The Sistan Suture Zone, eastern Iran: the exhumation history of oceanic HP/LT rocks and the geological significance of presumed granulite-facies mélange rocks.

这项建议寻求为实地研究活动提供资金，这些活动旨在为深入了解伊朗锡斯坦缝合带(SSZ)的混杂岩奠定坚实的岩石学、地球化学和地质年代学基础。该研究区提供了详细研究大洋HP/LT岩石及其逆行衍生岩的折返历史的绝佳机会。计划中的研究活动将集中在SSZ演化的关键方面，这些方面需要更详细的关注：热制度和掘尸历史。该提案建议开展综合实地活动、岩石学、块状岩石地球化学、同位素地球化学和地质年代学的活动。计划应用Rb-Sr年代学测定角闪岩和/或绿片岩相事件的年龄，并使用锆石和独居石U-Pb测年来确定推测麻粒岩和绿泥石片岩中记录的年龄。裂变径迹(锆石、磷灰石)和(U-Th-Sm)/He(磷灰石)分析将为后续冷却阶段提供信息。块状岩石地球化学和锶-钕同位素数据将被用来充分描述所研究的样品组。综上所述，这些数据是深入了解各种混杂岩所记录的地质历史的先决条件，这将有助于深入了解特定的俯冲带风格和折返机制。重点将放在以下问题上：锡斯坦洋的关闭是否与热俯冲环境有关？挖掘遗骸的时间和速度是多少？掘尸是发生在单一的短暂事件中，还是发生在较长时间跨度的不连续事件中？哪些过程控制着掘尸？这些问题的回答将对构造概念进行测试，以预测这种环境的快速和不连续的折返。新获得的知识将使SSZ的冷却路径和运动学发展与其他Neotethan缝合区联系起来，并评估缝合区动力学的机制。该项目将促进对锡斯坦缝合带中记录的俯冲-折返事件的理解，并有可能进一步深入了解增生杂岩的演化。

This proposal seeks funding for field-based research activities that aim at establishing a solid petrological, geochemical and geochronologic foundation for in-depth understanding of mélange rocks from the Sistan Suture Zone (SSZ), Iran. The study area provides the excellent opportunity to examine in detail the exhumation history of oceanic HP/LT rocks and their retrograde derivatives. The planned research activities will focus on key aspects of the SSZ evolution that demand more detailed attention: the thermal regime and the exhumation history. The proposal suggests activities which will integrate field activities, petrology, bulk-rock geochemistry, isotope geochemistry and geochronology. It is planned to apply Rb-Sr geochronology for dating the amphibolite and/or greenschist-facies event, and to use U-Pb zircon and monazite dating to determine ages recorded in presumed granulites and in chlorite schists. Fission-track (zircon, apatite) and (U-Th-Sm)/He (apatite) analyses will provide information for subsequent cooling stages. Bulk-rock geochemical and Sr-Nd isotope data will be used to fully characterize the studied sample suite. Taken together such data is a prerequisite for in-depth understanding of the geologic histories recorded by various mélange rocks that will help gaining insights into the specific subduction zone style and exhumation mechanisms. Emphasis will be placed on the following questions: Is the closure of the Sistan ocean associated with a hot subduction setting? What are the timescales and rates of exhumation? Did exhumation occur in a single short-lived event or in discontinuous episodes over a protracted time span? Which processes control exhumation? Answering of these questions will provide a test of tectonic concepts predicting fast and discontinuous exhumation for such settings. The newly gained knowledge will allow to link the cooling path and kinematic development of the SSZ to other Neotethyan suture zones, and to assess the mechanisms of suture zone dynamics. This project will advance the understanding of the subduction-exhumation events recorded in the Sistan suture and has the potential to provide further insight into the evolution of accretionary complexes.