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.
A Newly Characterized Granite from the Apollo 12 Regolith
Introduction: The Apollo 12 regolith is composed of a variety of mare and nonmare lithologies. Most are mare basalts, regolith breccias, and impact melt breccias. Rarer lithologies include brecciated anorthosites, granites, and alkali anorthosites. Because the site lies in the Procellarum KREEP Terrane, most of the nonmare rocks are rich in Th (Fig. 1). As part of a survey of 2–4-mm lithic fragments from the Apollo 12 regolith [1,2], we identified several unusual fragments. One such fragment is 12032,366-19, a 21-mg granite. We describe its petrography and geochemistry here. Methods: Methods: We determined the bulk compositions of 358 2–4-mm lithic fragments from the Apollo 12 regolith by INAA (instrumental neutron activation analysis) [1,2,3] (Fig. 1). The petrography, mineral assemblage, and textures were studied using back-scattered electron (BSE) elemental x-ray imaging. Mineral compositions were determined by EMPA (electron probe micro analyses) using wavelength dispersive spectroscopy on a JEOL 8200 Superprobe. Bulk Composition: With 5.0% FeO, 2.9% CaO, 2.1% Na2O, 4.8% K2O, 25 μg/g Sm, 61 μg/g Th, and <2 ng/g Ir, 12032,366-19 is similar to previously reported lunar granites and felsites [4,5,6]. Relative REE abundances are unlike those of typical Apollo 12 material (Fig. 2) but similar to other granites and felsites. Major Phases of 12032,366-19: 12032,366-19 (Figs. 3a,b,c) is a granite which is primarily composed of graphic intergrowths of K-feldspar (An1.2-6.1,Ab2533,Or58-74,Cn0.4-3.9) and silica, and to a lesser extent a graphic intergrowth of plagioclase (An38-48,Ab5264,Or0.9-1.3,Cn0.0-0.1) and silica (Table 1, Fig. 3). The plagioclase is unusually sodic lunar rock; in fact, the An values ~35 are the lowest values that we are aware of in any lunar sample. The associated mafic assemblage is well preserved in this sample. The mafic phases are Fe-rich and consist of hedenbergite (En4.66.2, Fs51-52, Wo43-44) and fayalite (Fo2.7, Fa97). Average compositions of the major mineral phases are in Table 2. for a Table 1. Mineralogy of 12032, 366-19 determined by image analysis. All values are converted to weight percent. Minor Phases of 12032,366-19: Elongate ilmenite, zirkelite, and baddeleyite are present in measurable amounts. Baddeleyite is found only in association with fayalite. Zirkelite is scattered throughout the section and occurs as very-fine-grained, elongate ‘strings’ and in one coarser (~0.1 mm), irregular grain (top of Fig. 3a, bright green). Zirkelite contains significant concentrations of HfO2 (0.6), Nb2O5 (7), Ta2O5 (0.3), ThO2 (2), UO2 (0.7), PbO (0.5), Y2O3 (9), RE2O3 (~10) (all in wt%, average of 10 analyses), and 28–29% ZrO2.
Archaeological Survey of Dangoyama Kofun by 3DGPR
We presented a three-dimensional ground penetrating radar (3DGPR) system for the archeological investigation in a harsh site, where we have to deal with many trees and/or great topographic variations. This system consists of a commercial GPR system with a laser positioning system. With this system, we can move the GPR antenna freely, on which a positioning detector can record accurate position for each GPR data trace. We applied our 3DGPR system at Dangoyama Kofun, a burial mound, in Fukushima prefecture, Japan. A lot of trees and bushes covered the survey area and cannot be cut. We acquired six datasets in two days in this area. We successfully imaged the boundary between the original surface of the burial mound and the covering soil clearly at about 0.3 m depth around the mound. Furthermore, we found some strong reflections appeared at 0.8 m depth in the top area of the mound, which can be from the artificial parts of the burial mound. The results would greatly aid the following archaeological excavation. In addition, we compared the non-interpolated depth slice with interpolated depth slice at same position and demonstrated that the interpolation process on threedimensional GPR data may introduce some artifacts which might mislead our interpretation.