Siderophile Elements in Tracing Planetary Formation and Evolution

Walker, Richard J.

doi:10.7185/geochempersp.5.1

Cited by 43 publications

(30 citation statements)

References 390 publications

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“…Chrome spinels derived from boninites in Ogasawara and Guam have low 187 Os/ 188 Os ratios of 0.120 1–0.126 2 and 0.120 8–0.131 5, respectively (Senda et al, ; Suzuki et al, ), most of which are less radiogenic than the average primitive upper mantle ( 187 Os/ 188 Os = 0.129 6) (Meisel, Walker, Irving, & Lorand, ) and chondritic uniform reservoir (CHUR) ( 187 Os/ 188 Os = 0.127 6) (Walker, Prichard, Ishiwatari, & Pimentel, ). More than half of the chrome spinel data are even lower than the estimated DMM value ( 187 Os/ 188 Os = 0.125 0) (Walker, ), suggesting the old Re depletion and isolation for a long time. Likewise, comparably low 187 Os/ 188 Os ratios (0.119 3–0.120 5) are known from depleted harzburgite drilled on serpentinite seamounts in the Izu and Mariana forearcs, which is proposed to be the source of boninites (Parkinson, Hawkesworth, & Cohen, ).…”

Section: Discussionmentioning

confidence: 95%

Did boninite originate from the heterogeneous mantle with recycled ancient slab?

et al. 2017

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Boninites are widely distributed along the western margin of the Pacific Plate extruded during the incipient stage of the subduction zone development in the early Paleogene period. This paper discusses the genetic relationships of boninite and antecedent protoarc basalt magmas and demonstrates their recycled ancient slab origin based on the T-P conditions and Pb-HfNd-Os isotopic modeling. Primitive melt inclusions in chrome spinel from Ogasawara and Guam islands show severely depleted high-SiO 2 , MgO (high-silica) and less depleted low-SiO 2 , MgO (low-silica and ultralow-silica) boninitic compositions. The genetic conditions of 1 346 C at 0.58 GPa and 1 292 C at 0.69 GPa for the low-and ultralow-silica boninite magmas lie on adiabatic melting paths of depleted mid-ocean ridge basalt mantle with a potential temperature of 1 430 C in Ogasawara and of 1 370 C in Guam, respectively. This is consistent with the model that the low-and ultralow-silica boninites were produced by remelting of the residue of the protoarc basalt during the forearc spreading immediately following the subduction initiation. In contrast, the genetic conditions of 1 428 C and 0.96 GPa for the high-silica boninite magma is reconciled with the ascent of more depleted harzburgitic source which pre-existed below the Izu-Ogasawara-Mariana forearc region before the subduction started. Mixing calculations based on the Pb-Nd-Hf isotopic data for the Mariana protoarc basalt and boninites support the above remelting model for the (ultra)low-silica boninite and the discrete harzburgite source for the high-silica boninite. Yb-Os isotopic modeling of the high-Si boninite source indicates 18-30 wt% melting of the primitive upper mantle at 1.5-1.7 Ga, whereas the source mantle of the protoarc basalt, the residue of which became the source of the (ultra)low-Si boninite, experienced only 3.5-4.0 wt% melt depletion at 3.6-3.1 Ga, much earlier than the average depleted mid-ocean ridge basalt mantle with similar degrees of melt depletion at 2.6-2.2 Ga. K E Y W O R D Sancient slab recycle, boninite, depleted mid-ocean ridge basalt mantle, mantle heterogeneity, Mariana forearc, Ogasawara forearc, Pb-Nd-Hf isotopes, Re-Os model age | INTRODUCTIONThe upper mantle is mainly composed of the depleted mid-ocean ridge basalt (MORB) mantle (DMM), which was considered to be a relatively uniform reservoir through stirring and homogenization by convection for over 4 billion years, at least in major element terms (Allégre, 2002;Tatsumi, 1995). On the contrary, accumulating evidence of isotopic and trace element observations indicates that the DMM is heterogeneous consisting of fertile and refractory peridotites including recycled crust (e.g. Allégre, 2002;Walker, 2016;Zindler & Hart, 1986;Zindler, Staudigel, & Batiza, 1984 Nowell, & Noble, 1999). The radiogenic affinity of the Indian-type mantle is ascribed to time-integrated contamination of plumes that brought up the remnants of subducted slab beneath the Gondwana continent (Anderson, 1982;Staudigel et al., 1991) o...

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Section: Discussionmentioning

confidence: 95%

Did boninite originate from the heterogeneous mantle with recycled ancient slab?

et al. 2017

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“…A stable crust slowed convection and thus pro-vided a continued conservation of mantle heterogeneities, revealed, for example, as small deviations of 182 W and 142 Nd isotope abundance from the average mantle composition [e.g., Walker, 2016]. This scenario is shared by most researchers of the earliest Earth's tectonics [Griffin et al, 2014;Johnson et al, 2014;O'Neill and Debaille, 2014;Van Hunen and Moyen, 2012;Van Thienen et al, 2004].…”

Section: The Ancient Crustmentioning

confidence: 83%

“…The chondritic NM relative abundances also follow from 190 Pt-187 187 Os isotopic systematics [Meisel et al, 2001;Walker, 2015]. This feature of the mantle NM abundances is known since long [e.g., Wanke et al, 1984] and is repeatedly discussed in the literature [Holzheid et al, 2000;Kramers, 1998;Maier et al, 2009;Walker, 2016]. Recently it was emphasized, that the Hadean Os isotopic signature was preserved in the convecting mantle due to high recycling efficiencies for Os [Jackson et al, 2016].…”

Section: Noble Metal Abundances In the Mantlementioning

confidence: 94%

“…Within the convective depleted mantle the sunken crust + regolith were (i) partially mixed with the mantle materials, thus providing the occurrence of NM in the Earth's mantle in chondritic relationships [Walker, 2016]; (ii) partially preserved as an isolated mantle reservoir [Jackson et al, 2010;Tolstikhin and Hofmann, 2005], thus providing the contributions of solar He, Ne [Graham, 2002], 129 Xe(I), 136 Xe(Pu), Q-Xe [Caracausi et al, 2016;Parai and Mukhopadhyay, 2015] and meteoritic Kr [Holland et al, 2009] in mantle rocks and gases.…”

Section: 83mentioning

confidence: 99%

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The late Earth's accretion: Processes and materials

Tolstikhin¹

2018

Russ. J. Earth Sci.

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In accord with the standard Earth accretion scenario, the late accretion supervened the last collision with a massive proto-planet, segregation of the core, and (partial) solidification of the magma ocean. These processes took place ≈ 40 Ma after Sun formation or somewhat later. Traces of the processes and respective materials have been preserved as specific elemental and isotopic abundances in the earth's mantle. Pu-238 U-129 I-Xe systematics trace the accreting materials and the rate of mantle mixing and degassing. Recently proposed interpretations of this last systematics appear to be precarious and are particularly discussed in this contribution. During the late accretion a terrestrial regolith, including chondritic and solar-wind-irradiated materials, was rapidly accumulating on the surface of the early thick basaltic crust, enriched in incompatible elements. This early crust had not been preserved. Its overturn(s) into the mantle during several 100th Ma after Sun formation and (partial) isolation from the mantle convection allow all principal observations, related to the informative systematics mentioned above, to be satisfied, providing the transfer of the crust®olith "cake" was not accompanying by fractionation and degassing, in contrast to present-day slab subduction.

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“…Fedkin et al (2015) suggested that impacting planetesimals that have differentiated CR chondrite-like composition could have produced CB metal grains and chondrules. Because the D metal/silicate values are generally in the order of Ir > Os > Re (Mann et al 2012;Brenan et al 2016;Walker 2016), it is conceivable that a core differentiated from a chondritic parent body had subchondritic Re/Os and Os/Ir ratios. However, the slope of the correlation between (Re/ Os) estim and Os/Ir ratios is too steep to fit the calculated condensation trajectories even if the gaseous reservoir initially had Re/Os and Os/Ir ratios as low as those of the sample B9 ([Re/Os] estim = 0.080, Os/Ir = 0.97).…”

Section: Re-os-ir Correlation In Cb a Metalsmentioning

confidence: 99%

Re‐Os isotope systematics and fractionation of siderophile elements in metal phases from CB_a chondrites

Nakanishi

Yokoyama

Okabayashi

et al. 2018

Meteorit & Planetary Scien

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We report Os isotope compositions of metal grains in two CBa chondrites (Bencubbin and Gujba) determined using a micromilling sampling coupled with thermal ionization mass spectrometry, together with the abundances of major and trace siderophile elements obtained by electron probe microanalysis and femtosecond laser ablation inductively coupled plasma–mass spectrometry. The CBa metal grains presented 187Os/188Os ratios akin to carbonaceous chondrites with limited variations (0.1257–0.1270). Most of the CBa metal grains were scattered along a 187Re‐187Os reference isochron of IIIAB iron meteorites, indicating that the CBa metals experienced limited Re‐Os fractionation at the time of their formation. The Re/Os ratios of sampling spots for the CBa metals, recast from the observed 187Os/188Os ratios, had a positive correlation with their Os/Ir ratios. In addition, the metal grains showed a positive correlation in a Pd/Fe versus Ni/Fe diagram. These correlations suggest that the CBa metal grains have formed via equilibrium condensation or evaporation from a gaseous reservoir at ~10−4 bar with enhanced metal abundances. Compared to the Bencubbin metals, the Gujba metals are characterized by having systematically lower Pd/Fe and Ni/Fe ratios that span subchondritic values. Such a difference was most likely induced by the compositionally heterogeneous impact plume from which the metals were condensed.

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Siderophile Elements in Tracing Planetary Formation and Evolution

Cited by 43 publications

References 390 publications

Did boninite originate from the heterogeneous mantle with recycled ancient slab?

Did boninite originate from the heterogeneous mantle with recycled ancient slab?

The late Earth's accretion: Processes and materials

Re‐Os isotope systematics and fractionation of siderophile elements in metal phases from CB_a chondrites

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Siderophile Elements in Tracing Planetary Formation and Evolution

Cited by 43 publications

References 390 publications

Did boninite originate from the heterogeneous mantle with recycled ancient slab?

Did boninite originate from the heterogeneous mantle with recycled ancient slab?

The late Earth's accretion: Processes and materials

Re‐Os isotope systematics and fractionation of siderophile elements in metal phases from CBa chondrites

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Resources

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Re‐Os isotope systematics and fractionation of siderophile elements in metal phases from CB_a chondrites