郯庐断裂带构造演化的同位素年代学制约

近年来在郯庐断裂带内获得了大量的同位素年龄，为了解该断裂带的演化规律与相关动力学过程提供了有效的制约。该断裂带早期走滑构造带内给出了238～236 Ma的白云母 40Ar/39Ar 变形年龄，指示其起源于华北与华南克拉通碰撞过程的深俯冲阶段，支持其造山期陆内转换断层成因观点。其晚中生代走滑韧性剪切带内已获得的较大白云母 40Ar/39Ar冷却年龄为162～150 Ma，表明其再次左行平移发生在晚侏罗世初或中 晚侏罗世之交，出现在区域压扭性动力学背景下。这一事件应代表了中国东部滨太平洋构造域的开始时间。已获得的一系列断裂带内岩体与火山岩锆石LA ICPMS年龄显示，该断裂带内伸展性背景下最早的岩浆活动时间为136 Ma。而断裂带所控制的断陷盆地内地层时代表明其伸展活动发生在早白垩世初（约145 Ma）。这应指示了中国东部转变为伸展性动力学背景的时间。该断裂带一系列长石40Ar/39Ar年龄与磷灰石裂变径迹年龄，显示其在晚白垩世与古近纪仍处于伸展活动之中。

Geochronological constraints on tectonic evolution of the Tan-Lu Fault Zone

Many isotopic ages from the Tan Lu Fault Zone effectively constrains evolution and relative geodynamic processes of the fault zone. Muscovite 40Ar/39Ar deformation ages of 238～236 Ma from the earlier strike slip belt demonstrate that the fault zone started at the deep subduction stage during collision of the North and South China Cratons，and support the syn orogenic，intra continental transform fault model. The older，obtained muscovite 40Ar/39Ar cooling ages from the sinistral ductile shear belt of Late Mesozoic range from 162 Ma to 150 Ma. The dating results suggest that the second phase of sinistral motion along the fault zone took place under regional transpressional regime in the earliest Late Jurassic or between Middle and Late Jurassic. This event should represent beginning of the circum Pacific regime in East China. A series of zircon LA ICPMS ages from plutons and volcanic rocks along the fault zone show that the earliest magmatism related to extension in the fault zone started as old as 136 Ma. Stratigraphic ages of the strata in the rift basins controlled by the Tan Lu Fault Zone suggest that extension along the fault zone started in the earliest Early Cretaceous(ca. 145 Ma). This agrees with the transition time to tensile geodynamic setting in East China. Many feldspar 40Ar/39Ar ages and apatite FT ages indicate that the Tan Lu Fault Zone was still involved in normal faulting during Late Cretaceous and Paleogene.