Thermochronology of the Meso–Cenozoic uplift and tectonic growth of the Longmenshan Thrust Belt

This paper is the result of geological survey engineering.

Objective This study focuses on the relationship between the vertical tectonic uplift and the lateral tectonic expansion that occurred during the Meso-Cenozoic in the Longmenshan thrust belt. To examine this relationship, low-temperature thermal chronology testing and analysis were conducted.

Methods The characteristics of tectonic evolution were examined by determining and analyzing apatite and zircon fission track ages.

Results The lengths of apatite fission tracks are within the range of (11.4 ± 2.6)–(12.2 ± 2.2) μm. This range effectively reflects the local tectonic uplift history. The thermal history simulation results show that the apatite samples experienced three critical stages: a rapid tectonic uplift, a stable tectonic stage, and a rapid tectonic uplift. The uplifting events occurred earlier in the northern area than in the southern area. The cooling rate of each rock sample was in the range of 1.211–6.053 °C/Ma. From the southeast to the northwest, the tectonic uplift rate increased gradually, while the time of uplifting was gradually delayed.

Conclusions The Longmenshan thrust belt has undergone tectonic deformation characterized by piggyback propagation from northwest to southeast since the Meso−Cenozoic (150 Ma). This deformation continued from the Late Cretaceous to the Eocene (70–50 Ma) and persisted into the Oligocene (approximately 20 Ma). The central and western regions of the Longmenshan thrust belt are characterized by multi-stage tectonic uplift and superposition.