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1 

2 

3 

Shock effects in “EH6” enstatite chondrites and implications 

for collisional heating of the EH and EL parent asteroids 

4 Alan E. Rubin a, *, John T. Wasson a,b,c 

5 Q1 

6 

7 

a 

Institute of Geophysics and Planetary Physics, University of California, Los Angeles, CA 90095-1567, USA 

b 

Department of Earth and Space Sciences, University of California, Los Angeles, CA 90095, USA 

c 

Department of Chemistry and Biochemistry, University of California, Los Angeles, CA 90095, USA 

89 Received 10 January 2011; accepted in revised form 5 April 2011 

10 Abstract 

GCA 7175 No. of Pages 25 

26 April 2011 Disk Used 

11 Of the six chondrites that were listed as EH6 or EH6-an during the course of this study, we confirm the EH classification of 

12 Y-8404, Y-980211 and Y-980223 and the EH-an classification of Y-793225; two chondrites (A-882039 and Y-980524) are 

13 reclassified as EL (the former contains ferroan alabandite and both contain kamacite with 1 wt% Si). All of the meteorites 

14 contain euhedral enstatite grains surrounded by metal ± sulfide (although this texture is rare in Y-793225), consistent with 

15 enstatite crystallizing from a mixed melt. All contain enstatite with 0.5,Mg



2 A.E. Rubin, J.T. Wasson / Geochimica et Cosmochimica Acta xxx (2011) xxx–xxx 

48 The current classification scheme for petrologic types is 

49 based on criteria developed by Van Schmus and Wood 

50 (1967) and modified by later workers. It can be applied to 

51 ordinary, carbonaceous, enstatite and R chondrites. In all 

52 of these groups, type-3 chondrites contain very sharply de- 

53 fined chondrules (some with primary igneous glass), fine- 

54 grained silicate-rich matrix material, polysynthetically 

55 twinned low-Ca clinopyroxene, and compositionally 

56 unequilibrated olivine and low-Ca pyroxene. Type-4 chon- 

57 drites contain well-defined chondrules (with little or no 

58 glass), matrix material that is either absent or recrystallized, 

59 relatively few grains of polysynthetically twinned low-Ca 

60 clinopyroxene, equilibrated olivine and largely equilibrated 

61 low-Ca pyroxene. Type-5 chondrites have readily delin- 

62 eated chondrules with no primary glass, no fine-grained 

63 matrix material, no polysynthetically twinned low-Ca clino- 

64 pyroxene, and compositionally uniform olivine and low-Ca 

65 pyroxene. Type-6 chondrites contain poorly defined chond- 

66 rules with no glass, no fine-grained matrix material, no 

67 polysynthetically twinned low-Ca clinopyroxene, uniform 

68 olivine and low-Ca pyroxene compositions, and many pla- 

69 gioclase grains that exceed 50 lm. (Olivine is absent in 

70 many type-4 and all type-5 and -6 enstatite chondrites.) 

71 Although some chondrites have been designated type 7 

72 because they are highly recrystallized or contain melt (or 

73 contain orthopyroxene with >1 wt% CaO; Dodd, 1974), 

74 many of these rocks (e.g., L7 PAT 91501; EL7 Ilafegh 

75 009) have been impact melted (e.g., McCoy et al., 1995; 

76 Mittlefehldt and Lindstrom, 2001) and should be classified 

77 as impact-melt rocks or impact-melt breccias. There are 

78 also many ordinary chondrites (OC) listed in the on-line 

79 Meteoritical Bulletin Database (MBDB) as type 6 that 

80 have been shown to be impact-melt breccias: e.g., H6 Yan- 

81 zhuang (Xie et al., 1991), L6 Chico (Bogard et al., 1990) 

82 and LL6 Bison (Dominik and Bussy, 1994). Even a few 

83 OC listed as type 5 are impact-melt breccias: e.g., H5 Rose 

84 City (Mason and Wiik, 1966; Fruland, 1975; Rubin, 

85 1995a) and L5 Cat Mountain (Kring et al., 1996). If the 

86 principal mechanism responsible for chondrite metamor- 

87 phism is collisional heating (e.g., Rubin, 1995b, 2004, 

88 2005) and not the decay of short-lived radionuclides 

89 (e.g., Lee et al., 1976; Miyamoto et al., 1981; Grimm 

90 and McSween, 1993; McSween et al., 2002), then the dis- 

91 tinction between impact-melt breccias and type-5, -6 and - 

92 7 chondrites becomes blurred. 

93 In the present study, we examined all six enstatite 

94 chondrites that had been classified by others (and listed 

95 in the MBDB during the course of this study) as EH6 

96 or EH6-an to determine whether or not they have 

97 petrologic features consistent with having been heated by 

98 impacts. These rocks include five EH6 chondrites 

99 (A-882039, 384 g; Y-8404, 10.7 g; Y-980211, 36.9 g; 

100 Y-980223, 116.2 g; Y-980524, 24.3 g) and one EH6-an 

101 chondrite (Y-793225, 75.6 g). Other than the study by 

102 Lin and Kimura (1998) that described Y-8404 as an im- 

103 pact-melt rock and Y-793225 as a new kind of enstatite 

104 chondrite (intermediate between EH and EL), the meteor- 

105 ites classified as EH6 chondrites have received scant atten- 

106 tion. As shown below, our new data have led us to accept 

107 the EH classifications of Y-8404, Y-980211 and Y-980223, 

to accept the EH-an classification of Y-793225, and to 

reclassify A-882039 and Y-980524 as EL chondrites. We 

also show that all six chondrites in this study exhibit textural 

and mineralogical characteristics indicative of impact 

melting (Appendix A) and are considered impact-melt 

rocks or impact-melt breccias. 

2. ANALYTICAL PROCEDURES 

The following thin sections were borrowed from the National 

Institute of Polar Research, Japan: A-882039,72-1; 

Y-793225,51-2; Y-8404,51-2; Y-980211,51-1; Y-980223,61- 

2 and Y-980524,51-1. These sections were examined in 

transmitted and reflected light with an Olympus BX60 petrographic 

microscope. Mineral compositions were determined 

with the JEOL electron microprobe at UCLA 

using natural and synthetic standards, a sample current of 

15 nA, an accelerating voltage of 15 keV, 20-s counting 

times per element, ZAF corrections, and a focused beam. 

Cobalt values were corrected for the interference of the 

Fe-Kb peak with the Co-Ka peak. It is possible that the 

enstatite FeO values in Table 1 are too high because of electron-beam 

overlap on tiny metal blebs included within the 

enstatite grains or because of excitation of Fe atoms in 

neighboring kamacite grains by bremsstrahlung or doubly 

backscattered electrons (Wasson et al., 1994). 

The modal abundance of silica was estimated in some 

samples by point counting on the electron microprobe 

(n = 50), moving the stage a fixed distance, and identifying 

the phase under the crosshairs by EDS. 

We used instrumental neutron activation analysis 

(INAA) to determine the bulk compositions of adjacent 

chips of Y-793225 (290.2 mg), A-882039 (273.8 mg), Y- 

980223 (299.9 mg) and EH4 Indarch (237.9 mg). Meteorites 

belonging to other chondrite groups (CM, CK, CR and R) 

were included in the runs, affording more control of the 

quality of the data set. Samples were generally analyzed 

as 3-mm-thick rectangular prisms. The sawn surfaces were 

cleaned with SiC paper; rusty patches on other surfaces 

were flaked off with stainless-steel dental tools. 

The samples have experienced only mild terrestrial 

weathering that should have minor to negligible effects on 

their bulk compositions: A-882039 is listed as weathering 

category A (Meteorite Newsletter 15), Y-980223 is listed 

as category A/B (Meteorite Newsletter 16), and although 

no weathering category is given for Y-793225, our examination 

of a thin section shows it to be weathering group W2 

on the scale developed by Wlotzka (1993). 

Samples were irradiated for 3hat the TRIGA Mark I 

reactor of the University of California, Irvine with a rotating-tray 

(lazy-susan) flux of 1.8 10 12 neutrons cm 2 s 1 

for the determination of isotopes with half-lives of several 

hours and more. For counting, the samples were mounted 

on cardboard slides. For standards we used the Allende 

meteorite (Jarosewich et al., 1987), the USGS international 

reference materials GSP-1 and BHVO-1 (Govindaraju, 

1994), and the North Chile (Filomena) IIAB iron meteorite. 

Analyses were carried out following a protocol similar to 

that described in Kallemeyn et al. (1989) and Choe et al. 

(2010). 

Please cite this article in press as: Rubin A. E. and Wasson J. T. Shock effects in “EH6” enstatite chondrites and implications for collisional 

heating of the EH and EL parent asteroids. Geochim. Cosmochim. Acta (2011), doi:10.1016/j.gca.2011.04.002 

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Table 1 

Mean compositions (wt%) of silicate phases. 

Enstatite Plagioclase Silica a 

Y-793225 Y-793225 Y-8404 Y-8404 Y-980211 Y-980223 A-882039 Y-980524 Y-793225 Y-793225 Y-8404 A-882039 Y-980524 Y-8404 

Source 1 2 1 2 1 1 1 1 1 2 2 1 1 1 

No. of grains 7 14 1 11 3 2 22 30 4 17 10 4 8 2 

SiO2 59.2 60.0 59.0 60.5 59.2 59.7 60.0 59.3 65.3 66.0 70.2 66.5 66.8 98.6 

TiO2




166 3. RESULTS 

167 3.1. Petrography 

168 Detailed petrographic descriptions of Y-8404, Y-980211, 

169 Y-980223, Y-980524, Y-793225 and A-882039 are in 

170 Appendix B; corresponding images are in Figs. 1–8. A sum- 

171 mary of the main petrographic features of these meteorites 

172 appears below. 

173 All of the rocks have major orthoenstatite; in all samples 

174 except Y-793225, euhedral enstatite grains are abundant 

175 (Figs. 1, 3, 4 and 6). Plagioclase is present in all of the sam- 

176 ples and abundant silica occurs in Y-8404 and Y-980223. 

177 All of the rocks contain kamacite and troilite; other opaque 

178 phases present in several samples include schreibersite, 

179 graphite and daubréelite (e.g., Fig. 7). Keilite occurs in Y- 

180 8404, Y-980211 and Y-980223; ferroan alabandite is pres- 

181 ent in Y-793225 and A-880239. 

182 Enstatite in each of these meteorites has sharp to mod- 

183 erately undulose extinction, corresponding to shock stages 

184 S1–S2 (Stöffler et al., 1991; Rubin et al., 1997). 

Fig. 1. Euhedral enstatite grains displaying prominent cleavage in 

Y-8404. (a) Black areas are opaque grains. Plane-polarized 

transmitted light. (b) The same region as in (a). White areas are 

kamacite; medium-gray areas are troilite. Reflected light. 

In all of the samples, enstatite is intergrown with other 

silicates. In Y-980211 and Y-980223, an opaque groundmass 

surrounds the silicate assemblages (Fig. 3). Y- 

793225 has a hypidiomorphic-granular texture (Fig. 5). Relict 

chondrules (e.g., Figs. 2, 4 and 8) are present in all of the 

rocks except Y-793225. In some cases, enstatite grains appear 

to have nucleated on the relict chondrules. 

3.2. Mineral chemistry 

In order to determine the proper classification of the 

meteorites in this study, it is necessary to compare their 

mineral chemistry to the established ranges for enstatite 

chondrites. EH3, EH4 and EH5 chondrites typically contain 

enstatite with 0.13–0.20 wt% MnO (e.g., Keil, 1968; 

Grossman et al., 1985); the MnO content of enstatite in 

each of the chondrites studied here is below the detection 

limit, i.e.,



Fig. 3. Kamacite–troilite nodule with euhedral enstatite grains in 

Y-980211. The troilite-rich side of the nodule at right grades into 

the groundmass. kam = kamacite; troi = troilite. Reflected light. 

201 MnO also occurs in EL6 chondrites (Keil, 1968) and in the 

202 Abee EH impact-melt breccia (Rubin and Keil, 1983; Ru- 

203 bin and Scott, 1997; Rubin, 2008). 

204 Plagioclase in Y-793225 (Ab81 Or5; Table 1) is less sodic 

205 and much more potassic than that in EH4 Indarch (Ab97.6 

Collisional heating of enstatite chondrites 5 

Or0.8; Keil, 1968). The published plagioclase composition of 

Y-8404 (Ab94 Or6) (Lin and Kimura, 1998; Table 1) appears 

to be non-stoichiometric; it is moderately enriched 

in SiO2 and Na2O and moderately depleted in Al2O3. Plagioclase 

in A-882039 (Ab79.5 Or4.7) and Y-980524 (Ab80.9 

Or4.4) (Table 1) are within the range of typical EL6 chondrites 

(Ab79.4–82.9 Or2.9–4.6; Keil, 1968) (although A- 

880239 plagioclase is slightly more potassic than the extreme 

value reported by Keil, 1968). 

Silica in Y-8404 contains 1.5 wt% minor oxides (Table 

1), consistent with the phase having an open crystal structure 

(i.e., cristobalite and/or tridymite) rather than quartz. 

(Quartz occurs in several EH3, EH4, EH5, EL3 and EL6 

chondrites as well as in the Y-82189 EH impact-melt rock 

(Mason, 1966; Kimura et al., 2005).) 

Whereas most EH3–5 chondrites have troilite with 0.05– 

0.11 wt% Mn (e.g., Keil, 1968), Y-8404, Y-980211 and Y- 

980223 contain troilite with much higher Mn (i.e., 0.19– 

0.30 wt%; Table 2). In contrast, the low Mn contents of 

troilite in Y-793225 (0.5,Fe




Fig. 5. Texture of EH6-an Y-793225. (a) Abundant enstatite grains 

form a hypidiomorphic-granular texture. Grains display prominent 

cleavage. Crossed nicols. (b) Different region than in (a). The rock 

has a high silicate/opaque modal abundance ratio. Opaques include 

kamacite (white) at bottom left and top left, troilite (medium gray) 

and terrestrial weathering products (light gray). Reflected light. 

kam = kamacite; sil = silicate; troi = troilite. 

231 [(Fe>0.5,Mg



Fig. 6. Euhedral enstatite grains in A-882039. (a) Several euhedral enstatite grains (medium gray) occur adjacent to troilite (light gray) at the 

side of a large kamacite grain (white). (b) Euhedral enstatite grain and a cluster of more-equant enstatite grains (dark gray) in a sulfide 

assemblage consisting of troilite (light gray), ferroan alabandite (medium gray) and tabular daubréelite (smooth texture, very light gray; top of 

assemblage). (c) Euhedral enstatite grains (medium gray) within kamacite (white) and adjacent to massive schreibersite (light gray; distinctly 

darker than kamacite). Also present within the metal are several intergrowths of graphite (dark gray). (d) Massive silicate assemblage (medium 

gray) protruding into kamacite grain (white) that contains graphite clusters and tabs (dark gray). en = enstatite; daub = daubréelite; 

troi = troilite; sil = silicate; alab = ferroan alabandite; kam = kamacite; sch = schreibersite; gr = graphite. All images in reflected light. 

311 In Fig. 9b the patterns for EH4 Indarch and EH6 Y- 

312 980223 are quite similar, implying that the EH group is lar- 

313 gely isochemical. All data plot within 10% of the EH line 

314 with the exception of Zn, for which abundance ratios are 

315 1.5–2 times higher than mean EH. Kallemeyn and Wasson 

316 (1986) also reported that Indarch had the highest Zn value 

317 among the EH falls that they studied, and was 1.4 times 

318 higher than their reported EH mean. The Indarch fall is 

319 one of the best-preserved EH4 chondrites, one that has lar- 

320 gely avoided impact alteration. 

321 At the other extreme is the pattern for Y-793225. All of 

322 the elements plot low; nevertheless, the replicates agree to 

323 within a factor of 1.2 with the exception of Zn (where 

324 the values vary by a factor of 1.5). It is possible that the sys- 

325 tematically low abundance ratios result from Cr values that 

326 are unrepresentatively high. (The data are normalized to 

327 Cr.) In fact, the Cr concentrations of 4.4 mg/g in Y- 

328 793225 are 33% higher than in any of the Kallemeyn and 

329 Wasson (1986) data for EH or EL chondrites. On the other 

330 hand, there is no petrographic evidence that either of the 

331 two values (which are essentially identical) is unrepresenta- 


tive for Y-793225. One test is provided by the lithophile 

plot (Fig. 9a) in which some well-determined elements 

(Sc, Sm) plot near the EH line. As discussed in this study, 

the bulk composition of Y-793225 seems to have been affected 

by impact processes, and it is possible that our INAA 

samples were enriched in a high-Cr component, perhaps 

daubréelite. (Lin and Kimura (1998) reported 1 vol% 

daubréelite in Y-793225.) 

In Fig. 9b the pattern of A-882039 is more similar to the 

mean EL pattern than to the mean EH line. The agreement 

with mean EL chondrites for Sb and the eight more-refractory 

elements would be excellent if the Cr values were 1.2 

times higher; in fact, the Cr concentrations are lower in 

A-882039 than those in all of the EH chondrites and all except 

two of the EL chondrites studied by Kallemeyn and 

Wasson (1986). The two more-volatile elements, Se and 

Zn, are slightly lower than EL, but are within the range observed 

for EL chondrites by Kallemeyn and Wasson (1986), 

even if one were to increase the Cr value by a factor of 1.2. 

The patterns appear less regular on the “lithophile” plot 

(Fig. 9a), but this is partly because the plotted range in 



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Fig. 7. Graphite books in A-882039. (a) Elongated graphite book 

(medium gray) occurring mainly inside silicate (dark gray) but with 

opposite termini touching troilite (light gray) and keilite (lightmedium 

gray). (b) Isolated graphite book (medium gray) completely 

enclosed within silicate (dark gray). gr = graphite; 

keil = keilite; sil = silicate; troi = troilite; kam = kamacite. Both 

images in reflected light. 

353 abundance ratios is only a factor of 5, much smaller than 

354 the factor of 120 plotted in Fig. 9b. In fact, all the replicate 

355 ratios agree to within a factor of 1.25 with the exception of 

356 Eu in Y-793225 and Ca, La, Sm and Eu in Y-980223; in all 

357 the latter cases, the abundance ratio in the second replicate 

358 is much lower than in the first. 

359 Even though Eu is a moderately well-determined ele- 

360 ment by our INAA technique, the overall range in Eu for 

361 the analyzed enstatite chondrites is a factor of 4. The dif- 

362 ferences between replicates for individual meteorites are 

363 much smaller; the factors range from 1.3 to 1.7. 

364 The bulk composition of siderophiles and chalcophiles 

365 in Y-980223 is very similar to that of EH4 Indarch in 

366 Fig. 9b, but the two meteorites show very different patterns 

367 for “lithophiles” (Fig. 9a). The two replicates of Y-980223 

368 show large differences that are almost certainly the result 

369 of sampling variations. 

370 Because of the scatter in the Y-980223 “lithophile” data 

371 (Fig. 9a), it is difficult to use these data to determine 

372 whether this meteorite is more closely related to EH or 

373 EL chondrites. In contrast, the siderophile and Zn data 

374 (Fig. 9b) indicate that Y-980223 is an EH chondrite. 

In Fig. 9a the abundance ratios for A-882039 agree to 

within a factor of 1.2 for all elements. The pattern is reasonably 

close to the EL curve, and would be even closer if 

Cr were increased by a factor of 1.1. 

4. DISCUSSION 

4.1. Group classification of impact-melted enstatite 

chondrites 

The principal petrographic, mineralogical and bulk 

compositional distinctions between EH and EL chondrites 

include mean chondrule size (ca. 220 lm in EH vs. 

550 lm in EL; Rubin, 2000), the Si content of kamacite 

(2.3–3.8 vs. 1.0–2.1 wt%, respectively; Keil, 1968), the identity 

of the cubic (Mg,Fe,Mn)S sulfide (niningerite or keilite 

in EH, ferroan alabandite in EL; Keil, 1968, 2007) and the 

bulk abundances of siderophile and chalcophile elements 

(high in EH, low in EL; Se and Zn are particularly good 

discriminators; e.g., Kallemeyn and Wasson, 1986). Because 

the chondrites studied here are recrystallized and evidently 

melted (Section 4.2), average chondrule size cannot 

be used as a distinguishing characteristic; most chondrules 

(particularly the small ones) have been recrystallized and 

rendered unrecognizable in these rocks. 

Y-8404, Y-980211 and Y-980223 are confirmed to be 

EH chondrites. Consistent with being members of the EH 

group, they contain P2.6 wt% Si in kamacite (Table 3); 

they also contain keilite and lack ferroan alabandite (Table 

2). Y-980223 has relatively high abundances of Se and Zn 

(Table 4). (Bulk compositions were not determined for Y- 

8404 or Y-980211.) These meteorites have all experienced 

high temperatures: they contain orthoenstatite to the exclusion 

of clinoenstatite; they have recrystallized textures and 

relict chondrules that are texturally partially integrated with 

the matrix. 

A-882039 and Y-980524 are reclassified as EL 

chondrites. They average 1.0 and 1.1 wt% Si in kamacite, 

respectively (Table 3). They both lack niningerite and keilite. 

A-882039 contains ferroan alabandite, but only troilite 

and daubréelite were identified in Y-980524 (Table 2). The 

low bulk abundances of siderophiles, Se and Zn in A- 

882039 (Table 4) are consistent with an EL classification. 

(A bulk composition was not determined for Y-980524.) 

A-882039 and Y-980524 exhibit high degrees of recrystallization 

and share a paucity of recognizable chondrules, consistent 

with annealing at high temperatures. 

We confirm the classification of Y-793225 as EH-an, 

although Lin and Kimura (1998) classified it as being intermediate 

between the EH and EL groups, mainly on the basis 

of its distinctive mineral chemistry. The property that is 

most consistent with an EH classification is the Si content 

of kamacite ( 3 wt%; Table 3) which is near the middle 

of the EH range (2.7–3.8 wt%) and is appreciably higher 

than that of EL chondrites (1.0–2.1 wt%) (Table 5 of Keil, 

1968). This is an important classificatory parameter and 

one we find persuasive. Nevertheless, the low Zn and low 

siderophile contents of bulk Y-793225 are more characteristic 

of EL than EH chondrites, supporting the classification 

of the rock as anomalous. 



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Fig. 8. Relict chondrules in A-882039. (a) Relict radial pyroxene chondrule fragment displaying radiating bars of enstatite. The border 

between the chondrule and the surrounding matrix is difficult to discern, but lies approximately at the ends of the elongated pyroxene laths. 

Transmitted light. (b) Same image as in (a) showing the radiating bars of enstatite (medium gray) intergrown with kamacite (white) and troilite 

(light gray). A thin fusion crust layer is visible at lower left at the interface with the glass slide. Reflected light. (c) Relict porphyritic pyroxene 

chondrule with quasi-equant grains of enstatite and plagioclase. The chondrule is bordered by opaque phases on all sides except bottom left; 

there is no sharp boundary between the chondrule and the surrounding host. Transmitted light. (d) Same image as in (c) showing the 

intergrowth of enstatite (medium gray) and plagioclase (dark gray). Adjacent to the chondrule are grains of kamacite (white) and troilite (light 

gray). Reflected light. en = enstatite; plag = plagioclase; troi = troilite; sil = silicate; kam = kamacite. 

432 4.2. Impact-melting in the EH6 chondrites 

433 Impacts can produce extreme heterogeneities in the de- 

434 gree of shock damage of target rocks. Shock waves can be- 

435 come chaotic as they interact with inhomogeneities in the 

436 rock (e.g., voids, cracks and solid components of different 

437 densities). The initial (nanosecond-scale) peak pressure in 

438 the shock front and the resulting shock temperature can 

439 have grain-to-grain variations of an order of magnitude 

440 (Sharp and DeCarli, 2006). 

441 Because many EH and EL chondrites have been altered 

442 by impacts (e.g., Rubin and Scott, 1997; Rubin et al., 1997; 

443 Kimura and Lin, 1999; Burbine et al., 2000; Fagan et al., 

444 2000; Patzer et al., 2004; Keil, 2007) and because impact 

445 processes can produce changes in bulk composition (e.g., 

446 Rubin et al., 2009) and mineralogy (e.g., Rubin, 1983b; Ru- 

447 bin and Scott, 1997) on a scale of 10 mm (e.g., Rubin, 

448 1984; Rubin et al., 2009), the standard taxonomic parame- 

449 ters may yield different results for different samples. Cau- 

450 tion must therefore be taken in weighting these parameters. 


The three confirmed EH chondrites in this study (Y- 

8404, Y-980211 and Y-980223) are discussed here; EH-an 

Y-793225, EL A-882039 and EL Y-980524 are discussed 

in the following sections. 

Y-8404, Y-980211 and Y-980223 each exhibits some 

unusual mineralogical and textural characteristics that appear 

to have resulted from impact melting as discussed in 

Appendix A. Y-8404, Y-980211 and Y-980223 contain 

euhedral enstatite grains surrounded by metal ± sulfide, 

indicating growth of the enstatite from a mixed melt. 

Y-980211 contains a millimeter-size kamacite globule 

(Fig. 3), similar to some in Abee (Dawson et al., 1960; Rubin 

and Keil, 1983), that most likely formed during melting. 

All three contain enstatite with




Table 2 

Mean compositions (wt%) of sulfide minerals. 

Daubréelite Troilite Keilite Ferroan 

alabandite 

Y-793225 Y-793225 A-882039 Y-980524 Y-793225 Y-793225 Y-8404 Y-980211 Y-980223 A-882039 Y-980524 Y-8404 Y-980211 Y-980223 A-882039 

Source 1 2 1 1 1 2 2 1 1 1 1 3 1 1 1 

No. of grains 3 29 11 7 3 23 18 2 6 25 15 27 1 2 11 

Fe 17.4 17.1 18.3 16.8 61.0 59.9 59.3 61.2 60.6 62.3 62.6 36.9 39.4 37.3 14.4 

Mg



Table 3 

Mean compositions (wt%) of kamacite and schreibersite. 

Kamacite Schreibersite 

Y-793225 Y-793225 Y-8404 Y-8404 Y-980211 Y-980223 A-882039 Y-980524 A-882039 

Source 1 2 1 2 1 1 1 1 1 

No. of grains 18 75 1 30 13 15 23 26 4 

P



Table 4 

Duplicate neutron activation analyses of 23 elements in some enstatite chondrites. 

Na (mg/g) K (mg/g) Ca (mg/g) Sc (mg/g) Cr (mg/g) Mn (mg/g) Fe (mg/g) Co (lg/g) Ni (mg/g) Zn (lg/g) Ga (lg/g) 

Y-793225 EH-an 5.54 644 7.0 7.57 4.43 3.67 234 646 12.6 7.10 6.9 

6.23 597 7.9 7.82 4.42 1.93 229 644 12.4 5.00 7.5 

Mean 5.89 620 7.4 7.70 4.42 2.80 232 645 12.5 6.05 7.2 

A-882039 EL 5.48 615 5.5 6.92 2.65 1.64 256 774 16.0 8.40 11.4 

5.21 563 6.9 7.15 2.73 0.83 284 919 17.0 10.6 12.7 

Mean 5.35 589 6.2 7.04 2.69 1.23 270 846 16.5 9.50 12.0 

Y-980223 EH 6.77 737 5.3 6.32 2.89 2.90 318 890 19.8 381 14.5 

8.31 820 8.2 7.68 3.24 1.82 301 842 18.6 513 14.2 

Mean 7.54 779 6.8 7.00 3.07 2.36 310 866 19.2 447 14.4 

Indarch EH 6.76 662 7.50 5.80 3.06 2.16 311 874 17.7 342 14.7 

As (lg/g) Se (lg/g) Br (lg/g) Ru (ng/g) Sb (ng/g) La (ng/g) Sm (ng/g) Eu (ng/g) Lu (ng/g) Os (ng/g) Ir (ng/g) Au (ng/g) 

Y-793225 EH-an 2.06 15.6 4.79 840 70.0 284 196 51 39.8 747 516 211 

2.48 14.7 3.97 537 58.5 313 235 69 38.0 536 481 216 

Mean 2.27 15.2 4.38 689 63.8 298 216 60 38.9 642 499 214 

A-882039 EL 2.69 13.0 5.81 840 72.0 212 133 68 19.3 738 615 269 

3.43 12.4 8.51 860 136 201 153 88 22.5 859 716 317 

Mean 3.06 12.7 7.16 850 104 206 143 78 20.9 799 666 293 

Y-980223 EH 3.94 28.9 5.56 1050 174 136 54.0 42 11.5 625 510 354 

3.63 29.4 5.89 995 201 90 17.0 28 12.7 551 502 328 

Mean 3.78 29.2 5.72 1023 188 113 35.5 35 12.1 588 506 341 

Indarch EH 3.58 23.5 21.1 890 172 180 124 66 23 685 557 357 



GCA 7175 No. of Pages 25



605 Because these samples have been impact melted, we 

606 can infer that the mechanism mainly responsible for 

607 EH-chondrite metamorphism is collisional heating. 

608 (2) These meteorites have been misclassified; they are 

609 impact-melted rocks and are not type-6 chondrites. 

610 In this case, “real” EH6 chondrites are unknown 

611 and the source of heating of “normal” EH-chondrites 

612 

613 

is unidentified. 

614 One way to choose between these alternatives is to 

615 examine other metamorphosed EH chondrites, i.e., those 

616 listed in the MBDB as EH4, EH4/5, EH5 and EH7. If many 

a 

abundance ratio (EH, Cr norm) 

b 

abundance ratio (EH, Cr norm) 

2.0 

1.5 

1.2 

1.0 

0.8 

0.7 

0.6 

0.5 

0.4 

2.0 

1.5 

1.0 

0.8 

0.5 

0.3 

0.2 

0.1 

0.05 

0.03 

0.02 

Y 793225 

A 882039 

Y 980223 

Indarch 

EL 

of them appear to have been impact melted, then impact 

heating is probably the dominant mechanism responsible 

for EH-chondrite metamorphism. If few show evidence of 

shock heating, then other heat sources (e.g., the decay of 

short-lived radionuclides) may be more likely. 

At the time of this writing, the MBDB lists 24 EH4 and 

EH4/5 chondrites including two probable pairing groups: 

{EET 96135, 96202, 96217, 96223, 96299, 96309, 96341} 

and {MET 00636 and 00783}. In addition, Kimura and 

Lin (1999) thought it likely that Y-791810 and Y-791811 

are paired due to their similarities in texture, mineral modal 

abundance and noble-gas composition (Patzer and Schultz, 

Sc Ca La Sm Eu Yb Lu Cr Mn Na K 

Y 793225 

A 882039 

Y 980223 

Indarch 

EL 

S i 10 


Os Ir Ni Co Fe Au As Ga Sb Se Zn 

Fig. 9. Elemental abundance ratios of the enstatite chondrites in this study; duplicate analyses are plotted. Data are normalized to mean EH 

chondrites and to Cr and are arranged from left to right in order of increasing volatility (except for REE which are listed in order of increasing 

atomic number). For most elements in each meteorite, the duplicate analyses are in good agreement. EH4 Indarch, which was included in one 

analytical run, plots near mean EH chondrites. Mean EL chondrites are shown for comparison. (a) “Lithophile” elements. There is a fair 

amount of spread among replicates, particularly for Ca, Sm, Eu and Lu (elements that partition into oldhamite). (b) Siderophile and 

chalcophile elements. Both A-88039 and Y-793225 have very low Zn abundances. 



617 

618 

619 

620 

621 

622 

623 

624 

625 

626 

627 

628




629 1998). Little published information is available for Y- 

630 791812, but its EH4 classification and sequential catalog 

631 number render it plausible that it is paired with Y-791810 

632 and Y-791811. For the purposes of the present manuscript 

633 we assume that Y-791812 is indeed paired with Y-791810 

634 and Y-791811, but our arguments are not dependent on this 

635 assumption. We conclude that, at present, there are 15 inde- 

636 pendent EH4 and EH4/5 chondrites in our collections. 

637 At least four of these rocks (Abee, Adhi Kot, ALH 82132, 

638 Y-791811) have been described as impact-melt breccias (Ru- 

639 bin, 1983a, 1997a; Rubin and Keil, 1983; Rubin and Scott, 

640 1997; Keil, 2007). Keil (2007) reported keilite in Abee, Adhi 

641 Kot and Y-791811. According to Keil (2007), “keilite occurs 

642 only in enstatite chondrite impact-melt rocks and impact- 

643 melt breccias;” it mainly formed from niningerite and troi- 

644 lite. In addition, euhedral graphite blades occur in Abee, 

645 Adhi Kot and Y-791810 (Rubin, 1983a, 1997a; Rubin and 

646 Keil, 1983). ALH 82132 is also an impact-melt breccia; it 

647 resembles Abee in containing euhedral enstatite grains en- 

648 closed within kamacite globules (Rubin and Scott, 1997). 

649 The wide-spread occurrence of euhedral enstatite and/or 

650 graphite in these rocks indicates that melting was extensive. 

651 The MBDB lists six EH5 chondrites: A-881475, LEW 

652 88180, QUE 93372, RKP A80259, St. Mark’s and Saint- 

653 Sauveur. At least three of these are probably impact-melt 

654 breccias: LEW 88180 contains keilite (Keil, 2007), RKP 

655 A80259 displays an igneous texture and contains impact- 

656 melted feldspar and keilite (Zhang et al., 1995; Fagan 

657 et al., 2000; Keil, 2007), and Saint-Sauveur contains keilite, 

658 low-MnO enstatite, euhedral enstatite grains surrounded by 

659 metallic Fe–Ni, cristobalite, and subhedral grains of fluor- 

660 richterite (Keil, 1968, 2007; Rubin, 1983a, 2008; Kimura 

661 et al., 2005). 

662 One meteorite, QUE 94204 (2.43 kg), is listed in the MDB 

663 as EH7. This is a chondrule-free rock that contains abundant 

664 euhedral enstatite grains with



747 MBDB, some of which have not been described in detail. If 

748 we omit the seven poorly described unpaired samples with 

749 masses




865 EH and EL chondrites include euhedral enstatite grains, 

866 nucleation of enstatite on relict chondrules, low-MnO 

867 enstatite, high-Mn troilite, high-Mn oldhamite, keilite, rel- 

868 atively abundant silica, euhedral graphite, euhedral sinoite, 

869 fluor-richterite and fluorphlogopite. Y-8404 (EH), Y- 

870 980211 (EH), Y-980223 (EH), Y-980524 (EL) and A- 

871 882039 (EL) contain rare relict chondrules and are im- 

872 pact-melt breccias; Y-793225 (EH-an) is a chondrule-free 

873 impact-melt rock. The conclusion that these chondrites 

874 have an impact-melt origin is based on their unusual tex- 

875 tural and mineralogical characteristics including the occur- 

876 rence of euhedral enstatite grains with low MnO that 

877 crystallized from the melt. The high abundance of these 

878 grains indicates that melting was extensive. These EH chon- 

879 drites also contain high-Mn troilite (due to partitioning of 

880 Mn into sulfide during crystallization) and keilite 

881 [(Fe >0.5,Mg



939 Atlanta, in which a sulfide-rich, metal-poor clast is present 

940 (Rubin, 1983c) and Blithfield, an impact-melt rock that has 

941 centimeter-size sulfide-rich, metal-poor clasts (Rubin, 

942 1984). 

943 (2) Diamonds. Abee contains 100 lg/g diamonds (Rus- 

944 sell et al., 1992) twinned on {111}; they were interpreted as a 

945 shock feature by Rubin and Scott (1997). This twinning fea- 

946 ture is shared with shocked synthetic diamonds (Daulton 

947 et al., 1994). Abee diamonds contain low N (




1061 SiO2-rich melts. Mobilization of Si-bearing phases and the 

1062 heterogeneous production of melt are probably responsible 

1063 for variations in the abundance of silica among impact 

1064 products. 

1065 (8) Euhedral graphite. Whereas graphite in unmelted 

1066 enstatite chondrites typically occurs as irregular or com- 

1067 pacted aggregates within kamacite (e.g., Fig. A37 of Ram- 

1068 dohr, 1973), some or all of the graphite in euhedral- 

1069 enstatite-bearing enstatite chondrites (e.g., Abee, Adhi 

1070 Kot) is present as euhedral grains (“books” in the terminol- 

1071 ogy of El Goresy et al., 2001) with pyramidal terminations 

1072 (Rubin, 1983a, 1997a; Rubin and Keil, 1983). These grains 

1073 texturally resemble those that crystallized from melts in the 

1074 ALHA 78019 and Nova 001 ureilites (Berkley and Jones, 

1075 1982; Treiman and Berkley, 1994) and in terrestrial ultra- 

1076 mafic xenoliths in alkali basalts (Figs. 5–7 of Kornprobst 

1077 et al., 1987). Euhedral graphite grains in enstatite chon- 

1078 drites probably crystallized from melts. Their precursors 

1079 probably occurred as aggregates within kamacite. 

1080 (9) Euhedral sinoite (Si2N2O). Euhedral grains of sinoite 

1081 occur in many EL6 chondrites (e.g., Forrest 033, Hvittis, 

1082 Jajh deh Kot Lalu, Neuschwanstein, Pillistfer, Ufana, Yil- 

1083 mia, ALHA81021, EET90102 and LEW88714; Rubin, 

1084 2006), leading to the suggestion (Petaev and Khodakovsky, 

1085 1986; Fogel et al., 1989; Meunow et al., 1992) that sinoite 

1086 formed at EL6 metamorphic temperatures (i.e., 950 °C; 

1087 Meunow et al., 1992; Wasson et al., 1994) over geologic 

1088 timescales. However, sinoite has been reported in portions 

1089 of the EL4 chondrites QUE 94368 (Rubin, 1997b) and 

1090 Grein 002 (Patzer et al., 2004) that also contain euhedral 

1091 grains of enstatite and graphite and are thus inferred to 

1092 have been formed by impact melting. Kimura et al. (2005) 

1093 reported sinoite in EH6-an Y-793225, a meteorite described 

1094 in this study as an impact-melt rock. 

1095 Sinoite may have formed at temperatures of 1400– 

1096 1500 °C (Brosset and Idrestedt, 1964) by a reaction such 

1097 

1098 

as that proposed by Ryall and Muan (1969): 

1100 SiO2 þ 3Si þ 2N2ðgÞ ¼2Si2N2O 

1101 (with the N2 possibly being derived from nitride conden- 

1102 sates; e.g., Rubin and Choi, 2009). Such high temperatures 

1103 are far beyond those envisioned for thermal metamorphism 

1104 in EL4 or even EL6 chondrites ( 700–950 °C) and would 

1105 have caused wide-spread melting of metal and sulfide. How- 

1106 ever, high temperatures are briefly present in portions of 

1107 impact melts and it seems likely that sinoite in EL4 chon- 

1108 drites crystallized from such melts. Euhedral sinoite in 

1109 EL6 chondrites may have crystallized directly from impact 

1110 melts (Rubin, 1997a; Bischoff et al., 2005a) or grown coar- 

1111 ser via post-impact annealing. A single grain of sinoite was 

1112 also reported in a perchloric-acid-resistant residue of Abee 

1113 (Lee et al., 1995). 

1114 (10) Fluor-richterite [Na2Ca(Mg,Fe)5Si8O22F2] and flu- 

1115 orphlogopite [KMg3(Si3Al)O10F2]. Fluor-richterite occurs 

1116 in Abee as rare 3.5-mm-long radiating acicular grains bun- 

1117 dled in clusters associated with enstatite, troilite and keilite 

1118 (Douglas and Plant, 1969; Olsen et al., 1973). In St. Sauv- 

1119 eur, fluor-richterite occurs as 40 100-lm-size subhedral 

1120 grains (Rubin, 1983a). The fluor-richterite grains probably 

1121 crystallized from the melt. 

Fluor-richterite has also been reported in the Mayo Belwa 

aubrite (Bevan et al., 1977; Graham et al., 1977) where it 

occurs as bundles of acicular grains in vugs; some bundles 

are up to 3 mm long and individual fluor-richterite blades 

are up to 1 mm long. Rubin (2010) interpreted Mayo Belwa 

as an impact-melt breccia on the basis of its possession of 

an intergranular melt matrix containing euhedral silicate 

grains, small opaque grains and numerous vugs. He proposed 

that volatiles in Mayo Belwa were vaporized during 

the impact event, forming cavities in the melt; fluor-richterite 

may have condensed in some of the cavities from the 

cooling vapor. 

Fluorphlogopite occurs in the EH impact-melt rock Y- 

82189 as rare subhedral, 10–30-lm-size grains in association 

with enstatite, silica and albite (Lin and Kimura, 

1998). This phase most likely crystallized from the melt. 

It is important to note that the only enstatite meteorites 

in which fluor-richterite and fluorphlogopite have been reported 

were interpreted as having been impact melted on 

the basis of other features. This correspondence is suggestive 

that these F-rich phases are themselves petrographic 

indicators of impact processing. 

A.1.2. Geochemical shock indicators 

Bogard et al. (2010) reviewed literature data and determined 

Ar–Ar ages for a suite of enstatite meteorites. They 

concluded that several EH and EL chondrites had experienced 

collisional heating early in solar system history that 

was sufficiently intense to have disturbed both the Ar–Ar 

and Rb–Sr chronometers. 

Argon–argon data (corrected for errors in the 40 K decay 

constant) show that the Abee and RKP 80259 EH impactmelt 

breccias have Ar–Ar ages of 4.52 and 4.24 Ga, 

respectively (Bogard et al., 2010 and references therein). 

The Blithfield brecciated EL impact-melt rock has a corrected 

Ar–Ar plateau age of 4.534 Ga (Bogard et al., 

2010). These dates range from 31 to 135 Ma after accretion 

occurred 4.565 Ga ago (Carlson and Lugmair, 2000; 

Wadhwa et al., 2008; Kleine et al., 2009) and are long after 

any 26 Al (t ½ = 730,000 years) that was initially present had 

decayed away. Impacts are the only plausible heat source at 

these late dates. 

A.2. Formation of Abee and other enstatite chondrites by 

impact melting 

Abee, a large, extensively studied observed fall, is the 

classic enstatite–chondrite impact-melt breccia. It is useful 

to review the numerous indicators for impact melting 

(and contra internal heating) in Abee and to compare these 

features to the properties of the enstatite chondrites in the 

present study. 

The brecciated texture of Abee and the occurrence of 

diamonds that were probably produced by shock (see 

above) suggest that other melt features in Abee (e.g., euhedral 

enstatite and euhedral graphite) could have resulted 

from impact melting. 

Several petrologic characteristics of Abee are inconsistent 

with long-term melting and slow cooling as expected 

from heating via the decay of short-lived radionuclides: 



1122 

1123 

1124 

1125 

1126 

1127 

1128 

1129 

1130 

1131 

1132 

1133 

1134 

1135 

1136 

1137 

1138 

1139 

1140 

1141 

1142 

1143 

1144 

1145 

1146 

1147 

1148 

1149 

1150 

1151 

1152 

1153 

1154 

1155 

1156 

1157 

1158 

1159 

1160 

1161 

1162 

1163 

1164 

1165 

1166 

1167 

1168 

1169 

1170 

1171 

1172 

1173 

1174 

1175 

1176 

1177 

1178



1179 (1) Many type-3 enstatite chondrites contain two varie- 

1180 ties of enstatite grains: low-MnO grains that exhibit 

1181 blue luminescence under electron bombardment and 

1182 MnO-bearing grains that exhibit red luminescence 

1183 (e.g., Keil, 1968; Leitch and Smith, 1982; Weisberg 

1184 et al., 1994). Although dominated by low-MnO 

1185 enstatite (Keil, 1968), Abee contains both varieties 

1186 (Fig. 7 of Leitch and Smith, 1982), indicating that 

1187 it was incompletely melted and incompletely 

1188 homogenized. 

1189 (2) The presence of readily recognizable chondrules also 

1190 indicates incomplete melting. 

1191 (3) SiC is abundant in EH3 chondrites. The presence of 

1192 SiC in Abee is inferred from the identification of 

1193 trace amounts of Ne–E (H) in an acid-etched residue 

1194 (Huss and Lewis, 1995); SiC is the host phase of Ne– 

1195 E (H) (e.g., Amari et al., 1994). 

1196 (4) Igneous textures in Abee occur both within the clasts 

1197 and in matrix regions between clasts; this indicates 

1198 that Abee experienced two separate melting episodes 

1199 (Rubin and Scott, 1997; Rubin, 2008). 

1200 (5) Different clast and matrix regions in Abee contain 

1201 appreciably different modal abundances of major 

1202 phases (Rubin and Keil, 1983): enstatite (22– 

1203 52 wt%), silica (0.9–16 wt%), plagioclase (4– 

1204 14 wt%), keilite (3–13 wt%), troilite (5–13 wt%) and 

1205 kamacite (20–65 wt%). Igneous rocks that formed 

1206 by slow melting processes would likely be much more 

1207 homogeneous unless post-crystallization brecciation 

1208 mixed diverse lithologies. 

1209 (6) The occurrence of keilite in Abee indicates that the 

1210 melt was quenched; if Abee had cooled slowly (or 

1211 had been subsequently annealed), keilite would have 

1212 exsolved into troilite and niningerite (Keil, 2007). 

1213 Quenching of Abee with little or no subsequent 

1214 annealing is consistent with the occurrence of tridy- 

1215 mite and cristobalite and the absence of quartz (Kim- 

1216 ura et al., 2005). The presence of cohenite exsolution 

1217 lamellae in Abee kamacite also indicates rapid cool- 

1218 ing (Herndon and Rudee, 1978; Rudee and Herndon, 

1219 1980). 

1220 (7) The acicular morphologies of fluor-richterite grains 

1221 in Abee and St. Sauveur and their occurrence in these 

1222 two rocks which have been interpreted as impact- 

1223 melt breccias suggest that fluor-richterite crystallized 

1224 

1225 

from the impact melt (Rubin, 2008). 

1226 Insofar as the other enstatite chondrites in this study 

1227 resemble Abee in containing euhedral enstatite and graphite 

1228 and having relict chondrules on which enstatite nucleated 

1229 from the melt, it is likely that these rocks formed by similar, 

1230 impact-related processes. 

1231 The occurrence of euhedral sinoite grains in regions of 

1232 QUE 94368 that also contain euhedral enstatite and euhe- 

1233 dral graphite (Rubin, 1997b) suggests that the sinoite 

1234 formed from an impact melt. Regions of QUE 94368 that 

1235 do not contain sinoite have normal chondritic textures 

1236 and do not contain euhedral enstatite or euhedral graphite. 

1237 By extrapolation, other enstatite chondrites that contain 


euhedral sinoite are likely to have experienced impact 

melting. 

APPENDIX B. PETROGRAPHIC CHARACTERISTICS 

OF EH6 CHONDRITES 

B.1. Y-8404 

The dominant phase is orthoenstatite, occurring mainly 

as euhedral grains, typically 10 50 lm in size, but ranging 

up to 25 120 lm (Fig. 1a and b). Many grains show welldeveloped 

{210} cleavage; most grains exhibit sharp optical 

extinction consistent with a whole-rock shock stage of S1. 

The majority of the euhedral enstatite grains are intergrown 

with other randomly oriented grains of euhedral enstatite 

and smaller (15–60-lm size) more-equant grains of enstatite, 

plagioclase and silica. Some of the euhedral enstatite 

grains are surrounded by 20–150-lm-diameter opaque 

patches consisting of troilite ± kamacite (Fig. 1b). Some 

opaque patches range up to 1500 lm in size and are nearly 

free of kamacite; they consist almost entirely of troilite surrounding 

silicate assemblages containing euhedral enstatite 

grains. 

Silica is abundant; Lin and Kimura (1998) reported a 

modal abundance of 17.7 vol%. Other opaque phases include 

minor keilite and accessory schreibersite. According 

to Lin and Kimura (1998), the silicate/opaque modal abundance 

ratio is 3.7. 

Although Lin and Kimura (1998) did not find chondrules 

or chondrule fragments in Y-8404, we found recognizable 

remnants of two radial pyroxene (RP) chondrules in 

the available thin section. The larger is 2 mm in diameter 

(Fig. 2a and b). It consists of radiating enstatite laths separated 

by 20-lm-thick bands of troilite; troilite constitutes 

50 vol% of this chondrule (Fig. 2b). The smaller RP chondrule 

is 400 lm in diameter and contains 5–10 vol% troilite 

occurring between radiating bars of enstatite. 

B.2. Y-980211 

The dominant phase is orthoenstatite, occurring mainly 

as euhedral grains ranging in size from 10 40 to 

60 300 lm. Many grains show well-developed {210} 

cleavage. Although most euhedral enstatite grains exhibit 

sharp optical extinction, about 25% exhibit undulose 

extinction, consistent with a whole-rock shock stage of 

S2. The majority of the euhedral enstatite grains are intergrown 

with more-equant, 10–40-lm-size grains of enstatite 

and plagioclase. Plagioclase grains range from 30 to 80 lm 

in maximum dimension. Silica was not identified; point 

counting (n = 50) on the electron microprobe gives an 

upper limit of




1292 (Fig. 3). Similarly sized kamacite globules occur in Abee 

1293 (Dawson et al., 1960; Rubin and Keil, 1983). 

1294 One relict RP chondrule fragment was identified in Y- 

1295 980211. It is 80 110 lm in size and is composed of a sheaf 

1296 of radiating enstatite laths with no interleaved troilite. 

1297 B.3. Y-980223 

1298 The meteorite is dominated by an opaque groundmass 

1299 consisting mainly of kamacite and troilite. Although the 

1300 groundmass is fairly uniformly distributed, different regions 

1301 consist mainly of either kamacite or troilite. Keilite is a 

1302 minor phase. Also present are 150–700-lm-diameter 

1303 rounded kamacite globules. Throughout the groundmass 

1304 and inside the globules are euhedral grains of orthoenstatite 

1305 ranging in size from 4 18 to 30 320 lm (Fig. 4a). Many 

1306 grains show well-developed {210} cleavage. Most enstatite 

1307 grains exhibit significant undulose extinction, consistent 

1308 with a whole-rock shock stage of S2. Plagioclase grains 

1309 range from 20 to 70 lm in size. Silica is abundant, consti- 

1310 tuting 15 vol% of the whole rock. 

1311 Relict chondrules include RP and porphyritic pyroxene 

1312 (PP) types. One relict RP chondrule fragment is 250 lm 

1313 across and contains 10-lm-size patches of troilite located 

1314 between bars of enstatite (Fig. 4b and c). It has been partly 

1315 resorbed but still contains much of its original radial tex- 

1316 ture. A few surrounding euhedral enstatite grains appear 

1317 to have nucleated at the chondrule surface (Fig. 4c). Also 

1318 present in the meteorite groundmass are a few quasi- 

1319 rounded, 200–250-lm-diameter, silicate clumps consisting 

1320 of 40-lm-size grains of enstatite and plagioclase; these ob- 

1321 jects are probably relict PP chondrules. 

1322 B.4. Y-980524 

1323 The meteorite consists of intergrown euhedral and anhe- 

1324 dral orthoenstatite (12 30 to 100 270 lm in size), pla- 

1325 gioclase grains with very fine ( 0.5 lm) polysynthetic 

1326 twin lamellae (and one grain with a Carlsbad twin), troilite 

1327 (some grains with patches of daubréelite or daubréelite 

1328 exsolution lamellae), kamacite, graphite (occurring as qua- 

1329 si-equant and irregular 10–100-lm-size patches within 

1330 kamacite, silicate and schreibersite, and as elongated 

1331 ( 5 55 lm) grains within kamacite), and patches of 

1332 schreibersite (8–1000 lm) adjacent to kamacite. The thin 

1333 section also contains a boomerang-shaped metal vein that 

1334 is 8 mm in length. A few small (2–8 lm) kamacite and 

1335 troilite grains are enclosed within silicate grains. 

1336 Most silicate grains exhibit sharp optical extinction indi- 

1337 cating that the rock is of shock-stage S1. 

1338 Two relict chondrules were identified in the thin section. 

1339 An RP chondrule is 1000 1060 lm in size; a PP chondrule 

1340 (500 550 lm) contains 30–70-lm-size enstatite 

1341 phenocrysts. 

1342 B.5. Y-793225 

1343 This rock is composed mainly of quasi-equant enstatite 

1344 grains 40–70 lm wide and 150–420 lm long (Fig. 5a and 

1345 b). Most grains show well-developed {210} cleavage and 

exhibit sharp optical extinction consistent with a wholerock 

shock stage of S1. Although most enstatite grains 

are anhedral or subhedral, some rare euhedral grains also 

occur. The enstatite grains are randomly oriented and are 

intergrown with plagioclase and minor silica, forming a 

hypidiomorphic-granular texture. We observed one 

10 60 lm euhedral enstatite grain attached to a more 

rounded silicate assemblage protruding into surrounding 

kamacite. Plagioclase grains range in size from 40 to 

160 lm. 

The rock is coarser grained than Y-8404, Y-980211 and 

Y-980223 and has a higher silicate/opaque-phase ratio 

(Fig. 5b). According to Lin and Kimura (1998), the silicate/opaque 

modal abundance ratio in Y-793225 is 7.6. 

There are scattered opaque patches 30–350 lm in size. 

They consist mainly of kamacite and troilite. Some of the 

troilite grains are associated with coarse grains of daubréelite, 

ranging in size from 20 30 to 50 100 lm; in addition, 

a few troilite grains contain relatively thin ( 8-lm 

wide) lamellae of daubréelite. Other opaque phases include 

accessory schreibersite and trace amounts of graphite, 

perryite and a Mn-rich, (Mg,Mn,Fe)S solid solution (probably 

ferroan alabandite) (Lin and Kimura, 1998). Kimura 

et al. (2005) also reported two 10-lm-size grains of sinoite. 

No keilite was observed. 

No chondrules or chondrule fragments were found. 

B.6. A-882039 

This rock is composed of major orthoenstatite intergrown 

with plagioclase. Both equant and euhedral enstatite 

grains occur; the euhedral grains range from 10 50 to 

120 450 lm (Fig. 6a–c). Very few of the grains show pronounced 

cleavage. Most enstatite grains exhibit undulose 

extinction but lack polysynthetic twins, indicating shock 

stage S2. Plagioclase grains are generally irregular in shape 

and range up to 70 lm in size. 

Many silicate intergrowths are surrounded by 30–1100lm-size 

opaque assemblages. Opaque phases include kamacite, 

schreibersite, troilite, daubréelite, ferroan alabandite 

[(Mn,Fe)S], and graphite. Daubréelite typically occurs 

within troilite, either as exsolution lamellae (typically 4– 

6 lm wide) or as tabular grains up to 70 lm thick 

(Fig. 6b). Ferroan alabandite occurs as massive grains adjacent 

to kamacite and/or troilite (Fig. 6b) and as rare 8–20lm-thick 

exsolution lamellae within troilite. Schreibersite 

occurs within kamacite near the border with surrounding 

silicate; in some opaque assemblages, the schreibersite is 

massive, ranging up to 250 lm in thickness (Fig. 6c). 

Graphite occurs within kamacite grains as 2–20-lm-size 

clusters and as large tabular grains up to 50 210 lm in 

size (Fig. 6c and d). Graphite is also present as isolated 

books (using the terminology of El Goresy et al., 2001) 

ranging from 6 100 to 30 250 lm. Some graphite books 

are adjacent to kamacite and/or troilite (Fig. 7a); others are 

completely enclosed within silicate (Fig. 7b). 

Rare relict chondrules and chondrule fragments are 

present. One 650 700-lm-size relict radial pyroxene 

(RP) chondrule fragment consists of a radiating sheaf of 

enstatite bars and minor sulfide (Fig. 8a and b). One 



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1404 750 820 lm relict PP chondrule is composed mainly of 

1405 100–200-lm-size quasi-equant enstatite and plagioclase 

1406 phenocrysts (Fig. 8c and d). 

1407 REFERENCES 

1408 Amari S., Lewis R. S. and Anders E. (1994) Interstellar grains in 

1409 meteorites: I. Isolation of SiC, graphite, and diamond; size 

1410 distribution of SiC and graphite. Geochim. Cosmochim. Acta 58, 

1411 459–470. 

1412 Berkley J. L. and Jones J. H. (1982) Primary igneous carbon in 

1413 ureilites: petrological implications. Proc. Lunar Planet. Sci. 

1414 Conf. 13, A353–A364. 

1415 Berkley J. L., Brown H. G., Keil K., Carter N. L., Mercie J.-C. C. 

1416 and Huss G. (1976) The Kenna ureilite: an ultramafic rock with 

1417 evidence for igneous, metamorphic, and shock origin. Geochim. 

1418 Cosmochim. Acta 40, 1429–1437. 

1419 Bevan A. W. R., Bevan J. C. and Francis J. G. (1977) Amphibole in 

1420 the Mayo Belwa meteorite: first occurrence in an enstatite 

1421 achondrite. Mineral. Mag. 41, 531–534. 

1422 Bhandari N., Shah V. G. and Wasson J. T. (1980) The Parsa 

1423 enstatite chondrite. Meteoritics 15, 225–234. 

1424 Binns R. A. (1967) Olivine in enstatite chondrites. Am. Mineral. 52, 

1425 1549–1554. 

1426 Binns R. A. (1970) (Mg,Fe) 2SiO 4 spinel in a meteorite. Phys. Earth 

1427 Planet. Inter. 3, 156–160. 

1428 Binns R. A., Davis R. J. and Reed S. B. J. (1969) Ringwoodite, 

1429 natural (Mg,Fe)2SiO4 in the Tenham meteorite. Nature 221, 

1430 943–944. 

1431 Birck J.-L. and Allègre C. J. (1988) Manganese–chromium isotope 

1432 systematics and the development of the early Solar System. 

1433 Nature 331, 579–584. 

1434 Bischoff A., Palme H., Geiger T. and Spettel B. (1992) Mineralogy 

1435 and chemistry of the EL-chondritic melt rock Ilafegh 009 

1436 (abstract). Lunar Planet. Sci. 23, 105–106. 

1437 Bischoff A., Grund T., Jording T., Heying B., Hoffmann R.-D., 

1438 Rodewald U. C. and Pöttgen R. (2005a) Occurrence, structure, 

1439 and formation of sinoite in enstatite chondrites (abstract). 

1440 Meteorit. Planet. Sci. 40, A20. 

1441 Bischoff A., Grund T., Jording T., Heying B., Hoffmann R.-D., 

1442 Rodewald U. C. and Pöttgen R. (2005b) First refinement of the 

1443 sinoite structure of a natural crystal from the Neuschwanstein 

1444 (EL6) meteorite. Z. Naturforsch. 60b, 1231–1234. 

1445 Bogard D. D., Garrison D. H., Scott E. R. D., Keil K., Taylor G. 

1446 J., Vogt S., Herzog G. F. and Klein J. (1990) The Chico, NM, 

1447 L-6 chondrite: a large, 500 My-old impact melt with a long 

1448 cosmic ray exposure (abstract). Lunar Planet. Sci. 21, 103–104. 

1449 Bogard D. D., Dixon E. T. and Garrison D. H. (2010) Ar–Ar ages 

1450 and thermal histories of enstatite meteorites. Meteorit. Planet. 

1451 Sci. 45, 723–742. 

1452 Brosset C. and Idrestedt I. (1964) Crystal structure of silicon 

1453 oxynitride, Si 2N 2O. Nature 201, 1211. 

1454 Burbine T. H., McCoy T. J. and Dickinson T. L. (2000) Origin of 

1455 plagioclase-“enriched”, igneous, enstatite meteorites (abstract). 


1457 Carlson R. W. and Lugmair G. W. (2000) Timescales of planetes- 

1458 imal formation and differentiation based on extinct and extant 

1459 radioisotopes. In Origin of the Earth and Moon (eds. R. Canup 

1460 and K. Righter). University of Arizona Press, Tucson, pp. 25– 

1461 44. 

1462 Chen M., Sharp T. G., El Goresy A., Wopenka B. and Xie X. 

1463 (1996) The majorite-pyrope + magnesiowüstite assemblage: 

1464 constraints on the history of shock veins in chondrites. Science 

1465 271, 1570–1573. 

1466 Chen M., Shu J. F., Xie X. D. and Mao H. K. (2003) Natural 

1467 CaTi 2O 4-structured FeCr 2O 4 polymorph in the Suizhou mete- 


orite and its significance in mantle mineralogy. Geochim. 

Cosmochim. Acta 67, 3937–3942. 

Choe W. H., Huber H., Rubin A. E., Kallemeyn G. W. and 

Wasson J. T. (2010) Compositions and taxonomy of 15 unusual 

carbonaceous chondrites. Meteorit. Planet. Sci. 45, 531–554. 

Clarke R. S., Appleman D. E. and Ross D. R. (1981) An Antarctic 

iron meteorite contains preterrestrial impact-produced diamond 

and lonsdaleite. Nature 291, 396–398. 

Crabb J. and Anders E. (1981) Noble gases in E-chondrites. 

Geochim. Cosmochim. Acta 45, 2443–2464. 

Daulton T. L., Eisenhour D. D., Buseck P. R., Lewis R. S. and 

Bernatowicz T. J. (1994) High-resolution transmission electron 

microscopy of meteoritic and terrestrial nano-diamonds 

(abstract). Lunar Planet. Sci. 25, 313–314. 

Dawson K. R., Maxwell J. A. and Parsons D. E. (1960) A 

description of the meteorite which fell near Abee, Alberta, 

Canada. Geochim. Cosmochim. Acta 21, 127–144. 

Dodd R. T. (1974) Petrology of the St. Mesmin chondrite. Contrib. 

Mineral. Petrol. 46, 129–145. 

Dominik B. and Bussy F. (1994) The Bison LL6 breccia. 

Meteoritics 29, 235–237. 

Douglas J. A. V. and Plant A. G. (1969) Amphibole: first 

occurrence in an enstatite chondrite (abstract). Meteoritics 4, 

166. 

Easton A. J. (1983) Grain-size distribution and morphology of 

metal in E-chondrites. Meteoritics 18, 19–27. 

El Goresy A. and Kullerud G. (1969) Phase relations in the system 

Cr–Fe–S. In Meteorite Research (ed. P. M. Millman). D. 

Reidel, Dordrecht, pp. 638–656. 

El Goresy A., Wadwha M., Nagel H.-J., Zinner E. K., Janicke J. 

and Crozaz G. (1992) 53 Cr– 53 Mn systematics of Mn-bearing 

sulfides in four enstatite chondrites (abstract). Lunar Planet. 

Sci. 23, 331–332. 

El Goresy A., Gillet P., Chen M., Künstler F., Graup G. and 

Stähle V. (2001) In situ discovery of shock-induced graphite– 

diamond phase transition in gneisses from the Ries Crater, 

Germany. Am. Mineral. 86, 611–621. 

Fagan T. J., Scott E. R. D., Keil K., Cooney T. F. and Sharma S. 

K. (2000) Formation of feldspathic and metallic melts by shock 

in enstatite chondrite Reckling Peak A80259. Meteorit. Planet. 

Sci. 35, 319–329. 

Floss C. and Crozaz G. (1993) Heterogeneous REE patterns in 

oldhamite from aubrites: their nature and origin. Geochim. 


Fogel R. A., Hess P. C. and Rutherford M. J. (1989) Intensive 

parameters of enstatite chondrite metamorphism. Geochim. 


Frondel C. and Marvin U. (1967) Lonsdaleite, a hexagonal 

polymorph of diamond. Nature 214, 587–589. 

Fruland R. M. (1975) Volatile movement in the Rose City 

meteorite, and implications concerning the impact and late 

thermal history of ordinary chondrites (abstract). Meteoritics 

10, 403–404. 

Gillet P., Chen M., Dubrovinsky L. and El Goresy A. (2000) 

Natural NaAlSi3O8-hollandite in the shocked Sixiangkou 

meteorite. Science 287, 1633–1636. 

Govindaraju K. (1994) Compilation of working values and 

descriptions for 383 geostandards. Geostand. Newslett. 118, 1– 

158. 

Grady M. M., Wright I. P., Carr L. P. and Pillinger C. T. (1986) 

Compositional differences in enstatite chondrites based on 

carbon and nitrogen stable isotope measurements. Geochim. 


Graham A. L., Easton A. J. and Hutchison R. (1977) The Mayo 

Belwa meteorite: a new enstatite achondrite fall. Mineral. Mag. 

41, 487–492. 



1468 

1469 

1470 

1471 

1472 

1473 

1474 

1475 

1476 

1477 

1478 

1479 

1480 

1481 

1482 

1483 

1484 

1485 

1486 

1487 

1488 

1489 

1490 

1491 

1492 

1493 

1494 

1495 

1496 

1497 

1498 

1499 

1500 

1501 

1502 

1503 

1504 

1505 

1506 

1507 

1508 

1509 

1510 

1511 

1512 

1513 

1514 

1515 

1516 

1517 

1518 

1519 

1520 

1521 

1522 

1523 

1524 

1525 

1526 

1527 

1528 

1529 

1530 

1531 

1532 

1533




1534 Grimm R. E. and McSween H. (1993) Heliocentric zoning of the 

1535 asteroid belt by 26-Al heating. Science 259, 653–655. 

1536 Grossman J. N., Rubin A. E., Rambaldi E. R., Rajan R. S. and 

1537 Wasson J. T. (1985) Chondrules in the Qingzhen type-3 

1538 enstatite chondrite: possible precursor components and com- 

1539 parison to ordinary chondrite chondrules. Geochim. Cosmo- 

1540 chim. Acta 49, 1781–1795. 

1541 Guan Y., Huss G. R. and Leshin L. A. (2007) 60 Fe– 60 Ni and 

1542 53 53 

Mn– Cr isotope systems in sulfides from unequilibrated 

1543 enstatite chondrites. Geochim. Cosmochim. Acta 71, 4082–4091. 

1544 Herndon J. M. and Rudee M. L. (1978) Thermal history of the 

1545 Abee enstatite chondrite. Earth Planet. Sci. Lett. 41, 101–106. 

1546 Huss G. R. and Lewis R. S. (1995) Presolar diamond, SiC, and 

1547 graphite in primitive chondrites: abundances as a function of 

1548 meteorite class and petrologic type. Geochim. Cosmochim. Acta 

1549 59, 115–160. 

1550 Irving A. J., Bunch T. E., Rubin A. E. and Wasson J. T. (2010) 

1551 Northwest Africa 2828/Al Haggounia 001 is a weathered 

1552 unequilibrated EL chondrite: trace element and petrologic 

1553 evidence. Meteorit. Planet. Sci. 45, A90. 

1554 Jarosewich E., Clarke R. S. and Barrows J. N. (1987) The Allende 

1555 meteorite reference sample. Smithson. Contrib. Earth Sci. 27, 1– 

1556 49. 

1557 Kallemeyn G. W. and Wasson J. T. (1986) Compositions of 

1558 enstatite (EH3, EH4, 5 and EL6) chondrites: implications 

1559 regarding their formation. Geochim. Cosmochim. Acta 50, 2153– 

1560 2164. 

1561 Kallemeyn G. W., Rubin A. E., Wang D. and Wasson J. T. 

1562 (1989) Ordinary chondrites: bulk compositions, classification, 

1563 lithophile-element fractionations, and composition–petro- 

1564 graphic type relationships. Geochim. Cosmochim. Acta 53, 

1565 2747–2767. 

1566 Karwowski L., Kryza R. and Przylibski T. (2007) New chemical 

1567 and physical data on keilite from the Zakłodzie enstatite 

1568 achondrite. Am. Mineral. 92, 204–209. 

1569 Keil K. (1968) Mineralogical and chemical relationships among 

1570 enstatite chondrites. J. Geophys. Res. 73, 6945–6976. 

1571 Keil K. (2007) Occurrence and origin of keilite, (Fe >0.5, Mg



1666 isotopic compositions of in situ diamonds and other carbon 

1667 phases in the Bencubbin meteorite. Earth Planet. Sci. Lett. 204, 

1668 89–100. 

1669 Nehru C. E., Prinz M., Weisberg M. K. and Delaney J. S. (1984) 

1670 Parsa: an unequilibrated enstatite chondrite (UEC) with an 

1671 aubrite-like impact melt clast (abstract). Lunar Planet. Sci. 15, 

1672 597–598. 

1673 Okada A., Keil K., Taylor G. J. and Newsom H. (1988) Igneous 

1674 history of the aubrite parent asteroid: evidence from the Norton 

1675 County enstatite achondrite. Meteoritics 23, 59–74. 

1676 Olsen E., Huebner J. S., Douglas J. A. V. and Plant A. G. (1973) 

1677 Meteoritic amphiboles. Am. Mineral. 58, 869–872. 

1678 Olsen E. J., Bunch T. E., Jarosewich E., Noonan A. F. and Huss G. 

1679 I. (1977) Happy Canyon: a new type of enstatite achondrite. 

1680 Meteoritics 12, 109–123. 

1681 Olsen E. J., Huss G. I. and Jarosewich E. (1988) The Eagle, 

1682 Nebraska, enstatite chondrite. Meteoritics 23, 379–380. 

1683 Petaev M. I. and Khodakovsky I. L. (1986) Thermodynamic 

1684 properties and conditions of formation of minerals in enstatite 

1685 meteorites. In Chemistry and Physics of Terrestrial Planets (ed. 

1686 S. K. Saxena). Springer-Verlag, New York, pp. 106–135. 

1687 Patzer A. and Schultz L. (1998) The exposure age distribution of 

1688 enstatite chondrites (abstract). Meteorit. Planet. Sci. 33, A120– 

1689 A121. 

1690 Patzer A. and Schultz L. (2001) Noble gases in enstatite chondrites: 

1691 I. Exposure ages, pairing, and weathering effects. Meteorit. 

1692 Planet. Sci. 36, 947–961. 

1693 Patzer A., Schlüter J., Schultz L., Tarkian M., Hill D. H. and 

1694 Boynton W. V. (2004) New findings for the equilibrated 

1695 enstatite chondrite Grein 002. Meteorit. Planet. Sci. 39, 1555– 

1696 1575. 

1697 Price G. D., Putnis A., Agrell S. O. and Smith D. G. W. (1983) 

1698 Wadsleyite, natural beta-(Mg,Fe)2SiO4 from the Peace River 

1699 meteorite. Can. Mineral. 21, 29–35. 

1700 Pryzlibski T. A., Zago_zd_zon P. P., Kryza R. and Pilski A. S. (2005) 

1701 The Zakłodzie enstatite meteorite: mineralogy, petrology, 

1702 origin and classification. Meteorit. Planet. Sci. 40, A185–A200. 

1703 Ramdohr P. (1973) The Opaque Minerals in Stony Meteorites. 

1704 Elsevier, Amsterdam, 245p. 

1705 Rubin A. E. (1983a) The Adhi Kot breccia and implications for the 

1706 origin of chondrules and silica-rich clasts in enstatite chon- 

1707 drites. Earth Planet. Sci. Lett. 64, 201–212. 

1708 Rubin A. E. (1983b) Impact melt-rock clasts in the Hvittis enstatite 

1709 chondrite breccia: implications for a genetic relationship 

1710 between EL chondrites and aubrites. Proc. Lunar Planet. Sci. 

1711 Conf. 14, B293–B300. 

1712 Rubin A. E. (1983c) The Atlanta enstatite chondrite breccia. 

1713 Meteoritics 18, 113–121. 

1714 Rubin A. E. (1984) The Blithfield meteorite and the origin of 

1715 sulfide-rich, metal-poor clasts and inclusions in brecciated 

1716 enstatite chondrites. Earth Planet. Sci. Lett. 67, 273–283. 

1717 Rubin A. E. (1985) Impact melt products of chondritic material. 

1718 Rev. Geophys. 23, 277–300. 

1719 Rubin A. E. (1997a) Igneous graphite in enstatite chondrites. 

1720 Mineral. Mag. 61, 699–703. 

1721 Rubin A. E. (1997b) Sinoite (Si 2N 2O): crystallization from EL 

1722 chondrite impact melts. Am. Mineral. 82, 1001–1006. 

1723 Rubin A. E. (2000) Petrologic, geochemical and experimental 

1724 constraints on models of chondrule formation. Earth-Sci. Rev. 

1725 50, 3–27. 

1726 Rubin A. E. (2004) Post-shock annealing and post-annealing shock 

1727 in equilibrated ordinary chondrites: implications for the ther- 

1728 mal and shock histories of chondritic asteroids. Geochim. 

1729 Cosmochim. Acta 68, 673–689. 

1730 Rubin A. E. (2006) Shock and annealing in EL chondrites. 



Rubin A. E. (2008) Explicating the behavior of Mn-bearing phases 

during shock melting and crystallization of the Abee EHchondrite 

impact-melt breccia. Meteorit. Planet. Sci. 43, 1481– 

1486. 

Rubin A. E. (2010) Impact melting in the Cumberland 

Falls and Mayo Belwa aubrites. Meteorit. Planet. Sci. 45, 

265–275. 

Rubin A. E. (1995a) Fractionation of refractory siderophile 

elements in metal from the Rose City meteorite. Meteoritics 

30, 412–417. 

Rubin A. E. (1995b) Petrologic evidence for collisional heating of 

chondritic asteroids. Icarus 113, 156–167. 

Rubin A. E. (2005) What heated the asteroids? Sci. Am. 292, 

80–87. 

Rubin A. E. and Choi B.-G. (2009) Origin of halogens and nitrogen 

in enstatite chondrites. Earth Moon Planets 105, 41–53. 

Rubin A. E. and Keil K. (1983) Mineralogy and petrology of the 

Abee enstatite chondrite breccia and its dark inclusions. Earth 

Planet. Sci. Lett. 62, 118–131. 

Rubin A. E. and Read W. F. (1984) The Brownell and Ness County 

(1894) L6 chondrites: further sorting-out of Ness County 

meteorites. Meteoritics 19, 153–160. 

Rubin A. E. and Scott E. R. D. (1997) Abee and related EH 

chondrite impact-melt breccias. Geochim. Cosmochim. Acta 61, 

425–435. 

Rubin A. E., Scott E. R. D. and Keil K. (1997) Shock metamorphism 

of enstatite chondrites. Geochim. Cosmochim. Acta 61, 

847–858. 

Rubin A. E., Huber H. and Wasson J. T. (2009) Possible impactinduced 

refractory-lithophile fractionations in EL chondrites. 

Geochim. Cosmochim. Acta 73, 1523–1537. 

Rudee M. L. and Herndon J. M. (1980) The thermal history of 

Abee (abstract). Meteoritics 15, 361. 

Russell S. S., Pillinger C. T., Arden J. W., Lee M. R. and Ott U. 

(1992) A new type of meteoritic diamond in the enstatite 

chondrite Abee. Science 256, 206–209. 

Russell S. S., Zipfel J., Folco L., Jones R., Grady M. M., McCoy 

T. and Grossman J. N. (2003) The Meteoritical Bulletin, No. 

87, 2003 July. Meteorit. Planet. Sci. 38, A189–A248. 

Ryall W. R. and Muan A. (1969) Silicon oxynitride stability. 

Science 165, 1363–1364. 

Sears D. W., Kallemeyn G. W. and Wasson J. T. (1982) 

The compositional classification of chondrites: II. The 

enstatite chondrite groups. Geochim. Cosmochim. Acta 46, 

597–608. 

Sharp T. G. and DeCarli P. S. (2006) Shock effects in meteorites. In 

Meteorites and the Early Solar System II (eds. D. S. Lauretta 

and H. Y. McSween). University of Arizona Press, Tucson, pp. 

653–677. 

Sharp T. G., Lingemann C. M., Dupas C. and Stöffler D. (1997) 

Natural occurrence of MgSiO3-ilmenite and evidence for 

MgSiO3-perovskite in a shocked L chondrite. Science 277, 

352–355. 

Shelkov D., Milledge H. J., Verchovsky A. B., Kaminsky F. and 

Pillinger C. T. (1996) Preliminary C, N, He and Ar study of 

shock produced diamonds from the Popigai Crater and 

Ebeliakh Placer, Siberia (abstract). Lunar Planet. Sci. 27, 

1187–1188. 

Smith J. V. and Mason B. (1970) Pyroxene–garnet transformation 

in Coorara meteorite. Science 168, 832. 

Stöffler D., Keil K. and Scott E. R. D. (1991) Shock metamorphism 

of ordinary chondrites. Geochim. Cosmochim. Acta 55, 3845– 

3867. 

Tomioka N. and Fujino K. (1997) Natural (Mg,Fe)SiO3-ilmenite and -perovskite in the Tenham meteorite. Science 277, 1084– 

1086. 



1732 

1733 

1734 

1735 

1736 

1737 

1738 

1739 

1740 

1741 

1742 

1743 

1744 

1745 

1746 

1747 

1748 

1749 

1750 

1751 

1752 

1753 

1754 

1755 

1756 

1757 

1758 

1759 

1760 

1761 

1762 

1763 

1764 

1765 

1766 

1767 

1768 

1769 

1770 

1771 

1772 

1773 

1774 

1775 

1776 

1777 

1778 

1779 

1780 

1781 

1782 

1783 

1784 

1785 

1786 

1787 

1788 

1789 

1790 

1791 

1792 

1793 

1794 

1795 

1796 

1797




1798 Treiman A. H. and Berkley J. L. (1994) Igneous petrology of the 

1799 new ureilites Nova 001 and Nullarbor 010. Meteoritics 29, 843– 

1800 848. 

1801 Van Schmus W. R. and Wood J. A. (1967) A chemical–petrologic 

1802 classification for the chondritic meteorites. Geochim. Cosmo- 

1803 chim. Acta 31, 747–765. 

1804 Vdovykin G. P. (1972) Forms of carbon in the new Haverö ureilite 

1805 of Finland. Meteoritics 7, 547–552. 

1806 Wadhwa M., Srinivasan G. and Carlson R. W. (2008) Timescales 

1807 of planetesimal differentiation in the early solar system. In 

1808 Meteorites and the Early Solar System II (eds. D. S. Lauretta 

1809 and H. Y. McSween). University of Arizona Press, Tucson, pp. 

1810 715–732. 

1811 Wasson J. T., Kallemeyn G. W. and Rubin A. E. (1994) 

1812 Equilibration temperatures of EL chondrules: a major down- 

1813 ward revision in the ferrosilite contents of enstatite. Meteoritics 

1814 29, 658–662. 

1815 Weisberg M. K. and Kimura M. (2004) Petrology and Raman 

1816 spectroscopy of shock phases in the Gujba CB chondrite and 

1817 the shock history of the CB parent body. Lunar Planet. Sci. 35. 

1818 Lunar Planet. Inst., Houston. #1599 (abstr.). 

1819 Weisberg M. K., Kimura M., Suzuki A., Ohtani E. and Sugiura N. 

1820 (2006) Discovery of coesite and significance of high pressure 

phases in the Gujba CB chondrite. Lunar Planet. Sci. 37. Lunar 

Planet. Inst., Houston. #1788 (abstr.). 

Weisberg M. K., Prinz M. and Fogel R. A. (1994) The 

evolution of enstatite and chondrules in unequilibrated 

enstatite chondrites: evidence from iron-rich pyroxene. 

Meteoritics 29, 362–373. 

Weisberg M. K., Prinz M. and Nehru C. E. (1997) QUE 94204: an 

EH-chondritic melt rock. Lunar Planet. Sci. 28, #1358 (abstr.). 

Wlotzka F. (1993) A weathering scale for the ordinary chondrites 

(abstract). Meteoritics 28, 460. 

Xie X., Li Z., Wang D., Liu J., Hu R. and Chen M. (1991) The new 

meteorite fall of Yanzhuang, a severely shocked H6 chondrite 

with black molten materials (abstract). Meteoritics 26, 411. 

Yang C. W., Williams D. B. and Goldstein J. I. (1996) A revision of 

the Fe–Ni phase diagram at low temperatures (

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