Titanium isotopes as a tracer for the plume or island arc affinity of felsic rocks

Deng, Zhengbin; Chaussidon, M.; Savage, Paul S.; Robert, François; Pik, Raphaël; Moynier, Frédéric

doi:10.1073/pnas.1809164116

Cited by 78 publications

(99 citation statements)

References 25 publications

(40 reference statements)

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“…thermodynamics of silicic magmas. The software is designed to constrain crystallization conditions, particularly related to feldspar crystallization, and has been successfully utilized in numerous petrographic studies (e.g., Deng et al 2019;Mutch et al 2019;Pearce and Reagan 2019). For this study, the models started with a superheated melt at 2000°C and evolved until crystallization was complete (with a minimum temperature of 700°C).…”

Section: Geochemical Modelingmentioning

confidence: 99%

Modeling the geochemical evolution of impact melts in terrestrial impact basins: Vredefort granophyre dikes and Sudbury offset dikes

Huber

Kovaleva

Riller

2020

Meteorit & Planetary Scien

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The Vredefort impact structure, South Africa, is comparable to the Sudbury impact structure, Canada, in size, age, and target rock composition. Both impact structures feature impact melt dikes. The melt sheet of the Sudbury impact (Sudbury Igneous Complex; SIC) is genetically linked to the Sudbury offset dikes in the underlying target rock. At Vredefort, the melt sheet was eroded so that only the granophyre dikes retain compositional melt sheet characteristics. XRF analyses of 43 samples from four granophyre dikes are similar to previous studies, but identify an anomalous mafic phase within one of the dikes. The results from the Vredefort granophyre dikes are compared to the Sudbury offset dikes and shown to follow similar geochemical trends, controlled by crystallization of feldspar and pyroxene. The mafic granophyre phase is compositionally remarkably similar to the offset dike compositions. The program Rhyolite-MELTS was used to test possible melt sheet compositions. Modeling results are broadly consistent with the overall chemical and mineral composition of the dikes. Modeling is consistent with offset dikes being derived from the basal mafic layer of the SIC, and the granophyre dikes being derived from alkalidepleted bulk continental crust. For all modeled compositions, crystallization primarily occurred at temperatures between 1150°C and 1000°C. The emplacement of the felsic granophyre dikes from a homogenized crustal melt suggests emplacement within tens of years after the impact event. The presence of the mafic phase in one of the granophyre dikes is explained by its emplacement following some differentiation of the Vredefort melt sheet.

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Section: Geochemical Modelingmentioning

confidence: 99%

Modeling the geochemical evolution of impact melts in terrestrial impact basins: Vredefort granophyre dikes and Sudbury offset dikes

Huber

Kovaleva

Riller

2020

Meteorit & Planetary Scien

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“…The Ti isotope composition of terrestrial samples (given as δ( 49 Ti/ 47 Ti) OL-Ti , relative to the Origins Lab reference material, henceforth δ 49 Ti; Millet and Dauphas, 2014) ranges between -0.046 and +1.8 ‰. Observed covariations between δ 49 Ti and SiO 2 , TiO 2, and FeO contents of terrestrial volcanic rocks suggest that stable Ti isotope variation is mainly driven by the onset of fractional crystallisation of Fe-Ti oxides during magmatic differentiation (Millet et al, 2016;Greber et al, 2017a,b;Deng et al, 2018aDeng et al, , 2019Mandl et al, 2018). Consequently, the Ti isotope composition of lunar magmas might be a sensitive indicator for the crystallisation of the IBC, and its assimilation or partial melting: Millet et al (2016) reported δ 49 Ti variations in three low-Ti mare basalts with a pooled δ 49 Ti of -0.008 ± 0.019 ‰ and five high-Ti mare basalts with δ 49 Ti between +0.011 and +0.033 ‰.…”

Section: Introductionmentioning

confidence: 99%

Unravelling lunar mantle source processes via the Ti isotope composition of lunar basalts

Horan¹,

Hilton

McCoy-West

et al. 2020

Geochem. Persp. Let.

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Formation and crystallisation of the Lunar Magma Ocean (LMO) was one of the most incisive events during the early evolution of the Moon. Lunar Magma Ocean solidification concluded with the coeval formation of K-, REE-and P-rich components (KREEP) and an ilmenite-bearing cumulate (IBC) layer. Gravitational overturn of the lunar mantle generated eruptions of basaltic rocks with variable Ti contents, of which their δ 49 Ti variations may now reflect variable mixtures of ambient lunar mantle and the IBC. To better understand the processes generating the spectrum of lunar low-Ti and high-Ti basalts and the role of Ti-rich phases such as ilmenite, we determined the mass dependent Ti isotope composition of four KREEP-rich samples, 12 low-Ti, and eight high-Ti mare basalts by using a 47 Ti-49 Ti double spike. Our data reveal significant variations in δ 49 Ti for KREEPrich samples (+0.117 to +0.296 ‰) and intra-group variations in the mare basalts (-0.030 to +0.055 ‰ for low-Ti and +0.009 to +0.115 ‰ for high-Ti basalts). We modelled the δ 49 Ti of KREEP using previously published HFSE data as well as the δ 49 Ti evolution during fractional crystallisation of the LMO. Both approaches yield δ 49 Ti KREEP similar to measured values and are in excellent agreement with previous studies. The involvement of ilmenite in the petrogenesis of the lunar mare basalts is further evaluated by combining our results with element ratios of HFSE, U and Th, revealing that partial melting in an overturned lunar mantle and fractional crystallisation of ilmenite must be the main processes accounting for mass dependent Ti isotope variations in lunar basalts. Based on our results we can also exclude formation of high-Ti basalts by simple assimilation of ilmenite by ascending melts from the depleted lunar mantle. Rather, our data are in accord with melting of these basalts from a hybrid mantle source formed in the aftermath of gravitational lunar mantle overturn, which is in good agreement with previous Fe isotope data.

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“…Kato and Moynier, 2017), or the formation and evolution of continental crust (e.g. Deng et al, 2019;Greber et al, 2017). Zirconium is one of the most refractory lithophile elements (half-mass condensation temperature of 1736 K) (Lodders, 2003).…”

Section: Introductionmentioning

confidence: 99%

The zirconium stable isotope compositions of 22 geological reference materials, 4 zircons and 3 standard solutions

et al. 2020

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Titanium isotopes as a tracer for the plume or island arc affinity of felsic rocks

Cited by 78 publications

References 25 publications

Modeling the geochemical evolution of impact melts in terrestrial impact basins: Vredefort granophyre dikes and Sudbury offset dikes

Modeling the geochemical evolution of impact melts in terrestrial impact basins: Vredefort granophyre dikes and Sudbury offset dikes

Unravelling lunar mantle source processes via the Ti isotope composition of lunar basalts

The zirconium stable isotope compositions of 22 geological reference materials, 4 zircons and 3 standard solutions

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