Magnetic mineral diagenesis in sediments of saline lake Lop Nur
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Saline lakes are useful repositories for paleo-climatic records. In recent years, magnetic properties of saline lake sediments have been widely applied to establish paleo-climatic change. However, the influence factors of magnetic properties in saline lakes have not been fully understood, which complicates the paleoenvironmental interpretation. Here, we present a rock magnetic analyses result of LOP1 profile (40°26′09″′N, 90°21′23″E) from Lop Nur, a well-known saline lake, located in the eastern Tarim Basin in northwestern China. We combined the particle size, total organic content, and mineral characteristics analysis to assess the influence factors of magnetic properties in Lop Nur and its environmental significance. The results indicate that early diagenesis is the major influence factor on magnetic properties of Lop Nur saline sediments. Authigenic greigite and pyrite are identified within organic-rich sediments, which produce zones with high and low magnetic susceptibilities, respectively. The different authigenic iron sulfide contents in different layers are related to sedimentary environment changes. Sufficient supplies of organic matter and sulphate and low sedimentation rates favour the pyritization process. Moreover, if pyritization was constrained, intermediate greigite formed and was preserved. In oxidizing environments, sediment magnetic properties are consistent with those of source materials from Tarim Basin and are mainly controlled by particle size and hydrodynamic sorting of mainly detrital magnetite is largely unaffected by early diagenesis. Our study demonstrates that magnetic properties can provide a robust approach for studying depositional environment change in saline lake. In addition, the information obtained in this study would also provide insights into the geochemical processes of iron element in saline lakes.
KeywordsEarly diagenesis Magnetic properties Saline lake Lop Nur
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This study was supported by the National Natural Science Foundation of China (Grant No. 41701012) and the project “Comprehensive Scientific Investigation of Natural and Cultural Heritage in the Lop Nur Region” (Grant No. 2014FY210500). We thank CHEN Dan for her help with drawing. We thank the anonymous reviewer for their constructive comments, and thank Andrew P. Roberts for the language improvement.
- Bloemendal J, Liu X (2005) Rock magnetism and geochemistry of two Plio-Pleistocene Chinese loess-palaeosol sequences—implications for quantitative palaeoprecipitation reconstruction. Palaeogeography, Palaeoclimatology, Palaeoecolog. 226(1): 149-166. https://doi.org/10.1016/j.palaeo.2005.05.008 CrossRefGoogle Scholar
- Cutter GA, Kluckhohn RS (1999) The cycling of particulate carbon, nitrogen, sulfur, and sulfur species(iron monosulfide, greigite, pyrite, and organic sulfur) in the water columns of Framvaren Fjord and the Black Sea. Marine Chemistry 67(3): 149–160. https://doi.org/10.1016/S0304-4203(99)00056-0 CrossRefGoogle Scholar
- Evans ME, Heller F (2003) Environmental Magnetism: Principles and Applications of Enviromagnetics. Academic Press, San Diego.Google Scholar
- Fu CF, Bloemendal J, Qiang XK, et al. (2015) Occurrence of greigite in the Pliocene sediments of Lake Qinghai, China, and its paleoenvironmental and paleomagnetic implications. Geochemistry Geophysics Geosystems.16(5): 1293–1306. https://doi.org/10.1002/2014GC005677
- Fu Y, von Dobeneck T, Franke C, et al. (2008) Rock magnetic identification and geochemical process models of greigite formation in Quaternary marine sediments from the Gulf of Mexico(IODP Hole U1319A). Earth and Planetary Science Letters 275(3–4): 233–245. https://doi.org/10.1016/j.epsl.2008.07.034 CrossRefGoogle Scholar
- Kao SJ, Horng CS, Roberts AP, et al. (2004) Carbon-sulfur-iron relationships in sedimentary rocks from southwestern Taiwan: Influence of geochemical environment on greigite and pyrrhotite formation. Chemical Geology 203(1): 153–168. https://doi.org/10.1016/j.chemgeo.2003.09.007 CrossRefGoogle Scholar
- King J, Banerjee SK, Marvin J (1982) A comparison of different magnetic methods for determining the relative grain size of magnetite in natural materials: Some results from lake sediments. Earth and Planetary Science Letters 59 (2):404–419. https://doi.org/10.1016/0012-821X(82)90142-X Google Scholar
- Maher BA (1988) Magnetic properties of some synthetic submicron magnetites. Geophysical Journal International 94(1): 83–96. https://doi.org/10.1111/j.1365-246X.1988.tb03429.x CrossRefGoogle Scholar
- Ron H, Nowaczyk NR, Frank U, et al. (2007) Greigite detected as dominating remanence carrier in Late Pleistocene sediments, Lisan formation, from Lake Kinneret(Sea of Galilee), Israel. Geophysical Journal International 170(1):117-131. https://doi.org/10.1111/j.1365-246X.2007.03425.x CrossRefGoogle Scholar
- Sagnotti L, Cascella A, Ciaranfi N, et al. (2010) Rock magnetism and palaeomagnetism of the Montalbano Jonico section (Italy): Evidence for late diagenetic growth of greigite and implications for magnetostratigraphy. Geophysical Journal International 180(3): 1049–1066. https://doi.org/10.1111/j.1365-246X.2009.04480.x CrossRefGoogle Scholar
- Wang ML, Liu CL, Jiao PC, et al. (2001) Saline Lake Potash Resources in the Lop Nur, Xinjiang. Geology Press, Beijing(In Chinese).Google Scholar
- Weaver R, Roberts AP, Barker AJ (2002) A late diagenetic(synfolding) magnetization carried by pyrrhotite: Implications for paleomagnetic studies from magnetic iron sulphide-bearing sediments. Earth and Planetary Science Letters 200(3–4): 371–386. https://doi.org/10.1016/S0012-821X(02)00652-0 CrossRefGoogle Scholar
- Xia XC, Wang FB, Zhao YJ (2007) Lop Nur of China. Science Press, Beijing(In Chinese).Google Scholar
- Yang Y, Wang RJ, Liu J, et al. (2015) Regional dust activity history during the past 45 ka reflected by sensitive grain-size components in Lop Nur, Xinjiang. Earth Science Frontiers 22(5): 247–258.(In Chinese).Google Scholar
- Yuan GY, Yuan L (1998) An approach to the environmental changes in Lop Nur history. Acta Geographica Sinica 53(Supplement): 83–89(In Chinese).Google Scholar