Morphotectonic characteristics of the northern part of the Carlsberg Ridge near the Owen Fracture Zone and the occurrence of oceanic core complex formation

Oceanic core complexes (OCC) are massifs in which lower-crustal and upper-mantle rocks are exposed at the sea floor. They form at mid-ocean ridges through slip on detachment faults rooted below the spreading axis. Carlsberg ridge (CR) is a typical slow spreading ridge, with the full spreading rate of 24-26 mm/Ma. During a 28-day geophysical survey of DY24 cruise in May-June, 2012, multibeam bathymetry, gravity, and magnetic data were collected. In this paper, we present the preliminary studies on the morphotectonic characteristics of the northern part of the Carlsberg Ridge near the Owen Fracture Zone. There are 9 core complexes were identified in the region between 10.4°N -8.8°N. Six of them locate near median valley, 3 of them locate off-axis. They are characterized by blocky dome-shaped highs 10-23 km across, rising to depths shallower than 2000 m, and dipping shallowly toward the axis near the ridge. Each is capped by spreading-parallel corrugations and corresponding to the gravity highs and magnetic lows. In contrast to the OCC formation, there are several NW-SE linear basaltic volcanic constructions running parallel to the ridge axis. They are usually 1-4 km in width, a few hundred meters high, and 10-24 km in length. Our observation displays that vigorous tectonic extension occurred in the segment of Carlsberg ridge between 10.4°N -8.8°N. Further geological sampling would provide information on the nature of the potential OCC formation for the study of the emplacement and evolution of lower ocean crust and shallow mantle of the investigated area of Carlsberg ridge. Acknowledgments: This study was supported by COMRA project DY125-12-R-03.