Diablo Meteorite Research Articles

Excellent mechanical properties of taenite in meteoric iron

Meteoric iron is the metal that humans first obtained and used in the earliest stage of metal culture. Advances in metallographic analysis techniques have revealed that meteoric iron largely comprises kamacite, taenite, and cohenite, which correspond to ferrite, austenite, and cementite in artificial steel, respectively. Although the mechanical properties of meteoric irons were measured previously to understand their origin and history, the genuine mechanical properties of meteoric iron remain unknown because of its complex microstructure and the pre-existing cracks in cohenite. Using micro-tensile tests to analyse the single-crystalline constituents of the Canyon Diablo meteorite, herein, we show that the taenite matrix exhibits excellent balance between yield strength and ductility superior to that of the kamacite matrix. We found that taenite is rich in nitrogen despite containing a large amount of nickel, which decreases the nitrogen solubility, suggesting that solid-solution strengthening via nitrogen is highly effective for the Fe–Ni system. Our findings not only provide insights for developing advanced high-strength steel but also help understand the mysterious relationship between nitrogen and nickel contents in steel. Like ancient peoples believed that meteoric iron was a gift from the heavens, the findings herein imply that this thought continues even now.

Response to the presentation of the Service Award of the Meteoritical Society

Response to the presentation of the Service Award of the Meteoritical Society

Reply to the comment by Andronicos et al. (2017) on “Composition and origin of holotype Al‐Cu‐Zn minerals in relation to quasicrystals in the Khatyrka meteorite” by Ivanova et al. (2017)

Reply to the comment by Andronicos et al. (2017) on “Composition and origin of holotype Al‐Cu‐Zn minerals in relation to quasicrystals in the Khatyrka meteorite” by Ivanova et al. (2017)

Nanocrystalline hexagonal diamond formed from glassy carbon.

Carbon exhibits a large number of allotropes and its phase behaviour is still subject to significant uncertainty and intensive research. The hexagonal form of diamond, also known as lonsdaleite, was discovered in the Canyon Diablo meteorite where its formation was attributed to the extreme conditions experienced during the impact. However, it has recently been claimed that lonsdaleite does not exist as a well-defined material but is instead defective cubic diamond formed under high pressure and high temperature conditions. Here we report the synthesis of almost pure lonsdaleite in a diamond anvil cell at 100 GPa and 400 °C. The nanocrystalline material was recovered at ambient and analysed using diffraction and high resolution electron microscopy. We propose that the transformation is the result of intense radial plastic flow under compression in the diamond anvil cell, which lowers the energy barrier by “locking in” favourable stackings of graphene sheets. This strain induced transformation of the graphitic planes of the precursor to hexagonal diamond is supported by first principles calculations of transformation pathways and explains why the new phase is found in an annular region. Our findings establish that high purity lonsdaleite is readily formed under strain and hence does not require meteoritic impacts.

The Canyon Diablo impact event: 2. Projectile fate and target melting upon impact

Abstract– Despite its centennial exploration history, there are still unresolved questions about Meteor Crater, the first recognized impact crater on Earth. This theoretical study addresses some of these questions by comparing model results with field and laboratory studies of Meteor Crater. Our results indicate that Meteor Crater was formed by a high‐velocity impact of a fragmented projectile, ruling out a highly dispersed swarm as well as a very low impact velocity. Projectile fragmentation caused many fragments to fall separately from the main body of the impactor, making up the bulk of the Canyon Diablo meteorites; most of these fragments were engulfed in the expansion plume as they approached the surface without suffering high shock compression, and were redistributed randomly around the crater. Thus, the distribution of Canyon Diablo meteorites is not representative of projectile trajectory, as is usual for impactor fragments in smaller strewn fields. At least 50% of the main impactor was ejected from the crater during crater excavation and was dispersed mostly downrange of the crater as molten particles (spheroids) and highly shocked solid fragments (shrapnel). When compared with the known distribution, model results suggest an impactor from the SW. Overall, every model case produced much higher amounts of pure projectile material than observed. The projectile‐target mixing was not considered in the models; however, this process could be the main sink of projectile melt, as all analyzed melt particles have high concentrations of projectile material. The fate of the solid projectile fragments is still not completely resolved. Model results suggest that the depth of melting in the target can reach the Coconino sandstone formation. However, most of the ejected melt originates from 30–40 m depth and, thus, is limited to Moenkopi and upper Kaibab material. Some melt remains in the target; based on the estimated volume of the breccia lens at Meteor Crater, our models suggest at most a 2% content of melt in the breccia. Finally, a high water table at the time of impact could have aided strong dispersion of target and projectile melt.

Sulfur isotopic composition of Fe‐Ni sulfide grains in CI and CM carbonaceous chondrites

Abstract– In situ secondary ion mass spectrometry analyses of 32S, 33S, and 34S in iron‐nickel sulfide grains in two CI1 chondrites and six CM chondrites were performed. The results show a wider range of both enrichment and depletion in δ34S relative to troilite from the Canyon Diablo meteorite (CDT) than has been observed in previous studies. All data points lie within error of a single mass dependent fractionation line. Sulfides from CI1 chondrites show δ34SCDT from −0.7 to 6.8‰, while sulfide grains in the CM1 chondrite are generally depleted in heavy sulfur relative to CDT (δ34S from −2.9 to 1.8‰). CM2 chondrites contain sulfide grains that show enrichment and depletion in 34S (δ34SCDT from −7.0 to 6.8‰). Sulfates forming from sulfide grains during aqueous alteration on the chondrite parent body are suggested to concentrate light sulfur, leaving the remaining sulfide grains enriched in the heavy isotopes of sulfur. The average degree of enrichment in 34S in CM chondrite sulfides is broadly consistent with previously suggested alteration sequences.

Using sulfur isotopes to determine the sources of vermillion in ancient burial mounds in Japan

AbstractThis study represents an attempt to determine the sources of vermillion found in ancient Japanese burial mounds of the 1st–6th centuries A.D., by comparing their ratios of sulfur isotopes with those of cinnabar ore samples collected in Japan and China. Cinnabar ore samples were taken from three mines in central Japan (Niu in Mie, Yamato in Nara, and Sui in Tokushima prefectures), and from Wanshan in China, where mining activity has been recorded back to the 6th century A.D. and earlier. When the ratios of a 34S and 32S were compared with the Canyon Diablo meteorite standard, a high δ34S value of +22.6 ± 3.6‰ was found for the Wanshan mine, as opposed to low values ranging from −7.3 ± 1.9 to −2.1 ± 1.6‰ for the Japanese mines. The ratios of sulfur isotopes in vermillion collected from ancient Japanese burial mounds also divided into two groups. High ratios (+11.1 to +22.8‰) were found in 1st‐ and 2nd‐ century burials in the western regions of northern Kyushu and San'in, suggesting that local, powerful chiefs obtained vermillion through relations with China. Lower ratios (−8.4 to −2.0‰) were found in burials of the 2nd through 6th centuries in central Japan, where the ancient Yamato dynasty emerged as the first unified polity around the end of the 2nd century A.D. We, therefore, conclude that the Yamato dynasty exploited local sources of vermillion, rather than depending solely on China. The present study demonstrates the feasibility of determining sources of vermillion using sulfur isotope ratios, and the relevance of such findings for archaeological research. © 2005 Wiley Periodicals, Inc.

An X-ray and electron microprobe study of Fe, Ni, Ga, and Ge distribution and local structure in a section of the Canyon Diablo iron meteorite

Using X-rays produced by a third generation synchrotron at the Pacific Northwest Consortium Collaborative Access Team (PNC-CAT), Advanced Photon Source (APS), Argonne National Laboratory, the distribution of Fe, Ni, Ga, and Ge in a sample of the Canyon Diablo iron meteorite has been mapped microscopically in situ with a 5 μm × 5 μm spatial resolution. The principal phases investigated were kamacite (αFe/Ni alloy, <6 wt% Ni), cohenite [a carbide, (Fe,Ni,Co)3C], and schreibersite [a phosphide, (Fe,Ni)3P]. A non-microscopic X-ray absorption analysis at the P edge indicated the presence of both phosphide and phosphate in the sample. Extended X-ray absorption fine structure (EXAFS) analysis of Fe in kamacite reflects the known bcc structure of kamacite. EXAFS analysis of Ni, Ga, and Ge indicates that these elements substitute for Fe within the kamacite bcc structure. Absorption edge shifts for these same elements are generally small relative to the metals themselves, suggestive of a metallic environment. Initial findings also suggest that Ga preferentially partitions into schreibersite (phosphide) rather than cohenite (carbide), whereas Ge behaves differently and is found principally in the kamacite. These observations further the understanding of the Ge and Ga budget within the Canyon Diablo meteorite, and the work also illustrates the potential of the X-ray microprobe technique for the study of meteorites. Other potential uses of the X-ray microprobe are indicated.

Crystal structure of iron nickel phosphide, Fe1.7Ni1.3P, a Schreibersite extracted from Canyon Diablo meteorite

1 Universitat Leipzig, Institut fur Mineralogie, Kristallographie und Materialwissenschaft, Schamhorststr. 20, D-04275 Leipzig, Germany " Mineralogisch-Petrologisches Institut und Museum der Rheinischen Friedrich-Wilhelms-Universitat Bonn, Poppelsdorfer Schlos, D-53115 Bonn, Germany 111 Universitat Bremen, EB 5 Geowissenschaften, Zentrallabor fur Kristallographie und angewandte Materialwissenschaft, Klagenfurter Str., D-28359 Bremen, Germany

Crystal structure of iron nickel phosphide, Fe1.7Ni1.3P, a Schreibersite extracted from Canyon Diablo meteorite

Abstract Fe1.7Ni1.3P8, tetragonal, I4̅ (No. 82), a = 9.049(1) Å, c = 4.4646(9) Å, V = 365.6 Å3, Z = 8, Rgt(F) = 0.042, wRref(F2) = 0.093, T = 293 K

Ferromagnetism of a graphite nodule from the Canyon Diablo meteorite.

There are recent reports of weak ferromagnetism in graphite and synthetic carbon materials such as rhombohedral C(60) (ref. 4), as well as a theoretical prediction of a ferromagnetic instability in graphene sheets. With very small ferromagnetic signals, it is difficult to be certain that the origin is intrinsic, rather than due to minute concentrations of iron-rich impurities. Here we take a different experimental approach to study ferromagnetism in graphitic materials, by making use of meteoritic graphite, which is strongly ferromagnetic at room temperature. We examined ten samples of extraterrestrial graphite from a nodule in the Canyon Diablo meteorite. Graphite is the major phase in every sample, but there are minor amounts of magnetite, kamacite, akaganéite, and other phases. By analysing the phase composition of a series of samples, we find that these iron-rich minerals can only account for about two-thirds of the observed magnetization. The remainder is somehow associated with graphite, corresponding to an average magnetization of 0.05 Bohr magnetons per carbon atom. The magnetic ordering temperature is near 570 K. We suggest that the ferromagnetism is a magnetic proximity effect induced at the interface with magnetite or kamacite inclusions.

Pre‐atmospheric depths and thermal histories of Canyon Diablo spheroids

Abstract— Despite having melted during formation, seven of eight Canyon Diablo spheroids weighing from 0.6 to 13 mg retain cosmic‐ray‐produced 38Ar (38Arcos) in concentrations (10−10 cm3 STP/g) ranging from 0.35 to 68. The presence of 38Arcos is consistent with pre‐atmospheric depths of &lt;2.3 m and most likely rules out an origin for the spheroids deep within the projectile, which had a radius of ˜15 m. Low levels of 21Necos indicate gas loss from these spheroids. Relative to most Canyon Diablo meteorites, the spheroids contain lower concentrations of cosmogenic noble gases. The difference partly reflects diffusion losses from the spheroids, especially for 3He and 21Ne, but also suggests deeper locations on average for the precursor material, consistent with independent results from 59Ni.

Kamacite sulfurization in the solar nebula

Abstract— The kinetics and mechanisms of kamacite sulfurization were studied experimentally at temperatures and H2S/H2 ratios relevant to the solar nebula. Pieces of the Canyon Diablo meteorite were heated at 558 K, 613 K, and 643 K in 50 parts per million by volume (ppmv) H2S‐H2 gas mixtures for up to one month. Optical microscopy and x‐ray diffraction analyses show that the morphology and crystal orientation of the resulting sulfide layers vary with both time and temperature. Electron microprobe analyses reveal three distinct phases in the reaction products: monosulfide solid solution (mss), (Fe, Ni, Co)1‐xS, pentlandite (Fe, Ni, Co)9‐xS8, and a P‐rich phase. The bulk composition of the remnant metal was not significantly changed by sulfurization. Kamacite sulfurization at 558 K followed parabolic kinetics for the entire duration of the experiments. Sulfide layers that formed at 613 K grew linearly with time, while those that formed at 643 K initially grew linearly with time then switched to parabolic kinetics upon reaching a critical thickness. The experimental results suggest that a variety of thermodynamic, kinetic, and physical processes control the final composition and morphology of the sulfide layers. We combine morphological, x‐ray diffraction, electron microprobe, and kinetic data to produce a comprehensive model of sulfide formation in the solar nebula. Then, we present a set of criteria to assist in the identification of solar nebula condensate sulfides in primitive meteorites.

Sulphur isotope data consistency improved

The standard used for reporting relative sulphur isotope-abundance data has, historically, been troilite (FeS) derived from the Canon Diablo meteorite, CDT. However, the isotopic inhomogeneity of this material — the variability in its sulphur-34/sulphur-32 isotope ratio is at least 0.4‰ — greatly exceeds the achievable analytical uncertainty of 0.05‰ (ref. 1). Accordingly, the International Union of Pure and Applied Chemistry (IUPAC) has recommended the setting up of a VCDT scale, which is expected to improve agreement between laboratories in measuring this ratio, δ34S.

Variations in the sulfur isotope composition of troilite from the Cañon Diablo iron meteorite

Cañon Diablo troilite (CDT), although accepted as the reference for the sulfur isotope scale, is not a Standard Reference Material manufactured for international distribution, and its sulfur isotope composition is not well characterized. We report high-precision sulfur isotope analyses of troilite from three different samples of Canon Diablo meteorite, and interlaboratory comparison of one CDT sample and of a reference SF 6 gas. The sulfur isotope composition of CDT displays a range in δ 34S values of 0.4%., significantly larger than our analytical uncertainty (0.05%.). CDT should not be used for calibration of the sulfur isotope scale. These results support the definition of a new sulfur isotope scale relative to a hypothetical Vienna-CDT, as recently proposed by the International Atomic Energy Agency.

Use of isotope fractionation of sulfate-sulfur and sulfate-oxygen to assess bacterial desulfurication in a sandy aquifer

The unconfined aquifer of the “Fuhrberger Feld” consists of 20–30m sands and gravelly sands with unevenly distributed reduced sulfur compounds and small lignitic pebbles. In vertical direction two hydrochemically different zones with specific solute transformations are present, an upper portion with bacterial denitrification (with reduced sulfur compounds as electron donors) and a deeper portion with hydrochemical indications of reduction of the aqueous sulfate. In the study area ten multilevel groundwater sampling wells were installed. Sampling and interpretation was based on a two-dimensional vertical-plane groundwater flownet and on the knowledge of the landuse upgradient of the multilevel wells. The concentration and isotopic composition of the sulfate at the entrance into the zone of sulfate reduction is controlled by sulfate of groundwater recharge as well as sulfate formed during denitrification. The recharge-sulfate shows clear landuse specific differences in concentration and isotopic composition: under arable land an average concentration of ≈ 60 mg SO 4l −1 with values of δ 34S close to +3‰ CDT Diablo Meteorite Standard (Can̄on) and of δ 18O about + 8‰ standard mean ocean water (SMOW) was measured, whereas under coniferous forest an average of ∼ 100 mg SO 4l −1 with δ 34 S ≈ + 2‰ and δ 18 O ≈ 4.5‰ was found. In the denitrification zone no significant sulfur isotope fractionation occurs during oxidation of reduced sulfur. The oxygenisotopic composition of the newly formed sulfate (“denitrification-sulfate”) depends on the 18O content of nitrate acting as oxygen donor and on the 18O content of groundwater in which the oxidation occurs; under certain assumptions a δ 18 O = +0.54‰ was calculated for the oxygen of the newly formed sulfate. Consequently, with increasing sulfate concentrations, i.e. with the admixture of “denitrification-sulfate”, a decrease of the δ 18O values from about +8‰ to +2‰ was observed. In the zone of sulfate reduction, both the δ 34S and δ 18O-values of the residual sulfate increase with decreasing sulfate concentrations thus proving the existence of bacterial reduction of the aqueous sulfate. This sulfate reduction follows a Rayleigh process with calculated enrichment factors of ϵ 34 = −9.7‰ for 34S and ϵ 18 ≈ −6‰ for 18O, respectively. A plot of δ 34S vs. δ 18O gives a good linear correlation with a slope close to 1: 1.4. Data on concentration and isotopic composition of sulfate and on the hydraulically derived groundwater age are used for kinetic considerations. The results of a multilevel well for depths between 10 and 17m are given as an example. The bacterial reduction can be considered as first-order reaction with a half-life between 75 and 100 years.

Compositional range in the Canyon Diablo meteoroid

The Ir distribution in the IAB Canyon Diablo meteorites associated with the formation of Meteor Crater, Arizona, ranges from 2.1 to 2.5 μg/g with peaks at 2.17 and 2.34 μg/g. Only Ir, Ni, and Cu show appreciably more variance in the large set of specimens than observed within a single specimen. The Ir peaks may reflect random sampling of the large (40–100 m), fractionated meteoroid or the presence of two distinct metallic regions differing in composition. None of the other elements we determined show strong correlations with Ir; the Au range is strikingly small (1.5–1.6 μg/g). The presence of chondritic silicates and high contents of planetary-type noble gases in IAB indicates that these solidified rapidly following melting, as expected if they originated as pools of impact-generated melt on a chondritic body. The absence of fractional crystallization trends is consistent with such a model. That 14 of 15 Ir contents fall into two “peaks” suggests the possibility that the meteoroid included two “pools”. The alternative that the distribution is continuous can be tested by the study of additional specimens; those from the crater rim are particularly important since these are largely shrapnel spalled from the trailing hemisphere of the meteoroid. Our studies show that the irons named Helt Township, Idaho, Las Vegas, Mamaroneck, Moab, and Pulaski County are probably mislabelled Canyon Diablo specimens; Jenny's Creek and Jenkins are also compositionally indistinguishable. Alexander County, Allan Hills A77283, Ashfork, Fairfield, and Rifle are compositionally distinct, independent falls.

Isotopic composition of osmium in terrestrial samples determined by accelerator mass spectrometry

Interest has revived in the rhenium/osmium system due to significant advances in detection methods1–4 and because of its use for the identification of extraterrestrial material at the Cretaceous/Tertiary boundary5. Another, perhaps more important application is its use as a tracer for the origin of crustal material. This application is, however, severely restricted by the very low concentrations typical of crustal rocks. We present here the first results for the isotopes 187Os, 188Os, and 189Os measured in sub-p.p.b. (parts per 109) level samples by accelerator mass spectrometry (AMS). Our first exploratory measurements on extraterrestrial and crustal material with Os concentrations between 2 p.p.m. (parts per 106) and 0.006 p.p.b. show a detection limit of ∼0.01 p.p.b. and a precision of better than 10%. The 187Os/186Os ratios measured for samples for the Canyon Diablo meteorite and from the East Clearwater crater in Quebec, Canada, were close to 1, typical of extraterrestrial material. In contrast, ratios in samples from the Ries crater in Germany were around 10, which is evidence of predominantly crustal osmium in these rocks.

A metallographic study of the disruption of the Cañon Diablo projectile

SummaryA metallographic investigation of macro- and micro-structures, supported by microprobe examination, has been made on similarly sized (&lt; ca. 200 g) individual Cañon Diablo meteorites of rim or plains type. Plains type specimens show heat alteration zones of the ablation type. They are extensively cracked in a brittle manner and in some instances the cracks are penetrated by ablation melt product. In all cases the cracks are now penetrated by terrestrial corrosion. Cohenite and schreibersite are cracked in a brittle manner. By contrast the rim type specimens are remarkably free of internal cracking or corrosion penetration. Instead the cohenite, schreibersite, taenite, and kamacite are transected by slip faults or shear displacements along the line of which all phases appear to have slipped in a non-brittle manner. These specimens have all been subject to shock loading and particular attention is paid to the effects of shock on sphalerite, on cloudy taenite, and on martensitic plessite.Plains specimens have broken from the original projectile in a brittle manner well above the earth's surface. Rim specimens have been scabbed from the rear of the projectile as it penetrated the earth's surface. Some of the rim specimens show signs of being heated by the blast of the crater-forming explosion.

Ore lead isotope ratios in a continuously changing earth

A critical re-assessment of the construction of simple ore lead isotopic development curves is followed by three fresh approximations, all designed to involve the minimum possible number of assumptions. All are based on the Russell-Reynolds algorithm which in its simplest form involves knowledge only of ratios, not of ages. We apply the calculations to a restricted class of ore leads, and employ the latest constant values for the U and Th isotopes. Model I treats all data as being of equal weight, and shows that the deletion or inclusion on the Canyon Diablo meteorite data makes no differences to the derived parameters. Model II demonstrates that essentially the same parameters result if the simple curve is forced through the meteorite point; i.e. questions about homogeneity or otherwise of “initial terrestral” Pb a unimportant to the regression. Model III makes allowance for the known discrepancy in young “model ages” by providing for a steady linear change in U/Pb and Th/Pb. The additional assumption of one fixed time point proves necessary. An age close to 430 m.y. for Captains Flat, N.S.W., yields acceptable age estimates for most other deposits investigated. No claim is made for the uniqueness of this solution, but the derived evidence for steady growth in U/Pb accompanied by a slight decline in Th/U, seems compatible with a crustal source for the lead ores concerned.