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Strontium isotopic variations of Neoproterozoic seawater - Implications for crustal evolutionHigh-precision Sr isotopic data were obtained on carbonate samples from the Neoproterozoic Shaler Group, Victoria Island (Canada). Results indicate that, between ca. 790 and 850 Ma, the Sr-87/Sr-86 ratio of seawater varied betweeen 0.70676 and 0.70561, with the minimum value at about 830 Ma. A curve of the Sr-87/Sr-86 seawater ratio vs. age showed that the new data substantially improve the existing isotopic record of Sr in seawater for the period 790-850 Ma. The Sr isotopic system data were coupled with data for the Nd isotopic system to model changes in the seafloor spreading rates (hydrothermal flux) and the continental erosion for the period 500-900 Ma. Results indicate that hydrothermal flux reached a maximum value at ca. 830 Ma, while a maximum in erosion rate occurred at ca. 570 Ma. These peaks are considered to be related to the developments in the Pan-African and related orogenic events.
Document ID
19920027931
Document Type
Reprint (Version printed in journal)
Authors
Asmerom, Yemane (Harvard Univ. Cambridge, MA, United States)
Jacobsen, Stein B. (Harvard Univ. Cambridge, MA, United States)
Knoll, Andrew H. (Harvard Univ. Cambridge, MA, United States)
Butterfield, Nicholas J. (Harvard University Cambridge, MA, United States)
Swett, Keene (Iowa, University Iowa City, United States)
Date Acquired
August 15, 2013
Publication Date
October 1, 1991
Publication Information
Publication: Geochimica et Cosmochimica Acta
Volume: 55
ISSN: 0016-7037
Subject Category
GEOPHYSICS
Funding Number(s)
CONTRACT_GRANT: NAGW-893
CONTRACT_GRANT: DE-FG02-88ER-13978
CONTRACT_GRANT: NSF EAR-89-04593
Distribution Limits
Public
Copyright
Other