Recent studies, focused on dihedral angles and intersection processes, have increased understandings of conjugate fault mechanisms. We present new 3‐D seismic data and microstructural core analysis in a case study of a large conjugate strike‐slip fault system from the intracratonic Tarim Basin, NW China. Within our study area, “X” type NE and NW trending faults occur within Cambrian‐Ordovician carbonates. The dihedral angles of these conjugate faults have narrow ranges, 19° to 62° in the Cambrian and 26° to 51° in the Ordovician, and their modes are 42° and 44° respectively. These data are significantly different from the ∼60° predicted by the Coulomb fracture criterion. It is concluded that: (1) The dihedral angles of the conjugate faults were not controlled by confining pressure, which was low and associated with shallow burial; (2) As dihedral angles were not controlled by pressure they can be used to determine the shortening direction during faulting; (3) Sequential slip may have played an important role in forming conjugate fault intersections; (4) The conjugate fault system of the Tarim basin initiated as rhombic joints; these subsequently developed into sequentially active “X” type conjugate faults; followed by preferential development of the NW‐trending faults; then reactivation of the NE trending faults. This intact rhombic conjugate fault system presents new insights into mechanisms of dihedral angle development, with particular relevance to intracratonic basins.

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Mud volcanoes and diapirs are geological structures formed due to arch piercing or diapiric intrusion of ductile sedimentary materials into the overlying strata along high permeability channels. A detailed study on the processes controlling the formation of mud volcanoes and diapirs in the northern continental margin of the South China Sea is of vital importance to the exploration of economically viable oil and gas reservoirs and can be helpful to the exploration of natural gas hydrate in a sedimentary basin. The fluid seepage structures that occur in the Mesozoic and Cenozoic sedimentary basins of the northern South China Sea show significant differences in their morphological and tectono-structural characteristics. We used high-resolution seismic profiles and instantaneous frequency profiles to understand the mechanisms that are critical with respect to the differential development of the investigated piercement structures. Differences in stress field do not directly lead to the difference in the scale of mud volcanoes or diapirs. Fractures may play an important role in the formation of mud volcanoes and diapirs. The thickness of the sediment was found to have a strong impact on the formation of fluid leakage structures that thicker sediments are more conducive to the development of mud diapirs and the thinner one is more likely to form mud volcanoes.

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We present new detrital zircon U–Pb chronological and whole‐rock geochemical data for the newly discovered black rock units in West Kunlun Orogen in an attempt to constrain the provenance variations of the siliciclastic rocks and the tectonic history of NW China. Geochemical data indicate these black rock units could have formed in an active continental margin to continental arc setting during the Late Ordovician and source rocks could have undergone modest chemical weathering under a relatively warm and humid climate during the deposition of the black rock units. U–Pb dating of 170 detrital zircons defines five major age populations at 459–545 Ma, 710–900 Ma, 1,300–900 Ma, 1,814–1,641 Ma, and 2,153–2,845 Ma, demonstrating that the black rock units deposited during the Late Ordovician and the tectonic events that occurred in the West Kunlun Orogen were related to the assembly and breakup of the supercontinents of Columbia and Rodinia. Prevalence of Early Palaeozoic magmatic zircons further indicates the black rock units were derived from a proximal source, most likely from the South Kunlun arc.