[meteorite-list] New Mars Meteorite Found: NWA 1110

From: Ron Baalke <baalke_at_meteoritecentral.com>
Date: Thu Apr 22 10:02:29 2004
Message-ID: <200203160056.QAA23627_at_zagami.jpl.nasa.gov>

NEW MARS METEORITE: NORTHWEST AFRICA 1110
March 15, 2002

Additional Mars meteorites fragments have been recovered from the
Sahara desert in northwest Africa. These new meteorite fragments were
purchased by Adam and Greg Hupe in November 2001 from a dealer
in Erfoud, Morocco, after receiving a much smaller sample in September,
2001. The recovery location could not be confirmed since
Moroccan dealers tend to keep their sources secret, but the strewn
field for this meteorite is believed to be in Morroco.
The meteorite has been given the official name of NWA 1110, and consists
of several fragments with a total known weight of 118 grams.
Photos of NWA 1110 provided by Adam and Greg Hupe are available here:

http://www.jpl.nasa.gov/snc/nwa1110.html

Samples and thin sections of the meteorite were provided to the University of
Washington in Seattle, Washington. Dr. Anthony Irving and
Dr. Scott Kuehner have identified the meteorite as a Mars meteorite (shergottite),
and have also paired it with NWA 1068, another Mars meteorite recovered by a French
team in April 2001. Since this meteorite is paired, the total number of Mars
meteorite remains at 24.

The following analysis of NWA 1110 is provided by Dr. Anthony Irving and
Dr. Scott Kuenher from the University of Washington.

Ron Baalke

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NWA 1110 Olivine-phyric basaltic shergottite paired with NWA 1068
Dr. Anthony Irving, Dr. Scott Kuenher
University of Washington

This sample consists of small olivine phenocrysts in a fine-grained
groundmass of complexly-zoned pigeonite and homogeneous plagioclase
(maskelynite; Ab46Or2) with minor ilmenite, Ti-magnetite and pyrrhotite.
Euhedral to subhedral olivine crystals have Mg-rich cores (Fa28, FeO/MnO
= 50) with narrow Fe-enriched rims (Fa51, FeO/MnO = 53), and contain
inclusions of chromite and glass (some with negative crystal outlines).
Augite (Fs33Wo21) occurs as rare inclusions within olivine megacrysts.
Pigeonite exhibits complex zoning typical of shergottites (Fs28Wo9 cores
with sharply defined Fs40Wo15 rims) and has FeO/MnO = 30 (by
comparison pigeonite analyzed concurrently in DaG 476 has FeO/MnO =
28). Rare chlorapatite is present in the mesostasis. Secondary features
include minor barite (commonly associated with chromite inclusions in
olivine), calcite in a cross-cutting glass veinlet, and narrow zones of
K-Al-bearing glass or clay minerals along grain boundaries between
pyroxene and plagioclase.

We are skeptical of the designation by Barrat et al. (2002) of this
shergottite (and by inference DaG 476 and SaU 005) as "picritic". We
have found 6-sided, euhedral crystals of olivine that appear to be
phenocrysts grown from magma rather than xenocrysts related to another
source. The interpretation of similar olivine megacrysts with Fe-rich
rims in DaG 476 is likewise controversial (Zipfel et al., 1999, 2000;
Wadhwa et al., 2000); however, it is possible that both phenocrystic and
xenocrystic olivine could be present in these samples, and therefore the
picritic designation may be valid.
Received on Fri 15 Mar 2002 07:56:48 PM PST