摘要
Climate and tectonism are both particularly intense in the Yarlung Zangbo (Tsangpo) Great Canyon in the eastern Himalayan syntaxis,which is characterized by the most rapid landscape evolution of anywhere in the world.Thus,the eastern Himalayan syntaxis is one of the best locations to study the interactions between climate and tectonics.This paper investigates the cooling ages of the Doxong La-Baibung profile using apatite fission track (AFT) dating on 11 bedrock samples at elevations ranging from 4210 to 710 m.There are topographic,climatic,metamorphic,and thermochronological gradients in the profile,providing good conditions to study interactions between climate and tectonics.AFT ages ranged from 4.6±0.6 Ma to 1.7±0.3 Ma,and the mean fission track lengths ranged from 11.0 to 12.4 μm.It was found that the cooling rates revealed by AFT ages increased with decreasing elevation.However,the tendency of the cooling rates revealed by the 40 Ar-39 Ar ages was different from that indicated by the AFT ages.Moreover,for most districts of the eastern Himalayan syntaxis,the compiled AFT age distribution correlates well with the annual average precipitation,indicating the coupling of the cooling and erosion rates of the near-surface rock and precipitation.The geothermal history modeling results indicate an obvious increase in the cooling and erosion rate between 1.0 and 0.5 Ma.This age is consistent with other research findings for this time,when the vapor channel of the Yarlung Zangbo Great Canyon began to take effect.These evidences suggest that climate,especially precipitation,has acting as a key factor influencing the rapid cooling and erosion in the Yarlung Zangbo Great Canyon since 1-0.5 Ma.
Climate and tectonism are both particularly intense in the Yarlung Zangbo （Tsangpo） Great Canyon in the eastern Himalayan syntaxis, which is characterized by the most rapid landscape evolution of anywhere in the world. Thus, the eastern Himalayan syntaxis is one of the best locations to study the interactions between climate and tectonics. This paper investigates the cooling ages of the Doxong La-Baibung profile using apatite fission track （AFT） dating on 11 bedrock samples at elevations ranging from 4210 to 710 m. There are topographic, climatic, metamorphic, and thermochronological gradients in the profile, providing good conditions to study interactions between climate and tectonics. AFT ages ranged from 4.6_＋0.6 Ma to 1.7_＋0.3 Ma, and the mean fission track lengths ranged from 11.0 to 12.4 jam. It was found that the cooling rates revealed by AFT ages increased with de- creasing elevation. However, the tendency of the cooling rates revealed by the 4~Ar-39Ar ages was different from that indicated by the AFT ages. Moreover, for most districts of the eastern Himalayan syntaxis, the compiled AFT age distribution correlates well with the annual average precipitation, indicating the coupling of the cooling and erosion rates of the near-surface rock and pre- cipitation. The geothermal history modeling results indicate an obvious increase in the cooling and erosion rate between 1.0 and 0.5 Ma. This age is consistent with other research findings for this time, when the vapor channel of the Yarlung Zangbo Great Canyon began to take effect. These evidences suggest that climate, especially precipitation, has acting as a key factor influencing the rapid cooling and erosion in the Yarlung Zangbo Great Canyon since 1-0.5 Ma.
基金
supported by the National Natural Science Foundation of China(40872149 and 40472100)
the National Natural Science Funds for Distinguished Young Scholar(41002067)
