Tracking the Earliest Stages of Aqueous Alteration in the Mildly Altered CM Chondrite EET 96029

Lindgren, P. and Lee, M.R. (2015) Tracking the Earliest Stages of Aqueous Alteration in the Mildly Altered CM Chondrite EET 96029. In: 46th Lunar and Planetary Science Conference, The Woodlands, TX, USA, 16-20 Mar 2015,

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The earliest stages of CM carbonaceous chondrite aqueous alteration are very poorly understood as mildly altered CMs are extremely rare. The Paris meteorite (CM2.7) [1-3] and QUE 97990 (CM2.6) [4,5] are among the least aqueously altered CMs described to date. However, neither of them contain the pristine attribute of chondrule mesostasis glass. Glass is highly reactive and so among the very first phases to undergo aqueous alteration [6]. Therefore, the CM carbonaceous chondrite EET 96029 is very unusual as it has been shown to have retained mesostasis glass in at least one chondrule [7]. According to the new CM classification scheme of [8], which is based on H content, EET 96029 has an index of 2.0 (data in [9]), meaning that it is less altered than all but one of the fifty CMs analysed by [8]. A caveat is that a low H content could be due to mild heating as well as a low degree of aqueous processing [9]. However, the bulk O oxygen isotope composition of EET 96029 (as determined by [10]) is consistent with a low degree of alteration as it is slightly closer to that of the CO3 falls (possible representatives of the anhydrous progenitors of the CMs) than even the least altered lithology of Paris (Fig. 1).<p></p> To better understand the earliest stages of CM aqueous alteration and its impact on mesostasis glass, we have undertaken a detailed study of chondrule mesostasis textures and compositions in the mildly aqueously altered CM chondrite EET 96029.<p></p>

Item Type:Conference Proceedings
Glasgow Author(s) Enlighten ID:Lee, Professor Martin and Lindgren, Dr Paula
Authors: Lindgren, P., and Lee, M.R.
College/School:College of Science and Engineering > School of Geographical and Earth Sciences
Copyright Holders:Copyright © 2015 The Authors
Publisher Policy:Reproduced in accordance with the copyright policy of the publisher
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