Weathering and precipitation after meteorite impact of Ni, Cr, Fe, Ca and Mn in K-T boundary clays from Stevns Klint

Miyano, Yumiko; Yoshiasa, Akira; Tobase, Tsubasa; Isobe, Hiroshi; Hongu, Hidetomo; Okube, Maki; Nakatsuka, Akihiko; Sugiyama, Kazumasa

doi:10.1088/1742-6596/712/1/012097

Cited by 2 publications

(3 citation statements)

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“…A quantitative estimation of non-and low crystalline phases in the sample cannot be performed using XRD. Using XAFS analyses, Miyano et al (2016) reported that the Ca local structure shows a diopside-like structure and the Fe local structure is midway between goethite and hematite in the same sample of K-T boundary sediments from Stevns Klint. In the iron oxide phases, low crystalline ferrihydrite (schwertmannite) was also observed by XAFS experiment in the same sample used in this study (Sakai et al, 2007).…”

Section: Samples and Experimental Methodsmentioning

confidence: 99%

“…Okube et al (2012) also proposed that precipitation of Zn took place under high pH conditions, such as in seawater. Furthermore, Miyano et al (2016) determined the local structures of Ca, Cr, Mn, Fe, and Ni atoms in K-T boundary sediments and clarified the effects of weathering, diagenesis, and life activity under the sedimentation. Tobase et al (2015) reported that the local structures of Zr in K-T sediments maintain a glass structure and keep the thermal quenching records by the asteroid impact in the Zr XAFS study in K-T boundary sediments.…”

Section: Introductionmentioning

confidence: 99%

“…Tobase et al (2015) reported that the local structures of Zr in K-T sediments maintain a glass structure and keep the thermal quenching records by the asteroid impact in the Zr XAFS study in K-T boundary sediments. The samples and XAFS measurement points of K-T boundary sediments used in Sakai et al (2007), Okube et al (2012), Miyano et al (2016), and Tobase et al (2015) were the same as those used in this study. In this study, we similarly determined the local structure around Sb atoms to obtain information about the chemical state and coordination environment of Sb atoms in K-T boundary sediments by Sb Kedge XAFS spectroscopy.…”

Section: Introductionmentioning

confidence: 99%

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XAFS study of Sb and As in Cretaceous–Tertiary boundary sediments: an index of soiling of the global environment with dust and ashes from impact ejecta falls

Hongu

Yoshiasa

Tobase

et al. 2019

Journal of Mineralogical and Petrological Sciences

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The local structure around antimony (Sb) atoms in Cretaceous-Tertiary (K-T) boundary sediments from Stevns Klint in Denmark was studied using Sb K-edge X-ray absorption fine structure (XAFS) spectroscopy to obtain information about the chemical state and coordination environment. We also performed arsenic (As) K-edge XAFS measurements. The Sb K-edge X-ray absorption near edge structure (XANES) spectrum of K-T boundary sediments was compared with those of various kinds of reference Sb minerals, such as Sb sulfides and Sb 5+ complex oxides, and soils containing ferrihydrite (schwertmannite), Sb 2 O 3 , and Sb 2 O 5. The XANES pattern and threshold energy of K-T boundary sediments are similar to those of ferrihydrite (schwertmannite) soil samples. There is no chemical shift in the threshold energies among K-T boundary sediments, Sb 5+ oxide complex minerals, and Sb 2 O 5. In As XAFS analyses, the threshold energy of K-T boundary sediments is approximately similar to those of As 5+ minerals, and the XANES pattern of K-T boundary sediments is almost similar to those of ferrihydrite (schwertmannite) soil samples. The oxidation states of Sb and As of K-T boundary sediments are estimated to be Sb 5+ and As 5+ , respectively. Sb and As in K-T boundary sediments are coordinated with oxide ions, and Sb and As exist in the same local structure positions as Sb and As in ferrihydrite (schwertmannite). The XANES spectra and radial structure function for Sb atoms also showed that Sb in K-T boundary sediments is stored in a SbO 6 octahedral coordination environment. The Sb-O interatomic distance in the K-T boundary sediments sample is 1.99(1) Å. Abundant ferric hydroxides occur in K-T boundary sediments. Sb is considered to be coprecipitated with As and Fe ions, and Sb and As in K-T boundary sediments are incorporated in low crystalline ferrihydrite (schwertmannite) throughout precipitation and sedimentation. The environment at K-T boundary sediments resembles that of soil contaminated by Sb and As in local areas at the present age. However, in an unusual environment, such as widely distributed K-T boundary sediments in the world, unusually high concentrations of Sb 5+ and As 5+ could become an index of the soiling of the global environment with dust and ashes derived from asteroid impact ejecta falls.

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Section: Samples and Experimental Methodsmentioning

confidence: 99%