Structure, Timing, and Mechanism of the Pliocene and Late Miocene Uplift Process of the Ailao Shan‐Diancang Shan, SE Tibet, China

Abstract

AbstractThe uplift of the Ailao Shan‐Diancang Shan (ASDS) along the Ailao Shan‐Red River (ASRR) shear zone is an important geological event in the southeastern margin of Qinghai‐Tibet Plateau tectonic domain in the Late Cenozoic, and it preserves important information on the structures, exhumational history and tectonic evolution of the ASRR shear zone. The uplift structural mode and uplift timing of the ASDS is currently an important scientific topic for understanding the ASDS formation and late stage movements and evolution of the ASRR shear zone. The formation of the ASDS has been widely considered to be the consequence of the strike‐slip movements of the ASRR shear zone. However, the shaping of geomorphic units is generally direct results of the latest tectonic activities. In this study, we investigated the timing and uplift structural mechanism of the ASDS and provided the following lines of supportive evidence. Firstly, the primary tectonic foliation of the ASDS shows significant characteristic variations, with steeply dipping tectonic foliation developed on the east side of the ASDS and the relatively horizontal foliation on the west side. Secondly, from northeast to southwest direction, the deformation and metamorphism gradually weakened and this zone can be further divided into three different metamorphic degree belts. Thirdly, the contact relationship between the ASDS and the Chuxiong basin‐Erhai lake is a normal fault contact which can be found on the east side of the ASDS. 40Ar/39 Argeochronology suggests that the Diancang Shan had experienced a fast cooling event during 3–4 Ma. The apatite fission track testing method gives the age of 6.6–10.7 Ma in the Diancang Shan and 4.6–8.4 Ma in the Ailao Shan, respectively. Therefore the uplift of the ASDS can be explained by tilted block mode in which the east side was uplifted much higher than the west side, and it is not main reason of the shearing movements of the ASRR shear zone. The most recent uplift stages of the ASDS happened in the Pliocene (3–4 Ma) and Late Miocene (6–10 Ma).