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Ulasitai: A new likely paired with Armanty (IIIE)

Item Type Article; text

Authors Xu, Lin; Miao, Bingkui; Lin, Yangting; Ouyang, Ziyuan

Citation Xu, L., Miao, B., Lin, Y., & Ouyang, Z. (2008). Ulasitai: A new likely paired with Armanty (IIIE). & Planetary Science, 43(8), 1263-1273.

DOI 10.1111/j.1945-5100.2008.tb00696.x

Publisher The

Journal Meteoritics & Planetary Science

Rights Copyright © The Meteoritical Society

Download date 06/10/2021 17:36:18

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Version Final published version

Link to Item http://hdl.handle.net/10150/656459 Meteoritics & Planetary Science 43, Nr 8, 1263–1273 (2008) Abstract available online at http://meteoritics.org

Ulasitai: A new iron meteorite likely paired with Armanty (IIIE)

Lin XU1, 3, 4, Bingkui MIAO2, 5, Yangting LIN2*, and Ziyuan OUYANG1

1Institute of Geochemistry, Chinese Academy of Sciences, Guiyang 550002, China 2Key Laboratory of the Earth’s Deep Interior, Institute of Geology and Geophysics, Chinese Academy of Sciences, Beijing 100029, China 3Graduate School of Chinese Academy of Sciences, Beijing 100118, China 4National Astronomical Observatories, Chinese Academy of Sciences, Beijing 100012, China 5Department of Resources & Environmental Engineering, Guilin University of Technology, Guilin 541004, China *Corresponding author. E-mail: [email protected] (Received 07 October 2007; revision accepted 04 January 2008)

Abstract–The Ulasitai iron was recently found about 130 km southeast to the find site of the Armanty (Xinjiang, IIIE) meteorite. It is a coarse with a bandwidth of 1.2 ± 0.2 (0.9–1.8) mm. is abundant, as is , kamacite, , and with various micro- structures. Schreibersite is Ni-rich (30.5–55.5 wt%) in plessite or coexisting with and daubreelite, in comparison with the coarse laths (20.6–21.2 wt%) between the Widmanstätten pattern plates. The correlation between the center Ni content and the half bandwidth of taenite suggest a cooling rate of ∼20 °C/Myr based on simulations. The petrography and chemistry of Ulasitai are similar to Armanty. The bulk samples of Ulasitai were measured, together with Armanty, Nandan (IIICD), and (IIICD), by inductively coupled plasma atomic emission spectrometry (ICP-AES) and mass spectrometry (ICP-MS). The results agree with literature data of the same , and our analyses of four samples of Armanty (L1, L12, L16, L17) confirm a homogeneous composition (Wasson et al. 1988). The bulk composition of Ulasitai is identical to that of Armanty, both plotting within the IIIE field. We classify Ulasitai as a new IIIE iron and suggest that it pairs with Armanty.

INTRODUCTION In this paper, we report petrography, mineral chemistry, and bulk composition of the Ulasitai meteorite. Ulasitai is a new iron meteorite, found in Mt. Beita, The bulk composition was analyzed with inductively Mulei County, Xinjiang Province, China (Connolly et al. coupled plasma atomic emission spectrometry (ICP-AES) 2006). The find site is about 130 km from that of Armanty and inductively coupled plasma mass spectrometry (ICP- (Xinjiang, IIIE), the third largest iron meteorite reported in MS). To assess the analytical accuracy and precision, we the world. Armanty was first classified as IIIAB group by also measured the Armanty (IIIE), Nandan (IIICD), and Kracher et al. (1980), but later reassigned to the small group Mundrabilla (IIICD) and compared the results with IIIE by Malvin et al. (1984) based on its lower Cu, Au and literature data acquired by neutron activation analysis Co, higher W, and wider kamacite bands (1.2–1.3 mm) (NAA). We classify the new iron meteorite based on relative to the IIIAB irons with same Ni content. Chen and petrography and bulk composition, and discuss its genetic Sun (1986) analyzed a suite of 26 samples sawed from relationship with Armanty. The heterogeneity issue of different locations on the surface of Armanty with Armanty is also discussed based on the new analyses. instrumental neutron activation analysis (INAA). They reported a variation of a factor up to 2 for Ge and Ir, and THE FINDING AND APPEARANCE attributed this mainly to experimental uncertainties. Cr shows a larger variation that they explained as heterogeneous The Ulasitai meteorite was discovered by Mr. Xiaodong distribution of sulfide inclusions. Wasson et al. (1988) re- Li, a geologist, on a hillside on 28 April 2004 when he was measured 15 out of the sample set and found either no surveying this area. The iron meteorite was buried at a depth of compositional variations attributable to magmatic about 10 cm in a Quaternary slope deposit. The underground crystallization. surface was severely weathered, forming a layer of rust (about

1263 © The Meteoritical Society, 2008. Printed in USA. 1264 L. Xu et al.

1450VP-type scanning electron microscope (SEM) equipped with energy dispersive spectrometry (EDS), and mineral chemistry was measured using a JEOL 8100-type electron probe microanalyzer (EPMA), both at Institute of Geology and Geophysics, Chinese Academy of Sciences. Pure metals, sulfides, and synthetic Fe3P were used as standards. Data were processed using the conventional ZAF method. Peak overlapping of Kα line of Co by Kβ of Fe was corrected. The Ulasitai meteorite consists mainly of kamacite (76 vol%), taenite (10 vol%), and plessite (10.6 vol%) with less abundant schreibersite (3.4 vol%) and minor troilite, cohenite, and daubreelite. The Widmanstätten pattern (Fig. 3) has bandwidths of kamacite in a range of 0.9–1.8 mm and an average of 1.2 ± 0.2 mm. Schreibersite mainly occurs as coarse laths with sizes up to 1.2 mm wide and 8.9 mm long observed on the etched polished sections (Fig. 3). Small grains of schreibersite (normally <20 µm thin) were also found along grain boundaries of kamacite, taenite, and sulfides, and inside of plessite. Plessite is zoned, from a taenite rim towards a kamacite- rich center (Fig. 4a). The structure of plessite usually changes from rims to cores and/or from grains to grains. Various forms of taenite in a kamacite matrix were observed, including comb, spheroid (Fig. 4b), and net (Fig. 4c). Taenite in plessite sometimes show microstructure of decomposition (Fig. 4d). Fig. 1. A map showing the find sites of Ulasitai and Armanty. Most of the cohenite and part of the schreibersite occur in the centers of plessite (Fig. 4e). Troilite occurs as rounded to 1 cm thick), and the upper part is brown in color with little subhedral inclusions (<400 µm) in kamacite, and usually has rust. It weighs about 430 kg, with 1.6 kg of the sample mass lamellae (<20 µm in width) of daubreelite (Fig. 4f ). on deposit at the Institute of Geology and Geophysics, Representative compositions of metallic Fe-Ni are listed Chinese Academy of Sciences, and the rest remained with the in Table 1. Kamacite contains 4.03–7.24 wt% (average of 6.08 ± finder. The find site of Ulasitai (44°57′24′′N, 91°24′09′′E) is 0.92 wt%) Ni and 0.46–0.75 wt% (average of 0.57 ± shown in Fig. 1, about 130 km southeast to that of Armanty, 0.07 wt%) Co. The lowest Ni contents of kamacite were the third largest iron meteorite found in the world. usually found in the grains inside of plessite, while the higher Besides the proximity of both sites, the appearance of values in the cores of kamacite bands. Taenite bands show the Ulasitai is similar to that of Armanty. The Ulasitai meteorite typical M-shaped compositional zoning (Fig. 5), with the Ni has an irregular shape and many concave surface features content increasing normally from 16–26 wt% at the cores to 43– (Fig. 2a). There are numerous band-like voids, especially on 47 wt% at the rims. A segment of a plessite lath showing no one side (Figs. 2a and 2b), which were probably formed by evidence of decomposition in BSE images, has the same weathering loss of schreibersite with a few grains remaining. M-shaped zoning with a low center Ni content (14.0 wt%). In the close-up photo (Fig. 2b), the Widmanstätten pattern can The Co content varies inversely with Ni decreasing from also be noted. Figure 2c shows the Armanty meteorite that 0.33 wt% to 0.17 wt% towards the rim. The small grains and was removed to Urumchi, Xinjiang province, in 1965. It is fine lamellae of taenite inside of plessite have a large range of now on exhibit in the front of the Geology and Mineral Ni content between 10.4–51.7 wt%. Resource Museum of Xinjiang. The Widmanstätten pattern Table 2 shows representative compositions of accessory and laths of schreibersite of Armanty (Fig. 2d) appear similar phases. Cohenite contains less Ni (4.83–5.02, average of 4.93 to those of the new iron meteorite, except that the latter is ± 0.07 wt%) and Co (0.13–0.20, average of 0.18 ± 0.03 wt%) more severely weathered as indicated by its rough surface. than kamacite, with a low analytical total of 93.6–94.4 wt% due to presence of C. The compensated C content is slightly PETROGRAPHY AND MINERAL CHEMISTRY lower than the stoichiometric composition of cohenite (Fe, Ni)3C, but significantly higher than that of (Fe, × Two polished sections of Ulasitai (with surfaces of 4.5 cm Ni)23C6, hence we refer the carbide as cohenite. Schreibersite 5.6 cm, 0.9 cm × 1.2 cm, respectively) were prepared and shows a correlation between occurrence and Ni content. The studied in this study. The sections were observed with a LEO large laths have a low Ni content (20.6–21.2 wt%), while the Ulasitai: A new iron meteorite likely paired with Armanty (IIIE) 1265

Fig. 2. Photos of the Ulasitai and Armanty iron meteorites. a) A top view of Ulasitai showing the concave surface features and lath-like voids on the right side. For reference, the length of the knife is 10 cm. b) A close-up view of Ulasitai. Note the Widmanstätten pattern and lath-like voids that are orientated. Scale bar is 2.4 cm. c) Photo of Armanty on exhibit in front of the main building of the Geology and Mineral Resource Museum of Xinjiang. The gap on the top was artificially cut. d) A close-up photo of Armanty, showing the Widmanstätten pattern and laths of schreibersite. Scale bar is 2.4 cm.

Fig. 3. The etched polished section of Ulasitai showing the Widmanstätten pattern. Plessite (Ps) occurs as light grey trapeziform triangle or rectangle forms usually with bright rims between kamacite (Ka) plates. The bright and rough laths mainly along the diagonal from lower right to upper left are schreibersite (Sch). The thin and dark grey laths between the kamacite plates are taenite (Tae). Scale bar is 1 cm. 1266 L. Xu et al.

Fig. 4. Backscattered electron (BSE) images of Ulasitai. a) A plessite showing the micro-Widmanstätten pattern consisting of taenite (Tae, bright) and kamacite (Ka, dark grey). Note the clean taenite rim and increase of the abundance of kamacite towards the core. Scale bar is 100 µm. b) A plessite, consisting of numerous spheroids and comb-like lamellae of taenite (bright) in kamacite (dark) matrix. Scale bar is 40 µm. c) A net-like form of taenite (bright) in kamacite (dark) matrix. Scale bar is 20 µm. d) The center of a plessite, showing variation in structure. Note the microstructure of decomposition of taenite lamellae (large arrows) at the lower left corner of the photo. Scale bar is 100 µm. e) Occurrence of cohenite (FC) in the center of a plessite, with smooth surface and many fine black cracks distinguished from dark grey and crack-free kamacite. A few bright grains mainly along the boundaries of cohenite are schreibersite (not distinguished from taenite here). Scale bar is 40 µm. f ) A troilite (Tr) inclusion in kamacite (Ka). Note the dark grey lamellae of daubreelite (Dau). A small schreibersite (Sch) at the top boundary of troilite can be seen. Scale bar is 20 µm. small grains at sulfide boundaries and inside of plessite have COOLING RATE OF ULASITAI higher Ni contents (30.5–55.5 wt%). Troilite usually contains minor Cr (0.3–0.7 wt%), Ni (0.08–0.29 wt%), Co The cooling rate of Ulasitai is determined from the (<0.11 wt%) and Cu (<0.14 wt%), but some grains with Cr up correlation between the center Ni content and the half to 10 wt% are probably due to very fine lamellae of bandwidth of taenite by matching simulations (Fig. 6). The daubreelite. However, the quantitative analyses of these bulk contents of Ni and P of Ulasitai are 10.0 wt% and grains are stoichiometric (Fe,Cr)S. Daubreelite is 0.52 wt% (see next section), respectively. The Widmanstätten stoichiometric with minor Cu (<0.45 wt%). pattern was formed via reaction of γ + schreibersite > γ + Ulasitai: A new iron meteorite likely paired with Armanty (IIIE) 1267

Fig. 6. The center Ni content versus the half bandwidth of taenite. Fig. 5. A typical M-type zoning profile of taenite in Ulasitai. The measurements can be simulated with a cooling rate from 10 to 40 °C/Myr. schreibersite + α, the mechanism II according to Yang and Goldstein (2005). This is consistent with the occurrence of the elements, following the method described by D’Orazio and coarse laths of schreibersite. The nucleation temperature of Folco (2003). The HNO3 and HCl were purified by sub- kamacite is 660 °C determined from the phase diagram of Fe- boiling distillation, and water was obtained from the 18 MΩ/ Ni-P system (Yang and Goldstein 2005). With the recently cm grade Millipore purification system. updated diffusion coefficients of kamacite and taenite in Fe- The sample solutions were diluted in 10 ml of 3% Ni and Fe-Ni-P systems (Yang and Goldstein 2004; Yang and HNO3 for ICP-AES and ICP-MS counting. Ni, Co and P Goldstein 2006), the cooling rate was estimated from 5 to were measured using a Thermoelemental IRIS Advantages 60 °C/Myr with an average of 20 °C/Myr. It should be noted ICP-AES, and other trace elements were analyzed with a that this cooling rate was not corrected for orientation of VG Plasma-Quad ExCell ICP-MS, both at the National taenite. In addition, the effect of C on the nucleation of Research Center for Geological Analysis, Chinese kamacite is not considered due to absence of the bulk content Academy of Geological Sciences. Multi-element solutions of C. However, this effect should be negligible, because that of 20 ppb were used as standards. During the instrumental cohenite is the only -rich phase and it is a minor analyzing procedure, we measured the standard solutions mineral in Ulasitai although Fig. 4e shows many of the grains 5 times to monitor stability of counting, and variation of in the center of a plessite. the results is less than 1%. Relative standard deviations of counting (2σ) are less than 3% for Cr, Co, Cu, Ga, Ge, As, INDUCTIVELY COUPLED PLASMA MASS and Mo, <5% for PGEs, 5–19% for Re, and <6% for Zn and SPECTROMETRY AND ATOMIC EMISSION W, respectively. The analytical isotopes and corrected SPECTROMETRY ANALYSIS interferences are listed in Table 3. The correction method for Ge is the same described by D’Orazio and Folco The bulk composition of Ulasitai was measured by (2003), but we measured the spectra at peaks 70, 72, 73, inductively coupled plasma mass spectrometry (ICP) atomic and 74. The interference of 58Ni16O1H+ on 75As was emission spectrometry (AES) for Ni, Co, and P, and by ICP- calculated from the ratio of hydroxide to nickel MS for trace elements. We also analyzed the Armanty (IIIE), oxide (0.23) and 58Ni16O+ that derived from the intensities Nandan (IIICD) and Mundrabilla (IIICD) iron meteorites for of peaks 70, 72, 73, and 74. The correction factors are comparison. All of the samples were sawdust in form. The about 0.8 (Ge, As) and 0.95 (Ga) for Ga-, Ge-poor Ulasitai samples of Armanty were selected from the same multi- and Armanty. Nandan and Mundrabilla are Ga-, Ge-rich, sample set measured in previous studies with INAA (Chen and the corrections for both elements are negligible, but a and Sun 1986; Wasson et al. 1988; Chen and Wang 1996), and correction factor of 0.8 for As was applied. A blank sample they were labeled as L1, L12, L16 and L17. The samples were for the HNO3 solutions and another one for aqua regia washed 4 times with an ultrasonic cleaning in analytic grade solutions were prepared in the same way as the iron acetone, then in 0.2% HCl, and finally in Millipore water, samples. The blank levels of most elements are negligible, respectively. Two aliquots (∼50 mg) of each sample were except for Re that is about 1/3 of the counts of Ulasitai and measured. One of the aliquots was digested in ∼1 ml of aqua Armanty. The background of Re was subtracted from the regia for analysis of PGEs, Re, Au, Mo and W, and the other analyses. The detection limits (Table 3) were calculated ∼ was dissolved in 2 ml of 6 M HNO3 for analysis of other from six times the square root of the blank solution counts 1268 L. Xu et al.

Fig. 7. ICP-MS analyses of (a) Armanty, (b) Nandan, and (c) Mundrabilla, in comparison with literature data, and (d) Ulasitai in comparison with Armanty. The elements are arranged from left to right with increasing volatility. It is evident that our analyses are consistent with the literature data of the same meteorites and the composition of Ulasitai is nearly identical to that of Armanty. Discrepancy is found for several chalcophile elements, including Cr and Zn, which could be attributed to heterogeneous distribution of sulfide inclusions. Literature data are from Weinke (1977), Onuma et al. (1979), Cao(1982), Wang et al. (1985), Pernicka and Wasson (1987), and Wasson et al. (1988). divided by the sensitivity of the standard solutions, which (Fig. 1d). Except for higher Ni and Mo, all other elements are much lower than their concentrations in the irons, are lower in L12 than in L1, L16, and L17, probably due to except for Re that is lower only by a factor of 3 than the dilution of schreibersite. The average composition of concentrations of Ulasitai and Armanty. Armanty (L12 excluded) is the same of the INAA result The analyses of the HNO3 sample solutions are within standard deviation (Tables 4 and 5), except for compiled in Table 4 and those of the aqua regia sample slightly higher Ni and Co contents of our ICP-AES solutions in Table 5. Previous analyses of Armanty, analysis. Except for L12, the other 3 samples of Armanty Nandan and Mundrabilla acquired with INAA or have very homogeneous compositions. The standard radiochemical neutron activation analysis (RNAA) are deviations of the analyses are <10%, except for Re (17%), also listed for comparison. It is noticed that our analyses W (18%) and the chalcophile elements (Cr, Mn, Cu, Zn: are well consistent with the previous NAA data of the same 24–112%). The new data confirm no significant magmatic meteorites (Tables 4 and 5, Fig. 7). The analyses of L1 and fractionation of Armanty (Wasson et al. 1988). L16 of Armanty agree within 10% of the INAA data The ICP-MS analyses of Nandan also agree with reported by Wasson et al. (1988), except for As (20%), W literature values (Tables 4 and 5, Fig. 7b). Our analyses are (40%), and Cr and Cu (up to 70%). These deviations can be nearly identical to the RNAA data reported by Cao (1982), mainly attributed to heterogeneity of the samples, because except for differences in Pt (13%) and Pd (24%). The analyses As, Cr, and Cu are chalcophile and enriched in sulfides that of Mundrabilla show deviation from literature values for occur as inclusions in irons. Relatively large variation of more elements, including Cr, Cu, Zn, Ga, Ru, Re, and Au these elements has been reported in previous NAA data (Table 4 and 5). The variations of Cr, Cu and Zn could be (Chen and Sun 1986; Wasson et al. 1988). L12 contains related to heterogeneous distribution of sulfide inclusions. unusually high P (by a factor of ∼10, Table 4), indicative of The bulk composition of Ulasitai appears to be almost over-sampling schreibersite that occurs as coarse laths identical to that of Armanty, with a similar elemental Ulasitai: A new iron meteorite likely paired with Armanty (IIIE) 1269 0.00 0.18 0.17 0.09 n.d. 37.5 36.4 43.6 43.8 0.15 0.08 0.13 n.d. n.d. n.d. 0.13 0.08 0.15 0.47 8.75 00 7.13 156 0.000 37.5 0 0.0004 0.0081 0.000 38.0 0.986 0.000 0.002 0.145 1.000 0.000 0.840 0.003 0.000 0.001 0.001 0.120 1.009 0.878 0.003 0.000 0.002 0.002 0.001 0.995 2.061 0.002 0.000 1.035 0.002 0.000 0.001 2.095 3.895 0.986 0.001 0.001 0.006 3.916 0.000 0.003 62.9 54.4 56.0 20.2 19.2 0.04 0.08 0.12 0.13 0.13 0.06 0.13 0.13 0.12 0.04 0.08 4.000 2.000 2.000 2.000 7.000 7.000 38.8 19.6 49.0 49.9 27.1 10.4 62.0 81.2 52.3 49.6 72.4 89.2 5 101.12 101.23 101.56 99.77 99.86 100.20 5 101.1299.86 101.2399.77 101.56 0.59 0.24 0.44 0.10 0.02 0.25 0.56 .71 93.64 100.44 101.04 99.91 101.47 101.20 . n.d. n.d. n.d. n.d. n.d. n.d. 92 4.98 0.22 0.18 0.16 n.d. n.d. n.d.92 4.98 0.16 0.18 0.22 . 6.29 6.36 0.954 0.962 Atomic ratios per formular unit % . % . % Kamacite Taenite 11–12: patch. 11–12: metallic Fe-Ni in Ulasitai, wt Schreibersite Carbide Troilite Daubreelite Band In plessite Band In plessite tween the analytical total and 100 rule, 10: lamellae, essite; 3–4: large laths. essite; 3–4: large 1234567891011 123456 789101112 1 Calculated from the difference be Calculated from the difference Note: 7: rim, 8: core; 9: sphe n.d.: not detected. CoNiCu 0.74 7.39 n.d.n.d. 0.69 6.94 n.d. 0.03 n.d. n.d. 0.61 7.16 0.59 4.03 0.08 0.55 5.73 6.35 PFen.d.n.d. n.d 0.12 0.21 0.12 92.9 93.7 n.d. 0.04 n.d. 92.4 95.2 n.d. 93.9 n.d. 92.9 n.d. Total 101.23 101.42 100.39 99.8599.8 100.14 Total 101.70 101.73 101.78 99.17 93 1 1–2: small grains in pl n.d.: not detected. SiPCrFeCo n.d.SNi 15.7 Cu 0.21 34.4 C n.d. n.d. 15.4 n.d. 0.04 51.2 Si 32.6 P 0.20 n.d.Cr 0.30 n.d. 15.2 Fe n.d. 53.4 Co n.d. 65.6 S 0.001Ni 14.8 0.31 0.11 1.011Cu 0.008 20.6 62.7 n.d. 0.07 C 1.229 n.d. n.d. n.d Total 0.001 0.001 0.28 88.7 0.998 n.d. 21.2 0.003 0.000 0.07 1.742 1.169 0.006 n.d. 0.13 n.d. 0.010 0.000 88.4 4.000 n.d. 4. 0.970 0.000 0.02 0.000 1.822 n.d. 0.19 2.320 0.000 0.008 0.010 n.d. n.d. 4.000 0.968 0.000 0.004 0.000 0.695 2.276 0.000 0.000 0.010 n.d. 0.000 4.000 0.005 2.889 0.00 36.6 0.733 0.004 0.00 0.000 n.d. 0.00 0.000 4.000 2.87 0.153 0.00 0.000 4.000 0.00 n.d. 0.15 0.00 n.d. Table 1. Representative analyses of Table Table 2. Representative analyses of accessory phases in Ulasitai, wt Table 1270 L. Xu et al.

Table 3. Analytical isotopes and corrected interferences of ICP-MS analysis. Isotopes Corrected interferences Determination limit (µg/g) 52Cr 0.084 55Mn 0.033 59Co 0.107 65Cu 0.057 66Zn 0.234 71Ga 54Fe16O1H+ 0.008 74Ge 57Fe16O1H+, 58Fe16O+, 58Ni16O+ 0.015 75As 58Fe16O1H+, 58Ni16O1H+ 0.076 95Mo 0.025 182W 0.010 101Ru 0.006 103Rh 0.004 105Pd 0.008 185Re 0.007 193Ir 0.001 195Pt 0.003 197Au 0.042

Table 4. Measurements of the bulk samples dissolved in HNO3 acid. P Ni Co Cr Mn Cu Zn Ga Ge As Sample Weight mg % % % µg/g µg/g µg/g µg/g µg/g µg/g µg/g Nandan 51.2 0.14 7.37 0.48 7.0 1.1 137.1 13.7 81.1 309.2 9.6 Mundrabilla 53.1 0.37 8.12 0.50 28.8 4.5 112.6 12.7 55.2 168.0 12.0 Ulasitai 51.9 0.52 10.03 0.54 33.3 29.1 85.8 28.3 15.3 24.5 11.7 Armanty: L1 50.7 0.35 10.59 0.54 37.6 14.9 186.4 24.6 15.6 25.2 11.3 : L121 50.9 3.19 10.91 0.49 26.3 12.5 78.2 7.4 12.4 20.7 9.0 : L16 52.8 0.54 10.40 0.55 23.1 9.0 90.6 1.9 15.7 26.7 11.4 : L17 51.6 0.28 10.88 0.56 31.7 38.6 101.5 6.0 15.8 26.0 13.6 Mean 0.39 10.62 0.55 30.8 20.8 126.2 10.8 16.5 33.5 15.3 ±σ ±0.14 ±0.24 ±0.01 ±7.3 ±15.6 ±52.4 ±12.1 ±0.1 ±0.9 ±1.6 Literature Nandan 1 7.09 0.48 3.1 12.9 81.9 291 13 Mundrabilla 2 0.35 7.88 0.52 16.8 68 19.5 67 173 15 Armanty: L1 3 9.88 0.51 53 106 16.6 14.5 : L16 3 9.67 0.52 72 101 16.4 14.1 Mean 3 9.76 0.515 46 103 16.7 14.4 ±σ ±0.24 ±0.005 ±11 ±5 ±0.7 ±1 1Probably sampling unusually more schreibersite, hence not included in the mean and standard deviation. Literature data: 1 Cao (1982), 2 Weinke (1977), 3 Wasson et al. (1988).

pattern of the latter (Tables 4 and 5, Fig. 7d). The Ga and Ge relative to the IIIAB group with comparable Ni concentrations of PGEs, Re, Au and Mo are slightly lower contents, and displace Co, As, Au and W to the higher Ni in Ulasitai than the mean values of Armanty. However, the side, and Cu to the lower Ni side of the IIIAB field (Malvin discrepancy is smaller if compared with L16 that also et al. 1984). The concentrations of Ga, Ge, Co, Cu, As, Au, contains slightly higher P than L1 and L17. The and W of Ulasitai all plot within the IIIE field in the concentrations of Ni, Co, Cr, Ga, Ge, and As in Ulasitai are elements-Ni diagrams (Fig. 8), suggestive of a chemical similar to the mean values of Armanty, and their group of IIIE. The Ir-Ni diagram cannot distinguish differences are <8%, comparable to the heterogeneity of Ulasitai from IIIAB, but this is consistent with other IIIE Armanty. The Mn, Cu and Zn show significant deviation irons. from the mean Armanty, but they are still within the ranges The bandwidth of kamacite in Ulasitai is 0.9–1.8 of the latter (Table 4). (average: 1.2 ± 0.2) mm, within the range of IIIE (1.3– 1.6 mm) but larger than ∼1.0 mm for IIIAB having similar Ni Classification of Ulasitai and Pairing with Armanty contents (Malvin et al. 1984). The cooling rate of Ulasitai is about 20 °C/Myr determined by the center Ni content versus IIIE is a small chemical group of iron meteorites (15, based the half bandwidth method. This is significantly lower in on the Meteoritical Bulletin Database). They are lower in comparison with 56–338 °C/Myr of IIIAB (Yang and Ulasitai: A new iron meteorite likely paired with Armanty (IIIE) 1271

Table 5. Measurements of the bulk samples dissolved in aqua regia. Ru Rh Pd Re Ir Pt Au Mo W Sample Weight mg µg/g µg/g µg/g µg/g µg/g µg/g µg/g µg/g µg/g Nandan 51.2 5.12 1.31 3.82 0.126 1.77 5.39 1.55 6.49 1.14 Mundrabilla 51.6 3.32 0.92 4.37 0.071 1.00 3.60 1.63 6.26 1.23 Ulasitai 51.4 1.30 0.90 5.07 0.014 0.22 1.75 1.76 6.93 0.40 Armanty: L1 51.5 1.61 1.08 5.90 0.016 0.25 1.93 1.96 8.90 0.41 : L121 51.5 1.46 0.95 5.08 0.013 0.21 1.69 1.55 11.97 0.31 : L16 51.0 1.59 1.00 5.62 0.013 0.25 1.86 1.93 7.66 0.37 : L17 52.3 1.72 1.14 6.26 0.018 0.27 2.10 2.12 7.78 0.29 Mean 1.64 1.07 5.93 0.02 0.26 1.96 2.00 8.11 0.36 ±σ 0.07 0.07 0.32 0.00 0.01 0.13 0.10 0.68 0.06 Literature Nandan 1 5.11 3.08 1.81 6.18 1.45 Mundrabilla 2 2.44 0.037 0.92 – 1.290 Armanty: L1 3 0.226 2.2 1.8 0.29 : L16 3 0.226 1.7 1.81 0.27 Mean 3 0.23 2.3 1.84 0.27 ±σ 0.007 0.4 0.04 0.03 1Probably sampling unusually more schreibersite, hence not included in the mean and standard deviation. Literature data: same as in Table 4.

Table 6. Summary of petrography and mineral chemistry of Ulasitai, in comparison with Armanty. Ulasitai Armanty This study Literature1 Bandwidth of kamacite av. ±σ (range) mm 1.2 ± 0.2 (0.9–1.8) 1.24 (1.08–1.43) Co content of kamacite (wt%) 0.46–0.75 0.53–0.89 Conter Ni content of taenite bands (wt%) 16–26 15.3–21.5 Ni contents of schreibersite Coarse laths 20.6–21.2 16.1–19.1 Other grains 30.5–55.5 35.0–50.8 Ni content of carbide 4.83–5.02 4.67–6.03 Co content of carbdie 0.13–0.20 <0.39 Accessary phases Carbide, troilite, daubreelite Carbide, troilite, daubreelite 1Literature data of Armanty from Chen and Wang (1989).

Goldstein 2006). Correction for the crystallographic has the same Ni and Co contents of cohenite in Ulasitai. The orientation of each band will increase somewhat the cooling center Ni content of taenite ranges from 16 to 37 wt% in rate, but it cannot explain such a difference by a factor of Ulasitai, in comparison with 15.3–21.5 wt% in Armanty. 3–17. Cohenite is a common accessory mineral in Ulasitai In summary, all the bulk chemical composition, and occurs inside of plessite as described above. The petrography, and mineral chemistry of Ulasitai are very petrography and mineral chemistry confirm the classification similar to Armanty. Distance between their find sites is a of Ulasitai as a new IIIE meteorite. further compelling line of evidence that both meteorites It is evident that Ulasitai is indistinguishable from are likely paired. The large Armanty located northwest to Armanty according to their bulk chemical compositions. the small Ulasitai, indicating the falling direction of the Furthermore, Ulasitai shares similar petrography and mineral meteorite. The Ulasitai is classified as a new IIIE chemistry with Armanty as summarized in Table 6. Both meteorite based on the bulk chemical composition and Ulasitai and Armanty have nearly identical bandwidths of petrography. kamacite (1.2 ± 0.2 mm versus 1.24 mm), common occurrence of Fe-Ni carbide inside of plessite, and presence Acknowledgments–The paper has been significantly improved of the coarse laths of schreibersite between the by the constructive reviews by N. Chabot, R. Clarker, J. Yang, Widmanstätten pattern plates as noted on their surfaces and H. Watson. The authors thank X. Li for supplying with the (Fig. 2) and on the etched polished section of Ulasitai sample of Ulasitai, W. Qu for assistance in ICP-MS analysis, (Fig. 3). These schreibersite laths in both meteorites contain and J. Yang for supplying with the software of cooling rate. distinctly lower Ni in comparison with the other small grains. This study was supported by the pilot project of knowledge The Fe-Ni carbide that was referred as haxonite in Armanty innovation program (grant no. kzcx2-yw-110) and “One- 1272 L. Xu et al.

Fig. 8. Plots of trace elements versus Ni of iron meteorites. All seven elements of Ulasitai (filled star) are plotted in the field of IIIE (open square), but there is no difference between IIIE and IIIIAB on the Ir-Ni diagram. The average of our analyses of Armanty (open star) is also plotted for comparison. The ranges of IIIAB (filled circle) and IIIE are after (Malvin et al. 1984). Ulasitai: A new iron meteorite likely paired with Armanty (IIIE) 1273

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