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Chemical composition of Luna 20 rocks and soil and Apollo 16 soils
G%ochimicaet Cosmochimi~ A&,
1973. Vol. 37. pp. 927 to 942. PergamonPrew. Printed in NorthernIreland
Chemical composition of Luna 20 rocks and soil and Apollo 16 soils J. C. LAUL and R. A. SCHMITT Department of Chemistry and The Radiation Center, Oregon State University Corvallis, Oregon 97331 (Received 12 Decenaber 1972; accepted in revised form20 January 1973) AM-The abundances of 24 major, minor and trace elements have been measured by INAA in Luna 20 metaigneous rocks 22006,l and 22007,1, breccia 22004 and soil 22001,9 and in Apollo 16 soils 62281, 66041 and 66081. An additional 12 trace meteoritic and non-meteoritic elements have also been determined in 22001 and 62281 soils by RNAA. The bulk compositions of L 20 and Ap 16 rocks and soils show close similarity between the two highlsnd sites. There are appreciable differences in bulk compositions between the L 20 highland and the L 16 mare site (120 km apart), suggesting little intermixing of rocks and soils from either site. Luna 20 rocks 22006 and 22007 are nearly identical in chemical composition to Ap 16 metaigneous rocks 61166 and 66096. Lune 20 rocks are feldspsthic and are similar to low K-type Fra Mauro bsstrlts. Such rocks and anorthositic gabbros appear to be the major components in highland soils. Luna 20 soil can be distinguished from Ap 16 soils by lower abundances of Also,, CaO and large ion lithophilic elements. Luna 20 breccia 22004 probably is compacted soil. All L 20 smmples show negative Eu anomalies with Sm/Eu ratios of 5.8, 7.2, 3.9 and 3.3 for rocks 22006, 22007, breccia 22004 and soil 22001, respectively. Norite-KREEP is insignifkant, 51 per cent, at the L 20 highland site. The derivation of the L 20 soil may be explained by ~33 per cent of L 20 metigneous rocks and ~66 per cent anorthositic gabbroic breccie rocks like 15418 (with a positive Eu anomaly) and ~2 per cent meteoritic contributions. Interelement correlations observed previously for maria are also found in highland samples. Luxm 20 and Ap 16 soils are low in alkalis. Both soils show an apparent Cd-Zn rich component similar to that observed at the mare sites and high Tl abundances relative to mare sites. The Ap 16 (62281) soil contains a fractionated meteoritic component (probably ancient) of w 1.6 per cent in addition to w 1.9 per cent Cl like material. Luna 20 soil may simply contain I.9 per cent Cl equivalent. INTRODUCTION BULK composition of the automatic probe ‘Lunrt-20’ samples taken from a typical mountainous ‘continental’ ares, of the moon, 120 km directly north of the Luna 16 site (Sea of Fertility) has been reported by VINO~UDOV(1972). The L 20 regolith material was sieved by NASA and our soil sample was derived from ‘finest fines’ fraction (cl25 ,u). About 40 mg of the soil (22001,9) was assigned to the Anders-Ehmann-Schmitt consortium for major, minor and trace element analyses. About one half split of the allocated soil was used by MORUAN et al. (1973), in the RNAA (radiochemical neutron activation analysis) of trace elements. The other half (18 mg) was first given to JAN~HORBANI et al. (1973) for the anelysis of Si, 0 and Al by 14 MeV neutron activation analysis and later on, the same aliquot wss analyzed by us, flrst by INAA (instrumental NAA) for 24 major, minor and trace elements and then by RNAA for an additional 12 trace elements. In addition, we received two ‘igneous’ rocks 22007,l (6.0 mg) and 220061 (12.2 mg) and one breccia 22004 (5.0 mg) from G. J. Wasserburg’s consortium. These three L 20 samples were subjected only to INAA for 24 major, minor and trace elements and subsequently used by PODOSEKet al. (1973) for dating and petrologic studies.
THE
14
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EXPERIMENTAL All sample preparations were carried out in our clean room, a sample preps,ration area whettno chemical hae ever been kept. The samples were weighed and transferred in sterilized hali dram polyethylene capsules and heat sealed. The half dram capsules were again heat setaleci into two-dram polyethylene capsules. We also included one Ap 16 (highland site) soil 62281 (36 mg) and one Ap 15 soil 15041 (26 mg) already analyzed by us (LAUL et al., 1972b), as a. safeguard against any systematic errors. In addition, we included four samples of USGS standards BCR-1 ranging from lo-40 mg and one sample of GSP-I (40 mg) in this batch as A control, thereby minimizing any geometry problems in our counting procedures. All samples were counted on both vertical and right angle (co-axial) Ge(Li) detectors (2.3 keV FWHM) coupled to a 2048 channel anrtlyzer, for an additional safety chettk on precision. In our sequential INAA work, the activation facilities of the Oregon State University TRIGA reactor were used. Samples along with appropriate monitors were exposed to a maximum neutron dose of 4 x 10*6.The detailed analytical procedure used here has been described by Scaaar et al. (19?0), REY et a2. (1970) and WAKITA et aE. (1910). For the additional 12 trace elementi analyzed by RNAA, the L 20 soil, after completion of the INAA work, was weighed and transferred into a high-purity silica tube asld sealed for high flux neutron a&v&ion. In the same package we included the soils 62281 and 15041, two carbonaceous chondritee, Orgueil (Cl) and Mu&&on (C2) obtained from Prof. E, Anders, and one sample of BCR-1 as a control. Appropriate monitors were dried on specpnre MgO (to minimize any self-shielding effect) in silica tubes and s-led. The samples and the monitors were activated for 100 hours in the University of Missouri reactor cat a neutron flux of 1.5 x lg4 n crnm2see-l. After about four days of decay, the tubes were broken open and the contents were tmnxferred into Zr crucibles with appropriate carriers already dried therein. The samples were fused with N%Os--NaOH mixture. The chemical procedure used here is essentially similar to that of KEAYS et al. (1971). The elements Ag, Au, Cd, In, Sb, Se and Zn were counted on single-channel NaI(T1) (2 in. x 2 in.) detectors coupled to a multi-channel analyzer to check for radiochemical purity. Cobalt, Ni via Co6s, Rb and Cs were counted on our Ge(Li) system. Thallium was counted on a low-level Beckman type beta counter with a blackground of O-4 Cijm. Half-lives were followed for Au, Cd and Rb. The chemical yield for In was obtained by reactivation. Cobalt is the only common link between INAA and RNA. in our procedure. RESULTS
The INAA and RNAA data ase presented in Tables 1 and 2. The overall accuracy and precision of our method in INAA is tested from replicate ~~1~ of BCR-I from our ls,b (16 repli&es) which in general agree well with those obtained by LAUL et al. (1972c). WAKITA et al. (1970), BRUNFELY and STEINNES (1971) and HASIUN et a8. (1970). In general, we include two BCR-1 samples in each a&iv&ion run. Only the average value of sever&l replicates of BCR-1 is listed in Table I; the duplica;te analysis of 15041 soil served as an addition& check in this cme. Whereever data, for L 20 soil are available for comparison, our INAA results for the soil are in fair agreement with V~OQRADOV (1972) and &gree well with BASAL et aE. (1972), PHILPOTTS et al. (1972) and NAVA and PHILPOTTS (1973). BA.NSAL et al. (1972) reported 7-O per cent and 8.4 per cent Fe0 for two &quanta of L 20 soil while NAVA and PEIILPOTTS(1973) found 7.4 per cent compased to our Fe0 value of 8-l per cent. These werenoes may be due to variations in the amount of m&c minerals, Regazdiug RNAA, we have a direct comparison (Table 2) for two samples Orgueil (Cl) and BCR-1 with the data of the Chicago group KR&X~NB@EL et ai!., 1973). The agreement is excellent. This places additional confidence in our lunar data. However, for the L 20 soil, our Au and Tl values of 7.8 and 10 ppb are higher
929
Chemicalcompositionof Luna 20 rocksand soil and Apollo 16 soils
Table 1. Elem&al abundancesin two Luna 20 metigneous rooks,one brewiaand one soil, three Apollo 16 and one Apollo 16 soil semplee*
Element
T%f %I
AU& Fe0
MgO cao Na,O $$ C&G Sc(ppm) V co L5 09 Sm Eu Tb z LU Hf : u
L 20 met&neoUa rooka 22007,l 22006.1 6.0 mg 12.2 mg 0.76 21.4 8.0 13 13.0 0.485 0.21 0.096 0.174 16.3 34 f 10 61 21.4 63 10.1 1.41 1.6 9.8 7.8 1.13 8.K 0.7 0.9 yo.2
22007 SmjEu
7.2
WA K/Hf K/Th FeO/MnO (FeO/FJo)lO-’
2:: 620 83 62
0.63 21.9 9-9 11 12.4 0.408 0.12 0.121 0.171 21 38 f 8 40 12*9 32 6.4 I.11 1.1 7.2 6.6 0.78 4.2 0.6 0.6 $6
22006 6.8 77 246 690 82 47
L 20 brecoia 22004,l
L 20 soil 22001,s
6.0 mg
18.3 mg
66041 186 mg
BCR-1
Notite-
62281
16041
usas
KREEP
208 mg
36 mg
26 mg
std.
avgS
0.4% 22.8 8.1 10 14.2 0,334 0.076 0.104 0.180 16.6 47 j, 7 27 6.2 16 3.1 0.92 0.63 4.0 2.6 0.43 2.6 0.3 1.0 <0*6
0.76 26.8 6.1 7 16.9 0449 0.11 0.072 0.118 10 26 38 13.7 36 6.6 1.24 I-2 a-2 4-6 0.71 4.4 0.64 2.1 0.7
0.76 26.8 6-6 6 17.0 0.446 O-11 0.073 0.123 11 26 42 14.7 37 7-l 1.23 1.3 8.4 6.0 @77 4.6 0.64 2.1 0.6
22004
22091
66041
6608X
3.9
34
0.67 22.8 8-l 11 16.3 0.382 0.086 0.093 0.166 16.6 I@* 11 32 7.9 20 3.9 1.00 0.77 4.6 3.2 O-62 3.0 0.6 0.7 ‘to-2
2: 690 87 62
2: 670 80 60
6.3 70 210 400 86 61
Ap 16 soils
66081
Ap 18 aoils
6.8 66 206 440 89 69
+ AbUndm were detwmined vi6 INAA. E&im&ed errors m: A&O*, X+0, FeC,~o,C0,~,Lu~dEf,~~6%; aO~.CeO,MgO,Eu,Dy.TbandTh,~IfllClO%; t D&e t&en from LAWL st of. (1972d). 3 Av. Nor&e-KREEP taken from LAUZ cl al. (197%).
O-64 27.6 b-6 7 16.4 0.439 0.11 0.062 o-110 ,aer,o 6 23 11.6 27 6.6 1.10 0.96 6.1 4.2 0.60 4.4 0.6 1.7 0.6
62281 6.1 80 210 540 88 61
1.7 14.1 14.3 11 1@4 0.424 0.21 0.187 O-367 26 110 40 26 68
2.23 13.7 12.3 3.4 7.0 3.31 l-71 o-174 0.0022 32 430 36 26.6 63
12.7 1.30 2*2 14 8.1 1.2 9.1 1.1 4.6 1.6
0.96 6.9 3.6 0.66 4.7 0.74 1.7
16041
1641Bt
9.8 70 290 380 80 66
26:;
f-0 76 110 530 a7 69
I.6 19 9 8 10.5 1.0 0.9 o-12 0*15 20 45 35 110 390 49 ,“., 60 39 3: 4 1% 6 NoriteKREEP 16 70 230 400 80 43
MnO, Cr,O,, Sa, La and Sm, --f 1-3 per cent; V,Ce,TeendU, ~&W-30%.
than the values of 3.6 and 6.6 ppb reported by MORGAXet al. (1973). Interestingly, the ratio of TlfAu is about the same in both L 20 soil aliquants. Our Rb value of 1.6 ppm and Cs value of 70 ppb for L 20 soil agree with the l-62 ppm Rb and 70-6 ppb Cs reported by PAFANASFASSIOU and WASS~~RBURU (1972), MORGANet at. (1973) and PHILPOTTSet al. (1972). VINOQRADOV’S(1972) results for Ag, Cs, Rb, Se and Zn,
obtained by spark source mass spectrometry, are in fair agreement with our data. Drsoussron Both the L 20 and Ap 16 samples were obtained from highland terrain, whereas Luna 16, 120 km S of L 20, is a mare sample. The Ap 11 samples returned from the Sea of Tranquility (-900 km W from the L 20 site) were also from a mare site. Thus our first approach is to compare the bulk composition of igneous and metaigneous
J. C. LAUL and R. A. SCHMITT
930
Table 2. Volatile and siderophilic abundances in Luna 20, Apollo 15, and 16 soils and carbonaceous chondrites* ---.--__I._ _.. . Soils Ap 16 Ap 15 BCR-1 L 20 62281 15041 Carbonaceous chondrites USGS 22001,9 <<1 mm
260
380
240
10200
10500
Co (ppm) Au(ppb) Se(ppb) Sb(ppb) Ag(ppb) In (ppb) Zn(ppm) Cd (ppb) Rb (ppm) Cs(ppb) Tl (ppb) K/Rb Rb/Cs
27 7.8 200 760 720
26 5.9 280 4.5 34 64 29 106 2.8 120 10 330 23
42 3.6 275 4.8 11 14 14 34 5.1 220 1.5 340 23
490 160 21600
480 150 19500 138 182 80 303 G40 1.9 192 145
10 21
19400 1.6 70 10 390 23
240 80 309 650 2.2 180 145
-36 0.44 86 720 24 90 132 135 46 980 270
* Italicized values are considered doubtful due to possible oontamination. Overall estimeted errors are N &5-10 o/ofor all elements. t Data taken from summaries cited in KRUXENB% et al. (1973), MASON (1963) and SCHMITTet al. (1972).
rocks and soils of these four sites (Table 3) to see if any trend exists. By analogy with Ap 16 rocks (LSPET, 1973), we suspect that the two ‘igneous’ L 20 rooks analyzed by us are also metaigneous. The petrology of 22006,l suggests that this rock has been heated and subsequently thermally homogenized (GANCARZet al., 1973). Data (Tables 3 and 5) for rocks and soils of Ap 11 and L 16 are taken from the Proceedings of the Alpok 11 and 8econd Lunar Science Conferences (1970, 1971). Data for Ap 16 rocks (Tables 3,4 and 5) are taken from LSPET (1973) and BANSAL et al. (1972). Ranges (Table 3) are also listed wherever the average value had a dispersion greater than lo-20 per cent. We note from Table 3 that Ap 11 igneous basaltic rocks are high in TiO, and low in Al,O, with respect to Luna 16 rocks. A similar trend is observed for the corresponding soils. Luna 20 metaigneous rocks overlap the range of Ap 16 metaigneous rocks. Closer examination reveals that annealed breccia rooks 61156 and 66095 are remarkably similar to the 22006 and 22007 rocks in bulk chemical composition and in their Y (indicative of REE contents) abundances (Table 4 for comparison). We did not analyze Y directly in our work but it is possible to extrapolate an Y value from our Tb and Dy data of Fig. 2. This comparison shows clearly that to the extent of the limited sampling of the L 20 site, the metaigneous rocks of the Ap 16 and L 20 highland terrain are very similar in bulk and presumably trace elemental composition. Luna 20 rocks are feldspathic and characterized by high A&O,, CaO, C&O, and MgO as well as low FeO, TiO,, Na,O and K,O contents. In their bulk composition, L 20 metaigneous rocks are similar to Fra Mauro basalt of low-K type (Rsn, ebal.,
Chemical composition of Luna 20 rocks and soil and Apollo 16
931
soils
Table 3. Comparison of bulk composition of L 20, L 16, Ap 11 and Ap 16 samples
Element
Si03( %I TiO, A%% Fe0 Mgo cao Na20 IGO MIiO cr303
X0&
45 0.32-1.3 17-28 4*5-105 44-13.1 IO+16.4 0.39056 066-0.35 0.06-0.12 O-13-0.21
L 16
L 20
Ap 16* Soils
Metaigneous rocks
soil
45 0.41-0.67 26-29 4*1-&l 4.2-6.2 155 0.3%055 O-06-0.13 0.07 0.12
43 067 22 8.9 12 12.7 0.44 0.12-0.21 0.11 0.17
45 0.50 23 8-l 10 14.2 0.34 0.076 0.10 0.18
M&aigneous
Ap 11 Soil
Igneous rocks
Soil
45 3.2 15.9 16.8 8.7 12 0.36 0.11 0.21 0.33
405 IO+--11.9 84-10.4 19.0 7.4 IO&-11.5 0.45 0~072-0*30 0.24 0.29
42 7.6 13.6 15.6 8 11.9 0.43 0.14 0.21 0.28
Igneous r00kS
44 4.4 13.8 18.6 65 11 0.38 o-15 0.23 0.28
* LSPET (1973). t We do not know whether the two L 20 rocks analyzed by us were truly igneous or metaigneous rocks. By analogy with Ap 16 rocks, we suspect the L 20 rouks are metaigneous. Table 4. Comparison of bulk composition of Luna 20 and ApoIlo 16 metaigneous rocks* Element
61156
22006
66095
22007
Ti03 ( %)
0.64 22.9 7.8 10.0 13.3 0.39 0.11 0.12 0.140 64
0.63 21.9 9.9 11 12.4 0.41 0.12 0.121 0.171 66t
0.71 23.5 7.2 9.0 13.7 O-42 0.16 o*os 0.147 72
0.76 21.4 8.0 13 13.0 0.48 o-21 0.096 0,174
A&*, Fe0 MgO CaO Ha,0 % Cr&+i Y(ppm)
74t
* Data for rocks 61166 and 66095 am taken from LSRET (1973). See also footnote t of Table 3. t Y abundances have been estimated from the chondritic normalized REE distributions. 1972) and not to norite-KREEP type basalt. Thus, we conclude that the low-K variety is a major component present on the highlands. The feldspathic L 20 snd Ap 16 coils diEer appreciably in their bulk and trace elements1 composition, i.e. L 20 soil he,s higher FeO, MgO, MnO and CrzO, abundances and lower C?aOaud A&O, contents and ~thop~~ trace elements3 abundances than Ap 16 soils. This is reflected in a higher content of mafic minerals in L 20 soil components and less ltnorthosite at the L 20 site than at the Ap 16 site. Higher SC and V abundances in L 20 soil relative to Ap 16 soil are attributed to the COvariances of Se-Fe0 cmd V-Cr,O, in pyroxenes and apinels, respe&iveIy; both minerals are apparently higher in L 20 soil. Soils 66041 and 66081, collected from gray and whitish patches on the St&. 6 regolith, respectively, are identical in their overall chemical composition (LAWLet al’., 1972d). In general, the highland materials of L 20 and Ap 16 are lower in TiO,, FeO, MnO, C&O8 and higher in Also, and CaO than mare samples of L 16 and Ap 11,
J. C. LAUL
932
and R. A. SCHMITT
Table 5. Comparison of trace elemental composition of L 20, 1, 16, Ap 11 and Ap 16 samplls,. Ap 16
Element
‘Igneous’ rock* 68415
Soil
SC V co Hf Th Brt La Ce Sm Eu Yb Lu Ta
76 6.8 18 3.1 1.1 2.3 0.34 --
10 25 23-42 4.5 2.0 140 11-14 27-37 5.6-7.1 1.2 4.6 0.73 0.60
Jd 20 Metaigneons rocks --.15-20 35 40-51 4.2-8.5 1.7-3.4 13-21 32-53 64-10.1 1.1-1.4 5.6-7.8 0+3-1.1 0.5-0.7
1, 16:
Soil 16 45 27 2.5 1.0 6.2 16 3.1 0.92 2.6 0.43 0.3
Igneous rocks 26-54 _.18 220 13 37 10 2.9 6.4 0.8
Ap 11t
Soil
Igneous rocks
55 79 35 5.9 1.2 170 12 35 9.0 2.3 6.5 0.97 -
86-94 77 17-29 12-20 1 .o-3.5 170-320 7-25 25-70 8-23 l-5-2.3 9-14 1.2-2.5 2.0
-.
Sol;
____ 58 ci3 31 10 2.3 180 15 4i
13 I.9 I1 1.5 1.3
* BANSAL et d. (1972). t Apolk 11 Lunar ScienceConference(1970). $ Luna 10 issue of Earth R!unet Sci. Lett. (1972).
Table 5 shows a comparison of refractory trace elements of the four sites. Apollo 11 rocks are in general higher in SC, Co, Hf, La and REE fhan L 16 rooks and so are
the corresponding soils. Trace element data for Ap 16 rocks presently are not available for comparison. However, BANSALet al. (1972) have reported Ba and REE abundances for the crystalline anorthositic gabbroic rock 68416. This rock is claimed to be an unambiguous igneous rock; however, H~RZ (1972) suggests that the light and dark colored parts of the rock are suggestive of completely resorbed clasts and therefore, the rock is not of genuine igneous origin. Luna 20 rocks 22006,l and 22007,l are ambiguously igneous rocks with plagioclase oontents of -168 per cent and ~60 per cent, respectively. Thus, a comparison of L 20 metaigneous rocks with rock 68415 may not be strictly valid. Furthermore, the rock 68415 lacks a negative Eu anomaly. The REE abundances of 68416 are nearly identical to those at L 20 soil (with the exception of the Eu anomaly in L 20 soil) and are low by a factor of ~2 compared to the L 20 rocks. In general, highland rooks and soils are lower in refractories than Ap 11 and L 16 mare sites. The above soil comparisons are shown in Fig. 1. We have plotted our data for 29 elements in L 20 soil and oompared fhese with our data of three Ap 16 and two L 16 soils (GILUINebd., 1972; LAUL et all.,1972a). @en symbols represent elemental abundances in the ppb range; closed symbols, the ppm range. It is evident that the L 20 site matches the Ap 16 sife more closely than the L 16 msae site. The appreciable overall differences between L 16 mare soil and L 20 highland soil suggest minor contributions to the respective soils from mare rocks ejected to the L 20 highland site and vice versa. The elements Au, Ni, Se, Ag, Zn and Tl show some variation (Fig. 1). These elements are derived from meteoritic material to a greater or lesser extent. This mpect is discussed in a later section. The detailed oomparison
Chemical composition of Luna 20 rocks and soil and Apollo 16 soils
Lunc20-2200189
soi/fppm/
933
*A
1. Abundances of bulk, minor and trace element8 in L 20 soil versus average ebundencea reported in three Ap 16 soils and two L 16 soils. The Si value is taken from JANGEORBANI et aZ. (1973). Data for Luna 16 soils are taken from the Luna I6 issue of Earth Planet. Sci. L&t. (1972).
Fig.
of L 20 soil with other Ap 11,12,14 and 16 soils are discussed by SCHMITT and LAUL (1973).
REE $uz.&m8 ad derivation of
soil
The chondrite-normalized REE patterns of L 20 rocks, breccia and soil are 2. They all show a negative Eu anomaly and 8 flat pattern for the heavy REE. The heavy REE are also depleted by a factor of ~2 for the rocks and -30 per cent for the breccia and soil with respect to the average light REE. The Sm/Eu ratio, a sensitive indicator for the degree of partial melting among other mechanisms, is 7*2,66,3*9 and 3.3 for the rocks 22007 and 22006, breccia 22004 and soil 22001, respectively. We have also included the average values of our three Ap 16 soils for comparison (Sm/Eu = 6.4). The Ap 16 soil pattern is similar to that of L 20 soil with a depletion of -45 per cent in Ap 16 soil of the heavy REE with respect to the light REE. Norite-KREEP, which is shown for comparison, has a similar depletion of ~40 per cent and a Sm/Eu ratio of 16. In the past, norite KREEP, a dominant component at the Ap 12, 14 and 16 sites has been used as one end-member in mixing models to explain the origin of soils. The presence of noriteKREEP always raises the REE abundances of soils and breccias except Eu with respect to the cornminuted igneous rock components. This, however, is not the case with L 20 soil and breccia (Fig. 2), where the REE abundances in the soil and breccia are lower than in rocks. Other refractory elements are also enriched in norite-KREEP (see Table 1). Based on our REE pattern, we suggest that norite-KREEP may be absent or shown in Fig.
934
J. %. LAUL and R. A. SCHNITT
REE
IONIC
RADII
Fig. 2. Chondritic normalized REE abundances in L 20 metigneous rocks 22006, 22007, brecois 22004 and soil 22001 and average of three soils of Ap 10. Data for anorthosite 16416 (>98 psr cent PI; HUEBUD et aZ., 1972) and anorthositio gabbroic breccia 15418 (72 per cent 91; LAG et al., 1972d) &nd average noriteKREEP (Lam et al., 19720, Table 1) are included for comparison. Chondritic abundances t&en for normaliz&kn we La 0.34, Ce O-91, Sm 0.195, Eu 0.073, Tb O-047,Dy O-30,Yb O-22,and Lu 0.034, respectively.
present to a negligible amount ( 98 per cent) with the lowest REE abundances observed so far (HUBBARDet al., 1972). ~UL and SUEBCITT (1972) also observed the same Eu enrichment but higher contents of other REE in the anorthosite 16362 (91, -97 per cent) and ~UL eEal. (1972d) s&o observed a
Chemicalcompositionof Luna 20 rooksand soil and Apollo I6 soils
936
large positive Eu anomaly in sawdust from the 16418 anorthositio gabbroic breccia (PI, -72 per cent), which was subsequently confirmed by BANSALet al. (1972). The sawdust of a breccia best represents the overall rock composition, as previously noted by SHOWALTER et al. (1972) for 12013. All low K-type anorthositic gabbros-anorthosites may have been derived from a common magma source (HUBBARDet al., 1972). A alight norite-KREEP contamination of 0.2-1.3 per cent added to 15415 ‘pure’ anorthosite could also account for the increasing REE and nearly constant Eu abundances in these anorthositic gabbros-anorthosites (LAUL et ab., 1972d). Thus, materials similar to low K-type plagioclase-enriched rocks 15416 or 15418 are possible end-members for mixing with L 20 (low-K Fra Mauro basalt) metaigneous rocks to derive the L 20 soil. We prefer the 16418 end-member in our mixing model for the reason that pure 15416~like anorthosites are apparently rare on the lunar highlands. During the early bombardment of the highlands, pure plagioclase-rich rocks may have been melted by impact and recrystallized with other more mafic components into metaigneous rocks, with an average anorthositic gabbroic composition of PI N 65-78 per cent. Furthermore, the bulk chemical composition of 15418 lies in the range of the Ap 16 cataclastic plagioclase-rich rocks (LSPET, 1973), and the composition of 15418 approximates the Surveyor 7 analysis near Tycho (TURKEVICH,1971). Also, the Al/Si ratio for 15418 is more compatible with lunar orbital evidence (ADLERet al., 1972). The chondrite-normalized REE pattern for a L 20 anorthositic basaltic rock (60 mg), probably troctolitic (~62 per cent PI; VINOQRADOV, 1972), is similar to the REE pattern observed in 16418. This suggests either that 16418, though collected at the Apennine Front, could have been ejected from the highlands (LAUL et al., 1972d) or that a considerable fraction of the Apennine Front has a composition similar to highland basalt. In Table 6, mass-balance calculations are presented for the soil, using a simple two-component mixing model for L 20 metaigneous rocks plus either 15418 plagioclase-rich rock or a pure anorthositic end-member like 15415. We have averaged the two rocks (22006 and 22007) in view of the small sample sizes. Data for 15415 are taken from LSPET (1972) and BANSALet al. (1972). Based on K, La, Sm and Eu abundances, we need about 33 per cent of the average L 20 metaigneous rocks and 66 per cent 15418-l& rock composition to obtain the composition of the L 20 soil (Table 6). The agreement is very good. The obvious anomalies marked with asterisks are Cr,O, and Co. The high Co value of 77 ppm for 16418 is most probably due to contamination during sawing. If we use a Co value of 20-26 ppm, which is the typical range for rocks and soils (see Table 6), for 15418, then it matches the soil value. However, the mass-balance for Cr,O, is poor and may be attributed to heterogeneous distribution of chrome spine1 minerals. The dispersion in V is attributed to poor precision (Table 1). If we use the 15416 anorthosite and the L 20 metaigneous rooks, the contributions to the soil turn out to be 38 per cent and 60 per cent, respectively, based only on average fractions calculated from REE and K data. The match for the soil is even worse for the major elements A&,0,, FeO, MgO and CaO. If we use different proportions to match the major elements, then the REE proportions do not agree. Thus we are forced to conclude either that pure anorthosite like 16415 is not a proper
936
J. C’. LAUL and 1%. A.
SCHMI~
Table 6. Mass-balance for the Luna 20 soil, in terms of two component model (ignoring 2 ‘A meteoritic contribution)
a Element
22006 + 22007 Av.
3 1541s*
0.69 21.6 9.0 12 12.7 0.446 0.16 0.108 0,172 18 36 45 6.3 2-6 17.1 42 8.2 1.26 6.7 0.95 0.60
0.37 26.4 7.5 5.3 15.8 0.282 0.01 I 0.086 0.280 13 42 77 0.8 0.13 1.2 0.69 0.73 0.81 0.12 0.09
C 15415t
Oa33A f 0.653
-
Ti%( %I
4%
Fe0 W@ C&O NaaO z: crjlos F(ppmI co Hf Th L& Ce
Sm Eu Yb Lu Tf&
0.02 355 O-23 0.09 19.7 0.34 0.015 0.12 0.33 0.047 0.81 O*OP 0.0034 -
0.47 24.2 7-8 7.4 14.4 0.330 0.060 0.092 0.2398 14 39 65§ 2-5 0.94 6.4 -_ 3.1 0.89 2.6 0.39 0.26
Observed i11 soil 22001
0.38A -IO~fiOC
0.49 22.8
0,27$ 29.55 3.59 4.6s 16.6$j 0.37 0.070 -
il:.:): 14.2 0.334 0,076 0.104 0.180 16 47 27 2.5 i-0 6.2 16 3.1 0.92 2.6 0.43 0.28
-
6.6 16 3-l 0.96 2.6 0.36 -
* LAUL et ai. (XQ72d). f HUBSet al. (1972). $ OurMgO valueshavelargeerrors. BANSAL & cd. (1972)reportedan averageof 8.5 -& O-1% MgO in two L 20 soil samples. g Anomdies (6eetext).
major component or that still another component is required in addition to 16415. Rock 16418 is the better choice for 8 two-~rn~ent system. The validity of our soil model depends on the assumption that the two analyzed L 20 me&igneous rouks are iudeed representative of the source rocks of L 20 soil. Based on our calcuh&ions, ~33 per cent L 20 rocks (Fra Mauro basaltic rooks, low-K type) and 5~65per mnt ~o~hositic gabbroic (p~~~-~~) rock like 15418 is a, two component mixture capable of matching L 20 soil. The L 20 breccia 22004 is similar in bulk chemicctlcomposition to the L 20 soil. This suggests that the brecoia is merely a compacted soil. The limited nature of our Ap 16 d&a predudes sim& ~~~&tions for soils from that site, TAX-LORebc-d.(1972) d a similar approach for derivation of the Ap 16 soil 68601. From their armlyses of the white feldspathic fragments with a positive Eu anomaly, and black fragments, with a negative Eu anomaly, of the Ap 15 breed& 15456, they concluded that a 60-40 per oent mixture of these two eorn~nen~ mahhes the composition of Ap 16 soil 68801.
Chemical composition of Luna 20 rocks and soil and Apollo 16 soils
937
Inter-element reZatd we had established a few interelement In a previous paper (L4UL et d., 1972c), correlations, which are useful constraints for any proposed model for magmatic processes and primordial abundances of the Moon. Our conclusions based on these interelement correlations have been strengthened by additional data on Ap 15 and 1972) as well as data obtained from 16 samples (L~aet al., 1972b; LAUX~~~SOHMITT, L 20 studies. In Table 1, we have obtained average ratios K/La (77), K/Hf (210), K/Th (500), FeO/MnO (85) and FeO/Sc (5400), and K/Rb (39) and Rb/Ca (23) in Table 2 for L 20 and Ap 16 samples. The K/La correlation was also reported by W~NICEet al. (1972). The ratios in Tables 1 and 2 are uniform within experimental and sampling error. Figure 3 shows one such correlation between MnO and Fe0 0.40
I
(J3*_
-
. . . * o n l . + 1.
I
I
I
I
I
1
’
I(
I
x
I
I
APOLLO II SOIL a ROCKS IP. 12 SOILS B ROCKS Ii? 14 f0ll.f a IGNEOUS ROWS P.P. 14 CLASTK ROCK SAWDUST 4~. ,4 CLASTS FROM BRECCIA ROCKS AP. IS SOILS LUNI 86 SOILS a mccws OCEANIC BASALTS CO+J,,nENT*L BISALTS KREEP-NOfllfE
Fig. 3. MnO-Fe0 COITd8tiOnSin lunar rocks and soils. Terrestrial and meteoritic are included for comparison. Thisoorrelation plot fhxt shown by LAUL et d. (19720) has been brought up to date. The K point on the previous graph6 by LAUL etd. (1972~) and LAUX and S(1972) was incorreot. The correlation coefficient is O-97 ( >QQ per cent oonfidence level) for all lunar value%
values
which ranges over a factor of 30 in abundance. Such a strong correlation suggests that Fe0 and Mu0 are strongly associated in ma& minerals and that Fe largely exists in the divalent state. The divalent nature of iron is further supported by Mossbauer studies in lunar rooks (~XUNERet cd., 1971). Note in Fig. 3 that anorthosites 10085 and 15362 match perfectly on the lower left portion of the line. The fact that the line passes through the origin implies that there has been no significant fractionation between Fe0 aud MnO during any lunar differentiation processes. Howardites and eucrites both fall far away from the lunar correlation line. This contradicts the hypothesis that howardites (XUWIN et d., 1972) and eucrites are the raw material for the Moon. A similar conclusion has also been reached by studies of oxygen isotopic compositions (ONUMAet al., 1972). If anorthositic rocks were
938
J. C. LAUL and R. A. SCHI\IIT~
derived from magmatic processes in the outer 10~200 km of the lunar crust, Cad lunar basalts, from partial melting in the lunar interior below 200 km (GAST and MocO~~ELL, 1972), then the strong MnO-Fe0 relationship for all lunar samples would seem to suggest a similar FeO/MnO = SOratio for the mafic minerals in the entire primordial Moon. Obviously sources such as chondrites, eucrites and howardites, as well as Earth mantle material, may be eliminated as the single primary source material for the Moon. Potassium, Rb and Cs are lithop~lic elements of increasing volatility, The fairly constant ratios of volatile to refractory elements such as K/La, K/Hf, K/Rb and K/Th and of two volatile elements Rb/Cs preclude any selective volatilization of alkalis and volatiles during lunar magmatic events. The correlations of Rb/Cs, Cs/U and Tl[U previously reported by ANDERSet nl. (197 1) and MORGAN et al. (1972b) also support the argument,
Lunar soils are enriched relative to rooks by up to about two orders of magnitude in the siderophile elements Ag, Au, Ni, Ir and Re and to lesser degrees in the volatile elements Bi, Br, Cd, In, Sb, Se, Te, Tl and Zn (Proc. Apollo II, Second and Third Lunar Science Co~~ere~ce~,1970, 1971, 1972). GA~JAY?AT~IY et al. f1970), LAUL et al. (1971) and MORQANet al. (1972a) have used the convention of normalizing the elemental abundances in soils relative to the corresponding elemental abundances in Cl chondrites (carbonaceous chondrites type 1) in order to calculate the amount of meteoritic material which has been admixed to the soil. The contributions of Cl material to the Ap 11, 12, 14 and 15 and Luna 16 sites range from 14-1.9 per cent Cl-like material. It seems probable that similar amo~ts of Cl material have been added to the whole Moon. Mature soils contain an admixture of 1.9 per cent Cllike material, whereas young soils, of low exposure age, contain lesser amounts of Cl material (MORGANet al., 1972b; BAEDECKERet a$., 1972). The relative abundances of siderophiles and volatiles characterize the type(s) of impacting meteorite. LAUI, ct al. (1971) and GANAPATHYet a$. (1972) observed fractionated meteoritic patterns in some Ap 12 and Ap 14 soils; these patterns are indicative of ancient meteoritic components (MORGANet ak., 1972a). In Table 2, the results of our analyses are given for L 20, Ap 16 (62281) and Ap 15 (15041, trench) soils. Unfortunately, the L 20 soil appears to be contaminated with the elements Ag, Cd, In, Sb and W and also Pb (G. J. Wasserburg, private eomm~i~ation). Comparison of our L 20 data with that reported by MOR~AXet at. (1973) suggests random heterogeneous oonta~ation of these elements. The Ag and In values in 62281 soil and the In value in 15041 soil are doubtful because of the notorious Ag-In vacuum gasket problem. Thus our discussion is focused primarily on our Ap 16 soil and Ap 15 soil (15041) and to a lesser degree on L 20 soil. We note that Zn and Cd are unusually high in soil 62281. A Cd-Zn rich component and Ag-B&Cd rich component have been found in mare samples from the Ap 12 and L 16 (LAUL et al., 1971, 1972a; BAEDECKERet d., 1971) and Ap 14 (MOR~AX et al., 1972a; BAEDECKEJR et aZ., 1972) sites. We conclude that a Cd-Zn rich component, which may be indigenous, is also present in the lunar highlands near the L 20 and Ap 16 sites. If we normalize, without indigenous corrections, the abundances of the remaining
Chemicalcompositionof Lum 20 rooksand soil and Apollo 16 soils
939
elements Au, Ni, Sb, Se and Tl in soil 62281 to their corresponding elemental abundances in Cl chondrites, the excess amounts of these elements in the soil range from 1-5-7 per cent Cl equivalent. The average Cl values are taken from ~ltI?Bthm et al. (1973). Indigenous corrections are not known for any of these soils (Table 2). Usually these corrections are low, less than ~5-10 per cent for Au and Ni but relatively higher for Sb, Se and Tl. Thus Au and Ni will be considered more reliable because of their small assumed corrections. Such a wide range of apparent meteoritio contributions, 15-7 per cent, suggests the presence of an optional ~om~nent in addition to the ubiquitous Cl component. Subtraction of 1.9 per cent Cl material (upper limit) from the 62281 soil abundances should yield residuals of additional component(s). Subtraction of less than 1.9 per cent Cl contribution will yield siderophile residuals which are slightly higher than volatile residuals. However, this would not alter the conclusion significantly. In addition, the following indigenous contributions are subtracted: Sb 05-l-O ppb, Se 150 ppb and Tl lm0ppb. These contributions are all based on other previous lunar rock analyses reported in the literature. The residual abundances are given below. Selenium shows a negative residual which is attributed to volatile loss by impact heating or solar wind interactions (MORGAN et al., 1973). AU
r-
1%=
Residud =f eaidurtl Cl
(mb)
Ni (mm)
Sb (mb)
Wb)
Tl
3.0
186
l-4
6.2
2.0
1-S
I-0
4.3
The high Tl residual abundance of 6.2 ppb in 62281 soil puzzles us. The rocks from which the soil is derived would be expected to be also alkali poor. Thallium correlates strongly with Rb and Cs over three orders of magnitude in rocks and a Tl/Cs ratio of (l-2 + 1.0) x IO+?, based on lunar rooks from 4 landing sites, has been used in computing the accretion ~mperat~e of the Moon (AIDS et ti., 1971; MORGIAN et al., 1972a). If this ratio also applied to the Apollo 16 site, then, on the basis of the Cs value of 120 ppb in 62281 soil (Table 2), the indigenous Tl abundance should be trivial at ~0.6 ppb. The low K value and REE pattern for the 62281 soil suggest a small (maximum 8-12 per cent) norite-KREEP contribution to Ap 16 highland soil. The ano~ho~tic gabbroic breccia 15418, used in our mixing model for the soils, is low in K and thus should also be low in Tl. We do not suspect the high Tl value on experimental grounds. Perhaps a Tl-rich component, which is deficient in alkalis, is present iu the highlands and not in the maria. A high Tl/Cs ratio of (5.3 f 2.4) 10-a has been noted by MOBUANet al. (1973) in Ap 16 and L 20 highland soils. Such variability of TljCs ratios between highland and mare rocks will of course require revisions in previous calc~ations of accretion tem~rat~es. Normalizing the residual abundances of Au, Ni and Sb to Cl abuudances, we observe a siderophile-rich and volatile-poor pattern, which is characteristic of fractionated meteorites. This fractionated component may be the same ancient component which was proposed by MOBUANet al. (1972a) and ANDERZJet al. (1973). The average contribution of this component is w l-5 per cent Cl equivalent material-
940
J. C'. LAUL
and R. ,4.
sCHMIT!E
Soil 16041 is dominated by the Cl component and has m21 per cent norite(LUL et al., 1972b). Subtraction of 1.9 per cent Cl equivalent abundances from soil 15041 abundances yields residual abundances which may be attributed to ;L norite-KREEP component (MORGAN et al., 1972a). Luna 20 soil is low in alkalis. The high Zn and Cd contents again suggest the presence of a component enriched in these elements. The soil is reported to have a short exposure age (PIUKEY and PRICE, 1973). Based on our Ni data, the meteoritic contribution at the L 20 site is l-9 per cent Cl equivalent material. MORGAN et al. (1973) report an ancient component in addition to Cl material.
KREEP
Acknowledgements-This work was supported by NASA grants 38-002-039 snd 38-002-020. We &re most grateful to Professor ALEXANDERVINOURADOV and the Soviet Academy of Sciences for the availability of these precious Luna 20 samples. We acknowledgethe assistanceof T. V. ANDERSONand W. CARPENTER at the Oregon State University TRIGA reactor group and of J. SCHLAPPER at the Missourireactor group for neutron activations. We 8re also indebted to T. D. COOPER,D. W. HILL and D. A. MILLERfor their assistancein some phases of this study. REFERENCES ADLER I., T~OMBKAJ., GERARDJ., LOWMANP., SCH~DEBECK R., BLOD~ETIf., ELLER E., YIN L., LAMOTEER., OSSWALDG., GORENSTEIN P., BJORKHOLM P., GURSKY H. and HARRIS B. (1972) Apollo 16 geochemicalX-ray fluorescenceexperiment: preliminary report. &&lace 177, 266-259. ANDER~E., GANAPATEY R., KR~EENB~HLU. and MORGANJ. W. (1973) Meteoritic material on the moon. The Moon. ANDER~E., GANAPATHY R., KEAYS R. R., LAUL J. C. and MORUANJ. W. (1971) Volatile and sideropbileelements in lunar rocks: comparisonwith terrestrialand meteoritic baealts. Proc. Second Lunur Sci. Conf., cfeochim. Coanzochim. Aeta Suppl. 2, 1021-1036. M.I.T. Press. BAEDECKER P. A., CHOWC. L. and WMSON J. T. (1972) The extrelunar component in lunar soils and breccias. Proc. Third Lunar Soi. Conf., Geochim. Coemochirn. Acta SW&. 8, 1343-1360. M.I.T. Press. BAEDECKERP. A., SCHAUDYR., ELZIE J. L., KIM~ERLINJ. and W~SSONJ. T. (1971) Trsce element studies of rocks and soils from OceanusProcellarumand Mere Tr8nquillitatis. Proc. Second Lunur SC&.Cmf., ffeoehim. Coamuchim. Acta Sup@. 2, 1037-1061. M.I.T. Press. BANSALB. M., CHURCHS. E., G&T P. W., HUBBARDN. J., RHODESJ. M. and WIES~~ H. (1972) The chemical composition of soil from the Apollo 16 and Luna 20 sites. Earth Planet. Sci. Lett. 17, 29-35. BRWBELT A. 0. and STEINNESE. (1971) A neutron activation scheme developed for the dctermination of 42 elements in lunar material. T&&a 18, 1197-1208. GANAPATHY R., KEAYS R. R., LAm, J. C. and ANDER~E. (1970) Trace elements in Apollo 11 lunar rocks: implicationsfor meteorite infiux and origin of moon. Proc. Apollo 11 Lunar Sci. Gonf., Geochirn. Coemochim. Aeta Sup@. 1, 1117-1142. Pergamon. CANAPATHY R., LAULJ. C., MOR~~LN J. W. and ANDERSE. (1972) Moon: possible nature of the body that produced the Imbrian basin, from the composition of Apollo 14 samples. Sciem 175, 55-59. GANCARZA. J., CHODOS A. A. and ALBEE A. L. (1973) Petrology of Luna 20 sample 22006, 1. Earth Planet. Sci. L&t. GASTP. W. and MCCONNELL R. K., JR. (1972) Evidence for initial chemicallayeringof the moon. Lunar Science III, (editor C. Watkins), pp. 289-290. Houston: Lunar Sci. Instit,ute Contrib. No. 88. GILLUMD. E., E-ANN W. D., WAKF~AH. and SCW~ITTR. A. (1972) Bulk and rare earth abundancesin the Lnna 16 soil levels A and D. Earth Planet. Sci. I&t. 13, 444-449. HAFNERS. S., Vmao D. and WARBURTON D. (1971) Cation distributionsand cooling history of clinopyroxenes from Oceanus Prooellarum. Proc. Second hnar Sci. Conf., Geochim. Cosmochim. Acta Suppl. 2, 91-108. M.I.T. Press.
Chemical composition of Luna 20 rocks and soil and Apollo 16 soils
941
HASKIN L. A., ALLEN R. O., HELMKEP. A., PILOTED T. P., ANDERSONM. R., KOR~TEVR. L. and Zwnnr~~ K. A. (1970) Rare earthe and other trace elements in Apollo 11 lunar samples. Proc. Apollo 11 Lunar Sci. Cmf., &o&m. &moch&n. A&a Sup@. 1, 1213-1231. Hsnz F. (1972) Rock 68416, 1. In Lunar [email protected] InfOrmationCatalog,Apollo 16. MSC-03210, Lunar Receiving Laboratory (Houston), 349. HTJBBMXD N. J., Gash P. W., Mnynn C., NYQUIBTL. E. and SEIE C. (1972) Chemicalcomposition of lunar anorthositesand their parent liquids. Ewth Planet. Sk Lett. 18, 71-76. W. D. (1973) Oxygen and bulk elementabundances JANUEORBANIM., GILL~~~D.E. andEn in Luna 20 fines. &c&h. Coemochirn.Acto 87, 906-908. KEAYS R. R., GANAPA~ R. and ANDE. (1971) Chemicalfraction&ions in meteorites-IV. Abundances of fourteen trace elements in L-chondrites; implicationsfor cosmothermometry. awcladm.Coemoohkm. AC&Za&337-363. KRAHENB~?HL TJ., MORGANJ. W., GANAPATWR. and ANDEBSE. (1973) Abundance of 17 trace elements in carbonaceouschondrites. &o&&n. Coemoohim.Acta. LAULJ.C.B~~S~EMITTR.A. (1972)BulkandREEabundanceginthreeApollo16iigneousrocks and six basaltic rake samples. The Apollo 15 Sampb, (editors J. W. Chamberlain and C. Watkins), pp. 226-228. Lunar Science Institute, Houston. LAUL J. C., MORGANJ. W., GAXAPATE~R. and AND= E. (1971) Meteoritic material in lunar samples: characterization from trace elements. Proc. Seemd Lunar Sci. Conf., &ochim. Comwchim. Act.aSuppl. 2, 1139-1168. M.I.T. Press. LAULJ. C., GANAPATH~ R., MORQANJ. W. and ANDEBBE. (19728)Meteoriticand non-meteoritic trace elements in Luna 16 samples. Earth Planet. Sk. L&t. l&460-464. LATJ’L J. C., S~ow&‘rnn D. L. and Sm R. A. (1972b) Elemental abundances of Apollo 16 four soils, a clod and five breccia rocks and two soils of Apollo 16. The Apollo 15 Swles, (editors J. W. Chamberlainand C. Watkins), pp. 229-232. Lunar Sci. Institute, Houston. LAUL J. C., WAKITA H., S~OWALTEBD. L., BOYPJTON W. V. and SamurnrR. A. (1972~) Bulk, rare earth and other trace elements in Apollo 14 and 16 and Luua 16 samples. Proc. Third Lmar Sci. Conf., &w&m. Coemochbn.Acta Suppl. $3, 1181-1200. M.1.T Press. LAULJ. C., WAKrI!AH. and S= R. A. (1972d) Bulk and REE abundancesin anorthosites and noritic fragments. The Apollo 15 Sam$es, (editors J. W. Chamberlainand C. Watkins), pp. 221-224. Lunar Science Institute, Houston. LSPET (APOLLO16 PRELIMINARY E~AMINATIONTEAM) (1973) The Apollo 16 lunar samples: petrographic and chemicsl description. Soience179,23-34. LSPET (LUND SAMPLE~AEY EXAMINATIONm) (1972) The Apollo 16 hmar samples: s preliminary description. Sc&ence175, 363-374. Luna 16 samples results. (1972) Earth Planet. SC&Lett. l&223-472. MAWIN U. B., REID J. B., JR., TAYLORG. J. and WOOD J. A. (1972) A survey of lithic and vitreous types in the Apollo 14 soil samples (sbstracts). In ti So&ace--III, (editor, C. Watkins), pp. 607609. Lunar ScienceInstitute Contrib. No. 88. WON B. (1963) The carbonaceouschondrites. Space Soi. Rev. 1, 621-646. MORGANJ. W., LAUL J. C., KR~~HENB~SHL U., GANAPATE~R. and ANDER~E. (1972s) Major impacts on the moon: characterization from trace elements in Apollo 12 and Apollo 14 samples. Proc. ThGrdLunar Sci. Conf., Ueochim.Comchim. ActaSuppl. 3,1377-1396. M.I.T. Press. MO~UANJ. W., KR&XENB~?EL U., GUAVAR. and WEBB E. (1972b) Trsce elements in ’ ’ Apollo 16 samples: imphcations for meteorite in&ix and volatile depletion on the moon. Proc. Third Lunar Sci. Conf., Ueo&iq?&. Coemoohint.ActaSwppZ. 8, 13661376. M.I.T. press. MORUANJ. W., KR&ENB~~HLU., GANAPA~ R. and ANDEBBE. (1973) Lima 20 soil: abun_ dance of 17 trace elements. Qeoch&n.Coemochba.Acta 87, 963-961. NAVA D. F. and P~ns~rrs J. A. (1973) A 1~na.rdifferentiationmodel in light of new chemical data on Luna 20 and Apollo 16 soils. tic?&. Coemwhina.Acta 37, 963-973. ONUMAN., CLAYTON R. N. and MAYEDA T. K. (1972) Oxygen isotope cosmothermomemr. Geochka.Coemoohim.Acta 36,169188. PAPANASTA~SIOU D. A. and WA~SERBVR~G. J. (1972) Rb-Sr systematics of Lime 20 and Apollo 16 samples. Earth Planet. Sci. L&t. 17, 62-64.
942
J. C. LAUL and R. A. SUHMITT.
PEAKEY P. P. and PRICE P. B. (1973) Luna 20-an extremely fresh soil. Cfeochim. ~osm~+i,t~. Acta 37, 975-977. PHILPOTTSJ. A., SCHOW~AN N S.,BICEEL A. L. and LUM R. K. L. (1972) Luna 20 and Apollo I6 core fines: large-ion lithophile trace element abundances. Earth Planet. Sci. Lett. 17, 13-l 8. PonOsEK F. A., HU-NE~EJ. C., GANCARZA. J. and WASSERBURQG. J. : The age and petrography of two Lu.na 20 fragments and inferences for widespread lunar metamorphism. Ceoehim. Cosmochim. Acta 37, 887-904. ProceediTbg.9Apollo 11 Lunar Science Conference (1970), Geochim. Cosmochim. Acta Suppi. 1, Vol. 2. Pergamon. Proceeding8SecondLear ScienceConference (1971), Cfeochim. Cosmochim. Acta Suppl. 2, Vol. 2. M.I.T. Press. ProceedingsThird Lunar Science Conference (1972), Geochim. Cosnzochim. Acta Suppl. 3, Vol. 2. M.I.T. Press. REID A. M., WARNER J., RIDLEY W. I. and BROWN R. W. (1972) Major element composition of glasses in three Apollo 15 soils. Meteoritic8 7, 395-416. REY P., WAEITA H. and SC= R. A. (1970) Radiochemical neutron activation analysis of indium, calcium, yttrium, and the 14 rare earth elements in rocks. Anal. Chim. Acta 51, 163-178. SCHMITTR. A. and LAUL J. C. (1973) An overview of the selenochemistry of major, minor and trace elements. The Moon. SCHMITT R. A., GOLES G. G., SMITHR. H. and OSBORNT. W. (1972) Elemental abundances in stone meteorites. Meteoritica 7, 131-213. Sc~~rrr R. A., LINN T. A., JR. and WAKITA H. (1970) The determination of fourteen common elements in rocks via sequential instrumental activation analysis. Radiochim. Acta 13, 200212. S~HNETZLERC. C. and PHILPOTTSJ. A. (1971) Alkali, alkaline earth and rare-earth element concentrations in some Apollo 12 soils, rooks and separated phases. Proc. Second Lunar Sci. Conf., Geochim. Cosmochim. Acta Suppl. 2, 1101-1122. M.I.T. Press. SHOWALTERD. L., WAIIITA H., SM~.CE R. H., SCHWTT R. A., GILL.~ D. E. and EEMAXN W. D. (1972) Chemical composition of sawdust from lunar rocks 12013 and comparison of a Java tektite with the rock. Science 175, 170-172. TAYLOR S. R., GORTONM. P., MUJR P., NANCE W., RUDOWS~I R. and WARE N. (1972) Trace element geochemistry of Apollo 16 soil 68601 from the Descartes Region, lunar highlands. Nature. TAYLOR G. J., DRAKE M. J., WOOD J. A. and MARVINU. B. (1973) The Luna 20 lithic fragmenm, and the composition and origin of the lunar highlands. Geochim. Cosmochim. Acta 37, 1087-1106. TURKEVICHA. L. (1971) Comparison of the analytical results from the Surveyor, Apollo and Luna missions. Proc. Second Lunar Sci. Conf., Geochim. Coemoohim. ActaSuppl. 2, 1209-1215. M.I.T. Press. VINOGRADOVA. (1972) Preliminary data on lunar soil obtained by the unmanned spacecraft Luna 20. Geokhimiya 7, 763-774. English translation Geochim. Coamochim. Acta 37, 721-729 (1973). WA~ITA H. and SCHMITTR. A. (1970) Lunar anorthosites: rare earth and other elemental abundances. Scknce 170, 969-974. WARITA H., Scnmrrr R. A. and REY P. (1970) Elemental abundances of major, minor, and trace elements in Apollo 11 lunar rocks, soil, and core samples. Proc. Apollo 11 Lunar Sci. Conf., Geochim. Cosnzochim. Acta Suppl. 1, 168%1717. Pergrunon. W;~NEE H., PALMERH., SPETTELB. and TESBEEEF. (1972) Multielement analyses and a comparison of the degree of oxidation of lunar and meteoritic matter. The Apollo 15 Samplee, (editors J. W. Chamberlain and C. Watkins), pp. 265467. Lunar Sci. Institute, Houston. WOOD J. A., DICKEYJ. S., ~VIN U. B. and POWELL B. N. (1970) Lunar anorthosites and a geophysical model of the moon. Proc. Apollo 11 Lunar Sci. Conf., Geochim. Cownochim. Acta Suppl. 1, 965-988. Pergsmon.
1973. Vol. 37. pp. 927 to 942. PergamonPrew. Printed in NorthernIreland
Chemical composition of Luna 20 rocks and soil and Apollo 16 soils J. C. LAUL and R. A. SCHMITT Department of Chemistry and The Radiation Center, Oregon State University Corvallis, Oregon 97331 (Received 12 Decenaber 1972; accepted in revised form20 January 1973) AM-The abundances of 24 major, minor and trace elements have been measured by INAA in Luna 20 metaigneous rocks 22006,l and 22007,1, breccia 22004 and soil 22001,9 and in Apollo 16 soils 62281, 66041 and 66081. An additional 12 trace meteoritic and non-meteoritic elements have also been determined in 22001 and 62281 soils by RNAA. The bulk compositions of L 20 and Ap 16 rocks and soils show close similarity between the two highlsnd sites. There are appreciable differences in bulk compositions between the L 20 highland and the L 16 mare site (120 km apart), suggesting little intermixing of rocks and soils from either site. Luna 20 rocks 22006 and 22007 are nearly identical in chemical composition to Ap 16 metaigneous rocks 61166 and 66096. Lune 20 rocks are feldspsthic and are similar to low K-type Fra Mauro bsstrlts. Such rocks and anorthositic gabbros appear to be the major components in highland soils. Luna 20 soil can be distinguished from Ap 16 soils by lower abundances of Also,, CaO and large ion lithophilic elements. Luna 20 breccia 22004 probably is compacted soil. All L 20 smmples show negative Eu anomalies with Sm/Eu ratios of 5.8, 7.2, 3.9 and 3.3 for rocks 22006, 22007, breccia 22004 and soil 22001, respectively. Norite-KREEP is insignifkant, 51 per cent, at the L 20 highland site. The derivation of the L 20 soil may be explained by ~33 per cent of L 20 metigneous rocks and ~66 per cent anorthositic gabbroic breccie rocks like 15418 (with a positive Eu anomaly) and ~2 per cent meteoritic contributions. Interelement correlations observed previously for maria are also found in highland samples. Luxm 20 and Ap 16 soils are low in alkalis. Both soils show an apparent Cd-Zn rich component similar to that observed at the mare sites and high Tl abundances relative to mare sites. The Ap 16 (62281) soil contains a fractionated meteoritic component (probably ancient) of w 1.6 per cent in addition to w 1.9 per cent Cl like material. Luna 20 soil may simply contain I.9 per cent Cl equivalent. INTRODUCTION BULK composition of the automatic probe ‘Lunrt-20’ samples taken from a typical mountainous ‘continental’ ares, of the moon, 120 km directly north of the Luna 16 site (Sea of Fertility) has been reported by VINO~UDOV(1972). The L 20 regolith material was sieved by NASA and our soil sample was derived from ‘finest fines’ fraction (cl25 ,u). About 40 mg of the soil (22001,9) was assigned to the Anders-Ehmann-Schmitt consortium for major, minor and trace element analyses. About one half split of the allocated soil was used by MORUAN et al. (1973), in the RNAA (radiochemical neutron activation analysis) of trace elements. The other half (18 mg) was first given to JAN~HORBANI et al. (1973) for the anelysis of Si, 0 and Al by 14 MeV neutron activation analysis and later on, the same aliquot wss analyzed by us, flrst by INAA (instrumental NAA) for 24 major, minor and trace elements and then by RNAA for an additional 12 trace elements. In addition, we received two ‘igneous’ rocks 22007,l (6.0 mg) and 220061 (12.2 mg) and one breccia 22004 (5.0 mg) from G. J. Wasserburg’s consortium. These three L 20 samples were subjected only to INAA for 24 major, minor and trace elements and subsequently used by PODOSEKet al. (1973) for dating and petrologic studies.
THE
14
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EXPERIMENTAL All sample preparations were carried out in our clean room, a sample preps,ration area whettno chemical hae ever been kept. The samples were weighed and transferred in sterilized hali dram polyethylene capsules and heat sealed. The half dram capsules were again heat setaleci into two-dram polyethylene capsules. We also included one Ap 16 (highland site) soil 62281 (36 mg) and one Ap 15 soil 15041 (26 mg) already analyzed by us (LAUL et al., 1972b), as a. safeguard against any systematic errors. In addition, we included four samples of USGS standards BCR-1 ranging from lo-40 mg and one sample of GSP-I (40 mg) in this batch as A control, thereby minimizing any geometry problems in our counting procedures. All samples were counted on both vertical and right angle (co-axial) Ge(Li) detectors (2.3 keV FWHM) coupled to a 2048 channel anrtlyzer, for an additional safety chettk on precision. In our sequential INAA work, the activation facilities of the Oregon State University TRIGA reactor were used. Samples along with appropriate monitors were exposed to a maximum neutron dose of 4 x 10*6.The detailed analytical procedure used here has been described by Scaaar et al. (19?0), REY et a2. (1970) and WAKITA et aE. (1910). For the additional 12 trace elementi analyzed by RNAA, the L 20 soil, after completion of the INAA work, was weighed and transferred into a high-purity silica tube asld sealed for high flux neutron a&v&ion. In the same package we included the soils 62281 and 15041, two carbonaceous chondritee, Orgueil (Cl) and Mu&&on (C2) obtained from Prof. E, Anders, and one sample of BCR-1 as a control. Appropriate monitors were dried on specpnre MgO (to minimize any self-shielding effect) in silica tubes and s-led. The samples and the monitors were activated for 100 hours in the University of Missouri reactor cat a neutron flux of 1.5 x lg4 n crnm2see-l. After about four days of decay, the tubes were broken open and the contents were tmnxferred into Zr crucibles with appropriate carriers already dried therein. The samples were fused with N%Os--NaOH mixture. The chemical procedure used here is essentially similar to that of KEAYS et al. (1971). The elements Ag, Au, Cd, In, Sb, Se and Zn were counted on single-channel NaI(T1) (2 in. x 2 in.) detectors coupled to a multi-channel analyzer to check for radiochemical purity. Cobalt, Ni via Co6s, Rb and Cs were counted on our Ge(Li) system. Thallium was counted on a low-level Beckman type beta counter with a blackground of O-4 Cijm. Half-lives were followed for Au, Cd and Rb. The chemical yield for In was obtained by reactivation. Cobalt is the only common link between INAA and RNA. in our procedure. RESULTS
The INAA and RNAA data ase presented in Tables 1 and 2. The overall accuracy and precision of our method in INAA is tested from replicate ~~1~ of BCR-I from our ls,b (16 repli&es) which in general agree well with those obtained by LAUL et al. (1972c). WAKITA et al. (1970), BRUNFELY and STEINNES (1971) and HASIUN et a8. (1970). In general, we include two BCR-1 samples in each a&iv&ion run. Only the average value of sever&l replicates of BCR-1 is listed in Table I; the duplica;te analysis of 15041 soil served as an addition& check in this cme. Whereever data, for L 20 soil are available for comparison, our INAA results for the soil are in fair agreement with V~OQRADOV (1972) and &gree well with BASAL et aE. (1972), PHILPOTTS et al. (1972) and NAVA and PHILPOTTS (1973). BA.NSAL et al. (1972) reported 7-O per cent and 8.4 per cent Fe0 for two &quanta of L 20 soil while NAVA and PEIILPOTTS(1973) found 7.4 per cent compased to our Fe0 value of 8-l per cent. These werenoes may be due to variations in the amount of m&c minerals, Regazdiug RNAA, we have a direct comparison (Table 2) for two samples Orgueil (Cl) and BCR-1 with the data of the Chicago group KR&X~NB@EL et ai!., 1973). The agreement is excellent. This places additional confidence in our lunar data. However, for the L 20 soil, our Au and Tl values of 7.8 and 10 ppb are higher
929
Chemicalcompositionof Luna 20 rocksand soil and Apollo 16 soils
Table 1. Elem&al abundancesin two Luna 20 metigneous rooks,one brewiaand one soil, three Apollo 16 and one Apollo 16 soil semplee*
Element
T%f %I
AU& Fe0
MgO cao Na,O $$ C&G Sc(ppm) V co L5 09 Sm Eu Tb z LU Hf : u
L 20 met&neoUa rooka 22007,l 22006.1 6.0 mg 12.2 mg 0.76 21.4 8.0 13 13.0 0.485 0.21 0.096 0.174 16.3 34 f 10 61 21.4 63 10.1 1.41 1.6 9.8 7.8 1.13 8.K 0.7 0.9 yo.2
22007 SmjEu
7.2
WA K/Hf K/Th FeO/MnO (FeO/FJo)lO-’
2:: 620 83 62
0.63 21.9 9-9 11 12.4 0.408 0.12 0.121 0.171 21 38 f 8 40 12*9 32 6.4 I.11 1.1 7.2 6.6 0.78 4.2 0.6 0.6 $6
22006 6.8 77 246 690 82 47
L 20 brecoia 22004,l
L 20 soil 22001,s
6.0 mg
18.3 mg
66041 186 mg
BCR-1
Notite-
62281
16041
usas
KREEP
208 mg
36 mg
26 mg
std.
avgS
0.4% 22.8 8.1 10 14.2 0,334 0.076 0.104 0.180 16.6 47 j, 7 27 6.2 16 3.1 0.92 0.63 4.0 2.6 0.43 2.6 0.3 1.0 <0*6
0.76 26.8 6.1 7 16.9 0449 0.11 0.072 0.118 10 26 38 13.7 36 6.6 1.24 I-2 a-2 4-6 0.71 4.4 0.64 2.1 0.7
0.76 26.8 6-6 6 17.0 0.446 O-11 0.073 0.123 11 26 42 14.7 37 7-l 1.23 1.3 8.4 6.0 @77 4.6 0.64 2.1 0.6
22004
22091
66041
6608X
3.9
34
0.67 22.8 8-l 11 16.3 0.382 0.086 0.093 0.166 16.6 I@* 11 32 7.9 20 3.9 1.00 0.77 4.6 3.2 O-62 3.0 0.6 0.7 ‘to-2
2: 690 87 62
2: 670 80 60
6.3 70 210 400 86 61
Ap 16 soils
66081
Ap 18 aoils
6.8 66 206 440 89 69
+ AbUndm were detwmined vi6 INAA. E&im&ed errors m: A&O*, X+0, FeC,~o,C0,~,Lu~dEf,~~6%; aO~.CeO,MgO,Eu,Dy.TbandTh,~IfllClO%; t D&e t&en from LAWL st of. (1972d). 3 Av. Nor&e-KREEP taken from LAUZ cl al. (197%).
O-64 27.6 b-6 7 16.4 0.439 0.11 0.062 o-110 ,aer,o 6 23 11.6 27 6.6 1.10 0.96 6.1 4.2 0.60 4.4 0.6 1.7 0.6
62281 6.1 80 210 540 88 61
1.7 14.1 14.3 11 1@4 0.424 0.21 0.187 O-367 26 110 40 26 68
2.23 13.7 12.3 3.4 7.0 3.31 l-71 o-174 0.0022 32 430 36 26.6 63
12.7 1.30 2*2 14 8.1 1.2 9.1 1.1 4.6 1.6
0.96 6.9 3.6 0.66 4.7 0.74 1.7
16041
1641Bt
9.8 70 290 380 80 66
26:;
f-0 76 110 530 a7 69
I.6 19 9 8 10.5 1.0 0.9 o-12 0*15 20 45 35 110 390 49 ,“., 60 39 3: 4 1% 6 NoriteKREEP 16 70 230 400 80 43
MnO, Cr,O,, Sa, La and Sm, --f 1-3 per cent; V,Ce,TeendU, ~&W-30%.
than the values of 3.6 and 6.6 ppb reported by MORGAXet al. (1973). Interestingly, the ratio of TlfAu is about the same in both L 20 soil aliquants. Our Rb value of 1.6 ppm and Cs value of 70 ppb for L 20 soil agree with the l-62 ppm Rb and 70-6 ppb Cs reported by PAFANASFASSIOU and WASS~~RBURU (1972), MORGANet at. (1973) and PHILPOTTSet al. (1972). VINOQRADOV’S(1972) results for Ag, Cs, Rb, Se and Zn,
obtained by spark source mass spectrometry, are in fair agreement with our data. Drsoussron Both the L 20 and Ap 16 samples were obtained from highland terrain, whereas Luna 16, 120 km S of L 20, is a mare sample. The Ap 11 samples returned from the Sea of Tranquility (-900 km W from the L 20 site) were also from a mare site. Thus our first approach is to compare the bulk composition of igneous and metaigneous
J. C. LAUL and R. A. SCHMITT
930
Table 2. Volatile and siderophilic abundances in Luna 20, Apollo 15, and 16 soils and carbonaceous chondrites* ---.--__I._ _.. . Soils Ap 16 Ap 15 BCR-1 L 20 62281 15041 Carbonaceous chondrites USGS 22001,9 <<1 mm
260
380
240
10200
10500
Co (ppm) Au(ppb) Se(ppb) Sb(ppb) Ag(ppb) In (ppb) Zn(ppm) Cd (ppb) Rb (ppm) Cs(ppb) Tl (ppb) K/Rb Rb/Cs
27 7.8 200 760 720
26 5.9 280 4.5 34 64 29 106 2.8 120 10 330 23
42 3.6 275 4.8 11 14 14 34 5.1 220 1.5 340 23
490 160 21600
480 150 19500 138 182 80 303 G40 1.9 192 145
10 21
19400 1.6 70 10 390 23
240 80 309 650 2.2 180 145
-36 0.44 86 720 24 90 132 135 46 980 270
* Italicized values are considered doubtful due to possible oontamination. Overall estimeted errors are N &5-10 o/ofor all elements. t Data taken from summaries cited in KRUXENB% et al. (1973), MASON (1963) and SCHMITTet al. (1972).
rocks and soils of these four sites (Table 3) to see if any trend exists. By analogy with Ap 16 rocks (LSPET, 1973), we suspect that the two ‘igneous’ L 20 rooks analyzed by us are also metaigneous. The petrology of 22006,l suggests that this rock has been heated and subsequently thermally homogenized (GANCARZet al., 1973). Data (Tables 3 and 5) for rocks and soils of Ap 11 and L 16 are taken from the Proceedings of the Alpok 11 and 8econd Lunar Science Conferences (1970, 1971). Data for Ap 16 rocks (Tables 3,4 and 5) are taken from LSPET (1973) and BANSAL et al. (1972). Ranges (Table 3) are also listed wherever the average value had a dispersion greater than lo-20 per cent. We note from Table 3 that Ap 11 igneous basaltic rocks are high in TiO, and low in Al,O, with respect to Luna 16 rocks. A similar trend is observed for the corresponding soils. Luna 20 metaigneous rocks overlap the range of Ap 16 metaigneous rocks. Closer examination reveals that annealed breccia rooks 61156 and 66095 are remarkably similar to the 22006 and 22007 rocks in bulk chemical composition and in their Y (indicative of REE contents) abundances (Table 4 for comparison). We did not analyze Y directly in our work but it is possible to extrapolate an Y value from our Tb and Dy data of Fig. 2. This comparison shows clearly that to the extent of the limited sampling of the L 20 site, the metaigneous rocks of the Ap 16 and L 20 highland terrain are very similar in bulk and presumably trace elemental composition. Luna 20 rocks are feldspathic and characterized by high A&O,, CaO, C&O, and MgO as well as low FeO, TiO,, Na,O and K,O contents. In their bulk composition, L 20 metaigneous rocks are similar to Fra Mauro basalt of low-K type (Rsn, ebal.,
Chemical composition of Luna 20 rocks and soil and Apollo 16
931
soils
Table 3. Comparison of bulk composition of L 20, L 16, Ap 11 and Ap 16 samples
Element
Si03( %I TiO, A%% Fe0 Mgo cao Na20 IGO MIiO cr303
X0&
45 0.32-1.3 17-28 4*5-105 44-13.1 IO+16.4 0.39056 066-0.35 0.06-0.12 O-13-0.21
L 16
L 20
Ap 16* Soils
Metaigneous rocks
soil
45 0.41-0.67 26-29 4*1-&l 4.2-6.2 155 0.3%055 O-06-0.13 0.07 0.12
43 067 22 8.9 12 12.7 0.44 0.12-0.21 0.11 0.17
45 0.50 23 8-l 10 14.2 0.34 0.076 0.10 0.18
M&aigneous
Ap 11 Soil
Igneous rocks
Soil
45 3.2 15.9 16.8 8.7 12 0.36 0.11 0.21 0.33
405 IO+--11.9 84-10.4 19.0 7.4 IO&-11.5 0.45 0~072-0*30 0.24 0.29
42 7.6 13.6 15.6 8 11.9 0.43 0.14 0.21 0.28
Igneous r00kS
44 4.4 13.8 18.6 65 11 0.38 o-15 0.23 0.28
* LSPET (1973). t We do not know whether the two L 20 rocks analyzed by us were truly igneous or metaigneous rocks. By analogy with Ap 16 rocks, we suspect the L 20 rouks are metaigneous. Table 4. Comparison of bulk composition of Luna 20 and ApoIlo 16 metaigneous rocks* Element
61156
22006
66095
22007
Ti03 ( %)
0.64 22.9 7.8 10.0 13.3 0.39 0.11 0.12 0.140 64
0.63 21.9 9.9 11 12.4 0.41 0.12 0.121 0.171 66t
0.71 23.5 7.2 9.0 13.7 O-42 0.16 o*os 0.147 72
0.76 21.4 8.0 13 13.0 0.48 o-21 0.096 0,174
A&*, Fe0 MgO CaO Ha,0 % Cr&+i Y(ppm)
74t
* Data for rocks 61166 and 66095 am taken from LSRET (1973). See also footnote t of Table 3. t Y abundances have been estimated from the chondritic normalized REE distributions. 1972) and not to norite-KREEP type basalt. Thus, we conclude that the low-K variety is a major component present on the highlands. The feldspathic L 20 snd Ap 16 coils diEer appreciably in their bulk and trace elements1 composition, i.e. L 20 soil he,s higher FeO, MgO, MnO and CrzO, abundances and lower C?aOaud A&O, contents and ~thop~~ trace elements3 abundances than Ap 16 soils. This is reflected in a higher content of mafic minerals in L 20 soil components and less ltnorthosite at the L 20 site than at the Ap 16 site. Higher SC and V abundances in L 20 soil relative to Ap 16 soil are attributed to the COvariances of Se-Fe0 cmd V-Cr,O, in pyroxenes and apinels, respe&iveIy; both minerals are apparently higher in L 20 soil. Soils 66041 and 66081, collected from gray and whitish patches on the St&. 6 regolith, respectively, are identical in their overall chemical composition (LAWLet al’., 1972d). In general, the highland materials of L 20 and Ap 16 are lower in TiO,, FeO, MnO, C&O8 and higher in Also, and CaO than mare samples of L 16 and Ap 11,
J. C. LAUL
932
and R. A. SCHMITT
Table 5. Comparison of trace elemental composition of L 20, 1, 16, Ap 11 and Ap 16 samplls,. Ap 16
Element
‘Igneous’ rock* 68415
Soil
SC V co Hf Th Brt La Ce Sm Eu Yb Lu Ta
76 6.8 18 3.1 1.1 2.3 0.34 --
10 25 23-42 4.5 2.0 140 11-14 27-37 5.6-7.1 1.2 4.6 0.73 0.60
Jd 20 Metaigneons rocks --.15-20 35 40-51 4.2-8.5 1.7-3.4 13-21 32-53 64-10.1 1.1-1.4 5.6-7.8 0+3-1.1 0.5-0.7
1, 16:
Soil 16 45 27 2.5 1.0 6.2 16 3.1 0.92 2.6 0.43 0.3
Igneous rocks 26-54 _.18 220 13 37 10 2.9 6.4 0.8
Ap 11t
Soil
Igneous rocks
55 79 35 5.9 1.2 170 12 35 9.0 2.3 6.5 0.97 -
86-94 77 17-29 12-20 1 .o-3.5 170-320 7-25 25-70 8-23 l-5-2.3 9-14 1.2-2.5 2.0
-.
Sol;
____ 58 ci3 31 10 2.3 180 15 4i
13 I.9 I1 1.5 1.3
* BANSAL et d. (1972). t Apolk 11 Lunar ScienceConference(1970). $ Luna 10 issue of Earth R!unet Sci. Lett. (1972).
Table 5 shows a comparison of refractory trace elements of the four sites. Apollo 11 rocks are in general higher in SC, Co, Hf, La and REE fhan L 16 rooks and so are
the corresponding soils. Trace element data for Ap 16 rocks presently are not available for comparison. However, BANSALet al. (1972) have reported Ba and REE abundances for the crystalline anorthositic gabbroic rock 68416. This rock is claimed to be an unambiguous igneous rock; however, H~RZ (1972) suggests that the light and dark colored parts of the rock are suggestive of completely resorbed clasts and therefore, the rock is not of genuine igneous origin. Luna 20 rocks 22006,l and 22007,l are ambiguously igneous rocks with plagioclase oontents of -168 per cent and ~60 per cent, respectively. Thus, a comparison of L 20 metaigneous rocks with rock 68415 may not be strictly valid. Furthermore, the rock 68415 lacks a negative Eu anomaly. The REE abundances of 68416 are nearly identical to those at L 20 soil (with the exception of the Eu anomaly in L 20 soil) and are low by a factor of ~2 compared to the L 20 rocks. In general, highland rooks and soils are lower in refractories than Ap 11 and L 16 mare sites. The above soil comparisons are shown in Fig. 1. We have plotted our data for 29 elements in L 20 soil and oompared fhese with our data of three Ap 16 and two L 16 soils (GILUINebd., 1972; LAUL et all.,1972a). @en symbols represent elemental abundances in the ppb range; closed symbols, the ppm range. It is evident that the L 20 site matches the Ap 16 sife more closely than the L 16 msae site. The appreciable overall differences between L 16 mare soil and L 20 highland soil suggest minor contributions to the respective soils from mare rocks ejected to the L 20 highland site and vice versa. The elements Au, Ni, Se, Ag, Zn and Tl show some variation (Fig. 1). These elements are derived from meteoritic material to a greater or lesser extent. This mpect is discussed in a later section. The detailed oomparison
Chemical composition of Luna 20 rocks and soil and Apollo 16 soils
Lunc20-2200189
soi/fppm/
933
*A
1. Abundances of bulk, minor and trace element8 in L 20 soil versus average ebundencea reported in three Ap 16 soils and two L 16 soils. The Si value is taken from JANGEORBANI et aZ. (1973). Data for Luna 16 soils are taken from the Luna I6 issue of Earth Planet. Sci. L&t. (1972).
Fig.
of L 20 soil with other Ap 11,12,14 and 16 soils are discussed by SCHMITT and LAUL (1973).
REE $uz.&m8 ad derivation of
soil
The chondrite-normalized REE patterns of L 20 rocks, breccia and soil are 2. They all show a negative Eu anomaly and 8 flat pattern for the heavy REE. The heavy REE are also depleted by a factor of ~2 for the rocks and -30 per cent for the breccia and soil with respect to the average light REE. The Sm/Eu ratio, a sensitive indicator for the degree of partial melting among other mechanisms, is 7*2,66,3*9 and 3.3 for the rocks 22007 and 22006, breccia 22004 and soil 22001, respectively. We have also included the average values of our three Ap 16 soils for comparison (Sm/Eu = 6.4). The Ap 16 soil pattern is similar to that of L 20 soil with a depletion of -45 per cent in Ap 16 soil of the heavy REE with respect to the light REE. Norite-KREEP, which is shown for comparison, has a similar depletion of ~40 per cent and a Sm/Eu ratio of 16. In the past, norite KREEP, a dominant component at the Ap 12, 14 and 16 sites has been used as one end-member in mixing models to explain the origin of soils. The presence of noriteKREEP always raises the REE abundances of soils and breccias except Eu with respect to the cornminuted igneous rock components. This, however, is not the case with L 20 soil and breccia (Fig. 2), where the REE abundances in the soil and breccia are lower than in rocks. Other refractory elements are also enriched in norite-KREEP (see Table 1). Based on our REE pattern, we suggest that norite-KREEP may be absent or shown in Fig.
934
J. %. LAUL and R. A. SCHNITT
REE
IONIC
RADII
Fig. 2. Chondritic normalized REE abundances in L 20 metigneous rocks 22006, 22007, brecois 22004 and soil 22001 and average of three soils of Ap 10. Data for anorthosite 16416 (>98 psr cent PI; HUEBUD et aZ., 1972) and anorthositio gabbroic breccia 15418 (72 per cent 91; LAG et al., 1972d) &nd average noriteKREEP (Lam et al., 19720, Table 1) are included for comparison. Chondritic abundances t&en for normaliz&kn we La 0.34, Ce O-91, Sm 0.195, Eu 0.073, Tb O-047,Dy O-30,Yb O-22,and Lu 0.034, respectively.
present to a negligible amount (
Chemicalcompositionof Luna 20 rooksand soil and Apollo I6 soils
936
large positive Eu anomaly in sawdust from the 16418 anorthositio gabbroic breccia (PI, -72 per cent), which was subsequently confirmed by BANSALet al. (1972). The sawdust of a breccia best represents the overall rock composition, as previously noted by SHOWALTER et al. (1972) for 12013. All low K-type anorthositic gabbros-anorthosites may have been derived from a common magma source (HUBBARDet al., 1972). A alight norite-KREEP contamination of 0.2-1.3 per cent added to 15415 ‘pure’ anorthosite could also account for the increasing REE and nearly constant Eu abundances in these anorthositic gabbros-anorthosites (LAUL et ab., 1972d). Thus, materials similar to low K-type plagioclase-enriched rocks 15416 or 15418 are possible end-members for mixing with L 20 (low-K Fra Mauro basalt) metaigneous rocks to derive the L 20 soil. We prefer the 16418 end-member in our mixing model for the reason that pure 15416~like anorthosites are apparently rare on the lunar highlands. During the early bombardment of the highlands, pure plagioclase-rich rocks may have been melted by impact and recrystallized with other more mafic components into metaigneous rocks, with an average anorthositic gabbroic composition of PI N 65-78 per cent. Furthermore, the bulk chemical composition of 15418 lies in the range of the Ap 16 cataclastic plagioclase-rich rocks (LSPET, 1973), and the composition of 15418 approximates the Surveyor 7 analysis near Tycho (TURKEVICH,1971). Also, the Al/Si ratio for 15418 is more compatible with lunar orbital evidence (ADLERet al., 1972). The chondrite-normalized REE pattern for a L 20 anorthositic basaltic rock (60 mg), probably troctolitic (~62 per cent PI; VINOQRADOV, 1972), is similar to the REE pattern observed in 16418. This suggests either that 16418, though collected at the Apennine Front, could have been ejected from the highlands (LAUL et al., 1972d) or that a considerable fraction of the Apennine Front has a composition similar to highland basalt. In Table 6, mass-balance calculations are presented for the soil, using a simple two-component mixing model for L 20 metaigneous rocks plus either 15418 plagioclase-rich rock or a pure anorthositic end-member like 15415. We have averaged the two rocks (22006 and 22007) in view of the small sample sizes. Data for 15415 are taken from LSPET (1972) and BANSALet al. (1972). Based on K, La, Sm and Eu abundances, we need about 33 per cent of the average L 20 metaigneous rocks and 66 per cent 15418-l& rock composition to obtain the composition of the L 20 soil (Table 6). The agreement is very good. The obvious anomalies marked with asterisks are Cr,O, and Co. The high Co value of 77 ppm for 16418 is most probably due to contamination during sawing. If we use a Co value of 20-26 ppm, which is the typical range for rocks and soils (see Table 6), for 15418, then it matches the soil value. However, the mass-balance for Cr,O, is poor and may be attributed to heterogeneous distribution of chrome spine1 minerals. The dispersion in V is attributed to poor precision (Table 1). If we use the 15416 anorthosite and the L 20 metaigneous rooks, the contributions to the soil turn out to be 38 per cent and 60 per cent, respectively, based only on average fractions calculated from REE and K data. The match for the soil is even worse for the major elements A&,0,, FeO, MgO and CaO. If we use different proportions to match the major elements, then the REE proportions do not agree. Thus we are forced to conclude either that pure anorthosite like 16415 is not a proper
936
J. C’. LAUL and 1%. A.
SCHMI~
Table 6. Mass-balance for the Luna 20 soil, in terms of two component model (ignoring 2 ‘A meteoritic contribution)
a Element
22006 + 22007 Av.
3 1541s*
0.69 21.6 9.0 12 12.7 0.446 0.16 0.108 0,172 18 36 45 6.3 2-6 17.1 42 8.2 1.26 6.7 0.95 0.60
0.37 26.4 7.5 5.3 15.8 0.282 0.01 I 0.086 0.280 13 42 77 0.8 0.13 1.2 0.69 0.73 0.81 0.12 0.09
C 15415t
Oa33A f 0.653
-
Ti%( %I
4%
Fe0 W@ C&O NaaO z: crjlos F(ppmI co Hf Th L& Ce
Sm Eu Yb Lu Tf&
0.02 355 O-23 0.09 19.7 0.34 0.015 0.12 0.33 0.047 0.81 O*OP 0.0034 -
0.47 24.2 7-8 7.4 14.4 0.330 0.060 0.092 0.2398 14 39 65§ 2-5 0.94 6.4 -_ 3.1 0.89 2.6 0.39 0.26
Observed i11 soil 22001
0.38A -IO~fiOC
0.49 22.8
0,27$ 29.55 3.59 4.6s 16.6$j 0.37 0.070 -
il:.:): 14.2 0.334 0,076 0.104 0.180 16 47 27 2.5 i-0 6.2 16 3.1 0.92 2.6 0.43 0.28
-
6.6 16 3-l 0.96 2.6 0.36 -
* LAUL et ai. (XQ72d). f HUBSet al. (1972). $ OurMgO valueshavelargeerrors. BANSAL & cd. (1972)reportedan averageof 8.5 -& O-1% MgO in two L 20 soil samples. g Anomdies (6eetext).
major component or that still another component is required in addition to 16415. Rock 16418 is the better choice for 8 two-~rn~ent system. The validity of our soil model depends on the assumption that the two analyzed L 20 me&igneous rouks are iudeed representative of the source rocks of L 20 soil. Based on our calcuh&ions, ~33 per cent L 20 rocks (Fra Mauro basaltic rooks, low-K type) and 5~65per mnt ~o~hositic gabbroic (p~~~-~~) rock like 15418 is a, two component mixture capable of matching L 20 soil. The L 20 breccia 22004 is similar in bulk chemicctlcomposition to the L 20 soil. This suggests that the brecoia is merely a compacted soil. The limited nature of our Ap 16 d&a predudes sim& ~~~&tions for soils from that site, TAX-LORebc-d.(1972) d a similar approach for derivation of the Ap 16 soil 68601. From their armlyses of the white feldspathic fragments with a positive Eu anomaly, and black fragments, with a negative Eu anomaly, of the Ap 15 breed& 15456, they concluded that a 60-40 per oent mixture of these two eorn~nen~ mahhes the composition of Ap 16 soil 68801.
Chemical composition of Luna 20 rocks and soil and Apollo 16 soils
937
Inter-element reZatd we had established a few interelement In a previous paper (L4UL et d., 1972c), correlations, which are useful constraints for any proposed model for magmatic processes and primordial abundances of the Moon. Our conclusions based on these interelement correlations have been strengthened by additional data on Ap 15 and 1972) as well as data obtained from 16 samples (L~aet al., 1972b; LAUX~~~SOHMITT, L 20 studies. In Table 1, we have obtained average ratios K/La (77), K/Hf (210), K/Th (500), FeO/MnO (85) and FeO/Sc (5400), and K/Rb (39) and Rb/Ca (23) in Table 2 for L 20 and Ap 16 samples. The K/La correlation was also reported by W~NICEet al. (1972). The ratios in Tables 1 and 2 are uniform within experimental and sampling error. Figure 3 shows one such correlation between MnO and Fe0 0.40
I
(J3*_
-
. . . * o n l . + 1.
I
I
I
I
I
1
’
I(
I
x
I
I
APOLLO II SOIL a ROCKS IP. 12 SOILS B ROCKS Ii? 14 f0ll.f a IGNEOUS ROWS P.P. 14 CLASTK ROCK SAWDUST 4~. ,4 CLASTS FROM BRECCIA ROCKS AP. IS SOILS LUNI 86 SOILS a mccws OCEANIC BASALTS CO+J,,nENT*L BISALTS KREEP-NOfllfE
Fig. 3. MnO-Fe0 COITd8tiOnSin lunar rocks and soils. Terrestrial and meteoritic are included for comparison. Thisoorrelation plot fhxt shown by LAUL et d. (19720) has been brought up to date. The K point on the previous graph6 by LAUL etd. (1972~) and LAUX and S(1972) was incorreot. The correlation coefficient is O-97 ( >QQ per cent oonfidence level) for all lunar value%
values
which ranges over a factor of 30 in abundance. Such a strong correlation suggests that Fe0 and Mu0 are strongly associated in ma& minerals and that Fe largely exists in the divalent state. The divalent nature of iron is further supported by Mossbauer studies in lunar rooks (~XUNERet cd., 1971). Note in Fig. 3 that anorthosites 10085 and 15362 match perfectly on the lower left portion of the line. The fact that the line passes through the origin implies that there has been no significant fractionation between Fe0 aud MnO during any lunar differentiation processes. Howardites and eucrites both fall far away from the lunar correlation line. This contradicts the hypothesis that howardites (XUWIN et d., 1972) and eucrites are the raw material for the Moon. A similar conclusion has also been reached by studies of oxygen isotopic compositions (ONUMAet al., 1972). If anorthositic rocks were
938
J. C. LAUL and R. A. SCHI\IIT~
derived from magmatic processes in the outer 10~200 km of the lunar crust, Cad lunar basalts, from partial melting in the lunar interior below 200 km (GAST and MocO~~ELL, 1972), then the strong MnO-Fe0 relationship for all lunar samples would seem to suggest a similar FeO/MnO = SOratio for the mafic minerals in the entire primordial Moon. Obviously sources such as chondrites, eucrites and howardites, as well as Earth mantle material, may be eliminated as the single primary source material for the Moon. Potassium, Rb and Cs are lithop~lic elements of increasing volatility, The fairly constant ratios of volatile to refractory elements such as K/La, K/Hf, K/Rb and K/Th and of two volatile elements Rb/Cs preclude any selective volatilization of alkalis and volatiles during lunar magmatic events. The correlations of Rb/Cs, Cs/U and Tl[U previously reported by ANDERSet nl. (197 1) and MORGAN et al. (1972b) also support the argument,
Lunar soils are enriched relative to rooks by up to about two orders of magnitude in the siderophile elements Ag, Au, Ni, Ir and Re and to lesser degrees in the volatile elements Bi, Br, Cd, In, Sb, Se, Te, Tl and Zn (Proc. Apollo II, Second and Third Lunar Science Co~~ere~ce~,1970, 1971, 1972). GA~JAY?AT~IY et al. f1970), LAUL et al. (1971) and MORQANet al. (1972a) have used the convention of normalizing the elemental abundances in soils relative to the corresponding elemental abundances in Cl chondrites (carbonaceous chondrites type 1) in order to calculate the amount of meteoritic material which has been admixed to the soil. The contributions of Cl material to the Ap 11, 12, 14 and 15 and Luna 16 sites range from 14-1.9 per cent Cl-like material. It seems probable that similar amo~ts of Cl material have been added to the whole Moon. Mature soils contain an admixture of 1.9 per cent Cllike material, whereas young soils, of low exposure age, contain lesser amounts of Cl material (MORGANet al., 1972b; BAEDECKERet a$., 1972). The relative abundances of siderophiles and volatiles characterize the type(s) of impacting meteorite. LAUI, ct al. (1971) and GANAPATHYet a$. (1972) observed fractionated meteoritic patterns in some Ap 12 and Ap 14 soils; these patterns are indicative of ancient meteoritic components (MORGANet ak., 1972a). In Table 2, the results of our analyses are given for L 20, Ap 16 (62281) and Ap 15 (15041, trench) soils. Unfortunately, the L 20 soil appears to be contaminated with the elements Ag, Cd, In, Sb and W and also Pb (G. J. Wasserburg, private eomm~i~ation). Comparison of our L 20 data with that reported by MOR~AXet at. (1973) suggests random heterogeneous oonta~ation of these elements. The Ag and In values in 62281 soil and the In value in 15041 soil are doubtful because of the notorious Ag-In vacuum gasket problem. Thus our discussion is focused primarily on our Ap 16 soil and Ap 15 soil (15041) and to a lesser degree on L 20 soil. We note that Zn and Cd are unusually high in soil 62281. A Cd-Zn rich component and Ag-B&Cd rich component have been found in mare samples from the Ap 12 and L 16 (LAUL et al., 1971, 1972a; BAEDECKERet d., 1971) and Ap 14 (MOR~AX et al., 1972a; BAEDECKEJR et aZ., 1972) sites. We conclude that a Cd-Zn rich component, which may be indigenous, is also present in the lunar highlands near the L 20 and Ap 16 sites. If we normalize, without indigenous corrections, the abundances of the remaining
Chemicalcompositionof Lum 20 rooksand soil and Apollo 16 soils
939
elements Au, Ni, Sb, Se and Tl in soil 62281 to their corresponding elemental abundances in Cl chondrites, the excess amounts of these elements in the soil range from 1-5-7 per cent Cl equivalent. The average Cl values are taken from ~ltI?Bthm et al. (1973). Indigenous corrections are not known for any of these soils (Table 2). Usually these corrections are low, less than ~5-10 per cent for Au and Ni but relatively higher for Sb, Se and Tl. Thus Au and Ni will be considered more reliable because of their small assumed corrections. Such a wide range of apparent meteoritio contributions, 15-7 per cent, suggests the presence of an optional ~om~nent in addition to the ubiquitous Cl component. Subtraction of 1.9 per cent Cl material (upper limit) from the 62281 soil abundances should yield residuals of additional component(s). Subtraction of less than 1.9 per cent Cl contribution will yield siderophile residuals which are slightly higher than volatile residuals. However, this would not alter the conclusion significantly. In addition, the following indigenous contributions are subtracted: Sb 05-l-O ppb, Se 150 ppb and Tl lm0ppb. These contributions are all based on other previous lunar rock analyses reported in the literature. The residual abundances are given below. Selenium shows a negative residual which is attributed to volatile loss by impact heating or solar wind interactions (MORGAN et al., 1973). AU
r-
1%=
Residud =f eaidurtl Cl
(mb)
Ni (mm)
Sb (mb)
Wb)
Tl
3.0
186
l-4
6.2
2.0
1-S
I-0
4.3
The high Tl residual abundance of 6.2 ppb in 62281 soil puzzles us. The rocks from which the soil is derived would be expected to be also alkali poor. Thallium correlates strongly with Rb and Cs over three orders of magnitude in rocks and a Tl/Cs ratio of (l-2 + 1.0) x IO+?, based on lunar rooks from 4 landing sites, has been used in computing the accretion ~mperat~e of the Moon (AIDS et ti., 1971; MORGIAN et al., 1972a). If this ratio also applied to the Apollo 16 site, then, on the basis of the Cs value of 120 ppb in 62281 soil (Table 2), the indigenous Tl abundance should be trivial at ~0.6 ppb. The low K value and REE pattern for the 62281 soil suggest a small (maximum 8-12 per cent) norite-KREEP contribution to Ap 16 highland soil. The ano~ho~tic gabbroic breccia 15418, used in our mixing model for the soils, is low in K and thus should also be low in Tl. We do not suspect the high Tl value on experimental grounds. Perhaps a Tl-rich component, which is deficient in alkalis, is present iu the highlands and not in the maria. A high Tl/Cs ratio of (5.3 f 2.4) 10-a has been noted by MOBUANet al. (1973) in Ap 16 and L 20 highland soils. Such variability of TljCs ratios between highland and mare rocks will of course require revisions in previous calc~ations of accretion tem~rat~es. Normalizing the residual abundances of Au, Ni and Sb to Cl abuudances, we observe a siderophile-rich and volatile-poor pattern, which is characteristic of fractionated meteorites. This fractionated component may be the same ancient component which was proposed by MOBUANet al. (1972a) and ANDERZJet al. (1973). The average contribution of this component is w l-5 per cent Cl equivalent material-
940
J. C'. LAUL
and R. ,4.
sCHMIT!E
Soil 16041 is dominated by the Cl component and has m21 per cent norite(LUL et al., 1972b). Subtraction of 1.9 per cent Cl equivalent abundances from soil 15041 abundances yields residual abundances which may be attributed to ;L norite-KREEP component (MORGAN et al., 1972a). Luna 20 soil is low in alkalis. The high Zn and Cd contents again suggest the presence of a component enriched in these elements. The soil is reported to have a short exposure age (PIUKEY and PRICE, 1973). Based on our Ni data, the meteoritic contribution at the L 20 site is l-9 per cent Cl equivalent material. MORGAN et al. (1973) report an ancient component in addition to Cl material.
KREEP
Acknowledgements-This work was supported by NASA grants 38-002-039 snd 38-002-020. We &re most grateful to Professor ALEXANDERVINOURADOV and the Soviet Academy of Sciences for the availability of these precious Luna 20 samples. We acknowledgethe assistanceof T. V. ANDERSONand W. CARPENTER at the Oregon State University TRIGA reactor group and of J. SCHLAPPER at the Missourireactor group for neutron activations. We 8re also indebted to T. D. COOPER,D. W. HILL and D. A. MILLERfor their assistancein some phases of this study. REFERENCES ADLER I., T~OMBKAJ., GERARDJ., LOWMANP., SCH~DEBECK R., BLOD~ETIf., ELLER E., YIN L., LAMOTEER., OSSWALDG., GORENSTEIN P., BJORKHOLM P., GURSKY H. and HARRIS B. (1972) Apollo 16 geochemicalX-ray fluorescenceexperiment: preliminary report. &&lace 177, 266-259. ANDER~E., GANAPATEY R., KR~EENB~HLU. and MORGANJ. W. (1973) Meteoritic material on the moon. The Moon. ANDER~E., GANAPATHY R., KEAYS R. R., LAUL J. C. and MORUANJ. W. (1971) Volatile and sideropbileelements in lunar rocks: comparisonwith terrestrialand meteoritic baealts. Proc. Second Lunur Sci. Conf., cfeochim. Coanzochim. Aeta Suppl. 2, 1021-1036. M.I.T. Press. BAEDECKER P. A., CHOWC. L. and WMSON J. T. (1972) The extrelunar component in lunar soils and breccias. Proc. Third Lunar Soi. Conf., Geochim. Coemochirn. Acta SW&. 8, 1343-1360. M.I.T. Press. BAEDECKERP. A., SCHAUDYR., ELZIE J. L., KIM~ERLINJ. and W~SSONJ. T. (1971) Trsce element studies of rocks and soils from OceanusProcellarumand Mere Tr8nquillitatis. Proc. Second Lunur SC&.Cmf., ffeoehim. Coamuchim. Acta Sup@. 2, 1037-1061. M.I.T. Press. BANSALB. M., CHURCHS. E., G&T P. W., HUBBARDN. J., RHODESJ. M. and WIES~~ H. (1972) The chemical composition of soil from the Apollo 16 and Luna 20 sites. Earth Planet. Sci. Lett. 17, 29-35. BRWBELT A. 0. and STEINNESE. (1971) A neutron activation scheme developed for the dctermination of 42 elements in lunar material. T&&a 18, 1197-1208. GANAPATHY R., KEAYS R. R., LAm, J. C. and ANDER~E. (1970) Trace elements in Apollo 11 lunar rocks: implicationsfor meteorite infiux and origin of moon. Proc. Apollo 11 Lunar Sci. Gonf., Geochirn. Coemochim. Aeta Sup@. 1, 1117-1142. Pergamon. CANAPATHY R., LAULJ. C., MOR~~LN J. W. and ANDERSE. (1972) Moon: possible nature of the body that produced the Imbrian basin, from the composition of Apollo 14 samples. Sciem 175, 55-59. GANCARZA. J., CHODOS A. A. and ALBEE A. L. (1973) Petrology of Luna 20 sample 22006, 1. Earth Planet. Sci. L&t. GASTP. W. and MCCONNELL R. K., JR. (1972) Evidence for initial chemicallayeringof the moon. Lunar Science III, (editor C. Watkins), pp. 289-290. Houston: Lunar Sci. Instit,ute Contrib. No. 88. GILLUMD. E., E-ANN W. D., WAKF~AH. and SCW~ITTR. A. (1972) Bulk and rare earth abundancesin the Lnna 16 soil levels A and D. Earth Planet. Sci. I&t. 13, 444-449. HAFNERS. S., Vmao D. and WARBURTON D. (1971) Cation distributionsand cooling history of clinopyroxenes from Oceanus Prooellarum. Proc. Second hnar Sci. Conf., Geochim. Cosmochim. Acta Suppl. 2, 91-108. M.I.T. Press.
Chemical composition of Luna 20 rocks and soil and Apollo 16 soils
941
HASKIN L. A., ALLEN R. O., HELMKEP. A., PILOTED T. P., ANDERSONM. R., KOR~TEVR. L. and Zwnnr~~ K. A. (1970) Rare earthe and other trace elements in Apollo 11 lunar samples. Proc. Apollo 11 Lunar Sci. Cmf., &o&m. &moch&n. A&a Sup@. 1, 1213-1231. Hsnz F. (1972) Rock 68416, 1. In Lunar [email protected] InfOrmationCatalog,Apollo 16. MSC-03210, Lunar Receiving Laboratory (Houston), 349. HTJBBMXD N. J., Gash P. W., Mnynn C., NYQUIBTL. E. and SEIE C. (1972) Chemicalcomposition of lunar anorthositesand their parent liquids. Ewth Planet. Sk Lett. 18, 71-76. W. D. (1973) Oxygen and bulk elementabundances JANUEORBANIM., GILL~~~D.E. andEn in Luna 20 fines. &c&h. Coemochirn.Acto 87, 906-908. KEAYS R. R., GANAPA~ R. and ANDE. (1971) Chemicalfraction&ions in meteorites-IV. Abundances of fourteen trace elements in L-chondrites; implicationsfor cosmothermometry. awcladm.Coemoohkm. AC&Za&337-363. KRAHENB~?HL TJ., MORGANJ. W., GANAPATWR. and ANDEBSE. (1973) Abundance of 17 trace elements in carbonaceouschondrites. &o&&n. Coemoohim.Acta. LAULJ.C.B~~S~EMITTR.A. (1972)BulkandREEabundanceginthreeApollo16iigneousrocks and six basaltic rake samples. The Apollo 15 Sampb, (editors J. W. Chamberlain and C. Watkins), pp. 226-228. Lunar Science Institute, Houston. LAUL J. C., MORGANJ. W., GAXAPATE~R. and AND= E. (1971) Meteoritic material in lunar samples: characterization from trace elements. Proc. Seemd Lunar Sci. Conf., &ochim. Comwchim. Act.aSuppl. 2, 1139-1168. M.I.T. Press. LAULJ. C., GANAPATH~ R., MORQANJ. W. and ANDEBBE. (19728)Meteoriticand non-meteoritic trace elements in Luna 16 samples. Earth Planet. Sk. L&t. l&460-464. LATJ’L J. C., S~ow&‘rnn D. L. and Sm R. A. (1972b) Elemental abundances of Apollo 16 four soils, a clod and five breccia rocks and two soils of Apollo 16. The Apollo 15 Swles, (editors J. W. Chamberlainand C. Watkins), pp. 229-232. Lunar Sci. Institute, Houston. LAUL J. C., WAKITA H., S~OWALTEBD. L., BOYPJTON W. V. and SamurnrR. A. (1972~) Bulk, rare earth and other trace elements in Apollo 14 and 16 and Luua 16 samples. Proc. Third Lmar Sci. Conf., &w&m. Coemochbn.Acta Suppl. $3, 1181-1200. M.1.T Press. LAULJ. C., WAKrI!AH. and S= R. A. (1972d) Bulk and REE abundancesin anorthosites and noritic fragments. The Apollo 15 Sam$es, (editors J. W. Chamberlainand C. Watkins), pp. 221-224. Lunar Science Institute, Houston. LSPET (APOLLO16 PRELIMINARY E~AMINATIONTEAM) (1973) The Apollo 16 lunar samples: petrographic and chemicsl description. Soience179,23-34. LSPET (LUND SAMPLE~AEY EXAMINATIONm) (1972) The Apollo 16 hmar samples: s preliminary description. Sc&ence175, 363-374. Luna 16 samples results. (1972) Earth Planet. SC&Lett. l&223-472. MAWIN U. B., REID J. B., JR., TAYLORG. J. and WOOD J. A. (1972) A survey of lithic and vitreous types in the Apollo 14 soil samples (sbstracts). In ti So&ace--III, (editor, C. Watkins), pp. 607609. Lunar ScienceInstitute Contrib. No. 88. WON B. (1963) The carbonaceouschondrites. Space Soi. Rev. 1, 621-646. MORGANJ. W., LAUL J. C., KR~~HENB~SHL U., GANAPATE~R. and ANDER~E. (1972s) Major impacts on the moon: characterization from trace elements in Apollo 12 and Apollo 14 samples. Proc. ThGrdLunar Sci. Conf., Ueochim.Comchim. ActaSuppl. 3,1377-1396. M.I.T. Press. MO~UANJ. W., KR&XENB~?EL U., GUAVAR. and WEBB E. (1972b) Trsce elements in ’ ’ Apollo 16 samples: imphcations for meteorite in&ix and volatile depletion on the moon. Proc. Third Lunar Sci. Conf., Ueo&iq?&. Coemoohint.ActaSwppZ. 8, 13661376. M.I.T. press. MORUANJ. W., KR&ENB~~HLU., GANAPA~ R. and ANDEBBE. (1973) Lima 20 soil: abun_ dance of 17 trace elements. Qeoch&n.Coemochba.Acta 87, 963-961. NAVA D. F. and P~ns~rrs J. A. (1973) A 1~na.rdifferentiationmodel in light of new chemical data on Luna 20 and Apollo 16 soils. tic?&. Coemwhina.Acta 37, 963-973. ONUMAN., CLAYTON R. N. and MAYEDA T. K. (1972) Oxygen isotope cosmothermomemr. Geochka.Coemoohim.Acta 36,169188. PAPANASTA~SIOU D. A. and WA~SERBVR~G. J. (1972) Rb-Sr systematics of Lime 20 and Apollo 16 samples. Earth Planet. Sci. L&t. 17, 62-64.
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J. C. LAUL and R. A. SUHMITT.
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