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A two-step K-Ar experiment on Mars: dating the diagenetic formation of jarosite from Amazonian groundwaters

Martin, P. E. and Farley, K. A. and Baker, M. B. and Malespin, C. A. and Schwenzer, S. P. and Cohen, B. A. and Mahaffy, P. R. and McAdam, A. C. and Ming, D. W. and Vasconcelos, P. M. and Navarro-González, R. (2017) A two-step K-Ar experiment on Mars: dating the diagenetic formation of jarosite from Amazonian groundwaters. Journal of Geophysical Research. Planets, 122 (12). pp. 2803-2818. ISSN 2169-9097.

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Following K-Ar dating of a mudstone and a sandstone, a third sample has been dated by the Curiosity rover exploring Gale Crater. The Mojave 2 mudstone, which contains relatively abundant jarosite, yielded a young K-Ar bulk age of 2.57 ± 0.39 Ga (1σ precision). A two-step heating experiment was implemented in an effort to resolve the K-Ar ages of primary and secondary mineralogical components within the sample. This technique involves measurement of ^(40)Ar released in low-temperature (500°C) and high-temperature (930°C) steps, and a model of the potassium distribution within the mineralogical components of the sample. Using this method, the high-temperature step yields a K-Ar model age of 4.07 ± 0.63 Ga associated with detrital plagioclase, compatible with the age obtained on the Cumberland mudstone by Curiosity. The low-temperature step, associated with jarosite mixed with K-bearing evaporites and/or phyllosilicates, gave a youthful K-Ar model age of 2.12 ± 0.36 Ga. The interpretation of this result is complicated by the potential for argon loss after mineral formation. Comparison with the results on Cumberland and previously published constraints on argon retentivity of the individual phases likely to be present suggests that the formation age of the secondary materials, correcting for plausible extents of argon loss, is still less than 3 Ga, suggesting post-3 Ga aqueous processes occurred in the sediments in Gale Crater. Such a result is inconsistent with K-bearing mineral formation in Gale Lake and instead suggests postdepositional fluid flow at a time after surface fluvial activity on Mars is thought to have largely ceased.

Item Type:Article
Related URLs:
URLURL TypeDescription
Martin, P. E.0000-0003-4243-2090
Farley, K. A.0000-0002-7846-7546
Malespin, C. A.0000-0002-5852-5016
Schwenzer, S. P.0000-0002-9608-0759
Cohen, B. A.0000-0001-5896-5903
Mahaffy, P. R.0000-0003-1896-1726
Ming, D. W.0000-0003-0567-8876
Additional Information:© 2017 American Geophysical Union. Received 12 SEP 2017; Accepted 27 NOV 2017; Accepted article online 5 DEC 2017; Published online 20 DEC 2017. We thank George Rossmann, Tom Bristow, Liz Rampe, Dick Morris, and Paul Asimow for numerous helpful discussions. We are indebted to the MSL science and engineering teams, who made (and continue to make) this work possible. Data contained in this paper are publicly available on the Planetary Data System (PDS; Funding was provided by NASA.
Funding AgencyGrant Number
Subject Keywords:K-Ar; jarosite; diagenetic; Amazonian; Mars; Geochronology
Issue or Number:12
Record Number:CaltechAUTHORS:20171206-084713977
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Official Citation:Martin, P. E., Farley, K. A., Baker, M. B., Malespin, C. A., Schwenzer, S. P., Cohen, B. A., … Navarro-González, R., (2017). A two-step K-Ar experiment on Mars: Dating the diagenetic formation of jarosite from Amazonian groundwaters. Journal of Geophysical Research: Planets, 122, 2803–2818.
Usage Policy:No commercial reproduction, distribution, display or performance rights in this work are provided.
ID Code:83720
Deposited By: Tony Diaz
Deposited On:07 Dec 2017 00:20
Last Modified:09 Mar 2020 13:19

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