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Title: Influence of redox conditions on the intensity of Mars crustal magnetic anomalies
Abstract We evaluate the relationship between the intensity of remanent magnetization andfO2in natural and synthetic Mars meteorites. The olivine‐phyric shergottite meteorite Yamato 980459 (Y‐980459) and a sulfur‐free synthetic analog (Y‐98*) of identical major element composition were analyzed to explore the rock magnetic and remanence properties of a basalt crystallized from a primitive melt, and to explore the role of magmatic and alteration environmentfO2on Mars crustal anomalies. The reducing conditions under which Y‐980459 is estimated to have formed (QFM‐2.5; Shearer et al. 2006) were replicated during the synthesis of Y‐98*. Y‐980459 contains pyrrhotite and chromite. Chromite is the only magnetic phase in Y‐98*. The remanence‐carrying capacity of Y‐980459 is comparable to other shergottites that formed in thefO2range of QFM‐3 to QFM‐1. The remanence‐carrying capacity of these lowfO2basalts is 1–2 orders of magnitude too weak to account for the intense crustal anomalies observed in Mars's southern cratered highlands. Moderately oxidizing conditions of >QFM‐1, which are more commonly observed in nakhlites and Noachian breccias, are key to generating either a primary igneous assemblage or secondary alteration assemblage capable of acquiring an intense remanent magnetization, regardless of the basalt character or thermal history. This suggests that if igneous rocks are responsible for the intensely magnetized crust, these oxidizing conditions must have existed in the magmatic plumbing systems of early Mars or must have existed in the crust during secondary processes that led to acquisition of a chemical remanent magnetization.  more » « less
Award ID(s):
0521069 0619402 0948262
PAR ID:
10530280
Author(s) / Creator(s):
; ; ; ;
Publisher / Repository:
The Meteoritical Society
Date Published:
Journal Name:
Meteoritics & Planetary Science
Volume:
50
Issue:
10
ISSN:
1086-9379
Page Range / eLocation ID:
1703 to 1717
Subject(s) / Keyword(s):
Yamato 980459 Y-980459 Mars meteorite crustal magnetic anomalies rock magnetism planetary magnetism hysteresis ARM, IRM
Format(s):
Medium: X
Sponsoring Org:
National Science Foundation
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