Study on Gravity and Magnetic Fields and Characteristics of Basement Faults in the Northern Ordos Basin
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摘要: 为了明确鄂尔多斯盆地北部基底断裂特征,在分析其重磁场特征基础上,采用小波多尺度分解和功率谱分析的方法获取了基底重磁异常场,并对其基底断裂构造进行了综合识别和解释。研究发现盆地北部布格重力异常场呈东高西低、航磁场呈近东西、正负相间排列的特征;盆内发育28条基底断裂,整体上以NE向和EW向基底断裂为主,NW和SN向基底断裂错断或斜交分布的构造格架;EW—NE向基底断裂形成于～1.95Ga阴山地块与鄂尔多斯地块的陆陆碰撞事件,其中新召北—泊尔江海子南(F4+F10)基底断裂带在中元古代之前是一条不同构造单元的分界线;SN—NW向基底断裂是上述陆陆碰撞过程中形成的撕裂构造,中元古代在近EW向拉张应力场下选择性激活。盆地北部基底断裂体系形成是不同陆块相互作用的产物,并在后期选择性活化,为研究华北克拉通化和再造过程提供了构造变形的证据。Abstract: To elucidate the characteristics of basement faults in the northern Ordos Basin, an analysis of its gravity and magnetic field characteristics was conducted. Wavelet multiscale decomposition and power spectrum analysis methods were used to comprehensively identify and interpret the obtained basement gravity and magnetic anomaly fields. The results reveal that the Bouguer Gravity anomaly field in the northern Ordos Basin exhibited higher values in the east and lower values in the west. Simultaneously, the aeromagnetic field was organized into zones of nearly east–west(EW) positive and negative. A total of 28 intra-basin basement faults were identified in the northern Ordos Basin, with north–east(NE) and EW trending basement faults being predominant, and NW and SN trending faults distributed in a staggered or oblique tectonic framework; The EW–NE basement fault originated from the continental collision event between the ～1.95 Ga Yinshan Block and the Ordos Block. The Xinzhao North–Porjianghaizi South(F4+F10) basement fault zone serves as a boundary of different tectonic units before the Mesoproterozoic. Moreover, The SN–NW trending faults are a tearing structure formed during the continental collision process, selectively activated in the EW-trending tensile stress field in the Mesoproterozoic. The formation of the basement fault system in the northern Ordos Basin is attributed to the interaction between different continents and is selectively activated in later stages. This evidence of structural deformation contributes valuable insights into the study of the North China cratonization and reactivation process.
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