Extremely light Li in orogenic eclogites: The role of isotope fractionation during dehydration in subducted oceanic crust

Zack, Thomas; Tomascak, Paul B.; Rudnick, Roberta L.; Dalpé, Claude; McDonough, William F.

doi:10.1016/s0012-821x(03)00035-9

Cited by 237 publications

(165 citation statements)

References 61 publications

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“…Small grey dots are orogenic eclogites (Zack et al, 2003;Marschall et al, 2007b). Dehydration curves were modeled in a similar fashion to the Rayleigh distillation models from Zack et al (2003), MTEC = MORB-type eclogite, AEC = amphibole eclogite, ZEC = zoisite eclogite m = measured; numbers in parentheses give the internal error of the measurement referring to the last significant digit i = initial; initial Sr and Nd isotopic compositions were calculated for T = 130 Ma Rb, Sr, Sm and Nd concentration data are from John et al (2010) and Halama et al (2010) John et al (2010) and Halama et al (2010) …”

Section: Constraints On Fluid Sourcesmentioning

confidence: 99%

“…Recent studies demonstrated that the Li isotope system is very sensitive to metasomatic enrichment processes (Marschall et al, 2009;Penniston-Dorland et al, 2010). A pioneering study by Zack et al (2003) interpreted low δ 7 Li values in orogenic eclogites as a result of Li isotopic fractionation during subduction dehydration, but the later investigation by Marschall et al (2007b), which incorporated new experimental data, showed that Li isotope fractionation is most likely due to diffusion. Metamorphic dehydration of shales is similarly unable to shift Li isotope signatures significantly (Teng et al, 2007).…”

Section: Introductionmentioning

confidence: 99%

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A stable (Li, O) and radiogenic (Sr, Nd) isotope perspective on metasomatic processes in a subducting slab

et al. 2011

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Two distinct types of eclogites from the Raspas Complex (Ecuador), which can be distinguished based on petrography and trace element geochemistry, were analyzed for their stable (Li, O) and radiogenic (Sr, Nd) isotope signature to constrain metasomatic changes due to fluid-overprinting in metabasaltic rocks at high-pressure conditions and to identify fluid sources. MORB-type eclogites are characterized by a relative LREE depletion similar to MORB. High-pressure (HP) minerals from this type of eclogite have highly variable oxygen isotope compositions (garnet: +4.1 to +9.

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Section: Constraints On Fluid Sourcesmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

A stable (Li, O) and radiogenic (Sr, Nd) isotope perspective on metasomatic processes in a subducting slab

et al. 2011

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“…Zack et al (2003) documented for the first time that distinct reservoirs with an isotopically light Li signature (δ 7 Li << ±0‰) exist in the Earth (Fig. 1, e.g., Chan and Edmond, 1988;Chan et al, 1992Chan et al, , 1994Chan et al, , 1999Chan et al, , 2002bYou and Chan, 1996;Huh et al, 1998Huh et al, , 2001Moriguti and Nakamura, 1998a, b;Zhang et al, 1998;Tomascak et al, 1999aTomascak et al, , 2000Tomascak et al, , 2002Chan and Kastner, 2000;James and Palmer, 2000;.…”

Section: Introductionmentioning

confidence: 99%

“…Recently, dramatically low δ 7 Li values have been reported in several mantle-derived xenoliths, about -17‰ (Nishio et al, 2004), and in eclogites from Trescolmen, Switzerland, about -11‰ (Zack et al, 2003). The Trescolmen eclogites are considered to be an analog of oceanic crust subducted along a warm geotherm (Zack et al, 2002(Zack et al, , 2003.…”

Section: Introductionmentioning

confidence: 99%

Lithium, strontium, and neodymium isotopic compositions of oceanic island basalts in the Polynesian region: constraints on a Polynesian HIMU origin

et al. 2005

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To investigate the origin of the HIMU (high-µ) reservoir in the mantle, we measured Li, Sr, and Nd isotopic compositions of several oceanic island basalts (OIBs) from the Polynesian region. We used a recently developed multiple-collector inductively coupled plasma mass spectrometry method that allows precise and accurate Li isotopic determinations. This study presents the first Li isotopic data on HIMU OIBs. Li] L-SVEC standard -1] × 1000) of the Polynesian HIMU OIBs (Mangaia, Tubuai, and Rurutu) range from +5.0‰ to +7.4‰, which are higher than those of fresh normal mid-ocean ridge basalt (N-MORB) glasses (ca. +3‰). The simultaneously measured K/Rb, Ba/Rb, and 87 Sr/ 86 Sr ratios indicate that the analyzed HIMU OIBs are free from significant posteruption alteration. These results suggest that the δ 7 Li value of the Polynesian HIMU source is never lower than those of the N-MORBs.Among the numerous models for the origin of the HIMU source, the most widely accepted model is that it involves subducted (dehydrated) oceanic crust. For this HIMU-origin model, our new Li isotopic results exclude the highly altered portion, that is, the uppermost part of the oceanic crust, because the δ 7 Li value of subducted highly altered MORB should be extremely low (δ 7 Li < fresh MORB). For these reasons, we propose that the Polynesian HIMU source is the relatively less-altered oceanic crust underlying the highly altered crust. Whereas Pb, Sr, and Nd isotopic signatures dominantly indicate the involvement of sediments in a source, the Li isotopic signature is more sensitive to the degree of alteration experienced by the basaltic crust and thus can be used to distinguish what part of the crust was trapped in the OIB magma. It therefore provides information complementary to that provided by the radiogenic isotopes.

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“…useful tracers of mantle processes such as partial melting, crystallization and metasomatism (e.g., You et al, 1996;Moriguchi and Nakamura, 1998;Seyfried et al, 1998;Seitz and Woodland, 2000;Paquin and Altherr, 2002;Tomascak, 2004;Woodland et al, 2002Woodland et al, , 2004Seitz et al, 2003;Zack et al, 2003;Brooker et al, 2004;Nishio et al, 2004;Elliott et al, 2006;Scambelluri et al, 2006). Woodland et al (2004) measured Li content of minerals in eclogites and garnet clinopyroxenites from various tectonic settings and divided the samples into high-Li and low-Li groups.…”

Section: Constraints On Metasomatism From LI Contents Of Mineralsmentioning

confidence: 99%

Constraints on the evolutionary history of aluminous mafic rocks in the Ronda peridotite massif (Spain) from trace-element compositions of clinopyroxene and garnet

et al. 2009

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Multiple trace-element compositions of clinopyroxene and garnet in aluminous mafic layers (±corundum and/or sapphirine) alternating with peridotites from the Ronda massif, Spain, were determined by an ArF 193 nm excimer laser system coupled with a quadrupole ICP-MS. The studied aluminous mafic rock is divided into several sublayers based on the modal mineral variations. Trace-element compositions of minerals vary between sublayers. Primitive mantle-normalized trace-element distribution patterns have more significant positive Eu anomaly for both garnet and clinopyroxene in the corundum-bearing sublayers than for those in the other sublayers whereas corundum-bearing sublayers contain more abundant secondary plagioclase than corundum-free sublayers. These geochemical signatures of the corundum-bearing sublayers intercalated with corundum-free sublayers were acquired as plagioclase-rich portions of gabbroic layered sequence originated at the lower crustal to the uppermost mantle sections rather than selective accumulation of metamorphic plagioclase due to deformation during the late stage of exhumation of the massif. Partition coefficients of trace elements between clinopyroxene and garnet show systematic variations with respect to major element composition, indicating local attainment of chemical equilibrium. The trace element compositions of clinopyroxene and garnet were equilibrated with secondary metamorphic plagioclase, i.e., at granulite-facies conditions, because plagioclase is required for the geochemical balance in Sr and Eu contents of the whole-rock trace element compositions. Positive Eu anomaly of clinopyroxene (±garnet) is also found in mantle-derived aluminous eclogitic xenoliths and eclogitic mineral inclusions in diamond captured in kimberlites, and is thus a useful indicator to explore recycled crustal components in the mantle.

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Extremely light Li in orogenic eclogites: The role of isotope fractionation during dehydration in subducted oceanic crust

Cited by 237 publications

References 61 publications

A stable (Li, O) and radiogenic (Sr, Nd) isotope perspective on metasomatic processes in a subducting slab

A stable (Li, O) and radiogenic (Sr, Nd) isotope perspective on metasomatic processes in a subducting slab

Lithium, strontium, and neodymium isotopic compositions of oceanic island basalts in the Polynesian region: constraints on a Polynesian HIMU origin

Constraints on the evolutionary history of aluminous mafic rocks in the Ronda peridotite massif (Spain) from trace-element compositions of clinopyroxene and garnet

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