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Water budget and partial melting in an Archean crustal column: example from the Dharwar Craton, India

Accepted version
Peer-reviewed

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Article

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Abstract

jats:titleAbstract</jats:title> jats:p The fluid budget of a composite crustal column is a critical parameter that influences many lithospheric processes. The amount of water introduced into the middle and lower crust can be quantified using phase equilibrium modelling. The Dharwar Craton, India, displays a now-exposed continuous crustal section from near-surface conditions to jats:italicc.</jats:italic> 30 km depth. This section records the different steps of a jats:italicc.</jats:italic> 15 myr-long high-temperature metamorphic event (60°C kbar jats:sup−1</jats:sup> ) responsible for the formation of syn- to post-tectonic anatectic intrusions. The global water budget is assessed using thermodynamic modelling on bulk-rock compositions of an average early Proterozoic supracrustal unit and jats:italicc.</jats:italic> 3.0 Ga felsic basement, the Peninsular gneisses. Results show the fast burial of a water-saturated supracrustal package (1.6 wt%) will release jats:italicc.</jats:italic> 50% of its mineral-bound water, triggering water-fluxed partial melting of the basement. Modelled anatectic magma compositions match the observed granitoid chemistries, and distinction can be made between water-fluxed melting and water-absent melting in the origin of syn- to post-tectonic anatectic granites. Findings from this study show the importance of crustal pile heterogeneity in controlling the nature of partial melting reactions, the composition of the magmas and the rheology of the crust. </jats:p>

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Keywords

37 Earth Sciences, 3703 Geochemistry, 3705 Geology, 3706 Geophysics

Journal Title

Geological Society, London, Special Publications

Conference Name

Journal ISSN

0305-8719
2041-4927

Volume Title

489

Publisher

Geological Society of London