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Christian Nicollet - One of the best experts on this subject based on the ideXlab platform.

  • trace Element Behavior during serpentinization de serpentinization of an eclogitized oceanic lithosphere a la icpms study of the lanzo ultramafic massif western alps
    Chemical Geology, 2013
    Co-Authors: Muriel Andreani, Marguerite Godard, Christian Nicollet, Stephane Schwartz, Romain Lafay
    Abstract:

    Serpentinites are one of the major components of the oceanic lithosphere and are stable in the slab and the mantle wedge up to 100-150 km depth in subduction zones. During oceanic mantle hydration and alteration, they trap trace and fluid mobile (FME: B, Li, As, Sb, Rb, Ba, Cs, Sr, U and Pb) Elements that participate to Elemental transfer occurring between the dehydrating slab and the mantle wedge in subduction context. The Lanzo massif is an eclogitized oceanic lithosphere that preserved its oceanic structure and recorded different steps of serpentinization/de-serpentinization from oceanic lizardite to prograde antigorite in subduction context, up to its dehydration and secondary olivine crystallization, and finally retrograde antigorite during massif exhumation. It constitutes a suitable place to study trace Element Behavior during serpentinization/de-serpentinization processes and associated chemical transfers between the different envelopes of the oceanic lithosphere and the mantle wedge. Geochemical analyses of serpentine and associated minerals show that the serpentinization/de-serpentinization of the Lanzo massif took place in a relatively closed system without significant trace Element transfer between the different parts of the oceanic lithosphere. In the deeper part of the lithosphere, from the slightly serpentinized mantle peridotites (SSP, 90% serpentinization). In that zone, the alpine deformation enhances the mobility of trace Elements and permits their redistribution and the homogenization of antigorite composition at massif scale. Locally, in the SSP and MS, the crystallization of metamorphic veins of ~ 1-2 m corresponds to channelized fluid flows that allowed fluid transfers - and thereby trace Elements - to longer distance. The successive crystallizations of antigorite and then olivine are accompanied by a diminution of some FME (B, Li, As, Sb, Ba, Rb) and Eu contents attesting that these Elements are removed from slab to mantle wedge during subduction.

  • trace Element Behavior during serpentinization de serpentinization of an eclogitized oceanic lithosphere a la icpms study of the lanzo ultramafic massif western alps
    Chemical Geology, 2013
    Co-Authors: Muriel Andreani, Marguerite Godard, Christian Nicollet, Stephane Schwartz, Romain Lafay
    Abstract:

    Serpentinites are one of the major components of the oceanic lithosphere and are stable in the slab and the mantle wedge up to 100-150 km depth in subduction zones. During oceanic mantle hydration and alteration, they trap trace and fluid mobile (FME: B, Li, As, Sb, Rb, Ba, Cs, Sr, U and Pb) Elements that participate to Elemental transfer occurring between the dehydrating slab and the mantle wedge in subduction context. The Lanzo massif is an eclogitized oceanic lithosphere that preserved its oceanic structure and recorded different steps of serpentinization/de-serpentinization from oceanic lizardite to prograde antigorite in subduction context, up to its dehydration and secondary olivine crystallization, and finally retrograde antigorite during massif exhumation. It constitutes a suitable place to study trace Element Behavior during serpentinization/de-serpentinization processes and associated chemical transfers between the different envelopes of the oceanic lithosphere and the mantle wedge. Geochemical analyses of serpentine and associated minerals show that the serpentinization/de-serpentinization of the Lanzo massif took place in a relatively closed system without significant trace Element transfer between the different parts of the oceanic lithosphere. In the deeper part of the lithosphere, from the slightly serpentinized mantle peridotites (SSP, 90% serpentinization). In that zone, the alpine deformation enhances the mobility of trace Elements and permits their redistribution and the homogenization of antigorite composition at massif scale. Locally, in the SSP and MS, the crystallization of metamorphic veins of ~ 1-2 m corresponds to channelized fluid flows that allowed fluid transfers - and thereby trace Elements - to longer distance. The successive crystallizations of antigorite and then olivine are accompanied by a diminution of some FME (B, Li, As, Sb, Ba, Rb) and Eu contents attesting that these Elements are removed from slab to mantle wedge during subduction.

  • high pressure serpentinites a trap and release system controlled by metamorphic conditions example from the piedmont zone of the western alps
    Chemical Geology, 2013
    Co-Authors: Romain Lafay, Stéphane Guillot, Marguerite Godard, Stephane Schwartz, Baptiste Debret, Fabien Deschamps, Christian Nicollet
    Abstract:

    We provide new insights into the geochemistry of serpentinites from the Alpine orogenic wedge representing a paleo-subduction zone. These serpentinites are derived from similar oceanic protoliths, but they have experienced different metamorphic conditions related to three different structural levels of the paleo-subduction zone ((1) obducted: Chenaillet ophiolite, (2) accretionary wedge: Queyras Schistes lustres complex and (3) serpentinite channel: Monviso ophiolite). Metamorphism undergone by these three units is well defined, increasing eastward from sub-greenschist to eclogite facies conditions, and allows us to examine trace Element Behavior from the oceanic ridge environment to subduction. Serpentinites first record moderate trace Element enrichment due to seawater interaction resulting in the replacement of olivine and pyroxene by chrysotile and lizardite below 300 °C. In the sediment-dominated accretionary wedge, serpentinites are strongly enriched in fluid-mobile-Elements (B, Li, As, Sb, and Cs) and act as a trapping system following the metamorphic gradient (from 300 to 390 °C) up to total replacement of the lizardite/chrysotile assemblage by antigorite. Under higher temperature conditions (T > 390 °C), no enrichment was observed, and some fluid-mobile Elements were released (B, Li, Cs, and Sr). Moreover, in the serpentinite channel (T > 460 °C), most of the fluid-mobile Elements are absent due to the scarcity of metasediments which prevent geochemical exchange between metasediments and serpentinites. This is also due to the onset of antigorite breakdown and the release of fluid-mobile Elements. Thus, we emphasize that the geochemistry of Alpine serpentinites is strongly dependent on (1) the grade of metamorphism and (2) the ability of metasediments to supply fluid-mobile Elements. We conclude that serpentinites act as a trap-and-release system for fluid-mobile Elements in a subduction context.

Romain Lafay - One of the best experts on this subject based on the ideXlab platform.

  • trace Element Behavior during serpentinization de serpentinization of an eclogitized oceanic lithosphere a la icpms study of the lanzo ultramafic massif western alps
    Chemical Geology, 2013
    Co-Authors: Muriel Andreani, Marguerite Godard, Christian Nicollet, Stephane Schwartz, Romain Lafay
    Abstract:

    Serpentinites are one of the major components of the oceanic lithosphere and are stable in the slab and the mantle wedge up to 100-150 km depth in subduction zones. During oceanic mantle hydration and alteration, they trap trace and fluid mobile (FME: B, Li, As, Sb, Rb, Ba, Cs, Sr, U and Pb) Elements that participate to Elemental transfer occurring between the dehydrating slab and the mantle wedge in subduction context. The Lanzo massif is an eclogitized oceanic lithosphere that preserved its oceanic structure and recorded different steps of serpentinization/de-serpentinization from oceanic lizardite to prograde antigorite in subduction context, up to its dehydration and secondary olivine crystallization, and finally retrograde antigorite during massif exhumation. It constitutes a suitable place to study trace Element Behavior during serpentinization/de-serpentinization processes and associated chemical transfers between the different envelopes of the oceanic lithosphere and the mantle wedge. Geochemical analyses of serpentine and associated minerals show that the serpentinization/de-serpentinization of the Lanzo massif took place in a relatively closed system without significant trace Element transfer between the different parts of the oceanic lithosphere. In the deeper part of the lithosphere, from the slightly serpentinized mantle peridotites (SSP, 90% serpentinization). In that zone, the alpine deformation enhances the mobility of trace Elements and permits their redistribution and the homogenization of antigorite composition at massif scale. Locally, in the SSP and MS, the crystallization of metamorphic veins of ~ 1-2 m corresponds to channelized fluid flows that allowed fluid transfers - and thereby trace Elements - to longer distance. The successive crystallizations of antigorite and then olivine are accompanied by a diminution of some FME (B, Li, As, Sb, Ba, Rb) and Eu contents attesting that these Elements are removed from slab to mantle wedge during subduction.

  • trace Element Behavior during serpentinization de serpentinization of an eclogitized oceanic lithosphere a la icpms study of the lanzo ultramafic massif western alps
    Chemical Geology, 2013
    Co-Authors: Muriel Andreani, Marguerite Godard, Christian Nicollet, Stephane Schwartz, Romain Lafay
    Abstract:

    Serpentinites are one of the major components of the oceanic lithosphere and are stable in the slab and the mantle wedge up to 100-150 km depth in subduction zones. During oceanic mantle hydration and alteration, they trap trace and fluid mobile (FME: B, Li, As, Sb, Rb, Ba, Cs, Sr, U and Pb) Elements that participate to Elemental transfer occurring between the dehydrating slab and the mantle wedge in subduction context. The Lanzo massif is an eclogitized oceanic lithosphere that preserved its oceanic structure and recorded different steps of serpentinization/de-serpentinization from oceanic lizardite to prograde antigorite in subduction context, up to its dehydration and secondary olivine crystallization, and finally retrograde antigorite during massif exhumation. It constitutes a suitable place to study trace Element Behavior during serpentinization/de-serpentinization processes and associated chemical transfers between the different envelopes of the oceanic lithosphere and the mantle wedge. Geochemical analyses of serpentine and associated minerals show that the serpentinization/de-serpentinization of the Lanzo massif took place in a relatively closed system without significant trace Element transfer between the different parts of the oceanic lithosphere. In the deeper part of the lithosphere, from the slightly serpentinized mantle peridotites (SSP, 90% serpentinization). In that zone, the alpine deformation enhances the mobility of trace Elements and permits their redistribution and the homogenization of antigorite composition at massif scale. Locally, in the SSP and MS, the crystallization of metamorphic veins of ~ 1-2 m corresponds to channelized fluid flows that allowed fluid transfers - and thereby trace Elements - to longer distance. The successive crystallizations of antigorite and then olivine are accompanied by a diminution of some FME (B, Li, As, Sb, Ba, Rb) and Eu contents attesting that these Elements are removed from slab to mantle wedge during subduction.

  • high pressure serpentinites a trap and release system controlled by metamorphic conditions example from the piedmont zone of the western alps
    Chemical Geology, 2013
    Co-Authors: Romain Lafay, Stéphane Guillot, Marguerite Godard, Stephane Schwartz, Baptiste Debret, Fabien Deschamps, Christian Nicollet
    Abstract:

    We provide new insights into the geochemistry of serpentinites from the Alpine orogenic wedge representing a paleo-subduction zone. These serpentinites are derived from similar oceanic protoliths, but they have experienced different metamorphic conditions related to three different structural levels of the paleo-subduction zone ((1) obducted: Chenaillet ophiolite, (2) accretionary wedge: Queyras Schistes lustres complex and (3) serpentinite channel: Monviso ophiolite). Metamorphism undergone by these three units is well defined, increasing eastward from sub-greenschist to eclogite facies conditions, and allows us to examine trace Element Behavior from the oceanic ridge environment to subduction. Serpentinites first record moderate trace Element enrichment due to seawater interaction resulting in the replacement of olivine and pyroxene by chrysotile and lizardite below 300 °C. In the sediment-dominated accretionary wedge, serpentinites are strongly enriched in fluid-mobile-Elements (B, Li, As, Sb, and Cs) and act as a trapping system following the metamorphic gradient (from 300 to 390 °C) up to total replacement of the lizardite/chrysotile assemblage by antigorite. Under higher temperature conditions (T > 390 °C), no enrichment was observed, and some fluid-mobile Elements were released (B, Li, Cs, and Sr). Moreover, in the serpentinite channel (T > 460 °C), most of the fluid-mobile Elements are absent due to the scarcity of metasediments which prevent geochemical exchange between metasediments and serpentinites. This is also due to the onset of antigorite breakdown and the release of fluid-mobile Elements. Thus, we emphasize that the geochemistry of Alpine serpentinites is strongly dependent on (1) the grade of metamorphism and (2) the ability of metasediments to supply fluid-mobile Elements. We conclude that serpentinites act as a trap-and-release system for fluid-mobile Elements in a subduction context.

Stephane Schwartz - One of the best experts on this subject based on the ideXlab platform.

  • trace Element Behavior during serpentinization de serpentinization of an eclogitized oceanic lithosphere a la icpms study of the lanzo ultramafic massif western alps
    Chemical Geology, 2013
    Co-Authors: Muriel Andreani, Marguerite Godard, Christian Nicollet, Stephane Schwartz, Romain Lafay
    Abstract:

    Serpentinites are one of the major components of the oceanic lithosphere and are stable in the slab and the mantle wedge up to 100-150 km depth in subduction zones. During oceanic mantle hydration and alteration, they trap trace and fluid mobile (FME: B, Li, As, Sb, Rb, Ba, Cs, Sr, U and Pb) Elements that participate to Elemental transfer occurring between the dehydrating slab and the mantle wedge in subduction context. The Lanzo massif is an eclogitized oceanic lithosphere that preserved its oceanic structure and recorded different steps of serpentinization/de-serpentinization from oceanic lizardite to prograde antigorite in subduction context, up to its dehydration and secondary olivine crystallization, and finally retrograde antigorite during massif exhumation. It constitutes a suitable place to study trace Element Behavior during serpentinization/de-serpentinization processes and associated chemical transfers between the different envelopes of the oceanic lithosphere and the mantle wedge. Geochemical analyses of serpentine and associated minerals show that the serpentinization/de-serpentinization of the Lanzo massif took place in a relatively closed system without significant trace Element transfer between the different parts of the oceanic lithosphere. In the deeper part of the lithosphere, from the slightly serpentinized mantle peridotites (SSP, 90% serpentinization). In that zone, the alpine deformation enhances the mobility of trace Elements and permits their redistribution and the homogenization of antigorite composition at massif scale. Locally, in the SSP and MS, the crystallization of metamorphic veins of ~ 1-2 m corresponds to channelized fluid flows that allowed fluid transfers - and thereby trace Elements - to longer distance. The successive crystallizations of antigorite and then olivine are accompanied by a diminution of some FME (B, Li, As, Sb, Ba, Rb) and Eu contents attesting that these Elements are removed from slab to mantle wedge during subduction.

  • trace Element Behavior during serpentinization de serpentinization of an eclogitized oceanic lithosphere a la icpms study of the lanzo ultramafic massif western alps
    Chemical Geology, 2013
    Co-Authors: Muriel Andreani, Marguerite Godard, Christian Nicollet, Stephane Schwartz, Romain Lafay
    Abstract:

    Serpentinites are one of the major components of the oceanic lithosphere and are stable in the slab and the mantle wedge up to 100-150 km depth in subduction zones. During oceanic mantle hydration and alteration, they trap trace and fluid mobile (FME: B, Li, As, Sb, Rb, Ba, Cs, Sr, U and Pb) Elements that participate to Elemental transfer occurring between the dehydrating slab and the mantle wedge in subduction context. The Lanzo massif is an eclogitized oceanic lithosphere that preserved its oceanic structure and recorded different steps of serpentinization/de-serpentinization from oceanic lizardite to prograde antigorite in subduction context, up to its dehydration and secondary olivine crystallization, and finally retrograde antigorite during massif exhumation. It constitutes a suitable place to study trace Element Behavior during serpentinization/de-serpentinization processes and associated chemical transfers between the different envelopes of the oceanic lithosphere and the mantle wedge. Geochemical analyses of serpentine and associated minerals show that the serpentinization/de-serpentinization of the Lanzo massif took place in a relatively closed system without significant trace Element transfer between the different parts of the oceanic lithosphere. In the deeper part of the lithosphere, from the slightly serpentinized mantle peridotites (SSP, 90% serpentinization). In that zone, the alpine deformation enhances the mobility of trace Elements and permits their redistribution and the homogenization of antigorite composition at massif scale. Locally, in the SSP and MS, the crystallization of metamorphic veins of ~ 1-2 m corresponds to channelized fluid flows that allowed fluid transfers - and thereby trace Elements - to longer distance. The successive crystallizations of antigorite and then olivine are accompanied by a diminution of some FME (B, Li, As, Sb, Ba, Rb) and Eu contents attesting that these Elements are removed from slab to mantle wedge during subduction.

  • high pressure serpentinites a trap and release system controlled by metamorphic conditions example from the piedmont zone of the western alps
    Chemical Geology, 2013
    Co-Authors: Romain Lafay, Stéphane Guillot, Marguerite Godard, Stephane Schwartz, Baptiste Debret, Fabien Deschamps, Christian Nicollet
    Abstract:

    We provide new insights into the geochemistry of serpentinites from the Alpine orogenic wedge representing a paleo-subduction zone. These serpentinites are derived from similar oceanic protoliths, but they have experienced different metamorphic conditions related to three different structural levels of the paleo-subduction zone ((1) obducted: Chenaillet ophiolite, (2) accretionary wedge: Queyras Schistes lustres complex and (3) serpentinite channel: Monviso ophiolite). Metamorphism undergone by these three units is well defined, increasing eastward from sub-greenschist to eclogite facies conditions, and allows us to examine trace Element Behavior from the oceanic ridge environment to subduction. Serpentinites first record moderate trace Element enrichment due to seawater interaction resulting in the replacement of olivine and pyroxene by chrysotile and lizardite below 300 °C. In the sediment-dominated accretionary wedge, serpentinites are strongly enriched in fluid-mobile-Elements (B, Li, As, Sb, and Cs) and act as a trapping system following the metamorphic gradient (from 300 to 390 °C) up to total replacement of the lizardite/chrysotile assemblage by antigorite. Under higher temperature conditions (T > 390 °C), no enrichment was observed, and some fluid-mobile Elements were released (B, Li, Cs, and Sr). Moreover, in the serpentinite channel (T > 460 °C), most of the fluid-mobile Elements are absent due to the scarcity of metasediments which prevent geochemical exchange between metasediments and serpentinites. This is also due to the onset of antigorite breakdown and the release of fluid-mobile Elements. Thus, we emphasize that the geochemistry of Alpine serpentinites is strongly dependent on (1) the grade of metamorphism and (2) the ability of metasediments to supply fluid-mobile Elements. We conclude that serpentinites act as a trap-and-release system for fluid-mobile Elements in a subduction context.

Marguerite Godard - One of the best experts on this subject based on the ideXlab platform.

  • trace Element Behavior during serpentinization de serpentinization of an eclogitized oceanic lithosphere a la icpms study of the lanzo ultramafic massif western alps
    Chemical Geology, 2013
    Co-Authors: Muriel Andreani, Marguerite Godard, Christian Nicollet, Stephane Schwartz, Romain Lafay
    Abstract:

    Serpentinites are one of the major components of the oceanic lithosphere and are stable in the slab and the mantle wedge up to 100-150 km depth in subduction zones. During oceanic mantle hydration and alteration, they trap trace and fluid mobile (FME: B, Li, As, Sb, Rb, Ba, Cs, Sr, U and Pb) Elements that participate to Elemental transfer occurring between the dehydrating slab and the mantle wedge in subduction context. The Lanzo massif is an eclogitized oceanic lithosphere that preserved its oceanic structure and recorded different steps of serpentinization/de-serpentinization from oceanic lizardite to prograde antigorite in subduction context, up to its dehydration and secondary olivine crystallization, and finally retrograde antigorite during massif exhumation. It constitutes a suitable place to study trace Element Behavior during serpentinization/de-serpentinization processes and associated chemical transfers between the different envelopes of the oceanic lithosphere and the mantle wedge. Geochemical analyses of serpentine and associated minerals show that the serpentinization/de-serpentinization of the Lanzo massif took place in a relatively closed system without significant trace Element transfer between the different parts of the oceanic lithosphere. In the deeper part of the lithosphere, from the slightly serpentinized mantle peridotites (SSP, 90% serpentinization). In that zone, the alpine deformation enhances the mobility of trace Elements and permits their redistribution and the homogenization of antigorite composition at massif scale. Locally, in the SSP and MS, the crystallization of metamorphic veins of ~ 1-2 m corresponds to channelized fluid flows that allowed fluid transfers - and thereby trace Elements - to longer distance. The successive crystallizations of antigorite and then olivine are accompanied by a diminution of some FME (B, Li, As, Sb, Ba, Rb) and Eu contents attesting that these Elements are removed from slab to mantle wedge during subduction.

  • trace Element Behavior during serpentinization de serpentinization of an eclogitized oceanic lithosphere a la icpms study of the lanzo ultramafic massif western alps
    Chemical Geology, 2013
    Co-Authors: Muriel Andreani, Marguerite Godard, Christian Nicollet, Stephane Schwartz, Romain Lafay
    Abstract:

    Serpentinites are one of the major components of the oceanic lithosphere and are stable in the slab and the mantle wedge up to 100-150 km depth in subduction zones. During oceanic mantle hydration and alteration, they trap trace and fluid mobile (FME: B, Li, As, Sb, Rb, Ba, Cs, Sr, U and Pb) Elements that participate to Elemental transfer occurring between the dehydrating slab and the mantle wedge in subduction context. The Lanzo massif is an eclogitized oceanic lithosphere that preserved its oceanic structure and recorded different steps of serpentinization/de-serpentinization from oceanic lizardite to prograde antigorite in subduction context, up to its dehydration and secondary olivine crystallization, and finally retrograde antigorite during massif exhumation. It constitutes a suitable place to study trace Element Behavior during serpentinization/de-serpentinization processes and associated chemical transfers between the different envelopes of the oceanic lithosphere and the mantle wedge. Geochemical analyses of serpentine and associated minerals show that the serpentinization/de-serpentinization of the Lanzo massif took place in a relatively closed system without significant trace Element transfer between the different parts of the oceanic lithosphere. In the deeper part of the lithosphere, from the slightly serpentinized mantle peridotites (SSP, 90% serpentinization). In that zone, the alpine deformation enhances the mobility of trace Elements and permits their redistribution and the homogenization of antigorite composition at massif scale. Locally, in the SSP and MS, the crystallization of metamorphic veins of ~ 1-2 m corresponds to channelized fluid flows that allowed fluid transfers - and thereby trace Elements - to longer distance. The successive crystallizations of antigorite and then olivine are accompanied by a diminution of some FME (B, Li, As, Sb, Ba, Rb) and Eu contents attesting that these Elements are removed from slab to mantle wedge during subduction.

  • high pressure serpentinites a trap and release system controlled by metamorphic conditions example from the piedmont zone of the western alps
    Chemical Geology, 2013
    Co-Authors: Romain Lafay, Stéphane Guillot, Marguerite Godard, Stephane Schwartz, Baptiste Debret, Fabien Deschamps, Christian Nicollet
    Abstract:

    We provide new insights into the geochemistry of serpentinites from the Alpine orogenic wedge representing a paleo-subduction zone. These serpentinites are derived from similar oceanic protoliths, but they have experienced different metamorphic conditions related to three different structural levels of the paleo-subduction zone ((1) obducted: Chenaillet ophiolite, (2) accretionary wedge: Queyras Schistes lustres complex and (3) serpentinite channel: Monviso ophiolite). Metamorphism undergone by these three units is well defined, increasing eastward from sub-greenschist to eclogite facies conditions, and allows us to examine trace Element Behavior from the oceanic ridge environment to subduction. Serpentinites first record moderate trace Element enrichment due to seawater interaction resulting in the replacement of olivine and pyroxene by chrysotile and lizardite below 300 °C. In the sediment-dominated accretionary wedge, serpentinites are strongly enriched in fluid-mobile-Elements (B, Li, As, Sb, and Cs) and act as a trapping system following the metamorphic gradient (from 300 to 390 °C) up to total replacement of the lizardite/chrysotile assemblage by antigorite. Under higher temperature conditions (T > 390 °C), no enrichment was observed, and some fluid-mobile Elements were released (B, Li, Cs, and Sr). Moreover, in the serpentinite channel (T > 460 °C), most of the fluid-mobile Elements are absent due to the scarcity of metasediments which prevent geochemical exchange between metasediments and serpentinites. This is also due to the onset of antigorite breakdown and the release of fluid-mobile Elements. Thus, we emphasize that the geochemistry of Alpine serpentinites is strongly dependent on (1) the grade of metamorphism and (2) the ability of metasediments to supply fluid-mobile Elements. We conclude that serpentinites act as a trap-and-release system for fluid-mobile Elements in a subduction context.

Muriel Andreani - One of the best experts on this subject based on the ideXlab platform.

  • trace Element Behavior during serpentinization de serpentinization of an eclogitized oceanic lithosphere a la icpms study of the lanzo ultramafic massif western alps
    Chemical Geology, 2013
    Co-Authors: Muriel Andreani, Marguerite Godard, Christian Nicollet, Stephane Schwartz, Romain Lafay
    Abstract:

    Serpentinites are one of the major components of the oceanic lithosphere and are stable in the slab and the mantle wedge up to 100-150 km depth in subduction zones. During oceanic mantle hydration and alteration, they trap trace and fluid mobile (FME: B, Li, As, Sb, Rb, Ba, Cs, Sr, U and Pb) Elements that participate to Elemental transfer occurring between the dehydrating slab and the mantle wedge in subduction context. The Lanzo massif is an eclogitized oceanic lithosphere that preserved its oceanic structure and recorded different steps of serpentinization/de-serpentinization from oceanic lizardite to prograde antigorite in subduction context, up to its dehydration and secondary olivine crystallization, and finally retrograde antigorite during massif exhumation. It constitutes a suitable place to study trace Element Behavior during serpentinization/de-serpentinization processes and associated chemical transfers between the different envelopes of the oceanic lithosphere and the mantle wedge. Geochemical analyses of serpentine and associated minerals show that the serpentinization/de-serpentinization of the Lanzo massif took place in a relatively closed system without significant trace Element transfer between the different parts of the oceanic lithosphere. In the deeper part of the lithosphere, from the slightly serpentinized mantle peridotites (SSP, 90% serpentinization). In that zone, the alpine deformation enhances the mobility of trace Elements and permits their redistribution and the homogenization of antigorite composition at massif scale. Locally, in the SSP and MS, the crystallization of metamorphic veins of ~ 1-2 m corresponds to channelized fluid flows that allowed fluid transfers - and thereby trace Elements - to longer distance. The successive crystallizations of antigorite and then olivine are accompanied by a diminution of some FME (B, Li, As, Sb, Ba, Rb) and Eu contents attesting that these Elements are removed from slab to mantle wedge during subduction.

  • trace Element Behavior during serpentinization de serpentinization of an eclogitized oceanic lithosphere a la icpms study of the lanzo ultramafic massif western alps
    Chemical Geology, 2013
    Co-Authors: Muriel Andreani, Marguerite Godard, Christian Nicollet, Stephane Schwartz, Romain Lafay
    Abstract:

    Serpentinites are one of the major components of the oceanic lithosphere and are stable in the slab and the mantle wedge up to 100-150 km depth in subduction zones. During oceanic mantle hydration and alteration, they trap trace and fluid mobile (FME: B, Li, As, Sb, Rb, Ba, Cs, Sr, U and Pb) Elements that participate to Elemental transfer occurring between the dehydrating slab and the mantle wedge in subduction context. The Lanzo massif is an eclogitized oceanic lithosphere that preserved its oceanic structure and recorded different steps of serpentinization/de-serpentinization from oceanic lizardite to prograde antigorite in subduction context, up to its dehydration and secondary olivine crystallization, and finally retrograde antigorite during massif exhumation. It constitutes a suitable place to study trace Element Behavior during serpentinization/de-serpentinization processes and associated chemical transfers between the different envelopes of the oceanic lithosphere and the mantle wedge. Geochemical analyses of serpentine and associated minerals show that the serpentinization/de-serpentinization of the Lanzo massif took place in a relatively closed system without significant trace Element transfer between the different parts of the oceanic lithosphere. In the deeper part of the lithosphere, from the slightly serpentinized mantle peridotites (SSP, 90% serpentinization). In that zone, the alpine deformation enhances the mobility of trace Elements and permits their redistribution and the homogenization of antigorite composition at massif scale. Locally, in the SSP and MS, the crystallization of metamorphic veins of ~ 1-2 m corresponds to channelized fluid flows that allowed fluid transfers - and thereby trace Elements - to longer distance. The successive crystallizations of antigorite and then olivine are accompanied by a diminution of some FME (B, Li, As, Sb, Ba, Rb) and Eu contents attesting that these Elements are removed from slab to mantle wedge during subduction.