1983chto.conf...44F 44 ciated subsequent single aware . chondrites, terrestrial tion. render and drules, between metamorphic are of drites. A matrix with recrystallization understanding petrographic petrographic (H3,4,5,6,7?) Four subsequently The Merrill Most individual partial their © chondrites, nature that crystalline distinguished varying typical Crystallinity, Lunar In show varying Department rocks ratios the early conventional Allegan history "Occasionally to (1929), of first their that type degrees types. H-group exemplify rock and of chondrites; (by by students or two of the degrees the even were classification and accreted equilibration; consolidation, a heat." sequences. Planetary the Textural of factor origin samples in pisolites from of this the chondrites Mineral controversial Metamorphism from also crystallinity the his stones students '1ndeed thermal of of apparently However, "primitive" of> of confusion lithic some last studies INTRODUCTION meteorites, Allegan with Recrystallization, crystallinity Fe/Mg commonly chondrites. Because Institute are [ 10); Sciences, has ~corresponding rather, the as work, were still fragments, metamorphism given even comminuted which the of to and concept confused is (HS), "homogeneous" in Kurt controversial; constant their in most ultrathin Tieschitz, of it reverse selected applying recrystallization, rise Smithsonian is considered reviewed • his this mainly noted. Ochansk unequilibrated are and causes. Provided -Merrill, chondrites of Fredriksson to structure "Handbook" occurs an thermal tuffaceous (by comparable once sections to induration, it the in equal Furthermore, " definition), petrologists, illustrate to chondrules, is (H4 more much could terms Institution, in Chondrites had fragments extraterrestrial inferred rock 1929 by the shown are equilibration AND confusion ), the of the Tieschitz and importantly, breccias, did Allegan "equilibrated" been and Equilibration, latter not of the concept by (Merrill, to certainly both while NASA that not SCOPE these a chondritic many difficulties be Washington, recognized two. individual on other form in (H3), undergo it (HS) few, among or implied, Al, in the chondrites] was of meteoric Astrophysics earlier From not chondritic "mixtures," they impacts Ca, part 1916) and thermal of if along fragments, and a considered any, and metamorphism with post-accretionary, are metamorphic the of different type these DC "unequilibrated" "since droplets studies the with Ti possible he complex chondrites metamorphism assigning as meteorites 20560 are show differences, in containing fragmental was and the data Data notably a a and stones and tuff, deterrents a heat cause breccia already that signs on rock. fact chondrites System are dust is its as wrote variable produced sufficient secondary fragments especially reviewed. crystallized and Analyses ofbreccia- of that to ultrafine argued parts Weston and and patently chon- to to changes within the chon- about the brec- form of as to by to in 1983chto.conf...44F K. system, system. see, Some some, fractionation evidences and close constituents contrary gases tion volatilization references, between petrographic Schmus (Suess (Wasson, (1969), and authors, constancy curators abundance detail composition improperly However, through Also, matrix." between particularly petrologic 1 -6(7) Fredriksson: remains Wood e.g, with The Other In and by during by of © would and for while the Still, was Lunar the in the and the Lipschutz cooling, Fe-rich, to Earlier, Keil chondrites the volatile renewed 1974, to in classification being quickly see petrologic early (e.g., expectations, used researchers of the work results 1 Wanke, to questioned indicate composition unexplained. types this Wood, the of during is In/ a through certainly (1982, Wasson, polymict take and difficult now few chondrites p. Equilibration as linear "oxidized" Ar period 1962, 1950's unaware there in elements of occasionally 76). describing require a and Planetary interest need on popular the ratio Mason his quantitative, that 1967). of 171 1967). type], 6 The was relationship more to 1963) who 197 not produce Ikramuddin, accretion different many grades scheme Wahl description breccias both. after In of remaining rationalize, references). an of in (Urey 4 importance only a in (1963) and olivines Because matrix type ). this have perfect and However, the second Institute open in in advanced the considered However, (1952) chondrites These (petrographic differ chondrites Ar, for by situ lower a classification 3 comparing crystallinity over of first and if also ("unequilibrated") system more and and of petrologists not chondrites geochemically and the of forms." constant of in rise they different requirements different 1978; high reemphasized period In Craig, • monomict, observed types the San of their linear, others its parent a the pyroxenes Tandon Provided and in marked the concluded the radical led (at simplicity chondrules. pressure temperature Lipschutz Emigdio analytical different "metamorphic" These were of vs. 1953), possibility breccia Ar contradicts Ar least throughout scale. (e.g., to with rapidly body, within but solidification petrologic; correlations and the metamorphic degree searched by the for which in quite also perceptive Keil exchange Thus shock the this exclusive which concept Wasson [ a specimens discovery most (Merrill, chondrites. a the gained et interpretations This few letter by brecciated of and could sufficient different, NASA al, of various the are different individual a some chemists some transformations, for concept, volatiles), Van apparently may common Fredriksson, the metamorphism and 1982; between concept petrologic has ( for wide now arguments and have of 1968) and 1888), model Astrophysics and of metamorphic Schmus, crystallization be chemical recently In correlations total experienced to structure the sometimes equilibration chemical described usage. happened Alaerts spite explained in even allow reported chondrites (for others searching provided implying volatiles he and remarkably also sequence. oflater are as 1964), 1969) and reviews been stated, Indeed group certain oxidized necessitated and moderated of he apparently in Data (iron) still as such via data rare found in sequence similar many reviewed and was the exaggerated were a parent for was warnings genomict Anders, the the part of a "There viable. and and direct it System gas Although showing as of metal-silicate like groups similar surrounding some brought is Fe paradoxical established. iron. to basis chondrites. higher the sometimes by references specialists fractiona- a useful exist material, by samples, and a a concept number relation in the silicate are 1979). closed closed by of Later, Dodd for types (Van great that, bulk rare (for fact to Mg the the the the for no 45 a a 1983chto.conf...44F should similar although approximately affect groundmass. chondrules-all different chondrites contradicts considered unequilibrated, ized "simple," Several <0.5 Smoke," that those thermal ratios brecciation (fragments, polished pyroxene primarily between and W, with with Fredriksson, m 46 2 ), Ir, never by modem other Studies The It Rambaldi regard fresh, g interested. in smaller © Au) is make scale, Wasson to analyses equilibration contrast degrees, Lunar them; not ultrathin from extremely rather apparently composed ( existed constituents <1 "cosmic" are whole a or elements broken to individual within regarding research, Mason 1964; it final and grains µm six shock Fe/Mg, micron-sized this clear breccias did and large et (1974, of Rather, the Rather, of chondrules, to in different rocks. (~4 which olivines al to chemical has small not and fine-grained, Planetary the surfaces the and a of homogeneous, that ( by strongly in effects, dust >0.5 ~ state (1981) carried (Rambaldi µm) evidence pp. but chondrules, scope not become pre-existing 35 various constant others) (or increasing Maynes refute chondrites CHONDRULES samples kg), chondrites. or 190-193) mm), and which occurred. similar purpose section. at olivine only of equilibration, and of Institute some enriched out included "homogeneous" the least chondritic pyroxenes are this recrystallized different for ( exhibit composition the even 1967) et also indicate with millimeter-sized possibility to their average their "equilibrated" constant chondrules and or metamorphism, paper al, are "Brownlee Note here mxue" that "mixtures") skeletal and material They contains pyroxene-like "primitive" • sophisticated relative 1981 Allegan not have no matrix Provided more is pieces the meteorites; to (in that and to recrystallization found metamorphic review ). in pyroxenes, of published or considerable VS. grains of present classified These the recently Allegan small and extensive to composition. indicates (1978) grains), thermally in in the size, chondrite volatile the by the (perhaps chondrules CHONDRITES an all the lithic including larger large observations grains techniques, amounts references evidence bulk, which may of a analysis by meteorite as Smithsonian particles." and whereas petrographic NASA recrystallization. the and that rocks. (e.g., enough grade Dodd equilibrated olivines variation were contain "primordial") even and is numerous is the involves Figure mineral in heat and of Allegan chemically indicating Na, Astrophysics included of fact chemically are often 3. cryptocrystalline found (1981, "unequilibrated fell to alone, in Chondrules for sources, fragments and the Thus Zn, fragments in Cl in in 1 Merrill's collection and probe deals fragments a shows complete grain arguments after to is 1899. ultrafine Sb) pyroxenes. pp. reviewed chondrites. chemical should that the Such an have matrix chemical homogeneous have 89-103). and with the analyses; Data size accretionary Extensive in accretionary the at and time recrystallized a variable and refractory be final an show least disequilibrium process matrix, been "equilibrated" materials of small dust" briefly structure System for matrix equilibration sufficient their This description. evenly structurally Also, olivine researchers accretion, one or However, summar- Keil minimal samples perhaps ( Fe/Mg finding against Origins ~ below, should on "Holy in large, some 1/10 (e.g., rock that, grey in and and and the the for to a 1983chto.conf...44F

K.

courtesy interstitial

similar Fig. right pound

structure section: including

~

Fredriksson:

10.8%

1

is

©

a

to

Lunar

FeO,

Photomicrographs

compound

1.1

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or

R.

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respectively).

and

in

Equilibration

Beauchamp,

in

the

in

the

Planetary

chondrule

(a).

nor

porphyritic

groundmass,

to

Olivine

cryptocrystalline

is

of

Clearly,

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in

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Institute

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of

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porphyritic

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have

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Provided

section

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shows

Length

(a)

µm)

recrystallization

does

Porphyritic

by

section

radiating

(i.e.,

partial

the

of

not

of

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NASA

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of

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the

Astrophysics

indicated

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a

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All

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(see

Data

Detail

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and

System

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a

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Length

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(Section

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with

and

47

of 1983chto.conf...44F + +2 + 48 + four correlated lowest +I that Has Weston, this show ( ents. CaO: and ordinary induration Fig. thermal -I quenching 1963 +I diagram the H-chondrites, pulverized 2 well Fredriksson The partial ), I © I' I 2.0, ALLEGAN Al ,, Ir WESTON SiO Kurat ' CaO : Lunar respectively. 2 metamorphism, as chondrites-the O cause, for 2.1, from processes 3 2 Land , content by 2.4-1.3 results (solid grades ( 1968), and individual 1.7, the a however, ( LL expressed molten 1982) H5 lines) Planetary varying and of = generally ,,., 4 did chondrites Thus and and I 1.1. I ' the \/ I/ 1.8; ,1\ has not and argue \ alleged state. \' chondrules Reid V The 5, bulk of the Al-Ca I , made , Al as but drastically ... Al Institute --, the increases highest X-axis 2 deviation and O 2 ' that analyses O \ positively studied...... evidence 3 constant correlation. electron : 3 (dashed Fredriksson ., 2.4, 2.4, the is , (metal r CaO • non-dimensional, from change ..... from Provided Weston Fe/Mg of , ___ correlated probe Fe/Mg of content chondrules lines) left removed) 1.7, equilibration-has bulk the ( (---42%) 1967). analyses and is ratios contents by compositions ratios chemistry a of for complex the an 1.8 from from These to are grade +3 Allegan + although NASA -I of for of right (wt.%) inherited pressed most various four Allegan, +I +I of authors, breccia, 3; OCHANSK (-57%). Astrophysics represented chondrule the been this olivines the of H-group Chondrules TIESCHIITZ pellets Allegan individual chondrites. is analyses from Ochansk, addressed to which also Al counter and and of is H4 the chondrites: processes by 2.0 Data meteorite over is Ca were chondrules pyroxenes case and also horizontal + Figures by Tieschitz, the are 5.8 300 System H3 their sorted indicated for Fredriksson necessity negatively = separated involving \ ""'...... constitu- all 7 Allegan 2 Origins .8; _: other in lines. and from such I ' ' '' and I, the ' the \ in of \ 3 1983chto.conf...44F K. -c( 0 0 somewhat (HS), are increases Tieschitz negatively (Fig. practically Nelen, 0 (Fig. CaO/TiO Al chondrites observed The brecciated Tieschitz, Fig. 2' I a ,., Fredriksson: 2 O 7 positively 2 e, 5 4 3 precision 3 3 2), 3) the /TiO © 1976), Lunar scatter ALLEGAN CaO decreasing have with rather in 2 contrasted correlated lower constant) as nature 2 .05 is H5 L and and in for increasing average (circles) correlated 13 and and from Fig. Equilibration similar than CaO TiO (Mason of • • LL Planetary .10 with the 2. Weston for (Fig. 2 ~5 to in /TiO chondrites. Al Increasing is TiO2 • • • and Ochansk the no all "unequilibrated" SiO -±10%. • • 2 increasing to by O 2) • and correlation . I -Bo 2 chondrites, bulk 3 • • Al ?;50, 2 • 5 ratios • and definition). in is q§o ; Institute in 2 • I the Maynes, reflected O the chondrites • • o samples Note CaO 3 size (H4), average while are . (squares) • • §o • 20 "equilibrated" SiO • of essentially the contents in • ~ 2 the symbols in the • 1967). Provided type (horizontal 16. Also, strong Furthermore, CaO Tieschitz the complex bulk In vs. 0 0 -c( ,!]3 - 5 a I "' varying 4 near 2 the and content the In constant, denotes positive TiO WESTON sample Allegan by the strong Allegan Ca/ weak(?) those (H3). lines). The breccia 2 1 .15 .10 degrees in is Al Al . c NASA correlation Ti 30 increasing individual of has ~ contrast, and ~, -~·· 0 and ratio Noteworthy 02 bulk 14 -c( 0 the to 0 0 correlation H4 2' I Weston a "' ratios 50% and~ Ochansk 4 of 3 5 2 Ca ratios bulk Astrophysics for • sample correlation. [b • are higher chondrules SiO chondrules • for • near samples these 17 (H3,4,5,6,7?; of oD .. • • positively .10 0 0 •• in the respectively, -c( 0 • a Al 2 I a OCHA chondrules is "'2 .., Al , a centered the 4. and 2 Ti chondrules •• O[Je I • that 2 "unequilibrated" O •• • O Again, TIESCHITZ or Data 02 3 Similar average 3 the NSK and .15 /TiO • somewhat • from a 0 Ca from correlated. A1 System .10 CaO the at Noonan (Fe and 2 and H4 2 O trends the TiO2 50 • a the is (which generally complex 3 and to to content 16, close Al type lower same .15 TiO 52%. H3 The and and are Mg H3 are 49 to is 3 2 1983chto.conf...44F similar chondrule their fine-grained and produce the including tallized structure, another olivine chondrites chondrites it diagrams, many material resolved vs. homogenized manuscript. ultrafine be shows 50 compositional oli Roccio. Wlotzka drites chondritic These those has vines classified the subsequently, Acknowledgments. These If Currently, constant of of of results © not and mixed reverse one or major and the In manifestation higher Lunar these by matrix and and (e.g., rare such not) formation, addition types. been are A pyroxene; are bulk data ion gross supposes, pyroxenes matrix. the Fredriksson negate as rather individual gases, Al/Ti trends, problems a chemically differences element trends to petrographic Tieschitz) and neither or components. there process metamorphic final thermally samples and achieve textural ( X-ray 4) Planetary helpful to the would and editing observations mixing in i.e., seems (2) continuing a of however, but uncommon supposition few compositions I would the may chondrules microprobe Ca/Ti and the addition DISCUSSION (1980) am the between and unequilibrated, and partially review grossly then be metamorphosed. was "deviating type types to unequilibrated of the lie This common bulk grateful Institute structural differences rocks; necessarily was be the done ratios; in have average that 3 by throughout occur of variable apparently due no type multiple, provide ("unequilibrated") variable correlated that thermally nor we Dr. Ca by (or Keil to Allegan described of rational and to olivines," • Ms. to 3 have type in E. "anomalous" INAA?) Drs. for Provided mixing the structurally unequilibrated have most the (1982) Olsen Al, (5) B. evidence AND chondrules nature chondrites compositions repetitious 3 Apparently available. chondrite B. the would L-group J. chondritic Ca, had Al, retention metamorphosed explanation to chondrules; another Fredriksson. Mason ratios is this analysis accretion accomplish: and concludes by the Ca, CONCLUSION also of a observed require meteorite that progenitor "cataclastic," these chondrites. Ti (Fredriksson, of as (Fig. and acknowledged. and and "unequilibrated" processes silicate. of chondrites material minor NASA such in of previously the for the for rocks. different Ti bulk and (3) Mr. 3). S. trace a this in H, Allegan well-closed "primitive(?)" (Figs. contains mineral R. ( separation the The exotic to Astrophysics S. chondrites, l) final Differences chondrules L, similar elements such is for This Taylor Dillon equilibration Chondrules its "equilibrated" and and and Weston the matrix 1982) believed. 2 Ms. break-up. other components present (HS) as problem and precursor associations free consequently LL the to Ripley HS P. for impacts, of system in and chondrites "equilibrated" components petrographic while SiO breccia, Brenner 3). chondritic of Ca and chondrite, composition in Data reading the composition type Rather, LL-group provided and from Similar 2 (by The other possibly , 336 Ochansk of during indicative preserving Fe-Mg System which present 4 diffusion) the produced their as in Al solution the and should samples as elements, expected, Moro breccias. "higher" ordinary they ( extreme financial (recrys- or and original well Origins stones. can type would higher of of chon- in (H4) after that and not the the the Ti) are the the do be as to of of 3 1983chto.conf...44F K. support funds Brownlee Alaerts Dodd Dodd Fredriksson Keil Fredriksson Lipschutz Lipschutz Keil Mason Kurat Mason Suess Rambaldi Merrill Merrill Merrill Tandon Reid Noonan 43, Planetary 756-769. Tieschitz gas-rich In L-group Proc. Institute, Lunar rhombic N!itional (A. chondrites. 161-203. Their 3609-3612. Connecticut, L-group Fredriksson: Abelson, K. Protostars A. K. through 547-553. G. H. R. R. H. © B. ( L. B. G. G. G. through M. 1982) U.S. Meteoritic S. ( and and Lunar A. T. T. Delsemme, and E. D. and 1968) (1963) M. M. P. H-chondrites P. P. chondrites E. N. chondrites. pyroxenes and Museum. Houston. meteorite. ed.), (1981) (1969) Science and K. K. E. F. Nat. (1888) (1916) (1929) Planetary E., Maynes the F.arth Fredriksson Anders R., and E. Composition ( chondrite. and and (1963) Fredriksson (1982) the 1978) The and pp. Wanke Biswas and Olivine Lunar Equilibration Mus. Fredriksson Wasson Analogs Meteorites. Metamorphism Planets Planet. S.I. Xlll, formation Nelen On The Handbook 170-203. Planetary ed.), from E. U.S. A. of lkramuddin In Interplanetary Geochim. Institute, Chondrules 124, (abstract). Chondrule (1979) and Fluid S., the chondrites. D. Meteorite story H. composition pp. pp. Nat. studies K. J. Sci J. ( and and (T. K. San (G. (1967) Planetary 1967) 1-12. 233-234. T. 375-383. Research (1964) A. of of B. (1%7) Wiley, Cambridge Mus. On Gehrels, origin Lett. and Mcsween Institute in J. Houston. (1968) Emigdio Cosmochim. chondrules meteorites. on J., (1976) In M. The chondrites Research Taylor the of compositions and J. descriptive Metamorphosis artificially BulL dust: Lunar 56, and 11, of N.Y. Chondrules the The in Geophys. (1978) kinetics Institute. composition Lunar Fund Univ. ed.), Gallium, chondritic the chondrites. 107- 111-130. meteorite. A ordinary REFERENCES Fredriksson 94. and • University H. Possible iron, and meteorite and Provided Smithsonian (P. petrographic pp. Acta Y. 207 126. and Condensation Toledo, of and heated L. catalogue Planetary Res. M. chondrites (1982) volatile 134-150. magnesium, germanium, L. in and pp. the breccias. 32, chondrites: Planetary implications of Millman, Proc. and Geochim. Wilkening, different 69, Press, primitive the chondrites. Ohio. Universities parent K. 1087-1109. by Chemical-petrologic loss 3487-3515. equilibrium of Science Allegan, Scientific (1981) the U.S. and Univ. and N.Y. In the from and/or Institute, ed.), bodies. NASA indium and type Cosmochim. A Workshop congeners. Nat. mineral some for meteorite eds.), 368 review. of Xlll, In chondrites. Primitive Bur-Gheluai pp. Space calcium Ser. chondrites Mus., Arizona Researches observations metamorphism: in pp. Astrophysics Trans. and Houston. pp. 185-190. pp. chemistry chondrites. 3, Geochim. on In Research collections and XI, 65-83. 439-440. iridium 1-115. Acta Lunar ultrafine distnbution Comets--Meteorites Press, N.Y. characteristics Geochim. 161-167. pre-solar and (abstract). in 27, Reidel, on LPI Acad. Geochemistry, variations Breccias study Tucson. Cosmochim. Cynthiana Association J. Data Lunar 1011-1024. chondrules in matrix Genesis Geophys. Tech. Cosmochim. interstellar the Dordrecht. in of Sci, System In and United and and olivines the in Rpt. in Lunar meteorites. ser. of Planetary a Soils provided Acta ordinary origin from the Res. Weston, 2 suite E- 82-02. grains. 2, States (P.H. Acta and and and and 33, 25, 72, 51 of of 1983chto.conf...44F 52 Wood Wood Wasson Wahl Wlotzka Van Van Urey Meteoritics meteorites. Geochim Cosmochim 145-184. Schmus Schmus H. © W. J. J. J. C. Lunar A. A. F. (1952) T. and (1963) (1962) and Cosmochim (1974) W. Geochim W. 15, Acta Craig and Fredriksson The 387-388. R. R. On Metamorphism 2, Planetary (1969) Meteorites. and H. brecciated 91-117. the Cosmochim ( Acta 1953) Wood origin The K. 4, Institute The Springer-Verlag, stony (1980) 36-82. J. mineralogy of in A. Acta chondrules composition chondrites. meteorites (1967) Morro 31, • Provided and 747-765. A and do N.Y. of Geochim and chemical-petrological petrology Roccio, chondrites. the meteorites by the 316 stone pp. Cosmochim an of meteorites NASA chondritic Icarus unequilibrated containing Astrophysics 2, Acta Chondrules classification and 152-180. meteorites. foreign the 26, H-5 origin 739-749. Data fragments. chondrite Ea,rth and for of System the the their Sci meteorites. chondritic (abstract). Geochim Origins Rev. 5,