Micro and Nanoscale Studies of Shock Features within the Chelyabinsk LL5 Meteorite

Abstract

Shock effects within meteorites are the products of impacts and collisions in the asteroid belt that eventually led to the ejection of the meteorite from its parent body. These collisions produce shock waves, which in turn lead to formation of high-pressure phases and deformation features within the host meteorite. The (P,T,t) history of the shock process can be deduced by studying these high-pressure phases which are produced either by solid state transformation or by crystallization of the shock melt [1]. Although detailed studies of shock effects within various highly shocked (S5-S6) L chondrites have been carried out in order to understand the P and T conditions during the impacts events [e.g., 1,2], very few studies have been done on LL and H chondrites [3,4]. Improved knowledge of shock effects on these other ordinary chondrites is desirable because of their different origin. Here, we present preliminary results from the Chelyabinsk meteorite that exploded over the Chelyabinsk area of Russia on February 15, 2013. Hundreds of fragments were collected subsequent to the airblast and were classified as LL5 ordinary chondrites [5] with impact melt rock clasts and shock-darkened lithologies. The LL5 classification was challenged by [6], who stated that Chelyabinsk is a complex genomict breccia that also contains LL6 lithologies. In this study we search for high pressure mineral phases in impact melt veins, found within a shock-darkened fragment.