Please use this identifier to cite or link to this item: https://hdl.handle.net/2440/126105
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Type: Journal article
Title: Phase relations and melting of nominally ‘dry’ residual eclogites with variable CaO/Na₂O from 3 to 5 GPa and 1250 to 1500 °C; implications for refertilisation of upwelling heterogeneous mantle
Other Titles: Phase relations and melting of nominally ‘dry’ residual eclogites with variable CaO/Na(2)O from 3 to 5 GPa and 1250 to 1500 °C; implications for refertilisation of upwelling heterogeneous mantle
Author: Rosenthal, A.
Yaxley, G.
Crichton, W.
Kovács, I.
Spandler, C.
Hermann, J.
Sándorné, J.
Rose-Koga, E.
Pelleter, A.
Citation: Lithos, 2018; 314-315:506-519
Publisher: Elsevier
Issue Date: 2018
ISSN: 0024-4937
1872-6143
Statement of
Responsibility: 
Anja Rosenthal, Gregory M. Yaxley, Wilson A. Crichton, István J. Kovács, Carl Spandler, Joerg Hermann, Judit K. Sándorné, Estelle Rose-Koga, Anne-Aziliz Pelleter
Abstract: This study investigates the phase and melting relations of nominally ‘dry’ residual eclogites (Res2 and Res3), with varying bulk CaO/Na2O ratios (4 and 12, respectively), from ~160 (5 GPa) to ~90 km (3 GPa) depth. Garnet, clinopyroxene and minor quartz/coesite are subsolidus phases in both compositions. In contrast to Res2, in Res3, the proportions of garnet always exceeding those of clinopyroxene. This also leads to higher modal quartz/coesite in Res3 relative to Res2. In modelling melting along a near-adiabatic upwelling path with a mantle potential temperature of ~1360 °C, at 5 GPa, near-solidus andesitic Res3 partial melts are much less siliceous and sodic, and are more calcic and magnesian than the incipient dacitic melts of Res2. Continuously self-fluxed melting increases considerably from 4 to 3 GPa due to the increased breakdown of Ca-Eskolaite solid solution component in clinopyroxene along the adiabat. This causes a steepening of the solidus, but more-so for Res2 than for Res3. At 3 GPa, the near exhaustion of residual clinopyroxene causes higher melt productivity for Res3 (~60%) than for Res2 (~30%), despite both melts being of basaltic-andesite composition. Resulting Res3 melts are therefore significantly more calcic and magnesian, and less sodic than those of Res2 melts. As Res3 undergoes a higher degree of melting relative to Res2 during adiabatic ascent, Res3 eclogitic residues become significantly more refractory; with relatively higher Mg# and grossular in garnet, higher Mg# and Ca-tschermaks, and lower jadeite components of clinopyroxene, and higher garnet/clinopyroxene ratios than eclogitic Res2 residuals. In upwelling heterogenous mantle domains, the siliceous eclogitic melts formed within a body of eclogite will react with encapsulating mantle peridotite, effectively refertilising it and producing hybrid pyroxene- and garnet-rich rocks. Subsequent melting of these sources may lead to compositionaly diverse primitive mantle-derived magmas, with high Ca/Al and low Na/Ca signatures indicators of preferential melting of a heterogeneous mantle, previously refertilised by recycled Ca-rich oceanic crustal material, and primitive magmas with low Ca/Al and high Na/Ca derived from melting of mantle with a ‘normal recycled crustal material signature’. Thus, compositional magma diversity may directly reflect precursor compositions of the mantle source region.
Keywords: Experimental petrology; residual eclogites; phase relations; heterogeneous mantle melting; petrogenesis of primitive mantle-derived magmas
Rights: © 2018 Elsevier B.V. All rights reserved.
DOI: 10.1016/j.lithos.2018.05.025
Grant ID: http://purl.org/au-research/grants/arc/DP0558189
Appears in Collections:Aurora harvest 4
Geology & Geophysics publications

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