A Thermal Pulse Induced by a Permian Mantle Plume in the Tarim Basin, Northwest China: Constraints From Clumped Isotope Thermometry and In Situ Calcite U‐Pb Dating

Abstract

High burial temperature and a lack of material for traditional thermal proxies significantly impede the understanding of the thermal history of carbonate stratigraphic sequences in deep time. Carbonate clumped isotope thermometry interpreted through models of solid‐state isotopic reordering and in situ U‐Pb dating provides a new methodology for reconstructing thermal histories of such successions. Calcite fabrics (micrite cements and veins) from deeply buried (5,000–8,000 m) Ordovician carbonate intervals in the Tarim Basin were analyzed for their carbonate clumped isotope compositions and U‐Pb ages, and the results were used to estimate maximum peak burial temperatures. Reconstructed burial temperatures reveal a previously ignored thermal pulse in the range of 160°C–190°C during the Permian period. Maximum geothermal gradients at the time of peak burial temperature varied from 26.8°C/km to 69.3°C/km, with higher values in the northern Tarim Basin. We show that the spatial patterns of peak burial temperature and geothermal gradients closely correspond to the distribution of the Tarim Large Igneous Province, which emplaced during the Permian following the emplacement of a mantle plume beneath the Tarim Basin. We thus propose that the thermal pulse recorded in Tarim Ordovician limestones resulted from Permian mantle plume activity. The reconstructed thermal history has important implications for our understanding of source‐rock hydrocarbon generating history, hydrocarbon accumulation, and fluid flow history in the Tarim Basin. This study also demonstrates the potential of the integration of Δ₄₇, U‐Pb dating of carbonates and solid‐state reordering models as an integrated thermochronological method for reconstructing thermal histories of deeply buried carbonate intervals.