台湾-吕宋双火山弧的可能成因:菲律宾板块北西向加速运动  

Potential reason of the Taiwan-Luzon double volcanic Chain:the NW accelerated movement of the Philippine Plate

作　　者：杨少华[1,2,3] 李海兵 潘家伟[1,2,3] 郑勇 柳畅[4] Yang Shaohua;Li Haibing;Pan Jiawei;Zheng Yong;Liu Chang(Key Laboratory of Deep-Earth Dynamics of Ministry of Natural Resources,Institute of Geology,Chinese Academy of Geological Sciences,Beijing 100037,China;Southern Marine Science and Engineering Guangdong Laboratory(Guangzhou),Guangzhou,Guangdong 511458,China;Jiangsu Donghai Continental Deep Hole Crustal Activity National Observation and Research Station,Donghai,Jiangsu 222300,China;State Key Laboratory of Marine Geology,Tongji University,Shanghai 200092,China)

机构地区：[1]中国地质科学院地质研究所,自然资源部深地动力学重点实验室,北京100037 [2]南方海洋科学与工程广东省实验室(广州),广东广州511458 [3]江苏东海大陆深孔地壳活动国家野外科学观测研究站,江苏东海222300 [4]同济大学,海洋地质国家重点实验室,上海200092

出　　处：《地质学报》2022年第8期2917-2926,共10页Acta Geologica Sinica

基　　金：南方海洋科学与工程广东省实验室(广州)人才团队引进重大专项(编号GML2019ZD0201);中国地质调查局项目(编号DD20221630);国家自然科学基金项目(编号41830217);自然资源部深地动力学重点实验室课题(编号J1901-22)联合资助的成果。

摘　　要：台湾-吕宋双火山弧绵延近500 km,南北向展布于台湾岛和吕宋岛之间,其成因尚无定论。前人将其归因于轻质物质(南海洋中脊或南海北部轻质高原)的俯冲,然而数值模拟研究并不能有效支持该观点。随着欧亚-菲律宾板块的会聚,南海东部次海盆被动俯冲于菲律宾板块之下。为了验证被动俯冲和主动俯冲对俯冲角度的控制作用,本文构建了二维高精度数值对比模型,在其他因素完全相同的情况下,考察会聚方向的差异对俯冲角度的影响。模拟结果显示,仅仅改变会聚方向,俯冲角度就能够发生巨大变化。在被动俯冲背景下如果条件合适则易于发生低角度俯冲。综合前人研究成果可以发现,南海-菲律宾俯冲系统的条件满足发生低角度俯冲的要求,表现在两方面:①南海东部次海盆的年龄从最新的洋中脊向北波动增加,最老为33 Ma,小于低角度俯冲洋盆年龄要求的40 Ma;②欧亚-菲律宾板块的会聚速率大于低角度俯冲速率要求的4 cm/a。由此,本文认为菲律宾-欧亚板块在被动俯冲背景下的低速会聚形成了高角度俯冲从而导致西弧的形成;之后菲律宾板块北西向加速运动导致俯冲角度减小,西弧停止活动而东弧开始形成。本文模型不需要俯冲的轻质物质提供额外的浮力进而促使板片角度减小。西弧和东弧存在分叉现象,我们认为原因可能是洋壳年龄向北增加和(或)菲律宾板块旋转。本文提出了台湾-吕宋双火山弧另一种可能的演化机制,有助于推进对该双火山弧和该俯冲系统的理解,也能够为认识其他被动俯冲过程提供参考实例。The Taiwan-Luzon double volcanic chain stretches for nearly 500 km and locates between Taiwan Island and Luzon Island in a north-south direction.Its origin has not been determined.It is attributed to the subduction of light materials(mid-ocean ridge of the South China Sea or light plateau in the northern part of the South China Sea).However,numerical modeling does not effectively support this viewpoint.Along with convergence of the Eurasian-Philippine Plate,the eastern sub-basin of the South China Sea was passively subducted beneath the Philippine Plate.In order to verify the control of passive subduction and active subduction on the subduction angle,two-dimensional high-precision numerical models are constructed in this study.The influence of convergence direction on the subduction angle is investigated.The simulation results suggest that the subduction angle can change dramatically only by transferring convergence direction.Under passive subduction,low-angle subduction occurs readily if conditions are appropriate.Based on a large number of previous multidisciplinary studies,it can be determined that the conditions of the South China Sea-Philippines subduction system meet the requirements of low-angle subduction,which is manifested in two aspects:(1)the age of the eastern South China Sea sub-basin decreases northward from the latest mid-ocean ridge,with the oldest of 33 Ma,less than the 40 Ma required for low-angle subduction;(2)the convergence rate of Eurasian-Philippine plate is higher than 4 cm/a required by low-angle subduction.Therefore,this study proposes that the low-rate convergence of the Philippine-Eurasian plate against the background of passive subduction formed a high-angle subduction,which led to the formation of the western arc.After that,the northwestward accelerated motion of the Philippine Plate resulted in the reduction of the subduction angle,thereby the activity of the western arc stopped and the eastern arc began to form.The new proposed model does not need the subducted low-density materia

关 键 词：台湾-吕宋双火山弧 马尼拉俯冲带 被动俯冲 板块旋转 

分 类 号：P542[天文地球—构造地质学]