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Research on the distribution of mantle CO2 should involve comprehensive analysis from CO2 source to accumulation. The crust‐mantle pathway system is the key controlling factor of the distribution of mantle CO2, but has received little attention. The pathway system and controlling factors of CO2 distribution in the Bohai Sea are analyzed using data on fault styles and information on the mantle and lithosphere. The relation between volcanic rocks and the distribution of mantle CO2 is reassessed using age data for CO2 accumulations. The distribution of mantle CO2 is controlled by uplift of the asthenosphere and upper mantle, magma conduits in the mantle and fault systems in the crust. Uplifted regions of the asthenosphere are accumulation areas for CO2. The area with uplift of the Moho exhibits accumulation of mantle CO2 at depth. CO2 was mainly derived from vertical migration through the upper mantle and lower crust. The fault style in the upper crust controls the distance of horizontal migration and the locations of CO2 concentrations. The distribution of mantle CO2 and volcanic rocks are not the same, but both probably followed the same pathways sometimes. Mantle CO2 in the Bohai Sea is concentrated in the Bozhong sag and the surrounding area, particularly in a trap that formed before 5.1 Ma and is connected to crustal faults (the Bozhang faults) and lithospheric faults (the Tanlu faults). [ABSTRACT FROM AUTHOR]

There are numerous controversies surrounding the tectonic properties and evolution of the Proto‐South China Sea (PSCS). By combining data from previously published works with our geological and paleontological observations of the South China Sea (SCS), we propose that the PSCS should be analyzed within two separate contexts: its paleogeographic location and the history of its oceanic crust. With respect to its paleogeographic location, the tectonic properties of the PSCS vary widely from the Triassic to the mid‐Late Cretaceous. In the Triassic, the Paleo‐Tethys and the Paleo‐Pacific Oceans were the major causes of tectonic changes in the SCS, while the PCSC may have been a remnant sea residing upon Tethys or Paleo‐Pacific oceanic crust. In the Jurassic, the Meso‐Tethys and the Paleo‐Pacific oceans joined, creating a PSCS back‐arc basin consisting of Meso‐Tethys and/or Paleo‐Pacific oceanic crust. From the Early Cretaceous to the mid‐Late Cretaceous, the Paleo‐Pacific Ocean was the main tectonic body affecting the SCS; the PSCS may have been a marginal sea or a back‐arc basin with Paleo‐Pacific oceanic crust. With respect to its oceanic crust, due to the subduction and retreat of the Paleo‐Pacific plate in Southeast Asia at the end of the Late Cretaceous, the SCS probably produced new oceanic crust, which allowed the PSCS to formally emerge. At this time, the PSCS was most likely a combination of a new marginal sea and a remnant sea; its oceanic crust, which eventually subducted and became extinct, consisted of both new oceanic crust and remnant oceanic crust from the Paleo‐Pacific Ocean. In the present day, the remnant PSCS oceanic crust is located in the southwestern Nansha Trough. [ABSTRACT FROM AUTHOR]

Based on the volume magnetic susceptibility and specific gravity measurements and mineral and lithologic identification results for 540 samples, the rock type, density, and magnetic susceptibility of rocks from northern Borneo were analyzed, and the applicability of gravity and magnetic data to the lithologic identification of the Mesozoic strata in the southern South China Sea was assessed accordingly. The results show that there are 3 types and 25 subtypes of rocks in northern Borneo, mainly intermediate‐mafic igneous rocks and exogenous clastic sedimentary rocks, with small amounts of endogenous sedimentary rocks, felsic igneous rocks, and metamorphic rocks. The rocks that are very strongly–strongly magnetic and have high–medium densities are mostly igneous rocks, tuffaceous sandstones, and their metamorphic equivalents. The rocks that are weakly magnetic‐non‐magnetic and have medium–very low densities are mostly conglomerates, sandstones, siltstones, mudstones, and coal. The rocks that are weakly magnetic‐diamagnetic and have high‐medium densities are mostly limestones and siliceous rocks. The Cenozoic rocks are characterized by low densities and medium susceptibilities; the Mesozoic rocks are characterized by medium densities and medium–high susceptibilities; and the pre‐Mesozoic rocks are characterized by high densities and low magnetism. Based on these results and the distribution characteristics of the various rock types, it was found that the pre‐Mesozoic rocks produce weak regional gravity anomalies; the Mesozoic sedimentary rocks produce negative regional gravity anomalies; whereas the Mesozoic igneous rocks produce positive regional gravity anomalies; and the Cenozoic igneous rocks produce positive regional gravity anomalies. The regional high magnetic anomalies in the southern part of the South China Sea originate from the Mesozoic mafic igneous rocks and their metamorphic equivalents; and the regional medium magnetic anomalies may be produced by the felsic igneous rocks and their metamorphic equivalents. Accordingly, the identification of the Mesozoic lithology in the southern South China Sea shows that the Mesozoic sedimentary rocks are distributed over a large area of the southern South China Sea. Thus, it is concluded that the Mesozoic strata in this area have the potential for oil and gas exploration. [ABSTRACT FROM AUTHOR]

A gas field consisting of volcanic reservoir rocks was discovered in the block‐T units of the Xihu Sag, East China Sea Basin. The lithology of the volcanic rocks is dominated by tuff and reworked tuff. The lithofacies are dominated by base surge deposits of explosive facies. As the architecture model of volcanic facies is still uncertain, it has restricted the exploration and development of mineral resources in this area. Using core and cuttings data, the lithology, lithofacies, geochemistry as well as grain size characteristics of volcanic rocks were analyzed. Based on these analyses, the volcanic rocks in the well section are divided into three eruptive stages. The transport direction of each volcanic eruption is analyzed using crystal fragment size analysis. The facies architecture of the block‐T units was established based on the reconstruction results of paleo‐geomorphology. The results show that the drilling reveals proximal facies (PF) and distal facies (DF) of the volcanic edifices. However, the crater‐near crater facies (CNCF) are not revealed. Compared with the reservoirs of the Songliao Basin, it is shown that the volcanic rocks in the Xihu Sag have good exploration potential; a favorable target area is the CNCF near the contemporaneous fault. [ABSTRACT FROM AUTHOR]

The Cenozoic volcanostratigraphy in the Changbaishan area had complex building processes. Twenty-two eruption periods have been determined from the Wangtian'e, Touxi, and Changbaishan volcanoes. The complex volcanostratigraphy of the Changbaishan area can be divided into four types of filling patterns from bottom to top. They are lava flows filling in valleys (LFFV), lava flows filling in platform (LFFP), lava flows formed the cone (LFFC), and pyroclastic Flow filling in crater or valleys (PFFC/V). LFFV has been divided into four layers and terminates as a lateral overlap. The topography of LFFV, which is controlled by the landform, is lens shaped with a wide flat top and narrow bottom. LFFP has been divided into three layers and terminates as a lateral downlap. The topography of LFFP is sheet and tabular shaped with a narrow top and wide bottom. It has large width to thickness ratio. It was built by multiple eruptive centers distributed along the fissure. The topography of LFFC, which is located above the LFFP, has a hummocky shape with a narrow sloping top and a wide flat bottom. It terminates as a later downlap or backstepping. It has large width to thickness ratio. It was built by a single eruptive center. The topography of PFFC/V, which located above the LFFC, LFFP, or valley, has the shape of fan and terminates as a lateral downlap or overlap. It has a small width to thickness ratio and was built by a single eruptive center. The filling pattern is controlled by temperature, SiO2 content, volatile content, magma volume, and the paleolandform. In the short term, the eruptive production of the Changbaishan area is comenditic ash or pumice of a Plinian type eruption. The eruptive volume in future should be smaller than that of the Baguamiao period, and the filling pattern should be PFFC/V, which may cause huge damage to adjacent areas. [ABSTRACT FROM AUTHOR]