The Bulawayan Supergroup: a late Archaean passive margin-related large igneous province in the Zimbabwe craton

The geological evolution of the Mozambique Channel sensu largowas controlled by three major transfer zones (Davie, Mozambique and Agulhas/Falklands), (1) related to the migration of four continents (Africa, Madagascar, Antarctica, South America), (2) recording five major volcanic episodes from 186 Ma to today and (3) contemporaneous of the uplift of several plateaus (e.g. Southern African Plateau), affecting a quite heterogeneous lithosphere of Archean to Neoproterozoic ages. This is therefore a unique area for a better understanding of (1) the evolution of transform margins in a volcanic setting and (2) the relationships between deformation, relief growth and sediment routing evolution. We established in the frame of the PAMELA (Passive Margin Experiment LAboratory) project (TOTAL, IFREMER, CNRS) a chart and nine paleogeographic maps (with tectonic structures, magmatism, catchments and sediment routing system) to better constrain the timing of evolution of this domain. The main results are as follows:(1) 255-240 Ma: a first E-W extension (Karoo &#8220;Rifts&#8221;) with no ocean opening;(2) 185-160 Ma: a second NW-SE extension between Antarctica/Madagascar and Africa coeval of the Karoo Large Igneous Province and initiation of volcanic margins along the future Somali Ocean;(3) 160-145 Ma: major change of the plate migration toward a N-S extensional initiation of very oblique margins along the Mozambique Fracture Zone (FZ), indicating an Antarctica motion toward SSE;(4) 134 Ma: onset of the migration of the Falkland continental domain along the Agulhas FZ;(5) 115 Ma: major deformation of the four plates with (i) end of the southward migration of Madagascar and (ii) major inversion along the Davie FZ (initiated around 135 Ma) and uplift of Madagascar;(6) 92-70 Ma: uplift of the Southern Africa Plateau first eastward (92 Ma) and second westward (81-70 Ma);(7) 40 Ma: onset of the uplift of the Zimbabwe/Zambia/Malawi Plateaus, East African Dome and Madagascar Plateau &#8211; last uplift of the Southern African Plateau;(6) 11-5 Ma: acceleration of the uplift of the Zimbabwe/Zambia/Malawi Plateaus and East African Dome &#8211; growth of a dome crossing the Mozambique Channel from Madagascar to southern offshore of the Limpopo Plain.

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Decision letter for "Mafic subvolcanic intrusions from the southern Paraná‐Etendeka Large Igneous Province, Brazil: Insights from geochemistry and Sr–Nd–Pb isotopes"

10.1002/gj.3993/v3/decision1 ◽

2020 ◽

Keyword(s):

Large Igneous Province ◽

Igneous Province

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Lithostratigraphy of the Palaeoproterozoic Hekpoort Formation (Pretoria Group, Transvaal Supergroup), South Africa

South African Journal of Geology ◽

10.25131/sajg.123.0043 ◽

2020 ◽

Vol 123 (4) ◽

pp. 655-668

Author(s):

N. Lenhardt ◽

W. Altermann ◽

F. Humbert ◽

M. de Kock

Keyword(s):

South Africa ◽

Bushveld Complex ◽

Sedimentary Rocks ◽

Type Locality ◽

Large Igneous Province ◽

Braided River ◽

River Systems ◽

The West ◽

Igneous Province ◽

Transvaal Supergroup

Abstract The Palaeoproterozoic Hekpoort Formation of the Pretoria Group is a lava-dominated unit that has a basin-wide extent throughout the Transvaal sub-basin of South Africa. Additional correlative units may be present in the Kanye sub-basin of Botswana. The key characteristic of the formation is its general geochemical uniformity. Volcaniclastic and other sedimentary rocks are relatively rare throughout the succession but may be dominant in some locations. Hekpoort Formation outcrops are sporadic throughout the basin and mostly occur in the form of gentle hills and valleys, mainly encircling Archaean domes and the Palaeoproterozoic Bushveld Complex (BC). The unit is exposed in the western Pretoria Group basin, sitting unconformably either on the Timeball Hill Formation or Boshoek Formation, which is lenticular there, and on top of the Boshoek Formation in the east of the basin. The unit is unconformably overlain by the Dwaalheuwel Formation. The type-locality for the Hekpoort Formation is the Hekpoort farm (504 IQ Hekpoort), ca. 60 km to the west-southwest of Pretoria. However, no stratotype has ever been proposed. A lectostratotype, i.e., the Mooikloof area in Pretoria East, that can be enhanced by two reference stratotypes are proposed herein. The Hekpoort Formation was deposited in a cratonic subaerial setting, forming a large igneous province (LIP) in which short-termed localised ponds and small braided river systems existed. It therefore forms one of the major Palaeoproterozoic magmatic events on the Kaapvaal Craton.

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Ultramafic-alkaline-carbonatite complexes as a result of two-stage melting of mantle plume: evidence from the mid-paleoproterozoic Tiksheozero intrusion, Northern Karelia, Russia

Доклады Академии наук ◽

10.31857/s0869-56524864460-465 ◽

2019 ◽

Vol 486 (4) ◽

pp. 460-465

Author(s):

E. V. Sharkov ◽

A. V. Chistyakov ◽

M. M. Bogina ◽

O. A. Bogatikov ◽

V. V. Shchiptsov ◽

...

Keyword(s):

Fractional Crystallization ◽

Mantle Plume ◽

Large Igneous Province ◽

Intrusive Complex ◽

Incongruent Melting ◽

Isotopic Data ◽

Two Stage ◽

Similar Composition ◽

Igneous Province ◽

Alkaline Magmas

Tiksheozero ultramafic-alkaline-carbonatite intrusive complex, like numerous carbonatite-bearing complexes of similar composition, is a part of large igneous province, related to the ascent of thermochemical mantle plume. Our geochemical and isotopic data evidence that ultramafites and alkaline rocks are joined by fractional crystallization, whereas carbonatitic magmas has independent origin. We suggest that origin of parental magmas of the Tiksheozero complex, as well as other ultramafic-alkaline-carbonatite complexes, was provided by two-stage melting of the mantle-plume head: 1) adiabatic melting of its inner part, which produced moderately-alkaline picrites, which fractional crystallization led to appearance of alkaline magmas, and 2) incongruent melting of the upper cooled margin of the plume head under the influence of CO2-rich fluids that arrived from underlying zone of adiabatic melting gave rise to carbonatite magmas.

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