Crystallization of the lunar magma ocean and the primordial mantle-crust differentiation of the Moon

The lack of contraction features on the Moon has been used to argue that the Moon underwent limited secular cooling, and thus had a relatively cool initial state. A cool early state in turn limits the depth of the lunar magma ocean. Recent GRAIL gravity measurements, however, suggest that dikes were emplaced in the lower crust, requiring global lunar expansion. Starting from the magma ocean state, we show that solidification of the lunar magma ocean would most likely result in expansion of the young lunar crust, and that viscous relaxation of the crust would prevent early tectonic features of contraction or expansion from being recorded permanently. The most likely process for creating the expansion recorded by the dikes is melting during cumulate overturn of the newly solidified lunar mantle.

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The vaporization behavior of carbon and hydrogen from the early global magma ocean

10.5194/egusphere-egu21-10847 ◽

2021 ◽

Author(s):

Natalia Solomatova ◽

Razvan Caracas

Keyword(s):

First Principles ◽

Atmospheric Pressure ◽

Considerable Effect ◽

Early Earth ◽

The Moon ◽

Magma Ocean ◽

Cooling History ◽

History Of ◽

Carbon Molecules ◽

Dense Atmosphere

Estimating the fluxes and speciation of volatiles during the existence of a global magma ocean is fundamental for understanding the cooling history of the early Earth and for quantifying the volatile budget of the present day. Using first-principles molecular dynamics, we predict the vaporization rate of carbon and hydrogen at the&#160;interface between the magma ocean and the hot dense atmosphere, just after the Moon-forming impact. The concentration of carbon and the oxidation state of the melts affect the speciation of the vaporized carbon molecules (e.g., the ratio of carbon dioxide to carbon monoxide), but do not appear to affect the overall volatility of carbon. We find that carbon is rapidly devolatilized even under pressure, while hydrogen remains mostly dissolved in the melt during the devolatilization process of carbon. Thus, in the early stages of the global magma ocean, significantly more carbon than hydrogen would have been released into the atmosphere, and it is only after the atmospheric pressure decreased, that much of the hydrogen devolatilized from the melt. At temperatures of 5000 K (and above), we predict that bubbles in the magma ocean contained a significant fraction of silicate vapor, increasing with decreasing depths with the growth of the bubbles, affecting the transport and rheological properties of the magma ocean. As the temperature cooled, the silicate species condensed back into the magma ocean, leaving highly volatile atmophile species, such as CO2 and H2O, as the dominant species in the atmosphere. Due to the greenhouse nature of CO2, its concentration in the atmosphere would have had a considerable effect on the cooling rate of the early Earth.

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

Proceedings of the National Academy of Sciences ◽

10.1073/pnas.1811377115 ◽

2018 ◽

Vol 116 (1) ◽

pp. 73-78 ◽

Cited By ~ 7

Author(s):

Fatemeh Sedaghatpour ◽

Stein B. Jacobsen

Keyword(s):

Isotopic Composition ◽

Isotopic Fractionation ◽

The Moon ◽

Magma Ocean ◽

Isotopic Analyses ◽

Lunar Samples ◽

Lunar Basalts ◽

Mg Isotopes ◽

Isotopic Variations ◽

Mare Basalts

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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Evaporative fractionation of volatile stable isotopes and their bearing on the origin of the Moon

Philosophical Transactions of The Royal Society A Mathematical Physical and Engineering Sciences ◽

10.1098/rsta.2013.0259 ◽

2014 ◽

Vol 372 (2024) ◽

pp. 20130259 ◽

Cited By ~ 61

Author(s):

James M. D. Day ◽

Frederic Moynier

Keyword(s):

Global Scale ◽

Parent Body ◽

The Moon ◽

Magma Ocean ◽

Volatile Elements ◽

Giant Impact ◽

The Earth ◽

Present Distribution ◽

Volatile Loss

The Moon is depleted in volatile elements relative to the Earth and Mars. Low abundances of volatile elements, fractionated stable isotope ratios of S, Cl, K and Zn, high μ ( 238 U/ 204 Pb) and long-term Rb/Sr depletion are distinguishing features of the Moon, relative to the Earth. These geochemical characteristics indicate both inheritance of volatile-depleted materials that formed the Moon and planets and subsequent evaporative loss of volatile elements that occurred during lunar formation and differentiation. Models of volatile loss through localized eruptive degassing are not consistent with the available S, Cl, Zn and K isotopes and abundance data for the Moon. The most probable cause of volatile depletion is global-scale evaporation resulting from a giant impact or a magma ocean phase where inefficient volatile loss during magmatic convection led to the present distribution of volatile elements within mantle and crustal reservoirs. Problems exist for models of planetary volatile depletion following giant impact. Most critically, in this model, the volatile loss requires preferential delivery and retention of late-accreted volatiles to the Earth compared with the Moon. Different proportions of late-accreted mass are computed to explain present-day distributions of volatile and moderately volatile elements (e.g. Pb, Zn; 5 to >10%) relative to highly siderophile elements (approx. 0.5%) for the Earth. Models of early magma ocean phases may be more effective in explaining the volatile loss. Basaltic materials (e.g. eucrites and angrites) from highly differentiated airless asteroids are volatile-depleted, like the Moon, whereas the Earth and Mars have proportionally greater volatile contents. Parent-body size and the existence of early atmospheres are therefore likely to represent fundamental controls on planetary volatile retention or loss.

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Rare Earth Elements in Planetary Crusts: Insights from Chemically Evolved Igneous Suites on Earth and the Moon

Minerals ◽

10.3390/min8100455 ◽

2018 ◽

Vol 8 (10) ◽

pp. 455 ◽

Cited By ~ 2

Author(s):

Claire McLeod ◽

Barry Shaulis

Keyword(s):

Rare Earth ◽

Rare Earth Elements ◽

Lunar Surface ◽

Ore Deposits ◽

Global Distribution ◽

Igneous Rocks ◽

The Moon ◽

Magma Ocean ◽

Chemical Signature ◽

Global Demand

The abundance of the rare earth elements (REEs) in Earth’s crust has become the intense focus of study in recent years due to the increasing societal demand for REEs, their increasing utilization in modern-day technology, and the geopolitics associated with their global distribution. Within the context of chemically evolved igneous suites, 122 REE deposits have been identified as being associated with intrusive dike, granitic pegmatites, carbonatites, and alkaline igneous rocks, including A-type granites and undersaturated rocks. These REE resource minerals are not unlimited and with a 5–10% growth in global demand for REEs per annum, consideration of other potential REE sources and their geological and chemical associations is warranted. The Earth’s moon is a planetary object that underwent silicate-metal differentiation early during its history. Following ~99% solidification of a primordial lunar magma ocean, residual liquids were enriched in potassium, REE, and phosphorus (KREEP). While this reservoir has not been directly sampled, its chemical signature has been identified in several lunar lithologies and the Procellarum KREEP Terrane (PKT) on the lunar nearside has an estimated volume of KREEP-rich lithologies at depth of 2.2 × 108 km3. This reservoir therefore offers a prospective location for future lunar REE exploration. Within the context of chemically evolved lithologies, lunar granites are rare with only 22 samples currently classified as granitic. However, these extraterrestrial granites exhibit chemical affinities to terrestrial A-type granites. On Earth, these anorogenic magmatic systems are hosts to U-Th-REE-ore deposits and while to date only U-Th regions of enrichment on the lunar surface have been identified, future exploration of the lunar surface and interior may yet reveal U-Th-REE regions associated with the distribution of these chemically distinct, evolved lithologies.

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Chronological evidence that the Moon is either young or did not have a global magma ocean

Nature ◽

10.1038/nature10328 ◽

2011 ◽

Vol 477 (7362) ◽

pp. 70-72 ◽

Cited By ~ 143

Author(s):

Lars E. Borg ◽

James N. Connelly ◽

Maud Boyet ◽

Richard W. Carlson

Keyword(s):

The Moon ◽

Magma Ocean

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Asymmetric shock heating and the terrestrial magma ocean origin of the Moon

Proceedings of the Japan Academy Series B ◽

10.2183/pjab.90.97 ◽

2014 ◽

Vol 90 (3) ◽

pp. 97-103 ◽

Cited By ~ 7

Author(s):

Shun-ichiro KARATO

Keyword(s):

The Moon ◽

Magma Ocean ◽

Shock Heating ◽

Asymmetric Shock ◽

Origin Of The Moon

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A long-lived magma ocean on a young Moon

Science Advances ◽

10.1126/sciadv.aba8949 ◽

2020 ◽

Vol 6 (28) ◽

pp. eaba8949 ◽

Cited By ~ 3

Author(s):

M. Maurice ◽

N. Tosi ◽

S. Schwinger ◽

D. Breuer ◽

T. Kleine

Keyword(s):

Thermal Conductivity ◽

Partial Melting ◽

Time Scale ◽

Solidification Time ◽

Heat Extraction ◽

The Moon ◽

Magma Ocean ◽

Lunar Crust ◽

Lunar Samples ◽

Remarkable Agreement

A giant impact onto Earth led to the formation of the Moon, resulted in a lunar magma ocean (LMO), and initiated the last event of core segregation on Earth. However, the timing and temporal link of these events remain uncertain. Here, we demonstrate that the low thermal conductivity of the lunar crust combined with heat extraction by partial melting of deep cumulates undergoing convection results in an LMO solidification time scale of 150 to 200 million years. Combining this result with a crystallization model of the LMO and with the ages and isotopic compositions of lunar samples indicates that the Moon formed 4.425 ± 0.025 billion years ago. This age is in remarkable agreement with the U-Pb age of Earth, demonstrating that the U-Pb age dates the final segregation of Earth’s core.

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Early differentiation of the Earth and the Moon

Philosophical Transactions of The Royal Society A Mathematical Physical and Engineering Sciences ◽

10.1098/rsta.2008.0125 ◽

2008 ◽

Vol 366 (1883) ◽

pp. 4105-4128 ◽

Cited By ~ 29

Author(s):

Bernard Bourdon ◽

Mathieu Touboul ◽

Guillaume Caro ◽

Thorsten Kleine

Keyword(s):

Mass Balance ◽

Magma Mixing ◽

The Moon ◽

Magma Ocean ◽

Nd Isotopes ◽

Early Differentiation ◽

Giant Impact ◽

Earth’S Mantle ◽

The Earth ◽

Differentiation Event

We examine the implications of new 182 W and 142 Nd data for Mars and the Moon for the early evolution of the Earth. The similarity of 182 W in the terrestrial and lunar mantles and their apparently differing Hf/W ratios indicate that the Moon-forming giant impact most probably took place more than 60 Ma after the formation of calcium-aluminium-rich inclusions (4.568 Gyr). This is not inconsistent with the apparent U–Pb age of the Earth. The new 142 Nd data for Martian meteorites show that Mars probably has a super-chondritic Sm/Nd that could coincide with that of the Earth and the Moon. If this is interpreted by an early mantle differentiation event, this requires a buried enriched reservoir for the three objects. This is highly unlikely. For the Earth, we show, based on new mass-balance calculations for Nd isotopes, that the presence of a hidden reservoir is difficult to reconcile with the combined 142 Nd– 143 Nd systematics of the Earth's mantle. We argue that a likely possibility is that the missing component was lost during or prior to accretion. Furthermore, the 142 Nd data for the Moon that were used to argue for the solidification of the magma ocean at ca 200 Myr are reinterpreted. Cumulate overturn, magma mixing and melting following lunar magma ocean crystallization at 50–100 Myr could have yielded the 200 Myr model age.

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