, depending of the extent of core merging, precursor body differentiation and the efficiency of sulfide liquid segregation, reduced precursor bodies that were incorporated in the early Earth were likely more rich in Volatile Elements than currently assumed.

  • Evaporation of moderately Volatile Elements from silicate melts: experiments and theory
    Geochimica et Cosmochimica Acta, 2019
    Co-Authors: Paolo A. Sossi, Jasper Berndt, Stephan Klemme, Hugh St. C. O'neill, Frederic Moynier
    Abstract:

    Abstract Moderately Volatile Elements (MVEs) are sensitive tracers of vaporisation in geological and cosmochemical processes owing to their balanced partitioning between vapour and condensed phases. Differences in their volatilities allows the thermodynamic conditions, particularly temperature and oxygen fugacity ( f O 2 ), at which vaporisation occurred to be quantified. However, this exercise is hindered by a lack of experimental data relevant to the evaporation of MVEs from silicate melts. We report a series of experiments in which silicate liquids are evaporated in one-atmosphere (1-atm) gas-mixing furnaces under controlled f O 2 s, from the Fe-“FeO” buffer (iron-wustite, IW) to air (10 -0.68 bars), bracketing the range of most magmatic rocks. Time- ( t ) and temperature ( T) series were conducted from 15 to 930 minutes and 1300-1550°C, at or above the liquidus for a synthetic ferrobasalt, to which 20 Elements, each at 1000 ppm, were added. Refractory Elements ( e.g. , Ca, Sc, V, Zr, REE) are quantitatively retained in the melt under all conditions. The MVEs show highly redox-dependent volatilities, where the extent of element loss as a function of f O 2 depends on the stoichiometry of the evaporation reaction(s), each of which has the general form M x+ n O (x+ n )/2 = M x O x/2 + n /4O 2 . Where n is positive (as in most cases), the oxidation state of the element in the gas is more reduced than in the liquid, meaning lower oxygen fugacity promotes evaporation. We develop a general framework, by integrating element vaporisation stoichiometries with Hertz-Knudsen-Langmuir (HKL) theory, to quantify evaporative loss as a function of t , T and f O 2 . Element volatilities from silicate melts differ from those during solar nebular condensation, and can thus constrain the conditions of Volatile loss in post-nebular processes. Evaporation in a single event strongly discriminates between MVEs, producing a step-like abundance pattern in the residuum, similar to that observed in the Moon or Vesta. Contrastingly, the gradual depletion of MVEs according to their volatility in the Earth is inconsistent with their loss in a single evaporation event, and instead likely reflects accretion from many smaller bodies that had each experienced different degrees of volatilisation.

  • Halogens in the Earth’s Mantle: What We Know and What We Don’t
    Springer Geochemistry, 2018
    Co-Authors: Stephan Klemme, Roland Stalder
    Abstract:

    The Earth’s mantle is known to contain significant amounts of Volatile Elements, such as hydrogen (H), carbon (C) and halogens. In the past decades our knowledge about the storage of H and C in mantle minerals, and their behavior during melting of mantle peridotite has improved considerably. In contrast, the behavior of other Volatile Elements, such as the halogens (Cl, F, I or Br) in the mantle is not so well constrained. Here we review the available experimental, analytical and theoretical data on halogen storage in mantle rocks and minerals, halogen concentrations in nominally halogen free minerals, and halogen partitioning during magmatic processes.

Glyn Williams-jones - One of the best experts on this subject based on the ideXlab platform.

  • Melt inclusion vapour bubbles: the hidden reservoir for major and Volatile Elements.
    Scientific reports, 2020
    Co-Authors: Swetha Venugopal, Federica Schiavi, Séverine Moune, Nathalie Bolfan-casanova, Timothy H. Druitt, Glyn Williams-jones
    Abstract:

    olivine-hosted melt inclusions (Mis) provide samples of magmatic liquids and their dissolved Volatiles from deep within the plumbing system. Inevitable post-entrapment modifications can lead to significant compositional changes in the glass and/or any contained bubbles. Reheating is a common technique to reverse MI crystallisation; however, its effect on Volatile contents has been assumed to be minor. We test this assumption using crystallised and glassy basaltic MIs, combined with Raman spectroscopy and 3D imaging, to investigate the changes in fluid and solid phases in the bubbles before and after reheating. Before reheating , the bubble contains CO 2 gas and anhydrite (caSo 4) crystallites. The rapid diffusion of major and Volatile Elements from the melt during reheating creates new phases within the bubble: So 2 , gypsum, Fe-sulphides. Vapour bubbles hosted in naturally glassy MIs similarly contain a plethora of solid phases (carbonates, sulphates, and sulphides) that account for up to 84% of the total MI sulphur, 80% of CO 2 , and 14% of FeO. In both reheated and naturally glassy MIs, bubbles sequester major and Volatile Elements that are components of the total magmatic budget and represent a "loss" from the glass. Analyses of the glass alone significantly underestimates the original magma composition and storage parameters. Olivine-hosted melt inclusions (MIs) provide insight into the nature of the magma mantle source, storage conditions , and pre-eruptive Volatile contents 1. Following entrapment, MIs undergo compositional modifications due to growth of the host olivine along the MI walls, and to crystallisation of daughter minerals from the glass due to slow ascent rates, and/or cooling 1,2. Another modification is the nucleation of a vapour bubble in response to decompression during cooling and post-entrapment crystallisation 1,2 , further reducing the solubility of Volatiles in the glass. Vapour, or shrinkage, bubbles produced by differential thermal contraction between the melt (glass) and the host crystal are considered to be inherent to the MI 1,2. However, pre-existing bubbles that formed externally in a vapour-saturated system may also become trapped inside MIs. Vapour bubbles may also form during MI leakage and decrepitation of the host crystal 3,4. Discriminating between various bubble types depends upon the size of the bubble relative to the total inclusion. Since the volumetric proportions of vapour bubbles depend on the cooling rate, Volatile content and melt composition, cooling-related shrinkage and melt-saturated bubbles normally comprise 0.2 to 10 vol% of the inclusion 3,4. Bubbles with greater volumetric proportions are not considered inherent to the MI 3,4. Due to the strong pressure-dependency of CO 2 solubility, the contraction of the melt and the decrease of the internal pressure in response to cooling and post-entrapment crystallisation first leads to rapid CO 2 saturation of the melt, and consequently, the transfer of CO 2 gas into the bubble 5-7 , so that analyses of the glass yield erroneously low magmatic CO 2 concentrations. This poses significant problems as the CO 2 content is commonly used to infer the pressure of crystallisation and MI entrapment, as well as magmatic storage depths. By only considering the glass, these values are grossly underestimated. Many of the post-entrapment modifications that occur within olivine-hosted MIs can be corrected using well-constrained exchange coefficients and recently established methods to quantify the amount of Volatiles, particularly CO 2 , sequestered by the bubble. These approaches include the use of trace element proxies, such as CO 2 / Nb, to determine the pre-eruptive CO 2 content of the undegassed melt 8 , reheating the MI to resorb the bubble