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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ftpangaea:oai:pangaea.de:doi:10.1594/PANGAEA.707365 2023-05-15T13:42:09+02:00 Chemical and isotopic compositions of altered MORB from ODP Holes 187-1154A, 187-1155B, and 187-1160B Krolikowska-Ciaglo, Sylwia Deyhle, Annette Hauff, Folkmar Hoernle, Kaj MEDIAN LATITUDE: -42.481413 * MEDIAN LONGITUDE: 131.435990 * SOUTH-BOUND LATITUDE: -44.008230 * WEST-BOUND LONGITUDE: 127.992360 * NORTH-BOUND LATITUDE: -41.477830 * EAST-BOUND LONGITUDE: 134.998350 * DATE/TIME START: 1999-12-01T19:00:00 * DATE/TIME END: 1999-12-24T06:00:00 2007-11-14 application/zip, 3 datasets https://doi.pangaea.de/10.1594/PANGAEA.707365 https://doi.org/10.1594/PANGAEA.707365 en eng PANGAEA https://doi.pangaea.de/10.1594/PANGAEA.707365 https://doi.org/10.1594/PANGAEA.707365 CC-BY-3.0: Creative Commons Attribution 3.0 Unported Access constraints: unrestricted info:eu-repo/semantics/openAccess CC-BY 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, https://doi.org/10.1016/j.chemgeo.2007.05.004 187-1154A 187-1155B 187-1160B DRILL Drilling/drill rig Indian Ocean Joides Resolution Leg187 Ocean Drilling Program ODP Dataset 2007 ftpangaea https://doi.org/10.1594/PANGAEA.707365 https://doi.org/10.1016/j.chemgeo.2007.05.004 2023-01-20T07:31:16Z 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 change from an early seawater dominated fluid towards a sediment-dominated fluid as a result of an increase in sediment cover with increasing age of the seafloor. The progression from heavy d11B towards lighter values with increasing degrees of alteration may also reflect increased formation of clay minerals (e.g., saponite). A comparison of 238U/204Pb and 206Pb/204Pb in fresh glass and variably altered basalt from Site 1160B shows extreme variations that are caused by secondary U enrichment during low temperature alteration. Modeling of the U-Pb isotope system confirms that some alteration events occurred early in the 21.5 Ma history of these rocks, even though a significant second pulse of alteration happened at ~12 Ma after formation of the crust. The U-Pb systematics of co-genetic basaltic glass and variably low temperature altered basaltic whole rocks are thus a potential tool to place age constraints on the timing of alteration and fluid flow in the ocean crust. Dataset Antarc* Antarctic PANGAEA - Data Publisher for Earth & Environmental Science Antarctic Australian-Antarctic Discordance ENVELOPE(124.000,124.000,-49.000,-49.000) Indian Pacific ENVELOPE(127.992360,134.998350,-41.477830,-44.008230) |
institution |
Open Polar |
collection |
PANGAEA - Data Publisher for Earth & Environmental Science |
op_collection_id |
ftpangaea |
language |
English |
topic |
187-1154A 187-1155B 187-1160B DRILL Drilling/drill rig Indian Ocean Joides Resolution Leg187 Ocean Drilling Program ODP |
spellingShingle |
187-1154A 187-1155B 187-1160B DRILL Drilling/drill rig Indian Ocean Joides Resolution Leg187 Ocean Drilling Program ODP Krolikowska-Ciaglo, Sylwia Deyhle, Annette Hauff, Folkmar Hoernle, Kaj Chemical and isotopic compositions of altered MORB from ODP Holes 187-1154A, 187-1155B, and 187-1160B |
topic_facet |
187-1154A 187-1155B 187-1160B DRILL Drilling/drill rig Indian Ocean Joides Resolution Leg187 Ocean Drilling Program ODP |
description |
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 change from an early seawater dominated fluid towards a sediment-dominated fluid as a result of an increase in sediment cover with increasing age of the seafloor. The progression from heavy d11B towards lighter values with increasing degrees of alteration may also reflect increased formation of clay minerals (e.g., saponite). A comparison of 238U/204Pb and 206Pb/204Pb in fresh glass and variably altered basalt from Site 1160B shows extreme variations that are caused by secondary U enrichment during low temperature alteration. Modeling of the U-Pb isotope system confirms that some alteration events occurred early in the 21.5 Ma history of these rocks, even though a significant second pulse of alteration happened at ~12 Ma after formation of the crust. The U-Pb systematics of co-genetic basaltic glass and variably low temperature altered basaltic whole rocks are thus a potential tool to place age constraints on the timing of alteration and fluid flow in the ocean crust. |
format |
Dataset |
author |
Krolikowska-Ciaglo, Sylwia Deyhle, Annette Hauff, Folkmar Hoernle, Kaj |
author_facet |
Krolikowska-Ciaglo, Sylwia Deyhle, Annette Hauff, Folkmar Hoernle, Kaj |
author_sort |
Krolikowska-Ciaglo, Sylwia |
title |
Chemical and isotopic compositions of altered MORB from ODP Holes 187-1154A, 187-1155B, and 187-1160B |
title_short |
Chemical and isotopic compositions of altered MORB from ODP Holes 187-1154A, 187-1155B, and 187-1160B |
title_full |
Chemical and isotopic compositions of altered MORB from ODP Holes 187-1154A, 187-1155B, and 187-1160B |
title_fullStr |
Chemical and isotopic compositions of altered MORB from ODP Holes 187-1154A, 187-1155B, and 187-1160B |
title_full_unstemmed |
Chemical and isotopic compositions of altered MORB from ODP Holes 187-1154A, 187-1155B, and 187-1160B |
title_sort |
chemical and isotopic compositions of altered morb from odp holes 187-1154a, 187-1155b, and 187-1160b |
publisher |
PANGAEA |
publishDate |
2007 |
url |
https://doi.pangaea.de/10.1594/PANGAEA.707365 https://doi.org/10.1594/PANGAEA.707365 |
op_coverage |
MEDIAN LATITUDE: -42.481413 * MEDIAN LONGITUDE: 131.435990 * SOUTH-BOUND LATITUDE: -44.008230 * WEST-BOUND LONGITUDE: 127.992360 * NORTH-BOUND LATITUDE: -41.477830 * EAST-BOUND LONGITUDE: 134.998350 * DATE/TIME START: 1999-12-01T19:00:00 * DATE/TIME END: 1999-12-24T06:00:00 |
long_lat |
ENVELOPE(124.000,124.000,-49.000,-49.000) ENVELOPE(127.992360,134.998350,-41.477830,-44.008230) |
geographic |
Antarctic Australian-Antarctic Discordance Indian Pacific |
geographic_facet |
Antarctic Australian-Antarctic Discordance Indian Pacific |
genre |
Antarc* Antarctic |
genre_facet |
Antarc* Antarctic |
op_source |
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, https://doi.org/10.1016/j.chemgeo.2007.05.004 |
op_relation |
https://doi.pangaea.de/10.1594/PANGAEA.707365 https://doi.org/10.1594/PANGAEA.707365 |
op_rights |
CC-BY-3.0: Creative Commons Attribution 3.0 Unported Access constraints: unrestricted info:eu-repo/semantics/openAccess |
op_rightsnorm |
CC-BY |
op_doi |
https://doi.org/10.1594/PANGAEA.707365 https://doi.org/10.1016/j.chemgeo.2007.05.004 |
_version_ |
1766163412239253504 |