An Earth–Moon silicon isotope model to track silicic magma origins

Poitrasson, Franck; Zambardi, Thomas

doi:10.1016/j.gca.2015.07.005

Cited by 30 publications

(39 citation statements)

References 63 publications

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“…The  30 Si value of the gneissic bedrock is -0.34 ± 0.08 ‰ (Table 1), which falls within the lowest part of the range defined for igneous rocks (Savage et al, 2012). The gneiss signature is consistent with the light signatures observed in metasediment-derived igneous bedrock (Savage et al, 2012, Poitrasson & Zambardi, 2015. The isotopic signatures of the bulk ferralsol samples are very close to those of the bedrock composition.…”

Section:  30 Si Values Of Bedrock Soils and Suspended Loadsupporting

confidence: 67%

Processes controlling silicon isotopic fractionation in a forested tropical watershed: Mule Hole Critical Zone Observatory (Southern India)

Riotte

Meunier

Zambardi

et al. 2018

Geochimica et Cosmochimica Acta

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Assessing the dynamics of the silica cycle in the critical zone remains challenging, particularly within the soil, where multiple processes are involved. To improve our understanding of this cycle in the Tropics, and more specifically the role played by vegetation, we combined elemental Si mass balance with the  30 Si signatures of the compartments involved in the water-plant-rock interactions of a tropical forested watershed, Mule Hole (Southern India). To accomplish this, we analysed (1) the  30 Si values of presentday litter phytoliths from tree leaves and grass, as well as soil amorphous silica (ASi); (2) the Si isotope fractionation induced by phytolith dissolution; (3) the silicon mass balance inferred from isotopes at the soil-plant scale; and (4) the consistency between water sources and the  30 Si signatures in the ephemeral stream. The  30 Si values of present-day litter phytoliths and soil ASi vary within a narrow range of 1.10 to 1.40 ‰ for all samples, but two deep vertisol samples which likely trapped phytoliths from different vegetation growing under more humid conditions, as indicated by pollen analysis. A homogeneous signature of litter is a minimum condition for using  30 Si as a

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Section:  30 Si Values Of Bedrock Soils and Suspended Loadsupporting

confidence: 67%

Processes controlling silicon isotopic fractionation in a forested tropical watershed: Mule Hole Critical Zone Observatory (Southern India)

Riotte

Meunier

Zambardi

et al. 2018

Geochimica et Cosmochimica Acta

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“…Melt assimilation of the weathered products described above may be used to explore past environments only if the isotopic composition of the whole rock (WR) and minerals--including zircon--partially, at least, reflect these original altered products. Such variations in WR Si isotope compositions, linked unequivocally to source variation, have been measured in several localities, including the Lachlan Fold Belt (21,22). Moreover, there is limited Si isotope fractionation caused by partial melting and igneous fractional crystallization; mantle rocks and mantlederived melts yield identical δ 30 Si values [bulk silicate Earth (BSE) δ 30 Si = −0.29 ± 0.07‰ relative to NBS28; 15].…”

Section: Significancementioning

confidence: 99%

Origin and significance of Si and O isotope heterogeneities in Phanerozoic, Archean, and Hadean zircon

Trail

Boehnke

Savage

et al. 2018

Proc. Natl. Acad. Sci. U.S.A.

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Hydrosphere interactions and alteration of the terrestrial crust likely played a critical role in shaping Earth’s surface, and in promoting prebiotic reactions leading to life, before 4.03 Ga (the Hadean Eon). The identity of aqueously altered material strongly depends on lithospheric cycling of abundant and water-soluble elements such as Si and O. However, direct constraints that define the character of Hadean sedimentary material are absent because samples from this earliest eon are limited to detrital zircons (ZrSiO4). Here we show that concurrent measurements of Si and O isotope ratios in Phanerozoic and detrital pre-3.0 Ga zircon constrain the composition of aqueously altered precursors incorporated into their source melts. Phanerozoic zircon from (S)edimentary-type rocks contain heterogeneous δ18O and δ30Si values consistent with assimilation of metapelitic material, distinct from the isotopic character of zircon from (I)gneous- and (A)norogenic-type rocks. The δ18O values of detrital Archean zircons are heterogeneous, although yield Si isotope compositions like mantle-derived zircon. Hadean crystals yield elevated δ18O values (vs. mantle zircon) and δ30Si values span almost the entire range observed for Phanerozoic samples. Coupled Si and O isotope data represent a constraint on Hadean weathering and sedimentary input into felsic melts including remelting of amphibolites possibly of basaltic origin, and fractional addition of chemical sediments, such as cherts and/or banded iron formations (BIFs) into source melts. That such sedimentary deposits were extensive enough to change the chemical signature of intracrustal melts suggests they may have been a suitable niche for (pre)biotic chemistry as early as 4.1 Ga.

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“…Therefore, the suggested diffusive fractionation origin for the light Fe isotopic composition of the dunite 72415, which is not recorded in the Mg isotopic composition of this rock, still remains enigmatic. The δ 26 Mg values of this dunite and the pristine troctolite 76535 (−0.336 ± 0.031‰) overlap with the estimated values of the Moon (−0.26 ± 0.16‰) (23), the Earth (−0.25 ± 0.07‰), chondrites (−0.28 ± 0.06‰) (41), and Mars (−0.271 ± 0.040‰) (35). These two Mg-suite samples of deep origin (72415 and 76535) have high modal abundance of olivine; hence, the similarity between their Mg isotopic compositions and that of the BSM (23) hints at no Mg isotopic fractionation during crystallization of the most magnesian olivine from the LMO (Fig.…”

Section: Significancementioning

confidence: 99%

“…The three FAN samples studied here are pristine highland rocks with very low siderophile and incompatible element abundances (58). Two anorthosites, 60015 and 60025, are enriched in heavy Mg isotopes (Δ 26 Mg sample-BSM ∼ 0.3‰). However, anorthosite 62236 has a δ 26 Mg value of −0.249‰ similar to that of the BSM (Fig.…”

Section: Significancementioning

confidence: 99%

“…Many experimental and theoretical models along with elemental and isotopic data of lunar samples, including both stable and radiogenic isotopes, were used to determine the Moon's origin and magmatic evolution as well as the origin of lunar basalts, which are presumably partial melts of the cumulates produced during the LMO crystallization (9)(10)(11)(12)(13)(14)(15)(16)(17)(18)(19). Over the last 2 decades, the nontraditional stable isotopes have also provided new insights into the accretion and magmatic evolution of planetary bodies including the Moon (20)(21)(22)(23)(24)(25)(26)(27)(28)(29)(30)(31)(32)(33)(34)(35). Most of the data (except for volatile elements such as K and Zn) show that among bodies in the solar system the bulk silicate Earth (BSE) and bulk silicate Moon (BSM) are uniquely similar, despite some variations among the lunar rocks.…”

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confidence: 99%

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Magnesium stable isotopes support the lunar magma ocean cumulate remelting model for mare basalts

Sedaghatpour

Jacobsen

2018

Proc. Natl. Acad. Sci. U.S.A.

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We report high-precision Mg isotopic analyses of different types of lunar samples including two pristine Mg-suite rocks (72415 and 76535), basalts, anorthosites, breccias, mineral separates, and lunar meteorites. The Mg isotopic composition of the dunite 72415 (δ25Mg = −0.140 ± 0.010‰, δ26Mg = −0.291 ± 0.018‰), the most Mg-rich and possibly the oldest lunar sample, may provide the best estimate of the Mg isotopic composition of the bulk silicate Moon (BSM). This δ26Mg value of the Moon is similar to those of the Earth and chondrites and reflects both the relative homogeneity of Mg isotopes in the solar system and the lack of Mg isotope fractionation by the Moon-forming giant impact. In contrast to the behavior of Mg isotopes in terrestrial basalts and mantle rocks, Mg isotopic data on lunar samples show isotopic variations among the basalts and pristine anorthositic rocks reflecting isotopic fractionation during the early lunar magma ocean (LMO) differentiation. Calculated evolutions of δ26Mg values during the LMO differentiation are consistent with the observed δ26Mg variations in lunar samples, implying that Mg isotope variations in lunar basalts are consistent with their origin by remelting of distinct LMO cumulates.

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An Earth–Moon silicon isotope model to track silicic magma origins

Cited by 30 publications

References 63 publications

Processes controlling silicon isotopic fractionation in a forested tropical watershed: Mule Hole Critical Zone Observatory (Southern India)

Processes controlling silicon isotopic fractionation in a forested tropical watershed: Mule Hole Critical Zone Observatory (Southern India)

Origin and significance of Si and O isotope heterogeneities in Phanerozoic, Archean, and Hadean zircon

Magnesium stable isotopes support the lunar magma ocean cumulate remelting model for mare basalts

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