Geochemistry of phosphatic crusts from the shelf off Peru

Authigenic phosphorite crusts from the shelf off Peru (9°40°S to 13°30°S) consist of a facies with phosphatic coated grains covered by younger phosphatic laminite. The crusts are composed of carbonate fluorapatite, which probably formed via an amorphous precursor close to the sediment water interface as indicated by low F/P2O5 ratios, Sr and Ca isotopes, as well as rare earth element patterns agreeing with seawater-dominated fluids. Small negative Ce anomalies and U enrichment in the laminite suggest suboxic conditions close to the sediment-water interface during its formation. Increased contents of chalcophilic elements and abundant sulfide minerals in the facies with phosphatic coated grains as well as in the laminite denote sulfate reduction and, consequently, point to episodical development of anoxic conditions during phosphogenesis. The Peruvian phosphorites formed episodically over an extended period of time lasting from Middle Miocene to Pleistocene. Individual phosphatic coated grains show a succession of phosphatic layers with varying contents of organic matter and sulfide-rich phosphatic layers. Coated grains supposedly formed as a result of episodic suspension caused by high turbulence and shifting redox conditions. Episodic anoxia in the pore water induced pyritization in the outermost carbonate fluorapatite layer. Phosphatic coated grains were later transported to the place of crust formation, where subsequent laminite formation was favored under lower energy conditions. A similar succession of phosphatic layers with varying contents of organic matter and sulfide-rich layers in the laminite suggests a formation mechanism analogous to that of individual coated grains.

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Arning, Esther T, Lückge, Andreas, Breuer, Christian, Gussone, Nikolaus, Birgel, Daniel, Peckmann, Jörn (2009). Dataset: Geochemistry of phosphatic crusts from the shelf off Peru. https://doi.org/10.1594/PANGAEA.755044

DOI retrieved: 2009

Additional Info

Field Value
Imported on November 30, 2024
Last update November 30, 2024
License CC-BY-3.0
Source https://doi.org/10.1594/PANGAEA.755044
Author Arning, Esther T
Given Name Esther T
Family Name Arning
More Authors
Lückge, Andreas
Breuer, Christian
Gussone, Nikolaus
Birgel, Daniel
Peckmann, Jörn
Source Creation 2009
Publication Year 2009
Resource Type application/zip - filename: Arning_2009
Subject Areas
Name: Lithosphere

Name: Oceans

Related Identifiers
Title: Genesis of phosphorite crusts off Peru
Identifier: https://doi.org/10.1016/j.margeo.2009.03.006
Type: DOI
Relation: IsSupplementTo
Year: 2009
Source: Marine Geology
Authors: Arning Esther T , Lückge Andreas , Breuer Christian , Gussone Nikolaus , Birgel Daniel , Peckmann Jörn .