Journal of Tropical Oceanography ›› 2019, Vol. 38 ›› Issue (4): 70-80.doi: 10.11978/2018110CSTR: 32234.14.2018110

• Marine Geology • Previous Articles     Next Articles

Variations in tectonic faulting and magmatism at the Southeast Indian Ridge at 108°-134°E

Shoujin LIU1,3,Jian LIN1,2(),Yiming LUO1,3   

  1. 1. CAS Key Laboratory of Ocean and Marginal Sea Geology, South China Sea Institute of Oceanology, Guangzhou 510301, China
    2. Department of Geology and Geophysics, Woods Hole Oceanographic Institution, Woods Hole, MA 02543, USA
  • Received:2018-10-19 Revised:2018-11-16 Online:2019-07-20 Published:2019-07-21
  • Supported by:
    Chinese Academy of Sciences Project((Y4SL021001););Chinese Academy of Sciences Project((YZ201325、YZ201534););China Ocean Mineral Resources R&D Association((DY135-S2-1-04););National Key Research and Development Program of China((2018YFC0309800););National Natural Science Foundation of China((91628301, U1606401, 41706056).)

Abstract:

The Southeast Indian Ridge (SEIR) at 108°-134°E has a relatively constant intermediate full spreading rate of 72-76 mm·a -1 but exhibits significant variations in seafloor tectonic faulting and magmatism. This section of the SEIR encompasses the Australian-Antarctic Discordance (AAD), shows a wide range of seafloor morphology similar to the diverse examples from slow- to fast-spreading ridges, and is associated with significant geophysical and geochemical anomalies. We used high- resolution multi-beam bathymetry data to calculate seafloor topographic slopes, ratio of fault scarp areas, map view and profile M factors. Combining residual mantle Bouguer anomaly and geochemical factors of Na8.0 and Fe8.0, we analyzed the fault tectonics and magmatic characteristics in our study area. A large number of Oceanic Core Complexes (OCC) zones are observed in Zone B within the AAD and Segment C5 immediately to the west of the AAD. The OCC features in Zone B are in general larger in size than those of Segment C5. The largest OCC is located in Segment B3, which extends~50 km along the SEIR spreading direction. In comparison to other segments, Zone B and Segment C5 have more negative residual mantle Bouguer anomalies, higher Na8.0 and lower Fe8.0, more fault scarp areas, and lower plane and profile M factors. These anomalies may reflect shallower initial mantle melting and lower degree of partial melting in Zone B and Segment C5, resulting in anomalously low magma supply, thin crust, and the development of OCC features when the magma supply is severely limited.

Key words: Southeast Indian Ridge, Australian-Antarctic Discordance, submarine faults, magma factor M, Oceanic Core Complex, multi-beam bathymetry, residual mantle Bouguer anomaly