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Communication Dans Un Congrès Année : 2021

A new tool to probe lithosphere evolution: OH signatures of pyroxenes

Résumé

Four OH stretching bands in the frequency range 3300 – 3700 cm-1 dominate the infrared spectraof lithospheric pyroxenes. Depending on their metasomatic history or geodynamic origin, theyhave characteristic OH signatures. Pyroxenes from continental lithosphere that undergone “wet”metasomatism have distinct signature of those having undergone “dry” metasomatism. Pyroxenesfrom oceanic lithosphere have yet a third type of signature. Our most recent analyses of xenolithsand a critical review of the literature show that the phenomenon is widely distributed amongcontinents and oceans. The phenomenon affects simultaneously opx and cpx from the same rockand various lithologies: peridotites, pyroxenites and granulites. In continental lithosphere,pyroxenes affected by “wet” metasomatism are dominated by OH bands at 3600 and 3415 cm-1 foropx and 3635 and 3445 cm-1 for cpx . Whereas pyroxenes affected by “dry” metasomatism aredominated by OH bands at 3570 and 3515 cm-1 for opx and 3595 and 3515 cm-1 for cpx. Opxsfrom oceanic lithosphere have OH spectra dominated by the band at 3415 cm-1, and with a smallerby bands at 3520 and 3570 cm-1 (Fig. 1).In all these observations it was not possible to correlate the signatures with a specific major, minoror trace element. Therefore, the exact nature of the observed signatures remains unidentified.Notwithstanding, these OH signatures are representative of specific lithospheric events and offer apotential new benchmark for the study of lithospheric processes.
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hal-03257123 , version 1 (10-06-2021)

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Jannick Ingrin. A new tool to probe lithosphere evolution: OH signatures of pyroxenes. EGU General Assembly 2021, EGU, Apr 2021, Vienna, Germany. ⟨hal-03257123⟩
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