The petrogenesis of the Kirwan Basalts of Dronning Maud Land, Antarctica
- Harris, Chris, Marsh, Julian S, Duncan, Andrew R, Erlank, Anthony J
- Authors: Harris, Chris , Marsh, Julian S , Duncan, Andrew R , Erlank, Anthony J
- Date: 1990
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/145472 , vital:38441 , https://doi.org/10.1093/petrology/31.2.341
- 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 (SiO2 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.
- Full Text: false
- Date Issued: 1990
- Authors: Harris, Chris , Marsh, Julian S , Duncan, Andrew R , Erlank, Anthony J
- Date: 1990
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/145472 , vital:38441 , https://doi.org/10.1093/petrology/31.2.341
- 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 (SiO2 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.
- Full Text: false
- Date Issued: 1990
Oxygen isotope geochemistry of the Mesozoic volcanics of the Etendeka Formation, Namibia
- Harris, Chris, Smith, H Stuart, Milner, Simon C, Erlank, Anthony J, Duncan, Andrew R, Marsh, Julian S, Ikin, Nicholas P
- Authors: Harris, Chris , Smith, H Stuart , Milner, Simon C , Erlank, Anthony J , Duncan, Andrew R , Marsh, Julian S , Ikin, Nicholas P
- Date: 1989
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/143272 , vital:38219 , https://doi.org/10.1007/BF00371087
- Description: The Etendeka Formation volcanics consist of a bimodal association of basalts and quartz latites. Forty three new whole rock oxygen isotope analyses are reported for all the major magma types. All the rocks except a minor suite of dolerites have higher δ18O values than normal mantle. The basic rocks (average of 29=8.8‰) have significantly different δ18O to the acid rocks (average of 10=14.4‰). These data are apparently consistent with previously published petrogenetic models, which propose that the basalts were affected by crustal contamination and that the quartz latites are crustally derived.
- Full Text: false
- Date Issued: 1989
- Authors: Harris, Chris , Smith, H Stuart , Milner, Simon C , Erlank, Anthony J , Duncan, Andrew R , Marsh, Julian S , Ikin, Nicholas P
- Date: 1989
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/143272 , vital:38219 , https://doi.org/10.1007/BF00371087
- Description: The Etendeka Formation volcanics consist of a bimodal association of basalts and quartz latites. Forty three new whole rock oxygen isotope analyses are reported for all the major magma types. All the rocks except a minor suite of dolerites have higher δ18O values than normal mantle. The basic rocks (average of 29=8.8‰) have significantly different δ18O to the acid rocks (average of 10=14.4‰). These data are apparently consistent with previously published petrogenetic models, which propose that the basalts were affected by crustal contamination and that the quartz latites are crustally derived.
- Full Text: false
- Date Issued: 1989
Tying up the continents
- Authors: Marsh, Julian S
- Date: 1989
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/143282 , vital:38220
- Full Text:
- Date Issued: 1989
- Authors: Marsh, Julian S
- Date: 1989
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/143282 , vital:38220
- Full Text:
- Date Issued: 1989
A laterally extensive geochemical discontinuity in the subcontinental Gondwana Lithosphere
- Erlank, Anthony J, Duncan, Andrew R, Marsh, Julian S, Sweeney, R J, Hawkesworth, C J, Milner, Simon C, Miller, R McG, Rogers, N W
- Authors: Erlank, Anthony J , Duncan, Andrew R , Marsh, Julian S , Sweeney, R J , Hawkesworth, C J , Milner, Simon C , Miller, R McG , Rogers, N W
- Date: 1988
- Language: English
- Type: text , abstracts
- Identifier: http://hdl.handle.net/10962/131678 , vital:36710
- Description: Cox et al. (1967) first delineated the existence of two major geochemical provinces in the Karoo basalts of southern Africa. Tholeiitic basalts in Zimbabwe are highly enriched in incompatible trace elements and constitute the "northern province". In contrast, basalts from Lesotho and from the southern segment of the Lebombo monocline have lower or “normal” abundances of these elements and were regarded as a "southern province'. Recent work has established that this change in composition takes place relatively rapidly in the Central Lebombo.
- Full Text:
- Date Issued: 1988
- Authors: Erlank, Anthony J , Duncan, Andrew R , Marsh, Julian S , Sweeney, R J , Hawkesworth, C J , Milner, Simon C , Miller, R McG , Rogers, N W
- Date: 1988
- Language: English
- Type: text , abstracts
- Identifier: http://hdl.handle.net/10962/131678 , vital:36710
- Description: Cox et al. (1967) first delineated the existence of two major geochemical provinces in the Karoo basalts of southern Africa. Tholeiitic basalts in Zimbabwe are highly enriched in incompatible trace elements and constitute the "northern province". In contrast, basalts from Lesotho and from the southern segment of the Lebombo monocline have lower or “normal” abundances of these elements and were regarded as a "southern province'. Recent work has established that this change in composition takes place relatively rapidly in the Central Lebombo.
- Full Text:
- Date Issued: 1988
Distribution and petrogenesis of the basic rocks of the Etendeka Formation of northwestern Namibia
- Marsh, Julian S, Duncan, Andrew R, Milner, Simon C, Erlank, Anthony J
- Authors: Marsh, Julian S , Duncan, Andrew R , Milner, Simon C , Erlank, Anthony J
- Date: 1988
- Language: English
- Type: text , abstracts
- Identifier: http://hdl.handle.net/10962/131667 , vital:36709
- Description: The igneous rocks which comprise the Etendeka Formation in northwestern Namibia cover an area of 78 000 km² and consist dominantly of interbedded basalts and quartz latites, with minor latites. They are spatially associated with, and intruded by, two suites of dolerites. The rocks of the Etendeka Formation are included in the Karoo Igneous Province but differ from most other Karoo volcanics with respect to their younger age (Cretaceous) and aspects of their mineralogy and geochemistry.
- Full Text:
- Date Issued: 1988
- Authors: Marsh, Julian S , Duncan, Andrew R , Milner, Simon C , Erlank, Anthony J
- Date: 1988
- Language: English
- Type: text , abstracts
- Identifier: http://hdl.handle.net/10962/131667 , vital:36709
- Description: The igneous rocks which comprise the Etendeka Formation in northwestern Namibia cover an area of 78 000 km² and consist dominantly of interbedded basalts and quartz latites, with minor latites. They are spatially associated with, and intruded by, two suites of dolerites. The rocks of the Etendeka Formation are included in the Karoo Igneous Province but differ from most other Karoo volcanics with respect to their younger age (Cretaceous) and aspects of their mineralogy and geochemistry.
- Full Text:
- Date Issued: 1988
The late Archaean Dominion Group, South Africa: petrogenesis of flood-type basalts and their mantle sources
- Marsh, Julian S, Rogers, N W, Bowen, M P, Bowen, T B
- Authors: Marsh, Julian S , Rogers, N W , Bowen, M P , Bowen, T B
- Date: 1988
- Language: English
- Type: text , abstracts
- Identifier: http://hdl.handle.net/10962/131690 , vital:36721
- Description: The Dominion group has an age of 2.7 - 2.8 Ga and is the earliest of the cover sequences overlying the granite greenstone terrane in the western part of the Archaean Kaapvaal Craton, southern Africa. The Dominion group is largely built of volcanic rocks and is preserved over an area of 15,000 km² with a maximum thickness of 2.7 km.
- Full Text:
- Date Issued: 1988
- Authors: Marsh, Julian S , Rogers, N W , Bowen, M P , Bowen, T B
- Date: 1988
- Language: English
- Type: text , abstracts
- Identifier: http://hdl.handle.net/10962/131690 , vital:36721
- Description: The Dominion group has an age of 2.7 - 2.8 Ga and is the earliest of the cover sequences overlying the granite greenstone terrane in the western part of the Archaean Kaapvaal Craton, southern Africa. The Dominion group is largely built of volcanic rocks and is preserved over an area of 15,000 km² with a maximum thickness of 2.7 km.
- Full Text:
- Date Issued: 1988
Some geochemical constraints upon models for the crystallization of the upper critical zone-main zone interval, northwestern Bushveld complex
- Eales, Hugh V, Marsh, Julian S, Mitchell, Andrew A, de Klerk, William J, Kruger, Floris J, Field, Matthew
- Authors: Eales, Hugh V , Marsh, Julian S , Mitchell, Andrew A , de Klerk, William J , Kruger, Floris J , Field, Matthew
- Date: 1986
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/136044 , vital:37331 , https://doi.org/10.1180/minmag.1986.050.358.03
- Description: Ratios between elements Mg, Fe, Co, Cr, Ni, V, and Sc are consistently different in mafic rocks of the upper critical zone, and those above the Bastard unit. Within the 300 m section above the Merensky Reef, 87Sr/86Sr ratios increase from c.0.7063 to c.0.7087, irrespective of rock type. Decoupling of Mg/(Mg + Fe2+) ratios and the Ca contents of plagioclase, and wide variations in the proportions of anorthosite within the Bastard, Merensky, and Merensky Footwall units, are inconsistent with anorthosite formation by simple fractional crystallization of magma batches of limited volume.
- Full Text:
- Date Issued: 1986
- Authors: Eales, Hugh V , Marsh, Julian S , Mitchell, Andrew A , de Klerk, William J , Kruger, Floris J , Field, Matthew
- Date: 1986
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/136044 , vital:37331 , https://doi.org/10.1180/minmag.1986.050.358.03
- Description: Ratios between elements Mg, Fe, Co, Cr, Ni, V, and Sc are consistently different in mafic rocks of the upper critical zone, and those above the Bastard unit. Within the 300 m section above the Merensky Reef, 87Sr/86Sr ratios increase from c.0.7063 to c.0.7087, irrespective of rock type. Decoupling of Mg/(Mg + Fe2+) ratios and the Ca contents of plagioclase, and wide variations in the proportions of anorthosite within the Bastard, Merensky, and Merensky Footwall units, are inconsistent with anorthosite formation by simple fractional crystallization of magma batches of limited volume.
- Full Text:
- Date Issued: 1986
The geochemistry of basic volcanics of the Dordabis Formation northeast of Dordabis and their significance for correlations within, and evolution of, the Rehoboth Magmatic Arc
- Marsh, Julian S, Williams-Jones, I E
- Authors: Marsh, Julian S , Williams-Jones, I E
- Date: 1985
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/69763 , vital:29577 , http://www.mme.gov.na/files/publications/95f_Williams-Jones and Marsh_Dordabis Fm.pdf
- Description: Gevers (1934) named the succession of quartzites, feld-spathic sandstones, massive conglomeratic arkoses and sedimentary breccias around Dordabis, the Dordabis Series. He considered this series to be of Nama age and the basic volcanics in the series to be post Nama, pre-Karoo eruptive diabase. Schalk (pers. comm.) has found the succession to be pre-Damara in age and possibly equivalent to the Sinclair Sequence. These ‘Dordabis Series’ rocks have since been incorrectly included into the Marienhof Formation of the Rehoboth Sequence on the 1980 1:1 000 000 Geological Map of SWA/Namibia. In this report, it is suggested that this succession be called the Dordabis Formation.
- Full Text:
- Date Issued: 1985
- Authors: Marsh, Julian S , Williams-Jones, I E
- Date: 1985
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/69763 , vital:29577 , http://www.mme.gov.na/files/publications/95f_Williams-Jones and Marsh_Dordabis Fm.pdf
- Description: Gevers (1934) named the succession of quartzites, feld-spathic sandstones, massive conglomeratic arkoses and sedimentary breccias around Dordabis, the Dordabis Series. He considered this series to be of Nama age and the basic volcanics in the series to be post Nama, pre-Karoo eruptive diabase. Schalk (pers. comm.) has found the succession to be pre-Damara in age and possibly equivalent to the Sinclair Sequence. These ‘Dordabis Series’ rocks have since been incorrectly included into the Marienhof Formation of the Rehoboth Sequence on the 1980 1:1 000 000 Geological Map of SWA/Namibia. In this report, it is suggested that this succession be called the Dordabis Formation.
- Full Text:
- Date Issued: 1985
The geochemistry of potassic lavas from Vulsini, central Italy and implications for mantle enrichment processes beneath the Roman region
- Rogers, N W, Hawkesworth, C J, Parker, R J, Marsh, Julian S
- Authors: Rogers, N W , Hawkesworth, C J , Parker, R J , Marsh, Julian S
- Date: 1985
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/136034 , vital:37330 , https://doi.org/10.1007/BF00378265
- Description: Major and trace element and 143Nd/144Nd (0.51209–0.51216) and 87Sr/86Sr (0.70879–0.71105) isotope analyses are presented on a representative group of lavas from the Vulsini district of the Roman magmatic province. Three distinct series are identified; the high-K and low-K series are similar to those described from other Italian volcanoes, while the third is represented by a group of relatively undifferentiated leucite basanites which are thought to be near-primary mantle melts.
- Full Text: false
- Date Issued: 1985
- Authors: Rogers, N W , Hawkesworth, C J , Parker, R J , Marsh, Julian S
- Date: 1985
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/136034 , vital:37330 , https://doi.org/10.1007/BF00378265
- Description: Major and trace element and 143Nd/144Nd (0.51209–0.51216) and 87Sr/86Sr (0.70879–0.71105) isotope analyses are presented on a representative group of lavas from the Vulsini district of the Roman magmatic province. Three distinct series are identified; the high-K and low-K series are similar to those described from other Italian volcanoes, while the third is represented by a group of relatively undifferentiated leucite basanites which are thought to be near-primary mantle melts.
- Full Text: false
- Date Issued: 1985
The mineralogy, petrology, and origin of the Merensky cyclic unit in the western Bushveld Complex
- Kruger, Floris J, Marsh, Julian S
- Authors: Kruger, Floris J , Marsh, Julian S
- Date: 1985
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/136024 , vital:37329 , https://doi.org/10.2113/gsecongeo.80.4.958
- Description: The Merensky cyclic unit of the Bushveld Complex represents the first products to crystallize after the influx and mixing of a large new batch of magma in the chamber. Excluding the Merensky pegmatoid, the Merensky cyclic unit grades upward from an orthopyroxenite at the base, through norite to anorthosite at the top of the sequence. It is followed by the very similar Bastard cyclic unit.
- Full Text: false
- Date Issued: 1985
- Authors: Kruger, Floris J , Marsh, Julian S
- Date: 1985
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/136024 , vital:37329 , https://doi.org/10.2113/gsecongeo.80.4.958
- Description: The Merensky cyclic unit of the Bushveld Complex represents the first products to crystallize after the influx and mixing of a large new batch of magma in the chamber. Excluding the Merensky pegmatoid, the Merensky cyclic unit grades upward from an orthopyroxenite at the base, through norite to anorthosite at the top of the sequence. It is followed by the very similar Bastard cyclic unit.
- Full Text: false
- Date Issued: 1985
Geochemistry and petrogenesis of the Etendeka volcanic rocks from SWA Namibia
- Erlank, Anthony J, Marsh, Julian S, Duncan, Andrew R, Miller, R M, Hawkesworth, C J, Betton, P J, Rex, D C
- Authors: Erlank, Anthony J , Marsh, Julian S , Duncan, Andrew R , Miller, R M , Hawkesworth, C J , Betton, P J , Rex, D C
- Date: 1984
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/133923 , vital:37041 , https://pascal-francis.inist.fr/vibad/index.php?action=getRecordDetailamp;idt=6519919
- Description: The volcanic rocks of the Etendeka Formation from north-west SWA/Namibia have a present-day coverage of 70,000 km² and comprise a series of interbedded basalts, latites and quartz latites, together with four varieties of intrusive dolerite. Apart from one group of dolerites (regional dolerites) which have mineralogical and geochemical similarities to the Lesotho Formation lavas from the Central area, the Etendeka volcanics differ from all other Karoo volcanics by virtue of their Cretaceous age, stratigraphy, mineralogy, geochemistry, and range in mineralogical, elemental and isotopic compositions for the basaltic rocks.
- Full Text:
- Date Issued: 1984
- Authors: Erlank, Anthony J , Marsh, Julian S , Duncan, Andrew R , Miller, R M , Hawkesworth, C J , Betton, P J , Rex, D C
- Date: 1984
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/133923 , vital:37041 , https://pascal-francis.inist.fr/vibad/index.php?action=getRecordDetailamp;idt=6519919
- Description: The volcanic rocks of the Etendeka Formation from north-west SWA/Namibia have a present-day coverage of 70,000 km² and comprise a series of interbedded basalts, latites and quartz latites, together with four varieties of intrusive dolerite. Apart from one group of dolerites (regional dolerites) which have mineralogical and geochemical similarities to the Lesotho Formation lavas from the Central area, the Etendeka volcanics differ from all other Karoo volcanics by virtue of their Cretaceous age, stratigraphy, mineralogy, geochemistry, and range in mineralogical, elemental and isotopic compositions for the basaltic rocks.
- Full Text:
- Date Issued: 1984
Geochemistry of Karoo basalts and dolerites in the northeastern Orange Free State: Recognition and origin of the new Karoo basalt magma types.
- Authors: Marsh, Julian S
- Date: 1984
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/71288 , vital:29830
- Description: One of the most significant results emerging from the Karoo Volcanics Project of the NGP ls the recognition of a number of geochemically distinct basalt magma types occurring within the lower part of the Karoo volcanic pile in the Northeastern Cape and Southern Lesotho.
- Full Text:
- Date Issued: 1984
- Authors: Marsh, Julian S
- Date: 1984
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/71288 , vital:29830
- Description: One of the most significant results emerging from the Karoo Volcanics Project of the NGP ls the recognition of a number of geochemically distinct basalt magma types occurring within the lower part of the Karoo volcanic pile in the Northeastern Cape and Southern Lesotho.
- Full Text:
- Date Issued: 1984
Karoo basalts of the Springbok Flats: geochemistry and correlation
- Authors: Marsh, Julian S
- Date: 1984
- Language: English
- Type: text , abstracts
- Identifier: http://hdl.handle.net/10962/131634 , vital:36706
- Description: Karoo basalts underlie an area of about 3750 km2 of the Springbok Flats. Four boreholes were logged and sampled for detailed petrographic and chemical analysis. The Springbok Flats basalt's chemical composition is compared with those of the Sabie River Formation of the Lebombo and the Lesotho type of the Central Karoo area. Sr- and Nd- isotopic data were also used in determining the chemical composition. The study also allows the geographical extent of the incompatible element-enriched clan of Karoo Lavas to be refined.
- Full Text:
- Date Issued: 1984
- Authors: Marsh, Julian S
- Date: 1984
- Language: English
- Type: text , abstracts
- Identifier: http://hdl.handle.net/10962/131634 , vital:36706
- Description: Karoo basalts underlie an area of about 3750 km2 of the Springbok Flats. Four boreholes were logged and sampled for detailed petrographic and chemical analysis. The Springbok Flats basalt's chemical composition is compared with those of the Sabie River Formation of the Lebombo and the Lesotho type of the Central Karoo area. Sr- and Nd- isotopic data were also used in determining the chemical composition. The study also allows the geographical extent of the incompatible element-enriched clan of Karoo Lavas to be refined.
- Full Text:
- Date Issued: 1984
Regional geochemistry of the Karoo igneous province
- Duncan, Andrew R, Erlank, Anthony J, Marsh, Julian S
- Authors: Duncan, Andrew R , Erlank, Anthony J , Marsh, Julian S
- Date: 1984
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/134154 , vital:37079 , https://inis.iaea.org/search/searchsinglerecord.aspx?recordsFor=SingleRecordamp;RN=15001076
- Description: The extrusive and intrusive rocks of the Karoo Igneous Province are dominantly of basaltic or rhyolitic (sensu lato) composition. There are, however, a considerable variety of other rock types within the province including picritic basalts, nephelinites, shoshonites, latites, andesites and dacites. This paper deals with the geochemistry of the Karoo igneous province.
- Full Text:
- Date Issued: 1984
- Authors: Duncan, Andrew R , Erlank, Anthony J , Marsh, Julian S
- Date: 1984
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/134154 , vital:37079 , https://inis.iaea.org/search/searchsinglerecord.aspx?recordsFor=SingleRecordamp;RN=15001076
- Description: The extrusive and intrusive rocks of the Karoo Igneous Province are dominantly of basaltic or rhyolitic (sensu lato) composition. There are, however, a considerable variety of other rock types within the province including picritic basalts, nephelinites, shoshonites, latites, andesites and dacites. This paper deals with the geochemistry of the Karoo igneous province.
- Full Text:
- Date Issued: 1984
Strontium isotope characterization of Karoo volcanic rocks
- Bristow, J W, Allsopp, H L, Erlank, Anthony J, Marsh, Julian S, Armstrong, R A
- Authors: Bristow, J W , Allsopp, H L , Erlank, Anthony J , Marsh, Julian S , Armstrong, R A
- Date: 1984
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/134176 , vital:37081 , https://pascal-francis.inist.fr/vibad/index.php?action=getRecordDetailamp;idt=6453595
- Description: Karoo volcanics of both mafic and felsic composition cover large areas of southern Africa, and are characterized by considerable ranges in their initial 87Sr/86Sr (i.e. Ro) ratios. Mafic volcanics from the eastern and western continental margins show the greatest range in Ro ratios, i.e. Lebombo-Nuanetsi area: 0.7035-0.7134 and Etendeka: 0.7030-0.7135 respectively. In the Central Karoo area the mafic rocks show a smaller spread of ratios: 0.7046-0.7094.
- Full Text:
- Date Issued: 1984
- Authors: Bristow, J W , Allsopp, H L , Erlank, Anthony J , Marsh, Julian S , Armstrong, R A
- Date: 1984
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/134176 , vital:37081 , https://pascal-francis.inist.fr/vibad/index.php?action=getRecordDetailamp;idt=6453595
- Description: Karoo volcanics of both mafic and felsic composition cover large areas of southern Africa, and are characterized by considerable ranges in their initial 87Sr/86Sr (i.e. Ro) ratios. Mafic volcanics from the eastern and western continental margins show the greatest range in Ro ratios, i.e. Lebombo-Nuanetsi area: 0.7035-0.7134 and Etendeka: 0.7030-0.7135 respectively. In the Central Karoo area the mafic rocks show a smaller spread of ratios: 0.7046-0.7094.
- Full Text:
- Date Issued: 1984
The chemistry and petrogenesis of igneous rocks of the Karoo central area, southern Africa
- Eales, Hugh V, Marsh, Julian S
- Authors: Eales, Hugh V , Marsh, Julian S
- Date: 1984
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/133934 , vital:37042 , https://pascal-francis.inist.fr/vibad/index.php?action=getRecordDetailamp;idt=6519911
- Description: Outcrops of the Jurassic Karoo basalts and dolerites in central South Africa are remnants of an intracratonic continental igneous suite whose volume probably once exceeded 1.5 x 106 km³. Basic rocks with 6-8% MgO, 50-55% Si02 and Mg-number = 53-67 are overwhelmingly dominant in the Central area suite. Application of discriminant analysis to a data set of major and trace element analyses of the basic rocks confirms field and petrographic evidence that a number of compositionally distinct basalt magma types exist in the Central area.
- Full Text:
- Date Issued: 1984
- Authors: Eales, Hugh V , Marsh, Julian S
- Date: 1984
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/133934 , vital:37042 , https://pascal-francis.inist.fr/vibad/index.php?action=getRecordDetailamp;idt=6519911
- Description: Outcrops of the Jurassic Karoo basalts and dolerites in central South Africa are remnants of an intracratonic continental igneous suite whose volume probably once exceeded 1.5 x 106 km³. Basic rocks with 6-8% MgO, 50-55% Si02 and Mg-number = 53-67 are overwhelmingly dominant in the Central area suite. Application of discriminant analysis to a data set of major and trace element analyses of the basic rocks confirms field and petrographic evidence that a number of compositionally distinct basalt magma types exist in the Central area.
- Full Text:
- Date Issued: 1984
The Karoo igneous province: an introduction
- Eales, Hugh V, Marsh, Julian S, Cox, K G
- Authors: Eales, Hugh V , Marsh, Julian S , Cox, K G
- Date: 1984
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/133945 , vital:37043 , http://pascal-francis.inist.fr/vibad/index.php?action=getRecordDetailamp;idt=6519910
- Description: The Karoo rocks are amongst the earliest manifestations of igneous activity accompanying the break-up of Gondwanaland during the early Mesozoic. Remnants of the once extensive lava sequence and the associated dolerite sills are found throughout southern Africa south of latitude 150S, the present outcrop being ca. 140,000 km². The main peak of volcanic activity is dated at about 190 m.y. and is probably coincident with the earliest stages of the opening of the Indian Ocean by the separation of Antarctica from southern Africa.
- Full Text:
- Date Issued: 1984
- Authors: Eales, Hugh V , Marsh, Julian S , Cox, K G
- Date: 1984
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/133945 , vital:37043 , http://pascal-francis.inist.fr/vibad/index.php?action=getRecordDetailamp;idt=6519910
- Description: The Karoo rocks are amongst the earliest manifestations of igneous activity accompanying the break-up of Gondwanaland during the early Mesozoic. Remnants of the once extensive lava sequence and the associated dolerite sills are found throughout southern Africa south of latitude 150S, the present outcrop being ca. 140,000 km². The main peak of volcanic activity is dated at about 190 m.y. and is probably coincident with the earliest stages of the opening of the Indian Ocean by the separation of Antarctica from southern Africa.
- Full Text:
- Date Issued: 1984
The role of continental lithosphere in the generation of the Karoo volcanic rocks: evidence from combined Nd-and Sr-isotope studies
- Hawkesworth, C J, Marsh, Julian S, Duncan, Andrew R, Erlank, Anthony J, Norry, M J
- Authors: Hawkesworth, C J , Marsh, Julian S , Duncan, Andrew R , Erlank, Anthony J , Norry, M J
- Date: 1984
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/134165 , vital:37080 , https://pascal-francis.inist.fr/vibad/index.php?action=getRecordDetailamp;idt=6453596
- Description: 143Nd/144Nd, 87Sr/86Sr, Sm and Nd analyses are reported on suites of Karoo volcanic rocks from the four sub-areas of Nuanetsi-north Lebombo, south Lebombo, the Central area, and north-west SWA/Namibia. Only seven (12%) of the samples analysed have positive ENd values similar to those found in the majority of recent mantle-derived rocks. Most of the rest have negative ENd (-1.0 to -17.1) and positive ESr, (+3.0 to +240) and thus must contain at least a contribution from source areas which were both old, and had lower Sm/Nd and higher Rh/Sr ratios than the bulk earth.
- Full Text:
- Date Issued: 1984
- Authors: Hawkesworth, C J , Marsh, Julian S , Duncan, Andrew R , Erlank, Anthony J , Norry, M J
- Date: 1984
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/134165 , vital:37080 , https://pascal-francis.inist.fr/vibad/index.php?action=getRecordDetailamp;idt=6453596
- Description: 143Nd/144Nd, 87Sr/86Sr, Sm and Nd analyses are reported on suites of Karoo volcanic rocks from the four sub-areas of Nuanetsi-north Lebombo, south Lebombo, the Central area, and north-west SWA/Namibia. Only seven (12%) of the samples analysed have positive ENd values similar to those found in the majority of recent mantle-derived rocks. Most of the rest have negative ENd (-1.0 to -17.1) and positive ESr, (+3.0 to +240) and thus must contain at least a contribution from source areas which were both old, and had lower Sm/Nd and higher Rh/Sr ratios than the bulk earth.
- Full Text:
- Date Issued: 1984
Al/Cr ratios of coexisting pyroxenes and spinellids in some ultramafic rocks
- Eales, Hugh V, Marsh, Julian S
- Authors: Eales, Hugh V , Marsh, Julian S
- Date: 1983
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/133534 , vital:36987 , https://doi.org/10.1016/0009-2541(83)90045-1
- Description: Al/Cr atomic ratios of coexisting spinellids and ortho- and clinopyroxenes show a pattern of sympathetic variation that persists through ultramafic rocks of layered mafic complexes of upper-crustal type, Alpine complexes, and the nodules found in kimberlites and alkaline basalts. Simple expressions are empirically derived to link (Al/Cr) orthopyroxene and (Al/Cr)spinel ratios in putatively equilibrated rocks. Equivalence of spinel compositions in shallow layered complexes and kimberlite nodules of deep-seated origin negates direct crystallochemical control of Al/Cr ratios of spinels by pressure.
- Full Text: false
- Date Issued: 1983
- Authors: Eales, Hugh V , Marsh, Julian S
- Date: 1983
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/133534 , vital:36987 , https://doi.org/10.1016/0009-2541(83)90045-1
- Description: Al/Cr atomic ratios of coexisting spinellids and ortho- and clinopyroxenes show a pattern of sympathetic variation that persists through ultramafic rocks of layered mafic complexes of upper-crustal type, Alpine complexes, and the nodules found in kimberlites and alkaline basalts. Simple expressions are empirically derived to link (Al/Cr) orthopyroxene and (Al/Cr)spinel ratios in putatively equilibrated rocks. Equivalence of spinel compositions in shallow layered complexes and kimberlite nodules of deep-seated origin negates direct crystallochemical control of Al/Cr ratios of spinels by pressure.
- Full Text: false
- Date Issued: 1983
Evolution of the continental lithosphere: evidence from volcanics and xenoliths in southern Africa
- Hawkesworth, C J, Erlank, Anthony J, Marsh, Julian S, Menzies, M A, Van Calsteren, Peter
- Authors: Hawkesworth, C J , Erlank, Anthony J , Marsh, Julian S , Menzies, M A , Van Calsteren, Peter
- Date: 1983
- Language: English
- Type: text , conference paper
- Identifier: http://hdl.handle.net/10962/133548 , vital:36989 , https://pascal-francis.inist.fr/vibad/index.php?action=getRecordDetailamp;idt=9641566
- Description: The geology of southern Africa offers a rare opportunity to study the evolution of a segment of continental lithosphere because its rocks range in age from 3.6 Ga to recent, and over the last 200 Ma both the upper mantle and the crust have been sampled by Karoo and Tertiary volcanism and as xenoliths in kimberlite pipes.
- Full Text:
- Date Issued: 1983
- Authors: Hawkesworth, C J , Erlank, Anthony J , Marsh, Julian S , Menzies, M A , Van Calsteren, Peter
- Date: 1983
- Language: English
- Type: text , conference paper
- Identifier: http://hdl.handle.net/10962/133548 , vital:36989 , https://pascal-francis.inist.fr/vibad/index.php?action=getRecordDetailamp;idt=9641566
- Description: The geology of southern Africa offers a rare opportunity to study the evolution of a segment of continental lithosphere because its rocks range in age from 3.6 Ga to recent, and over the last 200 Ma both the upper mantle and the crust have been sampled by Karoo and Tertiary volcanism and as xenoliths in kimberlite pipes.
- Full Text:
- Date Issued: 1983