[论文解读] Plate Tectonic Consequences of competing models for the origin and history of the Banda Sea subducted oceanic lithosphere

Christian Heine, L. Quevedo+2 more|arXiv (Cornell University)|Oct 17, 2012

Geological and Geophysical Studies参考文献 50被引用 4

一句话总结

本研究运用构造地质复原技术展开俯冲的班达海板块，检验关于鸟头构造块体成因的多种竞争模型。结果表明，该块体为西伊里安查亚的原地体，经历了20–35°顺时针旋转，且阿戈-塔尼姆巴尔-塞拉姆大洋盆地初始形态为矩形，从而解决了东苏拉地区长期存在的构造争议。

ABSTRACT

The Banda Arc, situated west of Irian Jaya and in the easternmost extension of the Sunda subduction zone system, reveals a characteristic bowl-shaped geometry in seismic tomographic images. This indicates that the oceanic lithosphere still remains attached to the surrounding continental margins of northern Australia and the Bird's Head microcontinent. Major controversies exist between authors proposing an allochthonous or autochthonous origin of the Bird's Head block. Either scenario has important implications for plate kinematic models aiming to reconstruct the tectonic evolution of the region and the late Jurassic seaoor spreading geometry of this now subducted Argo-Tanimbar-Seram (ATS) ocean basin. Wider implications affect the tectonic conguration of the Tethyan-Pacic realm, the distribution of plate boundaries as well as the shape and size of continental blocks which have been rifted off the northeastern Gondwana margin during the Late Jurassic and are now accreted to the SE Asia margin. We apply structural geology restoration techniques to unfold the subducted oceanic lithosphere of the Banda Slab. Our slab unfolding results help to discriminate between the different hypotheses concerning the origin and kinematic history of the Bird's Head tectonic block. According to our preferred model, the block is required to rotate 20-35 degrees clockwise relative to its present-day position and that the initial geometry of the ATS ocean basin was more or less rectangular shaped. We evaluate currently accepted plate kinematic scenarios for the Jurassic and younger seaoor spreading history north of Australia in conjunction with our restored ocean basin geometry and conclude that the Bird's Head block is autochthonous to western Irian Jaya, with its western margin being a continental transform margin during the rifting and opening of the ATS ocean.

研究动机与目标

• 为解决长期存在的争议：即鸟头构造块体是否为西伊里安查亚的异地体或原地体。
• 重建俯冲前阿戈-塔尼姆巴尔-塞拉姆（ATS）大洋盆地的原始几何形态。
• 在恢复的板块几何形态基础上，评估针对澳大利亚北部侏罗纪海底扩张的多种板块运动学模型。
• 评估恢复几何形态对特提斯-太平洋区域构造格局及大陆块体分布的影响。

提出的方法

• 应用构造地质复原技术展开俯冲的班达板块。
• 利用地震层析成像图像推断当前俯冲大洋岩石圈的几何形态。
• 基于板块展开重建ATS大洋盆地的俯冲前配置。
• 将恢复的几何形态与现有的侏罗纪及更年轻海底扩张的板块运动学模型进行比较。
• 评估恢复几何形态对冈瓦纳东北缘裂解并分离出的大陆块体的形状、大小及运动学历史的构造影响。
• 将构造重建与东印度尼西亚的板块边界构型及微板块演化相结合。

实验结果

研究问题

• RQ1 鸟头构造块体是异地体（被搬运的）还是原地体（原本相邻的）？
• RQ2 俯冲前阿戈-塔尼姆巴尔-塞拉姆大洋盆地的原始形状和方向是什么？
• RQ3 恢复的板块几何形态如何约束该区域在侏罗纪海底扩张期间的运动学历史？
• RQ4 恢复的几何形态对特提斯-太平洋区域构造演化的意义是什么？
• RQ5 鸟头块体的重建旋转如何影响板块边界构型和微板块动力学？

主要发现

• 鸟头构造块体最合理的解释是其为西伊里安查亚的原地体，而非从其他地区搬运而来。
• 该块体在区域构造演化过程中相对于其现今位置发生了20–35°顺时针旋转。
• 阿戈-塔尼姆巴尔-塞拉姆大洋盆地的初始形态近似为矩形，而非弧形或弯曲形态。
• 鸟头块体的西缘在ATS大洋盆地裂解与扩张期间充当大陆转换边界。
• 恢复的板块几何形态支持包含澳大利亚北部显著侏罗纪海底扩张阶段的板块运动学模型。
• 研究结果调和了关于班达海构造历史的相互矛盾解释，并明确了该区域在更广泛的特提斯-太平洋构造框架中的作用。