Tectonomagmatic Evolution of the Paleogene Arc System of Iran

来自加州理工学院的一组科学家与来自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相结合的研究，旨在了解伊朗东南部3500万至5000万年前的构造演化。这一地区的火山岩主要是碱性的，而不是大陆碰撞前与俯冲有关的火山活动相关的洋盆闭合所预期的钙碱性成分。该地区的构造与美国西部核杂岩中发现的构造相似，表明熔岩序列与伸展有关。研究小组正在检验弧系内岩浆活动与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形成的时间进行比较。伊朗东南部的萨格哈德地区正在进行构造、古地磁和热年代学研究。该小组正在绘制断层及其上盘叠瓦状正断层的地图，确定断层带下方糜棱岩的剪切方向，利用热年代学确定下盘片麻岩和岩体是否与内巴兹-查塔克断层带沿着的去顶有关而迅速冷却，并利用对白垩纪石灰岩的古地磁研究评估核心复合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.