Tectonomagmatic Evolution of the Paleogene Arc System of Iran

来自加州理工学院的一组科学家与德黑兰大学和里昂大学的科学家合作，正在进行一项实地和实验室联合研究，旨在了解3500万至5000万年前伊朗东南部的构造演化。该地区的火山岩主要是碱性的，而不是在大陆碰撞之前与洋盆闭合相关的俯冲相关的火山作用所预期的钙碱成分。该地区的构造与美国西部的岩心杂岩相似，表明熔岩层序与伸展有关。研究小组正在验证岩浆活动与弧系统内岩石圈伸展之间存在时间关系的假设，并将伸展的时间与碱性岩浆的发育时间进行比较。在伊朗东南部的Saghad地区正在进行构造、古地磁和热年代学研究。该团队正在绘制分离体及其上盘覆瓦状正断层的分布图，描绘断裂带下方糜伦岩的剪切方向，利用热年代学来确定下盘片麻岩和岩体是否随着内巴兹-恰塔克断裂带的拆顶而迅速冷却，并利用白垩纪石灰石的古地磁研究来评估核心复体内部和周围的垂直轴旋转。

A team of scientists from the California Institute of Technology, in collaboration with scientists from the University of Tehran and University of Lyon, are conducting a a combined field and laboratory study aimed at understanding the tectonic evolution of southeastern Iran between 35 and 50 million years ago. Volcanic rocks in this region are predominantly alkalic in character, rather than the calc-alkalic composition expected for subduction-related volcanism associated closure of an ocean basin prior to continental collision. Structures in this area are similar to those found in core complexes in western United States, suggesting that the lava sequences were associated with extension. The investigator team is testing the hypothesis that a temporal relationship exists between magmatism and lithospheric extension within the arc system and are comparing the timing of extension with that of the development of the alkaline magmas. Structural, paleomagnetic, and thermochronologic studies are being conducted in the Saghad area in southeastern Iran. The team is mapping the detachments and their hanging wall imbricate normal faults, characterizing the shear direction in mylonites below the fault zone, using thermochronology to determine whether footwall gneisses and plutons cooled rapidly in association with unroofing along the Neybaz-Chatak fault zone, and using paleomagnetic studies of Cretaceous limestones to assess vertical axis rotations within and around the core complexes.