Halogens in the mantle beneath the North Atlantic
F, Cl and Br contents of tholeiitic volcanic glasses dredged along the Mid-Atlantic Ridge from 53° to 28° N, including the transect over the Azores Plateau, are reported. The halogen variations parallel those of 87 Sr/ 86 Sr, La/Sm or other incompatible elements of varying volatility. The latitudina...
Published in: | Philosophical Transactions of the Royal Society of London. Series A, Mathematical and Physical Sciences |
---|---|
Format: | Article in Journal/Newspaper |
Language: | English |
Published: |
The Royal Society
1980
|
Subjects: | |
Online Access: | http://dx.doi.org/10.1098/rsta.1980.0208 https://royalsocietypublishing.org/doi/pdf/10.1098/rsta.1980.0208 |
id |
crroyalsociety:10.1098/rsta.1980.0208 |
---|---|
record_format |
openpolar |
spelling |
crroyalsociety:10.1098/rsta.1980.0208 2024-06-23T07:55:05+00:00 Halogens in the mantle beneath the North Atlantic 1980 http://dx.doi.org/10.1098/rsta.1980.0208 https://royalsocietypublishing.org/doi/pdf/10.1098/rsta.1980.0208 en eng The Royal Society https://royalsociety.org/journals/ethics-policies/data-sharing-mining/ Philosophical Transactions of the Royal Society of London. Series A, Mathematical and Physical Sciences volume 297, issue 1431, page 147-178 ISSN 0080-4614 2054-0272 journal-article 1980 crroyalsociety https://doi.org/10.1098/rsta.1980.0208 2024-06-04T06:22:55Z F, Cl and Br contents of tholeiitic volcanic glasses dredged along the Mid-Atlantic Ridge from 53° to 28° N, including the transect over the Azores Plateau, are reported. The halogen variations parallel those of 87 Sr/ 86 Sr, La/Sm or other incompatible elements of varying volatility. The latitudinal halogen variation pattern is not obliterated if only Mg-rich lavas are considered. Variations in extent of low-pressure fractional crystallization or partial melting conditions do not appear to be the primary cause of the halogen variations. Instead, mantle-derived heterogeneities in halogens, with major enrichments in the mantle beneath the Azores, are suggested. The Azores platform is not only a ‘hotspot’ but also a ‘wetspot’, which may explain the unusually intense Azores volcanic activity. The magnitude of the halogen and incompatible element enrichments beneath the Azores appear strongly dependent on the size of these anions and cations, but independent of relative volatility at low pressure. The large anions Cl and Br behave similarly to large cations Rb, Cs and Ba, and the smaller anion F similarly to Sr and P. Processes involving crystal and liquid (fluid and/or melt), CO 2 rather than H 2 O dominated, seem to have produced these largescale mantle heterogeneities. Geochemical ‘anomalies’ beneath the Azores are no longer apparent for coherent element pair ratios of similar ionic size. Values of such ‘unfractionated’ coherent trace element ratios provide an indication of the mantle composition and its nature before fractionation event (s) which produced the inferred isotopic and trace element heterogeneities apparently present beneath the North Atlantic. The relative trace element composition of this precursor mantle does not resemble that of carbonaceous chondrites except for refractory trace element pairs of similar ionic size. It is strongly depleted in halogens, and to a lesser extent in large alkali ions Rb and Cs relative to refractory Ba. These relative depletions are comparable within a factor of 5 to ... Article in Journal/Newspaper North Atlantic The Royal Society Mid-Atlantic Ridge Philosophical Transactions of the Royal Society of London. Series A, Mathematical and Physical Sciences 297 1431 147 178 |
institution |
Open Polar |
collection |
The Royal Society |
op_collection_id |
crroyalsociety |
language |
English |
description |
F, Cl and Br contents of tholeiitic volcanic glasses dredged along the Mid-Atlantic Ridge from 53° to 28° N, including the transect over the Azores Plateau, are reported. The halogen variations parallel those of 87 Sr/ 86 Sr, La/Sm or other incompatible elements of varying volatility. The latitudinal halogen variation pattern is not obliterated if only Mg-rich lavas are considered. Variations in extent of low-pressure fractional crystallization or partial melting conditions do not appear to be the primary cause of the halogen variations. Instead, mantle-derived heterogeneities in halogens, with major enrichments in the mantle beneath the Azores, are suggested. The Azores platform is not only a ‘hotspot’ but also a ‘wetspot’, which may explain the unusually intense Azores volcanic activity. The magnitude of the halogen and incompatible element enrichments beneath the Azores appear strongly dependent on the size of these anions and cations, but independent of relative volatility at low pressure. The large anions Cl and Br behave similarly to large cations Rb, Cs and Ba, and the smaller anion F similarly to Sr and P. Processes involving crystal and liquid (fluid and/or melt), CO 2 rather than H 2 O dominated, seem to have produced these largescale mantle heterogeneities. Geochemical ‘anomalies’ beneath the Azores are no longer apparent for coherent element pair ratios of similar ionic size. Values of such ‘unfractionated’ coherent trace element ratios provide an indication of the mantle composition and its nature before fractionation event (s) which produced the inferred isotopic and trace element heterogeneities apparently present beneath the North Atlantic. The relative trace element composition of this precursor mantle does not resemble that of carbonaceous chondrites except for refractory trace element pairs of similar ionic size. It is strongly depleted in halogens, and to a lesser extent in large alkali ions Rb and Cs relative to refractory Ba. These relative depletions are comparable within a factor of 5 to ... |
format |
Article in Journal/Newspaper |
title |
Halogens in the mantle beneath the North Atlantic |
spellingShingle |
Halogens in the mantle beneath the North Atlantic |
title_short |
Halogens in the mantle beneath the North Atlantic |
title_full |
Halogens in the mantle beneath the North Atlantic |
title_fullStr |
Halogens in the mantle beneath the North Atlantic |
title_full_unstemmed |
Halogens in the mantle beneath the North Atlantic |
title_sort |
halogens in the mantle beneath the north atlantic |
publisher |
The Royal Society |
publishDate |
1980 |
url |
http://dx.doi.org/10.1098/rsta.1980.0208 https://royalsocietypublishing.org/doi/pdf/10.1098/rsta.1980.0208 |
geographic |
Mid-Atlantic Ridge |
geographic_facet |
Mid-Atlantic Ridge |
genre |
North Atlantic |
genre_facet |
North Atlantic |
op_source |
Philosophical Transactions of the Royal Society of London. Series A, Mathematical and Physical Sciences volume 297, issue 1431, page 147-178 ISSN 0080-4614 2054-0272 |
op_rights |
https://royalsociety.org/journals/ethics-policies/data-sharing-mining/ |
op_doi |
https://doi.org/10.1098/rsta.1980.0208 |
container_title |
Philosophical Transactions of the Royal Society of London. Series A, Mathematical and Physical Sciences |
container_volume |
297 |
container_issue |
1431 |
container_start_page |
147 |
op_container_end_page |
178 |
_version_ |
1802647500457246720 |