SUPPLEMENTARY INFORMATION

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1 SUPPLEMENTARY INFORMATION DOI: /NGEO1155 Supplementary Online Material for Young poorly crystalline graphite in the >3.8 Gyr old Nuvvuagittuq banded iron formation PAPINEAU, D.,DE GREGORIO, B.T, CODY, G.D., O NEIL, J., STEELE, A., STROUD, R.M., AND FOGEL, M.L. Content Geological context o Ujaraaluk Unit Supplementary Figure S1 o Banded Iron Formations o Metamorphism o Age Constraints Methods o Raman Spectroscopy o Focused Ion Beam Milling o Transmission Electron Microscopy o Synchrotron-based Scanning Transmission X-Ray Microscopy o Isotope Ratio Mass Spectrometry on Bulk Powders Supplementary Figures S2 to S6 Supplementary Table S2 Supplementary references NATURE GEOSCIENCE 1

2 Geological context Ujaraaluk unit The Nuvvuagittuq supracrustal belt (NSB) spans approximately 10 km 2 and is located in the Superior Province, on the Eastern shore of Hudson Bay, Canada (Supplementary Fig. S1). The belt has been isoclinally folded into a north plunging synform and subsequently refolded into an open south-plunging antiform. It is dominated by mafic rocks and surrounded by tonalite. The main lithology of the supracrustal rocks is a heterogeneous mafic gneiss called the Ujaraaluk unit (also known as the Faux-amphibolite). The Ujaraaluk unit is intruded by a series of mafic and ultramafic sills and also comprises chemical sediments. Rocks from the Ujaraaluk unit are generally composed of cummingtonite + plagioclase + biotite ± garnet with variable mineralogical proportions, but with compositions that range from basaltic to andesitic (O Neil et al, 2007). Locally, the Ujaraaluk rocks are composed of cordierite-anthophyllitebiotite and are interpreted to represent hydrothermallyaltered mafic volcanic rocks (O Neil et al., 2011). Their high Mg content combined with their low Ca levels and significant negative Eu anomalies point to hydrothermal alteration by seawater. The Supplementary Figure S1: Geological map of the Nuvvuagittuq Supracrustal Belt with the location of the samples studied in this work (modified from O Neil et al. 2007). 2

3 Ujaraaluk rocks also exhibit compositional layering that suggests a pyroclastic-type protolith and that has been divided into three geochemical groups, based on major and trace elements (O Neil et al., 2011). In sequence, these groups comprise rocks of tholeiitic affinity, followed by modern-day boninite-type rocks, and finally, volcanic rocks that share similarities with calcalkaline volcanic rocks, which collectively suggest the possibility that the Ujaraaluk unit represents a suprasubduction sequence (O Neil et al., 2011). Banded Iron Formations The chemical sediments of the NSB are dominated by banded iron formations (BIF) and massive quartzites that locally occur with carbonate. The BIF can be traced almost continuously along strike over a distance of 2 km (Supplementary Fig. S1). The BIF is generally 5 to 30 meters wide and composed of quartz + magnetite + grunerite ± actinolite with alternations of quartz-rich and magnetite-rich fine laminations. Both grunerite and actinolite have been locally replaced by minnesoatite during retrograde metamorphism (O Neil et al., 2007). On a post- Archean shale-normalized REE+Y diagram, the Nuvvuagittuq BIFs display a concave up LREEdepleted profiles with flat HREE and Eu and Y positive anomalies (O Neil et al., 2007). These profiles are similar to other Archean BIFs precipitated from seawater (Bolhar et al., 2004). The Nuvvuagittuq BIFs also have heavy Fe isotopic compositions compared to enclosing lithologies, consistent a marine exhalite origin (Dauphas et al., 2007; O Neil et al., 2007). Metamorphism The belt has been metamorphosed to the upper amphibolite facies conditions (O Neil et al., 2007; Cates & Mojzsis 2009), with the possible exception in the southwestern corner of the map area, where the mafic rocks are dominated by a typical greenschist facies mineral assemblage of chlorite + epidote + actinolite (O Neil et al., 2007). Similar rocks are exposed in the southeastern edge of the belt. These rocks contain relicts of garnet that have been completely retrograded to chlorite, which suggest that the greenschist facies rocks may represent a retrograde assemblage. The BIFs comprised in these greenstones contain red jaspillite and grade into the more typical quartz-grunerite-magnetite mineral assemblage as the metamorphic gradient appears to develop into higher temperature regimes, where the BIF is embedded in the Ujaraaluk unit. 3

4 Age Constraints The oldest U-Pb dates from the Nuvvuagittuq greenstone belt have been obtained in rare thin felsic bands (10-50 cm in width) tonalitic in composition. These felsic bands have yielded zircons with U-Pb ages of 3817 ± 16 (David et al., 2009) and >3750 Ma (Cates and Mojzsis, 2007). These ages are interpreted to be the crystallization age of the felsic bands. Although the exact nature of these felsic bands remains unclear, they appear to be intrusive (O Neil et al., 2011) and to cross-cut supracrustal lithologies (Cates and Mojzsis, 2007), thereby providing a minimum age for the NSB. Rocks from the Ujaraaluk unit have a 7 to 15 ppm deficit in 142 Nd compared to terrestrial standards (O Neil et al., 2008). A correlation between the Sm/Nd ratios and the 142 Nd isotopic composition of the Nuvvuagittuq mafic rocks yields a slope that corresponds to an age of Ma, which suggests a Hadean age (O Neil et al., 2008). These rocks however define a scattered 147 Sm- 143 Nd isochron with an age of 3,800 Ma, alternatively suggesting that they may be Eoarchean in age. However, the considerable scatter of data for this 3,800 Ma isochron may also be the result of the 147 Sm- 143 Nd system being partially reset by a younger thermal event in the Ujaraaluk unit. The 147 Sm- 143 Nd data for massive gneissic gabbro sills intruding the amphibolites gives an age of 4,023 ± 110 Ma with significantly less scatter, which supports an older age for the intruded mafic Ujaraaluk rocks (O Neil et al., 2008). Regardless of the exact age of the NSB, it can be concluded that it is at least Eoarchean in age. There are no field relationships that can suggest that the Nuvvuagittuq BIFs were tectonically juxtaposed in the NSB and they are interpreted to be as old as the mafic surrounding lithologies, i.e. >3,800 Ma and perhaps as old as 4,280 Ma. Methods Detailed descriptions of the analytical procedures used in this work were described in Papineau et al. (2010a). Here, only brief descriptions are given. Raman Spectroscopy Confocal laser Raman spectroscopy was performed with a WITec a-snom imaging system with a frequency-doubled solid-state YAG laser (λ = 532 nm) with 0-8 mw output power. Raman hyperspectral scans were performed at 1000X magnification with a 50µm diameter optic fiber and collected on a Peltier-cooled EMCCD detector. Spatial resolution was 4

5 around 360 nm and spectral resolution was around 2.5 cm -1. Individual spectra shown in this work represent averages of selected regions with similar spectral characteristics. Detailed descriptions of this method can be found elsewhere (Steele et al., 2007; Fries and Steele, 2008; Bernard et al., 2008; Papineau et al., 2010a). Raman hyperspectral analyses were performed more than 5 microns below the thin section surface, therefore ruling out any potential artifact induced by polishing. Raman spectra of poorly crystalline graphite were extracted from several confocal planes: at 5, 6, 6.5, 7, 7.5, and 8.5 µm below the thin section surface and the spectral parameter are shown below. Raman spectra of mineral associations between poorly crystalline graphite and cronstedtite were compared with spectra from the online database Modeling of Raman spectra was performed to confirm that the hematite band at 1320 cm -1 insignificantly contributed to the high intensity of the D-band at 1348 cm -1 of the associated graphite (Supplementary Fig. S6; see also Marshall et al., 2011), which had a higher D/G intensity ratio of 1.3 to 1.4 than the graphitic target from PC0815 (Fig. 2c-d). Supplementary Table S1: Raman spectral characteristics of graphitic carbon in the two targets investigated by correlated micro-analyses Sample Depth (µm) G-band position G-band FWHM D-band position D-band FWHM 2D-band position 2D-band FWHM D-band area G +D2 band area D/G (intensity) 2D/G (intensity) T estimate Beyssac L a (Å)* PC PC Area with intense 2D-band * Estimated using the calibration by Tunistra and Koenig (1970) Focused Ion Beam Milling Focused ion beam (FIB) extraction was performed using a FEI Nova 600 DualBeam FIB- SEM. Targets located by secondary electron were protected by a Pt strap deposited on the thin section surface. Once the FIB foil was milled and lifted-out of the thin section, further thinning of the sides was done until a thickness of ~100 nm was achieved. Detailed description of the FIB micro-fabrication procedure can be found elsewhere (Zega et al., 2007; Wirth, 2009; Papineau et al., 2010a). 5

6 Transmission Electron Microscopy Samples were analyzed using a JEOL 2200FS field-emission transmission electron microscope (TEM) at an operating voltage of 200 kev. Full EDS hyperspectral images were obtained with the 2200FS operated in scanning (STEM) mode with a nominal probe size of 0.7 nm in order to map the elemental composition of the sections. High-angle annular dark-field (HAADF) imaging was used to quickly distinguish graphite, apatite, and quartz domains due to the large differences in atomic mass contrast. Sections prepared by FIB milling were inserted directly into the TEM without a conductive coating (Papineau et al., 2010a). Synchrotron-based Scanning Transmission X-Ray Microscopy Synchrotron-based scanning transmission X-Ray microscopy (STXM) analyses were performed at the Advanced Light Source (ALS) on beamline (Kilcoyne et al., 2003). X- ray absorption near-edge structure (XANES) spectra of the C K-edge, N K-edge, and O K-edge were acquired on two FIB sections containing graphitic carbon associated with apatite. Beamline at the ALS, harvests soft X-rays generated via a bending magnet while the electron current in the storage ring was held constant in topoff mode at 500 ma at a storage ring energy of 1.9 GeV. Dispersive and non-dispersive exit slits were set at 25 mm. After sample insertion in the STXM, the chamber was evacuated to 100 mtorr and back-filled with He. The monochromatic X-ray beam is focused on the sample using a Fresnel zone plate objective and an order-sorting aperture yielding a focused X-ray beam spot of 30 to 40 nm. STXM data were acquired as hyperspectral images (or stacks) and line scans, from which XANES spectra of regions of interest may be extracted (Jacobsen et al., 2000). XANES optical density (OD) spectra are calculated by calibrating the transmitted intensity (I) of the sample to the background transmission (I 0 ) as OD = -ln(i/i 0 ) (Stöhr, 1992). Isotope Ratio Mass Spectrometry on Bulk Powders Fresh samples of NSB BIFs were cut into cubes of 5-10 grams with a diamond saw. Samples were then manipulated with nitrile gloves and rinsed three times in DI water, followed by an ultrasonication cleaning step in dichloromethane to minimize surface contamination. After another rinse with DI water and drying, bulk powders were generated with a ceramic mortar and pestle rinsed several times with DI water and cleaned at least twice with pure quartz chips 6

7 muffled at 600 o C for 4 hours. Total organic carbon analyses were performed with a CE Instruments NA 2500 series elemental analyzer (EA) linked to a ThermoFisher Delta V Plus IRMS through a Conflo III interface as previously described (Papineau et al., 2010b). To ensure that no organic contamination was present in the analytes (e.g. from sample preparation or the modern environment in northern Québec), analyses of unaltered powders were compared to analyses on separate aliquots of powders muffled in air at 600 o C for 2 hours, which removes such contaminants (Supplementary Table S2). No significant difference between unaltered and muffled powders was found in comparisons of carbon isotopes or contents. Powders were also acidified in ultra pure 6N HCl (Sequanal Grade, Pierce) to remove carbonate minerals. Typically around mg of powdered sample was weighed in Ag boats pre-muffled at 600 o C for 2 hours. Analyses of 1 to 6 µg of organic carbon from a compositionally similar standard (Peru mud; δ 13 C org = -20.2, TOC = 6.6%wt) gave a 1σ reproducibility better than ±0.2 (n = 41) for δ 13 C and ±13% (n = 32) for total organic carbon (TOC). Muffled Ag boat contained less than 0.06 µg of carbon, and typically less than the detection limit of around 0.04 µg. Carbonate carbon isotopes were measured on about mg of whole-rock powders with a Gas Bench connected to a ThermoFischer Delta XL IRMS, also in continuous flow. Bulk rock powders inserted in Exetainer vials were reacted with 99.9% pure phosphoric acid at 70 o C. Analyses of carbonate standards NBS 18, NBS 19, and two in-house calcite and dolomite standards gave 1σ reproducibilities better than ±0.1 for δ 13 C carb and ±0.3 for δ 18 O carb (n = 5). All carbonate isotope analyses are reported with respect to the PDB standard. 7

8 a) b) 5 µm 100 nm c) d) 5 nm e) 0.2 nm nm Supplementary Figure S2 a) Bright-field image of the graphitic region in the FIB foil showing context for HRTEM images. b) BF HRTEM image showing a portion of the cronstedtite envelope on graphite showing crystalline defects. c) BF HRTEM images of the graphite associated with apatite. d) HRTEM image of a part of the graphite band, e) Selected area electron diffraction pattern of a graphitic sub-region from this target.

9 e Top of th a) b) c) tion thin sec d) 200 nm e) f) 0.2 nm-1 Supplementary Figure S3 a) Bright-field image of the extracted FIB foil. b) STXM image at ev of a portion of the FIB foil. c) STXM image at ev of the graphitic particle. d) BF HRTEM image of the porous area of the FIB foil. e) EDS chemical maps of the graphitic area. f) SAED pattern of the poorly crystalline graphite.

10 Supplementary Figure S4 a) nm 1 b) nm Amorphous CM 1 c) nm Energy (kev)

11 5 4 3 d) nm Energy (kev) Supplementary Figure S4 Energy Dispersive Spectra of selected spots in the associated BF TEM image of FIB foils from samples a) PC0815 and b-d) PC0814. Some spots in the FIB foil from PC0815 contained Cu that re-deposited from the holding half-grid during micro-milling and laminae in the porous area of the FIB foil from PC0814 contained Ga, which came from the re-deposition of primary beam material during FIB micro-milling.

12 a) c) e) 10 µm d) b) 10 µm f) 10 µm 10 µm g) Supplementary Figure S5 a) Transmitted light images of late botryoidal goethite veins in sample PC0814. a-b) at 100X and c-f) at 1000X. g) Average Raman spectrum of the goethite in the shaded area of the square in e), which shows the location of Fig. 3g. Note that Raman analyses of these veins did not reveal any associated carbonaceous material.

13 Raman shift (cm -1 ) Supplementary Figure S6 Comparison of Raman spectra for hematite from a Neoarchean jaspilitic BIF from the Abitibi Supracrustal terrain (AB0708) and goethite from NSB BIF (PC0814) along with Raman spectra for graphite in NSB BIF samples PC0814 and PC0815 and in Akilia quartz-pyroxene rock sample G Linear combinations of these spectra are modeled for hematite plus graphite and for goethite plus graphite to show that the resulting spectra do not reproduce the same intense D-band and other features that were seen in the Raman spectra for graphite from PC0814, which was closely associated with botryoidal Fe-rich siliceous material, interpreted to be goethite.

14 Supplementary Table S2 Stable isotope compositions * of carbon in carbonaceous material and of carbon and oxygen in carbonate for fourteen BIF samples from the NSB. Multiple analyses on different aliquots are shown on different lines and their averages and standard deviations are shown in bold. Sample Name Raw powder Muffled powder Acidified powder Acidified muffled powder Carbonate GPS coordinates BIF type of sample δ 13 C TC (%wt) δ 13 C TC (%wt) δ 13 Ug C C TOC (%wt) δ 13 Ug C C TOC (%wt) δ 13 C ± 1σ δ 18 O ± 1σ analyzed analyzed PC0802 N58 o W77 o qtz+mag+amp BIF average st. dev PC0814 N58 o W77 o amp+mag+qtz BIF average st. dev PC0815 N58 o W77 o amp+mag+qtz BIF average st. dev PC0822 N58 o W77 o jsp+qtz+mag BIF average st. dev PC0823 N58 o W77 o jsp+qtz+mag BIF average st. dev PC0824 N58 o W77 o jsp+qtz+mag BIF average st. dev PC0825 N58 o W77 o amp+mag+qtz BIF average st. dev

15 Sample Name Raw powder Muffled powder Acidified powder Acidified muffled powder Carbonate GPS coordinates of sample µg C µg C BIF type δ 13 C TC (%wt) δ 13 C TC (%wt) δ 13 C TOC (%wt) analyzed δ 13 C TOC (%wt) analyzed δ 13 C ± 1σ δ 18 O ± 1σ PC0828 N58 o W77 o jsp+qtz+mag BIF average st. dev PC0832 N58 o W77 o amp+mag+qtz BIF average st. dev PC0833 N58 o W77 o amp+mag+qtz BIF average st. dev PC0838 N58 o W77 o qtz+mag+amp BIF average st. dev PC0844 N58 o W77 o jsp+qtz+mag BIF average st. dev PC0848 N58 o W77 o qtz+mag+amp BIF average st. dev PC0849 N58 o W77 o qtz+mag+amp BIF average st. dev * All δ-values are in and reproducibility on δ 13 C org is better than ±0.2, as determined from multiple analyses (n=41) of an in-house standard.

16 Supplementary references Bernard, S., Beyssac, O., and Benzerara, K. (2008) Raman mapping using advanced linescanning systems: geological applications. Applied Spectroscopy 62, Bolhar, R., Kamber, B.S., Moorbath, S., Fedo, C.M., Whitehouse, M.J. (2004) Characterisation of early Archaean chemical sediments by trace element signatures, Earth and Planetary Science Letters 222, Cates, N.L. and Mojzsis, S.J. (2007) Pre-3750 Ma supracrustal rocks from the Nuvvuagittuq supracrustal belt, northern Québec. Earth and Planetary Science Letters 255, Cates, N.L. and Mojzsis, S.J. (2009) Metamorphic zircon, trace elements and Neoarchean metamorphism in the ca Ga Nuvvuagittuq supracrustal belt, Québec (Canada), Chemical Geology 261, Dauphas, N., Cates, N.L., Mojzsis, S.J., and Busigny, V. (2007) Identification of chemical sedimentary protoliths using iron isotopes in the ~3760 Ma Nuvvuagittuq supracrustal belt, Canada. Earth and Planetary Science Letters 254, David, J., Godin, L., Stevenson, R., O Neil, J., and Francis, D. (2009) U-Pb ages ( Ga) and Nd isotope data from the newly identified Eoarchean Nuvvuagittuq supracrustal belt, Superior Craton, Canada. Geological Society of America Bulletin 121, Fries, M. and Steele, A. (2008) Graphite whiskers in CV3 meteorites. Science 320, Jacobsen, C., Wirick, S., Flynn, G.J., and Zimba, C. (2000) Soft X-ray spectroscopy from image sequences with sub-100 nm spatial resolution, Journal of Microscopy 197, Kilcoyne, A. L. D., Tyliszczak, T., Steele, W. F., Fakra, S., Hitchcock, P. Franck, K., Anderson, E., Harteneck, B., Rightor, E. G., Mitchell, G. E., Hitchcock, A. P., Yang, L., Warwick, T., and Ade, H. (2003) Interferometer controlled scanning transmission microscopes at the Advanced Light Source. Journal of Synchrotron Radiation 10, Marshall, C.P., Emry, J.R, Olcott, A. (2011) Haematite pseudomicrofossils present in the 3.5- billion-year-old Apex Chert. Nature Geoscience - Advanced Online Publication. O Neil, J., Maurice, C., Stevenson, R.K., Larocque, J., Cloquet, C., David, J., and Francis, D. (2007) The geology of the 3.8 Ga Nuvvuagittuq (Porpoise Cove) Greenstone Belt, Northeastern Superior Province, Canada, in Van Kranendonk, M.J., et al., eds. Developments in Precambrian Geology, Vol. 15: Earth s Oldest Rocks: Amsterdam, Elsevier, p

17 O Neil, J., Carlson, R.W., Francis, D., and Stevenson, R.K. (2008) Neodymium-142 evidence for Hadean mafic crust. Science 321, O'Neil, J., Francis, D., and Carlson, R.W. (2011, in press). Implications of the Nuvvuagittuq Greenstone Belt for the formation of Earth s early crust. Journal of Petrology. Papineau, D., DeGregorio, B.T., Cody, G.D., Fries, M.D., Mojzsis, S.J., Steele, A., Stroud, R.M., Fogel, M.L. (2010a) Ancient graphite in the Eoarchean quartz-pyroxene rocks from Akilia in southern West Greenland I: Petrographic and spectroscopic characteristics. Geochimica et Cosmochimica Acta 74, Papineau, D., DeGregorio, B.T., Stroud, R.M., Steele, A., Pecoits, E., Konhauser, K., Wang. J., Fogel, M.L. (2010b) Ancient graphite in the Eoarchean quartz-pyroxene rock from Akilia Island in southern West Greenland II: Isotopic and chemical compositions and comparison with younger BIFs. Geochimica et Cosmochimica Acta 74, Steele, A., Fries, M.D., Amundsen, H.E.F., Mysen, B.O., Fogel, M.L., Schweizer, M., and Boctor, N.Z. (2007) Comprehensive imaging and Raman spectroscopy of carbonate globules from Martian meteorite ALH and a terrestrial analogue from Svalbard. Meteoritics and Planetary Science 42, Stöhr, J. (1992) NEXAFS Spectroscopy. Springer, Berlin. 403p. Tuinstra, F., and Koenig, J.L. (1970) Raman spectrum of graphite. Journal of Chemical Physics 53, Wirth, R. (2009) Focused Ion Beam (FIB) combined with SEM and TEM: Advanced analytical tools for studies of chemical composition, microstructure and crystal structure in geomaterials on a nanometer scale. Chemical Geology 261, Zega, T.J., Nittler, L.R., Busemann, H., Hoppe, P., and Stroud, R.M. (2007) Coordinated isotopic and mineralogic analyses of planetary materials enabled by in situ lift-out with a focused ion beam scanning electron microscope. Meteoritics and Planetary Science 42,