EXAMINING REGIONAL OLIVINE COMPOSITION IN TERRESTRIAL DUNITE SAMPLES TO BETTER UNDERSTAND COMPOSITIONS COLLECTED FROM APOLLO LUNAR DUNITE SAMPLES

As a Mineralogy class project, we sought to compare the olivine composition from a local dunite with those from similar rocks throughout Earth and the Moon in order to learn about the compositional variations present in olivine, as well as different analytical techniques. We analyzed the major and minor element content of olivine within a sample of dunite from the Webster-Addie ultramafic complex, located in Jackson County, North Carolina, because the modal mineralogy was relatively simple. Major and minor element contents of olivine were determined using the electron microprobe at the University of Tennessee, and the Forsterite values were compared to those of dunite from across the Earth and some lunar samples. Preliminary results indicate that the average Forsterite value within our Webster-Addie sample is Fo90, and the sample contains a range of Fo84 to Fo95. This is in agreement with some previously published values of olivine within the Webster-Addie complex. Comparably, other dunites within North America, such as in Pasadena, Ca and Abitibi, Ontario show similar ranges with ~Fo80-95. In contrast, dunites from some other locations on Earth, such as Oman and India, range ~Fo93-98. The olivine from terrestrial dunite is also in distinct from olivine within dunite from lunar rocks, which show a range of ~Fo86-89. This indicates that the origin of the Webster-Addie dunite likely has a different mode of formation to the dunites from other locations on Earth as well as the lunar dunites. We will present the detailed results of our electron microprobe analyses, as well as the petrologic context of out Webster-Addie sample in comparison to others from across Earth and the Moon.