Melting of the juvenile lower crust in a far-field response to roll-back of the southern Neotethyan oceanic lithosphere: the Oligocene adakitic dacites, NE Turkey

Karslı, Orhan; Caran, S. Christopher; Çoban, Hakan; Şengün, Fırat; Tekkanat, Osman; Andersen, Tom

doi:10.1016/j.lithos.2020.105614

Cited by 10 publications

(7 citation statements)

References 118 publications

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“…The XSG porphyritic granite samples plot between the depletedmantle and chondrite Hf isotopic lines with εHf(t) values of +2.4 − +4.6 (Figure 9a,b), indicating that the XSG porphyritic granite formed from magmas derived from a juvenile lower crust source (Karsli et al, 2020;Wang, Zheng, & Zhu, 2019;Zhou, Lü, & Wang, 2011). These samples also have T DM2 ages of 1,123-981 Ma, suggesting that their juvenile lower crustal source formed during the Mesoproterozoic-Neoproterozoic period.…”

Section: Middle Triassic Granitoidsmentioning

confidence: 98%

Middle to Late Triassic granitic magmatism in the East Kunlun Orogenic Belt, NW China: Petrogenesis and implications for a transition from subduction to post‐collision setting of the Palaeo‐Tethys Ocean

Gao

Sun

2021

Geological Journal

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In this study, we present new geochronological and petrogenetic data for the Triassic granitoids of the East Kunlun Orogenic Belt (EKOB), in order to constrain their precise ages, petrogenesis, and tectonic settings. LA-ICP-MS zircon U-Pb data indicate that the Triassic granitoids were emplaced in two stages: (a) Middle Triassic (247-240 Ma), represented by a suite of porphyritic granites and granodiorites; and (b) Late Triassic (234-227 Ma), forming an intrusive rock association of K-feldspar granites, granodiorites, and porphyritic granites. Geochemical analyses and mineral associations suggest that all the Triassic granitoids belong to I-type granites but have different origins. The Middle Triassic granitoids have high SiO 2 , low to moderate Mg # values (25-37 for XSG porphyritic granite; 45-47 for DB granodiorite), low Sr/Y ratios (2.2-4.6 for XSG porphyritic granite; 17.8-20.8 for DB granodiorite), and rela-tively restricted zircon εHf(t) values (+2.4 − +4.6 for the ca. 247 Ma porphyritic granite, and − 8.0 to −1.5 for the ca. 240 Ma granodiorite), indicating that they were dominantly generated from partial melting of different crust sources (either juvenile or ancient) in a normal lower crust level. In contrast, the Late Triassic granitoids have high SiO 2 , K 2 O, and Y contents, low MgO and HREE contents, and variable zircon εHf(t) values (from negative to positive, −4.9 to +3.3), implying a strong crustal-mantle interaction that occurred during the Late Triassic, and this stage of granitoids were derived from a complex magma source possibly a mixture of mantle-derived and ancient crustal-derived materials. By combining these new data with the previous data, we conclude that the two stages of Triassic granitoids were emplaced in an active continental margin setting and a post-collisional extension setting, respectively. Moreover, this study suggests a tectonic shift of the Palaeo-Tethys Ocean in the EKOB from subduction during the Middle Triassic to a post-collision during the Late Triassic.

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Section: Middle Triassic Granitoidsmentioning

confidence: 98%

Middle to Late Triassic granitic magmatism in the East Kunlun Orogenic Belt, NW China: Petrogenesis and implications for a transition from subduction to post‐collision setting of the Palaeo‐Tethys Ocean

Gao

Sun

2021

Geological Journal

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“…In such a scenario, the Meiji dacites might be products of magmas derived from the lower continental crust beneath the SCB. Modeling using whole Sm/Yb and La/Yb ratios (Karsli et al, 2020) suggests that the Meiji dacites can be produced by <40% partial melting of amphibolites containing ∼10% garnet in the lower continental crust (Figure 12A, B). On the other hand, the Meiji dacites are compositionally different from adakites produced by partial melting of a subducted slab (Defant and Drummond, 1990) or thickened lower crust (Ma et al, 2016).…”

Section: Petrogenesis Of the Meiji Atoll Dacitesmentioning

confidence: 99%

Petrogenesis of Dacites in a Triassic Volcanic Arc in the South China Sea: Constraints From Whole Rock and Mineral Geochemistry

Liu

Mitchell

et al. 2022

Front. Earth Sci.

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Triassic volcanic rocks, including basalts and dacites, were drilled from Meiji Atoll in the South China Sea (SCS), which represents a rifted slice from the active continental margin along the Cathaysia Block. In this study, we present apatite and whole rock geochemistry of Meiji dacites to decipher their petrogenesis. Apatite geochronology yielded U-Pb ages of 204–221 Ma, which are identical to zircon U-Pb ages within uncertainty and thus corroborate the formation of the Meiji volcanic rocks during the Late Triassic. Whole rock major elements suggest that Meiji dacites mainly belong to the high-K calc-alkaline series. They display enriched patterns in light rare earth elements (LREE) and flat patterns in heavy rare earth elements (HREE). They show enrichment in large-ion lithophile elements (LILE) and negative anomalies in Eu, Sr, P, Nb, Ta, and Ti. The dacites have initial 87Sr/86Sr ratios of 0.7094–0.7113, εNd(t) values of -5.9–-5.4 and εHf(t) values of -2.9–-1.7, whereas the apatite has relatively higher initial 87Sr/86Sr ratios (0.71289–0.71968) and similar εNd(t) (-8.13–-4.56) values. The dacites have homogeneous Pb isotopes, with initial 206Pb/204Pb of 18.73–18.87, 207Pb/204Pb of 15.75–15.80, and 208Pb/204Pb of 38.97–39.17. Modeling results suggest that Meiji dacites can be generated by <40% partial melting of amphibolites containing ∼10% garnet. Therefore, we propose that the Meiji dacites were produced by partial melting of the lower continental crust beneath the South China block, triggered by the underplating of mafic magmas as a response to Paleo-Pacific (Panthalassa) subduction during the Triassic. Meiji Atoll, together with other microblocks in the SCS, were rifted from the South China block and drifted southward due to continental extension and the opening of the SCS.

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“…Subduction of the southern Neotethys branch and subsequent Arabia-Eurasia collision and post-collision evolution generated Cenozoic magmatism in the Iranian Urumieh-Dokhtar (Chiu et al, 2013;Omrani et al, 2008) and Alborz magmatic arcs (Aghazadeh et al, 2011(Aghazadeh et al, , 2010Asiabanha and Foden, 2012;Castro et al, 2013;Verdel et al, 2011;Vincent et al, 2005), the SAB (Moritz et al, 2016b;Rezeau et al, 2018Rezeau et al, , 2017Rezeau et al, , 2016Sahakyan et al, 2016), the Eastern Pontides (Aydınçakır and S ¸en, 2013;Dokuz et al, 2019;Eyuboglu et al, 2017;Karsli et al, 2020bKarsli et al, , 2020aKarsli et al, , 2019Karsli et al, , 2011Kaygusuz and Öztürk, 2015) and the TAP ( ˙Imer et al, 2013;Keskin, 2003;Rabayrol et al, 2019;Schleiffarth et al, 2018).…”

Section: Geological Setting and Geodynamic Evolution Of The South Arm...mentioning

confidence: 99%

Arabia-Eurasia convergence and collision control on Cenozoic juvenile K-rich magmatism in the South Armenian block, Lesser Caucasus

Grosjean

Moritz

Rezeau

et al. 2022

Earth-Science Reviews

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Melting of the juvenile lower crust in a far-field response to roll-back of the southern Neotethyan oceanic lithosphere: the Oligocene adakitic dacites, NE Turkey

Cited by 10 publications

References 118 publications

Middle to Late Triassic granitic magmatism in the East Kunlun Orogenic Belt, NW China: Petrogenesis and implications for a transition from subduction to post‐collision setting of the Palaeo‐Tethys Ocean

Middle to Late Triassic granitic magmatism in the East Kunlun Orogenic Belt, NW China: Petrogenesis and implications for a transition from subduction to post‐collision setting of the Palaeo‐Tethys Ocean

Petrogenesis of Dacites in a Triassic Volcanic Arc in the South China Sea: Constraints From Whole Rock and Mineral Geochemistry

Arabia-Eurasia convergence and collision control on Cenozoic juvenile K-rich magmatism in the South Armenian block, Lesser Caucasus

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