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  Characterization and differentiation of rock varnish types from different environments by microanalytical techniques

Macholdt, D. S., Jochum, K. P., Pöhlker, C., Arangio, A., Förster, J.-D., Stoll, B., et al. (2017). Characterization and differentiation of rock varnish types from different environments by microanalytical techniques. Chemical Geology, 459, 91-118. doi:10.1016/j.chemgeo.2017.04.009.

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Macholdt, D. S.1, Author              
Jochum, K. P.1, Author              
Pöhlker, C.2, Author              
Arangio, A.3, Author              
Förster, J.-D.3, Author              
Stoll, B.1, Author              
Weis, U.1, Author              
Weber, B., Author
Müller, Maren, Author              
Kappl, Michael, Author              
Shiraiwa, M.3, Author              
Kilcoyne, A. L. D., Author
Weigand, M., Author              
Scholz, D., Author
Haug, G. H., Author
Al-Amri, A., Author
Andreae, M. O.2, Author              
1Climate Geochemistry, Max Planck Institute for Chemistry, Max Planck Society, ou_2237635              
2Biogeochemistry, Max Planck Institute for Chemistry, Max Planck Society, ou_1826286              
3Multiphase Chemistry, Max Planck Institute for Chemistry, Max Planck Society, ou_1826290              


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 Abstract: We investigated rock varnishes collected from several locations and environments worldwide by a broad range of microanalytical techniques. These techniques were selected to address the challenges posed by the chemical and structural complexity within the micrometer- to nanometer-sized structures in these geological materials. Femtosecond laser ablation-inductively coupled plasma-mass spectrometry (fs LA-ICP-MS), scanning transmission X-ray microscopy-near edge X-ray adsorption fine structure spectroscopy (STXM-NEXAFS) in combination with scanning electron microscopy (SEM) of focused ion beam (FIB) ultra-thin (100–200 nm) sections, conventional and polarization microscopy, as well as electron paramagnetic resonance (EPR) measurements were used to obtain information about these rock varnishes. Rock varnishes from different environments, which cannot readily be distinguished based on their macroscopic appearance, differ significantly in their constituent elemental mass fractions, e.g., of Mn, Fe, Ni, Co, Ba, and Pb, and their rare earth element (REE) patterns. Structural characteristics such as the particle sizes of embedded dust grains, internal structures such as layers of Mn-, Fe-, and Ca -rich material, and structures such as cavities varied between varnishes from different environments and regions in the world. The EPR spectra were consistent with aged biogenic Mn oxides in all samples, but showed subtle differences between samples of different origin. Our observations allow us to separate rock varnishes into different types, with differences that might be indicators of distinct geneses. Five different types of rock varnish could be distinguished, Type I–V, of which only Type I might be used as potential paleoclimate archive. Each varnish type has specific characteristics in terms of their elemental composition, element distribution, and structures. The combination of element ratios (Mn/Ba, Al/Ni, Mn/REY, Mn/Ce, Mn/Pb, LaN/YbN, and Ce/Ce*), total REE contents, and structures can be used to separate the different types of rock varnish from each other.


Language(s): eng - English
 Dates: 2017
 Publication Status: Published in print
 Pages: -
 Publishing info: -
 Table of Contents: -
 Rev. Type: -
 Identifiers: DOI: 10.1016/j.chemgeo.2017.04.009
 Degree: -



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Source 1

Title: Chemical Geology
  Other : Chem. Geol.
Source Genre: Journal
Publ. Info: Amsterdam : Elsevier
Pages: - Volume / Issue: 459 Sequence Number: - Start / End Page: 91 - 118 Identifier: ISSN: 0009-2541
CoNE: https://pure.mpg.de/cone/journals/resource/954925389240