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吴福元,王建刚,刘传周,刘通,张畅,纪伟强. 2019. 大洋岛弧的前世今生. 岩石学报, 35(1): 1-15
大洋岛弧的前世今生
作者单位
吴福元 中国科学院地质与地球物理研究所岩石圈演化国家重点实验室, 北京 100029
中国科学院大学地球与行星科学学院, 北京 100049 
王建刚 中国科学院地质与地球物理研究所岩石圈演化国家重点实验室, 北京 100029 
刘传周 中国科学院地质与地球物理研究所岩石圈演化国家重点实验室, 北京 100029
中国科学院大学地球与行星科学学院, 北京 100049 
刘通 中国科学院地质与地球物理研究所岩石圈演化国家重点实验室, 北京 100029 
张畅 中国科学院地质与地球物理研究所岩石圈演化国家重点实验室, 北京 100029 
纪伟强 中国科学院地质与地球物理研究所岩石圈演化国家重点实验室, 北京 100029 
基金项目:本文受国家自然科学基金项目(41888101、41130313、41672109)资助.
摘要:
      根据板块构造理论,板块的边界是地质作用最为强烈的地区,因而它们是当今固体地球科学研究的重点。依据应力性质的不同,地球上板块的边界类型有扩张的洋中脊、汇聚的俯冲带和调节板块运动差异的转换断层三种。就汇聚型板块边界而言,它又可进一步划分为洋-洋俯冲的大洋或洋内岛弧带(Intra-oceanic arc)、洋-陆俯冲的安第斯型活动大陆边缘带和陆-陆接触的大陆碰撞带三种。相对而言,大洋岛弧的研究程度最低。传统认为最典型的大洋岛弧——日本诸岛,已不再被认为是洋-洋俯冲的产物,因为已有研究显示它是从亚洲大陆裂解的碎块。根据目前的调查,现今的大洋岛弧主要集中在西太平洋地区,以太平洋与菲律宾板块间的Izu-Bonin-Mariana弧和太平洋-澳大利亚间的西南太平洋岛弧为代表。大洋岛弧研究的最重要问题是,洋洋之间如何产生了俯冲。目前多倾向于认为:大洋中的转换断层可使不同时代的大洋岩石圈相互接触,在这种情况下,较老的岩石圈由于冷却时间较长而密度相对较大,因而可下沉而俯冲到较年轻的岩石圈之下。这一模型也被誉为蛇绿岩形成的初始俯冲定律(Subduction Initial Rule,简称SIR)。但存在的问题是,目前全球还没发现有转换断层转变为俯冲带的实例。更何况,全球大洋中发育如此众多的转换断层,但为何只在西太平洋发育大洋岛弧?本文通过对资料的总结还发现,这些大洋岛弧基本都是从亚洲或者澳大利亚大陆东部边缘裂解的碎块,只是后期的弧后扩张作用使裂解的碎块发生强烈的改造,形成具有类似大洋岩石圈的特点。目前提出的洋-洋自发形成俯冲带的模型并没有理论基础,也没有实际地质事实的支持。但在加勒比海、斯科舍海和阿留申地区,大洋岛弧的出现与洋底高原诱发的俯冲带跃迁或俯冲极性反转有关。因此,板块构造理论中的洋洋初始俯冲模式需要进一步资料的验证。
英文摘要:
      According to the theory of plate tectonics, plate boundary is the locus of the various geological processes shaping our Earth, and thus the focus of the modern geology. It is generally accepted that the plate boundaries can be divided into three types, i.e., divergent (mid-oceanic ridge), convergent (subduction and collision zones), and strike-slip (transform fault). As for the convergent boundary, it can be further subdivided into intra-oceanic arc by oceanic-oceanic subduction, Andean continental arc by oceanic-continental subduction, and collisional belt by continental-continental collision. The intra-oceanic arc is relatively less studied compared to other types of convergent boundary. Traditionally, the Japanese islands were thought as an intra-oceanic arc, but this point of view is not hold anymore since it was found that they are fragments from the Asian continental margin. According to the available investigations, intra-oceanic arcs are mostly located along the western Pacific Ocean, represented by the Izu-Bonin-Mariana arc between the Pacific and Philippine plates, and the southwestern (SW) Pacific arc between the Pacific and Australian plates. The most important topic for the study of the intra-oceanic arc is that how subduction was initiated between oceanic-oceanic plates. It is mostly thought that the transform fault can make contact of the different aged oceanic plates, and subsequently in this case that the older and dense lithosphere can underthrust beneath the younger and less-dense plate, which is also ascribed as "Subduction Initial Rule-SIR". However, no actual example was found to date on the Earth for the situation described above, and moreover, it is hard to understand that the intra-oceanic arcs are extensively developed in SW Pacific, although the transform faults occurs everywhere in the seafloor. Data compilation indicates that the above intra-oceanic arcs are in fact continental relics rifted from the Australian continent. The subduction of the old and dense Pacific plate resulted in formation of the continental arc and associated back-arc basin, and the spreading within the back-arc basin then rifted the arc and made it evolved toward oceanic lithosphere. Therefore, the oceanic-oceanic subduction is not valid theoretically, and not documented in the geological records either. However, in the Caribbean, Scotia and Aleutian areas, the intra-oceanic arcs were formed by subduction jump and polarity reverse due to subduction of oceanic plateau. Whatever, the spontaneous initial subduction model needs further geological data to be verified.
关键词:大洋岛弧  洋-洋俯冲  洋-陆俯冲  弧后扩张  蛇绿岩
投稿时间:2018-11-27  修订日期:2018-12-19
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