Thermal processing contributes to chemical fractionation of matter in the early solar nebula on a variety of scales and can impart diagnostic mineralogical, chemical, and isotopic signatures to meteoritic components. We propose to use micro-mineralogical features of pallasites and Li isotope signatures of chondrites and olivine-rich achondrites to determine the role of thermal processing in their evolution, and to place constraints upon the physical settings in which these processes operated. Studies include: (1) TEM-based investigation (including FIB sample preparation, HRTEM, EELS, EDS and SAED) of multi-phase, crystallographically-oriented, tubular inclusions within pallasite olivines to determine their mineralogy, composition, oxidation state, crystallography, and micro-structural relationships.  These data will be used to examine the relationship between these features and the thermal, redox, and deformation histories of the pallasite parent body. (2) SIMS analysis of Li and d7Li zoning in pallasite minerals and in olivine from coarse-grained, olivine-rich achondrites to constrain thermal history using Li diffusion data. (3) SIMS analysis of micro-scale variations in Li and d7Li in minerals, chondrules and refractory inclusions from primitive chondritic meteorites (including Semarkona) to (a) distinguish between evaporation of chondrules or chondrule precursors and nebular or parent-body metasomatism and metamorphism and (b) constrain nebular conditions of evaporation and chondrule formation. Li studies will be complemented by SEM, EMP, and SIMS analyses of major-, minor-, and trace-elements, and include F and Be to trace halogen metasomatism and possible radioactive decay of short-lived 7Be, respectively. The proposed work will contribute to the NASA vision statement and goal to "Advance scientific knowledge of the origin and history of the solar system … ". Fundamental new knowledge will be generated regarding constituents of both primitive and processed meteorites and the information they can provide regarding early solar system events.

Thermal processing contributes to chemical fractionation of matter in the early solar nebula on a variety of scales and can impart diagnostic mineralogical, chemical, and isotopic signatures to meteoritic components. We propose to use micro-mineralogical features of pallasites and Li isotope signatures of chondrites and olivine-rich achondrites to determine the role of thermal processing in their evolution, and to place constraints upon the physical settings in which these processes operated. Studies include: (1) TEM-based investigation (including FIB sample preparation, HRTEM, EELS, EDS and SAED) of multi-phase, crystallographically-oriented, tubular inclusions within pallasite olivines to determine their mineralogy, composition, oxidation state, crystallography, and micro-structural relationships.  These data will be used to examine the relationship between these features and the thermal, redox, and deformation histories of the pallasite parent body. (2) SIMS analysis of Li and d7Li zoning in pallasite minerals and in olivine from coarse-grained, olivine-rich achondrites to constrain thermal history using Li diffusion data. (3) SIMS analysis of micro-scale variations in Li and d7Li in minerals, chondrules and refractory inclusions from primitive chondritic meteorites (including Semarkona) to (a) distinguish between evaporation of chondrules or chondrule precursors and nebular or parent-body metasomatism and metamorphism and (b) constrain nebular conditions of evaporation and chondrule formation. Li studies will be complemented by SEM, EMP, and SIMS analyses of major-, minor-, and trace-elements, and include F and Be to trace halogen metasomatism and possible radioactive decay of short-lived 7Be, respectively. The proposed work will contribute to the NASA vision statement and goal to "Advance scientific knowledge of the origin and history of the solar system ... ". Fundamental new knowledge will be generated regarding constituents of both primitive and processed meteorites and the information they can provide regarding early solar system events.