Papers by Marc Chaussidon
Petrology, 2009
Phosphorus-bearing Fe and Ni sulfides represent a new type of phosphorus compounds and are charac... more Phosphorus-bearing Fe and Ni sulfides represent a new type of phosphorus compounds and are characteristic accessory phases of CM chondrites. The proportions of atoms in the sulfides can be approximated by the equation (Fe + Ni)/P = 0.965 ± 0.003 (1 σ) • S / P + 1.255 ± 0.036 (1 σ). Sulfides with high S/P ratios are systematically richer in Fe and poorer in Ni compared with low-S/P sulfides. Their characteristic minor elements are Cr, Ca, Co, K, and Na. The contents of Cr and Ca may reach several weight percent, but their incorporation does not affect the relation between (Fe + Ni)/P and S/P. This is also true of light elements (O and H), which probably occur in the P-bearing sulfides in certain amounts. The sulfides are usually associated with schreibersite, barringerite, eskolaite, and daubreelite. A negative correlation was observed between the Fe/Ni ratios of coexisting P-bearing sulfides and phosphides. Metallic iron was never found in association with the sulfides. It can be suggested that P-bearing sulfide is a primary phase rather than a secondary alteration product formed under the conditions of the CM chondrite parent body. This phase had to be stable in the solar nebula after the formation of Ca-Al inclusions and before the condensation of Fe-Ni metal. At high temperatures, P-bearing sulfide with low Fe/Ni and S/P ratios coexists with schreibersite in the solar gas. During condensation schreibersite is replaced by barringerite, which is accompanied by a decrease in the Fe/Ni ratio of phosphides and an increase in the S/P and Fe/Ni ratios of P-bearing sulfides. Trace element data suggest that the P-bearing sulfides could be formed in the solar nebula by the sulfidization of a precursor phase of extrasolar origin.
Meteoritics & Planetary Science, 2009
The Sahara 03505 meteorite is a 65 g sulfide-rich iron found in an undisclosed locality of the Sa... more The Sahara 03505 meteorite is a 65 g sulfide-rich iron found in an undisclosed locality of the Sahara. It consists of roughly equal volumetric proportion of polycrystalline troilite (crystal size 1.5-7.5 mm) enclosing cellular/dendritic metallic Fe-Ni (width of the dendrite arms, ~100 µm). The mineral assemblage is completed by sparse skeletal crystals of chromite, abundant droplets, 5-100 µm in size, of anhydrous Fe-, Fe-Na-, and Fe-Mn-Mg-Ca-Na-K-phosphates, tiny crystals of schreibersite, and particles of metallic Cu. The medium-to fine-grained quench texture, and cooling modeling suggest that Sahara 03505 formed through crystallization of a sulfur-rich metallic melt under rapid cooling conditions (1-4°C s −1). The low troilite/metallic Fe-Ni ratio (~0.6 by weight) shows that this liquid was generated at much higher temperatures (>1300 °C) with respect to the FeS-Fe,Ni cotectic liquids. Based on bulk chemistry and oxygen isotope composition of chromite, we propose that Sahara 03505 formed by extensive impact melting of an ordinary chondrite lithology, followed by the efficient segregation of the immiscible silicate and metallic liquids. The sulfur-rich metallic liquid rapidly cooled either by radiation into space as a small lump, or by conduction to a chondrite country rock as a vein intruded into the walls of an impact crater. Sahara 03505 belongs to a small group of sulfide-rich iron meteorites which are characterized by medium-to fine-grained quench textures and by bulk chemistry that is different from the other iron meteorite groups. We propose here to use the descriptive term "sulfide-irons" for this meteorite group, by analogy with the stony-irons.
Earth and Planetary Science Letters, 2021
Primitive chondrites have bulk compositions close to that of the solar photosphere, with however ... more Primitive chondrites have bulk compositions close to that of the solar photosphere, with however significant variations of elemental ratio relative to the solar composition, depending on the volatility of the elements considered. This is classically understood as indicating a primary geochemical signature due to the formation of the components of chondrites (refractory inclusions, chondrules and matrix), or of their precursors, through condensation of a gas of near solar composition, plus secondary variations due to processes such as (i) incomplete volatilization of presolar components, (ii) complex high-temperature exchanges between condensed phases and the nebular gas, and (iii) sorting and transport of grains in the accretion disk before accretion of chondrite parent bodies. Because most of the mass of chondrites is made by elements which condense at high temperatures, equilibrium condensation produces in general little isotopic fractionation for these elements. Silicon is however an exception with per mil level equilibrium isotopic fractionation at high temperature between the SiO gas and condensed silicates, allowing to use silicon isotopes in chondrites to constrain the origin of their components and to put at test scenarios of condensation. Individual components (chondrule fragments, isolated olivines in the matrix, and matrix fragments) of the carbonaceous chondrite Allende were separated and analysed at high-precision for their silicon isotopic composition. Large variations have been found among chondrules (δ 30 Si from-0.86 ± 0.16 2 s.e. to +0.04 ± 0.03 for 11 chondrules), isolated olivines (δ 30 Si from-0.51 ± 0.12 2 s.e. to +0.20 ± 0.10 for 12 olivines), and matrix (δ 30 Si from-0.95 ± 0.08 2 s.e. to-0.41 ± 0.01 for 17 matrix fragments). These variations distribute on both sides of the bulk δ 30 Si value of Allende (-0.43 ± 0.03 2 s.e., Armytage et al., 2011; Pringle et al., 2013, 2014; Savage and Moynier, 2013). There is a global positive trend between δ 30 Si values and Mg/Fe ratio for chondrules and isolated olivines. This systematics appears in agreement with what can be modeled for producing Allende components, or their precursors, from fractionated condensation of a single gaseous reservoir having initially the silicon isotopic composition of bulk Allende. Mass balance taking into account the mean abundances and δ 30 Si values of Allende components is consistent with their accretion in the Allende parent body in the proportions produced by the condensation of the parent parcel of nebular gas. This supports complementarity between chondrules, olivines and matrix as being a primary feature. However, this conclusion cannot be definitive because of the uncertainties in defining mean δ 30 Si values for Allende components.
We describe the mineralogy, petrology, oxygen, and magnesium isotope compositions of three coarse... more We describe the mineralogy, petrology, oxygen, and magnesium isotope compositions of three coarse-grained, igneous, anorthite-rich (type C) Ca-Al-rich inclusions (CAIs) (ABC, TS26, and 93) that are associated with ferromagnesian chondrule-like silicate materials from the CV carbonaceous chondrite Allende. The CAIs consist of lath-shaped anorthite (An 99), Cr-bearing Al-Tidiopside (Al and Ti contents are highly variable), spinel, and highly åkermanitic and Na-rich melilite (Åk 63-74 , 0.4-0.6 wt% Na 2 O). TS26 and 93 lack Wark-Lovering rim layers; ABC is a CAI fragment missing the outermost part. The peripheral portions of TS26 and ABC are enriched in SiO 2 and depleted in TiO 2 and Al 2 O 3 compared to their cores and contain relict ferromagnesian chondrule fragments composed of forsteritic olivine (Fa 6-8) and low-Ca pyroxene/pigeonite (Fs 1 Wo 1-9). The relict grains are corroded by Al-Ti-diopside of the host CAIs and surrounded by haloes of augite (Fs 0.5 Wo 30-42). The outer portion of CAI 93 enriched in spinel is overgrown by coarse-grained pigeonite (Fs 0.5-2 Wo 5-17), augite (Fs 0.5 Wo 38-42), and anorthitic plagioclase (An 84). Relict olivine and low-Ca pyroxene/pigeonite in ABC and TS26, and the pigeonite-augite rim around 93 are 16 O-poor (Δ 17 O ~ −1‰ to −8‰). Spinel and Al-Ti-diopside in cores of CAIs ABC, TS26, and 93 are 16 O-enriched (Δ 17 O down to −20‰), whereas Al-Ti-diopside in the outer zones, as well as melilite and anorthite, are 16 O-depleted to various degrees (Δ 17 O = −11‰ to 2‰). In contrast to typical Allende CAIs that have the canonical initial 26 Al/ 27 Al ratio of ~5 × 10 −5 , ABC, 93, and TS26 are 26 Al-poor with (26 Al/ 27 Al) 0 ratios of (4.7 ± 1.4) × 10 −6 , (1.5 ± 1.8) × 10 −6 , and <1.2 × 10 −6 , respectively. We conclude that ABC, TS26, and 93 experienced remelting with addition of ferromagnesian chondrule silicates and incomplete oxygen isotopic exchange in an 16 O-poor gaseous reservoir, probably in the chondrule-forming region. This melting episode could have reset the 26 Al-26 Mg systematics of the host CAIs, suggesting it occurred ~2 Myr after formation of most CAIs. These observations and the common presence of relict CAIs inside chondrules suggest that CAIs predated formation of chondrules.
Large non mass-dependent oxygen isotopic variations are known to be present within meteoritic cho... more Large non mass-dependent oxygen isotopic variations are known to be present within meteoritic chondrules [1]. These variations are understood as reflecting the presence in the accretion disk of several reservoirs having various O contents. However, there is no general model based on simple physicochemical processes operating during the formation of chondrules which would be able to explain the different characteristics of the oxygen isotopic variations, namely the range of isotopic variations (δO and ΔO) and the slopes of the correlation lines between δO and δO in the 3 oxygen isotopes diagram. We will show that the systematics of the oxygen isotopic variations observed in Mg-rich porphyritic chondrules result from gas-melt exchanges taking place at high-temperatures between precursor silicate dust and a nebular gas enriched in SiO (and other elements) by the partial melting and evaporation of this precursor dust [2]. This models reproduces (i) the range of bulk oxygen isotopic comp...
Meteorites and the Early Solar System II
Proceedings of XII International Symposium on Nuclei in the Cosmos — PoS(NIC XII)
Presence of 60 Fe in early Solar System was established more than two decades ago, but the Solar ... more Presence of 60 Fe in early Solar System was established more than two decades ago, but the Solar System initial ratio of 60 Fe/ 56 Fe is, still, not well constrained. Isotopic studies of bulk meteorites samples from differentiated meteorites, achondrites, and chondrules suggest a low Solar System initial 60 Fe/ 56 Fe value of ~2×10-8 , while the in-situ studies using secondary ion mass spectrometer suggest a much higher Solar System initial value of ~7×10-7 .
European Journal of Mineralogy
Abstract: Optically and chemically zoned white micas are a major mineral phase in a small high-le... more Abstract: Optically and chemically zoned white micas are a major mineral phase in a small high-level microgranite body (Argemela, Central Portugal). Contacts between dioctahedral core (phengite) and trioctahedral rim (tril-ithionite) are sharp but irregular in detail. This ...
Science Advances, 2016
Meteoritic chondrules are submillimeter spherules representing the major constituent of nondiffer... more Meteoritic chondrules are submillimeter spherules representing the major constituent of nondifferentiated planetesimals formed in the solar protoplanetary disk. The link between the dynamics of the disk and the origin of chondrules remains enigmatic. Collisions between planetesimals formed at different heliocentric distances were frequent early in the evolution of the disk. We show that the presence, in some chondrules, of previously unrecognized magnetites of magmatic origin implies the formation of these chondrules under impact-generated oxidizing conditions. The three oxygen isotopes systematic of magmatic magnetites and silicates can only be explained by invoking an impact between silicate-rich and ice-rich planetesimals. This suggests that these peculiar chondrules are by-products of the early mixing in the disk of populations of planetesimals from the inner and outer solar system.
Introduction: Short-lived radionuclides (SRs) are radioactive elements with half-lives of ~ 1 Myr... more Introduction: Short-lived radionuclides (SRs) are radioactive elements with half-lives of ~ 1 Myr. Some SRs were present in the protoplanetary disk at abundances substantially higher than the levels expected for average interstellar medium [1]. The origin of SRs is highly debated, because it has important consequences for early solar system chronology, planetesimal heating and the astrophysical environment in which our solar system was born. Among SRs, 10 Be (which decays to 10 B with a recently remeasured half-life T 1/2 = 1.4 Myr [2]) plays a special role because, unlike i.e. 26 Al (T 1/2 = 0.74 Myr), it cannot be produced by stellar processes [3]. To account for the high abundance of 10 Be in the solar system, two kinds of models exist. Desch et al. [4] suggested that it was delivered within the dense core progenitor of our solar system by interstellar Galactic Cosmic Rays (GCRs). Alternatively, 10 Be was produced within the solar system via the interaction of solar energetic particles with gas and/or dust in the protoplanetary disk [3, 5-7]. The abundance of 10 Be in the early solar system is poorly known. In Calcium-, Aluminium-rich Inclusions (CAIs) from the CV3 meteorites (having a "canonical" 26 Al abundance), the ratio 10 Be/ 9 Be was ~ 0.8 x 10-3 [8-11]. In the refractory hibonites (which lack 26 Al) from the CM2 chondrite Murchison, the initial ratio 10 Be/ 9 Be was ~ 0.5 x 10-3 [12-14]. These pioneering data suggest that 10 Be abundance in the early solar system is decoupled from that of 26 Al [12, 13]. We have undertaken a systematic study of the Be-B and Al-Mg systematics in the Isheyevo (CH/CB) CAIs. Oxygen isotopes were also measured for each inclusion. CAIs from Isheyevo were chosen because of their ultrarefractory mineralogy, indicative of a primitive nature, and because most of them do not contain 26 Al [15] and are thefore believed to have formed very early in the protoplanetary disk [16]. These combined measurements will shed a light on the distribution of 10 Be within the protoplanetary disk, on its origin, as well as on its relationship to 26 Al. Experimental methods: Mineralogy of CAIs was determined using Scanning Electron Microscopy at MNHN and Electron Microprobe at the Université Paris 6. The B-Be concentrations and isotopic compositions were measured with the Nancy ims 1270 and 1280 ion microprobes according to procedures previously described [9]. Primary intensities of ~ 5 nA were used, which correspond to beam sizes of up to 25
Ninth Annual V M Goldschmidt Conference, Aug 1, 1999
Mineralogical Magazine, Aug 1, 2013
Geochim Cosmochim Acta, 1990
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Papers by Marc Chaussidon