Hf–Zr anomalies in clinopyroxene from mantle xenoliths from France and Poland: implications for Lu–Hf dating of spinel peridotite lithospheric mantle

Downes, Hilary; Vries, Caja de; Wittig, N.

doi:10.1007/s00531-014-1074-x

Cited by 16 publications

(17 citation statements)

References 60 publications

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“…Streap Com'laidh clinopyroxenes from Bonadiman et al (2008) have similar (Zr/Hf) N ratios as in 'primary' Loch Roag (LR80), but the characteristic convex LREE pattern of modal metasomatic phases, and substantially lower Th and U concentrations. Downes et al (2015) recently investigated the Zr and Hf composition of clinopyroxenes from French and Polish spinel peridotite mantle xenoliths. Initial extensive partial melting of primitive mantle removed both Zr and Hf, but these extreme depletions are rarely identified in mantle xenoliths globally.…”

Section: Rare-earth Elements Of the Sub-lewisian Lithospherementioning

confidence: 99%

Trace-element abundances in the shallow lithospheric mantle of the North Atlantic Craton margin: Implications for melting and metasomatism beneath Northern Scotland

et al. 2015

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Bulk rock geochemistry and major-and trace-element compositions of clinopyroxene have been determined for three suites of peridotitic mantle xenoliths from the North Atlantic Craton (NAC) in northern Scotland, to establish the magmatic and metasomatic history of subcontinental lithospheric mantle (SCLM) below this region. Spinel lherzolites from the southernmost locality (Streap Com'laidh) have non-NAC mantle compositions, while the two northern xenolith suites (Loch Roag and Rinibar) are derived from the thinned NAC marginal keel. Clinopyroxene compositions have characteristic trace-element signatures which show both 'primary' and 'metasomatic' origins. We use Zr and Hf abundances to identify ancient cryptic refertilization in 'primary' clinopyroxenes. We suggest that Loch Roag and Rinibar peridotite xenoliths represent an ancient ArchaeanPalaeoproterozoic SCLM with original depleted cratonic signatures which were overprinted by metasomatism around the time of intrusion of the Scourie Dyke Swarm (~2.4 Ga). This SCLM keel was preserved during Caledonian orogenesis, although some addition of material and/or metasomatism probably also occurred, as recorded by Rinibar xenoliths. Rinibar and Streap xenoliths were entrained in Permo-Carboniferous magmas and thus were isolated from the SCLM~200 Ma before Loch Roag xenoliths (in an Eocene dyke). Crucially, despite their geographical location, lithospheric mantle peridotite samples from Loch Roag show no evidence of recent melting or refertilization during the Palaeogene opening of the Atlantic.

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Section: Rare-earth Elements Of the Sub-lewisian Lithospherementioning

confidence: 99%

Trace-element abundances in the shallow lithospheric mantle of the North Atlantic Craton margin: Implications for melting and metasomatism beneath Northern Scotland

et al. 2015

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“…Since the major-and trace elements relationships in clinopyroxene are similar in Steinberg, we suggest that it originated here in a similar way. The deep Zr-Hf negative anomalies are rather rare and seem to be characteristic of the Lower Silesian -Upper Lusatian domain of European lithospheric mantle (Downes et al 2015) The occurrence of BA^harzburgites in both Krzeniów (offrift location) and Steinberg (on-rift) shows that the lithospheric mantle beneath the Eger Rift contains peridotites relatively little affected by pre-eruptive alkaline silicate melt metasomatism. Thus, the lithospheric mantle beneath the Eger Rift is possibly a mosaic of lithologies affected to different degrees by Cenozoic pre-eruptive metasomatism.…”

Section: Discussion Evolution Of Group a Harzburgitesmentioning

confidence: 96%

Depleted subcontinental lithospheric mantle and its tholeiitic melt metasomatism beneath NE termination of the Eger Rift (Europe): the case study of the Steinberg (Upper Lusatia, SE Germany) xenoliths

et al. 2015

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The ca. 30 Ma Steinberg basanite occurs at the NE termination of the Eger (Ohře) Rift in the NW Bohemian Massif, Central Europe, and belongs to the Cenozoic alkaline Central European Volcanic Province. The basanite hosts a suite of mantle xenoliths, most of which are harzburgites containing relatively magnesian olivine (Fo 90.5-91.6) and Alpoor (0.04-0.13 a pfu) orthopyroxene (mg# 0.90-0.92). Some of these harzburgites also contain volumetrically minor clinopyroxene (mg# 0.92-0.95, Al 0.03-0.13 a pfu) and have U-shaped LREE-enriched REE patterns. The Steinberg harzburgites are typical for the Lower Silesian -Upper Lusatian domain of the European subcontinental lithospheric mantle. They represent residual mantle that has undergone extensive partial melting and was subsequently affected by mantle metasomatism by mixed carbonatite-silicate melts. The Steinberg xenolith suite comprises also dunitic xenoliths affected by metasomatism by melt similar to the host basanite, which lowered the Fo content in olivine to 87.6 %. This metasomatism happened shortly before xenolith entrainment in the erupting lava. One of the xenoliths is a wehrlite (olivine Fo 73 %, clinopyroxene mg# 0.83-0.85, subordinate orthopyroxene mg# 0.76-0.77). Its clinopyroxene REE pattern is flat and slightly LREE-depleted. This wehrlite is considered to be a tholeiitic cumulate. One of the studied harzburgites contains clinopyroxene with similar trace element contents to those in wehrlite. This type of clinopyroxene records percolation of tholeiitic melt through harzburgite. The tholeiitic melt might be similar to Cenozoic continental tholeiites occurring in the Central European Volcanic Province (e.g., Vogelsberg, Germany).

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“…The trace element composition of melt in equilibrium with subgroup A2 clinopyroxene resembles that of host basanite-normalized patterns of both the melts are parallel except negative Ti, Zr-Hf and Nb-Ta anomalies occurring in a hypothetical melt. There is no consensus in the interpretation of Zr, Hf negative anomalies in mantle clinopyroxene (Downes et al 2015 and references therein). These anomalies can result from (1) melt extraction, or (2) crystallization from carbonatitic melt.…”

Section: Metasomatic Events In the Pilchowice Peridotitesmentioning

confidence: 99%

Lithospheric mantle beneath NE part of Bohemian Massif and its relation to overlying crust: new insights from Pilchowice xenolith suite, Sudetes, SW Poland

Ćwiek

Matusiak‐Małek

Puziewicz

et al. 2017

Int J Earth Sci (Geol Rundsch)

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The Oligocene/Miocene basanite from Pilchowice (Sudetes Mts., SW Poland) carries numerous small xenoliths of mantle peridotite, mostly harzburgite. The Pilchowice xenolith suite is dominated by harzburgites and dunites containing olivine Fo 90.2-91.5 (group A). The peridotites of group B (olivine Fo 88.6-89.4), and C (olivine Fo 83.2-86.5) are subordinate. The peridotites suffered from significant melt extraction (20-30%) and were subsequently subjected to metasomatism. Three different trace element compositional patterns of group A clinopyroxene occur, which are typical of silicate melt, carbonatite melt and silicate-carbonatite melt metasomatism, whereas groups B and C were affected by silicate melt metasomatism only. The Pilchowice basanite occurs at the contact of Karkonosze-Izera Block and Kaczawa Complex, two major geological units of Sudetes. The Pilchowice xenolith suite documents underlying lithospheric mantle of composition and depletion degree similar to those described in the whole Lower Silesian mantle domain, which forms NE termination of Saxo-Thuringian zone of the European Variscan orogen. The crustal structure of the orogen is, therefore, not mirrored in the mantellic root.

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Hf–Zr anomalies in clinopyroxene from mantle xenoliths from France and Poland: implications for Lu–Hf dating of spinel peridotite lithospheric mantle

Cited by 16 publications

References 60 publications

Trace-element abundances in the shallow lithospheric mantle of the North Atlantic Craton margin: Implications for melting and metasomatism beneath Northern Scotland

Trace-element abundances in the shallow lithospheric mantle of the North Atlantic Craton margin: Implications for melting and metasomatism beneath Northern Scotland

Depleted subcontinental lithospheric mantle and its tholeiitic melt metasomatism beneath NE termination of the Eger Rift (Europe): the case study of the Steinberg (Upper Lusatia, SE Germany) xenoliths

Lithospheric mantle beneath NE part of Bohemian Massif and its relation to overlying crust: new insights from Pilchowice xenolith suite, Sudetes, SW Poland

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