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Discovery of a zinc-rich mineral on the surface of lunar orange pyroclastic beads

Ma, Chi and Liu, Yang (2019) Discovery of a zinc-rich mineral on the surface of lunar orange pyroclastic beads. American Mineralogist, 104 (3). pp. 447-452. ISSN 0003-004X. http://resolver.caltech.edu/CaltechAUTHORS:20190301-110729511

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Abstract

We present the first discovery of a Zn-rich mineral on the pristine surface of orange pyroclastic beads from Apollo sample 74220. This Zn-rich mineral is wide occurring, trigonal or hexagonal in shape, with a normalized composition of ~59 wt% Zn, ~26 wt% O (calculated), ~6 wt% S, ~5 wt% Na, and ~4 wt% Cl. The crystal morphology, homogeneity, and chemistry of individual grains are most consistent with gordaite, a zinc chlorohydroxosulfate mineral, showing an empirical formula of Na_(1.02)Zn_(3.98)[(SO_4)_(0.84)(OH)_(0.30)](OH)_6[Cl_(0.50)(OH)_(0.50)]·nH_2O, albeit the exact amounts of OH and H_2O are uncertain. The pristine 74220 sample used in this study was only directly exposed to air for a cumulative period of 18 days before our study. The same Zn-rich crystals, examined 12 to 15 months apart, show no visible physical and chemical changes. Thus, this zinc-rich mineral likely formed through rapid alteration (oxidation and hydration) by terrestrial air of the original vapor-deposited Zn, Cl, S, and Na-bearing solids. The composition of the zinc-rich mineral indicates that the vapor condensates consist of metallic Zn and metallic Na with either ZnS or native S, and either ZnCl_2 or NaCl. This is the first direct evidence that metallic Zn and Na are key components in the vapor condensates of lunar volcanic gas, which implies lunar volcanic gas may be under higher pressure than previously thought, and the gas composition may be different than previously inferred. Our study is also relevant to the collection, handling, curation, and sample preparation of returned samples from other planetary bodies.


Item Type:Article
Related URLs:
URLURL TypeDescription
https://doi.org/10.2138/am-2019-6896DOIArticle
Additional Information:© 2019 Mineralogical Society of America. Y.L. acknowledges the partial support by NASA Cosmochemistry grant NNN13D465T. SEM, EDS, and EBSD analyses were carried out at the Caltech GPS Division Analytical Facility, which is supported, in part, by NSF Grants EAR-0318518 and DMR-0080065. A portion of the work was performed at Jet Propulsion Laboratory, which is managed by California Institute of Technology (Caltech) under a contract with NASA. We thank Ryan Zeigler, Linda Watts, and Andrea Mosie from JSC Lunar Curation Office for tracking down the process history of samples allocated for this work, George Rossman for running Raman analysis on the Zn-rich mineral, and Liong Ma for helping with SEM and EDS analyses. We are grateful to the constructive comments by an anonymous reviewer, and by David Pyle and Ts. Stanimirova.
Funders:
Funding AgencyGrant Number
NASANNN13D465T
NSFEAR-0318518
NSFDMR-0080065
NASA/JPL/CaltechUNSPECIFIED
Subject Keywords:Lunar orange beads, volcanic gas, vapor condensates, the Moon, zinc-rich mineral, gordaite
Record Number:CaltechAUTHORS:20190301-110729511
Persistent URL:http://resolver.caltech.edu/CaltechAUTHORS:20190301-110729511
Official Citation:Chi Ma, Yang Liu; Discovery of a zinc-rich mineral on the surface of lunar orange pyroclastic beads. American Mineralogist ; 104 (3): 447–452. doi: https://doi.org/10.2138/am-2019-6896
Usage Policy:No commercial reproduction, distribution, display or performance rights in this work are provided.
ID Code:93393
Collection:CaltechAUTHORS
Deposited By: Tony Diaz
Deposited On:01 Mar 2019 22:45
Last Modified:01 Mar 2019 22:45

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