Differential tectonic evolution of the depression-ridge system and its significance for sandstone-hosted uranium deposits in the southwestern of Songliao Basin, NE China: Constrains from apatite thermochronology

Numerous sandstone-type uranium deposits are significantly influenced by the uplift-depression structural framework within the southwestern Songliao Basin. Analogies were employed to examine the differential structural coupling processes between the Jiamatu (JMT) paleo-highland and the Qianjiadian (QJD) sag since the Cretaceous period， along with their influences on these sandstone-type uranium deposits through the integrated application of apatite fission track (AFT) and (U-Th)/He dating techniques. The results demonstrate that the fission track in detrital apatite from the Yaojia Formation has not been reset， yielding an AFT age of 140.6±6.8 Ma， which is notably older than the stratigraphic age (c. 86 Ma). While the AFT ages obtained for apatites within the Hercynian granite were ranged from 187.9±6.6 Ma to 152.6±4.2 Ma， with average AHe ages of 62.75±3.29 Ma， 43.3±2.25 Ma， and 23.02±1.25 Ma， respectively. The average lengths are varied from 11.9±0.15 μm to 13.4±0.13 μm， suggesting a prolonged residence time within the annealing zone for these samples. The thermal history modeling results revealed differential four-stage tectonic coupling process in the study area: (1) slow uplift of the paleo-highland and rapid subsidence of the sag during the Early Cretaceous; (2) slow subsidence of the paleo-highland and relatively rapid subsidence of the sag in the Early to Middle Period of Late Cretaceous; (3) slow uplift of the paleo-highland and rapid uplift-thermal disturbance of the sag from the Late Cretaceous to the end of the Eocene; (4) moderate rapid uplift of the paleo-highland and fast uplift of the sag from the Oligocene to the present. Thus， the proposed ore-controlling mechanism involves two stages: firstly， during the sedimentary period， the topographic barrier of the northwest-oriented JMT paleo-highland facilitated the convergence of NE-trending braided river channels in the QJD sag. This geological process influenced the development extent of water bodies and oases， thereby affecting the formation of primary gray reducing sand bodies containing carbonaceous fragmen. Secondly， due to the preferential erosion of thin sedimentary layers surrounding the JMT paleo-highland during the Cenozoic era， the local interlayer oxidation belt (Ⅱ)， with its development direction differing from the northeast-oriented regional interlayer oxidation belt (Ⅰ)， regulated the emergence and spatial distribution of dual-layer oxidation geochemical patterns and multi-layer tabular ore bodies during the mineralization stage. This study contributes a theoretical framework for uranium exploration in transitional zones between secondary structural units of the superimposed basin， partially transcending the conventional exploration limitations in the structural slopes of basin margin.