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NWA 1669 Al Mala'ika 

The shergottites are named for their type specimen, an achondrite that fell in Shergotty, India, in 1865. Comprising 17 distinct members, they represent the most abundant type of Martian meteorite. Shergottites are igneous rocks of volcanic or plutonic origin, and they resemble terrestrial rocks more closely than do any other achondrite group. They all show exceptionally young crystallization ages of about 150 to 200 million years, and they usually exhibit signs of severe shock-metamorphism. Typically, the plagioclase in shergottites has been converted to maskelynite, a glass that is produced when plagioclase is subjected to shock pressures of at least 30 GPa. It is likely that the maskelynite was formed by the impact forces that blasted the shergottites from the Martian surface and into space. Calculations show that it requires a major impact event to accelerate any material to a speed high enough to escape the planet's gravity - one of the reasons why the SNC meteorites are such a rare class. Based upon their mineral compositions, the shergottites are further subdivided into two distinct subgroups: the basaltic subgroup, and the lherzolitic subgroup.

NWA 1669 01

2.807 gr

Full slice with crust for this shergotitte with a TKW of only 36 gr

SOLD. 

NWA 1669 02

0.442 gr

Half Full slice with fusion crust 

SOLD

 

AL MALA’IKA (NWA 1669): A NEW SHERGOTTITE FROM MOROCCO/MINERALOGY AND PETROLOGY. A.Jambon1 , M. Bohn2, O. Boudouma1, H. Chennaoui-Aoudjehane1,3, and I. Franchi4, 1Université P. et M. Curie, Paris 6, (France), 2Université de Bretagne occidentale Brest, 3Univ Casablanca, 4OpenUniversity, Milton Keynes (UK).

Introduction: Al Mala’ika (NWA1669) a meteorite of 36g, found in 2001 has been recently identified as a shergottite. The single stone is covered with desert varnish with a few remnants of fusion crust. It is a fine grained rock, with two closely intricated pyroxenes: pigeonite En 58-25 Wo 9-19 Fs 32-61 and augite En 47-19 Wo 39-24 Fs 54-18. Their FeO/MnO ratio of 34 on the average, is typical for a shergottite. Their Mg indicate that augite crystallized first. Plagioclase transformed to maskelynite (Ab41-53 Or1-6 An58-42) is injected between pyroxene phenocrysts. Accessory minerals are: merrilite, Cl-apatite, pyrrhotite, ulvöspinel, ilmenite, silica and baddeleyite. Impact melt pockets contain submicrometric stishovite needles. The rock is highly fractured at all scales : the cores of pyroxenes are crosscut by wide fractures while their margins are cut only by numerous small fractures. Maskelynite is marginally affected by few of the largest ones. Secondary carbonate is present in some fractures. The major and trace element composition is under study. Oxygen Isotopes: .17O= 0.30‰, ä17O= 2.85‰, ä18O= 4.91‰. These values are in agreement with the martian origin of this meteorite. According to the experimental works, the compositions of pyroxenes indicate that augite crystallized first followed by the syncrystallisation of augite and pigeonite. According to the experimental work, this order of crystallization indicates a significant P(H2O), on the order of 0.2 Gpa, pointing out the significant abundance of water of the magma compared to the terrestrial basaltic equivalents.

 66th Annual Meteoritical Society Meeting (2003)

 

 

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