Comparison of 360 trace element analyses of clinopyroxenes from peridotites indicates that clinopyroxene composition cannot discriminate between suboceanic and subcontinental mantle. Clinopyroxenes from abyssal and fore-arc peridotites have the lowest incompatible element concentrations and record melting and basalt extraction as the dominant process. Clinopyroxenes from continental peridotite massifs partially overlap the composition of clinopyroxenes from abyssal peridotites and, in general, behave as a less depleted component in the chemical variation trends defined by the latter. In the peridotite massifs, subsolidus re-equilibration involving phase transitions (spinel to plagioclase facies) may cause significant element variations in clinopyroxene (e.g. Sr and Eu/Eu* decrease, REE, Ti increase). Metasomatic processes cause only comparatively minor trace element variations. Clinopyroxenes from mantle xenoliths in OIB and continental alkali basalts have the highest incompatible trace element concentrations and the largest compositional variations, They primarily record metasomatic enrichment processes, which are similar in suboceanic and subcontinental mantle. These processes induced the highest incompatible element enrichment in the clinopyroxenes from the most refractory peridotites, supporting the chromatographic nature of infiltration metasomatism. This enrichment, however, does not affect Ti, which is in the same concentration range in clinopyroxenes from both xenoliths and abyssal peridotites. The apparent Ti immobility may be due to several causes, such as reduced Ti solubility in hydrous fluids, fractionation of Ti-rich phases from percolating silicate melts, reaction with carbonatite melts formerly equilibrated with amphibole-peridotite. In general, clinopyroxene geochemistry does not allow a clear distinction between different metasomatic agents. The similarity between the geochemical characteristics of xenoliths from continental and oceanic environments supports previous results that the compositions of the pre-metasomatic lithosphere and of the asthenosphere, from where metasomatic agents derive, do not differ in the two environments.

Peridotite clinopyroxene chemistry reflects mantle processes rather than continental versus oceanic settings / Rivalenti, Giorgio; R., Vannucci; E., Rampone; Mazzucchelli, Maurizio; Gb, Piccardo; Em, Piccirillo; P., Bottazzi; L., Ottolini. - In: EARTH AND PLANETARY SCIENCE LETTERS. - ISSN 0012-821X. - STAMPA. - 139:(1996), pp. 423-437.

Peridotite clinopyroxene chemistry reflects mantle processes rather than continental versus oceanic settings

RIVALENTI, Giorgio;MAZZUCCHELLI, Maurizio;
1996

Abstract

Comparison of 360 trace element analyses of clinopyroxenes from peridotites indicates that clinopyroxene composition cannot discriminate between suboceanic and subcontinental mantle. Clinopyroxenes from abyssal and fore-arc peridotites have the lowest incompatible element concentrations and record melting and basalt extraction as the dominant process. Clinopyroxenes from continental peridotite massifs partially overlap the composition of clinopyroxenes from abyssal peridotites and, in general, behave as a less depleted component in the chemical variation trends defined by the latter. In the peridotite massifs, subsolidus re-equilibration involving phase transitions (spinel to plagioclase facies) may cause significant element variations in clinopyroxene (e.g. Sr and Eu/Eu* decrease, REE, Ti increase). Metasomatic processes cause only comparatively minor trace element variations. Clinopyroxenes from mantle xenoliths in OIB and continental alkali basalts have the highest incompatible trace element concentrations and the largest compositional variations, They primarily record metasomatic enrichment processes, which are similar in suboceanic and subcontinental mantle. These processes induced the highest incompatible element enrichment in the clinopyroxenes from the most refractory peridotites, supporting the chromatographic nature of infiltration metasomatism. This enrichment, however, does not affect Ti, which is in the same concentration range in clinopyroxenes from both xenoliths and abyssal peridotites. The apparent Ti immobility may be due to several causes, such as reduced Ti solubility in hydrous fluids, fractionation of Ti-rich phases from percolating silicate melts, reaction with carbonatite melts formerly equilibrated with amphibole-peridotite. In general, clinopyroxene geochemistry does not allow a clear distinction between different metasomatic agents. The similarity between the geochemical characteristics of xenoliths from continental and oceanic environments supports previous results that the compositions of the pre-metasomatic lithosphere and of the asthenosphere, from where metasomatic agents derive, do not differ in the two environments.
1996
139
423
437
Peridotite clinopyroxene chemistry reflects mantle processes rather than continental versus oceanic settings / Rivalenti, Giorgio; R., Vannucci; E., Rampone; Mazzucchelli, Maurizio; Gb, Piccardo; Em, Piccirillo; P., Bottazzi; L., Ottolini. - In: EARTH AND PLANETARY SCIENCE LETTERS. - ISSN 0012-821X. - STAMPA. - 139:(1996), pp. 423-437.
Rivalenti, Giorgio; R., Vannucci; E., Rampone; Mazzucchelli, Maurizio; Gb, Piccardo; Em, Piccirillo; P., Bottazzi; L., Ottolini
File in questo prodotto:
File Dimensione Formato  
1996RivalentiEtAl_daWeb.PDF

Accesso riservato

Tipologia: Versione dell'autore revisionata e accettata per la pubblicazione
Dimensione 1.37 MB
Formato Adobe PDF
1.37 MB Adobe PDF   Visualizza/Apri   Richiedi una copia
Pubblicazioni consigliate

Licenza Creative Commons
I metadati presenti in IRIS UNIMORE sono rilasciati con licenza Creative Commons CC0 1.0 Universal, mentre i file delle pubblicazioni sono rilasciati con licenza Attribuzione 4.0 Internazionale (CC BY 4.0), salvo diversa indicazione.
In caso di violazione di copyright, contattare Supporto Iris

Utilizza questo identificativo per citare o creare un link a questo documento: https://hdl.handle.net/11380/307042
Citazioni
  • ???jsp.display-item.citation.pmc??? ND
  • Scopus 62
  • ???jsp.display-item.citation.isi??? 49
social impact