Sample Preparation and Analytical Methods

In an early stage of the study in the year 2007, the “iron man” was neither in possession of, nor available to any of the authors. The owner provided the statue for geochemical analyses to a very limited degree (i.e., essentially nondestructive analysis). Accordingly, we had to use microsampling methods. Nevertheless, we managed to obtain some small samples for analysis of the elements, indicative for iron meteorites (e.g., Wasson et al. 1998) Fe, Ni, Cr, Ga, Ge (Table 1, columns #1–5), as well as the platinum group elements (PGEs; e.g., Kramar et al. 2001) Ir, Rh, Ru, Pd, and Pt (see Table 2, column #1).

Table 1. Concentrations of the crucial major, minor, and trace elements from the “iron man” fragments and the Chinga iron meteorite for comparison; column #1: data analyzed (EDX) at the Institut für Planetologie, Universität Stuttgart in 2007; columns #2–5: analyses (XRF) carried out at the Institut für Mineralogie und Geochemie, Universität Karlsruhe in 2007; columns #7–10: analyses (EPMA) carried out at the Department of Lithospheric Research, University of Vienna in 2009. Elements “Iron man” #12 Chinga #1 #2 #3 #4 #5 #6 (Average of #2–5) #7 #8 #9 #10 #11 (Average of #7–10) Fe (%) 84.98 85.02 84.98 84.99 84.99 84.99 83.50 83.49 83.33 83.33 83.41 83.1 Ni (%) 15.02 14.98 15.02 15.01 15.01 15.01 15.90 16.02 16.00 16.02 15.98 16.38 Co (%) – – – – – – 0.60 0.49 0.67 0.65 0.60 0.55 Cr (ppm) – 1830 – – – 1830 876 916 – – 896 810 Ga ppm) – 0.25 – – – 0.25 0.22 0.21 – – 0.22 0.181 Ge (ppm)* – 3.75 – – – 3.75 2.96 3.28 – – 3.12 0.082 Mo(ppm) – – – – – – 6.91 6.78 – – 6.85 7.42 Ag (ppm) – – – – – – 0.09 0.08 – – 0.09 – Cu (ppm) – – – – – – 14.1 14.0 – – 14.0 – P (ppm) – – – – – – 440.4 46.6 – – 443.5 – W (ppm) – – – – – – 0.58 0.65 – – 0.61 0.569 V (ppm) – – – – – – 7.88 8.33 – – 8.11 –

Table 2. Columns #1–3: platinum group element (PGE) contents of the “iron man”; column #1 analyzed from small splinters taken from the statue in the year 2007; columns #2 and #3: PGEs analyzed from bigger samples taken from the inner part of the statue (socket plate) in the year 2009. All analyses on PGEs (HR‐ICPMS) were carried out at the Institut für Mineralogie und Geochemie, Universität Karlsruhe. Column #4: PGE contents of the Chinga meteorite. The PGE contents of the Chinga iron meteorite (column #5) are compiled from , , , , and . Column #5: newer PGE data for the Chinga meteorite by . Platinum group elements #1 “Iron man” #2 “Iron man” #3 “Iron man” #4 Chinga #5 Chinga Ir (ppm) Ru (ppm) 3.31 ± 0.5 7.59 ± 0.7 3.31 ± 0.5 6.33 ± 0.7 3.31 ± 0.5 6.53 ± 0.7 3.60 6.10 4.13 7.86 Rh (ppm) 1.78 ± 0.1 1.75 ± 0.1 1.77 ± 0.1 2.00 2.464 Pt (ppm) 7.59 ± 0.5 7.99 ± 0.5 8.24 ± 0.5 11.00 9.56 Pd (ppm) 6.73 ± 0.2 6.51 ± 0.2 6.67 ± 0.2 9.00 7.89

For this first set of analyses, we took five samples (200–500 mg) extracted from the surface of the dorsal part of the sculpture by the use of a steel drilling bit. From these samples, a first analysis on major elements (iron and nickel; see Table 1, column #1) was carried out in the year 2007 by EDX method using a CamScan™ SC44 scanning electron microscope (SEM)—EDAX™ PV 9723/10 energy dispersive X‐Ray (EDX) system (Institut für Planetologie, Universität Stuttgart). A screening of major and minor elements (see Table 1, columns #2 to #5) was performed by nondestructive energy dispersive X‐ray fluorescence methods (XRF) on a 230 mg chip of the object at the Institut für Mineralogie und Geochemie, Universität Karlsruhe in 2007. The iron‐man samples were measured at a SPECTRACE 5000 X‐ray affiliation equipped with Rh tube operated at 50 kV/0.05 mÅ using a Pd primary beam filter to optimize the excitation of elements; further details of the procedure are explained by Kramar (1997). Except for Fe, Ni, and Cr, all elements analyzed are below the detection limits of approximately 10 μg g−1 in the Fe‐Ni‐rich main phase. Fe, Ni, and Cr were quantified by fundamental parameters. A first set of analyses on Cr, Ga, and Ge (see Table 1, column #2), as well as of the PGEs (see Table 2, column #1) were also performed at the Institut für Mineralogie und Geochemie, Universität Karlsruhe in 2007, using a High Resolution Inductively Coupled Plasma Mass Spectrometer (HR‐ICPMS) system (AXIOM from VG Elemental, UK). For PGE determinations, the whole chip was digested in 10 mL aqua regia and diluted to 50 ml. No preconcentration procedures for the PGEs were possible due to the small amount of sample material available. Element contents were calculated from the PGE isotopes 191Ir, 193Ir, 103Rh, 101Ru, 102Ru, 104Pd, 106Pd, 108Pd, 194Pt, 195Pt, and 196Pt. Detection limits mainly depend on blanks of the chemicals used and were estimated at 3 ppb for Ru, 40 ppb for Rh, 50 ppb for Pd, 4 ppb for Ir, and 300 ppb for Pt. The PGE concentrations were determined at a level of 30‐ to 3000‐fold the detection limit.

Since the year 2009, the statue has been in the possession of one of the authors and we were able to cut a plate (that was very lightly nital‐etched) from the socket of the statue in Vienna (for a picture of the socket plate, see Fig. 1); the slice of the socle is stored at the Naturhistorische Museum, Wien. The socket plate is approximately 1.5 cm thick and approximately 15 cm wide. We were now able to take more fresh samples from the inner part of the object. Two further analyses on the PGEs (Table 2, columns #2 and #3) were carried out on these fresher samples (each 320 mg in weight) in Karlsruhe in the year 2009. For analytical procedure, see description of PGE analyses in Karlsruhe in the text above.

Figure 1 Open in figure viewer PowerPoint A) Slice of the socle of the statue (very lightly natal‐etched, 15 cm in length); arrows mark position of inclusions and rust veins embedded in the structureless metallic groundmass that are depicted in the four photographs (B–E). B) Inclusion of daubreelite/Cr‐troilite intergrowth; troilite has 1–2 wt% Cr; black center is hole. C) Large spindle of daubreelite/Cr‐troilite intergrowth with curved lamellae. D) Detail of rare kamacite crystals (approximately 7 wt% Ni) in very fine‐grained metal matrix (approximately 15 wt% Ni). E) Rust vein with fragments of large daubreelite/Cr‐troilite intergrowths, partly brecciated, and a few Cr‐troilites and variable rust generations.

For internal control, we carried out further geochemical analyses of major and trace elements (Table 1, columns #6 to #10) at the Department of Lithospheric Research, University of Vienna in 2009, using a Cameca SX100 electron probe microanalyzer equipped with four WDS and one EDS. In addition, a high‐resolution inductively coupled mass spectrometer was utilized. Operating conditions for EPMA were 20 kV accelerating voltage and 10 nÅ beam current. A 5 μm defocused beam was used and the counting times at the peak position were 30 sec. Pure metals were used for calibration and the ZAF method for matrix correction procedures. The relative analytical error was below 5%. PGEs, Ga, and Ge data obtained are reported in Tables 1 and 2. In 2012, we carried out further analyses (EPMA) at the University of Vienna on the minerals kamacite, taenite, troilite, and daubreelite (Table 3) by using the equipment described above.

Table 3. Electron microprobe analyses of metal and sulfides from a slice of the socle of the “iron man”; standard deviation (in parentheses) in units of the last digit; n/a: not available; b/d: below detection limit. Minerals Kamacite Taenite Troilite Daubreelite Number of analyses n = 9 n = 8 n = 30 n = 26 Fe (wt%) 91.49 (44) 83.36 (44) 60.80 (21) 18.65 (24) Ni (wt%) 7.15 (22) 15.85 (20) 0.07 (03) b/d Co (wt%) 0.67 (05) 0.50 (02) b/d b/d Cr (wt%) 0.03 (01) 0.07 (02) 1.33 (12) 36.23 (21) V (wt%) b/d b/d 0.83 (09) 0.02 (01) S (wt%) n/a n/a 36.49 (24) 43.80 (24) Total (wt%) 99.34 99.79 99.52 98.70

We decided to rely mainly on the geochemical data achieved (at the Universities of Vienna and Karlsruhe) from the fresher samples from the inner part of the object taken in 2009 and to compare this data to the values of known iron meteorites mentioned in the literature. The material from the surface of the statue taken in 2007 and analyzed in Stuttgart and Karlsruhe might possibly be affected by weathering and/or forging.