Gondwana Research 28 (2015) 82–105 Contents lists available at ScienceDirect Gondwana Research journal homepage: www.elsevier.com/locate/gr Paleoproterozoic arc magmatism in the North China Craton: No Siderian global plate tectonic shutdown Qiong-Yan Yang a,M.Santosha,b,⁎ a School of Earth Sciences and Resources, China University of Geosciences Beijing, 29 Xueyuan Road, Beijing 100083, China b Faculty of Science, Kochi University, Akebono-cho 2-51, Kochi 780-8520, Japan article info abstract Article history: Arc magmatism in convergent plate margins has been a major contributor to continental growth. Following arc– Received 20 June 2014 arc and arc–continent collisions in the Archean leading to the amalgamation of micro-blocks, the North China Received in revised form 3 August 2014 Craton (NCC) witnessed major pulses of continental arc magmatism during the Paleoproterozoic. In this study, Accepted 3 August 2014 we present geochemistry, zircon U–Pb geochronology and Lu–Hf isotope data from a suite of magmatic rocks Available online 23 August 2014 sampled from the region of confluence of two major Paleoproterozoic suture zones in the NCC — the Inner – Handling Editor: S. Kwon Mongolia Suture Zone (IMSZ) and the Trans-North China Orogen (TNCO). Our zircon U Pb geochronological data indicate new zircon growth during multiple tectonothermal events as displayed in the 207Pb/206Pb weighted Keywords: mean ages of 2410 ± 41 Ma for metagranite, 2480 ± 12 Ma, 2125 ± 18 Ma, 1946 ± 8 Ma, 1900 ± 15 Ma and Zircon U–Pb geochronology 1879 ± 12 Ma from metagabbros, 2446 ± 11 Ma from charnockite, and 1904 ± 6 Ma and 1901 ± 9 Ma from Geochemistry metatuffs. The 207Pb/206Pb upper intercept age of zircons in the khondalite shows 2102 ± 76 Ma which is iden- Continental arc magmatism tical to the age obtained from the magmatic zircons in one of the metagabbros. The khondalites also carry a group Crustal growth and recycling of concordant metamorphic zircons with 207Pb/206Pb mean age of 1881 ± 20 Ma. Metamorphic zircons in the North China Craton gabbros and charnockites also yield similar ages of 1890 ± 14 Ma and 1852 ± 19 Ma respectively. The age data suggest prolonged arc magmatism in a convergent margin setting during ca. 2.48 to 1.9 Ga, followed by metamorphism at ca. 1.89–1.85 Ga associated with the final collision. Lu–Hf analyses reveal that the dominant populations of zircons from all the rock types are characterized by positive εHf values (−1.9 to 6.8; mean 1.8). C The εHf and TDM data suggest that the magmas were mostly derived from Neoarchean and Paleoproterozoic ju- venile components. The salient geochemical features of these rocks attest to magma generation from heteroge- neous sources involving subduction-derived arc components with minor input from continental crust. The results presented in this study, together with those from previous investigations in different domains of the IMSZ and TNCO suggest major Paleoproterozoic arc magmatic events in the NCC lasting for nearly 600 million years associated with the final assembly of the crustal blocks into a coherent craton. Construction of the final cratonic architecture of the NCC thus witnessed not only the arc–continent amalgamations at 2.7– 2.5 Ga, but also major crust building events in the Paleoproterozoic through melts generated from juvenile and recycled components in continental magmatic arc systems along an active convergent margin, followed by in- tense deformation and metamorphism during the final collision at 1.85–1.80 Ga. The prominent Paleoproterozoic magmatic records in the NCC do not support the proposal of global plate tectonic shutdown in the Siderian and confirm vigorous convergent margin magmatism and crust building processes throughout the Paleoproterozoic. © 2014 International Association for Gondwana Research. Published by Elsevier B.V. All rights reserved. 1. Introduction active continental margin setting associated with ocean–continent sub- duction (e.g., Manikyamba and Kerrich, 2012; Straub and Zellmer, The subduction of oceanic lithosphere in convergent margins 2012; Santosh et al., 2013a). Condie and Kröner (2013) noted that gives rise to arc magmatism (Stern, 2002), with a pronounced composi- with few exceptions, post-Archean accretionary orogens comprise tional link between the trench input and arc output (Straub and b10% of accreted oceanic arcs, whereas continental arcs compose Zellmer, 2012). Arc magmatism in space and time under different 40–80% of these orogens. From Nd and Hf isotopic data, they showed geodynamic settings ranges from intra-oceanic arcs associated with that accretionary orogens on the globe include 40–65% juvenile crustal ocean–ocean convergence, plume–arc interaction, arc–backarc, and components, with more than 50% of these produced in continental arcs. Due to higher degrees of partial melting in the mantle, oceanic arcs in the Archean were thicker as compared to their Proterozoic equivalents. ⁎ Corresponding author at: School of Earth Sciences and Resources, China University of Geosciences Beijing, 29 Xueyuan Road, Beijing 100083, China. Condie and Kröner (2013) suggested that the vigorous onset of plate E-mail address: [email protected] (M. Santosh). tectonics in the late Archean with rapid production of continental http://dx.doi.org/10.1016/j.gr.2014.08.005 1342-937X/© 2014 International Association for Gondwana Research. Published by Elsevier B.V. All rights reserved. Q.-Y. Yang, M. Santosh / Gondwana Research 28 (2015) 82–105 83 crust witnessed a major transition in the primary site of production of (TNCO), respectively. Post-collisional magmatism related to slab continental crust from accreted oceanic arcs and oceanic plateaus in break-off has also been recorded from a number of localities along the Archean to dominantly continental arcs thereafter. these suture zones (e.g., Yang et al., 2014a). Convergent plate margins are potential regions of crustal growth In this study, we investigate the geochemistry and zircon U–Pb geo- where magmas derived by melting of mantle wedge fluxed with slab- chronology and Lu–Hf isotopes in a suite of plutonic, volcanic and dehydrated fluids and subducted slab result in vertical growth and metasedimentary rocks from the zone linking the two major thickening of arc crust, whereas the accretion of oceanic and trench ma- Paleoproterozoic subduction systems in the NCC — the IMSZ and the terials onto the active continental margins causes lateral growth TNCO. We report a diverse assemblage of granitoids, charnockites, (Santosh, 2013). Subduction-derived mafic magmas and crust-derived gabbros, felsic volcanic tuffs and khondalites from this region which felsic magmas in arc settings thus contribute to vertical growth of the shows a common link to active convergent margin tectonics and crust (e.g., Foley et al., 2002; Rudnick and Gao, 2003). Tholeiitic to magmatism within continental arc settings. Our results compare with calc-alkaline mafic, intermediate and felsic magmas are generated in the isotopic data of Paleoproterozoic arc magmatic suites reported active margins through a combination of processes including influx of from elsewhere in these zones suggesting an important phase of conti- slab-dehydrated fluids and melts into mantle wedge, wedge melting, nent building in the NCC during the Paleoproterozoic. assimilation of crustal materials by arc magma and magma mixing (Gao et al., 2012; Santosh et al., 2013a; Samuel et al., 2014; 2. Geological setting Manikyamba et al., in press). In a recent model, Castro et al. (2013) pro- posed relamination from below the lithosphere as an alternate mecha- 2.1. North China Craton nism for new crust generation in magmatic arcs of active continental margins and mature intraoceanic arcs, and explained the dominantly The North China Craton (NCC) (Fig. 1) is a collage of several andesitic composition of the continental crust. micro-continents that preserve the history of Neoarchean crust for- The North China Craton (NCC) (Fig. 1) preserves important rock re- mation, which were subsequently incorporated into two major cords of early Precambrian crustal growth and microcontinent amal- crustal blocks by the late Neoarchean, the Eastern and Western gamation. The Neoarchean greenstone belts that surround the micro- Blocks (e.g., Zhai and Santosh, 2011; Geng et al., 2012; Zhao and blocks in the NCC are considered to represent the vestiges of older Zhai, 2013). The final collision and cratonization of these crustal arc–continent collision (Zhai and Santosh, 2011). Subsequently, the blocks occurred during the late Paleoproterozoic at around 1.85– NCC witnessed a prolonged subduction–accretion history from early 1.80 Ga (e.g., Wilde et al., 2002; Kusky and Li, 2003; Zhao et al., to the late Paleoproterozoic associated with the amalgamation of 2005; Kusky et al., 2007; Santosh et al., 2007; Zhao et al., 2008; major crustal blocks and the final cratonization (Zhai and Santosh, Santosh, 2010; Zhai and Santosh, 2011; Peng et al., 2011; Liu et al., 2011; Santosh et al., 2012, 2013b; Zhao and Zhai, 2013). Two major con- 2012; Santosh et al., 2013b; Zhao and Zhai, 2013). The NCC is bor- vergent margins, one running E–W between the Yinshan and Ordos dered on the south by the Qinling–Dabie Shan orogen, to the north Blocks and the other trending N–S between the Western and Eastern by the Central Asian Orogenic Belt, and to the east by the Su-Lu belt Blocks, possibly in a double-sided subduction realm (Santosh, 2010) (e.g., Zhai and Santosh, 2011; Zhao and Zhai, 2013). generated voluminous arc magmas of diverse composition during the The Western Block formed by amalgamation of the Ordos Block in Paleoproterozoic (e.g., Zhao et al., 2008; Dan et al., 2012; Liu et al., the south and the Yinshan Block in the north along the east–west- 2012; Santosh et al., 2012) which were subsequently incorporated trending IMSZ (incorporating the Khondalite Belt) at 1.90–1.95 Ga. within the two major collisional sutures, termed as the Inner This was followed by the final collision between the Western and East- Mongolia Suture Zone (IMSZ) and the Trans-North China Orogen ern Blocks along the TNCO at ca.