马里亚纳俯冲带分段性及其成因研究

发布时间：2018-03-01 05:04

本文关键词： 马里亚纳海沟俯冲带重力异常水深海山　出处：《中国海洋大学》2015年博士论文　论文类型：学位论文

【摘要】：本文通过对马里亚纳海沟及周围区域水深地形、地震、重力异常、洋壳年龄、钻孔等要素进行分析,研究马里亚纳俯冲带分段性特征及成因。主要研究方法为进行水深场、重力场分析,不同区域剖面对比,通过地震研究俯冲带贝尼奥夫带形态特征,结合布格重力异常对构造特征进行分析；最终总结这些要素分析俯冲带分段性产生的原因。研究结果表明马里亚纳海沟不同区域俯冲特征出现明显分段现象,这种俯冲分段性在海沟水深上有很好体现,由北向南水深及俯冲倾角逐渐变大。结合洋侧大洋岩石圈年龄,与北部伊豆—小笠原海沟的水深对比发现,在该区域影响海沟深度发育的重要因素是大量随太平洋板块运动至此的海山、海隆,而不是传统理解中的俯冲岩石圈年龄。对海沟深度形成影响的海山、海隆等又分为三种,一种是规模较小的海山,它们在移动到海沟轴部时会造成海沟深度变浅,但随着俯冲的进行它们逐渐沉没于海沟之中,最终海沟回归原始形态；第二种是相对孤立的大型海山,当它们随板块运动至海沟洋侧后,会减弱周围区域的板块俯冲作用,使海沟水深变浅,同时会发生海沟向洋侧的跃迁：第三种是连成片状的大范围的大型海山、海隆,当它们迫近海沟轴部时,会对海沟水深造成加大现象,并且在迎向板块俯冲的方向加大现象更为明显。在马里亚纳海沟中部明显变浅的水深、海沟轴部的不连续性以及马里亚纳弧前多变的地形特征,是相对孤立的大型海山侵入作用造成。在这些海山随俯冲板块运动至海沟轴部时,由于海山自身的填充作用、海山与上覆板块发生碰撞产生的块体填充作用,造成海沟水深变浅,轴部不连续。当它们越过海沟后会圈闭残余海沟形成弧前坳陷,随着俯冲作用的不断进行,大型的残余海山不断向火山弧移动,最终与火山弧连为一体达到相对稳定状态,造成火山弧的增生。在这个过程中,不同的发育时期弧前坳陷的规模、深度不同。该区域的五个大型坳陷可能正在经历由深变浅、由大变小的演化过程,最终演化结果是弧前坳陷基本消失,残余海山与火山弧连为一体。马里亚纳岛弧向东凸出弯曲的原因可能与数量众多的大型海山、海隆与海沟的相互作用有关。不断运动至海沟轴部附近的海山,会造成海沟的后退以及新俯冲带在海沟后侧的形成,随之俯冲板块下插到地幔中的位置也会慢慢向洋侧迁移,造成马里亚纳海槽扩张脊的向洋侧迁移。在海沟各处太平洋海山的侵入数量、规模存在差异,在数量多、规模大的海沟中段区域,海沟后退幅度相应增大,弧后扩张脊的迁移也会随之增大,最终造成马里亚纳岛弧及海沟在中段区域向洋侧的运动距离比北部区域偏大。而在海沟最南端,连成片的海山、海隆在越过海沟后,本应产生海沟跃迁的位置被新移动至此的海山所取代,所以海沟后退现象并不是十分明显。据此推断,在不考虑其它因素(诸如太平洋板块运动速率、方向等变化)影响下,预测海沟发展情况会持续向洋一侧后退,并且在海沟中段,太平洋火山分布众多的区域,海沟后退速度会更快,海沟及岛弧的凸出作用会更加明显。马里亚纳海沟南段挑战者深渊处以及海沟中段水深最大区域的成因,与其洋侧俯冲板块的块体被切割有重要联系。这些大型海山组成的海山链以及连成片状的海山、海隆、海台,会对俯冲块体造成切割,分割出一些相对较小的块体。在相同的俯冲环境下,形成的较小块体会有利于俯冲作用的进行,进而造成海沟水深的加大。所以在马里亚纳俯冲带不同区域产生分段性的原因,主要受随太平洋板块运动至此的大型海山、海隆与板块边界相互作用影响。由于它们的数量、规模、分布规律不同,引起的相互作用也就有多不同,最终导致不同区域海沟、岛弧的形态特征差异。
[Abstract]:This article through to the Mariana Trench and the surrounding area topography, seismic, gravity anomaly, oceanic crust age, analyze the factors such as drilling, study the Mariana subduction zone segmentation characteristics and causes. The main research methods for depth of field, gravity field analysis, comparison of different regional profiles, with morphological characteristics by subduction zone earthquake research Benioff, combined with the bug the structural characteristics of the gravity anomaly analysis; finally summarize the reasons of these elements of the subduction zone segment analysis. The research results show that the Mariana Trench in different regions of subduction characteristics appear obvious segmented phenomenon, the subduction segment in trenches has good water depth from the north to the south of the subduction depth and angle becomes larger. Combined with the ocean side of the ocean the age, compared with the depth of the northern Izu - Bonin trench in the region, the development of the important effect of trench depth for With a large number of elements is the movement of the Pacific plate to the seamount, seamounts, and subduction of lithospheric age is not the traditional understanding. The influence on the formation of trench depth of the seamount, seamounts and divided into three types, one is the smaller seamounts, they move in to the trench axis will cause the depth of shallow trench, but with the they were gradually sinking in subduction trench, the trench eventually return to the original form; the second is relatively isolated large seamounts, when they move to the ocean trench side plate subduction, will weaken the surrounding area, the trench depth, transitions occur simultaneously to the side of the ocean trench is: third as the large range of flake seamount, rise, when they are approaching the trench axis part, will cause the increase of the trench depth and the phenomenon, towards the direction of the plate subduction increase phenomenon is more obvious in the Mariana sea. The central sulcus obvious shallow water depth, trench axis discontinuity and Mariana fore arc varied terrain features, is relatively isolated large seamount intrusion caused. In these seamounts with the subducting plate movement to the trench axis, the filling effect of seamount itself, block mountain and sea filling effect of overlying plate the collision of the trench caused by shallow depth, the shaft is not continuous. When they crossed the trench after trench arc formed before the trap residual depression, with the subduction of the ongoing large residual seamount to volcano and volcano arc arc movement, eventually even as one to achieve a relatively stable state, caused by the volcano arc hyperplasia. In this process, the development of different periods of the forearc depression scale, different depth. Possibly suffering from deep shallow depression five large depression in the region, the evolution process from large to small, finally evolved. The fruit is the forearc depression disappeared, and the residual seamount volcano arc together. The reason of the bend to the East and Mariana Island projecting numerous large seamounts, interaction and ridge trench. Moving to the trench axis near the seamount, will cause the trench retreat and new subduction zones formed in the trench the rear side of the subducting plate, then inserted into the mantle position will gradually migrate to the ocean side, resulting in expansion of the Mariana Trough ridge migration to the ocean side. In the number of intrusive trench throughout the Pacific seamounts, there are differences in size, number, trench middle area large, retrotrench amplitude increases. Migration of the ridge back arc spreading will increase, resulting in the Mariana Island trench in the middle area and to the ocean side of the northern region is larger than the moving distance. While in the trench in the southernmost expanse of seamounts, sea Long across the trench, the trench should produce the transition position by the new mobile point of seamounts are replaced, so retrotrench phenomenon is not very obvious. Thus, without considering other factors (such as the Pacific plate movement rate and direction of change) under the influence of pre measured development will continue to back to the trench ocean side and, in the middle of the Pacific trench, many volcano distribution area of retrotrench faster, protruding trench and island arc effect will be more obvious. The southern section of Mariana Trench and the Challenger deep trench deep water causes middle maximum area, block and ocean side of the subducting plate cut has important links. These large seamounts consisting of seamounts and the chain into a slice of the seamount, seamounts, ridge, will cause the cutting of the subducted block segmentation, some relatively small blocks. In the same subduction environment, formation A piece of experience is conducive to the subduction, resulting in increased water depth. So in the Mariana Trench subduction zone in different regions causes segmentation, mainly by the movement of the Pacific plate so far with large seamounts, seamounts and impact plate boundary interaction. By the number, in their size, distribution, interaction there are many different causes, resulting in different regional differences in morphological characteristics of island arc trench.

【学位授予单位】：中国海洋大学
【学位级别】：博士
【学位授予年份】：2015
【分类号】：P736.1

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