Canyon Diablo
Iron, IAB complex, main group
Found 1891
35° 3′ N., 111° 2′ W.
A history revealed
Approximately 49,500 years ago an iron meteoriteIron meteorites consist mostly of metallic iron alloyed with typically between ~5 to ~30 wt% nickel. The main metal phases are kamacite α-(Fe, Ni) and taenite y-(Fe, Ni). Based on their group classification, they may also contain a small weight percentage of one or more of the following minerals: • measuring ~100–150 feet (46–66 m) in diameter (solid body) to 217 feet in diameter (tight swarm of fragments) in diameter and weighing at least 100,000 tons (100 million kg, up to 1.2 billion kg), and which is conjectured to have been infalling along a southwest to northeast (Rhinehart, 1958; Artemieva and Pierazzo, 2011) trajectory, was catastrophically disrupted at an altitude of 8.5 miles, forming a pancake-like debris cloud measuring ~400 feet across (Passy and Melosh [Separated Fragments model], Chyba et al., 1993 [Pancake model], Melosh and Collins, 2005; Artemieva, 2006; Artemieva and Pierazzo, 2007, 2009 [SOVA hydrocode model]). This mass of interacting fragments is believed to have struck the Earth at an angle of 45° at an estimated velocity of at least 33,500 mph (15–16 km/s, possibly up to 20 km/s) and experienced considerable ablationGradual removal of the successive surface layers of a material through various processes. • The gradual removal and loss of meteoritic material by heating and vaporization as the meteoroid experiences frictional melting during its passage through the atmosphere. The resulting plasma ablates the meteor and, in cases where a meteor and melting.
The resulting 2.5 megaton explosion created a craterBowl-like depression ("crater" means "cup" in Latin) on the surface of a planet, moon, or asteroid. Craters range in size from a few centimeters to over 1,000 km across, and are mostly caused by impact or by volcanic activity, though some are due to cryovolcanism. one mile in diameter and 600 feet deep, with a rim over 150 feet high. The event excavated 175 million metric tons of rock (Kring, 2006) from 40 m deep in the case of melt material, and up to 100 m deep in the case of non-melt material (Artemieva and Pierazzo, 2011). This created an organized inverted strataOriginally horizontal layers of rock. with Coconino Sandstone overlying Toroweap LimestoneA common form of calcium carbonate (CaCO3). Other common forms of CaCO3 include chalk and marble., overlying Kaibab Limestone, overlying units of the Moenkopi Formation (Hagerty et al., 2010). The total energy released by the entire meteoriteWork in progress. A solid natural object reaching a planet’s surface from interplanetary space. Solid portion of a meteoroid that survives its fall to Earth, or some other body. Meteorites are classified as stony meteorites, iron meteorites, and stony-iron meteorites. These groups are further divided according to their mineralogy and during its descent from ~9 miles altitude to the surface was calculated to have been as high as 6.5 MT (equivalent to 6.5 million metric tons of TNT; 1 MT = 4.184 × 1015 J), including an intense airblast near the ground. As a result the initial projectile was ejected and dispersed by the plume in the form of solids (26–30%), melt (45–50%), and vapor (20–29%) (Artmieva and Pierazzo, 2011).
After melting/ablation of the meteoroidSmall rocky or metallic object in orbit around the Sun (or another star)., ~30% (solid body) to 70% (fragmented swarm) of the mass survived as fragments that fell over an area ~6 miles in diameter centered on the crater, and many were heated to temperatures high enough to alter the Thomson (Widmanstätten) structure of the meteorites of the rim location. The fragments were rapidly cooled in less than two minutes, which created the iron–carbonElement commonly found in meteorites, it occurs in several structural forms (polymorphs). All polymorphs are shown to the left with * indicating that it been found in meteorites and impact structures: a. diamond*; b. graphite*; c. lonsdalite*; d. buckminsterfullerene* (C60); e. C540; f. C70; g. amorphous carbon; h. carbon nanotube*. alloyMetal-like substance produced by mixing two or more metals or by the mixture of a metal and another substance. Ceramics can also be mixed to form alloys. A binary alloy contains two components; a ternary alloy contains three. martensite. The shock waves created pressures inside the fragments greater than 600 kilobars (60 GPa), which injected metalElement that readily forms cations and has metallic bonds; sometimes said to be similar to a cation in a cloud of electrons. The metals are one of the three groups of elements as distinguished by their ionization and bonding properties, along with the metalloids and nonmetals. A diagonal line drawn into large graphite nodules, while transforming other graphiteOpaque form of carbon (C) found in some iron and ordinary chondrites and in ureilite meteorites. Each C atom is bonded to three others in a plane composed of fused hexagonal rings, just like those in aromatic hydrocarbons. The two known forms of graphite, α (hexagonal) and β (rhombohedral), have into microscopic diamonds and lonsdaleiteHexagonal polymorph of carbon (C) that forms from meteoric graphite during impact. The immense heat and stress of the impact transforms the graphite into diamond, but retains graphite's hexagonal crystal lattice (below). Lonsdaleite was first identified from the Canyon Diablo meteorite at Barringer Crater (also known as Meteor Crater) in. All of the diamond-bearing fragments have been recovered from the crater rim with the exception of one plains specimen, and all rim specimens are strongly shocked. The remaining plains specimens are only lightly to moderately shocked and contain no diamonds. This is consistant with other evidence supporting the theory that the diamonds were formed upon impact with the Earth. The graphite particles present in the meteorite were transformed by the compression waves into droplets of liquid carbon and then frozen into tiny diamonds when decompressed by the rarefaction wavePropagating disturbance which transmits energy from one point to another without physically transporting the oscillating quantity. A wave is characterized by wavelength and frequency.. The intense shock forces also acted on the local Coconino sandstone to produce coesiteHigh-pressure polymorph of silicon dioxide (SiO2). Has the same chemical composition as cristobalite, stishovite, seifertite and tridymite but possesses a different crystal structure. Coesite forms at intense pressures of above about 2.5 GPa (25 kbar) and temperature above about 700 °C, and was first found naturally on Earth in impact and stishoviteDense, high-pressure phase of quartz; so far identified only in shock-metamorphosed, quartz-bearing rocks from meteorite impact craters. Stishovite was synthesized in 1961 before it was discovered at Meteor Crater, Arizona. Its structure consists of parallel chains of single SiO6 octahedra. The octahedra are on their sides, sharing opposing edges. Image, establishing the first discovery in nature of these two high-pressure silicaSilicon dioxide, SiO2. polymorphs (both of which were discovered and named by Dr. Edward Ching-Te Chao, with the latter named after the Russian physicist Sergei Stishov who first synthesized it in a high-pressure laboratory experiment).
By relating known relationships among noble gasElement occurring in the right-most column of the periodic table; also called "inert" gases. In these gases, the outer electron shell is completely filled, making them very unreactive. isotopeOne of two or more atoms with the same atomic number (Z), but different mass (A). For example, hydrogen has three isotopes: H, H (deuterium), and H (tritium). Different isotopes of a given element have different numbers of neutrons in the nucleus. ratios, the cosmic ray exposure ageTime interval that a meteoroid was an independent body in space. In other words, the time between when a meteoroid was broken off its parent body and its arrival on Earth as a meteorite - also known simply as the "exposure age." It can be estimated from the observed effects can be ascertained for the Canyon Diablo object. The oldest isochron provides evidence for a collision in space 540 m.y. ago, while a secondary isochron of 170 m.y. is suggestive of a more recent collision. One fragment shows evidence of a third collision 15 m.y. ago. More than half of all iron meteorites found on Earth have exposure ages of between 500 and 600 m.y. Most H chondritesChondrites are the most common meteorites accounting for ~84% of falls. Chondrites are comprised mostly of Fe- and Mg-bearing silicate minerals (found in both chondrules and fine grained matrix), reduced Fe/Ni metal (found in various states like large blebs, small grains and/or even chondrule rims), and various refractory inclusions (such, representing the largest group of stony meteorites found on Earth, suffered intense shock and reheating about 520 m.y. ago. These events might represent the breakup of one or more sizable asteroids with diameters of at least 80 km and masses of 1015 tons. The asteroids today can be associated with others into about 30 families having similar orbits. Each family could represent the debris from the breakup of individual asteroids. Four families that are in Mars-crossing orbits are prime candidates for supplying the Earth with those meteorites in the 500–600 m.y. cosmic ray age group.
The cosmic ray exposure ages of the Canyon Diablo fragments can be correlated with the 3He and 59Ni isotope abundances in the fragments to determine the depth at which individual fragments were residing in the main body before Earth impact. This depth was correlated with the location at which each specimen had been collected, either on the rim or on the surrounding plains. The rim specimens had originally resided at a depth of ~3–6 feet (<3 m) within the projectiles rear surface area, while about half of the plains specimens had been closer to the surface of the projectile. The conclusion can be made that the more deeply buried fragments experienced greater shock, the shock produced diamonds from existing graphite, and these heavily shocked fragments (shrapnel) were ejected with low velocity to land on or near the rim. The mm-sized molten metallic spherules have a low content of the cosmogenic nuclideA nuclear species characterized by Z protons and N neutrons. 59Ni, which is consistent with this melt material originating from the inner portion of the projectile.
Some studies have calculated that all of the surviving material was likely derived from the rearmost 6 feet of the trailing hemisphere of the impactor, all of which constitute only about 15% of the original mass; these fragments were located in areas such as corners, humps, edges, or projections where cancellation between primary and reflected shock waves occurred. Using these parameters, of the more than 300,000 tons comprising the main massLargest fragment of a meteorite, typically at the time of recovery. Meteorites are commonly cut, sliced or sometimes broken thus reducing the size of the main mass and the resulting largest specimen is called the "largest known mass"., about 30,000–45,000 tons escaped melting/vaporization. More recent hydrocode modeling by Artemieva and Pierazzo (2007) indicates that over 50% of the impactor remained solid. Only about 2,000 tons can be accounted for today in meteorite fragments, shale balls, metallic spherules, and other oxidationOxidation and reduction together are called redox (reduction and oxidation) and generally characterized by the transfer of electrons between chemical species, like molecules, atoms or ions, where one species undergoes oxidation, a loss of electrons, while another species undergoes reduction, a gain of electrons. This transfer of electrons between reactants products. Isolated meteorite fragments account for only 30 tons of this material, much of it likely being transported from the site in ancient times, although fragments have only been described dating from ~1860.
The early history of the Canyon Diablo asteroid can also be described. Based on W- and Sm-isotopic data obtained by Schulza et al. (2012), accretionAccumulation of smaller objects into progressively larger bodies in the solar nebula leading to the eventual formation of asteroids, planetesimals and planets. The earliest accretion of the smallest particles was due to Van der Waals and electromagnetic forces. Further accretion continued by relatively low-velocity collisions of smaller bodies in the of the IAB parent bodyThe body from which a meteorite or meteoroid was derived prior to its ejection. Some parent bodies were destroyed early in the formation of our Solar System, while others like the asteroid 4-Vesta and Mars are still observable today. occurred ~2 m.y. after Solar SystemThe Sun and set of objects orbiting around it including planets and their moons and rings, asteroids, comets, and meteoroids. formation. SilicateThe most abundant group of minerals in Earth's crust, the structure of silicates are dominated by the silica tetrahedron, SiO44-, with metal ions occurring between tetrahedra). The mesodesmic bonds of the silicon tetrahedron allow extensive polymerization and silicates are classified according to the amount of linking that occurs between the melting and metal segregation to form a coreIn the context of planetary formation, the core is the central region of a large differentiated asteroid, planet or moon and made up of denser materials than the surrounding mantle and crust. For example, the cores of the Earth, the terrestrial planets and differentiated asteroids are rich in metallic iron-nickel. occurred ~3 m.y. later. During the next 0.5–1.5 b.y. the iron cooled through the temperature range of 700–400°C at a rate of about 1°C per m.y., creating the Thomson (Widmanstätten) structure of crystal formation. This cooling rate would be consistent with the asteroidal body being between 250 and 500 km in diameter, which is between one-third and two-thirds the size of the largest known asteroid, Ceres. Utilizing the short-lived 182Hf–182W chronometer, corrected for neutronCharge-neutral hadron with a mass of 1.6748 x 10 kg, equivalent to 939.573 MeV, and an intrinsic angular momentum, or spin, of ½ (in units of h/2π). The neutron is a nucleon, one of the two basic constituents of all atomic nuclei (apart from H, which consists of a single capture by 182W due to galactic cosmic raysHigh-energy subatomic particles mainly originating outside the Solar System that continuously bombard the Earth from all directions. They represent one of the few direct samples of matter from outside our solar system and travel through space at nearly the speed of light. These charged particles – positively charged protons or, Hunt et al. (2018) derived the timing of metal–silicate separation of all genetically-related IAB irons (at least the MG and sLL subgroup [possibly also the sLM subgroup] along with the ungroupedModifying term used to describe meteorites that are mineralogically and/or chemically unique and defy classification into the group or sub-group they most closely resemble. Some examples include Ungrouped Achondrite (achondrite-ung), Ungrouped Chondrite (chondrite-ung), Ungrouped Iron (iron-ung), and Ungrouped Carbonaceous (C-ung). Caddo County [Udei Station grouplet] and Livingstone [Algarrabo duo]) to 6.0 (±0.8) m.y. after CAIsSub-millimeter to centimeter-sized amorphous objects found typically in carbonaceous chondrites and ranging in color from white to greyish white and even light pink. CAIs have occasionally been found in ordinary chondrites, such as the L3.00 chondrite, NWA 8276 (Sara Russell, 2016). CAIs are also known as refractory inclusions since they. Based on the constraints provided by the timing of metal segregation, they modeled the early history of the 120(+)-km-diameter IAB parent body as outlined in the following diagram: 
Diagram credit: Hunt et al., EPSL, vol. 482, pp. 497 (2018, open access link)
‘Late metal–silicate separation on the IAB parent asteroid: Constraints from combined W and Pt isotopes and thermal modelling’
(https://doi.org/10.1016/j.epsl.2017.11.034)’ Dey et al. (2019) employed 17O and ε54Cr values for several irons and their associated silicates/oxides to investigate i) if each iron and its associated phases originated on a common parent body (i.e., an endogenous mixture of core and mantleMain silicate-rich zone within a planet between the crust and metallic core. The mantle accounts for 82% of Earth's volume and is composed of silicate minerals rich in Mg. The temperature of the mantle can be as high as 3,700 °C. Heat generated in the core causes convection currents in vs. an exogenous mixture through impact), and ii) if any genetic connection exists between the irons and other meteorite groups (e.g., IAB with winonaites, IIE with H chondrites, and Eagle Station pallasites with CK chondrites). Three IAB irons were employed in the study, and it was demonstrated on a coupled diagram that although the ε54Cr values for the iron component plot in the winonaitea partially differentiated asteroid that was disrupted just as it began to form an Fe core and a silicate-rich crust. This disrupting impact mixed silicates into molten Ni-Fe metal forming the silicated IAB irons, and mixed olivine-rich residues of partial melts into unmelted silicates, forming the winonaites. A few winonaites field, values for the silicate component plot in a distinct region on an O–Cr coupled diagram (see diagram below). From these results they ascertained that the the IAB silicated irons formed through an impact-generated mixture comprising iron from a winonaite-related parent body and silicate from an unrelated and otherwise unsampled parent body. Incorporation of the silicates into the FeNi-metal host took place at a depth greater than 2 km, allowing time for a Thomson (Widmanstätten) structure to develop during a long cooling phase. Fractional crystallizationA crystallization process in which minerals crystallizing from a magma are isolated from contact with the liquid. It is a key process in the formation of igneous rocks during the process of magmatic differentiation. Also known as crystal fractionation. occurred in some large molten metal pools, followed by very slow cooling, to produce the broad range of features found in certain IAB meteorites (e.g., silicate-poor, graphite–troilite-rich inclusions and extremely high Ni contents). Other results from their study can be found on the Miles and Eagle Station pages. 17O vs. ε54Cr for Irons and Pallasites
click on photo for a magnified view
Diagrams credit: Dey et al., 50th LPSC, #2977 (2019)
To learn more about the relationship between this and other iron chemical groups, click here. The specimen of Canyon Diablo shown above is a shrapnel fragment that was shaped during the violent impact event.
