New views on the Jurassic Clarens Formation: volcano-sedimentary interaction
- Holzforster, Frank, Holzforster, Heike W, Marsh, Julian S
- Authors: Holzforster, Frank , Holzforster, Heike W , Marsh, Julian S
- Date: 2002
- Language: English
- Type: text , abstract
- Identifier: http://hdl.handle.net/10962/132716 , vital:36874
- Description: The Lower Jurassic Clarens Formation of the Great Karoo Basin is usually viewed in the literature as a aeolian and, in places, fluvio-aeolian deposit of tremendous thickness variation form 0-250 m thickness. Interaction with the overlying Karoo Flood Basalts, particularly in the Eastern Cape area and in Lesotho, has been noted but was never a major topic. Relatively widespread pyroclastic deposits sandwiched between the Clarens Formation and the Karoo Flood Basalts have been interpreted as flood-lahars.
- Full Text:
- Date Issued: 2002
- Authors: Holzforster, Frank , Holzforster, Heike W , Marsh, Julian S
- Date: 2002
- Language: English
- Type: text , abstract
- Identifier: http://hdl.handle.net/10962/132716 , vital:36874
- Description: The Lower Jurassic Clarens Formation of the Great Karoo Basin is usually viewed in the literature as a aeolian and, in places, fluvio-aeolian deposit of tremendous thickness variation form 0-250 m thickness. Interaction with the overlying Karoo Flood Basalts, particularly in the Eastern Cape area and in Lesotho, has been noted but was never a major topic. Relatively widespread pyroclastic deposits sandwiched between the Clarens Formation and the Karoo Flood Basalts have been interpreted as flood-lahars.
- Full Text:
- Date Issued: 2002
The distribution of platinum group elements in the Insizwa lobe, Mount Ayliff Complex, South Africa: implications for Ni-Cu-PGE sulfide exploration in the Karoo igneous province
- Maier, W D, Marsh, Julian S, Barnes, Sarah-Jane, Dodd, D C
- Authors: Maier, W D , Marsh, Julian S , Barnes, Sarah-Jane , Dodd, D C
- Date: 2002
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/150353 , vital:38969 , https://0-doi.org.wam.seals.ac.za/10.2113/gsecongeo.97.6.1293
- Description: The Mount Ayliff Complex of the Eastern Cape province of South Africa is a layered intrusion of some 800 km2 surface area and up to 1,200 m thickness. On the basis of compositional similarities and spatial association, it is generally interpreted to form part of the Karoo igneous province. Similarities between the Mount Ayliff Complex and the staging chambers and feeder conduits to flood basalts that host magmatic sulfide ores elsewhere in the world suggest that the Mount Ayliff Complex may have an enhanced potential for Noril’sk-Talnakh–type massive Ni-Cu sulfide ores, an idea that is supported by the well-known sulfide occurrence at Waterfall Gorge.
- Full Text: false
- Date Issued: 2002
- Authors: Maier, W D , Marsh, Julian S , Barnes, Sarah-Jane , Dodd, D C
- Date: 2002
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/150353 , vital:38969 , https://0-doi.org.wam.seals.ac.za/10.2113/gsecongeo.97.6.1293
- Description: The Mount Ayliff Complex of the Eastern Cape province of South Africa is a layered intrusion of some 800 km2 surface area and up to 1,200 m thickness. On the basis of compositional similarities and spatial association, it is generally interpreted to form part of the Karoo igneous province. Similarities between the Mount Ayliff Complex and the staging chambers and feeder conduits to flood basalts that host magmatic sulfide ores elsewhere in the world suggest that the Mount Ayliff Complex may have an enhanced potential for Noril’sk-Talnakh–type massive Ni-Cu sulfide ores, an idea that is supported by the well-known sulfide occurrence at Waterfall Gorge.
- Full Text: false
- Date Issued: 2002
Field Trip A1: Karoo dykes, sills and volcanics in the Eastern Cape
- Authors: Marsh, Julian S
- Date: 2001
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/144835 , vital:38383
- Description: The Karoo Province (Fig. I I ) is one of the classic Mesozoic continental flood basalt provinces At present erosion levels it comprises numerous eroded remnants of extensive, thick, and largely volcanic sequence and a well-exposed subvolcanic intrusive complex of dykes and sheets.
- Full Text:
- Date Issued: 2001
- Authors: Marsh, Julian S
- Date: 2001
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/144835 , vital:38383
- Description: The Karoo Province (Fig. I I ) is one of the classic Mesozoic continental flood basalt provinces At present erosion levels it comprises numerous eroded remnants of extensive, thick, and largely volcanic sequence and a well-exposed subvolcanic intrusive complex of dykes and sheets.
- Full Text:
- Date Issued: 2001
Petrology of the alkaline core of the Messum igneous complex, Namibia: evidence for the progressively decreasing effect of crustal contamination
- Harris, Chris, Marsh, Julian S, Milner, Simon C
- Authors: Harris, Chris , Marsh, Julian S , Milner, Simon C
- Date: 1999
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/149746 , vital:38880 , https://doi.org/10.1093/petroj/40.9.1377
- Description: The Messum complex of NW Namibia, a part of the Paraná–Etendeka volcanic province, consists of a dominantly felsic central core, surrounded by older gabbros. The igneous rocks of the core can be divided, in order of decreasing age, into (1) a sub-alkaline suite, (2) an outer quartz syenite suite, and (3) an inner silica-undersaturated suite dominated by nepheline syenite. Compositional differences within the quartz syenite suite can be explained by fractional crystallization, but Sr- and O-isotope data indicate that these rocks contain a significant crustal component.
- Full Text: false
- Date Issued: 1999
- Authors: Harris, Chris , Marsh, Julian S , Milner, Simon C
- Date: 1999
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/149746 , vital:38880 , https://doi.org/10.1093/petroj/40.9.1377
- Description: The Messum complex of NW Namibia, a part of the Paraná–Etendeka volcanic province, consists of a dominantly felsic central core, surrounded by older gabbros. The igneous rocks of the core can be divided, in order of decreasing age, into (1) a sub-alkaline suite, (2) an outer quartz syenite suite, and (3) an inner silica-undersaturated suite dominated by nepheline syenite. Compositional differences within the quartz syenite suite can be explained by fractional crystallization, but Sr- and O-isotope data indicate that these rocks contain a significant crustal component.
- Full Text: false
- Date Issued: 1999
Excursion to Granitberg and the Klinghardt Mountains, southern Namibia
- Authors: Marsh, Julian S
- Date: 1998
- Language: English
- Type: text , field guide
- Identifier: http://hdl.handle.net/10962/132118 , vital:36801
- Description: Three small subvolcanic intrusions (Granitberg, Pomona and Drachenberg) and associated dykes of Cretaceous age, occur between Bogenfels and Prinzen Bucht, S of Luderitz, Namibia. This field trip will chiefly be concerned with rocks that have crystallized from magmas of nepheline syenite composition.
- Full Text:
- Date Issued: 1998
- Authors: Marsh, Julian S
- Date: 1998
- Language: English
- Type: text , field guide
- Identifier: http://hdl.handle.net/10962/132118 , vital:36801
- Description: Three small subvolcanic intrusions (Granitberg, Pomona and Drachenberg) and associated dykes of Cretaceous age, occur between Bogenfels and Prinzen Bucht, S of Luderitz, Namibia. This field trip will chiefly be concerned with rocks that have crystallized from magmas of nepheline syenite composition.
- Full Text:
- Date Issued: 1998
Geochemical variations in a long Karoo dyke, Eastern Cape
- Marsh, Julian S, Mndaweni, M J
- Authors: Marsh, Julian S , Mndaweni, M J
- Date: 1998
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/149715 , vital:38877 , https://hdl.handle.net/10520/EJC-1abee09c1f
- Description: A prominent vertical dolerite dyke, up to 30 m wide and which can be traced for over 100 km, is compositionally homogeneous along much of its length and shows no evidence of flow differentiation. Associated parallel dykes are compositionally distinct and are unrelated by closed-system processes. The main dyke has geochemical characteristics of the Maloti or Senqu Units in the upper part of the main Lesotho basalt sequence, whereas the parallel dykes are geochemically similar to the lower Mafika Lisiu Unit. On the basis of size and composition the main dyke may well represent a fissure which once fed effusions of Karoo basalt.
- Full Text:
- Date Issued: 1998
- Authors: Marsh, Julian S , Mndaweni, M J
- Date: 1998
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/149715 , vital:38877 , https://hdl.handle.net/10520/EJC-1abee09c1f
- Description: A prominent vertical dolerite dyke, up to 30 m wide and which can be traced for over 100 km, is compositionally homogeneous along much of its length and shows no evidence of flow differentiation. Associated parallel dykes are compositionally distinct and are unrelated by closed-system processes. The main dyke has geochemical characteristics of the Maloti or Senqu Units in the upper part of the main Lesotho basalt sequence, whereas the parallel dykes are geochemically similar to the lower Mafika Lisiu Unit. On the basis of size and composition the main dyke may well represent a fissure which once fed effusions of Karoo basalt.
- Full Text:
- Date Issued: 1998
The Marinkas Quellen Carbonatite Complex, southern Namibia: carbonatite magmatism with an uncontaminated depleted mantle signature in a continental setting
- Smithies, Robert H, Marsh, Julian S
- Authors: Smithies, Robert H , Marsh, Julian S
- Date: 1998
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/149736 , vital:38879 , https://doi.org/10.1016/S0009-2541(98)00029-1
- Description: The Marinkas Quellen Carbonatite Complex, in southern Namibia, forms part of the ca. 490–550 Ma Kuboos-Bremen Igneous Province, a zone of alkaline igneous rocks that intrude the Mesoproterzoic to Paleoproterozoic Namaqualand Metamorphic Province and Neoproterozoic platform sediments. The carbonatite complex includes Ca-rich, Mg-rich and Fe-rich carbonatites as well as late ferrocarbonatite dykes that show extreme enrichments in Mn, REE and Th. Compared to most carbonatites, those at Marinkas Quellen are generally depleted in most trace elements, particularly Ba and the LREE.
- Full Text: false
- Date Issued: 1998
- Authors: Smithies, Robert H , Marsh, Julian S
- Date: 1998
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/149736 , vital:38879 , https://doi.org/10.1016/S0009-2541(98)00029-1
- Description: The Marinkas Quellen Carbonatite Complex, in southern Namibia, forms part of the ca. 490–550 Ma Kuboos-Bremen Igneous Province, a zone of alkaline igneous rocks that intrude the Mesoproterzoic to Paleoproterozoic Namaqualand Metamorphic Province and Neoproterozoic platform sediments. The carbonatite complex includes Ca-rich, Mg-rich and Fe-rich carbonatites as well as late ferrocarbonatite dykes that show extreme enrichments in Mn, REE and Th. Compared to most carbonatites, those at Marinkas Quellen are generally depleted in most trace elements, particularly Ba and the LREE.
- Full Text: false
- Date Issued: 1998
Petrology and geochemistry of peridotite xenoliths from the Letlhakane kimberlites, Botswana
- Stiefenhofer, Johann, Viljoen, K S, Marsh, Julian S
- Authors: Stiefenhofer, Johann , Viljoen, K S , Marsh, Julian S
- Date: 1997
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/149705 , vital:38876 , https://doi.org/10.1007/s004100050272
- Description: The diamondiferous Letlhakane kimberlites are intruded into the Proterozoic Magondi Belt of Botswana. Given the general correlation of diamondiferous kimberlites with Archaean cratons, the apparent tectonic setting of these kimberlites is somewhat anomalous. Xenoliths in kimberlite diatremes provide a window into the underlying crust and upper mantle and, with the aid of detailed petrological and geochemical study, can help unravel problems of tectonic setting.
- Full Text: false
- Date Issued: 1997
- Authors: Stiefenhofer, Johann , Viljoen, K S , Marsh, Julian S
- Date: 1997
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/149705 , vital:38876 , https://doi.org/10.1007/s004100050272
- Description: The diamondiferous Letlhakane kimberlites are intruded into the Proterozoic Magondi Belt of Botswana. Given the general correlation of diamondiferous kimberlites with Archaean cratons, the apparent tectonic setting of these kimberlites is somewhat anomalous. Xenoliths in kimberlite diatremes provide a window into the underlying crust and upper mantle and, with the aid of detailed petrological and geochemical study, can help unravel problems of tectonic setting.
- Full Text: false
- Date Issued: 1997
The petrology and significance of a stratiform mafic segregation pegmatite in a Karoo-aged dolerite sheet
- Mitchell, Andrew A, Naicker, S B, Marsh, Julian S, Dunlevey, J N
- Authors: Mitchell, Andrew A , Naicker, S B , Marsh, Julian S , Dunlevey, J N
- Date: 1997
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/149496 , vital:38858 , https://hdl.handle.net/10520/EJC-9293fd659
- Description: A sub-horizontal stratiform mafic segregation pegmatite, of the order of 30 cm thick, occurs within 25 m of the top contact of a Karoo-aged dolerite sheet at Pietermaritzburg, South Africa. The host rock is an orthopyroxene-rich dolerite containing 5 - 8% interstitial granophyre. The pegmatite is similar to the host dolerite in many respects, except that the granophyre content is higher, and acicular augite is the only pyroxene. At its upper contact, a laterally continuous sub-horizontal joint forms a sharp boundary to the pegmatite, whilst the lower contact is gradational over a few millimetres. Low MgO and chalcophiles, and elevated incompatible element contents, are the main geochemical attributes of the pegmatite.
- Full Text:
- Date Issued: 1997
- Authors: Mitchell, Andrew A , Naicker, S B , Marsh, Julian S , Dunlevey, J N
- Date: 1997
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/149496 , vital:38858 , https://hdl.handle.net/10520/EJC-9293fd659
- Description: A sub-horizontal stratiform mafic segregation pegmatite, of the order of 30 cm thick, occurs within 25 m of the top contact of a Karoo-aged dolerite sheet at Pietermaritzburg, South Africa. The host rock is an orthopyroxene-rich dolerite containing 5 - 8% interstitial granophyre. The pegmatite is similar to the host dolerite in many respects, except that the granophyre content is higher, and acicular augite is the only pyroxene. At its upper contact, a laterally continuous sub-horizontal joint forms a sharp boundary to the pegmatite, whilst the lower contact is gradational over a few millimetres. Low MgO and chalcophiles, and elevated incompatible element contents, are the main geochemical attributes of the pegmatite.
- Full Text:
- Date Issued: 1997
The timing and duration of the Karoo igneous event, southern Gondwana
- Duncan, R A, Hooper, P R, Rehacek, J, Marsh, Julian S, Duncan, Andrew R
- Authors: Duncan, R A , Hooper, P R , Rehacek, J , Marsh, Julian S , Duncan, Andrew R
- Date: 1997
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/149485 , vital:38857 , https://doi.org/10.1029/97JB00972
- Description: A volcanic event of immense scale occurred within a relatively short period in early Jurassic time over large regions of the contiguous Gondwana supercontinent. In southern Africa, associated remnants of thick volcanic successions of lava flows and extensive dike and sill complexes of similar composition have been grouped together as the Karoo Igneous Province. Correlative volcanic and plutonic rocks occur in Antarctica and Australia as the Ferrar Province.
- Full Text:
- Date Issued: 1997
- Authors: Duncan, R A , Hooper, P R , Rehacek, J , Marsh, Julian S , Duncan, Andrew R
- Date: 1997
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/149485 , vital:38857 , https://doi.org/10.1029/97JB00972
- Description: A volcanic event of immense scale occurred within a relatively short period in early Jurassic time over large regions of the contiguous Gondwana supercontinent. In southern Africa, associated remnants of thick volcanic successions of lava flows and extensive dike and sill complexes of similar composition have been grouped together as the Karoo Igneous Province. Correlative volcanic and plutonic rocks occur in Antarctica and Australia as the Ferrar Province.
- Full Text:
- Date Issued: 1997
Alkaline rocks in the Kuboos-Bremen Igneous Province, southern Namibia: the Grootpenseiland and Marinkas Kwela Complexes
- Smithies, Robert H, Marsh, Julian S
- Authors: Smithies, Robert H , Marsh, Julian S
- Date: 1996
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/145838 , vital:38471
- Description: The early Cambrian Kuboos-Bremen Igneous Province of northwestern South Africa and southern Namibia comprises a series of intrusive bodies that collectively encompass virtually the entire range of alkaline rock types. Two of these bodies, the Grootpenseiland and Marinkas Kwela Complexes lie immediately north of the Orange River and are amongst the few that show this wide lithological range on a local scale.
- Full Text:
- Date Issued: 1996
- Authors: Smithies, Robert H , Marsh, Julian S
- Date: 1996
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/145838 , vital:38471
- Description: The early Cambrian Kuboos-Bremen Igneous Province of northwestern South Africa and southern Namibia comprises a series of intrusive bodies that collectively encompass virtually the entire range of alkaline rock types. Two of these bodies, the Grootpenseiland and Marinkas Kwela Complexes lie immediately north of the Orange River and are amongst the few that show this wide lithological range on a local scale.
- Full Text:
- Date Issued: 1996
Geochemical stratigraphy of the Mohale Dame-Katse Dam areas, Lesotho. Report on contract LHDA, Mohale Tunnel: Sampling and Testing of Cores. Lesotho Highlands Tunnel Partnership (Mohale)
- Authors: Marsh, Julian S
- Date: 1996
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/144857 , vital:38385
- Description: In monotonous basalt sequences, such as the Karoo basalt sequence in Lesotho, geochemistry can be a useful adjunct to stratigraphic studies. The acceptance of geochemical criteria in defining stratigraphic units arises from work in the Columbia River Group in NW SA (Swanson et al., 1979) and is now widely employed. It has recently been successfully applied in the Karoo basalts (Marsh et al., in press). In the current investigation a stratigraphic framework for construction work related to the Katse-Mohale tunnel has been developed using the compositions of basalt samples collected from a number of borehole cores in relation to the geochemical stratigraphy of Marshet al. (in press).
- Full Text:
- Date Issued: 1996
- Authors: Marsh, Julian S
- Date: 1996
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/144857 , vital:38385
- Description: In monotonous basalt sequences, such as the Karoo basalt sequence in Lesotho, geochemistry can be a useful adjunct to stratigraphic studies. The acceptance of geochemical criteria in defining stratigraphic units arises from work in the Columbia River Group in NW SA (Swanson et al., 1979) and is now widely employed. It has recently been successfully applied in the Karoo basalts (Marsh et al., in press). In the current investigation a stratigraphic framework for construction work related to the Katse-Mohale tunnel has been developed using the compositions of basalt samples collected from a number of borehole cores in relation to the geochemical stratigraphy of Marshet al. (in press).
- Full Text:
- Date Issued: 1996
Geology Field Trip Guide: Natural Sciences and Geography Educators visit
- Authors: Marsh, Julian S
- Date: 1996
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/144878 , vital:38387
- Description: This is a brief guide to some of the interesting geological features in the immediate vicinity of Grahamstown. It summarises the geological history of the area, emphasizes that small-scale geological features are frequently part of much larger features, demonstrates how careful observation of rocks can lead to solving geological problems and reconstruction of ancient environments in which rocks formed, the importance to society, and how rocks in the Grahamstown area have contributed to a global scale understanding of the dynamic nature of planet Earth.
- Full Text:
- Date Issued: 1996
- Authors: Marsh, Julian S
- Date: 1996
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/144878 , vital:38387
- Description: This is a brief guide to some of the interesting geological features in the immediate vicinity of Grahamstown. It summarises the geological history of the area, emphasizes that small-scale geological features are frequently part of much larger features, demonstrates how careful observation of rocks can lead to solving geological problems and reconstruction of ancient environments in which rocks formed, the importance to society, and how rocks in the Grahamstown area have contributed to a global scale understanding of the dynamic nature of planet Earth.
- Full Text:
- Date Issued: 1996
Karoo and Etendeks flood basalt provinces, southern Africa and the tectonic development of their adjacent margins:
- Marsh, Julian S, Watkeys, M K
- Authors: Marsh, Julian S , Watkeys, M K
- Date: 1996
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/144868 , vital:38386
- Description: Southern Africa hosts remnants of two continental flood basalt provinces emplaced in association with fragmentation of Gondwana. The earliest is the 183 Ma Karoo Province whose relationship to continental breakup and sea floor spreading is complex. Geochemical stratigraphy, Ar-Ar Dating and palaeomagnetism indicate that Karoo mafic igneous rocks throughout Southern Africa were emplaced over a very short interval at 183 Ma.
- Full Text:
- Date Issued: 1996
- Authors: Marsh, Julian S , Watkeys, M K
- Date: 1996
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/144868 , vital:38386
- Description: Southern Africa hosts remnants of two continental flood basalt provinces emplaced in association with fragmentation of Gondwana. The earliest is the 183 Ma Karoo Province whose relationship to continental breakup and sea floor spreading is complex. Geochemical stratigraphy, Ar-Ar Dating and palaeomagnetism indicate that Karoo mafic igneous rocks throughout Southern Africa were emplaced over a very short interval at 183 Ma.
- Full Text:
- Date Issued: 1996
Promotion of the Etendeka Formation to Group status: a new integrated stratigraphy
- Milner, Simon C, Duncan, Andrew R, Ewart, A, Marsh, Julian S
- Authors: Milner, Simon C , Duncan, Andrew R , Ewart, A , Marsh, Julian S
- Date: 1994
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/145482 , vital:38442
- Description: The Etendeka volcanic rocks of northwestem Namibia are currently defined as the upper part of the Karoo Sequence in Namibia and have thus been represented as stratigraphically equivalent to the volcanic rocks of the Karoo Sequence in South Africa, Botswana, Lesotho, Swaziland and Zimbabwe. However, the Etendeka volcanic rocks (130-135 Ma) are considerably younger than those of the Karoo Sequence (180-190 Ma) in the areas mentioned above. They are compositionally distinct from Karoo volcanic rocks, and constitute an eastern portion of the Parana Igneous Province of Brazil. Stratigraphic studies have shown the Etendeka Formation to be made up of several definable volcanic successions and it is suggested that these successions now be formally recognized as Formations within an Etendeka Group which itself should no longer be part of the Karoo Sequence. Prominent quartz latite units and sequences of basalt flows are defined as Members within the new Formations.
- Full Text:
- Date Issued: 1994
- Authors: Milner, Simon C , Duncan, Andrew R , Ewart, A , Marsh, Julian S
- Date: 1994
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/145482 , vital:38442
- Description: The Etendeka volcanic rocks of northwestem Namibia are currently defined as the upper part of the Karoo Sequence in Namibia and have thus been represented as stratigraphically equivalent to the volcanic rocks of the Karoo Sequence in South Africa, Botswana, Lesotho, Swaziland and Zimbabwe. However, the Etendeka volcanic rocks (130-135 Ma) are considerably younger than those of the Karoo Sequence (180-190 Ma) in the areas mentioned above. They are compositionally distinct from Karoo volcanic rocks, and constitute an eastern portion of the Parana Igneous Province of Brazil. Stratigraphic studies have shown the Etendeka Formation to be made up of several definable volcanic successions and it is suggested that these successions now be formally recognized as Formations within an Etendeka Group which itself should no longer be part of the Karoo Sequence. Prominent quartz latite units and sequences of basalt flows are defined as Members within the new Formations.
- Full Text:
- Date Issued: 1994
Petrogenesis of late Archaean flood-type basic lavas from the Klipriviersberg Group, Ventersdorp Supergroup, South Africa
- Marsh, Julian S, Bowen, M P, Rogers, N W, Bowen, T B
- Authors: Marsh, Julian S , Bowen, M P , Rogers, N W , Bowen, T B
- Date: 1992
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/145829 , vital:38470 , https://doi.org/10.1093/petrology/33.4.817
- Description: The Klipriviersberg Group is a small continental flood-type tholeiitic suite forming the basal unit of the Ventersdorp Supergroup, an undeformed late-Archaean supracrustal sequence covering 200000 km2 in the SW part of the Kaapvaal Craton. From the base up, the Klipriviersberg Group consists of the Westonaria, Alberton, Orkney, Jeannette, Loraine, and Edenville formations, with a maximum combined thickness of 1–8 km. Samples were obtained from several borehole cores in the Klerksdorp goldfield close to the type area of the Klipriviersberg Group.
- Full Text: false
- Date Issued: 1992
- Authors: Marsh, Julian S , Bowen, M P , Rogers, N W , Bowen, T B
- Date: 1992
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/145829 , vital:38470 , https://doi.org/10.1093/petrology/33.4.817
- Description: The Klipriviersberg Group is a small continental flood-type tholeiitic suite forming the basal unit of the Ventersdorp Supergroup, an undeformed late-Archaean supracrustal sequence covering 200000 km2 in the SW part of the Kaapvaal Craton. From the base up, the Klipriviersberg Group consists of the Westonaria, Alberton, Orkney, Jeannette, Loraine, and Edenville formations, with a maximum combined thickness of 1–8 km. Samples were obtained from several borehole cores in the Klerksdorp goldfield close to the type area of the Klipriviersberg Group.
- Full Text: false
- Date Issued: 1992
Preliminary geochemical data for dolerite dykes and sills of the southern part of the Etendeka Igneous Province
- Marsh, Julian S, Erlank, Anthony J, Duncan, Andrew R
- Authors: Marsh, Julian S , Erlank, Anthony J , Duncan, Andrew R
- Date: 1991
- Language: English
- Type: text , report
- Identifier: http://hdl.handle.net/10962/132133 , vital:36803
- Description: Over the last 15 years systematic geochemical and petrological investigation of the igneous rocks of the Early Cretaceous - Late Jurassic Etendeka Igneous Province of northwestern Namibia have focused on the tholeiitic basaltic lavas and interbedded silicic volcanic rocks and the large central subvolcanic complexes of Brandberg, Erongo, Okenyenya, Messum, Doros and Cape Cross. Previously these rocks were grouped into the Karoo Volcanic Province of South Africa, but in view of the distinct age difference between the igneous rocks of the Etendeka region and Karoo rocks occurring elsewhere in southern Africa , we propose to regard them as constituting a separate Etendeka Igneous Province which exhibits a close lithological, geochemical and temporal correlation with the Parana Flood Basalt Province of South America.
- Full Text:
- Date Issued: 1991
- Authors: Marsh, Julian S , Erlank, Anthony J , Duncan, Andrew R
- Date: 1991
- Language: English
- Type: text , report
- Identifier: http://hdl.handle.net/10962/132133 , vital:36803
- Description: Over the last 15 years systematic geochemical and petrological investigation of the igneous rocks of the Early Cretaceous - Late Jurassic Etendeka Igneous Province of northwestern Namibia have focused on the tholeiitic basaltic lavas and interbedded silicic volcanic rocks and the large central subvolcanic complexes of Brandberg, Erongo, Okenyenya, Messum, Doros and Cape Cross. Previously these rocks were grouped into the Karoo Volcanic Province of South Africa, but in view of the distinct age difference between the igneous rocks of the Etendeka region and Karoo rocks occurring elsewhere in southern Africa , we propose to regard them as constituting a separate Etendeka Igneous Province which exhibits a close lithological, geochemical and temporal correlation with the Parana Flood Basalt Province of South America.
- Full Text:
- Date Issued: 1991
REE fractionation and Ce anomalies in weathered Karoo dolerite
- Authors: Marsh, Julian S
- Date: 1991
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/145819 , vital:38469 , https://doi.org/10.1016/0009-2541(91)90099-D
- Description: Analyses of samples from a weathering profile on Karoo dolerite allow elements to be divided into three groups depending on their behaviour. Si, K, Na, Mg, Ca, Sr, Ba and V are mobilized and removed from weathered products. Fe, Al. Ti, Zr, Hf, Zn, Cu, Sc, Co and Ni are immobile. REE, Y, and to a lesser extent Cr, are mobile and redistributed within the profile without a net loss of these elements from the profile. Large positive Ce anomalies are developed in oxidized weathered products by preferential leaching of the other REE's. Negative Ce anomalies and REE enrichment is a feature of less altered dolerite.
- Full Text: false
- Date Issued: 1991
- Authors: Marsh, Julian S
- Date: 1991
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/145819 , vital:38469 , https://doi.org/10.1016/0009-2541(91)90099-D
- Description: Analyses of samples from a weathering profile on Karoo dolerite allow elements to be divided into three groups depending on their behaviour. Si, K, Na, Mg, Ca, Sr, Ba and V are mobilized and removed from weathered products. Fe, Al. Ti, Zr, Hf, Zn, Cu, Sc, Co and Ni are immobile. REE, Y, and to a lesser extent Cr, are mobile and redistributed within the profile without a net loss of these elements from the profile. Large positive Ce anomalies are developed in oxidized weathered products by preferential leaching of the other REE's. Negative Ce anomalies and REE enrichment is a feature of less altered dolerite.
- Full Text: false
- Date Issued: 1991
MORB-related dolerites associated with the final phases of Karoo flood basalt volcanism in southern Africa.
- Duncan, Andrew R, Armstrong, R A, Erlank, Anthony J, Marsh, Julian S, Watkins, R T
- Authors: Duncan, Andrew R , Armstrong, R A , Erlank, Anthony J , Marsh, Julian S , Watkins, R T
- Date: 1990
- Language: English
- Type: text , conference paper
- Identifier: http://hdl.handle.net/10962/143299 , vital:38222 , https://pascal-francis.inist.fr/vibad/index.php?action=getRecordDetailampidt=6938249
- Description: The Rooi Rand dyke swarm is approximately 200km long and up to 20km wide. It crops out in the southern portion of the Lebombo monocline where the dykes intrude basalts of the Sabie River Basalt Formation which is the major basaltic unit in the eastern portion of the Karoo volcanic succession. The Horingbaai dolerites form thin dykes and sills which intrude the base of the Etendeka lava pile (considered part of the Karoo Volcanics, but correlated with the Serra Geral Formation of Brazil) along the coast of Namibia. Both the Rooi Rand and Horingbaai magma types are similar in composition to enriched MORB and are compositionally distinct from most of the Karoo-basalts they intrude.
- Full Text:
- Date Issued: 1990
- Authors: Duncan, Andrew R , Armstrong, R A , Erlank, Anthony J , Marsh, Julian S , Watkins, R T
- Date: 1990
- Language: English
- Type: text , conference paper
- Identifier: http://hdl.handle.net/10962/143299 , vital:38222 , https://pascal-francis.inist.fr/vibad/index.php?action=getRecordDetailampidt=6938249
- Description: The Rooi Rand dyke swarm is approximately 200km long and up to 20km wide. It crops out in the southern portion of the Lebombo monocline where the dykes intrude basalts of the Sabie River Basalt Formation which is the major basaltic unit in the eastern portion of the Karoo volcanic succession. The Horingbaai dolerites form thin dykes and sills which intrude the base of the Etendeka lava pile (considered part of the Karoo Volcanics, but correlated with the Serra Geral Formation of Brazil) along the coast of Namibia. Both the Rooi Rand and Horingbaai magma types are similar in composition to enriched MORB and are compositionally distinct from most of the Karoo-basalts they intrude.
- Full Text:
- Date Issued: 1990
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/10962/145492 , vital:38443 , 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/10962/145492 , vital:38443 , 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