Kinetic analysis of dehydration in carbonaceous chondrites by in-situ heating FT-IR

Abstract

Some CI and CM carbonaceous chondrites are known to have been heated by impact or solar heating after these parent bodies experienced aqueous alteration at low temperature and have experienced dehydration of the OH groups from the hydrous mineral phyllosilicate at 400 to 770°C.Although heating experiments on carbonaceous chondrites have been conducted to constrain the heating temperature and the thermal process, the kinetic studies considering heating duration were limited. In this study, in order to constrain the thermal history of parent asteroids of heated CM, CI chondrites by determining the degree of dehydration of the hydrous minerals, we conducted thermal dehydration experiments on unheated Murchison (CM2.5) and Ivuna (CI) carbonaceous chondrites under infrared spectroscopy (FTIR) with a heating stage. The 2.72 µm OH bands were observed in situ and kinetic analysis was applied to evaluate the dehydration rates. Temperature-time-transformation (TTT) diagrams were obtained to represent the decrease in the -OH as a function of temperature and time. Thus, we expect to constrain the thermal processes of parent asteroids of heated carbonaceous chondrites.