KINEMATICS OF ACTIVE SPREADING IN THE CENTRAL NORTH FIJI BASIN (SOUTHWEST PACIFIC)

Based on a synthesis of magnetic and bathymetric data, we re-evaluate the kinematics of the recent opening of the central part of the North Fiji Basin (NFB). The westward motion of the Pacific plate along the l eft-lateral North Fiji Fracture Zone (NFFZ) results in the opening of two N-S trending spreading ridges, located at 173-degrees-30'E and 176 -degrees-E. Both ridges show complex features such as propagating rift s, ridge jumps and overlapping spreading centres. Their spreading rate s are similar: 7.6 to 4 cm yr-1 across the western ridge, 5.5 cm yr-1 across the eastern one. While the NFFZ is purely strike-slip to the ea st of the eastern ridge, it becomes more complex to the west: it chang es from transpressional to transtensional, then to purely transform an d finally joins the western N-S ridge in a RRR-type triple junction. O ur kinematic analysis shows that most of the left-lateral motion along the NFFZ is transferred to the eastern ridge at the RTF-type 176-degr ees-E triple junction. It suggests that the western N-S ridge is proba bly connected to the north with another left-lateral transform, possib ly the South Pandora ''ridge''.