Quick Search:    advanced search

GSW Home   GeoRef Home   My GSW Alerts   Contact GSW   About GSW   Journals List   Help

This Article Figures Only Full Text Full Text (PDF) Alert me when this article is cited Alert me if a correction is posted Citation Map Services Email this article to a friend Similar articles in this journal Alert me to new issues of the journal Download to citation manager Citing Articles Citing Articles via HighWire Citing Articles via Google Scholar Google Scholar Articles by Zolensky, M. E. Articles by Benedix, G. Search for Related Content GeoRef GeoRef Citation

Record of Low-Temperature Alteration in Asteroids

Astromaterials Research and Exploration Science, NASA Johnson Space Center, Houston, Texas 77058, U.S.A., michael.e.zolensky{at}nasa.gov

Alexander N. Krot

Hawai’i Institute of Geophysics and Planetology, School of Ocean and Earth Science and Technology, University of Hawai’i at Manoa, Honolulu, Hawaii 96822, U.S.A.

Gretchen Benedix

Department of Mineralogy, The Natural History Museum, London SW7 5BD, United Kingdom

Most chondritic materials experienced diverse styles of secondary alteration resulting in formation of hydrous and anhydrous oxygen-bearing minerals—silicates, oxides, and carbonates (phyllosilicates, magnetite, calcite, dolomite, breunnerite, ferrous olivine, hedenbergite, wollastonite, grossular, monticellite, forsterite, andradite, nepheline, sodalite) (Brearley 2003, 2005 and references therein). Petrographic, mineralogic, oxygen and short-lived isotope systematics (²⁶Al-²⁶Mg, ⁵³Mn-⁵³Cr, ¹²⁹I-¹²⁹Xe) suggest that alteration occurred in the presence of aqueous solutions under variable physico-chemical conditions (temperature, water:rock ratio, pH, f_O2, and fluid compositions) in an asteroidal setting; it started within 1–2 m.y. after formation of the CV CAIs, was multistage, and lasted up to 15 m.y. (Krot et al. 2006 and references therein). Here we review bulk O-isotopic compositions of chondritic materials, O-isotopic compositions of secondary minerals produced during asteroidal alteration, and possible effects of fluid-assisted thermal metamorphism on O-isotopic exchange in primary, high-temperature minerals (melilite and anorthite) in the CV and CO CAIs. The implications of these data for understanding temperatures of alteration, water:rock ratios, and oxygen isotopic composition of water, that probably accreted into chondrite parent bodies in the form of ice, are discussed. The inferred or measured O-isotopic composition of the meteoritic water is close to the terrestrial fractionation line (¹⁷O = ±2); it is very different from the inferred O-isotopic compositions of the Sun [¹⁷O ~ –25] (Clayton 2002; Yurimoto and Kuramoto 2004; Hashizume and Chaussidon 2005; Lyons and Young 2005), suggesting significant evolution of O-isotopic composition of the gaseous reservoir in the inner protoplanetary disk over its short (~3–5 m.y.) life time.

This article has been cited by other articles:

				I. A. Franchi Oxygen Isotopes in Asteroidal Materials Reviews in Mineralogy and Geochemistry, January 1, 2008; 68(1): 345 - 397. [Abstract] [Full Text] [PDF]