Front. Earth Sci. Frontiers in Earth Science Front. Earth Sci. 2296-6463 Frontiers Media S.A. 1083608 10.3389/feart.2022.1083608 Earth Science Original Research Generation of the Early Cretaceous granitoid in the Dazeshan region, Jiaodong Peninsula: Implications for the crustal reworking in the North China Craton Dong et al. 10.3389/feart.2022.1083608 Dong Leilei 1 * Yang Zhiming 1 2 Bai Xin 1 Deng Chen 3 1 School of Civil and Resource Engineering, University of Science and Technology Beijing, Beijing, China 2 Institute of Geology, Chinese Academy of Geological Sciences, Beijing, China 3 Postdoctoral Programme, Guosen Securities, Shenzhen, China

Edited by: Fei Xue, Hohai University, China

Reviewed by: Sam Uthup, National Taiwan Normal University, Taiwan

Jian Li, Shandong University of Technology, China

Chao Zhao, Chang’an University, China

 *Correspondence: Leilei Dong, leileidong@ustb.edu.cn

This article was submitted to Geochemistry, a section of the journal Frontiers in Earth Science

 30 01 2023 2022 10 1083608 29 10 2022 05 12 2022 Copyright © 2023 Dong, Yang, Bai and Deng. 2023 Dong, Yang, Bai and Deng

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Lower crust-derived granitic rocks provide constraints on the crustal reworking process and consequently give hints on the destruction mechanism of the cratons. The North China Craton (NCC) underwent extensive crustal melting in the Mesozoic. This study investigated granitic intrusions in the Dazeshan region of the Jiaodong Peninsula. Whole-rock major and trace element analyses and zircon U-Pb ages coupled with Hf isotopes were used to reveal the crustal reworking processes. Zircons separated from the quartz porphyry, Linglong granite, rhyolite porphyry, and biotite granite showed weighted mean 206Pb-238U ages of 119.2 ± 1.0 Ma, 140.2 ± 1.0 Ma, 120.6 ± 0.5 Ma, and 119.9 ± 0.7 Ma, respectively. The quartz porphyry, rhyolite porphyry, and biotite granite had high silica contents (SiO2 = 74–77 wt.%) but low MgO, Co, and Ni concentrations. The calculated ε Hf (t) values for the rhyolite porphyry and the biotite granite ranged from −18.3 to −20.0 and −17.8 to −20.2, respectively. These geochemical features imply ancient crust sources. The quartz porphyry showed distinct primitive mantle-normalized rare earth element (REE) patterns and was characterized by lower ΣREE content and lack of pronounced negative Eu anomalies. Whole-rock and zircon Dy/Yb ratios showed no correlation with whole-rock Rb/Sr ratios and zircon Hf contents, reflecting limited effects of crystal fractionation. The Ba/La ratios were also high (>150), but the Sr/Y and La/Yb ratios were low (Sr/Y < 50; La/Yb < 15). These features likely indicate that the quartz porphyry was generated by water-fluxed melting without differentiation. The rhyolite porphyry and biotite granite shared many geochemical similarities, denoting a unified source. The high La/Yb (>30) but low Sr/Y (<20) ratios and apparent negative Eu anomalies indicated plagioclase fractionation. Decreased zircon Dy/Yb with increasing Hf concentrations reflected noticeable amphibole fractionation. These two suites had fairly low Ba/La ratios. These data together point toward an identical source: dehydration melting of a relatively thickened crust. These melts experienced crystal fractionation after extraction. We propose that the intrusions were generated by the underplating of water-rich mafic magma, which provided both fluid and heat and finally induced two kinds of melting.

 Jiaodong North China Craton granite petrogenesis crustal reworking National Natural Science Foundation of China10.13039/501100001809 National Key Research and Development Program of China10.13039/501100012166 Fundamental Research Funds for the Central Universities10.13039/501100012226 1 Introduction

Cratons are generally considered the most stable part of the lithosphere because the great thickness of the continental mantle beneath cratons prevents them from being destroyed by the convective mantle. However, decades of research have greatly improved our understanding and we now know that stable cratons can be destroyed (Gao et al., 2004; Xu et al., 2009; Lee et al., 2011; Wu et al., 2019). The NCC has stabilized following the amalgamation between the western and eastern blocks at about 1.9 Ga (Zhao et al., 2005). However, it was reworked during the Mesozoic and the thick lithosphere underwent extensive thinning, particularly at the eastern part of the NCC (Menzies et al., 2007; Chen et al., 2008; Wu et al., 2019). The destruction of NCC was accompanied by crustal reworking and the development of extensional structures and many metamorphic core complexes (like the Gudaoling and Linglong) and sedimentary basins (Charles et al., 2012; Meng et al., 2019; Wu et al., 2019; Zheng and Gao, 2021). Thus, these processes are used as indicators of decratonization in the NCC.

This thinning process of the lithosphere mantle can be traced at the shallow crustal levels by Jurassic-Cretaceous granitic rocks, as they represent thermal or tectonic disturbances underneath the thick crust (Chappell, 2004; Weinberg and Hasalová, 2015; Gao et al., 2016; Zheng and Gao, 2021). Although extensive studies have been conducted on these magmatic rocks to demonstrate the timing and mechanisms of NCC destruction, some divergences exist regarding the timing and duration of the NCC destruction. The onset of NCC destruction remains elusive because the understanding of “destruction” differs (Xu et al., 2009). The northern and southern margins of the NCC were subducted by the Paleo-Asian Oceanic slab and the South China Block during the Carboniferous-Permian and Late Triassic, respectively (Windley et al., 2010). The resultant magmatism in the northern and southern margins indicated changes in lithospheric structure and thermal structure. Following this logic, the NCC destruction initiated in different craton margins in the Carboniferous and Triassic (Xu et al., 2009). Nevertheless, the destruction of NCC is now broadly recognized to have peaked in the Early Cretaceous (Wu et al., 2005a), as indicated by extensive granitic magmatism associated with mantle-crust interactions.

The mechanism of lithosphere thinning also remains under debate. One school of thought argues that the thinning occurs mechanically by delamination (Gao et al., 2004; Ma et al., 2014), while other researchers believe that the thinning proceeds gradually via a thermal-chemical erosion process (Xu et al., 2009; Geng et al., 2019). Hou et al. (2007) inferred that the ∼130 Ma Guojialing suite adakitic granitoids were formed by crustal thickening during the descent into the asthenosphere (delamination). Ma et al. (2014) proposed that the lithosphere mantle was rapidly replaced by the fertile asthenosphere mantle at ca. 120 Ma by delamination based on investigations of the mafic dykes in Jiaodong. These results drive the timing of delamination, if it occurred, towards later times. Therefore, the genesis of these Early Cretaceous magmatic rocks is crucial for understanding the crustal evolution of the NCC. However, how these granitic rocks were generated remains undetermined in the NCC (e.g., fluid fluxed or dehydration melting), particularly those magmatic rocks formed at ca. 120 Ma. This impedes our knowledge of decratonization processes. This study investigated the petrogenesis of the granitic rocks that intruded into the Jurassic Linglong granite in the Dazeshan region in Jiaodong Penisular, to reveal the crustal reworking processes.

 2 Geological background

The Jiaodong Penisular is an integral part of the NCC, which has Early Archean crustal remnants (Jahn and Zhang, 1984; Liu et al., 1992). The NCC was stabilized through the amalgamation of the eastern and western blocks during a Paleoproterozoic orogenic event along the Trans-North China Orogen (Figure 1) (Zhao, 2001). Both blocks are dominated by Late Archaean tonalitic–trondhjemitic–granodioritic (TTG) gneiss complexes with minor supracrustal rocks with metamorphic ages of ∼2.5 Ga (Zhao, 2001). The Jiaodong Penisula is located in the southeastern part of the NCC and was displaced to its current location by the approximately 2,400 km Tanlu fault (Zhu et al., 2009). Three main tectonic units constitute the Jiaodong Peninsula: the Jiaobei terrane, the Sulu orogen, and the Jiaolai basin (Figure 1).

(A) Geological map of the Jiaodong Peninsula, showing major structures, lithological units, and study area (Song et al., 2021). (B) The U-Pb ages obtained in this study are noted on the map.

The Jiaobei terrane, an integral part of the NCC, comprises Archean-Paleozoic metamorphic rocks and TTG gneiss (such as biotite gneiss and plagioclase amphibolite). These rock units are mainly located in the Qixia area. The Jurassic Linglong granite, along with the Luanjianhe and Biguo granites, intrudes into the Precambrian rocks and together constitute the composite Linglong pluton (Figure 1). The zircon U-Pb ages of this composite pluton range from 170 to 150 Ma (Yang et al., 2012; Yang et al., 2017). The volumetrically smaller Guojialing, Congjia, Beijie, and Shangzhuang granodiorite were subsequently emplaced during the Early Cretaceous. The zircon U-Pb ages of these plutonic rocks range from 130 to 127 Ma (Yang et al., 2012; Jiang et al., 2016). The Aishan and Nansu porphyry granites, which feature large K-feldspar phenosrysts, are emplaced within the Guojialing granodiorite and the Linglong granite, respectively, and have zircon U-Pb ages of 118–116 Ma (Goss et al., 2010; Li et al., 2012). The Sulu orogen is situated to the east of the Wulian-Qingdao-Yantai fault and is considered the suture zone separating the NCC and South China Block (Wu and Zheng, 2013). Many ultrahigh- to high-pressure metamorphic rocks are preserved in the Sulu orogen. Additionally, the Triassic alkaline complex in the Rongcheng area (Shidao) dates to 225–205 Ma and represents magmatism related to mantle upwelling after continent-continent collision (Chen et al., 2003). The Jiaolai basin comprises volcanic and sedimentary sequences deposited in the Early Cretaceous (Zhang et al., 2008). The main volcanic rocks in the Jiaolai basin are Qingshan group basic to felsic rocks, including rhyolite, andesite, dacite, and tuff. Laiyang and Wangshi group sedimentary rocks (sandstone and mudstone) cover the Qingshan group volcanic rocks. Cenozoic basalt, although rarely exposed, is mainly reported in the Penglai area (Figure 1).

 3 Samples and analytical methods

The samples investigated in this study were collected in the Dazeshan region at the Jiaobei terrane (Figure 1B). Four types of magmatic rocks were sampled: quartz porphyry (DZS-1), Linglong granite (DZS-2), rhyolite porphyry (DZS-3), and Dazeshan biotite granite (DZS-4) (Figure 2). From field observations, the quartz porphyry, rhyolite porphyry, and Dazeshan biotite granite all intruded the Linglong granite. The Linglong granite is predominantly composed of plagioclase, K-feldspar, quartz, and biotite (Figures 2A, 3A). The sizes of the plagioclase, K-feldspar, and quartz are similar (2–5 mm). The biotite crystals are smaller and appear to be tabular. The samples from the Linglong granite were fresh. The quartz porphyry is a fine-grained grayish felsic rock that contains quartz and minor K-feldspar phenocrysts (Figures 2B, 3B). The volume fraction of the quartz phenocryst is <5%. The matrix contains micron-scale quartz and feldspar crystals. The K-feldspar in both phenocrysts and matrix was subjected to weathering and formed small amounts of sericite. The rhyolite porphyry sample (DZS-3) contained quartz and K-feldspar phenocrysts (Figures 2C, 3C). The phenocrysts were approximately 2–5 mm in diameter. The Dazeshan biotite granite (DZS-4) is a coarse-grained plutonic rock that intruded into the Linglong granite (Figure 1). The Dazeshan biotite granite had the same mineral assemblages as the Linglong granite but with larger crystal sizes.

(A–D) Photographs of Linglong granite, quartz porphyry, rhyolite porphyry, and Dazeshan biotite granite.

Microscopic images of Linglong granite (A), quartz porphyry (B), rhyolite porphyry (C), and Dazeshan biotite granite (D). Abbreviations: Kfs = K-feldspar, Pl = plagioclase, Qz = quartz, Bt = biotite. The abbreviations for the minerals are after Whitney and Evans. (2010).

 3.1 Major and trace element analyses

Major element data for whole-rock samples were obtained by X-ray fluorescence (XRF) spectrometry on fused glass discs using a PANalytical AXIOS Minerals instrument at the Institute of Geology and Geophysics, Chinese Academy of Sciences. Glass discs for WD-XRF analyses were prepared by fusing 0.5 g of the standard sample with 5.0 g of lithium tetraborate-metaborate mixture (2:1) using Pt-Au crucibles and moulds on fusion equipment with gas burners. Loss on ignition (LOI) was measured as the weight loss of the samples after 1 h of baking at a constant temperature of 1,000°C in a muffle furnace. The ferrous iron content was determined using the titration method described by Xue et al. (2017). Whole-rock trace element analyses were performed at the National Research Center of Geoanalysis, Chinese Academy of Geological Science by inductively coupled plasma mass spectrometry (ICP-MS) on a TJA PQ-ExCell system. Standards GSR1 and GSR9 were used to monitor the analytical reproducibility. 2σ uncertainties are <5% for elements >10 ppm and <10% for elements <10 ppm.

 3.2 Zircon U-Pb dating and trace elements

Zircons were separated using conventional heavy liquid and magnetic separation techniques. They were mounted in epoxy and polished to a surface. Transmitted, reflected light and cathodoluminescence (CL) images were captured to acquire information about the inner structure, surface characteristics, and CL textures of the zircons, respectively. Laser ablation-inductively coupled plasma-mass spectrometry (LA-ICPMS) zircon U-Pb analyses were performed on an Agilent 7900 ICP-MS instrument equipped with a 193 nm laser ablation system at the Institute of Geology, Chinese Academy of Geological Sciences. A laser spot size of 30 μm was used to ionize the samples. The laser was operated at an energy of 2 J/cm2 and a repetition rate of 5 Hz.

 3.3 Zircon Lu-Hf isotopes

In situ zircon Lu-Hf isotopic analyses were performed on a Neptune MC-ICPMS coupled with a 193 nm laser ablation system at the National Research Center for Geoanalysis. An ArF excimer laser ablation system was used for the laser ablation analysis. The analyses used a laser repetition rate of 10 Hz at 100 mJ. A spot size of ca. 40 μm was applied depending on the size of the zircon grains. The ionized samples were carried by Ar gas. The detailed analytical procedures are described in (Wu et al., 2006).

 4 Analytical results 4.1 Whole-rock major and trace elements

Eleven sample powders from three intrusions (except for the Linglong granite) were analyzed. The whole-rock geochemical data are presented in Figures 4, 5, 6 and Table 1. Overall, the silica contents of the quartz porphyry, rhyolite porphyry, and Dazeshan biotite granite are high (74–77 wt.%). In the total alkali vs. silica diagram (Figure 4A), these samples plot in the granite field. They belong to the high-K calc-alkaline series in the plot of SiO2 vs. K2O diagram (Figure 4B). In the plots of SiO2 vs. CaO, Al2O3, MgO, TFeO, TiO2, and P2O5, the three types of magmatic rocks display distinct major element contents (Figure 5). CaO concentrations in the Dazeshan biotite granite are the highest among the samples, while the quartz porphyry and rhyolite porphyry have CaO contents around 0.4 wt.%. The aluminum content for the quartz porphyry is the highest among the three intrusions (14.01–14.34 wt.%), about 1–2 wt.% higher than the other two suites. The Al2O3 contents in the Dazeshan biotite granite are in the range of 13.22–13.29 wt.%. The MgO concentrations in the intrusions are low (<0.4 wt.%) and show negative correlations with SiO2 (Figure 5C). Total FeO contents are lower in the quartz porphyry and rhyolite porphyry (1.11–1.40 wt.% and 1.07–1.12 wt.%, respectively) and higher in the Dazeshan biotite granite (1.63–1.72 wt.%) (Figure 5D). The concentrations of TiO2 and P2O5 are elevated in the Dazeshan biotite granite compared to those in the quartz and rhyolite porphyries (Figures 5E, F).

Total alkaline vs. SiO2 (A) and SiO2 vs. K2O (B) diagrams (Peccerillo and Taylor, 1976; Le Bas et al., 1986).

(A–F) Harker-type diagrams of whole-rock CaO, Al2O3, MgO, total FeO, TiO2, and P2O5 versus SiO2 contents for the studied intrusions.

Primitive mantle-normalized REE patterns (A) and trace element variation diagrams (B) for the quartz porphyry, rhyolite porphyry, and Dazeshan biotite granite. The normalization values are from McDonough and Sun (1995). Black line: average granulite terrane/xenolith concentrations in the NCC (Jahn and Zhang, 1984; Liu et al., 2001; Zhai et al., 2001).

Major (wt %) and trace (ppm) element concentrations for igneous rocks in the Dazeshan region.

DZS-1A DZS-1B DZS-1E DZS-3A DZS-3B DZS-3D DZS-3E DZS-4A DZS-4B DZS-4D DZS-4E
SiO2 75.23 75.06 75.18 76.83 77.04 76.75 77.02 74.96 75.04 74.89 75.11
Al2O3 14.25 14.01 14.34 12.79 12.65 12.69 12.71 13.28 13.26 13.22 13.29
TFe2O3 1.11 1.40 1.26 1.12 1.07 1.08 1.11 1.63 1.72 1.71 1.66
MgO 0.18 0.28 0.21 0.13 0.13 0.14 0.12 0.31 0.26 0.29 0.30
CaO 0.35 0.33 0.37 0.42 0.39 0.44 0.41 0.96 0.81 0.76 0.93
Na2O 4.01 3.74 3.93 3.97 3.89 3.93 3.88 3.90 3.88 3.92 3.87
K2O 4.44 4.21 4.35 4.67 4.74 4.72 4.70 4.67 4.64 4.62 4.65
TiO2 0.10 0.11 0.10 0.11 0.11 0.10 0.11 0.16 0.14 0.15 0.13
P2O5 0.02 0.03 0.03 0.02 0.02 0.03 0.03 0.05 0.04 0.04 0.05
MnO 0.01 0.01 0.01 0.01 0.02 0.02 0.01 0.04 0.04 0.03 0.05
LOI 0.67 0.97 0.92 0.33 0.28 0.30 0.29 0.38 0.25 0.34 0.39
Total 100.36 100.14 100.70 100.41 100.35 100.20 100.39 100.34 100.08 99.97 100.43
Mg# 24 28 24 19 16 40 38 40 48 32 34
ppm
P 88 132 131 87 87 131 131 218 175 175 218
Ti 342 344 334 428 541 460 507 779 695 713 796
Sc 1.68 1.70 1.62 1.57 1.53 1.38 1.29 2.16 2.08 2.39 2.41
V 3.68 3.11 3.99 2.25 2.89 3.36 2.79 6.88 6.41 6.48 7.03
Cr 3.63 7.78 8.75 5.70 17.6 8.57 7.70 6.60 5.58 8.37 7.96
Co 0.36 0.48 0.77 0.57 0.57 0.69 0.67 1.40 1.10 1.21 1.18
Ni 0.36 0.98 2.89 0.83 0.25 1.87 1.62 1.65 1.67 2.25 3.58
Rb 89.9 92.4 87.1 227 264 242 275 191 194 195 189
Sr 194 179 162 23 28 24 22 174 157 153 181
Zr 63.8 58.1 56.7 66.9 87.0 67.9 80.3 90.5 86.8 92.1 90.9
Nb 5.12 4.77 4.84 16.9 20.5 18.1 20.9 16.0 16.6 16.6 16.1
Ba 1,114 1,084 1,014 75.1 88.6 87.6 76.3 660 528 570 682
Y 3.86 4.37 3.97 4.24 4.66 4.74 4.70 8.11 9.36 7.31 9.32
La 5.27 6.32 6.24 18.7 22.9 21.9 26.4 38.6 31.4 25.0 39.1
Ce 7.17 10.6 9.27 32.4 40.5 37.3 45.1 62.8 56.7 46.9 72.3
Pr 0.94 1.29 1.24 3.26 3.99 3.69 4.66 6.10 5.42 4.40 6.81
Nd 3.52 4.77 4.47 10.2 12.3 11.0 14.3 17.9 17.9 13.8 20.9
Sm 0.88 1.19 1.09 1.43 1.73 1.60 2.02 2.81 3.17 2.21 3.63
Eu 0.26 0.33 0.30 0.17 0.18 0.17 0.20 0.45 0.44 0.36 0.52
Gd 0.75 1.03 0.93 0.78 0.92 0.91 1.09 1.58 2.11 1.43 2.30
Tb 0.12 0.15 0.13 0.12 0.15 0.14 0.16 0.25 0.32 0.20 0.33
Dy 0.69 0.83 0.76 0.59 0.67 0.66 0.66 1.19 1.52 1.04 1.48
Ho 0.14 0.16 0.15 0.14 0.16 0.16 0.16 0.27 0.33 0.24 0.33
Er 0.42 0.48 0.44 0.48 0.56 0.53 0.54 0.85 1.05 0.76 0.98
Tm 0.06 0.06 0.06 0.08 0.09 0.09 0.09 0.13 0.16 0.13 0.16
Yb 0.44 0.46 0.44 0.65 0.76 0.73 0.73 0.99 1.18 0.98 1.16
Lu 0.06 0.06 0.06 0.11 0.12 0.12 0.13 0.16 0.19 0.17 0.17
Hf 2.67 2.61 2.49 3.20 3.95 3.31 3.83 3.46 3.54 3.73 3.72
Ta 0.44 0.46 0.42 1.56 1.82 1.62 1.87 1.53 2.08 1.67 1.99
Pb 20.2 14.2 14.7 33.7 36.8 33.9 36.9 35.6 36.9 33.9 36.6
Th 1.97 2.10 2.02 23.5 26.7 25.7 25.9 22.2 20.9 23.0 19.5
U 1.11 1.30 1.27 3.27 3.63 3.32 3.45 5.81 6.42 6.88 4.89
Cs 0.81 0.80 0.85 1.76 1.96 1.92 2.14 3.82 5.89 3.79 6.38
Cu 3.28 4.29 6.01 5.72 2.90 5.06 4.71 3.83 3.76 5.39 5.06
Zn 6.28 4.47 5.58 1.37 1.62 1.52 1.98 12.9 13.4 11.6 14.3
Ga 16.3 17.4 17.0 14.3 17.3 15.5 17.7 17.1 17.1 15.2 18.1
Bi 0.05 0.09 0.09 0.03 0.02 0.02 0.03 0.12 0.19 0.11 0.22

The whole-rock trace element data are normalized to the primitive mantle (PM) in REE and spider diagrams (Figure 6). In the REE diagram, the three intrusions display different enrichment and/or depletion patterns. The samples from quartz porphyry have low contents of total REE (20.7–27.7 ppm). Additionally, the light rare earth elements (La-Eu; LREE) are not strongly fractionated from the heavy rare earth elements (Gd-Lu; HREE) given the LREE/HREE ratios from 6.8 to 7.6. No apparent negative Eu anomaly is observed in the PM-normalized REE pattern. The calculated Eu/Eu* values range from 0.89 to 0.98 for the quartz porphyry samples (Eu/Eu* represents the europium anomaly calculated as EuN/(SmN×GdN)0.5, the subscript “N” denotes the PM normalized value from McDonough and Sun, 1995). In the spider diagram (Figure 6B), high field strength elements (HFSE) like P and Ti in the quartz porphyry show negative anomalies. However, the large ion lithophile elements (LILE) like Rb and Ba, along with fluid mobile element Pb, are strongly enriched.

The REE patterns for the rhyolite porphyry and Dazeshan biotite granite show contrasting features compared to the quartz porphyry. Generally, these two intrusions have elevated REE concentrations compared to the quartz porphyry and display listric-shaped patterns. Y These two porphyries also show obvious negative Eu anomalies. The Eu/Eu* for the rhyolite porphyry and Dazeshan biotite granite are 0.40–0.48 and 0.52–0.66, respectively. The LREE and HREE are strongly fractionated in these two intrusions. The LREE/HREE ratios are 23.7–26.0 for the rhyolite porphyry and 16.8–26.8 for the Dazeshan biotite granite. However, the Dazeshan biotite granite has higher total REE concentrations than that of the rhyolite porphyry (97.6–150.2 ppm vs. 69.7–96.4 ppm). In the spider diagram, the rhyolite porphyry and Dazeshan biotite granite display overall similar patterns except for Ba and Sr. The rhyolite porphyry shows more depletion of these two elements compared to the Dazeshan biotite granite (Figure 6B). Elements from Th to Pb in Figure 6B are elevated compared to the quartz porphyry.

 4.2 Zircon U-Pb ages and trace elements

Four sets of zircon U-Pb ages and trace element data were obtained in this study. The analytical results are presented in Figures 7, 8 and Table 2 and Table 3. The LA-ICPMS zircon data from each rock type are briefly described below.

Zircon U-Pb concordia and weighted mean 238U/206Pb ages of the studied magmatic rocks. The red circles in the zircon grains are analytical spots and are 30 μm in diameter. (A,B) Quartz porphyry; (C,D) Linglong granite; (E,F) rhyolite porphyry; (G,H) Dazeshan biotite granite.

Zircon REE concentrations of quartz porphyry, Linglong granite, rhyolite porphyry, and Dazeshan biotite granite, respectively (A–D). The normalization values are from Sun and McDonough (1989).

LA-ICPMS U-Pb age data for zircons from Dazeshan magmatic rocks.

No. 207 Pb/235U ±σ % 206 Pb/238U ±σ % ρ 207Pb/206 Pb ±σ % 207Pb/206 Pb age (Ma) ±σ 206 Pb/238U age (Ma) ±σ 207 Pb/235U age (Ma) ±σ U (ppm) Th (ppm) Th/U
DZS-1A
1 0.1297 0.0039 0.0188 0.0003 0.1710 0.0494 0.0015 150 65 120.1 1.9 123.5 3.5 1,307 758 0.58
2 0.1321 0.0075 0.0184 0.0003 0.0470 0.0518 0.0030 180 110 117.5 2.1 125.0 6.7 316 211 0.67
3 0.1332 0.0090 0.0188 0.0004 0.0568 0.0514 0.0035 140 130 120.1 2.4 125.7 8.0 230 237 1.03
4 0.1271 0.0092 0.0185 0.0004 0.1030 0.0502 0.0037 110 140 117.9 2.4 120.2 8.3 196 144 0.74
5 0.1231 0.0058 0.0185 0.0003 0.1388 0.0485 0.0024 77 97 118.1 2.0 117.3 5.2 515 358 0.70
6 0.1175 0.0082 0.0184 0.0004 0.0592 0.0461 0.0034 −30 130 117.7 2.4 112.7 7.6 259 209 0.81
7 0.1252 0.0086 0.0185 0.0004 −0.0354 0.0494 0.0036 70 140 118.3 2.6 118.6 7.8 180 91 0.51
8 0.1226 0.0077 0.0182 0.0004 0.1759 0.0482 0.0030 70 120 116.4 2.5 116.6 7.0 267 127 0.47
9 0.1210 0.0026 0.0184 0.0003 0.3541 0.0475 0.0010 75 46 117.3 1.9 115.8 2.4 3,411 2084 0.61
10 0.1200 0.0110 0.0183 0.0004 0.1542 0.0476 0.0044 10 170 117.1 2.7 114.0 10.0 184 115 0.62
11 0.1242 0.0052 0.0185 0.0004 0.3177 0.0487 0.0020 117 86 118.2 2.4 118.6 4.7 1,119 471 0.42
12 0.1292 0.0027 0.0187 0.0003 0.2960 0.0494 0.0011 154 46 119.5 1.8 123.2 2.4 2,601 1,356 0.52
13 0.1247 0.0061 0.0189 0.0004 0.0785 0.0481 0.0025 56 98 120.5 2.2 118.7 5.5 466 211 0.45
14 0.1295 0.0078 0.0196 0.0005 0.1936 0.0481 0.0029 60 120 125.1 3.0 123.7 7.2 270 135 0.50
15 0.1272 0.0040 0.0191 0.0004 0.2233 0.0484 0.0016 97 68 121.8 2.3 121.8 3.7 1,206 862 0.71
16 0.1240 0.0098 0.0192 0.0005 −0.0522 0.0473 0.0039 −30 150 122.5 3.2 117.4 8.8 201 200 0.99
17 0.1320 0.0110 0.0192 0.0005 0.0577 0.0507 0.0047 100 180 122.4 3.4 126.0 11.0 196 118 0.60
18 0.1327 0.0080 0.0196 0.0004 0.2092 0.0491 0.0029 90 110 124.8 2.7 125.5 7.2 262 95 0.36
19 0.1211 0.0086 0.0185 0.0004 0.2171 0.0474 0.0034 10 130 118.3 2.7 114.8 7.7 190 110 0.58
20 0.1340 0.0110 0.0187 0.0005 0.1470 0.0522 0.0042 130 150 119.3 2.9 125.9 9.6 169 74 0.43
21 0.1238 0.0079 0.0183 0.0004 0.1023 0.0486 0.0031 70 130 116.7 2.5 117.5 7.1 258 212 0.82
DZS-2A
1 0.1492 0.0036 0.0220 0.0003 0.2866 0.0490 0.0011 134 51 141.0 3.2 140.3 2.1 1844 937 0.51
2 0.1460 0.0036 0.0220 0.0003 0.3123 0.0479 0.0012 81 51 138.2 3.2 140.0 2.1 1835 1,188 0.65
3 0.1536 0.0039 0.0221 0.0003 0.2095 0.0503 0.0013 187 55 144.9 3.4 140.9 1.9 1,572 683 0.43
4 0.1536 0.0052 0.0227 0.0004 0.3013 0.0497 0.0017 157 74 144.8 4.6 144.5 2.7 1,467 789 0.54
5 0.1475 0.0028 0.0219 0.0004 0.2327 0.0489 0.0010 135 45 139.6 2.5 139.4 2.2 3,048 1866 0.61
6 0.1455 0.0033 0.0217 0.0003 0.1645 0.0485 0.0012 111 53 137.7 3.0 138.2 1.9 1,530 1,106 0.72
7 0.1465 0.0055 0.0215 0.0003 0.1122 0.0492 0.0018 137 80 138.8 4.9 137.1 2.0 593 188 0.32
8 0.1521 0.0061 0.0218 0.0003 0.0626 0.0508 0.0021 192 85 143.9 5.5 139.2 2.1 632 172 0.27
9 0.1454 0.0097 0.0221 0.0005 -0.0327 0.0478 0.0032 50 130 136.5 8.6 140.8 2.9 217 87 0.40
10 0.1536 0.0050 0.0218 0.0004 0.2430 0.0508 0.0016 209 68 144.8 4.4 139.2 2.2 852 258 0.30
11 0.1573 0.0056 0.0221 0.0004 0.2835 0.0514 0.0018 218 75 147.9 4.9 141.0 2.6 662 202 0.30
12 0.1508 0.0071 0.0225 0.0005 0.3310 0.0485 0.0022 100 93 141.9 6.3 143.5 3.2 453 58 0.13
13 0.1478 0.0043 0.0220 0.0004 0.2735 0.0484 0.0014 104 61 139.7 3.8 140.3 2.3 1,444 1,360 0.94
14 0.1540 0.0057 0.0221 0.0004 0.3470 0.0500 0.0017 167 72 145.0 5.0 140.8 2.8 849 72 0.08
15 0.1463 0.0077 0.0224 0.0005 0.3108 0.0469 0.0024 7 97 137.7 6.8 142.8 3.4 348 450 1.29
16 0.1553 0.0076 0.0224 0.0006 0.2971 0.0500 0.0024 180 100 146.2 6.6 142.9 3.5 876 68 0.08
17 6.7600 0.1300 0.3787 0.0056 0.4781 0.1295 0.0023 2078 30 2080 17.0 2069 26.0 134 85 0.63
18 5.0900 0.2300 0.3190 0.0077 0.2145 0.1181 0.0056 1838 86 1814 38.0 1781 37.0 14 40 2.85
19 5.3900 0.1200 0.3425 0.0072 0.5861 0.1123 0.0021 1826 35 1878 19.0 1900 35.0 164 96 0.59
20 0.1716 0.0078 0.0226 0.0005 0.3789 0.0546 0.0023 345 90 160.2 6.7 143.8 2.8 869 244 0.28
21 1.7700 0.2300 0.1120 0.0130 0.9813 0.1054 0.0034 1,687 63 921.0 78.0 668.0 71.0 349 86 0.25
22 0.2270 0.0170 0.0241 0.0006 0.3051 0.0678 0.0047 710 130 206.0 14.0 153.2 3.5 418 150 0.36
23 0.5630 0.0680 0.0451 0.0035 0.9629 0.0813 0.0036 1,144 89 423.0 38.0 283.0 21.0 480 160 0.33
DZS-3A
1 0.1331 0.0062 0.0188 0.0004 0.0072 0.0508 0.0025 180 100 126.3 5.6 119.8 2.3 360 187 0.52
2 0.1223 0.0086 0.0187 0.0004 0.0557 0.0472 0.0035 −10 130 116.1 7.7 119.5 2.6 236 224 0.95
3 0.1270 0.0045 0.0190 0.0003 0.2608 0.0480 0.0017 81 73 121.1 4.1 121.4 2.2 885 337 0.38
4 0.1287 0.0063 0.0187 0.0003 0.2528 0.0493 0.0024 121 98 122.3 5.6 119.6 2.2 374 255 0.68
5 0.1254 0.0044 0.0190 0.0003 0.1855 0.0473 0.0016 56 72 119.7 4.0 121.3 2.1 1,101 463 0.42
6 0.1245 0.0062 0.0187 0.0004 0.0921 0.0480 0.0024 60 100 118.5 5.6 119.2 2.3 375 228 0.61
7 0.1262 0.0075 0.0192 0.0004 0.0237 0.0479 0.0030 30 120 119.7 6.8 122.6 2.7 260 237 0.91
8 0.1270 0.0100 0.0187 0.0005 -0.0235 0.0492 0.0040 60 150 120.2 8.9 119.1 3.0 179 283 1.58
9 0.1251 0.0045 0.0189 0.0004 0.2859 0.0479 0.0017 91 72 119.4 4.1 120.5 2.2 998 691 0.69
10 0.1247 0.0038 0.0188 0.0003 0.3156 0.0482 0.0015 89 64 119.1 3.4 120.3 2.1 1,278 1,037 0.81
11 0.1228 0.0060 0.0187 0.0004 0.2471 0.0479 0.0023 68 97 117.1 5.4 119.5 2.4 483 261 0.54
12 0.1266 0.0057 0.0185 0.0004 0.0700 0.0497 0.0025 130 100 121.3 5.0 117.8 2.6 512 241 0.47
13 0.1275 0.0059 0.0188 0.0004 0.1818 0.0499 0.0024 136 98 121.9 5.4 119.9 2.5 435 353 0.81
14 0.1335 0.0041 0.0195 0.0004 0.3119 0.0500 0.0015 170 63 126.9 3.7 124.3 2.2 1,533 921 0.60
15 0.1270 0.0057 0.0188 0.0004 0.1453 0.0497 0.0024 128 96 120.9 5.2 120.1 2.5 492 234 0.48
16 0.1263 0.0039 0.0186 0.0004 0.2897 0.0496 0.0016 153 65 120.6 3.5 119.0 2.3 1,235 523 0.42
17 0.1250 0.0046 0.0189 0.0004 0.1310 0.0484 0.0019 94 78 119.2 4.1 120.9 2.2 799 409 0.51
18 0.1270 0.0070 0.0186 0.0004 0.1238 0.0498 0.0028 130 110 120.7 6.3 118.8 2.7 348 189 0.54
19 0.1247 0.0058 0.0189 0.0004 0.0851 0.0484 0.0024 87 98 119.5 5.4 120.8 2.6 544 290 0.53
20 0.1339 0.0092 0.0192 0.0005 0.0650 0.0517 0.0037 160 140 127.4 8.4 122.4 3.1 211 251 1.19
21 0.1308 0.0075 0.0191 0.0005 0.0510 0.0504 0.0030 150 120 124.1 6.7 121.7 3.2 281 279 0.99
22 0.1278 0.0088 0.0192 0.0004 0.1647 0.0490 0.0034 70 130 120.9 7.9 122.8 2.8 265 191 0.72
23 0.1288 0.0064 0.0190 0.0004 0.1900 0.0496 0.0024 135 99 122.4 5.8 121.5 2.8 442 239 0.54
24 0.1198 0.0099 0.0191 0.0005 0.1635 0.0461 0.0038 −70 150 113.3 8.9 121.9 3.2 185 305 1.65
DZS-4A
1 0.1257 0.0078 0.0188 0.0003 0.0917 0.0490 0.0031 70 120 119.3 7.0 120.3 2.1 284 203 0.72
2 0.1238 0.0093 0.0192 0.0004 0.1395 0.0472 0.0035 −20 140 117.9 8.4 122.6 2.6 208 235 1.13
3 0.1232 0.0028 0.0185 0.0003 0.4343 0.0484 0.0010 121 47 117.8 2.5 118.3 2.0 3,275 2,233 0.68
4 0.1226 0.0056 0.0187 0.0004 0.1726 0.0485 0.0024 77 96 116.9 5.0 119.1 2.7 403 390 0.97
5 0.1223 0.0048 0.0185 0.0003 0.3027 0.0483 0.0017 99 74 117.3 4.3 118.3 2.1 1,021 539 0.53
6 0.1292 0.0062 0.0188 0.0004 0.1193 0.0497 0.0024 150 99 122.7 5.6 119.9 2.6 540 787 1.46
7 0.1274 0.0044 0.0193 0.0003 0.2315 0.0483 0.0016 94 69 121.5 3.9 122.9 2.2 1,215 715 0.59
8 0.1270 0.0061 0.0187 0.0005 0.1663 0.0496 0.0025 150 100 121.0 5.5 119.1 2.9 707 676 0.96
9 0.1264 0.0076 0.0186 0.0004 0.0393 0.0501 0.0032 110 120 120.0 6.8 118.7 2.6 353 271 0.77
10 0.1273 0.0035 0.0187 0.0004 0.4760 0.0497 0.0012 167 53 121.4 3.1 119.1 2.4 2,703 1,268 0.47
11 0.1317 0.0043 0.0189 0.0003 0.2500 0.0509 0.0017 204 71 125.4 3.9 120.8 2.1 1,351 1,032 0.76
12 0.1254 0.0043 0.0186 0.0004 0.2975 0.0488 0.0016 118 71 119.7 3.9 119.1 2.3 1,159 679 0.59
13 0.1227 0.0062 0.0186 0.0004 0.1707 0.0478 0.0023 80 100 117.0 5.5 118.9 2.6 550 406 0.74
14 0.1287 0.0058 0.0193 0.0004 0.3724 0.0487 0.0020 111 83 122.5 5.2 123.1 2.6 940 790 0.84
15 0.1305 0.0037 0.0189 0.0004 0.4446 0.0500 0.0013 184 57 124.3 3.3 120.5 2.6 1825 1,428 0.78
16 0.1342 0.0058 0.0195 0.0004 0.1741 0.0507 0.0022 186 92 128.7 5.5 124.4 2.6 626 561 0.90
17 0.1268 0.0077 0.0189 0.0004 0.2470 0.0494 0.0030 90 120 121.1 7.1 120.6 2.8 298 230 0.77
18 0.1259 0.0070 0.0186 0.0004 0.1977 0.0496 0.0028 110 110 120.4 6.4 119.0 2.8 315 214 0.68
19 0.1242 0.0064 0.0188 0.0005 0.1944 0.0480 0.0025 90 100 119.0 5.9 119.9 3.0 409 279 0.68
20 0.1344 0.0060 0.0189 0.0004 0.2450 0.0519 0.0023 229 94 128.1 5.5 120.5 2.7 504 377 0.75
21 0.1236 0.0054 0.0185 0.0004 0.1627 0.0485 0.0021 104 90 117.8 4.9 118.3 2.5 568 396 0.70
22 0.1238 0.0066 0.0189 0.0006 0.2921 0.0476 0.0024 70 100 117.9 6.0 120.5 3.5 419 339 0.81
23 0.1268 0.0093 0.0185 0.0005 0.0179 0.0504 0.0039 100 150 119.8 8.4 117.8 3.4 181 148 0.82
24 0.1200 0.0078 0.0184 0.0005 0.0888 0.0480 0.0032 20 130 114.2 7.0 117.4 3.0 254 221 0.87
25 0.1231 0.0095 0.0185 0.0005 0.1911 0.0485 0.0038 20 140 116.5 8.5 118.2 3.2 189 155 0.82
26 0.1282 0.0084 0.0186 0.0005 0.2125 0.0503 0.0033 120 130 121.4 7.5 118.6 3.1 386 435 1.13

Zircon trace element data for zircons from Dazeshan magmatic rocks.

Age P Ti Y Nb La Ce Pr Nd Sm Eu Gd Tb Dy Ho Er Tm Yb Lu Hf
DZS_1A_3 120.1 440 7.6 3,600 15.3 0.005 51.4 0.083 1.66 8.61 5.52 64.3 23.6 304 117 559 115 1,034 200 11,160
DZS_1A_4 117.5 200 5.7 1,648 2.8 0.037 32.7 0.143 2.78 6.49 3.69 35.8 11.8 141 53.1 255 53.1 475 97.1 10,180
DZS_1A_6 120.1 260 8.5 1,680 2.0 0.036 48.4 0.294 4.72 10.1 5.75 49.6 14.6 155 56.1 264 51.6 467 97.2 9,170
DZS_1A_7 117.9 326 5.4 1,519 1.5 0.001 37.0 0.162 2.71 5.48 3.31 31.6 10.1 126 48.1 244 52.2 470 103 8,650
DZS_1A_8 118.1 302 4.5 2040 3.2 0.003 26.1 0.093 1.22 5.37 3.12 35.0 12.4 168 65.9 346 69.4 620 128 10,810
DZS_1A_9 117.7 245 8.9 1700 2.9 0.002 45.9 0.161 3.21 7.31 4.04 41.8 13.1 159 56.7 269 55.0 481 100 9,440
DZS_1A_10 118.3 152 4.6 976 1.0 0.050 20.6 0.164 3.21 5.81 2.95 25.9 7.57 88.6 31.9 151 31.5 284 58.6 9,950
DZS_1A_11 116.4 207 8.9 1,524 2.9 0.041 36.3 0.126 1.98 4.40 2.66 27.9 10.1 127 48.7 246 49.7 450 95.1 9,730
DZS_1A_12 117.3 329 10.2 4,190 35.0 — 58.9 0.093 2.30 13.1 7.83 94.6 33.2 395 140 606 117 934 171 13,710
DZS_1A_14 117.1 230 4.2 1,230 1.3 0.013 24.6 0.180 3.68 6.80 3.43 30.6 9.39 110 39.9 190 42.0 376 79.2 9,970
DZS_1A_15 118.2 301 8.6 3,690 15.2 — 47.2 0.066 1.58 7.13 5.56 63.4 23.8 311 121 576 115 1,005 194 12,110
DZS_1A_16 119.5 312 9.3 3,860 32.5 0.052 52.5 0.096 1.91 10.6 6.77 77.5 28.6 358 129 580 110 924 166 13,360
DZS_1A_18 120.5 217 10.0 2,595 7.3 — 50.1 0.097 1.86 5.69 4.10 47.1 17.3 221 86.3 409 80.5 718 143 10,920
DZS_1A_19 125.1 192 8.8 1,607 3.6 0.042 39.1 0.162 2.97 5.94 2.92 32.1 11.3 140 54.1 256 52.7 489 99.2 9,870
DZS_1A_20 121.8 272 11.3 2,880 16.0 — 61.1 0.109 2.66 9.23 5.86 64.6 21.5 261 96.4 441 86.4 759 143 11,110
DZS_1A_21 122.5 281 10.2 1884 2.5 0.018 59.9 0.288 5.38 9.34 5.05 48.6 14.4 175 65.7 300 61.5 561 117 8,710
DZS_1A_22 122.4 249 5.3 1,310 1.6 0.008 25.4 0.155 3.01 5.09 3.10 28.6 8.76 110 41.1 209 44.5 430 89.2 9,710
DZS_1A_23 124.8 191 7.9 1,362 3.7 0.002 28.3 0.090 1.49 4.03 2.42 26.1 9.34 115 46.6 227 47.4 406 88.4 9,970
DZS_1A_24 118.3 212 10.1 1,294 2.3 — 35.1 0.112 2.09 4.29 2.55 26.6 9.03 112 41.7 201 44.2 394 84.3 9,280
DZS_1A_26 119.3 176 7.2 1,006 1.7 — 24.1 0.098 1.59 3.28 1.87 20.5 6.74 84.4 34.2 165 34.3 312 65.2 9,390
DZS_1A_27 116.7 254 5.1 1829 2.0 0.033 48.8 0.473 7.70 13.0 7.07 56.9 15.6 179 60.5 283 58.2 545 107 10,170
DZS_2A_1 141.0 333 4.6 3,112 42.3 — 36.6 0.02 0.69 5.22 1.73 47.6 18.5 264 104 472 88.1 752 139 14,600
DZS_2A_2 138.2 556 6.0 3,990 37.4 — 41.5 0.05 1.81 8.49 1.57 69.6 25.8 355 131 568 107 843 152 15,900
DZS_2A_3 144.9 347 5.5 3,370 48.7 0.02 41.0 0.05 1.08 5.12 1.73 45.4 19.1 277 107 510 98.7 840 151 14,170
DZS_2A_4 144.8 385 10.3 5,700 36.6 — 47.6 0.07 2.09 10.9 4.43 102 38.0 492 189 825 152 1,233 213 12,450
DZS_2A_5 139.6 627 9.2 5,810 97.1 0.40 72.7 0.34 3.64 11.5 2.72 91.5 36.3 501 185 826 149 1,212 203 14,680
DZS_2A_8 137.7 288 7.8 3,121 33.2 — 40.5 0.05 1.86 7.83 2.99 58.9 22.2 278 103 455 85.9 678 125 13,210
DZS_2A_10 138.8 408 3.6 3,410 7.75 — 18.8 0.04 1.16 4.84 2.23 47.5 19.0 272 107 519 102 862 161 12,640
DZS_2A_11 143.9 499 3.7 4,330 14.2 — 22.0 0.03 0.65 5.37 2.23 49.9 22.4 330 137 674 138 1,206 229 12,260
DZS_2A_12 136.5 154 5.5 1772 2.08 0.00 9.22 0.10 1.88 4.94 3.09 35.2 11.8 148 56.1 262 49.7 428 84.9 10,220
DZS_2A_13 144.8 286 6.0 3,570 30.6 — 28.6 0.03 0.88 4.36 1.36 43.3 19.0 278 113 541 105 888 161 13,370
DZS_2A_15 147.9 391 2.9 2,790 12.6 — 16.8 0.02 0.51 3.37 1.10 34.6 15.3 223 90.5 438 87.2 765 143 12,940
DZS_2A_16 141.9 286 0.9 1,483 11.0 — 5.49 0.00 0.23 1.41 0.32 15.7 7.26 110 45.9 240 52.6 482 92.5 18,250
DZS_2A_18 139.7 344 17.9 3,850 33.2 0.01 60.2 0.39 7.90 17.2 6.87 98.3 31.1 349 122 534 97.4 778 138 12,090
DZS_2A_21 145.0 354 – 1,654 27.8 — 5.57 — — 0.90 0.18 14.3 7.35 115 55.7 289 69.4 641 125 23,950
DZS_2A_22 137.7 253 12.9 2,750 11.7 — 51.5 0.15 3.27 8.91 5.84 54.3 18.7 242 95.1 444 94.1 869 171 9,610
DZS_2A_23 146.2 349 1.3 1831 32.1 — 5.63 — — 1.11 0.20 15.8 8.52 133 55.7 319 77.0 712 140 23,900
DZS_2A_7 2078 336 5.4 996 5.10 — 17.7 0.06 1.36 2.96 0.36 21.3 7.24 90.3 34.1 161 33.1 289 58.6 10,750
DZS_2A_9 1838 198 6.1 253 0.35 — 4.09 0.03 0.33 0.90 0.09 4.94 1.92 22.0 8.42 39.2 7.98 72.2 14.9 12,150
DZS_2A_25 1826 531 4.9 1,281 8.96 — 11.6 0.02 0.54 1.96 0.38 18.3 7.86 108 44.6 225 47.2 421 81.5 11,970
DZS_2A_14 149.4 200 1.6 934 8.28 — 4.44 0.02 0.28 1.08 0.64 9.93 4.54 68.0 29.9 155 32.4 294 61.5 21,850
DZS_2A_17 160.2 563 4.1 3,850 28.5 1.72 27.1 1.03 6.73 6.62 1.52 47.0 21.3 287 120 584 113 989 175 15,540
DZS_2A_19 921.0 420 4.4 2,140 12.2 2.00 25.7 0.90 5.50 4.24 1.13 29.8 12.4 177 70.5 332 67.4 604 109 13,350
DZS_2A_20 206.0 337 6.0 2,510 5.37 0.06 13.4 0.07 1.08 4.32 2.05 36.7 14.0 198 78.8 396 78.4 735 133 10,230
DZS_2A_24 423.0 277 4.9 2,590 19.3 — 26.6 0.05 1.07 4.70 1.23 38.4 15.6 209 86.5 401 79.9 739 126 13,680
DZS_3A_2 119.8 112 3.9 734 4.05 — 36.7 0.05 0.82 2.35 0.84 13.1 4.20 53.6 21.1 112 26.7 270 60.6 10,810
DZS_3A_3 119.5 69.0 2.9 612 1.66 — 30.4 0.06 1.84 3.30 1.42 16.5 4.73 51.8 19.8 91.9 20.1 197 39.3 11,420
DZS_3A_4 121.4 51.0 1.8 526 3.21 0.00 22.9 0.03 0.52 1.07 0.41 6.89 2.35 29.8 13.1 75.6 20.6 238 57.0 14,130
DZS_3A_5 119.6 138 4.7 926 4.75 0.01 56.3 0.11 1.84 3.71 1.48 19.5 6.05 72.7 28.0 137 30.4 309 67.0 10,640
DZS_3A_6 121.3 167 2.1 848 5.02 — 30.8 0.03 0.57 1.48 0.54 9.69 3.44 46.9 21.5 127 32.6 367 92.0 12,760
DZS_3A_7 119.2 114 3.5 763 4.13 — 45.4 0.07 1.16 3.07 1.05 15.7 5.10 60.4 22.9 118 26.1 265 58.2 10,870
DZS_3A_8 122.6 288 5.1 1,085 2.71 0.02 56.5 0.26 3.76 6.75 2.60 30.9 8.66 96.7 34.0 154 31.3 292 57.1 10,220
DZS_3A_9 119.1 236 8.8 1,661 1.64 0.12 56.4 0.84 11.2 16.8 6.57 68.5 16.7 175 55.0 226 44.8 383 75.4 8,410
DZS_3A_10 120.5 123 3.4 1,461 7.41 0.01 59.4 0.13 2.39 5.25 1.64 26.8 7.91 95.7 40.2 209 51.0 513 115 11,960
DZS_3A_11 120.3 189 4.8 1805 10.5 0.45 79.8 0.33 3.68 6.59 2.02 33.2 10.1 130 50.8 252 62.1 618 132 11,160
DZS_3A_12 119.5 165 3.2 759 2.36 0.03 33.6 0.13 1.52 3.20 1.37 15.8 4.91 58.0 22.0 110 26.2 254 58.4 11,520
DZS_3A_13 117.8 132 3.3 683 3.15 0.01 28.7 0.04 1.09 2.60 0.83 12.2 3.92 48.6 20.6 103 25.7 266 63.3 11,890
DZS_3A_14 119.9 191 4.4 1,072 4.11 0.12 65.5 0.22 3.65 6.72 2.03 27.5 8.51 94.0 34.3 165 35.1 322 66.6 11,180
DZS_3A_15 124.3 125 4.2 1,582 17.3 0.03 79.1 0.09 1.36 2.96 1.02 19.0 6.99 96.6 43.0 238 60.8 670 151 12,830
DZS_3A_16 120.1 122 3.5 812 4.50 0.04 38.5 0.08 1.32 2.84 1.08 16.9 5.16 63.5 24.9 125 29.0 285 63.8 11,240
DZS_3A_17 119.0 131 2.0 993 4.34 0.03 26.3 0.07 1.01 3.29 1.18 18.1 5.95 71.1 26.8 146 33.5 361 77.1 13,170
DZS_3A_18 120.9 116 3.2 981 6.78 — 48.3 0.07 1.38 3.00 1.01 17.0 5.51 70.6 28.5 146 36.9 384 83.5 11,970
DZS_3A_19 118.8 131 4.2 808 4.29 — 44.2 0.08 1.18 2.72 1.21 15.8 5.18 65.0 24.8 124 27.1 272 58.2 10,510
DZS_3A_20 120.8 130 2.1 760 2.29 — 23.7 0.07 1.16 3.02 1.17 15.2 4.54 55.2 22.4 119 29.6 316 66.9 13,010
DZS_3A_21 122.4 304 9.3 1,260 3.80 0.07 76.2 0.34 4.39 8.01 2.90 36.6 9.64 115 40.3 189 38.7 360 69.6 8,800
DZS_3A_23 121.7 147 4.3 1,117 2.00 0.01 54.8 0.27 4.40 9.07 2.91 38.9 9.98 107 37.8 172 35.4 305 60.9 10,170
DZS_3A_24 122.8 129 4.5 743 3.72 0.11 54.3 0.12 1.64 3.29 1.28 18.1 5.18 64.7 24.7 116 27.2 252 49.8 9,970
DZS_3A_25 121.5 123 4.1 806 5.08 0.01 46.6 0.08 1.50 2.82 1.16 15.9 5.35 66.1 25.3 131 29.5 308 61.4 10,000
DZS_3A_26 121.9 221 7.4 1822 1.69 0.11 72.6 1.06 14.2 22.1 7.66 84.2 20.2 207 64.1 260 49.9 452 79.9 8,330
DZS_4A_1 120.3 106 2.9 714 3.50 — 41.5 0.06 1.18 2.78 0.88 14.5 4.80 56.4 21.5 113 24.4 238 52.2 11,420
DZS_4A_2 122.6 188 4.0 670 2.54 0.01 45.7 0.10 1.69 3.31 1.13 14.9 5.10 60.4 21.1 104 21.9 210 42.9 10,470
DZS_4A_3 118.3 157 2.6 2,331 22.4 0.30 73.4 0.16 1.70 4.00 0.88 27.7 10.4 139 61.5 353 88.9 966 214 14,730
DZS_4A_4 119.1 132 3.3 1,128 3.83 0.02 54.7 0.17 2.96 5.09 1.90 29.0 8.28 97.2 34.9 167 34.9 329 67.6 10,800
DZS_4A_5 118.3 127 3.2 896 5.67 0.13 42.7 0.14 1.59 3.37 1.11 18.2 5.41 66.9 26.3 137 31.9 312 69.2 11,940
DZS_4A_6 119.9 287 5.9 1819 6.74 0.04 135 0.46 7.45 13.0 3.69 59.4 16.1 182 61.1 274 53.4 491 94.9 9,440
DZS_4A_8 122.9 87.0 3.3 1,232 10.9 0.02 47.7 0.06 0.93 2.50 0.72 15.5 5.84 80.3 33.7 197 47.3 501 108 11,710
DZS_4A_9 119.1 108 2.7 872 5.63 0.04 55.2 0.08 1.27 3.00 0.93 15.8 5.08 66.0 24.7 128 29.4 281 61.3 11,470
DZS_4A_10 118.7 154 3.9 901 4.70 0.00 56.6 0.09 1.71 3.83 1.23 20.7 6.31 74.6 29.3 149 33.1 305 62.9 10,440
DZS_4A_11 119.1 270 2.1 1,388 13.2 0.01 62.8 0.05 0.91 2.17 0.43 13.6 5.31 78.2 36.1 216 59.0 683 151 13,610
DZS_4A_13 120.8 174 3.4 1,688 5.69 0.26 54.7 0.29 4.57 6.74 2.19 35.3 11.1 127 49.8 256 55.5 547 117 11,460
DZS_4A_14 119.1 199 2.1 710 5.47 — 22.6 0.03 0.37 1.22 0.26 8.10 2.99 41.2 17.4 113 28.6 316 70.8 12,530
DZS_4A_15 118.9 370 4.3 970 4.01 0.02 55.5 0.13 2.02 3.97 1.17 21.8 6.87 79.5 29.2 145 32.6 320 65.0 10,430
DZS_4A_16 123.1 190 4.8 1,332 7.85 0.01 76.7 0.13 2.71 5.83 1.43 29.3 9.47 109 41.7 203 47.2 431 89.6 10,780
DZS_4A_17 120.5 126 3.7 1999 9.92 0.26 60.2 0.40 5.34 8.70 2.43 42.2 12.4 152 57.5 305 70.6 736 148 12,640
DZS_4A_19 124.4 179 3.5 1,102 4.40 — 44.1 0.13 2.31 5.15 1.34 25.1 7.43 88.9 31.8 162 39.5 388 73.4 11,360
DZS_4A_20 120.6 255 4.5 888 2.60 0.01 44.4 0.14 2.15 4.62 1.32 21.4 6.43 74.9 29.8 134 31.8 265 53.4 10,730
DZS_4A_21 119.0 125 4.0 720 3.81 0.10 39.5 0.10 1.34 2.88 0.88 15.4 4.88 61.2 22.0 111 26.5 250 51.5 11,020
DZS_4A_22 119.9 135 3.8 826 5.12 — 47.6 0.08 1.28 3.24 0.95 16.1 5.27 67.7 25.1 129 29.8 290 58.5 10,500
DZS_4A_23 120.5 110 3.3 737 5.62 0.10 47.9 0.08 1.12 2.62 0.63 13.4 4.39 54.6 21.3 115 27.5 279 55.9 11,630
DZS_4A_24 118.3 145 4.4 1,108 7.26 0.08 60.5 0.10 1.59 3.40 1.09 21.6 6.89 86.6 34.8 173 41.3 413 81.6 10,820
DZS_4A_25 120.5 132 3.6 1,084 3.15 0.01 47.2 0.14 3.44 5.97 1.88 27.7 8.45 97.7 36.0 166 38.2 368 68.0 10,890
DZS_4A_26 117.8 313 4.7 666 2.19 — 44.4 0.12 1.76 3.85 1.09 17.4 5.73 60.8 20.9 102 21.7 208 38.3 9,320
DZS_4A_27 117.4 222 5.9 1,043 4.47 0.02 78.2 0.17 2.74 5.94 1.71 26.7 7.50 91.1 32.6 159 34.9 308 60.3 9,720
DZS_4A_28 118.2 423 4.1 727 2.29 4.60 59.4 1.56 9.00 4.97 1.47 20.6 6.34 63.8 23.5 115 24.5 235 42.5 9,850
DZS_4A_29 118.6 286 4.5 1,586 2.92 0.87 82.4 0.82 10.0 14.5 3.83 59.4 14.8 160 55.7 247 50.7 448 78.8 10,410
4.2.1 Quartz porphyry (DZS-1A)

Zircons from this sample are clear by microscopy and contain little mineral inclusions. Additionally, they display oscillatory zoning patterns under CL images. The lengths of these zircons are about 100–200 μm, while the widths are about 40–100 μm. Most of the zircons have a CL brighter grayish core without oscillatory zoning but are overgrown by CL dark rims with oscillatory zonings (Figure 7A). The zircon U-Pb ages in these two different areas are consistent. Twenty-one spot analyses on zircons were conducted. These isotope data cannot construct a well-defined Concordia U-Pb age but give a weighted mean 206Pb-238U age of 119.2 ± 1.0 Ma (Figures 7A, B; MSWD = 3.6, N = 21). The U and Th concentrations in the zircons have wide ranges (201–3,411 ppm and 74–2084 ppm, respectively), whereas the Th/U ratios are relatively restricted between 0.36 and 1.03, with an average value of 0.62 (Table 2).

 4.2.2 Linglong granite (DZS-2A)

Twenty-three zircons were analyzed in this sample. Most of these zircons are columnar with lengths of about 100–200 μm, and widths of 50–100 μm (mostly ∼50 μm). Mineral inclusions like apatite or rutile are common in these zircons. The zircons have simple CL textures, with or without an oscillatory zoning rim. The cores of the zircons appear to be dark gray. Inherit zircons, however, are frequently observed and featured by bright CL (Figure 7C inset). Six of the twenty-four zircons underwent Pb loss and fall out of the Concordia line, yet they construct two ages intercepting at 139 ± 37 and 1973 ± 48 Ma (MSWD = 4.9, N = 23). The two oldest zircons have 207Pb-236Pb ages of 2078 ± 30 Ma and 1838 ± 86 Ma, respectively. The young group of zircons constructs a weighted mean 206Pb-238Pb age of 140.2 ± 1.0 Ma (Figure 7D, MSWD = 2.4, N = 16). For the younger group zircons, which are considered the crystallization phase from the magma (see later discussion), the U concentrations range from 348 to 3,048 ppm, while the Th content varies between 58 and 1866 ppm (Table 2). The corresponding Th/U ratios are 0.08–1.29, with an average value of 0.47.

 4.2.3 Rhyolite porphyry (DZS-3A)

Twenty-four zircons were separated from the rhyolite porphyry sample. Zircon morphology exhibits tiny differences from the quartz porphyry and Linglong granite samples. These grains are equally sized, with length-to-width ratios of around 1.5–2.0. The lengths of most zircons are around 150 μm. Their CL characters vary. Some zircons have a bright core with CL dark/bright oscillatory zoning rims, while others have CL bright oscillatory zoning in the whole grain. Nevertheless, the zircon ages in these different areas are the same. All the zircons construct a Concordia U-Pb age of 120.7 ± 0.5 Ma (Figure 7E; MSWD = 1.7, N = 24 and a weighted mean 206Pb-238Pb age of 120.6 ± 0.5 Ma (Figure 7F; MSWD = 1.5, N = 24). The zircon U and Th concentrations are 179–1,533 ppm and 191–1,037 ppm, respectively. The average U and Th concentrations are 575 ppm and 360 ppm, respectively. The zircon Th/U ratios are 0.42–1.58.

 4.2.4 Dazeshan biotite granite (DZS-4A)

Zircons from the biotite granite are characterized by low length-to-width ratios (1–1.5). Most of these zircons are 100–150 μm in size and have CL bright/dark oscillatory zoning occupying the whole zircon grain. Generally, the CL bright zone is rimmed by a CL dark zone with or without oscillatory zoning patterns. The data of the 26 analyzed zircons yielded ages that intercept at 1,364 ± 800 Ma and 118.5 ± 2.0 Ma (Figure 7G, MSWD = 0.81). The weighted mean 206Pb-238Pb age is 119.9 ± 0.7 Ma (Figure 7H, MSWD = 1.9). The zircon U concentrations are 181–3,275 ppm, while the Th concentrations are 148–2,233 ppm. The Th/U ratios in zircons range from 0.47 to 1.46 (Table 2).

Zircon trace element data of the four samples are presented in Figure 8 and Table 3. All zircons feature HREE enrichment but LREE depletion (except for Ce, which displays a strong positive anomaly) in PM-normalized REE patterns (Figures 8A–D). Europium shows a relatively weak negative anomaly in zircons from the quartz porphyry. However, the negative Eu anomalies are strikingly obvious in the other three zircon samples.

 4.3 Zircon Lu-Hf isotopes

Zircon Hf isotopes were analyzed in rhyolite porphyry and the Dazeshan biotite granite. The hafnium isotope data are presented in Figure 9 and Table 4. For the rhyolite porphyry, 176Hf/177Hf values are 0.282133–0.282181. The calculated ε Hf (t) was −18.3 to −20.0. The two stage model ages are 3.2 to 3.4 Ga. Five spot analyses of zircons from the Dazeshan biotite granite give a176Hf/177Hf values between 0.282130 and 0.282195 (ε Hf (t) = −17.8 to −20.2).

Zircon Hf isotopic data from rhyolite porphyry (A) and Dazeshan biotite granite (B). Published zircon isotope data are compiled from Yang et al. (2012; 2017), Ma et al. (2013; 2014), and Li et al. (2019).

Zircon Hf isotope data for the rhyolite porphyry and Dazeshan biotite granite.

Spot no. 176Yb/177Hf 2σ 176Lu/177Hf 2σ 176Hf/177Hf 2σ εHf (t) TDM1 (Ma) TDM2 (Ma) fLu/Hf Age
DZS-3A-2 0.042275 0.000167 0.001093 0.000005 0.282177 0.000015 −18.5 1,521 3,290 −0.9671 119.8
DZS-3A-4 0.033602 0.000317 0.000916 0.000009 0.282133 0.000013 −20.0 1,575 3,425 −0.9724 121.4
DZS-3A-5 0.031352 0.000349 0.000776 0.000008 0.282175 0.000014 −18.5 1,510 3,292 −0.9766 119.6
DZS-3A-6 0.038969 0.000316 0.001067 0.000007 0.282181 0.000013 −18.3 1,513 3,273 −0.9679 121.3
DZS-3A-9 0.039306 0.000836 0.000937 0.000019 0.282181 0.000015 −18.4 1,508 3,276 −0.9718 119.1
DZS-3A-11 0.040962 0.000431 0.001003 0.000010 0.282140 0.000014 −19.8 1,568 3,404 −0.9698 120.3
DZS-4A-1 0.027038 0.000154 0.000678 0.000005 0.282195 0.000017 −17.8 1,479 3,229 −0.9796 120.3
DZS-4A-6 0.035255 0.000556 0.000911 0.000014 0.282161 0.000015 −19.0 1,536 3,336 −0.9726 122.9
DZS-4A-8 0.038623 0.000698 0.000964 0.000019 0.282130 0.000013 −20.2 1,580 3,436 −0.9710 119.1
DZS-4A-9 0.036108 0.000394 0.000882 0.000011 0.282147 0.000015 −19.6 1,554 3,385 −0.9734 118.7
DZS-4A-10 0.041680 0.000512 0.000988 0.000012 0.282141 0.000013 −19.8 1,566 3,402 −0.9702 119.9
5 Discussion 5.1 Genesis of the ∼120 Ma magmatic rocks

Granites are produced predominantly by anatexis of crustal rocks (Brown, 2013; Clemens et al., 2020), although in some cases, the granites are generated by fractional crystallization of mantle-derived melts (Soesoo, 2000; Thompson et al., 2002). For the samples investigated in this study, the SiO2 contents of the three intrusions (except for the Linglong granite) are very high (74–77 wt. %). Meanwhile, no considerable mafic melts occurred along with these granites (Figure 1), eliminating the possibility of fractional crystallization of mantle-derived melts. The Hf isotope compositions from the zircons also provide information on the sources of the melts well (Figure 9). The εHf(t) values are restricted for both the rhyolite porphyry and Dazeshan biotite granite (ca. −18 to −20), comparable to other granitic rocks reported in the Jiaodong Penisula (e.g., Linglong granite and Aishan granodiorite). For example, the Linglong granite was interpreted to be the melting products of the Archean lower crust, with almost no contribution from the mantle (Ma et al., 2013; Li et al., 2019). The two stage model ages calculated via zircon Hf isotope compositions are 3.2–3.4 Ga for the rhyolite porphyry and Dazeshan biotite granite (Table 4), demonstrating their ancient continental crust source. Therefore, these granite rocks are generated by crustal anatexis.

From the perspective of the whole-rock and zircon trace element data, the three intrusions have strikingly different geochemical features (Figures 6, 10). This implies that these intrusions probably experienced distinct melting or differentiation processes. The following section discusses the chemical variations in these magmatic rocks and their magmatic evolution.

Mg# vs. SiO2 (A) and Dy/Yb vs. Rb/Sr (B) diagrams. Adakite fields are adopted from Sen and Dunn (1994), Rapp and Watson (1995), and Rapp et al. (1999) and references therein.

 5.1.1 Quartz porphyry (DZS-1)

The quartz porphyry is characterized by low LREE content and a lack of negative Eu anomaly in the REE pattern (Figure 6A). The LREE concentrations in the quartz porphyry here are even lower than the average concentrations of the granulite terranes/xenoliths in the NCC, which were regarded as representative of the lower crust fragments (Liu et al., 1999; Zhai et al., 2001; Liu et al., 2004). Partial melting of the granulite rocks would give rise to higher REE content in the melt considering their incompatibility. The discordant REE patterns between the quartz porphyry and granulite terranes/xenoliths differ from what would be expected if the quartz porphyry is the melting product of lower-crust granulite. Magmatic processes like fractionation crystallization or magma mixing could exert a conspicuous influence on the compositions of the melt (DePaolo, 1981; Yang et al., 2004; Cao et al., 2022).

The whole-rock major and trace elements, trace elements ratios (Th/Nb, La/Sm, and Rb/Sr), and Mg# values vary little among the three samples from the quartz porphyry, indicating that fractionation crystallization of major mineral phases (e.g., amphibole, K-feldspar) probably plays a negligible role in generating such low REE concentrations. This supposition is supported by the fact that Dy/Yb in zircons does not decrease with increasing Hf concentrations (Figure 11A), implying no considerable amphibole fractionation (Davidson et al., 2007). Rather, Dy/Yb increases with Hf enrichment in zircons. This may indicate zircon separation, which reduces the Yb contents of the remnant melt. Eu/Eu* values in zircon are high and are not linearly correlated with Hf concentrations (Figure 11B), eliminating the potential influence of plagioclase fractionation.

Zircon Dy/Yb (A) and Eu/Eu* (B) vs. Hf contents for the studied magmatic rocks. (C) Sy/Y vs. Y plot. The adakite and normal andesite-dacite-rhyolite fields are from Richards and Kerrich (2007) and Castillo et al. (1999), respectively. (D) La/Yb vs. Yb plot. Ba/La vs. Th/Nb (E) and La/Sm (F) plots. See the text for explanation.

The effects of magma mixing, if it occurs, rely on the composition of the mixing end-members. The relatively depleted features of LREE require at least one end-member of REE-depleted melt, most likely the depleted mantle source. However, the low Mg# numbers (<30), together with low Ni and Co concentrations (<2 ppm) imply that the mantle component is not involved in the magma genesis for the quartz porphyry. Therefore, the quartz porphyry was probably generated by the remelting of the REE-depleted lower crust at around 120 Ma.

 5.1.2 Rhyolite porphyry (DZS-3)

The rhyolite porphyry also features extremely low Mg# values and low Ni and Co concentrations (Figure 10A; Table 1), ruling out the possibility of the involvement of the mantle component. These rocks show obvious Sr, P, and Ti depletion. Moreover, they are characterized by negative Eu anomalies and listric-shaped REE patterns (Figure 6A). These geochemical features imply that fractionation crystallization plays an important role in generating rhyolite porphyry. As shown in Figure 10B, whole-rock Dy/Yb ratios remain consistent with increasing Rb/Sr ratios, although the Rb/Sr ratios only show slight variation within samples. Zircon trace elements likely reflect more clear trends. The Zircon Dy/Yb ratio decreases from 0.45 to 0.1 when the Hf concentrations in zircon increase from 7,000 to 15,000 ppm (Figure 11A). Eu/Eu* values in zircon also show a decreasing trend with increasing Hf content (Figure 11B). This evidence supports the fractionation crystallization of amphibole and plagioclase. The amphibole incorporates more MREE (e.g., Dy) compared to HREE (e.g., Yb), thus leading to higher Dy/Yb values in the remnant melt (Davidson et al., 2007). Hafnium is an incompatible element during magmatic differentiation and its concentration will increase in the melt with progressive crystallization (Rollinson, 1993), which can be recorded in the co-crystallized zircon. In the current case, Dy/Yb decreases with increasing Hf content in zircon, implying amphibole fractionation. The negative Eu anomaly and decreasing zircon Eu/Eu* trend along with rising Hf concentrations reflect plagioclase fractionation because Eu preferentially partitions into plagioclase and replaces Ca in the lattice site under most geological environments.

Negative zircon Hf isotopes (−18.3 to −20.0) and the Archean two-stage Hf model ages suggest that the rhyolite porphyry is derived from the old crust source, consistent with the ancient nature of the NCC (Liu et al., 1992). Therefore, the rhyolite porphyry was derived from the melting of the ancient lower crust and experienced amphibole and plagioclase fractionation during magmatic evolution.

 5.1.3 Dazeshan biotite granite (DZS-4)

The Dazeshan biotite granite shares overall similar geochemical features to those of the rhyolite porphyry in both REE pattern and spider diagram (Figure 6). Zircon trace elements and Hf isotopic compositions were almost identical (Figures 8–9, 11). Therefore, the origin of Dazeshan biotite granite was certainly the same as that of the rhyolite porphyry (crust anatexis with limited mantle contribution). The minor differences in REE and Sr concentrations were likely the result of discrepancies in differentiation processes between these two intrusions. As noted above, the negative Eu anomaly in the PM-normalized REE pattern and low zircon Eu/Eu* values indicated plagioclase fractionation. The listric-shaped REE pattern and decreasing zircon Dy/Yb values with rising Hf concentrations reflect amphibole-dominated fractionation. Therefore, it is reasonable to conclude that the Dazeshan biotite granite is derived from the partial melting of the lower crust with subsequent fractionation crystallization.

 5.2 Multiple reworking events of the NCC lower crust

Previous studies have shown that the widely distributed Jurassic Linglong granite in the Jiaodong Penisular has adakite-like geochemical signatures with high Sr/Y and La/Yb ratios, which were considered to be the result of the melting of the thickened lower crust at the garnet stability field (Ma et al., 2013; Yang et al., 2017). The geodynamic model for the crustal thickening is probably related to the subduction of the Paleo-Pacific plate (Wu et al., 2005b; Ma et al., 2013). This left a residue with large portions of garnet in the lower crust, which by inference should be depleted of LILE and LREE due to the prior melt extraction. The crust-mantle interaction was strikingly extensive during the Early Cretaceous (∼130 Ma) given the widespread granitic and/or mafic magmatism and extensional deformation-related sedimentary basins (Wu et al., 2005b; Cai et al., 2013; Yang et al., 2018a, b; Meng et al., 2019). Furthermore, the ∼130 Ma granitic rocks in Jiaodong (e.g., Guojialing pluton), which also show adakite-like characters, were interpreted to be derived either from the melting of the delaminated eclogitic crust (Hou et al., 2007) or multi-stage magma mixing between Archean lower crust derived felsic magma and mafic lower crust-derived dioritic magma (Jiang et al., 2016).

The three intrusions are emplaced at around 120 Ma based on the zircon U-Pb ages obtained in the present study (Figure 7). These magmatic rocks were derived from the melting of the ancient lower crust of the NCC, as discussed in the previous section. The strontium concentrations for these samples (<200 ppm) are not as high as those in the Linglong and Guojialing magmatic rocks reported by Yang et al. (2012) (>300 ppm). Consequently, the Sr/Y values of the quartz porphyry, rhyolite porphyry, and the Dazeshan biotite granite are low (Figure 11C), unlike the Jurassic and Early Cretaceous granitoids in Jiaodong. However, the La/Yb ratios are high and plot within the “adakite field” (Figure 11D) (Condie, 2005; Castillo, 2006). This antinomy can be explained by the dominant crystal fractionation of amphibole and plagioclase during the magmatic evolution. As mentioned above, limited crystal fractionation occurred in the parent magma of the quartz porphyry. Therefore, the Sr/Y and La/Yb ratios probably represent its original character in these magmatic rocks. The low Sr/Y and La/Yb ratios (<50 and <15, respectively; Figures 11C, D), imply that little or no garnet remained as a residue phase in the source. Thus, the quartz porphyry may have been derived from a shallow crustal level rather than a thickened lower crust (>50 km) as in Linglong granite. Fluid flux played an important role in inducing the melting reaction because the Ba/La ratios for these samples are elevated (Figures 11E, F). Barium is a fluid mobile element, while the La is less so (Kessel et al., 2005). Therefore, the subduction-related fluid carried more Ba than La and generated high Ba/La ratios in the resultant magma.

The rhyolite porphyry and Dazeshan biotite granite, however, experienced amphibole + plagioclase fractionation, as evidenced by the geochemical data. Both suites have low Sr/Y but high La/Yb ratios. We propose that the plagioclase fractionation depleted the Sr concentration in the remnant melt but did not affect the La or Yb contents of the magma. Garnet, which retains most of the Y and Yb in the source, should have been stable when the parent magma of the rhyolite porphyry and the Dazeshan biotite granite formed. Under such a scenario, these two suites were probably generated by melting of a thicker crust compared to the quartz porphyry. These two suites were most likely formed by dehydration melting considering the low Ba/La but high Th/Nb and La/Sm ratios in these samples. Thorium is more incompatible than Nb while La is more incompatible than Sm; thus, Th/Nb and La/Sm ratios would be promoted during dehydration melting when no external element is introduced into the system.

Therefore, the melting may have occurred at different crustal levels at around 120 Ma, with distinct triggers. The fluid responsible for the fluxed melting very likely originated from the upwelling mafic magma, which was ultimately sourced from the dehydration of the subducted Paleo-Pacific plate (Windley et al., 2010; Geng et al., 2019). The dehydration melting in the case of rhyolite porphyry and the Dazeshan biotite granite may have been induced by heat loss from the underplated mafic magma. Regardless of fluid fluxed or dehydration melting, this change required a deeper source of heat and fluid. This required water-rich mafic magma, among which lithosphere mantle-derived magma is a possible candidate (Geng et al., 2019).

 6 Conclusion

The results of this study reveal that the magmatic rocks in the Dazeshan region have zircon ages of ∼120 Ma and were generated by crustal melting; however, they experienced different melting/differentiation processes. The quartz porphyry was formed by fluid-mediated melting without apparent crystal crystallization. The rhyolite porphyry and the Dazeshan biotite granite were produced by dehydration melting and underwent amphibole and plagioclase fractionation, as indicated by whole-rock and zircon trace element data. Our results imply that, in the Early Cretaceous, the lower crust of the NCC was reworked multiple times in different ways. The driving force for the reworking probably invoked the underplating of water-rich mafic magma under an extensional regime (Li et al., 2012), which not only provided fluid to generate the quartz porphyry but also released heat to promote the dehydration melting of the lower crust to form the rhyolite porphyry and biotite granite.

 Data availability statement

The original contributions presented in the study are included in the article/Supplementary Material. Further inquiries can be directed to the corresponding author.

 Author contributions

LD collected samples, performed whole-rock and zircon geochemical analyses, and wrote the manuscript. XB drew the maps and figures. CD performed the data processing. ZY reviewed and edited the manuscript.

 Funding

This study was financially supported by the National Natural Science Foundation of China-Shandong Joint Fund Program (U2006201), the National Key Research and Development Project of China (2016YFC0600305), and Fundamental Research Funds for the Central Universities (FRF-TP-20-042A1).

We express our sincere thanks to Li Huawei, Yu Chao, and Zhou Limin for their help with the LA-(MC)-ICPMS zircon U-Pb dating and Hf isotope analyses, and to Zhou Yiwei and Liu Yanhong for their help with the whole-rock major element analyses.

 Conflict of interest

CD was employed in the Postdoctoral Programme of the Guosen Securities company.

The remaining authors declare that the research was conducted in the absence of any commercial or financial relationships that could be construed as a potential conflict of interest.

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