Okinawa trough backarc basin: Early tectonic and magmatic evolution

Actively forming Kuroko-type volcanic-hosted massive sulfide (VHMS) mineralization at Iheya North, Okinawa Trough, Japan

“…The transition from arc to back-arc volcanism in the middle Okinawa Trough has been termed the VAMP area (Sibuet et al, 1987), with present day activity in the middle and southern Okinawa Trough associated with en echelon intra-trough grabens (Glasby and Notsu, 2003;Shinjo and Kato, 2000). The VAMP area is coincident with the subduction of the WNW-ENE trending Daito Ridge (Sibuet et al, 1998; Fig. 1a).…”

Hydrothermal Activity in the Okinawa Trough Back-Arc Basin: Geological Background and Hydrothermal Mineralization

“…Kimura (1985Kimura ( , 1990Kimura ( , 1996 argued that extensive rifting took place between the area of the current continental shelf and Ryukyu Arc in the first stage. The deposition of Shimajiri Group, which was widely prograding from the continental shelf to Ryukyu Trench (Sibuet et al 1998;Park et al 1998) took place during this event. Across the unconformity that was associated with subaerial exposure (Kimura 2000), the second stage of rifting was marked by the rapid subsidence and deposition of onlapping thick trough-infills which eventually shaped the present Okinawa Trough.…”

“…Such geophysical evidence suggests that backarc basin formation is most pronounced in the southernmost part of the Okinawa Trough. This area hosts major volcanic alignment which crosses the central graben, and called as the Cross-Backarc Volcanic Trail, or CBVT (Sibuet et al 1998). Chronological variations of the volcanism suggest complex backgrounds related to the collision in Taiwan (Shinjo 1999;Shinjo et al 1999).…”

“…As a result of such extensive volcanism, the VAMP area is spotted with regions of anomalously high heat flow (Yamano et al 1986) and several hydrothermal fields (Ishibashi and Urabe 1995). (Sibuet et al 1987) and CVST (Cross-Backarc Volcanic Trail) area (Sibuet et al 1998) The southernmost area which is close to Taiwan Is. has the topographically lowermost trough floor throughout the Okinawa Trough (Fig.…”

Regional seismicity and on‐land deformation in the Ryukyu arc: Implications for the kinematics of opening of the Okinawa Trough

“…The second part of this paper aims at reconstructing the paleostress trajectories along the arc by means of fracture analysis in Neogene and Quaternary strata of Okinawa Island. Three episodes of extension can be defined, which are afterward compared with the active deformation and with the extension stages determined offshore in the Okinawa Trough [Sibuet et al, 1998] and onshore in the southern and northern parts of the Ryukyu arc [Fabbri and Fottrnier, 1999;Fabbri, 2000]. It appears that since the late Miocene, the Ryukyu arc has been undergoing both an arc-perpendicular extensional deformation due to back arc crustal stretching and an arcparallel extension caused by the increase of the total length of the arc.…”