Paper No. 239-7
Presentation Time: 10:05 AM
LUNAR MANTLE HETEROGENEITY IN THE VICINITY OF OR BENEATH THE APOLLO 17 SITE EMPHASIZED BY NEW BASALT CLAST IN 79135
FAGAN, Amy L., Geosciences and Natural Resources, Western Carolina University, 331 Stillwell Building, Cullowhee, NC 28723; NASA Solar System Exploration Research Virtual Institute, Center for Lunar Science and Exploration, Lunar and Planetary Institute, 3600 Bay Area BLVD, Houston, TX 77058, BURNEY, David, Civil Engineering, Environmental Engineering, and Earth Science, University of Notre Dame, 156 Fitzpatrick Hall, Notre Dame, IN 46556, NEAL, Clive R., Civil Engineering, Environmental Engineering, and Earth Science, University of Notre Dame, 156 Fitzpatrick Hall, Notre Dame, IN 46556; NASA Solar System Exploration Research Virtual Institute, Center for Lunar Science and Exploration, Lunar and Planetary Institute, 3600 Bay Area BLVD, Houston, TX 77058, ZEIGLER, Ryan A., Astromaterials Acquisition and Curation Office, NASA Johnson Space Center, 2101 E NASA Parkway, Houston, TX 77058 and KRING, David A., NASA Solar System Exploration Research Virtual Institute, Center for Lunar Science and Exploration, Lunar and Planetary Institute, 3600 Bay Area BLVD, Houston, TX 77058; Lunar and Planetary Institute, 3600 Bay Area BLVD, Houston, TX 77058
Returned samples have illustrated mantle heterogeneity beneath the Apollo 17 site with distinct mare basalt types. A “new” coarse-grained high-Ti mare basalt clast (~2.9 mm diameter) in lunar regolith breccia 79135, distinct from previously studied Apollo samples, may further reveal the nature of this heterogeneity. An SEM elemental scan of 79135,14, augmented with electron microprobe chemical analyses of specific mineral phases, indicates the clast is composed of ~1.8% olivine (Fo
59-70), 6.3% plagioclase (An
85-87), 14.6% ilmenite (Mg# 9-16), 13.3% pigeonite (Wo
7-19, En
38-67), 64% augite (Wo
28-37, En
41-53), and trace amounts of K-feldspar and silica.
The texture and major/minor element mineral compositions of the clast are distinct from Apollo 17 Type B2, C, and D basalts. While mineral chemistry is similar to Type A and B1 basalts, the 79135 clast could potentially represent a new type of Apollo 17 basalt. At least one Type A basalt fragment (79265) has been identified from trench soils near the drive tube of Station 9 where 79135 was also collected; in contrast, if the clast is a B1 basalt, it would represent the first of its type identified from Station 9 and one of the few found east of Station 1, indicating a more pervasive presence of that basalt type.
Despite some broad similarities to other Apollo 17 basalt types, the 79135,14 clast may represent a unique basalt type, thus further emphasizing the mantle heterogeneity. The clast’s petrology (e.g., texture, modal mineralogy, and estimated bulk Mg#) and trace element chemistry (e.g., olivine Ti/V ratio) indicate that it may have been produced from a different mantle source region and/or via a different set of magmatic processes than previously described in Apollo 17 mare basalts.
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