The 16°40′ S triple junction in the North Fiji Basin (SW Pacific)

Abstract

Abstract. During the last three years, the North Fiji Basin (SW Pacific) has been intensively studied on three oceanographic cruises carried out by French, American and Japanese ships. One of the main goals of these cruises was to study by means of precise SeaBeam, SEAMARC II, seismic and magnetic surveys, the active spreading system and its associated hydrothermal processes. The North Fiji basin, bounded by the major Pacific and IndoAustralian plates, shows a complex polyphased tectonic evolution. One of the last phases of this evolution is the functioning since 3 Ma of a NS spreading center in the axial part of the basin. The tectonic instability of the area resulted in a permanent rearrangement of the ridge axis. Among others, the 16~ triple junction is one of the major manifestations of such an instability. Sinistral strike-slip motion 1 Ma ago, along the North Fiji Fracture Zone induced the change in direction of two segments of the axis from NS to N15 and N160. The first segment is characterized by a typical spreading ridge similar to various parts of the EPR, while the second shows an atypical 'en echelon' fan-shape opening. The N15 and N160 ridges converging with the North Fiji Fracture Zone constitute the 16~ Ridge-Ridge-Fracture Zone triple junction. The detailed morphologic and kinematic study of this junction allows us to understand one of the mechanisms of the deformation in the North Fiji basin.

Diffuse Extension of the Southern Mariana Margin

“…Another setting where limited hydration may affect plate boundary behavior is within backarc basin interiors distal from the trench. For example, in the North Fiji Basin, the curving New Hebrides trench leads to diverging rollback directions (Patriat et al, 2015) but narrow plate boundary zone triple junctions form in the plate interior (Auzende et al, 1994;Lafoy et al, 1990) (Figure 8b).…”

Do ridge–ridge–fault triple junctions exist on Earth? Evidence from the Aden–Owen–Carlsberg junction in the NW Indian Ocean

“…Similarly, Dyment (1993) reconstructed the evolution of the Indian Ocean triple junction in the early Tertiary and identified several successive RFF configurations. A RFF configuration has also been 3 proposed for the Macquarie triple junction (Falconer, 1972) and the 16˚40'S triple junction in the North Fiji Basin (Lafoy et al, 1990).…”

Subductions et ouvertures océaniques dans le Sud-Ouest Pacifique

“…4), from 21° 50' S to 14° 20' S, and consists of four segments trending N160°E to N15°E. It also includes a triple junction and a wide propagator, and is dotted with numerous active hydrothermal sites (Auzende et al, 1989(Auzende et al, , 1990Maillet et al, 1986Maillet et al, , 1989Lafoy et al, 1990;Nojiri et al, 1989;Ruellan et al, 1989Ruellan et al, , 1994aEissen et al, 1991Eissen et al, , 1994Grimaud et al, 1991;Bendel et al, 1993;de Alteriis et al, 1993;Jarvis and Kroenke, 1993;Gracia et al, 1994Gracia et al, , 1996Huchon et al, 1994;Ishibashi et al, 1994;Joshima et al, 1994;Kisimoto et al, 1994;Lagabrielle et al, 1994).…”