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Carbonation of ophiolitic ultramafic rocks: Listvenite formation in the Late Cretaceous ophiolites of eastern Iran

Carbonation of ophiolitic ultramafic rocks: Listvenite formation in the Late Cretaceous ophiolites of eastern Iran
Carbonation of ophiolitic ultramafic rocks: Listvenite formation in the Late Cretaceous ophiolites of eastern Iran
Late Cretaceous mantle peridotite of the Birjand ophiolite (eastern Iran) contains variably serpentinized and carbonated/listvenitized rocks. Transformation from harzburgite protolith to final listvenite (quartz + magnesite/± dolomite + relict Cr-spinel) reflects successive fluid-driven reactions, the products of which are preserved in outcrop. Transformation of harzburgite to listvenite starts with lizardite serpentinization, followed by contemporaneous carbonation and antigorite serpentinization, antigorite-talc-magnesite alteration, finally producing listvenite where alteration is most pervasive. The spectrum of listvenitic assemblages includes silica-carbonate, carbonate and silica listvenites with the latter (also known as birbirite) being the youngest, based on crosscutting relationships. The petrological observations and mineral assemblages suggest hydrothermal fluids responsible for the lizardite serpentinization had low aCO2, oxygen and sulfur fugacities, distinct from those causing antigorite serpentinization and carbonation/listvenitization, which had higher aCO2, aSiO2, and oxygen and sulfur fugacities. The carbonate and silica listvenite end-members indicate variations in aSiO2 and aCO2 of the percolating hydrothermal fluids, most likely driven by local variations in pH and temperature.

Beyond the addition of H2O, serpentinization did not significantly redistribute major elements. Progressive infiltration of CO2-rich fluids and consequent carbonation segregated Mg into carbonate and Si into silica listvenites. Trace element mobility resulted in different enrichments of fluid-mobile, high field strength, and light rare earth elements in listvenites, indicating a “listvenite mobility sequence”.

The δ13C, δ18O and 87Sr/86Sr values of magnesite and dolomite in carbonated lithologies and veins point to sedimentary carbonate as the main C source. Fluid-mobile element (e.g., As and Sb) patterns in carbonated lithologies are consistent with contribution of subducted sediments in a forearc setting, suggesting sediment-derived fluids. Such fluids were produced by expulsion of pore fluids and release of structurally bound fluid from carbonate-bearing sediments in the Sistan Suture Zone (SsSZ) accretionary complex at shallow parts of mantle wedge. The CO2-bearing fluids migrated up along the slab-mantle interface and circulated through the suture zone faults to be sequestered in mantle peridotites with marked element mobility signatures.
Birjand ophiolite, C, O and Sr isotopes, Element mobility, Listvenite, Lizardite-antigorite serpentinization, Peridotite CO-sequestration
0024-4937
Boskabadi, Arman
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Pitcairn, Iain K.
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Leybourne, Matthew I.
124ba28f-0da3-40c8-9d35-12c20507ec66
Teagle, Damon A.H.
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Cooper, Matthew J.
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Hadizadeh, Hossein
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Nasiri Bezenjani, Rasoul
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Monazzami Bagherzadeh, Reza
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Boskabadi, Arman
934a59ff-f764-465f-9b20-fe773474bcf9
Pitcairn, Iain K.
e6c79a72-1150-49fe-8b03-95db13e69c2e
Leybourne, Matthew I.
124ba28f-0da3-40c8-9d35-12c20507ec66
Teagle, Damon A.H.
396539c5-acbe-4dfa-bb9b-94af878fe286
Cooper, Matthew J.
54f7bff0-1f8c-4835-8358-71eef8529e7a
Hadizadeh, Hossein
eb70d1d0-f9d8-497a-8154-10da29ecb40b
Nasiri Bezenjani, Rasoul
17aa41c1-17ce-4259-b774-495dd459dbbc
Monazzami Bagherzadeh, Reza
7903a2be-a410-4fdc-b55a-7c4c6505ffea

Boskabadi, Arman, Pitcairn, Iain K., Leybourne, Matthew I., Teagle, Damon A.H., Cooper, Matthew J., Hadizadeh, Hossein, Nasiri Bezenjani, Rasoul and Monazzami Bagherzadeh, Reza (2020) Carbonation of ophiolitic ultramafic rocks: Listvenite formation in the Late Cretaceous ophiolites of eastern Iran. Lithos, 352-353, [105307]. (doi:10.1016/j.lithos.2019.105307).

Record type: Article

Abstract

Late Cretaceous mantle peridotite of the Birjand ophiolite (eastern Iran) contains variably serpentinized and carbonated/listvenitized rocks. Transformation from harzburgite protolith to final listvenite (quartz + magnesite/± dolomite + relict Cr-spinel) reflects successive fluid-driven reactions, the products of which are preserved in outcrop. Transformation of harzburgite to listvenite starts with lizardite serpentinization, followed by contemporaneous carbonation and antigorite serpentinization, antigorite-talc-magnesite alteration, finally producing listvenite where alteration is most pervasive. The spectrum of listvenitic assemblages includes silica-carbonate, carbonate and silica listvenites with the latter (also known as birbirite) being the youngest, based on crosscutting relationships. The petrological observations and mineral assemblages suggest hydrothermal fluids responsible for the lizardite serpentinization had low aCO2, oxygen and sulfur fugacities, distinct from those causing antigorite serpentinization and carbonation/listvenitization, which had higher aCO2, aSiO2, and oxygen and sulfur fugacities. The carbonate and silica listvenite end-members indicate variations in aSiO2 and aCO2 of the percolating hydrothermal fluids, most likely driven by local variations in pH and temperature.

Beyond the addition of H2O, serpentinization did not significantly redistribute major elements. Progressive infiltration of CO2-rich fluids and consequent carbonation segregated Mg into carbonate and Si into silica listvenites. Trace element mobility resulted in different enrichments of fluid-mobile, high field strength, and light rare earth elements in listvenites, indicating a “listvenite mobility sequence”.

The δ13C, δ18O and 87Sr/86Sr values of magnesite and dolomite in carbonated lithologies and veins point to sedimentary carbonate as the main C source. Fluid-mobile element (e.g., As and Sb) patterns in carbonated lithologies are consistent with contribution of subducted sediments in a forearc setting, suggesting sediment-derived fluids. Such fluids were produced by expulsion of pore fluids and release of structurally bound fluid from carbonate-bearing sediments in the Sistan Suture Zone (SsSZ) accretionary complex at shallow parts of mantle wedge. The CO2-bearing fluids migrated up along the slab-mantle interface and circulated through the suture zone faults to be sequestered in mantle peridotites with marked element mobility signatures.

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Boskabadi_et_al_Lithos - Accepted Manuscript
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Accepted/In Press date: 26 November 2019
e-pub ahead of print date: 29 November 2019
Published date: 1 January 2020
Keywords: Birjand ophiolite, C, O and Sr isotopes, Element mobility, Listvenite, Lizardite-antigorite serpentinization, Peridotite CO-sequestration

Identifiers

Local EPrints ID: 437033
URI: http://eprints.soton.ac.uk/id/eprint/437033
ISSN: 0024-4937
PURE UUID: d5b65da4-5ebc-4775-8344-9229adfc5d14
ORCID for Damon A.H. Teagle: ORCID iD orcid.org/0000-0002-4416-8409
ORCID for Matthew J. Cooper: ORCID iD orcid.org/0000-0002-2130-2759

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Date deposited: 15 Jan 2020 17:32
Last modified: 26 Nov 2021 05:36

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Contributors

Author: Arman Boskabadi
Author: Iain K. Pitcairn
Author: Matthew I. Leybourne
Author: Hossein Hadizadeh
Author: Rasoul Nasiri Bezenjani
Author: Reza Monazzami Bagherzadeh

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