Origin of Iron Meteorite Groups IAB and IIICD

1980 ◽  
Vol 35 (8) ◽  
pp. 781-795 ◽  
Author(s):  
John T. Wasson ◽  
John Willis ◽  
Chien M. Wai ◽  
Alfred Kracher
Keyword(s):  
Parent Body ◽  
Iron Meteorite ◽  
Iron Meteorites ◽  
Impact Melt ◽  
Equilibrium Crystallization ◽  
Ni Content ◽  
Oxide Phases ◽  
Host Metal ◽  
Impact Melts ◽  
The Impact

AbstractSeveral low-Ni iron meteorites previously assigned to group IAB are reclassified IIICD on the basis of lower Ge, Ga, W and Ir concentrations and higher As concentrations; the low-Ni extreme of IIICD is now 62 mg/g, that of IAB is 64 mg/g. The resulting fractionation patterns in the two groups are quite similar. It has long been established that, in contrast to the magmatic iron meteorite groups, IAB and IIICD did not form by fractional crystallization of a metallic magma. Other models have been proposed, but all have serious flaws. A new model is proposed involving the formation of each iron in small pools of impact melt on a parent body consisting of material similar to the chondritic inclusions found in some IAB and IIICD irons, but initially unequilibrated. These impact melts ranged in temperatures from ~ 1190 K to ~ 1350 K. The degree of equilibration between melt and unmelted solids ranged from minimal at the lowest temperature to moderate at the highest temperature. The lowest temperature melts were near the cotectic in the Fe-Ni-S system with Ni contents of ~ 12 atom %. Upon cooling, these precipitated metal having ~ 600 mg/g Ni by equilibrium crystallization. The Ni-rich melt resulted from the melting of Ni-rich sulfides and metal in the unequilibrated chondritic parent. Low-Ni irons formed in high temperature melts near the composition of the FeS-Fe eutectic or somewhat more metal rich. We suggest that the decreasing Ge, Ga and refractory abundances with increasing Ni concentration reflect the trapping of these elements in oxide phases in the unequilibrated chondritic material, and that very little entered the Ni-rich melt parental to the Oktibbeha County iron. The remaining elements tended to have element/Ni ratios in the melts that were more or less independent of temperature. The remarkable correlation between I-Xe age of the chondritic inclusions and Ni content of the host metal is explained by a detailed evolution of (mega)regolith in which these groups originated. The most Ni-rich melts could only be generated from an unequilibrated chondrite parent; as the continuing deposition of impact energy produced increasingly higher grades of metamorphism, the maximum Ni content of the impact melts (and their subsequently precipitated metal) gradually decreased.

scholarly journals The extremely reduced silicate-bearing iron meteorite Northwest Africa 6583: Implications on the variety of the impact melt rocks of the IAB-complex parent body

2013 ◽  
Vol 48 (12) ◽  
pp. 2451-2468 ◽  
Author(s):  
Agnese Fazio ◽  
Massimo D'Orazio ◽  
Luigi Folco ◽  
Jérôme Gattacceca ◽  
Corinne Sonzogni
Keyword(s):  
Parent Body ◽  
Iron Meteorite ◽  
Impact Melt ◽  
Northwest Africa ◽  
The Impact

scholarly journals Fe-Ni-P-S Melt Pockets in Elga IIE Iron Meteorite: Evidence for the Origin at High-Pressures Up to 20 GPa

Minerals ◽  
2019 ◽  
Vol 9 (10) ◽  
pp. 616 ◽  
Author(s):  
Konstantin Litasov ◽  
Svetlana Teplyakova ◽  
Anton Shatskiy ◽  
Konstantin Kuper
Keyword(s):  
Experimental Data ◽  
Solid Solution ◽  
Important Implication ◽  
High Pressures ◽  
Bulk Composition ◽  
Parent Body ◽  
Iron Meteorite ◽  
Iron Meteorites ◽  
High Pressures And Temperatures ◽  
Melt Pockets

Here we report new data on high-pressure microstructures in Elga group IIE iron meteorites, made of solidified Fe-Ni-P-S melt pockets and microcrystalline aggregates, which could be formed only at high pressures and temperatures according to the experimental data. The bulk composition of the melt pockets and crystals correspond to the Fe3P-Fe3S solid solution with the closure of an immiscibility gap at pressures near 20 GPa in static experiments. Some other melt pockets fit with the Fe2S-Fe2P compositions, which could also correspond to high pressures and temperatures. The results suggest a late shock episode during the formation of the IIE iron parent body, which may be prior or due to the final disruption that caused the meteorite arrival to Earth. It also has an important implication to the shock features in other meteorites, such as ureilite.

Evidences for Bimodal volcanism on 4-Vesta Asteroid from impact-melt clast

2020 ◽  
Author(s):  
Dwijesh Ray ◽  
Sambhunath Ghosh
Keyword(s):  
Melt Inclusions ◽  
Bulk Composition ◽  
Parent Body ◽  
Total Iron ◽  
Volcanic Complex ◽  
Element Geochemistry ◽  
Silicic Volcanism ◽  
Impact Melt ◽  
Acid Volcanism ◽  
The Impact

<p>Silicic / acid volcanism has not been widely described either on Moon, Mars or in Asteroid 4 Vesta. The occurrence of sialic crustal rocks on the lunar surface is extremely limited. Reports on silicic (non-mare) volcanic rocks on Moon is found to be associated in Compton-Belkovich volcanic complex, Hansteen Alpha volcanic crater, Lassell massif, Gruithuisen domes and ejecta of Aristarchus crater (Clegg-Watkins et al., 2017). The occurrence of several volcanic constructs (e.g. collapse features, domes) and volatile-rich pyroclastics in association with silicic rocks further emphasize existence of viscous magmas on Moon. A localized occurrence of silicic volcanism on Mars is also envisaged by the presence of tridymite in mudstone of Gale crater (Morris et al., 2016). However, the exact formation mechanism of silicic volcanism on Moon, Mars or even in 4-Vesta has been largely hindered due to lack of silicic meteorite samples or mission-returned samples.</p> <p>The HED (Howardite, Eucrite, Diogenite) meteorites is considered to have originated from a common parent body Asteroid 4-Vesta. Recent Dawn mission also attempts to validate its geologic context and formulate a possible HED-Vesta connection (McSween et al., 2013). Based on Dawn findings, Vesta’s surface appears to be similar to a mixture of basaltic eucrite and diogenite resembling a more complex breccia howardite (De Sanctis et al., 2012; Prettyman et al., 2012). A variety of clasts are apparently common in howardite. Here, we report the petrography and major element geochemistry of a new impact-melt clast from Lohawat howardite. Our results show that the clast composition is unique and unlikely to be explained by typical impact melting of HED mafic lithologies. One of the impact melts (~20µ across) hosted in ferroaugite (Wo<sub>42</sub>En<sub>2.7</sub>Fs<sub>55.3</sub>) clast substantially differ in composition from the other impact-melt (~50µ across) hosted in ilmenite clast, specially in terms of SiO<sub>2</sub> wt%, CaO wt%, K<sub>2</sub>O wt% and K<sub>2</sub>O / (K<sub>2</sub>O + Na<sub>2</sub>O) ratio. Moreover, one appears nearly homogeneous in contrast to evolved nature with limited heterogeneity as compared to other. Both the melts are oblong-shaped, smooth textured with sharp outline and embedded in the host monomict mineral clast of different composition belonging to possible parent of cumulate eucrite.</p> <p>The average bulk composition of Lohawat is consistent with basaltic crusts (SiO<sub>2</sub> ~50.3-51.8 wt%, Al<sub>2</sub>O<sub>3</sub> ~3.5-8.2 wt%, total iron-magnesia ~31.2-38.0 wt%, CaO ~2.2-7.6 wt%) (Chattopadhyay et al. 1998; Sisodia et al. 2001; Ghosh, 2011). Supplement to basaltic volcanism, we report for the first time the incipient acid volcanism in a HED meteorite based on two impact melt inclusions of nearly rhyolitic composition (SiO<sub>2</sub> ~76-79.5 wt%, Al<sub>2</sub>O<sub>3 </sub>~11.4 - 12.8 wt%, total alkali ~3 - 8 wt% with K<sub>2</sub>O/ (Na<sub>2</sub>O + K<sub>2</sub>O) ~0.21-0.95, CaO ~ 0.8 - 4.67wt% and low total iron-magnesia ~1-2 wt%). Our study thus reinforces to conceive the idea that some rhyolitic crusts formed due to differentiation of mafic magma were exposed on Vesta and heterogeneity of Vestan surface is definitely different from one as previously thought.</p> <p>References: Clegg-Watkins, R.N. et al. 2016, Icarus 285:169-184. Morris, R.V. et al. 2016, 113:7071-7076. McSween, H.Y. et al. 2013, MAPS 48:2090-2104. De Sanctis, M.C. et al. 2012, Science 336:697-700. Prettyman, T.H. et al. 2012, Science 338:242-246. Chattopadhyay, B. et al. 1998. JGSI 51:171-174. Sisodia, M.S. et al. 2001 MAPS 36:1457-1466. Ghosh, S. IJG 65:251-264.</p>

Meteorite traces on a shatter cone surface from the Agoudal impact site, Morocco

2015 ◽  
Vol 152 (4) ◽  
pp. 751-757 ◽  
Author(s):  
M. SCHMIEDER ◽  
H. CHENNAOUI AOUDJEHANE ◽  
E. BUCHNER ◽  
E. TOHVER
Keyword(s):  
Iron Meteorite ◽  
Impact Structure ◽  
Iron Meteorites ◽  
Electron Microscopic ◽  
Impact Site ◽  
Scanning Electron Microscopic Study ◽  
Scanning Electron Microscopic ◽  
Cone Surface ◽  
Shatter Cones ◽  
The Impact

AbstractThe recently discovered Agoudal impact site in Morocco is a small, eroded impact structure with well-developed shatter cones. A scanning electron microscopic study of a shatter cone surface has revealed the presence of schreibersite – a phosphide very rare on Earth but common in iron meteorites – and Fe–Ni oxides. This is the first reported evidence for primary meteoritic matter adherent to shatter cones and suggests that the Agoudal crater was formed by the impact of an iron meteorite, probably the Agoudal IIAB iron. Shatter cones from other terrestrial impact structures might also hold valuable information about the nature of the impacting projectiles.

scholarly journals Early volatile depletion on planetesimals inferred from C–S systematics of iron meteorite parent bodies

2021 ◽  
Vol 118 (13) ◽  
pp. e2026779118
Author(s):  
Marc M. Hirschmann ◽  
Edwin A. Bergin ◽  
Geoff A. Blake ◽  
Fred J. Ciesla ◽  
Jie Li
Keyword(s):  
Thermodynamic Modeling ◽  
Open System ◽  
Closed System ◽  
Small Body ◽  
Parent Body ◽  
Iron Meteorite ◽  
Terrestrial Planets ◽  
Iron Meteorites ◽  
Body Core ◽  
Volatile Loss

During the formation of terrestrial planets, volatile loss may occur through nebular processing, planetesimal differentiation, and planetary accretion. We investigate iron meteorites as an archive of volatile loss during planetesimal processing. The carbon contents of the parent bodies of magmatic iron meteorites are reconstructed by thermodynamic modeling. Calculated solid/molten alloy partitioning of C increases greatly with liquid S concentration, and inferred parent body C concentrations range from 0.0004 to 0.11 wt%. Parent bodies fall into two compositional clusters characterized by cores with medium and low C/S. Both of these require significant planetesimal degassing, as metamorphic devolatilization on chondrite-like precursors is insufficient to account for their C depletions. Planetesimal core formation models, ranging from closed-system extraction to degassing of a wholly molten body, show that significant open-system silicate melting and volatile loss are required to match medium and low C/S parent body core compositions. Greater depletion in C relative to S is the hallmark of silicate degassing, indicating that parent body core compositions record processes that affect composite silicate/iron planetesimals. Degassing of bare cores stripped of their silicate mantles would deplete S with negligible C loss and could not account for inferred parent body core compositions. Devolatilization during small-body differentiation is thus a key process in shaping the volatile inventory of terrestrial planets derived from planetesimals and planetary embryos.

Evidence for ordered Fe3Ni

1987 ◽  
Vol 45 ◽  
pp. 216-217
Author(s):  
K.B. Reuter ◽  
D.B. Williams ◽  
J.I. Goldstein
Keyword(s):  
Experimental Data ◽  
Martensitic Transformation ◽  
Electron Diffraction ◽  
Room Temperature ◽  
Direct Evidence ◽  
Transformation Product ◽  
Iron Meteorites ◽  
X Ray ◽  
Ni Content ◽  
Temperature Transformation

In the Fe-Ni system, although ordered FeNi and ordered Ni3Fe are experimentally well established, direct evidence for ordered Fe3Ni is unconvincing. Little experimental data for Fe3Ni exists because diffusion is sluggish at temperatures below 400°C and because alloys containing less than 29 wt% Ni undergo a martensitic transformation at room temperature. Fe-Ni phases in iron meteorites were examined in this study because iron meteorites have cooled at slow rates of about 10°C/106 years, allowing phase transformations below 400°C to occur. One low temperature transformation product, called clear taenite 2 (CT2), was of particular interest because it contains less than 30 wtZ Ni and is not martensitic. Because CT2 is only a few microns in size, the structure and Ni content were determined through electron diffraction and x-ray microanalysis. A Philips EM400T operated at 120 kV, equipped with a Tracor Northern 2000 multichannel analyzer, was used.

scholarly journals The Impact of Initial Conditions in N-Body Simulations of Debris Discs

2015 ◽  
Vol 32 ◽  
Author(s):  
E. Thilliez ◽  
S. T. Maddison
Keyword(s):  
Numerical Simulations ◽  
Initial Conditions ◽  
Parent Body ◽  
Dust Trapping ◽  
Physical Context ◽  
Disc Width ◽  
Wide Range ◽  
Belt Width ◽  
New Generation ◽  
The Impact

AbstractNumerical simulations are a crucial tool to understand the relationship between debris discs and planetary companions. As debris disc observations are now reaching unprecedented levels of precision over a wide range of wavelengths, an appropriate level of accuracy and consistency is required in numerical simulations to confidently interpret this new generation of observations. However, simulations throughout the literature have been conducted with various initial conditions often with little or no justification. In this paper, we aim to study the dependence on the initial conditions of N-body simulations modelling the interaction between a massive and eccentric planet on an exterior debris disc. To achieve this, we first classify three broad approaches used in the literature and provide some physical context for when each category should be used. We then run a series of N-body simulations, that include radiation forces acting on small grains, with varying initial conditions across the three categories. We test the influence of the initial parent body belt width, eccentricity, and alignment with the planet on the resulting debris disc structure and compare the final peak emission location, disc width and offset of synthetic disc images produced with a radiative transfer code. We also track the evolution of the forced eccentricity of the dust grains induced by the planet, as well as resonance dust trapping. We find that an initially broad parent body belt always results in a broader debris disc than an initially narrow parent body belt. While simulations with a parent body belt with low initial eccentricity (e ~ 0) and high initial eccentricity (0 < e < 0.3) resulted in similar broad discs, we find that purely secular forced initial conditions, where the initial disc eccentricity is set to the forced value and the disc is aligned with the planet, always result in a narrower disc. We conclude that broad debris discs can be modelled by using either a dynamically cold or dynamically warm parent belt, while in contrast eccentric narrow debris rings are reproduced using a secularly forced parent body belt.

scholarly journals Pb isotopes in the impact melt breccia 66095: Association with the Imbrium basin and the isotopic composition of lithologies at the Apollo 16 landing site

2017 ◽  
Vol 466 ◽  
pp. 608-616 ◽  
Author(s):  
Joshua F. Snape ◽  
Alexander A. Nemchin ◽  
Jeremy J. Bellucci ◽  
Martin J. Whitehouse
Keyword(s):  
Isotopic Composition ◽  
Landing Site ◽  
Pb Isotopes ◽  
Impact Melt ◽  
The Impact

scholarly journals Ocean resurge-induced impact melt dynamics on the peak-ring of the Chicxulub impact structure, Mexico

2021 ◽  
Author(s):  
Felix M. Schulte ◽  
◽  
Axel Wittmann ◽  
Stefan Jung ◽  
Joanna V. Morgan ◽  
...  
Keyword(s):  
Impact Structure ◽  
Physical Processes ◽  
Hydrothermal Conditions ◽  
Chemical Examination ◽  
Impact Melt ◽  
Target Rock ◽  
Single Process ◽  
Chicxulub Impact ◽  
The Impact

AbstractCore from Hole M0077 from IODP/ICDP Expedition 364 provides unprecedented evidence for the physical processes in effect during the interaction of impact melt with rock-debris-laden seawater, following a large meteorite impact into waters of the Yucatán shelf. Evidence for this interaction is based on petrographic, microstructural and chemical examination of the 46.37-m-thick impact melt rock sequence, which overlies shocked granitoid target rock of the peak ring of the Chicxulub impact structure. The melt rock sequence consists of two visually distinct phases, one is black and the other is green in colour. The black phase is aphanitic and trachyandesitic in composition and similar to melt rock from other sites within the impact structure. The green phase consists chiefly of clay minerals and sparitic calcite, which likely formed from a solidified water–rock debris mixture under hydrothermal conditions. We suggest that the layering and internal structure of the melt rock sequence resulted from a single process, i.e., violent contact of initially superheated silicate impact melt with the ocean resurge-induced water–rock mixture overriding the impact melt. Differences in density, temperature, viscosity, and velocity of this mixture and impact melt triggered Kelvin–Helmholtz and Rayleigh–Taylor instabilities at their phase boundary. As a consequence, shearing at the boundary perturbed and, thus, mingled both immiscible phases, and was accompanied by phreatomagmatic processes. These processes led to the brecciation at the top of the impact melt rock sequence. Quenching of this breccia by the seawater prevented reworking of the solidified breccia layers upon subsequent deposition of suevite. Solid-state deformation, notably in the uppermost brecciated impact melt rock layers, attests to long-term gravitational settling of the peak ring.

The Projectile of the Lappajärvi Impact Crater

1980 ◽  
Vol 35 (2) ◽  
pp. 197-203 ◽  
Author(s):  
Elke Göbel ◽  
Uwe Reimold ◽  
Hildegard Baddenhausen ◽  
Herbert Palme
Keyword(s):  
Impact Crater ◽  
Carbonaceous Chondrite ◽  
Volatile Elements ◽  
Rich Phase ◽  
Impact Melt ◽  
Siderophile Elements ◽  
High Concentrations ◽  
Impact Melts

Abstract Two impact melt samples from the Lappajärvi crater (Scandinavia) are highly enriched in siderophile elements, such as Ir, Re, and Os. This indicates the presence of a meteoritic component. The simultaneous enrichments of Ni, Co, Cr, and Se suggest a chondritic projectile. Because of the relatively large indigenous contributions to Ni, Co, and Cr, it is not possible to distinguish between a normal and a carbonaceous chondrite. The high concentrations of relatively volatile elements could point towards a volatile-rich projectile.The two melt samples have high Re/Ir ratios compared to chondritic ratios. Enrichment of Re relative to Ir is very unusual in terrestrial impact melts. Loss of Re, because of volatilisation under oxidizing conditions or by weathering is frequently observed.The high Re/Ir ratios and the high abundances of relatively volatile elements either indicate the presence of a volatile rich phase or they characterize a type of meteorite, which has not been sampled. Some lunar highland rocks have a pattern of meteoritic elements rather similar to that observed for the Lappajärvi meteorite.The Lappajärvi crater is, after Rocheehouart, the second European crater where a significant amount of meteoritic component has been found.A melt sample from the Lake St. Martin crater (Manitoba), did not show any enrichment in meteoritic elements.

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