Modification of oceanic lithospheric mantle by percolated melts sourced from recycled ancient crust: Evidence from Ca-Os isotopes of refractory harzburgites
Rui, H.; Namur, O.; Lian, D.; Cai, P.; Li, J.; Valdes Mariño, Y.; Yang, J.; He, H. (2025). Modification of oceanic lithospheric mantle by percolated melts sourced from recycled ancient crust: Evidence from Ca-Os isotopes of refractory harzburgites. Chem. Geol. 695: 123077. https://dx.doi.org/10.1016/j.chemgeo.2025.123077
In: Chemical Geology. Elsevier: New York; London; Amsterdam. ISSN 0009-2541; e-ISSN 1872-6836, more
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| Author keywords |
Re - Os isotope;Melt-peridotite interaction;Recycled ancient oceanic crust;Mantle harzburgite;highly siderophile elements;platinum-group elements;eastern cuba;abyssal peridotites;subduction zones;depleted mantle;volcanic-rocks;ortho-pyroxene;icp-ms;ophiolite |
| Authors | | Top |
- Rui, H.
- Namur, O., more
- Lian, D.
- Cai, P.
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- Li, J.
- Valdes Mariño, Y.
- Yang, J.
- He, H.
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| Abstract |
Oceanic lithospheric mantle, initially formed beneath the oceanic plate's spreading center, is frequently altered through interaction with mantle-derived mafic melts migrating upward to the crustal regions. Highly refractory harzburgites often retain trace interstitial clinopyroxene and base-metal sulfides (BMS) that precipitate during the interaction with percolating melts. In this study, we present the whole-rock and mineral Ca as well as ReOs isotope compositions of harzburgites from the Moa-Baracoa ophiolite in Cuba, to uncover the melt-peridotite interaction processes and evaluate their impact on the composition of the lithospheric mantle. Thermodynamic modeling indicates that the studied harzburgites have undergone a high degree (20-30 %) of partial melting compared to the depleted mid-ocean ridge basalts mantle, followed by interaction with a very small amount (<2 %) of fore-arc basaltic melts within the lithospheric mantle. The whole-rock delta(44)/Ca-40 values, ranging from 1.06 parts per thousand to 1.31 parts per thousand, are lower than those calculated for highly refractory harzburgites that have experienced 20-30 % partial melting. This suggests an offset caused by interstitial clinopyroxene with light delta(44)/Ca-40. Moreover, the elevated Os-187/Os-188 ratios (0.1271-0.1401), combined with low Re concentrations (0.03-0.64) and Re-187/Os-188 ratios (0.08-1.40), imply the addition of radiogenic Os derived either from the subducted slab or ancient crustal components recycled in the mantle. The negative trend of increasing Os-187/Os-188 ratios with decreasing delta(44)/Ca-40 values further validates the co-precipitation of sulfides and clinopyroxene in the Moa-Baracoa harzburgite. Notably, similar mineral assemblages and whole-rock radiogenic Os compositions are observed in certain abyssal peridotites and ophiolitic peridotites. Binary mixing calculations demonstrate that such ReOs characteristics can only occur when rare BMS precipitate from percolating mafic melts with small fractions originating from recycled ancient crust. |
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