Despite being essentially water-free, nominally anhydrous minerals such as plagioclase and pyroxene represent the biggest reservoir of water in most lunar rocks due to their sheer abundance. Apatite, which incorporates F, Cl, and OH into its mineral structure as essential crystal components, on the other hand, is the only other volatile-bearing phase common in lunar samples. Here, we present the first coordinated study of volatiles (e.g., H2O, Cl, F, and S) in nominally anhydrous minerals combined with isotopic measurements in apatite from the ancient lunar basalt fragments from meteorite Miller Range (MIL) 13317. Apatite in MIL 13317 basalt contains similar to 2000 ppm H2O and has an elevated SD values (+ 523-737 parts per thousand), similar to Apollo mare basalts, but has high delta Cl-37 values (+ 29-36 parts per thousand), similar to apatite found in several KREEP-rich samples. MIL 13317 is unique compared with other lunar basalts; it has both elevated SD and delta Cl-37 values currently only observed in highlands sample 79215 (a granulitic impactite). Based on measurements of H2O in nominally anhydrous minerals and in apatite, the source magma of MIL 13317 basalt is estimated to contain similar to 130-330 ppm H2O. Assuming reasonable levels of partial melting of the lunar mantle and magmatic degassing during eruption of the basalt, the Moon contained at least one reservoir with < 100 ppm H2O, a delta D value of < 0 parts per thousand similar to carbonaceous chondrites, and extensively fractionated Cl isotopes prior to 4.332 Gyr, the crystallization age of the MIL 13317 basalt.

The influence of the Indian summer monsoon (ISM) and mid-latitude westerlies on the central Tibetan Plateau (TP) during the Holocene, particularly during the mid-Holocene, is still unclear, limiting our understanding of past climate change in this region. Cuona Lake, located on the central TP, is a transitional zone of atmospheric circulation that is well situated for investigations on the interplay between the ISM and mid-latitude westerlies. In this study, multiple proxies of lacustrine sediments from Cuona Lake were measured, including total organic carbon (TOC), total nitrogen (TN), delta C-13(org), n-alkanes, and their hydrogen isotopes, to reconstruct the evolution of climate on the central TP over the past 13 cal kyr BP. Decreased TOC/TN ratios, dominant short-chain n-alkanes/alkanoic acid C-15/16/17, and lower values of n-alkane indicator ratios (carbon preference index and average chain length) throughout the investigated period suggest that the organic matter of the lake essentially originated from aquatic algae, and was weakly affected by terrestrial input. The historic variations in the delta D, TOC, and delta C-13(org) values revealed cold-wet conditions during 12.4-11.4 cal kyr BP, warm-wettest environments during the early Holocene (from 11.4 to 8.2 cal kyr BP), cool-wet conditions in the mid-late Holocene (from 5 to 3 cal kyr BP), and warm-dry conditions since 3 cal kyr BP. The reconstructed climatic variability in the Cuona area agrees well with previous indexes in south-central TP, indicating that the climatic pattern of the studied area is basically controlled by the monsoonal circulation from the late part of the last deglaciation to the early Holocene, with the ISM reaching the north-central TP at similar to 11 cal kyr BP. During the mid-late Holocene, the humid conditions coincided with an enhanced influence of westerlies, providing strong evidence for the contribution of westerlies-delivered moisture to the central TP. Based on a comparison of paleoclimate records, the Cuona region displays a transitional phase between monsoon circulation and westerly jets during the Holocene.

While it is now recognized that the Moon has indigenous water and volatiles, their total abundances are unclear, with current literature estimates ranging from nearly absent to Earth-like levels. Similarly unconstrained is the source of the Moon's water, which could be cometary, chondritic, or the primordial nebula. Here we measure H2O and D/H in olivine-hosted melt inclusions in lunar mare basalts 12018, 12035, and 12040, part of the consanguineous suite of Apollo 12 olivine basalts that differ primarily because of cooling rate (Walker et al., 1976). We find that the water contents are higher in the more rapidly cooled 12018 (62-740 ppm H2O) compared to the more slowly cooled basalts 12035 (28-156 ppm H2O) and 12040 (27-90 ppm H2O), suggesting that lunar basalts may have been dehydrating during slow cooling. D/H is similar in the olivine-hosted melt inclusions in all three samples, and indistinguishable from terrestrial water (dD = -183 +/- 212% to + 138 +/- 61%). When we compare the D/H of olivine-hosted melt inclusions to D/H of apatite in the same samples, the evolution of dD and water content can be better constrained. We propose that lunar magmas first exchange hydrogen with a low D/H reservoir during cooling, and then ultimately lose their water during extended subsolidus cooling. Due to high diffusion rates of hydrogen in olivine, it is likely that all basaltic olivine-hosted melt inclusions from the Moon exchanged hydrogen with a low D/H reservoir in near-surface magma chambers or lava flows. The most likely source of the low D/H reservoir on the Moon is the lunar regolith, which is known to have a significant solar wind hydrogen component.

Earth-like delta D values reported from lunar mare-basalt apatites have typically been interpreted to reflect the intrinsic isotopic composition of lunar mantle water. New data indicates that some of these basalts are also characterized by having experienced a slow cooling history after their emplacement onto the lunar surface. This suggests that these basalts may have experienced metasomatism by fluxes generated during the degassing of the lunar regolith induced by the long-duration, high-temperature residence times of overlying basalts.

Experimental degassing of H-, F-, Cl-, C-, and S-bearing species from volatile-bearing magma of lunar composition at low pressure and fo(2), close to the quartz-iron-fayalite buffer (QIF) indicates that the composition of the fluid/vapor phase that is lost changes overtime. A highly H-rich vapor phase is exsolved within the first 10 min of degassing leaving behind a melt that is effectively dehydrated. Some Cl, F, and S is also lost during this time, presumably as HCI, HF, and H2S gaseous species; however much of the original inventory of Cl, F, and S components are retained in the melt. After 10 min, the exsolved vapor is dry and dominated by S- and halogen-bearing phases, presumably consisting of metal halides and sulfides, which evolves over time toward F enrichment. This vapor evolution provides important constraints on the geochemistry of volatile-bearing lunar phases that form subsequent to or during degassing. The rapidity of H loss suggests that little if any OH-bearing apatite will crystallize from surface or near surface (similar to 7m) melts and that degassing of lunar magmas will cause the compositions of apatites to evolve first toward the F-CI apatite binary and eventually toward end-member fluorapatite during crystallization. During the stage of loss of primarily H component from the melt, Cl would have been lost primarily as HCI, which is reported not to fractionate Cl isotopes at magmatic temperatures (Sharp et al. 2010). After the loss of H-bearing species, continued loss of CI would result in the degassing of metal chlorides, which have been proposed as a mechanism to fractionate Cl isotopes (Sharp et al. 2010). After the onset of metal chloride degassing, the delta Cl-37 of the melt would necessarily increase to +6 (82% Cl loss), +8 (85% Cl loss), and +20 parts per thousand (95% Cl loss) at 1, 4, and 6 h, respectively, which was approximated using a computed trajectory of delta Cl-37 values in basalt during degassing of FeCl2. This strong enrichment of Cl-37 in the melt after metal chloride volatilization is fully consistent with values measured for the non-leachates of a variety of lunar samples and would be reflected in apatites crystallized from a degassing melt. Our results suggest that a range in delta Cl-37 from 0 to >20 parts per thousand is expected in lunar apatite, with heavy enrichment being the norm. While 95% loss in the initial Cl content of the melt (280 ppm Cl left in the melt) would cause an increase to +20 parts per thousand in delta Cl-37, the ability to measure this increase in a lunar sample is ultimately dependent upon the starting Cl abundances and whether or not a mechanism exists to concentrate the remaining CI such that it can be subsequently analyzed with sufficient accuracy. Therefore, the higher the starting Cl abundances in the initial melts, the heavier delta Cl-37 values that can be measurably preserved. Importantly, such enrichments can occur in spite of high initial hydrogen contents, and therefore, our experiments demonstrate that elevated values of delta Cl-37 cannot be used as supporting evidence for an anhydrous Moon. Furthermore, if the H-bearing vapor has a significant H-2 component, this process should also result in strong enrichment of delta D in the residual magmas that reach the lunar surface or near-surface environment. Apatites within some mare basalts exhibit elevated delta D of 1000 parts per thousand depending on the initial value (Tartese and Anand 2013) in addition to the delta Cl-37 values, but elevated delta Cl-37 values are accompanied by only modest enrichments in 51) in apatites from samples of the highlands crust (McCubbin et al. 2015a).

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.