Oceanic Material Recycled within the Sub-Patagonian Lithospheric Mantle (Cerro del Fraile, Argentina)
A detailed petrological study of mafic and ultramafic xenoliths from Cerro del Fraile (Southern Patagonia, Argentina) was developed to highlight (1) the mineralogical and geochemical composition of the lithospheric mantle beneath the area, (2) the nature of the metasomatizing agents that infiltrate...
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fthighwire:oai:open-archive.highwire.org:petrology:54/6/1211 2023-05-15T13:36:05+02:00 Oceanic Material Recycled within the Sub-Patagonian Lithospheric Mantle (Cerro del Fraile, Argentina) Faccini, B. Bonadiman, C. Coltorti, M. Grégoire, M. Siena, F. 2013-06-01 00:00:00.0 text/html http://petrology.oxfordjournals.org/cgi/content/short/54/6/1211 https://doi.org/10.1093/petrology/egt010 en eng Oxford University Press http://petrology.oxfordjournals.org/cgi/content/short/54/6/1211 http://dx.doi.org/10.1093/petrology/egt010 Copyright (C) 2013, Oxford University Press Original Papers TEXT 2013 fthighwire https://doi.org/10.1093/petrology/egt010 2013-05-28T10:55:35Z A detailed petrological study of mafic and ultramafic xenoliths from Cerro del Fraile (Southern Patagonia, Argentina) was developed to highlight (1) the mineralogical and geochemical composition of the lithospheric mantle beneath the area, (2) the nature of the metasomatizing agents that infiltrate the mantle wedge above the Antarctic plate, (3) the processes that allow the mantle to be refertilized, and (4) the nature of the material dragged down in the subduction zone and recycled within the South Patagonian sub-arc mantle. Major and trace element analyses of clinopyroxene and orthopyroxene in peridotitic and pyroxenitic rocks suggest that a proto-adakite, deriving from the melting of the subducting Antarctic plate, was responsible for the metasomatic features of the peridotitic rocks and the crystallization of the pyroxenites. A few composite xenoliths bridge the two processes—peridotite enrichment and pyroxenite crystallization—indicating that the variously depleted mantle reacts with the incoming melt to generate a newly fertile mantle domain. This reaction occurs under reducing conditions [Δlog f O 2 (QFM) –1·21 to –0·34], unusual for mantle wedge settings. Heavy rare earth elements and Al 2 O 3 and MgO contents in pyroxenes indicate a partial melting degree varying from 10 to 25%. The peculiar enrichment in Zr (–Hf), Th and U of the pyroxenes indicates the melting of oceanic sediments, which include manganese nodules and, possibly, organic matter, in agreement with the estimated low oxygen fugacity conditions. Some geochemical analogies have been found between the calculated metasomatic melts and the Austral Volcanic Zone adakites. In this case, the amount of sediment involved in the genesis of the infiltrating melts is larger than that previously proposed for the genesis of the erupted Patagonian adakites. Chemical–physical conditions favouring the upward percolation through the mantle wedge of these SiO 2 -rich and viscous melts are also discussed. Text Antarc* Antarctic HighWire Press (Stanford University) Antarctic The Antarctic Austral Patagonia Argentina Journal of Petrology 54 6 1211 1258 |
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HighWire Press (Stanford University) |
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fthighwire |
language |
English |
topic |
Original Papers |
spellingShingle |
Original Papers Faccini, B. Bonadiman, C. Coltorti, M. Grégoire, M. Siena, F. Oceanic Material Recycled within the Sub-Patagonian Lithospheric Mantle (Cerro del Fraile, Argentina) |
topic_facet |
Original Papers |
description |
A detailed petrological study of mafic and ultramafic xenoliths from Cerro del Fraile (Southern Patagonia, Argentina) was developed to highlight (1) the mineralogical and geochemical composition of the lithospheric mantle beneath the area, (2) the nature of the metasomatizing agents that infiltrate the mantle wedge above the Antarctic plate, (3) the processes that allow the mantle to be refertilized, and (4) the nature of the material dragged down in the subduction zone and recycled within the South Patagonian sub-arc mantle. Major and trace element analyses of clinopyroxene and orthopyroxene in peridotitic and pyroxenitic rocks suggest that a proto-adakite, deriving from the melting of the subducting Antarctic plate, was responsible for the metasomatic features of the peridotitic rocks and the crystallization of the pyroxenites. A few composite xenoliths bridge the two processes—peridotite enrichment and pyroxenite crystallization—indicating that the variously depleted mantle reacts with the incoming melt to generate a newly fertile mantle domain. This reaction occurs under reducing conditions [Δlog f O 2 (QFM) –1·21 to –0·34], unusual for mantle wedge settings. Heavy rare earth elements and Al 2 O 3 and MgO contents in pyroxenes indicate a partial melting degree varying from 10 to 25%. The peculiar enrichment in Zr (–Hf), Th and U of the pyroxenes indicates the melting of oceanic sediments, which include manganese nodules and, possibly, organic matter, in agreement with the estimated low oxygen fugacity conditions. Some geochemical analogies have been found between the calculated metasomatic melts and the Austral Volcanic Zone adakites. In this case, the amount of sediment involved in the genesis of the infiltrating melts is larger than that previously proposed for the genesis of the erupted Patagonian adakites. Chemical–physical conditions favouring the upward percolation through the mantle wedge of these SiO 2 -rich and viscous melts are also discussed. |
format |
Text |
author |
Faccini, B. Bonadiman, C. Coltorti, M. Grégoire, M. Siena, F. |
author_facet |
Faccini, B. Bonadiman, C. Coltorti, M. Grégoire, M. Siena, F. |
author_sort |
Faccini, B. |
title |
Oceanic Material Recycled within the Sub-Patagonian Lithospheric Mantle (Cerro del Fraile, Argentina) |
title_short |
Oceanic Material Recycled within the Sub-Patagonian Lithospheric Mantle (Cerro del Fraile, Argentina) |
title_full |
Oceanic Material Recycled within the Sub-Patagonian Lithospheric Mantle (Cerro del Fraile, Argentina) |
title_fullStr |
Oceanic Material Recycled within the Sub-Patagonian Lithospheric Mantle (Cerro del Fraile, Argentina) |
title_full_unstemmed |
Oceanic Material Recycled within the Sub-Patagonian Lithospheric Mantle (Cerro del Fraile, Argentina) |
title_sort |
oceanic material recycled within the sub-patagonian lithospheric mantle (cerro del fraile, argentina) |
publisher |
Oxford University Press |
publishDate |
2013 |
url |
http://petrology.oxfordjournals.org/cgi/content/short/54/6/1211 https://doi.org/10.1093/petrology/egt010 |
geographic |
Antarctic The Antarctic Austral Patagonia Argentina |
geographic_facet |
Antarctic The Antarctic Austral Patagonia Argentina |
genre |
Antarc* Antarctic |
genre_facet |
Antarc* Antarctic |
op_relation |
http://petrology.oxfordjournals.org/cgi/content/short/54/6/1211 http://dx.doi.org/10.1093/petrology/egt010 |
op_rights |
Copyright (C) 2013, Oxford University Press |
op_doi |
https://doi.org/10.1093/petrology/egt010 |
container_title |
Journal of Petrology |
container_volume |
54 |
container_issue |
6 |
container_start_page |
1211 |
op_container_end_page |
1258 |
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1766074107073396736 |