【摘要】 借助多种分析方法,对采自冲绳海槽北段和中段的火山岩进行了常量元素、稀土元素、Sr-Nd同位素组成分析及铀系组分法年龄测定,在此基础上对此地区的海槽岩浆的起源、演化及岩石类型进行了研究。结果表明:(1)海槽晚更新世(大约10万年)以来有一期广泛的酸性火山喷发活动;(2)受板块俯冲的控制,此期火山活动年龄按照与琉球岛弧距离的由近到远而由新到老;(3)海槽北、中段岩浆演化过程相似,其下很可能存在有巨大的、统一的岩浆房,但与海槽南段岩浆作用差异明显,岩浆物质很可能来源于PREMA地幔源区;(4)此地区的黑色浮岩为钙碱性系列流纹岩,岩石化学组成与海槽产出的白色浮岩相似,形成年代为17.7±2.1 ka。更多还原

【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 PREMA source area.Finally,the black pumice used in this study belongs to the cal-alkali rhyolite,and has similar geochemical features with the white pumices in the trough.The dating of black pumice is 17.7±2.1ka.更多还原