Feldspar–Ti-oxide metasomatism in off-cratonic continental and oceanic upper mantle

Ionov, Dmitri A.; Grégoire, Marilaure; Prikhod’ko, V. S.

doi:10.1016/s0012-821x(98)00253-2

Cited by 81 publications

(38 citation statements)

References 20 publications

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“…In general, these metasomatic assemblages are texturally similar to xenolith-hosted secondary mineral associations usually attributed to mantle metasomatism (e.g. Ionov et al 1994;Zinngrebbe & Foley 1995;Wullf-Pedersen et al 1996Ionov et al 1999). It is, however, highly possible that the observed textural relationships do not represent the original textures inherited from the mantle.…”

Section: Different Styles Of Mantle Modificationsupporting

confidence: 60%

Mafic alkaline metasomatism in the lithosphere underneath East Serbia: evidence from the study of xenoliths and the host alkali basalts

Cvetković

Downes

Höck

et al. 2010

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Effects of mafic alkaline metasomatism have been interpreted by study of East Serbian (SE Europe) mantle xenoliths and petrogenesis of their host alkaline rocks. Fertile xenoliths (addition of >10 %vol. of metasomatic clinopyroxene) and tiny assemblages found in depleted xenoliths are distinguished. The fertile lithology contains Ti-Al-Cr-rich clinopyroxene, Fe-rich olivine, Fe-Al-rich orthopyroxene and Al-rich spinel. The composition of this lithology is modeled by addition of 5-20 wt% of a basanitic-like melt to a refractory mantle. The small-scale assemblages occur as pocket-like, symplectitic or irregular deformation-assisted accumulations of metasomatic phases, generally composed of Ti-Al-and incompatible elements-rich Cr-diopside, Cr-Fe-Ti-rich spinel, altered glass, olivine, apatite, ilmenite, carbonate and feldspar, as well as relicts of a high-TiO2 (~11 wt%) phlogopite. Textural relationships imply the following reaction: opx + Cr-rich sp ±phlogopite + Si-poor alkaline melt = Ti-Al-cpx + Ti-rich sp ± ol ± other minor phases. The inversion modeling, performed on least contaminated and most isotopically uniform host basanites, implies a source which is enriched in highly and moderately incompatible elements (~35-40xchondrite for U-Th-Nb-Ta, 2xchondrite for heavy rare earth elements) suggesting that the primary magma of the host basanites was not derived by melting of a homogeneous asthenospheric source. D0 values of the calculated basanitic source are similar to D0 values of anhydrous metasomatized mantle with small additions of metasomatic clinopyroxene and carbonate (~5 %) and with traces of ilmenite (~1 %) and apatite (~0.05 %). A schematic two-phase model involves percolation of CO2-and H2O-rich fluids, precipitation of metasomatic hydrous minerals and their subsequent breakdown due to the further uplift of hot asthenospheric mantle. This model uses a general idea of linking intraplate alkaline magmatism to lithospheric mantle sources enriched by sub-lithospheric melts at some time in the past. Mantle metasomatism is generally believed to be responsible for small-scale heterogeneities within the lithosphere (Dawson 1984; Harte 1984Harte , 1987Menzies et al. 1987). Evidence from the study of mantle xenoliths entrained in alkali basalts proved to be particularly important for understanding the origin of such heterogeneities. Studies have shown that the major metasomatic agents are: (i) carbonatitic melts (Baker et al. 1998;Yaxley et al. 1998;Gorring & Kay 2000; Wang & Gasparik 2001), (ii) silicate melts (Menzies et al. 1987;Vannucci et al. 1998;Zangana et al. 1999;Gregoire et al. 2000;Kepezhinskas et al. 1995Kepezhinskas et al. , 1996Schiano et al. 2002) and (iii) fluids (O'Reilly & Griffin 1988;Baker et al. 1998;Gorring & Kay 2000;Larsen et al. 2003), the latter two having a wide range of compositions. All these agents produce different metasomatic styles recognized by changes in primary mantle mineralogy and specific enrichments in trace element composition. It is widely accepted that mafic al...

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Section: Different Styles Of Mantle Modificationsupporting

confidence: 60%

Mafic alkaline metasomatism in the lithosphere underneath East Serbia: evidence from the study of xenoliths and the host alkali basalts

Cvetković

Downes

Höck

et al. 2010

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“…All of these signatures are characteristics of carbonatite metasomatism (Dupuy et al, 1992;Rudnick et al, 1993) and suggest that the source region for these lamprophyres had been infiltrated by carbonate-rich magmas (Furman and Graham, 1999). Therefore, the observed Zr/Hf and Nb/Ta fractionations in these rocks favored a rutileand carbonate-rich metasomatic assemblage as that documented in off-cratonic and oceanic peridotite xenoliths (e.g., Ionov et al, 1999;Grégoire et al, 2000b), in good agreement with the presence of clinopyroxene, rutile and apatite exsolutions in garnet from the UHP rocks (Ye et al, 2000), which suggested that rutile and apatite might have been dissolved from the UHP eclogites and involved in the metasomatic melts during the subduction and/or exhumation of the continental slabs.…”

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confidence: 72%

Origin of early Cretaceous calc-alkaline lamprophyres from the Sulu orogen in eastern China: implications for enrichment processes beneath continental collisional belt

Guo

Wang

et al. 2004

Lithos

233

161

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“…Furthermore, although many detailed studies have found that the rocks have been substantially modified by later metasomatic processes (e.g. Agrinier et al, 1993;Arai and Yurimoto, 1994;Johnson et al, 1996;McPherson et al, 1996;Ionov et al, 1999;McInnes et al, 2001), there has been little investigation of how these processes relate to PGE mineralization. The Finero complex, where the dunite and chromitite appear to have formed by reaction of peridotite and melt (Grieco et al, 2001), offers a good opportunity to explore the influence of metasomatism on PGE mineralization.…”

Section: Introductionmentioning

confidence: 99%

The effect of metasomatism on the Cr-PGE mineralization in the Finero Complex, Ivrea Zone, Southern Alps

Grieco

Ferrario

Mathez

2004

Ore Geology Reviews

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The magmatic metasomatism that was responsible for producing chromitite -dunite bodies in the unusual phlogopite peridotite of the Finero Complex in Permian to Triassic times also influenced the Cr-platinum group elements (PGE) mineralization. At least the end stages of this metasomatism are recorded in compositional zoning of chromite grains in the podiform chromitite. Metasomatic melt, with or without vapor, reacted with chromite to produce core-to-rim Cr enrichment of extant chromite grains and was concurrent with pyroxene crystallization. Under conditions of lower melt/rock ratio, metasomatism resulted in core-to-rim Al enrichment in chromite and crystallization of amphibole between chromite and clinopyroxene. This early, high-temperature metasomatism is unrelated to the later and pervasive K-metasomatism that crystallized phlogopite and was associated with the intrusion of clinopyroxenite dikes that cut the peridotite. Much later, serpentinization of olivine locally depleted chromite in Al and enriched it in Fe and formed minor amounts of magnetite.The PGE, which are present mainly as laurite inclusions in chromite, were remobilized by the early metasomatism. This resulted in substantial variation in the PGE contents of chromitites and imposed a characteristic PGE pattern in which chondritenormalized Os, Ir, Ru and Rh contents are high but Pt and Pd contents are low. The slopes of PGE chondrite-normalized concentration patterns are systematically related to absolute PGE abundance and to rock mode. Chromitites with low modal orthopyroxene, clinopyroxene, and amphibole exhibit negative PGE slopes and contain relatively high PGE concentrations, whereas chromitites rich in these silicate minerals have positive slopes and low PGE contents.

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Feldspar–Ti-oxide metasomatism in off-cratonic continental and oceanic upper mantle

Cited by 81 publications

References 20 publications

Mafic alkaline metasomatism in the lithosphere underneath East Serbia: evidence from the study of xenoliths and the host alkali basalts

Mafic alkaline metasomatism in the lithosphere underneath East Serbia: evidence from the study of xenoliths and the host alkali basalts

Origin of early Cretaceous calc-alkaline lamprophyres from the Sulu orogen in eastern China: implications for enrichment processes beneath continental collisional belt

The effect of metasomatism on the Cr-PGE mineralization in the Finero Complex, Ivrea Zone, Southern Alps

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