Journal
EARTH AND PLANETARY SCIENCE LETTERS
Volume 309, Issue 1-2, Pages 100-112Publisher
ELSEVIER
DOI: 10.1016/j.epsl.2011.06.021
Keywords
(banded) iron formation; iron isotopes; Rapitan Group; Neoproterozoic; glaciation; rare earth elements
Categories
Funding
- U.S. National Science Foundation [OISE-0401772, OPP-9817244]
- CNRS
- University of Adelaide
- LMTG
Ask authors/readers for more resources
We have measured the iron isotope compositions and trace element concentrations of a suite of iron formation (IF) samples from the Neoproterozoic Rapitan Group, which was deposited during the older of two glacial episodes recorded in the Windermere Supergroup of the northern Canadian Cordillera. Like most other Neoproterozoic examples, iron in the Rapitan IF resides almost exclusively as hematite. This mineralogical simplicity compared to Archean and Paleoproterozoic banded iron formations is attributed to a limited supply of organic carbon to the Rapitan glacial ocean that inhibited diagenetic production of reduced iron phases. Sedimentological considerations indicate that the Rapitan IF was deposited during a rise in relative sea level related to a period of glacial advance and isostatic subsidence. Trace element data, including rare earth element plus yttrium (REE + Y) patterns, suggest an anoxic deep ocean dominated by low-temperature hydrothermal input and capped by a weakly oxic surface ocean. The iron isotope data show a trend of increasing delta(57)Pe (versus IRMM-14) up-section from similar to-0.7 parts per thousand to 1.2 parts per thousand, corresponding to a shift from a muddy IF facies to a dominantly jaspilitic IF facies. This distinct isotopic pattern likely records a steep isotopic gradient across the iron chemocline in Rapitan seawater. (C) 2011 Elsevier B.V. All rights reserved.
Authors
I am an author on this paper
Click your name to claim this paper and add it to your profile.
Reviews
Recommended
No Data Available