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Ordovician carbonate rocks on the northern slope of the Tazhong Uplift in the Tarim Basin are modified to varying degrees by hydrothermal fluids related to multiple tectonic-thermal events, but the nature, origin and circulation mechanisms of such hydrothermal fluids remain debated. In this article, in situ rare-earth elements and yttrium (REE + Y) concentrations, previously published geochemical datasets and petrographic investigations are integrated to develop a thermo-tectonic evolution model to improve understanding of silicification and dolomitisation occurring in the interior of the craton basin. δ 30 Si values, REE + Y ratios and fluid mixing models using modern black smoker fluid and seawater indicate that magma-sourced hydrothermal fluids, rather than basinal brine heated by magmatism, are responsible for the precipitation of cherts. Petrological and geochemical evidence suggests that deep-seated, ultramafic-derived hydrothermal fluids and/or magmatic fluids associated with Permian volcanism may have been involved in the formation of hydrothermal dolomites in the study area. Accompanying formation and reactivation of the strike-slip faults on the northern slope of the Tazhong Uplift, small volumes of hydrothermal fluids might have been triggered by seismic pumping. The early formed strike-slip fault systems may also have served as conduits for the subsequent large-scale transport of deep-seated, ultramafic-derived thermal fluids and/or Permian magmatic fluids, along which fluids were transported upwards at high flow rates. Carbonation of ultramafic rocks through interaction with deep-seated hydrothermal fluids rich in CO 2 may have served as a magnesium and silica source for dolomitisation and silicification. Trans-tensional troughs on NNE-trending strike-slip faults with positive flower structure are favourable locations for dolomitisation and silicification.

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