郯庐断裂带北延及中新生代构造体制转换问题的探讨

郯庐断裂带北段在进入东北地区后主要分为走向北东—北北东的三支断裂,由西向东依次为沈阳—长春—哈尔滨断裂、依兰—伊通断裂和敦化—密山断裂。由于不同时期的大地构造背景和地球动力学的不同,它们在中、新生代的构造体制转换主要表现有如下5个阶段:(1)早、中侏罗世直到早白垩世时以拉张为主,形成一系列断陷盆地或坳陷盆地,并伴有中-酸性岩浆侵入和喷发,形成了独特的火山-湖相沉积盆地;(2)早白垩世末,为北西—南东向的压缩构造应力场,使盆地内的中、上侏罗统地层发生走向近北东的逆冲推覆构造;(3)晚白垩世,为北东向左行剪切构造应力场,区内侏罗系和早白垩世早期的沉积物发生褶皱,与上覆地层呈明显的不整合;(4)古近纪时为北西—南东向拉张构造应力场,日本海从古近纪开始逐渐拉开,直到新近纪完成现在的格局;(5)新近纪时又转换为挤压构造应力场,以北西—南东向挤压为主,使古近系沉积物发生轻微的褶皱。

Discussion on Northward Extension of the Tanlu Fault Zone and Its Tectonic Regime Transformation

The northern part of Tanlu fault zone in NE China can be mainly subdivided into three faults of NE-NNE strike. They are Shenyang - Changchun - Harbin fault, Yilan - Yitong fault and Dunhua - Mishan fault from west to east. The faults have different tectonic background and dynamics in different periods. We find that these faults have five periods in tectonic regime transformation. 1) Extension mainly during Early-Middle Jurassic period, resulting in a series of down-faulted basins or sunken basins, accompanied with intermediate-acidic magmatic intrusions and eruptions, forming special volcano-lake sedimentation basins; 2) Compression in NW-SE direction in Early Cretaceous period, resulting in NE trending thrusting nappe of Middle-Late Jurassic strata in basins; 3) Left-lateral shear in Late Cretaceous period, leading to folding of Jurassic and Early Cretaceous sediments, which are un-conformable with upper layers; 4) Extension in NW-SE direction in Eogene Period. Japan Sea pulled open in Eo-gene and completed as the patterns as nowadays in Neocene period; 5) Compression in NW-SE direction in Neocene Period, making Neocene sediments folding slightly.