Decarbonation in an intracratonic setting: Insight from petrological‐thermomechanical modeling

Cratons form the stable core roots of the continental crust. Despite long‐term stability, cratons have failed in the past. Cratonic destruction (e.g., North Atlantic Craton) due to chemical rejuvenation at the base of the lithosphere remains poorly constrained numerically. We use 2‐D petrological‐th...

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Bibliographic Details
Published in:Journal of geophysical research. Solid earth 2017-08, Vol.122 (8), p.5992-6013
Main Authors: Gonzalez, Christopher M., Gorczyk, Weronika
Format: Article
Language:English
Subjects:
Breakup
Carbon dioxide
Carbon dioxide flux
Carbonates
Carbonation
Composition
Continental crust
Cratons
Decarbonation
Decay
Degassing
Duration
Fluxes
Geophysics
intracratonic decarbonation
intracratonic rifting
Isotopes
Lithosphere
Magma
Mantle
Mathematical models
Melting
Modelling
Preservation
Removal
Rheological properties
Rheology
Rifting
SCLM composition
Stability
Thermomechanical analysis
Thinning
Trends
Two dimensional models
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Summary:Cratons form the stable core roots of the continental crust. Despite long‐term stability, cratons have failed in the past. Cratonic destruction (e.g., North Atlantic Craton) due to chemical rejuvenation at the base of the lithosphere remains poorly constrained numerically. We use 2‐D petrological‐thermomechanical models to assess cratonic rifting characteristics and mantle CO2 degassing in the presence of a carbonated subcontinental lithospheric mantle (SCLM). We test two tectonothermal SCLM compositions: Archon (depleted) and Tecton (fertilized) using 2 CO2 wt % in the bulk composition to represent a metasomatized SCLM. We parameterize cratonic breakup via extensional duration (7–12 Ma; full breakup), tectonothermal age, TMoho (300–600°C), and crustal rheology. The two compositions with metasomatized SCLMs share similar rifting features and decarbonation trends during initial extension. However, we show long‐term (>67 Ma) stability differences due to lithospheric density contrasts between SCLM compositions. The Tecton model shows convective removal and thinning of the metasomatized SCLM during failed rifting. The Archon composition remained stable, highlighting the primary role for SCLM density even when metasomatized at its base. In the short‐term, three failed rifting characteristics emerge: failed rifting without decarbonation, failed rifting with decarbonation, and semifailed rifting with dry asthenospheric melting and decarbonation. Decarbonation trends were greatest in the failed rifts, reaching peak fluxes of 94 × 104 kg m−3. Increased TMoho did not alter the effects of rifting or decarbonation. Lastly, we show mantle regions where decarbonation, mantle melting in the presence of carbonate, and preservation of carbonated mantle occur during rifting. Key Points Varying subcontinental lithospheric mantle composition has little impact on decarbonation fluxes Greatest magnitude of CO2 fluxes observed during initial rifting stages and decays quickly during cooling of the thermal gradient Convective removal and thinning occurs in the Tecton SCLM composition, while the Archon SCLM composition remains stable
ISSN:2169-9313
2169-9356
DOI:10.1002/2017JB014051