Evidence for successive episodes of condensation at high temperature in a part of the solar nebula

Earth and P1anetary 5c1ence Letter5, 77 (1986) 129-148 E15ev1er 5c1ence Pu6115her5 8.V., Am5terdam - Pr1nted 1n 7he Nether1and5

129

[11

Ev1dence f0r 5ucce551ve ep150de5 0f c0nden5at10n at h19h temperature 1n a part 0f the 501ar ne6u1a D.A. Wark

Lunar and P1anetary La60rat0rv, Un1ver51ty0f Ar120na, 7uc50n, A2 85721 (U.5.A.) Rece1ved June 19, 1985; rev15ed ver510n accepted Decem6er 27, 1985 A cent1meter-512ed Ca-A1-r1ch 1nc1u510n, CA1 3643, 1n the A11ende mete0r1te ha5 pre5erved a rec0rd 0f 1t5 mu1t1p1e 5ta9e5 0f 9r0wth 6y c0nden5at10n at h19h temperature. 1t c0n515t5 0f three d15t1nct, c0ncentr1c 1ayer51c0re, mant1e and cru5t. 7he 0pen-textured c0re 15 c0mp05ed 0f h160n1te 1ath5, 1nter5t1t1a1 me1111teand v01d5, 9ra1n5 0f a1um1na, and 051r meta1 nu99et5 1n the 1nner c0re that are c0mp1ementary 1n c0mp051t10n t0 RuPt-r1ch nu99et51n the 0uter c0re. 7he c0re f0rmed 0ut 0f rap1d1y-a99re9ated cry5ta15 fr0m tw0 ep150de5 0f c0nden5at10n 1n the 5ame 9a5e0u5 re5erv01r. M0 and W dep1et10n51n the nu99et51nd1cate c0nden5at10n fr0m a re1at1ve1y0x1d121n9 9a5, w1th 60 t1me5 h19her H 2 0 / H 2 than 501ar 9a5. 7he c0mpact mant1e 0f c0ar5e me1111tec0nta1n5 per0v5k1te 1nc1u510n5 and rare N1Fe meta1 and 5u1f1de 9ra1n5. 7he c0mpact, f1ne-9ra1ned cru5t c0n515t5 0f me1111te,h160n1te, 5p1ne1, per0v5k1te, and 0pa4ue5 51m11ar t0 th05e,1n the mant1e. Ne1ther mant1e n0r cru5t ha5 6een m01ten; each 9rew 6y c0nden5at10n 0f 5011d5 d1rect1y 0nt0 the 5urface 0f the CA1. 7he f0rmed CA1 exper1enced 50me metam0rph1c recry5ta1112at10n 0f me1111te, and v01at11e a1terat10n pr0duc1n9 9r055u1ar, fe1d5path01d5 and hercyn1te. 7race e1ement ana1y5e5 0f per0v5k1te5 and a 6u1k 5amp1e 5h0w the mant1e and cru5t t0 6e dep1eted 1n refract0ry e1ement5 (1.e. 6r0up 11) and c0mp1ementary t0 the u1tra-refract0ry c0re. De5p1te d1fference5 1n texture and c0mp051t10n, the c0re, mant1e and cru5t d15p1ay a c0nt1nu1ty 1n the1r m0da1 m1nera1091ca1 c0mp051t10n5, the1r extreme A1203 enr1chment5 (53-69% cf. 25-45% f0r 0ther CA1•5) and the1r trace e1ement c0mp1ementar1ty. 7h15 1mp11e5 that a11 the 1ayer5 0f 3643 f0rmed fr0m the 5ame c0011n9 9a5e0u5 re5erv01r w1th1n a 11m1ted 1nterva1 0f t1me and 5pace, c0n515tent w1th an 0r191n 1n a 10ca1, tran51ent heat1n9 event 1n the CV ch0ndr1te f0rmat10n re910n 0f the ne6u1a.

1. 1ntr0duct10n R e f r a c t 0 r y , Ca-A1-r1ch 1nc1u510n5 (CA1•5) 1n ch0ndr1t1c mete0r1te5 are a m 0 n 9 the 01de5t mater1a15 1n the 501ar 5y5tem, a5 j u d 9 e d 6 y the1r extreme1y 10w 1n1t1a1 575r/~65r rat105 a n d exce55e5 0f 26M9 f r 0 m the 1n 51tu d e c a y 0f 5h0rt-11ved 26A1 nuc1e05ynthe512ed 0ut51de the 501ar 5y5tem [1,2]. 7 h e an0ma10u5 t1tan1um 150t0p1c c0mp051t10n5 0f CA1•5 [3] are p r 0 6 a 6 1 y a150 d u e t0 ear1y f0rmat10n, 6 e f 0 r e du5t 9ra1n5 f r 0 m d1fferent nuc1e05ynthet1c 50urce5 6 e c a m e we11 m1xed 1n the 501ar ne6u1a. 7 h e t 6 0 an0ma11e5 0f CA1•5 m a y h a v e a 51m11ar cau5e 0r m a y 6e d u e t0 612arre ph0t0chem1ca1 fract10nat10n pr0ce55e5 w1th1n the ne6u1a [4]. CA1•5 thu5 c0nta1n 1nf0rmat10n a 6 0 u t the f0rmat10n 0f the 501ar 5y5tem, a1th0u9h the1r c0mp1ex pr0pert1e5 5e1d0m y1e1d an une4u1v0ca1 p1cture. H 0 w e v e r , the un14ue A11ende CA1 3643 d0e5 p r 0 v1de rare, u n a m 6 1 9 u 0 u 5 ev1dence f0r the h19h t e m 0012-821X/86/$03.50

• 1986 E15ev1er5c1ence Pu6115her5 8.v.

p e r a t u r e c0nden5at10n a n d a99re9at10n 0f extreme1y r e f r a c t 0 r y 5011d 9ra1n5 wh1ch w e r e t h e n 0 v e r 9 r 0 w n 6y a c 0 n d e n 5 a t e 0f the rema1n1n9 1e55r e f r a c t 0 r y e1ement5.1t 15 a150 c1ear that the5e event5 t 0 0 k p1ace w1th1n a 5ma11 re910n 0 f 5pace a n d t1me 1n the 501ar ne6u1a, a n d n0t 1n 50me pre501ar 5te11ar 0utf10w [5].

2. Exper1menta1 meth0d5 7h15 w 0 r k 15 6a5ed 0n 5tud1e5 0f a p0115hed th1n 5ect10n 0f CA1 3643 6y 119ht a n d 5cann1n9 e1ectr0n m1cr05c0pe5, a n d e1ectr0n a n d p r 0 t 0 n m1cr0pr06e5.

2.1. 5cann1n9 e1ectr0n m1cr05c0pe ( 5 E M ) 7 h e J E 0 L J 5 M - 3 5 5 E M wa5 f1tted w1th a R061n50n 6 a c k 5 c a t t e r e d e1ectr0n 1ma91n9 5y5tem a n d a 154 eV re501ut10n E D A X 51(L1) ener9y-d15-

130 per51ve X-ray ana1y5er. 5111cate and 0x1de ana1y5e5 at 15 kV and - 0 . 5 nA current f0r 100 0r 200 5ec0nd5 were c0rrected 0n-11ne 6y Ware•5 pr09ram [6]. M1cr0meter-512ed meta1 9ra1n5 were ana1y5ed at 30 kV and 1 nA current f0r 11ve c0unt1n9 t1me5 0f 200 400 5ec0nd5. 8ack9r0und5 were 1nterp01ated and 5u6tracted 6y hand, a5 were the f0110w1n9 1nterference5:M0 L,, 0n 5 K,, (enc0untered 0n1y 0nce): N1 K1~ 0n W L,: Ru K# 0n Rh K,,: M0 K/~ 0n Ru and Rh K0; 05, 1r and Pt L,~ 0n each 0ther. 1nterference c0rrect10n fact0r5 were 06ta1ned fr0m pure-e1ement 5pectra. 7he net peak area5 were 2AF-c0rrected 6y the pr09ram 0f Ma50n et a1, [7]. 7he ana1y5e5 u5ed the K,~ peak5 0f 5, Fe. N1, Cu, 2n, M0, Ru and Rh and the L, peak5 0f W. Re, 05, 1r and Pt. 7he 0n1y 0ther X-ray 11ne5 065erved 1n the 5pectra were th05e 0f Na, M9, A1, 51, C1, K, Ca, 71, V and Cr exc1ted fr0m the 5111cate5 and 0x1de5 5urr0und1n9 the meta1 9ra1n5. 7he ••c0ntam1nat10n•• 0f Na, M9, A1, etc., 1n the ana1y5e5 0f the meta1 9ra1n5 wa5 19n0red and the t0ta15 were re-ca1cu1ated t0 100%. 7he p1at1num meta15 were n0t a110yed w1th 71 [8] a5 71 X-ray 11ne5 were n0t 5een 1n the 5pectra 0f meta1 9ra1n5 1n the 71-free 5111cate me1111te. 7he accuracy 0f the meta1 ana1yt1ca1 meth0d wa5 checked 6y ana1y21n9 tw0 natura1 05m1r1d1um 9ra1n5 prev10u51y ana1y2ed 6y m1cr0pr06e, and a 5ynthet1c a110y 0f Fe, N1, M0, Ru, W, 05, 1r and Pt 0f kn0wn c0mp051t10n. 7he 5EM and 0ther ana1y5e5 0f the5e te5t mater1a15 a9ree we11 w1th1n •+10% (re1at1ve) f0r m05t e1ement5. H0wever, the ana1y5e5 0f Rh, W and Re, the three 1ea5t a6undant refract0ry meta15, are 0f 10wer 4ua11ty. Rh K , ha5 p00r detect10n 5en51t1v1ty and re4u1re5 c0rrect10n f0r 1nterference5 fr0m the m0re a6undant meta15 M0 and Ru. 7he am0unt5 0f W, and part1cu1ar1y Re, were 6e10w detect10n 11m1t 1n the 5ma11e5t meta1 9ra1n5. Hence the avera9e c0ncentrat10n5 0f Re and W 1n 7a61e 4 are 10wer 11m1t5.

2.2. E1ectr0n m1cr0pr06e 7he J E 0 L JXA-5A m1cr0pr06e w1th three cry5ta1 5pectr0meter5 and 0n-11ne 2 A F data reduct10n 6y the Ma50n et a1. pr09ram wa5 0perated at 15 kV and 40 nA current f0r ana1y51n9 5111cate and 0x1de 9ra1n5. 1nterference5 fr0m 71 K# 0n V K,~ were e11m1nated 6y 5u1ta61e p051t10n1n9 0f the V 6ack9r0und5. 8u1k ana1y5e5 0f Na, M9, A1, 51, 5,

C1, K, Ca, 71, Cr, Fe and N11n 5e1ected p0rt10n5 0f 3643 were 06ta1ned 6y manua11y ra5ter1n9 the 5ect10n 6e10w the 30 ptm def0cu55ed 6eam. Peak and t.0ta1 6ack9r0und t1me5 0f 200 5ec0nd5 per e1ement tr1ad were u5ed. After 2 A F c0rrect10n, the t0ta15 were reca1cu1ated t0 100% t0 c0rrect f0r 6eam 1055 1n crack5. A kaer5ut1te 5tandard ana1y5ed 6ef0re and after 3643 9ave exce11ent a9reement except f0r Ca wh1ch wa5 10w 6y 10% (re1at1ve). A5 a further check, a 5ynthet1c c0ar5e-9ra1ned CA1 prev10u51y ana1y5ed accurate1y 6y X-ray f1u0re5cence (XRF) wa5 ana1y5ed [9]. 7he m1cr0pr06e and XRF ana1y5e5 0f the maj0r e1ement5 d1ffered 6y am0unt5 fr0m 0.1 t0 4.6% (re1at1ve).

2.3. Pr0t0n m1cr0pr06e 5evera1 per0v5k1te 9ra1n5 m 3643 and 0ther CA1•5 were ana1y2ed 6y the Me160urne Un1ver51ty pr0t0n m1cr0pr06e, wh1ch ha5 far h19her 5en51t1v1ty f0r many e1ement5 than the e1ectr0n m1cr0pr06e. A 5 /~m d1ameter 6eam 0f 3 MeV pr0t0n5 wa5 f1red 1nt0 the tar9et 9ra1n5. 7he em1tted X-ray5 were ana1y2ed 6y a 51(L1) detect0r 5creened w1th A1 and 8e f0115 t0 reduce the c0p10u5 f1ux 0f X-ray5 0f 1e55 than 4 keV [10]. 3. De5cr1pt10n 0f CA1 3643

3.1. Appearance and 5tructure 8r1an Ma50n f0und CA1 3643 a5 a wh1t15h patch 1n the fu510n cru5t. He rem0ved 1t, made a th1n 5ect10n, and 9r0und up the rema1nder f0r maj0r and trace e1ement ana1y515 [11]. 1n th1n 5ect10n (F19. 1), CA1 3643 ha5 a p01y90na1 5hape 9 mm acr055, and a c0nv01uted 5urface. A60ut ha1f 0f the 1nc1u510n appear5 t0 have 6een a61ated away dur1n9 atm05pher1c entry. 3643 c0n515t5 0f three d15t1nct 1ayer5 (F19. 2): (1) An 1rre9u1ar, 5 6 mm d1ameter ~c0re~. (Dark and 5peck1ed 1n F19. 1) (2) A d15c0nt1nu0u5 ••mant1e•• up t0 1.5 mm w1de 0ut51de the c0re. (Wh1te 0r 610tchy 1n F19. 1.) (3) An 0uter ••cru5t••. (Pa1e 9rey and 5peck1ed 1n F19. 1, and dark ju5t 6e10w the matr1x). Exam1nat10n 6y m1cr0pr06e and 5EM c0nf1rm5 the d1fference5 6etween the c0re, mant1e and cru5t 1n texture, 1n m0da1 m1nera1 a6undance5, 1n m1nera1 chem15try, and 1n maj0r and trace e1ement chem-

131

F19. 1. 8ack5cattered e1ectr0n ph0t09raph 0f p0115hed 5ect10n 0f CA1 3643 5h0w1n9 c0mp051t10na1 and textura1 d1fference5 6etween c0re, mant1e and cru5t. CA1 wa5 cut acr055 6y fu510n cru5t 0f mete0r1te. 81ack area5 are ep0xy-f111ed h01e5 pr0duced dur1n9 5ect10n preparat10n. N0te the 5harp 60undary 0f c0re, the c0nv01uted r1m 0f the CA1, and the dark, a1tered 1ayer ju5t 6e10w r1m. 5ee F19. 2 f0r key.

132

;1

( 1

F19, 2. Key t0 F19. 1, 5h0w1n9 10cat10n5 0f c0re (p1a1n), mant1e (cr055-hatched), cru5t (d1a90na1 5tr1pe), r1m (heavy 11ne) and matr1x (d0tted). 80undary 6etween 1nner and 0uter c0re 15 5h0wn 6y da5hed 11ne. Num6er5 5h0w 10cat10n5 0f refract0ry meta1 nu99et5 ana1y5ed 1n 7a61e 4. N0te the h19h1y 1rre9u1ar 5hape 0f the c0re, w1th e1ther a pr0ject1n9 0ut11er 0r a deep 1nf01d, and the very var1a61e th1ckne55 0f the mant1e.

1ca1 c0mp051t10n [9,12]. 7he5e d1fference5 are centra1 t0 an under5tand1n9 0f the c0mp1ex ne6u1ar pr0ce55e5 wh1ch created 3643.

3.2. De5cr1pt10n 0f the c0re 7he c0re c0n515t5 0f 1ath5 and w0rmy cry5ta15 0f c010r1e55 h160n1te, and f1ne-9ra1ned, 6r0wn 1nter5t1t1a1 mater1a1. 1t ha5 e1ther a deep1y 1nf01ded 5urface, 0r an 0ut11er 0f c0re mater1a1 c0nnected 6y a narr0w t0n9ue 0r p1ate t0 the re5t 0f the c0re (F195. 1 and 2). 7w0 textura11y d1fferent re910n5 can 6e 5een 1n tran5m1tted 119ht, th0u9h n0t 1n F19. 1. 1n the 1nner re910n (F19. 2), a60ut 0ne-f1fth 0f the c0re, h160n1te 0ccur5 a5 matted, f1ne-9ra1ned 1ath5. 1n the 0uter c0re, h160n1te5 are c0ar5er9ra1ned and w0rmy. 1n ref1ected 119ht (F19. 3A) the c0re appear5 6ad1y p0115hed due t0 v01d 5pace5 6etween h160n1te

cry5ta15. 7he 5EM revea15 many f1ner v01d5 1n the 5p0n9y 1nter5t1t1a1 mater1a1 (F19. 3D), wh1ch 15 c0mp05ed 0f me1111te, 9r055u1ar and 5ma11 am0unt5, 1n decrea51n9 0rder 0f a6undance, 0f nephe11ne, 50da11te, an a1um1na pha5e, p1a910c1a5e, a CaA1M9Fe 5111cate (aen19mat1te var1ant•), per0v5k1te, 5p1ne1 and refract0ry meta1 a110y nu99et5. H160n1te cry5ta15 1n the c0re typ1ca11y have ra99ed, em6ayed 5urface5 (5ee F195. 3A, 3D and 6A), and part5 0f 50me have 6een p5eud0m0rph0u51y rep1aced 6y me1111te and 9r055u1ar. 7here are 1ar9e, rand0m var1at10n5 1n c0mp051t10n 6etween h160n1te5, fr0m 0.1 t0 4.4% 710 2, 0.1-1.3% V20 3 and 0.4-2.8% M 9 0 (F19. 4). H160n1te c0mp051t10n5 1n the 1nner and 0uter c0re 0ver1ap, th0u9h th05e 1n the 1nner c0re may 6e 5119ht1y p00rer 0n avera9e 1n M9 and 71 than th05e 1n the 0uter c0re. 7he mean and ran9e 0f 32 h160n1te ana1y5e5 fr0m the c0re are 91ven 1n 7a61e 1. 7here are a150 5u65tant1a1 c0mp051t10na1 var1at10n5 w1th1n m05t h160n1te cry5ta15 1n the c0re. M 9 0 , V20 3 and 710 2 vary a1m05t a5 w1de1y w1th1n 50me cry5ta15 a5 the t0ta1 ran9e 6etween cry5ta15 n0ted a60ve. 1ntra-cry5ta1 var1at10n5 a150 5h0w up 1n: (1) cath0d01um1ne5cence var1at10n5 fr0m r e d / 0 r a n 9 e t0 n0ne, and rare1y, t0 61ue; (2) wavy 0pt1ca1 ext1nct10n5 p055161y due t0 the c0mp051t10na1 var1at10n5; (3) para11e1, ex501ved 9106u1e5, need1e5 and 61ade5 0f per0v5k1te; and (4) rare h160n1te/5p1ne11nter9r0wth5. (7he5e 1a5t tw0 ca5e5 pr0v1de m05t 0f the 0ccurrence5 0f per0v5k1te and 5p1ne1 1n the c0re.) 7he mean and ran9e 0f f1ve 5p1ne1 ana1y5e5 1n the c0re are 91ven 1n 7a61e 1, 6ut the m1cr0meter-512ed, ex501ved per0v5k1te5 were t00 5ma11 t0 6e ana1y5ed 6y pr0t0n 0r e1ectr0n m1cr0pr06e. Me1111te, the darker 9rey pha5e 1n F19. 3A, 15 the ma1n 1nter5t1t1a1 mater1a1 6etween h160n1te cry5ta15, typ1ca11y a5 a p0r0u5, 5p0n9y netw0rk (F195. 3D and 6A) 0r, near the mant1e, a5 5ma11 c0mpact patche5 d15p1ay1n9 perfect hexa90na1 j01nt1n9. 1t ha5 0n1y a narr0w ran9e 0f c0mp051t10n5 fr0m 1.9% ak t0 6.6% ak (7a61e 2). 7he 5ma11 9ra1n-t09ra1n var1at10n5 appear t0 6e rand0m and unre1ated t0 10cat10n 1n the c0re (5ee F19. 5). 6r055u1ar, w1th a 111ac-c010red cath0d01um1ne5cence, 15 1nt1mate1y a550c1ated w1th me1111te and 5ma11, 1rre9u1ar patche5 0f p1a910c1a5e, nephe11ne, 50da11te and (p055161y) aen19mat1te. 7h15 15 9r055u1ar•5 n0rma1 0ccurrence 1n CA1•5, a5 an a1terat10n

F19. 3. (A) C0re, (8) mant1e and (C) cru5t 0f CA1 3643 5h0wn 1n ref1ected 119ht t0 5ame 5ca1e. N0te 9reat d1fference5 1n texture. (D) 5EM ph0t09raph 0f c0re 5h0w1n9 0pen texture 0f c0rr0ded h160n1te 1ath5 (H16), 051r-r1ch meta1 nu99et (0x1r), 5p0n9y, 1nter5t1t1a1 me1111te (Me1), and 9r055u1ar ( 6 ) and nephe11ne (N) a1terat10n pr0duct5. (E) 7ran5m1tted 119ht v1ew w1th cr055ed p01ar12er5 5h0w1n9 c0ar5e-9ra1ned me1111te mant1e 1n centre f1anked 6y dark, f1ne-9ra1ned c0re and cru5t. Def0rmed me1111te5 1n mant1e 5h0w wavy ext1nct10n (examp1e arr0wed). (F) 5EM 1ma9e 0f c0mpact-textured cru5t. H160n1te 1ath5 have 6een part1y rep1aced 6y me1111te, 5p[ne1 (5p) and per0v5k1te (P~). N0te: 5ame 1etter1n9 key t0 pha5e5 1n a11 f19ure5 1n th15 w0rk.

134

FM-•

C0RE

AN7LE

R1M

CRU57

MAN7LE

• •

51

*1

1

0

9

e

• e

•

•

4~

1p D

1 e

e

m D e•

500

1000

1 0

1500

D15tance f r 0 m r1m 0 r mant1e 1n m1cr0n5 1000

~080

500

1500

F19. 4. D1a9ram p10tt1n9 wt.% 7102 1n 38 ana1y5ed h160n1te 9ra1n5 1n CA1 3643 v5. d15tance (1n #m) 0f 9ra1n fr0m r1m (f0r 9ra1n5 1n cru5t) 0r fr0m mant1e (f0r 9ra1n5 1n c0re). N0te: (1) 1ar9e 9ra1n-t0-9ra1n var1a6111ty; (2) h19her 7102 c0ntent 0f h160n1te5 1n cru5t; (3) p055161e c0rre1at10n 1n cru5t 6etween 710 2 c0ntent 0f 9ra1n and 1t5 d15tance fr0m r1m; and (4) a65ence 0f c0rre1at10n 1n c0re 6etween 7102 c0ntent 0f 9ra1n and 1t5 d15tance fr0m mant1e.

F19. 5. D1a9ram p10tt1n9 c0mp051t10n5 0f 57 ana1y2ed me1111te 9ra1n5 1n CA1 3643 v5. d15tance (1n /~m) 0f 9ra1n fr0m r1m (f0r 9ra1n5 1n cru5t 0r mant1e) 0r fr0m mant1e (f0r 9ra1n5 1n c0re), Me1111te c0mp051t10n5 are expre55ed a5 percent 0f akerman1te c0mp0nent 1n 5011d 501ut10n (% ak). N0te rand0m c0mp051t10na1 var1at10n unc0rre1ated w1th d15tance fr0m r1m 0r mant1e,

p r 0 d u c t 0f me1111te [13]. R e p r e 5 e n t a t 1 v e ana1y5e5

w1th1n me1111te, a n d t h e f a c t t h a t 1t ha5 n e v e r 6 e e n

a r e 91ven 1n 7 a 6 1 e 2.

f0und

D15tance

am0n9

the

fr0m

r1m 0 r m a n t 1 e 1 n

m1cr0na

a1terat10n p r 0 d u c t 5

1n 0 t h e r

me1111te a n d nephe11ne (F195. 3D, 6A). 7 h e ana1y515 0 f 0 n e 0f the5e f1ake5, c0nta1n1n9 97.6% A 1 2 0 > 15

CA1•5, 5tr0n91y 5u99e5t t h a t 1t 15 a pre-a1terat10n c 0 n 5 t 1 t u e n t 0 f 3643. Maj0r e1ement 6u1k ana1y5e5 w e r e m a d e 6y manua11y ra5ter1n9 t h e e1ectr0n m 1 c r 0 p r 0 6 e 6 e a m , a5 de5cr16ed 1n 5ect10n 2,2, 0ver 0pp051te ha1ve5 0f t h e c0re. E a c h ana1y515 1nc1uded 50me 1nner a n d

91ven 1n 7 a 6 1 e 2. 7 h e

5 0 m e 0 u t e r c0re. 7 h e ana1y5e5 (7a61e 3) 5h0w t h a t

An a1um1napha5e

15 a un14ue f e a t u r e 0 f t h e c 0 r e

0 f 3643. M 1 c r 0 m e t e r a n d 5 u 6 - m 1 c r 0 m e t e r 9ra1n5 a n d 1eafy f1ake5 0 f th15 p h a 5 e 0 c c u r 1nter5t1t1a11y a n d a5 d a r k , 1 0 w - a t 0 m 1 c - n u m 6 e r 1nc1u510n5 1n

0 c c u r r e n c e 0f th15 p h a 5 e

7A8LE 1 Cath0d0-1um1ne5cence (CL) c010r5, and mean5 and ran9e5 0f ana1y5e5 1n wt.%, 0f h160n1te and 5p1ne11n the c0re and cru5t 0f CA1 3643 Pha5e:

H160n1te

5p1ne1

c0re (32)

cru5t (6)

c0re (5)

cru5t (3)

mean

ran9e

mean

ran9e

mean

ran9e

51---0a 710, A120 3 V20 3 (•r203 M90 Ca0 Fe0 70ta1

0.31 2.16 86.39 0.73 0.05 1,55 8.44 0.05 ~

0.04-0.93 0.06-4.40 82.3-90.5 0.11 1.31 0.00-0.12 0,43-2.83 7.37-9.08 0.00-0.12 -

0.38 5.17 82.41 0.24 0.03 3.16 8.93 0.03 1~0~.35

0.18-0.65 4.1-6.1 80.0-84.8 0.18-0.28 0.00-0.06 2.6-3.8 8.4-9.4 0.00 0.11

0,14 0.04 70.57 0.09 0.07 26,72 0,17 1.52 99~

0.00 0.34 0.01 0.07 68.5 71.7 0.05-0.14 0.02 0.10 26.0-27.3 0.10 0.29 0.8 2.6 -

CL

red 0r n0ne

61ue

Num6er 0f ana1y5e5 1n each mean 15 5h0wn 1n parenthe5e5. ~ Pre5ence 0f > 0.5% Fe0 1n 5p1ne1 4uenche5 cath0d0-1um1ne5ccnce.

n0ne ~

mean 0.24 0.23 69.42 0.37 0.04 24.95 0.38 4.40

ran9e 0.04-0.49 0.18-0.26 68.7-69.8 0.18 0.47 0.02-0.10 24.4-27.7 0.38-0.39 0.2-7.8

wh1te 0r n0ne •

135 7A8LE 2 Repre5entat1ve ana1y5e5 1n wt.% 0f me1111te, 9r055u1ar, a1um1na pha5e, nephe11ne, per0v5k1te and p055161e aen19mat1te-11ke pha5e 1n the c0re, mant1e and cru5t 0f CA1 3643 Pha5e:

510 2 7102 A120 3 Cr203 M90 Ca0 Fe0 Na20 K 20 70ta1

Me1111te

6r055u1ar

c0re

mant1e

cru5t

c0re

cru5t

22.09 0.00 36.20 0.00 0.30 41.65 0.00 0.05 n.a. ~

22.74 0.04 33.92 0.00 0.78 41.61 0.07 0.00 n.a. 99.16

22.24 0.06 35.18 0.02 0.36 41.34 0.05 0.05 n.a. 9-4-,30

39.37 0.11 23.35 0.01 0.34 34.55 0.39 n.a. n.a. 9~97~2.12

38.9 0.0 23.2 0.0 0.1 37.6 0.2 n.a. 0.0 100.0

A1um1na c0re 0.4 0.0 97.6 0.0 1.7 0.1 0.2 n.a. 0.0 100.0

Nephe11ne c0re 40.6 0.0 37.9 0.0 0.0 4.3 0.1 15.5 1.6 ~

Per0v5k1te cru5t

Aen19mat1te(•) mant1e

0.0 56.8 0.0 0.2 0.0 42.5 0.5 n.a. 0.0 100.0

31.11 0.07 34.90 0.02 3.28 29.01 2.33 0.00 0.00 100.71

Ener9y-d15per51ve ana1y5e5 6y 5EM have 6een n0rma112ed t0 t0ta1 100%. n.a. = n0t ana1v2ed.

F19. 6. 5EM ph0t09raph5. (A) A1tered part 0f 3643 c0re, w1th em6ayed, c0rr0ded cry5ta15 0f h160n1te 5h0w1n9 part1a1 rep1acement 6y me1111te. 5p0n9y, 1nter5t1t1a1 me1111te 15 1nter9r0wn w1th 9r055u1ar and nephe11ne a1terat10n pr0duct5. Dark 5u6-/~m 5peck5 1n me1111te and nephe11ne are a1um1na pha5e. (8) Dark a1tered 1ayer 6e10w 3643 r1m. Me1111te ha5 6een rep1aced 6y an0rth1te (An0rth) and fe1d5path01d5. N0te: (1) 5harp, 1nner 60undary 0f a1tered 1ayer; (2) chan9e 1n t0ne 0f 5p1ne15 fr0m dark (Fe-free) 1n una1tered me1111te t0 pa1e (Fe-r1ch) 1n a1tered 1ayer; and (3) cha0t1c r1m 20ne.

136 the c0re c0nta1n5 51m11ar c0ncentrat10n5 0f Na, K, C1 and Fe a5 a1tered 7 y p e A CA1•5 [13] a n d thu5 u n d e r w e n t 51m11ar 1ar9e chan9e5 1n c0mp051t10n dur1n9 v01at11e a1terat10n, w1th a 1055 0f Ca and M9 and a 9a1n 0f Na, K, C1, F e a n d 51 [14]. U51n9 the m e t h 0 d de5cr16ed 1n [9,14], the c0re•5 pre-a1terat10n chem1ca1 (7a61e 3) and m1nera1091ca1 c0mp051t10n5 were ca1cu1ated, the 1atter 6e1n9 62% h160n1te a n d 38% me1111te. A5 the pr1mary c0ncentrat10n5 0f the u1tra-refract0ry 0x1de5 7 1 0 : (2.8%) and A120 3 (69.1%) 1n the c0re are appr0x1mate1y tw1ce the re5pect1ve c0ncentrat10n5 0f the5e 0x1de5 (1.2% and 35%) 1n typ1ca1 7 y p e A CA1•5, the c0re 0f 3643 wa5 ev1dent1y extreme1y refract0ry. Refract0r), meta1 nu99et5 1.e. 9ra1n5 0f a110y5 0f Re, W a n d M0 w1th the P1at1num-9r0up meta15 (Pt, 05, 1r, Ru, Rh), are pre5ent 1n the c0re a5 1nc1u510n5 1n me1111te, 9r055u1ar a n d h160n1te. 7 h e y have m1cr0meter t0 5u6-m1cr0meter 512e5, a n d c 0 m p a c t r 0 u n d e d 0r p01y90na1 5hape5 (5ee F19. 3D). 1n the 5 E M m05t a p p e a r t0 6e 51n91e-pha5e meta1: 0ut 0f 50 0n1y 0ne, nu99et 7, wa5 a mu1t1pha5e ••fremd11n9•• [36] c0n515t1n9 0f 051r 5peck5 e m 6 e d d e d 1n M 0 5u1f1de and P t F e R u a110y. A 5y5temat1c 5earch 6 y 5 E M at 1000 × ma9n1f1cat10n ea511y f0und 0.5 # m (and 5ma11er) nu99et5. 150 1ma9e frame5 were 5earched c0ver1n9 0.6 m m 2 area 1n the 1nner c0re and 1.7 m m 2 1n the 0uter c0re.

7 w e n t y a n d 30 nu99et5 re5pect1ve1y were f0und, 1nd1cat1n9 nu99et den51t1e5 0f 33 per m m 2 1n the 1nner c0re and 18 per m m 2 1n the 0uter c0re. 5eventeen nu99et5 were ana1y2ed at 10cat10n5 m a r k e d 1n F19. 2 . 7 h e 1 r c0mp051t10n5 a n d 512e5 are 91ven 1n 7a61e 4. 7he5e 065ervat10n5 5h0w that: (1) Nu99et5 are n0t un1f0rm1y d15tr16uted. F 0 r examp1e, 0ne 51de 0f the 1nner c0re c0nta1n5 an unu5ua11y den5e c0ncentrat10n. (2) W1th1n 5ma11 re910n5, m05t 0f the nu99et5 5eem t0 6e 51m11ar 1n 512e and c0mp051t10n; e.9. 6 0ut 0f 7 nu99et5 1n the a60ve c0ncentrat10n are 1ar9e (avera91n9 13 ~ m 2) and 05-r1ch (05 18-57%), wherea5 5 0ut 0f 5 nu99et5 1n a re910n 0n the 0pp051te 51de 0f the 0uter c0re are 5ma11 ( - 1/~m 2) a n d 0 5 - p 0 0 r (05 0-5%). 1n an 1nterven1n9 re910n, 3 0ut 0f 3 nu99et5 are very 5ma11 ( - 0.5 ~ m 2) and 1ntermed1ate 1n 0 5 (05 3-9%). (3) Nu99et5 1n the 1nner c0re are 9enera11y 6199er, m0re numer0u5, a n d m 0 r e refract0ry (m0re 05-r1ch) than th05e 1n the 0uter c0re. 7 h e tw0 ch1ef except10n5 are the 619, 05-r1ch nu99et 7 1n the 0uter c0re a n d the 1e55 refract0ry, Pt-r1ch nu99et 17 1n the 1nner c0re. (4) 7 h e nu99et5 fa11 1nt0 the f0110w1n9 tw0 9r0up5: (a) 1ar9e, 05-rkch nu99et5 1 - 7 , a n d (6) 5ma11, Pt-r1ch nu99et5 8 - 1 7 . (W1th few except10n5, the5e tw0 9r0up5 c0rre1ate re5pect1ve1y w1th 1nner a n d 0uter c0re.) 7he5e tw0 9r0up5 0f nu99et5 are

7A8LE 3 Maj0r e1ement 6u1k ana1y5e5 0f c0re and 0f mant1e-p1u5-cru5t 0f CA1 3643, 1n wt.%. Ana1y5e5 are 6y manua11y-ra5tered, f0cu55ed e1ectr0n m1cr0pr06e 6eam, n0rma112ed t0 t0ta1 100% t0 a110w f0r 1055 0f 6eam 1n crack5. 7w0 type5 0f ana1y5e5 are 91ven: (1) 0f the mea5ured, a1tered CA1, 5u6d1v1ded1nt0 f1ve area5, and (2) 0f the ca1cu1ated mean pr1mary, pre-a1terat10n, c0mp051t10n5 (5ee text) C0re

Mant1e + cru5t

mea5ured

mea5ured

ca1cu1ated

area 1

area 2

pr1mary

area 3

area 4

area 5

pr1mary

14.94 0.91 60.41 0.01 5.63 15.59 1.27 0.05 1.00 0.08 0.09 0.02

14.48 1.03 67.74 0.02 1.95 12.67 0.78 0.02 1.09 0.09 0.10 0.03 1~. 00

7.43 2.82 69.10 1.97 18.68

26.26 1.20 40.59 0.03 3.50 24.03 2.79 0.04 1.24 0.06 0.21 0.05 100.00

24.33 1.35 43.13 0.02 4.37 23.16 2.21 0.02 1.13 0.05 0.20 0.03 100.00

23.88 1.15 43.60 0.02 5.00 22.51 2.74 0.05 0.79 0.05 0.18 0.03 100~ff0

13.70 1.52 52.69 5.59 26.50 -

5102 7102 A1203

Cr203 M90 Ca0 Fe0 N10 Na 20 K 20 C1 5 70ta1

ca1cu1ated

~

~

137 7A8LE 4 Ana1y5e5 a 0f 17 r e f r a c t 0 r y meta1 nu99et5 1n the c0re 0f CA1 3643, a n d m e a n c0mp051t10n 0f 05-r1ch nu99et5 1 - 7 a n d Pt-r1ch nu99et5 8 - 1 7 , we19hted acc0rd1n9 t0 0 u t c r 0 p area5 0f nu99et5. La5t r 0 w 5h0w5 the ca1cu1ated c0ncentrat10n (1n p p m ) 0f each meta1 1n the c0re a5 a wh01e, tak1n9 1nt0 a c c 0 u n t the d1ffer1n9 512e5, n u m 6 e r 5 a n d c0mp051t10n5 0f nu99et5 1n 1nner a n d 0 u t e r c0re, a n d d1fferent re1at1ve area5 0f 1nner a n d 0 u t e r c0re (5ee text). 7 h e d a t a 1n the 1a5t three r0w5 are p10tted 1n F19. 7. Nu99et5 7 a n d 1 1 - 1 6 are 1n the 0 u t e r c0re; 0ther5 are 1n the 1nner c0re. D a t a f0r Rh, Re a n d W are 0f 10wer 4ua11ty (5ee 5ect10n 2.1) Nu99et

Fe

N1

M0

Ru

Rh

W

Re

05

1r

1.8 1.2

1.7

1.7 4.0

52.9 57.0 52.7

32.9 25.9 27.6

Pt

Area 6

05-r1ch 1 2 3

2.3 1.4 1.1

1.8 0.3 0.4

5.8 2.6

8.3 8.0 7.5

1.1

6.3 14 11

4 5

5.6 11.7

0.8 1.1

14.2 18.6

13.2 6.0

-

4.4 3.7

2.3 2.1

40.4 39.4

19.1 17.5

-

1.1 28

6 7

3.1 2.4

1.2 0.4

15.4 2.7

19.9 10.3

-

-

-

18.5 43.4

37.5 40.8

4.4

3.5 25

8 9

5.9 11.1

2.8 1.3

25.1

48.3 17.5

1.1 5.8

-

1.2 -

8.6 2.7

11.6 3.7

20.5 32.8

0.5 0.6

10 11 12 13 14

10.5 13.0 12.7 9.6 3.8

8.3 8.6 16.0 9.8 4.4

4.7 8.8 10.0 -

24.6 12.3 27.0 29.2 28.2

1.7 . 3.6 3.2

-

4.8 -

5.6 5.2

8.5 5.3

33.2 53.9 33.5 37.9 60.4

0.5 1.4 0.7 0.8 0.6

15 16 17

11.2 8.6 17.7

10.1 17.8 6.4

3.4 -

21.7 24.4 4.1

7.9 3.2 7.9

49.1 42.6 63.9

0.5 1.2 9.4

5.1

0.7

8.6

8.5

> 0.3

14.5

7.8

2.2

12.5

5.8

25

9

Pt-r1ch

We19hted mean, 1-7 We19hted mean, 8-17 Wh01e c0re (ppm)

26

47

- 4

.

.

.

-

-

-

.

-

-

.

.

.

> 1.4

> 1.5

45.1

28.5

0.3

12.7

-

> 0.2

1.0

1.2

54.8

1.6

> 4

> 4

170

126

38

8 y 5 E M , n0rma112ed t0 t0ta1 100 wt.%. 6 0 u t c r 0 p a r e a 0f nu99et 1n /~m2. - = e1ement 6e10w detect10n 11m1t.

c0mp1ementary 1n c0mp051t10n--the f1r5t 9r0up 15 r1ch 1n the m05t refract0ry meta15 Re, W, 05, 1r and M0, 6ut p00r 1n the 1e55 refract0ry meta15 Ru, Pt, Rh, Fe and N1. 1n the 5ec0nd 9r0up the5e a6undance5 are rever5ed. 7he avera9e c0mp051t10n 0f each 9r0up fr0m 7a61e 4 15 p10tted 1n F19. 7. 7he c0mp1ementar1ty can 6e c1ear1y 5een. We can e5t1mate the c0ncentrat10n5 0f the refract0ry meta15 1n the c0re 1f we a55ume that the5e e1ement5 are pre5ent 0n1y 1n nu99et5.7he num6er5 0f nu99et5 per mm 2 and the1r re5pect1ve avera9e 512e5 (fr0m 7a61e 4) y1e1d m0da1 a6undance5 0f (33 × 7.6/106

X 100)

v01. % and

(18 X 4.4/106

X

100) v01.%, 1.e. 0.025 v01.% and 0.0078 v01.% 1n the 1nner and 0uter c0re re5pect1ve1y. 51nce the meta1 15 appr0x1mate1y f0ur t1me5 a5 den5e a5 the h160n1te

and me1111te 0f the c0re, the t0ta1 we19ht c0ncentrat10n5 0f refract0ry meta15 are - 1010 ppm and - 3 1 0 ppm re5pect1ve1y. A5 the 1nner and 0uter re910n5 0ccupy appr0x1mate1y 1 / 5 and 4 / 5 0f the c0re, the we19hted avera9e c0ncentrat10n 0f refract0ry meta15 1n the c0re a5 a wh01e 15 - 450 ppm. 7 0 determ1ne the c0ncentrat10n5 0f 1nd1v1dua1 refract0ry meta15 1n the c0re, the area-we19hted mean nu99et c0mp051t10n5 0f 1nner and 0uter c0re5 are f1r5t ca1cu1ated fr0m 7a61e 4 and u5ed t0 app0rt10n the t0ta1 refract0ry meta1 c0ncentrat10n5 (1010 and 310 ppm); then the 1nner and 0uter c0re c0ntr16ut10n5 are added f0r each e1ement. 7he re5u1t5, 1n the 1a5t 11ne 0f 7a61e 4 and 1n F19. 7, 5h0w that the C1-n0rma112ed refract0ry meta1

138

•Rw 0~

11 1 1rM0Ru

1

1

1

Pt

RhN1Fe

1

t•

106

/

~1 0~

"~

105

, 2

•

\

10 4

0

0C

LLt (D

10 3

9 102

101

100

LL = 18f00

C 0 , ~16 6,eh 1 [L , , 1600

~1 ~, , 1400

50% C0NDEN5A710N 7EMPERA7URE (K)

F19. 7. C1-n0rma112ed mean c0mp051t10n5 0f refract0ry meta1 nu99et5 fr0m 7a61e 4 p10tted v5. v01at111ty (1.e. ca1cu1ated [9,37] temperature 0f 50% c0nden5at10n at 10 4 atm). Mean 0f 05-r1ch nu99et5 1 - 7 = 0; mean 0f Pt-r1ch nu99et5 8 - 1 7 = •: and ca1cu1ated refract0ry meta1 c0ncentrat10n5 1n wh01e c0re = × . Ca1cu1ated [39,44] c0nden5at10n temperature5 0f c0rundum, h160n1te and 9eh1en1te are 5h0wn. N0te: (1) c0mp1ementar1ty 0f 05-r1ch and Pt-r1ch nu99et c0mp051t10n5; (2) ne9at1ve M0 and W an0ma11e5; (3) decrea5e 1n refract0ry meta1 a6undance5 0f wh01e c0re a5 v01at111ty 1ncrea5e5; and (4) 5harp decrea5e 1n a6undance fr0m 1r t0 Ru.

Me1111te 15 the pred0m1nant pha5e: the mant1e c0nta1n5 n0 h160n1te and n0 5p1ne1. 7he me1111te 0ccur5 a5 c0ar5e-9ra1ned (100-200 /~m), 1nter10ck1n9, def0rmed 1ath5 w1th 6ent 0r k1nked c1eava9e5, en eche10n def0rmat10n tw1n5, and undu105e ext1nct10n (F19. 3E). A few tr1p1e-junct10ned, m05a1c-textured area5 1ack 519n5 0f def0rmat10n. F0rty ana1y5e5 0f me1111te 1n the mant1e have a mean 0f ak 4.8% and vary rand0m1y fr0m ak 1 t0 ak 12 w1th1n, and 6etween, cry5ta15. 7here 15 n0 06v10u5 c0rre1at10n 6etween me1111te c0mp051t10n and p051t10n 1n the mant1e (F19. 5). Many 0f the cry5ta15 c0nta1n 5h0wer5 0f m1cr0meter-512ed 9106u1e5, p1u5 a few 1ar9er w0rmy 1nc1u510n5 0f per0v5k1te. Per0v5k1te 1nc1u510n5 ana1y2ed f0r trace e1ement5 6y pr0t0n m1cr0pr06e have typ1ca1 P1XE 5pectra a5 5h0wn 1n F19. 8. 7he rat105 0f the c0m61ned peak5 0f the L 11ne5 0f the heavy REE•5 6 d - L u , and 0f the K 11ne5 0f Y and 2r, n0rma112ed t0 the 71 K~ peak, are a fact0r 0f 3-10 t1me5 5ma11er 1n 3643 than 1n per0v5k1te5 0f 6 r 0 u p 1 CA1•5. 7he 1nterpretat10n 0f th15 re5u1t [9,16,17] 15 a5 f0110w5: 1n CA1•5 c0mp05ed ma1n1y 0f me1111te,

105 1104 1

a6undance5 vary fr0m - 350 × C1 f0r 05 d0wn t0 - 20 × C1 f0r Rh, 1.e., there 15 extreme, v01at111ty-dependent fract10nat10n. A5 Re and W were 0ften 6e10w detect10n 11m1t, the1r ca1cu1ated 6u1k c0ncentrat10n5 are 10wer 11m1t5.7he dep1et10n 0f M0 ( - 30 X C1) re1at1ve t0 1r ( - 265 × C1), an e1ement 0f 51m11ar v01at111ty 1n 501ar 9a5, ref1ect5 f0rmat10n under m0re 0x1d121n9 c0nd1t10n5 [15].

105

•+

~03 P

c0

104

-

L02 ,~

103

10~ ,,~

0 10~ 101

3.3. De5cr1pt10n 0f the mant1e 0

1n tran5m1tted 119ht, the mant1e 5tand5 0ut a5 a tran5parent, c0ar5e-9ra1ned and a1m05t c0nt1nu0u5 1ayer up t0 1.5 m m th1ck 6etween the c0re and f1ne-9ra1ned cru5t (5ee F195. 2 and 3E). 1n ref1ected 119ht, 1t ha5 a we11-p0115hed 5urface (F19. 38) and 1n 5EM 1ma9e5 (F19. 1) 1t appear5 wh1te, 1nter1aced w1th 9rey. Mant1e/c0re and mant1e/cru5t c0ntact5 are a6rupt and u5ua11y 5tra19ht.

2

4

6

8

10

12

14

16

18

20

x - r 0 y ener9y {keV)

F19. 8. P1XE ener9y-d15per51ve 5pectra fr0m pr0t0n m1cr0pr06e ana1y5e5 0f per0v5k1te5 1n typ1ca1 6 r 0 u p 1 CA1 (upper) and 1n mant1e 0f 3643 (10wer). N0te: (1) Y and 2 r peak5 0f 3643 per0v5k1te are much 10wer (re1at1ve t0 n0rma1121n9 71 peak) than 1n 6 r 0 u p 1 per0v5k1te; (2) ••6u19e•• 1n 6 r 0 u p 1 5pectrum due t0 many 0ver1app1n9 6 d -Lu peak5 15 a65ent fr0m 3643 5pectrum; and (3) Ar5en1c (A5) peak5 1n 3643 may 6e due t0 ep0xy m0unt1n9 med1um.

139 per0v5k1te 15 the ch1ef h05t pha5e f0r the refract0ry 11th0ph11e trace e1ement5 5uch a5 the REE•5, Y and 2r. 7he c0ncentrat10n5 0f the5e e1ement5 1n the per0v5k1te thu5 m1rr0r the1r a6undance5 1n the CA1 a5 a wh01e and c1ear1y d15t1n9u15h CA1•5 w1th unfract10nated 6 r 0 u p 1 trace e1ement pattern5 fr0m CA1•5 w1th fract10nated, refract0ry-dep1eted 6 r 0 u p 11 pattern5 [11]. 1n F19. 8, per0v5k1te 1n the mant1e 0f 3643 5h0w5 the 10w a6undance5 0f Y, 2r and the m05t1y m0re refract0ry heavy REE•5 6 d - L u that are character15t1c 0f 6 r 0 u p 11 CA1•5. 7h15 re5u1t 15 5upp0rted 6y an 5EM 5earch 0f 130 frame5 (2 mm 2) 0f mant1e that d1d n0t f1nd a 51n91e refract0ry meta1 nu99et. 51m11ar 5EM 5earche5 0f kn0wn 6 r 0 u p 11 CA1•5 a150 f1nd v1rtua11y n0 refract0ry meta1 nu99et5, 1n c0ntra5t t0 the a6undant nu99et5 f0und 1n 6 r 0 u p 1 CA1•5 [9]. 7h15 15 n0t 5urpr151n9 51nce 6u1k ana1y5e5 0f 6 r 0 u p 11 CA1•5 5h0w that they are h19h1y dep1eted 1n 1r and 0ther refract0ry 51der0ph11e5 [18]. F1ne-9ra1ned 6r0wn mater1a1 0ut11ne5 9ra1n 60undar1e5 and crack5, and 1n p1ace5 f0rm5 a netw0rk 0f dark channe15 1n the wh1te me1111te mant1e (F19. 1). 1t c0n515t5 ma1n1y 0f 9r055u1ar, fe1d5path01d5 and a pha5e 0f var1a61e c0mp051t10n (5ee typ1ca1 ana1y515 1n 7a61e 2). 7h15 pha5e 15 c0mm0n 1n a1tered me1111te 1n many CA1•5 [9]. 1t5 c0mp051t10n5 vary 6y 5evera1 wt.% 0n e1ther 51de 0f the f0110w1n9 appr0x1mate ana1y5e5:5102 33%, A120 3 35%, N a 2 0 1%, and M 9 0 2%, F e 0 1%, C a 0 30% (f0r the 10w-M9Fe, h19h-Ca var1ant) 0r M 9 0 10%, F e 0 5%, C a 0 15% (f0r the h19h-M9Fe, 10w-Ca var1ant). 7he 6e5t f1t f0r f0rmu1ae ca1cu1ated fr0m the5e ana1y5e5 5eem5 t0 6e w1th 14 t0ta1 cat10n5 t0 20 0xy9en5. 1t may 6e a 5u65t1tuted aen19mat1te Na2F%(71516)020 [19] 1n wh1ch Ca rep1ace5 Na, and M9 and A1 rep1ace 50me Fe, 71 and 51, a5 f0110w5: Ca2(M9, Fe, Ca)5(A1, 81)7020.

3. 4. De5cr1pt10n 0f the cru5t 7he 0.5-2 mm w1de 1ayer 0f cru5t 6etween the mant1e and the 5urface 0f 3643 15 very f1ne-9ra1ned, typ1ca11y a60ut 10/~m, and c0n515t5 0f three 1ayer5, a5 f0110w5: (1) 7he 1nner 70% can 6e 5een 1n ref1ected 119ht (F19. 3C) and 5EM (F19. 3F) t0 6e c0mp05ed 0f me1111te w1th 1nc1u510n5 0f h160n1te, 5p1ne1 and per0v5k1te. (2) 7he dark, a1tered, 0.1-0.5 mm w1de 1ayer

1mmed1ate1y 6e10w the r1m (5ee F195. 1 and 68) 15 an0rth1te- and fe1d5path01d-r1ch. (3) 7he th1n, 1ayered r1m ( < 30 1~m) c0ntact5 the matr1x. Me1111te, the ma1n pha5e 1n the cru5t ( - 6 0 v01.%), 0ccur5 a5 5m00th, c0mpact area5 (F19. 3F), a5 tr1p1e-junct10ned, p01y90na1 m05a1c5, and a5 ra99ed, cavern0u5 9ra1n5 that are 0ften a550c1ated w1th 9r055u1ar, nephe11ne and 0ther 1nd1cat0r5 0f a1terat10n [13]. Me1111te ana1y5e5 (7a61e 2) ran9e fr0m ak 1.5 t0 ak 5.2, and 5h0w n0 5y5temat1c var1at10n w1th d15tance fr0m the r1m (F19. 5). H160n1te, the 5ec0nd m05t a6undant pha5e 1n the cru5t ( - 2 0 v01.%), 0ccur5 a5 ac1cu1ar, ra99ed 0r w0rmy 1nc1u510n5 1n me1111te. 1t 15 0ften 1nter9r0wn w1th 5p1ne1 (F19. 3F). H160n1te 1n the cru5t 15 d1fferent fr0m that 1n the c0re, and ha5 61ue cath0d01um1ne5cence (cf. red 0r n0ne 1n the c0re), h19her M9 and 71, and 10wer V (7a61e 1 and F19. 4). W1th1n the cru5t, h160n1te 9ra1n5 c105er t0 the r1m may 6e p00rer 1n M9 and 71 than th05e further away (5ee F19. 4). 5p1ne1 15 the th1rd m05t a6undant pha5e 1n the cru5t ( - 15 v01%) and 0ccur5 a5 w0rmy 9ra1n5 0r a5 ra99ed ac1cu1ar 9ra1n5 p5eud0m0rph0u5 after h160n1te, 6ut 0n1y rare1y a5 the e4uant cry5ta15 fam111ar 1n 0ther CA1•5 (F19. 3F). 1t typ1ca11y em1t5 a wh1te cath0d01um1ne5cence and 15 r1cher 1n 71 and V than 5p1ne1 1n the c0re (7a61e 1). Per0v5k1te, a m1n0r pha5e ( - 0.6 v01.%), 0ccur5 a5 w0rmy 1nc1u510n5 1n 5p1ne1 (F19. 3F). 7he 1ar9e5t 9ra1n5 were ana1y2ed 6y 5EM (7a61e 2) and pr0t0n m1cr0pr06e. L1ke the mant1e per0v5k1te5, they were 10w 1n Y, 2r and heavy REE•5 1nd1cat1n9 that the cru5t 15 0f 6 r 0 u p 11. 0pa4ue pha5e5. A 5EM 5earch 0f f1ve d1fferent area5 0f cru5t and mant1e am0unt1n9 t0 3.7 mm 2 f0und n0 refract0ry meta1 nu99et5, c0nf1rm1n9 the c1a551f1cat10n 0f the cru5t (and mant1e) a5 6 r 0 u p 11. 7he 5earch d1d, h0wever, f1nd 38 0ther 0pa4ue 9ra1n5, 22 0f wh1ch were ana1y5ed (7a61e 5). 7he f1ve 9ra1r15 ana1y5ed 1n the mant1e 1nc1uded three 0f meta1 (2 0f N1Fe, 1 0f CuN12n), tw0 0f FeN1 5u1f1de and 0ne pr06a61y 0f chr0m1te. 7he 51xteen 9ra1n5 ana1y2ed 1n the cru5t were 51m11ar t0 th05e 1n the mant1e and 1nc1uded n1ne N1Fe meta1, tw0 FeN1 5u1f1de, tw0 c0mp051te meta1/5u1f1de 9ra1n5, and three Fe 0x1de 9ra1n5. 7he 0vera11 avera9e 0utcr0p area 0f the ana1y2ed meta1 and 0x1de 9ra1n5 15 4.7 /~m2 and 0f the 5u1f1de5 9.8 ~m 2.

140

7A8LE

5

C0mp051t10n5 0f meta1 a n d 5u1f1de 9ra1n5 1n the mant1e a n d cru5t 0 f CA1 3643. Ana1y5e5 6 y 5 E M , n0rma112ed t0 t0ta1 100 wt.% 6ra1n a

5

Fe

N1

Cu

2n

Area 6

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16

0 0 0 0 0 0 0 0 0 0 0 0 40 47 46 44

22 23 25 28 28 31 32 35 67 27 25 1 55 35 41 42

78 77 75 72 72 69 68 65 33 73 75 18 5 16 13 14

0 0 0 0 0 0 0 0 0 0 0 65 0 0 0 0

0 0 0 0 0 0 0 0 0 0 0 16 1 2 0 0

8.4 2.3 7.1 1.1 2.1 5.7 3.5 11 2.8 2.3 2.4 5.2 18 4.6 8.4 2.3

c c c c c c c c c m m m c c m m

C ~ cru5t, rn = mant1e. 6 0 u t c r 0 p a r e a 0f 9ra1n 1n /.tm2.

0f h160n1te w1th 5p1ne1 1nc1u510n5, 0ver1a1n 6y an0rth1te and heden6er91te 1ayer5. 8ut 1n m05t p1ace5 the r1m 15 6r0ken up and cha0t1c (e.9. F19. 68). Maj0r e1ement 6u1k ana1y5e5 0f three d1fferent area5 0f mant1e-p1u5-cru5t were made 6y m1cr0pr06e (7a61e 3). 7he mant1e-p1u5-cru5t 15 r1cher 1n Na, C1 and Fe than the c0re, c0n515tent w1th the 1ntr0duct10n 0f v01at11e5 fr0m 0ut51de. 7he ca1cu1ated pr1mary c0mp051t10n 0f the mant1e-p1u5-cru5t 1n 7a61e 3 15 rad1ca11y d1fferent fr0m that 0f the c0re, wh1ch 15 r1cher 1n 71 and A1, and p00rer 1n M9 and 51. Pr1mary m0da1 m1nera1091ca1 c0mp051t10n5 ca1cu1ated fr0m the5e data a150 d1ffer 9reat1y: c0re 62% h160n1te, 38% me1111te v5. mant1e-p1u5cru5t 20% h160n1te, 65% me1111te, 15% 5p1ne1 and 0.6% per0v5k1te. 3.5. 8u1k chem1ca1 c0mp051t10n 0f 3643

a

51m11ar m1cr0meter-512ed N1Fe and 5u1f1de 9ra1n5 have a150 6een f0und 1n kn0wn 11A CA1•5 [9]. 7he maj0r1ty 0f the5e 9ra1n5 cann0t 6e c0ntam1nat10n fr0m the matr1x, 6ecau5e matr1x meta15 and 5u1f1de5 have d1fferent c0mp051t10n5 0f appr0x1mate1y 70% N1, 30% Fe and 40% 5, 42% Fe, 18% N1 re5pect1ve1y. 7he dark 0uter 1ayer ha5 the 5ame texture a5 the 1nner cru5t 6ut the p1ace 0f me1111te ha5 6een 1ar9e1y taken 6y an0rth1te p1u5 5ma11er am0unt5 0f nephe11ne, 50da11te and aen19mat1te (•), and the 5p1ne15 are Fe-r1ch. 7he rep1acement 0f Ca-r1ch me1111te 6y Na- and 51-r1ch nephe11ne and an0rth1te ha5 10wered the avera9e at0m1c num6er and hence darkened the 6ack5cattered e1ectr0n 1ma9e (F19. 68) 0f m05t 0f the 0uter 1ayer except1n9 the 5p1ne1 1nc1u510n5 wh1ch appear 6r19hter 6ecau5e 0f rep1acement 0f M9 6y h19her at0m1c num6er Fe. N0te 1n F19. 68 the dark 1ayer•5 5harp 60undary para11e1 t0 the r1m, and the c0nt1nu1ty 0f 5p1ne15 acr055 the 60undary. 7he 0uter 1ayer ha5 theref0re 6een meta50mat12ed, w1th pre5ervat10n 0f 1t5 0r191na1 texture, 6y v01at11e5 fr0m 0ut51de. 7he r1m. 7he 5urface 0f CA• 3643 15 r0u9h and c0nv01uted, 065cur1n9 the deta115 0f the c0ntact w1th the matr1x. 1n a few p1ace5 there are ••WarkL0ver1n9•• [20] r1m 1ayer5, 1n 0ther5 there 15 a 1ayer

Fr0m F19. 1, the pre-a61at10n rad1u5 0f the c0re 15 appr0x1mate1y 0.6 0f the avera9e rad1u5 0f the wh01e CA1. 7he c0re 15 theref0re (0.6) 3 1.e. appr0x1mate1y 21%, 0f 3643.7he 0vera11 c0mp051t10n 0f 3643 (a we19hted avera9e 0f the ana1y5e5 1n 7a61e 3, w1th 21% c0re and 79% mant1e-p1u5-cru5t) 15 c0mpared 6e10w w1th Ma50n and Mart1n•5 [11] ana1y515 (1n parenthe5e5) 0f a 5amp1e 0f 3643:5102 22.7% (24.9), 7102 1.2% (1.3), A1203 47.0% (36.3), M 9 0 4.2% .(7.5), C a 0 21.3% (19.9), F e 0 2,3% (6.0), N a 2 0 1.1% (1.1) and K 2 0 0.06% (0.05). 7he d15a9reement5 f0r A1, Fe and M9 5tr0n91y 5u99e5t that Ma50n and Mart1n 5amp1ed d1fferent mater1a1 than the th1n 5ect10n ana1y5ed 1n th15 w0rk. A5 we w111 5ee, the1r 5amp1e under-repre5ent5 the A1-r1ch c0re and may 1nc1ude 50me FeM951-r1ch matr1x trapped 1n the r1m c0nv01ut10n5. Ma50n and Mart1n mea5ured 0.60 ppm M0 1n 3643. H0wever, 1f the c0re make5 up 21% 0f 3643 and c0nta1n5 26 ppm M0 (7a61e 4), then the 10wer 11m1t f0r M0 1n 3643 w0u1d 6e 5.5 ppm. Ev1dent1y, Ma50n and Mart1n•5 5amp1e 1nc1ude5 much 1e55 c0re than the 5ect10n, and ma1n1y repre5ent5 the 0uter part5 0f 3643. U51n9 the a60ve M0 data, ma55 6a1ance ca1cu1at10n5 5h0w that Ma50n and Mart1n•5 5amp1e 1nc1ude5 a max1mum 0f 2.3% c0re (1f the mant1e-p1u5-cru5t c0ntr16ute n0 M0) 0r, m0re 11ke1y, a60ut 1.3% c0re (1f the mant1e-p1u5cru5t c0nta1n 0.27 ppm M0 [9], the mean M0 c0ntent 0f 11A CA1•5 [21] 1.e. 6 r 0 u p 11 7ype A

141

CA1•5, the 5ame chem1ca1/m1nera1091ca1 type a5 the mant1e and cru5t.) 7race e1ement ana1y5e5 0f a 5amp1e 0f 3643 were a150 made 6y Ma50n and Mart1n [11] and C1-n0rma112ed p10t5 0f the5e data are c0mpared 1n F19. 9 w1th the avera9e ana1y515 0f three 11A CA1•5 [9]. 7he 3643 5amp1e ha5 h19h1y fract10nated trace e1ement c0ncentrat10n5 ••9enera11y 51m11ar t0 th05e 0f 6 r 0 u p 11•• [11]. 7he 3643 pattern5, h0wever, are f1atter, 1.e. re1at1ve t0 the m0derate1y refract0ry e1ement5 1n the centre, the u1tra-refract0ry e1ement5 0n the 1eft are n0t a5 dep1eted 1n 3643 a5 1n the mean 11A CA1, pr06a61y due t0 the pre5ence 0f a 5ma11 am0unt 0f u1tra-refract0ry c0re 1n the 3643 5amp1e. 7he enr1chment5 0f u1tra-refract0ry e1ement5 1n the c0re can even 6e e5t1mated fr0m the data 1n F19. 9. 1f the rat10 0f u1tra-refract0ry (e.9. 2r, Y, Hf) t0 m0derate1y refract0ry (e.9. 7h, 8a, Ca) e1ement5 were the 5ame 1n 6u1k 3643 a5 1n the mean 11A CA1•5, then 2r, Y and H f 1n 6u1k 3643 w0u1d 6e enr1ched 0n1y - 1 . 5 × C1 1n5tead 0f the actua1 enr1chment 0f 3.8 x C1. A5-

,

1

1

,

,

•.

20

.0~=c ~< ~°105

2

1

1

1

,

1

"~-- -0.

"•••a.

"~--~ 2r Y Hf 71 Th A1 8a Ca Eu 5r Y6 U . . . . . . . . . . . . ~ .0•..-0----0----Q

c10 5

,

.0••

L

50

,

1

1

1

1

1

L

1

1

L

J

1

.~" 0••"

Lu Er H0 Dy 767m5m La d Ce Eu /NCREA5/N6 V0LA71L/7Y

p,

F19. 9. C1-n0rma112ed trace 11th0ph11e a6undance5 p10tted 1n e5t1mated 0rder 0f v01at111ty. 8u1k 3643 (e) data 0f [11] are c0mpared w1th mean ana1y515 [9] 0f three 11A CA1•5 ( 0 ) . 3643 6u1k 5amp1e c0n515ted m05t1y 0f mant1e and cru5t.

5um1n9 that the exce55 enr1chment 0f 2.3 × C1 15 due t0 the pre5ence 0f 1.3% 0f c0re 1n the 6u1k 3643 5amp1e, then the c0re mu5t c0nta1n - 200 × C1 a6undance5 0f 2r, Y and Hf. 7he u1tra-refract0ry REE•5 Lu, Er and H0 a150 5h0w an avera9e exce55 enr1chment 1n 3643 0f (6.0-3.7)× C1, 1.e. 2.3 × C1, 1ead1n9 t0 the 5ame - 200 × C1 u1tra-refract0ry 11th0ph11e enr1chment5 a5 6ef0re, 1n rea50na61e a9reement w1th th05e f0r 05 (350 X C1), 1r (265 × C1) and Ru (70 × C1), 5h0wn 1n F19. 7. 4. D15cu5510n

4.1. C0mpar150n 0f 3643 t0 0ther CA1•5 A5 we have 5een, 3643 c0n515t5 0f three 1ayer5--c0re, mant1e and cru5t--that are chem1ca11y, m1ner01091ca11y and textura11y d15t1nct fr0m 0ne an0ther. 7he c0re 15 h19h1y enr1ched 1n the u1tra-refract0ry 11th0ph11e ( - 200 × C1) and 51der0ph11e trace e1ement5 (e.9. 05, 350 × C1), and d15p1ay5 a 5teep fract10nat10n 0f the m0derate1y refract0ry meta15, wh05e a6undance5 decrea5e w1th 1ncrea51n9 v01at111ty d0wn t0 20 × C1 f0r Rh (F19. 7). C0mpared t0 the fa1r1y un1f0rm, m0de5t 10-40 × C1 enr1chment5 0f refract0ry trace e1ement5 1n 6 r 0 u p 1 and 6 r 0 u p 111 CA1•5 [11], the h19h1y fract10nated, tw0 hundred-f01d enr1chment5 1n the c0re 0f 3643 4ua11fy 1t a5 an u1tra-refract0ry 1nc1u510n. M1nera1091ca11y, the c0re can 6e further c1a551f1ed a5 7 y p e A 0n acc0unt 0f 1t5 pred0m1nant1y me1111te-p1u5-h160n1te c0mp051t10n [22]. 7he mant1e 15 5harp1y de11neated fr0m the c0re, 60th phy51ca11y and c0mp051t10na11y. 1t 1ack5 refract0ry meta1 nu99et5 and 1t5 per0v5k1te5 5h0w dep1et10n5 1n the u1tra-refract0ry e1ement5 Y, 2r and (m05t) heavy REE•5. 1t a150 p055e55e5 rare 9ra1n5 0f v01at11e 5u1f1de5 and N1Fe meta1, n0ne 0f wh1ch are f0und 1n the c0re. A11 0f the5e feature5 are 519nature5 0f refract0ry-dep1eted 6 r 0 u p 11 CA1•5 [9]. 7he cru5t, th0u9h textura11y and m1nera1091ca11y d1fferent fr0m the mant1e, 15 a1m05t 1dent1ca1 t0 1t 1n a11 the a60ve re5pect5, and th15 chem1ca1 51m11ar1ty 15 c0nf1rmed 6y the fact that Ma50n and Mart1n•5 6u1k 5amp1e (1ar9e1y mant1e-p1u5cru5t) ha5 a 6 r 0 u p 11 REE pattern [11]. F1na11y, the maj0r e1ement c0mp051t10n 0f mant1e-p1u5cru5t 15 5u65tant1a11y 1e55 refract0ry than that 0f the c0re, 6e1n9 10wer 1n A1 and 71, and h19her 1n re1at1ve1y v01at11e M9 and 51 (7a61e 3). M1nera1091-

142

ca11y, h0wever, th0u9h the mant1e and cru5t are d1fferent fr0m the c0re (and each 0ther), a11 three mu5t 6e c1a551f1ed a5 7 y p e A 51nce they are c0mp05ed ma1n1y 0f me1111te and h160n1te [22]. Hence, 3643 c0n515t5 0f an u1tra-refract0ry 7ype A c0re enc105ed 1n refract0ry-dep1eted ( 6 r 0 u p 11) 7 y p e A 1ayer5, and 15 un14ue am0n9 kn0wn CA1•5. 50 far a5 15 kn0wn, 0n1y f1ve 0ther u1tra-refract0ry 1nc1u510n5 have 6een de5cr16ed. 7he f1r5t tw0, M H 115 [23] and 5H-2 [24], are m1111meter-512ed, 5p1ne1-h160n1te a99re9ate5 [25] 1n Murch150n. Refract0ry e1ement enr1chment5 1n MH-115 ran9e fr0m - 100 × C1 f0r Lu, 5c and 1r d0wn t0 - 30 × C1 f0r La and 5m, wh11e 1n 5H-2 they ran9e fr0m 3000-4000 × C1 f0r Re and 05, 1000 1700 × C 1 f0r 1r, Hf and Lu, 1 1 0 × C 1 f0r La. 7he th1rd, a t1ny 1 /~9 06ject 1n 0rnan5 [26] c0n515t1n9 0f a ••fremd11n9•• 1n unkn0wn h05t mater1a1, ha5 enr1chment5 ran91n9 fr0m 15,000 × C1 f0r Re, 05 and 1r, 10,000 × C1 f0r Lu and Hf, t0 3920 × C1 f0r Ru, and < 30 x C1 f0r 5m. 7he f0urth, H A L [27], 15 a c0mp1ex1y 1ayered, h160n1te-c0red, 5 mm 1nc1u510n 1n A11ende and 5h0w5 var1a61e enr1chment5 0f 2r, Hf and Lu up t0 200 × C1 1n 50me 1ayer5, th0u9h never m0re than 3 × C1 f0r 05 and 1r. 7he f1fth c0n515t5 0f a c1u5ter 0f Re-W-05-1r-M0 nu99et5 [28] 1n a 5u6-m1111meter re910n 0f 5p1ne1 + 5111cate 1n51de a 1ar9er (5 mm), an0rth1te-r1ch 1C CA1 [21] named 6 / 1 1n A11ende. 7he 0nce-m01ten h05t CA1 (enr1ched a1m05t un1f0rm1y t0 0n1y - 10 × C1 1n 05, 1r, Ru and Pt) appear5 t0 have captured and part1y d19e5ted the 5ma11, u1tra-refract0ry 60dy [29]. Perhap5 the 250 t~m c0rundumh160n1te 5pheru1e 88-5 [30] (0r the 51m11ar 60dy 6 R - 1 [31]) 1n Murch150n 5h0u1d a150 6e c0unted a5 an • u1tra-refract0ry•• 06ject 51nce 1t f0rmed at a temperature h19h en0u9h t0 me1t h160n1te. H0wever, 1t ha5 0n1y 30-40 x C1 enr1chment5 0f refract0ry trace e1ement5. 7h15 6r1ef 5urvey 15 1ntended t0 5h0w that each u1tra-refract0ry 06ject, 1nc1ud1n9 the c0re 0f 3643, 15 un14ue. 7he 0uter 1ayer5 0f 3643, th0u9h n0m1na11y 11A CA1•5, are a150 un14ue 1n the1r unu5ua11y h19h 0vera11 enr1chment5 0f h160n1te and A1203 [9]. 1n add1t10n, n0 0ther kn0wn c0mp051te CA1 ha5 the 5ame 5e4uence 0r type 0f 1ayer5 a5 3 6 4 3 - - n 0 t the f1ne-9ra1ned, 20ned a99re9ate5 [32], n0r the c0mp051te 18-1n-1A CA1•5 [33], n0r the me1111te-r1ch c0mp051te CA1 1n E55e61 [34]. A further 1mp0rtant fact a60ut 3643 15 that,

de5p1te the d1fference5 and h1atu5e5 6etween 1ayer5, there 15 a150 c0nt1nu1ty 6etween them 1n: (1) 7he1r maj0r e1ement chem15tr1e5, a11 0f wh1ch are extreme1y r1ch 1n A120 3 (53-69%) c0mpared t0 m05t 0ther A11ende CA1•5 (7ype5 A, 8 and C have 25-46% A120 3 [9]). (2) 7he1r 51m11ar 5u1te5 0f maj0r pha5e5-9eh1en1te, h160n1te, 5p1ne1 and per0v5k1te. N0 akerman1t1c me1111te, 71-pyr0xene, f0r5ter1te 0r pr1mary an0rth1te are pre5ent, a1th0u9h the5e pha5e5 are c0mm0n 1n many 0ther CA1•5. (3) 7he 51m11ar 6 r 0 u p 11 pattern5 0f per0v5k1te5, and c0mp051t10n5 0f 0pa4ue5, 1n the mant1e and cru5t. 7he 065ervat10n5 a60ve p05e many 4ue5t10n5 a60ut 3643. 15 each 1ayer a c0nden5ate, an evap0rat1ve re51due, a pr0duct 0f 114u1d cry5ta1112at10n, 0r 0f metam0rph15m• D1d the 1ayer5 f0rm 1n 4u1ck 5ucce5510n, 0r were there 10n9 h1atu5e5 6etween them• D1d they f0rm fr0m the 5ame, 0r unre1ated, re5erv01r5• Are any 0f the 1ayer5 pre501ar, 0r d1d they f0rm 1n the 501ar ne6u1a• And f1na11y, t0 what extent have 5ec0ndary pr0ce55e5 065cured the ear11er rec0rd• 4.2. F0rmat10n 0f the c0re

7he key t0 the5e 4ue5t10n5 11e5 1n the refract0ry meta1 nu99et5 1n the c0re. 7he nu99et5• c0mp051t10n5 c0u1d n0t have 6een pr0duced 1n 51tu 6y 5e9re9at10n 0f e1ement5 acc0rd1n9 t0 cry5ta1-chem1ca1 preference5 0r chem1ca1 6ehav10ur5, a5 de5cr16ed 6y Fuch5 and 81ander [35]. 7he nu99et5 are 51n91e-pha5e a110y5 and n0t c0mp1ex mu1t1pha5e a55em61a9e5 (fremd11n9e [36]) pr0duced 6y the rem0va1 0f 0x1d12a61e M0, W 0r Fe 1nt0 a550c1ated 5u1f1de5 and 0x1de5, 6y the 5eparat10n 0f Pt 1nt0 FeN1 meta1, 0r 6y the 5e9re9at10n 0f 05 and Ru (wh1ch fav0r the hexa90na1 c105e-packed 5tructure) 1nt0 5eparate 9ra1n5 fr0m 1r (wh1ch prefer5 face-centred cu61c 5tructure5). 0 n the c0ntrary, the ana1y5e5 1n 7a61e 4 5h0w, f0r examp1e, that 05 and Ru are ant1-c0rre1ated wh11e 05 and 1r are p051t1ve1y c0rre1ated. Ev1dent1y, the a60ve 5e9re9at10n pr0ce55e5 were n0t 1mp0rtant 1n the f0rmat10n 0f the c0re. A5 we w111 n0w 5h0w, the nu99et5 1n the c0re (0r at 1ea5t the RuPt-r1ch, 051rFeN1-p00r 0ne5 1n the 0uter c0re) f0rmed a5 c0nden5ate5. 5upp05e that the c0re•5 5tart1n9 mater1a1 wa5 h0t, c0011n9 9a5 0f 501ar c0mp051t10n. Pa1me and

143

W10t2ka [37] and 81ander et a1. [28] have 5h0wn that the f1r5t c0nden5ate5 w0u1d 6e a110y5 c0mp05ed ma1n1y 0f the u1tra-refract0ry meta15 Re, W and 05. 0 n further c0011n9, m0re 1r and M0, and then Ru and Pt, w0u1d enter the a110y. 8ut 1t w0u1d 5t111 6e r1ch 1n 05, 1r and M0, and further c0011n9 w0u1d 51mp1y d11ute 1t w1th Fe and N1. 50 un1nterrupted c0nden5at10n fr0m 501ar 9a5 c0u1d never pr0duce an a110y r1ch 1n Ru and Pt 6ut p00r 1n 05, 1r, Fe and N1, 11ke the nu99et5 1n the 0uter c0re. 1f, 1n5tead, we heated 5011d mater1a1 0f c05m1c c0mp051t10n, we w0u1d f1r5t dr1ve 0ff m05t 0f the Fe and N1, then m05t 0f the Rh, Pt and Ru, 1eav1n9 the re51due r1ch 1n 1r, M0 and 05. 50 evap0rat10n a10ne c0u1d never pr0duce RuPt-r1ch, 051r-p00r nu99et5 e1ther. A three-5ta9e pr0ce55 15 nece55ary. F1r5t, make a 9a5 enr1ched 1n Ru, Pt and m0re v01at11e e1ement5 6y evap0rat1n9 c05m1c 5011d 0r 6y c0nden51n9 c05m1c 9a5, 1n e1ther ca5e 1nterrupt1n9 the pr0ce55 and rem0v1n9 the c0nden5ate 0r re51due c0nta1n1n9 the very refract0ry meta15 Re, W, 05, 1r and M0. 5ec0nd, 6e91n t0 c0nden5e the RuPtFeN1-r1ch 9a5. 7h1rd, 1nterrupt c0nden5at10n and 1501ate the RuPt-r1ch nu99et5 6ef0re they are 5wamped 6y c0nden51n9 Fe and N1. 7he5e 5ame three 5tep5, 80ynt0n [38] ha5 5h0wn, are a150 re4u1red t0 pr0duce 6 r 0 u p 11 mater1a15 wh1ch are ana1090u5 t0 the RuPt-r1ch nu99et5 1n 6e1n9 dep1eted 1n 60th the m05t refract0ry (Lu, Er, H0) and the m05t v01at11e (Eu, Y6) REE•5 (F19. 9), and 1n 11kew15e nece55ar11y 6e1n9 c0nden5ate5. 7he 1ne5capa61e c0nc1u510n fr0m the a60ve 15 that the RuPt-r1ch nu99et5 11-16 1n the 0uter c0re 0f 3643 are c0nden5ate5 fr0m a 9a5 0ut 0f wh1ch u1tra-refract0ry 9ra1n5 r1ch 1n 05, 1r, Re and W had prev10u51y 6een rem0ved. 7he pre5ence mere m1111meter5 away 1n the 1nner c0re 0f 5uch 051r-r1ch 9ra1n5 that are a1m05t exact1y c0mp1ementary 1n c0mp051t10n t0 the RuPt nu99et5 (F19. 7) 15 c0mpe111n9 ev1dence that the 051r nu99et5 were rem0ved fr0m the 5ame re5erv01r that 1ater pr0duced the RuPt nu99et5. Are the 051r nu99et5 a150 c0nden5ate5• 7he we11-f0rmed (hexa90na1) cry5ta1 5hape5 0f 50me 051r nu99et5 (e.9. F19. 3D) 1nd1cate that they were n0t m01ten dr0p1et5 and 5u99e5t that they c0u1d we11 6e c0nden5ate5. H0wever, we cann0t exc1ude the p05516111ty that the parenta1 9a5 and du5t were

heated 0n1y 5tr0n91y en0u9h t0 vap0r12e Ru, Pt and m0re v01at11e meta15, t09ether w1th a11 0x1de5 and 5111cate5( > 1690 K at 10 - 4 atm pre55ure [39]), 6ut n0t 5tr0n91y en0u9h t0 c0mp1ete1y vap0r12e 05-r1ch re51due5, wh1ch w0u1d 6e 5ta61e t0 > 1800 K [37]. 7hu5, 50me 051r nu99et5 c0u1d 6e re51due5, 0r re51due5 0ver9r0wn 6y c0nden5ate5 when the 9a5 c001ed a9a1n. F0r the maj0r pha5e5 1n the c0re, the ev1dence a150 fav0r5 a c0nden5at10n 0r191n. F1r5t1y, there 15 a c0mp1ete a65ence 0f c0mpact c10t5 0f u1tra-refract0ry m01ten re51due5, and the c0re a5 a wh01e ha5 never 6een m01ten 6ecau5e me1t1n9 w0u1d have m1xed up the du5ter5 0f 51m11ar type5 0f nu99et5. 5ec0nd1y, the c0n51dera61e 1nterna1 heter09ene1ty 0f the h160n1te cry5ta15, wh05e M9, 71 and V c0ncentrat10n5 vary w1de1y fr0m p01nt t0 p01nt, 15 c0n515tent w1th (th0u9h n0t pr00f 0f) a c0nden5ate 0r191n. F0r examp1e, the h160n1te c0nden5ate cry5ta15 1n the ••81ue An9e1•• [40] and 5p1ne1h160n1te 1nc1u510n5 [25,31] 1n Murch150n, and 1n • f1uffy•• 7ype A 1nc1u510n5 1n A11ende [9,22], 5h0w 1ar9e 1ntra-cry5ta1 heter09ene1t1e5. A1th0u9h the me1t-cry5ta1112ed h160n1te5 1n Murch150n 5p1ne1h160n1te ch0ndru1e5 [41] and 1n the c0re 0f the A11ende ••5c0rp10n•• CA1 [42] a150 5h0w 50me 1ntra-cry5ta1 heter09ene1t1e5, they are 0f 5ma11er ma9n1tude than th05e 1n the a60ve c0nden5ate5 0r 1n the c0re 0f 3643. 7h1rd1y, the 1n1t1a1 c0re 0f 3643 wa5 an 0pen netw0rk 0f h160n1te cry5ta15 (F19. 3D), a texture character15t1c 0f an a99re9ate 0f vap0r c0nden5ate5 [25,31]. We kn0w that the h160n1te framew0rk preceeded the f0rmat10n 0f the 1nter5t1t1a1 me1111te6ecau5e the h160n1te cry5ta15 have 6een c0rr0ded, em6ayed and 1n p1ace5 p5eud0m0rph0u51y rep1aced 6y me1111te (and 1t5 a1terat10n pr0duct5)--5ee F195. 3D and 6A. Furtherm0re, a c0re 0f 5011d h160n1te w0u1d have 6een c0rr0ded ma1n1y ar0und 1t5 per1phery. 1n5tead, a11 part5 0f the c0re appear t0 have 6een permeated 6y 9a5 wh1ch reacted w1th the h160n1te and c0nden5ed 1nter5t1t1a1 me1111te hav1n9 the 5ame narr0w ran9e 0f c0mp051t10n5 everywhere. 0 t h e r pr06a61e pr0duct5 0f the 9a5/h160n1te react10n are the t1ny 1nc1u510n5 0f a1um1na that are f0und 1n me1111te (and 1t5 1ater a1terat10n pr0duct5), 6ut n0t 1n h160n1te. What wa5 the 5e4uence 0f event5 dur1n9 3643 c0re f0rmat10n• We kn0w that the f0rmat10n 0f 051r nu99et5 had t0 precede the c0nden5at10n 0f

144 RuPt nu99et5. We a150 kn0w that the 051r-r1ch nu99et5 and the1r f1ne-9ra1ned h160n1te h05t5 1n the 1nner c0re are 5urr0unded 6y the 0uter c0re 0f c0ar5er h160n1te c0nta1n1n9 RuPt nu99et5. 7heref0re, 051r nu99et5 f0rmed and were 5caven9ed 6y f1ne h160n1te c0nden5ate cry5ta15 wh1ch a99re9ated t09ether. RuPt nu99et5 then c0nden5ed fr0m the re51dua1 9a5 and were 1n turn 5caven9ed 6y c0ar5er h160n1te cry5ta15 wh1ch 9athered ar0und the ear11er a99re9ate5. 7he 5eparate c1u5ter5 0f h19h-05 nu99et5 (N05. 1-6, 7a61e 4 and F19. 2), 10wer-05 nu99et5 (N05. 8-10) and h19h-Pt nu99et5 (N05. 11-16) 1nd1cate ep150de5 0f 5caven91n9 and a99re9at10n 0f nu99et5 0f 91ven type5. 7here 15 ev1dence that the f0rmat10n re5erv01r wa5 n0t un1f0rm thr0u9h0ut, 6ut that the var10u5 c1u5ter5 0f nu99et5 were fr0m d1fferent 10cat10n5 where c0nden5at10n had ev01ved t0 d1fferent 5ta9e5. F1r5t1y, the c0mp051t10n5 0f the nu99et5, even 1n the 5ame c1u5ter, and 0f the1r h05t h160n1te5, are 4u1te var1a61e (7a61e 4). 5ec0nd1y, 1n the c1u5ter 0f 051r nu99et5 (N05. 1-6) there 15 a f0re19n Pt-r1ch nu99et (N0. 17) wh1ch mu5t have c0nden5ed e15ewhere fr0m fract10nated 9a5 that had a1ready ev01ved further. 50meh0w, nu99et 17 wa5 tran5ferred acr055 and a99re9ated t09ether w1th the 051r nu99et5. 7h1rd1y, 051r nu99et 7 5trayed fr0m 1t5 parenta1 ce11 and wa5 captured 1n the 0uter c0re. 5uch 065ervat10n5 5u99e5t that the c0re-f0rm1n9 re5erv01r wa5 d1v1ded 1nt0 ce115 ev01v1n9 at d1fferent rate5, and that 50me reached the RuPt c0nden5at10n p01nt wh11e 0ther5 were 5t111 c0nden51n9 051r. 7he5e ce115 were 1ar9e en0u9h t0 ma1nta1n the1r P,7 d1fference5, ~yet n0t 50 1ar9e a5 t0 prevent cr055-m1x1n9 0f 9ra1n5. W1th1n ce115, 5caven91n9 and a99re9at10n mu5t have 6een 4u1ck re1at1ve t0 the t1me5ca1e f0r c0nden5at10n, 51nce m05t 0f the nu99et5 1n each c1u5ter had reached 51m11ar p01nt5 1n the c0nden5at10n pr0ce55. H0wever, the nu99et5 1n each c1u5ter c1ear1y had n0t e4u1116rated, and th15 p1ace5 an upper 11m1t 0n the durat10n 0f c0011n9 and c0nden5at10n. 7he c0re-f0rm1n9 re5erv01r wa5 thu5 a c0011n9, 5pat1a11y-1nh0m09ene0u5 re910n w1th 5u65tant1a1 1nterna1 P , 7 9rad1ent5. 7he c0re a5 a wh01e 5h0w5 decrea51n9 refract0ry meta1 a6undance5 w1th v01at111ty (F19. 7). Wh01e c0re C1-n0rma112ed enr1chment5 decrea5e fr0m 352 (05) t0 266 (1r) t0 67 (Ru) t0 38 (Pt). 7here wa5 thu5 a 5teady 1055 0f m0re v01at11e e1ement5 fr0m

the re5erv01r dur1n9 c0nden5at10n. 7he 10n9er an e1ement rema1ned 1n the 9a5, the m0re 0f 1t that e5caped fr0m the re910n. 7here 15 a 5harp decrea5e 1n a6undance 6etween 1r and Ru, wh05e c0nden5at10n temperature5 d1ffer 0n1y 6y a60ut 50 ° (F19. 7). (7he am0unt5 0f Ru and Pt 1n the wh01e c0re are 0n1y a60ut 1 / 5 0f the am0unt5 0f 05 and 1r.) 7h15 pr06a61y 0ccurred dur1n9 the h1atu5 6etween the f0rmat10n 0f the 1nner and 0uter c 0 r e - - a h1atu5 v15161e 1n the texture5 0f the h160n1te and 1n the c0mp051t10n5, 512e5 and num6er5 0f refract0ry meta1 nu99et5. Dur1n9 the h1atu5, the e1ement5 m0re v01at11e than 1r c0nt1nued t0 e5cape a5 9a5, 6ut m05t 0f the 05 and 1r had a1ready 6een 1nc0rp0rated a5 nu99et5. 0 n c e c0nden5ed, the 5ma11er RuPt nu99et5 may a150 have 6een 1e55 eff1c1ent1y 5caven9ed than the 619 051r nu99et5, a1th0u9h th15 w0u1d n0t exp1a1n the 10wer a6undance 0f Pt than Ru. A h1atu5 a150 0ccurred 6etween the c0nden5at10n (0r evap0rat10n) 0f 1r and Ru 1n the f0rmat10n 0f the u1tra-refract0ry 0rnan5 1nc1u510n [26], wh05e C1-n0rma112ed a6undance 0f Ru 15 0n1y 26% 0f that 0f 1r (cf. 28% 1n 3643). H0wever, th15 51m11ar1ty 15 pr06a61y f0rtu1t0u5 and n0t the 519na1 0f a un1ver5a1 event 1n the heat1n9/c0011n9 h15t0ry 0f u1tra-refract0ry 1nc1u510n5, 6ecau5e the 0rnan5 60dy 5h0w5 n0 h19her temperature fract10nat10n5 6etween 1 r / 0 5 0r 1 r / R e [26] wherea5 1n the c0re 0f 3643, a h19her temperature fract10nat10n d1d take p1ace t0 make 1r 0n1y 75% a5 enr1ched a5 05. Even h19her temperature fract10nat10n5 t00k p1ace 1n the u1tra-refract0ry 60dy 1n CA1 6 / 1 [28]: 1n 1t, Ru 15 enr1ched t0 0n1y 16% 0f the 1eve1 0f 1r, 1r 0n1y t0 57% 0f 05, and 05 0n1y t0 86% 0f Re. 1n 0ther w0rd5, the upper temperature 11m1t5 0n e1ementa1 fract10nat10n5 are var1a61e - - a t 1r 1n the 0rnan5 60dy, near 05 1n 3643~ and at Re 1n 6 / 1 . 7 h e 5 e fract10nat10n5 519n1fy that 6/1 wa5 heated t0 (0r c001ed fr0m) a very h19h temperature 5uff1c1ent1y 510w1y t0 a110w a h19h pr0p0rt10n 0f the m0re v01at11e e1ement5 t0 e5cape a5 vap0r. 7he 0rnan5 60dy wa5 n0t heated t0 (0r c001ed fr0m) a5 h19h a temperature, 6ut d1d 50 m0re rap1d1y, a110w1n9 1e55 0f the m0re v01at11e e1ement5 t0 e5cape. 7he 1ar9e ne9at1ve M0 and W an0ma11e5 1n the 3643 nu99et c0mp051t10n5 (F19. 7) 1nd1cate that the 9a5 fr0m wh1ch the c0re c0nden5ed wa5 m0re 0x1d121n9 than 501ar 9a5 [12], w1th a60ut 60 t1me5

145

h19her H 2 0 / H 2 , acc0rd1n9 t0 the ca1cu1at10n5 0f Fe91ey and Pa1me [15]. 7he 1ack 0f c010r 0f the h160n1te 1n 3643 a150 p01nt5 t0 0x1d121n9 c0nd1t10n5, 6ut m05t 11ke1y rec0rd5 event5 at a 10wer temperature than that at wh1ch the nu99et5 f0rmed [43]. Acc0rd1n9 t0 the M0 and W an0ma11e5, the f0rmat10n c0nd1t10n5 0f the c0re 0f 3643 (w1th C1-n0rma112ed W / 0 5 > 0.13 and M 0 / 1 r 0.11) were much m0re 0x1d121n9 than f0r the u1tra-refract0ry 60dy 1n CA1 6 / 1 ( W / 0 5 0.97, M 0 / 1 r 0.29) 6ut 1e55 0x1d121n9 than f0r the 0rnan5 60dy ( W / 0 5 0.04, M 0 / 1 r < 0.09). F0r the5e 5pec1men5, the 0rder 0f 1ncrea51n9 0x1dat10n p0tent1a1 15 the rever5e 0f the 0rder 0f max1mum fract10nat10n temperature. C0nden5at10n ca1cu1at10n5 (at 10 a atm 1n 501ar 9a5) 5u99e5t that h160n1te and me1111te 1n the c0re 0f 3643 f0rmed 6etween 1700 and 1500 K 0r, 1n m0re 0x1d121n9 9a5, at 50me h19her temperature dependent 0n whether 0xy9en a10ne had 1ncrea5ed (e.9. 6y vap0r12at10n 0f exce55 1cy du5t mant1e5) 0r 0xy9en p1u5 51, M9, Ca, etc. (e.9. 6y vap0r12at10n 0f exce55 du5t w1th 0r w1th0ut 1cy mant1e5) [15,39,44]. 7he5e temperature5 and th05e ca1cu1ated f0r the nu99et5 are n0t ent1re1y c0n515tent w1th 0ne an0ther, 0r w1th textura1 data. 0 n e pr061em 15 that n0ne 0f the nu99et c0mp051t10n5 fa115 0n Pa1me and W10t2ka•5 [37] ca1cu1ated c0mp051t10na1 traject0r1e5. F0r examp1e, f0r the 065erved 0 5 / 1 r rat10, the F e / 0 5 rat10 1n the mean 051r nu99et (7a61e 4) 15 h19her than pred1cted, 5u99e5t1n9 that the (unkn0wn) act1v1ty c0eff1c1ent 0f Fe 15 1e55 than un1ty. An0ther pr061em 15 that the ca1cu1ated [39] c0nden5at10n temperature 0f the h160n1te 15 h19her ( > 1650 K) than the ca1cu1ated 1501at10n temperature 0f the 051r nu99et5 ( < 1600 K). D1d the c0nden51n9 h160n1te n0t at f1r5t 5caven9e the nu99et5, 0r d1d the 9a5 6ec0me 5uper5aturated and n0t c0nden5e h160n1te unt11 1t had c001ed t0 6e10w 1600 K• A150, why 15 h160n1te 1n the 1nner c0re hard1y any m0re refract0ry (1.e. p00rer 1n M9 and 71) than the h160n1te 1n the 0uter c0re, a1th0u9h the 1atter 15 a550c1ated w1th RuPt nu99et5 wh05e 1501at10n temperature5 are < 1500 K (F19. 7)• F1na11y, the ca1cu1ated [44] c0nden5at10n temperature 0f the me1111te ( > 1544-1530 K) 15 h19her than the RuPt nu99et 1501at10n temperature, and yet the un1f0rm me1111te thr0u9h0ut the c0re apparent1y d1d n0t f0rm unt11 after the wh01e c0re 0f h160n1te p1u5 nu99et5 had a99re9ated. C1ear1y, the

e5t1mat10n 0f c0nden5at10n and evap0rat10n temperature5 15 an area re4u1r1n9 further 5tudy.

4.3. F0rmat10n 0f the mant1e 7he mant1e ha5 a 6 r 0 u p 11 c0mp051t10n dep1eted 1n u1tra-refract0ry trace e1ement5. D1d 1t f0rm fr0m the 5ame re5erv01r that the c0re had prev10u51y dep1eted 1n u1tra-refract0r1e5, 0r fr0m a d1fferent, unre1ated re5erv01r• 1n the 1atter ca5e, the 6 r 0 u p 11 c0mp051t10n w0u1d 6e mere1y a c01nc1dence--there m19ht a5 ea511y have 6een n0 1ayer5 0ut51de the c0re, 0r 1ayer5 0f 6 r 0 u p 1. 6 r 0 u p 111, etc. We w0u1d a150 have t0 acc0unt f0r the rem0va1 0f the c0re fr0m 1t5 re5erv01r w1th0ut further c0nden5at10n tak1n9 p1ace, and f0r the c0nt1nu1ty fr0m c0re t0 mant1e 1n me1111te c0mp051t10n. 1t theref0re 5eem5 pr06a61e that the mant1e d1d f0rm fr0m the 5ame re5erv01r a5 the c0re. 7he 6 r 0 u p 11 c0mp051t10n 0f the mant1e a150 te115 u5 that 1t 0r191nated a5 a c0nden5ate [38], a1th0u9h 1t c0u1d 5u65e4uent1y have 6een metam0rph05ed 0r even me1ted and re-5011d1f1ed. 7hree further c1ue5 5u99e5t that 1t d1d n0t cry5ta1112e fr0m a me1t: (1) 1t 15 v1rtua11y m0n0m1nera11c (me1111te), (2) very uneven 1n th1ckne55, and (3) n0t rad1a11y 20ned. Natura1 me1t5 rare1y cry5ta1112e t0 m0n0m1nera11c 5011d5; 5urface ten510n tend5 t0 5pread them even1y; and they cry5ta1112e rad1a11y 1nward5. 0 n the 0ther hand, 5011d c0nden5ate5 c0u1d 6e m0n0m1nera11c and c0u1d 6u11d up uneven1y and un20ned. 7he mant1e•5 c0mpact texture 15 un11ke that expected fr0m an a99re9ate 0f 5eparate1y-c0nden5ed cry5ta15, 6ut re5em61e5 the m0n011th1c• c0nden5ate5 d1rect 0n t0 the 5urface 0f certa1n 7 y p e A CA1•5 [9,33]. 7he metam0rph1c recry5ta1112at10n that ha5 06v10u51y 0ccurred may a150 have c0ntr16uted t0 the c0mpact texture. 7he narr0w c0mp051t10na1 ran9e 0f me1111te 1n the mant1e (cf. the var1a6111ty 0f h160n1te 1n the c0re) 1mp11e5 a1m05t 5tat1c P , 7 mant1e f0rmat10n c0nd1t10n5, 6ut c0u1d 6e due 1n part t0 metam0rph1c re-e4u1116rat10n.

4.4. F0rmat10n 0f the cru5t 7he a6rupt chan9e 1n texture and m1nera1091ca1 c0mp051t10n 6etween mant1e and cru5t 15 a1m05t certa1n1y due t0 a chan9e 1n P, 7 c0nd1t10n5 rather

146

than t0 a chan9e 1n the c0mp051t10n 0f the re5erv01r, 51nce 60th the mant1e and cru5t are 0f 6 r 0 u p 11 and c0nta1n 51m11ar per0v5k1te, me1111te, N1Fe meta1 and FeN1 5u1f1de. 8e1n9 6 r 0 u p 11, the cru5t mu5t have 0r191nated a5 a c0nden5ate [38]. 7he c0nv01uted r1m 0f the cru5t (F19. 1) 15 1nc0n515tent w1th f0rmat10n fr0m a me1t, and the cru5t d0e5 n0t c0nta1n any 0f the pha5e5 that are c0mm0n 1n CA1•5 that cry5ta1112ed fr0m 114u1d5--71pyr0xene, akerman1t1c me1111te and pr1mary an0rth1te. F0r the5e rea50n5, the cru5t 15 c0nc1uded t0 6e a 5011d c0nden5ate. 7he m05t1y c0mpact texture a9a1n ar9ue5 that 1t 15 n0t an a99re9ate 0f 5eparate cry5ta15, 6ut rather a m0n011th1c c0nden5ate, part1y metam0rph05ed and recry5ta1112ed 1n v1ew 0f the tr1p1e-junct10ned me1111te and p5eud0m0rph0u5 rep1acement 0f h160n1te 6y 5p1ne1 and me1111te (F19. 3F). 7he 5u99e5t10n 0f rad1a1 20nat10n w1th1n the cru5t, w1th h160n1te 6ec0m1n9 10wer 1n M9 and 71 t0ward the r1m (F19. 4), m19ht 1nd1cate c0nden5at10n under r151n9 temperature (0r fa111n9 pre55ure). 4. 5. A 1terat10n pr0ce55e5

CA1 3643 ha5 exper1enced var10u5 h19h- and 10w-temperature a1terat10n pr0ce55e5 dur1n9 and 51nce 1t5 f0rmat10n, 1nc1ud1n9: (1) Part1a1 rep1acement 0f h160n1te 1n the c0re 6y me1111te, and 0f 60th 6y 9r055u1ar. 7he dep051t10n 0f the me1111te mant1e may have f0110wed 500n after th15 5ta9e, 6ut the tw0 were n0t part5 0f the 5ame event, 51nce the c0re me1111tec0nta1n5 a1um1na 1nc1u510n5 n0t f0und 1n the mant1e, and the mant1e c0nta1n5 N1Fe 1nc1u510n5 a65ent fr0m the c0re. (2) Metam0rph1c recry5ta1112at10n and re-e4u1116rat10n 0f patche5 0f me1111te t0 f1ne-9ra1ned, 5tra1n-free m05a1c5, and 0f part1a1 rep1acement 0f h160n1te 6y 5p1ne1 and me1111te. 7he 51m11ar1ty 0f the5e patche5 1n the c0re, mant1e and cru5t 5u99e5t5 that recry5ta1112at10n 0ccurred after f0rmat10n 0f the wh01e CA1. (3) 5tra1n and def0rmat10n 0f me1111te cry5ta15 1n the mant1e. 7he cau5e 15 unkn0wn, 6ut 15 11ke1y t0 have f0110wed metam0rph15m wh1ch w0u1d tend t0 era5e def0rmat10n. (4) Meta50mat15m 0f me1111te t0 an0rth1te 1n a 1ayer 6e10w the r1m. 7h15 pr0ce55 wa5 apparent1y c0ntr011ed 6y 6u1k d1ffu510n 0f mater1a1 1nt0 a

c0mpact, un1f0rm, unfractured cru5t 6ecau5e the meta50mat12ed 1ayer reached an appr0x1mate1y c0n5tant d15tance 1n fr0m the r1m. 7h15 meta50mat15m mu5t have preceded v01at11e a1terat10n (d15cu55ed 6e10w) wh1ch created channe15 0r f0110wed crack5 penetrat1n9 deep 1nt0 the c0re. (5) A1ka11/ha109en/Fe vap0r a1terat10n 0f me1111te under 0x1d121n9 c0nd1t10n5 t0 a p0r0u5 ma55 0f 9r055u1ar-andrad1te, nephe11ne, 50da11te, p1a910c1a5e, and aen19mat1te (•). 7h15 type 0f a1terat10n 15 f0und 1n the c0re, mant1e and cru5t 0f 3643, 1nc1ud1n9 area5 affected 6y pr0ce55e5 (1) t0 (4) a60ve, and thu5 appear5 t0 6e the 1a5t maj0r pr0ce55 that affected 3643. A11 kn0wn A11ende CA1•5 were affected 6y th15 type 0f a1terat10n [13,141. 4. 6. C0nc1u510n5 and 1mp11cat10n5

(1) CA1 3643 c0n515t5 0f c0n5ecut1ve, h19h temperature, c0mp1ementary 5011d c0nden5ate5 that f0rmed 0ver a 11m1ted 1nterva1 0f t1me and 5pace fr0m a 51n91e, c0011n9, 9a5e0u5 re5erv01r. 7he c0nden5ate5 were at f1r5t extreme1y enr1ched 1n the m05t refract0ry trace e1ement5, 6ut 6ecame pr09re551ve1y dep1eted 1n them. 7he c0re 0f 3643 9rew a5 a 5er1e5 0f rap1d1y a99re9ated 5011d h160n1te c0nden5ate5 f0110wed 6y part1a1 react10n 0f the h160n1te w1th 9a5 t0 f0rm me1111te. 7he 0ver1y1n9 mant1e and cru5t were f0rmed a5 5011d c0nden5ate5 dep051ted d1rect1y 0n t0 the 5urface 0f the 06ject. 7he ent1re 5er1e5 0f c0nden5at10n5, a99re9at10n5 and 1nterven1n9 h1atu5e5 wa5 5uff1c1ent1y 6r1ef that the m1cr05c0p1c cry5ta111ne c0nden5ate5, the macr05c0p1c 9r0w1n9 CA1 and much 0f the 9a5e0u5 re5erv01r rema1ned t09ether at h19h temperature w1th0ut c0mp1ete1y d15per51n9. 7he pr1mary CA1 then exper1enced part1a1 recry5ta1112at10n 0f me1111te, meta50mat1c a1terat10n 0f me1111te t0 an0rth1te, and f1na11y, a1terat10n 0f me1111te 6y a1ka11-ha109en-Fe-r1ch vap0r. (2) U1tra-refract0ry e1ement5 (e.9. 05) were fract10nated fr0m m0derate1y refract0ry e1ement5 (e.9. Pt) 1n the actua1f0rmat10n env1r0nment 0f CA1 3643. Hence, 3643 wa5 n0t f0rmed acc0rd1n9 t0 the m0de15 0f W00d [5], Fe91ey and K0rnack1 [8] 0r C1ayt0n [45] 1n wh1ch the u1tra-refract0ry e1ement5 are fract10nated fr0m the1r 1e55-refract0ry c0mp1ement5 1n 5te11ar 0utf10w5 0r 0ther pre501ar

147

env1r0nment5 10n9 6ef0re the f0rmat10n 0f the CA1•5. 1n the5e m0de15, the fract10nated u1tra-refract0ry-r1ch and u1tra-refract0ry-p00r 9ra1n5 1ead 1ndependent pre501ar ex15tence5 6ef0re 6e1n9 rea55em61ed 1n var10u5 c0m61nat10n5 1n CA1•5. 5uch fract10nated 1nter5te11ar 9ra1n5 pr06a61y ex15t; h0wever, any pr10r chem1ca1 h15t0ry 0f 5uch 9ra1n5 wa5 105t 1n the t0ta1 (0r a1m05t t0ta1) vap0r12at10n event that created the 9a5 fr0m wh1ch CA1 3643 c0nden5ed. (3) CA1 3643 c0u1d n0t have 6een f0rmed acc0rd1n9 t0 W00d•5 dra9 heat1n9 m0de1 [46]. 3643•5 1ayered 5tructure 0f c0mp1ementary c0nden5ate5 and 1t5 5eparate c1u5ter5 0f d1fferent type5 0f 0pa4ue 9ra1n5 c0u1d n0t have 6een pr0duced 6y, 5urv1ved 1n, 0r c0nden5ed and a99re9ated 0n t0, pre501ar du5t6a115 that were me1ted 0n fa111n9 1nt0 the 501ar ne6u1a. (4) 7he f0rmat10n 0f 3643 de5cr16ed a60ve m19ht appear t0 f1t the m0de1 0f M0rr111 and VNk [47], 1n wh1ch v01ume e1ement5 0f 9a5 and du5t are tran5p0rted 1nt0 the h0tter, 1nner 501ar ne6u1a where 9ra1n5 vap0r12e. 50me v01ume e1ement5 are c0nvected 6ack 0ut t0ward the mete0r1te-f0rm1n9 re910n 6y rand0m tur6u1ence, a110w1n9 the c0011n9, and 510w1y d15per51n9, vap0r5 t0 rec0nden5e 5e4uent1a11y, ju5t a5 1nferred f0r 3643. H0wever, 1t 15 4ue5t10na61e whether a v01ume e1ement c0u1d rema1n at a very h19h temperature and av01d d15per5a1 f0r 10n9 en0u9h t0 a110w the ent1re 5er1e5 0f c0nden5at10n5 and a99re9at10n5 wh11e 1t wa5 51mu1tane0u51y 6e1n9 m0ved 60d11y a9a1n5t a 9enera1 1nf10w 0f matter 0ver va5t d15tance5. (3 A.U. t0 the a5ter01d 6e1t w0u1d re4u1re 5evera1 decade5 0f trave1 t1me, even at 50n1c 5peed wh1ch w0u1d 6e the max1mum p1au5161e f0r 6u1k tran5p0rt 0f 9a5 and du5t). A m0re 5er10u5 06ject10n 15 that each type 0f ch0ndr1t1c mete0r1te (e.9. 0rd1nary, E, CV, etc.) ha5 un14ue1y d15t1nct1ve c0mp0nent5 [50], and n0t the 5t0cha5t1c m1xture that a tur6u1ent tran5p0rt mechan15m w0u1d pr0duce. (5) Fr0m ev1dence 5uch a5 th15, 80ynt0n [48], W00d [49] and Wark [50] have c0nc1uded that the refract0ry c0mp0nent5 0f ch0ndr1t1c mete0r1te5 were f0rmed 1n the a5ter01d 6e1t a5 the re5u1t 0f tran51ent, 10ca1 heat1n9 event5 0f unkn0wn 0r191n. 7he pre5ent w0rk 111u5trate5 the 5er1e5 0f c0nden5at10n5 and a99re9at10n5 that re5u1ted fr0m 5uch an event w1th1n the CV ch0ndr1te f0rmat10n re910n.

Ackn0w1ed9ement5 1 thank 8r1an Ma50n f0r k1nd1y mak1n9 ava11a61e the th1n 5ect10n 0f CA1 3643. 7h15 w0rk wa5 5upp0rted 1n part 6y 9rant5 fr0m the Au5tra11an Re5earch 6rant5 C0mm1ttee t0 J.F. L0ver1n9 and 1n part 6y NA5A 9rant NA69-37 t0 W.V. 80ynt0n. 1 9ratefu11y ackn0w1ed9e he1pfu1 rev1ew5 6y H. Pa1me and an an0nym0u5 rev1ewer, and c0mment5 6y F. 8e9emann, W.V. 80ynt0n and J.H. J0ne5.

Reference5 1 C.M. 6 r a y , D.A. Papana5ta5510u and 6.J. Wa55er6ur9, 7 h e 1dent1f1cat10n 0f ear1y c0nden5ate5 fr0m the 501ar ne6u1a, 1caru5 20, 213 239, 1973. 2 1.D. Hutche0n, 10n pr06e M9 150t0p1c mea5urement5 0f A11ende 1nc1u510n5, 1n: Nuc1ear and Chem1ca1 Dat1n9 7echn14ue5:1nterpret1n9 the Env1r0nmenta1 Rec0rd, L.A. Curr1e, ed., p. 95, Amer1can Chem1ca1 50c1ety, 1981. 3 5. N1emeyer and 6 . W . Lu9ma1r, 71tan1um 150t0p1c an0ma11e5 1n mete0r1te5, 6e0ch1m. C05m0ch1m. Acta 48, 1401 1416, 1984. 4 M.H. 7h1emen5 and J.E. He1denre1ch, 7 h e ma55-1ndependent fract10nat10n 0f 0xy9en: a n0ve1 150t0pe effect and 1t5 p055161e c05m0chem1ca1 1mp11cat10n5, 5c1ence 219, 1073 1075~ 1983. 5 J.A. W00d, 7he 1nter5te11ar du5t a5 a precur50r 0f Ca-A1-r1ch 1nc1u510n5 1n car60nace0u5 ch0ndr1te5, Earth P1anet. 5c1. Lett. 56, 32-44, 1981. 6 5.J.8. Reed and N . 6 . Ware, Quant1tat1ve e1e~tr0n m1cr0pr06e ana1y515 u51n9 a 11th1um-dr1fted 5111c0n detect0r, X-ray 5pectr0m. 2, 69-74, 1973. 7 P.K. Ma50n, M.7. Fr05t and 5.J.8. Reed, Rep0rt 2, D1v. 1n0r9. Meta1.5truc., Nat. Phy5. La6., U.K., 1969. 8 8. Fe91ey and A.5. K0rnack1, 7he 9e0chem1ca1 6ehav10ur 0f refract0ry n061e meta15 and 11th0ph11e trace e1ement5 1n refract0ry 1nc1u510n5, Earth P1anet. 5c1. Lett. 68, 181-197. 1984. 9 D.A. Wark, 7he A11ende mete0r1te: 1nf0rmat10n fr0m CaA1-r1ch 1nc1u510n5 0n the f0rmat10n and ear1y ev01ut10n 0f the 501ar ne6u1a, Chapter5 3 and 8, Ph.D. 7he515, Un1ver51ty 0f Me160urne, Parkv111e, V1c., 1984. 10 M.A. Luca5, Pr0t0n m1cr0pr06e ana1y515 0f mete0r1te mater1a15, 1n: Pe11etr0n Pr09re55 Rep0rt 1979-1980, 5ch001 0f Phy51c5, Un1ver51ty 0f Me160urne, Parkv111e, V1c., 1980. 11 8. Ma50n and P.M. Mart1n, 6e0chem1ca1 d1fference5 am0n9 c0mp0nent5 0f the A11ende mete0r1te, 5m1th50n1an C0ntr16. Earth 5c1, 19, 84-95, 1977. 12 D.A. Wark, A11ende CA1 3 6 4 3 - - a 1ayered rec0rd 0f pr0t0501ar ne6u1a c0nden5at10n, Lunar P1anet. 5c1. X1, 1202-1204, 1980. 13 D.A. Wark, A1terat10n and meta50mat15m 0f A11ende CaA1-r1ch mater1a15, Lunar P1anet. 5c1. X11, 1145-1147, 1981. 14 D.A. Wark, 7he pre-a1terat10n c0mp051t10n5 0f A11ende Ca-A1-r1ch c0nden5ate5, Lunar P1anet. 5c1, X11, 1148-1150, 1981.

148 15 8. Fe91ey and H. Pa1me, Ev1dence f0r 0x1d121n9 c0nd1t10n5 1n the 501ar ne6u1a fr0m M0 and W dep1et10n5 1n refract0ry 1nc1u510n5 1n car60nace0u5 ch0ndr1te5, Earth P1anet. 5c1. Lett. 72, 311-326, 1985. 16 D.A. Wark, 7.C. Hu9he5, M. Luca5 and C.D. McKen21e, Pr0t0n m1cr0pr06e ana1y515 0f per0v5k1te 1n A11ende CaA1-r1ch 1nc1u510n5, Lunar P1anet. 5c1. X1, 1205 1207, 1980. 17 A.5. K0rnack1 and J.A. W00d, 7he 1dent1f1cat10n 0f 6 r 0 u p 11 1nc1u510n5 1n car60nace0u5 ch0ndr1te5 6y e1ectr0n pr06e m1cr0ana1y515 0f per0v5k1te, Earth P1anet. 5c1. Lett. 72, 74 86, 1985. 18 L. 6r055man and R. 6 a n a p a t h y , 7race e1ement5 1n the A11ende mete0r1te, 11. F1ne-9ra1ned, Ca-r1ch 1nc1u510n5, 6 e 0ch1m. C05m0ch1m. Acta 40, 967 977, 1976. 19 W.A. Deer, R.A. H0w1e and J. 2u55man, An 1ntr0duct10n t0 the R0ck F0rm1n9 M1nera15, 528 pp. L0n9man5, 1966. 20 D.A. Wark and J.F. L0ver1n9, Marker event5 1n the ear1y ev01ut10n 0f the 501ar 5y5tem: ev1dence fr0m r1m5 0n CaA1-r1ch 1nc1u510n5 1n car60nace0u5 ch0ndr1te5, Pr0c. 8th Lunar 5c1. C0nf., pp. 95-112. 1977. 21 D.A. Wark, C0m61ned chem1ca1/petr01091ca1 c1a551f1cat10n 0f Ca-A1-r1ch 1nc1u510n5, Lunar P1anet. 5c1. XV1, 887--888, 1985. 22 6.J. MacPher50n and L. 6r055man, ••F1uffy•• 7ype A CaA1-r1ch 1nc1u510n5 1n the A11ende mete0r1te, 6e0ch1m. C05m0ch1m. Acta 48, 29-46, 1984. 23 W.V. 80ynt0n. R.M. Fra21er and J.D. Macd0u9a11, 1dent1f1cat10n 0f an u1tra-refract0ry c0mp0nent 1n the Murch150n mete0r1te, Lunar P1anet. 5c1. X1, 103-105. 1980. 24 V. Ekam6aram, 1. Kawa6e, 7. 7anaka, A.M. Dav15 and L. 6r055man, Chem1ca1 c0mp051t10n5 0f refract0ry 1nc1u510n5 1n the Murch150n C2 ch0ndr1te, 6e0ch1m. C05m0ch1m. Acta 48, 2089 2106, 1984. 25 J.D. Macd0u9a11, Refract0ry-e1ement-r1ch 1nc1u510n5 1n CM mete0r1te5. Earth P1anet. 5c1. Lett. 42, 1 6, 1979. 26 H. Pa1me, F. W10t2ka, K. Na9e1 and A. E1 60re5y, An u1tra-refract0ry 1nc1u510n fr0m the 0rnan5 car60nace0u5 ch0ndr1te, Earth P1anet. 5c1. Lett. 61, 1-12, 1982. 27 A.M. Dav15, 7. 7anaka, L. 6r055man. 7. Lee and 6.J. Wa55er6ur9, Chem1ca1 c0mp051t10n 0f HAL, an 150t0p1ca11y-unu5ua1A11ende 1nc1u510n, 6e0ch1m. C05m0ch1m. Acta 46. 1627-1651, 1982. 28 M. 81ander, L.H. Fuch5, C. H0r0w1t2 and R. Land, Pr1m0rd1a1 refract0ry meta1 part1c1e5 1n the A11ende mete0r1te, 6e0ch1m. C05m0ch1m. Acta 44, 217-223, 1980. 29 D.A. Wark, J.F. L0ver1n9 and R.R. Keay5, P1a910c1a5e-r1ch 1nc1u510n5 1n car60nace0u5 ch0ndr1te mete0r1te5, 5u6m1tted t0 6e0ch1m. C05m0ch1m. Acta, 1985. 30 M. 8ar-Matthew5, 1.D. Hutche0n, 6.J. MacPher50n and L. 6r055man, A c0rundum-r1ch 1nc1u510n 1n the Murch150n car60nace0u5 ch0ndr1te, 6e0ch1m. C05m0ch1m. Acta 46. 31 41, 1982. 31 6.J. MacPher50n, L. 6r055man, A. Ha5h1m0t0, M. 8arMatthew5 and 7. 7anaka, Petr09raph1c 5tud1e5 0f refract0ry 1nc1u510n5 fr0m the Murch150n mete0r1te, Pr0c. 15th Lunar P1anet. 5c1. C0nf., Part 1: 5upp1. J. 6e0phy5. Re5. 89, C299-C312, 1984. 32 A.5. K0rnack1, R.E. C0hen and J.A. W00d, Petr09raphy and c1a551f1cat10n 0f refract0ry 1nc1u510n5 1n the A11ende

33

34

35

36

37

38

39 40

41

42

43

44 45 46

47

48

49

50

and M0k01a CV3 ch0ndr1te5, Pr0c. 8th 5ymp. 0n Antarct1c Mete0r1te5, Mem. Nat1. 1n5t. P01ar Re5., 70ky0, 5pec. 155ue 30, 45 60, 1983. D.A. Wark and J.F. L0ver1n9, Ev01ut10n 0f Ca-A1-r1ch 60d1e5 1n the ear11e5t 501ar 5y5tem: 9r0wth 6y 1nc0rp0rat10n, 6e0ch1m. C05m0ch1m. Acta 46, 2595-2607, 1982. A. E1 60re5y, H. Pa1me, H. Ya6uk1, K. Na9e1, 1. Herrwerth and P. Ramd0hr, A ca1c1um-a1um1num-r1ch 1nc1u510n fr0m the E55e61 (CM2) ch0ndr1te: ev1dence f0r captured 5p1ne1h160n1te 5pheru1e5 and f0r an u1tra-refract0ry r1mm1n9 5e4uence, 6e0ch1m. C05m0ch1m. Acta 48, 2283 2298, 1984. L.H. Fuch5 and M. 81ander, Refract0ry meta1 part1c1e5 1n refract0ry 1nc1u510n5 1n the A11ende mete0r1te, Pr0c. 11th Lunar 5c1. C0nf., pp. 929-944, 1980. A. E1 60re5y, K. Na9e1 and P. Ramd0hr, Fremd11n9e and the1r n061e re1at1ve5, Pr0c. 9th Lunar P1anet. 5c1. C0nf., pp. 1279-1303, 1978. H. Pa1me and F. W10t2ka, A meta1 part1c1e fr0m a Ca-A1-r1ch 1nc1u510n fr0m the mete0r1te A11ende and the c0nden5at10n 0f refract0ry 51der0ph11e e1ement5, Earth P1anet. 5c1. Lett. 33, 45-60, 1976. W.V. 80ynt0n, Fract10nat10n 1n the 501ar ne6u1a: c0nden5at10n 0f yttr1um and the rare earth e1ement5, 6e0ch1m. C05m0ch1m. Acta 39, 569-584, 1975. M.8. Fe91ey, H160n1te c0nden5at10n 1n the 501ar ne6u1a, Lunar P1anet. 5c1. X111, 211-212, 1982. J.7. Arm5tr0n9, 6.P. Meeker, J.C. Huneke and 6.J. Wa55er6ur9, 7 h e 81ue An9e1, 1 . 7 h e m1nera109y and petr09ene515 0f a h160n1te 1nc1u510n fr0m the Murch150n mete0r1te, 6e0ch1m. C05m0ch1m. Acta 46, 575-595, 1982. 6.J. MacPher50n, M. 8ar-Matthew5, 7. 7anaka, E. 015en and L. 6r055man, Refract0ry 1nc1u510n5 1n the Murch150n mete0r1te, 6e0ch1m. C05m0ch1m. Acta 47, 823-839, 1983. D.A. Wark and W.V. 80ynt0n, 7 h e 5c0rp10n, a n0ve1 5p1ne1-h160n1te-me1111te 1nc1u510n 1n the A11ende mete0r1te, Lunar P1anet. 5c1. X1V, 826-827, 1983. E. 5t01per and P. 1h1n9er, 7 h e c010r 0f mete0r1t1c h160n1te: an 1nd1cat0r 0f 0xy9en fu9ac1ty, Lunar P1anet. 5c1. X1V, 749 750, 1983. L. 6r055man, C0nden5at10n 1n the pr1m1t1ve 501ar ne6u1a, 6e0ch1m. C05m0ch1m. Acta 36, 597 619, 1972. D.D. C1ayt0n, C05m1c chem1ca1 mem0ry: a new a5tr0n0my, Q. J. R. A5tr0n. 50c. 23, 174-212, 1982. J.A. W00d, F0rmat10n 0f ch0ndru1e5 and CA1•5 fr0m 1nter5te11ar 9ra1n5 accret1n9 t0 the 501ar ne6u1a, Pr0c. 8th 5ymp. 0n Antarct1c Mete0r1te5, 70ky0, pp. 84-92, 1983. 6.E. M0rf111 and H.J. V~51k, 7ran5p0rt 0f du5t and vap0r and chem1ca1 fract10nat10n 1n the ear1y pr0t0501ar c10ud, Ap. J. 287, 371-395, 1984. W.V. 80ynt0n, 7 h e cha0t1c 501ar ne6u1a: ev1dence f0r ep150d1c c0nden5at10n 1n 5evera1 d15t1nct 20ne5, 1n : Pr0t05tar5 and P1anet5, 7. 6ehre15 ed., pp. 427-438, Un1ver51ty 0f Ar120na Pre55, 7uc50n, Ar12., 1978. J.A. W00d, Mete0r1t1c c0n5tra1nt5 0n pr0ce55e5 1n the 501ar ne6u1a: an 0verv1ew, 1n: Pr0t05tar5 and P1anet5 11, D.C. 81ack and M.5. Matthew5 ed5., pp. 687-702, Un1ver51ty 0f Ar120na Pre55, 7uc50n, Ar12., 1985. D.A. Wark, 065ervat10na1 c0n5tra1nt5 0n 501ar ne6u1a m0de15, Lunar P1anet. 5c1. XV1, 889-890, 1985.