Early Cretaceous subduction-modified lithosphere beneath the eastern Qinling Orogen revealed from the Daying volcanic sequence in central China

Feifei Zhang, Yuejun Wang, Yunpeng Dong, Peter A. Cawood, Weiming Fan

Research output: Contribution to journalArticleResearchpeer-review

Abstract

New geochronological, geochemical and Sr-Nd-Hf isotopic data for the early Cretaceous Daying volcanic sequence, eastern Qinling Orogen, provides a probe into the nature of, and tectonic process operating in, the underlying Mesozoic mantle. The volcanic rocks in the sequence are composed of basaltic trachyandesite, pyroxene-andesite, trachyandesite and trachyte. They yield zircon U-Pb and whole-rock 40 Ar/ 39 Ar plateau ages of 134–124 Ma, roughly synchronous with the Cretaceous igneous rocks throughout the eastern Qinling and Dabie orogens. Clinopyroxene and plagioclase phenocrysts of the volcanic rocks exhibit simple normal zonation with higher mg-number and An content in the core relative to the rim. The amphibole is characterized by tschermakite and tschermakitic hornblende with mg-number of 50–67. The Daying volcanic rocks have variable SiO 2 (54.27–63.44 wt%), Al 2 O 3 (15.39–20.34 wt%), FeO t (5.23–9.94 wt%), and MgO (1.05–4.03 wt%) contents with low mg-number (26–49). They exhibit arc-like REE- and PM-normalized patterns with significant negative Nb-Ta anomalies, and highly- enriched Sr-Nd isotopic composition with ( 87 Sr/ 86 Sr) i ratios of 0.7066–0.7078 and ε Nd (t) values of −15.5 ∼ −11.0. Their zircons exhibit strongly negative ε Hf (t) values ranging from −27.3 to −17.2 and two-staged model ages from 2.90 Ga to 2.28 Ga. Such geochemical signatures suggest that the Daying volcanic rocks were derived from a hybridized source of the North China Craton enriched mantle with the input of some Yangtze crustal materials created by Triassic deep-subduction digestion. They also share similar eruption time, as well as elemental and Sr-Nd-Hf isotopic compositions, with those in the southern margin of the North China Craton, suggesting a northward subduction of the Yangtze block. It is proposed that the volcanic rocks are petrogenetically related to an early Cretaceous extensional event along the Qinling- Dabie Orogenic belt in response to unrooting of the thickened lithosphere.

Original languageEnglish
Pages (from-to)209-228
Number of pages20
JournalJournal of Asian Earth Sciences
Volume176
DOIs
Publication statusPublished - 1 Jun 2019

Keywords

  • Early Cretaceous volcanics
  • Eastern Qinling Orogen
  • Geochronology
  • Sr–Nd–Hf isotopic compositions
  • Subduction-modified mantle source

Cite this

@article{526327a55abb4013b9ecdf03013a0893,
title = "Early Cretaceous subduction-modified lithosphere beneath the eastern Qinling Orogen revealed from the Daying volcanic sequence in central China",
abstract = "New geochronological, geochemical and Sr-Nd-Hf isotopic data for the early Cretaceous Daying volcanic sequence, eastern Qinling Orogen, provides a probe into the nature of, and tectonic process operating in, the underlying Mesozoic mantle. The volcanic rocks in the sequence are composed of basaltic trachyandesite, pyroxene-andesite, trachyandesite and trachyte. They yield zircon U-Pb and whole-rock 40 Ar/ 39 Ar plateau ages of 134–124 Ma, roughly synchronous with the Cretaceous igneous rocks throughout the eastern Qinling and Dabie orogens. Clinopyroxene and plagioclase phenocrysts of the volcanic rocks exhibit simple normal zonation with higher mg-number and An content in the core relative to the rim. The amphibole is characterized by tschermakite and tschermakitic hornblende with mg-number of 50–67. The Daying volcanic rocks have variable SiO 2 (54.27–63.44 wt{\%}), Al 2 O 3 (15.39–20.34 wt{\%}), FeO t (5.23–9.94 wt{\%}), and MgO (1.05–4.03 wt{\%}) contents with low mg-number (26–49). They exhibit arc-like REE- and PM-normalized patterns with significant negative Nb-Ta anomalies, and highly- enriched Sr-Nd isotopic composition with ( 87 Sr/ 86 Sr) i ratios of 0.7066–0.7078 and ε Nd (t) values of −15.5 ∼ −11.0. Their zircons exhibit strongly negative ε Hf (t) values ranging from −27.3 to −17.2 and two-staged model ages from 2.90 Ga to 2.28 Ga. Such geochemical signatures suggest that the Daying volcanic rocks were derived from a hybridized source of the North China Craton enriched mantle with the input of some Yangtze crustal materials created by Triassic deep-subduction digestion. They also share similar eruption time, as well as elemental and Sr-Nd-Hf isotopic compositions, with those in the southern margin of the North China Craton, suggesting a northward subduction of the Yangtze block. It is proposed that the volcanic rocks are petrogenetically related to an early Cretaceous extensional event along the Qinling- Dabie Orogenic belt in response to unrooting of the thickened lithosphere.",
keywords = "Early Cretaceous volcanics, Eastern Qinling Orogen, Geochronology, Sr–Nd–Hf isotopic compositions, Subduction-modified mantle source",
author = "Feifei Zhang and Yuejun Wang and Yunpeng Dong and Cawood, {Peter A.} and Weiming Fan",
year = "2019",
month = "6",
day = "1",
doi = "10.1016/j.jseaes.2019.02.013",
language = "English",
volume = "176",
pages = "209--228",
journal = "Journal of Asian Earth Sciences",
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Early Cretaceous subduction-modified lithosphere beneath the eastern Qinling Orogen revealed from the Daying volcanic sequence in central China. / Zhang, Feifei; Wang, Yuejun; Dong, Yunpeng; Cawood, Peter A.; Fan, Weiming.

In: Journal of Asian Earth Sciences, Vol. 176, 01.06.2019, p. 209-228.

Research output: Contribution to journalArticleResearchpeer-review

TY - JOUR

T1 - Early Cretaceous subduction-modified lithosphere beneath the eastern Qinling Orogen revealed from the Daying volcanic sequence in central China

AU - Zhang, Feifei

AU - Wang, Yuejun

AU - Dong, Yunpeng

AU - Cawood, Peter A.

AU - Fan, Weiming

PY - 2019/6/1

Y1 - 2019/6/1

N2 - New geochronological, geochemical and Sr-Nd-Hf isotopic data for the early Cretaceous Daying volcanic sequence, eastern Qinling Orogen, provides a probe into the nature of, and tectonic process operating in, the underlying Mesozoic mantle. The volcanic rocks in the sequence are composed of basaltic trachyandesite, pyroxene-andesite, trachyandesite and trachyte. They yield zircon U-Pb and whole-rock 40 Ar/ 39 Ar plateau ages of 134–124 Ma, roughly synchronous with the Cretaceous igneous rocks throughout the eastern Qinling and Dabie orogens. Clinopyroxene and plagioclase phenocrysts of the volcanic rocks exhibit simple normal zonation with higher mg-number and An content in the core relative to the rim. The amphibole is characterized by tschermakite and tschermakitic hornblende with mg-number of 50–67. The Daying volcanic rocks have variable SiO 2 (54.27–63.44 wt%), Al 2 O 3 (15.39–20.34 wt%), FeO t (5.23–9.94 wt%), and MgO (1.05–4.03 wt%) contents with low mg-number (26–49). They exhibit arc-like REE- and PM-normalized patterns with significant negative Nb-Ta anomalies, and highly- enriched Sr-Nd isotopic composition with ( 87 Sr/ 86 Sr) i ratios of 0.7066–0.7078 and ε Nd (t) values of −15.5 ∼ −11.0. Their zircons exhibit strongly negative ε Hf (t) values ranging from −27.3 to −17.2 and two-staged model ages from 2.90 Ga to 2.28 Ga. Such geochemical signatures suggest that the Daying volcanic rocks were derived from a hybridized source of the North China Craton enriched mantle with the input of some Yangtze crustal materials created by Triassic deep-subduction digestion. They also share similar eruption time, as well as elemental and Sr-Nd-Hf isotopic compositions, with those in the southern margin of the North China Craton, suggesting a northward subduction of the Yangtze block. It is proposed that the volcanic rocks are petrogenetically related to an early Cretaceous extensional event along the Qinling- Dabie Orogenic belt in response to unrooting of the thickened lithosphere.

AB - New geochronological, geochemical and Sr-Nd-Hf isotopic data for the early Cretaceous Daying volcanic sequence, eastern Qinling Orogen, provides a probe into the nature of, and tectonic process operating in, the underlying Mesozoic mantle. The volcanic rocks in the sequence are composed of basaltic trachyandesite, pyroxene-andesite, trachyandesite and trachyte. They yield zircon U-Pb and whole-rock 40 Ar/ 39 Ar plateau ages of 134–124 Ma, roughly synchronous with the Cretaceous igneous rocks throughout the eastern Qinling and Dabie orogens. Clinopyroxene and plagioclase phenocrysts of the volcanic rocks exhibit simple normal zonation with higher mg-number and An content in the core relative to the rim. The amphibole is characterized by tschermakite and tschermakitic hornblende with mg-number of 50–67. The Daying volcanic rocks have variable SiO 2 (54.27–63.44 wt%), Al 2 O 3 (15.39–20.34 wt%), FeO t (5.23–9.94 wt%), and MgO (1.05–4.03 wt%) contents with low mg-number (26–49). They exhibit arc-like REE- and PM-normalized patterns with significant negative Nb-Ta anomalies, and highly- enriched Sr-Nd isotopic composition with ( 87 Sr/ 86 Sr) i ratios of 0.7066–0.7078 and ε Nd (t) values of −15.5 ∼ −11.0. Their zircons exhibit strongly negative ε Hf (t) values ranging from −27.3 to −17.2 and two-staged model ages from 2.90 Ga to 2.28 Ga. Such geochemical signatures suggest that the Daying volcanic rocks were derived from a hybridized source of the North China Craton enriched mantle with the input of some Yangtze crustal materials created by Triassic deep-subduction digestion. They also share similar eruption time, as well as elemental and Sr-Nd-Hf isotopic compositions, with those in the southern margin of the North China Craton, suggesting a northward subduction of the Yangtze block. It is proposed that the volcanic rocks are petrogenetically related to an early Cretaceous extensional event along the Qinling- Dabie Orogenic belt in response to unrooting of the thickened lithosphere.

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KW - Eastern Qinling Orogen

KW - Geochronology

KW - Sr–Nd–Hf isotopic compositions

KW - Subduction-modified mantle source

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U2 - 10.1016/j.jseaes.2019.02.013

DO - 10.1016/j.jseaes.2019.02.013

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