Elsevier

Journal of Asian Earth Sciences

Volume 74, 25 September 2013, Pages 244-264
Journal of Asian Earth Sciences

Zircon U–Pb dating, trace element and Sr–Nd–Hf isotope geochemistry of Paleozoic granites in the Miao’ershan–Yuechengling batholith, South China: Implication for petrogenesis and tectonic–magmatic evolution

https://doi.org/10.1016/j.jseaes.2012.12.026Get rights and content

Abstract

The Miao’ershan–Yuechengling batholith (MYB) is one of the largest granitic batholiths in South China. At least five individual phases have been identified for the Paleozoic granites in the MYB. SHRIMP and LA–ICP–MS zircon U–Pb dating results imply that these granites were emplaced at 435 ± 4 Ma, 427 ± 3 Ma, 417 ± 6 Ma, 404 ± 6 Ma and 382 ± 2 Ma, respectively. The ages gradually decreased from the southeast to the northwest, implying that the MYB was incrementally emplaced from the southeast to the northwest lasting from early Silurian to late Devonian. Most granites are metaluminous to weakly peraluminous, and contain low P2O5 contents (<0.15%). These granites show enrichment of Rb, Th, U and depletion of Ba, Sr, Eu, Ti. They show relatively high (87Sr/86Sr)i ratios (>0.715), low εNd(t) values (−8.9 to −6.7), and low zircon εHf(t) values (−9.5 to −4.0). These geochemical and isotopic characteristics indicate that these granites may have formed from partial melting of Paleoproterozoic basement rocks. Slight geochemical differences between different phases can be interpreted as resulting from partial melting of heterogeneous sources or different proportion mixing of meta-igneous and meta-sedimentary rocks. Zircon Hf isotope model ages vary from 1.77 to 1.93 Ga, with an average value of 1.84 ± 0.07 Ga. These data indicate that crust growth in this region took place mainly during the Paleoproterozoic (ca. 1.84 Ga), and the basement in the MYB should belong to the Cathaysia Block. The formation of the Paleozoic granites in the MYB was suggested to be related to the late orogenic magmatism of the Wuyi–Yunkai orogeny. Thus, the late orogenic magmatism in the northwestern part of the Wuyi–Yunkai orogeny must have lasted until ca. 381 Ma and took place also to the east of the Anhua–Luocheng Fault.

Highlights

► The Paleozoic Miao’ershan–Yuechengling granites consist of five phases. ► The ages of the five phases are 435 ± 4, 427 ± 3, 417 ± 6, 404 ± 6 and 382 ± 2 Ma, respectively. ► The granites were formed from partial melting of Paleoproterozoic basement rocks. ► Crustal growth in the studied region took place mainly at ca. 1.84 Ga.

Introduction

The South China Block (SCB) was formed by the amalgamation between the Yangtze Block in the northwest and the Cathaysia Block in the southeast during the Neoproterozoic time (e.g. Li et al., 2009). It underwent three major tectonic–magmatic events after its formation, and abundant igneous rocks, especially granites, formed in response to these events (e.g. Zhou et al., 2006, Li and Li, 2007, Wang et al., 2007a, Wang et al., 2011, Li et al., 2007a, Li et al., 2010, Zhang et al., 2012). The granites in the SCB are commonly regarded as one of the largest granite province worldwide (e.g. Wang and Zhou, 2005). The granites in the SCB fall in four main age groups, namely, the Neoproterozoic, the Early Paleozoic (traditionally referred to as “Caledonian”), the Triassic (“Indosinian”) and the Jurassic–Cretaceous (“Yanshanian”). Origin and evolution of this large granite province is a hot topic of international interest. Despite intensive scientific research, the geological signatures and geodynamic mechanism of these granites remain controversial, and a series of contrasting models have been suggested (e.g. Hsü et al., 1988, Gilder et al., 1991, Jahn et al., 1990, Charvet et al., 1994, Zhou and Li, 2000, Zhou et al., 2006, Li and Li, 2007, Li et al., 2010, Wang et al., 2007a, Wang et al., 2012, Jiang et al., 2005, Jiang et al., 2009, Zhang et al., 2012, Zhao et al., 2012).

The Paleozoic granites are important parts and widespread in the eastern SCB (Fig. 1). They occur as laccoliths and batholiths to the east of the Anhua–Luocheng fault, and are usually of large volume with a total exposure area of over 20,000 km2. Studies on the Paleozoic granites are relatively fewer due to less economic mineralization than the Mesozoic granites in the SCB. Reliable ages and geochemistry for these granites have only become available in recent years (e.g. Wan et al., 2007, Wan et al., 2010, Wang et al., 2007b, Wang et al., 2011, Shen et al., 2008, Xu et al., 2009, Li et al., 2010, Zhang et al., 2009, Zhang et al., 2010, Zhang et al., 2012). Geochronological studies have defined an age-span of ca. 400–462 Ma for these granites (e.g. Li et al., 2010, Wang et al., 2011, Zhang et al., 2012). These granites are suggested to be petrogenetically related to the Kwangsian orogenic event (Wang et al., 2011, Zhang et al., 2012) or the Wuyi–Yunkai orogeny recently renamed by Li et al. (2010). The orogenic event was likely a major intra-plate orogenic event (Shu et al., 2008, Li et al., 2010). However, details about the orogeny still remain poorly defined, especially for the orogenic processes and affected temporal-spatial extents. Systematical geochronological and geochemical studies for all the Paleozoic metamorphic rocks and igneous rocks in the SCB are needed for a better understanding of the SCB tectonic evolution.

Syn-orogenic to late orogenic melting in the southeastern Wuyi–Yunkai orogeny has been constrained to occurring in the interval of ca. 450–420 Ma (Li et al., 2010). The Miao’ershan–Yuechengling batholith (simplified as MYB) lies in the northwestern part of the Wuyi–Yunkai orogeny (Fig. 1). The MYB is one of the largest granitic batholiths in South China (Fig. 1), with a total outcrop area of ca. 3400 km2. Early in 1950s, the MYB was suggested to be composed of the Devonian granites based on field observation that the granites intruded the Silurian strata but overlain by middle Devonian sandstone (Zhao and Zhang, 1958). The pioneering works gave variable ages of 364–422 Ma by whole-rock Rb–Sr dating method for these Devonian granites (Xu et al., 1994, Li and Zhou, 2002). However, due to the lack of systematical studies, the geochronology, petrogenesis and tectonic nature to these granites remain unclear. In this paper, we present systematic SHRIMP and LA–ICP–MS zircon U–Pb ages, geochemistry and Sr–Nd–Hf isotopic compositions for these granites in the MYB. The results are used to constraint their ages, petrogenesis, magma sources and tectonic environments. This study will also provide constraints on the temporal and spatial extents of orogenic magmatism in the northwestern part of the Wuyi–Yunkai orogeny.

Section snippets

Geological setting and petrography

The Yangtze and Cathaysia Blocks have distinctive crustal ages and tectonic evolution histories, and their amalgamation during the Neoproterozoic Jinningian orogeny led to the formation of the SCB. The Yangtze Block was mainly built upon a stable Archean–Proterozoic basement, consisting of Archean rocks up to 3.3 Ga (Jiao et al., 2009, Gao et al., 2011), with an average age of 2.7–2.8 Ga (Gao et al., 1991, Qiu et al., 2000). The Cathaysia Block appears to be much younger and consists

Analytical methods

Granite samples used in this study were collected from all the five phases. Zircon grains were extracted from granite samples by conventional heavy liquids and magnetic techniques, and then purified by hand picking under binocular microscope. Then zircon grains were mounted in epoxy resin and polished to approximately half their thickness. Examination of internal structures was performed using cathodoluminescence (CL) imaging technique with an Electron Microprobe at the Scanning Electron

Phase 1 (sample YCL-14A, N25o49′10.2″, E110o40′55.7″)

Zircon crystals from Sample YCL-14A show euhedral, elongated shape, with lengths ranging from 150 to 250 μm and widths ranging from 50 to 100 μm. Most length/width ratios vary from 2:1 to 3:1. In CL images, most zircon crystals display obviously euhedral concentric zoning (Fig. 4), implying their magmatic origin (e.g. Hoskin and Schaltegger, 2003, Wu and Zheng, 2004). A total of twelve spot analyses were carried out on ten zircon grains and the results are listed in Table 1. U contents vary from

Geochronological framework of Paleozoic granites in the MYB

Zhang et al. (2012) reported LA–ICP–MS zircon U–Pb ages of two samples from the Miao’ershan pluton. Sample 06HG84 from the northern part of the Miao’ershan pluton gave a weighted mean age of 400 ± 4 Ma. The sample location is near to the location of our sample MES-02A (404 ± 6 Ma in this study). Sample 06HG95 from the southern part of the pluton gave a weighted mean age of 415 ± 2 Ma. This age is similar to that of the Phase 3 (417 ± 6 Ma) in this study.

The new SHRIMP and LA–ICP–MS zircon U–Pb ages, in

Conclusions

  • (1)

    The Paleozoic granites in the Miao’ershan–Yuechengling batholith (MYB) in South China are at least consist of five phases, with the emplacement ages of 435 ± 4 Ma, 427 ± 3 Ma, 417 ± 6 Ma, 404 ± 6 Ma and 382 ± 2 Ma, respectively. The MYB was incrementally emplaced from the southeast to the northwest lasting from early Silurian to late Devonian.

  • (2)

    Most of these granites are metaluminous to weakly peraluminous, and contain low P2O5 contents (<0.15%). They show relatively high (87Sr/86Sr)i ratios (>0.715), low εNd(t

Acknowledgements

We are grateful to Prof. Dun-Yi Liu and Dr. Zhi-Qin Yang from Beijing SHRIMP Center for helping with zircon U–Pb analyses, and to Prof. Fu-Yuan Wu and Dr. Lie-Wen Xie from Institute of Geology and Geophysics, Chinese Academy of Sciences for helping with Hf isotope analyses. This work was supported by funding from a Major State Basic Research Program (973 Project, 2012CB416706), a project from the China National Science Foundation (No. 41173001), a key project from the Chinese Ministry of

References (93)

  • S.A. Gilder et al.

    Timing and spatial distribution of rifting in China

    Tectonophysics

    (1991)
  • W.L. Griffin et al.

    Zircon chemistry and magma mixing, SE China: in-situ analysis of Hf isotopes, Tonglu and Pingtan igneous complexes

    Lithos

    (2002)
  • S.B. Jacobsen et al.

    Sm–Nd isotopic evolution of chondrites

    Earth and Planetary Science Letter

    (1980)
  • B.M. Jahn et al.

    Evolution of the Kaapvaal Craton as viewed from geochemical and Sm–Nd isotopic analyses of intracratonic pelites

    Geochimica et Cosmochimica Acta

    (1995)
  • Y.-H. Jiang et al.

    Middle to late Jurassic felsic and mafic magmatism in southern Hunan province, southeast China: implications for a continental arc to rifting

    Lithos

    (2009)
  • X.H. Li et al.

    U–Pb zircon, geochemical and Sr–Nd–Hf isotopic constraints on age and origin of Jurassic I- and A-type granites from central Guangdong, SE China: a major igneous event in response to foundering of a subducted flat-slab?

    Lithos

    (2007)
  • X.H. Li et al.

    Amalgamation between the Yangtze and Cathaysia Blocks in South China: constraints from SHRIMP U–Pb zircon ages, geochemistry and Nd–Hf isotopes of the Shuangxiwu volcanic rocks

    Precambrian Research

    (2009)
  • X.H. Li et al.

    The Early Permian active continental margin and crustal growth of the Cathaysia Block: in situ U–Pb, Lu–Hf and O isotope analyses of detrital zircons

    Chemical Geology

    (2012)
  • G.W. Lugmair et al.

    Lunar initial 143Nd/144Nd: differential evolution of the lunar crust and mantle

    Earth and Planetary Science Letter

    (1978)
  • S.B. Peng et al.

    Petrochemistry, chronology, and tectonic setting of strong peraluminous anatectic granitoids in Yunkai Orogennic Belt, western Guangdong Province, China

    Journal of China University of Geosciences

    (2006)
  • L.S. Shu et al.

    Geochronological and geochemical features of the Cathaysia block (South China): new evidence for the Neoproterozoic breakup of Rodinia

    Precambrian Research

    (2011)
  • P.J. Sylvester

    Post-collisional strongly peraluminous granites

    Lithos

    (1998)
  • T. Tanaka et al.

    JNdi-1: a neodymium isotopic reference in consistency with LaJolla neodymium

    Chemical Geology

    (2000)
  • B.A. Walker et al.

    Geology and geochronology of the Spirit Mountain batholith, southern Nevada: implications for time-scales and physical processes of batholith construction

    Journal of Volcanology and Geothermal Research

    (2007)
  • Y. Wan et al.

    SHRIMP U–Pb zircon geochronology and geochemistry of metavolcanic and metasedimentary rocks in northwestern Fujian, Cathaysia block, China: tectonic implications and the need to redefine lithostratigraphic units

    Gondwana Research

    (2007)
  • Y. Wan et al.

    Evolution of the Yunkai Terrane, South China: evidence from SHRIMP zircon U–Pb dating, geochemistry and Nd isotope

    Journal of Asian Earth Sciences

    (2010)
  • J. Wang et al.

    History of Neoproterozoic rift basins in South China: implications for Rodinia break-up

    Precambrian Research

    (2003)
  • Y.J. Wang et al.

    Geochronological, geochemical and geothermal constraints on petrogenesis of the Indosinian peraluminous granites in the South China Block: a case study in the Hunan Province

    Lithos

    (2007)
  • Y.J. Wang et al.

    Zircon U–Pb geochronology of gneissic rocks in the Yunkai massif and its implications on the Caledonian event in the South China Block

    Gondwana Research

    (2007)
  • Y.J. Wang et al.

    Sr–Nd–Pb isotopic constraints on multiple mantle domains for Mesozoic mafic rocks beneath the South China Block hinterland

    Lithos

    (2008)
  • Y.J. Wang et al.

    Kwangsian crustal anatexis within the eastern South China Block: geochemical, zircon U–Pb geochronological and Hf isotopic fingerprints from the gneissoid granites of Wugong and Wuyi–Yunkai Domains

    Lithos

    (2011)
  • E.B. Watson et al.

    Zircon saturation revisited: temperature and composition effects in a variety of crustal magma types

    Earth and Planetary Science Letters

    (1983)
  • F.Y. Wu et al.

    Highly fractionated I-type granites in NE China (II): isotopic geochemistry and implications for crustal growth in the Phanerozoic

    Lithos

    (2003)
  • F.Y. Wu et al.

    Hf isotopic compositions of the standard zircons and baddeleyites used in U–Pb geochronology

    Chemical Geology

    (2006)
  • X. Xu et al.

    The crust of Cathaysia: age, assembly and reworking of two terranes

    Precambrian Research

    (2007)
  • J.H. Yu et al.

    A Paleoproterozoic orogeny recorded in a long-lived cratonic remnant (Wuyishan terrane), eastern Cathaysia Block, China

    Precambrian Research

    (2009)
  • J.H. Yu et al.

    Components and episodic growth of Precambrian crust in the Cathaysia Block, South China: evidence from U–Pb ages and Hf isotopes of zircons in Neoproterozoic sediments

    Precambrian Research

    (2010)
  • K.D. Zhao et al.

    Uranium-bearing and barren granites from the Taoshan Complex, Jiangxi Province, South China: geochemical and petrogenetic discrimination and exploration significance

    Journal of Geochemical Exploration

    (2011)
  • K.D. Zhao et al.

    Mineral chemistry, trace elements and Sr–Nd–Hf isotope geochemistry and petrogenesis of Cailing and Furong granites and mafic enclaves from the Qitianling batholith in the Shi-Hang zone, South China

    Gondwana Research

    (2012)
  • X.M. Zhou et al.

    Origin of Late Mesozoic igneous rocks in Southeastern China: implications for lithosphere subduction and underplating of mafic magmas

    Tectonophysics

    (2000)
  • W.L. Boynton

    Geochemistry of the rare earth elements: meteorite studies. Rare earth element geochemistry

    (1984)
  • B.W. Chappell et al.

    Two constrasting granite types

    Pacific Geology

    (1974)
  • B. Chen et al.

    The petrology and petrogenesis of Yunkai chemockite and its granulite inclusion, west Guangdong, South China

    Acta Petrologica Sinica

    (1994)
  • X. Chen et al.

    Ordovician graptolite-bearing strata in southern Jiangxi with a special reference to the Kwangsian Orogeny

    Science in China (Earth Sciences)

    (2010)
  • S.B. Cheng et al.

    Zircon SHRIMP U–Pb dating and geochemical characteristics of Daning batholith in northeast Guangxi

    Geology in China

    (2009)
  • J.D. Clemens et al.

    What controls chemical variation in granitic magmas?

    Lithos

    (2012)
  • Cited by (87)

    View all citing articles on Scopus
    View full text