Field calibration of 40Ar/39Ar K-feldspar multiple diffusion domain (MDD) thermal histories at the Grayback normal fault block, Arizona, USA

Abstract

Numerous studies suggest that 40Ar/39Ar K-feldspar analyses record continuous thermal histories from ∼300 °C to 150 °C due to the presence of multiple diffusion domains (MDDs). Such continuous thermal histories can provide significant advantages over thermochronometers that only record cooling through a single closure temperature. However, some studies have questioned the reliability of 40Ar/39Ar K-feldspar MDD models. This study tested whether MDD modeling produces accurate thermal histories that are calibrated to other thermochronometers. MDD models of samples from the Grayback fault block, Arizona, USA, which has a well-known thermal history and structure, and has accurately reproduced the expected thermal evolution, including the inception, rate, and magnitude of rapid cooling produced by tectonic exhumation. Absolute temperatures of the models also matched well with the known pre-extensional thermal structure of the block. These new data provide strong confirmation that MDD K-feldspar models can provide geologically meaningful and accurate continuous thermal histories.