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Evaluating Crustal Contamination Effects on the Lithophile Trace Element Budget of ShergottitesThe origin of the incompatible trace element (ITE) enriched compositions of shergottites has been a point of contention for decades [1-2]. Two scenarios have been proposed, the first is that enriched shergottite compositions reflect an ITE-enriched mantle source, whereas in the second, the ITE enrichment reflects crustal contamination of mantle-derived parent magmas. Evidence supporting the first scenario is that the ITE-enriched shergottite compositions are consistent with the outcomes of magma ocean crystallization [3], and that Os-Nd isotope relationships for shergottites cannot be explained by realistic crustal contamination models [4]. In contrast, Cl and S isotopes are consistent with shergottite magmas interacting with Mars crust [5,6], and ITE-enriched olivine-hosted melt inclusions and interstitial glass are found in depleted shergottite Yamato 980459 [7]. These findings indicate that some level of crustal interaction occurred but the question of whether ITE-enrichments in some bulk shergottites reflect crustal contamination remains open. Recently, a Mars crustal breccia meteorite has been found, NWA 7034 and its paired stones, that is our best analogue to an average of Mars ancient crust [8-10]. This allows for better constraints on crustal contamination of shergottite magmas. We modeled magma-crust mixing and assimilation-fractional crystallization (AFC) using ITE-depleted shergottite compositions and bulk NWA 7034 and its clasts as end-members. The results of these models indicate that crustal contamination can only explain the ITE-enriched compositions of some bulk shergottites under unusual circumstances. It is thus likely that the shergottite range of compositions reflects primarily mantle sources.
Document ID
20170004341
Acquisition Source
Johnson Space Center
Document Type
Conference Paper
Authors
Brandon, A. D.
(Houston Univ. Houston, TX, United States)
Ferdous, J.
(Houston Univ. Houston, TX, United States)
Peslier, A. H.
(Jacobs Technology, Inc. Houston, TX, United States)
Date Acquired
May 3, 2017
Publication Date
August 13, 2017
Subject Category
Lunar And Planetary Science And Exploration
Report/Patent Number
JSC-CN-39538
Meeting Information
Meeting: Goldschmidt Conference
Location: Paris
Country: France
Start Date: August 13, 2017
End Date: August 18, 2017
Sponsors: European Association of Geochemistry, Geochemical Society
Distribution Limits
Public
Copyright
Public Use Permitted.
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