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The Cenozoic opening of the South China Sea was one of the most significant tectonic events in SE Asia, coinciding with complex regional rifting, subduction, terrane collision, and large-scale continental strike-slip faulting. The timing of the initiation of seafloor spreading in the South China Sea remains controversial due to a scarcity of incontrovertible age data. This work provides the first report of an oceanic plagiogranite from the Penglai Seamount, located on the 17°N fossil spreading center of the East Sub-basin of the South China Sea, near the Manila Trench. Pyroxene and whole-rock 40 Ar/ 39 Ar dating yields ages of 32.3 ± 0.5 Ma and 28.9 ± 1.9 Ma, respectively. The plagiogranite show trace element and isotopic composition similar to those of mid-oceanic ridge basalts (MORB), with 87 Sr/ 86 Sr(t) = 0.70394; ε Nd (t) = 8.21; 206 Pb/ 204 Pb = 17.9930, 207 Pb/ 204 Pb = 15.4839, 208 Pb/ 204 Pb = 37.8852; ε Hf (t) = 20.95; and γ Os (t) = 15.89. It suggested that the rock formed due to differential cooling between adjacent layers of oceanic crust and asthenospheric shearing at the oceanic spreading ridge, resulting in the development of detachment faults. This triggered the subsequent ingress of seawater along the faults, which transformed into a hydrothermal fluid under the influence of shear and geothermal heating, altering the parent gabbro, and leading to the generation of the daughter plagiogranite by anatexis during the early Oligocene. This new geochronology also demonstrates that the initial opening of the South China Sea occurred before 32 Ma, thereby constraining the Cenozoic tectonic evolution of Southeast Asia. [ABSTRACT FROM AUTHOR]

Abstract: A number of previous models have been proposed to explain the formation of the South China Sea, the largest marginal sea basin in Southeast Asia, but no consensus has been reached. In this work, two-dimensional (2D) plan-view models (linear viscous rheology) are constructed to simulate the India–Eurasia collision, its resultant intra-plate deformation and lateral motion along the Red River Fault. We then use 2D cross-section models (a combination of linear viscous rheology and elastic–plastic rheology) to simulate the influence of deep asthenosphere upwelling on lithospheric deformation. The plan-view models show that the India–Eurasia collision can result in extensive east-southeastward tectonic extrusion, consistent with the prediction of the analogue experiments. During extrusion, the modelled Red River Fault first experienced huge left-lateral shearing and then changed to right-lateral shearing (reversal). The style of shearing motion along the Red River Fault is a function of the distance between the fault and the India–Eurasia collision frontier, which decreases with time and controls relative extrusion movement between the South China Block and Indochina Block. Our models also show that the extrusion can generate extension in an approximately N-S direction in the region containing the present-day South China Sea. Our cross-section models further demonstrate that such horizontal extension can only generate limited thinning of the continental lithosphere in the South China Sea region. In contrast, asthenosphere upwelling is much more efficient in generating lithospheric upper mantle thinning but still inefficient for crust thinning. It is the combination of mechanical extension and asthenosphere upwelling that proves to be the most efficient way to thin the entire lithosphere, and that represents the most likely driving mechanism for the opening and spreading of the South China Sea. [Copyright &y& Elsevier]

The article talks about Miocene tropical carbonates deposition in the South China Sea, carbonate platforms developed in topographic highs during the Eocene to Early Oligocene rifting phase, exhibiting platform fragmentation and contraction and controlled by syn-depositional. It talks about rise in sea level, growth of carbonates, accumulation rate of carbonate rocks, development of the outward progradation platform and differences in tectonic subsidence.

Abstract: Zircon fission track (ZFT), apatite fission track (AFT) and (U–Th)/He thermochronometric data are used to reconstruct the Cenozoic exhumation history of the South China continental margin. A south to north sample transect from coast to continental interior yielded ZFT ages between 116.6±4.7 Ma and 87.3±4.0, indicating that by the Late Cretaceous samples were at depths of 5–6 km in the upper crust. Apatite FT ages range between 60.9±3.6 and 37.3±2.3 Ma with mean track lengths between 13.26±0.16 µm and 13.95±0.19 µm whilst AHe ages are marginally younger 47.5±1.9–15.3±0.5 Ma. These results show the sampled rocks resided in the top 1–1.5 km of the crust for most of the Cenozoic. Thermal history modeling of the combined FT and (U–Th)/He datasets reveal a common three stage cooling history which differed systematically in timing inland away from the rifted margin. 1) Initial phase of rapid cooling that youngs to the north, 2) a period of relative (but not perfect) thermal stasis at ~70–60 °C which increases in duration from the south to the north; 3) final-stage cooling to surface temperatures that initiated in all samples between 15 and 10 Ma. The timing and pattern of rock uplift and erosion does not fit with conventional passive margin landscape models that require youngest exhumation ages to be concentrated at or close to the rifted margin. The history of South China margin is more complex aided by weakened crust from the active margin period that immediately preceded rifting and opening of the South China Sea. This rheological inheritance created a transition zone of steeply thinned crust that served as a flexural filter disconnecting the northern margin of the South China block and site of active rifting to the south. Consequently whilst the South China margin displays many features of a rifted continental margin its exhumation history does not conform to conventional images of a passive margin. [Copyright &y& Elsevier]

Mud volcanoes are important to understand hydrocarbon research and exploration, crustal movement and neotectonic activity, geological engineering, and climate change. They are widely distributed along the Alps‐Tethys suture zone, the Pacific belt, and continental slopes. Previous detailed studies on mud volcanoes concentrated mostly on onshore areas. Recent developments in geophysical technology have opened vast deepwater areas for research on mud volcanoes. Based on multibeam bathymetry, multichannel seismic reflection, gravity, and magnetics data, mud volcanoes in the northern Zhongjiannan Basin have been studied comprehensively and systematically. Abundant mud volcanoes were found in the whole Northern Depression of the basin, not only in the Zhongjian Valley but also in the Rizhao Valley, with different sizes, morphologies, and eruption intensities. Five types of mud volcanoes are identified in the study area, which include the following: deep source high‐energy large‐size mud volcanoes, shallow source low‐energy small‐size mud volcanoes, budding mud volcanoes (mud diapir), mud volcanoes related to canyon and bottom current channels, and mud volcanoes related to pockmarks and gas chimneys. At the developmental scale, the distribution and type of mud volcanoes (diapirs) in the Zhongjiannan Basin are obviously different than those in the Yinggehai Basin, which is famous for the development of a large number of large mud diapirs in the North‐western South China Sea. The region's tectonic and sedimentary environment is the main controlling factor of the development of mud volcanoes. Three sets of Tertiary thick mudstones in the Zhongjiannan Basin are the material basis for the formation of mud volcanoes. Overpressured fluid, generated from the combined factors of undercompaction, hydrocarbon generation, hydrothermal pressurization, and tectonic compression, is the driving force of the eruption of mud volcanoes. Furthermore, earthquakes that occurred in the surrounding areas of the Zhongjiannan Basin are the triggering mechanism of mud volcano eruptions. [ABSTRACT FROM AUTHOR]

Mud diapirs developed on the northern South China Sea continental slope are important indicators for gas hydrate exploration. The Guangzhou Marine Geological Survey (GMGS) of the Chinese Ministry of Land and Resources targeted mud diapirs and deployed gas hydrate drilling in the Shenhu area. Although an obvious bottom-simulating reflection (BSR) was detected below borehole number SH5, no gas hydrates were found at this borehole. Scientists encountered several contradictions when they analyzed the formation mechanism of hydrates related to mud diapirs. It was important to resolve this problem by sophisticated detection and thermodynamic analysis. In this study, we analyzed the thermodynamic mechanism of mud diapirs and their relationship to the occurrence of gas hydrates based on seismic profiles, mineral identification, sediment thermal conductivity measurements, and other available datasets. Our study concludes that gas hydrates were not detected at SH5 because a mud diapir pierced into the gas hydrate stability zone, leading to the decomposition of hydrates. The evolution of a mud diapir could be divided into three stages with a continuous geological process that controlled the accumulation of gas hydrates. The seismic profile and lithologic analysis showed that the mud diapir below SH5 was in the late stage of mud diapir evolution. The gas leakage system of the mud diapir was evident in the seismic profile, and the typical V-AMP (velocity-amplitude anomaly) structure displayed free gas accumulation under the BSR. The anaerobic oxidation of leaking methane promoted the formation of authigenic carbonate minerals. Thus, the deep layer of SH5 contained a relatively high percentage of carbonates and had a low thermal conductivity. In this stage, higher-temperature liquid migrated into the gas hydrate stability zone. The in situ temperature measured in this borehole was higher than the critical temperature of hydrate formation and decomposition. The liquid changed the temperature field of the region and altered the geothermal environment of hydrate accumulation, which led to the dissociation of hydrates. [ABSTRACT FROM AUTHOR]

Numerous ore-grade heavy mineral placer deposits occur in the northern South China Sea region. Previous studies on these deposits have focused on the heavy-mineral ore resources themselves, but the provenance and transport pathways of these heavy minerals are poorly constrained. This paper presents U–Pb ages of detrital zircons from sediments within the northwestern shelf of the South China Sea, and uses this new dataset to determine the provenance and transport pathway of the sediments. Zircons in sediments from ten areas of the northwestern shelf exhibit distinct age populations, suggesting that they have multiple provenances. Zircons in sediments from the Pearl River Mouth, Shangchuan Island, and Moyang River Mouth areas all have an obvious peak of Mesozoic ages, indicating that they have similar sediment provenances; i.e., mainly from the Pearl River, and to a lesser degree from the Moyang River. Zircons in sediments from the areas around the Jian River Mouth and Leizhou Bay, and off Hainan Island have an early Paleozoic age, suggesting that the sediments predominantly originate from the Yunkai massif. Zircons of the sediments from the remaining four areas, the Leiqiong Strait, Wanquan River Mouth, Qiongdongnan, and the Outer Shelf, have Yanshannian and Indosinian age peaks in addition to an obvious early Paleozoic population, implying mixed provenances, including the Yunkai massif and Hainan Island. The sediment transport may have involved two hydrodynamic conditions in two distinct stages. First, the Guangdong Longshore Current carried the river sediments to where they dispersed in the inner shelf; subsequently, wave-induced strong currents further transported sandy sediments southeastward to the outer shelf. In addition to explaining the provenance and transport pathways of heavy minerals within the northwestern shelf of the South China Sea, these results provide new information relevant to exploration for heavy-mineral placer deposits. [ABSTRACT FROM AUTHOR]

Marine heat flow is of great significance for the formation and occurrence of seabed oil, gas and gas hydrate resources. Geothermal gradient is an important parameter in determining the thickness of the hydrate stability zone. The northern slope of the South China Sea is rich in gas hydrate resources. Several borehole drilling attempts were successful in finding hydrates in the Shenhu area, while others were not. The failures demand further study on the distribution regularities of heat flow and its controlling effects on hydrate occurrence. In this study, forty-eight heat flow measurements are analyzed in the Shenhu gas hydrate drilling area, located in the northern South China Sea, together with their relationship to topography, sedimentary environment and tectonic setting. Canyons are well developed in the study area, caused mainly by the development of faults, faster sediment supply and slumping of the Pearl River Estuary since the late Miocene in the northern South China Sea. The heat flow values in grooves, occurring always in fault zones, are higher than those of ridges. Additionally, the heat flow values gradually increase from the inner fan, to the middle fan, to the external fan subfacies. The locations with low heat flow such as ridges, locations away from faults and the middle fan subfacies, are more conducive to gas hydrate occurrence. [ABSTRACT FROM AUTHOR]