SAMPLE 70215-121

70215 High-Ti Mare Basalt 8110 g, 23 x 13 x 10.5 cm

INTRODUCTION collected approximately 60m east Rutile and chromite exsolution of the Lunar Module. lamellae (< 0.005mm) occur in 70215 was described as a ilmenite, and ilmenite lamellae medium dark gray (with a occur in ulvospinel. Ilmenite also brownish tint), fine-grained occurs as rims on ulvospinel. PETROGRAPHY AND basalt (Fig. 1), containing zap MINERAL CHEMISTRY pits on all faces and rare vugs up Longhi et al. (1974) described to 3mm in diameter (Apollo 17 thin section 70215,149 as a Wilshire (Apollo 17 Lunar Sample Lunar Sample Information spherulitic, fine-grained, high-Ti Information Catalog, 1973) Catalog, 1973). These vugs basalt with a texture suggesting described 70215,7 as a fine- contain projecting plates and disequilibrium crystallization grained, sub-variolitic basalt with prisms of ilmenite and pyroxene. during a period of rapid cooling. microphenocrysts of ilmenite, The fabric is intersertal to These authors reported a mode of olivine, and clinopyroxene (Fig. intergranular and the shape 7% olivine, 42% clinopyroxene, 2ab). Sheafs of plagioclase laths blocky to subangular with one 29% plagioclase, 18% opaque flat surface. Surface T is are locally developed. Phenocrysts slickensided, This sample was make up 52% of this thin section.

Figure 1: Hand specimen photograph of 70215,0. SAMPLE 70215-122

2a: Transmitted light.

2b: Reflected light.

Figure 2: Photomicrographs of 70215. Fields of view in both cases are 2.5 mm. SAMPLE 70215 - 123

minerals (mostly ilmenite), and 4% plagioclase and clinopyroxene. groundmass (Fe/(Fe + Mg) silica phase. Two textural domains Olivine phenocrysts are skeletal 0.95) types. Muhich et al. (1990) exist. In the first, olivine and (i.e., rapid crystallization), some reported variations in ilmenite ilmenite phenocrysts (containing intergrown with ilmenite. An composition in 70215 which numerous inclusions) are set in a overgrowth of pyroxene is usually correlated with the degree of groundmass of smaller olivines, present. Cr-ulvospinel inclusions exsolution, Ilmenites with ilmenites, and 0.3mm "bowtie" may be present. Most ilmenites abundant exsolution were richer in spherulites of clinopyroxene and occur as skeletal needles with Mg relative to those without plagioclase. Interstitial silica, "sawtooth" edges, although blocky, exsolution. Armalcolite exhibits native Fe, and troilite are present. anhedral types occur. Rare only a minor range in composition In the second, coarser domain, armalcolites are rimmed with (Fe/ (Fe+Mg) = 0.48-0.53) and ilmenite and pink titan-augite form rutile-bearing ilmenite. spinel compositions are generally a subophitic texture with Furthermore, occasional uniform (Fe/ (Fe + Mg) = 0.82). spherulites of augite and skeletal phenocrysts of Cr ulvospinel Pyroxene compositions range from plagioclase, contain oriented lamellae of titan-augite to augite (phenocrysts) ilmenite. Plagioclase occurs as to more Fe-rich varieties Brown et al. (1975) described elongate untwinned grains scattered (groundmass). No pigeonite is 70215,142 as a Type IA Apollo 17 throughout the groundmass. present (Fig. 3; Px quad of Longhi high-Ti basalt, containing 9.2% et al., 1974). As Fe increases, Al, olivine, 37% opaques, 12.8% Mineral chemistry is generally Ti, and Cr decrease. Al/Ti ratios plagioclase, and 41% similar between the different thin are generally constant at ~2, clinopyroxene. The texture of this sections described above. Brown et although some of the aluminous sample is discussed within the al. (1975) described the mineral titan-augites contain Al/Ti ratios > confines of the general Type IA chemistry of 70215 within the 2, indicating the presence of AIVI. group defined by Brown et al. general context of Type IA basalts. Plagioclase exhibits little variation ( (1975). Dymek et al. (1975) noted olivine An75-81) compositions from F065-75 with only Dymek et al. (1975) studied minor core-to-rim zonation, The proposed crystallization 70215,158, describing it as a fine- whereas Longhi et al. (1974) noted sequence for 70215 is generally grained porphyritic basalt a larger olivine range (Fo50-75) olivine + armalcolite to ilmenite + comprised of clinopyroxene (58%), with no core-to-rim zonation. rutile to cpx -to plagioclase + Fe- plagioclase (18%, ilmenite (13%), Ilmenite composition is related to rich pyroxene + ilmenite + silica. " " olivine 6%), and SiO2 (4%), with crystal habit. Those with sawtooth Armalcolite and olivine react with minor amounts of armalcolite, Cr- margins have generally higher Mg the magma to form ilmenite and ulvospinel, rutile, troilite, and contents (Fe/ (Fe+Mg) = 0.84-0.89) clinopyroxene, respectively. native Fe. A small amount of K- than the blocky, subequant Longhi et al. (1974) concluded that rich mesostasis is present. (Fe/(Fe+Mg) = 0.88-0.93) and spinel 70215,158 is characterized by abundant phenocrysts of olivine, ilmenite; and clinopyroxene set in a texturally variable groundmass. Approximately three quarters of the groundmass consists of a variolitic intergrowth of acicular grains of plagioclase, SiO2, and ilmenite, with blocky to acicular clinopyroxene. The remainder consists of tiny needles of ilmenite that alternate with fan spherulites of

Figure 3: Pyroxene and olivine compositions of 70215. SAMPLE 70215- 124

crystallized between ilmenite and (1989) (Table 1). LSPET (1973) MREE reach 30-35 times cpx, whereas Dymek et al. (1975) report that 70215 is olivine- chondritic values. Shaffer et al. indicated that spinel crystallized normative. Selected trace elements (1990) used the LaJSm value of with olivine. E1 Goresy et al_ (Table 1) have been reported by 70215 in a discussion of mafic (1974ab, 1977ab) studied the LSPET (1973), Rhodes et al. cumulate fractionation in an initial opaque mineralogy of 70215 in (1974), Rose et al. (1974), Duncan lunar magma. detail. These authors concentrated et al. (1974), Brunfelt et al. (1974), upon the sub-solidus equilibration Masuda (1974), Shih et al. (1975), 70215 has also been used in more of the spinel-ilmenite assemblage Wanke et al. (1975), and Dickerson specialized studies of bulk and inverted zoning in chromian - et al. (1989). There is some composition. Hydrogen ulvospinel. variation between different concentrations have been reported analyses for both major and trace by Merlivat et al. (1974, 1976) as element abundances (Table 1). 0.62 - 0.75 pmole/g, whereas Gibson et al. (1986) report 2.3 pg/g WHOLE-ROCK CHEMISTRY The REE profile of 70215 has been H in 70215. Gibson et al. (1974,

determined by four different 1975, 1976) reported the sulfur The whole rock composition of authors (Brunfelt et al., 1974, content in 70215 as 2210 pg/g, 70215 has been reported by many Masuda et al., 1974; Wanke et al., whereas Petrowski et al. (1974) authors. Rhodes et al. (1976) 1975; Shih et al., 1975). The four reported 1689 ppm and Moore et classified 70215 as a Type B high- profiles are similar (Fig. 4) al. (1974) 2040 pg/g S. Nitrogen Ti basalt. 70215 is further classified although that determined by contents for 70215 have been as a Type B2 basalt using the Brunfelt et al. (1974) is the least reported as < 8 to 3 ppm by Muller criteria of Neal et al. (1990). The smooth. The profiles are all LREE- (1974, 1976), 88 pg/g by Moore major element composition of depleted, with a slight decrease in and Lewis (1976), and 16-23 ppm 70215 has been reported by Rhodes the HREE relative to the MREE. by Goel et al. (1975). Carbon et al. (1974, 1976), Rose et al. The negative Eu anomaly is of the abundances for 70215 have been (1974), LSPET (1973), Wanke et same magnitude in each case determined by Moore et al. (1974) al. (1975), Shih et al. (1975), ([Eu/Eu*] = 0.52-0.58). The and Moore and Lewis (1976) at 31 Duncan et al. (1974), and N pg/g. Dickinson et al

Figure 4: Chondrite-normalized rare-earth element profiles of 70215. SAMPLE 70215-125

Table 1: Whole-rock chemistry of 70215.

SAMPLE 70215-126

Table 1: (Concluded).

Germanium abundance in ppm Hf with a Zr/Hf ratio of the whole-rock. A meaningful 70215 was determined at 2.2 28.3± 4.6. isochron was not obtained from ppb by Dickinson et al. (1988) the mineral separates due to the (Table 1). Garg and Ehmann small range in 87Sr/86Sr ratio. No ISOTOPES (1976) and Hughes and Sm-Nd or Pb isotope data has

Schmitt (1985) reported Zr and been obtained from 70215. Rb-Sr isotope data for 70215 Hf abundances for 70215. have been reported by Bansal et Garg and Ehmann (1976) 39Ar-40Ar age dating has been al. (1975), and Nyquist et al. measured 213-215 ppm Zr and conducted on 70215 using whole- (1975, 1976) (Table 2). These 6.72-6.96 ppm Hf in 70215,46, rock (Kirsten and Horn, 1974) authors report a present day and Hughes and Schmitt (Table 3) and laser (Schaeffer et 87Sr/86Sr ratio of 0.69965±7 for (1985) reported 70215,78 as al., 1977) containing 6.2 ± 0.2 SAMPLE 70215-127

Table 2: Sr isotopic composition of 70215. Data from Nyquist et al. (1975, 1976) and Barisal et al. (1975).

Table 3: Ar-Ar and K-Ar data from 70215,21. Data from Kirsten and Horn (1974), Gas released in 10-8 ccSTP/g.

techniques (Table 4). Schaeffer contain a 8(40Ca/44Ca) value of - et al. (1977) reported mineral 1.1±0.2. Drozd et al. (1977) report EXPERIMENTAL ages ranging from 3.63-3.85 Ga a Kr-Kr exposure age of 126 ± 3 in 70215,182, whereas Kirsten Ma for 70215. 70215 has been used in a variety and Horn (1977) reported a of experiments ranging from whole-rock plateau age of Carbon and sulfur represent the crystallization sequences to 3.84±0.04 Ga and an exposure only stable isotope determinations electrical properties. Ahrens et al. age of 100 ± 12 Ma (Table 3). made upon 70215. Petrowski et al. (1977ab) used 70215 to study the (1974) reported a 813C Woo PDB) shock compression and dynamic Other radiogenic isotopes of -39.3 and Des Marais (1978) properties of 70215. Their results measured in 70215 include reported a 813C of -23.5 for 70215. implied that either previous mare 39 41 42 40 cratering ages were K/ K and K/ K (13.859 and The 8345 Woo CDT) has been 575.9, resp.) by Garner et al. reported as + 1.5 (Petrowski et al., overestimated, or that the (1975). Calcium isotopes have 1974), 0.0 (Gibson et al., 1975), integrated meteoroid influxes also been analyzed by Russell et and + 0.6 (Rees and Thode, 1974). may have undergone an even al. (1977), who reported 70215 sharper decline during the first to SAMPLE 70215-128

Table 4: Laser Ar-Ar data from 70215,182. Data from Schaeffer et al. (1977). Units in 10-12 cm3

.

1.5 Ga of lunar history than that Zr was preferentially Walker et al. (1974, 1975a,b, 1976) previously thought. partitioned into armalcolite. Other concluded that the source region partitioning experiments were for titaniferous basalts was a late- Mizutani and Osako (1974ab) conducted on 70215 by Longhi et stage ilmenite-rich cumulate analyzed elastic wave velocities al. (1978) in order to determine the produced from the residual liquid and thermal diffusivities in 70215. distribution of Fe and Mg between of the primordial differentiation of These authors demonstrated the olivine and lunar basaltic liquids. the outer portions of the Moon. different thermal conductivities According to this model, the between highland and mare Longhi et al. (1974), Green et al. ilmenite rich layer was sandwiched regions. (1974,1975ab), Walker et al. between the lunar feldspathic crust (1974,1975ab), and O'Hara and and a complementary cumulate. Tittman et al. (1975ab, 1976, 1978) Humphris (1975) used 70215 in reported the internal friction quality melting experiments in order to factor from 70215,85 under varying determine source mineralogy, MAGNETIC STUDIES pressures. Results demonstrated the degree of partial melting, and post- effect of adsorbed volatiles upon melting evolution. Green et al. 70215 has been used for a variety the internal friction quality factor (1974, 1975a,b) noted that at low of magnetic studies. These have (Q) and explains, in part, the pressures, olivine, armalcolite, and primarily concentrated upon: the differences between terrestrial and ilmenite are liquidus phases, intensity of, and changes in, ancient lunar seismic profiles through lack whereas at high-pressures the high- lunar magnetic fields (Cisowski et of adsorbed H O on the Moon. Ti parental magma is not saturated 2 al., 1977; Collinson et al., 1975); with an Fe-Ti oxide phase. Longhi remanent magnetism of specific Blank et al. (1981, 1984) used et al. (1974) concluded that 70215 lunar samples (Runcorn et al., 70215,159 to examine the trace can be generated by partial melting 1974; Nagata et al., 1974b; Pearce element partitioning between of an olivine + cpx + Fe-Ti oxide et al., 1974b; Sugiura and ilmenite and armalcolite, noting source at depths of 100-150 km. Strangeway, 1980a,b; Hargraves and Dorety, 1975; SAMPLE 70215-129

Stephenson et al., 1974, 1975); subdivided, but 4487.48 of 70215,3 PROCESSING Fe distribution and the metallic and 2769.0 g of 70215,4 remain.

Fe - ferrous Fe ratio (Huffmann To date, 26 thin sections have been et al., 1974; Schwerer and made of 70215. These sample Nagata, 1976); the effect of numbers are ,7-9 ,89, 128 ,141- meteorite impact upon magnetic , 149_,150-160_,251. 70215,0 has fields (Nagata etal., 1974a, 1975; been entirely Pearce et al., 1974a).