Pyroxenites embedded in peridotite are often invoked as a major cause of short-length scale isotopic heterogeneities in the upper mantle, but there has been little direct evidence. We report spatially controlled chemical and Sr-Nd isotopic compositions of pyroxenites and their host peridotites from an ophiolitic mantle sequence in the Northern Apennines, Italy, with depleted mantle compositions, representing a surface exposure of veined upper mantle, a potential source for mid-oceanic-ridge basalts (MORB). Interaction between pyroxenites and adjacent mantle rocks results in centimeter-scale chemical modifications in the host peridotites, systematically lowering their Sm/Nd ratios. Over time, this interaction causes the host peridotite at >0.1 m scale to acquire an isotopic heterogeneity larger than the range defined by the peridotite and pyroxenite end-members. Moreover, the Nd-143/Nd-144 variation of a single outcrop covers most of the global Nd isotopic variability documented in abyssal peridotites. Such pyroxenite-peridotite veined mantle domains may represent the enriched component rarely found in abyssal peridotites, but often invoked to account for the low end of Nd-143/Nd-144 variations in MORB.

Chemical and isotopic heterogeneity in meter-scale pyroxenite-peridotite mantle sequences from Northern Apennine ophiolites (Italy) / Borghini, G; Rampone, E; Zanetti, A; Class, C; Cipriani, Anna; Hofmann, A. W.; Goldstein, S. L.; Godard, M.. - In: RENDICONTI ONLINE DELLA SOCIETÀ GEOLOGICA ITALIANA. - ISSN 2035-8008. - 31, Suppl. 1:(2014). ((Intervento presentato al convegno The Future of the Italian Geosciences - The Italian Geosciences of the Future tenutosi a Milano nel 10-12/09/2014.

Chemical and isotopic heterogeneity in meter-scale pyroxenite-peridotite mantle sequences from Northern Apennine ophiolites (Italy)

CIPRIANI, Anna;
2014

Abstract

Pyroxenites embedded in peridotite are often invoked as a major cause of short-length scale isotopic heterogeneities in the upper mantle, but there has been little direct evidence. We report spatially controlled chemical and Sr-Nd isotopic compositions of pyroxenites and their host peridotites from an ophiolitic mantle sequence in the Northern Apennines, Italy, with depleted mantle compositions, representing a surface exposure of veined upper mantle, a potential source for mid-oceanic-ridge basalts (MORB). Interaction between pyroxenites and adjacent mantle rocks results in centimeter-scale chemical modifications in the host peridotites, systematically lowering their Sm/Nd ratios. Over time, this interaction causes the host peridotite at >0.1 m scale to acquire an isotopic heterogeneity larger than the range defined by the peridotite and pyroxenite end-members. Moreover, the Nd-143/Nd-144 variation of a single outcrop covers most of the global Nd isotopic variability documented in abyssal peridotites. Such pyroxenite-peridotite veined mantle domains may represent the enriched component rarely found in abyssal peridotites, but often invoked to account for the low end of Nd-143/Nd-144 variations in MORB.
The Future of the Italian Geosciences - The Italian Geosciences of the Future
Milano
10-12/09/2014
Borghini, G; Rampone, E; Zanetti, A; Class, C; Cipriani, Anna; Hofmann, A. W.; Goldstein, S. L.; Godard, M.
Chemical and isotopic heterogeneity in meter-scale pyroxenite-peridotite mantle sequences from Northern Apennine ophiolites (Italy) / Borghini, G; Rampone, E; Zanetti, A; Class, C; Cipriani, Anna; Hofmann, A. W.; Goldstein, S. L.; Godard, M.. - In: RENDICONTI ONLINE DELLA SOCIETÀ GEOLOGICA ITALIANA. - ISSN 2035-8008. - 31, Suppl. 1:(2014). ((Intervento presentato al convegno The Future of the Italian Geosciences - The Italian Geosciences of the Future tenutosi a Milano nel 10-12/09/2014.
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Utilizza questo identificativo per citare o creare un link a questo documento: https://hdl.handle.net/11380/1145481
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