9628552 Metcalf The Trinity terrane, in the eastern Klamath Mountains of California, lies between an early Devonian subduction-related trench and an immature early Devonian volcanic island arc, and constitutes the largest exposure of ultramafic rock in North America. However, lithologic and geochemical data are complex, with disparate implied tectonic environments. The project will test three current models to explain these rocks (single section of oceanic lithosphere, back-arc basin or a variant such as a supra-subduction zone origin). The main goals are to determine the age and duration of magmatism, determine the petrogenesis and tectonic setting of the mafic intrusive complexes, and to attempt to identify ultradepleted mantle that is coeval with the mafic-intrusive complexes as predicted by the favored model. Results have the potential to provide a unifying explanation for all lower Paleozoic lithotectonic elements in the eastern Klamath Mountains in which all three terranes evolved doing a single convergent margin tectonic episode.
