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Los Angeles: The Most Differentiated Basaltic Martian MeteoriteLos Angeles is a new martian meteorite that expands the compositional range of basaltic shergottites. Compared to Shergotty, Zagami, QUE94201, and EET79001-B, Los Angeles is more differentiated, with higher concentrations of incompatible elements (e.g., La) and a higher abundance of late-stage phases such as phosphates and K-rich feldspathic glass. The pyroxene crystallization trend starts at compositions more ferroan than in other martian basaits. Trace elements indicate a greater similarity to Shergotty and Zagami than to QUE94201 or EET79001-B, but the Mg/Fe ratio is low even compared to postulated parent melts of Shergotty and Zagami. Pyroxene in Los Angeles has 0.7-4-microns-thick exsolution lamellae, approx. 10 times thicker than those in Shergotty and Zaganii. Opaque oxide compositions suggest a low equilibration temperature at an oxygen fugacity near the fayafite-magnetitequartz buffer. Los Angeles cooled more slowly than Shergotty and Zagami. Slow cooling, coupled with the ferroan bulk composition, produced abundant fine-grained intergrowths of fayalite, hedenbergite, and silica, by the breakdown of pyroxferroite. Shock effects in Los Angeles include maskelynitized plagioclase, pyroxene with mosaic extinction, and rare fault zones. One such fault ruptured a previously decomposed zone of pyroxferroite. Although highly differentiated, the bulk composition of Los Angeles is not close to the low-Ca/Si composition or the globally wind-stirred soil of Mars.
Document ID
20010070504
Acquisition Source
Goddard Space Flight Center
Document Type
Reprint (Version printed in journal)
Authors
Rubin, Alan E.
(California Univ. Los Angeles, CA United States)
Warren, Paul H.
(California Univ. Los Angeles, CA United States)
Greenwood, James P.
(California Univ. Los Angeles, CA United States)
Verish, Robert S.
(Verish (Robert S.) Sunland, CA United States)
Leshin, Laurie A.
(Arizona State Univ. Tempe, AZ United States)
Hervig, Richard L.
(Arizona State Univ. Tempe, AZ United States)
Clayton, Robert N.
(Chicago Univ. Chicago, IL United States)
Mayeda, Toshiko K.
(Chicago Univ. Chicago, IL United States)
Date Acquired
August 20, 2013
Publication Date
November 1, 2000
Publication Information
Publication: Geology
Volume: 28
Issue: 11
Subject Category
Astrophysics
Funding Number(s)
CONTRACT_GRANT: NAG5-7640
CONTRACT_GRANT: NAG5-4766
CONTRACT_GRANT: NAG5-4215
CONTRACT_GRANT: NSF EAR-98-15338
Distribution Limits
Public
Copyright
Other

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