Abstract The Eastern Iranian range is seen as a large scale India-Eurasia collisional event and the subsequent amalgamation of the Afghan and Lut micro-continents, including the Neotethyan accretionary complexes and associated island arcs. Revised examination of the nature of tectono-stratigraphic units distributed in both sides of the N S elongated Eastern Iranian Orogen, reveals two remarkable facts: first, from a general perspective, it is structurally a giant, parallel antiform in profile view; second, lithologically, the most time-equivalent, comparable tectonic units from both northern and southern domains comprising the Eastern Iranian Orogen are connectable, follow the strike of hinge and limbs zones of the antiform and a M-shaped, disharmonic pattern in its core. These characters are thought to be formed in response to two principal deformational phases resulting from two perpendicular stress directions. The first was N S associated with the north-dipping subduction of the Tethyan oceanic lithosphere beneath the roughly ribbon-shaped Cimmerian supercontinent, including the Afghan and Lut blocks, before late Eocene. Afterward, the second was E–W shortening originated by the westward escape of the Afghan block as a consequence of the Indian plate indentation into Eurasia. This orogen-parallel stress was correspondingly accommodated by tens of degrees, counter-clockwise rotation of the Lut block around a vertical axis. The result of such shortening was oroclinal buckling and concomitant retreating of the subduction zone and closure of the Sistan Ocean, a remaining wedge-shaped part of the Neotethys Ocean formed by the ribbon curvature. The development of the Eastern Iranian Orogen already included “the Sistan suture zone”, an enormous mass of folded Eocene flysch deposits with a general N S axial surface and some Cretaceous ophiolitic remnants. The plate-scale buckling which was formed by this late-stage orogenic event is hereby considered as a secondary orocline, call “Eastern Iranian Orocline”. Lithosphere buckling around a vertical axis caused a large-scale crustal folding coeval with the bending of its mantle part, increasing the lithospheric thickness of the orocline compared to adjacent regions. The syn-orocline deformation, associated delamination and resulting magmatic events took place in eastern Iran during a short period of about 10 to 20 Ma in the Late Paleogene. The orocline hinge zone is occupied by the Khorasan outer arc and the Birjand core, while its limbs are composed of the Baluch inner arc and the southwestern and southeastern terminations of the Lut and Afghan blocks. The Eastern Iranian Orocline is the middle segment of a triple-bending belt with N S two-opposite facing bend including Afghan, Lut, and Sanandaj-Sirjan blocks. This large curvature is possibly an example of secondary oroclines which was formed by collision-related escape tectonics.

中文翻译：

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伊朗东部的东倾斜线

摘要 伊朗东部山脉被视为大规模的印度-欧亚大陆碰撞事件以及随后阿富汗和卢特微大陆的合并，包括新特提斯增生杂岩和相关岛弧。对分布在 NS 拉长的东伊朗造山带两侧的构造地层单元的性质进行修订检查，揭示了两个显着的事实：首先，从一般的角度来看，它在结构上是一个巨大的、平行的剖面图；其次，在岩性上，来自伊朗东部造山带的北部和南部区域的时间等效性最强、可比较的构造单元是可连接的，遵循反形式的铰链和四肢带的走向以及其核心的 M 形不和谐模式。这些特征被认为是响应由两个垂直应力方向产生的两个主要变形阶段而形成的。第一个是 NS 与始新世晚期之前特提斯大洋岩石圈在大致带状的 Cimmerian 超大陆（包括阿富汗和卢特地块）下方的北倾俯冲有关。之后，第二次是由于印度板块向欧亚大陆下陷导致阿富汗地块向西逃逸而引起的东西向缩短。这种平行于造山带的应力被相应地调节了数十度，Lut 块围绕垂直轴逆时针旋转。这种缩短的结果是俯冲带的俯冲屈曲和伴随的后退以及锡斯坦洋的闭合，由带状弯曲形成的新特提斯洋的剩余楔形部分。伊朗东部造山带的开发已经包括“锡斯坦缝合带”，这是一个巨大的折叠始新世复理石沉积物，具有一般的 NS 轴向表面和一些白垩纪蛇绿岩残余物。由这一晚期造山事件形成的板块尺度屈曲在此被认为是次要的斜斜，称为“伊朗东部斜斜”。围绕垂直轴的岩石圈屈曲导致与其地幔部分弯曲同时发生的大规模地壳折叠，与相邻区域相比，增加了山坡的岩石圈厚度。在古近纪晚期约 10 至 20 Ma 的短时期内，伊朗东部发生了同斜交变形、相关的分层和由此产生的岩浆事件。斜交铰链带由呼罗珊外弧和Birjand核心占据，其翼部由俾路支内弧以及Lut和Afghan块体的西南和东南端组成。东伊朗 Orocline 是三弯带的中间部分，具有 NS 两个对向弯，包括阿富汗、Lut 和 Sanandaj-Sirjan 区块。这种大曲率可能是由碰撞相关的逃逸构造形成的次生斜斜的一个例子。