Mobility of trace elements during subduction metamorphism as exemplified by the blueschists of the Kurtushibinsky Range, Western Sayan

Волкова, Н. И.; Stupakov, S. I.; Бабин, Г. А.; Руднев, С. Н.; Mongush, A. A.

doi:10.1134/s0016702909040053

Cited by 21 publications

(8 citation statements)

References 25 publications

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“…In contrast to the LILEs, HFSEs (e.g. Nb, Ta, Zr, Hf, and Ti) are fluid-immobile elements during water-rock interaction, as documented by petrological experiments (You et al 1996;Kogiso et al 1997) and studies of basalts (You et al 1996;Volkova et al 2009) and peridotites (Parkinson and Pearce 1998) from subduction zones. Global (Niu 2004) and regional data (Paulick et al 2006;Chen et al 2013) of peridotites indicate that the variation of HFSEs is attributed to magmatic processes such as mantle melting and melt refertilization.…”

Section: Geochemical Evidencementioning

confidence: 98%

Major and trace elements of abyssal peridotites: evidence for melt refertilization beneath the ultraslow-spreading Southwest Indian Ridge (53° E segment)

Chen

Chu

Zhu

et al. 2015

International Geology Review

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This study examines the geochemistry of major and trace elements of abyssal peridotites from the Southwest Indian Ridge (SWIR) (53°E amagmatic segment), to determine the influence of mafic melts on mantle peridotites during melt extraction. The results show a great geochemical variability in the~90 km-long ridge segment, with a degree of mantle melting ranging from 4% to 24%. An ancient melting event may explain the presence of highly depleted peridotites at the ultraslowspreading ridge. The 53°E segment peridotites show enrichment of light rare earth elements (LREEs) (average La N / Sm N = 1.87) and significant positive anomaly of U and Pb normalized to primitive mantle (PM). The positive correlations between LREEs (La, Ce, Pr, Nd) and high field strength elements (HFSEs; e.g. Nb and Zr) suggest that the enrichment of LREEs is caused by melt refertilization, which is also supported by prevalent magmatic microstructures in the peridotites. The melt refertilization model shows that the addition of 0.02-2.7% basaltic melts to peridotites can be responsible for the LREE enrichment. We suggest that the positive anomaly of U is probably attributed to fluid alteration whereas the enrichment of Pb is probably attributed to both melt refertilization and fluid alteration. Melt refertilization in the 53°E segment peridotites may be a result of melt-rock reaction and crystallization of melts trapped in peridotites. These processes may be enhanced by increased melt permeability in the mantle owing to the refractory peridotites produced by ancient melting and the decreasing efficiency of melt extraction in the cold and thick lithosphere at the 53°E ridge segment. The presence of melt refertilization implies that melt extraction is incomplete in the ridge mantle, which may be one of the reasons for the extremely thin and irregular variation of the crustal thickness at ultraslow-spreading ridges.

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Section: Geochemical Evidencementioning

confidence: 98%

Major and trace elements of abyssal peridotites: evidence for melt refertilization beneath the ultraslow-spreading Southwest Indian Ridge (53° E segment)

Chen

Chu

Zhu

et al. 2015

International Geology Review

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“…K, Rb, Cs), HFSEs (Nb, Ta, Zr, etc.) are essentially immobile to water-rock interaction (Woodhead et al 1993), which has been documented by dehydration experiments (Kogiso et al 1997), hydrothermal experiment (You et al 1996), and studies of metamorphism of oceanic crust during subduction and the formation of arc or back-arc basalts (Lau Workshop Report 2006; Volkova et al 2009). The variations of HFSE abundances can then be attributed to igneous processes such as partial melting, crystallization, or melt refertilization (Brunelli et al 2006;Paulick et al 2006).…”

Section: Correlations Between Hfse and Lreementioning

confidence: 98%

Influence of igneous processes and serpentinization on geochemistry of the Logatchev Massif harzburgites (14°45′N, Mid-Atlantic Ridge), and comparison with global abyssal peridotites

Chen

Zhou

Liu

et al. 2012

International Geology Review

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We acquired bulk-rock analyses of Mid-Atlantic Ridge (MAR) harzburgites in order to understand the influence of submarine igneous and metamorphic processes on the distribution of incompatible elements (especially rare Earth elements or REEs) in abyssal peridotites. The geochemical characteristics of these Logatchev Massif serpentinized and talc-altered harzburgites, and spatially associated metagabbros were then compared with a compilation of global abyssal peridotites. The Logatchev harzburgites show light rare earth element (LREE) enrichments (average La N /Yb N = 2.81), positive correlations between LREEs (e.g. La, Ce, Pr, and Nd) and high field strength elements (HFSEs; e.g. Nb and Zr), and positive correlations between HFSEs and Th. Most global abyssal peridotites show similar trends. We suggest that the systematic enrichment of incompatible elements probably reflects a post-partial fusion magmatic refertilization. The compositional scatter exhibited by some serpentinized peridotites in Nb-LREE diagrams is probably due to the elimination of diopside during partial melting and significant impregnation by a melt produced in the Opx-Ol-Sp melting field rather than to later hydrothermal alteration. The correlation between Pb and Nd observed for most global abyssal peridotites, including the Logatchev harzburgites, indicates magmatic generation. The scatter of Pb in some rocks suggests that lead is likely mobile during serpentinization or weathering. Low to moderate water/rock (W/R) ratios in the harzburgites calculated from Sr isotopic compositions (5.98-26.20 for a close system and 1.66-2.72 for an open system), and the low abundance of REEs in Logatchev hydrothermal fluids indicate that the REE contents of abyssal peridotites probably were little influenced by hydrothermal alteration. Compared to this later alteration, the presence of small proportions of gabbroic melt (from 1:30 to 1:3 in our sample) that crystallized in the residual harzburgites modified their REE patterns significantly by elevating the LREEs.

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“…As the volcanics are characterized by moderate to high L.O.I. and presence of secondary minerals (Section 4.1), they probably have undergone sub-marine hydrothermal alteration plus accretionrelated deformation and greenschist metamorphism, during which some elements, such as Rb, K, Na, Sr, Ba, Fe, and Pb, may be mobile (Safonova et al, 2008(Safonova et al, , 2012Volkova et al, 2009). The mobility of the light rare-earth elements (LREE) also can be proposed as they are more sensitive to secondary processes compared to the middle REE and the heavy REE (HREE), however that takes place only at high water/rock ratio or during carbonatization (Humphris, 1984), which is not observed in our case.…”

Section: Geochemistry: Background Alteration Key Featuresmentioning

confidence: 99%

“…The confusions caused by the use of geochemistry-based discrimination diagrams (see Section 6.1) may result from inaccurate or biased interpretation of geochemical data and from the changeability of initial compositions of basaltic rocks, because some elements, first of all, large-ion lithofile elements (LILE) but not only, could be mobile during post-magmatic processes including high-temperature hydrothermal alteration in sea-floor conditions, regional metamorphism and tectonic deformations (e.g., Humphris and Thompson, 1978;Thompson, 1991;Volkova et al, 2009;Safonova et al, 2012 and references therein). In addition, the lavas can be contaminated by crustal material in magmatic chambers or during their ascent to the surface.…”

Section: Discrimination Of Tectonics Settings: a Holistic Approach Bamentioning

confidence: 99%

Recognizing OIB and MORB in accretionary complexes: A new approach based on ocean plate stratigraphy, petrology and geochemistry

et al. 2016

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Mobility of trace elements during subduction metamorphism as exemplified by the blueschists of the Kurtushibinsky Range, Western Sayan

Cited by 21 publications

References 25 publications

Major and trace elements of abyssal peridotites: evidence for melt refertilization beneath the ultraslow-spreading Southwest Indian Ridge (53° E segment)

Major and trace elements of abyssal peridotites: evidence for melt refertilization beneath the ultraslow-spreading Southwest Indian Ridge (53° E segment)

Influence of igneous processes and serpentinization on geochemistry of the Logatchev Massif harzburgites (14°45′N, Mid-Atlantic Ridge), and comparison with global abyssal peridotites

Recognizing OIB and MORB in accretionary complexes: A new approach based on ocean plate stratigraphy, petrology and geochemistry

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