Shock-thermal history of Kavarpura IVA iron: Evidences from microtextures and nickel profiling

Abstract

We classify Kavarpura iron (fell in August, 2006, in Rajasthan, India), an inclusion-free member of high-Ni IVA group. Widmanstätten pattern and finger–cellular plessites textures characteristic of IVA group are present in Kavarpura. Symmetric and asymmetric textural zoning within the cloudy taenite and plessite refer to long term martensitisation process with mean metallographic cooling rate of 200°C/Ma. Imprints of variable shock pressure domains (Neumann bands and shock hatched ε kamacite) suggest alteration by up to 600kb shock pressure. Degeneration of cellular plessites, bending of finger plessites and plastic flowage of taenites bear textural evidences corresponding to post-shock annealing which is further confirmed by Ni profiles across the cloudy taenites and plessites under high shock pressure domains. Based on microtextural evidences and Ni profiling, we suggest Kavarpura had cooled at steady state and subsequently suffered multiple impacts.