气候变化领域集成服务门户(CCPortal): Comparative Rock Magnetic Study of Eocene Volcanogenic and Sedimentary Rocks From Yunnan, Southeastern Tibetan Plateau, and Its Geological Implications

CCPortal

DOI	10.1029/2019JB017946
	Comparative Rock Magnetic Study of Eocene Volcanogenic and Sedimentary Rocks From Yunnan, Southeastern Tibetan Plateau, and Its Geological Implications
	Shen M.; Zan J.; Yan M.; Zhang W.; Fang X.; Zhang D.; Zhang T.
发表日期	2020
ISSN	21699313
卷号	125 期号:2
英文摘要	Many recent biomagnetostratigraphic studies within and around the Tibetan Plateau have resulted in significant age differences, due to lack of radiometric age constraints. It has hindered the knowledge on the tectonic and paleoclimate evolutions of the Tibetan Plateau. Identifying barely visible tephra-bearing layers is urgent to solve the debate. Here we carry out a comparative rock magnetic study of Eocene volcanogenic and sedimentary rocks from the Jianchuan and Qujing Basins of the Yunnan Plateau. Our aim is to establish an effective method for tephra identification in sedimentary sequences. Petrographic and rare earth element analyses demonstrate that the volcanogenic rocks are of basic-intermediate magmatic origin with no sign of deformation or alteration, and the sedimentary rocks are unaffected by volcanic disturbance. Rock magnetic analyses reveal that the primary ferrimagnetic minerals of the volcanogenic rocks are Ti-poor titanomagnetite and/or magnetite, including pseudo-single-domain, viscous superparamagnetic and ultrafine superparamagnetic (true superparamagnetic, nonviscous around room temperature) grains. Hematite is the dominant magnetic mineral in the sedimentary rocks, and paramagnetic minerals are also abundant; pseudo-single-domain/single-domain magnetite and maghemite are also present. The enrichment of ultrafine superparamagnetic grains in the volcanogenic rocks may induce strikingly peaked signals in low-temperature frequency-dependent susceptibility measurement, in sharp contrast with pedogenically produced viscous superparamagnetic particles that show no peaks. Therefore, we attribute the low-temperature frequency-dependent susceptibility parameters to the effective and sensitive magnetic parameters for identifying tephra-bearing layers within the sedimentary sequences of the Yunnan Plateau. ©2020. American Geophysical Union. All Rights Reserved.
英文关键词	Eocene; low-temperature frequency-dependent susceptibility; rock magnetism; tephra-bearing layers; Yunnan Plateau
语种	英语
来源期刊	Journal of Geophysical Research: Solid Earth
文献类型	期刊论文
条目标识符	http://gcip.llas.ac.cn/handle/2XKMVOVA/187983
作者单位	Key Laboratory of Continental Collision and Plateau Uplift, Institute of Tibetan Plateau Research, Chinese Academy of Sciences, Beijing, China; University of Chinese Academy of Sciences, Beijing, China; Center for Excellence in Tibetan Plateau Earth Sciences, Chinese Academy of Sciences, Beijing, China; College of Tourism and Resource Environment, Zaozhuang University, Zaozhuang, China
推荐引用方式 GB/T 7714	Shen M.,Zan J.,Yan M.,et al. Comparative Rock Magnetic Study of Eocene Volcanogenic and Sedimentary Rocks From Yunnan, Southeastern Tibetan Plateau, and Its Geological Implications[J],2020,125(2).
APA	Shen M..,Zan J..,Yan M..,Zhang W..,Fang X..,...&Zhang T..(2020).Comparative Rock Magnetic Study of Eocene Volcanogenic and Sedimentary Rocks From Yunnan, Southeastern Tibetan Plateau, and Its Geological Implications.Journal of Geophysical Research: Solid Earth,125(2).
MLA	Shen M.,et al."Comparative Rock Magnetic Study of Eocene Volcanogenic and Sedimentary Rocks From Yunnan, Southeastern Tibetan Plateau, and Its Geological Implications".Journal of Geophysical Research: Solid Earth 125.2(2020).