Zhao Minghui

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Zhao
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Minghui
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  • Article
    Deep high-temperature hydrothermal circulation in a detachment faulting system on the ultra-slow spreading ridge
    (Nature Research, 2020-03-10) Tao, Chunhui ; Seyfried, William E. ; Lowell, Robert P. ; Liu, Yunlong ; Liang, Jin ; Guo, Zhikui ; Ding, Kang ; Zhang, Huatian ; Liu, Jia ; Qiu, Lei ; Egorov, Igor ; Liao, Shili ; Zhao, Minghui ; Zhou, JianPing ; Deng, Xianming ; Li, Huaiming ; Wang, Hanchuang ; Cai, Wei ; Zhang, Guoyin ; Zhou, Hongwei ; Lin, Jian ; Li, Wei
    Coupled magmatic and tectonic activity plays an important role in high-temperature hydrothermal circulation at mid-ocean ridges. The circulation patterns for such systems have been elucidated by microearthquakes and geochemical data over a broad spectrum of spreading rates, but such data have not been generally available for ultra-slow spreading ridges. Here we report new geophysical and fluid geochemical data for high-temperature active hydrothermal venting at Dragon Horn area (49.7°E) on the Southwest Indian Ridge. Twin detachment faults penetrating to the depth of 13 ± 2 km below the seafloor were identified based on the microearthquakes. The geochemical composition of the hydrothermal fluids suggests a long reaction path involving both mafic and ultramafic lithologies. Combined with numerical simulations, our results demonstrate that these hydrothermal fluids could circulate ~ 6 km deeper than the Moho boundary and to much greater depths than those at Trans-Atlantic Geotraverse and Logachev-1 hydrothermal fields on the Mid-Atlantic Ridge.
  • Article
    Three-dimensional seismic structure of a Mid-Atlantic Ridge segment characterized by active detachment faulting (Trans-Atlantic Geotraverse, 25°55′N-26°20′N)
    (American Geophysical Union, 2012-11-02) Zhao, Minghui ; Canales, J. Pablo ; Sohn, Robert A.
    We use air gun shots recorded by ocean bottom seismometers (OBSs) to generate a three-dimensional (3D) P-wave tomographic velocity model of the Trans-Atlantic Geotraverse (TAG) segment of the Mid-Atlantic Ridge, and to search for evidence of reflections from a shallow crustal fault interface. Near-vertical reflections were observed in some of the seismic records from OBSs deployed within the active seismicity zone defined by microearthquake hypocenters. Forward modeling of synthetic seismograms indicates that these reflections are consistent with a fault interface dipping at a low angle toward the ridge axis. Our observations suggest that the fault zone may extend beneath the volcanic blocks forming the eastern valley wall. Our 3D tomographic results show that the across-axis structural asymmetry associated with detachment faulting extends at least 15 km to the east of the ridge axis, indicating that detachment faulting and uplifting of deep lithologies has been occurring at the TAG segment for at least the last ∼1.35 Myr. The velocity model contains a 5 km by 8 km velocity anomaly within the detachment footwall. This anomaly, which is present beneath the active TAG hydrothermal mound, is characterized by a velocity inversion at 1.5–2.0 km below seafloor underlain by reduced P-wave velocities (∼6.2–6.5 km/s compared to surrounding areas ∼7.0–7.2 km/s) extending down to 3.5 km below seafloor. The velocity anomaly likely results from some combination of thermal and/or hydrothermal processes, and in either case our results suggest that hydrothermal fluids circulate within the upper section of the detachment footwall beneath the active mound.
  • Article
    The South China Sea is not a mini-Atlantic: plate-edge rifting vs intra-plate rifting
    (Oxford University Press, 2019-09-12) Wang, Pinxian ; Huang, Chi-Yue ; Lin, Jian ; Jian, Zhimin ; Sun, Zhen ; Zhao, Minghui
    The South China Sea, as ‘a non-volcanic passive margin basin’ in the Pacific, has often been considered as a small-scale analogue of the Atlantic. The recent ocean drilling in the northern South China Sea margin found, however, that the Iberian model of non-volcanic rifted margin from the Atlantic does not apply to the South China Sea. In this paper, we review a variety of rifted basins and propose to discriminate two types of rifting basins: plate-edge type such as the South China Sea and intra-plate type like the Atlantic. They not only differ from each other in structure, formation process, lifespan and geographic size, but also occur at different stages of the Wilson cycle. The intra-plate rifting occurred in the Mesozoic and gave rise to large oceans, whereas the plate-edge rifting took place mainly in the mid-Cenozoic, with three-quarters of the basins concentrated in the Western Pacific. As a member of the Western Pacific system of marginal seas, the South China Sea should be studied not in isolation on its origin and evolution, but in a systematic context to include also its neighboring counterparts.