Disequilibrium partial melting of metasediments in subduction zones: Evidence from O-Nd-Hf isotopes and trace elements in S-type granites of the Chinese Altai

Kong, Xianjing; Zhang, Chen; Liu, Dongdong; Jiang, Shu; Luo, Qun; Zeng, Jianhui; Liu, Luofu; Luo, Long; Shao, Hengbo; Liú, Dan; Liu, Xiaoyu; Wang, Xinpeng

doi:10.1130/l1039.1

Cited by 21 publications

(5 citation statements)

References 106 publications

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“…The studied A-type granites exhibit negative ε Nd (t) values (À10.1 to À8.40) and a wide range of ε Hf (t) values (À8.46 to +14.7) and significant Nd-Hf decoupling, indicating that they formed via complex magmatic processes. The Nd-Hf decoupling could be inherited from the magma source (Yu et al, 2017) or result of disequilibrium melting (Kong et al, 2018;Zhang, Liu, Santosh, Luo, & Zhang, 2017 (Maniar & Piccoli, 1989); and (c) K 2 O versus Na 2 O diagram (after Collins, Beams, White, & Chappell, 1982) degree at depths greater than a few kilometres in the continental crust (Clemens & Vielzeuf, 1987;Skjerlie, Patiño Douce, & Johnston, 1993), dehydration melting of hydrous minerals typically plays an important role in the generation of granitic magma (Patiño Douce, 1999;Tompson, 1996). In experimental tests of the effects of fluids on element partitioning, Sr is found to be more sensitive than Hf and Nd (Turner, Handler, Bindeman, & Suzuki, 2009;Woodhead, Hergt, Davidson, & Eggins, 2001;Zhang et al, 2017).…”

Section: Petrogenesis Of Granitesmentioning

confidence: 99%

Geochronology and geochemistry of granites from the Hengjian area, Qinling Orogenic Belt: Implications for the Late Palaeozoic tectonic evolution of the North Qinling Terrane, China

Han

Lin

et al. 2021

Geological Journal

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The North Qinling Orogen underwent subduction and collision processes during the Palaeozoic, but the tectonic framework remains unclear. To investigate the tectonic evolution of the North Qinling Orogen, we selected the Devonian granites from the northeastern margin of the North Qinling Terrane. Integrated petrographic, geochemical, and geochronological studies, as well as Sr-Nd-Hf isotopic analyses, were carried out on the newly identified Devonian granites from the Hengjian area in the northeastern North Qinling Terrane, Qinling Orogenic Belt. Zircon laser ablation inductively coupled plasma mass spectrometry U-Pb dating reveals that these granites were crystallized at 396-387 Ma. The granite samples are metaluminous to weakly peraluminous (A/CNK = Al 2 O 3 /(CaO+Na 2 O+K 2 O) = 0.86 to 1.12), with high SiO 2 (60.6-76.5 wt%) and high total alkaline (Na 2 O + K 2 O = 8.45-11.0 wt%) contents. The granites are enriched in Th, rare-earth element, Zr, and Hf and depleted in Sr, Nb, Ta, P, Eu, and Ti. They are characterized by high Zr + Nb + Ce + Y contents (511-990 ppm) and 10,000*Ga/Al ratios (2.71-3.32), as well as high zircon-saturation temperatures (T Zr = 819-885 C, average = 845 C), which indicate that they are typical A-type granites. The granites have low Y/Nb (0.39-0.67) and Yb/Ta (0.56-0.83) ratios, resembling those of the A 1 -type granite, which indicates that they are formed in anorogenic settings. They also have low ( 87 Sr/ 86 Sr) i ratios (0.7055-0.7071) and negative ε Nd (t) values (À10.1 to À8.40) and variable zircon ε Hf (t) values (À8.46 to +14.7), with the two-stage model ages of 2.0-1.8 Ga and 1.9-0.4 Ga, respectively. These geological features suggest that the granites of the Hengjian area were most likely generated by partial melting of mafic lower crust induced by asthenospheric ascent. The A-type granites were generated in a continental rift environment during 396-387 Ma, corresponding to the closure of the Shangdan Ocean and the opening of the Palaeo-Tethyan Ocean during the Early Devonian.

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Section: Petrogenesis Of Granitesmentioning

confidence: 99%

Geochronology and geochemistry of granites from the Hengjian area, Qinling Orogenic Belt: Implications for the Late Palaeozoic tectonic evolution of the North Qinling Terrane, China

Han

Lin

et al. 2021

Geological Journal

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“…The age versus δ 18 O diagrams of the XLKS, DKLS and YLM pegmatites, compared with Palaeozoic granites in the Chinese Altay (the data are from Kong et al, 2018; C. Zhang et al, 2019). DKLS, Dakalasu; XKLS, Xiaokalasu; YLM, Yelaman…”

Section: Discussionmentioning

confidence: 99%

Petrogenetic studies of Permian pegmatites in the Chinese Altay: Implications for a two‐stage post‐collisional magmatism model

Wang

Zhang

et al. 2022

Geological Journal

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Understanding the petrogenesis of rare‐metal pegmatites is important for understanding ore‐forming processes and their tectonic settings. In this study, we performed zircon U–Pb geochronological and Hf–O isotopic analyses of the Xiaokalasu, Dakalasu, and Yelaman pegmatites in the Chinese Altay orogen. These pegmatites have low εHf(t) values (−0.6 ~ +4.3), two‐stage model ages of 989 ~ 1,293 Ma, and high δ18O values (+6.52 ~ +11.31), indicating that they may have been derived from the anatexis of mature sedimentary rocks in the deep crust, with a small amount of mantle‐derived or juvenile material. Geochronological and Hf–O isotopic data for granitic intrusions in the Chinese Altay Mountains indicate that the εHf(t) values decreased from the Permian to the Triassic, which implies that two‐stage post‐collisional magmatism occurred in this region. During the Permian, the thin lower crust was cold; thus, magmatism likely originated in the deep crust close to the Moho surface and involved intense mantle–crust interactions. During the Triassic, asthenospheric upwelling provided heat to the lower crust, which increased the geothermal gradient and led to the anatexis of shallow crustal material.

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“…More recent studies proposed that peraluminous granites could also form in other geodynamic scenarios that provide an enhanced thermal gradient to the crust facilitating crustal melting including: ridge subduction (Cai et al, 2011;Kong et al, 2019), mantle plumes (Li et al, 2011).…”

Section: Tectonic Implicationsmentioning

confidence: 99%

Age, Petrogenesis and Tectonic Implications of the Late Permian Peraluminous and Metaluminous Magmatic Rocks in the Middle Gobi Volcanoplutonic Belt, Mongolia

Ganbat¹,

Tsujimori²,

Miao³

et al. 2021

Preprint

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The Mongol–Okhotsk Belt, the youngest segment of the Central Asian Orogenic Belt, formed by the evolution and closure of the Mongol–Okhotsk Ocean. The oceanic closure formed two volcanoplutonic belts: Selenge Belt in the north and Middle Gobi Belt in the south (in present day coordinates). However, the origin and tectonic evolution of the Mongol–Okhotsk Belt in general, the origin and formation age of the Middle Gobi Belt in particular, remain enigmatic. To better understand the history of the magmatic activity in the Middle Gobi Belt, we conducted geochemical, U–Pb geochronological, zircon Hf, whole-rock Nd isotopic analyses of volcanic and plutonic rocks of the Mandalgovi suite, the major component of the Middle Gobi Belt. Our results show that the Mandalgovi suite consists of (i) 265 ± 2 Ma biotite-granite; (ii) 250 ± 3 Ma hornblende-granitoids; (iii) their volcanic equivalents of both: and (iv) gabbro-diorites. The geochemical compositions indicate that their precursor magmas were derived from crustal source. The protoliths of the biotite and hornblende-granitoids were metagraywacke and metabasalt, respectively. They are characterized by positive whole-rock εNd(t) and zircon εHf(t) values, indicating the molten protoliths were juvenile crust. The biotite-granites formed by remelting of fore-arc sediments by ridge subduction and later hornblende-granites were emplaced at an intra-oceanic arc by the subduction of the Mongol–Okhotsk Ocean. We conclude that the magmatic rocks of the Middle Gobi formed in an active continental margin and/or intra-oceanic arc setting.

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Disequilibrium partial melting of metasediments in subduction zones: Evidence from O-Nd-Hf isotopes and trace elements in S-type granites of the Chinese Altai

Cited by 21 publications

References 106 publications

Geochronology and geochemistry of granites from the Hengjian area, Qinling Orogenic Belt: Implications for the Late Palaeozoic tectonic evolution of the North Qinling Terrane, China

Geochronology and geochemistry of granites from the Hengjian area, Qinling Orogenic Belt: Implications for the Late Palaeozoic tectonic evolution of the North Qinling Terrane, China

Petrogenetic studies of Permian pegmatites in the Chinese Altay: Implications for a two‐stage post‐collisional magmatism model

Age, Petrogenesis and Tectonic Implications of the Late Permian Peraluminous and Metaluminous Magmatic Rocks in the Middle Gobi Volcanoplutonic Belt, Mongolia

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