Mixed pyroxenite-peridotite sources for mafic and ultramafic dikes from the Antarctic segment of the Karoo continental flood basalt province
Primitive rocks that are related to continental flood basalts are rare, but often reveal crucial information on the ultimate sources of these huge outpourings of mantle-derived magma. Here we present mineral chemical data for mafic and ultramafic dikes from the Antarctic extension of the Jurassic (~...
Published in: | Lithos |
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Main Authors: | , , , |
Other Authors: | , , |
Format: | Article in Journal/Newspaper |
Language: | English |
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Elsevier Scientific Publ. Co
2014
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Subjects: | |
Online Access: | http://hdl.handle.net/10138/136189 |
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ftunivhelsihelda:oai:helda.helsinki.fi:10138/136189 |
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record_format |
openpolar |
institution |
Open Polar |
collection |
HELDA – University of Helsinki Open Repository |
op_collection_id |
ftunivhelsihelda |
language |
English |
topic |
Other natural sciences LARGE IGNEOUS PROVINCE MAGMATISM FLOOD BASALTS PYROXENITE MANTLE KAROO IGNEOUS PROVINCE KAROO MAGMATISM Geosciences |
spellingShingle |
Other natural sciences LARGE IGNEOUS PROVINCE MAGMATISM FLOOD BASALTS PYROXENITE MANTLE KAROO IGNEOUS PROVINCE KAROO MAGMATISM Geosciences Heinonen, Jussi S. Luttinen, Arto V. Riley, Teal R. Michallik, Radoslaw M. Mixed pyroxenite-peridotite sources for mafic and ultramafic dikes from the Antarctic segment of the Karoo continental flood basalt province |
topic_facet |
Other natural sciences LARGE IGNEOUS PROVINCE MAGMATISM FLOOD BASALTS PYROXENITE MANTLE KAROO IGNEOUS PROVINCE KAROO MAGMATISM Geosciences |
description |
Primitive rocks that are related to continental flood basalts are rare, but often reveal crucial information on the ultimate sources of these huge outpourings of mantle-derived magma. Here we present mineral chemical data for mafic and ultramafic dikes from the Antarctic extension of the Jurassic (~180 Ma) Karoo continental flood basalt province that was emplaced during the initial stages of the breakup of the Gondwana supercontinent. We concentrate on two previously recognized high-Ti dike rock suites (Group 3 and Group 4) that exhibit high MgO contents (up to 22 wt. %). Both groups are characterized by Mg-rich olivine phenocrysts (up to Fo90) that are not mantle xenocrysts and indicate derivation from relatively Mg-rich parental magmas. Orthopyroxene is a common phenocryst and groundmass phase indicating emplacement at mid-crustal pressures (2–5 kbar; depth of ~10–20 km). The parental magmas of Group 3 and Group 4 dikes can be associated with pyroxenite sources on the basis of high olivine NiO, high whole-rock Zn/Fe, and low whole-rock CaO. In the case of Group 3 dikes, however, the samples that contain the most Mg-rich olivine also exhibit the mildest pyroxenite fingerprint and indications of an additional olivine-bearing (peridotitic) source component. We propose that the pyroxenite fingerprint of Group 3 and Group 4 dikes reflects relatively low-degree melting of fertile mantle at high pressures beneath the thick and cold Gondwanan lithosphere. Such conditions limited high-degree melting of peridotite sources which may have been predominant in the generation of the Karoo low-Ti basalts within lithospheric thinning zones. Primitive rocks that are related to continental flood basalts are rare, but often reveal crucial information on the ultimate sources of these huge outpourings of mantle-derived magma. Here we present mineral chemical data for mafic and ultramafic dikes from the Antarctic extension of the Jurassic (~180 Ma) Karoo continental flood basalt province that was emplaced during the initial stages ... |
author2 |
Finnish Museum of Natural History Earth Sciences Unit Department of Geosciences and Geography |
format |
Article in Journal/Newspaper |
author |
Heinonen, Jussi S. Luttinen, Arto V. Riley, Teal R. Michallik, Radoslaw M. |
author_facet |
Heinonen, Jussi S. Luttinen, Arto V. Riley, Teal R. Michallik, Radoslaw M. |
author_sort |
Heinonen, Jussi S. |
title |
Mixed pyroxenite-peridotite sources for mafic and ultramafic dikes from the Antarctic segment of the Karoo continental flood basalt province |
title_short |
Mixed pyroxenite-peridotite sources for mafic and ultramafic dikes from the Antarctic segment of the Karoo continental flood basalt province |
title_full |
Mixed pyroxenite-peridotite sources for mafic and ultramafic dikes from the Antarctic segment of the Karoo continental flood basalt province |
title_fullStr |
Mixed pyroxenite-peridotite sources for mafic and ultramafic dikes from the Antarctic segment of the Karoo continental flood basalt province |
title_full_unstemmed |
Mixed pyroxenite-peridotite sources for mafic and ultramafic dikes from the Antarctic segment of the Karoo continental flood basalt province |
title_sort |
mixed pyroxenite-peridotite sources for mafic and ultramafic dikes from the antarctic segment of the karoo continental flood basalt province |
publisher |
Elsevier Scientific Publ. Co |
publishDate |
2014 |
url |
http://hdl.handle.net/10138/136189 |
genre |
Antarc* Antarctic Antarktis* |
genre_facet |
Antarc* Antarctic Antarktis* |
op_relation |
10.1016/j.lithos.2013.05.015 The comments of Sally Gibson and an anonymous reviewer, and the editorial remarks by Andrew Kerr helped to improve the content and readability of the manuscript and are highly appreciated. The field and air operations staff at Halley Base during 2000-2001 are thanked for their support. Lassi Pakkanen and Bo Johanson are thanked for their generous support in using the instruments at GTK. Matti Poutiainen is thanked for technical support in using the point counter. Some of the diagrams have been produced with the help of the GCDkit software (Janousek et al., 2006). Our research is funded by the Academy of Finland (Grant no. 252652). Heinonen , J S , Luttinen , A V , Riley , T R & Michallik , R M 2013 , ' Mixed pyroxenite-peridotite sources for mafic and ultramafic dikes from the Antarctic segment of the Karoo continental flood basalt province ' , Lithos , vol. 177 , pp. 366-380 . https://doi.org/10.1016/j.lithos.2013.05.015 ORCID: /0000-0002-3129-0392/work/30885312 ORCID: /0000-0001-8998-4357/work/32341627 http://hdl.handle.net/10138/136189 6a21d24c-a038-480d-90d7-8ff8e73c720d 84883055024 000324721000023 |
op_rights |
info:eu-repo/semantics/openAccess openAccess |
container_title |
Lithos |
container_volume |
177 |
container_start_page |
366 |
op_container_end_page |
380 |
_version_ |
1810289517982121984 |
spelling |
ftunivhelsihelda:oai:helda.helsinki.fi:10138/136189 2024-09-15T17:48:22+00:00 Mixed pyroxenite-peridotite sources for mafic and ultramafic dikes from the Antarctic segment of the Karoo continental flood basalt province Sekoittuneet pyrokseniitti-peridotiitti vaippalähteet mafisille ja ultramafisille juonille Karoon laakiobasalttiprovinssin Antarktisesta osasta Heinonen, Jussi S. Luttinen, Arto V. Riley, Teal R. Michallik, Radoslaw M. Finnish Museum of Natural History Earth Sciences Unit Department of Geosciences and Geography 2014-10-17T21:13:18Z 15 application/pdf http://hdl.handle.net/10138/136189 eng eng Elsevier Scientific Publ. Co 10.1016/j.lithos.2013.05.015 The comments of Sally Gibson and an anonymous reviewer, and the editorial remarks by Andrew Kerr helped to improve the content and readability of the manuscript and are highly appreciated. The field and air operations staff at Halley Base during 2000-2001 are thanked for their support. Lassi Pakkanen and Bo Johanson are thanked for their generous support in using the instruments at GTK. Matti Poutiainen is thanked for technical support in using the point counter. Some of the diagrams have been produced with the help of the GCDkit software (Janousek et al., 2006). Our research is funded by the Academy of Finland (Grant no. 252652). Heinonen , J S , Luttinen , A V , Riley , T R & Michallik , R M 2013 , ' Mixed pyroxenite-peridotite sources for mafic and ultramafic dikes from the Antarctic segment of the Karoo continental flood basalt province ' , Lithos , vol. 177 , pp. 366-380 . https://doi.org/10.1016/j.lithos.2013.05.015 ORCID: /0000-0002-3129-0392/work/30885312 ORCID: /0000-0001-8998-4357/work/32341627 http://hdl.handle.net/10138/136189 6a21d24c-a038-480d-90d7-8ff8e73c720d 84883055024 000324721000023 info:eu-repo/semantics/openAccess openAccess Other natural sciences LARGE IGNEOUS PROVINCE MAGMATISM FLOOD BASALTS PYROXENITE MANTLE KAROO IGNEOUS PROVINCE KAROO MAGMATISM Geosciences Article acceptedVersion 2014 ftunivhelsihelda 2024-06-25T14:22:46Z Primitive rocks that are related to continental flood basalts are rare, but often reveal crucial information on the ultimate sources of these huge outpourings of mantle-derived magma. Here we present mineral chemical data for mafic and ultramafic dikes from the Antarctic extension of the Jurassic (~180 Ma) Karoo continental flood basalt province that was emplaced during the initial stages of the breakup of the Gondwana supercontinent. We concentrate on two previously recognized high-Ti dike rock suites (Group 3 and Group 4) that exhibit high MgO contents (up to 22 wt. %). Both groups are characterized by Mg-rich olivine phenocrysts (up to Fo90) that are not mantle xenocrysts and indicate derivation from relatively Mg-rich parental magmas. Orthopyroxene is a common phenocryst and groundmass phase indicating emplacement at mid-crustal pressures (2–5 kbar; depth of ~10–20 km). The parental magmas of Group 3 and Group 4 dikes can be associated with pyroxenite sources on the basis of high olivine NiO, high whole-rock Zn/Fe, and low whole-rock CaO. In the case of Group 3 dikes, however, the samples that contain the most Mg-rich olivine also exhibit the mildest pyroxenite fingerprint and indications of an additional olivine-bearing (peridotitic) source component. We propose that the pyroxenite fingerprint of Group 3 and Group 4 dikes reflects relatively low-degree melting of fertile mantle at high pressures beneath the thick and cold Gondwanan lithosphere. Such conditions limited high-degree melting of peridotite sources which may have been predominant in the generation of the Karoo low-Ti basalts within lithospheric thinning zones. Primitive rocks that are related to continental flood basalts are rare, but often reveal crucial information on the ultimate sources of these huge outpourings of mantle-derived magma. Here we present mineral chemical data for mafic and ultramafic dikes from the Antarctic extension of the Jurassic (~180 Ma) Karoo continental flood basalt province that was emplaced during the initial stages ... Article in Journal/Newspaper Antarc* Antarctic Antarktis* HELDA – University of Helsinki Open Repository Lithos 177 366 380 |