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1 Lithos (2012) Contents lists available at SciVerse ScienceDirect Lithos journal homepage: Reactivation of the Archean lower crust: Implications for zircon geochronology, elemental and Sr Nd Hf isotopic geochemistry of late Mesozoic granitoids from northwestern Jiaodong Terrane, the North China Craton Kui-Feng Yang a, Hong-Rui Fan a,, M. Santosh b,c, Fang-Fang Hu a, Simon A. Wilde d, Ting-Guang Lan a, Li-Na Lu a, Yong-Sheng Liu e a Key Laboratory of Mineral Resources, Institute of Geology and Geophysics, Chinese Academy of Sciences, Beijing , China b Division of Interdisciplinary Science, Faculty of Science, Kochi University, Kochi , Japan c Geoscience Frontiers, China University of Geosciences, Xueyuan Road, Haidian District, Beijing , China d Department of Applied Geology, Curtin University of Technology, GPO Box U1987, Perth 6845, Australia e State Key Laboratory of Geological Processes and Mineral Resources, China University of Geosciences, Wuhan , China article info abstract Article history: Received 12 December 2011 Accepted 22 April 2012 Available online 12 May 2012 Keywords: Geochemistry Zircon geochronology Late Mesozoic granitoids Northwestern Jiaodong Terrane North China Craton The late Mesozoic granitoids widely distributed in the northwestern Jiaodong Terrane are important markers of cratonic destruction and lithospheric thinning of the eastern North China Craton (NCC). Here we investigate the Late Jurassic Linglong and Luanjiahe granites and report zircon U Pb emplacement ages of Ma. These rocks also contain abundant late Archean, Paleoproterozoic, Neoproterozoic, early Paleozoic and Triassic inherited zircons, suggesting the involvement of continental crustal materials from both the NCC and Yangtze Craton in magma tectonics. The rocks investigated in this study show high Na 2 O+K 2 O and low MgO and are peraluminous, with enrichment in LREEs and LILEs (Rb, Ba, U, and Sr) and depletion in HFSEs (Nb, Ta, P, and Ti). They also display low ε Hf (t) values and high Sr/Y ratios, comparable to adakitic rocks, suggesting that the Linglong and Luanjiahe granitoids formed under relatively high pressure conditions and were likely derived from the partial melting of the thickened lower crust of the NCC. The Guojialing granodiorites were emplaced in the early Cretaceous (129 Ma), and also contain abundant late Archean and Paleoproterozoic inherited zircons. The rocks possess high CaO, TFe 2 O 3 and MgO, and are metaluminous, with enrichment in LREEs and LILEs and depletion in HFSEs. They are also characterized by high Sr/Y ratios, and have higher ε Nd (t) and ε Hf (t) values than the Late Jurassic granitoids, suggesting the involvement of mantle components in the magmatic source. We correlate the magma tectonics with the processes accompanying the subduction of the Pacific Plate beneath the NCC and the associated asthenospheric upwelling Elsevier B.V. All rights reserved. 1. Introduction The North China Craton (NCC) preserves some of the oldest records of crustal evolution in the Precambrian Earth (Liu et al., 1992; Zhai and Santosh, 2011). The eastern part of the NCC had a thick (>200 km) lithosphere until the early Paleozoic as inferred from the presence of diamondiferous kimberlites such as those at Mengyin and Fuxian (Menzies et al., 1993; Yang et al., 2009; Zhang et al., 2010) (Fig. 1a). However, by the Cenozoic, the craton lost at least km of its keel, as recognized by the presence of spinel facies xenoliths in alkali basalts, as well as through evidence from geochemical and geophysical data (Gao et al., 2002; Rudnick et al., 2004; Wu et al., 2005; Yang et al., 2008; Zhang, 2012; Zhang et al., 2009, 2011; Zhou et al., 2002). The onset of lithospheric thinning has been linked to the Corresponding author. Tel.: ; fax: address: fanhr@mail.igcas.ac.cn (H-R. Fan). Central Asian Orogeny since the Late Carboniferous at the northern margin of the NCC (Li et al., 2009; Meng, 2003; Zhang et al., 2003, 2007; Zorin, 1999), and to the collision between the NCC and Yangtze Craton since the Late Triassic at the southern margin of the NCC (Gao et al., 1998; Li et al., 1993; Yang et al., 2007a, b; Zhang et al., 2002). The destruction of the NCC was a relatively slow process (continuing for more than 100 Ma), rather than a dramatic event (Xu et al., 2009). Many recent papers favor hydrous weakening over a considerable period of time as the potential cause for the lithospheric thinning (Kusky et al., 2007b; Santosh, 2010; Windley et al., 2010). During this period, abundant granitoids developed in the northwestern Jiaodong Terrane in the eastern NCC (Fig. 1b), and these have traditionally been divided into two 77 groups. Those of Late Jurassic ages ( Ma, e.g. Miao et al., 1997; Wang et al., 1998) are known locally as the Linglong and Luanjiahe suites. Those of Early Cretaceous ages ( Ma, e.g. Miao et al., 1997; Wang et al., 1998) are referred to as the Guojialing suite. Since these granitic rocks were coeval with lithospheric thinning of the eastern NCC (Wu et al., 2005), /$ see front matter 2012 Elsevier B.V. All rights reserved. doi: /j.lithos

2 K-F. Yang et al. / Lithos (2012) Fig. 1. Geological map of the North China Craton (a) and the Jiaodong Terrane (b), showing the distribution of the basement rocks, UHP metamorphic rocks and Mesozoic igneous rocks. Modified after Kusky et al. (2007a), Peng et al. (2007) and Goss et al. (2010). they possess important significance in providing information on the nature of the continental crust at this time. Of particular importance in this regard are the abundant Neoproterozoic magmatic inherited zircons with age at Ma, which are present in the Late Jurassic Linglong and Luanjiahe granitoids. Such Neoproterozoic ages are a prominent feature of the Yangtze Craton (Ames et al., 1996; Gao et al., 1996; Guo et al., 2005; Hacker et al., 1998; Rowley et al., 1997; Zheng et al., 2007; Zhou et al., 2006), and the corresponding igneous rocks were considered to have formed as a response to the breakup of the supercontinent Rodinia (Li et al., 2003; Ling et al., 2003; Zheng et al., 2006, 2007). The absence of Neoproterozoic granitic magmatism in the eastern NCC during this period is deemed to be an important basis to distinguish the eastern NCC and the Yangtze Craton (Hacker et al., 1998; Tang et al., 2008; Wan and Zeng, 2002). Miao et al. (1997) conducted a detailed statistical analysis of inherited zircon ages in these rocks, but they did not carry out in-depth discussion about their significance. The occurrence of Neoproterozoic magmatic zircons with an age signature of the Yangtze Craton within the eastern NCC more than 100 km north of the Sulu orogenic belt is noteworthy and provided the impetus for us to conduct further work in the area. This region is of critical importance to evaluate the lithosphere interaction during continental collision (Sulu Dabie orogen), and for reconstructing the Mesozoic lithospheric structure and crustal composition of the eastern margin of the NCC. In this paper, based on detailed petrological, geochronological and geochemical studies on the Late Mesozoic granitic rocks in the northwestern Jiaodong Terrane in the eastern NCC, we attempt to define their magmatic origin and tectonic setting, and to constrain the lithospheric composition and evolution history in the Late Mesozoic. 2. Geological background The NCC is bounded by the Central Asian Orogenic Belt (CAOB) to the north, the Sulu ultrahigh-pressure (UHP) metamorphic belt to the east and the Qinling Dabie orogenic belt to the south (Fig. 1a). The Sulu belt was originally part of the Qinling Dabie belt, but has subsequently been transported more than 500 km northeast along the Tanlu Fault (Ames et al., 1993; Xu and Zhu, 1994; Zhou et al., 2008a). The Qinling Dabie Sulu metamorphic belt is the result of subduction and collision between the NCC and Yangtze Craton (Mattauer et al., 1985). The Jiaodong Terrane refers to the area east of the Tanlu Fault, and forms the eastern margin of the NCC. The Sulu UHP metamorphic belt lies to the east and they are separated by the Baichihe Yantai Fault (Zhou et al., 2008b)(Fig. 1b). The Precambrian basement of the eastern NCC in the Jiaodong Terrane comprises the Archean Jiaodong Group composed of metamorphic volcanic sedimentary rocks and TTG gneiss, and the Paleoproterozoic Jingshan Group composed of metamorphic clastic rocks together with the Fenzhishan Group composed of metamorphosed chemical sediments (Guo et al., 2005). Jahn et al. (2008) offered new zircon U Pb SHRIMP data that established the existence of Mesoarchean (ca Ga) and Neoarchean (2.71 to 2.73 Ga) continental crust in the Jiaodong Terrane. However, the basement rocks of the Sulu Belt to the east are mainly composed of Neoproterozoic granitic gneisses. Zheng et al. (2006, 2008) considered that the protoliths of these granitic gneisses were produced by partial melting of continental crust in the northern margin of Yangtze Craton, which underwent Triassic UHP metamorphism (Ames et al., 1996; Guo et al., 2005; Hacker et al., 1998).

3 114 K-F. Yang et al. / Lithos (2012) Mesozoic igneous rocks form another major component of the Jiaodong Terrane (Fig. 1b), and include Late Jurassic granites, Early Cretaceous granites and granodiorites and Early Cretaceous volcanic rocks (Sang, 1984; Sang and You, 1992). The Late Jurassic granites are mainly composed of two suites in the Zhaoyuan Pingdu area in the northwestern Jiaodong Terrane, the Linglong and Luanjiahe granites. SHRIMP U Pb zircon geochronological data show that the Linglong and Luanjiahe intrusions were emplaced at Ma (Miao et al., 1997). The Early Cretaceous granodiorites that intrude the former suites are mainly composed of the Guojialing porphyritic hornblende biotite granodiorites in the north Zhaoyuan area. SHRIMP U Pb zircon geochronological data show that the Guojialing intrusions were emplaced at Ma (e.g. Miao et al., 1997). The Early Cretaceous granites are mainly distributed in the Sulu UHP metamorphic belt in the southeast Jiaodong Terrane, and a few small stocks in the northwest, which were emplaced at Ma (e.g. Goss et al., 2010). Early Cretaceous intermediate-acidic volcanic rocks are mainly distributed in the Jiaolai Basin, and were formed at Ma (e.g. Qiu et al., 2001). 3. Sampling and petrography Representative samples were collected from the Linglong granite, Luanjiahe granite and Guojialing granodiorite, evenly distributed in the northwest Jiaodong area (Fig. 2), for detailed petrographic and geochemical analysis. Two samples from each of the granitoids were selected for LA-ICP-MS (laser ablation inductively coupled plasma mass spectrometry) U Pb zircon dating and Lu Hf isotopic analysis Linglong granite suite The Linglong granite is located in the northwestern Jiaodong Terrane covering an area of more than 1000 km 2, and consists mainly of biotite granite with an allotriomorphic granular texture. Gneissic structures resulting from later deformation are generally developed in these rocks (Luo and Miao, 2002). The Linglong granite is gray in hand specimen (Fig. 3a) and the main minerals are plagioclase (25 30%), K-feldspar (35 40%), quartz (20 30%) and biotite (5 10%), with accessory titanite, garnet, zircon and apatite. The plagioclase is Fig. 2. Geological map of the Zhaoyuan Laizhou area in the northwestern Jiaodong Terrane showing sample locations. Modified after Wang et al. (1998).

4 K-F. Yang et al. / Lithos (2012) Fig. 3. Hand specimen photos and thin section microphotographs of the granitoids in the northwestern Jiaodong Terrane. Symbols for minerals: Pl, plagioclase; Kfs, K-feldspar; Qz, quartz; Bi, biotite; Hb, hornblende. albite andesine with multiple twins. The K-feldspar is microcline perthite with cross-hatched twins and locally forms a granophyric intergrowth with quartz (Fig. 3b). Biotite is typically aligned to form a gneissic structure, together with elongated quartz. Euhedral titanite is visible in hand specimens with grain size up to 2 mm. Garnet is purple and visible in the most hand specimens Luanjiahe granite suite The Luanjiahe granite is located in the northwestern Jiaodong Terrane covering an area of more than 800 km 2, and consists mainly of biotite granite with a coarse-grained allotriomorphic granular texture. The granite was thought to be the slightly later-intruded central phase of the Late Jurassic granitoids (BGMRS, 1991). The Luanjiahe granite is pale red in hand specimen (Fig. 3c) and the main minerals are plagioclase (25 45%), K-feldspar (30 50%), quartz (20 40%) and biotite (3 5%), with accessory garnet, zircon, apatite and opaque minerals. The plagioclase is mainly oligoclase with multiple twins, progressive zonal texture, and polysynthetic albite twinning at the crystal edge. The K feldspar is mainly microcline with cross hatched twins and it is extensively altered to clay minerals (Fig. 3d) Guojialing granodiorite suite The Guojialing granodiorite is located to the north of Zhaoyuan and is composed of five small intrusions (Fig. 2), emplaced within the Late Jurassic granitoids (Wang et al., 1998). The Guojialing granodiorite is pale red in hand specimen with a porphyritic texture (Fig. 3e). The main minerals are plagioclase (35 55%), K-feldspar (10 25%), quartz (15 30%), hornblende (5 10%) and minor biotite, with accessory titanite, zircon, apatite and monazite. The K feldspar is microcline perthite and locally forms granophyric intergrowth with quartz. The mineral occurs both as phenocrysts (up to 10 cm in length) and as a fine-granular phase. The plagioclase is mainly albite andesine and appears both as a phenocryst phase and in the matrix (Fig. 3f). Hornblende is bottle green in hand specimen and is present only in some samples. Titanite is euhedral and commonly associated with hornblende and the largest grain is up to 3 mm. 4. Analytical methods Fresh rock samples were crushed in a tungsten carbide mill to 200 mesh powder for major, trace element, and Sr Nd isotope

5 116 K-F. Yang et al. / Lithos (2012) analyses, and mesh for selecting zircon grains to use for U Pb dating and Hf isotope analyses Major and trace elements Major and trace elements were analyzed in the Laboratories of the Institute of Geology and Geophysics, Chinese Academy of Sciences (IGGCAS), Beijing. For major element analyses, mixtures of whole rock powder (0.5 g) and Li 2 B 4 O 7 +LiBO 2 (5 g) were made into glass disks and analyzed by X-ray fluorescence spectroscopy (XRF) with an AXIOS Minerals spectrometer. The analytical uncertainties were generally within 0.1 1% (RSD). For trace element analyses, whole rock powders (40 mg) were dissolved in distilled HF+HNO 3 in Teflon screw-cap capsules at 200 C for 5 days, dried, and then digested Fig. 4. Representative CL images of zircons analyzed from the Jiaodong Terrane and the scale bar is 100 μm (a). LA-ICP-MS zircon U Pb concordia diagrams of the Linglong granites (b, c), Luanjiahe granites (d, e) and Guojialing granodiorites (f, g) from the Jiaodong Terrane.

6 K-F. Yang et al. / Lithos (2012) with HNO 3 at 150 C for one day. They were taken to dryness again and digested with HNO 3 at 150 C for another day. Dissolved samples were diluted to 49 ml with 1% HNO 3 and 1 ml 500 ppb indium was added to the solution as an internal standard. Trace element abundances were determined by inductively coupled plasma mass spectrometry (ICP-MS) using a Finnigan MAT Element spectrometer, which has analytical uncertainties within 5% for most elements Sr and Nd isotopes Whole rock powders for Sr and Nd isotopic analyses were dissolved in Teflon bombs after being spiked with 87 Rb, 84 Sr, 149 Sm and 150 Nd tracers prior to HF+HNO 3 +HClO 4 dissolution. Rb, Sr, Sm and Nd were separated using conventional ion exchange procedures and measured using a Finnigan MAT262 multi-collector mass spectrometer at IGGCAS. Detailed descriptions of the analytical techniques have been documented in Chu et al. (2009). Procedural blanks are b100 pg for Sm and Nd, and b300 pg for Rb and Sr. The isotopic ratios were corrected for mass fractionation by normalizing to 86 Sr/ 88 Sr= and 146 Nd/ 144 Nd= , respectively. The measured values for the JNdi-1 Nd standard and NBS987 Sr standard were 143 Nd/ 144 Nd= ±12 (2σ, n=10) and 87 Sr/ 86 Sr= ±12 (2σ, n=10),respectively.usgs reference material BCR-2 was measured to monitor the accuracy of the analytical procedures, with 143 Nd/ 144 Nd= ±13 (2σ, n=12) and 87 Sr/ 86 Sr= ±12 (2σ, n=12) Zircon U Pb dating and in situ Hf isotopic analyses U Pb dating and trace element analyses of zircon were conducted synchronously by LA-ICP-MS at the State Key Laboratory of Geological Processes and Mineral Resources, China University of Geosciences, Wuhan. Detailed operating conditions for the laser ablation system, the ICP-MS instrument, and the data reduction process are described by Liu et al. (2010). Laser sampling was performed using a GeoLas An Agilent 7500a ICPMS was used to acquire ion-signal intensities. Each analysis incorporated a background acquisition of approximately s (gas blank) followed by 50 s data acquisition from the sample. An Agilent Chemstation was utilized for the acquisition of each individual analysis. Off-line selection and integration of background and analytical signals, time-drift correction, and quantitative calibration for trace element analyses and U Pb dating were performed by ICPMSDataCal (Liu et al., 2010). Zircon was used as the external standard for U Pb dating, and was analyzed twice every five analyses. Time-dependent drifts of U Th Pb isotopic ratios were corrected using a linear interpolation (with time) for every five analyses according to the variations of (Liu et al., 2010). Preferred U Th Pb isotopic ratios used for were from Wiedenbeck et al. (1995). Uncertainties of preferred values for the external standard were propagated through to the ultimate results of the samples. Concordia diagrams and weighted mean calculations were made using Isoplot/Ex ver3 (Ludwig, 2003). Trace element compositions of zircons were calibrated against reference material GSE-1G combined with internal standardization (Liu et al., 2010). In situ zircon Hf isotopic analyses were conducted in the same spots which were analyzed for U Pb dating. Hf isotopic compositions were determined by a Neptune MC ICP-MS equipped with a GeolasPlus 193 nm ArF excimer laser at the IGGCAS. A laser spot size of 40 μm and laser repetition of 8 Hz with energy density of 15 J/cm 2 was used during the analyses. The signal collection model is one block with two hundred cycles. Each cycle has s integration time and the total time is about 26 s for each analysis. Zircon was used as an external standard for Hf isotopic analyses and was analyzed twice every five analyses. Repeated analyses of yielded a mean 176 Hf/ 177 Hf ratio of ±37 (2σ, n=35), which is consistent with the 176 Hf/ 177 Hf ratios measured by Goolaerts et al. (2004). Detailed analytical procedures were described by Xie et al. (2008). 5. Results 5.1. Geochronology Linglong granite The zircon crystals in samples 08G33 and 08G59 of the Linglong granite are mostly prismatic and range from 60 to 200 μm in size. Most grains are transparent and pale yellow in color, and display oscillatory zoning. Some of the grains have circular or irregular cores mantled by euhedral overgrowths that also show oscillatory zoning (Fig. 4a). 19 spots from 13 grains were analyzed from 08G33 and the data yield a weighted mean 206 Pb/ 238 U age of 159±2 Ma (2σ) (Fig. 4b; Supplemental electronic data Table 1), which is taken to define the crystallization age of the granite. Of the six remaining grains, one grain shows a significantly older 207 Pb/ 206 Pb age of 2083 Ma and is likely an inherited zircon from the basement of the eastern NCC. Another grain yields a 206 Pb/ 238 U age of 774 Ma, which could be an inherited zircon from the northern margin of the Yangtze Craton. The remaining four grains have concordant ages that range from 220 Ma to 240 Ma, which is consistent with the age of UHP metamorphism in the Dabie Sulu orogen. 23 spots from 16 zircons were analyzed from sample 08G59 Linglong granite and the results show a weighted mean 206 Pb/ 238 U age of 159±1 Ma (2σ) (Fig. 4c; Supplemental electronic data Table 1), which is taken to define the crystallization age of the granite. Of the seven remaining grains, one grain yields a discordant age (Supplemental electronic data Table 1), which is not further considered. Another grain yields a 206 Pb/ 238 U age of 208 Ma, which correlates with the timing of magmatism following the mantle upwelling induced by slab breakoff after continental subduction of the Yangtze Craton (e.g., Guo et al., 2005). The remaining five grains show concordant to weakly discordant ages that range from 435 Ma to 514 Ma and from 751 Ma to 776 Ma, which correspond to representative ages recorded from the Yangtze Craton Luanjiahe granite The zircons in samples 08G40 and 08G42 of Luanjiahe granites are mostly prismatic and range from 100 to 200 μm in size with similar characteristics to samples from the Linglong granite (Fig. 4a). 19 spots were analyzed from 12 grains in sample 08G40 yielding a weighted mean 206 Pb/ 238 Uageof158±2Ma(2σ) (Fig. 4d; Supplemental electronic data Table 1), which is taken to define the crystallization age of the granite. Among the seven remaining grains, one yields a discordant younger age, which is discarded. Two other grains yield significantly older 207 Pb/ 206 Pb ages of 1792 Ma and 1952 Ma and are likely to be inherited zircons from the basement of the eastern NCC. Another two grains yield 206 Pb/ 238 Uagesof 688 Ma and 691 Ma, which are considered as inherited zircons from the northern margin of the Yangtze Craton. The remaining two grains yield 206 Pb/ 238 U ages of 200 Ma and 203 Ma. 21 spots were analyzed from 12 grains in sample 08G42and the data define a weighted mean 206 Pb/ 238 U age of 157±2 Ma (2σ) (Fig. 4e; Supplemental electronic data Table 1), which is taken to represent the crystallization age of the granite. Of the nine remaining grains, three yield discordant ages and are not discussed further. Two grains yield significantly older 207 Pb/ 206 Pb ages of 2213 Ma and 2857 Ma, and are likely inherited zircons from the basement of the eastern NCC. Two other grains yield 206 Pb/ 238 U ages of 683 Ma and 742 Ma, and may be inherited zircons from the northern margin of Yangtze Craton. The remaining two grains yield 206 Pb/ 238 U ages of 226 Ma and 235 Ma, and these ages are consistent with the timing of UHP metamorphism in the Dabie Sulu orogen.

7 Table 1 Major oxides (wt.%) and trace elements (ppm) for the Jiaodong granitoids. Sample no. 08G01 08G02 08G03 08G04 08G05 08G19 08G20 08G40 08G42 08G50 08G52 08G53 08G15 08G16 08G17 08G18 08G21 08G22 Rock-type Luanjiahe granite Linglong granite SiO TiO Al 2 O TFe 2 O MnO MgO CaO Na 2 O K 2 O P 2 O LOI Total Mg # Cr Ni Rb Ba Th U Pb Nb Ta La Ce Pr Sr Nd Zr Hf Sm Eu Gd Tb Dy Y Ho Er Tm Yb Lu (La/Yb) N Eu/Eu* K-F. Yang et al. / Lithos (2012)

8 Table 1 08G24 08G33 08G38 08G39 08G49 08G59 08G07 08G08 08G13 08G25 08G26 08G28 08G29 08G30 08G31 08G32 08G37 08G61 Linglong granite Guojialing granodiorite K-F. Yang et al. / Lithos (2012)

9 120 K-F. Yang et al. / Lithos (2012) Guojialing granodiorite The zircons in samples 08G32 and 08G37 from the Guojialing granodiorite are mostly prismatic and range from 50 to 150 μm in size. Most grains are transparent and pale yellow in color, and have oscillatory zoning. Some grains have circular or irregular cores mantled by euhedral overgrowths (Fig. 4a), similar to samples from the Linglong and Luanjiahe granites. 21 spots were analyzed from 19 grains in sample 08G32 yielding a weighted mean 206 Pb/ 238 U age of 129±1 Ma (2σ) (Fig. 4f; Supplemental electronic data Table 1), which is taken to define the crystallization age of the granodiorite. The other two grains show significantly older 207 Pb/ 206 Pb ages of 2435 Ma and 2438 Ma, which are likely to be inherited zircons from the basement of the eastern NCC. 20 spots on 15 grains from sample 08G37 yield a weighted mean 206 Pb/ 238 U age of 129±1 Ma (2σ) (Fig. 4g; Supplemental electronic data Table 1). Of the five remaining grains, one yields a 206 Pb/ 238 U age of 157 Ma, which is likely an inherited zircon from the Late Jurassic granitoid. The remaining four grains yield significantly older 207 Pb/ 206 Pb ages that range from 1789 Ma to 2356 Ma, which are likely to be inherited zircons from the basement of the eastern NCC Major and trace elements Most of the Late Jurassic granitoids in the northwestern Jiaodong Terrane, including the Linglong granite and Luanjiahe granite, have similar lithological features and emplacement ages. Their salient geochemical features as obtained from this study are briefly described below. The major and trace element data on all the granitoids examined in this study are presented in Table 1. The SiO 2 contents of the Late Jurassic granitoids range from 69.2 wt.% to 75.9 wt.%. In the R1 R2 classification diagram (De la Roche et al., 1980), most of the samples plot in the monzogranite and syenogranite fields (Fig. 5). All the samples are high in Na 2 O+K 2 O ( wt.%) and low in CaO ( wt.%, average 1.38 wt.%), TFe 2 O 3 ( wt.%, average 1.24 wt.%) and MgO ( wt.%). Most samples are peraluminous with high A/CNK ratio of (Fig. 6). The Mg # values of these rocks are relatively low and range from 13.4 to 32.7 (Table 1). Overall, many of the major oxides in the Late Jurassic granitoids show a strong negative correlation with SiO 2 (correlation coefficient from 0.6 to 0.9) (Fig. 7a, b and c), except for K 2 O which increases with SiO 2 (r=+0.7) (Fig. 7d). These correlations imply the rocks are co-magmatic. Most of the Linglong granites have low total REE content (ΣREE= ppm) and are enriched in light rare earth elements (LREE) [(La/Yb) N = ] (Fig. 8a). The Luanjiahe granites also have low total REE contents (ΣREE= ppm) and are slightly more enriched in LREE [(La/Yb) N = ] (Fig. 8c), except for a few samples (08G01, 08G05, 08G52, and 08G53) that have high heavy rare earth element (HREE) contents and show flat HREE patterns in the chondrite-normalized REE diagram (Fig. 8c). In the primitive mantle-normalized spider diagrams (Fig. 8b, d), all samples from the Linglong and Luanjiahe granitoids are enriched in large ion lithophile elements (LILE) such as Rb, Ba, U and Sr, and depleted in high-field strength elements (HFSE) such as Nb, Ta, P and Ti, except for Zr and Hf. Samples are also enriched in Sr ( ppm) and depleted in Y ( ppm), and have high Sr/Y ratios, which are features comparable with adakitic rocks (e.g., Defant and Drummond, 1990; Eyuboglu et al., 2011; Guo et al., 2006; Liu et al., 2009; Yu et al., 2011; Zhang et al., 2001). The silica contents of the Early Cretaceous Guojialing granodiorites range from 68.2 wt.% to 72.6 wt.%. In the R1 R2 classification diagram (De la Roche et al., 1980), nearly all of the samples plot in the granodiorite field (Fig. 5). Compared with the Linglong and Luanjiahe granitoids, the Guojialing granodiorites have higher CaO ( wt.%), TFe 2 O 3 ( wt.%) and MgO ( wt.%), Fig. 5. R2 (R2=6Ca+2Mg+Al) versus R1 [R1=4Si 11(Na+K) 2(Fe+Ti)] plot for the granitoids in the northwestern Jiaodong Terrane. (After De la Roche et al., 1980). suggesting their relatively more basic nature. All of the samples are metaluminous with low A/CNK ratios of (Fig. 6). The Mg # values of Guojialing granodiorites are higher than Linglong and Luanjiahe granitoids, and range from 40.0 to 58.9 (Table 1). Most of the Guojialing granodiorites have higher total REE content (ΣREE= ppm) than the Late Jurassic granitoids and are enriched in LREE [(La/Yb) N = ] (Fig. 8e). In the primitive mantle-normalized spider diagrams (Fig. 8f), all the samples are enriched in LILE such as Rb, Th, U, Ba and Sr, and depleted in HFSE such as Nb, Ta, Zr, Hf, P and Ti. Most of samples do not show significant Eu anomalies (Eu/Eu* = ). The rocks are also enriched in Sr ( ppm) and depleted in Y ( ppm), and have higher Sr/Y ratios and more obvious Nb and Ta negative anomaly than the Linglong and Luanjiahe granitoids Sr Nd isotopes Strontium and Nd isotopic compositions of the granitoids in the northwestern Jiaodong Terrane are presented in Table 2 and plotted in Fig. 9. The Linglong granites have uniform initial 87 Sr/ 86 Sr ratios Fig. 6. A/NK [molar ratio Al 2 O 3 /(Na 2 O+K 2 O)] vs. A/CNK [molar ratio Al 2 O 3 /(CaO + Na 2 O+K 2 O)] plot for the granitoids in the northwestern Jiaodong Terrane. (After Maniar and Piccoli, 1989).

10 K-F. Yang et al. / Lithos (2012) that range from to , and ε Nd (t) values that range from 21.6 to The isotope data from Luanjiahe granites clearly define two groups (Fig. 9). One group has composition similar to that of the Linglong granites, but the other (samples 08G01, 08G02, and 08G50) shows lower initial 87 Sr/ 86 Sr ratios that range from to , suggesting that the Luanjiahe granites were derived from more complex magmatic source. The Guojialing granodiorites have relatively uniform initial 87 Sr/ 86 Sr ratios that range from to , and ε Nd (t) values that range from 16.8 to 11.8, which is similar to the mafic dykes from the northwestern Jiaodong area (e.g., Yang et al., 2004) (Fig. 9) Zircon Hf isotope data In situ Hf isotopic analyses of zircons from the granitoids in the northwestern Jiaodong Terrane are listed in Supplemental electronic data Table 2 and plotted in Fig. 10. The zircons from the Linglong granites (08G33 and 08G59) yield ε Hf (t) values that range from 28.7 to 17.6 with an average of 25.1, except for the inherited zircons. One of the inherited zircons with an age of 2083 Ma yields an ε Hf (t)=0. The other grains with ages of Ma, Ma and Ma yield ε Hf (t) values ranging from 17.1 to 11.4, which mainly plot in between the 1.9 and 2.5 Ga crustal evolution lines in the Hf isotopic evolution diagram (Fig. 10). The age correlates with timing of the major crust formation event in the Yangtze Craton (Chen and Jahn, 1998). Zircons from the Luanjiahe granites (08G40 and 08G42) yield ε Hf (t) values that range from 28.2 to 17.4 with an average of 24.1, except for the inherited zircons. The inherited zircons with ages of Ma yield ε Hf (t) values that range from 16.4 to 1.9 and mainly plot in between the 2.5 and 3.0 Ga crustal evolution lines or below these in Fig. 10, suggesting that these rocks formed from partial melting of the ancient continental crust in the eastern NCC. The grains with ages of Ma and Ma yield ε Hf (t) values ranging from 19.3 to 5.6, which are similar to those of the Linglong granites. The zircons from the Guojialing granodiorites (08G32 and 08G37) yield ε Hf (t) values that range from 24.2 to 18.6 with an average of 20.1 (except for the inherited zircons), which is slightly higher than the values of the Linglong and Luanjiahe granitoids. The inherited zircons with ages of Ma yield ε Hf (t) values that range from 18.8 to 4.4 and plot mainly in the region between the 2.5 and 3.0 Ga crustal evolution lines. 6. Discussion 6.1. Petrogenesis The Late Jurassic granitoids in northwestern Jiaodong Terrane have high Sr/Y ratios, and most of the samples plot in the adakite region in the Sr/Y vs. Y diagram (Fig. 11), suggesting that the Linglong and Luanjiahe granitoids may have formed in a high pressure environment. These characteristics are comparable with the C-type adakitic rocks formed in thickened continental crust (e.g., Guo et al., 2006; Liu et al., 2009; Zhang et al., 2001). Furthermore, most of the ε Hf (t) values of zircons from these granitoids plot in between the 2.5 and 3.0 Ga crustal evolution lines (Fig. 10), which indicates that the Late Jurassic granitic magma might have originated from partial melting of the continental crust of the eastern NCC. Hou et al. (2007) proposed that the Linglong granitoids were derived by partial melting of Neoarchean metamorphic lower crustal rocks, based on detailed petrological and geochemical data. However, these granitoids also contain abundant Neoproterozoic ( Ma), Early Paleozoic ( Ma) and Triassic ( Ma) inherited zircons, as well as some Late Archean (2857 Ma) and Paleoproterozoic ( Ma) grains. The initial 87 Sr/ 86 Sr and ε Nd (t) values of most of the granitoids also plot between the region of upper crust of the NCC and lower crust of the Yangtze Craton (Fig. 9), which indicates that the Late Jurassic granitoids possess a complex source composition. The eastern margin of the NCC has no major magmatic records during Neoproterozoic, although this period marks the main crustal Fig. 7. Harker diagrams for the granitoids in the northwestern Jiaodong Terrane. Plots of MgO (a), Al 2 O 3 (b), K 2 O (c), CaO (d), vs. SiO 2 (wt.%).

11 122 K-F. Yang et al. / Lithos (2012) generation time of the Yangtze Craton (Chen and Jahn, 1998). There are numerous Neoproterozoic granites or granitic gneisses distributed in the Sulu orogenic belt, which are typical of the northern margin of the Yangtze Craton (Ames et al., 1996; Gao et al., 1996; Guo et al., 2005; Hacker et al., 1998; Rowley et al., 1997; Zheng et al., 2007; Zhou et al., 2006). Therefore the Neoproterozoic inherited zircons in the Linglong and Luanjiahe granitoids are likely to be derived from the Yangtze Craton. As the Triassic marks the important period of Dabie Sulu continental collision and exhumation of UHP metamorphic rocks, the presence of Triassic inherited zircons in the Linglong and Luanjiahe granitoids suggests that the UHP metamorphic rocks or collision-related magmatic rocks might have also contributed to the magma source of the Late Jurassic granitoids in the northwestern Jiaodong Terrane. Furthermore, there is no obvious correlation between SiO 2, ε Nd (t) and initial 87 Sr/ 86 Sr in the Late Jurassic granitoids, suggesting that source heterogeneity might have played an important role in the magma evolution rather than crustal contamination during emplacement. This heterogeneity may result from the mixing of continental crustal materials derived from the Yangtze Craton, which were carried down by the subducted slab of the Dabie Sulu collisional orogeny. This appears more obvious in the Luanjiahe granites. For example, four Luanjiahe granites samples (08G01, 08G05, 08G52, and 08G53) are high in HREE and show flat HREE patterns in the chondrite-normalized REE diagrams (Fig. 8c), which is similar to the characteristic pattern of Neoproterozoic metagranites from the northern margin of Yangtze Craton (e.g., Hu et al., 2010). Among these, three samples (08G01, 08G05, and 08G53) plot in the region of typical arc-derived rocks within the Sr/Y vs. Y diagram (Fig. 11), which is also similar to the Neoproterozoic granites from the Yangtze Craton (e.g., Zheng et al., 2006, 2008). Three more samples (08G01, 08G02, and 08G50) have relatively lower initial 87 Sr/ 86 Sr compositions than the others, and plot close to the region defining the lower crust of the Yangtze Craton in the ε Nd (t) versus initial 87 Sr/ 86 Sr diagram (Fig. 9), which is similar to the isotope composition of Late Triassic syenite in Sulu orogenic belt (Yang et al., 2005). These characteristics show Fig. 8. Chondrite-normalized REE patterns and Primitive Mantle (PM) normalized trace element diagrams for Linglong granites (a, b), Luanjiahe granites (c, d) and Guojialing granodiorites (e, f). Chondrite and PM values are from Sun and McDonough (1989).

12 K-F. Yang et al. / Lithos (2012) Table 2 Sr Nd isotopic compositions for the Jiaodong granitoids. Sample Rb (ppm) Sr (ppm) 87 Rb/ 86 Sr 87 Sr/ 86 Sr ±2σ 87 Sr/ 86 Sr (i) Sm (ppm) Nd (ppm) 147 Sm/ 144 Nd 143 Nd/ 144 Nd ±2σ ε Nd (t) Luanjiahe granite 08G G G G G G G Linglong granite 08G G G G G G Guojialing granodiorite 08G G G G G G G that the magma source of the Luanjiahe granites may have more in common with crustal materials of the Yangtze Craton than the eastern NCC. The Early Cretaceous granodiorites in the northwestern Jiaodong Terrane show large variations when compared with the Late Jurassic granitoids in terms of emplacement age and geochemistry. The granodiorites are metaluminous with high CaO and MgO contents. Most samples are enriched in LREE and show strong fractionation between LREE and HREE [(La/Yb) N values range from 23.6 to 122] (Table 1). The rocks are also enriched in Sr and depleted in Y, and have higher Sr/Y ratios than the Linglong and Luanjiahe granitoids. All of the samples plot in the adakite region in the Sr/Y vs. Y diagrams (Fig. 11). However, unlike typical adakitic rocks, the Guojialing granodiorites have high initial 87 Sr/ 86 Sr and negative ε Nd (t) values, which is similar to the TTG rocks and mafic dykes from the Jiaodong Terrane (Yang et al., 2003a). The common presence of Paleoproterozoic ( Ma) inherited zircons shows that basement rocks of the eastern NCC were involved in the formation of the Guojialing granodiorites. Nevertheless, the zircon ε Hf (t) values of the granodiorites are less negative than the Linglong and Luanjiahe granitoids and plot above the 2.5 Ga crustal evolution line (Fig. 10). The ε Nd (t) values of granodiorites are also higher than the Late Jurassic granitoids, and plot close to mafic dykes from the Jiaodong Terrane in Fig. 9, which suggest that some mantle source components were involved in the formation of these rock. Yang et al. (2003a) proposed that the Guojialing granodiorites were derived from dehydrational partial melting of mafic lower crust altered by ancient underplated mantlederived magma. Hou et al. (2007) argued that the Guojialing suite was formed by the reaction of delaminated eclogitic crust derived melt with the upwelling asthenospheric mantle. There are various indications that the Guojialing granodiorite was likely the result of crust mantle mixing Tectonic implications Guo et al. (2005) and Zhang et al. (2001) argued that the eastern part of the NCC underwent crustal thickening in the Mesozoic, which might have resulted from the collision between the NCC and the Yangtze Craton. Windley et al. (2010) also proposed that postcollisional thrusting thickened considerably the lower crust and the upper mantle root of the eastern NCC in the Jurassic. Multiple subduction of south Mongolia from the north since Late Carboniferous (Li et al., 2009; Zhang et al., 2007), Yangtze Craton from the south since Late Triassic (Yang et al., 2007a, b) and especially the Pacific Plate from the east since Late Triassic Early Jurassic beneath the NCC (Santosh, 2010; Wu et al., 2007; Zhou et al., 2009, 2010), and the water derived from the subducted plate remarkably weakened the sub-continental lithosphere and accordingly facilitated or triggered the cratonic destruction (Windley et al., 2010). The late Jurassic, the mountain root of Jiaodong Terrene gradually underwent collapse due to post-collisional lithospheric extension and regional thermal anomaly (Zhang, 2009). As mentioned above, the Late Jurassic granitoids ( Ma) in the Jiaodong Terrane at the eastern margin of the NCC are crustal-derived granites emplaced after the Dabie Sulu continental collision and exhumation of UHP Fig. 9. ε Nd (t) versus initial 87 Sr/ 86 Sr diagram for the granitoids from the northwestern Jiaodong Terrane. The isotopic composition of mafic dykes from Jiaodong (Yang et al., 2004) and syenites from Sulu UHP metamorphic belt (Yang et al., 2005) areshownfor comparison. The fields for lower crust of the Yangtze Craton, upper and lower crusts of the NCC are from Jahn et al. (1999). DM, EM1 and EM2 are from Zindler and Hart (1986). The ( 87 Sr/ 86 Sr)i and ε Nd (t) values of Linglong and Luanjiahe granitoids are recalculated at 160 Ma and the Guojialing granodiorites at 130 Ma. Chondrite Uniform Reservoir (CHUR) values of 87 Rb/ 86 Sr= and 87 Sr/ 86 Sr= (λ Rb = year 1 ), and 147 Sm/ 144 Nd= and 143 Nd/ 144 Nd= (λ Sm = year 1 )(Lugmair and Marti, 1978) are used for the calculation.

13 124 K-F. Yang et al. / Lithos (2012) Fig. 10. Diagram of Hf isotopic evolution in zircons for each sample analyzed. CHUR, chondritic uniform reservoir; CC, continental crust. Depleted mantle evolution is calculated by using ε Hf (t)=16.9 at t=0 Ga and ε Hf (t)=6.4 at t=3.0 Ga. The corresponding lines of crustal extraction are calculated by using the 176 Lu/ 177 Hf ratio of for the average continental crust (Griffin etal.,2002). The parameters of ( 176 Lu/ 177 Hf) CHUR = and ( 176 Hf/ 177 Hf) CHUR = , and ( 176 Lu/ 177 Hf) DM = and ( 176 Hf/ 177 Hf) DM = (λ Lu = year 1 )(Blichert-Toft and Albaréde, 1997; Griffin etal., 2000; Söderlund et al., 2004) were applied to the calculation. metamorphic rocks. They plot mostly in the post-collisional granitoid (POG) field in tectonic discrimination diagram (Fig. 12). Contemporary granitoids are also found in the Sulu orogenic belt such as the Kunyushan pluton (Guo et al., 2005). The Jurassic granitoids have trace element compositions similar to those of adakitic rocks, which formed under high pressure conditions and likely originated from the partial melting of residual thickened Archean lower crust (Fig. 13a). The presence of a large number of inherited zircons, especially the Neoproterozoic and Early Paleozoic populations that are representative for the Yangtze Craton, shows that the Late Jurassic granitoids have a relatively complex magmatic source composition. These crustal materials of the Yangtze Craton, including the Neoproterozoic granites, were likely carried beneath the eastern NCC by the subducted slab during the process of Dabie Sulu continental collision in the Triassic. The melts derived from the subducted Yangtze Craton accordingly promoted reactivating and partial melting of the residual Archean lower crust, thus forming the adakitic Linglong and Luanjiahe granitoids in the northwestern Jiaodong Terrane, which preserve the age signature of the Yangtze Craton. Fig. 11. Plot of Sr/Y versus Y for the granitoids in the northwestern Jiaodong Terrane. (After Defant and Drummond, 1990). Fig. 12. Tectonic discrimination diagram for the granitoids in the northwestern Jiaodong Terrane. Fields indicate island arc granitoids (IAG), continental arc granitoids (CAG), continental collision granitoids (CCG), post-collisional granitoids (POG), riftrelated granitoids (RRG) and continental epeirogenic uplift granitoids (CEUG). (After Maniar and Piccoli, 1989). Accompanied with asthenosphere upwelling, the eastern margin of the NCC entered a phase of cratonic destruction and lithospheric thinning (Gao et al., 2002, 2009). The Guojialing granodiorites formed at this stage with emplacement ages of Ma. There are also abundant felsic and mafic igneous rocks of Early Cretaceous ( Ma) age distributed not only along the margin of the NCC (e.g., Dabie Sulu orogenic belt, Jiaodong and Liaodong peninsulas) but also within the craton (e.g., Luxi Terrane, Yangshan and Taihang mountains, Fan et al., 2001; Goss et al., 2010; Guo et al., 2005; Kusky et al., 2007c; Wilde et al., 2003; Wu et al., 2005; Ying et al., 2006; Zhao and Zheng, 2009). These intrusives are considered as a principle marker for cratonic destruction and lithospheric thinning of the NCC (Xu et al., 2004, 2009). Such a major magmatic event must be related to strong lithospheric extension and large-scale asthenospheric upwelling. Previous research has attempted to explain the tectonic milieu including: a) collision between the NCC and the Yangtze Craton (Gao et al., 1998; Li et al., 1993; Yang et al., 2007a, b), b) collision between India and the Eurasian Plates (Menzies et al., 1993), c) collision between the Siberian and North China Mongolia Plates (Meng, 2003; Zorin, 1999), d) subduction of the Pacific Plate beneath China (Fan et al., 2000; Goss et al., 2010; Tatsunoto et al., 1992; Wu et al., 2005; Xu, 2007; Yang et al., 2003b), and e) a mantle plume (Deng et al., 2004). Subduction of the Pacific Plate is considered as the most likely explanation for lithospheric thinning in the eastern NCC (Goss et al., 2010; Santosh, 2010; Xu et al., 2009). During the Early Cretaceous, subduction of the Pacific Plate beneath the NCC, possibly with slab break-off and roll back, led to backarc spreading and asthenospheric upwelling, which would aid lithospheric thinning and partial delamination. This in turn led to partial melting of the lithospheric mantle, and the resulting mafic magmas were underplated below eastern China (Goss et al., 2010). These magmas provided the heat source for crustal melting which produced the Early Cretaceous granodiorites ( Ma). The high ε Hf (t) values of these rocks also indicate that mantle components were involved in the formation of the Guojialing granodiorites. Although the Guojialing granodiorites have adakitic compositions similar to that of the Linglong and Luanjiahe granitoids, their petrogenesis and tectonic setting are markedly different. The majority of samples of Linglong and Luanjiahe granitoids plot in the POG region in the tectonic discrimination diagram (Fig. 12), albeit the Guojialing granodiorites plot in the island arc granitoids (IAG), continental arc

14 K-F. Yang et al. / Lithos (2012) Fig. 13. Schematic map of Mesozoic lithospheric evolution of the Jiaodong Terrane. (Modified after Groves and Bierlein, 2007). granitoids (CAG) and continental collision granitoids (CCG) fields (Fig. 12). The former may result from reactivation of Archean lower crust and post-collisional lithospheric extension (Fig. 13a), but the latter is likely triggered by subduction of the Pacific Plate beneath the NCC and associated asthenospheric upwelling (Fig. 13b). It is worth mentioning that no Neoproterozoic or Early Paleozoic inherited zircons are found in the Guojialing granodiorites, which indicates that previous continental lithosphere of the eastern NCC in northwestern Jiaodong Terrane that was mixed with crustal materials from the Yangtze Craton, was either lost or exhausted. 7. Conclusions The Linglong and Luanjiahe granitoids were emplaced in the Late Jurassic ( Ma), and contain abundant Late Archean, Paleoproterozoic, Neoproterozoic, Early Paleozoic and Triassic inherited zircons, implying the involvement of continental crustal materials from both the eastern NCC and the Yangtze Craton. The Guojialing granodiorites were emplaced in the Early Cretaceous (129 Ma), and contain abundant Late Archean and Paleoproterozoic inherited zircons, but no Neoproterozoic and Early Paleozoic zircons are present. The Late Jurassic granitoids in the northwestern Jiaodong Terrane are peraluminous with enrichment in LREE and depletion in HFSE. The rocks are also high in Sr/Y and low in ε Hf (t) and plot in between the 2.5 and 3.0 Ga crustal evolution lines, suggesting that the Linglong and Luanjiahe granitoids were formed under relatively high pressure conditions, and were likely derived from the partial melting of a residual thickened Archean lower crust. The Early Cretaceous granodiorites are metaluminous with enrichment in LREE and depletion in HFSE. They show high in MgO and Sr/Y, and also have higher ε Nd (t) values than the Late Jurassic granitoids, indicating that some mantle components were involved in the magmatic source, and this was possibly triggered by subduction of the Pacific Plate beneath the NCC and accompanied by asthenospheric upwelling. Supplementary materials related to this article can be found online at Acknowledgments We owe our special thanks to Professor Hong-Fu Zhang, Dr. C.V. Dharma Rao and Editor-in-Chief Professor Nelson Eby for their many pertinent comments and patient revisions that greatly improved the manuscript. We are grateful to Chao-Feng Li and Xiang- Hui Li for help during Sr and Nd isotope analyses and Zhao-Chu Hu for help during zircon LA ICP-MS U Pb dating. This study was financially supported by the Natural Science Foundation of China ( ) and the Crisis Mines Continued Resources Exploration Project of the China Geological Survey ( ). References Ames, L., Tilton, G.R., Zhou, G., Timing of collision of the Sino Korean and Yangtze Cratons: U Pb zircon dating of coesite-bearing eclogites. Geology 21, Ames, L., Zhou, G.Z., Xiong, B.C., Geochronology and isotopic character of ultrahigh-pressure metamorphism with implications for collision of the Sino Korean and Yangtze Cratons, central China. Tectonics 15, BGMRS, Regional Geology of the Shandong Province. Geological Memories, Series 1, 26. Geological Publishing House, Beijing. in Chinese. Blichert-Toft, J., Albaréde, F., The Lu Hf isotope geochemistry of chondrites and the evolution of the mantle crust system. Earth and Planetary Science Letters 148, Chen, J., Jahn, B.M., Crustal evolution of southeastern China: Nd and Sr isotopic evidence. Tectonophysics 284,