| Many experimental studies of silicate mineral weathering have been carried out since the middle of the twentieth century, but until the past year there were no studies of natural weathering textures of olivine. Laboratory methods depend on highly corrosive solvents to achieve results within reasonable time frames, and use gem-quality olivine to isolate measurable effects. Natural weathering, however, must be analyzed by studying the morphology of end-state materials and drawing inferences from what is observed.;Thin sections and grain mounts of tectonized olivines from the Webster-Addie ultramafic body in western North Carolina were studied using optical microscopy and scanning electron microscopy. Most natural dissolution features, or etch pits, can be seen as variations of conic sections.;Etch pit fields observed in nature share a number of general characteristics with such features formed experimentally, including uniform size, spacing, and orientation. These observations support the conclusions of many studies of experimental kinetics that olivine dissolution is surface-reaction limited, and that dissolution textures result from preferential etching at edge and screw dislocations within the olivine. |
