摘要
郯庐断裂带与大别造山带在大别山东缘相复合 ,并将大别—苏鲁造山带左行错开达 5 0 0km。本文以大别山东缘为研究背景 ,通过对郯庐断裂带两期左旋走滑韧性剪切带温压条件的估算及热年代学信息的分析 ,来探讨大别造山带在早侏罗—早白垩世之间的折返历史与隆升量。通过矿物组合、矿物变形特征以及白云母—绿泥石地质温度计得到郯庐早、晚两期剪切带的形成温度均为 4 0 0～ 4 5 0℃。通过多硅白云母Si原子数地质压力计计算得到早、晚两期剪切带的形成压力分别为 0 .2 5～ 0 .36GPa和 0 .2 4～ 0 .39GPa。考虑到剪切摩擦加热和构造超压的影响 ,笔者推断郯庐两期走滑剪切带形成的最大深度均不超过 12km ,且两期走滑剪切带的形成深度至多相差 1～2km。郯庐断裂带在约 190Ma和 12 8Ma经历了两期走滑冷却事件 ,而在此期间 ,大别造山带东缘经历了一个构造平静期 ,基本没有发生隆升。根据郯庐断裂带的信息 ,造山带在早白垩世的热隆事件中的隆升幅度小于 12km。
The Tanlu fault zone joins the Dabie Mountains on its eastern margin, and offsets the Dabie and Sulu orogenic belts sinistrally for about 500 km. On the basis of calculation for temperatures and pressures experienced by the two phases of the fault zone as well as the thermo-chronological information of mylonite from the earlier and later Tanlu fault zones on the eastern margin of the Dabie Mountains, this paper discusses the delamination history and uplifting magnitudes of the Dabie Mountains from earlier Jurassic to earlier Cretaceous. From mineral assemblage, mineral deformation and muscovite-chlorite geothermometry calculation, it is known that temperatures experienced by the two phases of Tanlu fault zones are between 400 ℃ and 450 ℃, confining pressures are between 0.25GPa and 0.36GPa for the earlier shear zones and 0.24～0.39GPa for the late shear zones according to geobarometry of Si in phengite. By considering shear heating and tectonic over-pressure, it is concluded that the maximum formation depths for the two phases of the ductile shear zones are not more than 12 km. Differential formation depths for the two phases of shear zones are 1～2 km at most. At about 190Ma and 128Ma, the Tanlu fault zone experienced two phases cooling events. During the period, the eastern margin of the Dabie Mountains experienced a tectonic calm period with no uplifting. According to information from the Tanlu fault zone, the uplifting magnititude of the Dabie orogenic belt is not more than 12 km during the earlier Cretaceous.
出处
《大地构造与成矿学》
EI
CAS
CSCD
北大核心
2004年第3期228-238,共11页
Geotectonica et Metallogenia
基金
国家自然科学基金资助 (编号 :40 2 72 0 94)
关键词
大别山东缘
郯庐断裂带
造山带折返
多硅白云母
温度计
eastern margin of the Dabie Mountains
Tanlu fault zone
orogenic delamination
phengite
thermometry
