Geochemistry of the paleoproterozonic Nanying granitic gneisses in the Fuping complex: implications for the tectonic evolution of the Central Zone, North China Craton

https://doi.org/10.1016/j.jseaes.2003.10.010Get rights and content

Abstract

The Nanying granitic gneisses represent a major ∼2.0 Ga magmatic event in the Fuping Complex of the Central Zone of the North China Craton. They occur in the Chengnanzhuang shear zone, which is chiefly developed along the contact between the Neoarchean Fuping tonalite-trondhjemite-granodiorite (TTG) gneisses and the Wanzi paragneisses. The Nanying granitic gneisses were derived from monzogranite and syenogranite, with minor amounts of quartz diorite and granodiorite, and belong to the metaluminous to peraluminous, high-potassium calc-alkaline series, correlations between major and trace elements, and similarities in chondrite-normalized rare-earth-element (REE) patterns, support field relationships (e.g. gradational contacts) indicating that the Nanying granitic gneisses originated from similar magmas. The granodioritic, monzogranitic and syenogranitic gneisses have similar ranges of initial 87Sr/86Sr values (0.7030–0.7093, 0.7021–0.7193 and 0.7049–0.7111, respectively), although these variations are partly attributable to local resetting of the isotopic system during late deformation/hydrothermal alteration. The whole-rock 208Pb/204Pb, 206Pb/204Pb and 207Pb/204Pb values of the Nanying granitic gneisses are 37.32–76.8, 15.24–23.82 and 14.92–17.92, respectively. These Sr–Pb isotope systematics, together with previously published Nd isotope compositions, suggest that the Nanying granitic gneisses were derived from partal melting of the ∼2.50 Ga Fuping TTG gneisses, with local assimilation involving the Wanzi paragneisses.

The Nanying granitic gneisses are geochemically similar to the CCA and CCL groups of granitoids, except for a few samples, which plot in the HLO group. The Nanying granitic gneisses exhibit depletion in Rb, Sr, Ba, Ti and U, and enrichment in Th, Nb, Zr, Hf and REE, similar to those of syn-shear, high-potassium calc-alkaline granitoids and late-shear alkaline granitoids; they therefore represent the product of a syn-collisional to post- collisional magmatic event. This collisional event, which is significantly older than the ∼1.84–1.80 Ga event that has been proposed for the juxtaposition of the Eastern and Western Archean continental blocks in the final stabilization of the North China Craton, supports a tectonic model involving multiple collisional events for the amalgamation of the internal lithotectonic domains within the Central Zone and the assembly of the North China Craton as a whole.

Introduction

The Precambrian Fuping Complex (Fig. 1) of medium- to high-grade metamorphic rocks is located in the Taihangshan (i.e. Tai-Hang mountains), northern China. This complex was originally considered to be one of the continental nuclei involved in the early development of the North China Craton (Bai, 1986, Bai, 1996, Tian, 1991, Tian et al., 1992, Wang et al., 1996). Subsequent Sr–Nd–Pb isotopic studies and recent U–Pb geochronological analyses (Liu et al., 1985, Zhang et al., 1991, Sun et al., 1992, Wang et al., 1996, Wang et al., 2000, Wilde et al., 1997, Guan et al., 2002, Liu et al., 2002b, Zhao et al., 2002, Wilde et al., 1998, Wilde et al., 2002) revealed that the Fuping Complex formed between ∼2.8 and ∼1.8 Ga, which is considerably younger than the Mesoarchean basement rocks in other parts of the North China Craton (e.g. 3.85–3.2 Ga eastern Hebei and Anshan–Benxi complexes—Jahn et al., 1987, Jahn et al., 1988, Kröner et al., 1988, Liu et al., 1992, Song et al., 1996).

On the basis of geochronological data, Zhao and co-workers (Zhao et al., 1999a, Zhao et al., 1999b, Zhao et al., 2002a, Zhao et al., 2000b, Zhao et al., 2001a, Zhao et al., 2001b, Wilde et al., 2002) suggested that the Fuping Complex and the adjacent Wutaishan and Hengshan complexes (Fig. 1) are part of a younger ‘Central Zone’ that separates the North China Craton into Eastern and Western Archean Continental blocks (Fig. 1). They proposed that the Central Zone represents a Neoarchan continental island arc system that records a collisional event at ∼1.80 Ga, which amalgamated the two Archean continental blocks. On the basis of lithological associations, metamorphic/deformation history and geochronological data, Liu et al., 2004, Liu et al., 2002b suggested that the Fuping and Hengshan complexes had a similar origin and evolution, whereas the Wutaishan Complex might have originated and evolved independently.

These different tectonic models are largely based on geochronological data and metamorphic history (Zhao et al., 1999a, Zhao et al., 1999b, Wilde et al., 2002) and discrimination between them requires a better understanding of the major rock types in all lithotectonic domains of the Central Zone. Granitoid intrusions are widely distributed in the Central Zone, and are the dominant lithology in both the Fuping and Hengshan complexes. These intrusions range in age from ∼2.55 to ∼1.80 Ga, spanning a large part of the history of the Central Zone. Geochemical studies of granitoids in the Central zone should provide independent constraints on its tectonic evolution, but few studies have been reported. For example, the Nanying gneisses in the Fuping Complex, originally considered to be metasedimentary rocks, have only recently been recognized to represent granitoids intruding a major ductile shear zone (i.e. the Chengnanzhuang shear zone; Tang and Liu, 1997, Liu and Liang, 1999, Liu et al., 2000, Liu et al., 2002b). SHRIMP zircon U–Pb analyses (Zhao et al., 2002, Guan et al., 2002) showed that the Nanying granitic gneisses were emplaced at ∼2.0 Ga, significantly younger than the formation of TTG gneisses at ∼2.50 Ga, but older than the collisional event at ∼1.80 Ga (Wilde et al., 2002, Zhao et al., 2002).

In this contribution, we document the field relationships of the Nanying granitic gneisses in the Fuping Complex, and present new geochemical and Sr–Pb isotope data for these rocks. The main purposes of this study are to use the geochemical data, together with previously published Nd isotope data (Zhang et al., 1991, Sun et al., 1992, Liu et al., 2002b), to deduce the petrogenesis of this granitoid magmatism in the Fuping Complex and to test evidence for a collisional event before the ∼1.80 Ga collision that juxtaposed the two Archean continental blocks (Wilde et al., 2002, Zhao et al., 2002).

Section snippets

Geology of the Fuping Complex

The Fuping Complex (Fig. 2) was originally considered to represent an Archean high-grade metasedimentary terrain (Wu et al., 1989, Wu and Zhong, 1998), in contrast to the dominantly metavolcanic terrains of the Eastern Continental Block. Most of the fine-grained granitic gneisses in the Fuping Complex, including biotite (±hornblende) plagioclase gneisses, granodioritic gneisses and syenogranitic gneisses, were interpreted to be paragneisses (Wu et al., 1989, Tan et al., 1989). Wang et al., 1991

Analytical procedures

A total of 16 representative samples of the Nanying granitic gneisses were analyzed for major and trace element geochemistry (Table 1, Table 2). Theses samples were collected from 10 localities (Fig. 2) showing relatively low intensities of deformation and were selected to avoid apparent hydrothermal alteration and weathering. Samples were first crushed to minus 60 mesh (250 μm) and then pulverized to minus mesh (75 μm). Major and trace element geochemical analyses were performed in the Key

Major and trace element compositions

The major and trace element compositions of the Nanying granitic gneisses are given in Table 2. These samples are metaluminous to slightly peraluminous, with the alumina-saturation index [A/CNK=molar AI2O3/(CaO+Na2O+K2O)] increasing from granodioritic gneisses (0.85–0.96), through monzogranitic gneisses (0.87–1.18), to granodioritic gneisses (0.94–1.27; Table 2). Representative bivariant plots show that most major elements (e.g. Al2O3 and CaO) correlate negatively with SiO2, except that K2O

Origin and source of the Nanying granitic gneisses

Despite early debated about sedimentary versus igneous origins for the Nanying granitic gneisses, it is now well established, on the basis of field relationships (Fig. 3a) and U–Pb geochronological data (Zhao et al., 2002, Guan et al., 2002), that these gneisses along the Chengnanzhuang shear zone (Fig. 2) represent a major magmatic episode in the Fuping Complex at about ∼2.0 Ga. Using the field relationship and the presence of metasedimentary xenoliths, Liu and Liang (1999) suggested that the

Acknowledgements

We wish to thank K.M. Ansdell, H.W.Day, and M.F. Zhou for critical comments and helpful suggestions, S.A. Wilde and G.C. Zhao for many stimulating discussions, Z.Y. Chu, L.B. Gu, G.S. Qiao, H.X. Shao, and R.H. Zhang for analytical assistance, and the National Nature Science Foundation of China (49832030) for financial support.

References (54)

  • K.Y. Wang et al.

    The Wutaishan orogenic belt within the Shanxi Province, northern China: a record of late Archean collisional tectonics

    Precambrian Research

    (1996)
  • M.J. Whitehouse

    Sm–Nd evidence for diachronous crust accretion in the Lewisian Complex of Northwest Scotland

    Tectonophysics

    (1989)
  • S.A. Wilde et al.

    Development of the North China Craton during the late Archean and its amalgamation along a major 1.8 Ga collision zone: including speculations on its position within a global Paleoproterozoic Supercontinent

    Gondwana Research

    (2002)
  • R.E. Zartman et al.

    Plumbotectonics-the model

    Tectonophysics

    (1981)
  • G.C. Zhao et al.

    Petrology and P–T history of the Wutai amphibolites: implications for tectonic evolution of the Wutai complex, China

    Precambrian Research

    (1999)
  • G.C. Zhao et al.

    Archean blocks and their boundaries in the North China Craton; lithological, geochemical, structural and P–T path constraints and tectonic evolution

    Precambrian Research

    (2001)
  • J. Bai

    The Precambrian crustal evolution of the Wutai area

  • J. Bai

    Archean—a period of the amalgamation of continental nuclei

  • B. Barbarin

    Granitoids; main petrogenetic classifications in relation to origin and tectonic setting

    Geological Journal

    (1990)
  • M.J. Bickle et al.

    The age and origin of younger granitic plutons of the Shaw Batholith in the Archean Pilbara Block, Western Australia

    Contributions to Mineralogy and Petrology

    (1989)
  • J.H. Chen et al.

    The least radiogenic Pb in iron meteorites

    (1983)
  • C. John

    The Geology and mapping of granite batholiths

    (2000)
  • A. Kröner et al.

    Ages and tectonic setting of Late Archean greenstone-gneiss terrain in Henan Province, China, as revealed by single-grain zircon dating

    Geology

    (1988)
  • D.Y. Liu et al.

    Remnants of 3800 Ma crust in the Chinese part of the Sino-Korean craton

    Geology

    (1992)
  • S.W. Liu

    Study on the P–T path of granulities in Fuping area, Hebei Province

    Geological Journal of Universities

    (1996)
  • S.W. Liu

    Study on fluid-rock equilibrium systems of Fuping gneiss complex, Taihang Mountains

    Science in China, Series D

    (1997)
  • S.W. Liu et al.

    An Archean continental block in the Taihangshan-Hengshan regions: Constraints from geochronology and geochemistry

    Progress in Natural Sciences

    (2004)
  • Cited by (199)

    • Mineralogy and geochemistry of the peridotites and high-Cr podiform chromitites from the Tangbale Ophiolite Complex, West Junggar (NW China): Implications for the origin and tectonic environment of formation

      2020, Ore Geology Reviews
      Citation Excerpt :

      The analytical precision for the major oxides (SiO2, Al2O3, MgO, CaO, TFe2O3) is better than 0.1%, and for major oxides (MnO, Na2O, K2O, P2O5, TiO2) better than 0.01%. The detailed analytical procedures have been documented in Liu et al. (2005), and the results are listed in Table.3. The sample powders were pre-treated at the Key Laboratory of Crustal Dynamics, Institute of Crustal Dynamics, China Earthquake Administration.

    View all citing articles on Scopus
    View full text