¹Romain Tartèse, ^1,2Mahesh Anand, ³Katherine H. Joy, ¹Ian A. Franchi
¹Department of Physical Sciences, The Open University, Walton Hall, Milton Keynes, UK
²Department of Earth Sciences, The Natural History Museum, London, UK
³School of Earth, Atmospheric and Environmental Sciences, University of Manchester, Manchester, UK

We have investigated the H and Cl systematics in apatite from four brecciated lunar meteorites. In Northwest Africa (NWA) 4472, most of the apatites contain ∼2000–6000 ppm H2O with δD between −200 and 0‰, except for one grain isolated in the matrix, which contains ∼6000 ppm H2O with δD of ∼500–900‰. This low-δD apatite contains ∼2500–7500 ppm Cl associated with δ37Cl of ∼15–20‰, while the high-δD grain contains ∼2500 ppm Cl with δ37Cl of ∼7–15‰. In NWA 773, apatites in a first group contain ∼700–2500 ppm H2O with δD values averaging around ∼0 ± 100‰, while apatites in a second group contain ∼5500–16500 ppm H2O with δD ∼250 ± 50‰. In Sayh al Uhaymir (SaU) 169 and Kalahari (Kal) 009, apatites are similar in terms of their H2O contents (∼600–3000 ppm) and δD values (−100 to 200‰). In SaU 169, apatites contain ∼6000–10,000 ppm Cl, characterized by δ37Cl of ∼5–12‰. Overall, most of the analyzed apatite grains have δD within the range reported for carbonaceous chondrites, similar to apatite analyzed in ancient (>3.9 Ga) lunar magmatic. One grain in NWA 4472 has H and Cl isotope compositions similar to apatite from mare basalts. With an age of 4.35 Ga, this grain could be a representative of the oldest known lunar volcanic activity. Finally, since numerous evolved clasts in NWA 773 formed through silicate liquid immiscibility, the apatite grains with extremely high H2O contents, reaching pure hydroxylapatite composition, could provide insights into the effects of such process on the evolution of volatiles in lunar magmas.

Reference
Tartèse R, Anand M, Joy KH, Franchi IA (2014) H and Cl isotope systematics of apatite in brecciated lunar meteorites Northwest Africa 4472, Northwest Africa 773, Sayh al Uhaymir 169, and Kalahari 009. Meteoritics&Planetary Science (in Press)
Link to Article [DOI: 10.1111/maps.12398]

Published by arrangement with John Wiley&Sons

¹R. E. Merle, ^1,2A. A. Nemchin, ¹M. L. Grange, ²M. J. Whitehouse,¹R. T. Pidgeon
¹Department of Applied Geology, Curtin University, Perth, WA, Australia
²Swedish Museum of Natural History, Stockholm, Sweden

Previous age estimates of the Imbrium impact range from 3770 to 3920 Ma, with the latter being the most commonly accepted age of this basin-forming event. The occurrence of Ca-phosphates in Apollo 14 breccias, interpreted to represent ejecta formed by this impact, provides a new opportunity to date the Imbrium event as well as refining the impact history of the Moon. We present new precise U-Pb analyses of Ca-phosphates from impact breccia sample 14311 that are concordant and give a reliable weighted average age of 3938 ± 4 Ma (2σ). Comparison with previously published U-Pb data on phosphate from Apollo 14 samples indicate that all ages are statistically similar and suggest phosphates could have been formed by the same impact at 3934 Ma ± 3 Ma (2σ). However, this age is older than the 3770 to 3920 Ma range determined for other samples and also interpreted as formed during the Imbrium impact. This suggests that several impacts occurred during a 20–30 Ma period around 3900 Ma and formed breccias sampled by the Apollo missions.

Reference
Merle RE, Nemchin AA, Grange ML, Whitehouse MJ, Pidgeon RT (2014) High resolution U-Pb ages of Ca-phosphates in Apollo 14 breccias: Implications for the age of the Imbrium Impact. Meteoritics&Planetary Science (in Press)

Link to Article [DOI: 10.1111/maps.12395]

Published by arrangement with John Wiley&Sons

¹Luca Bindi et al. (>10)*
¹Dipartimento di Scienze della Terra, Università di Firenze, Via La Pira 4, I-50121 Florence, Italy

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Bindi L et al. (2014) Steinhardtite, a new body-centered-cubic allotropic form of aluminum from the Khatyrka CV3 carbonaceous chondrite. American Mineralogist 99, 2433-2436
Link to Article [doi:10.2138/am-2014-5108]

¹Kevin Righter, ²Lindsay P. Keller, ³Zia Rahman, ³Roy Christoffersen
¹NASA JSC, Mailcode KT, 2101 NASA Parkway, Houston, Texas 77058, U.S.A.
²NASA-JSC, Mailcode KR, 2101 NASA Parkway, Houston, Texas 77058, U.S.A.
³ESCG Jacobs, Houston, Texas, U.S.A.

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Reference
Righter K, Keller LP, Rahman Z, Christoffersen R (2014)Redox-driven exsolution of iron-titanium oxides in magnetite in Miller Range (MIL) 03346 nakhlite: Evidence for post crystallization oxidation in the nakhlite cumulate pile? American Mineralogist, 99,2313-2319
Link to Article [doi:10.2138/am-2014-4926]

¹Paul G. Lucey, ¹Jessica A. Norman, ^1,2Sarah T. Crites,
¹G. Jeffrey Taylor, ¹B. Ray Hawke, ^1,2Myriam Lemelin,³H. Jay Melosh
¹Hawaii Institute of Geophysics and Planetology, University of Hawaii at Manoa, 1680 East West Road, Honolulu, Hawaii 96822, U.S.A.
²Department of Geology and Geophysics, University of Hawaii at Manoa, 1680 East West Road, Honolulu, Hawaii 96822, U.S.A.
³Department of Earth, Atmospheric, and Planetary Sciences, Purdue University West Lafayette, Indiana 47907, U.S.A.

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Reference
Lucey PG, Norman JA, Crites ST, Taylor GJ, Hawke BR, Lemelin M, Melosh HJ (2014) A large spectral survey of small lunar craters: Implications for the composition of the lunar mantle.American Mineralogist, 99, 2251-2257
Link to Article [doi:10.2138/am-2014-4854]

¹Allan H. Treiman et al. (>10)*
¹Lunar and Planetary Institute, 3600 Bay Area Boulevard, Houston, Texas 77058, U.S.A.
*Find the extensive, full author and affiliation list on the publishers website

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Reference
Treiman AH et al. (2014) Ferrian saponite from the Santa Monica Mountains (California, U.S.A., Earth): Characterization as an analog for clay minerals on Mars with application to Yellowknife Bay in Gale Crater. American Mineralogist 99, 2234-2250.
Link to Article [doi: 10.2138/am-2014-4763]

^1,2Michael A. Velbel
¹Department of Geological Sciences, Michigan State University, 206 Natural Science Building, 288 Farm Lane, East Lansing, Michigan 48824-1115, U.S.A
²Division of Meteorites, Department of Mineral Sciences, National Museum of Natural History, Smithsonian Institution, 10th and Constitution Avenues NW, Washington, D.C. 20560-0119, U.S.A.

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Reference
Velbel MA (2014) Etch-pit size, dissolution rate, and time in the experimental dissolution of olivine: Implications for estimating olivine lifetime at the surface of Mars. American Mineralogist 99, 2227-2233
Link to Article [doi: 10.2138/am-2014-4654]

¹John Bridges
¹Space Research Centre, Department of Physics and Astronomy, University of Leicester, LE1 7RH, U.K.

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Reference
Bridges J (2014) Comparing clays from Mars and Earth: Implications for martian habitability. American Mineralogist 99, 2163-2164
Link to Article [doi: 10.2138/am-2014-5089]

¹Joseph A. Petrus, ²Doreen E. Ames,³Balz S. Kamber
¹Department of Earth Sciences, Laurentian University, Sudbury, Canada
²Geological Survey of Canada, Ottawa, Canada
³Department of Geology, Trinity College Dublin, Dublin 2, Ireland

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Reference
Petrus JA, Ames DE, Kamber BS (2014) On the track of the elusive sudbury impact: geochemical evidence for a chondrite or comet Bolide. Terra Nova (in Press)
Link to Article [DOI: 10.1111/ter.12125]

¹Brad Jolliff
¹Department of Earth and Planetary Sciences Washington University in St. Louis, Campus Box 1169, One Brookings Drive, St. Louis, Missouri 63130, U.S.A.

Merrillite, Ca18(Ca,□)Mg2(PO4)14–Ca18 Na2Mg2(PO4)14–Ca16REE2(Mg,Fe)2(PO4)14 occurs as a primary phosphate along with apatite, in lunar and martian rocks, and in meteorites. It is nominally anhydrous, but attempts to directly measure H in this mineral have not previously been reported. Because of the occurrence on Earth of whitlockite, Ca18(Mg,Fe2+)2(PO4)12[HPO4]2, and the apparent incorporation in whitlockite of a merrillite component, the lack of a whitlockite component in extraterrestrial merrillite could be taken as an indicator of low hydrogen fugacity, and this implication has been applied to lunar merrillite. On the other hand, for martian rocks, where magmatic OH or H2O contents were likely higher, apatite accordingly contains higher OH contents, yet coexists with anhydrous, Na-rich merrillite. With direct measurements by SIMS, McCubbin et al. (2014), which is in the July issue of American Mineralogist (p. 1347–1354), show that Shergotty merrillite is anhydrous and infer that the high T of crystallization of Shergotty precluded incorporation of a whitlockite component. The mineral pair apatite-merrillite in extraterrestrial rocks constitutes a powerful pair for recording magmatic conditions; however, as McCubbin et al. show, the implications of these minerals and their compositions must be interpreted in light of careful and complete analyses and crystal chemical constraints.

Reference
Jolliff B (2014) Merrillite and apatite as recorders of planetary magmatic processes. American Mineralogist 99, 2161-2162
Link to Article [doi: 10.2138/am-2014-5075]

Copyright: The Mineralogical Society of America