ZIRCON PETROCHRONOLOGY OF SALINIAN ARC MIDDLE CRUST, EASTERN SANTA LUCIA MOUNTAIN, CALIFORNIA

It is well accepted that large volumes of magma form above subduction zones at convergent margins, although how this magma forms and evolves during ascent through the crust remains uncertain. However, exposures within the Salinian block along the Central Coast of California are composed of igneous rocks and their high grade metamorphic framework that formed at variable pressures, and present a unique opportunity to investigate lower and middle crustal arc processes and magma evolution. To place new constraints on the timing of igneous intrusion and metamorphism within the Salinian block, we collected garnet-bearing samples of orthogneiss and paragneiss from a transect across the central portion of the Salinian block where previous studies have indicated metamorphism and crystallization at middle-crustal depths. We will present new petrographic observations and zircon U-Pb isotope and geochemistry measured via laser ablation inductively coupled plasma mass spectrometry (LA-ICP-MS) from these rocks to determine their igneous and metamorphic histories. Ultimately, this information will be used for comparison with results from lower-crustal arc exposures farther west in the Salinian block, and provide a more comprehensive chronology for the Salinian arc from lower to mid-crustal depths.