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Recently, a series of high-magnitude earthquakes, including the 2008 Wenchuan earthquake (M 8.0), have occurred in the Longmenshan tectonic region of southwestern China. Many researchers are currently examining the geological aspects of the activity, but little attention has been given to the huge travertine deposits along large fault zones. Carbon isotopes were measured in 106 samples, and the results indicate that the travertine originated from 13 C-enriched CO 2 sourced from deep reservoirs and can be characterized by notable positive δ 13 C values. CO 2 is thought to have originated from isotopic equilibrium fractionation under thermal metamorphism temperature conditions (within 350–850 °C). The re-equilibrium fractionation between the deep CO 2 and the dissolved carbonate composition during travertine formation is due to the declining temperature of thermo-genetic CO 2 , which in turn leads to higher δ 13 C carb values. Based on oil drilling data and geochemical thermometry modeling, the depth of the 13 C-enriched CO 2 source is inferred to be below 4643 m, which coincides with the measured focal depth of the Wenchuan earthquake and subsequent aftershocks. The variation of tectonic activity intensity and the quantity of CO 2 from deep formations are mainly responsible for the δ 13 C fluctuations observed in the travertine. The δ 13 C values in travertine deposits have increased dramatically, which implies the rapid upwelling of the CO 2 -bearing fluid, the enhancement of thermal metamorphism and the continuous increase of the internal pressure in deep reservoirs. These findings may contribute to a better understanding of the deep seismic activity and high-frequency aftershocks in the Longmenshan region. [ABSTRACT FROM AUTHOR]