Experimental simulation of oxygen isotopic exchange in olivine and implication for the formation of metamorphosed carbonaceous chondrites

Abstract

Abstract-We have conducted hydration-dehydration experiments on terrestrial olivine to investigate the behavior of oxygen isotopic fractionation to test the hypothesis that multiple cycles of aqueous and thermal processing on a parent asteroid comprise a genetic relationship between CM2s and metamorphosed carbonaceous chondrites (MCCs). Two experiments were undertaken. In the first experiment, serpentine was obtained by hydrating terrestrial olivine (Fo 90.9 ) in the laboratory. During this experiment, olivine was reacted with isotopically heavy water (d 18 O 21.5&) at T = 300°C, P H 2 O = 300 bar, for 100 days. The oxygen isotopic composition of the experimental serpentine was enriched in

Oxygen Ablation during Atmospheric Entry: Its Influence on the Isotopic Composition of Micrometeorites

“…Also the bulk whole rock of Orgueil and Tagish Lake has δ 18 O values of ∼16‰-19‰, closer to the atmospheric value (Thiemens et al 1995;Baker et al 2002;Pack et al 2017); and (d) the hydration-dehydration experiments by heating samples of Murchison and Mighei CM2 chondrites indicate that the oxygen isotopic composition of the precursor tends to be altered, becoming close to that of the hydration products (Ivanova et al 2013). This shows that heating particles from hydrated carbonaceous chondrite parent bodies has the potential to lose 16 O during phyllosilicate dehydration and to enrich δ 18 O by ∼5‰-10‰ above the precursor value, bringing it close to 20‰ as seen in many cosmic spherules (Clayton & Mayeda 1999;Baker et al 2002;Ivanova et al 2010Ivanova et al , 2013Rudraswami et al 2020;Suttle et al 2020). These studies demonstrate that the unmelted MMs are susceptible to alteration, and as a consequence many particles have values similar to those seen in melted cosmic spherules, although the amount of water on the parent body will potentially control the final alteration value (Ivanova et al 2010;Schrader & Davidson 2017;Suttle et al 2020).…”

“…The above fact is supported by various experimental studies: (a) experimental heating of CM chondrites has led to a high δ 18 O composition due to mass-independent fractionation (Clayton & Mayeda 1999;Ivanova et al 2010); (b) measurements of the oxygen isotopic composition of water from the Tagish Lake chondrite using stepped pyrolysis show a rise in δ 18 O values up to ∼20‰ at ∼1100 K (Baker et al 2002); (c) comparisons with Murchison and Orgueil point toward the smaller rise in δ 18 O value to ∼8‰-10‰ (Baker et al 2002). Also the bulk whole rock of Orgueil and Tagish Lake has δ 18 O values of ∼16‰-19‰, closer to the atmospheric value (Thiemens et al 1995;Baker et al 2002;Pack et al 2017); and (d) the hydration-dehydration experiments by heating samples of Murchison and Mighei CM2 chondrites indicate that the oxygen isotopic composition of the precursor tends to be altered, becoming close to that of the hydration products (Ivanova et al 2013). This shows that heating particles from hydrated carbonaceous chondrite parent bodies has the potential to lose 16 O during phyllosilicate dehydration and to enrich δ 18 O by ∼5‰-10‰ above the precursor value, bringing it close to 20‰ as seen in many cosmic spherules (Clayton & Mayeda 1999;Baker et al 2002;Ivanova et al 2010Ivanova et al , 2013Rudraswami et al 2020;Suttle et al 2020).…”

Abundance and importance of petrological type 1 chondritic material

“…Clayton and Mayeda (1999) suggested that CY meteorites may have been derived from CI meteorites from such a process. Ivanova et al (2013), working on analog material, found that isotopic fractionation to higher d 18 O compositions occurred during dehydration and Lindgren et al (2020) reported similar effects. However, Clayton and Mayeda (1999) artificially heated CI and CM meteorites and found both heavier and lighter compositions were produced.…”

“…Reaction of water with minerals will cause the mineral product to move toward heavier isotopic compositions and the fluid to become lighter by equilibrium mass fractionation (e.g., Nabalek, 1987;Schrader et al, 2011;Yurimoto et al, 2008). Finally, dehydration after alteration may also cause further mass fractionation (Clayton & Mayeda, 1999;Ivanova et al, 2013).…”

Water delivery to the Moon by asteroidal and cometary impacts

“…Studies of phyllosilicates in carbonaceous chondrites show that hydrated minerals do not begin to decompose until they reach temperatures of about 600-700 K (Akai, 1992). Molecular water contained in the meteorite and water from hydroxylated minerals can release at lower temperatures from 300 to 500 K (Garenne et al, 2014), and, contrariwise, at a temperature of 573 K hydration of olivine can go on (Ivanova et al, 2013). The highest temperatures of complete dehydration of serpentine and saponite with formation of water-free olivine and enstatite are from 1100 to 1200 K (Akai 1990;Ivanova et al, 2010).…”