The Petrogenesis of the Kirwan Basalts of Dronning Maud Land, Antarctica
The 420 m thick sequence of Kirwan basalt crops out along the southernmost 50 km of the Kirwanveggen Escarpment (74�S, 6�W). There is little variation in major element chemistry of these basalts (SiO 2 49�3–51�6 wt.%; MgO 5�1–6�6 wt.%), but the concentrations of certain incompatible elements (e.g.,...
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1990
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fthighwire:oai:open-archive.highwire.org:petrology:31/2/341 2023-05-15T13:48:22+02:00 The Petrogenesis of the Kirwan Basalts of Dronning Maud Land, Antarctica HARRIS, CHRIS MARSH, JULIAN S. DUNCAN, ANDREW R. ERLANK, ANTHONY J. 1990-04-01 00:00:00.0 text/html http://petrology.oxfordjournals.org/cgi/content/short/31/2/341 https://doi.org/10.1093/petrology/31.2.341 en eng Oxford University Press http://petrology.oxfordjournals.org/cgi/content/short/31/2/341 http://dx.doi.org/10.1093/petrology/31.2.341 Copyright (C) 1990, Oxford University Press Articles TEXT 1990 fthighwire https://doi.org/10.1093/petrology/31.2.341 2013-05-26T23:10:18Z The 420 m thick sequence of Kirwan basalt crops out along the southernmost 50 km of the Kirwanveggen Escarpment (74�S, 6�W). There is little variation in major element chemistry of these basalts (SiO 2 49�3–51�6 wt.%; MgO 5�1–6�6 wt.%), but the concentrations of certain incompatible elements (e.g., Zr) vary by factors of approximately two or more. Most interelement plots show rather poor correlation ( r <0�78), but rocks from opposite ends of the data array can be related by 30% fractionation of plagioclase, clinopyroxene, olivine, and magnetite in the proportions 51:35:11:3. Plagioclase is much more abundant in phenocryst assemblages (85%) and it appears that selective transport of plagioclase to the surface occurred. The range in incompatible element concentrations cannot be explained by crystal fractionation and is most probably a result of the parent liquids of these basalts being derived by slightly different degrees of partial melting of a common source, or alternatively of open-system (RTF) magma processes. The strontium isotope data for the freshest rocks ( R 0 =0�7049–0�7065) may be explained by ∼7% contamination by crustal material with an R 0 of 0�709 and bulk Sr of∼800 ppm, but there is little supporting evidence from other trace element variations for this hypothesis. Oxygen isotope determinations on whole-rock-plagioclase pairs show that alteration has resulted in a 0�5%o shift in (δ18O. Alteration also appears to have resulted in a greater spread of data, particularly for the LIL elements and Sr isotopes. The Sr and Nd isotopic composition of the suite is close to bulk Earth at 172 Ma and this, together with REE and other trace element data, shows these basalts to be similar in composition to the more primitive basalts among the Karoo basalt lavas. It is suggested that the Kirwan basalts were derived from a source which was similar to that of the southern Lebombo variant of the Sabie River Basalt Formation of the Karoo Volcanic Province. This part of the Karoo was closest to the Kirwanveggen ... Text Antarc* Antarctica Dronning Maud Land HighWire Press (Stanford University) Dronning Maud Land Kirwanveggen ENVELOPE(-3.500,-3.500,-73.500,-73.500) Journal of Petrology 31 2 341 369 |
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Articles HARRIS, CHRIS MARSH, JULIAN S. DUNCAN, ANDREW R. ERLANK, ANTHONY J. The Petrogenesis of the Kirwan Basalts of Dronning Maud Land, Antarctica |
topic_facet |
Articles |
description |
The 420 m thick sequence of Kirwan basalt crops out along the southernmost 50 km of the Kirwanveggen Escarpment (74�S, 6�W). There is little variation in major element chemistry of these basalts (SiO 2 49�3–51�6 wt.%; MgO 5�1–6�6 wt.%), but the concentrations of certain incompatible elements (e.g., Zr) vary by factors of approximately two or more. Most interelement plots show rather poor correlation ( r <0�78), but rocks from opposite ends of the data array can be related by 30% fractionation of plagioclase, clinopyroxene, olivine, and magnetite in the proportions 51:35:11:3. Plagioclase is much more abundant in phenocryst assemblages (85%) and it appears that selective transport of plagioclase to the surface occurred. The range in incompatible element concentrations cannot be explained by crystal fractionation and is most probably a result of the parent liquids of these basalts being derived by slightly different degrees of partial melting of a common source, or alternatively of open-system (RTF) magma processes. The strontium isotope data for the freshest rocks ( R 0 =0�7049–0�7065) may be explained by ∼7% contamination by crustal material with an R 0 of 0�709 and bulk Sr of∼800 ppm, but there is little supporting evidence from other trace element variations for this hypothesis. Oxygen isotope determinations on whole-rock-plagioclase pairs show that alteration has resulted in a 0�5%o shift in (δ18O. Alteration also appears to have resulted in a greater spread of data, particularly for the LIL elements and Sr isotopes. The Sr and Nd isotopic composition of the suite is close to bulk Earth at 172 Ma and this, together with REE and other trace element data, shows these basalts to be similar in composition to the more primitive basalts among the Karoo basalt lavas. It is suggested that the Kirwan basalts were derived from a source which was similar to that of the southern Lebombo variant of the Sabie River Basalt Formation of the Karoo Volcanic Province. This part of the Karoo was closest to the Kirwanveggen ... |
format |
Text |
author |
HARRIS, CHRIS MARSH, JULIAN S. DUNCAN, ANDREW R. ERLANK, ANTHONY J. |
author_facet |
HARRIS, CHRIS MARSH, JULIAN S. DUNCAN, ANDREW R. ERLANK, ANTHONY J. |
author_sort |
HARRIS, CHRIS |
title |
The Petrogenesis of the Kirwan Basalts of Dronning Maud Land, Antarctica |
title_short |
The Petrogenesis of the Kirwan Basalts of Dronning Maud Land, Antarctica |
title_full |
The Petrogenesis of the Kirwan Basalts of Dronning Maud Land, Antarctica |
title_fullStr |
The Petrogenesis of the Kirwan Basalts of Dronning Maud Land, Antarctica |
title_full_unstemmed |
The Petrogenesis of the Kirwan Basalts of Dronning Maud Land, Antarctica |
title_sort |
petrogenesis of the kirwan basalts of dronning maud land, antarctica |
publisher |
Oxford University Press |
publishDate |
1990 |
url |
http://petrology.oxfordjournals.org/cgi/content/short/31/2/341 https://doi.org/10.1093/petrology/31.2.341 |
long_lat |
ENVELOPE(-3.500,-3.500,-73.500,-73.500) |
geographic |
Dronning Maud Land Kirwanveggen |
geographic_facet |
Dronning Maud Land Kirwanveggen |
genre |
Antarc* Antarctica Dronning Maud Land |
genre_facet |
Antarc* Antarctica Dronning Maud Land |
op_relation |
http://petrology.oxfordjournals.org/cgi/content/short/31/2/341 http://dx.doi.org/10.1093/petrology/31.2.341 |
op_rights |
Copyright (C) 1990, Oxford University Press |
op_doi |
https://doi.org/10.1093/petrology/31.2.341 |
container_title |
Journal of Petrology |
container_volume |
31 |
container_issue |
2 |
container_start_page |
341 |
op_container_end_page |
369 |
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1766249192057995264 |