Oxygen isotope constraints on the origin and differentiation of the Moon
By M. Spicuzza, J. Day, L. Taylor, J. Valley. 2007
155 citations recorded by the source corpus.
We report new high-precision laser fluorination three-isotope oxygen data for lunar materials. Terrestrial silicates with a range of δ 18 O values (−0.5 to 22.9‰) were analyzed to independently determine the slope of the terrestrial fractionation line (TFL; λ=0.5259±0.0008; 95% confidence level). This new TFL determination allows direct comparison of lunar oxygen isotope systematics with those of Earth. Values of Δ 17 O for Apollo 12, 15, and 17 basalts and Luna 24 soil samples average 0.01‰ and are indistinguishable from the TFL. The δ 18 O values of high- and low-Ti lunar basalts are distinct. Average whole-rock δ 18 O values for low-Ti lunar basalts from the Apollo 12 (5.72±0.06‰) and Apollo 15 landing sites (5.65±0.12‰) are identical within error and are markedly higher than Apollo 17 high-Ti basalts (5.46±0.11‰). Evolved low-Ti LaPaz mare-basalt meteorite δ 18 O values (5.67±0.05‰) are in close agreement with more primitive low-Ti Apollo 12 and 15 mare basalts. Modeling of lunar mare-basalt source composition indicates that the high- and low-Ti mare-basalt mantle reservoirs were in oxygen isotope equilibrium and that variations in δ 18 O do not result from fractional crystallization. Instead, these differences are consistent with mineralogically heterogeneous mantle sources for mare basalts, and with lunar magma ocean differentiation models that result in a thick feldspathic crust, an olivine–pyroxene-rich mantle, and late-stage ilmenite-rich zones that were convectively mixed into deeper portions of the lunar mantle. Higher average δ 18 O (WR) values of low-Ti basalts compared to terrestrial mid ocean ridge basalts (Δ=0.18‰) suggest a possible oxygen isotopic difference between the terrestrial and lunar mantles. However, calculations of the δ 18 O of lunar mantle olivine in this study are only 0.05‰ higher than terrestrial mantle olivine. These observations may have important implications for understanding the formation of the Earth–Moon system. © 2006 Elsevier B.V. All rights reserved.
Subfields: Astronomy and Astrophysics, Atmospheric Science
View Paper: https://www.semanticscholar.org/paper/5460c6763f9294f2898a21ecbf0bf308cbd0f2a5
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Citations in the corpus
- Melting and differentiation of early-formed asteroids: The perspective from high precision oxygen isotope studies (2017, background): “With regard to an appropriate value of : some authors have selected a value based on the actual fractionation line given by a collection of terrestrial samples (e.g. Miller, 2002; Spicuzza et al., 2007; Pack et al., 2013); others have assigned it as the high temperature equilibrium limit value of 0.”
- Water in the Moon's interior: Truth and consequences (2015, background): “Oxygen isotopes, once thought to also be identical (Wiechert et al., 2001; Spicuzza et al., 2007; Hallis et al., 2010), may show a very small difference (Herwartz et al., 2014) that awaits confirmation.”
- Calcium-48 isotopic anomalies in bulk chondrites and achondrites: Evidence for a uniform isotopic reservoir in the inner protoplanetary disk (2014, background): “Various scenarios have been proposed to explain the isotopic similarity between lunar and terrestrial rocks for 17O (Clayton and Mayeda, 1975; Wiechert et al., 2001; Spicuzza et al., 2007; Hallis et al., 2010; Herwartz et al., 2014), 50Ti (Zhang et al.”