Mass Independently Fractionated Sulfur Component in Primitive Chondrites

Introduction: Sulfur is a cosmochemically important element with four stable isotopes. It is the only element besides oxygen where a mass independent fractionation (MIF) has been observed both in nature [1-4] and the laboratory [4,5]. Unlike oxygen, where more than one process can produce MIF, sulfur MIF is exclusively of photochemical origin. Recently we have demonstrated a mass independent sulfur of photochemical origin in achondritic meteorites [6]. Despite observations of mass independent sulfur in differentiated meteorites [6,7], such anomalous sulfur has not been observed in undifferentiated primitive chondrites (except a few isolated phases in Allende and Murchison) [3,7-10] where most of the anomalous component for other elements have been observed. It has been suggested that this component is also present in chondrites but the anomalous signature is obscured by the presence of relatively larger amounts of sulfur of normal (mass dependent) isotopic composition [6]. Alternatively, MI sulfur was incorporated in a chondrite parent body but was homogenized during parent body metamorphism. In order to search for anomalous MI sulfur in primitive meteorites, if exists, we investigated several chondrites for sulfur isotope with a different experimental approach. In our new approach, sulfur is extracted in number of steps with premise that various sulfur component would appear at different times based on their chemical resistance towards acid. Sulfur is extracted from various physically separated components such as fine-grained matrix, chondrules etc. from chondrites.