GEOCHEMICAL AND THIN SECTION ANALYSIS OF RING MOUNTAIN SERPENTINITE

Ring Mountain is a large geologic complex located on the Tiburon Peninsula in Marin County, Northern California. Ring Mountain lies within a broader collection of rocks called the Franciscan Complex which has been intensely studied by geologists due to the subduction and accretion during the Jurassic and Cretaceous periods. Ring Mountain has four main stratigraphic sections, the closest to the surface being the Coast Range Ophiolite. The stratigraphic layers within Ring Mountain have a puzzling geologic history because their organization is erratic and defies superposition. Additionally, these rock layers have long and arduous metamorphic histories shown via identifiable physical features. The Coast Range Ophiolite contains mafic and ultramafic material, specifically mantle peridotites which have undergone serpentinization. The basis of this study is a geochemical analysis of Ring Mountain serpentinites in order to determine their affinity between abyssal, mantle wedge, or subduction zone. Nine samples were collected from Ring Mountain and analyzed for major, minor, and trace element geochemical composition by XRF and textural analysis by thin-section study. The purpose of this research is to clarify the composition and identity of the serpentinites in Ring Mountain. This project will help geologists better understand serpentinization and how this process affects ultramafic material.