Fluid inclusions in stony meteorites

Abstract

We describe fluid inclusions in five stony meteorites: diogenite ALHA 77256 and chondrites Bjurbole (H4), Faith (H5), Holbrook (L4), and Juin (H5). This brings to seven the number of stony meteorites in which fluid inclusions have been confirmed. The fluid inclusions in diogenite ALHA 77256 display a vapor bubble that decreases in volume from −180°C, the lowest temperature attainable in our microthermometric runs, to homogenization of liquid plus vapor to liquid. Homogenization temperatures are reproducible in each inclusion, and range from 25°C to over 225°C; some vapor plus liquid inclusions remain at 225°C, the highest temperature in our microthermetric experiments. On cooling, the fluid in some inclusions apparently freezes, as indicated by deformation and immobilization of the vapor bubble at low temperatures. However, temperatures of melting are difficult to observe and are not reproducible. Preliminary laser Raman spectroscopy shows symmetric and antisymmetric stretch bands characteristic of H2O. Microthermometric data suggest that the fluid in diogenite ALHA 77256 is aqueous with a high solute content. Fluid inclusions discovered in four chondrites have similar properties.

Fluid inclusions in stony meteorites—A cautionary note

“…The distribution and physical properties of these new fluid inclusions indicate they may be artifacts of thin section preparation; we suggest that saw coolant was sucked into vacuum vesicles in glasses and minerals through submicroscopic fractures produced during sawing. The similarities between these fluid inclusions and fluid inclusions previously described by Warner et al (1983) lead us to conclude that many of the fluid inclusions reported earlier may be artifacts. Consequently, the origin of any fluid inclusions observed in thin sections of extraterrestrial materials must be interpreted with caution.…”

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Newly discovered fluid inclusions in thin sections of Bjurbole chondrules, shergottite EETA79001, lunar meteorite ALH A81005, and Apollo 16 glasses possess physical properties similar to those of fluid inclusions found in thin sections of five stony meteorites recently described by Warner et al (1983). The distribution and physical properties of these new fluid inclusions indicate they may be artifacts of thin section preparation; we suggest that saw coolant was sucked into vacuum vesicles in glasses and minerals through submicroscopic fractures produced during sawing.

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“…reported the presence of fluid inclusions in thin sections of diogenite ALHA77256, and Bjurbole, Faith, Holbrook, and Jilin chondrites. Fluid inclusions have been described in seven stony meteorites-those reported by Warner et al [1983], and the Peetz and St. Severin chondrites [Fieni et al, 1978]. We report on the existence of fluid inclusions in thin sections of meteorites and lunar rocks: shergottite EETA79001, numerous Bjurbole chondrules, grains from Jilin, ALHA81005 (the lunar meteorite), and Apollo 16 glass samples.…”

“…These are compared with observations and measurements of samples prepared using the standard thin section method. Our data lead us to call into question the extraterrestrial origin of many of the fluid inclusions reported in thin sections by Warner et al [1983]. The following describes these newly discovered inclusions and the observations leading to the •Now at Research School of Earth Sciences, The Australian National University.…”

Lunar Ice: Adsorbed Water on Subsurface Polar Dust

“…Ip and Fernandez (1988) estimated the impact rate of large comets, with masses greater than 7 × 10 13 kg, at 1 every 13 million years. Warner et al (1983) reported on fluid inclusions in stony meteorites, but any water release from such a source would be small.…”