Geochronological Constraints on Diachronous Post‐Collisional Slab Breakoff Along the Paleo‐Tethyan Sutures

The slab breakoff model is a preferred geodynamic interpretation for post‐collisional exhumation and associated magmatic flare‐ups. In this study, rutile U–Pb dating of retrograde eclogites revealed distinct stages of exhumation along the Paleo‐Tethyan sutures in southwest China. The studied samples yielded ages of 246.7 ± 8.5 and 239.7 ± 14.0 Ma in the Changning–Menglian suture zone, and 213.0 ± 10.0 and 205.6 ± 8.9 Ma in the Longmu Co–Shuanghu suture zone. These new rutile ages, along with published geochronological data for high‐pressure (HP) metamorphic and igneous rocks along the Paleo‐Tethyan sutures, reveal that Late Triassic tectonic exhumation was coeval with a regional magmatic flare‐up. Our results suggest that the Late Triassic tectonomagmatic activity occurred in a post‐collisional setting and was related to slab breakoff. The geochronological data for the HP metamorphic and igneous rocks show that the Late Triassic tectonomagmatic activity was diachronous along the suture. We propose that the spatiotemporal migration of these Late Triassic post‐collisional tectonothermal events was controlled mainly by the initiation and progression of slab breakoff. The results provide new insights into the tectonic evolution of the Tethyan geodynamic system and improve our understanding of post‐collisional tectonomagmatism in response to slab breakoff processes in a collision zone.