首页|Potassium isotopic signatures of modern offshore detrital sediments from different climatic regimes and the implications

Potassium isotopic signatures of modern offshore detrital sediments from different climatic regimes and the implications

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Potassium isotopes are a novel tracer for continental weathering.Previous K isotope studies on chemical weathering generally targeted weathering profiles under a particular climate region,yet the effects of chemical weathering on K isotopes under different climatic backgrounds remain unclear.Moreover,little is known about the K isotope signatures of modem unconsolidated detrital sediments.Here,we report K isotopic data of surficial seafloor sediments from continental shelves along the east coast of China(ECC),as well as those around the tropical Hainan island in the northern South China Sea.The ECC sediments have a relatively narrow distribution of δ41K(with reference to NIST3141a)values,which range from(-0.40±0.01)‰to(-0.57±0.04)％o,with an average of(-0.51±0.09)‰.By contrast,δ41k values of Hainan offshore sediments display a larger variation,ranging from(-0.28±0.07)‰ to(-0.67±0.02)‰.The δ41k values of Hainan offshore sediments exhibit negative correlations with the chemical index of alteration(CIA),Al/K,Ti/K,and total iron(FeT),which underlines the control of chemical weathering on K isotopic signatures of detritus inputs into oceans.We also measured Mg isotope compositions for the same samples;interestingly,the variability in δ26Mg of the samples is small(～0.24‰)for all ECC and Hainan offshore sediments,and δ26Mg values do not show clear correlations with indexes of chemical weathering.Our study demonstrates the link between K isotopic variability of detrital sediments and climatic conditions including rainfall intensity,which indicates that K isotopes of the detrital component of marine sediments could be applied to study Earth's climate in deep time.Theδ41Kvalues of the offshore detrital sediments are significantly less variable than those of pelagic marine sediments,highlighting the importance of distinguishing the effects of diagenesis and neoformation of clay minerals from continental weathering in attempts to study deep-time climate-weathering link by K isotopes in detrital sedimentary records.

Potassium isotopesMagnesium isotopesChemical weatheringDetrital sedimentsClimatic regimesMean annual precipitation

Jun MU、Tianyu CHEN、Qian YU、Shichao AN、Jianfang CHEN、Xuefa SHI、Weiqiang LI

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State Key Laboratory for Mineral Deposits Research,School of Earth Sciences and Engineering,Nanjing University,Nanjing 210023,China

Ministry of Education Key Laboratory for Coast and Island Development,School of Geography and Ocean Science,Nanjing University,Nanjing 210023,China

State Key Laboratory of Satellite Ocean Environment Dynamics,Second Institute of Oceanography,Ministry of Natural Resources,Hangzhou 310012,China

Key Laboratory of Marine Geology and Metallogeny,First Institute of Oceanography,Ministry of Natural Resources,Qingdao 266061,China

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National Natural Science Foundation of ChinaNational Natural Science Foundation of China

9235830141873004

2024

10.1007/s11430-023-1220-1

中国科学:地球科学(英文版)
中国科学院

中国科学:地球科学(英文版)

影响因子：1.002
ISSN：1674-7313
年,卷(期)：2024.67(2)
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