The Kyushu, Japan, chondrite

Geochimica et CosraochimicaActa. 1961, Vol. 21, pp. 27~ to 275. Pergamon Press Ltd. Printed In ,Northern Ireland

The Kyushu, Japan, chondrite BmA~- ~L~so.',- and H. B. ~VIIK The American Museum of Natural History, New York and Geologlska Forskningsanstalten, Otnfs, Finland

(Received ! 8 February 1960) Abstract--The K y u s h u chondrite has been analysed, with tlm following results: Fe 6.27, Ni 1.31, Co 0.046, FeS 5.89, SlOe 39.93, T i e 2 0.14, A1203 1.86, Cr203 0-54, F e e 15.44, MnO 0.33, MgO 24.71, CaO 1.70, ~'aO 0-74, K~O 0.13, P~O 5 0.31, H a O + 0-27, C 0.03; total 99:67. The mineralogical composition is olivine (Fo~), hyperstheno (Enrs), maskelynlte, nickel-iron, troilite, chromite and possibly apatitc. The density of the meteorite is 3.53. INTRODUCTION

O~- 26 October 1S86, at about three o'clock in the afternoon, a shower of meteoritic stones fell over a considerable area of the southern part of the island of Kyuslm, in t h e provinces of Satsuma and Osumi. The s y n o n y m y of this meteorite fall is extensive, since b o t h province and village names have been applied to individual stones from tlfis fall, and different transliterations have been used. P~IOR and HEY (1953) give the following names as synonyms: Ensigahara; Hanakai; Hishikari; Maeme; Oguchimura; Ogutimura; Oshinla; Oynehimura; Satsuma; Shigetome; Sigctome; Simagoe; Yamanomura; Yenshigahara; possibly Kanzaki. Since PRIOR and H E r accept the name K y u s h u this will be used here, although ]~ANDA (1952), in his list of Japanese meteorites, records the fall under the name Satsuma. The first reference to this fall we have found in the literature is a brief statement b y CLARKE ( 1 8 8 8 ) , a s follows: "The United States National Museum has recently received fragments of two new Japanese meteorites from the Educational Museum at Tokio. Both are greyish stones, showing a dull black crust. The first of the two fell at Fukutomi, Kinejima, Province of Hizen, March 19, 1882, at 1 p.m. Its total weight was 7680 grams. The second fell at Maeme, Hislugari, Province of Satsuma, N o v e m b e r l0 (sic), 1886, at 3 p.m. Its original weight was 328 grams." The second fall is t h a t now described as Kyushu. The circumstances of the fall, and the surface features of some of the stones, were extensively described b y JISIBO (1906). One of the stones was later figured and described in detail b y HIKI (1912). ]~ANDA (1952) states t h a t the total weight of the fall was 46.41 kg. P~IOR and H E r (1953) record the following distribution of material from this fall: 489kg. in Tokyo Science Museum; 920 g in Tokyo University; 840 g in the Geological Institute of Tokyo; 989kg in The American Museum of Natural History, New York; 31.3 kg (including the largest stone, 28.8 kg) in the British Museum (Natural History), London. Smaller amounts are present in other meteorite collections. As this meteorite seems never to have been analysed either mineralogieally or chemically, we decided to do so, and selected from the collection of The American Museum of Natural H i s t o r y a single stone (catalog no. 1072, weight 815 g) for this purpose. 272

The Kyushu, Japan, chondrite ~[INERALOGICAL CO~IPOSITION

The stone selected for investigation was completely coated with a thin black glassy crust. The interior was pale grey in colour, irregularly stained with thin films of brown ]imonitie material, probably produced by the o.xidation of a small a m o u n t oflawrencite (FeCl2). The density was determined on a piece weighing 170 g. This piece was placed in a beaker under a bell jar, and the jar evacuated by an oil pump to remove air from the pores; carbon tetraehloride was then run in, and the apparent loss of weight on suspension in this liquid measured. The density thereby determined was 3-53. The minerals identified in the stone are: olivine, hypersthene, maskelynite, nickel-iron, troilite, and chromite; a phosphate mineral (apatite or merrillite) is probably present in small amount. Notes on the silicate minerals follow: Olivine. The i n d i c e s of refraction are: cr ---- 1.683, y = 1.721, indicating a composition of :Fo;~, according to the determinative curve of 2OLDEIWAART (1950). This has been confirmed b y the X-ray method of YODE~ and SAtIA.~rX (1957). Hypersthene. The indices of refraction are: ~ ~ 1-679, y = 1.689, indicating a composition of En~s, according to the determinative curve of Ku~'o (1954). Maslcelynite. This material, which is present in small amount, was separated by digesting a sample of the meteorite powder in 1:1 tICI (thereby dissolving nickeliron, troilite and olivine), and obtaining a concentrate of maskelynite by centrifuging the residue in an a c e t o n e - m e t h y l e n e iodide mixture of density 2.9. The maskelynite was in the light fraction. I t is isotropie or practically isotropio with an index of refraction of 1.502, corresponding to a plagioelase glass of composition Ani~, according to the data of FOSTER (1955). Dr. It. S. YODER, Jr., of the Geophysical Laboratory has examined the maskelynite and writes as follows: " T h e glass from the meteorite is exceptionally interesting. I have circled a spot on the thin section where I see blades of feldspar in glass. T h e y appear to have grown in the glass. Some of the low index crystals in the glass of the powdered sample have all the aspects of the quench products often observed in studies of synthetic melts. On the other hand we see large feldspar crystals of irregular outline in glass in the separated powder. These I presume were partially melted." Dr. u observations thus suggest t h a t the maskelynite has been formed by the melting of pre-existing plagioclase, followed by rapid quenching of melt. A n X-ray powder photograph of nickel-iron separated magnetically from the crushed meteorite shows strong lines of kamacite and weak lines of taenite. A thin section of the meteorite shows chondrules 0.5-1 m m in diameter, of both olivine and hypersthene, set in u granular groundmass of olivine, hyperstheno and opaque material (nickel-iron, troilite and chromite). The maskelynite occurs as interstitial material, clear, isotropie, and with low relief. A certain amount of brown limonitic staining is associated with the opaque material. CItESIICAL COSIPOSITIOzN"

The chemical analysis is given in Table 1, in the conventional form expressed as oxides, troilito and metal; in terms of the individual elements; and recalculated on a volatile-free basis. 8

273

BRIA-'N"]~IASO-~and H. B. WIIX: T h e n o r m a t i v e m i n e r a l c o m p o s i t i o n , expressed as w e i g h t p e r c e n t a g e s , is g i v e n in T a b l e 2. This has been c a l c u l a t e d as s u g g e s t e d b y WAHL (1950), e x c e p t t h a t we prefer t o calculate P205 as a p a t i t e , n o t merrillite; t h e c o m p o s i t i o n o f merrillite is n o t well established, b e i n g b a s e d o n a single analysis o f a small a m o u n t o f i m p u r e material, a n d this m i n e r a l m a y well be a v a r i e t y o f a p a t i t e . Table 1. Chemical analysis of the Kyushu meteorite (A)

(B)

Fo

6-27

Ni

1.34

Co FeS SiO2 TiO 2 A1203 Cr20 a Fee ~InO ~IgO CaO Na20 K20 P205 H20 + C

0.046 5.89 39.93 0-140 1"86 0.54 15.44 0.33 24.71 1-70 0.74 0.13 0.31 0-27 0.03

I-I C O 2ffa ~Ig A1 Si P S K Ca Ti Cr Mn Fe Co /~i

(C) 0.029 0.03 36.82 0.54 14.90 0.98 18.66 0.14 2.15 0.10 1.21 0.08 0.37 0-26 22.02 0.046 1.34

99.67

Na Mg A1 Si P K Ca Ti Cr Mn Fo Co .Ni

0.89 24-55 1.61 30.75 0-23 0.16 1.99 0.13 0.61 0.43 36-30 0.076 2.21 99.94

99.67

(A) Chemical analysis expressed as nickel-iron, troilite and oxides (all 1:i as H~O), all C as C (both free and combined). (B) Chemical analysis expressed as elements, with calculated figure for oxygen. (C) Chemical analysis recalculated on a volatile-free (O, C, S, H) basis. Table 2. Normative mineral composition of the Kyushu meteorite

% Nickel-iron Troilite Olivine Hypersthene Diopside Albite Anorthito Ortheelaso Chromite Apatito IImenito

7.66 5.89 42.60 28.93 4.10 6.21 1.36 0-78 0.78 0-74 0.26

T h e n o r m a t i v e c o m p o s i t i o n correlates well w i t h t h e o b s e r v e d mineral c o m position. N o diopside was observed, a n d t h e c a l c i u m is p r o b a b l y p r e s e n t in solid solution in t h e h y p e r s t h e n e . T h e n o r m a t i v e p y r o x e n e is 33.03 p e r cent, n o r m a t i v e olivine 42.60 p e r c e n t , g i v i n g a r a t i o o f p y r o x e n e to olivine of 3:4, w h i c h agrees 274

The Kyushu, Japan, chondrito w i t h e s t i m a t e s f r o m t h i n sections a n d X - r a y p o w d e r p h o t o g r a p h s . N o r m a t i v e feldspar is 8-35 p e r cent, w h i c h is p r o b a b l y h i g h e r t h a n t h e a m o u n t o f m a s k e l y n i t e p r e s e n t , since some o f t h e Ale0 a c a l c u l a t e d as feldspar is in t h e p y r o x e n e . T h e 0.78 p e r c e n t n o r m a t i v e c h r o m i t e corresponds to t h e a m o u n t seen on polished surfaces. A l t h o u g h n e i t h e r a p a t i t e n o r merrillite were o b s e r v e d in t h i n section, t h e 0.74 p e r c e n t a p a t i t e in t h e n o r m could well be p r e s e n t ; it w o u l d be e x t r e m e l y difficult t o recognize it in a t h i n section, since it p r o b a b l y occurs in small grains i n t i m a t e l y m i x e d w i t h p y r o x e n e a n d olivine. T h e small a m o u n t o f t i t a n i u m c a l c u l a t e d as ilmenite is a l m o s t c e r t a i n l y in solid solution in t h e olivine a n d pyroxene. A cross-check b e t w e e n t h e chemical analysis a n d the mineralogical composition can be o b t a i n e d b y calculating t h e a m o u n t of :Fe0 a n d hIgO r e q u i r e d for t h e o b s e r v e d c o m p o s i t i o n o f t h e olivine a n d p y r o x e n e , a n d c o m p a r i n g these figures w i t h those g i v e n b y t h e a n a l y s i s . These results are as follows: :Fe0 (analysis) 15.44 p e r c e n t (calculated) 14.7 p e r c e n t ; ~IgO (analysis) 24.71 p e r cent, (calculated) 25.1 p e r cont. I n view o f t h e u n c e r t a i n t i e s in t h e d e r i v a t i o n o f the chemical c o m p o s i t i o n o f t h e minerals f r o m t h e i r optical p r o p e r t i e s , a n d t h e difficulty o f a r r i v i n g a t a precise figure for 17c0 b y chemical analysis, t h e a g r e e m e n t is good. T h e chemical analysis shows t h a t t h e K y u s h u stone, in P r i o r ' s classification, falls into his g r o u p o f h y p e r s t h e n e - o l i v i n e c h o n d r i t e s o f t h e B a r o t i a n d Soko-]3anj a t y p e s . A c c o r d i n g to the classification o f UI~EY a n d C~AIO (1953), it belongs to t h e i r L g r o u p since i t contains low t o t a l iron (22.02 p e r cent, t h e a v e r a g e for t h e i r L g r o u p being 22.33 p e r cent). ] { y u s h u is closely c o m p a r a b l e c h e m i c a l l y a n d mineralogically w i t h H o l b r o o k (MAsox a n d WIIK, 1960) a n d a n u m b e r o f o t h e r h y p e r s t h e n e olivine c h r o n d r i t e s . Acknowledgements--~Vo are indebted to the g. Lawrence Smith Fund of the National Academy of

Sciences for a grant towards the cost of this investigation. Our thanks are also due to Dr. I-I. S. YODEI~, Jr., for his examination and comments on the maskel:~aaite, and for critically reading the manuscript. I~EFERE~CES CL.C~-ZKEF. W. (1888) New meteorites. Amer. J . Sci. 35, 264. FOSTER ~V. 1-r (1955) Simple method for the determination of the plagioclase feldspars. Arner. .Min. 40, 179-185. ~hK[ T. (1912) The exte~-nal form of the meteoric iron "Okana." Beitr. Miner. Japan 4, 142-144. JBmo K. (1906) General note on Japanese meteorites. Beitr. llliner. J a p a n 2, 30-52. ](ANDA S. (1952) On the meteorites of Japan, Korea, and China. Sci. gep. Yokohama Univ. Ser. II, No. 1, 97-106. Ktr~o It. (1954} Study of orthopyroxenes from volcanic rocks. Amer. l]lin. 0~ 30-40. 5IASOh" 13. and ~VIIK I-I. /3. (1960) The Itolbrook, Arizona, chondrite. Geochim. ct Cosmochlm. Acta. 21, 276-283. rOLDErCV'AARTA. (1950) Correlation of physical properties and chemical composition in the plagioclaso, olivine, and orthopya'oxcne series. Amer..Min. 35, 1067-1079. Pitier G. T. and ttE-~ ~I. I-I. (1953) Catalogue of 3leteorites with Special Reference to those Repres. ented in the Collection of the BrRish l~luseum (Natural History). British ~Iuseum, London. U~EY It. 12. and CreAm I-I. (1953) The composition of the stone meteorites and the origin of the meteorites. Geochim. et Cosmochim. Acta 4, 36-82. ~VArtL, ~V. (1950) The statement of chemical analyses of stony meteorites and the interpretation of the analyses in terms of minerals. ,lIin..]~rag. 29, 416--426. YODEIt I-L S. and SAIrA.~tAT. G. (1957) Olivine X-ray determinative curve. Amer. ~]Iin. 42, 475-491. 275