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Petrography and Geochemistry of Feldspathic Lunar Meteorite Larkman Nunatak 06638
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Author and Affiliation:
Zeigler, Ryan A.(NASA Johnson Space Center, Houston, TX, United States);
Korotev, R. L.(Washington Univ., Saint Louis, MO, United States)
Abstract: LAR 06638 is a glassy-matrix lunar regolith breccia based on the presence of glass spherules, which also contains prominent clasts of a feldspathic fragmental breccia lithology. The similarity in composition of the two lithologies is unsurprising given the observed similarities in the clast populations and mineral compositions in both lithologies. The small differences in composition are likely explained by the incorporation of small amounts of more diverse material into the regolith breccia lithologies, e.g., KREEPy glass clasts to account for the higher siderophile and ITE concentrations and excess plagioclase to account for the lower concentrations of mafic elements and increased Na concentrations. Given the relatively small masses analyzed (approx.120 mg of each lithology), these small compositional differences could also be sampling effects. The presense of multiple generations of glass coatings on LAR 06638 is, to our knowledge, unique among lunar meteorites. The more mafic, schlieren and nanophase Fe bearing glass is similar in morphology to the South Ray Crater glass coatings at the Apollo 16 site [3] and likely has a similar origin. The outer, more feldspathic glass has a morphology typical of fusion crust observed on other feldspathic lunar meteorites. It is unclear at this time whether the partially melted glass area represents a partially formed fusion crust or incipient melting due to heating on the lunar surface, likely from an overlying (and possibly ablated) glass splash coating. LAR 06638 is unlikely to be source-crater paired with any other lunar meteorites. For all elements, it plots right in the range of "typical feldspathic lunar meteorites" [4]. Among lunar meteorites from Antarctica, LAR 06638 most closely resembles MAC 88104/5 in composition, although it is slightly more feldspathic and 1.8 richer in siderophile elements. Compositionally it is more similar to hot-desert meteorites like Dhofar 490/1084 and NWA 2200 [4].
Publication Date: Jan 01, 2013
Document ID:
20130009071
(Acquired Feb 07, 2013)
Subject Category: LUNAR AND PLANETARY SCIENCE AND EXPLORATION
Report/Patent Number: JSC-CN-27959
Document Type: Conference Paper
Meeting Information: Lunar and Planetary Science Conference; 18-22 Mar. 2013; The Woodlands, TX; United States
Contract/Grant/Task Num: NNX11AJ66G
Financial Sponsor: NASA Johnson Space Center; Houston, TX, United States
Organization Source: NASA Johnson Space Center; Houston, TX, United States
Description: 2p; In English; Original contains color and black and white illustrations
Distribution Limits: Unclassified; Publicly available; Unlimited
Rights: Copyright; Distribution as joint owner in the copyright
NASA Terms: BRECCIA; CRUSTS; FUSION (MELTING); LITHOLOGY; LUNAR ROCKS; METEORITES; MINERALOGY; MINERALS; PETROGRAPHY; PLAGIOCLASE; REGOLITH; SAMPLING
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