Ulasitai: A new iron meteorite likely paired with Armanty (IIIE)

Abstract

The Ulasitai iron was recently found about 130 km southeast to the find site of the Armanty (Xinjiang, IIIE) meteorite. It is a coarse octahedrite with a kamacite bandwidth of 1.2 ± 0.2 (0.9-1.8) mm. Plessite is abundant, as is taenite, kamacite, cohenite, and schreibersite with various microstructures. Schreibersite is Ni-rich (30.5-55.5 wt%) in plessite or coexisting with troilite and daubreelite, in comparison with the coarse laths (20.621.2 wt%) between the Widmansttten pattern plates. The correlation between the center Ni content and the half bandwidth of taenite suggest a cooling rate of ~20 °C/Myr based on simulations. The petrography and mineral chemistry of Ulasitai are similar to Armanty. The bulk samples of Ulasitai were measured, together with Armanty, Nandan (IIICD), and Mundrabilla (IIICD), by inductively coupled plasma atomic emission spectrometry (ICP-AES) and mass spectrometry (ICP-MS). The results agree with literature data of the same meteorites, and our analyses of four samples of Armanty (L1, L12, L16, L17) confirm a homogeneous composition (Wasson et al. 1988). The bulk composition of Ulasitai is identical to that of Armanty, both plotting within the IIIE field. We classify Ulasitai as a new IIIE iron and suggest that it pairs with Armanty.