The Zagros suture zone in Iran is part of the Tethyan orogenic belt that records convergence between the Eurasian and Arabian plates during the Mesozoic-Cenozoic. Prior to collision, which may have initiated in the Late Eocene-Early Oligocene, much of the convergence was accommodated by the Late Triassic-Early Jurassic subduction of the Neotethys beneath the Iranian Cimmerides, terranes accreted on the southern margin of Eurasia during the Permo-Triassic. The Sanandaj-Sirjan zone (SaSZ) is located immediately at the northeast of the Zagros suture zone. In this study, we review the available geological information pertinent to the SaSZ, with a particular emphasis on the Jurassic igneous record, in order to understand the geodynamics under which the SaSZ subduction zones initiated and evolved during the Jurassic. Based on igneous activity, the SaSZ can be divided into three main sectors: a Central sector, a Northwestern sector and a Southeastern sector. The Central sector is dominated by calc-alkaline rocks, whereas the other two sectors consist of calc-alkaline rocks and subordinate amounts of alkaline rocks with OIB-like geochemical signatures. In all sectors, the dominance of calc-alkaline rocks that are largely subparallel to the Zagros suture are robust evidence for their formation in a continental arc setting. By integrating the existing geochemical data and the stratigraphic constraints, as well as the distribution of S-type granites, two episodes of orogenesis are described in this study. They are the early stage (195–168 Ma: early-middle Jurassic) and the late stage (168–140 Ma: middle-late Jurassic). We propose, on the basis of existing geochemical data, that subduction zone initiation was episodic and it involved periods of subduction and trench retreat that were interrupted by short-lived contraction events. Each of these stages is followed by a small-scale OIB-like magmatic activity, respectively, in the northwestern and southeastern sectors of the SaSZ. We interpret the OIB-like magmatism to be formed by melting of convecting asthenospheric mantle in response to slab tearing and is comparable to processes that operate in modern subduction zones. Our new tectonic model for the SaSZ provides a regionally coherent explanation for the temporal and spatial distribution of Jurassic magmatism in this part of the Tethyan orogenic belt.

伊朗的扎格罗斯缝合带是特提斯造山带的一部分，该带记录了中新生代期间欧亚板块与阿拉伯板块之间的收敛。在碰撞之前（可能始于始新世晚期至渐新世），大部分收敛是由伊朗西密德底下的新特提斯晚三叠世-早侏罗世俯冲所调节的，地幔在二叠纪期间沉积在欧亚大陆的南缘三叠纪。Sanandaj-Sirjan区（SaSZ）位于Zagros缝合区的东北部。在这项研究中，我们回顾了与SaSZ有关的可用地质信息，特别强调了侏罗纪的火成岩记录，以了解SaSZ俯冲带在侏罗纪期间开始和演化的地球动力学。根据火成的活动，SaSZ可以分为三个主要部门：中央部门，西北部门和东南部门。中部地区以钙碱性岩石为主，而其他两个地区则由钙碱性岩石和次要数量的具有OIB样地球化学特征的碱性岩石组成。在所有部门中，钙碱性岩石的大部分在很大程度上平行于Zagros缝线，这是它们在大陆弧环境中形成的有力证据。通过整合现有的地球化学数据和地层约束以及S型花岗岩的分布，本研究描述了两次造山事件。它们是早期（195-168 Ma：侏罗纪中早）和晚期（168-140 Ma：侏罗纪中后期）。我们建议根据现有的地球化学数据，俯冲带的开始是偶发的，它涉及俯冲和trench陷期，这些期被短暂的收缩事件打断了。在这些阶段的每个阶段之后，分别在SaSZ的西北部和东南部进行了一次类似于OIB的小规模岩浆活动。我们认为类似OIB的岩浆作用是由对流软流圈地幔融化以响应板片撕裂而形成的，可与在现代俯冲带中进行的过程相媲美。我们对SaSZ的新构造模型为特提斯造山带这一部分的侏罗纪岩浆作用的时间和空间分布提供了区域连贯的解释。在这些阶段的每个阶段之后，分别在SaSZ的西北部和东南部进行了一次类似于OIB的小规模岩浆活动。我们认为类似OIB的岩浆作用是由对流软流圈地幔融化以响应板片撕裂而形成的，可与在现代俯冲带中进行的过程相媲美。我们对SaSZ的新构造模型为特提斯造山带这一部分的侏罗纪岩浆作用的时间和空间分布提供了区域连贯的解释。在这些阶段的每个阶段之后，分别在SaSZ的西北部和东南部进行了一次类似于OIB的小规模岩浆活动。我们认为类似OIB的岩浆作用是由对流软流圈地幔融化以响应板片撕裂而形成的，可与在现代俯冲带中进行的过程相媲美。我们对SaSZ的新构造模型为特提斯造山带这一部分的侏罗纪岩浆作用的时间和空间分布提供了区域连贯的解释。