Academic literature on the topic 'Pan-African orogeny'
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Journal articles on the topic "Pan-African orogeny"
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Ephraim, Bassey E., Barth N. Ekwueme, Mohssen Moazzen, and Monir Modjarrad. "P-T conditions of Pan-African orogeny in southeastern Nigeria." Central European Geology 51, no. 4 (2008): 359–78. http://dx.doi.org/10.1556/ceugeol.51.2008.4.5.
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Takigami, Yutaka. "Consideration of the Pan-African Orogeny from 40Ar-39Ar Age Results." Gondwana Research 4, no. 4 (2001): 796. http://dx.doi.org/10.1016/s1342-937x(05)70580-3.
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Okpoli, C. C., and D. Oludeyi. "Aeromagnetic Mapping of Iwo Region of Southwestern Nigeria for Lithostructural Delineation." Pakistan Journal of Geology 3, no. 2 (2019): 20–30. http://dx.doi.org/10.2478/pjg-2019-0008.
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AbstractThe IGRF filtered Aeromagnetic data over Iwo, southwestern part of Nigeria within the basement complex was subjected to reduction to magnetic equator filtering, residual filtering, upward and downward continuation filtering, automatic gain control filtering, tilt angle derivative, second vertical derivative, analytical signal and Euler deconvolution. This reveals the geologic information such as structural trend. Based on the result of the total magnetic intensity map, reduction to equator map, analytical signal map and residual magnetic intensity map, it can be concluded that; The rocks in the study area have a trend of approximately northeast-southwest direction as seen on the upward continuation map. Most of the delineated lineaments found within the study area strike mostly in NNE-SSW, NE-SW and NW-SE with minor trend of E-W and ENE-WSW direction. Structural lineament orientation suggested that they were products of Pan-African orogeny (NE-SW, NW-SE and NNE-SSW trends) and pre-Pan-African orogeny (NNW-SSE and E-W trend). The interpretation of the aeromagnetic dataset gave an insight into the regional geology and structural trends of the area.
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Weerakoon, M. W. K., K. Shuto, and H. Kagami. "Pan–African Orogeny in Sri Lanka: The Eppawala Carbonatite and Surrounding Rocks." Gondwana Research 2, no. 2 (1999): 312. http://dx.doi.org/10.1016/s1342-937x(05)70162-3.
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Bartlett, J. M. "Tectonic and Thermal Evolution of South India During the Pan-African Orogeny." Mineralogical Magazine 58A, no. 1 (1994): 55–56. http://dx.doi.org/10.1180/minmag.1994.58a.1.32.
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Abdel-Rahman, A. M. "Petrogenesis of anorogenic peralkaline granitic complexes from eastern Egypt." Mineralogical Magazine 70, no. 1 (2006): 27–50. http://dx.doi.org/10.1180/0026461067010311.
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AbstractThe Pan-African orogenic shield rocks of eastern Egypt were intruded by several anorogenic within- plate granitic complexes, including Mounts Abu-Kharif and El-Dob. These two massifs were emplaced at the intersection of a fault system and a shear zone. The two massifs are made up of hypersolvus peralkaline granites, consisting essentially of perthitic alkali feldspar (55–65 vol.%), quartz (30–35%), and alkali amphibole (ferrorichterite to arfvedsonite; 5–12%), with accessory zircon, apatite and ilmenite. The rocks are evolved in composition, are relatively enriched in Nb (53–75 ppm), Y (34–72 ppm), Zr (421–693 ppm), Ga (26–29 ppm), and the REE (294–562 ppm), and depleted in Al, Mg, Ca, Sr, Ba and Eu. The REE patterns are sub-parallel, LREE-enriched over HREE, and show prominent negative Eu anomalies. The rocks exhibit mineralogical and chemical traits typical of within-plate A-type granites. Rb-Sr radiometric age dating produced a Cambrian age of 522±21 Ma, and an initial 87Sr/86Sr ratio of 0.7080±0.0042. Thus, the investigated peralkaline granitic rocks were emplaced following the termination of the Pan-African orogeny. The rocks are interpreted to have formed in an extensional tectonic environment during a phase of cooling, relaxation, crustal attenuation, and fracturing of the newly-formed shield.Results of geochemical modelling indicate that the magma may have formed by a large degree of batch partial melting (F = 0.57) of Pan-African calc-alkaline shield rocks, which had been metasomatized possibly by a Na-rich fluid. The volatile flux may have caused fenitization-type reactions along fissures and re-activated Pan-African fractures prior to anatexis, and is considered to have played a role as an important agent of heat transfer. Shear heating, caused possibly by a rapid change in the direction of plate motions beneath eastern Egypt during the Early Palaeozoic, is likely to have produced temperatures necessary for crustal anatexis. The confining pressure must have been released by fissuring of the crust. Magma ascent may have been facilitated by reactivation of pre-existing Pan-African fractures.
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Ntiharirizwa, Seconde, Philippe Boulvais, Marc Poujol, et al. "Geology and U-Th-Pb Dating of the Gakara REE Deposit, Burundi." Minerals 8, no. 9 (2018): 394. http://dx.doi.org/10.3390/min8090394.
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The Gakara Rare Earth Elements (REE) deposit is one of the world’s highest grade REE deposits, likely linked to a carbonatitic magmatic-hydrothermal activity. It is located near Lake Tanganyika in Burundi, along the western branch of the East African Rift. Field observations suggest that the mineralized veins formed in the upper crust. Previous structures inherited from the Kibaran orogeny may have been reused during the mineralizing event. The paragenetic sequence and the geochronological data show that the Gakara mineralization occurred in successive stages in a continuous hydrothermal history. The primary mineralization in bastnaesite was followed by an alteration stage into monazite. The U-Th-Pb ages obtained on bastnaesite (602 ± 7 Ma) and on monazite (589 ± 8 Ma) belong to the Pan-African cycle. The emplacement of the Gakara REE mineralization most likely took place during a pre-collisional event in the Pan-African belt, probably in an extensional context.
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Torremans, Koen, Philippe Muchez, and Manuel Sintubin. "Non-cylindrical parasitic folding and strain partitioning during the Pan-African Lufilian orogeny in the Chambishi–Nkana Basin, Central African Copperbelt." Solid Earth 9, no. 4 (2018): 1011–33. http://dx.doi.org/10.5194/se-9-1011-2018.
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Abstract. A structural analysis has been carried out along the south-east margin of the Chambishi–Nkana Basin in the Central African Copperbelt, hosting the world-class copper and cobalt (Cu–Co) Nkana orebody. The geometrically complex structural architecture is interpreted to have been generated during a single NE–SW-oriented compressional event, clearly linked to the Pan-African Lufilian orogeny. This progressive deformation resulted primarily in asymmetric multiscale parasitic fold assemblages, characterised by non-cylindrical NW–SE-oriented periclinal folds that strongly interfere laterally, leading to fold linkage and bifurcation. The vergence and amplitude of these folds consistently reflect their position along an inclined limb of a NW-plunging megascale first-order fold. A clear relation is observed between the intensity of parasitic folding and the degree of shale content in the Copperbelt Orebody Member (COM), which hosts most of the ore. Differences in fold amplitude, wavelength and shape are explained by changes in mechanical stratigraphy caused by lateral lithofacies variation in ore-bearing horizons. In addition, strong differences in strain partitioning occur within the deforming basin, which is interpreted to be in part controlled by changes in mechanical anisotropy in the layered rock package. This work provides an essential backdrop to understand the influence of the Lufilian orogeny on metal mineralisation and (re-)mobilisation in the Copperbelt.
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Perpétuo, Marcela Paschoal, Wagner da Silva Amaral, Felipe Grandjean da Costa, Evilarde Carvalho Uchôa Filho, and Daniel Francisco Martins de Sousa. "Geochemistry of the Serra das Melancias Pluton in the Serra da Aldeia Suite: a classic post-collisional high Ba-Sr granite in The Riacho do Pontal Fold Belt, NE Brazil." Brazilian Journal of Geology 46, no. 2 (2016): 221–37. http://dx.doi.org/10.1590/2317-4889201620160002.
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ABSTRACT: The Serra da Aldeia Suite is composed by circular or oval-shaped plutons, intrusive in meta-sedimentary and meta-volcanosedimentary rocks in the Riacho do Pontal Fold Belt, NE Brazil. The Serra das Melancias Pluton, belonging to Serra da Aldeia Suite, is located southeastern of Piaui state, near Paulistana city. These plutons represent a major magmatic expression in this area and contain important information about the late magmatic/collisional geologic evolution of the Brasiliano Orogeny. Based on petrographic and geochemical data, three facies were defined in the Serra das Melancias Pluton: granites, syenites and quartz monzonites. The rocks display high-K and alkaline to shoshonitic affinities, are metaluminous and show ferrous character. They are enriched in Light Rare Earth Elements and Large Ion Lithophile Elements, with negative anomalies in Nb, Ta and Ti. Their high Ba, Sr, K/Rb, low Rb, relatively low U, Th, Nb to very low Heavy Rare Earth Elements and Y resemble those of typical high Ba-Sr granitoids. The geochemical data suggest the emplacement of Serra das Melancias Pluton in a transitional, late to post-orogenic setting in the Riacho do Pontal Fold Belt during the late Brasiliano-Pan African Orogeny.
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Rai, Abhishek, V. K. Gaur, S. S. Rai, and K. Priestley. "Seismic signatures of the Pan-African orogeny: implications for southern Indian high-grade terranes." Geophysical Journal International 176, no. 2 (2009): 518–28. http://dx.doi.org/10.1111/j.1365-246x.2008.03965.x.
Full textDissertations / Theses on the topic "Pan-African orogeny"
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Tregoning, Trevor Denzil. "The tectono-metallogenesis during the irumide and pan-African events in South West Africa/Namibia." Thesis, Rhodes University, 1987. http://hdl.handle.net/10962/d1004490.
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A large portion of South west Africa/Namibia is underlain by 2 great orogens. They are the Irumide (Sinclair/Rehoboth) and Damara Orogenies. The L-shaped Irumide Province forms part of a belt which extends over the subcontinent from Namaqualand to as far as Zambia. The volcano-sedimentary sequences of the Irumide are believed to have formed in intracratonic rifts and pull-apart basins during the period 1400 to 900 Ma. The evolution of the NW trending Sinclair Group proceeded by means of 3 major cycles each beginning with the emplacement of basic to intermediate magmas followed by felsic ones. The cycle ended off with subsidence, deposition of immature clastic debris and final tilting of the volcano-clastic sequence. It was suggested that the extensive calc-alkaline lavas present, developed within a magmatic arc above a subduction zone, but this proposal has not been generally accepted. The NE trending Klein Aub-Witvlei Basins consist essentially of red bed alluvial fans and lacustrine sediments with minor volcanics near the base. The red beds and aeolian sediments were deposited in an arid climatic condition. The regional greenschist facies metamorphism and deformation is attributed to a major tectono-thermal event at 1100 Ma. The Damara Orogen (900 - 550 Ma) forms part of the Pan-African mobile belt system of global proportions. The NE trending intracontinental branch (aulacogen) and 2 coastal branches constitute a triple junction with its focal point near Swakopmund. The NE extension of the intracontinental belt has been linked with the Lufilian Arc hosting the renown Zambian Copper Belt deposits. In South West Africa/Namibia this belt hosts many different mineral occurrences which can be grouped into rift and collision related deposits. The tectonic history of the Damara Orogen supports a geodynamic-evolution-with-time hypothesis and represents a transitional phase in which limited Wilson Cycle Tectonics was active. The Theory of Mantle Advection is invoked to explain rifting, thinning and subsidence. Extensive ensialic rifting resulted in a relatively stable Northern Carbonate Platform and several deep troughs hosting turbiditic sequences. Crustal rupture in the Khomas Trough allowed for the emplacement of ocean floor tholeiites known as the Matchless Amphibolite Belt. Subsequent ocean closure and collision resulted in deformation, metamorphism and generation of predominantly S-type granites. The southern continental plate was partially overridden by the northern plate during final collision at 550 Ma. These low angle thrust faults allowed for the emplacement of the Naukluft Nappe Complex on top of younger Nama sediments. The break up of Gondwanaland during the Mesozoic with the splitting of the Atlantic Ocean was responsible for the intrusion of anorogenic alkaline ring complexes along the extension of the NE trending transform faults within the intracontinental branch of the Damara Orogen. A close relationship between the tectonic setting and mineral deposits has been recognized in both the Irumide and Damara Orogenies. In the Irumide, stratiform syngenetic copper deposits are hosted by alluvial fan, playa and lacustrine sediments. The uninterrupted sedimentation from the Irumide to Damara Orogen resulted in similar stratiform copper deposits during the early stages of rifting. In the Damara Orogen the rifting (extensional) phase is characterized by 4 main mineralizing systems: diagenetic/syngenetic (Kupferschiefer-type), epigenetic/hydrothermal Cu-Pb-Zn (Mississippi Valley-type), volcanogenic cupriferous pyrite (Besshi-type) and volcano-exhalative Pb-Zn (Red Sea-type). The collision (compressional) phase was accompanied by 4 main mineralizing processes: epigenetic/hydrothermal Cu-Pb-Zn, hydrotheral/metasomatic Sn-W-rare earth, metamorphogenic Au and U-bearing anatectic melts. The key to the selection of viable exploration targets lies in the understanding of the field evidence and the geodynamics modelling to explain the evolution of the orogen and its associated mineral deposits.
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Belcher, Richard William. "Tectonostratigraphic evolution of the Swartland region and aspects of orogenic lode-gold mineralisation in the Pan-African Saldania Belt, Western Cape, South Africa." Thesis, Stellenbosch : Stellenbosch University, 2003. http://hdl.handle.net/10019.1/49789.
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Thesis (PhD)--Stellenbosch University, 2003.<br>ENGLISH ABSTRACT: The Swartland region in the western Cape, South Africa, covers approximately 5000
km2 and forms part of the Pan-African Saldania Belt that represents the
southernmost extremity of the Pan-African orogenic belts in southern Africa. Regional
mapping of the Swartland area shows that lithologies can be classified using
predominantly structural and to a lesser extent lithological criteria. This led to the
proposal of a new classification, were rocks of the previous classification of the
Malmesbury Group are divided into two new groups, namely the Swartland and
Malmesbury groups.
The Swartland group can be divided into the Berg River and Moorreesburg
formations, a series of quartz-chlorite-muscovite-feldspar schists, quartz schists,
graphitic schists and limestones; and the Bridgetown formation, a series of
metavolcanic rocks with WPB-MORB affinities that possibly represent seafloor.
Deposition of the sediments is suggested to have occurred concurrently with
deformation in an accretionary prism/fore-arc and was initiated with the opening of
the lapetus Ocean at ca. 600 Ma. This early deformation event, Dt (ca. 575 Ma), only
affected the Swartland group and exhibits pervasive bedding transposition, thrusting
and imbrication of units creating a tectonostratigraphic sequence. Where identified,
kinematic indicators and fold vergence indicate a top-to-the-west transport direction
during the early, low-angle Di deformation.
The Malmesbury group overlies the Swartland group, being locally separated by an
unconformity. The Malmesbury group is a succession of conglomerates, grits and
shales (Piketberg Formation), grading into greywackes, shales, siltstones,
sandstones and minor limestones of the Tygerberg and Porterville formations.
Sedimentation probably commenced after ca. 575 Ma and lasted until shortly after
560 Ma. Both the Swartland and Malmesbury groups were then deformed by the deformation event, D2 (ca. 552-545 Ma), and were intruded by the 552 to 510 Ma
Cape Granite Suite. The Franschhoek Formation, formally part of the Malmesbury
Group is now classified, along with the inferred ca. 535-510 Ma Magrug and
Populierbos Formations of the previous Klipheuwel Group. The redefined Klipheuwel
group documents a change in depositional environment from the continental
slope/ocean trench, marine and flyschoid deposits of the Malmesbury group to
continental, fluvial half-graben and graben deposits. Exhumation, extensive erosion
and the formation of a peneplain, was followed by the deposition of the Table
Mountain Sandstone Group around 550-510 Ma.
The Spitskop gold prospect, located 10 km south of Piketberg, represents the first
identified occurrence of mesothermal gold mineralisation in the Saldania Belt.
Metamorphic devolatilisation of the Swartland group during Di led to the scavenging
and transportation of gold along shallow-dipping shear zones that are contained
within the early, sub-horizontal So/Si tectonic fabric. Pervasive fluid movement in the
Spitskop area led to elevated gold values compared to background values
throughout the lithologies at Spitskop. The lack of any economic-grade gold
mineralisation is probably related to the absence of suitably orientated structures,
such as high-angle faults, that are commonly believed to represent the prerequisite
for large fluid throughputs that could result in economic-grade gold deposits. The
mineralisation at Spitskop, however, provides a genetic model for further exploration
of gold in the Swartland group.<br>AFRIKAANSE OPSOMMING: Die Swartland streek in die Wes-Kaap, Suid-Afrika, beslaan ongeveer 5000 km2 en
vorm deel van die Pan-Afrikaanse Saldania-gordel wat die mees suidelike deel van
die Pan-Afrikaanse orogene gordels in suidelike Afrika verteenwoordig. Regionale
kartering van die Swartland streek dui aan dat die gesteentes geklassifiseer kan word
deur oorwegend strukturele, en tot 'n mindere mate litologiese kriteria te gebruik.
Gevolglik word ‘n nuwe klassifikasie voorgestel, waar gesteentes volgens die vorige
klassifikasie van die Malmesbury groep verdeel word in twee groepe, naamlik die
Swartland en Malmesbury groepe.
Die Swartland groep kan verdeel word in die Bergrivier en Moorreesburg formasies,
‘n reeks kwarts-chloriet-muskoviet-veldspaat skis, kwarts skis, grafitiese skis en
kalksteen; en die Bridgetown formasie, ‘n reeks metavulkaniese gesteentes met
WPB-MORB affiniteite wat moontlik oseaanvloer verteenwoordig. Daar word
voorgestel dat afsetting van die sedimente gelyktydig plaasgevind het saam met
vervorming in ‘n akkresionere prisma/voorboog, geinisieer deur die opening van die
lapetus Oseaan (ca. 600 Ma). Hierdie vroee vervorming, Di (ca. 575 Ma), het slegs
die Swartland groep geaffekteer en vertoon deurdringende verplasing van
gelaagdheid, oorskuiwing en imbrikasie van eenhede en het ‘n tektonostratigrafiese
opeenvolging gevorm. Waar identifiseer, dui kinematiese aanwysers en plooi
kanteling op ‘n bokant-na-wes beweging gedurende die vroee, lae hoek Di
vervorming.
Die Malmesbury groep oordek die Swartland groep, plaaslik geskei deur ‘n
diskordansie. The Malmesbury groep bestaan uit ‘n opeenvolging konglomeraat,
grintsteen en skalie (Piketberg formasie), wat gradeer in grouwak, skalie, sliksteen,
sandsteen en ondergeskikte kalksteen van die Tygerberg en Porterville formasies.
Sedimentasie het waarskynlik begin na ca. 575 Ma en het voortgeduur tot kort na 560 Ma. Beide die Swartland en Malmesbury groepe is hierna vervorm deur D2, (ca.
552-545 Ma) en daaropvolgend ingedring deur die 552 tot 510 Ma Kaap Graniet
Suite. Die Franschhoek Formasie, voorheen deel van die Malmesbury Groep, word
nou geklassifiseer tesame met die afgeleide ca. 535-510 Ma Magrug en Populierbos
formasies as deel van die voorheen geklassifiseerde Klipheuwel groep. Die
hergedefinieerde Klipheuwel groep dui op 'n verandering in afsettingsomgewing
vanaf die kontinentale glooiing/oseaantrog, mariene en flyschoiede afsettings van die
Malmesbury groep na kontinentale, fluviale half-graben en graben afsettings.
Herblootstelling, omvattende erosie en die vorming van ‘n skiervlakte is gevolg deur
die afsetting van die Tafelberg Sandsteen Groep random 520-510 Ma.
Die Spitskop goudvoorkoms, 10 km suid van Piketberg, verteenwoordig die eerste
identifiseerde voorkoms van mesotermale goudmineralisasie in die Saldania Gordel.
Metamorfe ontvlugtiging van die Swartland groep gedurende Dt het aanleiding gegee
tot die roofuitruiling en vervoer van goud langs laaghellende skuifskeursones in die
vroee, subhorisontale S0/Si tektoniese maaksel. Deurdringende vloeistofbeweging in
die Spitskop omgewing het aanleiding gegee tot verhoogde goudwaardes in
vergelyking met agtergrond waardes dwarsdeur die litologiee by Spitskop. Die gebrek
aan ekonomiese graad goud mineralisasie is waarskynlik verwant aan die
afwesigheid van geskikte georienteerde strukture, soos hoe hoek verskuiwings, wat
oor die algemeen beskou word as ‘n voorvereiste vir die toevoer van groot
hoeveelhede vloeistof wat kon aanleiding gegee het tot ekonomiese graad
goudafsettings. Die mineralisasie by Spitskop verskaf egter 'n model vir verdere goud
eksplorasie in die Swartland groep.
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Brahimi, Sonia. "Caractérisation géophysique (méthodes potentielles, imagerie sismique) de structures géologiques : des terranes panafricains de la chaine trans-saharienne, aux vallées-tunnel et incisions glaciaires de la Mer du Nord et d'Algérie." Thesis, Strasbourg, 2019. http://www.theses.fr/2019STRAH005.
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L’analyse des données magnétiques et gravimétriques de la partie nord de la ceinture trans-saharienne a permis de proposer une carte de compartimentalisation géophysique et rhéologique des structures crustales et de visualiser les terranes du bouclier Touareg sur plus de 1000 km au nord, sous les bassins sédimentaires sahariens et plusieurs aspects ont pu être discutés. Un pseudo réseau de quatre générations successives de paléovallées et incisions a été mis en évidence dans la succession glaciaire de l’Ordovicien supérieur au NE du bassin d’Illizi sur la base des données sismiques de haute résolution. Pour chaque incision, la géométrie ainsi que les faciès sismiques de leur remplissage ont été déterminés. Un parallélisme entre la distribution de certaines paléovallées et l'orientation des anomalies magnétiques a été observé, mais aucune relation stratigraphique entre ces structures n'a été identifiée sur les sections sismiques. Un réseau complexe de vallées tunnel glaciaires du Pléistocène en mer du Nord a été identifié sur la base de données aéromagnétiques à haute résolution. Une analyse magnétique détaillée a été réalisée en combinant plusieurs méthodes magnétiques. A la fin, des modèles magnétiques synthétiques 2D ont été calculés pour les incisions ordoviciennes, appliqué pour le cas du bassin d’Illizi. Les résultats obtenus montrent que leur détection magnétique est possible, si toutes fois un levé magnétique à haute résolution serait disponible<br>The magnetic and gravimetric data analysis of the northern part of the trans-saharan belt allowed to propose a geophysical and rheological compartmentalization map of its crustal structures and to visualize the Tuareg shield terranes over 1000 km to the north, under the saharan sedimentary basins and several aspects have been discussed. A pseudo network of four successive generations of paleovalleys and incisions has been identified on the upper Ordovician glacial succession in the north-eastern part of the Illizi basin on the basis of high-resolution seismic data. For each incision, the geometry and seismic facies of their filling have been determined. Parallelism between the distribution of some paleovalleys and magnetic anomaly orientations has been observed, but no stratigraphic relationship between them has been identified on seismic sections. A complex network of Pleistocene glacial tunnel valleys in the North Sea has been identified on the basis of high-resolution aeromagnetic data. A detailed magnetic analysis was performed by combining several magnetic methods. Finally, 2D synthetic magnetic models were calculated for Ordovician incisions, applied in the case of the Illizi basin. The results obtained show that their magnetic detection is possible, if a high-resolution magnetic survey would still be available
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McDermott, P. F. "Granite petrogenesis and crustal evolution studies in the Damara Pan-African orogenic belt, Namibia." Thesis, Open University, 1986. http://oro.open.ac.uk/57005/.
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Major and trace element data for Damara granitoids distinguish three geochemically distinct granitoid groups, - crustal-melt granitoids, calc-alkaline granitoids and within-plate granitoids. The overwhelming majority of the Oamara granitoids are peraluminous crustal-melt leucogranites which have elevated <sup>87</sup>Sr/<sup>86</sup>Sr ratios (> 0.710) and old model Nd ages (~ 2.0 Ga). Calc-alkaline diorites are metaluminous and have the lowest <sup>87</sup>Sr/<sup>86</sup>Sr ratios (0.704 - 0.707) and model Nd ages (OM) in the range 1.1 -1.7 Ga. Within-plate granitoids are characterised by elevated high-field strength (HFS) abundances and have model Nd ages (OM) in the range 1.1 - 1.6 Ga. All Damara granitoids have model Nd ages (OM) older than about 1.0 Ga suggesting that intracrustal reworking was the dominant process and crustal growth was negligible. Damara granitoids define a hyperbola on an ∈ Sr vs. ∈ Nd diagram but cannot be modelled as simple binary mixtures between old continental crust and depleted mantle end-members. An episodic intracrustal remobilisation model is proposed to explain the hyperbola defined by granitoid data on an ∈ Sr vs. ∈ Nd diagram. Within the 10 km thick Damara metasedimentary pile <sup>87</sup>Sr/<sup>86</sup>Sr ratios increase systematically with depth. This trend is accompanied by a decrease in <sup>143</sup>Nd/<sup>144</sup>Nd ratios. Model Nd ages (CHUR) for the stratigraphically oldest Damara metasediments (Nosib Group) are about 2.0 Ga whereas the younger metasediments (Kuiseb Formation and Nama Group) have model Nd ages (CHUR) about 1.0 Ga reflecting sediment input from younger source terrains. The ratio of model ages (T<sup>Nd</sup><sub>CHUR</sub>/T<sup>Sr</sup><sub>BE</sub>) is used as an index of intracrustal reworking since it provides a measure of Rb/Sr fractionation (increases) relative to SmlNd fractionation. The older Damara metasediments (Nosib Group) have the highest model age ratios suggesting that their source terrains have suffered the largest amount of intracrustal reworking. However, the rate of intracrustal reworking was greatest in source terrains sampled by the younger Damara metasediments (Kuiseb Formation and Nama Group). This suggests that the rate of intracrustal reworking increased through time in the interval (2.0 - 1.0 Ga) in this segment of continental crust.
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Moulahoum, Omar. "Dualité du magmatisme d'âge pan-africain : Aspects structuraux et pétrologiques des granites subalcalins et alumineux de la région de Tamanrasset (Hoggar central, Algérie." Nancy 1, 1988. http://www.theses.fr/1988NAN10049.
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Durant l'orogène du "Pan-Africain" (~ 600 Ma), la région du Hoggar central, à l'instar de l'ensemble du Bouclier Touareg, a été intensément affectée. Cet évènement est accompagné de la mise en place d'ensembles magmatiques variés. Dans la région de Tamanrasset, deux magmatismes de nature différente sont mis en évidence : magmatisme subalcalin et magmatisme alumineux. Le premier est représenté par les massifs syn à tardi-orogéniques (Anfeg - Tifferkit), voire post-orogénique (Aheleheg') tandis que le second est exclusivement constitué par les plutons post-orogéniques (In-Tounine et intrusions granitiques à albite-topaze). Compte tenu des critères de terrain, pétrographiques, géochimiques et parfois isotopiques, trois groupes magmatiques peuvent être distingués.
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Isseini, Moussa. "Croissance et différenciation crustales au Néoprotérozoique : exemple du domaine panafricain du Mayo Kebbi au Sud-Ouest du Tchad." Thesis, Nancy 1, 2011. http://www.theses.fr/2011NAN10035/document.
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Le massif du Mayo Kebbi au sud-ouest du Tchad est localisé entre le craton du Congo au Sud, le craton Ouest Africain à l'Ouest et le Métacraton du Sahara à l'Est. Formé au cours de l'orogenèse panafricaine, entre 800 et 570 Ma, il est constitué de deux ceintures de roches vertes (Zalbi et Goueygoudoum), trois complexes magmatiques (Chutes Gauthiot, Léré et Figuil) et des intrusions post-tectoniques distingués sur la base de leurs caractères structuraux, pétrologiques, géochimiques et géochronologiques. L'évolution géodynamique de ce massif comprend les phases suivantes:Phase 1: Mise en place d'un complexe mafique et intermédiaire (CMI) dont la métadiorite de Boloro datée à 748 ± 4 Ma (U-Pb sur zircon). Cette métadiorite, riche en terres rares, se caractérise par LaN/YbN ~ 12, Sr/Y > 32, teneurs en LILE, Cr, Ni élevées et des anomalies négatives en Nb-Ta. Ces caractéristiques sont attribuées à la fusion partielle de la plaque océanique plongeante et interaction des magmas produits avec le coin mantellique au cours de leur ascension.Phase 2: Mise en place des métagabbros et métabasaltes (700 ± 10 Ma: U-Pb sur zircon) de la série métavolcano-sédimentaire de Zalbi. Ces roches sont caractérisées par un découplage LILE/HFSE, des anomalies négatives en Nb-Ta et des rapports LaN/YbN indiquant un fractionnement faible à modéré des terres rares. En particulier, leurs caractères géochimiques sont similaires à ceux des bassins arrière-arcs modernes. La signature isotopique en Sr et Nd de ces roches exclut toute contamination par une croûte continentale ancienne au moment de leur mise en place. CMI et série métavolcano-sédimentaires, regroupés dans le cadre des ceintures de roches vertes, représentent ainsi une accrétion juvénile en contextes d'arc insulaire/bassin arrière-arc.Phase 3: La métadiorite quartzique syntectonique du complexe magmatique des chutes Gauthiot (665 ± 1 Ma: âge U-Pb sur zircon, Penaye et al., 2006) correspond à la mise en place de magmas contemporains d'une première collision, qui implique le massif du Mayo Kebbi et le bloc rigide de l'Adamaoua-Yadé à l'Est. Cet évènement marque le début de la fermeture du bassin arrière-arc de Zalbi et d'un épaississement crustal.Phase 4 : L'épaississement est responsable de la différentiation intracrustale par fusion partielle des roches accrétées au cours des phases précédentes à la base de l'arc. Pendant cette phase se mettent en place des magmas tonalitiques, dont la tonalite à hornblende-biotite de Guegou (complexe magmatique de Léré) datée à 647 ± 5 Ma (U-Pb sur zircon). Les magmas produits ont des caractères de magmas TTG et laissent un résidu à grenat à la base de la croûte continentale.Phase 5: La tonalite syntectonique du complexe magmatique de Figuil, datée à 618 ± 6 Ma (U-Pb sur zircon), se distingue par eNd initial = -3 et 87Sr/86Sr initial = 0,7073. Les signatures isotopiques de cette tonalite démontrent l'implication dans le magmatisme d'une croûte Pré-Néoprotérozoïque. Elle est contemporaine d'une deuxième collision qui fait intervenir le massif du Mayo Kebbi et le domaine Occidental de la Ceinture Orogénique d'Afrique Centrale.Phase 6: La mise en place du granite de type A de Zabili à 567 ± 10 Ma (âge U-Pb sur zircon) est associée aux dernières manifestations magmatiques du cycle orogénique panafricain (intrusions post-tectoniques). Les caractères géochimiques (appauvrissement extrême en Sr, Eu, Ca, Mg, Ni) et isotopiques (eNd initial = +3 à +7) de ce granite indiquent une origine par cristallisation fractionnée à partir de magmas d'origine mantellique et contamination de ceux-ci au cours de leur mise en place dans la croûte supérieure par une composante crustale ancienne<br>The Mayo Kebbi massif (south-western Chad) is located between the Congo craton, the West African craton and the Saharan Metacraton. It consists of two greenstone belts (Zalbi and Goueygoudoum), three magmatic complexes (Gauthiot falls, Lere, Figuil) and post-tectonic intrusions distinguished on the basis of their structural, petrological, geochemical and geochronological characteristics. The geodynamic evolution of this massif includes the following phases:Phase 1: Emplacement of a Mafic to Intermediate Plutonic (MIP) complex. Boloro metadiorite, which belongs to this complex, is dated at 748 ± 4 Ma (U-Pb zircon age). This metadiorite is enriched in REE and characterized by LaN/YbN ~ 12, Sr/Y > 32, high LILE, Cr and Ni contents but negative anomalies in Nb-Ta. These features are attributed to partial melting of the slab followed by interaction of the produced magmas with the mantle wedge during their ascent.Phase 2: Emplacement of metagabbros and metabasalts (700 ± 10 Ma: U-Pb zircon age) of the Zalbi metavolcanic-sedimentary group. These rocks are characterized by a decoupling of LILE and HFSE, negative Nb-Ta anomalies, weak to moderate LREE fractionation relative to HREE. In particular, their geochemical characteristics are similar to modern back-arc basins. The isotopic compositions of Sr and Nd of these rocks preclude contamination by old continental crust of the related magmas during their emplacement. Accordingly, the MIP complex and the Zalbi metavolcanic-sedimentary group are associated to juvenile accretion in an island arc/back-arc basin tectonic setting.Phase 3: The syntectonic quartz metadiorite of Gauthiot Falls magmatic complex (665 ± 1 Ma: U-Pb zircon age, Penaye et al., 2006) is emplaced during a first collision event, which involves the Mayo Kebbi massif and the Adamaoua-Yade domain to the east. This event marks the beginning of the closure of the Zalbi back-arc basin and crustal thickening.Phase 4: The thickening is responsible of intra-crustal differentiation by partial melting of rocks accreted during the previous phases at the base of the arc. During this phase, several tonalitic intrusions are emplaced, including hornblende-biotite tonalites of Gauthiot Falls and Guegou tonalite (Lere magmatic complex). The latter is dated at 647 ± 5 Ma (U-Pb zircon age). The produced magmas have typical features of TTG magmas, leaving a garnet bearing residue at the base of the continental crust.Phase 5: The syntectonic tonalite of Figuil magmatic complex dated at 618 ± 6 Ma (U-Pb zircon age), is characterized by initial ?Nd = -3 and initial 87Sr/86Sr = 0.7073 attesting for the involvement of pre-Neoproterozoic crust on its origin. It marks a second collision event between the Mayo Kebbi massif and the Western domain of the Central African Orogenic Belt to the west.Phase 6: The Zabili A-type granite emplaced at 567 ± 10 Ma (U-Pb zircon age) and is related to the last magmatic events of the Pan-African orogenic cycle (post-tectonic intrusions). The geochemical (low Sr, Eu, Ca, Mg, Ni) and isotopic compositions (initial ?Nd = +3 à +7) of this granite point to an origin involving extreme fractionation of mantle-derived magmas which interacted with an old crustal component during their emplacement in the upper continental crust
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Bassahak, Jean. "Le complexe plutonique du Massif de Kogue (Poli-nord Cameroun) : Pétrologie, géochimie, pétrologie structurale, sa place dans le plutonisme de la chaîne panafricaine au Nord Cameroun." Nancy 1, 1988. http://www.theses.fr/1988NAN10017.
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L'architecture, la mise en place et la pétrogénèse du Massif du Kogue (Poli, Nord Cameroun) s'intègrent dans l'évolution tectonique et plutonique de la zone mobile panafricaine du Nord Cameroun. Intrusion dans les formations métamorphiques de Poli, le complexe plutonique de Kogue est formé de deux unités constituées par deux lignées de différenciation magmatique, d'affinité calco-alcaline. L'agencement et l'analyse des trajectoires des fluidalités planaires soulignent une mise en place syntectonique sous forme de dome diapir dans un couloir de cisaillement. L'état rhéologique des magmas granitique et dioritique, dans les zones de brèches magmatiques montre que ceux-ci sont contemporains et ont une mise en place synchrone
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Toteu, Sadrack-Félix. "Chronologie des grands ensembles structuraux de la région de Poli : Accretion crustale dans la chaîne panafricaine du Nord Cameroun." Nancy 1, 1987. http://www.theses.fr/1987NAN10057.
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Les nouvelles données structurales, géochimiques et géochronologiques indiquent un important volume de matériel d'âge protérozoïque supérieur dans le "complexe de base" et dans la "série de Poli". L'évolution tectonique et métamorphique est comparable pour les deux ensembles. Les caractéristiques géochimiques et isotopiques de l'essentiel des formations plutoniques et volcaniques de l'essentiel des formations plutoniques et volcaniques montrent qu'il s'agit de matériel juvénile nouvellement mis en place en bordure d'une croûte plus ancienne. Une chronologie des évènements panafricains est établie. Les nouveaux résultats permettent d'interprêter l'orogénèse panafricaine du Nord Cameroun en terme de tectonique des plaques
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Djerossem, Nenadji Félix. "Croissance et remobilisation crustales au Pan-Africain dans le sud du massif du Ouaddaï (Tchad)." Thesis, Toulouse 3, 2018. http://www.theses.fr/2018TOU30319/document.
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Cette thèse est consacrée à la croissance et à la remobilisation crustales au Pan-Africain dans le Sud du massif du Ouaddaï au Tchad, situé à la marge Sud du Métacraton du Sahara et au Nord du Craton du Congo. La cartographie du secteur d'étude a permis de distinguer des roches métasédimentaires comprenant des niveaux d'amphibolites et intrudées par des roches plutoniques de composition intermédiaire à felsique. Les amphibolites correspondent à des basaltes tholeiitiques dérivés de la fusion partielle d'un manteau appauvri (ƐNd540= 4). Les roches felsique, représentées par des leucogranites de type-S, donnant des âges U-Pb sur zircon de 635 ± 3 Ma et 612 ± 8 Ma, sont issues de la fusion partielle des métasédiments. Les granitoïdes potassiques calco-alcalin de type-I, donnant un âge U-Pb sur zircon à 538 ± 5 Ma, incluant une monzonite à pyroxène de nature shoshonitique datée autour de ca. 540 Ma, sont caractérisées par des signatures isotopiques radiogéniques (ƐNd620= -4 et -15) et sont attribuées à la fusion partielle d'un manteau enrichi plus ou moins contaminé. Les roches métasédimentaires sont caractérisées par une foliation composite S0 /S1-2 de direction NE-SW qui est associée à des plis isoclinaux P1 et P2 d'échelle centimétrique à hectométrique et qui porte une linéation L1-2 plongeant faiblement vers le NW. Cette foliation est également affectée par des plis droits ouverts P3 associés à une schistosité de plan axial S3 fortement pentée vers le NNW ou le NW. La présence de grains de zircon détritiques et leurs signatures Hf comprenant une composante héritée Archéenne à Paléoprotérozoique indique que les roches métasédimentaires sont issues de l'érosion des cratons voisins et un dépôt au début du Néoprotérozoique.[...]<br>This thesis is devoted to crustal growth and Pan-African reworking in the south of the Ouaddaï massif in Chad, located at the southern margin of the Sahara Metacraton and north of the Congo Craton. Geologic mapping has allowed to identify metasedimentary units alternating with amphibolites and intruded by plutonic rocks with intermediate to felsic composition. Amphibolites correspond to pre-tectonic tholeiitic basalts derived from the partial melting of the depleted mantle (ƐNd540= 4). The felsic rocks, represented by S-type leucogranites yielding U-Pb zircon ages of 635 ± 3 Ma and 612 ± 8 Ma, are derived from the partial melting of metasediments. High-K calc-alkaline I-type granitoids yielding U-Pb zircon ages at 538 ± 5 Ma, and including a shoshonitic pyroxene-monzonite yielding U-Pb zircon ages at 538 ± 5 Ma are characterized by radiogenic isotopic signatures (ƐNd540= -4 et -15) and are partial melting of an enriched mantle with a potential impact of mixing of mantle and crustal-derived magmas. Metasedimentary rocks display a NE-SW trending S0/S1-2 foliation associated with centimeter to hectometer scales F1 and F2 isoclinal folds delineating hook type interferences pattern and bearing a L1-2 lineation weakly dipping towards the NW. The S0/S1-2 foliation is also affected by upright open F3 folds marked by the development of a faint axial planar S3 schistosity variably dipping to the NNW or NW. Zircon detrital grains with Hf signatures pointing to an Archaean to Paleoproterozoic inheritance indicates that metasedimentary rocks are derived from erosion of the surrounding cratons and were deposited in the early Neoproterozoic. These rocks were subsequently affected by deformation and metamorphism dated at 627 ± 7 Ma (by Th-U-Pb on monazite) and at 602 ±3 Ma (by U-Pb on zircon), typical of green schist facies and amphibolite facies. [...]
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Hueck, Mathias. "Long-term activity of shear zones in the Dom Feliciano Belt and associated terranes (South America)." Doctoral thesis, 2018. http://hdl.handle.net/11858/00-1735-0000-002E-E503-6.
Full textBooks on the topic "Pan-African orogeny"
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Abdeen, Mamdouh M. Late orogenic basin evolution, deformation, and metamorphism in the Pan-African basement, Wadi Queih, Eastern Desert of Egypt. Forschungszentrum Jülich, Central Library, 1998.
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Samir, El-Gaby, and Greiling Reinhard, eds. The Pan-African belt of northeast Africa and adjacent areas: Tectonic evolution and economic aspects of a late Proterozoic orogen. Friedr. Vieweg, 1988.
Find full textBook chapters on the topic "Pan-African orogeny"
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Boullier, Anne-Marie. "The Pan-African Trans-Saharan Belt in the Hoggar Shield (Algeria, Mali, Niger): A Review." In The West African Orogens and Circum-Atlantic Correlatives. Springer Berlin Heidelberg, 1991. http://dx.doi.org/10.1007/978-3-642-84153-8_5.
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Kröner, A., and R. J. Stern. "Pan-African Orogeny." In Encyclopedia of Geology. Elsevier, 2005. http://dx.doi.org/10.1016/b978-0-08-102908-4.00431-8.
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Kröner, A., and R. J. Stern. "AFRICA | Pan-African Orogeny." In Encyclopedia of Geology. Elsevier, 2005. http://dx.doi.org/10.1016/b0-12-369396-9/00431-7.
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Taylor, W. E. G., Y. A. Hamed El Kazzaz, and A. A. Rashwan. "An outline of the tectonic framework for the Pan-African orogeny in the vicinity of Wadi Um Relan area, south Eastern Desert, Egypt." In Geoscientific Research in Northeast Africa. CRC Press, 2017. http://dx.doi.org/10.1201/9780203753392-6.
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Frimmel, Hartwig E. "Chapter 5.1 Configuration of Pan-African Orogenic Belts in Southwestern Africa." In Neoproterozoic-Cambrian Tectonics, Global Change And Evolution: A Focus On South Western Gondwana. Elsevier, 2009. http://dx.doi.org/10.1016/s0166-2635(09)01610-7.
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El-Makhrouf, Ali A., and P. D. Fullagar. "The rubidium-strontium geochronology of the Pan-African post-orogenic granites of the eastern Tibisti orogenic belt, Tibisti Massif, South-central Libya." In Geological Exploration in Murzuq Basin. Elsevier, 2000. http://dx.doi.org/10.1016/b978-044450611-5/50020-9.
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Montecinos de Almeida, Delia del Pilar, Farid Chemale, and Adriane Machado. "Late to Post-Orogenic Brasiliano-Pan-African Volcano-Sedimentary Basins in the Dom Feliciano Belt, Southernmost Brazil." In Petrology - New Perspectives and Applications. InTech, 2012. http://dx.doi.org/10.5772/25189.
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"Pan-African Tectonism and the Genesis of Base Metal Sulfide Deposits in the Northern Foreland of the Damara Orogen, Namibia." In Carbonate-Hosted Lead-Zinc Deposits. Society of Economic Geologists, 1996. http://dx.doi.org/10.5382/sp.04.13.
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Rogers, John J. W., and M. Santosh. "Gondwana and Pangea." In Continents and Supercontinents. Oxford University Press, 2004. http://dx.doi.org/10.1093/oso/9780195165890.003.0010.
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Pangea, the most recent supercontinent, attained its condition of maximum packing at ~250 Ma. At this time, it consisted of a northern part, Laurasia, and a southern part, Gondwana. Gondwana contained the southern continents—South America, Africa, India, Madagascar, Australia, and Antarctica. It had become a coherent supercontinent at ~500 Ma and accreted to Pangea largely as a single block. Laurasia consisted of the northern continents—North America, Greenland, Europe, and northern Asia. It accreted during the Late Paleozoic and became a supercontinent when fusion of these continental blocks with Gondwana occurred near the end of the Paleozoic. The configuration of Pangea, including Gondwana, can be determined accurately by tracing the patterns of magnetic stripes in the oceans that opened within it (chapters 1 and 9). The history of accretion of Laurasia is also well known, but the development of Gondwana is highly controversial. Gondwana was clearly a single supercontinent by ~500 Ma, but whether it formed by fusion of a few large blocks or the assembly of numerous small blocks is uncertain. Figure 8.1 shows Gondwana divided into East and West parts, but the boundary between them is highly controversial (see below). We start this chapter by investigating the history of Gondwana, using appendix SI to describe detailed histories of orogenic belts of Pan-African age (600–500-Ma). Then we continue with the development of Pangea, including the Paleozoic orogenic belts that led to its development. The next section summarizes the paleomagnetically determined movement of blocks from the accretion of Gondwana until the assembly of Pangea, and the last section discusses the differences between Gondwana and Laurasia in Pangea. The patterns of dispersal and development of modern oceans are left to chapter 9, and the histories of continents following dispersal to chapter 10. By the later part of the 1800s, geologists working in the southern hemisphere realized that the Paleozoic fossils that occurred there were very different from those in the northern hemisphere. They found similar fossils in South America, Africa, Madagascar, India, and Australia, and in 1913 they added Antarctica when identical specimens were found by the Scott expedition.
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Osman, A. F., R. O. Greiling, L. N. Warr, M. E. Hilmy, A. I. Ragab, and M. F. El Ramly. "Distinction of different syn- and late orogenic Pan-African sedimentary sequences by metamorphic grade and illite crystallinity (W. Zeidun, Central Eastern Desert, Egypt)." In Geoscientific Research in Northeast Africa. CRC Press, 2017. http://dx.doi.org/10.1201/9780203753392-4.
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