Reconstructing Thermal Histories in Carbonate Basins: A Clumped Isotope and U-Pb Dating Thermometry Approach from the Tarim Basin

The ability to reconstruct the thermal history of a basin is essential in modeling reservoir and source rock quality. In carbonate rocks, conventional thermal indicators could not be used, for apatites and vitrinite are hard to be found. The clumped isotope palaeothermometer and U-Pb dating are promising technique for constraining the thermal history of basins. In this study we test if carbonate clumped isotope thermometry could be used to explore the thermal histories.

This paper collects the drill cores of Cambrian and Ordovician carbonate rocks in Awati-Keping region, Tarim Basin, northwest China. The calcites and dolomites are relatively homogeneous. The Carbonate components of Ordovician strata yield statistically indistinguishable clumped isotope temperatures(TΔ₄₇), ranging from 108.4 to 189°C. The U-Pb ages are from 483 to 525Ma. The thermal evolution paths of the carbonate clumped isotope temperature (TΔ₄₇ ) in the Awati-Keping region are simulated using the first order rate approximation model.

From this study , it shows that the thermal history evolution of the Awati-Keping region can be divided into three stages: ① Slow heat flow decline stage: During the Cambrian-Ordovician periods, the heat flow values (45-55 mW/m²). As the Tarim Basin evolved into a craton, the terrestrial heat flow gradually decreased to 41-45 mW/m² by the Carboniferous. ② Rapid heat flow evolution stage: Influenced by Early Permian tectonic-thermal events, a transient peak heat flow (60-70 mW/m²) occurred in the Awati-Keping region. ③ Heat flow recession stage: During the Mesozoic-Cenozoic, heat flow values in the Awati-Keping region declined to 35-45 mW/m². The Early Permian high-temperature strata in the Awati-Keping region resulted from combined effects of burial depth and anomalous high heat flow events. Both magmatic eruptions and mantle plume upwelling contributed to the anomalous high heat flow event during the Early Permian.

The maturity evolution of the Yuertus Formation source rocks in the Awati-Keping region can be divided into three stages since deposition: gradual maturation during Cambrian-Early Carboniferous, rapid maturation acceleration during Late Carboniferous-Late Permian, and maturation stagnation from Triassic to present. The Shunbeixi area exhibits lower thermal evolution degree of source rocks, which is favorable for hydrocarbon accumulation.