Abstract
Abstract Detailed surveys (bathymetry, magnetism, seismicity and focal mechanism solutions) recorded on the junction between the southern New Hebrides Arc and the North Fiji Basin enlighten the geodynamic complexity of the area. The presently active c. N-S-oriented spreading structures of the North Fiji Basin are superimposed on ancient ones, which appeared during a N135°E spreading episode active before 3 Ma. A recent southward extension of the New Hebrides Arc occurred c. 2 Ma ago. Structural and geophysical consequences of both events partly obscure the present arc-ridge junction. For example, back-arc troughs do not exist to the south of the former arc termination. N45°E structural directions, present all over the studied area, are interpreted as older transform faults related to the N135°E spreading axis, which also left recognizable NW-SE magnetic anomalies. However, the New Hebrides Arc/North Fiji Basin junction remains geodynamically unstable, due to the concomitance of convergent, strike-slip and divergent movements. Their respective crustal expressions, i.e. arc volcanism, lateral displacements and seafloor spreading, are examined and considered in their regional environment. A provisional model of the arc-ridge junction that accounts for most of the parameters analysed above is presented.
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