Source region geochemistry from unmixing downstream sedimentary elemental compositions
File(s)
Published version
OA Location
Author(s)
Lipp, Alexander
Type
Journal Article
Abstract
The geochemistry of river sediments is routinely used to obtain information about geologic and environmental processes occurring upstream. For example, downstream samples are used to constrain chemical weathering and physical erosion rates upstream, as well as the locations of mineral deposits or contaminant sources. Previous work has shown that, by assuming conservative mixing, the geochemistry of downstream samples can be reliably predicted given a known source region geochemistry. In this study, we tackle the inverse problem and “unmix” the composition of downstream river sediments to produce geochemical maps of drainage basins (i.e., source regions). The scheme is tested in a case study of rivers draining the Cairngorms, UK. The elemental geochemistry of the urn:x-wiley:15252027:media:ggge22639:ggge22639-math-0001 μm fraction of 67 samples gathered from the beds of channels in this region is used to invert for concentrations of major and trace elements upstream. A smoothed inverse problem is solved using the Nelder-Mead optimization algorithm. Predictions of source region geochemistry are assessed by comparing the spatial distribution of 22 elements of different affinities (e.g., Be, Li, Mg, Ca, Rb, U, V) using independent geochemical survey data. The inverse approach makes reliable predictions of the major and trace element concentration in first order river sediments. We suggest this scheme could be a novel means to generate geochemical baselines across drainage basins and within river channels.
Date Issued
2021-10
Date Acceptance
2021-09-21
Citation
G3: Geochemistry, Geophysics, Geosystems: an electronic journal of the earth sciences, 2021, 22 (10), pp.1-25
ISSN
1525-2027
Publisher
American Geophysical Union
Start Page
1
End Page
25
Journal / Book Title
G3: Geochemistry, Geophysics, Geosystems: an electronic journal of the earth sciences
Volume
22
Issue
10
Copyright Statement
© 2021. The Authors.
This is an open access article under the terms of the Creative Commons Attribution License, which permits use, distribution and reproduction in any medium, provided the original work is properly cited.
This is an open access article under the terms of the Creative Commons Attribution License, which permits use, distribution and reproduction in any medium, provided the original work is properly cited.
License URL
Sponsor
Natural Environment Research Council [2006-2012]
Identifier
https://agupubs.onlinelibrary.wiley.com/doi/10.1029/2021GC009838
Grant Number
NE/L002515/1
Subjects
Geochemistry & Geophysics
02 Physical Sciences
04 Earth Sciences
Publication Status
Published
Date Publish Online
2021-09-30