An integrated study of the grain-size-dependent magnetic mineralogy of the Chinese loess/paleosol and its environmental significance
作者： Qingsong Liu , Subir K. Banerjee , Michael J. Jackson , Fahu Chen , Yongxin Pan
DOI: 10.1029/2002JB002264
关键词: Magnetite 、 Demagnetizing field 、 Maghemite 、 Analytical chemistry 、 Saturation (magnetic) 、 Superparamagnetism 、 Remanence 、 Single domain 、 Geology 、 Mineralogy 、 Magnetic mineralogy 、 Earth-Surface Processes 、 Ecology (disciplines) 、 Earth and Planetary Sciences (miscellaneous) 、 Space and Planetary Science 、 Palaeontology 、 Forestry 、 Aquatic science 、 Atmospheric Science 、 Soil science 、 Geochemistry and Petrology 、 Geophysics 、 Oceanography 、 Water Science and Technology
摘要: [1] To investigate the grain-size-dependent properties of magnetic minerals in Chinese loess/paleosol samples (Touxiangdao, Xining, Qinghai province, China), extracts were divided into two size fractions by gravitational settling. On basis hysteresis measurements, thermal demagnetization low-temperature saturation isothermal remanent magnetization, and nonmagnetic studies (SEM XRD) we identified phases both grain less residues to provide more accurate complete descriptions all components bulk natural samples. The results show that oxidation degree (nonstoichiometry) is strongly affected paleoclimatic environment which they deposited altered. In ascending order our samples, find (1) loess-coarse particles (LC) are multidomain (MD) magnetite with slight oxidation, (2) paleosol-coarse (PC) also MD but a higher compared LC, (3) loess-fine (LF) pseudo-single domain (PSD) high degree, (4) paleosol-fine (PF) PSD maghemite. Single (SD) superparamagnetic (SP) maghemite mainly stay residues. Further thermomagnetic analysis PF (PSD maghemite) revealed this has Curie temperature identical conversion efficiency transformation from hematite only about 50% after 700°C heating/cooling cycle. These new identify sources multicomponent NRM loess sequences as well clarify paleoenviromental controls on remanence components.
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