See more from this Division: General Discipline Sessions
See more from this Session: Structural Geology / Tectonics / Neotectonics/Paleoseismology I
Abstract:
Northwest-side-up dextral movement along 050°-trending shear zones of the central segment between the SSW and ENE segments is inconsistent with the promontory model. Furthermore, north-side-up dextral movement along the 110°-trending Aiken River shear zone along the ENE segment within the Superior Province remains unexplained. Thus, a simple promontory model is insufficient to explain the movements along all shear zones. Shear zones were either active at different time periods or the Superior Boundary Zone may be a zone of macroscopic brecciation, rather than a zone of rigidly moving domains. The latter would explain the presence of zones of brecciation along the central segment of the promontory.
At least part of the dextral, southeast-side-up movement on the Assean Lake shear zone occurred after ~1.84 Ga, based on a UPb zircon age of a deformed aplite. Movement may or may not have been concurrent with <1.77 Ga sinistral and subsequent southeast-side-up movement along the Setting Lake shear zone. Based on crosscutting relationships, movement on the Assean Lake shear zone outlasted movement on the Aiken River shear zone. Both shear zones probably also experienced earlier, Late Archean movement. The timing of movement along various shear zones is currently further being constrained by UPb and 40Ar/39Ar geochronology.
See more from this Division: General Discipline Sessions
See more from this Session: Structural Geology / Tectonics / Neotectonics/Paleoseismology I