Martian meteorite Dhofar 019: A new shergottite

Abstract

Abstract-Dhofar 019 is a new martian meteorite found in the desert ofOman. In texture, mineralogy, and major and trace element chemistry, this meteorite is classified as a basaltic shergottite. Olivine megacrysts are set within a groundmass composed of finer grained olivine, pyroxene (pigeonite and augite), and maskelynite. Minor phases are chromite-ulvospinel, ilmenite, silica, K-rich feldspar, merrillite, chlorapatite, and pyrrhotite. Secondary phases ofterrestrial origin include calcite, gypsum, celestite, Fe hydroxides, and smectite.Dhofar 019 is most similar to the Elephant Moraine (EETA) 79001 lithology A and Dar al Gani (DaG) 476/489 shergottites. The main features that distinguish Dhofar 019 from other shergottites are lack oforthopyroxene; lower Ni contents ofolivine; the heaviest oxygen-isotopic bulk composition; and larger compositional ranges for olivine, maskelynite, and spinel, as well as a wide range for pyroxenes. The large compositional ranges ofthe minerals are indicative ofrelatively rapid crystallization. Modeling of olivine chemical zonations yield minimum cooling rates of0.5--0.8°CIh. Spinel chemistry suggests that crystallization took place under one ofthe most reduced conditions for martian meteorites, at anfOz 3 log units below the quartz-fayalite-magnetite (QFM) buffer.The olivine megacrysts are heterogeneously distributed in the rock. Crystal size distribution analysis suggests that they constitute a population formed under steady-state conditions ofnucleation and growth, although a few grains may be cumulates. The parent melt is thought to have been derived from partial melting of a light rare earth element-and platinum group element-depleted mantle source. Shergottites, EETA79001 lithology A, DaG 476/489, and Dhofar 019, although of different ages, comprise a particular type ofmartian rocks. Such rocks could have formed from chemically similar source(s) and parent melt(s), with their bulk compositions affected by olivine accumulation.

Large‐ion lithophile element fractionation during the early differentiation of Mars and the composition of the martian primitive mantle

“…Other data sources included Dreibus et al (2000 for SaU 005 and Dhofar 378, Folco et al (2000) and Zipfel et al (2000) for Dar al Gani, Rubin et al (2000) for Los Angeles, Barrat et al (2001a, b) for NWA 480 and Dar al Gani, Jambon et al (2001) for NWA 856, and Taylor et al (2002) for Dhofar 019.…”

“…On the other hand, one has less of a reason to suspect that REE (particularly La) and Th distributions have been altered significantly by terrestrial weathering effects (e.g., Dreibus et al 2001) and so these elements are considered more reliable for these samples. One caveat is the possible occurrence of small Ce anomalies (e.g., in Dhofar 019) suggestive of terrestrial weathering effects (Taylor et al 2002).…”

“…The second development is the recent spate of new SNC meteorite finds, especially of basaltic shergottites (e.g., Dreibus et al 2000Folco et al 2000;Rubin et al 2000Barrat et al 2001aBarrat et al , b, 2002aJambon et al 2001;Taylor et al 2002) that, among the SNC meteorites, are most likely to be representative of the mantle of Mars. This increased sampling expands the compositional range of this meteorite group and makes it more likely that systematic geochemical behavior can be identified.…”

The evolution of a heterogeneous Martian mantle: Clues from K, P, Ti, Cr, and Ni variations in Gusev basalts and shergottite meteorites

“…F) TiO 2 vs. MgO. Data are from Anand et al (2008), Dreibus et al (2000Dreibus et al ( , 2002, Gellert et al (2006), Gillet et al (2005), Ikeda et al (2006), Jambon et al (2002), , Neal et al (2001), Rubin et al (2000), Shirai and Ebihara (2004), Taylor et al (2002), Treiman et al (1986), Warren et al (1996Warren et al ( , 1999. .…”

Shock and thermal annealing history of the ALH 77005 Martian meteorite: a micro-Raman spectroscopical investigation

“…Recently, some studies have shown that shock-induced heating processes do not make olivine brown, because olivine from the highly metamorphosed terrestrial rocks is not brown (Treiman et al 2006, and references therein). Taylor et al (2002), Goodrich et al (2003), and Herd (2006) found that brown olivine from the Martian meteorites is equilibrated at oxidizing (e.g. NWA 1068) and reducing (e.g.…”