PLIOCENE-QUATERNARY FAULTING PATTERN AND LEFT-SLIP PROPAGATION TECTONICS IN NORTH CHINA
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摘要: 华北地区包含两个新生代引张构造域,即太行山以西的鄂尔多斯周缘地堑系和以东的华北-渤海平原盆地。鄂尔多斯周缘地堑系上新世~第四纪的断裂作用表征为以正向倾滑活动为主,同时具有右旋或左旋走滑分量的运动型式,指示了NW-SE向地壳引张作用。华北-渤海盆地内上新世~第四纪的断裂作用发生在NNE至NE走向的断裂带上,具有右旋和正向倾滑的斜向运动特征。EW走向的秦岭断裂系构成了华北引张构造域的南界,显示左旋走滑运动。NNE走向的郯庐断裂带构成了华北引张构造域的东界,表现为右旋走滑,与EW向挤压和SN向引张构造应力作用一致。本文提出的一个构造运动学模式将华北地区上新世~第四纪的构造变形与青藏高原东北边缘海原和昆仑断裂的左旋走滑运动联系在一起,给出了中国大陆活动地块向东扩展的侧向挤出大地构造的新见解。在这个模式里,海原断裂的左旋走滑作用同时被鄂尔多斯地块的反时针旋转运动和沿该地块西南边缘冲断和褶皱作用所调整吸收;昆仑断裂带的左旋走滑运动继续沿秦岭断裂系向东扩展并影响整个华北东部地区,导致了NNE走向的先存断裂的复活。Abstract: North China includes two extensional domains:the grabens surrounding the Ordos block in the west, and Huabei-Bohai plain basins in the east.Pliocene-Quaternary faulting in grabens around the Ordos block displays predominantly normaldip slip displacements with a right-lateral or left-lateral slip component, indicating a NW-trending extension.Pliocene-Quaternary faulting in the Huabei-Bohai Plain basins has occurred along NNE-trending faults with oblique slip including right-lateral strile slip and normal components.The major EW-trending Qinling fault svstem bounds both extensional domains on the south and displays left-lateral slip decreasing in magnitude from west to east.The NNE-striking Tanlu fault zone bounds the extensional domains on the east and displays rightlateral strike slip movement, consistent with EW-trending compression and N-S-trending extension.A kinematic model linking North China deformation with left-lateral slip on the major Haiyuan fault on the NE margin of Qinhai-Tibetan plateau and on the Kunlun fault gives a new insight into eastward propagating extrusion tectonics in China.ln this model, displacement on the Haiyuan fault is accommodated by the counterclockwise rotation of the Ordos block and folding along its SW margin.Motion on the Kunlun fault continues along the Qinling fault system into eastern China where it is accommodated by reactivation of NNE-trending pre-existing faults.
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