DR Grimes, p. 1

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1 Grimes, p. 1 DATA REPOSITORY Description of Analytical Methods Figure DR1. Sample locations of rocks host to zircon analyzed in this study. Figure DR2. Photomicrograph of in situ ocean zircon (as inclusions in plagioclase, and cathodoluminescence) showing characteristic internal textures of ocean zircons. Figure DR3. Geochemical discriminant diagrams plotting Th vs. Yb and Th/Yb ratio vs. Hf, Y, and P for continental and ocean crustal zircons. Table DR1. SIMS trace element analyses of ocean crust and island arc zircon.

2 Grimes, p. 2 GSA Data Repository Item SIMS trace element zircon analyses and figures to accompany The Trace Element Chemistry of Zircons From Oceanic Crust: A Method for Distinguishing Detrital Zircon Provenance 1 Grimes, C.B., 1 John, B.E., 2 Kelemen, P.B, 3 Mazdab, F., 3 Wooden, J.L., 1 Cheadle, M.J., 2 Hanghøj, K., 1 Schwartz, J.J. 1 Dept. of Geology, University of Wyoming, Dept. 3006, Laramie, Wyoming Lamont-Doherty Earth Observatory, P.O. Box 1000, Palisades, NY U.S.G.S. Stanford Ion Microprobe Laboratory, 367 Panama Mall, Stanford, CA ANALYTICAL PROCEDURES Sampling and preparation Samples were collected from the slow- and ultraslow-spreading Mid-Atlantic and Southwest Indian ridges in ODP and IODP drill holes (735B, Dick et al. 2000; 1270D and 1275D, Kelemen et al., 2004; U1309D, Blackman et al., 2006), and by submersible and dredge (Blackman et al., 2004; MacLeod et al., 1998). Zircons were separated from whole rocks using standard crushing and mineral separation techniques and then mounted in epoxy, polished, cleaned in EDTA solution, and coated with 100 nm of Au prior to SEM cathodoluminescence (CL) imaging and SIMS. Trace-element concentrations in zircon Trace element measurements in zircon were made with the U.S.Geological Survey-Stanford SHRIMP-RG (Mazdab and Wooden, 2006; Wooden et al., 2006). Results for the ocean zircons are presented in Table DR1. Resolution of interfering isobars on certain trace elements is achieved by operating at a mass resolution (M/ΔM) of ~11,000 at 10% peak height. This is sufficient to effectively resolve 45 Sc + from 90 Zr 2+ (M/ΔM =12660), 48 Ti + from 96 Zr + (M/ΔM =7660), and the HREE from the MREE oxides (M/ΔM =~ ), while maintaining flat-topped peaks and high transmission. The high transmission allows for the use of a small spot size; a 3-6 na primary beam current and μm spot were used for all analyses. Each measurement consisted of one block of two cycles. Each cycle peak steps sequentially from 9 Be + to 254 UO +, although only data for currently calibrated elements are reported. The exceptions are data for Al, Ca, and Fe, which although absolute concentrations are not yet calibrated these elements serve as important tracers for identifying analyses where the ion beam may have

3 Grimes, p. 3 overlapped common inclusions such as titanite, fluorapatite, and Fe-Ti-oxides. From the middle REE though hafnium, thorium and uranium, the oxide peaks are measured rather than the elements due to their greater ion production. The total run time is approximately 15 minutes per analysis. Final crater depth in zircon is typically less than 2 μm. Analyses of roughly 10 unknowns are interspersed with analyses of two concentration standards, including a primary standard (a Sri Lankan megacryst- CZ3; Ireland and Williams, 2003), and/or the secondary standard (a gem quality crystal from Samé, Tanzania). Both standards have been repeatedly analyzed against synthetic trace element-doped zircon to verify their concentrations and homogeneity. Data are processed in MS Excel. M + / 30 Si ratios are derived from the time-averaged counts for each mass of interest for both the standards and unknowns. Values for unknowns are compared to those of the primary standard to determine concentrations; the secondary standard provides an independent check of data quality. For P, Sc, Ti, and Y, 1σ precision is less than 3%; for the measured REE (excluding La), Hf, Th, and U, 1σ precision ranges from 4-9%; for La the precision is ~15%. Fe, Al, and Ca values are listed in table DR1 as M + / 30 Si counts per second. Additional zircons were analyzed from ocean crustal and island arc rocks using the Woods Hole Cameca IMS 3f Ion Probe, with an emphasis on Yb, U, and Th. A primary beam current sufficient to get 75, ,000 cps of 96 Zr + on zircon was used, with a secondary accelerating voltage of 4410 with high voltage offset of -90 and energy window of 20eV. Each trace element was measured for 30 seconds, and 96 Zr + was measured for 5 seconds. Four consecutive analyses were performed on each individual grain. The zircon standard (Wiedenbeck et al., 1995) served as the calibration standard, and was analyzed between 4-6 times during each analytical session. Data from the Cameca IMS 3f Ion Probe are processed in MS Excel. M + / 96 Zr + ratios are derived from the time-averaged counts for each mass of interest for both the standards and unknowns. Values for unknowns are compared to those of the standard to determine concentrations for each analysis. Reported values are the mean of the 4 consecutive analyses. DISCUSSION ON DEFINING OCEAN CRUST ZIRCONS The discriminant diagrams shown in Fig. 2 (main text) illustrate that over 80% of the currently analyzed ocean crust zircons can be distinguished from the continental zircon field defined by more than 1700 analyses. Less than 20% of the oceanic zircon suite overlaps with the continental field, indicating that certain limitations apply when comparing other datasets to Figure

4 Grimes, p Lines defining the lower boundary of the continental field are visually determined and indicate our best estimate of the upper limit for zircons with an unambiguous origin from MORB. These boundaries may shift slightly with the acquisition of new datasets, but we believe they will still provide a robust discrimination of zircons from continental and oceanic crust based on the large number of analyses used to define the different fields. The provenance of grains falling in the overlap region cannot be distinguished with reasonable certainty. We recommend that the discrimination diagrams presented in figure 2, as well the similar diagrams in figure DR3, only be used for comparing populations of zircon when investigating provenance. We do not address the composition of metamorphic grains, which may plot in the ocean crust zircon field based only on U, Yb, Hf, Y, and P. An additional parameter that can be used for distinguishing metamorphic grains is the Th/U ratio (e.g., Hoskin and Black, 2000). All ocean crust zircons we analyzed have Th/U ratios that are above ~0.09, and more than 95% have a ratio above 0.2. Zircon with Th/U ratios less than ~0.09 are therefore not necessarily ocean crustal in origin, but rather likely to be metamorphic. Some metamorphic zircons may still overlap even the most restricted definition of the ocean crustal field, however, low Th/U ratios or possibly the presence of blurred primary zoning (e.g., Hoskin and Schaltegger, 2003) can help distinguish these. Finally, and as noted in the main text, additional tectonic settings, such as ocean islands, island arc, continental flood basalts, etc. may yield magmas with U, Th, and Yb compositions that overlap with both the continental and MORB fields. Because U/Yb and Th/Yb ratios in zircon reflect the U/Yb and Th/Yb ratio of the host rock, other tectonic settings could theoretically produce zircon that fall in either the oceanic or continental field. At this time no published trace element data for zircon from these environments (apart from that presented here) are known to the authors, however additional analytical data for zircon from these environments are needed to evaluate this possibility, and to assess the potential for using other parameters to distinguish zircon from these environments. REFERENCES CITED Blackman, D.K., Karson, J.A., Kelley, D.S., Cann, J.R., Früh-Green, G.L., Gee, J.S., Hurst, S.D., John, B.E., Morgan, J., Nooner, S.L., Ross, D.K., Schroeder, T.J., Williams, E.A., 2004, Geology of the Atlantis Massif (MAR 30N): implications for the evolution of an ultramafic oceanic core complex: Marine Geophysical Researches, v. 23, p , doi: /B:MARI

5 Grimes, p. 5 Blackman, D.K., and 50 others, 2006, Proceeding of the Integrated Ocean Drilling Program, Leg 304/305: College Station, TX. Online: iodp.tamu.edu/publications/exp304_305/30405toc.htm. Dick, H. J. B., and 27 others, 2000, A long in situ section of lower ocean crust: results of ODP Leg 176 drilling at the Southwest Indian Ridge: Earth and Planetary Science Letters, v. 179, p Hoskin, P.O., and Schaltegger, U., 2003, The composition of zircon and igneous and metamorphic petrogenesis: In Hanchar, J.M., and Hoskin, P.W.O., eds., Zircon, Reviews in Mineralogy and Geochemistry v. 53, Mineralogical Society of America, p Hoskin, P.O, and Black, L.P., 2000, Metamorphic zircon formation by solid-state recrystallization of protolith igneous zircon: Journal of Metamorphic Petrology, v. 18, p Ireland, T.R., and Williams, I.S., 2003, Considerations in zircon geochronology by SIMS: in Hanchar, J.M and Hoskin, P.W.O., eds, Zircon: Reviews in Mineralogy and Geochemistry, v. 53, p Kelemen, P.B., and 27 others, 2004, Drilling mantle peridotite along the mid-atlantic Ridge from 14º to 16º N: sites : Proceedings of ODP, Initial Reports, 209 [Online] wwwodp.tamu.edu/publications/209_ir/209ir.htm. MacLeod, C.J., Allerton, S., Dick, H.B.J., and Robinson, P.T., 1998, Geology of Atlantis Bank, SW Indian Ridge: preliminary results of RRS James Clark Ross Cruise 31: Eos (Transactions, American Geophysical Union), v. 79, F893. Mazdab, F.M., and Wooden, J.L., 2006, Trace element analysis in zircon by ion microprobe (SHRIMP-RG); technique and applications: Geochimica et Cosmochimica Acta (2006 Goldschmidt abstract volume). Wiedenbeck, M., Allé, P., Corfu, F., Griffin, W.L., Meier, M., Oberli, F., von Quadt, A., Roddick, J.C., and Spiegel, W., 1995, Three natural zircon standards for U-Th-Pb, Lu-Hf, trace element and REE analysis: Geostandards Newsletter, v. 19, p Wooden, J.L., Mazdab, F.K., Barth, A.P., Miller, C.F., and Lowery, L.E., 2006, Temperatures (Ti) and compositional characteristics of zircon: Early observations using high mass resolution on the USGS-Stanford SHRIMP-RG: Geochimica et Cosmichimica Acta (2006 Goldschmidt abstract volume). Table DR1. Representative SIMS trace element analyses of ocean crustal and island arc zircon. Analyses of ocean zircon presented here were chosen to 1) define the geochemical fields outlined by the entire dataset, 2) be representative of the spectrum of ocean crustal rock types found to host zircon, and 3) illustrate the significant intra-sample variation sometimes observed.

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9 Table DR1. Representative trace element analyses of ocean crust and island arc zircon P Sc Ti Y La Ce Pr Nd Sm Eu Gd Tb Dy Ho Er Tm Yb Lu Hf Th U Al/Si* Ca/Si* Fe/Si* ppm ppm ppm ppm ppm ppm ppm ppm ppm ppm ppm ppm ppm ppm ppm ppm ppm ppm ppm ppm ppm cps cps cps SHRIMP-RG 30º N MAR Tremolite-chlorite schist Altered gabbroic veins in serpentinized peridotite Gabbro 1309D D D D D D D D D D D D

10 1309D SWIR Oxide-bearing Gabbro JR JR JR Olivine Gabbro JR JR JR JR Cameca 3f Ion Probe ODP Hole 1275D Diorite to quartz diorite dikelets 75D144-a D144-a D144-a D144-a D144-a D144-a D144-a D180-a D180-a D180-a D180-a ODP Hole 1270C & 1270D Altered gabbroic veins in serpentinized peridotite 70C (1) C (2) D (1) D (2) D (3) Talkeetna Arc

11 Quartz diorite to tonalite dikelets TK1721M01 (1) TK1721M01 (2) TK1721M01 (3) TK0720G2 (1) TK0720G2 (2) TK0720G2 (3) TK2717M04 (1) TK2717M04 (2) TK2717M04 (3) *Presented as ratios of counts per second (cps) relative to Si³¹ cps.