Rare-gas-rich separates from carbonaceous chondrites

0016.7037 7x ,201.177590200.‘0

Geochima et Cosmochimica Acla. Vol 42. pp 1775 lo 1797. Q Pergamon Press Ltd. IY7X Prmted m Great Britam

Rare-gas-rich separates from carbonaceous chondrites J. H.

U.

REYNOLDS,*

FRICK,*t

J. M. NEIL**$ and D. L. PHINNEY*$

*Department of Physics. University of California, Berkeley, CA 94720, U.S.A. **Space Sciences Laboratory, University of California, Berkeley. CA 94720, U.S.A. (Received

1

September

1977: accepted

in

revised form 2

August

1978)

Abstract-Samples studied were residual, carbonaceous IAlates-a coined word to designate colloids prepared sometimes before and sometimes after acid demineralization-from Murray, Murchison, Cold Bokkeveld (type C2s) and Allende (type CV3) meteorites. Characterization: C2 IAlates, comprising 0.5% of the bulk meteorite are fine-grained (< 100A), amorphous, sulfide-free, oxidizable, 95% carbonaceous materials which pyrolyze bimodally at 20&700 and 80&12oo”C. Allende IAIates are similar but with traces of inferred spine1 and chromite and of sulfur, Rare gas results: Elemental: Release from stepwise heated Murray is bimodal with maximum release and upper temperature peak at looo”C, probably accompanying chemical reaction. All [Alates studied had very nearly the same elemental concentrations, distinctly planetary in pattern. Isotopic: Trapped neon compositions are unprecedentedly close to Pepin’s neon-8 corner but nevertheless show signs of complexity, as if accompanied by neon-E. The trapped 3He/4He ratio is essentially constant at (1.42 + 0.2 x 10m4. The isotopically anomalous heavy noble gases, easily detected in the residues of oxidized IAlates, were not conspicuous in this particular study. Comparison and Chicago results: Concentrations of heavy rare gases in our IAIates agree with concentrations measured directly (as opposed to inferred by difference) in acid resistant residues at Chicago. Alone, our results support the idea of a carbonaceous gas-carrier uniformly present in meteorites of various types, but Chicago characterizations of the samples can apply to both their samples and ours provided that the right amount of gas was lost in the Berkeley procedures to make the uniform gas contents in various samples a coincidence.

1. INTRODUCTION

Moon during the Apollo missions, we now can identify gas-rich breccias among the meteorites which THE RARE GASES in the carbonaceous chondrites, were clearly once regolith material on other unwhere they are abundant, continue to be interesting. screened parent bodies. By studies of rare gases and First studied comprehensively in 1960 (REYNOLDS, nuclear tracks, investigators are just beginning to read 1960), they were immediately seen to be characterized the rich record of solar history which the meteorites by interesting and significant isotopic patterns for undoubtedly contain because of this component (e.g. helium, argon and xenon. Soon afterwards (REYNOLDS,1961) it was recognized that the elemental patterns for the rare gases were importantly different in the carbonaceous chondrites than in the enormously gas-rich brecciated meteorites such as Pesyanoe, first analyzed by Russian workers (GERLING and LEVSKII,1956). The early designations ‘atmosphere-like’ and ‘cosmic-like’, used to differentiate the elemental patterns in the two kinds of stones, have given way as the subject developed to the designations presently in use, ‘planetary’ and ‘solar’ (SIGNER and SUESS,1963). Of much greater importance than the semantics involved has been the deepening understanding of these elemental patterns. For example, we now know beyond any doubt that the ‘solar’ rare gases have been implanted in space as ions streaming from the sun (SIGNER, 1964; SUESS et al., 1964; W~NKE, 1965; GEISS, 1973 and references cited therein). Able to study the process at first hand on the t Present address: School of Physics and Astronomy, University of Minnesota, Minneapolis, MN 55455. U.S.A. $ Present address: Lawrence Berkeley Laboratory, University of California, Berkeley, CA 94720, U.S.A. 8 Present address: Lockheed Electronics Co., Inc., Houston, TX 77058, U.S.A.

MACDOUGALLand PHINNEY,1977). The planetary component, meanwhile, has been equally fascinating. Drawing upon extensive surveys of meteoritic rare gases made at Heidelberg (Z~RINGER, 1966) showed that the trapped planetary component is widely present in the chondrites but to varying degrees and correlated in abundance with the metamorphic classification of VANSCHMUSand WCKID

(1967). Soon thereafter, OTTING and Z&RINGER (1967) were able to show that the contents of planetary gas correlate with the element carbon. Anders and his co-workers (ANDERS, 1964; ANDERS, 1971; LAUL et al., 1973 and references cited therein) have done a great deal to confirm and expand upon important correlations among the volatile elements in meteorites, arguing convincingly that the regularity of these correlations across a broad range of volatilities points to a two component origin: the planetary rare gases and other volatiles seem to have entered various chondrites non-selectively from some relatively low temperature reservoir. Isotopically the rare gases in the planetary component are interesting and complex. Systematization

by PEPIN (1967), BLACK and PEPIN (1969), ANDERS et al. (1970) and BLACK(1970, 1971, 1972a,b) has been

1775

J. H. REYNOLDS,U. FRICK, J. M. NEILand D. L. PHINNEY

1776

extensive. It was PEPIFI (1964, 1968) who first noted that there are universal isotopic correlations for xenon in chondrites. They were most visible among the possibly fissiogenic isotopes, 131-136 and indeed xenon from stepwise heating of Renazzo, then Murray, then other carbonaceous stones seemed to confirm the presence of a remarkably abundant ‘fissiogenie’ xenon component. For a time the fission hypothesis seemed to fit all the facts: its isotopic composition could be inferred in two quite different ways which agreed (PEPIN, 1968). ANDERSand HEYMANN (1969), DAKOWSKY(1969) and SRINIVASAN et al. (1969) independently suggested that an extinct superheavy element was responsible for the enigmatic fission component. Only such an element could be both fissile and volatile. KURODAand MANUEL(1970), KURODA et al. (1974, 1975) and MANUEL et al. (1970, 1972a) were particmarly critical of the superheavy hypothesis attributing the xenon isotopic correlations to mass fractionation. But it was MANUEL et al. (1972b) who first emphasized that the heavy isotopes enhancedly abundant in the ‘carbonaceous chondrite fission’ (CCF) component were accompanied by significant enrichments in the lightest xenon isotopestotally shielded from production by fission. This observation seems to have removed mass Fractionation from contention but has deepened the mystery. Throughout this report we will use the term CCFX for the xenon with enhanced heavy and light isotopes, a component designated X by MANUELet al. (1972b) or ‘anomalous’ by LEWISer al. (1975b) and by FRICK and MONIOT (1977). We recently redirected attention in this laboratory to gas studies in the carbonaceous meteorite-s. There was obvious need to disassemble these objects-little more progress could be foreseen for studies on the bulk material. We had just begun work on Murray when we were informed of exciting results at Chicago. Anders and his co-workers (SRINNASANet al., 1975; LEWISer al., 1975a,b, 1977) had continued their partitioning of carbonaceous meteorites by chemical means and had isolated a fraction of the Allende stone which is extraordinarily richer (orders of magnitude so) in planetary gases. Treatment of this fraction, furthermore, by oxidizing acids had produced a residue in which the isotopic effects noted by MANUEL et nl. (1972b) were ampfified. This paper reports the first of our studies which confirm and extend the Chicago results. Other measurements on krypton and xenon which were made later in this taboratory have been published earlier (FRICK and MONIOT, 1977; FRICK and REYNOLDS,1977; FRICK, 1977). 2. EXP~RIM~~AL

METHODS

2.1. Sample preparation Our choice of methods for sample preparation were influenced by results published by the Chicago group, but not entirely so. 21.1. Tjrpe C2 carbonaceous chondrites (Murray, Murchison, Co/d Bokkeveld). The samples, which were usually

1-2g mixtures of chips and powder, were first subjected to gentle disaggregation by a freeze-thaw technique. To the sample, loosely enveloped in aluminum and under partial vacuum, water was added and atmospheric pressure restored, thereby forcing water into the pores of the meteorite. The aluminum envelope was then aIte~ateIy frozen in liquid nitrogen and thawed in a 60°C water bath with ultrasonic agitation. After about 2 days of this treatment, cycling as convenient during the day and continuing the ultrasonic agitation during the night, the meteorite was considerably disaggregated as evidenced by frequent separated chondrutes and a soft, crushed texture in most of the matrix. The material was next treated with saturated LiCl solution (approx 20ml per g) for its dispersive effect upon the phyllosilicates (HERZOG and ANDERS, 1974). It was found unne~ssa~ to stir the material during the LiCl treatment except for occasional exposures to ultrasonic agitation. By avoiding stirring we greatly lessened contamination of the final sample with Teflon, much of which came from the stirring bar. Following the LiCl treatment the sample was washed under uttrasonic agitation by adding water, centrifuging, and discarding the water so long as it remained clear. After considerable washing, the water began to extract colloidal material from the washed solids and this colloid was collected in subsequent washings until they once again became clear. The accumulated colloids were then precipitated, from what had come to be litersized quantities of water, by slightly acidifying (pH - 2-3) with nitric acid. Before drying this fraction, it was washed in methanol under ultrasonic agitation and centrifuged. Since the essential process by which this material was separated from the disaggregated meteorites was the formation of the colloid we have designated these samples by W/I (for Eater coaoid). In the text of this paper, the WlI sample from Murray is sometimes referred to as Murray ‘phyllosilicat~‘. A typical yield of WI/ from 1 g of meteorite (C2) is 60-l lOma. An additional 40 me of colloid, designated Murray W/&l* was accumul%ed by several day-long periods of ultrasonic agitation in acetone of the residue from the principal extraction of colloid in water. Its color was much lighter than the dark brown water colloid and it proved to contain much less of the noble gases than the latter. The WI/ samples were then acid treated in a manner designed to destroy and remove silicious material. To the samples were added 5-10 ml of a 1: 1: 1 mixture of concentrated hydrochloric acid, 48% hydrofluoric acid. and water. The acids were refluxed by heating the mixture on the hot plate in a covered Teflon beaker. After several hours of refluxing, the Teflon cover was removed and the material taken to dryness. (The temperature of the dry residue could have reached 15t317o”C after fuming off the acids.) This acid treatment was then repeated. A final heating, with HCI only, dissolved the chlorides and fluorides which were poured elf after centrifugation. The residue was given a thorough wash under uftrasonic agitation first with 6N HCI and then with water which had been acidified slightly with nitric acid to prevent extraction of colloidal material. This residue was finally rinsed in methanol under ultrasonic agitation and centrifuged. After discarding the washings and drying the samples, they were designated WltA (for Eater colfoids, acid treated). A typical yield from dissolving IOOmg of WI/ is 6-9 mg (see Table 1 for details about yields). In the text of this paper the WllA samples are frequently referred to as ‘{Alates’. This designation-which also includes some separates from Allende in which the acid treatment preceded the colloidal extraction-contains the Ietters ‘/A[’ which are supposed to remind the reader that the acid treatment for some meteorites preceded, and for others followed the colloidal extraction. We should mention that the WllA sampies in this paper also received a wash in pure CS, with the intent to remove

Rare-gas-rich separates from carbonaceous

1777

chondrites

Table 1. Per cent of total noble gases in the meteorite recovered in various separates’“’ Sample Number Description

Acid-treated

Cold Bokkeveld WUA-1

22

Murchison

34

EIurray WLLA-1

WUA-1

(X’s referred to precursor separate Murray WLP-1)

42

Allende Allende

Water 31

Yield Percent

Percent QIe

of total 2 *t
gas in meteorite B’Kr ‘6Ar

recovered “OXe

References for gas c~ncentra Cions in the bulk meteorites

samples

21

41

wt.

ANPY-1 A-l

23-41

22-40

0.55(e)

3-7

0.63

3-12

0.52

19-124

19-72

16-83

(b)

(c)

(d)

3-9

17-71

14-58

15-110

(d)

(f)

(9)

3-10

25-30

16-37

18-30

(b)

(cl

(i)

(73)

(85)

(87)

(j )

17-33

Cc)

(8)

(k)

(cl

(i)

(7.8)

(50)

(56)

-0.1

3.4-4.4

3.7-5.3

0.75

14-19

9-17

84-162 I

20-35

17-22

16-23

70-93

46-86

7-24

6-19

31-41

19-44

1.6-2.1

l-Z.3

(ml

(0)

Co)

(P)

I (9)

colloids

I”1”rray WLL-1

8.3

(b) 32

(h)

,Yurray

WPL-1*

2

0.2-0.7

0.3-0.9

1.2-2

I

(a) Material loss during separation and handling may result in systematically low figures for yield and the recovered portion of noble gases. The maximum and minimum values for gas contents in bulk meteorites have been taken from the literature. (b) PEPIN and SIGNER (1965) and references cited therein. (c) MAZOR et al. (1970) (d) MACDOUGALL and PHINNEY (1977), matrix value. (e) For comparison, HAYATSU ef al. (1977) report 0.85% yield of solvent inextractable acid residue M4 from Murchison. (f) KURODA et al. (1975). (g) BOGARDet al. (1971). (h) SHERRILL(1976). (i) KURODAet al. (1974). (i) Yield and recovered gas referred to the precursor separate Murray Wll-1. (k) FIREMAN er al. (1970). (m) MANUEL et al. (1972a). (n) LEWIS et al. (1975b). (0) LEWIS et ai. (1977). (p) PHINNEY (1971). (q) DROZD ef al. (1977).

any elemental sulfur which might be in the samples, either as an original constituent or as a decomposition product of sulfides. We have since learned that this step is unnecessary and unwise: the washed samples show a higher sulfur background in energy-dispersive X-ray analysis (EDAX) with the scanning electron microscope than samples which have not been washed. 2.1.2. Allende meteorite. Starting material for Allende was a ‘rejected’ fraction, consisting of chips and powder, from a search for large inclusions. The typical processing described here is for -20g of material. The sample was treated with 5000 ml of 3N HCI in a covered Teflon beaker kept on the hot plate at just below boiling temperature, stirred only by occasional swirling. After a few hours of this treatment there was, above the meteorite sediment, a gelatinous layer of olivine decomposition products and, above that, a free liquid distinctly green in color. The free liquid was decanted, centrifuged and discarded, with the sediment returned to the original Teflon beaker. The acid was then renewed and the process repeated. After about 2 days and after the fifth or sixth additions of acid, the gelatinous layer and the green color no longer appeared, indicating that the olivine was mostly destroyed and eliminated. Perhaps 20% of the original material remained at this point. After removal of the HCI, the material was then treated with about 200ml of a 1:l:l mixture of concentrated hydrochloric acid, 48% hydrofluoric acid and water. Our intent at this step was to dissolve pyroxenes but not to expose the material to HF for an unnecessarily long period, which can dissolve spinel. After several hours on

the hot plate below the boiling point (- 7o”C), there was noticeable yellowish-green coloration in the hydrofluoric acid, which was then decanted, centrifuged, and discarded, with the sediment returned to the beaker. The acid was renewed and the process repeated. After three or four repetitions (and less than 24 hr exposure to the HF) no more color was seen. There followed replacement of the mixed acids by HCI, transfer to glass (to facilitate ultrasonic agitation), several washings with 3N HCI, each time using ultrasonic agitation and centrifugation, and several washings with acidified water (HNO,, pH 2-3) in order to avoid colloidal dissipation when removing chloride ion which can interfere with argon measurements in the mass spectrometry. The sample was finally rinsed in methanol before drying. A typical yield from 20 g of Allende starting material was 150mg of residue. A sample dried at this stage would be designated Allende A (for residues from acid treatment of Allende). More often the sample was not dried, but the acidified water replaced with methanol, at first without apparent effect. But after several methanol washings a colloidal suspension in the methanol was observed. This colloid was extracted repeatedly from the sample, using each time about 40ml of methanol and prolonged ultrasonic agitation. After two extractions daily for about 14 days, the sediment had definitely changed from black to light gray in color and the yield of colloid in the methanol extractions had greatly.diminished. The accumulated colloidal suspensions in methanol were dried under the heat lamp and this sample was designated AM[I (for residues from acid treatment serving as a source for methanol

J. H.

1778

REYNOLDS,U. FRICK,

colloid). It is possible (see Table 1) to extract about 20mg of this collotd from 150 mg of the acid residue. 2.2. Massspwtrometr) The rare gases from the samples for this paper were analyzed in a REYNOLDS(1956) mass spectrometer, locally designated as BMS #5 It is integrated with a programmable, automatic sample system in which the steps required to extract the gases during 30 min heating with subsequent purification can be programmed on a punched card and carried out with little intervention of the operator until the various rare gas fractions (He-Ne. Ar. Kr and Xe) are sequentially ready for mass spectrometer analysis. Table

J. M.

NEIL

and D. L. PHINNEY

This system together with Its digital data acquisition has been brtefly described in MACDOUGALL and PHINNEY (1977). Details of the mass spectrometry and calibrations are also given in FRICK and MONIOT (1977) and FRICK (1977).

The blanks were 1 x 10” cm3 STP ‘3He’ (largely HD+ and H;), 5 x lo-* cm3 STP 4He, 1 x 10-r” cm3 STP ‘aoNe (substanttal amounts of “‘A?+), 1 x lo-” cm3 STP 36Ar, 1 x 1Om8cm3 STP 40Ar. 4 x IO-r2 cm3 STP s4Kr, and 4 x IO-l3 cm3 STP ‘32Xe. These blanks, although relatively htgh compared to values obtained more recently (see FRICK, 1977). were nevertheless Independent of crucible temperature and rather constant (withm 20”:,

2a. Helium. neon and argon abundances m Murray separates (concentrations Sample

Xtr%tlUI, idr.

2’Ne

“He

"Ar

'Ue/'He

\ '%,"'Ne

0.000171 t 1u

, ! H.630 1 ! $5

Temp.

1650-c

33

:I”rr.lY wrb-0

5OU"C

34

xurray WLLA-1

I

Il.?

YAVate

1910

'.4

5110

7.5880

8.02 .64

b50OC

10710 750

3.17 .25

?50*C

14740 1030

4.81 .38

850°C

J4040 2400

1.20 .58

214 13

950-c

38310 2700

9.10 .73

105o*c

20770 1450

1150°C 1350°C

PMnte

6.46

36.6

91200 '150"

1800

-0.600 1.300

259 lb

/ 0.000,:: i 10 I

9.581 ,109

O.OJ104 30

0.1886 19

.464 1.800

14.44 1.16

497 30

'0.000146 10

8.791 ,093

0.03100 26

0.1x90 19

15" :900

13880 970

14.38 1.15

440 26

IO.000146 10

7.956 ,084

0.02979 19

0.1882 19

2510 180

3.24 .26

205 12

0.000147 16

8.687 ,177

0.03316 89

0.1896 20

-0.600 1.400

102.2 6.1

0.000150 70

9.029 ,859

0.02447 180

0.1885 19

1.300 5.400

0.000170 12

8.843 .095

0.02999 31

0.1883 19

-0.121 ,350

0.000249 15

9.918 .I16

0.04169 90

0.1886 30

0.45 .20

71.02 0.000188 3.55 20

9.215 ,100

0.04180 85

0 1883 20

2.6 .9

,853 ,068 65.3 2.3

31

*IMurray WLP-1 "pl,ylloslllcate"

44.10

25220 1770

9.07 .18

165O'C

32

Murray wee-l* "phyllosillcate"

26.11

3220 230

1.77 .14

3170 80 338.5 16.9

Table 2b. Krypton abundances m Murray separates (concentratrons Sample

h'eqhc

B'Kr

33

Murray WLLA-O Meate

5OOOC

34

Murray WPLA-1 exeate

11.2

6.46

78

23.5 4

j 13:;;

80

42

P3

BL

z

z

Bi

0.03924 30

0.2021

0.2029 7

0.311J 10

94 0.005734

0.039;,"

,.2,:;

0.2022b

14 0.3146

(cl

65O'C

2.187 ,109

0.005029 569

0.03930 15

0.2018 12

0.2079 10

0.3209 16

75OOC

2.764 .13a

0.005873 400

0.03929 15

0.2052 9

0.2043 8

0.3184 12

850°C

2.427 ,121

0.005189 508

0.03916 14

0.2039 9

0.2059 7

0.3164 1:

950°C

3.304 ,165

0.006546 350

0.03930 13

0.2057 8

0.2071 8

0.3141 11

10509c

6.532 ,327

0.005543 360

0.03863 14

O.?!J25 8

0.2018 7

0.3111 12

1150°C

4.957 ,248

U.006866 230

0.04009 15

0.2039 9

0.2047 7

0.3120 13

2.265 .113

0.006900 501*

0.03888 14

0.2052 a

0.2057 6

0.3153 15

1.118 ,056

0.007166 1073

0.03974 30

0.2064 10

0.2055 8

0.3100 25

39.13 .86

0.005959 134

0.3939 14

0.2034 10

0.2038 7

0.314J 1:

3.56 .18

0.005953 150

0.03921

0.2016

0 2024

0.3123

0.03862 16

0.1997 1;

0.2006 ,:

0.3087 ::,

1350°C

(lJ)

1500°C Total

(b)

1650°C

31

Hurray Iv'.U-1 "phylloslllcate"

44.10

1650°C

J2 "phyllosillcate" Murray W.-l*

26.11

,

:A;;

/0.0058;;

,020 .800

in lo-* cm3 STP g-r)

-6T

bl

[Illa]

165U"C

0.5804 2.0022

0.1873 19

165O'C

Nr.

j

a

0.1909 '.0022

0.03139 35

161800 4600

Temp.

2

"A;/;%I

‘Ill

93J 60

:tract~on

0.02872 35

isAr/'iA,

‘)

9.891

(b)

(b)

"lie/'%

g-

/ 0.000147

15OO'C

Total

in 10-s cm3 STP

I

J

Rare-gas-rich separates from carbonaceous

1779

chondrites

for He, Ne and Ar, and within a factor of 2 for Kr and Xe). The blank corrected data are given in Table 2. In the case of differing background in sample and blank runs we applied empirical interference corrections (hydrogen interference as HD+ or Hi on 3Hec: HisO+ and “OAr’+ on *ONe+; H:*O+ on “Ne+: CO:+ on “Ne+: and molecular benzene on “Kr+). The corrections were usually smaller than the quoted errors in Table 2.

ment with acids and by washing. Only a few milligrams of the /A/ate were obtained from 1OOmg of the precursor (see Table 1 for data on material balance). From work with a pilot sample (Murray W/IA-O) we learned that extensive washing is required to remove metals and silicon (seen on the SEM but not as Identifiable crystals) that we interpreted as contamination of the samples by secondary products of dissolved mmerals.

2.3. Work on sample characterization Certainly the most difficult aspect of research with these separates is their characterization. What follows is an account of attempts by many techniques to identify the material in which the planetary gases are concentrated. 2.3.1. The WllA-1 residuesfiom the C2 meteorites Mur-

parttcles were detected m the W/IA-l samples of grain size large enough to be resolved in the instrument (0.1 pm). Except for the few spots described below the energy dispersive X-ray analysis (EDAX) showed only a weak (< - 2’?:,) S peak above background. [One of our Allende samples, much richer in S, was analyzed by combustton at the Johnson Spacecraft Center and provided the basis for an S calibration of the Instrument (GIBSON. 1976).] We believe that a large portion of the S seen in our samples is con-

Scanning

ray. Cold Bokkeveld, and Murchison Genera/ statements-as described

earlier these /Alates from ‘phyllosihcate’ precursors by treat-

were separated

electron

Table 2c. Xenon abundances m Murray separates (concentrations
fir.

SF.mple

121

Weight [mnl

Temp. 165O'C

33

llurray W?LA-0 IAP.aCe

5OO'C

34

nLrray WEPA-1 kA.tate

11.2

6.46

126

ic

130

microscope

(SEM)

observations-No

in 10-s cm3 STP g-r)

128

129

131

132

Ilo

7i-i

Ilo

Z-L

131

136

z-i-

T-z

4.20 07

0.02934 0.02580 t 20? 19

0.50689 t 151

6.3722 t.0190

5.0280 r.0115

6.1479 t.0123

2.3463 t.0059

1.9737 ? 56

2.380 ,071

0.02855 50

0.02435 50

0.50350 200

6.3521 200

5.0827 180

6.1493 300

2.3458 170

1.9811 160

650°C

.2649 .0079

0.02766 37

0.02499 41

0.50886 162

6.4163 150

5.0713 165

6.1753 275

2.3573 153

1.9747 151

75o*c

.2595 .0078

0.02845 37

0.02559 41

0.50536 160

6.3882 150

5.0693 168

6.1725 270

2.3789 152

2.0035 151

850°C

.3923 .0118

0.03007 37

0.02642 40

0.50659 159

6.4156 149

5.0484 168

6.1625 272

2.3855 152

2.0178 152

95ooc

.5319 .0175

0.02988 36

0.02575 40

0.50903 157

6.3532 149

4.9968 167

6.1204 270

2.3306 150

1.9583 150

0.02913 36

0.02553 39

0.51412 155

6.4086 149

5.0467 165

6.0942 270

2.3422 149

1.9750 150

.9930 .0298

0.02938 40

O.U2542 40

0.50872 153

6.3990 150

5.0246 160

6.1197 270

2.3272 153

1.9645 153

.4303 .0129

0.02981 37

0.02661 40

0.51280 160

6.4013 185

5.0125 170

6.1042 281

2.3525 150

2.OOL8 152

,201s .0061

0.02943 38

0.02397 40

0.50998 162

6.3163 190

4.9267 175

6.0906 292

2.3246 15s

1.9712 156

6.b‘j .088

0.02905 40

0.02516 45

0.50784 170

6.3786 180

5.0480 170

6.1310 280

2.3456 160

1.9746 154

1.122 .034

105O'C

1150°C

1350'C

(b)

1500qc

Total

(b)

1650°C

31 Murray WI-1 "phyllosilicate"

44.1c

0.5919 .0178

0.02901 36

0.02577 39

0.50799 159

6.3760 175

5.0754 180

6.1122 275

2.3176 145

1.9543 150

1650°C

32

26.11

0.1405 .0042

0.02963 36

0.02613 40

0.50637 160

6.4141 180

5.0991 180

6.1005 277

2.3299 14.9

1.9710 151

?Lrray W-l* ",,hvlloslllcate"

Table 2d. Helium. neon and argon abundances m separates from carbonaceous (concentrations in lo-* cm3 STP gg ‘)

16:O'C

6.00

170940 t12000

87.3 z1.7

3383 t170

0.000127 12 t

n.311 t.092

0.03080 L 46

O.lM72 I 30

4.35

58460 4090

18.8 .4

1816 91

0.000151 13

8.862 .261

0.02901 18"

0.1910 30

1000°C

55910 3900

18.3 .4

459 23

~1.1~00123 17

8.700 .500

0.03000 200

0.1861 30

-0.623

165O'C

33010 2310

32.6 .7

1059 53

0.000141 14

8.303 ,106

0.03320 87

0.1927 30

0.170 ,200

147380 6100

69.70 .vo

3334 108

0.000138 1L

8.558 ,160

0.03123 80

0.1909 30

0.208 .150

105360 7400

98.5 2.0

3070 154

0.000129 15

8.764 ,101

0.01704 57

0.1896 30

0.86 .20

2049 101

0.000187 13

5OO'C

2lCold Bokkeveld LA!‘ate 22 Murchlsan LAtate

VLLA-1

chondrrtes

k'kP.A-1

Total (d)

1650°C

41Allende A MU-1 LAeiate

2.86

165OOC

42Allende A-l "acid residue"

2.49

Planetary (tieA, Ne A, AT A)

_-

__

__

8.540 0.06046 0.1910 .098 110 30 _._ .____... ._ 0.000140(r) 8.20(f) 0.0250(f)-0.1920(& 30 .40 30 30

Solar (He B, Ne B, Ar 8)

_-

-_

__

0.000390(h)12.5?(i~) 30 .18

_-

--

__

AIR

69420 58.43 4860 1.17 ~_~__.

I

:1.399"10-6(~)9.80(~) 13 .OH

0.0335(13 .15,

0.308 2.200

0.1860(h) 40

,300

1.06 .20 -___ __

0.0290(~)' 0.1880(L)296.0(k) 4 3 .5

i

J. H. REYNOLDS, U. FRICK, J. M. NEIL and D. L. PHINNEY

1780 Table

2e. Krypton eracrion Temp.

abundances

in separates

Sample

NT.

wel~ht

21 Cold Hokkeveld tA&te

lb50'C

from carbonaceous

[mg] I b.00 /

P,LGl

800°C 22 Murchison WUA-1 c,*k!atr

4.35

‘Bl;r

31.66 11.58

8Qhr

III IO-’

:m3 STP g-‘)

82Kr

EJKr

n"Kr

0.006351 210

0.03868 t 16

0.2001 ? 9

0.2023 t 8

0.3142 i 14

310

0.03995 20

0.2017 10

0.2025 9

0.3114 14

0.005844 507

0.03872 40

0.2023 11

0.2030 8

0.3092 16

10.94 .55

0.005863 460

0.03858 17

0.2005 9

0.2018 7

0.3160 16

34.99 1.13

0.005935 250

0.03934 25

0.2014 10

0.2024 10

0.3125 16

5.250 .263

lb50"C

(concentrations

I 18.797 ,950

1lJOO'C

;f / 0.006002

Total

d)

165O'C

41 Allende A MEL-1 eluate

2.86

27.92 1.40

0.006094 210

0.03848 JO

0.1995 10

0.2012 8

0.3144 15

lb50"C

42 Allende

2.49

18.32 .92

--

0.04002 20

0.2008 10

0.2026 9

0.3123 20

-_

0.005970 46

0.03919 30

0.2015 8

0.2017 8

0.3098 8

__

0.005932 47

0.03885 20

0.2005 8

0.2009 7

0.3050 7

0.006095 28

0.03960 15

0.2022 7

0.2016 6

0.3055 7

A-l

Planetary (AVCC)

(m)

Solar olEOC 12001) AIR

Table

8k

chondrites

3. Xenon Nr.


(n) (0)

(P)

abundances

m separates

from carbonaceous Ifl

l’OXe

Weight

Sample

[WI

165O'C 21 Cold Bokkeveld ll.QLlte

WPBA-1

800°C 12 ELurchrson wcin-1 VALate

6.00

4.35

/

chondrites

“”

(concentrations

”

”

I_l_t.

110

110

1

1

m 10m8 cm3 STP g-l) ”

2

130

130

“”

130

1

110

110

130

5.68 k.17

0.02910 t 37

0.02558 t 39

0.50719 t 159

6.3832 i 199

5.0483 f 175

6.1598 ? 272

2.3723 t 145

2.0156 t 151

3.163

0.02861

0.02545

0.50453

6.3816

5.0253

6.1215

2.3431

1.9599

40

0.02548 41

0.50686 162

6.3729 157

5.0332 181

6.1515 282

2.3625 160

1.9991 152

IO.03060 / 39

0.02624 39

0.51113 lb0

7.0329 150

5.0754 180

6.2069 275

2.4383 150

2.1091 151

IO.02914 37

0.02536 40 _ 0.02550 30

0.51228 161

6.9916 150

5.0991 180

6.2370 277

2.1065 151

0.50995 428

--

5.0809 395

2.4415 153 __----6.2189 2.3756 425 205

1.9963 i.35

0.02616 90

0.50401 280

6.3384 170

4.9632 110

6.0492 160

2.2346 80

1.8138 60

0.02198 10

0.4710 14

6.489 23

5.198 16

6.600 22

2,562 8

2.177 5 -

1OOO"L

lots1

d)

6.847 .I26

165O'C 41 Allende A MU-1 CALate

2.86

165O'C 42 Allende A-l

2.49

-_______ Planetary UVCC)

(m)

Solar (BEOC)

(n) (0)

AIR

(4)

15.27 .16

, ; 3.445 : .103 __

/ -_

i 0.02888 /

IO.02854 65

: 0.02931 70

__

; U.02360 10

_-.

All values are blank corrected; tabulated errors are statistical only (la) including statistical errors of peak height measurements and errors arising from extrapolation of peak heights and ratios to ‘zero time’ for the mass spectrometer runs. reproducibility (sensitivity and mass discrimination) of a large number of calibrations (air pipettes), and a blank associated error. The 3He/4He ratio has been calibrated with two Bruderheim standards the errors for which are also included. An additional error of l(r159/,, not affecting elemental ratios, should be added to the abundances owing to the uncertamties of the gas amounts delivered by the pipette. (a) Substantial blank corrections sometImes resulted in negative ratios and large errors. (b) 125O’C fraction lost because of system malfunction. The 165o’C temperature fraction (always examined) is not tabulated since it was virtually indistinguishable from the blanks. (c) Not determmed. large benzene interference at mass 78. (d) 12Oo’C temperature fraction lost because of operator error. (e) Inferred from Fig. 6 in BLACK (1972b). (f) PEPIN (1967). (g) Inferred from Fig. 1 in BLACK (1971). (h) BLACK (1972a). values determined directly from Al-foils exposed to solar wmd differ slightly (e.g. GEISS. 1973) (i) MAMYRIN et al. (1970). (J) EBERHARDT et al. (1965). (k) NIER (1950a). (m) EUGSTER et a/. (1967b). (n) EBERHARDT et al. (1972). (0) Values have been modified shghtly to conform with atmospheric ratios used m this work. (p) EUGSTER et al. (1967a). (q) NIER (1950b).

Rare-gas-rich separates from carbonaceous taminatlon with CS,, an agent used to remove elemental sulfur, either natural or produced by dissolution of sulfides during the chemical treatment. When we used Ccl., instead of CS, for that purpose, the final S content was lowered, although at the expense of an unwanted Cl contamination. A few singular spots in the target material showed minor but uniform amounts of Cl, Si, Fe and Mg, listed in order of decreasing intensity. Assuming that the hypothetical sulfide, suggested by LEWIS et a/. (1975b). consists of roughly equal numbers of sulfur and metallic ions (GROS and ANDERS,1977) we should unambiguously be able to detect amounts of about 0.5% by weight or more. This lower limit is given by the nose of the sulfur peak and the observation that the sulfur peak did not exhibit any increase when analyzing those areas with spotty signals for Cl, Si, Fe and Mg. The Cr peak was also completely obscured by the noise of the EDAX analysis; we are unable to estimate an upper limit for a possible chromite content owing to the lack of calibration with similar target material. Transmiwon

electron microscope (TEM)

obsercarions-

Observation with the 100 keV transmission electron microscope (TEM) showed the material to be exceedingly fine grained indeed (< lOOA) and generally amorphous. Target preparation for the TEM was difficult because only a small portion of the dried colloidal acid residues could be dispersed in the reqmred manner for transparency to the electrons. A few apparently hexagonal flakes (about 1OCOAin size) yielded electron diffraction patterns. Attempts to characterize these patterns were unsuccessful. Tentatively we relate these crystalline spots to the rare appearance of Cl, Si, Fe and Mg peaks in the EDAX. As judged from the TEM observations ‘contamination’ by this crystalline material is much less than 5s;. Oxidizing treatments-Several unsuccessful attempts were made to isolate a fraction of the [A/ate samples reslstant to oxidation. (1) Air combustion of small samples (0.3-l mg) in a quartz tube with an oxygen flame left no detectable or weighable residues, although the escape of small aerosol-like particles cannot be ruled out. The lgnition temperature was about 1200°C according to the rough temperature indicators employed. (2) When a 1.5 mg sample was treated for _ 24 hr in boiling, concentrated HN03 under reflux m a Teflon beaker and the solution was transferred to a glass tube and gently evaporated, no detectable residue was seen. (3) Experiments with hydrogen peroxide failed to give definitive and reproducible results. The attack with a 0.1 N NaOH/lO% H302 mixture was vigorous and appeared to be total, but had to be scrutinized as a solution because of the NaOH present. Different treatments with H,O, alone gave different results from one time to another. The samples always appeared to react but black flakes m the samples were not reproducibly dissolved. Vacuum pyrolysis-Half-milligram samples of Murray WI/A-0, a pilot sample, and Murchison (WI/A-l) were loaded into a quartz boat and pyrolyzed into the ion source of a high resolution mass spectrometer which contmually scanned the mass spectrum as the heatmg ensued, stormg the data on magnetic tape. The technique and the experimental arrangement have been described by SIMONEITet al. (1973a.b). The temperature of the sample was increased linearly from room temperature to 1400’~~ in approx 1 hr. Emphasis was placed m the study upon detection and identification of mmor constituents so that the detector was intentionally saturated by the ion currents from the principal pyrolyzates. This circumstance precluded quantitative assays for carbon which the method often affords. The pllot sample of Murray was noticeably contaminated. Slightly above 200°C the largest peak in the mass spectrum was from diethyl phthalate, a common contaminant used as a plasticizer in laboratory ware. From 450 to 575°C the spectrum was dominated by products from

chondrites

1781

the pyrolysis of Teflon. From 1100 to 1200 the most abundant ions were from SiF,, which almost certainly is somehow a residue from the HF treatments of the sample. Otherwise the major contributors to the spectrum were CO1 (between the phthalate and Teflon peaks) and CO (above the Teflon peak in temperature). The curve labeled Murray in Fig. 1 is a composite carbon-release curve contrived by summing the ion peaks for CO, CO, and two prominent hydrocarbons. Some of the lowest temperature peak and most of the sharp peak near 500” results from the contamination just described. Otherwise the curve roughly represents in shape (the vertical scale is arbitrary) how carbon in volatile forms Issues from the meteoritic sample as the heating progresses and reaction with water occurs. Near 135o’C the furnace burned out during the Murray run: the dropoff in the CO emission, shown dotted, occurred as the furnace cooled. The Murchison sample was much less contaminated than the Murray pilot sample, reflecting the conslderable improvement in techniques for sample preparation which had been affected between the two samples. For Murchison W/IA-l the ions from pyrolysis of Teflon were greatly reduced, the low temperature dimethyl phthalate peaks were almost absent and the high temperature SiF, peaks virtually undetectable. The carbon-release curve for Murchison was constructed by simply adding the CO1 peak (largest in the spectrum below 400’, absent above 9OU’) and the CO peak (strong throughout and dominant m the spectrum above 900”). The temperature of the furnace was

15

10 I’

5 0 icdi 0

500

1000

Temperature

(C)

Fig. 1. Release of noble gases during stepwise heating of Murray WI/A-l. The fractional release per step (Y+,per 100°C step) is adjusted for unorthodox steps, so that the area in each column is proportional to the fraction of gas releqsed and total areas of the histograms (lOO?J are the same m each plot. Also shown at the upper left are typlcal vacuum pyrolysis curves obtained by summing the CO+ and CO: in peaks (plus some prominent hydrocarbons peaks in the case of Murray only). The pyrolysis curves are normalized to maximum amplitude. The 1250°C temperature release (lost) has been interpolated between the 1150°C and the 1350°C fractions.

1782

J. H. REYNOLDS,U. FRICK, J. M. NEIL and D.

L. PHINNEY

Table 3. Summary of the vacuum pyrolysis experiments loo-3oo”c Temperature

300-

range

diethyl hthalate

! -.

SO2 so

Tef km

HCN

:)

co

HCN

HCN

C,H2*+2 (1

I-

--.co

CO2 co

CO2

ekeate

CC

i co

SiF4

4

N2 HCN

HCN

so

iethyl hthalate

co Sir

CO2 co

SO2

Wt&A-1

(b) _-

N2

(g:)

I Murchison

1

S iF4

S iFL

WLLA-0

P.A?ate

-

Tt

500-7oo”c

Teflon

Teflon

9 Murray

5oo”c

(a)

N2

co

f

co N2

N2 HCN

co

t

N2

I

S iF4

so 2 so Teflon SiF4

I

diethyl phthalate(c)

i

I i

(a) the most abundant species (Hz0 is omitted) are listed in order of decreasing ion current. (b) release when crucible temperature is held at 135(r14oo”C. (c) commonly used plasticizer, presumably from polypropylene ware used for sample preparation.

tive for all the rare gases and requires temperatures from 800 to 12oo’C (depending upon the environment and heating rate) for substantial pyrolysis and rare gas release. The foregoing and other qualitative results of the vacuum pyrolysis experiments are set out in Table 3, where for the indicated temperature ranges some of the identified species are listed in order of decreasing ion current. The pyrolysis of Murchison released much larger quantities of HCN and N2 than that for Murray. Perhaps the most significant result of the pyrolysis experiments IS the lack of any indication for a metallic sulfide in our /A/ate separates, as already described for Orgueil /A/ate (FRICK and MONIOT.1977): there was no sulfur release above 550°C. whereas it has been shown that in this system sulfur from troilite (FeS) has its major release around 1ooo’C. usually as CS2 when graphite or amorphous carbon is in the sample. We were not able to detect any CS2 release above 55O@C,even on a very expanded scale. The SO, patterns for the two pyrolyses are shown in Fig. 2. (SO is usually about 50”; of the SO, intensity: other sulfur compounds

‘held’, and not increased, above 1350’. accountmg for the drop m CO flow, shown dotted. While there are differences in detail, which may not be significant in view of the qualitative character of these particular pyrolysis runs, the carbon-release patterns for the two samples, after correction for the Teflon artifact in Murray, are basically similar and bimodal. We believe that the high temperature oxidation of the sample, which is known to be incomplete in the vacuum pyrolysis experiment because unreacted carbon is left behind, is the same feature-shlfted in temperature because of different heating kmetics and different chemical environments for the samples-as is responsible for the high temperature release of rare gases (below) shown in Fig. 1. The low temperature features for the carbon-release and the rare-gas-releases are superposed in temperature and undoubtedly related. There seem to be present in the /A/ate samples two host phases, one of which has already lost He and Ne, is pyrolyzed at low temperatures, and releases its rare gases along with the low temperature pyrolyzates. The other phase is reten-

0

200

400

-

Murchison

-a-

Murray

600

Temperature

800

WL1A-1 SO,

WfLA-0

1000

SO?

12cO

1400

(C)

Fig. 2. Release of sulfur durmg vacuum pyrolysis experiments. Plotted are the SO2 peaks from Murray and Murchison IAlates, normalized to the same maximum amplitude. (The SO release is Identical but only 50% of the SO2 release, while those for CS2 or H,S are lower by orders of magnitude.) Experiments with Cold Bokkeveld and Orgueil lA/ates resulted in similar low temperature release of S-i.e. no S02, SO, CS, or H2S peaks were seen above 500°C. even on an expanded scale.

Rare-gas-rich

separates

from carbonaceous

such as HZS or CSz exhibit lower intensities by orders of magnitude.) It is interesting to note that pyrolysis experiment on powdered bulk samples of Murray (WSZOLEK et al., 1973) or Murchison (SIMONEIT et al., 1973b) show gas release curves very different from those seen when analyzing ‘nude carbon’ samples in the same system. For the former the CO,, CO have their maximum release between 600 and 900°C. while the latter separates show bimodal release at substantially lower and higher temperatures. The sulfur release. mainly as SO,. SO and CSz is also more complex and dies out at higher temperatures (2 8oo’C) in these bulk samples. 2.3.2. The residues fromthe C3 meteorite AIlende. Of all the samples m this paper, the only one in which minerals could be positively identified were the samples designated Allende A (residues from acid treatment of Allende) which contain some crystals of spine1 and chromite larger than IOpm, roughly m the proportions 2:l. Identification of these crystals was straightforward with the SEM and its EDAX attachment which detected Mg, Al, Cr and Fe in the right proportions for these minerals. The chromite crystals looked sharp-edged but not typically euhedral. The spine1 grains were typically octahedral in shape but were rounded as if etched by HF. There is other evidence given in FRICK and REYNOLDS (1977) and FRICK (1977) for decomposition of the spmel component during the chemical treatments. Smaller amounts of other inorganic materials were tentatively identified as silicofluoride or chloride products of the demineralization as judged by wttnessing in the SEM preferential removal of Si and Cl during subsequent HCI washings. Such precipitates are frequently observed when deminerahzing silicate rocks. In a similar separate from Allende FRAUNDORF er al. (1977) positively identified additional rare phases including pentlandite ([FeNi]&) and rutile (TiO,). Based on an extensive body of chemical data the Chicago group (e.g. ANDERS et al.. 1975: GROS and ANDERS, 1977) inferred that S-IO?; of metallic sulfide was present m their Allende residues We believe that the SEM analysis of our Allende A sample should have revealed concentrations of a metallic sulfide as high as this, provided the grains were larger than about 0.2 pm. From these residues the AM/I samples were prepared by extraction of a methanol colloid. Their gram size was smaller than the resolution limit (1000 A) for the SEM. [FRAUND~RF et al. (1977) reported structures down to l&l00 A in size m the fine grained amorphous material of their Allende residue] The EDAX showed much lower amounts of spine1 and chromite than m the precursor A samples; contrary to the observations on the C2 IAlates, a virtually umform distribution of Mg, Al, S, Cl. Cr. Fe throughout the whole target was Indicated. Unless specifically washed, the AM// samples can contain up to 30”,, sulfur. accordmg to reproducible combustion analyses made at the NASA Johnson Space Center (GIBSON, 1976). After treatment with CS2, the sulfur content was in the range of I-Y,. Results quoted below are for washed samples. The Allende separates have been subJected to a number of oxidizmg treatments. Interesting rare gas measurements have been made on those samples (FRICK and REYNOLDS. 1977; FRICK, 1977). We can mention here a few results of that work which bear upon the question of sample characterization: (1) A vacuum pyrolysis showed that, as m the IA[ates from C2 meteorites, the sulfur release from the Allende IA/ate was at low temperature. The major carbon release mainly occurred as CO above 600°C with a maximum at 1300% perststing until the oven reached its maximum temperature at 1400°C. The pronounced low temperature release as CO, and CO, observed when pyrolyzing C2 residues (schematically shown m Fig. 3). was substantially

chondrites

1783

lower in Allende separates and may comprise only 5-IO”,, of the total carbon released in the pyrolysis experiment. (2) Two combustion analyses on a sample of Allende IA/ate gave identical results as follows: 6OS”/b C, 0.27P,, N, 4.8’; S. These analyses were carried out at NASA’s Ames Research Laboratory (CHANG. 1976). (3) Another sample of Allende AM/l was processed by atomic oxygen at a facility of the International Plasma Corporation. This low temperature treatment (T< IWC) was carried out for about 30 hr at 200 torr 02 pressure. Approximately 707; of the sample was combusted but the ashed sample still contained 11% C, 0.15% N and 0.8”:; S (CHANG, 1976). (4) At 6oo’C in 20 torr of 0,, 989, of the /Alate can be combusted (CHANG, 1976). This treatment may be mild enough not to outgas or alter possible high temperature mmerals and thus in the future may provide the basis for a further useful mineral ‘separation’. (5) An Allende A sample treated with 300:, H,Ot at 60°C for 1 day, lost 9916 of its heavy rare gases (sample 58, FRICK. 1977) without major loss of weight. This treatment modified the concentrations and elemental patterns for the rare gases m a manner suggestive of the postulated removal of mmeral ‘Q’ with HNOj by the Anders group (LEWIS et al., 1975b). 2.3.3. Interpret&ion ofthese results. The methods we had available for sample characterization (TEM, SEM, pyrolysis, and combustion) are less comprehensive than the neutron activation techniques used by the Chicago group (e.g. ANDERS et al., 1975; GRCI~ and ANDERS, 1977) and thus have to be interpreted carefully. On the other hand some of our techniques enable us to put new constraints on the occurrence of sulfur m our separates, whether it be elemental, in ‘organics’, or in sulfides. The acrd residues from type C2 meteorites-We estimate that the lAIates consist of about 954, or more of HCI/HF insoluble carbonaceous matter, consistent with the findings of SRINIVASAN et al. (1977) for their Murchison sample ICI. A /A/ate sample prepared from Orgueil, a Cl stone, exhibited similar ‘organic’ content (FRICK and MONIOT, 1977). In the reviews by HAYES (1967) and NAGY (1975) as well as in a recent attempt to characterize C2 carbonaceous matter (HAYATSU er al.. 1977) such substances are frequently referred to as ‘polymer’. It appears to be an agglomeration of various structural units-not monomers-arranged in a random pattern. SRINIVASAN et al. (1977) report the occurrence of chromite in their Murchison residue. We did not see this mineral m our Cl and C2 lA/ates Either we missed it or it was discrimmated agamst or destroyed by our procedures The pyrolysis of lA/ates offers a sensitive test for the occurrence of metallic sulfides. important because the noble gas carrier ‘Q’ has been tentatively identified as Fe,,Ni,,Cr,S, (GROS and ANDERS. 1977). The observed absenceof any-sulfur release between 550 and 14oo’C says to us that metallic sulfides are probably not present. We consider it unlikely that metallic sulfides were present in sigmficant concentrations but pyrolyzed outside the temperature range. The acid residues of the Alende C3 meteorite contam less carbonaceous matter (4&90”,,: LEWIS et al., 1975b, 1977; FRICK, 1977) than the C2 separates. Unfortunately the composition and structure of the HCI/HF insoluble carbonaceous matter are the least known among the ‘organic’ constituents of the meteorite: GREEN er al. (1971) identified graphite, thinly coating ohvine grains; BAUMAN et al. (1973) claimed evidence for ‘CHz-polymer’ in an acid residue of Allende; SIMMONDSef al. (1969) report its having structural similarities with the aromatic-type of kerogen, the acid insoluble orgamc matter in terrestrial sedimentary rocks, or with coal, while BREGER ef al. (1972) concluded from the absence of H and N m the ‘organic’ isolate that no macromolecular compounds are present. Based on this

1784

J. H. REYNOLDS,U.

FRICK, J. M. NEIL

observation the Chicago group uses the term ‘amorphous carbon’ for the ‘organic’ phase in Allende residues. Until further clarification we tend not to commit ourselves and designate the ‘organic’ phase as ‘acid (non-oxidizing) insoluble carbonaceous matter’, regardless of what meteorite cfass it has been prepared from. It is not understood m terms of one compound but rather as a substance likely to have random associations of building units and no definable structure (HAYES,1967: NAGY, 1975). Such matter IS expected to exhibit a wide spectrum of physical and chemical properties which may chara~eristically differ among various types of carbonaceous meteorites. The absence of any typlcal sulfur release in the pyrolysis experiments indicates that there might be far less metallic sulfide in our Allende residues than suggested by the Chicago group (e.g. LEWIS et al., 1975b, 1977). Although it cannot be entirely excluded, we consider it unlikely that the vacuum pyrolysis of such phases occurs above 1400°C. 3. RESULTS AND DISCUSSION Sampies Murray WllA-0 and Cold Bokkeveld W/IA-l were analyzed in melting runs. Sample Murchison (WZIA-I) was analyzed in an abbreviated temperature run. The numerical designation for the Murray sample is ‘0’ instead of ‘1’ because it was a preliminary sample, prepared before the methods described above had been completely worked out, and in several respects it seemed less pure than the ‘1’ separates which came later in the work. A second sample of Murray was processed by the regular methods, with samples of the ‘phyllosilicates’ (Murray W&l) and the ZAfate (WllA-1) analyzed in melting and stepwise heating runs, respectively. An additional Murray ‘phyllosilicate’ sample (W&l*), the last bit of colloidal material extracted from the lithium-disaggregated meteorite, was also anafyzed in a melting run. Allende AM&l was analyzed in a melting run. There was also a melting run made on a portion of the Allende Acid residue (A-l) which was the source of the methanol-extracted colloidal. The results for all these runs are set out in Table 2. We initially encountered several difficulties in weighing

and D. L. PHINNEY

Notable in this paper are the uniform and high concentrations of trapped rare gases in the IAlates, showing the planetary elemental pattern. These assertions are best exhibited graphically. In Fig. 3 the absolute gas concentrations (totalled in the case of stepwise heating@ for the IAiates in Table 2 are plotted

and compared

with other samples

rich in rare gases, including bulk samples of the Murray meteorite, The concentrations for lAIates all lie within the narrow black band of the figure. Gas-rich, acid residues from Allende prepared at Chicago (LEWIS et al., 1975b, samples 3C1 and 3SCl) would also plot very close to the black zone. At the time this figure was prepared, concentrations for Kr and Xe in the /Afates samples were the highest ever encountered in extraterrestrial samples. Some of the comparison spectra in Fig. 3 were selected in order to illustrate this fact. For example we plotted the rare gases from a very gas-rich lunar mineral, a 10.9 pm size-fraction of ilmenite from an Apollo 12 soil (EBERHARDTer al., 1972). The lunar ilmenite is an excellent example of the ‘solar’ pattern for the rare gases with which the planetary pattern in the lAlates samples can be contrasted. Another very interesting gas-rich sample, recently analyzed, is the graphite-diamond vein material picked out of the HaverG ureilite by WEBER ef al. (1976) who speculated that the material was derived by shock from the carrier phase for rare

gases in carbonaceous chondrites. The subsequent isolation of the gas-rich carbonaceous phase, as reported by LEWIS et al. (1975b) and in this paper certainly lends support to Weber et al.‘s surmise. The Havera separates also exhibit high concentrations of Kr and Xe. Otherwise they show a distorted planetary pattern (higher in Ar, lower in He and Ne) which might well have resulted from planetary gas imbedded in the diamonds by a complicated set of processes including shock. We have also plotted in Fig. 3 samples reliably, until we established more reproducible procedures. Earlier reports from the laboratory (PHINNEY (shaded region) the range of analyses for bulk samples et at., 1976) about the hydrophilic nature of the samples of Murray, taken from papers by MAZOR et ai. (1970) have not been confirmed using other methods of drying and by &PIN and SIGNER(1965). Compared in this before weighing. We have not yet found a satisfactory way, the spectra show that the 1Alates have the same explanation for the weight increases on the balance, preplanetary patterns but are higher in gas content by viously observed immediately after demineralization. The almost two orders of magnitude. Since the figure was Iiquids for the attempted quantitative transfer into a rather large weighing dish were removed by surface evaporation prepared extraterrestrial samples even rtcher in Kr with heat lamps. Possibly hydrophilic adsorption by acid and Xe have been described [acid reslstant residue remnants on the weighing dish-not obierved when weighfrom the Ornans meteorite (SRINIVASAN et al., 1977); ing a ‘blank’ container-could have caused these instabilidiamond inclusions from ureilites (GOEBEL et al., ties. Repeated weighing of the samples after about 2 days 1978)J. of ‘equilibration’ with room air were reproducible within 0.01 mg when wrapped in small aluminum packets of We are able to compare Murchison WI/A-l, about 40 mg (weights in Table 1). These weights are neverobtained by demineralization of a colloid, with a theless somewhat uncertain because extensive drying at HCl/HF resistant residue of this meteorite, prepared 120-15O’C in air seems to pyrolyze 10-500/0 of various meteoritic and terrestrial colloidal carbon samples. A by SRINIVA~ANet al. (1977). Although we have lost second sample of Allende AM& stored for several months the 1200°C fraction of the abbreviated temperature in the extraction system of the mass spectrometer where run, which contained 25-30’4 of the total heavy noble it was exposed to temperatures of 150-170°C for several gases by inference from the Chicago data, the Ar, Kr weeks, thereby lost 3%; of its weight (before weighing and and Xe concentrations of our sample are virtually the loading this sample the sample had been in a vacuum dissiccator at 120-140°C for several days). same. This is rather surprising considering the com-

Rare-gas-rich separates from carbonaceous

1785

chondrites

1 0

4

Murray bulk data (Mazor et a/., 1970; Pepin and Signer, 1965)

IIIIIIDTotol variation

---

Hover0

---

Hover6

-

Lunar

-

Pesyonoe

m

-1

rs, L -2 E WY

(Weber ilmenite

(Eberhardt

et ol.,

3 in temperature

19

12001 et al.,

(Weber (Morti,

run

et al., 1975

2

T Q : 0

’

;; a, s

3

E ‘s -f

1969)

1972)

::

-3 C -L: $ -4

-1

5 -0 c -5 2 0 m -6 _o -7

aJ ::

-2

0” 5 4 zl

-3

$

-4

-5 4He

20Ne

36Ar

s4Kr

‘32Xe

Fig. 3. Absolute noble gas concentrations for IAlates m this paper (black band) are compared with various analyses from the literature. Lunar ilmenite (10.9 pm size fraction from an Apollo I2 soil, EBERHARDT et al., 1972) illustrates a typical ‘solar’ pattern: the Murray bulk data are typical for ‘planetary’ abundances (PEPIN and SIGNER, 1965: MAZOR et al. 1970).

4He

“Ne

36Ar

“4Kr

132

Xe

Fig. 4. Elemental abundances normalized to 36Ar m the samples. All the separates from Table I plot within the black band. Temperature fractions from stepwise heating of Murray WI/A-l (the shaded zone) also exhibit a narrow range of elemental compositions The ‘planetary’ pattern contrasts with a ‘solar’ pattern, exemplified here by gases from Pesyanoe (MARTI. 1969). Diamond-rich veins of the HaverG urellite depict a somewhat modified planetary pattern with substantially lower He and Ne abundances (WEBER et al., 1976).

paratively harsh treatment of our samples (the temperatures reached at least 150°C when evaporating HF after demineralization and the samples were exposed to temperatures of 13&15o’C for several weeks when stored in the extraction line). Allende AM11 exhibits At. Kr and Xe concentrations similar to those for the most gas-rich Allende separates described by LEWIS et al. (1975b, 1977). The amounts of He and Ne in the latter, however, are substantially higher, perhaps indicating abundant chromite (e.g. FRICK and REYNOLDS,1977) or other phases with relatively high abundances of the light gases. On the other hand our rough treatment could have released lightly bound gases in our samples. Part of our Allende AM/l sample might also have been pyrolyzed slightly during preparation (we have already mentioned that an aliquot of this sample lost about 30% of its weight during storage in the vacuum system). In Fig. 4 we have plotted elemental abundances for samples relative to the concentrations of 36Ar in the samples. So normalized, the total gas samples show very consistent planetary patterns for all the separates in Table 2: these analyses define the black band in the figure. Even the temperature fractions for the stepwise heating of Murray WIIA-1, which a]] lie within the shaded zone on the plot, depart re]a-

tively little in elemental composition from the totals. In contrast to these planetary patterns are the plots of the solar composition, as exemplified now by gas from the Pesyanoe achondrite (MARTI, 1969) and the modified planetary pattern in the graphite-diamond inclusions from the ureilite Haverij (WEBER et al., 1976). 3.2. Thermal

release patterns

Fig. 1 shows thermal release patterns for the rare gases released by stepwise heating of Murray WI[A-1. An ‘abbreviated’ stepwlse heating of Murchison W/IA-l was carried out before the Murray run, serving as a pilot run which was helpful in fixing the conditions for the Murray run. The patterns for the two runs were similar, but the Murray run was on a cleaner sample with more temperature steps so is the more definitive. Data from both runs can be found in Table 2. We also plot in Fig. 1 some of the data obtained in analyses by high resolution mass spectrometry of the chemically active gases released in a vacuum pyrolysis of two samples which were subjected to linear heating from ambient temperature to 1400°C in about 1 hr. These samples were Murray WllA-0 and Murchison W/IA-l. Our discussion of the pyrolysis gases occurs above in section 2.3.1.

J. H. REYNOLDS, U. FRICK,J. M. NEILand D. L. PHINNEY

1786

The stepwise heating for the rare gas analysis was carried out in halfhour heatings at steps which were usually, but not always, 100°C. In plotting the data we divided the gas release for any unorthodox steps (# 100°C) by the unorthodox temperature interval, expressed in hundreds of centigrade degrees, creating thereby a histogram for which the areas represent gas amounts released. In other words the ordinate for these histograms is per cent gas released per lOOcentigrade-degree step. Consequently, the histograms in Fig. 1 all have the same area. corresponding to 100yb release. One immediately sees that the rare-gas, thermal histograms for Murray W/I-A-l are bimodal. The patterns for Ar, Kr and Xe are remarkably similar. Each has a low temperature release (20&5OO@C)during which about 35’4 of the gas came off, followed by a very symmetrical high-temperature release peak with maximum release near 1000°C and virtually complete release with the conclusion of the 1500°C heating (since the 1650°C temperature fraction- was virtually indistinguishable from the blanks). For He and Ne there are also high temperature release peaks, shifted only in the helium case to a slightly lower temperature (900”) for the maximum release. These lighter gases had a less significant low temperature release (16”a for helium and 11% for neon) as if this were a lightly bound component which had already been substantially outgassed for these lighter gases before our laboratory heating began. We so interpret the low temperature gas data. The retentivity for rare gases at such high temperatures is extraordinary in view of the very fine grain size (< - 100 A) for these 1Alates and it merits discussion here. The release patterns for the symmetrical high-temperature release peak can be fitted very well by either of two very simple models, a diffusion model or a ‘chemical reaction model’. The diffusion model supposes that the gases are released by simple volume diffusion from spheres of uniform size in which the gas was originally dissolved uniformly. Since the spherical particles in our IAlate samples have diameters of about 100 A and can be assumed to have a density close to 1 g/cm’, one calculates that particles outnumber rare gas atoms in our samples by a factor of about 100! The release data for Ar, Kr and Xe are fitted reasonably well by D/a2 = [D,/a2]

exp(-A@kT)

where OX/a2 ranges from 0.1 to 0.9 set- ’ and AE from 1.0 to 1.3 electron volts. We doubt very much, nevertheless, that there is any physical validity for this model. One of the reasons is that it seems certain from the pyrolysis results that there is appreciable chemical reaction of the /Alate particles before the temperatures at which the principal ‘diffusion’ takes place. It also seems unlikely that the diffusion coefficient could be so small with an activation energy for diffusion of only l-1.3eV. For our sample, where 100 A is a firm upper limit for the diameter of the par-

titles, D, must be less than lo- I3 cm2/sec. The smallest values of D, tabulated by FECHTIG and KALBITZER(1966) for minerals are of the order of lo-‘. A simple ‘chemical reaction model’, which fits our high temperature release patterns equally as well as the diffusion model, assumes that the surface of the spherical particles of uniform radius r is being chemically removed at a rate -dr/dt

= -(dr/dt),

exp(-AE/kT).

with the complete erosion of the particles occurring at the very end of the 1500°C heating step beyond which no gas release is observed. Then the only adjustable parameter is AE which turns out to be 0.5 eV. In this model one implicitly assumes that the activation energy for rare gas diffusion within the particles is very high so that little diffusion takes place and the gas release occurs only when the erosion eats down to the depth at which the gas atom resides. A clear advantage of this model is that it explains the identical release patterns for all the rare gases except helium. The pattern for helium is shifted slightly in temperature; one would say in this case that diffusion is also operating to some extent and thereby facilitating the process of gas release. Both models are obviously oversimplifications, but we prefer the reaction model for the reasons given. 3.3. Isotopic effects Isotopic abundance characteristics of the planetary gases have hitherto been inferred chiefly from analyses of gases extracted in meltings or in stepwise heatings of bulk samples of carbonaceous chondrites. The discovery by LEWIS et al. (1975a) that there are fractions of these stones in which the planetary gases are enriched in concentration by orders of magnitude, relative to the bulk meteorite, may create unprecedented opportunities for studying the isotopic composition of the planetary gases. In this section we examine our isotopic data. 3.3.1. Neon and helium. Neon is perhaps the most useful element for identifying planetary gas on the grounds of isotopic composition. Variations in the ratio 20Ne/22Ne are large and cosmic ray effects are rather easily monitored by means of the ratio 2’Ne/22Ne, which is much higher in the spallogenic component than in trapped components. &PIN (1967) deduced a composition (neon-A) which at the time was said to perhaps exemplify planetary neon. It was deduced as follows: carbonaceous chondrites with minimal amounts of solar-wind neon defined one line on a three-isotope plot for neon; gas-rich meteorites with minimal amounts of spallogenic neon defined another line, which passed through both solar-wind neon and terrestrial atmospheric neon, as if all ‘trapped neons’, including the neon we are familiar with on Earth, were mixtures of solar and planetary neon in various proportions. The intersection of those lines was dubbed neon-A by &PIN (1967) and put forth as a prime candidate for pure planetary neon,

Rare-ga+rich

14

t

swc 0 __ Neon

separates from carbonaceous

Ae = Allende CB = Cold Bokkeveld

B

d

\\

/

1

2

NeonE 011 0

I

1

01

02

03

04

05

"Ne

06

07

08

09

10

22Ne

Fig. 5. Three Isotope plot for neon. The rectangle on the left side (this area is enlarged in Fig. 8) contains all neon analyses obtamed m this paper, of which only the total fractions (unlabeled) are plotted. Samples labeled Ae (Allende) are from LEWIS ef al. (1975b) and samnles labeled bB (Coid Bokkeveld) are alsd taken from thk literature (CBI: KIRSTEN et al., 1963: CB2: Z~RINGER, 1962; CB3 and CB4: MAZOR et al., 1970). SWC stands for neon solar wind composition as measured m catcher foils (GEISS et al., 1972).

Its candidacy has held up amazingly well in view of subsequently discovered additional complexity in the neon natterns. matters we discuss below. The lines whose intersection defines neon-A are shown in Fig. 5. Most of the data obtained in this paper lie within the small rectangle on that Figure surrounding neon-A. Until our preliminary report (PHINNEY et al., 1976) no previously measured samples released total neon with a composition within that rectangle, including the Allende samples studied by LEWIS et a/. (1975a,b) (some of their neon samples as well as other serious ‘contenders’ for planetary neon are plotted in Fig. 5). In other words the planetary-rich neon samples examined in this paper are unprecedentedly close to the neon-A corner of the ‘classical’ neon triangle (SRINIVASAN et al., 1977 recently described similar neon data from Murchison) in support of the initial concept by PEPIN (1967) that neon-A exemplifies planetary neon. The ratio 3He/4He is also a useful parameter for identifying planetary gas in meteorites. ANDERS et al. (1970) and BLACK (1970) independently called attention to a correlation between trapped 3He/4He and trapped *‘Ne/**Ne in carbonaceous chondrites. Large and somewhat inaccurate corrections had to be applied to most of the data upon which the correlation was based, but both authors saw a pattern would associate which planetary neon (i.e. z”Ne/22Ne = 8.2) with helium for which the 3He/4He ratio (1.25 f 0.76) x 1O-4 (ANDERS et nZ., 1970), (1.76 + 0.40) x 10m4 (as inferred from Fig. 1 in BLACK, 1971), or (1.4 + 0.3) x 1O-4 (as inferred from Fig. 6 in BLACK, 1972b). Soon thereafter JEFFERY and ANDERS (1970) revised the ‘best’ He-Ne correlation in such a way as to give planetary helium a 3He/4He

chondrltes

1787

ratio of (1.43 x 0.40) x 10M4, which is close to the average (1.5 x 10m4) of the earlier ratios just quoted. Important caveat: The He-Ne correlations we have been discussing in the previous paragraph seem to take the form of straight lines on a plot of 3He/4He vs *ONe/**Ne. In considering such a plot one must remember, an erroneous statement by BLACK (1970) notwithstanding, that mixtures of parent gases with [definite 4He/22Ne ratios (as well as definite helium land neon isotopic ratios) for those parents will plot 4as straight lines joining the parent compositions onl) if the 4He/22Ne ratios are the same for the two purent gases. It is a somewhat anomalous and fortunate circumstance that for the solar system the planetary and solar ratios 4He/22Ne are approximately the same. This has enabled BLACK (1970) and others to use 3He/4He vs 20Ne/22Ne mixing Imes in their discussions about trapped rare gases in meteorites. One can note, by way of contrast, that conceptually the mixing paths on an argon-neon diagram should be curved owing to the differing argon/neon ratios in the planetary and solar components. Our Fig. 6 shows that the total gas from all the separates studied in this paper conform reasonably well to the standard A-B or planetary-solar correlation when the ratio ‘Hei4He is plotted vs *‘Ne/**Ne. The data in Fig. 6 are plotted with and without corrections for cosmogenic neon and cosmogenic-radiogenie helmm whenever the effect of that correction is significant compared to the indicated analytical errors. The tentative corrections were computed by assuming that the concentrations of cosmogenic and radiogenic nuclides in the separates could range as high as the literature values for the bulk meteorite (Allende, Cold Bokkeveld, Murray: compiled in MAZOR et al., 1970; Murchison, Allende: BOGARD et al., 1971). The arrows in Fig. 6 show the range of corrections which result thereby. Presence of cosmogenie neon in the separates would invariably shift trapped values, corrected for cosmogenic neon. to the right (towards larger values of *‘Ne/**Ne). Usually the correction to the 3He/4He ratio would be downwards (towards a smaller value of the ratio) because of possibly significant amounts of cosmogemc 3He in the separates, as inferred from the bulk meteorite, but insignificant amounts of radiogenic “He in comparison with the high concentrations of trapped 4He there. In the silicate samples, however, the corrections to 3He/4He could go either way as indicated. It is noteworthy that the fall of the uncorrected points near the A-B correlation line provides evidence that the full cosmogenic-radiogenic corrections inferred from the bulk meteorite do not apply. Another indication that the full corrections do not apply is the unrealistically small value for (2’Ne/2zNe) that remains after the correction-usually much less than the neon-A value for that ratio. For two samples the corrected (21Ne/2ZNe) ratio would be negative. In those cases there is a strict limit to the amount of cosmogenie 21Ne that can be subtracted (i.e. the amount

1788

J. H. REYNOLDS,U. FRICK. J. M. NEIL and D. L. PHINNEY I .

1Atoter” Ae CB Mll My-O My-l

I

Allende AM!l-I Cold Bokkeveld Wet A-l Murchwm W!!A-I Murray W(IA-0 Murray W1!AmI

TOTAL GAS COMPOSITIONS o Other Separates Ae Allende A-l MY Murray Wlf I MY' Murray Wff-1’ 0

I

s

9

IO

1

,

1

11

I2

13

20Ne,‘22Ne

Fig. 6. Correlations of 3He/4He vs “Ne/*‘Ne. Our separates are plotted with and without likely corrections for cosmogenic neon and cosmogenic-radiogenic helium, whenever the effect of that correction 1s significant compared to the analytical errors (see text). Since the corrections for He and Ne are not necessarily correlated, the extremes-in 3He/4He and 20Ne/22Ne permitted by errors and/or corrections define rectangular zones (not plotted) withm which the true point might reasonably lie. For two samples (Murray WI/-l and Murray W//-l*) the ‘likely’ corrections are excessive because they would lead to negative values for the ratio 2’Ne/ZZNe. For these two samples, the maximum possible correction for 20Ne/22Ne is shown by the dotted vertical line. The composition of He-A is inferred from Fig. 6 in BLACK (1972b), Ne-A is taken from PEPIN (1967), and He-B and Ne-B from BLACK(1972a). present!) and a corresponding strict upper limit for the corrected value of (20Ne/22Ne). The limiting values for these two cases are shown by the vertical dotted lines in Fig. 6. Full corrections would apply if the grain size of the separates is much less than the ranges of the spallation fragments and recoiling alpha particles (true enough for the IAlates), if the grains in the separates are gas-retentive (they certainly are for at least part of the trapped gases), and if the sources for the spallogenic and radiogenic nuclides were uniformly dispersed throughout the meteorite and not separated by ‘buffering’ grains from the small grains we have isolated in the separates (a more difficult condition to be certam about to say the least). A possible explanation for the lack of spallogenic and radiogenic gases in these very fine grained separates is that there has been etching of radiationdamaged material during our chemical treatment and that this etching has preferentially removed the rare gas atoms which were originally associated with that damage. A closer look at the He-Ne isotopic correlation plot in Fig. 6 reveals that the ‘other’ separates (as keyed in the figure) conform the most convincingly to the correlation. These separates indeed seem to contain both planetary and solar gas, as would seem reasonable since they are not extraordinarily gas-rich like the IAlates. We have already observed how these separates seem not to have retained cosmogenic and radiogenic nuclides from their own or neighboring grains. The interpretation of the position on this graph of the IAIates is more complex. One could say that they follow the A-B correlation loosely. One could also say that for Cold Bokkeveld, Murchison,

and Allende. and for Murray if cosmogenic corrections are applied, the 3He/4He ratio is approximately constant at the pure planetary value (0.00014) irrespective of variations in the *‘Ne/‘*Ne ratio. This latter interpretation of the data gets support from the stepwise heating run on Murray sample WI/A-1 as will now be described. We show the results of that heating run in two figures. The simpler and more revealing of these is Fig. 7 where we display ‘plateau plots’ (in the sense of 3gAr-40Ar dating) for the ratios 3He/4He and *‘Ne/‘*Ne. The abscissa in this plot is the cumulative fraction of the denominator isotope released in the successively higher temperature steps of which the run consisted. The ordinate is the isotope ratio observed for that fraction, plotted as a band of width 2a centered on the measured value. As in 3gAr-40Ar dating, a ‘plateau’ occurs when a horizontal line can be drawn through a substantial, consecutive segment of the results when displayed in the representation. The He line displays a plateau for all steps above and including 85o”C, comprising 70% of the total He released. value of the ‘plateau’ is The 0.000142 + O.OOOOO5 by the graphical method just described or 0.000143 f O.OOOOO5if the He isotopes released at 850” and above are summed and the ratio taken, summing the errors in quadrature. In our view this plateau is a stunning verification of the isotopic composition of planetary helium, previously inferred as we have described above, from correlation plots which gave the same value, according to JEFFERY and ANDERS (1970), error-laden though the plots were. The extent of possible corrections for cosmogenic helium in our determination is indicated in Fig. 7

Rare-gas-rich separates from carbonaceous

occo4

t

0

Murray

02

chondrltes

1789

Wf4A-1

04

06

08

10

Fraction of ‘He or “Ne released Fig. 7. Isotopic ratios of helium and neon versus cumulative release of the denominator Isotope. Isotopic ratios are plotted as a band of wtdth 20 centered on the measured value. Likely correctlons for spallogenie or radlogenic contributions are indicated for the total values. by showing its likely effect upon the total helium released from Murray WI/A-l. The total 3He/4He would be reduced from 0.000170 to 0.000152. A conservative view of our result would thus assign a possible error of 0.00002 in the ratio. There results a composition of (1.425 + 0.20) x 10m4 for planetary helium. Note that we do not make a cosmogenic correction to the ratio-it seems likely to us that a COSmogenic component is present in Murray W/IA-l but is released in the lower temperature steps before the occurrence of the plateau. In other words we really have more faith in the remarkably stable plateau value of 0.000142~ than our very conservative error of 0.00002 would indicate. The neon data in Fig. 7 tell quite a different story: there ‘are very substantial variations in the ratio 2oNe/22Ne. We show below that cosmogenic effects on the 2oNe/22Ne ratio are very small. It is also easy to show that atmospheric contamination cannot have affected the neon results detectably. Even though close to neon-A in isotopic composition. the neon from Murray WI/A-l is unquestionably a mixture of two or more components. BLACK (1972b) in his review and synthesis of the neon results for carbonaceous chondrites concluded that neon-A is a mixture of two components which he called neon-D and neon-E. Of the two, neon-E is much the better characterized. It is a component of extraordinarily low 2oNe/22Ne ratio [<3.4 from BLACK’S (1972b) data; C 1.5 from EBERHARDT’S(1975) data; < 1.29 from NIEDERER and EBERHARDT’S (1977) data] and, unlike cosmogenic neon, low 2’Ne/22Ne C~O.0192, BLACK (1972b)] as well. Neon-E was first discovered in stepwise heatings of various carbonaceous chondrites (BLACK and PEPIN, 1969) where it is released preferentially in the temperature range 900-1100°C. It has since (EBERHARDT, 1974, 1975) been seen highly enriched in the total neon from fine grained separates from the Orgueil type Cl carbonaceous chondrite and in graphite separates from the H-type chondrite (Dimmitt (NIEDERER and EBERHARDT, 1977). Black’s

explanation for this component is that it is entrapped in interstellar grains which entered the carbonaceous chondrites without the neon therein being isotopically mixed with the rest of the neon m these primitive objects. EBERHARDT(1974) has added the notion that they are ‘half-baked’ clay-like particles, which could explain why they are difficult to colloidize and why they show a sharp temperature threshold for the appearance of this component m thermal release [preheated material usually shows such sharp thresholds for gas release upon reheating according to BAUR et al. (1973), FRICK et al. (1973) and FUNK et al. (1973)]., We find it significant that the 20Ne/22Ne ratio in Fig. 7 drops starting at 1050” and rising again after 1150”. Such behavior is consistent with neon-E escaping preferentially in its usual temperature range and producing a dip there in the 20Ne/22Ne ratio, as Black would predict. The properties of the other neon component (neon-D) in Black’s proposed synthesis of neon-A are only weakly established. BLACK (1972a.b) assigns this component a 2oNe/22Ne ratio of 14.5 + 1.0 and attributes the gas to a pre-main sequence solar wind. BLACK (1972b) has excluded neon-B as the mlxmg partner of neon-E m forming neon-A by an argument which, strictly speaking, would require identical 4He/22Ne ratios in all these components. because his arguments are based upon straight lme constructs on a 3He/4He vs 2oNe/22Ne plot (see our caveat above). We digress here for a moment to show that Black’s conclusion is valid even If we perrnlt varlatlons m the 4He/22He ratio for components in the system We wish to show that gas B c3He/“He = 0.00039: 4He/22Ne = x; 20Ne/22Ne = 12 5) cannot rmx with gas E (3He/4He = c; 4He/Z2Ne = q: 20Ne/22Ne = 6 < 1.5) to form gas A (3He/4He = 0.00014: 4He/22Ne = 2220. from the average of our IAlates; Z”Ne/*2Ne = 8.2). If the fraction of ‘“Ne atoms in the A mixture from the E component is called fwe have 8 2 = Sf+ ‘12.5(1 - f). Inserting the lirmts 0 to 1.5 for 6 we find that f 1s rather

J. H.

1790

REYNOLDS U. FRICK, J. M. NEIL and D. L. PHINNEY

narrowly fixed, from 0.344 lo 0.391. For the 3He/22Ne in the mixture we can write (3He/22Ne),

= (0.00014)(2220)

= ~fl+

(000039)(x)(

ratio

1 - f)

and since q/ must be positive, there results (.u)( 1 -J) < 797. The lower limit for (1 -f) just deduced above is 1 - 0.391 = 0.609 which would say .Y < 1309 or (4He/toNe), < 105. Observed values for trapped 4He/ZoNe m meteorites cluster close to 2W300 for both planetary and solar contributions. as we have noted before. In some cases, such as in the Orguell magnetite (JEFFERY and ANDERS, 1970) higher values are seen, but to our knowledge a value as low as 105 would be totally out of accord with observation. especially for a solar component. Therefore. a proposed mixture of gas E and gas B lo form gas A is ruled out. The same result is obtamed for 3.4 as the upper limit for (ZoNe/Z’Ne),, which was the datum used I; the orlginal discussion of this pomt by BLACK (1972b). (3He/4He = 0.00015: Black’s orovosed gas D 4He/ZZNe 2 I’: 20Ne/22%e = 14.5) can mix with gas E to produce gas A. The only restrIction that results from examining this proposal. if we use .x’ > (14.5)(200) = 2900. is EV = (‘He/“Ne),

< 0.20

Our neon isotopic data for the lA/ates can be described further in the context of the Black mixing model for neon-A with the aid of the three isotope plot shown in Fig. 8. We have plotted only the small rectangular region from Fig. 5. containing the neon-A vertex of the usual neon triangle. The plot is divided into two parts: one shows the stepwise heating data: the other, the results for total neon from the samples. The possible extent of cosmogenic corrections is indicated on the plot for the total neon samples by the arrows. Again we have supposed that the concengas is trations in cm3 STP g-’ of the cosmogenic the same m the separates as given in the literature for the bulk meteorites. One notes that for the scales chosen in Fig. 8. the effect of cosmogenic correction

a5

a5 a0 75

0016

0 020

0 024

0 028

0 032

0 036

2’Ne/“Ne FIN. 8. Three

isotope plot for neon. In the upper graph stepwise heatmg dais fbr Murray /Alates are depicted. kn ‘excluded zone’ (barred area) is constructed from the 500°C ‘zone’ and the boundaries of neon-E (20Ne/22Ne < 1.5, 2’Ne/22Ne 4 0.0192: EBERHARDT. 1974). In the lower graph total neon from all lA/ates are plotted with possible cosmogemc corrections (see text).

is essentially a displacement to the left--towards lower values of “Ne/“Ne without much change in Z”Ne/2ZNe. An interesti.lg ‘excluded zone’ for points on this diagram can be constructed from the 500 point in the stepwise heating of Murray WIIA-1 and the boundaries of the neon-E region taken from the literature (20Ne/22Ne < 1.5; *‘Ne/**Ne < 0.0192; EBERHARDT, 1975). The 500” ‘point’ is also a region if one takes possible cosmogenic corrections and experimental errors into account. The excluded zone is determined by seeing how far to the right it is possible to draw straight lines which intersect both the 500 region and the neon-E region. It is the lower right hand corner of the 500” region which is definitive for this purpose, combined with the upper left and lower right corners of the neon-E region. These two straight lines define a slightly ‘dog-leg’ border for the excluded zone, shown as a barred area in Fig. 8. If the 500” point, after correction for possible cosmogenie effects, is a mixture of two components only and if one of them is neon-E, all other such mixtures and the neon-D point, to use Black’s notation, must lie to the left of the excluded zone because of the way it was defined. Although the raw data points are in the excluded region, the possible cosmogenic corrections are more than adequate to move the points into an allowed region except for Cold Bokkeveld. A much larger cosmogenic correction than appears reasonable is necessary in order to legitimize this point in terms of the mixing model. Nor can a content in Cold Bokkeveld of neon-B help the situation. A” correction for that shifts the Cold Bokkeveld point along a direction almost parallel to the boundary of the excluded zone; there is no intersection of the two lines in a physically realizable region. Correction of the 500” point for neon-B content would only worsen the situation: the extent of the excluded zone would be enlarged thereby. Our conclusion is that the model needs be more complex in order to handle both the 500‘ point from Murray WIIA-1 and the total neon point from Cold Bokkeveld or else we have underestimated the cosmogenic contributions to the neon in the latter. A ‘marriage’ of these two possibilities would be afforded by a precompaction irradiation of the IAlate phase of Cold Bokkeveld and not of most of the bulk meteorite. SRINIVASAN et al. (1977) have unearthed a similar problem for Murchison chromite. The run of the points on the three-isotope neon diagram for the stepwise heating of Murray WI/A-l is drawn freehand on the upper part of Fig. 8. We interpret its complex wanderings as a consequence of noncorrelated release for the spallogenic nuclides which produce the variations in the ratio *lNe/**Ne and the neon-E nuclides which produce the variations in the ratio “Ne/*‘Ne. each with very little dependence upon the other. Except for 1500”, where very little gas is released so that the isotopic data cannot be given much weight, the spallogenic component is least at 500’ and rises more or less monotonically throughout the temperature run. Except for 500”,

Rare-gas-rich separates from carbonaceous chondrites where there seems to be an isolated gas fraction rich in neon-E, the principal neon-E release is in the region including the 1050” and 1150” temperature steps, as usual. SMITH et al. (1978) identify some of the isotopic features of their high-resolution, stepwiserelease patterns for neon from bulk samples of type C2 meteorites as originating in components in the gas-rich separates, but we have been unable to develop that idea any further by comparisons with our data. The two studies have stepwise data in common only for Murchison where unfortunately our data comprise only three temperature steps. Close scrutiny shows a few points of similarity between our Murray pattern and their bulk C2 patterns. Such ‘microscrutiny’ of our data should not distract the reader from the main points derived from the helium-neon analyses: (1) The neon compositions are close to the neon-A corner supporting the original criteria by PEPIN(1967) for the identification of planetary neon. (2) Even so there is evidence in this ‘purest planetary neon’ for a separable component with different 20Ne/22Ne ratio, quite likely the neon-E proposed in this context by Black, judging from its effect upon the ratio as a function of temperature. (3) We can contrast isotopic variations in neon with the constancy of the helium isotopic ratio at a value which supports the planetary ratio for helium previously derived much less directly by ANDERSet al. (1970) and by BLACK(1970). 3.3.2. Argon. There is presently considerable confusion about the isotopic composition of trapped argon in meteorites. MAZOR et al. (1970) and BLACK(1971) examined correlations between 36Ar/38Ar and 20Ne/22Ne for carbonaceous chondrites. Black (see Fig. 1 in his paper) discerned a linear correlation between these two ratios which he called the ‘carbonaceous chondrite corridor’, but data in Table 4 of Mazor et al. do not substantiate the corridor in any detailed way. And, as those authors pointed out, it is clear that such a correlation would not be linear If it arose from mixing of planetary and solar gases because the Ne/Ar ratio is so different in those two reservoirs. Such variations as are seen in the 36Ar/38Ar ratio would thus have to be from complexIty in the planetary component. By all odds the planetary gases studied in this paper should have been ideal for studying any such complexity because the argon is free from large amounts of 40Ar (which often interferes with making precise measurements of the ratio 36Ar/38Ar) and because cosmogenic corrections to the argon data in this paper are almost totally insignificant. Unfortunately there were experimental weaknesses in the work (not fundamental in character so that future measurements can be expected to be useful) which have made the errors in the argon measurements large in comparison with the effects we are interested in. Since the work described in this paper, there has been another development which may further compli-

1791

cate attempts to understand the isotopic structure in planetary argon. We refer here to the correlation between 36Ar/38Ar and 136Xe/‘30Xe observed in arrays of Allende samples where the latter ratio exhibits large variations owing to varying concentrations of the CCFX component. This correlation was noted by MANUELand SABU(1975) and LEWIS et al. (1977) and has been discussed more recently and on the basis of more data by FRICK (1977). The isotopic composition of argon associated with AVCC-type xenon is rather well determined from this correlation, the 36Ar/38Ar ratio being 5.3 f 0.1. 3.3.3. Krypton and xenon. The lack of any distinct isotopic trends for Kr and Xe in this suite of samples was a disappointment. Both Kr and Xe data points for melt extractions scatter randomly around AVCC (EUGSTERet al., 1967b) when plotting 6(M/82) versus 6(86/82) or &M/130) vs 6(136/130) and they fall roughly within error on the correlation lines seen in Allende separates when various oxidizing treatments are applied (LEWIS et al., 1975b, 1977; FRICK, 1977), or in Orgueil [A/ate when stepwise heated (FRICK and MONIOT,1977). The range of variation in the 6(86/82) values and the S(136/130) values is about 60-70?&, with typical statistical errors between 3 and lo?,,. The data obtained from the temperature run of Murray WI/A-l display similar variations with very little systematics, except when plotting S(134/130) vs 6(136/130) where the data points follow correlations seen in’ Allende, Orgueil 1Alate and bulk meteorites (FRICK and MONIOT,1977). There is also a weak indication that the 6(78/82) ratios decrease with increasing 6(86/82) ratios as seen more clearly in our oxidized Allende samples (FRICK, 1977). The Xe from both our melt extractions and stepwise heating of Murray W/IA-l is also compatible with the arrays obtained when correlating the data obtained by stepwise heating of carbonaceous chondritic bulk samples of Orgueil and Cold Bokkeveld (PEPIN, 1976), Murray (KURODA et al., 1974; PEPIN, 1976), Renazzo (REYNOLDS and TURNER,1964) and Murchison (KURODA et al., 1975), as compiled in FRICK and MONIOT (1977). If we compare analytically the Xe isotopic composition of all our C2 separates with AVCC xenon (EUG STERet al., 1967b). the latter exhibits a small but systematic departure toward air xenon for all isotopes, indicating that AVCC is slightly contaminated (less than 5%) with atmospheric xenon. Additional evidence arises when we analyze stepwise heating data for lAlates from Orgueil (FRICK and MONIOT, 1977), Murchison, and Murray: little or no atmospheric Xe contamination can be detected, contrary to what is seen when bulk samples of carbonaceous chondrites are stepwise heated (e.g. see Fig. 2 and Fig. 5 in FRICK and MONIOT,1977): usually the low temperature fractions of such experiments show substantial amounts of Xe of atmospheric isotopic composition. Thus it seems that the disaggregation and separation processes somehow reduced the occurrence of air xenon

I792

J.

H REYNOLDS.U. FRICK, J. M. NEIL and D. L PHINNEY

in these meteorites, a component which-and this cannot be ruled out a priori--could be a genuine meteorite component. For the discussion of ‘anomalous’ CCFX xenon data obtained from stepwise degassing of acid residues (Allende, Orgueil) or oxidizing treatments (Allende. Murchison) we refer the reader to the extensive literature on this subject (e.g. LEWIS et a/., 1975b. 1977; SRINIVASAN et al., 1977: SRINIVASAN, 1977:

Planetary

Rare

[Anders __ Remavnder I99 6 wt%l

-

Gases and

m Allende

coworkersj

100% level uncerta,n ham lock of moter,ai batonce

rn

Carbon

1019wt%l

MANUEL and SABU, 1975: CLAYTON, 1975: BLAKE and SCHRAMM, 1976:

FRICK and

MONIOT, 1977: FRICK,

1977).

Chromite :016 wt-41

Q

4. COMPARISONS

AND

CONCLUSIONS

We have based this paper mostly on our own experiments and how we interpret them, deliberately trying not to be unduly influenced by results obtained meanwhile at the laboratory of Professor Anders at the University of Chicago. Nevertheless readers are understandably interested in comparisons between our results and those obtained elsewhere. For this reason we include in this final section a brief qualitative comparison between our results and those obtained at Chicago (LEWIS rr al., 1977: SRINIVASAN rr al.. 1977: and earlier papers referred to in these). Isotopic abundance data are in extremely good agreement between the two laboratories. The comparison of elemental amounts and concentrations is complicated by the fact that the two groups have prepared their samples differently and have discussed their results in different frameworks. At Berkeley we have prepared separates (IAlates) by a combination of acid demineralization and colloid extraction. Among such samples we observe remarkably similar gas concentrattons be they from the C3 Allende or from the C2 Murchison, Murray, or Cold Bokkeveld meteorites. The gas concentrations are also very similar in these lAIates to the highest concentrations measured direct/y (as opposed to inferred by difference) at Chicago in samples from Allende and Murchison. These facts have led us from the beginning, rightly or wrongly, to the belief that there was in common to all these meteorites a carbonaceous carrier fraction which was uniformly rich in the planetary gases. The approach at Chicago has been to specify samples to the maximum extent possible in terms of sub-phases whose properties and abundance are taken from the meteorite literature, or from operational definitions (e.g. ‘Q’ is that phase which does not dissolve in HF/HCI acids but does dissolve in HNOs). or from scattered chemical analyses of their separates, principally for carbon and chromium. Such specifications can be praised as honest efforts to use all available information, but often that information is scanty, or inferential, or based upon literature characterizations that are vague and poorly tested. All this is to say that we cannot honestly accept as yet these characterizations as definitive. Use of these ap-

1004

Wf%

?ONe

36Ar

B’Kr

13’Xe

Weight

Fig. 9. Characterrzatton of the rare-gas contents of Allende meteorite accordmg to LEWIS et al. (1977). Shown IS how the total trapped Ne. Ar. Kr and Xe in the meteorrte are thought to be distributed among sparse phases (carbon, chromite and Q) and the remamder of the stone Mostly the rare gases are m phases whtch account for very little of the wetght.

proximate characterizations to infer the rare gas contents and isotopic compositions by difSerence offers additional opportunities for error. Turning to cases, the Chicago charactertzations for Allende (Fig. 9) lead to estimates of 8996 of the xenon in the meteorite residing in the acid insoluble residues, with 82”, in ‘Q’ and the remaining 6 or 79, divided about equally between chromite and carbon. The Berkeley /A/ate from Allende contains (Fig. 10) only about one-fifth of the xenon expected from the Chicago data if the colloidal extraction does not reject xenon-bearing material. This comparison suggests that there has been substantial loss of an impor-

Chawo

I

Fig. 10. Recovery of lJZXe, in terms of amount per gram of bulk meteorite, in Chicago and Berkeley separates. The gas as studied at Chicago is thought to be partrtioned m sub-phases as shown. The Berkeley recovery is in a poorly characterized phase prepared by a combination of actd attack and colloid extractions. The comparison suggests that there has been a substantial loss of Q in preparing the Berkeley separates. Chicago data are from LEMS et al. (1977) and from SRINIVA~ANer al. (1977).

Rare-gas-rich separates Murchison

Q

q

(and

1793

from carbonaceous chondrites

Other

C2)

Concentrations

of ‘32Xe

2400 Murchison

Chicago

3

;

Berkeley

Separates

.L>.

Q

This

q

350

comparison

separates.

Note

meteorites

and

Allende

requires similarity

Concentrations

substantial among

(2) the most

of ‘32Xe

preservation (1) Berkeley

gas-rich

samples

of

Q

separates run

directly

in Berkeley from

different

at Chicago.

Fig. 11. Concentrations of ‘32Xe , in terms of amount per gram of sample, in Chicago and Berkeley separates. The gas as studied at Chicago is thought to be partitioned in sub-phases as shown. The high concentrations for Q are not measured directly but by difference. The Berkeley concentrations are for poorly characterized phases prepared by a combination of acid attack and colloid extractions. The comparison requires that there has been substantial pieservation of Q in the preparation of the Berkeley separates because the Berkeley concentrations are higher than for other (non-Q) Chicago sub-phases. Note the similarity among (1) Berkeley separates from different meteorites and (2) the most gas-rich samples run directly at Chicago. Chicago data are from LEWIS er al. (1977) and from SRINIVASANet al. (1977).

tant xenon-bearing phase, presumably ‘Q’, in the Berkeley chemistry. On the other hand when concentration data for the samples themselves are compared (Fig. ll), one finds that the xenon concentration for the LA/ate is much higher than the Chicago concentration for both the chromite and carbon so that, by inference, substantial amounts of ‘Q’ have survived the Berkeley treatment. And the fact remains that Berkeley 1Alates have xenon concentrations equal to the most xenon-rich material measured directly at Chicago. The situation with Murchison is similar. Here 90% of the xenon in the meteorite resides in the acid insoluble residues, according to Chicago work (Fig. 12), with 65% in ‘Q’, 13% in a polymer fraction which dissolves in nitric acid, 9% in a polymer which can be destroyed only by combustion, and 3.5% in a chromite residue. Again the Berkeley 1Alate from Murchison contains only 24% of the xenon expected from the Chicago data (Fig! lo), if the colloidal extraction does not eliminate xenon-bearing material. Again this comparison suggests that important xenon-bearing material, presumably ‘Q’, has been lost from the IAlates. On the other hand concentrations, as measured at Berkeley and Chicago (Fig. ll), require

that a substantial amount of ‘Q’ survived the Berkeley processing and the xenon content of the lAlate is not exceeded in any samples measured directly at Chicago. These two sets of data can coexist, provided just the right amount of gas was lost in the Berkeley chemistry to make the uniform gas contents of the various carbonaceous samples a coincidence. Because of the uncertainties involved in the Chicago characterizations and in some of the measurements of gas content and sample weight at both laboratories, we are not yet ready to abandon the idea that there may be a carbonaceous gas-carrier uniformly present in the various meteorites which have been studied. In isolation from the Chicago studies such would be the most important conclusion of the work reported in this paper.

SUMMARY We prepared carbon-rich separates by demineralization of colloidal fractions after disaggregation of bulk samples of Murray, ‘Murchison, and Cold Bokkeveld (type C2 meteorites). We also obtained acid resistant residues of the Allende meteorite (type C3V)

1794

J. H. REYNOLDS,U. FRICK, J. M. NEIL and D. L. PHINNEY Planetary Rare Gases (Anders

in Murchisan

Meteorite

and cowor&ers)

Acid residu

q Chromite 017 4%’

Combustible polymer 0 IO82 4%

Soluble polymer 0 iI21 wl%l

Q

1003 wrxi

Fig. 12. Characterization of the rare-gas contents of the Murchison meteorite according to SRINIVASAN et al. (1977). Shown is how the total trapped Ne, Ar, Kr and Xe in the meteorite are thought to be distributed among sparse phases (chromite, combustible polymer, soluble polymer and Q) and the remainder of the stone. Mostly the rare gases are in phases which account for very little weight.

by dissolution of most minerals in HCl and HF acids and from those residues extracted a methanol colloid. The carbonaceous separates (or IAlates-a coined word to designate colloids prepared sometimes before and sometimes after acid treatment) were characterized, with difficulty and incompletely as follows: C2 Mlates: Constituting 0.5% of the bulk meteorites by weight, they failed to show resolvable particles in the scanning electron microscope (SEM) and were mostly invisible to energy dispersive X-ray analyses (EDAX) which indicated
crystals but no metallic sulfides under the SEM, the /Abates themselves showed only traces of spine1 and chromite as inferred from relatively uniform distributions of Mg, Al, S, Cl, Cr and Fe throughout the sample. Unwashed samples can contain up to 30% sulfur, but samples washed in CSI showed sulfur contents in the range l-5%. Results obtained in this laboratory, but published elsewhere, on oxidized lA/ates from Allende are reviewed briefly in the main body of the paper. The carbonaceous material in the Allende lAlates is also poorly characterized and apparently free from metallic sulfides. A stepwise heating experiment on a Murray [A/ate showed bimodal release of all noble gases. The patterns for Ar, Kr and Xe were similar; each gas had a low temperature release (20%5oo”C) during which about 35”,/, of the gas came off, followed by a very symmetrical high temperature release with a maximum near 1ooo”C and a virtually complete release at 1500°C. Fitting the high temperature data with a diffusion model resulted in activation energies for the gases ranging from 1.0 to 1.3 eV but an unreasonably low diffusion coefficient, thus making chemical reactions more likely as the mechanism for gas release. It proved to be useful to discuss the isotopic data for helium and neon together. Neon compositions unprecedentedly close to the neon-A corner of the usual 3-isotope diagram supported the original criteria of PEPIN (1967) for the identification of planetary neon. Even so there is evidence in this ‘purest planetary neon’ for a separable component with different “Ne/*‘Ne ratio, quite likely the neon-E proposed in this context by BLACK (1972b). We can contrast the isotopic variations in neon with the constancy of the helium isotopic ratio, which provided a more accurate value for the isotopic composition of primordial helium [3He/4He = (1.42 + 0.2) x 10m4]. A simple

Rare-gas-rich separates from carbonaceous mixture of neon-E and -B, sometimes supposed to form neon-A, continues to be ruled out when examined correctly. Our data for 36Ar/38Ar were not sufficiently precise to illuminate the question of isotopic structure in planetary argon which these samples ought eventually to do, unless the larger variations for this ratio which correlate with the isotopic anomalies in krypton and xenon prove to be overpowering. In these samples, not further treated in this work with oxidizing reagents, we failed to detect the conspicuous occurrence of anomalous heavy noble gases when applying stepwise heating techniques alone. In the final section of the paper, we compare our results with results from the pace-setting program of investigation at Chicago. The Chicago group characterizes their samples (prepared differently from ours) in terms of sub-phases: ‘Q: chromite/carbon, and carbonaceous polymers with various resistance to destruction. The two sets of data have points of similarity (notably agreement in the highest concentrations of heavy rare gases measured directly-as opposed to inferred by difference) but are interpreted quite differently. The Chicago interpretation can apply to both sets of samples provided that the right amount of gas was lost in the Berkeley chemistry to make the uniform gas contents of the various carbonaceous samples a coincidence. In isolation from the Chicago results, our results support the idea of a carbonaceous gas-carrier uniformly present in meteorites of various

chondrites

1795

composition of primordial helium in carbonaceous chondrites. Geochim. Cosmochim. Acta 34, 127-131. ANDERSE., HIGUCHIH., CROS J., TAKAHASHIH. and MORGAN J. W. (1975) Extinct superheavy element m the Allende meteorite. Science 190, 1262-1271. BAUMANA. J.. DEVANEYJ. R. and BOLLINE. M. (1973) Allende meteorite carbonaceous phase: Intractable nature and scanning electron morphology. Nature 241, 264-261. BAUR H., FRICK U., FUNK H., PHINNEYD. L.. SCHULTZ L. and SIGNERP. (1973) Comparison of calculated and measured release patterns of trapped gases. Meteorltics 8, 325-326.

BLACK D. C. (1970) Trapped helmm and neon isotopic correlations in gas-rich meteorites and carbonaceous chondrites. Geochim. Cosmochim. Acta 34, 132-139. BLACKD. C. (1971) Trapped neon-argon isotopic correlations in gas-rich meteorites and carbonaceous chondrites. Geochim. Cosmochim. Acta 35, 230-235. BLACK D. C. (1972a) On the origins of trapped helium, neon, and argon isotopic variations in meteorites-I. Gas-rich meteorites. lunar soil and breccia. Geochlm. Cosmochim. Acta 36, 347-375.

BLACK D. C. (1972b) On the origin of trapped hehum, neon, and argon isotopic variations in meteorites--II. Carbonaceous chondrites. Geochim. Cosmochim. Acta 36, 377-394.

BLACK D. C. and PEPIN R. 0. (1969) Trapped neon m meteorites-II. Earth Planet. Scl. Left. 6, 395-405 BLAKEJ. B. and SCHRAMMD. N. (1976) Nucleosynthesis and anomalous Xe and Kr in carbonaceous chondrites. Nature 263, 701-708,

BOGARDD. D., CLARK R. S., KEITH J. E. and REYNOLDS M. A. (1971) Noble gases and radionuclides in Lost City and other recently fallen meteorites. J. Geophys. Res. 76, 407&4083.

BREGERJ. A., ZUBOVICP., CHANDLERJ. C. and CLARKE types. R. S., JR. (1972) Occurrence and significance of formaldehyde m the Allende carbonaceous chondrite. Nature 236, 155-158. Acknowledgements-The vacuum pyrolysis experiments CHANGS. (1976) Work in progress. were carried out in the laboratory of Dr. A. L. BURLCLAYTOND. D. (1975) Extinct radioactivities: trapped resiINGAME (Space Science Laboratory, Berkeley); we also duals of presolar grains? Astrophys. J. 199, 765-769. thank him for providing us with a large sample of the Allende meteorite. We are indebted to Dr. J. N. GOSWAMI DAKOWSKIM. (1969) The possibility of extinct superheavy elements occurrmg in meteorites. Earth Planet. Ser. Lett and S. NIEMEYERfor their assistance when using the scan6, 152-154. ning electron microscope, and to Prof. H. R. WENK and DROZD R. J., MORGANC. J., PODOSEKF A., POPEAUG.. Dr. H. U. NISSEN(Department of Geology and Geophysics, SHIRCKJ. R. and TAYLORG. J. (1977) 244Pu m the earlv Berkeley) for their expertise on the work with the transmissolar system? Astrophys. J. 212; 5671580. sion electron microscope. We gratefully acknowledge the P. (1974) A neon-E rich phase in the Orgueil contributions to the carbon chemistry by Dr. S. CHANG EBERHARDT carbonaceous chondrite. Earth Planet. Sci. Lett. 24, and K. LENNON(NASA Ames Research Center, Moffett 182-187. Field). We thank Prof. P. B. PRICE for the Murchison EBERHARDTP. (1975) Neon-E rich phase m Orgueil. sample and Dr. J. D. MACDOUGALLfor the Cold BokkeMeteordcs 10, 401 veld sample (a ‘rejected’ fraction from a search for large EBERHARDT P., EUGSTER0. and MARTI K. (1965) A redesilicates). We thank Dr. E. P. HENDERSONof the U.S. termination of the isotopic composition of atmospheric National Museum for providing the sample of Murray. neon. 2. Naturforsch. 2&x, 623-624. The authors appreciate the efforts of G. MCCRORYmainEBERHARDTP., GEISSJ., GRAF H., GR~GLER N., MENDIA taining the mass spectrometer in an operating mode and M. D., M~RGELIM., SCHWALLER H., STETTLER A., KRAwe finally thank J. AMORCJ~IJ for her help in preparing the HENJHJHL U. and VON GUNTEN H. R. (1972) Trapped manuscript. This work was supported in part by NASA solar wind noble gases m Apollo 12 lunar fines 12001 and in part by DOE and bears Code Number and Apollo 11 breccia 10046. Proc. Third Lunar Sci. UCB-34P32-109. Conf. Geochlm. Cosmochlm. Acta Suppl. 3, pp. 1821-1856. MIT. EUGSTER0.. EBERHARDTP. and GEISSJ. (1967a) The isoREFERENCES topic composition of krypton in unequilibrated and gasrich chondrrtes. Earth Planet. Sci. Lett. 2, 385-393. ANDERSE. (1964) Origin, age and composttion of meteorEUGSTERO., EBERHARDT P. and GEISSJ. (1967b) Krvoton ites. Space Sci. Rev. 3, 583-714. and xenon isotopic composrtion in three carbonaceous ANDERSE. (1971) Meteorites and the early solar system. chondrites. Earth Planet. Sci. Left. 3. 24!&257. Ann. Rec. Astron. Astrophys. 9, l-34. ANDERSE. and HEYMANND. (1969) Elements 112 to 119: FECHTIGH. and KALBITZE~(1966) The diffusion of Ar m K bearmg sohds. In Potassirrm Argon Datmg (eds. J. Were they present in meteorites? Science 164, 821-823. Zlhringer and 0. A. Schaeffer), pp. 68-107 Springer. ANDERSE., HEYMANND. and MAZOR E. (1970) Isotopic

1796

J. H. REYNOLDS,U FRICK, J. M. NEIL and D. L. PHINNEY

FIREMANE. L, DE FELICEJ. and NORTON E. (1970) Ages of the Allende meteorite. Geochrm. Cosmochim. Acfa 34.

ceous

chondrite

Murchtson.

J.

Geophyx

Res.

80,

1558-1570.

873-881. LAUL J. C., GANAPATHYR., ANDERSE. and MORGANJ. FRAUNDORFP., FLYNN G. J., SHIRCK J. R. and WALKER W. (1973) Chemical fracttonations m meteorites: VI. R. M. (1977) Search for fission tracks from superheavy Accretton temperatures of H-, LL- and E-chondrites from abundance of volatile trace elements. Geochim. Coselements in Allende. Earrh Planet. Sci. Left. 37, 285-295. FRICK U. (1977) Anomalous krypton in the Allende mochim. Acta 37. 329-357. meteorite. Proc. Eighth Lunar Sci. Conf Geochim. CosmoLEWISR. S., GROSJ. and ANDERSE. (1977) Isotopic anomchim. Acta Suppl. 8, pp. 273-292. Pergamon Press. alies of noble gases in meteorites and then origin-2. FRICK U., BAUR H., FUNK H., PHINNEYD., SCHAEFERCHR., Separated mmerals from Allende. J. Geophys. Res. 82, SCHULTZ L. and SIGNERP. (1973) Diffusion properties 779-792. of hght noble gases m lunar fines. Proc. Fourth Lunar LEWISR. S.. SRINIVASAN B. and ANDERSE. (1975a) Origin Sci. Conf: Geochim. Cosmochim. Acta Suppl. 4. pp. of noble gases m Allende-II. Sources of fission xenon. 1987-2002. Pergamon Press. Meteorttics 10, 444445 LEWIS R. S.. SRINIVASANB. and ANDERSE. (1975b) Host FRICI(. U. and MONIOTR. K. (1977) Planetary noble gas phase of a strange xenon component in Allende Science components in Orgueil. Proc. Eighth Lunar Sci. Conj: Geochim. Cosmochim. Acta Suppl. 8, pp. 229-261. Perga190, 1251-1262. MACDOUGALL J. D. and PHINNEYD. L. (1977) Noble gases mon Press. FRICK U. and REYNOLDS J H. (1977) On the host phases and particle tracks in olivine crystals from Murchison of planetary noble gases m Allende (abstract). In Lunar and Cold Bokkeveld. In Lunar Science VIII, pp. 605-607 Science VIII. pp. 319-321. The Lunar Sctence Instttute. Lunar Science Institute, Houston. Houston. MAMYRINB. D.. ANUFRIYEFG. S.. KAMENSKIYI D. and FUNK H.. BAUR H., FRICK U., PHINNEYD.. SCHULTZL. TOLSTIKHINI. N (1970) Determmation of the tsotopic and SIGNER P. (1973) Release patterns of natural and compositton of atmospheric hehum. Geochem. Int. 7, 498-505 (Transl. from Geohimiva 6, 721-730). low energy Implanted argon from separates of lunar fines. Meteorttics 8, 369-370. MANUEL0: K.. HENNECKEE. W: and SABU D. D. (1972b) GEISS J (1973) Solar wind compositton and tmplications Xenon m carbonaceous chondrites. Nature 240, 99-101. about the htstory of the solar system. 13th Int. Cosmic MANUEL0. K. and SABU D D. (1975) Elemental and isotoptc inhomogeneities in noble gases: the case for local Ray Conf: 1973, Vol. 5. pp. 3375-3398. Univ. of Denver, synthests of the chemical elements. Trans. Mtssouri Acad Denver. Colorado GEISS J.. BUEHLERF.. CERUTTIH., EBERHARD~ P. and FILSci. 9. 104-122. LEUX CH. (1972) Solar wind composition experiment. MANUEL0. K.. WRIGHTR J., MILLERD K. and KURODA P. K. (1970) Heavy noble gases in Leovilie. the case Apollo 16 Prelim. Sci. Report, NASA SP-315, Sec. 14, for fracttonated xenon in carbonaceous chondrites. J. pp. l-10. Geophys. Res. 75. 5693-5701. GERLINGE. K and LEVSKIIL. K. (1956) Origin of inert MANUEL0. K.. WRIGHTR. J., MILLERD K. and KURODA gases in stone meteorttes. Dokl. Akad. Nuuk. Sci. U.S.S.R. 110. 750-753 P. K. (1972a) Isotopic composition of rare gases in the GIBSON E. K. (1976) Prtvate communication: he detercarbonaceous chondrites Mokota and Allende. Geochim. Cosmochrm. Acta 36, 961-983. mmed the sulfur content of an Allende separate, used to calibrate work with energy dispersive X-ray analysts. MARTIK. (1969) Solar type xenon: a new isotopic compoGOEBELR.. OTT U. and BEGEMANNF. (1977) On trapped sition of xenon in the Pesyanoe meteortte. Science 166, noble gases in urethtes. J. Geophys. Res. 83, 8551867. 1263-1265. GREEN G. W.. RADCLIFFS. V. and HEUER A. H. (1971) MAZORE., HEYMANND. and ANDERSE. (1970) Noble gases Allende meteorite: a high voltage electron petrographic in carbonaceous chondrites. Geochim. Cosmochim. Acta study. Science 172, 936939. 34, 781-824. GROS J. and ANDERSE. (1977) Gas rtch mmerals in the NAGY B. (1975) Carbonaceous Meteorttes. Elsevter. Allende meteorrte: attempted chemical characterization NIEDERERF. and EBERHARDTP. (1977) A neon-E-rich Earth Planet. Sci. Lett. 33, 401-406. phase in Dtmmitt Meteoritic5 12, 327-331. HA~ATSUR, MATSUOKAS.. SCOTTR. G.. STUDIERM. H. NIER A. 0. (1950a) A redetermmation of the relative abunand ANDERSE. (1977) Origm of organic matter in the dances of the isotopes of carbon, nitrogen, oxygen, argon early solar system-VII. The orgamc polymer m carand potassmm. Phys. Rev. 77, 789-793. bonaceous chondrites. Geochim. Cosmochim. Acta 41, NIER A. 0. (1950b) A redetermination of the relative abun1325-1339. dances of the isotopes of neon, krypton. rubrdium, xenon HAYESJ. M. (1967) Organic constituents of meteorites-a and mercury. Phys. Ret’. 79, 451X454. review. Geochtm. Cosmochim. Acta 31, 1395-1440. OTTING W. and Z~HRINGERJ. (1967) Total carbon and HERZOG G. F. and ANDERSE. (1974) Primordial noble primordtal rare gases in chondrites Geochim. Cosmogases m separated meteorittc minerals-II. Earth Planet. chim. Acta 31, 194991960. Ser. Lett 24, 173-181. PEPIN R. 0. (1964) Isotopic analysis of xenon. In The OriJEFFERYP. M. and ANDERSE. (1970) Primordtal noble gin and Evolution of Atmospheres and Oceans (eds. P. J. gases m separated meteoritic mmerals-I. Geochtm. CosBrancazto and A. G. W. Cameron). pp. 191-234. Wiley. mochrm. Acta 34, 1175-l 198. PEPIN R. 0. (1967) Trapped neon in meteorites. Earth KIRSTENT, KRAN~OWSKID. and Z~HRINGERJ. (1963) Planet. Ser. Lett. 2, 13-18. Edelgas- und Kahumbesttmmungen an einer grosseren PEPIN R. 0. (1968) Neon and xenon in carbonaceous Anzahl von Steinmeteortten. Geochim. Cosmochim. Acta meteorites. In Origin and Distribution of the Elements (ed. 27, 13-42 L. H. Ahrens). pp. 379-386. Pergamon Press. KURODA P. K.. BECK J. N.. EFURD D. W. and MILLER PEPIN R. 0. (1976) Prtvate communication: provided us D. K. (1974) Xenon isotopic anomalies in the carbonaan extensive body of partially pubhshed and compiled ceous chondrite Murray. j. Geophys. Res. 79, 3981-3992 data. KURODAP. K. and MANUEL0. K. (1970) Mass fractionPEPIN R. 0. and SIGNERP. (1965) Primordial rare gases ation and isotope anomalies in neon and xenon. Nature m meteorites. Science 149, 253-266 227, 1113-1116. PHINNEY D. L. (1971) Heavy noble gases m selected KURODAP K., SHERRILLR. D.. EFURD D. W and BECK meteoritic and terrestrtal minerals. Ph D. thesis, UnwerJ N (1975) Xenon

isotopic

anomahes

m the carbona-

sity of Minnesota,

Minneapolis

Rare-gas-rich separates from carbonaceous PHINNEYD. L., FRICK U. and REYNOLDS J. H. (1976) Raregas-rich separates from carbonaceous chondrites (abstract). In Lunar Science VII. pp. 691-693. The Lunar Science Institute, Houston. REYNOLDSJ. H. (1956) High sensitivity mass spectrometer for noble gas analysis. Rev. Sci. Instrum. 27, 928-934. REYNOLDS J. H. (1960) Isotopic composition of primordial xenon. Phys. Rev. Lett. 4, 351-354. REYNOLDS J. H. (1961) Xenon in stone meteorites. In Prob/ems related to Interplanetary Matter. Nat. Acad. Sci.Nat. Res. Coun., Publ. 845, Report No. 33 in Nuclear SU. Series 9. 9-14.

REYNOLDS J H. and TURNERG. (1964) Rare gases in the chondrite Renazzo. J Geophys. Res. 69, 3263-3281. SHERRILLR. D. (1976) Rare gas Isotopic abundances in meteorites and terrestrial samples. Ph.D. thesis, Umverslty of Arkansas, Fayetteville. SIGNERP. and SUESSH. E. (1963) Rare gases in the sun, in the atmosphere and m meteorites. In Earth Scwnce and Meteoruics. pp. 241-272. North Holland. SIGNERP. (1964) Primordial rare gases in meteorites. In The Origin and Evolution of Atmospheres

and Oceans

(eds. P. J. Brancazlo and A. G. W. Cameron). pp. 183-196. Wdey. SIMMONDS P. G., BAUMANA. J., BOLLINE. M., GELP E. and 0~6 J. (1969) The unextractable organic fraction of the Pueblito de Allende meteorite: evidence for its indigenous nature. Proc. Nat/. Acad. Sci. U.S.A. 64, 1027-1034. SIMONEI~B. R., CHRISTIANSEN P. and BURLINGAME A. L. (1973b) Volatile element chemistry of selected lunar, meteoritic, and terrestrial samples. Proc. Fourth Lunar Sci. Conf Geochim. Cosmochlm. Acta Suppl. 4, pp. 1635-1650 Pergamon Press. SIMONEIT B. R., WSZOLEKP. C., CHRISTIANSEN P., JACKSON R. F. and BURLINGAME A. L. (1973a) Carbon chemistry of Luna 16 and Luna 20 samples. Geochim. Cosmochim. Acta 37, 1063-1074. SMITHS. P., HUNEKEJ. C. and WA~~ERBURG G. J. (1978) Neon in gas-rich samples of the carbonaceous chondrites

Mokola.

1797

chondrites Murchison,

and

Cold

Bokkeveld.

Earth

Planet. Sci. Lett. 39, l-13.

SRINIVASANB. (1977) Noble gases in SIX ordmary chondrltes: comparison of exposure ages from noble gases with 26A1 ages. Geochlm. Cosmochim Acta 41, 977-983. SRINIVASAN B., ALEXANDER E. C., JR., MANUEL0. K. and TROUTNERD. E. (1969) Xenon and krypton from the spontaneous fission of Cahfornium-252. Phvs. Rec. 179. 11661169. SRINIVASAN B., GROSJ. and ANDERSE. (1977) Noble gases in separated meteoritic mmerals: Murchlson C2, Ornans C3, Karoonda C5 and Abee E4. J Geophys. Res. 82, 762-778. SRINIVASAN B., LEWIS R. S. and ANDERSE (1975) Orlgm of noble gases m Allende-I. Host phases of fission xenon and other gases. Meteoritics 10, 491-492. SUESS H. E., W~NKE H. and WLOTZKAF. (1964) On the origin of gas-rich meteorites Geochim. Cosmochrm. Acta 28, 595607.

SCHMUSW. R. and WOOD J. A. (1967) A chemicalpetrologic classification for the chondritic meteorites.

VAN

Geochim. Cosmochim. Acta 31, 747-765.

WKNKEH. (1965) Der Sonnenwind als Quelle der Uredelgase in Steinmeteorlten. Z Naturforsch. 20a, 946-949. WEBERH. W., BEGEMANN F. and HINTENBERGER H. (1976) Primordial gases in graphite-diamond-kamazlte mclusions from the HaverG ureihte. Earth Planet Ser. Lett. 29, 81-90.

WSZOLEKP. C., SIMONEITB. R. and BURLINGAMEA. L. (1973) Studies of magnetic fines and volatile-rich sods: possible meteoritic and volcanic contributions to lunar carbon chemistry and light element chemistry. Proc. Fourth Lunar Sci. Conf Geochim. Cosmochlm. 4cta Suppl. 4, pp. 169%1706. Pergamon Press.

Z~HRINGERJ. (1962) Isotople-Effekt und Hiufigkeiten der Edelgase in Steinmeteorlten und auf der Erde. Z. Naturforsch. 17a, 46-71. Z;~HRINGER J. (1966) Primordial argon and the metamorphism of chondrites. Earth Planet. Scl. Lett I, 379-382