Geochemical Journal, Vol. 38, pp. 1 to 17, 2004

*Corresponding author (e-mail: jcchen@oc.ntu.edu.tw)

Copyright © 2004 by The Geochemical Society of Japan.

Geochemical studies of tektites from East Asia

YUNG-TAN LEE,1 JU-CHIN CHEN,1* KUNG-SUAN HO2 and WEN-SHING JUANG2

1Institute of Oceanography, National Taiwan University, Taipei, Taiwan 10617, R.O.C.2Department of Geology, National Museum of Natural Science, Taichung, Taiwan 40419, R.O.C.

(Received March 3, 2003; Accepted June 18, 2003)

Thirty tektites from East Asia (including Wenchang and Penglei of Hainan Island, Maoming of Guandong, China;Khon-Kaen of Thailand; Bao Loc of Vietnam; Rizal of Luzon, Philippines) have been analyzed for major and trace ele-ment contents and Rb-Sr isotopic compositions. All the samples studied are splash form tektites. The trace element ratiosBa/Rb (avg. 3.74), Th/Sm (avg. 2.31), Sm/Sc (avg. 0.43), Th/Sc (avg. 0.99) and the rare earth elements (REE) contents oftektites studied are similar to the average upper continental crust. The chemical data of tektites in this study indicate thatthey were derived from similar target rocks which may be related to post-Archean upper crustal materials. The tektitesfrom East Asia have high positive εSr(0) values-ranging from 164.2 to 198.6, indicating that they were not dominantlyderived from recent young sediments, such as soil or loess. The Ar-Ar ages (736.8 ± 55.5~814.6 ± 24.4 ka) of tektites ofthe present study are consistent with the age of other Australasian tektites, which indicates that all Australasian tektiteswere derived from a single impact event. Previous studies (Koeberl, 1992; Blum et al., 1992; Schnetzler, 1992) and thepresent chemical data suggest that these tektites are the result of melting at a single site, which is most probably located inthe southern part of the Thailand-Laos border. Mixing calculations based on the model suggested by Ho and Chen (1996)for various amounts and combinations of target rocks indicate that the best fit for East Asia tektites is a mixture of 61%greywacke, 32% sandstone and 7% shale.

Keywords: tektites, geochemistry, strewn field, East Asia, 40Ar-39Ar dating

Apart from the microtektites found in deep-seasediments (Glass, 1990; Lee and Wei, 2000), tektites onland can be subdivided into three groups: (a) normal orsplash form tektites, (b) aerodynamically ablated tektites,and (c) Muong Nong-type tektites (layered tektites)(Koeberl, 1992). The first two groups are only slight dif-ferent in their appearance and physical characteristics.The shapes of splash form tektites (spheres, droplets, tear-drops, dumbbells etc.) are often erroneously described asaerodynamical ablated tektites (flanged button). MuongNong-type tektites are named after a locality in Laoswhere they were first found by Lacroix (1935). They arelarger in size, less homogeneous, having higher abun-dances of volatile elements (e.g., B, Cu, Zn, Ga, As, Se,Sb and Pb) and water and contain more bubbles and somerelict minerals (e.g., coesite, zircon, corundum, rutile,chromite, etc.) which indicate a sedimentary rock as thesource rock (Koeberl, 1992). Besides, based on theirheavier weights and irregular shapes, some authors(Stauffer, 1978; Hartung and Rivolo, 1979) suggested thatMuong Nong-type tektites probably have not traveled farfrom their location of origin, and may therefore be closeto the impact crater.

The origin of tektites was a scientific puzzle for manyyears. Although O’Keefe (1976, 1994) favored a lunarvolcanic origin, most authors accept that tektites are the

INTRODUCTION

Tektites are relatively homogeneous, dense glass ob-jects found scattered over large areas of the Earth’s sur-face called strewn fields. Four strewn fields are knowncommon names and approximate ages are: NorthAmerican, 34.9 Ma (Storzer and Wagner, 1971); CentralEuropean, 14.5 Ma (Schwarz and Lippolt, 2002); IvoryCoast, 1.07 Ma (Koeberl et al., 1997) and Australasian,0.77 Ma (Izett and Obradovich, 1992). Tektites foundwithin a given strewn field are related with respect to theirphysical and chemical properties besides their age. Thesmallest strewn field is the Central European, and the larg-est is the Australasian field. Some of the strewn fieldscan be divided into different substrewn fields. For exam-ple, some of the North American tektites can besubclassified as bediasites (Texas) and georgiaites(Georgia). The Central European strewn field includestektites named moldavites from Moravia and Bohemia,whereas the Australasian strewn field consists of severalsubfields.

1

2 Y.-T. Lee et al.

product of hypervelocity impact on Earth and representmelted target rock ejected during crater formation (Glass,1990; Wasson, 1991; Blum et al., 1992; Koeberl, 1994).Recently, Futrell (2000) made a case for lunar provenance,based on the theory that tektites could have erupted asvolcanics at the lunar surface, but the case has been re-torted by Glass (2000), who argued that the silica-richigneous material in lunar samples is miniature and that itis petrographically and compositionally distinct fromtektite glass.

Lead isotope data (Wampler et al., 1969) indicate thatthe parent material of tektites is terrestrial, and consist-ent with young sediments, including oceanic sediments.Based on 10Be contents of tektites, several authors (Blumet al., 1992; Koeberl, 1992) favor a sedimentary originfor the parental material of Australasian tektites. Accord-ing to 10Be contents (about 1 × 108 atoms) ofAustralasian tektites, Pal et al. (1982) suggested that cos-mic-ray bombardment of the australites cannot producethe measured amounts of 10Be either at the earth’s sur-face or in space, indicating a sedimentary precursor thatadsorbed from precipitation 10Be produced in the atmos-phere.

The purpose of the present study is to analyze themajor and trace elements (including rare-earth elements,REE) and the Rb-Sr isotopic ratios and to date the tektitesby Ar-Ar method in order to shed some light on the ori-gin of the tektites, their parent material and the possiblesource crater.

SAMPLES AND ANALYTICAL METHODS

The tektites were sampled personally by K. S. Ho andW. S. Juang from Wenchang (5 samples) and Pengli (5samples) of Hainan Island, Maoming (5 samples) inGuandong, China, Khon-Kaen (5 samples) in Thailand,Bao Loc (5 samples) in Vietnam and Rizal (5 samples) inLuzon, Philippines (Fig. 1). All the tektite samples arecomplete pieces and their weights ranging from 3.88 g to7.09 g for Wenchang, 1.64 g to 9.27 g for Pengli, 34.8 gto 74.5 g for Maoming, 11.45 g to 17.83 g for Khon-Kaen,20.64 g to 30.02 g for Bao Loc and 11.4 g to 59.3 g forRizal. The 30 tektites samples in the present study allbelong to the splash-form and they are oval, elongated ordumbbell-shaped.

Thirty samples were cleaned with distilled water and

Fig. 1. Localities of analyzed East Asia tektites (stars) and the distribution of Jurassic exposures in Southeast Asia: 1, hachuredareas denote marine Jurassic exposures; 2, stippled areas show nonmarine Jurassic exposures (after Sato, 1992).

Geochemical studies of tektites 3

acetone in ultrasonic cleaner and crushed into chips by ahammer while the samples were wrapped with plasticsheets. Several larger glass chips were selected and groundinto powders in an agate mortar.

The chemical analyses of tektites from East Asia havebeen carried out by colorimetry (Si, Al, Ti, P), atomicabsorption (Fe, Mg, Ca, Na, K, Mn) and inductively cou-pled plasma mass spectrometry (Ba, Co, Cr, Cs, Cu, Hf,Ga, Li, Nb, Ni, Rb, Sc, Sr, Ta, Th, U, V, W, Y, Zr, Zn andREEs) at the National Taiwan and Tsing-Hua Universi-ties.

Calibration curves were constructed using U.S.G.S.standard rocks AGV-1, BCR-1, W-2, and G2 and NBS278 standard obsidian. Values for these rock standardswere adapted from compilations by Govindaraju (1994).The precision of the analyses in the present study are asfollows: ΣFeO ± 1.46%, MgO ± 1.14%, CaO ± 1.79%,Na2O ± 0.95%, K2O ± 1.58%, MnO ± 1.88%, Cr ± 1.93%,Cu ± 1.04%, Zn ± 1.37%, Rb ± 1.95%, Sr ± 1.16%,Y ± 1.99%, Nb ± 4.03%, Ba ± 1.14%, La ± 1.31%,Ce ± 1.47%, Nd ± 2.65%, Sm ± 1.45%, Eu ± 2.15%,Tb ± 3.19%, Yb ± 2.06%, Lu ± 3.45%, Hf ± 4.18% andTh ± 3.02%.

Seven tektites (TK-2, W-1, W-2, W-3, BL-12, BL-14and BL-20) were selected for Rb-Sr isotopic composi-tion analyses. Each tektite (about 2 gm) after cleaningwith acetone and distilled water, was individually dis-solved in a HF-HNO3 mixture; and tracers (84Sr and 87Rb)addition and chemical separations followed. Isotopic com-positions of the Rb and Sr were measured using a FinniganMAT 261 mass spectrometer at AMDEL Company,Thebarton, Australia.

Ages of five representative tektites (W-1, W-2, KK-1,M-01 and M-03) were analyzed by the Ar-Ar method.About 1.5 to 3 gm of 40–120 mesh from each sample waswrapped in aluminum foil packets and stacked inaluminum canister with LP-6 biotite standard (127.7 ±1.4 Ma, Odin, 1982) and HDB-1 biotite (24.7 ± 0.4 Ma,Fuhrmann et al., 1987) and irradiated in the Open PoolReactor at National Tsing-Hua University with neutronflux of 1.566 × 1013 n/cm2 sec for 8 hours. After irradia-tion, samples were loaded in degassed fused silica boats,and placed into a degassed fused quartz tube, baked at250°C for 24 hours and then incrementally heated fol-lowing a 30-min. per step schedule using a resistance fur-nace. The purified gas was analyzed with a Varian-MATGD 150 mass spectrometer. The concentrations of 36Ar,37Ar, 38Ar, 39Ar and 40Ar were corrected for system blanks,for radioactive decay of the nucleogenic isotopes and forminor interference reactions involving Ca, K and Cl, fol-lowing procedures outlined in detail by Lo and Lee (1994).A weighted mean of J values obtained from the analysesof irradiation standard minerals is adopted in the age cal-culations. Integrated dates were calculated from the sum

total of the peak heights and their errors from the squareroot of the sum of squares of the peak height errors, forall of the temperature steps. The detailed results of 40Ar/39Ar laser fusion experiments are listed in Table 5.

CHEMICAL CHARACTERISTICS OF

THE TEKTITES FROM EAST ASIA

Major element compositionKoeberl (1990) indicated that tektites are character-

ized by high SiO2 content (65 to 85 wt%) and rather highFeO and low alkali contents. Most tektites from East Asiahave SiO2 contents ranging from 71 to 81 wt% which isconsistent with previous observation on Australasiantektites (Table 1). Based on the high abundance of silicain the tektites and the occurrence of 10Be in the tektites(Tera et al., 1983; Englert et al., 1984; Pal et al., 1982),the lunar volcanic origin for tektites may be excluded.The major oxide composition of tektites from differentlocalities in the present study, except Al2O3 and CaO, aregenerally uniform. The relative depletion of Al2O3 intektites from Maoming, Guandong, China (Al2O3 aver-aging 7.06 wt%) and Rizal, Luzon Philippines (Al2O3averaging 6.07 wt%) may be related to the lower contentof shale in the source rocks. In addition, the variable con-tents of CaO in the East Asian tektites may be due to dif-ferent amounts of limestone involved during the forma-tion of the tektites.

Except for higher Na2O, the average chemical com-positions of tektites in this study closely resemble that ofsplash-form indochinites (Table 2). Except for Na2O, CaOand K2O the concentrations of the major oxides are simi-lar to those of the upper continental crust (Fig. 2) (Taylorand McLennan, 1985). The relatively lower Na2O, CaOand K2O contents found in the tektites of this study sug-gest that the source material probably contains relativelylow contents of carbonate and feldspar. Plots of total FeOversus other major oxides allow the tektites from differ-ent substrewn fields to be distinguished (Koeberl, 1990)(Fig. 3).

Trace element compositionExcept for Co, Ga and Sc, the average trace element

contents of the tektites in this study closely resemble theaverage composition of previously analyzed splash-formindochinites (Fig. 4). Comparison of trace element databetween tektites in this study and the average upper crust(Fig. 5) suggests that some trace elements correlationsare not close (i.e., Cr, Li, Sc, Co, Hf and Cs). However,Ba, Rb, Ga and U are closely correlated between thetektites analyzed and the upper continental crust.

Most scientists favor a terrestrial sedimentary precur-sor material for tektites (Taylor, 1973; Koeberl, 1986,1992). Sedimentary rocks have higher Th/U ratios than

4 Y.-T. Lee et al.

Tabl

e 1.

M

ajor

and

tra

ce e

lem

ent

com

posi

tion

s of

30

Eas

t A

sia

tekt

ites

Geochemical studies of tektites 5

n.d.

= n

ot d

eter

mi n

ed.

6 Y.-T. Lee et al.

igneous rocks (McLennan and Taylor, 1980). The highTh/U ratios (>6) found in tektites of this study indicatethat sedimentary rocks may be the major source materi-als of these tektites. The ratios of Ba/Rb, K/U, Th/Sm,Sm/Sc and Th/Sc were used by Koeberl (1994) to estab-

lish that the geochemistry of tektites is almost identicalto the composition of the terrestrial upper crust. We usethe Ba/Rb, Sm/Sc, Th/Sm and Th/Sc ratios to evaluatewhether the tektite compositions are compatible with aoceanic crustal, lower continental crustal or upper conti-

A B C D E F G H I J

[wt%]SiO2 72.49 73.06 73.25 72.93 78.53 75.87 74.36 78.93 72.70 66.00Al2O3 13.73 13.54 13.75 12.61 7.06 6.07 11.13 10.18 13.37 15.20MgO 3.38 1.70 2.69 2.62 2.31 2.87 2.59 1.43 2.14 2.20ΣFeO 5.16 4.55 5.15 4.52 5.11 5.45 4.99 3.74 4.85 4.50

CaO 1.10 1.97 0.43 1.76 3.01 4.58 2.14 1.21 1.98 4.20Na2O 1.40 1.53 1.40 1.32 1.30 1.62 1.43 0.92 1.05 3.90K2O 2.30 2.61 2.15 2.45 2.27 2.54 2.39 2.42 2.62 3.40MnO 0.10 0.09 0.10 0.11 0.11 0.11 0.10 0.08 0.08 0.08TiO2 0.75 0.77 0.74 0.83 0.78 0.82 0.78 0.63 0.78 0.50P2O5 0.09 0.09 0.04 0.04 n.d. n.d. 0.04 n.d. n.d. n.d.Total 100.49 99.98 99.71 99.20 100.49 99.92 99.97 99.54 99.57 99.98[ppm]Li 49.0 55.6 54.1 42.7 45.1 61.7 51.4 42.1 47.1 20.0Sc 10.6 13.7 13.4 9.9 17.8 39.4 17.5 7.7 10.5 11.0V 81 99 80 66 95 668 181 72 63 60Cr 91.4 85.1 77.3 53.0 67.8 103.5 79.7 60.6 63.0 35.0Co 13.0 15.9 11.9 10.6 23.1 30.2 17.4 12.6 11.0 10.0Ni 29.1 36.4 20.1 n.d. n.d. n.d. 14.3 48.6 19.0 20.0Cu 4.72 10.02 5.56 5.80 n.d. n.d. 4.4 14.3 4.0 25.0Zn 21 36 18 10 17 26 21 67 6 71Ga 11.9 11.8 10.1 6.7 18.0 24.0 13.7 24.2 8.2 17.0Rb 109 133 130 97 103 118 115 110 130 112Sr 150 147 134 141 141 183 150 135 90 350Y 37.4 39.1 41.2 27.4 48.4 90.9 47.4 n.d. n.d. n.d.Zr 265 323 273 245 429 974 418 280 252 190Nb 17.9 16.4 17.9 12.9 25.0 39.3 21.6 n.d. n.d. n.d.Cs 6.42 8.00 6.68 5.76 5.96 9.88 7.12 5.09 6.50 3.70Ba 389 385 419 370 417 603 430 341 360 550La 40.4 41.5 40.3 35.2 49.8 86.3 48.9 28.2 36.5 30.0Ce 84.0 87.6 80.7 72.1 97.6 157.0 96.5 60.7 73.1 64.0Nd 37.2 37.7 37.8 29.9 41.6 51.4 39.2 29.1 33.2 26.0Sm 7.5 7.5 7.2 5.9 7.4 9.2 7.5 4.9 6.6 4.5Eu 1.28 1.21 1.24 0.98 0.50 0.68 0.98 1.01 1.22 0.88Gd 5.73 5.56 5.58 5.40 5.25 6.81 5.72 4.30 5.24 3.80Tb 0.95 0.94 0.95 0.83 0.64 0.99 0.88 0.75 0.85 0.64Dy 5.83 5.98 5.68 4.47 n.d. n.d. 3.66 4.75 5.58 3.50Yb 2.87 3.21 2.89 2.46 2.82 3.92 3.03 2.71 2.90 2.20Lu 0.50 0.48 0.49 0.40 0.47 0.68 0.50 0.42 n.d. 0.32Hf 6.63 7.92 6.65 6.81 9.21 12.66 8.31 8.13 6.95 5.80Ta 1.6 0.6 1.5 1.0 1.3 1.8 1.3 1.17 1.6 2.2W 0.70 1.15 0.45 0.79 n.d. n.d. 0.52 1.02 0.29 2.00Th 14.2 16.8 14.0 12.9 18.1 27.2 17.2 11.1 14.0 10.7U 2.34 2.50 2.17 2.04 2.35 4.47 2.65 2.48 2.07 2.8

Table 2. Major and trace element compositions of average East Asia tektites compositions compared withaverage Muong Nong-type and splash-form indochinites, and average upper continental crust

A, Average Wenchang tektites (China); B, Average Penglei tektites (China); C, Average Khon-Kaen tektites (Thailand); D, Average Bao Loctektites (Vietnam); E, Average Maoming tektites (China); F, Average Rizal tektites (Philippines); G, Average 30 East Asia spalsh form tektites(this study); H, Average Muong Nong-type indochinites (Koeberl, 1992); I, Average splash-form indochinites (Koeberl, 1992); J, Average uppercontinental crust (Taylor and McLennan, 1985).n.d. = not determined.

Geochemical studies of tektites 7

nental crustal source. The average element ratios oftektites of the present study (Ba/Rb = 3.74, Th/Sm = 2.31,Sm/Sc = 0.43, Th/Sc = 0.99) (Table 3) are similar to thoseof average upper continental crust. The lunar provenanceof tektites suggested by Futrell (2000) is unlikely (Fig.6), on the other hand, a La vs. Th plot (Fig. 7) indicatesthat the tektites in this study cluster around the correla-tion line defind by post-Archean sediments (La/Th = 2.8)and differ from the Archean sediment correlation line (La/Th = 3.5; Taylor and McLennan, 1985) which indicatethat these tektites may be derived from post-Archean sedi-mentary rocks such as sandstones, greywacke and shale.

The rare-earth elements compositionThe rare-earth elements (REEs) are among the most

important trace elements useful in petrogenetic studiesof the parent rocks because their patterns are not affectedby melting or metamorphic processes. Impact processes

Fig. 2. Comparison of average major element compositions ofEast Asia splash form tektites (this study) with average compo-sitions of upper continental crust (Taylor and McLennan, 1985).

Fig. 3. Plots of total Fe (as FeO) versus major elements forsplash form tektites from East Asia (this study) and MuongNong-type tektites (Koeberl, 1992).

Fig. 4. Comparison of trace element compositions of East Asiasplash form tektites (this study) with (A) average trace elementcompositions of splash-form indochinites, (B) average traceelement compositions of Muong Nong-type indochinites(Koeberl, 1992).

8 Y.-T. Lee et al.

do not alter the REE patterns significantly, with the pos-sible exception of affecting the most volatile REEs if frac-tional vaporization took place (Koeberl, 1990). Severalauthors (Taylor and McLennan, 1979; Koeberl, 1990,1992; Wasson, 1991; Ho and Chen, 1996) concluded thatthe LREE in the Australasian tektites are strongly enrichedrelative to chondritic abundances and that the REE pat-terns of these tektites are similar to those of upper crustalsedimentary rocks.

The REE patterns for tektites in this study are similarto those of previously analyzed splash-form indochinites(Fig. 8), indicating that they are all derived from similarparent rocks of upper continental crust affinity. Thepresent authors further excluded the lower crust and oce-anic crust as source rocks of these tektites due to theirdifferent REE patterns (Fig. 9).

Regional compositional variationsThe upper continental crust (UCC, Taylor and

McLennan, 1985) normalized compositional distributionsof splash form tektites from East Asia (data from Table2) are shown in Fig. 10. It should be noted SiO2 and K2Oshow relatively restricted variation indicating that thecontribution of quartz and K-feldspar are relatively con-stant. MgO and CaO show some variations indicating thatthe contribution of parental carbonate rocks may beslightly variable.

For the trace elements, Rizal, Philippine tektites havehigher Sc, Th, Cr, Zr, Ta, La and Yb as compared withPenglei (China), Wenchang (China), Maoming (China),Khon-Kaen (Thailand) and Bao Loc (Vietnam) tektites.

Fig. 5. Comparison of average trace element composition ofEast Asia splash form tektites (this study) with average traceelement composition of upper continental crust (Taylor andMcLennan, 1985).

Fig. 6. Sm vs. Th and Rb vs. Ba plots for various tektites fromEast Asia (this study). The “Earth” line has been calculatedfrom average upper crustal material (Koeberl and Fredriksson,1986). East Asia tektites (this study) clearly show a terrestrialupper crustal ratio. Symbols same as in Fig. 3.

We suggest that Rizal splash form tektites may have morecontribution from heavy minerals such as zircon andchromite. The former is enriched in Zr, Ta, Th and REE,while the later is enriched in Cr and Fe. This is consistentwith the relatively higher total FeO content found in Rizalsplash form tektites averaging 5.45 wt% (Table 2).

Isotopic compositionNd and Sr isotopic studies of Australasian tektites pro-

vide information on the age and provenance of the targetmaterials and allow us to characterize the target area andthe impact process leading to tektite formation (Blum etal., 1992). Shaw and Wasserburg (1982) showed thattektites from each strewn field have well-defined rangesof Nd and Sr isotopic compositions. Each tektite group is

Geochemical studies of tektites 9

Fig. 7. Correlation diagram of La vs. Th for East Asia tektites.The data points for East Asia splash form tektites (this study)cluster around the correlation line defined for post-Archeansediments (data for Archean and post-Archean sediments fromTaylor and McLennan, 1985). Symbols same as in Fig. 3.

Wenchang Penglei Khon-Kaen Bao Loc Maoming Rizal Avg. East UCCChina China Thailand Vietnam China Philippines Asia tektites

Ba/Rb 3.57 2.95 3.24 3.83 4.04 5.13 3.74 4.91Th/Sm 1.90 2.25 1.94 2.18 2.46 2.95 2.31 2.38Sm/Sc 0.71 0.54 0.54 0.60 0.43 0.23 0.43 0.41Th/Sc 1.34 1.23 1.05 1.31 1.06 0.69 0.99 0.97

Table 3. The average Ba/Rb, Th/Sm, Sm/Sc and Th/Sc ratios of tektites from each location and theaverage of thirty East Asia splash form tektites (this study) compared with average upper continentalcrust (UCC, Taylor and McLennan, 1985)

Fig. 8. Chondrite-normalized REE diagram of East Asia splashform tektites (this study, average values) and various materi-als. Cl-normalized values after Evensen et al. (1978); data forMuong Nong-type and splash-form indochinites from Koeberl(1992); upper crust from Taylor and McLennan (1985).

characterized by a uniform Nd model age, TCHURNd , inter-

preted as the time of formation of the crustal segmentwhich weathered to form the parent sediment of thetektites: (1) ~1.15 AE for Australasian tektites; (2) ~1.91AE for Ivory Coast tektites; (3) ~0.9 AE for moldavites;(4) ~0.65 AE for North American. Several authors(Compston and Chapman, 1969; Taylor, 1969; Shaw andWasserburg, 1982) previously suggested that the age ofthe Australasian tektite source material is around 200 to400 Ma. Based on the Nd and Sr isotopic data, Blum etal. (1992) revealed that the Australasian tektites werederived dominantly from a sedimentary formation with anarrow range of stratigraphic ages, close to 170 Ma(Jurassic), by a single impact event.

Because of the wide age range and Rb/Sr ratios ofcrustal rocks, the continental crust has a heterogeneousSr isotopic composition. Tektites from the Australasian

strewn field are characterized by quite variable εSr(0) iso-topic composition (Table 4; Fig. 11). Wasson (1987, 1991)suggested that the source of tektites may be a soil such asloess which has a homogeneous Sr isotopic composition(Taylor et al., 1983). The variable Sr isotopic composi-tions found in the Australasian tektites may be used ascriteria to exclude soil or loess as the dominant parentalsource rocks.

The Sr isotopic data obtained by the present studysupport the conclusion reached by Blum et al. (1992) (Fig.12), since our data all fall within the wedge-shaped arraydefined by all Australasian tektites.

The age of the Australasian impact is known to beabout 0.77 Ma based on radiometric ages of the tektitesand the stratigraphic position of microtektites found indeep-sea sediments of the region (Gentner et al., 1967;Glass, 1979; Burns and Glass, 1989; Lee and Wei, 2000).The Ar-Ar ages of tektites obtained by the present study

10 Y.-T. Lee et al.

Fig. 9. Average REE composition of East Asia splash formtektites (this study) and various source materials normalizedto Cl-chondrite (Evensen et al., 1978). Data for upper conti-nental crust from Taylor and McLennan (1985), lower crustfrom Rudnick (1992), oceanic crust from Hofmann (1988).

Fig. 10. Upper continental crust (UCC, Taylor and McLennan,1985) normalized compositional distributions of splash formtektites from East Asia (data from Table 2). P: Penglei, China;W: Wenchang, China; M: Maoming, China; KK: Khon-Kaen,Thailand; BL: Bao Loc, Vietnam; R: Rizal, Philippines.

Sample number Location Rb (ppm) Sr (ppm) 87Rb/86Sr 87Sr/86Sr εSr fRb/Sr TSrUR (Ma)

W-1 Wenchang 108.1 159.8 1.960 0.716771 ± 6 174.2 22.70 460W-2 Wenchang 109.3 159.2 1.989 0.716818 ± 6 174.8 23.05 455W-3 Wenchang 102.4 155.9 1.903 0.717082 ± 10 178.6 22.01 487TK-2* Penglei 123.2 131.6 2.706 0.718490 ± 36 198.6 31.72 376BL-12 Bao Loc 101.0 137.0 2.207 0.716507 ± 16 170.4 25.69 398BL-14 Bao Loc 98.0 156.0 1.793 0.716066 ± 15 164.2 20.68 476BL-20 Bao Loc 97.0 134.0 2.846 0.716974 ± 27 177.1 33.41 318

Ratios (87Sr/86Sr) normalized to 87Sr/86Sr = 8.3752 and using 85Rb/87Rb = 2.600; λ(87Rb) = 1.42 × 10–11 yr–1.εSr, fRb/Sr and TSr

UR are calculated relative to the present day bulk earth composition of 87Rb/86Sr = 0.0827, 87Sr/86Sr = 0.7045 and usingλ(87Rb) = 1.42 × 10–11 yr–1.*From Ho and Chen (1996).

Table 4. Summary of Rb-Sr results and model age calculations

range from 736.8 ± 55.5 to 814.6 ± 24.4 ka (Table 5),which are consistent with the published ages (Burns andGlass, 1989; Wasson, 1991; Lee and Wei, 2000) of theAustralasian tektites indicating that the Australasiantektites are or probably are derived from a single impactevent.

SOURCE REGION FOR THE AUSTRALASIAN TEKTITE

STREWN FIELD

The Australasian tektites strewn field is the youngestand the largest one on earth which covers more than one-tenth of the Earth’s surface (Glass and Pizzuto, 1994).Three of the four recognized strewn fields have beenchemically and geochronologically associated with im-

pact craters: the Central European with the Ries crater inGermany at 14.5 Ma (Schwarz and Lippolt, 2002) andthe Ivory Coast strewn field with the Bosumtwi crater inGhana at 1.07 Ma (Koeberl et al., 1997). And the NorthAmerican may be associated with the Chesapeake Bay

Geochemical studies of tektites 11

structure (Poag et al., 1994; Koeberl et al., 1996). Thesite of the impact for the Australasian strewn field hasnot yet been determined.

Bentley (1979) concluded that there was no giantmeteorite crater in Wilks Land. Elgygytgyn Crater has adiameter of 18 km and an age of 3.50 ± 0.50 Ma andZhamanshin Crater has a diameter of 13.5 km and an ageof 0.7–1.0 Ma (Matsubara et al., 1991). Blum et al. (1992)and Koeberl (1994) considered that the source crater forAustralasian strewn field should have a diameter of 50 to

100 km. Based on masses of Australasian microtektites,Glass (1993, 2003) suggested that the minimum diam-eter of source crater for Australasian tektites is around40 km. Elgygytgyn Crater, Zhamanshin Crater and a struc-ture in Cambodia with a diameter of 10 km may be ex-cluded as source crater. Geographic variations in number,size, shape, petrography and composition of the Australa-sian tektites suggest that the source region may be inIndochina (Barnes, 1961; Chapman and Scheiber, 1969;Blum et al., 1992; Schmidt et al., 1993; Glass and Pizzuto,1994).

Based on the fluence of microtektites (number per cm2

of the column) recovered from marine cores from oce-anic regions near southeast Asia, the East Indies and Aus-tralia, Schmidt et al. (1993) concluded that microtektitefluences tend to decrease with increasing distance fromsoutheast Asia. Based on the microtektite concentrations

Fig. 11. Histogram of εSr(0) for East Asia tektites (this studyand Ho and Chen, 1996) showing ranges for Sr isotopic com-positions observed within the Australasian strewn field. Dataon old continental crust, mid-ocean ridge basalts (MORB),continental flood basalts (CFB), oceanic crust, indochinite andaustralites from Shaw and Wasserburg (1982) and Blum et al.(1992).

Fig. 12. Plot of TSrUR vs. 1/fRb/Sr for Australasian tektites (this

study and literature values by Blum et al., 1992, Ho and Chen,1996). The Y-intercept gives the time of last Rb-Sr fractionationand corresponds to the time of sedimentation of a sedimentaryparent material (Blum et al., 1992).

Fig. 13. Correlation plots of compositional data from the mix-ing model vs. compositional data for East Asia splash formtektites. Mixture used for this model is 61% greywacke, 32%sandstone and 7% shale (see Table 6 for compositional data).

12 Y.-T. Lee et al.

in core 17957-2 and ODP Hole 1144A as well as datafrom Glass and Pizzuto (1994) and Lee and Wei (2000),Glass (2003) predicted a source crater location for Aus-tralasian strewn field near 15°N and 105°E which is 3°farther north and 1° farther west than that predicted byGlass and Pizzuto (1994) and Lee and Wei (2000) butcloser to the location predicted by Schnetzler (1992). Inaddition, Ford (1988) noted that the size of Muong Nong-type tektites in Thailand decreased toward the west, andthat Muong Nong-type tektites from Hainan Island, Chinaare small. Schnetzler and McHone (1996) noted that a

small area in Laos has the greatest concentration of MuongNong-type layered tektites. All Australasian tektites maybe derived from a single sedimentary formation with anarrow range of stratigraphic ages close to ~170 Ma (Fig.12). The field work of Sato (1992) shows that the limitedarea near the southern part of the Thailand-Loas borderproposed by Schnetzler (1992) as the potential impact sitehas non-marine Jurassic exposures (Fig. 1) which is con-sistent with the hypothesis suggested by Blum et al.(1992) based on Sr isotopic data. The geochemical datadiscussed above support the hypothesis that the source

Table 5. The results of 40Ar/39Ar laser fusion experiments on representative tektite samplesfrom East Asia

J-value = 0.0035297 ± 0.0000341.Mean age = 746.7 ± 59.6 ka, STDEV = 37.8 ka.

No. Atmos. (%) 36Ar/39Ar 37Ar/39Ar 38Ar/39Ar 40Ar/39Ar 40Ar/36Ar Date (ka)

W-1 (Wenchang, China)

405 95.76 0.0095906 0.51343 0.016013 2.9477 307.36 787.8 ± 68.3406 92.47 0.0050470 0.51424 0.015057 1.5996 316.94 753.2 ± 74.8407 92.07 0.0046780 0.53416 0.015054 1.4864 317.74 736.2 ± 54.7408 91.22 0.0043500 0.54335 0.014809 1.3929 320.20 762.4 ± 79.0409 89.39 0.0034291 0.51489 0.014694 1.1189 326.29 736.8 _ 28.9501 87.74 0.0027632 0.51062 0.014879 0.91544 331.30 692.3 ± 36.0502 89.30 0.0033005 0.51057 0.015277 1.0777 326.54 714.7 ± 53.7503 97.29 0.0151460 0.52845 0.017340 4.5877 302.91 785.6 ± 57.8504 91.41 0.0040769 0.51150 0.014884 1.3045 319.97 698.0 ± 45.6505 89.57 0.0038014 0.53020 0.014863 1.2382 325.72 803.4 ± 57.5506 82.33 0.0021395 0.52165 0.014837 0.74884 350.00 810.3 ± 96.3507 75.18 0.0013408 0.50939 0.014134 0.50464 376.36 752.2 ± 25.0508 78.42 0.0015370 0.50200 0.014692 0.55961 364.09 729.6 ± 34.4509 85.19 0.0022572 0.48441 0.016824 0.76884 340.61 698.3 ± 57.2510 92.02 0.0046661 0.51168 0.014970 1.4852 318.30 740.3 ± 75.3

J-value = 0.0035297 ± 0.0000341.Mean age = 736.8 ± 55.5 ka, STDEV = 23.0 ka.

No. Atmos. (%) 36Ar/39Ar 37Ar/39Ar 38Ar/39Ar 40Ar/39Ar 40Ar/36Ar Date (ka)

W-2 (Wenchang, China)

1401 32.08 0.00032272 0.52072 0.013202 0.20364 631.00 756.7 ± 88.01402 13.55 0.00020247 0.54105 0.013434 0.16932 836.26 774.2 ± 30.51403 9.53 0.00017516 0.52379 0.013595 0.15761 899.79 742.8 ± 54.11404 23.82 0.00025239 0.53200 0.013557 0.17352 687.48 702.7 ± 73.31405 16.03 0.00021426 0.53140 0.013696 0.17390 811.63 776.6 ± 55.71406 29.58 0.00029306 0.53547 0.013473 0.18506 631.49 701.4 ± 49.61407 9.77 0.00017621 0.52387 0.013665 0.15755 894.13 740.5 ± 36.11408 25.16 0.00026730 0.52272 0.013858 0.18606 696.06 750.0 ± 77.91409 11.78 0.00018499 0.52702 0.013482 0.15565 841.38 713.3 ± 44.61410 23.85 0.00025434 0.52239 0.013549 0.17877 702.89 727.9 ± 64.31411 24.64 0.00026454 0.53463 0.013541 0.18247 689.75 738.1 ± 44.51412 8.46 0.00016745 0.51747 0.013516 0.15267 911.72 722.8 ± 31.01413 21.97 0.00024212 0.51873 0.013300 0.17641 728.60 734.1 ± 42.41414 11.75 0.00018615 0.52641 0.013657 0.15929 855.69 734.1 ± 48.2

Geochemical studies of tektites 13

Table 5. (continued)

J-value = 0.0035297 ± 0.0000341.Mean age = 755.3 ± 69.7 ka, STDEV = 42.8 ka.

No. Atmos. (%) 36Ar/39Ar 37Ar/39Ar 38Ar/39Ar 40Ar/39Ar 40Ar/36Ar Date (ka)

KK-1 (Khon-Kaen, Thailand)

511 98.68 0.027340 0.41756 0.018185 8.1837 299.34 685.5 ± 77.5512 98.78 0.032774 0.41111 0.019234 9.8017 299.07 759.1 ± 63.5513 92.57 0.0051497 0.41798 0.014366 1.6386 318.19 761.9 ± 75.8514 91.08 0.0042000 0.42543 0.013739 1.3561 322.88 753.8 ± 69.7515 98.25 0.022384 0.42618 0.017002 6.7282 300.59 747.0 ± 92.4601 90.81 0.0043560 0.41713 0.013682 1.4116 324.06 809.7 ± 74.0602 88.05 0.0032771 0.42628 0.013444 1.0920 333.22 809.1 ± 58.8603 91.33 0.0041593 0.41890 0.013517 1.3399 322.15 724.3 ± 54.5604 92.01 0.0048600 0.41862 0.013739 1.5553 320.02 777.0 ± 70.6605 94.93 0.0083177 0.41349 0.014548 2.5850 310.78 824.9 ± 63.6606 93.97 0.0059652 0.42007 0.013947 1.8709 313.63 707.7 ± 79.2607 96.61 0.011543 0.41690 0.014881 3.5267 305.53 754.7 ± 46.8608 99.03 0.038451 0.42149 0.019824 11.470 298.30 704.4 ± 67.8

J-value = 0.0035297 ± 0.0000341.Mean age = 741.6 ± 52.9 ka, STDEV = 36.5 ka.

No. Atmos. (%) 36Ar/39Ar 37Ar/39Ar 38Ar/39Ar 40Ar/39Ar 40Ar/36Ar Date (ka)

M-01 (Maoming, China)

301 90.81 0.0043038 0.38773 0.015238 1.3969 324.58 800.4 ± 48.0302 92.28 0.0049768 0.37834 0.015454 1.5915 319.78 768.2 ± 21.8303 94.74 0.0067283 0.37793 0.016117 2.0972 311.70 692.9 ± 44.4304 93.41 0.0056891 0.37774 0.015760 1.7980 316.05 742.9 ± 60.5305 87.64 0.0029052 0.37928 0.015002 0.97562 335.82 745.2 ± 47.0306 88.13 0.0031497 0.38458 0.015370 1.0519 333.97 773.5 ± 73.6307 84.43 0.0022619 0.37784 0.015062 0.78660 347.77 751.4 ± 24.4308 91.06 0.0044110 0.37966 0.015302 1.4287 323.89 797.0 ± 49.1309 93.00 0.0053403 0.38245 0.015397 1.6945 317.31 742.4 ± 66.2310 89.92 0.0035305 0.38065 0.015159 1.1569 327.70 723.9 ± 36.7401 88.96 0.0031163 0.38292 0.015361 1.0314 330.96 704.7 ± 63.2402 96.01 0.0090660 0.37594 0.016509 2.7895 307.69 701.3 ± 50.2403 81.02 0.0016783 0.38197 0.015111 0.60532 360.66 697.1 ± 71.6

crater for Australasian strewn field appears to be locatedin a limited area near the southern part of the Thailand-Laos border.

MIXING CALCULATIONS FOR APPROPRIATE TARGET

MATERIAL OF TEKTITES FROM EAST ASIA

On the basis of previous studies (Koeberl, 1992; Blumet al., 1992; Schnetzler, 1992) and the chemical data oftektites analyzed in the present study, the authors suggestthat these tektites may represent the result of melting at asingle site. The tektites of the present study are most likelyto be derived as splashed melt from Jurassic sedimentaryrocks forming the surface layer near the southern part ofthe Thailand-Laos border where Jurassic non-marine

sandstone, siltstone, shale, mudstone and conglomerateswith minor intercalation of limestone are exposed (Ridd,1978; Sato, 1992). Regrettably, appropriate chemical dataof target materials at the potential impact site at the Thai-land-Laos border are not available at present. In order toestablish a geochemical relationship between all the thirtytektites in this study and their parent materials, the presentauthors selected a variety of target rocks in the literatures(see Table 6) including average post-Archean Australianshale, average Phanerozoic sandstone and average Meso-Cenozoic greywacke, and perform mixing calculationsbased on the model proposed by Ho and Chen (1996) forvarious amounts as well as combinations of these rocks.The results of the mixing model for all the major and traceelements are listed in Table 6.

14 Y.-T. Lee et al.

The mixing model does not provide a perfect fit (Fig.13), some major elements (e.g., Na2O and MgO) and traceelements (e.g., Hf, Ta, Th, and U) contents do not agreeexactly. Besides, the REE contents in the mixing modelare generally lower than those of the tektites analyzed(Table 6). However the model is useful in determiningthe most possible fit for the parent material of the tektitesfrom East Asia. The best fit for the average compositionof thirty tektites analyzed by the present study is a mix-ture of 61% greywacke, 32% sandstone and 7% shale.

CONCLUSIONS

Based on REE patterns the present authors excludedthe lower crust and oceanic crust as the source rocks. Thetrace elememt ratios Ba/Rb (avg. 3.74), Th/Sm (avg. 2.31),

Sm/Sc (avg. 0.43), Th/Sc (avg. 0.99) and REE contentsof tektites studied are similar to the average upper conti-nental crust. The La/Th ratio (avg. 2.84) and REE pat-terns of East Asia tektites are similar to those of post-Archean sediments. Based on the results of the chemicaland isotopic data of this study, the lunar volcanic origin(Futrell, 2000) and multiple craters origin (Wasson, 1987,1991) may be excluded. The Ar-Ar ages of tektites of thisstudy are consistent with the published ages of theAustralasian tektites which indicate that the Australasiantektites were derived from a single impact event. On thebasis of Rb-Sr isotopic data, the tektites in this study werederived from a single sedimentary formation with astratigraphic age close to 170 Ma (Jurassic). The poten-tial impact site may be located in a limited area near thesouthern part of the Thailand-Laos border as suggested

Table 5. (continued)

No. Atmos. (%) 36Ar/39Ar 37Ar/39Ar 38Ar/39Ar 40Ar/39Ar 40Ar/36Ar Date (ka)

M-03 (Maoming, China)

2801 68.05 0.0010301 0.39690 0.014947 0.43204 419.41 865.4 ± 90.82802 15.00 0.00017409 0.39591 0.014404 0.17280 992.56 822.7 ± 69.42803 11.56 0.00015221 0.39670 0.014574 0.15916 1045.7 774.9 ± 52.62804 21.37 0.00021317 0.39879 0.014640 0.18284 857.70 814.0 ± 127.12805 7.36 0.00013248 0.39377 0.014561 0.15750 1188.8 801.5 ± 87.82901 23.53 0.00022858 0.38300 0.014462 0.19307 844.68 844.2 ± 110.52902 5.83 0.00012370 0.38677 0.014323 0.15576 1259.1 803.6 ± 158.02903 2.99 0.00011248 0.38949 0.014838 0.15889 1412.6 848.3 ± 64.02903 14.33 0.00016712 0.39157 0.014752 0.16746 1002.0 798.5 ± 64.02904 14.82 0.00017135 0.39002 0.014369 0.17205 1004.1 820.1 ± 68.22905 14.76 0.00016924 0.39179 0.014800 0.16748 989.64 794.5 ± 72.12906 4.13 0.00011354 0.37554 0.014749 0.15596 1373.6 819.5 ± 38.02907 14.33 0.00016712 0.39157 0.014752 0.16746 1002.0 798.5 ± 64.02907 6.50 0.00012690 0.38793 0.014622 0.15598 1229.1 799.4 ± 56.2

NoteJ-value: Weighted mean of the results for twenty three fusions of irradiation standard LP-6 Biotite, having a K-Ar age of 127.7 ± 1.4 Ma (Odinet al., 1982).The date is obtained by using the following equation:

Date JAr

Arand

Ar

Ar

Ar Ar Ar Ar Ar Ar Ar Ar

Ar Ar Ar Ar

Ar

Ar

K

K

m m Ca m

Ca m K

= +

=( ) − ( ) + ( ) ( )

− ( ) ( )−

∗

∗

11

295 5 295 5

1

40

39

40

39

40 39 36 39 36 37 37 39

39 37 37 39

40

39

λln ,

/ . / . / /

/ /

where ( )Ca and ( )K = isotope ratios of argon extracted from irradiated calcium and potassium salts;( )m = isotope ratio of argon extracted from irradiated unknown.Date (Ma) = the date calculated using the following decay constants: λε = 0.581 × 10–10 yr–1; λβ = 4.962 × 10–10 yr–1; λ = 5.543 × 10–10 yr–1;40K/K = 0.01167 atom % (Steiger and Jager, 1977).The quoted error is one standard deviation and does not include errors in the interference corrections.

J-value = 0.00372265 ± 0.00002407.Mean age = 814.6 ka, STDEV = 24.4 ka.

Geochemical studies of tektites 15

Table 6. Average data for East Asia tektites (wt% andppm, for major and trace elements respectively) com-pared with mixing model (M) proposed by Ho and Chen(1996). The mixing model is constructed based on allthe major and trace elements analyzed

A, average of 30 East Asia tektites (this study); PAAS, average post-Archean Australian Shales (Condie, 1993); APSS, average Phanero-zoic sandstones (Condie, 1993); AMCG, average Meso-Cenozicgreywackes (Condie, 1993); M, 7% PAAS + 32% APSS + 61% AMCG.

A PAAS APSS AMCG M

[wt%]SiO2 74.36 62.80 91.50 66.30 74.12Al2O3 11.13 18.90 3.62 15.50 11.94MgO 2.59 2.20 0.45 2.00 1.52FeO 4.99 6.50 1.13 6.20 4.60CaO 2.14 1.30 0.31 3.20 2.14Na2O 1.43 1.20 0.42 3.10 2.11K2O 2.39 3.70 0.91 2.30 1.95TiO2 0.78 1.00 0.25 0.72 0.59P2O5 0.04 0.16 0.02 0.14 0.10Total 99.97 97.76 99.61 99.46 99.39[ppm]Sc 17.5 16.0 2.0 14.0 10.3V 181 150 15 130 95Cr 79.7 110.0 30.0 70.0 60.0Co 17.4 23.0 2.5 15 11.6Ni 14.3 55.0 8.0 30.0 24.7Rb 115 160 25 100 80Sr 150 200 35 280 196Y 47.4 27.0 6.8 28.0 21.1Zr 418 210 105 145 137Nb 21.6 19.0 4.0 10.0 8.7Ba 430 650 150 650 490La 48.9 38.0 10.3 28.0 23.0Ce 96.5 80.0 22.3 61.0 49.9Nd 39.2 32.0 8.4 26.0 20.8Sm 7.5 5.6 1.6 4.9 3.9Eu 0.98 1.10 0.34 0.90 0.73Gd 5.72 4.70 1.44 4.34 3.44Tb 0.88 0.77 0.21 0.66 0.52Yb 3.03 2.80 0.61 2.20 1.73Lu 0.50 0.43 0.11 0.38 0.30Hf 8.31 5.00 3.10 3.90 3.72Ta 1.3 1.2 0.3 0.9 0.7Th 17.2 14.6 4.0 8.5 7.5U 2.65 3.10 1.10 1.80 1.67

by Schnetzler (1992). Mixing calculations for variousamounts and combinations of target rocks indicate thatthe best fit for the average composition of thirty tektitesin this study is a mixture of 61% greywacke, 32% sand-stone and 7% shale.

Acknowledgments—We thank Dr. C. H. Lo of NationalTaiwan University for technical assistance in Ar-Ar dating. Weare grateful to Mr. R. J. Lin and Ms. Y. Y. Su who assisted withthe chemical analyses of some tektite samples. We thank Dr. C.

Koeberl of University of Vienna and Dr. B. P. Glass of Univer-sity of Delaware for their penetrating reviews that lead to sig-nificant improvement of the manuscript. The present study wassupported by the National Science Council of the Republic ofChina.

REFERENCES

Barnes, V. E. (1961) Tektites. Sci. American 205 (5), 58–65.Bentley, C. R. (1979) No giant meteorite crater in Wilkes Land,

Antarctic. J. Geophys. Res. 84, 5681–5682.Blum, J. D., Papanastassiou, D. A., Koeberl, C. and Wasserburg,

G. J. (1992) Nd and Sr isotopic study of Australasiantektites: New constraints on the provenance and age of tar-get material. Geochim. Cosmochim. Acta 56, 483–492.

Burns, C. A. and Glass, B. P. (1989) Source region for theAustralasian tektite strewn field. Meteoritics 24, 257.

Chapman, D. A. and Scheiber, L. C. (1969) Chemical investi-gation of Australasian tektites. J. Geophys. Res. 74, 6737–6794.

Compston, W. and Chapman, D. R. (1969) Sr isotope patternwithin the Southeast Australasian strewn field. Geochim.Cosmochim. Acta 33, 1023–1036.

Condie, K. C. (1993) Chemical composition and evolution ofthe upper continental crust: Contrasting results from sur-face samples and shales. Chem. Geol. 104, 1–37.

Englert, P., Pal, D. K., Tuniz, C., Moniot, R. K., Savin, W.,Kruse, T. and Herzog, G. F. (1984) Manganese-53 and be-ryllium-10 contents of tektites (abs.). Lunar Planet. Sci. 15,250–251.

Evensen, M. N., Hamilton, P. J. and O’Nions, R. K. (1978) Rare-earth abundances in chondritic meteorites. Geochim.Cosmochim. Acta 42, 1199–1212.

Ford, R. J. (1988) An empirical model for the Australasiantektite strewn field. Australasian J. Earth Sci. 35, 483–490.

Fuhrmann, U., Lippolt, H. J. and Hess, J. C. (1987) Examina-tion of some proposed K-Ar standards: 40Ar/39Ar analysesand conventional K-Ar dating. Chem. Geol., Isot. Geosci.Sect. 66, 41–51.

Futrell, D. S. (2000) Tektite controversy. Meteorite 6, 36–37.Gentner, W., Kleinmann, B. and Wagner, G. A. (1967) New K-

Ar and fission track ages for impact glasses and tektites.Earth Planet. Sci. Lett. 2. 83–86.

Glass, B. P. (1979) Zhamanshin crater, a possible source ofAustralasian tektites. Geology 7, 351–353.

Glass, B. P. (1990) Tektites and microtektites: Key facts andinferences. Tectonophysics 171, 393–404.

Glass, B. P. (1993) Geographic variations in abundance of Aus-tralasian microtektites: Implications concerning the loca-tion and size of the source crater (abs.). Meteoritics 28, 354.

Glass, B. P. (2000) Tektite controversy (reply to Darryl S.Futrell’s comments). Meteorite 6, 38–40.

Glass, B. P. (2003) Australasian microtektites in the South ChinaSea: Implications regarding the location and size of thesource crater. Lunar and Planetary Science Conference 34.

Glass, B. P. and Pizzuto, J. E. (1994) Geographical variation inAustralasian microtektite concentrations: Implications con-cerning the location and size of the source crater. J. Geophys.Res. 99, 19075–19081.

16 Y.-T. Lee et al.

Govindaraju, K. (1994) Compilation of working values andsample descriptions for 383 geostandards. Geostand.Newlett. 18, 1–158.

Hartung, J. B. and Rivolo, A. R. (1979) A possible source inCambodia for Australasian tektites. Meteoritics 14, 153–159.

Ho, K. S. and Chen, J. C. (1996) Geochemistry and origin oftektites from the Penglei area, Hainan province, southernChina. J. SE. Asian Earth Sci. 13, 61–72.

Hofmann, A. W. (1988) Chemical differentiation of the Earth:The relationship between mantle, continental crust, and oce-anic crust. Earth Planet. Sci. Lett. 90, 297–314.

Izett, G. A. and Obradovich, J. D. (1992) Laser-fusion 40Ar/39Ar ages of Australasian tektites (abstract). Lunar Planet.Sci. 23, 593–594.

Koeberl, C. (1986) Geochemistry of tektites and impact glasses:An overview. Ann. Rev. Earth Planet. Sci. 14, 325–350.

Koeberl, C. (1990) The geochemistry of tektites: An overview.Tectonophysics 171, 405–422.

Koeberl, C. (1992) Geochemistry and origin of Muong Nong-type tektites. Geochim. Cosmochim. Acta 56, 1033–1064.

Koeberl, C. (1994) Tektite origin by hypervelocity asteroidalor cometary impact: Target rocks, source craters, and mecha-nisms. Basins of the Rio Grande Rift: Structure,Stratigraphy, and Tectonic Setting (Keller, G. R. and Cather,S. M., eds.), Geol. Soc. Am. Special Paper 293, 133–151.

Koeberl, C. and Fredriksson, K. (1986) Impact glasses fromthe Zhamanshin crater, USSR: Chemical composition anddiscussion of origin. Earth Planet. Sci. Lett. 78, 80–88.

Koeberl, C., Poag, C. W., Reimold, W. U. and Brandt, D. (1996)Impact origin of the Chesapeake Bay structure and thesource of the North American tektites. Science 271, 1263–1266.

Koeberl, C., Bottomley, R., Glass, B. P. and Storzer, D. (1997)Geochemistry and age of Ivory Coast tekti tes andmicrotektites. Geochim. Cosmochim. Acta 61, 1745–1772.

Lacroix, A. (1935) Les tectites sans formes figurees deI’Indochine. Compt. Rend. Acad. Sci. Paris 200, 2129–2132.

Lee, M. Y. and Wei, K. Y. (2000) Australasian microtektites inthe South China Sea and the western Philippine Sea: Impli-cations for age, size and location of the impact crater.Meteoritics Planet. Sci. 35, 1151–1155.

Lo, C. H. and Lee, C. Y. (1994) 40Ar-39Ar method of K-Ar agedetermination of geological samples using Tsing-Hua OpenPool Reactor (THOR). J. Geol. Soc. China 37(1), 1–22.

Matsubara, K., Matsuda, J. I. and Koeberl, C. (1991) Noblegases and K-Ar ages in Aouelloul, Zhamanshin, and LibyanDesert impact glasses. Geochim. Cosmochim. Acta 55,2951–2955.

McLennan, S. M. and Taylor, S. R. (1980) Th and U in sedi-mentary rocks: Crustal evolution and sedimentary recycling.Nature 285, 621–624.

Odin, G. S. (1982) Interlaboratory standards for dating potas-sium-argon age determinations. Numerical Dating inStratigraphy (Odin, G. S., ed.), 123–149, Wiley, Chiches-ter.

O’Keefe, J. A. (1976) Tektites and Their Origin. Elsevier,Amsterdam, 254 pp.

O’Keefe, J. A. (1994) The origin of tektites. Meteoritics 29,

73–78.Pal, D. K., Tuniz, C., Moniot, R. K., Kruse, T. H. and Herzog,

G. F. (1982) Beryllium-10 in Australasian tektite: Evidencefor a sedimentary precursor. Science 218, 787–789.

Poag, C. W., Powars, D. S., Poppe, L. J. and Mixon, R. B. (1994)Meteoroid mayhem in Ole Virginny: Source of the NorthAmerican tektite strewn field. Geology 22, 691–694.

Ridd, M. F. (1978) The Mesozoic: Thailand. The PhanerozoicGeology of the World II (Moullade, M. and Nairn, A. E. M.,eds.), 145–161, Elsevier.

Rudnick, R. L. (1992) Xenoliths-sample of the lower continen-tal crust. Continental Lower Crust (Fountain, D. M.,Arculus, R. and Kay, R. W., eds.), 269–316, Elsevier.

Sato, T. (1992) Regional geology and stratigraphy: SoutheastAsia and Japan. The Jurassic of the Circum-Pacific(Westermann, G. E. G., ed.), 194–213, Cambridge Univer-sity Press.

Schmidt, G., Zhou, L. and Wasson, J. T. (1993) Iridium anomalyassociated with the Australasian tektite-producing impact:Masses of the impactor and of the Australasian tektites.Geochim. Cosmochim. Acta 57, 4851–4859.

Schnetzler, C. C. (1992) Mechanism of Muong Nong-typetektite formation and speculation on the source of Australa-sian tektites. Meteoritics 27, 154–165.

Schnetzler, C. C. and McHone, J. F. (1996) Source of Australa-sian tektites: Investigating possible sites in Laos. MeteoriticsPlanet. Sci. 31, 73–76.

Schwarz, W. H. and Lippolt, H. J. (2002) Coeval argon-40/ar-gon-39 ages of moldavites from the Bohemian and Lusatianstrewn fields. Meteoritics Planet. Sci. 37, 1757–1763.

Shaw, H. F. and Wasserburg, G. J. (1982) Age and provenanceof the target materials for tektites and possible impactitesas inferred from Sm-Nd and Rb-Sr systematic. Earth Planet.Sci. Lett. 60, 155–177.

Stauffer, P. H. (1978) Anatomy of the Australasian tektitestrewn-field and the probable site of its source crater. Pro-ceedings of the 3rd Regional Conference on Geology andMineral Resources of Southeast Asia (Nutalaya, P., ed.),285–289.

Steiger, R. H. and Jager, E. (1977) Subcommission ongeochronology: Convention on the use of decay constant ingeo- and cosmochronology. Earth Planet. Sci. Lett. 36, 359–362.

Storzer, D. and Wagner, G. A. (1971) Fission track ages of NorthAmerican tektites. Earth Planet. Sci. Lett. 10, 435–444.

Taylor, S. R. (1969) Criteria for the source of australites. Chem.Geol. 4, 451–459.

Taylor, S. R. (1973) Tektites: A post-Apollo view. Earth Sci.Rev. 9, 101–123.

Taylor, S. R. and McLennan, S. M. (1979) Chemical relation-ships among irghizites, Zhamanshinites, Australasiantektites and Henbury impact glasses. Geochim. Cosmochim.Acta 43, 1551–1565.

Taylor, S. R. and McLennan, S. M. (1985) The ContinentalCrust: Its Composition and Evolution. Blackwell, London,312 pp.

Taylor, S. R., McLennan, S. M. and McCulloch, M. T. (1983)Geochemistry of loess, continental crust composition andcrustal model ages. Geochim. Cosmochim. Acta 47, 1897–

Geochemical studies of tektites 17

1905.Tera, F., Brown, L., Klein, J., Middleton, R. and Mason, B.

(1983) Beryllium-10 and aluminium-26 in tektites.Meteoritics 18, 405–406.

Wampler, J. M., Smith, D. M. and Cameron, A. E. (1969) Iso-topic comparison of lead in tektites with lead in earth mate-

rials. Geochim. Cosmochim. Acta 33, 1045–1055.Wasson, J. T. (1987) A multiple-impact origin of southeast Asian

tektites (abs.). Lunar Planet. Sci. 18, 1062–1063.Wasson, J. T. (1991) Layered tektites: A multiple impact origin

for the Australasian tektites. Earth Planet. Sci. Lett. 102,95–109.