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Deep partial melting of subducted carbon and the formation of sub-lithospheric diamonds and their mineral inclusions

Deep partial melting of subducted carbon and the formation of sub-lithospheric diamonds and their mineral inclusions

Objective

The key aspect of the Earth’s deep carbon cycle is how exogene carbon is recycled into the deeper earth via subduction of altered, carbonated, mafic oceanic crust. We aim to use ultrahigh-pressure experimental petrology to investigate the behaviour of subducted carbonate at pressures corresponding to the deep upper mantle, the mantle transition zone and the uppermost lower mantle. Earlier experimental studies showed that some residual crystalline carbonate in oceanic crust remains stable in subducting oceanic crust without decarbonation or melting, and may be transported to very deep levels in the mantle. It may form carbonate eclogite in the upper mantle and carbonate garnetite in the transition zone and uppermost lower mantle. How far carbon can survive this journey to extreme depths depends on the relationship between the pressure-temperature path followed by deeply subducting carbonated oceanic crust and its melting relations and solidus temperatures. We aim to use multi-anvil experimentation at the University of Bristol to determine melting relations in the deep upper mantle, transition zone, and uppermost lower mantle (9-21 GPa) of carbonate eclogite. We will explore the influences of pressure, temperature, oxygen fugacity and key bulk compositional variables such as Na2O/CO2 on very deep subduction of carbonate and on the volumes and compositions, and fates of carbonated partial melts. Fundamental research outcomes will include understanding of (1) the role of bulk composition in determining melting temperatures of deeply subducted, carbonate-bearing oceanic crust, and hence how deep carbonate melting can occur (2) how these carbonate melts interact with surrounding ambient peridotite mantle and what sort of geochemical sources and deeply derived magmas/fluids could be so generated (kimberlites, carbonatites, CH4-fluids), and (3) the formation of sublithospheric diamonds and their mineral inclusion suites.
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Coordinator

UNIVERSITY OF BRISTOL

Address

Beacon House Queens Road
Bs8 1qu Bristol

United Kingdom

Activity type

Higher or Secondary Education Establishments

EU Contribution

€ 154 617,60

Administrative Contact

Maria Davies (Mrs.)

Project information

Grant agreement ID: 623446

Status

Closed project

  • Start date

    12 January 2015

  • End date

    26 May 2017

Funded under:

FP7-PEOPLE

  • Overall budget:

    € 154 617,60

  • EU contribution

    € 154 617,60

Coordinated by:

UNIVERSITY OF BRISTOL

United Kingdom