** Progress in Earth and Planetary Science is the official journal of the Japan Geoscience Union, published in collaboration with its 50 society members.
Gallery View of PEPS Articles
Research
Space and planetary sciences
202110202110
An Almahata Sitta EL3 fragment: implications for the complex thermal history of enstatite chondrites
Kimura M, Weisberg M.K, Takaki A, Imae N, Yamaguchi A
Enstatite chondrite, Breccia, Thermal history, Opaque minerals
Combined elemental map in Mg (red), Ca (green), and Al (blue) showing a high abundance of well-defined chondrules and diopside (light green). The width of the section is 1.3 cm.
Almahata Sitta is a polymict breccia, consisting of many kinds of clasts. Here we present our mineralogical and petrological results on an EL3 fragment, MS-177 from Almahata Sitta. This fragment shows a typical type 3 chondritic texture, consisting of well-defined chondrules, isolated silicate minerals, and opaque nodules. Most chondrules are enstatite-rich with some having olivine. Although these components are typical of EL3 chondrites, the mineral abundances and compositions are different from the other EL3s. Diopside is unusually abundant in MS-177. On the other hand, perryite and daubreelite were not found. The major pyroxene is orthoenstatite, and the silica phase is quartz. Fe–Ni metal has relatively high P contents. Troilite is enriched in Cr and Mn. Keilite and buseckite are present in MS-177. From the mineralogy and texture, MS-177 experienced a high-temperature event under subsolidus conditions. Shock-induced heating for a short duration might explain this high-temperature event. We suggest that other E3 chondrites also experienced heating events under such subsolidus conditions on their parent bodies. On the other hand, the high abundance of diopside cannot be explained by a secondary thermal event and may have been a primary feature of MS-177, formed before accretion to the parent body.
