Identification of magnetic minerals in surface sediments of Miyun Lake, Beijing

作者：Han Fei; Wang Fu-Xian; Li Jin-Hua; Qin Hua-Feng; Deng Cheng-Long; Pan Yong-Xin^*

来源：Acta Geophysica Sinica, 2016, 59(8): 2937-2948.

DOI：10.6038/cjg20160818

• Sediment
• Rock magnetism
• Transmission Electron Microscopy (TEM)
• Magnetic extraction
• Biogenic magnetite

Understanding the magnetic properties of natural sediments, which include magnetic concentration, composition and grain size, is fundamental in paleomagnetic and paleoenvironmental studies. Systematic magnetic measurements and non-magnetic methods (e.g., transmission electron microscopy, TEM) provide detailed information of magnetic minerals. In this paper, we established a high efficient magnetic extraction method to separate magnetic minerals from surface sediments of Miyun lake in Beijing. We analyzed the bulk samples, magnetic extracts and residues. Saturation magnetization (M-s), volume magnetic susceptibility (kappa) and saturation isothermal remanent magnetization (SIRM) of the magnetic extracts is about 85%, 75% and 70% of the bulk samples, respectively. Multiple-parameter rock magnetic measurements indicated that the major magnetic minerals in sediments are multi-domain (MD) and single domain (SD) magnetite. TEM analyses revealed detrital MD titano-magnetite, biogenic SD magnetite (magnetofossils) and authigenic superparamagnetic (SP) magnetite. We propose that the combination of rock magnetism and TEM observations is useful to accurately identify the magnetic minerals in sediments.

• 单位
  中国科学院大学; 岩石圈演化国家重点实验室; 中国科学院地质与地球物理研究所兰州油气资源研究中心; 中国科学院地质与地球物理研究所