Work Description

Date: 17 March, 2024

Dataset Title: Data of the paper "Volatiles in Melt Inclusions from Lunar Mare Basalts: Bridging the Gap in the H2O/Ce ratio Between Melt Inclusions in Lunar Pyroclastic Sample 74220 and Other Mare Samples"

Dataset Creators: Xue Su, Youxue Zhang

Dataset Contact: xuesu@umich.edu

Funding: National Aeronautics and Space Administration (NASA)

Research Description:
The H2O concentration and H2O/Ce ratio in olivine-hosted melt inclusions are high (H2O up to 1410 ppm; H2O/Ce up to 77) in lunar sample 74220 but lower (H2O up to 430 ppm; H2O/Ce up to 9.4) in all other lunar samples studied before this work. This difference is absent for other volatiles (F, S, and Cl) in melt inclusions in 74220 and other lunar samples. Because H2O (or H) is a critical volatile component with significant ramifications on the origin and evolution of the Moon, it is important to understand what causes such a large gap in H2O/Ce ratio between 74220 and other lunar samples. Two explanations have been advanced. One is that volcanic product in sample 74220 has the highest cooling rate and thus best preserved H2O in melt inclusions compared to melt inclusions in other samples. The other explanation is that sample 74220 is a localized heterogeneity enriched in some volatiles. To distinguish the two possibilities, here we present new data from three rapidly cooled lunar samples: olivine-hosted glassy melt inclusions (OHMIs) in 74220 regolith and 79135 regolith breccia, and pyroxene-hosted glassy melt inclusions (PHMIs) in 15597 pigeonite basalts. If the gap is due to the difference in cooling rates, samples with cooling rates between 74220 and other studied lunar samples should have preserved intermediate H2O concentrations and H2O/Ce ratios. Our results show that melt inclusions in 79135 and 15597 contain high H2O concentrations (up to 969 ppm in 79135 and up to 793 ppm in 15597) and high H2O/Ce ratios (up to 21 in 79135 and up to 13 in 15997). Combined with literature data, we confirm that H2O/Ce ratios of different lunar samples are positively correlated to the cooling rates and independent of the type of mare basalts. Our work bridges the big gap in H2O/Ce ratio among 74220 and other lunar samples. We hence reinforce the interpretation that the lunar sample with the highest cooling rate best represents pre-eruptive volatiles in lunar basalts due to the least degassing. H2O, F, P, S and Cl concentrations in the lunar primitive mantle are also estimated in this work.

Methodology:
We aimed at studying naturally glassy melt inclusions in lunar basalts. Glassy melt inclusions imply rapid cooling and hence have a better chance to preserve pre-eruptive H2O. We investigated glassy melt inclusions in two lunar samples (15597,81, and 79135,176) based on their rapid quench rate. For comparison, we also analyzed two large and glassy OHMIs from lunar sample 74220,892. Major and minor element compositions of the melt inclusions of three lunar samples and glassy groundmass of 15597 were determined using a CAMECA SX-100 Electron Microprobe (EMP) at the University of Michigan. For large enough melt inclusions (preferentially > 10 µm in every dimension) and groundmass, concentrations of volatiles and non-volatile trace elements were measured in two different sessions using a CAMECA IMS 7-f GEO Secondary Ion Mass Spectrometry (SIMS) at Caltech. Each selected point on a melt inclusion was measured in two SIMS sessions, with the first session for volatiles and the second session on the same position but drilling deeper for other non-volatile trace elements.

Instrument specifications: SEM, EMPA, SIMS

The span of time that the data were collected and processed: 2019-2023

Files contained here:
- An excel file named "Su_Zhang2024GCA_deconvlution" contains the data that are used for deconvolution (sheet named "15597_SIMS&EMPA" and "15597EMPA") and shows how the deconvolution is carried out (sheet named "Deconvolution").
- *A python script named "Su_Zhang2024GCA_deconvolution_codes" is the program that is used for deconvolution calculation.
- An excel file named "Su_Zhang2024GCA_SIMS_data" contains raw volatiles data of all samples and standards directly measured from SIMS in this work. Different sheets represent different SIMS sessions labeled by dates.
- *An excel file named "Su_Zhang2024GCA_Data_For_Figures" contains the data that are used for figures in the paper.
- *An excel file named "Su_Zhang2024GCA_Manuscript_Tables" contains data in tables (for easy use by readers) for the paper.
- *An excel file named "Su_Zhang2024GCA_MELTs_results" shows the calculation results from MELTs. Different sheets represent the condition used for calculation and composition information of melt and pyroxenes with comparison to natural samples.
- *Three pdf files show additional backscattered electron images of sample 15597, sample 74220 and sample 79135, respectively.

(an * means that this data file is newly added to the repository)

Related publication(s):
Su, X. and Zhang, Y. (2024) Volatiles in Melt Inclusions from Lunar Mare Basalts: Bridging the Gap in the H2O/Ce ratio Between Melt Inclusions in Lunar Pyroclastic Sample 74220 and Other Mare Samples. Geochimica et Cosmochimica Acta

Use and Access:
This data set is made available under an Attribution-NonCommercial 4.0 International license (CC BY-NC 4.0).

To Cite Data:
Su, X., Zhang, Y. Data of the paper "Volatiles in Melt Inclusions from Lunar Mare Basalts: Bridging the Gap in the H2O/Ce ratio Between Melt Inclusions in Lunar Pyroclastic Sample 74220 and Other Mare Samples" [Data set], University of Michigan - Deep Blue Data.