The Cenozoic Exhumation History Of The SE Tibetan Plateau From Low Temperature Thermochronology

As an important part of the Tibetan Plateau,the SE Tibetan Plateau experienced significant tectonic uplift,fault activity,climate change,and river system reorganization during the Cenozoic and these processes were accompanied with rapid rock exhumation.Therefore,the SE Tibetan Plateau has become one of the hottest areas of research focus.However,great debate exists regarding the exhumation process and forcing mechanism of the SE Tibetan Plateau during the Cenozoic.Reconstructing rock exhumation history and figuring out the underlying forcing mechanism of the SE Tibetan Plateau are helpful to improve our understanding of uplift history and mechanisms of the Tibetan Plateau.In this dissertation,we select Lincang granite area of the SE Tibetan Plateau as the research area.Firstly,I reconstruct the Cenozoic exhumation history of the Lincang granite area,based on multi-system low temperature thermochronology(including apatite(U-Th)/He,zircon(U-Th)/He and apatite fission track)and thermal history modeling(QTQt and Pecube).Secondly,I explore possible forcing mechanisms of recorded several phases of rapid rock cooling in this area by integrating regional climatic and tectonic data.Finally,I integrate the low temperature thermochronology data generated in this work with other low temperature thermochronology data from the SE Tibetan Plateau in order to cast light on regional exhumation pattern during the Cenozoic.The preliminary conclusions are as follows:(1)The Lincang granite area experienced three phases of rapid exhumation during the Cenozoic(late Eocene,Oligocene and middle Miocene).(2)Combined with regional climate and geological data,we suggest that the late Eocene rapid cooling event of Lincang granite area was mainly caused by crustal shortening,and the Oligocene rapid cooling event was associated with crustal shortening and lateral extrusion together.The occurrence of these two events may be inevitably connected with the oblique subduction of the Indian plate.In contrast,the middle Miocene rapid cooling event was closely related to the Asian summer monsoon intensification.The intensified monsoon precipitation would have likely increased the power of river incision,which accelerated the geomorphic evolution of this region.(3)Three-dimensional thermo-kinematic modeling(Pecube)analysis reveals that uplift of the SE Tibetan Plateau mainly occurred in the early Cenozoic era.(4)During the Cenozoic,the SE Tibetan Plateau has experienced at least six phases of rapid cooling,that is,?61-58 Ma,38-35 Ma,32-23 Ma,18-13 Ma,11-6 Ma,and 4-3 Ma.(5)The SE Tibetan Plateau experienced spatially inhomogeneous exhumation during the Cenozoic using a Gaussian linear inversion approach(Glide).Regional tectonics and(or)climate change can explain the inferred inhomogeneous exhumation.