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Geochemical behavior of U and Th during exhalative sedimentary processes
Luleå tekniska universitet.
1978 (English)In: Genesis of the manganese nodules: symposia of the Centre National de la Recherche Scientifique. Gif-sur-Yvette. 25-30 September 1978 / [ed] B.M. Sorensen, Centre National de la Recherche Scientifique, CNRS , 1978, p. 151-166Conference paper, Published paper (Refereed)
Abstract [en]

Exhalative sediments are formed on a large scale on spreading (or active) ridges. Such sediments on the crest of the East Pacific Rise (EPR) are on the average rich in U (38 ppm) and poor in Th (2.4 ppm), contrary to other pelagic sediments that contan 3-6 ppm U and 3-11 ppm Th in the non-biogenic fraction. Most U in active ridge deposits is absorbed from sea water but some derives from different volcanic sources: (a) Shallow hydrothermal leaching of basalts form solutions with high SUP-234 U/SUP-238 U values; (b) Deep seated sources deliver solutions which are very rich in U but with radiochemical equilibrium between SUP-234 U and SUP-238 U; (c) Hydrothermal leaching of sediments is possibly an additional process. Bottom waters over the EPR show normal sea-water values for SUP-234 U/SUP-238 U, suggesting that volcanic U is delivered intemittently. Terrigenous matter delivers most of the Th, whereas biological matter probably is of negligible importance on active ridges as a source for Th. Volcanic processes are negligible sources of U in deposits formed far from spreading centers, such as the bauer Deep sediments and manganese nodules, since any adsorbed U is redissolved during diagenesis. Metamorphic alterations of U rich exhalative deposits could give them the reappearance of vein deposits; a detailed study of such deposits will probably reveal that many of them originally were sedimentary deposits.

Place, publisher, year, edition, pages
Centre National de la Recherche Scientifique, CNRS , 1978. p. 151-166
National Category
Geochemistry
Research subject
Applied Geology
Identifiers
URN: urn:nbn:se:ltu:diva-35828Local ID: a82219f0-30e7-11df-be83-000ea68e967bOAI: oai:DiVA.org:ltu-35828DiVA, id: diva2:1009082
Conference
Colloques Internationaux du Centre Natonal de la Recherche Scientifique : 25/09/1978 - 30/09/1978
Note
Godkänd; 1978; 20100316 (andbra)Available from: 2016-09-30 Created: 2016-09-30Bibliographically approved

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