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The SNC meteorites; basaltic igneous processes on Mars

J. C. Bridges and P. H. Warren
The SNC meteorites; basaltic igneous processes on Mars
Journal of the Geological Society of London (March 2006) 163 (2): 229-251


A group of 32 meteorites, the SNC (Shergotty, Nakhla, Chassigny) group, was derived from Mars as a product of 4-7 ejection events, probably from Tharsis and Elysium-Amazonis. The SNCs either have basaltic mineralogy or some are ultramafic cumulates crystallized from basaltic melts. The SNCs can be classified both petrographically and geochemically. We classify the shergottite SNC meteorites on the basis of their light rare earth element (LREE) depletion into highly depleted, moderately depleted and slightly depleted. The slightly depleted samples (which are mainly but not exclusively aphyric basalts) show high log (sub 10) fO (sub 2) values (QFM -1.0, where QFM is quartz-fayalite-magnetite). Highly depleted samples, which are mainly olivine-phyric basalts, have low log (sub 10) fO (sub 2) values (QFM -3.5). On the basis of mixing calculations between La/Lu and (super 87) Sr/ (super 86) Sr we favour models linking the correlation between LREE abundances and log (sub 10) fO (sub 2) to mantle heterogeneity rather than contamination by oxidized, LREE-rich crustal fluids. SNC chemistry in general reflects the Fe-rich mantle of Mars (which contains twice as much FeO as the Earth's mantle), the late accretion of chondritic material into the mantle, and possibly the presence of a plagioclase-rich magma ocean, which acted to variably deplete the mantle in Al. The high FeO contents of the SNC melts are associated with high melt densities (allowing the ponding of large magma bodies) and low viscosities, both of which are consistent with the large scale of many observed martian lava flows.

ISSN: 0016-7649
EISSN: 2041-479X
Serial Title: Journal of the Geological Society of London
Serial Volume: 163
Serial Issue: 2
Title: The SNC meteorites; basaltic igneous processes on Mars
Affiliation: Natural History Museum, Department of Mineralogy, London, United Kingdom
Pages: 229-251
Published: 200603
Text Language: English
Publisher: Geological Society of London, London, United Kingdom
References: 149
Accession Number: 2006-024990
Categories: Petrology of meteorites and tektitesExtraterrestrial geology
Document Type: Serial
Bibliographic Level: Analytic
Illustration Description: illus. incl. 6 tables
S90°00'00" - S61°00'00", W180°00'00" - E180°00'00"
Secondary Affiliation: University of California in Los Angeles, USA, United States
Country of Publication: United Kingdom
Secondary Affiliation: GeoRef, Copyright 2017, American Geosciences Institute. Reference includes data from GeoScienceWorld, Alexandria, VA, United States. Reference includes data from The Geological Society, London, London, United Kingdom
Update Code: 200613
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