Newly Recognized Ductile Shear Zone in the Northern Klamath Mountains, Oregon.Implications for Nevadan Accretion

摘要

One of the most frequently encountered problems in structural analysis ofcomplexly deformed metamorphic terranes is the determination of the sense of movement in sheared rocks. In regions composed of accreted terranes, such as the Klamath Mountains, such information can shed light on the relative motions of large blocks of crust and thus may enhance our understanding of the processes by which accretion takes place. This study uses mesoscopic structural data, petrographic criteria, and quartz petrofabric analysis to deduce the sense of shear in ductilely deformed quartzites and semi-pelitic schists from a newly discovered mylonitic shear zone separating the May Creek Schist and structurally underlying amphibolite in the northernmost Klamath Mountains.