Late Cretaceous–Cenozoic thermochronology in the southern Songliao Basin, NE China: New insights from apatite and zircon fission track analysis

Abstract

The Late Cretaceous–Cenozoic thermochronology in the southern Songliao Basin was determined using apatite and zircon fission track analysis data. It is crucial to deciphering the evolution of the Songliao Basin and changes in the movement direction of the Pacific Plate. We present eight new apatite and eight corresponding zircon fission track data from borehole samples across the Baixingtu uplift. The apatite fission track (AFT) thermochronological modeling reveals that the basin underwent two distinct compression- and extension-related uplift stages of rapid cooling during the Late Cretaceous–Cenozoic: stage I during the Late Cretaceous–Early Paleogene (∼70–52 Ma), stage II in the Late Paleogene–Early Neogene (∼38–10 Ma). The AFT data vary from 76.0 ± 5.0 to 25.3 ± 1.9 Ma and the zircon binomial peak fitting ages ranged from 79 to 61 Ma, all younger than the stratigraphic ages (∼92–88 Ma) of their host rocks. One sample had similar fission track ages (apatite 76.0 ± 5.0 Ma and zircon 79.0 ± 3.0 Ma) within reasonable error, representing a magmatic event. The data were divided into four groups. (i) 79–76 Ma: magmatic cooling event, (ii) 69–61 Ma: uplift of the whole region and exhumation and erosion, (iii) 37–34 Ma and (iv) ∼25 Ma: various uplift events related to tectonic inversion, causing partial uplift, exhumation and erosion in the basin. This created favorable conditions for formation and storage of mineral resources, especially sandstone uranium ore deposits. Our results combined with previous research suggest that the variation in uplift and exhumation began in the basin’s SE part and propagated to the NW ∼5–8 Ma later. The tectonic inversion in the southern Songliao Basin at least began ∼37–34 Ma. This corresponds with the time of the Paleo-Pacific Plate shifting to NWW motion and the India–Asia collision. These regional-scale uplift, exhumation and inversion events were probably responses to the subduction and turning of the Paleo-Pacific Plate from the southeast and the collision of the Indian subcontinent from the southwest. It is important to study the tectonic inversion in the whole east of China since the Late Cretaceous and the change of the direction of the Pacific plate movement.