Detailed bathymetry and magnetic anomaly in the Central Ryukyu Arc, Japan: implications for a westward shift of the volcanic front after approximately 2.1 Ma

Abstract

Detailed bathymetry and magnetic anomalies in the southern part of the Central Ryukyu Arc reveal recent volcanic structures in a southwestward extension of the active volcanic front of the Ryukyu Arc. A line of bathymetric highs running subparallel to this recent volcanic front was observed approximately 20 km to the east. A set of small, sharply defined magnetic anomalies extends southward from this line of bathymetric highs to the islands Kume-jima and Aguni-jima, suggesting the former existence of an ancient volcanic front. The ages of volcanic rocks from these islands indicate that magmatic activity along the ancient volcanic front continued until at least approximately 2.1 Ma. The presence of magnetic anomalies between the two volcanic fronts suggests that the volcanic front has moved gradually westward. This shift can be explained by the termination of asthenospheric upwelling and/or the rapid retreat of the Ryukyu Trench after its change in subduction direction.

Molybdenum isotopes in hydrothermal manganese crust from the Ryukyu arc system: Implications for the source of molybdenum

“…The recently active volcanoes are mostly in the northern part of the Ryukyu arc (North Ryukyu) and are scarce in the southern part (Central and South Ryukyu) (e.g. Sato et al, 2014). The Okinawa Trough is an active back-arc basin that is considered to be in an early stage of rifting (e.g.…”

Pleistocene magnetostratigraphy of four cores in the West Philippian Basin and regional sedimentary shift during the Mid‐Pleistocene transition

“…The West Philippine Basin, a well-preserved, extinct, marginal basin, located in the western part of the Philippine Sea Plate (Figure 1), was formed by seafloor spreading during the Palaeogene. On the east side is the Kyushu-Palau Ridge and on the north side is the Oki-Daito Ridge, and it is subducting northwestward underneath the Ryukyu-Taiwan-Philippine Arcs (Sato, Oda, Ishizuka, & Arai, 2014). The NW-SE Central Basin Fault in the central part is a fossil spreading axis (Deschamps, Okino, & Fujioka, 2002;Fujioka et al, 1999;Louden, 1976;Uyeda & Ben-Avraham, 1972).…”

A revised spreading model of the West Philippine Basin

“…The WPB is subducting northwestward underneath the Ryukyu-Taiwan-Philippine arcs and controls volcanic activity there (e.g., Sato et al 2014). The NW-SE trending CBF rift (previously called the Central Basin Fault) in the central part of the WPB is considered to be a fossil spreading axis (e.g., Uyeda and Ben-Avraham 1972;Louden 1976;Fujioka et al 1999;.…”