Egorov A.

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Egorov
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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
    Hydrothermal activity on the ultra-slow spreading southern Knipovich Ridge
    (American Geophysical Union, 2007-08-28) Connelly, Douglas P. ; German, Christopher R. ; Asada, Miho ; Okino, K. ; Egorov, A. ; Naganuma, T. ; Pimenov, N. ; Cherkashev, G. ; Tamaki, K.
    We report first evidence for hydrothermal activity from the southern Knipovich Ridge, an ultra-slow spreading ridge segment in the Norwegian-Greenland Sea. Evidence comes from optical backscatter anomalies collected during a systematic side-scan sonar survey of the ridge axis, augmented by the identification of biogeochemical tracers in the overlying water column that are diagnostic of hydrothermal plume discharge (Mn, CH4, ATP). Analysis of coregistered geologic and oceanographic data reveals that the signals we have identified are consistent with a single high-temperature hydrothermal source, located distant from any of the axial volcanic centers that define second-order segmentation along this oblique ridge system. Rather, our data indicate a hydrothermal source associated with highly tectonized seafloor that may be indicative of serpentinizing ultramafic outcrops. Consistent with this hypothesis, the hydrothermal plume signals we have detected exhibit a high methane to manganese ratio of 2–3:1. This is higher than that typical of volcanically hosted vent sites and provides further evidence that the source of the plume signals reported here is most probably a high-temperature hydrothermal field that experiences some ultramafic influence (compare to Rainbow and Logachev sites, Mid-Atlantic Ridge). While such sites have previously been invoked to be common on the SW Indian Ridge, this may be the first such site to be located along the Arctic ultra-slow spreading ridge system.