Paleoproterozoic intraplate magmatism and basin development on the Kaapvaal Craton: Age, paleomagnetism and geochemistry of ~1.93 to ~1.87 Ga post-Waterberg dolerites
TL;DR: Pb baddeleyite crystallization ages of ~1927 and ~1879 to ~1872 Ma for dolerite sills intruding the Waterberg Group in Botswana and South Africa were reported in this article.
Abstract: We report U–Pb baddeleyite crystallization ages of ~1927 and ~1879 to ~1872 Ma for dolerite sills intruding the Waterberg Group in Botswana and South Africa. These data increase the known extent of ~1.9 Ga intraplate magmatism in southern Africa and place tighter age constraints on the Waterberg Group than previously available. In South Africa, ~1.88 Ga dolerite intrudes upper Waterberg strata, constraining most, if not all, of the succession to have accumulated between ~2.06 Ga (age of the underlying Bushveld Complex) and ~1.88 Ga. This is consistent with derivation of much of the group from uplifted sources in reactivated segments of the Limpopo Belt. The dolerites are typical continental tholeiites, but their trace-element contents discriminate them from dolerite sills of the 1.1 Ga Umkondo Igneous Province, which occur in the same region. Paleomagnetic samples from dolerite intrusions in the Waterberg Group in South Africa (including one sill with a U–Pb baddeleyite age of ~1872 Ma), and from dolerite sills and basalt flows in the Soutpansberg Group to the east-northeast, yield antipodal directions with a site mean pole at 15.6°north, 17.1°east, A95 = 8.9°. These data are interpreted to indicate that the ~1879 to ~1872 Ma dolerites were intruded into the Waterberg Group during voluminous magmatism associated with development of the Soutpansberg rift basin. Older, ~1927 Ma dolerite in Botswana is similar in age and geochemistry to basalts in the craton-margin Olifantshoek Supergroup, suggesting that the mafic magmatism in those two regions is genetically related.
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TL;DR: A newly recognized remnant of a Paleoproterozoic Large Igneous Province has been identified in the southern Bastar craton and nearby Cuddapah basin from the adjacent Dharwar craton, India as mentioned in this paper.
299 citations
TL;DR: In this article, a new methodology using Large Igneous Provinces (LIPs) offers an opportunity for fast-tracking progress toward robust Precambrian reconstructions.
213 citations
TL;DR: In this article, the authors reported seven high precision U-Pb age determinations for mafic dykes from a number of major Precambrian swarms located in the Dharwar craton, south India.
196 citations
TL;DR: In this article, a series of time-slice maps illustrating the development of the Kaapvaal Craton is presented, linking geochronological data to GIS coverages.
Abstract: Geochronological comparisons of large datasets are facilitated by the use of structured databases. Data for the Precambrian of South Africa, Swaziland, Lesotho and Botswana have been compiled in a DateView database and linked to chronostratigraphy and GIS databases to produce a series of ‘time-slice’ maps illustrating the development of the Kaapvaal Craton. Linking geochronological data to GIS coverages provides a valuable visual perspective on the development of the southern African lithosphere.
The oldest preserved rock formation dates occur south of the Barberton Greenstone Belt in South Africa and Swaziland. Subsequent scattered development of new crust occurred in the south eastern, eastern and northern Kaapvaal Craton before being ‘stitched’ together by extensive granitoid intrusions at ~3.25 Ga and ~3.1 Ga. Coeval development of new crust occurred in what would later become the central zone of the Limpopo Belt. The patterns of igneous activity from ~3.1 Ga to ~2.8 Ga, outboard of major cratonic lineaments (Colesberg lineament in the west and Thabazimbi-Murchison lineament in the north) may indicate that these lineaments represent suture zones along which the younger domains were accreted during formation of the Kaapvaal Craton.
By ~3 Ga the lithosphere was sufficiently rigid to support development of the Dominion, Witwatersrand and Pongola sedimentary basins, followed by extensive volcanism during the Ventersdorp and concomitant granitoid activity throughout the Craton. Subsequent geological activity, not necessarily evident in the available geochronological record, was concentrated on craton with the development of the widespread Transvaal Supergroup followed by essentially coeval extrusion of the Rooiberg felsites and intrusion of the Bushveld Complex at ~2.06 Ga. Deposition of sediments comprising the Waterberg and Soutpansberg Groups followed.
Igneous activity along the south-western edge of the Kaapvaal Craton terminated at ~1.93 Ga with formation of the Hartley basalts, Olifantshoek Supergroup. Post-Olifantshoek Supergroup and pre-Volop Group tectonism has been reported from the western margin of the Kaapvaal Craton. There is currently no geochronological evidence for major igneous or metamorphic activity post-dating formation of the Olifantshoek Supergroup until the early stages of the Namaqua-Natal Belt subsequent to ~1.4 Ga i.e . there is no geochronological evidence for a major late-Palaeoproterozoic ‘Kheisian orogeny’. Off-craton, new crust formed in the Richtersveld Sub-province at ~1.8 Ga but was presumably only accreted to the Kaapvaal Craton some 700 million years later during the Namaqua-Natal orogenesis.
185 citations
Cites background from "Paleoproterozoic intraplate magmati..."
...…of predominantly siliciclastic sediments of the Waterberg and Soutpansberg Groups were poorly constrained but U-Pb baddeleyite data presented by Hanson et al. (2004) demonstrate that several of the units comprising the Waterberg Group were deposited prior to 1.88 Ga, when dolerites intruded…...
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TL;DR: In this article, the authors used the Precambrian mafic dykes intruding granitoids and supracrustals of the Archean Bundelkhand craton (BC) in northern Penin-Sular India to constrain the position of India at 2.0 and 1.1 Ga.
154 citations
Cites background or methods from "Paleoproterozoic intraplate magmati..."
...The precisely dated Umkondo dolerite paleomagnetic data from the Kalahari craton are often correlated with Keweenawan igneous suite of Laurentia (Hanson et al., 2004a; Gose et al., 2006; Jacobs et al., 2008)....
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...…Piper, 1984). n directions from NE–SW trending third set of dykes (Dec = 189.3◦ and Inc = 64.5◦) A key, well-dated paleomagnetic pole, from the Kalahari craton at ∼1.1 Ga is based on the Umkondo dolerites and the Kalkpunt poles (Hanson et al., 2004a; Gose et al., 2004, 2006; Jacobs et al., 2008)....
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...Based on the available paleomagnetic data from Kalahari and aurentia, Kalahari is located too far south of Laurentia to suport any linkage between the two blocks (Hanson et al., 2004a; ose et al., 2006)....
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...…of Antarctica after restoring East Antarctica to its position next to South Africa at ∼1.1 Ga (Jones and McElhinny, 1966; Renne et al., 1990; Hargraves et al., 1994; Jones and Powell, 2001; Powell et al., 2001; Pesonen et al., 2003; Hanson et al., 2004a; Gose et al., 2006; Jacobs et al., 2008)....
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References
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01 Jan 1989
TL;DR: In this article, trace-element data for mid-ocean ridge basalts and ocean island basalts are used to formulate chemical systematics for oceanic basalts, interpreted in terms of partial-melting conditions, variations in residual mineralogy, involvement of subducted sediment, recycling of oceanic lithosphere and processes within the low velocity zone.
Abstract: Summary Trace-element data for mid-ocean ridge basalts (MORBs) and ocean island basalts (OIB) are used to formulate chemical systematics for oceanic basalts. The data suggest that the order of trace-element incompatibility in oceanic basalts is Cs ≈ Rb ≈ (≈ Tl) ≈ Ba(≈ W) > Th > U ≈ Nb = Ta ≈ K > La > Ce ≈ Pb > Pr (≈ Mo) ≈ Sr > P ≈ Nd (> F) > Zr = Hf ≈ Sm > Eu ≈ Sn (≈ Sb) ≈ Ti > Dy ≈ (Li) > Ho = Y > Yb. This rule works in general and suggests that the overall fractionation processes operating during magma generation and evolution are relatively simple, involving no significant change in the environment of formation for MORBs and OIBs. In detail, minor differences in element ratios correlate with the isotopic characteristics of different types of OIB components (HIMU, EM, MORB). These systematics are interpreted in terms of partial-melting conditions, variations in residual mineralogy, involvement of subducted sediment, recycling of oceanic lithosphere and processes within the low velocity zone. Niobium data indicate that the mantle sources of MORB and OIB are not exact complementary reservoirs to the continental crust. Subduction of oceanic crust or separation of refractory eclogite material from the former oceanic crust into the lower mantle appears to be required. The negative europium anomalies observed in some EM-type OIBs and the systematics of their key element ratios suggest the addition of a small amount (⩽1% or less) of subducted sediment to their mantle sources. However, a general lack of a crustal signature in OIBs indicates that sediment recycling has not been an important process in the convecting mantle, at least not in more recent times (⩽2 Ga). Upward migration of silica-undersaturated melts from the low velocity zone can generate an enriched reservoir in the continental and oceanic lithospheric mantle. We propose that the HIMU type (eg St Helena) OIB component can be generated in this way. This enriched mantle can be re-introduced into the convective mantle by thermal erosion of the continental lithosphere and by the recycling of the enriched oceanic lithosphere back into the mantle.
19,221 citations
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TL;DR: In this paper, a system was presented whereby volcanic rocks may be classified chemically as follows: Subalkaline Rocks:A.B. Tholeiitic basalt series:Tholeitic picrite-basalt; tholeiite, tholeitic andesite; dacite; rhyolite.
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