Diagenesis of the Paleogene Sandstones in the DN2 Gas Field, Kuqa Foreland Basin and Its Link with Tectonics

Abstract

AbstractWe investigated the diagenesis of sandstones from DN2 Gas Field of Kuqa Foreland Basin (KFB) to infer timing of fluid migration and discuss link between fluids and tectonics. Textures and chemical composition of authigenic minerals, fluid evidence from fluid inclusions and formation water measurements were used to fulfill the aim. Eodiagenesis occurred with the participation of meteoric waters and connate waters. Mesodiagenesis are related to high salinity fluids, which were attributed to originate from overlying Neogene Jidike Formation evaporite (main minerals including halite, anhydrite, glauberite, carnallite and thenardite). The onset of high salinity fluid migration was inferred to occur during the late Miocene (12.4–9.2 Ma) by using integration of Th measured in the present study and K‐Ar dating of authigenetic illites from previous study. The period is consistent with the crucial phase (13–10 Ma) witnessing the rapid uplift of southern Tianshan Mts and the stage when calcite and anhydrite veins formed in the studied strata. We thus argue that diagenesis related to high salinity fluids occurred as a response to Tianshan Mts's rapid uplift and related tectonic processes. The flow of high salinity fluids was probably driven by density gradient and channeled and focused by fractures formed contemporaneously.