Metasedimentary melting in the formation of charnockite: Petrological and zircon U-Pb-Hf-O isotope evidence from the Darongshan S-type granitic complex in southern China

Jiao, Shujuan; Li, Xian‐Hua; Huang, Hongyan; Deng, Xiaoyun

doi:10.1016/j.lithos.2015.10.004

Cited by 100 publications

(60 citation statements)

References 77 publications

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“…14B), suggesting anomalous behavior of Hf isotopes in causing Nd-Hf isotopic decoupling. This is further supported by the distinct ε Hf (t) values as compared to typical S-type granites (Appleby et al, 2010;Jiao et al, 2015).…”

Section: Nd-hf-o Isotopic Decouplingsupporting

confidence: 52%

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

et al. 2018

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Late Cambrian to Devonian granitic magmatism in the Chinese Altai provides a critical view of geodynamic processes active during crustal growth in the Central Asian orogenic belt. In this study, we report results of zircon U-Pb and Hf-O isotopic compositions, whole-rock geochemical signatures, and Nd isotopic data for late Cambrian-Early Devonian granites in the Chinese Altai. These granites were emplaced between 497 and 397 Ma and have high SiO 2 (66.02-72.07 wt%) and K 2 O (3.18-5.19 wt%) contents, and low Fe 2 O 3 t (1.94-5.63 wt%), MgO (0.21-2.23 wt%), and CaO (0.62-1.25 wt%) contents, with A/CNK ratios of 1.16-1.53 (where A/CNK = molar ratio of Al 2 O 3 /[CaO + Na 2 O + K 2 O]). Moreover, these granites are geochemically similar to S-type granites. They are characterized by negative ε Nd (t) values (-3.84 to-1.54), high δ 18 O values (+9.34‰ to +13.82‰), and low CaO/Na 2 O and (Na 2 O + K 2 O)/(MgO + FeO + TiO 2) ratios, implying a mafic-metapelitic source. The ε Hf (t) values of the granites (−11.17 to +13.27) are decoupled from the ε Nd (t) and δ 18 O isotope values. This is suggested to be a result of disequilibrium during melting of the source wherein residual zircons were preserved and retained large amounts of Hf, producing Hf-depleted melts and Hf-enriched xenocrystic zircons. Variable zircon dissolution rates during melting and melt loss are ascribed to explain the observed variance in Hf concentrations. Based on the results and published data, a ridge subduction model was established to explain the 497-397 Ma high-temperature magmatism in the Chinese Altai.

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Section: Nd-hf-o Isotopic Decouplingsupporting

confidence: 52%

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

et al. 2018

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“…Although late Paleozoic and Indosinian igneous rocks are widespread further inland in southeastern South China, such as the Permian Wuyishan syenite (~254 Ma; Wang et al, ), potassic to calc‐alkaline Hainan granitoids (~290–260 Ma; Li et al, ; Li et al, ; Xie et al, ), the Shiwandashan granites and volcanic rocks (~260–230 Ma; Chen et al, ; Gao et al, ; Jiao et al, ; Li et al, ; Xu et al, ), and the Yunkai gneissic granites (~250–242 Ma; Peng et al, ; J. C. Zhou, Jiang, et al, ; X.‐M. Zhou, Sun, et al, ; Zhou et al, ), these Permian‐Triassic granites are unlikely important detrital sources for our Early‐Middle Triassic samples because (1) these igneous rocks have mainly negative zircon ε Hf( t ) values (e.g., Darongshan granites: ε Hf( t ) = −31.9 to −1.8; Jiao et al, ), distinct from the mainly positive ε Hf( t ) (~60%) values of the above‐mentioned Ailaoshan 280–237 Ma detrital zircon grains; (2) Proterozoic to early Paleozoic inherited zircon grains are common in these rocks (Chen et al, ; Jiao et al, ; Li et al, ) but absent in our samples; and (3) the intervening late Paleozoic‐Triassic Youjiang and Shiwandashan basins (east and southeast of Ailaoshan) would have likely barred the South China inland‐derived sediments from reaching Ailaoshan. In fact, the Lower‐Middle Triassic sedimentary rocks in the Youjiang and Shiwandashan basins are characterized by multiple detrital zircon age populations (Hu et al, , , ; Yang, Cawood, Du, Huang, & Hu, ; Figure ), clearly distinct from our Early‐Middle Triassic western South China samples.…”

Section: Discussionmentioning

confidence: 99%

When Did the Paleotethys Ailaoshan Ocean Close: New Insights From Detrital Zircon U‐Pb age and Hf Isotopes

Xia

Lai

et al. 2019

Tectonics

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We present new laser ablation (LA)‐multicollector‐inductively coupled plasma mass spectrometry detrital zircon U‐Pb age and Hf isotope data of the Triassic sedimentary rocks from the eastern and western sides of the Ailaoshan suture in SW China, which separate the Indochina and South China blocks. Detrital zircon grains of the Lower‐Middle Triassic sequences from western South China show single age population of 280–237 Ma (peak at 254–251 Ma) with mainly positive εHf(t) values (+0.15 to +9.11, ~60%). The Middle Triassic samples from eastern Indochina also contain single age population of 273–236 Ma (peak at 246–242 Ma), but with mainly negative εHf(t) values (−18.95 to −1.83, ~88%). The unimodal detrital zircon age pattern and Hf isotope features suggest that the Permian‐Triassic magmatic arcs had supplied detritus for the Lower‐Middle Triassic sequences on both sides of the Ailaoshan suture. In contrast, the Upper Triassic sequences on the either side of the suture display similar polymodal age populations at 290–230, 500–400, 850–700, 1000–900, 2000–1800, and 2600–2400 Ma. This indicates a dramatic change in detrital provenance across the Middle‐Late Triassic boundary. We interpret this change to be resulted from the closure of the Paleotethyan Ailaoshan Ocean in the early Late Triassic. The ocean closure and consequent Indochina‐South China continent‐continent collision may have connected the drainage systems of the two blocks, leading to the marked similarities in their post‐Middle Triassic sedimentary provenance.

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“…Moreover, I-type granites generally contain amphibole, whereas the S-type granites usually contain minerals such as cordierite or tourmaline, but contain no amphibole (e.g. Jiao et al 2015; Tan et al 2017). The gneissic monzogranites in the Yunkai massif contain tourmaline but carry no amphibole.…”

Section: Discussionmentioning

confidence: 99%

Petrogenesis of the Early Palaeozoic granitoids from the Yunkai massif, South China block: implications for a tectonic transition from compression to extension during the Caledonian orogenic event

et al. 2017

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A comprehensive geochronological and geochemical study was carried out on the gneissic monzogranites, porphyritic granodiorites and charnockites in the Gaozhou complex of the Yunkai massif in the southern part of the South China block to better understand the Early Palaeozoic tectonic regime of the South China block. Laser ablation – inductively coupled plasma – mass spectrometry (LA-ICP-MS) U–Pb dating of zircons indicates an age of 453.2 ± 5.1 Ma to the formation of the gneissic monzogranites, whereas the porphyritic granodiorites and charnockites were generated at 437.0 ± 1.5 Ma and 435.2 ± 2.2 Ma, respectively. The gneissic monzogranites show geochemical features consistent with the high-K, calc-alkaline rock series and are strongly peraluminous. They have SiO2contents ranging from 67.75 to 69.65 wt. % and relatively low CaO contents (1.66–1.94 wt. %). Their REE patterns are fractionated with enriched LREEs and negative Eu anomalies. The samples also show enrichment in LILEs (e.g. Rb and K) and Pb, and depletion in Sr, Ba and HFSEs (e.g. Nb, Ta, Ti and P). They haveεNd(t) values of −8.2 to −7.7. Conversely, the porphyritic granodiorites and charnockites are characterized as medium-K, calc-alkaline rock series and weakly to strongly peraluminous. They exhibit pronounced depletions in HFSEs and positive Pb anomalies. Compared to the earlier gneissic monzogranites, these rocks have relatively lower SiO2(65.50–69.36 wt. %), but higher CaO contents (3.34–4.05 wt. %), and have slightly lowerεNd(t) values (−9.1 to −8.4). Petrography and geochemical compositions of the gneissic monzogranites indicate that they are S-type granite and likely formed by partial melting of Neoproterozoic to Early Palaeozoic immature metagreywackes; whereas The porphyritic granodiorites and charnockites are A-type granite and likely derived from low degrees of partial melting of the dry, granulitic residue depleted by prior extraction of granitic melt. The new data for the Caledonian granitoids in the Yunkai massif suggest that they were formed in a post-collisional tectonic setting. They represent the earliest post-collisional alkaline magmatism reported so far in the Yunkai massif, and thus indicate a tectonic regime switch, from compression to extension, as early as the Late Ordovician to Early Silurian (~450–435 Ma).

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Metasedimentary melting in the formation of charnockite: Petrological and zircon U-Pb-Hf-O isotope evidence from the Darongshan S-type granitic complex in southern China

Cited by 100 publications

References 77 publications

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

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

When Did the Paleotethys Ailaoshan Ocean Close: New Insights From Detrital Zircon U‐Pb age and Hf Isotopes

Petrogenesis of the Early Palaeozoic granitoids from the Yunkai massif, South China block: implications for a tectonic transition from compression to extension during the Caledonian orogenic event

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