Supporting Online Material for

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1 Originally posted 19 July 2007; corrected 20 July Supporting Online Material for The Crystallization Age of Eucrite Zircon G. Srinivasan,* M. J. Whitehouse, I. Weber, A. Yamaguchi This PDF file includes Materials and Methods Figs. S1 to S3 Tables S1 to S4 References *To whom correspondence should be addressed. Published 20 July 2007, Science 317, 345 (2005) DOI: /science Correction 20 July 2007: The figures are attached to this SOM; the copy-editor is at fault.

2 Supporting Online Material Materials and Methods The Cameca IMS1270 ion microprobe at the Swedish Museum of Natural History, Stockholm, (NORDSIMS facility) was used to determine the Hf-W composition of eucrite and terrestrial zircon grains. This instrument is routinely used for U-Pb dating of zircons from terrestrial rocks using well-established techniques (S1 S2). The present study utilized the multicollector detection system on the IMS1270. The detector assembly consists of five movable detectors, three on the low mass side of the beam axis designated [L2], [L1] and [C] (the latter capable of being positioned on the axis) and two on the high mass side designated [H1] and [H2]). The Hf-W measurements were carried out using the multi-collector system at its highest nominal mass resolution of ~ 8000 (M/ΔM) (Figure S1). W has five isotopes, 180 (abundance ~ 0.12%), 182 (~26.3%), 183 (~14.3%), 184 (~30.7%), and 186 (~28.0%) and Hf has five isotopes 176 (~5.20%), 177 (~18.6%), 178 (~27.3%), 179 (~13.6%), 180 (~35.1%). The signal strength of [WO] + is higher compared to the atomic species W + (e.g., S3) but the presence of additional interference from di-oxides of REEs that require M/ΔM ~ 8600 (e.g. 166 Er 16 O 2 on mass 182 W 16 O) compromises the measurements for [WO] +. Additionally, 181 Ta 16 OH at mass 198 interferes with 182 W 16 O, the critical peak for the eucrite zircon study where excess 182 W is expected and is unresolvable with the IMS1270 (M/ΔM ~26000). When W was measured as an oxide in a terrestrial zircon (G-zircon), which should have no excess 182 W, the apparent excess due to signal contribution from oxides of REEs and/or 181 Ta 16 OH was ca For this reason, the W isotopes were measured as metal. Five peaks were measured simultaneously in the multicollector electron multipliers during the first analytical session (July 2003, run sequence 1 to 26 in Table S2): 178 Hf + [L2], 182 W + [L1], 183 W + [C], 186 W + [H1] and 184 W 16 O + [H2]. The WO peak, which was not used in any calculations, was omitted from the second analytical session (July 2005, run sequence in Table S2) and a slightly different configuration used in order to accommodate an exchange of the [L1] electron multiplier to a Faraday cup: 178 Hf + [L2], 182 W + [C], 183 W + [H1] and 186 W + [H2]. Detector [L2], which was used for mass centering the large 178 Hf peak at the start of each measurement, was shifted to the lower mass side by 5milli-amu so that the detectors measuring the W signals were centered on higher mass of the W peak flats. This increased effective mass resolution and reduced signal contribution from oxides of REE (e.g., 166 Er 16 O at mass 182) to W signals. The improvement in signal integrity was achieved without increasing the actual mass resolution (for example, by closing the entrance slit) or resorting to energy filtering, both of which attenuate signal resulting in lower measurement precision. The counting time for each cycle was 30 seconds for session 1 which included eucrite A and 10 seconds for session 2 which included eucrites A and EET Total analytical time was comparable at 720 seconds (24 cycles) and 600 (60 cycles) seconds respectively. The typical primary current was in the range of ~ Amperes for both analytical sessions and secondary count rates were comparable. The very low count rates of W encountered in zircon (both terrestrial and meteorite) required special attention to detector backgrounds, particularly for the three detectors measuring W. The Hamamatsu 416 electron multipliers used in the Cameca IMS1270 detector array can be set up to strongly discriminate against spurious counts from electronic noise. This was done using the Cameca pulse height analysis routine to arrive at a combination of detector high voltage and 2

3 threshold voltage in order to obtain maximum detector yield with lowest noise. Before each analytical session, the results of this optimization were checked by running a long (1 hour or more) background measurement with the primary beam and all secondary beam lenses energized as they would be in a normal run, but with the secondary beam electrostatically blanked. During the two analytical sessions, these measurements yielded and 0.02 counts/sec (cps) on the detector measuring 182 W, and cps on the 183 W detector and and on the 186 W detector respectively. In comparison, meteorite zircon signals ranged from 0.1 to 0.6 cps for 182 W, to 0.08 cps for 183 W and 0.01 to 0.12 cps for 186 W. Because of the random nature of the very low background signal, no corrections were applied to the final data presented in Table S2. The ion microprobe uses a primary ion beam to sputter atoms from a sample. The sputtered atoms/ions are expected to be nominally representative of sample composition. However, different elements ionize to varying degrees resulting in elemental fractionation during the sputtering process. Therefore, the measured elemental ratios of [Hf] and [W] need correction to account for the ionization efficiencies of both elements relative to each other; this correction factor is commonly referred to as relative sensitivity factor (RSF) (e.g., S4). The RSF is a function of chemical composition and crystalline structure. W abundances in zircon standards are not known accurately. Hf/W relative sensitivity factor (RSF) was determined using silicate glass standard NIST610 with accepted reference concentrations of Hf and W of ~ 418 and 445 ppm respectively (S5). The Hf/W RSF was estimated to be 0.21±0.01. In NIST 610 Hf, and W abundances are similar while in zircons the typical Hf concentration is about ~1% and even higher while W abundance is few ppm. Hafnon (HfSiO 4 ) forms a complete solid solution with zircon (S6 S7), and is therefore, an important structural component of the zircon crystal while W is a trace element. The estimated (Hf/W)-RSF for NIST 610 is therefore not suitable for zircon. The abundance of Yb, a trace element in zircon, is documented accurately. A method that uses Yb as a proxy for W to estimate the correction factor determined for RSF [Hf/W] in NIST 610 was outlined earlier (S3). The abundance of Hf and Yb is well established for NIST 610 [Hf 418ppm and Yb 462ppm] (S5) and the zircon standards [Hf ~ 5588 ppm Yb ~ 64ppm] (S5, S8 S9) and SL13 [Hf 6808ppm and Yb 12.4ppm] (S7, S10). The measured ionic ratios of Hf/Yb isotopes and the estimated Hf/W using NIST610 (Hf/Yb)-RSF can be compared with the Hf/Yb determined from the absolute abundances determined (S5, S10) to estimate the correction factor for (Hf/Yb)-RSF for NIST. The correction factor for (Hf/Yb)-NIST RSF is 2.5 which means that [Hf]/[Yb] = {[NIST-RSF]/2.5}*[Hf + ]/[Yb + ]. We applied a similar correction to the [Hf/W] RSF determined from NIST values to estimate elemental ratios from measured ionic ratios of [Hf/W] in zircon. In the absence of W concentration data in standard zircon, use of Yb as a proxy for W in zircons is the only way to estimate the [Hf/W] zircon -RSF, and therefore, is the best possible estimate of [Hf/W] elemental ratio in zircon (S3). Standards: We analyzed terrestrial W metal and silicate glass standard NIST610 and 3 terrestrial zircons, standard zircon (S8-S9), G Zircon, and 97SU-51 (S11) : This ca Ma zircon is a well-characterised and distributed standard (S8 S9) that has been used extensively by both ion microprobe and laser ablation ICPMS laboratories. G Zircon: This is a gravel sized euhedral zircon crystal from commercial heavy mineral deposits in Zirconia, North Carolina. The polished crystal that was analysed (ca. 5 mm across) is used for instrument tuning and alignment ( G is an internal laboratory nomenclature). This zircon is of unknown age. 3

4 97SU-51: This is ~ 300 micrometer prismatic zircon from a Lewisian complex tonalite on South Uist, Outer Hebrides, Great Britain (S11). The single Hf-W analysis was made in the ca. 2800Ma core of grain #2. REE measurement: Two individual meteorite zircon grains Z-3 and Z-2 from A and terrestrial G Zircon and were analyzed for their REE abundance (Table S1, Figure S2) using multicollector methods similar to those described in (S2). There is progressive relative enrichment from light to heavy REE in these zircons. The meteorite zircons have marked Eu depletion but no Ce anomaly. The individual zircon REE patterns are essentially parallel. Hf-W Isotope Measurements: The Hf-W composition was measured in terrestrial standards, and zircons and pyroxenes from the meteorites A , A and EET90020 (Table S2). We used 182 W/ 186 W = and 183 W/ 186 W = as the reference value for W isotopic composition (S12). The average instrumental mass fractionation estimated for W from NIST 610 analyses is ~ 10 /amu (Table S2). For the heavy masses of W isotopes the instrumental mass fractionation is not expected to be significantly different between NIST 610 (silicate glass) and zircon (silicate). The measurement uncertainty in W isotopic composition due to low counting statistics is between ~ 25-50%, which is significantly more than fractionation correction. The change in the inferred initial 182 Hf abundance in the absence of fractionation correction is negligible, and can therefore be ignored for these measurements. Assignment of the observed values of 182 W/ 186 W ratio to an actual excess requires that the measured signal has no molecular interferences which, in zircon, may be contributed by oxides and/or dioxides of the rare-earth elements (REE). This contribution can be evaluated by comparing REE abundances in terrestrial and meteoritic zircons (Figure S2). The elevation in light REE abundance in meteorite zircons relative to their terrestrial counterpart is not a concern because the W isotopes of interest are adequately mass resolved from light REE dioxides. However, the heavy REE monoxides and oxy-hydrides are much closer in mass to the W isotopes and, even operating at the highest mass resolution possible with the IMS1270 multicollector array (M/ΔM ~ 8000), may contribute some signal to the W isotopes of interest. To assess this possibility, we investigated the terrestrial G zircon which has heavy REE abundance ~ 10 to 100 times more than meteorite zircons and therefore has the potential to contribute a much higher REE-oxide interference. The normal W isotopic composition obtained from this terrestrial zircon rules out oxides and oxy-hydroxides of REE as the cause for excess δ 182 W in meteorite zircons. Since analyses of terrestrial zircon were interleaved in the sequence with meteorite zircon (Figure S3), the presence of any drift-related instrument artefact (such as degradation of peak shape compromising mass resolution) can also be effectively ruled out. Initial 182 Hf/ 180 Hf Abundance in Eucrites: The initial 182 Hf/ 180 Hf for eucrites A and A has been calculated using Isoplot (S13) is reported in Table S3. The W abundance in meteoritic phases and terrestrial zircon is extremely small (sub-ppm) leading to extremely small count rates for the measured W isotopes (182, 183, 186). The common denominator 186 W in the ratios 182 W/ 186 W and 180 Hf/ 186 W and the low counting statistics for W isotopes results in strongly correlated errors for the measured ratios which are tabulated in Table S2. We have calculated the initial 182 Hf/ 180 Hf values using different components and models (S13). These values (Table S3) are our best possible estimates and supersede all previously reported initial values (S14, S15) which were calculated using unreliable estimates of RSF (S14, S3) and data treatment without using correlated errors (S15). 4

5 Calculation of Relative Age Difference: We have used the recently measured radioactive decay constant of 182 Hf (S16) value of 0.078±0.002 Myr -1 to determine the relative age difference based on variations in 182 Hf abundance (Table S4). If two objects E1 and E2 have initial 182 Hf abundance given by ( 182 Hf/ 180 Hf) E1 and ( 182 Hf/ 180 Hf) E2 determined from mineral isochrons of these objects then the time difference between their formation is given by: References Δt = 1/λ ln {( 182 Hf/ 180 Hf) E1/ ( 182 Hf/ 180 Hf) E2 } S1. Whitehouse M.J., Kamber B and Moorbath S. (1999) Chemical Geology 160, S2. Whitehouse M.J., and Kamber, B.S. (2005). Journal of Petrology 46, S3. Ireland T.R. and Bukovanska M. (2003) Geochimica Cosmochimica Acta 67, S4. Zinner E.K. and Crozaz G. (1986) Int. J. Mass Spectrum. Ion Processes 69, S5. Pearce N.G.J., Perkins W.T., Westgate J.A., Gorton M.P., Kackson S.E., O Neal C.R., and Chearny S.P. (1997) Geostand Newsl. 21, S6. Ramakrishnan S.S., Gokhale K.V.G.K. and Subbarao E.C. (1969) Mater Res. Bull. 4, S7. Hoskin P.W.O. and Rodgers K.A. (1996) Eu. J. Solid State Inorg. Chem. 33, S8. Wiedenbeck W., Alle P., Corfu F., Griffin W.L., Oberli F., von Quadt A., Roddick J.C. and Spiegel W. (1995) Geostand. Newsl. 19, S9. Wiedenbeck, M., Hanchar, J., Peck, W.H., Sylvester, P., Valley, J., Whitehouse, M., Kronz, A., Morishita, Y. Nasdala, L. & twenty one others (2004). Geostandards and Geoanalytical Research 28, S10. Hoskin P.W.O (1998) J Trace Microprobe Techniques 16, S11. Whitehouse M.J. (2003) In Vance, D., Muller W., and Villa I. (eds). Geochronology: Linking the Isotopic Record with Petrology and Textures. Geological Society of London, Special Publications 220, S12. Schoenberg R., Kamber B.S., Collerson K.D. and Eugster O. (2002) Geochimica Cosmochimica Acta 66, S13. Ludwig, K.R. (1999). IsoplotEx v Special Publication 1a. Berkeley Geochronological Center. S14. Srinivasan G., Whitehouse M J., Weber I., and Yamaguchi A. (2004) Lunar and Planetary Science XXXV #1709. S15. Srinivasan G., Whitehouse M J., Weber I., and Yamaguchi A. (2006) Lunar and Planetary Science XXXVII #2042. S16. Vockenhuber C et al. (2004) Phys. Rev. Lett. 93, S17. Kleine T., Mezgar K., Münker C., Palme H., and Bischoff A. (2004) Geochimica Cosmochimica Acta 68, S18. Kleine T., M Mezgar K., Palme H., Scherer E. and Münker C. (2005) Earth and Planetary Science Letters 231,

6 Figure Captions: Figure S1. High Mass Resolution of the measured signals for ions of interest for terrestrial G zircon (above) and NIST610 silicate glass reference material with 500ppm of Hf and W. The red dashed line at secondary B field = 0 is the center of the peak for 178 Hf + which is used as the centering peak. Figure S2. REE data for terrestrial zircons G and and the meteorite zircons (Z3 and Z2) from A Elements are spaced according to ionic radius in the zircon structure as indicated on the upper axis in picometres. Figure S3. The δ 182 W (upper panel) and δ 183 W (lower panel) values of all measured samples are reported in their order of measurement. All errors are 2σ m. See (17) for definition of δ 182 W and δ 183 W. The horizontal solid lines labelled δ 182 W = 0 (upper panel) and δ 183 W = 0 (lower panel) represent normal W isotopic composition. The terrestrial phases have normal δ 182 W and δ 183 W within errors. The eucrite zircons in A , A and EET90020 have δ 182 W > 0 and δ 183 W = 0 within errors. Table S1. Zircon REE abundance (ppm). G zircon: Gravel sized euhedral zircon crystal of unknown age from commercial heavy mineral deposits in Zirconia, North Carolina (light REE and Eu not analyzed) : Zircon standard used extensively for microanalytical work (S8 S9). A zircons Terrestrial zircons Z-2 Z-3 G Zircon La Ce Pr Nd Sm Eu Gd Dy Er Eb

7 Table S2. Hf-W composition of terrestrial standards and meteoritic minerals. W metal, silicate glass standard NIST 610, and terrestrial standard zircon (S8 S9), as well as G Zircon and 97-SU51 (S11) were analyzed in two sessions with the overall sequence number recorded in the column headed seq.#. Individually photo-documented meteorite zircons are labelled as Z1, Z2, etc for identification, with repeat analyses on the same zircon labelled as rpt. The meteorite pyroxenes are labelled as px. Measurements in terrestrial phases are reported as 1, 2, etc. Error correlation ρ is that between 180 Hf/ 186 W and 182 W/ 186 W ratios. For the ratios we report 1σ mean errors. The δ 182 W and δ 183 W values are respectively defined by the equations [( 182 W/ 186 W)sample/( 182 W/ 186 W)standard) 1] 1000 and [( 183 W/ 186 W)sample/( 183 W/ 186 W)standard) 1] 1000 and reported with 2σ uncertainties. The accepted values for 182 W/ 186 W = and 183 W/ 186 W = were recalculated from (S12). The measured 178 Hf+/ 186 W+ ionic ratios were converted to 180 Hf+/ 186 W+ values using the value 180 Hf/ 178 Hf = The calculated ionic 180 Hf+/ 186 W+ ratios were corrected for relative ionization efficiency using the RSF value of determined using Hf, W and Yb abundances in glass standard NIST610 and zircon standards and SL13 [following method outlined in (S3)]. For A px, no 183 W counts were registered and so 183 W/ 186 W and δ 183 W and their corresponding errors are left blank. Sample Seq.# 180 Hf/ 186 W 182 W/ 186 W ± σ ρ 183 W/ 186 W ± σ δ 182 W ± 2σ δ 183 W ± 2σ Metal ± ± ± ± 1.9 NIST 610 glass ± ± ± ± ± ± ± ± ± 15 6 ± ± ± ± ± ± ± ± ± ± ± ± ± ± ± ± ± ± ± ± ± ± ± ± ± ± ± ± ± ± ± ± ± ± ± ± 64 G zircon 1 5 (1.21 ± 0.13) x ± ± ± ± (1.04 ± 0.11) x ± ± ± ± (10.0 ± 0.7) x ± ± ± ± (11.6 ± 0.9) x ± ± ± ± (11.7 ± 0.8) x ± ± ± ± (4.27 ± 0.45) x ± ± ± ± (4.67 ± 0.35) x ± ± ± ± (12.7 ± 0.9) x ± ± ± ± (8.01 ± 0.59) x ± ± ± ± (1.85 ± 0.11) x ± ± ± ± (16.6 ± 1.0) x ± ± ± ± zircon 1 21 (1.72 ± 0.27) x ± ± ± ± (2.32 ± 0.36) x ± ± ± ± (2.39 ± 0.40) x ± ± 0.22 (1.1 ± 0.9) x ± (2.08 ± 0.48) x ± ± 0.27 (1.4 ± 1.0) x 10 3 (1.4 ± 1.1) x (1.87 ± 0.42) x ± ± 0.23 (1.3 ± 1.3) x ± (1.78 ± 0.37) x ± ± 0.38 (1.0 ± 1.1) x 10 3 (1.6 ± 1.5) x (1.82 ± 0.38) x ± ± ± ± SU51 zircon grain ± ± ± ± ± 86 A zircon and pyroxene Z3 13 (8.4 ± 1.0) x ± ± 0.12 (5.8 ± 1.8) x ± 480 Z4 15 (1.66 ± 0.19) x ± ± (1.1 ± 0.6) x ± 350 Z6 16 (4.46 ± 0.62) x ± ± 0.12 (2.9 ± 1.2) x ± 470 Z7 17 (3.42 ± 0.44) x ± ± 0.15 (1.6 ± 0.8) x ± 610 Z2 18 (7.7 ± 1.1) x ± ± 0.12 (4.3 ± 1.7) x ± 490 Z3 rpt. 24 (5.96 ± 0.78) x ± ± 0.15 (4.5 ± 1.6) x ± 610 Z2 rpt. 25 (1.29 ± 0.25) x ± ± 0.31 (9.1 ± 4.2) x 10 3 (1.3 ± 1.2) x 10 3 px ± ± ± 0.66 (0.4 ± 1.4) x 10 3 (1.4 ± 2.6) x 10 3 A zircon and pyroxene Z1 40 (1.18 ± 0.30) x ± ± 0.33 (8.9 ± 5.5) x 10 3 (0.9 ± 1.3) x 10 3 Z2 41 (9.5 ± 2.2) x ± ± 0.20 (3.4 ± 2.2) x ± 790 Z3 42 (2.19 ± 0.55) x ± ± 0.33 (17.0 ± 9.5) x 10 3 (1.0 ± 1.3) x 10 3 Z4 43 (1.27 ± 0.50) x ± ± 0.31 (7.3 ± 6.7) x 10 3 (0.0 ± 1.2) x 10 3 px ± ± (1.8 ± 2.8) x 10 3 px rpt ± ± ± ± ± 470 EET90020 zircon Z1 47 (9.2 ± 1.4) x ± ± ± ± 580 Z ± ± ± 0.47 (1.3 ± 1.5) x 10 3 (1.9 ± 1.9) x

8 Table S3. Summary of age regressions from Asuka eucrites. Regression models according to (S13). Model 1 fits take account of individual data point uncertainties and use correlated (corr.) or uncorrelated (uncorr.) errors. Model 2 regression fits assume equally weighting of all data points and uncorrelated errors. Robust regression does not take into account data point uncertainties. Column 2 shows number of points included in regression analyses with number of points omitted in parentheses. Slope is equivalent to initial 182 Hf/ 180 Hf ratio and intercept is equal to initial 182 W/ 186 W ratio. The mean square of weighted deviates is appropriate only for model 1 regressions (probability shown in parentheses). NA, not applicable. Components Model No. incl. (rej.) Slope ± 2σ ( 10 5 ) Intercept ± 2σ MSWD (prob.) A zrn & px 1 (corr.) 5 (1) 7.5 ± ± (0.21) zrn & px 1 (corr.) ± ± (<0.01) zrn & px ± ± (<0.01) zrn & px 1 (uncorr.) ± ± (0.26) zrn only 1 (corr.) ± ± (0.46) zrn & px robust regr / / 7.7 NA A zrn & px 1 (corr.) 7 (1) 6.0 ± ± (0.12) zrn & px 1 (corr.) ± ± (<0.02) zrn & px ± ± (<0.02) zrn & px 1 (uncorr.) ± ± (0.79) zrn only 1 (corr.) 6 (1) 6.0 ± ± (0.07) zrn & px robust regr / / 1.1 NA Table S4. Age differences. The time difference (column 2) refers to the difference between metal-silicate differentiation and crystallization of zircons based on difference in 182 Hf abundance. Absolute age was calculated using the model absolute age of EWR and the time difference between metal-silicate differentiation and crystallization of zircons. Column 4 shows the difference between age of crystallization and age of metamorphism (4547±2 My) (S18). Column 5 shows lower limit on time difference is between age of crystallization and age of metamorphism based on 4547 (±2) My (S18). NA, Age difference and lower limit are not applicable in case of zircon from EET Initial 182 Hf/ 180 Hf Time difference (My) Absolute age (My) Age difference (My) EWR* 7.25 (±0.5) ± 1.5 A (±0.9) ± ± ± A (±1.4) ± ± ± Lower limit (My) EET >30 < NA NA *Initial value according to (S17). Estimated model 182 Hf abundance. 8

9 10000 G-zircon Intensity (cps) NIST610 L2 ( 178 Hf) 182 L1 ( W) 184 C ( W) 186 H1 ( W) H2 ( W O) Sec. B-field (digits)

10 sample/chondrite A Z3 A Z2 G zircon (HREE only) La Ce Pr Nd Sm Eu Gd Dy Er Yb

11 Figure W / / A zircon/pyr A zircon/pyr EET90020 zircon G-zircon 97SU-51 NIST610 glass W metal W analysis sequence number