Isotopic feature and Uranium-series component dating of the volcanic rocks in Okinawa Trough

Key words:  Okinawa Trough  volcanic rocks  Sr-Nd isotopic ratio  magmatic evolution  Uranium-series component dating method

Abstract:

By different analyzing methods，major and rare earth elements，Sr-Nd isotopic composition and Uranium-series component dating for volcanic rocks were conducted， to detail and systemic study the origin and evolution of magmas and rock-types in the Okinawa Trough. The flowing points are noteworthy. Firstly， the Okinawa Trough held widely acidic volcanic activities from late Pleistocene to recent (about 100 ka). Secondly，controlled by the plate subduction，the volcanic activities and the age of volcanic activities increase with the distance from the location of volcano to the Ryukyu Arc increasing. Thirdly，the evolutionary process is similar in the northern and middle of trough，under which a huge，uniform magma reservoir different with that in the southern trough may possibly exist. The magmas under the Okinawa Trough comes from PREMIA source area. Finally，the black pumice used in this study belongs to the cal-alkali rhyolite， and has similar geo-chemictl features with the white pumices in the trough. The dating of black pumice is 17, 7 ± 2,1ka.