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Journal articles on the topic 'East African Orogen'

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Author: Grafiati

Published: 10 December 2022

Last updated: 28 January 2023

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1

JACOBS, J. "The East Antarctic Orogen: Southern Continuation of the East African Orogen into Antarctica." Gondwana Research 4, no. 2 (April 2001): 171. http://dx.doi.org/10.1016/s1342-937x(05)70682-1.

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2

Fritz, H., M. Abdelsalam, K. A. Ali, B. Bingen, A. S. Collins, A. R. Fowler, W. Ghebreab, et al. "Orogen styles in the East African Orogen: A review of the Neoproterozoic to Cambrian tectonic evolution." Journal of African Earth Sciences 86 (October 2013): 65–106. http://dx.doi.org/10.1016/j.jafrearsci.2013.06.004.

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3

Stern, Robert J. "Crustal evolution in the East African Orogen: a neodymium isotopic perspective." Journal of African Earth Sciences 34, no. 3-4 (April 2002): 109–17. http://dx.doi.org/10.1016/s0899-5362(02)00012-x.

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4

BOYD, R., O. NORDGULEN, R. J. THOMAS, B. BINGEN, T. BJERKGARD, T. GRENNE, I. HENDERSON, et al. "THE GEOLOGY AND GEOCHEMISTRY OF THE EAST AFRICAN OROGEN IN NORTHEASTERN MOZAMBIQUE." South African Journal of Geology 113, no. 1 (March 1, 2010): 87–129. http://dx.doi.org/10.2113/gssajg.113.1.87.

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5

Collins, A. S. "The Tectonic Evolution of Madagascar: Its Place in the East African Orogen." Gondwana Research 3, no. 4 (October 2000): 549–52. http://dx.doi.org/10.1016/s1342-937x(05)70760-7.

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6

Ueda, Kosuke, Joachim Jacobs, Robert James Thomas, Jan Kosler, Matt S. A. Horstwood, Jo-Anne Wartho, Fred Jourdan, Benjamin Emmel, and Rogerio Matola. "Postcollisional High-Grade Metamorphism, Orogenic Collapse, and Differential Cooling of the East African Orogen of Northeast Mozambique." Journal of Geology 120, no. 5 (September 2012): 507–30. http://dx.doi.org/10.1086/666876.

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7

Collins, Alan S., Ian C. W. Fitzsimons, Bregje Hulscher, and Théodore Razakamanana. "Structure of the eastern margin of the East African Orogen in central Madagascar." Precambrian Research 123, no. 2-4 (June 2003): 111–33. http://dx.doi.org/10.1016/s0301-9268(03)00064-0.

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8

Beyth, M., D. Avigad, H. U. Wetzel, A. Matthews, and S. M. Berhe. "Crustal exhumation and indications for Snowball Earth in the East African Orogen: north Ethiopia and east Eritrea." Precambrian Research 123, no. 2-4 (June 2003): 187–201. http://dx.doi.org/10.1016/s0301-9268(03)00067-6.

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9

Yoshida, Masaru, Joachim Jacobs, M. Santosh, and H. M. Rajesh. "Role of Pan-African events in the Circum-East Antarctic Orogen of East Gondwana: a critical overview." Geological Society, London, Special Publications 206, no. 1 (2003): 57–75. http://dx.doi.org/10.1144/gsl.sp.2003.206.01.05.

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10

GRENNE, T., R. B. PEDERSEN, T. BJERKGÅRD, A. BRAATHEN, M. G. SELASSIE, and T. WORKU. "Neoproterozoic evolution of Western Ethiopia: igneous geochemistry, isotope systematics and U–Pb ages." Geological Magazine 140, no. 4 (July 2003): 373–95. http://dx.doi.org/10.1017/s001675680300801x.

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New geochemical, isotopic and age data from igneous rocks complement earlier models of a long-lived and complex accretionary history for East African Orogen lithologies north of the Blue Nile in western Ethiopia, but throw doubt on the paradigm that ultramafic complexes of the region represent ophiolites and suture zones. Early magmatism is represented by a metavolcanic sequence dominated by pyroclastic deposits of predominantly basaltic andesite composition, which give a Rb–Sr whole-rock errorchron of 873±82 Ma. Steep REE patterns and strong enrichments of highly incompatible trace elements are similar to Andean-type, high-K to medium-K calc-alkaline rocks; εNd values between 4.0 and 6.8 reflect a young, thin continental edge. Interlayered basaltic flows are transitional to MORB and compare with mafic rocks formed in extensional, back-arc or inter-arc regimes. The data point to the significance of continental margin magmatism already at the earliest stages of plate convergence, in contrast with previous models for the East African Orogen. The metavolcanites overlap compositionally with the Kilaj intrusive complex dated at 866±20 Ma (U–Pb zircon) and a related suite of dykes that intrude thick carbonate-psammite sequences of supposedly pre-arc, continental shelf origin. Ultramafic complexes are akin to the Kilaj intrusion and the sediment-hosted dykes, and probably represent solitary intrusions formed in response to arc extension. Synkinematic composite plutons give crystallization ages of 699±2 Ma (Duksi, U–Pb zircon) and 651±5 Ma (Dogi, U–Pb titanite) and testify to a prolonged period of major (D1) contractional deformation during continental collision and closure of the ‘Mozambique Ocean’. The plutons are characterized by moderately peraluminous granodiorites and granites with εNd values of 1.0–2.0. They were coeval with shoshonitic, latitic, trachytic and rare trachybasaltic intrusions with very strong enrichments of highly incompatible trace elements and εNd of 0.4–8.0. The mafic end-member is ascribed to partial melting of enriched sub-continental mantle that carried a subduction component inherited from pre-collision subduction. Contemporaneous granodiorite and granite formation was related to crustal underplating of the mafic magmas and consequent melting of lower crustal material derived from the previously accreted, juvenile arc terranes of the East African Orogen.

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11

Andresen, A., L. E. Augland, G. Y. Boghdady, A. M. Lundmark, O. M. Elnady, M. A. Hassan, and M. A. Abu El-Rus. "Structural constraints on the evolution of the Meatiq Gneiss Dome (Egypt), East-African Orogen." Journal of African Earth Sciences 57, no. 5 (July 2010): 413–22. http://dx.doi.org/10.1016/j.jafrearsci.2009.11.007.

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12

Jacobs, J., R. Klemd, C. M. Fanning, W. Bauer, and F. Colombo. "Extensional collapse of the late Neoproterozoic-early Palaeozoic East African-Antarctic Orogen in central Dronning Maud Land, East Antarctica." Geological Society, London, Special Publications 206, no. 1 (2003): 271–87. http://dx.doi.org/10.1144/gsl.sp.2003.206.01.14.

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13

COLLINS, ALAN S., THEODORE RAZAKAMANANA, and BRIAN F. WINDLEY. "Neoproterozoic extensional detachment in central Madagascar: implications for the collapse of the East African Orogen." Geological Magazine 137, no. 1 (January 2000): 39–51. http://dx.doi.org/10.1017/s001675680000354x.

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A laterally extensive, Neoproterozoic extensional detachment (the Betsileo shear zone) is recognized in central Madagascar separating the Itremo sheet (consisting of Palaeoproterozoic to Mesoproterozoic sediments and underlying basement rocks) from the Antananarivo block (Archaean/Palaeoproterozoic crust re-metamorphosed in the Neoproterozoic). Non-coaxial deformation gradually increases to a maximum at a lithological contrast between the granitoids and gneisses of the footwall and the metasedimentary rocks of the hangingwall. Ultramylonites at this highest-strained zone show mineral-elongation lineations that plunge to the southwest.σ-, δ- and C/S-type fabrics imply top-to-the-southwest extensional shear sense. Contrasting metamorphic grades are found either side of the shear zone. In the north, where this contrast is greatest, amphibolite-grade footwall rocks are juxtaposed with lower-greenschist-grade hangingwall rocks. The metamorphic grade in the hangingwall increases to the south, suggesting that a crustal section is preserved.The Betsileo shear zone facilitated crustal-scale extensional collapse of the East African Orogeny, and thus represents a previously poorly recognized structural phase in the story of Gondwanan amalgamation. Granitic magmatism and granulite/amphibolite-grade metamorphism in the footwall are all associated with formation of the Betsileo shear zone, making recognition of this detachment important in any attempt to understand the tectonic evolution of central Gondwana.

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14

Goodenough, K. M., R. J. Thomas, B. De Waele, R. M. Key, D. I. Schofield, W. Bauer, R. D. Tucker, et al. "Post-collisional magmatism in the central East African Orogen: The Maevarano Suite of north Madagascar." Lithos 116, no. 1-2 (April 2010): 18–34. http://dx.doi.org/10.1016/j.lithos.2009.12.005.

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15

Collins, Alan S., Simon Johnson, Ian C. W. Fitzsimons, Chris McA Powell, Bregje Hulscher, Jenny Abello, and Théodore Razakamanana. "Neoproterozoic deformation in central Madagascar: a structural section through part of the East African Orogen." Geological Society, London, Special Publications 206, no. 1 (2003): 363–79. http://dx.doi.org/10.1144/gsl.sp.2003.206.01.17.

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16

Bauer, W., H. Siemes, G. Spaeth, and J. Jacobs. "Quartz microfabrics of shear zones of the western orogenic front of the East African/Antarctic Orogen: result of transpressive deformation?" Geotectonic Research 97, no. 1 (September 1, 2015): 1–3. http://dx.doi.org/10.1127/1864-5658/2015-01.

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17

Ravikant, V. "Sm‐Nd Isotopic Evidence for Late Mesoproterozoic Metamorphic Relics in the East African Orogen from the Schirmacher Oasis, East Antarctica." Journal of Geology 114, no. 5 (September 2006): 615–25. http://dx.doi.org/10.1086/506163.

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18

Alonso-Chaves, F., J. I. Soto, M. Orozco, A. A. Kilias, and M. D. Tranos. "TECTONIC EVOLUTION OF THE BETIC CORDILLERA: AN OVERVIEW." Bulletin of the Geological Society of Greece 36, no. 4 (January 1, 2004): 1598. http://dx.doi.org/10.12681/bgsg.16563.

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The Betic (Southern Spain) and the Rif (Morocco) mountain chains, connected through the Gibraltar Strait, shapes a W-E elongated and arcuate Alpine orogenic belt. The Alborân Sea, in continuity to the east with the South Balearic Basin, is located in the inner part of this alpine belt. The Iberian and African continental forelands bound the region as a whole to the north and south, respectively, and to the east it is connected to the oceanic Sardine-Balearic Basin. The peculiarities of these westernmost Mediterranean chains result from: (1) its position between two large convergent plates -Africa and Europe- that have had variable directions of relative motion since the late Cretaceous; and (2) the Neogene westward migration of the orogenic hinterland and its simultaneous "back-arc"-like extension, generating the Alborén Sea basin. The complexes and large paleogeographic terrains traditionally recognized in the Betic and Rif chains belong to four pre-Neogene crustal domains: the South-Iberian and Maghrebian passive continental paleomargins (External Zones of the orogen), the Flysch Units, and the Alborân Crustal Domain composed mainly of a pre- Miocene metamorphosed thrust-stack (Nevado-Filabride, Alpujârride, and Malaguide complexes, from bottom to top). The boundaries between the main metamorphic complexes of the Alborân Domain are extensional detachments, which finally developed under brittle conditions and are commonly sealed by middle-to-late Miocene marine-to-continental sediments. They, nonetheless, are not the most recent structures in the Alborân Domain, because upright, E-W open folds warp the extensional detachments, and finally, high-angle normal faults and strike-slip faults, many of which are still active, offset folds and extensional detachments. The tectonic evolution of the Betic Alborân orogenic system shows close similarities with the one depicted in other arcuate-shaped, Alpine mountain ranges in the Mediterranean, such as the Hellenic Arc and the Aegean Sea. Like in the westernmost Mediterranean, a thickened (pre Miocene) crust is bounding there a thinned, continental (?) basin. Extension is also formed here in a "back-arc" setting, being developed simultaneously with the N-S convergence between the African and European plates.

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19

ENGVIK, A. K., and B. BINGEN. "Granulite-facies metamorphism of the Palaeoproterozoic – early Palaeozoic gneiss domains of NE Mozambique, East African Orogen." Geological Magazine 154, no. 3 (April 13, 2016): 491–515. http://dx.doi.org/10.1017/s0016756816000145.

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AbstractGranulite-facies metamorphism recorded in NE Mozambique is attributed to three main tectonothermal events, covering more than 1400 Ma from Palaeoproterozoic – early Palaeozoic time. (1) Usagaran–Ubendian high-grade metamorphism of Palaeoproterozoic age is documented in the Ponta Messuli Complex by Grt-Sil-Crd-bearing metapelites, estimated to pressure (P) 0.75 ± 0.08 GPa and temperature (T) 765 ± 96°C. The post-peak P-T path is characterized by decompression followed by near-isobaric cooling. (2) Irumidian medium- to high-pressure granulite-facies metamorphism is evident in the Unango and Marrupa complexes of late Mesoproterozoic – early Neoproterozoic age. High-pressure granulite-facies is documented by Grt-Cpx-Pl-Rt-bearing mafic granulites in the northwestern part of the Unango Complex, with peak conditions up to P = 1.5 GPa and T = 850°C. Medium-pressure granulite-facies conditions recording P of c. 1.15 GPa and T of 875°C are documented by Grt-Opx-Cpx-Pl assemblage in mafic granulites and charnockitic gneisses of the central part of the Unango Complex. (3) Tectonothermal activity during the Ediacaran–Cambrian Kuunga Orogeny is recorded in the Mesoproterozoic gneiss complexes as amphibolite facies to medium-pressure granulite-facies metamorphism. Granulite facies are documented by Grt-Opx-Cpx-Pl-bearing mafic granulites and charnockitic gneisses, reporting P = 0.99 ± 13 GPa at T = 738 ± 84°C in the Unango Complex and P = 0.92 ± 18 GPa at T = 841 ± 135°C in the Marrupa Complex. This metamorphism is attributed to crustal thickening related to overriding of the Cabo Delgado Nappe Complex, and shorthening along the Lurio Belt during the early Palaeozoic Kuunga Orogeny.

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20

Stern, R. J., D. Avigad, N. R. Miller, and M. Beyth. "Evidence for the Snowball Earth hypothesis in the Arabian-Nubian Shield and the East African Orogen." Journal of African Earth Sciences 44, no. 1 (January 2006): 1–20. http://dx.doi.org/10.1016/j.jafrearsci.2005.10.003.

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21

Jarrar, G., R. J. Stern, G. Saffarini, and H. Al-Zubi. "Late- and post-orogenic Neoproterozoic intrusions of Jordan: implications for crustal growth in the northernmost segment of the East African Orogen." Precambrian Research 123, no. 2-4 (June 2003): 295–319. http://dx.doi.org/10.1016/s0301-9268(03)00073-1.

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22

Pant, N. C., A. Kundu, M. J. D'Souza, and Ashima Saikia. "Petrology of the Neoproterozoic granulites from Central Dronning Maud Land, East Antarctica – Implications for southward extension of East African Orogen (EAO)." Precambrian Research 227 (April 2013): 389–408. http://dx.doi.org/10.1016/j.precamres.2012.06.013.

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23

Ishikawa, Masahiro, Tetsuo Kawakami, M. Satish-Kumar, Geoffrey H. Grantham, Yuichi Hokazono, Megumi Saso, and Noriyoshi Tsuchiya. "Late Neoproterozoic extensional detachment in eastern Sør Rondane Mountains, East Antarctica: Implications for the collapse of the East African Antarctic Orogen." Precambrian Research 234 (September 2013): 247–56. http://dx.doi.org/10.1016/j.precamres.2013.04.015.

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24

Stern, R. J. "ARC Assembly and Continental Collision in the Neoproterozoic East African Orogen: Implications for the Consolidation of Gondwanaland." Annual Review of Earth and Planetary Sciences 22, no. 1 (May 1994): 319–51. http://dx.doi.org/10.1146/annurev.ea.22.050194.001535.

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25

Fritz, H., V. Tenczer, C. A. Hauzenberger, E. Wallbrecher, G. Hoinkes, S. Muhongo, and A. Mogessie. "Central Tanzanian tectonic map: A step forward to decipher Proterozoic structural events in the East African Orogen." Tectonics 24, no. 6 (December 2005): n/a. http://dx.doi.org/10.1029/2005tc001796.

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26

Petrescu, Laura, Silvia Pondrelli, Simone Salimbeni, and Manuele Faccenda. "Mantle flow below the central and greater Alpine region: insights from SKS anisotropy analysis at AlpArray and permanent stations." Solid Earth 11, no. 4 (July 8, 2020): 1275–90. http://dx.doi.org/10.5194/se-11-1275-2020.

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Abstract. The Alpine chain in western and central Europe is a complex orogen developed as a result of the African–Adriatic plate convergence towards the European continent and the closure of several Tethys oceanic branches. Seismic tomography studies detected high-wave-speed slabs plunging beneath the orogen to variable depths and a potential change in subduction polarity beneath the Central Alps. Alpine subduction is expected to leave a significant imprint on the surrounding mantle fabrics, although deformation associated with the Hercynian Orogeny, which affected Europe prior to the collision with Adria, may have also been preserved in the European lithosphere. Here we estimate SKS anisotropy beneath the central and greater Alpine region at 113 broadband seismic stations from the AlpArray experiment as well as permanent networks from Italy, Switzerland, Austria, Germany, and France. We compare the new improved dataset with previous studies of anisotropy, mantle tomography, lithospheric thickness, and absolute plate motion, and we carry out Fresnel analysis to place constraints on the depth and origin of anisotropy. Most SKS directions parallel the orogen strike and the orientation of the Alpine slabs, rotating clockwise from west to east along the chain, from −45 to 90∘ over a ∼700 km distance. No significant changes are recorded in Central Alps at the location of the putative switch in subduction polarity, although a change in direction variability suggests simple asthenospheric flow or coupled deformation in the Swiss Central Alps transitions into more complex structures beneath the Eastern Alps. SKS fast axes follow the trend of high seismic anomalies across the Alpine Front, far from the present-day boundary, suggesting slabs act as flow barriers to the ambient mantle surrounding them for hundreds of km. Further north across the foreland, SKS fast axes parallel Hercynian geological structures and are orthogonal to the Rhine Graben and crustal extension. However, large splitting delay times (>1.4 s) are incompatible with a purely lithospheric contribution but rather represent asthenospheric flow not related to past deformational events. West of the Rhine Graben, in northeastern France, anisotropy directions are spatially variable in the proximity of a strong positive seismic anomaly in the upper mantle, perhaps perturbing the flow field guided by the nearby Alpine slabs.

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27

RAMBELOSON, R. "The Central Granites-Gneiss-Migmatite Belt (CGGMB) of Madagascar: the Eastern Neoproterozoic Suture of the East African Orogen." Gondwana Research 6, no. 4 (October 2003): 641–51. http://dx.doi.org/10.1016/s1342-937x(05)71013-3.

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28

Liu, Xiaochun, Bin Fu, Qiuli Li, Yue Zhao, Jian Liu, and Hong Chen. "The impact of the Pan-African-aged tectonothermal event on high-grade rocks at Mount Brown, East Antarctica." Antarctic Science 32, no. 1 (January 29, 2020): 45–57. http://dx.doi.org/10.1017/s0954102019000518.

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AbstractThis study presents monazite and rutile U–Pb and hornblende and biotite 40Ar/39Ar geochronological data for high-grade rocks of the eastern Grenville-aged Rayner orogen at Mount Brown in order to analyse the extent and degree of Pan-African-aged reworking. Monazite from paragneiss yields U–Pb ages of 910 Ma for larger granular grains and 670–630 Ma for smaller globular beads around garnet porphyroblasts or hosted by symplectites. Rutile from leucogneiss yields U–Pb ages of 520–515 Ma. Hornblende and biotite from different rock types yield 40Ar/39Ar plateau ages of 744 and 520–505 Ma, respectively. Combining these results with published zircon U–Pb age data suggests that granulite facies metamorphism occurred at 910 Ma, with a local low-temperature fluid flow event at 670–630 Ma and thermal reworking at 520–505 Ma. The older age of 744 Ma may reflect cooling or partial resetting of the hornblende 40Ar/39Ar system, indicating that Pan-African-aged reworking did not exceed temperatures much higher than the hornblende Ar closure temperature. These data also suggest that the complete isotopic resetting of some minerals may occur without the growth of new mineral phases, providing an example of the style of reworking that is likely to occur in polymetamorphic terranes.

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29

Bauer, Wilfried, Heinrich Siemes, Gerhard Spaeth, and Joachim Jacobs. "Transpression and tectonic exhumation in the Heimefrontfjella, western orogenic front of the East African/Antarctic Orogen, revealed by quartz textures of high strain domains." Polar Research 35, no. 1 (January 2016): 25420. http://dx.doi.org/10.3402/polar.v35.25420.

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30

Jacobs, J., W. Bauer, and C. M. Fanning. "Late Neoproterozoic/Early Palaeozoic events in central Dronning Maud Land and significance for the southern extension of the East African Orogen into East Antarctica." Precambrian Research 126, no. 1-2 (September 2003): 27–53. http://dx.doi.org/10.1016/s0301-9268(03)00125-6.

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31

Braathen, A., T. Grenne, M. G. Selassie, and T. Worku. "Juxtaposition of Neoproterozoic units along the Baruda–Tulu Dimtu shear-belt in the East African Orogen of western Ethiopia." Precambrian Research 107, no. 3-4 (April 2001): 215–34. http://dx.doi.org/10.1016/s0301-9268(00)00143-1.

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32

KRONER, A. "The East African Orogen: New Zircon and Nd Ages and Implications for Rodinia and Gondwana Supercontinent Formation and Dispersal." Gondwana Research 4, no. 2 (April 2001): 179–81. http://dx.doi.org/10.1016/s1342-937x(05)70685-7.

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33

Küster, Dirk, and Ulrich Harms. "Post-collisional potassic granitoids from the southern and northwestern parts of the Late Neoproterozoic East African Orogen: a review." Lithos 45, no. 1-4 (December 1998): 177–95. http://dx.doi.org/10.1016/s0024-4937(98)00031-0.

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34

Ravikant, V., Y. J. Bhaskar Rao, and K. Gopalan. "Schirmacher Oasis as an Extension of the Neoproterozoic East African Orogen into Antarctica: New Sm‐Nd Isochron Age Constraints." Journal of Geology 112, no. 5 (September 2004): 607–16. http://dx.doi.org/10.1086/422669.

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35

El-Sayed, Mohamed M., Harald Furnes, and S. Abou Shagar. "Growth of the Egyptian crust in the northern East African Orogen: A review of existing models and proposed modifications." Neues Jahrbuch für Mineralogie - Abhandlungen 183, no. 3 (April 1, 2007): 317–41. http://dx.doi.org/10.1127/0077-7757/2007/0078.

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36

Engvik, Ane K., Einar Tveten, and Arne Solli. "High-grade metamorphism during Neoproterozoic to Early Palaeozoic Gondwana assembly, exemplified from the East African Orogen of northeastern Mozambique." Journal of African Earth Sciences 151 (March 2019): 490–505. http://dx.doi.org/10.1016/j.jafrearsci.2018.12.021.

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37

Jacobs, Joachim, Bernard Bingen, Robert J. Thomas, Wilfried Bauer, Michael T. D. Wingate, and Paulino Feitio. "Early Palaeozoic orogenic collapse and voluminous late-tectonic magmatism in Dronning Maud Land and Mozambique: insights into the partially delaminated orogenic root of the East African–Antarctic Orogen?" Geological Society, London, Special Publications 308, no. 1 (2008): 69–90. http://dx.doi.org/10.1144/sp308.3.

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38

Wu, Guochao, Fausto Ferraccioli, Wenna Zhou, Yuan Yuan, Jinyao Gao, and Gang Tian. "Tectonic Implications for the Gamburtsev Subglacial Mountains, East Antarctica, from Airborne Gravity and Magnetic Data." Remote Sensing 15, no. 2 (January 4, 2023): 306. http://dx.doi.org/10.3390/rs15020306.

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The Gamburtsev Subglacial Mountains (GSMs) in interior East Antarctic Craton are entirely buried under the massive ice sheet, with a ~50–60 km thick crust and ~200 km thick lithosphere, but little is known of the crustal structure and uplift mechanism. Here, we use airborne gravity and aeromagnetic anomalies for characteristic analysis and inverse calculations. The gravity and magnetic images show three distinct geophysical domains. Based on the gravity anomalies, a dense lower crustal root is inferred to underlie the GSMs, which may have been formed by underplating during the continental collision of Antarctica and India. The high frequency linear magnetic characteristics parallel to the suture zone suggest that the upper crustal architecture is dominated by thrusts, consisting of a large transpressional fault system with a trailing contractional imbricate fan. A 2D model along the seismic profile is created to investigate the crustal architecture of the GSMs with the aid of depth to magnetic source estimates. Combined with the calculated crustal geometry and physical properties and the geological background of East Antarctica, a new evolutionary model is proposed, suggesting that the GSMs have been a part of the Pan-African advancing accretionary orogen superimposed on the Precambrian basement.

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39

Johnson, Peter R. "Post-amalgamation basins of the NE Arabian shield and implications for Neoproterozoic III tectonism in the northern East African orogen." Precambrian Research 123, no. 2-4 (June 2003): 321–37. http://dx.doi.org/10.1016/s0301-9268(03)00074-3.

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40

Lundmark, Anders Mattias, Arild Andresen, Mohamed A. Hassan, Lars Eivind Augland, and Gamal Yehia Boghdady. "Repeated magmatic pulses in the East African Orogen in the Eastern Desert, Egypt: An old idea supported by new evidence." Gondwana Research 22, no. 1 (July 2012): 227–37. http://dx.doi.org/10.1016/j.gr.2011.08.017.

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41

Jacobs, Joachim, and Robert J. Thomas. "Himalayan-type indenter-escape tectonics model for the southern part of the late Neoproterozoic–early Paleozoic East African– Antarctic orogen." Geology 32, no. 8 (2004): 721. http://dx.doi.org/10.1130/g20516.1.

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42

Petrescu, Laura, Graham Stuart, Gregory Houseman, and Ian Bastow. "Upper mantle deformation signatures of craton–orogen interaction in the Carpathian–Pannonian region from SKS anisotropy analysis." Geophysical Journal International 220, no. 3 (January 13, 2020): 2105–18. http://dx.doi.org/10.1093/gji/ggz573.

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SUMMARY Since the Mesozoic, central and eastern European tectonics have been dominated by the closure of the Tethyan Ocean as the African and European plates collided. In the Miocene, the edge of the East European Craton and Moesian Platform were reworked in collision during the Carpathian orogeny and lithospheric extension formed the Pannonian Basin. To investigate the mantle deformation signatures associated with this complex collisional-extensional system, we carry out SKS splitting analysis at 123 broad-band seismic stations in the region. We compare our measurements with estimates of lithospheric thickness and recent seismic tomography models to test for correlation with mantle heterogeneities. Reviewing splitting delay times in light of xenolith measurements of anisotropy yields estimates of anisotropic layer thickness. Fast polarization directions are mostly NW–SE oriented across the seismically slow West Carpathians and Pannonian Basin and are independent of geological boundaries, absolute plate motion direction or an expected palaeo-slab roll-back path. Instead, they are systematically orthogonal to maximum stress directions, implying that the indenting Adria Plate, the leading deformational force in Central Europe, reset the upper-mantle mineral fabric in the past 5 Ma beneath the Pannonian Basin, overprinting the anisotropic signature of earlier tectonic events. Towards the east, fast polarization directions are perpendicular to steep gradients of lithospheric thickness and align along the edges of fast seismic anomalies beneath the Precambrian-aged Moesian Platform in the South Carpathians and the East European Craton, supporting the idea that craton roots exert a strong influence on the surrounding mantle flow. Within the Moesian Platform, SKS measurements become more variable with Fresnel zone arguments indicating a shallow fossil lithospheric source of anisotropy likely caused by older tectonic deformation frozen in the Precambrian. In the Southeast Carpathian corner, in the Vrancea Seismic Zone, a lithospheric fragment that sinks into the mantle is sandwiched between two slow anomalies, but smaller SKS delay times reveal weaker anisotropy occurs mainly to the NW side, consistent with asymmetric upwelling adjacent to a slab, slower mantle velocities and recent volcanism.

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Ghebreab, Woldai, Christopher J. Talbot, and Laurence Page. "Time constraints on exhumation of the East African Orogen from field observations and 40Ar/39Ar cooling ages of low-angle mylonites in Eritrea, NE Africa." Precambrian Research 139, no. 1-2 (August 2005): 20–41. http://dx.doi.org/10.1016/j.precamres.2005.05.009.

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Thomas, R. J., J. Jacobs, M. S. A. Horstwood, K. Ueda, B. Bingen, and R. Matola. "The Mecubúri and Alto Benfica Groups, NE Mozambique: Aids to unravelling ca. 1 and 0.5Ga events in the East African Orogen." Precambrian Research 178, no. 1-4 (April 2010): 72–90. http://dx.doi.org/10.1016/j.precamres.2010.01.010.

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45

Johnson, P. R., M. G. Abdelsalam, and R. J. Stern. "The Bi'r Umq-Nakasib Suture Zone in the Arabian-Nubian Shield: A Key to Understanding Crustal Growth in the East African Orogen." Gondwana Research 6, no. 3 (July 2003): 523–30. http://dx.doi.org/10.1016/s1342-937x(05)71003-0.

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46

Woldehaimanot, B., and J. H. Behrmann. "A study of metabasite and metagranite chemistry in the Adola region (south Ethiopia): implications for the evolution of the East African orogen." Journal of African Earth Sciences 21, no. 3 (October 1995): 459–76. http://dx.doi.org/10.1016/0899-5362(95)00098-e.

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47

Johnson, Peter R., and Beraki Woldehaimanot. "Development of the Arabian-Nubian Shield: perspectives on accretion and deformation in the northern East African Orogen and the assembly of Gondwana." Geological Society, London, Special Publications 206, no. 1 (2003): 289–325. http://dx.doi.org/10.1144/gsl.sp.2003.206.01.15.

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48

Bhandari, Saunak, Wenjiao Xiao, Songjian Ao, Brian F. Windley, Rixiang Zhu, Rui Li, Hao Y. C. Wang, and Rasoul Esmaeili. "Rifting of the northern margin of the Indian craton in the Early Cretaceous: Insight from the Aulis Trachyte of the Lesser Himalaya (Nepal)." Lithosphere 11, no. 5 (July 12, 2019): 643–51. http://dx.doi.org/10.1130/l1058.1.

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Abstract To reconstruct the early tectonic history of the Himalayan orogen before final India-Asia collision, we carried out geochemical and geochronological studies on the Early Cretaceous Aulis Trachyte of the Lesser Himalaya. The trace-element geochemistry of the trachytic lava flows suggests formation in a rift setting, and zircon U-Pb ages indicate that volcanism occurred in Early Cretaceous time. The felsic volcanics show enrichment of more incompatible elements and rare earth elements, a pattern that is identical to the trachyte from the East African Rift (Kenya rift), with conspicuous negative anomalies of Nb, P, and Ti. Although much of the zircon age data are discordant, they strongly suggest an Early Cretaceous eruption age, which is in agreement with the fossil age of intravolcanic siltstones. The Aulis Trachyte provides the first corroboration of Cretaceous rifting in the Lesser Himalaya as suggested by paleomagnetic data associated with the concept that the northern margin of India separated as a microcontinent and drifted north in the Neo-Tethys before terminal collision of India with Asia.

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FREEMAN, S. R., R. W. H. BUTLER, R. A. CLIFF, S. INGER, and A. C. BARNICOAT. "Deformation migration in an orogen-scale shear zone array: an example from the Basal Briançonnais Thrust, internal Franco-Italian Alps." Geological Magazine 135, no. 3 (May 1998): 349–67. http://dx.doi.org/10.1017/s0016756898008693.

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Combined structural, geochemical and isotopic studies have allowed an understanding of the timing and nature of an orogen-scale fault array. The results indicate that the deformation loci within the internal western Alps, during the Alpine collision, occurred as a foreland propagating thrust sequence. The east to west deformation migration within the internal zones is apparently in-sequence in relation to the external zones. Rb–Sr white mica dating of syn-kinematic greenschist-facies mineral assemblages from the Basal Briançonnais Thrust indicate that thrusting ceased between 27 and 32 Ma, several million years after shearing in the hinterland and several million years prior to shearing in the foreland. The Briançonnais Domain, which constitutes the hanging wall to the Basal Briançonnais Thrust, preserves two major shearing episodes. The first, with a top-to-the-northwest overshear, has been tentatively dated at 45 Ma. The second, a very pervasive, east–west orientated, greenschist-facies event was previously dated at 34 Ma on the hinterland margin of the Briançonnais Domain and has now been dated at 27–32 Ma on the foreland margin of the Briançonnais Domain. The period between 34 and 27 Ma apparently dates the migration of deformation through the relict European passive margin, represented by the Briançonnais Domain. This is believed to be in response to overthrusting of Adria/Africa and its associated subduction complex. Structural mapping indicates that the present Basal Briançonnais Thrust in the Col du Petit St Bernard region, Franco-Italian Alps, is a break-back thrust which cuts through an already imbricated pile. Geochronological evidence suggests that the early imbrication of the Briançonnais stratigraphy occurred prior to full interaction of the European and Adria/African plates, that is, during subduction, docking and escape from the subduction complex under Adria. Therefore, although the present Basal Briançonnais Thrust is a break-back thrust in terms of local structural geometries, it is an in-sequence foreland-propagating structure. Geochronological, micro-structural and micro-chemical data indicate that the Briançonnais Domain in the Col du Petit St Bernard zone is formed from granitoid material which intruded and cooled at approximately 320 Ma. During the Alpine event, deformation and metamorphism were insufficient to affect the Sr isotopic system. This suggests that this portion of the Briançonnais Domain was probably subducted to much shallower depths and underwent much less pervasive deformation than the other internal European basement material.

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KROHNE, NICOLE, FRANK LISKER, GEORG KLEINSCHMIDT, ANDREAS KLÜGEL, ANDREAS LÄUFER, SOLVEIG ESTRADA, and CORNELIA SPIEGEL. "The Shackleton Range (East Antarctica): an alien block at the rim of Gondwana?" Geological Magazine 155, no. 4 (December 12, 2016): 841–64. http://dx.doi.org/10.1017/s0016756816001011.

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AbstractThe Shackleton Range is a truncated Pan-African Orogen situated at the Weddell Sea margin of East Antarctica. It almost exclusively consists of basement rocks exposed at an elevated, escarpment-bound palaeosurface and is covered locally by patchy remnants of Ordovician, Permian and, controversially, Jurassic terrestrial deposits. This inventory does not match the geological record of any other place in Antarctica. Here we reconstruct the Phanerozoic evolution of the Shackleton Range by means of a multi-disciplinary approach combining petrological, geochemical and geochronological data with thermal history models of zircon and apatite fission track (ZFT, AFT) and (U–Th–Sm)/He (AHe) data. Petrographic, geochemical and 40Ar/39Ar analyses of a sedimentary cover sequence identify volcaniclastic rocks related to the Ferrar/Karoo magmatic event. Thermal history modelling of ZFT ages of 160–215 Ma, AFT ages of 124–225 Ma, AHe ages of 95–169 Ma and kinematic proxies in combination with geological information indicates a complex thermal history comprising at least three cooling episodes interrupted by reheating pulses. Thermal history refers to inversion of part of the Carboniferous–Triassic Transantarctic Basin prior to the 180 Ma Ferrar/Karoo Event and formation of an up to 3.4 km deep extensional Jurassic – Early Cretaceous basin due to Weddell Sea rifting. Basin depth was diminished by regional middle Cretaceous stress field changes. Final basin inversion and surface uplift were likely triggered by far-field tectonics and climatic influence. This history represents a typical example for the transition from an active to passive margin setting along the outer rim of Gondwana.

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