论文部分内容阅读
1 引 言 对弧后盆地的形成已提出了几个模式。可是看来还没有一个关于弧后盆地形成的统一解释(Tamaki和Honza,1991)。在西太平洋内与弧有关的大多数弧后盆地似乎是第三纪来形成的(表1)。弧后盆地看来与俯冲活动有紧密关系,俯冲活动也对应于边缘盆地形成的持续时间。这种关系在位于太平洋板块中部和西南缘的第三纪弧链的弧后盆地内得到很好证实 (Honza,1991)。 在弧后盆地内,扩张轴的方向通常不能用来寻找欧拉极,它与转换断层外交。这与洋中脊完全不同,在那里脊在大环内垂直于转换断层走向;可是,起伏出现在大多数脊内。斜向扩张可归因于与张开初期侵入作用有关的低的软流圈粘度,这正如在雷克雅内斯脊内所表明的,在那里该脊与冰岛火山中心相关。 据认为,在大西洋陆缘,在初始大陆裂谷作用期间有岩石圈的拉张,在那里岩石圈拉张通过被动上涌的较流圈的去压作用引起了部分熔融。在弧后盆地的初始裂谷阶段,也被认为有一些拉伸陆块的残余体,如在日本盆地所指出的(Tamaki等,1992)。这些碎块正如在大西洋边缘所认为的有侵入作用。 第二期是洋壳侵位在与扩张作用有关的盆地中心区。在这时期的大多数弧后盆地通过大
1 Introduction Several patterns have been proposed for the formation of backarc basins. However, there does not appear to be a single interpretation of the formation of a backarc basin (Tamaki and Honza, 1991). Most of the arc-related backarc basins in the western Pacific appear to have been formed in the Tertiary (Table 1). The backarc basin appears to be closely related to subduction activity, which also corresponds to the duration of the formation of the marginal basin. This relationship is well documented in the backarc basin of Tertiary arcs located in the central and southwestern margins of the Pacific Ocean (Honza, 1991). In the backarc basin, the direction of the expansion axis can not usually be used to find the Euler pole, it diplomatic transitional fault. This is completely different from mid-ocean ridges, where the ridges are perpendicular to the transitional fault within the macrocycle; however, the ridges and valleys appear in most of the ridges. The diagonal expansion can be attributed to the low asthenospheric viscosity associated with the onset of open flaring, as indicated within the Reykjanes ridge, where it correlates with the Icelandic volcanic center. It is believed that during the continental rifting of the Atlantic Ocean a lithospheric extension occurred during the continental rifting of the Atlantic where the lithospheric pull-off caused a partial melting by the depressurization of the passive upwelling overmajor circulation. In the initial rifting phase of the backarc basin, it is also thought that there are some remnants of the tensile block, as indicated in the Japanese basin (Tamaki et al., 1992). These fragments are as intrusive as the one at the edge of the Atlantic. The second phase is the emplacement of the oceanic crust in the center of the basin associated with its expansion. Most of the back arc basins in this period pass large