摘要
智利三联点(CTJ)位于纳兹卡板块、南极洲板块与南美板块的交界处,由南极洲—纳兹卡板块之间的智利洋脊俯冲到智利海沟而形成.巴塔哥尼亚板片窗的发展是智利洋脊长期扩张俯冲的结果之一.随着纳兹卡板块的不断东向俯冲,纳兹卡板块范围逐渐变小,CTJ同时向北移动.本文采用数值模拟方法,建立了关于洋脊海沟碰撞的简单二维模型,来研究智利三联点南部扩张洋脊俯冲区域岩石层的热结构.模拟结果表明,洋脊的位置、板块相对汇聚速度及上覆大陆板块的存在均对俯冲区域海洋板块的温度结构有着很大影响,并且大陆板块下方海洋板块温度变化最大的位置距洋脊的水平距离与洋脊到板片窗范围的水平距离两者之间具有较好的一致性.同时,当存在两两板块间的相对汇聚时,洋脊右侧大陆板块下表面的温度升高,俯冲带内海洋板块温度接近于地幔温度.纳兹卡板块以7.8 cm·a-1的速度急速俯冲于南美板块之下的过程中,同时伴随着智利洋脊的持续扩张俯冲,在智利三联点南部,南美板块之下纳兹卡板块的温度因而可以更快地达到地幔软流层的约1300℃温度,并最终消亡于地幔之中.
The Chile Triple Junction(CTJ)is located at the junction of the Nazca Plate,the Antarctic Plate and the South American Plate,formed by the Chile spreading ridge between the Antarctic-Nazka plate subducting into the Chile trench.The development of the Patagonia slab window on the South American plate is one of the results of the long-term expansion and subduction of the Chile ridge.As the Nazca plate continues to be subducted eastward,the Nazca plate becomes smaller.At the same time,the Chile Triple Junction moves north.In this paper,a simple two-dimensional numerical model of ridge-trench collision was established by numerical simulation,to study the lithospheric thermal structure in the subduction zone of the southern extension of the CTJ.The simulation results showed that the location of ridge,the relative convergence velocities of the plate and the existence of the overlying continental plate had a strong impact on the temperature structure of the oceanic plate in the subduction zone.We find that the horizontal distance from the ridge to the location where the temperature of the oceanic plate below the continental plate was up to the maximum and the horizontal distance from the ridge to the slab window have good consistency.At the same time,when there is a relative convergence between these two plates,the temperature of the lower surface of the right continental plate of the oceanic ridge increases while the temperature of the oceanic plate in the subduction zone was close to the mantle temperature.The Nazca plate was rapidly subducted beneath the South American plate at a rate of 7.8 cm·a-1,accompanied by the continuous expansion of the Chile Ridge.In the southern part of the Chile Triple Junction,the temperature of the Nazca plate under the South American plate can thus quickly reached the temperature of the mantle plume at about 1300℃and eventually disappeared into the mantle.
作者
徐佳静
王振山
王少坡
魏东平
XU JiaJing;WANG ZhenShan;WANG ShaoPo;WEI DongPing(Key Laboratory of Computational Geodynamics,Chinese Academy of Sciences,Beijing 100049,China;College of Earth and planetary Science,University of Chinese Academy of Sciences,Beijing 100049,China)
出处
《地球物理学报》
SCIE
EI
CAS
CSCD
北大核心
2019年第12期4729-4737,共9页
Chinese Journal of Geophysics
基金
国家自然科学基金项目(41874115,41474086)
中国科学院与国家外国专家局创新团队国际合作伙伴计划项目(KZZD-EW-TZ-19)资助
关键词
扩张洋脊俯冲
智利三联点
温度结构
板片窗
数值模拟
Spreading-ridge subduction
Chile Triple Junction
Thermal structure
Slab window
Numerical modeling
