Chemical and isotopic compositions of altered MORB from ODP Holes 187-1154A, 187-1155B, and 187-1160B ...

Boron and Pb isotopic compositions together with B-U-Th-Pb concentrations were determined for Pacific and Indian mantle-type mid-ocean ridge basalts (MORB) obtained from shallow drill holes near the Australian Antarctic Discordance (AAD). Boron contents in the altered samples range from 29.7 to 69.6...

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Bibliographic Details
Main Authors: Krolikowska-Ciaglo, Sylwia, Deyhle, Annette, Hauff, Folkmar, Hoernle, Kaj
Format: Article in Journal/Newspaper
Language:English
Published: PANGAEA 2007
Subjects:
Online Access:https://dx.doi.org/10.1594/pangaea.707365
https://doi.pangaea.de/10.1594/PANGAEA.707365
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Summary:Boron and Pb isotopic compositions together with B-U-Th-Pb concentrations were determined for Pacific and Indian mantle-type mid-ocean ridge basalts (MORB) obtained from shallow drill holes near the Australian Antarctic Discordance (AAD). Boron contents in the altered samples range from 29.7 to 69.6 ppm and are extremely enriched relative to fresh MORB glass with 0.4-0.6 ppm B. Similarly the d11B values range from 5.5‰ to 15.9‰ in the altered basalts and require interaction with a d11B enriched fluid similar to seawater ~39.5‰ and/or boron isotope fractionation during the formation of secondary clays. Positive correlations between B concentrations and other chemical indices of alteration such as H2O CO2, K2O, P2O5, U and 87Sr/86Sr indicate that B is progressively enriched in the basalts as they become more altered. Interestingly, d11B shows the largest isotopic shift to +16‰ in the least altered basalts, followed by a continual decrease to +5-6‰ in the most altered basalts. These observations may indicate a ... : Supplement to: Krolikowska-Ciaglo, Sylwia; Deyhle, Annette; Hauff, Folkmar; Hoernle, Kaj (2007): Boron isotope geochemistry and U/Pb systematics of altered MORB from the Australian Antarctic discordance (ODP Leg 187). Chemical Geology, 242(3-4), 455-469 ...