Differential Tectono-Thermal Evolution Along the South–North Direction in the Central Qiangtang Basin and Implications for Hydrocarbon Generation Potential

The Qiangtang Basin in the Tibetan Plateau exhibits a paradoxically reversed source-rock maturity pattern (high margins, low center), which presents a challenge to classical basin models. Critically, the unclear genetic mechanism behind this anomaly has impeded hydrocarbon exploration. To address this, this study investigates a north–south-oriented 2D geological section across the central basin. By employing an integrated methodology, the genetic mechanism was elucidated through systematic calculations of paleo-burial depth, paleotemperature, and vitrinite reflectance (Ro) at ten control points (C1–C10). Specifically, tectonic burial history was reconstructed using the backstripping method, while mantle heat flow was corrected by integrating the McKenzie extensional and Royden compressional models. Maturity evolution was quantified using the Easy%Ro model. The results demonstrate that (1) since the Early Jurassic, the basin has undergone five tectono-thermal evolution stages, with the geothermal gradient reaching 30–36 °C/km during the end of the Early Cretaceous); (2) Ro values range from 1.2% to 1.68% at the northern basin margin (C1–C4), are approximately 1.15% in the Central Uplift Zone (C5–C7), and range from 1.45% to 1.6% at the southern basin margin (C8–C10); (3) importantly, the reversed distribution was jointly controlled by three factors: deep burial at the basin margins (5–6 km), early uplift in the central part (initiating from the Late Cretaceous), and local magmatic thermal disturbance. Their estimated contribution ratios are 40–50%, 30–40%, and 10–20%, respectively. Consequently, regions such as the Luxiongcuo Syncline, the Bandaohu–Qingshuihu area, and the Chibuzhangcuo area are identified as having favorable exploration potential.