40Ar/39Ar age evidence for Altyn fault tectonic activities in western China

• 作 者: Liu Yongjiang J.Genser Ge Xiao
• 机 构: College of Earth Sciences,Institute of Geology and Paleontology,Statigraphic Research Center for Oil
• 出 处: 科学通报
• 发表日期: 2004年期
• 关键词: Altyn fault 40Ar/39Ar age tectono-thermal event western China
• 基金项目: 吉林大学校科研和教改项目;国家自然科学基金

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, respectively. 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 Devonian, 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 plateau 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 movement 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 activities under the tectonic setting of convergence between the Indian and Eurasian continents.