This study investigates the complex, episodic development of an ancient mountain belt (the Yanshan belt), relics of which now form the rugged terrain underlying the Great Wall of China north of Beijing. Recent work in the Yanshan belt has begun to document a complex geologic history that includes multiple, cyclic episodes of crustal shortening, extension, and volcanism that took place from approximately 200 to 100 million years ago. The causes of this tectonic cyclicity are presently unclear (although multiple potential drivers exist), in part because the timing and geographic extent of each individual event is imprecisely known. The purpose of this study is to use field geologic mapping, sedimentary basin analysis, geochemistry, and radiometric dating (U-Pb zircon dating of volcanic and plutonic rocks, and detrital U-Pb and Hf dating) to better constrain the age and extent of the multiple events evident in the geology of the Yanshan. Resultant data would have bearing on major questions such as: (1) Can the variety of structures developed in the Yanshan be deconvolved into individual events that tie to discrete plate boundary processes, or is deformational complexity in the Yanshan the result of long-term, progressive deformation associated with multiple drivers?; (2) Can the magnitude of shortening be quantified in the Yanshan belt?; (3) When and by what process did lithosphere loss occur in the eastern North China craton?
Establishment of a robust tectonic history for the Yanshan region will place much-needed additional constraints on key events in the evolution of eastern Asia. These events include multiple continental collisions that were responsible for the early assembly of Asia, the initiation and development of the western Pacific plate boundary, and a mysterious loss of the ancient continental lithosphere that once underpinned the Yanshan belt and surrounding regions. This work may also yield insights into the development of mountain belts in general, including how crustal extension, compression, and volcanism interact in time and space during mountain building, how the continental crust and lithosphere respond to repeated magmatic and tectonic events, and how the lithosphere and mantle interact during crustal thickening.
This project is an extension of a long-term collaborative venture between the PI and Chinese researchers from China University of Geosciences, Beijing. The project will support summer research in China for DePauw University undergraduate students and foster collaborative relationships between these students and students from China University of Geosciences, Beijing. This project is supported by the Earth Sciences Division Tectonics Program and the NSF Office of International Science and Engineering.
