摘要
Four 40Ar/39Ar age groups of mica, hornblende and K-feldspar were obtained from Proterozoic and early Paleozoic metamorphic rocks in the Aksay-Dangjin Pass area, western China. The samples away from the middle shear zone of the Altyn fault belt yield two plateau age groups in the range of 461—445.2 Ma and 414.9—342.8 Ma, respec-tively. They represent the tectono-thermal events that had been recorded in the rocks that were displaced by the Altyn strike-slip fault in late Ordovician-early Silurian and Devo-nian, respectively. These two age groups should be related to the closures of Northern and Southern Qilian Oceans. The deformed granitic gneiss from the northern belt gives a pla-teau age group of 178.4—137.5 Ma, which is interpreted as the active age of the Altyn fault in the middle-late Jurassic- early Cretaceous and should be related to the accretion of Lhasa block to the north. The sample from the middle shear zone of the Altyn fault belt yields two plateau ages of 36.4 and 26.3 Ma, respectively, suggesting the strike-slip move-ment with strong metamorphism at greenschist facies along the Altyn fault in the late Eocene. This event occurred in the most areas of the northern Tibet Plateau and should be in response in the north to the collision between Indian and Eurasian continents. The present study demonstrates that the Altyn fault is characterized by multiple pulse-style activi-ties under the tectonic setting of convergence between the Indian and Eurasian continents.
Four 40Ar/39Ar age groups of mica, hornblende and K-feldspar were obtained from Proterozoic and early Paleozoic metamorphic rocks in the Aksay-Dangjin Pass area, western China. The samples away from the middle shear zone of the Altyn fault belt yield two plateau age groups in the range of 461—445.2 Ma and 414.9—342.8 Ma, respec-tively. They represent the tectono-thermal events that had been recorded in the rocks that were displaced by the Altyn strike-slip fault in late Ordovician-early Silurian and Devo-nian, respectively. These two age groups should be related to the closures of Northern and Southern Qilian Oceans. The deformed granitic gneiss from the northern belt gives a pla-teau age group of 178.4—137.5 Ma, which is interpreted as the active age of the Altyn fault in the middle-late Jurassic- early Cretaceous and should be related to the accretion of Lhasa block to the north. The sample from the middle shear zone of the Altyn fault belt yields two plateau ages of 36.4 and 26.3 Ma, respectively, suggesting the strike-slip move-ment with strong metamorphism at greenschist facies along the Altyn fault in the late Eocene. This event occurred in the most areas of the northern Tibet Plateau and should be in response in the north to the collision between Indian and Eurasian continents. The present study demonstrates that the Altyn fault is characterized by multiple pulse-style activi-ties under the tectonic setting of convergence between the Indian and Eurasian continents.
作者
LIU Yongjiang1, J. Genser2, GE Xiaohong1, F. Neubauer2, G. Friedl2, CHANG Lihua1, REN Shoumai3 & R. Handler2 1. College of Earth Sciences, Jilin University, Changchun 130061, China
2. Institute of Geology and Paleontology, Salzburg University, Salzburg A-5020, Austrilia
3. Statigraphic Research Center for Oil and Natural Gas, Ministry of Land and Resources, Beijing 100034, China Correspondence should be addressed to Liu Yongjiang (e-mail: liuyj@ email.jlu.edu.cn)
