Author ' s personal copy Apollo 12 revisited
We present compositional data for 358 lithic fragments (2–4-mm size range) and 15 soils (<1-mm fines) from regolith samples collected at the Apollo 12 site. The regolith is dominated by mare basalt, KREEP impact-melt breccias (crystalline and glassy), and regolith breccias. Minor components include alkali anorthosite, alkali norite, granite, quartz monzogabbro, and anorthositic rocks from the feldspathic highlands. The typical KREEP impact-melt breccia of Apollo 12 (mean Th: 16 lg/g) is similar to that of the Apollo 14 site (16 lg/g), 180 km away. Both contain a minor component (0.3% at Apollo 12, 0.6% at Apollo 14) of FeNi metal that is dissimilar to metal in ordinary chondrites but is similar to metal found in Apollo 16 impactmelt breccias. The Apollo 12 regolith contains another variety of KREEP impact-melt breccia that differs from any type of breccia described from the Apollo sites in being substantially richer in Th (30 lg/g) but with only moderate concentrations of K. It is, however, similar in composition to the melt breccia lithology in lunar meteorite Sayh al Uhaymir 169. The average composition of typical mature soil corresponds to a mixture of 65% mare basalt, 20% typical KREEP impact-melt breccia, 7% high-Th impact-melt breccia, 6% feldspathic material, 2.6% alkali noritic anorthosite, and 0.9% CM chondrite. Thus, although the site was resurfaced by basaltic volcanism 3.1–3.3 Ga ago, a third of the material in the present regolith is of nonmare origin, mainly in the form of KREEP impact-melt breccias and glass. These materials occur in the Apollo 12 regolith mainly as a result of moderate-sized impacts into surrounding Fra Mauro and Alpes Formations that formed craters Copernicus (93 km diameter, 406 km distance), Reinhold (48 km diameter, 196 km distance), and possibly Lansberg (39 km diameter, 108 km distance), aided by excavation of basalt interlayers and mixing of regolith by small, local impacts. Anomalous immature soil samples 12024, 12032, and 12033 contain a lesser proportion of mare basalt and a correspondingly greater proportion of KREEP lithologies. These samples consist mainly of fossil or paleoregolith, likely ejecta from Copernicus, that was buried beneath the mixing zone of micrometeorite gardening, and then brought to the near surface by local craters such as Head, Bench, and Sharp Craters. 2010 Elsevier Ltd. All rights reserved.
Geochemistry and Petrography of High-Th, Mafic Impact-Melt Breccia from Apollo 12 and Sayh Al Uhaymir 169
particles found during surveys of 2-4 mm particles from the Apollo 12 [3] and 14 [4] sites. The other 2-4 mm particles analyzed in those studies are shown as magenta and green crosses, respectively. Also included are the IMB (yellow circles) and regolith breccia (red circles; Reg. Brec.) lithologies of the lunar meteorite SaU 169. GEOCHEMISTRY AND PETROGRAPHY OF HIGH-TH, MAFIC IMPACT-MELT BRECCIA FROM APOLLO 12 AND SAYH AL UHAYMIR 169. R. A. Zeigler, R. L. Korotev, B. L. Jolliff, Dept. Earth and Planetary Sciences, Washington University, Campus Box 1169, St. Louis, MO 63130 zeigler@levee.wustl.edu.
Stratigraphies of Apollo and Luna Highland Landing Sites and Provenances of Materials from the Perspective of Basin Impact Ejecta Modeling
What are the provenances of the non-mare materials collected at the Apollo and Luna sampling sites? Results from basin ejecta modeling suggest that much of it came from distant basins. Additional information is contained in the original extended abstract.