Probing Deep and Surface Processes in Central Tibet – DSP-Tibet

How and when the Tibetan plateau developed has long been a puzzling question with implications for the current understanding of the behavior of the continental lithosphere in convergent zones. The Central Tibetan plateau provides the ideal existing laboratory to understand the evolution of a large scale collisional orogen. Its evolution is now well constrained by an increasing amount of high quality surface and subsurface data. The integration of these data has led to the proposition of the achetypical models of orogenic evolution. Some models focus on the importance of the underthrusting of the rigid Indian and Asian plates beneath Tibet, others argue that the crust and lithosphere are weak and the thickening of the Asian lithosphere is distributed. In this project, we target Central Tibet. Although it remains the least studied part of the collision zone, it constitutes a key element for reconstructions and models involving processes such as continental subduction, underplating or extrusion to be evidenced there. We will provide detailed quantitative data on rates and mechanisms of thickening processes in central Tibet based on an integrate petrologic study of volcanic rocks and associated mantle and lower crustal xenoliths, paleomagnetic data acquired on volcanic rocks, reappraisal of available geophysical data (tomography, heat flow, Bouguer anomaly, refraction and reflection seismicity) and numerical modeling. The comparison with the geometry, lithology and evolution of the Bohemian massif will offer an overarching vision of the evolution of large scale orogens through time. These different approaches, although highly complementary, are rarely integrated within a single project to study a particular mountain belt. We propose to develop an integrated study of deep and surface processes evolution in the core of the orogen. Our aim is to focus on the Central part of the Tibet, Qiangtang Terrane and to compare it with the Moldanubian zone in the Bohemian massif as these zones correspond to the core of the orogen far away from the preserved continental subductions zones that rejunavated the initial orogenic recordings. The interest to compare the Bohemian massif with the Qiangtang Terrane is that the former offers the opportunity to observe directly in the field the root of the orogen while the second is a still active unroofed orogenic zone.