The Klinghardt phonolites, South West Africa: Tertiary volcanism in western southern Africa
- Authors: Marsh, Julian S , Lock, B E
- Date: 1975
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/70164 , vital:29627
- Description: Over 1OO phonolite bodies of mid-Tertiary age occur in the Klinghardt Mountains, 1OO km SE of Luderitz in Southern South West Africa the only published account of these rocks is that of Kaiser (1926) who gives a generalized map and describes briefly the mode of occurrence and petrography of the phonolites. The phonolite bodies are concentrated in an area roughly 8OO km2 and constitute an excellent example of an areal volcanic field (Rittmann, 1962), i.e. the activity occurred at a number of vents spread over a wide area and in most cases only a single eruptive episode took place at each vent.
- Full Text:
- Date Issued: 1975
- Authors: Marsh, Julian S , Lock, B E
- Date: 1975
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/70164 , vital:29627
- Description: Over 1OO phonolite bodies of mid-Tertiary age occur in the Klinghardt Mountains, 1OO km SE of Luderitz in Southern South West Africa the only published account of these rocks is that of Kaiser (1926) who gives a generalized map and describes briefly the mode of occurrence and petrography of the phonolites. The phonolite bodies are concentrated in an area roughly 8OO km2 and constitute an excellent example of an areal volcanic field (Rittmann, 1962), i.e. the activity occurred at a number of vents spread over a wide area and in most cases only a single eruptive episode took place at each vent.
- Full Text:
- Date Issued: 1975
The Luderitz Alkaline Province, South West Africa I: descriptive petrology of the Granitberg Foyaite Complex
- Authors: Marsh, Julian S
- Date: 1975
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/132951 , vital:36912
- Description: The Granitberg foyaite complex is one of three known alkaline igneous complexes, which, together with a dyke swarm, constitute the Liüderitz Alkaline Province of Lower Cretaceous age. The near-circular complex is emplaced into dolomites and sandstones of the Bogenfels Formation. A large fragment of these sedimentary rocks, originally forming the roof of the intrusion, is preserved in the centre of the complex.
- Full Text:
- Date Issued: 1975
- Authors: Marsh, Julian S
- Date: 1975
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/132951 , vital:36912
- Description: The Granitberg foyaite complex is one of three known alkaline igneous complexes, which, together with a dyke swarm, constitute the Liüderitz Alkaline Province of Lower Cretaceous age. The near-circular complex is emplaced into dolomites and sandstones of the Bogenfels Formation. A large fragment of these sedimentary rocks, originally forming the roof of the intrusion, is preserved in the centre of the complex.
- Full Text:
- Date Issued: 1975
The Luderitz Alkaline Province, South West Africa II: metasomatism and assimilation in the contact aureole of the Granitberg Foyaite Complex
- Authors: Marsh, Julian S
- Date: 1975
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/132963 , vital:36913
- Description: Reactions between the Outer Foyaite magma of the Granitberg Complex and the sedimentary country rocks are striking. At sandstone contacts the magma has assimilated quartz-rich sedimentary material and a suite of pulaskites, peralkaline nordmarkites, and peralkaline granites have been generated by a complex process involving both assimilation and crystal fractionation.
- Full Text:
- Date Issued: 1975
- Authors: Marsh, Julian S
- Date: 1975
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/132963 , vital:36913
- Description: Reactions between the Outer Foyaite magma of the Granitberg Complex and the sedimentary country rocks are striking. At sandstone contacts the magma has assimilated quartz-rich sedimentary material and a suite of pulaskites, peralkaline nordmarkites, and peralkaline granites have been generated by a complex process involving both assimilation and crystal fractionation.
- Full Text:
- Date Issued: 1975
The Lüderitz alkaline province, South West Africa, III: the Pomona and Drachenberg Syenite Complexes
- Authors: Marsh, Julian S
- Date: 1976
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/132984 , vital:36915 , https://hdl.handle.net/10520/AJA10120750_2853
- Description: The Pomona ring complex consists of several intrusive masses of syenitic magma that define a differentiation trend towards silica oversaturation. Volume relations, sequence of intrusion, and broad chemical characteristics are consistent with the syenites being derived by feldspar fractionation from an immediate syenitic parent. A plug of nepheline syenite and tinguaite dykes indicate the availability of silica-undersaturated magma generally in the Luderitz Province.
- Full Text:
- Date Issued: 1976
The Lüderitz alkaline province, South West Africa, III: the Pomona and Drachenberg Syenite Complexes
- Authors: Marsh, Julian S
- Date: 1976
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/132984 , vital:36915 , https://hdl.handle.net/10520/AJA10120750_2853
- Description: The Pomona ring complex consists of several intrusive masses of syenitic magma that define a differentiation trend towards silica oversaturation. Volume relations, sequence of intrusion, and broad chemical characteristics are consistent with the syenites being derived by feldspar fractionation from an immediate syenitic parent. A plug of nepheline syenite and tinguaite dykes indicate the availability of silica-undersaturated magma generally in the Luderitz Province.
- Full Text:
- Date Issued: 1976
Base-metal mineralization in alkaline pyroclastics: the Regenstein Vent, South West Africa
- Ferreira, C A M, Jacob, Roger E, Marsh, Julian S
- Authors: Ferreira, C A M , Jacob, Roger E , Marsh, Julian S
- Date: 1979
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/133220 , vital:36950 , https://hdl.handle.net/10520/AJA10120750_1123
- Description: Geochemical analysis of soil samples taken from the area underlain by the Regenstein alkaline diatreme indicated potential areas for Pb-Zn-Ag mineralization, and these were subsequently proved by drilling. The pipelike body, emplaced into quartzites of the Damara Supergroup, consists of lithic and volcanic breccias. The breccias have been intruded, first by phonolite dykes, and then by numerous bodies of alkaline mafic and ultramafic rocks.
- Full Text:
- Date Issued: 1979
- Authors: Ferreira, C A M , Jacob, Roger E , Marsh, Julian S
- Date: 1979
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/133220 , vital:36950 , https://hdl.handle.net/10520/AJA10120750_1123
- Description: Geochemical analysis of soil samples taken from the area underlain by the Regenstein alkaline diatreme indicated potential areas for Pb-Zn-Ag mineralization, and these were subsequently proved by drilling. The pipelike body, emplaced into quartzites of the Damara Supergroup, consists of lithic and volcanic breccias. The breccias have been intruded, first by phonolite dykes, and then by numerous bodies of alkaline mafic and ultramafic rocks.
- Full Text:
- Date Issued: 1979
High-Mg tholeiitic rocks and their significance in the Karroo Central Province
- Eales, Hugh V, Marsh, Julian S
- Authors: Eales, Hugh V , Marsh, Julian S
- Date: 1979
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/${Handle} , vital:36916 , https://hdl.handle.net/10520/AJA00382353_5039
- Description: Averages for the composition of dolerites from the Southern and Eastern Cape, and the correlative basaltic lavas of the Stormberg, are presented for major elements and 8 of the more significant trace elements. The remarkable correspondence between these averages is indicative of the uniformity in composition of the magma emplaced over a very large area.
- Full Text:
- Date Issued: 1979
- Authors: Eales, Hugh V , Marsh, Julian S
- Date: 1979
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/${Handle} , vital:36916 , https://hdl.handle.net/10520/AJA00382353_5039
- Description: Averages for the composition of dolerites from the Southern and Eastern Cape, and the correlative basaltic lavas of the Stormberg, are presented for major elements and 8 of the more significant trace elements. The remarkable correspondence between these averages is indicative of the uniformity in composition of the magma emplaced over a very large area.
- Full Text:
- Date Issued: 1979
New chemical analyses of the Suurberg volcanic rocks and their significance in relation to Mesozoic volcanism in Southern Africa
- Marsh, Julian S, Lock, B E, Fuchter, W H
- Authors: Marsh, Julian S , Lock, B E , Fuchter, W H
- Date: 1979
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/133231 , vital:36951
- Description: Volcanic rocks are found associated with several of the late Mesozoic basins of southern South Africa. Bentonites are known from Plettenberg Bay and, according to an unconfirmed report, they are also found in the Worcester Basin, while vitric tuffs have been recorded from east of Oudtshoorn. The most extensive occurrences, however, are those of the Suurberg Group, which crops out sporadically around the margins of the Algoa Basin.
- Full Text:
- Date Issued: 1979
- Authors: Marsh, Julian S , Lock, B E , Fuchter, W H
- Date: 1979
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/133231 , vital:36951
- Description: Volcanic rocks are found associated with several of the late Mesozoic basins of southern South Africa. Bentonites are known from Plettenberg Bay and, according to an unconfirmed report, they are also found in the Worcester Basin, while vitric tuffs have been recorded from east of Oudtshoorn. The most extensive occurrences, however, are those of the Suurberg Group, which crops out sporadically around the margins of the Algoa Basin.
- Full Text:
- Date Issued: 1979
Tertiary phonolite volcanism in the Klinghardt Mountains of South West Africa/Namibia
- Authors: Marsh, Julian S , Lock, B E
- Date: 1981
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/133242 , vital:36953 , https://hdl.handle.net/10520/AJA10120750_2789
- Description: The Klinghardt Mountains in South West Africa (Namibia) were the site of an important volcanic outburst late in the Eocene or early in the Oligocene. Over a hundred endogenous domes and several lava flows of the coulee type were emplaced: all analysed samples (more than 60) comprise varieties of phonolite. A sequence of ash-flow tuffs of limited areal extent is present on Glasrucken.
- Full Text:
- Date Issued: 1981
- Authors: Marsh, Julian S , Lock, B E
- Date: 1981
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/133242 , vital:36953 , https://hdl.handle.net/10520/AJA10120750_2789
- Description: The Klinghardt Mountains in South West Africa (Namibia) were the site of an important volcanic outburst late in the Eocene or early in the Oligocene. Over a hundred endogenous domes and several lava flows of the coulee type were emplaced: all analysed samples (more than 60) comprise varieties of phonolite. A sequence of ash-flow tuffs of limited areal extent is present on Glasrucken.
- Full Text:
- Date Issued: 1981
Karoo basalts, South Africa: Petrogenesis and the nature of their mantle rocks
- Marsh, Julian S, Eales, Hugh V
- Authors: Marsh, Julian S , Eales, Hugh V
- Date: 1982
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/70141 , vital:29625
- Description: Outcrops of the Jurassic Karoo basalts and dolerites in central South Africa are remnants of a intracratonic continental igneous suite whose volume probably once exceeded 10 6km3.
- Full Text:
- Date Issued: 1982
- Authors: Marsh, Julian S , Eales, Hugh V
- Date: 1982
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/70141 , vital:29625
- Description: Outcrops of the Jurassic Karoo basalts and dolerites in central South Africa are remnants of a intracratonic continental igneous suite whose volume probably once exceeded 10 6km3.
- Full Text:
- Date Issued: 1982
Petrogenesis of Karoo magmas from Namibia and the nature of their source areas
- Authors: Marsh, Julian S , Miller, R
- Date: 1982
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/71299 , vital:29831
- Full Text:
- Date Issued: 1982
- Authors: Marsh, Julian S , Miller, R
- Date: 1982
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/71299 , vital:29831
- Full Text:
- Date Issued: 1982
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
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
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