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

Authors:
; ; ; ; ; ; ; ; ; ; ; ; ; ; ; ;
Publication Date:
Sponsoring Org.:
USDOE Office of Science (SC), Basic Energy Sciences (BES) (SC-22)
OSTI Identifier:
1413374
Grant/Contract Number:
AC02-05CH11231
Resource Type:
Journal Article: Publisher's Accepted Manuscript
Journal Name:
Chemical Geology
Additional Journal Information:
Journal Volume: 459; Journal Issue: C; Related Information: CHORUS Timestamp: 2017-12-14 11:50:17; Journal ID: ISSN 0009-2541
Publisher:
Elsevier
Country of Publication:
Netherlands
Language:
English

Citation Formats

Macholdt, D. S., Jochum, K. P., Pöhlker, C., Arangio, A., Förster, J. -D., Stoll, B., Weis, U., Weber, B., Müller, M., Kappl, M., Shiraiwa, M., Kilcoyne, A. L. D., Weigand, M., Scholz, D., Haug, G. H., Al-Amri, A., and Andreae, M. O. Characterization and differentiation of rock varnish types from different environments by microanalytical techniques. Netherlands: N. p., 2017. Web. doi:10.1016/j.chemgeo.2017.04.009.
Macholdt, D. S., Jochum, K. P., Pöhlker, C., Arangio, A., Förster, J. -D., Stoll, B., Weis, U., Weber, B., Müller, M., Kappl, M., Shiraiwa, M., Kilcoyne, A. L. D., Weigand, M., Scholz, D., Haug, G. H., Al-Amri, A., & Andreae, M. O. Characterization and differentiation of rock varnish types from different environments by microanalytical techniques. Netherlands. doi:10.1016/j.chemgeo.2017.04.009.
Macholdt, D. S., Jochum, K. P., Pöhlker, C., Arangio, A., Förster, J. -D., Stoll, B., Weis, U., Weber, B., Müller, M., Kappl, M., Shiraiwa, M., Kilcoyne, A. L. D., Weigand, M., Scholz, D., Haug, G. H., Al-Amri, A., and Andreae, M. O. Mon . "Characterization and differentiation of rock varnish types from different environments by microanalytical techniques". Netherlands. doi:10.1016/j.chemgeo.2017.04.009.
@article{osti_1413374,
title = {Characterization and differentiation of rock varnish types from different environments by microanalytical techniques},
author = {Macholdt, D. S. and Jochum, K. P. and Pöhlker, C. and Arangio, A. and Förster, J. -D. and Stoll, B. and Weis, U. and Weber, B. and Müller, M. and Kappl, M. and Shiraiwa, M. and Kilcoyne, A. L. D. and Weigand, M. and Scholz, D. and Haug, G. H. and Al-Amri, A. and Andreae, M. O.},
abstractNote = {},
doi = {10.1016/j.chemgeo.2017.04.009},
journal = {Chemical Geology},
number = C,
volume = 459,
place = {Netherlands},
year = {Mon May 01 00:00:00 EDT 2017},
month = {Mon May 01 00:00:00 EDT 2017}
}

Journal Article:
Free Publicly Available Full Text
Publisher's Version of Record at 10.1016/j.chemgeo.2017.04.009

Citation Metrics:
Cited by: 2works
Citation information provided by
Web of Science

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  • We investigated rock varnishes collected from several locations and environments worldwide by a wide 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. Rockmore » 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, La N /Yb N , and Ce/Ce*), total REE contents, and structures can be used to separate the different types of rock varnish from each other.« less
  • The authors report the successful application of magnetic techniques to the study of rock varnish, a surficial coating that forms on rocks in arid environments. Using thin wafers of varnished and unvarnished greywacke sandstone, they have detected a stable remanent magnetization that can be unambiguously attributed to the rock varnish. They have also measured several rock magnetic properties of the rock varnish and have shown that the primary magnetic carrier is either magnetite or maghemite. These results demonstrate the feasibility of applying magnetic techniques to the study of geomorphic surfaces. Subsequent rock magnetic and paleomagnetic studies of rock varnish shouldmore » provide new information about the geochemical processes involved in the formation of rock varnish and about the validity of a new chronological technique known as rock varnish dating.« less
  • Seven asphaltenes isolated from oils from different source rock types have been examined by x-ray photoelectron spectroscopy (XPS) to determine their gross nitrogen speciation. Five-membered ring pyrrolic nitrogen and six-membered ring pyridinic nitrogen species are the main types present, with pyrrolic nitrogen dominated in all samples. Pyrrolic nitrogen:pyridinic nitrogen ratios were in the range of 1.44-4.26.