Oxygen isotope systematics of South African olivine melilitites and implications for HIMU mantle reservoirs

Day, James M.D.; Peters, Bradley J.; Janney, P. E.

doi:10.1016/j.lithos.2014.05.009

Cited by 38 publications

(20 citation statements)

References 66 publications

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“…To arrive at a value of −13.7%, at least one further phase of evaporation and condensation is required, or a lower α factor would have to be imparted (∼0.985), contrasting with the subdued bulk α factor determined in analogs (24). Conversely, the δ 37 Cl of the Rusty Rock requires vapor condensates from a highly depleted source that was already depleted in bulk Cl and enriched in 37 Cl.…”

Section: Significancementioning

confidence: 99%

“…Melt breccia formation ages for 66095, from Rb−Sr and U−Pb isotope systematics, indicate that fumerolic activity probably occurred at the same time-or slightly after-the impact processes responsible for forming the rock, with the Pb content controlled by sulfide. Impact melt rocks can have heavier δ 37 Cl than mare basalts (7), and 66095 has high δ 37 Cl, low initial Rb/Sr, and radiogenic 206 Pb/ 204 Pb. The Pb implies long-term development in a high-μ source [ 238 U/ 204 Pb = ∼800 at 4.5 Ga], and, with the low Rb/Sr and low Cl content implied from heavy δ 37 Cl, can only be reconciled through vapor condensation from an ancient, volatile-poor lunar interior source, not from possible volatile-rich sources involved in the formation of the impact melt breccia.…”

Section: Volatile-poor Lunar Sourcementioning

confidence: 99%

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Late-stage magmatic outgassing from a volatile-depleted Moon

Day

Moynier

Shearer

2017

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

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The abundance of volatile elements and compounds, such as zinc, potassium, chlorine, and water, provide key evidence for how Earth and the Moon formed and evolved. Currently, evidence exists for a Moon depleted in volatile elements, as well as reservoirs within the Moon with volatile abundances like Earth's depleted upper mantle. Volatile depletion is consistent with catastrophic formation, such as a giant impact, whereas a Moon with Earth-like volatile abundances suggests preservation of these volatiles, or addition through late accretion. We show, using the "Rusty Rock" impact melt breccia, 66095, that volatile enrichment on the lunar surface occurred through vapor condensation. Isotopically light Zn (δZn = -13.7‰), heavy Cl (δCl = +15‰), and high U/Pb supports the origin of condensates from a volatile-poor internal source formed during thermomagmatic evolution of the Moon, with long-term depletion in incompatible Cl and Pb, and lesser depletion of more-compatible Zn. Leaching experiments on mare basalt 14053 demonstrate that isotopically light Zn condensates also occur on some mare basalts after their crystallization, confirming a volatile-depleted lunar interior source with homogeneous δZn ≈ +1.4‰. Our results show that much of the lunar interior must be significantly depleted in volatile elements and compounds and that volatile-rich rocks on the lunar surface formed through vapor condensation. Volatiles detected by remote sensing on the surface of the Moon likely have a partially condensate origin from its interior.

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Section: Significancementioning

confidence: 99%

Section: Volatile-poor Lunar Sourcementioning

confidence: 99%

Late-stage magmatic outgassing from a volatile-depleted Moon

Day

Moynier

Shearer

2017

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

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“…CT = Carius tube digestion; HPA = high-pressure asher digestion; ONB = olivine-normative basalt; PNB = pigeonite-normative basalt; INB = ilmenite-normative basalt; FNB = feldspathic-normative basalt; IlmB = ilmenite-rich basalt; Low-Ti Met = low titanium mare basalt meteorite. W abundance measurements were performed using methods described in Day et al (2014). W concentrations for standards run with the samples were as follows: BHVO-2 = 204 ± 47 ng g −1 ; BIR-1 = 67.5 ± 33 ng g −1 .…”

Section: Magmatic Fractionation Processesmentioning

confidence: 99%

Highly siderophile element depletion in the Moon

Day

Walker

2015

Earth and Planetary Science Letters

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125

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70135) mare basalts, along with mare basalt meteorites La Paz icefield (LAP) 04841 and Miller Range (MIL) 05035. These mare basalts have consistently low HSE abundances, at ∼2 × 10 −5 to 2 × 10 −7 the chondritic abundance. The most magnesian samples have broadly chondrite-relative HSE abundances and chondritic measured and calculated initial 187 Os/ 188 Os. The lower abundances and fractionated HSE compositions of more evolved mare basalts can be reproduced by modeling crystalliquid fractionation using rock/melt bulk-partition coefficients of ∼2 for Os, Ir, Ru, Pt and Pd and ∼1.5 for Re. Lunar mare basalt bulk-partition coefficients are probably higher than for terrestrial melts as a result of more reducing conditions, leading to increased HSE compatibility. The chondritic-relative abundances and chondritic 187 Os/ 188 Os of the most primitive high-MgO mare basalts cannot readily be explained through regolith contamination during emplacement at the lunar surface. Mare basalt compositions are best modeled as representing ∼5-11% partial melting of metal-free sources with low Os, Ir, Ru, Pd (∼0.1 ng g −1 ), Pt (∼0.2 ng g −1 ), Re (∼0.01 ng g −1 ) and S (∼75 μg g −1 ), with sulphide-melt partitioning between 1000 and 10,000. Apollo 12 olivine-, pigeonite-and ilmenite normative mare basalts define an imprecise 187 Re-187 Os age of 3.0 ± 0.9 Ga with an initial 187 Os/ 188 Os of 0.107 ± 0.010. This age is within uncertainty of 147 Sm-143 Nd ages for the samples. The initial Os isotopic composition of Apollo 12 samples indicates that the source of these rocks evolved with Re/Os within ∼10% of chondrite meteorites, from the time that the mantle source became a system closed to siderophile additions, to the time that the basalts erupted. Similarity in absolute HSE abundances between mare basalts from the Apollo 12, 15 and 17 sites, and from unknown regions of the Moon (La Paz mare basalts, MIL 05035), indicates relatively homogeneous and low HSE abundances within the lunar interior. Low absolute HSE abundances and chondritic Re/Os of mare basalts are consistent with a late accretion addition of ∼0.02 wt.% of the Moon's mass to the mantle, prior to the formation of the lunar crust. Late accretion must also have occurred significantly prior to cessation of lunar mantle differentiation (>4.4 Ga), to enable efficient mixing and homogenization within the mantle. Low lunar HSE abundances are consistent with proportionally 40 times more late accretion to Earth than the Moon. Disproportional late accretion to the two bodies is consistent with the small 182 W excess (∼21-28 ppm) measured in lunar rocks, compared to the silicate Earth.

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“…The method for trace-element abundance was otherwise identical to that described previously (Day et al, 2014). Briefly, 50-100 mg of the crush powder was precisely weighed and digested in a 1:4 mixture of concentrated Optima-grade HNO 3 :HF for >72 h at 150°C on a hotplate.…”

Section: Trace-element Abundance Analysesmentioning

confidence: 99%

“…For example, a He-rich source (e.g., DMM, high-3 He/ 4 He mantle) can 'overprint' pre-existing mantle He-isotope heterogeneity, if He contents are sufficiently low in the host protoliths (e.g., recycled oceanic crust and lithosphere). Alternatively, at high temperatures, diffusion of He will lead to isotopic equilibration of He (see Section 5.2), such that only completely isolated, or (Eiler et al, 1996(Eiler et al, , 1997Day and Hilton, 2011) and South African melilitites with HIMU-type Pb isotope compositions (Janney et al, 2002;Day et al, 2005Day et al, , 2014. Samples of OIB are broken into those with HIMU (here defined as 206 Pb/ 204 Pb > 20), HIMU-type Canary Island, and OIB without HIMU (e.g., EM1, EM2, FOZO) affinity.…”

Section: He/ 4 He Of Recycled Oceanic Crust Proxies and Implicationmentioning

confidence: 99%