1,2Xuanyu Liu (>10)
Meteoritics & Planetary Science, (in Press), 1–17
Link to Article [DOI: 10.1111/maps.70263]
1Department of Earth, Environmental, and Planetary Sciences, Washington University in St. Louis, St. Louis, Missouri, USA
2McDonnell Center for the Space Sciences, Washington University in St. Louis, St. Louis, Missouri, USA
Published by arrangement with John Wiley & Sons
CI chondrite water-leaching experiments are commonly used to investigate solubleinventories formed during parent-body aqueous alteration, but terrestrial weathering maymodify them. We performed water-leaching experiments on pristine Bennu samples togetherwith Orgueil (CI) and Murchison (CM). The pristine Bennu aggregate sample OREX-800107-127 released only 0.23 wt% cations, dominated by Na. In contrast, Bennu aggregatesample OREX-800107-0 (114, 115, and 116), flash-heated to 600 °C for 20 s undercontinuous helium flow, and a curated Orgueil sample released 2.0 and 2.2 wt% cations,respectively. Both thermally treated Bennu and Orgueil released much more Mg and Ca thanuntreated Bennu, while also releasing more Na in absolute terms. The thermally treatedBennu leachate was dominated by Mg (38 wt%), Na (23 wt%), Fe (17 wt%), and Ca (14 wt%), broadly resembling the Orgueil leachate, except for its higher Fe fraction than Orgueil(3.6 wt%). Mass-balance models indicate that carbonate dissolution supplied mainly Ca andMn, Mg came from carbonates and phyllosilicate-associated reservoirs, and the increases inFe and Ni record substantial sulfide mobilization. Broadly CI-like materials can possessmarkedly different soluble inventories. Returned samples retain labile alteration productswhen stored under anaerobic conditions, whereas meteorites are unavoidably modified inoxidizing terrestrial environments
