Mechanisms of Mantle Metasomatism: Geochemical Evidence from the Lherz Orogenic Peridotite

Bodinier, Jean-Louis; Vasseur, G.; Vernieres, J.; Dupuy, C.; Fabriès, Jacques

doi:10.1093/petrology/31.3.597

Cited by 428 publications

(186 citation statements)

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“…Peridotite analyses by many authors have shown no correlation between increasing degree of serpentinization and REE pattern shape or REE concentrations (Bodinier et al, 1990;Frey et al, 1985;Gruau et al, 1991). However, we observe a significant difference in the Nd-isotope composition between pyroxenes and serpentine separated from the same sample (Fig.…”

Section: Relationship Between Leg 153 Peridotites and Magmatic Rockscontrasting

confidence: 43%

Petrology and geochemistry of nodular websterite inclusions in harzburgite, Hole 920D

Kempton¹,

Stephens²

1997

Proceedings of the Ocean Drilling Program, 153 Scientific Results

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Two nodular websterite inclusions (3-4 cm in diameter) were identified in the predominantly harzburgitic core in Hole 920D. These inclusions and a representative harzburgite from the same drill hole have been analyzed for their Sr-, Nd-, and Pbisotope ratios along with major-element mineral compositions to better understand their origin and significance. Elevated Srand Pb-isotope ratios provide abundant evidence for seawater interaction;208 Pb/ 204 Pb ratios are higher for a given 206 Pb/ 204 Pb than those of normal (i.e., away from plume/hotspot influences) mid-ocean ridge basalt (N-MORB) from the North Atlantic and are consistent with a model for alteration involving a component of pelagic sediment. In contrast, Nd isotopes are largely unaffected by alteration processes. The pyroxenes separated from the Site 920 peridotites have higher 143 Nd/ 144 Nd ratios than most North Atlantic N-MORB, and higher than any measured abyssal peridotite to date. Nodular websterites have slightly higher Nd-isotope ratios than the analyzed harzburgite. Both websterites and harzburgite are isotopically distinct from all magmatic rocks in the Mid-Atlantic Ridge south of the Kane Fracture Zone (MARK) area, including gabbros, diabase dikes, and recent basalts. Thus, in terms of their isotopic compositions, the analyzed peridotites are not representative of the mantle source of the MARK magmatic rocks. High aluminum, iron, and titanium contents in the websterite pyroxenes suggest a vein origin, possibly as a result of decompression melting in an upwelling diapir. These veins preceded the more numerous clinopyroxenite veinlets and gabbroic dikes observed throughout the Site 920 core and probably formed in the asthenosphere. These inclusions may thus be analogous to Type I/Type I composite relationships found in alpine peridotites and alkali-basalt hosted xenolith suites. They provide evidence that interaction between basaltic melts and peridotite residues is a common and varied occurrence in the genesis of oceanic lithosphere.

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Section: Relationship Between Leg 153 Peridotites and Magmatic Rockscontrasting

confidence: 43%

Petrology and geochemistry of nodular websterite inclusions in harzburgite, Hole 920D

Kempton¹,

Stephens²

1997

Proceedings of the Ocean Drilling Program, 153 Scientific Results

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“…Actually, in ultramafic xenoliths MREEenrichment with respect to HREE (e.g., high Tb/Yb ratios; Figs. 5b and c) and, more generally, the variable (from depleted to enriched) contents in highly incompatible trace elements (Nb, Ta, Rb, Ba and U), might be explained as the chromatographic effect induced by plumederived melts percolating through a depleted peridotite and affecting incompatible elements and REE in order of increasing partition coefficient (up to MREE; Bodinier et al, 1990;Takazawa et al, 1992;Bedini et al, 1997).…”

Section: Discussionmentioning

confidence: 99%

Ultramafic xenoliths from the Veneto Volcanic Province (Italy): Petrological and geochemical evidence for multiple metasomatism of the SE Alps mantle lithosphere

et al. 2006

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Petrologic and geochemical characteristics of whole rocks and minerals may be explained by metasomatism of the local mantle lithosphere induced by both alkaline magmas upwelling to the surface (OIB-like mantle diapirism) and interaction with slab-derived material. In comparison with the geochemistry of xenoliths carried by alkaline magmas in typical withinplate tectonic environments, the Veneto xenoliths record a major heterogeneity of the local lithosphere. This appears to be related to a geodynamic scenario that was previously dominated by active continental collision, in which plume-like magmatism subsequently manifested itself.

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“…These values for alkali basalt were used by Bodinier et al (1990) as a source of metasomatism and melt infiltration reacting on solid peridotite; they are appropriate for the present model. Even with an influx factor of only 10%, these lead to an order-of-magnitude increase for the LREE (note the logarithmic scale in Figure 14b).…”

Section: Discussionmentioning

confidence: 99%

Continuous (Dynamic) Melting Theory Revisited

Shaw¹

2000

The Canadian Mineralogist

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The concept of trace element behavior during mantle melting, in which melt is partially retained in the residue, was introduced by Langmuir et al. (1977), but without an explicit treatment of the process. Many subsequent workers have explored possible mechanisms, using both incremental (stepped) and continuous melting; most have discussed the melting of mantle to form basalt. Because calculations with the available models do not always give identical results, and because the assumptions embodied in those models are not always clear, this paper presents a complete statement of the formalism needed for modeling the melting of simple closed and open mantle systems, and the consequences of choosing particular values for model parameters.Keywords: melting, continuous melting, step melting, trace elements, incompatible elements, fractionation. SOMMAIRELe concept du comportement d'un élément trace au cours d'une fusion du manteau dans laquelle une partie du liquide est retenue dans le résidu a été introduit par Langmuir et al. (1977), mais sans traitement explicite du processus. Plusieurs chercheurs ont par la suite étudié des mécanismes possibles, en appliquant une fusion par étapes ou bien continue; la plupart ont traité de la fusion du manteau pour donner un liquide basaltique. Les calculs avec les modèles disponibles ne donnent pas toujours les mêmes réponses, parce que les suppositions de départ implicites ne sont pas toujours clairement exprimées. Cet article contient une expression complète du formalisme requis pour construire un modèle de fusion simple du manteau, soit en système ouvert ou fermé, et des conséquences d'un choix de valeurs particulières des paramètres du modèle.(Traduit par la Rédaction)

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Mechanisms of Mantle Metasomatism: Geochemical Evidence from the Lherz Orogenic Peridotite

Cited by 428 publications

References 0 publications

Petrology and geochemistry of nodular websterite inclusions in harzburgite, Hole 920D

Petrology and geochemistry of nodular websterite inclusions in harzburgite, Hole 920D

Ultramafic xenoliths from the Veneto Volcanic Province (Italy): Petrological and geochemical evidence for multiple metasomatism of the SE Alps mantle lithosphere

Continuous (Dynamic) Melting Theory Revisited

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