Middle–Late Jurassic high-
The Liaodong Peninsula is located in the northeast of the North China Craton
(NCC). The northeastern NCC was influenced by three main tectonic regimes in
the Mesozoic related to the subduction of the Paleo-Asian, Paleo-Pacific,
and Mongol–Okhotsk oceans (Tang et al., 2018). The superposition of these
different regimes resulted in changing tectonic and magmatic patterns over
time. Middle–Late Jurassic granitic rocks are extensively exposed in the
northern parts of the Liaodong Peninsula, such as the Yutun mylonitic
granite, Xiaoheishan granodiorite, Heigou monzogranite (Wu et al., 2005a),
Wulong two-mica monzogranite (Yang et al., 2018), and Huangdi biotite
monzogranite (Xue et al., 2020). Most of these rocks are characterized by
high
The geodynamic settings and petrogenesis of adakite and geochemically
similar high-
The Middle–Late Jurassic granitic rocks in the Liaodong Peninsula are
commonly proposed to be the products of partial melting of thickened mafic
crust with garnet in the residue (Wu et al., 2005a; F. C. Yang et al., 2015,
2018; Tang et al., 2018). However, the source composition has not been fully
considered in the petrogenesis of the high-
In this paper, we examined the high-
The Zhoujiapuzi granite is located in the middle of the Liaodong Peninsula at the northeastern margin of the NCC (Fig. 1). The Paleoproterozoic Liaohe Group and Liaoji granite are the basement in the study area. The Liaohe Group includes the Lieryu, Gaojiayu, Dashiqiao, and Gaixian formations. Although stratigraphic terms are used, these rocks are metamorphic, and the group consists of leptynite, leptite, granulite, amphibolite, marble, and phyllite. The protoliths of the Liaohe Group include marine volcanics, clastics, carbonates, and claystones. The formation age of the metasedimentary rocks in the Liaohe Group is 2.0–1.9 Ga (Wan et al., 2006; Li et al., 2015). It is in unconformable contact with the overlying strata of the Mesoproterozoic Cuocaogou Formation and Xiaoling Formation.
The study area experienced strong magmatic activity in the Paleoproterozoic,
which can be divided into two stages of 2.2–2.1 and
In the Mesozoic, the region of the Liaodong Peninsula was influenced by the circum-Pacific tectonic regime, the Mongol–Okhotsk tectonic regime, and the Paleo-Asian Ocean tectonic regime. The joint influence of multiple tectonic regimes resulted in intensive magmatism during the Mesozoic (Fig. 1b). These Mesozoic magmatic rocks can be divided into three stages, namely the Triassic (233–212 Ma), Jurassic (180–156 Ma), and Early Cretaceous (131–117 Ma) (Wu et al., 2005b).
The Triassic magmatic rocks are less exposed and are mainly alkaline rocks, diabase, diorites, and granites (Wu et al., 2005b). Among them, the granites mainly have A-type affinity and may have formed in an extensional setting (Tang et al., 2018; Wang et al., 2019). Magmatism has been related to either the subduction of the Paleo-Pacific slab, closure of the Paleo-Asian Ocean, or the collision between the NCC and the Yangtze Craton (Tang et al., 2018; Wang et al., 2019). The majority of the Jurassic magmatic rocks are monzogranite and granodiorite, which are generally calc–alkaline I-type granites, and show characteristics of adakite-like rocks. Some of them, exposed near later extensional structures, have undergone regional ductile deformation. These Jurassic magmatic rocks are generally considered to relate to the subduction of the Paleo-Pacific slab (Wu et al., 2005a; Zhai et al., 2004). In the Early Cretaceous, basic–acidic–alkaline rocks were widely developed. Among them, the granites have mainly A- and I-type affinities. These rocks are generally considered to have formed in an intense extensional environment, which is connected with either the rollback or low-angle subduction of the Paleo-Pacific slab (Wu et al., 2005c; Zheng et al., 2018).
The Zhoujiapuzi granite is located to the east of Xiuyan in the middle of the Liaodong Peninsula (Fig. 1b). It intruded into the Lieryu Formation of the Liaohe Group. Eight samples of the Zhoujiapuzi granite were collected at locations shown in Fig. 1c.
The Zhoujiapuzi granite is generally gray in color and with fine-grained
texture (Fig. 2a). The mineral assemblage contains K-feldspar
(
Outcrop photograph
The cathodoluminescence (CL) images of zircon were obtained by the Chengpu
Geological Testing Co. Ltd, Langfang, China, using the Tescan Integrated Mineral Analyzer (TIMA). The
LA-ICP-MS zircon U–Pb analyses were performed using an Agilent Technologies
7700x ICP-MS with a Teledyne Cetac Technologies Analyte Excite
laser-ablation system at Nanjing FocuMS Contract Testing Co. Ltd. The
analyses were carried out with a 35
The in situ Lu–Hf isotopic analyses of zircon were performed by LA-MC-ICP-MS
using a Teledyne Cetac laser-ablation system and a Nu Plasma II MC-ICP-MS at
Nanjing FocuMS Contract Testing Co. Ltd. The 193 nm ArF excimer laser was
focused on the zircon surface with a fluence of 6.0 J cm
Zircon Raman analyses were carried out using an RM2000 laser Raman
spectrometer at the State Key Laboratory of Nuclear Resources and
Environment, East China University of Technology. The selected incident
wavelengths were 532 and 785 nm in order to clearly identify the
luminescence bands due to low concentration impurities. The beam power was
20 mW. The Leica
Six fresh rock samples were selected for geochemical analysis. The elemental
analyses were conducted at Analytical Chemistry & Testing Services (ALS)
Chemex (Guangzhou) Ltd. Major oxides were analyzed using wave-dispersive
X-ray fluorescence (XRF) (ME-XRF26). Analytical precision was better than
The data for major and trace elements, Raman microprobe data, zircon trace elements, zircon U–Pb ages, and zircon Hf isotopes are shown in Tables S1, S2, S3, S4, and S5 in the Supplement, respectively.
SiO
Geochemical classification diagrams for the Zhoujiapuzi granite.
The samples of the Zhoujiapuzi granite exhibit variable REEs, with total
REEs ranging from 59 to 302 ppm. The
Chondrite-normalized REE patterns and primitive mantle-normalized trace element patterns of the Zhoujiapuzi granite (chondrite and primitive mantle values are from Sun and McDonough, 1989).
CL images of zircons from the Zhoujiapuzi granite are shown in Fig. 5.
Zircons commonly have crystal sizes between 150 and 250
CL images of zircons. Circles denote U–Pb analysis spot. Numbers in the circles are the spot numbers. Numbers near the analytical spots are the U–Pb ages (Ma).
Six light-CL core spots and six dark-CL rim spots were analyzed for Raman
spectra. The light-CL cores have antisymmetric stretching vibration
(
A total of 20 light-CL core spots, 18 dark-CL rim spots, and 6 inherited
zircon spots were analyzed for trace and rare earth elements. The light-CL
core spots have lower U content (28–677 ppm) than the dark-CL rim spots
(U
Chondrite-normalized REE patterns of zircon (chondrite values are from Sun and McDonough, 1989).
A total of 77 spots were analyzed for U–Pb isotope composition from samples
XY-001 and XY-008. In the U–Pb concordia diagram (Fig. 7a, c), both the
light-CL core and dark-CL rim spots overlap within uncertainty on the
concordia curve. There is a large degree of overlap between the 29 spots of the
dark-CL rim and 32 spots of the light-CL core in terms of
Concordia diagrams for zircon LA-ICP-MS U–Pb analyses.
A total of 24 zircons were analyzed for Lu–Hf isotope composition. The
variation in Hf isotopic data is limited: between nine spots from the light-CL core
and nine spots from the dark-CL rim. A total of 18 spots exhibit a range of
Zircon
Generally, zircon with high U content can easily break down into the
metamict state because of the radiation damage to the lattice caused by
Both the light-CL core and dark-CL rim have oscillatory zoning patterns, and their chondrite-normalized REE patterns are characterized by steeply positive slopes from the LREE to HREE with strong negative Eu anomalies and pronounced positive Ce anomalies. The above characteristics are consistent with those of igneous zircon (Hoskin and Schaltegger, 2003). Although hydrothermal zircon can also have oscillatory zoning patterns similar to magmatic zircons, there are obvious differences in trace elements between the magmatic and hydrothermal zircon (Hoskin, 2005). In the discrimination diagram (Fig. 9), the spots of both the light-CL core and dark-CL rim fall in or near the magmatic field, which is obviously different from hydrothermal zircon. Hence, the above characteristics indicate that both the light-CL core and dark-CL rim have a magmatic origin.
Discrimination plots for magmatic and hydrothermal zircon (Hoskin, 2005).
The light-CL core was overgrown continuously by the dark-CL rim. In
addition, the contact between the light-CL core and dark-CL rim is euhedral.
Such core–mantle overgrowth relationships indicate that the light-CL core
domains are not inherited zircons. The similar Hf isotopic data for the
light-CL core and dark-CL rim are also consistent with this interpretation.
For the age population, samples XY-001 and XY-008 have MSWD of 1.3
and 1.2, respectively, which are both within the expected range for the 95 %
confidence interval (Mahon, 1996). Although the
The
Covariation diagrams for zircon from the Zhoujiapuzi granite.
Watson and Harrison (2005) found that the Ti content of zircon has a strong
dependence on temperature (
Cerium exists in magmas as both Ce
The absence of enclaves and disequilibrium textures in the Zhoujiapuzi
granite and uniform
Zircon U–Pb dating is the most commonly used method in geochronology,
especially dating the emplacement age of magmatic rocks. A weighted mean age
or upper intercept age is usually obtained to represent the emplacement time
of a magmatic rock. However, the autocrystic zircons in this study record
two different magmatic evolution stages. Previous studies, such as Wang et
al. (2007), Zhao et al. (2014), and Chen et al. (2020), also show that
zircons can crystallize continually or intermittently in a single phase of
magmatism, showing several growth zones of clearly different internal
structure and distinct time difference. Therefore, autocrystic zircon can be
formed in two or more evolution stages during one distinct pulse or
increment of magma. Some scholars even consider the possibility that the age difference of
different stages can be more than dozens of millions of years (Wang et al., 2007).
Therefore, if the zircon ages in the same magmatic rock have a large range
of variation, this could be caused by the zircons recording different stages
in magmatic evolution related to different levels of magma within the crust
and/or different temperature regimes. In this paper, although the apparent
age of the dark-CL rim is generally younger than that of the light-CL core,
the age difference between the two is within the error range of the in situ
LA-ICP-MS analyses (individual spot of
The Zhoujiapuzi granite has low Zr (113–242 ppm), Ce (26.5–121.5 ppm),
Zr
Chemical variation diagrams for the Zhoujiapuzi granite.
The samples of the Zhoujiapuzi granite have
The samples of the Zhoujiapuzi granite have high
Adakite discrimination diagrams for the Zhoujiapuzi granite (after Defant and Drummond, 1990).
The partial melting of the young, hot, and hydrated subducted oceanic slab in
the garnet stability field is the classical formation model of adakite (high-
Source characteristics (
High-density, garnet-bearing mafic lower crust delaminating or foundering
into the asthenosphere mantle and subsequent interaction with mantle
peridotite could produce high-
Low-pressure fractional crystallization (involving olivine
However, the composition of the Zhoujiapuzi granite is relatively uniform,
including SiO
The Zhoujiapuzi granite has a high
Experimental studies have shown that the partial melt of basaltic LCC in the
garnet stabilization zone ( This ratio of ( Studies of
lower-crustal xenoliths show that garnet may not be a common mineral in the
lower crust of the NCC (Ma et al., 2012). As shown in the discrimination
diagrams of granite sources (Fig. 13f, g), all samples fall in the range of
metagraywacke-derived melts. Therefore, the Zhoujiapuzi granite was
considered to have been derived from crustal anatexis of metagraywacke (or
intermediate-acid igneous rock with similar mineral composition) rather
than basaltic lower crust.
Studies have shown that when a source rock has a high
The Zhoujiapuzi granite has similar mineral assemblages (contains abundant
K-feldspar and lacks hornblende) and geochemical composition (Fig. 13h) as
the Tsutsugatake intrusion, which is explained by partial melting of
arc-type tonalite or adakitic granodiorite (Kamei et al., 2009). Among the
inherited zircons from Zhoujiapuzi granite, the
The fields of zircon compositions used as discriminants for different rock types (after Belousova et al., 2002). “Granitoids” include (1) aplites and leucogranites, (2) granites, and (3) granodiorites and tonalities.
Some of the Liaoji granites, such as the Muniuhe granite (comprising
granodiorite and syenogranite with no distinct boundary between the two),
have adakitic signatures as well as similar REE and trace element patterns as the
Zhoujiapuzi granite (Fig. 4). Based on a model of batch melting (Shaw, 1970)
using the experiments of Conrad et al. (1988), the high-
In our modeling, we choose the XY-005 sample to approximately represent the
primitive melt composition for the following reasons. As mentioned above,
the high-
A large number of Yanshanian adakites (or high-
A large number of Early Jurassic arc-like igneous rocks occur in the northeastern part of NCC–Korean Peninsula–Hida belt, which belong to the middle- to high-K calc–alkaline series and are characterized by enrichment in LILE and depletions in HFSE (Wu et al., 2007; Tang et al., 2018, and references therein). In addition, the Early Jurassic accretionary complexes in the eastern margin of the Eurasian continent and the Japan islands, such as the Heilongjiang complex, the Khabarovsk complex, and the Mino-Tamba complex, are considered to be related to subduction (Wu et al., 2007; Tang et al., 2018, and references therein). It is generally accepted that the Paleo-Pacific slab subducted westwards in the Early Jurassic (Tang et al., 2018; Zhu and Xu, 2019).
In the Middle–Late Jurassic, I-type granites are dominant in the Liaodong Peninsula, such as the Zhoujiapuzi granite (this study), Heigou pluton, Gaoliduntai pluton (Wu et al., 2005a), Waling granite (F. C. Yang et al., 2015), and Wulong granite (Yang et al., 2018). There are no A-type granites, and mantle-derived magmatism is extremely rare. These granites were formed by partial melting of crustal materials without an obvious contribution of mantle-derived magma (Wu et al., 2005a; M. C. Yang et al., 2015; Yang et al., 2018; Xue et al., 2020). In addition, WNW–ESE compression during 157–143 Ma was widespread in the Liaodong Peninsula (Yang et al., 2004; Zhang et al., 2020). It not only mylonitized the granite plutons in middle–lower crust levels, but also intensely deformed the thick sedimentary cover in the upper crust (Qiu et al., 2018; Ren et al., 2020). Hence, Late Jurassic magmatism in the Liaodong Peninsula is most likely related to subduction of the Paleo-Pacific plate in a mature continental arc, with crust previously thickened by compressional tectonics, related to both the oceanic subduction and the earlier Mesozoic collisions at the northern and southern margins of the NCC. This setting would produce the conditions required for extensive crustal melting of pre-existing basement. There is a potential resemblance to the modern arc of the central Andes (Allmendinger et al., 1997), where crustal thickening and plateau growth developed over the Cenozoic (Scott et al., 2018), and melting of older basement took place during subduction of the Nazca plate (Miller and Harris, 1989). This model is also consistent with the idea that much of eastern China was a high orogenic plateau during the Mesozoic, before widespread Early Cretaceous extension and core complex development (Meng, 2003; Chu et al., 2020).
LA-ICP-MS zircon U–Pb dating indicates that the Zhoujiapuzi granite in
the Liaodong Peninsula formed at Zircon growth in Zhoujiapuzi granite can be divided into two distinct
stages. The light-CL core was formed in a deeper, hotter magma chamber,
which had low oxygen fugacity and high temperature. The dark-CL rim formed
from later, more evolved magma. Oxygen fugacity significantly increased and
the temperature decreased at this stage. The Zhoujiapuzi granite is a case
study of multistage generation and emplacement of magma revealed by
zircons, with no signals discernible in the bulk petrology or
geochemistry. The I-type Zhoujiapuzi granite originated from partial melting of the
Paleoproterozoic Liaoji granites. The high The Late Jurassic tectonic setting of the Liaodong Peninsula and the
eastern NCC resembled the modern orogenic plateau of the central Andes,
where silicic magmatism may occur by partial melting of older continental
crust in a compressional environment, related to the subduction of the
Paleo-Pacific plate.
All the data presented in this paper are available upon request.
The Supplement contains the table of major element (wt %) and trace
element (ppm) compositions of the Zhoujiapuzi granite, Raman microprobe
data, the zircon major elements (wt %), and trace elements (ppm) from the
Zhoujiapuzi granite, as well as zircon La-ICP-MS U–Pb isotopic data with ages of the
Zhoujiapuzi granite and zircon Hf isotopic data for the Zhoujiapuzi granite. The supplement related to this article is available online at:
RZ was responsible for fieldwork, conceptualization, methodology, and writing (original draft, review, and editing). MBA was responsible for conceptualization, supervision, and writing (review and editing). XM was responsible for funding acquisition and project administration. JL was responsible for funding acquisition and project administration. JY was responsible for review and editing. JW was responsible for laboratory analyses.
At least one of the (co-)authors is a member of the editorial board of
Publisher's note: Copernicus Publications remains neutral with regard to jurisdictional claims in published maps and institutional affiliations.
We thank Wenzhou Xiao, Jiajie Chen, and Quan Ou for constructive reviews and useful suggestions. We are also grateful to Ying Liu, Chunying Guo, Jianxiong Hu, and Ziming Hu for their help with the fieldwork.
This research was funded by the National Nature Science Foundation of China (grant nos. 42030809, 41772349, 41902075, 42002095, and 42162013), the China Scholarship Council (grant no. 202008360018), the Geological Exploration Program of China Nuclear Geology (grant no. D1802), research grants from the East China University of Technology (grant no. DHBK2017103), and the Open Research Fund Program of the State Key Laboratory of Nuclear Resources and Environment (East China University of Technology) (grant no. 2020NRE13).
This paper was edited by Johan Lissenberg and reviewed by Simon Large and one anonymous referee.