Silicate diffusion in alkali-carbonatite and hydrous melts at 16.5 and 24GPa

Implication for the melt transport by dissolution-precipitation in the transition zone and uppermost lower mantle

Anton Shatskiy, Konstantin D. Litasov, Yuriy M. Borzdov, Tomoo Katsura, Daisuke Yamazaki, Eiji Ohtani

Research output: Contribution to journalArticle

20 Citations (Scopus)

Abstract

The diffusivity of dissolved Mg2SiO4 in wadsleyite saturated KMC melt (K2Mg(CO3)2+25.7wt.% MgSiO3) at 16.5GPa and 1700°C, MgSiO3 diffusivity in perovskite saturated KMCH (K2Mg(CO3)2×2H2O+31.7wt.% MgSiO3) and HM (H2O+75.7wt.% MgSiO3) melts at 24GPa and 1500°C were determined experimentally using a scaled-up version of a Kawai-type multi-anvil apparatus. During a diffusion experiment, silicate saturation was maintained at different levels in the two temperature regions by placing the diffusion cell in the thermal gradient of 20°C/mm. The diffusivity was computed from the total mass of silicate transported from "hot" to the "cold" region during the course of an experiment. At given conditions silicate diffusivities were estimated to be DKMCMg2SiO4=2×10-9m2/s, DKMCHMgSiO3=4×10-9m2/s, and DHMMgSiO3=5×10-8m2/s.Using obtained diffusivities we estimated possible migration rates of dispersed melt inclusion in the deep mantle by means of dissolution-precipitation considering different driving forces. The rates of melt migration driven by the lateral thermal gradient of 1°C/km in the mantle plume range from 4×10-8 to 8×10-7m/year. This means that during plume ascent time of about 50Ma, the melt can be moved by 2-40m. These values clearly demonstrate that the thermal gradient is very weak driving force in terms of melt segregation in the deep mantle. On the other hand, at typical mantle stress of 1MPa and droplet size of 100μm the migration rates of the HM, KMCH and KMC melts are estimated to be 22.5, 0.9 and 0.2m/year, respectively, which are 2-3 orders of magnitude faster than ascent rate of the mantle plume. This implies that all melt droplets on the way of ascending plume would be entrapped by the stressed zone in front of plume and accumulated in the plume head. This mechanism may explain segregation of mantle magmas with the source regions deeper than 150-250km, such as kimberlites.

Original languageEnglish
Pages (from-to)1-11
Number of pages11
JournalPhysics of the Earth and Planetary Interiors
Volume225
DOIs
Publication statusPublished - Dec 2013

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carbonatite
lower mantle
transition zone
plumes
alkalies
silicates
dissolving
Earth mantle
silicate
diffusivity
dissolution
melt
plume
mantle
ascent
gradients
mantle plume
droplet
wadsleyite
anvils

Keywords

  • Carbonatite
  • Diffusion
  • Dissolution-precipitation
  • Earth's mantle
  • Hydrous melt
  • Kimberlite
  • Melt percolation

ASJC Scopus subject areas

  • Geophysics
  • Space and Planetary Science
  • Physics and Astronomy (miscellaneous)
  • Astronomy and Astrophysics

Cite this

Silicate diffusion in alkali-carbonatite and hydrous melts at 16.5 and 24GPa : Implication for the melt transport by dissolution-precipitation in the transition zone and uppermost lower mantle. / Shatskiy, Anton; Litasov, Konstantin D.; Borzdov, Yuriy M.; Katsura, Tomoo; Yamazaki, Daisuke; Ohtani, Eiji.

In: Physics of the Earth and Planetary Interiors, Vol. 225, 12.2013, p. 1-11.

Research output: Contribution to journalArticle

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abstract = "The diffusivity of dissolved Mg2SiO4 in wadsleyite saturated KMC melt (K2Mg(CO3)2+25.7wt.{\%} MgSiO3) at 16.5GPa and 1700°C, MgSiO3 diffusivity in perovskite saturated KMCH (K2Mg(CO3)2×2H2O+31.7wt.{\%} MgSiO3) and HM (H2O+75.7wt.{\%} MgSiO3) melts at 24GPa and 1500°C were determined experimentally using a scaled-up version of a Kawai-type multi-anvil apparatus. During a diffusion experiment, silicate saturation was maintained at different levels in the two temperature regions by placing the diffusion cell in the thermal gradient of 20°C/mm. The diffusivity was computed from the total mass of silicate transported from {"}hot{"} to the {"}cold{"} region during the course of an experiment. At given conditions silicate diffusivities were estimated to be DKMCMg2SiO4=2×10-9m2/s, DKMCHMgSiO3=4×10-9m2/s, and DHMMgSiO3=5×10-8m2/s.Using obtained diffusivities we estimated possible migration rates of dispersed melt inclusion in the deep mantle by means of dissolution-precipitation considering different driving forces. The rates of melt migration driven by the lateral thermal gradient of 1°C/km in the mantle plume range from 4×10-8 to 8×10-7m/year. This means that during plume ascent time of about 50Ma, the melt can be moved by 2-40m. These values clearly demonstrate that the thermal gradient is very weak driving force in terms of melt segregation in the deep mantle. On the other hand, at typical mantle stress of 1MPa and droplet size of 100μm the migration rates of the HM, KMCH and KMC melts are estimated to be 22.5, 0.9 and 0.2m/year, respectively, which are 2-3 orders of magnitude faster than ascent rate of the mantle plume. This implies that all melt droplets on the way of ascending plume would be entrapped by the stressed zone in front of plume and accumulated in the plume head. This mechanism may explain segregation of mantle magmas with the source regions deeper than 150-250km, such as kimberlites.",
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T2 - Implication for the melt transport by dissolution-precipitation in the transition zone and uppermost lower mantle

AU - Shatskiy, Anton

AU - Litasov, Konstantin D.

AU - Borzdov, Yuriy M.

AU - Katsura, Tomoo

AU - Yamazaki, Daisuke

AU - Ohtani, Eiji

PY - 2013/12

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N2 - The diffusivity of dissolved Mg2SiO4 in wadsleyite saturated KMC melt (K2Mg(CO3)2+25.7wt.% MgSiO3) at 16.5GPa and 1700°C, MgSiO3 diffusivity in perovskite saturated KMCH (K2Mg(CO3)2×2H2O+31.7wt.% MgSiO3) and HM (H2O+75.7wt.% MgSiO3) melts at 24GPa and 1500°C were determined experimentally using a scaled-up version of a Kawai-type multi-anvil apparatus. During a diffusion experiment, silicate saturation was maintained at different levels in the two temperature regions by placing the diffusion cell in the thermal gradient of 20°C/mm. The diffusivity was computed from the total mass of silicate transported from "hot" to the "cold" region during the course of an experiment. At given conditions silicate diffusivities were estimated to be DKMCMg2SiO4=2×10-9m2/s, DKMCHMgSiO3=4×10-9m2/s, and DHMMgSiO3=5×10-8m2/s.Using obtained diffusivities we estimated possible migration rates of dispersed melt inclusion in the deep mantle by means of dissolution-precipitation considering different driving forces. The rates of melt migration driven by the lateral thermal gradient of 1°C/km in the mantle plume range from 4×10-8 to 8×10-7m/year. This means that during plume ascent time of about 50Ma, the melt can be moved by 2-40m. These values clearly demonstrate that the thermal gradient is very weak driving force in terms of melt segregation in the deep mantle. On the other hand, at typical mantle stress of 1MPa and droplet size of 100μm the migration rates of the HM, KMCH and KMC melts are estimated to be 22.5, 0.9 and 0.2m/year, respectively, which are 2-3 orders of magnitude faster than ascent rate of the mantle plume. This implies that all melt droplets on the way of ascending plume would be entrapped by the stressed zone in front of plume and accumulated in the plume head. This mechanism may explain segregation of mantle magmas with the source regions deeper than 150-250km, such as kimberlites.

AB - The diffusivity of dissolved Mg2SiO4 in wadsleyite saturated KMC melt (K2Mg(CO3)2+25.7wt.% MgSiO3) at 16.5GPa and 1700°C, MgSiO3 diffusivity in perovskite saturated KMCH (K2Mg(CO3)2×2H2O+31.7wt.% MgSiO3) and HM (H2O+75.7wt.% MgSiO3) melts at 24GPa and 1500°C were determined experimentally using a scaled-up version of a Kawai-type multi-anvil apparatus. During a diffusion experiment, silicate saturation was maintained at different levels in the two temperature regions by placing the diffusion cell in the thermal gradient of 20°C/mm. The diffusivity was computed from the total mass of silicate transported from "hot" to the "cold" region during the course of an experiment. At given conditions silicate diffusivities were estimated to be DKMCMg2SiO4=2×10-9m2/s, DKMCHMgSiO3=4×10-9m2/s, and DHMMgSiO3=5×10-8m2/s.Using obtained diffusivities we estimated possible migration rates of dispersed melt inclusion in the deep mantle by means of dissolution-precipitation considering different driving forces. The rates of melt migration driven by the lateral thermal gradient of 1°C/km in the mantle plume range from 4×10-8 to 8×10-7m/year. This means that during plume ascent time of about 50Ma, the melt can be moved by 2-40m. These values clearly demonstrate that the thermal gradient is very weak driving force in terms of melt segregation in the deep mantle. On the other hand, at typical mantle stress of 1MPa and droplet size of 100μm the migration rates of the HM, KMCH and KMC melts are estimated to be 22.5, 0.9 and 0.2m/year, respectively, which are 2-3 orders of magnitude faster than ascent rate of the mantle plume. This implies that all melt droplets on the way of ascending plume would be entrapped by the stressed zone in front of plume and accumulated in the plume head. This mechanism may explain segregation of mantle magmas with the source regions deeper than 150-250km, such as kimberlites.

KW - Carbonatite

KW - Diffusion

KW - Dissolution-precipitation

KW - Earth's mantle

KW - Hydrous melt

KW - Kimberlite

KW - Melt percolation

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