Key Laboratory of Submarine Geosciences, Ministry of Natural Resources, Hangzhou 310012, China
Second Institute of Oceanography, Ministry of Natural Resources, Hangzhou 310012, China
School of Oceanography, Shanghai Jiao Tong University, Shanghai 200030, China
College of Oceanography, Hohai University, Nanjing 210098, China
The National Key Research and Development Program of China under contract No. 2016YFC0304905; the National Natural Science Foundation of China under contract No. 41806076; the Scientific Research Fund of the Second Institute of Oceanography, MNR under contract No. JG1804; the China Ocean Mineral Resources R&D Association (COMRA) Major Project under contract Nos DY135-S1-1-01, DY135-S1-1-02 and DY135-S1-1-09.
Hydrothermal vent incidence was once thought to be proportional to the spreading rate of the mid-ocean ridges (MORs). However, more and more studies have shown that the ultraslow-spreading ridges (e.g., Southwest Indian Ridge (SWIR)) have a relatively higher incidence of hydrothermal venting fields. The Qiaoyue Seamount (52.1°E) is located at the southern side of segment #25 of the SWIR, to the west of the Gallieni transform fault. The Chinese Dayang cruises conducted eight preliminary deep-towed surveys of hydrothermal activity in the area during 2009 and 2018. Here, through comprehensive analyses of the video and photos obtained by the deep-towed platforms, rock samples, and water column turbidity anomalies, a high-temperature, ultramafic-hosted hydrothermal system is predicted on the northern flank of the Qiaoyue Seamount. We propose that this hydrothermal system is most likely to be driven by gabboric intrusions. Efficient hydrothermal circulation channels appear against a backdrop of high rock permeability related to the detachment fault.
Figure 1. Bathymetric map of the Southwest Indian Ridge between the Indomed and Gallieni transform fault (TF), with the location of the Qiaoyue Seamount (a). Inset shows the location of Fig1.a in the SWIR. High-resolution bathymetric map of the Qiaoyue Seamount on the SWIR (The bathymetric data were collected by multi-beam surveys) (b). The red solid line in Fig.1a show the first-order ridge axis between the Indomed TF and Gallieni TF. The white dots in Fig1.b show the epicenter of the study area (data source: http://www.isc.ac.uk/). The red solid line indicates the axis of segment #25 (second-order ridge). The orange dotted line shows the upper limit of a large fault. The second-order segments cited in the text and/or other figures are identified by their numbers, following the nomenclature of Cannat et al. (1999) and Liu (2019). BTJ: Bouvet Triple Junction; RTJ: Rodrigues Triple Junction; CIR: Central Indian Ridge; SEIR: Southeast Indian Ridge.
Figure 2. Generalized geological map of the Qiaoyue Seamount, interpreted from the surface geology and locations of photographs features (a); pelagic sediment with ripple marks (the black and red arrows indicate the forward direction of the camera and the direction of the bottom currents, respectively) (b); rock breccia/debris covered with sediments (c); pillow lava covered with sediments (d); a small scarp with exposed rock/breccia (e); serpentinized peridotite and/or serpentine covered with thin-layer sediments (f); suspected hydrothermally altered debris (g).
Figure 3. Water column turbidity profile obtained from line 3 (in Fig. 2a) deep-towed survey line and the blue band show the range of the significant water column turbidity anomaly (0.02–0.025 ΔNTU) (a). blue translucent area indicates a potential hydrothermal venting field (the blue solid line shows line 3 survey line trace, while the red solid line indicates the trace of a significant water column turbidity anomaly) (b).
Figure 4. Schematic model of hydrothermal system on Qiaoyue Seamount