Trace element and Sr and Nd isotope geochemistry of peridotite xenoliths from the Eifel (West Germany) and their bearing on the evolution of the subcontinental lithosphere

Abstract Ultramafic xenoliths in alkali basalts from Jeju Island, Korea, are mostly spinel lherzolites with subordinate amounts of spinel harzburgites and pyroxenites. The compositions of major oxides and compatible to moderately incompatible elements of the Jeju peridotite xenoliths suggest that they are residues after various extents of melting. The estimated degrees of partial melting from compositionally homogeneous and unfractionated mantle to form the residual xenoliths reach 30%. However, their complex patterns of chondrite‐normalized rare earth element, from light rare earth element (LREE)‐depleted through spoon‐shaped to LREE‐enriched, reflect an additional process. Metasomatism by a small amount of melt/fluid enriched in LREE followed the former melt removal, which resulted in the enrichment of the incompatible trace elements. Sr and Nd isotopic ratios of the Jeju xenoliths display a wide scatter from depleted mid‐oceanic ridge basalt (MORB)‐like to near bulk‐earth estimates along the MORB–oceanic island basalt (OIB) mantle array. The varieties in modal proportions of minerals, (La/Yb) N ratio and Sr‐Nd isotopes for the xenoliths demonstrate that the lithospheric mantle beneath Jeju Island is heterogeneous. The heterogeneity is a probable result of its long‐term growth and enrichment history.

Xenolith

Peridotite

Alkali basalt

Ultramafic rock

Incompatible element

Metasomatism

Primitive mantle

10.1046/j.1440-1738.2002.00367.x

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Citations (33)

Contrasting Enrichments in High- and Low-Temperature Mantle Xenoliths from Nushan, Eastern China: Results of a Single Metasomatic Event during Lithospheric Accretion?

Journal of Petrology (2004)

Yi‐Gang Xu

Distinct equilibration temperatures, deformation and trace element characteristics are observed in amphibole-bearing and amphibole-free peridotite xenoliths from Nushan, Sino-Korean Craton, eastern China. Amphibole-free peridotites are predominantly deformed, fine-grained (∼1 mm) and equilibrated at 990–1110°C. Their cpx are characterized by either light rare earth element (LREE)-depleted or relatively flat REE patterns with only a slight depletion in high field strength elements (HFSE). LREE enrichment is generally associated with Fe-rich samples, consistent with 'wall-rock' metasomatism adjacent to basaltic veins. In contrast, amphibole-bearing peridotites are less deformed, coarse-grained (>3 mm) and display chemical zonation in the pyroxenes suggesting cooling from 1050 to 850°C. Their cpx show a large variation in LREE (Cen = 1·7–68) and almost constant heavy rare earth element (HREE) contents (Ybn = 9·8–11·6). The highest LREE contents occur in cpx from amphibole-rich samples, coupled with Fe enrichment, strong enrichment in Th and U, and marked depletion in the HFSE. These characteristics may be accounted for by combined 'wall-rock' and 'diffuse' metasomatism involving an agent rich in volatiles and incompatible elements. As such the Nushan xenoliths could represent samples from two spatially separate metasomatic aureoles. Conversely, the cryptic and modal metasomatism could be genetically related, because the amphibole-peridotites and Fe-rich amphibole-free samples show similar Sr–Nd isotopic ranges that are indistinguishable from those of the Cenozoic basalts from eastern China. The different metasomatic assemblage and the trace element composition can be accounted for in terms of P–T control on amphibole stability and progressive chemical evolution of asthenosphere-derived melts during upward migration. Trace element signatures and metasomatic assemblages, together with the fertile composition of the Nushan peridotites, suggest an origin as newly accreted lithosphere rather than as relic cratonic mantle. Metasomatism may have occurred after late Mesozoic lithospheric thinning, which marked a dramatic change in lithospheric architecture beneath the Sino-Korean Craton.

Metasomatism

Amphibole

Peridotite

Xenolith

Trace element

Rare-earth element

Primitive mantle

10.1093/petrology/egg098

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Citations (68)

Enrichment of upper mantle peridotite: petrological, trace element and isotopic evidence in xenoliths from SE China

Chemical Geology (2003)

Xisheng Xu Suzanne Y. O′Reilly William L. Griffin Xinmin Zhou

Metasomatism

Peridotite

Xenolith

Trace element

Incompatible element

Primitive mantle

Radiogenic nuclide

10.1016/s0009-2541(03)00004-4

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Citations (118)

Metasomatism in the subcontinental mantle beneath the Eastern Carpathians (Romania): new evidence from trace element geochemistry

Contributions to Mineralogy and Petrology (1997)

Fran x E oise Chalot-Prat Anne‐Marie Boullier

Metasomatism

Amphibole

Trace element

Peridotite

Xenolith

10.1007/s004100050338

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Citations (50)

Experimental modal metasomatism of a spinel lherzolite and the production of amphibole-bearing peridotite

Contributions to Mineralogy and Petrology (1995)

Cüneyt Şen Todd Dunn

Amphibole

Metasomatism

Peridotite

10.1007/bf00286939

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Citations (0)

Multiple Metasomatism beneath the Nógrád–Gömör Volcanic Field (Northern Pannonian Basin) Revealed by Upper Mantle Peridotite Xenoliths

Journal of Petrology (2017)

Nóra Liptai Levente Patkó István Kovàcs Károly Hidas Zsanett Pintér

Peridotite xenoliths from the Nógrád–Gömör Volcanic Field (NGVF) record the geochemical evolution of the subcontinental lithospheric mantle beneath the northern margin of the Pannonian Basin. This study is focused on spinel lherzolites and presents petrography, and major and trace element geochemistry for 51 xenoliths selected from all xenolith-bearing localities of the NGVF. The xenoliths consist of olivine, orthopyroxene, clinopyroxene and spinel ± amphibole. No correlations between modal composition and textures were recognized; however, major and trace element geochemistry reveals several processes, which allow the distinction of xenolith groups with different geochemical evolution. The xenoliths have undergone varying degrees (∼7–25%) of partial melting with overprinting by different metasomatic processes. Based on their Mg#, the xenoliths can be subdivided into two major groups. Group I has olivine Mg# between 89 and 91, whereas Group II has Mg# <89, significant enrichment of Fe and Mn in olivine and pyroxenes, and high Ti in spinel. Trace element contents of the xenoliths vary widely, allowing a further division based on light rare earth element (LREE) enrichment or depletion in pyroxenes. REE patterns of amphiboles match those of clinopyroxenes in each xenolith where they appear, and are inferred to have different origins based on their Nb (and other high field strength element) contents. It is proposed that Nb-poor amphiboles record the oldest metasomatic event, caused by subduction-related volatile-bearing silicate melts or fluids, followed by at least two further metasomatic processes: one that resulted in U–Th–(Nb–Ta)–LREE enrichment and crystallization of Nb-rich amphibole, affecting selective domains under the entire NGVF, and another evidenced by Fe–Mn–Ti–LREE enrichment, which overprinted early geochemical signatures. We suggest that the metasomatic agents in both cases were basaltic silicate melts, compositionally similar to the host basalts. These melts were generated during the Miocene extension of the Pannonian Basin. The effects of heating and subsequent cooling are evident in significantly different equilibration temperatures.

Metasomatism

Xenolith

Peridotite

Amphibole

Trace element

Incompatible element

Fractional crystallization (geology)

Primitive mantle

Rare-earth element

10.1093/petrology/egx048

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Citations (27)

Mechanisms and Sources of Mantle Metasomatism: Major and Trace Element Compositions of Peridotite Xenoliths from Spitsbergen in the Context of Numerical Modelling

Journal of Petrology (2002)

Dmitri A. Ionov Jean‐Louis Bodinier Samuel S.B. Mukasa Alberto Zanetti

Mineral and whole-rock chemical data for peridotite xenoliths in basaltic lavas on Spitsbergen are examined to reassess mechanisms of melt–fluid interaction with peridotites and their relative role versus melt composition in mantle metasomatism. The enrichment patterns in the xenoliths on primitive mantle-normalized diagrams range from Th–La–Ce ‘inflections’ in weakly metasomatized samples (normally without amphibole) to a continuous increase in abundances from Ho to Ce typical for amphibole-bearing xenoliths. Numerical modelling of interaction between depleted peridotites and enriched melts indicates that these patterns do not result from simple mixing of the two end-members but can be explained by chromatographic fractionation during reactive porous melt flow, which produces a variety of enrichment patterns in a single event. Many metasomatized xenoliths have negative high field strength element and Pb anomalies and Sr spikes relative to rare earth elements of similar compatibility, and highly fractionated Nb/Ta and Zr/Hf. Although amphibole precipitation can produce Nb–Ta anomalies, some of these features cannot be attributed to percolation-related fractionation alone and have to be a signature of the initial melt (possibly carbonate rich). In general, chemical and mineralogical fingerprints of a metasomatic medium are strongest near its source (e.g. a vein) whereas element patterns farther in the metasomatic ‘column’ are increasingly controlled by fractionation mechanisms.

Metasomatism

Peridotite

Xenolith

Amphibole

Trace element

Incompatible element

10.1093/petrology/43.12.2219

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Citations (341)

Contrasting styles of hydrous metasomatism in the upper mantle: An ion microprobe investigation

Geochimica et Cosmochimica Acta (1996)

Kathleen E. Johnson A. M. Davis L. Taras Bryndzia