Skip to Main content Skip to Navigation
Journal articles

Halogen Bearing Amphiboles, Aqueous Fluids, and Melts in Subduction Zones: Insights on Halogen Cycle From Electrical Conductivity

Abstract : Amphiboles are hydrous minerals that are formed in the oceanic crust via hydrothermal alteration. The partial substitution of halogens for OH− makes amphibole one of the principal hosts of Cl and F in the subducting slab. In this study, we investigated the electrical conductivity of a suite of halogen bearing amphibole minerals at 1.5 GPa up to 1,400 K. The discontinuous electrical behavior indicates dehydration of amphibole at ∼915 K. This is followed by dehydration induced hydrous melting at temperatures above 1,070 K. We find that the released aqueous fluids have an electrical conductivity of ∼0.1 S/m. This high electrical conductivity is likely to explain anomalously high electrical conductivity observed in certain subduction zone settings. This high electrical conductivity of an order of magnitude greater than the electrical conductivity of pure aqueous fluids at similar conditions is likely due to the partitioning of the F and Cl into the aqueous fluids. We also noted that subsequent to the dehydration, secondary phases form due to the breakdown of the primary halogen bearing amphibole. Chemical analyses of these secondary phases indicate that they are repositories of F and Cl. Hence, we infer that upon dehydration of the primary halogen bearing amphibole, first the F and Cl are partitioned into the aqueous fluids and then the halogens are partitioned back to the secondary mineral phases. These secondary minerals are likely to transport the halogen to the deep Earth and may in part explain the halogen concentration observed in ocean island basalt.
Document type :
Journal articles
Complete list of metadata

https://hal.uca.fr/hal-03181956
Contributor : Sylvaine Jouhannel <>
Submitted on : Friday, March 26, 2021 - 8:40:47 AM
Last modification on : Tuesday, March 30, 2021 - 3:47:26 AM
Long-term archiving on: : Sunday, June 27, 2021 - 6:16:39 PM

File

Manthilake et al. 2021.pdf
Files produced by the author(s)

Identifiers

Collections

Citation

Geeth Manthilake, Kenneth Koga, Y. Peng, M. Mookherjee. Halogen Bearing Amphiboles, Aqueous Fluids, and Melts in Subduction Zones: Insights on Halogen Cycle From Electrical Conductivity. Journal of Geophysical Research : Solid Earth, American Geophysical Union, 2021, 126 (3), ⟨10.1029/2020JB021339⟩. ⟨hal-03181956⟩

Share

Metrics

Record views

57

Files downloads

82