| 1. |
- Alebouyeh Semami, Farnaz, et al.
(författare)
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New U–Pb geochronologic and palaeomagnetic constraints on the late Palaeoproterozoic Hartley magmatic event : evidence for a potential large igneous province in the Kaapvaal Craton during Kalahari assembly, South Africa
- 2016
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Ingår i: GFF. - : Informa UK Limited. - 1103-5897 .- 2000-0863. ; 138:1, s. 164-182
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Tidskriftsartikel (refereegranskat)abstract
- The volcanic Hartley Formation (part of the Olifantshoek Supergroup, which is dominated by red bed successions) in South Africa recorded depositional and tectonic conditions along the western Kaapvaal Craton during the late Palaeoproterozoic. It formed in association with red bed deposition elsewhere in the cratonic hinterland and along the craton’s northern margin. However, the exact correlation of the Olifantshoek Supergroup with these other red-bed successions is hindered by poor geochronological constraints. Herein, we refine the age and palaeopole of the Hartley Formation, and provide geochronological constraints for large-scale 1.93–1.91 Ga bimodal magmatism on the Kaapvaal Craton (herein named the Hartley large igneous province). We present new age constraints for the mafic and felsic phases of this event at 1923 ± 6 Ma and 1920 ± 4 Ma, respectively, which includes the first reported age dating of the Tsineng Dyke Swarm that has been linked to Hartley volcanism. A mean 1.93–1.91 Ga palaeomagnetic pole for the Hartley large igneous province at 22.7°N, 328.6°E with A95 = 11.7° represents a significant improvement on a previously published virtual geomagnetic pole. This improved pole is used to refine the late Palaeoproterozoic apparent polar wander path of the Kaapvaal Craton. This can assist in correlation of red-bed successions in southern Africa.
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| 2. |
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| 3. |
- Djeutchou, Cedric, et al.
(författare)
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Late Paleoproterozoic mafic magmatism and the Kalahari craton during Columbia assembly
- 2021
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Ingår i: Geology. - 0091-7613. ; 49:11, s. 1375-1380
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Tidskriftsartikel (refereegranskat)abstract
- The 1.87–1.84 Ga Black Hills dike swarm of the Kalahari craton (South Africa) is coeval with several regional magmatic provinces used here to resolve the craton’s position during Columbia assembly. We report a new 1850 ± 4 Ma (U-Pb isotope dilution–thermal ionization mass spectrometry [ID-TIMS] on baddeleyite) crystallization age for one dike and new paleomagnetic data for 34 dikes of which 8 have precise U-Pb ages. Results are constrained by positive baked-contact and reversal tests, which combined with existing data produce a 1.87–1.84 Ga mean pole from 63 individual dikes. By integrating paleomagnetic and geochronological data sets, we calculate poles for three magmatic episodes and produce a magnetostratigraphic record. At 1.88 Ga, the Kalahari craton is reconstructed next to the Superior craton so that their ca. 2.0 Ga poles align. As such, magmatism forms part of a radiating pattern with the coeval ca. 1.88 Ga Circum-Superior large igneous province
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| 4. |
- Gumsley, Ashley, et al.
(författare)
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Neoarchean large igneous provinces on the Kaapvaal Craton in southern Africa re-define the formation of the Ventersdorp Supergroup and its temporal equivalents
- 2020
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Ingår i: Geological Society of America Bulletin. - 0016-7606. ; 132:9-10, s. 1829-1844
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Tidskriftsartikel (refereegranskat)abstract
- U-Pb geochronology on baddeleyite is a powerful technique that can be applied effectively to chronostratigraphy. In southern Africa, the Kaapvaal Craton hosts a well-preserved Mesoarchean to Paleoproterozoic geological record, including the Neoarchean Ventersdorp Supergroup. It overlies the Witwatersrand Supergroup and its world-class gold deposits. The Ventersdorp Supergroup comprises the Klipriviersberg Group, Platberg Group, and Pniel Group. However, the exact timing of formation of the Ventersdorp Supergroup is controversial. Here we present 2789 ± 4 Ma and 2787 ± 2 Ma U-Pb isotope dilution- thermal ionization mass spectrometry (ID-TIMS) baddeleyite ages and geochemistry on mafic sills intruding the Witwatersrand Supergroup, and we interpret these sills as feeders to the overlying Klipriviersberg Group flood basalts. This constrains the age of the Witwatersrand Supergroup and gold mineralization to at least ca. 2.79 Ga. We also report 2729 ± 5 Ma and 2724 ± 7 Ma U-Pb ID-TIMS baddeleyite ages and geochemistry from a mafic sill intruding the Pongola Supergroup and on an east-northeast-trending mafic dike, respectively. These new ages distinguish two of the Ventersdorp Supergroup magmatic events: the Klipriviersberg and Platberg. The Ventersdorp Supergroup can now be shown to initiate and terminate with two large igneous provinces (LIPs), the Klipriviersberg and Allanridge, which are separated by Platberg volcanism and sedimentation. The age of the Klipriviersberg LIP is 2791-2779 Ma, and Platberg volcanism occurred at 2754-2709 Ma. The Allanridge LIP occurred between 2709-2683 Ma. Klipriviersberg, Platberg, and Allanridge magmatism may be genetically related to mantle plume(s). Higher heat flow and crustal melting resulted as a mantle plume impinged below the Kaapvaal Craton lithosphere, and this was associated with rifting and the formation of LIPs.
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| 5. |
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| 6. |
- Gumsley, Ashley P., et al.
(författare)
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Timing and tempo of the Great Oxidation Event
- 2017
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Ingår i: Proceedings of the National Academy of Sciences of the United States of America. - : Proceedings of the National Academy of Sciences. - 0027-8424. ; 114:8, s. 1811-1816
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Tidskriftsartikel (refereegranskat)abstract
- The first significant buildup in atmospheric oxygen, the Great Oxidation Event (GOE), began in the early Paleoproterozoic in association with global glaciations and continued until the end of the Lomagundi carbon isotope excursion ca. 2,060 Ma. The exact timing of and relationships among these events are debated because of poor age constraints and contradictory stratigraphic correlations. Here, we show that the first Paleoproterozoic global glaciation and the onset of the GOE occurred between ca. 2,460 and 2,426 Ma, ∼100 My earlier than previously estimated, based on an age of 2,426 ± 3 Ma for Ongeluk Formation magmatism from the Kaapvaal Craton of southern Africa. This age helps define a key paleomagnetic pole that positions the Kaapvaal Craton at equatorial latitudes of 11° ± 6° at this time. Furthermore, the rise of atmospheric oxygen was not monotonic, but was instead characterized by oscillations, which together with climatic instabilities may have continued over the next ∼200 My until ≤2,250-2,240 Ma. Ongeluk Formation volcanism at ca. 2,426 Ma was part of a large igneous province (LIP) and represents a waning stage in the emplacement of several temporally discrete LIPs across a large low-latitude continental landmass. These LIPs played critical, albeit complex, roles in the rise of oxygen and in both initiating and terminating global glaciations. This series of events invites comparison with the Neoproterozoic oxygen increase and Sturtian Snowball Earth glaciation, which accompanied emplacement of LIPs across supercontinent Rodinia, also positioned at low latitude.
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| 7. |
- Gumsley, Ashley Paul, et al.
(författare)
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U-Pb TIMS and in-situ SIMS dating of baddeleyite and zircon from sub-volcanic sills of the Ongeluk Formation (Transvaal Supergroup) in the Griqualand West sub-basin, Kaapvaal Craton, with implications for Snowball Earth and the Great Oxygenation Event
- 2015
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Konferensbidrag (refereegranskat)abstract
- The Great Oxygenation Event (GOE) in the Paleoproterozoic coincides with a complex series of glacial episodes preserved in supracrustal successions on the world’s cratons. These Paleoproterozoic glacial rocks are bracketed in age between 2.46 and 2.22 Ga, based on the glacial record in the Huronian Supergroup on the Superior Craton in Canada). In southern Africa, the cover successions of the western Kaapvaal Craton preserve possible glacial correlatives of the Huronian Supergroup in the Griqualand West sub-basin of the Transvaal Supergroup. This potential correlative is the glacial diamictites of the Makganyene Formation. The Makganyene Formation is in turn conformably overlain by the Ongeluk Formation, a series of subaqueous mafic volcanic rocks with a putative age of ca. 2.22 Ga. However, both local and global correlations using glacial units of the Transvaal and Huronian supergroups are hampered by a lack of robust well-placed geochronological data. The timing of the Ongeluk Formation itself has been challenged. Here, the sub-volcanic sills of the Ongeluk volcanic rocks have been dated using U-Pb in-situ SIMS analysis on baddeleyite to ca. 2.43 Ga. This has been coupled with ID TIMS dating and paleomagnetism studies on the coeval Westerberg Sill Suite. This suggests that the Ongeluk Formation volcanic rocks, and the immediately underlying Makganyene Formation glacial deposits, are approximately 200 Myr older than generally assumed. These new ages lend support to three glacial epochs around the GOE, of which the first was low-latitude in the Makganyene Formation. The Makganyene diamictites could correlate to diamictites from the Duitsland Formation in the more eastern Transvaal sub-basin of the Transvaal Supergroup, with a significant revision of regional stratigraphic correlations, that is in itself not without challenges. In such a scenario, the Ongeluk volcanic rocks could be correlated with the Bushy Bend volcanics, and not the ≤ 2.25 Ga Hekpoort Formation volcanics. This new magmatic event may be linked with the evolution of the Vaalbara continent, the Kenorland supercontinent, and global environmental changes related to magmatism and weathering in the Paleoproterozoic Era.
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| 8. |
- Gumsley, Ashley, et al.
(författare)
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Precise U-Pb baddeleyite age dating of the Usushwana Complex, southern Africa - Implications for the Mesoarchaean magmatic and sedimentological evolution of the Pongola Supergroup, Kaapvaal Craton
- 2015
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Ingår i: Precambrian Research. - : Elsevier BV. - 0301-9268. ; 267, s. 174-185
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Tidskriftsartikel (refereegranskat)abstract
- The Usushwana Complex of the south-eastern Kaapvaal Craton (South Africa and Swaziland), intrudes the ca. 3.6-3.1 Ga basement of the craton, as well as the Mesoarchaean volcanic and sedimentary cover succession of the Pongola Supergroup. New high-precision U-Pb dating of gabbros belonging to the Piet Retief Suite of the Usushwana Complex yield ages of 2989 +/- 1 Ma, 2990 +/- 2 Ma and 2978 +/- 2 Ma. The Piet Retief Suite represents part of an intricate magmatic feeder to a major volcanic event which gave rise to the oldest known continental flood basalts on Earth, the Nsuze volcanic rocks. Broadly coeval SE-trending dolerite dykes of the Barberton-Badplaas Dyke Swarm in the larger region of the south-eastern Kaapvaal Craton formed along the same structural trend as the Usushwana Complex. One such dyke is dated herein to 2980 +/- 1 Ma. Using the high-precision U-Pb geochronological data, the Nsuze volcanic rocks can now be resolved into at least two magmatic episodes which can be correlated with parts of the Pongola Supergroup. The first episode at ca. 2.99-2.98 Ga is broadly coeval with the Pypklipberg (Nhlebela) volcanic rocks, whereas the second at ca. 2.97-2.96 Ga was near synchronous to the Agatha volcanic rocks. A dolerite sill intruding into the Mozaan Group of the Pongola Supergroup, thought to be part of the Usushwana Complex, was dated to 2869 +/- 5 Ma, and is instead coeval with the Hlagothi Complex further to the south, and provides a new minimum age for deposition of the Mozaan Group. (C) 2015 Elsevier B.V. All rights reserved.
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| 9. |
- Gumsley, Ashley, et al.
(författare)
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U–Pb baddeleyite geochronology and geochemistry of the White Mfolozi Dyke Swarm : unravelling the complexities of 2.70–2.66 Ga dyke swarms across the eastern Kaapvaal Craton, South Africa
- 2016
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Ingår i: GFF. - : Informa UK Limited. - 1103-5897 .- 2000-0863. ; 138:1, s. 115-132
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Tidskriftsartikel (refereegranskat)abstract
- On the south-easternmost Kaapvaal Craton, a NE-trending plagioclase-megacrystic dolerite dyke swarm, herein named the White Mfolozi Dyke Swarm (WMDS), has been identified. New U–Pb baddeleyite ages presented here indicate that the WMDS was emplaced within less than 10 million years, with our three most robust results yielding a weighted mean age of 2662 ± 2 Ma. The WMDS is coeval with the youngest dykes of a 2.70–2.66 Ga radiating dyke swarm already identified further north on the eastern side of the Kaapvaal Craton. This dyke swarm radiates out from the eastern lobe of the ca. 2.05 Ga Bushveld Complex. A clustering of ages from the WMDS and the 2.70–2.66 Ga radiating dyke swarm identify potential magmatic peaks at 2701–2692 Ma, 2686–2683 Ma and 2665–2659 Ma. Geochemical signatures of the dykes do not correlate with these age groups, but are rather unique to specific areas. The northern part of the eastern Kaapvaal Craton hosts relatively differentiated 2.70–2.66 Ga dolerite dykes that could have been derived from a moderately enriched mantle source, whereas the ca. 2.66 Ga WMDS from the southernmost area exhibit much more depleted signatures. In between these two margins, the central area hosts more andesitic 2.70–2.66 Ga dykes that may have assimilated substantial amounts of partly digested tonalite–trondhjemite–granodiorite crust from the basement. We investigate the evolution for the Kaapvaal Craton during a highly magmatic period that extends for over 60 million years from extensive Ventersdorp volcanism to the eruption of proto-basinal volcanic rocks at the base of the Transvaal Supergroup.
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| 10. |
- Gumsley, Ashley
(författare)
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Validating the existence of the supercraton Vaalbara in the Mesoarchaean to Palaeoproterozoic
- 2017
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Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- In this thesis, the longevity and continuity of the Vaalbara supercraton is addressed in six papers aimed at placing new temporal and spatial constraints onthe supercraton in the Mesoarchean to Paleoproterozoic. It has been speculated since the 1960’s that the Kaapvaal Craton in southern Africa, together withthe Pilbara Craton in Western Australia existed as a single landmass during the Precambrian – the Vaalbara supercraton. Many studies have demonstrated thegeological similarities between the cratons, particularly in terms of their Mesoarchean to Paleoproterozoic unconformity-bounded sequences. These unconformity-bounded sequences have continuously been refined and developed, especially since the 1990’s. The first main stratigraphic similarities lie in the volcanic and sedimentary successions found in the Neoarchean Fortescue Group and Ventersdorp Supergroup basins on the Pilbara and Kaapvaal cratons, respectively, along with other associated basins. The unconformably overlying Hammersley (and Turee Creek) Group and Transvaal Supergroup on the Pilbara and Kaapvaal cratons, respectively, also show many stratigraphic similarities, and both host world-class deposits of hydrothermally-upgraded iron formations. However, no marker beds or precise age matches have yet been made, especially in the extensive Mesoarchean to Paleoproterozoic mafic dyke swarms and sill provinces present in each craton from the time interval discussed in this thesis. Regardless, the geological discussions has been aided by geochronological and paleomagnetic studies, which have both credited and discredited the existence of the Pilbara and Kaapvaal cratons as nearest neighbours for the time interval between ca. 2.87 Ga and ca. 2.65 Ga.In this thesis, the so-called magmatic barcode record of large igneous provinces (LIPs), which are extensive and short-lived volcanic events, of the KaapvaalCraton is presented together with that of the Pilbara Craton in conjunction with previous geochronological and paleomagnetic studies. This magmatic barcoderecord refines temporal, and through paleomagnetism, spatial constraints, and invalidates the existence of Vaalbara as a distinct continuous supercraton. Magmatic and paleomagnetic linkages between the 2.99-2.98 Ga Usushwana Complex on the Kaapvaal Craton and the ca. 2.87 Ga Millindinna Complex on thePilbara Craton are shown to be incorrect with new ages for the Usushwana Complex and Badplaas dyke swarm presented in Gumsley et al. (2015). Extensivemafic dyke swarms associated with Neoarchean Fortescue volcanism on the Pilbara Craton and Ventersdorp volcanism on the Kaapvaal Craton also show lesssimilarities from new paleomagnetic and geochronological constraints. These constraints are presented in Gumsley et al. (2016) and Evans et al. (2017) for thenewly identified White Mfolozi and Black Range mafic dyke swarms, respectively, on the Kaapvaal and Pilbara cratons. Gumsley et al. (2017) and Kampmannet al. (2015) also present a new LIP, the Ongeluk, on the Kaapvaal Craton which has not been identified on the Pilbara Craton. This new LIP is composed ofthe Ongeluk Formation in the Transvaal Supergroup on the western margin of the Kaapvaal Craton, as well as the Westerberg Sill Province and a north-trendingmafic dyke swarm. The Ongeluk LIP appears to break some of the stratigraphic comparison between the upper Transvaal Supergroup on the Kaapvaal Cratonand the Turee Creek Group on the Pilbara Craton. In addition, a new late Paleoproterozoic mafic dyke swarm, the Tsineng swarm, is presented for the western Kaapvaal Craton in Alebouyeh Semami et al. (2016), which is correlated with Hartley Formation volcanism in the Olifantshoek Supergroup. This magmaticevent may also define a new LIP on the western Kaapvaal Craton. This mafic dyke swarm and its associated volcanism has also not been documented on thePilbara Craton.Instead, it is proposed that the Pilbara and Kaapvaal cratons were part of a much larger continent or supercontinent in the Neoarchean to Paleoproterozoic.This large crustal block likely included the Wyoming, Superior and Hearne cratons of North America, together with the Kola-Karelia Craton located between Russia and Finland, as well as possibly the Singhbhum Craton of India and the Samartia terrane of Russia and Ukraine. This continent or supercontinent, termed ‘Supervaalbara’ here, allows for the Kaapvaal and Pilbara cratons to share many geological similarities without being nearest neighbours, along possiblythe same passive margin. The geological evolution of all these cratons is very similar, particularly in the Paleoproterozoic, and which may have been driven byglobal processes. These global processes may include true polar wander, the submergence and subsequent remergence of continents with sea-level rise and fall, as well as atmospheric oxygenation and global glaciation. Paleomagnetic studies provide further continuity supporting the existence of Supervaalbara, which appears geologically distinct from the Rae family of cratons, suggesting perhaps two different continents in the early Paleoproterozoic before the assembly of the supercontinent Columbia (Nuna) in the late Paleoproterozoic.
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| 11. |
- Kampmann, Tobias Christoph, et al.
(författare)
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U-Pb geochronology and paleomagnetism of the Westerberg Sill Suite, Kaapvaal Craton - Support for a coherent Kaapvaal-Pilbara Block (Vaalbara) into the Paleoproterozoic?
- 2015
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Ingår i: Precambrian Research. - : Elsevier BV. - 0301-9268 .- 1872-7433. ; 269, s. 58-72
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Tidskriftsartikel (refereegranskat)abstract
- Precise geochronology, combined with paleomagnetism on mafic intrusions, provides first-order information for paleoreconstruction of crustal blocks, revealing the history of supercontinental formation and break-up. These techniques are used here to further constrain the apparent polar wander path of the Kaapvaal Craton across the Neoarchean-Paleoproterozoic boundary. U-Pb baddeleyite ages of 2441 +/- 6 Ma and 2426 +/- 1 Ma for a suite of mafic sills located on the western Kaapvaal Craton in South Africa (herein named the Westerberg Sill Suite), manifests a new event of magmatism within the Kaapvaal Craton of southern Africa. These ages fall within a ca. 450 Myr temporal gap in the paleomagnetic record between 2.66 and 2.22 Ga on the craton. Our older Westerberg Suite age is broadly coeval with the Woongarra magmatic event on the Pilbara Craton in Western Australia. In addition, the Westerberg Suite on the Kaapvaal Craton intrudes a remarkably similar Archean-Proterozoic sedimentary succession to that on the Pilbara Craton, supporting a stratigraphic correlation between Kaapvaal and Pilbara (i.e., Vaalbara). The broadly coeval Westerberg-Woongarra igneous event may represent a Large Igneous Province. The paleomagnetic results are more ambiguous, with several different possibilities existing. A Virtual Geomagnetic Pole obtained from four sites on the Westerberg sills is 18.9 degrees N, 285.0 degrees E, A(95) = 14.1 degrees, K = 43.4 (Sample based VGP, n=34: 16.8 degrees N, 2879.9 degrees E, dp=4.4 degrees, dm=7.7 degrees). If primary (i.e., 2441-2426 Ma), it would provide a further magmatic event within a large temporal gap in the Kaapvaal Craton's Paleoproterozoic apparent polar wander path. It would suggest a relatively stationary Kaapvaal Craton between 2.44 Ga and 2.22 Ga, and ca. 35 degrees of latitudinal drift of the craton between ca. 2.66 Ga and 2.44 Ga. This is not observed for the Pilbara Craton, suggesting breakup of Vaalbara before ca. 2.44 Ga. However, it is likely that the Woongarra paleopole represents a magnetic overprint acquired during the Ophtalmian or Capricorn Orogeny, invalidating a paleomagnetic comparison with the Westerberg Sill Suite. Alternatively, our Westerberg Virtual Geographic Pole manifests a 2.22 Ga magnetic overprint related to Ongeluk volcanism. The similarity between Ongeluk and Westerberg paleopoles however may also infer magmatic connections if both are primary directions, despite the apparent 200 million year age this difference. (C) 2015 Elsevier B.V. All rights reserved.
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| 12. |
- Pandey, Om Prakash, et al.
(författare)
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Major-trace element and Sr-Nd isotope compositions of mafic dykes of the Singhbhum Craton : Insights into evolution of the lithospheric mantle
- 2021
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Ingår i: Lithos. - : Elsevier BV. - 0024-4937. ; 382-383
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Tidskriftsartikel (refereegranskat)abstract
- The Singhbhum Craton in eastern India is host to at least seven sets of mafic dyke swarms. Four previously dated swarms (studied here) include the NNE-trending Keshargaria (ca. 2.80 Ga) and Ghatgaon (ca. 2.76 - 2.75 Ga) swarms, the ENE-trending Kaptipada swarm (ca. 2.26 Ga), and the ESE-trending Pipilia swarm (ca.1.76 Ga). The dykes range in composition from basalt to andesite and have transitional tholeiitic to calc-alkaline affinities. They show intra- and inter-swarm geochemical and Sr-Nd isotopic heterogeneities and have SiO2 content ranging from 47 to 60 wt.%. The chondrite normalized REE patterns show enrichment in LREE and the Primitive-Mantle normalized multi-element patterns show elevated U, Th, Cs, Rb, K, and Pb; and depletion in Nb, Ta, and Ti. These characteristics indicate involvement of crustal component in the petrogenesis of these dykes. The dykes of different swarms have variable 87Sr/86Sri and εNd(i) values, which define a crust-like isotopic growth trajectory with time from a common chondritic to depleted source that was enriched contemporaneously with the formation of the crustal rocks of the Singhbhum Craton. The isotope data indicate involvement of older enriched crustal material in the petrogenesis of these dykes. Variable but mostly high (compared to similarly evolved magmas) Ni (40 - 590 ppm), Cr (40 - 1110 ppm), and V (120 - 434 ppm) contents particularly of the most primitive dykes indicate that parental melts were in equilibrium with mantle peridotite and experienced only minor fractional crystallization of olivine, pyroxene, and magnetite. The Sr-Nd isotope ratios do not show any correlation with differentiation indices which indicates that the melts were not modified significantly by crustal assimilation during ascent and emplacement. The crust-like secular trend of the Sr and Nd isotopic compositions suggests that the enriched crustal material was incubated in the mantle (i.e., metasomatized lithospheric mantle) for a long time and this source was periodically tapped leading to multiple dyke emplacement events over at least 1 Gyr. The recycled crustal material played a role in metasomatizing the subcontinental lithospheric mantle prior to ca. 2.80 Ga. Mantle plume activity triggered melting of the metasomatized lithospheric mantle many times, leading to the emplacement of mafic dykes of different generations across the craton.
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| 13. |
- Salminen, Johanna, et al.
(författare)
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Direct Mesoproterozoic connection of the Congo and Kalahari cratons in proto-Africa : Strange attractors across supercontinental cycles
- 2018
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Ingår i: Geology. - 0091-7613. ; 46:11, s. 1011-1014
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Tidskriftsartikel (refereegranskat)abstract
- Mobilistic plate-tectonic interpretation of Precambrian orogens requires that two conjoined crustal blocks may derive from distant portions of the globe. Nonetheless, many proposed Precambrian cratonic juxtapositions are broadly similar to those of younger times (socalled "strange attractors"), raising the specter of bias in their construction. We evaluated the possibility that the Congo and Kalahari cratons (Africa) were joined together prior to their amalgamation along the Damara-Lufilian-Zambezi orogen in Cambrian time by studying diabase dikes of the Huila-Epembe swarm and sills in the southern part of the Congo craton in Angola and in Namibia. We present geologic, U-Pb geochronologic, and paleomagnetic evidence showing that these two cratons were directly juxtaposed at ca. 1.1 Ga, but in a slightly modified relative orientation compared to today. Recurring persistence in cratonic connections, with slight variations from one supercontinent to the next, may signify a style of supercontinental transition similar to the northward motion of Gondwana fragments across the Tethys-Indian oceanic tract, reuniting in Eurasia.
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