Kinematics of Pre‐Miocene ductile deformation in the Santa Catalina Core Complex and adjacent regions

Abstract

This paper describes structures within mylonites and metamorphic rocks from the Santa Catalina and Tortolita‐Suizo metamorphic core complexes, southeastern Arizona, United States. In these areas, mylonitic rocks constitute an easterly low‐dipping slab more than 4 km thick. Mapping of principal strain directions and analysis of shear sense have been carried out through the whole pile of mylonites. It is shown that although the stretching lineation appears to have a uniform mean SW‐NE trend, three successive shearing events are involved. The first shearing event is toward the west and is accompanied in part by the emplacement of the Leatherwood Quartz Diorite dated at 64 Ma. The second shearing event is toward the NE and is accompanied by the emplacement of the Wilderness Granitic Suite dated at 49 Ma. The third shearing event is localized and directed toward the SW. The top‐to‐west shearing and top‐to‐NE shearing are possibly related to Laramide thrusting. The last ductile shearing is related to post‐Eocene extension.