内蒙古中部主要断裂对晚古生代地层分布的控制研究

Control on Distribution of Major Fault in Neopaleozoic Layer in the Middle of Inner Mongolia

通过重磁、反射地震等地球物理资料处理、解释并结合地面露头调查,重点研究了内蒙古中部地区的贺根山断裂、西拉木伦断裂的构造特征及其对晚古生代地层发育的控制,其中西拉木伦河断裂与贺根山断裂对地层的控制尤为明显。沿贺根山断裂出露大量的海西期、印支期花岗岩和超基性岩体、古陆核残片,具有缝合线特征,在地震剖面上,断裂北倾,且受后期改造而可能具有走滑性质;西拉木伦断裂同样具有缝合线性质,但在地震剖面上表现为逆冲推覆构造,推测该断裂晚古生代-中生代为逆冲断裂,新生代为张性断裂,因此具有负反转特征;晚古生代地层受断裂活动影响,西部剥蚀严重,东部残留厚度较大;泥盆系主要分布在贺根山断裂以北地区,南部大多缺失;石炭-二叠系全区广泛,东部和北部厚度大,其他地区残留,且残留厚度差异较大。

This paper is mainly researched the structural characteristics and the control on distribution of Neopaleozoic layer lays in Hegenshan Fault and Xar Moron River Fault in the middle of Inner Mongolia,especially,the control of Hegenshan Fault and Xar Moron River Fault is the most obvious,which is clear through geophysical processing and interpretation of gravity,magnetism and reflected seismos,the research of surface outcrop.There has a feature of suture line showing Hercynian and Indo-Chinese epoch granite,ultra basic rock and craton relics;there has strike-slip formed at the late stage and breaks northward at seismic sections.Similarly,there has a feature of suture line in Xar Moron River Fault,but shows thrusting decken structure in seismic sections.It is supposed that this fault is thrusting fault at Neopaleozoic-Mesozoic Era,and is tensional fault at Cenozoic Era,thus it has negative reverse.The study area is affected by fault movement in Neopaleozoic,the west of it is denuded severely and the east has thickness remained largely.The Devonian is mainly distributed at the north of Hegenshan Fault;the Carboniferous-Permian is allocated widely in the whole area,which has a large thickness in THE east and north,the other area remainS few and the difference of remained thickness between them is large.