Iron isotopic fractionation during continental weathering

Online Access: Get full text
doi: 10.1016/j.epsl.2004.10.013
Author(s): Fantle, Matthew S.; DePaolo, Donald J.
Author Affiliation(s): Primary:
University of California at Berkeley, Department of Earth and Planetary Science, Berkeley, CA, United States
Volume Title: Earth and Planetary Science Letters
Source: Earth and Planetary Science Letters, 228(3-4), p.547-562. Publisher: Elsevier, Amsterdam, Netherlands. ISSN: 0012-821X CODEN: EPSLA2
Note: In English. 88 refs.; illus., incl. 1 plate, 1 table, sketch map
Summary: The effect of continental weathering on the iron isotope compositions of natural materials is investigated. Unweathered igneous rocks, pelagic clay, and dust fall within the range δ56Fe=0±0.3ppm. Rivers with large suspended loads also have δ56Fe values near zero. Dilute streams have δ56Fe values that trend towards lower δ56Fe (∼-1) suggesting that dissolved riverine iron is isotopically light relative to igneous rocks. Bulk soil and soil leaches display systematically different δ56Fe profiles, indicating that isotopically distinct Fe pools are generated during pedogenesis. Nannofossil ooze, which contains Fe scavenged from the ocean water column, has δ56Fe≈0, but is consistent with seawater dissolved Fe having negative δ56Fe. It is inferred that continental weathering under modern oxidizing Earth surface conditions preferentially releases dissolved Fe with negative δ56Fe, which is transported in rivers to the ocean. A preliminary analysis of the marine Fe budget suggests that riverine Fe has a substantial role in determining the δ56Fe of both the modern and ancient oceans, but other inputs, particularly that from diagenesis of marine sediments, may also be important. Since the chemical pathways of Fe processing during weathering are dependent on oxidation state and biological activity, Fe isotopes may prove useful for detecting changes in these parameters in the geologic past. Abstract Copyright (2004) Elsevier, B.V.
Year of Publication: 2004
Research Program: DSDP Deep Sea Drilling Project
IPOD International Phase of Ocean Drilling
Key Words: 02 Geochemistry; Alaska; Assemblages; Bedrock; Biogenic processes; British Columbia; California; Canada; Cenozoic; Coniferales; DSDP Site 590; Deep Sea Drilling Project; Diagenesis; Fe-54; Fe-56; Fe-56/Fe-54; Fluvial features; Geochemical cycle; Geochemistry; Gymnospermae; Hydrology; IPOD; Igneous rocks; Iron; Isotope fractionation; Isotope ratios; Leg 90; Long Valley; Marine sediments; Marine terraces; Mass spectra; Mendocino County California; Metals; North Pacific; Oxidation; Pacific Ocean; Paleoenvironment; Pedogenesis; Pinaceae; Pinus; Plantae; Rainfall; Rivers; Sedimentary rocks; Sediments; Shore features; Soil profiles; Soils; Spectra; Spermatophyta; Terrestrial environment; Tertiary; Thermal ionization mass spectra; United States; Vegetation; Weathering; Western Canada
Coordinates: N384500 N400000 W1224700 W1240000
N302000 N302000 W1575000 W1575000
Record ID: 2006014433
Copyright Information: GeoRef, Copyright 2017 American Geosciences Institute. Reference includes data from CAPCAS, Elsevier Scientific Publishers, Amsterdam, Netherlands