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Journal articles on the topic 'Post-orogenic extension'

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Published: 10 December 2022
Last updated: 28 January 2023

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1

Tavarnelli, Enrico. "Normal faults in thrust sheets: pre-orogenic extension, post-orogenic extension, or both?" Journal of Structural Geology 21, no. 8-9 (August 1999): 1011–18. http://dx.doi.org/10.1016/s0191-8141(99)00034-6.

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2

Gaudemer, Yves, Claude Jaupart, and Paul Tapponnier. "Thermal control on post-orogenic extension in collision belts." Earth and Planetary Science Letters 89, no. 1 (June 1988): 48–62. http://dx.doi.org/10.1016/0012-821x(88)90032-5.

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3

Mareschal, Jean-Claude. "Thermal regime and post-orogenic extension in collision belts." Tectonophysics 238, no. 1-4 (November 1994): 471–84. http://dx.doi.org/10.1016/0040-1951(94)90069-8.

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4

PACE, PAOLO, VALERIA PASQUI, ENRICO TAVARNELLI, and FERNANDO CALAMITA. "Foreland-directed gravitational collapse along curved thrust fronts: insights from a minor thrust-related shear zone in the Umbria–Marche belt, central-northern Italy." Geological Magazine 154, no. 2 (April 14, 2016): 381–92. http://dx.doi.org/10.1017/s0016756816000200.

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AbstractGravitational collapse occurs during the mature evolution of orogenic belts, but its signature is difficult to discriminate in macroscopic structures from that of pre-, syn- or late-/post-orogenic extension, so reliable mesoscopic examples are particularly useful. A composite fabric developed along a lateral thrust ramp in the Apennines reveals mesoscopic normal faults that truncate the thrust surface, overprint the S-fabric and merge downwards in a foreland-directed splay, leaving the thrust footwall undeformed. These relationships indicate syn-/late-thrusting extension, which we interpret as induced by hanging-wall gravitational collapse. Our study provides critical constraints for reconstructing the kinematic evolution of collapsing thrust fronts.
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5

Braathen, Alvar, and Per Terje Osmundsen. "Extensional tectonics rooted in orogenic collapse: Long-lived disintegration of the Semail Ophiolite, Oman." Geology 48, no. 3 (December 9, 2019): 258–62. http://dx.doi.org/10.1130/g47077.1.

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Abstract Significant post-orogenic extension of the renowned Semail Ophiolite and substrata in Oman resulted in the formation of metamorphic core complexes juxtaposed with an array of Maastrichtian-Paleogene extensional basins. During this evolution, basins became progressively localized. The geometry of the large-scale and long-lived extensional system changes laterally across the core complexes and reveals several generations of domes and detachments, some of which were progressively exhumed. Progressive excision and dismemberment of the ophiolite link to major fabrics in the core complexes and gradual focusing of extensional basins.
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6

Ma, Aiai, Hao Guan, Lifei Zou, and Lanlan Sun. "Geochemical Characteristics and Tectonic Significance of the Acidic Volcanic Rocks from the Shetang-Boyang Area, Western Qinling Orogenic Belt, China." Earth Science Research 5, no. 2 (July 30, 2016): 209. http://dx.doi.org/10.5539/esr.v5n2p209.

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Acidic volcanic rocks of Shetang-Boyang area are located in the western Qinling orogenic belt, consist of rhyolite and granite porphyry. They are comparable in the chemical composition, enriched in Si, alkali, Al and a little bit of Mg, Ca and Ti. The contents of HFSE (Zr, Hf) and LILE (Rb, Th, U) are high, however, the content of Ba, Sr, Ti, P have obviously depleted and there are obvious negative Eu anomalies (Eu/Eu*=0.06-0.13). These geochemical characteristics are revealed that these volcanic rocks have an A1 type affinity. Geochemical data combined with regional studies, show that these volcanic rocks were formed in a continental extension setting and the western Qinling orogenic belt in 211Ma has been in the tectonic setting of post-collisional extension.
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7

Spencer, B. M., J. R. Thigpen, R. D. Law, C. A. Mako, C. S. McDonald, K. V. Hodges, and K. T. Ashley. "Rapid cooling during late-stage orogenesis and implications for the collapse of the Scandian retrowedge, northern Scotland." Journal of the Geological Society 178, no. 1 (August 13, 2020): jgs2020–022. http://dx.doi.org/10.1144/jgs2020-022.

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New 40Ar/39Ar thermochronological and deformation temperature analyses in the Scandian (c. 435–420 Ma) orogenic retrowedge of northern Scotland demonstrate accelerated cooling during late syn- to post-orogenic exhumation of the high-grade orogenic core. Initial cooling rates of 10–30°C myr−1 immediately following peak orogenesis transitioned to rapid rates of 45–90°C myr−1 during final exhumation of the Naver thrust sheet in the orogenic core. The flanking ductile thrust sheets exhibit a similar, albeit less pronounced, acceleration of cooling, with rates increasing by c. 150–300% following peak orogenesis. Closer to the foreland, the Moine thrust sheet did not experience increased cooling rates. Calculated unroofing rates of 3.75 mm a−1 in the high-grade Naver thrust sheet suggest increasing, rapid exhumation in the orogenic core during a presumed collapse phase of orogenesis. This is contrary to the expectation of decreasing erosional efficiency as topography is diminished and is interpreted to suggest that unroofing of the Scottish Caledonides may have been partially enhanced by upper crustal extensional deformation during ductile flow of the infrastructure of the orogenic core. Similar processes have been interpreted in the East Greenland Caledonides, which form the northern extension of the Scandian retrowedge.Supplementary material:40Ar/39Ar analytical data for muscovite (Supplementary Data Table 1), 40Ar/39Ar analytical data for amphibole (Supplementary Data Table 2), and electron microprobe analytical data for amphibole samples (Supplementary Data Table 3) is available at: https://doi.org/10.6084/m9.figshare.c.5087057
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8

Chenin, Pauline, Suzanne Picazo, Suzon Jammes, Gianreto Manatschal, Othmar Müntener, and Garry Karner. "Potential role of lithospheric mantle composition in the Wilson cycle: a North Atlantic perspective." Geological Society, London, Special Publications 470, no. 1 (March 6, 2018): 157–72. http://dx.doi.org/10.1144/sp470.10.

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AbstractAlthough the Wilson cycle is usually considered in terms of wide oceans floored with normal oceanic crust, numerous orogens result from the closure of embryonic oceans. We discuss how orogenic and post-orogenic processes may be controlled by the size/maturity of the inverted basin. We focus on the role of lithospheric mantle in controlling deformation and the magmatic budget. We describe the physical properties (composition, density, rheology) of three types of mantle: inherited, fertilized and depleted oceanic mantle. By comparing these, we highlight that fertilized mantle underlying embryonic oceans is mechanically weaker, less dense and more fertile than other types of mantle. We suggest that orogens resulting from the closure of a narrow, immature extensional system are essentially controlled by mechanical processes without significant thermal and lithological modification. The underlying mantle is fertile and thus has a high potential for magma generation during subsequent tectonic events. Conversely, the thermal state and lithology of orogens resulting from the closure of a wide, mature ocean are largely modified by subduction-related arc magmatism. The underlying mantle wedge is depleted, which may inhibit magma generation during post-orogenic extension. These end-member considerations are supported by observations derived from the Western Europe–North Atlantic region.
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9

Vozárová, Anna, Sergey Presnyakov, Katarína Šarinová, and Miloš Šmelko. "First evidence for Permian-Triassic boundary volcanism in the Northern Gemericum: geochemistry and U-Pb zircon geochronology." Geologica Carpathica 66, no. 5 (October 1, 2015): 375–91. http://dx.doi.org/10.1515/geoca-2015-0032.

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AbstractSeveral magmatic events based on U-Pb zircon geochronology were recognized in the Permian sedimentary succession of the Northern Gemeric Unit (NGU). The Kungurian magmatic event is dominant. The later magmatism stage was documented at the Permian-Triassic boundary. The detrital zircon assemblages from surrounding sediments documented the Sakmarian magmatic age. The post-orogenic extensional/transtensional faulting controlled the magma ascent and its emplacement. The magmatic products are represented by the calc-alkaline volcanic rocks, ranging from basaltic metaandesite to metarhyolite, associated with subordinate metabasalt. The whole group of the studied NGU Permian metavolcanics has values for the Nb/La ratio at (0.44–0.27) and for the Nb/U ratio at (9.55–4.18), which suggests that they represent mainly crustal melts. Magma derivation from continental crust or underplated crust is also indicated by high values of Y/Nb ratios, ranging from 1.63 to 4.01. The new206U–238Pb zircon ages (concordia age at 269 ± 7 Ma) confirm the dominant Kungurian volcanic event in the NGU Permian sedimentary basin. Simultaneously, the Permian-Triassic boundary volcanism at 251 ± 4 Ma has been found for the first time. The NGU Permian volcanic activity was related to a polyphase extensional tectonic regime. Based on the new and previous U-Pb zircon ages, the bulk of the NGU Permian magmatic activity occurred during the Sakmarian and Kungurian. It was linked to the post-orogenic transpression/transtension tectonic movements that reflected the consolidation of the Variscan orogenic belt. The Permian-Triassic boundary magmatism was accompanied by extension, connected with the beginning of the Alpine Wilson cycle.
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10

Jolivet, Laurent, Gaëtan Rimmelé, Roland Oberhänsli, Bruno Goffé, and Osman Candan. "Correlation of syn-orogenic tectonic and metamorphic events in the Cyclades, the Lycian nappes and the Menderes massif. Geodynamic implications." Bulletin de la Société Géologique de France 175, no. 3 (May 1, 2004): 217–38. http://dx.doi.org/10.2113/175.3.217.

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Abstract The recent discovery of HP-LT parageneses in the basal unit of the Lycian nappes and in the Mesozoic cover of the Menderes massif leads us to reconsider and discuss the correlation of this region with the nearby collapsed Helle-nides in the Aegean domain. Although similarities have long been pointed out by various authors, a clear correlation has not yet been proposed and most authors insist more on differences than similarities. The Menderes massif is the eastern extension of the Aegean region but it has been less severely affected by the Aegean extension during the Oligo-Miocene. It would thus be useful to use the structure of the Menderes massif as an image of the Aegean region before a significant extension has considerably reduced its crustal thickness. But the lack of correlation between the two regions has so far hampered such comparisons. We describe the main tectonic units and metamorphic events in the two regions and propose a correlation. We then show possible sections of the two regions before the Aegean extension and discuss the involvement of continental basement in the Hellenic accretionary complex. In our interpretation the Hellenic-Tauric accretionary complex was composed of stacked basement and cover units which underwent variable P-T histories. Those which were not exhumed early enough later followed a high-T evolution which led to partial melting in the Cyclades during post-orogenic extension. Although the Menderes massif contains a larger volume of basement units it does not show significant evidence for the Oligo-Miocene migmatites observed in the center of the Cyclades suggesting that crustal partial melting is strictly related to post-orogenic extension in this case.
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11

Md Ali, M. A., E. Willingshofer, L. Matenco, T. Francois, T. P. Daanen, T. F. Ng, N. I. Taib, and M. K. Shuib. "Kinematics of post-orogenic extension and exhumation of the Taku Schist, NE Peninsular Malaysia." Journal of Asian Earth Sciences 127 (September 2016): 63–75. http://dx.doi.org/10.1016/j.jseaes.2016.06.020.

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12

Pease, V., J. H. Scarrow, I. G. Nobre Silva, and A. Cambeses. "Devonian magmatism in the Timan Range, Arctic Russia — subduction, post-orogenic extension, or rifting?" Tectonophysics 691 (November 2016): 185–97. http://dx.doi.org/10.1016/j.tecto.2016.02.002.

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13

Mellado, Esteban, Mercè Corbella, Didac Navarro, and Andrew Kylander. "The enriched Variscan lithosphere of NE Iberia: data from postcollisional Permian calc-alkaline lamprophyre dykes of Les Guilleries." Geologica Acta 19 (December 7, 2021): 1–23. http://dx.doi.org/10.1344/geologicaacta2021.19.15.

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Post-collisional mafic dykes crosscut the Paleozoic metamorphic basement and late-Variscan plutons in Les Guilleries massif (Catalan Coastal Ranges, NE Iberia). The predominance of mafic phenocrysts, porphyritic texture, abundant amphibole, high MgO and volatile content, together with crustal-like trace-element patterns indicate that the dykes correspond to calc-alkaline lamprophyres, mainly spessartites. Their enrichment in LILE, HFSE and REE and initial Sr-Nd isotopic compositions (87Sr/86Sri between 0.70851 and 0.71127, epsilon Ndi between -5.23 and -4.63) are consistent with an enriched subcontinental lithospheric mantle source. U-Pb ages of matrix titanite crystals yield concordia ages of 262±7Ma, congruent with crosscutting relationships. Postmagmatic processes are evidenced by intense chloritization and albitization of the lamprophyres, together with systematic variations of Na2O vs SiO2, K2O, CaO, Ba, Rb, Cs, Pb, Sr, Tl, and Zn, and possibly the removal of F. The geochemical and geochronological data support an orogenic geochemical affinity, in accordance with the transitional tectonic regime between Variscan compression/transpression and post-collisional transtension/extension, related to the fragmentation of Pangea and thinning of the lithosphere. The lamprophyre dykes studied could represent the youngest pulse of Variscan orogenic magmatism and, therefore, mark its end in NE Iberia before the onset of the generalized Triassic extension.
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14

Zengqian, Hou, Wang Liquan, Khin Zaw, Mo Xuanxue, Wang Mingjie, Li Dingmou, and Pan Guitang. "Post-collisional crustal extension setting and VHMS mineralization in the Jinshajiang orogenic belt, southwestern China." Ore Geology Reviews 22, no. 3-4 (March 2003): 177–99. http://dx.doi.org/10.1016/s0169-1368(02)00141-5.

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15

Rossetti, Federico, Claudio Faccenna, Laurent Jolivet, Renato Funiciello, Francesca Tecce, and Christophe Brunet. "Syn- versus post-orogenic extension: the case study of Giglio Island (Northern Tyrrhenian Sea, Italy)." Tectonophysics 304, no. 1-2 (March 1999): 71–93. http://dx.doi.org/10.1016/s0040-1951(98)00304-7.

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16

Scisciani, Vittorio, Stefano Patruno, Enrico Tavarnelli, Fernando Calamita, Paolo Pace, and David Iacopini. "Multi-phase reactivations and inversions of Paleozoic–Mesozoic extensional basins during the Wilson cycle: case studies from the North Sea (UK) and the Northern Apennines (Italy)." Geological Society, London, Special Publications 470, no. 1 (2019): 205–43. http://dx.doi.org/10.1144/sp470-2017-232.

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AbstractThe Caledonian and Variscan orogens in northern Europe and the Alpine-age Apennine range in Italy are classic examples of thrust belts that were developed at the expense of formerly rifted, passive continental margins that subsequently experienced various degrees of post-orogenic collapse and extension. The outer zones of orogenic belts, and their adjoining foreland domains and regions, where the effects of superposed deformations are mild to very mild make it possible to recognize and separate structures produced at different times and to correctly establish their chronology and relationships. In this paper we integrate subsurface data (2D and 3D seismic reflection and well logs), mainly from the North Sea, and structural field evidence, mainly from the Apennines, with the aim of reconstructing and refining the structural evolution of these two provinces which, in spite of their different ages and present-day structural framework, share repeated pulses of alternating extension and compression. The main outcome of this investigation is that in both scenarios, during repeated episodes of inversion that are a characteristic feature of the Wilson cycle, inherited basement structures were effective in controlling stress localization along faults affecting younger sedimentary cover rocks.
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17

Dirks, Paul H. G. M., E. Guy Charlesworth, M. Richard Munyai, and Richard Wormald. "Stress analysis, post-orogenic extension and 3.01Ga gold mineralisation in the Barberton Greenstone Belt, South Africa." Precambrian Research 226 (March 2013): 157–84. http://dx.doi.org/10.1016/j.precamres.2012.12.007.

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18

Tang, LiMei, HanLin Chen, ChuanWan Dong, ShuFeng Yang, ZhongYue Shen, XiaoGan Cheng, and LuLu Fu. "Middle triassic post-orogenic extension on Hainan Island: Chronology and geochemistry constraints of bimodal intrusive rocks." Science China Earth Sciences 56, no. 5 (March 7, 2013): 783–93. http://dx.doi.org/10.1007/s11430-012-4562-5.

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19

Knapp, J. H., C. C. Diaconescu, M. A. Bader, V. B. Sokolov, S. N. Kashubin, and A. V. Rybalka. "Seismic reflection fabrics of continental collision and post-orogenic extension in the Middle Urals, central Russia." Tectonophysics 288, no. 1-4 (March 1998): 115–26. http://dx.doi.org/10.1016/s0040-1951(97)00288-6.

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20

Walcott, C. R., and S. H. White. "Constraints on the kinematics of post-orogenic extension imposed by stretching lineations in the Aegean region." Tectonophysics 298, no. 1-3 (November 1998): 155–75. http://dx.doi.org/10.1016/s0040-1951(98)00182-6.

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21

Ali, Shehata, Rainer Abart, M. I. Sayyed, Christoph A. Hauzenberger, and Mabrouk Sami. "Petrogenesis of the Wadi El-Faliq Gabbroic Intrusion in the Central Eastern Desert of Egypt: Implications for Neoproterozoic Post-Collisional Magmatism Associated with the Najd Fault System." Minerals 13, no. 1 (December 22, 2022): 10. http://dx.doi.org/10.3390/min13010010.

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The late Neoproterozoic gabbroic intrusion of the Wadi El-Faliq area in the central Eastern Desert of Egypt (north Arabian–Nubian Shield; henceforth, ANS) is a fresh, undeformed elliptical body elongated in a NW–SE trend following the main sinistral strike-slip faults of the Najd fault system. Mineralogical and geochemical evidence suggest that they were derived from hydrous tholeiitic mafic magmas with arc-like geochemical fingerprints resembling the post-collisional gabbroic intrusions in Saudi Arabia. Despite the arc-like signatures, their fresh and undeformed nature, together with the field relationships, indicates that the studied gabbroic intrusion post-dates the main collisional phase, supporting its emplacement after subduction ceased and during the post-collisional stage. As a result, the arc-like signatures were possibly transmitted from the earlier ANS subduction episode. Indeed, the high (La/Sm)N, and negative-Nb and positive-Pb anomalies suggest contributions from subduction components. Lithospheric delamination was possibly facilitated by the Najd faults and shear zones formed during the post-orogenic crustal extension associated with the Pan-African orogenic collapse. The delamination process could have generated a rapid upwelling and melting of the asthenosphere mantle. The melt-rock reaction process likely played an important role in the genesis of the studied rocks through the interaction of the asthenosphere melts with lithosphere mantle rocks during ascent. The HREE fractionation suggests a probable mixing between melts from both spinel- and garnet-bearing peridotites. We suggest that the Wadi El-Faliq gabbroic intrusion was likely emplaced due to the stretching and thinning of the lithosphere during the extensional tectonism following the Pan-African orogeny.
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22

Muhtar, M. N., Chang-Zhi Wu, M. Santosh, Ru-Xiong Lei, Lian-Xing Gu, Si-Meng Wang, and Kai Gan. "Late Paleozoic tectonic transition from subduction to post-collisional extension in Eastern Tianshan, Central Asian Orogenic Belt." GSA Bulletin 132, no. 7-8 (December 23, 2019): 1756–74. http://dx.doi.org/10.1130/b35432.1.

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Abstract Late Paleozoic large-scale transcurrent tectonics and synkinematic intrusions are prominent features in the Eastern Tianshan segment of the southwestern Central Asian Orogenic Belt. However, the spatial and temporal relationship between synkinematic intrusions and crustal-scale shear zones remains unclear. Here we report petrology, geochemistry, and geochronology of the Qiziltag pluton associated with the Kanggur-Huangshan Shear Zone (KHSZ) with a view to characterize the spatial and temporal relationship between synkinematic intrusions and large-scale transcurrent shearing. Field relations and zircon U-Pb ages indicate that the Qiziltag pluton was formed through two stages of magmatism, with earlier stage granitoids (gneissic biotite granite: 288.9 ± 1.9 Ma, biotite monzogranite: 291.5 ± 1.7 Ma, K-feldspar granite: 287.9 ± 3.1 Ma), and later stage bimodal intrusions (biotite quartz monzonite: 278.5 ± 1.8 Ma, gabbro: 278.1 ± 2.3 Ma). The earlier stage granitoids are high-K calc-alkaline, enriched in light rare earth elements (LREEs) and large ion lithophile elements (LILEs; e.g., Rb, Th, and U), and depleted in high field strength elements (HFSEs; e.g., Nb, Ta, and Ti). Combined with their depleted isotopic compositions (εNd(t) = +6.29 to +7.48) and juvenile model ages (TDM2 = 450–610 Ma), we infer that the granitoids were derived from juvenile lower crust in a post-collisional tectonic transition (from compression to extension). The structural and temporal features indicate that the earlier stage (ca. 290 Ma) granitoids formed prior to the regional large-scale dextral strike slip. The later stage bimodal intrusions are dominated by biotite quartz monzonite as the felsic member and gabbro as the mafic component. The biotite quartz monzonite is high-K calc-alkaline with enriched LREEs and LILEs (e.g., Rb, Th, and U), and depleted HFSEs (e.g., Nb, Ta, and Ti), whereas the gabbro is subalkalic with depleted LREEs and HFSEs (e.g., Nb and Ta), resembling normal mid-ocean ridge basalt features. The bimodal intrusions show similar isotopic compositions (εNd(t) = +6.41 to +6.72 and εHf(t) = +9.55 to + 13.85 for biotite quartz monzonite; εNd(t) = +9.13 to +9.69 and εHf(t) = +4.80 to +14.07 for gabbro). These features suggest that the later stage (ca. 280 Ma) bimodal intrusions were derived from partial melting of depleted mantle and anatectic melting of lower crust materials induced by synchronous underplating of basaltic magma in a post-collisional extension. The structural features of the bimodal intrusions indicate that the later stage (ca. 280 Ma) magmatism was coeval with the development of the KHSZ. In conjunction with spatial and temporal evolution of magmatism and sedimentary records of Eastern Tianshan, we infer that transition between the northward closure of the North Tianshan Ocean and subsequent collision between the Central Tianshan Massif and the Qoltag Arc belt occurred at ca. 300 Ma.
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Fan, Wei-Ming, Feng Guo, Yue-Jun Wang, and Ge Lin. "Late Mesozoic calc-alkaline volcanism of post-orogenic extension in the northern Da Hinggan Mountains, northeastern China." Journal of Volcanology and Geothermal Research 121, no. 1-2 (February 2003): 115–35. http://dx.doi.org/10.1016/s0377-0273(02)00415-8.

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24

Zhang, Xi-Song, Xi-Sheng Xu, Yan Xia, and Lei Liu. "Early Paleozoic intracontinental orogeny and post-orogenic extension in the South China Block: Insights from volcanic rocks." Journal of Asian Earth Sciences 141 (June 2017): 24–42. http://dx.doi.org/10.1016/j.jseaes.2016.07.016.

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25

Zhang, Liqi, Hongfei Zhang, Chris Hawkesworth, Biji Luo, and He Yang. "Mafic rocks from the southern Alxa block of Northwest China and its geodynamic evolution in the Paleozoic." Journal of the Geological Society 178, no. 3 (February 4, 2021): jgs2020–038. http://dx.doi.org/10.1144/jgs2020-038.

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The southern margin of the Alxa Terrane is located between the North Qilian Orogenic Belt and the inner Alxa block, and Paleozoic mafic magmatism records the geodynamic evolution at different stages in the orogenic cycle. New zircon U−Pb ages and whole-rock geochemistry reveal three groups of mafic rocks in the southern margin of the Alxa block: (i) c. 480 Ma Xijing gabbros, characterized by high Ba/Th and low Th/La ratios with low εNd(t) (−5.7 to −4.9) values, implying their derivation from enriched mantle metasomatized by slab-derived fluids; (ii) c. 440 Ma Xijing and Jiling hornblende gabbros which have high Th/La and low Ba/Th ratios, suggesting that they were produced by partial melting of mantle modified by previously subducted sediments; (iii) c. 250 Ma Xijing pyroxenites, which are cumulates with relatively high εNd(t) (+5.2 to + 5.9), indicating that their host magmas were derived from relatively depleted mantle. Together with published results, these new data highlight that the c. 480 and c. 440 Ma mafic magmas were related to the northward subduction of the North Qilian oceanic slab and later post-collisional lithospheric delamination, respectively. The c. 250 Ma Xijing pyroxenites were related to younger lithospheric extension in the development of the Central Asian Orogenic Belt in the Alxa block.Supplementary material: Supplementary tables A1–A7 are available at https://doi.org/10.6084/m9.figshare.c.5287657
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26

MUNYAI, M. R., P. H. G. M. DIRKS, and E. G. CHARLESWORTH. "ARCHAEAN GOLD MINERALISATION DURING POST-OROGENIC EXTENSION IN THE NEW CONSORT GOLD MINE, BARBERTON GREENSTONE BELT, SOUTH AFRICA." South African Journal of Geology 114, no. 2 (June 1, 2011): 121–44. http://dx.doi.org/10.2113/gssajg.114.2.121.

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27

Wang, Xiao-Lei, Liang-Shu Shu, Guang-Fu Xing, Jin-Cheng Zhou, Ming Tang, Xu-Jie Shu, Liang Qi, and Yan-Hua Hu. "Post-orogenic extension in the eastern part of the Jiangnan orogen: Evidence from ca 800–760Ma volcanic rocks." Precambrian Research 222-223 (December 2012): 404–23. http://dx.doi.org/10.1016/j.precamres.2011.07.003.

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28

Pe-Piper, G. "Magnesian andesites from the island of Skyros, Greece: geochemistry and regional significance." Geological Magazine 128, no. 6 (November 1991): 585–93. http://dx.doi.org/10.1017/s0016756800019701.

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AbstractHigh-magnesian andesites outcrop in a subvolcanic complex in the island of Skyros in the central Aegean Sea. Mineralogical indicators of this high-Mg content include bronzite and clinopyroxene phenocrysts, the former with high Cr2O3, and some phlogopite. Plagioclase (oligoclase–andesine) and Fe–Ti oxides were late phases to appear at the liquidus. Whole-rock geochemistry shows trace element features similar to those of subduction-related rocks. Radiometric dating indicates an early Serravallian (middle Miocene) age, approximately synchronous with the onset of post-orogenic rifting and extension of the Aegean Sea. This tectonic setting is consistent with an origin by adiabatic decompression of mantle peridotite previously modified by subduction-related fluids.
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Lima, Rodrigo D., Nicholas W. Hayman, and Elena Miranda. "Rheological inheritance: lessons from the Death Valley region, US Basin and Range Province." Geological Society, London, Special Publications 470, no. 1 (May 21, 2018): 173–204. http://dx.doi.org/10.1144/sp470.14.

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AbstractRheological inheritance occurs when older metamorphic and deformational fabrics impact the mechanics of younger tectonic provinces, such as occurs in extensional provinces developed on sites of previous orogenesis. The Funeral and Black Mountains from the Death Valley region of the US Basin and Range provide the opportunity to study such rheological inheritance. The Funeral Mountains expose shear zones containing high-grade metamorphic fabrics and evidence for synkinematic, decompression-driven melt of Late Cretaceous, orogenic origin. Quartz <c>- and [a]-axes patterns from the shear zones correlate with high-temperature slip systems. The quartz microstructures were formed via grain-boundary migration, and these are overprinted by high-strain layers of mixed-phase aggregates that underwent grain boundary sliding. Reaction textures from the Funeral Mountains illustrate that much of the fabric development post-dates melting, but locally involved melt–rock reactions. In contrast with the Funeral Mountains, the basement complex in the Black Mountains preserves few peak-metamorphic textures, largely owing to the overprinting by Cenozoic magmatism and deformation. However, local relicts of high-grade deformational fabrics yielding Late Cretaceous-through-Eocene magmatic zircon ages are overprinted by greenschist grade fabrics. Using outcrop and microstructural (including electron backscatter diffraction) observations, and thermodynamic modelling, we detail how segregation of melt products during orogenic partial melting resulted in chemically isolated compositional domains, favouring localization via the formation of fine-grained retrograde fabrics. We propose a conceptual model that builds on our results wherein the heterogeneous distribution of peak, orogenic metamorphic phases and melt products governs lower crustal strength and fabric evolution during extension. The Wilson Cycle may be sensitive to rheological inheritance as the width of continental margins formed during rifting will be sensitive to the fabrics and compositions formed during collision.
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ZHU, PINGPING, QIUMING CHENG, ZHENJIE ZHANG, and ZIYE WANG. "Genesis and implications of the Late Jurassic Hailesitai granites in the northern Greater Khingan Range: evidence from zircon U–Pb dating and Hf isotope." Geological Magazine 154, no. 5 (July 11, 2016): 963–82. http://dx.doi.org/10.1017/s0016756816000534.

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AbstractThe tectonic setting and geodynamic model of the Greater Khingan Range (GKR) is highly controversial due to the lack of reliable geological, isotopic and geochronological evidence. In the current study, the Hailesitai pluton, located at the west of the suture between the northern and southern GKR in the east of the Central Asian Orogenic Belt, is selected to address this issue. These granites of the high potassium calc-alkaline series belong to the A1-type granites with typical geochemical characteristics including high contents of Al2O3, extremely low contents of Ti, P, enriched LREE, LILE, depleted HFSE, and a medium Eu negative anomaly. Laser ablation inductively coupled plasma mass spectrometer (LA-ICP-MS) zircon U−Pb dating indicates that the granites can be divided into two stages: c. 152 and c. 161 Ma. The intrusion of A1-type granites at ~161 Ma implies that intra-plate orogenesis of the northern GKR started at c. 161 Ma at latest. The Hailesitai pluton has relatively homogeneous Hf isotope compositions with a εHf (t) value (+6.0 − +9.0), and two-stage depleted mantle model ages of 579−738 Ma show that the original magma is a mixture of juvenile and crustal source rocks. Extensional collapse of the Mongol−Okhotsk belt between the Siberia block and the northern GKR resulted in the formation of late Jurassic A1-type granites in the northern GKR. The Hailesitai pluton formed in response to post-orogenic extensional collapse of the Mongol–Okhotsk belt, coupled with back-arc extension related to Palaeo-Pacific plate subduction.
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31

Rohrmeier, M. K., A. von Quadt, T. Driesner, C. A. Heinrich, R. Handler, M. Ovtcharova, Z. Ivanov, P. Petrov, S. Sarov, and I. Peytcheva. "Post-Orogenic Extension and Hydrothermal Ore Formation: High-Precision Geochronology of the Central Rhodopian Metamorphic Core Complex (Bulgaria-Greece)." Economic Geology 108, no. 4 (May 2, 2013): 691–718. http://dx.doi.org/10.2113/econgeo.108.4.691.

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32

Dai, Liming, Sanzhong Li, Zhong-Hai Li, Ian Somerville, and Xiaochun Liu. "Dynamic processes and mechanisms for collision to post-orogenic extension in the Western Dabie Orogen: Insights from numerical modeling." Geological Journal 52 (August 30, 2017): 44–58. http://dx.doi.org/10.1002/gj.2993.

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33

Innocent, Christophe, Louis Briqueu, and Bruno Cabanis. "Sr-Nd isotope and trace-element geochemistry of late Variscan volcanism in the Pyrenees: Magmatism in post-orogenic extension?" Tectonophysics 238, no. 1-4 (November 1994): 161–81. http://dx.doi.org/10.1016/0040-1951(94)90054-x.

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34

Kroner, Uwe, Peter Hallas, and Franz Müller. "The anisotropic properties of granites – effects of tectonic emplacement mode on potential crystalline host rocks for nuclear waste deposits in Germany." Safety of Nuclear Waste Disposal 1 (November 10, 2021): 67–68. http://dx.doi.org/10.5194/sand-1-67-2021.

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Abstract. For permanent nuclear waste disposal sites, crystalline rocks, especially granitic/granodioritic batholiths, are considered an appropriate host rock. Principally, three types of granitic plutons occur in the extra-alpine crystalline basement of Germany that were consolidated during the late Paleozoic Variscan orogeny of Central Europe: (i) Pre-Variscan voluminous granodiorites that are hardly affected by the subsequent continent–continent collision; (ii) voluminous granites in various tectonic settings intruded during the late orogenic stage of the Variscides; (iii) post-orogenic granites related to vast Permian intracontinental extension. Thus, in terms of the syn-intrusive tectonic setting and post-intrusive processes there are significant differences. Although it can be expected that different tectonic environments caused significant differences in the material properties, for Germany, however, there is no systematic study regarding the fabric of such plutonites. In order to find the most suitable “granite” we investigate the primary anisotropy of granites evolved during the emplacement and crystallization of the melt. For this we sample rocks of all three principal types and various syn-intrusive tectonic settings, i.e., compression, extension, strike-slip, transtension, and transpression. By means of combined measurements of the “Anisotropy of the Magnetic Susceptibility” and the “Shape Preferred Orientation” we characterize the syn-intrusive flow pattern, i.e., the magmatic foliation and lineation. The Crystallographic Preferred Orientation is analyzed by a combination of neutron time-of-flight experiments and electron backscatter diffraction measurements at the Frank Laboratory of Neutron Physics at JINR, Dubna, Russia, and the TU Bergakademie Freiberg respectively. Furthermore, special attention is given to the systematic mapping of annealed microcracks evolved during late magmatic fluid escape and/or post-crystallization hydrothermal activity. In a second step we compare the primary anisotropy with the post-magmatic fracture pattern of the particular granites. Those fractures constitute probable fluid pathways and, thus, the first-order risk for a potential permanent nuclear waste disposal. All datasets are organized in a Geological Information System allowing for a complete traceability of the different investigation steps. The results of this study will serve as a basis for a future detailed exploration.
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COSTA, JOÃO B. S., YOCITERU HASUI, RUTH L. BEMERGUY, ADILSON V. SOARES-JÚNIOR, and JAVIER M. C. VILLEGAS. "Tectonics and paleogeography of the Marajó Basin, northern Brazil." Anais da Academia Brasileira de Ciências 74, no. 3 (September 2002): 519–31. http://dx.doi.org/10.1590/s0001-37652002000300013.

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The Marajó Basin area presents geologic and geomorphologic features chiefly due to the Mesozoic extension and post-Miocene neotectonics. The extension event with an Early and a Late Cretaceous phases originated four sub-basins that constitutes the Marajó Basin, with a thick continental clastic sequence showing marine influence. NW and NNW normal faults and NE and ENE strike-slip faults controlled the basin geometry. The extension, related to the Equatorial Atlantic opening, propagated into the continent along crustal weakness zones of the Precambrian Tumucumaque, Amapá and Araguaia orogenic belts. The neotectonic event is a strike-slip regime which developed transtensional basins filled in by Upper Tertiary shallow marine (Pirabas Formation) and transitional sequences (Barreiras Group), followed by Quaternary fluvial deposits and transitional sequences derived from the Amazon and Tocantins rivers and the Marajoara estuary. The current landscape has a typical estuarine morphology. The coast morphology presents sea-cliffs on transitional Upper Tertiary sequences, while inwards dominate hills sustained by Mid-Pleistocene lateritic crust, with a flat erosive surface at 70 m. In the eastern Marajó Island several generations of paleochannels associated with fluvial-estuarine sequences are recognized, while a fluvial-marine plain is widespread on its western side.
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36

Koehl, Jean-Baptiste P., and Jhon M. Muñoz-Barrera. "From widespread Mississippian to localized Pennsylvanian extension in central Spitsbergen, Svalbard." Solid Earth 9, no. 6 (December 21, 2018): 1535–58. http://dx.doi.org/10.5194/se-9-1535-2018.

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Abstract. In the Devonian–Carboniferous, a rapid succession of clustered extensional and contractional tectonic events is thought to have affected sedimentary rocks in central Spitsbergen, Svalbard. These events include Caledonian post-orogenic extensional collapse associated with the formation of thick Early–Middle Devonian basins, Late Devonian–Mississippian Ellesmerian contraction, and Early–Middle Pennsylvanian rifting, which resulted in the deposition of thick sedimentary units in Carboniferous basins like the Billefjorden Trough. The clustering of these varied tectonic settings sometimes makes it difficult to resolve the tectono-sedimentary history of individual stratigraphic units. Notably, the context of deposition of Mississippian clastic and coal-bearing sedimentary rocks of the Billefjorden Group is still debated, especially in central Spitsbergen. We present field evidence (e.g., growth strata and slickensides) from the northern part of the Billefjorden Trough, in Odellfjellet, suggesting that tilted Mississippian sedimentary strata of the Billefjorden Group deposited during active (Late/latest?) Mississippian extension. WNW–ESE-striking basin-oblique faults showing Mississippian growth strata systematically die out upwards within Mississippian to lowermost Pennsylvanian strata, thus suggesting a period of widespread WNW–ESE-directed extension in the Mississippian and an episode of localized extension in Early–Middle Pennsylvanian times. In addition, the presence of abundant basin-oblique faults in basement rocks adjacent to the Billefjorden Trough suggests that the formation of Mississippian normal faults was partly controlled by reactivation of preexisting Neoproterozoic (Timanian?) basement-seated fault zones. We propose that these preexisting faults reactivated as transverse or accommodation cross faults in or near the crest of transverse folds reflecting differential displacement along the Billefjorden Fault Zone. In Cenozoic times, a few margin-oblique faults (e.g., the Overgangshytta fault) may have mildly reactivated as oblique thrusts during transpression–contraction, but shallow-dipping, bedding-parallel, duplex-shaped décollements in shales of the Billefjorden Group possibly prevented substantial movement along these faults.
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Li, Min, Houtian Xin, Bangfang Ren, Yunwei Ren, and Wengang Liu. "Early–Middle Permian post-collisional granitoids in the northern Beishan orogen, northwestern China: evidence from U–Pb ages and Sr–Nd–Hf isotopes." Canadian Journal of Earth Sciences 57, no. 6 (June 2020): 681–97. http://dx.doi.org/10.1139/cjes-2019-0088.

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The geochemistry and Sr–Nd isotope, zircon U–Pb, and zircon Hf isotope compositions are reported for monzogranites and granodiorites from the Hazhu area in the northern Beishan orogen, northwestern China. Zircon U–Pb dating yielded ages of 270.1 ± 1.1 and 277.4 ± 1.2 Ma for the monzogranites and 263.6 ± 1.2 and 262.2 ± 1.1 Ma for the granodiorites. These monzogranites and granodiorites are metaluminous to weakly peraluminous I-type and belong to mid-K calc-alkaline and high-K calc-alkaline series. They exhibit high Mg# values and moderate degrees of differentiation (D.I. = 70.7–88.1). They are enriched in large-ion lithophile elements and light rare earth elements and depleted in high field strength elements. They show high (87Sr/86Sr)i ratios of 0.6995–0.7070 and high εNd(t) values of 4.37–5.70 with Nd model ages (TDM) of 522–789 Ma, suggesting a juvenile crustal origin. Furthermore, their εHf(t) values are all positive, and Hf isotopic crustal model ages ([Formula: see text] = 394–1097 Ma) also indicate a juvenile crustal origin. According to the data obtained in this study and other regional geological data acquired recently, the Hazhu granitoids were derived from common sources of melting from the Neoproterozoic to late Paleozoic juvenile crusts. The younger intrusions (granodiorites) are more basic, likely as a result of more juvenile lower crust being melted along with asthenospheric upwelling, which led to the addition of more basic components. These granitoids formed in a post-collisional setting. The tectonic regime transformed from an arc-related compressional setting to post-collisional extension, likely as a result of lithospheric extension and thinning in response to oceanic lithospheric delamination. These granitoids in the northern Beishan orogen were probably emplaced in a post-collisional extensional setting and suggest vertical continental crustal growth in the southern Central Asian Orogenic Belt.
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38

Zhang, Guo Rui, Jiu Hua Xu, Li Hua Shan, Hui Zhang, and Xiao Feng Wei. "The Saidu Gold Deposit of Southern Altai, China: Mineralizing Stages and Ore-Forming Fluids Evolution." Advanced Materials Research 734-737 (August 2013): 215–18. http://dx.doi.org/10.4028/www.scientific.net/amr.734-737.215.

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The Saidu gold deposit is located in the northwest part of Ertix Tectonic Zone in Xinjiang. The ore bodies occur in altered mylonite zones within the Mar-kakol giant fault zone and are controlled by the ductile shear zone. The structural-metallogenic fluids of the early stage are characterized by mesothermal-hydrothermal CO2-N2-rich fluids, with homogenization temperatures of fluid inclusions being 252~408°C. The tectonic-metallogenic fluids at the middle stage are characterized by CO2-H2O fluids, with homogenization temperatures being 203~326°C. The fluids at the late stage were epithermal-mesothermal low salinity aqueous solutions, with homogenization temperatures being 120~221°C. The main gold mineralization was related to the post-orogenic extension environment, with the evolution characteristics corresponding to the evolution of shear zones.
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39

LIU, CHANGFENG, ZHIGUANG ZHOU, YONGJU TANG, CHEN WU, HONGYING LI, YAN ZHU, TIAN JIANG, WENCAN LIU, and BAOYING YE. "Geochronology and tectonic settings of Late Jurassic – Early Cretaceous intrusive rocks in the Ulanhot region, central and southern Da Xingan Range." Geological Magazine 154, no. 5 (June 24, 2016): 923–45. http://dx.doi.org/10.1017/s0016756816000418.

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AbstractZircon U–Pb dating and whole-rock geochemical analysis have been performed on Late Jurassic – Early Cretaceous intrusive rocks of the Ulanhot area, NE China, with the aim of constraining the tectonic evolution of the central and southern Da Xingan Range. Zircon U–Pb dating indicates that Late Jurassic – Early Cretaceous magmatic events experienced four stages at:c.155 Ma;c.144 Ma; 135–130 Ma; andc.126 Ma. Thec.155 Ma magmatic event consists of quartz diorite and granite-porphyryp with the geochemical characteristic of high Sr and Sr/Y or high A/CNK (1.38), implying the primary magma was derived from partial melting of a thickened lower crust which induced the closure of the Mongol–Okhotsk Ocean. Thec.144 Ma magmatic event consists of quartz monzodiorite with the geochemical characteristics of alkaline series, and indicates the delamination of a thickened crust. The 135–130 Ma magmatic event consists of syenogranite and granite-porphyry with characteristics of both I-type and A-type granites, which induced both the subduction of the Palaeo-Pacific oceanic plate and the post-orogenic extension of the Mongol–Okhotsk Orogenic Belt. Thec.126 Ma magmatic event consisted of highly fractionated I-type biotite granite and alkaline series gabbro, marking the end of the Mongol–Okhotsk Orogen, and implying that the study area was controlled by the circum-Pacific tectonic system during this stage.
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40

Wang, Zhigang, Ke Li, Zhicheng Zhang, Jianzhou Tang, and Yan Chen. "Early Permian magmatism in northern Inner Mongolia, southeastern Central Asian Orogenic Belt: Implications on lithospheric extension in a post-collisional setting." Lithos 426-427 (October 2022): 106803. http://dx.doi.org/10.1016/j.lithos.2022.106803.

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41

Tavarnelli, Enrico, Pietro Renda, Valeria Pasqui, and Mariano Tramutoli. "The effects of post-orogenic extension on different scales: an example from the Apennine-Maghrebide fold-and-thrust belt, SW Sicily." Terra Nova 15, no. 1 (February 2003): 1–7. http://dx.doi.org/10.1046/j.1365-3121.2003.00466.x.

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42

Lana, Cristiano, Ian Buick, Gary Stevens, Riana Rossouw, and Willem De Wet. "3230–3200 Ma post-orogenic extension and mid-crustal magmatism along the southeastern margin of the Barberton Greenstone Belt, South Africa." Journal of Structural Geology 33, no. 5 (May 2011): 844–58. http://dx.doi.org/10.1016/j.jsg.2011.03.007.

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43

Qiu, Liang, Dan-Ping Yan, Shuang-Li Tang, Feng Chen, Zhi-Dong Song, Tian Gao, and Yi-Xi Zhang. "Insights into post-orogenic extension and opening of the Palaeo-Tethys Ocean recorded by an Early Devonian core complex in South China." Journal of Geodynamics 135 (April 2020): 101708. http://dx.doi.org/10.1016/j.jog.2020.101708.

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44

Sizova, Elena, Christoph Hauzenberger, Harald Fritz, Shah Wali Faryad, and Taras Gerya. "Late Orogenic Heating of (Ultra)High Pressure Rocks: Slab Rollback vs. Slab Breakoff." Geosciences 9, no. 12 (November 27, 2019): 499. http://dx.doi.org/10.3390/geosciences9120499.

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Some (ultra)high-pressure metamorphic rocks that formed during continental collision preserve relict minerals, indicating a two-stage evolution: first, subduction to mantle depths and exhumation to the lower-crustal level (with simultaneous cooling), followed by intensive heating that can be characterized by a β-shaped pressure–temperature–time (P–T–t) path. Based on a two-dimensional (2D) coupled petrological–thermomechanical tectono-magmatic numerical model, we propose a possible sequence of tectonic stages that could lead to these overprinting metamorphic events along an orogenic β-shaped P–T–t path: the subduction and exhumation of continental crust, followed by slab retreat that leads to extension and subsequent asthenospheric upwelling. During the last stage, the exhumed crustal material at the crust–mantle boundary undergoes heating from the underlying hot asthenospheric mantle. This slab rollback scenario is further compared numerically with the classical continental collision scenario associated with slab breakoff, which is often used to explain the late heating impulse in the collisional orogens. The mantle upwelling occurring in the experiments with slab breakoff, which is responsible for the heating of the exhumed crustal material, is not related to the slab breakoff but can be caused either by slab bending before slab breakoff or by post-breakoff exhumation of the subducted crust. Our numerical modeling predictions align well with a variety of orogenic P–T–t paths that have been reported from many Phanerozoic collisional orogens, such as the Variscan Bohemian Massif, the Triassic Dabie Shan, the Cenozoic Northwest Himalaya, and some metamorphic complexes in the Alps.
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Sun, J. L., Y. Qian, J. Y. Li, S. N. Tian, B. Chen, T. Zheng, C. J. Zhao, and F. Y. Sun. "The Late Paleoproterozoic A-Type Granites in the Jiao-Liao-Ji Orogenic Belt, North China Craton: Petrogenesis and Implications for Post-Collision Extension." Geochemistry International 59, no. 4 (April 2021): 388–412. http://dx.doi.org/10.1134/s0016702921040078.

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46

Cui, Xing, Min Sun, Guochun Zhao, and Yunying Zhang. "Origin of Permian mafic intrusions in southern Chinese Altai, Central Asian Orogenic Belt: A post-collisional extension system triggered by slab break-off." Lithos 390-391 (June 2021): 106112. http://dx.doi.org/10.1016/j.lithos.2021.106112.

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47

Xin, Yujia, Jianhua Li, Lothar Ratschbacher, Guochun Zhao, Yueqiao Zhang, Shuwen Dong, Xiao-Ping Xia, and Yingqi Yu. "Early Devonian (415–400 Ma) A-type granitoids and diabases in the Wuyishan, eastern Cathaysia: A signal of crustal extension coeval with the separation of South China from Gondwana." GSA Bulletin 132, no. 11-12 (March 18, 2020): 2295–317. http://dx.doi.org/10.1130/b35412.1.

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Abstract The evolution of the South China continental crust and its linkage to the assembly and rifting of eastern Gondwana are key issues in the understanding of the early Paleozoic evolution of eastern Asia. We report U-Pb zircon ages and geochemical and Lu-Hf isotopic data for the South Fufang and Yingshang granitoids and the Mayuan diabases from the Wuyishan of eastern South China. The zircons yielded U-Pb ages of ca. 414–404 and ca. 409–401 Ma for the granitoids and diabases, respectively. Petrographic and geochemical features indicate that the granitoids are peraluminous A-type granites, expressed by high Ga/Al ratios and high Zr, Nb, Ce, Y, and rare earth element contents. They show negative zircon εHf(t) values (–15.4 to –5.8), consistent with the derivation from a crustal source. The granitoids likely originated from partial melting of dry granulite residues in the lower crust. The diabases show depletion in Ti, and negative correlations between FeOt and Mg#, and SiO2 and TiO2/FeOt, reflecting clinopyroxene, olivine, and Fe-Ti oxide fractionation. Their negative zircon εHf(t) values (–4.5 to –0.4) indicate an ancient enriched-mantle origin. The diabases likely originated from partial melting of a sub-continental lithospheric mantle. We interpret these A-type granitoids and diabases as post-orogenic, formed during extensional collapse of thickened crust. Their generation indicates that South China experienced crustal extension during the Early Devonian. The extension occurred coevally with global rifting that led to the separation of the continental blocks of eastern Asia from eastern Gondwana, which was associated with the Early Devonian opening of the paleo–Tethys Ocean.
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Wang, Chao, Shuguang Song, Yaoling Niu, Chunjing Wei, and Li Su. "TTG and Potassic Granitoids in the Eastern North China Craton: Making Neoarchean Upper Continental Crust during Micro-continental Collision and Post-collisional Extension." Journal of Petrology 57, no. 9 (November 25, 2016): 1775–810. http://dx.doi.org/10.1093/petrology/egw060.

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As the major component, Archean granitoids provide us with an insight into the formation of the early continental crust. We report the study of a series of Neoarchean granitoids, including tonalite–trondhjemite–granodiorite (TTG) and potassic granitoids, in the Xingcheng region of the eastern North China Craton. Zircon U–Pb dating shows that the TTG granitoids were emplaced in the Neoarchean within a 75 Myr period (2595–2520 Ma), with coeval mafic magmatic enclaves, followed by intrusion of potassic granitoids. The geochemistry of the TTG granitoids is consistent with partial melting of Mesoarchean enriched mafic crustal sources at different depths (up to 10–12 kbar equivalent pressure) during a continental collision event. The potassic granitoids are derived from either low-degree melting of Mesoarchean enriched mafic crustal sources or remelting of Mesoarchean TTGs in response to post-collisional extension, and were hybridized with Neoarchean mantle-derived mafic melts to various degrees. The TTG and potassic granitoids in the Xingcheng region record the evolution from collision of micro-continental blocks to post-collisional extension, consistent with other studies, suggesting that the amalgamation of micro-continental blocks is what gave rise to the cratonization of the North China Craton at the end of the Archean. The rock assemblage of these granitoids resembles those of syn- and post-collisional magmatism in Phanerozoic orogenic belts, and the estimated average composition is similar to that of the present-day upper continental crust, suggesting that a prototype upper continental crust might have been developed at the end of the Archean from a mixture of TTG and potassic granitoids. Together with concurrent high-grade metamorphism in the North China Craton, we conclude that collisional orogenesis is responsible for continental cratonization at the end of the Archean in the North China Craton.
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MOGHAZI, ABDEL-KADER M. "Magma source and evolution of Late Neoproterozoic granitoids in the Gabal El-Urf area, Eastern Desert, Egypt: geochemical and Sr–Nd isotopic constraints." Geological Magazine 136, no. 3 (May 1999): 285–300. http://dx.doi.org/10.1017/s0016756899002563.

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Granitoids in the Gabal El-Urf area in Eastern Egypt consist of a monzogranite pluton, belonging to the Younger Granite province, emplaced in granodioritic rocks. Whole rock Rb–Sr dating indicate ages of 650±95 Ma and 600±11 Ma for the granodiorites and monzogranites, respectively. The granodiorites (65–70% SiO2) are calc-alkaline and metaluminous with low Rb/Sr, Th and Nb contents, moderate enrichment in the LILE (K2O, Rb, and Ba) and display most of the chemical and field characteristics of syn-to late-tectonic I-type granitoids described elsewhere in the Arabian–Nubian Shield. The monzogranites (72–77% SiO2) are metaluminous to mildly peraluminous, highly fractionated and depleted in Al2O3, MgO, CaO, TiO2, Sr and Ba with corresponding enrichment in Rb, Nb, Zr, and Y. They can be correlated with the undeformed post-orogenic granites in the Arabian–Nubian Shield that chemically resemble A-type granites emplaced in extensional settings. The mineralogical and chemical variations within the granodiorites and monzogranites are consistent with their evolution by fractional crystallization. The granodiorites have a low initial 87Sr/86Sr ratio (0.7024) and high ∈Nd values (+6.9–+7.3) and are significantly different from those (initial 87Sr/86Sr ratio=0.7029, ∈Nd values=+5.2–+5.8) of the monzogranites. These data suggest a predominant mantle derivation for both granite types and demonstrate that they originated from different source materials.The granodiorite melt was most probably generated through vapour-saturated partial melting of an early Neoproterozoic depleted mafic lower-crust reservoir due to crustal thickening associated with orogenic compression and/or arc magma underplating. The mineralogical and geochemical data of the A-type monzogranites are consistent with their derivation as a residual granitic liquid from a LILE-enriched mafic magma through crystal-liquid fractionation of plagioclase, amphibole, Fe–Ti oxides and apatite. The parental mafic magma was originated in the upper mantle due to crustal thinning associated with extension in the late stage of the Neoproterozoic crustal evolution of north-eastern Egypt.
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50

Asan, Kürşad. "Whole-Rock Elemental and Sr-Nd Isotope Geochemistry and Petrogenesis of the Miocene Elmadağ Volcanic Complex, Central Anatolia (Ankara, Turkey)." Geosciences 10, no. 9 (September 3, 2020): 348. http://dx.doi.org/10.3390/geosciences10090348.

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Abstract:
This study presented whole-rock elemental and Sr-Nd isotope geochemistry data with the purpose to decipher the origin and evolution of the Miocene Elmadağ Volcanic Complex, Central Anatolia (Ankara, Turkey). Volcanic products spanned in composition from mildly alkaline basaltic (47–52 wt% SiO2) and medium- to high-K calc-alkaline intermediate (54–62 wt% SiO2; andesite to trachyandesite) to felsic (64–74 wt% SiO2; dacite to rhyolite) units. Despite a homogeneous major element composition, basaltic rocks were characterized by two distinct trace element and isotopic signatures, which have been correlated with different mantle sources. The first group of basaltic rocks was similar to those of oceanic island basalts (OIB) and was derived from asthenospheric mantle source. The second group had geochemical characteristics of orogenic basalts derived from subduction-modified lithospheric mantle source and represented parental magma of the intermediate to felsic rocks. By coupling geochemical and textural analyses of the rocks from the Elmadağ Volcanic Complex, I suggest that crystallization of olivine + clinopyroxene + apatite played an important role in the evolution of basaltic rocks, while plagioclase + amphibole + apatite + Fe-Ti oxides ± zircon crystallization was major process involved in the evolution of intermediate to felsic rocks. The EVC basaltic rocks were associated with the post-collisional extensional tectonic regime in the Central Anatolia, but the coexistence of the OIB-like volcanism implies variations in the extension dynamics during Miocene.
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