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T H Burbine - One of the best experts on this subject based on the ideXlab platform.
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Geochemistry and oxygen isotope composition of main-group pallasites and olivine-rich clasts in Mesosiderites: Implications for the “Great Dunite Shortage” and HED-Mesosiderite connection
Geochimica et Cosmochimica Acta Supplement, 2015Co-Authors: Richard C. Greenwood, Ian A. Franchi, Jean-alix Barrat, Henning Haack, P. C. Buchanan, Akira Yamaguchi, Diane Johnson, A. W. R. Bevan, Edward R.d. Scott, T H BurbineAbstract:Evidence from iron meteorites indicates that a large number of differentiated planetesimals formed early in Solar System history. These bodies should have had well-developed olivine-rich mantles and consequentially such materials ought to be abundant both as asteroids and meteorites, which they are not. To investigate this "Great Dunite Shortage" we have undertaken a geochemical and oxygen isotope study of main-group pallasites and dunitic rocks from Mesosiderites. Oxygen isotope analysis of 24 main-group pallasites (103 replicates) yielded a mean Delta O-17 value of -0.187 +/- 0.016 parts per thousand (2 sigma), which is fully resolved from the HED Delta O-17 value of -0.246 +/- 0.014 (2 sigma) obtained in our earlier study and demonstrates that both groups represent distinct populations and were derived from separate parent bodies. Our results show no evidence for Delta O-17 bimodality within the main-group pallasites, as suggested by a number of previous studies. Olivine-rich materials from the Vaca Muerta, Mount Padbury and Lamont Mesosiderites, and from two related dunites (NWA 2968 and NWA 3329), have Delta O-17 values within error of the Mesosiderite average. This indicates that these olivine-rich materials are co-genetic with other Mesosiderite clasts and are not fragments from an isotopically distinct pallasite-like impactor. Despite its extreme lithologic diversity the Mesosiderite parent body was essentially homogeneous with respect to Delta O-17, a feature best explained by an early phase of large-scale melting (magma ocean), followed by prolonged igneous differentiation. Based on the results of magma ocean modeling studies, we infer that Mg-rich olivines in Mesosiderites formed as cumulates in high-level chambers and do not represent samples of the underlying mantle. By analogy, recently documented Mg-rich olivines in howardites may have a similar origin. Although the Dawn mission did not detect Mesosiderite-like material on Vesta, evidence linking the Mesosiderites and HEDs includes: (i) their nearly identical oxygen isotope compositions; (ii) the presence in both of coarse-grained Mg-rich olivines; (iii) both have synchronous Lu-Hf and Mn-Cr ages; (iv) there are compositional similarities between the metal in both; and (v) Mesosiderite-like material has been identified in a howardite breccia. The source of the Mesosiderites remains an outstanding question in meteorite science. The underrepresentation of olivine-rich materials amongst both asteroids and meteorites results from a range of factors. However, evidence from pallasites and Mesosiderites indicates that the most important reason for this olivine shortage lies in the early, catastrophic destruction of planetesimals in the terrestrial planet-forming region and the subsequent preferential loss of their olivine-rich mantles
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Geochemistry and oxygen isotope composition of main-group pallasites and olivine-rich clasts in Mesosiderites: Implications for the “Great Dunite Shortage” and HED-Mesosiderite connection
Geochimica et Cosmochimica Acta, 2015Co-Authors: Richard C. Greenwood, Ian A. Franchi, Jean-alix Barrat, Edward Scott, Henning Haack, P. C. Buchanan, Akira Yamaguchi, Diane Johnson, A. W. R. Bevan, T H BurbineAbstract:Evidence from iron meteorites indicates that a large number of differentiated planetesimals formed early in Solar System history. These bodies should have had welldeveloped olivine-rich mantles and consequentially such materials ought to be abundant both as asteroids and meteorites, which they are not. To investigate this “Great Dunite Shortage” we have undertaken a geochemical and oxygen isotope study of main-group pallasites and dunitic rocks from Mesosiderites. Oxygen isotope analysis of 24 main-group pallasites (103 replicates) yielded a mean 17O value of -0.187±0.016‰ (2 ), which is fully resolved from the HED 17O value of -0.246 ± 0.014 (2 ) obtained in our earlier study and demonstrates that both groups represent distinct populations and were derived from separate parent bodies. Our results show no evidence for 17O bimodality within the main-group pallasites, as suggested by a number of previous studies. Olivine-rich materials from the Vaca Muerta, Mount Padbury and Lamont Mesosiderites, and from two related dunites (NWA 2968 and NWA 3329), have 17O values within error of the Mesosiderite average. This indicates that these olivine-rich materials are co-genetic with other Mesosiderite clasts and are not fragments from an isotopically distinct pallasite-like impactor. Despite its extreme lithologic diversity the Mesosiderite parent body was essentially homogeneous with respect to 17O, a feature best explained by an early phase of large-scale melting (magma ocean), followed by prolonged igneous differentiation. Based on the results of magma ocean modeling studies, we infer that Mg-rich olivines in Mesosiderites formed as cumulates in high-level chambers and do not represent samples of the underlying mantle. By analogy, recently documented Mg-rich olivines in howardites may have a similar origin. Although the Dawn mission did not detect Mesosiderite-like material on Vesta, evidence linking the Mesosiderites and HEDs includes: i) their nearly identical oxygen isotope compositions; ii) the presence in both of coarse-grained Mg-rich olivines; iii) both have synchronous Lu-Hf and Mn-Cr ages; iv) there are compositional similarities between the metal in both; and v) Mesosiderite-like material has been identified in a howardite breccia. The source of the Mesosiderites remains an outstanding question in meteorite science. The underrepresentation of olivine-rich materials amongst both asteroids and meteorites results from a range of factors. However, evidence from pallasites and Mesosiderites indicates that the most important reason for this olivine shortage lies in the early, catastrophic destruction of planetesimals in the terrestrial planet-forming region and the subsequent preferential loss of their olivine-rich mantles.
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Reflectance spectra of Mesosiderites: Implications for asteroid 4 Vesta
2007Co-Authors: T H Burbine, Ian A. Franchi, Richard C. Greenwood, P. C. Buchanan, Caroline SmithAbstract:Oxygen isotopic data argues that HEDs and Mesosiderites may be from the same parent body. A spectral survey of Mesosiderites was done to determine their spectral properties in the visible and near-infrared and compare to HEDs.
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oxygen isotope variation in stony iron meteorites
Science, 2006Co-Authors: R C Greenwood, Albert Jambon, Ian A. Franchi, Jean-alix Barrat, T H BurbineAbstract:Asteroidal material, delivered to Earth as meteorites, preserves a record of the earliest stages of planetary formation. High-precision oxygen isotope analyses for the two major groups of stony-iron meteorites (main-group pallasites and Mesosiderites) demonstrate that each group is from a distinct asteroidal source. Mesosiderites are isotopically identical to the howardite-eucrite-diogenite clan and, like them, are probably derived from the asteroid 4 Vesta. Main-group pallasites represent intermixed core-mantle material from a single disrupted asteroid and have no known equivalents among the basaltic meteorites. The stony-iron meteorites demonstrate that intense asteroidal deformation accompanied planetary accretion in the early Solar System.
Matthew L. Morgan - One of the best experts on this subject based on the ideXlab platform.
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A “Mesosiderite” rock from northern Siberia, Russia: Not a meteorite
Meteoritics & Planetary Science, 2002Co-Authors: Allan H. Treiman, Ian A. Franchi, David J. Lindstrom, C. Schwandt, Matthew L. MorganAbstract:A possible Mesosiderite meteorite was found in the area of the Putorana Plateau, Noril'sk district, Siberia, Russia. Although this rock resembles a Mesosiderite in its hand-sample aspect and in having Ni-bearing iron metal, it is not a meteorite. This inference is based on the lack of a fusion crust, the lack of cosmogenic nuclides, oxygen with terrestrial isotope ratios, and several mineral chemical criteria. Most likely, the rock is from the iron-metal-bearing basalts of the Siberian Trap basalt sequence, which are mined for their base and platinum-group metals. Mesosiderite imposters like this may be recognized by: (1) the presence of Cu metal in hand sample or as microscopic blebs in the low-Ni metal (kamacite), (2) the absence of high-Ni metal (taenite), and (3) the presence of iron carbide (cohenite) enclosing the kamacite. Even if these macroscopic tests are inconclusive, isotopic and mineral chemical tests will also distinguish rocks like this from Mesosiderites.
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a Mesosiderite rock from northern siberia russia not a meteorite
Meteoritics & Planetary Science, 2002Co-Authors: Allan H. Treiman, David J. Lindstrom, C. Schwandt, I A Franchi, Matthew L. MorganAbstract:A possible Mesosiderite meteorite was found in the area of the Putorana Plateau, Noril'sk district, Siberia, Russia. Although this rock resembles a Mesosiderite in its hand-sample aspect and in having Ni-bearing iron metal, it is not a meteorite. This inference is based on the lack of a fusion crust, the lack of cosmogenic nuclides, oxygen with terrestrial isotope ratios, and several mineral chemical criteria. Most likely, the rock is from the iron-metal-bearing basalts of the Siberian Trap basalt sequence, which are mined for their base and platinum-group metals. Mesosiderite imposters like this may be recognized by: (1) the presence of Cu metal in hand sample or as microscopic blebs in the low-Ni metal (kamacite), (2) the absence of high-Ni metal (taenite), and (3) the presence of iron carbide (cohenite) enclosing the kamacite. Even if these macroscopic tests are inconclusive, isotopic and mineral chemical tests will also distinguish rocks like this from Mesosiderites.
Akira Yamaguchi - One of the best experts on this subject based on the ideXlab platform.
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Two generations of exsolution lamellae in pyroxene from Asuka 09545: Clues to the thermal evolution of silicates in Mesosiderite
American Mineralogist, 2019Co-Authors: Lidia Pittarello, Akira Yamaguchi, S. Mckibbin, Dominique Schryvers, Vinciane Debaille, Philippe ClaeysAbstract:Abstract Mesosiderite meteorites consist of a mixture of crustal basaltic or gabbroic material and metal. Their formation process is still debated due to their unexpected combination of crust and core materials, possibly derived from the same planetesimal parent body, and lacking an intervening mantle component. Mesosiderites have experienced an extremely slow cooling rate from ca. 550 °C, as recorded in the metal (0.25–0.5 °C/Ma). Here we present a detailed investigation of exsolution features in pyroxene from the Antarctic Mesosiderite Asuka (A) 09545. Geothermobarometry calculations, lattice parameters, lamellae orientation, and the presence of clinoenstatite as the host were used in an attempt to constrain the evolution of pyroxene from 1150 to 570 °C and the formation of two generations of exsolution lamellae. After pigeonite crystallization at ca. 1150 °C, the first exsolution process generated the thick augite lamellae along (100) in the temperature interval 1000–900 °C. By further cooling, a second order of exsolution lamellae formed within augite along (001), consisting of monoclinic low-Ca pyroxene, equilibrated in the temperature range 900–800 °C. The last process, occurring in the 600–500 °C temperature range, was likely the inversion of high to low pigeonite in the host crystal, lacking evidence for nucleation of orthopyroxene. The formation of two generations of exsolution lamellae, as well as of likely metastable pigeonite, suggest non-equilibrium conditions. Cooling was sufficiently slow to allow the formation of the lamellae, their preservation, and the transition from high to low pigeonite. In addition, the preservation of such fine-grained lamellae limits long-lasting, impact reheating to a peak temperature lower than 570 °C. These features, including the presence of monoclinic low-Ca pyroxene as the host, are reported in only a few Mesosiderites. This suggests a possibly different origin and thermal history from most Mesosiderites and that the crystallography (i.e., space group) of low-Ca pyroxene could be used as parameter to distinguish Mesosiderite populations based on their cooling history.
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Mesosiderite formation on asteroid 4 Vesta by a hit-and-run collision
Nature Geoscience, 2019Co-Authors: Makiko K. Haba, Akira Yamaguchi, Jörn-frederik Wotzlaw, Maria SchönbächlerAbstract:Collision and disruption processes of protoplanetary bodies in the early Solar System are key to understanding the genesis of diverse types of main-belt asteroids. Mesosiderites are stony-iron meteorites that formed by the mixing of howardite–eucrite–diogenite-like crust and molten core materials and provide unique insights into the catastrophic break-up of differentiated asteroids. However, the enigmatic formation process and the poorly constrained timing of metal–silicate mixing complicate the assignment to potential parent bodies. Here we report the high-precision uranium–lead dating of Mesosiderite zircons by isotope dilution thermal ionization mass spectrometry to reveal an initial crust formation 4,558.5 ± 2.1 million years ago and metal–silicate mixing at 4,525.39 ± 0.85 million years ago. The two distinct ages coincide with the timing of the crust formation and a large-scale reheating event on the eucrite parent body, probably the asteroid Vesta. This chronological coincidence corroborates that Vesta is the parent body of Mesosiderite silicates. Mesosiderite formation on Vesta can be explained by a hit-and-run collision 4,525.4 million years ago that caused the thick crust observed by NASA’s Dawn mission and explains the missing olivine in Mesosiderites, howardite–eucrite–diogenite meteorites and vestoids. Mesosiderite meteorites may originate from a hit-and-run impact on the parent asteroid of eucrite meteorites (probably Vesta), as Mesosiderite zircon U–Pb ages are found to coincide with those for eucrites.
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Trace element composition and U-Pb age of zircons from Estherville: Constraints on the timing of the metal-silicate mixing event on the Mesosiderite parent body
Geochimica et Cosmochimica Acta, 2017Co-Authors: Makiko K. Haba, Akira Yamaguchi, Hiroyuki Kagi, Keisuke Nagao, Hiroshi HidakaAbstract:Abstract Mesosiderites are a group of stony-iron meteorites, which are thought to be the result of mixing of silicates with Fe-Ni metal. In this study, we combined textural observations with geochemical and chronological studies of two zircon grains found in the Estherville Mesosiderite. One of the zircons (Zrc1) occurs with pyroxene, plagioclase, troilite, and silica, and the other (Zrc2) is located at a boundary between Fe-Ni metal and a silicate part mainly composed of pyroxene and plagioclase. The textural observations demonstrate that Zrc1 is relatively homogenous, whereas Zrc2 is composed of at least two chemically distinct domains. Trace element analyses of Zrc2 resolve large concentration gradients within this single grain with variations that are an order of magnitude for rare earth elements (REE) and two orders of magnitude for U and Th. The lowest trace element concentration in Zrc2 is more than an order of magnitude lower than those of lunar and eucritic zircons. However, it is similar to those of Zrc1 and a zircon from the Vaca Muerta Mesosiderite. The calculated REE composition of the melt in equilibrium with Zrc2 shows that Zrc2 and perhaps also Zrc1 did not crystallize from a melt that was produced by fractional crystallization of the primary magmatic mineral assemblages. The zircons with low REE, U, and Th concentrations can be interpreted to have formed in a residual melt after incorporation of large amounts of REE, U, and Th into secondary phosphate minerals, which formed during the metal-silicate mixing event. The large concentration gradients observed in Zrc2 suggest significant heterogeneities in the melt from which the zircon crystallized. Alternatively, either mixing or diffusion between a relict zircon and a newly formed zircon could explain the observed concentration gradients. However, the REE patterns of Zrc2 cannot be explained by mixing or diffusion between the two distinct generations of zircons. These considerations suggest that Zrc1 and Zrc2 formed during a high-temperature reheating event, which is probably related to the metal-silicate mixing event. The weighted average 207 Pb- 206 Pb age obtained by SIMS from both zircons is 4521 ± 26 Ma (2σ). This age is younger than that of a primary magmatic zircon from Vaca Muerta (4563 ± 15 Ma) and probably corresponds to the timing of the metal-silicate mixing event or a later impact event.
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Geochemistry and oxygen isotope composition of main-group pallasites and olivine-rich clasts in Mesosiderites: Implications for the “Great Dunite Shortage” and HED-Mesosiderite connection
Geochimica et Cosmochimica Acta Supplement, 2015Co-Authors: Richard C. Greenwood, Ian A. Franchi, Jean-alix Barrat, Henning Haack, P. C. Buchanan, Akira Yamaguchi, Diane Johnson, A. W. R. Bevan, Edward R.d. Scott, T H BurbineAbstract:Evidence from iron meteorites indicates that a large number of differentiated planetesimals formed early in Solar System history. These bodies should have had well-developed olivine-rich mantles and consequentially such materials ought to be abundant both as asteroids and meteorites, which they are not. To investigate this "Great Dunite Shortage" we have undertaken a geochemical and oxygen isotope study of main-group pallasites and dunitic rocks from Mesosiderites. Oxygen isotope analysis of 24 main-group pallasites (103 replicates) yielded a mean Delta O-17 value of -0.187 +/- 0.016 parts per thousand (2 sigma), which is fully resolved from the HED Delta O-17 value of -0.246 +/- 0.014 (2 sigma) obtained in our earlier study and demonstrates that both groups represent distinct populations and were derived from separate parent bodies. Our results show no evidence for Delta O-17 bimodality within the main-group pallasites, as suggested by a number of previous studies. Olivine-rich materials from the Vaca Muerta, Mount Padbury and Lamont Mesosiderites, and from two related dunites (NWA 2968 and NWA 3329), have Delta O-17 values within error of the Mesosiderite average. This indicates that these olivine-rich materials are co-genetic with other Mesosiderite clasts and are not fragments from an isotopically distinct pallasite-like impactor. Despite its extreme lithologic diversity the Mesosiderite parent body was essentially homogeneous with respect to Delta O-17, a feature best explained by an early phase of large-scale melting (magma ocean), followed by prolonged igneous differentiation. Based on the results of magma ocean modeling studies, we infer that Mg-rich olivines in Mesosiderites formed as cumulates in high-level chambers and do not represent samples of the underlying mantle. By analogy, recently documented Mg-rich olivines in howardites may have a similar origin. Although the Dawn mission did not detect Mesosiderite-like material on Vesta, evidence linking the Mesosiderites and HEDs includes: (i) their nearly identical oxygen isotope compositions; (ii) the presence in both of coarse-grained Mg-rich olivines; (iii) both have synchronous Lu-Hf and Mn-Cr ages; (iv) there are compositional similarities between the metal in both; and (v) Mesosiderite-like material has been identified in a howardite breccia. The source of the Mesosiderites remains an outstanding question in meteorite science. The underrepresentation of olivine-rich materials amongst both asteroids and meteorites results from a range of factors. However, evidence from pallasites and Mesosiderites indicates that the most important reason for this olivine shortage lies in the early, catastrophic destruction of planetesimals in the terrestrial planet-forming region and the subsequent preferential loss of their olivine-rich mantles
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Geochemistry and oxygen isotope composition of main-group pallasites and olivine-rich clasts in Mesosiderites: Implications for the “Great Dunite Shortage” and HED-Mesosiderite connection
Geochimica et Cosmochimica Acta, 2015Co-Authors: Richard C. Greenwood, Ian A. Franchi, Jean-alix Barrat, Edward Scott, Henning Haack, P. C. Buchanan, Akira Yamaguchi, Diane Johnson, A. W. R. Bevan, T H BurbineAbstract:Evidence from iron meteorites indicates that a large number of differentiated planetesimals formed early in Solar System history. These bodies should have had welldeveloped olivine-rich mantles and consequentially such materials ought to be abundant both as asteroids and meteorites, which they are not. To investigate this “Great Dunite Shortage” we have undertaken a geochemical and oxygen isotope study of main-group pallasites and dunitic rocks from Mesosiderites. Oxygen isotope analysis of 24 main-group pallasites (103 replicates) yielded a mean 17O value of -0.187±0.016‰ (2 ), which is fully resolved from the HED 17O value of -0.246 ± 0.014 (2 ) obtained in our earlier study and demonstrates that both groups represent distinct populations and were derived from separate parent bodies. Our results show no evidence for 17O bimodality within the main-group pallasites, as suggested by a number of previous studies. Olivine-rich materials from the Vaca Muerta, Mount Padbury and Lamont Mesosiderites, and from two related dunites (NWA 2968 and NWA 3329), have 17O values within error of the Mesosiderite average. This indicates that these olivine-rich materials are co-genetic with other Mesosiderite clasts and are not fragments from an isotopically distinct pallasite-like impactor. Despite its extreme lithologic diversity the Mesosiderite parent body was essentially homogeneous with respect to 17O, a feature best explained by an early phase of large-scale melting (magma ocean), followed by prolonged igneous differentiation. Based on the results of magma ocean modeling studies, we infer that Mg-rich olivines in Mesosiderites formed as cumulates in high-level chambers and do not represent samples of the underlying mantle. By analogy, recently documented Mg-rich olivines in howardites may have a similar origin. Although the Dawn mission did not detect Mesosiderite-like material on Vesta, evidence linking the Mesosiderites and HEDs includes: i) their nearly identical oxygen isotope compositions; ii) the presence in both of coarse-grained Mg-rich olivines; iii) both have synchronous Lu-Hf and Mn-Cr ages; iv) there are compositional similarities between the metal in both; and v) Mesosiderite-like material has been identified in a howardite breccia. The source of the Mesosiderites remains an outstanding question in meteorite science. The underrepresentation of olivine-rich materials amongst both asteroids and meteorites results from a range of factors. However, evidence from pallasites and Mesosiderites indicates that the most important reason for this olivine shortage lies in the early, catastrophic destruction of planetesimals in the terrestrial planet-forming region and the subsequent preferential loss of their olivine-rich mantles.
Ian A. Franchi - One of the best experts on this subject based on the ideXlab platform.
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Geochemistry and oxygen isotope composition of main-group pallasites and olivine-rich clasts in Mesosiderites: Implications for the “Great Dunite Shortage” and HED-Mesosiderite connection
Geochimica et Cosmochimica Acta Supplement, 2015Co-Authors: Richard C. Greenwood, Ian A. Franchi, Jean-alix Barrat, Henning Haack, P. C. Buchanan, Akira Yamaguchi, Diane Johnson, A. W. R. Bevan, Edward R.d. Scott, T H BurbineAbstract:Evidence from iron meteorites indicates that a large number of differentiated planetesimals formed early in Solar System history. These bodies should have had well-developed olivine-rich mantles and consequentially such materials ought to be abundant both as asteroids and meteorites, which they are not. To investigate this "Great Dunite Shortage" we have undertaken a geochemical and oxygen isotope study of main-group pallasites and dunitic rocks from Mesosiderites. Oxygen isotope analysis of 24 main-group pallasites (103 replicates) yielded a mean Delta O-17 value of -0.187 +/- 0.016 parts per thousand (2 sigma), which is fully resolved from the HED Delta O-17 value of -0.246 +/- 0.014 (2 sigma) obtained in our earlier study and demonstrates that both groups represent distinct populations and were derived from separate parent bodies. Our results show no evidence for Delta O-17 bimodality within the main-group pallasites, as suggested by a number of previous studies. Olivine-rich materials from the Vaca Muerta, Mount Padbury and Lamont Mesosiderites, and from two related dunites (NWA 2968 and NWA 3329), have Delta O-17 values within error of the Mesosiderite average. This indicates that these olivine-rich materials are co-genetic with other Mesosiderite clasts and are not fragments from an isotopically distinct pallasite-like impactor. Despite its extreme lithologic diversity the Mesosiderite parent body was essentially homogeneous with respect to Delta O-17, a feature best explained by an early phase of large-scale melting (magma ocean), followed by prolonged igneous differentiation. Based on the results of magma ocean modeling studies, we infer that Mg-rich olivines in Mesosiderites formed as cumulates in high-level chambers and do not represent samples of the underlying mantle. By analogy, recently documented Mg-rich olivines in howardites may have a similar origin. Although the Dawn mission did not detect Mesosiderite-like material on Vesta, evidence linking the Mesosiderites and HEDs includes: (i) their nearly identical oxygen isotope compositions; (ii) the presence in both of coarse-grained Mg-rich olivines; (iii) both have synchronous Lu-Hf and Mn-Cr ages; (iv) there are compositional similarities between the metal in both; and (v) Mesosiderite-like material has been identified in a howardite breccia. The source of the Mesosiderites remains an outstanding question in meteorite science. The underrepresentation of olivine-rich materials amongst both asteroids and meteorites results from a range of factors. However, evidence from pallasites and Mesosiderites indicates that the most important reason for this olivine shortage lies in the early, catastrophic destruction of planetesimals in the terrestrial planet-forming region and the subsequent preferential loss of their olivine-rich mantles
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Geochemistry and oxygen isotope composition of main-group pallasites and olivine-rich clasts in Mesosiderites: Implications for the “Great Dunite Shortage” and HED-Mesosiderite connection
Geochimica et Cosmochimica Acta, 2015Co-Authors: Richard C. Greenwood, Ian A. Franchi, Jean-alix Barrat, Edward Scott, Henning Haack, P. C. Buchanan, Akira Yamaguchi, Diane Johnson, A. W. R. Bevan, T H BurbineAbstract:Evidence from iron meteorites indicates that a large number of differentiated planetesimals formed early in Solar System history. These bodies should have had welldeveloped olivine-rich mantles and consequentially such materials ought to be abundant both as asteroids and meteorites, which they are not. To investigate this “Great Dunite Shortage” we have undertaken a geochemical and oxygen isotope study of main-group pallasites and dunitic rocks from Mesosiderites. Oxygen isotope analysis of 24 main-group pallasites (103 replicates) yielded a mean 17O value of -0.187±0.016‰ (2 ), which is fully resolved from the HED 17O value of -0.246 ± 0.014 (2 ) obtained in our earlier study and demonstrates that both groups represent distinct populations and were derived from separate parent bodies. Our results show no evidence for 17O bimodality within the main-group pallasites, as suggested by a number of previous studies. Olivine-rich materials from the Vaca Muerta, Mount Padbury and Lamont Mesosiderites, and from two related dunites (NWA 2968 and NWA 3329), have 17O values within error of the Mesosiderite average. This indicates that these olivine-rich materials are co-genetic with other Mesosiderite clasts and are not fragments from an isotopically distinct pallasite-like impactor. Despite its extreme lithologic diversity the Mesosiderite parent body was essentially homogeneous with respect to 17O, a feature best explained by an early phase of large-scale melting (magma ocean), followed by prolonged igneous differentiation. Based on the results of magma ocean modeling studies, we infer that Mg-rich olivines in Mesosiderites formed as cumulates in high-level chambers and do not represent samples of the underlying mantle. By analogy, recently documented Mg-rich olivines in howardites may have a similar origin. Although the Dawn mission did not detect Mesosiderite-like material on Vesta, evidence linking the Mesosiderites and HEDs includes: i) their nearly identical oxygen isotope compositions; ii) the presence in both of coarse-grained Mg-rich olivines; iii) both have synchronous Lu-Hf and Mn-Cr ages; iv) there are compositional similarities between the metal in both; and v) Mesosiderite-like material has been identified in a howardite breccia. The source of the Mesosiderites remains an outstanding question in meteorite science. The underrepresentation of olivine-rich materials amongst both asteroids and meteorites results from a range of factors. However, evidence from pallasites and Mesosiderites indicates that the most important reason for this olivine shortage lies in the early, catastrophic destruction of planetesimals in the terrestrial planet-forming region and the subsequent preferential loss of their olivine-rich mantles.
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Reflectance spectra of Mesosiderites: Implications for asteroid 4 Vesta
2007Co-Authors: T H Burbine, Ian A. Franchi, Richard C. Greenwood, P. C. Buchanan, Caroline SmithAbstract:Oxygen isotopic data argues that HEDs and Mesosiderites may be from the same parent body. A spectral survey of Mesosiderites was done to determine their spectral properties in the visible and near-infrared and compare to HEDs.
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oxygen isotope variation in stony iron meteorites
Science, 2006Co-Authors: R C Greenwood, Albert Jambon, Ian A. Franchi, Jean-alix Barrat, T H BurbineAbstract:Asteroidal material, delivered to Earth as meteorites, preserves a record of the earliest stages of planetary formation. High-precision oxygen isotope analyses for the two major groups of stony-iron meteorites (main-group pallasites and Mesosiderites) demonstrate that each group is from a distinct asteroidal source. Mesosiderites are isotopically identical to the howardite-eucrite-diogenite clan and, like them, are probably derived from the asteroid 4 Vesta. Main-group pallasites represent intermixed core-mantle material from a single disrupted asteroid and have no known equivalents among the basaltic meteorites. The stony-iron meteorites demonstrate that intense asteroidal deformation accompanied planetary accretion in the early Solar System.
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A “Mesosiderite” rock from northern Siberia, Russia: Not a meteorite
Meteoritics & Planetary Science, 2002Co-Authors: Allan H. Treiman, Ian A. Franchi, David J. Lindstrom, C. Schwandt, Matthew L. MorganAbstract:A possible Mesosiderite meteorite was found in the area of the Putorana Plateau, Noril'sk district, Siberia, Russia. Although this rock resembles a Mesosiderite in its hand-sample aspect and in having Ni-bearing iron metal, it is not a meteorite. This inference is based on the lack of a fusion crust, the lack of cosmogenic nuclides, oxygen with terrestrial isotope ratios, and several mineral chemical criteria. Most likely, the rock is from the iron-metal-bearing basalts of the Siberian Trap basalt sequence, which are mined for their base and platinum-group metals. Mesosiderite imposters like this may be recognized by: (1) the presence of Cu metal in hand sample or as microscopic blebs in the low-Ni metal (kamacite), (2) the absence of high-Ni metal (taenite), and (3) the presence of iron carbide (cohenite) enclosing the kamacite. Even if these macroscopic tests are inconclusive, isotopic and mineral chemical tests will also distinguish rocks like this from Mesosiderites.
Allan H. Treiman - One of the best experts on this subject based on the ideXlab platform.
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A “Mesosiderite” rock from northern Siberia, Russia: Not a meteorite
Meteoritics & Planetary Science, 2002Co-Authors: Allan H. Treiman, Ian A. Franchi, David J. Lindstrom, C. Schwandt, Matthew L. MorganAbstract:A possible Mesosiderite meteorite was found in the area of the Putorana Plateau, Noril'sk district, Siberia, Russia. Although this rock resembles a Mesosiderite in its hand-sample aspect and in having Ni-bearing iron metal, it is not a meteorite. This inference is based on the lack of a fusion crust, the lack of cosmogenic nuclides, oxygen with terrestrial isotope ratios, and several mineral chemical criteria. Most likely, the rock is from the iron-metal-bearing basalts of the Siberian Trap basalt sequence, which are mined for their base and platinum-group metals. Mesosiderite imposters like this may be recognized by: (1) the presence of Cu metal in hand sample or as microscopic blebs in the low-Ni metal (kamacite), (2) the absence of high-Ni metal (taenite), and (3) the presence of iron carbide (cohenite) enclosing the kamacite. Even if these macroscopic tests are inconclusive, isotopic and mineral chemical tests will also distinguish rocks like this from Mesosiderites.
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a Mesosiderite rock from northern siberia russia not a meteorite
Meteoritics & Planetary Science, 2002Co-Authors: Allan H. Treiman, David J. Lindstrom, C. Schwandt, I A Franchi, Matthew L. MorganAbstract:A possible Mesosiderite meteorite was found in the area of the Putorana Plateau, Noril'sk district, Siberia, Russia. Although this rock resembles a Mesosiderite in its hand-sample aspect and in having Ni-bearing iron metal, it is not a meteorite. This inference is based on the lack of a fusion crust, the lack of cosmogenic nuclides, oxygen with terrestrial isotope ratios, and several mineral chemical criteria. Most likely, the rock is from the iron-metal-bearing basalts of the Siberian Trap basalt sequence, which are mined for their base and platinum-group metals. Mesosiderite imposters like this may be recognized by: (1) the presence of Cu metal in hand sample or as microscopic blebs in the low-Ni metal (kamacite), (2) the absence of high-Ni metal (taenite), and (3) the presence of iron carbide (cohenite) enclosing the kamacite. Even if these macroscopic tests are inconclusive, isotopic and mineral chemical tests will also distinguish rocks like this from Mesosiderites.
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An improbable concentration of basaltic meteorite falls (HED and Mesosiderite) in the mid-20th century
Meteoritics, 1993Co-Authors: Allan H. TreimanAbstract:The fall rate of HED basaltic meteorites (howardites, eucrites, diogenites) has not been constant in the 20th century, while the fall rate of chondrites has been constant within error. Thirteen of the 26 dated HED falls (day of fall known, 1900 through 1989) fell in 1924 through 1939. A fall cluster (not a meteorite stream) like this will occur in less than one in 100 random distributions of fall days. The proportions of HED types in the whole cluster are statistically identical to those of the whole historical record of HED falls, as is the distribution of cosmic ray exposure ages. In a subset of the cluster, 1924 through 1933, eight of those nine HED falls from have exposure ages of 10–20 Ma; this grouping is statistically distinct from that of the historical record. The Mesosiderite meteorites share many chemical and isotopic properties with the HEDs but are not from the same parent body. However, the dates of the three Mesosiderite falls of the 20th century (all in 1924 through 1939) are a likely sampling of the distribution of HED fall dates; less than one in 200 random distributions of three fall dates would have them all in a given IS year interval of the 20th century. If the concentration of HED and Mesosiderite falls in 1924 through 1939 is not a result of chance (odds of less than 1 in 200), it must have had a cause or causes. The cause(s) are not dear but appear(s) to have operated: on parent bodies only of basaltic meteorites; on a number of such parent bodies (Mesosiderite and at least one HED); distant from Earth; and so as to produce a duster of only 15 years duration. This duration is much shorter than the expected time scales or orbital evolution of asteroidal fragments.