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Apollo 15 green glasses
Physics of the Earth and Planetary Interiors, 7 (1973) 133—136 © North-Holland Publishing Company, Amsterdam — Printed in The Netherlands
APOLLO 15 GREEN GLASSES W.I. RIDLEY*, A.M. REID**, J.L. WARNER** and R.W. BROWN*** *
Lunar Science Institute, Houston, Texas (U LA.), ***
**
Johnson Space Center, Houston, Texas (USA.),
Lockheed Electronics Corporation, Houston, Texas (U LA.) Accepted for publication 1 September 1972
Apollo 15 breccia 15427 and soils 15101, 15261 and 15301 contain abundant spheres and fragments of a green glass that is remarkably constant in composition. The glass is rich in Fe and Mg, and low in Ti, unlike any known lunar basalt, and may be derived from material of pyroxenitic composition in the Apennine Front.
Green glasses, commonly present as spheres or portions of spheres, are a distinctive component in several Apollo 15 soils (Apollo 15 P.E.T., 1972). The abundance of these glasses varies from soil to soil, but there appears to be a general correlation between abundance of green glass and proximity to the Apennine Front. The highest concentration of the green spheres is in the “green clods” 15425, 15426 and 15427 from station 7 at Spur Crater. In this report we discuss the composition of these glasses in 15427 and in soil samples 15101 from station 2 at St. George Crater, 15261 from station 6 at the Front, and 15301 from station 7 at Spur Crater.
abundant crystallites of olivine. Table I shows the average composition and standard deviations of 11 green glasses. Other distinctive glasses occur in 15427 (Table II). Red-brown glass high in titanium is a minor component that is found in both Apollo 11 and 12 soils (Reid et al., 1972b) and corresponds to ilmenite pyroxenite. Spheres and irregular fragments of bright yellow glass have compositions like those of mare basalts (Table II), with high Fe, moderate Ti and Cr, and low Al. These glasses may derive from basalts in the Imbrium basin. In 15427 some of the green glass spheres contain ciystallites of olivine (Fo76, Table II). The residual
28 spheres, portions of spheres, and angular fragments from the less than 1 mm fraction of soil 15101, 127 were analyzed. Other glasses are present in the sample, a few of which are greenish in color, but these are distinctly different in composition from the more abundant emerald-green glasses. Each glass grain is devoid of inclusions and is homogeneous, i.e., no vanation above counting precision was found for any major element (Table I). Emerald green glasses from the other soils (15261 and 15301, Table I) are identical to those from 15101. The chemical homogeneity of these glasses is not matched by that of any other group of lunar glasses we have analyzed. Sample 15426, a weakly coherent breccia, has green glass as a major component. Two “types” of green glass occur in this rock the clear emerald green glass and yellowish green glass spheres with
liquid, enriched in Ca, Al, Ti and Cr over the bulk green glass and with a higher Fe/Mg ratio, occurs as a glass or as a very fine-grained devitrified aggregate whose constituents cannot readily be separated. The composition of the green glass is unlike that of any other major lunar glass group. Fe content is comparable to that in mare basalts, but Ti is much lower (Ti02 = 0.4 weight percent). Mg is much higher than in most lunar materials analyzed to date, and Cr is also high. The low Al content is comparable to that of mare basalt glasses. Na is low and K is below 0.05 weight percent. Seven glasses of similar composition have been reported from the Mare Tranquihitatis site (Chao et al., 1970; Fredriksson et al., 1970; Lovering and Ware, 1970; Prinz et al., 1971). Among 500 analyzed Fra Mauro glasses (Brown et al., 1971; Reid et al., 1971) only three have this composition; none was found
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134
Ridley etal., Apollo 15 green glasses
TABLE I Composition of green glass
Si0
2
Ti02 A1203
Cr2O3 FeO MgO
CaO Na20
K20 Total Number of analyses
15101 (soil)
15261 (soil)
15301 (soil)
15427 (green clod)
45.21 (0.31)
45.20 (0.39) 0.42 (0.19)
45.27 (0.23) 0.47 (0.01) 7.45 (0.09)
45.38 (0.32) 0.39 (0.01) 7.34 (0.18)
0.43 (0.02)
7.63 (0.16) 0.43 (0.01)
7.58 (0.16)
0.39 (0.01)
19.73 (0.39) 17.89 (0.33) 8.14 (0.17) 0.13 (0.03)
19.66 17.68 8.28 0.13
0.00 (0.00)
(0.27) (0.22) (0.09) (0.02)
19.60 17.80 8.32 0.13
0.00 (0.00)
(0.17) (0.17) (0.10) (0.04)
0.02 (0.01)
0.44 (0.01) 19.44 17.29 8.49 0.13
(0.50) (0.17) (0.10) (0.01)
0.02 (0.01)
99.59 28
98.95 5
99.45
99.42 11
Plagioclase An content Clinopyroxene Orthopyroxene
21.3 94.5 16.6 29.0
Olivine
31.5
21.2 94.5 17.2 28.6 31.4 0.62
20.8 94.4 17.7 28.5 31.1 0.62 0.6 0.9
22.0 94.7 17.6 29.1 29.6 0.62 0.7 0.7
CI.F. W-norms
Mol. Mg/(Mg+Fe) Chromite llmenite
0.62 0.6 0.8
0.8
Numbers in parentheses are on standard deviation. Glasses also contain 0.24 weight percent MnO.
TABLE II Compositions of other glasses in 15427,3 1 Red-brown glass
Yellow glass 1
Yellow glass 2
Colorless glass
5i02
36.16
Ti02
13.48
A1203 Cr203 FeO MgO CaO Na20 K20 Total Number of analyses
8.54 0.58 20.48 10.65 8.89 0.64 0.50 99.94 1
42.47 3.96 9.01 0.57 21.78 12.39 9.23 0.53 0.45 100.35 2
43:88 4.64 10.75 0.38 19.21 9.96 10.27 0.58 0.55 100.22 1
49.04 0.07 33.06 0.12 0.49 0.29 16.51 1.71 0.50 101.81 1
among 250 analyzed Mare Fecunditatis glasses (Jakes et al., 1972). The range of composition of the Apollo 15 green glasses described here is considerably less than, and outside that of, the green glasses described by Marvin et al., (1972) from the Fra Mauro and Mare
Olivine in green glass 38.15
22.42 38.51 1.17
100.65 1
Fecunditatis sites. We have proposed elsewhere that preferred glass compositions in the lunar soils are indicative of the compositions of the rocks from which the glasses were derived (Reid et al., 1972a; Apollo Soil Survey,
WI. Ridley et al., Apollo 15 green glasses
1971). Even with limited data it is obvious that these glasses represent a strongly preferred composition. The equivalent crystalline rock would be an ultramafic rock with 45% pyroxene, 31% olivine, 21% plagioclase feldspar and minor ilmenite and chromite, if the glass composition is recalculated to normative constituents. The abundance of green glass in the soils from the Apennine Front suggest that the Front may contain such an ultramafic rock or its glassy equivalent. If the Front comprises upthrust fault blocks of Imbrium ejecta, then it should contain materials formed at several kilometers depth, and possibly much deeper. The major-element composition of the green glass resembles the composition of howardite meteorites but the green glass has lower Si and higher Fe. The Mg/Fe ratio is lower than in the howardites and the Ca/Al ratio higher. Green glass separated from sample 15301, from station 7 at Spur Crater, has been analyzed for rare-earth elements (Hubbard et al., 1972). The green glass has rare-earth abundances that are approximately 4½times chondritic and has a chondrite-like RE. E.-pattern with a very small negative europium anomaly. The rare-earth abundances (other than La) are strikingly similar to those of howardites (Fig. 1). The green glass composition is unlike that of any lunar rock yet recognized. Ringwood (1970) and others have postulated the existence of a pyroxenitic layer at depth in the moon, as a source region for the mare basalts. The green glass may ultimately be derived from deep-seated ultramafic rocks of the type that formed ii 6
~
~ ~
•/
•
Il
-~
~ Z,,,en~ -~
the source region for mare basalts. The major element chemistry is notably similar to that suggested by Gast (1972) for the outer lunar mantle. In addition, the rare-earth abundances for the green glass are close to the values deduced by Hubbard and Gast (1971) for the source material of the Apollo 12 mare basalts. It is questionable, however, whether with this hypothesis the low Mg/(Mg+Fe) ratio of the glass is cornpatible with the presence of magnesian pigeonites (Mg/(Mg+Fe) = 0.7) in some mare basalts (Bence et al., 1971). The small negative europium anomaly in the rareearth pattern (Fig. 1) may be due to removal of a small amount of plagioclase, but feldspar fractionation has apparently not played a major role in the formation of the green glass composition. Thus, if the green glass is representative of deep seated pyroxenites these are unlikely to be residues from or complimentary differentiates to the anorthositic gabbro that appears to be abundant in the lunar highlands (Reid et al., 1972a).
Acknowledgments Lunar Science Institute Contribution no. 119. Part of this research was performed at the Lunar Science Institute under contract no. NSR 09—05 1— 001 with NASA.
References Apollo Soil Survey, 1971. Earth Planet. Sci. Lett., 12: 49.
-
~
135
2
ha La Ce Nd Sm ~uGd t~Er Yb Lu Fig. 1. Rare earth normalized pattern for green glass from 15301,76 (Hubbard et aL, 1972). Comparative data for two howardites (Bununu and Zmenj) are taken from Schnetzler and Philpotts (1969).
Apollo 15 Preliminary Examination Team, 1972. Science, 175: 363. Bence, A.E., Papike, J.J. and Lindsley, D.H., 1971. In: A.A. Levinson (Editor), Proceedings of the Second Lunar Science Conference. M.I.T. Press, Cambridge, Mass. Brown, R.W., Reid, A.M., Ridley, W.I., Warner, J.L., Jakes, P., Butler, P., Williams, R.J. and Anderson, D.H., 1971. NASA Tech. Memo., TMX-58080. Chao, E.C.T., James, O.B., Minkin, J.A. and Boreman, J.A., 1970. In: A.A. Levinsin (Editor), Proceedings of the Apollo 11 Lunar Science Conference. M.I.T. Press, Cambridge, Mass., 1, 287. Fredrikkson, K., Nelen, J., Melson, W.G., 1970. In: A.A. Levinson (Editor), Proceedings of the Apollo 11 Lunar Science Conference. M.I.T. Press, Cambridge, Mass., 1, 419. Gast, P.W., 1972. The Moon. In press. Hubbard, N.J. and Gast, P.W., 1971. In: A.A. Levinson (Edi-
136
WI. Ridley etal., Apollo 15 green glasses
tor), Proceedings of the Second Lunar Science Conference. M.I.T. Press, Cambridge, Mass., 1, 999. Hubbard, N.J., Ridley, W.I., Rhodes, M.J., Bansel, B. and Weismann, H., 1972. Submitted for publication. Jakes, P., Warner, J.L., Ridley, W.I., Reid, A.M., Harmon, R.S., Brett, R. and Brown, R.W., 1972. Earth Planet. Sci. Lett., 13: 257. Lovering, J.F. and Ware, N.W., 1970. In: A.A. Levinson (Editor), Proceedings of the Apollo 11 Lunar Science Conference. M.I.T. Press, Cambridge, Mass., 1, 633. Marvin, U.B., Reid, Jr., J.B., Taylor, G.J. and Wood, J.A., 1972. Lunar Science III, Abstr. Third Lunar Sd. Conf., Lunar Sd. Inst. Contr., 88. Prinz, M., Bunch, T.E. and Keil, K., 1971. Contrib. Mineral. Petrol., 32: 211.
Reid, A.M., Ridley, W.I., Jakes, P. and Warner, J.L.,
1971. NASA Tech. Memo., TMX-58081. Reid, A.M., Ridley, W.I., Harmon, R.S., Warner, J.L., Brett, R., Jakes, P. and Brown, R.W., 1972a. Geochirn. Cosmochina Acta, in press. Reid, A.M., Warner, J.L., Ridley, W.I., Johnston, D.A., Harmon, R.S., Jakes, P. and Brown, R.W., 1972b. Geochim. Cosmochim. Acta, in press. Ringwood, A.E., 1970. J. Geophys. Res., 75: 6453. Schnetzler, C.C. and Philpotts, J.A., 1969. In: P.M. Millman (Editor), Meteorite Research. Springer, Berlin, p. 206. Winchell, H. and Skinner, B.J., 1970. In: A.A. Levinson (Editor), Proceedings of the Apollo 11 Lunar Science Conference, 1, 957.
APOLLO 15 GREEN GLASSES W.I. RIDLEY*, A.M. REID**, J.L. WARNER** and R.W. BROWN*** *
Lunar Science Institute, Houston, Texas (U LA.), ***
**
Johnson Space Center, Houston, Texas (USA.),
Lockheed Electronics Corporation, Houston, Texas (U LA.) Accepted for publication 1 September 1972
Apollo 15 breccia 15427 and soils 15101, 15261 and 15301 contain abundant spheres and fragments of a green glass that is remarkably constant in composition. The glass is rich in Fe and Mg, and low in Ti, unlike any known lunar basalt, and may be derived from material of pyroxenitic composition in the Apennine Front.
Green glasses, commonly present as spheres or portions of spheres, are a distinctive component in several Apollo 15 soils (Apollo 15 P.E.T., 1972). The abundance of these glasses varies from soil to soil, but there appears to be a general correlation between abundance of green glass and proximity to the Apennine Front. The highest concentration of the green spheres is in the “green clods” 15425, 15426 and 15427 from station 7 at Spur Crater. In this report we discuss the composition of these glasses in 15427 and in soil samples 15101 from station 2 at St. George Crater, 15261 from station 6 at the Front, and 15301 from station 7 at Spur Crater.
abundant crystallites of olivine. Table I shows the average composition and standard deviations of 11 green glasses. Other distinctive glasses occur in 15427 (Table II). Red-brown glass high in titanium is a minor component that is found in both Apollo 11 and 12 soils (Reid et al., 1972b) and corresponds to ilmenite pyroxenite. Spheres and irregular fragments of bright yellow glass have compositions like those of mare basalts (Table II), with high Fe, moderate Ti and Cr, and low Al. These glasses may derive from basalts in the Imbrium basin. In 15427 some of the green glass spheres contain ciystallites of olivine (Fo76, Table II). The residual
28 spheres, portions of spheres, and angular fragments from the less than 1 mm fraction of soil 15101, 127 were analyzed. Other glasses are present in the sample, a few of which are greenish in color, but these are distinctly different in composition from the more abundant emerald-green glasses. Each glass grain is devoid of inclusions and is homogeneous, i.e., no vanation above counting precision was found for any major element (Table I). Emerald green glasses from the other soils (15261 and 15301, Table I) are identical to those from 15101. The chemical homogeneity of these glasses is not matched by that of any other group of lunar glasses we have analyzed. Sample 15426, a weakly coherent breccia, has green glass as a major component. Two “types” of green glass occur in this rock the clear emerald green glass and yellowish green glass spheres with
liquid, enriched in Ca, Al, Ti and Cr over the bulk green glass and with a higher Fe/Mg ratio, occurs as a glass or as a very fine-grained devitrified aggregate whose constituents cannot readily be separated. The composition of the green glass is unlike that of any other major lunar glass group. Fe content is comparable to that in mare basalts, but Ti is much lower (Ti02 = 0.4 weight percent). Mg is much higher than in most lunar materials analyzed to date, and Cr is also high. The low Al content is comparable to that of mare basalt glasses. Na is low and K is below 0.05 weight percent. Seven glasses of similar composition have been reported from the Mare Tranquihitatis site (Chao et al., 1970; Fredriksson et al., 1970; Lovering and Ware, 1970; Prinz et al., 1971). Among 500 analyzed Fra Mauro glasses (Brown et al., 1971; Reid et al., 1971) only three have this composition; none was found
—
wI.
134
Ridley etal., Apollo 15 green glasses
TABLE I Composition of green glass
Si0
2
Ti02 A1203
Cr2O3 FeO MgO
CaO Na20
K20 Total Number of analyses
15101 (soil)
15261 (soil)
15301 (soil)
15427 (green clod)
45.21 (0.31)
45.20 (0.39) 0.42 (0.19)
45.27 (0.23) 0.47 (0.01) 7.45 (0.09)
45.38 (0.32) 0.39 (0.01) 7.34 (0.18)
0.43 (0.02)
7.63 (0.16) 0.43 (0.01)
7.58 (0.16)
0.39 (0.01)
19.73 (0.39) 17.89 (0.33) 8.14 (0.17) 0.13 (0.03)
19.66 17.68 8.28 0.13
0.00 (0.00)
(0.27) (0.22) (0.09) (0.02)
19.60 17.80 8.32 0.13
0.00 (0.00)
(0.17) (0.17) (0.10) (0.04)
0.02 (0.01)
0.44 (0.01) 19.44 17.29 8.49 0.13
(0.50) (0.17) (0.10) (0.01)
0.02 (0.01)
99.59 28
98.95 5
99.45
99.42 11
Plagioclase An content Clinopyroxene Orthopyroxene
21.3 94.5 16.6 29.0
Olivine
31.5
21.2 94.5 17.2 28.6 31.4 0.62
20.8 94.4 17.7 28.5 31.1 0.62 0.6 0.9
22.0 94.7 17.6 29.1 29.6 0.62 0.7 0.7
CI.F. W-norms
Mol. Mg/(Mg+Fe) Chromite llmenite
0.62 0.6 0.8
0.8
Numbers in parentheses are on standard deviation. Glasses also contain 0.24 weight percent MnO.
TABLE II Compositions of other glasses in 15427,3 1 Red-brown glass
Yellow glass 1
Yellow glass 2
Colorless glass
5i02
36.16
Ti02
13.48
A1203 Cr203 FeO MgO CaO Na20 K20 Total Number of analyses
8.54 0.58 20.48 10.65 8.89 0.64 0.50 99.94 1
42.47 3.96 9.01 0.57 21.78 12.39 9.23 0.53 0.45 100.35 2
43:88 4.64 10.75 0.38 19.21 9.96 10.27 0.58 0.55 100.22 1
49.04 0.07 33.06 0.12 0.49 0.29 16.51 1.71 0.50 101.81 1
among 250 analyzed Mare Fecunditatis glasses (Jakes et al., 1972). The range of composition of the Apollo 15 green glasses described here is considerably less than, and outside that of, the green glasses described by Marvin et al., (1972) from the Fra Mauro and Mare
Olivine in green glass 38.15
22.42 38.51 1.17
100.65 1
Fecunditatis sites. We have proposed elsewhere that preferred glass compositions in the lunar soils are indicative of the compositions of the rocks from which the glasses were derived (Reid et al., 1972a; Apollo Soil Survey,
WI. Ridley et al., Apollo 15 green glasses
1971). Even with limited data it is obvious that these glasses represent a strongly preferred composition. The equivalent crystalline rock would be an ultramafic rock with 45% pyroxene, 31% olivine, 21% plagioclase feldspar and minor ilmenite and chromite, if the glass composition is recalculated to normative constituents. The abundance of green glass in the soils from the Apennine Front suggest that the Front may contain such an ultramafic rock or its glassy equivalent. If the Front comprises upthrust fault blocks of Imbrium ejecta, then it should contain materials formed at several kilometers depth, and possibly much deeper. The major-element composition of the green glass resembles the composition of howardite meteorites but the green glass has lower Si and higher Fe. The Mg/Fe ratio is lower than in the howardites and the Ca/Al ratio higher. Green glass separated from sample 15301, from station 7 at Spur Crater, has been analyzed for rare-earth elements (Hubbard et al., 1972). The green glass has rare-earth abundances that are approximately 4½times chondritic and has a chondrite-like RE. E.-pattern with a very small negative europium anomaly. The rare-earth abundances (other than La) are strikingly similar to those of howardites (Fig. 1). The green glass composition is unlike that of any lunar rock yet recognized. Ringwood (1970) and others have postulated the existence of a pyroxenitic layer at depth in the moon, as a source region for the mare basalts. The green glass may ultimately be derived from deep-seated ultramafic rocks of the type that formed ii 6
~
~ ~
•/
•
Il
-~
~ Z,,,en~ -~
the source region for mare basalts. The major element chemistry is notably similar to that suggested by Gast (1972) for the outer lunar mantle. In addition, the rare-earth abundances for the green glass are close to the values deduced by Hubbard and Gast (1971) for the source material of the Apollo 12 mare basalts. It is questionable, however, whether with this hypothesis the low Mg/(Mg+Fe) ratio of the glass is cornpatible with the presence of magnesian pigeonites (Mg/(Mg+Fe) = 0.7) in some mare basalts (Bence et al., 1971). The small negative europium anomaly in the rareearth pattern (Fig. 1) may be due to removal of a small amount of plagioclase, but feldspar fractionation has apparently not played a major role in the formation of the green glass composition. Thus, if the green glass is representative of deep seated pyroxenites these are unlikely to be residues from or complimentary differentiates to the anorthositic gabbro that appears to be abundant in the lunar highlands (Reid et al., 1972a).
Acknowledgments Lunar Science Institute Contribution no. 119. Part of this research was performed at the Lunar Science Institute under contract no. NSR 09—05 1— 001 with NASA.
References Apollo Soil Survey, 1971. Earth Planet. Sci. Lett., 12: 49.
-
~
135
2
ha La Ce Nd Sm ~uGd t~Er Yb Lu Fig. 1. Rare earth normalized pattern for green glass from 15301,76 (Hubbard et aL, 1972). Comparative data for two howardites (Bununu and Zmenj) are taken from Schnetzler and Philpotts (1969).
Apollo 15 Preliminary Examination Team, 1972. Science, 175: 363. Bence, A.E., Papike, J.J. and Lindsley, D.H., 1971. In: A.A. Levinson (Editor), Proceedings of the Second Lunar Science Conference. M.I.T. Press, Cambridge, Mass. Brown, R.W., Reid, A.M., Ridley, W.I., Warner, J.L., Jakes, P., Butler, P., Williams, R.J. and Anderson, D.H., 1971. NASA Tech. Memo., TMX-58080. Chao, E.C.T., James, O.B., Minkin, J.A. and Boreman, J.A., 1970. In: A.A. Levinsin (Editor), Proceedings of the Apollo 11 Lunar Science Conference. M.I.T. Press, Cambridge, Mass., 1, 287. Fredrikkson, K., Nelen, J., Melson, W.G., 1970. In: A.A. Levinson (Editor), Proceedings of the Apollo 11 Lunar Science Conference. M.I.T. Press, Cambridge, Mass., 1, 419. Gast, P.W., 1972. The Moon. In press. Hubbard, N.J. and Gast, P.W., 1971. In: A.A. Levinson (Edi-
136
WI. Ridley etal., Apollo 15 green glasses
tor), Proceedings of the Second Lunar Science Conference. M.I.T. Press, Cambridge, Mass., 1, 999. Hubbard, N.J., Ridley, W.I., Rhodes, M.J., Bansel, B. and Weismann, H., 1972. Submitted for publication. Jakes, P., Warner, J.L., Ridley, W.I., Reid, A.M., Harmon, R.S., Brett, R. and Brown, R.W., 1972. Earth Planet. Sci. Lett., 13: 257. Lovering, J.F. and Ware, N.W., 1970. In: A.A. Levinson (Editor), Proceedings of the Apollo 11 Lunar Science Conference. M.I.T. Press, Cambridge, Mass., 1, 633. Marvin, U.B., Reid, Jr., J.B., Taylor, G.J. and Wood, J.A., 1972. Lunar Science III, Abstr. Third Lunar Sd. Conf., Lunar Sd. Inst. Contr., 88. Prinz, M., Bunch, T.E. and Keil, K., 1971. Contrib. Mineral. Petrol., 32: 211.
Reid, A.M., Ridley, W.I., Jakes, P. and Warner, J.L.,
1971. NASA Tech. Memo., TMX-58081. Reid, A.M., Ridley, W.I., Harmon, R.S., Warner, J.L., Brett, R., Jakes, P. and Brown, R.W., 1972a. Geochirn. Cosmochina Acta, in press. Reid, A.M., Warner, J.L., Ridley, W.I., Johnston, D.A., Harmon, R.S., Jakes, P. and Brown, R.W., 1972b. Geochim. Cosmochim. Acta, in press. Ringwood, A.E., 1970. J. Geophys. Res., 75: 6453. Schnetzler, C.C. and Philpotts, J.A., 1969. In: P.M. Millman (Editor), Meteorite Research. Springer, Berlin, p. 206. Winchell, H. and Skinner, B.J., 1970. In: A.A. Levinson (Editor), Proceedings of the Apollo 11 Lunar Science Conference, 1, 957.