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The Louisville Ridge-Tonga Trench collision: Implications for subduction zone dynamics

路易斯维尔海岭-汤加海沟碰撞：对俯冲带动力学的影响

基本信息

批准号：
NE/F005318/1
负责人：
Anthony Brian Watts
金额：
$ 52.12万
依托单位：
University of Oxford
依托单位国家：
英国
项目类别：
Research Grant
财政年份：
2010
资助国家：
英国
起止时间：
2010 至无数据
项目状态：
已结题

来源：
https://gtr.ukri.org/projects?ref=NE%2FF005318%2F1
关键词：
Louisville Ridge Tonga Trench collision

项目摘要

The plate tectonics paradigm provides the fundamental model for the destruction of oceanic lithosphere at subduction zones. But the dynamics of subduction zones are also responsible for the construction of arc lithosphere whose features include some of the largest and most active volcanoes on Earth and the majority of large earthquakes. The arcuate system of island arcs and deep sea trenches that comprise the SW Pacific is amongst the most structurally complex, geologically active section of the global subduction system and has the highest concentration of volcanic, seismic and associated tsunami hazard on Earth. Understanding the dynamics of this system is complicated by the diversity in the age, morphology and tectonic setting of the material that is entering the subduction zone, and yet it is the influence of this material which is a major factor in determining the architecture and composition of the entire trench, island arc, and back-arc system. Between ~5S-35S in the SW Pacific, the Tonga-Kermadec Trench subduction system has a deep, linear topographic depression at which Cretaceous Pacific oceanic crust is subducting beneath the Indo-Australian plate. However, at ~25S the Tonga Trench intersects with the Louisville Ridge, a linear chain of seamounts that runs obliquely to and is being subducted at the fastest rate of plate convergence on Earth (~80 mm/yr). Subduction of this ridge locally deforms the trench, and the point of collision is progressively moving north-to-south at ~118 mm/yr due to the oblique subduction geometry. The Tonga system can thus be divided into three parts. To the south of 27S, normal oceanic lithosphere of the Pacific plate is being subducted. Between 26S-25S, the thickened crust and seamount chain of the Louisville Ridge is entering the subduction zone with seamounts either being subducted intact or decapitated and subsumed into the overriding plate. North of 24S, the Louisville Ridge has been subducted and its long-term effect on the overriding plate is preserved in the wake of the point of collision. Two disparate phenomena appear spatially related to this intersection. Firstly, the current site of ridge subduction is characterised by a pronounced shallowing of the trench and extensive deformation and uplift of the arc; and secondly, a quiescent gap in the shallow seismicity is observed at the point of collision. The unusual tectonic setting of the intersection of the Louisville Ridge and the Tonga Trench therefore makes it a unique location in which to study the relationships between subduction input, subduction zone behaviour, and system architecture and dynamics. This study will provide unique models of crustal structure throughout the collision zone and obtain the necessary direct observations to parameterise and constrain numerical modelling of the thermo-mechanically coupled visco-plastic-elastic response of the lithosphere and the distribution of deformation within the subducting and overriding plates. The observations and measurements on which this study is based will be made during an expedition to the collision zone by a research ship. State-of-the-art equipment will be used to determine the structure of the Earth's crust and uppermost mantle to depths of ~40km sub-seabed using sound waves, recording these signals with instruments deployed onto the seabed in water depths of up to 6000m and towed behind the ship itself. Our target is a 500x300km region of the Tonga island arc-trench system that extends from the outer rise where flexural bending stresses are deforming the subducting plate, across the trench at the point of ridge collision and into the island arc. The resulting images of the crust, uppermost mantle and seabed will allow us to determine how the crust was constructed, modified and deformed, and how the plate boundary system is evolving over time in response to the subduction of significant plate topography.

板块构造范式为大洋岩石圈在俯冲带的破坏提供了基本模型。但是，俯冲带的动力学也对弧形岩石圈的形成负有责任，弧形岩石圈的特征包括地球上一些最大、最活跃的火山和大多数大地震。西南太平洋由岛弧和深海海沟组成的弧形系统是全球俯冲系统中结构最复杂、地质活动最活跃的部分之一，也是地球上火山、地震和相关海啸危险最集中的地区。由于进入俯冲带的物质的年代、形态和构造背景的多样性，理解该体系的动力学变得复杂，但正是这些物质的影响，决定了整个海沟、岛弧和弧后体系的结构和组成。在西南太平洋~5S-35S之间，汤加-克马德克海沟俯冲系统具有一个深的线性地形凹陷，白垩纪太平洋地壳在该凹陷处俯冲至印澳板块之下。然而，在南纬25度左右，汤加海沟与路易斯维尔海岭相交，路易斯维尔海岭是一条线性的海山链，它斜向路易斯维尔海岭，并以地球上最快的板块收敛速度（~80毫米/年）俯冲。该脊的俯冲使海沟局部变形，由于斜向俯冲的几何形状，碰撞点以约118毫米/年的速度从北向南逐渐移动。因此，汤加体系可以分为三个部分。在南纬27S以南，太平洋板块的正常海洋岩石圈正在俯冲。在26S-25S之间，路易斯维尔岭的增厚地壳和海山链进入俯冲带，海山要么完整俯冲，要么断头并入上覆板块。在南纬24度以北，路易斯维尔山脊已经俯冲，它对上覆板块的长期影响在碰撞点之后被保留下来。两种完全不同的现象在空间上与这个交叉点相关。首先，目前的洋脊俯冲位置表现为海沟明显变浅和弧的广泛变形和隆起；其次，在碰撞点观察到浅层地震活动的静止间隙。因此，路易斯维尔岭和汤加海沟交汇的独特构造环境使其成为研究俯冲输入、俯冲带行为、系统结构和动力学之间关系的独特位置。这项研究将为整个碰撞带的地壳结构提供独特的模型，并获得必要的直接观测，以参数化和约束岩石圈热-机械耦合粘-塑性-弹性响应的数值模拟，以及俯冲和上覆板块内变形的分布。这项研究所依据的观察和测量结果将由一艘科考船在对碰撞区进行考察期间进行。将使用最先进的设备，利用声波确定海床以下约40公里深处的地壳和上地幔的结构，并将这些信号用部署在水深达6000米的海床上的仪器记录下来，并拖在船本身后面。我们的目标是汤加岛弧-海沟系统的一个500 × 300公里的区域，该区域从外隆起处的弯曲弯曲应力使俯冲板块变形，穿过山脊碰撞点的海沟，进入岛弧。由此产生的地壳、上地幔和海床的图像将使我们能够确定地壳是如何构造、修改和变形的，以及板块边界系统如何随着时间的推移而演变，以响应重要板块地形的俯冲。

项目成果

期刊论文数量（10）

专著数量（0）

科研奖励数量（0）

会议论文数量（0）

专利数量（0）

Crustal structure of the Kermadec arc from MANGO seismic refraction profiles

DOI：
10.1002/2016jb013194
发表时间：
2016-10
期刊：
Journal of Geophysical Research: Solid Earth
影响因子：
0
作者：
D. Bassett;H. Kopp;R. Sutherland;S. Henrys;A. Watts;C. Timm;M. Scherwath;I. Grevemeyer;C. D. Ronde
通讯作者：
D. Bassett;H. Kopp;R. Sutherland;S. Henrys;A. Watts;C. Timm;M. Scherwath;I. Grevemeyer;C. D. Ronde

Structure and deformation of the Kermadec forearc in response to subduction of the Pacific oceanic plate

克马德克弧前的结构和变形对太平洋板块俯冲的响应