In the Jinshan aulacogen on the southern margin of the Ordos Basin, volcanic rocks of the Mesoproterozoic Changchengian System Xiong'er Group were first encountered by Well PT1, and the drilling operations have revealed the complete strata of Changchengian System within the basin. A systematic analysis of Well PT1 data, including lithological assemblage, zircon U–Pb dating, and geochemical testing, provided the following key findings. (1) The Mesoproterozoic Changchengian System shows a typical sequence consisting of three parts: the Xiong’er Group (volcanic and volcaniclastic rocks) at the bottom, the Ruyang Group (clastic rock) in the middle, and the Luoyu Group (fine clastic–carbonate rocks) at the top. (2) The Xiong’er Group experienced multiple stages of basaltic magma eruptions, dated at 1731 ± 27 Ma and 1756 ± 19 Ma. This suggests that the Ordos Basin was rifted along with the breakup of the Columbia supercontinent, indicating that the Jinshan aulacogen functioned as a rift system. (3) A 28-m-thick dark mudstone, interval with a total organic carbon (TOC) content of up to 1.58%, was encountered in the Changchengian System Cuizhuang Formation. This mudstone has been identified as the oldest source rock discovered in the Ordos Basin. The tensional tectonic environment associated with the breakup of the Columbia supercontinent created favorable conditions for the deposition of Mesoproterozoic source rocks, making them promising targets for Proterozoic exploration in the Ordos Basin.
Pan et al. (Fri,) studied this question.