首页|Effect of barite-bound Sr on detrital Sr isotope systematics in marine sediments

Effect of barite-bound Sr on detrital Sr isotope systematics in marine sediments

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  • NSTL
  • Elsevier
In marine sediments, the Sr content and isotope composition (~(87)Sr/~(86)Sr) of the terrigenous detrital component are widely used to track changes in provenance and related transport and weathering processes. Accurately separating detrital-Sr from other sedimentary Sr-phases is a prerequisite for such studies. Conventionally, it is assumed that Sr in the carbonate-free residue corresponds to detrital Sr alone. However, the decarbonated residue may contain barite with significant Sr content and a non-detrital ~(87)Sr/~(86)Sr composition; this may substantially affect the measured Sr signal. To examine this chronically overlooked phenomenon, the Mediterranean Sea is an ideal area because 1) detailed provenance studies have been done using Sr and ~(87)Sr/~(86)Sr of the residual fraction, and 2) enhanced levels of barite repeatedly occurred in association with distinct, organic-rich sapropel sediments. Here, we use the most-recent sapropel S1 interval to evaluate the effect of barite-bound Sr in the residual fraction after decarbonation. A total of 130 samples were taken from 10 cores in the eastern Mediterranean Sea (EMS) and 1 core in the western Mediterranean Sea. This selection represents a geographic and bathymetric coverage of the EMS and permits the basin-wide comparison between organic-rich and -lean sediments. After decarbonation using 1 M HCl solution, the residual sediments were subject to NH_4Cl extraction (2 M, pH 7), known to selectively dissolve barite. Our results demonstrate the presence of Sr-bearing barite after traditional carbonate removal and its effect on the derived "detrital" Sr signature. This barite-Sr effect is considerable for samples with barite-Ba >400 μg/g in bulk sediment. The impact of barite is prominent if accompanied by a detrital provenance background of high ~(87)Sr/~(86)Sr (>0.713) or low Sr/Al (<1.0 mg/g). In such cases, removal of remaining barite is required to obtain an unbiased detrital Sr signal. We recommend an improved

Strontium (Sr)Sr isotopesBariteBarium (Ba)SapropelMediterranean SeaProvenanceMarine sediments

Gert J. de Lange、Jiawang Wu、Zhifei Liu、Annie Michard、Kazuyo Tachikawa、Amalia Filippidi、Zhiwei He、Rick Hennekam、Shouye Yang、Gareth R. Davies

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State Key Laboratory of Marine Geology, School of Earth and Ocean Science, Tongji University, Siping 1239, 200092 Shanghai, China

Aix Marseille University, CNRS, IRD, INRAE, Coll France, CEREGE, 13545 Aix-en-Provence, France

Department of Earth Sciences-Geochemistry, Faculty of Geosciences, Utrecht University, Princetonplein 9, 3584 CC Utrecht, the Netherlands

Geology & Geochemistry, Department of Earth Sciences, VU Amsterdam University, De Boelelaan 1085, 1081 HV Amsterdam, the Netherlands

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2022

10.1016/j.chemgeo.2021.120613

Chemical geology

Chemical geology

EISCI
ISSN：0009-2541
年,卷(期)：2022.587
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