Distribution of titanium and the rare earth elements between peridotitic minerals

McDonough, William F.; Stosch, H.-G.; Ware, N. G.

doi:10.1007/bf00310747

Cited by 108 publications

(40 citation statements)

References 29 publications

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“…However, when whole rock TiO2 concentrations are calculated using opx and cpx proportions and compositions, samples from dredges 3, 62 and 69 are less refractory than suggested by TiO2 contents in the only cpx, although dredges 3 and 69 still plot slightly below the abyssal peridotite trend in the TiO2 versus MgO diagram (Figure 13). Similar conclusion, that opx does take in a greater proportion of the whole rock Ti as melt depletion increases, was reached for other peridotite suites by Rampone et al [1991] and McDonough et al [1992]. This suggests that, in the most refractory peridotites, a high proportion of bulk TiO2 resides in the opx.…”

Section: Degree Of Melting Of Edul Peridotitessupporting

confidence: 68%

Evidence for major‐element heterogeneity in the mantle source of abyssal peridotites from the Southwest Indian Ridge (52° to 68°E)

Seyler

Cannat

Mével

2003

Geochem Geophys Geosyst

144

166

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[1] A suite of 53 samples of mantle spinel lherzolites and harzburgites dredged at 13 sites between 52°E and 68°E along the Southwest Indian Ridge has been studied for petrography and mineral major element chemistry. Results show that the residual mantle beneath this very slow-spreading/cold ridge is strongly heterogeneous in modal and mineral compositions at local and regional scales and underwent greater extents of melting than predicted by melting model and by compositions of the basalts dredged with the peridotites. Along-axis, the peridotite compositional variability defines a concave pattern with increasing depletion at both ends of the studied section (e.g., approaching Rodrigues Triple Junction to the East and Gallieni fracture zone to the west) that cannot be matched with the basalt compositions. Clinoyroxenes reflect depleted compositions (low modal abundances, high Cr and Mg, low Ti contents) but are paradoxally enriched in jadeite component, a feature that distinguishes these peridotites from common abyssal peridotites. Textural data show that major depletion in basaltic components and pyroxene Na enrichment are early features of the studied peridotites. In most samples, Na is nevertheless correlated with Ti suggesting that initial clinopyroxenes had high Na/Ti contents. Samples at both ends of the studied area have even higher Na/Ti ratios because of higher Na enrichment and higher Ti depletion, indicating metasomatic interaction. We conclude that along-axis compositional variations characterizing these peridotites are primary controlled by major element heterogeneity in the initial mantle, that have been preserved because of low degrees of melting beneath the Southwest Indian Ridge.

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Section: Degree Of Melting Of Edul Peridotitessupporting

confidence: 68%

Evidence for major‐element heterogeneity in the mantle source of abyssal peridotites from the Southwest Indian Ridge (52° to 68°E)

Seyler

Cannat

Mével

2003

Geochem Geophys Geosyst

144

166

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“…Contrasting to the previous work the values for D (chrome-spinel / clinopyroxene) are lower and for some elements were obtained from the chrome-spinels from peridotites provided in the xenoliths from alkaline basalts of Dreiser Weiher province (Germany): Eu -0.0007, Sm -0.0006 [52].…”

Section: Chrome-spinelscontrasting

confidence: 80%

Consistent patterns of rare earth element distribution in accessory minerals from rocks of mafic-ultramafic complexes

Lesnov

2013

Open Geosciences

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This paper summarizes analytical data accumulated in the world literature and other materials about the regularities of the REE distribution in minerals contained in ultramafic and mafic rocks as accessory phases. These minerals are tentatively divided into two groups. The first includes garnets, zircons, apatites and perovskites, which can accumulate increased amounts of REE in their structure. The second consists of minerals whose structure can accumulate only limited contents of these trace elements. These are chrome-spinels, ilmenites, and micas. These minerals, in respect of REE geochemistry, are studied to a varying degree because of the different levels of accumulations of these elements, different degrees of occurrence in rocks, tiny sizes of their grains and other reasons. The analytical database formed on their basis includes about 600 original analyses. The overwhelming majority of presently available data on REE geochemistry in accessory minerals from ultramafic and mafic rocks have been published only in the recent 15 years. The studies became possible due to the development and introduction of new highly sensible microprobe analyses allowing detection of REE and many other trace elements in minerals grains directly in thin sections. The greatest numbers of these analyses were performed for garnets and zircons, fewer for apatites, and the fewest for chrome-spinels, ilmenites, micas, and perovskites. In general, the regularities of REE distribution in these minerals from ultramafic and mafic rocks are less studied compared to the rock-forming minerals from ultramafic and mafic rocks. Among the analytical methods, which were used to study the REE composition of accessory minerals, the most efficient was the mass-spectrometry with inductively coupled plasma (ICP-MS).Keywords: REE distribution • ultramafic and mafic rocks • accessory minerals © Versita Sp. z o.o.

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“…Higher La/Yb ratio in spinel peridotite xenolith indicates that they have either been more strongly enriched in LREE during their formation or modified/metasomatized by the melt/fluid with a higher La/Yb ratio (McDonough 1990). Lower REE abundance and La/Yb ratio in garnet peridotite xenolith than in spinel peridotite xenolith are possibly caused by different olivine and clinopyroxene modes because clinopyroxene and garnet have been postulated to be main reservoirs of REE (Stosch 1982;McDonough et al 1992).…”

Section: Further Constraints On the Composition Of Lithospheric Mantlementioning

confidence: 87%

Geochemical syntheses among the cratonic, off-cratonic and orogenic garnet peridotites and their tectonic implications

Zhang

Tang

et al. 2010

Int J Earth Sci (Geol Rundsch)

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Garnet-bearing mantle peridotites, occurring as either xenoliths in volcanic rocks or lenses/massifs in high-pressure and ultrahigh-pressure terrenes within orogens, preserve a record of deep lithospheric mantle processes. The garnet peridotite xenoliths record chemical equilibrium conditions of garnet-bearing mineral assemblage at temperatures (T) ranging from *700 to 1,400°C and pressures (P) [ 1. 6-8.9 GPa, corresponding to depths of *52-270 km. A characteristic mineral paragenesis includes Cr-bearing pyropic garnet (64-86 mol% pyrope; 0-10 wt% Cr 2 O 3 ), Cr-rich diopside (0.5-3.5 wt% Cr 2 O 3 ), Al-poor orthopyroxene (0-5 wt% Al 2 O 3 ), high-Cr spinel (Cr/(Cr ? Al) 9 100 atomic ratio = 2-86) and olivine (88-94 mol% forsterite). In some cases, partial melting, re-equilibration involving garnet-breakdown, deformation, and mantle metasomatism by kimberlitic and/or carbonatitic melt percolations are documented. Isotope model ages of Archean and Proterozoic are ubiquitous, but Phanerozoic model ages are less common. In contrast, the orogenic peridotites were subjected to ultrahigh-pressure (UHP) metamorphism at temperature ranging from *700 to 950°C and pressure [3.5-5.0 GPa, corresponding to depths of [110-150 km. The petrologic comparisons between 231 garnet peridotite xenoliths and 198 orogenic garnet peridotites revealed that (1) bulk-rock REE (rare earth element) concentrations in xenoliths are relatively high, (2) clinopyroxene and garnet in orogenic garnet peridotites show a highly fractionated REE pattern and Ce-negative anomaly, respectively, (3) Fo contents of olivines for off-cratonic xenolith are in turn lower than those of orogenic garnet and cratonic xenolith but mgnumber of garnet for orogenic is less than that of offcratonic and on-cratonic xenolith, (4) Al 2 O 3 , Cr 2 O 3 , CaO and Cr# of pyroxenes and chemical compositions of whole rocks are very different between these garnet peridotites, (5) orogenic garnet peridotites are characterized by low T and high P, off-cratonic by high T and low P, and cratonic by medium T and high P and (6) garnet peridotite xenoliths are of Archean or Proterozoic origin, whereas most of orogenic garnet peridotites are of Phanerozoic origin. Taking account of tectonic settings, a new orogenic garnet peridotite exhumation model, crustmantle material mixing process, is proposed. The composition of lithospheric mantle is additionally constrained by comparisons and compiling of the off-cratonic, oncratonic and orogenic garnet peridotite.

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Distribution of titanium and the rare earth elements between peridotitic minerals

Cited by 108 publications

References 29 publications

Evidence for major‐element heterogeneity in the mantle source of abyssal peridotites from the Southwest Indian Ridge (52° to 68°E)

Evidence for major‐element heterogeneity in the mantle source of abyssal peridotites from the Southwest Indian Ridge (52° to 68°E)

Consistent patterns of rare earth element distribution in accessory minerals from rocks of mafic-ultramafic complexes

Geochemical syntheses among the cratonic, off-cratonic and orogenic garnet peridotites and their tectonic implications

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