MORPHOLOGY AND PHYSICO-CHEMICAL CHARACTERISTICS OF AN IRON FRAGMENT FROM CHACO PROVINCE I.A. BUCURICA1,2, C. RADULESCU1,3*, A.A. POINESCU4*, I.V.POPESCU1,3,5, I.D. DULAMA1, C.M. NICOLESCU1, S. TEODORESCU1, M. BUMBAC3, G. PEHOIU6*, O. MURARESCU6 1
2
3
Valahia University of Targoviste, Institute of Multidisciplinary Research for Science and Technology, 130004 Targoviste, Romania; E-mail:
[email protected]
University of Bucharest, Faculty of Physics, Doctoral School of Physics, 050107 Bucharest, Romania
Valahia University of Targoviste, Faculty of Sciences and Arts, 130004 Targoviste, Romania; E-mail:
[email protected] 4
Valahia University of Targoviste, Faculty of Materials Engineering and Mechanics, 130004 Targoviste, Romania; E-mail:
[email protected]
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Academy of Romanian Scientists, 050094 Bucharest, Romania; E-mail:
[email protected] 6
Valahia University of Targoviste, Faculty of Humanities, 130105 Targoviste, Romania; E-mail:
[email protected] *Corresponding authors:
[email protected];
[email protected];
[email protected]
Abstract. This study aims to demonstrate that the investigated sample is nickel-rich, a signature of the meteorites composed of iron, in order to establish if studied sample belongs or not to Campo del Cielo meteorite group. The discrete structure found in meteorites is a fingerprint fully justified by structural analysis using optical microscopy (OM) and scanning electron microscopy (SEM), X-ray diffraction (XRD), as well as by elemental content using energy dispersive spectrometry (EDS) and inductive coupled plasma mass spectrometry (ICP-MS). The presence of crystalline phase’s kamacite and taenite was confirmed, with a good correlation between experimental results and standard diffraction data (i.e. ICDD card numbers of minerals). Vickers hardness tests (HV 0.1 and HV 1.0) were achieved in accordance with STAS 492/1-85 and the average values (247 – 255.2 N/mm2) include the fragment into iron meteorite hardness category. The isotopic signature of kamacite (δ 56/54Fe=0.15‰ and δ62/60Ni=0.81‰) determined by ICP-MS, certify the origin of metallic fragment in Campo del Cielo meteoritic group. Key words: iron-nickel meteorite, optical microscopy, SEM-EDS, XRD, Vickers hardness, ICP-MS, isotope ratio.
1. INTRODUCTION Not once, the objects discovered near the meteorites craters, wrongly been considered fragments of meteorites. For that, many scientists from all over the world are contribute to reveal the authenticity of the outer space matter, found on Earth’s surface. As known, the meteorite is the last stage of a meteoroid transformation on its way to Earth. The meteoroid originates from the
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decomposition of asteroids / comets, as a result of which fragments of them enter the atmosphere of the Earth and, more often than not, they break down by burning. Passing through the atmosphere of the Earth leads to the appearance of a luminous effect called a meteor / shooting star. The meteoroid falled on Earth is called the meteorite. If meteoroids are large enough, the heating effects affect only the external portion, leaving the interior unaffected [1]. Meteorites can be classified into three main groups: irons (hardness 4-5 Mohs scale), stones (hardness 6 Mohs scale) and mixed meteorites (hardness 6-7 Mohs scale). From the mineralogical point of view, meteorites consist of different amounts of iron-nickel alloys, silicates, sulphides and other phases in small quantities [2]. Considering Wasson and Kallemeyn [3] evaluations, all the irons meteorites that contain graphite and carbides are member of IAB group complex, these irons commonly contain silicates, like those in group IIE, and were not formed by fractional cristallization in metalic cores of asteroids, but in localized metallic pools by processes that are still poorly understood [4, 5]. Depending on the percentage of nickel in iron, these subdivisions are classified into: hexahedrites ( 17% Ni). Octaedrites are the most common type of iron meteorite showing unique structure, called the Widmanstatten structure. This unique structure is the result of the combination of kamacite and taenite present in approximately equal amounts [6]. Obviously, the recognizing of meteorite is not easy at all, many of them being quite often confused with terrestrial rocks. As a distinctive sign for most of the meteorites is the melting crust. It usually has a dark or dark gray color, differing from the shading surfaces, colored lighter (usually gray), also, in the structure of the crust can be observed mainly the traces of the action of atmospheric currents. But there are meteorites where crust is transparent or rusty. In this study a metallic object, supposed to be a meteorite fragment from New Campo del Cielo group (Argentina), was investigated from the physico-chemical point of view. By deduction, this fragment was marked as possible part of the ironbased meteor group, discovered in the provinces of Chaco and Santiago del Estero since 1576. The Campo del Cielo meteorites are considered to be a silicate-bearing iron type which has been classified as belonging to the IAB Main Group [3]. Most of the Campo del Cielo samples are dominantly FeNi metal (bulk composition 6.68% Ni), and approximately 10% are silicate-rich [7]. These silicate-rich samples are mainly characterized by silicate clasts contained within metal, and a small proportion is dominated by silicate material with networks of metal veins. The silicate material in these samples is C- and S-enriched [7]. In the meteorological catalog of the Natural History Museum in London (UK), these discovered fragments are classified as belonging to coarse octaedrites category [3, 8, 9]. In this respect, several complementary techniques have been used and the obtained results were compared with the scientific literature [10-16], but also with the catalogs of the International Society for Meteorics and Planetary Science [9].
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2. MATERIALS AND METHODS 2.1 Materials and sample preparation The dark-grey solid fragment presented in Figure 1 have a weight of 7.3 g and a melted non-uniform structure and is supposed to be some kind of out of space object. This item has no authenticity certificate and was received from an anonymous collector. From the owner testimonial it is know the fact that originates from South America, more precisely, near Chaco province in Argentina.
Figure 1 - Metallic object suppose to be a meteorit fragment from New Campo del Cielo group (Argentina).
All chemical reagents were of analytical grade. Distilled deionized water (Milli-Q Water System Millipore), hydrochloric acid (37%, Merck) and nitric acid (high purity, Merck) were used for digestion process, as well for blank preparation. For hardness tests, Optical Microscopy (OM) and Scanning Electron Microscopy coupled with Energy Dispersive Spectrometry (SEM-EDS), the sample was polished with sand paper (different granulometry) and diamond paste, and etched with 2% Nital solution (2% nitric acid in methanol). In the end, the sample was cleaned with distilled ionized water and dry with high pressure nitrogen flux (2 atm). For the XRD analysis, a piece weighing 2.06 g, overall dimensions of 14 x 11 x 3 mm, and having two distinct sides was provided. Visual examination showed a metallic appearance, without sandy or stony insertions. One side had a specific cut and treatment of an optical investigation that was previously performed, to search for corresponding characteristics such as Widmanstätten pattern etc. The second side had no treatment. This untreated side was considered to belong to the outer side of the parent meteorite body, when this was reaching the atmosphere and broke into pieces. For ICP-MS analysis, the sample (i.e. 50 mg) was digested with 3 mL HNO3 and 9 mL HCl on a hot plate by using a TOPwave Microwave-assisted pressure system (Analytik Jena). After digestion process, the PTFE-TFM vessel with sample was cooled for one hour, and then the solution was transferred with distilled water
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to 100 mL volumetric flasks. Finally, the clear solution sample was analyzed by ICP-MS. For this stage, ultra-pure argon (99.999% pure) was used as cooling, auxiliary, and nebulizer gas. 2.2 Calibration standards Solutions for quantitative measurements were prepared using Certipur® Certified Reference Material ICP multi-element standard IV (~1000 mg/L in 6.5% HNO3, Merck) in 5% HNO3 without further purification. The standard multielement solution contain: Ag (1011 mg/L), Al (999 mg/L), B (990 mg/L), Ba (1009 mg/L), Bi (1000 mg/L), Ca (995 mg/L), Cd (999 mg/L), Co (998 mg/L), Cr (999 mg/L), Cu (998 mg/L), Fe (999 mg/L), Ga (997 mg/L), In (998 mg/L), K (1003 mg/L), Li (999 mg/L), Mg (1001 mg/L), Mn (1001 mg/L), Na (1003 mg/L), Ni (999 mg/L), Pb (1001 mg/L), Sr (998 mg/L), Tl (1002 mg/L), and Zn (999 mg/L). 2.3 Analytical techniques Optical Microscopy Stemi 2000-C and Axio Imager M2m microscopes by Zeiss’s were used for optical investigations due to different approach of the study. On first stage, the stereo microscope Stemi 2000-C, designated for high volume samples that require variable working distance was used at 40x magnification range. Also, this microscope, through its attached Axiocam 105 digital video camera (5 megapixel HD), allowed real-time image acquisition. After preliminary information were obtained, Axio Imager M2m and its capabilities was considered to be more suited for reaching even closer to the surface, so, by using AxioCam ICc5 and 50x EC Epiplan-NEOFLUAR objective, were performed new series of optical analysis for more accurate surface images. In both cases, the microscopes have used reflected light setup. Scanning Electron Microscopy coupled with Energy Dispersive Spectrometry Scanning Electron Microscopy (SEM) investigations were carried out using a Hitachi SU-70 field-emission microscope. Secondary electrons (SE) images were acquired in high-vacuum mode with an accelerating voltage of 25 kV and a working distance of 16.3 mm. Energy Dispersive Spectrometry (EDS) was performed using an UltraDry spectrometer (Thermo Scientific) coupled on SEM column. This equipment allows qualitative and quantitative analysis from 4Be to 94Pu and also, by NSS software, the elemental distribution maps have been recorded. The EDS data were achieved using the same work parameters as SEM. X-ray Diffraction Several researchers successfully used X-ray Diffraction (XRD) as an effective tool for microstructure analysis of meteorites [17, 18]. This technique was used as a non-destructive analysis, to provide information related to presence and structural characteristics of mineral crystalline phases in investigated sample. The sample was analyzed by scanning the both sides, previously described. The corresponding X-ray patterns were recorded using the parallel beam geometry; sample was mounted in the standard attachment device of a Rigaku Ultima IV
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diffractometer, and the monochromatized Cu Kα radiation (λ = 1.54056 Å) was obtained from a fixed anode X-ray tube operated at 40 kV and 20 mA. Diffractograms were recorded for the 2-theta range of 3-155 degrees; the appropriate setup was chosen to be: continuous scan mode, 1 degree/minute speed, 0.02 degrees step width. Data processing for the microstructure analysis was performed by using functionalities of the software PDXL v. 2.2 and International Centre for Diffraction Data (ICDD) data base PDF4+ v. 2016. The XRD graphical representations included in this work show only the 2-theta range with visible peaks. Also, one pattern was plotted as the recorded lines were similar for the two sample sides. Vickers Hardness test The Vickers hardness testing for solid sample was performed using fully automatic tester Duramin-100 by Struers, USA. The tester uses a diamond pyramid with square base as a penetrator tool. Since the diamond has the highest hardness of all materials used in the industry, the method can be applied without limits to determine the hardness. In particular, it is recommended to determine the hardness of materials with a probability of more than 300 daN / mm2. The method consists in pressing a penetrator at a reduced speed and with a predetermined force F on the surface of the material to be tested. The Vickers hardness, symbolized by HV, is expressed by the ratio of the applied force F to the area of the lateral surface of the residual traces produced by the penetrator. The trace is considered as a right pyramid with a square base, with diagonal d, having the same angle as the penetrator at the top. The Vickers hardness is determined by equation 1 [19]:
HV F / S
(1)
Expressing the S surface of the penetration tracer, depending on the diagonal d, it was obtained the Vickers hardness computation relation 2 [19]:
F 1.8544 F d2 HV 136 d2 2sin 2
(2)
Inductively Coupled Plasma Mass Spectrometry Inductively Coupled Plasma Mass Spectrometry (ICP-MS) analyses were performed using a quadrupole spectrometer iCAP Qc (Thermo Fisher Scientific). The typical instrumental and data acquisition parameters are shown in Table 1. Table 1 Instrumental and data acquisition parameters of ICP-MS Parameter Plasma RF power Nebulizer Ar flow Cooling Ar flow Auxiliary Ar flow Sample uptake rate
Value / status 1500-1600 W 1 L/min 13 L/min 1 L/min 0.4 mL/min
Parameter Uptake time Washout time Number of main runs Peristaltic pump speed Measuring mode
Value / status 70 s 70 s 5 60 rpm Standard
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The ICP-MS determinations were achieved in standard mode using calibration curve method. After calibration, five blank samples were measured in order to calculate the limit of detection (LOD) and the limit of quantification (LOQ) using the following equations (3 –5):
x x n
s
i 1
2
i
(3)
n 1
xLOD x blanck 3 sblanck
(4)
xLOQ xblanck 10 sblanck
(5)
where: s represents the standard deviation; xi represents the measured value; x represents the mean value; n represents the number of measurements; xLOD represents the limit of detection; xLOQ represents the limit of quantification. The obtained values for xLOD and xLOQ are presented in Table 2. Table 2 The xLOD and xLOQ values for Al, Cr, Mn, Fe, Ni, Cu, and Zn.
x1 x2 x3 x4 x5 x
s xLOD xLOQ
Al [μg/L] 16.335 16.002 16.132 15.982 16.222 16.135 0.149 16.581 17.624
Cr [μg/L] 1.078 1.302 1.222 1.301 1.228 1.226 0.091 1.500 2.139
Mn [μg/L] 0.464 0.433 0.452 0.449 0.455 0.451 0.011 0.485 0.564
Fe [μg/L] 4.152 3.884 3.926 3.879 4.005 3.969 0.114 4.311 5.109
Ni [μg/L] 0.708 0.689 0.712 0.701 0.692 0.700 0.010 0.730 0.800
Cu [μg/L] 1.085 1.009 1.102 1.099 1.100 1.079 0.040 1.198 1.476
Zn [μg/L] 8.692 8.832 8.771 8.696 8.705 8.739 0.061 8.922 9.349
RESULTS AND DISCUSSION For optical analysis, two microscopes were chosen for this study and the recorded images are shown in Figure 2. From the first images (Figure 2 a - c), several granular irregularities of the structures were observed on the sample surface. At first glance, they appear to be the result of some sort of mechanical removal of the material, but after more in-depth investigations (Figure 2 d - f ), these structures can be rather categorized as a result of a complex conglomerate of oxidized metallic materials.
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a
b
c
d
e
f
Figure 2 - Optical microscopy images: a – c Magnification range 40X (microscope Stemi 2000C); d – f Magnification range 500X (microscope Axio Imager M2m).
The areas of interest (AOI) were marked to be investigated by complex physico-chemical methods. One of the methods which can be real helpfully in determining the structure and chemical composition is SEM microscopy coupled with EDS. In this way, a deeper morphological identification of the surface can be made (Figure 3) and also a representation in the form of a distribution map of the contained elements could be achieved (Figure 4).
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a
b
c
d
e
f
Figure 3 - SEM images of the investigated areas
Figures 3a and 4a shows different inclusions of iron-nickel alloy (ratio 40: 5), known as taenite (Nabawy and Rochette, 2016, Evans et al., 2017, Schluter et al., 2002), delimited outside the area of interest by a contour predominantly based on phosphorus, chlorine and oxygen. The inclusions (Figures 3b and 4b) are represented in the form of flat, irregularly shaped structures, delimitated by iron oxides.
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a
b
c
d
e
10
f
Figure 4 - Elemental distribution maps obtained on investigated areas
The contour (Figures 3c and 4c) with alloy-like composition generally called rhabdite [10, 11], presents a compact and uniform structure, crossed by transverse microsheets. In a similar note to the previously discussed images, a number of uneven clusters near the outline (Figures 3d and 4d) were noted based on high iron and silicon content (iron silicate) [12]. The SEM-EDS data presented in Figures 3e and 4e have shown that the base matrix consists of large kamacite granules (iron-nickel alloy 90:10) [10, 11, 13] contoured by several thinner parallel lines – about 1 μm thick. This type of structure was found on the entire surface of the sample, the geometry of the forms pointed out being random. The small exceptions to the uniform structure of the sample are represented by the porous granular structures shown in Figures 3f and 4f. This highlights that the sample surface was mechanically removed or oxidized, as the chemical composition is similar to that of the taenite [14-16]. Table 3 presents the values for the major and minority constituents of the regions of interest as well as their calculated averages. These values represent the mirror of the elemental distribution maps obtained through SEM-EDS (Figure 4). Microstructural analysis was performed in this study by X-ray diffraction technique. The presence of several mineral crystalline phases was confirmed in the studied sample. It is generally accepted that sample material availability may be a critical aspect in meteorite analysis, the amount being usually limited. Figure 5 shows the XRD pattern recorded for the investigated sample. It may be observed that recorded peaks are rather sharp, suggesting a crystalline character. The slight broadening of some peaks may be attributed to low dimensions of the crystallites. From a taxonomic perspective, iron meteorites were classified in relation with their structure in three major categories: hexahedrites, ataxites and octahedrites. More complex classifications were also proposed, their chemical composition in elements likes Ni, Ga, Ge and others were used to group these meteorites, and to interpret the data in terms of a genetic classification scheme. Scott and Watson proposed a classification in 12 genetic groups, by considering their structural and compositional properties.
Table 3 Elemental content (wt.% ± error%) of investigated areas. Element [wt. %] C O Na Al Si P S Cl K Ca Fe Ni
Scanned area a 7.65±0.09 4.53±0.07 ni/nd 0.45±0.01 0.07±0.01 1.73±0.02 ni/nd 0.45±0.01 0.04±0.01 0.03±0.01 76.56±0.14 8.49±0.07
b 5.63±0.16 6.98±0.12 ni/nd 0.26±0.03 ni/nd 10.79±0.08 ni/nd 0.66±0.02 ni/nd ni/nd 50.28±0.14 25.40±0.14
c 3.06±0.12 34.30±0.19 ni/nd 0.31±0.01 0.09±0.01 0.12±0.01 ni/nd 4.30±0.03 ni/nd ni/nd 56.32±0.14 1.50±0.07
d 39.44±0.20 33.23±0.44 0.54±0.02 0.80±0.02 7.74±0.03 0.03±0.01 0.16±0.01 0.07±0.01 0.09±0.01 0.31±0.01 9.35±0.04 ni/nd
e 3.24±0.07 ni/nd ni/nd 0.61±0.02 0.08±0.01 0.10±0.01 ni/nd ni/nd ni/nd ni/nd 89.73±0.18 6.24±0.09
f 12.14±0.13 32.87±0.22 0.23±0.03 0.33±0.02 0.72±0.02 0.16±0.01 0.03±0.01 4.02±0.02 0.09±0.01 0.95±0.01 41.88±0.10 4.65±0.06
Mean value 11.86±0.13 17.49±0.17 0.13±0.01 0.46±0.02 1.45±0.01 2.16±0.02 0.03±0.01 1.58±0.02 0.04±0.01 0.22±0.01 54.02±0.24 7.71±0.07
Figure 5 - The X-ray pattern recorded for the investigated sample.
The main minerals contained by iron meteorites are kamacite and taenite, both corresponding to Fe-Ni alloys: the first being nickel-poor with body-centeredcubic structure [BCC, α-(Fe, Ni)] and the second being nickel-rich with facecentered-cubic structure [FCC, γ-(Fe, Ni)]. While the hexahedrites are usually kamacite only and most of the ataxites are purely taenite, the octahedrites, the most widespread category of iron meteorites, contain both kamacite and taenite, showing a structural peculiar feature named octahedral Widmanstätten pattern. This is a characteristic arrangement of the interlocking crystals of these two mineral phases, and is generally accepted that the kamacite phase, occurring as elongated plates or lamellae, is generated by a solid-state phase transformation at the taenite/taenite boundary when the material is slowly cooled down [1, 4]. Other minerals like schreibersite (an iron nickel phosphide), cohenite iron-nickel-cobalt carbide), and troilite (an iron sulphide), may also be present in iron meteorites. Considering the above mentioned information, diffractogram obtained for the sample identified the presence of the phases kamacite (ICDD-pdf card no. 00-0370474), taenite (ICDD-pdf card no. 04-008-8475), and tetrataenite (ICDD-pdf card no. 01-083-3765). Lower peaks for schreibersite (ICDD-pdf card no. 04-0042129), cohenite (ICDD-pdf card no. 00-034-0001), and troilite (ICDD-pdf card no. 00-037-0477) were also observed. Identified phases were marked in Figure 5, near the visible peaks. According to recorded peaks, presence of taenite and kamacite phases was confirmed, with a good agreement between calculated lattice parameters and the standard diffraction data. For instance, for the peak recorded at 2θ of 44.54 ̊ ± 0.52, the calculated interplanar spacing (d) in the crystalline structure of sample was 2.0324 Å, and the ICDD data for taenite with Miller indices (1,1,1) are 43.5691 ̊
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(2θ) and 2.0755 Å (d), and for kamacite (1,1,0) the ICDD data are 44.6454 ̊ (2θ) and 2.0280 Å (d). Other crystalline phases like schreibersite and tetrataenite may be also present in the sample; however their diffraction patterns were barely detectable. This may be due to lower amounts of these phases relative to kamacite and taenite. For Vickers tests were used diamond penetrators with identical peak angles also identical geometric traces were obtained regarding the test force, and as a result, it can be said that the hardness is independent of the size of the load. In accordance with STAS 492/1-85, the Vickers hardness tests with low loads, HV1.0 and Vickers hardness tests with microarrays HV0.1 (Table 4) were used. Table 4 Vickers hardness tests.
Test 1
Distance 0.25 0.50 0.75 Mean
Vickers hardness value [N/mm2] 267 229 245 247
Vickers method
Diagonal
HV 0.1 HV 0.1 HV 0.1
0.03 0.03 0.03
HV 1 HV 1 HV 1 HV 1 HV 1
0.09 0.09 0.08 0.08 0.09
Test 2
0.25 0.50 0.75 1.00 1.25 Mean
254 249 261 262 250 255.2
By ICP-MS measurements were identified and quantified the main isotopes of iron and nickel; Table 5 shows the calculated isotopic ratios for: 54Fe/56Fe, 57 Fe/56Fe, 58Fe/56Fe, 60Ni/58Ni, 61Ni/58Ni, 62Ni/58Ni, and 64Ni/58Ni. According with the scientific literature [20], standard materials NIST SRM986 and IRMM014 were
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used as internal standard. The δ56/54Fe and δ62/60Ni were calculated by following equations (6)-(7) [20, 21]:
56 Fe / 54 Fe sample x1000 Fe 56 1 Fe / 54 Fe IRMM 014
(5)
62 Ni / 60 Ni sample x1000 Ni 62 1 Ni / 60 Ni NIST SRM 986
(6)
56 / 54
62 / 60
Table 5 Isotopic ratios of sample determined by ICP-MS. Isotopic ratio 54 Fe / 56Fe 57 Fe / 56Fe 58 Fe / 56Fe 60 Ni / 58Ni 61 Ni / 58Ni 62 Ni / 58Ni 64 Ni / 58Ni
Value 0.055 0.104 0.001 0.324 0.012 0.081 0.004
The results (δ56/54Fe=0.15‰ and δ62/60Ni=0.81‰) complement the XRD analysis which reveal that kamacite [20] represents the main component of the sample and conclude the investigation by confirming that fragment is indeed an iron meteorite. Furthermore, comparing these results with other study [21] it can be assumed that the iron meteorite could belong to Campo del Cielo meteorites group. CONCLUSIONS
The hypothesis regarding the possibility that this metallic fragment could be a melted matter fell from out of space was investigated using different physico-chemical methods. The information regarding the true origin of the sample was poor and has not offered enough reasons to be considered a real meteorite fragment. It is known the fact that originates from Argentina, near to the borders of Santiago del Estero and Chaco provinces though which is been for some time one of the most known areas from South America in the matter of meteorites. In many cases the studied fragments are proved to be not more than some kind of molded metals from forging factories or Earth crust. Although, after completing all the aspects of proposed investigations and reaching to some final arguments it can be summarize that is very important to characterize an object from different points of view in order to obtain the big picture as much as close to reality. For this matter, in this particularly study were chosen five complementary techniques as follow: Optical Microscopy for
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preliminary imagistic information, Scanning Electron Microscopy for advanced imagistic and morphology, Energy Diffraction Spectrometry for elemental composition, X-ray diffractometry for crystalline phase determination and not at last a Vickers Hardness testing. It was highlighted the presence of inclusions on the sample surface, the elements which are defining the chemical structure in accordance with IAB meteorite group classification. Through the X-ray diffraction technique, presence of crystalline phase’s kamacite and taenite was confirmed, with a good correlation between experimental and standard diffraction data for ICDD card numbers of these minerals. The hardness test was pointing that the solid fragment belongs to iron meteorite classification (hardness: 4-5 Mohs scale ~ 247 – 255.2 N/mm2 on Vickers’s scale). Since not all information could still certify the origin, ICP-MS analysis and isotopic ratios, along with scientific references add important correlations regarding the true origin of the sample. So, if at beginning of this study, were some doubts referring to the nature of the metallic fragment, in the end, after using different analytical techniques it can be stated that sample probably belongs to the Campo del Cielo iron meteorite group, fallen in Chaco and Santiago del Estero provinces. Acknowledgement: This work was supported by the project entitled Health risk assessment associated with abandoned copper and uranium mine tailings from Banat Region, Romania, according with Protocol no. 4748-4-2018/2019, bilateral project of Joint Institute for Nuclear Research and Valahia University of Targoviste, on theme 03-4-1128-2017/2019. REFERENCES [1] F. Grazzi, A. Scherillo, V. Moggi-Cecchi, M. Morelli, G. Pratesi, S., Caporali, Minerals 8, Article no. 19 (2018). [2] G.F. Vander Voort, Adv. Mat. Proces. 159(2), 37 – 41 (2001). [3] J.T. Wasson, G.W. Kallemeyn, Geochim. Cosmochim. Acta 66, 2445 – 2473 (2002). [4] J.I. Goldstein, E.R.D. Scott, N.L. Chabot, Chem. Erde. 69, 293 – 325 (2009). [5] J.I. Goldstein, J. Yang, P.G. Kotula, J.R. Michael, E.R.D. Scott, Meteorit. Planet. Sci. 44(3), 343 – 358 (2009). [6] R.J. Harrison, J.F.J. Bryson, C.I.O. Nichols, B. Weiss, Magnetic mineralogy of meteoritic metal: Paleomagnetic evidence for dynamo activity on differentiated planetesimals. In: L.T. Elkins-Tanton, B.P. Weiss (Eds), Planetesimals: Early differentiation and consequences for planets, Cambridge University Press, Cambridge, 2017, pp. 204-223. [7] A.G. Tomkins, E.R. Mare, M. Raveggi, Geochim. Cosmochim. Acta 117, 80 – 98 (2013). [8] Natural History Museum, The Catalogue of Meteorites, available online http://www.nhm.ac.uk/our-science/data/metcat/, last accessed 4th July 2018. [9] The Meteoritical Society, Meteoritical Bulletin Database, available online https://www.lpi.usra.edu/meteor/, last accessed 4th July 2018. [10] E.D. Cabanillas, T.A. Palacios, Microsc. Microanal. 9(S2), 632 – 633 (2003). [11] E.D. Cabanillas, T.A. Palacios, Planet. Space Sci. 54(3), 303 – 309 (2006). [12] A. Ruzicka, Chem. Erde. 74(1), 3 – 48 (2014).
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[13] E. Berkey, D.E. Fisher, Geochim. Cosmochim. Acta 31(10), 1543 – 1558 (1967). [14] B.S. Nabawy, P. Rochette, Acta Geophys. 64(5), 1942 – 1969 (2016). [15] W.T. Evans, K.E. Neely, A.M. Strauss, G.E. Cook, Acta Astronaut. 140, 452 – 458 (2017). [16] J. Schluter, L. Schultz, F. Thiedig, B.O. Al-Mahdi, A.E. Abu Aghreb, Meteorit. Planet. Sci. 37(8), 1079 – 1093 (2002). [17] T.L. Dunn, G. Cressey, H.Y. McSween Jr., T.J. McCoy, Meteorit. Planet. Sci. 45(1), 123 – 134 (2010). [18] F.R.D. De Andrade, L.A. Polo, V.A. Janasi, F.M.S. Carvalho, J. Volcanol. Geotherm. Res. 355, 219 – 231 (2018). [19] B. Guo, L. Zhang, L. Cao, T. Zhang, F. Jiang, L. Yan, J. Mater. Process. Technol. 255, 426 – 433 (2018). [20] S.M. Chernonozhkin, M. Weyrauch, S. Goderis, M. Oeser, S.J. McKibbin, I. Horn, L. Hecht, S. Weyer, P. Clays, F. Vanhaecke, Geochim. Cosmochim. Acta 217, 95 – 111 (2017). [21] S.M. Chernonozhkin, S. Goderis, M. Costas-Rodrigues, P. Clays, F. Vanhaecke, Geochim. Cosmochim. Acta 186, 168 – 188 (2016).
