Elevated water contents in various lunar materials have invigorated the discussion on the volatile content of the lunar interior and on the extent to which the volatile element inventory of lunar magmatic rocks is controlled by volatility and degassing. Abundances of moderately volatile and siderophile elements can reveal insights into lunar processes such as core formation, late accretion and volatile depletion. However, previous assessments relied on incomplete data sets and data of variable quality. Here we report mass fractions of the siderophile volatile elements Cu, Se, Ag, S, Te, Cd, In, and Tl in lunar magmatic rocks, analyzed by state-of-the-art isotope dilution-inductively coupled plasma mass spectrometry. The new data enable us to disentangle distribution processes during the formation of different magmatic rock suites and to constrain mantle source compositions. Mass fractions of Cu, S, and Se in mare basalts and magnesian suite norites clearly correlate with indicators of fractional crystallization. Similar mass fractions and fractional crystallization trends in mafic volcanic and plutonic rocks indicate that the latter elements are less prone to degassing during magma ascent and effusion than proposed previously. The latter processes predominate only for specific elements (e.g., Tl, Cd) and complementary enrichments of these elements also occur in some brecciated highland rocks. A detailed comparison of elements with different affinities to metal or sulfide and gas phase reveals systematic differences between lunar magmatic rock suites. The latter observation suggests a predominant control of the variations of S, Se, Cu, and Ag by mantle source composition instead of late-stage magmatic degassing. New estimates of mantle source compositions of two low-Ti mare basalt suites support the notion of a lunar mantle that is strongly depleted in siderophile volatile elements compared to the terrestrial mantle.(C) 2022 Elsevier B.V. All rights reserved.

The traditional view of a dry, volatile-poor Moon has been challenged by the identification of water and other volatiles in lunar samples, but the volatile budget delivery time (s), source (s) and temporal evolution remain poorly constrained. Here we show that hydrogen and chlorine isotopic ratios in lunar apatite changed significantly during the Late Accretion (LA, 4.1-3.8 billion years ago). During this period, deuterium/hydrogen ratios in the Moon changed from initial carbonaceous-chondrite-like values to values consistent with an influx of ordinary-chondrite-like material and pre-LA elevated delta Cl-37 values drop towards lower chondrite-like values. Inferred pre-LA lunar interior water contents are significantly lower than pristine values suggesting degassing, followed by an increase during the LA. These trends are consistent with dynamic models of solar-system evolution, suggesting that the Moon's (and Earth's) initial volatiles were replenished similar to 0.5 Ga after their formation, with their final budgets reflecting a mixture of sources and delivery times.

Recent analytical advances have enabled first successful in-situ detection of water (measured as OH) in lunar volcanic glasses, and, melt inclusions and minerals from mare basalts. These in-situ measurements in lunar materials, coupled with observations made by orbiting spacecraft missions have challenged the traditional view of the Moon as an anhydrous body. By synthesizing and modeling of previously published data on OH contents and H isotope compositions of apatite from mare basalts, we demonstrate that a model of hydrogen delivery into the lunar interior by late accretion of chondritic materials adequately accounts for the measured water content and its hydrogen isotopic composition in mare basalts. In our proposed model, water in the lunar interior was mostly constituted by hydrogen, delivered by the late accretion of chondrite-type materials. Our model is also consistent with previously proposed models to account for other geochemical characteristics of the lunar samples. (C) 2012 Elsevier B.V. All rights reserved.