Differential (re-)activation and hydrocarbon enrichment of segments of intracratonic strike-slip faults in the central Tarim Basin, northwestern China

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Intracratonic strike-slip faults are pivotal in controlling hydrocarbon migration and accumulation within deep carbonate reservoirs, yet their multiphase reactivation histories and spatio-temporal coupling with hydrocarbon charging remain poorly constrained. This study integrates calcite U-Pb geochronology, fluid inclusion microthermometry, and fluorescence spectroscopy to resolve the evolution of the F117 and F119 strike-slip fault systems in the ultradeep (>7000 m) Ordovician strata of the Tarim Basin. The F117 fault records six reactivation phases, from the middle Caledonian Orogeny episode II (452 ± 3.3 Ma) to the Himalayan Orogeny (68 ± 54 Ma), and the F119 fault exhibits five phases, terminating at the Indosinian Orogeny but with intensified activity associated with the late Hercynian–Indosinian Orogenies (251 ± 24 and 264 ± 49 Ma). Hydrocarbon charging occurred in three distinct episodes: middle–late Caledonian Orogeny (443.2 ± 6.1, 445.3 ± 3.9, 444.8 ± 8.6, and ca. 440–420 Ma) migration of low-maturity oils (wavelength of maximum intensity [λmax]: 520–480 nm), late Hercynian–Indosinian Orogenies (ca. 290–210, ca. 350–250, 264 ± 49, and ca. 310–210 Ma) recharging of high-maturity oils (λmax: 480–435 nm), and a unique Himalayan-phase methane influx (68 ± 54 Ma) in F117. Critically, fault segment architecture governs reservoir heterogeneity: linear segments (e.g., F117–HD32, F119–MS7-H4) preserved Caledonian oils due to structural stability; extensional segments and intersections (e.g., F117–MS5, F119–MS701) experienced post-Caledonian leakage and Hercynian–Indosinian recharging; and contractional segments (e.g., F117–MS2, F119–MS702) retained hydrocarbons only during late-stage (Hercynian–Indosinian) fault reactivation.